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Sample records for conjugate addition reactions

  1. Pentanidium-catalyzed enantioselective phase-transfer conjugate addition reactions

    KAUST Repository

    Ma, Ting

    2011-03-09

    A new chiral entity, pentanidium, has been shown to be an excellent chiral phase-transfer catalyst. The enantioselective Michael addition reactions of tert-butyl glycinate-benzophenone Schiff base with various α,β- unsaturated acceptors provide adducts with high enantioselectivities. A successful gram-scale experiment at a low catalyst loading of 0.05 mol % indicates the potential for practical applications of this methodology. Phosphoglycine ester analogues can also be utilized as the Michael donor, affording enantioenriched α-aminophosphonic acid derivatives and phosphonic analogues of (S)-proline. © 2011 American Chemical Society.

  2. Pd-NHC catalyzed conjugate addition versus the Mizoroki-Heck reaction.

    Science.gov (United States)

    Gottumukkala, Aditya L; de Vries, Johannes G; Minnaard, Adriaan J

    2011-03-07

    Ace of base: A catalytic system is presented that, solely by choice of the base, selectively switches between conjugate addition and the Mizoroki-Heck reaction of aryl halides with Michael acceptors (see scheme; R, R' = alkyl, aryl). For conjugate addition reactions, this avoids the preparation and use of organometallics. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Highly enantio- and diastereoselective reactions of γ-substituted butenolides through direct vinylogous conjugate additions

    KAUST Repository

    Zhang, Wen

    2012-09-05

    The strength of the weak: An L-tert-leucine-derived amine-thiourea catalyst (see scheme, green box) promotes the asymmetric vinylogous conjugate addition reaction between γ-aryl- and alkyl-substituted butenolides with the butenamides and enoates shown. Computational studies show the preference for the observed stereochemistry is a result of favourable weak non-bonding interactions, which stabilize the transition state. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. HIGHLY DIASTEREOSELECTIVE MICHAEL REACTION UNDER SOLVENT-FREE CONDITIONS USING MICROWAVES: CONJUGATE ADDITION OF FLAVANONE TO ITS CHALCONE PRECURSOR

    Science.gov (United States)

    Microwave-assisted reaction of 2'-hydroxychalcones in the presence of DBU resulted in the formation of hitherto unknown dimers by conjugate addition of the intermediate cyclic ketone to the starting enone.

  5. Synthesis of the Hemoglobin-Conjugated Polymer Micelles by Thiol Michael Addition Reactions.

    Science.gov (United States)

    Qi, Yanxin; Li, Taihang; Wang, Yupeng; Wei, Xing; Li, Bin; Chen, Xuesi; Xie, Zhigang; Jing, Xiabin; Huang, Yubin

    2016-06-01

    Amphiphilic triblock copolymers mPEG-b-PMAC-b-PCL are synthesized using methoxyl poly(ethylene glycol), cyclic carbonic ester monomer including acryloyl group, and ε-caprolactone. Copolymers are self-assembled into core-shell micelles in aqueous solution. Thiolated hemoglobin (Hb) is conjugated with micelles sufficiently through thiol Michael addition reaction to form hemoglobin nanoparticles (HbNs) with 200 nm in diameter. The conjugation of Hb onto the micelle surface is further confirmed by X-ray photoelectron spectroscopy. Feeding ratio of copolymer micelles to Hb at 1:3 would lead to the highest hemoglobin loading efficiency 36.7 wt%. The UV results demonstrate that the gas transporting capacity of HbNs is well remained after Hb is conjugated with polymeric micelles. Furthermore, the obtained HbNs have no obvious detrimental effects on blood components in vitro. This system may thus have great potential as one of the candidates to be developed as oxygen carriers and provide a reference for the modification of protein drugs. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Ring Walking/Oxidative Addition Reactions for the Controlled Synthesis of Conjugated Polymers

    Energy Technology Data Exchange (ETDEWEB)

    Bazan, Guillermo C

    2012-04-03

    Power conversion efficiencies of plastic solar cells depend strongly on the molecular weight characteristics of the semiconducting polymers used for their fabrication. The synthesis of these materials typically relies on transition metal mediated catalytic reactions. In many instances, the ideal structures cannot be attained because of deficiencies in these reactions, particularly when it comes to being able to achieve high number average molecular weights and narrow molecular weight distributions. Another important conjugated polymer structure of interest is one in which a single functional group is attached at the end group of the chain. Such systems would be ideal for modifying surface properties at interfaces and for labeling biomolecular probes used in fluorescent biosensors. To respond to the challenges above, our efforts have centered on the design of homogenous transition metal complexes that are easy to prepare and effective in carrying out living, or quasi-living, condensative chain polymerization reactions. The key mechanistic challenge for the success of this reaction is to force the insertion of one monomer unit at a time via a process that involves migration of the transition metal-containing fragment to one terminus of the polymer chain. Chain growth characteristics are therefore favored when the metal does not dissociate from the newly formed reductive elimination product. We have proposed that dissociation is disfavored by the formation of a -complex, in which the metal can sample various locations of the electronically delocalized framework, a process that we term ring-walking , and find the functionality where oxidative addition takes place. Success has been achieved in the nickel-mediated cross coupling reaction of Grignard reagents with aromatic halides by using bromo[1,2-bis(diphenylphosphino)ethane]phenylnickel. This reagent can yield poly(thiophene)s (one of the most widely used type of polymer in plastic solar cells) with excellent

  7. On the Role of DNA in DNA-based Catalytic Enantioselective Conjugate Addition Reactions

    NARCIS (Netherlands)

    Dijk, Ewold W.; Boersma, Arnold J.; Roelfes, Gerard; Feringa, Bernard

    2010-01-01

    A kinetic study of DNA-based catalytic enantioselective Friedel–Crafts alkylation and Michael addition reactions showed that DNA affects the rate of these reactions significantly. Whereas in the presence of DNA, a large acceleration was found for the Friedel–Crafts alkylation and a modest

  8. Heterogeneous versus homogeneous copper(II) catalysis in enantioselective conjugate-addition reactions of boron in water.

    Science.gov (United States)

    Kitanosono, Taku; Xu, Pengyu; Kobayashi, Shū

    2014-01-01

    We have developed Cu(II)-catalyzed enantioselective conjugate-addition reactions of boron to α,β-unsaturated carbonyl compounds and α,β,γ,δ-unsaturated carbonyl compounds in water. In contrast to the previously reported Cu(I) catalysis that required organic solvents, chiral Cu(II) catalysis was found to proceed efficiently in water. Three catalyst systems have been exploited: cat. 1: Cu(OH)2 with chiral ligand L1; cat. 2: Cu(OH)2 and acetic acid with ligand L1; and cat. 3: Cu(OAc)2 with ligand L1. Whereas cat. 1 is a heterogeneous system, cat. 2 and cat. 3 are homogeneous systems. We tested 27 α,β-unsaturated carbonyl compounds and an α,β-unsaturated nitrile compound, including acyclic and cyclic α,β-unsaturated ketones, acyclic and cyclic β,β-disubstituted enones, acyclic and cyclic α,β-unsaturated esters (including their β,β-disubstituted forms), and acyclic α,β-unsaturated amides (including their β,β-disubstituted forms). We found that cat. 2 and cat. 3 showed high yields and enantioselectivities for almost all substrates. Notably, no catalysts that can tolerate all of these substrates with high yields and high enantioselectivities have been reported for the conjugate addition of boron. Heterogeneous cat. 1 also gave high yields and enantioselectivities with some substrates and also gave the highest TOF (43,200 h(-1) ) for an asymmetric conjugate-addition reaction of boron. In addition, the catalyst systems were also applicable to the conjugate addition of boron to α,β,γ,δ-unsaturated carbonyl compounds, although such reactions have previously been very limited in the literature, even in organic solvents. 1,4-Addition products were obtained in high yields and enantioselectivities in the reactions of acyclic α,β,γ,δ-unsaturated carbonyl compounds with diboron 2 by using cat. 1, cat. 2, or cat. 3. On the other hand, in the reactions of cyclic α,β,γ,δ-unsaturated carbonyl compounds with compound 2, whereas 1,4-addition products

  9. Preliminary studies towards the preparation of reactive 3-pyrrolin-2-ones in conjugate addition reactions for the syntheses of potentially bioactive 2-pyrrolidinones and pyrrolidines

    Energy Technology Data Exchange (ETDEWEB)

    Alves, Jose C.F. [Universidade Federal Fluminense, (UFF) Niteroi, RJ (Brazil). Inst. de Quimica]. E-mail: alvesjcf@yahoo.com.br

    2007-07-01

    Pyrrolin-2-ones and 2-pyrrolidinones are moieties often found in the structure of several biologically active natural products and 3-pyrrolin-2-ones are valuable starting materials in organic synthesis due to their ability to react as acceptors in conjugate addition reactions. In this article we report the initial results about the performed study aiming at the syntheses of reactive 3-pyrrolin-2-ones in conjugate addition reactions and the preparation of a potential precursor for the synthesis of the nootropic (+/-)-nebracetam. (author)

  10. The Conjugate Addition- Elimination Reaction of Morita-Baylis-Hillman C- Adducts: A Density Functional Theory Study

    KAUST Repository

    Tan, Davin

    2011-12-01

    The Morita-Baylis-Hillman (MBH) reaction is a very versatile synthetic protocol to synthesize various useful compounds containing several functional groups. MBH acetates and carbonates are highly valued compounds as they have good potential to be precursors for organic synthesis reactions due to their ease of modification and synthesis. This thesis utilizes Density Functional Theory (DFT) calculations to understand the mechanism and selectivity of an unexpected tandem conjugate addition-elimination (CA-E) reaction of allylic alkylated Morita-Baylis-Hillman C- adducts. This synthetic protocol was developed by Prof. Zhi-Yong Jiang and co-workers from Henan University, China. The reaction required the use of sub-stoichiometric amounts of an organic or inorganic Brøndst base as a catalyst and was achieved with excellent yields (96%) in neat conditions. TBD gave the highest yield amongst the organocatalysts and Cs2CO3 gave the highest yield amongst all screened bases. A possible mechanistic pathway was proposed and three different energy profiles were modeled using 1,5,7-triaza-bicyclo-[4.4.0]-dec-5-ene (TBD), Cs2CO3 and CO32- as catalysts. All three models were able to explain the experimental observations, revealing both kinetic and thermodynamic factors influencing the selectivity of the CA-E reaction. CO32- model gave the most promising result, revealing a significant energy difference of 17.9 kcal/mol between the transition states of the two differing pathways and an energy difference of 20.9 kcal/mol between the two possible products. Although TBD modeling did not show significant difference in the transition states of the differing pathways, it revealed an unexpected secondary non-covalent electrostatic interaction, involving the electron deficient C atom of the triaza CN3 moiety of the TBD catalyst and the O atom of a neighboring NO2- group in the intermediate. Subsequent modeling using a similar substrate proved the possibility of this non

  11. Catalytic diastereoselective tandem conjugate addition-elimination reaction of Morita-Baylis-Hillman C adducts by C-C bond cleavage

    KAUST Repository

    Yang, Wenguo

    2012-02-08

    Through the cleavage of the C-C bond, the first catalytic tandem conjugate addition-elimination reaction of Morita-Baylis-Hillman C adducts has been presented. Various S N2′-like C-, S-, and P-allylic compounds could be obtained with exclusive E configuration in good to excellent yields. The Michael product could also be easily prepared by tuning the β-C-substituent group of the α-methylene ester under the same reaction conditions. Calculated relative energies of various transition states by DFT methods strongly support the observed chemoselectivity and diastereoselectivity. © 2012 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim.

  12. Reaction of allene esters with Selectfluor/TMSX (X = I, Br, Cl and Selectfluor/NH4SCN: Competing oxidative/electrophilic dihalogenation and nucleophilic/conjugate addition

    Directory of Open Access Journals (Sweden)

    A. Srinivas Reddy

    2015-09-01

    Full Text Available Reaction of benzyl and ethyl allenoates with TMSX (X = I, Br, Cl and with NH4SCN were investigated in MeCN, DMF, and in imidazolium ionic liquids [BMIM][NTf2] and [BMIM][PF6] as solvent, in the presence and absence of Selectfluor. Comparative product analysis studies demonstrate that the ability of Selectflour to promote oxidative/electrophilic dihalogenation/dithiocyanation with TMSX/NH4SCN (as observed previously for 1-arylallenes is diminished in allenoates, most significantly in reactions with TMSCl, and essentially disappearing in reactions with NH4SCN, in favor of nucleophilic/conjugate addition. The study underscores the contrasting reactivity patterns in 1-arylallenes and allenoates toward electrophilic and nucleophilic additions in halofunctionalization with TMSX/Selectfluor and thiocyanation reactions with NH4SCN/Selectfluor. These competing pathways are influenced by the nature of the anion, allene structure, and the choice of solvent.

  13. Polar reactions of acyclic conjugated bisallenes

    Directory of Open Access Journals (Sweden)

    Reiner Stamm

    2013-01-01

    Full Text Available The chemical behaviour of various alkyl-substituted, acyclic conjugated bisallenes in reactions involving polar intermediates and/or transition states has been investigated on a broad scale for the first time. The reactions studied include lithiation, reaction of the thus formed organolithium salts with various electrophiles (among others, allyl bromide, DMF and acetone, oxidation to cyclopentenones and epoxides, hydrohalogenation (HCl, HBr addition, halogenation (Br2 and I2 addition, and [2 + 2] cycloaddition with chlorosulfonyl isocyanate. The resulting adducts were fully characterized by spectroscopic and analytical methods; they constitute interesting substrates for further organic transformations.

  14. Glutathione conjugation as a bioactivation reaction

    NARCIS (Netherlands)

    Bladeren, P.J. van

    2000-01-01

    In general, glutathione conjugation is regarded as a detoxication reaction. However, depending on the properties of the substrate, bioactivation is also possible. Four types of activation reaction have been recognized: direct-acting compounds, conjugates that are activated through cysteine conjugate

  15. Catalytic enantioselective conjugate addition with Grignard reagents

    NARCIS (Netherlands)

    Lopez, Fernando; Minnaard, Adriaan J.; Feringa, Ben L.

    In this Account, recent advances in catalytic asymmetric conjugate addition of Grignard reagents are discussed. Synthetic methodology to perform highly enantioselective Cu-catalyzed conjugate addition of Grignard reagents to cyclic enones with ee's up to 96% was reported in 2004 from our

  16. Conjugate addition–enantioselective protonation reactions

    Directory of Open Access Journals (Sweden)

    James P. Phelan

    2016-06-01

    Full Text Available The addition of nucleophiles to electron-deficient alkenes represents one of the more general and commonly used strategies for the convergent assembly of more complex structures from simple precursors. In this review the addition of diverse protic and organometallic nucleophiles to electron-deficient alkenes followed by enantioselective protonation is summarized. Reactions are first categorized by the type of electron-deficient alkene and then are further classified according to whether catalysis is achieved with chiral Lewis acids, organocatalysts, or transition metals.

  17. Copper-catalyzed enantioselective conjugate addition of organometallic reagents to acyclic dienones

    NARCIS (Netherlands)

    Sebesta, Radovan; Pizzuti, M. Gabriella; Minnaard, Adriaan J.; Feringa, Ben L.; Šebesta, Radovan

    The enantioselective, copper/phosphoramidite-catalyzed 1,4-addition of dialkylzinc reagents to acyclic dienones is described. The products of this reaction, obtained with enantioselectivities of up to 95%, can be further functionalized by a second conjugate addition, or employed in an enolate

  18. Niobium Pentachloride Activation of Enone Derivatives: Diels-Alder and Conjugate Addition Products

    Directory of Open Access Journals (Sweden)

    Gil Valdo José da Silva

    2002-05-01

    Full Text Available Niobium pentachloride has proven to be a powerful activating agent for Diels-Alder or conjugate addition reactions of cycloenones. The Diels-Alder product was obtained only with an unsubstituted enone (cyclohexenone and the highly reactive diene cyclopentadiene; substituents in the b-position of enones seem to prevent Diels-Alder reaction: oxygenated substituents favor the formation of vinyl chlorides (ethyl ether or dichloromethane as solvents or enol ethers (ethyl acetate as solvent, while a methyl substituent prevents any kind of transformation with NbCl5. Less reactive dienes, furan and 2-methylfuran gave the conjugate addition products of the furan ring to the enone system.

  19. A One-Pot Synthesis of Pyranone and Pyrrole Derivatives from β-Chlorovinyl Ketones via Direct Conjugate Addition Approach.

    Science.gov (United States)

    Kim, Hun Young; Oh, Kyungsoo

    2017-09-15

    The direct conjugate addition reactions of imino esters to β-chlorovinyl ketones have been accomplished in the presence of a substoichiometric amount of hard base, LiHMDS. An in situ generated species from the conjugate addition reaction readily acted as autocatalyst to convert the imino esters to its corresponding enolates. By utilizing a sequence of conjugate addition/elimination/lactonization followed by either reduction or reaction with amines, the novel one-pot syntheses of highly functionalized pyranone and pyrrole derivatives were accomplished in good to excellent yields.

  20. Propargylamine-isothiocyanate reaction: efficient conjugation chemistry in aqueous media

    DEFF Research Database (Denmark)

    Viart, Helene Marie-France; Larsen, T. S.; Tassone, Chiara

    2014-01-01

    A coupling reaction between secondary propargyl amines and isothiocyanates in aqueous media is described. The reaction is high-yielding and affords cyclized products within 2-24 h. A functionalized ether lipid was synthesized in 8 steps, formulated as liposomes with POPC and conjugated to FITC un...

  1. Catalytic asymmetric conjugate addition of Grignard reagents to chromones

    NARCIS (Netherlands)

    Vila, Carlos; Hornillos, Valentin; Fananas-Mastral, Martin; Feringa, Ben L.

    2013-01-01

    A highly regio- and enantioselective copper catalysed direct conjugate addition of Grignard reagents to chromones has been developed taking advantage of the reduced reactivity of the resulting magnesium enolates. This methodology tolerates a broad scope of alkyl Grignards including secondary alkyl

  2. Reactions of halophosphines with conjugated heterodienes

    Energy Technology Data Exchange (ETDEWEB)

    Levina, Elina Ya; Kibardin, A M [A.E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Centre of the Russian Academy of Sciences, Kazan (Russian Federation)

    1999-02-28

    Data on reactions of halophosphines PHal{sub 3}, -PHal{sub 2} and >PHal with hetero-1,3-dienes resulting mostly in the formation of phosphorus-containing heterocycles are generalised and systematised. The influence of the nature, the number and positions of heteroatoms (O, N) in the heterodiene system, and of the nature of the substituents at the phosphorus atom on the reaction pathways and mechanisms is analysed. The bibliography includes 155 references.

  3. Versatile phosphoramidation reactions for nucleic acid conjugations with peptides, proteins, chromophores, and biotin derivatives.

    Science.gov (United States)

    Wang, Tzu-Pin; Chiou, Yi-Jang; Chen, Yi; Wang, Eng-Chi; Hwang, Long-Chih; Chen, Bing-Hung; Chen, Yen-Hsu; Ko, Chun-Han

    2010-09-15

    successfully synthesize nucleic acid-tetraglycine conjugates. In addition, phosphoramidation reactions provided a facile approach to prepare nucleic acid-BSA conjugates with good yields. In summary, the new approach to phosphoramidation reactions offers a universal method to prepare POCs and other nucleic acid conjugates with high yields in aqueous solutions. The methods can be easily adapted to typical chemistry or biology laboratory setups which will expedite the applications of POCs for basic research and medicine.

  4. Conjugate products of pyocyanin-glutathione reactions.

    Science.gov (United States)

    Cheluvappa, Rajkumar; Eri, Rajaraman

    2015-08-05

    This "Letter to the Editor" is a "gentle but purposeful rejoinder" to specific comments made in pages 36-37 of your Muller and Merrett (2015) publication regarding the data presented in our Cheluvappa et al. (2008) paper. Our rebuttal topics include the effect of oxygen on the pyocyanin-glutathione reaction, relevance of reaction-duration to pathophysiology, rationale of experiments, veracity of statements germane to molecular-structure construction, and correction of hyperbole. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  5. Conjugate Addition of Nucleophiles to the Vinyl Function of 2-Chloro-4-vinylpyrimidine Derivatives

    Directory of Open Access Journals (Sweden)

    Lucjan Strekowski

    2010-03-01

    Full Text Available Conjugate addition reaction of various nucleophiles across the vinyl group of 2-chloro-4-vinylpyrimidine, 2-chloro-4-(1-phenylvinylpyrimidine and 2-chloro-4-vinylquinazoline provides the corresponding 2-chloro-4-(2-substituted ethylpyrimidines and 2-chloro-4-(2-substituted ethylquinazolines. Treatment of these products, without isolation, with N-methylpiperazine results in nucleophilic displacement of chloride and yields the corresponding 2,4-disubstituted pyrimidines and quinazolines.

  6. Chiral amides via copper-catalysed enantioselective conjugate addition.

    Science.gov (United States)

    Schoonen, Anne K; Fernández-Ibáñez, M Ángeles; Fañanás-Mastral, Martín; Teichert, Johannes F; Feringa, Ben L

    2014-01-07

    A highly enantioselective one pot procedure for the synthesis of β-substituted amides was developed starting from the corresponding α,β-unsaturated esters. This new methodology is based on the copper-catalysed enantioselective conjugate addition of Grignard reagents to α,β-unsaturated esters and subsequent direct formation of amides by quenching the corresponding enolates with different amines. Various primary and secondary amines bearing alkyl or aryl substituents can be used giving rise to a large variety of β-substituted amides with excellent enantioselectivities.

  7. Do π-conjugative effects facilitate SN2 reactions?

    Science.gov (United States)

    Wu, Chia-Hua; Galabov, Boris; Wu, Judy I-Chia; Ilieva, Sonia; Schleyer, Paul von R; Allen, Wesley D

    2014-02-26

    Rigorous quantum chemical investigations of the SN2 identity exchange reactions of methyl, ethyl, propyl, allyl, benzyl, propargyl, and acetonitrile halides (X = F(-), Cl(-)) refute the traditional view that the acceleration of SN2 reactions for substrates with a multiple bond at Cβ (carbon adjacent to the reacting Cα center) is primarily due to π-conjugation in the SN2 transition state (TS). Instead, substrate-nucleophile electrostatic interactions dictate SN2 reaction rate trends. Regardless of the presence or absence of a Cβ multiple bond in the SN2 reactant in a series of analogues, attractive Cβ(δ(+))···X(δ(-)) interactions in the SN2 TS lower net activation barriers (E(b)) and enhance reaction rates, whereas repulsive Cβ(δ(-))···X(δ(-)) interactions increase E(b) barriers and retard SN2 rates. Block-localized wave function (BLW) computations confirm that π-conjugation lowers the net activation barriers of SN2 allyl (1t, coplanar), benzyl, propargyl, and acetonitrile halide identity exchange reactions, but does so to nearly the same extent. Therefore, such orbital interactions cannot account for the large range of E(b) values in these systems.

  8. Catalytic enantioselective 1,6-conjugate additions of propargyl and allyl groups

    Science.gov (United States)

    Meng, Fanke; Li, Xiben; Torker, Sebastian; Shi, Ying; Shen, Xiao; Hoveyda, Amir H.

    2016-09-01

    Conjugate (or 1,4-) additions of carbanionic species to α,β-unsaturated carbonyl compounds are vital to research in organic and medicinal chemistry, and there are several chiral catalysts that facilitate the catalytic enantioselective additions of nucleophiles to enoates. Nonetheless, catalytic enantioselective 1,6-conjugate additions are uncommon, and ones that incorporate readily functionalizable moieties, such as propargyl or allyl groups, into acyclic α,β,γ,δ-doubly unsaturated acceptors are unknown. Chemical transformations that could generate a new bond at the C6 position of a dienoate are particularly desirable because the resulting products could then be subjected to further modifications. However, such reactions, especially when dienoates contain two equally substituted olefins, are scarce and are confined to reactions promoted by a phosphine-copper catalyst (with an alkyl Grignard reagent, dialkylzinc or trialkylaluminium compounds), a diene-iridium catalyst (with arylboroxines), or a bisphosphine-cobalt catalyst (with monosilyl-acetylenes). 1,6-Conjugate additions are otherwise limited to substrates where there is full substitution at the C4 position. It is unclear why certain catalysts favour bond formation at C6, and—although there are a small number of catalytic enantioselective conjugate allyl additions—related 1,6-additions and processes involving a propargyl unit are non-existent. Here we show that an easily accessible organocopper catalyst can promote 1,6-conjugate additions of propargyl and 2-boryl-substituted allyl groups to acyclic dienoates with high selectivity. A commercially available allenyl-boron compound or a monosubstituted allene may be used. Products can be obtained in up to 83 per cent yield, >98:2 diastereomeric ratio (for allyl additions) and 99:1 enantiomeric ratio. We elucidate the mechanistic details, including the origins of high site selectivity (1,6- versus 1,4-) and enantioselectivity as a function of the catalyst

  9. Fluorogenic reaction-based prodrug conjugates as targeted cancer theranostics.

    Science.gov (United States)

    Lee, Min Hee; Sharma, Amit; Chang, Min Jung; Lee, Jinju; Son, Subin; Sessler, Jonathan L; Kang, Chulhun; Kim, Jong Seung

    2018-01-02

    Theranostic systems are receiving ever-increasing attention due to their potential therapeutic utility, imaging enhancement capability, and promise for advancing the field of personalized medicine, particularly as it relates to the diagnosis, staging, and treatment of cancer. In this Tutorial Review, we provide an introduction to the concepts of theranostic drug delivery effected via use of conjugates that are able to target cancer cells selectively, provide cytotoxic chemotherapeutics, and produce readily monitored imaging signals in vitro and in vivo. The underlying design concepts, requiring the synthesis of conjugates composed of imaging reporters, masked chemotherapeutic drugs, cleavable linkers, and cancer targeting ligands, are discussed. Particular emphasis is placed on highlighting the potential benefits of fluorogenic reaction-based targeted systems that are activated for both imaging and therapy by cellular entities, e.g., thiols, reactive oxygen species and enzymes, which are present at relatively elevated levels in tumour environments, physiological characteristics of cancer, e.g., hypoxia and acidic pH. Also discussed are systems activated by an external stimulus, such as light. The work summarized in this Tutorial Review will help define the role fluorogenic reaction-based, cancer-targeting theranostics may have in advancing drug discovery efforts, as well as improving our understanding of cellular uptake and drug release mechanisms.

  10. Double Conjugate Addition of Dithiols to Propargylic Carbonyl Systems To Generate Protected 1,3-Dicarbonyl Compounds

    NARCIS (Netherlands)

    Sneddon, Helen F.; Heuvel, Alexandra van den; Hirsch, Anna K.H.; Booth, Richard A.; Shaw, David M.; Gaunt, Matthew J.; Ley, Steven V.

    2006-01-01

    The work describes the efficient double conjugate addition of ethane and propane dithiols in the presence of sodium methoxide to a wide variety of propargylic carbonyl containing compounds. The products of these reactions are differentiated, 1,3-dicarbonyl systems useful for various synthesis

  11. Characterization and Oxidative Addition Reactions of Different ...

    African Journals Online (AJOL)

    NJD

    Characterization and Oxidative Addition Reactions of. Different Rhodium and Iridium Triazolato Complexes. Alfred J. Muller, Jeanet Conradie*, Walter Purcell*, Stephen S. Basson and Johan A. Venter. Department of Chemistry, University of the Free State, Bloemfontein 9300, South Africa. Received 17 June 2009, revised 7 ...

  12. Recyclable surfaces for amine conjugation chemistry via redox reaction

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Inseong; Yeo, Woon Seok [Dept. of Bioscience and Biotechnology, Bio/Molecular Informatics Center, Konkuk University, Seoul (Korea, Republic of); Bae, Se Won [Green Materials and Process Group, Research Institute of Sustainable Manufacturing System, Korea Institute of Industrial Technology, Cheonan (Korea, Republic of)

    2017-02-15

    In this study, we extended this strategy to present a switchable surface that allows surface functionalization and removal of functional groups repeatedly. The substrate presenting a benzoquinone acid group is first used to immobilize with an amine-containing (bio)molecule using well-known conjugation chemistry. The benzoquinone group is then converted to the corresponding hydroquinone by treating with a reducing agent. We have described a strategy for the dynamic control of surface properties with recyclability via a simple reduction/ oxidation reaction. A stimuli-responsive quinone derivative was harnessed for the repeated immobilization and release of (bio)molecules, and thus, for the repeated dynamic change of the surface properties according to the characteristics of the immobilized (bio)molecules.

  13. Rhodium(I-Complexes Catalyzed 1,4-Conjugate Addition of Arylzinc Chlorides to N-Boc-4-pyridone

    Directory of Open Access Journals (Sweden)

    Fenghai Guo

    2017-05-01

    Full Text Available Rhodium(I-complexes catalyzed the 1,4-conjugate addition of arylzinc chlorides to N-Boc-4-pyridone in the presence of chlorotrimethylsilane (TMSCl. A combination of [RhCl(C2H42]2 and BINAP was determined to be the most effective catalyst to promote the 1,4-conjugate addition reactions of arylzinc chlorides to N-Boc-4-pyridone. A broad scope of arylzinc reagents with both electron-withdrawing and electron-donating substituents on the aromatic ring successfully underwent 1,4-conjugate addition to N-Boc-4-pyridone to afford versatile 1,4-adducts 2-substituted-2,3-dihydropyridones in good to excellent yields (up to 91% and excellent ee (up to 96% when (S-BINAP was used as chiral ligand.

  14. Conjugation-promoted reaction of open-cage fullerene: A density functional theory study

    KAUST Repository

    Guo, Yong

    2012-01-20

    Density functional theory calculations are performed to study the addition mechanism of e-rich moieties such as triethyl phosphite to a carbonyl group on the rim of a fullerene orifice. Three possible reaction channels have been investigated. The obtained results show that the reaction of a carbonyl group on a fullerene orifice with triethyl phosphite most likely proceeds along the classical Abramov reaction; however, the classical product is not stable and is converted into the experimental product. An attack on a fullerene carbonyl carbon will trigger a rearrangement of the phosphate group to the carbonyl oxygen as the conversion transition state is stabilized by fullerene conjugation. This work provides a new insight on the reactivity of open-cage fullerenes, which may prove helpful in designing new switchable fullerene systems. Not that classical: The reaction of a carbonyl group on the fullerene orifice with triethyl phosphite most likely proceeds following the Abramov reaction to firstly form a classical product. However, this product is not stable and turns into an experimental product as the conversion transition state is stabilized by fullerene conjugation (see picture). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Site-Specific Tandem Knoevenagel Condensation-Michael Addition To Generate Antibody-Drug Conjugates.

    Science.gov (United States)

    Kudirka, Romas A; Barfield, Robyn M; McFarland, Jesse M; Drake, Penelope M; Carlson, Adam; Bañas, Stefanie; Zmolek, Wes; Garofalo, Albert W; Rabuka, David

    2016-11-10

    Expanded ligation techniques are sorely needed to generate unique linkages for the growing field of functionally enhanced proteins. To address this need, we present a unique chemical ligation that involves the double addition of a pyrazolone moiety with an aldehyde-labeled protein. This ligation occurs via a tandem Knoevenagel condensation-Michael addition. A pyrazolone reacts with an aldehyde to generate an enone, which undergoes subsequent attack by a second pyrazolone to generate a bis-pyrazolone species. This rapid and facile ligation technique is performed under mild conditions in the absence of catalyst to generate new architectures that were previously inaccessible via conventional ligation reactions. Using this unique ligation, we generated three site-specifically labeled antibody-drug conjugates (ADCs) with an average of four drugs to one antibody. The in vitro and in vivo efficacies along with pharmacokinetic data of the site-specific ADCs are reported.

  16. Conjugate-base-stabilized Brønsted acids: catalytic enantioselective Pictet-Spengler reactions with unmodified tryptamine.

    Science.gov (United States)

    Mittal, Nisha; Sun, Diana X; Seidel, Daniel

    2014-02-07

    A conjugate-base-stabilized Brønsted acid facilitates catalytic enantioselective Pictet-Spengler reactions with unmodified tryptamine. The chiral carboxylic acid catalyst is readily assembled in just two steps and enables the formation of β-carbolines with up to 92% ee. Achiral acid additives or in situ Boc-protection facilitate catalyst turnover.

  17. Structure and antimicrobial mechanism of ɛ-polylysine-chitosan conjugates through Maillard reaction.

    Science.gov (United States)

    Liang, Chunxuan; Yuan, Fang; Liu, Fuguo; Wang, Yingying; Gao, Yanxiang

    2014-09-01

    The aim of the study was to testify the formation and antimicrobial activity of ɛ-polylysine-chitosan conjugate through Maillard reaction. The results of UV absorbance, browning index and fluorescence changes of Maillard reaction products (MRPs) between ɛ-polylysine and chitosan indicated there existed Maillard reaction between ɛ-polylysine and chitosan and the formation of their conjugate. The conjugate showed strong antibacterial activity against Escherichia coli, Staphylococcus aureus, Bacillus subtilis and beer yeast. Morphologies of E. coli and S. aureus treated with the conjugate were observed by transmission electron microscopy (TEM). The results revealed that the conjugate of ɛ-polylysine and chitosan increased the permeability of the outer membrane (OM) and inner membrane (IM) and ultimately disrupted bacterial cell membranes, with the release of cellular cytoplasm. Crown Copyright © 2014. Published by Elsevier B.V. All rights reserved.

  18. Catalytic enantioselective conjugate addition of diethylzinc using NiII-DAIB complexes

    NARCIS (Netherlands)

    Jansen, Johan F.G.A.; Feringa, Bernard

    The conjugate addition of diethylzinc to chalcone, catalyzed by a NiII complex of the chiral aminoalcohol (-)-DAIB, resulted in the formation of (R)-1,3-diphenyl-penta-1-one with enantiomeric excess up to 85%.

  19. Unprecedented copper-catalyzed asymmetric conjugate addition of organometallic reagents to alpha,beta-unsaturated lactams

    NARCIS (Netherlands)

    Pineschi, M.; Del Moro, F.; Gini, F.; Minnaard, A.J.; Feringa, B.L.

    2004-01-01

    For the first time, an excellent enantioselectivity has been obtained in the conjugate addition of hard organometallic reagents to alpha, beta-unsaturated lactams bearing appropriate protecting-activating groups on the nitrogen.

  20. Galactodendritic porphyrinic conjugates as new biomimetic catalysts for oxidation reactions.

    Science.gov (United States)

    Castro, Kelly A D F; Silva, Sandrina; Pereira, Patrícia M R; Simões, Mário M Q; Neves, Maria da Graça P M S; Cavaleiro, José A S; Wypych, Fernando; Tomé, João P C; Nakagaki, Shirley

    2015-05-04

    This work employed [5,10,15,20-tetrakis(pentafluorophenyl)porphyrin] ([H2(TPPF20)], H2P1) as the platform to prepare a tetrasubstituted galactodendritic conjugate porphyrin (H2P3). After metalation with excess copper(II) acetate, H2P3 afforded a new solid porphyrin material, Cu4CuP3S. This work also assessed the ability of the copper(II) complex (CuP3) of H2P3 to coordinate with zinc(II) acetate, to yield the new material Zn4CuP3S. UV-visible, Fourier transform infrared, and electron paramagnetic resonance spectroscopies aided full characterization of the synthesized solids. (Z)-Cyclooctene epoxidation under heterogeneous conditions helped to evaluate the catalytic activity of Cu4CuP3S and Zn4CuP3S. The efficiency of Cu4CuP3S in the oxidation of another organic substrate, catechol, was also investigated. According to the results obtained in the heterogeneous process, Cu4CuP3S mimicked the activity of cytochrome P-450 and catecholase. In addition, Cu4CuP3S was reusable after recovery and reactivation. The data obtained herein were compared with the results achieved for the copper complex (CuP1) of [H2(TPPF20)] and for CuP3 under homogeneous conditions.

  1. Enantioselective conjugate silyl additions to cyclic and acyclic unsaturated carbonyls catalyzed by Cu complexes of chiral N-heterocyclic carbenes.

    Science.gov (United States)

    Lee, Kang-Sang; Hoveyda, Amir H

    2010-03-10

    An efficient Cu-catalyzed protocol for enantioselective addition of a dimethylphenylsilanyl group to a wide range of cyclic and acyclic unsaturated ketones, esters, acrylonitriles, and alpha,beta,gamma,delta-dienones is disclosed. Reactions are performed in the presence of 1-2 mol % of commercially available and inexpensive CuCl, a readily accessible monodentate imidazolinium salt, and commercially available (dimethylphenylsilyl)pinacolatoboron. Cu-catalyzed enantioselective conjugate additions proceed to completion within only 2 h to afford the desired silanes in 87-97% yield and 90:10-99:1 enantiomeric ratio (er). Use of a proton source (e.g., MeOH) is not required; accordingly, synthetically versatile alpha-silyl boron enolates can be obtained. The special utility of the present protocol, in comparison with the related catalytic enantioselective aldol and boronate conjugate additions, is discussed and illustrated through various functionalizations of the enantiomerically enriched beta-silylcarbonyls.

  2. Synthesis of indole terpenoid mimics through a functionality-tolerated Eu(fod)3 -catalyzed conjugate addition.

    Science.gov (United States)

    Xiong, Xiaochun; Zhang, Deliang; Li, Jian; Sun, Yu; Zhou, Shupeng; Yang, Ming; Shao, Huawu; Li, Ang

    2015-04-01

    The chemical synthesis of indole terpenoids of structural and biological interests has attracted remarkable attention. Here we report an Eu(fod)3 -catalyzed indole conjugate addition reaction, which tolerates various acid-sensitive functional groups. A collection of indole terpenoid mimics have been prepared from natural product-derived α,β-unsaturated enones on the basis of this reaction. The further conversion of the indole adducts into more complex natural product-like molecules has also been demonstrated. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Exploring the Catalytic Promiscuity of Phenolic Acid Decarboxylases: Asymmetric, 1,6-Conjugate Addition of Nucleophiles Across 4-Hydroxystyrene.

    Science.gov (United States)

    Payer, Stefan E; Sheng, Xiang; Pollak, Hannah; Wuensch, Christiane; Steinkellner, Georg; Himo, Fahmi; Glueck, Silvia M; Faber, Kurt

    2017-06-19

    The catalytic promiscuity of a ferulic acid decarboxylase from Enterobacter sp. (FDC_ E s) and phenolic acid decarboxylases (PADs) for the asymmetric conjugate addition of water across the C=C bond of hydroxystyrenes was extended to the N-, C- and S-nucleophiles methoxyamine, cyanide and propanethiol to furnish the corresponding addition products in up to 91% ee . The products obtained from the biotransformation employing the most suitable enzyme/nucleophile pairs were isolated and characterized after optimizing the reaction conditions. Finally, a mechanistic rationale supported by quantum mechanical calculations for the highly ( S )-selective addition of cyanide is proposed.

  4. Functional properties of nisin-carbohydrate conjugates formed by radiation induced Maillard reaction

    Science.gov (United States)

    Muppalla, Shobita R.; Sonavale, Rahul; Chawla, Surinder P.; Sharma, Arun

    2012-12-01

    Nisin-carbohydrate conjugates were prepared by irradiating nisin either with glucose or dextran. Increase in browning and formation of intermediate products was observed with a concomitant decrease in free amino and reducing sugar groups indicating occurrence of the Maillard reaction catalyzed by irradiation. Nisin-carbohydrate conjugates showed a broad spectrum antibacterial activity against Gram negative bacteria (Escherichia coli, Pseudomonas fluorescence) as well as Gram positive bacteria (Staphylococcus aureus, Bacillus cereus). Results of antioxidant assays, including that of DPPH radical-scavenging activity and reducing power, showed that the nisin-dextran conjugates possessed better antioxidant potential than nisin-glucose conjugate. These results suggested that it was possible to enhance the functional properties of nisin by preparing radiation induced conjugates suitable for application in food industry.

  5. Method for promoting Michael addition reactions

    Science.gov (United States)

    Shah, Pankaj V.; Vietti, David E.; Whitman, David William

    2010-09-21

    Homogeneously dispersed solid reaction promoters having an average particle size from 0.01 .mu.m to 500 .mu.m are disclosed for preparing curable mixtures of at least one Michael donor and at least one Michael acceptor. The resulting curable mixtures are useful as coatings, adhesives, sealants and elastomers.

  6. Lanthanoid triflate catalyzed conjugate addition of amines to [alpha], [beta]-unsaturated esters; A facile route to optically active [beta]-lactam

    Energy Technology Data Exchange (ETDEWEB)

    Matsubara, Seijiro; Yoshioka, Masahito; Utimoto, Kiitiro (Kyoto Univ. (Japan). Faculty of Engineering)

    1994-05-01

    Catalytic amount of lanthanoid(III) triflates promoted the conjugate addition of amines to 2-alkenoic acid esters to give [beta]-amino esters. The reaction of benzylamine with [alpha], [beta]-unsaturated esters containing a stereogenic center at [gamma]-position proceeded diastereoselectivity to yield optically active [beta]-lactam precursors. (author).

  7. CATALYTIC ENANTIOSELECTIVE CONJUGATE ADDITION OF DIETHYLZINC USING NI(II) DAIB COMPLEXES

    NARCIS (Netherlands)

    JANSEN, JFGA; FERINGA, BL

    The conjugate addition of diethylzinc to chalcone, catalyzed by a NiII complex of the chiral amino-alcohol (-)-DAIB, resulted in the formation of (R)-1,3-diphenyl-penta-1-one with enantiomeric excess up to 85%.

  8. Biphenol-based phosphoramidite ligands for the enantioselective copper-catalyzed conjugate addition of diethylzinc.

    Science.gov (United States)

    Alexakis, Alexandre; Polet, Damien; Rosset, Stéphane; March, Sébastien

    2004-08-20

    Phosphoramidite ligands, based on ortho-substituted biphenols and a chiral amine, induce high enantioselectivities (ee's up to 99%) in the copper-catalyzed conjugate addition of dialkylzinc reagents to a variety of Michael acceptors. Particularly, the best reported ee's were obtained for acyclic nitroolefins. Copyright 2004 American Chemical Society

  9. ENANTIOSELECTIVE CONJUGATE ADDITION OF DIETHYLZINC TO CHALCONES CATALYZED BY CHIRAL NI(II) AMINOALCOHOL COMPLEXES

    NARCIS (Netherlands)

    DEVRIES, AHM; JANSEN, JFGA; FERINGA, BL

    1994-01-01

    Conjugate addition of diethylzinc to chalcones is catalysed by complexes prepared in situ from Ni(acac)(2) and cis-exo-N,N-dialkyl-3-aminoisoborneols or (+)-cis-endo-N,N-dimethyl-3-aminoborneol ((+)- DAB) (13b). The products are obtained with enantioselectivities up to 84 %. When scalemic

  10. Enantioselective Conjugate Addition of Diethylzinc to Chalcones Catalysed by Chiral Ni(II) Aminoalcohol Complexes

    NARCIS (Netherlands)

    Vries, André H.M. de; Jansen, Johan F.G.A.; Feringa, Bernard

    1994-01-01

    Conjugate addition of diethylzinc to chalcones is catalysed by complexes prepared in situ from Ni(acac)2 and cis-exo-N,N-dialkyl-3-aminoisoborneols or (+)-cis-endo-N,N-dimethyl-3-aminoborneol ((+)-DAB) (13b). The products are obtained with enantioselectivities up to 84 %. When scalemic

  11. Asymmetric conjugate addition of alkylzirconium reagents to α,β-unsaturated lactones.

    Science.gov (United States)

    Maciver, Eleanor E; Maksymowicz, Rebecca M; Wilkinson, Nancy; Roth, Philippe M C; Fletcher, Stephen P

    2014-06-20

    The asymmetric synthesis of β-substituted lactones by catalytic asymmetric conjugate addition of alkyl groups to α,β-unsaturated lactones is reported. The method uses alkylzirconium nucleophiles prepared in situ from alkenes and the Schwartz reagent. Enantioselective additions to 6- and 7-membered lactones proceed at rt, tolerate a wide variety of functional groups, and are readily scalable. The method was used in a formal asymmetric synthesis of mitsugashiwalactone.

  12. Reaction of NO(2) with selected conjugated alkenes.

    Science.gov (United States)

    Bernard, François; Cazaunau, Mathieu; Mu, Yujing; Wang, Xinming; Daële, Véronique; Chen, Jianmin; Mellouki, Abdelwahid

    2013-12-27

    The gas phase reactions of selected alkenes (isoprene, myrcene, ocimene, and 1,3-cyclohexadiene) with NO2 under dark condition have been investigated at T ∼ 298 K and P ∼ 760 Torr of purified air. The kinetic studies were performed under pseudo-first-order conditions using a large excess of NO2 concentration to those of the alkenes. The rate coefficients (in 10(-19) cm(3) molecule(-1) s(-1)) obtained are 1.1 ± 0.2 for isoprene, 2.5 ± 0.3 for myrcene, 8.5 ± 1.2 for ocimene, and 15 ± 1 for 1,3-cyclohexadiene. Several products were identified by using in situ Fourier transform infrared (FT-IR) spectrometry, and acetone was found to be the major product from the reactions of NO2 with myrcene and ocimene, with a formation yield of 22 ± 3% and 26 ± 7%, respectively. The oxidation products from the reactions of NO2 with isoprene and 1,3-cyclohexadiene were found to be mainly nitro compounds identified by FT-IR spectroscopy. Reaction mechanisms were proposed to account for the products observed.

  13. Probing the Mechanism of 1,4-Conjugate Elimination Reactions Catalyzed by Terpene Synthases

    OpenAIRE

    Faraldos, Juan A.; Gonzalez, Veronica; Li, Amang; Yu, Fanglei; Köksal, Mustafa; Christianson, David W.; Allemann, Rudolf K.

    2012-01-01

    The reaction mechanisms of (E)-β-farnesene synthase (EBFS) and isoprene synthase (ISPS), enzymes that catalyze a formal regioespecific 1,4-conjugate elimination of hydrogen-diphosphate from (E, E)-farnesyl and dimethylallyl diphosphate (FDP and DMADP) to generate the semiochemicals (E)-β-farnesene and isoprene, respectively, were probed with substrate analogs and kinetic measurements. The results support stepwise reaction mechanisms through analogous enzyme-bound allylic cationic intermediate...

  14. THE IMPACT OF CONJUGATED LINOLEIC ACID ADDITION ON PH VALUE OF LONGISSIMUS DORSI MUSCLE

    Directory of Open Access Journals (Sweden)

    Przemysław WASILEWSKI

    2009-08-01

    Full Text Available The subject of research was 60 crossbred gilts, divided into 6 groups, fed the fodder with addition of conjugated linoleic acid (CLA or sunflower oil (SFO in amount: 0.5; 1.0; and 2.0 %, respectively. Animals were slaughtered with the body weight ca. 95 kg. The aim of research was to determine pH value of loin meat tissue (Longissimus dorsi of right half-carcass in 45 minutes, 2, 3, 4, 5, 6 hours and 24 hours after slaughter. Results were statistically elaborated using one-way variance analysis. Longissimus dorsi muscle pH values measured 45 minutes after slaughter in case of all groups of pigs were in range from 6.34 up to 6.47, what shows good meat quality. The lowest pH1 (measured 45 minutes after slaughter had meat of fatteners where addition of 2 % sunflower oil was given into fodder and the highest value of this trait was in group of individuals where also was given sunflower oil in 1 % amount. Statistical significant differences in pH value measured in different time after slaughter i.e. after 45 minutes, 2, 3, 4, 6 and 24 hours between tested groups of pigs were not stated. The exception is the result of pH measurement 5 hours after slaughter. Statistical significant differences were between group of pigs getting 0.5 % addition of conjugated linoleic acid characterized by the highest pH value of meat and group of animals fed the fodder with 1 % addition of conjugated linoleic acid (P≤0.01. On the basis of the results obtained in presented paper may be stated that feeding pigs with addition of conjugated linoleic acid in amounts 0.5; 1.0 and 2.0 % did not impact negatively on meat quality defined by pH value.

  15. Excretion pattern and metabolism of hexachlorobutadiene in rats. Evidence for metabolic activation by conjugation reactions.

    Science.gov (United States)

    Reichert, D; Schütz, S; Metzler, M

    1985-02-15

    Excretion, covalent binding and metabolism of hexachloro-1,3-butadiene (HCBD), a nephrotoxic and nephrocarcinogenic compound, have been studied in female rats. Seventy-two hours after administration of a single oral dose of 1 mg/kg [14C]HCBD, 5.3% of the dose were exhaled as unchanged HCBD and 76.3% were metabolized and excreted in urine and feces or exhaled as 14CO2. After a 50 mg/kg dose of [14C]HCBD, the amount of exhaled parent compound was nearly unchanged at 5.4%. At the higher dose the gastro-intestinal absorption of HCBD appeared to be saturated with the result that unchanged HCBD constituted the major portion of the 69% radioactivity eliminated. Covalent binding to proteins in kidney and liver agreed well with the organ-specific toxicity of HCBD: binding was higher in the kidney, independent of the dose. It increased significantly when the rats were pretreated with phenobarbital, an inducer of monooxygenases; it decreased when the inhibitor piperonyl butoxide was given. Urinary radioactivity in 24 hr urine was separated by column chromatography into four fractions. High performance liquid chromatography, radio gas chromatography and gas chromatography/mass spectrometry were used for further separation and identification. Two major metabolites were identified as pentachlorobutadiene methylthio ether and pentachlorobutadiene carboxymethylthio ether. Their formation is plausibly explained via glutathione conjugation, which appears to be the first step in HCBD metabolism. The mechanism of the conjugation at the olefinic double bond of HCBD is explained by an addition-elimination reaction. This pathway, which appears to lead to a destabilization of the HCBD molecule, could explain the distinct nephrotoxic effects of HCBD.

  16. One-pot, additive-free preparation of functionalized polyurethanes via amine-thiol-ene conjugation

    OpenAIRE

    Espeel, Pieter; Goethals, Fabienne; Driessen, Frank; Nguyen, Le Thu Thi; Du Prez, Filip

    2013-01-01

    A straightforward, isocyanate-free method for the synthesis of functionalized polyurethanes, based on amine-thiol-ene conjugation, was elaborated. Aminolysis of a readily available AB'-urethane monomer, containing both an acrylate (A) and a thiolactone unit (B'), facilitates the preparation of various reactive thiol-acrylates. In situ polymerization via Michael addition proceeds under ambient conditions, yielding polyurethanes with a large variety of chemical functionalities. Side-chain funct...

  17. One-Pot Synthesis of Thermoresponsive Amyloidogenic Peptide-Polymer Conjugates via Thio-Bromo "Click" Reaction of RAFT Polymers.

    Science.gov (United States)

    Kumar, Sonu; Deike, Stefanie; Binder, Wolfgang H

    2018-01-01

    A synthetic strategy to efficiently prepare main-chain peptide-polymer conjugates probing their aggregation in solution is described. An in situ tandem reaction based on aminolysis/thio-bromo "click" reaction is performed to tether an amyloidogenic peptide fragment amyloid-β17-20 (Leu-Val-Phe-Phe (LVFF)) to the ω-chain end of poly(diethylene glycol methyl ether acrylate) (PDEGA), prepared via reversible addition fragmentation chain transfer polymerization. Structural confirmation of the constructed conjugates PDEGA-LVFF (Mn,SEC = 5600, Ð = 1.21), (Mn,SEC = 7600, Ð = 1.16), and (Mn,SEC = 8900, Ð = 1.15) is successfully made by combined studies of 1 H NMR, size-exclusion chromatography, matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, and electrospray ionization time-of-flight (ESI-TOF) mass spectrometry. The effect of the peptidic constituent on the thermoresponsive behavior of the polymer is examined by UV-vis spectroscopy, and the self-assembly behavior of the amphiphilic conjugate is further exploited, exhibiting micellar morphology in aqueous solution. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Copper-catalyzed asymmetric conjugate addition of organometallic reagents to extended Michael acceptors

    Directory of Open Access Journals (Sweden)

    Thibault E. Schmid

    2015-12-01

    Full Text Available The copper-catalyzed asymmetric conjugate addition (ACA of nucleophiles onto polyenic Michael acceptors represents an attractive and powerful methodology for the synthesis of relevant chiral molecules, as it enables in a straightforward manner the sequential generation of two or more stereogenic centers. In the last decade, various chiral copper-based catalysts were evaluated in combination with different nucleophiles and Michael acceptors, and have unambiguously demonstrated their usefulness in the control of the regio- and enantioselectivity of the addition. The aim of this review is to report recent breakthroughs achieved in this challenging field.

  19. Molecular Modeling of an Electrophilic Addition Reaction with "Unexpected" Regiochemistry

    Science.gov (United States)

    Best, Katherine T.; Li, Diana; Helms, Eric D.

    2017-01-01

    The electrophilic addition of a hydrohalic acid (HX) to an alkene is often one of the first reactions learned in second-year undergraduate organic chemistry classes. During the ensuing discussion of the mechanism, it is shown that this reaction follows Markovnikov's rule, which states that the hydrogen atom will attach to the carbon with fewer…

  20. The retro Grignard addition reaction revisited: the reversible addition of benzyl reagents to ketones

    DEFF Research Database (Denmark)

    Christensen, Stig Holden; Holm, Torkil; Madsen, Robert

    2014-01-01

    The Grignard addition reaction is known to be a reversible process with allylic reagents, but so far the reversibility has not been demonstrated with other alkylmagnesium halides. By using crossover experiments it has been established that the benzyl addition reaction is also a reversible...

  1. Chemo- and Regioselective Direct Functional Group Installation through Catalytic Hydroxy Group Selective Conjugate Addition of Amino Alcohols to α,β-Unsaturated Sulfonyl Compounds.

    Science.gov (United States)

    Li, Zhao; Yazaki, Ryo; Ohshima, Takashi

    2016-07-15

    A chemoselective functional group installation through catalytic hydroxy group selective conjugate addition of amino alcohols to a variety of functionalized α,β-unsaturated sulfonyl derivatives was developed. Azide group installation for click chemistry and facile fluorescent labeling onto the less reactive hydroxy group demonstrated the synthetic utility of the present chemoselective catalysis. Moreover, chemo- and regioselective reaction of an unprotected amino diol was achieved for the first time.

  2. Conjugate addition of isocyanides to chromone 3-carboxylic acid: an efficient one-pot synthesis of chroman-4-one 2-carboxamides.

    Science.gov (United States)

    Neo, Ana G; Díaz, Jesús; Marcaccini, Stefano; Marcos, Carlos F

    2012-05-07

    We report a novel Lewis acid catalysed tandem reaction of isocyanides, chromone 3-carboxylic acid and nucleophiles. An experimentally very simple procedure, involving the use of microwave irradiation in the presence of a Lewis acid catalyst, affords a representative collection of chromone-2-carboxamides and chromone-2-carboxamido-3-esters in high yields, in just a few minutes. Such an unprecedented strategy is formally equivalent to a conjugate addition of isocyanides to Michael acceptors.

  3. HBTU mediated 1-hydroxybenzotriazole (HOBt) conjugate addition: synthesis and stereochemical analysis of β-benzotriazole N-oxide substituted γ-amino acids and hybrid peptides.

    Science.gov (United States)

    Mali, Sachitanand M; Ganesh Kumar, Mothukuri; Katariya, Mona M; Gopi, Hosahudya N

    2014-11-14

    HBTU is a standard coupling agent commonly used for the activation of free carboxylic acids during the solution and solid phase peptide synthesis. 1-Hydroxybenzotriazole (HOBt) plays a significant role in reducing the racemization during peptide synthesis; hence it is regularly used as a coupling additive. Here, we are reporting the mild and facile conjugate addition of HOBt to E-vinylogous γ-amino acids mediated by the HBTU. The reaction is moderately diastereoselective and novel β-benzotriazole N-oxide (β-BtO) substituted γ-amino acids were isolated in moderate to good yields. The single crystal analysis of methyl esters of major (anti) and minor (syn) conjugate addition products infers the formation of exclusively N-alkylated benzotriazole N-oxides instead of O-alkylation of HOBt. In addition, we showed the utilization of β-BtO substituted γ-amino acids in peptide synthesis and studied their conformations in single crystals.

  4. Samarium(II) iodide-mediated intramolecular conjugate additions of alpha,beta-unsaturated lactones.

    Science.gov (United States)

    Molander, Gary A; St Jean, David J

    2002-05-31

    Samarium(II) iodide, in the presence of catalytic amounts of nickel(II) iodide, has been used to promote intramolecular conjugate additions of alkyl halides onto alpha,beta-unsaturated lactones. This process has been shown to be applicable to a number of alpha,beta-unsaturated lactones, including tetrasubstituted olefins, and has been demonstrated to be quite general for the formation of saturated bicyclic and tricyclic lactones. The method presented herein provides a mild, efficient process to form structurally complex lactones from simple precursors.

  5. Enantioselective conjugate addition of diethylzinc to chalcone catalyzed by Co(acac)2 and chiral amino alcohols

    NARCIS (Netherlands)

    Vries, André H.M. de; Feringa, Bernard

    1997-01-01

    Co(acac)2 in the presence of chiral ligands has been employed as catalyst for the enantioselective conjugate addition of diethylzinc to chalcone. With chiral amino alcohols derived from (+)-camphor, enantioselectivities up to 83% were achieved.

  6. Probing the mechanism of 1,4-conjugate elimination reactions catalyzed by terpene synthases.

    Science.gov (United States)

    Faraldos, Juan A; Gonzalez, Veronica; Li, Amang; Yu, Fanglei; Köksal, Mustafa; Christianson, David W; Allemann, Rudolf K

    2012-12-26

    The reaction mechanisms of (E)-β-farnesene synthase (EBFS) and isoprene synthase (ISPS), enzymes that catalyze a formal regiospecific 1,4-conjugate elimination of hydrogen diphosphate from (E,E)-farnesyl and dimethylallyl diphosphate (FDP and DMADP) to generate the semiochemicals (E)-β-farnesene and isoprene, respectively, were probed with substrate analogs and kinetic measurements. The results support stepwise reaction mechanisms through analogous enzyme-bound allylic cationic intermediates. For EBFS, we demonstrate that the elimination reaction can proceed via the enzyme-bound intermediate trans-nerolidyl diphosphate, while for ISPS the intermediacy of 2-methylbut-3-enyl 2-diphosphate can be inferred from the product outcome when deuterated DMADPs are used as substrates. Possible implications derived from the mechanistic details of the EBFS-catalyzed reaction for the evolution of sesquiterpene synthases are discussed.

  7. Solvent-free microwave-mediated Michael addition reactions

    Indian Academy of Sciences (India)

    Unknown

    “green chemistry”, a reaction should ideally, be con- ducted under solvent-free conditions with minimal or no side-product formation and with utmost atom- economy.10 Even though microwave-assisted sol- vent-free Michael addition reactions on BiCl3 or CdI2,11. EuCl3,12 CeCl3.5H2O,13 and alumina14 surfaces are.

  8. Adverse reactions to food additives in children with atopic symptoms

    DEFF Research Database (Denmark)

    Fuglsang, G.; Madsen, Charlotte Bernhard; Halken, S.

    1994-01-01

    dermatitis, asthma, urticaria, gastrointestinal symptoms), and citric acid (atopic dermatitis, gastrointestinal symptoms). The incidence of intolerance of food additives was 2% (6/335), as based on the double-blind challenge, and 7% (23/335), as based on the open challenge with lemonade. Children with atopic......, rhinitis, or urticaria. After a 2-week period on an additive-free diet, the children were challenged with the eliminated additives. The food additives investigated were coloring agents, preservatives, citric acid, and flavoring agents. Carbonated ''lemonade'' containing the dissolved additives was used...... and 335 were subjected to open challenge. A total of 23 children developed positive reactions after the open challenge. Sixteen of these patients accepted the double-blind challenge, and six showed a positive reaction to preservatives (atopic dermatitis, asthma, rhinitis), coloring agents (atopic...

  9. Adverse reactions to food additives in children with atopic symptoms

    DEFF Research Database (Denmark)

    Fuglsang, G; Madsen, G; Halken, S

    1994-01-01

    dermatitis, asthma, urticaria, gastrointestinal symptoms), and citric acid (atopic dermatitis, gastrointestinal symptoms). The incidence of intolerance of food additives was 2% (6/335), as based on the double-blind challenge, and 7% (23/335), as based on the open challenge with lemonade. Children with atopic......, rhinitis, or urticaria. After a 2-week period on an additive-free diet, the children were challenged with the eliminated additives. The food additives investigated were coloring agents, preservatives, citric acid, and flavoring agents. Carbonated "lemonade" containing the dissolved additives was used...... and 335 were subjected to open challenge. A total of 23 children developed positive reactions after the open challenge. Sixteen of these patients accepted the double-blind challenge, and six showed a positive reaction to preservatives (atopic dermatitis, asthma, rhinitis), coloring agents (atopic...

  10. cyclo-addition reaction of triplet carbonyl compounds to substituted ...

    Indian Academy of Sciences (India)

    Unknown

    MC-SCF/6-31G* study of the singlet and triplet Pa- terno–Büchi reaction using formaldehyde and ethylene as model systems ... theoretical study on the regioselectivity of the Pa- terno–Büchi photocyclo-addition of triplet acetone ...... A103 1274; (c) Chattaraj P K and Pod- dar J 1999 J. Phys. Chem. A103 8691; (d) Sengupta.

  11. Stereo- and regioselectivity of the hetero-Diels-Alder reaction of nitroso derivatives with conjugated dienes.

    Science.gov (United States)

    Brulíková, Lucie; Harrison, Aidan; Miller, Marvin J; Hlaváč, Jan

    2016-01-01

    The hetero-Diels-Alder reaction between a nitroso dienophile and a conjugated diene to give the 3,6-dihydro-2H-1,2-oxazine scaffold is useful for the synthesis of many biologically interesting molecules due to the diverse opportunities created by subsequent transformations of the resulting 1,2-oxazine ring. This review discusses the rationale for the observed regio- and stereoselectivity and the methods developed in recent years used to control and improve the stereo- and regioselectivity for the synthesis of 1,2-oxazine scaffolds.

  12. Stereo- and regioselectivity of the hetero-Diels–Alder reaction of nitroso derivatives with conjugated dienes

    Directory of Open Access Journals (Sweden)

    Lucie Brulíková

    2016-09-01

    Full Text Available The hetero-Diels–Alder reaction between a nitroso dienophile and a conjugated diene to give the 3,6-dihydro-2H-1,2-oxazine scaffold is useful for the synthesis of many biologically interesting molecules due to the diverse opportunities created by subsequent transformations of the resulting 1,2-oxazine ring. This review discusses the rationale for the observed regio- and stereoselectivity and the methods developed in recent years used to control and improve the stereo- and regioselectivity for the synthesis of 1,2-oxazine scaffolds.

  13. Conjugate Addition/[3,3] Sigmatropic Shift Processes for Formation of Medium-Ring Cyclic Amines - Do They Circumvent the Woodward-Hoffmann Rules?

    Science.gov (United States)

    Painter, Phillip P; Siebert, Matthew R; Tantillo, Dean J

    2015-12-04

    Herein we describe our exploration, using density functional theory calculations, of a conjugate addition-rearrangement sequence that leads to medium-ring cyclic amines. On the basis of the results of our calculations, we conclude that the rearrangement step is rate determining. In addition, we analyze the role of a carbanion lone pair in the rearrangement step, concluding that it functions as a substituent on a [3,3] sigmatropic shift, rather than a nucleophile; thus, the Woodward-Hoffmann rules are not circumvented in this reaction via involvement of orthogonal orbitals on an atom involved in the rearrangement.

  14. From the N-Heterocyclic Carbene-Catalyzed Conjugate Addition of Alcohols to the Controlled Polymerization of (Meth)acrylates.

    Science.gov (United States)

    Ottou, Winnie Nzahou; Bourichon, Damien; Vignolle, Joan; Wirotius, Anne-Laure; Robert, Fredéric; Landais, Yannick; Sotiropoulos, Jean-Marc; Miqueu, Karinne; Taton, Daniel

    2015-06-22

    Among various N-heterocyclic carbenes (NHCs) tested, only 1,3-bis(tert-butyl)imidazol-2-ylidene (NHC(tBu) ) proved to selectively promote the catalytic conjugate addition of alcohols onto (meth)acrylate substrates. This rather rare example of NHC-catalyzed 1,4-addition of alcohols was investigated as a simple means to trigger the polymerization of both methyl methacrylate and methyl acrylate (MMA and MA, respectively). Well-defined α-alkoxy poly(methyl (meth)acrylate) (PM(M)A) chains, the molar masses of which could be controlled by the initial [(meth)acrylate]0/[ROH]0 molar ratio, were ultimately obtained in N,N-dimethylformamide at 25 °C. A hydroxyl-terminated poly(ethylene oxide) (PEO-OH) macro-initiator was also employed to directly access PEO-b-PMMA amphiphilic block copolymers. Investigations into the reaction mechanism by DFT calculations revealed the occurrence of two competitive concerted pathways, involving either the activation of the alcohol or that of the monomer by NHC(tBu) . © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Stereoselective synthesis of perillaldehyde-based chiral β-amino acid derivatives through conjugate addition of lithium amides

    Directory of Open Access Journals (Sweden)

    Zsolt Szakonyi

    2014-11-01

    Full Text Available The Michael addition of dibenzylamine to (+-tert-butyl perillate (3 and to (+-tert-butyl phellandrate (6, derived from (S-(−-perillaldehyde (1, resulted in diastereomeric β-amino esters 7A–D in a moderately stereospecific reaction in a ratio of 76:17:6:1. After separation of the diastereoisomers, the major product, cis isomer 7A, was quantitatively isomerized to the minor component, trans-amino ester 7D. All four isomers were transformed to the corresponding β-amino acids 10A–D, which are promising building blocks for the synthesis of β-peptides and 1,3-heterocycles in three steps. The steric effects of the isopropyl group at position 4 and of the α-methyl substituent of (R-N-benzyl-N-α-methylbenzylamine on the reactivity were also studied and, upon application of a chiral amine, excellent stereoselectivity of the conjugate addition was observed. Amino ester 11 was obtained as a single product and transformed to the corresponding amino acids 10A and 10D in good yields on the gram scale.

  16. Lewis base activation of Lewis acids: catalytic, enantioselective vinylogous aldol addition reactions.

    Science.gov (United States)

    Denmark, Scott E; Heemstra, John R

    2007-07-20

    The generality of Lewis base catalyzed, Lewis acid mediated, enantioselective vinylogous aldol addition reactions has been investigated. The combination of silicon tetrachloride and chiral phosphoramides is a competent catalyst for highly selective additions of a variety of alpha,beta-unsaturated ketone-, 1,3-diketone-, and alpha,beta-unsaturated amide-derived dienolates to aldehydes. These reactions provided high levels of gamma-site selectivity for a variety of substitution patterns on the dienyl unit. Both ketone- and morpholine amide-derived dienol ethers afforded high enantio- and diastereoselectivity in the addition to conjugated aldehydes. Although alpha,beta-unsaturated ketone-derived dienolate did not react with aliphatic aldehydes, alpha,beta-unsaturated amide-derived dienolates underwent addition at reasonable rates affording high yields of vinylogous aldol product. The enantioselectivities achieved with the morpholine derived-dienolate in the addition to aliphatic aldehydes was the highest afforded to date with the silicon tetrachloride-chiral phosphoramide system. Furthermore, the ability to cleanly convert the morpholine amide to a methyl ketone was demonstrated.

  17. Organobase catalyzed 1,4-conjugate addition of 4-hydroxycoumarin on chalcones: Synthesis, NMR and single-crystal X-ray diffraction studies of novel warfarin analogues

    Science.gov (United States)

    Talhi, Oualid; Fernandes, José A.; Pinto, Diana C. G. A.; Almeida Paz, Filipe A.; Silva, Artur M. S.

    2015-08-01

    The synthesis of a new series of warfarin analogues by convenient organobase catalyzed 1,4-conjugate addition of 4-hydroxycoumarin to chalcone derivatives is described. 1H NMR spectroscopy evidenced the presence of a predominant acyclic open-form together with the cyclic hemiketal tautomers of the resulting Michael adducts. The acyclic open-form has been unequivocally proved by single-crystal X-ray diffraction analysis. The use of the B ring ortho-hydroxychalcone synthons in this reaction has led to a diastereoselective synthesis of warfarin bicyclo[3.3.1]nonane ketal derivatives.

  18. A two-dimensional conjugated aromatic polymer via C-C coupling reaction

    Science.gov (United States)

    Liu, Wei; Luo, Xin; Bao, Yang; Liu, Yan Peng; Ning, Guo-Hong; Abdelwahab, Ibrahim; Li, Linjun; Nai, Chang Tai; Hu, Zhi Gang; Zhao, Dan; Liu, Bin; Quek, Su Ying; Loh, Kian Ping

    2017-06-01

    The fabrication of crystalline 2D conjugated polymers with well-defined repeating units and in-built porosity presents a significant challenge to synthetic chemists. Yet they present an appealing target because of their desirable physical and electronic properties. Here we report the preparation of a 2D conjugated aromatic polymer synthesized via C-C coupling reactions between tetrabromopolyaromatic monomers. Pre-arranged monomers in the bulk crystal undergo C-C coupling driven by endogenous solid-state polymerization to produce a crystalline polymer, which can be mechanically exfoliated into micrometre-sized lamellar sheets with a thickness of 1 nm. Isothermal gas-sorption measurements of the bulk material reveal a dominant pore size of ~0.6 nm, which indicates uniform open channels from the eclipsed stacking of the sheets. When employed as an organic anode in an ambient-temperature sodium cell, the material allows a fast charge/discharge of sodium ions, with impressive reversible capacity, rate capability and stability metrics.

  19. Trans-Selective Rhodium Catalysed Conjugate Addition of Organoboron Reagents to Dihydropyranones

    Directory of Open Access Journals (Sweden)

    Hannah J. Edwards

    2015-04-01

    Full Text Available The selective synthesis of 2,6-trans-tetrahydropyran derivatives employing the rhodium catalysed addition of organoboron reagents to dihydropyranone templates, derived from a zinc-catalysed hetero-Diels-Alder reaction, is reported. The addition of both arylboronic acids and potassium alkenyltrifluoroborates have been accomplished in high yields using commercially-available [Rh(cod(OH]2 catalyst. The selective formation of the 2,6-trans-tetrahydropyran stereoisomer is consistent with a mechanism involving alkene association and carbometalation on the less hindered face of the dihydropyranone.

  20. Enantioselective conjugate addition of diethylzinc to chalcone catalyzed by Co(acac)(2) and chiral amino alcohols

    NARCIS (Netherlands)

    de Vries, A.H.M.; Feringa, B.L.

    1997-01-01

    Co(acac)(2) in the presence of chiral ligands has been employed as catalyst for the enantioselective conjugate addition of diethylzinc to chalcone. With chiral amino alcohols derived from (+)-camphor, enantioselectivities up to 83% were achieved. (C) 1997 Elsevier Science Ltd.

  1. Hydrogen bond donor–acceptor–donor organocatalysis for conjugate addition of benzylidene barbiturates via complementary DAD– ADA hydrogen bonding

    NARCIS (Netherlands)

    Leung, King-Chi; Cui, Jian-Fang; Hui, Tsz-Wai; Zhou, Zhong-Yuan; Wong, Man-Kin

    2014-01-01

    A new class of hydrogen bond donor-acceptor-donor (HB-DAD) organocatalysts has been developed for conjugate addition of benzylidene barbiturates. HB-DAD organocatalyst 1a (featuring para-chloro-pyrimidine as the hydrogen bond acceptor (HBA), N-H as the hydrogen bond donor (HBD) and a trifluoroacetyl

  2. Asymmetric construction of binaphthyl by the chiral diether-mediated conjugate addition of naphthyllithium to naphthalenecarboxylic acid 2,6-di-t-butyl-4-methoxyphenyl ester.

    Science.gov (United States)

    Shindo, Mitsuru; Yamamoto, Yasutomo; Yamada, Ken-Ichi; Tomioka, Kiyoshi

    2009-07-01

    Two ways for the synthesis of binaphthyl were examined based on a chiral ligand-mediated asymmetric conjugate addition of 1-naphthyllithium to naththalene-2-carboxylic acid 2,6-di-t-butyl-4-methoxyphenyl esters. The one pot method by conjugate addition-elimination gave a relatively higher enantioselectivity than the two step synthesis based on addition and subsequent oxidative aromatization.

  3. ELECTRIC CONDUCTIVITY OF LONGISSIMUS DORSI MUSCLE OF PIGS FED THE FODDER WITH ADDITION OF CONJUGATED LINOLEIC ACID

    Directory of Open Access Journals (Sweden)

    Przemysław WASILEWSKI

    2009-06-01

    Full Text Available The aim of research was to investigate the impact of feeding pigs the fodder with addition of different level of conjugated linoleic acid on results of electric conductivity of Longissimus dorsi muscle. Electric conductivity (LF, Ger. Leitfähigkeitmessung is the method of meat quality estimation. This technique uses high relationships between electric conductivity and the other parameters of meat quality. In breeding and production of pigs the aim is to obtain fatteners of low fat and high meat content simultaneously keeping good meat tissue quality. One of the ways of their quality improvement is using fodder supplements as i.e. conjugated linoleic acid (CLA. Results of many research proved that conjugated linoleic acid impacts also in a favourable way on humans health because reduces cholesterol level, prevents from heart attacks and some cancers, stimulates immune system and has antiinfl ammatory properties. Statistical analysis covered the results of 60 crossbred gilts, divided into 6 groups, fed the fodder with addition of conjugated linoleic acid (CLA or sunfl ower oil (SFO in amounts: 0.5; 1.0; and 2.0 %, respectively. Fattening period of animals lasted for 8 weeks with ad-libitum feeding. In 1, 3, 6 hour, 24 hours, 3 and 7 days after slaughter electric conductivity of muscle tissue was measured – muscle Longissimus dorsi. Electric conductivity measured in different time after slaughter was not statistically diversed between tested groups of animals. The results concerned electric conductivity of muscle Longissimus dorsi of pigs fed the fodder with addition of conjugated linoleic acid should be stated as satisfactory and proved normal meat. Therefore, feeding pigs the fodder with CLA addition in amount of 0.5; 1.0 and 2.0 % did not impacts negatively on meat quality.

  4. Hypersensitivity reactions to β-lactams: relevance of hapten-protein conjugates.

    Science.gov (United States)

    Ariza, A; Mayorga, C; Fernandez, T D; Barbero, N; Martín-Serrano, A; Pérez-Sala, D; Sánchez-Gómez, F J; Blanca, M; Torres, M J; Montanez, M I

    2015-01-01

    β-Lactams (BL) are the drugs most frequently involved in allergic reactions. They are classified according to their chemical structure as penicillins, cephalosporins, monobactams, carbapenems, and clavams. All BL antibiotics have a BL ring that is fused to a 5-member or 6-member ring (except in monobactams) and has 1, 2 or 3 side chains (except in clavams). Differences in chemical structure mean that a wide range of BLs are recognized by the immune system, and patients may experience clinical reactions to one BL while tolerating others. Diagnosis is based on skin and in vitro testing, although both display low sensitivity, possibly because they are based on drugs or drug conjugates that are not optimally recognized by the immune system. BLs are haptens that need to bind to proteins covalently to elicit an immune response. These drugs have a high capacity to form covalent adducts with proteins through nucleophilic attack of amino groups in proteins on the BL ring. Allergenic determinants have been described for all BLs, although benzylpenicillin is the most widely studied. Moreover, formation of BL-protein adducts is selective, as we recently demonstrated for amoxicillin, which mainly modifies albumin, transferrin, and immunoglobulin heavy and light chains in human serum. Given the complexity of BL allergy, understanding the immunological mechanisms involved and optimization of diagnostic methods require multidisciplinary approaches that take into account the chemical structures of the drugs and the carrier molecules, as well as the patient immune response.

  5. Diels-Alder reactions: The effects of catalyst on the addition reaction

    Science.gov (United States)

    Yilmaz, Özgür; Kus, Nermin Simsek; Tunç, Tuncay; Sahin, Ertan

    2015-10-01

    The reaction between 2,3-dimethyl-1,3-butadiene and dimethyl 7-oxabicyclo[2.2.1]hepta-2,5-diene-2,3-dicarboxylate is efficiently achieved with small amounts of catalyst, i.e. phenol, AcOH, nafion, and β-cyclodextrin. Exo-diastereoselective cycloaddition reactions were observed both without catalyst and different catalysts for 48 days. As a result, different products (tricyclicmolecule 5, retro-Diels-Alder product 6, and oxidation product 7) were obtained with different catalysts. In addition, we synthesized Diels-Alders product 8 and tricyclocyclitol 10 via Diels-Alder reaction. The structures of these products were characterized by 1H NMR, 13C NMR, MS and IR spectroscopy.

  6. BF3·Et2O promoted conjugate addition of ethanethiol to electron-deficient alkynes

    Institute of Scientific and Technical Information of China (English)

    Qing Fa Zhou; Xue Ping Chu; Shen Zhao; Tao Lu; Wei Fang Tang

    2012-01-01

    An effective method for the synthesis of vinyl thioethers through the conjugate addition of ethanethiol to electron-deficient alkynes promoted by BF3·Et2O has been developed.Electron-deficient internal alkynes react with ethanethiol in this system to yield mainly Z-isomer of vinyl thioether adducts,while electron-deficient terminal alkynes afford mainly E-isomer of vinyl thioether adducts.

  7. Oxygen binding and oxidation reactions of human hemoglobin conjugated to carboxylate dextran.

    Science.gov (United States)

    Jia, Yiping; Wood, Francine; Menu, Patrick; Faivre, Béatrice; Caron, Alexis; Alayash, Abdu I

    2004-06-11

    Human hemoglobin (Hb) conjugated to benzene tetracarboxylate substituted dextran produces a polymeric Hb (Dex-BTC-Hb) with similar oxygen affinity to that of red blood cells (P(50)=28-29 mm Hg). Under physiological conditions, the oxygen affinity (P(50)) of Dex-BTC-Hb is 26 mm Hg, while that of native purified human HbA(0) is 14 mm Hg, but it exhibits a slight reduction in cooperativity (n(50)), Bohr effect, and lacks sensitivity to inositol hexaphosphate (IHP), when compared to HbA(0). Oxygen-binding kinetics, measured by rapid mixing stopped-flow method showed comparable oxygen dissociation and association rates for both HbA(0) and Dex-BTC-Hb. The rate constant for NO-mediated oxidation of the oxy form of Dex-BTC-Hb, which is governed by NO entry to the heme pocket, was reduced to half of the value obtained for HbA(0). Moreover, Dex-BTC-Hb is only slightly more sensitive to oxidative reactions than HbA(0), as shown by about 2-fold increase in autoxidation, and slightly higher H(2)O(2) reaction and heme degradation rates. Dextran-BTC-based modification of Hb produced an oxygen-carrying compound with increased oxygen release rates, decreased oxygen affinity and reduced nitric oxide scavenging, desirable properties for a viable blood substitute. However, the reduction in the allosteric function of this protein and the lack of apparent quaternary T-->R transition may hinder its physiological role as an oxygen transporter.

  8. A Conjugated Microporous Polymer for Palladium-Free, Visible Light-Promoted Photocatalytic Stille-Type Coupling Reactions.

    Science.gov (United States)

    Ghasimi, Saman; Bretschneider, Simon A; Huang, Wei; Landfester, Katharina; Zhang, Kai A I

    2017-08-01

    The Stille coupling reaction is a versatile method to mainly form aromatic C-C bonds. However, up to now, the use of palladium catalysts is necessary. Here, a palladium-free and photocatalytic Stille-type coupling reaction of aryl iodides and aryl stannanes catalyzing a conjugated microporous polymer-based phototcatalyst under visible light irradiation at room temperature is reported. The novel coupling reaction mechanism occurs between the photogenerated aryl radical under oxidative destannylation of the aryl stannane, and the electron-activated aryl iodide, resulting into the aromatic C-C bond formation reaction. The visible light-promoted Stille-type coupling reaction using the polymer-based pure organic photocatalyst offers a simple, sustainable, and more economic synthetic pathway toward palladium-free aromatic C-C bond formation.

  9. Antioxidative, Antibacterial, and Food Functional Properties of the Half-Fin Anchovy Hydrolysates-Glucose Conjugates Formed via Maillard Reaction

    Directory of Open Access Journals (Sweden)

    Ru Song

    2016-06-01

    Full Text Available The antioxidative, antibacterial, and food functional properties of the half-fin anchovy hydrolysates (HAHp-glucose conjugates formed by Maillard reaction (MR were investigated, respectively. Results of sugar and amino acid contents loss rates, browning index, and molecular weight distribution indicated that the initial pH of HAHp played an important role in the process of MR between HAHp and glucose. HAHp-glucose Maillard reaction products (HAHp-G MRPs demonstrated enhanced antioxidative activities of reducing power and scavenging DPPH radicals compared to control groups. HAHp-G MRPs produced from the condition of pH 9.6 displayed the strongest reducing power. The excellent scavenging activity on DPPH radicals was found for HAHp(5.6-G MRPs which was produced at pH 5.6. Additionally, HAHp(5.6-G MRPs showed variable antibacterial activities against Escherichia coli, Pseudomonas fluorescens, Proteus vulgaris, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis, Bacillus megaterium, and Sarcina lutea, with the MIC values ranging from 8.3 to 16.7 μg/mL. Result of scanning electron microscopy (SEM on E. coli suggested that HAHp(5.6-G MRPs exhibited antibacterial activity by destroying the cell integrity through membrane permeabilization. Moreover, HAHp(5.6-G MRPs had excellent foaming ability and stability at alkaline conditions of pH 8.0, and showed emulsion properties at acidic pH 4.0. These results suggested that specific HAHp-G MRPs should be promising functional ingredients used in foods.

  10. Antioxidative, Antibacterial, and Food Functional Properties of the Half-Fin Anchovy Hydrolysates-Glucose Conjugates Formed via Maillard Reaction.

    Science.gov (United States)

    Song, Ru; Yang, Peiyu; Wei, Rongbian; Ruan, Guanqiang

    2016-06-20

    The antioxidative, antibacterial, and food functional properties of the half-fin anchovy hydrolysates (HAHp)-glucose conjugates formed by Maillard reaction (MR) were investigated, respectively. Results of sugar and amino acid contents loss rates, browning index, and molecular weight distribution indicated that the initial pH of HAHp played an important role in the process of MR between HAHp and glucose. HAHp-glucose Maillard reaction products (HAHp-G MRPs) demonstrated enhanced antioxidative activities of reducing power and scavenging DPPH radicals compared to control groups. HAHp-G MRPs produced from the condition of pH 9.6 displayed the strongest reducing power. The excellent scavenging activity on DPPH radicals was found for HAHp(5.6)-G MRPs which was produced at pH 5.6. Additionally, HAHp(5.6)-G MRPs showed variable antibacterial activities against Escherichia coli, Pseudomonas fluorescens, Proteus vulgaris, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis, Bacillus megaterium, and Sarcina lutea, with the MIC values ranging from 8.3 to 16.7 μg/mL. Result of scanning electron microscopy (SEM) on E. coli suggested that HAHp(5.6)-G MRPs exhibited antibacterial activity by destroying the cell integrity through membrane permeabilization. Moreover, HAHp(5.6)-G MRPs had excellent foaming ability and stability at alkaline conditions of pH 8.0, and showed emulsion properties at acidic pH 4.0. These results suggested that specific HAHp-G MRPs should be promising functional ingredients used in foods.

  11. Cascade Polymerization via Controlled Tandem Olefin Metathesis/Metallotropic 1,3-Shift Reactions for the Synthesis of Fully Conjugated Polyenynes.

    Science.gov (United States)

    Kang, Cheol; Park, Hyeon; Lee, Jin-Kyung; Choi, Tae-Lim

    2017-08-23

    We demonstrate the first example of cascade polymerization by combining olefin metathesis and metallotropic 1,3-shift reactions to form unique conjugated polyenynes. Rational design of monomers enabled controlled polymerization, and kinetic investigation of the polymerization mechanism was conducted.

  12. Advanced aqueous-phase phosphoramidation reactions for effectively synthesizing peptide-oligonucleotide conjugates trafficked into a human cell line.

    Science.gov (United States)

    Wang, Tzu-Pin; Ko, Ni Chien; Su, Yu-Chih; Wang, Eng-Chi; Severance, Scott; Hwang, Chi-Ching; Shih, Ying Ting; Wu, Min Hui; Chen, Yen-Hsu

    2012-12-19

    Peptide-oligonucleotide conjugates (POCs) have held promise as effective therapeutic agents in treating microbial infections and human genetic diseases including cancers. In clinical applications, POCs are especially useful to circumvent cellular delivery and specificity problems of oligonucleotides. We previously reported that nucleic acid phosphoramidation reactions performed in aqueous solutions have the potential for facile POC synthesis. Here, we carried out further studies to significantly improve aqueous-phase two-step phosphoramidation reaction yield. Optimized reactions were employed to effectively synthesize POCs for delivery into human A549 cells. We achieved optimization of aqueous-phase two-step phosphoramidation reaction and improved reaction yield by (1) determining appropriate co-solutes and co-solute concentrations to acquire higher reaction yields, (2) exploring a different nucleophilicity of imidazole and its derivatives to stabilize essential nucleic acid phosphorimidazolide intermediates prior to POC formation, and (3) enhancing POC synthesis by increasing reactant nucleophilicity. The advanced two-step phosphoramidation reaction was exploited to effectively conjugate a well-studied cell penetrating peptide, the Tat(48-57) peptide, with oligonucleotides, bridged by either no linkers or a disulfide-containing linker, to have the corresponding POC yields of 47-75%. Phosphoramidation-synthesized POCs showed no cytotoxicity to human A549 cells at studied POC concentrations after 24 h inoculation and were successfully trafficked into the human A549 cell line as demonstrated by flow cytometry, fluorescent microscopy, and confocal laser scanning microscopy study. The current report provides insight into aqueous-phase phosphoramidation reactions, the knowledge of which was used to develop effective strategies for synthesizing POCs with crucial applications including therapeutic agents for medicine.

  13. Synthesis, characterization and the release kinetics of antiproliferative agents from polyamidoamine conjugates

    CSIR Research Space (South Africa)

    Aderibigbe, BA

    2015-01-01

    Full Text Available Polyamidoamine conjugates containing curcumin and bisphosphonate were synthesized via a one-pot aqueous phase Michael addition reaction. In the design of the conjugate, bisphosphonate formed an integral part of the polymer carrier backbone. Curcumin...

  14. Organocatalytic conjugate-addition polymerization of linear and cyclic acrylic monomers by N-heterocyclic carbenes: mechanisms of chain initiation, propagation, and termination.

    Science.gov (United States)

    Zhang, Yuetao; Schmitt, Meghan; Falivene, Laura; Caporaso, Lucia; Cavallo, Luigi; Chen, Eugene Y-X

    2013-11-27

    This contribution presents a full account of experimental and theoretical/computational investigations into the mechanisms of chain initiation, propagation, and termination of the recently discovered N-heterocyclic carbene (NHC)-mediated organocatalytic conjugate-addition polymerization of acrylic monomers. The current study specifically focuses on three commonly used NHCs of vastly different nucleophilicity, 1,3-di-tert-butylimidazolin-2-ylidene (I(t)Bu), 1,3-dimesitylimidazolin-2-ylidene (IMes), and 1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene (TPT), and two representative acrylic monomers, the linear methyl methacrylate (MMA) and its cyclic analog, biomass-derived renewable γ-methyl-α-methylene-γ-butyrolactone (MMBL). For MMA, there exhibits an exquisite selectivity of the NHC structure for the three types of reactions it promotes: enamine formation (single-monomer addition) by IMes, dimerization (tail-to-tail) by TPT, and polymerization by I(t)Bu. For MMBL, all three NHCs promote no dimerization but polymerization, with the polymerization activity being highly sensitive to the NHC structure and the solvent polarity. Thus, I(t)Bu is the most active catalyst of the series and converts quantitatively 1000-3000 equiv of MMBL in 1 min or 10,000 equiv in 5 min at room temperature to MMBL-based bioplastics with a narrow range of molecular weights of M(n) = 70-85 kg/mol, regardless of the [MMBL]/[I(t)Bu] ratio employed. The I(t)Bu-catalyzed MMBL polymerization reaches an exceptionally high turnover frequency up to 122 s(-1) and a high initiator efficiency value up to 1600%. Unique chain-termination mechanisms have been revealed, accounting for the production of relative high-molecular-weight linear polymers and the catalytic nature of this NHC-mediated conjugate-addition polymerization. Computational studies have provided mechanistic insights into reactivity and selectivity between two competing pathways for each NHC-monomer zwitterionic adduct, namely

  15. Organocatalytic conjugate-addition polymerization of linear and cyclic acrylic monomers by N-heterocyclic carbenes: Mechanisms of chain initiation, propagation, and termination

    KAUST Repository

    Zhang, Yuetao

    2013-11-27

    This contribution presents a full account of experimental and theoretical/computational investigations into the mechanisms of chain initiation, propagation, and termination of the recently discovered N-heterocyclic carbene (NHC)-mediated organocatalytic conjugate-addition polymerization of acrylic monomers. The current study specifically focuses on three commonly used NHCs of vastly different nucleophilicity, 1,3-di-tert-butylimidazolin-2-ylidene (ItBu), 1,3- dimesitylimidazolin-2-ylidene (IMes), and 1,3,4-triphenyl-4,5-dihydro-1H-1,2,4- triazol-5-ylidene (TPT), and two representative acrylic monomers, the linear methyl methacrylate (MMA) and its cyclic analog, biomass-derived renewable γ-methyl-α-methylene-γ-butyrolactone (MMBL). For MMA, there exhibits an exquisite selectivity of the NHC structure for the three types of reactions it promotes: enamine formation (single-monomer addition) by IMes, dimerization (tail-to-tail) by TPT, and polymerization by ItBu. For MMBL, all three NHCs promote no dimerization but polymerization, with the polymerization activity being highly sensitive to the NHC structure and the solvent polarity. Thus, ItBu is the most active catalyst of the series and converts quantitatively 1000-3000 equiv of MMBL in 1 min or 10 000 equiv in 5 min at room temperature to MMBL-based bioplastics with a narrow range of molecular weights of Mn = 70-85 kg/mol, regardless of the [MMBL]/[ItBu] ratio employed. The ItBu-catalyzed MMBL polymerization reaches an exceptionally high turnover frequency up to 122 s -1 and a high initiator efficiency value up to 1600%. Unique chain-termination mechanisms have been revealed, accounting for the production of relative high-molecular-weight linear polymers and the catalytic nature of this NHC-mediated conjugate-addition polymerization. Computational studies have provided mechanistic insights into reactivity and selectivity between two competing pathways for each NHC-monomer zwitterionic adduct, namely enamine

  16. Metal halide hydrates as lewis acid catalysts for the conjugated friedel-crafts reactions of indoles and activated olefins

    Energy Technology Data Exchange (ETDEWEB)

    Schwalm, Cristiane S.; Ceschi, Marco Antonio; Russowsky, Dennis, E-mail: dennis@iq.ufrgs.b [Universidade Federal do Rio Grande do Sul (IQ/UFRGS), Porto Alegre, RS (Brazil). Inst. de Quimica

    2011-07-01

    Metal halide hydrates such as SnCl{sub 2{center_dot}}2H{sub 2}O, MnCl{sub 2{center_dot}}4H{sub 2}O, SrCl{sub 2{center_dot}}6H{sub 2}O, CrCl{sub 2{center_dot}}6H{sub 2}O, CoCl{sub 2{center_dot}}6H{sub 2}O e CeCl{sub 3{center_dot}}7H{sub 2}O were investigated as mild Lewis acids catalysts for the conjugate Friedel-Crafts reaction between indoles and activated olefins. The reactions were carried out with aliphatic unsaturated ketones over a period of days at room temperature, while chalcones reacted only under reflux conditions. The reactions with nitrostyrene s were either performed in solvent or under solventless conditions. In all cases reasonable to good yields were obtained. (author)

  17. Implications of Partial Conjugation of Whey Protein Isolate to Durian Seed Gum through Maillard Reactions: Foaming Properties, Water Holding Capacity and Interfacial Activity

    Directory of Open Access Journals (Sweden)

    Bahareh Tabatabaee Amid

    2013-12-01

    Full Text Available This paper deals with the conjugation of durian seed gum (DSG with whey protein isolate (WPI through Maillard reactions. Subsequently, the functional properties of durian seed gum in the non-conjugated (control sample and conjugated forms were compared with several commercial gums (i.e., Arabic gum, sodium alginate, kappa carrageenan, guar gum, and pectin. The current study revealed that the conjugation of durian seed gum with whey protein isolate significantly (p < 0.05 improved its foaming properties. In this study, the conjugated durian seed gum produced the most stable foam among all samples. On the other hand, the emulsion stabilized with the conjugated durian seed gum also showed more uniform particles with a larger specific surface area than the emulsion containing the non-conjugated durian seed gum. The conjugated durian seed gum showed significant different foaming properties, specific surface area, particle uniformity and water holding capacity (WHC as compared to the target polysaccharide gums. The conjugated durian seed gum showed more similar functional properties to Arabic gum rather than other studied gums.

  18. Solvent-free microwave-mediated Michael addition reactions

    Indian Academy of Sciences (India)

    Facile Michael addition of active methylene compounds to ,-unsaturated carbonyl compounds takes place on the surface of potassium carbonate under microwave irradiation. Further studies on microwave-mediated Robinson annulations reveal a convenient and facile method for condensation of chalcone with ...

  19. Development of transition metal-free polymerization route to functional conjugated polydiynes from haloalkyne-based organic reaction

    OpenAIRE

    Zhang, Yun; Zhao, Engui; Deng, Haiqin; Lam, Jacky Wing Yip; Tang, Ben Zhong

    2016-01-01

    The development of an efficient transition metal-free polymerization route has been an active research topic in polymer science owing to its low synthetic cost and decreased metal residue and hence elevated material performance in the products. In this work, we report a new such method for constructing conjugated polydiynes based on the organic reaction of 1-haloalkyne. In the presence of potassium iodide, the polymerizations of 1,2-bis[4-(iodoethynyl)phenyl]-1,2-diphenylethene (1), 1,4-bis(2...

  20. Parallel Synthesis of photoluminescent π-conjugated polymers by polymer reactions of an organotitanium polymer with a titanacyclopentadiene unit.

    Science.gov (United States)

    Matsumura, Yoshimasa; Fukuda, Katsura; Inagi, Shinsuke; Tomita, Ikuyoshi

    2015-04-01

    A regioregular organometallic polymer with titanacyclopentadiene unit, obtained by the reaction of a 2,7-diethynylfluorene derivative and a low-valent titanium complex, is subjected to the reaction with three kinds of electrophiles (i.e., sulfur monochloride, hydrochloric acid, and dichlorophenylphosphine) to give π-conjugated polymers possessing both fluorene and building blocks originated from the transformation of the titanacycles in the main chain. For example, a phosphole-containing polymer whose number-average molecular weight is estimated as 5000 is obtained in 50% yield. The obtained thiophene, butadiene, and phosphole-containing polymers exhibit efficient photoluminescence (PL) with emission colors of blue, green, and yellow, respectively. For example, the phosphole-containing polymer exhibits yellow PL with an emission maximum (Emax ) of 533 nm and a quantum yield (Φ) of 0.37. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Enantioselective conjugate additions of α-amino radicals via cooperative photoredox and Lewis acid catalysis.

    Science.gov (United States)

    Ruiz Espelt, Laura; McPherson, Iain S; Wiensch, Eric M; Yoon, Tehshik P

    2015-02-25

    We report the highly enantioselective addition of photogenerated α-amino radicals to Michael acceptors. This method features a dual-catalyst protocol that combines transition metal photoredox catalysis with chiral Lewis acid catalysis. The combination of these two powerful modes of catalysis provides an effective, general strategy to generate and control the reactivity of photogenerated reactive intermediates.

  2. Elephant grass silage with the addition of crambe bran conjugated to different specific mass

    Directory of Open Access Journals (Sweden)

    Arilson Moraes Cardoso

    2016-11-01

    Full Text Available This study aimed to evaluate the effects of inclusion of crambe bran concentrations (Crambe abyssinica Hochst. with different specific masses in elephant grass silage (Penninsetum purpureum Schum.. For that, the bromatological and microbiological compositions of the experimental silages were determined. We used 48 mini silos distributed in a completely randomized design, arranged in a factorial 4 × 3, four levels of inclusion of crambe bran (0; 10; 20 and 30% and three specific masses (400; 500 and 600 kg MN m-3, with four replications. After 240 days of fermentation the silos were opened. It was observed linear effect on DM, CP, NDFap, ADFap, HEM, LIG, NFC, TC and population of bacteria that produce lactic acid with the addition of crambe meal. There was interaction between the crambe bran factors and specific masses on the values of pH and N-NH3. For MM variables and yeast count there was a negative linear effect due to the evaluated specific mass. The inclusion of crambe bran helps to increase the fermentative profile and the bromatological composition of elephant grass silages studied, and the best results were obtained with the addition of 30% of this coproduct, based on the natural matter.

  3. Olefin Metathesis Reaction in Water and in Air Improved by Supramolecular Additives.

    Science.gov (United States)

    Tomasek, Jasmine; Seßler, Miriam; Gröger, Harald; Schatz, Jürgen

    2015-10-21

    A range of water-immiscible commercially available Grubbs-type precatalysts can be used in ring-closing olefin metathesis reaction in high yields. The synthetic transformation is possible in pure water under ambient conditions. Sulfocalixarenes can help to boost the reactivity of the metathesis reaction by catalyst activation, improved mass transfer, and solubility of reactants in the aqueous reaction media. Additionally, the use of supramolecular additives allows lower catalyst loadings, but still high activity in pure water under aerobic conditions.

  4. Investigating the chemical changes of chlorogenic acids during coffee brewing: conjugate addition of water to the olefinic moiety of chlorogenic acids and their quinides.

    Science.gov (United States)

    Matei, Marius Febi; Jaiswal, Rakesh; Kuhnert, Nikolai

    2012-12-12

    Coffee is one of the most popular and consumed beverages in the world and is associated with a series of benefits for human health. In this study we focus on the reactivity of chlorogenic acids, the most abundant secondary metabolites in coffee, during the coffee brewing process. We report on the hydroxylation of the chlorogenic acid cinnamoyl substituent by conjugate addition of water to form 3-hydroxydihydrocaffeic acid derivatives using a series of model compounds including monocaffeoyl and dicaffeoylquinic acids and quinic acid lactones. The regiochemistry of conjugate addition was established based on targeted tandem MS experiments. Following conjugate addition of water a reversible water elimination yielding cis-cinnamoyl derivatives accompanied by acyl migration products was observed in model systems. We also report the formation of all of these derivatives during the coffee brewing process.

  5. Application of the Law of Additive Reaction Times to Fluid-Solid Reactions in Porous Pellets with Changing Effective Diffusivity

    Science.gov (United States)

    Sohn, Hong Yong; Perez-Fontes, Silvia E.

    2010-12-01

    An approximate closed-form solution, which is based on the Law of Additive Reaction Times for a fluid-solid reaction formulated previously, is presented for the reaction of a fluid with a porous solid in which there is a change of porosity and, thus, effective diffusivity during the reaction. The proposed solution was compared with exact solutions reported in the literature in terms of the effects of various parameters on the fractional conversion. The closed-form expression was found to give satisfactory results and, thus, makes it unnecessary to use a numerical solution. This study represents another of many examples in which Sohn’s Law has provided useful closed-form solutions.

  6. (+)-camphor-derived tri- and tetradentate amino alcohols; synthesis and application as ligands in the nickel catalyzed enantioselective conjugate addition of diethylzinc

    NARCIS (Netherlands)

    Vries, André H.M. de; Imbos, Rosalinde; Feringa, Bernard

    1997-01-01

    Several novel tri- and tetradentate amino alcohol ligands, all derived from (+)-camphor, have been synthesized by using specific N-alkylation procedures. The amino alcohols were employed as chiral ligands in the nickel catalyzed conjugate additions of diethylzine to chalcone and cyclohexenone as

  7. Hexafluorobenzene: A powerful solvent for a noncovalent stereoselective organocatalytic Michael addition reaction

    KAUST Repository

    Lattanzi, Alessandra

    2012-01-01

    A dramatic enhancement of the diastereo- and enantioselectivity in the nitro-Michael addition reaction organocatalysed by a commercially available α,α-l-diaryl prolinol was disclosed when performing the reaction in unconventional hexafluorobenzene as a medium. DFT calculations were performed to clarify the origin of stereoselectivity and the role of C 6F 6. © The Royal Society of Chemistry 2012.

  8. Emitting oligomer containing quinoline group: Synthesis and photophysical properties of conjugated oligomer obtained by Wittig reaction

    Energy Technology Data Exchange (ETDEWEB)

    Karpagam, S., E-mail: skarpagam80@yahoo.com [Organic Chemistry Division, School of Advanced Science, VIT University, Vellore 14, Tamil Nadu (India); Guhanathan, S. [Department of Chemistry, Muthurangam Government Arts College, Vellore, Tamil Nadu (India)

    2014-01-15

    Dichloro quinoline substituted phenylene vinylene oligomer (QUI-OPV) was synthesized via Wittig route. Formation of the oligomer was characterized by spectral (FTIR, {sup 1}H and {sup 13}C NMR), elemental and gel permeation chromatography analysis. The oligomer possesses excellent thermal stability (decomposition temperature 470 °C), solubility in common organic solvents and high glass transition temperature (61 °C). The morphology of the oligomer film of one dimensional (1D) and three dimensional (3D) architectures was observed using atomic force microscopy (AFM). In CHCl{sub 3} solution, the oligomer showed the absorption maxima at 382 nm and also observed excellent photoluminescence (PL) with bluish green emission maxima at shorter wavelengths of 477 nm. The introduction of quinoline to the main chain resulted in a slight decrease of effective conjugation length and exhibited the blue shift in both the absorption and emission spectra. -- Highlights: • Simple synthesis of quinoline functionalized phenylene vinylene oligomer by Wittig route. • The materials had good organosolubility and intrinsic viscosity. • High thermal stability and good surface roughness morphology were observed. • Performance of luminescence improved via introducing quinoline into PPV. • Electrochemical and optical band gap of the oligomer were consistent with each other.

  9. Catalytic Asymmetric Addition Reaction of Dialkylzinc to Nitrone Utilizing Tartaric Acid Ester as a Chiral Auxiliary

    National Research Council Canada - National Science Library

    Ukaji, Yutaka; Shimizu, Yuuko; Kenmoku, Yuuichi; Ahmed, Alauddin; Inomata, Katsuhiko

    1997-01-01

    The catalytic asymmetric addition reaction of dialkylzinc to carbon-nitrogen double bond in 3,4-dihydroisoquinoline N-oxide derivatives was achieved by utilizing a catalytic amount of dicyclopentyl (R,R...

  10. Microwave (MW) irradiated Ugi four-component reaction (Ugi-4CR): Expedited synthesis of steroid-amino acid conjugates--A novel class of hybrid compounds.

    Science.gov (United States)

    Borah, Preetismita; Borah, Juri Moni; Chowdhury, Pritish

    2015-06-01

    Microwave (MW) assisted chemical reactions are currently gaining considerable importance in organic synthesis to contribute in green technology. Considering the importance of peptidomimetic steroid-amino acid conjugates - a novel class of hybrid compounds having diverse biological properties, we report here synthesis of these compounds of alanine and valine methyl esters with seco-steroids (A, B and D ring cleavage) in expedited way by MW promoted Ugi-four-component reaction (Ugi-4CR). Copyright © 2015 Elsevier Inc. All rights reserved.

  11. Olefin Metathesis Reaction in Water and in Air Improved by Supramolecular Additives

    Directory of Open Access Journals (Sweden)

    Jasmine Tomasek

    2015-10-01

    Full Text Available A range of water-immiscible commercially available Grubbs-type precatalysts can be used in ring-closing olefin metathesis reaction in high yields. The synthetic transformation is possible in pure water under ambient conditions. Sulfocalixarenes can help to boost the reactivity of the metathesis reaction by catalyst activation, improved mass transfer, and solubility of reactants in the aqueous reaction media. Additionally, the use of supramolecular additives allows lower catalyst loadings, but still high activity in pure water under aerobic conditions.

  12. Covalent binding of aniline to humic substances. 2. 15N NMR studies of nucleophilic addition reactions

    Science.gov (United States)

    Thorn, K.A.; Pettigrew, P.J.; Goldenberg, W.S.; Weber, E.J.

    1996-01-01

    Aromatic amines are known to undergo covalent binding with humic substances in the environment. Although previous studies have examined reaction conditions and proposed mechanisms, there has been no direct spectroscopic evidence for the covalent binding of the amines to the functional groups in humic substances. In order to further elucidate the reaction mechanisms, the Suwannee River and IHSS soil fulvic and humic acids were reacted with 15N-labeled aniline at pH 6 and analyzed using 15N NMR spectrometry. Aniline underwent nucleophilic addition reactions with the quinone and other carbonyl groups in the samples and became incorporated in the form of anilinohydroquinone, anilinoquinone, anilide, imine, and heterocyclic nitrogen, the latter comprising 50% or more of the bound amine. The anilide and anilinohydroquinone nitrogens were determined to be susceptible to chemical exchange by ammonia. In the case of Suwannee River fulvic acid, reaction under anoxic conditions and pretreatment with sodium borohydride or hydroxylamine prior to reaction under oxic conditions resulted in a decrease in the proportion of anilinohydroquinone nitrogen incorporated. The relative decrease in the incorporation of anilinohydroquinone nitrogen with respect to anilinoquinone nitrogen under anoxic conditions suggested that inter- or intramolecular redox reactions accompanied the nucleophilic addition reactions.

  13. In situ hybridization chain reaction mediated ultrasensitive enzyme-free and conjugation-free electrochemcial genosensor for BRCA-1 gene in complex matrices.

    Science.gov (United States)

    Yang, Hui; Gao, Yang; Wang, Siqi; Qin, You; Xu, Lu; Jin, Dan; Yang, Fan; Zhang, Guo-Jun

    2016-06-15

    In this study, we report an enzyme-free and conjugation-free electrochemical genosensor enabling an ultrasensitive readout of BRCA-1, a breast cancer susceptibility gene. The sensor employs a target-responsive hybridization chain reaction (HCR) to significantly amplify the detectable current signals. By means of a functional auxiliary probe pair and a versatile initiator sequence, a linear DNA concatemer structure can be formed via spontaneous and continuous polymerization of DNA oligomers in the presence of target sequence. Such a DNA nanoassembly endows the genosensor an ultrahigh sensitivity up to 1 aM, which is higher than that of the nanomaterials-based or enzyme mediated amplification approaches by several orders of magnitude. More importantly, the sensor's responsive peak current exhibits a favorable linear correlation to the logarithm of the concentrations of target sequence ranging from 1 aM to 10 pM. In addition, the sensor is highly selective, and can discriminate a single mismatched sequence. This HCR-based genosensor is also capable of probing low-abundance BRCA-1 gene sequence directly in complex matrices, such as 50% human serum, with minimal interference. These advantages will make our tailor-engineered HCR-based electrochemical genosensor appealing to genetic analysis and clinical diagnostics. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Lateral extension of π conjugation along the bay regions of bisanthene through a diels-alder cycloaddition reaction

    KAUST Repository

    Li, Jinling

    2011-11-14

    Diels-Alder cycloaddition reactions at the bay regions of bisanthene (1) with dienophiles such as 1,4-naphthoquinone have been investigated. The products were submitted to nucleophilic addition followed by reductive aromatization reactions to afford the laterally extended bisanthene derivatives 2 and 3. Attempted synthesis of a larger expanded bisanthene 4 revealed an unexpected hydrogenation reaction at the last reductive aromatization step. Unusual Michael addition was observed on quinone 14, which was obtained by Diels-Alder reaction between 1 and 1,4-anthraquinone. Compounds 1-3 exhibited near-infrared (NIR) absorption and emission with high-to-moderate fluorescent quantum yields. Their structures and absorption spectra were studied by density function theory and non-planar twisted structures were calculated for 2 and 3. All compounds showed amphoteric redox behavior with multiple oxidation/reduction waves. Oxidative titration with SbCl 5 gave stable radical cations, and the process was followed by UV/Vis/NIR spectroscopic measurements. Their photostability was measured and correlated to their different geometries and electronic structures. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. CRISPR-Cas and Restriction-Modification Act Additively against Conjugative Antibiotic Resistance Plasmid Transfer in Enterococcus faecalis

    Science.gov (United States)

    Price, Valerie J.; Huo, Wenwen; Sharifi, Ardalan

    2016-01-01

    ABSTRACT Enterococcus faecalis is an opportunistic pathogen and a leading cause of nosocomial infections. Conjugative pheromone-responsive plasmids are narrow-host-range mobile genetic elements (MGEs) that are rapid disseminators of antibiotic resistance in the faecalis species. Clustered regularly interspaced short palindromic repeat (CRISPR)-Cas and restriction-modification confer acquired and innate immunity, respectively, against MGE acquisition in bacteria. Most multidrug-resistant E. faecalis isolates lack CRISPR-Cas and possess an orphan locus lacking cas genes, CRISPR2, that is of unknown function. Little is known about restriction-modification defense in E. faecalis. Here, we explore the hypothesis that multidrug-resistant E. faecalis strains are immunocompromised. We assessed MGE acquisition by E. faecalis T11, a strain closely related to the multidrug-resistant hospital isolate V583 but which lacks the ~620 kb of horizontally acquired genome content that characterizes V583. T11 possesses the E. faecalis CRISPR3-cas locus and a predicted restriction-modification system, neither of which occurs in V583. We demonstrate that CRISPR-Cas and restriction-modification together confer a 4-log reduction in acquisition of the pheromone-responsive plasmid pAM714 in biofilm matings. Additionally, we show that the orphan CRISPR2 locus is functional for genome defense against another pheromone-responsive plasmid, pCF10, only in the presence of cas9 derived from the E. faecalis CRISPR1-cas locus, which most multidrug-resistant E. faecalis isolates lack. Overall, our work demonstrated that the loss of only two loci led to a dramatic reduction in genome defense against a clinically relevant MGE, highlighting the critical importance of the E. faecalis accessory genome in modulating horizontal gene transfer. Our results rationalize the development of antimicrobial strategies that capitalize upon the immunocompromised status of multidrug-resistant E

  16. Chemical reactions of organic molecules adsorbed on ice 1. Chlorine addition to propene

    Energy Technology Data Exchange (ETDEWEB)

    Graham, J.D.; Roberts, J.T.

    2000-02-10

    Chemical reactions that are promoted or catalyzed by the surface or near surface regions of ice particles in type II polar stratospheric clouds (PSCs) have been shown to play a role in the annual sequence of events that ultimately opens the Antarctic ozone hole. A new ice-catalyzed chemical reaction is reported, namely the addition of Cl{sub 2} to the C--C double bond of propene (C{sub 3}H{sub 6}) to form 1,2-dichloropropane. The reaction, which was investigated with temperature-programmed desorption mass spectrometry (TPD), was carried out on ultrathin (10--100 monolayer thick) films of ice deposited on single-crystal metal substrates under ultrahigh vacuum. The Cl{sub 2}-addition product was identified as 1,2-dichloropropane on the basis of its fragmentation pattern in the mass spectrometer. 1,2-Dichloropropane formation occurs below 150 K, and no chlorohydrin (e.g., 2-chloro-1-propanol) evolution is ever observed. The reaction of coadsorbed propene and chlorine is very different from what occurs in aqueous solutions, where chlorohydrin formation occurs readily. Possible mechanisms of the ice-surface-catalyzed reaction are discussed.

  17. A theoretical study of the mechanism of the addition reaction between carbene and azacyclopropane

    Directory of Open Access Journals (Sweden)

    XIAOJUN TAN

    2010-05-01

    Full Text Available The mechanism of the addition reaction between carbene and azacyclopropane was investigated using the second-order Moller–Plesset perturbation theory (MP2. By using the 6-311+G* basis set, geometry optimization, vibrational analysis and the energy properties of the involved stationary points on the potential energy surface were calculated. From the surface energy profile, it can be predicted that there are two reaction mechanisms. The first one (1 is carbene attack at the N atom of azacyclopropane to form an intermediate, 1a (IM1a, which is a barrier-free exothermic reaction. Then, IM1a can isomerize to IM1b via a transition state 1a (TS1a, in which the potential barrier is 30.0 kJ/mol. Subsequently, IM1b isomerizes to a product (Pro1 via TS1b with a potential barrier of 39.3 kJ/mol. The other one (2 is carbene attack at the C atom of azacyclopropane, firstly to form IM2 via TS2a, the potential barrier is 35.4 kJ/mol. Then IM2 isomerizes to a product (Pro2 via TS2b with a potential barrier of 35.1 kJ/mol. Correspondingly, the reaction energy for the reactions (1 and (2 is –478.3 and –509.9 kJ/mol, respectively. Additionally, the orbital interactions are also discussed for the leading intermediate.

  18. Using chiral ionic liquid additives to enhance asymmetric induction in a Diels-Alder reaction.

    Science.gov (United States)

    Goodrich, P; Nimal Gunaratne, H Q; Hall, L; Wang, Y; Jin, L; Muldoon, M J; Ribeiro, A P C; Pombeiro, A J L; Pârvulescu, V I; Davey, P; Hardacre, C

    2017-01-31

    A bis-oxazoline ligand has been complexed using Cu(ii) and Zn(ii) trifluoromethanesulfonate and a range of chiral ionic liquid (CIL) additives based on natural products were used as a co-catalyst for a Diels-Alder reaction. The catalytic performance of these systems was compared for the asymmetric Diels-Alder reaction between N-acryloyloxazolidinone and cyclopentadiene with and without the presence of a CIL additive. In the absence of the CIL, both catalysts resulted in low enantioselectivities in conventional solvents and ionic liquids. However, whilst only a minor effect of the CIL was observed for the Cu based catalyst, in the case of the Zn based catalyst, significant enhancements in endo enantioselectivity of up to 50% were found on the addition of a CIL.

  19. Boron-Heteroatom Addition Reactions via Borylative Heterocyclization: Oxyboration, Aminoboration, and Thioboration.

    Science.gov (United States)

    Issaian, Adena; Tu, Kim N; Blum, Suzanne A

    2017-10-17

    Organoboron compounds and heterocycles are powerful building blocks and precursors for organic synthesis, including for drug discovery and agrochemical and material synthesis. The common strategy for the synthesis of borylated heterocycles involves two separate synthetic steps: first, synthesis of the heterocyclic core, and second, borylation of the core through established methods such as transition-metal-catalyzed C-H or C-X activation/borylation or lithiation/borylation. In this Account, we describe our laboratory's development of borylative heterocyclization reactions that access the heterocyclic core and install boron in one synthetic step. These methods provide complementary bond disconnections, regiochemistry, and functional-group compatibility to current methods. We describe our methods with two categories: a direct borylation method that refers to addition reactions starting from a preformed B-element σ bond, which is essential in the mechanistic route to product formation, and a formal borylation method that refers to addition reactions that do not require formation of a B-element bond but instead proceed through carbon-carbon π-bond activation by an electrophilic boron source followed by dealkylation or deacylation. Through electrophilic activation of the alkyne rather than activation of the B-element bond, formal borylation provides a complementary strategy toward neutral organoboron reagents. We first studied direct oxyboration toward the formation of borylated benzofurans, where a preformed boron-oxygen σ bond is added across an alkyne activated by a carbophilic gold catalyst. We describe detailed mechanistic and kinetic studies of this class of reactions. Application of the knowledge gained from these studies aided in the future development of additional direct borylation reactions involving boron-nitrogen and boron-oxygen σ bonds to form borylared indoles and isoxazoles, respectively. Formal addition of boron/oxygen equivalents to effect

  20. Studies on the reaction sintered zirconia-mullite-alumina composites with titania as additive

    Directory of Open Access Journals (Sweden)

    D. Chandra

    2013-09-01

    Full Text Available Zirconia-mullite-alumina composites were prepared by reaction sintering of micro fine calcined alumina and zircon flour in different ratios. TiO2 was added in different proportions as an additive and the starting materials were iso-statically pressed. The Al2O3 / ZrO2 ratios and the proportions of the TiO2 additive content were found to influence the physico-mechanical properties of the compacts significantly. The fabricated compacts exhibited exceptionally high sintered density, mechanical strength and corrosion resistance. From the micro-structural analysis of the sintered compacts it has been observed that the relative size of the ZrO2 grains and relative proportion of t-ZrO2 phase in the batches with TiO2 additive was more compared to batches without TiO2 additive.

  1. Sequence specific visual detection of LAMP reactions by addition of cationic polymers

    Directory of Open Access Journals (Sweden)

    Hirano Tsuyoshi

    2006-01-01

    Full Text Available Abstract Background Development of a practical gene point-of-care testing device (g-POCT device requires innovative detection methods for demonstrating the results of the gene amplification reaction without the use of expensive equipment. We have studied a new method for the sequence-specific visual detection of minute amounts of nucleic acids using precipitation reaction by addition of cationic polymers to amplicons of Loop mediated isothermal Amplification (LAMP. Results Oligo DNA probes labeled with different fluorescent dyes were prepared for multiple nucleic acid templates, and the templates were amplified by the LAMP reactions under the existence of the probes. At completion of the LAMP reaction, an optimal amount of low molecular weight polyethylenimine (PEI was added, resulting in the precipitation of the insoluble LAMP amplicon-PEI complex. The fluorescently labeled Oligo DNA probes hybridized to the LAMP product were incorporated into the precipitation, and the precipitate emitted fluorescence corresponding to the amplified nucleic acid templates. The color of emitted fluorescence can be detected easily by naked eye on a conventional UV illuminator. Conclusion The presence or absence of minute amount of nucleic acid templates could be detected in a simple manner through visual assessment for the color of the LAMP amplicon-PEI complex precipitate. We conclude that this detection method may facilitate development of small and simple g-POCT device.

  2. Amplified detection of femtomolar DNA based on a one-to-few recognition reaction between DNA-Au conjugate and target DNA

    Science.gov (United States)

    Wang, Zhijuan; Zhang, Juan; Zhu, Changfeng; Wu, Shixin; Mandler, Daniel; Marks, Robert S.; Zhang, Hua

    2014-02-01

    A sensitive electrochemical DNA biosensor based on the amplification of Au nanoparticles (AuNPs) has been developed. The AuNPs were modified with two types of signaling reporter DNAs, i.e. a methylene blue probe (MB-probe 2-SH) and T10 with a methylene blue signaling molecule (MB-T10-SH), forming DNA-AuNP conjugates. The MB-probe 2-SH is complementary to the target DNA, while MB-T10-SH is not. The presence of MB-T10-SH reduces the cross-reaction between target DNA and MB-probe 2-SH on the AuNPs, resulting in increased sensitivity of the biosensor. In our assay, the DNA sensor is fabricated by immobilizing a capture probe on the surface of the Au electrode, which then hybridizes with the corresponding target DNA, and further hybridizes with a DNA-Au conjugate. The signal of MB is measured by differential pulse voltammetry, while the DNA-Au conjugate enables the detection of target DNA in the linear range of 10-13 to 10-8 M with the detection limit as low as 50 fM.A sensitive electrochemical DNA biosensor based on the amplification of Au nanoparticles (AuNPs) has been developed. The AuNPs were modified with two types of signaling reporter DNAs, i.e. a methylene blue probe (MB-probe 2-SH) and T10 with a methylene blue signaling molecule (MB-T10-SH), forming DNA-AuNP conjugates. The MB-probe 2-SH is complementary to the target DNA, while MB-T10-SH is not. The presence of MB-T10-SH reduces the cross-reaction between target DNA and MB-probe 2-SH on the AuNPs, resulting in increased sensitivity of the biosensor. In our assay, the DNA sensor is fabricated by immobilizing a capture probe on the surface of the Au electrode, which then hybridizes with the corresponding target DNA, and further hybridizes with a DNA-Au conjugate. The signal of MB is measured by differential pulse voltammetry, while the DNA-Au conjugate enables the detection of target DNA in the linear range of 10-13 to 10-8 M with the detection limit as low as 50 fM. Electronic supplementary information (ESI

  3. A catalyst-free addition reaction of zinc amide enolates to N-sulfonyle imines

    Energy Technology Data Exchange (ETDEWEB)

    Joo, Seong Ryu; Im, Pyeong Won; Kim, Jong Sung; Kim, Seung Hoi [Dept. of Chemistry, Dankook University, Cheonan (Korea, Republic of); Park Soo Youl [Interface Chemistry and Engineering Research Team, Korea Research Institute of Chemical Technology, Daejon (Korea, Republic of)

    2016-12-15

    Despite the remarkable expansion of the imino-Reformatsky reaction, one interesting aspect is that, to the best of our knowledge, zinc enolates derived solely from α-halo esters have been mainly used in the recent progress. In contrast, a few limited examples have been reported concerning the application of zinc enolates derived from α-halo amide to the imino-Reformatsky reaction. In recent years, Rodriguez-Solla and co-workers reported the addition reaction of samarium enolates derived from both α-halo esters and amides to imines, resulting in the synthe- sis of β-amino esters or amides. In conclusion, we established a potential synthetic proto- col for the preparation of β-amino amides. This work was accomplished by the direct addition of zinc amide enolates to N-sulfonyl imines in the absence of any metal-catalyst under mild conditions. Due to the operational simplicity of the proposed method, it can be further utilized in synthetic organic chemistry. Further studies to elucidate the scope of this approach are currently underway in our laboratory.

  4. Study on the conjugation mechanism of colistin sulfate with bovine serum albumin and effect of the metal ions on the reaction

    Energy Technology Data Exchange (ETDEWEB)

    Liu Baosheng, E-mail: lbs@hbu.edu.cn [Key Laboratory of Medical Chemistry and Molecular Diagnosis, Ministry of Education, College of Chemistry and Environmental Science, Hebei University, Baoding 071002 (China); Yang Chao; Yan Xiaona; Wang Jing; Lv Yunkai [Key Laboratory of Medical Chemistry and Molecular Diagnosis, Ministry of Education, College of Chemistry and Environmental Science, Hebei University, Baoding 071002 (China)

    2012-05-15

    Colistin sulfate (CS) can quench the fluorescence of bovine serum albumin (BSA) in an aqueous solution at pH 7.40. The static fluorescence-quenching process between BSA and CS was confirmed and the binding constant, the number of binding sites and thermodynamic data for the interaction between BSA and CS were also obtained. Results showed that the order of magnitude of binding constant (K{sub a}) was 10{sup 4}, and the number of binding site (n) in the binary system was approximately equal to 1; electrostatic force played an important role on the conjugation reaction between BSA and CS. On the basis of the Foerster theory of the resonance energy transfer, the binding distance (r) between CS and BSA was less than 7 nm. Comparing the quenching of protein fluorescence excited at 280 nm and 295 nm and from the site marker replacement experiments, it was shown that the primary CS binding site was located in the sub-domain IIA (site I) of BSA. Synchronous fluorescence spectra clearly revealed that the binding of CS with BSA can induce conformation changes in BSA. In addition, the effects of common metal ions on the binding constants of CS-BSA complex were also discussed. It was shown that, except Cu{sup 2+}, the high metal ion concentrations improved the CS efficacy. - Highlights: Black-Right-Pointing-Pointer Complex formation is dominant for the reduction of BSA fluorescence. Black-Right-Pointing-Pointer Primary binding site for drug is located in the sub-domain IIA of BSA. Black-Right-Pointing-Pointer Electrostatic force played a main role between the drug and the BSA. Black-Right-Pointing-Pointer The BSA structure changes upon drug complexation. Black-Right-Pointing-Pointer Higher concentrations of metal ions have good effects to improve efficacy of drug except Cu{sup 2+}.

  5. Adverse reactions to simultaneous influenza and pneumococcal conjugate vaccinations in children : randomized double-blind controlled trial

    NARCIS (Netherlands)

    Jansen, Angelique G S C; Sanders, Elisabeth A M; Smulders, Sara; Hoes, Arno W; Hak, Eelko

    In a randomized double-blind controlled trial, the safety was assessed of simultaneous administration of influenza and pneumococcal conjugate vaccines in children with previous physician-diagnosed respiratory tract infections. In total, 579 children aged 18-72 months were assigned to receive

  6. N-Heterocyclic Carbene-Catalysed Diastereoselective Vinylogous Michael Addition Reaction of gamma-Substituted deconjugated Butenolides

    KAUST Repository

    Guo, Hao

    2015-11-16

    An efficient N-heterocyclic carbene (NHC)-catalysed vinylogous Michael addition of deconjugated butenolides was developed. In the presence of 5 mol% of the NHC catalyst, both γ-alkyl and aryl-substituted deconjugated butenolides undergo vinylogous Michael addition with various α, β-unsaturated ketones, esters, or nitriles to afford γ,γ-disubstituted butenolides containing adjacent quaternary and tertiary carbon centers in good to excellent yields with excellent diastereoselectivities. In this process, the free carbene is assumed to act as a strong Brønsted base to promote the conjugate addition.

  7. Cross-conjugated Trienamine Catalysis with α'-Alkylidene 2-Cyclohexenones: Application in β,γ-Regioselective Aza-Diels-Alder Reaction.

    Science.gov (United States)

    Zhou, Zhi; Wang, Zhou-Xiang; Ouyang, Qin; Xiao, Wei; Du, Wei; Chen, Ying-Chun

    2017-02-24

    Endo-type cross-conjugated trienamines between highly congested α'-alkylidene 2-cyclohexenones and a chiral primary amine catalyst serve as HOMO-raised dienophiles in inverse-electron-demand aza-Diels-Alder cycloadditions with a number of 1-azadiene substrates. The reactions exhibit exclusive β,γ-regioselectivity, and multifunctional products with high molecular complexity are efficiently constructed in excellent diastereo- and enantioselectivity (>19:1 d.r., up to 99 % ee). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Precipitation Reactions in Age-Hardenable Alloys During Laser Additive Manufacturing

    Science.gov (United States)

    Jägle, Eric A.; Sheng, Zhendong; Wu, Liang; Lu, Lin; Risse, Jeroen; Weisheit, Andreas; Raabe, Dierk

    2016-03-01

    We describe and study the thermal profiles experienced by various age-hardenable alloys during laser additive manufacturing (LAM), employing two different manufacturing techniques: selective laser melting and laser metal deposition. Using scanning electron microscopy and atom probe tomography, we reveal at which stages during the manufacturing process desired and undesired precipitation reactions can occur in age-hardenable alloys. Using examples from a maraging steel, a nickel-base superalloy and a scandium-containing aluminium alloy, we demonstrate that precipitation can already occur during the production of the powders used as starting material, during the deposition of material (i.e. during solidification and subsequent cooling), during the intrinsic heat treatment effected by LAM (i.e. in the heat affected zones) and, naturally, during an ageing post-heat treatment. These examples demonstrate the importance of understanding and controlling the thermal profile during the entire additive manufacturing cycle of age-hardenable materials including powder synthesis.

  9. Enzymatic hydrolysate-induced displacement reaction with multifunctional silica beads doped with horseradish peroxidase-thionine conjugate for ultrasensitive electrochemical immunoassay.

    Science.gov (United States)

    Lin, Youxiu; Zhou, Qian; Lin, Yuping; Tang, Dianping; Niessner, Reinhard; Knopp, Dietmar

    2015-08-18

    A novel (invertase) enzymatic hydrolysate-triggered displacement reaction strategy with multifunctional silica beads, doped with horseradish peroxidase-thionine (HRP-Thi) conjugate, was developed for competitive-type electrochemical immunoassay of small molecular aflatoxin B1 (AFB1). The competitive-type displacement reaction was carried out on the basis of the affinity difference between enzymatic hydrolysate (glucose) and its analogue (dextran) for concanavalin A (Con A) binding sites. Initially, thionine-HRP conjugates were doped into nanometer-sized silica beads using the reverse micelle method. Then monoclonal anti-AFB1 antibody and Con A were covalently conjugated to the silica beads. The immunosensor was prepared by means of immobilizing the multifunctional silica beads on a dextran-modified sensing interface via the dextran-Con A binding reaction. Gold nanoparticles functionalized with AFB1-bovine serum albumin conjugate (AFB1-BSA) and invertase were utilized as the trace tag. Upon target AFB1 introduction, a competitive-type immunoreaction was implemented between the analyte and the labeled AFB1-BSA on the nanogold particles for the immobilized anti-AFB1 antibody on the electrode. The invertase followed by gold nanoparticles hydrolyzed sucrose into glucose and fructose. The produced glucose displaced the multifunctional silica beads from the electrode based on the classical dextran-Con A-glucose system, thus decreasing the catalytic efficiency of the immobilized HRP on the electrode relative to that of the H2O2-thionine system. Under optimal conditions, the detectable electrochemical signal increased with the increasing target AFB1 in a dynamic working range from 3.0 pg mL(-1) to 20 ng mL(-1) with a detection limit of 2.7 pg mL(-1). The strong bioconjugation with two nanostructures also resulted in a good repeatability and interassay precision down to 9.3%. Finally, the methodology was further validated for analysis of naturally contaminated or spiked AFB1

  10. High operational and environmental stability of high-mobility conjugated polymer field-effect transistors through the use of molecular additives

    KAUST Repository

    Nikolka, Mark

    2016-12-12

    Due to their low-temperature processing properties and inherent mechanical flexibility, conjugated polymer field-effect transistors (FETs) are promising candidates for enabling flexible electronic circuits and displays. Much progress has been made on materials performance; however, there remain significant concerns about operational and environmental stability, particularly in the context of applications that require a very high level of threshold voltage stability, such as active-matrix addressing of organic light-emitting diode displays. Here, we investigate the physical mechanisms behind operational and environmental degradation of high-mobility, p-type polymer FETs and demonstrate an effective route to improve device stability. We show that water incorporated in nanometre-sized voids within the polymer microstructure is the key factor in charge trapping and device degradation. By inserting molecular additives that displace water from these voids, it is possible to increase the stability as well as uniformity to a high level sufficient for demanding industrial applications.

  11. Infrared spectroscopic evidence of a direct addition reaction between palygorskite and pyromellitic dianhydride

    Energy Technology Data Exchange (ETDEWEB)

    Yan Wenchang [CAS Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); School of Civil Engineering, Anhui University of Architecture, Hefei 230022 (China); Yuan Peng, E-mail: yuanpeng@gig.ac.cn [CAS Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Chen Ming [CAS Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China); Wang Linjiang [College of Materials Science and Engineering, Guilin University of Technology, Guangxi 541004 (China); Liu Dong [CAS Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (China)

    2013-01-15

    Highlights: Black-Right-Pointing-Pointer A direct addition reaction between palygorskite and pyromellitic dianhydride. Black-Right-Pointing-Pointer The graft of anhydride to the bound water on the external surface of palygorskite. Black-Right-Pointing-Pointer Application of palygorskite without organo-modification. - Abstract: Palygorskite covalently grafted with pyromellitic dianhydride was investigated. Untreated and grafted samples were characterized by X-ray diffraction, thermogravimetry, and Fourier transform infrared spectroscopy. Infrared results showed the direct grafting of anhydride onto the bound water molecules on the external surfaces of the palygorskite. The grafting modification makes palygorskite more readily compatible with anhydride, resulting in substantial enhancements in the glass transition temperature and flexural strength of the anhydride-cured epoxy resin/palygorskite nanocomposites.

  12. Secondary Pollutants from Ozone Reaction with Ventilation Filters and Degradation of Filter Media Additives

    Energy Technology Data Exchange (ETDEWEB)

    Destaillats, Hugo; Chen, Wenhao; Apte, Michael; Li, Nuan; Spears, Michael; Almosni, Jérémie; Brunner, Gregory; Zhang, Jianshun (Jensen); Fisk, William J.

    2011-05-01

    Prior research suggests that chemical processes taking place on the surface of particle filters employed in buildings may lead to the formation of harmful secondary byproducts. We investigated ozone reactions with fiberglass, polyester, cotton/polyester and polyolefin filter media, as well as hydrolysis of filter media additives. Studies were carried out on unused media, and on filters that were installed for 3 months in buildings at two different locations in the San Francisco Bay Area. Specimens from each filter media were exposed to {approx}150 ppbv ozone in a flow tube under a constant flow of dry or humidified air (50percent RH). Ozone breakthrough was recorded for each sample over periods of {approx}1000 min; the ozone uptake rate was calculated for an initial transient period and for steady-state conditions. While ozone uptake was observed in all cases, we did not observe significant differences in the uptake rate and capacity for the various types of filter media tested. Most experiments were performed at an airflow rate of 1.3 L/min (face velocity = 0.013 m/s), and a few tests were also run at higher rates (8 to 10 L/min). Formaldehyde and acetaldehyde, two oxidation byproducts, were quantified downstream of each sample. Those aldehydes (m/z 31 and 45) and other volatile byproducts (m/z 57, 59, 61 and 101) were also detected in real-time using Proton-Transfer Reaction - Mass Spectrometry (PTR-MS). Low-ppbv byproduct emissions were consistently higher under humidified air than under dry conditions, and were higher when the filters were loaded with particles, as compared with unused filters. No significant differences were observed when ozone reacted over various types of filter media. Fiberglass filters heavily coated with impaction oil (tackifier) showed higher formaldehyde emissions than other samples. Those emissions were particularly high in the case of used filters, and were observed even in the absence of ozone, suggesting that hydrolysis of additives

  13. No impact of a phytogenic feed additive on digestion and unspecific immune reaction in piglets.

    Science.gov (United States)

    Muhl, A; Liebert, F

    2007-10-01

    Two 35 day experiments were conducted to examine the influence of a commercial phytogenic feed additive (PFA) on nutrient digestibility and unspecific immune reaction of piglets in the post-weaning period. The PFA composition was inulin, an essential oil mix (carvacrol and thymol), chestnut meal (tannins), and cellulose powder as carrier substance. In each experiment, immediately after weaning 40 male castrated piglets were divided into four experimental groups (n = 10). Diets were based on wheat, barley, soy bean meal and fishmeal using lysine as the first limiting amino acid. In experiment 1, graded levels of the PFA were supplied (A: control; B: 0.05% PFA; C: 0.1% PFA; D: 0.15% PFA). Experiment 2 utilized equal diets with 0.1% of the PFA, but different lysine supply (A: control; B: 0.1% PFA; C: +0.35% lysine; D: 0.1% PFA + 0.35% lysine). At the end of the experimental period, acute phase proteins (APPs) haptoglobin and C-reactive protein were examined in individual blood plasma samples. Following each growth study, 16 animals (n = 4) were taken for sampling of ileal chyme and assessing of praecaecal digestibility of protein and amino acids. In addition, digesta samples of the duodenum and the total pancreatic tissue were utilized for determining the enzyme activity of alpha-amylase and trypsin. APP, praecaecal digestibility and enzyme activities did not significantly respond to the PFA supplementaion in diets.

  14. Multi-modular, tris(triphenylamine) zinc porphyrin-zinc phthalocyanine-fullerene conjugate as a broadband capturing, charge stabilizing, photosynthetic 'antenna-reaction center' mimic.

    Science.gov (United States)

    Kc, Chandra B; Lim, Gary N; D'Souza, Francis

    2015-04-21

    A broadband capturing, charge stabilizing, photosynthetic antenna-reaction center model compound has been newly synthesized and characterized. The model compound is comprised of a zinc porphyrin covalently linked to three units of triphenylamine entities and a zinc phthalocyanine entity. The absorption and fluorescence spectra of zinc porphyrin complemented that of zinc phthalocyanine offering broadband coverage. Stepwise energy transfer from singlet excited triphenylamine to zinc porphyrin, and singlet excited zinc porphyrin to zinc phthalocyanine (kENT ∼ 10(11) s(-1)) was established from spectroscopic and time-resolved transient absorption techniques. Next, an electron acceptor, fullerene was introduced via metal-ligand axial coordination to both zinc porphyrin and zinc phthalocyanine centers, and they were characterized by spectroscopic and electrochemical techniques. An association constant of 4.9 × 10(4) M(-1) for phenylimidazole functionalized fullerene binding to zinc porphyrin, and 5.1 × 10(4) M(-1) for it binding to zinc phthalocyanine was obtained. An energy level diagram for the occurrence of different photochemical events within the multi-modular donor-acceptor conjugate was established from spectral and electrochemical data. Unlike the previous zinc porphyrin-zinc phthalocyanine-fullerene conjugates, the newly assembled donor-acceptor conjugate has been shown to undergo the much anticipated initial charge separation from singlet excited zinc porphyrin to the coordinated fullerene followed by a hole shift process to zinc phthalocyanine resulting in a long-lived charge separated state as revealed by femto- and nanosecond transient absorption spectroscopic techniques. The lifetime of the final charge separated state was about 100 ns.

  15. Novel Interecting Blends Based on Amino Terminited Oligoimides by Using Michael Addition Reaction-II

    Directory of Open Access Journals (Sweden)

    Rita R. Patel

    2012-01-01

    Full Text Available New amino terminated oligoimides (AOIs were prepared by the Michael addition reaction of various bismaleimide (1, namely, 1-(4-((4-((2, 5-dioxocyclopent-3 enylamino methyl cyclohexyl methyl cyclohexyl-1, 6-dihydropyridine-2, 5-dione with excess of various diamines (2a-c. These AOIs were characterized by elemental analysis, FT-IR spectral studies and number average molecular weight estimated by non-aqueous conductometric titrations. AOIs were then treated with acrylol chloride and resultant acryl terminated oligoimides (AcOIs samples were also characterized thermogravimetrically. Each of these AcOI was then combined with the N-phenyl maleimide (PM in THF solvent. The resultant suspensions were then heated in the presence of azobisisobutyronitrile (AIBN as an initiator. The AcOI and PM polymerized through double bond simultaneously and form interacting blends, which were analyzed thermogravimetrically. The glass fiber reinforced composites were fabricated by using the suspensions of the AcOI and PM. The composites of Interacting blends were analyzed for their mechanical, chemical and electrical properties.

  16. AGET ATRP of acrylonitrile with ionic liquids as reaction medium without any additional ligand

    Energy Technology Data Exchange (ETDEWEB)

    Chen Hou, E-mail: lduchenhou@hotmail.com [School of Chemistry and Materials Science, Ludong University, Yantai 264025 (China); Liang Ying; Liu Delong; Tan Zhi; Zhang Shaohong; Zheng Meiling; Qu Rongjun [School of Chemistry and Materials Science, Ludong University, Yantai 264025 (China)

    2010-05-10

    Atom transfer radical polymerization using activators generated by electron transfer (AGET ATRP) of acrylonitrile (AN) was carried out for the first time in 1-methylimidazolium acetate ([mim][AT]), 1-methylimidazolium propionate([mim][PT]), and 1-methylimidazolium butyrate ([mim][BT]), respectively. The polymerization was approached by using ascorbic acid (VC) as a reducing agent, ethyl 2-bromoisobutyrate (EBiB) as initiator, only FeBr{sub 3} as catalyst without any additional ligand. Kinetic studies showed that both AGET ATRP of AN in the absence of oxygen and in the presence of air proceeded in a well-controlled manner. Under the same conditions, the polymerization in the presence of air provided rather slower reaction rate and showed better control of molecular weight and its distribution than in the absence of oxygen. The sequence of the apparent polymerization rate constants of AGET ATRP of AN in three ionic liquids was k{sub app}([mim][AT]) > k{sub app}([mim][PT]) > k{sub app}([mim][BT]). The living nature of the polymerization was confirmed by chain end analysis and block copolymerization of methyl methacrylate with polyacrylonitrile as macroinitiator. All the three ionic liquids and FeBr{sub 3} could be recycled and reused and had no effect on the living nature of polymerization.

  17. Synthesis and characterization of polyacids from palm acid oil and sunflower oil via addition reaction.

    Science.gov (United States)

    Zeimaran, Ehsan; Kadir, Mohammed Rafiq Abdul; Nor, Hussin Mohd; Kamarul, Tunku; Djordjevic, Ivan

    2013-12-15

    In this study aliphatic polyacids were synthesized using palm acid oil (PAO) and sunflower oil (SFO) via addition reaction technique. The synthesized materials were characterized using Fourier-transform infra-red (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF-MS) and thermo-gravimetric analysis (TGA). Mixing formic acid and hydrogen peroxide with PAO or SFO at the ratio 3:10:1 produced the lowest iodine value of 10.57 and 9.24 respectively, indicating the increase in epoxidization of both oils. Adding adipic acid to the epoxidized oils at a ratio of 1:10 increases the acid values of SFO and PAO to 11.22 and 6.73 respectively. The existence of multi-acid groups present in synthesized polyacid was confirmed by MALD-ToF-MS. This feature indicates a possible value to the biomaterials development. Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. Modification of the performance of WO3-ZrO2 catalysts by metal addition in hydrocarbon reactions

    Directory of Open Access Journals (Sweden)

    Gerardo Carlos Torres

    2012-01-01

    Full Text Available A study of the different hydrocarbon reactions over Ni doped WO3-ZrO2 catalysts was performed. Ni was found as NiO at low Ni concentration while at high Ni concentrations a small fraction was present as a metal. For both cases, Ni strongly modified total acidity and concentration of strong acid sites. In the cyclohexane dehydrogenation reaction, Ni addition promotes both benzene and methyl cyclopentane production. The hydroconversion activity (n-butane and n-octane increases with the augment of total acidity produced by Ni. The selectivity to reaction products is modified according to the acid strength distribution changes produced by Ni addition.

  19. Insights into the Halogen Oxidative Addition Reaction to Dinuclear Gold(I) Di(NHC) Complexes

    KAUST Repository

    Baron, Marco

    2016-06-14

    Gold(I) dicarbene complexes [Au2(MeIm-Y-ImMe)2](PF6)2(Y=CH2(1), (CH2)2(2), (CH2)4(4), MeIm=1-methylimidazol-2-ylidene) react with iodine to give the mixed-valence complex [Au(MeIm-CH2-ImMe)2AuI2](PF6)2(1 aI) and the gold(III) complexes [Au2I4(MeIm-Y-ImMe)2](PF6)2(2 cIand 4 cI). Reaction of complexes 1 and 2 with an excess of ICl allows the isolation of the tetrachloro gold(III) complexes [Au2Cl4(MeIm-CH2-ImMe)2](PF6)2(1 cCl) and [Au2Cl4(MeIm-(CH2)2-ImMe)2](Cl)2(2 cCl-Cl) (as main product); remarkably in the case of complex 2, the X-ray molecular structure of the crystals also shows the presence of I-Au-Cl mixed-sphere coordination. The same type of coordination has been observed in the main product of the reaction of complexes 3 or 4 with ICl. The study of the reactivity towards the oxidative addition of halogens to a large series of dinuclear bis(dicarbene) gold(I) complexes has been extended and reviewed. The complexes react with Cl2, Br2and I2to give the successive formation of the mixed-valence gold(I)/gold(III) n aXand gold(III) n cX(excluding compound 1 cI) complexes. However, complex 3 affords with Cl2and Br2the gold(II) complex 3 bX[Au2X2(MeIm-(CH2)3-ImMe)2](PF6)2(X=Cl, Br), which is the predominant species over compound 3 cXeven in the presence of free halogen. The observed different relative stabilities of the oxidised complexes of compounds 1 and 3 have also been confirmed by DFT calculations. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Direct protein-protein conjugation by genetically introducing bioorthogonal functional groups into proteins.

    Science.gov (United States)

    Kim, Sanggil; Ko, Wooseok; Sung, Bong Hyun; Kim, Sun Chang; Lee, Hyun Soo

    2016-11-15

    Proteins often function as complex structures in conjunction with other proteins. Because these complex structures are essential for sophisticated functions, developing protein-protein conjugates has gained research interest. In this study, site-specific protein-protein conjugation was performed by genetically incorporating an azide-containing amino acid into one protein and a bicyclononyne (BCN)-containing amino acid into the other. Three to four sites in each of the proteins were tested for conjugation efficiency, and three combinations showed excellent conjugation efficiency. The genetic incorporation of unnatural amino acids (UAAs) is technically simple and produces the mutant protein in high yield. In addition, the conjugation reaction can be conducted by simple mixing, and does not require additional reagents or linker molecules. Therefore, this method may prove very useful for generating protein-protein conjugates and protein complexes of biochemical significance. Copyright © 2016. Published by Elsevier Ltd.

  1. Theoretical Kinetics Analysis for Ḣ Atom Addition to 1,3-Butadiene and Related Reactions on the Ċ4H7Potential Energy Surface.

    Science.gov (United States)

    Li, Yang; Klippenstein, Stephen J; Zhou, Chong-Wen; Curran, Henry J

    2017-10-12

    The oxidation chemistry of the simplest conjugated hydrocarbon, 1,3-butadiene, can provide a first step in understanding the role of polyunsaturated hydrocarbons in combustion and, in particular, an understanding of their contribution toward soot formation. On the basis of our previous work on propene and the butene isomers (1-, 2-, and isobutene), it was found that the reaction kinetics of Ḣ-atom addition to the C═C double bond plays a significant role in fuel consumption kinetics and influences the predictions of high-temperature ignition delay times, product species concentrations, and flame speed measurements. In this study, the rate constants and thermodynamic properties for Ḣ-atom addition to 1,3-butadiene and related reactions on the Ċ 4 H 7 potential energy surface have been calculated using two different series of quantum chemical methods and two different kinetic codes. Excellent agreement is obtained between the two different kinetics codes. The calculated results including zero-point energies, single-point energies, rate constants, barrier heights, and thermochemistry are systematically compared among the two quantum chemical methods. 1-Methylallyl (Ċ 4 H 7 1-3) and 3-buten-1-yl (Ċ 4 H 7 1-4) radicals and C 2 H 4 + Ċ 2 H 3 are found to be the most important channels and reactivity-promoting products, respectively. We calculated that terminal addition is dominant (>80%) compared to internal Ḣ-atom addition at all temperatures in the range 298-2000 K. However, this dominance decreases with increasing temperature. The calculated rate constants for the bimolecular reaction C 4 H 6 + Ḣ → products and C 2 H 4 + Ċ 2 H 3 → products are in excellent agreement with both experimental and theoretical results from the literature. For selected C 4 species, the calculated thermochemical values are also in good agreement with literature data. In addition, the rate constants for H atom abstraction by Ḣ atoms have also been calculated, and it is

  2. Part I: Reverse-docking studies of a squaramide-catalyzed conjugate addition of a diketone to a nitro-olefin Part II: The development of ChemSort: an education game for organic chemistry

    Science.gov (United States)

    Granger, Jenna Christine

    Part 1: Reverse-docking studies of a squaramide-catalyzed conjugate addition of a diketone to a nitro-olefin. Asymmetric organocatalysis, the catalysis of asymmetric reactions by small organic molecules, is a rapidly growing field within organic synthesis. The ability to rationally design organocatalysts is therefore of increasing interest to organic chemists. Computational chemistry is quickly proving to be an extremely successful method for understanding and predicting the roles of organocatalysts, and therefore is certain to be of use in the rational design of such catalysts. A methodology for reverse-docking flexible organocatalysts to rigid transition state models of asymmetric reactions has been previously developed by the Deslongchamps group. The investigation of Rawal's squaramide-based organocatalyst for the addition of a diketone to a nitro-olefin is described, and the results of the reverse docking of Rawal's catalyst to the geometry optimized transition state models of the uncatalyzed reaction for both the R and S-product enantiomers are presented. The results of this study indicate a preference for binding of the organocatalyst to the R-enantiomer transition state model with a predicted enantiomeric excess of 99%, which is consistent with the experimental results. A plausible geometric model of the transition state for the catalyzed reaction is also presented. The success of this study demonstrates the credibility of using reverse docking methods for the rational design of asymmetric organocatalysts. Part 2: The development of ChemSort: an educational game for organic chemistry. With the advent of the millennial learner, we need to rethink traditional classroom approaches to science learning in terms of goals, approaches, and assessments. Digital simulations and games hold much promise in support of this educational shift. Although the idea of using games for education is not a new one, well-designed computer-based "serious games" are only beginning to

  3. Synthesis, Chemosensory Properties, and Self-Assembly of Terpyridine-Containing Conjugated Polycarbazole through RAFT Polymerization and Heck Coupling Reaction

    Directory of Open Access Journals (Sweden)

    Po-Chih Yang

    2017-09-01

    Full Text Available We report the responsive fluorescence chemosensory phenomena of a carbazole-functionalized crosslinked polymer (PCaT with pendent terpyridine (tpy groups as receptors of metal ions. The polymer was synthesized using Heck polymerization between 3,6-dibromide groups in a carbazole-based polymer (PC2Br and divinyl tpy monomer. The effects of the polymeric structure on the optical and chemosensory properties of the PCaT were compared with those of a carbazole-tpy alternating conjugated polymer (PCT. Photoluminescence titrations demonstrated that the PCaT and PCT had the high sensing ability toward Fe3+ ions, with Stern–Volmer constants of 8.10 × 104 and 6.68 × 104 M−1, respectively. The limit of detection (LOD toward Fe3+ of the PCaT and PCT was estimated to be 1.31 × 10−6 and 1.81 × 10−6 M, respectively, and the superior LOD of the PCaT was ascribed to its lowly crosslinked structure. The fluorescence of the solutions of these polymers that were quenched by Fe3+ ions recovered when trace CN− anions were added because of the high stability constant of the CN−–Fe3+ complex. Micellar aggregates with a mean diameter of approximately 239.5 nm were formed by dissolving the PCaT in tetrahydrofuran (THF solution. Our results suggest that the PCaT is a promising material for chemosensory applications.

  4. Synthesis of polyhydroxylated decalins via two consecutive one-pot reactions: 1,4-addition/aldol reaction followed by RCM/syn-dihydroxylation

    Directory of Open Access Journals (Sweden)

    Michał Malik

    2016-12-01

    Full Text Available Synthesis of novel polyhydroxylated derivatives of decalin is described. The presented methodology consists in a one-pot copper-catalyzed 1,4-addition of vinylmagnesium bromide to sugar-derived cyclohexenone, followed by an aldol reaction with a derivative of but-3-enal. The obtained diene is then subjected to an assisted tandem catalytic sequence: ring-closing metathesis with the subsequent reuse of the Ru-catalyst in the syn-dihydroxylation. The stereochemical outcome of these reactions is discussed.

  5. Concerted action of three distinct domains in the DNA cleaving-joining reaction catalyzed by relaxase (TraI) of conjugative plasmid RP4.

    Science.gov (United States)

    Pansegrau, W; Schröder, W; Lanka, E

    1994-01-28

    The TraI protein of plasmid RP4 (IncP alpha) catalyzes a site- and strand-specific cleaving-joining reaction on form I or single-stranded DNA. Thus, TraI is one of the key components involved in the initiation and termination of horizontal DNA transfer by bacterial conjugation. Amino acid sequence comparison revealed three motifs in the TraI sequence conserved in relaxases from different origins. Site-directed mutagenesis of the traI structural gene and application of purified mutant TraI proteins for in vitro assays served to evaluate the functional importance of conserved amino acid residues. Two regions of TraI designated as motifs I and III are involved in catalyzing the cleaving-joining reaction. Motif I carries the tyrosine residue (Tyr-22), which covalently attaches TraI in a transesterification reaction to the 5' terminus of the cleaved DNA. Motif III contains one histidine residue (His-116) essential for relaxase activity and therefore proposed to activate the aromatic hydroxyl group of tyrosine 22 by proton abstraction. Exchange of a serine residue (Ser-74), located in motif II, against alanine prevents formation of stable relaxosomes but strongly enhances topoisomerase activity of the combination TraI/TraJ on form I oriT DNA. Motif II therefore might represent the DNA recognition domain of TraI. Our studies allowed us to establish a model of the interplay of three motifs located in the N-terminal region (amino acid positions 19-124) of TraI.

  6. A computerized method of estimation of sensor motor reaction, complicated with additional cognitive component

    Directory of Open Access Journals (Sweden)

    Gennadij V. Ganin

    2011-05-01

    Full Text Available This article is related to new integrated approach to objective computerizing evaluation of cognitive-component which delays the latent period of the sensor-motor reaction on specific visual stimuli, which carried different semantic information. It is recommended to use this method for clinical diagnostic of pathologies associated with disorders of cognitive human activity and for assessment of mental fatigue.

  7. Addition of CFCl3 to Aromatic Aldehydes via in Situ Grignard Reaction

    Directory of Open Access Journals (Sweden)

    Balaka Barkakaty

    2015-08-01

    Full Text Available Synthetic modification of trichlorofluoromethane (CFCl3 to non-volatile and useful fluorinated precursors is a cost-effective and an environmentally benign strategy for the safe consumption/destruction of the ozone depleting potential of the reagent. In this report, we present a novel method for in situ Grignard reaction using magnesium powder and CFCl3 for synthesis of dichlorofluoromethyl aromatic alcohols.

  8. Highly Efficient Electrocatalysts for Oxygen Reduction Reaction Based on 1D Ternary Doped Porous Carbons Derived from Carbon Nanotube Directed Conjugated Microporous Polymers

    KAUST Repository

    He, Yafei

    2016-10-11

    © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.One-dimensional (1D) porous materials have shown great potential for gas storage and separation, sensing, energy storage, and conversion. However, the controlled approach for preparation of 1D porous materials, especially porous organic materials, still remains a great challenge due to the poor dispersibility and solution processability of the porous materials. Here, carbon nanotube (CNT) templated 1D conjugated microporous polymers (CMPs) are prepared using a layer-by-layer method. As-prepared CMPs possess high specific surface areas of up to 623 m2 g-1 and exhibit strong electronic interactions between p-type CMPs and n-type CNTs. The CMPs are used as precursors to produce heteroatom-doped 1D porous carbons through direct pyrolysis. As-produced ternary heteroatom-doped (B/N/S) 1D porous carbons possess high specific surface areas of up to 750 m2 g-1, hierarchical porous structures, and excellent electrochemical-catalytic performance for oxygen reduction reaction. Both of the diffusion-limited current density (4.4 mA cm-2) and electron transfer number (n = 3.8) for three-layered 1D porous carbons are superior to those for random 1D porous carbon. These results demonstrate that layered and core-shell type 1D CMPs and related heteroatom-doped 1D porous carbons can be rationally designed and controlled prepared for high performance energy-related applications.

  9. Additive effects of trans-10, cis-12 conjugated linoleic acid and propionic acid on milk fat content and composition in dairy cows.

    Science.gov (United States)

    Maxin, Gaëlle; Glasser, Frédéric; Rulquin, Henri

    2010-08-01

    Diet is a relatively simple way to modify milk fat yield and composition in dairy cows as the end-products of digestion are precursors or inhibitors of milk fat synthesis. The individual effects of these end-products are well-known, but it is still not known whether these nutrients have an additive effect or an interaction effect on milk fat secretion. Thus our objective was to investigate the effects of two of these nutrients on milk fat secretion, trans-10, cis-12 conjugated linoleic acid (CLA) and propionic acid (C3) supplied alone or together, under the same experimental conditions. Four Holstein dairy cows were used in a 4x4 Latin square design with 14-d periods. Treatments were control, CLA (duodenal infusion of 1.85 g/d of trans-10, cis-12 CLA), C3 (ruminal infusion of 500 g/d of C3) and CLA+C3 (duodenal infusion of 1.85 g/d of trans-10, cis-12 CLA plus ruminal infusion 500 g/d of C3). Infusions of trans-10, cis-12 CLA reduced milk fat content and yield by 18% whereas C3 infusions had no significant effect on milk fat secretion. Trans-10, cis-12 CLA decreased the yields of all milk fatty acids (FA). This reduction was proportionally greater for FA synthesized de novo than for preformed long-chain FA. Infusions of C3 decreased the yields and percentages of 4:0 and 18:0 and increased the yields and percentages of all odd-chain FA. Interactions between trans-10, cis-12 CLA and C3 infusions on milk fat content, yield and FA composition were never significant. Overall, this study showed that trans-10, cis-12 CLA has different and greater effects on milk fat secretion than C3. Moreover, under our experimental conditions, their effects on milk FA yields, which reflect their effects on mammary lipogenesis, were additive, whatever their individual effect.

  10. Gold nanoparticle-enzyme conjugates based FRET for highly sensitive determination of hydrogen peroxide, glucose and uric acid using tyramide reaction.

    Science.gov (United States)

    Huang, Xiangyi; Lan, Tao; Zhang, Bocheng; Ren, Jicun

    2012-08-21

    In this paper, we report a new strategy for highly sensitive determination of hydrogen peroxide, glucose and uric acid based on fluorescence resonance energy transfer (FRET) using gold nanoparticles (AuNPs) as energy acceptors. The principle is based on highly sensitive reaction of tetramethyl rhodamine (TMR) labeled tyramide and hydrogen peroxide catalysed by horseradish peroxidase (HRP), and the fluorescence spectrum of TMR (EX(max) 575 nm) partially overlaps with the visible absorption bands of AuNPs. We demonstrated an efficient FRET between tyramide labeled TMR (as energy donors) and HRP (BSA) conjugated AuNPs (as energy acceptors) due to the formation of TMR-labeled HRP-AuNPs or TMR-labeled BSA-AuNPs in the presence of H(2)O(2). We observed that the quenching of the fluorescence signal depended linearly on the H(2)O(2) concentration within a range of concentrations from 25 to 400 nM and the detection limit of this assay was 10 nM. Based on the principle for determination of H(2)O(2), we developed a new strategy for assay of glucose and uric acid by coupling with glucose oxidase (GOx)-mediated and uricase-mediated reaction. The established methods were successfully used for determination of glucose and uric acid levels in human sera, and the results obtained are in good agreement with commercially available methods. Our methods are at least 1 order of magnitude more sensitive than the commercially available methods. More importantly, our method described here can be extended to other assay designs using different oxidase enzymes, energy donors and energy acceptors, such as fluorescent quantum dots, near-infrared (NIR)-to-visible upconversion nanoparticles and even other metallic nanoparticles.

  11. Improvement of Emulsifying Properties of Wheat Gluten Hydrolysate λ-Carrageenan Conjugates

    Directory of Open Access Journals (Sweden)

    Jin-Shui Wang

    2006-01-01

    Full Text Available Gluten hydrolysate was prepared through limited enzymatic hydrolysis of wheat gluten resulting from the byproducts of wheat starch. The enzyme applied in the present study was Protamex. Response surface methodology was used to investigate the effects of pH, gluten hydrolysate (GHPλ-carrageenan (C ratio and reaction time on emulsifying properties of the GHP-C conjugate. The regression model for emulsion activity index (EAI was significant at p=0.001, while reaction time had a significant effect on EAI of the conjugate with regression coefficient of 4.25. The interactions of pH and GHP/ C ratio, and GHP/C ratio and reaction time significantly affected the EAI of the conjugate. Both the emulsifying property and nitrogen solubility index (NSI of GHP-C conjugate prepared under the optimal conditions increased more remarkably, compared to the control. The denaturation temperature of GHP-C conjugate obviously increased compared to wheat gluten. The addition of GHP-C conjugate had different effects on dough characteristics. Moreover, this conjugate can delay the increase in the bread crumb firmness during storage. It demonstrated that this conjugate couldimprove the dough characteristics and had anti-staling properties of bread.

  12. Evaluation of the kinetics of beta-elimination reactions of selenocysteine Se-conjugates in human renal cytosol : possible implications for the use as kidney selective prodrugs

    NARCIS (Netherlands)

    Rooseboom, M; Vermeulen, N P; Andreadou, I; Commandeur, J N

    This study was performed to evaluate whether selenocysteine Se-conjugates are substrates for human cysteine conjugate beta-lyase enzymes. By testing kidney cytosols of three different humans, we studied interindividual differences in beta-lyase enzymes in humans. A series of 22 selenocysteine

  13. Third O2 addition reactions promote the low-temperature auto-ignition of n-alkanes

    KAUST Repository

    Wang, Zhandong

    2016-01-20

    Comprehensive low-temperature oxidation mechanisms are needed to accurately predict fuel auto-ignition properties. This paper studies the effects of a previously unconsidered third O2 addition reaction scheme on the simulated auto-ignition of n-alkanes. We demonstrate that this extended low-temperature oxidation scheme has a minor effect on the simulation of n-pentane ignition; however, its addition significantly improves the prediction of n-hexane auto-ignition under low-temperature rapid compression machine conditions. Additional simulations of n-hexane in a homogeneous charge compression ignition engine show that engine-operating parameters (e.g., intake temperature and combustion phasing) are significantly altered when the third O2 addition kinetic mechanism is considered. The advanced combustion phasing is initiated by the formation and destruction of additional radical chain-branching intermediates produced in the third O2 addition process, e.g. keto-dihydroperoxides and/or keto-hydroperoxy cyclic ethers. Our results indicate that third O2 addition reactions accelerate low-temperature radical chain branching at conditions of relevance to advance engine technologies, and therefore these chemical pathways should also be considered for n-alkanes with 6 or more carbon atoms. © 2015 The Combustion Institute.

  14. One-pot peptide and protein conjugation: a combination of enzymatic transamidation and click chemistry.

    Science.gov (United States)

    Rachel, N M; Pelletier, J N

    2016-02-11

    Enzymatic transamidation and copper-catalyzed azide-alkyne cycloaddition (CuAAC) were combined to yield covalently conjugated peptides and proteins. The addition of glutathione preserved enzymatic activity in the presence of copper. Tuning the reaction kinetics was key to success, providing up to 95% conversion. This one-pot reaction allowed for targeted fluorescent protein labeling.

  15. A versatile and efficient approach for the synthesis of chiral 1,3-nitroamines and 1,3-diamines via conjugate addition to new (S,E-γ-aminated nitroalkenes derived from L-α-amino acids

    Directory of Open Access Journals (Sweden)

    Vera Lúcia Patrocinio Pereira

    2013-04-01

    Full Text Available New chiral (S,E-γ-N,N-dibenzylated nitroalkenes 2a–c were synthesized from natural L-(α-amino acids in five steps with overall yields of 68–88%. The conjugate addition of hydride, methoxide, nitronate and azide nucleophiles to 2a–c led to the corresponding chiral 1,3-nitroamines in 74–90% yield. The conjugate addition of cyanide anion to 2a,b was followed by HNO2 elimination affording chiral aminated acrylonitriles (73–98%. On the other hand, the azide anion reacted with 2a, in acetonitrile, via a [3 + 2]-cycloaddition in which HNO2 was lost, providing the corresponding 1,2,3-triazole derivative. Direct reduction of 1,3-nitroamine derivatives 9a,b produced the corresponding 1,3-diamines in good yields.

  16. A versatile and efficient approach for the synthesis of chiral 1,3-nitroamines and 1,3-diamines via conjugate addition to new (S,E)-γ-aminated nitroalkenes derived from L-α-amino acids.

    Science.gov (United States)

    Pereira, Vera Lúcia Patrocinio; Moura, André Luiz da Silva; Vieira, Daniel Pais Pires; de Carvalho, Leandro Lara; Torres, Eliz Regina Bueno; Costa, Jeronimo da Silva

    2013-01-01

    New chiral (S,E)-γ-N,N-dibenzylated nitroalkenes 2a-c were synthesized from natural L-(α)-amino acids in five steps with overall yields of 68-88%. The conjugate addition of hydride, methoxide, nitronate and azide nucleophiles to 2a-c led to the corresponding chiral 1,3-nitroamines in 74-90% yield. The conjugate addition of cyanide anion to 2a,b was followed by HNO2 elimination affording chiral aminated acrylonitriles (73-98%). On the other hand, the azide anion reacted with 2a, in acetonitrile, via a [3 + 2]-cycloaddition in which HNO2 was lost, providing the corresponding 1,2,3-triazole derivative. Direct reduction of 1,3-nitroamine derivatives 9a,b produced the corresponding 1,3-diamines in good yields.

  17. The GC-MS Observation of Intermediates in a Stepwise Grignard Addition Reaction

    Science.gov (United States)

    Latimer, Devin

    2007-01-01

    Preparation of phenylmagnesium bromide described by Eckert, addition of three equivalents of Grignard reagent to diethyl carbonate to form triphenylmethanol and a series of GC-MS procedures that form intermediates. The analysis is consistent with a gas chromatogram and mass spectrum for each of the expected intermediates and final product of the…

  18. Synthesis of a Fluorescent Acridone Using a Grignard Addition, Oxidation, and Nucleophilic Aromatic Substitution Reaction Sequence

    Science.gov (United States)

    Goodrich, Samuel; Patel, Miloni; Woydziak, Zachary R.

    2015-01-01

    A three-pot synthesis oriented for an undergraduate organic chemistry laboratory was developed to construct a fluorescent acridone molecule. This laboratory experiment utilizes Grignard addition to an aldehyde, alcohol oxidation, and iterative nucleophilic aromatic substitution steps to produce the final product. Each of the intermediates and the…

  19. RRKM and master equation kinetic analysis of parallel addition reactions of isomeric radical intermediates in hydrocarbon flames

    Science.gov (United States)

    Winter, Pierre M.; Rheaume, Michael; Cooksy, Andrew L.

    2017-08-01

    We have calculated the temperature-dependent rate coefficients of the addition reactions of butadien-2-yl (C4H5) and acroylyl (C3H3O) radicals with ethene (C2H4), carbon monoxide (CO), formaldehyde (H2CO), hydrogen cyanide (HCN), and ketene (H2CCO), in order to explore the balance between kinetic and thermodynamic control in these combustion-related reactions. For the C4H5 radical, the 1,3-diene form of the addition products is more stable than the 1,2-diene, but the 1,2-diene form of the radical intermediate is stabilized by an allylic delocalization, which may influence the relative activation energies. For the reactions combining C3H3O with C2H4, CO, and HCN, the opposite is true: the 1,2-enone form of the addition products is more stable than the 1,3-enone, whereas the 1,3-enone is the slightly more stable radical species. Optimized geometries and vibrational modes were computed with the QCISD/aug-cc-pVDZ level and basis, followed by single-point CCSD(T)-F12a/cc-pVDZ-F12 energy calculations. Our findings indicate that the kinetics in all cases favor reaction along the 1,3 pathway for both the C4H5 and C3H3O systems. The Rice-Ramsperger-Kassel-Marcus (RRKM) microcanonical rate coefficients and subsequent solution of the chemical master equation were used to predict the time-evolution of our system under conditions from 500 K to 2000 K and from 10-5 bar to 10 bars. Despite the 1,3 reaction pathway being more favorable for the C4H5 system, our results predict branching ratios of the 1,2 to 1,3 product as high as 0.48 at 1 bar. Similar results hold for the acroylyl system under these combustion conditions, suggesting that under kinetic control the branching of these reactions may be much more significant than the thermodynamics would suggest. This effect may be partly attributed to the low energy difference between 1,2 and 1,3 forms of the radical intermediate. No substantial pressure-dependence is found for the overall forward reaction rates until pressures

  20. TREHALOSE-BASED ADDITIVE IMPROVED INTER-PRIMER BINDING SITE REACTIONS FOR DNA ISOLATED FROM RECALCITRANT PLANTS

    Directory of Open Access Journals (Sweden)

    Veronika Lancíková

    2014-02-01

    Full Text Available Trehalose-based (TBT-PAR additive was tested in order to optimize PCR amplification for DNA isolated from recalcitrant plants. Retrotransposon-based inter-primer binding site reactions were significantly improved with TBT-PAR solution using genomic DNA isolated from flax (Linum usitatissimum L., genotypes Kyivskyi, Bethune grown in radio-contaminated and non-radioactive remediated Chernobyl experimental fields. Additionally, similar improvements were observed using 19 recalcitrant genotypes of maize (Zea mays L. and three genotypes of yacon (Smallanthus sonchifolius, Poepp. et Endl., genotypes PER05, ECU45, BOL22 grown in standard field conditions.

  1. Combustion Synthesis of UHTC Composites from Ti–B4C Solid State Reaction with Addition of VIb Transition Metals

    Directory of Open Access Journals (Sweden)

    Chun-Liang Yeh

    2017-06-01

    Full Text Available UHTC composites were prepared by self-propagating high-temperature synthesis (SHS from the Ti–B4C reaction system with addition of Cr, Mo, and W. The starting sample composition was formulated as (3−xTi + B4C + xMe with x = 0.1–1.0 and Me = Cr, Mo, or W. For all samples conducted in this study, self-sustaining combustion was well established and propagated with a distinct reaction front. With no addition of Cr, Mo, or W, solid state combustion of the 3Ti + B4C sample featuring a combustion front temperature (Tc of 1766 °C and a combustion wave velocity (Vf of 16.5 mm/s was highly exothermic and produced an in situ composite of 2TiB2 + TiC. When Cr, Mo, or W was adopted to replace a portion of Ti, the reaction exothermicity was lowered, and hence, a significant decrease in Tc (from 1720 to 1390 °C and Vf (from 16.1 to 3.9 mm/s was observed. With addition of Cr, Mo, and W, the final products were CrB-, MoB-, and WB-added TiB2–TiC composites. The absence of CrB2, MoB2, and WB2 was attributed partly to the loss of boron from thermal decomposition of B4C and partly to lack of sufficient reaction time inherent to the SHS process.

  2. Conjugal violence

    Directory of Open Access Journals (Sweden)

    Simona Mihaiu

    2015-10-01

    Full Text Available Scientific knowledge of different aspects related to conjugal violence is highly important for people directly involved, such as researchers, practitioners and the entire society. In this respect, globally, specialised studies continue to advance, offer correct definitions, clear descriptions, convincing assessments to certain issues, encouraging thus long-term research, since some specialists have managed to overcome restrictive or ideological methods and explanations. Moreover, in practice, debates reach almost all social, political and legal dimensions regarding appropriate and efficient forms of preventing conjugal violence. Unfortunately, in Romania there are fewer research and prevention approaches of this social problem. In general, attention is directed to domestic violence and conjugal violence is dealt with only implicitly. Considering the given context, the aim of the paper is to outline, by analysing specialised literature, a new research direction and implicitly, social intervention. I specify that this article represents a stage in the ongoing postdoctoral research project, entitled "Conjugal homicide. Aggressors and victims".

  3. Reaction Mechanism of Organocatalytic Michael Addition of Nitromethane to Cinnamaldehyde: A Case Study on Catalyst Regeneration and Solvent Effects.

    Science.gov (United States)

    Świderek, Katarzyna; Nödling, Alexander R; Tsai, Yu-Hsuan; Luk, Louis Y P; Moliner, Vicent

    2018-01-11

    The Michael addition of nitromethane to cinnamaldehyde has been computationally studied in the absence of a catalyst and the presence of a biotinylated secondary amine by a combined computational and experimental approach. The calculations were performed at the density functional theory (DFT) level with the M06-2X hybrid functional, and a polarizable continuum model has been employed to mimic the effect of two different solvents: dichloromethane (DCM) and water. Contrary to common assumption, the product-derived iminium intermediate was absent in both of the solvents tested. Instead, hydrating the C1-C2 double bond in the enamine intermediate directly yields the tetrahedral intermediate, which is key for forming the product and regenerating the catalyst. Enamine hydration is concerted and found to be rate-limiting in DCM but segregated into two non-rate-limiting steps when the solvent is replaced with water. However, further analysis revealed that the use of water as solvent also raises the energy barriers for other chemical steps, particularly the critical step of C-C bond formation between the iminium intermediate and nucleophile; this consequently lowers both the reaction yield and enantioselectivity of this LUMO-lowering reaction, as experimentally detected. These findings provide a logical explanation to why water often enhances organocatalysis when used as an additive but hampers the reaction progress when employed as a solvent.

  4. Glutathione conjugation and contaminant transformation

    Science.gov (United States)

    Field, Jennifer A.; Thurman, E.M.

    1996-01-01

    The recent identification of a novel sulfonated metabolite of alachlor in groundwater and metolachlor in soil is likely the result of glutathione conjugation. Glutathione conjugation is an important biochemical reaction that leads, in the case of alachlor, to the formation of a rather difficult to detect, water-soluble, and therefore highly mobile, sulfonated metabolite. Research from weed science, toxicology, and biochemistry is discussed to support the hypothesis that glutathione conjugation is a potentially important detoxification pathway carried out by aquatic and terrestrial plants and soil microorganisms. A brief review of the biochemical basis for glutathione conjugation is presented. We recommend that multidisciplinary research focus on the occurrence and expression of glutathione and its attendant enzymes in plants and microorganisms, relationships between electrophilic substrate structure and enzyme activity, and the potential exploitation of plants and microorganisms that are competent in glutathione conjugation for phytoremediation and bioremediation.

  5. Density functional theoretical study on the C-F and C-O oxidative addition reaction at an AI center

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yong Seong [Dept. of Science Education, Kyungnam University, Masan (Korea, Republic of); Cho, Hyun; Hwang, Sungu [Dept. of Nanomechatronics Engineering, Pusan National University, Miryang (Korea, Republic of)

    2017-02-15

    In this study, B3LYP/LACVP** level calculations were chosen because the level of theory was applied successfully to calculations of the thermodynamic and kinetic features of the oxidative addition reactions of alkyl and aryl halides to pincer-type complexes. This study examined the effects of the substituents on the phenyl rings of the Al(I) center. Isopropyl side chains in the phenyl rings attached to N atoms of the pincer ligand were replaced with a methyl (Me) (2) or tertiary butyl ( t Bu) group. The oxidative addition of C[BOND]F and C[BOND]O bonds to an Al (I) center was investigated computationally by DFT calculations. The geometries, thermodynamic, and kinetic features were in good agreement with the experimental data, as in previous studies on the transition metal complexes. The computational results showed that the DFT calculations could provide qualitative insight into the reactivity and thermodynamics of the oxidative addition reactions of C[BOND]F bonds.

  6. The role of solvent on selective hydrogenation of conjugated and isolated C dbnd C of Citral (3,7-dimethyl 2,6-octadienal) - a self-consistent reaction field study

    Science.gov (United States)

    Chatterjee, Abhijit; Chatterjee, Maya; Ikushima, Yutaka; Mizukami, Fujio

    2004-09-01

    Self-consistent reaction field study was performed to rationalize the selective formation of 3,7-dimethyloctanal by hydrogenation of citral (3,7-dimethyl 2,6-octadienal) exclusively in supercritical carbon dioxide medium. We have used density functional theory (DFT) to calculate and compare the reactivity of the atoms present in the reactant molecule for a range of solvent with variable dielectric constant. Solvent with low dielectric constant was found to be reducing the electrophilicity of the sites present and hence enhances the selectivity of an isolated and conjugated C dbnd C bond-breaking phenomenon. In contrast to that, solvents with high dielectric constant prefer to hydrogenate the conjugated C dbnd C. The geometric and electronic aspects were compared to propose a plausible explanation for the unprecedented selectivity observed in supercritical carbon dioxide medium.

  7. Understanding the influence of temperature change and cosolvent addition on conversion rate of enzymatic suspension reactions based on regime analysis.

    Science.gov (United States)

    Wolff, A; Zhu, L; Wong, Y W; Straathof, A J; Jongejan, J A; Heijnen, J J

    1999-01-20

    It is a commonly held belief that enzymatic conversions of substrate in aqueous suspensions can be speeded up by raising the temperature or adding organic solvents to promote dissolution of the substrate. To quantify the impact of such changes, we studied the alpha-chymotrypsin-catalyzed hydrolysis of dimethyl benzylmethylmalonate as a model system. It was found that, upon addition of organic cosolvents, longer process times were actually required, even though the substrate solubility increased severalfold as expected. Upon raising the temperature from 25 degrees C to 37 degrees C, on the other hand, both the substrate solubility, the substrate dissolution rate, and the enzymatic reaction rate increased, leading to shorter process times. A dissolution-reaction model incorporating the kinetics of enzyme deactivation could be developed. A simple relation for the prediction of the overall process time was established by evaluating the time constants for the subprocesses: substrate dissolution; enzymatic conversion; and enzyme deactivation. Using regime analysis, rules of thumb for the optimization of an enzymatic suspension reaction were derived. Copyright 1999 John Wiley & Sons, Inc.

  8. Citrus Peel Additives for One-Pot Triazole Formation by Decarboxylation, Nucleophilic Substitution, and Azide-Alkyne Cycloaddition Reactions

    Science.gov (United States)

    Mendes, Desiree E.; Schoffstall, Allen M.

    2011-01-01

    This undergraduate organic laboratory experiment consists of three different reactions occurring in the same flask: a cycloaddition reaction, preceded by decarboxylation and nucleophilic substitution reactions. The decarboxylation and cycloaddition reactions occur using identical Cu(I) catalyst and conditions. Orange, lemon, and other citrus fruit…

  9. Hydrogenation of O and OH on Pt(111): a comparison between the reaction rates of the first and the second hydrogen addition steps.

    Science.gov (United States)

    Näslund, L-Å

    2014-03-14

    The formation of water through hydrogenation of oxygen on platinum occurs at a surprisingly low reaction rate. The reaction rate limited process for this catalytic reaction is, however, yet to be settled. In the present work, the reaction rates of the first and the second hydrogen addition steps are compared when hydrogen is obtained through intense synchrotron radiation that induces proton production in a water overlayer on top of the adsorbed oxygen species. A substantial amount of the produced hydrogen diffuses to the platinum surface and promotes water formation at the two starting conditions O/Pt(111) and (H2O+OH)/Pt(111). The comparison shows no significant difference in the reaction rate between the first and the second hydrogen addition steps, which indicates that the rate determining process of the water formation from oxygen on Pt(111) is neither the first nor the second H addition step or, alternatively, that both H addition steps exert rate control.

  10. Antibody-protein A conjugated quantum dots for multiplexed imaging of surface receptors in living cells.

    Science.gov (United States)

    Jin, Takashi; Tiwari, Dhermendra K; Tanaka, Shin-Ichi; Inouye, Yasushi; Yoshizawa, Keiko; Watanabe, Tomonobu M

    2010-11-01

    To use quantum dots (QDs) as fluorescent probes for receptor imaging, QD surface should be modified with biomolecules such as antibodies, peptides, carbohydrates, and small-molecule ligands for receptors. Among these QDs, antibody conjugated QDs are the most promising fluorescent probes. There are many kinds of coupling reactions that can be used for preparing antibody conjugated QDs. Most of the antibody coupling reactions, however, are non-selective and time-consuming. In this paper, we report a facile method for preparing antibody conjugated QDs for surface receptor imaging. We used ProteinA as an adaptor protein for binding of antibody to QDs. By using ProteinA conjugated QDs, various types of antibodies are easily attached to the surface of the QDs via non-covalent binding between the F(c) (fragment crystallization) region of antibody and ProteinA. To show the utility of ProteinA conjugated QDs, HER2 (anti-human epidermal growth factor receptor 2) in KPL-4 human breast cancer cells were stained by using anti-HER2 antibody conjugated ProteinA-QDs. In addition, multiplexed imaging of HER2 and CXCR4 (chemokine receptor) in the KPL-4 cells was performed. The result showed that CXCR4 receptors coexist with HER2 receptors in the membrane surface of KPL-4 cells. ProteinA mediated antibody conjugation to QDs is very useful to prepare fluorescent probes for multiplexed imaging of surface receptors in living cells.

  11. Physicochemical properties of β-carotene emulsions stabilized by chlorogenic acid-lactoferrin-glucose/polydextrose conjugates.

    Science.gov (United States)

    Liu, Fuguo; Wang, Di; Xu, Honggao; Sun, Cuixia; Gao, Yanxiang

    2016-04-01

    In this study, the influence of chlorogenic acid (CA)-lactoferrin (LF)-glucose (Glc) conjugate and CA-LF-polydextrose (PD) conjugate on the physicochemical characteristics of β-carotene emulsions was investigated. Novel emulsifiers were formed during Maillard reaction between CA-LF conjugate and Glc/PD. The physicochemical properties of β-carotene emulsions were characterized by droplet size, ζ-potential, rheological behavior, transmission changes during centrifugal sedimentation and β-carotene degradation. Results showed that the covalent attachment of Glc or PD to CA-LF conjugate effectively increased the hydrophilicity of the oil droplets surfaces and strengthened the steric repulsion between the oil droplets. Glucose was better than polydextrose for the conjugation with CA-LF conjugate to stabilize β-carotene emulsions. In comparison with LF and CA-LF-Glc/PD mixtures, CA-LF-Glc/PD ternary conjugates exhibited better emulsifying properties and improved physical stability of β-carotene emulsions during the freeze-thaw treatment. In addition, CA-LF-Glc/PD conjugates significantly enhanced chemical stability of β-carotene in the emulsions against ultraviolet light exposure. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Aza-Michael Reaction for an Undergraduate Organic Chemistry Laboratory

    Science.gov (United States)

    Nigam, Manisha; Rush, Brittney; Patel, Jay; Castillo, Raul; Dhar, Preeti

    2016-01-01

    A green, aza-Michael reaction is described that can be used to teach undergraduate students conjugate addition of nitrogen nucleophile to an a,ß-unsaturated ester. Students analyze spectral data of the product obtained from the assigned reaction to determine product structure and propose the mechanism of its formation. The experiment requires…

  13. Effects of the method of apatite seed crystals addition on setting reaction of α-tricalcium phosphate based apatite cement.

    Science.gov (United States)

    Tsuru, Kanji; Ruslin; Maruta, Michito; Matsuya, Shigeki; Ishikawa, Kunio

    2015-10-01

    Appropriate setting time is an important parameter that determines the effectiveness of apatite cement (AC) for clinical application, given the issues of crystalline inflammatory response phenomena if AC fails to set. To this end, the present study analyzes the effects of the method of apatite seed crystals addition on the setting reaction of α-tricalcium phosphate (α-TCP) based AC. Two ACs, both consisting of α-TCP and calcium deficient hydroxyapatite (cdHAp), were analyzed in this study. In one AC, cdHAp was added externally to α-TCP and this AC was abbreviated as AC(EA). In the other AC, α-TCP was partially hydrolyzed to form cdHAp on the surface of α-TCP. This AC was referred to as AC(PH). Results indicate a decrease in the setting time of both ACs with the addition of cdHAp. Among them, for the given amount of added cdHAp, AC(PH) showed relatively shorter setting time than AC(EA). Besides, the mechanical strength of the set AC(PH) was also higher than that of set AC(EA). These properties of AC(PH) were attributed to the predominant crystal growth of cdHAp in the vicinity of the α-TCP particle surface. Accordingly, it can be concluded that the partial hydrolysis of α-TCP may be a better approach to add low crystalline cdHAp onto α-TCP based AC.

  14. Characterization and mechanism insight of accelerated catalytic promiscuity of Sulfolobus tokodaii (ST0779) peptidase for aldol addition reaction.

    Science.gov (United States)

    Li, Rong; Perez, Bianca; Jian, Hui; Jensen, Mads Mørk; Gao, Renjun; Dong, Mingdong; Glasius, Marianne; Guo, Zheng

    2015-11-01

    A novel peptidase from thermophilic archaea Sulfolobus tokodaii (ST0779) is examined for its catalytic promiscuity of aldol addition, which shows comparable activity as porcine pancreatic lipase (PPL, one of the best enzymes identified for biocatalytic aldol addition) at 30 °C but much accelerated activity at elevated temperature. The molecular catalytic efficiency kcat/Km (M(-1) s(-1)) of this thermostable enzyme at 55 °C adds up to 140 times higher than that of PPL at its optimum temperature 37 °C. The fluorescence quenching analysis depicts that the binding constants of PPL are significantly higher than those of ST0779, and their numbers of binding sites show opposite temperature dependency. Thermodynamic parameters estimated by fluorescence quenching analysis unveil distinctly different substrate-binding modes between PPL and ST0779: the governing binding interaction between PPL and substrates is hydrophobic force, while the dominating substrate-binding forces for ST0779 are van der Waals and H-bonds interactions. A reasonable mechanism for ST0779-catalyzed aldol reaction is proposed based on kinetic study, spectroscopic analysis, and molecular stereostructure simulation. This work represents a successful example to identify a new enzyme for catalytic promiscuity, which demonstrates a huge potential to discover and exploit novel biocatalyst from thermophile microorganism sources.

  15. Conjugal violence

    OpenAIRE

    Simona Mihaiu

    2015-01-01

    Scientific knowledge of different aspects related to conjugal violence is highly important for people directly involved, such as researchers, practitioners and the entire society. In this respect, globally, specialised studies continue to advance, offer correct definitions, clear descriptions, convincing assessments to certain issues, encouraging thus long-term research, since some specialists have managed to overcome restrictive or ideological methods and explanations. Moreover, in practice,...

  16. A STUDY OF THE ADDITION OF CHOLESTERIN TO THE ALCOHOLIC EXTRACTS OF TISSUES USED FOR ANTIGENS IN THE WASSERMANN REACTION.

    Science.gov (United States)

    Walker, I C; Swift, H F

    1913-07-01

    1. The addition of cholesterin to an alcoholic extract of heart or fetal liver increases the antigenic value of the extracts in the Wassermann reaction. 2. The optimum amount of cholesterin to be added to heart extract or fetal liver extract was found to be 0.4 per cent. 3. Cholesterin-heart extracts are superior to cholesterin-liver extracts and to alcoholic extracts of syphilitic livers, as well as to ether extracts of dried hearts. 4. Cholesterin-heart extracts prepared from different human hearts are practically equal in anticomplementary and antigenic value. Similar extracts prepared from guinea pig hearts have the same antigenic value as those prepared from human hearts. Both the human heart and the guinea pig heart extracts are superior to beef heart extract when the same amount of cholesterin is added to each of the extracts. 5. In testing blood serum for diagnostic purposes, it is not safe to use more than one fourth of the anticomplementary dose of the 0.4 per cent. cholesterin heart extract. In the work here presented, this consisted of a 1 in 10 emulsion. 6. In testing cerebrospinal fluids, 1 in 10 emulsions give slightly better reactions with smaller quantities of the fluid than do 1 in 6 emulsions. 7. Because of the simple preparation, the superior antigenic property, and the constant antigen value of cholesterin-heart extracts prepared from human hearts, we agree with McIntosh and Fildes that this form of extract fulfills the requirements of a standard antigen.

  17. High-Performance Long-Term-Stable Dopant-Free Perovskite Solar Cells and Additive-Free Organic Solar Cells by Employing Newly Designed Multirole π-Conjugated Polymers.

    Science.gov (United States)

    Kranthiraja, Kakaraparthi; Gunasekar, Kumarasamy; Kim, Hyunji; Cho, An-Na; Park, Nam-Gyu; Kim, Seonha; Kim, Bumjoon J; Nishikubo, Ryosuke; Saeki, Akinori; Song, Myungkwan; Jin, Sung-Ho

    2017-06-01

    Perovskite solar cells (PSCs) and organic solar cells (OSCs) are promising renewable light-harvesting technologies with high performance, but the utilization of hazardous dopants and high boiling additives is harmful to all forms of life and the environment. Herein, new multirole π-conjugated polymers (P1-P3) are developed via a rational design approach through theoretical hindsight, further successfully subjecting them into dopant-free PSCs as hole-transporting materials and additive-free OSCs as photoactive donors, respectively. Especially, P3-based PSCs and OSCs not only show high power conversion efficiencies of 17.28% and 8.26%, but also display an excellent ambient stability up to 30 d (for PSCs only), owing to their inherent superior optoelectronic properties in their pristine form. Overall, the rational approach promises to support the development of environmentally and economically sustainable PSCs and OSCs. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. The Coupled Photothermal Reaction and Transport in a Laser Additive Metal Nanolayer Simultaneous Synthesis and Pattering for Flexible Electronics.

    Science.gov (United States)

    Tsai, Song-Ling; Liu, Yi-Kai; Pan, Heng; Liu, Chien-Hung; Lee, Ming-Tsang

    2016-01-08

    The Laser Direct Synthesis and Patterning (LDSP) technology has advantages in terms of processing time and cost compared to nanomaterials-based laser additive microfabrication processes. In LDSP, a scanning laser on the substrate surface induces chemical reactions in the reactive liquid solution and selectively deposits target material in a preselected pattern on the substrate. In this study, we experimentally investigated the effect of the processing parameters and type and concentration of the additive solvent on the properties and growth rate of the resulting metal film fabricated by this LDSP technology. It was shown that reactive metal ion solutions with substantial viscosity yield metal films with superior physical properties. A numerical analysis was also carried out the first time to investigate the coupled opto-thermo-fluidic transport phenomena and the effects on the metal film growth rate. To complete the simulation, the optical properties of the LDSP deposited metal film with a variety of thicknesses were measured. The characteristics of the temperature field and the thermally induced flow associated with the moving heat source are discussed. It was shown that the processing temperature range of the LDSP is from 330 to 390 K. A semi-empirical model for estimating the metal film growth rate using this process was developed based on these results. From the experimental and numerical results, it is seen that, owing to the increased reflectivity of the silver film as its thickness increases, the growth rate decreases gradually from about 40 nm at initial to 10 nm per laser scan after ten scans. This self-controlling effect of LDSP process controls the thickness and improves the uniformity of the fabricated metal film. The growth rate and resulting thickness of the metal film can also be regulated by adjustment of the processing parameters, and thus can be utilized for controllable additive nano/microfabrication.

  19. The Coupled Photothermal Reaction and Transport in a Laser Additive Metal Nanolayer Simultaneous Synthesis and Pattering for Flexible Electronics

    Directory of Open Access Journals (Sweden)

    Song-Ling Tsai

    2016-01-01

    Full Text Available The Laser Direct Synthesis and Patterning (LDSP technology has advantages in terms of processing time and cost compared to nanomaterials-based laser additive microfabrication processes. In LDSP, a scanning laser on the substrate surface induces chemical reactions in the reactive liquid solution and selectively deposits target material in a preselected pattern on the substrate. In this study, we experimentally investigated the effect of the processing parameters and type and concentration of the additive solvent on the properties and growth rate of the resulting metal film fabricated by this LDSP technology. It was shown that reactive metal ion solutions with substantial viscosity yield metal films with superior physical properties. A numerical analysis was also carried out the first time to investigate the coupled opto-thermo-fluidic transport phenomena and the effects on the metal film growth rate. To complete the simulation, the optical properties of the LDSP deposited metal film with a variety of thicknesses were measured. The characteristics of the temperature field and the thermally induced flow associated with the moving heat source are discussed. It was shown that the processing temperature range of the LDSP is from 330 to 390 K. A semi-empirical model for estimating the metal film growth rate using this process was developed based on these results. From the experimental and numerical results, it is seen that, owing to the increased reflectivity of the silver film as its thickness increases, the growth rate decreases gradually from about 40 nm at initial to 10 nm per laser scan after ten scans. This self-controlling effect of LDSP process controls the thickness and improves the uniformity of the fabricated metal film. The growth rate and resulting thickness of the metal film can also be regulated by adjustment of the processing parameters, and thus can be utilized for controllable additive nano/microfabrication.

  20. Low-molecular-weight model study of peroxide cross-linking of ethylene-propylene-diene rubber using gas chromatography and mass spectrometry: II. Addition and combination reactions

    NARCIS (Netherlands)

    Peters, R.; van Duin, M.; Tonoli, D.; Kwakkenbos, G.; Mengerink, Y.; van Benthem, R.A.T.M.; de Koster, C.G.; Schoenmakers, P.J.; van der Wal, S.

    2008-01-01

    The dicumyl-peroxide-initiated addition and combination reactions of mixtures of alkanes (n-octane, n-decane) and alkenes [5,6-dihydrodicyclopentadiene (DCPDH), 5-ethylidene-2-norbornane (ENBH) and 5-vinylidene-2-norbornane (VNBH)] were studied to mimic the peroxide cross-linking reactions of

  1. Enantioselective Cu-II-Catalyzed Diels-Alder and Michael Addition Reactions in Water Using Bio-Inspired Triazacyclophane-Based Ligands

    NARCIS (Netherlands)

    Albada, H. Bauke; Rosati, Fiora; Coquiere, David; Roelfes, Gerard; Liskamp, Rob M. J.

    A triazacyclophane (TAC) scaffold decorated with three histidine amino acid residues was used as a tridentate ligand in asymmetric copper(II)-catalysed Diels-Alder and Michael addition reactions in water. Enantiomeric excesses up to 55% were obtained in Diels-Alder reactions using ligands in which

  2. Additive effects of inflammation and stress reaction on Toll-like receptor 4-mediated growth of endometriotic stromal cells.

    Science.gov (United States)

    Khan, Khaleque Newaz; Kitajima, Michio; Inoue, Tsuneo; Tateishi, Seiko; Fujishita, Akira; Nakashima, Masahiro; Masuzaki, Hideaki

    2013-10-01

    for ESCs from control women. Exogenous treatment with either HSP70 or LPS significantly stimulated the production of IL-6 and TNFα by M[Symbol: see text] and promoted the proliferation of ESCs, and a significant additive effect between LPS and HSP70 was observed. While individual treatment with either polymyxin B, an LPS antagonist, or anti-HSP70 antibody was unable to suppress the combined effects of LPS and HSP70 on cytokine secretion or ESC proliferation, pretreatment of cells with the anti-TLR4 antibody was able to significantly suppress their combined effects. Further studies are needed to examine the mutual role between other secondary inflammatory mediators and endogenous stress proteins in promoting pelvic inflammation and growth of endometriotic stromal cells. Our findings suggest that endotoxin and HSP70 are mutually involved in a stress reaction and in inflammation. A combined effect between local inflammation and a stress reaction in pelvic environment may be involved in TLR4-mediated growth of endometriotic cells. Since endometriosis is a multi-factorial disease, it is difficult to explain uniformly its growth regulation by a single factor. Our findings may provide some new insights in understanding the physiopathology or pathogenesis of endometriosis and may hold new therapeutic potential. This work was supported by Grants-in-Aid for Scientific Research (grant no. 16591671 and 18591837) from the Ministry of Education, Sports, Culture, Science and Technology of Japan (to K.N.K.). There is no conflict of interest related to this study. Not applicable.

  3. Influence of Zn additions on the interfacial reaction and microstructure of Sn37Pb/Cu solder joints

    Science.gov (United States)

    Qiu, Yu; Hu, Xiaowu; Li, Yulong; Jiang, Xiongxin

    2017-10-01

    The effects of Zn (5 and 10 wt%) additions into Sn37Pb solder and isothermal solid state aging on the interfacial reactions between Sn37Pb- xZn solders and Cu substrates were investigated in this study. It was found that the addition of Zn changed the types and morphologies of interfacial IMC layers during reflowing and thereafter under aging condition. During reflowing, the planar-type Cu5Zn8 compound was the interfacial IMC for Sn37Pb- xZn (5 and 10 wt%) solder, while the scallop-type Cu6Sn5 was the interfacial IMC for Sn37Pb solder. After aging, the final interfacial structure for Sn37Pb-5Zn solder was solder/Cu5Zn8/Cu6(Sn,Zn)5/Cu, while solder/Cu6Sn5/Cu3Sn/Cu for Sn37Pb solder and solder/Cu5Zn8/Cu for Sn37Pb-10Zn solder, respectively. The Kirkendall voids disappeared with Zn addition into Sn37Pb solder. For the Sn37Pb-5Zn/Cu solder joint, the thickness of Cu6(Sn,Zn)5 layer increased, while the thickness of Cu5Zn8 layer decreased with aging time extended to 360 h due to the decomposition of the Cu5Zn8 IMC layer by diffusing Cu and Zn atoms into nether IMC layer, combining Sn atoms diffused from solder matrix to form Cu6(Sn,Zn)5 IMCs. Furthermore, the growth of Cu6Sn5 and Cu3Sn layers for Sn37Pb/Cu solder joint and the total IMC layer at the interface of Sn37Pb- xZn ( x = 0, 5, and 10 wt%) solder with Cu substrate followed the diffusion control mechanism. Compared to the Sn37Pb-5Zn/Cu solder joint, higher Zn concentration depressed the growth of Cu5Zn8 layer for Sn37Pb-10Zn solder. In the end, refining effect on IMC grains was found by the addition of Zn into Sn37Pb solder and the 10 wt% Zn-doping significantly refined the interfacial IMC grains.

  4. Mixed N-Heterocyclic Carbene-Bis(oxazolinyl)borato Rhodium and Iridium Complexes in Photochemical and Thermal Oxidative Addition Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Songchen [Ames Laboratory; Manna, Kuntal [Ames Laboratory; Ellern, Arkady [Ames Laboratory; Sadow, Aaron D [Ames Laboratory

    2014-12-08

    In order to facilitate oxidative addition chemistry of fac-coordinated rhodium(I) and iridium(I) compounds, carbene–bis(oxazolinyl)phenylborate proligands have been synthesized and reacted with organometallic precursors. Two proligands, PhB(OxMe2)2(ImtBuH) (H[1]; OxMe2 = 4,4-dimethyl-2-oxazoline; ImtBuH = 1-tert-butylimidazole) and PhB(OxMe2)2(ImMesH) (H[2]; ImMesH = 1-mesitylimidazole), are deprotonated with potassium benzyl to generate K[1] and K[2], and these potassium compounds serve as reagents for the synthesis of a series of rhodium and iridium complexes. Cyclooctadiene and dicarbonyl compounds {PhB(OxMe2)2ImtBu}Rh(η4-C8H12) (3), {PhB(OxMe2)2ImMes}Rh(η4-C8H12) (4), {PhB(OxMe2)2ImMes}Rh(CO)2 (5), {PhB(OxMe2)2ImMes}Ir(η4-C8H12) (6), and {PhB(OxMe2)2ImMes}Ir(CO)2 (7) are synthesized along with ToMM(η4-C8H12) (M = Rh (8); M = Ir (9); ToM = tris(4,4-dimethyl-2-oxazolinyl)phenylborate). The spectroscopic and structural properties and reactivity of this series of compounds show electronic and steric effects of substituents on the imidazole (tert-butyl vs mesityl), effects of replacing an oxazoline in ToM with a carbene donor, and the influence of the donor ligand (CO vs C8H12). The reactions of K[2] and [M(μ-Cl)(η2-C8H14)2]2 (M = Rh, Ir) provide {κ4-PhB(OxMe2)2ImMes'CH2}Rh(μ-H)(μ-Cl)Rh(η2-C8H14)2 (10) and {PhB(OxMe2)2ImMes}IrH(η3-C8H13) (11). In the former compound, a spontaneous oxidative addition of a mesityl ortho-methyl to give a mixed-valent dirhodium species is observed, while the iridium compound forms a monometallic allyl hydride. Photochemical reactions of dicarbonyl compounds 5 and 7 result in C–H bond oxidative addition providing the compounds {κ4-PhB(OxMe2)2ImMes'CH2}RhH(CO) (12) and {PhB(OxMe2)2ImMes}IrH(Ph)CO (13). In 12, oxidative addition results in cyclometalation of the mesityl ortho-methyl similar to 10, whereas the iridium compound reacts with the benzene solvent to give a rare crystallographically characterized cis

  5. Bifunctional Molecular Photoswitches Based on Overcrowded Alkenes for Dynamic Control of Catalytic Activity in Michael Addition Reactions.

    Science.gov (United States)

    Pizzolato, Stefano F; Collins, Beatrice S L; van Leeuwen, Thomas; Feringa, Ben L

    2017-05-02

    The emerging field of artificial photoswitchable catalysis has recently shown striking examples of functional light-responsive systems allowing for dynamic control of activity and selectivity in organocatalysis and metal-catalysed transformations. While our group has already disclosed systems featuring first generation molecular motors as the switchable central core, a design based on second generation molecular motors is lacking. Here, the syntheses of two bifunctionalised molecular switches based on a photoresponsive tetrasubstituted alkene core are reported. They feature a thiourea substituent as hydrogen-donor moiety in the upper half and a basic dimethylamine group in the lower half. This combination of functional groups offers the possibility for application of these molecules in photoswitchable catalytic processes. The light-responsive central cores were synthesized by a Barton-Kellogg coupling of the prefunctionalized upper and lower halves. Derivatization using Buchwald-Hartwig amination and subsequent introduction of the thiourea substituent afforded the target compounds. Control of catalytic activity in the Michael addition reaction between (E)-3-bromo-β-nitrostyrene and 2,4-pentanedione is achieved upon irradiation of stable-(E) and stable-(Z) isomers of the bifunctional catalyst 1. Both isomers display a decrease in catalytic activity upon irradiation to the metastable state, providing systems with the potential to be applied as ON/OFF catalytic photoswitches. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Modification of the performance of WO{sub 3}-ZrO{sub 2} catalysts by metal addition in hydrocarbon reactions

    Energy Technology Data Exchange (ETDEWEB)

    Torres, Gerardo Carlos; Manuale, Debora Laura; Benitez, Viviana Monica; Vera, Carlos Roman; Yori, Juan Carlos, E-mail: jyori@fiq.unl.edu.ar [Instituto de Investigaciones en Catalisis y Petroquimica, Facultad de Ingenieria Quimica, Universidad Nacional del Litoral, Consejo Nacional de Investigaciones Cientifica y Tecnicas, Santiago del Estero Santa Fe (Argentina)

    2012-07-01

    A study of the different hydrocarbon reactions over Ni doped WO{sub 3}-ZrO{sub 2} catalysts was performed. Ni was found as NiO at low Ni concentration while at high Ni concentrations a small fraction was present as a metal. For both cases, Ni strongly modified total acidity and concentration of strong acid sites. In the cyclohexane dehydrogenation reaction, Ni addition promotes both benzene and methyl cyclopentane production. The hydroconversion activity (n-butane and n-octane) increases with the augment of total acidity produced by Ni. The selectivity to reaction products is modified according to the acid strength distribution changes produced by Ni addition. (author)

  7. Palladium-Catalysed Enantioselective Conjugate Addition of Aromatic Amines to α,β-Unsaturated N-Imides. Effect of the Chelating Moiety

    NARCIS (Netherlands)

    Phua, Pim Huat; Vries, Johannes G. de; Hii, King Kuok

    2005-01-01

    Palladium-catalysed enantioselective additions of aromatic amines to α,β-unsaturated N-imides are reported. The N-substituent of the Michael acceptor appears to have an unusual modulating effect on the amine activity. The effects of introducing different substituents are examined. Overall, the yield

  8. Ciliates rapidly enhance the frequency of conjugation between Escherichia coli strains through bacterial accumulation in vesicles.

    Science.gov (United States)

    Matsuo, Junji; Oguri, Satoshi; Nakamura, Shinji; Hanawa, Tomoko; Fukumoto, Tatsuya; Hayashi, Yasuhiro; Kawaguchi, Kouhei; Mizutani, Yoshihiko; Yao, Takashi; Akizawa, Kouzi; Suzuki, Haruki; Simizu, Chikara; Matsuno, Kazuhiko; Kamiya, Shigeru; Yamaguchi, Hiroyuki

    2010-10-01

    The mechanism underlying bacterial conjugation through protozoa was investigated. Kanamycin-resistant Escherichia coli SM10λ+ carrying pRT733 with TnphoA was used as donor bacteria and introduced by conjugation into ciprofloxacin-resistant E. coli clinical isolate recipient bacteria. Equal amounts of donor and recipient bacteria were mixed together in the presence or absence of protozoa (ciliates, free-living amoebae, myxamoebae) in Page's amoeba saline for 24 h. Transconjugants were selected with Luria broth agar containing kanamycin and ciprofloxacin. The frequency of conjugation was estimated as the number of transconjugants for each recipient. Conjugation frequency in the presence of ciliates was estimated to be approximately 10⁻⁶, but in the absence of ciliates, or in the presence of other protozoa, it was approximately 10⁻⁸. Conjugation also occurred in culture of ciliates at least 2 h after incubation. Successful conjugation was confirmed by the polymerase chain reaction. Addition of cycloheximide or latrunculin B resulted in suppression of conjugation. Heat killing the ciliates or bacteria had no effect on conjugation frequency. Co-localization of green fluorescent protein-expressing E. coli and PKH-67-vital-stained E. coli was observed in the same ciliate vesicles, suggesting that both donor and recipient bacteria had accumulated in the same vesicle. In this study, the conjugation frequency of bacteria was found to be significantly higher in vesicles purified from ciliates than those in culture suspension. We conclude that ciliates rapidly enhance the conjugation of E. coli strains through bacterial accumulation in vesicles. Copyright © 2010 Elsevier Masson SAS. All rights reserved.

  9. Theoretical Kinetics Analysis for $\\dot{H}$ Atom Addition to 1,3-Butadiene and Related Reactions on the $\\dot{C}$4H7 Potential Energy Surface

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yang [National Univ. of Ireland, Galway (Ireland). Combustion Chemistry Centre; Klippenstein, Stephen J. [Argonne National Lab. (ANL), Argonne, IL (United States). Chemical Sciences and Engineering Division; Zhou, Chong-Wen [Beihang Univ., Beihang (China). School of Energy and Power Engineering; Curran, Henry J. [National Univ. of Ireland, Galway (Ireland). Combustion Chemistry Centre

    2017-09-29

    The oxidation chemistry of the simplest conjugated hydrocarbon, 1,3-butadiene, can provide a first step in understanding the role of poly-unsaturated hydrocarbons in combustion and, in particular, an understanding of their contribution towards soot formation. Based on our previous work on propene and the butene isomers (1-, 2- and isobutene), it was found that the reaction kinetics of H-atom addition to the C=C double bond plays a significant role in fuel consumption kinetics and influences the predictions of high-temperature ignition delay times, product species concentrations and flame speed measurements. In this study, the rate constants and thermodynamic properties for $\\dot{H}$-atom addition to 1,3-butadiene and related reactions on the $\\dot{C}$4H7 potential energy surface have been calculated using two different series of quantum chemical methods and two different kinetic codes. Excellent agreement is obtained between the two different kinetics codes. The calculated results including zero point energies, single point energies, rate constants, barrier heights and thermochemistry are systematically compared among the two quantum chemical methods. 1-methylallyl ($\\dot{C}$4H71-3) and 3-buten-1- yl ($\\dot{C}$4H71-4) radicals and C2H4 + $\\dot{C}$2H3 are found to be the most important channels and reactivity promoting products, respectively. We calculated that terminal addition is dominant (> 80%) compared to internal $\\dot{H}$-atom addition at all temperatures in the range 298 – 2000 K. However, this dominance decreases with increasing temperature. The calculated rate constants for the bimolecular reaction C4H6 + $\\dot{H}$ → products and C2H4 + $\\dot{C}$2H3 → products are in excellent agreement with both experimental and theoretical results from the literature. For selected C4 species the

  10. Effect of guar gum conjugation on functional, antioxidant and antimicrobial activity of egg white lysozyme.

    Science.gov (United States)

    Hamdani, Afshan Mumtaz; Wani, Idrees Ahmed; Bhat, Naseer Ahmad; Siddiqi, Raushid Ahmad

    2018-02-01

    This study was undertaken to analyze the effect of conjugation of egg-white lysozyme with guar gum. Lysozyme is an antimicrobial polypeptide that can be used for food preservation. Its antibacterial activity is limited to gram positive bacteria. Conjugation with polysaccharides like guar gum may broaden its activity against gram negatives. Conjugate was developed through Maillard reaction. Assays carried out included sugar estimation, SDS-PAGE, GPC, color, FT-IR, DSC, thermal stability, solubility, emulsifying, foaming and antioxidant activity. In addition, antimicrobial activity of the conjugate was determined against two gram positive (Staphyllococcus aureus and Enterococcus) and two gram negative pathogens (E. coli and Salmonella). Results showed higher functional properties of lysozyme-guar gum conjugate. The antioxidant properties increased from 2.02-35.80% (Inhibition of DPPH) and 1.65-4.93AAE/g (reducing power) upon guar gum conjugation. Conjugate significantly inhibited gram negative bacteria and the antibacterial activity also increased significantly against gram positive pathogens. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Highly diastereoselective conjugate addition of nitroalkanes to α,β-unsaturated sugar lactones for the efficient synthesis of chiral 2-pyrrolidones.

    Science.gov (United States)

    Li, Yan-Ping; Li, Zhong-Jun; Meng, Xiang-Bao

    2011-09-27

    A series of 4,5-substituted chiral γ-lactams were synthesized through a highly diastereoselective addition-rearrangement approach from 2,3-unsaturated sugar lactones. The single-crystal X-ray structure of one product indicated that the sugar ring was attacked from the axial side. Partial reduction of the nitro group produced N-hydroxy-γ-lactams, which were further reduced with TiCl(3) to yield the 4,5-substituted chiral γ-lactams. The absolute configuration of C5 of the γ-lactam was determined by NOESY spectra. Copyright © 2011 Elsevier Ltd. All rights reserved.

  12. Quantum Chemical Study of CH3 + O2 Combustion Reaction System: Catalytic Effects of Additional CO2 Molecule.

    Science.gov (United States)

    Masunov, Artëm E; Wait, Elizabeth; Vasu, Subith S

    2017-08-03

    The supercritical carbon dioxide diluent is used to control the temperature and to increase the efficiency in oxycombustion fossil fuel energy technology. It may affect the rates of combustion by altering mechanisms of chemical reactions, compared to the ones at low CO2 concentrations. Here, we investigate potential energy surfaces of the four elementary reactions in the CH3 + O2 reactive system in the presence of one CO2 molecule. In the case of reaction CH3 + O2 → CH2O + OH (R1 channel), van der Waals (vdW) complex formation stabilizes the transition state and reduces the activation barrier by ∼2.2 kcal/mol. Alternatively, covalently bonded CO2 may form a six-membered ring transition state and reduce the activation barrier by ∼0.6 kcal/mol. In case of reaction CH3 + O2 → CH3O + O (R2 channel), covalent participation of CO2 lowers the barrier for the rate limiting step by 3.9 kcal/mol. This is expected to accelerate the R2 process, important for the branching step of the radical chain reaction mechanism. For the reaction CH3 + O2 → CHO + H2O (R3 channel) with covalent participation of CO2, the activation barrier is lowered by 0.5 kcal/mol. The reaction CH2O + OH → CHO + H2O (R4 channel) involves hydrogen abstraction from formaldehyde by OH radical. Its barrier is reduced from 7.1 to 0.8 kcal/mol by formation of vdW complex with spectator CO2. These new findings are expected to improve the kinetic reaction mechanism describing combustion processes in supercritical CO2 medium.

  13. Efficient Boron-Copper Additions to Aryl-Substituted Alkenes Promoted by NHC–Based Catalysts. Enantioselective Cu-Catalyzed Hydroboration Reactions

    OpenAIRE

    Lee, Yunmi; Hoveyda, Amir H.

    2009-01-01

    A Cu-catalyzed method for efficient boron-copper addition processes involving acyclic and cyclic disubstituted aryl olefins are reported. Reactions are promoted with 0.5–5 mol % of a readily available N-heterocyclic carbene (NHC) complex; the presence of MeOH promotes in situ protonation of the C–Cu bond and leads to efficient catalyst turnover, constituting a net Cu-catalyzed hydroboration process. Reactions proceed in >98:

  14. Stereoselective Synthesis of (2Z)-2,4-Dienamides via NBS-Mediated Allyloxyl Addition-Claisen Rearrangement-Dehydrobromination Cascade Reaction of Ynsulfonamides.

    Science.gov (United States)

    Ding, Runbo; Li, Yun; Tao, Cheng; Cheng, Bin; Zhai, Hongbin

    2015-08-21

    An NBS-promoted allyloxyl addition-Claisen rearrangement-dehydrobromination cascade reaction has been developed. More than 20 substituted alkynylsulfonamides were reacted with allyl alcohols to generate (2Z)-2,4-dienamides in moderate to high yields. A mechanistic model has been proposed to account for the overall reaction sequence including the stereochemical outcome. Theoretical calculations suggested that a [3,3] sigmatropic rearrangement be the rate-limiting step.

  15. Dihydroazulene-buckminsterfullerene conjugates

    DEFF Research Database (Denmark)

    Santella, Marco; Mazzanti, Virginia; Jevric, Martyn

    2012-01-01

    The dihydroazulene (DHA)/vinylheptafulvene (VHF) photo/thermoswitch has recently attracted interest as a molecular switch for molecular electronics. In this field, Buckminsterfullerene, C(60), has been shown to be a useful anchoring group for adhering a molecular wire to an electrode. Here we have...... combined the two units with the overall aim to elucidate how C(60) influences the DHA-VHF switching events. Efficient synthetic protocols for making covalently linked DHA-C(60) conjugates were developed, using Prato, Sonogashira, Hay, and Cadiot-Chodkiewicz reactions. These syntheses provide as well...... a variety of potentially useful DHA and C(60) building blocks for acetylenic scaffolding. The two units were separated by bridges of various lengths, such as oligo(phenyleneethynylene) (OPE2 and OPE3) wires. The distance of separation was found to influence strongly the light-induced ring-opening reaction...

  16. Theoretical Investigation of Electrophilic Transannular Addition Reactions of Bromine to Face-to-Face (Juxtaposed) Double Bonds in Strained Polycyclic Hydrocarbons.

    Science.gov (United States)

    Abbasoglu, Rza

    2017-06-01

    Transannular electrophilic addition reaction of halogens to face-to-face(juxtaposed) double bonded strained alkenes were theoretically investigated. General rules that allow us to stipulate the factors that direct the main steps of the energy hypersurface of reactions as well as the products were established. Direction of the reaction flow is determined by direction of intramolecular skeletal isomerisation of cyclic-bridged halogenium cation and isomerisation takes place to create a more stable skeletal structure. Stability of resultant skeletal structure is determined by the number of σ bonds between isolated double bonds of the alkene and bonding-type of double bonds (N- and U-type). When the number of σ bonds between double bonds of the alkene is three (m = 3), the reaction takes place to predominantly give an N-type product, and when four (m = 4), N- and U-type products are formed. Structure and stability of cation intermediates (bridged, N- and U-type cations) of electrophilic addition reaction of homohipostrofen molecule, whose double bonds were linked by three σ bonds, with bromine were investigated by DFT methods in detail. Also the addition reaction of endo,endo-tetracyclo[6.2.2.23,6.02,7]tetradeca-4,9-dien molecule, whose double bonds were linked by four σ bonds, with bromine were investigated by quantum chemistry.

  17. Mechanisms of initiation and termination reactions in conjugative DNA processing. Independence of tight substrate binding and catalytic activity of relaxase (TraI) of IncPalpha plasmid RP4.

    Science.gov (United States)

    Pansegrau, W; Lanka, E

    1996-05-31

    The relaxase (TraI) of plasmid RP4 (IncPalpha) plays a key role in initiation and termination of transfer DNA replication during conjugative transmission of the plasmid. TraI functions as a DNA strand transferase that cleaves a unique phosphodiester bond at nic of the transfer origin. The cleavage reaction consists in a reversible transesterification that leads to transfer of the 5' phosphoryl at nic to the hydroxyl group of TraI Tyr-22. Hence, cleavage results in the covalent attachment of TraI to the 5' terminus of the plasmid strand destined for transfer. To investigate the protein's ability to function in a "second cleavage" reaction proposed to terminate rolling circle mode transfer DNA replication, single-stranded oligonucleotides containing the nic region were immobilized at their 3' ends on magnetic beads and cleaved by TraI. The resulting covalent TraI-oligonucleotide adducts were active in the joining reaction but unable to cleave oligonucleotides containing an intact nic region, indicating that second cleavage probably requires a TraI dimer, since a monomer is insufficient. The covalently attached oligonucleotide determines the affinity of the relaxase for the 3' terminus of the T-strand. To further the biochemical characterization of TraI-catalyzed reactions, we used specific TraI mutants, showing that amino acid residues in each relaxase motif are involved in substrate binding. To uncouple substrate binding and cleaving-joining, we applied partially biotinylated TraI mutant proteins that were immobilized to magnetic beads. Using this approach we could demonstrate that tight DNA substrate binding and cleaving-joining are independent processes. Enhanced topoisomerase activity of some TraI mutants was correlated with low specific substrate binding affinity in conjunction with high cleaving-joining activity.

  18. Effect of Ag additions on the β phase formation reaction in the Cu–9 wt.%Al–6 wt.%Mn alloy

    Energy Technology Data Exchange (ETDEWEB)

    Adorno, A.T., E-mail: atadorno@iq.unesp.br [Departamento de Físico-Química, Instituto de Química, UNESP, Caixa Postal 355, 14801-970 Araraquara, SP (Brazil); Carvalho, T.M. [Departamento de Físico-Química, Instituto de Química, UNESP, Caixa Postal 355, 14801-970 Araraquara, SP (Brazil); Silva, R.A.G. [Departamento de Ciências Exatas e da Terra, UNIFESP, 09972-270 Diadema, SP (Brazil); Santos, C.M.A.; Magdalena, A.G. [Departamento de Físico-Química, Instituto de Química, UNESP, Caixa Postal 355, 14801-970 Araraquara, SP (Brazil)

    2015-09-15

    Highlights: • The results suggest a multi-step process involving reversible reactions. • Ag solubilizes preferably at the Cu matrix. • Ag additions decrease the activation energy for the process. - Abstract: The influence of 4 and 5 wt.%Ag additions on the kinetics of β [T{sub 7}-(CuMn){sub 3}Al] phase formation reaction in the Cu–9 wt.%Al–6 wt.%Mn alloy was studied using differential scanning calorimetry (DSC), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The results indicate that the conversion dependence of the activation energy has a descending shape, suggesting a multi-step process involving reversible reactions. The presence of Ag facilitates the formation of the β phase. The results also showed that the Ag precipitates formation includes the dissolution of Mn and Al atoms, thus decreasing the partial fraction of these elements available to react.

  19. Asymmetric Michael addition reactions of 3-substituted benzofuran-2(3H)-ones to nitroolefins catalyzed by a bifunctional tertiary-amine thiourea.

    Science.gov (United States)

    Li, Xin; Xue, Xiao-Song; Liu, Cong; Wang, Bin; Tan, Bo-Xuan; Jin, Jia-Lu; Zhang, Yue-Yan; Dong, Nan; Cheng, Jin-Pei

    2012-01-14

    The current work reports an organocatalytic strategy for the asymmetric catalysis of chiral benzofuran-2(3H)-ones bearing 3-position all-carbon quaternary stereocenters. Accordingly, highly enantioselective Michael addition reactions of 3-substituted benzofuran-2(3H)-ones to nitroolefins have been developed by utilizing a bifunctional tertiary-amine thiourea catalyst. The reactions accommodate a number of nitroolefins and 3-substituted benzofuran-2(3H)-ones to give the desired chiral benzofuran-2(3H)-one products with moderate to excellent yields (up to 98%) and moderate to very good selectivities (up to 19 : 1 dr and up to 91% ee). Theoretical calculations using the DFT method on the origin of the stereoselectivity were conducted. The effect of the nitroolefin substituent position on the stereoselectivity of the Michael addition reaction was also theoretically rationalized.

  20. Preparation of a Rapidly Forming Poly(ferrocenylsilane)-Poly(ethylene glycol)-based Hydrogel by a Thiol–Michael Addition Click Reaction

    NARCIS (Netherlands)

    Sui, Xiaofeng; van Ingen, Lennard; Hempenius, Mark A.; Vancso, Gyula J.

    2010-01-01

    The synthesis of a rapidly forming redox responsive poly(ferrocenylsilane)-poly(ethylene glycol) (PFS-PEG)-based hydrogel is described, achieved by a thiol-Michael addition click reaction. PFS bearing acrylate side groups (PFS-acryl) was synthesized by side group modification of

  1. Aza‐Michael addition reaction: Post‐polymerization modification and preparation of PEI/PEG‐based polyester hydrogels from enzymatically synthesized reactive polymers

    DEFF Research Database (Denmark)

    Hoffmann, Christian; Stuparu, Mihaiela C.; Daugaard, Anders Egede

    2015-01-01

    The utility of aza‐Michael addition chemistry for post‐polymerization functionalization of enzymatically prepared polyesters is established. For this, itaconate ester and oligoethylene glycol are selected as monomers. A Candida Antarctica lipase B catalyzed polycondensation reaction between the t...

  2. Catalytic asymmetric 1,4-addition reactions using alpha,beta-unsaturated N-acylpyrroles as highly reactive monodentate alpha,beta-unsaturated ester surrogates.

    Science.gov (United States)

    Matsunaga, Shigeki; Kinoshita, Tomofumi; Okada, Shigemitsu; Harada, Shinji; Shibasaki, Masakatsu

    2004-06-23

    Synthesis and application of alpha,beta-unsaturated N-acylpyrroles as highly reactive, monodentate ester surrogates in the catalytic asymmetric epoxidation and Michael reactions are described. alpha,beta-Unsaturated N-acylpyrroles with various functional groups were synthesized by the Wittig reaction using ylide 2. A Sm(O-i-Pr)(3)/H(8)-BINOL complex was the most effective catalyst for the epoxidation to afford pyrrolyl epoxides in up to 100% yield and >99% ee. Catalyst loading was successfully reduced to as little as 0.02 mol % (substrate/catalyst = 5000). The high turnover frequency and high volumetric productivity of the present reaction are also noteworthy. In addition, a sequential Wittig olefination-catalytic asymmetric epoxidation reaction was developed, providing efficient one-pot access to optically active epoxides from various aldehydes in high yield and ee (96-->99%). In a direct catalytic asymmetric Michael reaction of hydroxyketone promoted by the Et(2)Zn/linked-BINOL complex, Michael adducts were obtained in good yield (74-97%), dr (69/31-95/5), and ee (73-95%). This represents the first direct catalytic asymmetric Michael reaction of unmodified ketone to an alpha,beta-unsaturated carboxylic acid derivative. The properties of alpha,beta-unsaturated N-acylpyrrole are also discussed. Finally, the utility of the N-acylpyrrole unit for further transformations is demonstrated.

  3. Nano-organocatalyst: magnetically retrievable ferrite-anchored glutathione for microwave-assisted Paal–Knorr reaction, aza-Michael addition, and pyrazole synthesis

    KAUST Repository

    Polshettiwar, Vivek

    2010-01-01

    Postsynthetic Surface modification of magnetic nanoparticles by glutathione imparts desirable chemical functionality and enables the generation of catalytic sites on the surfaces of ensuing organocatalysts. In this article, we discuss the developments, unique activity, and high selectivity of nano-organocatalysts for microwave-assisted Paal-Knorr reaction, aza-Michael addition, and pyrazole synthesis. Their insoluble character Coupled with paramagnetic nature enables easy separation of these nano-catalysts from the reaction mixture using external magnet, which eliminates the requirement of catalyst filtration. Published by Elsevier Ltd.

  4. Additional Evidence That Transaldolase Exchange, Isotope Discrimination During the Triose-Isomerase Reaction, or Both Occur in Humans

    Science.gov (United States)

    Basu, Rita; Chandramouli, Visvanthan; Schumann, William; Basu, Ananda; Landau, Bernard R.; Rizza, Robert A.

    2009-01-01

    OBJECTIVE To determine whether deuterium enrichment on carbons 5 and 3 (C5/C3) in plasma glucose is influenced by processes other than gluconeogenesis and, if so, whether these processes are altered by type 2 diabetes. RESEARCH DESIGN AND METHODS In this study, 10 obese diabetic and 10 obese nondiabetic subjects were infused intravenously with [3,5-2H2] galactose enriched at a C5-to-C3 ratio of 1.0 as well as the enrichment of deuterium on C5 and C3 of plasma glucose, measured with nuclear magnetic resonance using the acetaminophen glucuronide method. RESULTS The ratio of deuterium enrichment on C5 and C3 of glucose was deuterium at the level of the triose-isomerase reaction, or both occur in humans. This also indicates that the net effect of these processes on the C5-to-C3 ratio is the same in people with and without type 2 diabetes. The possible effects of transaldolase exchange or selective retention of deuterium (or tritium) at the level of the triose-isomerase reaction on tracee labeling and tracer metabolism should be considered when the deuterated water method is used to measure gluconeogenesis or [3-3H] glucose is used to measure glucose turnover in humans. PMID:19366865

  5. Low-molecular-weight model study of peroxide cross-linking of ethylene-propylene-diene rubber using gas chromatography and mass spectrometry II. Addition and combination reactions.

    Science.gov (United States)

    Peters, R; van Duin, M; Tonoli, D; Kwakkenbos, G; Mengerink, Y; van Benthem, R A T M; de Koster, C G; Schoenmakers, P J; van der Wal, Sj

    2008-08-08

    The dicumyl-peroxide-initiated addition and combination reactions of mixtures of alkanes (n-octane, n-decane) and alkenes [5,6-dihydrodicyclopentadiene (DCPDH), 5-ethylidene-2-norbornane (ENBH) and 5-vinylidene-2-norbornane (VNBH)] were studied to mimic the peroxide cross-linking reactions of terpolymerised ethylene, propylene and a diene monomer (EPDM). The reaction products of the mixtures were separated by both gas chromatography (GC) and comprehensive two-dimensional gas chromatography (GCxGC). The separated compounds were identified from their mass spectra and their GC and GCxGC elution pattern. Quantification of the various alkyl/alkyl, alkyl/allyl and allyl/allyl combination products shows that allylic-radicals comprise approximately 60% of the substrate radicals formed. The total concentration of the products formed by combination is found to be independent of the concentration and the type of alkene. The total concentration of the products formed by addition to the alkene increases with increasing concentration of alkene. In addition, the total concentration of the formed addition products depends strongly on the type of the alkene used, viz. VNBH>ENBH approximately DCPDH, which is a consequence of differences in steric hindrance of the unsaturation. The peroxide curing efficiency, defined as the number of moles of cross-linked products formed per mol of peroxide, is 173% using 9% (w/w) 5-vinylidene-2-norbornane (VNBH). This indicates that the addition reaction is recurrent. All these findings are consistent with experimental studies on peroxide curing of EPDM rubber. In addition, the present results provide more-detailed structural information, increasing the understanding of the mechanism of peroxide curing of EPDM. The described approach to use low-molecular-weight model compounds followed by GC-mass spectrometry (MS) and GCxGC-MS analysis is proven to be a very powerful tool to study the cross-linking of EPDM.

  6. Xenobiotic conjugation with phosphate - a metabolic rarity.

    Science.gov (United States)

    Mitchell, Stephen C

    2016-08-01

    1. Although not unknown, the conjugation of a xenobiotic with phosphate appears a rarity amongst the routes available for foreign compound metabolism. This is especially true in mammals and may be somewhat surprising as conjugation with sulphate, a seemingly similar moiety, is commonplace. 2. Information from the literature, where xenobiotic phosphate conjugates have been described or suggested, has been collated and presented in this article. By bringing together this diverse material, hopefully interest will be generated in this unusual xenobiotic reaction, and perhaps further research undertaken to better understand and delineate the reasons for its relative absence from the xenobiotic scene.

  7. Theoretical Evidence for Low-Ligated Palladium(0): [Pd-L] as the Active Species in Oxidative Addition Reactions

    DEFF Research Database (Denmark)

    Ahlquist, Mårten Sten Gösta; Fristrup, Peter; Tanner, David Ackland

    2006-01-01

    The oxidative addition of PhI to Pd0 has been studied by DFT with a continuum representation of the solvent. It is shown that the preferred number of ligands on palladium is lower than would be expected from “conventional wisdom” and the 18-electron rule. The most favored oxidative addition...... is obtained when Pd is coordinated by only the aryl iodide and one additional ligand in a linear arrangement. The calculations indicate that p-orbitals on the central metal are not involved in bonding in any of the complexes described herein, in good agreement with classic ligand field theory and also...... with a recent bonding analysis by Weinhold and Landis, but in apparent violation of the 18-electron rule....

  8. Multifunctional Electrochemical Platforms Based on the Michael Addition/Schiff Base Reaction of Polydopamine Modified Reduced Graphene Oxide: Construction and Application.

    Science.gov (United States)

    Huang, Na; Zhang, Si; Yang, Liuqing; Liu, Meiling; Li, Haitao; Zhang, Youyu; Yao, Shouzhuo

    2015-08-19

    In this paper, a new strategy for the construction of multifunctional electrochemical detection platforms based on the Michael addition/Schiff base reaction of polydopamine modified reduced graphene oxide was first proposed. Inspired by the mussel adhesion proteins, 3,4-dihydroxyphenylalanine (DA) was selected as a reducing agent to simultaneously reduce graphene oxide and self-polymerize to obtain the polydopamine-reduced graphene oxide (PDA-rGO). The PDA-rGO was then functionalized with thiols and amines by the reaction of thiol/amino groups with quinine groups of PDA-rGO via the Michael addition/Schiff base reaction. Several typical compounds containing thiol and/or amino groups such as 1-[(4-amino)phenylethynyl] ferrocene (Fc-NH2), cysteine (cys), and glucose oxidase (GOx) were selected as the model molecules to anchor on the surface of PDA-rGO using the strategy for construction of multifunctional electrochemical platforms. The experiments revealed that the composite grafted with ferrocene derivative shows excellent catalysis activity toward many electroactive molecules and could be used for individual or simultaneous detection of dopamine hydrochloride (DA) and uric acid (UA), or hydroquinone (HQ) and catechol (CC), while, after grafting of cysteine on PDA-rGO, simultaneous discrimination detection of Pb(2+) and Cd(2+) was realized on the composite modified electrode. In addition, direct electron transfer of GOx can be observed when GOx-PDA-rGO was immobilized on glassy carbon electrode (GCE). When glucose was added into the system, the modified electrode showed excellent electric current response toward glucose. These results inferred that the proposed multifunctional electrochemical platforms could be simply, conveniently, and effectively regulated through changing the anchored recognition or reaction groups. This study would provide a versatile method to design more detection or biosensing platforms through a chemical reaction strategy in the future.

  9. Time resolved studies of the addition reactions of silylenes and unsaturated hydrocarbons in the gas phase (an investigation of the strain energies of silirane and silirene rings)

    CERN Document Server

    Dormer, G

    1999-01-01

    This thesis reports the measurement of absolute rate constants for number of silylene addition reactions with unsaturated hydrocarbons. The reactions of SiH sub 2 , SiD sub 2 and Me sub 2 Si with alkene and alkynes were studied. The silylenes were formed, in situ, by the photolysis of an organosilicon precursor, and the rate constants obtained by the direct observation of the absorption decay of the silylene reactant. The reactions were studied in the gas phase and their temperature and pressure dependence investigated. The reaction of SiH sub 2 and 1,3-butadiene was investigated and found to be pressure dependent. The following Arrhenius equation was yielded at infinite pressure; log(k supinfinity/cm sup 3 molecule sup - sup 1 s sup - sup 1) = (-9.57 +- 0.05) + (3.22 +- 0.35) kJmol sup - sup 1 /RT ln 10. The reaction was found to proceed via a two-channel pathway, leading to the products vinylsilirane and silacyclopentane. RRKM modelling of the system was carried out and led to the calculation of the strain ...

  10. Ligandless Suzuki-Miyaura reaction in neat water with or without native β-cyclodextrin as additive

    KAUST Repository

    Decottignies, Audrey

    2013-02-01

    Efficient green ligand-free Suzuki cross coupling in neat water was developed by using low loading of catalyst (0.5 mol%) in neat water in the presence or not of β-cyclodextrin (0.5 mol%) as additive at 25 C and 100 C respectively. © 2012 Elsevier B.V.

  11. A Computational Study on the Addition of HONO to Alkynes toward the Synthesis of Isoxazoles; a Bifurcation, Pseudopericyclic Pathways and a Barrierless Reaction on the Potential Energy Surface.

    Science.gov (United States)

    Zuo, Ang; Birney, David M

    2017-09-01

    Homopropargyl alcohols react with t-BuONO to form acyloximes which can be oxidatively cyclized to yield ioxazoles. The mechanism for the initial reaction of HONO with alkynes to form acyloximes (e.g., 13c) has been explored at the B3LYP/6-31G(d,p) + ZPVE level of theory. The observed chemoselectivity and regioselectivity are explained via an acid-catalyzed mechanism. Furthermore, the potential energy surface revealed numerous surprising features. The addition of HONO (8) to protonated 1-phenylpropyne (18) is calculated to follow a reaction pathway involving sequential transition states (TS6 and TS8), for which reaction dynamics likely play a role. This reaction pathway can bypass the expected addition product 21 as well as transition state TS8, directly forming the rearranged product 23. Nevertheless, TS8 is key to understanding the potential energy surface; there is a low barrier for the pseudopericylic [1,3]-NO shift, calculated to be only 8.4 kcal/mol above 21. This places TS8 well below TS6, making the valley-ridge inflection point (VRI or bifurcation) and direct formation of 23 possible. The final tautomerization step to the acyloxime can be considered to be a [1,5]-proton shift. However, the rearrangement in the case of 17h to 13c is calculated to be barrierless, arguably because the pathway is pseudopericyclic and exothermic.

  12. Conjugated Microporous Polymers for Heterogeneous Catalysis.

    Science.gov (United States)

    Zhou, Yun-Bing; Zhan, Zhuang-Ping

    2018-01-04

    Conjugated microporous polymers (CMPs) are a class of crosslinked polymers that combine permanent micropores with π-conjugated skeletons and possess three-dimensional (3D) networks. Compared with conventional materials such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), CMPs usually have superior chemical and thermal stability. CMPs have made significant progress in heterogeneous catalysis in the past seven years. With a bottom-up strategy, catalytic moieties can be directly introduced into in the framework to produce heterogeneous CMP catalysts. Higher activity, stability, and selectivity can be obtained with heterogeneous CMP catalysts in comparison with their homogeneous analogs. In addition, CMP catalysts can be easily isolated and recycled. In this review, we focus on CMPs as an intriguing platform for developing various highly efficient and recyclable heterogeneous catalysts in organic reactions. The design, synthesis, and structure of these CMP catalysts are also discussed in this focus review. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. A palladium-catalysed multicomponent coupling approach to conjugated poly(1,3-dipoles) and polyheterocycles

    Science.gov (United States)

    Leitch, David C.; Kayser, Laure V.; Han, Zhi-Yong; Siamaki, Ali R.; Keyzer, Evan N.; Gefen, Ashley; Arndtsen, Bruce A.

    2015-06-01

    Conjugated polymers have emerged over the past several decades as key components for a range of applications, including semiconductors, molecular wires, sensors, light switchable transistors and OLEDs. Nevertheless, the construction of many such polymers, especially highly substituted variants, typically involves a multistep synthesis. This can limit the ability to both access and tune polymer structures for desired properties. Here we show an alternative approach to synthesize conjugated materials: a metal-catalysed multicomponent polymerization. This reaction assembles multiple monomer units into a new polymer containing reactive 1,3-dipoles, which can be modified using cycloaddition reactions. In addition to the synthetic ease of this approach, its modularity allows easy adaptation to incorporate a range of desired substituents, all via one-pot reactions.

  14. A palladium-catalysed multicomponent coupling approach to conjugated poly(1,3-dipoles) and polyheterocycles

    Science.gov (United States)

    Leitch, David C.; Kayser, Laure V.; Han, Zhi-Yong; Siamaki, Ali R.; Keyzer, Evan N.; Gefen, Ashley; Arndtsen, Bruce A.

    2015-01-01

    Conjugated polymers have emerged over the past several decades as key components for a range of applications, including semiconductors, molecular wires, sensors, light switchable transistors and OLEDs. Nevertheless, the construction of many such polymers, especially highly substituted variants, typically involves a multistep synthesis. This can limit the ability to both access and tune polymer structures for desired properties. Here we show an alternative approach to synthesize conjugated materials: a metal-catalysed multicomponent polymerization. This reaction assembles multiple monomer units into a new polymer containing reactive 1,3-dipoles, which can be modified using cycloaddition reactions. In addition to the synthetic ease of this approach, its modularity allows easy adaptation to incorporate a range of desired substituents, all via one-pot reactions. PMID:26077769

  15. Segmented conjugated polymers

    Indian Academy of Sciences (India)

    Abstract. Segmented conjugated polymers, wherein the conjugation is randomly truncated by varying lengths of non-conjugated segments, form an interesting class of polymers as they not only represent systems of varying stiffness, but also ones where the backbone can be construed as being made up of chromophores of ...

  16. Segmented conjugated polymers

    Indian Academy of Sciences (India)

    Segmented conjugated polymers, wherein the conjugation is randomly truncated by varying lengths of non-conjugated segments, form an interesting class of polymers as they not only represent systems of varying stiffness, but also ones where the backbone can be construed as being made up of chromophores of varying ...

  17. Evaluation of gold nanoparticles as the additive in real-time polymerase chain reaction with SYBR Green I dye

    Energy Technology Data Exchange (ETDEWEB)

    Yang Wenchao; Cao Xueyan; Zhang Xiaodong; Hu Jun [Nanobiology Laboratory, Bio-X Life Science Research Center, College of Life Science and Biotechnology, Shanghai JiaoTong University, Shanghai 200240 (China); Mi Lijuan; Fan Chunhai [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, PO Box 800-204, Shanghai 201800 (China)], E-mail: xdzhang@sjtu.edu.cn

    2008-06-25

    Gold nanoparticles (AuNPs) have been proven to be able to improve the specificity or increase the efficiency of a polymerase chain reaction (PCR) when a suitable amount of AuNPs was used. However, there is still a lack of systematic evaluation of AuNPs in real-time PCR. In this study, DNA degradation and the fluorescence quenching effect of AuNPs were first tested in real-time PCR. Then two different kinds of Taq DNA polymerase, native and recombinant Taq polymerase, were employed to evaluate the AuNPs' effect on the threshold cycle (C{sub T}) values, standard curves and melting curves in real-time PCR. Different ratios of the amount of native Taq DNA polymerase to the amount of AuNPs were also tested. It was found that AuNPs could be applied in real-time PCR with correlation coefficient R{sup 2}>0.989. The combination of 2.09 nM AuNPs with 3.75 U of native Taq DNA polymerase could make the amplification curves shift to the left and enhance the efficiency of the real-time PCR (0.628 39 without AuNPs compared with 0.717 89 with 2.09 nM AuNPs), thus enabling faster detection in comparison with those of control samples. However, no improvement ability of AuNPs was found in real-time PCR based on recombinant rTaq DNA polymerase. Besides, the results suggest that a complex interaction exists between AuNPs and native Taq DNA polymerase.

  18. Palladium-Catalyzed Asymmetric Conjugate Addition of Arylboronic Acids to Five-, Six-, and Seven-Membered β-Substituted Cyclic Enones: Enantioselective Construction of All-Carbon Quaternary Stereocenters

    KAUST Repository

    Kikushima, Kotaro

    2011-05-11

    The first enantioselective Pd-catalyzed construction of all-carbon quaternary stereocenters via 1,4-addition of arylboronic acids to β-substituted cyclic enones is reported. Reaction of a wide range of arylboronic acids and cyclic enones using a catalyst prepared from Pd(OCOCF(3))(2) and a chiral pyridinooxazoline ligand yields enantioenriched products bearing benzylic stereocenters. Notably, this transformation is tolerant to air and moisture, providing a practical and operationally simple method of synthesizing enantioenriched all-carbon quaternary stereocenters.

  19. Functional separation of oxidation–reduction reactions and electron transport in PtRu/ND and conductive additive hybrid electrocatalysts during methanol oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yan; Wang, Yanhui [State Key Laboratory of Metastable Materials Science and Technology, College of Materials Science and Engineering, Yanshan University, Qinhuangdao 066004 (China); Bian, Linyan [College of Physics and Chemistry, Henan Polytechnic University, Jiaozuo, Henan 454000 (China); Lu, Rui [State Key Laboratory of Metastable Materials Science and Technology, College of Materials Science and Engineering, Yanshan University, Qinhuangdao 066004 (China); Zang, Jianbing, E-mail: jbzang@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, College of Materials Science and Engineering, Yanshan University, Qinhuangdao 066004 (China)

    2016-02-28

    Graphical abstract: - Highlights: • Functional separation of reactions and electron transport in PtRu/ND + AB (or CNT). • A conductive network was formed after the addition of AB or CNT. • PtRu/ND + AB (or CNT) exhibited enhanced activity and stability than PtRu/ND. - Abstract: Undoped nanodiamond (ND) supported PtRu (PtRu/ND) electrocatalyst for methanol oxidation reactions (MOR) in direct methanol fuel cells was prepared by a microwave-assisted polyol reduction method. Sp{sup 3}-bonded ND possesses high electrochemical stability but low conductivity, while sp{sup 2}-bonded carbon nanomaterials with high conductivity are prone to oxidation. Therefore, the functions of the supporting material were separated in this study. ND (sp{sup 3}), as a support, and AB or CNTs (sp{sup 2}), as a conductive additive, were combined to form the hybrid electrocatalysts PtRu/ND + AB and PtRu/ND + CNT for MOR. The morphology of the electrocatalysts was characterized by scanning electron microscopy and electrochemical measurements were performed using an electrochemical workstation. The results indicated that the electrocatalytic activity of PtRu/ND for MOR was improved with the addition of AB or CNTs as a conductive additive. Moreover, adding CNTs to PtRu/ND as a conductive additive showed better electrocatalytic activities than adding AB, which can be ascribed to the better electron-transfer ability of CNTs.

  20. Biodegradation of 2,4,6-TCA by the white-rot fungus Phlebia radiata is initiated by a phase I (O-demethylation)-phase II (O-conjugation) reactions system: implications for the chlorine cycle.

    Science.gov (United States)

    Campoy, Sonia; Alvarez-Rodríguez, María Luisa; Recio, Eliseo; Rumbero, Angel; Coque, Juan-José R

    2009-01-01

    Thirteen species of white-rot fungi tested have been shown to efficiently biodegrade 1 mM 2,4,6-trichloroanisole (2,4,6-TCA) in liquid cultures. The maximum biodegradation rate (94.5% in 10-day incubations) was exhibited by a Phlebia radiata strain. The enzymes of the ligninolytic complex, laccase, lignin peroxidase (LiP), manganese peroxidase (MnP) and versatile peroxidase (VP) were not able to transform 2,4,6-TCA in in vitro reactions, indicating that the ligninolytic complex was not involved in the initial attack to 2,4,6-TCA. Instead, the first biodegradative steps were carried out by a phase I and phase II reactions system. Phase I reaction consisted on a O-demethylation catalysed by a microsomal cytochrome P-450 monooxygenase to produce 2,4,6-trichlorophenol (2,4,6-TCP). Later, in a phase II reaction catalysed by a microsomal UDP-glucosyltransferase, 2,4,6-TCP was detoxified by O-conjugation with D-glucose to produce 2,4,6-TCP-1-O-d-glucoside (TCPG). This compound accumulated in culture supernatants, reaching its maximum concentration between 48 and 72 h of growth. TCPG levels decreased constantly by the end of fermentation, indicating that it was subsequently metabolized. A catalase activity was able to break in vitro the glycosidic link to produce 2,4,6-TCP, whereas ligninolytic enzymes did not have a significant effect on the biotransformation of that compound. Once formed, 2,4,6-TCP was further degraded as detected by a concomitant release of 2.6 mol of chloride ions by 1 mol of initial 2,4,6-TCA, indicating that this compound underwent almost a complete dehalogenation and biodegradation. It was concluded that P. radiata combines two different degradative mechanisms in order to biodegrade 2,4,6-TCA. The significance of the capability of white-rot fungi to O-demethylate chloroanisoles for the global chlorine cycle is discussed.

  1. Interfacial Reactions of Zn-Al Alloys with Na Addition on Cu Substrate During Spreading Test and After Aging Treatments

    Science.gov (United States)

    Gancarz, Tomasz; Pstruś, Janusz; Berent, Katarzyna

    2016-08-01

    Spreading tests for Cu substrate with Zn-Al eutectic-based alloys with 0.2, 0.5, and 1.0 wt.% of Na were studied using the sessile drop method in the presence of QJ201 flux. Spreading tests were performed for 1, 3, 8, 15, 30, and 60 min of contact, at the temperatures of 475, 500, 525, and 550 °C. After cleaning the flux residue from solidified samples, the spreading area of Zn-Al + Na on Cu was determined in accordance with ISO 9455-10:2013-03. Selected, solidified solder-substrate couples were cross-sectioned and subjected to scanning electron microscopy of the interfacial microstructure. The experiment was designed to demonstrate the effect of Na addition on the kinetics of formation and growth of CuZn, Cu5Zn8, and CuZn4 phases, which were identified using x-ray diffraction and energy-dispersive spectroscopy analysis. The addition of Na to eutectic Zn-Al caused the spreading area to decrease and the thickness of intermetallic compound layers at the interface to reduce. Samples after the spreading test at 500 °C for 1 min were subjected to aging for 1, 10, and 30 days at 120,170, and 250 °C. The greater thicknesses of IMC layers were obtained for a temperature of 250 °C. With increasing Na content in Zn-Al + Na alloys, the thickness reduced, which correlates to the highest value of activation energy for Zn-Al with 1% Na.

  2. Defect-free network formation and swelling behavior in ionic liquid-based electrolytes of tetra-arm polymers synthesized using a Michael addition reaction.

    Science.gov (United States)

    Yoshitake, Mari; Kamiyama, Yuji; Nishi, Kengo; Yoshimoto, Nobuko; Morita, Masayuki; Sakai, Takamasa; Fujii, Kenta

    2017-11-01

    The gelation mechanism of tetra-arm poly(ethylene glycol) (TetraPEG) prepolymers via a Michael addition reaction was investigated from the viewpoint of chemical reaction kinetics. The polymer network was formed by mixing two different TetraPEGs functionalized with maleimide and thiol terminal groups (TetraPEG-MA and TetraPEG-SH) in aqueous solutions, and the gelation rate was strongly dependent on the solution pH. We found that the gelation reaction can be a second-order reaction when the acid-base equilibrium of the terminal SH groups (-SH ⇆ -S(-) + H(+)) was taken into account, resulting in a quantitative estimation of the rate constant (kgel) in the current polymer solution system. Based on the kgel value, the network connectivity (p), which corresponds to efficiency at the linking point, was evaluated to be p > 95% at the end of the reaction; thus, the resulting TetraPEG hydrogels have a homogeneous polymer network without network defects. We used the TetraPEG network as a polymer matrix in a lithium-ion battery gel electrolyte: dried TetraPEG gels were swollen with ionic liquid-based electrolytes containing Li salts to prepare TetraPEG ion gel electrolytes. Swelling behaviors of the TetraPEG network were characterized from the swelling rate and the equilibrium swelling ratio, and we found that these swelling behaviors were significantly affected by the Li-ion component. We concluded that an intermolecular interaction between Li-ions and the polymer (Li-ion coordination with the O atoms within the PEG chains) plays a key role in the fundamental physical properties of the gel electrolyte.

  3. The influence of an additional load on time and force changes in the ground reaction force during the countermovement vertical jump.

    Science.gov (United States)

    Vaverka, Frantisek; Jakubsova, Zlatava; Jandacka, Daniel; Zahradnik, David; Farana, Roman; Uchytil, Jaroslav; Supej, Matej; Vodicar, Janez

    2013-01-01

    The aim of this study was to determine how an additional load influences the force-vs-time relationship of the countermovement vertical jump (CMVJ). The participants that took part in the experiment were 18 male university students who played sport recreationally, including regular games of volleyball. They were asked to perform a CMVJ without involving the arms under four conditions: without and with additional loads of 10%, 20%, and 30% of their body weight (BW). The vertical component of the ground reaction force (GRF) was measured by a force plate. The GRF was used to calculate the durations of the preparatory, braking, and acceleration phases, the total duration of the jump, force impulses during the braking and acceleration phases, average forces during the braking and acceleration phases, and the maximum force of impact at landing. Results were evaluated using repeated-measures ANOVA. Increasing the additional load prolonged both the braking and acceleration phases of the jump, with statistically significant changes in the duration of the acceleration phase found for an additional load of 20% BW. The magnitude of the force systematically and significantly increased with the additional load. The force impulse during the acceleration phase did not differ significantly between jumps performed with loads of 20% and 30% BW. The results suggest that the optimal additional load for developing explosive strength in vertical jumping ranges from 20% to 30% of BW, with this value varying between individual subjects.

  4. The Synthesis of Substituted Piperazine-cholesterol Conjugates for ...

    African Journals Online (AJOL)

    A small library of cholesterol-piperazine conjugates were synthesized by the reaction of cholesteryl chloroformate with a set of substituted piperazines in dichloromethane at room temperature. The conjugates, all obtained in good to excellent yields, were synthesized to be key components of nucleic acid transfection ...

  5. Synthesis of sugars catalysed by microgel conjugated rabbit muscle ...

    African Journals Online (AJOL)

    Microgel has been prepared and covalently conjugated to rabbit muscle aldolase and employed to catalyse reactions between dihydroxyacetone phosphate, DHAP natural and non-natural acceptors aldehydes in aqueous, aqueous – organic solvents at ambient temperature. The microgel conjugated enzyme was found to ...

  6. Metallo-Phthalocyanine Near-IR Fluorophores: Oligonucleotide Conjugates and Their Applications in PCR Assays

    Science.gov (United States)

    Nesterova, Irina V.; Verdree, Vera T.; Pakhomov, Serhii; Strickler, Karen L.; Allen, Michael W.; Hammer, Robert P.; Soper, Steven A.

    2011-01-01

    Water soluble, metallo-pthalocyanine (MPc) near-IR fluorophores were designed, synthesized, and evaluated as highly stable and sensitive reporters for fluorescence assays. Their conjugation to oligonucleotides was achieved via succinimidyl ester-amino coupling chemistry with the conditions for conjugation extensively examined and optimized. In addition, various conjugate purification and isolation techniques were evaluated as well. Results showed that under proper conditions and following purification using reverse-phase ion-pair chromatography, labeling efficiencies near 80% could be achieved using ZnPc (Zn phthalocyanine) as the labeling fluorophore. Absorption and fluorescence spectra accumulated for the conjugates indicated that the intrinsic fluorescence properties of the MPc’s were not significantly altered by covalent attachment to oligonucleotides. As an example of the utility of MPc reporters, we used the MPc–oligonucleotide conjugates as primers for PCR (polymerase chain reaction) amplifications with the products sorted via electrophoresis and detected using near-IR fluorescence (λex = 680 nm). The MPc dyes were found to be more chemically stable under typical thermal cycling conditions used for PCR compared to the carbocyanine-based near-IR reporter systems typically used and produced single and narrow bands in the electrophoretic traces, indicative of producing a single PCR product during amplification. PMID:18030995

  7. Effect of Maillard Conjugates on the Physical Stability of Zein Nanoparticles Prepared by Liquid Antisolvent Coprecipitation.

    Science.gov (United States)

    Davidov-Pardo, Gabriel; Joye, Iris J; Espinal-Ruiz, Mauricio; McClements, David Julian

    2015-09-30

    Protein nanoparticles are often not very stable in a complex food matrix because they are primarily stabilized by electrostatic repulsion. In this study, we envisaged the stabilization of zein nanoparticles through Maillard conjugation reactions with polysaccharides of different molecular mass. Zein nanoparticles (0.5% w/v) containing resveratrol (0.025% w/v grape skin extract) were produced by liquid antisolvent precipitation and coated with Maillard conjugates (MC) of sodium caseinate and different molecular mass carbohydrates during particle production. Zein nanoparticles coated with conjugated polysaccharides of 2.8, 37, and 150 kDa had diameters of 198 ± 5, 176 ± 6, and 180 ± 3 nm, respectively. The encapsulation efficiency (∼83%) was not affected by conjugation, but the conjugates significantly improved particle stability against changes in pH (2.0-9.0), CaCl2 addition (up to 100 mM), and heat treatment (30-90 °C, 30 min). Zein nanoparticles coated by MC may therefore be suitable delivery systems for hydrophobic bioactive molecules in a wide range of commercial products.

  8. Synthesis, characterization and the release kinetics of antiproliferative agents from polyamidoamine conjugates.

    Science.gov (United States)

    Aderibigbe, B A; Sadiku, E R; Ray, S S; Mbianda, X Y; Fotsing, M C; Jayaramudu, J; Owonubi, S J

    2015-01-01

    Polyamidoamine conjugates containing curcumin and bisphosphonate were synthesized via a one-pot aqueous phase Michael addition reaction. In the design of the conjugate, bisphosphonate formed an integral part of the polymer carrier backbone. Curcumin was incorporated onto the polyamidoamine backbone via piperazine linker. The conjugates were characterized by Fourier transform spectroscopy, energy-dispersive X-ray analysis, atomic force spectroscopy and nuclear magnetic resonance spectroscopy and it confirmed the successful incorporation of the antiproliferative agents onto the carriers. The weight percentage incorporation of bisphosphonate to the carriers was found to be between 2.56% and 3.34%. The in vitro release studies of curcumin from the polyamidoamine conjugate were performed in dialysis bag at selected pH values. The release of curcumin was significantly slower at pH 7.4 when compared to pH 5.8. The release profiles indicate that the conjugates are more stable at pH 7.4 and are potential sustained drug-delivery systems for combination therapy.

  9. Nanostructured Conjugated Polymers for Energy-Related Applications beyond Solar Cells.

    Science.gov (United States)

    Xie, Jian; Zhao, Cui-E; Lin, Zong-Qiong; Gu, Pei-Yang; Zhang, Qichun

    2016-05-20

    To meet the ever-increasing requirements for the next generation of sustainable and versatile energy-related devices, conjugated polymers, which have potential advantages over small molecules and inorganic materials, are among the most promising types of green candidates. The properties of conjugated polymers can be tuned through modification of the structure and incorporation of different functional moieties. In addition, superior performances can be achieved as a result of the advantages of nanostructures, such as their large surface areas and the shortened pathways for charge transfer. Therefore, nanostructured conjugated polymers with different properties can be obtained to be applied in different energy-related organic devices. This review focuses on the application and performance of the recently reported nanostructured conjugated polymers for high-performance devices, including rechargeable lithium batteries, microbial fuel cells (MFCs), thermoelectric generators, and photocatalytic systems. The design strategies, reaction mechanisms, advantages, and limitations of nanostructured conjugated polymers are further discussed in each section. Finally, possible routes to improve the performances of the current systems are also included in the conclusion. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Controlled gas–liquid interfacial plasmas for synthesis of nano-bio-carbon conjugate materials

    Science.gov (United States)

    Kaneko, Toshiro; Hatakeyama, Rikizo

    2018-01-01

    Plasmas generated in contact with a liquid have been recognized to be a novel reactive field in nano-bio-carbon conjugate creation because several new chemical reactions have been yielded at the gas–liquid interface, which were induced by the physical dynamics of non-equilibrium plasmas. One is the ion irradiation to a liquid, which caused the spatially selective dissociation of the liquid and the generation of additive reducing and oxidizing agents, resulting in the spatially controlled synthesis of nanostructures. The other is the electron irradiation to a liquid, which directly enhanced the reduction action at the plasma–liquid interface, resulting in temporally controlled nanomaterial synthesis. Using this novel reaction field, gold nanoparticles with controlled interparticle distance were synthesized using carbon nanotubes as a template. Furthermore, nanoparticle–biomolecule conjugates and nanocarbon–biomolecule conjugates were successfully synthesized by an aqueous-solution contact plasma and an electrolyte plasma, respectively, which were rapid and low-damage processes suitable for nano-bio-carbon conjugate materials.

  11. Optical phase conjugation

    CERN Document Server

    Fisher, Robert A

    1983-01-01

    This book appears at a time of intense activity in optical phase conjugation. We chose not to await the maturation of the field, but instead to provide this material in time to be useful in its development. We have tried very hard to elucidate and interrelate the various nonlinear phenomena which can be used for optical phase conjugation.

  12. Mixtures of l-Amino Acids as Reaction Medium for Formation of Iron Nanoparticles: The Order of Addition into a Ferrous Salt Solution Matters

    Directory of Open Access Journals (Sweden)

    Radek Zbořil

    2013-09-01

    Full Text Available Owing to Mössbauer spectroscopy, an advanced characterization technique for iron-containing materials, the present study reveals previously unknown possibilities using l-amino acids for the generation of magnetic particles. Based on our results, a simple choice of the order of l-amino acids addition into a reaction mixture containing ferrous ions leads to either superparamagnetic ferric oxide/oxyhydroxide particles, or magnetically strong Fe0-Fe2O3/FeOOH core-shell particles after chemical reduction. Conversely, when ferric salts are employed with the addition of selected l-amino acids, only Fe0-Fe2O3/FeOOH core-shell particles are observed, regardless of the addition order. We explain this phenomenon by a specific transient/intermediate complex formation between Fe2+ and l-glutamic acid. This type of complexation prevents ferrous ions from spontaneous oxidation in solutions with full air access. Moreover, due to surface-enhanced Raman scattering spectroscopy we show that the functional groups of l-amino acids are not destroyed during the borohydride-induced reduction. These functionalities can be further exploited for (i attachment of l-amino acids to the as-prepared magnetic particles, and (ii for targeted bio- and/or environmental applications where the surface chemistry needs to be tailored and directed toward biocompatible species.

  13. Detection of OXA-48-type carbapenemase-producing Enterobacteriaceae in diagnostic laboratories can be enhanced by addition of bicarbonates to cultivation media or reaction buffers.

    Science.gov (United States)

    Studentova, Vendula; Papagiannitsis, Costas C; Izdebski, Radoslaw; Pfeifer, Yvonne; Chudackova, Eva; Bergerova, Tamara; Gniadkowski, Marek; Hrabak, Jaroslav

    2015-03-01

    Carbapenemase-mediated resistance to carbapenems in Enterobacteriaceae has become the main challenge in the treatment and prevention of infections recently. The partially unnoticed spread of OXA-48-type carbapenemase producers is usually assigned to low minimum inhibitory concentrations (MICs) of carbapenems that OXA-48-producing isolates often display. Therefore, there is an urgent need of specific and sensitive methods for isolation and detection of OXA-48 producers in clinical microbiology diagnostics. The influence of bicarbonates on carbapenem MICs against carbapenemase-producing Enterobacteriaceae was tested. We also checked whether the addition of bicarbonates to liquid media supplemented with meropenem may facilitate the selective enrichment of various carbapenemase producers in cultures. Furthermore, the sensitivity of carbapenemase confirmation by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS) and spectrophotometric hydrolysis assays upon the addition of NH4HCO3 was examined. The addition of NaHCO3 significantly increased MICs of ertapenem and meropenem for OXA-48 producers. Furthermore, liquid media supplemented with NaHCO3 and meropenem were reliable for the selective enrichment of carbapenemase producers. The presence of NH4HCO3 in buffers used in the spectrophotometric and MALDI-TOF MS carbapenemase detection increased the sensitivity of that assay. Our results demonstrate that bicarbonates in media or reaction buffers can enhance the sensitivity of screening methods and diagnostic tests for carbapenemase producers.

  14. Asymmetric synthesis of α-amino acids via homologation of Ni(II) complexes of glycine Schiff bases. Part 3: Michael addition reactions and miscellaneous transformations.

    Science.gov (United States)

    Aceña, José Luis; Sorochinsky, Alexander E; Soloshonok, Vadim

    2014-09-01

    The major goal of this review is a critical discussion of the literature data on asymmetric synthesis of α-amino acids via Michael addition reactions involving Ni(II)-complexes of amino acids. The material covered is divided into two conceptually different groups dealing with applications of: (a) Ni(II)-complexes of glycine as C-nucleophiles and (b) Ni(II)-complexes of dehydroalanine as Michael acceptors. The first group is significantly larger and consequently subdivided into four chapters based on the source of stereocontrolling element. Thus, a chiral auxiliary can be used as a part of nucleophilic glycine Ni(II) complex, Michael acceptor or both, leading to the conditions of matching vs. mismatching stereochemical preferences. The particular focus of the review is made on the practical aspects of the methodology under discussion and mechanistic considerations.

  15. Effect of Ca, Ce or K oxide addition on the activity of Ni/SiO{sub 2} catalysts for the methane decomposition reaction

    Energy Technology Data Exchange (ETDEWEB)

    Zapata, Beatriz; Torres-Garcia, Enelio [Instituto Mexicano del Petroleo, Programa de Procesos y Reactores, Eje C. 152, Mexico, D.F., C.P. 07730 (Mexico); Valenzuela, Miguel A.; Palacios, Jorge [Instituto Politecnico Nacional-ESIQIE, Lab. Catalisis y Materiales, Zacatenco, Mexico, D.F., C.P. 07738 (Mexico)

    2010-11-15

    To increase the activity and stability of Ni/SiO{sub 2} catalysts, a series of Ni-Ca, Ni-K and Ni-Ce promoted catalysts were prepared by successive impregnations. The textural properties, reducibility and catalytic performance in the methane decomposition reaction were investigated. The catalyst containing 30 wt.% Ni and 30 wt.% cerium oxide greatly increased the conversion of methane (90% of equilibrium value) and improved the stability, whereas the Ni-K and Ni-Ca were less active and stable than the Ni/SiO{sub 2} catalyst. The results suggest that Ce addition prevents the sintering of nickel particles during reduction process maintaining a random distribution between the silica and cerium oxide improving the distribution and migration of deposited carbon. (author)

  16. Formation of the Thiol Conjugates and Active Metabolite of Clopidogrel by Human Liver Microsomes

    Science.gov (United States)

    Lau, Wei C.; Hollenberg, Paul F.

    2012-01-01

    We reported previously the formation of a glutathionyl conjugate of the active metabolite (AM) of clopidogrel and the covalent modification of a cysteinyl residue of human cytochrome P450 2B6 in a reconstituted system (Mol Pharmacol 80:839–847, 2011). In this work, we extended our studies of the metabolism of clopidogrel to human liver microsomes in the presence of four reductants, namely, GSH, l-Cys, N-acetyl-l-cysteine (NAC), and ascorbic acid. Our results demonstrated that formation of the AM was greatly affected by the reductant used and the relative amounts of the AM formed were increased in the following order: NAC (17%) clopidogrel. It was observed that the AM was slowly converted to the thiol conjugate, with a half-life of ∼10 h. Addition of dithiothreitol to the reaction mixture reversed the conversion, which resulted in a decrease in AM-thiol conjugate levels and a concomitant increase in AM levels, whereas addition of NAC led to the formation of AM-NAC and a concomitant decrease in AM-GSH levels. These results not only confirm that the AM is formed through oxidative opening of the thiolactone ring but also suggest the existence of an equilibrium between the AM, the thiol conjugates, and the reductants. These factors may affect the effective concentrations of the AM in vivo. PMID:22584220

  17. Unprecedented Nucleophilic Additions of Highly Polar Organometallic Compounds to Imines and Nitriles Using Water as a Non-Innocent Reaction Medium.

    Science.gov (United States)

    Dilauro, Giuseppe; Dell'Aera, Marzia; Vitale, Paola; Capriati, Vito; Perna, Filippo Maria

    2017-08-14

    In contrast to classic methods carried out under inert atmospheres with dry volatile organic solvents and often low temperatures, the addition of highly polar organometallic compounds to non-activated imines and nitriles proceeds quickly, efficiently, and chemoselectively with a broad range of substrates at room temperature and under air with water as the only reaction medium. Secondary amines and tertiary carbinamines are furnished in yields of up to and over 99 %. The significant solvent D/H isotope effect observed for the on-water nucleophilic additions of organolithium compounds to imines suggests that the on-water catalysis arises from proton transfer across the organic-water interface. The strong intermolecular hydrogen bonds between water molecules may play a key role in disfavoring protonolysis, which occurs extensively in other protic media such as methanol. This work lays the foundation for reshaping many fundamental s-block metal-mediated organic transformations in water. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Novel β-cyclodextrin–eosin conjugates

    Directory of Open Access Journals (Sweden)

    Gábor Benkovics

    2017-03-01

    Full Text Available Eosin B (EoB and eosin Y (EoY, two xanthene dye derivatives with photosensitizing ability were prepared in high purity through an improved synthetic route. The dyes were grafted to a 6-monoamino-β-cyclodextrin scaffold under mild reaction conditions through a stable amide linkage using the coupling agent 4-(4,6-dimethoxy-1,3,5-triazin-2-yl-4-methylmorpholinium chloride. The molecular conjugates, well soluble in aqueous medium, were extensively characterized by 1D and 2D NMR spectroscopy and mass spectrometry. Preliminary spectroscopic investigations showed that the β-cyclodextrin–EoY conjugate retains both the fluorescence properties and the capability to photogenerate singlet oxygen of the unbound chromophore. In contrast, the corresponding β-cyclodextrin–EoB conjugate did not show either relevant emission or photosensitizing activity probably due to aggregation in aqueous medium, which precludes any response to light excitation.

  19. Methotrexate and epirubicin conjugates as potential antitumor drugs

    Directory of Open Access Journals (Sweden)

    Szymon Wojciech Kmiecik

    2017-07-01

    Full Text Available Introduction: The use of hybrid molecules has become one of the most significant approaches in new cytotoxic drug design. This study describes synthesis and characterization of conjugates consisting of two well-known and characterized chemotherapeutic agents: methotrexate (MTX and epirubicin (EPR. The synthesized conjugates combine two significant anticancer strategies: combinatory therapy and targeted therapy. These two drugs were chosen because they have different mechanisms of action, which can increase the anticancer effect of the obtained conjugates. MTX, which is a folic acid analog, has high cytotoxic properties and can serve as a targeting moiety that can reach folate receptors (FRs overexpresing tumor cells. Combination of nonselective drugs such as EPR with MTX can increase the selectivity of the obtained conjugates, while maintaining the high cytotoxic properties.Materials and methods: Conjugates were purified by RP-HPLC and the structure was investigated by MS and MS/MS methods. The effect of the conjugates on proliferation of LoVo, LoVo/Dx, MCF-7 and MV-4-11 human cancer cell lines was determined by SRB or MTT assay.Results: The conjugation reaction results in the formation of monosubstituted (α, γ and disubstituted MTX derivatives. In vitro proliferation data demonstrate that the conjugates synthesized in our study show lower cytotoxic properties than both chemotherapeutics used alone.Discussion: Epirubicin cytotoxicity was not observed in obtained conjugates. Effective drugs release after internalization needs further investigation.

  20. Maillard reaction products from chitosan-xylan ionic liquid solution.

    Science.gov (United States)

    Luo, Yuqiong; Ling, Yunzhi; Wang, Xiaoying; Han, Yang; Zeng, Xianjie; Sun, Runcang

    2013-10-15

    A facile method is reported to prepare Maillard reaction products (MRPs) from chitosan and xylan in co-solvent ionic liquid. UV absorbance and fluorescence changes were regarded as indicators of the occurrence of Maillard reaction. FT-IR, NMR, XRD and TG were used to investigate the structure of chitosan-xylan conjugate. The results revealed that when chitosan reacted with xylan in ionic liquid, the hydrogen bonds in chitosan were destroyed, the facts resulted in the formation of chitosan-xylan MRPs. Moreover, when the mass ratio of chitosan to xylan was 1:1, the Maillard reaction proceeded easily. In addition, relatively high antioxidant property was also noted for the chitosan-xylan conjugate with mass ratio 1:1. So the obtained chitosan-xylan MRP is a promising antioxidant agent for food industry. Copyright © 2013 Elsevier Ltd. All rights reserved.

  1. Long-term immune responses to pneumococcal conjugate vaccines in children previously vaccinated with 7-valent pneumococcal conjugate vaccine.

    Science.gov (United States)

    Klein, Nicola P; Ensor, Kathy; Jouve, Sylvie; Northington, Robert; Moscariello, Michele; McGovern, Paul C

    2013-09-01

    Seven-valent pneumococcal conjugate vaccine (PCV7) has reduced incidence of vaccine-serotype pneumococcal diseases. Using a single dose of 13-valent pneumoccal conjugate vaccine (PCV13), we evaluated late immune responses 10 years after vaccination with PCV7 in infancy, compared with a PCV7-naïve cohort. In this open-label study, we administered 1 dose of PCV13 to children aged 11-14 years who had previously received PCV7 (PCV7/PCV13) or meningococcal group C conjugate vaccine (MnCC/PCV13) during infancy. We evaluated serotype-specific immunoglobulin G concentrations and opsonophagocytic activity prevaccination and 1 week and 1 month postvaccination. We recorded local reactions and systemic events for 4 days postvaccination and adverse events for 6 months. Seventy-four subjects received PCV13 (PCV7/PCV13, n = 38; MnCC/PCV13, n = 36). Prevaccination with PCV13, >62.9% of subjects had immunoglobulin G concentrations ≥0.35 µg/mL for all serotypes except serotype 4 (28-29%); proportions increased at 1 month postvaccination to 100% for all serotypes except serotypes 3 (PCV7/PCV13, 94.7%; MnCC/PCV13, 97.0%) and 14 (MnCC/PCV13, 97.1%). Immunoglobulin G and opsonophagocytic activity concentrations for the 7 common and 6 additional serotypes were similar in both groups prevaccination and increased in both groups from prevaccination to 1 week and 1 month postvaccination. Local reactions and fever were mild or moderate; no serious adverse events were reported. Late immune responses after a single dose of PCV13 were similar in children aged 11-14 years regardless of previous vaccination with PCV7 or MnCC. PCV13 was immunogenic, safe and well tolerated.

  2. Conjugate Gaze Palsies

    Science.gov (United States)

    ... version Home Brain, Spinal Cord, and Nerve Disorders Cranial Nerve Disorders Conjugate Gaze Palsies Horizontal gaze palsy Vertical ... Version. DOCTORS: Click here for the Professional Version Cranial Nerve Disorders Overview of the Cranial Nerves Internuclear Ophthalmoplegia ...

  3. Polymers for Protein Conjugation

    Directory of Open Access Journals (Sweden)

    Gianfranco Pasut

    2014-01-01

    Full Text Available Polyethylene glycol (PEG at the moment is considered the leading polymer for protein conjugation in view of its unique properties, as well as to its low toxicity in humans, qualities which have been confirmed by its extensive use in clinical practice. Other polymers that are safe, biodegradable and custom-designed have, nevertheless, also been investigated as potential candidates for protein conjugation. This review will focus on natural polymers and synthetic linear polymers that have been used for protein delivery and the results associated with their use. Genetic fusion approaches for the preparation of protein-polypeptide conjugates will be also reviewed and compared with the best known chemical conjugation ones.

  4. Qualidade conjugal: mapeando conceitos

    Directory of Open Access Journals (Sweden)

    Clarisse Mosmann

    2006-12-01

    Full Text Available Apesar da ampla utilização do conceito de qualidade conjugal, identifica-se falta de clareza conceitual acerca das variáveis que o compõem. Esse artigo apresenta revisão da literatura na área com o objetivo de mapear o conceito de qualidade conjugal. Foram analisadas sete principais teorias sobre o tema: Troca Social, Comportamental, Apego, Teoria da Crise, Interacionismo Simbólico. Pelos postulados propostos nas diferentes teorias, podem-se identificar três grupos de variáveis fundamentais na definição da qualidade conjugal: recursos pessoais dos cônjuges, contexto de inserção do casal e processos adaptativos. Neste sentido, a qualidade conjugal é resultado do processo dinâmico e interativo do casal, razão deste caráter multidimensional.

  5. Synthetic Studies Toward (−)-FR901483 Using a Conjugate Allylation to Install the C-1 Quaternary Carbon

    OpenAIRE

    Gotchev, Dimitar B.; Comins, Daniel L.

    2006-01-01

    Two approaches to the aza-tricyclo dodecane skeleton of (−)-FR901483 are reported. Both routes utilized a Grignard addition to an N-acylpyridinium salt to establish the absolute stereochemistry at C-6 and a highly diastereoselective conjugate allylation reaction to form the quaternary center at C-1 of the natural product in excellent yield. Although the desired polysubstituted piperidine intermediates were prepared regio- and stereoselectively, the construction of the C-8/C-9 bond connectivit...

  6. Biocatalytic Synthesis of Fluorescent Conjugated Indole Oligomers

    Directory of Open Access Journals (Sweden)

    Ryan M. Bouldin

    2014-12-01

    Full Text Available Fluorescent conjugated materials exhibiting reasonable biocompatibility that are capable of interacting with biological molecules are of interest for bio-sensing and imaging applications. Traditional approaches do not allow for the synthesis of conjugated materials in the presence of biologically relevant substrates. Further conjugated polymers synthesized using conventional methods are doped and not fluorescent. Here we explore the possibility of synthesizing fluorescent oligomers of indole using enzymes as catalyst under mild conditions. The peroxidase catalyzed coupling reaction presented here creates a photoluminescent material that allows for direct utilization (without purification and separation of the dopant in biosensing applications. The polymerization reaction proceeds smoothly in just deionized water and ethanol. Monitoring of the absorption and fluorescence spectra over one hour shows that the concentration of both absorbing and emitting species grows steadily over time. The presence of anionic buffers and templates is shown to effectively retard the development of light emitting species and instead leads to the formation of an electrically doped conjugated polymer. Structural characterization through FTIR and 1H-NMR analysis suggests that the oligomer is coupled through the 2 and 3 positions on the indole ring.

  7. Molecular Characterization of Thiols in Fossil Fuels by Michael Addition Reaction Derivatization and Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry.

    Science.gov (United States)

    Wang, Meng; Zhao, Suoqi; Liu, Xuxia; Shi, Quan

    2016-10-04

    Thiols widely occur in sediments and fossil fuels. However, the molecular composition of these compounds is unclear due to the lack of appropriate analytical methods. In this work, a characterization method for thiols in fossil fuels was developed on the basis of Michael addition reaction derivatization followed by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). Model thiol compound studies showed that thiols were selectively reacted with phenylvinylsulfone and transformed to sulfones with greater than 98% conversions. This method was applied to a coker naphtha, light and heavy gas oils, and crude oils from various geological sources. The results showed that long alkyl chain thiols are readily present in petroleum, which have up to 30 carbon atoms. Large DBE dispersity of thiols indicates that naphthenic and aromatic thiols are also present in the petroleum. This method is capable of detecting thiol compounds in the part per million range by weight. This method allows characterization of thiols in a complex hydrocarbon matrix, which is complementary to the comprehensive analysis of sulfur compounds in fossil fuels.

  8. Study on the Formation of Reaction Phase to Si Addition in Boron Steel Hot-Dipped in Al–7Ni Alloy

    Directory of Open Access Journals (Sweden)

    Jung-Gil Yun

    2017-11-01

    Full Text Available In order to reduce the intermetallic compounds formed during the application of an Al–7Ni wt % hot-dip multifunctional coating on boron steel, developed for Tailor Welded Blanks (TWB and hot stamping, 2–6 wt % Si was added to the coating to change the reaction layer. The coating was run at 690 °C for 120 s. Al9FeNi phases were formed on the steel interface, Fe2Al5 was formed on the steel, FeAl3 was generated between the existing layers, and flake-type Al2Fe3Si3 was formed in the Fe2Al5 phase, depending on the Si content. In addition, as Si was added to the coating, the thickness of the Fe2Al5 phase decreased and the thickness of the Al9FeNi phase and Al2Fe3Si3 increased. The decrease in the thickness of the Fe2Al5 phase was mainly due to the effect of the Si solid solution and the Al2Fe3Si3 formation in the Fe2Al5 phase. The reason for the growth of Al9FeNi is that the higher the Si content in the coating, the more the erosion of the interface of the steel material due to the coating solution. Therefore, the outflow of Fe into the coating liquid increased.

  9. Photoresponsive peptide azobenzene conjugates that specifically interact with platinum surfaces

    Science.gov (United States)

    Dinçer, S.; Tamerler, C.; Sarıkaya, M.; Pişkin, E.

    2008-05-01

    The aim of this study is to prepare photoresponsive peptide-azobenzene compounds which interacts with platinum surfaces specifically, in order to create smart surfaces for further novel applications in design of smart biosensors and array platforms. Here, a water-soluble azobenzene molecule, 4-hydroxyazo benzene,4-sulfonic acid was synthesized by diazo coupling reaction. A platinum-specific peptide, originally selected by a phage display technique was chemically synthesized/purchased, and conjugated with the azobenzene compound activated with carbonyldiimidazole. Both azobenzene and its conjugate were characterized (including photoresponsive properties) by FTIR, NMR, and UV-spectrophotometer. The yield of conjugation reaction estimated by ninhydrin assay was about 65%. Peptide incorporation did not restrict the light-sensitivity of azobenzene. Adsorption of both the peptide and its azobenzene conjugate was followed by Quartz Crystal Microbalance (QCM) system. The kinetic evaluations exhibited that both molecules interact platinum surfaces, quite rapidly and strongly.

  10. New cysteine-S-conjugate precursors of volatile sulfur compounds in bell peppers (Capsicum annuum L. cultivar).

    Science.gov (United States)

    Starkenmann, Christian; Niclass, Yvan

    2011-04-13

    The objective of this study was to verify whether the volatile organic sulfur compounds recently discovered in bell pepper (Capsicum annuum, L. cultivars), such as the mercapto-ketones: 4-sulfanyl-2-heptanone and 2-sulfanyl-4-heptanone, the mercapto-alcohols: 4-sulfanyl-2-heptanol and 2-sulfanyl-4-heptanol, and heptane-2,4-dithiol, originate from their corresponding cysteine-S-conjugates. Analysis of aqueous extracts of red and green bell pepper by ultraperformance liquid chromatography-mass spectrometry with electrospray ionization in the positive mode (UPLC-MS ESI(+)) displayed masses corresponding to the expected cysteine-S-conjugates. To confirm this observation, four cysteine-S-conjugates were prepared as authentic samples: S-(3-hydroxy-1-methylhexyl)-L-cysteine, S-(3-hydroxy-1-propylbutyl)-L-cysteine, S-(3-oxo-1-propylbutyl)-L-cysteine, and (2R,2'R)-3,3'-(4-hydroxyheptane-2,6-diyl)bis(sulfanediyl) bis(2-aminopropanoic acid). By comparison with the fragmentation patterns and retention times of synthetic mixtures of cysteine-S-conjugate diastereoisomers, the natural occurrence of cysteine conjugates was confirmed in bell peppers. In addition, the cysteine-S-conjugates from red and green bell pepper extracts were concentrated by ion exchange chromatography and the fractions incubated with a β-lyase (apotryptophanase). The liberated thiols were concentrated by affinity chromatography, and their occurrence, detected by gas chromatography-mass spectrometry, confirmed our predictions. Moreover, 3-sulfanyl-1-hexanol was also detected and the occurrence of S-(1(2-hydroxyethyl)butyl)-L-cysteine confirmed. A quantitative estimation based on external calibration curves, established by UPLC-MS ESI(+) in selected reaction monitoring mode, showed that cysteine-S-conjugates were present at concentrations in the range of 1 to 100 μg/kg (±20%).

  11. Double conjugate laser amplifier

    Energy Technology Data Exchange (ETDEWEB)

    Chandra, S.; Daunt, G.H.

    1991-01-29

    This paper describes a double conjugate laser amplifier system for producing a stable output laser beam in line with a laser oscillator input beam. It comprises: a laser oscillator which produces a low energy oscillator laser beam therefrom directly along a laser beam axis of the system; an amplification means comprised of double conjugate laser amplifiers further comprised of a first and a second singly phase conjugate amplifiers laterally opposite each other about the laser beam axis; polarizers with one of the polarizers positioned between each of the first and second singly phase conjugate amplifiers on the laser beam axis; Pockels cells with on of the Pockels cells positioned on the laser beam axis immediately prior to one of the polarizers; and a means for selectively switching the amplifier means comprised of applying a half-wave voltage at each of the Pockels cells to provide a polarization rotation of the input beam through 90{degrees} for routing of the oscillator laser beam directly through or reflected off the polarizes as an input beam to the amplification means wherein the amplification means amplifies the input beam twice in each of the first and second singly phase conjugate amplifiers and reflects the amplified laser beam off the polarizers as an amplified laser output beam in exactly the same direction as the input laser beam.

  12. Ferrocene conjugated oligonucleotide for electrochemical detection of DNA base mismatch.

    Science.gov (United States)

    Hasegawa, Yusuke; Takada, Tadao; Nakamura, Mitsunobu; Yamana, Kazushige

    2017-08-01

    We describe the synthesis, binding, and electrochemical properties of ferrocene-conjugated oligonucleotides (Fc-oligos). The key step for the preparation of Fc-oligos contains the coupling of vinylferrocene to 5-iododeoxyuridine via Heck reaction. The Fc-conjugated deoxyuridine phosphoramidite was used in the Fc-oligonucleotide synthesis. We show that thiol-modified Fc-oligos deposited onto gold electrodes possess potential ability in electrochemical detection of DNA base mismatch. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Regioselective Cleavage of Thioether Linkages in Microcystin Conjugates.

    Science.gov (United States)

    Zemskov, Ivan; Kropp, Heike M; Wittmann, Valentin

    2016-07-25

    Microcystins are cyanobacterial toxins that can be found in fresh and coastal waters during algal blooms. Microcystin contamination of water can cause severe poisoning of animals and humans. Quantification of these toxins in biological samples is complicated because a major proportion of microcystins is covalently linked to proteins through thioether bonds formed through a Michael-type addition of cysteine residues of proteins to an N-methyldehydroalanine residue in the microcystins. We investigated chemical methods that can be used to cleave such thioether bonds by means of an elimination reaction that leaves the microcystin backbone intact for subsequent analysis. The known reagent O-mesitylenesulfonylhydroxylamine (MSH) led to regioselective thioether cleavage, but a large excess of reagent was needed, thus making purification challenging. An unexpected side reaction observed during the investigation of the base-induced elimination inspired us to develop a new thioether-cleavage methodology based on the addition of propargylamine as a nucleophile that can trap the elimination product. This methodology could be successfully applied to the quantitative cleavage of a microcystin-LF-glutathione conjugate. The alkyne moiety introduced by this procedure offers the possibility for further reactions with azides by using click chemistry, which might be useful for the derivatization or isolation of microcystins. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. The Cytology of Bacterial Conjugation.

    Science.gov (United States)

    Gilmour, Matthew W; Lawley, Trevor D; Taylor, Diane E

    2004-12-01

    This review focuses on the membrane-associated structures present at cell-cell contact sites during bacterial conjugation. These transfer proteins/structures have roles in the formation and stabilization of mating contacts and ultimately the passage of substrate across the cell envelope between two bacterial cells. The review presents evidence for the dynamic interaction between donor and recipient cells, including the assembly of a transmembrane protein complex, and concludes with a refined model for the mechanism of bacterial conjugation. Bacterial conjugation, in addition to being a mechanism for genome evolution, can be considered as a mechanism for macromolecular secretion. In particular, plasmid-conjugative transfer is classified as a type IV secretion (T4S) system and represents the only known bacterial system for secretion of DNA. In all known conjugative transfer systems, a multitude of proteins are required for both plasmid transfer and pilus production. The plasmids discussed in the review include the F factor; the P group of plasmids, including RP4 and R751 (rigid); and the H plasmid group, including R27 (also thick flexible). With the LacI-GFP/lacO system, the F, P, and H plasmids were observed to reside at well-defined positions located at the mid and quarter-cell positions of Escherichia coli throughout the vegetative cycle. In this review, recent observations based on bacterial cell biology techniques, including visualization of plasmid DNA and proteins at the subcellular level, have been combined with electron and light microscopy studies of mating cells to create an integrated overview of gram-negative bacterial conjugation, a concept referred to as the conjugative cycle.

  15. High performance addition-type thermoplastics (ATTs) - Evidence for the formation of a Diels-Alder adduct in the reaction of an acetylene-terminated material and a bismaleimide

    Science.gov (United States)

    Pater, R. H.; Soucek, M. D.; Chang, A. C.; Partos, R. D.

    1991-01-01

    Recently, the concept and demonstration of a new versatile synthetic reaction for making a large number of high-performance addition-type thermoplastics (ATTs) were reported. The synthesis shows promise for providing polymers having an attractive combination of easy processability, good toughness, respectable high temperature mechanical performance, and excellent thermo-oxidative stability. The new chemistry involves the reaction of an acetylene-terminated material with a bismaleimide or benzoquinone. In order to clarify the reaction mechanism, model compound studies were undertaken in solutions as well as in the solid state. The reaction products were purified by flash chromatography and characterized by conventional analytical techniques including NMR, FT-IR, UV-visible, mass spectroscopy, and high pressure liquid chromatography. The results are presented of the model compound studies which strongly support the formation of a Diels-Alder adduct in the reaction of an acetylene-terminated compound and a bismaleimide or benzoquinone.

  16. Conjugate Meningococcal Vaccines Development: GSK Biologicals Experience

    Directory of Open Access Journals (Sweden)

    Jacqueline M. Miller

    2011-01-01

    Full Text Available Meningococcal diseases are serious threats to global health, and new vaccines specifically tailored to meet the age-related needs of various geographical areas are required. This paper focuses on the meningococcal conjugate vaccines developed by GSK Biologicals. Two combined conjugate vaccines were developed to help protect infants and young children in countries where the incidence of meningococcal serogroup C or serogroup C and Y disease is important: Hib-MenC-TT vaccine, which offers protection against Haemophilus influenzae type b and Neisseria meningitidis serogroup C diseases, is approved in several countries; and Hib-MenCY-TT vaccine, which adds N. meningitidis serogroup Y antigen, is currently in the final stages of development. Additionally, a tetravalent conjugate vaccine (MenACWY-TT designed to help protect against four meningococcal serogroups is presently being evaluated for global use in all age groups. All of these vaccines were shown to be highly immunogenic and to have clinically acceptable safety profiles.

  17. Synthesis and bioactivity of new Finasteride conjugate.

    Science.gov (United States)

    Shuang, Zhao; Jiazhen, Wu; Lijuan, Yang; Zhuo, Li; Dahai, Yu; Jinfeng, Li; Jing, Yu; Yongtao, Liang; En-Si, Wang; Xuexun, Fang

    2011-06-01

    Finasteride is a synthetic 4-azasteroid compound that acts by inhibiting type II 5α-reductase, the enzyme that converts the androgen testosterone to 5α-dihydrotestosterone. It was approved by the US FDA for the treatment of benign prostatic hyperplasia and male pattern baldness. Here the acylation product of Finasteride C-18 amide N-polimod was synthesized by employing acylation reaction with polimod amide as a pivotal intermediate. The structure of the key intermediate and target molecule was confirmed by infrared spectrum, (1)H NMR and (13)C NMR spectra and mass spectrum, and the inhibition of the steroid 5α-reductase and the rats' benign prostatic hyperplasia by the new Finasteride conjugate and Finasteride was also determined. The inhibition of the Finasteride conjugate on 5α-reductase was stronger than that of Finasteride. Prostate hyperplasia of rats was reduced by Finasteride conjugate treatment similar to the Finasteride treatment. However, the Finasteride conjugate treated animals showed better viable condition than the Finasteride treated ones, suggesting the new compound may have improved toxicity profile than Finasteride. Copyright © 2011 Elsevier Ltd. All rights reserved.

  18. DNA-cell conjugates

    Science.gov (United States)

    Hsiao, Shih-Chia; Francis, Matthew B.; Bertozzi, Carolyn; Mathies, Richard; Chandra, Ravi; Douglas, Erik; Twite, Amy; Toriello, Nicholas; Onoe, Hiroaki

    2016-05-03

    The present invention provides conjugates of DNA and cells by linking the DNA to a native functional group on the cell surface. The cells can be without cell walls or can have cell walls. The modified cells can be linked to a substrate surface and used in assay or bioreactors.

  19. Low-Valent Ate Complexes Formed in Cobalt-Catalyzed Cross-Coupling Reactions with 1,3-Dienes as Additives.

    Science.gov (United States)

    Kreyenschmidt, Friedrich; Koszinowski, Konrad

    2018-01-24

    The combination of CoCl2 and 1,3-dienes is known to catalyze challenging alkyl-alkyl cross-coupling reactions between Grignard reagents and alkyl halides, but the mechanism of these valuable transformations remains speculative. Herein, electrospray-ionization mass spectrometry is used to identify and characterize the elusive intermediates of these and related reactions. The vast majority of detected species contain low-valent cobalt(I) centers and diene molecules. Charge tagging, deuterium labeling, and gas-phase fragmentation experiments elucidate the likely origin of these species and show that the diene not only binds to Co as a π ligand, but also undergoes migratory insertion reactions into Co-H and Co-R bonds. The resulting species have a strong tendency to form anionic cobalt(I) ate complexes, the superior nucleophilicity of which should render them highly reactive toward electrophilic substrates and, thus, presumably is the key to the high catalytic efficiency of the system under investigation. Upon the reaction of the in situ formed cobalt(I) ate complexes with organyl halides, only the final cross-coupling product could be detected, but no cobalt(III) species. This finding implies that this reaction step proceeds in a direct manner without any intermediate or, alternatively, that it involves an intermediate with a very short lifetime. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Synthetic studies toward (-)-FR901483 using a conjugate allylation to install the C-1 quaternary carbon.

    Science.gov (United States)

    Gotchev, Dimitar B; Comins, Daniel L

    2006-12-08

    Two approaches to the aza-tricyclo dodecane skeleton of (-)-FR901483 are reported. Both routes utilized a Grignard addition to an N-acylpyridinium salt to establish the absolute stereochemistry at C-6 and a highly diastereoselective conjugate allylation reaction to form the quaternary center at C-1 of the natural product in an excellent yield. Although the desired polysubstituted piperidine intermediates were prepared regio- and stereoselectively, the construction of the C-8/C-9 bond connectivity could not be achieved. All attempts at a pinacol cyclization or an intramolecular 6-exo-tet epoxide opening were unsuccessful because of an unfavorable A(1,3) strain inherent in the molecule.

  1. Toward the in vivo study of captopril-conjugated quantum dots

    Science.gov (United States)

    Manabe, Noriyoshi; Hoshino, Akiyoshi; Liang, Yi-qiang; Goto, Tomomasa; Kato, Norihiro; Yamamoto, Kenji

    2005-04-01

    Photo-luminescent semiconductor quantum dots are nanometer-size probes that have the potential to be applied to the fields of the bio-imaging and the study of the cell mobility inside the body. At the same time, on the other hand, quantum dots are expected to carry some kind of molecules to the local organ inside of the animal body, which leads to the expectation that they can be used as a medicine-carrier. For this purpose, we conjugate (2S)-1-[(2s)-2-Methyl-3-sulfanylpropionyl]pyrrolidine-2-carboxylic acid (cap) with the quantum dot. Cap has the effect as an anti-hypertension drug, which inhibits angiotensin 1 converting enzyme. We conjugated the quantum dot with cap by the exchange reaction avoiding the regions which holds medicinal effect. Quantum dot conjugated with cap (QD-cap) were 3-times brighter than thioglycerol-coated quantum dots (QD-OH). The particle size of cap was 1.1nm and that of QD-cap was 12nm. QD-cap was permeated into the HeLa cells, while QD-MUA were taken into the HeLa cells by endocytosis. In addition, no apoptosis was detected against the cells that permeated QD-cap, because there was no damage to DNA. These results indicated that QD-conjugated medicines (QD-medicine) could be safe in the experiment on the level of the cell. More over, when QD-cap was intravenously injected into Stroke-prone Spontaneously Hypertensive Rats (SHRSP), they reduced blood pressure at systole. Therefore, the anti-hypertension effect of cap remained after conjugated with the quantum dot. These results suggested that QD-medicine were effective on the animal level.

  2. Proton Transfer Reaction Mass Spectrometry detects rapid changes in volatile metabolite emission by Mycobacterium smegmatis after the addition of specific antimicrobial agents

    NARCIS (Netherlands)

    Crespo, E.; Cristescu, S. M.; de Ronde, H.; Kuijper, S.; Kolk, A.H.J.; Anthony, R.M.; Harren, F. J. M.

    2011-01-01

    The metabolic activity of plants, animals or microbes can be monitored by gas headspace analysis. This can be achieved using Proton Transfer Reaction Mass Spectrometry (PTR-MS), a highly sensitive detection method for trace gas analysis. PTR-MS is rapid and can detect metabolic responses on-line as

  3. Analysing the Temperature Effect on the Competitiveness of the Amine Addition versus the Amidation Reaction in the Epoxidized Oil/Amine System by MCR-ALS of FTIR Data

    Directory of Open Access Journals (Sweden)

    Vanessa del Río

    2011-01-01

    Full Text Available The evaluation of the temperature effect on the competitiveness between the amine addition and the amidation reaction in a model cure acid-catalysed reaction between the epoxidized methyl oleate (EMO, obtained from high oleic sunflower oil, and aniline is reported. The study was carried out analysing the kinetic profiles of the chemical species involved in the system, which were obtained applying multivariate curve resolution-alternating least squares (MCR-ALS to the Fourier transform infrared spectra data obtained from the reaction monitoring at two different temperatures (60 °C and 30 °C. At both experimental temperatures, two mechanisms were postulated: non-autocatalytic and autocatalytic. The different behaviour was discussed considering not only the influence of the temperature on the amidation reaction kinetic, but also the presence of the homopolymerization of the EMO reagent.

  4. The F-plasmid TraI protein contains three functional domains required for conjugative DNA strand transfer.

    Science.gov (United States)

    Matson, Steven W; Ragonese, Heather

    2005-01-01

    The F-plasmid-encoded TraI protein, also known as DNA helicase I, is a bifunctional protein required for conjugative DNA transfer. The enzyme catalyzes two distinct but functionally related reactions required for the DNA processing events associated with conjugation: the site- and strand-specific transesterification (relaxase) reaction that provides the nick required to initiate strand transfer and a processive 5'-to-3' helicase reaction that provides the motive force for strand transfer. Previous studies have identified the relaxase domain, which encompasses the first approximately 310 amino acids of the protein. The helicase-associated motifs lie between amino acids 990 and 1450. The function of the region between amino acids 310 and 990 and the region from amino acid 1450 to the C-terminal end is unknown. A protein lacking the C-terminal 252 amino acids (TraIDelta252) was constructed and shown to have essentially wild-type levels of transesterase and helicase activity. In addition, the protein was capable of a functional interaction with other components of the minimal relaxosome. However, TraIDelta252 was not able to support conjugative DNA transfer in genetic complementation experiments. We conclude that TraIDelta252 lacks an essential C-terminal domain that is required for DNA transfer. We speculate this domain may be involved in essential protein-protein interactions with other components of the DNA transfer machinery.

  5. α(δ')-Michael addition of alkyl amines to dimethyl (E)-hex-2-en-4-ynedioate: synthesis of α,β-dehydroamino acid derivatives.

    Science.gov (United States)

    Chavan, Arjun S; Deng, Jie-Cheng; Chuang, Shih-Ching

    2013-02-27

    The direct nucleophilic addition of alkyl amines to the α(δ')-carbon atom of dimethyl (E)-hex-2-en-4-ynedioate to generate α,β-dehydroamino acid derivatives is reported. Herein, we have studied the reactivity of various primary and secondary alkyl amines in the α-selective nucleophilic conjugate addition to conjugated dimethyl (E)-hex-2-en-4-ynedioate. The reaction with primary alkyl amines gives only the (2E,4E)-stereoisomer, while that with secondary alkyl amines gives the (2E,4E) and (2Z,4E)-stereoisomers of dimethyl (2-alkylamino)-muconic ester.

  6. Role of WC additive on reaction, solid-solution and densification in HfB2–SiC ceramics

    DEFF Research Database (Denmark)

    Hu, Dong-Li; Zheng, Qiang; Gu, Hui

    2014-01-01

    A comparative study of phase components and compositions was performed for the pressureless sintered HfB2–SiC–WC composites by various analytical methods. The relative decrease of HfB2 phase leads to a new reaction of HfO2 removal by WC to create B2O3. By using SiC instead of Si3N4 as milling med...

  7. Visible-Light Photoredox-Catalyzed Giese Reaction: Decarboxylative Addition of Amino Acid Derived α-Amino Radicals to Electron-Deficient Olefins

    KAUST Repository

    Millet, Anthony

    2016-06-20

    A tin- and halide-free, visible-light photoredox-catalyzed Giese reaction was developed. Primary and secondary α-amino radicals were generated readily from amino acids in the presence of catalytic amounts of an iridium photocatalyst. The reactivity of the α-amino radicals has been evaluated for the functionalization of a variety of activated olefins. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  8. New three-step domino reaction, "thiophilic addition-beta-elimination of fluoride-[3,3] sigmatropic rearrangement": Synthesis of alpha-allylic and alpha,alpha-bis(allylic) alpha-trifluoromethyl dithioesters.

    Science.gov (United States)

    Grellepois, Fabienne; Timoshenko, Vadim M; Shermolovich, Yuriy G; Portella, Charles

    2006-09-14

    The three-step domino reaction, "thiophilic addition of an organomagnesium reagent onto dithioester-beta-elimination of fluoride-[3,3] sigmatropic rearrangement", provides the product of formal regiospecific substitution of a fluorine atom by an allyl group. This mild and versatile methodology was applied to the synthesis of various alpha-allylic and alpha,alpha-bis(allylic) alpha-trifluoromethyl dithioesters.

  9. Potential Large-Scale Production of Conjugated Soybean Oil Catalyzed by Photolyzed Iodine in Hexanes

    Science.gov (United States)

    A laboratory apparatus is described for the production of conjugated soybean oil (SBO) in pound quantities via irradiation with visible-light. Under our reaction conditions, quantitative conversions (determined by NMR spectroscopy) of SBO to conjugated SBO, in hexanes at reflux temperatures, were a...

  10. Phospha-Michael addition reaction of maleimides employing N-heterocyclic phosphine-thiourea as a phosphonylation reagent: synthesis of 1-aryl-2,5-dioxopyrrolidine-3-yl-phosphonate derivatives.

    Science.gov (United States)

    Molleti, Nagaraju; Bjornberg, Chad; Kang, Jun Yong

    2016-12-07

    N-Heterocyclic phosphine (NHP)-thiourea as a novel phosphonylation reagent has been successfully applied for the phospha-Michael reaction of maleimides under catalyst and additive free reaction conditions. This methodology enables desymmetrization of a variety of maleimide derivatives to provide 1-aryl-2,5-dioxopyrrolidine-3-yl-phosphonates in up to 92% yield. Synthetic manipulation of this Michael adduct afforded an ethylphosphonate and a phosphino lactam. Furthermore, a scale-up experiment for its practical usage as a versatile precursor in organic synthesis was readily demonstrated.

  11. Physicochemical Changes and Glycation Reaction in Intermediate-Moisture Protein-Sugar Foods with and without Addition of Resveratrol during Storage.

    Science.gov (United States)

    Sheng, Zhanwu; Gu, Mantun; Hao, Wangjun; Shen, Yixiao; Zhang, Weimin; Zheng, Lili; Ai, Binling; Zheng, Xiaoyan; Xu, Zhimin

    2016-06-22

    An intermediate-moisture food (IMF) model consisting of whey protein isolate and glucose and an IMF model fortified with resveratrol were used to study the effect of resveratrol on physicochemical changes and glycation of protein-sugar-rich foods during storage. The water activity (aw) of the storage was controlled at 0.75 or 0.56. The browning rate or hardness of fortified IMFs was significantly lower than that of IMFs after 45-day storage. The rate of Maillard reaction in the samples stored at aw 0.56 was higher than that of samples stored at aw 0.75. The fortified IMFs had lower levels of AGEs (advanced glycation end products), CML (N(ε)-(carboxymethyl)-l-lysine), and insoluble protein during storage. The inhibition capability of resveratrol against glycation was also confirmed by using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), liquid chromatography mass spectrometry (LC-MS), and Fourier transform infrared spectroscopy (FTIR) analysis to monitor glycated proteins and protein aggregation in the samples. The results of this study suggested that resveratrol could be used as an inhibitor to reduce the formation of undesirable AGEs and other Maillard reaction products in foods during storage.

  12. Additional evidence that transaldolase exchange, isotope discrimination during the triose-isomerase reaction, or both occur in humans: effects of type 2 diabetes.

    Science.gov (United States)

    Basu, Rita; Chandramouli, Visvanthan; Schumann, William; Basu, Ananda; Landau, Bernard R; Rizza, Robert A

    2009-07-01

    To determine whether deuterium enrichment on carbons 5 and 3 (C5/C3) in plasma glucose is influenced by processes other than gluconeogenesis and, if so, whether these processes are altered by type 2 diabetes. In this study, 10 obese diabetic and 10 obese nondiabetic subjects were infused intravenously with [3,5-(2)H(2)] galactose enriched at a C5-to-C3 ratio of 1.0 as well as the enrichment of deuterium on C5 and C3 of plasma glucose, measured with nuclear magnetic resonance using the acetaminophen glucuronide method. The ratio of deuterium enrichment on C5 and C3 of glucose was deuterium at the level of the triose-isomerase reaction, or both occur in humans. This also indicates that the net effect of these processes on the C5-to-C3 ratio is the same in people with and without type 2 diabetes. The possible effects of transaldolase exchange or selective retention of deuterium (or tritium) at the level of the triose-isomerase reaction on tracee labeling and tracer metabolism should be considered when the deuterated water method is used to measure gluconeogenesis or [3-(3)H] glucose is used to measure glucose turnover in humans.

  13. Site-Selective Conjugation of Native Proteins with DNA.

    Science.gov (United States)

    Trads, Julie B; Tørring, Thomas; Gothelf, Kurt V

    2017-06-20

    Conjugation of DNA to proteins is increasingly used in academia and industry to provide proteins with tags for identification or handles for hybridization to other DNA strands. Assay technologies such as immuno-PCR and proximity ligation and the imaging technology DNA-PAINT require DNA-protein conjugates. In DNA nanotechnology, the DNA handle is exploited to precisely position proteins by self-assembly. For these applications, site-selective conjugation is almost always desired because fully functional proteins are required to maintain the specificity of antibodies and the activity of enzymes. The introduction of a bioorthogonal handle at a specific position of a protein by recombinant techniques provides an excellent approach to site-specific conjugation, but for many laboratories and for applications where several proteins are to be labeled, the expression of recombinant proteins may be cumbersome. In recent years, a number of chemical methods that target conjugation to specific sites at native proteins have become available, and an overview of these methods is provided in this Account. Our laboratory has investigated DNA-templated protein conjugation (DTPC), which offers an alternative approach to site-selective conjugation of DNA to proteins. The method is inspired by the concept of DNA-templated synthesis where functional groups conjugated to DNA strands are preorganized by DNA hybridization to dramatically increase the reaction rate. In DPTC, we target metal binding sites in proteins to template selective covalent conjugation reactions. By chelation of a DNA-metal complex with a metal binding site of the protein, an electrophile on a second DNA strand is aligned for reaction with a lysine side chain on the protein in the proximity of the metal binding site. The method is quite general because approximately one-third of all wild-type proteins contain metal-binding sites, including many IgG antibodies, and it is also applicable to His-tagged proteins. This

  14. Preparation of bioconjugates by solid-phase conjugation to ion exchange matrix-adsorbed carrier proteins

    DEFF Research Database (Denmark)

    Houen, G.; Olsen, D.T.; Hansen, P.R.

    2003-01-01

    protein was conjugated with glutathione, the conjugation ratio determined by acid hydrolysis, and amino acid analysis performed with quantification of carboxymethyl cysteine. Elution of conjugates from the resin by a salt gradient revealed considerable heterogeneity in the degree of derivatization...... of ovalbumin and various peptides were prepared in a similar manner and used for production of peptide antisera by direct immunization with the conjugates bound to the ion exchanger. Advantages of the method are its solid-phase nature, allowing fast and efficient reactions and intermediate washings...

  15. Correlating structure with fluorescence emission in phase-separated conjugated-polymer blends.

    Science.gov (United States)

    Chappell, John; Lidzey, David G; Jukes, Paul C; Higgins, Anthony M; Thompson, Richard L; O'Connor, Stephen; Grizzi, Ilaria; Fletcher, Robert; O'Brien, Jim; Geoghegan, Mark; Jones, Richard A L

    2003-09-01

    Blends of conjugated polymers are frequently used as the active semiconducting layer in light-emitting diodes and photovoltaic devices. Here we report the use of scanning near-field optical microscopy, scanning force microscopy and nuclear-reaction analysis to study the structure of a thin film of a phase-separated blend of two conjugated polymers prepared by spin-casting. We show that in addition to the well-known micrometre-scale phase-separated morphology of the blend, one of the polymers preferentially wets the surface and forms a 10-nm-thick, partially crystallized wetting layer. Using near-field microscopy we identify unexpected changes in the fluorescence emission from the blend that occurs in a 300-nm-wide band located at the interface between the different phase-separated domains. Our measurements provide an insight into the complex structure of phase-separated conjugated-polymer thin films. Characterizing and controlling the properties of the interfaces in such films will be critical in the further development of efficient optoelectronic devices.

  16. Kinetics of the addition reaction of methyl radicals with nitric oxide studied by pulse radiolysis combined with infrared diode laser spectroscopy

    DEFF Research Database (Denmark)

    Jodkowski, J.T.; Ratajczak, E.; Sillesen, A.

    1993-01-01

    The reaction CH3 + NO (+ M) --> CH3NO ( + M) was initiated by pulse radiolysis of acetone/nitric oxide mixtures and the kinetics of methyl radicals was studied by time-resolved infrared absorption spectroscopy. The rate constant was found to be strongly pressure dependent in the range of p (M) = 6.......5-150 mbar at 298 K with M = acetone as the third body. The experimental results are represented in terms of a fall-off curve centered at 37 mbar with limiting high- and low-pressure rate constants of k(rec,infinity) = (6.6 +/- 0.9) x 10(9) x (T/300)0.6 M-1 s-1 and k(rec,0)/[M] = (4.4 +/- 0.4) x 10(12) x (T...

  17. Asymmetric synthesis of α-amino acids via homologation of Ni(II) complexes of glycine Schiff bases. Part 2: aldol, Mannich addition reactions, deracemization and (S) to (R) interconversion of α-amino acids.

    Science.gov (United States)

    Sorochinsky, Alexander E; Aceña, José Luis; Moriwaki, Hiroki; Sato, Tatsunori; Soloshonok, Vadim

    2013-11-01

    This review provides a comprehensive treatment of literature data dealing with asymmetric synthesis of α-amino-β-hydroxy and α,β-diamino acids via homologation of chiral Ni(II) complexes of glycine Schiff bases using aldol and Mannich-type reactions. These reactions proceed with synthetically useful chemical yields and thermodynamically controlled stereoselectivity and allow direct introduction of two stereogenic centers in a single operation with predictable stereochemical outcome. Furthermore, new application of Ni(II) complexes of α-amino acids Schiff bases for deracemization of racemic α-amino acids and (S) to (R) interconversion providing additional synthetic opportunities for preparation of enantiomerically pure α-amino acids, is also reviewed. Origin of observed diastereo-/enantioselectivity in the aldol, Mannich-type and deracemization reactions, generality and limitations of these methodologies are critically discussed.

  18. Oxidative addition reactions of alkyl halides with the group 13 carbene analogue [In{N(Dipp)C(Me)}2CH] (Dipp=2,6-iPr2C6H3).

    Science.gov (United States)

    Hill, Michael S; Hitchcock, Peter B; Pongtavornpinyo, Ruti

    2007-04-30

    Reactions of the well-defined two-coordinate indium "carbene analogue" [In{N(Dipp)-C(Me)}2CH] (Dipp=2,6-iPr2C6H3) have been studied. Reactions of MeI, iPrI, and tBuI with [In{N(Dipp)C(Me)}2CH] formed by the in situ reaction of InI, [K{N(SiMe3)2}], and the iminoenamine ligand precursor successfully yielded the oxidative addition products [InRI{N(Dipp)C(Me)}2CH] (R=Me, iPr, tBu). The results of NMR investigations, which indicated the formation of a series of four-coordinate indium(III) complexes in C6D6 solution, were confirmed in the solid-state by single-crystal X-ray diffraction. Similar reactions employing alkyl bromides were unsuccessful and resulted in the isolation of the corresponding iodides, apparently by metathesis of the bromide oxidative addition product with KI formed during the initial InI metathesis. Reactions of isolated samples of [In{N(Dipp)C(Me)}2CH] with iPrBr and tBuBr, however, were straightforward and resulted in the successful isolation of the analogous iso-propyl and tert-butyl indium(III) bromide complexes. These were also fully characterized by 1H and 13C NMR and single-crystal X-ray diffraction experiments. In contrast, no reaction was observed between [In{N(Dipp)-C(Me)}2CH] and aryl halides or alkyl chlorides.

  19. Nonnatural amino acids for site-specific protein conjugation

    NARCIS (Netherlands)

    Graaf, Albert J. de; Kooijman, M.; Hennink, W.E.; Mastrobattista, E.

    2009-01-01

    Over the years, several chemical reactions have been developed that enable the covalent conjugation of synthetic molecules to natural proteins. The resulting bioconjugates have become important tools in the study of natural proteins. Furthermore, they form a new class of protein-based

  20. Asymmetric Diels Alder reactions and Michael type additions with 6(R)-3’(R)-Pantolactone-substituted-2H-Pyran-3(6H)-one.

    NARCIS (Netherlands)

    Knol, Joop; Jansen, Johan F.G.A.; Bolhuis, Fré van; Feringa, Bernard

    1991-01-01

    The preparation of optically pure pyranone 2a, using d-pantolactone as a chiral auxiliairy, and its successful application in Diels Alder and Michael type additions with d.r.’s of 89/11 up to 100/0 is described.

  1. ASYMMETRIC DIELS-ALDER REACTIONS AND MICHAEL TYPE ADDITIONS WITH 6(R)-3'-(R)-PANTOLACTONE-SUBSTITUTED-2H-PYRAN-3(6H)-ONE

    NARCIS (Netherlands)

    KNOL, J; JANSEN, JFGA; VANBOLHUIS, F; FERINGA, BL

    1991-01-01

    The preparation of optically pure pyranone 2a, using d-pantolactone as a chiral auxiliairy, and its successful application in Diels Alder and Michael type additions with d.r.'s of 89/11 up to 100/0 is described.

  2. Design and synthesis of multivalent neoglycoconjugates by click conjugations

    Directory of Open Access Journals (Sweden)

    Feiqing Ding

    2014-06-01

    Full Text Available A highly stereoselective BF3∙OEt2-promoted tandem hydroamination/glycosylation on glycal scaffolds has been developed to form propargyl 3-tosylamino-2,3-dideoxysugars in a one-pot manner. Subsequent construction of multivalent 3-tosylamino-2,3-dideoxyneoglycoconjugates with potential biochemical applications was presented herein involving click conjugations as the key reaction step. The copper-catalyzed regioselective click reaction was tremendously accelerated with assistance of microwave irradiation.

  3. Metal-Free Reaction of ortho-Carbonylated Alkynyl-Substituted Arylaldehydes with Common Amines: Selective Access to Functionalized Isoindolinone and Indenamine Derivatives.

    Science.gov (United States)

    Cao, Ziping; Zhu, Hongbo; Meng, Xin; Guan, Jun; Zhang, Qiang; Tian, Laijin; Sun, Xuejun; Chen, Guang; You, Jinmao

    2016-11-14

    Herein we describe a reaction of ortho-carbonylated alkynyl-substituted arylaldehydes with common primary amines that can provide functionalized isoindolinone and 3-hydroxylindenamine products in high yields. Depending on the substituent size of primary amines, two distinct reaction pathways were exploited selectively, that are, an initial aza-conjugate addition followed by hydrogen transfer to access isoindolinone framework and a unique oxa-conjugate addition followed by Petasis-Ferrier rearrangement to afford indenamine derivatives. In the presence of Et3 N, the reaction property of small primary amines was changed, proceeding to afford 3-hydroxylindenamine derivatives efficiently. These products contain interesting substructures that exist in many natural products and bioactive molecules. The reaction features contain the use of transition-metal-free catalysts, simple operation, broad substrate scope, and product diversity. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Long-term stabilization of maleimide-thiol conjugates.

    Science.gov (United States)

    Fontaine, Shaun D; Reid, Ralph; Robinson, Louise; Ashley, Gary W; Santi, Daniel V

    2015-01-21

    Michael-addition of a thiol to a maleimide is commonly used for bioconjugation of drugs to macromolecules. Indeed, both current FDA-approved antibody-drug conjugates-Brentuximab vedotin and Trastuzumab emtansine-and one approved PEGylated conjugate-Cimzia-contain a thiol-maleimide adduct. However, the ultimate in vivo fate of such adducts is to undergo disruptive cleavage by thiol exchange or stabilizing ring opening. Therapeutic efficacy of a conjugate can be compromised by thiol exchange and the released drug may show toxicities. However, if the succinimide moiety of a maleimide-thiol conjugate is hydrolyzed, the ring-opened product is stabilized toward cleavage. We determined rates of ring-opening hydrolysis and thiol exchange of a series of N-substituted succinimide thioethers formed by maleimide-thiol conjugation. Ring-opening of conjugates prepared with commonly used maleimides were too slow to serve as prevention against thiol exchange. However, ring-opening rates are greatly accelerated by electron withdrawing N-substituents, and ring-opened products have half-lives of over two years. Thus, conjugates made with electron-withdrawing maleimides may be purposefully hydrolyzed to their ring-opened counterparts in vitro to ensure in vivo stability.

  5. Synthesis and antimicrobial activity of gold nanoparticle conjugates with cefotaxime

    Science.gov (United States)

    Titanova, Elena O.; Burygin, Gennady L.

    2016-04-01

    Gold nanoparticles (GNPs) have attracted significant interest as a novel platform for various applications to nanobiotechnology and biomedicine. The conjugates of GNPs with antibiotics and antibodies were also used for selective photothermal killing of protozoa and bacteria. Also the conjugates of some antibiotics with GNPs decreased the number of bacterial growing cells. In this work was made the procedure optimization for conjugation of cefotaxime (a third-generation cephalosporin antibiotic) with GNPs (15 nm) and we examined the antimicrobial properties of this conjugate to bacteria culture of E. coli K-12. Addition of cefotaxime solution to colloidal gold does not change their color and extinction spectrum. For physiologically active concentration of cefotaxime (3 μg/mL), it was shown that the optimum pH for the conjugation was more than 9.5. A partial aggregation of the GNPs in saline medium was observed at pH 6.5-7.5. The optimum concentration of K2CO3 for conjugation cefotaxime with GNPs-15 was 5 mM. The optimum concentration of cefotaxime was at 0.36 μg/mL. We found the inhibition of the growth of E. coli K12 upon application cefotaxime-GNP conjugates.

  6. Enhanced bactericidal action and masking of allergen structure of soy protein by attachment of chitosan through maillard-type protein-polysaccharide conjugation.

    Science.gov (United States)

    Usui, Masakatsu; Tamura, Hiroshi; Nakamura, Kimiko; Ogawa, Tadashi; Muroshita, Mayumi; Azakami, Hiroyuki; Kanuma, Shin; Kato, Akio

    2004-02-01

    The soy protein-chitosan conjugate was formed by the Maillard reaction in dry state (relative humidity 65%) at 60 degrees C for 2 weeks to improve the functional properties. The antimicrobial activity of the Maillard-type soy protein-chitosan conjugates enhanced 2-3 times that of soy protein-chitosan mixture. The soy protein-chitosan conjugate showed excellent emulsifying property with the progress of Maillard-type conjugation. The allergenicity of soy protein was greatly decreased by the attachment of chitosan through Maillard reaction. The immonoblotting analysis with patient's sera revealed that soy protein-chitosan conjugate was more effective to mask the allergen structure of soy protein causing from 34 kDa-protein (Gly m Bd 30K) than soy protein-galactomannan conjugate. The Western blotting showed that allergen (34 kDa-protein) was completely masked by soy protein-chitosan conjugation, while it was not completely masked by soy protein-galactomannan conjugation.

  7. HER2 specific delivery of methotrexate by dendrimer conjugated anti-HER2 mAb

    Energy Technology Data Exchange (ETDEWEB)

    Shukla, Rameshwer; Thomas, Thommey P; Desai, Ankur M; Kotlyar, Alina; Park, Steve J; Baker, James R Jr [Michigan Nanotechnology Institute for Medicine and Biological Sciences, University of Michigan, 9220 MSRB III, Box 0648, Ann Arbor, MI 48109 (United States)], E-mail: rameshwe@umich.edu, E-mail: jbakerjr@med.umich.edu

    2008-07-23

    Herceptin, a humanized monoclonal antibody that binds to human growth factor receptor-2 (HER2), was covalently attached to a fifth-generation (G5) polyamidoamine dendrimer containing the cytotoxic drug methotrexate. The specific binding and internalization of this conjugate labeled with FITC was clearly demonstrated in cell lines overexpressing HER2 by flow cytometry as well as confocal microscopic analysis. In addition, binding and uptake of antibody conjugated dendrimers was completely blocked by excess non-conjugated herceptin. The dendrimer conjugate was also shown to inhibit the dihydrofolate reductase with similar activity to methotrexate. Co-localization experiments with lysotracker red indicate that antibody conjugate, although internalized efficiently into cells, has an unusually long residence time in the lysosome. Somewhat lower cytotoxicity of the conjugate in comparison to free methotrexate was attributed to the slow release of methotrexate from the conjugate and its long retention in the lysosomal pocket.

  8. Organometallic B12-DNA conjugate

    DEFF Research Database (Denmark)

    Hunger, Miriam; Mutti, Elena; Rieder, Alexander

    2014-01-01

    Design, synthesis, and structural characterization of a B12-octadecanucleotide are presented herein, a new organometallic B12-DNA conjugate. In such covalent conjugates, the natural B12 moiety may be a versatile vector for controlled in vivo delivery of oligonucleotides to cellular targets in hum...

  9. Directed nucleophilic addition of phenoxides to cyclopropenes.

    Science.gov (United States)

    Yamanushkin, Pavel; Lu-Diaz, Michael; Edwards, Andrew; Aksenov, Nicolai A; Rubina, Marina; Rubin, Michael

    2017-10-04

    The alkali metal-templated addition of aryloxides across the double bond of non-conjugated cyclopropenes is described. High cis-selectivity is achieved through a directing effect of a strategically positioned carboxamide functionality.

  10. Conjugated Polymer Nanoparticles for Bioimaging

    Directory of Open Access Journals (Sweden)

    Yasmine Braeken

    2017-12-01

    Full Text Available During the last decade, conjugated polymers have emerged as an interesting class of fluorescence imaging probes since they generally show high fluorescence brightness, high photostability, fast emission rates, non-blinking behavior and low cytotoxicity. The main concern related to most conjugated polymers is their lack of hydrophilicity and thereby poor bio-availability. This can, however, be overcome by the formulation of conjugated polymer nanoparticles in aqueous medium. This review provides an overview of the different techniques employed for the preparation of conjugated polymer nanoparticles, together with methods to improve their photoluminescence quantum yields. For selective targeting of specific cells, dedicated surface functionalization protocols have been developed, using different functional groups for ligand immobilization. Finally, conjugated polymer nanoparticles have recently also been employed for theranostic applications, wherein the particles are simultaneously used as fluorescent probes and carriers for anti-tumor drugs.

  11. A study of the sequential Michael addition-ring closure reaction of ethyl acetoacetate with chalcone: influence of quaternary ammonium cations as phase transfer catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Lopes, Regina C.V.; Oliveira, Maria da Conceicao F. de; Lemos, Telma L.G. de; Mattos, Marcos C. de [Universidade Federal do Ceara, Fortaleza, CE (Brazil). Dept. de Quimica Organica e Inorganica]. E-mail: mcdmatto@ufc.br

    2005-09-15

    The Michael addition of ethyl acetoacetate 1 to chalcone 2 under Solid/Liquid Phase Transfer Catalysis (SL-PTC), solvent free, afforded Michael adduct 3 and an annulated compound 4 in good yield. The cyclic compound 4 was obtained in the majority via an annulation process of the Michael adduct 3. The proportion of 4 in the ratio of 3/4 was dependant on the structure of the quaternary ammonium cation. The results were interpreted on the basis of the organophilicity and accessibility of the catalysts as well as by invoking a 6-membered ring transition state for the formation of 4 due to the chelation level with Q{sup +}. (author)

  12. Generalized conjugate gradient squared

    Energy Technology Data Exchange (ETDEWEB)

    Fokkema, D.R.; Sleijpen, G.L.G. [Utrecht Univ. (Netherlands)

    1994-12-31

    In order to solve non-symmetric linear systems of equations, the Conjugate Gradient Squared (CGS) is a well-known and widely used iterative method. In practice the method converges fast, often twice as fast as the Bi-Conjugate Gradient method. This is what you may expect, since CGS uses the square of the BiCG polynomial. However, CGS may suffer from its erratic convergence behavior. The method may diverge or the approximate solution may be inaccurate. BiCGSTAB uses the BiCG polynomial and a product of linear factors in an attempt to smoothen the convergence. In many cases, this has proven to be very effective. Unfortunately, the convergence of BiCGSTAB may stall when a linear factor (nearly) degenerates. BiCGstab({ell}) is designed to overcome this degeneration of linear factors. It generalizes BiCGSTAB and uses both the BiCG polynomial and a product of higher order factors. Still, CGS may converge faster than BiCGSTAB or BiCGstab({ell}). So instead of using a product of linear or higher order factors, it may be worthwhile to look for other polynomials. Since the BiCG polynomial is based on a three term recursion, a natural choice would be a polynomial based on another three term recursion. Possibly, a suitable choice of recursion coefficients would result in method that converges faster or as fast as CGS, but less erratic. It turns out that an algorithm for such a method can easily be formulated. One particular choice for the recursion coefficients leads to CGS. Therefore one could call this algorithm generalized CGS. Another choice for the recursion coefficients leads to BiCGSTAB. It is therefore possible to mix linear factors and some polynomial based on a three term recursion. This way one may get the best of both worlds. The authors will report on their findings.

  13. Star-Shaped Conjugated Systems

    Directory of Open Access Journals (Sweden)

    Heiner Detert

    2010-05-01

    Full Text Available The present review deals with the preparation and the properties of star-shaped conjugated compounds. Three, four or six conjugated arms are attached to cross-conjugated cores, which consist of single atoms (B, C+, N, benzene or azine rings or polycyclic ring systems, as for example triphenylene or tristriazolotriazine. Many of these shape-persistent [n]star compounds tend to π-stacking and self-organization, and exhibit interesting properties in materials science: Linear and non-linear optics, electrical conductivity, electroluminescence, formation of liquid crystalline phases, etc.

  14. Synthesis and evaluation of anticancer activity in cells of novel stoichiometric pegylated fullerene-doxorubicin conjugates.

    Science.gov (United States)

    Magoulas, George E; Bantzi, Marina; Messari, Danai; Voulgari, Efstathia; Gialeli, Chrisostomi; Barbouri, Despoina; Giannis, Athanassios; Karamanos, Nikos K; Papaioannou, Dionissios; Avgoustakis, Konstantinos

    2015-05-01

    To synthesize pegylated stoichiometrically and structurally well-defined conjugates of fullerene (C60) with doxorubicin (DOX) and investigate their antiproliferative effect against cancer cell lines. Stoichiometric (1:1 and 1:2) pegylated conjugates of C60 with DOX were synthesized using the Prato reaction to create fulleropyrrolidines equipped with a carboxyl function for anchoring a polyethylene glycol (PEG) moiety and either a hydroxyl group for attaching one molecule of DOX or a terminal alkyne group for attaching two molecules of DOX through a click reaction. In both conjugates, the DOX moieties are held through a urethane-type bond. Drug release was studied in phosphate buffer (PBS, pH 7.4) and MCF-7 cancer cells lysate. The uptake of the conjugates by MCF-7 cancer cells and their intracellular localization were studied with fluorescence microscopy. The antiproliferative activity of the conjugates was investigated using the WST-1 test. One or two DOX molecules were anchored on pegylated C60 particles to form DOX-C60-PEG conjugates. Drug liberation from the conjugates was significantly accelerated in the presence of tumor cell lysate compared to PBS. The conjugates could be internalized by MCF-7 cells. DOX from the conjugates exhibited much delayed, compared to free DOX, localization in the nucleus and antiproliferative activity. Pegylated DOX-C60 conjugates (1:1) and (2:1) with well-defined structure were successfully synthesized and found to exhibit comparable, but with a delayed onset, antiproliferative activity with free DOX against MCF-7 cancer cells. The results obtained justify further investigation of the potential of these conjugates as anticancer nanomedicines.

  15. Antibody drug conjugates: design and selection of linker, payload and conjugation chemistry.

    Science.gov (United States)

    McCombs, Jessica R; Owen, Shawn C

    2015-03-01

    Antibody drug conjugates (ADCs) have emerged as an important pharmaceutical class of drugs designed to harness the specificity of antibodies with the potency of small molecule therapeutics. The three main components of ADCs are the antibody, the linker, and the payload; the majority of early work focused intensely on improving the functionality of these pieces. Recently, considerable attention has been focused on developing methods to control the site and number of linker/drug conjugated to the antibody, with the aim of producing more homogenous ADCs. In this article, we review popular conjugation methods and highlight recent approaches including "click" conjugation and enzymatic ligation. We discuss current linker technology, contrasting the characteristics of cleavable and non-cleavable linkers, and summarize the essential properties of ADC payload, centering on chemotherapeutics. In addition, we report on the progress in characterizing to determine physicochemical properties and on advances in purifying to obtain homogenous products. Establishing a set of selection and analytical criteria will facilitate the translation of novel ADCs and ensure the production of effective biosimilars.

  16. Synthesis and study of conjugated polymers containing Di- or Triphenylamine

    Energy Technology Data Exchange (ETDEWEB)

    Sukwattanasinitt, M.

    1996-06-21

    This thesis consists of two separate parts. The first part addresses the synthesis and study of conjugated polymers containing di- or triphenylamine. Two types of polymers: linear polymers and dendrimers, were synthesized. The polymers were characterized by NMR, IR, UV, GPC, TGA and DSC. Electronic and optical properties of the polymers were studied through the conductivity measurements and excitation- emission spectra. the second part of this thesis deals with a reaction of electron-rich acetylenes with TCNE. The discovery of the reaction from charge transfer complex studies and the investigation of this reaction on various electron-rich acetylenes are presented.

  17. pH-responsive fluorescence chemical sensor constituted by conjugated polymers containing pyridine rings.

    Science.gov (United States)

    Adachi, Naoya; Kaneko, Yuki; Sekiguchi, Kazuki; Sugiyama, Hiroki; Sugeno, Masafumi

    2015-12-01

    Poly(p-pyridinium phenylene ethynylene)s (PPyPE) functionalized with alternating donor-acceptor repeat units were synthesized by a Pd-catalyzed Sonogashira coupling reaction between diethynyl monomer and di-iodopyridine for use as a pH-responsive fluorescence chemical sensor. The synthesized PPyPE, containing pyridine units, was characterized by FT-IR, (1)H and (13)C NMR, UV-visible and fluorescence spectroscopies. We investigated the relationship between changes of optical properties and protonation/deprotonation of PPyPE containing pyridine units in solution. Addition of HCl decreased and red-shifted the fluorescence intensity of the conjugated polymers that contained pyridine rings; fluorescence intensity of the polymers increased upon addition of NaOH solution. The synthesized PPyPE was found to be an effective and reusable chemical sensor for pH sensing. Copyright © 2015 John Wiley & Sons, Ltd.

  18. cycloaddition reactions

    Indian Academy of Sciences (India)

    Unknown

    models of regioselectivity in pericyclic reactions. In addition, local hard and soft acid base (HSAB) princi- ples have been also employed to predict the observed regioselectivity.2 In recent years, the conceptual density functional theory has been remarkably successful in explaining the reactivity and site selectivity.3 The.

  19. Trilobolide-porphyrin conjugates: on synthesis and biological effects evaluation.

    Science.gov (United States)

    Tomanová, Pavla; Rimpelová, Silvie; Jurášek, Michal; Buděšínský, Miloš; Vejvodová, Lucie; Ruml, Tomáš; Kmoníčková, Eva; Drašar, Pavel B

    2015-05-01

    Trilobolide (Tb), a potent natural counterpart of thapsigargin, is a sesquiterpene lactone of guaianolide type isolated from horse caraway (Laser trilobum, L. Borkh). Tb exerts remarkable pharmacological properties based on irreversible inhibition of sarco/endoplasmic reticulum calcium ATPase (SERCA), thus being of increasing interest for cancer cure. Additionally, another pharmacological activity of Tb, as well as of thapsigargin, was reported in several studies, Tb as being an effective inductor of nitric oxide and cytokine production. These extraordinary biological properties move these molecules in further pre-clinical evaluation. Because of ubiquitous character of SERCA expression, development of specifically targeted bioactive molecules is inevitable. Since it is well known that porphyrins are preferentially taken up by cancer cells, we have designed and synthesized novel Tb-porphyrin conjugates. Copper-catalyzed azide-alkyne cycloaddition was used to link Tb with porphyrin at once. Two model conjugates of Tb and porphyrin were synthesized and properly characterized. Employing naturally occurring fluorescence properties of porphyrins, we investigated the intracellular localization of the conjugates employing fluorescence microscopy in living cells. Intriguingly, the prepared conjugates localized both in mitochondria and lysosomes of HeLa and LNCaP cells. Furthermore, the cytotoxicity of Tb-porphyrin conjugates was assessed in a number of human cancer cell lines and rat peritoneal cells. Likewise in cancer cell lines, viability of rat peritoneal cells was not affected by the tested conjugates. Interestingly, we observed dose-dependent nitric oxide (iNOS) production induced by the tested conjugates. The effect was related to the type of a linker used and the overall size of the molecule. Another potent immunobiological effects are under evaluation. In summary, the results presented here indicate notable immunobiological potential of the prepared Tb conjugates

  20. Determination of conjugation rates on solid surfaces

    OpenAIRE

    del Campo I.; Ruiz R; Cuevas A.; Revilla C.; Vielva L.; de la Cruz F.

    2012-01-01

    A cytometric method for the estimation of end-point conjugation rates is developed and adapted to surface conjugation. This method improves the through-put of conjugation assays based on replica-plating and results in less noisy experimental data. Although conjugation on solid surfaces deviates from ideal conditions in which cells are continuously mixed, results show that, within the limits of high initial population densities and short mating times, end-point estimates of the conjugation rat...

  1. Contribution towards a Metabolite Profile of the Detoxification of Benzoic Acid through Glycine Conjugation : An Intervention Study

    NARCIS (Netherlands)

    Irwin, C.; van Reenen, M.; Mason, S.; Mienie, L.J.; Westerhuis, J.A.; Reinecke, C.J.

    2016-01-01

    Benzoic acid is widely used as a preservative in food products and is detoxified in humans through glycine conjugation. Different viewpoints prevail on the physiological significance of the glycine conjugation reaction and concerns have been raised on potential public health consequences following

  2. Nano-sized clusters of a teicoplanin ψ-aglycon-fullerene conjugate. Synthesis, antibacterial activity and aggregation studies.

    Science.gov (United States)

    Tollas, Szilvia; Bereczki, Ilona; Sipos, Attila; Rőth, Erzsébet; Batta, Gyula; Daróczi, Lajos; Kéki, Sándor; Ostorházi, Eszter; Rozgonyi, Ferenc; Herczegh, Pál

    2012-08-01

    Glycopeptide antibiotic derivative teicoplanin ψ-aglycone has been bound covalently to a fullerenopyrrolidine derivative using azide-alkyne 1,3-dipolar cycloaddition reaction. The aggregation of the antibiotic-fullerene conjugate in aqueous solution has been studied. The conjugate exhibited antibacterial activity against enterococci resistant to teicoplanin. Copyright © 2012. Published by Elsevier Masson SAS.

  3. Simple, direct conjugation of bacterial O-SP-core antigens to proteins: development of cholera conjugate vaccines.

    Science.gov (United States)

    Xu, Peng; Alam, Mohammad Murshid; Kalsy, Anuj; Charles, Richelle C; Calderwood, Stephen B; Qadri, Firdausi; Ryan, Edward T; Kováč, Pavol

    2011-10-19

    Bacterial O-SP-core antigens can be conjugated to proteins in the same, simple way as synthetic, linker-equipped carbohydrates by applying squaric acid chemistry. Introduction of spacers (linkers) to either O-SP-core antigens or protein carriers, which is involved in commonly applied protocols, is not required. The newly developed method described here consists of preparation of a squaric acid monoester derivative of O-SP-core antigen, utilizing the amino group inherent in the core, and reaction of the monoester with the carrier protein. The intermediate monoester can be easily purified; its conjugation can be monitored by SELDI-TOF mass spectrometry and, thus, readily controlled, since the conjugation can be terminated when the desired carbohydrate-protein ratio is reached. Here, we describe production of conjugates containing the O-SP-core antigen of Vibrio cholerae O1, the major cause of cholera, a severe dehydrating diarrheal disease of humans. The resultant products are recognized by convalescent phase sera from patients recovering from cholera in Bangladesh, and anti-O-SP-core-protein responses correlate with plasma antilipopolysaccharide and vibriocidal responses, which are the primary markers of protection from cholera. The results suggest that such conjugates have potential as vaccines for cholera and other bacterial diseases.

  4. A Simple, Direct Conjugation of Bacterial O-SP–Core Antigens to Proteins: Development of Cholera Conjugate Vaccines

    Science.gov (United States)

    Xu, Peng; Alam, Mohammad Murshid; Kalsy, Anuj; Charles, Richelle C.; Calderwood, Stephen B.; Qadri, Firdausi; Ryan, Edward T.; Kováč, Pavol

    2011-01-01

    Bacterial O-SP–core antigens can be conjugated to proteins in the same, simple way as synthetic, linker-equipped carbohydrates by applying squaric acid chemistry. Introduction of spacers (linkers) to either O-SP–core antigens or protein carriers, which is involved in commonly applied protocols, is not required. The newly developed method here described consists of preparation of a squaric acid monoester derivative of O-SP–core antigen, utilizing the amino group inherent in the core, and reaction of the monoester with the carrier protein. The intermediate monoester can be easily purified, its conjugation can be monitored by SELDI-TOF mass spectrometry and, thus, readily controlled, since the conjugation can be terminated when the desired carbohydrate–protein ratio is reached. Here we describe production of conjugates containing the O-SP-core antigen of Vibrio cholerae O1, the major cause of cholera, a severe dehydrating diarrheal disease of humans. The resultant products are recognized by convalescent phase sera from patients recovering from cholera in Bangladesh, and anti-O-SP-core-protein responses correlate with plasma anti-lipopolysaccharide and vibriocidal responses, which are the primary markers of protection from cholera. The results suggest that such conjugates have potential as vaccines for cholera and other bacterial diseases. PMID:21899371

  5. Conjugation effects on antibody-drug conjugates: evaluation of interaction kinetics in real time on living cells.

    Science.gov (United States)

    Bondza, Sina; Stenberg, Jonas; Nestor, Marika; Andersson, Karl; Björkelund, Hanna

    2014-11-03

    Antibody-drug conjugates (ADC) have shown promising effects in cancer therapy by combining the target specificity of an antibody with the toxicity of a chemotherapeutic drug. As the number of therapeutic antibodies is significantly larger than those used as ADCs, there is unused potential for more effective therapies. However, the conjugation of an additional molecule to an antibody may affect the interaction with its target, altering association rate, dissociation rate, or both. Any changes of the binding kinetics can have subsequent effects on the efficacy of the ADCs, thus the kinetics are important to monitor during ADC development and production. This paper describes a method for the analysis of conjugation effects on antibody binding to its antigen, using the instrument LigandTracer and a fluorescent monovalent anti-IgG binder denoted FIBA, which did not affect the interaction. All measurements were done in real time using living cells which naturally expressed the antigens. With this method the binding profiles of different conjugations of the therapeutic anti-EGFR antibody cetuximab and the anti-CD44v6 antibody fragment AbD15171 were evaluated and compared. Even comparatively small modifications of cetuximab altered the interaction with the epidermal growth factor receptor (EGFR). In contrast, no impact on the AbD15171-CD44v6 interaction was observed upon conjugation. This illustrates the importance to study the binding profile for each ADC combination, as it is difficult to draw any general conclusion about conjugation effects. The modification of interaction kinetics through conjugation opens up new possibilities when optimizing an antibody or an ADC, since the conjugations can be used to create a binding profile more apt for a specific clinical need.

  6. Highly Enantioselective Construction of Tertiary Thioethers and Alcohols via Phosphine-Catalyzed Asymmetric γ-Addition reactions of 5H-Thiazol-4-ones and 5H-Oxazol-4-ones: Scope and Mechanistic Understandings

    KAUST Repository

    Wang, Tianli

    2015-06-02

    Phosphine-catalyzed highly enantioselective γ-additions of 5H-thiazol-4-ones and 5H-oxazol-4-ones to allenoates have been developed for the first time. With the employment of amino-acid derived bifunctional phosphines, a wide range of substituted 5H-thiazol-4-one and 5H-oxazol-4-one derivatives bearing heteroarom (S or O)-containing tertiary chiral centers were constructed in high yields and excellent enantioselectivities. The reported method provides a facile access to enantioenriched tertiary thioether/alcohols. The mechanism of γ-addition reaction was investigated by performing DFT calculations, and the hydrogen bonding interactions between the Brønsted acid moiety of the phosphine catalysts and the “C=O” unit of donor molecules were shown to be crucial in asymmetric induction.

  7. Recent advances in conjugated polymers for light emitting devices.

    Science.gov (United States)

    Alsalhi, Mohamad Saleh; Alam, Javed; Dass, Lawrence Arockiasamy; Raja, Mohan

    2011-01-01

    A recent advance in the field of light emitting polymers has been the discovery of electroluminescent conjugated polymers, that is, kind of fluorescent polymers that emit light when excited by the flow of an electric current. These new generation fluorescent materials may now challenge the domination by inorganic semiconductor materials of the commercial market in light-emitting devices such as light-emitting diodes (LED) and polymer laser devices. This review provides information on unique properties of conjugated polymers and how they have been optimized to generate these properties. The review is organized in three sections focusing on the major advances in light emitting materials, recent literature survey and understanding the desirable properties as well as modern solid state lighting and displays. Recently, developed conjugated polymers are also functioning as roll-up displays for computers and mobile phones, flexible solar panels for power portable equipment as well as organic light emitting diodes in displays, in which television screens, luminous traffic, information signs, and light-emitting wallpaper in homes are also expected to broaden the use of conjugated polymers as light emitting polymers. The purpose of this review paper is to examine conjugated polymers in light emitting diodes (LEDs) in addition to organic solid state laser. Furthermore, since conjugated polymers have been approved as light-emitting organic materials similar to inorganic semiconductors, it is clear to motivate these organic light-emitting devices (OLEDs) and organic lasers for modern lighting in terms of energy saving ability. In addition, future aspects of conjugated polymers in LEDs were also highlighted in this review.

  8. Recent Advances in Conjugated Polymers for Light Emitting Devices

    Directory of Open Access Journals (Sweden)

    Mohan Raja

    2011-03-01

    Full Text Available A recent advance in the field of light emitting polymers has been the discovery of electroluminescent conjugated polymers, that is, kind of fluorescent polymers that emit light when excited by the flow of an electric current. These new generation fluorescent materials may now challenge the domination by inorganic semiconductor materials of the commercial market in light-emitting devices such as light-emitting diodes (LED and polymer laser devices. This review provides information on unique properties of conjugated polymers and how they have been optimized to generate these properties. The review is organized in three sections focusing on the major advances in light emitting materials, recent literature survey and understanding the desirable properties as well as modern solid state lighting and displays. Recently, developed conjugated polymers are also functioning as roll-up displays for computers and mobile phones, flexible solar panels for power portable equipment as well as organic light emitting diodes in displays, in which television screens, luminous traffic, information signs, and light-emitting wallpaper in homes are also expected to broaden the use of conjugated polymers as light emitting polymers. The purpose of this review paper is to examine conjugated polymers in light emitting diodes (LEDs in addition to organic solid state laser. Furthermore, since conjugated polymers have been approved as light-emitting organic materials similar to inorganic semiconductors, it is clear to motivate these organic light-emitting devices (OLEDs and organic lasers for modern lighting in terms of energy saving ability. In addition, future aspects of conjugated polymers in LEDs were also highlighted in this review.

  9. Recent Advances in Conjugated Polymers for Light Emitting Devices

    Science.gov (United States)

    AlSalhi, Mohamad Saleh; Alam, Javed; Dass, Lawrence Arockiasamy; Raja, Mohan

    2011-01-01

    A recent advance in the field of light emitting polymers has been the discovery of electroluminescent conjugated polymers, that is, kind of fluorescent polymers that emit light when excited by the flow of an electric current. These new generation fluorescent materials may now challenge the domination by inorganic semiconductor materials of the commercial market in light-emitting devices such as light-emitting diodes (LED) and polymer laser devices. This review provides information on unique properties of conjugated polymers and how they have been optimized to generate these properties. The review is organized in three sections focusing on the major advances in light emitting materials, recent literature survey and understanding the desirable properties as well as modern solid state lighting and displays. Recently, developed conjugated polymers are also functioning as roll-up displays for computers and mobile phones, flexible solar panels for power portable equipment as well as organic light emitting diodes in displays, in which television screens, luminous traffic, information signs, and light-emitting wallpaper in homes are also expected to broaden the use of conjugated polymers as light emitting polymers. The purpose of this review paper is to examine conjugated polymers in light emitting diodes (LEDs) in addition to organic solid state laser. Furthermore, since conjugated polymers have been approved as light-emitting organic materials similar to inorganic semiconductors, it is clear to motivate these organic light-emitting devices (OLEDs) and organic lasers for modern lighting in terms of energy saving ability. In addition, future aspects of conjugated polymers in LEDs were also highlighted in this review. PMID:21673938

  10. Click chemistry based biomolecular conjugation monitoring using surface-enhanced Raman spectroscopy mapping

    DEFF Research Database (Denmark)

    Palla, Mirko; Kumar, Shiv; Li, Zengmin

    2016-01-01

    We describe here a novel surface-enhanced Raman spectroscopy (SERS) based technique for monitoring the conjugation of small molecules by the well-known click reaction between an alkyne and azido moiety on the partner molecules. The monitoring principle is based on the loss of the characteristic...... alkyne/azide Raman signal with triazole formation in the reaction as a function of time. Since these universal Raman reporter groups are specific for click reactions, this method may facilitate a broad range of applications for monitoring the conjugation efficiency of molecules in diverse areas...

  11. Conjugated polymer nanoparticles, methods of using, and methods of making

    KAUST Repository

    Habuchi, Satoshi

    2017-03-16

    Embodiments of the present disclosure provide for conjugated polymer nanoparticle, method of making conjugated polymer nanoparticles, method of using conjugated polymer nanoparticle, polymers, and the like.

  12. Benzotrifuran (BTFuran): a building block for π-conjugated systems.

    Science.gov (United States)

    Ferreira, Renan B; Figueroa, Jose M; Fagnani, Danielle E; Abboud, Khalil A; Castellano, Ronald K

    2017-08-24

    Reported here is the first synthesis, X-ray crystal structure, and derivatization of benzotrifuran (BTFuran). Single crystal X-ray analysis of BTFuran shows a tight hexagonal packing stabilized by π-stacking interactions and C-H···O contacts. α-Lithiation of BTFuran enables the preparation of reactive intermediates suitable for cross-coupling reactions, allowing access to representative BTFuran-containing π-conjugated systems.

  13. Are conjugated linolenic acid isomers an alternative to conjugated linoleic acid isomers in obesity prevention?

    Science.gov (United States)

    Miranda, Jonatan; Arias, Noemi; Fernández-Quintela, Alfredo; del Puy Portillo, María

    2014-04-01

    Despite its benefits, conjugated linoleic acid (CLA) may cause side effects after long-term administration. Because of this and the controversial efficacy of CLA in humans, alternative biomolecules that may be used as functional ingredients have been studied in recent years. Thus, conjugated linolenic acid (CLNA) has been reported to be a potential anti-obesity molecule which may have additional positive effects related to obesity. According to the results reported in obesity, CLNA needs to be given at higher doses than CLA to be effective. However, because of the few studies conducted so far, it is still difficult to reach clear conclusions about the potential use of these CLNAs in obesity and its related changes (insulin resistance, dyslipidemia, or inflammation). Copyright © 2012 SEEN. Published by Elsevier Espana. All rights reserved.

  14. Antagonistic Donor Density Effect Conserved in Multiple Enterococcal Conjugative Plasmids

    Science.gov (United States)

    Bandyopadhyay, Arpan; O'Brien, Sofie; Frank, Kristi L.; Dunny, Gary M.

    2016-01-01

    ABSTRACT Enterococcus faecalis, a common causative agent of hospital-acquired infections, is resistant to many known antibiotics. Its ability to acquire and transfer resistance genes and virulence determinants through conjugative plasmids poses a serious concern for public health. In some cases, induction of transfer of E. faecalis plasmids results from peptide pheromones produced by plasmid-free recipient cells, which are sensed by the plasmid-bearing donor cells. These plasmids generally encode an inhibitory peptide that competes with the pheromone and suppresses self-induction of donors. We recently demonstrated that the inhibitor peptide encoded on plasmid pCF10 is part of a unique quorum-sensing system in which it functions as a “self-sensing signal,” reducing the response to the pheromone in a density-dependent fashion. Based on the similarities between regulatory features controlling conjugation in pAD1 and pAM373 and those controlling conjugation in pCF10, we hypothesized that these plasmids are likely to exhibit similar quorum-sensing behaviors. Experimental findings indicate that for both pAD1 and pAM373, high donor densities indeed resulted in decreased induction of the conjugation operon and reduced conjugation frequencies. This effect was restored by the addition of exogenous inhibitor, confirming that the inhibitor serves as an indicator for donor density. Donor density also affects cross-species conjugative plasmid transfer. Based on our experimental results, we propose models for induction and shutdown of the conjugation operon in pAD1 and pAM373. IMPORTANCE Enterococcus faecalis is a leading cause of hospital-acquired infections. Its ability to transfer antibiotic resistance and virulence determinants by sharing its genetic material with other bacteria through direct cell-cell contact via conjugation poses a serious threat. Two antagonistic signaling peptides control the transfer of plasmids pAD1 and pAM373: a peptide pheromone produced by

  15. Oligonucleotide conjugates for therapeutic applications.

    Science.gov (United States)

    Winkler, Johannes

    2013-07-01

    Insufficient pharmacokinetic properties and poor cellular uptake are the main hurdles for successful therapeutic development of oligonucleotide agents. The covalent attachment of various ligands designed to influence the biodistribution and cellular uptake or for targeting specific tissues is an attractive possibility to advance therapeutic applications and to expand development options. In contrast to advanced formulations, which often consist of multiple reagents and are sensitive to a variety of preparation conditions, oligonucleotide conjugates are defined molecules, enabling structure-based analytics and quality control techniques. This review gives an overview of current developments of oligonucleotide conjugates for therapeutic applications. Attached ligands comprise peptides, proteins, carbohydrates, aptamers and small molecules, including cholesterol, tocopherol and folic acid. Important linkage types and conjugation methods are summarized. The distinct ligands directly influence biochemical parameters, uptake mechanisms and pharmacokinetic properties.

  16. Phase conjugation of acoustic beams

    Science.gov (United States)

    Bunkin, F. V.; Vlasov, D. V.; Kravtsov, Iu. A.

    The paper presents a classification of methods for the phase conjugation (PC) of wave fields of various physical natures on the basis of such nonliner interactions as stimulated scattering, and three- and four-wave interactions. Among the latter, attention is given to holographic (volume and surface) and parametric PC schemes, permitting PC with amplification. The possibility of developing phase-conjugated devices using acoustic PC devices on the basis of various nonlinear effects is considered. Experimental results pertaining to the PC of sound fields are presented, and possible applications of acoustic PC devices are indicated.

  17. Unconjugated bile salts shuttle through hepatocyte peroxisomes for taurine conjugation.

    NARCIS (Netherlands)

    Rembacz, K.P.; Woudenberg, J.; Hoekstra, M.; Jonkers, E.Z.; Heuvel, F.A. van den; Buist-Homan, M.; Woudenberg-Vrenken, T.E.; Rohacova, J.; Marin, M.L.; Miranda, M.A.; Moshage, H.; Stellaard, F.; Faber, K.N.

    2010-01-01

    Bile acid-CoA:amino acid N-acyltransferase (BAAT) conjugates bile salts to glycine or taurine, which is the final step in bile salt biosynthesis. In addition, BAAT is required for reconjugation of bile salts in the enterohepatic circulation. Recently, we showed that BAAT is a peroxisomal protein,

  18. Unconjugated Bile Salts Shuttle Through Hepatocyte Peroxisomes for Taurine Conjugation

    NARCIS (Netherlands)

    Rembacz, Krzysztof P.; Woudenberg, Jannes; Hoekstra, Mark; Jonkers, Elles Z.; van den Heuvel, Fiona A. J.; Buist-Homan, Manon; Woudenberg-Vrenken, Titia E.; Rohacova, Jana; Luisa Marin, M.; Miranda, Miguel A.; Moshage, Han; Stellaard, Frans; Faber, Klaas Nico

    2010-01-01

    Bile acid-CoA.amino acid N-acyltransferase (BAAT) conjugates bile salts to glycine or taurine, which is the final step in bile salt biosynthesis In addition, BAAT is required for reconjugation of bile salts in the enterohepatic circulation Recently, we showed that BAAT is a peroxisomal protein,

  19. New pneumococcal conjugate vaccine introductions in four sub ...

    African Journals Online (AJOL)

    Background: Pneumonia is a main cause of under-five mortality in low-income settings. The pneumococcal conjugate vaccine (PCV) has been introduced in many countries as a tool in the disease's prevention. Although PCV's effectiveness has been established, less is known about the effects of introducing additional ...

  20. Tumor accumulation of {epsilon}-poly-lysines-based polyamines conjugated with boron clusters

    Energy Technology Data Exchange (ETDEWEB)

    Umano, Masayuki; Uechi, Kazuhiro; Uriuda, Takatoshi; Murayama, Sayuri; Azuma, Hideki [Department of Applied Chemistry and Bioengineering, Graduate School of Engineering, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 5588585 (Japan); Shinohara, Atsuko [Department of Epidemiology and Environmental Health, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 1138421 (Japan); Liu, Young; Ono, Koji [Research Reactor Institute, Kyoto University, 2-1010 Asashiro-nishi, Kumatori 5900494 (Japan); Kirihata, Mitsunori [Department of Bioscience and Informatics, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai 5998531 (Japan); Yanagie, Hironobu [Department of Nuclear Engineering and Management, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 1138656 (Japan); Nagasaki, Takeshi, E-mail: nagasaki@bioa.eng.osaka-cu.ac.jp [Department of Applied Chemistry and Bioengineering, Graduate School of Engineering, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 5588585 (Japan)

    2011-12-15

    Boron Neutron Capture Therapy (BNCT) is one of the potent cancer radiotherapies using nuclear reaction between {sup 10}B atoms and the neutron. Whether BNCT will succeed or not depends on tumor selective delivery of {sup 10}B compounds. {epsilon}-Poly-L-lysine is a naturally occurring polyamine characterized by the peptide linkages between the carboxyl and {epsilon}-amino groups of L-lysine. Because of high safety {epsilon}-PLL is applied practically as a food additive due to its strong antimicrobial activity. In this study, we focus on a development of a novel polymeric delivery system for BNCT using biodegradable {epsilon}-PLL conjugated with {sup 10}B-containing clusters (BSH). This polymeric boron carrier will be expected to deliver safely and efficiently into tumor tissues based on Enhanced Permeability and Retention (EPR) effect.

  1. Immune Response Modulation of Conjugated Agonists with Changing Linker Length.

    Science.gov (United States)

    Ryu, Keun Ah; Slowinska, Katarzyna; Moore, Troy; Esser-Kahn, Aaron

    2016-12-16

    We report immune response modulation with linked Toll-like receptor (TLR) agonists. Conjugating two agonists of synergistic TLRs induce an increase in immune activity compared to equal molarity of soluble agonists. Additionally, varying the distance between the agonists by changing the linker length alters the level of macrophage NF-κB activity as well as primary bone marrow derived dendritic cell IL-6 production. This modulation is effected by the size of the agonists and the pairing of the stimulated TLRs. The sensitivity of linker-length-dependent immune activity of conjugated agonists provides the potential for developing application specific therapeutics.

  2. Intracellular SERS hybrid probes using BSA-reporter conjugates.

    Science.gov (United States)

    Hornemann, Andrea; Drescher, Daniela; Flemig, Sabine; Kneipp, Janina

    2013-07-01

    Surface-enhanced Raman scattering (SERS) hybrid probes are characterized by the typical spectrum of a reporter molecule. In addition, they deliver information from their biological environment. Here, we report SERS hybrid probes generated by conjugating different reporter molecules to bovine serum albumin (BSA) and using gold nanoparticles as plasmonic core. Advantages of the BSA-conjugate hybrid nanoprobes over other SERS nanoprobes are a high biocompatibility, stabilization of the gold nanoparticles in the biological environment, stable reporter signals, and easy preparation. The coupling efficiencies of the BSA-reporter conjugates were determined by MALDI-TOF-MS. The conjugates' characteristic SERS spectra differ from the spectra of unbound reporter molecules. This is a consequence of the covalent coupling, which leads to altered SERS enhancement and changes in the chemical structures of the reporter and of BSA. The application of the BSA-reporter conjugate hybrid probes in 3T3 cells, including duplex imaging, is demonstrated. Hierarchical cluster analysis and principal components analysis were applied for multivariate imaging using the SERS signatures of the incorporated SERS hybrid nanoprobes along with the spectral information from biomolecules in endosomal structures of cells. The results suggest more successful applications of the SERS hybrid probes in cellular imaging and other unordered high-density bioanalytical sensing.

  3. Bacterial conjugation in the cytoplasm of mouse cells.

    Science.gov (United States)

    Lim, Yin Mei; de Groof, Ad J C; Bhattacharjee, Mrinal K; Figurski, David H; Schon, Eric A

    2008-11-01

    Intracellular pathogenic organisms such as salmonellae and shigellae are able to evade the effects of many antibiotics because the drugs are not able to penetrate the plasma membrane. In addition, these bacteria may be able to transfer genes within cells while protected from the action of drugs. The primary mode by which virulence and antibiotic resistance genes are spread is bacterial conjugation. Salmonellae have been shown to be competent for conjugation in the vacuoles of cultured mammalian cells. We now show that the conjugation machinery is also functional in the mammalian cytosol. Specially constructed Escherichia coli strains expressing Shigella flexneri plasmid and chromosomal virulence factors for escape from vacuoles and synthesizing the invasin protein from Yersinia pseudotuberculosis to enhance cellular entry were able to enter 3T3 cells and escape from the phagocytic vacuole. One bacterial strain (the donor) of each pair to be introduced sequentially into mammalian cells had a conjugative plasmid. We found that this plasmid could be transferred at high frequency. Conjugation in the cytoplasm of cells may well be a general phenomenon.

  4. The Use of Mass Spectrometric Techniques to Differentiate Isobaric and Isomeric Flavonoid Conjugates from Axyris amaranthoides

    Directory of Open Access Journals (Sweden)

    Łukasz Marczak

    2016-09-01

    Full Text Available Flavonoids are a group of compounds that are commonly found in various plants, where they play important roles in many processes, including free radical scavenging and UV protection. These compounds can also act as chemical messengers, physiological regulators or protectants against pathogens in the defense reactions of plants. Flavonoid activity is regulated by the addition of various substituents, usually mono- or oligosaccharides of common sugars, such as glucose, rhamnose or galactose. In some plants, glucuronic acid is attached, and this sugar is often acylated by phenylpropanoic acids. Identification of these compounds and their derivatives is of great importance to understanding their role in plant metabolism and defense mechanisms; this research is important because flavonoids are frequently a significant constituent of the human diet. In this study, we identify the flavonoid conjugates present in Axyris amaranthoides L. extracts and demonstrate the usefulness of high-resolution mass spectrometry (HRMS analyzers for the differentiation of isobaric compounds and the utility of fragmentation spectra for the differentiation of isomeric structures. According to our knowledge, some of the structures, especially dehydrodiferulated conjugates of tricin, whose structures are proposed here have been found for the first time in plant material.

  5. Ubiquitin-Conjugating Enzyme 9 Promotes Epithelial Ovarian Cancer Cell Proliferation in Vitro

    Directory of Open Access Journals (Sweden)

    Mei Dong

    2013-05-01

    Full Text Available Epithelial ovarian cancer (EOC is one of the leading causes of cancer deaths in women worldwide. Ubiquitin-conjugating enzyme 9 (Ubc9, the sole conjugating enzyme for sumoylation, regulates protein function and plays an important role in sumoylation-mediated cellular pathways. Although sumoylation plays a key role in DNA repair and tumorgenesis, whether Ubc9 is involved in EOC progression remains unknown. In the present study, we constructed Ubc-9 expressed recombined plasmid pEGFP-N1-Ubc9. The mRNA levels of Ubc9 were confirmed in human ovarian cell lines before and after transfection with pEGFP-N1-Ubc9 or small interfering RNA (siRNA targeted Ubc9 by real-time polymerase chain reaction (PCR. The MTT (3-(4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide assay was used to observe the effect of Ubc9 on cell proliferation. The protein levels of Ubc9, and proliferation-related signals Akt and physphorylated Akt were determined by Western blot. Our results showed that proliferation of EOC cells increased significantly in Ubc9 overexpressing cells, but decreased in Ubc9 knockdown cells. The physphorylation of Akt showed similar trends. In addition, the inhibitor of PI3K/Akt signaling pathway, LY294002, dramatically inhibited the growth of Ubc9 overexpressing cells. Therefore, Ubc9 gene plays an important role in cell proliferation in EOC through PI3K/Akt signaling pathway.

  6. Antioxidant evaluation and oxidative stability of structured lipids from extravirgin olive oil and conjugated linoleic acid.

    Science.gov (United States)

    Lee, Jeung Hee; Lee, Ki-teak; Akoh, Casimir C; Chung, Shin Kyo; Kim, Mee Ree

    2006-07-26

    Structured lipid (SL) was synthesized from extravirgin olive oil (EVOO) and conjugated linoleic acid (CLA) via a lipase-catalyzed reaction. CLA provides a variety of health benefits, but it is not consumed in free fatty acid form. The synthesized SL olive oil contained 42.5 mol % CLA isomers, and the major isomers were cis-9,trans-11-CLA (16.9 mol %) and trans-10,cis-12-CLA (24.2 mol %). The antioxidant activity determined by the radical scavenging capacity with the 2,2-diphenyl-1-picrylhydrazyl radical was lower in SL olive oil than in EVOO. The oxidative stability was also lower in SL olive oil since it had a higher peroxide value, rho-anisidine value, and 2-thiobarbituric acid reactive substances values during 20 days of storage at 60 degrees C. This observation could be due to the reduction in the natural phenolic compounds (97%) and tocopherols (56%), and the incorporated CLA with two conjugated double bonds in the SL olive oil. The oxidative stability of SL olive oil was increased by added rosemary extracts at concentrations of 100, 200, and 300 ppm. The present study suggests that the SL olive oil may be a suitable way to incorporate or deliver CLA into human diets. However, the addition of a proper antioxidant would be required for improving its oxidative stability.

  7. High pressure structural studies of conjugated molecules

    DEFF Research Database (Denmark)

    Knaapila, Matti; Torkkeli, Mika; Scherf, Ullrich

    2018-01-01

    This chapter highlights high pressure GPa level structural studies of conjugated polymers and their analogues: conjugated oligomers and molecules, and rigid rod polymers. Attention is placed on our recent studies of polyfluorenes.......This chapter highlights high pressure GPa level structural studies of conjugated polymers and their analogues: conjugated oligomers and molecules, and rigid rod polymers. Attention is placed on our recent studies of polyfluorenes....

  8. A phthalocyanine--fluorescein conjugate

    OpenAIRE

    ÜN, İlker; ZORLU, YUNUS; İBİŞOĞLU, Hanife; Dumoulin, Fabienne

    2013-01-01

    A phthalocyanine--fluorescein conjugate was designed and prepared. Its photophysical properties (electronic absorption and fluorescence) were determined and compared with those of an analogous derivative functionalized by a simple triazole without chromophore. It is likely to be used as a theranostic agent in photodynamic therapy.

  9. Orderings for conjugate gradient preconditionings

    Science.gov (United States)

    Ortega, James M.

    1991-01-01

    The effect of orderings on the rate of convergence of the conjugate gradient method with SSOR or incomplete Cholesky preconditioning is examined. Some results also are presented that help to explain why red/black ordering gives an inferior rate of convergence.

  10. Subgap Absorption in Conjugated Polymers

    Science.gov (United States)

    Sinclair, M.; Seager, C. H.; McBranch, D.; Heeger, A. J; Baker, G. L.

    1991-01-01

    Along with X{sup (3)}, the magnitude of the optical absorption in the transparent window below the principal absorption edge is an important parameter which will ultimately determine the utility of conjugated polymers in active integrated optical devices. With an absorptance sensitivity of fluorination.

  11. Actinomycete integrative and conjugative elements

    NARCIS (Netherlands)

    Poele, Evelien M. te; Bolhuis, Henk; Dijkhuizen, Lubbert

    This paper reviews current knowledge on actinomycete integrative and conjugative elements (AICEs). The best characterised AICEs, pSAM2 of Streptomyces ambofaciens (10.9 kb), SLP1 (17.3 kb) of Streptomyces coelicolor and pMEA300 of Amycolatopsis methanolica (13.3 kb), are present as integrative

  12. Actinomycete integrative and conjugative elements

    NARCIS (Netherlands)

    Te Poele, E.M.; Bolhuis, H.; Dijkhuizen, L.

    2008-01-01

    This paper reviews current knowledge on actinomycete integrative and conjugative elements (AICEs). The best characterised AICEs, pSAM2 of Streptomyces ambofaciens (10.9 kb), SLP1 (17.3 kb) of Streptomyces coelicolor and pMEA300 of Amycolatopsis methanolica (13.3 kb), are present as integrative

  13. Persistence Mechanisms of Conjugative Plasmids

    DEFF Research Database (Denmark)

    Bahl, Martin Iain; Hansen, Lars H.; Sørensen, Søren Johannes

    2009-01-01

    maintenance in the host cell. These importantly include the ability to self-mobilize in a process termed conjugative transfer, which may occur across species barriers. Other plasmid stabilizing mechanisms include the multimer resolution system, active partitioning, and post-segregational-killing of plasmid...

  14. Conjugative Plasmids of Neisseria gonorrhoeae

    NARCIS (Netherlands)

    Pachulec, Emilia; van der Does, Chris

    2010-01-01

    Many clinical isolates of the human pathogen Neisseria gonorrhoeae contain conjugative plasmids. The host range of these plasmids is limited to Neisseria species, but presence of a tetracycline (tetM) determinant inserted in several of these plasmids is an important cause of the rapid spread of

  15. Enhanced photophysics of conjugated polymers

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Liaohai [Darien, IL

    2007-06-12

    A particulate fluorescent conjugated polymer surfactant complex and method of making and using same. The particles are between about 15 and about 50 nm and when formed from a lipsome surfactant have a charge density similar to DNA and are strongly absorbed by cancer cells.

  16. Galois conjugates of topological phases

    Science.gov (United States)

    Freedman, M. H.; Gukelberger, J.; Hastings, M. B.; Trebst, S.; Troyer, M.; Wang, Z.

    2012-01-01

    Galois conjugation relates unitary conformal field theories and topological quantum field theories (TQFTs) to their nonunitary counterparts. Here we investigate Galois conjugates of quantum double models, such as the Levin-Wen model. While these Galois-conjugated Hamiltonians are typically non-Hermitian, we find that their ground-state wave functions still obey a generalized version of the usual code property (local operators do not act on the ground-state manifold) and hence enjoy a generalized topological protection. The key question addressed in this paper is whether such nonunitary topological phases can also appear as the ground states of Hermitian Hamiltonians. Specific attempts at constructing Hermitian Hamiltonians with these ground states lead to a loss of the code property and topological protection of the degenerate ground states. Beyond this, we rigorously prove that no local change of basis can transform the ground states of the Galois-conjugated doubled Fibonacci theory into the ground states of a topological model whose Hermitian Hamiltonian satisfies Lieb-Robinson bounds. These include all gapped local or quasilocal Hamiltonians. A similar statement holds for many other nonunitary TQFTs. One consequence is that these nonunitary TQFTs do not describe physical realizations of topological phases. In particular, this implies that the “Gaffnian” wave function can not be the ground state of a gapped fractional quantum Hall state.

  17. Conjugal Pairing in Escherichia Coli

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 13; Issue 8. Conjugal Pairing in Escherichia Coli. Joshua Lederberg. Classics Volume 13 Issue 8 August 2008 pp 793-794. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/013/08/0793-0794 ...

  18. Bacteriophytochromes control conjugation in Agrobacterium fabrum.

    Science.gov (United States)

    Bai, Yingnan; Rottwinkel, Gregor; Feng, Juan; Liu, Yiyao; Lamparter, Tilman

    2016-08-01

    Bacterial conjugation, the transfer of single stranded plasmid DNA from donor to recipient cell, is mediated through the type IV secretion system. We performed conjugation assays using a transmissible artificial plasmid as reporter. With this assay, conjugation in Agrobacterium fabrum was modulated by the phytochromes Agp1 and Agp2, photoreceptors that are most sensitive in the red region of visible light. In conjugation studies with wild-type donor cells carrying a pBIN-GUSINT plasmid as reporter that lacked the Ti (tumor inducing) plasmid, no conjugation was observed. When either agp1(-) or agp2(-) knockout donor strains were used, plasmid DNA was delivered to the recipient, indicating that both phytochromes suppress conjugation in the wild type donor. In the recipient strains, the loss of Agp1 or Agp2 led to diminished conjugation. When wild type cells with Ti plasmid and pBIN-GUS reporter plasmid were used as donor, a high rate of conjugation was observed. The DNA transfer was down regulated by red or far-red light by a factor of 3.5. With agp1(-) or agp2(-) knockout donor cells, conjugation in the dark was about 10 times lower than with the wild type donor, and with the double knockout donor no conjugation was observed. These results imply that the phytochrome system has evolved to inhibit conjugation in the light. The decrease of conjugation under different temperature correlated with the decrease of phytochrome autophosphorylation. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Synthesis of Conjugated Polymers via Polymer Elimination Reactions.

    Science.gov (United States)

    1987-04-16

    8217 ."". . . - .,,".?" ",,"""". "" . . " -;"""". - ,’ "’.", , , , 7 " """ " ".a ’ ’ ’ - "- ". Literature Cited 1. Skotheim , T.A., (Ed.) Handbook of Conducting

  20. Probing Conformational Change of Bovine Serum Albumin–Dextran Conjugates under Controlled Dry Heating

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Shuqin; Li, Yunqi; Zhao, Qin; Li, Ji; Xia, Qiuyang; Zhang, Xiaoming; Huang, Qingrong (Rutgers); (Chinese Aca. Sci.); (Jiangnan)

    2015-04-29

    The time-dependent conformational change of bovine serum album (BSA) during Maillard reaction with dextran under controlled dry heating has been studied by small-angle X-ray scattering, fluorescence spectroscopy, dynamic light scattering, and circular dichroism analysis. Through the research on the radii of gyration (Rg), intrinsic fluorescence, and secondary structure, conjugates with dextran coating were found to inhibit BSA aggregation and preserve the secondary structure of native BSA against long-time heat treatment during Maillard reaction. The results suggested that the hydrophilic dextran was conjugated to the compact protein surface and enclosed it and more dextran chains were attached to BSA with the increase of the heating time. The study presented here will be beneficial to the understanding of the conformational evolution of BSA molecules during the dry-heating Maillard reaction and to the control of the protein–polysaccharide conjugate structure.

  1. Photodynamic therapy of melanoma skin cancer using carbon dot - chlorin e6 - hyaluronate conjugate.

    Science.gov (United States)

    Beack, Songeun; Kong, Won Ho; Jung, Ho Sang; Do, In Hwan; Han, Seulgi; Kim, Hyemin; Kim, Ki Su; Yun, Seok Hyun; Hahn, Sei Kwang

    2015-10-01

    Despite wide application of photodynamic therapy (PDT) for the treatment of melanoma skin cancers, there are strong biomedical unmet needs for the effective generation of singlet oxygen after targeted delivery of photosensitizers. Here, we investigated a facile PDT of melanoma skin cancer using transdermal carbon dot - chlorine e6 - hyaluronate (Cdot-Ce6-HA) conjugates. The Cdot-Ce6-HA conjugate was synthesized by the coupling reaction of diaminohexane modified HA (DAH-HA) with the carboxylic group of Ce6. The singlet oxygen generation of Cdot-Ce6-HA conjugates in aqueous solution was more significant than that of free Ce6. The enhanced transdermal and intracellular delivery of Cdot-Ce6-HA conjugates to B16F10 melanoma cells in tumor model mice were corroborated by confocal microscopy and two-photon microscopy. The laser irradiation after topical treatment with Cdot-Ce6-HA conjugates resulted in complete suppression of melanoma skin cancers. The antitumor effect was confirmed by histological analysis with H&E staining and TUNEL assay for tumor apoptosis. Taken together, we could confirm the feasibility of Cdot-Ce6-HA conjugate for transdermal PDT of melanoma skin cancers. To our knowledge, this is the first report on a facile transdermal photodynamic therapy (PDT) of melanoma skin cancer using carbon dot - chlorine e6 - hyaluronate (Cdot-Ce6-HA) conjugates. We found that the singlet oxygen generation of Cdot-Ce6-HA conjugates in aqueous solution was more significant than that of free Ce6. Confocal microscopy and two-photon microscopy clearly confirmed the enhanced transdermal and intracellular delivery of Cdot-Ce6-HA conjugates to B16F10 melanoma cells in tumor model mice. Taken together, we could confirm the feasibility of Cdot-Ce6-HA conjugate for transdermal PDT of melanoma skin cancers. Copyright © 2015 Acta Materialia Inc. All rights reserved.

  2. Ultra-Fast RAFT-HDA Click Conjugation: An Efficient Route to High Molecular Weight Block Copolymers.

    Science.gov (United States)

    Inglis, Andrew J; Stenzel, Martina H; Barner-Kowollik, Christopher

    2009-11-02

    The use of the reversible addition fragmentation chain transfer-hetero Diels-Alder (RAFT-HDA) click reaction for the modular construction of block copolymers is extended to the generation of high molecular weight materials. Cyclopentadienyl end-functionalized polystyrene (PS-Cp) prepared via both atom transfer radical polymerization (ATRP) and the RAFT process are conjugated to poly(isobornyl acrylate) (PiBoA) (also prepared via RAFT polymerization) to achieve well-defined block copolymers with molecular weights ranging from 34 000 to over 100 000 g · mol(-1) and with small polydispersities (PDI < 1.2). The conjugation reactions proceeded in a very rapid fashion (less than 10 min in the majority of cases) under ambient conditions of temperature and atmosphere. The present study demonstrates-for the first time-that RAFT-HDA click chemistry can provide access to high molecular weight block copolymers in a simple and straight-forward fashion. Copyright © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. TAT Peptide and Its Conjugates: Proteolytic Stability

    OpenAIRE

    Grunwald, Jacob; Rejtar, Tomas; Sawant, Rupa; Wang, Zhouxi; Torchilin, Vladimir P.

    2009-01-01

    The proteolytic cleavage of TATp, TATp-PEG1000-PE conjugate (TATp-conjugate), and TATp as TATp-conjugate in mixed micelles made of TATp-conjugate and PEG5000-PE (2.5% mol of TATp-conjugate, TATp-Mic) were studied by HPLC with fluorescent detection using fluorenylmethyl chloroformate (FMOC) labeling and by MALDI-TOF MS analysis. The cleavage kinetics were analyzed in human blood plasma and in trypsin-containing phosphate buffered saline (PBS), pH 7.4, to simulate the proteolytic activity of hu...

  4. The coordination dynamics of mobile conjugate reinforcement.

    Science.gov (United States)

    Kelso, J A Scott; Fuchs, Armin

    2016-02-01

    What we know about infant learning and memory is founded largely on systematic studies by the late Carolyn Rovee-Collier (1942-2014) and her associates of a phenomenon called mobile conjugate reinforcement. Experiments show that when a ribbon is attached from a 3-month-old infant's foot to a mobile suspended overhead the baby quickly realizes it can make the mobile move. The mobile, which offers interesting sights and sounds, responds conjugately to the baby's vigorous kicks which increase in rate by a factor of 3-4. In this paper, using the concepts, methods and tools of coordination dynamics, we present a theoretical model which reproduces the experimental observations of Rovee-Collier and others and predicts a number of additional features that can be experimentally tested. The model is a dynamical system consisting of three equations, one for the baby's leg movements, one for the jiggling motion of the mobile and one for the functional coupling between the two. A key mechanism in the model is positive feedback which is shown to depend sensitively on bifurcation parameters related to the infant's level of attention and inertial properties of the mobile. The implications of our model for the dynamical (and developmental) origins of agency are discussed.

  5. Antibody-Conjugated Nanoparticles for Biomedical Applications

    Directory of Open Access Journals (Sweden)

    Manuel Arruebo

    2009-01-01

    Full Text Available Nanoscience and Nanotechnology have found their way into the fields of Biotechnology and Medicine. Nanoparticles by themselves offer specific physicochemical properties that they do not exhibit in bulk form, where materials show constant physical properties regardless of size. Antibodies are nanosize biological products that are part of the specific immune system. In addition to their own properties as pathogens or toxin neutralizers, as well as in the recruitment of immune elements (complement, improving phagocytosis, cytotoxicity antibody dependent by natural killer cells, etc., they could carry several elements (toxins, drugs, fluorochroms, or even nanoparticles, etc. and be used in several diagnostic procedures, or even in therapy to destroy a specific target. The conjugation of antibodies to nanoparticles can generate a product that combines the properties of both. For example, they can combine the small size of nanoparticles and their special thermal, imaging, drug carrier, or magnetic characteristics with the abilities of antibodies, such as specific and selective recognition. The hybrid product will show versatility and specificity. In this review, we analyse both antibodies and nanoparticles, focusing especially on the recent developments for antibody-conjugated nanoparticles, offering the researcher an overview of the different applications and possibilities of these hybrid carriers.

  6. Organocatalytic chemo- and regioselective oxyarylation of styrenes via a cascade reaction: remote activation of hydroxyl groups.

    Science.gov (United States)

    Zhang, Yu-Chen; Jiang, Fei; Wang, Shu-Liang; Shi, Feng; Tu, Shu-Jiang

    2014-07-03

    The first organocatalytic oxyarylation of styrenes has been established through a cascade of vinylogous Michael addition/alkoxyl transfer reactions of o- or p-hydroxylstyrenes with quinone imine ketals. The process leads to a highly chemo- and regioselective oxyarylation of styrenes and provides access to m-alkylated anilines in generally high yields and excellent diastereoselectivity (up to 99% yield, >95:5 dr). An investigation of the reaction pathway revealed that the existence and position of the hydroxyl group of styrene played crucial roles in the cascade reaction, suggesting that the two reactants were simultaneously activated by binaphthyl-derived phosphoric acid via hydrogen bonding interactions and long-distance conjugative effects. In addition, the activating group of the hydroxyl functionality in the products can be easily removed or transformed, demonstrating the applicability and utility of this strategy in styrene oxyarylation and in the synthesis of styrene-based compounds.

  7. Reactions of 5-[1-(2-phenylmethylidene]-3-phenylimidazolidine-2,4-diones with some organometallic reagents

    Directory of Open Access Journals (Sweden)

    Teresa A. R. Akeng'a

    2005-06-01

    Full Text Available The reaction of Grignard reagents with 5-[1-(2-chlorophenylmethylidene]-3-phenylimidazolidine-2,4-dione, 4, and 5-[1-(2-bromophenylmethylidene]-3-phenylimidazolidine-2,4-dione, 5, gave exclusively 1,2-addition products, 6-8, in 70-80% yields. Lithium dibutylcuprate reacted with 4 to yield exclusively 1,2-addition product 9 (92%. No conjugate or 1,4-addition products were obtained. These results indicate that 5-[1-(2-phenylmethylidene]-3-phenylimidazolidine-2,4-diones do not react like normal unsaturated carbonyl compounds.

  8. Commercially Supplied Amine-Modified siRNAs May Require Ultrafiltration prior to Conjugation with Amine-Reactive Compounds

    Directory of Open Access Journals (Sweden)

    Shannen Lau

    2011-01-01

    Full Text Available Conjugation of siRNA to macromolecules such as serum albumin has multiple potential benefits, including enhanced extravasation via albumin-mediated transcytosis across endothelial cells and reduced renal clearance. In attempting to conjugate siRNA to albumin, we used commercially sourced amine-modified siRNA and reacted it with the heterobifunctional linker succinimidyl 4-[N-maleimidomethyl]cyclohexane-1-carboxylate (SMCC to introduce a maleimide group suitable for conjugation to the thiol group of the surface-exposed cysteine residue (Cys 34 within albumin. We found the conjugation of the SMCC-treated siRNA to bovine serum albumin (BSA to be very inefficient and investigated the cause of the low yield of conjugate. Ultrafiltration with phosphate-buffered saline prior to activation with SMCC dramatically increased the yield of siRNA-albumin conjugate (~15-fold. Communication with the commercial supplier revealed that ammonium acetate buffer was used in a desalting step as part of the siRNA purification process prior to supply, likely resulting in ammonium counterions to the siRNA polyanion, which would interfere with conjugation by consuming the SMCC. After ultrafiltration, a greatly reduced amount of SMCC could be used to affect conjugation, without significant reduction in yield. These data indicate that amine-modified siRNA sourced commercially may require ultrafiltration or dialysis prior to use in conjugation reactions.

  9. Comparison of linoleic and conjugated linoleic acids in enzymatic acidolysis of tristearin

    DEFF Research Database (Denmark)

    Yang, Tiankui; Xu, Xuebing; Li, L.T.

    2001-01-01

    The acyl incorporation and migration of linoleic and conjugated linoleic acids in enzymatic acidolysis were compared in a solvent-free system. Two systems were used in the Lipozyme RM IM-catalyzed acidolysis at 60C temperature and 5% by weight enzyme load (based on substrates). One included...... with gas chromatography, pancreatic lipase hydrolysis, and high performance liquid chromatography. Both acyl incorporation and migration of linoleic acid were faster than those of conjugated linoleic acid. At 5 h reaction, there were 13.0% LLL, 46.5% LSL, 27.7% LSS, and 5.6% SSS in the product for a system...... tristearin (SSS) and linoleic (L) or conjugated linoleic (cL) acids (1:6, mol/mol). The other was between tristearin and the mixture of linoleic and conjugated linoleic acids (1:3:3, mol/mol/mol). Acyl incorporation and migration together with triacylglycerol composition of the products were monitored...

  10. K2CO3-Mediated Synthesis of Functionalised 4-Substituted-2-amino-3-cyano-4H-chromenes via Michael-Cyclization Reactions

    Directory of Open Access Journals (Sweden)

    Yanyang He

    2014-11-01

    Full Text Available An efficient approach for the synthesis of functionalized 4-substituted-2-amino-3-cyano-4H-chromenes moderate to high yields (up to 98% has been achieved via a tandem K2CO3 catalyzed conjugate addition-cyclization reaction of malononitrile and a range of Knoevenagel adducts previously formed from oxindole, pyrazolone, nitromethane, N,N-dimethylbarbituric acid or indanedione. This methodology differs from the previous classical methods in its simplicity and ready availability of the catalyst.

  11. Conjugate Vaccines from Bacterial Antigens by Squaric Acid Chemistry: A Closer Look.

    Science.gov (United States)

    Xu, Peng; Kelly, Meagan; Vann, Willie F; Qadri, Firdausi; Ryan, Edward T; Kováč, Pavol

    2017-04-18

    By using O-SP-core (O-SPcNH2 ) polysaccharide, isolated from Vibrio cholera O1 lipopolysaccharide (LPS) and related synthetic substances, a detailed study of factors that affect conjugation of bacterial polysaccharides to protein carriers through squaric acid chemistry to form conjugate vaccines has been carried out. Several previously unrecognized processes that take place during the squarate labeling of the O-SPcNH2 and subsequent conjugation of the formed squarate (O-SPcNH-SqOMe) have been identified. The efficiency of conjugation at pH 8.5, 9.0, and 9.5 to bovine serum albumin (BSA) and to the recombinant tetanus toxin fragment C (rTT-Hc) has been determined. The study led to a protocol for more efficient labeling of O-SPcNH2 antigen with the methyl squarate group, to yield a higher-quality, more potent squarate conjugation reagent. Its use resulted in about twofold increases in conjugation efficiency (from 23-26 % on BSA to 51 % on BSA and 55 % on rTT-Hc). The spent conjugation reagent could be recovered and regenerated by treatment with MeI in the absence of additional base. The immunological properties of the experimental vaccine made from the regenerated conjugation reagent were comparable with those of the immunogen made from the parent O-SPcNH-SqOMe. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Fiber bundle phase conjugate mirror

    Science.gov (United States)

    Ward, Benjamin G.

    2012-05-01

    An improved method and apparatus for passively conjugating the phases of a distorted wavefronts resulting from optical phase mismatch between elements of a fiber laser array are disclosed. A method for passively conjugating a distorted wavefront comprises the steps of: multiplexing a plurality of probe fibers and a bundle pump fiber in a fiber bundle array; passing the multiplexed output from the fiber bundle array through a collimating lens and into one portion of a non-linear medium; passing the output from a pump collection fiber through a focusing lens and into another portion of the non-linear medium so that the output from the pump collection fiber mixes with the multiplexed output from the fiber bundle; adjusting one or more degrees of freedom of one or more of the fiber bundle array, the collimating lens, the focusing lens, the non-linear medium, or the pump collection fiber to produce a standing wave in the non-linear medium.

  13. Conjugated Polymers for Energy Production

    DEFF Research Database (Denmark)

    Livi, Francesco

    This dissertation is aimed at developing materials for flexible, large area, ITO-free polymer solar cells (PSCs) fully printed under ambient conditions. A large screening of conjugated polymers, both novel and well-known materials, has been carried out in order to find suitable candidates...... for scalable PSCs fully printed under ambient conditions [Adv. Energy Mater. 2015, 5, 1402186]. PPDTBT resulted to be the conjugated polymer with the best photovoltaic performance within the 104 synthesized macromolecules. Therefore, further studies have been done on such material. The impact of side chain...... arylation (DAr) and direct arylation polymerization (DArP) have been applied to the preparation of PPDTBT, making this polymer readily available in only 4 synthetic steps and thus easily transferable to a large scale-production setup. DArP avoids organometallic species and therefore is an appealing...

  14. HPMA copolymer conjugates of paclitaxel and docetaxel with pH-controlled drug release.

    Science.gov (United States)

    Etrych, Tomás; Sírová, Milada; Starovoytova, L; Ríhová, Blanka; Ulbrich, Karel

    2010-08-02

    In this paper we describe the synthesis, physicochemical characteristics and data on the biological activity of polymer prodrugs based on the anticancer drugs paclitaxel (PTX) and docetaxel (DTX) conjugated with a water-soluble N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer drug carrier. The drugs were derivatized and then attached to the polymer backbone via a spacer that is stable under physiological conditions (pH 7.4) and hydrolytically degradable in mild acidic environments (e.g., endosomes, pH approximately 5). Polymer-drug conjugates were designed to achieve prolonged blood circulation and release of the active compound in target cells. Six types of conjugates differing in the structure of the keto acid (levulic, 3-(acetyl)acrylic acid) and 4-(2-oxopropyl)benzoic acid-containing spacer or in the amount of drug bound to the HPMA copolymer were synthesized. In all the conjugates, the linkage susceptible to hydrolytic cleavage was formed by the reaction of the carbonyl group of a drug derivative with the hydrazide group-terminated side chains of the polymer. In vitro incubation of the conjugates in buffers resulted in much faster release of drugs or their derivatives from the polymer at pH 5 than at pH 7.4 with the rate depending on the detailed structure of the spacer. Conjugates containing drugs acylated with levulic acid were tested for their anticancer activity in vivo using two murine models. The PTX-containing conjugate showed better antitumor efficacy in the 4T1 model of mammary carcinoma than the parent drug and its derivative. The DTX-containing conjugate demonstrated high activity in treating EL4 T cell lymphoma. The treatment with the polymer conjugates was devoid of side toxicity. In both models, we achieved complete regression of established tumors accompanied by a durable tumor resistance in most of the cured animals.

  15. An N-Linked Bidentate Phosphoramidite Ligand (N-Me-BIPAM for Rhodium-Catalyzed Asymmetric 1,4-Addition of Arylboronic Acids to α,β-Unsaturated Ketones

    Directory of Open Access Journals (Sweden)

    Norio Miyaura

    2012-12-01

    Full Text Available A new bidentate phosphoramidite (N-Me-BIPAM based on Shibasaki’s N-linked BINOL was synthesized. This ligand appears to be highly effective for rhodium-catalyzed asymmetric conjugated addition of arylboronic acids to α,β-unsaturated enones. The reaction of ortho-substituted arylboronic acid with acyclic and cyclic enones provides the corresponding products in good yields and enantioselectivities.

  16. PifC and Osa, Plasmid Weapons against Rival Conjugative Coupling Proteins

    Science.gov (United States)

    Getino, María; Palencia-Gándara, Carolina; Garcillán-Barcia, M. Pilar; de la Cruz, Fernando

    2017-01-01

    Bacteria display a variety of mechanisms to control plasmid conjugation. Among them, fertility inhibition (FI) systems prevent conjugation of co-resident plasmids within donor cells. Analysis of the mechanisms of inhibition between conjugative plasmids could provide new alternatives to fight antibiotic resistance dissemination. In this work, inhibition of conjugation of broad host range IncW plasmids was analyzed in the presence of a set of co-resident plasmids. Strong FI systems against plasmid R388 conjugation were found in IncF/MOBF12 as well as in IncI/MOBP12 plasmids, represented by plasmids F and R64, respectively. In both cases, the responsible gene was pifC, known also to be involved in FI of IncP plasmids and Agrobacterium T-DNA transfer to plant cells. It was also discovered that the R388 gene osa, which affects T-DNA transfer, also prevented conjugation of IncP-1/MOBP11 plasmids represented by plasmids RP4 and R751. Conjugation experiments of different mobilizable plasmids, helped by either FI-susceptible or FI-resistant transfer systems, demonstrated that the conjugative component affected by both PifC and Osa was the type IV conjugative coupling protein. In addition, in silico analysis of FI proteins suggests that they represent recent acquisitions of conjugative plasmids, i.e., are not shared by members of the same plasmid species. This implies that FI are rapidly-moving accessory genes, possibly acting on evolutionary fights between plasmids for the colonization of specific hosts. PMID:29201021

  17. Reaction Automata

    OpenAIRE

    Okubo, Fumiya; Kobayashi, Satoshi; YOKOMORI, Takashi

    2011-01-01

    Reaction systems are a formal model that has been introduced to investigate the interactive behaviors of biochemical reactions. Based on the formal framework of reaction systems, we propose new computing models called reaction automata that feature (string) language acceptors with multiset manipulation as a computing mechanism, and show that reaction automata are computationally Turing universal. Further, some subclasses of reaction automata with space complexity are investigated and their la...

  18. Direct targeted glycation of the free sulfhydryl group of cysteine residue (Cys-34) of BSA. Mapping of the glycation sites of the anti-tumor Thomsen-Friedenreich neoglycoconjugate vaccine prepared by Michael addition reaction.

    Science.gov (United States)

    Demian, Wael L L; Kottari, Naresh; Shiao, Tze Chieh; Randell, Edward; Roy, René; Banoub, Joseph H

    2014-12-01

    We present in this manuscript the characterization of the exact glycation sites of the Thomsen-Friedenreich antigen-BSA vaccine (TF antigen:BSA) prepared using a Michael addition reaction between the saccharide antigen as an electrophilic acceptor and the nucleophilic thiol and L-Lysine ε-amino groups of BSA using different ligation conditions. Matrix laser desorption ionization time-of-flight mass spectrometry of the neoglycoconjugates prepared with TF antigen:protein ratios of 2:1 and 8:1, allowed to observe, respectively, the protonated molecules for each neoglycoconjugates: [M + H](+) at m/z 67,599 and 70,905. The measurements of these molecular weights allowed us to confirm exactly the carbohydrate:protein ratios of these two synthetic vaccines. These were found to be closely formed by a TF antigen:BSA ratios of 2:1 and 8:1, respectively. Trypsin digestion and liquid chromatography coupled with electrospray ionization mass spectrometry allowed us to identify the series of released glycopeptide and peptide fragments. De novo sequencing affected by low-energy collision dissociation tandem mass spectrometry was then employed to unravel the precise glycation sites of these neoglycoconjugate vaccines. Finally, we identified, respectively, three diagnostic and characteristic glycated peptides for the synthetic glycoconjugate possessing a TF antigen:BSA ratio 2:1, whereas we have identified for the synthetic glycoconjugate having a TF:BSA ratio 8:1 a series of 14 glycated peptides. The net increase in the occupancy sites of these neoglycoconjugates was caused by the large number of glycoforms produced during the chemical ligation of the synthetic carbohydrate antigen onto the protein carrier. Copyright © 2014 John Wiley & Sons, Ltd.

  19. The Tcp conjugation system of Clostridium perfringens.

    Science.gov (United States)

    Wisniewski, Jessica A; Rood, Julian I

    2017-05-01

    The Gram-positive pathogen Clostridium perfringens possesses a family of large conjugative plasmids that is typified by the tetracycline resistance plasmid pCW3. Since these plasmids may carry antibiotic resistance genes or genes encoding extracellular or sporulation-associated toxins, the conjugative transfer of these plasmids appears to be important for the epidemiology of C. perfringens-mediated diseases. Sequence analysis of members of this plasmid family identified a highly conserved 35kb region that encodes proteins with various functions, including plasmid replication and partitioning. The tcp conjugation locus also was identified in this region, initially based on low-level amino acid sequence identity to conjugation proteins from the integrative conjugative element Tn916. Genetic studies confirmed that the tcp locus is required for conjugative transfer and combined with biochemical and structural analyses have led to the development of a functional model of the Tcp conjugation apparatus. This review summarises our current understanding of the Tcp conjugation system, which is now one of the best-characterized conjugation systems in Gram-positive bacteria. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Designer diatom episomes delivered by bacterial conjugation

    National Research Council Canada - National Science Library

    Karas, Bogumil J; Diner, Rachel E; Lefebvre, Stephane C; McQuaid, Jeff; Phillips, Alex P R; Noddings, Chari M; Brunson, John K; Valas, Ruben E; Deerinck, Thomas J; Jablanovic, Jelena; Gillard, Jeroen T F; Beeri, Karen; Ellisman, Mark H; Glass, John I; Hutchison, 3rd, Clyde A; Smith, Hamilton O; Venter, J Craig; Allen, Andrew E; Dupont, Christopher L; Weyman, Philip D

    2015-01-01

    .... Here we describe the first nuclear episomal vector for diatoms and a plasmid delivery method via conjugation from Escherichia coli to the diatoms Phaeodactylum tricornutum and Thalassiosira pseudonana...

  1. The reaction of cinnamaldehyde and cinnam(oyl derivatives with thiols

    Directory of Open Access Journals (Sweden)

    Alessandro Autelitano

    2017-07-01

    Full Text Available Spurred by the alleged relevance of the thia-Michael reaction in the bioactivity of various classes of cinnam(oyl natural products and by the development of a quick NMR assay to study this reaction, we have carried out a systematic study of the “native” reactivity of these compounds with dodecanethiol and cysteamine as models, respectively, of simple thiols and reactive protein thiols that can benefit from iminium ion catalysis in Michael reactions. Cinnamoyl esters and amides, as well as cinnamyl ketones and oximes, did not show any reactivity with the two probe thiols, while cinnamaldehyde (1a reacted with cysteamine to afford a mixture of a thiazoline derivative and compounds of multiple addition, and with aliphatic thiols to give a single bis-dithioacetal (6. Chalchones and their vinylogous C5-curcuminoid derivatives were the only cinnamoyl derivatives that gave a thia-Michael reaction. From a mechanistic standpoint, loss of conjugation in the adduct might underlie the lack of a native Michael reactivity. This property is restored by the presence of another conjugating group on the carbonyl, as in chalcones and C5-curcuminoids. A critical mechanistic revision of the chemical and biomedical literature on cinnamaldehyde and related compounds seems therefore required.

  2. Mechanism of electron transfer reaction of ternary ...

    Indian Academy of Sciences (India)

    The rate of the reaction increases with increasing pH due to the deprotonation equilibria of the complex. The experimental rate law is consistent with a mechanism in which the deprotonated form [CrIII(DPA)(OX)(OH)]2− is more reactive than the conjugated acid. It is proposed that electron transfer proceeds through an ...

  3. Test of charge conjugation invariance.

    Science.gov (United States)

    Nefkens, B M K; Prakhov, S; Gårdestig, A; Allgower, C E; Bekrenev, V; Briscoe, W J; Clajus, M; Comfort, J R; Craig, K; Grosnick, D; Isenhower, D; Knecht, N; Koetke, D; Koulbardis, A; Kozlenko, N; Kruglov, S; Lolos, G; Lopatin, I; Manley, D M; Manweiler, R; Marusić, A; McDonald, S; Olmsted, J; Papandreou, Z; Peaslee, D; Phaisangittisakul, N; Price, J W; Ramirez, A F; Sadler, M; Shafi, A; Spinka, H; Stanislaus, T D S; Starostin, A; Staudenmaier, H M; Supek, I; Tippens, W B

    2005-02-04

    We report on the first determination of upper limits on the branching ratio (BR) of eta decay to pi0pi0gamma and to pi0pi0pi0gamma. Both decay modes are strictly forbidden by charge conjugation (C) invariance. Using the Crystal Ball multiphoton detector, we obtained BR(eta-->pi0pi0gamma)pi0pi0pi0gamma)<6 x 10(-5) at the 90% confidence level, in support of C invariance of isovector electromagnetic interactions.

  4. Optimal conjugation of catechol group onto hyaluronic acid in coronary stent substrate coating for the prevention of restenosis

    Directory of Open Access Journals (Sweden)

    Eugene Lih

    2016-12-01

    Full Text Available Although endovascular stenting has been used as an interventional therapy to treat cardio- and cerebro-vascular diseases, it is associated with recurrent vascular diseases following stent thrombosis and in-stent restenosis. In this study, a metallic stent was coated with dopamine-conjugated hyaluronic acid with different ratios of catechol group to improve hemocompatibility and re-endothelialization. Especially, we were interested in how much amount of catechol group is appropriate for the above-mentioned purposes. Therefore, a series of dopamine-conjugated hyaluronic acid conjugates with different ratios of catechol group were synthesized via a carbodiimide coupling reaction. Dopamine-conjugated hyaluronic acid conjugates were characterized with 1H-nuclear magnetic resonance and Fourier transform infrared spectroscopy, and the amount of catechol group in dopamine-conjugated hyaluronic acid was measured by ultraviolet spectrometer. Co-Cr substrates were polished and coated with various dopamine-conjugated hyaluronic acid conjugates under pH 8.5. Dopamine-conjugated hyaluronic acid amounts on the substrate were quantified by micro-bicinchoninic acid assay. Surface characteristics of dopamine-conjugated hyaluronic-acid-coated Co-Cr were evaluated by water contact angle, scanning electron microscopy, and atomic force microscopy. The hemocompatibility of the surface-modified substrates was assessed by protein adsorption and platelet adhesion tests. Adhesion and activation of platelets were confirmed with scanning electron microscopy and lactate dehydrogenase assay. Human umbilical vein endothelial cells were cultured on the substrates, and the viability, adhesion, and proliferation were investigated through cell counting kit-8 assay and fluorescent images. Obtained results demonstrated that optimal amounts of catechol group (100 µmol in the dopamine-conjugated hyaluronic acid existed in terms of various properties such as hemocompatibility and

  5. Click-chemistry approaches to π-conjugated polymers for organic electronics applications.

    Science.gov (United States)

    Marrocchi, Assunta; Facchetti, Antonio; Lanari, Daniela; Santoro, Stefano; Vaccaro, Luigi

    2016-10-01

    Given the wide utility of click-chemistry reactions for the preparation of simple moieties within large architecturally complex materials, this minireview article aims at surveying papers exploring their scope in the area of π-conjugated polymers for application in organic electronics to enable advanced functional properties.

  6. Click-chemistry approaches to π-conjugated polymers for organic electronics applications

    Science.gov (United States)

    Facchetti, Antonio; Lanari, Daniela; Santoro, Stefano

    2016-01-01

    Given the wide utility of click-chemistry reactions for the preparation of simple moieties within large architecturally complex materials, this minireview article aims at surveying papers exploring their scope in the area of π-conjugated polymers for application in organic electronics to enable advanced functional properties. PMID:28567241

  7. High-quality conjugated polymers via one-pot Suzuki-Miyaura homopolymerization

    NARCIS (Netherlands)

    Zhou, Difei; Doumon, Nutifafa Y.; Abdu-Aguye, Mustapha; Bartesaghi, Davide; Loi, Maria A.; Koster, L. Jan Anton; Chiechi, Ryan C.; Hummelen, Jan C.

    2017-01-01

    This paper describes a one-pot Suzuki-Miyaura homopolymerization that involves in situ borylation/cross coupling of dibrominated donor-acceptor conjugated macromonomers, in contrast to the standard Stille copolymerization of thienosilole and isoindigo monomers. Reaction kinetics investigation

  8. Corn fiber gum and milk protein conjugates with improved emulsion stability

    Science.gov (United States)

    Corn fiber gum (CFG), an alkaline hydrogen peroxide extract of the corn kernel milling by-product “corn fiber” was covalently conjugated with Beta-lactoglobulin (Beta-LG) and whey protein isolate (WPI). Covalent coupling of CFG to protein was achieved by dry heating reaction (Maillard-type) of CFG ...

  9. Potlining Additives

    Energy Technology Data Exchange (ETDEWEB)

    Rudolf Keller

    2004-08-10

    In this project, a concept to improve the performance of aluminum production cells by introducing potlining additives was examined and tested. Boron oxide was added to cathode blocks, and titanium was dissolved in the metal pool; this resulted in the formation of titanium diboride and caused the molten aluminum to wet the carbonaceous cathode surface. Such wetting reportedly leads to operational improvements and extended cell life. In addition, boron oxide suppresses cyanide formation. This final report presents and discusses the results of this project. Substantial economic benefits for the practical implementation of the technology are projected, especially for modern cells with graphitized blocks. For example, with an energy savings of about 5% and an increase in pot life from 1500 to 2500 days, a cost savings of $ 0.023 per pound of aluminum produced is projected for a 200 kA pot.

  10. Dipeptide-Derived Multifunctional Quaternary Phosphonium Salt Catalyzed Asymmetric Cyclizations via a Tandem Michael Addition/SN 2 Sequence.

    Science.gov (United States)

    Cao, Dongdong; Zhang, Jiaxing; Wang, Hongyu; Zhao, Gang

    2015-07-06

    A novel family of dipeptide-based multifunctional quaternary phosphonium salts has been developed as chiral phase-transfer catalysts, which feature ready accessibility and structure modularity, allowing easy fine-tunings of activity. They demonstrated high efficiency in catalyzing the tandem asymmetric Michael addition/intramolecular SN 2 reaction between 6 or 7-substituted conjugate enones and malonates, providing synthetically important five or six-membered carbocycles and heterocycles in good yields and with good to excellent enantioselectivities. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Direct (Hetero)arylation Polymerization: Simplicity for Conjugated Polymer Synthesis.

    Science.gov (United States)

    Pouliot, Jean-Rémi; Grenier, François; Blaskovits, J Terence; Beaupré, Serge; Leclerc, Mario

    2016-11-23

    Direct (hetero)arylation polymerization (DHAP) has recently been established as an environmentally benign method for the preparation of conjugated polymers. This synthetic tool features the formation of C-C bonds between halogenated (hetero)arenes and simple (hetero)arenes with active C-H bonds, thereby circumventing the preparation of organometallic derivatives and decreasing the overall production cost of conjugated polymers. Since its inception, selectivity and reactivity of DHAP procedures have been improved tremendously through the careful scrutinity of polymerization outcomes and the fine-tuning of reaction conditions. A broad range of monomers, from simple arenes to complex functionalized heteroarenes, can now be readily polymerized. The successful application of DHAP now leads to nearly defect-free conjugated polymers possessing comparable, if not slightly better, characteristics than their counterparts prepared using classical cross-coupling methods. This comprehensive review describes the mechanisms involved in this process from experimental and theoretical standpoints, presents an up-to-date compendium of materials obtained by this means, and exposes its current limitations and challenges.

  12. Comparison of genetic algorithms with conjugate gradient methods

    Science.gov (United States)

    Bosworth, J. L.; Foo, N. Y.; Zeigler, B. P.

    1972-01-01

    Genetic algorithms for mathematical function optimization are modeled on search strategies employed in natural adaptation. Comparisons of genetic algorithms with conjugate gradient methods, which were made on an IBM 1800 digital computer, show that genetic algorithms display superior performance over gradient methods for functions which are poorly behaved mathematically, for multimodal functions, and for functions obscured by additive random noise. Genetic methods offer performance comparable to gradient methods for many of the standard functions.

  13. Synthesis of nucleotide–amino acid conjugates designed for photo-CIDNP experiments by a phosphotriester approach

    Directory of Open Access Journals (Sweden)

    Tatyana V. Abramova

    2013-12-01

    Full Text Available Conjugates of 2’-deoxyguanosine, L-tryptophan and benzophenone designed to study pathways of fast radical reactions by the photo Chemically Induced Dynamic Nuclear Polarization (photo-CIDNP method were obtained by the phosphotriester block liquid phase synthesis. The phosphotriester approach to the oligonucleotide synthesis was shown to be a versatile and economic strategy for preparing the required amount of high quality samples of nucleotide–amino acid conjugates.

  14. Visible light mediated metal-free thiol?yne click reaction? ?Electronic supplementary information (ESI) available. See DOI: 10.1039/c6sc02132h Click here for additional data file.

    OpenAIRE

    Zalesskiy, Sergey S.; Shlapakov, Nikita S.; Ananikov, Valentine P.

    2016-01-01

    The carbon?sulfur bond formation reaction is of paramount importance for functionalized materials design, as well as for biochemical applications. The use of expensive metal-based catalysts and the consequent contamination with trace metal impurities are challenging drawbacks of the existing methodologies. Here, we describe the first environmentally friendly metal-free photoredox pathway to the thiol?yne click reaction. Using Eosin Y as a cheap and readily available catalyst, C?S coupling pro...

  15. Conjugative Plasmid Transfer in Xylella fastidiosa Is Dependent on tra and trb Operon Functions

    OpenAIRE

    Burbank, Lindsey P.; Van Horn, Christopher R.

    2017-01-01

    The insect-transmitted plant pathogen Xylella fastidiosa is capable of efficient horizontal gene transfer (HGT) and recombination. Natural transformation occurs at high rates in X. fastidiosa, but there also is evidence that certain strains of X. fastidiosa carry native plasmids equipped with transfer and mobilization genes, suggesting conjugation as an additional mechanism of HGT in some instances. Two operons, tra and trb, putatively encoding a conjugative type IV secretion system, are foun...

  16. Production of carrier-peptide conjugates using chemically reactive unnatural amino acids

    Science.gov (United States)

    Young, Travis; Schultz, Peter G

    2013-12-17

    Provided are methods of making carrier polypeptide that include incorporating a first unnatural amino acid into a carrier polypeptide variant, incorporating a second unnatural amino acid into a target polypeptide variant, and reacting the first and second unnatural amino acids to produce the conjugate. Conjugates produced using the provided methods are also provided. In addition, orthogonal translation systems in methylotrophic yeast and methods of using these systems to produce carrier and target polypeptide variants comprising unnatural amino acids are provided.

  17. Quantification of residual solvents in antibody drug conjugates using gas chromatography

    Energy Technology Data Exchange (ETDEWEB)

    Medley, Colin D., E-mail: medley.colin@gene.com [Genentech Inc., Small Molecule Pharmaceutical Sciences, 1 DNA Way, South San Francisco, CA 94080 (United States); Kay, Jacob [Research Pharmaceutical Services, 520 Virginia Dr. Fort, Washington, PA (United States); Li, Yi; Gruenhagen, Jason; Yehl, Peter; Chetwyn, Nik P. [Genentech Inc., Small Molecule Pharmaceutical Sciences, 1 DNA Way, South San Francisco, CA 94080 (United States)

    2014-11-19

    Highlights: • Sensitive residual solvents detection in ADCs. • 125 ppm QL for common conjugation solvents. • Generic and validatable method. - Abstract: The detection and quantification of residual solvents present in clinical and commercial pharmaceutical products is necessary from both patient safety and regulatory perspectives. Head-space gas chromatography is routinely used for quantitation of residual solvents for small molecule APIs produced through synthetic processes; however residual solvent analysis is generally not needed for protein based pharmaceuticals produced through cultured cell lines where solvents are not introduced. In contrast, antibody drug conjugates and other protein conjugates where a drug or other molecule is covalently bound to a protein typically use solvents such as N,N-dimethylacetamide (DMA), N,N‑dimethylformamide (DMF), dimethyl sulfoxide (DMSO), or propylene glycol (PG) to dissolve the hydrophobic small molecule drug for conjugation to the protein. The levels of the solvent remaining following the conjugation step are therefore important to patient safety as these parental drug products are introduced directly into the patients bloodstream. We have developed a rapid sample preparation followed by a gas chromatography separation for the detection and quantification of several solvents typically used in these conjugation reactions. This generic method has been validated and can be easily implemented for use in quality control testing for clinical or commercial bioconjugated products.

  18. The Syntheses of Click PEG – Dexamethasone Conjugates for the Treatment of Rheumatoid Arthritis

    Science.gov (United States)

    Liu, Xin-Ming; Quan, Ling-dong; Tian, Jun; Laquer, Frederic C.; Ciborowski, Pawel; Wang, Dong

    2010-01-01

    A novel linear multifunctional polyethylene glycol (PEG)-dexamethasone (Dex) conjugate (click PEG-Dex) was synthesized using facile Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition (a click reaction). Dex was conjugated to the click PEG via an acid-labile hydrazone bond to allow the drug release in pathophysiological environment. To evaluate click PEG’s potential as a versatile drug delivery platform, the click PEG-Dex conjugates were tested in an adjuvant-induced arthritis (AA) rat model. In vivo optical imaging data confirmed the arthrotropism of the conjugates in the arthritic rats. Long-term treatment study revealed that a single click PEG-Dex conjugate administration provided sustained (> 15 days) amelioration of ankle joint inflammation to the AA rats. Treatment with equivalent dose of dexamethasone phosphate sodium (free Dex) only provides temporal resolution of the arthritis, which recurred upon treatment withdrawal. Further histological and bone mineral density comparison between the ankle joints from both click PEG-Dex and free Dex treatment groups confirmed the superior anti-inflammatory and disease modifying effects of the novel polymer-drug conjugates. PMID:20831200

  19. Syntheses of click PEG-dexamethasone conjugates for the treatment of rheumatoid arthritis.

    Science.gov (United States)

    Liu, Xin-Ming; Quan, Ling-dong; Tian, Jun; Laquer, Frederic C; Ciborowski, Pawel; Wang, Dong

    2010-10-11

    A novel linear multifunctional polyethylene glycol (PEG)-dexamethasone (Dex) conjugate (click PEG-Dex) was synthesized using facile Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition (a click reaction). Dex was conjugated to the click PEG via an acid-labile hydrazone bond to allow the drug release in a pathophysiological environment. To evaluate click PEG's potential as a versatile drug delivery platform, the click PEG-Dex conjugates were tested in an adjuvant-induced arthritis (AA) rat model. In vivo optical imaging data confirmed the arthrotropism of the conjugates in the arthritic rats. A long-term treatment study revealed that a single click PEG-Dex conjugate administration provided sustained (>15 days) amelioration of ankle joint inflammation to the AA rats. Treatment with an equivalent dose of dexamethasone phosphate sodium (free Dex) only provided temporal resolution of the arthritis, which recurred upon treatment withdrawal. Further histological and bone mineral density comparison between the ankle joints from both click PEG-Dex and free Dex treatment groups confirmed the superior anti-inflammatory and disease modifying effects of the novel polymer-drug conjugates.

  20. Fragment-based solid-phase assembly of oligonucleotide conjugates with peptide and polyethylene glycol ligands.

    Science.gov (United States)

    Dirin, Mehrdad; Urban, Ernst; Noe, Christian R; Winkler, Johannes

    2016-10-04

    Ligand conjugation to oligonucleotides is an attractive strategy for enhancing the therapeutic potential of antisense and siRNA agents by inferring properties such as improved cellular uptake or better pharmacokinetic properties. Disulfide linkages enable dissociation of ligands and oligonucleotides in reducing environments found in endosomal compartments after cellular uptake. Solution-phase fragment coupling procedures for producing oligonucleotide conjugates are often tedious, produce moderate yields and reaction byproducts are frequently difficult to remove. We have developed an improved method for solid-phase coupling of ligands to oligonucleotides via disulfides directly after solid-phase synthesis. A 2'-thiol introduced using a modified nucleotide building block was orthogonally deprotected on the controlled pore glass solid support with N-butylphosphine. Oligolysine peptides and a short monodisperse ethylene glycol chain were successfully coupled to the deprotected thiol. Cleavage from the resin and full removal of oligonucleotide protection groups were achieved using methanolic ammonia. After standard desalting, and without further purification, homogenous conjugates were obtained as demonstrated by HPLC, gel electrophoresis, and mass spectrometry. The attachment of both amphiphilic and cationic ligands proves the versatility of the conjugation procedure. An antisense oligonucleotide conjugate with hexalysine showed pronounced gene silencing in a cell culture tumor model in the absence of a transfection reagent and the corresponding ethylene glycol conjugate resulted in down regulation of the target gene to nearly 50% after naked application. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  1. Photoluminescence of Conjugated Star Polymers

    Science.gov (United States)

    Ferguson, J. B.; Prigodin, N. V.; Epstein, A. J.; Wang, F.

    2000-10-01

    Higher dimensionality "star" polymers provide new properties beyond those found in their linear analogs. They have been used to improving electronic properties for nonlinear optics through exciton transfer and molecular antenna structures for example (M. Kawa, J. M. J. Frechet, Chem. Mater. 10, 286 (1998).). We report on photoluminescence properties of star polymers with a hyperbranched core (both hyperbranched phenlyene and hyperbranched triphenylamine) and polyhexylthiophene arms. The arm is a conjugated oligomer of polythiophene that has been investigated extensively for metallic like conductivity when doped as well as utilized in field effect transistors in its undoped form (A. Tsumara, H. Koezuka, T. Ando, Appl. Phys. Lett. 49, 1210 (1986).). The cores are respectively, a nonconjugated polymer in the case of hyperbranched phenlyene and a conjugated polymer in the case of hyperbranched triphenylamine. The photoluminesce spectrum (λ_max at 575 nm) is identical for both star polymers with the two electronically different hyperbranched cores and for linear polythiophene alone. We conclude the wave functions of the core and arms do not strongly interact to form states different from their individual states and excitons formed on the hyperbranched cores migrate to the lower bandgap polythiophene before recombining.

  2. Thermal Stability of siRNA Modulates Aptamer- conjugated siRNA Inhibition

    Directory of Open Access Journals (Sweden)

    Alexey Berezhnoy

    2012-01-01

    Full Text Available Oligonucleotide aptamer-mediated in vivo cell targeting of small interfering RNAs (siRNAs is emerging as a useful approach to enhance the efficacy and reduce the adverse effects resulting from siRNA-mediated genetic interference. A current main impediment in aptamer-mediated siRNA targeting is that the activity of the siRNA is often compromised when conjugated to an aptamer, often requiring labor intensive and time consuming design and testing of multiple configurations to identify a conjugate in which the siRNA activity has not been significantly reduced. Here, we show that the thermal stability of the siRNA is an important parameter of siRNA activity in its conjugated form, and that siRNAs with lower melting temperature (Tm are not or are minimally affected when conjugated to the 3′ end of 2′F-pyrimidine-modified aptamers. In addition, the configuration of the aptamer-siRNA conjugate retains activity comparable with the free siRNA duplex when the passenger strand is co-transcribed with the aptamer and 3′ overhangs on the passenger strand are removed. The approach described in this paper significantly reduces the time and effort necessary to screening siRNA sequences that retain biological activity upon aptamer conjugation, facilitating the process of identifying candidate aptamer-siRNA conjugates suitable for in vivo testing.

  3. A clinical trial examining the effect of increased total CRM(197) carrier protein dose on the antibody response to Haemophilus influenzae type b CRM(197) conjugate vaccine.

    Science.gov (United States)

    Usonis, Vytautas; Bakasenas, Vytautas; Lockhart, Stephen; Baker, Sherryl; Gruber, William; Laudat, France

    2008-08-18

    CRM(197) is a carrier protein in certain conjugate vaccines. When multiple conjugate vaccines with the same carrier protein are administered simultaneously, reduced response to vaccines and/or antigens related to the carrier protein may occur. This study examined responses of infants who, in addition to diphtheria toxoid/tetanus toxoid/acellular pertussis vaccine (DTaP) received either diphtheria CRM(197)-based Haemophilus influenzae type b conjugate vaccine (HbOC) or HbOC and a diphtheria CRM(197)-based combination 9-valent pneumococcal conjugate vaccine/meningococcal group C conjugate vaccine. Administration of conjugate vaccines with CRM(197) carrier protein load >50 microg did not reduce response to CRM(197) conjugate vaccines or immunogenicity to immunologically cross-reactive diphtheria toxoid.

  4. Determinants of pneumococcal conjugate vaccine uptake among ...

    African Journals Online (AJOL)

    Determinants of pneumococcal conjugate vaccine uptake among children attending immunisation services at Kenyatta National Hospital, Nairobi, Kenya. ... Results: The study established that the determinants of uptake of Pneumococcal Conjugate Vaccine are age(OR 5.8, CI 1.4-23.4, p=0.014), level of education (OR 5.8, ...

  5. Preconditioning the modified conjugate gradient method ...

    African Journals Online (AJOL)

    In this paper, the convergence analysis of the conventional conjugate Gradient method was reviewed. And the convergence analysis of the modified conjugate Gradient method was analysed with our extension on preconditioning the algorithm. Convergence of the algorithm is a function of the condition number of M-1A.

  6. DENDRIMER CONJUGATES FOR SELECTIVE OF PROTEIN AGGREGATES

    DEFF Research Database (Denmark)

    2004-01-01

    Dendrimer conjugates are presented, which are formed between a dendrimer and a protein solubilising substance. Such dendrimer conjugates are effective in the treatment of protein aggregate-related diseases (e.g. prion-related diseases). The protein solubilising substance and the dendrimer together...

  7. CONJUGATED BLOCK-COPOLYMERS FOR ELECTROLUMINESCENT DIODES

    NARCIS (Netherlands)

    Hilberer, A; Gill, R.E; Herrema, J.K; Malliaras, G.G; Wildeman, J.; Hadziioannou, G

    In this article we review results obtained in our laboratory on the design and study of new light-emitting polymers. We are interested in the synthesis and characterisation of block copolymers with regularly alternating conjugated and non conjugated sequences. The blocks giving rise to luminescence

  8. Bio-Conjugates for Nanoscale Applications

    DEFF Research Database (Denmark)

    Villadsen, Klaus

    Bio-conjugates for Nanoscale Applications is the title of this thesis, which covers three different projects in chemical bio-conjugation research, namely synthesis and applications of: Lipidated fluorescent peptides, carbohydrate oxime-azide linkers and N-aryl O-R2 oxyamine derivatives. Lipidated...

  9. Supplementary Information DA conjugated polymers containing ...

    Indian Academy of Sciences (India)

    D-A conjugated polymers containing substituted thiophene, 1,3,4-oxadiazole and non-conjugation linkers: Synthesis and study of optical and electrochemical properties. PRASHANTH KUMAR K Ra, UDAYAKUMAR Da,*, SIJI NARENDRAN N Kb, CHANDRASEKHARAN Kb and RITU SRIVASTAVAc. aDepartment of ...

  10. Essential motifs of relaxase (TraI) and TraG proteins involved in conjugative transfer of plasmid RP4.

    Science.gov (United States)

    Balzer, D; Pansegrau, W; Lanka, E

    1994-07-01

    Two essential transfer genes of the conjugative plasmid RP4 were altered by site-directed mutagenesis: traG of the primase operon and traI of the relaxase operon. To evaluate effects on the transfer phenotype of the point mutations, we have reconstituted the RP4 transfer system by fusion of the transfer regions Tra1 and Tra2 to the small multicopy replicon ColD. Deletions in traG or traI served to determine the Tra phenotype of mutant plasmids by trans complementation. Two motifs of TraG which are highly conserved among TraG-like proteins in several other conjugative DNA transfer systems were found to be essential for TraG function. One of the motifs resembles that of a nucleotide binding fold of type B. The relaxase (TraI) catalyzes the specific cleaving-joining reaction at the transfer origin needed to initiate and terminate conjugative DNA transfer (W. Pansegrau, W. Schröder, and E. Lanka, Proc. Natl. Acad. Sci. USA 90:2925-2929, 1993). Phenotypes of mutations in three motifs that belong to the active center of the relaxase confirmed previously obtained biochemical evidence for the contributions of the motifs to the catalytic activity of TraI. Expression of the relaxase operon is greatly increased in the absence of an intact TraI protein. This finding suggests that the relaxosome which assembles only in the presence of the TraI in addition to its enzymatic activity plays a role in gene regulation.

  11. Facile and stabile linkages through tyrosine: bioconjugation strategies with the tyrosine-click reaction.

    Science.gov (United States)

    Ban, Hitoshi; Nagano, Masanobu; Gavrilyuk, Julia; Hakamata, Wataru; Inokuma, Tsubasa; Barbas, Carlos F

    2013-04-17

    The scope, chemoselectivity, and utility of the click-like tyrosine labeling reaction with 4-phenyl-3H-1,2,4-triazoline-3,5(4H)-diones (PTADs) is reported. To study the utility and chemoselectivity of PTAD derivatives in peptide and protein chemistry, we synthesized PTAD derivatives possessing azide, alkyne, and ketone groups and studied their reactions with amino acid derivatives and peptides of increasing complexity. With proteins we studied the compatibility of the tyrosine click reaction with cysteine and lysine-targeted labeling approaches and demonstrate that chemoselective trifunctionalization of proteins is readily achieved. In particular cases, we noted that PTAD decomposition resulted in formation of a putative isocyanate byproduct that was promiscuous in labeling. This side reaction product, however, was readily scavenged by the addition of a small amount of 2-amino-2-hydroxymethyl-propane-1,3-diol (Tris) to the reaction medium. To study the potential of the tyrosine click reaction to introduce poly(ethylene glycol) chains onto proteins (PEGylation), we demonstrate that this novel reagent provides for the selective PEGylation of chymotrypsinogen, whereas traditional succinimide-based PEGylation targeting lysine residues provided a more diverse range of PEGylated products. Finally, we applied the tyrosine click reaction to create a novel antibody-drug conjugate. For this purpose, we synthesized a PTAD derivative linked to the HIV entry inhibitor aplaviroc. Labeling of the antibody trastuzumab with this reagent provided a labeled antibody conjugate that demonstrated potent HIV-1 neutralization activity demonstrating the potential of this reaction in creating protein conjugates with small molecules. The tyrosine click linkage demonstrated stability to extremes of pH, temperature, and exposure to human blood plasma indicating that this linkage is significantly more robust than maleimide-type linkages that are commonly employed in bioconjugations. These

  12. Refinement of the Diatom Episome Maintenance Sequence and Improvement of Conjugation-based DNA Delivery Methods

    Directory of Open Access Journals (Sweden)

    Rachel E Diner

    2016-08-01

    Full Text Available Conjugation of episomal plasmids from bacteria to diatoms advances diatom genetic manipulation by simplifying transgene delivery and providing a stable and consistent gene expression platform. To reach its full potential, this nascent technology requires new optimized expression vectors and a deeper understanding of episome maintenance. Here we present the development of an additional diatom vector (pPtPBR1, based on the parent plasmid pBR322, to add a plasmid maintained at medium copy number in E. coli to the diatom genetic toolkit. Using this new vector, we evaluated the contribution of individual yeast DNA elements comprising the 1.4-kb tripartite CEN6-ARSH4-HIS3 sequence that enables episome maintenance in P. tricornutum. While various combinations of these individual elements enable efficient conjugation and high ex-conjugant yield in P. tricornutum, individual elements alone do not. Conjugation of episomes containing CEN6-ARSH4 and a small sequence from the low GC content 3’ end of HIS3 produced the highest number of diatom ex-conjugant colonies, resulting in a smaller and more efficient vector design. Our findings suggest that the CEN6 and ARSH4 sequences function differently in yeast and diatoms, and that low GC content regions of greater than ~500 bp are a potential indicator of a functional diatom episome maintenance sequence. Additionally, we have developed improvements to the conjugation protocol including a higher-throughput option utilizing 12-well plates, and plating methods that improve ex-conjugant yield and reduce time and materials required for the conjugation protocol. The data presented offer additional information regarding the mechanism by which the yeast-derived sequence enables diatom episome maintenance, and demonstrate options for flexible vector design.

  13. The Hermitian -Conjugate Generalized Procrustes Problem

    Directory of Open Access Journals (Sweden)

    Hai-Xia Chang

    2013-01-01

    Full Text Available We consider the Hermitian -conjugate generalized Procrustes problem to find Hermitian -conjugate matrix such that is minimum, where , , , and (, are given complex matrices, and and are positive integers. The expression of the solution to Hermitian -conjugate generalized Procrustes problem is derived. And the optimal approximation solution in the solution set for Hermitian -conjugate generalized Procrustes problem to a given matrix is also obtained. Furthermore, we establish necessary and sufficient conditions for the existence and the formula for Hermitian -conjugate solution to the linear system of complex matrix equations , , ( and are positive integers. The representation of the corresponding optimal approximation problem is presented. Finally, an algorithm for solving two problems above is proposed, and the numerical examples show its feasibility.

  14. Approximate error conjugation gradient minimization methods

    Science.gov (United States)

    Kallman, Jeffrey S

    2013-05-21

    In one embodiment, a method includes selecting a subset of rays from a set of all rays to use in an error calculation for a constrained conjugate gradient minimization problem, calculating an approximate error using the subset of rays, and calculating a minimum in a conjugate gradient direction based on the approximate error. In another embodiment, a system includes a processor for executing logic, logic for selecting a subset of rays from a set of all rays to use in an error calculation for a constrained conjugate gradient minimization problem, logic for calculating an approximate error using the subset of rays, and logic for calculating a minimum in a conjugate gradient direction based on the approximate error. In other embodiments, computer program products, methods, and systems are described capable of using approximate error in constrained conjugate gradient minimization problems.

  15. Stability, cytotoxicity and cell uptake of water-soluble dendron–conjugated gold nanoparticles with 3, 12 and 17 nm cores† †Electronic supplementary information (ESI) available: Additional characterization methods and procedures in addition to the data for the characterization of glutathione-capped gold nanoparticles and dendron-conjugated gold nanoparticles including FT-IR spectra (Fig. S1 and S2), UV-vis spectra (Fig. S3 and S6), TEM images (Fig. S4), MALDI-TOF/TOF spectra (Fig. S5), fluorescence spectra (Fig. S6 and S7), In vitro cytotoxic assay results (Fig. S9) and ICP-MS results (Tables 1 and 2). DOI: 10.1039/c5tb00608b Click here for additional data file.

    Science.gov (United States)

    Deol, Suprit; Weerasuriya, Nisala

    2015-01-01

    This article describes the synthesis of water-soluble dendron–conjugated gold nanoparticles (Den–AuNPs) with various average core sizes and the evaluation of stability, cytotoxicity, cell permeability and uptake of these materials. The characterization of Den–AuNPs using various techniques including transmission electron microscopy (TEM), matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS), 1H NMR, FT-IR, and UV-vis spectroscopy confirms the dendron conjugation to the glutathione-capped gold nanoparticles (AuNPs). The stability of AuNPs and Den–AuNPs in solutions of different pH and salt concentration is determined by monitoring the changes in surface plasmon bands of gold using UV-vis spectroscopy. The stability of Den–AuNPs at different pH remained about the same compared to that of AuNPs. In comparison, the Den–AuNPs are found to be more stable than the precursor AuNPs maintaining their solubility in the aqueous solution with the salt concentration of up to 100 mM. The improved stability of Den–AuNPs suggests that the post-functionalization of thiol-capped gold nanoparticle surfaces with dendrons can further improve the physiological stability and biocompatibility of gold nanoparticle-based materials. Cytotoxicity studies of AuNPs and Den–AuNPs with and without fluorophores are also performed by examining cell viability for 3T3 fibroblasts using a MTT cell proliferation assay. The conjugation of dendrons to the AuNPs with a fluorophore is able to decrease the cytotoxicity brought about by the fluorophore. The successful uptake of Den–AuNPs in mouse fibroblast 3T3 cells shows the physiological viability of the hybrid materials. PMID:26366289

  16. Direct synthesis of benzofuro[2,3-b]pyrroles through a radical addition/[3,3]-sigmatropic rearrangement/cyclization/lactamization cascade.

    Science.gov (United States)

    Ueda, Masafumi; Ito, Yuta; Ichii, Yuki; Kakiuchi, Maiko; Shono, Hiroko; Miyata, Okiko

    2014-05-26

    A straightforward synthetic method for the construction of benzofuro[2,3-b]pyrrol-2-ones by a novel domino reaction through a radical addition/[3,3]-sigmatropic rearrangement/cyclization/lactamization cascade has been developed. The domino reaction of O-phenyl-conjugated oxime ether with an alkyl radical allows the construction of two heterocycles with three stereogenic centers as a result of the formation of two C-C bonds, a C-O bond, and a C-N bond in a single operation, leading to pyrrolidine-fused dihydrobenzofurans, which are not easily accessible by existing synthetic methods. Furthermore, asymmetric synthesis of benzofuro[2,3-b]pyrrol-2-one derivatives through a diastereoselective radical addition reaction to a chiral oxime ether was also developed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Functionalization of Fatty Acid Vesicles through Newly Synthesized Bolaamphiphile-DNA Conjugates

    DEFF Research Database (Denmark)

    Wamberg, M. C.; Wieczorek, R.; Brier, S. B.

    2014-01-01

    of these structures, only one novel bola-amphiphile DNA conjugate could interact efficiently with or spontaneously pierce into the vesicle bilayers without jeopardizing their self-assembly or stability. This molecule was synthesized via a Cu(I)-catalyzed [3 + 2] azide-alkyne cycloaddition (click reaction......), and consists of a single hydrocarbon chain of 20 carbons having on one end a triazole group linked to the S'-phosphate of the nucleic acid and on the other side a hydroxyl-group. Its insertion was so effective that a fluorescent label on the DNA complementary to the conjugate could be used to visualize fatty...

  18. Peptide-LNA oligonucleotide conjugates

    DEFF Research Database (Denmark)

    Astakhova, I Kira; Hansen, Lykke Haastrup; Vester, Birte

    2013-01-01

    Although peptide-oligonucleotide conjugates (POCs) are well-known for nucleic acids delivery and therapy, reports on internal attachment of peptides to oligonucleotides are limited in number. To develop a convenient route for preparation of internally labeled POCs with improved biomedical...... properties, peptides were introduced into oligonucleotides via a 2'-alkyne-2'-amino-LNA scaffold. Derivatives of methionine- and leucine-enkephalins were chosen as model peptides of mixed amino acid content, which were singly and doubly incorporated into LNA/DNA strands using highly efficient copper......(i)-catalyzed azide-alkyne cycloaddition (CuAAC) "click" chemistry. DNA/RNA target binding affinity and selectivity of the resulting POCs were improved in comparison to LNA/DNA mixmers and unmodified DNA controls. This clearly demonstrates that internal attachment of peptides to oligonucleotides can significantly...

  19. Photoconductive properties of conjugated polymers

    CERN Document Server

    Halls, J J M

    1997-01-01

    The research described in my dissertation has involved the fabrication and characterisation of photovoltaic cells based on conjugated polymers, including the widely studied polymer poly(p-phenylenevinylene). These materials have semiconducting properties which arise from the delocalisation of electrons along the pi-electron systems of the polymer chains. Research into these materials is motivated both by their novel electronic properties, and also their potential for use in a wide range of applications including light-emitting diodes (LEDs), thin-film transistors, and photovoltaic cells (solar cells and light detectors). Light absorbed in a photovoltaic cell generates opposite charges which are collected at two different electrodes, giving rise to an electric current

  20. A conjugate heat transfer analysis of a hermetic reciprocating compressor

    Science.gov (United States)

    DİNCER, M.; SARIOĞLU, K.; GÜNEŞ, H.

    2017-08-01

    Thermodynamic efficiency of a household refrigeration compressor is considerably affected by superheating that occurs inside the compressor. This phenomenon can be defined as the temperature increment of the refrigerant before entering the compression volume. On its flow path; refrigerant gains heat from suction pipe, suction muffler, suction chamber and related compressor components, which are at higher temperatures. In purpose of investigating conjugated heat transfer mechanism inside a hermetic reciprocating compressor a detailed numerical model is presented. The numerical conjugate heat and flow model is formed both with fluid domain (refrigerant) and solid domain (compressor components). Effects of using different materials on temperature distribution of some key components such as the crankcase, cylinder head and the valve plate are investigated. In addition to steady state analysis, transient CFD analysis is performed in order to understand fluid flow characteristics and its influence on superheating of the refrigerant.

  1. Physicochemical property of starch-pectin conjugates with resistance to enzymatic activity.

    Science.gov (United States)

    Zhang, Juan; Chen, Lei; Cui, Junhui; Xiao, Lin; Wang, Zhengwu

    2014-06-01

    In view of the high nutritional values and bioactivities of resistant starch and pectin, it would be a good choice to chemically combine pectin and starch to give a new type of chemically modified resistant starch. A new type of chemically modified resistant starch has been prepared by cross-linking starch and pectin using sodium trimetaphosphate. Starch-pectin conjugates can well prevent the hydrolysis catalysed by different enzymes, such as α-amylase, amyloglucosidase, pancreatin as well as β-amylase and glucosidase. Although the conjugates do not change the crystal type of starch, they increase the degree of crystallinity. Moreover, thermal stability and structural homogeneity of the conjugates are positively correlated with double-helical order in the crystalline region. This study gives a new method for the preparation of resistant starch-pectin conjugates which can be widely used as a new type of food additive in the industry. © 2013 Society of Chemical Industry.

  2. Preparation of surfactant-stabilized gold nanoparticle-peptide nucleic acid conjugates

    Energy Technology Data Exchange (ETDEWEB)

    Duy, Janice, E-mail: janice.duy@umit.maine.ed [University of Maine, Graduate School of Biomedical Sciences (United States); Connell, Laurie B. [University of Maine, School of Marine Sciences (United States); Eck, Wolfgang [University of Heidelberg, Applied Physical Chemistry (Germany); Collins, Scott D. [University of Maine, Department of Chemistry (United States); Smith, Rosemary L. [University of Maine, Electrical and Computer Engineering Department (United States)

    2010-09-15

    A simple, two-step method of producing stable and functional peptide nucleic acid (PNA)-conjugated gold nanoparticles using a surfactant stabilization step is presented. PNA are DNA analogs with superior chemical stability and target discrimination, but their use in metallic nanoparticle systems has been limited by the difficulty of producing stable colloids of nanoparticle-PNA conjugates. In this work, the nonionic surfactant Tween 20 (polyoxyethylene (20) sorbitan monolaurate) was used to sterically shield gold surfaces prior to the addition of thiolated PNA, producing conjugates which remain dispersed in solution and retain the ability to hybridize to complementary nucleic acid sequences. The conjugates were characterized using transmission electron microscopy, dynamic light scattering, and UV-visible absorbance spectroscopy. PNA attachment to gold nanoparticles was confirmed with an enzyme-linked immunoassay, while the ability of nanoparticle-bound PNA to hybridize to its complement was demonstrated using labeled DNA.

  3. Locking the Coplanar Conformation of π-Conjugated Molecules and Macromolecules Using Dynamic Noncovalent Bonds.

    Science.gov (United States)

    Zhu, Congzhi; Fang, Lei

    2017-06-27

    Torsional conformation of the backbone of a π-conjugated molecule or macromolecule shapes its solubility, optoelectronic characteristics, rheological behaviors, and ultimately solid-state functions. In order to tailor these molecular, supramolecular, and materials properties, the desired coplanar conformation in π-conjugated systems can be locked by using dynamic noncovalent bonds. In this article, the syntheses, characterizations, and unique properties of conjugated molecules/polymers involving a variety of bridging noncovalent bonds are disussed in the context of coplanar backbone conformation. In addition, challenges in this specific field are identified and discussed for future breakthroughs in exploiting the promising potential of noncovalent-bond-bridged, π-conjugated organic materials. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Autocatalytic, bistable, oscillatory networks of biologically relevant organic reactions

    Science.gov (United States)

    Semenov, Sergey N.; Kraft, Lewis J.; Ainla, Alar; Zhao, Mengxia; Baghbanzadeh, Mostafa; Campbell, Victoria E.; Kang, Kyungtae; Fox, Jerome M.; Whitesides, George M.

    2016-09-01

    Networks of organic chemical reactions are important in life and probably played a central part in its origin. Network dynamics regulate cell division, circadian rhythms, nerve impulses and chemotaxis, and guide the development of organisms. Although out-of-equilibrium networks of chemical reactions have the potential to display emergent network dynamics such as spontaneous pattern formation, bistability and periodic oscillations, the principles that enable networks of organic reactions to develop complex behaviours are incompletely understood. Here we describe a network of biologically relevant organic reactions (amide formation, thiolate-thioester exchange, thiolate-disulfide interchange and conjugate addition) that displays bistability and oscillations in the concentrations of organic thiols and amides. Oscillations arise from the interaction between three subcomponents of the network: an autocatalytic cycle that generates thiols and amides from thioesters and dialkyl disulfides; a trigger that controls autocatalytic growth; and inhibitory processes that remove activating thiol species that are produced during the autocatalytic cycle. In contrast to previous studies that have demonstrated oscillations and bistability using highly evolved biomolecules (enzymes and DNA) or inorganic molecules of questionable biochemical relevance (for example, those used in Belousov-Zhabotinskii-type reactions), the organic molecules we use are relevant to metabolism and similar to those that might have existed on the early Earth. By using small organic molecules to build a network of organic reactions with autocatalytic, bistable and oscillatory behaviour, we identify principles that explain the ways in which dynamic networks relevant to life could have developed. Modifications of this network will clarify the influence of molecular structure on the dynamics of reaction networks, and may enable the design of biomimetic networks and of synthetic self-regulating and evolving

  5. Aptamer conjugated paclitaxel and magnetic fluid loaded fluorescently tagged PLGA nanoparticles for targeted cancer therapy

    Science.gov (United States)

    Aravind, Athulya; Nair, Remya; Raveendran, Sreejith; Veeranarayanan, Srivani; Nagaoka, Yutaka; Fukuda, Takahiro; Hasumura, Takahashi; Morimoto, Hisao; Yoshida, Yasuhiko; Maekawa, Toru; Sakthi Kumar, D.

    2013-10-01

    Controlled and targeted drug delivery is an essential criterion in cancer therapy to reduce the side effects caused by non-specific drug release and toxicity. Targeted chemotherapy, sustained drug release and optical imaging have been achieved using a multifunctional nanocarrier constructed from poly (D, L-lactide-co-glycolide) nanoparticles (PLGA NPs), an anticancer drug paclitaxel (PTX), a fluorescent dye Nile red (NR), magnetic fluid (MF) and aptamers (Apt, AS1411, anti-nucleolin aptamer). The magnetic fluid and paclitaxel loaded fluorescently labeled PLGA NPs (MF-PTX-NR-PLGA NPs) were synthesized by a single-emulsion technique/solvent evaporation method using a chemical cross linker bis (sulfosuccinimidyl) suberate (BS3) to enable binding of aptamer on to the surface of the nanoparticles. Targeting aptamers were then introduced to the particles through the reaction with the cross linker to target the nucleolin receptors over expressed on the cancer cell surface. Specific binding and uptake of the aptamer conjugated magnetic fluid loaded fluorescently tagged PLGA NPs (Apt-MF-NR-PLGA NPs) to the target cancer cells induced by aptamers was observed using confocal microscopy. Cytotoxicity assay conducted in two cell lines (L929 and MCF-7) confirmed that targeted MCF-7 cancer cells were killed while control cells were unharmed. In addition, aptamer mediated delivery resulting in enhanced binding and uptake to the target cancer cells exhibited increased therapeutic effect of the drug. Moreover, these aptamer conjugated magnetic polymer vehicles apart from actively transporting drugs into specifically targeted tumor regions can also be used to induce hyperthermia or for facilitating magnetic guiding of particles to the tumor regions.

  6. Aptamer conjugated paclitaxel and magnetic fluid loaded fluorescently tagged PLGA nanoparticles for targeted cancer therapy

    Energy Technology Data Exchange (ETDEWEB)

    Aravind, Athulya; Nair, Remya; Raveendran, Sreejith; Veeranarayanan, Srivani; Nagaoka, Yutaka; Fukuda, Takahiro; Hasumura, Takahashi; Morimoto, Hisao; Yoshida, Yasuhiko; Maekawa, Toru; Sakthi Kumar, D., E-mail: sakthi@toyo.jp

    2013-10-15

    Controlled and targeted drug delivery is an essential criterion in cancer therapy to reduce the side effects caused by non-specific drug release and toxicity. Targeted chemotherapy, sustained drug release and optical imaging have been achieved using a multifunctional nanocarrier constructed from poly (D, L-lactide-co-glycolide) nanoparticles (PLGA NPs), an anticancer drug paclitaxel (PTX), a fluorescent dye Nile red (NR), magnetic fluid (MF) and aptamers (Apt, AS1411, anti-nucleolin aptamer). The magnetic fluid and paclitaxel loaded fluorescently labeled PLGA NPs (MF-PTX-NR-PLGA NPs) were synthesized by a single-emulsion technique/solvent evaporation method using a chemical cross linker bis (sulfosuccinimidyl) suberate (BS3) to enable binding of aptamer on to the surface of the nanoparticles. Targeting aptamers were then introduced to the particles through the reaction with the cross linker to target the nucleolin receptors over expressed on the cancer cell surface. Specific binding and uptake of the aptamer conjugated magnetic fluid loaded fluorescently tagged PLGA NPs (Apt-MF-NR-PLGA NPs) to the target cancer cells induced by aptamers was observed using confocal microscopy. Cytotoxicity assay conducted in two cell lines (L929 and MCF-7) confirmed that targeted MCF-7 cancer cells were killed while control cells were unharmed. In addition, aptamer mediated delivery resulting in enhanced binding and uptake to the target cancer cells exhibited increased therapeutic effect of the drug. Moreover, these aptamer conjugated magnetic polymer vehicles apart from actively transporting drugs into specifically targeted tumor regions can also be used to induce hyperthermia or for facilitating magnetic guiding of particles to the tumor regions. - Highlights: • Aptamer escorted, theranostic biodegradable PLGA carriers were developed. • Can target cancer cells, control drug release, image and magnetically guide. • Highly specific to the targeted cancer cells thus delivering

  7. Multi-modal switching in responsive DNA block co-polymer conjugates.

    Science.gov (United States)

    Yaşayan, Gökçen; Magnusson, Johannes P; Sicilia, Giovanna; Spain, Sebastian G; Allen, Stephanie; Davies, Martyn C; Alexander, Cameron

    2013-10-14

    New classes of information-rich DNA block co-polymer conjugates were synthesised, encoded with thermoresponsive and biocompatible poly(tri(ethylene glycol)ethyl ether methacrylate) (pTriEGMA) chains and oligomeric nucleic acids connected by either bioreducible or non-reducible links. The pTriEGMA chains were grown from initiator-functionalised hybridised DNA, designed to assemble with toehold overhangs. Functional information in the conjugates was explored via dynamic light scattering (DLS) and atomic force microscopy (AFM), in order to evaluate (i) reversible self-assembly into supramolecular structures across the pTriEGMA phase transition temperature; (ii) conformational change via addition of competing DNA sequences across the toeholds, and (iii) reductive cleavage of polymer-DNA links. The results showed that discrete nanoscale conjugates could reversibly associate through pTriEGMA phase behaviour and that size and association behaviour in one class of conjugate could be switched by addition of a competing DNA sequence and by reduction to break the polymer-DNA links. Preliminary experiments with the DNA-conjugates as delivery systems for doxorubicin to a cancer cell line indicated good tolerability of the conjugates alone and cytotoxic efficacy when loaded with the drug.

  8. Drug Reactions

    Science.gov (United States)

    ... or diabetes. But medicines can also cause unwanted reactions. One problem is interactions, which may occur between ... more serious. Drug allergies are another type of reaction. They can be mild or life-threatening. Skin ...

  9. Making peanut allergens indigestible: a model system for reducing or preventing an allergic reaction

    Science.gov (United States)

    Peanut allergens are not totally resistant to digestion as previously known. Creating peanut allergen conjugates that are more resistant to digestion may prevent absorption of the allergens into the bloodstream, and thereby, an allergic reaction. Peanut allergen conjugates were prepared by covalen...

  10. Pneumococcal Conjugate Vaccine (PCV13)

    Science.gov (United States)

    ... the United States.Treatment of pneumococcal infections with penicillin and other drugs is not as effective as ... Anyone who has ever had a life-threatening allergic reaction to a dose of this vaccine, to an ...

  11. TAT peptide and its conjugates: proteolytic stability.

    Science.gov (United States)

    Grunwald, Jacob; Rejtar, Tomas; Sawant, Rupa; Wang, Zhouxi; Torchilin, Vladimir P

    2009-08-19

    The proteolytic cleavage of TATp, TATp-PEG(1000)-PE conjugate (TATp-conjugate), and TATp as TATp-conjugate in mixed micelles made of TATp-conjugate and PEG(5000)-PE (2.5% mol of TATp-conjugate, TATp-Mic) were studied by HPLC with fluorescent detection using fluorenylmethyl chloroformate (FMOC) labeling and by MALDI-TOF MS analysis. The cleavage kinetics were analyzed in human blood plasma and in trypsin-containing phosphate buffered saline (PBS), pH 7.4, to simulate the proteolytic activity of human plasma. The trypsinolysis of free TATp, TATp-conjugate, and TATp-Mic revealed that the main initial fragmentation is an endocleavage at the carboxyl terminus resulting in an Arg-Arg (RR) dimer. The trypsinolysis followed pseudo-first-order kinetics. The cleavage of the free TATp was relatively fast with a half-life of a few minutes (t(1/2) ∼ 3.5 min). The TATp-conjugate showed more stability with about a 3-fold increase in half-life (t(1/2) ∼ 10 min). TATp in TATp-Mic was highly protected against proteolysis with an over 100-fold increase in half-life (t(1/2) ∼ 430 min). The shielding of TATp by PEG moieties in the proposed TATp-Mic is of great importance for its potential use as a cell-penetrating moiety for multifunctional "smart" drug delivery systems with detachable PEG.

  12. Addition of e-aq and H atoms to hypoxanthine and inosine and the reactions of alpha-hydroxyalkyl radicals with purines. A pulse radiolysis and product analysis study.

    Science.gov (United States)

    Aravindakumar, C T; Mohan, H; Mudaliar, M; Rao, B S; Mittal, J P; Schuchmann, M N; Von Sonntag, C

    1994-10-01

    The reactions of hydrated electrons e-aq with hypoxanthine and inosine were followed using pulse radiolysis methods. In a neutral solution the electron adduct of inosine is immediately protonated at the heteroatoms of the purine ring by water (k > 2.5 x 10(6)s-1) to give In(N,O-H).. These N,O-protonated intermediates have a single absorption maximum at 300 nm. In basic solution the protonation of the electron adduct of inosine by water leads to other intermediate products with an absorption maximum at 350 nm. These intermediates are believed to be the C-protonated electron adducts of inosine (In(N,O-H).). In (N,O-H). and In(C-H). differ strongly in their ability to reduce p-nitroacetophenone (PNAP). In(N,O-H). are strong reductants and reduce PNAP quantitatively to PNAP.-. Based on the pH dependence of PNAP.- yields, two types of tautomers of In(C-H). could be distinguished. One of the tautomers can reduce PNAP, albeit with slower rate than In(N,O-H)., the other tautomer has no reducing properties. The latter is the one with the higher pKa and therefore thermodynamically more stable. The absorption spectrum of the intermediates produced in the reaction of e-aq with hypoxanthine at neutral pH is very similar to that of In(N,O-H). with a maximum at 300 nm. However, no build-up at 350 nm was observed in basic solution as in the case of the electron adduct of inosine. The reaction of H atoms with inosine produces in basic solution intermediate radicals with the same absorption spectrum as the C-protonated electron adducts of inosine. It is suggested that both the reactions of e-aq and H. with inosine in basic solution produce the same radical, namely the H-adduct of inosine (In(C-H)) with the highest pKa. alpha-Hydroxyalkyl radicals were found to react very slowly with purine bases and nucleosides in neutral to basic solutions. In acidic solution their reactivity increases and a number of rate constants were determined by pulse radiolysis measurements at pH 0.4. The

  13. [Conjugal violence during pregnancy: a literature review.].

    Science.gov (United States)

    Séguin, L; Pimont, M; Rinfret-Raynor, M; Cantin, S

    2000-01-01

    Conjugal violence is a complicated issue which scope and consequences are increasingly documented. Among the many facets of the phenomenon, its occurrence during pregnancy is particularly worrisome. This article reviews the scientific literature pertaining to this issue. After establishing the prevalence of conjugal violence during pregnancy, the authors examine the major studies analyzing factors associated with this violence as well as its consequences for the mother and the infant. The article concludes that the current informations, although partial, are sufficient to justify early detection of conjugal violence in order to help future mothers efficiently.

  14. Modelling conjugation with stochastic differential equations

    DEFF Research Database (Denmark)

    Philipsen, Kirsten Riber; Christiansen, Lasse Engbo; Hasman, Henrik

    2010-01-01

    Conjugation is an important mechanism involved in the transfer of resistance between bacteria. In this article a stochastic differential equation based model consisting of a continuous time state equation and a discrete time measurement equation is introduced to model growth and conjugation of two...... Enterococcus faecium strains in a rich exhaustible media. The model contains a new expression for a substrate dependent conjugation rate. A maximum likelihood based method is used to estimate the model parameters. Different models including different noise structure for the system and observations are compared...

  15. HEC-cysteamine conjugates: influence of degree of thiolation on efflux pump inhibitory and permeation enhancing properties.

    Science.gov (United States)

    Rahmat, Deni; Sakloetsakun, Duangkamon; Shahnaz, Gul; Sarti, Federica; Laffleur, Flavia; Schnürch, Andreas Bernkop

    2012-01-17

    Within the present study hydroxyethyl cellulose-cysteamine conjugates are investigated regarding biocompatibility, in situ gelling, permeation enhancing and efflux pump inhibitory properties. For this purpose, a series of concentrations of sodium periodate was prepared to oxidize HEC leading to ring opening of glucose subunits. The resulting polymers showing varying degrees of oxidation (DO) were then conjugated with cysteamine stabilized via reductive amination. Consequently, HEC-cysteamine conjugates with increasing degree in thiolation were obtained. Since the conjugates are positively charged, potency of cytotoxicity was tested by resazurin assay. In situ gelling properties of the conjugates were studied to investigate change of their viscosity due to inter- and/or intramolecular crosslinking via disulfide bonds. The influence of the presence of the conjugates on transport of rhodamine 123 and fluoresceinisothiocyanate-dextran 4 (FD4) representing model compounds for P-glycoprotein (P-gp) inhibition and permeation enhancing studies, respectively, across Caco-2 cell monolayers was determined. The conjugates showed a degree of thiolation in the range of 316-2158 μmol/g. Within 30 min, dynamic viscosity of the conjugate with the lowest degree of thiolation 0.5% (m/v) increased up to 300-fold. The conjugates showed a degree of thiolation-dependent increase in cytotoxicity but they all were found comparatively low cytotoxic. The addition of the conjugate with thiol group content of 1670 μmol/g resulted in the highest improvement in the transport of both rhodamine 123 and FD4 as compared to buffer control. Accordingly, the degree of thiolation strongly influences the properties of the conjugates and the modulation of the degree of thiolation could be exploited for development of various drug delivery systems. Copyright © 2011 Elsevier B.V. All rights reserved.

  16. Characterization of ester- or thioamide-functionalized single-walled carbon nanotube-azithromycin conjugates

    Science.gov (United States)

    Darabi, Hossein Reza; Roozkhosh, Atefeh; Jafar Tehrani, Mohammad; Aghapoor, Kioumars; Sayahi, Hani; Balavar, Yadollah; Mohsenzadeh, Farshid

    2014-01-01

    Functionalization of single-walled carbon nanotubes (SWCNTs) with nitrile groups, followed by further reactions allowed direct attachment of azithromycin and its N-demethyl derivative to the side-walls of SWCNTs for the first time. With these approaches, the cleavable ester or thioamide bonds are formed to connect azithromycin to SWCNTs resulting in azithromycin-SWCNT conjugates. These cleavable bonds are able to control molecular release from nanotube surfaces which are generally applicable to a variety of hybrid materials based on SWCNTs. A non-covalent azithromycin-SWCNT has also been compared with azithromycin-SWCNTs conjugates. Thermogravimetric analysis (TGA), Fourier-transformed infrared (FT-IR), UV-vis, and Raman spectroscopies give hints on the characterization of azithromycin-SWCNT. Both drug release and antimicrobial activity of azithromycin-SWCNT conjugates were also tested.

  17. Effect of methotrexate conjugated PAMAM dendrimers on the viability of MES-SA uterine cancer cells

    Directory of Open Access Journals (Sweden)

    Samreen Khatri

    2014-01-01

    Full Text Available The aim of this work was to synthesize methotrexate (MTX-polyamidoamine (PAMAM dendritic nanoconjugates and to study their effect on cell viability in uterine sarcoma cells. The amide-bonded PAMAM dendrimer-MTX conjugates were prepared by conjugation between the amine-terminated G5 dendrimer and the carboxylic groups of the MTX using a dicyclohexylcarbodiimide coupling reaction. The formation of conjugates was evaluated by ultraviolet (UV and 1 H nuclear magnetic resonance ( 1 H NMR spectroscopy studies. The cell survival of MES-SA cells, a uterine sarcoma cell line, was evaluated in the presence of the dendrimer-MTX nanoconjugate, using appropriate controls. The UV and 1 H NMR study confirmed the formation of covalent bonds between the drug and the dendrimer. The cell viability study indicated that the nanoconjugates had significantly improved cell killing compared to the free MTX.

  18. Synthesis and evaluation of the biostability and cell compatibility of novel conjugates of nucleobase, peptidic epitope, and saccharide

    Directory of Open Access Journals (Sweden)

    Dan Yuan

    2015-08-01

    Full Text Available This article reports the synthesis of a new class of conjugates containing a nucleobase, a peptidic epitope, and a saccharide and the evalution of their gelation, biostability, and cell compatibility. We demonstrate a facile synthetic process, based on solid-phase peptide synthesis of nucleopeptides, to connect a saccharide with the nucleopeptides for producing the target conjugates. All the conjugates themselves (1–8 display excellent solubility in water without forming hydrogels. However, a mixture of 5 and 8 self-assembles to form nanofibers and results in a supramolecular hydrogel. The proteolytic stabilities of the conjugates depend on the functional peptidic epitopes. We found that TTPV is proteolytic resistant and LGFNI is susceptible to proteolysis. In addition, all the conjugates are compatible to the mammalian cells tested.

  19. The role of IgE recognition in allergic reactions to amoxicillin and clavulanic acid.

    Science.gov (United States)

    Torres, M J; Montañez, M I; Ariza, A; Salas, M; Fernandez, T D; Barbero, N; Mayorga, C; Blanca, M

    2016-02-01

    Betalactam (BL) antibiotics are the drugs most frequently involved in IgE-mediated reactions. The culprit BL varies according to consumption patterns, with amoxicillin (AX) more prevalent in Southern Europe and penicillin V in Scandinavian countries. Nowadays, the combination of AX and clavulanic acid (CLV) is the most highly consumed BL containing medicine worldwide. Both BLs, AX and CLV, can independently be involved in reactions, which poses a diagnostic challenge. In patients with immediate allergic reactions to AX, two patterns of responses have been described, those responding to benzylpenicillin (cross-reactors) and those selective to AX. In addition, selective reactions to CLV account for around 30% of allergic reactions to the combination AX-CLV. These patterns of IgE recognition could be related to differences in the haptenation process, in the immunological response, or in the BL involved in the first sensitization. In this regard, patients with selective responses to CLV are generally younger than those allergic to AX or benzylpenicillin. So far, no evidence of cross-reactivity between CLV and other BLs has been reported. This shows the importance of an accurate diagnosis of CLV allergy, as patients with selective reactions to CLV could take other BLs including AX. Diagnosis can be performed in vivo and in vitro, although no immunoassay currently exists. Research regarding the CLV antigenic determinants and protein conjugates is essential to improve diagnosis. BLs need to covalently bind to a carrier protein to be immunogenic. The antigenic determinant of AX is the amoxicilloyl amide, but CLV leads to unstable structures, many of which are unknown. Moreover, the nature of the BL-protein conjugates plays an important role in IgE recognition. This review aims to summarize current knowledge on the immunochemistry, diagnostic approaches as well as chemical and proteomic studies for both AX and CLV. © 2015 John Wiley & Sons Ltd.

  20. Characterization of the Conjugation Pattern in Large Polysaccharide-Protein Conjugates by NMR Spectroscopy.

    Science.gov (United States)

    Giuntini, Stefano; Balducci, Evita; Cerofolini, Linda; Ravera, Enrico; Fragai, Marco; Berti, Francesco; Luchinat, Claudio

    2017-10-10

    Carbohydrate-based vaccines are among the safest and most effective vaccines and represent potent tools for prevention of life-threatening bacterial infectious diseases, like meningitis and pneumonia. The chemical conjugation of a weak antigen to protein as a source of T-cell epitopes generates a glycoconjugate vaccine that results more immunogenic. Several methods have been used so far to characterize the resulting polysaccharide-protein conjugates. However, a reduced number of methodologies has been proposed for measuring the degree of saccharide conjugation at the possible protein sites. Here we show that detailed information on large proteins conjugated with large polysaccharides can be achieved by a combination of solution and solid-state NMR spectroscopy. As a test case, a large protein assembly, l-asparaginase II, has been conjugated with Neisseria meningitidis serogroup C capsular polysaccharide and the pattern and degree of conjugation were determined. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Nephrotoxicity of halogenated alkenyl cysteine-S-conjugates

    Energy Technology Data Exchange (ETDEWEB)

    Nagelkerke, J.F.; Boogaard, P.J. (Univ. of Leiden (Netherlands))

    1991-01-01

    In 1916 a relationship was postulated between the occurrence of aplastic anemia in cattle and the soy bean meal that they had been fed, which had been extracted with trichloroethylene. The toxic compound was later identified as S-(1,2-dichlorovinyl)-L-cysteine (DCV-Cys). In addition to effects on the hemopoietic system it also produced nephrotoxicity in calves. In rats only renal tubular necrosis was found. Further research demonstrated that other halogenated hydrocarbons produced similar nephrotoxicity. The haloalkenyl cysteine-S-conjugates (Cys-D-conjugates) have extensively been studied; this has provided new insight into the biochemical processes that lead to nephrotoxicity. It has been shown that a combination of transport processes and specific metabolic pathways, resulting in reactive intermediates that bind to cellular macromolecules, makes the kidney vulnerable to the noxious effects of the haloakenyl Cys-S-conjugates. The first part of this review gives a brief overview of the bioactivation of the haloalkenes; in the second part the present knowledge of the underlying mechanisms of cytotoxicity is outlined.

  2. Synthesis of a bifunctional cytidine derivative and its conjugation to RNA for in vitro selection of a cytidine deaminase ribozyme

    Directory of Open Access Journals (Sweden)

    Nico Rublack

    2014-08-01

    Full Text Available Over the past 20 years, the generation of functional RNAs by in vitro selection has become a standard technique. Apart from aptamers for simple binding of defined ligands, also RNAs for catalysis of chemical reactions have been selected. In the latter case, a key step often is the conjugation of one of the two reactants to the library, requiring suitable strategies for terminal or internal RNA functionalization. With the aim of selecting a ribozyme for deamination of cytidine, we have set up a selection scheme involving the attachment of the cytidine acting as deamination substrate to the 3'-terminus of the RNAs in the library, and library immobilization. Here, we report the synthesis of a bifunctional cytidine derivative suitable for conjugation to RNA and linkage of the conjugated library to a streptavidine-coated surface. Successful conjugation of the cytidine derivative to the 3'-terminus of a model RNA is demonstrated.

  3. Synthesis and Immunological Comparison of Differently Linked Lipoarabinomannan Oligosaccharide-Monophosphoryl Lipid A Conjugates as Antituberculosis Vaccines.

    Science.gov (United States)

    Wang, Lizhen; Feng, Shaojie; Wang, Subo; Li, Hui; Guo, Zhongwu; Gu, Guofeng

    2017-11-20

    A monophosphoryl lipid A (MPLA) derivative having the 6'-OH group substituted with an NH2 group was synthesized and coupled with the upstream terminal tetrasaccharide of mycobacterial lipoarabinomannan (LAM) via an amide bond to create a novel type of MPLA-based fully synthetic glycoconjugate vaccine. The same tetrasaccharide was also coupled with MPLA at the 1-O-position. Immunological activities of the two synthetic conjugates were evaluated in mice and compared. Both afforded robust overall and IgG antibody responses, but intraperitoneal injection elicited responses significantly stronger than those from subcutaneous injection. It was thus speculated that MPLA conjugates might act via stimulating B1 lymphocytes present in the intrapleural and peritoneal cavities. Moreover, the 6'-N-conjugate afforded antibody titers much higher than those of the 1-O-conjugate. These results revealed not only the self-adjuvant property of MPLA conjugates to elicit robust IgG antibody responses but also the impact of MPLA structure on the immunological activity of its conjugates. It was concluded that LAM oligosaccharide-MPLA conjugates, especially 6'-N-linked, are promising candidates as antituberculosis vaccines worthy of further investigation. Additionally, the 6'-amino derivative of MPLA was proved to be a useful carrier for the development of fully synthetic carbohydrate-based conjugate vaccines.

  4. Design and Application of Antimicrobial Peptide Conjugates.

    Science.gov (United States)

    Reinhardt, Andre; Neundorf, Ines

    2016-05-11

    Antimicrobial peptides (AMPs) are an interesting class of antibiotics characterized by their unique antibiotic activity and lower propensity for developing resistance compared to common antibiotics. They belong to the class of membrane-active peptides and usually act selectively against bacteria, fungi and protozoans. AMPs, but also peptide conjugates containing AMPs, have come more and more into the focus of research during the last few years. Within this article, recent work on AMP conjugates is reviewed. Different aspects will be highlighted as a combination of AMPs with antibiotics or organometallic compounds aiming to increase antibacterial activity or target selectivity, conjugation with photosensitizers for improving photodynamic therapy (PDT) or the attachment to particles, to name only a few. Owing to the enormous resonance of antimicrobial conjugates in the literature so far, this research topic seems to be very attractive to different scientific fields, like medicine, biology, biochemistry or chemistry.

  5. Design and Application of Antimicrobial Peptide Conjugates

    Directory of Open Access Journals (Sweden)

    Andre Reinhardt

    2016-05-01

    Full Text Available Antimicrobial peptides (AMPs are an interesting class of antibiotics characterized by their unique antibiotic activity and lower propensity for developing resistance compared to common antibiotics. They belong to the class of membrane-active peptides and usually act selectively against bacteria, fungi and protozoans. AMPs, but also peptide conjugates containing AMPs, have come more and more into the focus of research during the last few years. Within this article, recent work on AMP conjugates is reviewed. Different aspects will be highlighted as a combination of AMPs with antibiotics or organometallic compounds aiming to increase antibacterial activity or target selectivity, conjugation with photosensitizers for improving photodynamic therapy (PDT or the attachment to particles, to name only a few. Owing to the enormous resonance of antimicrobial conjugates in the literature so far, this research topic seems to be very attractive to different scientific fields, like medicine, biology, biochemistry or chemistry.

  6. Nonenzymatic displacement of chlorine and formation of free radicals upon the reaction of glutathione with PCB quinones.

    Science.gov (United States)

    Song, Yang; Wagner, Brett A; Witmer, Jordan R; Lehmler, Hans-Joachim; Buettner, Garry R

    2009-06-16

    The reactions of glutathione (GSH) with polychlorinated biphenyl (PCB) quinones having different degrees of chlorination on the quinone ring were examined. EPR spectroscopy and MS revealed 2 types of reactions yielding different products: (i) a nonenzymatic, nucleophilic displacement of chlorine on the quinone ring yielding a glutathiylated conjugated quinone and (ii) Michael addition of GSH to the quinone, a 2-electron reduction, yielding a glutathiylated conjugated hydroquinone. The pK(a) of parent hydroquinone decreased by 1 unit as the degree of chlorination increased. This resulted in a corresponding increase in the oxidizability of these chlorinated hydroquinones. The reaction with oxygen appears to be first-order each in ionized hydroquinone and dioxygen, yielding hydrogen peroxide stoichiometrically. The generation of semiquinone radicals, superoxide, and hydroxyl radicals was observed by EPR; however, the mechanisms and yields vary depending on the degree of the chlorination of hydroquinone/quinone and the presence or absence of GSH. Our discovery that chlorinated quinones undergo a rapid, nonenzymatic dechlorination upon reaction with GSH opens a different view on mechanisms of metabolism and the toxicity of this class of compounds.

  7. Confirmation of conjugation processes during TNT metabolism by axenic plant roots

    Energy Technology Data Exchange (ETDEWEB)

    Bhadra, R.; Wayment, D.G.; Hughes, J.B.; Shanks, J.V. [Rice Univ., Houston, TX (United States)

    1999-02-01

    This paper examines processes in plants for the formation of fate products of TNT beyond its animated reduction products, 2-amino-4,6-dinitrotoluene and 4-amino-2,6-dinitrotoluene. TNT metabolites were isolated and characterized in combination with temporal analyses of production profiles and {sup 14}C distribution, in microbe-free, axenic root cultures of Catharanthus roseus. Four unique TNT-derived compounds were isolated. Using evidence from {sup 1}H NMR, mass spectroscopy, HPLC, acid hydrolysis, and enzymatic hydrolysis with {beta}-glucuronidase and {beta}-glucosidase, they were established as conjugates formed by reactions of the amine groups of 2-amino-4,6-dinitrotoluene and 4-amino-2,6-dinitrotoluene. From the mass spectral evidence, at least a six-carbon unit from the plant intracellular milleu was involved in conjugate formation. Mass balance analysis indicated that, by 75 h after TNT amendment of the initial TNT radiolabel, extractable conjugates comprised 22%, bound residues comprised another 29%, 2-amino-4,6-dinitrotoluene was 4%, and the rest remained unidentified. Isolates from TNT-amended roots versus monoamino-dinitrotoluene-amended roots were not identical, suggesting numerous possible outcomes for the plant-based conjugation of 2-amino-2,6-dinitrotoluene or 4-amino-2,6-dinitrotoluene. This study is the first direct evidence for the involvement of the primary reduction products of TNT--2-amino-4,6-dinitrotoluene ad 4-amino--2,6-dinitrotoluene--in conjugation process in plant detoxification of TNT.

  8. Accurate determination of tissue steroid hormones, precursors and conjugates in adult male rat.

    Science.gov (United States)

    Maeda, Naoyuki; Tanaka, Emi; Suzuki, Tomokazu; Okumura, Kanako; Nomura, Sachiko; Miyasho, Taku; Haeno, Satoko; Yokota, Hiroshi

    2013-01-01

    The actual levels of steroid hormones in organs are vital for endocrine, reproductive and neuronal health and disorders. We developed an accurate method to determine the levels of steroid hormones and steroid conjugates in various organs by an efficient preparation using a solid-phase-extraction cartridge. Each steroid was identified by the precursor ion spectra using liquid chromatography-electrospray ionization time-of-flight mass spectrometry, and the respective steroids were quantitatively analysed in the selected reaction monitoring mode by liquid chromatograph-mass spectrometry/mass spectrometry (LC-MS/MS). The data showed that significant levels of testosterone, corticosterone and precursors of both hormones were detected in all organs except liver. The glucuronide conjugates of steroid hormones and the precursors were detected in all organs except liver, but sulfate conjugates of these steroids were observed only in the target organs of the hormones and kidney. Interestingly, these steroids and the conjugates were not observed in the liver except pregnenolone. In conclusion, an accurate determination of tissue steroids was developed using LC-MS analysis. Biosynthesis of steroid hormones from the precursors was estimated even in the target organs, and the delivery of these steroid conjugates was also suggested via the circulation without any significant hepatic participation.

  9. Women experiencing the intergenerationality of conjugal violence

    OpenAIRE

    Paixão,Gilvânia Patrícia do Nascimento; Gomes,Nadirlene Pereira; Diniz,Normélia Maria Freire; Lira,Margaret Ollinda de Souza Carvalho e; Carvalho,Milca Ramaiane da Silva; Silva,Rudval Souza da

    2015-01-01

    Objective: to analyze the family relationship, in childhood and adolescence, of women who experience conjugal violence. Method: qualitative study. Interviews were held with 19 women, who were experiencing conjugal violence, and who were resident in a community in Salvador, Bahia, Brazil. The project was approved by the Research Ethics Committee (N. 42/2011). Results: the data was organized using the Discourse of the Collective Subject, identifying the summary central ideas: they witnessed vio...

  10. Role of surface-reaction layer in HBr/fluorocarbon-based plasma with nitrogen addition formed by high-aspect-ratio etching of polycrystalline silicon and SiO2 stacks

    Science.gov (United States)

    Iwase, Taku; Matsui, Miyako; Yokogawa, Kenetsu; Arase, Takao; Mori, Masahito

    2016-06-01

    The etching of polycrystalline silicon (poly-Si)/SiO2 stacks by using VHF plasma was studied for three-dimensional NAND fabrication. One critical goal is achieving both a vertical profile and high throughput for multiple-stack etching. While the conventional process consists of multiple steps for each stacked layer, in this study, HBr/fluorocarbon-based gas chemistry was investigated to achieve a single-step etching process to reduce process time. By analyzing the dependence on wafer temperature, we improved both the etching profile and rate at a low temperature. The etching mechanism is examined considering the composition of the surface reaction layer. X-ray photoelectron spectroscopy (XPS) analysis revealed that the adsorption of N-H and Br was enhanced at a low temperature, resulting in a reduced carbon-based-polymer thickness and enhanced Si etching. Finally, a vertical profile was obtained as a result of the formation of a thin and reactive surface-reaction layer at a low wafer temperature.

  11. Specific Conjugation of the Hinge Region for Homogeneous Preparation of Antibody Fragment-Drug Conjugate: A Case Study for Doxorubicin-PEG-anti-CD20 Fab' Synthesis.

    Science.gov (United States)

    Zhou, Zhan; Zhang, Jing; Zhang, Yan; Ma, Guanghui; Su, Zhiguo

    2016-01-20

    Conventional preparation strategies for antibody-drug conjugates (ADCs) result in heterogeneous products with various molecular sizes and species. In this study, we developed a homogeneous preparation strategy by site-specific conjugation of the anticancer drug with an antibody fragment. The model drug doxorubicin (DOX) was coupled to the Fab' fragment of anti-CD20 IgG at its permissive sites through a heterotelechelic PEG linker, generating an antibody fragment-drug conjugate (AFDC). Anti-CD20 IgG was digested and reduced specifically with β-mercaptoethylamine to generate the Fab' fragment with two free mercapto groups in its hinge region. Meanwhile, DOX was conjugated with α-succinimidylsuccinate ω-maleimide polyethylene glycol (NHS-PEG-MAL) to form MAL-PEG-DOX, which was subsequently linked to the free mercapto containing Fab' fragment to form a Fab'-PEG-DOX conjugate. The dual site-specific bioconjugation was achieved through the combination of highly selective reduction of IgG and introduction of heterotelechelic PEG linker. The resulting AFDC provides an utterly homogeneous product, with a definite ratio of one fragment to two drugs. Laser confocal microscopy and cell ELISA revealed that the AFDC could accumulate in the antigen-positive Daudi tumor cell. In addition, the Fab'-PEG-DOX retained appreciable targeting ability and improved antitumor activity, demonstrating an excellent therapeutic effect on the lymphoma mice model for better cure rate and significantly reduced side effects.

  12. Stereochemical aspects of the glutathione S-transferase-catalyzed conjugations of alkyl halides.

    Science.gov (United States)

    Ridgewell, R E; Abdel-Monem, M M

    1987-01-01

    (R,S)-2-iodooctane and (R,S)-2-bromooctane were found to be substrates for the glutathione S-transferases from rat liver. The conjugation reactions of the enantiomeric 2-halooctanes and glutathione were found to proceed with inversion of configuration at the chiral carbon of the substrate. Selective titration of the free cysteine residues of the glutathione S-transferases provided no observable effect on the stereochemical course of these conjugation reactions. No evidence for substrate stereoselectivity was observed. The diastereomeric S-(2-octyl)glutathiones were produced in approximately equal amounts from racemic 2-halooctane substrates. With S-(+)-2-iodooctane as the electrophilic substrate, a biphasic double reciprocal plot of glutathione concentration vs. initial velocity of product formation was observed suggesting complex kinetics. The S-2-octylglutathione diastereomers were found to be potent inhibitors of the glutathione S-transferase-catalyzed conjugation of 1-chloro-2,4-dinitrobenzene. These results provide support for a single displacement mechanism for the conjugation of 2-halooctanes and glutathione catalyzed by the glutathione S-transferases with product inhibition at low glutathione concentrations.

  13. Delineation of downstream signalling components during acrosome reaction mediated by heat solubilized human zona pellucida

    Directory of Open Access Journals (Sweden)

    Talwar Pankaj

    2010-01-01

    Full Text Available Abstract Background Human egg is enveloped by a glycoproteinaceous matrix, zona pellucida (ZP, responsible for binding of the human spermatozoa to the egg and induction of acrosomal exocytosis in the spermatozoon bound to ZP. In the present manuscript, attempts have been made to delineate the downstream signalling components employed by human ZP to induce acrosome reaction. Methods Heat-solubilized human ZP (SIZP was used to study the induction of acrosome reaction in capacitated human spermatozoa using tetramethylrhodamine isothiocyanate conjugated Pisum sativum agglutinin (TRITC-PSA in absence or presence of various pharmacological inhibitors. In addition, intracellular calcium ([Ca2+]i levels in sperm using Fluo-3 acetoxymethyl ester as fluorescent probe were also estimated in response to SIZP. Results SIZP induces acrosomal exocytosis in capacitated human sperm in a dose dependent manner accompanied by an increase in [Ca2+]i. Human SIZP mediated induction of acrosome reaction depends on extracellular Ca2+ and involves activation of Gi protein-coupled receptor, tyrosine kinase, protein kinases A & C and phosphoinositide 3 (PI3- kinase. In addition, T-type voltage operated calcium channels and GABA-A receptor associated chloride (Cl- channels play an important role in SIZP mediated induction of acrosome reaction. Conclusions Results described in the present study provide a comprehensive account of the various downstream signalling components associated with human ZP mediated acrosome reaction.

  14. Multifunctional adhesive polymers: Preactivated thiolated chitosan-EDTA conjugates.

    Science.gov (United States)

    Netsomboon, Kesinee; Suchaoin, Wongsakorn; Laffleur, Flavia; Prüfert, Felix; Bernkop-Schnürch, Andreas

    2017-02-01

    The aim of this study was to synthesis preactivated thiolated chitosan-EDTA (Ch-EDTA-cys-2MNA) conjugates exhibiting in particular high mucoadhesive, cohesive and chelating properties. Thiol groups were coupled with chitosan by carbodiimide reaction and further preactivated by attachment with 2-mercaptonicotinic acid (2MNA) via disulfide bond formation. Determinations of primary amino and sulfhydryl groups were performed by TNBS and Ellman's tests, respectively. Cytotoxicity was screened by resazurin assay in Caco-2 cells. Mucoadhesive properties and bivalent cation binding capacity with Mg(2+) and Ca(2+) in comparison to chitosan-EDTA (Ch-EDTA) and thiolated Ch-EDTA (Ch-EDTA-cys) were evaluated. Determination of 2MNA and total sulfhydryl groups indicated that 80% of thiol groups were preactivated. The results from cytotoxicity studies demonstrated that Ch-EDTA-cys and Ch-EDTA-cys-2MNA were not toxic to the cells at the polymer test concentration of 0.25% (w/v) while cell viability decreased by increasing the concentration of Ch-EDTA. Although EDTA molecule was modified by thiolation and preactivation, approximately 50% of chelating properties of the conjugates were maintained compared to Ch-EDTA. Ch-EDTA-cys-2MNA adhered on freshly excised porcine intestinal mucosa up to 6h while Ch-EDTA adhered for just 1h. According to the combination of mucoadhesive and chelating properties of the conjugates synthesized in this study, Ch-EDTA-cys-2MNA might be useful for various mucosal drug delivery systems. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Assessment of the effect of testosterone on the acrosome reaction of human spermatozoa.

    Science.gov (United States)

    Vigil, P; Barrientos, V M; Vargas, G G; Machuca, D A; Cortés, M E

    2012-05-01

    In the acrosome reaction, the spermatozoon plasma membrane fuses with the outer acrosomal membrane, resulting in the release of the acrosomal content. Several compounds, such as sex steroids, are known to modulate the acrosomal exocytosis. Testosterone regulates various functions in male reproductive physiology; however, little is known about the relationship between testosterone and the acrosome reaction. Thus, our objective was to study the effect of testosterone on the acrosome reaction of human spermatozoa. To evaluate the acrosomal exocytosis, spermatozoa were incubated with testosterone (0.2, 2.0 and 20 nmol l(-1)), progesterone and control medium for 60, 120, 240 and 1440 min. The acrosome reaction was assessed by staining with Hoechst 33258 and fluorescein isothiocyanate-conjugated P. sativum agglutinin lectin. In general, spermatozoa incubated with progesterone had the highest percentage of acrosomal exocytosis. The percentage of acrosome reaction obtained in the three treatments with testosterone differed from that observed for progesterone at 120, 240 and 1440 min (24 h). Additionally, significant differences were found between testosterone (2.0 and 20 nmol l(-1)) and progesterone after 60 min. Differences between control and the three testosterone treatments studied were obtained only at 1440 min. In general terms, these results show that testosterone exerts no inductor effects on the acrosome reaction of human spermatozoa. © 2011 Blackwell Verlag GmbH.

  16. Modeling σ-Bond Activations by Nickel(0) Beyond Common Approximations: How Accurately Can We Describe Closed-Shell Oxidative Addition Reactions Mediated by Low-Valent Late 3d Transition Metal?

    Science.gov (United States)

    Hu, Lianrui; Chen, Kejuan; Chen, Hui

    2017-10-10

    Accurate modelings of reactions involving 3d transition metals (TMs) are very challenging to both ab initio and DFT approaches. To gain more knowledge in this field, we herein explored typical σ-bond activations of H-H, C-H, C-Cl, and C-C bonds promoted by nickel(0), a low-valent late 3d TM. For the key parameters of activation energy (ΔE‡) and reaction energy (ΔER) for these reactions, various issues related to the computational accuracy were systematically investigated. From the scrutiny of convergence issue with one-electron basis set, augmented (A) basis functions are found to be important, and the CCSD(T)/CBS level with complete basis set (CBS) limit extrapolation based on augmented double-ζ and triple-ζ basis pair (ADZ and ATZ), which produces deviations below 1 kcal/mol from the reference, is recommended for larger systems. As an alternative, the explicitly correlated F12 method can accelerate the basis set convergence further, especially after its CBS extrapolations. Thus, the CCSD(T)-F12/CBS(ADZ-ATZ) level with computational cost comparable to the conventional CCSD(T)/CBS(ADZ-ATZ) level, is found to reach the accuracy of the conventional CCSD(T)/A5Z level, which produces deviations below 0.5 kcal/mol from the reference, and is also highly recommendable. Scalar relativistic effects and 3s3p core-valence correlation are non-negligible for achieving chemical accuracy of around 1 kcal/mol. From the scrutiny of convergence issue with the N-electron basis set, in comparison with the reference CCSDTQ result, CCSD(T) is found to be able to calculate ΔE‡ quite accurately, which is not true for the ΔER calculations. Using highest-level CCSD(T) results of ΔE‡ in this work as references, we tested 18 DFT methods and found that PBE0 and CAM-B3LYP are among the three best performing functionals, irrespective of DFT empirical dispersion correction. With empirical dispersion correction included, ωB97XD is also recommendable due to its improved performance.

  17. Multifunctional nanoparticle-protein conjugates with controllable bioactivity and pH responsiveness

    Science.gov (United States)

    Liu, Feng; Xue, Lulu; Yuan, Yuqi; Pan, Jingjing; Zhang, Chenjie; Wang, Hongwei; Brash, John L.; Yuan, Lin; Chen, Hong

    2016-02-01

    The modulation of protein activity is of significance for disease therapy, molecular diagnostics, and tissue engineering. Nanoparticles offer a new platform for the preparation of protein conjugates with improved protein properties. In the present work, Escherichia coli (E. coli) inorganic pyrophosphatase (PPase) and poly(methacrylic acid) (PMAA) were attached together to gold nanoparticles (AuNPs), forming AuNP-PPase-PMAA conjugates having controllable multi-biofunctionalities and responsiveness to pH. By treating with poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and regulating the pH, the bioactivity of the conjugate becomes ``on/off''-switchable. In addition, by taking advantage of the ability of AuNPs to undergo reversible aggregation/dispersion, the conjugates can be recycled and reused multiple times; and due to the shielding effect of the PMAA, the conjugated enzyme has high resistance to protease digestion. This approach has considerable potential in areas such as controlled delivery and release of drugs, biosensing, and biocatalysis.The modulation of protein activity is of significance for disease therapy, molecular diagnostics, and tissue engineering. Nanoparticles offer a new platform for the preparation of protein conjugates with improved protein properties. In the present work, Escherichia coli (E. coli) inorganic pyrophosphatase (PPase) and poly(methacrylic acid) (PMAA) were attached together to gold nanoparticles (AuNPs), forming AuNP-PPase-PMAA conjugates having controllable multi-biofunctionalities and responsiveness to pH. By treating with poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and regulating the pH, the bioactivity of the conjugate becomes ``on/off''-switchable. In addition, by taking advantage of the ability of AuNPs to undergo reversible aggregation/dispersion, the conjugates can be recycled and reused multiple times; and due to the shielding effect of the PMAA, the conjugated enzyme has high resistance to protease digestion

  18. Influence of ions on aqueous acid-base reactions.

    Science.gov (United States)

    Cox, M Jocelyn; Siwick, Bradley J; Bakker, Huib J

    2009-01-12

    We study the effects of bromide salts on the rate and mechanism of the aqueous proton/deuteron-transfer reaction between the photoacid 8-hydroxy-1,3,6-pyrenetrisulfonic acid (HPTS) and the base acetate. The proton/deuteron release is triggered by exciting HPTS with 400 nm femtosecond laser pulses. Probing the electronic and vibrational resonances of the photoacid, the conjugate photobase, the hydrated proton/deuteron and the accepting base with femtosecond visible and mid-infrared pulses monitors the proton transfer. Two reaction channels are identified: 1) direct long-range proton transfer over hydrogen-bonded water bridges that connect the acid and base and 2) acid dissociation to produce fully solvated protons followed by proton scavenging from solution by acetate. We observe that the addition of salt affects the long-range reaction pathway, and reduces both the rate at which protons are released to solution by HPTS and the rate at which solvated protons are scavenged from solution by acetate. We study the dependence of these effects on the nature and concentration of the dissolved salt.

  19. Identification of a Novel Conjugative Plasmid in Mycobacteria That Requires Both Type IV and Type VII Secretion

    KAUST Repository

    Ummels, R.

    2014-09-23

    Conjugative plasmids have been identified in a wide variety of different bacteria, ranging from proteobacteria to firmicutes, and conjugation is one of the most efficient routes for horizontal gene transfer. The most widespread mechanism of plasmid conjugation relies on different variants of the type IV secretion pathway. Here, we describe the identification of a novel type of conjugative plasmid that seems to be unique for mycobacteria. Interestingly, while this plasmid is efficiently exchanged between different species of slow-growing mycobacteria, including Mycobacterium tuberculosis, it could not be transferred to any of the fast-growing mycobacteria tested. Genetic analysis of the conjugative plasmid showed the presence of a locus containing homologues of three type IV secretion system components and a relaxase. In addition, a new type VII secretion locus was present. Using transposon insertion mutagenesis, we show that in fact both these secretion systems are essential for conjugation, indicating that this plasmid represents a new class of conjugative plasmids requiring two secretion machineries. This plasmid could form a useful new tool to exchange or introduce DNA in slow-growing mycobacteria. IMPORTANCE: Conjugative plasmids play an important role in horizontal gene transfer between different bacteria and, as such, in their adaptation and evolution. This effect is most obvious in the spread of antibiotic resistance genes. Thus far, conjugation of natural plasmids has been described only rarely for mycobacterial species. In fact, it is generally accepted that M. tuberculosis does not show any recent sign of horizontal gene transfer. In this study, we describe the identification of a new widespread conjugative plasmid that can also be efficiently transferred to M. tuberculosis. This plasmid therefore poses both a threat and an opportunity. The threat is that, through the acquisition of antibiotic resistance markers, this plasmid could start a rapid spread of

  20. Genetic engineering and chemical conjugation of potato virus X.

    Science.gov (United States)

    Lee, Karin L; Uhde-Holzem, Kerstin; Fischer, Rainer; Commandeur, Ulrich; Steinmetz, Nicole F

    2014-01-01

    Here we report the genetic engineering and chemical modification of potato virus X (PVX) for the presentation of various peptides, proteins, and fluorescent dyes, or other chemical modifiers. Three different ways of genetic engineering are described and by these means, peptides are successfully expressed not only when the foot and mouth disease virus (FMDV) 2A sequence or a flexible glycine-serine linker is included, but also when the peptide is fused directly to the PVX coat protein. When larger proteins or unfavorable peptide sequences are presented, a partial fusion via the FMDV 2A sequence is preferable. When these PVX chimeras retain the ability to assemble into viral particles and are thus able to infect plants systemically, they can be utilized to inoculate susceptible plants for isolation of sufficient amounts of virus particles for subsequent chemical modification. Chemical modification is required for the display of nonbiological ligands such as fluorophores, polymers, and small drug compounds. We present three methods of chemical bioconjugation. For direct conjugation of small chemical modifiers to solvent exposed lysines, N-hydroxysuccinimide chemistry can be applied. Bio-orthogonal reactions such as copper-catalyzed azide-alkyne cycloaddition or hydrazone ligation are alternatives to achieve more efficient conjugation (e.g., when working with high molecular weight or insoluble ligands). Furthermore, hydrazone ligation offers an attractive route for the introduction of pH-cleavable cargos (e.g., therapeutic molecules).

  1. Delivery of antisense oligonucleotides using HPMA polymer: synthesis of A thiol polymer and its conjugation to water-soluble molecules.

    Science.gov (United States)

    Wang, L; Kristensen, J; Ruffner, D E

    1998-01-01

    Here, we report the synthesis and characterization of an HPMA-based polymer for use as a carrier for the delivery of water soluble drugs. The polymer contains active-sulfhydryl groups for coupling of ligands through a disulfide linkage. The polymer can also be prepared containing pendant amino groups in addition to the active-sulfhydryl moiety. This allows the use of different chemistries to conjugate a variety of ligands to the polymer. We demonstrate that a sulfhydryl-terminated antisense oligonucleotide can be efficiently and rapidly conjugated to the polymer. The polymer-oligonucleotide conjugate is efficiently taken up by cultured cells.

  2. Calcium ions effectively enhance the effect of antisense peptide nucleic acids conjugated to cationic tat and oligoarginine peptides

    DEFF Research Database (Denmark)

    Shiraishi, Takehiko; Pankratova, Stanislava; Nielsen, Peter E

    2005-01-01

    La cells of a variety of peptide nucleic acid (PNA) peptide conjugates is significantly enhanced by addition of 6 mM Ca(2+) (as well as by the lysosomotrophic agent chloroquine). In particular, the antisense activities of Tat(48-60) and heptaarginine-conjugated PNAs were increased 44-fold and 8.5-fold......, respectively. Evidence is presented that the mechanism involves endosomal release. The present results show that Ca(2+) can be used as an effective enhancer for in vitro cellular delivery of cationic peptide-conjugated PNA oligomers, and also emphasize the significance of the endosomal escape route...

  3. Changes in physical, chemical and functional properties of whey protein isolate (WPI) and sugar beet pectin (SBP) conjugates formed by controlled dry-heating

    Science.gov (United States)

    A Maillard type reaction in the dry state was utilized to create conjugates between whey protein isolate (WPI) and sugar beet pectin (SBP) to achieve improved functional properties including solubility, colloidal stability and oil-in-water emulsion stability. To optimize the reaction conditions, mi...

  4. Anti-CD20 multivalent HPMA copolymer-Fab' conjugates for the direct induction of apoptosis.

    Science.gov (United States)

    Chu, Te-Wei; Yang, Jiyuan; Kopeček, Jindřich

    2012-10-01

    A hybrid biomimetic system comprising high-molecular-weight, linear copolymer of N-(2-hydroxypropyl)methacrylamide (HPMA) grafted with multiple Fab' fragments of anti-CD20 monoclonal antibody (mAb) was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization followed by attachment of Fab' fragments via thioether bonds. Exposure of human non-Hodgkin's lymphoma (NHL) Raji B cells to the multivalent conjugates resulted in crosslinking of CD20 receptors and commencement of apoptosis. Five conjugates with varying molecular weight and valence (amount of Fab' per polymer chain) were synthesized. One of the copolymers contained enzyme degradable peptide sequences (GFLG) in the backbone. The multivalency led to higher avidity and apoptosis induction compared to unconjugated whole mAb. Time-dependent studies showed that the cytotoxicity of conjugates exhibited a slower onset at shorter exposure times than mAb hyper-crosslinked with a secondary Ab; however, at longer time intervals the HPMA copolymer conjugates achieved significantly higher biological efficacies. In addition, study of the relationship between the structure of conjugates and Raji B cell apoptosis revealed that both valency and polymer molecular weight influenced biological activities, while insertion of peptide sequences into the backbone was not a factor in vitro. Copyright © 2012 Elsevier Ltd. All rights reserved.

  5. Anti-CD20 multivalent HPMA copolymer-Fab′ conjugates for the direct induction of apoptosis

    Science.gov (United States)

    Chu, Te-Wei; Yang, Jiyuan; Kopeček, Jindřich

    2012-01-01

    A hybrid biomimetic system comprising high-molecular-weight, linear copolymer of N-(2-hydroxypropyl)methacrylamide (HPMA) grafted with multiple Fab′ fragments of anti-CD20 monoclonal antibody (mAb) was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization followed by attachment of Fab′ fragments via thioether bonds. Exposure of human non-Hodgkin’s lymphoma (NHL) Raji B cells to the multivalent conjugates resulted in crosslinking of CD20 receptors and commencement of apoptosis. Five conjugates with varying molecular weight and valence (amount of Fab′ per polymer chain) were synthesized. One of the copolymers contained enzyme degradable peptide sequences (GFLG) in the backbone. The multivalency led to higher avidity and apoptosis induction compared to unconjugated whole mAb. Time-dependent studies showed that the cytotoxicity of conjugates exhibited a slower onset at shorter exposure times than mAb hyper-crosslinked with a secondary Ab; however, at longer time intervals the HPMA copolymer conjugates achieved significantly higher biological efficacies. In addition, study of the relationship between the structure of conjugates and Raji B cell apoptosis revealed that both valency and polymer molecular weight influenced biological activities, while insertion of peptide sequences into the backbone was not a factor in vitro. PMID:22795544

  6. Nitrogen-Rich Conjugated Microporous Polymers: Facile Synthesis, Efficient Gas Storage, and Heterogeneous Catalysis.

    Science.gov (United States)

    Liao, Yaozu; Cheng, Zhonghua; Zuo, Weiwei; Thomas, Arne; Faul, Charl F J

    2017-11-08

    Nitrogen-rich conjugated microporous polymers (NCMPs) have attracted great attention in recent years owing to their polarity, basicity, and ability to coordinate metal ions. Herein, three NCMPs, structurally close to polyaniline, were facilely synthesized via chemical oxidative polymerization between multiconnected aniline precursors. The NCMPs with high N content (11.84 wt %), intrinsic ultramicroporosity (94% activity in Suzuki-Miyaura coupling reactions after six continuous runs.

  7. A New Synthesis of Porphyrins with Extended Conjugation and their Photophysics

    Science.gov (United States)

    2005-04-21

    optics, conducting materials, photosensitizers for photodynamic therapy (PDT), solar systems, and so on.1 Although TBPs and TNPs have already been...sensitizers of photo dynamic therapy of cancer. We are developing a new method for the preparation of such p-conjugated porphyrins based on the retro Diels...treated with 15 overnight. The neutralization of the reaction mixture with triethylamine and the oxidation with 2,3-dichloro-5,6-dicyano-p- benzoquinone

  8. Chemoselective Switch in the Asymmetric Organocatalysis of 5 H -Oxazol-4-ones and N -Itaconimides: Addition-Protonation or [4+2] Cycloaddition

    KAUST Repository

    Zhu, Bo

    2015-12-09

    © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. We report a synthetic strategy for a chemoselective switch and a diastereo-divergent approach for the asymmetric reaction of 5H-oxazol-4-ones and N-itaconimides catalyzed by L-tert-leucine-derived tertiary amine-urea compounds. The reaction was modulated to harness either tandem conjugate addition-protonation or [4+2] cycloaddition as major product with excellent enantio- and diastereoselectivities. Subjecting the enantio-enriched cycloaddition products to a basic silica gel reagent yields the diastereomer vis-à-vis the product directly obtained under conditions for addition-protonation, thus opening a diastereo-divergent route for creating 1,3-tertiary-hetero-quaternary stereocenters. Quantum chemical studies further provide stereochemical analysis for the [4+2] process and a plausible mechanism for this chemoselective switch is proposed.

  9. Nucleic acid-metal organic framework (MOF) nanoparticle conjugates.

    Science.gov (United States)

    Morris, William; Briley, William E; Auyeung, Evelyn; Cabezas, Maria D; Mirkin, Chad A

    2014-05-21

    Nanoparticles of a metal-organic framework (MOF), UiO-66-N3 (Zr6O4OH4(C8H3O4-N3)6), were synthesized. The surface of the MOF was covalently functionalized with oligonucleotides, utilizing a strain promoted click reaction between DNA appended with dibenzylcyclooctyne and azide-functionalized UiO-66-N3 to create the first MOF nanoparticle-nucleic acid conjugates. The structure of the framework was preserved throughout the chemical transformation, and the surface coverage of DNA was quantified. Due to the small pore sizes, the particles are only modified on their surfaces. When dispersed in aqueous NaCl, they exhibit increased stability and enhanced cellular uptake when compared with unfunctionalized MOF particles of comparable size.

  10. Prony-Householder method applied to 31P NMR signals: II. Study of conjugates of ara-AMP with lactosaminated albumin.

    Science.gov (United States)

    Polichetti, A; Viti, V; Barone, P; Colonna, F; Fiume, L

    1992-12-01

    Conjugates of 9-beta-D-arabinofuranosyladenine 5'-monophosphate (ara-AMP) with lactosaminated albumin (L-SA), obtained by using two different coupling procedures, produce antibodies in rats and mice which display only a small cross-reactivity. 31P NMR signals from the two conjugates have been examined to clarify whether different lysine and histidine residues are involved in the two reaction pathways. The occurrence of different chemical shifts and linewidths between the two conjugates, as evidenced by processing the signals with the Prony-Householder method, indicates the formation of two different complexes.

  11. Controlling photo-oxidation processes of a polyfluorene derivative: The effect of additives and mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, G.R. [Laboratory of Polymers and Electronic Properties of Materials – UFOP, Ouro Preto, MG (Brazil); Nowacki, B. [Paulo Scarpa Polymer Laboratory – UFPR, Curitiba, PR (Brazil); Magalhães, A. [Instituto de Química, Universidade Estadual de Campinas – UNICAMP, Campinas, SP (Brazil); Azevedo, E.R. de [Instituto de Física de São Carlos, Universidade de São Paulo – USP, São Carlos, SP (Brazil); Sá, E.L. de [Chemistry Department, Federal University of Parana, Curitiba, PR (Brazil); Akcelrud, L.C. [Paulo Scarpa Polymer Laboratory – UFPR, Curitiba, PR (Brazil); Bianchi, R.F., E-mail: bianchi@iceb.ufop.br [Laboratory of Polymers and Electronic Properties of Materials – UFOP, Ouro Preto, MG (Brazil)

    2014-08-01

    The control of the photo degradation of a fluorene–vinylene–phenylene based-polymer, poly(9,9-di-hexylfluorenediylvinylene-alt-1,4-phenylenevinylene) (LaPPS16) was achieved by addition of a radical scavenger (RS) (enhancing photo resistance) or a radical initiator (RI) (reducing photo resistance). Photoluminescence, UV–Vis absorption, {sup 1}H NMR spectroscopies and gel permeation chromatography (GPC) revealed that the incorporating small amounts of RS or RI is an efficient way to control the rates of the photo-oxidation reactions, and thus to obtain the conjugated polymer with foreseeable degradation rates for applications in blue-light sensitive detectors for neonatal phototherapy. - Highlights: • Photo degradation control of a fluorene–vinylene–phenylene based polymer was achieved. • A radical scavenger enhanced photo resistance and radical initiator decreased it. • Color change rate with irradiation dose provided a basis for dosimeter construction.

  12. Ferrocene-oligonucleotide conjugates for electrochemical probing of DNA.

    Science.gov (United States)

    Ihara, T; Maruo, Y; Takenaka, S; Takagi, M

    1996-01-01

    Toward the development of a universal, sensitive and convenient method of DNA (or RNA) detection, electrochemically active oligonucleotides were prepared by covalent linkage of a ferrocenyl group to the 5'-aminohexyl-terminated synthetic oligonucleotides. Using these electrochemically active probes, we have been able to demonstrate the detection of DNA and RNA at femtomole levels by HPLC equipped with an ordinary electrochemical detector (ECD) [Takenaka,S., Uto,Y., Kondo,H., Ihara,T. and Takagi,M. (1994) Anal. Biochem., 218, 436-443]. Thermodynamic and electrochemical studies of the interaction between the probes and the targets are presented here. The thermodynamics obtained revealed that the conjugation stabilizes the triple-helix complexes by 2-3 kcal mol-1 (1-2 orders increment in binding constant) at 298 K, which corresponds to the effect of elongation of additional several base triplets. The main cause of this thermodynamic stabilization by the conjugation is likely to be the overall conformational change of whole structure of the conjugate rather than the additional local interaction. The redox potential of the probe was independent of the target structure, which is either single- or double stranded. However, the potential is slightly dependent (with a 10-30 mV negative shift on complexation) on the extra sequence in the target, probably because the individual sequence is capable of contacting or interacting with the ferrocenyl group in a slightly different way from each other. This small potential shift itself, however, does not cause any inconvenience on practical applications in detecting the probes by using ECD. These results lead to the conclusion that the redox-active probes are very useful for the microanalysis of nucleic acids due to the stability of the complexes, high detection sensitivity and wide applicability to the target structures (DNA and RNA; single- and double strands) and the sequences. PMID:8932383

  13. Therapeutic anti-methamphetamine antibody fragment-nanoparticle conjugates: synthesis and in vitro characterization.

    Science.gov (United States)

    Nanaware-Kharade, Nisha; Gonzalez, Guillermo A; Lay, Jackson O; Hendrickson, Howard P; Peterson, Eric C

    2012-09-19

    Treatments specific to the medical problems caused by methamphetamine (METH) abuse are greatly needed. Toward this goal, we are developing new multivalent anti-METH antibody fragment-nanoparticle conjugates with customizable pharmacokinetic properties. We have designed a novel anti-METH single chain antibody fragment with an engineered terminal cysteine (scFv6H4Cys). Generation 3 (G3) polyamidoamine dendrimer nanoparticles were chosen for conjugation due to their monodisperse properties and multiple amine functional groups. ScFv6H4Cys was conjugated to G3 dendrimers via a heterobifunctional PEG cross-linker that is reactive to a free amine on one end and a thiol group on the other. PEG modified dendrimers were synthesized by reacting the PEG cross-linker with dendrimers in a stoichiometric ratio of 11:1, which were further reacted with 3-fold molar excess of anti-METH scFv6H4Cys. This reaction resulted in a heterogeneous mix of G3-PEG-scFv6H4Cys conjugates (dendribodies) with three to six scFv6H4Cys conjugated to each dendrimer. The dendribodies were separated from the unreacted PEG modified dendrimers and scFv6H4Cys using affinity chromatography. A detailed in vitro characterization of the PEG modified dendrimers and the dendribodies was performed to determine size, purity, and METH binding function. The dendribodies were found to have affinity for METH identical to that of the unconjugated scFv6H4Cys in saturation binding assays, whereas the PEG modified dendrimers had no affinity for METH. These data suggest that an anti-METH scFv can be successfully conjugated to a PEG modified dendrimer nanoparticle with no adverse effects on METH binding properties. This study is a critical step toward preclinical characterization and development of a novel nanomedicine for the treatment of METH abuse.

  14. HPMA copolymer-based polymer conjugates for the delivery and controlled release of retinoids.

    Science.gov (United States)

    Lidický, O; Šírová, M; Etrych, T

    2016-10-20

    In this paper, we describe the synthesis, physicochemical characterization, drug release kinetics and preliminary biological evaluation of several N-(2-hydroxypropyl)methacrylamide (HPMA)-based polymer-retinoid conjugates designed for solid tumor immunotherapy. The conjugates are supposed to inhibit the immunosuppressive activity of myeloid-derived suppressor cells (MDSC) accumulated in the solid tumor microenvironment. All-trans retinoic acid (ATRA) was derivatized to hydrazide (AtrHy) and then attached to the polymer backbone via a spacer that is stable at the normal pH of blood (7.4) and hydrolytically degradable in mildly acidic environments (e.g. in endosomes or lysosomes, pH~5.0-6.5). Polymer-AtrHy conjugates were designed to achieve prolonged blood circulation and release of the immunomodulator intracellularly or extracellularly in solid tumor tissue. Three types of polymer precursors, differing in the structure of the keto acid-containing side chains, were synthesized. A linkage susceptible to hydrolytic cleavage was formed by the conjugation reaction of the carbonyl group-terminated side chains of the polymer precursors with the hydrazide group of a drug derivative. In vitro incubation of the conjugates in buffers resulted in much faster release of the drugs or their derivatives from the polymer at pH 5.0 than at pH 7.4, with the rate depending on the detailed structure of the spacer. Both the AtrHy derivative and its polymer conjugates showed the ability to induce the differentiation of retinoid-responsive HL-60 cells, thus demonstrating the required biological activity.

  15. Correlating Physicochemical Properties of Boronic Acid-Chitosan Conjugates to Glucose Adsorption Sensitivity

    Directory of Open Access Journals (Sweden)

    Nashiru Billa

    2012-12-01

    Full Text Available Phenyl boronic acid (PBA, which is known to interact with glucose, was covalently bonded to chitosan by direct reductive N-alkylation of chitosan with 4-formylphenylboronic acid (4-FPBA. Evidence of PBA bonding on chitosan was assessed by FTIR, ToF-SIMS, SEM, DSC and glucose adsorption sensitivity measurements. FTIR spectra showed strong signals at 1560 and 630 cm−1 indicating the formation of p-substituted benzene. Similarly, ToF-SIMS analyses on the conjugates registered fragments of boron ion (B− at 11.0 m/z whose intensity increased in proportion to 4-FPBA loading. The degree to which PBA was bonded to chitosan was related to the 4-FPBA load used in the reaction (termed F1 through to F6 with increasing 4-FPBA load. Glucose adsorption sensitivity to PBA-bonded chitosan was directly related to the amount of PBA functionality within the conjugates and the physical nature of the matrices (porous or crystalline. Topographic analysis by SEM revealed that PBA-chitosan conjugates F1, F2 and F3 have porous matrices and their sensitivity to glucose adsorption was directly proportional to the degree of PBA substitution onto chitosan. Conversely, conjugates F4, F5 and F6 appeared crystalline under SEM and glucose adsorption sensitivity decreased in proportion to amount of PBA bonded to chitosan. The crystalline nature of the conjugates was confirmed by DSC, where the exothermic event related to the melting of the bonded PBA moiety, occurred at 338 °C. Thus, decreased sensitivity to glucose adsorption by the conjugates can be ascribed to the crystallinity imparted by increased content of the bonded PBA moiety, providing an optimal loading of PBA in terms of maximizing response to glucose.

  16. Conjugation of type I antifreeze protein to polyallylamine increases thermal hysteresis activity.

    Science.gov (United States)

    Can, Ozge; Holland, Nolan B

    2011-10-19

    Antifreeze proteins (AFPs) are ice binding proteins found in some plants, insects, and Antarctic fish allowing them to survive at subzero temperatures by inhibiting ice crystal growth. The interaction of AFPs with ice crystals results in a difference between the freezing and melting temperatures, termed thermal hysteresis, which is the most common measure of AFP activity. Creating antifreeze protein constructs that reduce the concentration of protein needed to observe thermal hysteresis activities would be beneficial for diverse applications including cold storage of cells or tissues, ice slurries used in refrigeration systems, and food storage. We demonstrate that conjugating multiple type I AFPs to a polyallylamine chain increases thermal hysteresis activity compared to the original protein. The reaction product is approximately twice as active when compared to the same concentration of free proteins, yielding 0.5 °C thermal hysteresis activity at 0.3 mM protein concentration. More impressively, the amount of protein required to achieve a thermal hysteresis of 0.3 °C is about 100 times lower when conjugated to the polymer (3 μM) compared to free protein (300 μM). Ice crystal morphologies observed in the presence of the reaction product are comparable to those of the protein used in the conjugation reaction.

  17. Phase conjugate Michelson interferometer for optical logic

    Science.gov (United States)

    Khoury, Jed

    2017-05-01

    The interference theory is developed for of the phase conjugate Michelson interferometer in which its ordinary mirrors are replaced by a single externally pumped phase conjugate mirror. According to the theory, it was found that for an interferometer with two equal arms, the path length difference depends solely on the initial alignment of the two input beams, and the vertical alignment readout. Small vertical misalignments in the readout beam by mrad causes a huge change in the phase difference in the phase between the two interferometer arms beam. The phase difference is proportional to the interferometer arm lengths. The overlap between the phase conjugate beams is not affected by the interferometer beam alignment. The interferometer is proposed for nondestructive testing and the design all optical logic and associated fuzzy logic for ultrafast optical pattern recognition.

  18. Nonlinear conjugate gradient methods in micromagnetics

    Science.gov (United States)

    Fischbacher, J.; Kovacs, Alexander; Oezelt, Harald; Schrefl, T.; Exl, L.; Fidler, J.; Suess, D.; Sakuma, N.; Yano, M.; Kato, A.; Shoji, T.; Manabe, A.

    2017-04-01

    Conjugate gradient methods for energy minimization in micromagnetics are compared. The comparison of analytic results with numerical simulation shows that standard conjugate gradient method may fail to produce correct results. A method that restricts the step length in the line search is introduced, in order to avoid this problem. When the step length in the line search is controlled, conjugate gradient techniques are a fast and reliable way to compute the hysteresis properties of permanent magnets. The method is applied to investigate demagnetizing effects in NdFe12 based permanent magnets. The reduction of the coercive field by demagnetizing effects is μ0ΔH = 1.4 T at 450 K.

  19. Biomedical Applications of Organometal-Peptide Conjugates

    Science.gov (United States)

    Metzler-Nolte, Nils

    Peptides are well suited as targeting vectors for the directed delivery of metal-based drugs or probes for biomedical investigations. This chapter describes synthetic strategies for the preparation of conjugates of medically interesting peptides with covalently bound metal complexes. Peptides that were used include neuropeptides (enkephalin, neuropeptide Y, neurotensin), uptake peptides (TAT and poly-Arg), and intracellular localization sequences. To these peptides, a whole variety of transition metal complexes has been attached in recent years by solid-phase peptide synthesis (SPPS) techniques. The metal complex can be attached to the peptide on the resin as part of the SPPS scheme. Alternatively, the metal complex may be attached to the peptide as a postsynthetic modification. Advantages as well as disadvantages for either strategy are discussed. Biomedical applications include radiopharmaceutical applications, anticancer and antibacterial activity, metal-peptide conjugates as targeted CO-releasing molecules, and metal-peptide conjugates in biosensor applications.

  20. Bacterial conjugation-based antimicrobial agents.

    Science.gov (United States)

    Filutowicz, Marcin; Burgess, Richard; Gamelli, Richard L; Heinemann, Jack A; Kurenbach, Brigitta; Rakowski, Sheryl A; Shankar, Ravi

    2008-07-01

    A clear imperative exists to generate radically different antibacterial technologies that will reduce the usage of conventional chemical antibiotics. Here we trace one route into this new frontier of drug discovery, a concept that we call the bacterial conjugation-based technologies (BCBT). One of the objectives of the BCBT is to exploit plasmid biology for combating the rising tide of antibiotic-resistant bacteria. Specifically, the concept utilizes conjugationally delivered plasmids as antimicrobial agents, and it builds on the accumulated work of many scientists dating back to the discoveries of conjugation and plasmids themselves. Each of the individual components that comprise the approach has been demonstrated to be feasible. We discuss the properties of bacterial plasmids to be employed in BCBT.

  1. Conjugate gradient algorithms using multiple recursions

    Energy Technology Data Exchange (ETDEWEB)

    Barth, T.; Manteuffel, T.

    1996-12-31

    Much is already known about when a conjugate gradient method can be implemented with short recursions for the direction vectors. The work done in 1984 by Faber and Manteuffel gave necessary and sufficient conditions on the iteration matrix A, in order for a conjugate gradient method to be implemented with a single recursion of a certain form. However, this form does not take into account all possible recursions. This became evident when Jagels and Reichel used an algorithm of Gragg for unitary matrices to demonstrate that the class of matrices for which a practical conjugate gradient algorithm exists can be extended to include unitary and shifted unitary matrices. The implementation uses short double recursions for the direction vectors. This motivates the study of multiple recursion algorithms.

  2. Tight-binding treatment of conjugated polymers

    DEFF Research Database (Denmark)

    Lynge, Thomas Bastholm

    This PhD thesis concerns conjugated polymers which constitute a constantly growing research area. Today, among other things, conjugated polymers play a role in plastic based solar cells, photodetectors and light emitting diodes, and even today such plastic-based components constitute an alternative...... of tomorrow. This thesis specifically treats the three conjugated polymers trans-polyacetylene (tPA), poly(para-phenylene) (PPP) and poly(para-phe\\-nylene vinylene) (PPV). The present results, which are derived within the tight-binding model, are divided into two parts. In one part, analytic results...... are derived for the optical properties of the polymers expressed in terms of the optical susceptibility both in the presence and in the absence of a static electric field. In the other part, the cumputationally efficient Density Functional-based Tight-Binding (DFTB) model is applied to the description...

  3. CO-releasing molecule (CORM) conjugate systems.

    Science.gov (United States)

    Kautz, Anna Christin; Kunz, Peter C; Janiak, Christoph

    2016-11-15

    The development of CORMs (CO-releasing molecules) as a prodrug for CO administration in living organisms has attracted significant attention. CORMs offer the promising possibility of a safe and controllable release of CO in low amounts triggered by light, ligands, enzymes, etc. For the targeting of specific tissues or diseases and to prevent possible side effects from metals and other residues after CO release, these CORMs are attached to biocompatible systems, like peptides, polymers, nanoparticles, dendrimers, protein cages, non-wovens, tablets, and metal-organic frameworks. We discuss in this review the known CORM carrier conjugates, in short CORM conjugates, with covalently-bound or incorporated CORMs for medicinal and therapeutic applications. Most conjugates are nontoxic, show increasing half-lives of CO release, and make use of the EPR-effect, but still show problems because of a continuous background of CO release and the absence of an on/off-switch for the CO release.

  4. Uniform polymer-protein conjugate by aqueous AGET ATRP using protein as a macroinitiator.

    Science.gov (United States)

    Zhu, Binbin; Lu, Diannan; Ge, Jun; Liu, Zheng

    2011-05-01

    In situ aqueous activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP) in air, using an enzyme as a macroinitiator, has been proposed to prepare uniform polymer-protein conjugates with improved stability under adverse conditions. In the first step, an initiator, 2-bromoisobutyryl bromide (BIB), was grafted onto the protein surface by reaction with the amino groups. The second step was in situ AGET ATRP polymerization in air using CuBr(2)/1,1,4,7,7-pentamethyldiethylenetriamine as a catalyst and ascorbic acid as a reducing agent. The effectiveness of this method has been demonstrated using horseradish peroxidase (HRP) as a model protein and acrylamide as the monomer, which yielded HRP-polyacrylamide conjugate with a mean particle size of about 20-30 nm. The grafting of BIB onto HRP and the subsequent polymerization yielding a polyacrylamide chain were confirmed by nuclear magnetic resonance and matrix-assisted laser desorption ionization time-of-flight spectrometry analysis. The size of the conjugate was shown to be a function of monomer loading and reaction time. The HRP conjugates yielded essentially retained the catalytic behavior of HRP in free form, as shown by K(m) and V(max) values, but exhibited significantly enhanced thermal stability against high temperature and trypsin digestion. The use of protein as the macroinitiator prevented the formation of copolymer and thus facilitated purification of the protein conjugate. The uniform size indicates a well-defined composition of protein and polymer, which is essential for applications that request a precise control of the dosage of enzyme activity. Copyright © 2011. Published by Elsevier Ltd.

  5. Antibacterial activity, computational analysis and host toxicity study of thymol-sulfonamide conjugates.

    Science.gov (United States)

    Swain, Shasank S; Paidesetty, Sudhir K; Padhy, Rabindra N

    2017-04-01

    Methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin resistant Enterococcus faecalis (VRE) are notorious pathogenic multidrug resistant (MDR) bacteria in both hospital and community sectors, and today the first antibacterial drug sulfamethoxazole is ineffective. The monoterpene phenol, thymol was conjugated with seven sulfa drug derivatives individually, adopting the dye-azo synthesis protocol, and conjugates were characterized using spectral analysis techniques such as, UV, FTIR, MS, HPLC, 1H NMR, 13C NMR and SEM. Conjugates were assessed for antibacterial activity in vitro and in silico; the zone of inhibition, MIC and MBC values of each conjugate were determined against isolated MRSA and VRE strains from clinical samples. As 3-dimentional structures of dihydropteroate synthases (DHPSs) of targeted bacteria are not available in protein database, homology models of DHPS enzymes of both bacteria were generated and validated by Ramachandran plots. Seven conjugates were used as ligands in molecular docking against MRSA-DHPS and VRE-DHPS. Additionally bioinformatics tools, PASS prediction, Lipinski rules of five, computational LD50 value, toxicity class, HOMO, LUMO and EPS plots were carried out to assess standard drug-likeliness properties of conjugates. Zone size inhibition of the conjugate, 4b (thymol+sulfadiazine) against MRSA and VRE strains on agar plates were 20 and 40μg/mL as the lowest MIC and MBC values, respectively; while the reference antibiotic ampicillin had the lowest MIC and MBC values at 80 to 180μg/mL. In vitro host-toxicity testing was carried out with cultured human-lymphocytes from umbilical cord blood, and 4b was broadly non-toxic to human cells at 15,000mg/L. Thus, 4b could be promoted a newer antibacterial, against gruesome MDR bacteria. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  6. METHOD OF CONJUGATED CIRCULAR ARCS TRACING

    Directory of Open Access Journals (Sweden)

    N. Ageyev Vladimir

    2017-01-01

    Full Text Available The geometric properties of conjugated circular arcs connecting two points on the plane with set directions of tan- gent vectors are studied in the work. It is shown that pairs of conjugated circular arcs with the same conditions in frontier points create one-parameter set of smooth curves tightly filling all the plane. One of the basic properties of this set is the fact that all coupling points of circular arcs are on the circular curve going through the initially given points. The circle radius depends on the direction of tangent vectors. Any point of the circle curve, named auxiliary in this work, determines a pair of conjugated arcs with given boundary conditions. One more condition of the auxiliary circle curve is that it divides the plane into two parts. The arcs going from the initial point are out of the circle limited by this circle curve and the arcs coming to the final point are inside it. These properties are the basis for the method of conjugated circular arcs tracing pro- posed in this article. The algorithm is rather simple and allows to fulfill all the needed plottings using only the divider and ruler. Two concrete examples are considered. The first one is related to the problem of tracing of a pair of conjugated arcs with the minimal curve jump when going through the coupling point. The second one demonstrates the possibility of trac- ing of the smooth curve going through any three points on the plane under condition that in the initial and final points the directions of tangent vectors are given. The proposed methods of conjugated circular arcs tracing can be applied in solving of a wide variety of problems connected with the tracing of cam contours, for example pattern curves in textile industry or in computer-aided-design systems when programming of looms with numeric control.

  7. Phase conjugation of high energy lasers.

    Energy Technology Data Exchange (ETDEWEB)

    Bliss, David E; Valley, Michael T.; Atherton, Briggs W.; Bigman, Verle Howard; Boye, Lydia Ann; Broyles, Robin Scott; Kimmel, Mark W.; Law, Ryan J.; Yoder, James R.

    2013-01-01

    In this report we explore claims that phase conjugation of high energy lasers by stimulated Brillouin scattering (SBS) can compensate optical aberrations associated with severely distorted laser amplifier media and aberrations induced by the atmosphere. The SBS media tested was a gas cell pressurized up to 300 psi with SF6 or Xe or both. The laser was a 10 Hz, 3J, Q-switched Nd:YAG with 25 ns wide pulses. Atmospheric aberrations were created with space heaters, helium jets and phase plates designed with a Kolmogorov turbulence spectrum characterized by a Fried parameter, ro , ranging from 0.6 6.0 mm. Phase conjugate tests in the laboratory were conducted without amplification. For the strongest aberrations, D/ro ~ 20, created by combining the space heaters with the phase plate, the Strehl ratio was degraded by a factor of ~50. Phase conjugation in SF6 restored the peak focusable intensity to about 30% of the original laser. Phase conjugate tests at the outdoor laser range were conducted with laser amplifiers providing gain in combination with the SBS cell. A large 600,000 BTU kerosene space heater was used to create turbulence along the beam path. An atmospheric structure factor of Cn2 = 5x10-13 m2/3 caused the illumination beam to expand to a diameter 250mm and overfill the receiver. The phase conjugate amplified return could successfully be targeted back onto glints 5mm in diameter. Use of a lenslet arrays to lower the peak focusable intensity in the SBS cell failed to produce a useful phase conjugate beam; The Strehl ratio was degraded with multiple random lobes instead of a single focus. I will review literature results which show how multiple beams can be coherently combined by SBS when a confocal reflecting geometry is used to focus the laser in the SBS cell.

  8. Quantitative Conjugated Payload Measurement Using Enzymatic Release of Antibody-Drug Conjugate with Cleavable Linker.

    Science.gov (United States)

    Rago, Brian; Tumey, L Nathan; Wei, Cong; Barletta, Frank; Clark, Tracey; Hansel, Steven; Han, Xiaogang

    2017-02-15

    As antibody-drug conjugate (ADC) design is evolving with novel payload, linker, and conjugation chemistry, the need for sensitive and precise quantitative measurement of conjugated payload to support pharmacokinetics (PK) is in high demand. Compared to ADCs containing noncleavable linkers, a strategy specific to linkers which are liable to pH, chemical reduction, or enzymatic cleavage has gained popularity in recent years. One bioanalytical approach to take advantage of this type of linker design is the development of a PK assay measuring released conjugated payload. For the ADC utilizing a dipeptide ValCit linker studied in this report, the release of payload PF-06380101 was achieved with high efficiency using a purified cathepsin B enzyme. The subsequent liquid chromatography mass spectrometry (LC/MS) quantitation leads to the PK profile of the conjugated payload. For this particular linker using a maleimide-based conjugation chemistry, one potential route of payload loss would result in an albumin adduct of the linker-payload. While this adduct's formation has been previously reported, here, for the first time, we have shown that payload from a source other than ADC contributes only up to 4% of total conjugated payload while it accounts for approximately 35% of payload lost from the ADC at 48 h after dosing to rats.

  9. Analysis of anabolic androgenic steroids as sulfate conjugates using high performance liquid chromatography coupled to tandem mass spectrometry.

    Science.gov (United States)

    Rzeppa, S; Heinrich, G; Hemmersbach, P

    2015-01-01

    Improvements in doping analysis can be effected by speeding up analysis time and extending the detection time. Therefore, direct detection of phase II conjugates of doping agents, especially anabolic androgenic steroids (AAS), is proposed. Besides direct detection of conjugates with glucuronic acid, the analysis of sulfate conjugates, which are usually not part of the routine doping control analysis, can be of high interest. Sulfate conjugates of methandienone and methyltestosterone metabolites have already been identified as long-term metabolites. This study presents the synthesis of sulfate conjugates of six commonly used AAS and their metabolites: trenbolone, nandrolone, boldenone, methenolone, mesterolone, and drostanolone. In the following these sulfate conjugates were used for development of a fast and easy analysis method based on sample preparation using solid phase extraction with a mixed-mode sorbent and detection by high performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS). Validation demonstrated the suitability of the method with regard to the criteria given by the technical documents of the World Anti-Doping Agency (WADA). In addition, suitability has been proven by successful detection of the synthesized sulfate conjugates in excretion urines and routine doping control samples. Copyright © 2015 John Wiley & Sons, Ltd.

  10. Inhibition of bacterial conjugation by phage M13 and its protein g3p: quantitative analysis and model.

    Science.gov (United States)

    Lin, Abraham; Jimenez, Jose; Derr, Julien; Vera, Pedro; Manapat, Michael L; Esvelt, Kevin M; Villanueva, Laura; Liu, David R; Chen, Irene A

    2011-01-01

    Conjugation is the main mode of horizontal gene transfer that spreads antibiotic resistance among bacteria. Strategies for inhibiting conjugation may be useful for preserving the effectiveness of antibiotics and preventing the emergence of bacterial strains with multiple resistances. Filamentous bacteriophages were first observed to inhibit conjugation several decades ago. Here we investigate the mechanism of inhibition and find that the primary effect on conjugation is occlusion of the conjugative pilus by phage particles. This interaction is mediated primarily by phage coat protein g3p, and exogenous addition of the soluble fragment of g3p inhibited conjugation at low nanomolar concentrations. Our data are quantitatively consistent with a simple model in which association between the pili and phage particles or g3p prevents transmission of an F plasmid encoding tetracycline resistance. We also observe a decrease in the donor ability of infected cells, which is quantitatively consistent with a reduction in pili elaboration. Since many antibiotic-resistance factors confer susceptibility to phage infection through expression of conjugative pili (the receptor for filamentous phage), these results suggest that phage may be a source of soluble proteins that slow the spread of antibiotic resistance genes.

  11. Inhibition of bacterial conjugation by phage M13 and its protein g3p: quantitative analysis and model.

    Directory of Open Access Journals (Sweden)

    Abraham Lin

    Full Text Available Conjugation is the main mode of horizontal gene transfer that spreads antibiotic resistance among bacteria. Strategies for inhibiting conjugation may be useful for preserving the effectiveness of antibiotics and preventing the emergence of bacterial strains with multiple resistances. Filamentous bacteriophages were first observed to inhibit conjugation several decades ago. Here we investigate the mechanism of inhibition and find that the primary effect on conjugation is occlusion of the conjugative pilus by phage particles. This interaction is mediated primarily by phage coat protein g3p, and exogenous addition of the soluble fragment of g3p inhibited conjugation at low nanomolar concentrations. Our data are quantitatively consistent with a simple model in which association between the pili and phage particles or g3p prevents transmission of an F plasmid encoding tetracycline resistance. We also observe a decrease in the donor ability of infected cells, which is quantitatively consistent with a reduction in pili elaboration. Since many antibiotic-resistance factors confer susceptibility to phage infection through expression of conjugative pili (the receptor for filamentous phage, these results suggest that phage may be a source of soluble proteins that slow the spread of antibiotic resistance genes.

  12. Conjugated Polymers as Actuators: Modes of Actuation

    DEFF Research Database (Denmark)

    Skaarup, Steen

    The physical and chemical properties of conjugated polymers often depend very strongly on the degree of doping with anions or cations. The movement of ions in and out of the polymer matrix as it is redox cycled is also accompanied by mechanical changes. Both the volume and the stiffness can exhibit...... significant differences between the oxidized and reduced states. These effects form the basis of the use of conjugated polymers as actuators (or “artificial muscles”) controllable by a small (1-10 V) voltage. Three basic modes of actuation (bending, linear extension and stiffness change) have been proposed....... This work discusses their relative merits and possible areas of application....

  13. Conjugated polymers as actuators: modes of actuation

    DEFF Research Database (Denmark)

    Skaarup, Steen

    2007-01-01

    The physical and chemical properties of conjugated polymers often depend very strongly on the degree of doping with anions or cations. The movement of ions in and out of the polymer matrix as it is redox cycled is also accompanied by mechanical changes. Both the volume and the stiffness can exhibit...... significant differences between the oxidized and reduced states. These effects form the basis of the use of conjugated polymers as actuators (or “artificial muscles”) controllable by a small (1-10 V) voltage. Three basic modes of actuation (bending, linear extension and stiffness change) have been proposed....... This work discusses their relative merits and possible areas of application....

  14. F conjugation: back to the beginning.

    Science.gov (United States)

    Arutyunov, Denis; Frost, Laura S

    2013-07-01

    Bacterial conjugation as mediated by the F plasmid has been a topic of study for the past 65 years. Early research focused on events that occur on the cell surface including the pilus and its phages, recipient cell receptors, mating pair formation and its prevention via surface or entry exclusion. This short review is a reminder of the progress made in those days that will hopefully kindle renewed interest in these subjects as we approach a complete understanding of the mechanism of conjugation. Copyright © 2013 Elsevier Inc. All rights reserved.

  15. Functionalized conjugated polyelectrolytes design and biomedical applications

    CERN Document Server

    Wang, Shu

    2014-01-01

    Functionalized Conjugated Polyelectrolytes presents a comprehensive review of these polyelectrolytes and their biomedical applications. Basic aspects like molecular design and optoelectronic properties are covered in the first chapter. Emphasis is placed on the various applications including sensing (chemical and biological), disease diagnosis, cell imaging, drug/gene delivery and disease treatment. This book explores a multi-disciplinary topic of interest to researchers working in the fields of chemistry, materials, biology and medicine. It also offers an integrated perspective on both basic research and application issues. Functionalized conjugated polyelectrolyte materials, which have already drawn considerable interest, will become a major new direction for biomedicine development.

  16. Chemical microarrays constructed by selective attachment of hydrazide-conjugated substances to epoxide surfaces and their applications.

    Science.gov (United States)

    Park, Sungjin; Lee, Myung-Ryul; Shin, Injae

    2010-01-01

    Microarray technology has received considerable attention for rapid analysis of biomolecular interactions and high-throughput screening to identify binding partners. An efficient and selective immobilization technique of substances on the surface is essential for successful construction of microarrays. Although a variety of immobilization methods have been exploited to prepare microarrays over the past decade, a superior technique needs to be developed for diverse applications. Recently, an efficient and simple method that relies on selective reactions between the hydrazide conjugated to substances and the epoxide derivatized on the solid surface was developed to fabricate chemical microarrays. Reactions between hydrazides with epoxides are highly selective in that they take place even in the presence of other potent nucleophiles such as amines and thiols. This technique is utilized to immobilize various substances such as small molecules, carbohydrates, and peptides to glass surfaces. The microarrays constructed by this immobilization method are used to evaluate protein binding to carbohydrates, peptides, and small molecules. In addition, the microarrays are also employed to determine binding affinities between proteins and binding partners as well as profiling of enzyme activities.

  17. Porphyrin-peptoid conjugates: face-to-face display of porphyrins on peptoid helices.

    Science.gov (United States)

    Kang, Boyeong; Chung, Solchan; Ahn, Young Deok; Lee, Jiyoun; Seo, Jiwon

    2013-04-05

    Distance, orientation, and number controlled porphyrin-peptoid conjugates (PPCs) were efficiently synthesized. Cofacial (1, 2, and 4), slipped-cofacial (3), and unstructured (5) arrangements of porphyrins provided distinct optical and electronic properties characterized by UV-vis and circular dichroism spectroscopy. In addition, ECCD spectra confirmed the handedness of peptoid helices.

  18. Smaller Counter Cation for Higher Transconductance in Anionic Conjugated Polyelectrolytes

    KAUST Repository

    Schmidt, Martina M.

    2017-12-11

    Conjugated polyelectrolytes (CPEs) are a focus of research because combine their inherent electrical conductivity and the ability to interact with ions in aqueous solutions or biological systems. However, it is still not understood to what degree the counter ion in CPEs influences the properties of the CPE itself and the performance of electronic transducers. In order to investigate this, three different conjugated polyelectrolytes, poly(6-(thiophen-3-yl)hexane-1-sulfonate)s (PTHS−X+), are synthesized, which have the same polythiophene backbone but different X+ counter ions: the bulky tetrabutylammonium (TBA+), tetraethylammonium (TEA+), and the smallest tetramethylammonium (TMA+). At the interface with biological systems, thin CPE films have to be stable in an aqueous environment and should allow the inward and outward flow of ions from the electrolyte. Since the studied PTHS−X+ have different solubilities in water, the optical properties of pristine PTHS−X+ as well as of crosslinked PTHS−X+ via UV–vis absorption spectroscopy are investigated additionally. PTHS−TMA+ exhibits better aggregation, fast interdiffusion of ions, and fast recovery from the oxidized state. Additionally, spectroelectrochemical and cyclic voltammetric as well as electrochemical capacitance investigations show that PTHS−TMA+ can be oxidized to a higher degree. This leads to a better performance of PTHS−TMA+-based organic electrochemical transistors.

  19. Site selectivity and reversibility in the reactions of titanium hydrazides with Si-H, Si-X, C-X and H+ reagents: Ti=N(α) 1,2-silane addition, Nβ alkylation, Nα protonation and σ-bond metathesis.

    Science.gov (United States)

    Tiong, Pei Jen; Nova, Ainara; Schwarz, Andrew D; Selby, Jonathan D; Clot, Eric; Mountford, Philip

    2012-02-28

    We report a combined experimental and computational comparative study of the reactions of the homologous titanium dialkyl- and diphenylhydrazido and imido compounds Cp*Ti{MeC(N(i)Pr)(2)}(NNR(2)) (R = Me (1) or Ph (2)) and Cp*Ti{MeC(N(i)Pr)(2)}(NTol) (3) with silanes, halosilanes, alkyl halides and [Et(3)NH][BPh(4)]. Compound 1 underwent reversible Si-H 1,2-addition to Ti=N(α) with RSiH(3) (experimental ΔH ca. -17 kcal mol(-1)), and irreversible addition with PhSiH(2)X (X = Cl, Br). DFT found that the reaction products and certain intermediates were stabilised by β-NMe(2) coordination to titanium. The Ti-D bond in Cp*Ti{MeC(N(i)Pr)(2)}(D){N(NMe(2))SiD(2)Ph} underwent σ-bond metathesis with BuSiH(3) and H(2). Compound 1 reacted with RR'SiCl(2) at N(α) to transfer both Cl atoms to Ti; 2 underwent a similar reaction. Compound 3 did not react with RSiH(3) or alkyl halides but formed unstable Ti=N(α) 1,2-addition or N(α) protonation products with PhSiH(2)X or [Et(3)NH][BPh(4)]. Compound 1 underwent exclusive alkylation at N(β) with RCH(2)X (R = H, Me or Ph; X = Br or I) whereas protonation using [Et(3)NH][BPh(4)] occurred at N(α). DFT studies found that in all cases electrophile addition to N(α) (with or without NMe(2) chelation) was thermodynamically favoured compared to addition to N(β).

  20. Iterative solution of the inverse Cauchy problem for an elliptic equation by the conjugate gradient method

    Science.gov (United States)

    Vasil'ev, V. I.; Kardashevsky, A. M.; Popov, V. V.; Prokopev, G. A.

    2017-10-01

    This article presents results of computational experiment carried out using a finite-difference method for solving the inverse Cauchy problem for a two-dimensional elliptic equation. The computational algorithm involves an iterative determination of the missing boundary condition from the override condition using the conjugate gradient method. The results of calculations are carried out on the examples with exact solutions as well as at specifying an additional condition with random errors are presented. Results showed a high efficiency of the iterative method of conjugate gradients for numerical solution

  1. Liquid scintillators with near infrared emission based on organoboron conjugated polymers.

    Science.gov (United States)

    Tanaka, Kazuo; Yanagida, Takayuki; Yamane, Honami; Hirose, Amane; Yoshii, Ryousuke; Chujo, Yoshiki

    2015-11-15

    The organic liquid scintillators based on the emissive polymers are reported. A series of conjugated polymers containing organoboron complexes which show the luminescence in the near infrared (NIR) region were synthesized. The polymers showed good solubility in common organic solvents. From the comparison of the luminescent properties of the synthesized polymers between optical and radiation excitation, similar emission bands were detected. In addition, less significant degradation was observed. These data propose that the organoboron conjugated polymers are attractive platforms to work as an organic liquid scintillator with the emission in the NIR region. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. Self-Adjuvanting Glycopeptide Conjugate Vaccine against Disseminated Candidiasis

    Science.gov (United States)

    Xin, Hong; Cartmell, Jonathan; Bailey, Justin J.; Dziadek, Sebastian; Bundle, David R.; Cutler, Jim E.

    2012-01-01

    Our research on pathogenesis of disseminated candidiasis led to the discovery that antibodies specific for Candida albicans cell surface β-1, 2–mannotriose [β-(Man)3] protect mice. A 14 mer peptide Fba, which derived from the N-terminal portion of the C. albicans cytosolic/cell surface protein fructose-bisphosphate aldolase, was used as the glycan carrier and resulted in a novel synthetic glycopeptide vaccine β-(Man)3-Fba. By a dendritic cell-based immunization approach, this conjugate induced protective antibody responses against both the glycan and peptide parts of the vaccine. In this report, we modified the β-(Man)3-Fba conjugate by coupling it to tetanus toxoid (TT) in order to improve immunogenicity and allow for use of an adjuvant suitable for human use. By new immunization procedures entirely compatible with human use, the modified β-(Man)3-Fba-TT was administered either alone or as a mixture made with alum or monophosphoryl lipid A (MPL) adjuvants and given to mice by a subcutaneous (s.c.) route. Mice vaccinated with or, surprisingly, without adjuvant responded well by making robust antibody responses. The immunized groups showed a high degree of protection against a lethal challenge with C. albicans as evidenced by increased survival times and reduced kidney fungal burden as compared to control groups that received only adjuvant or DPBS buffer prior to challenge. To confirm that induced antibodies were protective, sera from mice immunized against the β-(Man)3-Fba-TT conjugate transferred protection against disseminated candidiasis to naïve mice, whereas C. albicans-absorbed immune sera did not. Similar antibody responses and protection induced by the β-(Man)3-Fba-TT vaccine was observed in inbred BALB/c and outbred Swiss Webster mice. We conclude that addition of TT to the glycopeptide conjugate results in a self-adjuvanting vaccine that promotes robust antibody responses without the need for additional adjuvant, which is novel and represents a

  3. Site-selective covalent reactions on proteinogenic amino acids.

    Science.gov (United States)

    So, Wing Ho; Zhang, Yu; Kang, Wei; Wong, Clarence T T; Sun, Hongyan; Xia, Jiang

    2017-07-05

    To achieve precise control of the signaling events or to achieve unmistakable synthesis of biomolecules, nature has evolved organic reactions involving proteinogenic amino acids with unparalleled site selectivity. For example, dedicated enzymes accurately dictate the site of post-translational modifications in signaling proteins, and ribosomes precisely link the C-terminal carboxylic acid of one unprotected amino acid with the N-terminal amino group of the other amino acid through spatially confined proximity. For many years, chemists have been striving to achieve site selectivity on biomolecules by mimicking nature. Driven by the development of chemoselective protein conjugation reactions, enzymology and protein-protein interactions, the past decade has witnessed a boom in site-selective protein conjugation reactions. (In this review, a site-selective protein conjugation reaction is defined as an organic reaction that targets a single amino acid instead of a kind of amino acids in a protein or a proteome under physiological conditions, for example, a single cysteine residue among all of the cysteines.) In this review, we summarize the recent advancements of bioconjugation reactions that demonstrate this feature of precise site selectivity, focusing on the reactions of the proteinogenic amino acids (excluding those at non-coded or non-proteinogenic amino acids that are introduced to proteins through genetic manipulations). Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Social behavior and decision making in bacterial conjugation

    National Research Council Canada - National Science Library

    Koraimann, Günther; Wagner, Maria A

    2014-01-01

    Bacteria frequently acquire novel genes by horizontal gene transfer (HGT). HGT through the process of bacterial conjugation is highly efficient and depends on the presence of conjugative plasmids (CPs...

  5. Synthesis and structural elucidation of glutathione and N-aceyl-cysteine conjugates of 5-aminosalicylic acid

    DEFF Research Database (Denmark)

    Jensen, J.; Cornett, Claus; Olsen, C. E.

    1993-01-01

    The ability of 5-aminosalicylic acid (5-ASA) to be oxidized to a quinone monoimine compound capable of conjugating with nucleophilic compounds such as N-acetyl-cysteine (NAC) and glutathione (GSH) has been investigated in vitro. Three isomeric conjugates of 5-ASA and NAC as well as three isomeric...... conjugates of 5-ASA and GSH were found to be formed. 5-ASA was initially oxidized by PbO2 in a solution of TRIS-HCl buffer pH 9.3 followed by the in situ addition of N-acetyl-cysteine or glutathione to the oxidized 5-ASA at pH 7.5. The resulting conjugates were N-acetylated at the aromatic amino group...... dose of 5-ASA into mercapturic acids of 5-ASA, when 1 g of 5-ASA was ingested. In spite of the low detection limits, none of the mercapturic acid conjugates was detected in the urine from persons treated with 5-ASA....

  6. Auxin conjugated to fluorescent dyes--a tool for the analysis of auxin transport pathways.

    Science.gov (United States)

    Sokołowska, K; Kizińska, J; Szewczuk, Z; Banasiak, A

    2014-09-01

    Auxin is a small molecule involved in most processes related to plant growth and development. Its effect usually depends on the distribution in tissues and the formation of concentration gradients. Until now there has been no tool for the direct tracking of auxin transport at the cellular and tissue level; therefore the majority of studies have been based on various indirect methods. However, due to their various restrictions, relatively little is known about the relationship between various pathways of auxin transport and specific developmental processes. We present a new research tool: fluorescently labelled auxin in the form of a conjugate with two different fluorescent tracers, FITC and RITC, which allows direct observation of auxin transport in plant tissues. Chemical analysis and biological tests have shown that our conjugates have auxin-like biological activity and transport; therefore they can be used in all experimental systems as an alternative to IAA. In addition, the conjugates are a universal tool that can be applied in studies of all plant groups and species. The conjugation procedure presented in this paper can be adapted to other fluorescent dyes, which are constantly being improved. In our opinion, the conjugates greatly expand the possibilities of research concerning the role of auxin and its transport in different developmental processes in plants. © 2014 German Botanical Society and The Royal Botanical Society of the Netherlands.

  7. Synthesis and cellular uptake of folic acid-conjugated cellulose nanocrystals for cancer targeting.

    Science.gov (United States)

    Dong, Shuping; Cho, Hyung Joon; Lee, Yong Woo; Roman, Maren

    2014-05-12

    Elongated nanoparticles have recently been shown to have distinct advantages over spherical ones in targeted drug delivery applications. In addition to their oblong geometry, their lack of cytotoxicity and numerous surface hydroxyl groups make cellulose nanocrystals (CNCs) promising drug delivery vectors. Herein we report the synthesis of folic acid-conjugated CNCs for the targeted delivery of chemotherapeutic agents to folate receptor-positive cancer cells. Folate receptor-mediated cellular binding/uptake of the conjugate was demonstrated on human (DBTRG-05MG, H4) and rat (C6) brain tumor cells. Folate receptor expression of the cells was verified by immunofluorescence staining. Cellular binding/uptake of the conjugate by DBTRG-05MG, H4, and C6 cells was 1452, 975, and 46 times higher, respectively, than that of nontargeted CNCs. The uptake mechanism was determined by preincubation of the cells with the uptake inhibitors chlorpromazine or genistein. DBTRG-05MG and C6 cells internalized the conjugate primarily via caveolae-mediated endocytosis, whereas H4 cells internalized the conjugate primarily via clathrin-mediated endocytosis.

  8. Photocatalysts Based on Cobalt-chelating Conjugated Polymers for Hydrogen Evolution from Water

    Energy Technology Data Exchange (ETDEWEB)

    Li, Lianwei; Hadt, Ryan G.; Yao, Shiyu; Lo, Waiyip; Cai, Zhengxu; Wu, Qingliu; Pandit, Bill; Chen, Lin X.; Yu, Luping

    2016-08-09

    Developing photocatalytic systems for water splitting to generate oxygen and hydrogen is one of the biggest chemical challenges in solar energy utilization. In this work, we report the first example of heterogeneous photocatalysts for hydrogen evolution based on in-chain cobalt-chelating conjugated polymers. Four conjugated polymers chelated with earth abundant cobalt ions were synthesized and found to evolve hydrogen photocatalytically from water. These polymers are designed to combine functions of the conjugated backbone as light-harvesting antenna and electron transfer conduit with the in-chain bipyridyl chelated transition metal centers as catalytic active sites. In addition, these polymers are soluble in organic solvents, enabling effective interactions with the substrates as well as detailed characterization. We also found a polymer-dependent optimal cobalt chelating concentration at which the highest photocatalytic hydrogen production (PHP) activity can be achieved.

  9. Cloning and characterization of IAR1, a gene required for auxin conjugate sensitivity in Arabidopsis.

    Science.gov (United States)

    Lasswell, J; Rogg, L E; Nelson, D C; Rongey, C; Bartel, B

    2000-12-01

    Most indole-3-acetic acid (IAA) in higher plants is conjugated to amino acids, sugars, or peptides, and these conjugates are implicated in regulating the concentration of the free hormone. We identified iar1 as an Arabidopsis mutant that is resistant to the inhibitory effects of several IAA-amino acid conjugates but remains sensitive to free IAA. iar1 partially suppresses phenotypes of a mutant that overproduces IAA, suggesting that IAR1 participates in auxin metabolism or response. We used positional information to clone IAR1, which encodes a novel protein with seven predicted transmembrane domains and several His-rich regions. IAR1 has homologs in other multicellular organisms, including Drosophila, nematodes, and mammals; in addition, the mouse homolog KE4 can functionally substitute for IAR1 in vivo. IAR1 also structurally resembles and has detectable sequence similarity to a family of metal transporters. We discuss several possible roles for IAR1 in auxin homeostasis.

  10. (Ultra)fast catalyst-free macromolecular conjugation in aqueous environment at ambient temperature.

    Science.gov (United States)

    Glassner, Mathias; Delaittre, Guillaume; Kaupp, Michael; Blinco, James P; Barner-Kowollik, Christopher

    2012-05-02

    Tailor-made water-soluble macromolecules, including a glycopolymer, obtained by living/controlled RAFT-mediated polymerization are demonstrated to react in water with diene-functionalized poly(ethylene glycol)s without pre- or post-functionalization steps or the need for a catalyst at ambient temperature. As previously observed in organic solvents, hetero-Diels-Alder (HDA) conjugations reached quantitative conversion within minutes when cyclopentadienyl moieties were involved. However, while catalysts and elevated temperatures were previously necessary for open-chain diene conjugation, additive-free HDA cycloadditions occur in water within a few hours at ambient temperature. Experimental evidence for efficient conjugations is provided via unambiguous ESI-MS, UV/vis, NMR, and SEC data. © 2012 American Chemical Society

  11. Novel Luminescent Multilayer Films Containing π-Conjugated Anionic Polymer with Electronic Microenvironment

    Directory of Open Access Journals (Sweden)

    Tianlei Wang

    2016-09-01

    Full Text Available Layered double hydroxides (LDHs, luminescent π-conjugated anionic polymer and montmorillonite (MMT were orderly assembled into luminescent multilayer films via layer-by-layer self-assembly method. The electronic microenvironment (EME, the structure of which is like a traditional capacitor, can be constructed by exfoliated LDHs or MMT nanosheets. In addition, the rigid inorganic laminated configuration can offer stable surroundings between the interlayers. As a result, we conclude that EME can extend the luminescent lifespans of multilayer films substantially, due to affecting relaxation times of π-conjugated anionic polymer. Consequently, because of the remarkable impact on better photoemission behaviors of luminescent π-conjugated anionic polymer, EME assembled by LDHs or MMT nanosheets have had high hopes attached to them. They are expected to have the potential for designing, constructing, and investigating novel light-emitting thin films.

  12. Molecular Recognition and Immobilization of Ligand-Conjugated Redox-Responsive Polymer Nanocontainers.

    Science.gov (United States)

    de Vries, Wilke C; Tesch, Matthias; Studer, Armido; Ravoo, Bart Jan

    2017-12-06

    We present the preparation of ligand-conjugated redox-responsive polymer nanocontainers by the supramolecular decoration of cyclodextrin vesicles with a thin redox-cleavable polymer shell that displays molecular recognition units on its surface. Two widely different recognition motifs (mannose-Concanavalin A and biotin-streptavidin) are compared and the impact of ligand density on the nanocontainer surface as well as an additional functionalization with nonadhesive poly(ethylene glycol) is studied. Aggregation assays, dynamic light scattering, and a fluorometric quantification reveal that the molecular recognition of ligand-conjugated polymer nanocontainers by receptor proteins is strongly affected by the multivalency of interactions and the association strength of the recognition motif. Finally, microcontact printing is used to prepare streptavidin-patterned surfaces, and the specific immobilization of biotin-conjugated nanocontainers is demonstrated. As a prototype of a nanosensor, these tethered nanocontainers can sense a reductive environment and react by releasing a payload.

  13. Isolation, Structure Elucidation, and Absolute Configuration of Syncarpic Acid-Conjugated Terpenoids from Rhodomyrtus tomentosa.

    Science.gov (United States)

    Zhang, Ya-Long; Zhou, Xu-Wei; Wu, Lin; Wang, Xiao-Bing; Yang, Ming-Hua; Luo, Jun; Luo, Jian-Guang; Kong, Ling-Yi

    2017-04-28

    Three new syncarpic acid-conjugated sesquiterpenoids, tomentodiones E-G (1-3), and six new syncarpic acid-conjugated monoterpenoids, tomentodiones H-M (4-9), were isolated from the leaves of Rhodomyrtus tomentosa. Compounds 1-3 represent the first examples of β-calacorene-based meroterpenoids. Their structures and absolute configurations were determined by a combination of NMR and ECD spectroscopy and X-ray diffraction analysis. On the basis of ECD data analysis for isolated and synthesized compounds, an empirical rule was proposed to determine the absolute configuration at C-7' of syncarpic acid-conjugated terpenoids. Additionally, a study of the reversal effect of multidrug resistance in doxorubicin-resistant human breast cancer cells showed that the noncytotoxic (+)-4 exerted the strongest potentiation effect of doxorubicin susceptibility, with an enhancement of 16.5-fold at a concentration of 30 μM.

  14. Incorporation of conjugated linoleic acid (CLA and α-linolenic acid (LNA in pacu fillets

    Directory of Open Access Journals (Sweden)

    Deoclécio José Barilli

    2014-03-01

    Full Text Available The objective of this study was to evaluate the incorporation of conjugated linoleic acid and α-linolenic acid in fillets of pacu fish raised in net cages and fed diets enriched with these acids. The fish were fed for 49 days, and at the end of this period the fatty acid content in the fillets was determined by gas chromatography. Concentrations of α-linolenic acid, eicosapentaenoic acid, and the total omega-3 (n-3 fatty acid in the fillets increased, improving the n-6/n-3 ratio. In addition, the incorporation of conjugated linoleic acid in the fish fillets proved well established. This study showed that the use of diets enriched with conjugated linoleic acid and α-linolenic acid results in the incorporation of these acids in the of pacu fish fillets, improving their nutritional quality.

  15. One-pot conversion of RAFT-generated multifunctional block copolymers of HPMA to doxorubicin conjugated acid- and reductant-sensitive crosslinked micelles.

    Science.gov (United States)

    Jia, Zhongfan; Wong, Lingjiun; Davis, Thomas P; Bulmus, Volga

    2008-11-01

    N-(2-Hydroxypropyl)methacrylamide (HPMA) containing polymers that are widely used as anticancer drug carriers. We have synthesized new amphiphilic block copolymers of HPMA with a functional monomer 2-(2-pyridyldisulfide)ethylmethacrylate (PDSM) via reversible addition-fragmentation chain transfer (RAFT) polymerization. In a one-pot reaction, the versatility of PDS groups on poly(PDSM)- b-poly(HPMA) was used to conjugate an anticancer drug, doxorubicin (DOX), and also simultaneously crosslink the micellar assemblies via acid-cleavable hydrazone bonds and reducible disulfide bonds. DOX-conjugated crosslinked micelles with an average diameter of approximately 60 nm were observed to be formed in aqueous medium. Disintegration of the micelles into unimers in the presence of a disulfide reducing agent confirmed the crosslinking via disulfide bonds. While the release of DOX from the crosslinked micelles at pH 5.0 was faster compared to the release at pH 7.4, a high proportion of released DOX was found to retain the original active structure. Overall results demonstrate the simplicity and the versatility of the poly(PDSM)- b-poly(HPMA) system, which are potentially important in the design of new generation of polymer therapeutics.

  16. Easy and efficient (111)Indium labeling of long-term stored DTPA conjugated protein

    DEFF Research Database (Denmark)

    Nalla, Amarnadh; Buch, Inge; Hesse, Birger

    2011-01-01

    -diethylene-triamine-pentaacetic acid (cDTAP) was conjugated to a polyclonal immunoglobulin-G (IgG) in borate buffer, pH 8.2 at +4oC for 4 hours. Then the DTPA-conjugate was dialyzed against 50 mmol/l sodium citrate buffer saline, pH 6.0 and stored at -80o C in aliquots of 1 mg/0.5 ml. The DTPA-conjugate was labeled with 111In......-chloride in citrate buffer, pH 6. The labelling reaction was incubated at room temperature (RT) for 30 min and at +4oC for 90 min. Determi- nation of labelling efficiency was performed using ITLC and an instant chromatography scanner equipped with a NaI crystal. The labelling efficiency of the DTPA...... months. Conclusion: Our study shows that 111In-labelling can easily be performed within 30 min at RT for thermo-stable proteins like polyclonal, DTPA-conjugated IgG stored long-term at -80oC with a high 111In-labelling effi- ciency....

  17. Easy and Efficient 111Indium Labeling of Long-Term Stored DTPA Conjugated Protein

    DEFF Research Database (Denmark)

    Nalla, Amarnadh; Buch, Inge; Hesse, Birger

    2011-01-01

    -diethylene-triamine-pentaacetic acid (cDTAP) was conjugated to a polyclonal immunoglobulin-G (IgG) in borate buffer, pH 8.2 at +4?C for 4 hours. Then the DTPA-conjugate was dialyzed against 50 mmol/l sodium citrate buffer saline, pH 6.0 and stored at -80° C in aliquots of 1 mg/0.5 ml. The DTPA-conjugate was labeled with 111In......-chloride in citrate buffer, pH 6. The labelling reaction was incubated at room temperature (RT) for 30 min and at +4?C for 90 min. Determination of labelling efficiency was performed using ITLC and an instant chromatography scanner equipped with a NaI crystal. The labelling efficiency of the DTPA...... months. Conclusion: Our study shows that 111In-labelling can easily be performed within 30 min at RT for thermo-stable proteins like polyclonal, DTPA-conjugated IgG stored long-term at -80°C with a high 111In-labelling efficiency....

  18. Conjugated polymer/nanocrystal nanocomposites for renewable energy applications in photovoltaics and photocatalysis.

    Science.gov (United States)

    Su, Yu-Wei; Lin, Wei-Hao; Hsu, Yung-Jung; Wei, Kung-Hwa

    2014-11-01

    Conjugated polymer/nanocrystal composites have attracted much attention for use in renewable energy applications because of their versatile and synergistic optical and electronic properties. Upon absorbing photons, charge separation occurs in the nanocrystals, generating electrons and holes for photocurrent flow or reduction/oxidation (redox) reactions under proper conditions. Incorporating these nanocrystals into conjugated polymers can complement the visible light absorption range of the polymers for photovoltaics applications or allow the polymers to sensitize or immobilize the nanocrystals for photocatalysis. Here, the current developments of conjugated polymer/nanocrystal nanocomposites for bulk heterojunction-type photovoltaics incorporating Cd- and Pb-based nanocrystals or quantum dots are reviewed. The effects of manipulating the organic ligands and the concentration of the nanocrystal precursor, critical factors that affect the shape and aggregation of the nanocrystals, are also discussed. In the conclusion, the mechanisms through which conjugated polymers can sensitize semiconductor nanocrystals (TiO2 , ZnO) to ensure efficient charge separation, as well as how they can support immobilized nanocrystals for use in photocatalysis, are addressed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Capture and conversion of CO2 at ambient conditions by a conjugated microporous polymer

    Science.gov (United States)

    Xie, Yong; Wang, Ting-Ting; Liu, Xiao-Huan; Zou, Kun; Deng, Wei-Qiao

    2013-01-01

    Conjugated microporous polymers are a new class of porous materials with an extended π-conjugation in an amorphous organic framework. Owing to the wide-ranging flexibility in the choice and design of components and the available control of pore parameters, these polymers can be tailored for use in various applications, such as gas storage, electronics and catalysis. Here we report a class of cobalt/aluminium-coordinated conjugated microporous polymers that exhibit outstanding CO2 capture and conversion performance at atmospheric pressure and room temperature. These polymers can store CO2 with adsorption capacities comparable to metal-organic frameworks. The cobalt-coordinated conjugated microporous polymers can also simultaneously function as heterogeneous catalysts for the reaction of CO2 and propylene oxide at atmospheric pressure and room temperature, wherein the polymers demonstrate better efficiency than a homogeneous salen-cobalt catalyst. By combining the functions of gas storage and catalysts, this strategy provides a direction for cost-effective CO2 reduction processes. PMID:23727768

  20. Theoretical study of conjugated porphyrin polymers

    DEFF Research Database (Denmark)

    Pedersen, T.G.; Lynge, T.B.; Kristensen, P.K.

    2005-01-01

    for these applications. From a theoretical analysis of excitons in long metalloporphyrin chains, we demonstrate that the binding energy is much lower than in usual conjugated polymers. Our calculated absorption spectra are in good agreement with measurements. (c) 2004 Elsevier B.V. All rights reserved....