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Sample records for conjugate addition reactions

  1. Diastereoselective and enantioselective conjugate addition reactions utilizing α,β-unsaturated amides and lactams

    Directory of Open Access Journals (Sweden)

    Katherine M. Byrd

    2015-04-01

    Full Text Available The conjugate addition reaction has been a useful tool in the formation of carbon–carbon bonds. The utility of this reaction has been demonstrated in the synthesis of many natural products, materials, and pharmacological agents. In the last three decades, there has been a significant increase in the development of asymmetric variants of this reaction. Unfortunately, conjugate addition reactions using α,β-unsaturated amides and lactams remain underdeveloped due to their inherently low reactivity. This review highlights the work that has been done on both diastereoselective and enantioselective conjugate addition reactions utilizing α,β-unsaturated amides and lactams.

  2. 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.

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

    KAUST Repository

    Zhang, Wen; Tan, Davin; Lee, Richmond; Tong, Guanghu; Chen, Wenchao; Qi, Baojian; Huang, Kuo-Wei; Tan, Choonhong; Jiang, Zhiyong

    2012-01-01

    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 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.

  5. Asymmetric Construction of Benzindoloquinolizidine: Application of An Organocatalytic Enantioselective Conjugate Addition-Cyclization Cascade Reaction

    International Nuclear Information System (INIS)

    Kim, Cheolwoong; Seo, Seung Woo; Lee, Yona; Kim, Sunggon

    2014-01-01

    We have developed the synthetic methodology of enantioenriched benzindoloquinolizidines based on the organocatalytic enantioselective conjugate addition-cyclization cascade reaction of o-N-(3-indoleacetyl)amino-cinnamaldehydes with malonates followed by an acid-catalyzed intramolecular Pictet-Spengler type cyclization. The asymmetric reaction using diphenylprolinol TMS ether as an organocatalyst produces the desired products with good to excellent yields and high enantioselectivities (up to 98% ee). The evaluation of the applications of this synthetic methodology for generating enantioenriched benzindolo-quinolizidines and studies on the biological activity of these compounds against human prostate cancer in particular are now in progress. Results of these studies will be presented in due course. Many new types of chemical reactions have been developed to facilitate easier synthesis of complex compounds. Among the strategies, domino reactions, which have been utilized for the efficient and stereoselective construction of complex molecules from simple precursors in a single process, are widely used due to their high synthetic efficiency by reducing both the number of synthetic operation required and the quantities of chemicals and solvents used

  6. DNA-Accelerated Copper Catalysis of Friedel-Crafts Conjugate Addition/Enantioselective Protonation Reactions in Water

    NARCIS (Netherlands)

    García-Fernández, Almudena; Megens, Rik P.; Villarino, Lara; Roelfes, Gerard

    2016-01-01

    DNA-induced rate acceleration has been identified as one of the key elements for the success of the DNA-based catalysis concept. Here we report on a novel DNA-based catalytic Friedel-Crafts conjugate addition/enantioselective protonation reaction in water, which represents the first example of a

  7. 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

    International Nuclear Information System (INIS)

    Alves, Jose C.F.

    2007-01-01

    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)

  8. 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

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

    KAUST Repository

    Yang, Wenguo; Tan, Davin; Lee, Richmond; Li, Lixin; Pan, Yuanhang; Huang, Kuo-Wei; Tan, Choonhong; Jiang, Zhiyong

    2012-01-01

    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

  10. N,2,3,4-Tetrasubstituted Pyrrolidines through Tandem Lithium Amide Conjugate Addition/Radical Cyclization/Oxygenation Reactions

    Czech Academy of Sciences Publication Activity Database

    Kafka, František; Pohl, Radek; Císařová, I.; Mackman, R.; Bahador, G.; Jahn, Ullrich

    2016-01-01

    Roč. 2016, č. 22 (2016), s. 3862-3871 ISSN 1434-193X R&D Projects: GA ČR GA13-40188S Grant - others:COST(XE) CM1201 Institutional support: RVO:61388963 Keywords : tandem reactions * nitrogen heterocycles * Michael addition * radical reactions * cyclization * enolates Subject RIV: CC - Organic Chemistry Impact factor: 2.834, year: 2016

  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. Enantioselective conjugate addition of hydroxylamines to pyrazolidinone acrylamides.

    Science.gov (United States)

    Sibi, M P; Liu, M

    2001-12-27

    Chiral relay templates provide amplification of selectivity in conjugate addition reactions. Reversal of stereochemistry of the product isoxazolidinones has also been demonstrated by a simple change of the Lewis acid. [reaction: see text

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

    KAUST Repository

    Tan, Davin

    2011-01-01

    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

  14. Lanthanide Lewis acid-mediated enantioselective conjugate radical additions.

    Science.gov (United States)

    Sibi, Mukund P; Manyem, Shankar

    2002-08-22

    [reaction: see text] Lanthanide triflates along with proline-derived ligands have been found to be efficient catalysts for enantioselective conjugate addition of nucleophilic radicals to enoates. N-Acyl oxazolidinones, when used as achiral additives, gave meaningful enhancements in the ees for the product.

  15. Regioselectivity of conjugate additions to monoalkyl-1,4-benzoquinones

    Directory of Open Access Journals (Sweden)

    SNEZANA TRIFUNOVIC

    2002-09-01

    Full Text Available The regioselectivity of the reaction of conjugate addition of thiols, amines, methanol and hydrogen chloride with the monoalkyl-1,4-benzoquinones avarone and 2-tert-butyl-1,4-benzoquinone was investigated. It was shown that the regioselectivity of the reaction is influenced by the electrophilicity of position 5 in unprotonated 2-alkylquinones, the increased electrophilicity of position 6 in acidic medium, and by the acidity of the intermediate hydroquinones.

  16. Calcium(ii)-catalyzed enantioselective conjugate additions of amines.

    Science.gov (United States)

    Uno, Brice E; Dicken, Rachel D; Redfern, Louis R; Stern, Charlotte M; Krzywicki, Greg G; Scheidt, Karl A

    2018-02-14

    The direct enantioselective chiral calcium(ii)·phosphate complex (Ca[CPA] 2 )-catalyzed conjugate addition of unprotected alkyl amines to maleimides was developed. This mild catalytic system represents a significant advance towards the general convergent asymmetric amination of α,β-unsaturated electrophiles, providing medicinally relevant chiral aminosuccinimide products in high yields and enantioselectivities. Furthermore, the catalyst can be reused directly from a previously chromatographed reaction and still maintain both high yield and selectivity.

  17. 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.

  18. 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...

  19. Enantioselective conjugate radical addition to alpha'-hydroxy enones.

    Science.gov (United States)

    Lee, Sunggi; Lim, Chae Jo; Kim, Sunggak; Subramaniam, Rajesh; Zimmerman, Jake; Sibi, Mukund P

    2006-09-14

    Enantioselective conjugate radical addition to alpha'-hydroxy alpha,beta-unsaturated ketones, compounds containing bidentate donors, has been investigated. It has been found that radical additions to alpha'-hydroxy alpha,beta-unsaturated ketones in the presence of Mg(NTf2)2 and bisoxazoline ligand 5a proceeded cleanly, yielding the addition products in high chemical yields and good enantiomeric excesses.

  20. Chiral amides via copper-catalysed enantioselective conjugate addition

    NARCIS (Netherlands)

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

    2014-01-01

    A highly enantioselective one pot procedure for the synthesis of beta-substituted amides was developed starting from the corresponding alpha,beta-unsaturated esters. This new methodology is based on the copper-catalysed enantioselective conjugate addition of Grignard reagents to

  1. Stereoselective conjugate radical additions: application of a fluorous oxazolidinone chiral auxiliary for efficient tin removal.

    Science.gov (United States)

    Hein, Jason E; Zimmerman, Jake; Sibi, Mukund P; Hultin, Philip G

    2005-06-23

    [reaction: see text] A series of asymmetric free-radical-mediated intermolecular conjugate additions using a fluorous oxazolidinone chiral auxiliary has been completed. The fluorous auxiliary facilitated product isolation using fluorous solid phase extractions (FSPE), effectively removing excess organic and organometallic reagents. Parallel reactions carried out with a similar but nonfluorous norephedrine-derived oxazolidinone demonstrated the superior stereoselectivity and purification obtainable with the fluorous chiral auxiliary.

  2. 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.

  3. Enantioselective conjugate addition of silylketene acetals to beta-enamidomalonates. Synthesis of beta-amino acid derivatives.

    Science.gov (United States)

    Sibi, Mukund P; Chen, Jianxie

    2002-08-22

    [reaction: see text] Conjugate addition of silylketene acetals or enolsilanes to enamidomalonates proceeds with excellent chemical efficiency and good selectivity using Cu(OTf)2 and a chiral bisoxazoline. The effect of the Lewis acid, ligand, the N-acyl substituent, and the nucleophile on yield and selectivity for the addition product have been evaluated.

  4. Allergic and immunologic reactions to food additives.

    Science.gov (United States)

    Gultekin, Fatih; Doguc, Duygu Kumbul

    2013-08-01

    For centuries, food additives have been used for flavouring, colouring and extension of the useful shelf life of food, as well as the promotion of food safety. During the last 20 years, the studies implicating the additives contained in foods and medicine as a causative factor of allergic reactions have been proliferated considerably. In this review, we aimed to overview all of the food additives which were approved to consume in EU and find out how common and serious allergic reactions come into existence following the consuming of food additives.

  5. Food Protein-polysaccharide Conjugates Obtained via the Maillard Reaction: A Review.

    Science.gov (United States)

    de Oliveira, Fabíola Cristina; Coimbra, Jane Sélia Dos Reis; de Oliveira, Eduardo Basílio; Zuñiga, Abraham Damian Giraldo; Rojas, Edwin E Garcia

    2016-05-18

    The products formed by glycosylation of food proteins with carbohydrates via the Maillard reaction, also known as conjugates, are agents capable of changing and improving techno-functional characteristics of proteins. The Maillard reaction uses the covalent bond between a group of a reducing carbohydrates and an amino group of a protein. This reaction does not require additional chemicals as it occurs naturally under controlled conditions of temperature, time, pH, and moisture. Moreover, there is growing interest in modifying proteins for industrial food applications. This review analyses the current state of art of the Maillard reaction on food protein functionalities. It also discusses the influence of the Maillard reaction on the conditions and formulation of reagents that improve desirable techno-functional characteristics of food protein.

  6. 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.

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

    Science.gov (United States)

    Guo, Fenghai; McGilvary, Matthew A; Jeffries, Malcolm C; Graves, Briana N; Graham, Shekinah A; Wu, Yuelin

    2017-05-01

    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(C₂H₄)₂]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.

  8. 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.

  9. Click and chemically triggered declick reactions through reversible amine and thiol coupling via a conjugate acceptor

    Science.gov (United States)

    Diehl, Katharine L.; Kolesnichenko, Igor V.; Robotham, Scott A.; Bachman, J. Logan; Zhong, Ye; Brodbelt, Jennifer S.; Anslyn, Eric V.

    2016-10-01

    The coupling and decoupling of molecular units is a fundamental undertaking of organic chemistry. Herein we report the use of a very simple conjugate acceptor, derived from Meldrum's acid, for the sequential ‘clicking’ together of an amine and a thiol in aqueous conditions at neutral pH. Subsequently, this linkage can be ‘declicked’ by a chemical trigger to release the original amine and thiol undisturbed. The reactivity differs from that of other crosslinking agents because the selectivity for sequential functionalization derives from an altering of the electrophilicity of the conjugate acceptor on the addition of the amine. We describe the use of the procedure to modify proteins, create multicomponent libraries and synthesize oligomers, all of which can be declicked to their starting components in a controlled fashion when desired. Owing to the mild reaction conditions and ease of use in a variety of applications, the method is predicted to have wide utility.

  10. Conjugation-promoted reaction of open-cage fullerene: a density functional theory study.

    Science.gov (United States)

    Guo, Yong; Yan, Jingjing; Khashab, Niveen M

    2012-02-01

    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. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Functional properties of nisin–carbohydrate conjugates formed by radiation induced Maillard reaction

    International Nuclear Information System (INIS)

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

    2012-01-01

    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. - Highlights: ► Nisin–carbohydrate conjugates were prepared using radiation induced Maillard reaction. ► Conjugation of nisin with dextran/glucose resulted in improvement of antibacterial spectrum. ► Conjugates of nisin with dextran/glucose had significant radical scavenging activity.

  12. 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.

  13. Preparation and characterization of conjugated polymers made by postpolymerization reactions of alternating polyketones.

    Science.gov (United States)

    Cheng, Chen; Guironnet, Damien; Barborak, James; Brookhart, Maurice

    2011-06-29

    Conjugated polymers possessing a poly(2,5-dimethylene-2,5-dihydrofuran) backbone were prepared through postpolymerization reaction of styrenic polyketones with bromine in one-pot reactions. The modification is proposed to proceed via condensation of two repeating units to form a fully characterized polymer with a poly(2,5-dimethylenetetrahydrofuran) backbone. Subsequent bromination and elimination of HBr yield a polymer with a fully conjugated carbon backbone. The new conjugated polymers were characterized by NMR, IR, and UV-vis spectroscopies and by CV. These polymers have strong absorption in the visible region, with the absorption peaks shifted to the NIR region upon doping with acids. The ease of the synthesis of the starting polyketone and of the modifications allows large-scale preparation of those conjugated polymers.

  14. Part I. An investigation into the mechanism of the samarium (II)-promoted Barbier reaction: Sequential radical cyclization/organometallic addition. Part II. Conjugate addition reactions of organosamarium reagents by in situ transmetalation to cuprates. Part III. Approximate absolute rate constants for the reaction of tributyltin radicals with aryl and vinyl halides. Part IV. An investigation into the synthetic utility of tri-n-butylgermanium hydride

    Energy Technology Data Exchange (ETDEWEB)

    Totleben, M.J.

    1992-01-01

    An investigation of the mechanism of the samarium diiodide mediated Barbier reaction was conducted. Through a series of alkyl halide-carbonyl coupling and deuterium labelling experiments, evidence supportive of an organometallic addition mechanism was collected. Further probing led to an expansion of the utility of SmI[sub 2] in synthesis. The author has shown that radical cyclization of aryl and alkyl radicals to olefins, followed by reduction to primary and secondary organosamarium species is feasible. Organosamarium (III) reagents, produced by the reduction of alkyl and select aryl halides with 2 equiv of SmI[sub 2] in THF/HMPA, were treated with copper (I) salts and complexes to effect in situ transmetalation to cuprates. This allowed the 1,4-addition to [alpha],[beta]-unsaturated ketones. This new methodology allows for the sequential formation of carbon-carbon bonds through a combination of free radical and cuprate chemistry. Absolute rate constants for the abstraction of bromine atoms (k[sub Br]) by tri-n-butyltin radicals from a series of vinyl and aryl bromides have been determined. Atom abstraction was modestly enhanced by proximity of the halogen to a substituent in the following order: para < meta < ortho. Tri-n-butyl germanium hydride is known to be a poorer hydrogen atom donor than its tin analog. This feature makes it attractive for use in slow radical cyclizations where tin hydride would provide mainly for reduction. A brief study was executed to improve on the utility of the reagent as current conditions do not yield desired products in high amounts. Initial investigations examined the effect of initiator on reduction by germanium hydride, and subsequent experiments probed solvent effects. t-Butyl alcohol was determined to be superior to benzene or acetonitrile, giving consistently higher yields of reduction products.

  15. Evaluation of achiral templates with fluxional Brønsted basic substituents in enantioselective conjugate additions.

    Science.gov (United States)

    Adachi, Shinya; Takeda, Norihiko; Sibi, Mukund P

    2014-12-19

    Enantioselective conjugate addition of malononitrile to pyrazolidinone-derived enoates proceeds in excellent yields and high enantioselectivities. A comparison of fluxional substituents with and without a Brønsted basic site and their impact on selectivity is detailed. Molecular sieves as an additive were found to be essential to achieve high enantioselectivity.

  16. Ionic liquids as precatalysts in the highly stereoselective conjugate addition of α,β-unsaturated aldehydes to chalcones.

    Science.gov (United States)

    Ta, Linda; Axelsson, Anton; Bijl, Joachim; Haukka, Matti; Sundén, Henrik

    2014-10-20

    Imidazolium-based ionic liquids (ILs) serve both as recyclable reaction media and as precatalysts for the N-heterocyclic carbene-catalyzed conjugate addition of α,β-unsaturated aldehydes to chalcones. The reaction produces a broad scope of 1,6-ketoesters incorporating an anti-diphenyl moiety in high yields and with high stereoselectivity. In recycling experiments, the IL can be reused up to five times with retained reactivity and selectivity. Moreover, the 1,6-ketoesters form self-assembled organogels in aliphatic hydrocarbons. The reaction protocol is robust, easily operated, scalable and highly functionalized compounds can be obtained from inexpensive and readily accessible starting materials. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Conjugate addition of diethyl 1-fluoro-1-phenylsulfonylmethanephosphonate to alpha,beta-unsaturated compounds

    Czech Academy of Sciences Publication Activity Database

    Opekar, Stanislav; Pohl, Radek; Eigner, V.; Beier, Petr

    2013-01-01

    Roč. 78, č. 9 (2013), s. 4573-4579 ISSN 0022-3263 R&D Projects: GA ČR GP203/08/P310 Institutional support: RVO:61388963 Keywords : fluorine * phosphonate * conjugate addition Subject RIV: CC - Organic Chemistry Impact factor: 4.638, year: 2013

  18. 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.

  19. Reduction of Allergenicity of Litchi chinensis Flowers Pollen Protein Conjugated with Polysaccharide by Maillard Reaction

    Directory of Open Access Journals (Sweden)

    Ranajit Kumar Shaha

    2012-04-01

    Full Text Available Background: Allergy to pollen from gymnosperms is well documented in the west. The objective was to define the allergologic protein from Litchi chinensis (Litchi pollen and conjugate the protein with polysaccharides by Maillard reaction to reduce the allergic effect of that protein. Methods: Total soluble proteins were extracted from the pollen of Litchi flower pollen and subjected to ammonium sulphate precipitation at 80% saturation. Pollen antigen from Litchi chinensis (Litchi was prepared by gel cutting method and characterized by biochemical and designated by LFPP. The homogeneity of this protein was demonstrated by a single band on SDS-PAGE. The protein then conjugated with galactomannan through Maillard Reaction. The resulting purified pollen protein and conjugated protein were administered to the Swiss albino mice as amount of 5.8mg/kg body weight. Results: The total protein was then separated on a 12% SDS-Polyacrylamide gel which revealed 5 bands between molecular weight range of 29kDa and 69kDa. Each band was recovered from the gel by electroelution and sent for skin tests. 28kDa proteins was the only allergenic protein while others were not shown reactivity in patients. Intraperitoneal injection of the purified protein (LFPP caused a significant rise in the levels of neutrophils (38-81% and eosinophils (3-14% compared to control (P < 0.001 whereas conjugated protein caused only a 2% increase of both neutrophils and eosinophils level. On the other hand treatment with LFPP-galactomannan conjugate causes no such change in physical appearance with eosinophils and neutrophils level. Conclusion: The present study demonstrates that the protein extracted and purified from Litchi flowers pollen has been recognized as a new allergen from Bangladesh for the first time and the allergic effects can be reduced by conjugation with polysaccharides.

  20. Investigation of the use of Maillard reaction inhibitors for the production of patatin-carbohydrate conjugates.

    Science.gov (United States)

    Seo, Sooyoun; Karboune, Salwa

    2014-12-17

    Selected Maillard reaction inhibitors, including aminoguanidine, cysteine, pyridoxamine, and sodium bisulfite, were evaluated for their effect on the production of carbohydrate conjugated proteins with less cross-linking/browning. Patatin (PTT), a major potato protein, was glycated with galactose, xylose, galactooligosaccharides, xylooligosaccharides, galactan, and xylan under controlled conditions. The effectiveness of the inhibitors to control the glycation reaction was assessed by monitoring the glycation extent, the protein cross-linking, and the formation of dicarbonyl compounds. Sodium bisulfite was the most effective inhibitor for PTT-galactose and PTT-xylan reaction systems (reaction control ratios of 210.0 and 12.8). On the other hand, aminoguanidine and cysteine led to the highest reaction control ratios for the PTT-xylose/xylooligosaccharide (160.0 and 143.0) and PTT-galactooligosaccharides/galactan (663.0 and 71.0) reaction systems, respectively. The use of cysteine and aminoguanidine as inhibitors led to 1.7-99.4% decreases in the particle size distribution of the PTT conjugates and to 0.4-9.3% increases in their relative digestibility, per 5% blocked lysine.

  1. Free-radical-mediated conjugate additions. Enantioselective synthesis of butyrolactone natural products: (-)-enterolactone, (-)-arctigenin, (-)-isoarctigenin, (-)-nephrosteranic acid, and (-)-roccellaric acid.

    Science.gov (United States)

    Sibi, Mukund P; Liu, Pingrong; Ji, Jianguo; Hajra, Saumen; Chen, Jian-xie

    2002-03-22

    Lewis acid-mediated conjugate addition of alkyl radicals to a differentially protected fumarate 10 produced the monoalkylated succinates with high chemical efficiency and excellent stereoselectivity. A subsequent alkylation or an aldol reaction furnished the disubstituted succinates with syn configuration. The chiral auxiliary, 4-diphenylmethyl-2-oxazolidinone, controlled the stereoselectivity in both steps. Manipulation of the disubstituted succinates obtained by alkylation furnished the natural products (-)-enterolactone, (-)-arctigenin, and (-)-isoarctigenin. The overall yields for the target natural products were 20-26% over six steps. Selective functionalization of the disubstituted succinates obtained by aldol condensation gave the paraconic acid natural products (-)-nephrosteranic acid (8) and (-)-roccellaric acid (9). The overall yield of the natural products 8 and 9 over four steps was 53% and 42%, respectively.

  2. Conjugate additions of a simple monosilylcopper reagent with use of the CuI.DMS complex: stereoselectivities and a dramatic impact by DMS.

    Science.gov (United States)

    Dambacher, Jesse; Bergdahl, Mikael

    2005-01-21

    Conjugate additions utilizing the simple monosilylcuprate reagent Li[PhMe2SiCuI] to alpha,beta-unsaturated carbonyl compounds are described. The presence of dimethyl sulfide (DMS), either as a component originating from the (CuI)4(DMS)3 complex or as a solvent added, has an amazing influence on both chemical yield and the level of diastereomeric ratio (dr) of the products. Gilman-type silylcyanocuprates {Li(Ph2MeSi)2Cu/LiCN} have previously been used to guarantee good results in conjugate addition reactions. External additives such as HMPA, tributylphosphine, or dialkylzinc are not necessary in conjunction with the simple Li[PhMe2SiCuI] reagent. It is demonstrated that the monosilylcuprate reagent with DMS as the solvent is very useful with sterically hindered (beta,beta-disubstituted) enones, and provides very high yields of the beta-silylated 1,4-addition products. Since there is no oligomerization problem associated with the simple monosilylcuprate reagent, this reagent should be considered as a very useful 1,4-silyl donor to enals, enones, and enoates in conjugate addition reactions.

  3. 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.

  4. Site-specific chemical conjugation of human Fas ligand extracellular domain using trans-cyclooctene - methyltetrazine reactions.

    Science.gov (United States)

    Muraki, Michiro; Hirota, Kiyonori

    2017-07-03

    Fas ligand plays a key role in the human immune system as a major cell death inducing protein. The extracellular domain of human Fas ligand (hFasLECD) triggers apoptosis of malignant cells, and therefore is expected to have substantial potentials in medical biotechnology. However, the current application of this protein to clinical medicine is hampered by a shortage of the benefits relative to the drawbacks including the side-effects in systemic administration. Effective procedures for the engineering of the protein by attaching useful additional functions are required to overcome the problem. A procedure for the site-specific chemical conjugation of hFasLECD with a fluorochrome and functional proteins was devised using an inverse-electron-demand Diels-Alder reaction between trans-cyclooctene group and methyltetrazine group. The conjugations in the present study were attained by using much less molar excess amounts of the compounds to be attached as compared with the conventional chemical modification reactions using maleimide derivatives in the previous study. The isolated conjugates of hFasLECD with sulfo-Cy3, avidin and rabbit IgG Fab' domain presented the functional and the structural integrities of the attached molecules without impairing the specific binding activity toward human Fas receptor extracellular domain. The present study provided a new fundamental strategy for the production of the engineered hFasLECDs with additional beneficial functions, which will lead to the developments of the improved diagnostic systems and the effective treatment methods of serious diseases by using this protein as a component of novel molecular tools.

  5. Anaphylactic reaction to polyethylene-glycol conjugated-asparaginase: premedication and desensitization may not be sufficient.

    Science.gov (United States)

    Sahiner, Umit M; Yavuz, S Tolga; Gökce, Muge; Buyuktiryaki, Betul; Altan, Ilhan; Aytac, Selin; Tuncer, Murat; Tuncer, Ayfer; Sackesen, Cansin

    2013-08-01

    In hypersensitive reactions to native L-asparaginase, either premedication and desensitization or substitution with polyethylene glycol conjugated asparaginase (PEG-ASP) is preferred. Anaphylaxis with PEG-ASP is rare. An 8-year-old girl and a 2.5-year-old boy, both diagnosed as having acute lymphoblastic leukemia, presented with native L-asparaginase hypersensitivity and substitution with PEG-ASP was preferred. They received a premedication (methylprednisolone, hydroxyzine and ranitidine) followed by desensitization with PEG-ASP infusion. Both patients developed anaphylaxis with peg-asparaginase. These are the first reported cases of anaphylactic reaction to PEG-ASP, despite the application of both premedication and desensitization. Anaphylaxis with PEG-ASP is very rare and premedication and desensitization protocols may not prevent these hypersensitive reactions. © 2013 The Authors. Pediatrics International © 2013 Japan Pediatric Society.

  6. Effect of ultrasound pretreatment and Maillard reaction on structure and antioxidant properties of ultrafiltrated smooth-hound viscera proteins-sucrose conjugates.

    Science.gov (United States)

    Abdelhedi, Ola; Mora, Leticia; Jemil, Ines; Jridi, Mourad; Toldrá, Fidel; Nasri, Moncef; Nasri, Rim

    2017-09-01

    The effect of ultrasound (US) pre-treatment on the evolution of Maillard reaction (MR), induced between low molecular weight (LMW) peptides and sucrose, was studied. LMW peptides (reaction, a marked decrease in pH values, coupled to the increase in colour of the Maillard reaction products (MRPs), were recorded. In addition, after sonication, the glycation degree was significantly enhanced in Esperase-derived peptides/sucrose conjugates (p<0.05). Moreover, results showed that thermal heating, particularly after US treatment, reduced the bitter taste and enhanced the antioxidant capacities of the resulting conjugates. Hence, it could be concluded that US leads to efficient mixing of sugar-protein solution and efficient heat/mass transfer, contributing to increase the MR rate. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. 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.

  8. 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-2 H -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.

  9. Exploring Tyrosine-Triazolinedione (TAD) Reactions for the Selective Conjugation and Cross-Linking of N-Carboxyanhydride (NCA) Derived Synthetic Copolypeptides.

    Science.gov (United States)

    Hanay, Saltuk B; Ritzen, Bas; Brougham, Dermot; Dias, Aylvin A; Heise, Andreas

    2017-07-01

    Highly efficient functionalization and cross-linking of polypeptides is achieved via tyrosine-triazolinedione (TAD) conjugation chemistry. The feasibility of the reaction is demonstrated by the reaction of 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) with tyrosine containing block copolymer poly(ethylene glycol)-Tyr 4 as well as a statistical copolymer of tyrosine and lysine (poly(Lys 40 -st-Tyr 10 )) prepared form N-carboxyanhydride polymerization. Selective reaction of PTAD with the tyrosine units is obtained and verified by size exclusion chromatography and NMR spectroscopy. Moreover, two monofunctional and two difunctional TAD molecules are synthesized. It is found that their stability in the aqueous reaction media significantly varied. Under optimized reaction conditions selective functionalization and cross-linking, yielding polypeptide hydrogels, can be achieved. TAD-mediated conjugation can offer an interesting addition in the toolbox of selective (click-like) polypeptide conjugation methodologies as it does not require functional non-natural amino acids. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Hydrogen addition reactions of aliphatic hydrocarbons in comets

    Science.gov (United States)

    Kobayashi, Hitomi; Watanabe, N.; Watanabe, Y.; Fukushima, T.; Kawakita, H.

    2013-10-01

    Comets are thought as remnants of early solar nebula. Their chemical compositions are precious clue to chemical and physical evolution of the proto-planetary disk. Some hydrocarbons such as C2H6, C2H2 and CH4 in comets have been observed by using near-infrared spectroscopy. Although the compositions of C2H6 were about 1% relative to the water in normal comets, there are few reports on the detection of C2H6 in ISM. Some formation mechanisms of C2H6 in ISM have been proposed, and there are two leading hypotheses; one is the dimerizations of CH3 and another is the hydrogen addition reactions of C2H2 on cold icy grains. To evaluate these formation mechanisms for cometary C2H6 quantitatively, it is important to search the C2H4 in comets, which is the intermediate product of the hydrogen addition reactions toward C2H6. However, it is very difficult to detect the C2H4 in comets in NIR (3 microns) regions because of observing circumstances. The hydrogen addition reactions of C2H2 at low temperature conditions are not well characterized both theoretically and experimentally. For example, there are no reports on the reaction rate coefficients of those reaction system. To determine the production rates of those hydrogen addition reactions, we performed the laboratory experiments of the hydrogenation of C2H2 and C2H4. We used four types of the initial composition of the ices: pure C2H4, pure C2H2, C2H2 on amorphous solid water (ASW) and C2H4 on ASW at three different temperatures of 10, 20, and 30K. We found 1) reactions are more efficient when there are ASW in the initial compositions of the ice; 2) hydrogenation of C2H4 occur more rapid than that of C2H2.

  11. Additive effects of acetic acid upon hydrothermal reaction of amylopectin

    International Nuclear Information System (INIS)

    Sugano, Motoyuki; Katoh, Harumi; Komatsu, Akihiro; Kobayashi, Hiroshi; Okado, Kohta; Kakuta, Yusuke; Hirano, Katsumi

    2012-01-01

    It is well known that over 0.8 kg kg −1 of starch is consisted of amylopectin (AP). In this study, production of glucose for raw material of ethanol by hydrothermal reaction of AP as one of the model compound of food is discussed. Further, additive effects of acetic acid upon hydrothermal reactions of AP are also investigated. During hydrothermal reaction of AP, production of glucose occurred above 453 K, and the glucose yield increased to 0.48 kg kg −1 at 473 K. Upon hydrothermal reaction of AP at 473 K, prolongation of the holding time was not effective for the increase of the glucose yield. Upon hydrothermal reaction of AP at 473 K for 0 s, the glucose yield increased significantly by addition between 0.26 mol L −1 and 0.52 mol L −1 of acetic acid. However, the glucose yield decreased and the yield of the other constituents increased with the increases of concentration of acetic acid from 0.65 mol L −1 to 3.33 mol L −1 . It was considered that hydrolysis of AP to yield glucose was enhanced due to the increase of the amount of proton derived from acetic acid during hydrothermal reaction with 0.52 mol L −1 of acetic acid. -- Highlights: ► Glucose production by hydrothermal reaction of amylopectin (AP) at 473 K. ► Glucose yield increased to 0.48 kg kg -1 at 473 K. ► Prolongation of holding time was not effective for glucose yield. ► Glucose yield increased significantly by acetic acid (0.26–0.52 mol L-1) addition. ► Hydrolysis of AP to glucose was enhanced due to increase of proton from acetic acid.

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

    DEFF Research Database (Denmark)

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

    1994-01-01

    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......, 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...... for the open challenge. Two doses were used: a low dose and a 10-fold higher dose. Gelatin capsules were used for a double-blind challenge. The children were 4-15 years old, and they were attending an outpatient pediatric clinic for the first time. Of the 379 patients who entered the study, 44 were excluded...

  13. Solvent-free microwave-mediated Michael addition reactions

    Indian Academy of Sciences (India)

    Unknown

    obviously difficult to scale up. In this context ... eco-friendly features such as, (i) no solvent is required to conduct the ... water soluble, addition of reaction mixture after com- ..... Yield: 855 mg (89%; viscous liquid). 3.4 Ethyl .... Jung M E 1993 Comprehensive organic synthesis ... Leshcheva I F and Bundel Y G 1997 Mendeleev.

  14. Synthesis of purines bearing functionalized C-substituents by the conjugate addition of nucleophiles to 6-vinylpurines and 6-ethynylpurines

    Czech Academy of Sciences Publication Activity Database

    Kuchař, Martin; Pohl, Radek; Votruba, Ivan; Hocek, Michal

    -, č. 22 (2006), s. 5083 -5098 ISSN 1434-193X R&D Projects: GA MŠk(CZ) 1M0508; GA AV ČR(CZ) 1QS400550501 Institutional research plan: CEZ:AV0Z40550506 Keywords : purines * Michael addition * conjugate additions * cross-coupling Subject RIV: CC - Organic Chemistry Impact factor: 2.769, year: 2006

  15. Discovery of Amadori-Type Conjugates in a Peptide Maillard Reaction and Their Corresponding Influence on the Formation of Pyrazines.

    Science.gov (United States)

    Zou, Tingting; Liu, Jianbin; Song, Huanlu; Liu, Ye

    2018-05-10

    Knowledge of the role of peptides in the Maillard reaction is rather limited. In this study, peptide Maillard reaction model systems were established. Volatile and nonvolatile MRPs (Maillard reaction products) were investigated by GC-O-MS and LC-MS. Carbohydrate module labeling (CAMOLA) experiments were performed to elucidate the carbon skeleton of these compounds. Results showed that the peptide reaction system generated more pyrazines than the free amino acid group. Several new Amadori-type conjugates were identified as novel Maillard reaction products that could greatly influence the formation of pyrazines. Our work suggested anew mechanism involving these Amadori-type conjugates and subsequent investigation revealed that the conjugates could be important intermediate products in the reaction between dicarbonyl and dipeptide. Our findings demonstrate anew pyrazine generation mechanism in the dipeptide Maillard reaction. We found that a dipeptide Maillard reaction system generated more pyrazines than a reaction system composed of free amino acids. New cross-linked peptide-sugar compounds were identified and found to impact the formation of pyrazines. The results of this study may help in the preparation of thermal reaction flavors using enzymatically hydrolyzed vegetable/animal proteins, which contain a considerable amount of peptides, as one of the major reactants. © 2018 Institute of Food Technologists®.

  16. 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.

  17. Double Michael Addition Reaction of Bischalcone under Ultrasound

    Institute of Scientific and Technical Information of China (English)

    LI,Ji-Tai; XU,Wen-Zhi; CHEN,Guo-Feng; LI,Tong-Shuang

    2004-01-01

    @@ The Michael addition of 1,5-diaryl-1,4-pentadien-3-ones with active methylene compounds has been the subjects of many investigations. Ultrasound has increasingly been used in organic synthesis in the last three decades. Compared with traditional methods, this method is more convenient and easily controlled. A large number of organic reactions can be carried out in higher yield, shorter reaction time or milder conditions under ultrasonic irradiation. KF/Al2O3 as a useful solid supported catalyst has received considerable attention because of their high level of chemoselectivity and environmental compatibility as well as simplicity of operation and their ready availability at low cost. Herein we report the double Michael addition of dibenzalacetone with active methlene compounds such as dimethyl malonate, diethyl malonate,methyl cyanoacetate and ethyl cyanoacetate catalyzed by KF/Al2O3 under ultrasound irradiation.

  18. 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.

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

    KAUST Repository

    Guo, Yong; Yan, Jingjing; Khashab, Niveen M.

    2012-01-01

    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

  20. 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

  1. 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.

  2. 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

    transformation. The retro benzyl reaction was shown by the addition of benzylmagnesium chloride to di-tert-butyl ketone followed by exchange of both the benzyl and the ketone moiety with another substrate. Similar experiments were performed with phenylmagnesium bromide and tert-butylmagnesium chloride...

  3. Phosphite radicals and their reactions. Examples of redox, substitution, and addition reactions

    International Nuclear Information System (INIS)

    Schaefer, K.; Asmus, K.D.

    1980-01-01

    Phosphite radicals HPO 3 - and PO 3 2 -, which exist in an acid-base equilibrium with pK = 5.75, are shown to take part in various types of reactions. In the absence of scavengers, they disappear mainly by second-order disproportionation and combination; a first-order contribution to the decay is also indicated. HPO 3 - and PO 3 2 - are good reductants toward electron acceptors such as tetranitromethane. In this reaction phosphate and C(NO 2 ) 3 - are formed. Phosphite radicals can, however, also act as good oxidants, e.g., toward thiols and thiolate ions. These reactions lead to the formation of RS. radicals which were identified either directly, as in the case of penicillamine, through the optical absorption of PenS. or more indirectly through equilibration of RS. with RS- to the optically absorbing RSSR-. disulfide radical anion. A homolytic substitution reaction (S/sub H/2) occurs in the reaction of the phosphite radicals with aliphatic disulfides, yielding RS. radicals and phosphate thioester RSPO 3 2 -. Lipoic acid, as an example of a cyclic disulfide, is reduced to the corresponding RSSR-. radical anion and also undergoes the S/sub H/2 reaction with about equal probability. An addition reaction is observed between phosphite radicals and molecular oxygen. The resulting peroxo phosphate radicals establish an acid-base equilibrium HPO 5 - . reversible PO 5 2- . + H+ with a pK = 3.4. Absolute rate constants were determined for all reactions discussed

  4. Regioselective 1,4- and 1,6-Conjugate Additions of Grignard Reagent-Derived Organozinc(II)ates to Polyconjugated Esters.

    Science.gov (United States)

    Hatano, Manabu; Mizuno, Mai; Ishihara, Kazuaki

    2016-09-16

    Regioselective synthetic methods were developed for 1,4- and 1,6-conjugate additions of Grignard reagent-derived organozinc(II)ates to malonate-derived polyconjugated esters. By taking advantage of the tight ion-pair control of organozinc(II)ates, it was possible to switch between 1,4- and 1,6-conjugate additions by introducing a terminal ethoxy moiety in the conjugation.

  5. The role of the achiral template in enantioselective transformations. Radical conjugate additions to alpha-methacrylates followed by hydrogen atom transfer.

    Science.gov (United States)

    Sibi, Mukund P; Sausker, Justin B

    2002-02-13

    We have evaluated various achiral templates (1a-g, 10, and 16) in conjunction with chiral Lewis acids in the conjugate addition of nucleophilic radicals to alpha-methacrylates followed by enantioselective H-atom transfer. Of these, a novel naphthosultam template (10) gave high enantioselectivity in the H-atom-transfer reactions with ee's up to 90%. A chiral Lewis acid derived from MgBr(2) and bisoxazoline (2) gave the highest selectivity in the enantioselective hydrogen-atom-transfer reactions. Non-C(2) symmetric oxazolines (20-25) have also been examined as ligands, and of these, compound 25 gave optimal results (87% yield and 80% ee). Insights into rotamer control in alpha-substituted acrylates and the critical role of the tetrahedral sulfone moiety in realizing high selectivity are discussed.

  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. Selective binding of carotenoids with a shorter conjugated chain to the LH2 antenna complex and those with a longer conjugated chain to the reaction center from Rubrivivax gelatinosus.

    Science.gov (United States)

    Kakitani, Yoshinori; Fujii, Ritsuko; Hayakawa, Yoshihiro; Kurahashi, Masahiro; Koyama, Yasushi; Harada, Jiro; Shimada, Keizo

    2007-06-19

    Rubrivivax gelatinosus having both the spheroidene and spirilloxanthin biosynthetic pathways produces carotenoids (Cars) with a variety of conjugated chains, which consist of different numbers of conjugated double bonds (n), including the C=C (m) and C=O (o) bonds. When grown under anaerobic conditions, the wild type produces Cars for which n = m = 9-13, whereas under semiaerobic conditions, it additionally produces Cars for which n = m + o = 10 + 1, 13 + 1, and 13 + 2. On the other hand, a mutant, in which the latter pathway is genetically blocked, produces only Cars for which n = 9 and 10 under anaerobic conditions and n = 9, 10, and 10 + 1 under semianaerobic conditions. Those Cars that were extracted from the LH2 complex (LH2) and the reaction center (RC), isolated from the wild-type and the mutant Rvi. gelatinosus, were analyzed by HPLC, and their structures were determined by mass spectrometry and 1H NMR spectroscopy. The selective binding of Cars to those pigment-protein complexes has been characterized as follows. (1) Cars with a shorter conjugated chain are selectively bound to LH2 whereas Cars with a longer conjugated chain to the RC. (2) Shorter chain Cars with a hydroxyl group are bound to LH2 almost exclusively. This rule holds either in the absence or in the presence of the keto group. The natural selection of shorter chain Cars by LH2 and longer chain Cars by the RC is discussed, on the basis of the results now available, in relation to the light-harvesting and photoprotective functions of Cars.

  8. 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.

  9. Modelling of charge carrier transport in conjugated polymers doped by polar additives

    Czech Academy of Sciences Publication Activity Database

    Toman, Petr; Nešpůrek, Stanislav; Bartkowiak, W.

    2009-01-01

    Roč. 27, č. 3 (2009), s. 797-812 ISSN 0137-1339. [International Conference on Electrical and Related Properties of Organic Solids /11./. Piechowice, 13.07.2008-17.07.2008] R&D Projects: GA ČR GA203/06/0285; GA AV ČR KAN400720701; GA MŠk MEB050815 Institutional research plan: CEZ:AV0Z40500505 Keywords : conjugated polymers * charge carrier transport * molecular electronics Subject RIV: CD - Macromolecular Chemistry Impact factor: 0.384, year: 2009

  10. 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.

  11. 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.

  12. Regio- and Stereoselective Conjugate Addition of Aldehydes to β-Tosyl Enones under the Catalysis of a Binaphthyl-Modified Chiral Amine.

    Science.gov (United States)

    Kano, Taichi; Sugimoto, Hisashi; Maruyama, Hiroki; Maruoka, Keiji

    2015-07-13

    A simple axially chiral amine catalyst promoted the regio-, diastereo-, and enantioselective conjugate addition of aldehydes to β-tosyl enones, which serve as ynone surrogates. The adducts were readily converted by treatment with L-selectride into less accessible enones with a γ stereogenic center. Such compounds cannot be prepared through the amine-catalyzed conjugate addition of aldehydes to ynones. The obtained enones underwent further conjugate addition of diorganozinc compounds in the presence of a copper catalyst. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Deep eutectic solvents as performance additives in biphasic reactions

    NARCIS (Netherlands)

    Lan, Dongming; Wang, Xuping; Zhou, Pengfei; Hollmann, F.; Wang, Yonghua

    2017-01-01

    Deep eutectic solvents act as surfactants in biphasic (hydrophobic/aqueous) reaction mixtures enabling higher interfacial surface areas at lower mechanical stress as compared to simple emulsions. Exploiting this effect the rate of a chemoenzymatic epoxidation reaction was increased more than

  14. 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...

  15. 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.

  16. 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; Schmitt, Meghan L.; Falivene, Laura; Caporaso, Lucia; Cavallo, Luigi; Chen, Eugene You Xian

    2013-01-01

    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

  17. 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

  18. Base-catalyzed tandem Michael/dehydro-Diels-Alder reaction of α,α-dicyanoolefins with electron-deficient 1,3-conjugated enynes: a facile entry to angularly fused polycycles.

    Science.gov (United States)

    Zhang, Mingrui; Zhang, Junliang

    2014-01-07

    Angularly fused carbocyclic frameworks and their heteroatom-substituted analogues exist in many natural products that display a broad and interesting range of biological activities. Preparation of polycyclic products by cycloaddition reactions have been the long-standing hot topic in the synthetic community. Dehydro-Diels-Alder (DDA) reactions are one class of dehydropericyclic reactions that are derived conceptually by systematic removal of hydrogen atom pairs. A base-promoted tandem Michael addition and DDA reaction of α,α-dicyanoolefins with electron-deficient 1,3-conjugated enynes was realized in which a DDA reaction takes place between the arylalkynes and electron-deficient tetrasubstituted olefin. The control experiments support the stepwise anionic reaction pathway rather than the concerted reaction pathway. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    DEFF Research Database (Denmark)

    Fuglsang, G; Madsen, G; Halken, S

    1994-01-01

    , 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...... 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...

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

    DEFF Research Database (Denmark)

    Fuglsang, G; Madsen, G; Halken, S

    1994-01-01

    In a multicenter study conducted at four Danish hospital pediatric departments, the parents of 472 consecutive children were informed of this project to determine the incidence of intolerance of food additives among children referred to an allergy clinic with symptoms of asthma, atopic dermatitis......, 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...... 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...

  1. A versatile method for the preparation of conjugates of peptides with DNA/PNA/analog by employing chemo-selective click reaction in water

    Science.gov (United States)

    Gogoi, Khirud; Mane, Meenakshi V.; Kunte, Sunita S.; Kumar, Vaijayanti A.

    2007-01-01

    The specific 1,3 dipolar Hüisgen cycloaddition reaction known as ‘click-reaction’ between azide and alkyne groups is employed for the synthesis of peptide–oligonucleotide conjugates. The peptide nucleic acids (PNA)/DNA and peptides may be appended either by azide or alkyne groups. The cycloaddition reaction between the azide and alkyne appended substrates allows the synthesis of the desired conjugates in high purity and yields irrespective of the sequence and functional groups on either of the two substrates. The versatile approach could also be employed to generate the conjugates of peptides with thioacetamido nucleic acid (TANA) analog. The click reaction is catalyzed by Cu (I) in either water or in organic medium. In water, ∼3-fold excess of the peptide-alkyne/azide drives the reaction to completion in 2 h with no side products. PMID:17981837

  2. Direct enantioselective conjugate addition of carboxylic acids with chiral lithium amides as traceless auxiliaries.

    Science.gov (United States)

    Lu, Ping; Jackson, Jeffrey J; Eickhoff, John A; Zakarian, Armen

    2015-01-21

    Michael addition is a premier synthetic method for carbon-carbon and carbon-heteroatom bond formation. Using chiral dilithium amides as traceless auxiliaries, we report the direct enantioselective Michael addition of carboxylic acids. A free carboxyl group in the product provides versatility for further functionalization, and the chiral reagent can be readily recovered by extraction with aqueous acid. The method has been applied in the enantioselective total synthesis of the purported structure of pulveraven B.

  3. Direct Enantioselective Conjugate Addition of Carboxylic Acids with Chiral Lithium Amides as Traceless Auxiliaries

    Science.gov (United States)

    2016-01-01

    Michael addition is a premier synthetic method for carbon–carbon and carbon–heteroatom bond formation. Using chiral dilithium amides as traceless auxiliaries, we report the direct enantioselective Michael addition of carboxylic acids. A free carboxyl group in the product provides versatility for further functionalization, and the chiral reagent can be readily recovered by extraction with aqueous acid. The method has been applied in the enantioselective total synthesis of the purported structure of pulveraven B. PMID:25562717

  4. Metal-Free Catalytic Enantioselective C–B Bond Formation: (Pinacolato)boron Conjugate Additions to α,β-Unsaturated Ketones, Esters, Weinreb Amides and Aldehydes Promoted by Chiral N-Heterocyclic Carbenes

    Science.gov (United States)

    Wu, Hao; Radomkit, Suttipol; O’Brien, Jeannette M.; Hoveyda, Amir H.

    2012-01-01

    The first broadly applicable metal-free enantioselective method for boron conjugate addition (BCA) to α,β-unsaturated carbonyls is presented. The C–B bond forming reactions are promoted in the presence of 2.5–7.5 mol % of a readily accessible C1-symmetric chiral imidazolinium salt, which is converted, in situ, to the catalytically active diastereo- and enantiomerically pure N-heterocyclic carbene (NHC) by the common organic base 1,8-diazabicyclo[5.4.0]undec-7-ene (dbu). In addition to the commercially available bis(pinacolato)diboron [B2(pin)2], and in contrast to reactions with the less sterically demanding achiral NHCs, the presence of MeOH is required for high efficiency. Acyclic and cyclic α,β-unsaturated ketones, as well as acyclic esters, Weinreb amides and aldehydes can serve as suitable substrates; the desired β-boryl carbonyls are isolated in up to 94% yield and >98:2 enantiomer ratio (er). Transformations are often carried out at ambient temperature. In certain cases, such as when the relatively less reactive unsaturated amides are used, elevated temperatures are required (50–66 °C); nonetheless, reactions remain highly enantioselective. The utility of the NHC-catalyzed method is demonstrated through comparison with the alternative Cu-catalyzed protocols; in cases involving a polyfunctional substrate, unique profiles in chemoselectivity are exhibited by the metal-free approach (e.g., conjugate addition vs reaction with an alkyne, allene or aldehyde). PMID:22559866

  5. Characterization and emulsifying properties of β-lactoglobulin-gum Acacia Seyal conjugates prepared via the Maillard reaction.

    Science.gov (United States)

    Bi, Binwei; Yang, Hao; Fang, Yapeng; Nishinari, Katsuyoshi; Phillips, Glyn O

    2017-01-01

    Gum Acacia Seyal (ASY) is less valued than is gum Acacia Senegal, due to its poor emulsifying ability. The present study investigated the Maillard reaction between ASY and β-lactoglobulin (BLG) and its impact on the emulsifying properties of ASY. The reaction products of BLG/ASY mixture (r=1/4), prepared by dry-heating at 60°C and a relative humidity of 79%, as a function of incubation time, were characterized by SDS-PAGE, GPC-MALLS and DSC. The results showed that 12-24h of dry-heating under the given conditions was sufficient for conjugation, meanwhile avoiding the formation of deeply coloured and insoluble melanoidins. More than 64% of the protein was incorporated into ASY, resulting in a two-fold increase in arabinogalactan-protein (AGP) content and 3.5 times increase in weight-average molecular mass of ASY. The conjugation with BLG markedly improved the stability of ASY-stabilized emulsions and their resistance against severe conditions, such as low pH and high saline conditions. Copyright © 2016 Elsevier Ltd. All rights reserved.

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

    KAUST Repository

    Lattanzi, Alessandra; De Fusco, Claudia; Russo, Alessio; Poater, Albert; Cavallo, Luigi

    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

  7. 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.

  8. Arenethiolatecopper(I) complexes as homogeneous catalysts for Michael addition reactions

    NARCIS (Netherlands)

    Koten, G. van; Klaveren, M. van; Lambert, F.; Eijkelkamp, D.J.F.M.; Grove, D.M.

    1994-01-01

    Arenethiolatocopper(I) complexes are shown to be efficient homogeneous catalysts in Michael addition reactions of several Grignard reagents to acyclic enones; the addition products are formed with excellent chemoselectivity (>99%) and good enantioselectivity (76% e.e.).

  9. Pd(II)/Bipyridine-Catalyzed Conjugate Addition of Arylboronic Acids to α,β-Unsaturated Carboxylic Acids. Synthesis of β-Quaternary Carbons Substituted Carboxylic Acids.

    Science.gov (United States)

    Liu, Rui; Yang, Zhenyu; Ni, Yuxin; Song, Kaixuan; Shen, Kai; Lin, Shaohui; Pan, Qinmin

    2017-08-04

    Pd(II)/bipyridine-catalyzed conjugate addition of arylboronic acids to α,β-unsaturated carboxylic acids (including β,β-disubstituted acrylic acids) was developed and optimized, which provided a mild and convenient method for the highly challenging synthesis of β-quaternary carbons substituted carboxylic acids.

  10. (+)-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

  11. F/Cl + C2H2 reactions: Are the addition and hydrogen abstraction direct processes?

    International Nuclear Information System (INIS)

    Li Jilai; Geng Caiyun; Huang Xuri; Zhan Jinhui; Sun Chiachung

    2006-01-01

    The reactions of atomic radical F and Cl with acetylene have been studied theoretically using ab initio quantum chemistry methods and transition state theory. The doublet potential energy surfaces were calculated at the CCSD(T)/aug-cc-pVDZ//CCSD/6-31G(d,p), CCSD(T)/aug-cc-pVDZ//UMP2/6-311++G(d,p) and compound method Gaussian-3 levels. Two reaction mechanisms including the addition-elimination and the hydrogen abstraction reaction mechanisms are considered. In the addition-elimination reactions, the halogen atoms approach C 2 H 2 , perpendicular to the C≡C triple bond, forming the pre-reactive complex C1 at the reaction entrance. C1 transforms to intermediate isomer I1 via transition state TSC1/1 with a negative/small barrier for C 2 H 2 F/C 2 H 2 Cl system, which can proceed by further eliminating H atom endothermally. While the hydrogen abstraction reactions also involve C1 for the fluorine atom abstraction of hydrogen, yet the hydrogen abstraction by chlorine atom first forms a collinear hydrogen-bonded complex C2. The other reaction pathways on the doublet PES are less competitive due to thermodynamical or kinetic factors. According to our results, the presence of pre-reactive complexes indicates that the simple hydrogen abstraction and addition in the halogen atoms reaction with unsaturated hydrocarbon should be more complex. Furthermore, based on the analysis of the kinetics of all channels through which the addition and abstraction reactions proceed, we expect that the actual feasibility of the reaction channels may depend on the reaction conditions in the experiment. The present study may be helpful for probing the mechanisms of the title reactions and understanding the halogen chemistry

  12. Highly Functionalized Cyclopentane Derivatives by Tandem Michael Addition/Radical Cyclization/Oxygenation Reactions

    Czech Academy of Sciences Publication Activity Database

    Holan, Martin; Pohl, Radek; Císařová, I.; Klepetářová, Blanka; Jones, P. G.; Jahn, Ullrich

    2015-01-01

    Roč. 21, č. 27 (2015), s. 9877-9888 ISSN 0947-6539 R&D Projects: GA ČR GA13-40188S Institutional support: RVO:61388963 Keywords : cyclization * domino reactions * electron transfer * Michael addition * radical reactions Subject RIV: CC - Organic Chemistry Impact factor: 5.771, year: 2015

  13. 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.

  14. Coupled sensitizer-catalyst dyads: electron-transfer reactions in a perylene-polyoxometalate conjugate.

    Science.gov (United States)

    Odobel, Fabrice; Séverac, Marjorie; Pellegrin, Yann; Blart, Errol; Fosse, Céline; Cannizzo, Caroline; Mayer, Cédric R; Elliott, Kristopher J; Harriman, Anthony

    2009-01-01

    Ultrafast discharge of a single-electron capacitor: A variety of intramolecular electron-transfer reactions are apparent for polyoxometalates functionalized with covalently attached perylene monoimide chromophores, but these are restricted to single-electron events. (et=electron transfer, cr=charge recombination, csr=charge-shift reaction, PER=perylene, POM=polyoxometalate).A new strategy is introduced that permits covalent attachment of an organic chromophore to a polyoxometalate (POM) cluster. Two examples are reported that differ according to the nature of the anchoring group and the flexibility of the linker. Both POMs are functionalized with perylene monoimide units, which function as photon collectors and form a relatively long-lived charge-transfer state under illumination. They are reduced to a stable pi-radical anion by electrolysis or to a protonated dianion under photolysis in the presence of aqueous triethanolamine. The presence of the POM opens up an intramolecular electron-transfer route by which the charge-transfer state reduces the POM. The rate of this process depends on the molecular conformation and appears to involve through-space interactions. Prior reduction of the POM leads to efficient fluorescence quenching, again due to intramolecular electron transfer. In most cases, it is difficult to resolve the electron-transfer products because of relatively fast reverse charge shift that occurs within a closed conformer. Although the POM can store multiple electrons, it has not proved possible to use these systems as molecular-scale capacitors because of efficient electron transfer from the one-electron-reduced POM to the excited singlet state of the perylene monoimide.

  15. Tuning a Protein-Labeling Reaction to Achieve Highly Site Selective Lysine Conjugation.

    Science.gov (United States)

    Pham, Grace H; Ou, Weijia; Bursulaya, Badry; DiDonato, Michael; Herath, Ananda; Jin, Yunho; Hao, Xueshi; Loren, Jon; Spraggon, Glen; Brock, Ansgar; Uno, Tetsuo; Geierstanger, Bernhard H; Cellitti, Susan E

    2018-04-16

    Activated esters are widely used to label proteins at lysine side chains and N termini. These reagents are useful for labeling virtually any protein, but robust reactivity toward primary amines generally precludes site-selective modification. In a unique case, fluorophenyl esters are shown to preferentially label human kappa antibodies at a single lysine (Lys188) within the light-chain constant domain. Neighboring residues His189 and Asp151 contribute to the accelerated rate of labeling at Lys188 relative to the ≈40 other lysine sites. Enriched Lys188 labeling can be enhanced from 50-70 % to >95 % by any of these approaches: lowering reaction temperature, applying flow chemistry, or mutagenesis of specific residues in the surrounding protein environment. Our results demonstrated that activated esters with fluoro-substituted aromatic leaving groups, including a fluoronaphthyl ester, can be generally useful reagents for site-selective lysine labeling of antibodies and other immunoglobulin-type proteins. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. New heparin–indomethacin conjugate with an ester linkage: Synthesis, self aggregation and drug delivery behavior

    Energy Technology Data Exchange (ETDEWEB)

    Li, Nan-Nan; Zheng, Bing-Na [DSAPM Lab and PCFM Lab, Institute of Polymer Science, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275 (China); Lin, Jian-Tao [DSAPM Lab and PCFM Lab, Institute of Polymer Science, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275 (China); Guangdong Medical College, Dongguan 523808 (China); Zhang, Li-Ming, E-mail: ceszhlm@mail.sysu.edu.cn [DSAPM Lab and PCFM Lab, Institute of Polymer Science, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275 (China)

    2014-01-01

    New heparin–indomethacin conjugate with an ester linkage was prepared by the carbodiimide-mediated condensation reaction, and then characterized by FTIR and {sup 1}HNMR analyses. Due to its amphiphilic character, such a conjugate could self-aggregate into spherical nanoparticles in aqueous system, as confirmed by fluorescence spectroscopy, dynamic light scattering and transmission electron microscopy. By the in vitro drug release tests, the resultant conjugate nanoparticles were found to have a sustained and esterase-sensitive release behavior for conjugated indomethacin. In addition, the uptake of these conjugate nanoparticles into human nasopharyngeal carcinoma CNE1 cells was confirmed by fluorescence microscopy. - Highlights: • New heparin–indomethacin conjugate with an ester linkage was prepared. • Such a conjugate could self-aggregate into spherical nanoparticles in aqueous system. • The resultant conjugate nanoparticles exhibited an esterase-sensitive drug release behavior. • The resultant conjugate nanoparticles showed the cellular uptake ability in CNE1 cells.

  17. O ensino de reações orgânicas usando química computacional: I. reações de adição eletrofílica a alquenos Teaching organic reactions using computational chemistry: I. eletrophilic addition reactions to alkenes

    Directory of Open Access Journals (Sweden)

    Arquimedes Mariano

    2008-01-01

    Full Text Available Basic concepts that play an important role in some organic reactions are revisited in this paper, which reports a pedagogical experience involving undergraduate and graduate students. A systematic procedure has been applied in order to use widespread available computational tools. This paper aims to discuss the use of computers in teaching electrophilic addition reactions to alkenes. Two classical examples have been investigated: addition to non-conjugated alkenes and addition to conjugated dienes. The results were compared with those normally discussed in organic textbooks. Several important concepts, such as conformational analysis and energy control (kinetic and thermodynamic involved in reaction mechanisms can be taught more efficiently if one connects theoretical and practical tools.

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

    OpenAIRE

    Price, Valerie J.; Huo, Wenwen; Sharifi, Ardalan; Palmer, Kelli L.

    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.?fa...

  19. In-depth evaluation of the cycloaddition-retro-Diels-Alder reaction for in vivo targeting with [111In]-DTPA-RGD conjugates

    International Nuclear Information System (INIS)

    Laverman, Peter; Meeuwissen, Silvie A.; Berkel, Sander S. van; Oyen, Wim J.G.; Delft, Floris L. van; Rutjes, Floris P.J.T.; Boerman, Otto C.

    2009-01-01

    Introduction: The spontaneous copper-free tandem 1,3-dipolar cycloaddition-retro-Diels-Alder (tandem crDA) reaction between cyclic Arg-Gly-Asp-D-Phe-Orn(N 3 ) [c(RGDfX)] and oxanorbornadiene-DTPA (o-DTPA) or methyloxanorbornadiene-DTPA (mo-DTPA) into two DTPA-c(RGDfX) regioisomers is characterized. Since there is no information on the stability and reaction rate of the tandem crDA reaction in biological media, we set out to characterize these reaction parameters. Methods: The effects of concentration of the reactants, temperature, pH and reaction environment (serum, blood) on the kinetics of the reaction were determined using 111 In-labeled oxanorbornadiene-DTPA analogs. The affinity of the radiolabeled conjugate was determined in a solid-phase α v β 3 integrin binding assay. Furthermore, the octanol-water partition coefficient was determined and, finally, the biodistribution of the labeled compounds in mice with subcutaneous α v β 3 -expressing tumors was determined. Results: Fifty percent conversion was reached after 26 h. Kinetic experiments furthermore established that the reaction rate of the tandem crDA reaction follows temperature- and concentration-dependent second-order kinetics, but is independent of the pH of the medium. Affinity of the two [ 111 In]DTPA-cRGDfX conjugates for α v β 3 integrin is 191 nM. Biodistribution studies showed specific (α v β 3 -mediated) uptake of [ 111 In]DTPA-c(RGDfX) in the tumor and in α v β 3 -expressing tissues. Conclusion: The tandem crDA reaction using methyl-substituted oxanorbornadiene is a versatile method for a single-step ligation that proceeds independently of pH and also proceeds in serum and blood. Currently, we are further looking into enhancement of reaction kinetics and exploitation of tandem crDA in vivo.

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

    KAUST Repository

    Li, Jinling; Jiao, Chongjun; Huang, Kuo-Wei; Wu, Jishan

    2011-01-01

    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.

  1. 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.

  2. 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; Palmer, Kelli L

    2016-01-01

    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. faecalis. IMPORTANCE

  3. The chemical foundations of nitroalkene fatty acid signaling through addition reactions with thiols.

    Science.gov (United States)

    Turell, Lucía; Steglich, Martina; Alvarez, Beatriz

    2018-03-22

    Nitroalkene fatty acids can be formed in vivo and administered exogenously. They exert pleiotropic signaling actions with cytoprotective and antiinflammatory effects. The presence of the potent electron withdrawing nitro group confers electrophilicity to the adjacent β-carbon. Thiols (precisely, thiolates) are strong nucleophiles and can react with nitroalkene fatty acids through reversible Michael addition reactions. In addition, nitroalkene fatty acids can undergo several other processes including metabolic oxidation, reduction, esterification, nitric oxide release and partition into hydrophobic compartments. The signaling actions of nitroalkenes are mainly mediated by reactions with critical thiols in regulatory proteins. Thus, the thio-Michael addition reaction provides a framework for understanding the molecular basis of the biological effects of nitroalkene fatty acids at the crossroads of thiol signaling and electrophilic lipid signaling. In this review, we describe the reactions of nitroalkene fatty acids in biological contexts. We focus on the Michael addition-elimination reaction with thiols and its mechanism, and extrapolate kinetic and thermodynamic considerations to in vivo settings. Copyright © 2018 Elsevier Inc. All rights reserved.

  4. DNA-based catalytic enantioselective intermolecular oxa-Michael addition reactions

    NARCIS (Netherlands)

    Megens, Rik P.; Roelfes, Gerard

    2012-01-01

    Using the DNA-based catalysis concept, a novel Cu(II) catalyzed enantioselective oxa-Michael addition of alcohols to enones is reported. Enantioselectivities of up to 86% were obtained. The presence of water is important for the reactivity, possibly by reverting unwanted side reactions such as

  5. 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.

  6. Kinetics of Hydrogen Abstraction and Addition Reactions of 3-Hexene by ȮH Radicals.

    Science.gov (United States)

    Yang, Feiyu; Deng, Fuquan; Pan, Youshun; Zhang, Yingjia; Tang, Chenglong; Huang, Zuohua

    2017-03-09

    Rate coefficients of H atom abstraction and H atom addition reactions of 3-hexene by the hydroxyl radicals were determined using both conventional transition-state theory and canonical variational transition-state theory, with the potential energy surface (PES) evaluated at the CCSD(T)/CBS//BHandHLYP/6-311G(d,p) level and quantum mechanical effect corrected by the compounded methods including one-dimensional Wigner method, multidimensional zero-curvature tunneling method, and small-curvature tunneling method. Results reveal that accounting for approximate 70% of the overall H atom abstractions occur in the allylic site via both direct and indirect channels. The indirect channel containing two van der Waals prereactive complexes exhibits two times larger rate coefficient relative to the direct one. The OH addition reaction also contains two van der Waals complexes, and its submerged barrier results in a negative temperature coefficient behavior at low temperatures. In contrast, The OH addition pathway dominates only at temperatures below 450 K whereas the H atom abstraction reactions dominate overwhelmingly at temperature over 1000 K. All of the rate coefficients calculated with an uncertainty of a factor of 5 were fitted in a quasi-Arrhenius formula. Analyses on the PES, minimum reaction path and activation free Gibbs energy were also performed in this study.

  7. An unprecedented chemospecific and stereoselective tandem nucleophilic addition/cycloaddition reaction of nucleophilic carbenes with ketenimines.

    Science.gov (United States)

    Cheng, Ying; Ma, Yang-Guang; Wang, Xiao-Rong; Mo, Jun-Ming

    2009-01-16

    The first study of the reaction between nucleophilic carbenes and ketenimines is reported. The interaction of thiazole and benzothiazole carbenes with ketenimines proceeded in a chemospecific and stereoselective manner to produce thiazole- and benzothiazole-spiro-pyrrole derivatives generally in good yields. The reaction was proposed to proceed via a tandem nucleophilic addition of carbene to the C=N bond of ketenimine followed by a stepwise [3+2] cycloaddition of the 1,3-dipolar intermediate with the C=C bond of ketenimine. This reaction provides a powerful protocol for the construction of novel polyfunctional thiazole-spiro-pyrrole or benzothiazole-spiro-pyrrole compounds that are not readily accessible by other methods.

  8. Quantifying atom addition reactions on amorphous solid water: a review of recent laboratory advances

    Science.gov (United States)

    He, Jiao; Vidali, Gianfranco

    2018-06-01

    Complex organic molecules found in space are mostly formed on and in the ice mantle covering interstellar dust grains. In clouds where ionizing irradiation is insignificant, chemical reactions on the ice mantle are dominated by thermal processes. Modeling of grain surface chemistry requires detailed information from the laboratory, including sticking coefficients, binding energies, diffusion energy barriers, mechanism of reaction, and chemical desorption rates. In this talk, recent laboratory advances in obtaining these information would be reviewed. Specifically, this talk will focus on the efforts in our group in: 1) Determining the mechanism of atomic hydrogen addition reactions on amorphous solid water (ASW); 2) Measuring the chemical desorption coefficient of H+O3-->O2+OH using the time-resolved scattering technique; and 3) Measuring the diffusion energy barrier of volatile molecules on ASW. Further laboratory studies will be suggested.This research was supported by NSF Astronomy & Astrophysics Research Grant #1615897.

  9. The kinetics of free radical metathetical and addition reactions in silane solutions

    International Nuclear Information System (INIS)

    Aloni, R.

    1976-12-01

    In this work radiolytic technique was employed for the initiation of free radical chainreactions in silane solution. The kinetic analysis of the chain mechanism in various solutions enabled the determination of the Arrhenius parameters for metathesis, addition and unimolecular decomposition reactions which make up the chainpropagation sequence in the systems studied. The following radical reactions were investigated: chlorine atom abstraction from chloromethanes by SiCl 3 and Et 3 Si radicals, and chlorine atom abstraction from chloroethanes by Et 3 Si radicals; unimolecular decomposition reactions and hydrogen atom abstraction, *from the solvent, of chloroethyl radicals in triethylsilane solutions; addition and abstraction reactions of Et 3 Si radicals with chloroolefins. Arrhenius parameters were determined for abstraction of chlorine atom from CH 3 Cl, CH 2 Cl 2 , CHCl 3 and CCl 4 , by SiCl 3 radicals and from CCl 4 , CHCl 3 , CH 2 Cl 2 , CCl 3 CN, C 2 Cl 5 H, sym-C 2 Cl 4 H 2 , asym-C 2 Cl 4 H 2 , 1.1.1-C 2 Cl 3 H 3 , 1.1.1-C 2 Dl 3 F 3 and 1.1-C 2 Cl 2 H 4 by Et 3 Si radicals. (author)

  10. Addition and spin exchange rate constants by longitudinal field μSR: the Mu + NO reaction

    International Nuclear Information System (INIS)

    Senba, Masayoshi; Gonzalez, A.C.; Kempton, J.R.; Arseneau, D.J.; Pan, J.J.; Tempelmann, A.; Fleming, D.G.

    1991-01-01

    The addition reaction Mu + NO + M → MuNO + M and the spin exchange reaction Mu(↑) + NO(↓)→Mu(↓)+NO(↑) have been measured by longitudinal field μSR at room temperature in the presence of up to 58 atm of N 2 as inert collider. The pressure dependence of the longitudinal relaxation rate due to the addition reaction (λ c ) demonstrates that the system is still in the low pressure regime in this pressure range. The corresponding termolecular rate constant has been determined as k 0.Mu =(1.10±0.25)x10 -32 cm 6 molecules -2 s -1 , almost 4 times smaller than the corresponding H atom reaction k 0,H =3.90x10 -32 cm 6 molecules -2 s -1 . The average value of the spin exchange rate constants in the 2.5-58 atm pressure range, k SE = (3.16±0.06)x10 -10 cm 3 molecule -1 s -1 , is in good agreement with previous values obtained by transverse field μSR. (orig.)

  11. 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

  12. 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.

  13. In-depth evaluation of the cycloaddition-retro-Diels-Alder reaction for in vivo targeting with [{sup 111}In]-DTPA-RGD conjugates

    Energy Technology Data Exchange (ETDEWEB)

    Laverman, Peter [Department of Nuclear Medicine, Radboud University Nijmegen Medical Centre, 6500 HB Nijmegen (Netherlands)], E-mail: p.laverman@nucmed.umcn.nl; Meeuwissen, Silvie A. [Department of Nuclear Medicine, Radboud University Nijmegen Medical Centre, 6500 HB Nijmegen (Netherlands); Institute for Molecules and Materials, Radboud University Nijmegen, 6500 GL Nijmegen (Netherlands); Berkel, Sander S. van [Institute for Molecules and Materials, Radboud University Nijmegen, 6500 GL Nijmegen (Netherlands); Oyen, Wim J.G. [Department of Nuclear Medicine, Radboud University Nijmegen Medical Centre, 6500 HB Nijmegen (Netherlands); Delft, Floris L. van; Rutjes, Floris P.J.T. [Institute for Molecules and Materials, Radboud University Nijmegen, 6500 GL Nijmegen (Netherlands); Boerman, Otto C. [Department of Nuclear Medicine, Radboud University Nijmegen Medical Centre, 6500 HB Nijmegen (Netherlands)

    2009-10-15

    Introduction: The spontaneous copper-free tandem 1,3-dipolar cycloaddition-retro-Diels-Alder (tandem crDA) reaction between cyclic Arg-Gly-Asp-D-Phe-Orn(N{sub 3}) [c(RGDfX)] and oxanorbornadiene-DTPA (o-DTPA) or methyloxanorbornadiene-DTPA (mo-DTPA) into two DTPA-c(RGDfX) regioisomers is characterized. Since there is no information on the stability and reaction rate of the tandem crDA reaction in biological media, we set out to characterize these reaction parameters. Methods: The effects of concentration of the reactants, temperature, pH and reaction environment (serum, blood) on the kinetics of the reaction were determined using {sup 111}In-labeled oxanorbornadiene-DTPA analogs. The affinity of the radiolabeled conjugate was determined in a solid-phase {alpha}{sub v}{beta}{sub 3} integrin binding assay. Furthermore, the octanol-water partition coefficient was determined and, finally, the biodistribution of the labeled compounds in mice with subcutaneous {alpha}{sub v}{beta}{sub 3}-expressing tumors was determined. Results: Fifty percent conversion was reached after 26 h. Kinetic experiments furthermore established that the reaction rate of the tandem crDA reaction follows temperature- and concentration-dependent second-order kinetics, but is independent of the pH of the medium. Affinity of the two [{sup 111}In]DTPA-cRGDfX conjugates for {alpha}{sub v}{beta}{sub 3} integrin is 191 nM. Biodistribution studies showed specific ({alpha}{sub v}{beta}{sub 3}-mediated) uptake of [{sup 111}In]DTPA-c(RGDfX) in the tumor and in {alpha}{sub v}{beta}{sub 3}-expressing tissues. Conclusion: The tandem crDA reaction using methyl-substituted oxanorbornadiene is a versatile method for a single-step ligation that proceeds independently of pH and also proceeds in serum and blood. Currently, we are further looking into enhancement of reaction kinetics and exploitation of tandem crDA in vivo.

  14. 76 FR 32332 - BASF Corp.; Filing of Food Additive Petition (Animal Use); Methyl Esters of Conjugated Linoleic...

    Science.gov (United States)

    2011-06-06

    .... FDA-2011-F-0365] BASF Corp.; Filing of Food Additive Petition (Animal Use); Methyl Esters of... petition proposing that the food additive regulations be amended to provide for the safe use of methyl... is given that a food additive petition (FAP 2269) has been filed by BASF Corp. (BASF), 100 Campus Dr...

  15. Study of Ni/Si(1 0 0) solid-state reaction with Al addition

    International Nuclear Information System (INIS)

    Huang Yifei; Jiang Yulong; Ru Guoping; Li Bingzong

    2008-01-01

    The characteristics of Ni/Si(1 0 0) solid-state reaction with Al addition (Ni/Al/Si(1 0 0), Ni/Al/Ni/Si(1 0 0) and Al/Ni/Si(1 0 0)) is studied. Ni and Al films were deposited on Si(1 0 0) substrate by ion beam sputtering. The solid-state reaction between metal films and Si was performed by rapid thermal annealing. The sheet resistance of the formed silicide film was measured by four-point probe method. The X-ray diffraction (XRD) was employed to detect the phases in the silicide film. The Auger electron spectroscopy was applied to reveal the element profiles in depth. The influence of Al addition on the Schottky barrier heights of the formed silicide/Si diodes was investigated by current-voltage measurements. The experimental results show that NiSi forms even with the addition of Al, although the formation temperature correspondingly changes. It is revealed that Ni silicidation is accompanied with Al diffusion in Ni film toward the film top surface and Al is the dominant diffusion species in Ni/Al system. However, no Ni x Al y phase is detected in the films and no significant Schottky barrier height modulation by the addition of Al is observed

  16. 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.

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

    International Nuclear Information System (INIS)

    Joo, Seong Ryu; Im, Pyeong Won; Kim, Jong Sung; Kim, Seung Hoi; Park Soo Youl

    2016-01-01

    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

  18. Different Effect of the Additional Electron-Withdrawing Cyano Group in Different Conjugation Bridge: The Adjusted Molecular Energy Levels and Largely Improved Photovoltaic Performance.

    Science.gov (United States)

    Li, Huiyang; Fang, Manman; Hou, Yingqin; Tang, Runli; Yang, Yizhou; Zhong, Cheng; Li, Qianqian; Li, Zhen

    2016-05-18

    Four organic sensitizers (LI-68-LI-71) bearing various conjugated bridges were designed and synthesized, in which the only difference between LI-68 and LI-69 (or LI-70 and LI-71) was the absence/presence of the CN group as the auxiliary electron acceptor. Interestingly, compared to the reference dye of LI-68, LI-69 bearing the additional CN group exhibited the bad performance with the decreased Jsc and Voc values. However, once one thiophene moiety near the anchor group was replaced by pyrrole with the electron-rich property, the resultant LI-71 exhibited a photoelectric conversion efficiency increase by about 3 folds from 2.75% (LI-69) to 7.95% (LI-71), displaying the synergistic effect of the two moieties (CN and pyrrole). Computational analysis disclosed that pyrrole as the auxiliary electron donor (D') in the conjugated bridge can compensate for the lower negative charge in the electron acceptor, which was caused by the CN group as the electron trap, leading to the more efficient electron injection and better photovoltaic performance.

  19. Conformationally constrained dipeptide surrogates with aromatic side-chains: synthesis of 4-aryl indolizidin-9-one amino acids by conjugate addition to a common alpha,omega-diaminoazelate enone intermediate.

    Science.gov (United States)

    Cluzeau, Jérôme; Lubell, William D

    2004-03-05

    Four methyl 9-oxo-8-(N-(Boc)-amino)-4-phenyl-1-azabicyclo[4.3.0]nonane carboxylates (11, 4-Ph-I(9)aa-OMe) were synthesized from (2S,8S,5E)-di-tert-butyl-4-oxo-5-ene-2,8-bis[N-(PhF)amino]azelate [(5E)-7, PhF = 9-(9-phenylfluorenyl)] via a seven-step process featuring a conjugate addition/reductive amination/lactam cyclization sequence. Various nucleophiles were used in the conjugate addition reactions on enone (5E)-7 as a general route for making alpha,omega-diaminoazelates possessing different substituents in good yield albeit low diastereoselectivity except in the case of aryl Grignard reagents (9/1 to 15/1 drs). 6-Phenylazelates (6S)-8d and (6R)-8d were separated by chromatography and diastereoselective precipitation and independently transformed into 4-Ph-I(9)aa-OMe. From (6S)-8d, (2S,4R,6R,8S)-4-Ph-I(9)aa-OMe 11 was prepared selectively in 51% yield. Reductive amination of (6R)-8d provided the desired pipecolates 9 along with desamino compound 10, which was minimized by performing the hydrogenation in the presence of ammonium acetate. Subsequent ester exchange, lactam cyclization, and amine protection provided three products (2R,4S,6S,8R)-, (2R,4S,6S,8S)-, and (2S,4S,6R,8S)-4-Ph-I(9)aa-OMe 11 in 10, 6, and 6% yields, respectively, from (6R)-8d. Ester hydrolysis of (2S,4R,6R,8S)-11 furnished 4-phenyl indolizidin-9-one N-(Boc)amino acid 3 as a novel constrained Ala-Phe dipeptide surrogate for studying conformation-activity relationships of biologically active peptides.

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

    KAUST Repository

    Guo, Hao; Xing, Fen; Du, Guang-Fen; Huang, Kuo-Wei; Dai, Bin; He, Lin

    2015-01-01

    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.

  1. 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.

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

    KAUST Repository

    Nikolka, Mark; Nasrallah, Iyad; Rose, Bradley Daniel; Ravva, Mahesh Kumar; Broch, Katharina; Sadhanala, Aditya; Harkin, David; Charmet, Jerome; Hurhangee, Michael; Brown, Adam; Illig, Steffen; Too, Patrick; Jongman, Jan; McCulloch, Iain; Bredas, Jean-Luc; Sirringhaus, Henning

    2016-01-01

    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.

  3. 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.

  4. Transparent Ethenylene-Bridged Polymethylsiloxane Aerogels: Mechanical Flexibility and Strength and Availability for Addition Reaction.

    Science.gov (United States)

    Shimizu, Taiyo; Kanamori, Kazuyoshi; Maeno, Ayaka; Kaji, Hironori; Doherty, Cara M; Nakanishi, Kazuki

    2017-05-09

    Transparent, low-density ethenylene-bridged polymethylsiloxane [Ethe-BPMS, O 2/2 (CH 3 )Si-CH═CH-Si(CH 3 )O 2/2 ] aerogels from 1,2-bis(methyldiethoxysilyl)ethene have successfully been synthesized via a sol-gel process. A two-step sol-gel process composed of hydrolysis under acidic conditions and polycondensation under basic conditions in a liquid surfactant produces a homogeneous pore structure based on cross-linked nanosized colloidal particles. Visible-light transmittance of the aerogels varies with the concentration of the base catalyst and reaches as high as 87% (at a wavelength of 550 nm for a 10 mm thick sample). Gelation and aging temperature strongly affect the deformation behavior of the resultant aerogels against uniaxial compression, and the obtained aerogels prepared at 80 °C show high elasticity after being unloaded. This highly resilient behavior is primarily derived from the rigidity of ethenylene groups, which is confirmed by a comparison with other aerogels with similar molecular structures, ethylene-bridged polymethylsiloxane and polymethylsilsesquioxane. Applicability of the addition reaction using a Diels-Alder reaction of benzocyclobutene has also been investigated, revealing that a successful addition takes place on the ethenylene linkings, which is verified using Raman and solid-state NMR spectroscopies. Insights into the effect of molecular structure on mechanical properties and the availability of surface functionalization provided in this study are important for realizing transparent aerogels with the desired functionality.

  5. Innocuous oil as an additive for reductive reactions involving zero valence iron

    International Nuclear Information System (INIS)

    Cary, J.W.; Cantrell, K.J.

    1994-11-01

    Reductive reactions involving zero valence iron appear to hold promise for in situ remediation of sites containing chlorinated hydrocarbon solvents and certain reducible metals and radionuclides. Treatment involves the injection of metallic iron and the creation of low levels of dissolved oxygen in the aqueous phase through oxidation of the metallic iron. The use of a biodegradable immiscible and innocuous organic liquid such as vegetable oil as an additive offers several intriguing possibilities. The oil phase creates a large oil-water interface that is immobile with respect to flow in the aqueous phase. This phase will act as a trap for chlorinated hydrocarbons and could potentially increase the reaction efficiency of reductive dehalogenation of chlorinated hydrocarbons by the metallic iron. When iron particles are suspended in the oil before injection they are preferentially held in the oil phase and tend to accumulate at the oil-water interface. Thus oil injection can serve as a mechanism for creating a stable porous curtain of metallic iron in the vadose to maintain a low oxygen environment which will minimize the consumption of the iron by molecular oxygen

  6. 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.

  7. 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

  8. Correction: Synthesis of pyrrolidine-3-carboxylic acid derivatives via asymmetric Michael addition reactions of carboxylate-substituted enones.

    Science.gov (United States)

    Yin, Feng; Garifullina, Ainash; Tanaka, Fujie

    2018-04-25

    Correction for 'Synthesis of pyrrolidine-3-carboxylic acid derivatives via asymmetric Michael addition reactions of carboxylate-substituted enones' by Feng Yin et al., Org. Biomol. Chem., 2017, 15, 6089-6092.

  9. 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.

  10. 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.

  11. 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.

  12. Theoretical Kinetics Analysis for Ḣ Atom Addition to 1,3-Butadiene and Related Reactions on the Ċ4H7 Potential 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

  13. Conjugated polymers developed from alkynes

    Institute of Scientific and Technical Information of China (English)

    Yajing Liu; Jacky W.Y.Lam; Ben Zhong Tang

    2015-01-01

    The numerous merits of conjugated polymers(CPs) have encouraged scientists to develop a variety of synthetic routes to CPs with diverse structures and functionalities. Among the large scope of substrates,alkyne plays an important role in constructing polymers with conjugated backbones. In addition to some well-developed reactions including Glaser–Hay and Sonogashira coupling, azide/thiol-yne click reaction and cyclotrimerization, some novel alkyne-based reactions have also been explored such as oxidative polycoupling, decarbonylative polycoupling and multicomponent tandem polymerizations. his review focuses on the recent progress on the synthetic methodology of CPs in the last ive years using monomers with two or more triple bonds and some of their high-technological applications. Selected examples of materials properties of these CPs are given in this review, such as luorescence response to chemical or physical stimuli, magnetism, white light emission, cell imaging and bioprobing. Finally, a short perspective is raised in regard to the outlook of the preparation methodologies, functionalities as well as potential applications of CPs in the future.

  14. Influence of additives on microstructures, mechanical properties and shock-induced reaction characteristics of Al/Ni composites

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, Wei; Zhang, Xianfeng, E-mail: lynx@mail.njust.edu.cn; Wu, Yang; He, Yong; Wang, Chuanting; Guo, Lei

    2015-11-05

    Granular composites containing aluminum (Al) and nickel (Ni) are typical structural energetic materials, which possess ideal combination of both mechanical properties and energy release capability. The influence of two additives, namely Teflon (PTFE) and copper (Cu), on mechanical properties and shock-induced chemical reaction (SICR) characteristics of Al/Ni material system has been investigated. Three composites, namely Al/Ni, Al/Ni/PTFE and Al/Ni/Cu with same volumetric ratio of Al powder to Ni powder, were processed by means of static pressing. Scanning electron microscopy was used to study the microstructure of the mentioned three composites. Quasi static compression tests were also conducted to determine the mechanical properties and fracture behavior of the mentioned three composites. It was shown that the additives affected both compressive strength and fracture mode of the three composites. Impact initiation experiments on the mentioned three composites were performed to determine their shock-induced chemical reaction characteristics by considering pressure histories measured in the test chamber. The experimental results showed that the additives had significant effects on critical initiation velocity, reaction rate, reaction efficiency and post-reaction behavior. - Highlights: • .Al/Ni, Al/Ni/PTFE and Al/Ni/Cu were processed by means of static pressing. • .Microstructures, mechanical properties and shock-induced reactions were studied. • .Microstructures affect both compressive strength and fracture mode. • .Impact velocity is an important factor in shock-induced chemical characteristics. • .Each additive has significant effects on energy release behavior.

  15. Influence of additives on microstructures, mechanical properties and shock-induced reaction characteristics of Al/Ni composites

    International Nuclear Information System (INIS)

    Xiong, Wei; Zhang, Xianfeng; Wu, Yang; He, Yong; Wang, Chuanting; Guo, Lei

    2015-01-01

    Granular composites containing aluminum (Al) and nickel (Ni) are typical structural energetic materials, which possess ideal combination of both mechanical properties and energy release capability. The influence of two additives, namely Teflon (PTFE) and copper (Cu), on mechanical properties and shock-induced chemical reaction (SICR) characteristics of Al/Ni material system has been investigated. Three composites, namely Al/Ni, Al/Ni/PTFE and Al/Ni/Cu with same volumetric ratio of Al powder to Ni powder, were processed by means of static pressing. Scanning electron microscopy was used to study the microstructure of the mentioned three composites. Quasi static compression tests were also conducted to determine the mechanical properties and fracture behavior of the mentioned three composites. It was shown that the additives affected both compressive strength and fracture mode of the three composites. Impact initiation experiments on the mentioned three composites were performed to determine their shock-induced chemical reaction characteristics by considering pressure histories measured in the test chamber. The experimental results showed that the additives had significant effects on critical initiation velocity, reaction rate, reaction efficiency and post-reaction behavior. - Highlights: • .Al/Ni, Al/Ni/PTFE and Al/Ni/Cu were processed by means of static pressing. • .Microstructures, mechanical properties and shock-induced reactions were studied. • .Microstructures affect both compressive strength and fracture mode. • .Impact velocity is an important factor in shock-induced chemical characteristics. • .Each additive has significant effects on energy release behavior

  16. 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.

  17. 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; Gehrig, Dominik; Zhang, Fan; Lu, Chenbao; Zhang, Chao; Cai, Ming; Wang, Yuanyuan; Laquai, Fré dé ric; Zhuang, Xiaodong; Feng, Xinliang

    2016-01-01

    © 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.

  18. 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.

  19. Effect of ultrasound treatment on the wet heating Maillard reaction between mung bean [Vigna radiate (L.)] protein isolates and glucose and on structural and physico-chemical properties of conjugates.

    Science.gov (United States)

    Wang, Zhongjiang; Han, Feifei; Sui, Xiaonan; Qi, Baokun; Yang, Yong; Zhang, Hui; Wang, Rui; Li, Yang; Jiang, Lianzhou

    2016-03-30

    The objective of this study was to determine the effect of ultrasound treatment on the wet heating Maillard reaction between mung bean protein isolates (MBPIs) and glucose, and on structural and physico-chemical properties of the conjugates. The degree of glycosylation of MBPI-glucose conjugates treated by ultrasound treatment and wet heating (MBPI-GUH) was higher than that of MBPI-glucose conjugates only treated by wet heating (MBPI-GH). Solubility, emulsification activity, emulsification stability and surface hydrophobicity of MBPI-GUH were higher than that of MBPI-GH. Grafted MBPIs had a lower content of α-helix and unordered coil, but a higher content of β-sheet and β-turn structure than MBPIs. No significant structural changes were observed in β-turn and random coil structure of MBPI-GUH, while α-helix content increased with ultrasonic time, and decreased at 300 W ultrasonic power with the increase of β-sheet. MBPI-GUH had a less compact tertiary structure compared to MBPI-GH and MBPI. Grafting MBPIs with glucose formed conjugates of higher molecular weight, while no significant changes were observed in electrophoresis profiles of MBPI-GUH. Ultrasound-assisted wet heating Maillard reaction between MBPIs and glucose could be a promising way to improve functional properties of MBPIs. © 2015 Society of Chemical Industry.

  20. Theoretical study of the oxidation mechanisms of naphthalene initiated by hydroxyl radicals: the O2 addition reaction pathways.

    Science.gov (United States)

    Shiroudi, A; Deleuze, M S; Canneaux, S

    2015-05-28

    Atmospheric oxidation of the naphthalene-OH adduct [C10H8OH]˙ (R1) by molecular oxygen in its triplet electronic ground state has been studied using density functional theory along with the B3LYP, ωB97XD, UM05-2x and UM06-2x exchange-correlation functionals. From a thermodynamic viewpoint, the most favourable process is O2 addition at the C2 position in syn mode, followed by O2 addition at the C2 position in anti mode, O2 addition at the C4 position in syn mode, and O2 addition at the C4 position in anti mode, as the second, third and fourth most favourable processes. The syn modes of addition at these positions are thermodynamically favoured over the anti ones by the formation of an intramolecular hydrogen bond between the hydroxyl and peroxy substituents. Analysis of the computed structures, bond orders and free energy profiles demonstrate that the reaction steps involved in the oxidation of the naphthalene-OH adduct by O2 satisfy Hammond's principle. Kinetic rate constants and branching ratios under atmospheric pressure and in the fall-off regime have been supplied, using transition state and RRKM theories. By comparison with experiment, these data confirm the relevance of a two-step reaction mechanism. Whatever the addition mode, O2 addition in C4 position is kinetically favoured over O2 addition in C2 position, in contrast with the expectations drawn from thermodynamics and reaction energies. Under a kinetic control of the reaction, and in line with the computed reaction energy barriers, the most efficient process is O2 addition at the C4 position in syn mode, followed by O2 addition at the C2 position in syn mode, O2 addition at the C4 position in anti mode, and O2 addition at the C2 position in anti mode as the second, third and fourth most rapid processes. The computed branching ratios also indicate that the regioselectivity of the reaction decreases with increasing temperatures and decreasing pressures.

  1. 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.

  2. Addition reaction of adamantylideneadamantane with Br2 and 2Br2: a computational study.

    Science.gov (United States)

    Islam, Shahidul M; Poirier, Raymond A

    2008-01-10

    Ab initio calculations were carried out for the reaction of adamantylideneadamantane (Ad=Ad) with Br2 and 2Br2. Geometries of the reactants, transition states, intermediates, and products were optimized at HF and B3LYP levels of theory using the 6-31G(d) basis set. Energies were also obtained using single point calculations at the MP2/6-31G(d)//HF/6-31G(d), MP2/6-31G(d)//B3LYP/6-31G(d), and B3LYP/6-31+G(d)//B3LYP/6-31G(d) levels of theory. Intrinsic reaction coordinate (IRC) calculations were performed to characterize the transition states on the potential energy surface. Only one pathway was found for the reaction of Ad=Ad with one Br2 producing a bromonium/bromide ion pair. Three mechanisms for the reaction of Ad=Ad with 2Br2 were found, leading to three different structural forms of the bromonium/Br3- ion pair. Activation energies, free energies, and enthalpies of activation along with the relative stability of products for each reaction pathway were calculated. The reaction of Ad=Ad with 2Br2 was strongly favored over the reaction with only one Br2. According to B3LYP/6-31G(d) and single point calculations at MP2, the most stable bromonium/Br3- ion pair would form spontaneously. The most stable of the three bromonium/Br3- ion pairs has a structure very similar to the observed X-ray structure. Free energies of activation and relative stabilities of reactants and products in CCl4 and CH2ClCH2Cl were also calculated with PCM using the united atom (UA0) cavity model and, in general, results similar to the gas phase were obtained. An optimized structure for the trans-1,2-dibromo product was also found at all levels of theory both in gas phase and in solution, but no transition state leading to the trans-1,2-dibromo product was obtained.

  3. Gamma-induced reactions of bromo-ethane with olefines. Addition of ethyl radicals to hexene-1 and propylene

    International Nuclear Information System (INIS)

    Myshkin, V.E.; Shostenko, A.G.; Zagorets, P.A.; Pchelkin, A.I.; Markova, K.G.

    1978-01-01

    Radiation interaction of bromo-ethane with propylene and 1-hexene has been studied with the aim to investigate the action of γ-radiation on bromalkanes. The absorbed dose rate is 50 rad/s. The reaction products separated by preparative chromatography have been identified with infrared spectroscopy, elemental, chromatographic, and other physico-chemical methods of analysis. It has been established that the reaction with propylene gives rise to telomers whereas interaction of bromo-ethane with 1-hexene yields only the addition product (4-bromoctane). The activation energy of the reactions of adding ethyl radicals to 1-hexene and propylene has been found equal to (3.8+-0.4 kcal/mol) and (2.2+-0.2 kcal/mol), respectively. The activation energy of the reaction of chain transfer through bromo-ethane is (3.7+-0.3 kcal/mol.)

  4. Reactions of homolytic addition of polyhalogenoalkanes to unsafurated tin-organic compounds and their application in organic synthesis

    International Nuclear Information System (INIS)

    Rakhlin, V.I.; Mirskov, R.G.; Voronkov, M.G.

    1996-01-01

    Reactions of homolytic addition of polyhalogenoalkanes; including iodine compounds, to tin trialkylalkenyl derivatives are considered. They may be used as convenient method for synthesis of various polyhalogenoalkylsubstituted alicycles and heterocycles: cyclopropane, 1.3-dioxocycloalkanes, thiacycloalkanes, various nitrogen-containing heterocycles. 27 refs

  5. Small angle scattering from protein/sugar conjugates

    Energy Technology Data Exchange (ETDEWEB)

    Jackson, Andrew [Research School of Chemistry, Australian National University, Canberra, ACT 0200 (Australia)]. E-mail: ajj@nist.gov; White, John [Research School of Chemistry, Australian National University, Canberra, ACT 0200 (Australia)

    2006-11-15

    The Maillard reaction between free amine groups on proteins and sugars is well known. We have examined the effect of the reaction of the casein group of milk proteins with sugars on their nanoscale structure and aggregation. The small angle neutron scattering from beta casein and sodium caseinate and their sugar conjugates have been studied as a function of solution concentration. At high conjugate concentration (greater than ca. 5mg/ml) the addition of sugar reduces supra-micellar aggregation of the protein whilst at lower concentration, where the protein is expected to be deaggregated already, little effect is seen. Guinier analysis of the scattering data show a radius of gyration of around 75A-bar for beta casein in solution and around 80A-bar for the sucrose conjugate.

  6. Small angle scattering from protein/sugar conjugates

    International Nuclear Information System (INIS)

    Jackson, Andrew; White, John

    2006-01-01

    The Maillard reaction between free amine groups on proteins and sugars is well known. We have examined the effect of the reaction of the casein group of milk proteins with sugars on their nanoscale structure and aggregation. The small angle neutron scattering from beta casein and sodium caseinate and their sugar conjugates have been studied as a function of solution concentration. At high conjugate concentration (greater than ca. 5mg/ml) the addition of sugar reduces supra-micellar aggregation of the protein whilst at lower concentration, where the protein is expected to be deaggregated already, little effect is seen. Guinier analysis of the scattering data show a radius of gyration of around 75A-bar for beta casein in solution and around 80A-bar for the sucrose conjugate

  7. Small angle scattering from protein/sugar conjugates

    Science.gov (United States)

    Jackson, Andrew; White, John

    2006-11-01

    The Maillard reaction between free amine groups on proteins and sugars is well known. We have examined the effect of the reaction of the casein group of milk proteins with sugars on their nanoscale structure and aggregation. The small angle neutron scattering from beta casein and sodium caseinate and their sugar conjugates have been studied as a function of solution concentration. At high conjugate concentration (greater than ca. 5 mg/ml) the addition of sugar reduces supra-micellar aggregation of the protein whilst at lower concentration, where the protein is expected to be deaggregated already, little effect is seen. Guinier analysis of the scattering data show a radius of gyration of around 75 A˚ for beta casein in solution and around 80 A˚ for the sucrose conjugate.

  8. Development of a quantum chemical molecular dynamics tribochemical simulator and its application to tribochemical reaction dynamics of lubricant additives

    International Nuclear Information System (INIS)

    Onodera, T; Tsuboi, H; Hatakeyama, N; Endou, A; Miyamoto, A; Miura, R; Takaba, H; Suzuki, A; Kubo, M

    2010-01-01

    Tribology at the atomistic and molecular levels has been theoretically studied by a classical molecular dynamics (MD) method. However, this method inherently cannot simulate the tribochemical reaction dynamics because it does not consider the electrons in nature. Although the first-principles based MD method has recently been used for understanding the chemical reaction dynamics of several molecules in the tribology field, the method cannot simulate the tribochemical reaction dynamics of a large complex system including solid surfaces and interfaces due to its huge computation costs. On the other hand, we have developed a quantum chemical MD tribochemical simulator on the basis of a hybrid tight-binding quantum chemical/classical MD method. In the simulator, the central part of the chemical reaction dynamics is calculated by the tight-binding quantum chemical MD method, and the remaining part is calculated by the classical MD method. Therefore, the developed tribochemical simulator realizes the study on tribochemical reaction dynamics of a large complex system, which cannot be treated by using the conventional classical MD or the first-principles MD methods. In this paper, we review our developed quantum chemical MD tribochemical simulator and its application to the tribochemical reaction dynamics of a few lubricant additives

  9. 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.

  10. 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…

  11. An efficient oxa-Michael addition to diethyl vinylphosphonate under mild reaction conditions

    Czech Academy of Sciences Publication Activity Database

    Baszczyňski, Ondřej; Jansa, Petr; Dračínský, Martin; Kaiser, Martin Maxmilian; Špaček, Petr; Janeba, Zlatko

    2012-01-01

    Roč. 2, č. 4 (2012), s. 1282-1284 ISSN 2046-2069 R&D Projects: GA MV VG20102015046 Institutional research plan: CEZ:AV0Z40550506 Keywords : oxa-Michael addition * secondary alcohols * diethyl vinylphosphonate Subject RIV: CC - Organic Chemistry Impact factor: 2.562, year: 2012

  12. Delocalization model of regioselectivity and reactivity of free radicals in reactions of addition to olefins

    International Nuclear Information System (INIS)

    Volovik, S.V.; Dyadyusha, G.G.; Staninets, V.I.

    1987-01-01

    On the basis of the concept of polarity (philicity) of free radicals as proposed by the authors, within the framework of methods of qualitative surfaces of potential energy (linear combinations of configurations of fragments) and stabilization energy, an effective model has been developed for the regioselectivity and reactivity of radicals in processes of addition. A critical examination is made of certain key aspects of the change in regiochemistry and reactivity with changes in the electronic structure of the free radical and substrate. The dominant trends in regioselectivity and reactivity in processes of free-radical addition to olefins are controlled by electronic effects and can be predicted by analyzing interactions of diabatic potential energy surfaces or orbital interactions for a system consisting of a free radical and an unsaturated substrate

  13. Reaction phenomena of catalytic partial oxidation of methane under the impact of carbon dioxide addition and heat recirculation

    International Nuclear Information System (INIS)

    Chen, Wei-Hsin; Lin, Shih-Cheng

    2015-01-01

    The reaction phenomena of CPOM (catalytic partial oxidation of methane) in a Swiss-roll reactor are studied numerically where a rhodium-based catalyst bed is embedded at the center of the reactor. CO 2 is added into the feed gas and excess enthalpy recovery is performed to evaluate their influences on CPOM performance. In the study, the mole ratio of O 2 to CH 4 (O 2 /CH 4 ratio) is fixed at 0.5 and the mole ratio of CO 2 to O 2 (CO 2 /O 2 ratio) is in the range of 0–2. The results reveal that CO 2 addition into the influent has a slight effect on methane combustion, but significantly enhances dry reforming and suppresses steam reforming. The reaction extents of steam reforming and dry reforming in CPOM without heat recovery and CO 2 addition are in a comparable state. Once CO 2 is added into the feed gas, the dry reforming is enhanced, thereby dominating CH 4 consumption. Compared to the reactor without excess enthalpy recovery, heat recirculation drastically increases the maximum reaction temperature and CH 4 conversion in the catalyst bed; it also intensifies the H 2 selectivity, H 2 yield, CO 2 conversion, and syngas production rate. The predictions indicate that the heat recirculation is able to improve the syngas formation up to 45%. - Highlights: • Catalytic partial oxidation of methane with CO 2 addition and heat recovery is studied. • CO 2 addition has a slight effect on methane combustion. • CO 2 addition significantly enhances dry reforming and suppresses steam reforming. • Dry reforming dominates CH 4 consumption when CO 2 addition is large. • Heat recirculation can improve the syngas formation up to 45%

  14. 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.

  15. A Fluorescent Molecular Probe for the Detection of Hydrogen Based on Oxidative Addition Reactions with Crabtree-Type Hydrogenation Catalysts.

    Science.gov (United States)

    Kos, Pavlo; Plenio, Herbert

    2015-11-02

    A Crabtree-type Ir(I) complex tagged with a fluorescent dye (bodipy) was synthesized. The oxidative addition of H2 converts the weakly fluorescent Ir(I) complex (Φ=0.038) into a highly fluorescent Ir(III) species (Φ=0.51). This fluorogenic reaction can be utilized for the detection of H2 and to probe the oxidative addition step in the catalytic hydrogenation of olefins. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Effect of reaction systems and surfactant additives on the morphology evolution of hydroxyapatite nanorods obtained via a hydrothermal route

    Energy Technology Data Exchange (ETDEWEB)

    Ma Tianyuan; Xia Zhiguo [School of Materials Sciences and Technology, China University of Geosciences, Beijing 100083 (China); Liao Libing, E-mail: lbliao@cugb.edu.cn [School of Materials Sciences and Technology, China University of Geosciences, Beijing 100083 (China)

    2011-02-15

    Well-dispersed hydroxyapatite (HA) nanorods with different morphologies were synthesized by a hydrothermal method in oleic acid, ethanol and water reaction system, and the surfactant assisted modifications effect was also comparatively studied. The structure and morphology of samples were characterized using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM), respectively. The effect of reaction systems and surfactant additives on the morphology evolution of HA nanorods were discussed in detail. The results showed that the controlled experimental conditions in the systems, such as the content ratio of oleic acid/ethanol, pH value and the content ratio of Ca/P source had an significant effect on the morphology evolution of as-prepared HA nanorods. Further, the selected surfactant additives, such as cetyltriethylammnonium bromide (CTAB), sodium dodecyl sulfate (K12) also play an important role in the formation of the uniform morphology of HA nanorods. Some possible formation mechanisms of the HA nanorods in the present reaction systems is proposed.

  17. Etching kinetics of swift heavy ion irradiated silicone rubber with insoluble additives or reaction products

    International Nuclear Information System (INIS)

    Fink, D.; Mueller, M.; Petrov, A.; Farenzena, L.; Behar, M.; Papaleo, R.P.

    2003-01-01

    It is normally understood as a basic precondition of the etching of swift heavy ion tracks in polymers that both the additives and etching products are soluble in the etchant. If this is not given, the polymer surface may be gradually blocked by the deposition of the insoluble material that acts as a diffusion barrier for the penetration of fresh etchant into the tracks, and therefore the effective track etching speed will gradually be reduced. The etching kinetics is developed for that case, and the theory is compared with first experimental findings. For that purpose we have taken commercial silicone rubber foils as test materials, that were irradiated with GeV heavy ions through a mask at a fluence that corresponds to the onset of track overlapping. After etching with NaOH, the corresponding etching speed was recorded via the reduction of the foil thickness. The etching speed is seen to decrease with exposure time, in parallel to the development of an insoluble surface layer. It is discussed how to prevent that surface blocking, to maintain a high etching speed

  18. Influence of Mg O and B2O3 addition on reaction sintering, properties and microstructure of Aluminum titanate

    International Nuclear Information System (INIS)

    Ajami, R.; Sarpoolaki, H.; Akbari, G. H.

    2007-01-01

    The effect of Mg O and B 2 O 3 on the formation, physical properties, phase analysis and microstructure of aluminum titanate was investigated. Density results showed the sample containing of 1 wt percent B 2 O 3 and 2 wt percent Mg O leads to the highest density while the lowest density was seen in samples containing 1 wt percent B 2 O 3 compared to pure aluminum titanate. Regarding the phase analysis of samples, Mg O was found most effective additive on reaction sintering of aluminum titanate through the intermediate phases. Furthermore at the temperatures above 1350 d eg C , B 2 O 3 promote the formation reaction of aluminum titanate. Microstructural analysis showed the samples containing Mg O are fine grain and homogeneous. Thermal expansion coefficient of samples with additives is greater than pure aluminum titanate. Pure aluminum titanate samples and one containing B 2 O 3 additive decompose to Al 2 O 3 and TiO 2 after 5 hours heat treatment at 1150 d eg C while the samples containing 2 wt percent Mg O was stable even after 25 hours

  19. 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.

  20. Novel support effects on the mechanism of propene-deuterium: Addition and exchange reactions over dispersed ZrO2

    International Nuclear Information System (INIS)

    Naito, Shuichi; Tanimoto, Mitsutoshi

    1995-01-01

    The effect on the rate and mechanisms of propene-deuterium reactions of dispersing ZrO 2 on various supports such as silica, alumina, and titanium dioxide has been studied by microwave spectroscopic analysis of monodeuteropropene as well as by kinetic investigation. By dispersal of ZrO 2 on these supports, the rate of the C 3 H 6 -D 2 reactions is increased considerbly compared to that over unsupported ZrO 2 , with the decrease of activation energy. Hydrogen exchange in propene proceeds simultaneously with addition via the associative mechanism through n-propyl and s-propyl intermediates. Through XPS analysis of ZrO 2 /SiO 2 , it was found that a monolayer of ZrO 2 is formed over the silica support. The monolayer catalyst exhibits catalytic behavior quite different from that of unsupported ZrO 2 . On the other hand, alumina surfaces modified by ZrO 2 layers may be the main active sites in the case of ZrO 2 /Al 2 O 3 . The marked enhancement of the reaction rate in the lower loading region of ZrO 2 /TiO 2 may be explained by the strong interaction of atomically dispersed zirconium ions with active centers on TiO 2 . 28 refs., 10 figs., 1 tab

  1. The effect of addition of primary positive salts, complex salt, on the ionic strength and rate constant at various temperatures by reaction kinetics

    Science.gov (United States)

    Kurade, S. S.; Ramteke, A. A.

    2018-05-01

    In this work, we have investigated the rate of reaction by using ionic strength at different temperatures. The main goal of this experiment is to determine the relation between ionic strength with reaction rate, reaction time and rate constant with temperature. It is observed that the addition of positive salt indicate the increasing ionic strength with increase in run time at various temperatures. Thus the temperature affects the speed of reaction and mechanism by which chemical reaction occurs and time variable plays vital role in the progress of reaction at different temperatures.

  2. Reactions of N+ ions with ethylene: a theoretical study on the addition mechanism into the olefin double bond

    International Nuclear Information System (INIS)

    Di Stefano, Marco; Rosi, Marzio; Sgamellotti, Antonio

    2004-01-01

    The potential energy surface of the reaction between ethylene molecules and N + ions is investigated by using the DFT hybrid functional B3LYP with the 6-31G* basis set. The addition channel leading to the intermediate C 2 NH 4 + is considered. We study eighteen structures of the triplet C 2 NH 4 + cations and the transition states for their isomerizations. Then, we consider the release of a H atom to form the doublet C 2 NH 3 + cations. To obtain more accurate values of reaction energetics and barrier heights, coupled cluster CCSD(T) calculations with the 6-311G** basis set are performed on the B3LYP/6-31G* optimized geometries. The addition of N + into C 2 H 4 is computed as a barrierless process leading to the triplet 1-aziridynil cation which, by ring opening, can easily evolve into the 2-azaallyl isomer. This species can then release a hydrogen atom to form the 2-azaallene cation, process that is computed to be the most likely channel

  3. A stereo-controlled route to conjugated E-enediynes

    Institute of Scientific and Technical Information of China (English)

    ZHOU Lei; JIANG Huanfeng

    2007-01-01

    3-Ene-1,5-diynes are important components of many enediyne antitumor agents and luminescent materials.A stereo-controlled approach to the synthesis of E-enediynes was developed,and it consists of the following two steps:(1)a mild and economical synthesis of dihalo vinyl derivatives via addition of CuBr2 to alkynes;(2) the Sonogashira coupling reaction of the dihalo vinyl derivatives with terminal alkynes to form conjugated enediynes.

  4. Diastereoselective synthesis of pyridyl substituted thiazolidin-4-ones. New ligands for the Cu(I) catalyzed asymmetric conjugate addition of diethylzinc to enones

    NARCIS (Netherlands)

    Vries, André H.M. de; Hof, Robert P.; Staal, Danny; Kellogg, Richard M.; Feringa, Bernard

    1997-01-01

    Several novel thiazolidin-4-ones have been synthesized from chiral non-racemic alpha-mercapto acids by a three component reaction in high yields and with diastereomeric excesses up to 91%. After recrystallization, the thiazolidinones were obtained diastereomerically pure and were employed as chiral

  5. Reaction

    African Journals Online (AJOL)

    abp

    19 oct. 2017 ... Reaction to Mohamed Said Nakhli et al. concerning the article: "When the axillary block remains the only alternative in a 5 year old child". .... Bertini L1, Savoia G, De Nicola A, Ivani G, Gravino E, Albani A et al ... 2010;7(2):101-.

  6. 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…

  7. 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…

  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; Lee, Richmond; Li, Jiangtao; Ye, Xinyi; Hong, San-Ni; Qiu, Shuai; Coote, Michelle L.; Jiang, Zhiyong

    2015-01-01

    -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

  9. 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.

  10. Pyridine group assisted addition of diazo-compounds to imines in the 3-CC reaction of 2-aminopyridines, aldehydes, and diazo-compounds.

    Science.gov (United States)

    Gulevich, Anton V; Helan, Victoria; Wink, Donald J; Gevorgyan, Vladimir

    2013-02-15

    A novel three-component coupling (3-CC) reaction of 2-aminoazines, aromatic aldehydes, and diazo-compounds producing polyfunctional β-amino-α-diazo-compounds has been developed. The reaction features an unprecedented heterocycle-assisted addition of a diazo-compound to an imine. The obtained diazoesters were efficiently converted into valuable heterocycles as well as β-amino acid derivatives.

  11. 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.

  12. Properties of acid gels made from sodium caseinate-maltodextrin conjugates prepared by a wet heating method.

    Science.gov (United States)

    Zhang, Shuwen; Gong, Yuansheng; Khanal, Som; Lu, Yanjie; Lucey, John A

    2017-11-01

    Covalent attachment of polysaccharides to proteins (conjugation) via the Maillard reaction has been extensively studied. Conjugation can lead to a significant improvement in protein functionality (e.g., solubility, emulsification, and heat stability). Caseins have previously been successfully conjugated with maltodextrin (Md), but the effect on the detailed acid gelation properties has not been examined. We studied the effect of conjugating sodium caseinate (NaCN) with 3 different sized Md samples via the Maillard reaction in aqueous solutions. The Md samples had dextrose equivalents of 4 to 7, 9 to 12, and 20 to 23 for Md40, Md100, and Md200, respectively. The conjugation reaction was performed in mixtures with 5% NaCN and 5% Md, which were heated at 90°C for 10 h. The degree of conjugation was estimated from the reduction in free amino groups as well as color changes. Sodium dodecyl sulfate-PAGE analysis was performed to confirm conjugation by employing staining of both protein and carbohydrate bands. The molar mass of samples was determined by size-exclusion chromatography coupled with multi-angle laser light scattering. After the conjugation reaction, samples were then gelled by the addition of 0.63% (wt/vol) glucono-δ-lactone at 30°C, such that samples reached pH 4.6 after about 13 h. The rheological properties of samples during acidification was monitored by small-strain dynamic oscillatory rheology. The microstructure of acid gels at pH 4.6 was examined by fluorescence microscopy. Conjugation resulted in a loss of 10.8, 8.8, and 11.9% of the available amino groups in the protein for the NaCN-Md40 conjugates (C40), NaCN-Md100 conjugates (C100), and NaCN-Md100 conjugates (C200), respectively. With a decrease in the size of the type of Md, an increase occurred in the molar mass of the resultant conjugate. The weight average molar masses of NaCN-Md samples were 340, 368, and 425 kDa for the conjugates C40, C100, and C200, respectively. Addition of Md to Na

  13. Probing the Influence of the Conjugated Structure and Halogen Atoms of Poly-Iron-Phthalocyanine on the Oxygen Reduction Reaction by X-ray Absorption Spectroscopy and Density Functional Theory

    International Nuclear Information System (INIS)

    Peng, Yingxiang; Cui, Lufang; Yang, Shifeng; Fu, Jingjing; Zheng, Lirong; Liao, Yi; Li, Kai; Zuo, Xia; Xia, Dingguo

    2015-01-01

    Metal-phthalocyanine (MPc) macrocyclic catalysts have been perceived as promising alternatives to Pt and Pt-based catalysts for the oxygen reduction reaction (ORR). However, the effect of different MPc molecular structures on the ORR has rarely been reported in depth. Herein, iron-phthalocyanine polymers (poly-FePcs) and multi-walled carbon nanotubes (MWCNTs) composites with different structures were synthesized using microwave method. The relationship between their molecular structure and electrocatalytic activity was fully revealed by density functional theory (DFT) and X-ray fine absorption spectroscopy (XAFS). DFT calculations revealed that the introduction of halogen atoms can increase the ion potential (IP) and the dioxo-binding energy () of the poly-FePcs. Meanwhile, their conjugated structure not only facilitates electronic transmission, but also significantly increases . XAFS analysis indicated that the poly-FePc/MWCNTs composites had a square planar structure and a smaller of phthalocyanine ring (Fe-N 4 structure) skeleton structure radius when a larger conjugated structure or introduced halogen atoms was present. The experimental results suggest that the these changes in properties arising from the different structures of the MPc macrocyclic compounds led to a huge effect on their ORR electrochemical activities, and provide a guide to obtaining promising electrochemical catalysts

  14. Part I. Naltrexone-derived conjugate addition ligands for opioid receptors. Part II. Chemical and enantioselective aspects of the metabolism of verapamil

    International Nuclear Information System (INIS)

    Olsen, L.D.

    1987-01-01

    Selective chemoaffinity ligands to aid in identification and purification of opioid receptor subtypes were prepared from 6α- and 6β-naltrexol, obtained stereoselectively from the μ-receptor antagonist naltrexone. The targets were the 6α- and 6β-methacrylate ethers and 6α- and 6β-methacrylate esters prepared from reaction of 6α- and 6β-naltrexol with methyl α-(bromomethyl)acrylate or methacryloyl chloride. Of three methacrylate derivatives, the 6α-ether was the most potent in an opioid receptor binding assay with [ 3 H]-naltrexone. In the presence of sodium ion, preincubation of the 6α-ether resulted in recovery of about 60% of original [ 3 H]-naltrexone binding suggesting some irreversible effects. The methacrylate esters precipitated withdrawal in morphine dependent monkeys. The enantiomers of verapamil, a calcium channel antagonist, have different pharmacological and pharmacokinetic properties. The oxidative metabolism of verapamil was studied in rat and human liver microsomes and in man after a single oral dose

  15. Part I. Naltrexone-derived conjugate addition ligands for opioid receptors. Part II. Chemical and enantioselective aspects of the metabolism of verapamil

    Energy Technology Data Exchange (ETDEWEB)

    Olsen, L.D.

    1987-01-01

    Selective chemoaffinity ligands to aid in identification and purification of opioid receptor subtypes were prepared from 6..cap alpha..- and 6..beta..-naltrexol, obtained stereoselectively from the ..mu..-receptor antagonist naltrexone. The targets were the 6..cap alpha..- and 6..beta..-methacrylate ethers and 6..cap alpha..- and 6..beta..-methacrylate esters prepared from reaction of 6..cap alpha..- and 6..beta..-naltrexol with methyl ..cap alpha..-(bromomethyl)acrylate or methacryloyl chloride. Of three methacrylate derivatives, the 6..cap alpha..-ether was the most potent in an opioid receptor binding assay with (/sup 3/H)-naltrexone. In the presence of sodium ion, preincubation of the 6..cap alpha..-ether resulted in recovery of about 60% of original (/sup 3/H)-naltrexone binding suggesting some irreversible effects. The methacrylate esters precipitated withdrawal in morphine dependent monkeys. The enantiomers of verapamil, a calcium channel antagonist, have different pharmacological and pharmacokinetic properties. The oxidative metabolism of verapamil was studied in rat and human liver microsomes and in man after a single oral dose.

  16. 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

  17. 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)

  18. Transition-metal-free synthesis of N-(1-alkenyl)imidazoles by potassium phosphate-promoted addition reaction of alkynes to imidazoles.

    Science.gov (United States)

    Lu, Linhua; Yan, Hong; Liu, Defu; Rong, Guangwei; Mao, Jincheng

    2014-01-01

    The addition reaction of alkynes to N-heterocycles by simply heating in DMSO with potassium phosphate is reported. Good yields with high stereoselectivity could be achieved for a range of substrates. The scope is quite general for both amines and phenylacetylenes. In addition, internal alkynes and α-bromostyrene were also examined in this reaction. This process is efficient and useful for the synthesis of (Z)-N-(1-alkenyl)imidazoles and related Z products. Thus, the reaction is useful because of the importance of the imidazole scaffold. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Asymmetric synthesis of all-carbon benzylic quaternary stereocenters via Cu-catalyzed conjugate addition of dialkylzinc reagents to 5-(1-arylalkylidene) Meldrum's acids.

    Science.gov (United States)

    Fillion, Eric; Wilsily, Ashraf

    2006-03-08

    The asymmetric synthesis of all-carbon benzylic quaternary stereocenters has been successfully achieved through copper-catalyzed addition of dialkylzinc reagents to 5-(1-arylalkylidene) and 5-(dihydroindenylidene) Meldrum's acids in the presence of phosphoramidite ligand. The resulting benzyl-substituted Meldrum's acids and 1,1-disubstituted indanes were obtained in good yields and up to 99% ee. The significance of substituting the position para, meta, and ortho to the electrophilic benzylic center was highlighted. A benzyl Meldrum's acid product was further transformed to a 3,3-disubstituted 1-indanone and a beta,beta-disubstituted pentanoic acid.

  20. 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; Holder, Jeffrey C.; Gatti, Michele; Stoltz, Brian M.

    2011-01-01

    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

  1. Protein carriers of conjugate vaccines

    Science.gov (United States)

    Pichichero, Michael E

    2013-01-01

    The immunogenicity of polysaccharides as human vaccines was enhanced by coupling to protein carriers. Conjugation transformed the T cell-independent polysaccharide vaccines of the past to T cell-dependent antigenic vaccines that were much more immunogenic and launched a renaissance in vaccinology. This review discusses the conjugate vaccines for prevention of infections caused by Hemophilus influenzae type b, Streptococcus pneumoniae, and Neisseria meningitidis. Specifically, the characteristics of the proteins used in the construction of the vaccines including CRM, tetanus toxoid, diphtheria toxoid, Neisseria meningitidis outer membrane complex, and Hemophilus influenzae protein D are discussed. The studies that established differences among and key features of conjugate vaccines including immunologic memory induction, reduction of nasopharyngeal colonization and herd immunity, and antibody avidity and avidity maturation are presented. Studies of dose, schedule, response to boosters, of single protein carriers with single and multiple polysaccharides, of multiple protein carriers with multiple polysaccharides and conjugate vaccines administered concurrently with other vaccines are discussed along with undesirable consequences of conjugate vaccines. The clear benefits of conjugate vaccines in improving the protective responses of the immature immune systems of young infants and the senescent immune systems of the elderly have been made clear and opened the way to development of additional vaccines using this technology for future vaccine products. PMID:23955057

  2. Reactions of tritium atoms with amino acids, deuterated amino acids and mixtures of amino acids. Additivity property and isotope effect

    International Nuclear Information System (INIS)

    Badun, G.A.; Filatov, Eh.S.

    1988-01-01

    Interaction of tritium atoms with glycine (1) and leucine (2) amino acids, deuterated amino acids, their mixtures and glycylleucine (3) peptide in the 77-300 K temperature range is studied in isothermal and gradient regimes. Tagged amino acids were separated from targets after conducting the reaction. At T 150 K are associated with intermolecular transmission of free valence in the mixture of amino acids. Regularities of the reaction found for the mixture of amino acids are conserved for (3) as well, i.e. the peptide bond does not essentially affect the reaction of isotopic exchange conditioned by atomic tritium

  3. Misonidazole-glutathione conjugates in CHO cells

    International Nuclear Information System (INIS)

    Varghese, A.J.; Whitmore, G.F.

    1984-01-01

    Misonidazole, after reduction to the hydroxylamine derivative, reacts with glutathione (GSH) under physiological conditions. The reaction product has been identified as a mixture of two isomeric conjugates. When water soluble extracts of CHO cells exposed to misonidazole under hypoxic conditions are subjected to HPLC analysis, misonidazole derivatives, having the same chromatographic properties as the GSH-MISO conjugates, were detected. When CHO cells were incubated with misonidazole in the presence of added GSH, a substantial increase in the amount of the conjugate was detected. When extracts of CHO cells exposed to misonidazole under hypoxia were subsequently exposed to GSH, an increased formation of the conjugate was observed. A rearrangement product of the hydroxylamine derivative of misonidazole is postulated as the reactive intermediate responsible for the formation of the conjugate

  4. Pyridine Group-Assisted Addition of Diazo-Compounds to Imines in the 3-CC Reaction of 2-Aminopyridines, Aldehydes, and Diazo-Compounds

    Science.gov (United States)

    Gulevich, Anton V.; Helan, Victoria; Wink, Donald J.

    2013-01-01

    A novel three-component (3-CC) coupling reaction of 2-aminoazines, aromatic aldehydes and diazo-compounds producing polyfunctional β-amino-α-diazo-compounds has been developed. The reaction features an unprecedented heterocycle-assisted addition of a diazo-compound to an imine. The obtained diazoesters were efficiently converted into valuable heterocycles, as well as to β-amino acid derivatives. PMID:23373731

  5. A nanodiamond-fluorescein conjugate for cell studies

    Science.gov (United States)

    Pedroso-Santana, Seidy; Fleitas-Salazar, Noralvis; Sarabia-Sainz, Andrei; Silva-Campa, Erika; Burgara-Estrella, Alexel; Angulo-Molina, Aracely; Melendrez, Rodrigo; Pedroza-Montero, Martin; Riera, Raul

    2018-03-01

    The use of nanodiamonds in studies with living systems generally involves the modification of their surfaces with functional groups. Fluorescent molecules can be attached to these groups, so that one can know the exact position of the particles in each moment of the interaction with the cells. Here we modify the surface of detonation nanodiamonds and nitrogen-vacancy center nanodiamonds using carboxylation and hydroxylation procedures. Subsequent reactions with silicates and cysteine, before addition of fluorescein allow to obtain fluorescent nano-conjugates. We used confocal microscopy to observe the position of nanodiamonds interacting with HeLa cells. At 3 h post-incubation the green fluorescence is localized in extracellular rounded like-vesicles assemblies while at 24 h the conjugates can be observed inside the cells. The measurement of the fluorescence emitted by both conjugates allowed to find an enhanced emission of fluorescein isothiocyanate (FITC) when the nitrogen-vacancy center is present. We propose the existence of a fluorescence enhancement by electron transference process. The procedure described in this work allows the functionalization of nanodiamonds with FITC and other molecules using functional surface groups and small size mediators. Also, as was proved in our work, the nanodiamond-fluorescein conjugates can be used to track nanoparticles position within the cell. Localization studies are particularly important for drug delivery applications of nanodiamonds.

  6. Synthesis of Novel C-2- or C-15-Labeled BODIPY—Estrone Conjugates

    Directory of Open Access Journals (Sweden)

    Ildikó Bacsa

    2018-04-01

    Full Text Available Novel BODIPY–estrone conjugates were synthesized via Cu(I-catalyzed azide–alkyne cycloaddition (CuAAC. Estrone-alkynes or an estrone-azide as starting compounds were synthesized via Michael addition or Sonogashira reaction as key steps. Fluorescent dyes based on BODIPY-core were provided by azide or alkyne functional groups. Fluorescent labeling of estrone was efficiently achieved at the C-2 or C-15 position. The newly-elaborated coupling procedures might have a broad applicability in the synthesis of fluorescent-labeled estrone conjugates suitable for biological assays.

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

    KAUST Repository

    Wang, Zhandong; Sarathy, Mani

    2016-01-01

    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

  8. 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.

  9. Effect of addition of water-soluble salts on the hydrogen generation of aluminum in reaction with hot water

    International Nuclear Information System (INIS)

    Razavi-Tousi, S.S.; Szpunar, J.A.

    2016-01-01

    Aluminum powder was ball milled for different durations of time with different weight percentages of water-soluble salts (NaCl and KCl). The hydrogen generation of each mixture in reaction with hot water was measured. A scanning electron microscope (SEM) as well as energy-dispersive spectroscopy (EDS) were used to investigate the morphology, surfaces and cross sections of the produced particles. The results show that the presence of salts in the microstructure of the aluminum considerably increases the hydrogen generation rate. At shorter milling times, the salt covers the aluminum particles and becomes embedded in layers within the aluminum matrix. At higher milling durations, salt and aluminum phases form composite particles. A higher percentage of the second phase significantly decreases the milling time needed for activation of the aluminum particles. Based on the EDS results from cross sections of the milled particles, a mechanism for improvement of the hydrogen generation rate in the presence of salts is suggested. - Highlights: • Milling and water soluble salts have a synergic effect on hydrogen generation. • Salt and aluminum form composite particles by milling. • Salt is dissolved in water leaving aluminum with much fresh surfaces for the reaction. • The chemical effect of salt on the reaction is negligible compared to its structural effect.

  10. Evaluation of iodovinyl antibody conjugates: Comparison with a p-iodobenzoyl conjugate and direct radioiodination

    International Nuclear Information System (INIS)

    Hadley, S.W.; Wilbur, D.S.

    1990-01-01

    The preparations and conjugations of 2,3,5,6-tetrafluorophenyl 5-[125I/131I]iodo-4-pentenoate (7a) and 2,3,5,6-tetrafluorophenyl 3,3-dimethyl-5-[125I/131I]iodo-4-pentenoate (7b) to monoclonal antibodies are reported. Reagents 7a and 7b were prepared in high radiochemical yield by iododestannylation of their corresponding 5-tri-n-butylstannyl precursors. Radioiodinated antibody conjugates were prepared by reaction of 7a or 7b with the protein at basic pH. Evaluation of these conjugates by several in vitro procedures demonstrated that the radiolabel was attached to the antibody in a stable manner and that the conjugates maintained immunoreactivity. Comparative dual-isotope biodistribution studies of a monoclonal antibody Fab fragment conjugate of 7a and 7b with the same Fab fragment labeled with N-succinimidyl p-[131I]iodobenzoate (PIB, p-iodobenzoate, 2) or directly radioiodinated have been carried out in tumor-bearing nude mice. Coinjection of the Fab conjugate of 7a with the Fab conjugate of 2 demonstrated that the biodistributions were similar in most organs, except the neck tissue (thyroid-containing) and the stomach, which contained substantially increased levels of the 7a label. Coinjection of the Fab conjugate of 7a with the Fab fragment radioiodinated by using the chloramine-T method demonstrated that the biodistributions were remarkably similar, suggesting roughly equivalent in vivo deiodination of these labeled antibody fragments. Coinjection of the Fab conjugate of 7a with the Fab conjugate of 7b indicated that there was ∼ a 2-fold reduction in the amount of in vivo deiodination of the 7b conjugate as compared to the 7a conjugate

  11. Not all food additive related reactions originate from commercial foods: chronic urticaria due to home-made canned tomato.

    Science.gov (United States)

    Ozturk, S; Karaayvaz, M; Caliskaner, Z; Gulec, M

    2005-01-01

    Additives and preservatives in commercial foods have been implicated in the etiology of chronic urticaria, but such foods have not been widely accepted. In some countries, as in ours, people prefer to use home-made foodstuffs to avoid potentially hazardous commercial additives. However, not all home-made foodstuffs are safe, especially regarding allergies. In this report, we describe a patient with chronic urticaria due to home-made canned tomato prepared using "tomato drug" as a "safe (!)" additive.

  12. 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 ob...

  13. Enantioselective radical addition/trapping reactions with alpha,beta-disubstituted unsaturated imides. Synthesis of anti-propionate aldols.

    Science.gov (United States)

    Sibi, Mukund P; Petrovic, Goran; Zimmerman, Jake

    2005-03-02

    This manuscript describes a highly diastereo- and enantioselective intermolecular radical addition/hydrogen atom transfer to alpha,beta-disubstituted enoates. Additionally, we show that anti-propionate aldol-like products can be easily prepared from alpha-methyl-beta-acyloxyenoates in good yields and high diastereo- and enantioselectivities.

  14. The Effect of Mg Addition and Manufacturing Conditions on the Interfacial Reactions between Al and CNT in Al-CNT Pellets

    International Nuclear Information System (INIS)

    Lim, Jung-Kyu; Choi, Soon-Yool; Choe, Kyong-Hwan; Cho, Gue-Serb; Kim, Sang-Sub

    2013-01-01

    In the present study, Al-CNT pellets were investigated to understand the effect of Mg addition and manufacturing conditions on the interfacial reactions between Al and CNTs in Al-CNT pellets. The pellets were heated and held at 700 °C and 800 °C for 2 hours under nitrogen (N_2) atmosphere. To confirm the reactions between Al and CNT in the pellets under different manufacturing conditions, the microstructures were observed by optical microscopy (OM) and field emission scanning electro microscopy (FESEM). And, the composition and reaction phases were analyzed by energy dispersive X-ray spectroscory (EDXS) and X-ray diffractometry (XRD). The presence of oxidation products and Mg on the surface of Al powder in the pellets appeared to prevent the formation of Al_4C_3. But, Al_4C_3 reaction products were increased due to the high temperature of 800 °C, which produced a high amount of reduced aluminium and increased the reaction areas between Al and CNT. The Al-CNT pellets compacted under air atmosphere prohibited the reaction between Al and CNT because of the high amount of oxidation products, such as MgO and MgAl_2O_4.

  15. Diclofenac in Arabidopsis cells: Rapid formation of conjugates.

    Science.gov (United States)

    Fu, Qiuguo; Ye, Qingfu; Zhang, Jianbo; Richards, Jaben; Borchardt, Dan; Gan, Jay

    2017-03-01

    Pharmaceutical and personal care products (PPCPs) are continuously introduced into the soil-plant system, through practices such as agronomic use of reclaimed water and biosolids containing these trace contaminants. Plants may accumulate PPCPs from soil, serving as a conduit for human exposure. Metabolism likely controls the final accumulation of PPCPs in plants, but is in general poorly understood for emerging contaminants. In this study, we used diclofenac as a model compound, and employed 14 C tracing, and time-of-flight (TOF) and triple quadruple (QqQ) mass spectrometers to unravel its metabolism pathways in Arabidopsis thaliana cells. We further validated the primary metabolites in Arabidopsis seedlings. Diclofenac was quickly taken up into A. thaliana cells. Phase I metabolism involved hydroxylation and successive oxidation and cyclization reactions. However, Phase I metabolites did not accumulate appreciably; they were instead rapidly conjugated with sulfate, glucose, and glutamic acid through Phase II metabolism. In particular, diclofenac parent was directly conjugated with glutamic acid, with acyl-glutamatyl-diclofenac accounting for >70% of the extractable metabolites after 120-h incubation. In addition, at the end of incubation, >40% of the spiked diclofenac was in the non-extractable form, suggesting extensive sequestration into cell matter. The rapid formation of non-extractable residue and dominance of diclofenac-glutamate conjugate uncover previously unknown metabolism pathways for diclofenac. In particular, the rapid conjugation of parent highlights the need to consider conjugates of emerging contaminants in higher plants, and their biological activity and human health implications. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Tin-free enantioselective radical reactions using silanes.

    Science.gov (United States)

    Sibi, Mukund P; Yang, Yong-Hua; Lee, Sunggi

    2008-12-04

    Readily available hexyl silane is an excellent choice as a H-atom donor and a chain carrier in Lewis acid mediated enantioselective radical reactions. Conjugate radical additions to alpha,beta-unsaturated imides at room temperature proceed in good yields and excellent enantioselectivities.

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

    KAUST Repository

    Polshettiwar, Vivek; Varma, Rajender S.

    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.

  18. Pattern formation and control of spatiotemporal chaos in a reaction diffusion prey–predator system supplying additional food

    International Nuclear Information System (INIS)

    Ghorai, Santu; Poria, Swarup

    2016-01-01

    Spatiotemporal dynamics of a predator–prey system in presence of spatial diffusion is investigated in presence of additional food exists for predators. Conditions for stability of Hopf as well as Turing patterns in a spatial domain are determined by making use of the linear stability analysis. Impact of additional food is clear from these conditions. Numerical simulation results are presented in order to validate the analytical findings. Finally numerical simulations are carried out around the steady state under zero flux boundary conditions. With the help of numerical simulations, the different types of spatial patterns (including stationary spatial pattern, oscillatory pattern, and spatiotemporal chaos) are identified in this diffusive predator–prey system in presence of additional food, depending on the quantity, quality of the additional food and the spatial domain and other parameters of the model. The key observation is that spatiotemporal chaos can be controlled supplying suitable additional food to predator. These investigations may be useful to understand complex spatiotemporal dynamics of population dynamical models in presence of additional food.

  19. 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.

  20. Reactivity of N-heterocyclic carbene-pyridine palladacyclopentadiene complexes toward halogen addition. The unpredictable course of the reaction.

    Science.gov (United States)

    Visentin, Fabiano; Santo, Claudio; Scattolin, Thomas; Demitri, Nicola; Canovese, Luciano

    2017-08-08

    As an extension of a previously published work we have reacted some palladacyclopentadiene complexes stabilized by bidentate N-heterocyclic carbene-pyridine or monodentate N-heterocyclic carbene-pyridine and isocyanide ligands with the halogens I 2 and Br 2 . All the bidentate and monodentate complexes react with halogens to give at first the expected σ-coordinated butadienyl fragment. However, two of the less hindered NHC carbene-pyridine bidentate butadienyl iodo derivatives undergo a further rearrangement and novel Pd(ii) complexes characterized by a ten term coordinative ring were isolated and characterized. In the most favorable case we were able to carry out the kinetics of rearrangement and measure its reaction rate. Moreover, we have surmised a plausible mechanism on the basis of a dedicated computational approach and in one case the surprising structure characterized by the ten term coordinative ring was resolved by X-ray diffraction.

  1. Investigation on the Effect of Addition of Fe3+ Ion into the Colloidal AgNPs in PVA Solution and Understanding Its Reaction Mechanism

    Directory of Open Access Journals (Sweden)

    Roto Roto

    2017-11-01

    Full Text Available Analysis of Fe3+ ion present in aqueous solutions is always of interests. Recently, this ion has been analyzed by colorimetric methods using colloid of silver nanoparticles (AgNPs in capping agents of polymers. The reaction mechanism between AgNPs and Fe3+ is still subject to the further investigation. In this work, 1,10-phenanthroline was used to probe the reaction mechanism between AgNPs and Fe3+ ion in the solution. The colloids of AgNPs were prepared in the polyvinyl alcohol (PVA solution and reacted with Fe3+. The colloid surface plasmon absorbance decreases linearly along with the increase in Fe3+ concentration. The addition of 1,10-phenanthroline to mixture changes the solution to red, indicating that the reaction produces Fe2+. This suggests that the reduction of the AgNPs absorbance is the result of oxidation of the Ag nanoparticles along with the reduction of Fe3+.

  2. ON THE SYNTHESIS OF MOLYBDENUM CARBIDE WITH COBALT ADDITION VIA GAS-SOLID REACTIONS IN A CH4/H2 ATMOSPHERE

    Directory of Open Access Journals (Sweden)

    C. P. B. Araujo

    Full Text Available Abstract Due to ever more severe environmental regulations regarding SOx, NOx and other pollutants' emissions, there has been an interest in developing new and improved catalysts for hydroprocessing reactions. Mo2C has been reported to display good selectivity and activity for those reactions, especially for HDS. Addition of another metal to the carbide structure may improve catalytic properties. Mo2C with low cobalt addition (2.5 and 5% was obtained via gas-solid reaction in a fixed bed reactor with CH4 (5%/H2 atmosphere. XRD and TG/DTA analysis of the precursors were carried out in order to understand its mass loss profile, doping metal presence and phase distributions. CoMoO4 as well as MoO3 were identified after calcining doped precursors at 600 °C/180min. SEM, XRD, XRF, TOC, BET and laser granulometric analysis of the reaction products were also performed. Compositions verified by XRF and theoretical values were compatible. At 700 °C both carbide (Mo2C and oxide (MoO2 phases are present, as identified in XRD analysis and observed by SEM. At 750 °C only single phase Mo2C was verified by XRD, indicating Co dispersion on the carbide matrix. Morphology at this temperature is compatible with pure Mo2C, though XRF indicates Co presence on the material.

  3. 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.

  4. Solvent-free, catalyst-free aza-Michael addition of cyclohexylamine to diethyl maleate: reaction mechanism and kinetics

    Czech Academy of Sciences Publication Activity Database

    Bláha, Michal; Trhlíková, Olga; Podešva, Jiří; Abbrent, Sabina; Steinhart, Miloš; Dybal, Jiří; Dušková-Smrčková, Miroslava

    2018-01-01

    Roč. 74, č. 1 (2018), s. 58-67 ISSN 0040-4020 Institutional support: RVO:61389013 Keywords : Aza-Michael addition * solvent-free * catalyst-free Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 2.651, year: 2016

  5. Investigation of the O+allyl addition/elimination reaction pathways from the OCH2CHCH2 radical intermediate

    International Nuclear Information System (INIS)

    FitzPatrick, Benjamin L.; Lau, K.-C.; Butler, Laurie J.; Lee, S.-H.; Lin, Jim Jr-Min

    2008-01-01

    These experiments study the preparation of and product channels resulting from OCH 2 CHCH 2 , a key radical intermediate in the O+allyl bimolecular reaction. The data include velocity map imaging and molecular beam scattering results to probe the photolytic generation of the radical intermediate and the subsequent pathways by which the radicals access the energetically allowed product channels of the bimolecular reaction. The photodissociation of epichlorohydrin at 193.3 nm produces chlorine atoms and c-OCH 2 CHCH 2 radicals; these undergo a facile ring opening to the OCH 2 CHCH 2 radical intermediate. State-selective resonance-enhanced multiphoton ionization (REMPI) detection resolves the velocity distributions of ground and spin-orbit excited state chlorine independently, allowing for a more accurate determination of the internal energy distribution of the nascent radicals. We obtain good agreement detecting the velocity distributions of the Cl atoms with REMPI, vacuum ultraviolet (VUV) photoionization at 13.8 eV, and electron bombardment ionization; all show a bimodal distribution of recoil kinetic energies. The dominant high recoil kinetic energy feature peaks near 33 kcal/mol. To elucidate the product channels resulting from the OCH 2 CHCH 2 radical intermediate, the crossed laser-molecular beam experiment uses VUV photoionization and detects the velocity distribution of the possible products. The data identify the three dominant product channels as C 3 H 4 O (acrolein)+H, C 2 H 4 +HCO (formyl radical), and H 2 CO (formaldehyde)+C 2 H 3 . A small signal from C 2 H 2 O (ketene) product is also detected. The measured velocity distributions and relative signal intensities at m/e=27, 28, and 29 at two photoionization energies show that the most exothermic product channel, C 2 H 5 +CO, does not contribute significantly to the product branching. The higher internal energy onset of the acrolein+H product channel is consistent with the relative barriers en route to

  6. Investigation of the O+allyl addition/elimination reaction pathways from the OCH2CHCH2 radical intermediate

    Science.gov (United States)

    Fitzpatrick, Benjamin L.; Lau, Kai-Chung; Butler, Laurie J.; Lee, Shih-Huang; Lin, Jim-Min, Jr.

    2008-08-01

    These experiments study the preparation of and product channels resulting from OCH2CHCH2, a key radical intermediate in the O+allyl bimolecular reaction. The data include velocity map imaging and molecular beam scattering results to probe the photolytic generation of the radical intermediate and the subsequent pathways by which the radicals access the energetically allowed product channels of the bimolecular reaction. The photodissociation of epichlorohydrin at 193.3 nm produces chlorine atoms and c-OCH2CHCH2 radicals; these undergo a facile ring opening to the OCH2CHCH2 radical intermediate. State-selective resonance-enhanced multiphoton ionization (REMPI) detection resolves the velocity distributions of ground and spin-orbit excited state chlorine independently, allowing for a more accurate determination of the internal energy distribution of the nascent radicals. We obtain good agreement detecting the velocity distributions of the Cl atoms with REMPI, vacuum ultraviolet (VUV) photoionization at 13.8 eV, and electron bombardment ionization; all show a bimodal distribution of recoil kinetic energies. The dominant high recoil kinetic energy feature peaks near 33 kcal/mol. To elucidate the product channels resulting from the OCH2CHCH2 radical intermediate, the crossed laser-molecular beam experiment uses VUV photoionization and detects the velocity distribution of the possible products. The data identify the three dominant product channels as C3H4O (acrolein)+H, C2H4+HCO (formyl radical), and H2CO (formaldehyde)+C2H3. A small signal from C2H2O (ketene) product is also detected. The measured velocity distributions and relative signal intensities at m/e=27, 28, and 29 at two photoionization energies show that the most exothermic product channel, C2H5+CO, does not contribute significantly to the product branching. The higher internal energy onset of the acrolein+H product channel is consistent with the relative barriers en route to each of these product channels

  7. 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 two...... monomers provides the polyesters, which carry an activated carbon‐carbon double bond in the polymer backbone. These electron deficient alkenes represent suitable aza‐Michael acceptors and can be engaged in a nucleophilic addition reaction with small molecular mono‐amines (aza‐Michael donors) to yield...... functionalized linear polyesters. Employing a poly‐amine as the aza‐Michael donor, on the other hand, results in the formation of hydrophilic polymer networks....

  8. Effects of Ag addition on solid–state interfacial reactions between Sn–Ag–Cu solder and Cu substrate

    International Nuclear Information System (INIS)

    Yang, Ming; Ko, Yong-Ho; Bang, Junghwan; Kim, Taek-Soo; Lee, Chang-Woo; Li, Mingyu

    2017-01-01

    Low–Ag–content Sn–Ag–Cu (SAC) solders have attracted much recent attention in electronic packaging for their low cost. To reasonably reduce the Ag content in Pb–free solders, a deep understanding of the basic influence of Ag on the SAC solder/Cu substrate interfacial reaction is essential. Previous studies have discussed the influence of Ag on the interfacial intermetallic compound (IMC) thickness. However, because IMC growth is the joint result of multiple factors, such characterizations do not reveal the actual role of Ag. In this study, changes in interfacial IMCs after Ag introduction were systemically and quantitatively characterized in terms of coarsening behaviors, orientation evolution, and growth kinetics. The results show that Ag in the solder alloy affects the coarsening behavior, accelerates the orientation concentration, and inhibits the growth of interfacial IMCs during solid–state aging. The inhibition mechanism was quantitatively discussed considering the individual diffusion behaviors of Cu and Sn atoms, revealing that Ag inhibits interfacial IMC growth primarily by slowing the diffusion of Cu atoms through the interface. - Highlights: •Role of Ag in IMC formation during Sn–Ag–Cu soldering was investigated. •Ag affects coarsening, crystallographic orientation, and IMC growth. •Diffusion pathways of Sn and Cu are affected differently by Ag. •Ag slows Cu diffusion to inhibit IMC growth at solder/substrate interface.

  9. Effects of Ag addition on solid–state interfacial reactions between Sn–Ag–Cu solder and Cu substrate

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ming [Micro-Joining Center, Korea Institute of Industrial Technology (KITECH), Incheon 21999 (Korea, Republic of); Ko, Yong-Ho [Micro-Joining Center, Korea Institute of Industrial Technology (KITECH), Incheon 21999 (Korea, Republic of); Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291, Daehak-ro, Yuseong-gu, Daejeon 34141 (Korea, Republic of); Bang, Junghwan [Micro-Joining Center, Korea Institute of Industrial Technology (KITECH), Incheon 21999 (Korea, Republic of); Kim, Taek-Soo [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291, Daehak-ro, Yuseong-gu, Daejeon 34141 (Korea, Republic of); Lee, Chang-Woo, E-mail: cwlee@kitech.re.kr [Micro-Joining Center, Korea Institute of Industrial Technology (KITECH), Incheon 21999 (Korea, Republic of); Li, Mingyu, E-mail: myli@hit.edu.cn [Shenzhen Key Laboratory of Advanced Materials, Harbin Institute of Technology Shenzhen Graduate School, Shenzhen 518055 (China)

    2017-02-15

    Low–Ag–content Sn–Ag–Cu (SAC) solders have attracted much recent attention in electronic packaging for their low cost. To reasonably reduce the Ag content in Pb–free solders, a deep understanding of the basic influence of Ag on the SAC solder/Cu substrate interfacial reaction is essential. Previous studies have discussed the influence of Ag on the interfacial intermetallic compound (IMC) thickness. However, because IMC growth is the joint result of multiple factors, such characterizations do not reveal the actual role of Ag. In this study, changes in interfacial IMCs after Ag introduction were systemically and quantitatively characterized in terms of coarsening behaviors, orientation evolution, and growth kinetics. The results show that Ag in the solder alloy affects the coarsening behavior, accelerates the orientation concentration, and inhibits the growth of interfacial IMCs during solid–state aging. The inhibition mechanism was quantitatively discussed considering the individual diffusion behaviors of Cu and Sn atoms, revealing that Ag inhibits interfacial IMC growth primarily by slowing the diffusion of Cu atoms through the interface. - Highlights: •Role of Ag in IMC formation during Sn–Ag–Cu soldering was investigated. •Ag affects coarsening, crystallographic orientation, and IMC growth. •Diffusion pathways of Sn and Cu are affected differently by Ag. •Ag slows Cu diffusion to inhibit IMC growth at solder/substrate interface.

  10. 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 ...

  11. Theoretical study on the reaction mechanisms of Michael chirality addition between propionaldehyde and nitroalkene catalyzed by an enantioselective catalyst.

    Science.gov (United States)

    Zhou, Xinming; Li, Ling; Sun, Xuejun; Wang, Yajun; Du, Dongmei; Fu, Hui

    2018-06-01

    The asymmetric Michael addition between propionaldehyde and nitroalkene catalyzed by 8-(ethoxycarbonyl)-1,2,3,3a,8,8a-hexahydropyrrolo[2,3-b]indole-2-carboxylic acid has obtained relatively high yields and excellent enantioselectivities at room temperature. In this study, the molecular structures and optical activity of the most stable conformation I are optimized at B3LYP/6-311++ G(d,p) level. We find that levorotatory conformation I catalyzing the same Michael addition can produce laevo-product A and dextrorotatory conformation I' can obtain the dextral-product A'. These results have guiding significance for further studying on the new chemzymes and the mechanism of the obtained different chiral products. © 2018 Wiley Periodicals, Inc.

  12. Synthesis of New Chiral Benzimidazolylidene–Rh Complexes and Their Application in Asymmetric Addition Reactions of Organoboronic Acids to Aldehydes

    Directory of Open Access Journals (Sweden)

    Weiping He

    2016-09-01

    Full Text Available A series of novel chiral N-heterocyclic carbene rhodium complexes (NHC–Rh based on benzimidazole have been prepared, and all of the NHC–Rh complexes were fully characterized by NMR and mass spectrometry. These complexes could be used as catalysts for the asymmetric 1,2-addition of organoboronic acids to aldehydes, affording chiral diarylmethanols with high yields and moderate enantioselectivities.

  13. 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.

  14. Free-radical coupling, cleavage, and redox reactions in 60Co γ radiolysis of aqueous methyl acetate. Effects of additives

    International Nuclear Information System (INIS)

    Bernath, T.; Parsons, G.H. Jr.; Cohen, S.G.

    1975-01-01

    Reaction of methyl acetate with e - /sub aq/ may lead to CH 3 C(O )OCH 3 (I - ), CH 3 C(OH)OCH 3 (II), and CH 3 CO (IIA), and with .OH and H. to .CH 2 CO 2 CH 3 (III), and to CH 3 CO 2 CH 2 . (IV). Methyl acetate is consumed, G = --3.5, and the loss is decreased by formate which scavenges .H and .OH, and increased by N 2 O which converts e - /sub aq/ to .OH. Hydrogen is formed, G = 1.1, and this is decreased by scavengers for H., and increased by H + which converts e - /sub aq/ to H.. In radiolysis of 0.027 M methyl acetate, 1.5 x 10 22 ev/l., radical combination products are: ethylene diacetate (CH 3 CO 2 CH 2 CH 2 OCOCH 3 ) (EDA), G = 0.48, from IV + IV; methyl β-acetoxypropionate (CH 3 CO 2 CH 2 CH 2 CO 2 CH 3 ) (MAP), G = 0.28, from IV + III; dimethyl succinate (DMS), G = 0.05, from III + III; and a mixture of methyl acetoacetate and acetonyl acetate (MAA and AA), (MAS and AA), G = 0.07. Biacetyl is not observed. β-Mercaptopropionic acid, 0.0005 M, prevents formation of coupling products, as it reduces radicals III and IV, and thiyl radical oxidizes radical II back to methyl acetate. Other sources of .OH, Fenton's reagent and H 2 O 2 -uv, lead to EDA, MAP, and DMS with a high IV/III ratio. H. preferentially attacks acyl C--H; .OH preferentially attacks alkoxyl C--H. Yields of radicals involved in formation of coupling products and acetic acid are estimated: G(II and IIA) = 1.2; G(III) = 1.4; G(IV) = 1.7. Part of the radicals, G approximately 1.6, regenerate methyl acetate by self-repair reduction of IV and III by II. Deuterium is introduced into methyl acetate during radiolysis in D 2 O. (U.S.)

  15. Application of enantioselective radical reactions: synthesis of (+)-ricciocarpins A and B.

    Science.gov (United States)

    Sibi, Mukund P; He, Liwen

    2004-05-27

    Enantioselective synthesis of (+)-ricciocarpins A and B has been achieved in 41 and 45% overall yields, respectively, starting from a beta-substituted oxazolidinone. The key steps in the strategy are an enantioselective conjugate radical addition and the addition of a furyl organometallic to a key aldehyde intermediate. [reaction--see text

  16. 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.

  17. 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.

  18. Influence of reaction products of K-getter fuel additives on commercial vanadia-based SCR catalysts

    DEFF Research Database (Denmark)

    Castellino, Francesco; Jensen, Anker Degn; Johnsson, Jan Erik

    2009-01-01

    , deactivation rates up to 3%/day have been measured. The spent catalysts have been characterized by bulk chemical analysis, Hg-porosimetry and SEM-EDX. NH3-chemisorption tests on the spent elements and activity tests on catalyst powders obtained by crushing the monoliths have also been carried out. The catalyst...... characterization has shown that poisoning by K is the main deactivation mechanism. The results show that binding K in K–P salts will not reduce the rate of catalyst deactivation....... as a K-getter additive. The formed aerosols have been characterized by using both a SMPS system and a low pressure cascade impactor, showing a dual-mode volume-based size distribution with a first peak at around 30 nm and a second one at diameters >1 μm. The different peaks have been associated...

  19. Novel ?-cyclodextrin?eosin conjugates

    OpenAIRE

    Benkovics, G?bor; Afonso, Damien; Darcsi, Andr?s; B?ni, Szabolcs; Conoci, Sabrina; Fenyvesi, ?va; Szente, Lajos; Malanga, Milo; Sortino, Salvatore

    2017-01-01

    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 an...

  20. Structure Property Relationships in Organic Conjugated Systems

    OpenAIRE

    O'Neill, Luke; Lynch, Patrick; McNamara, Mary

    2005-01-01

    A series of π conjugated oligomers were studied by absorption and photoluminescence spectroscopy. A linear relationship between the positioning of the absorption and photoluminescence maxima plotted against inverse conjugation length is observed. The relationships are in good agreement with the simple particle in a box method, one of the earliest descriptions of the properties of one-dimensional organic molecules. In addition to the electronic transition energies, it was observed that the Sto...

  1. Effects of citric acid additive on photoluminescence properties of YAG:Ce3+ nanoparticles synthesized by glycothermal reaction

    International Nuclear Information System (INIS)

    Asakura, R.; Isobe, T.; Kurokawa, K.; Takagi, T.; Aizawa, H.; Ohkubo, M.

    2007-01-01

    We synthesize Y 3 Al 5 O 12 :Ce 3+ (YAG:Ce 3+ ) nanoparticles in the presence of citric acid by glycothermal method. Fourier transform infrared absorption spectroscopy measurement indicates that the intensity of the peak corresponding to carboxyl groups coordinating to the nanoparticles increases with increasing amount of citric acid. At the same time, the primary particle diameter decreases from 10.2 to 4.0 nm. In addition, the internal quantum efficiency of the photoluminescence (PL) due to the 4f-5d transition of Ce 3+ increases from 22.0% to 40.1% with increasing amount of citric acid. Two kinds of PL decay lifetimes, 16-26 and 72-112 ns, are detected for YAG:Ce 3+ nanoparticles, whereas the micron sized YAG:Ce 3+ bulk shows the lifetime of 57 ns. We discuss these phenomena from the aspects of the coordination of citric acid and the incorporation of Ce 3+ ions into the nanoparticles

  2. Lead extraction from Cathode Ray Tube (CRT) funnel glass: Reaction mechanisms in thermal reduction with addition of carbon (C).

    Science.gov (United States)

    Lu, Xingwen; Ning, Xun-An; Chen, Da; Chuang, Kui-Hao; Shih, Kaimin; Wang, Fei

    2018-06-01

    This study quantitatively determined the extraction of lead from CRT funnel glass and examined the mechanisms of thermally reducing lead in the products of sintering Pb-glass with carbon in the pre-heated furnace. The experimentally derived results indicate that a 90.3 wt% lead extraction efficiency can be achieved with 20 wt% of C addition at 950 °C for 3 min under air. The formation of viscous semi-liquid glass blocked the oxygen supply between the interaction of C and Pb-glass, and was highly effective for the extraction of metallic Pb. A maximum of 87.3% lead recover was obtained with a C to Na 2 CO 3 ratio of 1/3 at 1200 °C. The decrease of C/Na 2 CO 3 ratio enhanced the metallic lead recovery by increasing the glass viscosity for effective sedimentation of metallic lead in the bottom. However, with the further increase of temperature and treatment time, re-vitrification of lead back to silicate-glass matrix was detected in both Pb-glass/C and Pb-glass/C/Na 2 CO 3 systems. The findings indicated that with proper controls, using C as an inexpensive reagent can effectively reduce treatment time and energy, which is crucial to a waste-to-resource technology for economically recovering lead from the waste CRT glass. Copyright © 2018 Elsevier Ltd. All rights reserved.

  3. The nuclear reaction analysis (NRA) as a means for detecting carbon in GaAs and in source materials and additives

    International Nuclear Information System (INIS)

    Bethge, K.; Mader, A.; Michelmann, R.; Krauskopf, J.; Thee, P.; Meyer, J.D.

    1991-01-01

    The nuclear reaction ananlysis (NRA) on the basis of the reaction 12 C (d,p) 13 C is a method allowing the detection and description of both lateral and depth profiles of the presence of carbon in GaAs and in the source materials and additives. The NRA is an absolute method with a detection limit for C of approx. 4x10 15 cm 3 . The achievable detection range in depth under the experimental conditions goes from the surface down to 6 μm. Combined with channeling measurements, NRA is capable of identifying the position of carbon in the GaAs crystal lattice, and thus permits to examine the mobility of C in GaAs. (BBR) With 11 refs [de

  4. 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.

  5. 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.

  6. Accurate multiplicity scaling in isotopically conjugate reactions

    International Nuclear Information System (INIS)

    Golokhvastov, A.I.

    1989-01-01

    The generation of accurate scaling of mutiplicity distributions is presented. The distributions of π - mesons (negative particles) and π + mesons in different nucleon-nucleon interactions (PP, NP and NN) are described by the same universal function Ψ(z) and the same energy dependence of the scale parameter which determines the stretching factor for the unit function Ψ(z) to obtain the desired multiplicity distribution. 29 refs.; 6 figs

  7. Effects of Interface Coating and Nitride Enhancing Additive on Properties of Hi-Nicalon SiC Fiber Reinforced Reaction-Bonded Silicon Nitride Composites

    Science.gov (United States)

    Bhatt, Ramakrishana T.; Hull, David R.; Eldridge, Jeffrey I.; Babuder, Raymond

    2000-01-01

    Strong and tough Hi-Nicalon SiC fiber reinforced reaction-bonded silicon nitride matrix composites (SiC/ RBSN) have been fabricated by the fiber lay-up approach. Commercially available uncoated and PBN, PBN/Si-rich PBN, and BN/SiC coated SiC Hi-Nicalon fiber tows were used as reinforcement. The composites contained approximately 24 vol % of aligned 14 micron diameter SiC fibers in a porous RBSN matrix. Both one- and two-dimensional composites were characterized. The effects of interface coating composition, and the nitridation enhancing additive, NiO, on the room temperature physical, tensile, and interfacial shear strength properties of SiC/RBSN matrix composites were evaluated. Results indicate that for all three coated fibers, the thickness of the coatings decreased from the outer periphery to the interior of the tows, and that from 10 to 30 percent of the fibers were not covered with the interface coating. In the uncoated regions, chemical reaction between the NiO additive and the SiC fiber occurs causing degradation of tensile properties of the composites. Among the three interface coating combinations investigated, the BN/SiC coated Hi-Nicalon SiC fiber reinforced RBSN matrix composite showed the least amount of uncoated regions and reasonably uniform interface coating thickness. The matrix cracking stress in SiC/RBSN composites was predicted using a fracture mechanics based crack bridging model.

  8. 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.

  9. Novel β-cyclodextrin-eosin conjugates.

    Science.gov (United States)

    Benkovics, Gábor; Afonso, Damien; Darcsi, András; Béni, Szabolcs; Conoci, Sabrina; Fenyvesi, Éva; Szente, Lajos; Malanga, Milo; Sortino, Salvatore

    2017-01-01

    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.

  10. 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.

  11. 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.

  12. 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 ...

  13. Conjugated Polymer Solar Cells

    National Research Council Canada - National Science Library

    Paraschuk, Dmitry Y

    2006-01-01

    This report results from a contract tasking Moscow State University as follows: Conjugated polymers are promising materials for many photonics applications, in particular, for photovoltaic and solar cell devices...

  14. 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.

  15. Facile synthesis of conjugated polymeric Schiff base as negative electrodes for lithium ion batteries

    International Nuclear Information System (INIS)

    Ye, Haijun; Jiang, Fangqing; Li, Hongqin; Xu, Zheng; Yin, Jiao; Zhu, Hui

    2017-01-01

    Graphical abstract: Polymeric Schiff base (PSB) exhibits a stable cyclability as an organic Li-ion battery anode Display Omitted -- Highlights: •A conjugated Schiff base polymer has been synthesized by a solid-phase reaction. •The polymer suppresses the dissolution of organic monomer into the organic electrolyte. •The polymer demonstrates high reversible capacity and excellent cyclic performance. -- Abstract: The redox-active organic compounds show great potentials as anodes for high energy density Li-ion batteries (LIBs), comparing with the traditional transition metal-based inorganic compounds. However, the inevitable dissolution behaviors of these organics in organic electrolyte will arouse the recession in their cycling stabilities. To circumvent this problem, we successfully applied an electrochemically active imine group to connect the carbonyl compound to form conjugated polymer, where the occurrence of multi-electron reactions suppressed the dissolution of anthraquinone in the organic electrolyte with improved cycling stability and high capacity for LIBs. In detail, by virtue of a facile solid-phase reaction between 1, 4-diaminoanthraquinone (14DAAQ) and p-phthalaldehyde (PPD), a highly conjugated polymeric Schiff base (PSB) was synthesized. The obtained PSB exhibited a reversible specific capacity of 175 mAh g −1 at a current density of 10 mA g −1 . In addition, after 100 cycles, a cycling stability with 90% capacity retention can be maintained, manifesting a promising application of the organic material in high performance anodes for LIBs.

  16. 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.

  17. 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)

  18. Atypical profiles and modulations of heme-enzymes catalyzed outcomes by low amounts of diverse additives suggest diffusible radicals' obligatory involvement in such redox reactions.

    Science.gov (United States)

    Manoj, Kelath Murali; Parashar, Abhinav; Venkatachalam, Avanthika; Goyal, Sahil; Satyalipsu; Singh, Preeti Gunjan; Gade, Sudeep K; Periyasami, Kalaiselvi; Jacob, Reeba Susan; Sardar, Debosmita; Singh, Shanikant; Kumar, Rajan; Gideon, Daniel A

    2016-06-01

    Peroxidations mediated by heme-enzymes have been traditionally studied under a single-site (heme distal pocket), non-sequential (ping-pong), two-substrates binding scheme of Michaelis-Menten paradigm. We had reported unusual modulations of peroxidase and P450 reaction outcomes and explained it invoking diffusible reactive species [Manoj, 2006; Manoj et al., 2010; Andrew et al., 2011, Parashar et al., 2014 & Venkatachalam et al., 2016]. A systematic investigation of specific product formation rates was undertaken to probe the hypothesis that involvement of diffusible reactive species could explain undefined substrate specificities and maverick modulations (sponsored by additives) of heme-enzymes. When the rate of specific product formation was studied as a function of reactants' concentration or environmental conditions, we noted marked deviations from normal profiles. We report that heme-enzyme mediated peroxidations of various substrates are inhibited (or activated) by sub-equivalent concentrations of diverse redox-active additives and this is owing to multiple redox equilibriums in the milieu. At low enzyme and peroxide concentrations, the enzyme is seen to recycle via a one-electron (oxidase) cycle, which does not require the substrate to access the heme centre. Schemes are provided that explain the complex mechanistic cycle, kinetics & stoichiometry. It is not obligatory for an inhibitor or substrate to interact with the heme centre for influencing overall catalysis. Roles of diffusible reactive species explain catalytic outcomes at low enzyme and reactant concentrations. The current work highlights the scope/importance of redox enzyme reactions that could occur "out of the active site" in biological or in situ systems. Copyright © 2016 Elsevier B.V. and Société française de biochimie et biologie Moléculaire (SFBBM). All rights reserved.

  19. 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.

  20. Effect of sodium acetate additive in successive ionic layer adsorption and reaction on the performance of CdS quantum-dot-sensitized solar cells

    Science.gov (United States)

    Liu, I.-Ping; Chen, Liang-Yih; Lee, Yuh-Lang

    2016-09-01

    Sodium acetate (NaAc) is utilized as an additive in cationic precursors of the successive ionic layer adsorption and reaction (SILAR) process to fabricate CdS quantum-dot (QD)-sensitized photoelectrodes. The effects of the NaAc concentration on the deposition rate and distribution of QDs in mesoporous TiO2 films, as well as on the performance of CdS-sensitized solar cells are studied. The experimental results show that the presence of NaAc can significantly accelerate the deposition of CdS, improve the QD distribution across photoelectrodes, and thereby, increase the performance of solar cells. These results are mainly attributed to the pH-elevation effect of NaAc to the cationic precursors which increases the electrostatic interaction of the TiO2 film to cadmium ions. The light-to-energy conversion efficiency of the CdS-sensitized solar cell increases with increasing concentration of the NaAc and approaches a maximum value (3.11%) at 0.05 M NaAc. Additionally, an ionic exchange is carried out on the photoelectrode to transform the deposited CdS into CdS1-xSex ternary QDs. The light-absorption range of the photoelectrode is extended and an exceptional power conversion efficiency of 4.51% is achieved due to this treatment.

  1. Conjugated Fatty Acid Synthesis

    Science.gov (United States)

    Rawat, Richa; Yu, Xiao-Hong; Sweet, Marie; Shanklin, John

    2012-01-01

    Conjugated linolenic acids (CLNs), 18:3 Δ9,11,13, lack the methylene groups found between the double bonds of linolenic acid (18:3 Δ9,12,15). CLNs are produced by conjugase enzymes that are homologs of the oleate desaturases FAD2. The goal of this study was to map the domain(s) within the Momordica charantia conjugase (FADX) responsible for CLN formation. To achieve this, a series of Momordica FADX-Arabidopsis FAD2 chimeras were expressed in the Arabidopsis fad3fae1 mutant, and the transformed seeds were analyzed for the accumulation of CLN. These experiments identified helix 2 and the first histidine box as a determinant of conjugase product partitioning into punicic acid (18:3 Δ9cis,11trans,13cis) or α-eleostearic acid (18:3 Δ9cis,11trans,13trans). This was confirmed by analysis of a FADX mutant containing six substitutions in which the sequence of helix 2 and first histidine box was converted to that of FAD2. Each of the six FAD2 substitutions was individually converted back to the FADX equivalent identifying residues 111 and 115, adjacent to the first histidine box, as key determinants of conjugase product partitioning. Additionally, expression of FADX G111V and FADX G111V/D115E resulted in an approximate doubling of eleostearic acid accumulation to 20.4% and 21.2%, respectively, compared with 9.9% upon expression of the native Momordica FADX. Like the Momordica conjugase, FADX G111V and FADX D115E produced predominantly α-eleostearic acid and little punicic acid, but the FADX G111V/D115E double mutant produced approximately equal amounts of α-eleostearic acid and its isomer, punicic acid, implicating an interactive effect of residues 111 and 115 in punicic acid formation. PMID:22451660

  2. The dehydrogenation performance and reaction mechanisms of Li{sub 3}AlH{sub 6} with TiF{sub 3} additive

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Shu-Sheng [Materials and Thermochemistry Laboratory, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Graduate School of Chinese Academy of Sciences, Beijing 100049 (China); Zhang, Yao; Sun, Li-Xian; Zhang, Jian; Zhao, Jun-Ning [Materials and Thermochemistry Laboratory, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Xu, Fen [Faculty of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian 116029 (China); Huang, Feng-Lei [State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081 (China)

    2010-05-15

    For Li{sub 3}AlH{sub 6} prepared by mechanical milling method, the dissociation reaction enthalpy and activation energy are calculated to be 22.1 kJ mol{sup -1} H{sub 2} and 133.7 {+-} 2.7 kJ mol{sup -1}, respectively. The dehydrogenation performance of Li{sub 3}AlH{sub 6} is greatly enhanced by TiF{sub 3} additive, especially in the kinetic behaviors. For the Li{sub 3}AlH{sub 6} + 10 mol% TiF{sub 3} sample, the starting temperature of dehydrogenation is obviously decreased by 60 C from that of pure Li{sub 3}AlH{sub 6} (190 C), and 3.0 wt.% H{sub 2} may be released within 1000 s at 120 C under an initial vacuum. With the amount of TiF{sub 3} increasing, the starting temperature decreases and the kinetics improves due to the decrease in the activation energy. The X-ray diffraction (XRD) together with thermogravimetric analysis (TGA) results show that there are three mechanochemical reactions involved during milling: i) Li{sub 3}AlH{sub 6} + TiF{sub 3} {yields} 3 LiF + Al + Ti + 3H{sub 2}, ii) Ti + H{sub 2} {yields} TiH{sub 2}, iii) 3 Al + Ti {yields} Al{sub 3}Ti. The in-situ formed Ti species (TiH{sub 2} and Al{sub 3}Ti) co-catalyze the thermal dehydrogenation of Li{sub 3}AlH{sub 6}. (author)

  3. Hydrolyzed caseinomacropeptide conjugated galactooligosaccharides support the growth and enhance the bile tolerance in Lactobacillus strains.

    Science.gov (United States)

    Muthaiyan, Arunachalam; Hernandez-Hernandez, Oswaldo; Moreno, F Javier; Sanz, Maria Luz; Ricke, Steven C

    2012-07-11

    In this study bioactive caseinomacropeptide was conjugated with prebiotic galactooligosaccharides (hCMP:GOS) by Maillard reaction to synthesize value added prebiotic compounds to Lactobacillus strains. Growth study showed the ability of hCMP:GOS to serve as a sole carbon source for Lactobacillus strains. A significant amount of acetate and lactate was detected in cell free culture supernatant by HPLC. It demonstrated the ability of Lactobacillus strains to ferment the hCMP:GOS as a carbon source. In addition, hCMP:GOS grown Lactobacillus cells exhibited enhanced bile tolerance and retained 90% viability. Overall results of this study indicate that the hCMP conjugated GOS can be potential multipurpose prebiotic substrates to enhance the growth and bile tolerance in Lactobacillus strains and serve as a fermentable substrate to produce beneficial metabolites in the host.

  4. Conjugate Meningococcal Vaccines Development: GSK Biologicals Experience

    Science.gov (United States)

    Miller, Jacqueline M.; Mesaros, Narcisa; Van Der Wielen, Marie; Baine, Yaela

    2011-01-01

    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. PMID:21991444

  5. 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.

  6. Peptide/protein-polymer conjugates: synthetic strategies and design concepts.

    Science.gov (United States)

    Gauthier, Marc A; Klok, Harm-Anton

    2008-06-21

    This feature article provides a compilation of tools available for preparing well-defined peptide/protein-polymer conjugates, which are defined as hybrid constructs combining (i) a defined number of peptide/protein segments with uniform chain lengths and defined monomer sequences (primary structure) with (ii) a defined number of synthetic polymer chains. The first section describes methods for post-translational, or direct, introduction of chemoselective handles onto natural or synthetic peptides/proteins. Addressed topics include the residue- and/or site-specific modification of peptides/proteins at Arg, Asp, Cys, Gln, Glu, Gly, His, Lys, Met, Phe, Ser, Thr, Trp, Tyr and Val residues and methods for producing peptides/proteins containing non-canonical amino acids by peptide synthesis and protein engineering. In the second section, methods for introducing chemoselective groups onto the side-chain or chain-end of synthetic polymers produced by radical, anionic, cationic, metathesis and ring-opening polymerization are described. The final section discusses convergent and divergent strategies for covalently assembling polymers and peptides/proteins. An overview of the use of chemoselective reactions such as Heck, Sonogashira and Suzuki coupling, Diels-Alder cycloaddition, Click chemistry, Staudinger ligation, Michael's addition, reductive alkylation and oxime/hydrazone chemistry for the convergent synthesis of peptide/protein-polymer conjugates is given. Divergent approaches for preparing peptide/protein-polymer conjugates which are discussed include peptide synthesis from synthetic polymer supports, polymerization from peptide/protein macroinitiators or chain transfer agents and the polymerization of peptide side-chain monomers.

  7. Peptide-Carrier Conjugation

    DEFF Research Database (Denmark)

    Hansen, Paul Robert

    2015-01-01

    To produce antibodies against synthetic peptides it is necessary to couple them to a protein carrier. This chapter provides a nonspecialist overview of peptide-carrier conjugation. Furthermore, a protocol for coupling cysteine-containing peptides to bovine serum albumin is outlined....

  8. Photoluminescence in conjugated polymers

    International Nuclear Information System (INIS)

    Furst, J.E.; Laugesen, R.; Dastoor, P.; McNeill, C.

    2002-01-01

    Full text: Conjugated polymers combine the electronic and optical properties of semiconductors with the processability of polymers. They contain a sequence of alternate single and double carbon bonds so that the overlap of unhybridised p z orbitals creates a delocalised ρ system which gives semiconducting properties with p-bonding (valence) and p* -antibonding (conduction) bands. Photoluminesence (PL) in conjugated polymers results from the radiative decay of singlet excitons confined to a single chain. The present work is the first in a series of studies in our laboratory that will characterize the optical properties of conjugated polymers. The experiment involves the illumination of thin films of conjugated polymer with UV light (I=360 nm) and observing the subsequent fluorescence using a custom-built, fluorescence spectrometer. Photoluminesence spectra provide basic information about the structure of the polymer film. A typical spectrum is shown in the accompanying figure. The position of the first peak is related to the polymer chain length and resolved multiple vibronic peaks are an indication of film structure and morphology. We will also present results related to the optical degradation of these materials when exposed to air and UV light

  9. 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

    2018-05-15

    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.

  10. 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.

  11. 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.

  12. 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.

  13. Reaction of dimethyl hydrogen phosphite with acecyclone

    International Nuclear Information System (INIS)

    Arbuzov, B.A.; Fuzhenkova, A.V.; Tyryshkin, N.I.

    1987-01-01

    In the presence of bases acecyclone reacts with dimethyl hydrogen phosphite with the formation of gamma-keto phosphonates with conjugated and unconjugated structures, and also an enol phosphate, a product containing a bond between oxygen of the cyclone and phosphorus. In the absence of bases, as well as the beta-keto phosphonate, gamma-keto phosphonates of cis and trans structure are formed; they are products of the 1,4 addition of dimethyl hydrogen phosphite to the conjugated fragment C=C-C=O of the cyclone. The compositions of the reaction mixture were determined by IR and NMR spectroscopy and TLC. Full-scale analysis of chemical shifts and spin-spin coupling constants was performed

  14. Targeting Mast Cells and Basophils with Anti-FcεRIα Fab-Conjugated Celastrol-Loaded Micelles Suppresses Allergic Inflammation.

    Science.gov (United States)

    Peng, Xia; Wang, Juan; Li, Xianyang; Lin, Lihui; Xie, Guogang; Cui, Zelin; Li, Jia; Wang, Yuping; Li, Li

    2015-12-01

    Mast cells and basophils are effector cells in the pathophysiology of allergic diseases. Targeted elimination of these cells may be a promising strategy for the treatment of allergic disorders. Our present study aims at targeted delivery of anti-FcεRIα Fab-conjugated celastrol-loaded micelles toward FcεRIα receptors expressed on mast cells and basophils to have enhanced anti-allergic effect. To achieve this aim, we prepared celastrol-loaded (PEO-block-PPO-block-PEO, Pluronic) polymeric nanomicelles using thin-film hydration method. The anti-FcεRIα Fab Fragment was then conjugated to carboxyl groups on drug-loaded micelles via EDC amidation reaction. The anti-FcεRIα Fab-conjugated celastrol-loaded micelles revealed uniform particle size (93.43 ± 12.93 nm) with high loading percentage (21.2 ± 1.5% w/w). The image of micelles showed oval and rod like. The anti-FcεRIα Fab-conjugated micelles demonstrated enhanced cellular uptake and cytotoxity toward target KU812 cells than non-conjugated micelles in vitro. Furthermore, diffusion of the drug into the cells allowed an efficient induction of cell apoptosis. In mouse model of allergic asthma, treatment with anti-FcεRIα Fab-conjugated micelles increased lung accumulation of micelles, and significantly reduced OVA-sIgE, histamine and Th2 cytokines (IL-4, IL-5, TNF-α) levels, eosinophils infiltration and mucus production. In addition, in mouse model of passive cutaneous anaphylaxis, anti-FcεRIα Fab-conjugated celastrol-loaded micelles treatment significantly decreased extravasated evan's in the ear. These results indicate that anti-FcεRIα Fab-conjugated celastrol-loaded micelles can target and selectively kill mast cells and basophils which express FcεRIα, and may be efficient reagents for the treatment of allergic disorders and mast cell related diseases.

  15. Enhanced photodynamic efficacy of zinc phthalocyanine by conjugating to heptalysine.

    Science.gov (United States)

    Li, Linsen; Luo, Zhipu; Chen, Zhuo; Chen, Jincan; Zhou, Shanyong; Xu, Peng; Hu, Ping; Wang, Jundong; Chen, Naisheng; Huang, Jinling; Huang, Mingdong

    2012-11-21

    Zinc phthalocyanine (ZnPc) is a promising photosensitizer for photodynamic therapy, but faces some challenges: ZnPc is insoluble in water and thus requires either special formulation of ZnPc by, e.g., liposome or Cremophor EL, or chemical modification of Pc ring to enhance its bioavailability and photodynamic efficacy. Here, we conjugated monosubstituted ZnPc-COOH with a series of oligolysine moieties with different numbers of lysine residues (ZnPc-(Lys)(n) (n = 1, 3, 5, 7, 9) to improve the water solubility of the ZnPc conjugates. We measured the photosensitizing efficacies and the cellular uptakes of this series of conjugates on a normal and a cancerous cell line. In addition, we developed a sensitive in situ method to distinguish the difference in photodynamic efficacy among conjugates. Our results showed that ZnPc-(Lys)(7) has the highest photodynamic efficacy compared to the other conjugates investigated.

  16. Preparation and immunological properties of procaine-protein conjugates

    International Nuclear Information System (INIS)

    Liakopoulou, A.

    1981-01-01

    Procaine was conjugated to BSA and rat and rabbit Gf using the carbodiimide method and 14 C-procaine as tracer. The composition of the conjugates could be varied depending on the time of incubation and the concentration of procaine in the reaction mixtures. Procaine-BSA conjugates were soluble in water or saline. However, procaine conjugates to rat or rabbit Gf were not readily soluble in saline. These conjugates were good for immunization purposes, but it was cumbersome to work with them when clear solutions were needed, as in the immunochemical procedures used in this study. The immunological properties of the conjugates were studied in rats and rabbits. Rats responded with production of IgGa and precipitating antibodies to the procaine group, but IgE antibodies to the immunogen could not be detected. Furthermore, precipitating antibodies towards the procaine group were raised in rabbits. When BSA was the protein carrier, antibodies to the carrier molecule were also detected in both rats and rabbits. The conjugates of procaine to rat or rabbit Gf did not elicit antibody response to the carrier molecule when used in the homologous species. Hapten inhibition studies suggested that, in the rabbit, antibodies were also produced with specificity directed towards the molecular configuration of the hapten-carrier bond. (author)

  17. Preparation and biodistribution study of 99Tcm labelled dextran conjugates

    International Nuclear Information System (INIS)

    Yang Chunhui; Li Hongyu; Liang Jixin; Lu Jia; Luo Hongyi; Zheng Deqiang; Sun Guiquan

    2012-01-01

    99 Tc m Mannosylated dextran conjugates were prepared through [ 99 Tc m (CO) 3 ] + precursor synthesized by carbonyl Isolink kit. The labelled conjugates were injected sub-dermally into the rear foots of the mice, and the patent blue solution was injected at the same site 10 min before sacrifice. The mice were killed at 1 h and 4 h postinjection, and the samples of different tissues including SLN, 2LN, injection site, liver, spleen, blood were dissected and counted. The uptake in terms was calculated. The results of biodistribution demonstrated that the SLN uptakes of radiopharmaceutical (without mannose in the molecules) were rather low and in vivo excretion of these conjugates were comparatively faster, and the uptake of injection site was also low; on the other hand, the SLN uptakes of radio pharmaceutical (with mannose in their molecules) were much higher than those of their corresponding dextran conjugates without mannose, but the retention in the injection site of these conjugates increased too. The results indicated that the affinity of mannosyl-dextran conjugates to the receptors on the surface of macrophages in the lymph node. In addition, the different relative molecular mass of dextran conjugates also cause different biodistribution results, the major one had higher SLN uptake, the difference was significant (P 99 Tc m (CO) 3 ] + labelled mannosylated dextran conjugates showed promising properties as SLN imaging agent and worth further investigation. (authors)

  18. A Convenient Synthesis of Conjugated Acetylenic Ketones by Copper(l)-Catalyzed under Microwave Irradiation

    Institute of Scientific and Technical Information of China (English)

    WANG JinXian; WEI BangGuo; ZHAO LianBiao; HU YuLai; KANG LiQing

    2001-01-01

    @@ Alkynyl ketones are useful precursors and intermediates in synthetic organic chemistry1 and has evoked considerable interest. A number of methods for the synthesis of conjugated acetylenic ketones involve the reaction a metal acetylide with an acyl chlorides or another carboxylic acid derivative have been developed 2. Recently, the synthesis of α, β-conjugated acetylenic ketones catalyzed by Pd(Ⅱ) or by copper(Ⅰ)pd(Ⅱ) reaction of 1-alkynes and acyl chlorides have been described. The acylation of terminal alkynes by acyl chlorides in the presence of catalytic amounts copper(Ⅰ) salts leading to α, β-conjugated acetylenic ketones has also been reported. However, many of these reactions suffer from lack of high pressure (17 atm), long reaction time (30 h)and require low temperatures (-78℃). Our work involves the synthesis of conjugated acetylenic ketones via the reaction of terminal alkynes with aroyl chlorides in the presence of cuprous iodide under microwave irradiation conditions.

  19. Probing Surface-Adlayer Conjugation on Organic-Modified Si(111) Surfaces with Microscopy, Scattering, Spectroscopy, and Density Functional Theory

    International Nuclear Information System (INIS)

    Kellar, Joshua A.; Lin, Jui-Ching; Kim, Jun-Hyun; Yoder, Nathan L.; Bevan, Kirk H.; Stokes, Grace Y.; Geiger, Franz M.; Nguyen, SonBinh T.; Bedzyk, Michael J.; Hersam, Mark C.

    2009-01-01

    Highly conjugated molecules bound to silicon are promising candidates for organosilicon electronic devices and sensors. In this study, 1-bromo-4-ethynylbenzene was synthesized and reacted with a hydrogen-passivated Si(111) surface via ultraviolet irradiation. Through an array of characterization and modeling tools, the binding configuration and morphology of the reacted molecule were thoroughly analyzed. Atomic force microscopy confirmed an atomically flat surface morphology following reaction, while X-ray photoelectron spectroscopy verified reaction to the surface via the terminal alkyne moiety. In addition, synchrotron X-ray characterization, including X-ray reflectivity, X-ray fluorescence, and X-ray standing wave measurements, enabled sub-angstrom determination of the position of the bromine atom with respect to the silicon lattice. This structural characterization was quantitatively compared with density functional theory (DFT) calculations, thus enabling the π-conjugation of the terminal carbon atoms to be deduced. The X-ray and DFT results were additionally corroborated with the vibrational spectrum of the organic adlayer, which was measured with sum frequency generation. Overall, these results illustrate that the terminal carbon atoms in 1-bromo-4-ethynylbenzene adlayers on Si(111) retain π-conjugation, thus revealing alkyne molecules as promising candidates for organosilicon electronics and sensing.

  20. Selective alkylation of T–T mismatched DNA using vinyldiaminotriazine–acridine conjugate

    Science.gov (United States)

    Onizuka, Kazumitsu; Usami, Akira; Yamaoki, Yudai; Kobayashi, Tomohito; Hazemi, Madoka E; Chikuni, Tomoko; Sato, Norihiro; Sasaki, Kaname; Katahira, Masato

    2018-01-01

    Abstract The alkylation of the specific higher-order nucleic acid structures is of great significance in order to control its function and gene expression. In this report, we have described the T–T mismatch selective alkylation with a vinyldiaminotriazine (VDAT)–acridine conjugate. The alkylation selectively proceeded at the N3 position of thymidine on the T–T mismatch. Interestingly, the alkylated thymidine induced base flipping of the complementary base in the duplex. In a model experiment for the alkylation of the CTG repeats DNA which causes myotonic dystrophy type 1 (DM1), the observed reaction rate for one alkylation increased in proportion to the number of T–T mismatches. In addition, we showed that primer extension reactions with DNA polymerase and transcription with RNA polymerase were stopped by the alkylation. The alkylation of the repeat DNA will efficiently work for the inhibition of replication and transcription reactions. These functions of the VDAT–acridine conjugate would be useful as a new biochemical tool for the study of CTG repeats and may provide a new strategy for the molecular therapy of DM1. PMID:29309639

  1. Selective alkylation of T-T mismatched DNA using vinyldiaminotriazine-acridine conjugate.

    Science.gov (United States)

    Onizuka, Kazumitsu; Usami, Akira; Yamaoki, Yudai; Kobayashi, Tomohito; Hazemi, Madoka E; Chikuni, Tomoko; Sato, Norihiro; Sasaki, Kaname; Katahira, Masato; Nagatsugi, Fumi

    2018-02-16

    The alkylation of the specific higher-order nucleic acid structures is of great significance in order to control its function and gene expression. In this report, we have described the T-T mismatch selective alkylation with a vinyldiaminotriazine (VDAT)-acridine conjugate. The alkylation selectively proceeded at the N3 position of thymidine on the T-T mismatch. Interestingly, the alkylated thymidine induced base flipping of the complementary base in the duplex. In a model experiment for the alkylation of the CTG repeats DNA which causes myotonic dystrophy type 1 (DM1), the observed reaction rate for one alkylation increased in proportion to the number of T-T mismatches. In addition, we showed that primer extension reactions with DNA polymerase and transcription with RNA polymerase were stopped by the alkylation. The alkylation of the repeat DNA will efficiently work for the inhibition of replication and transcription reactions. These functions of the VDAT-acridine conjugate would be useful as a new biochemical tool for the study of CTG repeats and may provide a new strategy for the molecular therapy of DM1.

  2. Maillard Conjugation of Sodium Alginate to Whey Protein for Enhanced Resistance to Surfactant-Induced Competitive Displacement from Air-Water Interfaces.

    Science.gov (United States)

    Cai, Bingqing; Saito, Anna; Ikeda, Shinya

    2018-01-24

    Whey protein adsorbed to an interface forms a viscoelastic interfacial film but is displaced competitively from the interface by a small-molecule surfactant added afterward. The present study evaluated the impact of the covalent conjugation of high- or low-molecular-weight sodium alginate (HA or LA) to whey protein isolate (WPI) via the Maillard reaction on the ability of whey protein to resist surfactant-induced competitive displacement from the air-water interface. Surfactant added after the pre-adsorption of conjugate to the interface increased surface pressure. At a given surface pressure, the WPI-LA conjugate showed a significantly higher interfacial area coverage and lower interfacial film thickness compared to those of the WPI-HA conjugate or unconjugated WPI. The addition of LA to the aqueous phase had little effect on the interfacial area and thickness of pre-adsorbed WPI. These results suggest the importance of the molecular weight of the polysaccharide moiety in determining interfacial properties of whey protein-alginate conjugates.

  3. Charge transport behavior of benodithiophene-diketopyrrololpyrrole-based conjugated polymer in organic field-effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jin Kuen [Dept. of Chemistry, Hankuk University of Foreign Studies, Yongin (Korea, Republic of)

    2015-07-15

    Organic optoelectronic devices, such as light-emitting diodes, organic solar cells (OSCs), and organic field effect transistors (OFETs), have emerged due to the development of π-conjugated polymers. Because the delocalized π-framework can significantly reduce the energy gap between the highest-occupied molecular orbital (HOMO) and the lowest-unoccupied molecular orbital (LUMO), their intrinsic optoelectronic properties can be tunable with their conjugation length in terms of average molecular weights and their π-backbone structures. The new type of low bandgap conjugated polymer (P1) has been successively polymerized via a palladium- catalyzed Stille cross-coupling reaction with bis-ethylhexyl BDT and bis-n-decane DPP. With a linear alkyl chain in the DPP units, the intermolecular packing structure was thought to be enhanced by proving the UV–Vis and UPS spectra. In addition, the electronic properties of P1 via field-effect transistors well illustrate the typical p-type semiconducting property without showing the significant improvement by thermal annealing. From a broader perspective, this research indicates that a wider choice of linear alkyl chain length in DPP units and modification of the interface between dielectric and active layers should be sought to further optimize device performance. Hence, progressive works with the strategy presented in this report will be pursued to address the different challenges in attaining target OFET performances.

  4. 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

    A solid-phase conjugation method utilizing carrier protein bound to an ion exchange matrix was developed. Ovalbumin was adsorbed to an anion exchange matrix using a batch procedure, and the immobilized protein was then derivatized with iodoacetic acid N-hydroxysuccinimid ester. The activated......, and immunization experiments with the eluted conjugates showed that the more substituted conjugates gave rise to the highest titers of glutathione antibodies. Direct immunization with the conjugates adsorbed to the ion exchange matrix was possible and gave rise to high titers of glutathione antibodies. Conjugates...... 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...

  5. Utilization of niobium pentoxide as additive for reducing the ''in situ'' reaction temperature of ceramic composites in the system mullite-zirconia

    International Nuclear Information System (INIS)

    Melo, F.C.L. de; Cairo, C.A.A.; Piorino Neto, F.; Cunha, P.A.; Devezas, T.C.

    1988-01-01

    Ceramics Composites of the system mullite-zirconia were produced trough reaction sintering, following the equation: 2ZrSiO 4 +3Al 2 O 3 +x(Al 2 O 3 +Nb 2 O 5 )--> 2ZrO 2 +Al 6 Si 2 O 13 +2xAlNbO 4 , with different x values (0.05,0.1 e 0.25), trying to investigate the role of niobia as sintering aid. Through x-ray diffraction was evaluated the fraction of zirconia tetragonal phase retained in the ceramic matrix, and the produced composites were caracterized as to the apparent porosity and density, sintering shrinkage and rupture strenght. The reaction sintering temperature was reduced from 1600 0 C (x=0) to 1400 0 C (with x=0.1). (author) [pt

  6. Nanostructured conjugated polymers in chemical sensors: synthesis, properties and applications.

    Science.gov (United States)

    Correa, D S; Medeiros, E S; Oliveira, J E; Paterno, L G; Mattoso, Luiz C

    2014-09-01

    Conjugated polymers are organic materials endowed with a π-electron conjugation along the polymer backbone that present appealing electrical and optical properties for technological applications. By using conjugated polymeric materials in the nanoscale, such properties can be further enhanced. In addition, the use of nanostructured materials makes possible miniaturize devices at the micro/nano scale. The applications of conjugated nanostructured polymers include sensors, actuators, flexible displays, discrete electronic devices, and smart fabric, to name a few. In particular, the use of conjugated polymers in chemical and biological sensors is made feasible owning to their sensitivity to the physicochemical conditions of its surrounding environment, such as chemical composition, pH, dielectric constant, humidity or even temperature. Subtle changes in these conditions bring about variations on the electrical (resistivity and capacitance), optical (absorptivity, luminescence, etc.), and mechanical properties of the conjugated polymer, which can be precisely measured by different experimental methods and ultimately associated with a specific analyte and its concentration. The present review article highlights the main features of conjugated polymers that make them suitable for chemical sensors. An especial emphasis is given to nanostructured sensors systems, which present high sensitivity and selectivity, and find application in beverage and food quality control, pharmaceutical industries, medical diagnosis, environmental monitoring, and homeland security, and other applications as discussed throughout this review.

  7. 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.

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

    KAUST Repository

    Millet, Anthony; Lefebvre, Quentin; Rueping, Magnus

    2016-01-01

    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

  9. 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

  10. Experience in using the covariances of some ENDF/B-V dosimetry cross sections: proposed improvements and addition of cross-reaction covariances

    International Nuclear Information System (INIS)

    Fu, C.Y.; Hetrick, D.M.

    1982-01-01

    Recent ratio data, with carefully evaluated covariances, were combined with eleven of the ENDF/B-V dosimetry cross sections using the generalized least-squares method. The purpose was to improve these evaluated cross sections and covariances, as well as to generate values for the cross-reaction covariances. The results represent improved cross sections as well as realistic and usable covariances. The latter are necessary for meaningful intergral-differential comparisons and for spectrum unfolding

  11. 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...

  12. 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...

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

    International Nuclear Information System (INIS)

    Shukla, Rameshwer; Thomas, Thommey P; Desai, Ankur M; Kotlyar, Alina; Park, Steve J; Baker, James R Jr

    2008-01-01

    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

  14. Kinetic, stereochemical, and molecular association factors in the hydralumination of group IV subtituted alkynes. The role of p/sub π/-d/sub π/ conjugation in the addition of diisobutylaluminum hydride to trimethyl(phenylethynyl)silane

    International Nuclear Information System (INIS)

    Eisch, J.J.; Rhee, S.G.

    1975-01-01

    The kinetic, stereochemistry, and molecular association factors for the addition of diisobutylaluminum hydride to trimethyl(phenylethynyl)silane were studied in the temperature range of -10 to 38 0 . Hydralumination was found to have a kinetic true order of essentially one in the alkyne and one-third in the hydride. Although the trans adduct is the predominating product (approximately 99 percent) after completion of the hydralumination, the variation of the proportion of cis adduct and the initial rate law are consistent with a kinetically controlled cis hydralumination by monomeric R 2 'AlH, followed by a rapid isomerization to the trans adduct. The trans adduct formed a complex with l equivalent to the hydride. This complexation had to be taken into account, in order to explain the observed rate retardation and to obtain satisfactory integrated rate expressions for hydraluminations monitored to high conversion. Since in hydralumination this silylacetylene shows a stereospecificity and regiospecificity exactly opposite that of tert-butyl(phenyl)acetylene, as well as a heightened reactivity, a critical consideration of possible p/sub π/--d/sub π/ electronic effects was undertaken. The unusually facile isomerization of the resulting silyl-substituted vinylalanes, however, does seem more persuasive evidence for a p/sub π/--d/sub π/ effect, which promotes isomerization by electrophilic attack of R 2 'AlH on the carbon α to the Me 3 Si group. (U.S.)

  15. Human platelet as an independent unit for sulfate conjugation

    International Nuclear Information System (INIS)

    Khoo, B.Y.; Sit, K.H.; Wong, K.P.

    1988-01-01

    The human platelets possess a full complement of enzymes capable of synthesizing N-acetyldopamine (NADA) 35 sulfate from ATP, Mg ++ and sodium 35 sulfate. The pH optimum for this three-step overall sulfate conjugation (comprising of the ATP sulfurylase, APS kinase and phenolsulfotransferase reactions) is 8.6 and the reactions proceeded progressively for several hours. Both ATP and Mg ++ ions, above their respective optimal concentrations of 5 and 7 mM, inhibited the sulfate conjugation of NADA. The apparent Km values for NADA as determined by the phenolsulfotransferase (PST) and overall reactions were similar in magnitude being 2.6 and 4.8 μM, respectively, while that for sodium 35 sulfate was 202 μM. A comparison of these two activities in 62 platelet preparations of normal subjects showed that the rate of the PST reaction was generally higher than the overall reaction even though the PST assay was carried out at suboptimal concentration of PAPS. There was a positive correlation (r=0.82) between the two sets of data, suggesting that the PST reaction probably has some control over the rate of overall sulfate conjugation

  16. Preparation, structural analysis and bioactivity of ribonuclease A-albumin conjugate: tetra-conjugation or PEG as the linker.

    Science.gov (United States)

    Li, Chunju; Lin, Qixun; Wang, Jun; Shen, Lijuan; Ma, Guanghui; Su, Zhiguo; Hu, Tao

    2012-12-31

    Ribonuclease A (RNase A) is a therapeutic enzyme with cytotoxic action against tumor cells. Its clinical application is limited by the short half-life and insufficient stability. Conjugation of albumin can overcome the limitation, whereas dramatically decrease the enzymatic activity of RNase A. Here, three strategies were proposed to prepare the RNase A-bovine serum albumin (BSA) conjugates. R-SMCC-B (a conjugate of four RNase A attached with one BSA) and R-PEG-B (a mono-conjugate) were prepared using Sulfo-SMCC (a short bifunctional linker) and mal-PEG-NHS (a bifunctional PEG), respectively. Mal-PEG-NHS and hexadecylamine (HDA) were used to prepare the mono-conjugate, R-HDA-B, where HDA was adopted to bind BSA. The PEG linker can elongate the proximity between RNase A and BSA. In contrast, four RNase A were closely located on BSA in R-SMCC-B. R-SMCC-B showed the lowest K(m) and the highest relative enzymatic activity and k(cat)/K(m) in the three conjugates. Presumably, the tetravalent interaction of RNase A in R-SMCC-B can increase the binding affinity to its substrate. In addition, the slow release of BSA from R-HDA-B may increase the enzymatic activity of R-HDA-B. Our study is expected to provide strategies to develop protein-albumin conjugate with high therapeutic potential. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. Conjugation in Escherichia coli

    Science.gov (United States)

    Boyer, Herbert

    1966-01-01

    Boyer, Herbert (Yale University, New Haven, Conn.). Conjugation in Escherichia coli. J. Bacteriol. 91:1767–1772. 1966.—The sex factor of Escherichia coli K-12 was introduced into an E. coli B/r strain by circumventing the host-controlled modification and restriction incompatibilities known to exist between these closely related strains. The sexual properties of the constructed F+ B strain and its Hfr derivatives were examined. These studies showed that the E. coli strain B/r F+ and Hfr derivatives are similar to the E. coli strain K-12 F+ and Hfr derivatives. However, the site of sex factor integration was found to be dependent on the host genome. PMID:5327905

  18. Electrochromic in conjugated polymers

    International Nuclear Information System (INIS)

    Picado Valenzuela, Alfredo

    2007-01-01

    This revision considered object the description of one of the materials with the greatest potential in the field of electrochromic (mainly in the visible region): the conjugated polymers (CP), area of enormous potential both now and in a short time ahead. The CP are insulating materials and organic semiconductors in a state not doped. They can be doped positively or negatively being observed a significant increase in the conductivity and being generated a color change in these materials. The understanding of how optical properties vary based on the chemical structure of the polymer or its mixtures and more precisely of the alternatives that can be entered into the conjugated system or π system to obtain a material that besides to be flexible, environmentally stable, presents the colored states. The revision was centred chiefly in the polypyrrole (Ppy), the polythiophene (PTh) and their derivatives such as poly (3.4-ethylenedioxythiophene) (PEDOT). The advantage of using monomers with variable structure, to adjust the composition of the copolymer, or to blend with the PC, allows to obtain a variety of colored states that can be modulated through the visible spectrum and even with applications to wavelengths outside of this region. Because the PC presented at least two different colored states can be varied continuously as a function of the voltage applied. In some cases, they may submit multicoloured statements, which offers a range of possibilities for their application in flexible electronic devices type screens and windows. Applications include smart windows, camouflage clothing and data screens. This type of material is emerging as one of the substitutes of the traditional inorganic semiconductor, with the advantage of its low cost, high flexibility and the possibility to generate multiple colors through the handling of the monomers in the structure and control of energy of his band gap. (author) [es

  19. Metal-free bioconjugation reactions.

    Science.gov (United States)

    van Berkel, Sander S; van Delft, Floris L

    2013-01-01

    The recent strategy to apply chemical reactions to address fundamental biological questions has led to the emergence of entirely new conjugation reactions that are fast and irreversible, yet so mild and selective that they can be performed even in living cells or organisms. These so-called bioorthogonal reactions open novel avenues, not only in chemical biology research, but also in many other life sciences applications, including the modulation of biopharmaceuticals by site-specific modification approaches.

  20. The Gas-Phase Photophysics of Eosin Y and its Maleimide Conjugate.

    Science.gov (United States)

    Daly, Steven; Kulesza, Alexander; Knight, Geoffrey; MacAleese, Luke; Antoine, Rodolphe; Dugourd, Philippe

    2016-05-26

    The use of the xanthene family of dyes as fluorescent probes in a wide range of applications has provided impetus for the studying of their photophysical properties. In particular, recent advances in gas-phase techniques such as FRET that utilize such chromophores have placed a greater importance on the characterization of these properties in the gas phase. Additionally, the use of synthetic linker chains to graft the chromophores in a site-specific manner to their target system is ubiquitous. There is, however, often limited information on how the addition of such a linker chain may affect the photophysical properties of the chromophores, which is of fundamental importance for interpretation of experimental data reliant on grafted chromophores. Here, we present data on the optical spectroscopy of different protonation states of Eosin Y, a fluorescein derivative. We compare the photophysics of Eosin Y to its maleimide conjugate, and to the thioether product of the reaction of this conjugate with cysteamine. Comparison of the mass spectra following laser irradiation shows that very different relaxation takes place upon addition of the maleimide moiety but that the photophysics of the bare chromophore are restored upon addition of cysteamine. This radical change in the photophysics is interpreted in terms of charge-transfer states, whose energy relative to the S1 ← S0 transition of the chromophore is dependent on the conjugation of the maleimide moiety. We also show that the shape of the absorption band is unchanged in the gas-phase as compared to the solution-phase, showing a maximum with a shoulder toward the blue, and examination of isotope distributions of the isolated ions show that this shoulder cannot be due to the presence of dimers. Consideration of the fluorescence emission spectrum allows a tentative assignment of the shoulder to be due to a vibrational progression with a high Franck-Condon factor.

  1. Palladium-catalyzed regio- and stereoselective cross-addition of terminal alkynes to ynol ethers and synthesis of 1,4-enyn-3-ones.

    Science.gov (United States)

    Babu, Madala Hari; Dwivedi, Vikas; Kant, Ruchir; Reddy, Maddi Sridhar

    2015-03-16

    Conjugated enynes, enol ethers, and enynones are versatile building blocks that can be elaborated by a wide variety of synthetic transformations. The selective synthesis of such units is a prerequisite for their effective utilization. The synthesis of conjugated 2-phenoxyenynes through a palladium-catalyzed cross-addition of terminal alkynes to phenylethynyl ethers (hydroalkynylation) is now presented. The reaction is highly regio-, stereo-, and chemoselective, and shows excellent tolerance toward functional groups. The addition further features very mild reaction conditions (room temperature) and an inexpensive catalytic system (without a ligand and with a cheaply available Pd catalyst). The thus synthesized enynyl ethers with allylic hydroxy tethers, which survived the reaction, were shown to be ready precursors for valuable 1-en-4-yn-3-ones. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. 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...

  3. 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.

  4. Block-conjugate-gradient method

    International Nuclear Information System (INIS)

    McCarthy, J.F.

    1989-01-01

    It is shown that by using the block-conjugate-gradient method several, say s, columns of the inverse Kogut-Susskind fermion matrix can be found simultaneously, in less time than it would take to run the standard conjugate-gradient algorithm s times. The method improves in efficiency relative to the standard conjugate-gradient algorithm as the fermion mass is decreased and as the value of the coupling is pushed to its limit before the finite-size effects become important. Thus it is potentially useful for measuring propagators in large lattice-gauge-theory calculations of the particle spectrum

  5. Asymmetric Domino Aza-Michael Addition/[3+2] Cycloaddition Reactions as a Versatile Approach to alpha,beta,gamma,-Triamino Acid Derivatives

    Czech Academy of Sciences Publication Activity Database

    Kapras, Vojtěch; Pohl, Radek; Císařová, I.; Jahn, Ullrich

    2014-01-01

    Roč. 16, č. 4 (2014), s. 1088-1091 ISSN 1523-7060 Institutional support: RVO:61388963 Keywords : 1,3-dipolar cycloaddition * lithium amides * aza-Michael addition * amino acids * pyrazoles Subject RIV: CC - Organic Chemistry Impact factor: 6.364, year: 2014

  6. Polyfunctional beta-Dicarbonyl Compounds by Michael Addition Reactions of Ester Enolates to alpha-Benzylidene and alpha-Alkylidene-beta-dicarbonyl Compounds

    Czech Academy of Sciences Publication Activity Database

    Holan, Martin; Pohl, Radek; Císařová, I.; Jahn, Ullrich

    -, č. 18 (2012), s. 3459-3475 ISSN 1434-193X R&D Projects: GA ČR GA203/09/1936 Institutional research plan: CEZ:AV0Z40550506 Keywords : Michael addition * diastereoselectivity * regioselectivity * enols * dicarbonyl compounds Subject RIV: CC - Organic Chemistry Impact factor: 3.344, year: 2012

  7. Effect of Zr addition on structure and electrical properties of SmFeO3 prepared by solid state reaction method

    Directory of Open Access Journals (Sweden)

    Abdalla M. Abdalla

    2017-12-01

    Full Text Available Series of Sm1-xFe1-3xZr3xO3 (SFZO, where x = 0.0, 0.01, 0.02, 0.033, 0.05, 0.1 and 0.15, was synthesised by the solid state reaction method and sintered at 1500 °C in air. X-ray diffraction (XRD and scanning electron microscopy (SEM were used to investigate the structure of the materials. The XRD results indicated that the pure SmFeO3 and Sm0.99Fe0.97Zr0.03O3 samples are single phase materials with an orthorhombic symmetry and Pbnm space group. The increase of Zr content (x ≥ 0.02 causes a phase change from single to two-phase system with orthorhombic (Pbnm and fluorite symmetry (Fm3m. The microstructural analyses showed that the Zr4+ doping resulted in an increase of porosity in the sintered SFZO compared to SmFeO3 sample. The direct current (DC electrical conductivity at 850 °C in air was found to be 0.045 S/cm and 0.007 S/cm for Sm0.99Fe0.97Zr0.03O3 and SmFeO3, respectively, showing a significant enhancement compared to the pure SmFeO3.

  8. Entanglements in Conjugated Polymers

    Science.gov (United States)

    Xie, Renxuan; Lee, Youngmin; Aplan, Melissa; Caggiano, Nick; Gomez, Enrique; Colby, Ralph

    Conjugated polymers, such as poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly-((9,9-dioctylfluorene)-2,7-diyl-alt-[4,7-bis(thiophen-5-yl)-2,1,3-benzothiadiazole]-2',2''-diyl) (PFTBT), are widely used as hole and electron transport materials in a variety of electronic devices. However, fundamental knowledge regarding chain entanglements and nematic-to-isotropic transition is still lacking and are crucial to maximize charge transport properties. A systematic melt rheology study on P3HT with various molecular weights and regio regularities was performed. We find that the entanglement molecular weight Me is 5.0 kg/mol for regiorandom P3HT, but the apparent Me for regioregular P3HT is significantly higher. The difference is postulated to arise from the presence of a nematic phase only in regioregular P3HT. Analogously, PFTBT shows a clear rheological signature of the nematic-to-isotropic transition as a reversible sharp transition at 278 C. Shearing of this nematic phase leads to anisotropic crystalline order in PFTBT. We postulate that aligning the microstructure will impact charge transport and thereby advance the field of conducting polymers. National Science Foundation.

  9. Photodynamic tissue adhesion with chlorin(e6) protein conjugates.

    Science.gov (United States)

    Khadem, J; Veloso, A A; Tolentino, F; Hasan, T; Hamblin, M R

    1999-12-01

    To test the hypothesis that a photodynamic laser-activated tissue solder would perform better in sealing scleral incisions when the photosensitizer was covalently linked to the protein than when it was noncovalently mixed. Conjugates and mixtures were prepared between the photosensitizer chlorin(e6) and various proteins (albumin, fibrinogen, and gelatin) in different ratios and used to weld penetrating scleral incisions made in human cadaveric eyes. A blue-green (488-514 nm) argon laser activated the adhesive, and the strength of the closure was measured by increasing the intraocular pressure until the wound showed leakage. Both covalent conjugates and noncovalent mixtures showed a light dose-dependent increase in leaking pressure. A preparation of albumin chlorin(e6) conjugate with additional albumin added (2.5 protein to chlorin(e6) molar ratio) showed significantly higher weld strength than other protein conjugates and mixtures. This is the first report of dye-protein conjugates as tissue solders. These conjugates may have applications in ophthalmology.

  10. Protein carriers of conjugate vaccines: characteristics, development, and clinical trials.

    Science.gov (United States)

    Pichichero, Michael E

    2013-12-01

    The immunogenicity of polysaccharides as human vaccines was enhanced by coupling to protein carriers. Conjugation transformed the T cell-independent polysaccharide vaccines of the past to T cell-dependent antigenic vaccines that were much more immunogenic and launched a renaissance in vaccinology. This review discusses the conjugate vaccines for prevention of infections caused by Hemophilus influenzae type b, Streptococcus pneumoniae, and Neisseria meningitidis. Specifically, the characteristics of the proteins used in the construction of the vaccines including CRM, tetanus toxoid, diphtheria toxoid, Neisseria meningitidis outer membrane complex, and Hemophilus influenzae protein D are discussed. The studies that established differences among and key features of conjugate vaccines including immunologic memory induction, reduction of nasopharyngeal colonization and herd immunity, and antibody avidity and avidity maturation are presented. Studies of dose, schedule, response to boosters, of single protein carriers with single and multiple polysaccharides, of multiple protein carriers with multiple polysaccharides and conjugate vaccines administered concurrently with other vaccines are discussed along with undesirable consequences of conjugate vaccines. The clear benefits of conjugate vaccines in improving the protective responses of the immature immune systems of young infants and the senescent immune systems of the elderly have been made clear and opened the way to development of additional vaccines using this technology for future vaccine products.

  11. 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.

  12. Quantum dot-polymer conjugates for stable luminescent displays.

    Science.gov (United States)

    Ghimire, Sushant; Sivadas, Anjaly; Yuyama, Ken-Ichi; Takano, Yuta; Francis, Raju; Biju, Vasudevanpillai

    2018-05-23

    The broad absorption of light in the UV-Vis-NIR region and the size-based tunable photoluminescence color of semiconductor quantum dots make these tiny crystals one of the most attractive antennae in solar cells and phosphors in electrooptical devices. One of the primary requirements for such real-world applications of quantum dots is their stable and uniform distribution in optically transparent matrices. In this work, we prepare transparent thin films of polymer-quantum dot conjugates, where CdSe/ZnS quantum dots are uniformly distributed at high densities in a chitosan-polystyrene copolymer (CS-g-PS) matrix. Here, quantum dots in an aqueous solution are conjugated to the copolymer by a phase transfer reaction. With the stable conjugation of quantum dots to the copolymer, we prevent undesired phase separation between the two and aggregation of quantum dots. Furthermore, the conjugate allows us to prepare transparent thin films in which quantum dots are uniformly distributed at high densities. The CS-g-PS copolymer helps us in not only preserving the photoluminescence properties of quantum dots in the film but also rendering excellent photostability to quantum dots at the ensemble and single particle levels, making the conjugate a promising material for photoluminescence-based devices.

  13. 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.

  14. Effect of Ni addition to the Cu substrate on the interfacial reaction and IMC growth with Sn3.0Ag0.5Cu solder

    Science.gov (United States)

    Zhang, Xudong; Hu, Xiaowu; Jiang, Xiongxin; Li, Yulong

    2018-04-01

    The formation and growth of intermetallic compound (IMC) layer at the interface between Sn3.0Ag0.5Cu (SAC305) solder and Cu- xNi ( x = 0, 0.5, 1.5, 5, 10 wt%) substrate during reflowing and aging were investigated. The soldering was conducted at 270 °C using reflowing method, following by aging treatment at 150 °C for up to 360 h. The experimental results indicated that the total thickness of IMC increased with increasing aging time. The scallop-like Cu6Sn5 and planar-like Cu3Sn IMC layer were observed between SAC305 solder and purely Cu substrate. As the content of Ni element in Cu substrate was 0.5% or 1.5%, the scallop-like Cu6Sn5 and planar-like Cu3Sn IMC layer were still found between solder and Cu-Ni substrate and the total thickness of IMC layer decreased with the increasing Ni content. Besides, when the Ni content was up to 5%, the long prismatic (Cu,Ni)6Sn5 phase was the only product between solder and substrate and the total thickness of IMC layer increased significantly. Interestingly, the total thickness of IMC decreased slightly as the Ni addition was up to 10%. In the end, the grains of interfacial IMC layer became coarser with aging time increasing while the addition of Ni in Cu substrate could refine IMC grains.

  15. Synthesis and characterization of nido-carborane-cobalamin conjugates

    International Nuclear Information System (INIS)

    Hogenkamp, Harry P.C.; Collins, Douglas A.; Live, David; Benson, Linda M.; Naylor, Stephen

    2000-01-01

    Three vitamin B 12 (cyanocobalamin) conjugates bearing one nido-carborane molecule or two nido-carborane molecules linked to the propionamide side chains via a four carbon linker have been synthesized. Reaction of o-carboranoylchloride with 1,4-diaminobutane in pyridine produced nido-carboranoyl(4-amidobutyl)amine, which was linked to the b- and d-monocarboxylic acids and the b,d-dicarboxylic acid of cyanocobalamin. Mass spectrometry analysis as well as 11 B nuclear magnetic resonance demonstrated that during the reaction of o-carboranonylchloride with diaminobutane one of the boron atoms was eliminated. In vitro biological activity of the cyanocobalamin-nido-carborane conjugates was assessed by the unsaturated vitamin B 12 binding capacity assay. When compared with 57 Co cyanocobalamin, the biological activity of cyanocobalamin-b-nido-carborane, cyanocobalamin-d-nido-carborane, and cyanocobalamin-b-d-bis-nido-carborane conjugates were 92.93%, 35.75%, and 37.02%, respectively. These findings suggest that the 10 B cobalamin conjugates might be useful agents in treating malignant tumors via neutron capture therapy

  16. Optimization of condition for conjugation of enrofloxacin to enzymes in chemiluminescence enzyme immunoassay

    Science.gov (United States)

    Yu, Songcheng; Yu, Fei; Zhang, Hongquan; Qu, Lingbo; Wu, Yongjun

    2014-06-01

    In this study, in order to find out a proper method for conjugation of enrofloxacin to label enzymes, two methods were compared and carbodiimide condensation was proved to be better. The results showed that the binding ratio of enrofloxacin and alkaline phosphatase (ALP) was 8:1 and that of enrofloxacin and horseradish peroxidase (HRP) was 5:1. This indicated that conjugate synthesized by carbodiimide condensation was fit for chemiluminescence enzyme immunoassay (CLEIA). Furthermore, data revealed that dialysis time was an important parameter for conjugation and 6 days was best. Buffer to dilute conjugate had little effect on CLEIA. The storage condition for conjugates was also studied and it was shown that the conjugate was stable at 4 °C with no additive up to 30 days. These data were valuable for establishing CLEIA to quantify enrofloxacin.

  17. 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

  18. Preparation, isolation and identification of non-conjugated C18:2 fatty acid isomers.

    Science.gov (United States)

    Fardin-Kia, Ali Reza

    2016-12-01

    Non-conjugated geometric/positional isomers of linoleic acid (c9,c12-18:2) are often present in processed foods and oils. The following work presents a simple addition/elimination reaction for preparation of non-conjugated 18:2 fatty acid isomers. A mixture containing positional and geometric isomers of C18:2 fatty acids was produced by addition of hydrobromic acid to the fatty acid double bonds, followed by its elimination with a strong sterically hindered base. Pure 8,12-, 8,13-, 9,12-, and 9,13-18:2 fatty acid methyl esters were isolated from the synthetic mixture by a combination of sub-ambient RP-HPLC and Ag + -HPLC. The determination of the double bond position was achieved by GC-MS using picolinyl esters derivatives. The determination of the fatty acid double bond geometric configuration was obtained by partial hydrogenation of the isolated isomer with hydrazine, followed by the GC-FID analysis. Published by Elsevier Ireland Ltd.

  19. Research study of conjugate materials; Conjugate material no chosa kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-03-01

    The paper reported an introductory research on possibilities of new glass `conjugate materials.` The report took up the structure and synthetic process of conjugate materials to be researched/developed, classified them according to structural elements on molecular, nanometer and cluster levels, and introduced the structures and functions. Further, as glasses with new functions to be proposed, the paper introduced transparent and high-strength glass used for houses and vehicles, light modulation glass which realizes energy saving and optical data processing, and environmentally functional glass which realizes environmental cleaning or high performance biosensor. An initial survey was also conducted on rights of intellectual property to be taken notice of in Japan and abroad in the present situation. Reports were summed up and introduced of Osaka National Research Institute, Electrotechnical Laboratory, and National Industrial Research Institute of Nagoya which are all carrying out leading studies of conjugate materials. 235 refs., 135 figs., 6 tabs.

  20. 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.

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

    KAUST Repository

    Habuchi, Satoshi; Piwonski, Hubert Marek; Michinobu, Tsuyoshi

    2017-01-01

    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.

  2. Conjugated polymer zwitterions and solar cells comprising conjugated polymer zwitterions

    Science.gov (United States)

    Emrick, Todd; Russell, Thomas; Page, Zachariah; Liu, Yao

    2018-06-05

    A conjugated polymer zwitterion includes repeating units having structure (I), (II), or a combination thereof ##STR00001## wherein Ar is independently at each occurrence a divalent substituted or unsubstituted C3-30 arylene or heteroarylene group; L is independently at each occurrence a divalent C1-16 alkylene group, C6-30arylene or heteroarylene group, or alkylene oxide group; and R1 is independently at each occurrence a zwitterion. A polymer solar cell including the conjugated polymer zwitterion is also disclosed.

  3. 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...

  4. EXPERIENCE OF USE OF PNEUMOCOCCAL CONJUGATED 7-VALENT VACCINE IN SOME REGIONS OF RUSSIA

    Directory of Open Access Journals (Sweden)

    A.A. Ruleva

    2010-01-01

    Full Text Available An experience of immunization with pneumococcal conjugated 7-valent vaccine Prevenar in 234 children under 5 years old with different state of health was analyzed. There were no any severe reactions, postvaccinal complications or local reactions to the vaccine injection. Mild and moderate postvaccinal reactions were detected in 3,4% (n = 8 of children. The vaccine can be used in children under 5 years old.Key words: children, vaccination, pneumococcal conjugated 7-valent vaccine, safety.(Voprosy sovremennoi pediatrii — Current Pediatrics. 2010;9(2:119-123

  5. 99mTC-dextran-antibody conjugates. Labelling procedures

    International Nuclear Information System (INIS)

    Marquez, M.; Westlin, J.E.; Nilsson, S.; Holmberg, A.R.

    1996-01-01

    Dextran forms stable chelates with 99m Tc, a radionuclide with ideal properties for planar scintigraphic and tomographic imaging. This study investigates some of the factors of importance to the formation of 99m Tc-dextran. The complex was used for the technetium labelling of a monoclonal antibody. Two radiolabelling methods were studied: Direct dextran labelling with the reductant dissolved in HCl and labelling via a weak 'transfer' chelator (tartaric acid) with the reductant dissolved in ethanol. Different conditions during the labelling reaction were studied. Finally, dextran was coupled to a monoclonal anticytokeratin antibody and the conjugate was subsequently radiolabelled with 99m Tc. Gel filtration (GFR) and thin layer chromatography (TLC) were compared as methods for estimation of the labelling efficiency. When using 10-500 μM of ligand, 5-100 μM SnC1 2 with 10-500 MBq of technetium at pH7 incubated for 10-15 min, the radiolabelling seemed optimal (70-75% labelling efficiency). It was found that 100 μM tartaric acid used as a weak intermediate chelator with SnCl 2 dissolved in ethanol improved the reproducibility of the labelling. The labelling efficiency was not affected by either the presence of oxygen or the addition of an oxygen scavenger during the labelling incubation. In general, TLC showed higher labelling efficiencies than GFR, indicating inadequate separation of the different moieties. (orig.)

  6. 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.

  7. Radiolabeling optimization and characterization of (68)Ga labeled DOTA-polyamido-amine dendrimer conjugate - Animal biodistribution and PET imaging results.

    Science.gov (United States)

    Ghai, Aanchal; Singh, Baljinder; Panwar Hazari, Puja; Schultz, Michael K; Parmar, Ambika; Kumar, Pardeep; Sharma, Sarika; Dhawan, Devinder; Kumar Mishra, Anil

    2015-11-01

    The present study describes the optimization of (68)Ga radiolabeling with PAMAM dendrimer-DOTA conjugate. A conjugate (PAMAM-DOTA) concentration of 11.69µM, provided best radiolabeling efficiency of more than 93.0% at pH 4.0, incubation time of 30.0min and reaction temperature ranging between 90 and 100°C. The decay corrected radiochemical yield was found to be 79.4±0.01%. The radiolabeled preparation ([(68)Ga]-DOTA-PAMAM-D) remained stable (radiolabeling efficiency of 96.0%) at room temperature and in serum for up to 4-h. The plasma protein binding was observed to be 21.0%. After intravenous administration, 50.0% of the tracer cleared from the blood circulation by 30-min and less than 1.0% of the injected activity remained in blood by 1.0h. The animal biodistribution studies demonstrated that the tracer excretes through the kidneys and about 0.33% of the %ID/g accumulated in the tumor at 1h post injection. The animal organ's biodistribution data was supported by animal PET imaging showing good 'non-specific' tracer uptake in tumor and excretion is primarily through kidneys. Additionally, DOTA-PAMAM-D conjugation with αVβ3 receptors targeting peptides and drug loading on the dendrimers may improve the specificity of the (68)Ga labeled product for imaging and treating angiogenesis respectively. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Synthesis of polycyclic aromatic hydrocarbon-protein conjugates for preparation and immunoassay of antibodies.

    Science.gov (United States)

    Glushkov, Andrey N; Kostyanko, Mikhail V; Cherno, Sergey V; Vasilchenko, Ilya L

    2002-04-01

    The method is described dealing with the synthesis of conjugates protein-polycyclic aromatic hydrocarbons (PAHs), highly soluble in water, stable without special stabilizers and containing the minimum quantity of cross-linked products. The reaction of protein with PAH containing an aldehyde group, has been carried out in an alkaline solution, and stabilization of the conjugate has been achieved by reduction with sodium borohydride in the presence of a compound blocking the formation of an insoluble polymeric fraction. The efficiency of synthesized conjugates for the induction and immunoassay of Abs to PAH for benzo[a]pyrene is shown.

  9. Safety and immunogenicity of meningococcal A and C polysaccharide conjugate vaccine in adults.

    OpenAIRE

    Anderson, E L; Bowers, T; Mink, C M; Kennedy, D J; Belshe, R B; Harakeh, H; Pais, L; Holder, P; Carlone, G M

    1994-01-01

    A meningococcal vaccine containing group A and C polysaccharides conjugated to CRM197 was evaluated in 50 adults. Vaccinees were entered into one of five groups: 30 adults received a single dose of either 22, 11, or 5.5 micrograms of the conjugated A-C vaccine; 10 received an approved meningococcal vaccine; and 10 received saline injections. Local and systemic reactions to vaccines were recorded, and immune responses were determined. The experimental meningococcal vaccine was well tolerated, ...

  10. Bifunctional Rhodium Intercalator Conjugates as Mismatch-Directing DNA Alkylating Agents

    OpenAIRE

    Schatzschneider, Ulrich; Barton, Jacqueline K.

    2004-01-01

    A conjugate of a DNA mismatch-specific rhodium intercalator, containing the bulky chrysenediimine ligand, and an aniline mustard has been prepared, and targeting of mismatches in DNA by this conjugate has been examined. The preferential alkylation of mismatched over fully matched DNA is found by a mobility shift assay at concentrations where untethered organic mustards show little reaction. The binding site of the Rh intercalator was determined by DNA photocleavage, and the position of covale...

  11. Zero-energy modes, charge conjugation, and fermion number

    International Nuclear Information System (INIS)

    Sudarshan, E.C.G.; Yajnik, U.A.

    1986-01-01

    States with a half-integer fermion number occur when a fermionic field coupled to a soliton possesses a zero mode. This paper spells out the circumstances under which one can retain an integer fermion number as also a charge-conjugation-invariant ground state. It is necessary to make the representation reducible but it is kept irreducible by introducing an additional operator

  12. Free and conjugated dopamine in human ventricular fluid

    International Nuclear Information System (INIS)

    Sharpless, N.S.; Thal, L.J.; Wolfson, L.I.; Tabaddor, K.; Tyce, G.M.; Waltz, J.M.

    1981-01-01

    Free dopamine and an acid hydrolyzable conjugate of dopamine were measured in human ventricular fluid specimens with a radioenzymatic assay and by high performance liquid chromatography (HPLC) with electrochemical detection. Only trace amounts of free norepinephrine and dopamine were detected in ventricular fluid from patients with movement disorders. When the ventricular fluid was hydrolyzed by heating in HClO 4 or by lyophilization in dilute HClO 4 , however, a substantial amount of free dopamine was released. Values for free plus conjugated dopamine in ventricular fluid from patients who had never taken L-DOPA ranged from 139 to 340 pg/ml when determined by HPLC and from 223 to 428 pg/ml when measured radioenzymatically. The correlation coefficient for values obtained by the two methods in the same sample of CSF was 0.94 (P<0.001). Patients who had been treated with L-DOPA had higher levels of conjugated dopamine in their ventricular CSF which correlated inversely with the time between the last dose of L-DOPA and withdrawal of the ventricular fluid. Additionally, one patient with acute cerebral trauma had elevated levels of free norepinephrine and both free and conjugated dopamine in his ventricular fluid. Conjugation may be an important inactivation pathway for released dopamine in man. (Auth.)

  13. 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.

  14. 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; Yu, Zhaoyuan; Hoon, Ding Long; Huang, Kuo-Wei; Lan, Yu; Lu, Yixin

    2015-01-01

    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.

  15. 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.

  16. 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: https://www.ias.ac.in/article/fulltext/reso/013/08/0793-0794 ...

  17. Persistence Mechanisms of Conjugative Plasmids

    DEFF Research Database (Denmark)

    Bahl, Martin Iain; Hansen, Lars H.; Sørensen, Søren Johannes

    2009-01-01

    Are plasmids selfish parasitic DNA molecules or an integrated part of the bacterial genome? This chapter reviews the current understanding of the persistence mechanisms of conjugative plasmids harbored by bacterial cells and populations. The diversity and intricacy of mechanisms affecting the suc...

  18. 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.

  19. 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.

  20. REVIEW ARTICLE Conjugated Hyperbilirubinaemia in Early Infancy ...

    African Journals Online (AJOL)

    REVIEW ARTICLE Conjugated Hyperbilirubinaemia in Early Infancy. AOK Johnson. Abstract. Conjugated hyperbilirubinaemia exists when the conjugated serum bilirubin level is more than 2 mg/dl or more than 20 per cent of the total serum bilirubin. It is always pathological in early infancy. The causes are many and diverse ...

  1. Purification of SUMO conjugating enzymes and kinetic analysis of substrate conjugation

    Science.gov (United States)

    Yunus, Ali A.; Lima, Christopher D.

    2009-01-01

    SUMO conjugation to protein substrates requires the concerted action of a dedicated E2 ubiquitin conjugation enzyme (Ubc9) and associated E3 ligases. Although Ubc9 can directly recognize and modify substrate lysine residues that occur within a consensus site for SUMO modification, E3 ligases can redirect specificity and enhance conjugation rates during SUMO conjugation in vitro and in vivo. In this chapter, we will describe methods utilized to purify SUMO conjugating enzymes and model substrates which can be used for analysis of SUMO conjugation in vitro. We will also describe methods to extract kinetic parameters during E3-dependent or E3-independent substrate conjugation. PMID:19107417

  2. Synthesis, characterisation and biomedical applications of curcumin conjugated chitosan microspheres.

    Science.gov (United States)

    Saranya, T S; Rajan, V K; Biswas, Raja; Jayakumar, R; Sathianarayanan, S

    2018-04-15

    Curcumin is a diaryl heptanoid of curcuminoids class obtained from Curcuma longa. It possesses various biological activities like anti-inflammatory, hypoglycemic, antioxidant, wound-healing, and antimicrobial activities. Chitosan is a biocompatible, biodegradable and non-toxic natural polymer which enhances the adhesive property of the skin. Chemical conjugation will leads to sustained release action and to enhance the bioavailability. This study aims to synthesis and characterize biocompatible curcumin conjugated chitosan microspheres for bio-medical applications. The Schiff base reaction was carried out for the preparation of curcumin conjugated chitosan by microwave method and it was characterised using FTIR and NMR. Curcumin conjugated chitosan microspheres (CCCMs) were prepared by wet milling solvent evaporation method. SEM analysis showed these CCCMs were 2-5μm spherical particles. The antibacterial activities of the prepared CCCMs were studied against Staphylococcus aureus and Escherichia coli, the zone of inhibition was 28mm and 23mm respectively. Antioxidant activity of the prepared CCCMs was also studied by DPPH and H 2 O 2 method it showed IC 50 esteem value of 216μg/ml and 228μg/ml, and anti-inflammatory activity results showed that CCCMs having IC 50 value of 45μg/ml. The results conclude that the CCCMs having a good antibacterial, antioxidant and anti-inflammatory activities. This, the prepared CCCMs have potential application in preventing skin infections. Copyright © 2017. Published by Elsevier B.V.

  3. Raman and FTIR spectroscopic studies on two hydroxylated tung oils (HTO) bearing conjugated double bonds

    Science.gov (United States)

    Zhuang, Yuwei; Ren, Zhiyong; Jiang, Lei; Zhang, Jiaxiang; Wang, Huafen; Zhang, Guobao

    2018-06-01

    Tung oil (TO) was used as a model compound to study two hydroxylated tung oils (HTO), prepared from TO by either aminolysis (HTO-am) or alcoholysis (HTO-al). Main bands in Raman and FTIR spectra were initially assigned based on the detailed analysis of the compound spectra before and after exposure to elevated temperature (200 °C). The effect of heat treatment in air on spectral bands, and especially on the changes associated with double bonds, were then investigated. In the present work, changes in spectral bands due to heat treatment were compared with those revealed in the previous work of others. The results show that the conjugated triene structure of TO has been retained during alcoholysis and aminolysis, to yield the HTOs studied; yet the change of the triene structure caused by heating is different among the three samples; the H-bonding strength between OH and Cdbnd O in HTO-am is higher than that in HTO-al; the changes in HTO vOH and vCdbnd O bands in FTIR caused by the present heat treatment were significant; for TO, there is a big difference between changes in spectra as caused by thermal exposure, compared to those caused by ageing under UV light or exposure to a catalyst. The present work has laid additional groundwork for further study of the reactions of such triply conjugated double bond structures under different ageing conditions.

  4. The extended regulatory networks of SXT/R391 integrative and conjugative elements and IncA/C conjugative plasmids.

    Science.gov (United States)

    Poulin-Laprade, Dominic; Carraro, Nicolas; Burrus, Vincent

    2015-01-01

    Nowadays, healthcare systems are challenged by a major worldwide drug resistance crisis caused by the massive and rapid dissemination of antibiotic resistance genes and associated emergence of multidrug resistant pathogenic bacteria, in both clinical and environmental settings. Conjugation is the main driving force of gene transfer among microorganisms. This mechanism of horizontal gene transfer mediates the translocation of large DNA fragments between two bacterial cells in direct contact. Integrative and conjugative elements (ICEs) of the SXT/R391 family (SRIs) and IncA/C conjugative plasmids (ACPs) are responsible for the dissemination of a broad spectrum of antibiotic resistance genes among diverse species of Enterobacteriaceae and Vibrionaceae. The biology, diversity, prevalence and distribution of these two families of conjugative elements have been the subject of extensive studies for the past 15 years. Recently, the transcriptional regulators that govern their dissemination through the expression of ICE- or plasmid-encoded transfer genes have been described. Unrelated repressors control the activation of conjugation by preventing the expression of two related master activator complexes in both types of elements, i.e., SetCD in SXT/R391 ICEs and AcaCD in IncA/C plasmids. Finally, in addition to activating ICE- or plasmid-borne genes, these master activators have been shown to specifically activate phylogenetically unrelated mobilizable genomic islands (MGIs) that also disseminate antibiotic resistance genes and other adaptive traits among a plethora of pathogens such as Vibrio cholerae and Salmonella enterica.

  5. The extended regulatory networks of SXT/R391 integrative and conjugative elements and IncA/C conjugative plasmids.

    Directory of Open Access Journals (Sweden)

    Dominic ePoulin-Laprade

    2015-08-01

    Full Text Available Nowadays, healthcare systems are challenged by a major worldwide drug resistance crisis caused by the massive and rapid dissemination of antibiotic resistance genes and associated emergence of multidrug resistant pathogenic bacteria, in both clinical and environmental settings. Conjugation is the main driving force of gene transfer among microorganisms. This mechanism of horizontal gene transfer mediates the translocation of large DNA fragments between two bacterial cells in direct contact. Integrative and conjugative elements (ICEs of the SXT/R391 family (SRIs and IncA/C conjugative plasmids (ACPs are responsible for the dissemination of a broad spectrum of antibiotic resistance genes among diverse species of Enterobacteriaceae and Vibrionaceae. The biology, diversity, prevalence and distribution of these two families of conjugative elements have been the subject of extensive studies for the past 15 years. Recently, the transcriptional regulators that govern their dissemination through the expression of ICE- or plasmid-encoded transfer genes have been described. Unrelated repressors control the activation of conjugation by preventing the expression of two related master activator complexes in both types of elements, i.e. SetCD in SXT/R391 ICEs and AcaCD in IncA/C plasmids. Finally, in addition to activating ICE- or plasmid-borne genes, these master activators have been shown to specifically activate phylogenetically unrelated mobilizable genomic islands (MGIs that also disseminate antibiotic resistance genes and other adaptive traits among a plethora of pathogens such as Vibrio cholerae and Salmonella enterica.

  6. Synthesis and evaluation of the antioxidative potential of minoxidil-polyamine conjugates.

    Science.gov (United States)

    Hadjipavlou-Litina, Dimitra; Magoulas, George E; Bariamis, Stavros E; Tsimali, Zinovia; Avgoustakis, Konstantinos; Kontogiorgis, Christos A; Athanassopoulos, Constantinos M; Papaioannou, Dionissios

    2013-07-01

    A series of conjugates (MNX-CO-PA) of minoxidil (MNX) with the polyamines (PAs) putrescine (PUT), spermidine (SPD) and spermine (SPM) as well as dopamine were produced through activation of MNX with N,N'-carbonyldiimidazole, followed by reaction with dopamine or selectively protected PAs and acid-mediated deprotection. These conjugates together with conjugates of the general type MNX-PA or PA-MNX-PA, readily produced using literature protocols, were tested as antioxidants. The most potent inhibitors of lipid peroxidation were the conjugates MNX-SPM (2, 94%), SPM-MNX-SPM (4, 94%) and MNX-N(4)-SPD (7, 91%) and MNX (91%). The most powerful lipoxygenase (LOX) inhibitors were MNX (IC50 = 20 μM) and the conjugates MNX-N(8)-SPD (9, IC50 = 22.1 μM), MNX-CO-dopamine (11, IC50 = 28 μM) and MNX-N(1)-SPD (8, IC50 = 30 μM). The most interesting conjugates 2, MNX-CO-PUT (5), 8 and 11 as well as MNX were generally found to exhibit weaker (22-36.5%) or no (conjugate 8) anti-inflammatory activity than indomethacin (47%) with the exception of MNX which showed almost equal potency (49%) to indomethacin. The cytocompatibility of conjugates and MNX at the highest concentration of 100 μM showed a survival percentage of 87-107%, with the exception of conjugates with SPM (compound 2) and MNX-CO-SPM (6), which showed considerable cytotoxicity (survival percentage 8-14%). Molecular docking studies were carried on conjugate 9 and the parent compound MNX and were found to be in accordance with our experimental biological results. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

  7. 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.

  8. 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.

  9. Steric Effects in Reactions of Decamethyltitanocene Hydride with Internal Alkynes, Conjugated Diynes, and Conjugated Dienes

    Czech Academy of Sciences Publication Activity Database

    Pinkas, Jiří; Gyepes, Robert; Císařová, I.; Kubišta, Jiří; Horáček, Michal; Mach, Karel

    2014-01-01

    Roč. 33, č. 13 (2014), s. 3399-3413 ISSN 0276-7333 R&D Projects: GA ČR(CZ) GAP207/12/2368; GA ČR GP203/09/P276 Institutional support: RVO:61388955 Keywords : atoms * complexation * Electron spin resonance spectroscopy Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.126, year: 2014

  10. Folate coupled poly(ethyleneglycol) conjugates of anionic poly(amidoamine) dendrimer for inflammatory tissue specific drug delivery.

    Science.gov (United States)

    Chandrasekar, Durairaj; Sistla, Ramakrishna; Ahmad, Farhan J; Khar, Roop K; Diwan, Prakash V

    2007-07-01

    Folate receptor is overexpressed on the activated (but not quiescent) macrophages in both animal models and human patients with naturally occurring rheumatoid arthritis. The aim of this study was to prepare folate targeted poly(ethylene glycol) (PEG) conjugates of anionic dendrimer (G3.5 PAMAM) as targeted drug delivery systems to inflammation and to investigate its biodistribution pattern in arthritic rats. Folate-PEG-PAMAM conjugates, with different degrees of substitution were synthesized by a two-step reaction through a carbodiimide-mediated coupling reaction and loaded with indomethacin. Folate-PEG conjugation increased the drug loading efficiency by 10- to 20-fold and the in vitro release profile indicated controlled release of drug. The plasma pharmacokinetic parameters indicated an increased AUC, circulatory half-life and mean residence time for the folate-PEG conjugates. The tissue distribution studies revealed significantly lesser uptake by stomach for the folate-PEG conjugates, thereby limiting gastric-related side effect. The time-averaged relative drug exposure (r(e)) of the drug in paw for the folate-PEG conjugates ranged from 1.81 to 2.37. The overall drug targeting efficiency (T(e)) was highest for folate-PEG conjugate (3.44) when compared to native dendrimer (1.72). The folate-PEG-PAMAM conjugates are the ideal choice for targeted delivery of antiarthritic drugs to inflammation with reduced side-effects and higher targeting efficiency. Copyright 2007 Wiley Periodicals, Inc.

  11. Lectins as carriers: preparation and purification of a concanavalin A-trypsin conjugate

    International Nuclear Information System (INIS)

    Shier, W.T.

    1985-01-01

    The scheme for the preparation and purification of Con A-trypsin demonstrates the presence of Con A in the conjugate by affinity purification and by hemagglutination. The presence of Con A was demonstrated in two additional ways. The conjugate was prepared using trypsin labeled with iodine 125 and unlabeled Con A. The resulting conjugate containing 42,800 cpm/mg protein was used to demonstrate prolonged retention of the conjugated trypsin in mouse footpads. The presence of trypsin was also demonstrated in the conjugate by affinity chromatography and by the esterase activity characteristic of trypsin with tosyl-L-arginine methyl ester as substrate. Con A-trypsin was also assayed for proteolytic activity with a macromolecular substrate azocasein. A comparison of proteolytic activities with these two substrates indicated that 50-80% of the proteolytic activity observed with the small substrate is retained with macromolecular substrates

  12. Ti-Catalyzed Hydroamination for the Synthesis of Amine-Containing π-Conjugated Materials.

    Science.gov (United States)

    Hao, Han; Thompson, Kyle A; Hudson, Zachary M; Schafer, Laurel L

    2018-04-11

    A series of conjugated enamines were prepared by Ti catalyzed anti-Markovnikov hydroamination. The synthetic route is efficient with yields of up to 94 % and the 100 % atom efficiency of the reaction means that these products are easily isolated and purified. Due to the extended conjugated system, the enamine tautomers were observed exclusively in both solid and solution phases, as determined by X-ray crystallography and NMR spectroscopy. These new conjugated molecules, with N incorporated into the backbone, show interesting photophysical properties including photo-luminescent quantum yields of up to 0.26. Notably, through the incorporation of B to give a donor-acceptor π-conjugated system, a redshift of approximately 100 nm is observed for the emission maximum along with the anticipated solvatochromic shifts. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Double diffusive conjugate heat transfer: Part I

    Science.gov (United States)

    Azeem, Soudagar, Manzoor Elahi M.

    2018-05-01

    The present work is undertaken to investigate the effect of solid wall being placed at left of square cavity filled with porous medium. The presence of a solid wall in the porous medium turns the situation into a conjugate heat transfer problem. The boundary conditions are such that the left vertical surface is maintained at highest temperature and concentration whereas right vertical surface at lowest temperature and concentration in the medium. The top and bottom surfaces are adiabatic. The additional conduction equation along with the regular momentum and energy equations of porous medium are solved in an iterative manner with the help of finite element method. It is seen that the heat and mass transfer rate is lesser due to smaller thermal and concentration gradients.

  14. Mefenamic acid conjugates based on a hydrophilic biopolymer hydroxypropylcellulose: novel prodrug design, characterization and thermal analysis

    International Nuclear Information System (INIS)

    Hussain, M.A.; Kausar, R.; Amin, M.

    2015-01-01

    Macromolecular prodrugs (MPDs) of mefenamic acid were designed onto a cellulose ether derivative hydroxypropylcellulose (HPC) as ester conjugates. Fabrication of HPC-mefenamic acid conjugates was achieved by using p-toluenesulfonyl chloride as carboxylic acid (a functional group in drug) activator at 80 degree C for 24 h under nitrogen atmosphere. Reaction was preceded under homogeneous reaction conditions as HPC was dissolved before use in DMAc solvent. Imidazole was used as a base. Easy workup reactions resulted in good yields (55-65%) and degree of substitution (DS) of drug (0.37-0.99) onto HPC. The DS was calculated by acid-base titration after saponification and UV/Vis spectrophotometry after hydrolysis. DS by both of the methods was found in good agreement with each other. Aqueous and organic soluble novel prodrugs of mefenamic acid were purified and characterized by different spectroscopic and thermal analysis techniques. The initial, maximum and final degradation temperatures of HPC, mefenamic acid and HPC-mefenamic acid conjugates were drawn from thermogravimetric (TG) and derivative TG curves and compared to access relative thermal stability. The TG analysis has indicated that samples obtained were thermally more stable especially with increased stability of mefenamic acid in HPC-mefenamic acid conjugates. These novel MPDs of mefenamic acid (i.e., HPC-mefenamic acid conjugates) may have potential applications in pharmaceutically viable drug design due to wide range of solubility and extra thermal stability imparted after MPD formation. (author)

  15. A Convenient Synthesis of Conjugated Acetylenic Ketones by Copper(l)-Catalyzed under Microwave Irradiation

    Institute of Scientific and Technical Information of China (English)

    WANG; JinXian

    2001-01-01

    Alkynyl ketones are useful precursors and intermediates in synthetic organic chemistry1 and has evoked considerable interest. A number of methods for the synthesis of conjugated acetylenic ketones involve the reaction a metal acetylide with an acyl chlorides or another carboxylic acid derivative have been developed 2. Recently, the synthesis of α, β-conjugated acetylenic ketones catalyzed by Pd(Ⅱ) or by copper(Ⅰ)pd(Ⅱ) reaction of 1-alkynes and acyl chlorides have been described. The acylation of terminal alkynes by acyl chlorides in the presence of catalytic amounts copper(Ⅰ) salts leading to α, β-conjugated acetylenic ketones has also been reported. However, many of these reactions suffer from lack of high pressure (17 atm), long reaction time (30 h)and require low temperatures (-78℃). Our work involves the synthesis of conjugated acetylenic ketones via the reaction of terminal alkynes with aroyl chlorides in the presence of cuprous iodide under microwave irradiation conditions.……

  16. Surface and Electrical Characterization of Conjugated Molecular Wires

    Science.gov (United States)

    Demissie, Abel Tesfahun

    This thesis describes the surface and electrical characterization of ultrathin organic films and interfaces. These films were synthesized on the surface of gold by utilizing layer by layer synthesis via imine condensation. Film growth by imine click (condensation) chemistry is particularly useful for molecular electronics experiments because it provides a convenient means to obtain and extend ?-conjugation in the growth direction. However, in the context of film growth from a solid substrate, the reaction yield per step has not been characterized previously, though it is critically important. To address these issues, my research focused on a comprehensive characterization of oligophenyleneimine (OPI) wires via Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), reflection-absorption infrared spectroscopy (RAIRS), and cyclic voltammetry (CV). In addition, we had the unique opportunity of developing the first of its kind implementation of nuclear reaction analysis (NRA) to probe the intensity of carbon atoms after each addition step. Overall the combination of various techniques indicated that film growth proceeds in a quantitative manner. Furthermore, the NRA experiment was optimized to measure the carbon content in self-assembled monolayers of alkyl thiols. The results indicated well-resolved coverage values for ultrathin films with consecutive steps of 2 carbon atoms per molecule. Another fundamental problem in molecular electronics is the vast discrepancy in the values of measured resistance per molecule between small and large area molecular junctions. In collaboration with researchers at the National University of Singapore, we addressed these issues by comparing the electrical properties of OPI wires with the eutectic gallium indium alloy (EGaIn) junction (1000 mum2), and conducting probe atomic force microscopy (CP-AFM) junction (50 nm2). Our results showed that intensive (i.e., area

  17. Organocatalytic Asymmetric Michael Addition of 4-Hydroxycoumarin to β,γ-Unsaturated α-Keto Esters

    Energy Technology Data Exchange (ETDEWEB)

    Suh, Chang Won; Han, Tae Hyun; Kim, Dae Young [Soonchunhyang Univ., Asan (Korea, Republic of)

    2013-06-15

    In conclusion, we have developed organocatalytic enantioselective conjugate addition reaction of 4-hydroxycoumarin (1) to β,γ-unsaturated α-keto esters 2 to afford biologically valuable warfarin derivatives 3. The process is efficiently catalyzed by a binaphthyl-modified thiourea organocatalyst. The coumarin core is present as a characteristic structural motif in a large number of natural products and biologically active molecules.1 Particularly, many of these naturally occurring 4-hydroxycoumarin and their synthetic analogues are important precursors for the synthesis of natural products and pharmaceuticals. Enantioselective organocatalytic conjugate addition of 4-hydroxycoumarin to α,β-unsaturated ketones is a straightforward method to access warfarin which is an effective anticoagulants. Although a number of reactions of α,β-unsaturated ketones as Michael acceptors have been reported, the corresponding β,γ-unsaturated α-keto esters have received relatively little attention as Michael acceptors. Recently, several groups have reported the asymmetric Michael addition of 4-hydroxycoumarin to β,γ-unsaturated α-keto esters catalyzed by Cu(II)-bisoxazoline, N,N'-dioxide-Ni(II) complexes, thiourea catalysts. Although several efficient methods have been achieved by these systems, an effective method for the synthesis of warfarin analogues is still a challenge.

  18. Organocatalytic Asymmetric Michael Addition of 4-Hydroxycoumarin to β,γ-Unsaturated α-Keto Esters

    International Nuclear Information System (INIS)

    Suh, Chang Won; Han, Tae Hyun; Kim, Dae Young

    2013-01-01

    In conclusion, we have developed organocatalytic enantioselective conjugate addition reaction of 4-hydroxycoumarin (1) to β,γ-unsaturated α-keto esters 2 to afford biologically valuable warfarin derivatives 3. The process is efficiently catalyzed by a binaphthyl-modified thiourea organocatalyst. The coumarin core is present as a characteristic structural motif in a large number of natural products and biologically active molecules.1 Particularly, many of these naturally occurring 4-hydroxycoumarin and their synthetic analogues are important precursors for the synthesis of natural products and pharmaceuticals. Enantioselective organocatalytic conjugate addition of 4-hydroxycoumarin to α,β-unsaturated ketones is a straightforward method to access warfarin which is an effective anticoagulants. Although a number of reactions of α,β-unsaturated ketones as Michael acceptors have been reported, the corresponding β,γ-unsaturated α-keto esters have received relatively little attention as Michael acceptors. Recently, several groups have reported the asymmetric Michael addition of 4-hydroxycoumarin to β,γ-unsaturated α-keto esters catalyzed by Cu(II)-bisoxazoline, N,N'-dioxide-Ni(II) complexes, thiourea catalysts. Although several efficient methods have been achieved by these systems, an effective method for the synthesis of warfarin analogues is still a challenge

  19. 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.

  20. Iminoboronate Formation Leads to Fast and Reversible Conjugation Chemistry of α-Nucleophiles at Neutral pH.

    Science.gov (United States)

    Bandyopadhyay, Anupam; Gao, Jianmin

    2015-10-12

    Bioorthogonal reactions that are fast and reversible under physiological conditions are in high demand for biological applications. Herein, it is shown that an ortho boronic acid substituent makes aryl ketones rapidly conjugate with α-nucleophiles at neutral pH. Specifically, 2-acetylphenylboronic acid and derivatives were found to conjugate with phenylhydrazine with rate constants of 10(2) to 10(3) M(-1) s(-1) , comparable to the fastest bioorthogonal conjugations known to date. (11) B NMR analysis revealed the varied extent of iminoboronate formation of the conjugates, in which the imine nitrogen forms a dative bond with boron. The iminoboronate formation activates the imines for hydrolysis and exchange, rendering these oxime/hydrazone conjugations reversible and dynamic under physiological conditions. The fast and dynamic nature of the iminoboronate chemistry should find wide applications in biology. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Bispecific small molecule-antibody conjugate targeting prostate cancer.

    Science.gov (United States)

    Kim, Chan Hyuk; Axup, Jun Y; Lawson, Brian R; Yun, Hwayoung; Tardif, Virginie; Choi, Sei Hyun; Zhou, Quan; Dubrovska, Anna; Biroc, Sandra L; Marsden, Robin; Pinstaff, Jason; Smider, Vaughn V; Schultz, Peter G

    2013-10-29

    Bispecific antibodies, which simultaneously target CD3 on T cells and tumor-associated antigens to recruit cytotoxic T cells to cancer cells, are a promising new approach to the treatment of hormone-refractory prostate cancer. Here we report a site-specific, semisynthetic method for the production of bispecific antibody-like therapeutics in which a derivative of the prostate-specific membrane antigen-binding small molecule DUPA was selectively conjugated to a mutant αCD3 Fab containing the unnatural amino acid, p-acetylphenylalanine, at a defined site. Homogeneous conjugates were generated in excellent yields and had good solubility. The efficacy of the conjugate was optimized by modifying the linker structure, relative binding orientation, and stoichiometry of the ligand. The optimized conjugate showed potent and selective in vitro activity (EC50 ~ 100 pM), good serum half-life, and potent in vivo activity in prophylactic and treatment xenograft mouse models. This semisynthetic approach is likely to be applicable to the generation of additional bispecific agents using drug-like ligands selective for other cell-surface receptors.

  2. Bispecific small molecule–antibody conjugate targeting prostate cancer

    Science.gov (United States)

    Kim, Chan Hyuk; Axup, Jun Y.; Lawson, Brian R.; Yun, Hwayoung; Tardif, Virginie; Choi, Sei Hyun; Zhou, Quan; Dubrovska, Anna; Biroc, Sandra L.; Marsden, Robin; Pinstaff, Jason; Smider, Vaughn V.; Schultz, Peter G.

    2013-01-01

    Bispecific antibodies, which simultaneously target CD3 on T cells and tumor-associated antigens to recruit cytotoxic T cells to cancer cells, are a promising new approach to the treatment of hormone-refractory prostate cancer. Here we report a site-specific, semisynthetic method for the production of bispecific antibody-like therapeutics in which a derivative of the prostate-specific membrane antigen-binding small molecule DUPA was selectively conjugated to a mutant αCD3 Fab containing the unnatural amino acid, p-acetylphenylalanine, at a defined site. Homogeneous conjugates were generated in excellent yields and had good solubility. The efficacy of the conjugate was optimized by modifying the linker structure, relative binding orientation, and stoichiometry of the ligand. The optimized conjugate showed potent and selective in vitro activity (EC50 ∼100 pM), good serum half-life, and potent in vivo activity in prophylactic and treatment xenograft mouse models. This semisynthetic approach is likely to be applicable to the generation of additional bispecific agents using drug-like ligands selective for other cell-surface receptors. PMID:24127589

  3. Structure Property Relationships in Organic Conjugated Systems

    OpenAIRE

    O'Neill, Luke

    2008-01-01

    A series of pi(п) conjugated oligomers containing 1 to 6 monomer units were studied by absorption and photoluminescence spectroscopies. The results are discussed and examined with regard to the variation of the optical properties with the increase of effective conjugation length. It was found that there was a linear relationship between the positioning of the absorption and photoluminescence maxima plotted against inverse conjugation length. The relationships are in good agreement with the si...

  4. Formation of primary sperm conjugates in a haplogyne spider (Caponiidae, Araneae) with remarks on the evolution of sperm conjugation in spiders.

    Science.gov (United States)

    Lipke, Elisabeth; Michalik, Peter

    2012-11-01

    Sperm conjugation, where two or more sperm are physically united, is a rare but widespread pheno-menon across the animal kingdom. One group well known for its different types of sperm conjugation are spiders. Particularly, haplogyne spiders show a high diversity of sperm traits. Besides individual cleistospermia, primary (synspermia) and secondary (coenospermia, "spermatophore") sperm conjugation occurs. However, the evolution of sperm conjugates and sperm is not understood in this group. Here, we look at how sperm are transferred in Caponiidae (Haplogynae) in pursuit of additional information about the evolution of sperm transfer forms in spiders. Additionally, we investigated the male reproductive system and spermatozoa using light- and transmission electron-microscopy and provide a 3D reconstruction of individual as of well as conjugated spermatozoa. Mature spermatozoa are characterized by an extremely elongated, helical nucleus resulting in the longest spider sperm known to date. At the end of spermiogenesis, synspermia are formed by complete fusion of four spermatids. Thus, synspermia might have evolved early within ecribellate Haplogynae. The fused sperm cells are surrounded by a prominent vesicular area. The function of the vesicular area remains still unknown but might be correlated with the capacitation process inside the female. Further phylogenetic and functional implications of the spermatozoa and sperm conjugation are discussed. Copyright © 2012 Elsevier Ltd. All rights reserved.

  5. 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...... polymerization method for industrial production of polymers. Several DArP protocols have been employed for the synthesis of PPDTBT leading to polymers with high structural regularity and photovoltaic performances comparable with the same materials synthesized via Stille cross-coupling polymerization...

  6. Test of charge conjugation invariance

    International Nuclear Information System (INIS)

    Nefkens, B.M.K.; Prakhov, S.; Gaardestig, A.; Clajus, M.; Marusic, A.; McDonald, S.; Phaisangittisakul, N.; Price, J.W.; Starostin, A.; Tippens, W.B.; Allgower, C.E.; Spinka, H.; Bekrenev, V.; Koulbardis, A.; Kozlenko, N.; Kruglov, S.; Lopatin, I.; Briscoe, W.J.; Shafi, A.; Comfort, J.R.

    2005-01-01

    We report on the first determination of upper limits on the branching ratio (BR) of η decay to π 0 π 0 γ and to π 0 π 0 π 0 γ. Both decay modes are strictly forbidden by charge conjugation (C) invariance. Using the Crystal Ball multiphoton detector, we obtained BR(η→π 0 π 0 γ) -4 at the 90% confidence level, in support of C invariance of isoscalar electromagnetic interactions of the light quarks. We have also measured BR(η→π 0 π 0 π 0 γ) -5 at the 90% confidence level, in support of C invariance of isovector electromagnetic interactions

  7. Conjugated hyperbilirubinemia in infancy associated with parenteral alimentation.

    Science.gov (United States)

    Bernstein, J; Chang, C H; Brough, A J; Heidelberger, K P

    1977-03-01

    Liver biopsy was performed to exclude anatomic obstruction of the biliary tract in five prematurely born infants who had developed conjugated hyperbilirubinemia during intravenous alimentation with a protein hydrolysate. Each was being treated after having undergone a segmental intestinal resection for necrotizing enterocolitis. Bacterial and viral infections, metabolic disorders, and isoimmune hemolytic disease were excluded as possible causes of jaundice. Light microscopic and ultrastructural analysis disclosed cholestasis and hepatocellular injury without significant inflammatory reaction. Jaundice abated following permanent discontinuation of parenteral alimentation. The jaundice and cholestasis are interpreted to be hepatotoxic effects because of (1) their temporal relationship to the treatment and (2) the presence of hepatocellular damage.

  8. 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.

  9. A Spectral Conjugate Gradient Method for Unconstrained Optimization

    International Nuclear Information System (INIS)

    Birgin, E. G.; Martinez, J. M.

    2001-01-01

    A family of scaled conjugate gradient algorithms for large-scale unconstrained minimization is defined. The Perry, the Polak-Ribiere and the Fletcher-Reeves formulae are compared using a spectral scaling derived from Raydan's spectral gradient optimization method. The best combination of formula, scaling and initial choice of step-length is compared against well known algorithms using a classical set of problems. An additional comparison involving an ill-conditioned estimation problem in Optics is presented

  10. 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.

  11. Formation of high-quality self-assembled monolayers of conjugated dithiols on gold : Base matters

    NARCIS (Netherlands)

    Valkenier, Hennie; Huisman, Everardus H.; Hal, Paul A. van; de Leeuw, Dagobert; Chiechi, Ryan C.; Hummelen, Jan C.

    2011-01-01

    This Article reports a systematic study on the formation of self-assembled monolayers (SAMs) of conjugated molecules for molecular electronic (ME) devices. We monitored the deprotection reaction of acetyl protected dithiols of oligophenylene ethynylenes (OPEs) in solution using two different bases

  12. compounds with N=N, C≡C or conjugated double-bonded systems

    Indian Academy of Sciences (India)

    Unusual products in the reactions of phosphorus(III) compounds with. N=N, C≡C or conjugated double-bonded systems. K C KUMARA SWAMY,* E BALARAMAN, M PHANI PAVAN, N N BHUVAN KUMAR,. K PRAVEEN KUMAR and N SATISH KUMAR. School of Chemistry, University of Hyderabad, Hyderabad 500 046.

  13. Drug-conjugated PLA-PEG-PLA copolymers: a novel approach for controlled delivery of hydrophilic drugs by micelle formation.

    Science.gov (United States)

    Danafar, H; Rostamizadeh, K; Davaran, S; Hamidi, M

    2017-12-01

    A conjugate of the antihypertensive drug, lisinopril, with triblock poly(lactic acid)-poly(ethylene glycol)-poly(lactic acid) (PLA-PEG-PLA) copolymer was synthesized by the reaction of PLA-PEG-PLA copolymer with lisinopril in the presence of dicyclohexylcarbodiimide and dimethylaminopyridine. The conjugated copolymer was characterized in vitro by hydrogen nuclear magnetic resonance (HNMR), Fourier transform infrared (FTIR), differential scanning calorimetry (DSC) and gel permeation chromatography (GPC) techniques. Then, the lisinopril conjugated PLA-PEG-PLA were self-assembled into micelles in aqueous solution. The resulting micelles were characterized further by various techniques such as dynamic light scattering (DLS) and atomic force microscopy (AFM). The results revealed that the micelles formed by the lisinopril-conjugated PLA-PEG-PLA have spherical structure with the average size of 162 nm. The release behavior of conjugated copolymer, micelles and micelles physically loaded by lisinopril were compared in different media. In vitro release study showed that in contrast to physically loaded micelles, the release rate of micelles consisted of the conjugated copolymer was dependent on pH of media where it was higher at lower pH compared to the neutral medium. Another feature of the conjugated micelles was their more sustained release profile compared to the lisinopril-conjugated copolymer and physically loaded micelles.

  14. 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 materials. We have used PDS to measure the optical absorption spectra of the conjugated polymers poly(1,4-phenylene-vinylene) (and derivitives) and polydiacetylene-4BCMU in the spectral region from 0.55 eV to 3 eV. Our spectra show that the shape of the absorption edge varies considerably from polymer to polymer, with polydiacetylene-4BCMU having the steepest absorption edge. The minimum absorption coefficients measured varied somewhat with sample age and quality, but were typically in the range 1 cm{sup {minus}1} to 10 cm{sup {minus}1}. In the region below 1 eV, overtones of C-H stretching modes were observed, indicating that further improvements in transparency in this spectral region might be achieved via deuteration of fluorination.

  15. Subgap absorption in conjugated polymers

    Energy Technology Data Exchange (ETDEWEB)

    Sinclair, M.; Seager, C.H. (Sandia National Labs., Albuquerque, NM (USA)); McBranch, D.; Heeger, A.J. (California Univ., Santa Barbara, CA (USA)); Baker, G.L. (Bell Communications Research, Inc., Red Bank, NJ (USA))

    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 < 10{sup {minus}5}, Photothermal Deflection Spectroscopy (PDS) is ideal for determining the absorption coefficients of thin films of transparent'' materials. We have used PDS to measure the optical absorption spectra of the conjugated polymers poly(1,4-phenylene-vinylene) (and derivitives) and polydiacetylene-4BCMU in the spectral region from 0.55 eV to 3 eV. Our spectra show that the shape of the absorption edge varies considerably from polymer to polymer, with polydiacetylene-4BCMU having the steepest absorption edge. The minimum absorption coefficients measured varied somewhat with sample age and quality, but were typically in the range 1 cm{sup {minus}1} to 10 cm{sup {minus}1}. In the region below 1 eV, overtones of C-H stretching modes were observed, indicating that further improvements in transparency in this spectral region might be achieved via deuteration of fluorination. 11 refs., 4 figs.

  16. 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...

  17. 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.

  18. 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.

  19. The development of catalytic nucleophilic additions of terminal alkynes in water.

    Science.gov (United States)

    Li, Chao-Jun

    2010-04-20

    One of the major research endeavors in synthetic chemistry over the past two decades is the exploration of synthetic methods that work under ambient atmosphere with benign solvents, that maximize atom utilization, and that directly transform natural resources, such as renewable biomass, from their native states into useful chemical products, thus avoiding the need for protecting groups. The nucleophilic addition of terminal alkynes to various unsaturated electrophiles is a classical (textbook) reaction in organic chemistry, allowing the formation of a C-C bond while simultaneously introducing the alkyne functionality. A prerequisite of this classical reaction is the stoichiometric generation of highly reactive metal acetylides. Over the past decade, our laboratory and others have been exploring an alternative, the catalytic and direct nucleophilic addition of terminal alkynes to unsaturated electrophiles in water. We found that various terminal alkynes can react efficiently with a wide range of such electrophiles in water (or organic solvent) in the presence of simple and readily available catalysts, such as copper, silver, gold, iron, palladium, and others. In this Account, we describe the development of these synthetic methods, focusing primarily on results from our laboratory. Our studies include the following: (i) catalytic reaction of terminal alkynes with acid chloride, (ii) catalytic addition of terminal alkynes to aldehydes and ketones, (iii) catalytic addition of alkynes to C=N bonds, and (iv) catalytic conjugate additions. Most importantly, these reactions can tolerate various functional groups and, in many cases, perform better in water than in organic solvents, clearly defying classical reactivities predicated on the relative acidities of water, alcohols, and terminal alkynes. We further discuss multicomponent and enantioselective reactions that were developed. These methods provide an alternative to the traditional requirement of separate steps in

  20. Thiolated pectin-doxorubicin conjugates: Synthesis, characterization and anticancer activity studies.

    Science.gov (United States)

    Cheewatanakornkool, Kamonrak; Niratisai, Sathit; Manchun, Somkamol; Dass, Crispin R; Sriamornsak, Pornsak

    2017-10-15

    In this paper, pectin was cross-linked by a coupling reaction with either thioglycolic acid or cystamine dihydrochloride to form thiolated pectins. The thiolated pectins were then coupled with doxorubicin (DOX) derivative to obtain thiolated pectin-DOX conjugates by two different methods, disulfide bond formation and disulfide bond exchange. The disulfide bond exchange method provided a simple, fast, and efficient approach for synthesis of thiolated pectin-DOX conjugates, compared to the disulfide bond formation. Characteristics, physicochemical properties, and morphology of thiolated pectins and thiolated pectin-DOX conjugates were determined. DOX content in thiolated pectin-DOX conjugates using low methoxy pectin was found to be higher than that using high methoxy pectin. The in vitro anticancer activity of thiolated pectin-DOX conjugates was significantly higher than that of free DOX, in mouse colon carcinoma and human bone osteosarcoma cells, but insignificantly different from that of free DOX, in human prostate cancer cells. Due to their promising anticancer activity in mouse colon carcinoma cells, the thiolated pectin-DOX conjugates might be suitable for building drug platform for colorectal cancer-targeted delivery of DOX. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Simple Protein Modification Using Zwitterionic Polymer to Mitigate the Bioactivity Loss of Conjugated Insulin.

    Science.gov (United States)

    Xie, Jinbing; Lu, Yang; Wang, Wei; Zhu, Hui; Wang, Zhigang; Cao, Zhiqiang

    2017-06-01

    Polymer-protein conjugation has been extensively explored toward a better protein drug with improved pharmacokinetics. However, a major problem with polymer-protein conjugation is that the polymers drastically reduce the bioactivity of the modified protein. There is no perfect solution to prevent the bioactivity loss, no matter the polymer is conjugated in a non-site specific way, or a more complex site-specific procedure. Here the authors report for the first time that when zwitterionic carboxybetaine polymer (PCB) is conjugated to insulin through simple conventional coupling chemistry. The resulting PCB-insulin does not show a significant reduction of in vitro bioactivity. The obtained PCB-insulin shows two significant advantages as a novel pharmaceutical agent. First, its therapeutic performance is remarkable. For PCB-insulin, there is a 24% increase of in vivo pharmacological activity of lowering blood glucose compared with native insulin. Such uncommonly seen increase has rarely been reported and is expected to be due to both the improved pharmacokinetics and retained bioactivity of PCB-insulin. Second, the production is simple from manufacturing standpoints. Conjugation procedure involves only one-step coupling reaction without complex site-specific linkage technique. The synthesized PCB-insulin conjugates do not require chromatographic separation to purify and obtain particular isoforms. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. 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.

  3. Emulsifying properties of maillard conjugates produced from sodium caseinate and locust bean gum

    Directory of Open Access Journals (Sweden)

    F. A. Perrechil

    2014-06-01

    Full Text Available Emulsifying properties of sodium caseinate -locust bean gum Maillard conjugates produced at different temperatures (54 - 96 ºC, protein/polysaccharide ratios (0.3 - 1.0 and reaction times (1 - 24 hours were evaluated. Conjugate formation was confirmed by formation of color and high molecular weight fractions and the decrease of the αs- and β-casein bands. The emulsions stabilized by Maillard conjugates showed good stability. The mean droplet diameter (d32 tended to decrease with the increase of incubation time and temperature, except at extreme conditions (24 hours and 90 ºC or 96 ºC when the partial degradation of the conjugates was probably favored, resulting in phase separation of emulsions. The emulsion viscosity decreased with the increase in the protein/polysaccharide ratio and with the degradation of the conjugates. The conditions used in the experimental design made the optimization of the conjugate production viable, which showed greater emulsifier properties than the pure protein under acid conditions.

  4. Synthesis and Characterization of Water-soluble Conjugates of Cabazitaxel Hemiesters-Dextran.

    Science.gov (United States)

    Parhizkar, Elahehnaz; Ahmadi, Fatemeh; Daneshamouz, Saeid; Mohammadi-Samani, Soliman; Sakhteman, Amirhossein; Parhizkar, Golnaz

    2017-11-24

    Cabazitaxel (CTX) is a second- generation taxane derivative, a class of potent anticancer drugs with very low water solubility. CTX is used in patients with resistant prostate cancer unresponsive to the first generation taxane, docetaxel. Currently marketed formulations of CTX contain high concentrations of surfactant and ethanol, which cause severe hypersensitivity reactions in patients. In order to increase its solubility, two hemiester analogs; CTX-succinate and CTX-glutarate were synthesized and characterized. To improve the solubility of hemiesters even more, dextran as a biocompatible polymer was also conjugated to hemiester analogs. MTT assay was performed on MCF-7 cell line to evaluate the cytotoxicity effect of hemiesters and conjugates. Based on the results, hemiester analogs increased water solubility of the drug up to about 3 and 8 fold. Conjugation to dextran enhanced the CTX solubility to more than 1500 fold. These conjugates released the conjugated CTX in less than 24 hours in a pH dependent manner and showed proper hemocompatibility characteristics. The hemiesters had approximately similar cytotoxicity in comparison with CTX and the dextran conjugates showed higher cytotoxicity effect on MCF-7 cell line. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  5. Additive manufacturing.

    Science.gov (United States)

    Mumith, A; Thomas, M; Shah, Z; Coathup, M; Blunn, G

    2018-04-01

    Increasing innovation in rapid prototyping (RP) and additive manufacturing (AM), also known as 3D printing, is bringing about major changes in translational surgical research. This review describes the current position in the use of additive manufacturing in orthopaedic surgery. Cite this article: Bone Joint J 2018;100-B:455-60.

  6. Redox-active triazatruxene-based conjugated microporous polymers for high-performance supercapacitors† †Electronic supplementary information (ESI) available: Synthetic procedures and characterization data for all new compounds; general experimental method; thermogravimetry curves; PXRD patterns; SEM and TEM images; XPS spectra. See DOI: 10.1039/c6sc05532j Click here for additional data file.

    Science.gov (United States)

    Li, Xiang-Chun; Zhang, Yizhou; Wang, Chun-Yu; Wan, Yi

    2017-01-01

    Conjugated polymers (CPs) have been intensively explored for various optoelectronic applications in the last few decades. Nevertheless, CP based electrochemical energy storage devices such as supercapacitors remain largely unexplored. This is mainly owing to the low specific capacitance, poor structural/electrochemical stability, and low energy density of most existing CPs. In this contribution, a novel set of redox-active conjugated microporous polymers, TAT-CMP-1 and TAT-CMP-2, based on nitrogen-rich and highly conductive triazatruxene building blocks, were successfully designed and synthesized to explore their potential application as efficient and stable electrode materials for supercapacitors. Despite a moderate surface area of 88 m2 g–1 for TAT-CMP-1 and 106 m2 g–1 for TAT-CMP-2, exceptional specific capacitances of 141 F g–1 and 183 F g–1 were achieved at a current density of 1 A g–1. The resulting polymers exhibited unusually high areal specific capacitance (>160 μF cm–2), which is attributed to the pseudocapacitance resulting from redox-active structures with high nitrogen content. More importantly, the TAT-CMP-2 electrode exhibits excellent cycling stability: only 5% capacitance fading is observed after 10 000 cycles at a high current density of 10 A g–1, enabling the possible use of these materials as electrodes in electrochemical devices. PMID:28451362

  7. 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.

  8. Androgen Receptor Antagonism By Divalent Ethisterone Conjugates In Castrate-Resistant Prostate Cancer Cells

    Science.gov (United States)

    Levine, Paul M.; Lee, Eugine; Greenfield, Alex; Bonneau, Richard; Logan, Susan K.; Garabedian, Michael J.; Kirshenbaum, Kent

    2013-01-01

    Sustained treatment of prostate cancer with Androgen Receptor (AR) antagonists can evoke drug resistance, leading to castrate-resistant disease. Elevated activity of the AR is often associated with this highly aggressive disease state. Therefore, new therapeutic regimens that target and modulate AR activity could prove beneficial. We previously introduced a versatile chemical platform to generate competitive and non-competitive multivalent peptoid oligomer conjugates that modulate AR activity. In particular, we identified a linear and a cyclic divalent ethisterone conjugate that exhibit potent anti-proliferative properties in LNCaP-abl cells, a model of castrate-resistant prostate cancer. Here, we characterize the mechanism of action of these compounds utilizing confocal microscopy, time-resolved fluorescence resonance energy transfer, chromatin immunoprecipitation, flow cytometry, and microarray analysis. The linear conjugate competitively blocks AR action by inhibiting DNA binding. In addition, the linear conjugate does not promote AR nuclear localization or co-activator binding. In contrast, the cyclic conjugate promotes AR nuclear localization and induces cell-cycle arrest, despite its inability to compete against endogenous ligand for binding to AR in vitro. Genome-wide expression analysis reveals that gene transcripts are differentially affected by treatment with the linear or cyclic conjugate. Although the divalent ethisterone conjugates share extensive chemical similarities, we illustrate that they can antagonize the AR via distinct mechanisms of action, establishing new therapeutic strategies for potential applications in AR pharmacology. PMID:22871957

  9. Peptide- and saccharide-conjugated dendrimers for targeted drug delivery: a concise review

    Science.gov (United States)

    Liu, Jie; Gray, Warren D.; Davis, Michael E.; Luo, Ying

    2012-01-01

    Dendrimers comprise a category of branched materials with diverse functions that can be constructed with defined architectural and chemical structures. When decorated with bioactive ligands made of peptides and saccharides through peripheral chemical groups, dendrimer conjugates are turned into nanomaterials possessing attractive binding properties with the cognate receptors. At the cellular level, bioactive dendrimer conjugates can interact with cells with avidity and selectivity, and this function has particularly stimulated interests in investigating the targeting potential of dendrimer materials for the design of drug delivery systems. In addition, bioactive dendrimer conjugates have so far been studied for their versatile capabilities to enhance stability, solubility and absorption of various types of therapeutics. This review presents a brief discussion on three aspects of the recent studies to use peptide- and saccharide-conjugated dendrimers for drug delivery: (i) synthesis methods, (ii) cell- and tissue-targeting properties and (iii) applications of conjugated dendrimers in drug delivery nanodevices. With more studies to elucidate the structure–function relationship of ligand–dendrimer conjugates in transporting drugs, the conjugated dendrimers hold promise to facilitate targeted delivery and improve drug efficacy for discovery and development of modern pharmaceutics. PMID:23741608

  10. 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.

  11. 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...

  12. Tetrafullerene conjugates for all-organic photovoltaics

    NARCIS (Netherlands)

    Fernández, G.; Sánchez, L.; Veldman, D.; Wienk, M.M.; Atienza, C.M.; Guldi, D.M.; Janssen, R.A.J.; Martin, N.

    2008-01-01

    The synthesis of two new tetrafullerene nanoconjugates in which four C60 units are covalently connected through different -conjugated oligomers (oligo(p-phenylene ethynylene) and oligo(p-phenylene vinylene)) is described. The photovoltaic (PV) response of these C60-based conjugates was evaluated by

  13. 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

  14. The Conjugate Acid-Base Chart.

    Science.gov (United States)

    Treptow, Richard S.

    1986-01-01

    Discusses the difficulties that beginning chemistry students have in understanding acid-base chemistry. Describes the use of conjugate acid-base charts in helping students visualize the conjugate relationship. Addresses chart construction, metal ions, buffers and pH titrations, and the organic functional groups and nonaqueous solvents. (TW)

  15. 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...

  16. Class, Kinship Density, and Conjugal Role Segregation.

    Science.gov (United States)

    Hill, Malcolm D.

    1988-01-01

    Studied conjugal role segregation in 150 married women from intact families in working-class community. Found that, although involvement in dense kinship networks was associated with conjugal role segregation, respondents' attitudes toward marital roles and phase of family cycle when young children were present were more powerful predictors of…

  17. 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.

  18. 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.

  19. Modelling conjugation with stochastic differential equations

    DEFF Research Database (Denmark)

    Philipsen, Kirsten Riber; Christiansen, Lasse Engbo; Hasman, Henrik

    2010-01-01

    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......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...... using a likelihood-ratio test and Akaike's information criterion. Experiments indicating conjugation on the agar plates selecting for transconjugants motivates the introduction of an extended model, for which conjugation on the agar plate is described in the measurement equation. This model is compared...

  20. Food additives

    Science.gov (United States)

    ... GO About MedlinePlus Site Map FAQs Customer Support Health Topics Drugs & Supplements Videos & Tools Español You Are Here: Home → Medical Encyclopedia → Food additives URL of this page: //medlineplus.gov/ency/article/ ...

  1. Synthesis, characterization, and in vivo efficacy evaluation of PGG–docetaxel conjugate for potential cancer chemotherapy

    Directory of Open Access Journals (Sweden)

    Jiang X

    2012-02-01

    Full Text Available Danbo Yang1, Sang Van2, Yingyi Shu1, Xiaoqing Liu1, Yangfeng Ge1, Xinguo Jiang3, Yi Jin2, Lei Yu1,21Biomedical Engineering and Technology Institute, Institutes for Advanced Interdisciplinary Research, East China Normal University, Shanghai, People’s Republic of China; 2Biomedical Group, Nitto Denko Technical Corporation, CA, USA; 3School of Pharmacy, Fudan University, Shanghai, People’s Republic of ChinaAim: This work is intended to develop and evaluate a biopolymeric poly(L-γ-glutamyl-glutamine (PGG–docetaxel (DTX conjugate that can spontaneously self-assemble in aqueous solutions to become nanoparticles.Methods: DTX was covalently attached to hydrophilic PGG by direct esterification, and the conjugate was characterized by proton nuclear magnetic resonance spectroscopy, molecular weight gel permeation chromatography, solubility, size distribution and morphology, and hemolysis. Conjugated DTX was found to have 2000 times improved water solubility compared with free DTX. Dynamic light scattering, transmission electron microscopy, and atomic force microscopy revealed the particle size, distribution and morphology of the PGG–DTX conjugate. In addition, the conjugate was further tested for in vitro cytotoxicity and in vivo antitumor efficacy on the human non-small cell lung cancer cell line NCI-H460.Results: Conjugated DTX was found to have 2000 times improved water solubility compared with free DTX. The conjugate formed nanoparticles with an average diameter of 30 nm in spherical shape and unimodal particle size distribution. The conjugate exhibited about 2% hemolysis at 10 mg/mL, compared with 56% for Tween 80® at 0.4 mg/mL, and 33% for Cremophor EL® at 10 mg/mL. In addition, the conjugate was further tested for in vitro cytotoxicity and in vivo antitumor efficacy on the human non-small cell lung cancer cell line NCI-H460. As expected, conjugated DTX exhibited lower cytotoxicity compared to that of free DTX, in concentration

  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 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. REACTIONS OF 5-[1-(2-PHENYL)METHYLIDENE

    African Journals Online (AJOL)

    4-DIONES WITH SOME ORGANOMETALLIC REAGENTS. ... KEY WORDS: Imidazolidine-2,4-diones, a,b-Unsaturated carbonyl compounds, 1,2-Addition, conjugate addition, Grignard reagents, Lithium dibutylcuprate. Bull. Chem. Soc. Ethiop.

  4. Effects of the conjugation of whey proteins with gellan polysaccharides on surfactant-induced competitive displacement from the air-water interface.

    Science.gov (United States)

    Cai, B; Ikeda, S

    2016-08-01

    Whey proteins can be used to stabilize foams and emulsions against coalescence because of their ability to form viscoelastic films at the interface that resist film rupture on collision between colloidal particles. However, whey proteins are competitively displaced from the interface if small-molecule surfactants are added, leading to destabilization of the entire system. This is because surfactants are more effective in molecular packing at the interface, and they lower interfacial tension to a greater degree than whey proteins do, but their interfacial films are poor in viscoelasticity. We hypothesized that whey proteins would become more resistant to surfactant-induced competitive displacement if they were conjugated with network-forming polysaccharides. The protein moiety of the conjugate would be expected to enable its adsorption to the interface, and the polysaccharide moiety would be expected to form self-assembled networks, strengthening the interfacial film as a whole. In this study, whey proteins were conjugated with gellan polysaccharides using the Maillard reaction. Atomic force microscopy images of interfacial films formed by the whey protein-gellan conjugate at the air-water interface and transferred onto mica sheets using the Langmuir-Blodgett method revealed that gellan did form self-assembled networks at the interface and that interfacial films also contained a large number of unconjugated whey protein molecules. Following the addition of a small-molecule surfactant (Tween 20) to the sub-phase, surface pressure increased, indicating spontaneous adsorption of surfactants to the interface. Atomic force microscopy images showed decreases in interfacial area coverage by whey proteins as surface pressure increased. At a given surface pressure, the interfacial area coverage by whey protein-gellan conjugates was greater than coverage by unconjugated whey proteins, confirming that whey proteins became more resistant to surfactant-induced displacement after

  5. Transglutaminase-treated conjugation of sodium caseinate and corn fiber gum hydrolysate: Interfacial and dilatational properties.

    Science.gov (United States)

    Liu, Yan; Selig, Michael J; Yadav, Madhav P; Yin, Lijun; Abbaspourrad, Alireza

    2018-05-01

    This study compliments previous work where peroxidase was successfully used to crosslink corn fiber gum (CFG) with bovine serum albumin and improve CFG's emulsifying properties. Herein, an alternative type of enzyme, transglutaminase, was used to prepare conjugates of CFG and sodium caseinate. Additionally, the CFG was partially hydrolyzed by sulfuric acid and its crosslinking pattern with caseinate was evaluated. The interfacial crosslinking degree between caseinate and CFG increased after hydrolysis according to high performance size exclusion chromatography. The equilibrium interfacial tension of CFG hydrolysate-caseinate conjugate was lower than that of CFG-caseinate conjugate as the rearrangement rate of the CFG hydrolysate-caseinate conjugate was higher. The dilatational modulus of CFG hydrolysate decreased from that of CFG. Copyright © 2018 Elsevier Ltd. All rights reserved.

  6. DNA-templated antibody conjugation for targeted drug delivery to cancer cells

    DEFF Research Database (Denmark)

    Liu, Tianqiang

    2016-01-01

    -templated organic synthesis due to the wide existence of the 3-histidine cluster in most wild-type proteins. In this thesis, three projects that relate to targeted drug delivery to cancer cells based on the DTPC method is described. The first project was a delivery system which uses transferrin as the targeting....... The study shows that DNA is a highly useful tool for the assembly of proteins with potential therapeutic applications. The DNA-templated protein conjugation shows a promising application in constructing antibody-toxin conjugates or antibody-drug conjugates. In addition, DNA strands used for antibody...... either antibody engineering or special expression systems and are both time and labor consuming. To avoid the drawbacks caused by conventional chemical modification and recombinant methodologies, an ideal site specific conjugation technique would use natural amino acid residues to the protein by a new...

  7. 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

  8. Novel Aflatoxin Derivatives and Protein Conjugates

    Directory of Open Access Journals (Sweden)

    Reinhard Niessner

    2007-03-01

    Full Text Available Aflatoxins, a group of structurally related mycotoxins, are well known for their toxic and carcinogenic effects in humans and animals. Aflatoxin derivatives and protein conjugates are needed for diverse analytical applications. This work describes a reliable and fast synthesis of novel aflatoxin derivatives, purification by preparative HPLC and characterisation by ESI-MS and one- and two-dimensional NMR. Novel aflatoxin bovine serum albumin conjugates were prepared and characterised by UV absorption and MALDI-MS. These aflatoxin protein conjugates are potentially interesting as immunogens for the generation of aflatoxin selective antibodies with novel specificities.

  9. Study on radiation grafting of NASI on sephadex and conjugation of the copolymer with BSA

    International Nuclear Information System (INIS)

    Yi Min; Li Jun; Wei Jinshan; Ha Hongfei

    1997-01-01

    N-acryloxysuccinimide (NASI) with a function ester group is grafted on Sephadex G75 and Sephadex G50 separately by radiation technology. The radiation grafting conditions including absorbed dose, dose rate, monomer concentration in solvent are investigated. The conjugation reactions between the grafted copolymers Sephadex G75-NASI, and bovine serum albumin (BSA) or Sephadex G50-NASI and bovine serum albumin (BSA) are followed. The experiment results show that the conjugate of Sephadex G75-NASI with larger holes and BSA (M r = 6.6 x 10 4 ) is obtained successfully, however, the Sephadex G50 with small holes can be only conjugated with neutral red (M r = 2.58 x 10 2 )

  10. Bifunctional rhodium intercalator conjugates as mismatch-directing DNA alkylating agents.

    Science.gov (United States)

    Schatzschneider, Ulrich; Barton, Jacqueline K

    2004-07-21

    A conjugate of a DNA mismatch-specific rhodium intercalator, containing the bulky chrysenediimine ligand, and an aniline mustard has been prepared, and targeting of mismatches in DNA by this conjugate has been examined. The preferential alkylation of mismatched over fully matched DNA is found by a mobility shift assay at concentrations where untethered organic mustards show little reaction. The binding site of the Rh intercalator was determined by DNA photocleavage, and the position of covalent modification was established on the basis of the enhanced depurination associated with N-alkylation. The site-selective alkylation at mismatched DNA renders these conjugates useful tools for the covalent tagging of DNA base pair mismatches and new chemotherapeutic design.

  11. 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.

  12. Development and preclinical evaluation of new 124I-folate conjugates for PET imaging of folate receptor-positive tumors

    International Nuclear Information System (INIS)

    AlJammaz, I.; Al-Otaibi, B.; Al-Rumayan, F.; Al-Yanbawi, S.; Amer, S.; Okarvi, S.M.

    2014-01-01

    In an attempt to develop new folate radiotracers with favorable biochemical properties for detecting folate receptor-positive cancers, we have synthesized [ 124 I]-SIB- and [ 124 I]-SIP-folate conjugates using a straightforward and two-step simple reactions. Radiochemical yields for [ 124 I]-SIB- and [ 124 I]-SIP-folate conjugates were greater than 90 and 60% respectively, with total synthesis time of 30–40 min. Radiochemical purities were always greater than 98% without HPLC purification. These synthetic approaches hold considerable promise as rapid and simple method for 124 I-folate conjugate preparation with high radiochemical yield in short synthesis time. In vitro tests on KB cell line showed that the significant amounts of the radioconjugates were associated with cell fractions. In vivo characterization in normal Balb/c mice revealed rapid blood clearance of these radioconjugates and favorable biodistribution profile for [ 124 I]-SIP-folate conjugate over [ 124 I]-SIB-folate conjugate. Biodistribution studies of [ 124 I]-SIP-folate conjugate in nude mice bearing human KB cell line xenografts, demonstrated significant tumor uptake. The uptake in the tumors was blocked by excess injection of folic acid, suggesting a receptor-mediated process. These results demonstrate that [ 124 I]-SIP-folate conjugate may be useful as a molecular probe for detecting and staging of folate receptor-positive cancers, such as ovarian cancer and their metastasis as well as monitoring tumor response to treatment

  13. [Optimizing synthesis of conjugates of superoxide dismutase and catalase with aldehyde dextrans in surfactant microemulsions in heptane].

    Science.gov (United States)

    Eremin, A N; Metelitsa, D I

    1997-01-01

    Stable microemulsions in heptane retaining considerable amounts of the polar phase were obtained by using Aerosol OT (AOT), Triton X-45, and catalase. Conjugates of superoxide dismutase (SOD) and catalase with aldehyde dextrans (AD) were synthesized in surfactant microemulsions in heptane. Effects of the reaction duration, the microemulsion polar phase volume, and concentrations of enzymes and modifiers on the properties of these conjugates were studied. The catalytic properties of conjugates depended on the nature of the surfactants used to stabilize the microemulsions, the initial concentration of protein in the reaction mixture, and the enzyme: modifier ratio. The degree of modification of the enzymes and the stabilities of their conjugates during isolation from microemulsions by a water-acetone solution depended on the concentration of the AD used. The catalytic properties of the conjugates synthesized were compared, and their stabilities in the presence of H2O2 were described. We suggested a simple method of transformation of whole kinetic curves of H2O2 conversion in coordinates 1/ln([H2O2]0/[H2O2]t - 1/t for simultaneous measurement of the constant of the catalase inactivation rate by H2O2 (Cin, S-1) and the rate constant of the catalase complex 1 interaction with the second H2O2 molecule (C2, M-1 S-1). This method was tested experimentally. Values C2 and Cin for catalase and its conjugates with ADs were compared, and these results were discussed.

  14. Conjugate descent formulation of backpropagation error in ...

    African Journals Online (AJOL)

    nique of backpropagation was popularized in a paper by Rumelhart, et al. ... the training of a multilayer neural network using a gradient descent approach applied to a .... superior convergence of the conjugate descent method over a standard ...

  15. Multicomponent Reactions in Ligation and Bioconjugation Chemistry.

    Science.gov (United States)

    Reguera, Leslie; Méndez, Yanira; Humpierre, Ana R; Valdés, Oscar; Rivera, Daniel G

    2018-05-25

    Multicomponent reactions (MCRs) encompass an exciting class of chemical transformations that have proven success in almost all fields of synthetic organic chemistry. These convergent procedures incorporate three or more reactants into a final product in one pot, thus combining high levels of complexity and diversity generation with low synthetic cost. Striking applications of these processes are found in heterocycle, peptidomimetic, and natural product syntheses. However, their potential in the preparation of large macro- and biomolecular constructs has been realized just recently. This Account describes the most relevant results of our group in the utilization of MCRs for ligation/conjugation of biomolecules along with significant contributions from other laboratories that validate the utility of this special class of bioconjugation process. Thus, MCRs have proven to be efficient in the ligation of lipids to peptides and oligosaccharides as well as the ligation of steroids, carbohydrates, and fluorescent and affinity tags to peptides and proteins. In the field of glycolipids, we highlight the power of isocyanide-based MCRs with the one-pot double lipidation of glycan fragments functionalized as either the carboxylic acid or amine. In peptide chemistry, the versatility of the multicomponent ligation strategy is demonstrated in both solution-phase lipidation protocols and solid-phase procedures enabling the simultaneous lipidation and biotinylation of peptides. In addition, we show that MCRs are powerful methods for synchronized lipidation/labeling and macrocyclization of peptides, thus accomplishing in one step what usually requires long sequences. In the realm of protein bioconjugation, MCRs have also proven to be effective in labeling, site-selective modification, immobilization, and glycoconjugation processes. For example, we illustrate a successful application of multicomponent polysaccharide-protein conjugation with the preparation of multivalent

  16. Meeting the challenge: prevention of pneumococcal disease with conjugate vaccines

    Directory of Open Access Journals (Sweden)

    Echániz-Avilés Irma Gabriela

    2001-01-01

    Full Text Available Streptococcus pneumoniae is one of the leading causes of both invasive and noninvasive diseases in the pediatric population and continues to represent a significant public health burden worldwide. The increasing incidence of antibioticresistant strains of the pathogen has complicated treatment and management of the various pneumococcal disease manifestations. Thus, the best management strategy may be the prevention of pneumococcal diseases through vaccination. Although several pneumococcal conjugate vaccines have been clinically studied in infants and children, only a 7-valent conjugate vaccine (PNCRM7; Prevnar®/Prevenar® is currently approved for the prevention of invasive disease. Vaccination with PNCRM7 is safe and effective in infants and young children. Routine vaccination with the conjugate vaccine could improve outcomes by safeguarding against the development of antibiotic-resistant strains of S. pneumoniae, thus simplifying the management of pneumococcal disease. Additionally, the overall costs associated with the treatment of pneumococcal diseases could be substantially reduced, particularly in developing countries. The time has come for fully applying this new advancement against S. pneumoniae, to benefit the children of the world. The Spanish version of this paper is available at: http://www.insp.mx/salud/index.html

  17. Radiation curable Michael addition compounds

    International Nuclear Information System (INIS)

    Gruber, G.W.; Friedlander, C.B.; McDonald, W.H.; Dowbenko, R.

    1979-01-01

    Radiation polymerizable acrylyloxy-containing reaction products are provided from Michael addition reaction of an amide containing at least two acrylate groups with a primary or secondary amine. The resulting amine adducts of the amide, which contain at least one acrylate group per molecule, possesses high cure rates in air and are useful in compositions for forming coatings. (author)

  18. Sleeve reaction chamber system

    Science.gov (United States)

    Northrup, M Allen [Berkeley, CA; Beeman, Barton V [San Mateo, CA; Benett, William J [Livermore, CA; Hadley, Dean R [Manteca, CA; Landre, Phoebe [Livermore, CA; Lehew, Stacy L [Livermore, CA; Krulevitch, Peter A [Pleasanton, CA

    2009-08-25

    A chemical reaction chamber system that combines devices such as doped polysilicon for heating, bulk silicon for convective cooling, and thermoelectric (TE) coolers to augment the heating and cooling rates of the reaction chamber or chambers. In addition the system includes non-silicon-based reaction chambers such as any high thermal conductivity material used in combination with a thermoelectric cooling mechanism (i.e., Peltier device). The heat contained in the thermally conductive part of the system can be used/reused to heat the device, thereby conserving energy and expediting the heating/cooling rates. The system combines a micromachined silicon reaction chamber, for example, with an additional module/device for augmented heating/cooling using the Peltier effect. This additional module is particularly useful in extreme environments (very hot or extremely cold) where augmented heating/cooling would be useful to speed up the thermal cycling rates. The chemical reaction chamber system has various applications for synthesis or processing of organic, inorganic, or biochemical reactions, including the polymerase chain reaction (PCR) and/or other DNA reactions, such as the ligase chain reaction.

  19. Enhancement of anti-tumor activity of hybrid peptide in conjugation with carboxymethyl dextran via disulfide linkers.

    Science.gov (United States)

    Gaowa, Arong; Horibe, Tomohisa; Kohno, Masayuki; Tabata, Yasuhiko; Harada, Hiroshi; Hiraoka, Masahiro; Kawakami, Koji

    2015-05-01

    To improve the anti-tumor activity of EGFR2R-lytic hybrid peptide, we prepared peptide-modified dextran conjugates with the disulfide bonds between thiolated carboxymethyl dextran (CMD-Cys) and cysteine-conjugated peptide (EGFR2R-lytic-Cys). In vitro release studies showed that the peptide was released from the CMD-s-s-peptide conjugate in a concentration-dependent manner in the presence of glutathione (GSH, 2μM-2mM). The CMD-s-s-peptide conjugate exhibited a similar cytotoxic activity with free peptide alone against human pancreatic cancer BxPC-3 cells in vitro. Furthermore, it was shown that the CMD-s-s-peptide conjugates were highly accumulated in tumor tissue in a mouse xenograft model using BxPC-3 cells, and the anti-tumor activity of the conjugate was more effective than that of the free peptide. In addition, the plasma concentrations of peptide were moderately increased and the elimination half-life of the peptide was prolonged after intravenous injection of CMD-s-s-peptide conjugates. These results demonstrated that the conjugate based on thiolated CMD polymer would be potentially useful carriers for the sustained release of the hybrid peptide in vivo. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Micelle-like nanoassemblies based on polymer-drug conjugates as an emerging platform for drug delivery.

    Science.gov (United States)

    Liu, Zhihong; Wang, Yutao; Zhang, Na

    2012-07-01

    During the past decades, polymer-drug conjugates are one of the hottest topics in novel drug development fields. Amphiphilic polymer-drug conjugates in aqueous solution could form micelles or micelle-like nanoassemblies. Compared with polymer-drug conjugates and the micelles into which drugs are physically entrapped, micelles or micelle-like nanoassemblies based on polymer-drug conjugates bring several additional advantages, including increased drug-loading capacity, enhanced intracellular uptake, reduced systemic toxicity, and improved therapeutic efficacy. This review focuses on recent progress achieved in the research field of micelles or micelle-like nanoassemblies based on polymer-drug conjugates. Firstly, properties of polymers, drugs, and linkers which could be used to build polymer-drug conjugate micelles or micelle-like nanoassemblies are summarized. Then, the characterization methods are described. Finally, the drug-targeting mechanisms are discussed. Micelles or micelle-like nanoassemblies based on polymer-drug conjugates as an emerging platform have the potential to achieve medical treatments with enhanced therapeutic effect. The application of micelles or micelle-like nanoassemblies based on polymer-drug conjugates may give new life to old active compounds abandoned due to their low solubility problems. For clinical application, there is a need to further optimize the properties of the polymer, drug, and linker.

  1. A pH-responsive carboxymethyl dextran-based conjugate as a carrier of docetaxel for cancer therapy.

    Science.gov (United States)

    Han, Hwa Seung; Lee, Minchang; An, Jae Yoon; Son, Soyoung; Ko, Hyewon; Lee, Hansang; Chae, Yee Soo; Kang, Young Mo; Park, Jae Hyung

    2016-05-01

    Although docetaxel is available for the treatment of various cancers, its clinical applications are limited by its poor water solubility and toxicity to normal cells, resulting in severe adverse effects. In this study, we synthesized a polymeric conjugate with an acid-labile ester linkage, consisting of carboxymethyl dextran (CMD) and docetaxel (DTX), as a potential anticancer drug delivery system. The conjugate exhibited sustained release of DTX in physiological buffer (pH 7.4), whereas its release rate increased remarkably under mildly acidic conditions (pH < 6.5), mimicking the intracellular environment. Cytotoxicity tests conducted in vitro demonstrated that the conjugate exhibited much higher toxicity to cancer cells under mildly acidic conditions than at physiological buffer (pH 7.4). These results implied that the ester linkage in the conjugate allowed for selective release of biologically active DTX under mildly acidic conditions. The in vivo biodistribution of a Cy5.5-labeled conjugate was observed using the noninvasive optical imaging technique after its systemic administration into tumor-bearing mice. The conjugate was effectively accumulated into the tumor site, which may have been because of an enhanced permeability and retention effect. In addition, in vivo antitumor efficacy of the conjugate was significantly higher than that of free DTX. Overall, the CMD-based conjugate might have promising potential as a carrier of DTX for cancer therapy. © 2015 Wiley Periodicals, Inc.

  2. Soluble polymer conjugates for drug delivery.

    Science.gov (United States)

    Minko, Tamara

    2005-01-01

    The use of water-soluble polymeric conjugates as drug carriers offers several possible advantages. These advantages include: (1) improved drug pharmacokinetics; (2) decreased toxicity to healthy organs; (3) possible facilitation of accumulation and preferential uptake by targeted cells; (4) programmed profile of drug release. In this review, we will consider the main types of useful polymeric conjugates and their role and effectiveness as carriers in drug delivery systems.: © 2005 Elsevier Ltd . All rights reserved.

  3. Diffeomorphisms Holder conjugate to Anosov diffeomorphisms

    OpenAIRE

    Gogolev, Andrey

    2008-01-01

    We show by means of a counterexample that a $C^{1+Lip}$ diffeomorphism Holder conjugate to an Anosov diffeomorphism is not necessarily Anosov. The counterexample can bear higher smoothness up to $C^3$. Also we include a result from the 2006 Ph.D. thesis of T. Fisher: a $C^{1+Lip}$ diffeomorphism Holder conjugate to an Anosov diffeomorphism is Anosov itself provided that Holder exponents of the conjugacy and its inverse are sufficiently large.

  4. Rapid modification of retroviruses using lipid conjugates

    International Nuclear Information System (INIS)

    Mukherjee, Nimisha G; Le Doux, Joseph M; Andrew Lyon, L

    2009-01-01

    Methods are needed to manipulate natural nanoparticles. Viruses are particularly interesting because they can act as therapeutic cellular delivery agents. Here we examine a new method for rapidly modifying retroviruses that uses lipid conjugates composed of a lipid anchor (1,2-distearoyl-sn-glycero-3-phosphoethanolamine), a polyethylene glycol chain, and biotin. The conjugates rapidly and stably modified retroviruses and enabled them to bind streptavidin. The implication of this work for modifying viruses for gene therapy and vaccination protocols is discussed.

  5. Degradations and Rearrangement Reactions

    Science.gov (United States)

    Zhang, Jianbo

    This section deals with recent reports concerning degradation and rearrangement reactions of free sugars as well as some glycosides. The transformations are classified in chemical and enzymatic ways. In addition, the Maillard reaction will be discussed as an example of degradation and rearrangement transformation and its application in current research in the fields of chemistry and biology.

  6. 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...... to investigate whether such conjugates are excreted in the urine from persons treated with 5-ASA. The N-acetyl-cysteine conjugates could be detected by fluorescense, which resulted in low detection limits ranging from 0.02 mug to 0.06 mug per ml corresponding to the transformation of about 0.003% of the daily...

  7. alpha-Glucosidase-albumin conjugates: effect of chronic administration in mice

    International Nuclear Information System (INIS)

    Allen, T.M.; Murray, L.; Bhardwaj, D.; Poznansky, M.J.

    1985-01-01

    Enzyme albumin conjugates have been proposed as a means of increasing the efficacy of enzyme use in vivo and decreasing immune response to the enzyme. Particulate drug carriers, however, have a pronounced tendency to localize in the mononuclear phagocyte (reticuloendothelial) system. The authors have examined in mice the effect on phagocytic index, tissue distribution and organ size of continued administration of conjugates of alpha-glucosidase with either homologous or heterologous albumin. Mice received 10 X 2-mg injections of bovine serum albumin (BSA) or mouse serum albumin (MSA), either free, polymerized or conjugated with alpha-glucosidase. Experiments involving BSA had to be terminated before the end of the experiment because of anaphylaxis, but these reactions were less severe to the polymerized albumin than to free albumin. Free BSA, BSA polymer and BSA-enzyme conjugates all caused a decrease in phagocytic index after six injections. Mice receiving MSA showed no evidence of anaphylaxis, but mice receiving six or more injections of free MSA, MSA polymer or MSA-enzyme conjugate had significantly decreased phagocytic indices as compared to controls. Phagocytic indices had returned to normal by 7 days after the final injection. Tissue distribution of 125 I-labeled albumin preparations was determined in either naive or chronically injected mice

  8. 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

    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...... 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...... between tristearin and linoleic acid; whereas there were 2.4% cLcLcL, 10.4% cLScL, 50.9% cLSS, and 36.2% SSS in the product for a system between tristearin and conjugated linoleic acid. The results suggest that linoleic acid was more reactive than conjugated linoleic acid in the enzymatic acidolysis...

  9. Statistical nuclear reactions

    International Nuclear Information System (INIS)

    Hilaire, S.

    2001-01-01

    A review of the statistical model of nuclear reactions is presented. The main relations are described, together with the ingredients necessary to perform practical calculations. In addition, a substantial overview of the width fluctuation correction factor is given. (author)

  10. 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.

  11. Actinic radiation-curable formulations from the reaction product of organic isocyanate, poly(alkylene oxide) polyol and an unsaturated addition-polymerizable monomeric compound having a single isocyanate-reactive hydrogen group

    International Nuclear Information System (INIS)

    Howard, D.D.

    1979-01-01

    Energy-curable compositions which can be cured in the presence of air by exposure to actinic radiation contain at least one unsaturated urethane oligomer. The oligomer comprises the reaction product of at least one poly(alkylene oxide) polyol, at least one polyisocyanate, and at least one unsaturated active hydrogen-containing compound

  12. 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.

  13. Labeling of monoclonal antibody conjugates with 90Y

    International Nuclear Information System (INIS)

    Motta-Hennessy, Cecilia; Sharkey, R.M.; Goldenberg, D.M.

    1991-01-01

    An anti-carcinoembryonic antigen (CEA) antibody, NP-4, was labeled with 90 Y using p-isothiocyanatobenzyl DTPA (SCN-Bz-DTPA) and its derivatives 1-(p-isothiocyanatobenzyl)-3-methyl-DTPA (1B3M), 2-(p-isothiocyanatobenzyl)-4-methyl-DTPA (1M3B), 1-(2)-methyl-4-isothiocyanatobenzyl-DTPA (MX-DTPA) as the chelating agents. The 90 Y conjugates were purified from unbound 90 Y by two different methods, HPLC or acrylamide size exclusion gel chromatography, in order to evaluate the best purification method. Labeling efficiency, reaction kinetics and immunoreactivity were compared to the same antibodies labeled with [ 111 In]citrate. Labeling efficiency, as determined by either HPLC or ITLC (instant thin layer chromatography), was consistently higher by ITLC than HPLC for 90 Y-labeled MAb, but equal for 111 In-labeled MAbs. Discrepancies between the 2 methods were linked to impurities in the 90 Y that remained at the origin of ITLC plates. After purification by acrylamide gel filtration, recovery was 50-60% of loaded 90 Y activity, but was more than 87% for the 111 In compounds. Using HPLC, the recovery measured 85% for 90 Y-labeled MAb and more than 93% for 111 In-labeled conjugates. Immunoreactivity of the [ 90 Y]MAb was comparable to the 111 In-labeled conjugates. These studies indicate that HPLC purification of the [ 90 Y] MAbs improves recovery of activity, and suggests that impurities found in the 90 Y and metal-binding properties of acrylamide may have contributed to the poor recoveries from acrylamide gels. (author)

  14. Labeling of monoclonal antibody conjugates with sup 90 Y

    Energy Technology Data Exchange (ETDEWEB)

    Motta-Hennessy, Cecilia; Sharkey, R.M.; Goldenberg, D.M. (Center for Molecular Medicine and Immunology, Newark, NJ (USA))

    1991-01-01

    An anti-carcinoembryonic antigen (CEA) antibody, NP-4, was labeled with {sup 90}Y using p-isothiocyanatobenzyl DTPA (SCN-Bz-DTPA) and its derivatives 1-(p-isothiocyanatobenzyl)-3-methyl-DTPA (1B3M), 2-(p-isothiocyanatobenzyl)-4-methyl-DTPA (1M3B), 1-(2)-methyl-4-isothiocyanatobenzyl-DTPA (MX-DTPA) as the chelating agents. The {sup 90}Y conjugates were purified from unbound {sup 90}Y by two different methods, HPLC or acrylamide size exclusion gel chromatography, in order to evaluate the best purification method. Labeling efficiency, reaction kinetics and immunoreactivity were compared to the same antibodies labeled with ({sup 111}In)citrate. Labeling efficiency, as determined by either HPLC or ITLC (instant thin layer chromatography), was consistently higher by ITLC than HPLC for {sup 90}Y-labeled MAb, but equal for {sup 111}In-labeled MAbs. Discrepancies between the 2 methods were linked to impurities in the {sup 90}Y that remained at the origin of ITLC plates. After purification by acrylamide gel filtration, recovery was 50-60% of loaded {sup 90}Y activity, but was more than 87% for the {sup 111}In compounds. Using HPLC, the recovery measured 85% for {sup 90}Y-labeled MAb and more than 93% for {sup 111}In-labeled conjugates. Immunoreactivity of the ({sup 90}Y)MAb was comparable to the {sup 111}In-labeled conjugates. These studies indicate that HPLC purification of the ({sup 90}Y) MAbs improves recovery of activity, and suggests that impurities found in the {sup 90}Y and metal-binding properties of acrylamide may have contributed to the poor recoveries from acrylamide gels. (author).

  15. A Study on Catalysis and Electrolyte Engineering for H2/O2 Electrochemical Reactions

    KAUST Repository

    Shinagawa, Tatsuya

    2016-01-01

    placed on milder conditions, to rationalize and improve its performance. Microkinetic analysis was performed for the cathodic half-reaction in conjugation with mass transport evaluation using various electrode materials. The analysis revealed a

  16. Nuclear reactions

    International Nuclear Information System (INIS)

    Lane, A.M.

    1980-01-01

    In reviewing work at Harwell over the past 25 years on nuclear reactions it is stated that a balance has to be struck in both experiment and theory between work on cross-sections of direct practical relevance to reactors and on those relevant to an overall understanding of reaction processes. The compound nucleus and direct process reactions are described. Having listed the contributions from AERE, Harwell to developments in nuclear reaction research in the period, work on the optical model, neutron capture theory, reactions at doorway states with fine structure, and sum-rules for spectroscopic factors are considered in more detail. (UK)

  17. Noncanonical Reactions of Flavoenzymes

    Directory of Open Access Journals (Sweden)

    Pablo Sobrado

    2012-11-01

    Full Text Available Enzymes containing flavin cofactors are predominantly involved in redox reactions in numerous cellular processes where the protein environment modulates the chemical reactivity of the flavin to either transfer one or two electrons. Some flavoenzymes catalyze reactions with no net redox change. In these reactions, the protein environment modulates the reactivity of the flavin to perform novel chemistries. Recent mechanistic and structural data supporting novel flavin functionalities in reactions catalyzed by chorismate synthase, type II isopentenyl diphosphate isomerase, UDP-galactopyranose mutase, and alkyl-dihydroxyacetonephosphate synthase are presented in this review. In these enzymes, the flavin plays either a direct role in acid/base reactions or as a nucleophile or electrophile. In addition, the flavin cofactor is proposed to function as a “molecular scaffold” in the formation of UDP-galactofuranose and alkyl-dihydroxyacetonephosphate by forming a covalent adduct with reaction intermediates.

  18. 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

  19. 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).

  20. Reaction-based Indicator displacement Assay (RIA) for the selective colorimetric and fluorometric detection of peroxynitrite† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c4sc03983a Click here for additional data file.

    Science.gov (United States)

    Sun, Xiaolong; Lacina, Karel; Ramsamy, Elena C.; Flower, Stephen E.; Fossey, John S.; Qian, Xuhong

    2015-01-01

    Using the self-assembly of aromatic boronic acids with Alizarin Red S (ARS), we developed a new chemosensor for the selective detection of peroxynitrite. Phenylboronic acid (PBA), benzoboroxole (BBA) and 2-(N,N-dimethylaminomethyl)phenylboronic acid (NBA) were employed to bind with ARS to form the complex probes. In particular, the ARS–NBA system with a high binding affinity can preferably react with peroxynitrite over hydrogen peroxide and other ROS/RNS due to the protection of the boron via the solvent-insertion B–N interaction. Our simple system produces a visible colorimetric change and on–off fluorescence response towards peroxynitrite. By coupling a chemical reaction that leads to an indicator displacement, we have developed a new sensing strategy, referred to herein as RIA (Reaction-based Indicator displacement Assay). PMID:28706677

  1. Stereochemistry of 1,2-elimination and proton-transfer reactions: toward a unified understanding.

    Science.gov (United States)

    Mohrig, Jerry R

    2013-07-16

    Many mechanistic and stereochemical studies have focused on the breaking of the C-H bond through base-catalyzed elimination reactions. When we began our research, however, chemists knew almost nothing about the stereospecificity of addition-elimination reactions involving conjugated acyclic carbonyl compounds, even though the carbonyl group is a pivotal functional group in organic chemistry. Over the last 25 years, we have studied the addition-elimination reactions of β-substituted acyclic esters, thioesters, and ketones in order to reach a comprehensive understanding of how electronic effects influence their stereochemistry. This Account brings together our understanding of the stereochemistry of 1,2-elimination and proton-transfer reactions, describing how each study has built upon previous work and contributed to our understanding of this field. When we began, chemists thought that anti stereospecificity in base-catalyzed 1,2-elimination reactions occurred via concerted E2 mechanisms, which provide a smooth path for anti elimination. Unexpectedly, we discovered that some E1cBirrev reactions produce the same anti stereospecificity as E2 reactions even though they proceed through diffusionally equilibrated, "free" enolate-anion intermediates. This result calls into question the conventional wisdom that anti stereochemistry must result from a concerted mechanism. While carrying out our research, we developed insights ranging from the role of historical contingency in the evolution of hydratase-dehydratase enzymes to the influence of buffers on the stereochemistry of H/D exchange in D2O. Negative hyperconjugation is the most important concept for understanding our results. This idea provides a unifying view for the largely anti stereochemistry in E1cBirrev elimination reactions and a basis for understanding the stereoelectronic influence of electron-withdrawing β-substituents on proton-transfer reactions.

  2. 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...

  3. Molecular design toward highly efficient photovoltaic polymers based on two-dimensional conjugated benzodithiophene.

    Science.gov (United States)

    Ye, Long; Zhang, Shaoqing; Huo, Lijun; Zhang, Maojie; Hou, Jianhui

    2014-05-20

    As researchers continue to develop new organic materials for solar cells, benzo[1,2-b:4,5-b']dithiophene (BDT)-based polymers have come to the fore. To improve the photovoltaic properties of BDT-based polymers, researchers have developed and applied various strategies leading to the successful molecular design of highly efficient photovoltaic polymers. Novel polymer materials composed of two-dimensional conjugated BDT (2D-conjugated BDT) have boosted the power conversion efficiency of polymer solar cells (PSCs) to levels that exceed 9%. In this Account, we summarize recent progress related to the design and synthesis of 2D-conjugated BDT-based polymers and discuss their applications in highly efficient photovoltaic devices. We introduce the basic considerations for the construction of 2D-conjugated BDT-based polymers and systematic molecular design guidelines. For example, simply modifying an alkoxyl-substituted BDT to form an alkylthienyl-substituted BDT can improve the polymer hole mobilities substantially with little effect on their molecular energy level. Secondly, the addition of a variety of chemical moieties to the polymer can produce a 2D-conjugated BDT unit with more functions. For example, the introduction of a conjugated side chain with electron deficient groups (such as para-alkyl-phenyl, meta-alkoxyl-phenyl, and 2-alkyl-3-fluoro-thienyl) allowed us to modulate the molecular energy levels of 2D-conjugated BDT-based polymers. Through the rational design of BDT analogues such as dithienobenzodithiophene (DTBDT) or the insertion of larger π bridges, we can tune the backbone conformations of these polymers and modulate their photovoltaic properties. We also discuss the influence of 2D-conjugated BDT on polymer morphology and the blends of these polymers with phenyl-C61 (or C71)-butyric acid methyl ester (PCBM). Finally, we summarize the various applications of the 2D-conjugated BDT-based polymers in highly efficient PSC devices. Overall, this Account

  4. Synthesis of metalloporphyrin-based conjugated microporous polymer spheres directed by bipyridine-type ligands.

    Science.gov (United States)

    Ji, Guipeng; Yang, Zhenzhen; Zhao, Yanfei; Zhang, Hongye; Yu, Bo; Xu, Jilei; Xu, Huanjun; Liu, Zhimin

    2015-04-30

    Zinc porphyrin (TP-Zn)-based conjugated microporous polymer (Zn-CMP) spheres were obtained via Sonagashira-Hagihara cross coupling reactions between 5,10,15,20-tetrakis(4-ethynylphenyl)porphyrin-Zn(II) and brominated monomers directed by bidentate bipyridine (BP)-type ligands for the first time, and the sphere diameters could be adjusted from 320 to 740 nm. The coordination between BP and TP-Zn was proved to be the key to forming spheres.

  5. Analytical characterization of polymer-drug conjugates

    International Nuclear Information System (INIS)

    Rizzo, V.; Gigli, M.; Pinciroli, V.

    1998-01-01

    A few polymeric conjugates of antitumor drugs have been recently developed in view of possible therapeutic advantages: solubilization of sparingly soluble drugs in water, improvement of therapeutic index, organ targeting through a second chemical species bound to the same polymeric chain. In this article it's described the analytical approach used in the characterization of the conjugates for chemical identity, purity and strength of the contained active ingredient. The techniques are: high field NMR and size exclusion chromatography with non-aqueous mobile phase for identity; selective hydrolysis and HPLC for strength and purity. A complete and reliable picture is thus obtained both for qualitative and for quantitative aspects. This is an important step forward in the direction of further development and marketing of polymer-drug conjugates [it

  6. Nonlinear conjugate gradient methods in micromagnetics

    Directory of Open Access Journals (Sweden)

    J. Fischbacher

    2017-04-01

    Full Text Available 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.

  7. 125I Radioimmunoassay of serum ursodeoxycholyl conjugates

    International Nuclear Information System (INIS)

    Hill, A.; Ross, P.E.; Bouchier, I.A.D.

    1983-01-01

    A radioimmunoassay for serum ursodeoxycholic conjugates using an iodine-125 ligand has been developed. The bile acid was present in normal fasting serum (0.19 +- SD 0.19 μmol/l, n=24) and 2-hour post-prandial serum (0.8 +- SD 0.8 μmol/l, n=16). Gallstone patients undergoing oral ursodeoxycholic acid therapy had significantly higher post-prandial serum levels (21.5 +- SD 14.0 μmol/l, n=15) by radioimmunoassay. Gas liquid chromatography analysis indicated that in normal serum ursodeoxycholic acid was totally conjugated, whereas sera from gallstone patients contained a proportion as the free bile acid (10.2 +- SD 8.1 μmol/l, n=15). Following an oral dose of ursodeoxycholic acid, both unconjugated and conjugated forms of the bile acid appeared in the serum of healthy individuals. (Auth.)

  8. Deciphering conjugative plasmid permissiveness in wastewater microbiomes

    DEFF Research Database (Denmark)

    Jacquiod, Samuel Jehan Auguste; Brejnrod, Asker Daniel; Milani, Stefan Morberg

    2017-01-01

    Wastewater treatment plants (WWTPs) are designed to robustly treat polluted water. They are characterized by ceaseless flows of organic, chemical and microbial matter, followed by treatment steps before environmental release. WWTPs are hotspots of horizontal gene transfer between bacteria via...... still remains largely uncharted. Furthermore, current in vitro methods used to assess conjugation in complex microbiomes do not include in situ behaviours of recipient cells, resulting in partial understanding of transfers. We investigated the in vitro conjugation capacities of WWTP microbiomes from...... inlet sewage and outlet treated water using the broad-host range IncP-1 conjugative plasmid, pKJK5. A thorough molecular approach coupling metagenomes to 16S rRNA DNA/cDNA amplicon sequencing was established to characterize microbiomes using the ecological concept of functional response groups. A broad...

  9. 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.

  10. The preparation and properties of a highly specific antiserum elicited with 3-dehydrocholylglycine 3-succinyl-bovine serum albumin conjugate

    International Nuclear Information System (INIS)

    Orban, E.C.; Pal, Z.

    1986-01-01

    This report describes the synthesis of a new cholylglycine derivative-bovine serum albumin conjugate. The hapten is linked to the carrier protein at the C-3 position, through a hemisuccinate bridge. Antiserum elicited by this antigen is highly specific to cholylglycine. Cross-reactions with free cholic acid (less than 0.1%) or cholyltaurine (0.5%) are minimal. (author)

  11. Vibrational Coupling in Conjugated π Systems with a view to Optimization of Fluorescence Yield through Phonon Confinement

    OpenAIRE

    O'Neill, Luke; Lynch, Patrick; McNamara, Mary; Byrne, Hugh J.

    2005-01-01

    A series of π conjugated systems were studied by absorption, photoluminescence and vibrational spectroscopy. As is common for these systems, a linear relationship between the positioning of the absorption and photoluminescence maxima plotted against inverse conjugation length is observed. The relationships are in good agreement with the simple particle in a box method, one of the earliest descriptions of the properties of one-dimensional organic molecules. In addition to the electronic transi...

  12. 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.

  13. Interaction of Avelox with Bovine Serum Albumin and Effect of the Coexistent Drugs on the Reaction

    Directory of Open Access Journals (Sweden)

    Baosheng Liu

    2012-01-01

    Full Text Available The interaction between Avelox and bovine serum albumin (BSA was investigated at different temperatures by fluorescence spectroscopy. Results showed that Avelox could quench the intrinsic fluorescence of BSA strongly, and the quenching mechanism was a static quenching process with Förester spectroscopy energy transfer. The electrostatic force played an important role on the conjugation reaction between BSA and Avelox. The order of magnitude of binding constants (Ka was 104, and the number of binding site (n in the binary system was approximately equal to 1. The binding distance (r was less than 3 nm and the primary binding site for Avelox was located in subdomain IIA of BSA. Synchronous fluorescence spectra clearly revealed that the microenvironment of amino acid residues and the conformation of BSA were changed during the binding reaction. In addition, the effect of some antibiotics on the binding constant of Avelox with BSA was also studied.

  14. Conjugated Polymers as Actuators: Modes of Actuation

    DEFF Research Database (Denmark)

    Skaarup, Steen

    2004-01-01

    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...

  15. 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...

  16. 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.

  17. Conjugating folate on superparamagnetic Fe3O4@Au nanoparticles using click chemistry

    International Nuclear Information System (INIS)

    Shen, Xiaofang; Ge, Zhaoqiang; Pang, Yuehong

    2015-01-01

    Gold-coated magnetic core@shell nanoparticles, which exhibit magneto-optical properties, not only enhance the chemical stability of core and biocompatibility of surface, but also provide a combination of multimodal imaging and therapeutics. The conjugation of these tiny nanoparticles with specific biomolecules allows researchers to target the desired location. In this paper, superparamagnetic Fe 3 O 4 @Au nanoparticles were synthesized and functionalized with the azide group on the surface by formation of self-assembled monolayers. Folate (FA) molecules, non-immunogenic target ligands for cancer cells, are conjugated with alkyne and then immobilized on the azide-terminated Fe 3 O 4 @Au nanoparticles through copper(I)-catalyzed azide-alkyne cycloaddition (click reaction). Myelogenous leukemia K562 cells were used as a folate receptor (FR) model, which can be targeted and extracted by magnetic field after interaction with the Fe 3 O 4 @Au–FA nanoparticles. - Graphical abstract: Self-assembled azide-terminated group on superparamagnetic Fe 3 O 4 @Au nanoparticles followed by click reaction with alkyne-functionalized folate, allowing the nanoparticles target folate receptor of cancer cells. - Highlights: • Azidoundecanethiol was coated on the superparamagnetic Fe 3 O 4 @Au nanoparticles by forming self-assembled monolayers. • Alkyne-terminated folate was synthesized from a reaction between the amine and the carboxylic acid. • Conjugation of Fe 3 O 4 @Au nanoparticles with folate was made by copper-catalyzed azide-alkyne cycloaddition click chemistry

  18. Coupling of biologically active steroids to conjugating arms through ether linkages for use in immunochemistry.

    Science.gov (United States)

    Kohl, Michel J; Lejeune, Robert G

    2002-01-01

    Conjugation of haptens through ether linkages avoids leakage problems in immunoassays, but this procedure is not easily applied to most steroids that bear low reacting hydroxyls. A new technique allowing the ether coupling of biologically active steroids with conjugating arms in mild conditions compatible with thermosensitive protecting groups is presented. In the first step, the solvent (an aromatic hydrocarbon) was dehydrated by azeotropic distillation in a soxhlet apparatus using a cartridge filled with 0.3 nm and 0.4 nm molecular sieves. In this protected medium, a thallium steroid alkoxide was completely formed by reaction of the steroid with thallium ethoxide and by the continuous elimination of ethanol. The halogenated chain was then introduced into the same medium and reacted in the absence of moisture to give the ether. 17beta-Hydroxy and 11alpha-hydroxy derivatives were involved in this reaction. The coupling was effective for all of the compounds tested after 2-36 h of reaction time and at temperatures between 80 and 140 degrees C. The conjugates were at least 95% pure, and yields ranged from 15 to 95%.

  19. Radioiodinated iodobenzoyl conjugates of a monoclonal antibody Fab fragment. In vivo comparisons with chloramine-T-labeled Fab

    International Nuclear Information System (INIS)

    Wilbur, D.S.; Hadley, S.W.; Grant, L.M.; Hylarides, M.D.

    1991-01-01

    A comparative investigation of the biodistributions of radioiodinated p- and m-iodobenzoyl conjugates of a monoclonal antibody Fab fragment, NR-LU-10 Fab, and the same antibody Fab fragment radioiodinated by the chloramine-T (ChT) method has been carried out in mice. Coinjected, dual-isotope studies in athymic mice with tumor xenografts have demonstrated that there are only minor differences in the in vivo distributions of the iodobenzoyl-labeled Fabs, except in the excretory organs, kidneys, and intestines, where major differences were observed. Similarly, coinjection of either the p-iodobenzoyl or m-iodobenzoyl conjugate of NR-LU-10 Fab with the Fab radioiodinated with ChT/radioiodide into BALB/c mice provided additional data that indicated that the two iodobenzoyl conjugates distributed similar in a number of selected tissues. The tissue-distribution differences of the regioisomeric iodobenzoyl conjugates in relation to the ChT-radioiodinated Fab were large for the stomach and neck, consistent with previous studies. The most notable difference between the two iodobenzoyl conjugates was the kidney activity, where the m-iodobenzoyl conjugate was similar to the directly labeled Fab, but the p-iodobenzoyl-conjugated Fab was higher by nearly a factor of 2

  20. 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.

  1. 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.

  2. Carbonyl-Olefin Exchange Reaction: Present State and Outlook

    Science.gov (United States)

    Kalinova, Radostina; Jossifov, Christo

    The carbonyl-olefin exchange reaction (COER) is a new reaction between carbonyl group and olefin double bond, which has a formal similarity with the olefin metathesis (OM) - one carbon atom in the latter is replaced with an oxygen atom. Till now the new reaction is performed successfully only when the two functional groups (carbonyl group and olefin double bond) are in one molecule and are conjugated. The α, β-unsaturated carbonyl compounds (substituted propenones) are the compounds with such a structure. They polymerize giving substituted polyacetylenes. The chain propagation step of this polymerization is in fact the COER. The question arises: is it possible the COER to take place when the two functional groups are not in one molecule and are not conjugated, and could this reaction became an alternative of the existing carbonyl olefination reactions?

  3. 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.

  4. 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

  5. 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 (ΔE R ) 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 ΔE R 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

  6. 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

  7. Surface conjugation of poly (dimethyl siloxane) with itaconic acid-based materials for antibacterial effects

    Science.gov (United States)

    Birajdar, Mallinath S.; Cho, Hyunjoo; Seo, Youngmin; Choi, Jonghoon; Park, Hansoo

    2018-04-01

    Poly (dimethyl siloxane) (PDMS) is widely used in various biomedical applications. However, the PDMS surface is known to cause bacterial adhesion and protein absorption issues due to its high hydrophobicity. Therefore, the development of antibacterial and anti-protein products is necessary to prevent these problems. In this study, to improve its antibacterial property and prevent protein adsorption, PDMS surfaces were conjugated with itaconic acid (IA) and poly (itaconic acid) (PIA) via a chemical method. Additionally, IA and PIA were physically blended with PDMS to compare the antibacterial properties of these materials with those of the chemically conjugated PDMS surfaces. The successful synthesis of the PIA polymer structure was confirmed by proton nuclear magnetic resonance (1H NMR) spectroscopy. The successful conjugation of IA and PIA on PDMS was confirmed by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), water contact angle measurements, and microbicinchoninic acid (BCA) protein assay analyses. The PDMS surfaces functionalized with IA and PIA by the conjugation method better prevented protein adsorption than the bare PDMS. Therefore, these surface-conjugated PDMS can be used in various biomedical applications.

  8. Ibuprofen-conjugated hyaluronate/polygalacturonic acid hydrogel for the prevention of epidural fibrosis.

    Science.gov (United States)

    Lin, Cheng-Yi; Peng, Hsiu-Hui; Chen, Mei-Hsiu; Sun, Jui-Sheng; Chang, Chih-Ju; Liu, Tse-Ying; Chen, Ming-Hong

    2016-05-01

    The formation of fibrous tissue is part of the natural healing response following a laminectomy. Severe scar tissue adhesion, known as epidural fibrosis, is a common cause of failed back surgery syndrome. In this study, by combining the advantages of drug treatment with a physical barrier, an ibuprofen-conjugated crosslinkable polygalacturonic acid and hyaluronic acid hydrogel was developed for epidural fibrosis prevention. Conjugation was confirmed and measured by 1D(1)H NMR spectroscopy.In vitroanalysis showed that the ibuprofen-conjugated polygalacturonic acid-hyaluronic acid hydrogel showed low cytotoxicity. In addition, the conjugated ibuprofen decreased prostaglandin E2production of the lipopolysaccharide-induced RAW264.7 cells. Histological data inin vivostudies indicated that the scar tissue adhesion of laminectomized male adult rats was reduced by the application of our ibuprofen-conjugated polygalacturonic acid-hyaluronic acid hydrogel. Its use also reduced the population of giant cells and collagen deposition of scar tissue without inducing extensive cell recruitment. The results of this study therefore suggest that the local delivery of ibuprofenviaa polygalacturonic acid-hyaluronic acid-based hydrogel reduces the possibility of epidural fibrosis. © The Author(s) 2016.

  9. 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.

  10. Poly(ethylene glycol-Prodrug Conjugates: Concept, Design, and Applications

    Directory of Open Access Journals (Sweden)

    Shashwat S. Banerjee

    2012-01-01

    Full Text Available Poly(ethylene glycol (PEG is the most widely used polymer in delivering anticancer drugs clinically. PEGylation (i.e., the covalent attachment of PEG of peptides proteins, drugs, and bioactives is known to enhance the aqueous solubility of hydrophobic drugs, prolong circulation time, minimize nonspecific uptake, and achieve specific tumor targetability through the enhanced permeability and retention effect. Numerous PEG-based therapeutics have been developed, and several have received market approval. A vast amount of clinical experience has been gained which has helped to design PEG prodrug conjugates with improved therapeutic efficacy and reduced systemic toxicity. However, more efforts in designing PEG-based prodrug conjugates are anticipated. In light of this, the current paper highlights the synthetic advances in PEG prodrug conjugation methodologies with varied bioactive components of clinical relevance. In addition, this paper discusses FDA-approved PEGylated delivery systems, their intended clinical applications, and formulations under clinical trials.

  11. The studies on the preparation of hapten conjugates for extension of the applicability of radioligandassay

    International Nuclear Information System (INIS)

    Kim, J.

    1979-01-01

    The stability of T 4 - 125 I has been secured by addition of a small amount of cysteine in the T 4 - 125 I solution. Various methods for the preparation of thyroid hormone-BSA conjugates were reviewed and an efficient preparation method as well as a qualitative and quantitative analysis procedures for the conjugates has been established. The results of analysis of the prepared hapten conjugates indicated that the mole ratios of BSA: T 3 (acid form) and BSA: T 4 (ethyl ester form) are 1:12 and 1:10, respectively, and the binding % of T 3 (acid form) and T 4 (ethyl ester form) to BSA molecule are 25% and 20%, respectively. (author)

  12. 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.

  13. Superoxide dismutase and catalase conjugated to polyethylene glycol increases endothelial enzyme activity and oxidant resistance

    International Nuclear Information System (INIS)

    Beckman, J.S.; Minor, R.L. Jr.; White, C.W.; Repine, J.E.; Rosen, G.M.; Freeman, B.A.

    1988-01-01

    Covalent conjugation of superoxide dismutase and catalase with polyethylene glycol (PEG) increases the circulatory half-lives of these enzymes from 125 I-PEG-catalase or 125 I-PEG-superoxide dismutase produced a linear, concentration-dependent increase in cellular enzyme activity and radioactivity. Fluorescently labeled PEG-superoxide dismutase incubated with endothelial cells showed a vesicular localization. Mechanical injury to cell monolayers, which is known to stimulate endocytosis, further increased the uptake of fluorescent PEG-superoxide dismutase. Addition of PEG and PEG-conjugated enzymes perturbed the spin-label binding environment, indicative of producing an increase in plasma membrane fluidity. Thus, PEG conjugation to superoxide dismutase and catalase enhances cell association of these enzymes in a manner which increases cellular enzyme activities and provides prolonged protection from partially reduced oxygen species

  14. Plasmid transfer by conjugation in Xylella fastidiosa.

    Science.gov (United States)

    Recombination and horizontal gene transfer have been implicated in the adaption of Xylella fastidiosa (Xf) to infect a wide variety of different plant species. There is evidence that certain strains of Xf carry native plasmids equipped with transfer and mobilization genes, suggesting conjugation as ...

  15. Theory of periodic conjugate heat transfer

    CERN Document Server

    Zudin, Yuri B

    2016-01-01

    This book presents the theory of periodic conjugate heat transfer in detail. It offers a simplified description of the interaction between a solid body and a fluid as a boundary value problem of the heat conduction equation for the solid body.

  16. Conjugate Problems in Convective Heat Transfer: Review

    Directory of Open Access Journals (Sweden)

    Abram Dorfman

    2009-01-01

    Full Text Available A review of conjugate convective heat transfer problems solved during the early and current time of development of this modern approach is presented. The discussion is based on analytical solutions of selected typical relatively simple conjugate problems including steady-state and transient processes, thermal material treatment, and heat and mass transfer in drying. This brief survey is accompanied by the list of almost two hundred publications considering application of different more and less complex analytical and numerical conjugate models for simulating technology processes and industrial devices from aerospace systems to food production. The references are combined in the groups of works studying similar problems so that each of the groups corresponds to one of selected analytical solutions considered in detail. Such structure of review gives the reader the understanding of early and current situation in conjugate convective heat transfer modeling and makes possible to use the information presented as an introduction to this area on the one hand, and to find more complicated publications of interest on the other hand.

  17. Stochastic differential equations used to model conjugation

    DEFF Research Database (Denmark)

    Philipsen, Kirsten Riber; Christiansen, Lasse Engbo

    Stochastic differential equations (SDEs) are used to model horizontal transfer of antibiotic resis- tance by conjugation. The model describes the concentration of donor, recipient, transconjugants and substrate. The strength of the SDE model over the traditional ODE models is that the noise can...

  18. Immunogenicity of novel sulfadimethoxide conjugates | Chen ...

    African Journals Online (AJOL)

    Immunogenicity of novel sulfadimethoxide conjugates. L Chen, J Su, X Zhang, L Li, X He. Abstract. Sulfadimethoxine (SDM) is an antibiotic commonly added to animal feeds. Anti-SDM antibodies are useful for the detection of residual SDM in foods, feeds and biological fluids by ELISA. In this study, we show that SDM is ...

  19. Women experiencing the intergenerationality of conjugal violence

    Directory of Open Access Journals (Sweden)

    Gilvânia Patrícia do Nascimento Paixão

    2015-10-01

    Full Text Available 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 violence between their parents; they suffered repercussions from the violence between their parents: they were angry about the mother's submission to her partner; and they reproduced the conjugal violence. The discourse showed that the women witnessed, in childhood and adolescence, violence between their parents, and were injured both physically and psychologically. As a result of the mother's submission, feelings of anger arose in the children. However, in the adult phase of their own lives, they noticed that their conjugal life resembled that of their parents, reproducing the violence.Conclusion: investment is necessary in strategies designed to break inter-generational violence, and the health professionals are important in this process, as it is a phenomenon with repercussions in health. Because they work in the Family Health Strategy, which focuses on the prevention of harm and illness, health promotion and interdepartmentality, the nurses are essential in the process of preventing and confronting this phenomenon.

  20. Integrated circuits based on conjugated polymer monolayer.

    Science.gov (United States)

    Li, Mengmeng; Mangalore, Deepthi Kamath; Zhao, Jingbo; Carpenter, Joshua H; Yan, Hongping; Ade, Harald; Yan, He; Müllen, Klaus; Blom, Paul W M; Pisula, Wojciech; de Leeuw, Dago M; Asadi, Kamal

    2018-01-31

    It is still a great challenge to fabricate conjugated polymer monolayer field-effect transistors (PoM-FETs) due to intricate crystallization and film formation of conjugated polymers. Here we demonstrate PoM-FETs based on a single monolayer of a conjugated polymer. The resulting PoM-FETs are highly reproducible and exhibit charge carrier mobilities reaching 3 cm 2  V -1  s -1 . The high performance is attributed to the strong interactions of the polymer chains present already in solution leading to pronounced edge-on packing and well-defined microstructure in the monolayer. The high reproducibility enables the integration of discrete unipolar PoM-FETs into inverters and ring oscillators. Real logic functionality has been demonstrated by constructing a 15-bit code generator in which hundreds of self-assembled PoM-FETs are addressed simultaneously. Our results provide the state-of-the-art example of integrated circuits based on a conjugated polymer monolayer, opening prospective pathways for bottom-up organic electronics.

  1. Conjugate problems in convective heat transfer

    CERN Document Server

    Dorfman, Abram S

    2009-01-01

    The conjugate heat transfer (CHT) problem takes into account the thermal interaction between a body and fluid flowing over or through it, a key consideration in both mechanical and aerospace engineering. Presenting more than 100 solutions of non-isothermal and CHT problems, this title considers the approximate solutions of CHT problems.

  2. Compositions for directed alignment of conjugated polymers

    Science.gov (United States)

    Kim, Jinsang; Kim, Bong-Gi; Jeong, Eun Jeong

    2016-04-19

    Conjugated polymers (CPs) achieve directed alignment along an applied flow field and a dichroic ratio of as high as 16.67 in emission from well-aligned thin films and fully realized anisotropic optoelectronic properties of CPs in field-effect transistor (FET).

  3. Conjugate Gradient Algorithms For Manipulator Simulation

    Science.gov (United States)

    Fijany, Amir; Scheid, Robert E.

    1991-01-01

    Report discusses applicability of conjugate-gradient algorithms to computation of forward dynamics of robotic manipulators. Rapid computation of forward dynamics essential to teleoperation and other advanced robotic applications. Part of continuing effort to find algorithms meeting requirements for increased computational efficiency and speed. Method used for iterative solution of systems of linear equations.

  4. Conjugated Polymer Actuators: Prospects and Limitations

    DEFF Research Database (Denmark)

    Skaarup, Steen

    2007-01-01

    Actuators constructed with a conjugated polymer as the active part have been predicted to have a number of highly desirable properties: Large mechanical strength, high power density, i.e. high actuation speeds possible, sufficient maximum strain values, high reversibility and safe, low voltages (1...

  5. Some aspects of geomagnetically conjugate phenomena

    Energy Technology Data Exchange (ETDEWEB)

    Rycroft, M.J.

    1987-12-01

    Both charged particles and waves convey information about the thermosphere, ionosphere and magnetosphere from the Northern to the Southern Hemisphere and vice versa, along geomagnetic flux tubes.The interhemispheric travel time of electrons or ions, being dependent upon L-value , pitch angle and energy (which may lie between less than or equal to 1 eV and greater than or equal to 1 MeV) may be many hours, ranging down to less than or equal to 1 s. However, the one-hop propagation time for magnetohydrodynamic or whistler mode waves generally lies between 10/sup 2/s and 1 s. Such times, therefore, give the time scales of transient phenomena that are geomagnetically conjugate and of changes in steady-state plasma processes occurring in geomagnetically conjugate regions. Contrasting examples are presented of conjugate physical phenomena, obtained using satellite, rocket, aircraft and ground-based observations; the latter capitalise upon the rather rare disposition of land - rather than ocean - at each end of a geophysically interesting flux tube. Particular attention is paid to the interactions between whistler mode waves and energetic electrons. Geomagnetic, radio, optical and plasma observations, taken together with model computations, provide a wealth of knowledge on conjugate phenomena and their dependence on conditions in the solar wind, substorms, L-value, etc... Finally, some suggestions are made for future lines of research.

  6. Numerical Modeling of Conjugate Heat Transfer in Fluid Network

    Science.gov (United States)

    Majumdar, Alok

    2004-01-01

    Fluid network modeling with conjugate heat transfer has many applications in Aerospace engineering. In modeling unsteady flow with heat transfer, it is important to know the variation of wall temperature in time and space to calculate heat transfer between solid to fluid. Since wall temperature is a function of flow, a coupled analysis of temperature of solid and fluid is necessary. In cryogenic applications, modeling of conjugate heat transfer is of great importance to correctly predict boil-off rate in propellant tanks and chill down of transfer lines. In TFAWS 2003, the present author delivered a paper to describe a general-purpose computer program, GFSSP (Generalized Fluid System Simulation Program). GFSSP calculates flow distribution in complex flow circuit for compressible/incompressible, with or without heat transfer or phase change in all real fluids or mixtures. The flow circuit constitutes of fluid nodes and branches. The mass, energy and specie conservation equations are solved at the nodes where as momentum conservation equations are solved at the branches. The proposed paper describes the extension of GFSSP to model conjugate heat transfer. The network also includes solid nodes and conductors in addition to fluid nodes and branches. The energy conservation equations for solid nodes solves to determine the temperatures of the solid nodes simultaneously with all conservation equations governing fluid flow. The numerical scheme accounts for conduction, convection and radiation heat transfer. The paper will also describe the applications of the code to predict chill down of cryogenic transfer line and boil-off rate of cryogenic propellant storage tank.

  7. 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.

  8. Cross-Conjugated n-Dopable Aromatic Polyketone

    NARCIS (Netherlands)

    Voortman, Thomas P.; Bartesaghi, Davide; Koster, L. Jan Anton; Chiechi, Ryan C.

    2015-01-01

    This paper describes the synthesis and characterization of a high molecular weight cross-conjugated polyketone synthesized via scalable Friedel Crafts chemistry. Cross-conjugated polyketones are precursors to conjugated polyions; they become orders of magnitude more conductive after a two-electron

  9. Bis-polymer lipid-peptide conjugates and nanoparticles thereof

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Ting; Dong, He; Shu, Jessica; Dube, Nikhil

    2018-04-24

    The present invention provides bis-polymer lipid-peptide conjugates containing a hydrophobic block and headgroup containing a helical peptide and two polymer blocks. The conjugates can self-assemble to form helix bundle subunits, which in turn assemble to provide micellar nanocarriers for drug cargos and other agents. Particles containing the conjugates and methods for forming the particles are also disclosed.

  10. 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.

  11. Thiolated polymers--thiomers: development and in vitro evaluation of chitosan-thioglycolic acid conjugates.

    Science.gov (United States)

    Kast, C E; Bernkop-Schnürch, A

    2001-09-01

    The aim of this study was to improve mucoadhesive properties of chitosan by the covalent attachment of thiol moieties to this cationic polymer. Mediated by a carbodiimide, thioglycolic acid (TGA) was covalently attached to chitosan. This was achieved by the formation of amide bonds between the primary amino groups of the polymer and the carboxylic acid group of TGA. Dependent on the pH-value and the weight ratio of polymer to TGA during the coupling reaction the resulting thiolated polymers, the so-called thiomers, displayed 6.58, 9.88, 27.44, and 38.23 micromole thiol groups per gram polymer. Tensile studies carried out with these chitosan-TGA conjugates on freshly excised porcine intestinal mucosa demonstrated a 6.3-, 8.6-, 8.9-, and 10.3-fold increase in the total work of adhesion (TWA) compared to the unmodified polymer, respectively. In contrast, the combination of chitosan and free unconjugated TGA showed almost no mucoadhesion. These data were in good correlation with further results obtained by another mucoadhesion test demonstrating a prolonged residence time of thiolated chitosan on porcine mucosa. The swelling behavior of all conjugates was thereby exactly in the same range as for an unmodified polymer pretreated in the same way. Furthermore, it could be shown that chitosan-TGA conjugates are still biodegradable by the glycosidase lysozyme. According to these results. chitosan-TGA conjugates represent a promising tool for the development of mucoadhesive drug delivery systems.

  12. Mechanistic studies on the conjugation of methyl isocyanate with N-Acetyl-Cysteine in rats

    International Nuclear Information System (INIS)

    Hu, P.; Davis, M.R.; Baillie, T.A.

    1996-01-01

    In order to investigate the utility of selected thiols as scavengers of MIC, we first assessed the chemical stability of SMG, AMCC and SMC by measuring their rates of reaction in vitro with thiorphan. The initial rates of carbamoylation of thiorpan (0.5 mM) by the above conjugates (0.5 mM) in aqeous buffer at pH 7.4 and 37 deg C were 2.51, 0.76 and 8.47 μmol L -1 min -1 , repectively, indicating that the mercapturate AMCC was the most stable of the three MIC conjugates. In light of these results, studies were conducted to examine the effect of pretreatment with N-acetyl-L-cysteine (L-NAC; 500 mg kg -1 , i.p.) on the urinary elimination of AMCC in rats dosed with MIC (15 mg kg -1 , i.p.). In separate experiments, groups of rats were pretreated with either N-acetyl-D-cysteine (D-NAC) or N-trideuteroacetyl-L-cysteine (d 3 -L-NAC) in order to explore the mechanism by which MIC undergoes conjugation to AMCC in vivo. The results indicated that exogenous NAC effectively enhancess the urinary excretion of MIC in the form of AMCC, and that it does so lagerly by direct conjugation with the isocyanate, rather than via biosynthesis to GSH. (author). 9 refs., 5 figs

  13. Molecular basis of sperm capacitation acrosome reaction and interaction with eggs

    International Nuclear Information System (INIS)

    Sheikhnejad, G.

    1985-01-01

    A phospholipase C (PLC) which can hydrolyze 14 C-phosphatidylcholine was purified from bull seminal plasma. This PLC has an optimum at pH 7.2 and its PI was about 5.0. The enzyme was inhibited by EDTA, Cd 2+ , Pb 2+ , Ni 2+ , Fe 2+ , and Zn 2+ . PLC consists of two subunits one 69,000 and the other 55,000 daltons. The purified PLC was examined for induction of capacitation and acrosome reaction of guinea pig spermatozoa. Sperm were examined for the acrosome reaction 10 min after addition of 3.4 mM Ca 2+ . Fifty percent of the sperm underwent the acrosome reaction while the control had less than 5% acrosome reacted sperm. The antiserum to the inneracrosomal membrane isolated from sperm was labeled with FITC conjugated goat anti-guinea pig IgG. The conjugated antibody was used to localize sperm antigens. The antigens located on the IAM were only fluoresced when rabbit sperm were treated with methanol and/or MgCl 2 . Therefore anti-IAM antibody did not bind to the sperm plasma membrane. In vivo capacitated rabbit sperm were incubated with anti-IAM antibody (intact IgG and F(ab') 2 fragments) for 30 min prior to addition of rabbit eggs. After 24 h the eggs were examined for cleavage. The control eggs were fertilized (90%) while the antibody completely inhibited the fertilization of ova in vitro. The eggs incubated with antibody prior to the addition of sperm were still fertilizable. Thus, anti-IAM did not have any noticeable effect on the eggs. It was also shown that antibody inhibited fertilization of zona-free rabbit eggs in vitro as well

  14. Quasielastic reactions

    International Nuclear Information System (INIS)

    Henning, W.

    1979-01-01

    Quasielastic reaction studies, because of their capability to microscopically probe nuclear structure, are still of considerable interest in heavy-ion reactions. The recent progress in understanding various aspects of the reaction mechanism make this aim appear closer. The relation between microscopic and macroscopic behavior, as suggested, for example, by the single proton transfer data to individual final states or averaged excitation energy intervals, needs to be explored. It seems particularly useful to extend measurements to higher incident energies, to explore and understand nuclear structure aspects up to the limit of the energy range where they are important

  15. Incorporating functionalized polyethylene glycol lipids into reprecipitated conjugated polymer nanoparticles for bioconjugation and targeted labeling of cells

    Science.gov (United States)

    Kandel, Prakash K.; Fernando, Lawrence P.; Ackroyd, P. Christine; Christensen, Kenneth A.

    2011-03-01

    ) lipids by reprecipitation. These nanoparticles retain the fundamental spectroscopic properties of conjugated polymer nanoparticles prepared without PEG lipid, but demonstrate greater hydrophilicity and quantum yield compared to unmodified conjugated polymer nanoparticles. The sizes of these nanoparticles, as determined by TEM, were 21-26 nm. Notably, these nanoparticles were prepared with several PEG lipid functional end groups, including biotin and carboxy moieties that can be easily conjugated to biomolecules. We have demonstrated the availability of these end groups for functionalization using the interaction of biotin PEG lipid conjugated polymer nanoparticles with streptavidin. Biotinylated PEG lipid conjugated polymer nanoparticles bound streptavidin-linked magnetic beads, while carboxy and methoxy PEG lipid modified nanoparticles did not. Similarly, biotinylated PEG lipid conjugated polymer nanoparticles bound streptavidin-coated glass slides and could be visualized as diffraction-limited spots, while nanoparticles without PEG lipid or with non-biotin PEG lipid end groups were not bound. To demonstrate that nanoparticle functionalization could be used for targeted labelling of specific cellular proteins, biotinylated PEG lipid conjugated polymer nanoparticles were bound to biotinylated anti-CD16/32 antibodies on J774A.1 cell surface receptors, using streptavidin as a linker. This work represents the first demonstration of targeted delivery of conjugated polymer nanoparticles and demonstrates the utility of these new nanoparticles for fluorescence based imaging and sensing. Electronic supplementary information (ESI) available: Additional TEM data, supplemental light scattering measurements, absorbance and fluorescence emission spectra, and photostability measurements. See DOI: 10.1039/c0nr00746c

  16. Improved Conjugate Gradient Bundle Adjustment of Dunhuang Wall Painting Images

    Science.gov (United States)

    Hu, K.; Huang, X.; You, H.

    2017-09-01

    Bundle adjustment with additional parameters is identified as a critical step for precise orthoimage generation and 3D reconstruction of Dunhuang wall paintings. Due to the introduction of self-calibration parameters and quasi-planar constraints, the structure of coefficient matrix of the reduced normal equation is banded-bordered, making the solving process of bundle adjustment complex. In this paper, Conjugate Gradient Bundle Adjustment (CGBA) method is deduced by calculus of variations. A preconditioning method based on improved incomplete Cholesky factorization is adopt to reduce the condition number of coefficient matrix, as well as to accelerate the iteration rate of CGBA. Both theoretical analysis and experimental results comparison with conventional method indicate that, the proposed method can effectively conquer the ill-conditioned problem of normal equation and improve the calculation efficiency of bundle adjustment with additional parameters considerably, while maintaining the actual accuracy.

  17. IMPROVED CONJUGATE GRADIENT BUNDLE ADJUSTMENT OF DUNHUANG WALL PAINTING IMAGES

    Directory of Open Access Journals (Sweden)

    K. Hu

    2017-09-01

    Full Text Available Bundle adjustment with additional parameters is identified as a critical step for precise orthoimage generation and 3D reconstruction of Dunhuang wall paintings. Due to the introduction of self-calibration parameters and quasi-planar constraints, the structure of coefficient matrix of the reduced normal equation is banded-bordered, making the solving process of bundle adjustment complex. In this paper, Conjugate Gradient Bundle Adjustment (CGBA method is deduced by calculus of variations. A preconditioning method based on improved incomplete Cholesky factorization is adopt to reduce the condition number of coefficient matrix, as well as to accelerate the iteration rate of CGBA. Both theoretical analysis and experimental results comparison with conventional method indicate that, the proposed method can effectively conquer the ill-conditioned problem of normal equation and improve the calculation efficiency of bundle adjustment with additional parameters considerably, while maintaining the actual accuracy.

  18. EXPERIENCE OF APPLICATION AND SAFETY ASSESSMENT OF THE 13-VALENT PNEUMOCOCCAL CONJUGATE VACCINE IN UNDER-5 CHILDREN

    Directory of Open Access Journals (Sweden)

    M. V. Fedoseenko

    2014-01-01

    Full Text Available Compulsory use of the 7-valent pneumococcal conjugate vaccine in the framework of national pediatric immunization schedules of the developed countries resulted in significant decrease in the prevalence of the pneumococcal infections induced by the vaccinal serotypes. However, a growth in prevalence of the pneumonia and acute otitis media caused by non-vaccinal strains has also been observed. This required introduction of a new 13-valent pneumococcal conjugate vaccine with a wider range of pneumococcal population coverage. The experience of application accumulated in various countries (2010 onwards and results of the authors’ observations indicate high safety of the 13-valent pneumococcal conjugate vaccine for both healthy under-5 children and patients with various medical issues. The article presents results of the 13-valent pneumococcal conjugate vaccination tolerance assessment. The study involved 110 children from 2 months to 5 years of age. In most cases immunization concurred with other pediatric vaccines. The incidence of local reactions in vaccinated children did not exceed 33%, of generalized reactions – 11%. The authors observed a comparable incidence of side reactions in both virtually healthy children and children with various medical issues.

  19. Inhibition of HeLa cell growth by doxorubicin-loaded and tuftsin-conjugated arginate-PEG microparticles

    Directory of Open Access Journals (Sweden)

    Tianmu Hu

    2018-03-01

    Full Text Available In order to improve the release pattern of chemotherapy drug and reduce the possibility of drug resistance, poly(ethylene glycol amine (PEG-modified alginate microparticles (ALG-PEG MPs were developed then two different mechanisms were employed to load doxorubicin (Dox: 1 forming Dox/ALG-PEG complex by electrostatic attractions between unsaturated functional groups in Dox and ALG-PEG; 2 forming Dox-ALG-PEG complex through EDC-reaction between the amino and carboxyl groups in Dox and ALG, respectively. Additionally, tuftsin (TFT, a natural immunomodulation peptide, was conjugated to MPs in order to enhance the efficiency of cellular uptake. It was found that the Dox-ALG-PEG-TFT MPs exhibited a significantly slower release of Dox than Dox/ALG-PEG-TFT MPs in neutral medium, suggesting the role of covalent bonding in prolonging Dox retention. Besides, the release of Dox from these MPs was pH-sensitive, and the release rate was observably increased at pH 6.5 compared to the case at pH 7.4. Compared with Dox/ALG-PEG MPs and Dox-ALG-PEG MPs, their counterparts further conjugated with TFT more efficiently inhibited the growth of HeLa cells over a period of 48 h, implying the effectiveness of TFT in enhancing cellular uptake of MPs. Over a period of 48 h, Dox-ALG-PEG-TFT MPs inhibited the growth of HeLa cells less efficiently than Dox/ALG-PEG-TFT MPs but the difference was not significant (p > 0.05. In consideration of the prolonged and sustained release of Dox, Dox-ALG-PEG-TFT MPs possess the advantages for long-term treatment.

  20. cycloaddition reactions

    Indian Academy of Sciences (India)

    Unknown

    Molecular Modeling Group, Organic Chemical Sciences, Indian Institute of Chemical Technology,. Hyderabad ... thus obtained are helpful to model the regioselectivity ... compromise to model Diels–Alder reactions involving ...... acceptance.

  1. Outer membrane protein complex of Meningococcus enhances the antipolysaccharide antibody response to pneumococcal polysaccharide-CRM₁₉₇ conjugate vaccine.

    Science.gov (United States)

    Lai, Zengzu; Schreiber, John R

    2011-05-01

    Bacterial polysaccharides (PS) are T cell-independent antigens that do not induce immunologic memory and are poor immunogens in infants. Conjugate vaccines in which the PS is covalently linked to a carrier protein have enhanced immunogenicity that resembles that of T cell-dependent antigens. The Haemophilus influenzae type b (Hib) conjugate vaccine, which uses the outer membrane protein complex (OMPC) from meningococcus as a carrier protein, elicits protective levels of anti-capsular PS antibody (Ab) after a single dose, in contrast to other conjugate vaccines, which require multiple doses. We have previously shown that OMPC robustly engages Toll-like receptor 2 (TLR2) and enhances the early anti-Hib PS Ab titer associated with an increase in TLR2-mediated induction of cytokines. We now show that the addition of OMPC to the 7-valent pneumococcal PS-CRM₁₉₇ conjugate vaccine during immunization significantly increases the anti-PS IgG and IgM responses to most serotypes of pneumococcus contained in the vaccine. The addition of OMPC also increased the likelihood of anti-PS IgG3 production against serotypes 4, 6B, 9V, 18C, 19F, and 23F. Splenocytes from mice who had received OMPC with the pneumococcal conjugate vaccine produced significantly more interleukin-2 (IL-2), IL-4, IL-6, IL-10, tumor necrosis factor alpha (TNF-α), and gamma interferon (IFN-γ) than splenocytes from mice who received phosphate-buffered saline (PBS) plus the conjugate vaccine. We conclude that OMPC enhances the anti-PS Ab response to pneumococcal PS-CRM₁₉₇ conjugate vaccine, an effect associated with a distinct change in cytokine profile. It may be possible to reduce the number of conjugate vaccine doses required to achieve protective Ab levels by priming with adjuvants that are TLR2 ligands.

  2. Conjugate Compressible Fluid Flow and Heat Transfer in Ducts

    Science.gov (United States)

    Cross, M. F.

    2011-01-01

    A computational approach to modeling transient, compressible fluid flow with heat transfer in long, narrow ducts is presented. The primary application of the model is for analyzing fluid flow and heat transfer in solid propellant rocket motor nozzle joints during motor start-up, but the approach is relevant to a wide range of analyses involving rapid pressurization and filling of ducts. Fluid flow is modeled through solution of the spatially one-dimensional, transient Euler equations. Source terms are included in the governing equations to account for the effects of wall friction and heat transfer. The equation solver is fully-implicit, thus providing greater flexibility than an explicit solver. This approach allows for resolution of pressure wave effects on the flow as well as for fast calculation of the steady-state solution when a quasi-steady approach is sufficient. Solution of the one-dimensional Euler equations with source terms significantly reduces computational run times compared to general purpose computational fluid dynamics packages solving the Navier-Stokes equations with resolved boundary layers. In addition, conjugate heat transfer is more readily implemented using the approach described in this paper than with most general purpose computational fluid dynamics packages. The compressible flow code has been integrated with a transient heat transfer solver to analyze heat transfer between the fluid and surrounding structure. Conjugate fluid flow and heat transfer solutions are presented. The author is unaware of any previous work available in the open literature which uses the same approach described in this paper.

  3. Dielectrophoresis of gold nanoparticles conjugated to DNA origami structures

    Directory of Open Access Journals (Sweden)

    Anja Henning-Knechtel

    2016-07-01

    Full Text Available DNA nanostructures are promising construction materials to bridge the gap between self-assembly of functional molecules and conventional top-down fabrication methods in nanotechnology. Their positioning onto specific locations of a microstructured substrate is an important task towards this aim. Here we study manipulation and positioning of pristine and of gold nanoparticle-conjugated tubular DNA origami structures using ac dielectrophoresis. The dielectrophoretic behavior was investigated employing fluorescence microscopy. For the pristine origami, a significant dielectrophoretic response was found to take place in the megahertz range, whereas, due to the higher polarizability of the metallic nanoparticles, the nanoparticle/DNA hybrid structures required a lower electrical field strength and frequency for a comparable trapping at the edges of the electrode structure. The nanoparticle conjugation additionally resulted in a remarkable alteration of the DNA structure arrangement. The growth of linear, chain-like structures in between electrodes at applied frequencies in the megahertz range was observed. The long-range chain formation is caused by a local, gold nanoparticle-induced field concentration along the DNA nanostructures, which in turn, creates dielectrophoretic forces that enable the observed self-alignment of the hybrid structures.

  4. Fluorescent nanodiamond-bacteriophage conjugates maintain host specificity.

    Science.gov (United States)

    Trinh, Jimmy T; Alkahtani, Masfer H; Rampersaud, Isaac; Rampersaud, Arfaan; Scully, Marlan; Young, Ryland F; Hemmer, Philip; Zeng, Lanying

    2018-06-01

    Rapid identification of specific bacterial strains within clinical, environmental, and food samples can facilitate the prevention and treatment of disease. Fluorescent nanodiamonds (FNDs) are being developed as biomarkers in biology and medicine, due to their excellent imaging properties, ability to accept surface modifications, and lack of toxicity. Bacteriophages, the viruses of bacteria, can have exquisite specificity for certain hosts. We propose to exploit the properties of FNDs and phages to develop phages conjugated with FNDs as long-lived fluorescent diagnostic reagents. In this study, we develop a simple procedure to create such fluorescent probes by functionalizing the FNDs and phages with streptavidin and biotin, respectively. We find that the FND-phage conjugates retain the favorable characteristics of the individual components and can discern their proper host within a mixture. This technology may be further explored using different phage/bacteria systems, different FND color centers and alternate chemical labeling schemes for additional means of bacterial identification and new single-cell/virus studies. © 2018 Wiley Periodicals, Inc.

  5. Formation of Conjugated Double Bonds to Induce Polystyrene Conductivity by using Different Concentrations of Methoxo-Oxo Bis (8-Quinolyloxo Vanadium (V

    Directory of Open Access Journals (Sweden)

    Basim Mohamad Hasan

    2017-02-01

    Full Text Available The effect of different concentrations of additive compound methoxo–oxo bis (8-quinolyloxo vanadium (v on formation of conjugated double bonds as part of photo transformation of polystyrene has been investigated. The UV-Vis spectrophotometery has been used in this work. The results are show that additive concentrations applied increase the formation of conjugated double bond as compared with polystyrene. In this study methoxo – oxo bis (8-quinolyloxo vanadium (v indicates great activity to enhance the conductivity of polystyrene by formation of conjugated double bonds.

  6. Application of optical phase conjugation to plasma diagnostics (invited)

    International Nuclear Information System (INIS)

    Jahoda, F.C.; Anderson, B.T.; Forman, P.R.; Weber, P.G.

    1985-01-01

    Several possibilities for plasma diagnostics provided by optical phase conjugation and, in particular, self-pumped phase conjugation in barium titanate (BaTiO 3 ) are discussed. These include placing a plasma within a dye laser cavity equipped with a phase conjugate mirror for intracavity absorption measurements, time differential refractometry with high spatial resolution, and simplified real-time holographic interferometry. The principles of phase conjugation with particular reference to photorefractive media and the special advantages of self-pumped phase conjugation are reviewed prior to the discussion of the applications. Distinctions are made in the applications between those for which photorefractive conjugators are essential and those for which they only offer experimental simplification relative to other types of phase conjugators

  7. Implications of the Maillard reaction on bovine alpha-lactalbumin and its proteolysis during in vitro infant digestion.

    Science.gov (United States)

    Joubran, Yousef; Moscovici, Alice; Portmann, Reto; Lesmes, Uri

    2017-06-21

    This study investigated the functionality and digestibility of Maillard reaction products (MRPs) of alpha-lactalbumin (α-la), a major whey protein and component of infant formulas. The impact of different carbohydrates (glucose, galactose or galacto-oligosaccharides (GOS)) and heating duration was studied. SDS-PAGE, UV and color measurements monitored reaction extent, which varied between carbohydrates whereby galactose reacted more readily than glucose. Surface hydrophobicity and antioxidant capacity were found to be significantly (p Maillard conjugation, with GOS-based MRPs elevating antioxidant capacity ∼50-fold compared to α-la. In addition, the digestive proteolysis of MRPs was evaluated using an infant in vitro gastro-duodenal model. SDS-PAGE analyses of digesta revealed Maillard conjugation generally increased α-la's susceptibility to proteolysis. Interestingly, GOS-based MRPs presented an optimization challenge, since heating for 12 h delayed proteolysis, while extended heating resulted in the highest susceptibility to proteolysis. Proteomic analyses further demonstrated the differences in enzymatic cleavage patterns and helped identify bioactive peptides rendered bioaccessible during the digestion of α-la or its MRPs. Bioinformatic mining of the proteomic data using PeptideRanker also gave rise to two potentially novel bioactive peptides, FQINNKIW and GINYWLAHKALCS. Finally, antioxidant capacity of luminal contents, measured by DPPH, revealed Maillard conjugation increased the antioxidant capacity of both gastric and duodenal digesta. Overall, this work draws a link between the Maillard reaction, digestive proteolysis and the bioaccessibility of bioactive peptides and antioxidant species in the infant alimentary canal. This could help rationally process infant formulas towards improved nutritional and extra-nutritional benefits.

  8. A simple protocol for the michael addition of indoles with electron ...

    Indian Academy of Sciences (India)

    Administrator

    attracted much attention in organic synthesis be- cause of their biological activities. 2,3. The conjugate addition ... mations, like selective oxidation of benzyl alcohols,. 17 have been ..... The colour change was assessed visually and the highest ...

  9. Structure-processing-property correlations in thin films of conjugated polymer nanocomposites and blends

    Science.gov (United States)

    Sreeram, Arvind

    Conjugated polymers have found several applications in recent years, in energy conversion and storage devices such as organic light emitting diodes, solar cells, batteries, and super capacitors. Thin films of polymers used for these applications need to be mechanically and thermally stable to withstand the harsh operating conditions. Although there is significant information on the optoelectronic properties of many of these polymers, there are only few studies on their mechanical properties. There is little information in the literature on how processing of these films influence mechanical properties. In the first part of this study, poly(p-phenylene vinylene) (PPV) films were prepared by thermolytic conversion of poly[p -phenylene (tetrahydrothiophenium)ethylene chloride] precursor films, at different temperatures and the kinetics of reaction was investigated using thermogravimetry and Fourier transform infrared (FTIR) spectroscopy. The mechanical properties of the films, studied using nanoindentation, showed a dependence on the extent of conversion and chemical composition of the films. The presence of chemical defects (e.g., carbonyl groups, detected using FTIR spectroscopy), was also found to have a noticeable effect on the modulus and hardness of the films. The storage modulus, E', and plasticity decreased with an increase in conversion, whereas the loss modulus, E", showed the opposite trend. Both the precursor and the fully-converted PPV films were found to have significantly lower E" than E', consistent with the glassy nature of the polymers at room temperature. In the second part of the study, polyacetylene films were synthesized by acid-catalyzed dehydration reaction of poly(vinyl alcohol) (PVA) precursor films. The kinetics of this reaction was monitored by thermogravimetry. The chemical structure of the conjugated polymer films was characterized by Raman and IR spectroscopy. Polyacetylene films incorporated with 1-propyl-3-methylimidazolium ionic liquid

  10. NIR photoregulated chemo- and photodynamic cancer therapy based on conjugated polyelectrolyte-drug conjugate encapsulated upconversion nanoparticles

    Science.gov (United States)

    Yuan, Youyong; Min, Yuanzeng; Hu, Qinglian; Xing, Bengang; Liu, Bin

    2014-09-01

    The design of nanoplatforms with target recognition and near-infrared (NIR) laser photoregulated chemo- and photodynamic therapy is highly desirable but remains challenging. In this work, we have developed such a system by taking advantage of a conjugated polyelectrolyte (CPE)-drug conjugate and upconversion nanoparticles (UCNPs). The poly(ethylene glycol) (PEG) grafted CPE not only serves as a polymer matrix for UCNP encapsulation, but also as a fluorescent imaging agent, a photosensitizer as well as a carrier for chemotherapeutic drug doxorubicin (DOX) through a UV-cleavable ortho-nitrobenzyl (NB) linker. Upon 980 nm laser irradiation, the UCNPs emit UV and visible light. The up-converted UV light is utilized for controlled drug release through the photocleavage of the ortho-nitrobenzyl linker, while the up-converted visible light is used to initiate the polymer photosensitizer to produce reactive oxygen species (ROS) for photodynamic therapy. The NIR photo-regulated UCNP@CPE-DOX showed high efficiency of ROS generation and controlled drug release in cancer cells upon single laser irradiation. In addition, the combination therapy showed enhanced inhibition of U87-MG cell growth as compared to sole treatments. As two light sources with different wavelengths are always needed for traditional photodynamic therapy and photoregulated drug release, the adoption of UCNPs as an NIR light switch is highly beneficial to combined chemo- and photodynamic therapy with enhanced therapeutic effects.

  11. Heavy ion transfer reactions

    International Nuclear Information System (INIS)

    Weisser, D.C.

    1977-06-01

    To complement discussions on the role of γ rays in heavy ion induced reactions, the author discusses the role played by particle detection. Transfer reactions are part of this subject and are among those in which one infers the properties of the residual nucleus in a reaction by observing the emerging light nucleus. Inelastic scattering ought not be excluded from this subject, although no particles are transferred, because of the role it plays in multistep reactions and in fixing O.M. parameters describing the entrance channel of the reaction. Heavy ion transfer reaction studies have been under study for some years and yet this research is still in its infancy. The experimental techniques are difficult and the demands on theory rigorous. One of the main products of heavy ion research has been the thrust to re-examine the assumptions of reaction theory and now include many effects neglected for light ion analysis. This research has spurred the addition of multistep processes to simple direct processes and coupled channel calculations. (J.R.)

  12. Context Dependent Effects of Chimeric Peptide Morpholino Conjugates Contribute to Dystrophin Exon-skipping Efficiency.

    Science.gov (United States)

    Yin, Haifang; Boisguerin, Prisca; Moulton, Hong M; Betts, Corinne; Seow, Yiqi; Boutilier, Jordan; Wang, Qingsong; Walsh, Anthony; Lebleu, Bernard; Wood, Matthew Ja

    2013-09-24

    We have recently reported that cell-penetrating peptides (CPPs) and novel chimeric peptides containing CPP (referred as B peptide) and muscle-targeting peptide (referred as MSP) motifs significantly improve the systemic exon-skipping activity of morpholino phosphorodiamidate oligomers (PMOs) in dystrophin-deficient mdx mice. In the present study, the general mechanistic significance of the chimeric peptide configuration on the activity and tissue uptake of peptide conjugated PMOs in vivo was investigated. Four additional chimeric peptide-PMO conjugates including newly identified peptide 9 (B-9-PMO and 9-B-PMO) and control peptide 3 (B-3-PMO and 3-B-PMO) were tested in mdx mice. Immunohistochemical staining, RT-PCR and western blot results indicated that B-9-PMO induced significantly higher level of exon skipping and dystrophin restoration than its counterpart (9-B-PMO), further corroborating the notion that the activity of chimeric peptide-PMO conjugates is dependent on relative position of the tissue-targeting peptide motif within the chimeric peptide with respect to PMOs. Subsequent mechanistic studies showed that enhanced cellular uptake of B-MSP-PMO into muscle cells leads to increased exon-skipping activity in comparison with MSP-B-PMO. Surprisingly, further evidence showed that the uptake of chimeric peptide-PMO conjugates of both orientations (B-MSP-PMO and MSP-B-PMO) was ATP- and temperature-dependent and also partially mediated by heparan sulfate proteoglycans (HSPG), indicating that endocytosis is likely the main uptake pathway for both chimeric peptide-PMO conjugates. Collectively, our data demonstrate that peptide orientation in chimeric peptides is an important parameter that determines cellular uptake and activity when conjugated directly to oligonucleotides. These observations provide insight into the design of improved cell targeting compounds for future therapeutics studies.Molecular Therapy-Nucleic Acids (2013) 2, e124; doi:10.1038/mtna.2013

  13. Context Dependent Effects of Chimeric Peptide Morpholino Conjugates Contribute to Dystrophin Exon-skipping Efficiency

    Directory of Open Access Journals (Sweden)

    HaiFang Yin

    2013-01-01

    Full Text Available We have recently reported that cell-penetrating peptides (CPPs and novel chimeric peptides containing CPP (referred as B peptide and muscle-targeting peptide (referred as MSP motifs significantly improve the systemic exon-skipping activity of morpholino phosphorodiamidate oligomers (PMOs in dystrophin-deficient mdx mice. In the present study, the general mechanistic significance of the chimeric peptide configuration on the activity and tissue uptake of peptide conjugated PMOs in vivo was investigated. Four additional chimeric peptide-PMO conjugates including newly identified peptide 9 (B-9-PMO and 9-B-PMO and control peptide 3 (B-3-PMO and 3-B-PMO were tested in mdx mice. Immunohistochemical staining, RT-PCR and western blot results indicated that B-9-PMO induced significantly higher level of exon skipping and dystrophin restoration than its counterpart (9-B-PMO, further corroborating the notion that the activity of chimeric peptide-PMO conjugates is dependent on relative position of the tissue-targeting peptide motif within the chimeric peptide with respect to PMOs. Subsequent mechanistic studies showed that enhanced cellular uptake of B-MSP-PMO into muscle cells leads to increased exon-skipping activity in comparison with MSP-B-PMO. Surprisingly, further evidence showed that the uptake of chimeric peptide-PMO conjugates of both orientations (B-MSP-PMO and MSP-B-PMO was ATP- and temperature-dependent and also partially mediated by heparan sulfate proteoglycans (HSPG, indicating that endocytosis is likely the main uptake pathway for both chimeric peptide-PMO conjugates. Collectively, our data demonstrate that peptide orientation in chimeric peptides is an important parameter that determines cellular uptake and activity when conjugated directly to oligonucleotides. These observations provide insight into the design of improved cell targeting compounds for future therapeutics studies.

  14. pH-responsive polymer–drug conjugates as multifunctional micelles for cancer-drug delivery

    International Nuclear Information System (INIS)

    Kang, Yang; Ha, Wei; Ma, Yuan; Ding, Li-Sheng; Li, Bang-Jing; Liu, Ying-Qian; Fan, Min-Min; Zhang, Sheng

    2014-01-01

    We developed a novel linear pH-sensitive conjugate methoxy poly(ethylene glycol)-4β-aminopodophyllotoxin (mPEG-NPOD-I) by a covalently linked 4β-aminopodophyllotoxin (NPOD) and PEG via imine bond, which was amphiphilic and self-assembled to micelles in an aqueous solution. The mPEG-NPOD-I micelles simultaneously served as an anticancer drug conjugate and as drug carriers. As a drug conjugate, mPEG-NPOD-I showed a significantly faster NPOD release at a mildly acidic pH of 5.0 and 4.0 than a physiological pH of 7.4. Notably, it was confirmed that this drug conjugate could efficiently deliver NPOD to the nuclei of the tumor cells and led to much more cytotoxic effects to A549, Hela, and HepG2 cancer cells than the parent NPOD. The half maximal inhibitory concentration (IC 50 ) of mPEG-NPOD-I was about one order magnitude lower than that of the NPOD. In vivo, mPEG-NPOD-I reduced the size of the tumors significantly, and the biodistribution studies indicated that this drug conjugate could selectively accumulate in tumor tissues. As drug carriers, the mPEG-NPOD-I micelles encapsulated hydrophobic PTX with drug-loading efficiencies of 57% and drug-loading content of 16%. The loaded PTX also showed pH-triggered fast release behavior, and good additive cytotoxicity effect was observed for the PEG-NPOD-I/PTX. We are convinced that these multifunctional drug conjugate micelles have tremendous potential for targeted cancer therapy. (paper)

  15. Elucidation of the Structure Formation of Polymer-Conjugated Proteins in Solution and Block Copolymer Templates

    Science.gov (United States)

    Ferebee, Rachel L.

    The broader technical objective of this work is to contribute to the development of enzyme-functionalized nanoporous membranes that can function as autonomous and target selective dynamic separators. The scientific objective of the research performed within this thesis is to elucidate the parameters that control the mixing of proteins in organic host materials and in block copolymers templates in particular. A "biomimetic" membrane system that uses enzymes to selectively neutralize targets and trigger a change in permeability of nanopores lined with a pH-responsive polymer has been fabricated and characterized. Mechanical and functional stability, as well as scalability, have been demonstrated for this system. Additional research has focused on the role of polymeric ligands on the solubility characteristics of the model protein, Bovine Serum Albumin (BSA). For this purpose BSA was conjugated with poly(ethylene glycol) (PEG) ligands of varied degree of polymerization and grafting density. Combined static and dynamic light scattering was used (in conjunction with MALDI-TOF) to determine the second virial coefficient in PBS solutions. At a given mass fraction PEG or average number of grafts, the solubility of BSA-PEG conjugates is found to increase with the degree of polymerization of conjugated PEG. This result informs the synthesis of protein-conjugate systems that are optimized for the fabrication of block copolymer blend materials with maximum protein loading. Blends of BSA-PEG conjugates and block copolymer (BCP) matrices were fabricated to evaluate the dispersion morphology and solubility limits in a model system. Electron microscopy was used to evaluate the changes in lamellar spacing with increased filling fraction of BSA-PEG conjugates.

  16. Direct Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Austern, N. [University of Pittsburgh, Pittsburgh, PA (United States)

    1963-01-15

    In order to give a unified presentation of one point of view, these lectures are devoted only to a detailed development of the standard theories of direct reactions, starting from basic principles. Discussion is given of the present status of the theories, of the techniques used for practical calculation, and of possible future developments. The direct interaction (DI) aspects of a reaction are those which involve only a few of the many degrees of freedom of a nucleus. In fact the minimum number of degrees of freedom which must be involved in a reaction are those required to describe the initial and final channels, and DI studies typically consider these degrees of freedom and no others. Because of this simplicity DI theories may be worked out in painstaking detail. DI processes concern only part of the wave function for a problem. The other part involves complicated excitations of many degrees of freedom, and gives the compound nucleus (CN) effects. While it is extremely interesting to learn how to separate DI and CN effects in an orderly manner, if they are both present in a reaction, no suitable method has yet been found. Instead, current work stresses the kinds of reactions and the kinds of final states in which DI effects dominate and in which CN effects may almost be forgotten. The DI cross-sections which are studied are often extremely large, comparable to elastic scattering cross-sections. (author)

  17. Thiolated polymers: synthesis and in vitro evaluation of polymer-cysteamine conjugates.

    Science.gov (United States)

    Bernkop-Schnürch, A; Clausen, A E; Hnatyszyn, M

    2001-09-11

    The purpose of the present study was to synthesize and characterize novel thiolated polymers. Mediated by a carbodiimide cysteamine was covalently linked to sodium carboxymethylcellulose (CMC) and polycarbophil (PCP). The resulting CMC-cysteamine conjugates displayed 77.9+/-6.7 and 365.1+/-8.7 micromol thiol groups per gram of polymer, whereas the PCP-cysteamine conjugates showed 26.3+/-1.9 and 122.7+/-3.8 micromol thiol groups per gram of polymer (mean+/-S.D.; n=3). In aqueous solutions above pH 5.0 both modified polymers were capable of forming inter- and/or intra-molecular disulfide bonds. The reaction velocity of this oxidation process was accelerated with a decrease in the proton concentration. The oxidation proceeded more rapidly within thiolated CMC than within thiolated PCP. Permeation studies carried out in Ussing-type chambers with freshly excised intestinal mucosa from guinea pigs utilizing sodium fluorescein as model drug for the paracellular uptake revealed an enhancement ratio (R=P(app) (conjugate)/P(app) (control)) of 1.15 and 1.41 (mean+/-S.D.; n=3) for the higher thiolated CMC-cysteamine (0.5%; m/v) and PCP-cysteamine conjugate (1.0%; m/v), respectively. The decrease in the transepithelial electrical resistance values was in good correlation with the enhancement ratios. Due to a high crosslinking tendency by the formation of disulfide bonds stabilizing drug carrier systems based on thiolated polymers and a permeation enhancing effect, CMC- and PCP-cysteamine conjugates represent promising excipients for the development of novel drug delivery systems.

  18. Elucidation of the Biotransformation Pathways of a Galnac3-conjugated Antisense Oligonucleotide in Rats and Monkeys

    Directory of Open Access Journals (Sweden)

    Colby S Shemesh

    2016-01-01

    Full Text Available Triantennary N-acetyl galactosamine (GalNAc3 is a high-affinity ligand for hepatocyte-specific asialoglycoprotein receptors. Conjugation with GalNAc3 via a trishexylamino (THA-C6 cluster significantly enhances antisense oligonucleotide (ASO potency. Herein, the biotransformation, disposition, and elimination of the THA cluster of ION-681257, a GalNAc3-conjugated ASO currently in clinical development, are investigated in rats and monkey. Rats were administered a single subcutaneous dose of 3H-radiolabeled (3H placed in THA or nonradiolabeled ION-681257. Mass balance included radiometric profiling and metabolite fractionation with characterization by mass spectrometry. GalNAc3-conjugated ASOs were extensively distributed into liver. The THA-C6 triantenerrary GalNAc3 conjugate at the 5′-end of the ASO was rapidly metabolized and excreted with 25.67 ± 1.635% and 71.66 ± 4.17% of radioactivity recovered in urine and feces within 48 hours postdose. Unchanged drug, short-mer ASOs, and linker metabolites were detected in urine. Collectively, 14 novel linker associated metabolites were discovered including oxidation at each branching arm, initially by monooxidation at the β-position followed by dioxidation at the α-arm, and lastly, tri and tetra oxidations on the two remaining β-arms. Metabolites in bile and feces were identical to urine except for oxidized linear and cyclic linker metabolites. Enzymatic reaction phenotyping confirmed involvement of N-acetyl-β-glucosaminidase, deoxyribonuclease II, alkaline phosphatase, and alcohol + aldehyde dehydrogenases on the complex metabolism pathway for THA supplementing in vivo findings. Lastly, excreta from monkeys treated with ION-681257 revealed the identical series as observed in rat. In summary, our findings provide an improved understanding of GalNAc3-conjugated-ASO metabolism pathways which facilitate similar development programs.

  19. Sequential charged particle reaction

    International Nuclear Information System (INIS)

    Hori, Jun-ichi; Ochiai, Kentaro; Sato, Satoshi; Yamauchi, Michinori; Nishitani, Takeo

    2004-01-01

    The effective cross sections for producing the sequential reaction products in F82H, pure vanadium and LiF with respect to the 14.9-MeV neutron were obtained and compared with the estimation ones. Since the sequential reactions depend on the secondary charged particles behavior, the effective cross sections are corresponding to the target nuclei and the material composition. The effective cross sections were also estimated by using the EAF-libraries and compared with the experimental ones. There were large discrepancies between estimated and experimental values. Additionally, we showed the contribution of the sequential reaction on the induced activity and dose rate in the boundary region with water. From the present study, it has been clarified that the sequential reactions are of great importance to evaluate the dose rates around the surface of cooling pipe and the activated corrosion products. (author)

  20. Stochastic Spectral and Conjugate Descent Methods

    KAUST Repository

    Kovalev, Dmitry

    2018-02-11

    The state-of-the-art methods for solving optimization problems in big dimensions are variants of randomized coordinate descent (RCD). In this paper we introduce a fundamentally new type of acceleration strategy for RCD based on the augmentation of the set of coordinate directions by a few spectral or conjugate directions. As we increase the number of extra directions to be sampled from, the rate of the method improves, and interpolates between the linear rate of RCD and a linear rate independent of the condition number. We develop and analyze also inexact variants of these methods where the spectral and conjugate directions are allowed to be approximate only. We motivate the above development by proving several negative results which highlight the limitations of RCD with importance sampling.