General protein-protein cross-linking.

PubMed

Alegria-Schaffer, Alice

2014-01-01

This protocol describes a general protein-to-protein cross-linking procedure using the water-soluble amine-reactive homobifunctional BS(3) (bis[sulfosuccinimidyl] suberate); however, the protocol can be easily adapted using other cross-linkers of similar properties. BS(3) is composed of two sulfo-NHS ester groups and an 11.4 Å linker. Sulfo-NHS ester groups react with primary amines in slightly alkaline conditions (pH 7.2-8.5) and yield stable amide bonds. The reaction releases N-hydroxysuccinimide (see an application of NHS esters on Labeling a protein with fluorophores using NHS ester derivitization). © 2014 Elsevier Inc. All rights reserved.

Heterobimetallic lanthanide/sodium phenoxides: efficient catalysts for amidation of aldehydes with amines.

PubMed

Li, Junmei; Xu, Fan; Zhang, Yong; Shen, Qi

2009-03-20

Heterobimetallic lanthanide/sodium phenoxides were found to be efficient catalysts for amidation of aldehydes with amines under mild conditions. The reactivity follows the order Nd < Y < Sm for metals and 2,6-(Me)2C6H3O < 2,6-(iPr)2C6H3O < 2,6-(tBu)2C6H3O for phenoxide groups. In comparison with the corresponding monometallic complexes, heterobimetallic complexes show higher activity and a wider range of scope of amines. A cooperation of lanthanide and sodium in this process is proposed to contribute to the high activity of the present catalyst.

Pyridoxylamine reactivity kinetics as an amine based nucleophile for screening electrophilic dermal sensitizers

PubMed Central

Chipinda, Itai; Mbiya, Wilbes; Adigun, Risikat Ajibola; Morakinyo, Moshood K.; Law, Brandon F.; Simoyi, Reuben H.; Siegel, Paul D.

2015-01-01

Chemical allergens bind directly, or after metabolic or abiotic activation, to endogenous proteins to become allergenic. Assessment of this initial binding has been suggested as a target for development of assays to screen chemicals for their allergenic potential. Recently we reported a nitrobenzenethiol (NBT) based method for screening thiol reactive skin sensitizers, however, amine selective sensitizers are not detected by this assay. In the present study we describe an amine (pyridoxylamine (PDA)) based kinetic assay to complement the NBT assay for identification of amine-selective and non-selective skin sensitizers. UV-Vis spectrophotometry and fluorescence were used to measure PDA reactivity for 57 chemicals including anhydrides, aldehydes, and quinones where reaction rates ranged from 116 to 6.2 × 10−6 M−1 s−1 for extreme to weak sensitizers, respectively. No reactivity towards PDA was observed with the thiol-selective sensitizers, non-sensitizers and prohaptens. The PDA rate constants correlated significantly with their respective murine local lymph node assay (LLNA) threshold EC3 values (R2 = 0.76). The use of PDA serves as a simple, inexpensive amine based method that shows promise as a preliminary screening tool for electrophilic, amine-selective skin sensitizers. PMID:24333919

Ionic liquids as silica deactivating agents in gas chromatography for direct analysis of primary amines in water.

PubMed

Krzyżaniak, Agnieszka; Weggemans, Wilko; Schuur, Boelo; de Haan, André B

2011-12-16

Analysis of primary amines in aqueous samples remains a challenging analytical issue. The preferred approach by gas chromatography is hampered by interactions of free silanol groups with the highly reactive amine groups, resulting in inconsistent measurements. Here, we report a method for direct analysis of aliphatic amines and diamines in aqueous samples by gas chromatography (GC) with silanol deactivation using ionic liquids (ILs). ILs including trihexyl(tetradecyl)phosphonium bis 2,4,4-(trimethylpentyl)phosphinate (Cyphos IL-104), 1-methyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide [pmim][Tf(2)N] and N″-ethyl-N,N,N',N'-tetramethylguanidinium tris(pentafluoroethyl)trifluorophosphate [etmg][FAP] were tested as deactivating media for the GC liner. Solutions of these ILs in methanol were injected in the system prior to the analysis of primary amines. Butane-1,4-diamine (putrescine, BDA) was used as a reference amine. The best results were obtained using the imidazolium IL [pmim][Tf(2)N]. With this deactivator, excellent reproducibility of the analysis was achieved, and the detection limit of BDA was as low as 1mM. The applicability of the method was proven for the analysis of two different primary amines (C4-C5) and pentane-1,5-diamine. Copyright © 2011 Elsevier B.V. All rights reserved.

Michael Addition Polymerization of Trifunctional Amine and Acrylic Monomer: A Versatile Platform for Development of Biomaterials.

PubMed

Cheng, Weiren; Wu, Decheng; Liu, Ye

2016-10-10

Michael addition polymerizations of amines and acrylic monomers are versatile approaches to biomaterials for various applications. A combinatorial library of poly(β-amino ester)s and diverse poly(amido amine)s from diamines and diacrylates or bis(acrylamide)s have been reported, respectively. Furthermore, novel linear and hyperbranched polymers from Michael addition polymerizations of trifunctional amines and acrylic monomers significantly enrich this category of biomaterials. In this Review, we focus on the biomaterials from Michael addition polymerizations of trifunctional amines and acrylic monomers. First we discuss how the polymerization mechanisms, which are determined by the reactivity sequence of the three types of amines of trifunctional amines, i.e., secondary (2°) amines (original), primary (1°) amines, and 2° amines (formed), are affected by the chemistry of monomers, reaction temperature, and solvent. Then we update how to design and synthesize linear and hyperbranched polymers based on the understanding of polymerization mechanisms. Linear polymers containing 2° amines in the backbones can be obtained from polymerizations of diacrylates or bis(acrylamide)s with equimolar trifunctional amine, and several approaches, e.g., 2A 2 +BB'B″, A 3 +2BB'B', A 2 +BB'B″, to hyperbranched polymers are developed. Further through molecular design of monomers, conjugation of functional species to 2° amines in the backbones of linear polymers and the abundant terminal groups of hyperbranched polymers, the amphiphilicity of polymers can be adjusted, and additional stimuli, e.g., thermal, redox, reactive oxidation species (ROS), and light, responses can be integrated with the intrinsic pH response. Finally we discuss the applications of the polymers for gene/drug delivery and bioimaging through exploring their self-assemblies in various motifs, e.g., micelles, polyplexes particles/nanorings and hydrogels. Redox-responsive hyperbranched polymers can display 300 times higher in vitro gene transfection efficiency and provide a higher in vivo siRNA efficacy than PEI. Also redox-responsive micelle carriers can improve the efficacy of anticancer drug and the bioimaging contrast. Further molecular design and optimization of this category of polymers together with in vivo studies should provide safe and efficient biomaterials for clinical applications.

Reactivity of amine antioxidants relative to OH and anti e

DOE Office of Scientific and Technical Information (OSTI.GOV)

Minkhadzhidinova, D.R.; Nikiforov, G.A.; Khrapova, N.G.

1986-06-20

An ESR study was carried out on the reactivity of various types of amines relative to OH/sup ./ and anti e. The selection of these compounds having anti-oxidant properties was also based on the circumstance that amine molecules contain a set of functional groups which may be potential sites for the attack of both OH and anti e radicals. A sample of 6 M H/sub 3/PO/sub 4/ was used for the matrix solutions and forms a glass upon rapid insertion into liquid nitrogen. The phosphoric acid solutions of these compounds taken in concentrations from 0.025 to 0.05 M were flushedmore » with argon to remove oxygen. Ampules containing the solutions were inserted into liquid nitrogen and irradiated from a cobalt source. The ESR spectra of the irradiated solutions clearly show the components of the atomic hydrogen doublet with a = 50 mT and of H/sub 2/PO/sub 4//sup ./ radicals in the central region of the spectrum.« less

Probing the Compound I-like reactivity of a bare high-valent oxo iron porphyrin complex: the oxidation of tertiary amines.

PubMed

Chiavarino, Barbara; Cipollini, Romano; Crestoni, Maria Elisa; Fornarini, Simonetta; Lanucara, Francesco; Lapi, Andrea

2008-03-12

The mechanisms of oxidative N-dealkylation of amines by heme enzymes including peroxidases and cytochromes P450 and by functional models for the active Compound I species have long been studied. A debated issue has concerned in particular the character of the primary step initiating the oxidation sequence, either a hydrogen atom transfer (HAT) or an electron transfer (ET) event, facing problems such as the possible contribution of multiple oxidants and complex environmental effects. In the present study, an oxo iron(IV) porphyrin radical cation intermediate 1, [(TPFPP)*+ Fe(IV)=O]+ (TPFPP = meso-tetrakis (pentafluorophenyl)porphinato dianion), functional model of Compound I, has been produced as a bare species. The gas-phase reaction with amines (A) studied by ESI-FT-ICR mass spectrometry has revealed for the first time the elementary steps and the ionic intermediates involved in the oxidative activation. Ionic products are formed involving ET (A*+, the amine radical cation), formal hydride transfer (HT) from the amine ([A(-H)]+, an iminium ion), and oxygen atom transfer (OAT) to the amine (A(O), likely a carbinolamine product), whereas an ionic product involving a net initial HAT event is never observed. The reaction appears to be initiated by an ET event for the majority of the tested amines which included tertiary aliphatic and aromatic amines as well as a cyclic and a secondary amine. For a series of N,N-dimethylanilines the reaction efficiency for the ET activated pathways was found to correlate with the ionization energy of the amine. A stepwise pathway accounts for the C-H bond activation resulting in the formal HT product, namely a primary ET process forming A*+, which is deprotonated at the alpha-C-H bond forming an N-methyl-N-arylaminomethyl radical, A(-H)*, readily oxidized to the iminium ion, [A(-H)]+. The kinetic isotope effect (KIE) for proton transfer (PT) increases as the acidity of the amine radical cation increases and the PT reaction to the base, the ferryl group of (TPFPP)Fe(IV)=O, approaches thermoneutrality. The ET reaction displayed by 1 with gaseous N,N-dimethylaniline finds a counterpart in the ET reactivity of FeO+, reportedly a potent oxidant in the gas phase, and with the barrierless ET process for a model (P)*+ Fe(IV)=O species (where P is the porphine dianion) as found by theoretical calculations. Finally, the remarkable OAT reactivity of 1 with C6F5N(CH3)2 may hint to a mechanism along a route of diverse spin multiplicity.

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

PubMed

Beatty, Joel W; Stephenson, Corey R J

2015-05-19

While the use of visible light to drive chemical reactivity is of high importance to the development of environmentally benign chemical transformations, the concomitant use of a stoichiometric electron donor or acceptor is often required to steer the desired redox behavior of these systems. The low-cost and ubiquity of tertiary amine bases has led to their widespread use as reductive additives in photoredox catalysis. Early use of trialkylamines in this context was focused on their role as reductive excited state quenchers of the photocatalyst, which in turn provides a more highly reducing catalytic intermediate. In this Account, we discuss some of the observations and thought processes that have led from our use of amines as reductive additives to their use as complex substrates and intermediates for natural product synthesis. Early attempts by our group to construct key carbon-carbon bonds via free-radical intermediates led to the observation that some trialkylamines readily behave as efficient hydrogen atom donors under redox-active photochemical conditions. In the wake of in-depth mechanistic studies published in the 1970s, 1980s and 1990s, this understanding has in turn allowed for a systematic approach to the design of a number of photochemical methodologies through rational tuning of the amine component. Minimization of the C-H donicity of the amine additive was found to promote desired C-C bond formation in a number of contexts, and subsequent elucidation of the amine's redox fate has sparked a reevaluation of the amine's role from that of reagent to that of substrate. The reactivity of tertiary amines in these photochemical systems is complex, and allows for a number of mechanistic possibilities that are not necessarily mutually exclusive. A variety of combinations of single-electron oxidation, C-H abstraction, deprotonation, and β-scission result in the formation of reactive intermediates such as α-amino radicals and iminium ions. These processes have been explored in depth in the photochemical literature and have resulted in a firm mechanistic grasp of the behavior of amine radical cations in fundamental systems. Harnessing the synthetic potential of these transient species represents an ongoing challenge for the controlled functionalization of amine substrates, because these mechanistic possibilities may result in undesired byproduct formation or substrate decomposition. The presence of tertiary amines in numerous alkaloids, pharmaceuticals, and agrochemicals lends credence to the potential utility of this chemistry in natural product synthesis, and herein we will discuss how these transformations might be controlled for synthetic purposes.

Spectroscopic Studies of the Chan-Lam Amination: A Mechanism-Inspired Solution to Boronic Ester Reactivity.

PubMed

Vantourout, Julien C; Miras, Haralampos N; Isidro-Llobet, Albert; Sproules, Stephen; Watson, Allan J B

2017-04-05

We report an investigation of the Chan-Lam amination reaction. A combination of spectroscopy, computational modeling, and crystallography has identified the structures of key intermediates and allowed a complete mechanistic description to be presented, including off-cycle inhibitory processes, the source of amine and organoboron reactivity issues, and the origin of competing oxidation/protodeboronation side reactions. Identification of key mechanistic events has allowed the development of a simple solution to these issues: manipulating Cu(I) → Cu(II) oxidation and exploiting three synergistic roles of boric acid has allowed the development of a general catalytic Chan-Lam amination, overcoming long-standing and unsolved amine and organoboron limitations of this valuable transformation.

Kinetics of the reactions of the acid anhydrides with aromatic amines in aprotic solvents. M.S. Thesis. Final Report

NASA Technical Reports Server (NTRS)

Sugg, E.; Mason, J. G.

1983-01-01

Work has revealed that diamine derivatives of diphenylmethane (IV), diphenyl ether (V), benzophenone (IV), fluorene (VII), and fluorenone (VIII) polymerizations with pyromellitic dianhydride in DMA were dependent on the basicity of the amine compound. The correlation between the basicity of the amine and its reactivity with phthalic anhydride was determined. Basicity measurements were made by potentiometric titration of each amine in an acetonitrile-water solvent system, from which the pKa of the amine could be determined. Reactivity was defined in terms of the second order rate constant derived form spectrophotometric examination of the reaction between each amine and phthalic anhydride in DMA. This reaction was expected to proceed in either one (for a monoamine) or two (for a diamine) stages.

Formation rates, stability and reactivity of sulfuric acid - amine clusters predicted by computational chemistry

NASA Astrophysics Data System (ADS)

Kurtén, Theo; Ortega, Ismael; Kupiainen, Oona; Olenius, Tinja; Loukonen, Ville; Reiman, Heidi; McGrath, Matthew; Vehkamäki, Hanna

2013-04-01

Despite the importance of atmospheric particle formation for both climate and air quality, both experiments and non-empirical models using e.g. sulfuric acid, ammonia and water as condensing vapors have so far been unable to reproduce atmospheric observations using realistic trace gas concentrations. Recent experimental and theoretical evidence has shown that this mystery is likely resolved by amines. Combining first-principles evaporation rates for sulfuric acid - dimethylamine clusters with cluster kinetic modeling, we show that even sub-ppt concentrations of amines, together with atmospherically realistic concentrations of sulfuric acid, result in formation rates close to those observed in the atmosphere. Our simulated cluster formation rates are also close to, though somewhat larger than, those measured at the CLOUD experiment in CERN for both sulfuric acid - ammonia and sulfuric acid - dimethylamine systems. A sensitivity analysis indicates that the remaining discrepancy for the sulfuric acid - amine particle formation rates is likely caused by steric hindrances to cluster formation (due to alkyl groups of the amine molecules) rather than by significant errors in the evaporation rates. First-principles molecular dynamic and reaction kinetic modeling shed further light on the microscopic physics and chemistry of sulfuric acid - amine clusters. For example, while the number and type of hydrogen bonds in the clusters typically reach their equilibrium values on a picosecond timescale, and the overall bonding patterns predicted by traditional "static" quantum chemical calculations seem to be stable, the individual atoms participating in the hydrogen bonds continuously change at atmospherically realistic temperatures. From a chemical reactivity perspective, we have also discovered a surprising phenomenon: clustering with sulfuric acid molecules slightly increases the activation energy required for the abstraction of alkyl hydrogens from amine molecules. This implies that the oxidation rate of amines by OH and possibly other oxidants may be decreased by clustering, thus prolonging the chemical lifetime of amines in the air.

Phase I and phase II reductive metabolism simulation of nitro aromatic xenobiotics with electrochemistry coupled with high resolution mass spectrometry.

PubMed

Bussy, Ugo; Chung-Davidson, Yu-Wen; Li, Ke; Li, Weiming

2014-11-01

Electrochemistry combined with (liquid chromatography) high resolution mass spectrometry was used to simulate the general reductive metabolism of three biologically important nitro aromatic molecules: 3-trifluoromethyl-4-nitrophenol (TFM), niclosamide, and nilutamide. TFM is a pesticide used in the Laurential Great Lakes while niclosamide and nilutamide are used in cancer therapy. At first, a flow-through electrochemical cell was directly connected to a high resolution mass spectrometer to evaluate the ability of electrochemistry to produce the main reduction metabolites of nitro aromatic, nitroso, hydroxylamine, and amine functional groups. Electrochemical experiments were then carried out at a constant potential of -2.5 V before analysis of the reduction products by LC-HRMS, which confirmed the presence of the nitroso, hydroxylamine, and amine species as well as dimers. Dimer identification illustrates the reactivity of the nitroso species with amine and hydroxylamine species. To investigate xenobiotic metabolism, the reactivity of nitroso species to biomolecules was also examined. Binding of the nitroso metabolite to glutathione was demonstrated by the observation of adducts by LC-ESI(+)-HRMS and the characteristics of their MSMS fragmentation. In conclusion, electrochemistry produces the main reductive metabolites of nitro aromatics and supports the observation of nitroso reactivity through dimer or glutathione adduct formation.

The direct reductive amination of electron-deficient amines with aldehydes: the unique reactivity of the Re2O7 catalyst.

PubMed

Das, Braja Gopal; Ghorai, Prasanta

2012-08-25

An unprecedented direct reductive amination of electron-deficient amines such as Cbz-, Boc-, EtOCO-, Fmoc-, Bz-, ArSO(2)-, Ar(2)PO-, etc. protected amines with aldehydes is achieved using the Re(2)O(7) catalyst and silanes as the hydride source. Excellent regioselective mono-alkylation and chemoselective reductive-amination were observed.

Palladium-catalyzed one-pot three- or four-component coupling of aryl iodides, alkynes, and amines through C-N bond cleavage: efficient synthesis of indole derivatives.

PubMed

Hao, Wei; Geng, Weizhi; Zhang, Wen-Xiong; Xi, Zhenfeng

2014-02-24

An efficient synthesis of N-substituted indole derivatives was realized by combining the Pd-catalyzed one-pot multicomponent coupling approach with cleavage of the C(sp(3))-N bonds. Three or four components of aryl iodides, alkynes, and amines were involved in this coupling process. The cyclopentadiene-phosphine ligand showed high efficiency. A variety of aryl iodides, including cyclic and acyclic tertiary amino aryl iodides, and substituted 1-bromo-2-iodobenzene derivatives could be used. Both symmetric and unsymmetric alkynes substituted with alkyl, aryl, or trimethylsilyl groups could be applied. Cyclic secondary amines such as piperidine, morpholine, 4-methylpiperidine, 1-methylpiperazine, 2-methylpiperidine, and acyclic amines including secondary and primary amines all showed good reactivity. Further application of the resulting indole derivatives was demonstrated by the synthesis of benzosilolo[2,3-b]indole. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Degradation and ecotoxicity of dye Reactive Black 5 after reductive-oxidative process : Environmental Science and Pollution Research.

PubMed

Cuervo Lumbaque, Elisabeth; Gomes, Monike Felipe; Da Silva Carvalho, Vanessa; de Freitas, Adriane Martins; Tiburtius, Elaine Regina Lopes

2017-03-01

This research paper describes the study of a reduction-oxidation system using commercial steel wool (Fe 0 ) and H 2 O 2 for degradation of the dye Reactive Black 5 and aromatic compounds in water. The reductive process alone allowed the almost complete removal of color (97 ± 1 %) after 60 min of reaction. The decrease in spectral area (λ = 599 nm) associated with the chromophore group indicates breakage of the azo bonds. Moreover, the significant change in UV spectra can be associated with the formation of aromatic amines. Regarding the transformation products, a spectrophotometric method based on the diazotization reaction was employed to identify aromatic amines after reductive process, using sulfanilic acid as a model of aromatic amines. In addition, association with Fenton reagents improved the efficiency in the system with 93 ± 1 % degradation of intermediates formed during the reductive process. Ecotoxicological analysis revealed that the dye solution, after the reductive and oxidative processes, was not toxic to Lactuca sativa seeds. For Daphnia magna, the EC 50 (%) values observed revealed that dye solution has an EC 50 (%) = 74.1 and after reductive process, the toxicity increased (EC 50 (%) = 63.5), which might be related to the formation of aromatic amines. However, after the Fenton process, the EC 50 (%) was >100. These results demonstrated that the Fenton reaction using steel wool as an iron source was very efficient to decrease color, aromatic transformation products, and the ecotoxicity of Reactive Black 5 in solution.

Continuous-flow oxidative cyanation of primary and secondary amines using singlet oxygen.

PubMed

Ushakov, Dmitry B; Gilmore, Kerry; Kopetzki, Daniel; McQuade, D Tyler; Seeberger, Peter H

2014-01-07

Primary and secondary amines can be rapidly and quantitatively oxidized to the corresponding imines by singlet oxygen. This reactive form of oxygen was produced using a variable-temperature continuous-flow LED-photoreactor with a catalytic amount of tetraphenylporphyrin as the sensitizer. α-Aminonitriles were obtained in good to excellent yields when trimethylsilyl cyanide served as an in situ imine trap. At 25°C, primary amines were found to undergo oxidative coupling prior to cyanide addition and yielded secondary α-aminonitriles. Primary α-aminonitriles were synthesized from the corresponding primary amines for the first time, by an oxidative Strecker reaction at -50 °C. This atom-economic and protecting-group-free pathway provides a route to racemic amino acids, which was exemplified by the synthesis of tert-leucine hydrochloride from neopentylamine. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Part I. Cobalt thiolate complexes modeling the active site of cobalt nitrile hydratase. Part II. Formation of inorganic nanoparticles on protein scaffolding in Escherichia coli glutamine synthetase

NASA Astrophysics Data System (ADS)

Kung, Irene Yuk Man

Part I. A series of novel cobalt dithiolate complexes with mixed imine/amine ligand systems is presented here as electronic and structural models for the active site in the bacterial enzyme class, nitrile hydratase (NHase). Pentadentate cobalt(II) complexes with S2N 3 ligand environments are first studied as precursors to the more relevant cobalt(III) complexes. Adjustment of the backbone length by removal of a methylene group increases the reactivity of the system; whereas reduction of the two backbone imine bonds to allow free rotation about those bonds may decrease reactivity. Reactivity change due to the replacement of the backbone amine proton with a more sterically challenging methyl group is not yet clear. Upon oxidation, the monocationic pentadentate cobalt(III) complex, 1b, shows promising reactivity similar to that of NHase. The metal's open coordination site allows reversible binding of the endogenous, monoanionic ligands, N 3- and NCS-. Oxygenation of the thiolate sulfur atoms by exposure to O2 and H2O 2 produces sulfenate and sulfinate ligands in complex 8, which resembles the crystal structure of "deactivated" Fe NHase. However, its lack of reactivity argues against the oxygenated enzyme structure as the active form. Six-coordinate cobalt(III) complexes with S2N4 amine/amine ligand systems are also presented as analogues of previously reported iron(III) compounds, which mimic the spectroscopic properties of Fe NHase. The cobalt complexes do not seem to similarly model Co NHase. However, the S = 0 cobalt(III) center can be spectroscopically silent and difficult to detect, making comparison with synthetic models using common techniques hard. Part II. Dodecameric Escherichia coli glutamine synthetase mutant, E165C, stacks along its six-fold axis to produce tubular nanostructures in the presence of some divalent metal ions, as does the wild type enzyme. The centrally located, engineered Cys-165 residues appear to bind to various species and may serve as scaffolding for inorganic mineralization. US nanoclusters of discreet size seem to grow in the presence of E165C in aqueous solution spontaneously. Commercially available mono(maleimido)undecagold seem to bind only to E165C through the reactive cysteine side chains. Reduction of Au3+ to elemental gold in solution with E165C, generates long, linear structures of approximately 100-nm diameter.

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

PubMed Central

2016-01-01

Conspectus While the use of visible light to drive chemical reactivity is of high importance to the development of environmentally benign chemical transformations, the concomitant use of a stoichiometric electron donor or acceptor is often required to steer the desired redox behavior of these systems. The low-cost and ubiquity of tertiary amine bases has led to their widespread use as reductive additives in photoredox catalysis. Early use of trialkylamines in this context was focused on their role as reductive excited state quenchers of the photocatalyst, which in turn provides a more highly reducing catalytic intermediate. In this Account, we discuss some of the observations and thought processes that have led from our use of amines as reductive additives to their use as complex substrates and intermediates for natural product synthesis. Early attempts by our group to construct key carbon–carbon bonds via free-radical intermediates led to the observation that some trialkylamines readily behave as efficient hydrogen atom donors under redox-active photochemical conditions. In the wake of in-depth mechanistic studies published in the 1970s, 1980s and 1990s, this understanding has in turn allowed for a systematic approach to the design of a number of photochemical methodologies through rational tuning of the amine component. Minimization of the C–H donicity of the amine additive was found to promote desired C–C bond formation in a number of contexts, and subsequent elucidation of the amine’s redox fate has sparked a reevaluation of the amine’s role from that of reagent to that of substrate. The reactivity of tertiary amines in these photochemical systems is complex, and allows for a number of mechanistic possibilities that are not necessarily mutually exclusive. A variety of combinations of single-electron oxidation, C–H abstraction, deprotonation, and β-scission result in the formation of reactive intermediates such as α-amino radicals and iminium ions. These processes have been explored in depth in the photochemical literature and have resulted in a firm mechanistic grasp of the behavior of amine radical cations in fundamental systems. Harnessing the synthetic potential of these transient species represents an ongoing challenge for the controlled functionalization of amine substrates, because these mechanistic possibilities may result in undesired byproduct formation or substrate decomposition. The presence of tertiary amines in numerous alkaloids, pharmaceuticals, and agrochemicals lends credence to the potential utility of this chemistry in natural product synthesis, and herein we will discuss how these transformations might be controlled for synthetic purposes. PMID:25951291

Certain tricyclic and pentacyclic-hetero nitrogen rhodol dyes

DOEpatents

Haugland, Richard P.; Whitaker, James E.

1993-01-01

Novel fluorescent dyes based on the rhodol structure are provided. The new reagents contain functional groups capable of forming a stable fluorescent product with functional groups typically found in biomolecules or polymers including amines, phenols, thiols, acids, aldehydes and ketones. Reactive groups in the rhodol dyes include activated esters, isothiocyanates, amines, hydrazines, halides, acids, azides, maleimides, aldehydes, alcohols, acrylamides and haloacetamides. The products are detected by their absorbance or fluorescence properties. The spectral properties of the fluorescent dyes are sufficiently similar in wavelengths and intensity to fluorescein or rhodamine derivatives as to permit use of the same equipment. The dyes, however, show less spectral sensitivity to pH in the physiological range than does fluorescein, have higher solubility in non-polar solvents and have improved photostability and quantum yields.

α-Oxo-Ketenimines from Isocyanides and α-Haloketones: Synthesis and Divergent Reactivity.

PubMed

Mamboury, Mathias; Wang, Qian; Zhu, Jieping

2017-09-18

The palladium-catalyzed reaction of α-haloketones with isocyanides afforded α-oxo-ketenimines through β-hydride elimination of the β-oxo-imidoyl palladium intermediates. Reaction of these relatively stable α-oxo-ketenimines with nucleophiles such as hydrazines, hydrazoic acid, amines, and Grignard reagent afforded pyrazoles, tetrazole, β-keto amidines, and enaminone, respectively, with high chemoselectivity. Whereas amines attack exclusively on the ketenimine functions, the formal [3+2] cycloaddition between N-monosubstituted hydrazines and α-oxo-ketenimines was initiated by nucleophilic addition to the carbonyl group. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photoredox activation of carbon dioxide for amino acid synthesis in continuous flow

NASA Astrophysics Data System (ADS)

Seo, Hyowon; Katcher, Matthew H.; Jamison, Timothy F.

2017-05-01

Although carbon dioxide (CO2) is highly abundant, its low reactivity has limited its use in chemical synthesis. In particular, methods for carbon-carbon bond formation generally rely on two-electron mechanisms for CO2 activation and require highly activated reaction partners. Alternatively, radical pathways accessed via photoredox catalysis could provide new reactivity under milder conditions. Here we demonstrate the direct coupling of CO2 and amines via the single-electron reduction of CO2 for the photoredox-catalysed continuous flow synthesis of α-amino acids. By leveraging the advantages of utilizing gases and photochemistry in flow, a commercially available organic photoredox catalyst effects the selective α-carboxylation of amines that bear various functional groups and heterocycles. The preliminary mechanistic studies support CO2 activation and carbon-carbon bond formation via single-electron pathways, and we expect that this strategy will inspire new perspectives on using this feedstock chemical in organic synthesis.

Oxidation of fluoroquinolone antibiotics and structurally related amines by chlorine dioxide: Reaction kinetics, product and pathway evaluation.

PubMed

Wang, Pei; He, Yi-Liang; Huang, Ching-Hua

2010-12-01

Fluoroquinolones (FQs) are a group of widely prescribed antibiotics and have been frequently detected in the aquatic environment. The reaction kinetics and transformation of seven FQs (ciprofloxacin (CIP), enrofloxacin (ENR), norfloxacin (NOR), ofloxacin (OFL), lomefloxacin (LOM), pipemidic acid (PIP) and flumequine (FLU)) and three structurally related amines (1-phenylpiperazine (PP), N-phenylmorpholine (PM) and 4-phenylpiperidine (PD)) toward chlorine dioxide (ClO(2)) were investigated to elucidate the behavior of FQs during ClO(2) disinfection processes. The reaction kinetics are highly pH-dependent, can be well described by a second-order kinetic model incorporating speciation of FQs, and follow the trend of OFL > ENR > CIP ∼ NOR ∼ LOM > > PIP in reactivity. Comparison among FQs and related amines and product characterization indicate that FQs' piperazine ring is the primary reactive center toward ClO(2). ClO(2) likely attacks FQ's piperazinyl N4 atom followed by concerted fragmentation involving piperazinyl N1 atom, leading to dealkylation, hydroxylation and intramolecular ring closure at the piperazine moiety. While FQs with tertiary N4 react faster with ClO(2) than FQs with secondary N4, the overall reactivity of the piperazine moiety also depends strongly on the quinolone ring through electronic effects. The reaction rate constants obtained in clean water matrix can be used to model the decay of CIP by ClO(2) in surface water samples, but overestimate the decay in wastewater samples. Overall, transformation of FQs, particularly for those with tertiary N4 amines, could be expected under typical ClO(2) disinfection conditions. However, the transformation may not eliminate antibacterial activity because of little destruction at the quinolone ring. Copyright © 2010 Elsevier Ltd. All rights reserved.

Highly Reactive, General and Long-Lived Catalysts for Palladium-Catalyzed Amination of Heteroaryl and Aryl Chlorides, Bromides and Iodides: Scope and Structure-Activity Relationships

PubMed Central

Shen, Qilong; Ogata, Tokutaro; Hartwig, John F.

2010-01-01

We describe a systematic study of the scope and relationship between ligand structure and activity for a highly efficient and selective class of catalysts for the amination of heteroaryl and aryl chlorides, bromides and iodides containing sterically hindered chelating alkylphosphines. In the presence of this catalyst, aryl and heteroaryl chlorides, bromides and iodides react with many primary amines in high yields with part-per-million quantities of palladium precursor and ligand. Many reactions of primary amines with both heteroaryl and aryl chlorides, bromides and iodides occur to completion with 0.0005-0.05 mol % catalysts. A comparison of the reactivity of this catalyst for coupling of primary amines at these loadings is made with catalysts generated from hindered monophosphines and carbenes, and these data illustrate the benefits of chelation. Thus, these complexes constitute a fourth-generation catalyst for the amination of aryl halides, whose activity complements catalysts based on monophosphines and carbenes. PMID:18444639

Aminative umpolung of aldehydes to α-amino anion equivalents for Pd-catalyzed allylation: an efficient synthesis of homoallylic amines.

PubMed

Ding, Lei; Chen, Jing; Hu, Yifan; Xu, Juan; Gong, Xing; Xu, Dongfang; Zhao, Baoguo; Li, Hexing

2014-02-07

An attractive strategy for generation of α-amino anions from aldehydes with applications in synthesis of homoallylic amines is described. Aromatic aldehydes can be converted to α-amino anion equivalents via amination with 2,2-diphenylglycine and subsequent decarboxylation. The in situ generated α-imino anions are highly reactive for Pd-catalyzed allylation, forming the corresponding homoallylic amines in high yields with excellent regioselectivity.

Regioselectivity switch in chiral amine-catalysed asymmetric addition of aldehydes to reactive enals.

PubMed

Kano, Taichi; Maruyama, Hiroki; Sakamoto, Ryu; Maruoka, Keiji

2015-06-21

In this communication, we present a regioselectivity switch for the chiral amine-catalysed asymmetric addition of aldehydes to reactive enals to afford either aldol adducts or conjugate adducts in a stereoselective fashion. The unprecedented asymmetric aldol reaction of aldehydes with enals was realized by the use of a diarylprolinol catalyst, giving synthetically useful and important chiral allylic alcohols.

Electronic and steric influences of pendant amine groups on the protonation of molybdenum bis (dinitrogen) complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Labios, Liezel A.; Heiden, Zachariah M.; Mock, Michael T.

2015-05-04

The synthesis of a series of P EtP NRR' (P EtP NRR' = Et₂PCH₂CH₂P(CH₂NRR')₂, R = H, R' = Ph or 2,4-difluorophenyl; R = R' = Ph or iPr) diphosphine ligands containing mono- and disubstituted pendant amine groups, and the preparation of their corresponding molybdenum bis(dinitrogen) complexes trans-Mo(N₂)₂(PMePh₂)₂(P EtP NRR') is described. In situ IR and multinuclear NMR spectroscopic studies monitoring the stepwise addition of (HOTf) to trans-Mo(N₂)₂(PMePh₂)₂(P EtP NRR') complexes in THF at -40 °C show that the electronic and steric properties of the R and R' groups of the pendant amines influence whether the complexes are protonated atmore » Mo, a pendant amine, a coordinated N2 ligand, or a combination of these sites. For example, complexes containing mono-aryl substituted pendant amines are protonated at Mo and pendant amine to generate mono- and dicationic Mo–H species. Protonation of the complex containing less basic diphenyl-substituted pendant amines exclusively generates a monocationic hydrazido (Mo(NNH₂)) product, indicating preferential protonation of an N₂ ligand. Addition of HOTf to the complex featuring more basic diisopropyl amines primarily produces a monocationic product protonated at a pendant amine site, as well as a trace amount of dicationic Mo(NNH₂) product that contain protonated pendant amines. In addition, trans-Mo(N₂)₂(PMePh₂)₂(depe) (depe = Et₂PCH₂CH₂PEt₂) without a pendant amine was synthesized and treated with HOTf, generating a monocationic Mo(NNH₂) product. Protonolysis experiments conducted on select complexes in the series afforded trace amounts of NH₄⁺. Computational analysis of the series of trans-Mo(N₂)₂(PMePh₂)₂(P EtP NRR') complexes provides further insight into the proton affinity values of the metal center, N₂ ligand, and pendant amine sites to rationalize the differing reactivity profiles. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Computational resources provided by the National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.« less

Nylon surface modification: 2. Nylon-supported composite films.

PubMed

Herrera-Alonso, Margarita; McCarthy, Thomas J; Jia, Xinqiao

2006-02-14

We have developed techniques for the introduction of reactive functional groups to nylon surfaces via site-specific reactions targeting at the naturally abundant amide repeating units on the surface. In this report, we describe the fabrication of nylon-supported composite surfaces using the most efficient modification methods we have developed. N-Alkylation with (3-glycidoxypropyl)triethoxysilane (GPTES) in the presence of potassium tert-butoxide (t-BuOK) leads to surfaces with silica-like reactivity. Subsequent chemical vapor deposition using tetrachlorosilane (SiCl4) and water results in composite films with a thin layer of silica, which was made hydrophobic by reaction with a fluorinated silane reagent. Reduction of the amide groups with borane-THF (BH3-THF) complex leads to a 69% conversion of surface amides to the corresponding secondary amine groups. Alginate was chosen as the model polyelectrolyte for the introduction of a hydrated surface layer. Because of the strong electrostatic interaction between alginate and the amine-enriched nylon surfaces, the adsorption is fast and concentration-independent (within the concentration range studied). The polysaccharide coats the surface homogeneously, without the formation of large aggregates. The amine surfaces obtained by reduction with BH3-THF ((BH3-THF)nylon-NH) and by alkylation with 2-bromoethylamine hydrobromide (BEA-HBr, (EBA-HBr)nylon-NH2) were also used to study gold deposition through electroless plating. Immobilization of a negatively charged metal complex (AuCl4(-)) was achieved through electrostatic interaction. Gold particles disperse preferentially in the bulk of (EBA-HBr)nylon-NH2 films, while they remain confined to the outer surface layer of (BH3-THF)nylon-NH films.

Direct asymmetric N-specific reaction of nitrosobenzene with aldehydes catalyzed by a chiral primary amine-based organocatalyst.

PubMed

Qin, Long; Li, Lei; Yi, Lei; Da, Chao-Shan; Zhou, Yi-Feng

2011-08-01

Nitroso compounds have two reactive nitrogen and oxygen atoms. It is interesting and important to perform a nitrogen or oxygen selective reaction with interesting substrates. These atom specific reactions are crucial to specifically synthesis of specific compounds. An enantioselective N-specific reaction of nitrosobenzene with unmodified aldehydes was successfully achieved catalyzed first by a variety of primary amine-based organocatalysts with higher yield and enantioselectivity. The bulkier substituted groups of the organocatalyst and two hydrogen bonds from the organocatalyst and the oxygen atom of nitrosobenzene make the reaction preferentially N-specific and predominantly afford R products. Copyright © 2011 Wiley-Liss, Inc.

Silicone-containing composition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohamed, Mustafa

A silicone-containing composition comprises the reaction product of a first component and an excess of an isocyanate component relative to the first component to form an isocyanated intermediary. The first component is selected from one of a polysiloxane and a silicone resin. The first component includes a carbon-bonded functional group selected from one of a hydroxyl group and an amine group. The isocyanate component is reactive with the carbon-bonded functional group of the first component. The isocyanated intermediary includes a plurality of isocyanate functional groups. The silicone-containing composition comprises the further reaction product of a second component, which is selectedmore » from the other of the polysiloxane and the silicone resin. The second component includes a plurality of carbon-bonded functional groups reactive with the isocyanate functional groups of the isocyanated intermediary for preparing the silicone-containing composition.« less

Organic chloramines in drinking water: An assessment of formation, stability, reactivity and risk.

PubMed

How, Zuo Tong; Linge, Kathryn L; Busetti, Francesco; Joll, Cynthia A

2016-04-15

Although organic chloramines are known to form during the disinfection of drinking water with chlorine, little information is currently available on their occurrence or toxicity. In a recent in vitro study, some organic chloramines (e.g. N-chloroglycine) were found to be cytotoxic and genotoxic even at micromolar concentrations. In this paper, the formation and stability of 21 different organic chloramines, from chlorination of simple amines and amino acids, were studied, and the competition between 20 amino acids during chlorination was also investigated. For comparison, chlorination of two amides was also conducted. The formation and degradation of selected organic chloramines were measured using either direct UV spectroscopic or colorimetric detection. Although cysteine, methionine and tryptophan were the most reactive amino acids towards chlorination, they did not form organic chloramines at the chlorine to precursor molar ratios that were tested. Only 6 out of the 21 organic chloramines formed had a half-life of more than 3 h, although this group included all organic chloramines formed from amines. A health risk assessment relating stability and reactivity data from this study to toxicity and precursor abundance data from the literature indicated that only N-chloroglycine is likely to be of concern due to its stability, toxicity and abundance in water. However, given the stability of organic chloramines formed from amines, more information about the toxicity and precursor abundance for these chloramines is desirable. Copyright © 2016 Elsevier Ltd. All rights reserved.

An ATR-FTIR Study on the Effect of Molecular Structural Variations on the CO2 Absorption Characteristics of Heterocyclic Amines, Part II

PubMed Central

Robinson, Kelly; McCluskey, Adam; Attalla, Moetaz I

2012-01-01

This paper reports on an ATR-FTIR spectroscopic investigation of the CO2 absorption characteristics of a series of heterocyclic diamines: hexahydropyrimidine (HHPY), 2-methyl and 2,2-dimethylhexahydropyrimidine (MHHPY and DMHHPY), hexahydropyridazine (HHPZ), piperazine (PZ) and 2,5- and 2,6-dimethylpiperazine (2,6-DMPZ and 2,5-DMPZ). By using in situ ATR-FTIR the structure–activity relationship of the reaction between heterocyclic diamines and CO2 is probed. PZ forms a hydrolysis-resistant carbamate derivative, while HHPY forms a more labile carbamate species with increased susceptibility to hydrolysis, particularly at higher CO2 loadings (>0.5 mol CO2/mol amine). HHPY exhibits similar reactivity toward CO2 to PZ, but with improved aqueous solubility. The α-methyl-substituted MHHPY favours HCO3− formation, but MHHPY exhibits comparable CO2 absorption capacity to conventional amines MEA and DEA. MHHPY show improved reactivity compared to the conventional α-methyl- substituted primary amine 2-amino-2-methyl-1-propanol. DMHHPY is representative of blended amine systems, and its reactivity highlights the advantages of such systems. HHPZ is relatively unreactive towards CO2. The CO2 absorption capacity CA (mol CO2/mol amine) and initial rates of absorption RIA (mol CO2/mol amine min−1) for each reactive diamine are determined: PZ: CA=0.92, RIA=0.045; 2,6-DMPZ: CA=0.86, RIA=0.025; 2,5-DMPZ: CA=0.88, RIA=0.018; HHPY: CA=0.85, RIA=0.032; MHHPY: CA=0.86, RIA=0.018; DMHHPY: CA=1.1, RIA=0.032; and HHPZ: no reaction. Calculations at the B3LYP/6-31+G** and MP2/6-31+G** calculations show that the substitution patterns of the heterocyclic diamines affect carbamate stability, which influences hydrolysis rates. PMID:22517608

Chemically Functional Alkanethiol Derivitized Magnetic Nanoparticles

DTIC Science & Technology

2003-01-01

reactive groups such as alcohols, amines and carboxylic acids . This paper presents our preliminary investigations of the voltammetry of the former class of...1.62 mmol) TOPO, 1.75g (7.25 mmol) HDA and 0. l4mL (1.06 mmol) Fe(CO)5 is heated and injected into the TOPO mixture, and stirred for at least an

Silane coupling agent bearing a photoremovable succinimidyl carbonate for patterning amines on glass and silicon surfaces with controlled surface densities.

PubMed

Nakayama, Hidekazu; Nakanishi, Jun; Shimizu, Takahiro; Yoshino, Yutaro; Iwai, Hideo; Kaneko, Shingo; Horiike, Yasuhiro; Yamaguchi, Kazuo

2010-03-01

Patterned immobilization of synthetic and biological ligands on material surfaces with controlled surface densities is important for various bioanalytical and cell biological purposes. This paper describes the synthesis, characterization, and application of a novel silane coupling agent bearing a photoremovable succinimidyl carbonate, which enables the photopatterning of various primary amines on glass and silicon surfaces. The silane coupling agent is 1-[5-methoxy-2-nitro-4-(3-trimethoxysilylpropyloxy)phenyl]ethyl N-succinimidyl carbonate. The distinct feature of this molecule is that it has a photocleavable 2-nitrobenzyl switch between a trimethoxysilyl group and a succinimidyl carbonate, each reactive to the hydroxy groups of inorganic oxides and primary amines. Based on this molecular design, the compound allows for the one-step introduction of succinimidyl carbonates onto the surface of glass and silicon, immobilization of primary amines, and region-selective and dose-dependent release of the amines by near-UV irradiation. Therefore, we were able to pattern amine ligands on the substrates in given surface densities and arbitrary geometries by controlling the doses and regions of photoirradiation. These features were verified by UV-vis spectroscopy, contact angle measurements, infrared (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), ellipsometry, and atomic force microscopy (AFM). The compound was applied to form a chemical density gradient of amino-biotin on a silicon substrate in a range of 0.87-0.12 chains/nm(2) by controlling photoirradiation under a standard fluorescence microscope. Furthermore, we also succeeded in forming a chemical density gradient at a lower surface density range (0.15-0.011 chains/nm(2)) on the substrate by diluting the feed amino-biotin with an inert control amine.

Effect of Bronsted Acids and Bases, and Lewis Acid (Sn(2+)) on the Regiochemistry of the Reaction of Amines with Trifluoromethyl-β-diketones: Reaction of 3-Aminopyrrole to Selectively Produce Regioisomeric 1H-Pyrrolo[3,2-b]pyridines.

PubMed

De Rosa, Michael; Arnold, David; Hartline, Douglas; Truong, Linda; Verner, Roman; Wang, Tianwei; Westin, Christian

2015-12-18

Reaction of 3-aminopyrrole (as its salt) with trifluoromethyl-β-diketones gave γ-1H-pyrrolo[3,2-b]pyridines via reaction at the less reactive carbonyl group. The trifluoromethyl group increased the electrophilicity of the adjacent carbonyl group and decreased the basicity of the hydroxyl group of the CF3 amino alcohol formed. This amino alcohol was formed faster, but its subsequent dehydration to the β-enaminone was slow resulting in the preferential formation of the γ-regioisomer. Reaction of 4,4,4-trifluoro-1-phenyl-1,3-butadione with 3-aminopyrrole was carried out using a series of 6 amine buffers. Yields of the α-1H-pyrrolo[3,2-b]pyridine increased as the pKa of the amine buffer decreased. Surprisingly the yield went down at higher pKas. There was a change in mechanism as the reaction mixture became more basic. With strong amines trifluoromethyl-β-diketones were present mainly or completely as the enolate. Under reductive conditions (3-nitropyrrole/Sn/AcOH/trifluoromethyl-β-diketone) the α-1H-pyrrolo[3,2-b]pyridine was the major product as a result of Lewis acid catalysis by Sn(2+). Similar α-regiochemistry was observed when the reaction of the 3-aminopyrrole salt with trifluoromethyl-β-diketones was carried out in the presence of base and tin(II) acetate.

Sensitization and cross-reactivity patterns of contact allergy to diisocyanates and corresponding amines: investigation of diphenylmethane-4,4'-diisocyanate, diphenylmethane-4,4'-diamine, dicyclohexylmethane-4,4'-diisocyanate, and dicylohexylmethane-4,4'-diamine.

PubMed

Hamada, Haneen; Bruze, Magnus; Zimerson, Erik; Isaksson, Marléne; Engfeldt, Malin

2017-10-01

Isocyanates are used in polyurethane production. Dermal exposure to isocyanates can induce contact allergy. The most common isocyanate is diphenylmethane diisocyanate used for industrial purposes. The isomer diphenylmethane-4,4'-diisocyanate (4,4'-MDI) is used in patch testing. Diphenylmethane-4,4'-diamine (4,4'-MDA) is its corresponding amine. Concurrent reactions to 4,4'-MDI and 4,4'-MDA have been reported, as have concurrent reactions to 4,4'-MDI and dicyclohexylmethane-4,4'-diisocyanate (4,4'-DMDI). To investigate the sensitization capacities and the cross-reactivity of 4,4'-MDI, 4,4'-MDA, 4,4'-DMDI, and dicyclohexylmethane-4,4'-diamine (4,4'-DMDA). The guinea-pig maximization test (GPMT) was used. The GPMT showed sensitizing capacities for all investigated substances: 4,4'-MDI, 4,4'-MDA, 4,4'-DMDI, and 4,4'-DMDA (all p < 0.001). 4,4'-MDI-sensitized animals showed cross-reactivity to 4,4'-MDA (p < 0.001) and 4,4'-DMDI (all p < 0.05). 4,4'-MDA-sensitized animals showed cross-reactivity to 4,4'-DMDA (p = 0.008). All of the investigated substances were shown to be strong sensitizers. Animals sensitized to 4,4'-MDI showed cross-reactivity to 4,4'-MDA and 4,4'-DMDI, supporting previous findings in the literature. The aromatic amine 4,4'-MDA showed cross-reactivity to the aliphatic amine 4,4'-DMDA. © 2017 The Authors. Contact Dermatitis published by John Wiley & Sons Ltd.

Oxidative versus Non-oxidative Decarboxylation of Amino Acids: Conditions for the Preferential Formation of Either Strecker Aldehydes or Amines in Amino Acid/Lipid-Derived Reactive Carbonyl Model Systems.

PubMed

Zamora, Rosario; León, M Mercedes; Hidalgo, Francisco J

2015-09-16

Comparative formation of both 2-phenylethylamine and phenylacetaldehyde as a consequence of phenylalanine degradation by carbonyl compounds was studied in an attempt to understand if the amine/aldehyde ratio can be changed as a function of reaction conditions. The assayed carbonyl compounds were selected because of the presence in the chain of both electron-donating and electron-withdrawing groups and included alkenals, alkadienals, epoxyalkenals, oxoalkenals, and hydroxyalkenals as well as lipid hydroperoxides. The obtained results showed that the 2-phenylethylamine/phenylacetaldehyde ratio depended upon both the carbonyls and the reaction conditions. Thus, it can be increased using electron-donating groups in the chain of the carbonyl compound, small amounts of carbonyl compound, low oxygen content, increasing the pH, or increasing the temperature at pH 6. Opposed conditions (use of electron-withdrawing groups in the chain of the carbonyl compound, large amounts of carbonyl compound, high oxygen contents, low pH values, and increasing temperatures at low pH values) would decrease the 2-phenylethylamine/phenylacetaldehyde ratio, and the formation of aldehydes over amines in amino acid degradations would be favored.

Latent curing systems stabilized by reaction equilibrium in homogeneous mixtures of benzoxazine and amine

PubMed Central

Wang, Jun; Xu, Ya Zhen; Fu, Ya Fei; Liu, Xiang Dong

2016-01-01

Latent curing systems are widely used in industrial thermosets in applications such as adhesion, coating, and composites. Despite many attempts to improve the practicality of this dormant reaction system, the majority of commercially available latent products still use particulate hardeners or liquid compounds with blocked active groups. These formulations generally lack fluidity or rapid reaction characteristics and thus are problematic in some industry applications. Here we describe a novel concept that stabilizes highly reactive benzoxazine/amine mixtures by reaction equilibrium. These new latent benzoxazine curing systems have a long storable lifetime but very short gel time at 150 °C. The reversible reaction between benzoxazine and amine is further demonstrated by FT-IR spectral measurements and rheological experiments, and it is shown that the overall characteristics of the latent system are promising for many industrial applications. PMID:27917932

Gas Phase Reactivity of Carboxylates with N-Hydroxysuccinimide Esters

PubMed Central

Peng, Zhou; McGee, William M.; Bu, Jiexun; Barefoot, Nathan Z.; McLuckey, Scott A.

2015-01-01

N-hydroxysuccinimide (NHS) esters have been used for gas phase conjugation reactions with peptides at nucleophilic sites, such as primary amines (N-terminus, ε-amine of lysine) or guanidines, by forming amide bonds through a nucleophilic attack on the carbonyl carbon. The carboxylate has recently been found to also be a reactive nucleophile capable of initiating a similar nucleophilic attack to form a labile anhydride bond. The fragile bond is easily cleaved, resulting in an oxygen transfer from the carboxylate-containing species to the reagent, nominally observed as a water transfer. This reactivity is shown for both peptides and non-peptidic species. Reagents isotopically labeled with O18 were used to confirm reactivity. This constitutes an example of distinct differences in reactivity of carboxylates between the gas-phase, where they are shown to be reactive, and the solution-phase, where they are not regarded as reactive with NHS esters. PMID:25338221

Carbonyl-Phenol Adducts: An Alternative Sink for Reactive and Potentially Toxic Lipid Oxidation Products.

PubMed

Zamora, Rosario; Hidalgo, Francisco J

2018-02-14

Different from the well-characterized function of phenolics as antioxidants, their function as lipid-derived carbonyl scavengers is mostly unknown. However, phenolics react with lipid-derived carbonyls as a function of the nucleophilicity of their reactive groups and the electronic effects and steric hindrances present in the reactive carbonyls. Furthermore, the reaction produces a wide variety of carbonyl-phenol adducts, some of which are stable and have been isolated and characterized but others polymerize spontaneously. This perspective updates present knowledge about the lipid-derived carbonyl trapping ability of phenolics, its competition with carbonyl-amine reactions produced in foods, and the presence of carbonyl-phenol adducts in food products.

Frustrated Lewis pairs beyond the main group: cationic zirconocene-phosphinoaryloxide complexes and their application in catalytic dehydrogenation of amine boranes.

PubMed

Chapman, Andy M; Haddow, Mairi F; Wass, Duncan F

2011-06-15

The cationic zirconocene-phosphinoaryloxide complexes [Cp(2)ZrOC(6)H(4)P(t-Bu)(2)][B(C(6)F(5))(4)] (3) and [Cp*(2)ZrOC(6)H(4)P(t-Bu)(2)][B(C(6)F(5))(4)] (4) were synthesized by the reaction of Cp(2)ZrMe(2) or Cp*(2)ZrMe(2) with 2-(diphenylphosphino)phenol followed by protonation with [2,6-di-tert-butylpyridinium][B(C(6)F(5))(4)]. Compound 3 exhibits a Zr-P bond, whereas the bulkier Cp* derivative 4 was isolated as a chlorobenzene adduct without this Zr-P interaction. These compounds can be described as transition-metal-containing versions of linked frustrated Lewis pairs (FLPs), and treatment of 4 with H(2) under mild conditions cleaved H(2) in a fashion analogous to that for main-group FLPs. Their reactivity in amine borane dehydrogenation also mimics that of main-group FLPs, and they dehydrogenate a range of amine borane adducts. However, in contrast to main-group FLPs, 3 and 4 achieve this transformation in a catalytic rather than stoichiometric sense, with rates superior to those for previous high-valent catalysts. © 2011 American Chemical Society

Simple route for nano-hydroxyapatite properties expansion.

PubMed

Rojas, L; Olmedo, H; García-Piñeres, A J; Silveira, C; Tasic, L; Fraga, F; Montero, M L

2015-10-20

Simple surface modification of nano-hydroxyapatite, through acid-basic reactions, allows expanding the properties of this material. Introduction of organic groups such as hydrophobic alkyl chains, carboxylic acid, and amide or amine basic groups on the hydroxyapatite surface systematically change the polarity, surface area, and reactivity of hydroxyapatite without modifying its phase. Physical and chemical properties of the new derivative particles were analyzed. The biocompatibility of modified Nano-Hap on Raw 264.7 cells was also assessed.

Amine oxidases as important agents of pathological processes of rhabdomyolysis in rats.

PubMed

Gudkova, O O; Latyshko, N V; Shandrenko, S G

2016-01-01

In this study we have tested an idea on the important role of amine oxidases (semicarbazide-sensitive amine oxidase, diamine oxidase, polyamine oxidase) as an additional source of oxidative/carbonyl stress under glycerol-induced rhabdomyolysis, since the enhanced formation of reactive oxygen species and reactive carbonyl species in a variety of tissues is linked to various diseases. In our experiments we used the sensitive fluorescent method devised for estimation of amine oxidases activity in the rat kidney and thymus as targeted organs under rhabdomyolysis. We have found in vivo the multiple rises in activity of semicarbazide-sensitive amine oxidase, diamine oxidase, polyamine oxidase (2-4.5 times) in the corresponding cell fractions, whole cells or their lysates at the 3-6th day after glycerol injection. Aberrant antioxidant activities depended on rhabdomyolysis stage and had organ specificity. Additional treatment of animals with metal chelator ‘Unithiol’ adjusted only the activity of antioxidant enzymes but not amine oxidases in both organs. Furthermore the in vitro experiment showed that Fenton reaction (hydrogen peroxide in the presence of iron) products alone had no effect on semicarbazide-sensitive amine oxidase activity in rat liver cell fraction whereas supplementation with methylglyoxal resulted in its significant 2.5-fold enhancement. Combined action of the both agents had additive effect on semicarbazide-sensitive amine oxidase activity. We can assume that biogenic amine and polyamine catabolism by amine oxidases is upregulated by oxidative and carbonyl stress factors directly under rhabdomyolysis progression, and the increase in catabolic products concentration contributes to tissue damage in glycerol-induced acute renal failure and apoptosis stimulation in thymus.

Reactivity and biological properties of a series of cytotoxic PtI2(amine)2 complexes, either cis or trans configured.

PubMed

Messori, Luigi; Cubo, Leticia; Gabbiani, Chiara; Álvarez-Valdés, Amparo; Michelucci, Elena; Pieraccini, Giuseppe; Ríos-Luci, Carla; León, Leticia G; Padrón, José M; Navarro-Ranninger, Carmen; Casini, Angela; Quiroga, Adoración G

2012-02-06

Six diiodido-diamine platinum(II) complexes, either cis or trans configured, were prepared, differing only in the nature of the amine ligand (isopropylamine, dimethylamine, or methylamine), and their antiproliferative properties were evaluated against a panel of human tumor cell lines. Both series of complexes manifested pronounced cytotoxic effects, with the trans isomers being, generally, more effective than their cis counterparts. Cell cycle analysis revealed different modes of action for these new Pt(II) complexes with respect to cisplatin. The reactivity of these platinum compounds with a number of biomolecules, including cytochrome c, two sulfur containing modified amino acids, 9-ethylguanine, and a single strand oligonucleotide, was analyzed in depth by mass spectrometry and NMR spectroscopy. Interestingly, significant differences in the reactivity of the investigated compounds toward the various model biomolecules were observed: in particular we observed that trans complexes preferentially release their iodide ligands upon biomolecule binding, while the cis isomers may release the amine ligands with retention of iodides. Such differences in reactivity may have important mechanistic implications and a relevant impact on the respective pharmacological profiles.

Functional copolymer/organo-MMT nanoarchitectures. VI. Synthesis and characterization of novel nanocomposites by interlamellar controlled/living radical copolymerization via preintercalated RAFT-agent/organoclay complexes.

PubMed

Rzayev, Zakir M O; Söylemez, A Ernur

2011-04-01

We have developed a new approach for the synthesis of polymer nanocomposites using a bifunctional reversible addition-fragmentation chain transfer (RAFT) agent, two types of organo-montmorillonites, such as a non-reactive dimethyldodecyl ammonium (DMDA)-MMT and a reactive octadecylamine (ODA)-MMT organoclays, and a radical initiator. The method includes the following stages: (1) synthesis of RAFT intercalated O-MMTs by a physical or chemical interaction of the RAFT agent having two pendant carboxylic groups [S,S-bis(alpha,alpha'-dimethyl-alpha"-acetic acid)trithiocarbonate] with surface alkyl amines of O-MMT containing tertiary ammonium cation or primary amine groups through strong H-bonding and complexing/amidization reactions, respectively, and (2) utilization of these well-dispersed and intercalated RAFT ... O-MMT complexes and their amide derivatives as new modified RAFT agents in radical-initiated interlamellar controlled/living copolymerization of itaconic acid (IA)-n-butylmethacrylate (BMA) monomer pair. The structure and compositions of the synthesized RAFT ... O-MMT complexes and functional copolymer/O-MMT hybrids were confirmed by FTIR, XRD, thermal (DSC-TGA), SEM and TEM morphology analyses. It was demonstrated that the degree of interaction/exfoliation, morphology and thermal behavior of nanocomposites significantly depended on the type of organoclay and in situ interaction, as well as on the content of flexible butyl-ester linkages as a internal plasticizer. The results of the comparative analysis of the nanocomposites structure-composition-property relations show that the functional copolymer-organoclay hybrids prepared with reactive RAFT ... ODA-MMT complex and containing a combination of partially intercalated and predominantly exfoliated nano-structures exhibit relatively higher thermal stability and fine dispersed morphology. These effects were explained by in situ interfacial chemical reactions through amidization of RAFT with surface alkyl amine of MMT clay in interlamellar copolymerization. This simple and versatile method can be applied to a wide range of functional monomer/comonomer systems and mono- and bifunctional RAFT compounds for preparation new generation of nanomaterials.

Systematic evaluation and optimization of modification reactions of oligonucleotides with amines and carboxylic acids for the synthesis of DNA-encoded chemical libraries.

PubMed

Franzini, Raphael M; Samain, Florent; Abd Elrahman, Maaly; Mikutis, Gediminas; Nauer, Angela; Zimmermann, Mauro; Scheuermann, Jörg; Hall, Jonathan; Neri, Dario

2014-08-20

DNA-encoded chemical libraries are collections of small molecules, attached to DNA fragments serving as identification barcodes, which can be screened against multiple protein targets, thus facilitating the drug discovery process. The preparation of large DNA-encoded chemical libraries crucially depends on the availability of robust synthetic methods, which enable the efficient conjugation to oligonucleotides of structurally diverse building blocks, sharing a common reactive group. Reactions of DNA derivatives with amines and/or carboxylic acids are particularly attractive for the synthesis of encoded libraries, in view of the very large number of building blocks that are commercially available. However, systematic studies on these reactions in the presence of DNA have not been reported so far. We first investigated conditions for the coupling of primary amines to oligonucleotides, using either a nucleophilic attack on chloroacetamide derivatives or a reductive amination on aldehyde-modified DNA. While both methods could be used for the production of secondary amines, the reductive amination approach was generally associated with higher yields and better purity. In a second endeavor, we optimized conditions for the coupling of a diverse set of 501 carboxylic acids to DNA derivatives, carrying primary and secondary amine functions. The coupling efficiency was generally higher for primary amines, compared to secondary amine substituents, but varied considerably depending on the structure of the acids and on the synthetic methods used. Optimal reaction conditions could be found for certain sets of compounds (with conversions >80%), but multiple reaction schemes are needed when assembling large libraries with highly diverse building blocks. The reactions and experimental conditions presented in this article should facilitate the synthesis of future DNA-encoded chemical libraries, while outlining the synthetic challenges that remain to be overcome.

Polymer Claw: Instant Underwater Adhesive

DTIC Science & Technology

2012-03-23

technology is the use of pressure sensitive microcapsules , which release reactive amine crosslinkers into an adhesive putty when pressed against the...PROIECT GOALS AND OBIECTIVES 2 2 KEY ACCOMPLISHMENTS 2 3.1 KICKOFF MEETING 3 3.2 AMINE MICROENCAPSULATION 3 3.3 CAUSTIC CLEANING AGENT 5 3.4...caustic, and the abrasive brush. We successfully synthesized amine-filled microcapsules and a dry mixture of caustic ingredients that only activate when

High performance N2O4/amine elements: Data dump covering. Task 1: Literature review

NASA Technical Reports Server (NTRS)

Hines, W. S.; Nurick, W. H.

1974-01-01

The phenomenon of reactive stream separation (RSS) in the N2O4/amine earth-storable propellant combinations is reviewed. Early theoretical models of RSS are presented, as are experimental combustion data under simulated rocket conditions. N2O4/amine combustion chemistry data is also provided. More recent work in the development of a comprehensive model is described.

Isocyanide-mediated multicomponent synthesis of C-oximinoamidines.

PubMed

Mercalli, Valentina; Meneghetti, Fiorella; Tron, Gian Cesare

2013-11-15

By capitalizing on the different reactivity of nitrile N-oxides with isocyanides and amine, α-oximinoamidines, a so far elusive class of compounds, have been synthesized in a straightforward way by reacting isocyanides, syn-chlorooximes, and amines in a multicomponent fashion.

Highly Chemoselective Reduction of Amides (Primary, Secondary, Tertiary) to Alcohols using SmI2/Amine/H2O under Mild Conditions

PubMed Central

2014-01-01

Highly chemoselective direct reduction of primary, secondary, and tertiary amides to alcohols using SmI2/amine/H2O is reported. The reaction proceeds with C–N bond cleavage in the carbinolamine intermediate, shows excellent functional group tolerance, and delivers the alcohol products in very high yields. The expected C–O cleavage products are not formed under the reaction conditions. The observed reactivity is opposite to the electrophilicity of polar carbonyl groups resulting from the nX → π*C=O (X = O, N) conjugation. Mechanistic studies suggest that coordination of Sm to the carbonyl and then to Lewis basic nitrogen in the tetrahedral intermediate facilitate electron transfer and control the selectivity of the C–N/C–O cleavage. Notably, the method provides direct access to acyl-type radicals from unactivated amides under mild electron transfer conditions. PMID:24460078

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Yudie; Institute of Intelligent Machines, Chinese Academy of Sciences, Hefei 230031; Liu, Honglin, E-mail: hlliu@iim.ac.cn

Graphical abstract: - Highlights: • Mercapto groups were grafted to chitosan molecule by a reactive amine reduction. • Functional polymer with well-defined monomer units controls AuNPs assembly. • Assembled morphologies depend on the ratio of AuNPs to thiolate groups. • Microcubes with side length of ∼20 μm was synthesized through a dialysis step. • A edge-to-middle growth mechanism of gold microcubes was observed. - Abstract: The L-cysteine molecules were successfully grafted to the 2-amino group of chitosan by a reactive amine reduction, and the as-synthesized thiolated chitosan (TC) molecules were used as the templates to direct the self-assembly of goldmore » nanoparticles and induce the transformation of these assemblies to gold microcubes through a deep-going dialysis. We found that the ratio of gold nanoparticles to TC molecules could greatly affect the shape of the assembled clusters. Different stages of these clusters and microstructures during the dialysis process were characterized by scanning electron microscope (SEM), and the microcubes with average side length of about 20 μm were successfully synthesized. According to the morphology evolution of the assembly, it could be concluded that the microcubes were formed from external to internal. The SERS area mapping images of microcubes and some clusters were also collected to study the formation mechanism of gold microcubes. Our work demonstrates a simple and highly effective way to assemble gold nanoparticles into microcubes with unique properties.« less

Method for detecting the reactivity of chemicals towards peptides as an alternative test method for assessing skin sensitization potential.

PubMed

Cho, Sun-A; Jeong, Yun Hyeok; Kim, Ji Hoon; Kim, Seoyoung; Cho, Jun-Cheol; Heo, Yong; Heo, Young; Suh, Kyung-Do; Shin, Kyeho; An, Susun

2014-02-10

Cosmetics are normally composed of various ingredients. Some cosmetic ingredients can act as chemical haptens reacting toward proteins or peptides of human skin and they can provoke an immunologic reaction, called as skin sensitization. This haptenation process is very important step of inducing skin sensitization and evaluating the sensitizing potentials of cosmetic ingredients is very important for consumer safety. Therefore, animal alternative methods focusing on monitoring haptenation potential are undergoing vigorous research. To examine the further usefulness of spectrophotometric methods to monitor reactivity of chemicals toward peptides for cosmetic ingredients. Forty chemicals (25 sensitizers and 15 non-sensitizers) were reacted with 2 synthetic peptides, e.g., the cysteine peptides (Ac-RFAACAA-COOH) with free thiol group and the lysine peptides (Ac-RFAAKAA-COOH) with free amine group. Unreacted peptides can be detected after incubating with 5,5'-dithiobis-2-nitrobenzoic acid or fluorescamine™ as detection reagents for free thiol and amine group, respectively. Chemicals were categorized as sensitizers when they induced more than 10% depletion of cysteine peptides or more than 30% depletion of lysine peptides. The sensitivity, specificity, and accuracy were 80.0%, 86.7% and 82.5%, respectively. These results demonstrate that spectrophotometric methods can be an easy, fast, and high-throughput screening tools predicting the skin sensitization potential of chemical including cosmetic ingredient. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Chlorotrimethylsilane activation of acylcyanamides for the synthesis of mono-N-acylguanidines

PubMed Central

Haussener, Travis J.; Mack, James B. C.

2011-01-01

A simple and efficient one-pot method for the synthesis of mono-protected guanidines is presented. Treatment of an acylcyanamide with chlorotrimethylsilane generates a reactive N-silylcarbodiimide capable of guanylating a variety of amines. Typically the reaction is complete in 15 min for primary and secondary aliphatic amines at rt. Hindered amines and anilines are also competent nucleophiles but require extended reaction times. PMID:21732649

Primary amines protect against retinal degeneration in mouse models of retinopathies

PubMed Central

Maeda, Akiko; Golczak, Marcin; Chen, Yu; Okano, Kiichiro; Kohno, Hideo; Shiose, Satomi; Ishikawa, Kaede; Harte, William; Palczewska, Grazyna; Maeda, Tadao; Palczewski, Krzysztof

2011-01-01

Vertebrate vision is initiated by photoisomerization of the visual pigment chromophore, 11-cis-retinal, and is maintained by continuous regeneration of this retinoid through a series of reactions termed the retinoid cycle. However, toxic side reaction products, especially those involving reactive aldehyde groups of the photoisomered product, all-trans-retinal, can cause severe retinal pathology. Here we lowered peak concentrations of free all-trans-retinal with primary amine-containing FDA-approved drugs that did not inhibit chromophore regeneration in mouse models of retinal degeneration. Schiff base adducts between all-trans-retinal and these amines were identified by mass spectrometry. Adducts were observed in mouse eyes only when an experimental drug protected the retina from degeneration in both short-term and long-term treatment experiments. This study demonstrates a molecular basis of all-trans-retinal-induced retinal pathology and identifies an assemblage of FDA-approved compounds with protective effects against this pathology in a mouse model that displays features of Stargardt’s and age-related retinal degeneration. PMID:22198730

Carbonic anhydrase immobilized on hollow fiber membranes using glutaraldehyde activated chitosan for artificial lung applications

PubMed Central

Kimmel, J. D.; Arazawa, D. T.; Ye, S.-H.; Shankarraman, V.; Wagner, W. R.

2013-01-01

Extracorporeal CO2 removal from circulating blood is a promising therapeutic modality for the treatment of acute respiratory failure. The enzyme carbonic anhydrase accelerates CO2 removal within gas exchange devices by locally catalyzing HCO3− into gaseous CO2 within the blood. In this work, we covalently immobilized carbonic anhydrase on the surface of polypropylene hollow fiber membranes using glutaraldehyde activated chitosan tethering to amplify the density of reactive amine functional groups for enzyme immobilization. XPS and a colorimetric amine assay confirmed higher amine densities on the chitosan coated fiber compared to control fiber. Chitosan/CA coated fibers exhibited accelerated CO2 removal in scaled-down gas exchange devices in buffer and blood (115 % enhancement vs. control, 37 % enhancement vs. control, respectively). Carbonic anhydrase immobilized directly on hollow fiber membranes without chitosan tethering resulted in no enhancement in CO2 removal. Additionally, fibers coated with chitosan/carbonic anhydrase demonstrated reduced platelet adhesion when exposed to blood compared to control and heparin coated fibers. PMID:23888352

Atmospheric reactivity studies of aliphatic amines

USDA-ARS?s Scientific Manuscript database

Ambient studies of particulate matter have shown that alkyl amines are often present in particles in areas impacted by agricultural emissions. These locations include California’s Central Valley and Inland Empire and Utah’s Cache Valley. These compounds are not typically observed in airsheds that so...

Formation of NDMA and halogenated DBPs by chloramination of tertiary amines: the influence of bromide ion.

PubMed

Le Roux, Julien; Gallard, Hervé; Croué, Jean-Philippe

2012-02-07

The formation of NDMA and other DBPs (including THMs, HANs, and HKs) has been investigated by chloramination of several tertiary amines in the absence and presence of bromide ion. NDMA formation from the most reactive tertiary amines (e.g., dimethylaminomethylfurfuryl alcohol or DMP30) was enhanced in the presence of bromide due to the formation of brominated oxidant species such as bromochloramine (NHBrCl) and the hypothetical UDMH-Br as an intermediate. The formation of NDMA by chloramination of less reactive model compounds was inhibited in the presence of bromide. This can be explained by competitive reactions leading to the production of brominated DBPs (i.e., THMs). In the presence of bromide, the formation of brominated THMs during chloramination can be attributed to the presence of small amounts of HOBr produced by the decomposition of chloramines and bromamines. The results are of particular interest to understand NDMA formation mechanisms, especially during chloramination of wastewaters impacted by anthropogenic tertiary amines and containing bromide ion.

Effects of plant polyphenols and α-tocopherol on lipid oxidation, microbiological characteristics, and biogenic amines formation in dry-cured bacons.

PubMed

Wang, Yongli; Li, Feng; Zhuang, Hong; Li, Lianghao; Chen, Xiao; Zhang, Jianhao

2015-03-01

Effects of plant polyphenols (tea polyphenol [TP], grape seed extract [GSE], and gingerol) and α-tocopherol on physicochemical parameters, microbiological counts, and biogenic amines were determined in dry-cured bacons at the end of ripening. Results showed that plant polyphenols and α-tocopherol significantly decreased pH, thiobarbituric acid reactive substances content, and total volatile basic nitrogen (TVBN) compared with the control (P < 0.05). Microbial counts and biogenic amine contents in dry-cured bacons were affected by plant polyphenols or α-tocopherol, with TP being the most effective (P < 0.05) in reducing aerobic plate counts, Enterobacteriaceae, Micrococcaceae, yeast, and molds, as well as in inhibiting formation of putrescine, cadaverine, tyramine, and spermine. Principal component analysis indicated that the first 2 principal components (PC) explained about 85.5% of the total variation. PC1 was related with physicochemical factors, parts of biogenic amines, and spoilage microorganisms, whereas PC2 grouped the TVBN, tyramine, 2-phenylethylamine, yeast, and molds. These findings suggest that plant polyphenols, especially TP, could be used to process dry-cured bacons to improve the quality and safety of finished products. © 2015 Institute of Food Technologists®

Facile reductive amination of aldehydes with electron-deficient anilines by acyloxyborohydrides in TFA: application to a diazaindoline scale-up.

PubMed

Boros, Eric E; Thompson, James B; Katamreddy, Subba R; Carpenter, Andrew J

2009-05-01

A scale-up of diazaindoline 1 was achieved in four stages and 32% overall yield. The key step involved rapid reductive amination of aldehyde 8 with aniline 5 by sodium triacetoxyborohydride (STAB-H) and TFA followed by ring closure of intermediate amine 9 to compound 1 in the same pot. These reaction conditions were also applied to facile reductive aminations with anilines known to have little reactivity under STAB-H/AcOH conditions. Spectral data supported the tris(trifluoroacetoxy)borohydride anion (16) as the active reducing agent.

Assessing Chemical Transformation of Reactive, Interfacial Thin Films Made of End-Tethered Poly(2-vinyl-4,4-dimethyl azlactone) (PVDMA) Chains

DOE PAGES

Aden, Bethany; Kite, Camille M.; Hopkins, Benjamin W.; ...

2017-01-24

Designing thin films or surface scaffolds with an appropriate display of chemical functionality is useful for biomedical applications, sensing platforms, adhesives, and barrier coatings. Relationships between the structural characteristics of model thin films based on reactive poly(2-vinyl-4,4-dimethyl azlactone) (PVDMA) brushes and the amount and distribution of primary amines used to chemically functionalize these layers in situ are quantitatively detailed via neutron reflectometry and compared with results from ellipsometry. After functionalization, the PVDMA brush thickness increases as a result of the primary amines reacting with the azlactone rings. Both techniques show that the extent of functionalization by small-molecule amines depends onmore » the size of the amine, the grafting density of brush chains, and their molecular weight. However, constrained analysis of neutron reflectivity data predicated on that technique’s sensitivity to isotopic substitution and its ability to resolve structure at the nanoscale shows that the extent of functionalization is not accurately represented by the average extent of functionalization determined from ellipsometric thickness: reactive modification is not uniform, even in modestly dense brushes, except when the penetrant is small. In addition, there appears to be a loss of PVDMA chains during functionalization, attributed to chain scission resulting from additional stretching brought about by functionalization. In conclusion, these findings provide unprecedented insight into the alteration of surface properties by reactive modification and broadly support efforts to produce tailored surfaces in which properties such as friction, colloidal stability, adhesion, wettability, and biocompatibility can be modulated in situ by chemical modification.« less

Novel Micro/Nano Approaches for Glucose Measurement Using pH-Sensitive

DTIC Science & Technology

2006-06-01

step, the anionic enzyme was assembled in multilayers in alternation with poly(allylamine hydrochloride ) (PAH) (polycation). A total of three...group of D- glucosamine residues in chitosan can be conjugated with amine-reactive dyes, such as succinimidyl esters (Alexa Fluor 647™, CY5...measured values for FITC-chitosan were found to be: A494nm=0.153276 MW=161 [D- glucosamine ]=0.77g/L εdye=68000cm-1M-1

Supramolecular Recognition Allows Remote, Site-Selective C-H Oxidation of Methylenic Sites in Linear Amines.

PubMed

Olivo, Giorgio; Farinelli, Giulio; Barbieri, Alessia; Lanzalunga, Osvaldo; Di Stefano, Stefano; Costas, Miquel

2017-12-18

Site-selective C-H functionalization of aliphatic alkyl chains is a longstanding challenge in oxidation catalysis, given the comparable relative reactivity of the different methylenes. A supramolecular, bioinspired approach is described to address this challenge. A Mn complex able to catalyze C(sp 3 )-H hydroxylation with H 2 O 2 is equipped with 18-benzocrown-6 ether receptors that bind ammonium substrates via hydrogen bonding. Reversible pre-association of protonated primary aliphatic amines with the crown ether selectively exposes remote positions (C8 and C9) to the oxidizing unit, resulting in a site-selective oxidation. Remarkably, such control of selectivity retains its efficiency for a whole series of linear amines, overriding the intrinsic reactivity of C-H bonds, no matter the chain length. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A simple, broad-scope nickel(0) precatalyst system for direct amination of allyl alcohols.

PubMed

Sweeney, Joseph B; Ball, Anthony; Lawrence, Philippa; Sinclair, Mackenzie; Smith, Luke

2018-06-25

The preparation of allylic amines is traditionally accomplished by reaction of amines with reactive electrophiles, such as allylic halides, sulfonates or oxyphosphonium species; such methods involve hazardous reagents, generate stoichiometric waste streams, and often suffer from side-reactions (such as over-alkylation). We report here the first nickel-catalysed direct amination of allyl alcohols which enables allylation of primary, secondary and electron-deficient amines, using an inexpensive Ni(II)-Zn couple, without need for glove-box techniques. Under mild conditions, primary and secondary aliphatic amines react smoothly with a range of allyl alcohols, giving secondary and tertiary amines efficiently. This 'totally catalytic' method can be also applied to electron-deficient nitrogen nucleophiles with effective results; the practicality of the process has been demonstrated in an efficient, gram-scale preparation of the calcium antagonist drug substance flunarizine (Sibelium®). © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Temperature- and pH-dependent aqueous-phase kinetics of the reactions of glyoxal and methylglyoxal with atmospheric amines and ammonium sulfate

NASA Astrophysics Data System (ADS)

Sedehi, Nahzaneen; Takano, Hiromi; Blasic, Vanessa A.; Sullivan, Kristin A.; De Haan, David O.

2013-10-01

Reactions of glyoxal (Glx) and methylglyoxal (MG) with primary amines and ammonium salts may produce brown carbon and N-containing oligomers in aqueous aerosol. 1H NMR monitoring of reactant losses and product appearance in bulk aqueous reactions were used to derive rate constants and quantify competing reaction pathways as a function of pH and temperature. Glx + ammonium sulfate (AS) and amine reactions generate products containing C-N bonds, with rates depending directly on pH: rate = (70 ± 60) M-1 s-1fAld [Glx]totfAm [Am]tot, where fAld is the fraction of aldehyde with a dehydrated aldehyde functional group, and fAm is the fraction of amine or ammonia that is deprotonated at a given pH. MG + amine reactions generate mostly aldol condensation products and exhibit less pH dependence: rate = 10[(0.36 ± 0.06) × pH - (3.6 ± 0.3)] M-1 s-1fAld [MG]tot [Am]tot. Aldehyde + AS reactions are less temperature-dependent (Ea = 18 ± 8 kJ mol-1) than corresponding amine reactions (Ea = 50 ± 11 kJ mol-1). Using aerosol concentrations of [OH] = 10-12 M, [amine]tot = [AS] = 0.1 M, fGlx = 0.046 and fMG = 0.09, we estimate that OH radical reactions are normally the major aerosol-phase sink for both dicarbonyl compounds. However, reactions with AS and amines together can account for up to 12 and 45% of daytime aerosol-phase glyoxal and methylglyoxal reactivity, respectively, in marine aerosol at pH 5.5. Reactions with AS and amines become less important in acidic or non-marine aerosol, but may still be significant atmospheric sources of brown carbon, imidazoles, and nitrogen-containing oligomers.

Heterolytic Cleavage of H2 by Bifunctional Manganese(I) Complexes: Impact of Ligand Dynamics, Electrophilicity, and Base Positioning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hulley, Elliott B.; Helm, Monte L.; Bullock, R. Morris

2014-12-01

We report the synthesis, characterization, and reactivity with H2 of a series of MnI complexes of the type [(P-P)Mn(L2)CO]+ (L2 = dppm, bppm, or (CO)2; P-P = PPhNMePPh or PPh2 NBn2 ) that bear pendant amine ligands designed to function as proton relays. The pendant amine was found to function as a hemilabile ligand; its binding strength is strongly affected by the ancillary ligand environment around Mn. Tuning the electrophilicity of the Mn center leads to systems capable of reversible heterolytic cleavage of the H-H bond. The strength of pendant amine binding can be balanced to protect the Mn centermore » while still leading to facile reactivity with H2. Neutral amine-bearing MnIH species were found to react with one-electron oxidants and, after proton and electron transfer reactions, regenerate MnI cationic species. The reactivity presented herein indicate that the Mn complexes we have developed are a promising platform for Mn-based H2 oxidation electrocatalyst development. The research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for DOE.« less

C-H bond functionalization via hydride transfer: formation of α-arylated piperidines and 1,2,3,4-tetrahydroisoquinolines via stereoselective intramolecular amination of benzylic C-H bonds.

PubMed

Vadola, Paul A; Carrera, Ignacio; Sames, Dalibor

2012-08-17

We here report a study of the intramolecular amination of sp(3) C-H bonds via the hydride transfer cyclization of N-tosylimines (HT-amination). In this transformation, 5-aryl aldehydes are subjected to N-toluenesulfonamide in the presence of BF(3)·OEt(2) to effect imine formation and HT-cyclization, leading to 2-arylpiperidines and 3-aryl-1,2,3,4-tetrahydroisoquinolines in a one-pot procedure. We examined the reactivity of a range of aldehyde substrates as a function of their conformational flexibility. Substrates of higher conformational rigidity were more reactive, giving higher yields of the desired products. However, a single substituent on the alkyl chain linking the N-tosylimine and the benzylic sp(3) C-H bonds was sufficient for HT-cyclization to occur. In addition, an examination of various arenes revealed that the electronic character of the hydridic C-H bonds dramatically affects the efficiency of the reaction. We also found that this transformation is highly stereoselective; 2-substituted aldehydes yield cis-2,5-disubstituted piperidines, while 3-substituted aldehydes afford trans-2,4-disubstituted piperidines. The stereoselectivity is a consequence of thermodynamic control. The pseudoallylic strain between the arene and tosyl group on the piperidine ring is proposed to rationalize the greater stability of the isomer with the aryl ring in the axial position. This preferential placement of the arene is proposed to affect the observed stereoselectivity.

Borylnitrenes: electrophilic reactive intermediates with high reactivity towards C-H bonds.

PubMed

Bettinger, Holger F; Filthaus, Matthias

2010-12-21

Borylnitrenes (catBN 3a and pinBN 3b; cat = catecholato, pin = pinacolato) are reactive intermediates that show high tendency towards insertion into the C-H bonds of unactivated hydrocarbons. The present article summarizes the matrix isolation investigations that were aimed at identifying, characterizing and investigating the chemical behaviour of 3a by spectroscopic means, and of the experiments in solution and in the gas phase that were performed with 3b. Comparison with the reactivity reported for difluorovinylidene 1a in solid argon indicates that 3a shows by and large similar reactivity, but only after photochemical excitation. The derivative 3b inserts into the C-H bonds of hydrocarbon solvents in high yields and thus allows the formation of primary amines, secondary amines, or amides from "unreactive" hydrocarbons. It can also be used for generation of methylamine or methylamide from methane in the gas phase at room temperature. Remaining challenges in the chemistry of borylnitrenes are briefly summarized.

Efficient CO2 capture by functionalized graphene oxide nanosheets as fillers to fabricate multi-permselective mixed matrix membranes.

PubMed

Li, Xueqin; Cheng, Youdong; Zhang, Haiyang; Wang, Shaofei; Jiang, Zhongyi; Guo, Ruili; Wu, Hong

2015-03-11

A novel multi-permselective mixed matrix membrane (MP-MMM) is developed by incorporating versatile fillers functionalized with ethylene oxide (EO) groups and an amine carrier into a polymer matrix. The as-prepared MP-MMMs can separate CO2 efficiently because of the simultaneous enhancement of diffusivity selectivity, solubility selectivity, and reactivity selectivity. To be specific, MP-MMMs were fabricated by incorporating polyethylene glycol- and polyethylenimine-functionalized graphene oxide nanosheets (PEG-PEI-GO) into a commercial low-cost Pebax matrix. The PEG-PEI-GO plays multiple roles in enhancing membrane performance. First, the high-aspect ratio GO nanosheets in a polymer matrix increase the length of the tortuous path of gas diffusion and generate a rigidified interface between the polymer matrix and fillers, enhancing the diffusivity selectivity. Second, PEG consisting of EO groups has excellent affinity for CO2 to enhance the solubility selectivity. Third, PEI with abundant primary, secondary, and tertiary amine groups reacts reversibly with CO2 to enhance reactivity selectivity. Thus, the as-prepared MP-MMMs exhibit excellent CO2 permeability and CO2/gas selectivity. The MP-MMM doped with 10 wt % PEG-PEI-GO displays optimal gas separation performance with a CO2 permeability of 1330 Barrer, a CO2/CH4 selectivity of 45, and a CO2/N2 selectivity of 120, surpassing the upper bound lines of the Robeson study of 2008 (1 Barrer = 10(-10) cm(3) (STP) cm(-2) s(-1) cm(-1) Hg).

Oxidation of tertiary amines by cytochrome p450-kinetic isotope effect as a spin-state reactivity probe.

PubMed

Li, Chunsen; Wu, Wei; Cho, Kyung-Bin; Shaik, Sason

2009-08-24

Two types of tertiary amine oxidation processes, namely, N-dealkylation and N-oxygenation, by compound I (Cpd I) of cytochrome P450 are studied theoretically using hybrid DFT calculations. All the calculations show that both N-dealkylation and N-oxygenation of trimethylamine (TMA) proceed preferentially from the low-spin (LS) state of Cpd I. Indeed, the computed kinetic isotope effects (KIEs) for the rate-controlling hydrogen abstraction step of dealkylation show that only the KIE(LS) fits the experimental datum, whereas the corresponding value for the high-spin (HS) process is much higher. These results second those published before for N,N-dimethylaniline (DMA), and as such, they further confirm the conclusion drawn then that KIEs can be a sensitive probe of spin state reactivity. The ferric-carbinolamine of TMA decomposes most likely in a non-enzymatic reaction since the Fe-O bond dissociation energy (BDE) is negative. The computational results reveal that in the reverse reaction of N-oxygenation, the N-oxide of aromatic amine can serve as a better oxygen donor than that of aliphatic amine to generate Cpd I. This capability of the N-oxo derivatives of aromatic amines to transfer oxygen to the heme, and thereby generate Cpd I, is in good accord with experimental data previously reported.

Kinetic mechanism and structural requirements of the amine-catalyzed decarboxylation of oxaloacetic acid.

PubMed

Thalji, Nabil K; Crowe, William E; Waldrop, Grover L

2009-01-02

The kinetic and chemical mechanism of amine-catalyzed decarboxylation of oxaloacetic acid at pH 8.0 has been reevaluated using a new and versatile assay. Amine-catalyzed decarboxylation of oxaloacetic acid proceeds via the formation of an imine intermediate, followed by decarboxylation of the intermediate and hydrolysis to yield pyruvate. The decrease in oxaloacetic acid was coupled to NADH formation by malate dehydrogenase, which allowed the rates of both initial carbinolamine formation (as part of the imination step) and decarboxylation to be determined. By comparing the rates observed for a variety of amines and, in particular, diamines, the structural and electronic requirements for diamine-catalyzed decarboxylation at pH 8.0 were identified. At pH 8.0, monoamines were found to be very poor catalysts, whereas some diamines, most notably ethylenediamine, were excellent catalysts. The results indicate that the second amino group of diamines enhances the rate of imine formation by acting as a proton shuttle during the carbinolamine formation step, which enables diamines to overcome high levels of solvation that would otherwise inhibit carbinolamine, and thus imine, formation. The presence of the second amino group may also enhance the rate of the carbinolamine dehydration step. In contrast to the findings of previous reports, the second amino group participates in the reaction by enhancing the rate of decarboxylation via hydrogen-bonding to the imine nitrogen to either stabilize the negative charge that develops on the imine during decarboxylation or preferentially stabilize the reactive imine over the unreactive enamine tautomer. These results provide insight into the precise catalytic mechanism of several enzymes whose reactions are known to proceed via an imine intermediate.

Catalytic Properties of Unsupported Palladium Nanoparticle Surfaces Capped with Small Organic Ligands

PubMed Central

Gavia, Diego J.

2015-01-01

This Minireview summarizes a variety of intriguing catalytic studies accomplished by employing unsupported, either solubilized or freely mobilized, and small organic ligand-capped palladium nanoparticles as catalysts. Small organic ligands are gaining more attention as nanoparticle stabilizers and alternates to larger organic supports, such as polymers and dendrimers, owing to their tremendous potential for a well-defined system with spatial control in surrounding environments of reactive surfaces. The nanoparticle catalysts are grouped depending on the type of surface stabilizers with reactive head groups, which include thiolate, phosphine, amine, and alkyl azide. Applications for the reactions such as hydrogenation, alkene isomerization, oxidation, and carbon-carbon cross coupling reactions are extensively discussed. The systems defined as “ligandless” Pd nanoparticle catalysts and solvent (e.g. ionic liquid)-stabilized Pd nanoparticle catalysts are not discussed in this review. PMID:25937846

Kinetic determinations of accurate relative oxidation potentials of amines with reactive radical cations.

PubMed

Gould, Ian R; Wosinska, Zofia M; Farid, Samir

2006-01-01

Accurate oxidation potentials for organic compounds are critical for the evaluation of thermodynamic and kinetic properties of their radical cations. Except when using a specialized apparatus, electrochemical oxidation of molecules with reactive radical cations is usually an irreversible process, providing peak potentials, E(p), rather than thermodynamically meaningful oxidation potentials, E(ox). In a previous study on amines with radical cations that underwent rapid decarboxylation, we estimated E(ox) by correcting the E(p) from cyclic voltammetry with rate constants for decarboxylation obtained using laser flash photolysis. Here we use redox equilibration experiments to determine accurate relative oxidation potentials for the same amines. We also describe an extension of these experiments to show how relative oxidation potentials can be obtained in the absence of equilibrium, from a complete kinetic analysis of the reversible redox kinetics. The results provide support for the previous cyclic voltammetry/laser flash photolysis method for determining oxidation potentials.

Protecting-group-free synthesis of amines: synthesis of primary amines from aldehydes via reductive amination.

PubMed

Dangerfield, Emma M; Plunkett, Catherine H; Win-Mason, Anna L; Stocker, Bridget L; Timmer, Mattie S M

2010-08-20

New methodology for the protecting-group-free synthesis of primary amines is presented. By optimizing the metal hydride/ammonia mediated reductive amination of aldehydes and hemiacetals, primary amines were selectively prepared with no or minimal formation of the usual secondary and tertiary amine byproduct. The methodology was performed on a range of functionalized aldehyde substrates, including in situ formed aldehydes from a Vasella reaction. These reductive amination conditions provide a valuable synthetic tool for the selective production of primary amines in fewer steps, in good yields, and without the use of protecting groups.

Application of chemical reaction mechanistic domains to an ecotoxicity QSAR model, the KAshinhou Tool for Ecotoxicity (KATE).

PubMed

Furuhama, A; Hasunuma, K; Aoki, Y; Yoshioka, Y; Shiraishi, H

2011-01-01

The validity of chemical reaction mechanistic domains defined by skin sensitisation in the Quantitative Structure-Activity Relationship (QSAR) ecotoxicity system, KAshinhou Tools for Ecotoxicity (KATE), March 2009 version, has been assessed and an external validation of the current KATE system carried out. In the case of the fish end-point, the group of chemicals with substructures reactive to skin sensitisation always exhibited higher root mean square errors (RMSEs) than chemicals without reactive substructures under identical C- or log P-judgements in KATE. However, in the case of the Daphnia end-point this was not so, and the group of chemicals with reactive substructures did not always have higher RMSEs: the Schiff base mechanism did not function as a high error detector. In addition to the RMSE findings, the presence of outliers suggested that the KATE classification rules needs to be reconsidered, particularly for the amine group. Examination of the dependency of the organism on the toxic action of chemicals in fish and Daphnia revealed that some of the reactive substructures could be applied to the improvement of the KATE system. It was concluded that the reaction mechanistic domains of toxic action for skin sensitisation could provide useful complementary information in predicting acute aquatic ecotoxicity, especially at the fish end-point.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aden, Bethany; Kite, Camille M.; Hopkins, Benjamin W.

Designing thin films or surface scaffolds with an appropriate display of chemical functionality is useful for biomedical applications, sensing platforms, adhesives, and barrier coatings. Relationships between the structural characteristics of model thin films based on reactive poly(2-vinyl-4,4-dimethyl azlactone) (PVDMA) brushes and the amount and distribution of primary amines used to chemically functionalize these layers in situ are quantitatively detailed via neutron reflectometry and compared with results from ellipsometry. After functionalization, the PVDMA brush thickness increases as a result of the primary amines reacting with the azlactone rings. Both techniques show that the extent of functionalization by small-molecule amines depends onmore » the size of the amine, the grafting density of brush chains, and their molecular weight. However, constrained analysis of neutron reflectivity data predicated on that technique’s sensitivity to isotopic substitution and its ability to resolve structure at the nanoscale shows that the extent of functionalization is not accurately represented by the average extent of functionalization determined from ellipsometric thickness: reactive modification is not uniform, even in modestly dense brushes, except when the penetrant is small. In addition, there appears to be a loss of PVDMA chains during functionalization, attributed to chain scission resulting from additional stretching brought about by functionalization. In conclusion, these findings provide unprecedented insight into the alteration of surface properties by reactive modification and broadly support efforts to produce tailored surfaces in which properties such as friction, colloidal stability, adhesion, wettability, and biocompatibility can be modulated in situ by chemical modification.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aden, Bethany; Kite, Camille M.; Hopkins, Benjamin W.

Designing thin films or surface scaffolds with an appropriate display of chemical functionality is useful for biomedical applications, sensing platforms, adhesives, and barrier coatings. Relationships between the structural characteristics of model thin films based on reactive poly(2-vinyl-4,4-dimethylazlactone) (PVDMA) brushes and the amount and distribution of primary amines used to chemically functionalize the layer in situ are quantitatively detailed via neutron reflectometry and compared with results from ellipsometry. After functionalization, the PVDMA brush thickness increases as a result of the primary amines reacting with the azlactone rings. Both techniques show that the extent of functionalization by small-molecule amines depends on themore » size of the amine, the grafting density of brush chains and their molecular weight. However, constrained analysis of neutron reflectivity data predicated on that technique’s sensitivity to isotopic substitution and its ability to resolve structure at the nanoscale, shows that the extent of functionalization is not accurately represented by the average extent of functionalization determined from ellipsometric thickness: reactive modification is not uniform, even in modestly dense brushes, except when the penetrant is small. Additionally, there appears to be a loss of PVDMA chains during functionalization, attributed to chain scission resulting from additional stretching brought about by functionalization. These findings provide unprecedented insight into the alteration of surface properties by reactive modification and broadly support efforts to produce tailored surfaces in which properties such as friction, colloidal stability, adhesion, wettability, and biocompatibility can be modulated in situ by chemical modification.« less

Role of Amine Functionality for CO2 Chemisorption on Silica.

PubMed

Hahn, Maximilian W; Jelic, Jelena; Berger, Edith; Reuter, Karsten; Jentys, Andreas; Lercher, Johannes A

2016-03-03

The mechanism of CO2 adsorption on primary, secondary, and bibasic aminosilanes synthetically functionalized in porous SiO2 was qualitatively and quantitatively investigated by a combination of IR spectroscopy, thermogravimetry, and quantum mechanical modeling. The mode of CO2 adsorption depends particularly on the nature of the amine group and the spacing between the aminosilanes. Primary amines bonded CO2 preferentially through the formation of intermolecular ammonium carbamates, whereas CO2 was predominantly stabilized as carbamic acid, when interacting with secondary amines. Ammonium carbamate formation requires the transfer of the carbamic acid proton to a second primary amine group to form the ammonium ion and hence two (primary) amine groups are required to bind one CO2 molecule. The higher base strength of secondary amines enables the stabilization of carbamic acid, which is thereby hindered to interact further with nearby amine functions, because their association with Si-OH groups (either protonation or hydrogen bonding) does not allow further stabilization of carbamic acid as carbamate. Steric hindrance of the formation of intermolecular ammonium carbamates leads to higher uptake capacities for secondary amines functionalized in porous SiO2 at higher amine densities. In aminosilanes possessing a primary and a secondary amine group, the secondary amine group tends to be protonated by Si-OH groups and therefore does not substantially interact with CO2.

C-H Bond Functionalization via Hydride Transfer: Formation of α-Arylated Piperidines and 1,2,3,4-Tetrahydroisoquinolines via Stereoselective Intramolecular Amination of Benzylic C-H Bonds

PubMed Central

Vadola, Paul A.; Carrera, Ignacio; Sames, Dalibor

2012-01-01

We here report a study of the intramolecular amination of sp3 C-H bonds via the hydride transfer cyclization of N-tosylimines (HT-amination). In this transformation, 5-aryl-aldehydes are subjected to N-toluenesulfonamide in the presence of BF3•OEt2 to effect imine formation and HT-cyclization, leading to 2-aryl-piperidines and 3-aryl-1,2,3,4-tetrahydroisoquinolines in a one-pot procedure. We examined the reactivity of a range of aldehyde substrates as a function of their conformational flexibility. Substrates of higher conformational rigidity were more reactive, giving higher yields of the desired products. However, a single substituent on the alkyl chain linking the N-tosylimine and the benzylic sp3 C-H bonds was sufficient for HT-cyclization to occur. In addition, an examination of various arenes revealed that the electronic character of the hydridic C-H bonds dramatically affects the efficiency of the reaction. We also found that this transformation is highly stereoselective; 2-substituted aldehydes yield cis-2,5-disubstituted piperidines, while 3-substituted aldehydes afford trans-2,4-disubstituted piperidines. The stereoselectivity is a consequence of thermodynamic control. The pseudo-allylic strain between the arene and tosyl group on the piperidine ring is proposed to rationalize the greater stability of the isomer with the aryl ring in the axial position. This preferential placement of the arene is proposed to affect the observed stereoselectivity. PMID:22672002

Use of phosphoimidazolide-activated guanosine to investigate the nucleophilicity of spermine and spermidine

NASA Technical Reports Server (NTRS)

Kanavarioti, A.; Baird, E. E.; Smith, P. J.

1995-01-01

Guanosine 5'-phosphate 2-methylimidazolide (2-MeImpG), a labile phosphoimidazolide analog of guanosine triphosphate, was used to test the reactivity of the natural polyamines (PAs), spermine (spm) and spermidine (spd). The products are the guanosine 5'-phosphate-polyamine derivatives (PA-pG: spd-pG and spm-pG) which are quite stable in the range 4 < pH < 11. Our study is the first of which we are aware that reports on the nucleophilicity of these amines. The main findings are as follows. (i) HPLC analysis of the products indicates the formation of only two of the three possible spd products and only one of the two possible spm products. These results can be explained if only the primary amino groups of the two polyamines are reactive, while the secondary amino groups are rendered unreactive by a steric effect. The reactions of 2-MeImpG and other phosphoimidazolide derivatives of nucleosides (ImpNs) with primary and secondary monoamines support this interpretation (Kanavarioti et al. J. Org. Chem. 1995, 60, 632). (ii) The product ratio of the two spd-pG adducts derived from the primary amino groups varies between 2.40 and 0.71 in the range 6.1 < or equal to pH < or equal to 11.9. Such small variation in the product ratio can only be rationalized by the similar, but not identical, basicity of the two primary amino groups and provides strong support for a previously reported model for polyamine ionization (Onasch et. al. Biophys. Chem. 1984, 19, 245). (iii) On the basis of our kinetic determinations conditions at which the nucleophilicity of these amines is at a minimum and at which other interactions with ImpNs could be tested can be chosen.

Unexpectedly Facile Rh(I) Catalyzed Polymerization of Ethynylbenzaldehyde Type Monomers: Synthesis of Polyacetylenes Bearing Reactive and Easy Transformable Pendant Carbaldehyde Groups.

PubMed

Sedláček, Jan; Havelková, Lucie; Zedník, Jiří; Coufal, Radek; Faukner, Tomáš; Balcar, Hynek; Brus, Jiří

2017-04-01

The chain coordination polymerization of (ethynylarene)carbaldehydes with unprotected carbaldehyde groups, namely ethynylbenzaldehydes, 1-ethynylbenzene-3,5-dicarboxaldehyde, and 3-[(4-ethynylphenyl)ethynyl]benzaldehyde, is reported for the first time. Polymerization is catalyzed with various Rh(I) catalysts and yields poly(arylacetylene)s with one or two pendant carbaldehyde groups per monomeric unit. Surprisingly, the carbaldehyde groups of the monomers do not inhibit the polymerization unlike the carbaldehyde group of unsubstituted benzaldehyde that acts as a strong inhibitor of Rh(I) catalyzed polymerization of arylacetylenes. The inhibition ability of carbaldehyde groups in (ethynylarene)carbaldehydes seems to be eliminated owing to a simultaneous presence of unsaturated ethynyl groups in (ethynylarene)carbaldehydes. The reactive carbaldehyde groups make poly[(ethynylarene)carbaldehyde]s promising for functional appreciation via various postpolymerization modifications. The introduction of photoluminescence or chirality to poly(ethynylbenzaldehyde)s via quantitative modification of their carbaldehyde groups in reaction with either photoluminescent or chiral primary amines under formation of the polymers with Schiff-base-type pendant groups is given as an example. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reactivity measurement in estimation of benzoquinone and benzoquinone derivatives’ allergenicity

PubMed Central

Mbiya, Wilbes; Chipinda, Itai; Simoyi, Reuben H.; Siegel, Paul D.

2015-01-01

Benzoquinone (BQ) and benzoquinone derivatives (BQD) are used in the production of dyes and cosmetics. While BQ, an extreme skin sensitizer, is an electrophile known to covalently modify proteins via Michael Addition (MA) reaction whilst halogen substituted BQD undergo nucleophilic vinylic substitution (SNV) mechanism onto amine and thiol moieties on proteins, the allergenic effects of adding substituents on BQ have not been reported. The effects of inserting substituents on the BQ ring has not been studied in animal assays. However, mandated reduction/elimination of animals used in cosmetics testing in Europe has led to an increased need for alternatives for the prediction of skin sensitization potential. Electron withdrawing and electron donating substituents on BQ were assessed for effects on BQ reactivity toward nitrobenzene thiol (NBT). The NBT binding studies demonstrated that addition of EWG to BQ as exemplified by the chlorine substituted BQDs increased reactivity while addition of EDG as in the methyl substituted BQDs reduced reactivity. BQ and BQD skin allerginicity was evaluated in the murine local lymph node assay (LLNA). BQD with electron withdrawing groups had the highest chemical potency followed by unsubstituted BQ and the least potent were the BQD with electron donating groups. The BQD results demonstrate the impact of inductive effects on both BQ reactivity and allergenicity, and suggest the potential utility of chemical reactivity data for electrophilic allergen identification and potency ranking. PMID:26612505

Reactive Landing of Dendrimer Ions onto Activated Self-assembled Monolayer Surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Qichi; Laskin, Julia

2014-02-06

The reactivity of gaseous, amine-terminated polyamidoamine (PAMAM) dendrimer ions with activated self-assembled monolayer (SAM) surfaces terminated with N-hydroxysuccinimidyl ester groups (NHS-SAM) is examined using mass-selected ion deposition combined with in situ infrared reflection absorption spectroscopy (IRRAS). The reaction extent is determined from depletion of the infrared band at 1753 cm-1, corresponding to the stretching vibration of the NHS carbonyl groups following ion deposition. For reaction yields below 10%, NHS band depletion follows a linear dependence on the ion dose. By comparing the kinetics plots obtained for 1,12-dodecanediamine and different generations of dendrimer ions (G0–G3) containing 4, 8, 16, and 32more » terminal amino group, we demonstrate that the relative reaction efficiency increases linearly with the number of NH2 groups in the molecule. This finding is rationalized assuming the formation of multiple amide bonds upon collision of higher-generation dendrimers with NHS-SAM. Furthermore, by comparing the NHS band depletion following deposition of [M+4H]4+ ions of the G2 dendrimer at 30, 80, and 120 eV, we demonstrate that the ion’s kinetic energy has no measurable effect on reaction efficiency. Similarly, the ion’s charge state only has a minor effect on the reactive landing efficiency of dendrimer ions. Our results indicate that reactive landing is an efficient approach for highly selective covalent immobilization of complex multifunctional molecules onto organic surfaces terminated with labile functional groups.« less

Exploring the role of pendant amines in transition metal complexes for the reduction of N2 to hydrazine and ammonia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhattacharya, Papri; Prokopchuk, Demyan E.; Mock, Michael T.

2017-03-01

This review examines the synthesis and acid reactivity of transition metal dinitrogen complexes bearing diphosphine ligands containing pendant amine groups in the second coordination sphere. This manuscript is a review of the work performed in the Center for Molecular Electrocatalysis. This work was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy (U.S. DOE), Office of Science, Office of Basic Energy Sciences. EPR studies on Fe were performed using EMSL, a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located atmore » PNNL. Computational resources were provided by the National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory. Pacific Northwest National Laboratory is operated by Battelle for the U.S. DOE.« less

Monocyclic aromatic amines as potential human carcinogens: old is new again

PubMed Central

Skipper, Paul L.; Kim, Min Young; Sun, H.-L. Patty; Wogan, Gerald N.; Tannenbaum, Steven R.

2010-01-01

Alkylanilines are a group of chemicals whose ubiquitous presence in the environment is a result of the multitude of sources from which they originate. Exposure assessments indicate that most individuals experience lifelong exposure to these compounds. Many alkylanilines have biological activity similar to that of the carcinogenic multi-ring aromatic amines. This review provides an overview of human exposure and biological effects. It also describes recent investigations into the biochemical mechanisms of action that lead to the assessment that they are most probably more complex than those of the more extensively investigated multi-ring aromatic amines. Not only is nitrenium ion chemistry implicated in DNA damage by alkylanilines but also reactions involving quinone imines and perhaps reactive oxygen species. Recent results described here indicate that alkylanilines can be potent genotoxins for cultured mammalian cells when activated by exogenous or endogenous phase I and phase II xenobiotic-metabolizing enzymes. The nature of specific DNA damage products responsible for mutagenicity remains to be identified but evidence to date supports mechanisms of activation through obligatory N-hydroxylation as well as subsequent conjugation by sulfation and/or acetylation. A fuller understanding of the mechanisms of alkylaniline genotoxicity is expected to provide important insights into the environmental and genetic origins of one or more human cancers and may reveal a substantial role for this group of compounds as potential human chemical carcinogens. PMID:19887514

Metabolite screening of aromatic amine hair dyes using in vitro hepatic models.

PubMed

Skare, J A; Hewitt, N J; Doyle, E; Powrie, R; Elcombe, C

2009-11-01

Aromatic amines and heterocyclic amines are widely used ingredients in permanent hair dyes. However, little has been published on their potential for oxidation via hepatic cytochrome P450s. Therefore, the authors screened nine such compounds for their potential to undergo oxidative metabolism in human liver microsomes. Toluene-2,5-diamine (TDA), p-aminophenol, m-aminophenol, p-methylaminophenol, N,N'-bis(2-hydroxyethyl)-p-phenylenediamine, and 1-hydroxyethyl-4,5-diaminopyrazole showed no evidence of oxidative metabolism. Oxidized metabolites of 4-amino-2-hydroxytoluene (AHT), 2-methyl-5- hydroxyethylaminophenol (MHEAP), and phenyl methyl pyrazolone (PMP) were detected, but there was no evidence of beta-nicotinamide adenine dinucleotide phosphate (NADPH)-dependent covalent binding to microsomal protein, suggesting that these are not reactive metabolites. Metabolism of AHT, MHEAP, PMP, and TDA was further studied in human hepatocytes. All these compounds underwent conjugation, but no oxidative metabolites were found. The results suggest that none of the hair dye ingredients tested showed evidence of hepatic metabolism to potentially biologically reactive oxidized metabolites.

Amino Acid Degradations Produced by Lipid Oxidation Products.

PubMed

Hidalgo, Francisco J; Zamora, Rosario

2016-06-10

Differently to amino acid degradations produced by carbohydrate-derived reactive carbonyls, amino acid degradations produced by lipid oxidation products are lesser known in spite of being lipid oxidation a major source of reactive carbonyls in food. This article analyzes the conversion of amino acids into Strecker aldehydes, α-keto acids, and amines produced by lipid-derived free radicals and carbonyl compounds, as well as the role of lipid oxidation products on the reactions suffered by these compounds: the formation of Strecker aldehydes and other aldehydes from α-keto acids; the formation of Strecker aldehydes and olefins from amines; the formation of shorter aldehydes from Strecker aldehydes; and the addition reactions suffered by the olefins produced from the amines. The relationships among all these reactions and the effect of reaction conditions on them are discussed. This knowledge should contribute to better control food processing in order to favor the formation of desirable beneficial compounds and to inhibit the production of compounds with deleterious properties.

Immobilization-stabilization of proteins on nanofibrillated cellulose derivatives and their bioactive film formation.

PubMed

Arola, Suvi; Tammelin, Tekla; Setälä, Harri; Tullila, Antti; Linder, Markus B

2012-03-12

In a number of different applications for enzymes and specific binding proteins a key technology is the immobilization of these proteins to different types of supports. In this work we describe a concept for protein immobilization that is based on nanofibrillated cellulose (NFC). NFC is a form of cellulose where fibers have been disintegrated into fibrils that are only a few nanometers in diameter and have a very large aspect ratio. Proteins were conjugated through three different strategies using amine, epoxy, and carboxylic acid functionalized NFC. The conjugation chemistries were chosen according to the reactive groups on the NFC derivatives; epoxy amination, heterobifunctional modification of amino groups, and EDC/s-NHS activation of carboxylic acid groups. The conjugation reactions were performed in solution and immobilization was performed by spin coating the protein-NCF conjugates. The structure of NFC was shown to be advantageous for both protein performance and stability. The use of NFC allows all covalent chemistry to be performed in solution, while the immobilization is achieved by a simple spin coating or spreading of the protein-NFC conjugates on a support. This allows more scalable methods and better control of conditions compared to the traditional methods that depend on surface reactions.

Fischer carbene mediated covalent grafting of a peptide nucleic acid on gold surfaces and IR optical detection of DNA hybridization with a transition metalcarbonyl label

NASA Astrophysics Data System (ADS)

Srivastava, Pratima; Ghasemi, Mahsa; Ray, Namrata; Sarkar, Amitabha; Kocabova, Jana; Lachmanova, Stepanka; Hromadova, Magdalena; Boujday, Souhir; Cauteruccio, Silvia; Thakare, Pramod; Licandro, Emanuela; Fosse, Céline; Salmain, Michèle

2016-11-01

Amine-reactive surfaces comprising N-hydroxysuccinimide ester groups as well as much more unusual Fischer alkoxymetallocarbene groups were generated on gold-coated surfaces via self-assembled monolayers of carboxy- and azido-terminated thiolates, respectively. These functions were further used to immobilize homothymine peptide nucleic acid (PNA) decamer in a covalent fashion involving the primary amine located at its N-terminus. These stepwise processes were monitored by polarization modulation reflection - absorption infrared spectroscopy (PM-RAIRS) that gave useful information on the molecular composition of the organic layers. PNA grafting and hybridization with complementary DNA strand were successfully transduced by quartz crystal microbalance (QCM) measurements. Unfortunately, attempts to transduce the hybridization optically by IR in a label-free fashion were inconclusive. Therefore we undertook to introduce an IR reporter group, namely a transition metalcarbonyl (TMC) entity at the 5‧ terminus of complementary DNA. Evidence for the formation of PNA-DNA heteroduplex was brought by the presence of ν(Ctbnd O) bands in the 2000 cm-1 region of the IR spectrum of the gold surface owing to the metalcarbonyl label.

Exploring the potential energy surface for the interaction of sterically hindered trichloro(diethylenetriamine)gold(III) complexes with water.

PubMed

Dos Santos, Hélio F; Paschoal, Diego; Burda, Jaroslav V

2012-11-15

The reactivity of gold(III) complexes is analyzed for a series of derivatives of 3-azapentane-1,5-diamine (dien) tridentate ligand that can contain some bulky substituents. Two distinct series of compounds are considered where the dien ligand is either deprotonated (R-dien-H) or protonated (R-dien) at the secondary amine where R = ethyl (Et) or methyl (Me). While the deprotonated species will occur in neutral and basic solutions, the protonated forms are likely to be present in acidic environment. Hydration reaction (water/Cl(-) ligand exchange) of 14 complexes is modeled with quantum chemical calculations. Our calculations predict that the reactivity decreases with the increase in the molecular volume of the substituted dien ligand, and the calculated rate constants are in satisfactory agreement with experimental results. In addition, quantitative structure/reactivity models are proposed where the angle between the entering and leaving groups in the transition state structure (the reactivity angle) is used as a molecular descriptor. These models explain the trend of the relative reactivity of these complexes and can be used to design new ligands for gold(III) complexes aiming to adjust the reactivity of the complex.

Mechanochemical route to the synthesis of nanostructured Aluminium nitride

PubMed Central

Rounaghi, S. A.; Eshghi, H.; Scudino, S.; Vyalikh, A.; Vanpoucke, D. E. P.; Gruner, W.; Oswald, S.; Kiani Rashid, A. R.; Samadi Khoshkhoo, M.; Scheler, U.; Eckert, J.

2016-01-01

Hexagonal Aluminium nitride (h-AlN) is an important wide-bandgap semiconductor material which is conventionally fabricated by high temperature carbothermal reduction of alumina under toxic ammonia atmosphere. Here we report a simple, low cost and potentially scalable mechanochemical procedure for the green synthesis of nanostructured h-AlN from a powder mixture of Aluminium and melamine precursors. A combination of experimental and theoretical techniques has been employed to provide comprehensive mechanistic insights on the reactivity of melamine, solid state metal-organic interactions and the structural transformation of Al to h-AlN under non-equilibrium ball milling conditions. The results reveal that melamine is adsorbed through the amine groups on the Aluminium surface due to the long-range van der Waals forces. The high energy provided by milling leads to the deammoniation of melamine at the initial stages followed by the polymerization and formation of a carbon nitride network, by the decomposition of the amine groups and, finally, by the subsequent diffusion of nitrogen into the Aluminium structure to form h-AlN. PMID:27650956

"Clickable", trifunctional magnetite nanoparticles and their chemoselective biofunctionalization.

PubMed

Das, Manasmita; Bandyopadhyay, Debarati; Mishra, Debasish; Datir, Satyajit; Dhak, Prasanta; Jain, Sanyog; Maiti, Tapas Kumar; Basak, Amit; Pramanik, Panchanan

2011-06-15

A multifunctional iron oxide based nanoformulation for combined cancer-targeted therapy and multimodal imaging has been meticulously designed and synthesized using a chemoselective ligation approach. Novel superparamagnetic magnetite nanoparticles simultaneously functionalized with amine, carboxyl, and azide groups were fabricated through a sequence of stoichiometrically controllable partial succinylation and Cu (II) catalyzed diazo transfer on the reactive amine termini of 2-aminoethylphosphonate grafted magnetite nanoparticles (MNPs). Functional moieties associated with MNP surface were chemoselectively conjugated with rhodamine B isothiocyanate (RITC), propargyl folate (FA), and paclitaxel (PTX) via tandem nucleophic addition of amine to isothithiocyanates, Cu (I) catalyzed azide--alkyne click chemistry and carbodiimide-promoted esterification. An extensive in vitro study established that the bioactives chemoselectively appended to the magnetite core bequeathed multifunctionality to the nanoparticles without any loss of activity of the functional molecules. Multifunctional nanoparticles, developed in the course of the study, could selectively target and induce apoptosis to folate-receptor (FR) overexpressing cancer cells with enhanced efficacy as compared to the free drug. In addition, the dual optical and magnetic properties of the synthesized nanoparticles aided in the real-time tracking of their intracellular pathways also as apoptotic events through dual fluorescence and MR-based imaging.

Evaluation of the persistence of transformation products from ozonation of trace organic compounds - a critical review.

PubMed

Hübner, Uwe; von Gunten, Urs; Jekel, Martin

2015-01-01

Ozonation is an efficient treatment system to reduce the concentration of trace organic compounds (TrOCs) from technical aquatic systems such as drinking water, wastewater and industrial water, etc. Although it is well established that ozonation generally improves the removal of organic matter in biological post-treatment, little is known about the biodegradability of individual transformation products resulting from ozonation of TrOCs. This publication provides a qualified assessment of the persistence of ozone-induced transformation products based on a review of published product studies and an evaluation of the biodegradability of transformation products with the biodegradability probability program (BIOWIN) and the University of Minnesota Pathway Prediction System (UM-PPS). The oxidation of TrOCs containing the four major ozone-reactive sites (olefins, amines, aromatics and sulfur-containing compounds) follows well described reaction pathways leading to characteristic transformation products. Assessment of biodegradability revealed a high sensitivity to the formed products and hence the ozone-reactive site present in the target compound. Based on BIOWIN, efficient removal can be expected for products from cleavage of olefin groups and aromatic rings. In contrast, estimations and literature indicate that hydroxylamines and N-oxides, the major products from ozonation of secondary and tertiary amines are not necessarily better removed in biological post-treatment. According to UM-PPS, degradation of these products might even occur via reformation of the corresponding amine. Some product studies with sulfide-containing TrOCs showed a stoichiometric formation of sulfoxides from oxygen transfer reactions. However, conclusions on the fate of transformation products in biological post-treatment cannot be drawn based on BIOWIN and UM-PPS.

Permanganate oxidation of diclofenac: The pH-dependent reaction kinetics and a ring-opening mechanism.

PubMed

Cheng, Hanyang; Song, Dean; Liu, Huijuan; Qu, Jiuhui

2015-10-01

In this work, the fate of diclofenac (DCF) during permanganate (Mn(VII)) oxidation was investigated at environmentally relevant pH conditions (from 5 to 9). The batch experiments showed that the kinetics of the Mn(VII)/DCF reaction follows a second-order rate law with an apparent rate constant of 1.57±0.02 M(-1) s(-1) at pH 7 and 20 °C. The half-value of DCF was calculated to be 37.5 min, when the concentration of Mn(VII) (0.4 mM) was 20-fold excess of DCF. The pH-dependence of the reaction kinetics was investigated, and the DCF reactivity with Mn(VII) was found to decrease with increasing pH. The second-order rate constants were then quantitatively described by incorporating the species distribution of DCF. A lower reactivity of the anionic DCF (DCF(-)) in comparison with its neutral counterpart (DCF(0)) was most likely attributable to the interaction between the ionized carboxylate group and amine nitrogen position, which can reduce the nucleophilicity of amine nitrogen by inductive and resonance effects. Moreover, a range of degradation products and the corresponding structures were proposed on the basis of the LC-Q-TOF-MS analysis. A detailed ring-opening reaction mechanism was proposed as follows: Mn(VII) acts as an electrophile to attack the amine moiety, leading to the formation of the primary intermediate products 2,6-dichloroaniline and 5-hydroxy-diclofenac, which can be further transformed. The further degradation proceeded through a multistep process including ring-opening, decarboxylation, hydroxylation, and cyclation reactions. Copyright © 2014 Elsevier Ltd. All rights reserved.

Multicolor Upconversion Nanoparticles for Protein Conjugation

PubMed Central

Wilhelm, Stefan; Hirsch, Thomas; Patterson, Wendy M.; Scheucher, Elisabeth; Mayr, Torsten; Wolfbeis, Otto S.

2013-01-01

We describe the preparation of monodisperse, lanthanide-doped hexagonal-phase NaYF4 upconverting luminescent nanoparticles for protein conjugation. Their core was coated with a silica shell which then was modified with a poly(ethylene glycol) spacer and N-hydroxysuccinimide ester groups. The nanoparticles were characterized by transmission electron microscopy, Raman spectroscopy, X-ray diffraction, and dynamic light scattering. The N-hydroxysuccinimide ester functionalization renders them highly reactive towards amine nucleophiles (e.g., proteins). We show that such particles can be conjugated to proteins. The protein-reactive UCLNPs and their conjugates to streptavidin and bovine serum albumin display multicolor emissions upon 980-nm continuous wave laser excitation. Surface plasmon resonance studies were carried out to prove bioconjugation and to compare the affinity of the particles for proteins immobilized on a thin gold film. PMID:23606910

Synthesis of Thieno[3,2-b]indoles via Halogen Dance and Ligand-Controlled One-Pot Sequential Coupling Reaction.

PubMed

Hayashi, Yuki; Okano, Kentaro; Mori, Atsunori

2018-02-16

A two-pot synthesis of thieno[3,2-b]indole from 2,5-dibromothiophene is described. A halogen dance of 2,5-dibromothiophene was performed with LDA, and subsequent Negishi coupling was performed with 2-iodoaniline derivatives to provide the corresponding coupling products. The resulting two bromo groups have different reactivities, which were utilized for the one-pot Suzuki-Miyaura coupling/intramolecular Buchwald-Hartwig amination to produce thieno[3,2-b]indole via an assisted tandem catalysis that involved in situ ligand exchange.

Combining Amine-Reactive Cross-Linkers and Photo-Reactive Amino Acids for 3D-Structure Analysis of Proteins and Protein Complexes.

PubMed

Lössl, Philip; Sinz, Andrea

2016-01-01

During the last 15 years, the combination of chemical cross-linking and high-resolution mass spectrometry (MS) has matured into an alternative approach for analyzing 3D-structures of proteins and protein complexes. Using the distance constraints imposed by the cross-links, models of the protein or protein complex under investigation can be created. The majority of cross-linking studies are currently conducted with homobifunctional amine-reactive cross-linkers. We extend this "traditional" cross-linking/MS strategy by adding complementary photo-cross-linking data. For this, the diazirine-containing unnatural amino acids photo-leucine and photo-methionine are incorporated into the proteins and cross-link formation is induced by UV-A irradiation. The advantage of the photo-cross-linking strategy is that it is not restricted to lysine residues and that hydrophobic regions in proteins can be targeted, which is advantageous for investigating membrane proteins. We consider the strategy of combining cross-linkers with orthogonal reactivities and distances to be ideally suited for maximizing the amount of structural information that can be gained from a cross-linking experiment.

Effects of ultraviolet light on biogenic amines and other quality indicators of chicken meat during refrigerated storage.

PubMed

Lázaro, C A; Conte-Júnior, C A; Monteiro, M L G; Canto, A C V S; Costa-Lima, B R C; Mano, S B; Franco, R M

2014-09-01

Radiation from UV-C has been demonstrated as a potential surface decontamination method in addition to several advantages over regular sanitation methods. However, UV-C radiation possibly affects the physicochemical properties of meat products. To determine the optimum exposure time for bacterial reduction, 39 chicken breasts, inoculated with a pool of Salmonella spp., were submitted to 3 levels of UV-C intensities (0.62, 1.13, and 1.95 mW/cm²) for up to 120 s. After the optimum exposure time of 90 s was determined, changes in the biogenic amines, total aerobic mesophilic bacteria, Enterobacteriaceae, lipid oxidation, pH, and instrumental color were evaluated in 84 chicken breasts that were irradiated (0.62, 1.13, and 1.95 mW/cm²) and stored at 4°C for 9 d. The groups treated with UV-C radiation exhibited an increase in tyramine, cadaverine, and putrescine contents (P < 0.05). The highest UV-C intensity (1.95 mW/cm²) promoted a decrease in the initial bacterial load, and extended the lag phase and the shelf life. The groups irradiated with 1.13 and 1.95 mW/cm² exhibited a more stable b* value than the other groups; similar trends for L*, a*, pH, and TBA reactive substance values were observed among all groups. The UV-C light was demonstrated to be an efficient alternative technology to improve the bacteriological quality of chicken meat without negatively affecting the physical and chemical parameters of chicken breast meat. Nonetheless, the increases on the biogenic amines content should be considered as an effect of the UV processing and not as an indicator of bacterial growth. © 2014 Poultry Science Association Inc.

Reactive polymer multilayers fabricated by covalent layer-by-layer assembly: 1,4-conjugate addition-based approaches to the design of functional biointerfaces.

PubMed

Bechler, Shane L; Lynn, David M

2012-05-14

We report on conjugate addition-based approaches to the covalent layer-by-layer assembly of thin films and the post-fabrication functionalization of biointerfaces. Our approach is based on a recently reported approach to the "reactive" assembly of covalently cross-linked polymer multilayers driven by the 1,4-conjugate addition of amine functionality in poly(ethyleneimine) (PEI) to the acrylate groups in a small-molecule pentacrylate species (5-Ac). This process results in films containing degradable β-amino ester cross-links and residual acrylate and amine functionality that can be used as reactive handles for the subsequent immobilization of new functionality. Layer-by-layer growth of films fabricated on silicon substrates occurred in a supra-linear manner to yield films ≈ 750 nm thick after the deposition of 80 PEI/5-Ac layers. Characterization by atomic force microscopy (AFM) suggested a mechanism of growth that involves the reactive deposition of nanometer-scale aggregates of PEI and 5-Ac during assembly. Infrared (IR) spectroscopy studies revealed covalent assembly to occur by 1,4-conjugate addition without formation of amide functionality. Additional experiments demonstrated that acrylate-containing films could be postfunctionalized via conjugate addition reactions with small-molecule amines that influence important biointerfacial properties, including water contact angles and the ability of film-coated surfaces to prevent or promote the attachment of cells in vitro. For example, whereas conjugation of the hydrophobic molecule decylamine resulted in films that supported cell adhesion and growth, films treated with the carbohydrate-based motif D-glucamine resisted cell attachment and growth almost completely for up to 7 days in serum-containing media. We demonstrate that this conjugate addition-based approach also provides a means of immobilizing functionality through labile ester linkages that can be used to promote the long-term, surface-mediated release of conjugated species and promote gradual changes in interfacial properties upon incubation in physiological media (e.g., over a period of at least 1 month). These covalently cross-linked films are relatively stable in biological media for prolonged periods, but they begin to physically disintegrate after ≈ 30 days, suggesting opportunities to use this covalent layer-by-layer approach to design functional biointerfaces that ultimately erode or degrade to facilitate elimination.

Rethinking Cysteine Protective Groups: S-Alkylsulfonyl-l-Cysteines for Chemoselective Disulfide Formation.

PubMed

Schäfer, Olga; Huesmann, David; Muhl, Christian; Barz, Matthias

2016-12-12

The ability to reversibly cross-link proteins and peptides grants the amino acid cysteine its unique role in nature as well as in peptide chemistry. We report a novel class of S-alkylsulfonyl-l-cysteines and N-carboxy anhydrides (NCA) thereof for peptide synthesis. The S-alkylsulfonyl group is stable against amines and thus enables its use under Fmoc chemistry conditions and the controlled polymerization of the corresponding NCAs yielding well-defined homo- as well as block co-polymers. Yet, thiols react immediately with the S-alkylsulfonyl group forming asymmetric disulfides. Therefore, we introduce the first reactive cysteine derivative for efficient and chemoselective disulfide formation in synthetic polypeptides, thus bypassing additional protective group cleavage steps. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A reductive aminase from Aspergillus oryzae

NASA Astrophysics Data System (ADS)

Aleku, Godwin A.; France, Scott P.; Man, Henry; Mangas-Sanchez, Juan; Montgomery, Sarah L.; Sharma, Mahima; Leipold, Friedemann; Hussain, Shahed; Grogan, Gideon; Turner, Nicholas J.

2017-10-01

Reductive amination is one of the most important methods for the synthesis of chiral amines. Here we report the discovery of an NADP(H)-dependent reductive aminase from Aspergillus oryzae (AspRedAm, Uniprot code Q2TW47) that can catalyse the reductive coupling of a broad set of carbonyl compounds with a variety of primary and secondary amines with up to >98% conversion and with up to >98% enantiomeric excess. In cases where both carbonyl and amine show high reactivity, it is possible to employ a 1:1 ratio of the substrates, forming amine products with up to 94% conversion. Steady-state kinetic studies establish that the enzyme is capable of catalysing imine formation as well as reduction. Crystal structures of AspRedAm in complex with NADP(H) and also with both NADP(H) and the pharmaceutical ingredient (R)-rasagiline are reported. We also demonstrate preparative scale reductive aminations with wild-type and Q240A variant biocatalysts displaying total turnover numbers of up to 32,000 and space time yields up to 3.73 g l-1 d-1.

Evolution of a Fourth Generation Catalyst for the Amination and Thioetherification of Aryl Halides

PubMed Central

Hartwig, John F.

2010-01-01

Conspectus Synthetic methods to form the carbon-nitrogen bonds in aromatic amines are fundamental enough to be considered part of introductory organic courses. Arylamines are important because they are common precursors to or substructures within active pharmaceutical ingredients and herbicides produced on ton scales, as well as conducting polymers and layers of organic light-emitting diodes produced on small scale. For many years, this class of compound was prepared from classical methods, such as nitration, reduction and reductive alkylation, copper-mediated chemistry at high temperatures, addition to benzyne intermediates, or direct nucleophilic substitution on particularly electron-poor aromatic or heteroaromatic halides. During the past decade, these methods to form aromatic amines have been largely supplanted by palladium-catalyzed coupling reactions of amines with aryl halides. The scope and efficiency of the palladium-catalyzed processes has gradually improved with successive generations of catalysts to the point of being useful for the synthesis of both milligrams and kilograms of product. This Account describes the conceptual basis and utility of our latest, “fourth-generation” catalyst for the coupling of amines and related reagents with aryl halides. The introductory sections of this account describe the progression of catalyst development from the first-generation to current systems and the motivation for selection of the components of the fourth-generation catalyst. This progression began with catalysts containing palladium and sterically hindered monodentate aromatic phosphines used initially for coupling of tin amides with haloarenes in the first work on C-N coupling. A second generation of catalysts was then developed based on the combination of palladium and aromatic bisphosphines. These systems were then followed by third-generation systems catalysts on the combination of palladium and a sterically hindered alkylmonophosphine or N-heterocyclic carbene. During the past five years, we have studied a fourth-generation catalyst for these reactions containing ligands that combine the chelating properties of the second-generation systems with the steric hindrance and strong electron donation of the third-generation systems. This combination has created a catalyst that couples aryl chlorides, bromides and iodides with primary amines, N-H imines, and hydrazones in high yield, with broad scope, high functional group tolerance, nearly perfect selectivity for monoarylation, and the lowest levels of palladium that have been used for C-N coupling. This catalyst is based on palladium and a sterically hindered version of the Josiphos family of ligands that possesses a ferrocenyl-1-ethylbackbone, a hindered di-tert-butylphosphino group, and a hindered dicyclohexylphosphino group. This latest generation of catalyst not only improves the coupling of primary amines and related nucleophiles, but it has dramatically improved the coupling of thiols with haloarenes to form C-S bonds. This catalyst system couples both aliphatic and aromatic thiols with chloroarenes with much greater scope, functional group tolerance, and turnover numbers than had been observed previously. The effects of structural features of the Josiphos ligand on catalyst activity have been revealed by examining the reactivity of catalysts generated from ligands lacking one or more of the structural elements of the most active catalyst. These modified ligands lack the relative stereochemistry of the ferrocenyl-1-ethyl backbone, the strong electron donation of the dialkylphosphino groups, the steric demands of the alkylphosphine groups, or the stability of the ferrocenyl unit. This set of studies showed that each one of these structural features contributed to the high reactivity and selectivity of the catalyst containing the hindered, bidentate Josiphos ligand. Finally, a series of studies on the effect of electronic properties on the rates of reductive elimination have recently distinguished between the effect of the properties of the M-N σ-bond and the nitrogen electron pair on the rate of reductive elimination. These studies have shown that the effect of substituents attached to the metal-bound nitrogen or carbon atoms on the rate of reductive elimination are similar. Because the amido ligands contain an electron pair, while the alkyl ligands do not, we have concluded that the major electronic effect is transmitted through the σ-bond. In other words, we have concluded that the electronic effect on the metal-nitrogen σ bond dominates an electronic effect on the nitrogen electron pair. PMID:18681463

Design and Synthesis of Bifunctional Oxime Reactivators of OP- inhibited Cholinesterase

DTIC Science & Technology

2013-08-01

was introduce the 2- aldehyde as a nitrile via the pyridine N-oxide. Another approach (II), was to simply perform 2- hydoxymethylation of pyridines...original design plan called for introducing an aldehyde that could be coupled to various amines and diamines through reductive amination. Interestingly...chromatography DCM: MeOH (90:10) as a yellow oil. Synthesis of 37 (Oxime formation general procedure) To the ketone 36 (340 mg, 1,123 mmol) in 1

Polyacrolein microspheres

NASA Technical Reports Server (NTRS)

Rembaum, Alan (Inventor)

1983-01-01

Microspheres of acrolein homopolymers and co-polymer with hydrophillic comonomers such as methacrylic acid and/or hydroxyethylmethacrylate are prepared by cobalt gamma irradiation of dilute aqueous solutions of the monomers in presence of suspending agents, especially alkyl sulfates such as sodium dodecyl sulfate. Amine or hydroxyl modification is achieved by forming adducts with diamines or alkanol amines. Carboxyl modification is effected by oxidation with peroxides. Pharmaceuticals or other aldehyde reactive materials can be coupled to the microspheres. The microspheres directly form antibody adducts without agglomeration.

Polyacrolein microspheres

NASA Technical Reports Server (NTRS)

Rembaum, Alan (Inventor)

1986-01-01

Microspheres of acrolein homopolymers and copolymer with hydrophillic comonomers such as methacrylic acid and/or hydroxyethylmethacrylate are prepared by cobalt gamma irradiation of dilute aqueous solutions of the monomers in presence of suspending agents, especially alkyl sulfates such as sodium dodecyl sulfate. Amine or hydroxyl modification is achieved by forming adducts with diamines or alkanol amines. Carboxyl modification is effected by oxidation with peroxides. Pharmaceuticals or other aldehyde reactive materials can be coupled to the microspheres. The microspheres directly form antibody adducts without agglomeration.

Polyacrolein microspheres

NASA Technical Reports Server (NTRS)

Rembaum, Alan (Inventor)

1987-01-01

Microspheres of acrolein homopolymers and copolymer with hydrophillic comonomers such as methacrylic acid and/or hydroxyethylmethacrylate are prepared by cobalt gamma irradiation of dilute aqueous solutions of the monomers in presence of suspending agents, especially alkyl sulfates such as sodium dodecyl sulfate. Amine or hydroxyl modification is achieved by forming adducts with diamines or alkanol amines. Carboxyl modification is effected by oxidation with peroxides. Pharmaceuticals or other aldehyde reactive materials can be coupled to the microspheres. The microspheres directly form antibody adducts without agglomeration.

Geometry dependence of electron donating or accepting abilities of amine groups in 4,4‧-disulfanediylbis(methylene)dithiazol-2-amine: Pyramidal versus planar

NASA Astrophysics Data System (ADS)

Karabıyık, Hasan; Kırılmış, Cumhur; Karabıyık, Hande

2017-08-01

The molecular and crystal structure of the title compound in which two thiazole-2-amine rings are linked to each other by disulfide bridge (sbnd Csbnd Ssbnd Ssbnd Csbnd) were studied by single-crystal X-ray diffraction, FT-IR, NMR spectroscopy, quantum chemical calculations and topological analyses on the electron density. A novel synthesis route for the compounds having symmetrical disulfide bridge is reported. The most important result regarding the compound is about electron donating or accepting properties of the terminal amine groups. Planar amine group acts as an electron-donating group, while pyramidal amine behaves as electron-accepting group. This inference was confirmed by scrutiny of crystallographic geometry and quantum chemical studies. To ascertain underlying reasons for this fact, intermolecular interactions (Nsbnd H⋯N type H-bonds and Csbnd H···π interactions) were studied. These interactions involving aromatic thiazole rings are verified by topological electron density and Hirshfeld surface analyses. Intermolecular interactions do not have an effect on the differentiation in electron donating or accepting ability of amine groups, because both amine groups are involved in Nsbnd H⋯N type H-bonds. In methodological sense, it has been understood that Ehrenfest forces acting on electron density are useful theoretical probe to analyze intra-molecular charge transfer processes.

Nanoporous carbon for electric double layer supercapacitor electrodes

NASA Astrophysics Data System (ADS)

Garcia, Betzaida Batalla

The subject of this study is the synthesis, characterization, chemical composition, and tuning of the porous structure of organic and carbon cryogels for electrochemical applications, particularly supercapacitors. Alternate methods such as an improved synthesis using a reactive catalyst, surface chemical modifications and an electrochemical characterization that takes into account the pore morphology are discussed. Impedance spectroscopy, complex capacitance and power were used to identify key energy losses in the capacitor; an optimal pore size of ca. 2 nm and other features were found. Also, synthesis modification and surface chemistry were used to improve the chemistry and structure of the electrodes reducing metal impurities and removing detrimental functional groups. First, carbon cryogels produced without metal ion impurities were synthesized using hexamine (an amine base catalyst), resorcinol, furaldehyde and solvent mixtures. These metal ion free amine-catalyzed gels also produced strong cryogels that can be machined. The carbon cryogels produced using the amine catalyst have cycle stability performances that exceed that of commercial samples. Carbon cryogels were also doped using ammonia borane to promote boron and nitrogen esters and improved the capacitance up to 30% due to faradaic reactions. Furthermore, nitrogen esters were also introduced into the carbon (via pyrolysis of hexamine) with yields of up to 14 at%. These new esters have low content of oxygen and increased the capacitance up to 50%.

Characterization of N-nitrosodimethylamine formation from the ozonation of ranitidine.

PubMed

Lv, Juan; Wang, Lin; Li, Yongmei

2017-08-01

N-nitrosodimethylamine (NDMA) is an emerging disinfection by-product which is formed during water disinfection in the presence of amine-based precursors. Ranitidine, as one kind of amine-based pharmaceuticals, has been identified as NDMA precursor with high NDMA molar conversion during chloramination. This study focused on the characterization of NDMA formation during ozonation of ranitidine. Influences of operational variables (ozone dose, pH value) and water matrix on NDMA generation as well as ranitidine degradation were evaluated. The results indicate high reactivity of ranitidine with ozone. Dimethylamine (DMA) and NDMA were generated due to ranitidine oxidation. High pH value caused more NDMA accumulation. NDMA formation was inhibited under acid conditions (pH≤5) mainly due to the protonation of amines. Water matrix such as HCO 3 - and humic acid impacted NDMA generation due to OH scavenging. Compared with OH, ozone molecules dominated the productions of DMA and NDMA. However, OH was a critical factor in NDMA degradation. Transformation products of ranitidine during ozonation were identified using gas chromatography-mass spectrometry. Among these products, just DMA and N,N-dimethylformamide could contribute to NDMA formation due to the DMA group in the molecular structures. The NDMA formation pathway from ranitidine ozonation was also proposed. Copyright © 2017. Published by Elsevier B.V.

Fate and transformation products of amine-terminated PAMAM dendrimers under ozonation and irradiation.

PubMed

Santiago-Morales, Javier; Rosal, Roberto; Hernando, María D; Ulaszewska, Maria M; García-Calvo, Eloy; Fernández-Alba, Amadeo R

2014-02-15

This article deals with the degradation of a third-generation (G3) poly(amidoamine) (PAMAM) dendrimer under ozonation and irradiation. The identification and quantification of G3 PAMAM dendrimer and its transformation products has been performed by liquid chromatography-electrospray ionization-hybrid quadrupole time-of-flight-mass spectrometry. The dendrimer was completely depleted by ozone in less than 1 min. The effect of ultraviolet irradiation was attributed to hydroxyl-mediated oxidation. The transformation products were attributed to the oxidation of amines, which resulted in highly oxidized structures with abundance of carboxylic acids, which started from the formation of amine oxide and the scission of the CN bond of the amide group. We studied the toxicity of treated mixtures for six different organisms: the acute toxicity for the bacterium Vibrio fischeri and the microcrustacean Daphnia magna, the multigenerational growth inhibition of the alga Pseudokirchneriella subcapitata, and the seed germination phytotoxicity of Licopersicon esculentum, Lactuca sativa and Lolium perenne. Ozonation and irradiation originated transformation products are more toxic than the parent dendrimer. The toxicity of the dendrimer for the green alga was linked to a strong increase of intracellular reactive oxygen species with intense lipid peroxidation. Copyright © 2013 Elsevier B.V. All rights reserved.

Organometallics in High Energy Chemistry.

DTIC Science & Technology

1983-10-31

Luines Physeical ftaenc Chemistry DepatneWu. SJI International. Menlo PWr *. CaiOwrnia M10 Rceived Nouvber 8. 1IM The otslytic formation of6nw carbon...support the idea that the metalloazocyclopropane intermediate is the reactive intermediate that leads to transalkylation. A discussion of the...exceptionally good correlation between the catalytic reactivity patterns of palladium black in its reactions with tertiary amines and those of homogeneous

Preparation of aminated chitosan/alginate scaffold containing halloysite nanotubes with improved cell attachment.

PubMed

Amir Afshar, Hamideh; Ghaee, Azadeh

2016-10-20

The chemical nature of biomaterials play important role in cell attachment, proliferation and migration in tissue engineering. Chitosan and alginate are biodegradable and biocompatible polymers used as scaffolds for various medical and clinical applications. Amine groups of chitosan scaffolds play an important role in cell attachment and water adsorption but also associate with alginate carboxyl groups via electrostatic interactions and hydrogen bonding, consequently the activity of amine groups in the scaffold decreases. In this study, chitosan/alginate/halloysite nanotube (HNTs) composite scaffolds were prepared using a freeze-drying method. Amine treatment on the scaffold occurred through chemical methods, which in turn caused the hydroxyl groups to be replaced with carboxyl groups in chitosan and alginate, after which a reaction between ethylenediamine, 1-ethyl-3,(3-dimethylaminopropyl) carbodiimide (EDC) and scaffold triggered the amine groups to connect to the carboxyl groups of chitosan and alginate. The chemical structure, morphology and mechanical properties of the composite scaffolds were investigated by FTIR, CHNS, SEM/EDS and compression tests. The electrostatic attraction and hydrogen bonding between chitosan, alginate and halloysite was confirmed by FTIR spectroscopy. Chitosan/alginate/halloysite scaffolds exhibit significant enhancement in compressive strength compared with chitosan/alginate scaffolds. CHNS and EDS perfectly illustrate that amine groups were effectively introduced in the aminated scaffold. The growth and cell attachment of L929 cells as well as the cytotoxicity of the scaffolds were investigated by SEM and Alamar Blue (AB). The results indicated that the aminated chitosan/alginate/halloysite scaffold has better cell growth and cell adherence in comparison to that of chitosan/alginate/halloysite samples. Aminated chitosan/alginate/halloysite composite scaffolds exhibit great potential for applications in tissue engineering, ideally in cell culture. Copyright © 2016 Elsevier Ltd. All rights reserved.

New reactive polymer for protein immobilisation on sensor surfaces.

PubMed

Kyprianou, Dimitris; Guerreiro, Antonio R; Chianella, Iva; Piletska, Elena V; Fowler, Steven A; Karim, Kal; Whitcombe, Michael J; Turner, Anthony P F; Piletsky, Sergey A

2009-01-01

Immobilisation of biorecognition elements on transducer surfaces is a key step in the development of biosensors. The immobilisation needs to be fast, cheap and most importantly should not affect the biorecognition activity of the immobilised receptor. A novel protocol for the covalent immobilisation of biomolecules containing primary amines using an inexpensive and simple polymer is presented. This tri-dimensional (3D) network leads to a random immobilisation of antibodies on the polymer and ensures the availability of a high percentage of antibody binding sites. The reactivity of the polymer is based on the reaction between primary amines and thioacetal groups included in the polymer network. These functional groups (thioacetal) do not need any further activation in order to react with proteins, making it attractive for sensor fabrication. The novel polymer also contains thiol derivative groups (disulphide groups or thioethers) that promote self-assembling on a metal transducer surface. For demonstration purposes the polymer was immobilised on Au Biacore chips. The resulting polymer layer was characterised using contact angle meter, atomic force microscopy (AFM) and ellipsometry. A general protocol suitable for the immobilisation of bovine serum albumin (BSA), enzymes and antibodies such as polyclonal anti-microcystin-LR antibody and monoclonal anti-prostate specific antigen (anti-PSA) antibody was then optimised. The affinity characteristics of developed immunosensors were investigated in reaction with microcystin-LR, and PSA. The calculated detection limit for analytes depended on the properties of antibodies. The detection limit for microcystin-LR was 10 ngmL(-1) and for PSA 0.01 ngmL(-1). The non-specific binding of analytes to synthesised polymers was very low. The polymer-coated chips were stored for up to 2 months without any noticeable deterioration in their ability to react with proteins. These findings make this new polymer very promising for the development of low-cost, easy to prepare and sensitive biosensors.

Polyethylene Glycol Propionaldehydes

NASA Technical Reports Server (NTRS)

Harris, Joe M.; Sedaghat-Herati, Mohammad R.; Karr, Laurel J.

1992-01-01

New class of compounds derived from polyethylene glycol (PEG's) namely, PEG-propionaldehydes, offers two important advantages over other classes of PEG aldehyde derivatives: compounds exhibit selective chemical reactivity toward amino groups and are stable in aqueous environment. PEG's and derivatives used to couple variety of other molecules, such as, to tether protein molecules to surfaces. Biotechnical and biomedical applications include partitioning of two phases in aqueous media; immobilization of such proteins as enzymes, antibodies, and antigens; modification of drugs; and preparation of protein-rejecting surfaces. In addition, surfaces coated with PEG's and derivatives used to control wetting and electroosmosis. Another potential application, coupling to aminated surfaces.

Formation Mechanism of NDMA from Ranitidine, Trimethylamine, and Other Tertiary Amines during Chloramination: A Computational Study

PubMed Central

2015-01-01

Chloramination of drinking waters has been associated with N-nitrosodimethylamine (NDMA) formation as a disinfection byproduct. NDMA is classified as a probable carcinogen and thus its formation during chloramination has recently become the focus of considerable research interest. In this study, the formation mechanisms of NDMA from ranitidine and trimethylamine (TMA), as models of tertiary amines, during chloramination were investigated by using density functional theory (DFT). A new four-step formation pathway of NDMA was proposed involving nucleophilic substitution by chloramine, oxidation, and dehydration followed by nitrosation. The results suggested that nitrosation reaction is the rate-limiting step and determines the NDMA yield for tertiary amines. When 45 other tertiary amines were examined, the proposed mechanism was found to be more applicable to aromatic tertiary amines, and there may be still some additional factors or pathways that need to be considered for aliphatic tertiary amines. The heterolytic ONN(Me)2–R+ bond dissociation energy to release NDMA and carbocation R+ was found to be a criterion for evaluating the reactivity of aromatic tertiary amines. A structure–activity study indicates that tertiary amines with benzyl, aromatic heterocyclic ring, and diene-substituted methenyl adjacent to the DMA moiety are potentially significant NDMA precursors. The findings of this study are helpful for understanding NDMA formation mechanism and predicting NDMA yield of a precursor. PMID:24968236

Formation mechanism of NDMA from ranitidine, trimethylamine, and other tertiary amines during chloramination: a computational study.

PubMed

Liu, Yong Dong; Selbes, Meric; Zeng, Chengchu; Zhong, Rugang; Karanfil, Tanju

2014-01-01

Chloramination of drinking waters has been associated with N-nitrosodimethylamine (NDMA) formation as a disinfection byproduct. NDMA is classified as a probable carcinogen and thus its formation during chloramination has recently become the focus of considerable research interest. In this study, the formation mechanisms of NDMA from ranitidine and trimethylamine (TMA), as models of tertiary amines, during chloramination were investigated by using density functional theory (DFT). A new four-step formation pathway of NDMA was proposed involving nucleophilic substitution by chloramine, oxidation, and dehydration followed by nitrosation. The results suggested that nitrosation reaction is the rate-limiting step and determines the NDMA yield for tertiary amines. When 45 other tertiary amines were examined, the proposed mechanism was found to be more applicable to aromatic tertiary amines, and there may be still some additional factors or pathways that need to be considered for aliphatic tertiary amines. The heterolytic ONN(Me)2-R(+) bond dissociation energy to release NDMA and carbocation R(+) was found to be a criterion for evaluating the reactivity of aromatic tertiary amines. A structure-activity study indicates that tertiary amines with benzyl, aromatic heterocyclic ring, and diene-substituted methenyl adjacent to the DMA moiety are potentially significant NDMA precursors. The findings of this study are helpful for understanding NDMA formation mechanism and predicting NDMA yield of a precursor.

Visible light induced green transformation of primary amines to imines using a silicate supported anatase photocatalyst.

PubMed

Zavahir, Sifani; Zhu, Huaiyong

2015-01-26

Catalytic oxidation of amine to imine is of intense present interest since imines are important intermediates for the synthesis of fine chemicals, pharmaceuticals, and agricultural chemicals. However, considerable efforts have been made to develop efficient methods for the oxidation of secondary amines to imines, while little attention has until recently been given to the oxidation of primary amines, presumably owing to the high reactivity of generated imines of primary amines that are easily dehydrogenated to nitriles. Herein, we report the oxidative coupling of a series of primary benzylic amines into corresponding imines with dioxygen as the benign oxidant over composite catalysts of TiO2 (anatase)-silicate under visible light irradiation of λ > 460 nm. Visible light response of this system is believed to be as a result of high population of defects and contacts between silicate and anatase crystals in the composite and the strong interaction between benzylic amine and the catalyst. It is found that tuning the intensity and wavelength of the light irradiation and the reaction temperature can remarkably enhance the reaction activity. Water can also act as a green medium for the reaction with an excellent selectivity. This report contributes to the use of readily synthesized, environmentally benign, TiO2 based composite photocatalyst and solar energy to realize the transformation of primary amines to imine compounds.

Quantification of amine functional groups and their influence on OM/OC in the IMPROVE network

NASA Astrophysics Data System (ADS)

Kamruzzaman, Mohammed; Takahama, Satoshi; Dillner, Ann M.

2018-01-01

Recently, we developed a method using FT-IR spectroscopy coupled with partial least squares (PLS) regression to measure the four most abundant organic functional groups, aliphatic C-H, alcohol OH, carboxylic acid OH and carbonyl C=O, in atmospheric particulate matter. These functional groups are summed to estimate organic matter (OM) while the carbon from the functional groups is summed to estimate organic carbon (OC). With this method, OM and OM/OC can be estimated for each sample rather than relying on one assumed value to convert OC measurements to OM. This study continues the development of the FT-IR and PLS method for estimating OM and OM/OC by including the amine functional group. Amines are ubiquitous in the atmosphere and come from motor vehicle exhaust, animal husbandry, biomass burning, and vegetation among other sources. In this study, calibration standards for amines are produced by aerosolizing individual amine compounds and collecting them on PTFE filters using an IMPROVE sampler, thereby mimicking the filter media and collection geometry of ambient standards. The moles of amine functional group on each standard and a narrow range of amine-specific wavenumbers in the FT-IR spectra (wavenumber range 1 550-1 500 cm-1) are used to develop a PLS calibration model. The PLS model is validated using three methods: prediction of a set of laboratory standards not included in the model, a peak height analysis and a PLS model with a broader wavenumber range. The model is then applied to the ambient samples collected throughout 2013 from 16 IMPROVE sites in the USA. Urban sites have higher amine concentrations than most rural sites, but amine functional groups account for a lower fraction of OM at urban sites. Amine concentrations, contributions to OM and seasonality vary by site and sample. Amine has a small impact on the annual average OM/OC for urban sites, but for some rural sites including amine in the OM/OC calculations increased OM/OC by 0.1 or more.

General Dialdehyde Click Chemistry for Amine Bioconjugation.

PubMed

Elahipanah, Sina; O'Brien, Paul J; Rogozhnikov, Dmitry; Yousaf, Muhammad N

2017-05-17

The development of methods for conjugating a range of molecules to primary amine functional groups has revolutionized the fields of chemistry, biology, and material science. The primary amine is a key functional group and one of the most important nucleophiles and bases used in all of synthetic chemistry. Therefore, tremendous interest in the synthesis of molecules containing primary amines and strategies to devise chemical reactions to react with primary amines has been at the core of chemical research. In particular, primary amines are a ubiquitous functional group found in biological systems as free amino acids, as key side chain lysines in proteins, and in signaling molecules and metabolites and are also present in many natural product classes. Due to its abundance, the primary amine is the most convenient functional group handle in molecules for ligation to other molecules for a broad range of applications that impact all scientific fields. Because of the primary amine's central importance in synthetic chemistry, acid-base chemistry, redox chemistry, and biology, many methods have been developed to efficiently react with primary amines, including activated carboxylic acids, isothiocyanates, Michael addition type systems, and reaction with ketones or aldehydes followed by in situ reductive amination. Herein, we introduce a new traceless, high-yield, fast click-chemistry method based on the rapid and efficient trapping of amine groups via a functionalized dialdehyde group. The click reaction occurs in mild conditions in organic solvents or aqueous media and proceeds in high yield, and the starting dialdehyde reagent and resulting dialdehyde click conjugates are stable. Moreover, no catalyst or dialdehyde-activating group is required, and the only byproduct is water. The initial dialdehyde and the resulting conjugate are both straightforward to characterize, and the reaction proceeds with high atom economy. To demonstrate the broad scope of this new click-conjugation strategy, we designed a straightforward scheme to synthesize a suite of dialdehyde reagents. The dialdehyde molecules were used for applications in cell-surface engineering and for tailoring surfaces for material science applications. We anticipate the broad utility of the general dialdehyde click chemistry to primary amines in all areas of chemical research, ranging from polymers and bioconjugation to material science and nanoscience.

Hemoglobin binding of aromatic amines: molecular dosimetry and quantitative structure-activity relationships for N-oxidation.

PubMed Central

Sabbioni, G

1993-01-01

Aromatic amines are important intermediates in industrial manufacturing. N-Oxidation to N-hydroxyarylamines is a key step in determining the genotoxic properties of aromatic amines. N-Hydroxyarylamines can form adducts with DNA, with tissue proteins, and with the blood proteins albumin and hemoglobin in a dose-dependent manner. The determination of hemoglobin adducts is a useful tool for biomonitoring exposed populations. We have established the hemoglobin binding index (HBI) [(mmole compound/mole hemoglobin)/(mmole compound/kg body weight)] of several aromatic amines in female Wistar rats. Including the values from other researchers obtained in the same rat strain, the logarithm of hemoglobin binding (logHBI) was plotted against the following parameters: the sum of the Hammett constants(sigma sigma = sigma p + sigma m), pKa, logP (octanol/water), the half-wave oxidation potential (E1/2), and the electronic descriptors of the amines and their corresponding nitrenium ions obtained by semi-empirical calculations (MNDO, AMI, and PM3), such as atomic charge densities, energies of the highest occupied molecular orbit and lowest occupied molecular orbit and their coefficients, the bond order of C-N, the dipole moments, and the reaction enthalpy [MNDOHF, AM1HF or PM3HF = Hf(nitrenium) - Hf(amine)]. The correlation coefficients were determined from the plots of all parameters against log HBI for all amines by means of linear regression analysis. The amines were classified in three groups: group 1, all parasubstituted amines (maximum, n = 9); group 2, all amines with halogens (maximun, n = 11); and group 3, all amines with alkyl groups (maximum, n = 13).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8319626

Dehydrogenation and dehalogenation of amines in MALDI-TOF MS investigated by isotopic labeling.

PubMed

Kang, Chuanqing; Zhou, Yihan; Du, Zhijun; Bian, Zheng; Wang, Jianwei; Qiu, Xuepeng; Gao, Lianxun; Sun, Yuequan

2013-12-01

Secondary and tertiary amines have been reported to form [M-H](+) that correspond to dehydrogenation in matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). In this investigation, we studied the dehydrogenation of amines in MALDI-TOF MS by isotopic labeling. Aliphatic amines were labeled with deuterium on the methylene of an N-benzyl group, which resulted in the formation of [M-D](+) and [M-H](+) ions by dedeuteration and dehydrogenation, respectively. This method revealed the proton that was removed. The spectra of most tertiary amines with an N-benzyl group showed high-intensity [M-D](+) and [M-H](+) ion peaks, whereas those of secondary amines showed low-intensity ion peaks. Ratios between the peak intensities of [M-D](+) and [M-H](+) greater than 1 suggested chemoselective dehydrogenation at the N-benzyl groups. The presence of an electron donor group on the N-benzyl groups enhanced the selectivity. The dehalogenation of amines with an N-(4-halobenzyl) group was also observed alongside dehydrogenation. The amino ions from dehalogenation can undergo second dehydrogenation. These results provide the first direct evidence about the position at which dehydrogenation of an amine occurs and the first example of dehalogenation of haloaromatic compounds in MALDI-TOF MS. These results should be helpful in the structural identification and elucidation of synthetic and natural molecules. Copyright © 2013 John Wiley & Sons, Ltd.

Fabrication of Covalently Crosslinked and Amine-Reactive Microcapsules by Reactive Layer-by-Layer Assembly of Azlactone-Containing Polymer Multilayers on Sacrificial Microparticle Templates

PubMed Central

Saurer, Eric M.; Flessner, Ryan M.; Buck, Maren E.; Lynn, David M.

2011-01-01

We report on the fabrication of covalently crosslinked and amine-reactive hollow microcapsules using ‘reactive’ layer-by-layer assembly to deposit thin polymer films on sacrificial microparticle templates. Our approach is based on the alternating deposition of layers of a synthetic polyamine and a polymer containing reactive azlactone functionality. Multilayered films composed of branched poly(ethylene imine) (BPEI) and poly(2-vinyl-4,4-dimethylazlactone) (PVDMA) were fabricated layer-by-layer on the surfaces of calcium carbonate and glass microparticle templates. After fabrication, these films contained residual azlactone functionality that was accessible for reaction with amine-containing molecules. Dissolution of the calcium carbonate or glass cores using aqueous ethylenediamine tetraacetic acid (EDTA) or hydrofluoric acid (HF), respectively, led to the formation of hollow polymer microcapsules. These microcapsules were robust enough to encapsulate and retain a model macromolecule (FITC-dextran) and were stable for at least 22 hours in high ionic strength environments, in low and high pH solutions, and in several common organic solvents. Significant differences in the behaviors of capsules fabricated on CaCO3 and glass cores were observed and characterized using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Whereas capsules fabricated on CaCO3 templates collapsed upon drying, capsules fabricated on glass templates remained rigid and spherical. Characterization using EDS suggested that this latter behavior results, at least in part, from the presence of insoluble metal fluoride salts that are trapped or precipitate within the walls of capsules after etching of the glass cores using HF. Our results demonstrate that the assembly of BPEI/PVDMA films on sacrificial templates can be used to fabricate reactive microcapsules of potential use in a wide range of fields, including catalysis, drug and gene delivery, imaging, and biomedical research. PMID:21383867

Freestanding and Reactive Thin Films Fabricated by Covalent Layer-by-Layer Assembly and Subsequent Lift-Off of Azlactone-Containing Polymer Multilayers

PubMed Central

Buck, Maren E.

2010-01-01

We report an approach to the fabrication of freestanding and amine-reactive thin films that is based on the reactive layer-by-layer assembly and subsequent lift-off of azlactone-containing polymer multilayers. We demonstrate that covalently crosslinked multilayers fabricated using the azlactone-functionalized polymer poly(2-vinyl-4,4-dimethylazlactone) (PVDMA) and a primary amine-containing polymer [poly(ethyleneimine) (PEI)] can be delaminated from planar glass and silicon surfaces by immersion in mildly acidic aqueous environments to yield flexible freestanding membranes. These freestanding membranes are robust and can withstand exposure to strong acid, strong base, or incubation in high ionic strength solutions that typically lead to the disruption and erosion of polymer multilayers assembled by reversible weak interactions (e.g., ‘polyelectrolyte multilayers’ assembled by electrostatic interactions or hydrogen bonding). We demonstrate further that these PEI/PVDMA assemblies contain residual reactive azlactone functionality that can be exploited to chemically modify the films (either directly after fabrication or after they have been lifted off of the substrates on which they were fabricated) using a variety of amine-functionalized small molecules. These freestanding membranes can also be transferred readily onto other objects (for example, onto the surfaces of planar substrates containing holes or pores) to fabricate suspended polymer membranes and other film-functionalized interfaces. In addition to planar, two-dimensional freestanding films, this approach can be used to fabricate and isolate three-dimensional freestanding membranes (e.g., curved films or tubes) by layer-by-layer assembly on, and subsequent lift-off from, the surfaces of topologically complex substrates (e.g., the curved ends of glass tubing, etc.). The results of this investigation, when combined, suggest the basis of methods for the fabrication of stable, chemically-reactive, and flexible polymer thin films and membranes of potential utility in a variety of fundamental and applied contexts. PMID:20857952

Striking Confinement Effect: AuCl[subscript 4][superscript -] Binding to Amines in a Nanocage Cavity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henao, Juan D.; Suh, Young-Woong; Lee, Jeong-Kyu

2009-02-23

Binding of AuCl{sub 4}{sup -} to amine groups tethered to the interior of a 2 nm siloxane nanocage was determined in solutions containing various concentrations of acid. The mode of binding was inferred from EXAFS and UV-vis spectra to be by ligand exchange of amine for chloride, which implies that the amines remain unprotonated. Cyclic voltammetry confirmed that the Au complexes bind to the nanocage interior and established a 1:1 relationship between bound Au complex and amine groups. The results suggested a 5-7 pH unit shift in the protonation constant of the interior amines relative to free amines in solution.

Versatile Synthesis of Amino Acid Functional Polymers without Protection Group Chemistry.

PubMed

Brisson, Emma R L; Xiao, Zeyun; Franks, George V; Connal, Luke A

2017-01-09

The copolymerization of N-isopropylacrylamide (NiPAm) with aldehyde functional monomers facilitates postpolymerization functionalization with amino acids via reductive amination, negating the need for protecting groups. In reductive amination, the imine formed from the condensation reaction between an amine and an aldehyde is reduced to an amine. In this work, we categorize amino acids into four classes based on the functionality of their side chains (acidic, polar neutral, neutral, and basic) and use their amine groups in condensation reactions with aldehyde functional polymers. The dynamic nature of the imine as well as the versatility of reductive amination to functionalize a polymer with a range of amino acids is highlighted. In this manner, amino acid functional polymers are synthesized without the use of protecting groups with high yields, demonstrating the high functional group tolerance of carbonyl condensation chemistry and the subsequent reduction of the imine. Prior to the reduction of the imine bond, transimination reactions are used to demonstrate dynamic polymers that shuffle from a glycine- to a histidine-functional polymer.

Synthesis and Reactivity of Tripodal Complexes Containing Pendant Bases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blacquiere, Johanna M.; Pegis, Michael L.; Raugei, Simone

2014-09-02

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

Quantum chemical study of relative reactivities of a series of amines and nitriles - Relevance to prebiotic chemistry

NASA Technical Reports Server (NTRS)

Loew, G. H.; Berkowitz, D.; Chang, S.

1975-01-01

Using the Iterative Extended Huckel Theory (IEHT) calculations of the electron distribution and orbital energies of a series of thirteen amines, nitriles and amino-nitriles relevant to prebiotic and cosmo-chemistry have been carried out. Ground state properties such as the energy and nature of the highest occupied (HOMO) and lowest empty (LEMO) molecular orbitals, net atomic charges and number of nonbonding electrons have been identified as criteria for correlating the relative nucleophilicity of amine and nitrile nitrogens and the electrophilicity of nitrile and other unsaturated carbon atoms. The results of such correlations can be partially verified by known chemical behavior of these compounds and are used to predict and understand their role in prebiotic organic synthesis.

Computational Identification and Analysis of the Key Biosorbent Characteristics for the Biosorption Process of Reactive Black 5 onto Fungal Biomass

PubMed Central

Yang, Yu-Yi; Li, Ze-Li; Wang, Guan; Zhao, Xiao-Ping; Crowley, David E.; Zhao, Yu-Hua

2012-01-01

The performances of nine biosorbents derived from dead fungal biomass were investigated for their ability to remove Reactive Black 5 from aqueous solution. The biosorption data for removal of Reactive Black 5 were readily modeled using the Langmuir adsorption isotherm. Kinetic analysis based on both pseudo-second-order and Weber-Morris models indicated intraparticle diffusion was the rate limiting step for biosorption of Reactive Black 5 on to the biosorbents. Sorption capacities of the biosorbents were not correlated with the initial biosorption rates. Sensitivity analysis of the factors affecting biosorption examined by an artificial neural network model showed that pH was the most important parameter, explaining 22%, followed by nitrogen content of biosorbents (16%), initial dye concentration (15%) and carbon content of biosorbents (10%). The biosorption capacities were not proportional to surface areas of the sorbents, but were instead influenced by their chemical element composition. The main functional groups contributing to dye sorption were amine, carboxylic, and alcohol moieties. The data further suggest that differences in carbon and nitrogen contents of biosorbents may be used as a selection index for identifying effective biosorbents from dead fungal biomass. PMID:22442697

Deposition of chemically reactive and repellent sites on biosensor chips for reduced non-specific binding.

PubMed

Gandhiraman, R P; Gubala, V; Le, N C H; Nam, Le Cao Hoai; Volcke, C; Doyle, C; James, B; Daniels, S; Williams, D E

2010-08-01

The performances of new polymeric materials with excellent optical properties and good machinability have led the biomedical diagnostics industry to develop cheap disposable biosensor platforms appropriate for point of care applications. Zeonor, a type of cycloolefin polymer (COP), is one such polymer that presents an excellent platform for biosensor chips. These polymer substrates have to be modified to have suitable physico-chemical properties for immobilizing proteins. In this work, we have demonstrated the amine functionalization of COP substrates, by plasma enhanced chemical vapour deposition (PECVD), through codeposition of ethylene diamine and 3-aminopropyltriethoxysilane precursors, for building chemistries on the plastic chip. The elemental composition, adhesion, ageing and reactivity of the plasma polymerized film were examined. The Si-O functionality present in amino silane contributed for a good interfacial adhesion of the coating to COP substrates and also acted as a network building layer for plasma polymerization. Wet chemical modification was then carried out on the amine functionalized chips to create chemically reactive isothiocyanate sites and protein repellent fluorinated sites on the same chip. The density of the reactive and repellent sites was altered by choosing appropriate mixtures of homofunctional phenyldiisothiocyanate (PDITC), pentafluoroisothiocyanate (5FITC) and phenylisothiocyanate (PITC) compounds. By tailoring the density of reactive binding sites and protein repellent sites, the non-specific binding of ssDNA has been decreased to a significant extent. Copyright 2010 Elsevier B.V. All rights reserved.

Carbon Dioxide-Mediated C(sp3)-H Arylation of Amine Substrates.

PubMed

Kapoor, Mohit; Liu, Daniel; Young, Michael C

2018-05-25

Elaborating amines via C-H functionalization has been an important area of research over the past decade but has generally relied on an added directing group or sterically hindered amine approach. Since free-amine-directed C(sp 3 )-H activation is still primarily limited to cyclization reactions and to improve the sustainability and reaction scope of amine-based C-H activation, we present a strategy using CO 2 in the form of dry ice that facilitates intermolecular C-H arylation. This methodology has been used to enable an operationally simple procedure whereby 1° and 2° aliphatic amines can be arylated selectively at their γ-C-H positions. In addition to potentially serving as a directing group, CO 2 has also been demonstrated to curtail the oxidation of sensitive amine substrates.

Polyamines are traps for reactive intermediates in furan metabolism

PubMed Central

Peterson, Lisa A.; Phillips, Martin B.; Lu, Ding; Sullivan, Mathilde M.

2011-01-01

Furan is toxic and carcinogenic in rodents. Because of the large potential for human exposure, furan is classified as a possible human carcinogen. The detailed mechanism by which furan causes toxicity and cancer is not yet known. Since furan toxicity requires cytochrome P450-catalyzed oxidation of furan, we have characterized the urinary and hepatocyte metabolites of furan to gain insight into the chemical nature of the reactive intermediate. Previous studies in hepatocytes indicated that furan is oxidized to the reactive α,β-unsaturated dialdehyde, cis-2-butene-1,4-dial (BDA), which reacts with glutathione (GSH) to form 2-(S-glutathionyl)-succinaldehyde (GSH-BDA). This intermediate forms pyrrole cross-links with cellular amines such as lysine and glutamine. In this report, we demonstrate that GSH-BDA also forms cross-links with ornithine, putrescine and spermidine when furan is incubated with rat hepatocytes. The relative levels of these metabolites are not completely explained by hepatocellular levels of the amines or by their reactivity with GSH-BDA. Mercapturic acid derivatives of the spermidine cross-links were detected in the urine of furan-treated rats, which indicates that this metabolic pathway occurs in vivo. Their detection in furan-treated hepatocytes and in urine from furan-treated rats indicates that polyamines may play an important role in the toxicity of furan PMID:21842885

Chemoselective amide formation using O-(4-nitrophenyl)hydroxylamines and pyruvic acid derivatives.

PubMed

Kumar, Sonali; Sharma, Rashi; Garcia, Megan; Kamel, Joseph; McCarthy, Caroline; Muth, Aaron; Phanstiel, Otto

2012-12-07

A series of O-(4-nitrophenyl)hydroxylamines were synthesized from their respective oximes using a pulsed addition of excess NaBH(3)CN at pH 3 in 65-75% yield. Steric hindrance near the oxime functional group played a key role in both the ease by which the oxime could be reduced and the subsequent reactivity of the respective hydroxylamine. Reaction of the respective hydroxylamines with pyruvic acid derivatives generated the desired amides in good yields. A comparison of phenethylamine systems bearing different leaving groups revealed significant differences in the rates of these systems and suggested that the leaving group ability of the N-OR substituent plays an important role in determining their reactivity with pyruvic acid. Competition experiments (in 68% DMSO/phosphate buffered saline) using 1 equiv of N-phenethyl-O-(4-nitrophenyl)hydroxylamine and 2 equiv of pyruvic acid in the presence of other nucleophiles such as glycine, cysteine, phenol, hexanoic acid, and lysine demonstrated that significant chemoselectivity is present in this reaction. The results suggest that this chemoselective reaction can occur in the presence of excess α-amino acids, phenols, acids, thiols, and amines.

Low cytotoxic tissue adhesive based on oxidized dextran and epsilon-poly-L-lysine.

PubMed

Hyon, Suong-Hyu; Nakajima, Naoki; Sugai, Hajime; Matsumura, Kazuaki

2014-08-01

A novel adhesive hydrogel consisting of dextran and epsilon-poly(L-lysine) (dextran-PL) with multiple biomedical applications was developed. Periodate oxidation in aqueous media almost stoichiometrically introduces aldehyde groups in dextran molecules, and aldehyde dextran can react with the primary amino groups in epsilon-PL (ɛ-PL) at neutral pH to form a hydrogel. The gelation time of the hydrogel can be easily controlled by the extent of oxidation in dextran and of the acylation in ɛ-PL by anhydrides. The shear adhesion strength of dextran-PL was 10 times higher than that of fibrin glue, when wet collagen sheets were selected as test specimens. The cytotoxicity of aldehyde dextran and ɛ-PL were 1000 times lower than that of glutaraldehyde and poly(allylamine). The considerably low cytotoxicity of aldehyde dextran could be ascribed to its low reactivity with amine species when compared with glutaraldehyde. In contrast, a high reactivity of amino groups in ɛ-PL was observed when compared with glycine, L-lysine, and gelatin, which could be explained by their poor dissociation at neutral pH, thus leading to low cytotoxicity. © 2013 Wiley Periodicals, Inc.

The roles of tertiary amine structure, background organic matter and chloramine species on NDMA formation.

PubMed

Selbes, Meric; Kim, Daekyun; Ates, Nuray; Karanfil, Tanju

2013-02-01

N-nitrosodimethylamine (NDMA), a probable human carcinogen, is a disinfection by-product that has been detected in chloraminated and chlorinated drinking waters and wastewaters. Formation mechanisms and precursors of NDMA are still not well understood. The main objectives of this study were to systematically investigate (i) the effect of tertiary amine structure, (ii) the effect of background natural organic matter (NOM), and (iii) the roles of mono vs. dichloramine species on the NDMA formation. Dimethylamine (DMA) and 20 different tertiary aliphatic and aromatic amines were carefully examined based on their functional groups attached to the basic DMA structure. The wide range (0.02-83.9%) of observed NDMA yields indicated the importance of the structure of tertiary amines, and both stability and electron distribution of the leaving group of tertiary amines on NDMA formation. DMA associated with branched alkyl groups or benzyl like structures having only one carbon between the ring and DMA structure consistently gave higher NDMA yields. Compounds with electron withdrawing groups (EWG) reacted preferentially with monochloramine, whereas compounds with electron donating group (EDG) showed tendency to react with dichloramine to form NDMA. When the selected amines were present in NOM solutions, NDMA formation increased for compounds with EWG while decreased for compounds with EDG. This impact was attributed to the competitions between NOM and amines for chloramine species. The results provided additional information to the commonly accepted mechanism for NDMA formation including chloramine species reacting with tertiary amines and the role of the leaving group on overall NDMA conversion. Copyright © 2012 Elsevier Ltd. All rights reserved.

Evaluation of different electrochemical methods on the oxidation and degradation of Reactive Blue 4 in aqueous solution.

PubMed

Carneiro, Patricia A; Osugi, Marly E; Fugivara, Cecílio S; Boralle, Nivaldo; Furlan, Maysa; B Zanoni, Maria Valnice

2005-04-01

The oxidation of a reactive dye, Reactive Blue 4, RB4, (C.I. 61205), widely used in the textile industries to color natural fibers, was studied by electrochemical techniques. The oxidation on glassy carbon electrode and reticulated vitreous carbon electrode occurs in only one step at 2.0 < pH < 12 involving a two-electron transfer to the amine group leading to the imide derivative. Dye solution was not decolorized effectively in this electrolysis process. Nevertheless, the oxidation of this dye on Ti/SnO2/SbO(x) (3% mol)/RuO2 (1% mol) electrode showed 100% of decolorization and 60% of total organic carbon removal in Na2SO4 0.2 M at pH 2.2 and potential of +2.4V. Experiments on degradation photoelectrocatalytic were also carried out for RB4 degradation in Na2SO4 0.1 M, pH 12, using a Ti/TiO2 photoanode biased at +1.0 V and UV light. After 1h of electrolysis the results indicated total color removal and 37% of mineralization.

A catalytic tethering strategy: simple aldehydes catalyze intermolecular alkene hydroaminations.

PubMed

MacDonald, Melissa J; Schipper, Derek J; Ng, Peter J; Moran, Joseph; Beauchemin, André M

2011-12-21

Herein we describe a catalytic tethering strategy in which simple aldehyde precatalysts enable, through temporary intramolecularity, room-temperature intermolecular hydroamination reactivity and the synthesis of vicinal diamines. The catalyst allows the formation of a mixed aminal from an allylic amine and a hydroxylamine, resulting in a facile intramolecular hydroamination event. The promising enantioselectivities obtained with a chiral aldehyde also highlight the potential of this catalytic tethering approach in asymmetric catalysis and demonstrate that efficient enantioinduction relying only on temporary intramolecularity is possible. © 2011 American Chemical Society

Thio-,amine-,nitro-,and macrocyclic containing organic aerogels & xerogels

DOEpatents

Fox, Glenn A.; Tillotson, Thomas M.

2005-08-02

An organic aerogel or xerogel formed by a sol-gel reaction using starting materials that exhibit similar reactivity to the most commonly used resorcinol starting material. The new starting materials, including thio-, amine- and nitro-containing molecules and functionalized macrocyclic molecules will produce organic xerogels and aerogels that have improved performance in the areas of detection and sensor technology, as well as water stream remediation. Also, further functionalization of these new organic aerogels or xerogels will yield material that can be extracted with greater facility than current organic aerogels.

Monomers for thermosetting and toughening epoxy resins. [glycidyl amine derivatives, propargyl-containing amines, and mutagenic testing of aromatic diamines

NASA Technical Reports Server (NTRS)

Pratt, J. R.

1981-01-01

Eight glycidyl amines were prepared by alkylating the parent amine with epichlorohydrin to form chlorohydrin, followed by cyclization with aqueous NaOH. Three of these compounds contained propargyl groups with postcuring studies. A procedure for quantitatively estimating the epoxy content of these glycidyl amines was employed for purity determination. Two diamond carbonates and several model propargly compounds were prepared. The synthesis of three new diamines, two which contain propargyloxy groups, and another with a sec-butyl group is in progress. These materials are at the dinitro stage ready for the final hydrogenation step. Four aromatic diamines were synthesized for mutagenic testing purposes. One of these compounds rapidly decomposes on exposure to air.

Mechanistic Studies of the N-formylation of Edivoxetine, a Secondary Amine-Containing Drug, in a Solid Oral Dosage Form.

PubMed

Hoaglund Hyzer, Cherokee S; Williamson, Michele L; Jansen, Patrick J; Kopach, Michael E; Scherer, R Brian; Baertschi, Steven W

2017-05-01

Edivoxetine (LY2216684 HCl), although a chemically stable drug substance, has shown the tendency to degrade in the presence of carbohydrates that are commonly used tablet excipients, especially at high excipient:drug ratios. The major degradation product has been identified as N-formyl edivoxetine. Experimental evidence including solution and solid-state investigations, is consistent with the N-formylation degradation pathway resulting from a direct reaction of edivoxetine with (1) formic acid (generated from decomposition of microcrystalline cellulose or residual glucose) and (2) the reducing sugar ends (aldehydic carbons) of either residual glucose or the microcrystalline cellulose polymer. Results of labeling experiments indicate that the primary source of the formyl group is the C1 position from reducing sugars. Presence of water or moisture accelerates this degradation pathway. Investigations in solid and solution states support that the glucose Amadori Rearrangement Product does not appear to be a direct intermediate leading to N-formyl degradation of edivoxetine, and oxygen does not appear to play a significant role. Solution-phase studies, developed to rapidly assess propensity of amines toward Maillard reactivity and formylation, were extended to show comparative behavior with example systems. The cyclic amine systems, such as edivoxetine, showed the highest propensity toward these side reactions. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Conformation-induced remote meta-C-H activation of amines

NASA Astrophysics Data System (ADS)

Tang, Ri-Yuan; Li, Gang; Yu, Jin-Quan

2014-03-01

Achieving site selectivity in carbon-hydrogen (C-H) functionalization reactions is a long-standing challenge in organic chemistry. The small differences in intrinsic reactivity of C-H bonds in any given organic molecule can lead to the activation of undesired C-H bonds by a non-selective catalyst. One solution to this problem is to distinguish C-H bonds on the basis of their location in the molecule relative to a specific functional group. In this context, the activation of C-H bonds five or six bonds away from a functional group by cyclometallation has been extensively studied. However, the directed activation of C-H bonds that are distal to (more than six bonds away) functional groups has remained challenging, especially when the target C-H bond is geometrically inaccessible to directed metallation owing to the ring strain encountered in cyclometallation. Here we report a recyclable template that directs the olefination and acetoxylation of distal meta-C-H bonds--as far as 11 bonds away--of anilines and benzylic amines. This template is able to direct the meta-selective C-H functionalization of bicyclic heterocycles via a highly strained, tricyclic-cyclophane-like palladated intermediate. X-ray and nuclear magnetic resonance studies reveal that the conformational biases induced by a single fluorine substitution in the template can be enhanced by using a ligand to switch from ortho- to meta-selectivity.

Conformation-induced remote meta-C-H activation of amines.

PubMed

Tang, Ri-Yuan; Li, Gang; Yu, Jin-Quan

2014-03-13

Achieving site selectivity in carbon-hydrogen (C-H) functionalization reactions is a long-standing challenge in organic chemistry. The small differences in intrinsic reactivity of C-H bonds in any given organic molecule can lead to the activation of undesired C-H bonds by a non-selective catalyst. One solution to this problem is to distinguish C-H bonds on the basis of their location in the molecule relative to a specific functional group. In this context, the activation of C-H bonds five or six bonds away from a functional group by cyclometallation has been extensively studied. However, the directed activation of C-H bonds that are distal to (more than six bonds away) functional groups has remained challenging, especially when the target C-H bond is geometrically inaccessible to directed metallation owing to the ring strain encountered in cyclometallation. Here we report a recyclable template that directs the olefination and acetoxylation of distal meta-C-H bonds--as far as 11 bonds away--of anilines and benzylic amines. This template is able to direct the meta-selective C-H functionalization of bicyclic heterocycles via a highly strained, tricyclic-cyclophane-like palladated intermediate. X-ray and nuclear magnetic resonance studies reveal that the conformational biases induced by a single fluorine substitution in the template can be enhanced by using a ligand to switch from ortho- to meta-selectivity.

Conjugate and method for forming aminomethyl phosphorus conjugates

DOEpatents

Katti, Kattesh V.; Berning, Douglas E.; Volkert, Wynn A.; Ketring, Alan R.; Churchill, Robert

1999-01-01

A method of forming phosphine-amine conjugates includes reacting a hydroxymethyl phosphine group of an amine-free first molecule with at least one free amine group of a second molecule to covalently bond the first molecule with the second molecule through an aminomethyl phosphorus linkage and the conjugates formed thereby.

Quantitative Reactivity Scales for Dynamic Covalent and Systems Chemistry.

PubMed

Zhou, Yuntao; Li, Lijie; Ye, Hebo; Zhang, Ling; You, Lei

2016-01-13

Dynamic covalent chemistry (DCC) has become a powerful tool for the creation of molecular assemblies and complex systems in chemistry and materials science. Herein we developed for the first time quantitative reactivity scales capable of correlation and prediction of the equilibrium of dynamic covalent reactions (DCRs). The reference reactions are based upon universal DCRs between imines, one of the most utilized structural motifs in DCC, and a series of O-, N-, and S- mononucleophiles. Aromatic imines derived from pyridine-2-carboxyaldehyde exhibit capability for controlling the equilibrium through distinct substituent effects. Electron-donating groups (EDGs) stabilize the imine through quinoidal resonance, while electron-withdrawing groups (EWGs) stabilize the adduct by enhancing intramolecular hydrogen bonding, resulting in curvature in Hammett analysis. Notably, unique nonlinearity induced by both EDGs and EWGs emerged in Hammett plot when cyclic secondary amines were used. This is the first time such a behavior is observed in a thermodynamically controlled system, to the best of our knowledge. Unified quantitative reactivity scales were proposed for DCC and defined by the correlation log K = S(N) (R(N) + R(E)). Nucleophilicity parameters (R(N) and S(N)) and electrophilicity parameters (R(E)) were then developed from DCRs discovered. Furthermore, the predictive power of those parameters was verified by successful correlation of other DCRs, validating our reactivity scales as a general and useful tool for the evaluation and modeling of DCRs. The reactivity parameters proposed here should be complementary to well-established kinetics based parameters and find applications in many aspects, such as DCR discovery, bioconjugation, and catalysis.

The Effect of the Local Delivery of Platelet-derived Growth Factor from Reactive Two-Component Polyurethane Scaffolds on the Healing in Rat Skin Excisional Wounds

PubMed Central

Li, Bing; Davidson, Jeffrey M.; Guelcher, Scott A.

2009-01-01

A key tenet of tissue engineering is the principle that the scaffold can perform the dual roles of biomechanical and biochemical support through presentation of the appropriate mediators to surrounding tissue. While growth factors have been incorporated into scaffolds to achieve sustained release, there are a limited number of studies investigating release of biologically active molecules from reactive two-component polymers, which have potential application as injectable delivery systems. In this study, we report the sustained release of platelet-derived growth factor (PDGF) from a reactive two-component polyurethane. The release of PDGF was bi-phasic, characterized by an initial burst followed by a period of sustained release for up to 21 days. Despite the potential for amine and hydroxyl groups in the protein to react with the isocyanate groups in the reactive polyurethane, the in vitro bioactivity of the released PDGF was largely preserved when added as a lyophilized powder. PUR/PDGF scaffolds implanted in rat skin excisional wounds accelerated wound healing relative to the blank PUR control, resulting in almost complete healing with reepithelization at day 14. The presence of PDGF attracted both fibroblasts and mononuclear cells, significantly accelerating degradation of the polymer and enhancing formation of new granulation tissue as early as day 3. The ability of reactive two-component PUR scaffolds to promote new tissue formation in vivo through local delivery of PDGF may present compelling opportunities for the development of novel injectable therapeutics. PMID:19328544

The effect of elastomer chain length on properties of silicone-modified polyimide adhesives

NASA Technical Reports Server (NTRS)

St.clair, A. K.; St.clair, T. L.; Ezzell, S.

1981-01-01

A series of polyimides containing silicone elastomers was synthesized in order to study the effects of the elastomer chain length on polymer properties. The elastomer with repeat units varying from n=10 to 105 was chemically reacted into the backbone of an addition polyimide oligomer via reactive aromatic amine groups. Glass transition temperatures of the elastomer and polyimide phases were observed by torsional braid analysis. The elastomer-modified polyimides were tested as adhesives for bonding titanium in order to determine their potential for aerospace applications. Adhesive lap shear tests were performed before and after aging bonded specimens at elevated temperatures.

A Hydrazone-Based exo-Directing-Group Strategy for β C-H Oxidation of Aliphatic Amines.

PubMed

Huang, Zhongxing; Wang, Chengpeng; Dong, Guangbin

2016-04-18

Described is a new hydrazone-based exo-directing group (DG) strategy developed for the functionalization of unactivated primary β C-H bonds of aliphatic amines. Conveniently synthesized from protected primary amines, the hydrazone DGs are shown to site-selectively promote the β-acetoxylation and tosyloxylation via five-membered exo-palladacycles. Amines with a wide scope of skeletons and functional groups are tolerated. Moreover, the hydrazone DG can be readily removed, and a one-pot C-H acetoxylation/DG removal protocol was also discovered. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

NASA Astrophysics Data System (ADS)

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.

Kinetics of nitrosamine and amine reactions with NO3 radical and ozone related to aqueous particle and cloud droplet chemistry

NASA Astrophysics Data System (ADS)

Weller, Christian; Herrmann, Hartmut

2015-01-01

Aqueous phase reactivity experiments with the amines dimethylamine (DMA), diethanolamine (DEA) and pyrrolidine (PYL) and their corresponding nitrosamines nitrosodimethylamine (NDMA), nitrosodiethanolamine (NDEA) and nitrosopyrrolidine (NPYL) have been performed. NO3 radical reaction rate coefficients for DMA, DEA and PYL were measured for the first time and are 3.7 × 105, 8.2 × 105 and 8.7 × 105 M-1 s-1, respectively. Rate coefficients for NO3 + NDMA, NDEA and NPYL are 1.2 × 108, 2.3 × 108 and 2.4 × 108 M-1 s-1. Compared to OH radical rate coefficients for reactions with amines, the NO3 radical will most likely not be an important oxidant but it is a potential nighttime oxidant for nitrosamines in cloud droplets or deliquescent particles. Ozone is unreactive towards amines and nitrosamines and upper limits of rate coefficients suggest that aqueous ozone reactions are not important in atmospheric waters.

Cross-Linking Studies of Lysozyme Nucleation

NASA Technical Reports Server (NTRS)

Forsythe, Elizabeth; Pusey, Marc

2000-01-01

Tetragonal chicken egg white crystals consist of 4(sub 3) helices running in alternating directions, the helix rows having a two fold symmetry with each other. The unit cell consists of one complete tetrameric turn from each of two adjacent helices (an octamer). PBC analysis indicates that the helix intermolecular bonds are the strongest in the crystal, therefore likely formed first. AFM analysis of the (110) surface shows only complete helices, no half steps or bisected helices being found, while AFM line scans to measure the growth step increments show that they are multiples of the 4(sub 3) helix tetramer dimensions. This supports our thesis that the growth units are in fact multiples of the four molecule 4(sub 3) helix unit, the "average" growth unit size for the (110) face being an octamer (two turns about the helix) and the (101) growth unit averaging about the size of a hexamer. In an effort to better understand the species involved in the crystal nucleation and growth process, we have initiated an experimental program to study the species formed in solution compared to what is found in the crystal through covalent cross-linking studies. These experiments use the heterobifunctional cross-linking agent aminoethyl-4-azidonitroanaline (AEANA). An aliphatic amine at one end is covalently attached to the protein by a carbodiimide-mediated reaction, and a photo reactive group at the other can be used to initiate crosslinking. Modifications to the parent structure can be used to alter the distance between the two reactive groups and thus the cross-linking agents "reach". In practice, the cross-linking agent is first coupled to the asp101 side chain through the amine group. Asp101 lies within the active site cleft, and previous work with fluorescent probes had shown that derivatives at this site still crystallize in the tetragonal space group. This was also found to be the case with the AEANA derivative, which gave red tetragonal crystals. The protein now has a reactive group that can be photoactivated at a specific point in the nucleation or crystal growth process to "capture" protein molecules bound within reach of the crosslinking agent. If those bound protein molecules have a defined geometric relationship with the capturing molecule, such as would be found in a crystal, then the photoreacted cross-linking site should be consistent. Random protein interactions, typical of an amorphous precipitate or interaction, would show a random cross-linking reaction. The results of these and other experiments will be presented.

DEVELOPMENT OF SULFHYDRYL-REACTIVE SILICA FOR PROTEIN IMMOBILIZATION IN HIGH-PERFORMANCE AFFINITY CHROMATOGRAPHY

PubMed Central

Mallik, Rangan; Wa, Chunling; Hage, David S.

2008-01-01

Two techniques were developed for the immobilization of proteins and other ligands to silica through sulfhydryl groups. These methods made use of maleimide-activated silica (the SMCC method) or iodoacetyl-activated silica (the SIA method). The resulting supports were tested for use in high-performance affinity chromatography by employing human serum albumin (HSA) as a model protein. Studies with normal and iodoacetamide-modified HSA indicated that these methods had a high selectivity for sulfhydryl groups on this protein, which accounted for the coupling of 77–81% of this protein to maleimide- or iodacetyl-activated silica. These supports were also evaluated in terms of their total protein content, binding capacity, specific activity, non-specific binding, stability and chiral selectivity for several test solutes. HSA columns prepared using maleimide-activated silica gave the best overall results for these properties when compared to HSA that had been immobilized to silica through the Schiff base method (i.e., an amine-based coupling technique). A key advantage of the supports developed in this work is that they offer the potential of giving greater site-selective immobilization and ligand activity than amine-based coupling methods. These features make these supports attractive in the development of protein columns for such applications as the study of biological interactions and chiral separations. PMID:17297940

Use of T-2 toxin-immobilized amine-activated beads as an efficient affinity purification matrix for the isolation of specific IgY.

PubMed

Edupuganti, Soujanya Ratna; Edupuganti, Om Prakash; O'Kennedy, Richard; Defrancq, Eric; Boullanger, Stéphanie

2013-04-01

An affinity purification method that isolates T-2 toxin-specific IgY utilizing a T-2-toxin-immobilized column was developed. The T-2 toxin was covalently coupled via a carbonyldiimidazole-activated hydroxyl functional group to amine-activated sepharose beads. The affinity-purified IgY was characterized by gel electrophoresis, fast protein liquid chromatography, enzyme-linked immunosorbant assay, surface plasmon resonance and mass spectrometry. A competitive inhibition ELISA (CI-ELISA) was performed using affinity-purified IgY with a T-2 toxin detection sensitivity of 30 ng/mL, which falls within the maximum permissible limit of 100 ng/mL. The cross reactivity of IgY towards deoxynivalenol, zearalenone, fumonisin B1 and HT-2 was significantly reduced after affinity purification. A surface plasmon resonance (SPR)-based inhibition assay was also applied for quantitative determination of T-2 toxin in spiked wheat samples. The results obtained indicate the feasibility of utilizing this IgY-based assay for the detection of T-2 toxin in food samples.

Specific and total N-nitrosamines formation potentials of nitrogenous micropollutants during chloramination.

PubMed

Piazzoli, Andrea; Breider, Florian; Aquillon, Caroline Gachet; Antonelli, Manuela; von Gunten, Urs

2018-05-15

N-nitrosamines are a group of potent human carcinogens that can be formed during oxidative treatment of drinking water and wastewater. Many tertiary and quaternary amines present in consumer products (e.g., pharmaceuticals, personal care and household products) are known to be N-nitrosodimethylamine (NDMA) precursors during chloramination, but the formation of other N-nitrosamines has been rarely studied. This study investigates the specific and total N-nitrosamine (TONO) formation potential (FP) of various precursors from nitrogen-containing micropollutants (chlorhexidine, metformin, benzalkonium chloride and cetyltrimethylammonium chloride) and tertiary and quaternary model amines (trimethyl amine, N,N-dimethylbutyl amine, N,N-dimethylbenzyl amine and tetramethyl ammonium). All the studied nitrogenous micropollutants displayed quantifiable TONO FP, with molar yields in the range 0.04-11.92%. However, the observed TONO pools constituted mostly of uncharacterized species, not included in US-EPA 8270 N-nitrosamines standard mix. Only the quaternary ammonium compound benzalkonium chloride showed quantifiable NDMA FP (0.56% molar yield), however, explaining only a minor fraction of the observed TONO FP. The studied model amines showed molar NDMA yields from 0.10% (trimethyl amine) to 5.05% (N,N-dimethylbenzyl amine), very similar to the molar TONO yields. The comparison of the FPs of micropollutants and model compounds showed that the presence of electron donating functional groups (such as a benzyl group) in tertiary and quaternary amine precursors leads to a higher formation of NDMA and uncharacterized N-nitrosamines, respectively. LC-qTOF screening of a list of proposed N-nitrosamine structures has enabled to identify a novel N-nitrosamine (N-nitroso-N-methyldodecylamine) from the chloramination of benzalkonium chloride. This finding supports the hypothesis that different functional groups in quaternary amines can act as leaving groups during chloramination and form differing N-nitrosamine structures at significant yield. Molar TONO yields determined for micropollutants were finally validated under experimental conditions closer to real water matrices, confirming their representativeness also for lower concentration ranges. Copyright © 2018 Elsevier Ltd. All rights reserved.

CuH-catalysed hydroamination of arylalkynes with hydroxylamine esters – a computational scrutiny of rival mechanistic pathways† †Electronic supplementary information (ESI) available: Complete account of all examined pathways, computational details, full description of reported key species (energies and Cartesian coordinates in angstroms). See DOI: 10.1039/c7sc01107e Click here for additional data file.

PubMed Central

Tobisch, Sven

2017-01-01

An in-depth computational mechanistic probe of the CuH-mediated hydroamination of internal arylalkynes with an archetype hydroxylamine ester and hydrosilane by a (Xantphos)CuH catalyst (Xantphos ≡ {P^P} ≡ 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene) is presented. This first comprehensive computational study of the CuH-mediated electrophilic alkyne hydroamination has identified the most accessible pathway for the rival avenues for direct and reductive hydroamination. The mechanistic picture derived from smooth energy profiles obtained by employing a reliable computational protocol applied to a realistic catalyst model conforms to all available experimental data. The crucial vinyl- and alkylcopper intermediates were found to display a distinct chemodivergence in their reactivity towards amine electrophile and alcohol, which ensures the successful formation of α-branched alkylamines together with (E)-enamines. On the one hand, the vinylcopper is somewhat preferably approached by the alcohol, thereby rendering the reductive hydroamination avenue favourable in the presence of both amine electrophile and alcohol. In contrast, the greater kinetic demands for protonation versus electrophilic amination predicted for the alkylcopper prevents the reductive hydroamination avenue to become non-productive. Electronically modified hydroxylamine esters are found to influence the chemoselectivity in reactivity towards amine electrophile and alcohol achievable for the vinyl- and alkylcopper, thereby offering an opportunity for process improvement. PMID:28660063

Hydrothermal Reactivity of Amines

NASA Astrophysics Data System (ADS)

Robinson, K.; Shock, E.; Hartnett, H. E.; Williams, L. B.; Gould, I.

2013-12-01

The reactivity of aqueous amines depends on temperature, pH, and redox state [1], all of which are highly variable in hydrothermal systems. Temperature and pH affect the ratio of protonated to unprotonated amines (R-NH2 + H+ = R-NH3+), which act as nucleophiles and electrophiles, respectively. We hypothesize that this dual nature can explain the pH dependence of reaction rates, and predict that rates will approach a maximum at pH = pKa where the ratio of protonated and unprotonated amines approaches one and the two compounds are poised to react with one another. Higher temperatures in hydrothermal systems allow for more rapid reaction rates, readily reversible reactions, and unique carbon-nitrogen chemistry in which water acts as a reagent in addition to being the solvent. In this study, aqueous benzylamine was used as a model compound to explore the reaction mechanisms, kinetics, and equilibria of amines under hydrothermal conditions. Experiments were carried out in anoxic silica glass tubes at 250°C (Psat) using phosphate-buffered solutions to observe changes in reaction rates and product distributions as a function of pH. The rate of decomposition of benzylamine was much faster at pH 4 than at pH 9, consistent with the prediction that benzylamine acts as both nucleophile and an electrophile, and our estimate that the pKa of benzylamine is ~5 at 250°C and Psat. Accordingly, dibenzylamine is the primary product of the reaction of two benzylamine molecules, and this reaction is readily reversible under hydrothermal conditions. Extremely acidic or basic pH can be used to suppress dibenzylamine production, which also suppresses the formation of all other major products, including toluene, benzyl alcohol, dibenzylimine, and tribenzylamine. This suggests that dibenzylamine is the lone primary product that then itself reacts as a precursor to produce the above compounds. Analog experiments performed with ring-substituted benzylamine derivatives and chiral methylbenzylamine suggest an SN2 mechanism for the formation of dibenzylamine. These results show the interdependence of pH and speciation with amine reaction rates. We predict the distribution of primary, secondary, tertiary, and quaternary amines in hydrothermal solutions can be used to solve for the pH of subsurface reaction zones in hydrothermal systems. [1] McCollom, T.M. (2013) The influence of minerals on decomposition of the n-alkyl-α-amino acid norvaline under hydrothermal conditions. Geochim. Cosmochim. Acta, 104, 330-357.

Polyimide Aerogels with Three-Dimensional Cross-Linked Structure

NASA Technical Reports Server (NTRS)

Panek, John

2010-01-01

Polyimide aerogels with three-dimensional cross-linked structure are made using linear oligomeric segments of polyimide, and linked with one of the following into a 3D structure: trifunctional aliphatic or aromatic amines, latent reactive end caps such as nadic anhydride or phenylethynylphenyl amine, and silica or silsesquioxane cage structures decorated with amine. Drying the gels supercritically maintains the solid structure of the gel, creating a polyimide aerogel with improved mechanical properties over linear polyimide aerogels. Lightweight, low-density structures are desired for acoustic and thermal insulation for aerospace structures, habitats, astronaut equipment, and aeronautic applications. Aerogels are a unique material for providing such properties because of their extremely low density and small pore sizes. However, plain silica aerogels are brittle. Reinforcing the aerogel structure with a polymer (X-Aerogel) provides vast improvements in strength while maintaining low density and pore structure. However, degradation of polymers used in cross-linking tends to limit use temperatures to below 150 C. Organic aerogels made from linear polyimide have been demonstrated, but gels shrink substantially during supercritical fluid extraction and may have lower use temperature due to lower glass transition temperatures. The purpose of this innovation is to raise the glass transition temperature of all organic polyimide aerogel by use of tri-, tetra-, or poly-functional units in the structure to create a 3D covalently bonded network. Such cross-linked polyimides typically have higher glass transition temperatures in excess of 300 400 C. In addition, the reinforcement provided by a 3D network should improve mechanical stability, and prevent shrinkage on supercritical fluid extraction. The use of tri-functional aromatic or aliphatic amine groups in the polyimide backbone will provide such a 3D structure.

Functional electrospun nanofibers for multimodal sensitive detection of biogenic amines in food via a simple dipstick assay.

PubMed

Yurova, Nadezhda S; Danchuk, Alexandra; Mobarez, Sarah N; Wongkaew, Nongnoot; Rusanova, Tatiana; Baeumner, Antje J; Duerkop, Axel

2018-01-01

Electrospun nanofibers (ENFs) are promising materials for rapid diagnostic tests like lateral flow assays and dipsticks because they offer an immense surface area while excluding minimal volume, a variety of functional surface groups, and can entrap functional additives within their interior. Here, we show that ENFs on sample pads are superior in comparison to standard polymer membranes for the optical detection of biogenic amines (BAs) in food using a dipstick format. Specifically, cellulose acetate (CA) fibers doped with 2 mg/mL of the chromogenic and fluorogenic amine-reactive chameleon dye Py-1 were electrospun into uniform anionic mats. Those extract cationic BAs from real samples and Py-1 transduces BA concentrations into a change of color, reflectance, and fluorescence. Dropping a BA sample onto the nanofiber mat converts the weakly fluorescent pyrylium dye Py-1 into a strongly red emitting pyridinium dye. For the first time, a simple UV lamp excites fluorescence and a digital camera acts as detector. The intensity ratio of the red to the blue channel of the digital image is dependent on the concentration of most relevant BAs indicating food spoilage from 10 to 250 μM. This matches the permitted limits for BAs in foods and no false positive signals arise from secondary and tertiary amines. BA detection in seafood samples was also demonstrated successfully. The nanofiber mat dipsticks were up to sixfold more sensitive than those using a polymer membrane with the same dye embedded. Hence, nanofiber-based tests are not only superior to polymer-based dipstick assays, but will also improve the performance of established tests related to food safety, medical diagnostics, and environmental testing. Graphical Absract ᅟ.

Reactive Uptake of Dimethylamine by Ammonium Sulfate and Ammonium Sulfate-Sucrose Mixed Particles.

PubMed

Chu, Yangxi; Chan, Chak K

2017-01-12

Short-chain alkyl amines can undergo gas-to-particle partitioning via reactive uptake by ammonium salts, whose phases have been thought to largely influence the extent of amine uptake. Previous studies mainly focused on particles of single ammonium salt at either dry or wet conditions without any addition of organic compounds. Here we report the uptake of dimethylamine (DMA) by ammonium sulfate (AS) and AS-sucrose mixed particles at different relative humidities (RHs) using an electrodynamic balance coupled with in situ Raman spectroscopy. DMA is selected as a representative of short-chain alkyl amines, and sucrose is used as a surrogate of viscous and hydrophilic organics. Effective DMA uptake was observed for most cases, except for the water-limiting scenario at <5% RH and the formation of an ultraviscous sucrose coating at 10% RH and below. DMA uptake coefficients (γ) were estimated using the particle mass measurements during DMA uptake. Addition of sucrose can increase γ by absorbing water or inhibiting AS crystallization and decrease γ by elevating the particle viscosity and forming a coating layer. DMA uptake can be facilitated for crystalline AS or retarded for aqueous AS with hydrophilic viscous organics (e.g., secondary organic material formed via the oxidation of biogenic volatile organic compounds) present in aerosol particles.

Proton Mediated Chemistry and Catalysis in a Self-Assembled Supramolecular Host

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pluth, Michael; Bergman, Robert; Raymond, Kenneth

2009-04-10

Synthetic supramolecular host assemblies can impart unique reactivity to encapsulated guest molecules. Synthetic host molecules have been developed to carry out complex reactions within their cavities, despite the fact that they lack the type of specifically tailored functional groups normally located in the analogous active sites of enzymes. Over the past decade, the Raymond group has developed a series of self-assembled supramolecules and the Bergman group has developed and studied a number of catalytic transformations. In this Account, we detail recent collaborative work between these two groups, focusing on chemical catalysis stemming from the encapsulation of protonated guests and expandingmore » to acid catalysis in basic solution. We initially investigated the ability of a water-soluble, self-assembled supramolecular host molecule to encapsulate protonated guests in its hydrophobic core. Our study of encapsulated protonated amines revealed rich host-guest chemistry. We established that self-exchange (that is, in-out guest movement) rates of protonated amines were dependent on the steric bulk of the amine rather than its basicity. The host molecule has purely rotational tetrahedral (T) symmetry, so guests with geminal N-methyl groups (and their attendant mirror plane) were effectively desymmetrized; this allowed for the observation and quantification of the barriers for nitrogen inversion followed by bond rotation. Furthermore, small nitrogen heterocycles, such as N-alkylaziridines, N-alkylazetidines, and N-alkylpyrrolidines, were found to be encapsulated as proton-bound homodimers or homotrimers. We further investigated the thermodynamic stabilization of protonated amines, showing that encapsulation makes the amines more basic in the cavity. Encapsulation raises the effective basicity of protonated amines by up to 4.5 pK{sub a} units, a difference almost as large as that between the moderate and strong bases carbonate and hydroxide. The thermodynamic stabilization of protonated guests was translated into chemical catalysis by taking advantage of the potential for accelerating reactions that take place via positively charged transition states, which could be potentially stabilized by encapsulation. Orthoformates, generally stable in neutral or basic solution, were found to be suitable substrates for catalytic hydrolysis by the assembly. Orthoformates small enough to undergo encapsulation were readily hydrolyzed by the assembly in basic solution, with rate acceleration factors up to 3900 compared with those of the corresponding uncatalyzed reactions. Furthering the analogy to enzymes that obey Michaelis-Menten kinetics, we observed competitive inhibition with the inhibitor NPr{sub 4}{sup +}, thereby confirming that the interior cavity of the assembly was the active site for catalysis. Mechanistic studies revealed that the assembly is required for catalysis and that the rate-limiting step of the reaction involves proton transfer from hydronium to the encapsulated substrate. Encapsulation in the assembly changes the orthoformate hydrolysis from an A-1 mechanism (in which decomposition of the protonated substrate is the rate-limiting step) to an A-S{sub E}2 mechanism (in which proton transfer is the rate-limiting step). The study of hydrolysis in the assembly was next extended to acetals, which were also catalytically hydrolyzed by the assembly in basic solution. Acetal hydrolysis changed from the A-1 mechanism in solution to an A-2 mechanism inside the assembly, where attack of water on the protonated substrate is rate limiting. This work provides rare examples of assembly-catalyzed reactions that proceed with substantial rate accelerations despite the absence of functional groups in the cavity and with mechanisms fully elucidated by quantitative kinetic studies.« less

Quantitative analysis by UV-Vis absorption spectroscopy of amino groups attached to the surface of carbon-based nanoparticles

NASA Astrophysics Data System (ADS)

Saraswati, T. E.; Astuti, A. R.; Rismana, N.

2018-03-01

Carbon-based nanoparticles must be modified due to their wide array of applications, especially when they are used as biomaterials. After modifying, quantitative analysis of the functional group is essential to evaluate a number of the available functional groups applied for further functionalization. In this study, we modified the carbon-based nanoparticles by amino group using submerged arc discharge in different liquids. The attached amino groups were then characterised and quantified by UV-Vis spectroscopy. This amino group functionalization was also confirmed by Fourier transform infrared (FTIR) spectra. The FTIR spectra of amine-modified nanoparticles show the definitive absorption peaks of N—H amine, C—H, C=O, C—N and Fe—O at 3418.97; 3000–2850 1700–1600 1400–1100 and 480-550 cm-1, respectively. The amine groups have different performance signals between the amine-modified and unmodified nanoparticles. The FTIR spectra results were correlated with the UV-Vis absorption spectroscopy method using acidic methyl orange. The UV-Vis absorption spectroscopy shows that the absorbance of methyl orange represented to amino groups number was 1.3 times higher when the pH of the solution was increased. The absorbance intensity was then used to estimate the quantity of amine groups attached.

Novel polyelectrolytes

NASA Technical Reports Server (NTRS)

Rembaum, Alan (Inventor); Yen, Shiao-Ping Siao (Inventor)

1978-01-01

Cationic polyelectrolytes are formed by the polymerization in absence of oxygen of a monomer of the general formula: ##STR1## where x is 3 or more than 6 and Z is I, Br or Cl to form high charge density linear polymers. Segments of the linear polymer may be attached to or formed in the presence of polyfunctional reactive tertiary amines or halogen polymeric substrates or polyfunctional lower molecular reactive polyfunctional substrates to form branched or star polyelectrolytes by a quaternization polymerization reaction.

Pd-Catalyzed Acetoxylation of γ-C(sp3)-H Bonds of Amines Directed by a Removable Bts-Protecting Group.

PubMed

Zheng, Yong; Song, Weibin; Zhu, Yefu; Wei, Bole; Xuan, Lijiang

2018-02-16

Pd-catalyzed acetoxylation of γ-C(sp 3 )-H bonds directed by Bts-protected amines using inexpensive PhI(OAc) 2 as oxidant is reported. The Bts-protecting group is easily introduced and removed under mild conditions. This protocol provides an important strategy for the construction of γ-hydroxyl amine derivatives.

Host-guest chemistry of dendrimer-drug complexes. 2. Effects of molecular properties of guests and surface functionalities of dendrimers.

PubMed

Hu, Jingjing; Cheng, Yiyun; Wu, Qinglin; Zhao, Libo; Xu, Tongwen

2009-08-06

The host-guest chemistry of dendrimer-drug complexes is investigated by NMR techniques, including (1)H NMR and 2D-NOESY studies. The effects of molecular properties of drug molecules (protonation ability and spatial steric hindrance of charged groups) and surface functionalities of dendrimers (positively charged amine groups and negatively charged carboxylate groups) on the host-guest interactions are discussed. Different interaction mechanisms between dendrimers and drug molecules are proposed on the basis of NMR results. Primary amine- and secondary amine-containing drugs preferentially bind to negatively charged dendrimers by strong electrostatic interactions, whereas tertiary amine and quaternary ammonium-containing drugs have weak binding ability with dendrimers due to relatively low protonation ability of the tertiary amine group and serious steric hindrance of the quaternary ammonium group. Positively charged drugs locate only on the surface of negatively charged dendrimers, whereas negatively charged drugs locate both on the surface and in the interior cavities of positively charged dendrimers. The host-guest chemistry of dendrimer-drug complexes is promising for the development of new drug delivery systems.

Anomalous length dependence of conductance of aromatic nanoribbons with amine anchoring groups

NASA Astrophysics Data System (ADS)

Bilić, Ante; Sanvito, Stefano

2012-09-01

Two sets of aromatic nanoribbons, based around a common hexagonal scaffolding, with single and dual terminal amine groups have been considered as potential molecular wires in a junction formed by gold leads. Charge transport through the two-terminal device has been modeled using density functional theory (with and without self-interaction correction) and the nonequilibrium Green's function method. The effects of wire length, multiple terminal contacts, and pathways across the junction have been investigated. For nanoribbons with the oligopyrene motif and conventional single amine terminal groups, an increase in the wire length causes an exponential drop in the conductance. In contrast, for the nanoribbons with the oligoperylene motif and dual amine anchoring groups the predicted conductance rises with the wire length over the whole range of investigated lengths. Only when the effects of self-interaction correction are taken into account, the conductance of the oligoperylene ribbons exhibits saturation for longer members of the series. The oligoperylene nanoribbons, with dual amine groups at both terminals, show the potential to fully harness the highly conjugated system of π molecular orbitals across the junction.

High capacity immobilized amine sorbents

DOEpatents

Gray, McMahan L [Pittsburgh, PA; Champagne, Kenneth J [Fredericktown, PA; Soong, Yee [Monroeville, PA; Filburn, Thomas [Granby, CT

2007-10-30

A method is provided for making low-cost CO.sub.2 sorbents that can be used in large-scale gas-solid processes. The improved method entails treating an amine to increase the number of secondary amine groups and impregnating the amine in a porous solid support. The method increases the CO.sub.2 capture capacity and decreases the cost of utilizing an amine-enriched solid sorbent in CO.sub.2 capture systems.

Photoredox-catalyzed Direct Reductive Amination of Aldehydes without an External Hydrogen/Hydride Source.

PubMed

Alam, Rauful; Molander, Gary A

2018-05-04

The direct reductive amination of aromatic aldehydes has been realized using a photocatalyst under visible light irradiation. The single electron oxidation of an in situ formed aminal species generates the putative α-amino radical that eventually delivers the reductive amination product. This method is operationally simple, highly selective, and functional group tolerant, which allows the direct synthesis of benzylic amines by a unique mechanistic pathway.

Solvent-Free Reductive Amination: An Organic Chemistry Experiment

ERIC Educational Resources Information Center

Goldstein, Steven W.; Cross, Amely V.

2015-01-01

The reductive amination reaction between an amine and an aldehyde or ketone is an important method to add an additional alkyl group to an amine nitrogen. In this experiment, students react a selection of benzylamines with aldehydes to form the corresponding imines. These imines are reduced with a mixture of "p"-toluenesulfonic acid…

A catalytic role of surface silanol groups in CO2 capture on the amine-anchored silica support.

PubMed

Cho, Moses; Park, Joonho; Yavuz, Cafer T; Jung, Yousung

2018-05-03

A new mechanism of CO2 capture on the amine-functionalized silica support is demonstrated using density functional theory calculations, in which the silica surface not only acts as a support to anchor amines, but also can actively participate in the CO2 capture process through a facile proton transfer reaction with the amine groups. The surface-mediated proton transfer mechanism in forming a carbamate-ammonium product has lower kinetic barrier (8.1 kcal mol-1) than the generally accepted intermolecular mechanism (12.7 kcal mol-1) under dry conditions, and comparable to that of the water-assisted intermolecular mechanism (6.0 kcal mol-1) under humid conditions. These findings suggest that the CO2 adsorption on the amine-anchored silica surface would mostly occur via the rate-determining proton transfer step that is catalyzed by the surface silanol groups.

Synthesis of 6-amino-5-cyano-1,4-disubstituted-2(1H)-pyrimidinones via copper-(I)-catalyzed alkyne-azide 'click chemistry' and their reactivity.

PubMed

Najahi, Ennaji; Sudor, Jan; Chabchoub, Fakher; Nepveu, Françoise; Zribi, Fethi; Duval, Romain

2010-12-03

In this paper we present the room temperature synthesis of a novel serie of 1,4-disubstituted-1,2,3-triazoles 4a-l by employing the (3+2) cycloaddition reaction of pyrimidinones containing alkyne functions with different model azides in the presence of copper sulphate and sodium ascorbate. To obtain the final triazoles, we also synthesized the major precursors 6-amino-5-cyano-1,4-disubstituted-2(1H)-pyrimidinones 3a-r from ethyl 2,2-dicyanovinylcarbamate derivatives 2a-c and various primary aromatic amines containing an alkyne group. The triazoles were prepared in good to very good yields.

Pyrimidine Nucleosides with a Reactive (β-Chlorovinyl)sulfone or (β-Keto)sulfone Group at the C5 Position, Their Reactions with Nucleophiles and Electrophiles, and Their Polymerase-Catalyzed Incorporation into DNA

PubMed Central

2018-01-01

Transition-metal-catalyzed chlorosulfonylation of 5-ethynylpyrimidine nucleosides provided (E)-5-(β-chlorovinyl)sulfones A, which undergo nucleophilic substitution with amines or thiols affording B. The treatment of vinyl sulfones A with ammonia followed by acid-catalyzed hydrolysis of the intermediary β-sulfonylvinylamines gave 5-(β-keto)sulfones C. The latter reacts with electrophiles, yielding α-carbon-alkylated or -sulfanylated analogues D. The 5′-triphosphates of A and C were incorporated into double-stranded DNA, using open and one-nucleotide gap substrates, by human or Escherichia coli DNA-polymerase-catalyzed reactions. PMID:29732453

New diamine hardeners for epoxies

NASA Technical Reports Server (NTRS)

Bell, V. L.; St. Clair, T. L.

1977-01-01

Stronger amine-cured polyepoxides can be obtained by using those diaminobenzophenones and diaminodiphenylmethanes that have amine groups located at ortho or meta positions to carbonyl or methylene groups joining two benzene rings.

In situ synthesis of gold nanoparticles in exponentially-growing layer-by-layer films

PubMed Central

Shen, Liyan; Rapenne, Laetitia; Chaudouet, Patrick; Ji, Jian; Picart, Catherine

2014-01-01

In situ synthesis of inorganic nanoparticles (NPs) in polyelectrolytes multilayers (PEMs) has recently gained much attention. Due to the versatility of their composition, PEMs offer a unique opportunity to synthesize a variety of NPs. So far, mostly cationic precursors have been used and only few studies have investigated the possibility of using amine groups to bind anionic precursors. Here, we use exponentially growing poly(L-lysine)/hyaluronan (PLL/HA) films as a nanoreservoir to bind and sequester aurochlorate (AuCl4−) anions thanks to the large number of free amine groups. The polypeptide-polysaccharide reactive template enabled the formation in a spatially-confined environment of gold NP at a very high yield. The synthesized gold NPs were homogenous and well-dispersed in the nanocomposite. Importantly, there was no particular effect of the film-ending layer (either PLL or HA). The largest particles of ~ 9 nm and the largest amount of gold were obtained at acidic pH of 3. When the pH was increased, smaller and more numerous NPs were synthesized but the total amount of gold was lower. Based on UV-visible spectrometry, FTIR and TEM data, we finally propose a scheme for the mechanism of gold NPs formation, in which several groups of PLL and HA contribute to the binding of gold ions, the nucleation and growth of NPs, and their stabilization in the “bulk” of the film. PMID:22981588

[Algicidal effect of (2-isobutoxyphenyl) amine on Alexandrium tamarense].

PubMed

Zhang, Huajun; Peng, Yun; Zhang, Su; An, Xinli; Li, Yi; Zheng, Wei; Zheng, Tianling

2015-07-04

A strain named BS01 showed strong algicidal activity to Alexandrium tamarense and we got algicidal compound (2-isobutoxyphenyl) amine from BS01 to study its algicidal effect on A. tamarense. We studied the algicidal mechanism of (2-isobutoxyphenyl) amine on photosynthetic process, antioxidant enzyme activities and morphological change of A. tamarense. After 24 hours treatment with (2-isobutoxyphenyl) amine, algicidal activity was 84. 1% with the concentration of 20 µg/mL. The compound could induce a reactive oxygen species burst in P. globosa in 0. 5 hours which could cause serious oxidative damage to algal cells. The Fv/Fm value which could reflect photosystem II (PS II) electron flow status also decreased. To eliminate the excess ROS, the activities of the antioxidant systems (including superoxide dismutase and catalase) increased significantly during exposure. Transmission electron microscope analysis showed obvious morphological modifications of chloroplast dismantling as a part of the algicidal process. These results indicated that the lysis mechanism of algicidal compound on algae may primarily be the increasing level of ROS in the algal cells.

Self-assembling holographic biosensors and biocomputers.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Light, Yooli Kim; Bachand, George David; Schoeniger, Joseph S.

2006-05-01

We present concepts for self-assembly of diffractive optics with potential uses in biosensors and biocomputers. The simplest such optics, diffraction gratings, can potentially be made from chemically-stabilized microtubules migrating on nanopatterned tracks of the motor protein kinesin. We discuss the fabrication challenges involved in patterning sub-micron-scale structures with proteins that must be maintained in aqueous buffers to preserve their activity. A novel strategy is presented that employs dry contact printing onto glass-supported amino-silane monolayers of heterobifunctional crosslinkers, followed by solid-state reactions of these cross-linkers, to graft patterns of reactive groups onto the surface. Successive solution-phase addition of cysteine-mutant proteins andmore » amine-reactive polyethylene glycol allows assembly of features onto the printed patterns. We present data from initial experiments showing successful micro- and nanopatterning of lines of single-cysteine mutants of kinesin interleaved with lines of polyethylene, indicating that this strategy can be employed to arrays of features with resolutions suitable for gratings.« less

Assessment of Mexican Arnica (Heterotheca inuloides Cass) and Rosemary (Rosmarinus officinalis) Extracts on Dopamine and Selected Biomarkers of Oxidative Stress in Stomach and Brain of Salmonella typhimurium Infected rats.

PubMed

Guzmàn, David Calderón; Herrera, Maribel Ortiz; Brizuela, Norma Osnaya; Mejía, Gerardo Barragàn; García, Ernestina Hernàndez; Olguín, Hugo Juàrez; Peraza, Armando Valenzuela; Ruíz, Norma Labra; Del Angel, Daniel Santamaría

2017-01-01

The effects of some natural products on dopamine (DA) and 5-hydroxyindole acetic acid (5-HIAA) in brain of infected models are still unclear. The purpose of this study was to measure the effect of Mexican arnica/rosemary (MAR) water extract and oseltamivir on both biogenic amines and some oxidative biomarkers in the brain and stomach of young rats under infection condition. Female Wistar rats (weight 80 g) in the presence of MAR or absence (no-MAR) were treated as follows: group 1, buffer solution (controls); oseltamivir (100 mg/kg), group 2; culture of Salmonella typhimurium ( S.Typh ) (1 × 10 6 colony-forming units/rat) group 3; oseltamivir (100 mg/kg) + S.Typh (same dose) group 4. Drug and extracts were administered intraperitoneally every 24 h for 5 days, and S.Typh was given orally on days 1 and 3. On the fifth day, blood was collected to measure glucose and hemoglobin. The brains and stomachs were obtained to measure levels of DA, 5-HIAA, glutathione (GSH), TBARS, H 2 O 2 , and total ATPase activity using validated methods. DA levels increased in MAR group treated with oseltamivir alone but decreased in no-MAR group treated with oseltamivir plus S.Typh . 5-HIAA, GSH, and H 2 O 2 decreased in this last group, and ATPase activity increased in MAR group treated with oseltamivir plus S.Typh . TBARS (lipid peroxidation) increased in MAR group that received oseltamivir alone. Most of the biomarkers were not altered significantly in the stomach. MAR extract alters DA and metabolism of 5-HIAA in the brain of young animals infected. Antioxidant capacity may be involved in these effects. The purpose of this study was to measure the effect of Mexican arnica/rosemary water extract and oseltamivir on both biogenic amines and some oxidative biomarkers in the brain and stomach of young rats under infection condition. Results: Mexican arnica and rosemary extract alter dopamine and metabolism of 5-HIAA in the brain of young animals infected. Antioxidant capacity may be involved in these effects. Abbreviations used: AS: Automated system, ATP: Adenosine triphosphate, CNS: Central nervous system, CFU: Colony-forming unit, DA: Dopamine EDTA: Ethylenediaminetetraacetic acid, 5-HIAA: Äcido 5-hidroxindolacético (serotonina), GABA: γ-aminobutyric acid, GSH: Glutathione, H2O2: Hidrogen peroxide, HCLO4: Perchloric acid, iNOS: Inducible nitric oxide synthase, LPS: Lipopolysaccharides, MAR: Arnica/Rosemary, NaCl: Sodium Chloride, NOGSH: nitrosoglutathione, NOS: Nitric oxide, OPT: Ortho-phtaldialdehyde, Pbs: Phosphate buffered saline, pH: potential of Hydrogen, Pi: Inorganic phosphate, ROS: Reactive oxygen species, RNSs: Reactive nitrogen species Tba: Thiobarbaturic acid, TBARS: Thiobarbituric aid reactive, Tca: Trichloroacetic, Tris-HCL: Tris hydrochloride, TSA: Trypticasein Soya Agar.

Assessment of Mexican Arnica (Heterotheca inuloides Cass) and Rosemary (Rosmarinus officinalis) Extracts on Dopamine and Selected Biomarkers of Oxidative Stress in Stomach and Brain of Salmonella typhimurium Infected rats

PubMed Central

Guzmàn, David Calderón; Herrera, Maribel Ortiz; Brizuela, Norma Osnaya; Mejía, Gerardo Barragàn; García, Ernestina Hernàndez; Olguín, Hugo Juàrez; Peraza, Armando Valenzuela; Ruíz, Norma Labra; Del Angel, Daniel Santamaría

2017-01-01

Background: The effects of some natural products on dopamine (DA) and 5-hydroxyindole acetic acid (5-HIAA) in brain of infected models are still unclear. Objective: The purpose of this study was to measure the effect of Mexican arnica/rosemary (MAR) water extract and oseltamivir on both biogenic amines and some oxidative biomarkers in the brain and stomach of young rats under infection condition. Methods: Female Wistar rats (weight 80 g) in the presence of MAR or absence (no-MAR) were treated as follows: group 1, buffer solution (controls); oseltamivir (100 mg/kg), group 2; culture of Salmonella typhimurium (S.Typh) (1 × 106 colony-forming units/rat) group 3; oseltamivir (100 mg/kg) + S.Typh (same dose) group 4. Drug and extracts were administered intraperitoneally every 24 h for 5 days, and S.Typh was given orally on days 1 and 3. On the fifth day, blood was collected to measure glucose and hemoglobin. The brains and stomachs were obtained to measure levels of DA, 5-HIAA, glutathione (GSH), TBARS, H2O2, and total ATPase activity using validated methods. Results: DA levels increased in MAR group treated with oseltamivir alone but decreased in no-MAR group treated with oseltamivir plus S.Typh. 5-HIAA, GSH, and H2O2 decreased in this last group, and ATPase activity increased in MAR group treated with oseltamivir plus S.Typh. TBARS (lipid peroxidation) increased in MAR group that received oseltamivir alone. Most of the biomarkers were not altered significantly in the stomach. Conclusion: MAR extract alters DA and metabolism of 5-HIAA in the brain of young animals infected. Antioxidant capacity may be involved in these effects. SUMMARY The purpose of this study was to measure the effect of Mexican arnica/rosemary water extract and oseltamivir on both biogenic amines and some oxidative biomarkers in the brain and stomach of young rats under infection condition. Results: Mexican arnica and rosemary extract alter dopamine and metabolism of 5-HIAA in the brain of young animals infected. Antioxidant capacity may be involved in these effects. Abbreviations used: AS: Automated system, ATP: Adenosine triphosphate, CNS: Central nervous system, CFU: Colony-forming unit, DA: Dopamine EDTA: Ethylenediaminetetraacetic acid, 5-HIAA: Äcido 5-hidroxindolacético (serotonina), GABA: γ-aminobutyric acid, GSH: Glutathione, H2O2: Hidrogen peroxide, HCLO4: Perchloric acid, iNOS: Inducible nitric oxide synthase, LPS: Lipopolysaccharides, MAR: Arnica/Rosemary, NaCl: Sodium Chloride, NOGSH: nitrosoglutathione, NOS: Nitric oxide, OPT: Ortho-phtaldialdehyde, Pbs: Phosphate buffered saline, pH: potential of Hydrogen, Pi: Inorganic phosphate, ROS: Reactive oxygen species, RNSs: Reactive nitrogen species Tba: Thiobarbaturic acid, TBARS: Thiobarbituric aid reactive, Tca: Trichloroacetic, Tris-HCL: Tris hydrochloride, TSA: Trypticasein Soya Agar PMID:28539708

Fluorescent silica nanoparticles with chemically reactive surface: Controlling spatial distribution in one-step synthesis.

PubMed

Vera, María L; Cánneva, Antonela; Huck-Iriart, Cristián; Requejo, Felix G; Gonzalez, Mónica C; Dell'Arciprete, María L; Calvo, Alejandra

2017-06-15

The encapsulation of fluorescent dyes inside silica nanoparticles is advantageous to improve their quality as probes. Inside the particle, the fluorophore is protected from the external conditions and its main emission parameters remains unchanged even in the presence of quenchers. On the other hand, the amine-functionalized nanoparticle surface enables a wide range of applications, as amino groups could be easily linked with different biomolecules for targeting purposes. This kind of nanoparticle is regularly synthesized by methods that employ templates, additional nanoparticle formation or multiple pathway process. However, a one-step synthesis will be an efficient approach in this sort of bifunctional hybrid nanoparticles. A co-condensation sol-gel synthesis of hybrid fluorescent silica nanoparticle where developed. The chemical and morphological characterization of the particles where investigated by DRIFTS, XPS, SEM and SAXS. The nanoparticle fluorescent properties were also assessed by excitation-emission matrices and time resolved experiments. We have developed a one-pot synthesis method that enables the simultaneous incorporation of functionalities, the fluorescent molecule and the amino group, by controlling co-condensation process. An exhaustive characterization allows the definition of the spatial distribution of the fluorescent probe, fluorescein isothiocyanate, inside the particle and reactive amino groups on the surface of the nanoparticle with diameter about 100nm. Copyright © 2017 Elsevier Inc. All rights reserved.

Chemical copatterning strategies using azlactone-based block copolymers

DOE PAGES

Masigol, Mohammadali; Barua, Niloy; Retterer, Scott T.; ...

2017-09-01

Interfaces can be modified with azlactone-functional polymers in order to manipulate the chemical surface reactivity. Azlactone groups are highly reactive toward amine, thiol, and alcohol nucleophiles, providing a versatile coupling chemistry for secondary surface modification. Azlactone-based surface polymers have been explored in numerous applications, including chemical and biological capture, sensing, and cell culture. These applications often require that the polymer is copatterned within a chemically or biologically inert background; however, common fabrication methods degrade azlactone groups during processing steps or result in polymer films with poorly controlled thicknesses. Here, the authors develop fabrication strategies using parylene lift-off and interface-directed assemblymore » methods to generate microscale patterns of azlactone-based block copolymer in chemically or biologically inert backgrounds. The functionality of azlactone groups was preserved during fabrication, and patterned films appeared as uniform, 80–120nm brushlike films. The authors also develop a patterning approach that uses a novel microcontact stamping method to generate cross-linked, three-dimensional structures of azlactone-based polymers with controllable, microscale thicknesses. The authors identify the benefits of each approach and expect these polymers and patterning strategies to provide a versatile toolbox for developing synthetic interfaces with tuned chemical and physical features for sensing, cell culture, or material capture applications.« less

Chemical copatterning strategies using azlactone-based block copolymers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masigol, Mohammadali; Barua, Niloy; Retterer, Scott T.

Interfaces can be modified with azlactone-functional polymers in order to manipulate the chemical surface reactivity. Azlactone groups are highly reactive toward amine, thiol, and alcohol nucleophiles, providing a versatile coupling chemistry for secondary surface modification. Azlactone-based surface polymers have been explored in numerous applications, including chemical and biological capture, sensing, and cell culture. These applications often require that the polymer is copatterned within a chemically or biologically inert background; however, common fabrication methods degrade azlactone groups during processing steps or result in polymer films with poorly controlled thicknesses. Here, the authors develop fabrication strategies using parylene lift-off and interface-directed assemblymore » methods to generate microscale patterns of azlactone-based block copolymer in chemically or biologically inert backgrounds. The functionality of azlactone groups was preserved during fabrication, and patterned films appeared as uniform, 80–120nm brushlike films. The authors also develop a patterning approach that uses a novel microcontact stamping method to generate cross-linked, three-dimensional structures of azlactone-based polymers with controllable, microscale thicknesses. The authors identify the benefits of each approach and expect these polymers and patterning strategies to provide a versatile toolbox for developing synthetic interfaces with tuned chemical and physical features for sensing, cell culture, or material capture applications.« less

Characterizing monoclonal antibody structure by carboxyl group footprinting

PubMed Central

Kaur, Parminder; Tomechko, Sara E; Kiselar, Janna; Shi, Wuxian; Deperalta, Galahad; Wecksler, Aaron T; Gokulrangan, Giridharan; Ling, Victor; Chance, Mark R

2015-01-01

Structural characterization of proteins and their antigen complexes is essential to the development of new biologic-based medicines. Amino acid-specific covalent labeling (CL) is well suited to probe such structures, especially for cases that are difficult to examine by alternative means due to size, complexity, or instability. We present here a detailed account of carboxyl group labeling (with glycine ethyl ester (GEE) tagging) applied to a glycosylated monoclonal antibody therapeutic (mAb). The experiments were optimized to preserve the structural integrity of the mAb, and experimental conditions were varied and replicated to establish the reproducibility of the technique. Homology-based models were generated and used to compare the solvent accessibility of the labeled residues, which include aspartic acid (D), glutamic acid (E), and the C-terminus (i.e., the target probes), with the experimental data in order to understand the accuracy of the approach. Data from the mAb were compared to reactivity measures of several model peptides to explain observed variations in reactivity. Attenuation of reactivity in otherwise solvent accessible probes is documented as arising from the effects of positive charge or bond formation between adjacent amine and carboxyl groups, the latter accompanied by observed water loss. A comparison of results with previously published data by Deperalta et al using hydroxyl radical footprinting showed that 55% (32/58) of target residues were GEE labeled in this study whereas the previous study reported 21% of the targets were labeled. Although the number of target residues in GEE labeling is fewer, the two approaches provide complementary information. The results highlight advantages of this approach, such as the ease of use at the bench top, the linearity of the dose response plots at high levels of labeling, reproducibility of replicate experiments (<2% variation in modification extent), the similar reactivity of the three target probes, and significant correlation of reactivity and solvent accessible surface area. PMID:25933350

Comparison of Hydrazone Heterobifunctional Crosslinking Agents for Reversible Conjugation of Thiol-Containing Chemistry

PubMed Central

Christie, R. James; Anderson, Diana J.; Grainger, David W.

2010-01-01

Reversible covalent conjugation chemistries that allow site- and condition-specific coupling and uncoupling reactions are attractive components in nanotechnologies, bioconjugation methods, imaging and drug delivery systems. Here, we compare three heterobifunctional crosslinkers, containing both thiol- and amine- reactive chemistry, to form pH-labile hydrazones with hydrazide derivatives of the known and often published water-soluble polymer, poly[N-(2-hydroxypropyl methacrylamide)] (pHPMA), while subsequently coupling thiol-containing molecules to the crosslinker via maleimide addition. Two novel crosslinkers were prepared from the popular heterobifunctional crosslinking agent, succinimidyl-4-(N-maleimidomethyl) cyclohexane-1-carboxylate (SMCC), modified to contain either terminal aldehyde groups (i.e., 1-(N-3-propanal)-4-(N-maleimidomethyl) cyclohexane carboxamide, PMCA) or methylketone groups (i.e., 1-(N-3-butanone)-4-(N-maleimidomethyl) cyclohexane carboxamide, BMCA). A third crosslinking agent was the commercially available N-4-acetylphenyl maleimide (APM). PMCA and BMCA exhibited excellent reactivity towards hydrazide-derivatized pHPMA with essentially complete hydrazone conjugation to polymer reactive sites, while APM coupled only ~ 60% of available reactive sites on the polymer despite a 3-fold molar excess relative to polymer hydrazide groups. All polymer hydrazone conjugates bearing these bifunctional agents were then further reacted with thiol-modified tetramethylrhodamine dye, confirming crosslinker maleimide reactivity after initial hydrazone polymer conjugation. Incubation of dye-labeled polymer conjugates in phosphate buffered saline at 37°C showed that hydrazone coupling resulting from APM exhibited the greatest difference in stability between pH 7.4 and 5.0, with hydrolysis and dye release increased at pH 5.0 over a 24hr incubation period. Polymer conjugates bearing hydrazones formed from crosslinker BMCA exhibited intermediate stability with hydrolysis much greater at pH 5.0 at early time points, but hydrolysis at pH 7.4 was significant after 5 hrs. Hydrazones formed with the PMCA crosslinker showed no difference in release rates at pH 7.4 and 5.0. PMID:20695431

Direct and Efficient Dehydrogenation of Tetrahydroquinolines and Primary Amines Using Corona Discharge Generated on Ambient Hydrophobic Paper Substrate.

PubMed

Davis, Kathryn M; Badu-Tawiah, Abraham K

2017-04-01

The exposure of an aqueous-based liquid drop containing amines and graphite particles to plasma generated by a corona discharge results in heterogeneous aerobic dehydrogenation reactions. This green oxidation reaction occurring in ambient air afforded the corresponding quinolines and nitriles from tetrahydroquinolines and primary amines, respectively, at >96% yields in less than 2 min of reaction time. The accelerated dehydrogenation reactions occurred on the surface of a low energy hydrophobic paper, which served both as container for holding the reacting liquid drop and as a medium for achieving paper spray ionization of reaction products for subsequent characterization by ambient mass spectrometry. Control experiments indicate superoxide anions (O 2 •- ) are the main reactive species; the presence of graphite particles introduced heterogeneous surface effects, and enabled the efficient sampling of the plasma into the grounded analyte droplet solution. Graphical Abstract ᅟ.

Direct and Efficient Dehydrogenation of Tetrahydroquinolines and Primary Amines Using Corona Discharge Generated on Ambient Hydrophobic Paper Substrate

NASA Astrophysics Data System (ADS)

Davis, Kathryn M.; Badu-Tawiah, Abraham K.

2017-04-01

The exposure of an aqueous-based liquid drop containing amines and graphite particles to plasma generated by a corona discharge results in heterogeneous aerobic dehydrogenation reactions. This green oxidation reaction occurring in ambient air afforded the corresponding quinolines and nitriles from tetrahydroquinolines and primary amines, respectively, at >96% yields in less than 2 min of reaction time. The accelerated dehydrogenation reactions occurred on the surface of a low energy hydrophobic paper, which served both as container for holding the reacting liquid drop and as a medium for achieving paper spray ionization of reaction products for subsequent characterization by ambient mass spectrometry. Control experiments indicate superoxide anions (O2 •-) are the main reactive species; the presence of graphite particles introduced heterogeneous surface effects, and enabled the efficient sampling of the plasma into the grounded analyte droplet solution.

Chemoselective Aliphatic C–H Bond Oxidation Enabled by Polarity Reversal

PubMed Central

2017-01-01

Methods for selective oxidation of aliphatic C–H bonds are called on to revolutionize organic synthesis by providing novel and more efficient paths. Realization of this goal requires the discovery of mechanisms that can alter in a predictable manner the innate reactivity of these bonds. Ideally, these mechanisms need to make oxidation of aliphatic C–H bonds, which are recognized as relatively inert, compatible with the presence of electron rich functional groups that are highly susceptible to oxidation. Furthermore, predictable modification of the relative reactivity of different C–H bonds within a molecule would enable rapid diversification of the resulting oxidation products. Herein we show that by engaging in hydrogen bonding, fluorinated alcohols exert a polarity reversal on electron rich functional groups, directing iron and manganese catalyzed oxidation toward a priori stronger and unactivated C–H bonds. As a result, selective hydroxylation of methylenic sites in hydrocarbons and remote aliphatic C–H oxidation of otherwise sensitive alcohol, ether, amide, and amine substrates is achieved employing aqueous hydrogen peroxide as oxidant. Oxidations occur in a predictable manner, with outstanding levels of product chemoselectivity, preserving the first-formed hydroxylation product, thus representing an extremely valuable tool for synthetic planning and development. PMID:29296677

Chemoselective Aliphatic C-H Bond Oxidation Enabled by Polarity Reversal.

PubMed

Dantignana, Valeria; Milan, Michela; Cussó, Olaf; Company, Anna; Bietti, Massimo; Costas, Miquel

2017-12-27

Methods for selective oxidation of aliphatic C-H bonds are called on to revolutionize organic synthesis by providing novel and more efficient paths. Realization of this goal requires the discovery of mechanisms that can alter in a predictable manner the innate reactivity of these bonds. Ideally, these mechanisms need to make oxidation of aliphatic C-H bonds, which are recognized as relatively inert, compatible with the presence of electron rich functional groups that are highly susceptible to oxidation. Furthermore, predictable modification of the relative reactivity of different C-H bonds within a molecule would enable rapid diversification of the resulting oxidation products. Herein we show that by engaging in hydrogen bonding, fluorinated alcohols exert a polarity reversal on electron rich functional groups, directing iron and manganese catalyzed oxidation toward a priori stronger and unactivated C-H bonds. As a result, selective hydroxylation of methylenic sites in hydrocarbons and remote aliphatic C-H oxidation of otherwise sensitive alcohol, ether, amide, and amine substrates is achieved employing aqueous hydrogen peroxide as oxidant. Oxidations occur in a predictable manner, with outstanding levels of product chemoselectivity, preserving the first-formed hydroxylation product, thus representing an extremely valuable tool for synthetic planning and development.

SEDIMENT-ASSOCIATED REACTIONS OF AROMATIC AMINES: QSAR DEVELOPMENT

EPA Science Inventory

Despite the common occurrence of the aromatic amine functional group in environmental contaminants, few quantitative structure-activity relationships (QSARs) have been developed to predict sorption kinetics for aromatic amines in natural soils and sediments. Towards the goal of d...

Aryl-O reductive elimination from reaction of well-defined aryl-Cu(III) species with phenolates: the importance of ligand reactivity.

PubMed

Casitas, Alicia; Ioannidis, Nikolaos; Mitrikas, George; Costas, Miquel; Ribas, Xavi

2011-09-21

Well-defined aryl-Cu(III) species undergo rapid reductive elimination upon reaction with phenolates (PhO(-)), to form aryl-OPh cross-coupling products. Kinetic studies show that the reaction follows a different mechanistic pathway compared to the reaction with phenols. The pH active cyclized pincer-like ligand undergoes an initial amine deprotonation that triggers a faster reactivity at room temperature. A mechanistic proposal for the enhanced reactivity and the role of EPR-detected Cu(II) species will be discussed in detail. This journal is © The Royal Society of Chemistry 2011

A Comparison of Five Bioconjugatable Ferrocenes for Labeling of Biomolecules†

PubMed Central

Ge, Dongbiao; Levicky, Rastislav

2010-01-01

Five electroactive ferrocene tags for labelling of biomolecules are contrasted with regard to conjugation reactivity with amine and thiol moieties, stability to loss of electrochemical activity, and impact of molecular structure on the redox potential of the free and DNA-conjugated forms. PMID:20740226

Tailoring pore properties of MCM-48 silica for selective adsorption of CO2.

PubMed

Kim, Sangil; Ida, Junichi; Guliants, Vadim V; Lin, Jerry Y S

2005-04-07

Four different types of amine-attached MCM-48 silicas were prepared and investigated for CO(2) separation from N(2). Monomeric and polymeric hindered and unhindered amines were attached to the pore surface of the MCM-48 silica and characterized with respect to their CO(2) sorption properties. The pore structures and amino group content in these modified silicas were investigated by XRD, FT-IR, TGA, N(2) adsorption/desorption at 77 K and CHN/Si analysis, which confirmed that in all cases the amino groups were attached to the pore surface of MCM-48 at 1.5-5.2 mmol/g. The N(2) adsorption/desorption analysis showed a considerable decrease of the pore volume and surface area for the MCM-48 silica containing a polymeric amine (e.g., polyethyleneimine). The CO(2) adsorption rates and capacities of the amine-attached MCM-48 samples were studied employing a sorption microbalance. The results obtained indicated that in addition to the concentration of surface-attached amino groups, specific interactions between CO(2) and the surface amino groups, and the resultant pore structure after amine group attachment have a significant impact on CO(2) adsorption properties of these promising adsorbent materials.

Chlorination of tramadol: Reaction kinetics, mechanism and genotoxicity evaluation.

PubMed

Cheng, Hanyang; Song, Dean; Chang, Yangyang; Liu, Huijuan; Qu, Jiuhui

2015-12-01

Tramadol (TRA) is one of the most detected analgesics in environmental matrices, and it is of high significance to study the reactivity of TRA during chlorination considering its potential toxicity to the environment. The chlorine/TRA reaction is first order with respect to the TRA concentration, and a combination of first-order and second-order with respect to chlorine concentration. The pH dependence of the observed rate constants (kobs) showed that the TRA oxidation reactivity increased with increasing pH. kobs can be quantitatively described by considering all active species including Cl2, Cl2O and HOCl, and the individual rate constants of HOCl/TRA(0), HOCl/TRAH(+), Cl2/TRA and Cl2O/TRA reactions were calculated to be (2.61±0.29)×10(3)M(-1)s(-1), 14.73±4.17M(-1)s(-1), (3.93±0.34)×10(5)M(-1)s(-1) and (5.66±1.83)×10(6)M(-1)s(-1), respectively. Eleven degradation products were detected with UPLC-Q-TOF-MS, and the corresponding structures of eight products found under various pH conditions were proposed. The amine group was proposed to be the initial attack site under alkaline pH conditions, where reaction of the deprotonated amine group with HOCl is favorable. Under acidic and neutral pH conditions, however, two possible reaction pathways were proposed. One is an electrophilic substitution on the aromatic ring, and another is an electrophilic substitution on the nitrogen, leading to an N-chlorinated intermediate, which can be further oxidized. Finally, the SOS/umu test showed that the genotoxicity of TRA chlorination products increased with increasing dosage of chlorine, which was mostly attributed to the formation of some chlorine substitution products. Copyright © 2015 Elsevier Ltd. All rights reserved.

Isotope-labeled cross-linkers and Fourier transform ion cyclotron resonance mass spectrometry for structural analysis of a protein/peptide complex.

PubMed

Ihling, Christian; Schmidt, Andreas; Kalkhof, Stefan; Schulz, Daniela M; Stingl, Christoph; Mechtler, Karl; Haack, Michael; Beck-Sickinger, Annette G; Cooper, Dermot M F; Sinz, Andrea

2006-08-01

For structural studies of proteins and their complexes, chemical cross-linking combined with mass spectrometry presents a promising strategy to obtain structural data of protein interfaces from low quantities of proteins within a short time. We explore the use of isotope-labeled cross-linkers in combination with Fourier transform ion cyclotron resonance (FTICR) mass spectrometry for a more efficient identification of cross-linker containing species. For our studies, we chose the calcium-independent complex between calmodulin and a 25-amino acid peptide from the C-terminal region of adenylyl cyclase 8 containing an "IQ-like motif." Cross-linking reactions between calmodulin and the peptide were performed in the absence of calcium using the amine-reactive, isotope-labeled (d0 and d4) cross-linkers BS3 (bis[sulfosuccinimidyl]suberate) and BS2G (bis[sulfosuccinimidyl]glutarate). Tryptic in-gel digestion of excised gel bands from covalently cross-linked complexes resulted in complicated peptide mixtures, which were analyzed by nano-HPLC/nano-ESI-FTICR mass spectrometry. In cases where more than one reactive functional group, e.g., amine groups of lysine residues, is present in a sequence stretch, MS/MS analysis is a prerequisite for unambiguously identifying the modified residues. MS/MS experiments revealed two lysine residues in the central alpha-helix of calmodulin as well as three lysine residues both in the C-terminal and N-terminal lobes of calmodulin to be cross-linked with one single lysine residue of the adenylyl cyclase 8 peptide. Further cross-linking studies will have to be conducted to propose a structural model for the calmodulin/peptide complex, which is formed in the absence of calcium. The combination of using isotope-labeled cross-linkers, determining the accurate mass of intact cross-linked products, and verifying the amino acid sequences of cross-linked species by MS/MS presents a convenient approach that offers the perspective to obtain structural data of protein assemblies within a few days.

SEDIMENT-ASSOCIATED REACTIONS OF AROMATIC AMINES. 2. QSAR DEVELOPMENT

EPA Science Inventory

The fate of aromatic amines in soils and sediments is dominated by irreversible binding through nucleophilic addition and oxidative radical coupling. Despite the common occurrence of the aromatic amine functional group in organic chemicals, the molecular properties useful for pr...

PEGylated PAMAM dendrimers: Enhancing efficacy and mitigating toxicity for effective anticancer drug and gene delivery.

PubMed

Luong, Duy; Kesharwani, Prashant; Deshmukh, Rahul; Mohd Amin, Mohd Cairul Iqbal; Gupta, Umesh; Greish, Khaled; Iyer, Arun K

2016-10-01

Poly(amidoamine) dendrimers (PAMAM) are well-defined, highly branched, nanoscale macromolecules with numerous active amine groups on the surface. PAMAM dendrimer can enhance the solubility of hydrophobic drugs, and with numerous reactive groups on the surface PAMAM dendrimer can be engineered with various functional groups for specific targeting ability. However, in physiological conditions, these amine groups are toxic to cells and limit the application of PAMAM. In the recent years, polyethylene glycol (PEG) conjugation has been the most widely used approach to reduce the toxicity of the active group on dendrimer surface. PEG molecules are known to be inert, non-immunogenic, and non-antigenic with a significant water solubility. PEGylated PAMAM-mediated delivery could not only overcome the limitations of dendrimer such as drug leakage, immunogenicity, hemolytic toxicity, systemic cytotoxicity but they also have the ability to enhance the solubilization of hydrophobic drugs and facilitates the potential for DNA transfection, siRNA delivery and tumor targeting. This review focuses on the recent developments on the application and influence of PEGylation on various biopharmaceutical properties of PAMAM dendrimers. It is well established that dendrimers have demonstrated promising potentials for drug delivery. However, the inherent toxicity poses challenges for its clinical translation. In this regard, PEGylation has helped mitigate some of the toxicity concerns of dendrimers and have paved the way forward for testing its translational potentials. The review is a collection of articles demonstrating the utility of PEGylation of the most studied PAMAM dendrimers. To our knowledge, this is a first such attempt to draw reader's attention, specifically, towards PEGylated PAMAM dendrimers. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Ketene reactions with tertiary amines.

PubMed

Allen, Annette D; Andraos, John; Tidwell, Thomas T; Vukovic, Sinisa

2014-01-17

Tertiary amines react rapidly and reversibly with arylketenes in acetonitrile forming observable zwitterions, and these undergo amine catalyzed dealkylation forming N,N-disubstituted amides. Reactions of N-methyldialkylamines show a strong preference for methyl group loss by displacement, as predicted by computational studies. Loss of ethyl groups in reactions with triethylamine also occur by displacement, but preferential loss of isopropyl groups in the phenylketene reaction with diisopropylethylamine evidently involves elimination. Quinuclidine rapidly forms long-lived zwitterions with arylketenes, providing a model for catalysis by cinchona and related alkaloids in stereoselective additions to ketenes.

Aminosilica materials as adsorbents for the selective removal of aldehydes and ketones from simulated bio-oil.

PubMed

Drese, Jeffrey H; Talley, Anne D; Jones, Christopher W

2011-03-21

The fast pyrolysis of biomass is a potential route to the production of liquid biorenewable fuel sources. However, degradation of the bio-oil mixtures due to reaction of oxygenates, such as aldehydes and ketones, reduces the stability of the liquids and can impact long-term storage and shipping. Herein, solid aminosilica adsorbents are described for the selective adsorptive removal of reactive aldehyde and ketone species. Three aminosilica adsorbents are prepared through the reaction of amine-containing silanes with pore-expanded mesoporous silica. A fourth aminosilica adsorbent is prepared through the ring-opening polymerization of aziridine from pore-expanded mesoporous silica. Adsorption experiments with a representative mixture of bio-oil model compounds are presented using each adsorbent at room temperature and 45 °C. The adsorbent comprising only primary amines adsorbs the largest amount of aldehydes and ketones. The overall reactivity of this adsorbent increases with increasing temperature. Additional aldehyde screening experiments show that the reactivity of aldehydes with aminosilicas varies depending on their chemical functionality. Initial attempts to regenerate an aminosilica adsorbent by acid hydrolysis show that they can be at least partially regenerated for further use. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of Monomer Structure on Curing Behavior, CO2 Solubility, and Gas Permeability of Ionic Liquid-Based Epoxy-Amine Resins and Ion-Gels

DOE Office of Scientific and Technical Information (OSTI.GOV)

McDanel, WM; Cowan, MG; Barton, JA

2015-04-29

New imidazolium- and pyrrolidinium-based bis(epoxide)-functionalized ionic liquid (IL) monorners were synthesized: and reacted with multifunctional amine monomers to produce cross-linked, epoxy-amine poly(ionic liquid) (PIL) resins and PIL/IL ion-gel membranes. The length and chemical nature (i.e., alkyl versus ether) between the irrildazolium group and epokitie groups were studied to determine their effects on CO2 affinity. The CO2 uptake (millimoles per gram) of the epoxy amine resins (between 0.1 and 1 mmol/g) was found to depend predominately on the epoxide-to-amine ratio and the bis(epoxide) IL molecular weight. The effect of using a primary versus a secondary amine-containing multifunctional monoiner was also assessedmore » for the resin-synthesis. Secondary amines can increase CO2 permeability but also increase the iime required for biS(epoxide) coriversion. When either the epoxide or athine monomer structure is changed, the CO2 solubility and permeability of the resulting PIL resins and ion-sel membranes can be tuned.« less

Development and validation of an LC-MS/MS method for the determination of biogenic amines in wines and beers.

PubMed

Nalazek-Rudnicka, Katarzyna; Wasik, Andrzej

2017-01-01

Biogenic amines are group of organic, basic, nitrogenous compounds that naturally occur in plant, microorganism, and animal organisms. Biogenic amines are mainly produced through decarboxylation of amino acids. They are formed during manufacturing of some kind of food and beverages such as cheese, wine, or beer. Histamine, cadaverine, agmatine, tyramine, putrescine, and β -phenylethylamine are the most common biogenic amines found in wines and beers. This group of compounds can be toxic at high concentrations; therefore, their control is very important. Analysis of biogenic amines in alcoholic drinks (beers and wines) was carried out by HPLC-MS/MS after their derivatization with p -toluenesulfonyl chloride (tosyl chloride). The developed method has been applied for analysis of seventeen biogenic amines in twenty-eight samples of lager beers and in twelve samples of different homemade wines (white grape, red grape, strawberry, chokeberry, black currant, plum, apple, raspberry, and quince). The developed method is sensitive and repeatable for majority of the analytes. It is versatile and can be used for the determination of biogenic amines in various alcoholic beverages.

Loading and release of amine drugs by ion-exchange fibers: role of amine type.

PubMed

Gao, Yanan; Liu, Hongzhuo; Yuan, Jing; Yang, Yang; Che, Xin; Hou, Yanlong; Li, Sanming

2014-04-01

With more production and application of ion-exchange fibers (IEFs), it becomes necessary to understand the interaction between IEFs and amine compounds, an important group of organic drugs and structural components of large organic molecules in biological systems. However, so far few experimental studies have been conducted to systematically investigate the exchanging mechanism of amine compounds to IEFs. Therefore, 15 amine drugs were selected to investigate the effect of amine type on the loading and release of them from the related IEFs. Loading affinity of these drugs by IEFs decreased in the order of secondary, tertiary, and primary. The following items: basicity, aromaticity, molar volume, rotatability, and so on, were emphatically discussed to address the underlying mechanism of drug loading and releasing extent and rate of IEFs. It was evident that strong alkaline drugs strengthened the ionic bond between the amine groups and IEFs, and thus the loading affinity. These results will advance the understanding of the exchanging behavior of IEFs in the drug delivery system. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

Design of a glutamine substrate tag enabling protein labelling mediated by Bacillus subtilis transglutaminase.

PubMed

Oteng-Pabi, Samuel K; Clouthier, Christopher M; Keillor, Jeffrey W

2018-01-01

Transglutaminases (TGases) are enzymes that catalyse protein cross-linking through a transamidation reaction between the side chain of a glutamine residue on one protein and the side chain of a lysine residue on another. Generally, TGases show low substrate specificity with respect to their amine substrate, such that a wide variety of primary amines can participate in the modification of specific glutamine residue. Although a number of different TGases have been used to mediate these bioconjugation reactions, the TGase from Bacillus subtilis (bTG) may be particularly suited to this application. It is smaller than most TGases, can be expressed in a soluble active form, and lacks the calcium dependence of its mammalian counterparts. However, little is known regarding this enzyme and its glutamine substrate specificity, limiting the scope of its application. In this work, we designed a FRET-based ligation assay to monitor the bTG-mediated conjugation of the fluorescent proteins Clover and mRuby2. This assay allowed us to screen a library of random heptapeptide glutamine sequences for their reactivity with recombinant bTG in bacterial cells, using fluorescence assisted cell sorting. From this library, several reactive sequences were identified and kinetically characterized, with the most reactive sequence (YAHQAHY) having a kcat/KM value of 19 ± 3 μM-1 min-1. This sequence was then genetically appended onto a test protein as a reactive 'Q-tag' and fluorescently labelled with dansyl-cadaverine, in the first demonstration of protein labelling mediated by bTG.

The Preparation and Reaction of Phenyl-Substituted Pyrylium and Pyridinium Salts.

ERIC Educational Resources Information Center

Awartani, Radi; And Others

1986-01-01

Describes this reaction sequence involving reactivity and synthesis of heterocycles: (1) synthesis of 2,4,6-triphenylpyrylium tetrafluoroborate, II; (2) its reaction with nucleophiles; (3) reaction of pyrylium salt II with a primary amine (benzylamine, p-methoxybenzylamine, and furfurylamine) to form the N-substituted-2,4,6-triphenylpyridinium…

69 FR 41789 - Notice of Availability of Government-Owned Inventions; Available for Licensing

Federal Register 2010, 2011, 2012, 2013, 2014

2004-07-12

...,441: Phthalonitrile Prepolymer as High Temperature Sizing Material for Composite Fibers, Navy Case No... Microwave Electrode Structures, Navy Case No. 74,654.//U.S. Patent No. 5,410,404: Fiber Grating-based...,001,926: Fiber-reinforced Phthalonitrile Composite Cured with Low-reactivity Aromatic Amine Curing...

Magnetic graphitic carbon nitride: its application in the C–H activation of amines

EPA Science Inventory

Magnetic graphitic carbon nitride, Fe@g-C3N4, has been synthesized by adorning graphitic carbon nitride (g-C3N4) support with iron oxide via non-covalent interaction. The magnetically recyclable catalyst showed excellent reactivity for expeditious C-H activation and cyanation of ...

DETERMINATION OF ALIPHATIC AMINES IN WATER USING DERIVATIZATION WITH FLUORESCEIN ISOTHIOCYANATE AND CAPILLARY ELECTROPHORESIS/LASER-INDUCED FLUORESCENCE DETECTION.

EPA Science Inventory

Detection-oriented derivatization of aliphatic amines and amine functional groups in coumpounds of environmental interest was studied using fluorescein isothiocyanate (FITC) with separation/determination by capillary electrophoresis/laser-induced fluorescence. Determinative level...

Novel highly luminescent amine-functionalized bridged silsesquioxanes

NASA Astrophysics Data System (ADS)

Pereira, Rui F. P.; Nunes, Sílvia C.; Toquer, Guillaume; Cardoso, Marita A.; Valente, Artur J. M.; Ferro, Marta C.; Silva, Maria M.; Carlos, Luís D.; Ferreira, Rute A. S.; de Zea Bermudez, Verónica

2017-12-01

Amine-functionalized bridged silsesquioxanes were synthesized from bis[(3-trimethoxysilyl)propyl] amine via a solvent-mediated route. BS-1 and BS-2 were obtained with neutral pH with sub- and stoichiometric amounts of water, respectively, and high tetrahydrofuran content. BS-3 was prepared with hyperstoichiometric water concentration, high tetrahydrofuran content and hydrochloric acid. BS-4 was synthesized with hyperstoichiometric water concentration, high ethanol content and sodium hydroxide. BS-1 and BS-2 were produced as transparent films, whereas BS-3 and BS-4 formed white powders. Face-to-face stacking of flat or folded lamellae yielded quasi-hydrophobic platelets with emission quantum yields of 0.05±0.01 (BS-1 and BS-2) or superhydrophilic onion-like nanoparticles with exciting emission quantum yields of 0.38±0.03 (BS-3) and 0.33±0.04 (BS-4), respectively. The latter two values are the largest ever reported for amine-functionalized siloxane-based hybrids lacking aromatic groups. Fast Grotthus proton hopping between =NH2+/=NH groups (BS-3) and =N-/=NH groups (BS-4), promoted by H+ and OH- ions, respectively, and aided by short amine-amine contacts provided by the onion-like morphology, account for this unique optical behavior.

Synthesis and characterization of bifunctional surfaces with tunable functional group pairs

NASA Astrophysics Data System (ADS)

Galloway, John M.; Kung, Mayfair; Kung, Harold H.

2016-06-01

Grafting of pairs of functional groups onto a silica surface was demonstrated by tethering both terminals of an organochlorosilane precursor molecule, Cl2(CH3)Si(CH2)4(CO)(OSi(i-Pr)2)(CH2)2Si(CH3)Cl2, that possess a cleavable silyl ester bond, onto a silica surface. Hydrolytic cleavage of the silyl ester bond of the grafted molecule resulted in the generation of organized pairs of carboxylic acid and organosilanol groups. This organosilanol moiety was easily transformed into other functional groups through condensation reactions to form, together with the neighboring acid group, pairs such as carboxylic acid/secondary amine, carboxylic acid/pyridine, and carboxylic acid/phosphine. In the case of carboxylic acid/amine pairing, there was evidence of the formation of amide. A sample grafted with amine-carboxylic acid pairs was three times more active (per free amine) than a sample without such pairs for the nitroaldol condensation of 4-nitrobenzaldehyde and nitromethane.

Copper-Hydroperoxo Mediated N-Debenzylation Chemistry Mimicking Aspects of Copper Monoxygenases

PubMed Central

Maiti, Debabrata; Narducci Sarjeant, Amy A.; Karlin, Kenneth D.

2008-01-01

Substantial oxidative N-debenzylation reaction along with PhCH=O formation occurs from a hydroperoxo copper(II) complex which has a dibenzylamino substrate (-N(CH2Ph)2 appended as a substituent on one pyridyl group of its tripodal tetradentate TMPA {≡ TPA ≡ tris(2-pyridylmethyl)amine)} ligand framework. During the course of the (LN(CH2Ph)2)CuII(−OOH) reactivity, formation of a substrate and −OOH (an oxygen atom) derived alkoxo CuII(−OR) complex occurs. The observation that the same CuII(−OR) species occurs from CuI/PhIO chemistry suggests the possibility that a copper-oxo (cupryl) reactive intermediate forms during alkoxo species formation, and new ESI-MS data obtained provides some further support for this high-valent intermediate. Net H-atom abstraction chemistry is proposed, based on kinetic isotope effect studies provided here and that previously published for a closely related CuII(−OOH) species incorporating dimethylamine (-N(CH3)2) as the internal substrate (J. Am. Chem. Soc. 2007, 129, 6720-6721); the CuI/PhIO reactivity, with similar isotope effect results, provides further support. The reactivity of these chemical systems closely resembles proposed oxidative N-dealkylation mechanisms effected by the copper-monooxygenases dopamine β-monooxygenase (DβM) or peptidylglycine-α-hydroxylating monooxygenase (PHM). PMID:18783212

Non-enzymatic palladium recovery on microbial and synthetic surfaces.

PubMed

Rotaru, Amelia-Elena; Jiang, Wei; Finster, Kai; Skrydstrup, Troels; Meyer, Rikke Louise

2012-08-01

The use of microorganisms as support for reduction of dissolved Pd(II) to immobilized Pd(0) nanoparticles is an environmentally friendly approach for Pd recovery from waste. To better understand and engineer Pd(0) nanoparticle synthesis, one has to consider the mechanisms by which Pd(II) is reduced on microbial surfaces. Escherichia coli, Shewanella oneidensis, and Pseudomonas putida were used as model organisms in order to elucidate the role of microbial cells in Pd(II) reduction under acidic conditions. Pd(II) was reduced by formate under acidic conditions, and the process occurred substantially faster in the presence of cells as compared to cell-free controls. We found no difference between native (untreated) and autoclaved cells, and could demonstrate that even a non-enzymatic protein (bovine serum albumin) stimulated Pd(II) reduction as efficiently as bacterial cells. Amine groups readily interact with Pd(II), and to specifically test their role in surface-assisted Pd(II) reduction by formate, we replaced bacterial cells with polystyrene microparticles functionalized with amine or carboxyl groups. Amine-functionalized microparticles had the same effect on Pd(II) reduction as bacterial cells, and the effect could be hampered if the amine groups were blocked by acetylation. The interaction with amine groups was confirmed by infrared spectroscopy on whole cells and amine-functionalized microparticles. In conclusion, bio-supported Pd(II) reduction on microbial surfaces is possibly mediated by a non-enzymatic mechanism. We therefore suggest the use of amine-rich biomaterials rather than intact cells for Pd bio-recovery from waste. Copyright © 2012 Wiley Periodicals, Inc.

Versatility of Alkyne-Modified Poly(Glycidyl Methacrylate) Layers for Click Reactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soto-Cantu, Dr. Erick; Lokitz, Bradley S; Hinestrosa Salazar, Juan Pablo

2011-01-01

Functional soft interfaces are of interest for a variety of technologies. We describe three methods for preparing substrates with alkyne groups, which show versatility for 'click' chemistry reactions. Two of the methods have the same root: formation of thin, covalently attached, reactive interfacial layers of poly(glycidyl methacrylate) (PGMA) via spin coating onto silicon wafers followed by reactive modification with either propargylamine or 5-hexynoic acid. The amine or the carboxylic acid moieties react with the epoxy groups of PGMA, creating interfacial polymer layers decorated with alkyne groups. The third method consists of using copolymers comprising glycidyl methacrylate and propargyl methacrylate (pGP).more » The pGP copolymers are spin coated and covalently attached on silicon wafers. For each method, we investigate the factors that control film thickness and content of alkyne groups using ellipsometry, and study the nanophase structure of the films using neutron reflectometry. Azide-terminated polymers of methacrylic acid and 2-vinyl-4,4-dimethylazlactone synthesized via reversible addition-fragmentation chain transfer polymerization were attached to the alkyne-modified substrates using 'click' chemistry, and grafting densities in the range of 0.007-0.95 chains nm{sup -2} were attained. The maximum density of alkyne groups attained by functionalization of PGMA with propargylamine or 5-hexynoic acid was approximately 2 alkynes nm{sup -3}. The alkyne content obtained by the three decorating approaches was sufficiently high that it was not the limiting factor for the click reaction of azide-capped polymers.« less

Biosynthesis of CdS nanoparticles in banana peel extract.

PubMed

Zhou, Guang Ju; Li, Shuo Hao; Zhang, Yu Cang; Fu, Yun Zhi

2014-06-01

Cadmium sulfide (CdS) nanoparticles (NPs) were synthesized by using banana peel extract as a convenient, non-toxic, eco-friendly 'green' capping agent. Cadmium nitrate and sodium sulfide are main reagents. A variety of CdS NPs are prepared through changing reaction conditions (banana extracts, the amount of banana peel extract, solution pH, concentration and reactive temperature). The prepared CdS colloid displays strong fluorescence spectrum. X-ray diffraction analysis demonstrates the successful formation of CdS NPs. Fourier transform infra-red (FTIR) spectrogram indicates the involvement of carboxyl, amine and hydroxyl groups in the formation of CdS NPs. Transmission electron microscope (TEM) result reveals that the average size of the NPs is around 1.48 nm.

The vascular effects of trace amines and amphetamines.

PubMed

Broadley, Kenneth J

2010-03-01

Trace amines, including tyramine, beta-phenylethylamine (beta-PEA), tryptamine and octopamine, are biologically active amines mostly based on phenylethylamine, occurring in the body in trace amounts. They are a diverse group of naturally occurring and synthetic amines, which are also found in the diet and in herbal plants, such as ephedrine and cathinone. They include amphetamine and its analogues, such as MDMA ('ecstasy'), and synthetic proprietary sympathomimetic agents such as phenylpropanolamine and pseudoephedrine. On the vascular system they cause vasoconstriction and a rise in blood pressure. This effect is the basis of their use as nasal decongestants. For over 50 years, they have been assumed to be indirectly acting sympathomimetic amines, their responses being due to the release of noradrenaline from sympathetic neurones. There are, however, results that suggest that this is not their only mechanism of action and that they may also exert direct vascular effects independent of a noradrenergic mechanism. Recently, a group of novel trace amine-associated receptors (TAARs) have been cloned and identified in the brain and peripheral tissues including blood vessels. Trace amines bind to these cloned receptors and it is suggested that their vasoconstrictor effects can in part be attributed to this mechanism. This review describes the cardiovascular pharmacology of this diverse group of amines, their structures and uses and their endogenous synthesis and metabolism. The review also considers their clinical relevance as constituents of the diet, as therapeutic agents (ritodrine, phenylpropanolamine, and pseudoephedrine) and as drugs of abuse (amphetamine, 'ecstasy') and their mechanisms of action. 2009 Elsevier Inc. All rights reserved.

Frustration across the periodic table: heterolytic cleavage of dihydrogen by metal complexes.

PubMed

Bullock, R Morris; Chambers, Geoffrey M

2017-08-28

This perspective examines frustrated Lewis pairs (FLPs) in the context of heterolytic cleavage of H 2 by transition metal complexes, with an emphasis on molecular complexes bearing an intramolecular Lewis base. FLPs have traditionally been associated with main group compounds, yet many reactions of transition metal complexes support a broader classification of FLPs that includes certain types of transition metal complexes with reactivity resembling main group-based FLPs. This article surveys transition metal complexes that heterolytically cleave H 2 , which vary in the degree that the Lewis pairs within these systems interact. Many of the examples include complexes bearing a pendant amine functioning as the base with the metal functioning as the hydride acceptor. Consideration of transition metal compounds in the context of FLPs can inspire new innovations and improvements in transition metal catalysis.This article is part of the themed issue 'Frustrated Lewis pair chemistry'. © 2017 The Author(s).

Enantioselective direct α-amination of aldehydes via a photoredox mechanism: a strategy for asymmetric amine fragment coupling.

PubMed

Cecere, Giuseppe; König, Christian M; Alleva, Jennifer L; MacMillan, David W C

2013-08-07

The direct, asymmetric α-amination of aldehydes has been accomplished via a combination of photoredox and organocatalysis. Photon-generated N-centered radicals undergo enantioselective α-addition to catalytically formed chiral enamines to directly produce stable α-amino aldehyde adducts bearing synthetically useful amine substitution patterns. Incorporation of a photolabile group on the amine precursor obviates the need to employ a photoredox catalyst in this transformation. Importantly, this photoinduced transformation allows direct and enantioselective access to α-amino aldehyde products that do not require postreaction manipulation.

Time-dependent vibrational spectral analysis of first principles trajectory of methylamine with wavelet transform.

PubMed

Biswas, Sohag; Mallik, Bhabani S

2017-04-12

The fluctuation dynamics of amine stretching frequencies, hydrogen bonds, dangling N-D bonds, and the orientation profile of the amine group of methylamine (MA) were investigated under ambient conditions by means of dispersion-corrected density functional theory-based first principles molecular dynamics (FPMD) simulations. Along with the dynamical properties, various equilibrium properties such as radial distribution function, spatial distribution function, combined radial and angular distribution functions and hydrogen bonding were also calculated. The instantaneous stretching frequencies of amine groups were obtained by wavelet transform of the trajectory obtained from FPMD simulations. The frequency-structure correlation reveals that the amine stretching frequency is weakly correlated with the nearest nitrogen-deuterium distance. The frequency-frequency correlation function has a short time scale of around 110 fs and a longer time scale of about 1.15 ps. It was found that the short time scale originates from the underdamped motion of intact hydrogen bonds of MA pairs. However, the long time scale of the vibrational spectral diffusion of N-D modes is determined by the overall dynamics of hydrogen bonds as well as the dangling ND groups and the inertial rotation of the amine group of the molecule.

Secondary Organic Aerosol and Brown Carbon Formation in the Sunlit Aqueous Phase: Aldehyde Photooxidation in the Presence of Ammonium Salts and Amines

NASA Astrophysics Data System (ADS)

De Haan, D. O.; Galloway, M. M.; Sharp, K. D.; Jiménez, N. G.

2014-12-01

The chemistry of water-soluble carbonyl compounds in clouds is now acknowledged as an important source of secondary organic aerosol. These reactive carbonyl compounds are oxidized to carboxylic acids and form oligomers by radical-radical reactions and by "dark reactions" with ammonium salts (AS) and/or amines. The latter class of reactions also produces light-absorbing brown carbon compounds, especially reactions involving methylglyoxal or glyoxal and amines. However, recent work has found that UV light fades the color of glyoxal + AS and methylgyloxal + AS reaction mixtures. We recently studied aldehyde-AS-amine reactions in sunlight and in control vessels at the same temperature to determine the effects of solar radiation on the aqueous-phase production of brown carbon. In sunlight, methylglyoxal reaction mixtures lost their initial color and failed to brown, indicating the photolytic loss of reactants and/or pre-brown intermediates. In many other reactions, brown products are lost to photolysis, reducing the overall browning of solutions exposed to sunlight. In other experiments, hydrogen peroxide was added to generate OH radicals by photolysis. In the presence of OH radicals, some carbonyl compound mixtures (e.g. those containing hydroxyacetone or glycolaldehyde) browned more rapidly when exposed to sunlight. This indicates the existence of uncharacterized photooxidative browning pathways involving aqueous-phase OH radicals, carbonyls, ammonium salts, and/or amine compounds.

The Azomethine Ylide Route to Amine C–H Functionalization: Redox-Versions of Classic Reactions and a Pathway to New Transformations

PubMed Central

2016-01-01

Conspectus Redox-neutral methods for the functionalization of amine α-C–H bonds are inherently efficient because they avoid external oxidants and reductants and often do not generate unwanted byproducts. However, most of the current methods for amine α-C–H bond functionalization are oxidative in nature. While the most efficient variants utilize atmospheric oxygen as the terminal oxidant, many such transformations require the use of expensive or toxic oxidants, often coupled with the need for transition metal catalysts. Redox-neutral amine α-functionalizations that involve intramolecular hydride transfer steps provide viable alternatives to certain oxidative reactions. These processes have been known for some time and are particularly well suited for tertiary amine substrates. A mechanistically distinct strategy for secondary amines has emerged only recently, despite sharing common features with a range of classic organic transformations. Among those are such widely used reactions as the Strecker, Mannich, Pictet–Spengler, and Kabachnik–Fields reactions, Friedel–Crafts alkylations, and iminium alkynylations. In these classic processes, condensation of a secondary amine with an aldehyde (or a ketone) typically leads to the formation of an intermediate iminium ion, which is subsequently attacked by a nucleophile. The corresponding redox-versions of these transformations utilize identical starting materials but incorporate an isomerization step that enables α-C–H bond functionalization. Intramolecular versions of these reactions include redox-neutral amine α-amination, α-oxygenation, and α-sulfenylation. In all cases, a reductive N-alkylation is effectively combined with an oxidative α-functionalization, generating water as the only byproduct. Reactions are promoted by simple carboxylic acids and in some cases require no additives. Azomethine ylides, dipolar species whose usage is predominantly in [3 + 2] cycloadditions and other pericyclic processes, have been identified as common intermediates. Extension of this chemistry to amine α,β-difunctionalization has been shown to be possible by way of converting the intermediate azomethine ylides into transient enamines. This Account details the evolution of this general strategy and the progress made to date. Further included is a discussion of related decarboxylative reactions and transformations that result in the redox-neutral aromatization of (partially) saturated cyclic amines. These processes also involve azomethine ylides, reactive intermediates that appear to be far more prevalent in condensation chemistry of amines and carbonyl compounds than previously considered. In contrast, as exemplified by some redox transformations that have been studied in greater detail, iminium ions are not necessarily involved in all amine/aldehyde condensation reactions. PMID:25560649

The azomethine ylide route to amine C-H functionalization: redox-versions of classic reactions and a pathway to new transformations.

PubMed

Seidel, Daniel

2015-02-17

Conspectus Redox-neutral methods for the functionalization of amine α-C-H bonds are inherently efficient because they avoid external oxidants and reductants and often do not generate unwanted byproducts. However, most of the current methods for amine α-C-H bond functionalization are oxidative in nature. While the most efficient variants utilize atmospheric oxygen as the terminal oxidant, many such transformations require the use of expensive or toxic oxidants, often coupled with the need for transition metal catalysts. Redox-neutral amine α-functionalizations that involve intramolecular hydride transfer steps provide viable alternatives to certain oxidative reactions. These processes have been known for some time and are particularly well suited for tertiary amine substrates. A mechanistically distinct strategy for secondary amines has emerged only recently, despite sharing common features with a range of classic organic transformations. Among those are such widely used reactions as the Strecker, Mannich, Pictet-Spengler, and Kabachnik-Fields reactions, Friedel-Crafts alkylations, and iminium alkynylations. In these classic processes, condensation of a secondary amine with an aldehyde (or a ketone) typically leads to the formation of an intermediate iminium ion, which is subsequently attacked by a nucleophile. The corresponding redox-versions of these transformations utilize identical starting materials but incorporate an isomerization step that enables α-C-H bond functionalization. Intramolecular versions of these reactions include redox-neutral amine α-amination, α-oxygenation, and α-sulfenylation. In all cases, a reductive N-alkylation is effectively combined with an oxidative α-functionalization, generating water as the only byproduct. Reactions are promoted by simple carboxylic acids and in some cases require no additives. Azomethine ylides, dipolar species whose usage is predominantly in [3 + 2] cycloadditions and other pericyclic processes, have been identified as common intermediates. Extension of this chemistry to amine α,β-difunctionalization has been shown to be possible by way of converting the intermediate azomethine ylides into transient enamines. This Account details the evolution of this general strategy and the progress made to date. Further included is a discussion of related decarboxylative reactions and transformations that result in the redox-neutral aromatization of (partially) saturated cyclic amines. These processes also involve azomethine ylides, reactive intermediates that appear to be far more prevalent in condensation chemistry of amines and carbonyl compounds than previously considered. In contrast, as exemplified by some redox transformations that have been studied in greater detail, iminium ions are not necessarily involved in all amine/aldehyde condensation reactions.

Green-Light-Sensitive BODIPY Photoprotecting Groups for Amines

PubMed Central

2018-01-01

We describe a series of easily accessible, visible-light-sensitive (λ > 500 nm) BODIPY (boron-dipyrromethene)-based photoprotecting groups (PPGs) for primary and secondary amines, based on a carbamate linker. The caged compounds are stable under aqueous conditions for 24 h and can be efficiently uncaged in vitro with visible light (λ = 530 nm). These properties allow efficient photodeprotection of amines, rendering these novel PPGs potentially suitable for various applications, including the delivery of caged drugs and their remote activation. PMID:29369628

Transamination at the Crossroad of the One-Pot Synthesis of N-Substituted Quinonediimines and C-Substituted Benzobisimidazoles.

PubMed

Andeme Edzang, Judicaelle; Chen, Zhongrui; Audi, Hassib; Canard, Gabriel; Siri, Olivier

2016-10-10

A green and very efficient synthesis of N-substituted benzoquinonediimines or C-substituted benzo-bis(imidazole) derivatives is described under similar conditions. The different reaction pathway is only controlled by the nature of the primary amines, which tunes the reactivity of the intermediates.

BINDING OF CARCINOGENS TO DNA AND COVALENT ADDUCTS DNA DAMAGE - PAH, AROMATIC AMINES, NITRO-AROMATIC COMPOUNDS, AND HALOGENATED COMPOUNDS

EPA Science Inventory

DNA adducts are the covalent addition products resulting from binding of reactive chemical species to DNA bases. The cancer initiating role of DNA adducts is well-established, and is clearly reflected in the high cancer incidence observed in individuals with deficiencies in any o...

Modeling Bacteria Surface Acid-Base Properties: The Overprint Of Biology

NASA Astrophysics Data System (ADS)

Amores, D. R.; Smith, S.; Warren, L. A.

2009-05-01

Bacteria are ubiquitous in the environment and are important repositories for metals as well as nucleation templates for a myriad of secondary minerals due to an abundance of reactive surface binding sites. Model elucidation of whole cell surface reactivity simplifies bacteria as viable but static, i.e., no metabolic activity, to enable fits of microbial data sets from models derived from mineral surfaces. Here we investigate the surface proton charging behavior of live and dead whole cell cyanobacteria (Synechococcus sp.) harvested from a single parent culture by acid-base titration using a Fully Optimized ContinUouS (FOCUS) pKa spectrum method. Viability of live cells was verified by successful recultivation post experimentation, whereas dead cells were consistently non-recultivable. Surface site identities derived from binding constants determined for both the live and dead cells are consistent with molecular analogs for organic functional groups known to occur on microbial surfaces: carboxylic (pKa = 2.87-3.11), phosphoryl (pKa = 6.01-6.92) and amine/hydroxyl groups (pKa = 9.56-9.99). However, variability in total ligand concentration among the live cells is greater than those between the live and dead. The total ligand concentrations (LT, mol- mg-1 dry solid) derived from the live cell titrations (n=12) clustered into two sub-populations: high (LT = 24.4) and low (LT = 5.8), compared to the single concentration for the dead cell titrations (LT = 18.8; n=5). We infer from these results that metabolic activity can substantively impact surface reactivity of morphologically identical cells. These results and their modeling implications for bacteria surface reactivities will be discussed.

Turnip yellow mosaic virus as a chemoaddressable bionanoparticle.

PubMed

Barnhill, Hannah N; Reuther, Rachel; Ferguson, P Lee; Dreher, Theo; Wang, Qian

2007-01-01

Viruses and virus-like particles (VLPs) have been demonstrated to be robust scaffolds for the construction of nanomaterials. In order to develop new nanoprobes for time-resolved fluoroimmuno assays as well as to investigate the two-dimensional self-assembly of viruses and VLPs, the icosahedral turnip yellow mosaic virus (TYMV) was investigated as a potential building block in our study. TYMV is an icosahedral plant virus with an average diameter of 28 nm that can be isolated inexpensively in gram quantities from turnips or Chinese cabbage. There are 180 coat protein subunits per TYMV capsid. The conventional N-hydroxysuccinimide-mediated amidation reaction was employed for the chemical modification of the viral capsid. Tryptic digestion with sequential MALDI-TOF MS analysis identified that the amino groups of K32 of the flexible N-terminus made the major contribution for the reactivity of TYMV toward N-hydroxysuccinimide ester (NHS) reagents. The reactivity was also monitored with UV-vis absorbance and fluorescence, which revealed that approximately 60 lysines per particle could be addressed. We hypothesized that the flexible A chain contains the reactive lysine because the crystal structure of TYMV has shown that chain A is much more flexible compared to B and C, especially at the N-terminal region where the Lys-32 located. In addition, about 90 to 120 carboxyl groups, located in the most exposed sequence, could be modified with amines catalyzed with 1-(3-dimethylaminopropyl-3-ethylcarbodiimide) hydrochloride (EDC) and sulfo-NHS. TYMV was stable to a wide range of reaction conditions and maintained its integrity after the chemical conjugations. Therefore, it can potentially be employed as a reactive scaffold for the display of a variety of materials for applications in many areas of nanoscience.

Efficient and Scalable Synthesis of 4-Carboxy-Pennsylvania Green Methyl Ester: A Hydrophobic Building Block for Fluorescent Molecular Probes.

PubMed

Woydziak, Zachary R; Fu, Liqiang; Peterson, Blake R

2014-01-01

Fluorinated fluorophores are valuable tools for studies of biological systems. However, amine-reactive single-isomer derivatives of these compounds are often very expensive. To provide an inexpensive alternative, we report a practical synthesis of 4-carboxy-Pennsylvania Green methyl ester. Derivatives of this hydrophobic fluorinated fluorophore, a hybrid of the dyes Oregon Green and Tokyo Green, are often cell permeable, enabling labeling of intracellular targets and components. Moreover, the low pKa of Pennsylvania Green (4.8) confers bright fluorescence in acidic cellular compartments such as endosomes, enhancing its utility for chemical biology investigations. To improve access to the key intermediate 2,7-difluoro-3,6-dihydroxyxanthen-9-one, we subjected bis-(2,4,5-trifluorophenyl)methanone to iterative nucleophilic aromatic substitution by hydroxide on scales of > 40 g. This intermediate was used to prepare over 15 grams of pure 4-carboxy-Pennsylvania Green methyl ester in 28% overall yield without requiring chromatography. This compound can be converted into the amine reactive N -hydroxysuccinimidyl ester in essentially quantitative yield for the synthesis of a wide variety of fluorescent molecular probes.

Spectroscopic Investigation into Oxidative Degradation of Silica-Supported Amine Sorbents for CO2 Capture

PubMed Central

Srikanth, Chakravartula S; Chuang, Steven S C

2012-01-01

Oxidative degradation characteristics of silica-supported amine sorbents with varying amounts of tetraethylenepentamine (TEPA) and polyethylene glycol (PEG; P200 or P600 represents PEG with molecular weights of 200 or 600) have been studied by IR and NMR spectroscopy. Thermal treatment of the sorbents and liquid TEPA at 100 °C for 12 h changed their color from white to yellow. The CO2 capture capacity of the TEPA/SiO2 sorbents (i.e., SiO2-supported TEPA with a TEPA/SiO2 ratio of 25:75) decreased by more than 60 %. IR and NMR spectroscopy studies showed that the yellow color of the degraded sorbents resulted from the formation of imide species. The imide species, consisting of NH associated with two C—O functional groups, were produced from the oxidation of methylene groups in TEPA. Imide species on the degraded sorbent are not capable of binding CO2 due to its weak basicity. The addition of P200 and P600 to the supported amine sorbents improved both their CO2 capture capacities and oxidative degradation resistance. IR spectroscopy results also showed that TEPA was immobilized on the SiO2 surface through hydrogen bonding between amine groups and the silanol groups of SiO2. The OH groups of PEG interact with NH2/NH of TEPA through hydrogen bonding. Hydrogen bonds disperse TEPA on SiO2 and block O2 from accessing TEPA for oxidation. Oxidative degradation resistance and CO2 capture capacity of the supported amine sorbents can be optimized through adjusting the ratio of hydroxyl to amine groups in the TEPA/PEG mixture. PMID:22744858

Adsorption of CO2 from flue gas streams by a highly efficient and stable aminosilica adsorbent.

PubMed

Liu, Shou-Heng; Lin, Yuan-Chung; Chien, Yi-Chi; Hyu, Han-Ren

2011-02-01

Three ordered mesoporous silicas (OMSs) with different pore sizes and pore architectures were prepared and modified with amine functional groups by a postgrafting method. The carbon dioxide (CO2) adsorption on these amine-modified OMSs was measured by using microbalances at 348 K, and their adsorption capacities were found to be 0.2-1.4 mmol g(-1) under ambient pressure using dry 15% CO2. It was found experimentally that the CO2 adsorption capacity and adsorption rate were attributed to the density of amine groups and pore volume, respectively. A simple method is described for the production of densely anchored amine groups on a solid adsorbent invoking direct incorporation of tetraethylenepentamine onto the as-synthesized OMSs. Unlike conventional amine-modified OMSs, which typically show CO2 adsorption capacity less than 2 mmol g(-1), such organic template occluded amine-OMS composites possessed remarkably high CO2 uptake of approximately 4.6 mmol g(-1) at 348 K and 1 atm for a dry 15% CO2/nitrogen feed mixture. The enhancement of 8% in CO2 adsorption capacity was also observed in the presence of 10.6% water vapor. Durability tests done by cyclic adsorption-desorption revealed that these adsorbents also possess excellent stability.

Recent advances in surface functionalization techniques on polymethacrylate materials for optical biosensor applications.

PubMed

Hosseini, Samira; Ibrahim, Fatimah; Djordjevic, Ivan; Koole, Leo H

2014-06-21

Biosensor chips for immune-based assay systems have been investigated for their application in early diagnostics. The development of such systems strongly depends on the effective protein immobilization on polymer substrates. In order to achieve this complex heterogeneous interaction the polymer surface must be functionalized with chemical groups that are reactive towards proteins in a way that surface functional groups (such as carboxyl, -COOH; amine, -NH2; and hydroxyl, -OH) chemically or physically anchor the proteins to the polymer platform. Since the proteins are very sensitive towards their environment and can easily lose their activity when brought in close proximity to the solid surface, effective surface functionalization and high level of control over surface chemistry present the most important steps in the fabrication of biosensors. This paper reviews recent developments in surface functionalization and preparation of polymethacrylates for protein immobilization. Due to their versatility and cost effectiveness, this particular group of plastic polymers is widely used both in research and in industry.

A new approach to the immobilisation of poly(ethylene oxide) for the reduction of non-specific protein adsorption on conductive substrates

NASA Astrophysics Data System (ADS)

Cole, Martin A.; Thissen, Helmut; Losic, Dusan; Voelcker, Nicolas H.

2007-04-01

Biomedical and biotechnological devices often require surface modifications to improve their performance. In most cases, uniform coatings are desired which provide a specific property or lead to a specific biological response. In the present work, we have generated pinhole-free coatings providing amine functional groups achieved by electropolymerisation of tyramine on highly doped silicon substrates. Furthermore, amine groups were used for the subsequent grafting of poly(ethylene oxide) aldehyde via reductive amination. All surface modification steps were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The results indicate that the stability and the density of amine functional groups introduced at the surface via electropolymerisation compare favourably with alternative coatings frequently used in biomedical and biotechnological devices such as plasma polymer films. Furthermore, protein adsorption on amine and poly(ethylene oxide) coatings was studied by XPS and a colorimetric assay to test enzymatic activity. The grafting of poly(ethylene oxide) under cloud point conditions on electropolymerised tyramine layers resulted in surfaces with extremely low protein fouling character.

Electrogenerated chemiluminescence of tris(2,2'-bipyridine)ruthenium(II) using N-(3-aminopropyl)diethanolamine as coreactant.

PubMed

Kitte, Shimeles Addisu; Wang, Chao; Li, Suping; Zholudov, Yuriy; Qi, Liming; Li, Jianping; Xu, Guobao

2016-10-01

Coreactant plays a critical role for the application of electrochemiluminescence (ECL). Herein, N-(3-aminopropyl)diethanolamine (APDEA) has been explored as a potential coreactant for enhancing tris(2,2'-bipyridyl)ruthenium(II) ECL. It is much more effective than tripropylamine at gold and platinum electrodes although it has one primary amine group besides a tertiary amine group. The presence of primary amine group and hydroxyl groups in APDEA promotes the oxidation rates of amine and thus remarkably increases ECL intensity. The ECL intensities of the Ru(bpy)3 (2+)/APDEA system are approximately 10 and 36 times stronger than that of Ru(bpy)3 (2+)/tripropylamine system and about 1.6 and 1.14 times stronger than that of Ru(bpy)3 (2+)/N-butyldiethanolamine system at Au and Pt electrodes, respectively. The ECL intensity of the Ru(bpy)3 (2+)/APDEA system is 2.42 times stronger than that of Ru(bpy)3 (2+)/N-butyldiethanolamine at glassy carbon electrodes.

Smoking influences salivary histamine levels in periodontal disease.

PubMed

Bertl, K; Haririan, H; Laky, M; Matejka, M; Andrukhov, O; Rausch-Fan, X

2012-05-01

Histamine, a potent vasoactive amine, is increased in saliva of periodontitis patients. The present study aimed to further investigate the diagnostic potential of histamine for periodontal disease and assessed smoking, a major risk factor of periodontitis, as a possible influencing factor. Salivary and serum samples of 106 participants (60 periodontitis patients, 46 controls) were collected. Salivary histamine was determined by a commercially available ELISA kit, and serum C-reactive protein was measured by a routine laboratory test. Cigarettes per day and packyears were assessed as smoking exposure parameters. Statistically significantly increased levels of salivary histamine and serum C-reactive protein were detected between the patient and control group (P = 0.022 and P = 0.001). Salivary histamine levels were significantly higher in smoking compared with non-smoking patients (P < 0.001), and salivary histamine as well as serum C-reactive protein correlated significantly positively with smoking exposure parameters (P < 0.05). Smoking, an established and common risk factor of periodontitis, was assessed as a possible influencing factor for salivary histamine. Most interestingly, salivary histamine differed highly significantly between smoking and non-smoking periodontitis patients. Our results suggest a possible involvement of histamine in tobacco-exacerbated periodontal disease, but do not suggest salivary histamine as a reliable diagnostic marker for periodontitis. © 2011 John Wiley & Sons A/S.

Adhesive Properties of Cured Phenylethynyl Containing Imides

NASA Technical Reports Server (NTRS)

Jensen, Brian J.; Chang, Alice C.

1997-01-01

Considerable attention has been directed towards acetylene terminated oligomers over the last 20 years' and recent work has focused on phenylethynyl terminated imide (PETI) oligomers. These reactive oligomers possess several features which make them attractive candidates for use as composite matrices and adhesives. The phenylethynyl group can be readily incorporated into many different functionalized oligomers. The reactive oligomers possess relatively low melt viscosities and thermally cure without the evolution of volatile by-products. Once cured, they typically display high glass transition temperatures (Tgs), excellent solvent resistance and high mechanical properties. new modified phenylethynyl-terminated imide (LaRC MPEI) oligomers were synthesized at various molecular weights utilizing a small amount of trifunctional amine. As long as the amount of triamine is relatively small, this approach produces a mixture of linear, star-shaped and branched polymer chains that has lower melt and solution viscosity than an equivalent molecular weight linear phenylethynyl terminated imide oligomers. The work reported herein involves the synthesis and characterization of a copolymer using this approach and the preparation of blends utilizing a phenylethynyl containing reactive plasticizer of lower molecular weight called LaRC LV-121. The chemistry and properties of this new MPEI as well as some blends of MPEI with LV-121, are presented and compared to the linear version, LARC-PETI-5.

Enantioselective Direct α-Amination of Aldehydes via a Photoredox Mechanism: A Strategy for Asymmetric Amine Fragment Coupling

PubMed Central

Cecere, Giuseppe; Koenig, Christian M.; Alleva, Jennifer L.

2013-01-01

The direct, asymmetric α-amination of aldehydes has been accomplished via a combination of photoredox and organocatalysis. Photon-generated, nitrogen-centered radicals undergo enantioselective α-addition to catalytically formed chiral enamines to directly produce stable α-amino aldehyde adducts bearing synthetically useful amine substitution patterns. Incorporation of a photolabile group on the amine precursor obviates the need to employ a photoredox catalyst in this transformation. Importantly, this photoinduced transformation allows direct and enantioselective access to α-amino aldehyde products that do not require post-reaction manipulation. PMID:23869694

Copper-catalyzed α-amination of aliphatic aldehydes.

PubMed

Tian, Jie-Sheng; Loh, Teck-Peng

2011-05-21

A highly efficient copper-catalyzed α-amination of aliphatic aldehydes for the synthesis of α-amino acetals using secondary amines with readily removable protecting groups as a nitrogen source was developed. This reaction can be operated under very mild conditions, affording the desired products in moderate to good yields. © The Royal Society of Chemistry 2011

Carbon dioxide adsorption on micro-mesoporous composite materials of ZSM-12/MCM-48 type: The role of the contents of zeolite and functionalized amine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Santos, S.C.G.; Pedrosa, A.M.Garrido; Souza, M.J.B., E-mail: mjbsufs@gmail.com

2015-10-15

Highlights: • Synthesis of the micro-mesoporous composite materials of ZSM-12/MCM-48 type. • Application of these adsorbents in the carbon dioxide adsorption. • Effects of the contents of zeolite and amino group in the material surface on the CO{sub 2} capture efficiency. - Abstract: In this study ZSM-12/MCM-48 adsorbents have been synthesized at three ZSM-12 content, and also were functionalizated with amine groups by grafting. All the adsorbents synthesized were evaluated for CO{sub 2} capture. The X-ray diffraction analysis of the ZSM-12/MCM-48 composite showed the main characteristic peaks of ZSM-12 and MCM-48, and after the functionalization, the structure of MCM-48 onmore » the composite impregnated was affected due amine presence. For the composites without amine, the ZSM-12 content was the factor determining in the adsorption capacity of CO{sub 2} and for the composites with amine the amount of amine was that influenced in the adsorption capacity.« less

Resist surface crosslinking using amine-based reactive rinses to mitagate pattern collapse in thin film lithography

NASA Astrophysics Data System (ADS)

Yeh, Wei-Ming; Lawson, Richard A.; Tolbert, Laren M.; Henderson, Clifford L.

2012-03-01

As the semiconductor industry continues to push to smaller critical dimensions, pattern collapse during lithographic processing caused by unbalanced capillary forces during the final rinse and drying process has become an important problem that can limit the practical resolution of a resist material to feature sizes larger than its intrinsic resolution limit. One of the primary modes of pattern collapse is via elastoplastic pattern deformation which is strongly related to the mechanical properties of the resist. One approach to mitigating such collapse problems is to enhance the mechanical properties of the resist features. Since such modification of resist physical properties for pattern collapse purposes is difficult to achieve through modified formulation of the resist itself (i.e. due to the complex set of requirements that a resist must satisfy and the complex set of physical and chemical phenomena that underlie the imaging processing itself), we have pursued an alternative strategy for improving the resist mechanical properties after features are developed in the film but before they are rinsed and dried. The family of techniques being developed in this work function through the use of aqueous compatible reactive rinse solutions that can be applied to developed resist features while they are wet during normal rinse processing on a track system. By applying these techniques during the rinse process, the resist features can be strengthened before they are subjected to significant capillary forces during the final drying step. In this work, the use of diamine compounds to reactively crosslink the surface of resists containing carboxylic acid groups through formation of amide bonds using carbodiimide chemistry has been explored. One advantage of this approach is that it is an aqueous process that should be easily compatible with high volume, track-based lithographic processes. Contact angle studies and x-ray photoelectron spectroscopy (XPS) were used to characterize the surface crosslinking reaction using such diamine surface rinse treatments. Pattern collapse test structures were fabricated and analyzed to measure the amount of mechanical property improvement imparted by such treatments. Application of such amine reactive rinses was found to clearly result in an improvement in the resistance of resists to pattern collapse as observed by SEM. A comparison of the critical stress at the point of pattern collapse as a function of resist feature size also clearly shows a significant improvement in mechanical resilience of resist samples processed with the reactive rinse treatment.

Biodegradable Poly(ester urethane)urea Elastomers with Variable Amino Content for Subsequent Functionalization with Phosphorylcholine

PubMed Central

Fang, Jun; Ye, Sang-Ho; Shankarraman, Venkat; Huang, Yixian; Mo, Xiumei; Wagner, William R.

2015-01-01

While surface modification is well suited for imparting biomaterials with specific functionality for favorable cell interactions, the modification of degradable polymers would be expected to provide only temporary benefit. Bulk modification by incorporating pendant reactive groups for subsequent functionalization of biodegradable polymers would provide a more enduring approach. Towards this end, a series of biodegradable poly(ester urethane)urea elastomers with variable amino content (PEUU-NH2 polymers) were developed. Carboxylated phosphorycholine was synthesized and conjugated to the PEUU-NH2 polymers for subsequent bulk functionalization to generate PEUU-PC polymers. Synthesis was verified by 1H NMR, X-ray photoelectron spectroscopy and ATR-FTIR. The impact of amine incorporation and phosphorylcholine conjugation was shown on mechanical, thermal and degradation properties. Water absorption increased with increasing amine content, and further with PC conjugation. In wet conditions, tensile strength and initial modulus generally decreased with increasing hydrophilicity, but remained in the range of 5–30 MPa and 10–20 MPa respectively. PC conjugation was associated with significantly reduced platelet adhesion in blood contact testing and the inhibition of rat vascular smooth muscle cell proliferation. These biodegradable PEUU-PC elastomers offer attractive properties for applications as non-thrombogenic, biodegradable coatings and for blood-contacting scaffold applications. Further, the PEUU-NH2 base polymers offer the potential to have multiple types of biofunctional groups conjugated onto the backbone to address a variety of design objectives. PMID:25132273

Autonomic composite hydrogels by reactive printing: materials and oscillatory response.

PubMed

Kramb, R C; Buskohl, P R; Slone, C; Smith, M L; Vaia, R A

2014-03-07

Autonomic materials are those that automatically respond to a change in environmental conditions, such as temperature or chemical composition. While such materials hold incredible potential for a wide range of uses, their implementation is limited by the small number of fully-developed material systems. To broaden the number of available systems, we have developed a post-functionalization technique where a reactive Ru catalyst ink is printed onto a non-responsive polymer substrate. Using a succinimide-amine coupling reaction, patterns are printed onto co-polymer or biomacromolecular films containing primary amine functionality, such as polyacrylamide (PAAm) or poly-N-isopropyl acrylamide (PNIPAAm) copolymerized with poly-N-(3-Aminopropyl)methacrylamide (PAPMAAm). When the films are placed in the Belousov-Zhabotinsky (BZ) solution medium, the reaction takes place only inside the printed nodes. In comparison to alternative BZ systems, where Ru-containing monomers are copolymerized with base monomers, reactive printing provides facile tuning of a range of hydrogel compositions, as well as enabling the formation of mechanically robust composite monoliths. The autonomic response of the printed nodes is similar for all matrices in the BZ solution concentrations examined, where the period of oscillation decreases in response to increasing sodium bromate or nitric acid concentration. A temperature increase reduces the period of oscillations and temperature gradients are shown to function as pace-makers, dictating the direction of the autonomic response (chemical waves).

Matrix effect and cross-reactivity of select amphetamine-type substances, designer analogues, and putrefactive amines using the Bio-Quant direct ELISA presumptive assays for amphetamine and methamphetamine.

PubMed

Apollonio, Luigino G; Whittall, Ian R; Pianca, Dennis J; Kyd, Jennelle M; Maher, William A

2007-05-01

The aim of this study was to evaluate the Bio-Quant Direct ELISA assays for amphetamine and methamphetamine in the routine presumptive screening of biological fluids. Standard concentration curves of the target analytes were assayed to assess sensitivity, and known concentrations of common amphetamine-type substances (ephedrine, pseudoephedrine, phentermine), designer analogues (MDA, MDMA, MDEA, MBDB, PMA, 4-MTA, 2CB), and putrefactive amines (phenylethylamine, putrescine, tryptamine, tyramine) were analyzed to determine cross-reactivity. Results of the standard curve studies show the capacity of both Direct ELISA kits to confidently detect down to 3 ng/mL interday (PBS matrix; CVs 6.3-15.5%). Cross-reactivity relative to that of 50 ng/mL preparations of the target compounds demonstrated that the Direct ELISA kit for amphetamine also detected MDA (282%), PMA (265%), 4-MTA (280%), and phentermine (61%), and the Direct ELISA for methamphetamine also assayed positive for MDMA (73%), MDEA (18%), pseudoephedrine (19%), MBDB (8%), and ephedrine (9%). Matrix studies demonstrated that both ELISA kits could be applied to screening of blood, urine, and saliva to a concentration of 6 ng/mL or lower. In conclusion, the Bio-Quant Direct ELISA kits for amphetamine and methamphetamine are fast and accurate and have demonstrated themselves to be useful tools in routine toxicological testing.

Immobilization of biomolecules to plasma polymerized pentafluorophenyl methacrylate.

PubMed

Duque, Luis; Menges, Bernhard; Borros, Salvador; Förch, Renate

2010-10-11

Thin films of plasma polymerized pentafluorophenyl methacrylate (pp-PFM) offer highly reactive ester groups throughout the structure of the film that allow for subsequent reactions with different aminated reagents and biological molecules. The present paper follows on from previous work on the plasma deposition of pentafluorophenyl methacrylate (PFM) for optimum functional group retention (Francesch, L.; Borros, S.; Knoll, W.; Foerch, R. Langmuir 2007, 23, 3927) and reactivity in aqueous solution (Duque, L.; Queralto, N.; Francesch, L.; Bumbu, G. G.; Borros, S.; Berger, R.; Förch, R. Plasma Process. Polym. 2010, accepted for publication) to investigate the binding of a biologically active peptide known to induce cellular adhesion (IKVAV) and of biochemically active proteins such as BSA and fibrinogen. Analyses of the films and of the immobilization of the biomolecules were carried out using infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The attachment of the biomolecules on pulsed plasma polymerized pentafluorophenyl methacrylate was monitored using surface plasmon resonance spectroscopy (SPR). SPR analysis confirmed the presence of immobilized biomolecules on the plasma polymer and was used to determine the mass coverage of the peptide and proteins adsorbed onto the films. The combined analysis of the surfaces suggests the covalent binding of the peptide and proteins to the surface of the pp-PFM.

Milestones and recent discoveries on cell death mediated by mitochondria and their interactions with biologically active amines.

PubMed

Grancara, Silvia; Ohkubo, Shinji; Artico, Marco; Ciccariello, Mauro; Manente, Sabrina; Bragadin, Marcantonio; Toninello, Antonio; Agostinelli, Enzo

2016-10-01

Mitochondria represent cell "powerhouses," being involved in energy transduction from the electrochemical gradient to ATP synthesis. The morphology of their cell types may change, according to various metabolic processes or osmotic pressure. A new morphology of the inner membrane and mitochondrial cristae, significantly different from the previous one, has been proposed for the inner membrane and mitochondrial cristae, based on the technique of electron tomography. Mitochondrial Ca(2+) transport (the transporter has been isolated) generates reactive oxygen species and induces the mitochondrial permeability transition of both inner and outer mitochondrial membranes, leading to induction of necrosis and apoptosis. In the mitochondria of several cell types (liver, kidney, and heart), mitochondrial oxidative stress is an essential step in the induction of cell death, although not in brain, in which the phenomenon is caused by a different mechanism. Mitochondrial permeability transition drives both apoptosis and necrosis, whereas mitochondrial outer membrane permeability is characteristic of apoptosis. Adenine nucleotide translocase remains the most important component involved in membrane permeability, with the opening of the transition pore, although other proteins, such as ATP synthase or phosphate carriers, have been proposed. Intrinsic cell death is triggered by the release from mitochondria of proteic factors, such as cytochrome c, apoptosis inducing factor, and Smac/DIABLO, with the activation of caspases upon mitochondrial permeability transition or mitochondrial outer membrane permeability induction. Mitochondrial permeability transition induces the permeability of the inner membrane in sites in contact with the outer membrane; mitochondrial outer membrane permeability forms channels on the outer membrane by means of various stimuli involving Bcl-2 family proteins. The biologically active amines, spermine, and agmatine, have specific functions on mitochondria which distinguish them from other amines. Enzymatic oxidative deamination of spermine by amine oxidases in tumor cells may produce reactive oxygen species, leading to transition pore opening and apoptosis. This process could be exploited as a new therapeutic strategy to combat cancer.

Novel protocol for highly efficient gas-phase chemical derivatization of surface amine groups using trifluoroacetic anhydride

NASA Astrophysics Data System (ADS)

Duchoslav, Jiri; Kehrer, Matthias; Hinterreiter, Andreas; Duchoslav, Vojtech; Unterweger, Christoph; Fürst, Christian; Steinberger, Roland; Stifter, David

2018-06-01

In the current work, chemical derivatization of amine (NH2) groups with trifluoroacetic anhydride (TFAA) as an analytical method to improve the information scope of X-ray photoelectron spectroscopy (XPS) is investigated. TFAA is known to successfully label hydroxyl (OH) groups. With the introduction of a newly developed gas-phase derivatization protocol conducted at ambient pressure and using a catalyst also NH2 groups can now efficiently be labelled with a high yield and without the formation of unwanted by-products. By establishing a comprehensive and self-consistent database of reference binding energies for XPS a promising approach for distinguishing hydroxyl from amine groups is presented. The protocol was verified on different polymers, including poly(allylamine), poly(ethyleneimine), poly(vinylalcohol) and chitosan, the latter one containing both types of addressed chemical groups.

Chitosan-rectorite nanospheres embedded aminated polyacrylonitrile nanofibers via shoulder-to-shoulder electrospinning and electrospraying for enhanced heavy metal removal

NASA Astrophysics Data System (ADS)

Huang, Mengtian; Tu, Hu; Chen, Jiajia; Liu, Rong; Liang, Zhaoyi; Jiang, Linbin; Shi, Xiaowen; Du, Yumin; Deng, Hongbing

2018-04-01

Chitosan (CS) has a high amine group content, while polyacrylonitrile (PAN) contains cyano-groups that can be easily converted to amine groups. Herein, a novel adsorbent consisting of PAN-CS mats was successfully prepared via the shoulder-to-shoulder electrospinning and electrospraying techniques, which could eliminate the obstacle of selecting a co-solvent system for dissolving PAN and CS together. The morphology of the resultant adsorbent with adherent nanofibers-nanospheres was observed due to the immobilization of the CS electrosprayed nanospheres into PAN electrospun nanofibrous mats. Furthermore, CS nanospheres and PAN nanofibers were alternately arranged which could enlarge the space between the nanofibers, facilitating the diffusion of heavy metals in solution. Afterwards, rectorite (REC) was introduced into the mats to achieve the predesigned intercalated structure formed between the CS chains and the interlayer of REC even acquired the desirable enhanced adsorption ability towards heavy metals. Based on this improvement, chemical modification was performed on the surface of PAN nanofibers to form aminated PAN (APAN) with more amine groups for reinforcing the adsorption performance. The adsorption experiments results showed that APAN-CS/REC mats exhibited at least a 2.0 times increase in the adsorption capacity of Pb2+ compared to the original PAN-CS composite mats.

Diastereoselective oxidative α-amination of aliphatic aldehydes catalyzed by iodine: synthesis of syn-γ-hydroxy-α-amino acetals.

PubMed

Zhang, Yun-Xiao; Zhang, An-Qi; Tian, Jie-Sheng; Loh, Teck-Peng

2013-12-28

Aldehydes can react with secondary amines to give α-amino acetals via the α-amination of aliphatic aldehydes catalyzed by iodine. The presence of an asymmetric hydroxylated center at the γ-position of the aldehyde was found to induce the stereoselective amino group. This method represents a stereoselective α-amination of γ-hydroxyaldehydes for the synthesis of syn-γ-hydroxy-α-amino acetals in good yields and reasonable diastereoselectivities under very mild conditions.

Operationally Simple Synthesis of N,N-Diethyl-3-Methylbenzamide (DEET) Using COMU as a Coupling Reagent

ERIC Educational Resources Information Center

Withey, Jonathan M.; Bajic, Andrea

2015-01-01

A novel procedure is described where students use COMU [(1-cyano-2-ethoxy-2-oxoethylidenaminooxy)dimethylamino-morpholino-carbenium hexafluorophosphate], as a nonhazardous partner, in the one-pot coupling of a carboxylic acid and amine producing N,N-diethyl-3-methylbenzamide (DEET). Fundamental principles of carbonyl reactivity are understood,…

Bioconjugation of Oligodeoxynucleotides Carrying 1,4-Dicarbonyl Groups via Reductive Amination with Lysine Residues.

PubMed

Yang, Bo; Jinnouchi, Akiko; Usui, Kazuteru; Katayama, Tsutomu; Fujii, Masayuki; Suemune, Hiroshi; Aso, Mariko

2015-08-19

We evaluated the efficacy of bioconjugation of oligodeoxynucleotides (ODNs) containing 1,4-dicarbonyl groups, a C4'-oxidized abasic site (OAS), and a newly designed 2'-methoxy analogue, via reductive amination with lysine residues. Dicarbonyls, aldehyde and ketone at C1- and C4-positions of deoxyribose in the ring-opened form of OAS allowed efficient reaction with amines. Kinetic studies indicated that reductive amination of OAS-containing ODNs with a proximal amine on the complementary strand proceeded 10 times faster than the corresponding reaction of an ODN containing an abasic site with C1-aldehyde. Efficient reductive amination between the DNA-binding domain of Escherichia coli DnaA protein and ODNs carrying OAS in the DnaA-binding sequence proceeded at the lysine residue in proximity to the phosphate group at the 5'-position of the OAS, in contrast to unsuccessful conjugation with abasic site ODNs, even though they have similar aldehydes. Theoretical calculation indicated that the C1-aldehyde of OAS was more accessible to the target lysine than that of the abasic site. These results demonstrate the potential utility of cross-linking strategies that use dicarbonyl-containing ODNs for the study of protein-nucleic acid interactions. Conjugation with a lysine-containing peptide that lacked specific affinity for ODN was also successful, further highlighting the advantages of 1,4-dicarbonyls.

Total synthesis and antibacterial testing of the A54556 cyclic acyldepsipeptides isolated from Streptomyces hawaiiensis.

PubMed

Goodreid, Jordan D; Wong, Keith; Leung, Elisa; McCaw, Shannon E; Gray-Owen, Scott D; Lough, Alan; Houry, Walid A; Batey, Robert A

2014-10-24

The first total synthesis of all six known A54556 acyldepsipeptide (ADEP) antibiotics from Streptomyces hawaiiensis is reported. This family of compounds has a unique mechanism of antibacterial action, acting as activators of caseinolytic protease (ClpP). Assembly of the 16-membered depsipeptide core was accomplished via a pentafluorophenyl ester-based macrolactamization strategy. Late stage amine deprotection was carried out under neutral conditions by employing a mild hydrogenolysis strategy, which avoids the formation of undesired ring-opened depsipeptide side products encountered during deprotection of acid-labile protecting groups. The free amines were found to be significantly more reactive toward late stage amide bond formation as compared to the corresponding ammonium salts, giving final products in excellent yields. A thorough NMR spectroscopic analysis of these compounds was carried out to formally assign the structures and to aid with the spectroscopic assignment of ADEP analogues. The identity of two of the structures was confirmed by comparison with biologically produced samples from S. hawaiiensis. An X-ray crystallographic analysis of an ADEP analogue reveals a conformation similar to that found in cocrystal structures of ADEPs with ClpP protease. The degree of antibacterial activity of the different compounds was evaluated in vitro using MIC assays employing both Gram-positive and Gram-negative strains and a fluorescence-based biochemical assay.

Photoaffinity Labeling via Nitrenium Ion Chemistry: Protonation of the Nitrene Derived from a 4-Amino-3-nitrophenylazide to Afford Reactive Nitrenium Ion Pairs

PubMed Central

Voskresenska, Valentyna; Wilson, R. Marshall; Panov, Maxim; Tarnovsky, Alexander N.; Krause, Jeanette A.; Vyas, Shubham; Winter, Arthur H.; Hadad, Christopher M.

2009-01-01

Phenyl azides with powerful electron-donating substituents are known to deviate from the usual photochemical behavior of other phenyl azides. They do not undergo ring expansion, but form basic nitrenes that protonate to form nitrenium ions. The photochemistry of the widely used photoaffinity labeling system 4-amino-3-nitrophenyl azide, 5, has been studied by transient absorption spectroscopy from femtosecond to microsecond time domains and from a theoretical perspective. The nitrene generation from azide 5 occurs on the S2 surface, in violation of Kasha's rule. The resulting nitrene is a powerful base and abstracts protons extremely rapidly from a variety of sources to form a nitrenium ion. In methanol, this protonation occurs in about 5 ps, which is the fastest intermolecular protonation observed to date. Suitable proton sources include alcohols, amine salts, and even acidic C-H bonds such as acetonitrile. The resulting nitrenium ion is stabilized by the electron-donating 4-amino group to afford a diiminoquinone-like species that collapses relatively slowly to form the ultimate cross-linked product. In some cases in which the anion is a good hydride donor, cross-linking is replaced by reduction of the nitrenium ion to the corresponding amine. PMID:19624129

(Bio)transformation of 2,4-dinitroanisole (DNAN) in Soils

PubMed Central

Olivares, Christopher I.; Abrell, Leif; Khatiwada, Raju; Chorover, Jon; Sierra-Alvarez, Reyes; Field, Jim A.

2015-01-01

Recent studies have begun to assess the environmental fate and toxicity of 2,4-dinitroanisole (DNAN), an insensitive munition compound of interest to defense agencies. Aerobic and anaerobic DNAN biotransformation in soils was evaluated in this study. Under aerobic conditions, there was little evidence of transformation; most observed removal was attributed to adsorption and subsequent slow chemical reactions. Under anaerobic conditions, DNAN was reductively (bio)transformed and the rate of the transformation was positively correlated with soil organic carbon (OC) up to a threshold of 2.07% OC. H2 addition enhanced the nitroreduction rate compared to endogenous treatments lacking H2. Heat-killed treatments provided rates similar to the endogenous treatment, suggesting that abiotic factors play a role in DNAN reduction. Ten (bio)transformation products were detected by high-resolution mass spectrometry. The proposed transformation pathway involves reduction of DNAN to aromatic amines, with putative reactive nitroso-intermediates coupling with the amines to form azo dimers. Secondary reactions include N-alkyl substitution, O-demethylation (sometimes followed by dehydroxylation), and removal of an N-containing group. Globally, our results suggest that the main reaction DNAN undergoes in anaerobic soils is nitroreduction to 2-methoxy-5-nitroaniline (MENA) and 2,4-diaminoanisole (DAAN), followed by anaerobic coupling reactions yielding azo-dimers. The dimers were subsequently subject to further (bio)transformations. PMID:26551225

Fabrication and functionalization of single asymmetric nanochannels for electrostatic/hydrophobic association of protein molecules

NASA Astrophysics Data System (ADS)

Ali, Mubarak; Bayer, Veronika; Schiedt, Birgitta; Neumann, Reinhard; Ensinger, Wolfgang

2008-12-01

We have developed a facile and reproducible method for surfactant-controlled track-etching and chemical functionalization of single asymmetric nanochannels in PET (polyethylene terephthalate) membranes. Carboxyl groups present on the channel surface were converted into pentafluorophenyl esters using EDC/PFP (N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride/pentafluorophenol) coupling chemistry. The resulting amine-reactive esters were further covalently coupled with ethylenediamine or propylamine in order to manipulate the charge polarity and hydrophilicity of the nanochannels, respectively. Characterization of the modified channels was done by measuring their current-voltage (I-V) curves as well as their permselectivity before and after the chemical modification. The electrostatic/hydrophobic association of bovine serum albumin on the channel surface was observed through the change in rectification behaviour upon the variation of pH values.

High temperature ablative foam

NASA Technical Reports Server (NTRS)

Liu, Matthew T. (Inventor)

1992-01-01

An ablative foam composition is formed of approximately 150 to 250 parts by weight polymeric isocyanate having an isocyanate functionality of 2.6 to 3.2; approximately 15 to 30 parts by weight reactive flame retardant having a hydroxyl number range from 200-260; approximately 10 to 40 parts by weight non-reactive flame retardant; approximately 10 to 40 parts by weight nonhydrolyzable silicone copolymer having a hydroxyl number range from 75-205; and approximately 3 to 16 parts by weight amine initiated polyether resin having an isocyanate functionality greater than or equal to 3.0 and a hydroxyl number range from 400-800.

Role of Additives in Composite PEI/Oxide CO 2 Adsorbents: Enhancement in the Amine Efficiency of Supported PEI by PEG in CO 2 Capture from Simulated Ambient Air

DOE PAGES

Sakwa-Novak, Miles A.; Tan, Shuai; Jones, Christopher W.

2015-10-20

Supported amines are promising candidate adsorbents for the removal of CO 2 from flue gases and directly from ambient air. The incorporation of additives into polymeric amines such as poly(ethylenimine) (PEI) supported on mesoporous oxides is an effective strategy to improve the performance of the materials. Here, several practical aspects of this strategy are addressed with regards to direct air capture. The influence of three additives (CTAB, PEG200, PEG1000) was systematically explored under dry simulated air capture conditions (400 ppm of CO 2, 30 °C). With SBA-15 as a model support for poly(ethylenimine) (PEI), the nature of the additive inducedmore » heterogeneities in the deposition of organic on the interior and exterior of the particles, an important consideration for future scale up to practical systems. The PEG200 additive increased the observed thermodynamic performance (~60% increase in amine efficiency) of the adsorbents regardless of the PEI content, while the other molecules had less positive effects. A threshold PEG200/PEI value was identified at which the diffusional limitations of CO 2 within the materials were nearly eliminated. The threshold PEG/PEI ratio may have physical origin in the interactions between PEI and PEG, as the optimal ratio corresponded to nearly equimolar OH/reactive (1°, 2°) amine ratios. As a result, the strategy is shown to be robust to the characteristics of the host support, as PEG200 improved the amine efficiency of PEI when supported on two varieties of mesoporous γ-alumina with PEI.« less

Role of Additives in Composite PEI/Oxide CO 2 Adsorbents: Enhancement in the Amine Efficiency of Supported PEI by PEG in CO 2 Capture from Simulated Ambient Air

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sakwa-Novak, Miles A.; Tan, Shuai; Jones, Christopher W.

Supported amines are promising candidate adsorbents for the removal of CO 2 from flue gases and directly from ambient air. The incorporation of additives into polymeric amines such as poly(ethylenimine) (PEI) supported on mesoporous oxides is an effective strategy to improve the performance of the materials. Here, several practical aspects of this strategy are addressed with regards to direct air capture. The influence of three additives (CTAB, PEG200, PEG1000) was systematically explored under dry simulated air capture conditions (400 ppm of CO 2, 30 °C). With SBA-15 as a model support for poly(ethylenimine) (PEI), the nature of the additive inducedmore » heterogeneities in the deposition of organic on the interior and exterior of the particles, an important consideration for future scale up to practical systems. The PEG200 additive increased the observed thermodynamic performance (~60% increase in amine efficiency) of the adsorbents regardless of the PEI content, while the other molecules had less positive effects. A threshold PEG200/PEI value was identified at which the diffusional limitations of CO 2 within the materials were nearly eliminated. The threshold PEG/PEI ratio may have physical origin in the interactions between PEI and PEG, as the optimal ratio corresponded to nearly equimolar OH/reactive (1°, 2°) amine ratios. As a result, the strategy is shown to be robust to the characteristics of the host support, as PEG200 improved the amine efficiency of PEI when supported on two varieties of mesoporous γ-alumina with PEI.« less

Editing the stereochemical elements in an iridium catalyst for enantioselective allylic amination

PubMed Central

Leitner, Andreas; Shu, Chutian; Hartwig, John F.

2004-01-01

Individual diastereomeric phosphoramidites and mixtures of diastereomeric phosphoramidites were evaluated in the iridium-catalyzed amination of allylic carbonates. The original process was conducted with a phosphoramidite ligand containing a resolved 2,2-dihydroxy-1,1-binaphthyl (BINOL) group and a diastereomerically and enantiomerically pure bis(phenethyl)amino group. Evaluation of the structure of the active catalyst and relative rates for reactions in the presence of catalysts containing diastereomeric ligands led to the identification of a phosphoramidite that provided the amination product with enantiomeric excess similar to the original, more structurally and stereochemically complex ligand and that contains a racemic BINOLate and an N-benzylphenethylamino group on phosphorus. PMID:15067140

Enhanced amine and amino acid analysis using Pacific Blue and the Mars Organic Analyzer microchip capillary electrophoresis system.

PubMed

Chiesl, Thomas N; Chu, Wai K; Stockton, Amanda M; Amashukeli, Xenia; Grunthaner, Frank; Mathies, Richard A

2009-04-01

The fluorescent amine reactive probe Pacific Blue succinimidyl ester (PB) is used for the detection of trace amounts of amines and amino acids by microchip capillary electrophoresis on the Mars Organic Analyzer (MOA). The spectral and chemical properties of PB provide a 200-fold increase in sensitivity and improved resolution compared to fluorescamine derivatization. With the use of cross injection and PB labeling, the MOA detected amino acids at concentrations as low as 75 pM (sub-parts-per-trillion). Micellar electrokinetic chromatography (MEKC) which separates PB-labeled amino acids by their hydrophobicity is also demonstrated. The optimized MEKC conditions (45 mM CHAPSO, pH 6 at 5 degrees C) effectively separated amines and 25 amino acids with enantiomeric resolution of alanine, serine, and citrulline. Samples from the Yungay Hills region in the Atacama Desert, Chile, and from the Murchison meteorite are successfully analyzed using both techniques, and amino acids are found in the parts-per-billion range. Abiotic amino acids such as beta-alanine and epsilon-aminocaprioc acid are detected along with several neutral and acidic amino acids in the Murchison sample. The Atacama Desert sample is found to contain homochiral L-alanine and L-serine indicating the presence of extant or recently extinct life.

Quantitative effects of amination degree on the magnetic iron oxide nanoparticles (MIONPs) using as adsorbents to remove aqueous heavy metal ions.

PubMed

Lin, Sen; Xu, Meng; Zhang, Wei; Hua, Xiufu; Lin, Kuangfei

2017-08-05

The hierarchical effect of amine-functionalization on nanoparticle properties, magnetism especially, and adsorption of Cu 2+ , Ni 2+ , Pb 2+ and Zn 2+ by aminated MIONPs were investigated elaboratively. The results reflected that the dispersibility and stability of nanoparticles in aqueous solution were both enhanced as MIONPs grafted with amine groups, while saturation magnetism and magnetic recovery conveniences had a negatively correlative relation with the amination degree. In addition, the adsorption performances of Cu 2+ , Ni 2+ , Pb 2+ and Zn 2+ by different aminated MIONPs were also studied comprehensively. The results showed that the initial adsorption rates and adsorption capacities of heavy metal ions increased with the amination degree. In addition, the quantitative correlation between amination degree and adsorption capacities of different heavy metal ions could be described well by a model built on basis of adsorption processes. Copyright © 2017. Published by Elsevier B.V.

Direct α-C-H bond functionalization of unprotected cyclic amines

NASA Astrophysics Data System (ADS)

Chen, Weijie; Ma, Longle; Paul, Anirudra; Seidel, Daniel

2018-02-01

Cyclic amines are ubiquitous core structures of bioactive natural products and pharmaceutical drugs. Although the site-selective abstraction of C-H bonds is an attractive strategy for preparing valuable functionalized amines from their readily available parent heterocycles, this approach has largely been limited to substrates that require protection of the amine nitrogen atom. In addition, most methods rely on transition metals and are incompatible with the presence of amine N-H bonds. Here we introduce a protecting-group-free approach for the α-functionalization of cyclic secondary amines. An operationally simple one-pot procedure generates products via a process that involves intermolecular hydride transfer to generate an imine intermediate that is subsequently captured by a nucleophile, such as an alkyl or aryl lithium compound. Reactions are regioselective and stereospecific and enable the rapid preparation of bioactive amines, as exemplified by the facile synthesis of anabasine and (-)-solenopsin A.

Chlorine transfer between glycine, taurine, and histamine: reaction rates and impact on cellular reactivity.

PubMed

Peskin, Alexander V; Midwinter, Robyn G; Harwood, David T; Winterbourn, Christine C

2005-02-01

Hypochlorous acid formed by activated neutrophils reacts with amines to produce chloramines. Chloramines vary in stability, reactivity, and cell permeability. We have examined whether chloramine exchange occurs between physiologically important amines or amino acids and if this affects interactions of chloramines with cells. We have demonstrated transchlorination reactions between histamine, glycine, and taurine chloramines by measuring chloramine decay rates with mixtures as well as by mass spectrometry. Kinetic analysis suggested the formation of an intermediate complex with a high Km. Apparent second-order rate constants, determined for concentrations

Chlorine transfer between glycine, taurine, and histamine: reaction rates and impact on cellular reactivity.

PubMed

Peskin, Alexander V; Midwinter, Robyn G; Harwood, David T; Winterbourn, Christine C

2004-11-15

Hypochlorous acid formed by activated neutrophils reacts with amines to produce chloramines. Chloramines vary in stability, reactivity, and cell permeability. We have examined whether chloramine exchange occurs between physiologically important amines or amino acids and if this affects interactions of chloramines with cells. We have demonstrated transchlorination reactions between histamine, glycine, and taurine chloramines by measuring chloramine decay rates with mixtures as well as by mass spectrometry. Kinetic analysis suggested the formation of an intermediate complex with a high K(m). Apparent second-order rate constants, determined for concentrations

Reductive trapping of substrate to bovine plasma amine oxidase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hartmann, C.; Klinman, J.P.

1987-01-25

Plasma amine oxidases catalyze the oxidative deamination of amines to aldehydes, followed by a 2e- reduction of O/sub 2/ to H/sub 2/O/sub 2/. Pyrroloquinoline quinone (PQQ), previously believed to be restricted to prokaryotes, has recently been proposed to be the cofactor undergoing reduction in the first half-reaction of bovine plasma amine oxidase (Ameyama, M., Hayashi, U., Matsushita, K., Shinagawa, E., and Adachi, O. (1984) Agric. Biol. Chem. 48, 561-565; Lobenstein-Verbeek, C. L., Jongejan, J. A., Frank, J., and Duine, J. A. (1984) FEBS Lett. 170, 305-309). This result is unexpected, since model studies with PQQ implicate Schiff's base formation betweenmore » a reactive carbonyl and substrates, whereas experiments with bovine plasma amine oxidase have failed to provide evidence for a carbonyl cofactor. We have, therefore, re-examined putative adducts between substrate and enzyme-bound cofactor, employing a combination of (/sup 14/C)benzylamine and (/sup 3/H)NaCNBH/sub 3/. The use of the relatively weak reductant, NaCNBH/sub 3/, affords Schiff's base specificity and permits the study of enzyme below pH 7.0. As we show, enzyme can only be inactivated by NaCNBH/sub 3/ in the presence of substrate, leading to the incorporation of 1 mol of (/sup 14/C)benzylamine/mol of enzyme subunit at complete inactivation. By contrast, we are unable to detect any labeling with (/sup 3/H)NaCNBH/sub 3/, analogous to an earlier study with (/sup 3/H)NaCNBH/sub 4/ (Suva, R. H., and Abeles, R. H. (1978) Biochemistry 17, 3538-3545). We conclude, first, that our inability to obtain adducts containing both carbon 14 and tritium rules out the reductive trapping either of amine substrate with pyridoxal phosphate or of aldehyde product with a lysyl side chain and, second, that the observed pattern of labeling is fully consistent with the presence of PQQ at the active site of bovine plasma amine oxidase.« less

One-Pot Anti-Markovnikov Hydroamination of Unactivated Alkenes by Hydrozirconation and Amination

PubMed Central

Strom, Alexandra E.

2013-01-01

A one-pot hydroamination of alkenes is reported. The synthesis of primary and secondary amines from unactivated olefins was accomplished in the presence of a variety of functional groups. Hydrozirconation, followed by amination with nitrogen electrophiles, provides exclusive anti-Markovnikov selectivity, and most products are isolated in high yields without the use of column chromatography. PMID:23899320

Synthesis of substituted pyrazines

DOEpatents

Pagoria, Philip F.; Zhang, Mao Xi

2016-10-04

A method for synthesizing a pyrazine-containing material according to one embodiment includes contacting an iminodiacetonitrile derivative with a base and a reagent selected from a group consisting of hydroxylamine, a hydroxylamine salt, an aliphatic primary amine, a secondary amine, an aryl-substituted alkylamine a heteroaryl-substituted alkyl amine, an alcohol, an alkanolamine and an aryl alcoholamine. Additional methods and several reaction products are presented. ##STR00001##

Synthesis and characterization of chitosan alkyl urea.

PubMed

Wang, Jing; Jiang, Ji-Zhou; Chen, Wei; Bai, Zheng-Wu

2016-07-10

Chitosan is a versatile material employed for various purposes in many fields including the development of chiral stationary phases for enantioseparation. Chitosan alkyl urea is a kind of intermediate used to prepare enantioseparation materials. In order to synthesize the intermediates, in the present work, a new way to prepare chitosan alkyl urea has been established: chitosan was first reacted with methyl chloroformate yielding N-methoxyformylated chitosan, which was then converted to chitosan alkyl urea through amine-ester exchange reaction. With a large excess of methyl chloroformate and primary amine of low stereohindrance, the amino group in chitosan could be almost completely converted to ureido group. The as-prepared chitosan alkyl urea derivatives were characterized by IR, (1)H NMR, (13)C NMR,(1)H-(1)H COSY and (1)H-(13)C HSQC NMR spectra. The chemical shifts of hydrogen and carbon atoms of glucose unit were assigned. It was found that the degree of substitution was obviously lower if cyclopropyl amine, aniline, tert-butyl amine and diethyl amine were used as reactants for the amine-ester exchange reaction. The reason was explained with the aid of theoretical calculations. Copyright © 2016 Elsevier Ltd. All rights reserved.

Morphogen Electrochemically Triggered Self-Construction of Polymeric Films Based on Mussel-Inspired Chemistry.

PubMed

Maerten, Clément; Garnier, Tony; Lupattelli, Paolo; Chau, Nguyet Trang Thanh; Schaaf, Pierre; Jierry, Loïc; Boulmedais, Fouzia

2015-12-15

Inspired by the strong chemical adhesion mechanism of mussels, we designed a catechol-based electrochemically triggered self-assembly of films based on ethylene glycol molecules bearing catechol groups on both sides and denoted as bis-catechol molecules. These molecules play the role of morphogens and, in contrast to previously investigated systems, they are also one of the constituents, after reaction, of the film. Unable to interact together, commercially available poly(allylamine hydrochloride) (PAH) chains and bis-catechol molecules are mixed in an aqueous solution and brought in contact with an electrode. By application of defined potential cycles, bis-catechol molecules undergo oxidation leading to molecules bearing "reactive" quinone groups which diffuse toward the solution. In this active state, the quinones react with amino groups of PAH through Michael addition and Schiff's base condensation reaction. The application of cyclic voltammetry (CV) between 0 and 500 mV (vs Ag/AgCl, scan rate of 50 mV/s) of a PAH/bis-catechol solution results in a fast self-construction of a film that reaches a thickness of 40 nm after 60 min. The films present a spiky structure which is attributed to the use of bis-functionalized molecules as one component of the films. XPS measurements show the presence of both PAH and bis-catechol cross-linked together in a covalent way. We show that the amine/catechol ratio is an important parameter which governs the film buildup. For a given amine/catechol ratio, it does exist an optimum CV scan rate leading to a maximum of the film thickness as a function of the scan rate.

Use of hydrostatic pressure for modulation of protein chemical modification and enzymatic selectivity.

PubMed

Makarov, Alexey A; Helmy, Roy; Joyce, Leo; Reibarkh, Mikhail; Maust, Mathew; Ren, Sumei; Mergelsberg, Ingrid; Welch, Christopher J

2016-05-11

Using hydrostatic pressure to induce protein conformational changes can be a powerful tool for altering the availability of protein reactive sites and for changing the selectivity of enzymatic reactions. Using a pressure apparatus, it has been demonstrated that hydrostatic pressure can be used to modulate the reactivity of lysine residues of the protein ubiquitin with a water-soluble amine-specific homobifunctional coupling agent. Fewer reactive lysine residues were observed when the reaction was carried out under elevated pressure of 3 kbar, consistent with a pressure-induced conformational change of ubiquitin that results in fewer exposed lysine residues. Additionally, modulation of the stereoselectivity of an enzymatic transamination reaction was observed at elevated hydrostatic pressure. In one case, the minor diasteromeric product formed at atmospheric pressure became the major product at elevated pressure. Such pressure-induced alterations of protein reactivity may provide an important new tool for enzymatic reactions and the chemical modification of proteins.

GC/MS determination of amines following exhaustive trifluoroacetylation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomson, J.S.; Green, J.B.; McWilliams, T.B.

An analytical method for trifluoroacetylation of aromatic amines and GC/MS of the resulting derivatives has been developed. The key feature of the method is its capability to differentiate d tertiary amines; since, using the conditions described in the report, most primary, secondary, an primary amines add two and secondary amines add one trifluoroacetyl group. In general, tertiary amines do not react. Since conventional trifluoroacetylation procedures introduce only a single trifluoroacetyl group into both primary and secondary aminess the procedure reported here improves GC/MS identification of the relatively large number of isomers of nitrogen compounds found in petroleum or similarly complexmore » mixtures. For example, using exhaustive trifluoroacetylation, it is possible to differentiate isomeric forms of C{sub 9}H{sub 11}N (e.g., cyclohexenopyridines, aminoindans, 1,2,3,4-tetrahydroquinoline and tetrahydroisoquinolines). Examples of the application of the method to petroleum and coal liquid products are provided. Because of the limited thermal stability of the derivatives of primary amines, the method is applicable only to distillates boiling below 370{degrees}C (700{degrees}F). To expedite utilization of the method by others, GC retention indices and relative GC/MS total ion current response factors for 102 trifluoroacetyl derivatives are included in the body of the report and their 70 ev mass spectra are reported in Appendix A.« less

Facile fabrication of HDPE-g-MA/nanodiamond nanocomposites via one-step reactive blending.

PubMed

Song, Ping'an; Yu, Youming; Wu, Qiang; Fu, Shenyuan

2012-06-29

In this letter, nanocomposites based on maleic anhydride grafted high density polyethylene (HDPE-g-MA) and amine-functionalized nanodiamond (ND) were fabricated via one-step reactive melt-blending, generating a homogeneous dispersion of ND, as evidenced by transmission electron microscope observations. Thermal analysis results suggest that addition of ND does not affect significantly thermal stability of polymer matrix in nitrogen. However, it was interestingly found that incorporating pure ND decreases the thermal oxidation degradation stability temperature, but blending amino-functionalized ND via reactive processing significantly enhances it of HDPE in air condition. Most importantly, cone tests revealed that both ND additives and reactive blending greatly reduce the heat release rate of HDPE. The results suggest that ND has a potential application as flame retardant alternative for polymers. Tensile results show that adding ND considerably enhances Young's modulus, and reactive blending leads to further improvement in Young's modulus while hardly reducing the elongation at break of HDPE.

Facile fabrication of HDPE-g-MA/nanodiamond nanocomposites via one-step reactive blending

PubMed Central

2012-01-01

In this letter, nanocomposites based on maleic anhydride grafted high density polyethylene (HDPE-g-MA) and amine-functionalized nanodiamond (ND) were fabricated via one-step reactive melt-blending, generating a homogeneous dispersion of ND, as evidenced by transmission electron microscope observations. Thermal analysis results suggest that addition of ND does not affect significantly thermal stability of polymer matrix in nitrogen. However, it was interestingly found that incorporating pure ND decreases the thermal oxidation degradation stability temperature, but blending amino-functionalized ND via reactive processing significantly enhances it of HDPE in air condition. Most importantly, cone tests revealed that both ND additives and reactive blending greatly reduce the heat release rate of HDPE. The results suggest that ND has a potential application as flame retardant alternative for polymers. Tensile results show that adding ND considerably enhances Young’s modulus, and reactive blending leads to further improvement in Young’s modulus while hardly reducing the elongation at break of HDPE. PMID:22747773

Correlation Between Structural, Spectroscopic, and Reactivity Properties Within a Series of Structurally Analogous Metastable Manganese(III)-Alkylperoxo Complexes

PubMed Central

Coggins, Michael K.; Martin-Diaconescu, Vlad; DeBeer, Serena; Kovacs, Julie A.

2013-01-01

Manganese–peroxos are proposed as key intermediates in a number of important biochemical and synthetic transformations. Our understanding of the structural, spectroscopic, and reactivity properties of these metastable species is limited, however, and correlations between these properties have yet to be established experimentally. Herein we report the crystallographic structures of a series of structurally related metastable Mn(III)–OOR compounds, and examine their spectroscopic and reactivity properties. The four reported Mn(III)–OOR compounds extend the number of known end-on Mn(III)–(η1-peroxos) to six. The ligand backbone is shown to alter the metal–ligand distances and modulate the electronic properties key to bonding and activation of the peroxo. The mechanism of thermal decay of these metastable species is examined via variable-temperature kinetics. Strong correlations between structural (O–O and Mn⋯Npy,quin distances), spectroscopic (E(πv*(O–O) → Mn CT band), νO–O), and kinetic (ΔH‡ and ΔS‡) parameters for these complexes provide compelling evidence for rate-limiting O–O bond cleavage. Products identified in the final reaction mixtures of Mn(III)–OOR decay are consistent with homolytic O–O bond scission. The N-heterocyclic amines and ligand backbone (Et vs Pr) are found to modulate structural and reactivity properties, and O–O bond activation is shown, both experimentally and theoretically, to track with metal ion Lewis acidity. The peroxo O–O bond is shown to gradually become more activated as the N-heterocyclic amines move closer to the metal ion causing a decrease in π-donation from the peroxo πv*(O–O) orbital. The reported work represents one of very few examples of experimentally verified relationships between structure and function. PMID:23432090

Correlation between structural, spectroscopic, and reactivity properties within a series of structurally analogous metastable manganese(III)-alkylperoxo complexes.

PubMed

Coggins, Michael K; Martin-Diaconescu, Vlad; DeBeer, Serena; Kovacs, Julie A

2013-03-20

Manganese-peroxos are proposed as key intermediates in a number of important biochemical and synthetic transformations. Our understanding of the structural, spectroscopic, and reactivity properties of these metastable species is limited, however, and correlations between these properties have yet to be established experimentally. Herein we report the crystallographic structures of a series of structurally related metastable Mn(III)-OOR compounds, and examine their spectroscopic and reactivity properties. The four reported Mn(III)-OOR compounds extend the number of known end-on Mn(III)-(η(1)-peroxos) to six. The ligand backbone is shown to alter the metal-ligand distances and modulate the electronic properties key to bonding and activation of the peroxo. The mechanism of thermal decay of these metastable species is examined via variable-temperature kinetics. Strong correlations between structural (O-O and Mn···N(py,quin) distances), spectroscopic (E(πv*(O-O) → Mn CT band), ν(O-O)), and kinetic (ΔH(‡) and ΔS(‡)) parameters for these complexes provide compelling evidence for rate-limiting O-O bond cleavage. Products identified in the final reaction mixtures of Mn(III)-OOR decay are consistent with homolytic O-O bond scission. The N-heterocyclic amines and ligand backbone (Et vs Pr) are found to modulate structural and reactivity properties, and O-O bond activation is shown, both experimentally and theoretically, to track with metal ion Lewis acidity. The peroxo O-O bond is shown to gradually become more activated as the N-heterocyclic amines move closer to the metal ion causing a decrease in π-donation from the peroxo πv*(O-O) orbital. The reported work represents one of very few examples of experimentally verified relationships between structure and function.

Water-Base Coatings

DTIC Science & Technology

1974-11-01

reacted with hydroxypropyl methacrylate and 1-butanol modifier in butyl acrylate -isobutyl methacrylate reactive diluent mixture using dibutyltin dilaurate...disadvantages are: 1. only a few commercial systems (e. g., acrylic resins ) are available; 2. after application, the polymer must somehow be insolubilized...a bisphenol in the presence of an emulsifier and a water-miscible solvent (9); 2. emulsification of an epoxy resin -amine curing agent mixture , e.g

Biodecoloration of Reactive Black 5 by the methylotrophic yeast Candida boidinii MM 4035.

PubMed

Martorell, María M; Pajot, Hipólito F; Ahmed, Pablo M; de Figueroa, Lucía I C

2017-03-01

Azo dyes are extensively used in textile dyeing and other industries. Effluents of dying industries are specially colored and could cause severe damage to the environment. The anaerobic treatment of textile dying effluents is nowadays the preferred option, but it could generate carcinogenic aromatic amines. Recently, yeasts have become a promising alternative, combining unicellular growth with oxidative mechanisms. This work reports the characterization of the first methylotrophic yeast with dye decolorizing ability, Candida boidinii MM 4035 and some insights into its decoloration mechanism. The analysis of two selected media revealed a possible two stages mechanism of Reactive Black 5 decoloration. In glucose poor media, decoloration is incomplete and only the first stage proceeds, leading to the accumulation of a purple compound. In media with higher glucose concentrations, the yeast is able to decolorize totally an initial concentration of 200mg/L. The entire process is co-metabolic, being largely dependent on glucose concentration but being able to proceed with several nitrogen sources. Manganese dependent peroxidase but not laccase activity could be detected during decoloration. Aromatic amines do not accumulate in culture media, supporting an oxidative decoloration mechanism of unknown ecophysiological relevance. Copyright © 2016. Published by Elsevier B.V.

Crosslinking reactions of 4-amino-6-oxo-2-vinylpyrimidine with guanine derivatives and structural analysis of the adducts

PubMed Central

Kusano, Shuhei; Ishiyama, Shogo; Lam, Sik Lok; Mashima, Tsukasa; Katahira, Masato; Miyamoto, Kengo; Aida, Misako; Nagatsugi, Fumi

2015-01-01

DNA interstrand crosslinks (ICLs) are the primary mechanism for the cytotoxic activity of many clinical anticancer drugs, and numerous strategies for forming ICLs have been developed. One such method is using crosslink-forming oligonucleotides (CFOs). In this study, we designed a 4-amino-6-oxo-2-vinylpyrimidine (AOVP) derivative with an acyclic spacer to react selectively with guanine. The AOVP CFO exhibited selective crosslinking reactivity with guanine and thymine in DNA, and with guanine in RNA. These crosslinking reactions with guanine were accelerated in the presence of CoCl2, NiCl2, ZnCl2 and MnCl2. In addition, we demonstrated that the AOVP CFO was reactive toward 8-oxoguanine opposite AOVP in the duplex DNA. The structural analysis of each guanine and 8-oxoguanine adduct in the duplex DNA was investigated by high-resolution NMR. The results suggested that AOVP reacts at the N2 amine in guanine and at the N1 or N2 amines in 8-oxoguanine in the duplex DNA. This study demonstrated the first direct determination of the adduct structure in duplex DNA without enzyme digestion. PMID:26245348

Enhanced Stability of PtRu Supported on N-Doped Carbon for the Anode of a DMFC

DTIC Science & Technology

2012-09-18

nitrogen functionalities are most likely limited to pyrrolic , N-C=O and amine groups. In the case of PtRu/C (N- doped), the ion implantation introduces...suggesting the presence of graphitic, quaternary, pyridinic, C-N=O, pyrrolic , amine and nitrile groups.32,46 Initial DMFC performance and electrochemical

Ion-conducting membranes

DOEpatents

Masel, Richard I.; Sajjad, Syed Dawar; Gao, Yan; Liu, Zengcai; Chen, Qingmei

2017-12-26

An anion-conducting polymeric membrane comprises a terpolymer of styrene, vinylbenzyl-R.sub.s and vinylbenzyl-R.sub.x. R.sub.s is a positively charged cyclic amine group. R.sub.x is at least one constituent selected from the group consisting Cl, OH and a reaction product between an OH or Cl and a species other than a simple amine or a cyclic amine. The total weight of the vinylbenzyl-R.sub.x groups is greater than 0.3% of the total weight of the membrane. In a preferred embodiment, the membrane is a Helper Membrane that increases the faradaic efficiency of an electrochemical cell into which the membrane is incorporated, and also allows product formation at lower voltages than in cells without the Helper Membrane.

The Function of Emulsions on the Biogenic Amine Formation and their Indices of Sea Bass Fillets (Dicentrarchus Labrax) Stored in Vacuum Packaging.

PubMed

Ozogul, Yesim; Durmus, Mustafa; Kuley Boga, Esmeray; Uçar, Yılmaz; Ozogul, Fatih

2018-02-01

The impacts of emulsions based on commercial oils on the biogenic amine formation and their indices of vacuumed packed sea bass fillets were investigated. The results showed that among biogenic amines, cadaverine, putrescine, spermidine, spermine, serotonin, dopamine, and agmatine were predominant amines in sea bass fillets stored under vacuum packaging. Significant differences (P < 0.05) in biogenic amines concentrations of vacuumed packed sea bass treated with emulsions were observed. All groups contained histamine lower than 5.0 mg/100 g, regarded as the allowable limit by the U.S. Food and Drug Administration. Polyamine levels were not affected by application of emulsion. Quality index (QI) showed an increase and after 14 d of storage it decreased in all groups. The control generally seemed to higher QI value than those of treatment groups except at 14 and 18 days while soybean and corn gave lower QI among treatment groups. Only biogenic amine index correlated with sensory acceptability of vacuumed packed sea bass, indicating that this index can be used for determination of the degree of spoilage of vacuumed packed sea bass. Emulsions extended the shelf-life (approximately 2 to 4 d) of vacuumed packed sea bass fillets by inhibiting microbial growth compared to the control. Emulsions have become popular since they are regarded as ideal carrier for the delivery of lipophilic substances due to the ease of preparation, small particle size, their enhanced bioavailability, and long term kinetic stability. They have been proven to be self-preserving antimicrobials due to bound water in their structure and thus no available water to microorganisms. Antimicrobial emulsions have potential applications in many fields because they are inexpensive, stable, and nontoxic agents. © 2018 Institute of Food Technologists®.

Reactive thin polymer films as platforms for the immobilization of biomolecules.

PubMed

Feng, Chuan Liang; Zhang, Zhihong; Förch, Renate; Knoll, Wolfgang; Vancso, G Julius; Schönherr, Holger

2005-01-01

Spin-coated thin films of poly(N-hydroxysuccinimidyl methacrylate) (PNHSMA) on oxidized silicon and gold surfaces were investigated as reactive layers for obtaining platforms for biomolecule immobilization with high molecular loading. The surface reactivity of PNHSMA films in coupling reactions with various primary amines, including amine-terminated poly(ethylene glycol) (PEG-NH2) and fluoresceinamine, was determined by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), fluorescence microscopy, and ellipsometry measurements, respectively. The rate constants of PEG-NH2 attachment on the PNHSMA films were found to be significantly increased compared to the coupling on self-assembled monolayers (SAMs) of 11,11'-dithiobis(N-hydroxysuccinimidylundecanoate) (NHS-C10) on gold under the same conditions. More significantly, the PEG loading observed was about 3 times higher for the polymer thin films. These data indicate that the coupling reactions are not limited to the very surface of the polymer films, but proceed into the near-surface regions of the films. PNHSMA films were shown to be stable in contact with aqueous buffer; the swelling analysis, as performed by atomic force microscopy (AFM), indicated a film thickness independent swelling of approximately 2 nm. An increased loading was also observed by surface plasmon resonance for the covalent immobilization of amino-functionalized probe DNA. Hybridization of fluorescently labeled target DNA was successfully detected by fluorescence microscopy and surface plasmon resonance enhanced fluorescence spectroscopy (SPFS), thereby demonstrating that thin films of PNHSMA comprise an attractive and simple platform for the immobilization of biomolecules with high densities.

Key intermediates in nitrogen transformation during microwave pyrolysis of sewage sludge: a protein model compound study.

PubMed

Zhang, Jun; Tian, Yu; Cui, Yanni; Zuo, Wei; Tan, Tao

2013-03-01

The nitrogen transformations with attention to NH3 and HCN were investigated at temperatures of 300-800°C during microwave pyrolysis of a protein model compound. The evolution of nitrogenated compounds in the char, tar and gas products were conducted. The amine-N, heterocyclic-N and nitrile-N compounds were identified as three important intermediates during the pyrolysis. NH3 and HCN were formed with comparable activation energies competed to consume the same reactive substances at temperatures of 300-800°C. The deamination and dehydrogenation of amine-N compounds from protein cracking contributed to the formation of NH3 (about 8.9% of Soy-N) and HCN (6.6%) from 300 to 500°C. The cracking of nitrile-N and heterocyclic-N compounds from the dehydrogenation and polymerization of amine-N generated HCN (13.4%) and NH3 (31.3%) between 500 and 800°C. It might be able to reduce the HCN and NH3 emissions through controlling the intermediates production at temperatures of 500-800°C. Copyright © 2013 Elsevier Ltd. All rights reserved.

Amination with Pd-NHC complexes: rate and computational studies involving substituted aniline substrates.

PubMed

Hoi, Ka Hou; Çalimsiz, Selçuk; Froese, Robert D J; Hopkinson, Alan C; Organ, Michael G

2012-01-02

The amination of aryl chlorides with various aniline derivatives using the N-heterocyclic carbene-based Pd complexes Pd-PEPPSI-IPr and Pd-PEPPSI-IPent (PEPPSI=pyridine, enhanced precatalyst, preparation, stabilization, and initiation; IPr=diisopropylphenylimidazolium derivative; IPent= diisopentylphenylimidazolium derivative) has been studied. Rate studies have shown a reliance on the aryl chloride to be electron poor, although oxidative addition is not rate limiting. Anilines couple best when they are electron rich, which would seem to discount deprotonation of the intermediate metal ammonium complex as being rate limiting in favour of reductive elimination. In previous studies with secondary amines using PEPPSI complexes, deprotonation was proposed to be the slow step in the cycle. These experimental findings relating to mechanism were corroborated by computation. Pd-PEPPSI-IPr and the more hindered Pd-PEPPSI-IPent catalysts were used to couple deactivated aryl chlorides with electron poor anilines; while the IPr catalysis was sluggish, the IPent catalyst performed extremely well, again showing the high reactivity of this broadly useful catalyst. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of structurally diverse major groove DNA interstrand crosslinks using three different aldehyde precursors

PubMed Central

Mukherjee, Shivam; Guainazzi, Angelo; Schärer, Orlando D.

2014-01-01

DNA interstrand crosslinks (ICLs) are extremely cytotoxic lesions that block essential cellular processes, such as replication and transcription. Crosslinking agents are widely used in cancer chemotherapy and form an array of structurally diverse ICLs. Despite the clinical success of these agents, resistance of tumors to crosslinking agents, for example, through repair of these lesions by the cellular machinery remains a problem. We have previously reported the synthesis of site-specific ICLs mimicking those formed by nitrogen mustards to facilitate the studies of cellular responses to ICL formation. Here we extend these efforts and report the synthesis of structurally diverse major groove ICLs that induce severe, little or no distortion in the DNA. Our approach employs the incorporation of aldehyde precursors of different lengths into complementary strands and ICL formation using a double reductive amination with a variety of amines. Our studies provide insight into the structure and reactivity parameters of ICL formation by double reductive amination and yield a set of diverse ICLs that will be invaluable for exploring structure–activity relationships in ICL repair. PMID:24782532

Sillica Gel-Amine from Geothermal Sludge

NASA Astrophysics Data System (ADS)

Muljani, S.; Pujiastuti, C.; Wicaksono, P.; Lutfianingrum, R.

2018-01-01

Silica Gel-Amine (SGA) has been made from geothermal sludge by grafting amine method. Sodium silicate solution is prepared by extracted geothermal sludge powder using sodium hidroxide solution then acidification in the range of pH 5 - 9 by using tartaric acid 1N. The grafting process uses 1 ml of ammonia solution and 10 ml of toluene at a rate of 0.1 ml min-1 accompanied by a reflux process. The amine grafting is done in two methods. The first method is grafting amine in silicate solution and the second method is grafting amine in washed gel. Product SGA was confirmed by FTIR, TGA-DTG and BET characterization. The results show that the pH affects the amount of amine that is grafted onto silica gel. Differences in grafting method affect the size of the pore and surface area. SGA product prepared by grafting washed gel at pH 8 have pore diameter of 12.06 nm, surface area of 173.44 m2g-1, and mass of decomposed amine compound 0.4 mg. In the presence of amine groups on the silica gel surface, these adsorbents may be able to selectively adsorb CO2 gas from natural gas.

Reductive Activation of O2 by Non-Heme Iron(II) Benzilate Complexes of N4 Ligands: Effect of Ligand Topology on the Reactivity of O2-Derived Oxidant.

PubMed

Chakraborty, Biswarup; Jana, Rahul Dev; Singh, Reena; Paria, Sayantan; Paine, Tapan Kanti

2017-01-03

A series of iron(II) benzilate complexes (1-7) with general formula [(L)Fe II (benzilate)] + have been isolated and characterized to study the effect of supporting ligand (L) on the reactivity of metal-based oxidant generated in the reaction with dioxygen. Five tripodal N 4 ligands (tris(2-pyridylmethyl)amine (TPA in 1), tris(6-methyl-2-pyridylmethyl)amine (6-Me 3 -TPA in 2), N 1 ,N 1 -dimethyl-N 2 ,N 2 -bis(2-pyridylmethyl)ethane-1,2-diamine (iso-BPMEN in 3), N 1 ,N 1 -dimethyl-N 2 ,N 2 -bis(6-methyl-2-pyridylmethyl)ethane-1,2-diamine (6-Me 2 -iso-BPMEN in 4), and tris(2-benzimidazolylmethyl)amine (TBimA in 7)) along with two linear tetradentate amine ligands (N 1 ,N 2 -dimethyl-N 1 ,N 2 -bis(2-pyridylmethyl)ethane-1,2-diamine (BPMEN in 5) and N 1 ,N 2 -dimethyl-N 1 ,N 2 -bis(6-methyl-2-pyridylmethyl)ethane-1,2-diamine (6-Me 2 -BPMEN in 6)) were employed in the study. Single-crystal X-ray structural studies reveal that each of the complex cations of 1-3 and 5 contains a mononuclear six-coordinate iron(II) center coordinated by a monoanionic benzilate, whereas complex 7 contains a mononuclear five-coordinate iron(II) center. Benzilate binds to the iron center in a monodentate fashion via one of the carboxylate oxygens in 1 and 7, but it coordinates in a bidentate chelating mode through carboxylate oxygen and neutral hydroxy oxygen in 2, 3, and 5. All of the iron(II) complexes react with dioxygen to exhibit quantitative decarboxylation of benzilic acid to benzophenone. In the decarboxylation pathway, dioxygen becomes reduced on the iron center and the resulting iron-oxygen oxidant shows versatile reactivity. The oxidants are nucleophilic in nature and oxidize sulfide to sulfoxide and sulfone. Furthermore, complexes 2 and 4-6 react with alkenes to produce cis-diols in moderate yields with the incorporation of both the oxygen atoms of dioxygen. The oxygen atoms of the nucleophilic oxidants do not exchange with water. On the basis of interception studies, nucleophilic iron(II) hydroperoxides are proposed to generate in situ in the reaction pathways. The difference in reactivity of the complexes toward external substrates could be attributed to the geometry of the O 2 -derived iron-oxygen oxidant. DFT calculations suggest that, among all possible geometries and spin states, high-spin side-on iron(II) hydroperoxides are energetically favorable for the complexes of 6-Me 3 -TPA, 6-Me 2 -iso-BPMEN, BPMEN, and 6-Me 2 -BPMEN ligands, while high spin end-on iron(II) hydroperoxides are favorable for the complexes of TPA, iso-BPMEN, and TBimA ligands.

Nucleophilic addition of nitrogen to aryl cations: mimicking Titan chemistry.

PubMed

Li, Anyin; Jjunju, Fred P M; Cooks, R Graham

2013-11-01

The reactivity of aryl cations toward molecular nitrogen is studied systematically in an ion trap mass spectrometer at 10(2) Pascal of nitrogen, the pressure of the Titan main haze layer. Nucleophilic addition of dinitrogen occurs and the nature of aryl group has a significant influence on the reactivity, through inductive effects and by changing the ground state spin multiplicity. The products of nitrogen activation, aryldiazonium ions, react with typical nitriles, aromatic amines, and alkynes (compounds that are relevant as possible Titan atmosphere constituents) to form covalently bonded heterocyclic products. Theoretical calculations at the level [DFT(B3LYP)/6-311++G(d,p)] indicate that the N2 addition reaction is exothermic for the singlet aryl cations but endothermic for their triplet spin isomers. The -OH and -NH2 substituted aryl ions are calculated to have triplet ground states, which is consistent with their decreased nitrogen addition reactivity. The energy needed for the generation of the aryl cations from their protonated precursors (ca. 340 kJ/mol starting with protonated aniline) is far less than that required to directly activate the nitrogen triple bond (the lowest energy excited state of N2 lies ca. 600 kJ/mol above the ground state). The formation of aza-aromatics via arene ionization and subsequent reactions provide a conceivable route to the genesis of nitrogen-containing organic molecules in the interstellar medium and Titan haze layers.

Divergent synthesis and chemical reactivity of bicyclic lactone fragments of complex rearranged spongian diterpenes.

PubMed

Schnermann, Martin J; Beaudry, Christopher M; Genung, Nathan E; Canham, Stephen M; Untiedt, Nicholas L; Karanikolas, Breanne D W; Sütterlin, Christine; Overman, Larry E

2011-11-02

The synthesis and direct comparison of the chemical reactivity of the two highly oxidized bicyclic lactone fragments found in rearranged spongian diterpenes (8-substituted 6-acetoxy-2,7-dioxabicyclo[3.2.1]octan-3-one and 6-substituted 7-acetoxy-2,8-dioxabicyclo[3.3.0]octan-3-one) are reported. Details of the first synthesis of the 6-acetoxy-2,7-dioxabicyclo[3.2.1]octan-3-one ring system, including an examination of several possibilities for the key bridging cyclization reaction, are described. In addition, the first synthesis of 7-acetoxy-2,8-dioxabicyclo[3.3.0]octanones containing quaternary carbon substituents at C6 is disclosed. Aspects of the chemical reactivity and Golgi-modifying properties of these bicyclic lactone analogs of rearranged spongian diterpenes are also reported. Under both acidic and basic conditions, 8-substituted 2,7-dioxabicyclo[3.2.1]octanones are converted to 6-substituted-2,8-dioxabicyclo[3.3.0]octanones. Moreover, these dioxabicyclic lactones react with primary amines and lysine side chains of lysozyme to form substituted pyrroles, a conjugation that could be responsible for the unique biological properties of these compounds. These studies demonstrate that acetoxylation adjacent to the lactone carbonyl group, in either the bridged or fused series, is required to produce fragmented Golgi membranes in the pericentriolar region that is characteristic of macfarlandin E.

Fluorescent labeling of proteins with amine-specific 1,3,2-(2H)-dioxaborine polymethine dye.

PubMed

Gerasov, Andriy; Shandura, Mykola; Kovtun, Yuriy; Losytskyy, Mykhaylo; Negrutska, Valentyna; Dubey, Igor

2012-01-15

A novel water-soluble amine-reactive dioxaborine trimethine dye was synthesized in a good yield and characterized. The potential of the dye as a specific reagent for protein labeling was demonstrated with bovine serum albumin and lysozyme. Its interaction with proteins was studied by fluorescence spectroscopy and gel electrophoresis. The covalent binding of this almost nonfluorescent dye to proteins results in a 75- to 78-fold increase of its emission intensity accompanied by a red shift of the fluorescence emission maximum by 27 to 45 nm, with fluorescence wavelengths of labeled biomolecules being more than 600 nm. The dye does not require activation for the labeling reaction and can be used in a variety of bioassay applications. Copyright © 2011 Elsevier Inc. All rights reserved.

N-15 NMR Spectroscopy as a Method for Comparing the Rates of Imidization of Several Diamines

NASA Technical Reports Server (NTRS)

Johnson, J. Christopher; Kuczmarski, Maria A.

2006-01-01

The relative rates of the conversion of amide-acid to imide was measured for a series or aromatic diamines that have been identified as potential replacements for 4,4'-methylene dianiline (MDA) in high-temperature polyimides and polymer composites. These rates were compared with the N-15 NMR resonances of the unreacted amines. The initial rates of imidization track with the difference in chemical shift between the amine nitrogens in MDA and those in the subject diamines. This comparison demonstrated that N-15 NMR spectroscopy is appropriate for the rapid screening of candidate diamines to determine their reactivity relative to MDA, and can serve to provide guidance to the process of creating the time-temperature profiles used in processing these materials into polymer matrix composites.

Process for producing organic products containing silicon, hydrogen, nitrogen, and carbon by the direct reaction between elemental silicon and organic amines and products formed thereby

DOEpatents

Pugar, E.A.; Morgan, P.E.D.

1988-04-04

A process is disclosed for producing, at a low temperature, a high purity organic reaction product consisting essentially of silicon, hydrogen, nitrogen, and carbon. The process comprises reacting together a particulate elemental high purity silicon with a high purity reactive amine reactant in a liquid state at a temperature of from about O/degree/C up to about 300/degree/C. A high purity silicon carbide/silicon nitride ceramic product can be formed from this intermediate product, if desired, by heating the intermediate product at a temperature of from about 1200-1700/degree/C for a period from about 15 minutes up to about 2 hours or the organic reaction product may be employed in other chemical uses.

Process for producing organic products containing silicon, hydrogen, nitrogen, and carbon by the direct reaction between elemental silicon and organic amines

DOEpatents

Pugar, Eloise A.; Morgan, Peter E. D.

1990-04-03

A process is disclosed for producing, at a low temperature, a high purity organic reaction product consisting essentially of silicon, hydrogen, nitrogen, and carbon. The process comprises reacting together a particulate elemental high purity silicon with a high purity reactive amine reactant in a liquid state at a temperature of from about 0.degree. C. up to about 300.degree. C. A high purity silicon carbide/silicon nitride ceramic product can be formed from this intermediate product, if desired, by heating the intermediate product at a temperature of from about 1200.degree.-1700.degree. C. for a period from about 15 minutes up to about 2 hours or the organic reaction product may be employed in other chemical uses.

Synthesis of Sequence-Specific DNA-Protein Conjugates via a Reductive Amination Strategy

PubMed Central

Wickramaratne, Susith; Mukherjee, Shivam; Villalta, Peter W.; Schärer, Orlando D.; Tretyakova, Natalia

2013-01-01

DNA-protein cross-links (DPCs) are ubiquitous, structurally diverse DNA lesions formed upon exposure to bis-electrophiles, transition metals, UV light, and reactive oxygen species. Because of their super-bulky, helix distorting nature, DPCs interfere with DNA replication, transcription, and repair, potentially contributing to mutagenesis and carcinogenesis. However, the biological implications of DPC lesions have not been fully elucidated due to the difficulty of generating site-specific DNA substrates representative of DPC lesions formed in vivo. In the present study, a novel approach involving post-synthetic reductive amination has been developed to prepare a range of hydrolytically stable lesions structurally mimicking the DPCs produced between the N7 position of guanine in DNA and basic lysine or arginine side chains of proteins and peptides. PMID:23885807

Relationship of phospholipid chemistry to serological reactivity in the Venereal Disease Research Laboratory slide test antigen.

PubMed Central

Reeves, M W; McGrew, B E; McLaurin, B; Pine, L

1981-01-01

A total of 13 egg lecithins, 12 beef heart lecithins, and 15 beef heart cardiolipins were assayed for the ability to function in the Venereal Disease Research Laboratory microflocculation test, as well as for purity, fatty acid composition, free amines, metals, and products of oxidation. We found that the presence of peroxides and oxidation-related ultraviolet-absorbing chromophores showed a close inverse relationship to acceptable serological activity. The degree of purity of the lipids had only a slight influence on serological activity, whereas fatty acid composition, saturation, and configuration had none at all. We did not detect contaminating iron, copper, cobalt, nickel, or free amines in these lipids. We discuss the implications of our findings for improving the chemical standards for these lipids. Images PMID:7263853

Poly(Amido Amine)s Containing Agmatine and Butanol Side Chains as Efficient Gene Carriers.

PubMed

Won, Young-Wook; Ankoné, Marc; Engbersen, Johan F J; Feijen, Jan; Kim, Sung Wan

2016-04-01

A new type of bioreducible poly(amido amine) copolymer is synthesized by the Michael addition polymerization of cystamine bisacrylamide (CBA) with 4-aminobutylguanidine (agmatine, AGM) and 4-aminobutanol (ABOL). Since the positively charged guanidinium groups of AGM and the hydroxybutyl groups of ABOL in the side chains have shown to improve the overall transfection efficiency of poly(amido amine)s, it is hypothesized that poly(CBA-ABOL/AGM) synthesized at the optimal ratio of both components would result in high transfection efficiency and minimal toxicity. In this study, a series of the poly(CBA-ABOL/AGM) copolymers is synthesized as gene carriers. The polymers are characterized and luciferase transfection efficiencies of the polymers in various cell lines are investigated to select the ideal ratio between AGM and ABOL. The poly(CBA-ABOL/AGM) containing 80% AGM and 20% ABOL has shown the best transfection efficiency with the lowest cytotoxicity, indicating that this polymer is very promising as a potent and nontoxic gene carrier. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chemical modification of poly(ethylene terephthalate) and immobilization of the selected enzymes on the modified film

NASA Astrophysics Data System (ADS)

Irena, Gancarz; Jolanta, Bryjak; Karolina, Zynek

2009-07-01

Poly(ethylene terephthalate) (PET) film was modified by reaction with hydrazine (HD), ethylenediamine (EDA), 1,2-diaminopropane (1,2-DAP) and 1,3-diaminopropane (1,3-DAP). The maximal amount of amine functionalities introduced in the chosen conditions on the surface was found as 0.07, 3.35, 0.76 and 1.99 nmol cm -2 for HD, EDA, 1,2-DAP and 1,3-DAP respectively. During the modification process etching of the sample and an increase of stiffness takes place. FTIR-ATR spectra prove that the surface chemistry after modification in amine solution is very complex. The lack of clear correlation between the surface tension and surface concentration of amine functionalities seems to confirm that. For immobilization purpose invertase, laccase and tyrosinase were used. The amount of covalently attached proteins at first increases with the increase of surface concentration of amine groups but after reaching a certain level of amine groups, decrease of the immobilization level was observed. All enzymes tested showed highest activity for a moderate level of aminolysis and this activity had the highest values for EDA-modified PET.

Silanol-assisted carbinolamine formation in an amine-functionalized mesoporous silica surface: Theoretical investigation by fragmentation methods

DOE PAGES

de Lima Batista, Ana P.; Zahariev, Federico; Slowing, Igor I.; ...

2015-12-15

The aldol reaction catalyzed by an amine-substituted mesoporous silica nanoparticle (amine-MSN) surface was investigated using a large molecular cluster model (Si 392O 958C 6NH 361) combined with the surface integrated molecular orbital/molecular mechanics (SIMOMM) and fragment molecular orbital (FMO) methods. Three distinct pathways for the carbinolamine formation, the first step of the amine-catalyzed aldol reaction, are proposed and investigated in order to elucidate the role of the silanol environment on the catalytic capability of the amine-MSN material. Here the computational study reveals that the most likely mechanism involves the silanol groups actively participating in the reaction, forming and breaking covalentmore » bonds in the carbinolamine step. Furthermore, the active participation of MSN silanol groups in the reaction mechanism leads to a significant reduction in the overall energy barrier for the carbinolamine formation. In addition, a comparison between the findings using a minimal cluster model and the Si 392O 958C 6NH 361 cluster suggests that the use of larger models is important when heterogeneous catalysis problems are the target.« less

The adsorption of biogenic amines on carbon nanotubes

NASA Astrophysics Data System (ADS)

Sidorenko, I. G.; Markitan, O. V.; Vlasova, N. N.; Zagorovskii, G. M.; Lobanov, V. V.

2009-06-01

The adsorption of phenylethylamine, tryptamine, and tyramine on carbon nanotubes from aqueous solutions (pH 7.4) was studied depending on time and sorbate concentration. The suggestion was made that their interaction with electrodes was determined by electrostatic attraction between protonated amino groups and oxygen-containing functional groups of the surface of carbon. An increase in the adsorption of biological amines was caused by the interaction of the π systems of their aromatic rings with carbon surface hexagons. The adsorption of biogenic amines on carbon nanotubes was necessary for their possible electrooxidation and analytic determination by electrochemical methods with the use of carbon electrodes.

Functional-Group-Tolerant, Silver-Catalyzed N-N Bond Formation by Nitrene Transfer to Amines.

PubMed

Maestre, Lourdes; Dorel, Ruth; Pablo, Óscar; Escofet, Imma; Sameera, W M C; Álvarez, Eleuterio; Maseras, Feliu; Díaz-Requejo, M Mar; Echavarren, Antonio M; Pérez, Pedro J

2017-02-15

Silver(I) promotes the highly chemoselective N-amidation of tertiary amines under catalytic conditions to form aminimides by nitrene transfer from PhI═NTs. Remarkably, this transformation proceeds in a selective manner in the presence of olefins and other functional groups without formation of the commonly observed aziridines or C-H insertion products. The methodology can be applied not only to rather simple tertiary amines but also to complex natural molecules such as brucine or quinine, where the products derived from N-N bond formation were exclusively formed. Theoretical mechanistic studies have shown that this selective N-amidation reaction proceeds through triplet silver nitrenes.

Self-assembly of a superparamagnetic raspberry-like silica/iron oxide nanocomposite using epoxy-amine coupling chemistry.

PubMed

Cano, Manuel; de la Cueva-Méndez, Guillermo

2015-02-28

The fabrication of colloidal nanocomposites would benefit from controlled hetero-assembly of ready-made particles through covalent bonding. Here we used epoxy-amine coupling chemistry to promote the self-assembly of superparamagnetic raspberry-like nanocomposites. This adaptable method induced the covalent attachment of iron oxide nanoparticles sparsely coated with amine groups onto epoxylated silica cores in the absence of other reactants.

Formation of NDMA from ranitidine and sumatriptan: the role of pH.

PubMed

Shen, Ruqiao; Andrews, Susan A

2013-02-01

N-nitrosodimethylamine (NDMA) is an emerging disinfection by-product (DBP) which can be formed via the chloramination of amine-based precursors. The formation of NDMA is mainly determined by the speciation of chloramines and the precursor amine groups, both of which are highly dependent on pH. The impact of pH on NDMA formation has been studied for the model precursor dimethylamine (DMA) and natural organic matter (NOM), but little is known for amine-based pharmaceuticals which have been newly identified as a group of potential NDMA precursors, especially in waters impacted by treated wastewater effluents. This study investigates the role of pH in the formation of NDMA from two amine-based pharmaceuticals, ranitidine and sumatriptan, under drinking water relevant conditions. The results indicate that pH affects both the ultimate NDMA formation as well as the reaction kinetics. The maximum NDMA formation typically occurs in the pH range of 7-8. At lower pH, the reaction is limited due to the lack of non-protonated amines. At higher pH, although the initial reaction is enhanced by the increasing amount of non-protonated amines, the ultimate NDMA formation is limited because of the lack of dichloramine. Copyright © 2012 Elsevier Ltd. All rights reserved.

Visible Light Responsive Liquid Crystal Polymers Containing Reactive Moieties with Good Processability.

PubMed

Liu, Yuyun; Wu, Wei; Wei, Jia; Yu, Yanlei

2017-01-11

Two types of novel reactive linear liquid crystal polymers (LLCPs) with different azotolene concentrations have been synthesized and processed into films and fibers by solution and melting processing methods. Then, the LLCPs in the obtained monodomain fiber and polydomain film were easily cross-linked with difunctional primary amines. The resulted cross-linked liquid crystal polymers (CLCPs) underwent reversible photoinduced bending and unbending behaviors in response to 445 and 530 nm visible light at room temperature, respectively. The post-cross-linking method provides a facile way to prepare the CLCP films and fibers with different shapes from LLCPs, which can be processed by traditional melting and solution methods.

Transition metal-catalyzed process for addition of amines to carbon-carbon double bonds

DOEpatents

Hartwig, John F.; Kawatsura, Motoi; Loeber, Oliver

2002-01-01

The present invention is directed to a process for addition of amines to carbon-carbon double bonds in a substrate, comprising: reacting an amine with a compound containing at least one carbon-carbon double bond in the presence a transition metal catalyst under reaction conditions effective to form a product having a covalent bond between the amine and a carbon atom of the former carbon-carbon double bond. The transition metal catalyst comprises a Group 8 metal and a ligand containing one or more 2-electron donor atoms. The present invention is also directed to enantioselective reactions of amine compounds with compounds containing carbon-carbon double bonds, and a calorimetric assay to evaluate potential catalysts in these reactions.

Hybrid Amine-Functionalized Graphene Oxide as a Robust Bifunctional Catalyst for Atmospheric Pressure Fixation of Carbon Dioxide using Cyclic Carbonates.

PubMed

Saptal, Vitthal B; Sasaki, Takehiko; Harada, Kei; Nishio-Hamane, Daisuke; Bhanage, Bhalchandra M

2016-03-21

An environmentally-benign carbocatalyst based on amine-functionalized graphene oxide (AP-GO) was synthesized and characterized. This catalyst shows superior activity for the chemical fixation of CO2 into cyclic carbonates at the atmospheric pressure. The developed carbocatalyst exhibits superior activity owing to its large surface area with abundant hydrogen bonding donor (HBD) capability and the presence of well-defined amine functional groups. The presence of various HBD and amine functional groups on the graphene oxide (GO) surface yields a synergistic effect for the activation of starting materials. Additionally, this catalyst shows high catalytic activity to synthesize carbonates at 70 °C and at 1 MPa CO2 pressure. The developed AP-GO could be easily recovered and used repetitively in up to seven recycle runs with unchanged catalyst activity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Composites of ionic liquid and amine-modified SAPO 34 improve CO2 separation of CO2-selective polymer membranes

NASA Astrophysics Data System (ADS)

Hu, Leiqing; Cheng, Jun; Li, Yannan; Liu, Jianzhong; Zhang, Li; Zhou, Junhu; Cen, Kefa

2017-07-01

Mixed matrix membranes with ionic liquids and molecular sieve particles had high CO2 permeabilities, but CO2 separation from small gas molecules such as H2 was dissatisfied because of bad interfacial interaction between ionic liquid and molecular sieve particles. To solve that, amine groups were introduced to modify surface of molecular sieve particles before loading with ionic liquid. SAPO 34 was adopted as the original filler, and four mixed matrix membranes with different fillers were prepared on the outer surface of ceramic hollow fibers. Both surface voids and hard agglomerations disappeared, and the surface became smooth after SAPO 34 was modified by amine groups and ionic liquid [P66614][2-Op]. Mixed matrix membranes with composites of amine-modified SAPO 34 and ionic liquid exhibited excellent CO2 permeability (408.9 Barrers) and CO2/H2 selectivity (22.1).

Control of multiwall carbon nanotubes dispersion in polyamide6 matrix: An assessment through electrical conductivity

NASA Astrophysics Data System (ADS)

Kodgire, Pravin V.; Bhattacharyya, Arup R.; Bose, Suryasarathi; Gupta, Nitin; Kulkarni, Ajit R.; Misra, Ashok

2006-12-01

The homogeneous dispersion of carbon nanotubes (CNT) remains a hindrance in exploiting the exceptional properties associated with CNT in polymer/CNT composites. Here we present for the first time the key role of sodium salt of 6-aminohexanoic acid (Na-AHA) in assisting debundling the multiwall carbon nanotubes (MWNT) through specific interactions leading to homogeneous dispersion within polyamide6 (PA6) matrix during melt-mixing. The composite fabricated via this route exhibits low electrical percolation threshold of 0.5 wt% at room temperature, the lowest reported value in this system so far. FTIR and Raman spectroscopy reveal the existence of 'cation-π' interaction between Na-AHA and MWNT. The phenomenon of reactive coupling between amine functionality of Na-AHA and acid end group of PA6 during melt-mixing is also established.

Z-Selective iridium-catalyzed cross-coupling of allylic carbonates and α-diazo esters.

PubMed

Thomas, Bryce N; Moon, Patrick J; Yin, Shengkang; Brown, Alex; Lundgren, Rylan J

2018-01-07

A well-defined Ir-allyl complex catalyzes the Z -selective cross-coupling of allyl carbonates with α-aryl diazo esters. The process overrides the large thermodynamic preference for E -products typically observed in metal-mediated coupling reactions to enable the synthesis of Z , E -dieneoates in good yield with selectivities consistently approaching or greater than 90 : 10. This transformation represents the first productive merger of Ir-carbene and Ir-allyl species, which are commonly encountered intermediates in allylation and cyclopropanation/E-H insertion catalysis. Potentially reactive functional groups (aryl halides, ketones, nitriles, olefins, amines) are tolerated owing to the mildness of reaction conditions. Kinetic analysis of the reaction suggests oxidative addition of the allyl carbonate to an Ir-species is rate-determining. Mechanistic studies uncovered a pathway for catalyst activation mediated by NEt 3 .

Nanostructured bio-functional polymer brushes.

PubMed

Padeste, Celestino; Farquet, Patrick; Potzner, Christian; Solak, Harun H

2006-01-01

Structured poly(glycidyl methracrylate) (poly-GMA) brushes have been grafted onto flexible fluoro-polymer films using a radiation grafting process. The reactive epoxide of poly-GMA provides the basis for a versatile biofunctionalization of the grafted brushes. Structure definition by extreme ultraviolet (EUV) exposure allowed nanometer-scale resolution of periodic patterns. By variation of the exposure dose the height of the grafted structures can be adapted in a wide range. Derivatization of the grafted brushes included reaction with various amines with different side chains, hydrolysis of the epoxide to diols to increase protein resistance and introduction of ionic groups to yield poly-electrolytes. As an example for biofunctionalization, biotin was linked to the grafted brush and biofunctionality was demonstrated in a competitive biotin-streptavidin assay. In this article we also present a brief review of other approaches to obtain structured biofunctional polymer brushes.

Cleaning agents and asthma.

PubMed

Quirce, S; Barranco, P

2010-01-01

Although cleaners represent a significant part of the working population worldwide, they remain a relatively understudied occupational group. Epidemiological studies have shown an association between cleaning work and asthma, but the risk factors are uncertain. Cleaning workers are exposed to a large variety of cleaning products containing both irritants and sensitizers, as well as to common indoor allergens and pollutants. Thus, the onset or aggravation of asthma in this group could be related to an irritant-induced mechanism or to specific sensitization. The main sensitizers contained in cleaning products are disinfectants, quaternary ammonium compounds (such as benzalkonium chloride), amine compounds, and fragrances.The strongest airway irritants in cleaning products are bleach (sodium hypochlorite), hydrochloric acid, and alkaline agents (ammonia and sodium hydroxide), which are commonly mixed together. Exposure to the ingredients of cleaning products may give rise to both new-onset asthma, with or without a latency period, and work-exacerbated asthma. High-level exposure to irritants may induce reactive airways dysfunction syndrome. Cleaning workers may also have a greater relative risk of developing asthma due to prolonged low-to-moderate exposure to respiratory irritants. In addition, asthma-like symptoms without confirmed asthma are also common after exposure to cleaning agents. In many cleaners, airway symptoms induced by chemicals and odors cannot be explained by allergic or asthmatic reactions. These patients may have increased sensitivity to inhaled capsaicin, which is known to reflect sensory reactivity, and this condition is termed airway sensory hyperreactivity.

AMMO-Prot: amine system project 3D-model finder.

PubMed

Navas-Delgado, Ismael; Montañez, Raúl; Pino-Angeles, Almudena; Moya-García, Aurelio A; Urdiales, José Luis; Sánchez-Jiménez, Francisca; Aldana-Montes, José F

2008-04-25

Amines are biogenic amino acid derivatives, which play pleiotropic and very important yet complex roles in animal physiology. For many other relevant biomolecules, biochemical and molecular data are being accumulated, which need to be integrated in order to be effective in the advance of biological knowledge in the field. For this purpose, a multidisciplinary group has started an ontology-based system named the Amine System Project (ASP) for which amine-related information is the validation bench. In this paper, we describe the Ontology-Based Mediator developed in the Amine System Project (http://asp.uma.es) using the infrastructure of Semantic Directories, and how this system has been used to solve a case related to amine metabolism-related protein structures. This infrastructure is used to publish and manage not only ontologies and their relationships, but also metadata relating to the resources committed with the ontologies. The system developed is available at http://asp.uma.es/WebMediator.

A practical and catalyst-free trifluoroethylation reaction of amines using trifluoroacetic acid

NASA Astrophysics Data System (ADS)

Andrews, Keith G.; Faizova, Radmila; Denton, Ross M.

2017-06-01

Amines are a fundamentally important class of biologically active compounds and the ability to manipulate their physicochemical properties through the introduction of fluorine is of paramount importance in medicinal chemistry. Current synthesis methods for the construction of fluorinated amines rely on air and moisture sensitive reagents that require special handling or harsh reductants that limit functionality. Here we report practical, catalyst-free, reductive trifluoroethylation reactions of free amines exhibiting remarkable functional group tolerance. The reactions proceed in conventional glassware without rigorous exclusion of either moisture or oxygen, and use trifluoroacetic acid as a stable and inexpensive fluorine source. The new methods provide access to a wide range of medicinally relevant functionalized tertiary β-fluoroalkylamine cores, either through direct trifluoroethylation of secondary amines or via a three-component coupling of primary amines, aldehydes and trifluoroacetic acid. A reduction of in situ-generated silyl ester species is proposed to account for the reductive selectivity observed.

Platinum-Catalyzed, Terminal-Selective C(sp(3))-H Oxidation of Aliphatic Amines.

PubMed

Lee, Melissa; Sanford, Melanie S

2015-10-14

This Communication describes the terminal-selective, Pt-catalyzed C(sp(3))-H oxidation of aliphatic amines without the requirement for directing groups. CuCl2 is employed as a stoichiometric oxidant, and the reactions proceed in high yield at Pt loadings as low as 1 mol%. These transformations are conducted in the presence of sulfuric acid, which reacts with the amine substrates in situ to form ammonium salts. We propose that protonation of the amine serves at least three important roles: (i) it renders the substrates soluble in the aqueous reaction medium; (ii) it limits binding of the amine nitrogen to Pt or Cu; and (iii) it electronically deactivates the C-H bonds proximal to the nitrogen center. We demonstrate that this strategy is effective for the terminal-selective C(sp(3))-H oxidation of a variety of primary, secondary, and tertiary amines.

Platinum-Catalyzed Terminal-Selective C(sp3)–H Oxidation of Aliphatic Amines

PubMed Central

Lee, Melissa; Sanford, Melanie S.

2016-01-01

This paper describes the terminal-selective Pt-catalyzed C(sp3)–H oxidation of aliphatic amines without the requirement for directing groups. CuCl2 is employed as a stoichiometric oxidant, and the reactions proceed in high yield at Pt loadings as low as 1 mol %. These transformations are conducted in the presence of sulfuric acid, which reacts with the amine substrates in situ to form ammonium salts. We propose that protonation of the amine serves at least three important roles: (i) it renders the substrates soluble in the aqueous reaction medium; (ii) it limits binding of the amine nitrogen to Pt or Cu; and (ii) it electronically deactivates the C–H bonds proximal to the nitrogen center. We demonstrate that this strategy is effective for the terminal-selective C(sp3)–H oxidation of a variety of primary, secondary and tertiary amines. PMID:26439251

Strong, low-density nanocomposites by chemical vapor deposition and polymerization of cyanoacrylates on aminated silica aerogels.

PubMed

Boday, Dylan J; Stover, Robert J; Muriithi, Beatrice; Keller, Michael W; Wertz, Jason T; Defriend Obrey, Kimberly A; Loy, Douglas A

2009-07-01

Strong polymer-silica aerogel composites were prepared by chemical vapor deposition of cyanoacrylate monomers onto amine-modified aerogels. Amine-modified silica aerogels were prepared by copolymerizing small amounts of (aminopropyl)triethoxysilane with tetraethoxysilane. After silation of the aminated gels with hexamethyldisilazane, they were dried as aerogels using supercritical carbon dioxide processing. The resulting aerogels had only the amine groups as initiators for the cyanoacrylate polymerizations, resulting in cyanoacrylate macromolecules that were higher in molecular weight than those observed with unmodified silica and that were covalently attached to the silica surface. Starting with aminated silica aerogels that were 0.075 g/cm(3) density, composite aerogels were made with densities up to 0.220 g/cm(3) and up to 31 times stronger (flexural strength) than the precursor aerogel and about 2.3 times stronger than an unmodified silica aerogel of the same density.

Observations of alkylamines at a costal site in the East Mediterranean

NASA Astrophysics Data System (ADS)

Tzitzikalaki, Evaggelia; Kieloaho, Antti-Jussi; Hellén, Heidi; Hakola, Hannele; Kalivitis, Nikolaos; Kouvarakis, Giorgos; Kerminen, Veli-Matti; Mihalopoulos, Nikolaos; Kanakidou, Maria

2016-04-01

Amines are reactive volatile base in the atmosphere and play a key role in new particle formation. Due to their height reactivity, concentration measurements are scare and mostly concentrated within short period of time. The present study provided the first long- term measurements of alkylamines in the Eastern Mediterranean. Measurements took place at a remote coastal site on the north east side of the island of Crete at the Finokalia monitoring station of the University of Crete (finokalia.chemistry.uoc.gr; 35°20΄N, 25°40΄E, 250m a.s.l.) from January 2013 to December 2015. The samples were collected in glass fiber filters impregnated with phosphoric acid that trap gas-phase amines as salt. Samples were subsequently transported to the lab where they were stored in refrigeration until the analysis that took place in a Liquid Chromatography Triple Quadrupole Mass Spectrometer (TSQ Quantum, Thermo Finnigan). The alkylamines that were detected were ethylamine (EA), dimethylamine (DMA), trimethylamine (TMA), propylamine (PA), diethylamine (DEA) and triethylamine (TEA). DMA & EA and TMA & PA were handled as pairs as they couldn't be separated. The most abundant amines were found to be DMA & EA, whereas BA and TMA were under the detection limits. The highest concentrations for DMA & EA and DEA were observed during summer, while for TMA & PA no clear annual cycle was found. The results are analyzed together with observations of new particle formation at the Finokalia station to estimate possible links of alkylamines to the formation of atmospheric particles in the area. This work has been partially supported by the European FP7 collaborative project BACCHUS (Impact of Biogenic versus Anthropogenic emissions on Clouds and Climate: towards a Holistic UnderStanding).

Coupling in the absence of tertiary amines.

PubMed

Bodanszky, M; Bednarek, M A; Bodanszky, A

1982-10-01

In order to avoid base catalyzed side reactions during coupling, attempts were made to render superfluous the addition of tertiary amines to the reaction mixture. Weak acids were applied for the removal of acid labile protecting groups. Acetic acid and other carboxylic acids were considered unsuitable for this purpose coupling step. Pentachlorophenol and 2,4-dinitrophenol cleaved the Bpoc, Nps and Trt groups but more practical rates were reached with solutions of 1-hydroxybenzotriazole (HOBt) in trifluoroethanol, in acetic acid, or in a mixture of phenol and p-cresol. In addition to acidolysis, HOBt salts of amino components could also be obtained through hydrogenolysis of the Z group or thiolysis of the Nps group in the presence of HOBt, or by the displacement of acetic acid from acetate salts with HOBt. Acylation of HOBt salts of amino components with symmetrical or mixed anhydrides or with active esters did not require the addition of tertiary amine.

Durability of MWCNT Composites under Electron and Neutron Irradiation

DTIC Science & Technology

2012-03-22

atoms to form a hexagonal network. The covalent bond or σ-bond is a strong chemical bond and plays a vital role in the mechanical properties of...amine molecule. The “resin” or “ compound “ consist of monomers or short chain polymers with an epoxy group at either end. The “hardener or “activator...consists of polyamine monomers. When these two compounds are mixed together, the amine groups react with an epoxy group. The resulting polymer

Effect of metal ions on the reactions of the cumyloxyl radical with hydrogen atom donors. Fine control on hydrogen abstraction reactivity determined by Lewis acid-base interactions.

PubMed

Salamone, Michela; Mangiacapra, Livia; DiLabio, Gino A; Bietti, Massimo

2013-01-09

A time-resolved kinetic study on the effect of metal ions (M(n+)) on hydrogen abstraction reactions from C-H donor substrates by the cumyloxyl radical (CumO(•)) was carried out in acetonitrile. Metal salt addition was observed to increase the CumO(•) β-scission rate constant in the order Li(+) > Mg(2+) > Na(+). These effects were explained in terms of the stabilization of the β-scission transition state determined by Lewis acid-base interactions between M(n+) and the radical. When hydrogen abstraction from 1,4-cyclohexadiene was studied in the presence of LiClO(4) and Mg(ClO(4))(2), a slight increase in rate constant (k(H)) was observed indicating that interaction between M(n+) and CumO(•) can also influence, although to a limited extent, the hydrogen abstraction reactivity of alkoxyl radicals. With Lewis basic C-H donors such as THF and tertiary amines, a decrease in k(H) with increasing Lewis acidity of M(n+) was observed (k(H)(MeCN) > k(H)(Li(+)) > k(H)(Mg(2+))). This behavior was explained in terms of the stronger Lewis acid-base interaction of M(n+) with the substrate as compared to the radical. This interaction reduces the degree of overlap between the α-C-H σ* orbital and a heteroatom lone-pair, increasing the C-H BDE and destabilizing the carbon centered radical formed after abstraction. With tertiary amines, a >2-order of magnitude decrease in k(H) was measured after Mg(ClO(4))(2) addition up to a 1.5:1 amine/Mg(ClO(4))(2) ratio. At higher amine concentrations, very similar k(H) values were measured with and without Mg(ClO(4))(2). These results clearly show that with strong Lewis basic substrates variations in the nature and concentration of M(n+) can dramatically influence k(H), allowing for a fine control of the substrate hydrogen atom donor ability, thus providing a convenient method for C-H deactivation. The implications and generality of these findings are discussed.

Highly specific enrichment of N-glycoproteome through a nonreductive amination reaction using Fe3O4@SiO2-aniline nanoparticles.

PubMed

Zhang, Ying; Yu, Meng; Zhang, Cheng; Wang, Yali; Di, Yi; Wang, Changchun; Lu, Haojie

2015-04-07

A novel method based on the conjunction of aldehydes from oxidized glycopeptides to aniline groups on magnetic nanoparticles via nonreductive amination is reported for the highly selective enrichment of N-glycopeptides. For the first time, a nonreductive amination reaction has been introduced into N-glycoproteome extraction, and correspondingly a new type of aniline-functionalized nanoparticle has been designed and synthesized.

Comparative study of polyethylene polyamines as activator molecules for a structurally unstable group I ribozyme.

PubMed

Gulshan, Mst Ara; Matsumura, Shigeyoshi; Higuchi, Tsunehiko; Umezawa, Naoki; Ikawa, Yoshiya

2018-04-26

Polyamines are a promising class of molecules that can modulate RNA enzyme activities. To analyze the effects of the number of amine moieties systematically, we employed four polyamines sharing dimethylene units to connect amine moieties. As a model RNA enzyme, we used a structurally unstable group I ribozyme, which was activated most and least efficiently by tetraethylenepentamine and diethylenetriamine respectively.

Occupational contact dermatitis caused by 1,3-benzenedimethanamine, N-(2-phenylethyl) derivatives in hardeners for epoxy paints and coatings.

PubMed

Pesonen, Maria; Kuuliala, Outi; Suomela, Sari; Aalto-Korte, Kristiina

2016-12-01

Amines in epoxy hardeners are significant causes of occupational allergic contact dermatitis among workers who use epoxy resin systems. To describe a novel group of contact allergens: N-(2-phenylethyl) derivatives of the reactive amine 1,3-benzenedimethanamine (1,3-BDMA). We describe the clinical examinations and exposure of 6 patients with occupational contact allergy to derivatives of 1,3-BDMA. Of the 6 patients, 4 were spray painters who used epoxy paints, 1 was a floor layer who handled a variety of epoxy coatings, and 1 was a worker in epoxy hardener manufacture. We were able to confirm exposure to epoxy hardeners that contained derivatives of 1,3-BDMA in 5 of the 6 sensitized patients. Despite the close structural resemblance between derivatives of 1,3-BDMA and m-xylylenediamine (MXDA), only 3 patients reacted positively to MXDA. Concomitant contact allergy to diglycidyl ether of bisphenol A resin was seen in 2 of the 6 patients. Because of the lack of a commercially available patch test substance, the diagnosis of contact allergy to derivatives of 1,3-BDMA requires patch testing with either the epoxy hardener product or a hardener ingredient that contains the derivatives of 1,3-BDMA. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Silylative Reductive Amination of α,β-Unsaturated Aldehydes: A Convenient Synthetic Route to β-Silylated Secondary Amines.

PubMed

Kim, Eunae; Park, Sehoon; Chang, Sukbok

2018-04-17

Described here is a reductive amination/hydrosilylation cascade of α,β-unsaturated aldehydes mediated by a Lewis acidic borane catalyst. The present reaction system provides an one-pot synthetic route towards β-silylated secondary amines that have not been accessible by other previous catalysis. Comparative 1 H NMR studies on the silylative reduction of enimines revealed that steric bulkiness of primary amine reactants strongly affects both catalytic efficiency and regioselectivity. This strategy was applicable to a broad range of substrates and amenable to one-pot gram-scale synthesis. Moreover, a diastereoselective introduction of the β-silyl group was also found to be feasible (d.r. up to 71:29). © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Proline Editing: A General and Practical Approach to the Synthesis of Functionally and Structurally Diverse Peptides. Analysis of Steric versus Stereoelectronic Effects of 4-Substituted Prolines on Conformation within Peptides

PubMed Central

Pandey, Anil K.; Naduthambi, Devan; Thomas, Krista M.; Zondlo, Neal J.

2013-01-01

Functionalized proline residues have diverse applications. Herein we describe a practical approach, proline editing, for the synthesis of peptides with stereospecifically modified proline residues. Peptides are synthesized by standard solid-phase-peptide-synthesis to incorporate Fmoc-Hydroxyproline (4R-Hyp). In an automated manner, the Hyp hydroxyl is protected and the remainder of the peptide synthesized. After peptide synthesis, the Hyp protecting group is orthogonally removed and Hyp selectively modified to generate substituted proline amino acids, with the peptide main chain functioning to “protect” the proline amino and carboxyl groups. In a model tetrapeptide (Ac-TYPN-NH2), 4R-Hyp was stereospecifically converted to 122 different 4-substituted prolyl amino acids, with 4R or 4S stereochemistry, via Mitsunobu, oxidation, reduction, acylation, and substitution reactions. 4-Substituted prolines synthesized via proline editing include incorporated structured amino acid mimetics (Cys, Asp/Glu, Phe, Lys, Arg, pSer/pThr), recognition motifs (biotin, RGD), electron-withdrawing groups to induce stereoelectronic effects (fluoro, nitrobenzoate), handles for heteronuclear NMR (19F:fluoro; pentafluorophenyl or perfluoro-tert-butyl ether; 4,4-difluoro; 77SePh) and other spectroscopies (fluorescence, IR: cyanophenyl ether), leaving groups (sulfonate, halide, NHS, bromoacetate), and other reactive handles (amine, thiol, thioester, ketone, hydroxylamine, maleimide, acrylate, azide, alkene, alkyne, aryl halide, tetrazine, 1,2-aminothiol). Proline editing provides access to these proline derivatives with no solution phase synthesis. All peptides were analyzed by NMR to identify stereoelectronic and steric effects on conformation. Proline derivatives were synthesized to permit bioorthogonal conjugation reactions, including azide-alkyne, tetrazinetrans-cyclooctene, oxime, reductive amination, native chemical ligation, Suzuki, Sonogashira, cross-metathesis, and Diels-Alder reactions. These proline derivatives allowed three parallel bioorthogonal reactions to be conducted in one solution. PMID:23402492

Amine-Functionalized Sugarcane Bagasse: A Renewable Catalyst for Efficient Continuous Flow Knoevenagel Condensation Reaction at Room Temperature.

PubMed

Qiao, Yanhui; Teng, Junjiang; Wang, Shuangfei; Ma, Hao

2017-12-24

A biomass-based catalyst with amine groups (-NH₂), viz., amine-functionalized sugarcane bagasse (SCB-NH₂), was prepared through the amination of sugarcane bagasse (SCB) in a two-step process. The physicochemical properties of the catalyst were characterized through FT-IR, elemental analysis, XRD, TG, and SEM-EDX techniques, which confirmed the -NH₂ group was grafted onto SCB successfully. The catalytic performance of SCB-NH₂ in Knoevenagel condensation reaction was tested in the batch and continuous flow reactions. Significantly, it was found that the catalytic performance of SCB-NH₂ is better in flow system than that in batch system. Moreover, the SCB-NH₂ presented an excellent catalytic activity and stability at the high flow rate. When the flow rate is at the 1.5 mL/min, no obvious deactivation was observed and the product yield and selectivity are more than 97% and 99% after 80 h of continuous reaction time, respectively. After the recovery of solvent from the resulting solution, a white solid was obtained as a target product. As a result, the SCB-NH₂ is a promising catalyst for the synthesis of fine chemicals by Knoevenagel condensation reaction in large scale, and the modification of the renewable SCB with -NH₂ group is a potential avenue for the preparation of amine-functionalized catalytic materials in industry.

Oxidation of suspected N-nitrosodimethylamine (NDMA) precursors by ferrate (VI): kinetics and effect on the NDMA formation potential of natural waters.

PubMed

Lee, Changha; Lee, Yunho; Schmidt, Carsten; Yoon, Jeyong; Von Gunten, Urs

2008-01-01

The potential of ferrate (Fe(VI)) oxidation to remove N-nitrosodimethylamine (NDMA) precursors during water treatment was assessed. Apparent second-order rate constants (k(app)) for the reactions of NDMA and its suspected precursors (dimethylamine (DMA) and 7 tertiary amines with DMA functional group) with Fe(VI) were determined in the range of pH 6-12. Four model NDMA precursors (dimethyldithiocarbamate, dimethylaminobenzene, 3-(dimethylaminomethyl)indole and 4-dimethylaminoantipyrine) showed high reactivity toward Fe(VI) with k(app) values at pH 7 between 2.6 x 10(2) and 3.2 x 10(5)M(-1)s(-1). The other NDMA precursors (DMA, trimethylamine, dimethylethanolamine, dimethylformamide) and NDMA had k(app) values ranging from 0.55 to 9.1M(-1)s(-1) at pH 7. In the second part of the study, the NDMA formation potentials (NDMA-FP) of the model NDMA precursors and natural waters were measured with and without pre-oxidation by Fe(VI). For most of the NDMA precursors with the exception of DMA, a significant reduction of the NDMA-FP (>95%) was observed after complete transformation of the NDMA precursor. This result was supported by low yields of DMA from the Fe(VI) oxidation of tertiary amine NDMA precursors. Pre-oxidation of several natural waters (rivers Rhine, Neckar and Pfinz) with a high dose of Fe(VI) (0.38 mM = 21 mg L(-1) as Fe) led to removals of the NDMA-FP of 46-84%. This indicates that the NDMA precursors in these waters have a low reactivity toward Fe(VI) because it has been shown that for fast-reacting NDMA precursors Fe(VI) doses of 20 microM (1.1 mg L(-1) as Fe) are sufficient to completely oxidize the precursors.

Functionalized boron nitride nanotubes

DOEpatents

Sainsbury, Toby; Ikuno, Takashi; Zettl, Alexander K

2014-04-22

A plasma treatment has been used to modify the surface of BNNTs. In one example, the surface of the BNNT has been modified using ammonia plasma to include amine functional groups. Amine functionalization allows BNNTs to be soluble in chloroform, which had not been possible previously. Further functionalization of amine-functionalized BNNTs with thiol-terminated organic molecules has also been demonstrated. Gold nanoparticles have been self-assembled at the surface of both amine- and thiol-functionalized boron nitride Nanotubes (BNNTs) in solution. This approach constitutes a basis for the preparation of highly functionalized BNNTs and for their utilization as nanoscale templates for assembly and integration with other nanoscale materials.

Sorption of uranyl ions from various acido systems by amphoteric epoxy amine ion-exchange resins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rychkov, V.N.; Radionov, B.K.; Molochnikov, L.S.

1995-03-01

Sorption of uranyl ions by epoxy amine ampholytes with N-monomethylenephosphonic acid groups modified with pyridine or quaternary ammonium groups was studied under dynamic conditions. Heterocyclic nitrogen favors sorption of uranyl ion from fluoride, sulfate, and fluoride-sulfate solutions. The ESR studies of mono- and bimetallic forms of nitrogen-containing ampholytes with copper(II) as paramagnetic marker revealed the characteristics of uranium(VI) interaction with cation- and anion-exchange groups and its dependence on the fluoride content in solution.

Growth of large zeolite crystals in space

NASA Technical Reports Server (NTRS)

Sacco, A., Jr.; Dixon, A.; Thompson, R.; Scott, G.; Ditr, J.

1988-01-01

Synthesis studies performed using close analogs of triethanolamine (TEA) have shown that all three hydroxyl groups and the amine group in this molecule are necessary to provide nucleation suppression. Studies using C-13 nuclear magnetic resonance (NMR) revealed that the hydroxyl ions and the amine group are involved in the formation of an aluminum complex. It was also shown that silicate species fo not interact this way with TEA in an alkaline solution. These results suggest that successful aluminum complexation leads to nucleation in zeolite-A crystallization.

Nanoparticle strategies for cancer therapeutics: Nucleic acids, polyamines, bovine serum amine oxidase and iron oxide nanoparticles (Review).

PubMed

Agostinelli, Enzo; Vianello, Fabio; Magliulo, Giuseppe; Thomas, Thresia; Thomas, T J

2015-01-01

Nanotechnology for cancer gene therapy is an emerging field. Nucleic acids, polyamine analogues and cytotoxic products of polyamine oxidation, generated in situ by an enzyme-catalyzed reaction, can be developed for nanotechnology-based cancer therapeutics with reduced systemic toxicity and improved therapeutic efficacy. Nucleic acid-based gene therapy approaches depend on the compaction of DNA/RNA to nanoparticles and polyamine analogues are excellent agents for the condensation of nucleic acids to nanoparticles. Polyamines and amine oxidases are found in higher levels in tumours compared to that of normal tissues. Therefore, the metabolism of polyamines spermidine and spermine, and their diamine precursor, putrescine, can be targets for antineoplastic therapy since these naturally occurring alkylamines are essential for normal mammalian cell growth. Intracellular polyamine concentrations are maintained at a cell type-specific set point through the coordinated and highly regulated interplay between biosynthesis, transport, and catabolism. In particular, polyamine catabolism involves copper-containing amine oxidases. Several studies showed an important role of these enzymes in developmental and disease-related processes in animals through the control of polyamine homeostasis in response to normal cellular signals, drug treatment, and environmental and/or cellular stress. The production of toxic aldehydes and reactive oxygen species (ROS), H2O2 in particular, by these oxidases suggests a mechanism by which amine oxidases can be exploited as antineoplastic drug targets. The combination of bovine serum amine oxidase (BSAO) and polyamines prevents tumour growth, particularly well if the enzyme has been conjugated with a biocompatible hydrogel polymer. The findings described herein suggest that enzymatically formed cytotoxic agents activate stress signal transduction pathways, leading to apoptotic cell death. Consequently, superparamagnetic nanoparticles or other advanced nanosystem based on directed nucleic acid assemblies, polyamine-induced DNA condensation, and bovine serum amine oxidase may be proposed for futuristic anticancer therapy utilizing nucleic acids, polyamines and BSAO. BSAO based nanoparticles can be employed for the generation of cytotoxic polyamine metabolites.

Determination of NH2 concentration on 3-aminopropyl tri-ethoxy silane layers and cyclopropylamine plasma polymers by liquid-phase derivatization with 5-iodo 2-furaldehyde

NASA Astrophysics Data System (ADS)

Manakhov, Anton; Čechal, Jan; Michlíček, Miroslav; Shtansky, Dmitry V.

2017-08-01

The quantification of concentration of primary amines, e.g. in plasma polymerized layers is a very important task for surface analysis. However, the commonly used procedure, such as gas phase derivatization with benzaldehydes, shows several drawbacks, the most important of which are the side reaction effects. In the present study we propose and validate a liquid phase derivatization using 5-iodo 2-furaldehyde (IFA). It was demonstrated that the content of NH2 groups can be determined from the atomic concentrations measured by X-ray photoelectron spectroscopy (XPS), in particular from the ratio of I 3d and N 1s peak intensities. First, we demonstrate the method on a prototypical system such as 3-aminopropyl tri-ethoxy silane (APTES) layer. Here the XPS analysis carried out after reaction of APTES layer with IFA gives the fraction of primary amines (NH2/N) of 38.3 ± 7.9%. Comparing this value with that obtained by N 1s curve fitting of APTES layer giving 40.9 ± 9.5% of amine groups, it can be concluded that all primary amines were derivatized by reaction with IFA. The second system to demonstrate the method comprises cyclopropylamine (CPA) plasma polymers that were free from conjugated imines. In this case the method gives the NH2 fraction ∼8.5%. This value is closely matching the NH2/N ratio estimated by 4-trifluoromethyl benzaldehyde (TFBA) derivatization. The reaction of IFA with CPA plasma polymer exhibiting high density of conjugated imines revealed the NH2/N fraction of ∼10.8%. This value was significantly lower compared to 17.3% estimated by TFBA derivatization. As the overestimated density of primary amines measured by TFBA derivatization is probably related to the side reaction of benzaldehydes with conjugated imines, the proposed IFA derivatization of primary amines can be an alternative procedure for the quantification of surface amine groups.

Practical Synthesis of Amides via Copper/ABNO-Catalyzed Aerobic Oxidative Coupling of Alcohols and Amines.

PubMed

Zultanski, Susan L; Zhao, Jingyi; Stahl, Shannon S

2016-05-25

A modular Cu/ABNO catalyst system has been identified that enables efficient aerobic oxidative coupling of alcohols and amines to amides. All four permutations of benzylic/aliphatic alcohols and primary/secondary amines are viable in this reaction, enabling broad access to secondary and tertiary amides. The reactions exhibit excellent functional group compatibility and are complete within 30 min-3 h at rt. All components of the catalyst system are commercially available.

Synthesis of quantum dots

DOEpatents

McDaniel, Hunter

2017-10-17

Common approaches to synthesizing alloyed quantum dots employ high-cost, air-sensitive phosphine complexes as the selenium precursor. Disclosed quantum dot synthesis embodiments avoid these hazardous and air-sensitive selenium precursors. Certain embodiments utilize a combination comprising a thiol and an amine that together reduce and complex the elemental selenium to form a highly reactive selenium precursor at room temperature. The same combination of thiol and amine acts as the reaction solvent, stabilizing ligand, and sulfur source in the synthesis of quantum dot cores. A non-injection approach may also be used. The optical properties of the quantum dots synthesized by this new approach can be finely tuned for a variety of applications by controlling size and/or composition of size and composition. Further, using the same approach, a shell can be grown around a quantum dot core that improves stability, luminescence efficiency, and may reduce toxicity.

Triazolylidene-Iridium Complexes with a Pendant Pyridyl Group for Cooperative Metal-Ligand Induced Catalytic Dehydrogenation of Amines.

PubMed

Valencia, Marta; Pereira, Ana; Müller-Bunz, Helge; Belderraín, Tomás R; Pérez, Pedro J; Albrecht, Martin

2017-07-03

Two iridium(III) complexes containing a C,N-bidentate pyridyl-triazolylidene ligand were prepared that are structurally very similar but differ in their pendant substituent. Whereas complex 1 contains a non-coordinating pyridyl unit, complex 2 has a phenyl group on the triazolylidene substituent. The presence of the basic pyridyl unit has distinct effects on the catalytic activity of the complex in the oxidative dehydrogenation of benzylic amines, inducing generally higher rates, higher selectivity towards formation of imines versus secondary amines, and notable quantities of tertiary amines when compared to the phenyl-functionalized analogue. The role of the pyridyl functionality has been elucidated from a set of stoichiometric experiments, which demonstrate hydrogen bonding between the pendant pyridyl unit and the amine protons of the substrate. Such N pyr ⋅⋅⋅H-N interactions are demonstrated by X-ray diffraction analysis, 1 H NMR, and IR spectroscopy, and suggest a pathway of substrate bond-activation that involves concerted substrate binding through the Lewis acidic iridium center and the Lewis basic pyridyl site appended to the triazolylidene ligand, in agreement with ligand-metal cooperative substrate activation. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation of amine functionalized carbon nanotubes via a bioinspired strategy and their application in Cu2+ removal

NASA Astrophysics Data System (ADS)

Zhang, Xiaoyong; Huang, Qiang; Liu, Meiying; Tian, Jianwen; Zeng, Guangjian; Li, Zhen; Wang, Ke; Zhang, Qinsong; Wan, Qing; Deng, Fengjie; Wei, Yen

2015-07-01

The environmental applications of carbon nanotubes (CNTs) have attracted great research attention since their first discovery. However, the performance of pristine CNTs for removal of heavy metal ions is greatly limited by their severe aggregation and lack of functional groups. In this work, a novel method has been developed for preparation of amine functionalized CNTs via combination of mussel inspired chemistry and Michael addition reaction. CNTs were first coated with polydopamine (PDA) through mussel inspired chemistry. And then commercial available agent polyethylene polyamine with a number of amine groups was further conjugated with PDA coated CNTs via Michael addition reaction. A series of characterization techniques have demonstrated that the amine functionalized CNTs have been successfully prepared. Furthermore, the adsorption application of thus amine functionalized CNTs for Cu2+ was examined. The effects of various parameters including pH solution, temperature, initial Cu2+ concentration and the adsorbent concentration were investigated. The data from experiments were analyzed by the Langmuir and Freundlich models of adsorption. Due to the universal of mussel inspired chemistry, the method described in this work should be a general strategy for surface modification of materials for environmental applications.

A Visible Light Initiating System for Free Radical Promoted Cationic Polymerization

DTIC Science & Technology

1994-02-02

identify the end groups in the polymer of cyclohexene oxide. N,N-Dimethylnaphthyl amine (DNA), a compound with high fluorescence quantum yield, was used...candidates to be polymerized via a cationic mechanism include cyclic ethers, cyclic formals and acetals, vinyl ethers, and epoxy compounds . Of these...reported sensitizer, bears two dimethylamino groups, is direct evidence that an aromatic amine can be present in a cationically photopolymerizable system

Study of Reactive Materials for Development of new Protective Clothing Concepts

DTIC Science & Technology

1977-10-01

G, and V agents and must not unduly change the fabric permeability. Microencapsulation , the technique of encasing extremely small droplets or...preparing and evaluating decontaminating microcapsules that contain strong-base alkali- metal hydroxides, s-Im-bis(N,chloro-2,4,6-trichlorophenyl) urea...and various amines as the core phase. We are now identifying and developing microcapsule wall materials that will be stable to the highly basic core

Polymer Claw: Instant Underwater Adhesive

DTIC Science & Technology

2012-08-27

technology is the use of pressure sensitive microcapsules , which release reactive amine crosslinkers into an adhesive putty when pressed against the surface...CLEANING AGENT RHEOLOGY 3 3.3 PRESSURE-ACTIVATED ADHESIVE 5 3.3.1 PROCESSING IMPROVEMENTS 5 3.3.2 MICROCAPSULE DIAMETER 5 3.3.3 MICROCAPSULE /RESIN...to attain a reasonable shelf life (- l wk.). The microcapsule diameter has been halved in order to improve mixing in the pressure-activated

Active chemisorption sites in functionalized ionic liquids for carbon capture.

PubMed

Cui, Guokai; Wang, Jianji; Zhang, Suojiang

2016-07-25

Development of novel technologies for the efficient and reversible capture of CO2 is highly desired. In the last decade, CO2 capture using ionic liquids has attracted intensive attention from both academia and industry, and has been recognized as a very promising technology. Recently, a new approach has been developed for highly efficient capture of CO2 by site-containing ionic liquids through chemical interaction. This perspective review focuses on the recent advances in the chemical absorption of CO2 using site-containing ionic liquids, such as amino-based ionic liquids, azolate ionic liquids, phenolate ionic liquids, dual-functionalized ionic liquids, pyridine-containing ionic liquids and so on. Other site-containing liquid absorbents such as amine-based solutions, switchable solvents, and functionalized ionic liquid-amine blends are also investigated. Strategies have been discussed for how to activate the existent reactive sites and develop novel reactive sites by physical and chemical methods to enhance CO2 absorption capacity and reduce absorption enthalpy. The carbon capture mechanisms of these site-containing liquid absorbents are also presented. Particular attention has been paid to the latest progress in CO2 capture in multiple-site interactions by amino-free anion-functionalized ionic liquids. In the last section, future directions and prospects for carbon capture by site-containing ionic liquids are outlined.

Bond formations by intermolecular and intramolecular trappings of acylketenes and their applications in natural product synthesis†

PubMed Central

Reber, Keith P.; Tilley, S. David

2011-01-01

The reactive intermediates known as acylketenes exhibit a rich chemistry and have been extensively utilized for many types of inter- and intramolecular bond-forming reactions within the field of organic synthesis. Characteristic reactions of acylketenes include cycloadditions, carbon–carbon bond-forming reactions, and nucleophilic capture with alcohols or amines to give β-keto acid derivatives. In particular, the intramolecular capture of acylketene intermediates with pendant nucleophiles represents a powerful method for forming both medium-sized rings and macrocycles, often in high yield. This tutorial review examines the history, generation, and reactivity of acylketenes with a special focus on their applications in the synthesis of natural products. PMID:19847338

Dissociative adsorption of a multifunctional compound on a semiconductor surface: a theoretical study of the adsorption of hydroxylamine on Ge(100).

PubMed

Park, Hyunkyung; Kim, Do Hwan

2018-06-06

The adsorption behavior of hydroxylamine on a Ge(100) surface was investigated using density functional theory (DFT) calculations. These calculations predicted that hydroxylamine, a multifunctional compound consisting of a hydroxyl group and an amine group, would initially become adsorbed through N-dative bonding, or alternatively through the hydroxyl group via O-H dissociative adsorption. An N-O dissociative reaction may also occur, mainly via N-dative molecular adsorption, and the N-O dissociative product was calculated to be the most stable of all the possible adsorption structures. The calculations furthermore indicated the formation of the N-O dissociative product from the N-dative structure to be nearly barrierless and the dissociated hydroxyl and amine groups to be bonded to two Ge atoms of adjacent Ge dimers. Simulated STM images suggested the change in electron density that would occur upon adsorption of hydroxylamine in various adsorption configurations, and specifically indicated the N-O dissociative product to have greater electron density around the amine groups, and the hydroxyl groups to mainly contribute electron density to the unoccupied electronic states.

CO2-induced degradation of amine-containing adsorbents: reaction products and pathways.

PubMed

Sayari, Abdelhamid; Heydari-Gorji, Aliakbar; Yang, Yong

2012-08-22

A comprehensive study was conducted to investigate the stability of a wide variety of mesoporous silica-supported amine-containing adsorbents in the presence of carbon dioxide under dry conditions. CO(2)-induced degradation of grafted primary and secondary monoamines (pMono, sMono), diamines with one primary and one secondary amines (Diamine) and triamine with one primary and two secondary amines (TRI) as well as different impregnated polyamines such as branched and linear polyethylenimine (BPEI and LPEI) and polyallylamine (PALL) was investigated using extensive CO(2) adsorption-desorption cycling as well as diffuse reflectance infrared Fourier transform (DRIFT) and (13)C CP MAS NMR measurements. Except for sMono, all other supported amines underwent significant deactivation in the presence of dry CO(2) under mild conditions. In all cases, the decrease in CO(2) uptake was associated with the formation of urea linkages at the expense of amine groups. The urea-containing species were identified, and the deactivation pathways were delineated.

The Synthesis of Methyl Salicylate: Amine Diazotization.

ERIC Educational Resources Information Center

Zanger, Murray; McKee, James R.

1988-01-01

Notes that this experiment takes safety and noncarcinogenic reactants into account. Demonstrates the use of diazonium salts for the replacement of an aromatic amine group by a phenolic hydroxyl. Involves two pleasant-smelling organic compounds, methyl anthranilate (grape) and methyl salicylate (oil of wintergreen). (MVL)

Surface functionalization of microwave plasma-synthesized silica nanoparticles for enhancing the stability of dispersions

NASA Astrophysics Data System (ADS)

Sehlleier, Yee Hwa; Abdali, Ali; Schnurre, Sophie Marie; Wiggers, Hartmut; Schulz, Christof

2014-08-01

Gas phase-synthesized silica nanoparticles were functionalized with three different silane coupling agents (SCAs) including amine, amine/phosphonate and octyltriethoxy functional groups and the stability of dispersions in polar and non-polar dispersing media such as water, ethanol, methanol, chloroform, benzene, and toluene was studied. Fourier transform infrared spectroscopy showed that all three SCAs are chemically attached to the surface of silica nanoparticles. Amine-functionalized particles using steric dispersion stabilization alone showed limited stability. Thus, an additional SCA with sufficiently long hydrocarbon chains and strong positively charged phosphonate groups was introduced in order to achieve electrosteric stabilization. Steric stabilization was successful with hydrophobic octyltriethoxy-functionalized silica nanoparticles in non-polar solvents. The results from dynamic light scattering measurements showed that in dispersions of amine/phosphonate- and octyltriethoxy-functionalized silica particles are dispersed on a primary particle level. Stable dispersions were successfully prepared from initially agglomerated nanoparticles synthesized in a microwave plasma reactor by designing the surface functionalization.

Spectroscopic Evidence for Covalent Binding of Sulfadiazine to Natural Soils via 1,4-nucleophilic addition (Michael Type Addition) studied by Spin Labeling ESR

NASA Astrophysics Data System (ADS)

Aleksandrova, Olga

2015-04-01

Among different classes of veterinary pharmaceuticals, Sulfadiazine (SDZ) is widely used in animal husbandry. Its residues were detected in different environmental compartments. However, soil is a hot spot for SDZ as it receives a large portion of excreted compounds through the application of manure during soil fertilization. Ample studies on the fate of SDZ in soils showed that a large portion forms nonextractable residues (NER) along with transformation products and a low mineralization (Mueller et al., 2013). A common observation was an initially fast formation of NER up to 10% of the applied amount promptly after the application of SDZ to soil, and this portion increased up to 50% within a few days (Mueller et al., 2013; Nowak et al., 2011). A common finding for SDZ, as for other sulfonamides, was biphasic kinetics of the formation of NER, which was attributed to the occurrence of two reaction processes: a rapid, often reversible process and a slower, irreversible process (Weber et al., 1996). A single-phase reaction process was also established under anaerobic treatment (Gulkowska et al., 2014). A major focus of this work is to elucidate a reaction mechanism of covalent binding of SDZ to soil that is currently required to estimate a risk of NER formed by SDZ in soils for human health. Taking into account a key role of the amine functional groups of SDZ on its reactivity in soil, nitroxide radicals with the sewed aromatic or aliphatic amines labeled soil samples and then, were investigated by means of ESR spectroscopy. 2,5,5-Trimethyl-2-(3-aminophenyl)pyrrolidin-1-yloxy and 4-amino-2,2,6,6-Tetramethylpiperidin-1-oxyl modeled decomposition products of SDZ with the aromatic and aliphatic amines, respectively. The application of the defined combination of both spin labels (SL) to different soils well simulated a change of a paramagnetic signal of soil organic radicals interacted with SDZ. After their application to soil, SL were found in soil sites characterized with different polarity. As shown by the spin labeling ESR experiment, molecules modeling SDZ were promptly bound to non-hydrolysable network of soil organic matter only via the aromatic amines that was accompanied by a prompt enlargement of humic particles binding aromatic amines, whereas binding of decomposition products of SDZ to humic acids of soil via the aliphatic amines was not observable. The ESR spectra obviously showed a single-phase process of covalent binding of the aromatic amines. Repeated washouts of labeled soil samples using distil water and ultrafiltration through the membrane of 5000 MWCO PES confirmed irreversible binding of the aromatic amines, and showed that via the aliphatic amines, binding of SDZ or decomposition products of SDZ to soil might also occur but reversibly and only to small soil molecules, which don't enter into the composition of non-hydrolysable part of soil organic matter. SL ESR experiments of different soils at the presence of Laccase highlighted that covalent binding of the aromatic amines to humic particles occurred in the specific hydrophobic areas of soil found as depleted in oxygen. All measured data evidenced that first, SDZ might be decomposed that allowed for measuring the same change of a paramagnetic signal of soil organic matter influenced by both aromatic and aliphatic amines as in the experiment of the interaction of soil with SDZ. Second, a decomposition product of SDZ with the aromatic amine might be bound to non-hydrolysable parts of soil organic matter under specific anaerobic conditions only via 1,4 - nucleophilic addition, Michael-type addition. Gulkowska, A., Thalmann, B., D., Hollender, J., & Krauss, M. (2014). Chemosphere, 107, 366 - 372. Müller, T., Rosendahl, I., Focks, A., Siemens, J., Klasmeier, J., & Matthies. (2013). Environmental Pollution, 172,180 - 185. Nowak, K.M., Miltner, A., Gehre, M., Schaeffer, A., & Kaestner, M. (2011). Environmental Science & Technology 45, 999 - 1006. Weber, E.J., Spidle, D.L., & Thron, K.A. (1996). Environmental Science & Technology, 30 (9), 2755-2763.

Synthesis and Analgesic Properties of Lidocaine Derivatives with Substituted Aminobenzothiazoles.

PubMed

Ahmadi, Abbas; Khalili, Mohsen; Mohammadinoude, Mohammad Kazem; Nahri-Niknafs, Babak

2016-01-01

Local anesthetics are the most widely consumed drugs in the practice of medicine which provide a loss of sensation in a certain body part without loss of consciousness or impairment of central control of essential functions. Lidocaine (I) is the most commonly local anaesthetic drug which is widely used in all species due to its fabulous diffusing and penetrating properties as well as prompt onset of surgical analgesia. In this study, new aminobenzothiazole (with many useful biological and pharmacological properties) analogues were synthesized by changing of amine moiety of I. Both acute and chronic pain properties of new compounds (II-VI) were studied by using the tail immersion and formalin tests on mice and the outcomes were compared with control and lidocaine groups. According to the results, aminobenzothiazole derivatives are better candidates than diethylamine group for replacement on amine moiety of I. Also, derivatives with electron-withdrawing groups on this amine (V and VI) could decrease pain better than electron-donating ones (II and III) (specially on position 6 of this amine, II and V) which may be of concern for blockade of specific sodium channels by these new compounds.

‘Umpolung’ Reactivity in Semiaqueous Amide and Peptide Synthesis

PubMed Central

Shen, Bo; Makley, Dawn M.; Johnston, Jeffrey N.

2010-01-01

The amide functional group is one of Nature’s key functional and structural elements, most notably within peptides. Amides are also key intermediates in the preparation of a diverse range of therapeutic small molecules. Its construction using available methods focuses principally upon dehydrative approaches, although oxidative and radical-based methods are representative alternatives. During the carbon-nitrogen bond forming step in most every example, the carbon and nitrogen bear electrophilic and nucleophilic character, respectively. Here we show that activation of amines and nitroalkanes with an electrophilic iodine source in wet THF can lead directly to amide products. Preliminary observations support a mechanistic construct in which reactant polarity is reversed (umpolung) during C-N bond formation relative to traditional approaches. The use of nitroalkanes as acyl anion equivalents provides a conceptually innovative approach to amide and peptide synthesis, and one that might ultimately provide for efficient peptide synthesis that is fully reliant on enantioselective methods. PMID:20577205

Mannich Bases: An Important Pharmacophore in Present Scenario

PubMed Central

Sharma, Neha; Kajal, Anu; Saini, Vipin

2014-01-01

Mannich bases are the end products of Mannich reaction and are known as beta-amino ketone carrying compounds. Mannich reaction is a carbon-carbon bond forming nucleophilic addition reaction and is a key step in synthesis of a wide variety of natural products, pharmaceuticals, and so forth. Mannich reaction is important for the construction of nitrogen containing compounds. There is a number of aminoalkyl chain bearing Mannich bases like fluoxetine, atropine, ethacrynic acid, trihexyphenidyl, and so forth with high curative value. The literature studies enlighten the fact that Mannich bases are very reactive and recognized to possess potent diverse activities like anti-inflammatory, anticancer, antifilarial, antibacterial, antifungal, anticonvulsant, anthelmintic, antitubercular, analgesic, anti-HIV, antimalarial, antipsychotic, antiviral activities and so forth. The biological activity of Mannich bases is mainly attributed to α, β-unsaturated ketone which can be generated by deamination of hydrogen atom of the amine group. PMID:25478226

Multifunctional mussel-inspired copolymerized epigallocatechin gallate (EGCG)/arginine coating: the potential as an ad-layer for vascular materials.

PubMed

Luo, Rifang; Tang, Linlin; Xie, Lingxia; Wang, Jin; Huang, Nan; Wang, Yunbing

2016-12-01

Surface properties are considered to be important factors in addressing proper functionalities. In this paper, a multifunctional mussel-inspired coating was prepared via the direct copolymerization of epigallocatechin gallate (EGCG) and arginine. The coating formation was confirmed by X-ray photoelectron spectroscopy and Fourier transform infrared spectra. The EGCG/arginine coating contained diverse functional groups like amines, phenols and carboxyls, whose densities were also tunable. Such mussel-inspired coating could also be applied as an ad-layer for its secondary reactivity, demonstrated by quartz crystal microbalance technique. Moreover, the tunable surface density of phenols showed potential ability in modulating endothelial cell and smooth muscle cell viability. The coatings rich in phenols presented excellent free radical scavenging property. Current results strongly indicated the potential of EGCG/arginine coatings to be applied as an ad-layer for vascular materials.

Enantioselective construction of C-chiral allylic sulfilimines via the iridium-catalyzed allylic amination with S,S-diphenylsulfilimine: asymmetric synthesis of primary allylic amines† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c4sc01317d Click here for additional data file.

PubMed Central

Grange, Rebecca L.; Clizbe, Elizabeth A.; Counsell, Emma J.

2015-01-01

We have devised a highly regio- and enantioselective iridium-catalyzed allylic amination reaction with the sulfur-stabilized aza-ylide, S,S-diphenylsulfilimine. This process provides a robust and scalable method for the construction of aryl-, alkyl- and alkenyl-substituted C-chiral allylic sulfilimines, which are important functional groups for organic synthesis. Additionally, the combination of the allylic amination with an in situ deprotection of the sulfilimine constitutes a convenient one-pot protocol for the construction of chiral nonracemic primary allylic amines. PMID:28936319

Chemoselective Amination of Propargylic C(sp3)–H Bonds via Co(II)-Based Metalloradical Catalysis**

PubMed Central

Li, Chaoqun; Jiang, Huiling; Lizardi, Christopher L.

2014-01-01

Highly chemoselective intramolecular amination of propargylic C(sp3)–H bonds has been demonstrated for N-bishomopropargylic sulfamoyl azides via Co(II)-based metalloradical catalysis. Supported by D2h-symmetric amidoporphyrin ligand 3,5-DitBu-IbuPhyrin, the Co(II)-catalyzed C–H amination process can proceed effectively under neutral and nonoxidative conditions without the need of any additives, generating N2 as the only byproduct. The metalloradical amination is suitable to both secondary and tertiary propargylic C–H substrates with an unusually high degree of functional group tolerance, providing a direct method for high-yielding synthesis of functionalized propargylamine derivatives. PMID:24840605

Carbon nanotube-supported Au-Pd alloy with cooperative effect of metal nanoparticles and organic ketone/quinone groups as a highly efficient catalyst for aerobic oxidation of amines.

PubMed

Deng, Weiping; Chen, Jiashu; Kang, Jincan; Zhang, Qinghong; Wang, Ye

2016-05-21

Functionalised carbon nanotube (CNT)-supported Au-Pd alloy nanoparticles were highly efficient catalysts for the aerobic oxidation of amines. We achieved the highest turnover frequencies (>1000 h(-1)) for the oxidative homocoupling of benzylamine and the oxidative dehydrogenation of dibenzylamine. We discovered a cooperative effect between Au-Pd nanoparticles and ketone/quinone groups on CNTs.

Amination of activated carbon for enhancing phenol adsorption: Effect of nitrogen-containing functional groups

NASA Astrophysics Data System (ADS)

Yang, Guo; Chen, Honglin; Qin, Hangdao; Feng, Yujun

2014-02-01

To study the contribution of different nitrogen-containing functional groups to enhancement of phenol adsorption, the aminated activated carbons (AC) were characterized by N2 adsorption/desorption, XPS, Boehm titration, and pH drift method and tested for adsorption behaviors of phenol. Adsorption isotherm fitting revealed that the Langmuir model was preferred for the aminated ACs. The adsorption capacity per unit surface area (qm/SSABET) was linearly correlated with the amount of pyridinic and pyrrolic N, which suggested that these two functional groups played a critical role in phenol adsorption. The enhancement of adsorption capacity was attributed to the strengthened π-π dispersion between phenol and basal plane of AC by pyridinic, pyrrolic N. The adsorption kinetics was found to follow the pseudo-second-order kinetic model, and intraparticle diffusion was one of the rate-controlling steps in the adsorption process.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Happe, J.A.; Morgan, R.J.; Walkup, C.M.

The chemical composition of commercial BF/sub 3/:amine complexes are variable and contain BF/sub 4//sup -/ and BF/sub 3/(OH)/sup -/ salts together with other unidentified highly reactive species. The BF/sub 3/:amine complexes, which are susceptible to hydrolysis, also partially convert to the BF/sub 4//sup -/ salt (i.e. BF/sub 4//sup -/NH/sub 3//sup +/C/sub 2/H/sub 5/) upon heating. This salt formation is accelerated in dimethyl sulfoxide solution and in the presence of the epoxides that are present in commercial prepregs. Commercial C fiber-epoxy prepregs are shown to contain either BF/sub 3/:NH/sub 2/C/sub 2/H/sub 5/ or BF/sub 3/:NHC/sub 5/H/sub 10/ species together with theirmore » BF/sub 4//sup -/ salts and a variety of boron-fluorine or carbon-fluorine prepreg species. Considerable variation in the relative quantities of BF/sub 3/:amine to its BF/sub 4//sup -/ salt was observed from prepreg lot to lot, which will cause variable viscosity-time-temperature prepreg cure profiles. It is concluded that the chemically stable and mobile BF/sub 4//sup -/ salt is the pre-dominant catalytic species, acting as a cationic catalyst for the prepreg cure reactions. During the early stages of cure the BF/sub 3/:amine catalyst converts to the BF/sub 4//sup -/ salt in the presence of epoxides, whereas the BF/sub 3/-prepreg species are susceptible to catalytic deactivation and immobilization.« less

Vinyl sulfoxides as stereochemical controllers in intermolecular Pauson-Khand reactions: applications to the enantioselective synthesis of natural cyclopentanoids.

PubMed

Rodríguez Rivero, Marta; Alonso, Inés; Carretero, Juan C

2004-10-25

The use of sulfoxides as chiral auxiliaries in asymmetric intermolecular Pauson-Khand reactions is described. After screening a wide variety of substituents on the sulfur atom in alpha,beta-unsaturated sulfoxides, the readily available o-(N,N-dimethylamino)phenyl vinyl sulfoxide (1 i) has proved to be highly reactive with substituted terminal alkynes under N-oxide-promoted conditions (CH3CN, 0 degrees C). In addition, these Pauson-Khand reactions occurred with complete regioselectivity and very high diastereoselectivity (de=86->96 %, (S,R(S)) diastereomer). Experimental studies suggest that the high reactivity exhibited by the vinyl sulfoxide 1 i relies on the ability of the amine group to act as a soft ligand on the alkyne dicobalt complex prior to the generation of the cobaltacycle intermediate. On the other hand, both theoretical and experimental studies show that the high stereoselectivity of the process is due to the easy thermodynamic epimerization at the C5 center in the resulting 5-sulfinyl-2-cyclopentenone adducts. When it is taken into account that the known asymmetric intermolecular Pauson-Khand reactions are limited to the use of highly reactive bicyclic alkenes, mainly norbornene and norbornadiene, this novel procedure constitutes the first asymmetric version with unstrained acyclic alkenes. As a demonstration of the synthetic interest of this sulfoxide-based methodology in the enantioselective preparation of stereochemically complex cyclopentanoids, we have developed very short and efficient syntheses of the antibiotic (-)-pentenomycin I and the (-)-aminocyclopentitol moiety of a hopane triterpenoid.

Relative quantification of enantiomers of chiral amines by high-throughput LC-ESI-MS/MS using isotopic variants of light and heavy L-pyroglutamic acids as the derivatization reagents.

PubMed

Mochizuki, Toshiki; Taniguchi, Sayuri; Tsutsui, Haruhito; Min, Jun Zhe; Inoue, Koichi; Todoroki, Kenichiro; Toyo'oka, Toshimasa

2013-04-22

L-Pyroglutamic acid (L-PGA) was evaluated as a chiral labeling reagent for the enantioseparation of chiral amines in terms of separation efficiency by reversed-phase chromatography and detection sensitivity by ESI-MS/MS. Several amines and amino acid methyl esters were used as typical representatives of the chiral amines. Both enantiomers of the chiral amines were easily labeled with L-PGAS at room temperature for 60 min in the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and 1-hydroxy-1H-benzotriazole as the activation reagents. The resulting diastereomers were completely separated by reversed-phase chromatography using the small particle (1.7 μm) ODS column (Rs=1.6-6.8). A highly sensitive detection at a low-fmol level (1-4 fmol) was also obtained from the multiple reaction monitoring (MRM) chromatograms. Therefore, a high-throughput determination was achieved by the present UPLC-ESI-MS/MS method. An isotope labeling strategy using light and heavy L-PGAs for the differential analysis of chiral amines in different sample groups was also proposed in this paper. As a model study, the differential analysis of the R and S ratio of 1-phenylethylamine (PEA) was performed according to the proposed procedure using light and heavy reagents, i.e., L-PGA and L-PGA-d5. The R/S ratio of PEA, spiked at the different concentrations in rat plasma, was almost similar to the theoretical values. Consequently, the proposed strategy using light and heavy chiral labeling reagents seems to be applicable for the differential analysis of chiral amine enantiomers in different sample groups, such as healthy persons and disease patients. Copyright © 2013 Elsevier B.V. All rights reserved.

Synthesis and processing of ELISA polymer substitute: The influence of surface chemistry and morphology on detection sensitivity

NASA Astrophysics Data System (ADS)

Hosseini, Samira; Ibrahim, Fatimah; Djordjevic, Ivan; Rothan, Hussin A.; Yusof, Rohana; van der Marel, Cees; Koole, Leo H.

2014-10-01

Despite the known drawbacks of enzyme-linked immunosorbent assay (ELISA), one of the deficiencies that have relatively been ignored is the performance of ELISA substrate itself. Polystyrene (PS), as the cost effective material of choice for mass production of ELISA well-plates, has shown obvious lacks of suitable physical and chemical properties for protein attachment. The general concept of this work was to develop a potential substrate that can be suggested as a material of choice for production of a new generation of ELISA analytical kits. Spin-coated thin films of polymethyl methacrylate-co-methacrylic acid (PMMA-co-MAA) on silicon surfaces were designed and processed for detection of dengue virus. Coated surfaces of different molar ratios have been investigated as carboxyl-functionalized layers for obtaining platform for biomolecule immobilization with high level of protein activity. To improve the sensitivity of detection, we have used amine functional "spacers", hexamethylenediamine (HMDA) and polyethyleneimine (PEI), which were covalently bonded to the surfaces of PMMA-co-MAA coatings. Results demonstrate that the variation of surface concentration of carboxyl groups of PMMA-co-MAA can be used to control the amine surface concentration after carbodiimide coupling with HMDA and PEI spacers. The presence of amine spacers increases hydrophilicity of the coatings and significantly impacts the polymer surface morphology. In particular, protein immobilization via amine-bearing spacers has been achieved in two effective steps: (1) carbodiimide bonding between amine spacer molecules and PMMA-co-MAA polymer coatings; and (2) covalent immobilization of antibody via glutaraldehyde reaction with amine groups from amine-treated surfaces. The application of PEI spacer in comparison to HMDA has shown much higher intensity of detection signal in ELISA experiment, indicating better immobilization efficiency and preservation of antibody activity upon attachment to the polymer surface.

Reactions of a Ruthenium Complex with Substituted N-Propargyl Pyrroles.

PubMed

Chia, Pi-Yeh; Huang, Shou-Ling; Liu, Yi-Hong; Lin, Ying-Chih

2016-04-05

In an investigation into the chemical reactions of N-propargyl pyrroles 1 a-c, containing aldehyde, keto, and ester groups on the pyrrole ring, with [Ru]-Cl ([Ru]=Cp(PPh3 )2 Ru; Cp=C5 H5 ), an aldehyde group in the pyrrole ring is found to play a crucial role in stimulating the cyclization reaction. The reaction of 1 a, containing an aldehyde group, with [Ru]-Cl in the presence of NH4 PF6 yields the vinylidene complex 2 a, which further reacts with allyl amine to give the carbene complex 6 a with a pyrrolizine group. However, if 1 a is first reacted with allyl amine to yield the iminenyne 8 a, then the reaction of 8 a with [Ru]-Cl in the presence of NH4 PF6 yields the ruthenium complex 9 a, containing a cationic pyrrolopyrazinium group, which has been fully characterized by XRD analysis. These results can be adequately explained by coordination of the triple bond of the propargyl group to the ruthenium metal center first, followed by two processes, that is, formation of a vinylidene intermediate or direct nucleophilic attack. Additionally, the deprotonation of 2 a by R4 NOH yields the neutral acetylide complex 3 a. In the presence of NH4 PF6 , the attempted alkylation of 3 a resulted in the formation the Fischer-type amino-carbene complex 5 a as a result of the presence of NH3, which served as a nucleophile. With KPF6, the alkylation of 3 a with ethyl and benzyl bromoacetates afforded the disubstituted vinylidene complexes 10 a and 11 a, containing ester groups, which underwent deprotonation reactions to give the furyl complexes 12 a and 13 a, respectively. For 13 a, containing an O-benzyl group, subsequent 1,3-migration of the benzyl group was observed to yield product 14 a with a lactone unit. Similar reactivity was not observed for the corresponding N-propargyl pyrroles 1 b and 1 c, which contained keto and ester groups, respectively, on the pyrrole ring. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Amine functionalized graphene oxide/CNT nanocomposite for ultrasensitive electrochemical detection of trinitrotoluene.

PubMed

Sablok, Kavita; Bhalla, Vijayender; Sharma, Priyanka; Kaushal, Roohi; Chaudhary, Shilpa; Suri, C Raman

2013-03-15

Binding of electron-deficient trinitrotoluene (TNT) to the electron rich amine groups on a substrate form specific charge-transfer Jackson-Meisenheimer (JM) complex. In the present work, we report formation of specific JM complex on amine functionalized reduced graphene oxide/carbon nanotubes- (a-rGO/CNT) nanocomposite leading to sensitive detection of TNT. The CNT were dispersed using graphene oxide that provides excellent dispersion by attaching to CNT through its hydrophobic domains and solubilizes through the available OH and COOH groups on screen printed electrode (SPE). The GO was reduced electrochemically to form reduced graphene that remarkably increases electrochemical properties owing to the intercalation of high aspect CNT on graphene flakes as shown by TEM micrograph. The surface amine functionalization of dropcasted and rGO/CNT was carried out using a bi-functional cross linker ethylenediamine. The extent of amine functionalization on modified electrodes was confirmed using energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS) and confocal microscopy. The FTIR and Raman spectra further suggested the formation of JM complex between amine functionalized electrodes and TNT leading to a shift in peak intensity together with peak broadening. The a-rGO/CNT nanocomposite prepared electrode surface leads to ultra-trace detection of TNT upto 0.01 ppb with good reproducibility (n=3). The a-rGO/CNT sensing platform could be an alternate for sensitive detection of TNT explosive for various security and environmental applications. Copyright © 2013 Elsevier B.V. All rights reserved.

Quinone Methide Signal Amplification: Covalent Reporter Labeling of Cancer Epitopes using Alkaline Phosphatase Substrates.

PubMed

Polaske, Nathan W; Kelly, Brian D; Ashworth-Sharpe, Julia; Bieniarz, Christopher

2016-03-16

Diagnostic assays with the sensitivity required to improve cancer therapeutics depend on the development of new signal amplification technologies. Herein, we report the development and application of a novel amplification system which utilizes latent quinone methides (QMs) activated by alkaline phosphatase (AP) for signal amplification in solid-phase immunohistochemical (IHC) assays. Phosphate-protected QM precursor substrates were prepared and conjugated to either biotin or a fluorophore through an amine-functionalized linker group. Upon reaction with AP, the phosphate group is cleaved, followed by elimination of the leaving group and formation of the highly reactive and short-lived QM. The QMs either react with tissue nucleophiles in close proximity to their site of generation, or are quenched by nucleophiles in the reaction media. The reporter molecules that covalently bind to the tissue were then detected visually by fluorescence microscopy in the case of fluorophore reporters, or brightfield microscopy using diaminobenzidine (DAB) in the case of biotin reporters. With multiple reporters deposited per enzyme, significant signal amplification was observed utilizing QM precursor substrates containing either benzyl difluoro or benzyl monofluoro leaving group functionalities. However, the benzyl monofluoro leaving group gave superior results with respect to both signal intensity and discretion, the latter of which was found to be imperative for use in diagnostic IHC assays.

Redox self-sufficient whole cell biotransformation for amination of alcohols.

PubMed

Klatte, Stephanie; Wendisch, Volker F

2014-10-15

Whole cell biotransformation is an upcoming tool to replace common chemical routes for functionalization and modification of desired molecules. In the approach presented here the production of various non-natural (di)amines was realized using the designed whole cell biocatalyst Escherichia coli W3110/pTrc99A-ald-adh-ta with plasmid-borne overexpression of genes for an l-alanine dehydrogenase, an alcohol dehydrogenase and a transaminase. Cascading alcohol oxidation with l-alanine dependent transamination and l-alanine dehydrogenase allowed for redox self-sufficient conversion of alcohols to the corresponding amines. The supplementation of the corresponding (di)alcohol precursors as well as amino group donor l-alanine and ammonium chloride were sufficient for amination and redox cofactor recycling in a resting buffer system. The addition of the transaminase cofactor pyridoxal-phosphate and the alcohol dehydrogenase cofactor NAD(+) was not necessary to obtain complete conversion. Secondary and cyclic alcohols, for example, 2-hexanol and cyclohexanol were not aminated. However, efficient redox self-sufficient amination of aliphatic and aromatic (di)alcohols in vivo was achieved with 1-hexanol, 1,10-decanediol and benzylalcohol being aminated best. Copyright © 2014 Elsevier Ltd. All rights reserved.

Conformation of the Phosphate D-alanine Zwitterion in Bacterial Teichoic Acid from Nuclear Magnetic Resonance Spectroscopy

PubMed Central

Garimella, Ravindranath; Halye, Jeffrey L.; Harrison, William; Klebba, Phillip E.; Rice, Charles V.

2009-01-01

The conformation of D-alanine (D-Ala) groups of bacterial teichoic acid is a central, yet untested, paradigm of microbiology. The D-Ala binds via the C-terminus, thereby allowing the amine to exist as a free cationic NH3+ group with the ability to form a contact-ion-pair with the nearby anionic phosphate group. This conformation hinders metal chelation by the phosphate because the zwitterion pair is charge neutral. To the contrary, the repulsion of cationic antimicrobial peptides (CAMPs) is attributed to the presence of the D-Ala cation; thus the ion-pair does not form in this model. Solid-state nuclear magnetic resonance (NMR) spectroscopy has been used to measure the distance between amine and phosphate groups within cell wall fragments of Bacillus subtilis. The bacteria were grown on media containing 15N D-Ala and β-chloroalanine racemase inhibitor. The rotational-echo double-resonance (REDOR) pulse sequence was used to measure the internuclear dipolar coupling and the results demonstrate: 1) the metal-free amine-to-phosphate distance is 4.4 Å and 2) the amine-to-phosphate distance increases to 5.4 Å in the presence of Mg2+ ions. As a result, the zwitterion exists in a nitrogen-oxygen ion-pair configuration providing teichoic acid with a positive charge to repel CAMPs. Additionally, the amine of D-Ala does not prevent magnesium chelation in contradiction to the prevailing view of teichoic acids in metal binding. Thus, the NMR-based description of teichoic acid structure resolves the contradictory models, advances the basic understanding of cell wall biochemistry, and provides possible insight into the creation of new antibiotic therapies. PMID:19746945

Comparison between amine fluoride and chlorhexidine with institutionalized elders: a pilot study.

PubMed

López, Rosa Moreno; Uribe, Manuel Ribera; Rodríguez, Belisa Olmo; Casasempere, Inmaculada Vela

2013-06-01

Compare the efficacy of amine fluoride toothpaste and gel with chlorhexidine spray in an institutionalised population. People who live in nursing homes have poorer oral hygiene because of their dependency for the basic activities of daily living as they rely on caregivers. Twenty-six people over 65 years old who had at least four teeth and living in a nursing home. They were assigned to three groups: A: amine fluoride toothpaste and once a week amine fluoride gel (Elmex(®) ), B: 0.12% spray-chlorhexidine once a day (Perio-Aid(®) ) and C: brush teeth without toothpaste. The plaque and gingival index of Silness and Löe, General Oral Health Assessment Index, McLeran and Pfeiffer index were recorded, and the number of colonies of Streptoccocus mutans and Lactobacillus and the remineralisation of caries were evaluated using Diagnodent(®). Measurements were taken at the beginning of the study and after 6 months.   Twenty-two people finished the study. No group showed a statistical difference in the plaque or gingival index, but there was a tendency to show improvement in the amine fluoride group. There was also no difference between the number of colonies of either S. mutans or lactobacillus. There was a significant difference between the plaque and gingival index and the cognitive status (p=0.0054), along with their requirement for assistance to perform good oral hygiene (p=0.0001). Both products remineralised the carious lesions in this period compared with the control group (p=0.0151). The plaque and gingival indices did not improve during the study, but both products remineralised the previous caries lesions. © 2012 John Wiley & Sons A/S and The Gerodontology Society. Published by John Wiley & Sons Ltd.

Quantitation of buried contamination by use of solvents. Part 1: Solvent degradation of amine cured epoxy resins

NASA Technical Reports Server (NTRS)

Rheineck, A. E.; Heskin, R. A.; Hill, L. W.

1972-01-01

The solubility and/or swelling of cured epoxy resins was studied using the solubility parameter method. Determination of solubility parameters were found in order to select solvents for solvent-assisted degradation of cured epoxy polymers used in spacecraft. A method for improving recovery of seeded spores is suggested for assay of buried contaminants. Three commercial epoxy resins were cured using four different alkyl amines. For each resin-amine combination, three levels of amine were used, corresponding to 1/3, 2/3, and all of the amine required to react with the oxirane groups of the resin. The solubility parameters of the 36 resulting model compounds were determined in poorly and moderately hydrogen-bonded solvents. No strongly hydrogen-bonded solvents caused dissolution or swelling. The tolerance of cured resins is discussed in terms of polymer structure.

Systematic Investigations of Biomimetic Catalysts in the Synthesis of Reactive Metal Oxide Nanoparticle Networks

DTIC Science & Technology

2012-09-01

dioxide and aluminum oxide. Numerous polymeric templates (Table 1), such as polyallyamine (PAA), were investigated, along with amine- functionalized ...SephadexTM LH60 (an anionic functionalized resin) and SephadexTM G-100 (unfunctionalized) were used as the functionalized surface. The reaction conditions...formed with all of the polymers tested and from some of the functionalized surface. SEM images (Figure 1) show that with the exception of the

Studies in Aromatic and Amine Nitration.

DTIC Science & Technology

1980-05-20

of Commerce, May 1978. 4. J. Hoggett , R. Moodie, F. Penton, and K. Schofield, Nitration and Aromatic Reactivity (Cambridge University Press, 1971). 5...Moodie, K. Schofield, and G. Tobin, J. Chem. Soc., Chem. Comm., 180 (1978); (b) J. Hoggett , R. Moodie, and K. Schofield, Chem. Comm. 605 (1969). 10. (a) S...W. Benson, Thermochemical Kinetics (John Wiley and Sons, Inc., New York, 1968); (b) G. Charlot, D. Bezier, and J. Courtot, Selected Constants--Oxydo

The Reactions of Nitrogen Peroxide with Possible Stabilisers for Propellants

DTIC Science & Technology

1957-03-01

ether Carbamite Phe nyl-be nzyl-ure thane (pure) Cyclohexanyl-urethane Cyclohexano ne Die thyl phthalate Di-isoamyl phthalate Dibutyl oxalate Glycollic...saponification" arises from the presence of phenyl urethane and diphenyl urea; differences in contents of these impurities and of benzyl aniline...nitrogen that is recovered from a product. 4.2.2 Ure are fairly reactive. Triphenylethylurea present with diphenyl - amine in 蠢 compound" leads to a

Reductive amination of tertiary anilines and aldehydes.

PubMed

Lv, Yunhe; Zheng, Yiying; Li, Yan; Xiong, Tao; Zhang, Jingping; Liu, Qun; Zhang, Qian

2013-10-09

An unprecedented oxidant-mediated reductive amination of tertiary anilines and aldehydes without external reducing agents was developed via the nucleophilic attack of the oxygen atom of the carbonyl group to in situ generated iminium ions, in which tertiary anilines were used as both nitrogen source and reducing agent for the first time.

Silica Fume Functionalized With Amine-Based Additives as a Modifier to Enhance Asphalt Resistance to Oxidation

NASA Astrophysics Data System (ADS)

Abutalib, Nader Turki

This dissertation investigates the practical feasibility of functionalizing silica fume particles with the amine groups in Bio-binder and pure APTES chemical to disperse silica fume in asphalt binder matrix to produce silica-fume-modified binder (SFMB). Dispersed silica fume was then introduced to asphalt to reduce oxidative aging. It has been widely reported that asphalt binder oxidation is one of the phenomena that reduces the service life of asphalt pavement by negatively affecting its rheological properties. This in turn can lead to a more brittle pavement, which is more prone to cracks due to thermal stress and traffic loading. It has been shown that the introduction of 4% silica fume to asphalt can reduce asphalt oxidative aging. However, the challenge with a higher percentage of silica fume was found to be the agglomeration of nano- particles to form micro-size clusters, which can reduce the effectiveness of silica fume while making asphalt binder more susceptible to shear. Therefore, this dissertation studies the effectiveness of functionalizing the SFMB to reduce asphalt oxidative aging while alleviating the agglomeration effect. To do so, various percentages of bio-binder (BB) and bio-char (BC) were introduced to SFMB, and the rheological properties and high-temperature performance of each specimen were evaluated by measuring the rotational viscosity and complex shear modulus before and after oxidative aging. It is hypothesized that fine-graded BC and BB with nano- to micro-level particles can be used to reduce asphalt oxidation and create a new generation of low- agglomeration SFMB with higher resistance to oxidative aging. To further study the effects of functionalization on dispersion of silica fume, silica fume particles were produced with different functional groups: amine (APTES) groups and phosphonate (THPMP) groups. Agglomeration studies using a scanning electron microscope and zeta potential analysis indicate that modifying asphalt binder with amine-modified silica fume particles can reduce the agglomeration of the silica fume particles. The performance characteristics of functionalized silica fume particles and non-functionalized silica fume particles are compared with those of base asphalt. The following research hypotheses were investigated: 1) Functionalized and well-dispersed silica fume will enhance asphalt's aging resistance. 2) The amine groups in functionalizing agent interact with silica fume particles and promote their dispersion. To test these hypotheses, a rotational viscometer was used to study the effect of functionalized-silica-fume-modified binder on the high-temperature properties of the asphalt binder. Fourier transform infrared spectroscopy analysis was used to determine the chemical compounds of the amine-group silica-fume- modified binder matrix. Scanning electron microscopy was used to observe the surface morphology and analyze the microstructure characteristics of materials. The positive effect of amine groups on the rheological properties of SFMB could be attributed to the high surface area of the silica fume and its granular particles with high polarity, factors that could improve the blending properties of the bio-modified silica fume and result in a uniformly distributed silica- fume-modified matrix with enhanced oxidative aging resistance. Surface adsorption of amines on silica fume particles helps promote repulsive forces between them to enhance dispersion.

Dynamic Covalent Chemistry within Biphenyl Scaffolds: Reversible Covalent Bonding, Control of Selectivity, and Chirality Sensing with a Single System.

PubMed

Ni, Cailing; Zha, Daijun; Ye, Hebo; Hai, Yu; Zhou, Yuntao; Anslyn, Eric V; You, Lei

2018-01-26

Axial chirality is a prevalent and important phenomenon in chemistry. Herein we report a combination of dynamic covalent chemistry and axial chirality for the development of a versatile platform for the binding and chirality sensing of multiple classes of mononucleophiles. An equilibrium between an open aldehyde and its cyclic hemiaminal within biphenyl derivatives enabled the dynamic incorporation of a broad range of alcohols, thiols, primary amines, and secondary amines with high efficiency. Selectivity toward different classes of nucleophiles was also achieved by regulating the distinct reactivity of the system with external stimuli. Through induced helicity as a result of central-to-axial chirality transfer, the handedness and ee values of chiral monoalcohol and monoamine analytes were reported by circular dichroism. The strategies introduced herein should find application in many contexts, including assembly, sensing, and labeling. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Multistep divergent synthesis of benzimidazole linked benzoxazole/benzothiazole via copper catalyzed domino annulation.

PubMed

Liao, Jen-Yu; Selvaraju, Manikandan; Chen, Chih-Hau; Sun, Chung-Ming

2013-04-21

An efficient, facile synthesis of structurally diverse benzimidazole integrated benzoxazole and benzothiazoles has been developed. In a multi-step synthetic sequence, 4-fluoro-3-nitrobenzoic acid was converted into benzimidazole bis-heterocycles, via the intermediacy of benzimidazole linked ortho-chloro amines. The amphiphilic reactivity of this intermediate was designed to achieve the title compounds by the reaction of various acid chlorides and isothiocyanates in a single step through the in situ formation of ortho-chloro anilides and thioureas under microwave irradiation. A versatile one pot domino annulation reaction was developed to involve the reaction of benzimidazole linked ortho-chloro amines with acid chlorides and isothiocyanates. The initial acylation and urea formation followed by copper catalyzed intramolecular C-O and C-S cross coupling reactions furnished the angularly oriented bis-heterocycles which bear a close resemblance to the streptomyces antibiotic UK-1.

Synthesis and characterization of MOF-aminated graphite oxide composites for CO2 capture

NASA Astrophysics Data System (ADS)

Zhao, Yunxia; Ding, Huiling; Zhong, Qin

2013-11-01

A kind of metal-organic frameworks (MOF-5) and aminated graphite oxide (AGO) composites were prepared for CO2 capture to mitigate global warming. MOF-5, MOF-5/GO (composite of MOF-5 and graphite oxide) and MOF-5/AGO samples were characterized by X-ray powder diffraction (XRD), infrared spectroscopy (IR), scanning electron microscope (SEM), nitrogen adsorption as well as thermogravimetric analysis to figure out their chemistry and structure information. Three types of samples with suitable specific surface area and pore diameter were chosen to test CO2 adsorption performance and stability under humidity conditions. The results indicate that high surface area and pore volume, pore similar in size to the size of gas adsorbate, and extra reactive sites modified in the composites contributes to the high CO2 capacity. Besides, the composites involved by GO or AGO show better anti-moisture performance than the parent MOF.

A Mobile Device App to Reduce Time to Drug Delivery and Medication Errors During Simulated Pediatric Cardiopulmonary Resuscitation: A Randomized Controlled Trial.

PubMed

Siebert, Johan N; Ehrler, Frederic; Combescure, Christophe; Lacroix, Laurence; Haddad, Kevin; Sanchez, Oliver; Gervaix, Alain; Lovis, Christian; Manzano, Sergio

2017-02-01

During pediatric cardiopulmonary resuscitation (CPR), vasoactive drug preparation for continuous infusion is both complex and time-consuming, placing children at higher risk than adults for medication errors. Following an evidence-based ergonomic-driven approach, we developed a mobile device app called Pediatric Accurate Medication in Emergency Situations (PedAMINES), intended to guide caregivers step-by-step from preparation to delivery of drugs requiring continuous infusion. The aim of our study was to determine whether the use of PedAMINES reduces drug preparation time (TDP) and time to delivery (TDD; primary outcome), as well as medication errors (secondary outcomes) when compared with conventional preparation methods. The study was a randomized controlled crossover trial with 2 parallel groups comparing PedAMINES with a conventional and internationally used drugs infusion rate table in the preparation of continuous drug infusion. We used a simulation-based pediatric CPR cardiac arrest scenario with a high-fidelity manikin in the shock room of a tertiary care pediatric emergency department. After epinephrine-induced return of spontaneous circulation, pediatric emergency nurses were first asked to prepare a continuous infusion of dopamine, using either PedAMINES (intervention group) or the infusion table (control group), and second, a continuous infusion of norepinephrine by crossing the procedure. The primary outcome was the elapsed time in seconds, in each allocation group, from the oral prescription by the physician to TDD by the nurse. TDD included TDP. The secondary outcome was the medication dosage error rate during the sequence from drug preparation to drug injection. A total of 20 nurses were randomized into 2 groups. During the first study period, mean TDP while using PedAMINES and conventional preparation methods was 128.1 s (95% CI 102-154) and 308.1 s (95% CI 216-400), respectively (180 s reduction, P=.002). Mean TDD was 214 s (95% CI 171-256) and 391 s (95% CI 298-483), respectively (177.3 s reduction, P=.002). Medication errors were reduced from 70% to 0% (P<.001) by using PedAMINES when compared with conventional methods. In this simulation-based study, PedAMINES dramatically reduced TDP, to delivery and the rate of medication errors. ©Johan N Siebert, Frederic Ehrler, Christophe Combescure, Laurence Lacroix, Kevin Haddad, Oliver Sanchez, Alain Gervaix, Christian Lovis, Sergio Manzano. Originally published in the Journal of Medical Internet Research (http://www.jmir.org), 01.02.2017.

One phase growth of in-situ functionalized gold and silver nanoparticles and luminescent nanoclusters

NASA Astrophysics Data System (ADS)

Aldeek, Fadi; Muhammed, M. A. H.; Mattoussi, Hedi

2013-02-01

We describe the growth and characterization of a set of gold and silver nanoparticles (NPs) as well as fluorescent nanoclusters (NCs) using one-step reduction (in aqueous phase) of Au and Ag precursors in the presence of modular bifunctional ligands. These ligands are made of bidentate (lipoic acid) anchoring groups appended with poly(ethylene glycol) segment, LA-PEG. The particle size can be easily controlled by varying the metal-to-ligand molar ratio during growth. We found that while high metal-to-ligand molar ratios promote the formation of NPs, small size and highly fluorescent NCs are exclusively formed when molar excesses of ligands are used. Both sets of NCs emit in the red to near infrared (NIR) region of the optical spectrum, though the exact location of the emission depends on the material used. The growth strategy further permitted the in-situ functionalization of the NCs with reactive groups (e.g., carboxylic acid or amine), which opens up the opportunity to conjugate these materials to biomolecules using simple to implement coupling chemistries.

Cu/Nitroxyl Catalyzed Aerobic Oxidation of Primary Amines into Nitriles at Room Temperature

PubMed Central

Kim, Jinho; Stahl, Shannon S.

2013-01-01

An efficient catalytic method has been developed for aerobic oxidation of primary amines to the corresponding nitriles. The reactions proceed at room temperature and employ a catalyst consisting of (4,4′-tBu2bpy)CuI/ABNO (ABNO = 9-azabicyclo[3.3.1]nonan-3-one N-oxyl). The reactions exhibit excellent functional group compatibility and substrate scope, and are effective with benzylic, allylic and aliphatic amines. Preliminary mechanistic studies suggest that aerobic oxidation of the Cu catalyst is the turnover-limiting step of the reaction. PMID:24015373

Directed amination of non-acidic arene C-H bonds by a copper-silver catalytic system.

PubMed

Tran, Ly Dieu; Roane, James; Daugulis, Olafs

2013-06-03

Amine meets arene: A method for direct amination of β-C(sp(2))-H bonds of benzoic acid derivatives and γ-C(sp(2))-H bonds of benzylamine derivatives has been developed. The reaction is catalyzed by Cu(OAc)2 and a Ag2CO3 cocatalyst, and shows high generality and functional-group tolerance, as well as providing a straightforward means for the preparation of ortho-aminobenzoic acid derivatives. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

New Stable Cu(I) Catalyst Supported on Weakly Acidic Polyacrylate Resin for Green C-N Coupling: Synthesis of N-(Pyridin-4-yl)benzene Amines and N,N-Bis(pyridine-4-yl)benzene Amines.

PubMed

Kore, Nitin; Pazdera, Pavel

2016-12-22

A method for preparation of a new stable Cu(I) catalyst supported on weakly acidic polyacrylate resin without additional stabilizing ligands is described. A simple and efficient methodology for Ullmann Cu(I) catalyzed C-N cross coupling reactions using this original catalyst is reported. Coupling reactions of 4-chloropyridinium chloride with anilines containing electron donating (EDG) or electron withdrawing (EWG) groups, naphthalen-2-amine and piperazine, respectively, are successfully demonstrated.

Cu/Nitroxyl Catalyzed Aerobic Oxidation of Primary Amines into Nitriles at Room Temperature.

PubMed

Kim, Jinho; Stahl, Shannon S

2013-07-05

An efficient catalytic method has been developed for aerobic oxidation of primary amines to the corresponding nitriles. The reactions proceed at room temperature and employ a catalyst consisting of (4,4'- t Bu 2 bpy)CuI/ABNO (ABNO = 9-azabicyclo[3.3.1]nonan-3-one N -oxyl). The reactions exhibit excellent functional group compatibility and substrate scope, and are effective with benzylic, allylic and aliphatic amines. Preliminary mechanistic studies suggest that aerobic oxidation of the Cu catalyst is the turnover-limiting step of the reaction.

Formation and Human Risk of Carcinogenic Heterocyclic Amines Formed from Natural Precursors in Meat

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knize, M G; Felton, J S

2004-11-22

A group of heterocyclic amines that are mutagens and rodent carcinogens form when meat is cooked to medium and well-done states. The precursors of these compounds are natural meat components: creatinine, amino acids and sugars. Defined model systems of dry-heated precursors mimic the amounts and proportions of heterocyclic amines found in meat. Results from model systems and cooking experiments suggest ways to reduce their formation and, thus, to reduce human intake. Human cancer epidemiology studies related to consumption of well-done meat products are listed and compared.

Amine-pillared Nanosheet Adsorbents for CO2 Capture Applications

NASA Astrophysics Data System (ADS)

Jiang, Hui

Amine-functionalized solid adsorbents have gained attention within the last decade for their application in carbon dioxide capture, due to their many advantages such as low energy cost for regeneration, tunable structure, elimination of corrosion problems, and additional advantages. However, one of the challenges facing this technology is to accomplish both high CO 2 capture capacity along with high CO2 diffusion rates concurrently. Current amine-based solid sorbents such as porous materials similar to SBA-15 have large pores diffusion entering molecules; however, the pores become clogged upon amine inclusion. To meet this challenge, our group's solution involves the creation of a new type of material which we are calling-amino-pillared nanosheet (APN) adsorbents which are generated from layered nanosheet precursors. These materials are being proposed because of their unique lamellar structure which exhibits ability to be modified by organic or inorganic pillars through consecutive swelling and pillaring steps to form large mesoporous interlayer spaces. After the expansion of the layer space through swelling and pillaring, the large pore space can be functionalized with amine groups. This selective functionalization is possible by the choice of amine group introduced. Our choice, large amine molecules, do not access the micropore within each layer; however, either physically or chemically immobilized onto the surface of the mesoporous interlayer space between each layer. The final goal of the research is to investigate the ability to prepare APN adsorbents from a model nanoporous layered materials including nanosheets precursor material MCM-22(P) and nanoporous layered silicate material AMH-3. MCM-22(P) contains 2-dimensional porous channels, 6 membered rings (MB) openings perpendicular to the layers and 10 MB channels in the plane of the layers. However, the transport limiting openings (6 MB) to the layers is smaller than CO2 gas molecules. In contrast, AMH-3 has 3D microporous layers with 8 MB openings in the plane of the layers, as well as perpendicular to the layers, which are larger than CO2 molecules. Based on the structure differences between nanosheets precursor material MCM-22(P) and nanoporous layered silicate material AMH-3, the latter might be more suitable for CO 2 capturer application as an APN candidate material. However, none of the assumptions above have been approved experimentally. In this study, the influence of the amine loading on adsorption capacity and kinetics of adsorption for the mixed porosity material pillared MCM-22 (P) (also called MCM-36) is studied systematically, in order to determine a potential route to achieve a final material with both high amine loading and high adsorption capacity. We first synthesized MCM-22(P), followed by swelling and pillaring to create MCM-36. Polymeric amines such as polyethylenimine (PEI) are used as an organic component of the supported amine adsorbents, with varying polymer loadings within the adsorbents used. The kinetics and diffusion properties of carbon dioxide capture on a MCM-36 pillared material impregnated with amine containing Polyethylenimine polymers has been investigated. It was determined that the introduction of amine polymer cannot be used to improve the capture capacity of the support over that of the bare material, due to the fact that with the addition of a high loading of amine polymer the large pore diffusion channels become impossible for carbon dioxide molecules to diffuse through. This sets an upper limit to the capture capacity of polymer impregnated MCM-36 for carbon dioxide which does not surpass that for the initial bare material, and greatly reduces the utility of using this sort of amine-solid adsorbent for carbon capture plans in the future.

Effect of competing amines on the removal of tetramethylammonium hydroxide from solution using ion exchange.

PubMed

Citraningrum, H M; Liu, Jhy-Chern

Tetramethylammonium hydroxide (TMAH, TMA(+)) has been widely used as the photoresist developer in semiconductor and thin film transistor liquid crystal display manufacturing. In this study, TMAH-containing wastewater was treated by ion exchange method. Strong acid cation exchange resin was used. A kinetics study revealed that the ion exchange reaction reached equilibrium within 20 min and it could be described by a pseudo-second-order model. To assess the effects of competing ions, wastewater was spiked with three different amines, namely ethylamine (EA(+)), diethylamine (DEA(+)), and triethylamine (TEA(+)). TMAH uptake decreased when in the presence of amines, and it decreased in the order EA(+) < DEA(+) < TEA(+). It could be attributed to different proton affinity (PA) and the strength of affinity between amine molecules and resin matrix, as found from the ab initio calculation values and Langmuir isotherm parameters. However, the interaction energy between sulphonic acid groups and interfering amines in solution using density functional theory (DFT) calculation resulted in a different trend compared with that of PA. The difference might be caused by stabilization of amines by resin matrix and different molecular structures.

Kinetics of fluoride bioavailability in supernatant saliva and salivary sediment.

PubMed

Naumova, E A; Sandulescu, T; Bochnig, C; Gaengler, P; Zimmer, S; Arnold, W H

2012-07-01

The assessment of the fluoride kinetics in whole saliva as well as in the different salivary phases (supernatant saliva and sediment) is essential for the understanding of fluoride bioavailability. To assess the fluoride content, provided by sodium fluoride and amine fluoride, in the supernatant saliva and in salivary sediment. Seven trained volunteers were randomly attributed to 2 groups in a cross-over design and brushed their teeth in the morning for 3 min with a product containing either sodium fluoride or amine fluoride. Saliva was collected before, immediately after tooth brushing and 30, 120, and 360 min later and measured. The samples were centrifuged 10 min at 3024 × g. Fluoride content of the supernatant saliva and of the sediment was analysed using a fluoride sensitive electrode. All subjects repeated the study cycles 2 times, and statistical analyses were made using the nonparametric sign test for related samples, the Wilcoxon-Mann-Whitney-test for independent samples. There was a significant increase in fluoride immediately after tooth brushing in both groups in saliva and sediment. The distribution of fluoride between salivary sediment and supernatant saliva (ratio) varied considerably at the different collection times: decreased from 17.87 in baseline samples of saliva to 0.07 immediately and to 0.86 half an hour after tooth brushing in the sodium fluoride group and from 14.33 to 2.85 and to 3.09 in the amine fluoride group. Furthermore after 120 min and after 360 min after tooth brushing the ratio increased from 17.6 to 31.6 in the sodium fluoride group and from 20.5 to 25.76 in the amine fluoride group. No difference was found in the sediment-supernatant saliva ratio between the sodium fluoride and the amine fluoride groups 360 min after tooth brushing. For the assessment of fluoride kinetics in whole saliva it is necessary to pay attention to at least four factors: fluoride formulation, time after fluoride application, fluoride concentration in supernatant saliva and fluoride concentration in salivary sediment. This study was approved by the Ethical Committee of the University of Witten/Herdecke permission 21/2008. Copyright © 2012 Elsevier Ltd. All rights reserved.

Impact of biogenic amine molecular weight and structure on surfactant adsorption at the air-water interface.

PubMed

Penfold, Jeffrey; Thomas, Robert K; Li, Peixun

2016-02-01

The oligoamines, such as ethylenediamine to pentaethylenetetramine, and the aliphatic biogenic amines, such as putrescine, spermidine and spermine, strongly interact with anionic surfactants, such as sodium dodecylsulfate, SDS. It has been shown that this results in pronounced surfactant adsorption at the air-water interface and the transition from monolayer to multilayer adsorption which depends upon solution pH and oligoamine structure. In the neutron reflectivity, NR, and surface tension, ST, results presented here the role of the oligoamine structure on the adsorption of SDS is investigated more fully using a range of different biogenic amines. The effect of the extent of the intra-molecular spacing between amine groups on the adsorption has been extended by comparing results for cadavarine with putrescine and ethylenediamine. The impact of more complex biogenic amine structures on the adsorption has been investigated with the aromatic phenethylamine, and the heterocyclic amines histamine and melamine. The results provide an important insight into how surfactant adsorption at interfaces can be manipulated by the addition of biogenic amines, and into the role of solution pH and oligoamine structure in modifying the interaction between the surfactant and oligoamine. The results impact greatly upon potential applications and in understanding some of the important biological functions of biogenic amines. Copyright © 2015 Elsevier Inc. All rights reserved.

Designing tri-branched multiple-site SO2 capture materials.

PubMed

Li, Chenchen; Lu, Dongmei; Wu, Chao

2018-06-07

SO2 capture materials usually have multiple reactive sites located within a limited space, thus absorptions (or adsorptions) of disparate strengths and low effective capacity per sorption-desorption cycle become the natural results of the so-called "coverage effects" (due to both the electronic and steric effects). Here, we propose a tri-branched framework with separated reactive sites and nearly uniform charge distribution on the reacting atoms. Through density functional theory (DFT)-based calculations and simulated isotherms, two N-centered anionic structures (terminated with amine (TAEA) and imidazolyl (TIA) groups, respectively) are selected from a series of representative tri-branched species. The TAEA-based ILs are predicted to exhibit the highest uptakes (about 6.1 mol SO2 per mole IL) at 1 bar of SO2 and 20 °C, which reach the ceiling capacity that a negative charge can provide. The TIA-based ILs have small differences in their SO2 sequential binding energies and they are estimated to have the best effective SO2 capacity during a sorption-desorption cycle (about 2.6 mol SO2 per mole IL, absorption at 1 bar of SO2 and 20 °C and desorption at 1 bar of SO2 and 120 °C). Moreover, we also find that the designed species can efficiently capture other gases like NO.

Cu-Fe-S Nanocrystals Exhibiting Tunable Localized Surface Plasmon Resonance in the Visible to NIR Spectral Ranges.

PubMed

Gabka, Grzegorz; Bujak, Piotr; Ostrowski, Andrzej; Tomaszewski, Waldemar; Lisowski, Wojciech; Sobczak, Janusz W; Pron, Adam

2016-07-05

Cu-Fe-S nanocrystals exhibiting a strong localized surface plasmon resonance (LSPR) effect were synthesized for the first time. The elaborated reproducible preparation procedure involved copper(II) oleate, iron(III) stearate, and sulfur powder dissolved in oleylamine (OLA) as precursors. The wavelength of the plasmonic resonance maximum could be tuned by changing the Cu/Fe ratio in the resulting nanocrystals, being the most energetic for the 1:1 ratio (486 nm) and undergoing a bathochromic shift to ca. 1200 nm with an increase to 6:1. LSPR could also be observed in nanocrystals prepared from the same metal precursors and sulfur powder dissolved in 1-octadecene (ODE), provided that the sulfur precursor was taken in excess. Detailed analysis of the reaction mixture by chromatographic techniques, supplemented by mass spectrometry and (1)H NMR spectroscopy enabled the identification of the true chemical nature of the sulfur precursor in S/OLA, namely, (C18H35NH3(+))(C18H35NH-S8(-)), a reactive product of the reduction of elemental sulfur by the amine groups of OLA. In the case of the S/ODE precursor, the true precursors are much less reactive primary or secondary thioethers and dialkyl polysulfides.

Laminate comprising fibers embedded in cured amine terminated bis-imide

NASA Technical Reports Server (NTRS)

Kumar, D. (Inventor); Fohlen, G. M. (Inventor); Parker, J. A. (Inventor)

1986-01-01

Amine terminated bisaspartimides are prepared by a Michael type reaction of an aromatic bismaleimide and an aromatic diamine in an aprotic solvent. These bisaspartimides are thermally polymerized to yield tough, resinous polymers crosslinked through -NH- groups. Such polymers are useful in applications requiring materials with resistance to change at elevated temperatures.

Characterization of the active site, substrate specificity and kinetic properties of acetyl-CoA:arylamine N-acetyltransferase from pigeon liver.

PubMed

Andres, H H; Kolb, H J; Schreiber, R J; Weiss, L

1983-08-16

It could be demonstrated that a sulfhydryl group is involved in the catalysis of acetyl-CoA:arylamine N-acetyltransferase from pigeon liver (EC 2.3.1.5). From ping-pong kinetics it was concluded that there is a covalent acetyl-enzyme intermediate. The respective intermediate could be isolated and chemically characterized as a cysteinyl thioester. Electrophoretically homogeneous acetyl-CoA:acylamine N-acetyltransferase from pigeon liver was able to acetylate a broad variety of aromatic and aliphatic amines from different acetyldonors such as acetyl-CoA, p-nitroacetanilide and p-nitrophenylacetate. Apparent Km values were determined for a number of acetyl donors and acetyl acceptors. Additionally, Ki values were evaluated for CoA, 3',5'-ADP and AMP. Correlation studies of basicity of acceptor amines and acetylation rate demonstrated that there is a limit of the pKa value (about pKa = 1) where the covalently-bound acetyl-enzyme intermediate can still be saponified. Testing crude liver homogenates of several animals including turkey, duck, chicken, cow, pig, horse, sheep, carp, trout and herring the outstanding nature of the pigeon liver enzyme in acetylating very weakly basic amines could be demonstrated. It is shown that the enzyme is quite flexible concerning sterically different acceptor amines, because arylamines whose amino group was effected by large o-substituents could be quantitatively acetylated. After enzymatic acetylation of the first amino group, 1,2-phenylendiamine formed the heterocyclic compound 2-methylbenzimidazole by a spontaneous condensation reaction. There is evidence that with distinct amines formation of heterocyclic compounds may also occur in vivo.

Artifacts Generated During Azoalkane Peroxy Radical Oxidative Stress Testing of Pharmaceuticals Containing Primary and Secondary Amines.

PubMed

Nefliu, Marcela; Zelesky, Todd; Jansen, Patrick; Sluggett, Gregory W; Foti, Christopher; Baertschi, Steven W; Harmon, Paul A

2015-12-01

We report artifactual degradation of pharmaceutical compounds containing primary and secondary amines during peroxy radical-mediated oxidative stress carried out using azoalkane initiators. Two degradation products were detected when model drug compounds dissolved in methanol/water were heated to 40°C with radical initiators such as 2,2'-azobis(2-methylpropionitrile) (AIBN). The primary artifact was identified as an α-aminonitrile generated from the reaction of the amine group of the model drug with formaldehyde and hydrogen cyanide, generated as byproducts of the stress reaction. A minor artifact was generated from the reaction between the amine group and isocyanic acid, also a byproduct of the stress reaction. We report the effects of pH, initiator/drug molar ratio, and type of azoalkane initiator on the formation of these artifacts. Mass spectrometry and nuclear magnetic resonance were used for structure elucidation, whereas mechanistic studies, including stable isotope labeling experiments, cyanide analysis, and experiments exploring the effects of butylated hydroxyanisole addition, were employed to support the degradation pathways. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

pH-triggered conduction of amine-functionalized single ZnO wire integrated on a customized nanogap electronic platform

PubMed Central

2014-01-01

The electrical conductance response of single ZnO microwire functionalized with amine-groups was tested upon an acid pH variation of a solution environment after integration on a customized gold electrode array chip. ZnO microwires were easily synthesized by hydrothermal route and chemically functionalized with aminopropyl groups. Single wires were deposited from the solution and then oriented through dielectrophoresis across eight nanogap gold electrodes on a platform single chip. Therefore, eight functionalized ZnO microwire-gold junctions were formed at the same time, and being integrated on an ad hoc electronic platform, they were ready for testing without any further treatment. Experimental and simulation studies confirmed the high pH-responsive behavior of the amine-modified ZnO-gold junctions, obtaining in a simple and reproducible way a ready-to-use device for pH detection in the acidic range. We also compared this performance to bare ZnO wires on the same electronic platform, showing the superiority in pH response of the amine-functionalized material. PMID:24484615

Elastomer toughened polyimide adhesives

NASA Technical Reports Server (NTRS)

St.clair, A. K.; St.clair, T. L. (Inventor)

1983-01-01

A rubber-toughened addition-type polyimide composition is disclosed which has excellent high temperature bonding characteristics in the fully cured state, and improved peel strength and adhesive fracture resistance physical property characteristics. The process for making the improved adhesive involves preparing the rubber containing amic acid prepolymer by chemically reacting an amine-terminated elastomer and an aromatic diamine with an aromatic dianhydride with which a reactive chain stopper anhydride was mixed, and utilizing solvent or mixture of solvents for the reaction.

Oxidation of primary amines to oximes with molecular oxygen using 1,1-diphenyl-2-picrylhydrazyl and WO3/Al2O3 as catalysts.

PubMed

Suzuki, Ken; Watanabe, Tomonari; Murahashi, Shun-Ichi

2013-03-15

The oxidative transformation of primary amines to their corresponding oximes proceeds with high efficiency under molecular oxygen diluted with molecular nitrogen (O2/N2 = 7/93 v/v, 5 MPa) in the presence of the catalysts 1,1-diphenyl-2-picrylhydrazyl (DPPH) and tungusten oxide/alumina (WO3/Al2O3). The method is environmentally benign, because the reaction requires only molecular oxygen as the terminal oxidant and gives water as a side product. Various alicyclic amines and aliphatic amines can be converted to their corresponding oximes in excellent yields. It is noteworthy that the oxidative transformation of primary amines proceeds chemoselectively in the presence of other functional groups. The key step of the present oxidation is a fast electron transfer from the primary amine to DPPH followed by proton transfer to give the α-aminoalkyl radical intermediate, which undergoes reaction with molecular oxygen and hydrogen abstraction to give α-aminoalkyl hydroperoxide. Subsequent reaction of the peroxide with WO3/Al2O3 gives oximes. The aerobic oxidation of secondary amines gives the corresponding nitrones. Aerobic oxidative transformation of cyclohexylamines to cyclohexanone oximes is important as a method for industrial production of ε-caprolactam, a raw material for Nylon 6.

Rhodium-catalysed syn-carboamination of alkenes via a transient directing group.

PubMed

Piou, Tiffany; Rovis, Tomislav

2015-11-05

Alkenes are the most ubiquitous prochiral functional groups--those that can be converted from achiral to chiral in a single step--that are accessible to synthetic chemists. For this reason, difunctionalization reactions of alkenes (whereby two functional groups are added to the same double bond) are particularly important, as they can be used to produce highly complex molecular architectures. Stereoselective oxidation reactions, including dihydroxylation, aminohydroxylation and halogenation, are well established methods for functionalizing alkenes. However, the intermolecular incorporation of both carbon- and nitrogen-based functionalities stereoselectively across an alkene has not been reported. Here we describe the rhodium-catalysed carboamination of alkenes at the same (syn) face of a double bond, initiated by a carbon-hydrogen activation event that uses enoxyphthalimides as the source of both the carbon and the nitrogen functionalities. The reaction methodology allows for the intermolecular, stereospecific formation of one carbon-carbon and one carbon-nitrogen bond across an alkene, which is, to our knowledge, unprecedented. The reaction design involves the in situ generation of a bidentate directing group and the use of a new cyclopentadienyl ligand to control the reactivity of rhodium. The results provide a new way of synthesizing functionalized alkenes, and should lead to the convergent and stereoselective assembly of amine-containing acyclic molecules.

Structure, IR and Raman spectra of phosphotrihydrazide studied by DFT

NASA Astrophysics Data System (ADS)

Furer, V. L.; Vandyukov, A. E.; Majoral, J. P.; Caminade, A. M.; Kovalenko, V. I.

2016-09-01

The FTIR and FT Raman measurements of the phosphotrihydrazide (S)P[N(Me)-NH2]3 have been performed. This compound is a zero generation dendrimer G0 with terminal amine groups. Structural optimization and normal mode analysis were obtained for G0 by the density functional theory (DFT). Optimized geometric bond length and angles obtained by DFT show good agreement with experiment. The amine terminal groups are characterized by the well-defined bands at 3321, 3238, 1614 cm- 1 in the experimental IR spectrum and by bands at 3327, 3241 cm- 1 in the Raman spectrum of G0. The experimental frequencies of asymmetric and symmetric NH2 stretching vibrations of amine group are lower than theoretical values due to intramolecular Nsbnd H ⋯ S hydrogen bond. This hydrogen bond is also responsible for higher experimental infrared intensity of these bands as compared with theoretical values. Relying on DFT calculations a complete vibrational assignment is proposed for the studied dendrimer.

A Bunch-Like Tertiary Amine Grafted Polysulfone Membrane for VRFBs with Simultaneously High Proton Conductivity and Low Vanadium Ion Permeability.

PubMed

Tan, Qinglong; Lu, Shanfu; Si, Jiangju; Wang, Haining; Wu, Chunxiao; Li, Xianfeng; Xiang, Yan

2017-04-01

Novel polysulfone membranes with bunch-like tertiary amine groups are synthesized with high ion selectivity and outstanding chemical stability for vanadium redox flow batteries (VRFBs). The bunch-like tertiary amine groups simultaneously act as an ionic conductor for proton hopping and vanadium ion transport obstacles. The performance of the membrane is tuned via controlling the grafting degree of the chloromethylated polysulfone. The results show that membranes show increasing proton over vanadium ion (σ/p) selectivity with increasing functional tertiary groups. VRFBs assembled with the prepared membranes demonstrate an impressive Coulombic efficiency of 98.9% and energy efficiency of 90.9% at a current density of 50 mA cm -2 . Furthermore, the prepared membrane reported in this work shows excellent stability in 1 m VO 2 + solution at 35 °C over 240 h. Overall, the synthesized polymers provide a new insight into the design of high-performance membranes toward VRFB applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Transition-Metal-Controlled Inorganic Ligand-Supported Non-Precious Metal Catalysts for the Aerobic Oxidation of Amines to Imines.

PubMed

Yu, Han; Zhai, Yongyan; Dai, Guoyong; Ru, Shi; Han, Sheng; Wei, Yongge

2017-10-09

Most state-of-art transition-metal catalysts usually require organic ligands, which are essential for controlling the reactivity and selectivity of reactions catalyzed by transition metals. However, organic ligands often suffer from severe problems including cost, toxicity, air/moisture sensitivity, and being commercially unavailable. Herein, we show a simple, mild, and efficient aerobic oxidation procedure of amines using inorganic ligand-supported non-precious metal catalysts 1, (NH 4 ) n [MMo 6 O 18 (OH) 6 ] (M=Cu 2+ ; Fe 3+ ; Co 3+ ; Ni 2+ ; Zn 2+ , n=3 or 4), synthesized by a simple one-step method in water at 100 °C, demonstrating that the catalytic activity and selectivity can be significantly improved by changing the central metal atom. In the presence of these catalysts, the catalytic oxidation of primary and secondary amines, as well as the coupling of alcohols and amines, can smoothly proceed to afford various imines with O 2 (1 atm) as the sole oxidant. In particular, the catalysts 1 have transition-metal ion core, and the planar arrangement of the six Mo VI centers at their highest oxidation states around the central heterometal can greatly enhance the Lewis acidity of catalytically active sites, and also enable the electrons in the center to delocalize onto the six edge-sharing MO 6 units, in the same way as ligands in traditional organometallic complexes. The versatility of this methodology maybe opens a path to catalytic oxidation through inorganic ligand-coordinated metal catalysis. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Aromatic amine metabolism: immunochemical relationships of N-acetyltransferase and N,O-acyltransferase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Land, S.; Allaben, W.T.; King, C.M.

1986-05-01

Mutagenic and carcinogenic aromatic amines are acetylated in most organisms. Acetyl CoA and arylhydroxamic acids can serve as acetyl donors for N-Acetylation of amines to yield stable amides, or by O-acetylation of hydroxylamine derivatives to produce reactive metabolites that can react covalently with nucleic acid. Polyclonal antibodies against rat arylhydroxamic acid, N,O-acyltransferase (AHAT) have been compared for their abilities to react with this enzyme and the acetyl CoA-dependent N-acetyltransferase (NAT) of the rat, rabbit, hamster, mouse and human. Liver cytosols were treated with increasing quantities of antibodies from immune or control rabbits. Immune complexes were removed by treatment with proteinmore » A-Sepharose before assay of nucleic acid adduct formation by AHAT activation of N-hydroxy-2-acetylaminofluorene and the acetylation of 2-aminofluorene by NAT. Both rat activities, the AHAT of the hamster and the NAT of the mouse and human were removed by this treatment. No decrease in NAT activity of hamster, or of either rabbit cytosol activity was observed. Neither mouse nor human liver has appreciable AHAT activity. These data support the idea that AHAT and NAT of rat, AHAT of hamster and NAT of mouse and human liver are immunochemically related, but that NAT of the hamster is an immunochemically distinct peptide.« less

Comparison of the reactivity of alkyl and alkyl amine precursors with native oxide GaAs(100) and InAs(100) surfaces

NASA Astrophysics Data System (ADS)

Henegar, A. J., , Dr.; Gougousi, T., , Prof.

2016-12-01

In this manuscript we compare the interaction of alkyl (trimethyl aluminum) and alkyl amine (tetrakis dimethylamino titanium) precursors during thermal atomic layer deposition with III-V native oxides. For that purpose we deposit Al2O3 and TiO2, using H2O as the oxidizer, on GaAs(100) and InAs(100) native oxide surfaces. We find that there are distinct differences in the behavior of the two films. For the Al2O3 ALD very little native oxide removal happens after the first few ALD cycles while the interaction of the alkyl amine precursor for TiO2 and the native oxides continues well after the surface has been covered with 2 nm of TiO2. This difference is traced to the superior properties of Al2O3 as a diffusion barrier. Differences are also found in the behavior of the arsenic oxides of the InAs and GaAs substrates. The arsenic oxides from the InAs surface are found to mix more efficiently in the growing dielectric film than those from the GaAs surface. This difference is attributed to lower native oxide stability as well as an initial diffusion path formation by the indium oxides.

Secondary Amine Functional Disiloxanes as CO2 Sorbents

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Brien, MJ; Farnum, RL; Perry, RJ

2014-05-01

A series of two different types of secondary amine functional disiloxanes were prepared and screened as CO2 capture solvents. The first group of materials contained RNHCH2CH2CH2 side chains where the R groups were C1-6 alkyls. When R was a primary alkyl group, these materials exhibited CO2 uptake values slightly in excess of theoretical. As the alkyl groups were changed to more sterically hindered secondary or tertiary alkyls, the uptake was less efficient. Heats of absorption values for these materials were generally in the range 2000-2200 kJ/kg of CO2, values significantly lower than those obtained for primary amine functional disiloxanes (2500-2700more » kJ/kg of CO2). Also explored were a series of secondary amine functional disiloxanes with X-CH2CH2NH-CH2CH2CH2 - substituents. When X was an electron-donating group (RO-, R2N-, RO-CH2-) the CO2 uptake was also in excess of theoretical. Interestingly, these compounds were generally found to produce carbamate salts that were flowable, low-viscosity oils. Furthermore, the heat of absorption values determined for these materials were even lower. Most compounds gave values below 2000 kJ/kg of CO2. Overall the most promising results were obtained with a methoxyethylaminopropyl derivative, an ethoxyethylaminopropyl-containing material, and a dimethylaminoethylaminopropyl-based compound. These materials showed excellent CO2 uptake, had low heats of absorption, and produced carbamate salts that were flowable liquids even at room temperature.« less

Synthesis and in vitro characterization of a novel S-protected thiolated alginate.

PubMed

Hauptstein, Sabine; Dezorzi, Stefanie; Prüfert, Felix; Matuszczak, Barbara; Bernkop-Schnürch, Andreas

2015-06-25

The object of this study was to synthesize and characterize a novel S-protected thiolated polymer with a high degree of modification. In this regard, an alginate-cysteine and an alginate-cysteine-2-mercaptonicotinic acid conjugate were synthesized. To achieve a high coupling rate of the thiol group bearing ligand cysteine to the polymer, the carbohydrate was activated by an oxidative ring opening with sodium periodate followed by a reductive amination to bind the primary amino group of cysteine to resulting reactive aldehyde groups. The obtained thiolated polymer displayed 1561±130μmol thiol groups per gram polymer. About one third of these thiol groups were S-protected by the implementation of a thiol bearing aromatic protection group via disulfide bond formation. Test tablets of both modified polymers showed improved stability against oxidation in aqueous environment compared to the unmodified alginate and exhibit higher water-uptake capacity. Rheological investigations revealed an increased viscosity of the S-protected thiolated polymer whereat the thiolated non S-protected polymer showed gelling properties after the addition of hydrogen peroxide. The mucoadhesive properties could be improved significantly for both derivatives and no alteration in biocompatibility tested on Caco-2 cell monolayer employing an MTT assay could be detected after modification. According to these results, both new derivatives seem promising for various applications. Copyright © 2015 Elsevier Ltd. All rights reserved.

Direct Air Capture of CO2 with an Amine Resin: A Molecular Modeling Study of the CO2 Capturing Process

PubMed Central

2017-01-01

Several reactions, known from other amine systems for CO2 capture, have been proposed for Lewatit R VP OC 1065. The aim of this molecular modeling study is to elucidate the CO2 capture process: the physisorption process prior to the CO2-capture and the reactions. Molecular modeling yields that the resin has a structure with benzyl amine groups on alternating positions in close vicinity of each other. Based on this structure, the preferred adsorption mode of CO2 and H2O was established. Next, using standard Density Functional Theory two catalytic reactions responsible for the actual CO2 capture were identified: direct amine and amine-H2O catalyzed formation of carbamic acid. The latter is a new type of catalysis. Other reactions are unlikely. Quantitative verification of the molecular modeling results with known experimental CO2 adsorption isotherms, applying a dual site Langmuir adsorption isotherm model, further supports all results of this molecular modeling study. PMID:29142339

A metal-free general procedure for oxidation of secondary amines to nitrones.

PubMed

Gella, Carolina; Ferrer, Eric; Alibés, Ramon; Busqué, Félíx; de March, Pedro; Figueredo, Marta; Font, Josep

2009-08-21

An efficient and metal-free protocol for direct oxidation of secondary amines to nitrones has been developed, using Oxone in a biphasic basic medium as the sole oxidant. The method is general and tolerant with other functional groups or existing stereogenic centers, providing rapid access to enantiomerically pure compounds in good yields.

Transition Metal-Free Selective Double sp(3) C-H Oxidation of Cyclic Amines to 3-Alkoxyamine Lactams.

PubMed

Osorio-Nieto, Urbano; Chamorro-Arenas, Delfino; Quintero, Leticia; Höpfl, Herbert; Sartillo-Piscil, Fernando

2016-09-16

The first chemical method for selective dual sp(3) C-H functionalization at the alpha-and beta positions of cyclic amines to their corresponding 3-alkoxyamine lactams is reported. Unlike traditional Cα-H oxidation of amines to amides mediated by transition metals, the present protocol, which involves the use of NaClO2/TEMPO/NaClO in either aqueous or organic solvent, not only allows the Cα-H oxidation but also the subsequent functionalization of the unreactive β-methylene group in an unprecedented tandem fashion and using environmentally friendly reactants.

Diamond surface functionalization with biomimicry - Amine surface tether and thiol moiety for electrochemical sensors

NASA Astrophysics Data System (ADS)

Sund, James B.; Causey, Corey P.; Wolter, Scott D.; Parker, Charles B.; Stoner, Brian R.; Toone, Eric J.; Glass, Jeffrey T.

2014-05-01

The surface of conducting diamond was functionalized with a terminal thiol group that is capable of binding and detecting nitrogen-oxygen species. The functionalization process employed multiple steps starting with doped diamond films grown by plasma enhanced chemical vapor deposition followed by hydrogen termination and photochemical attachment of a chemically protected amine alkene. The surface tether was deprotected to reveal the amine functionality, which enabled the tether to be extended with surface chemistry to add a terminal thiol moiety for electrochemical sensing applications. Each step of the process was validated using X-ray photoelectron spectroscopy analysis.

Optimization of functionalization conditions for protein analysis by AFM

NASA Astrophysics Data System (ADS)

Arroyo-Hernández, María; Daza, Rafael; Pérez-Rigueiro, Jose; Elices, Manuel; Nieto-Márquez, Jorge; Guinea, Gustavo V.

2014-10-01

Activated vapor silanization (AVS) is used to functionalize silicon surfaces through deposition of amine-containing thin films. AVS combines vapor silanization and chemical vapor deposition techniques and allows the properties of the functionalized layers (thickness, amine concentration and topography) to be controlled by tuning the deposition conditions. An accurate characterization is performed to correlate the deposition conditions and functional-film properties. In particular, it is shown that smooth surfaces with a sufficient surface density of amine groups may be obtained with this technique. These surfaces are suitable for the study of proteins with atomic force microscopy.

O2 and CO binding to tetraaza-tripodal-capped iron(II) porphyrins.

PubMed

Ruzié, Christian; Even, Pascale; Ricard, David; Roisnel, Thierry; Boitrel, Bernard

2006-02-06

A series of tris(2-aminoethylamine) (tren) capped iron(II) porphyrins has been synthesized and characterized and their affinities for dioxygen and carbon monoxide measured. The X-ray structure of the basic scaffold with nickel inserted in the porphyrin is also reported. All the ligands differ by the nature of the group(s) attached to the secondary amine functions of the cap. These various substitutions were introduced to probe if a hydrogen bond with these secondary amine groups acting as the donor could rationalize the high affinity of these myoglobin models. This work clearly indicates that the cage structure of the tren predominates over all the other appended groups with the exception of p-nitrophenol.

An Inner-Sphere Mechanism for Molecular Oxygen Reduction Catalyzed by Copper Amine Oxidases

PubMed Central

Mukherjee, Arnab; Smirnov, Valeriy V.; Lanci, Michael P.; Brown, Doreen E.; Shepard, Eric M.; Dooley, David M.; Roth, Justine P.

2008-01-01

Copper and topaquinone (TPQ) containing amine oxidases utilize O2 for the metabolism of biogenic amines while concomitantly generating H2O2 for use by the cell. The mechanism of O2 reduction has been the subject of long-standing debate due to the obscuring influence of a proton-coupled electron transfer between the tyrosine-derived TPQ and copper, a rapidly established equilibrium precluding assignment of the enzyme in its reactive form. Here we show that substrate-reduced pea seedling amine oxidase (PSAO) exists predominantly in the CuI, TPQ semiquinone state. A new mechanistic proposal for O2 reduction is advanced on the basis of thermodynamic considerations together with kinetic studies (at varying pH, temperature and viscosity), the identification of steady-state intermediates and the analysis of competitive oxygen kinetic isotope effects: 18O KIEs, [kcat/KM(16,16O2)]/[kcat/KM(16,18O2)]. The 18O KIE = 1.0136 ± 0.0013 at pH 7.2 is independent of temperature from 5 to 47°C and insignificantly changed to 1.0122 ± 0.0020 upon raising the pH to 9, thus indicating the absence of kinetic complexity. Using density functional methods, the effect is found to be precisely in the range expected for reversible O2 binding to CuI to afford a superoxide, [CuII(η1-O2)−I]+, intermediate. Electron transfer from the TPQ semiquinone follows in the first irreversible step to form a peroxide, CuII(η1-O2)−II, intermediate driving the reduction of O2. The similar 18O KIEs reported for copper amine oxidases from other sources raise the possibility that all enzymes react by related inner-sphere mechanisms although additional experiments are needed to test this proposal. PMID:18582059

Frustrated Lewis pairs: from concept to catalysis.

PubMed

Stephan, Douglas W

2015-02-17

CONSPECTUS: Frustrated Lewis pair (FLP) chemistry has emerged in the past decade as a strategy that enables main-group compounds to activate small molecules. This concept is based on the notion that combinations of Lewis acids and bases that are sterically prevented from forming classical Lewis acid-base adducts have Lewis acidity and basicity available for interaction with a third molecule. This concept has been applied to stoichiometric reactivity and then extended to catalysis. This Account describes three examples of such developments: hydrogenation, hydroamination, and CO2 reduction. The most dramatic finding from FLP chemistry was the discovery that FLPs can activate H2, thus countering the long-existing dogma that metals are required for such activation. This finding of stoichiometric reactivity was subsequently evolved to employ simple main-group species as catalysts in hydrogenations. While the initial studies focused on imines, subsequent studies uncovered FLP catalysts for a variety of organic substrates, including enamines, silyl enol ethers, olefins, and alkynes. Moreover, FLP reductions of aromatic anilines and N-heterocycles have been developed, while very recent extensions have uncovered the utility of FLP catalysts for ketone reductions. FLPs have also been shown to undergo stoichiometric reactivity with terminal alkynes. Typically, either deprotonation or FLP addition reaction products are observed, depending largely on the basicity of the Lewis base. While a variety of acid/base combinations have been exploited to afford a variety of zwitterionic products, this reactivity can also be extended to catalysis. When secondary aryl amines are employed, hydroamination of alkynes can be performed catalytically, providing a facile, metal-free route to enamines. In a similar fashion, initial studies of FLPs with CO2 demonstrated their ability to capture this greenhouse gas. Again, modification of the constituents of the FLP led to the discovery of reaction systems that demonstrated stoichiometric reduction of CO2 to either methanol or CO. Further modification led to the development of catalytic systems for the reduction of CO2 by hydrosilylation and hydroboration or deoxygenation. As each of these areas of FLP chemistry has advanced from the observation of unusual stoichiometric reactions to catalytic processes, it is clear that the concept of FLPs provides a new strategy for the design and application of main-group chemistry and the development of new metal-free catalytic processes.

Novel Micro/Nano Approaches for Glucose Measurement Using pH-Sensitive Hydrogels

DTIC Science & Technology

2005-06-01

hydrochloride ) (PAH) (polycation). A total of three bilayers of GOx/PAH were assembled, and enzyme activity was confirmed by colorimetric assay...D- glucosamine residues in chitosan can be conjugated with amine-reactive dyes, such as succinimidyl esters (Alexa Fluor 647TM, CY5®), isothiocyanates...were found to be: A 4 94 nm=0.153276 MW=161 [D- glucosamine ]=0.77g/L Sdye=68000cm-M-1 DOL=4.71 x 10-’ Therefore, the labeling ratio of FITC:chitosan

Photochemical Carboxylation of Activated C(sp3 )-H Bonds with CO2.

PubMed

Gui, Yong-Yuan; Zhou, Wen-Jun; Ye, Jian-Heng; Yu, Da-Gang

2017-04-10

From ugly duckling to beautiful C1: Although CO 2 may represent an ideal C1 source, it is challenging to use it as a raw material and direct carboxylation with CO 2 has mainly been confined to highly reactive species. However, recent significant breakthroughs have been made in photochemical carboxylation of challenging, un-acidic, C(sp 3 )-H bonds, including benzylic, allylic and amine C-H bonds. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Medullary layer activity of the rat adrenals after a flight on the Kosmos-1129 biosatellite].

PubMed

Kvetnanský, R; Blazicek, P; Tigranian, R A

1982-01-01

After a 18.5-day space flight on Cosmos-1129 rat adrenals were investigated for the concentration of catecholamines and activity of enzymes involved in their synthesis, i.e. tyrosine hydroxylase, dopamine-beta-hydroxylase, and phenyl ethanol amine-N-methyl transferase. It was found that inflight the sympatho-adreno-medullary system of rats was not exposed to a prolonged or strong stressogenic effect. Postflight the rats showed an increased reactivity to the immobilization stress.

Diamines Containing Pendent Phenylethynyl Groups

NASA Technical Reports Server (NTRS)

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

1997-01-01

Controlled molecular weight imide oligomers and co-oligomers containing pendent phenylethynyl groups (PEPIs) and endcapped with nonreactive or phenylethynyl groups have been prepared by the cyclodehydration of the precursor amide acid oligomers or co-oligomers containing pendent phenylethynyl groups and endcapped with nonreactive or phenylethynyl groups. The amine terminated amide acid oligomers or co-oligomers are prepared from the reaction of dianhydride(s) with an excess of diamine(s) and diamine containing pendent phenylethynyl groups and subsequently endcapped with a phenylethynyl phthalic anhydride or monofunctional anhydride. The anhydride terminated amide acid oligomers and co-oligomers are prepared from the reaction of diamine(s) and diamine containing pendent phenylethynyl group(s) with an excess of dianhydride(s) and subsequently endcapped with a phenylethynyl amine or monofunctional amine. The polymerizations are carried out in polar aprotic solvents such as and N,N-dimethylacetamide under nitrogen at room temperature. The amide acid oligomers or co-oligomers are subsequently cyclodehydrated either thermally or chemically to the corresponding imide oligomers. The polymers and copolymers prepared from these materials exhibit a unique and unexpected combination of properties that includes higher glass transition temperatures after curing and higher retention of neat resin, adhesive and carbon fiber reinforced mechanical properties at temperatures up to 204 C under wet conditions without sacrificing melt flow behavior and processability as compared to similar materials. These materials are useful as adhesives, coatings, films, moldings, and composite matrices.

Chelate effects in sulfate binding by amide/urea-based ligands.

PubMed

Jia, Chuandong; Wang, Qi-Qiang; Begum, Rowshan Ara; Day, Victor W; Bowman-James, Kristin

2015-07-07

The influence of chelate and mini-chelate effects on sulfate binding was explored for six amide-, amide/amine-, urea-, and urea/amine-based ligands. Two of the urea-based hosts were selective for SO4(2-) in water-mixed DMSO-d6 systems. Results indicated that the mini-chelate effect provided by a single urea group with two NH binding sites appears to provide enhanced binding over two amide groups. Furthermore, additional urea binding sites incorporated into the host framework appeared to overcome to some extent competing hydration effects with increasing water content.

Tunneling conductance of amine-linked alkyl chains.

PubMed

Prodan, Emil; Car, Roberto

2008-06-01

The tunneling transport theory developed in ref 9 (Phys. Rev. B 2007, 76, 115102) is applied to molecular devices made of alkyl chains linked to gold electrodes via amine groups. Using the analytic expression of the tunneling conductance derived in our previous work, we identify the key physical quantities that characterize the conductance of these devices. By investigating the transport characteristics of three devices, containing four, six, and eight methyl groups, we extract the dependence of the tunneling conductance on the chain's length, which is an exponential decay law in agreement with recent experimental data.

Highly Sensitive Thin-Film Field-Effect Transistor Sensor for Ammonia with the DPP-Bithiophene Conjugated Polymer Entailing Thermally Cleavable tert-Butoxy Groups in the Side Chains.

PubMed

Yang, Yang; Zhang, Guanxin; Luo, Hewei; Yao, Jingjing; Liu, Zitong; Zhang, Deqing

2016-02-17

The sensing and detection of ammonia have received increasing attention in recent years because of the growing emphasis on environmental and health issues. In this paper, we report a thin-film field-effect transistor (FET)-based sensor for ammonia and other amines with remarkable high sensitivity and satisfactory selectivity by employing the DPP-bithiophene conjugated polymer pDPPBu-BT in which tert-butoxycarboxyl groups are incorporated in the side chains. This polymer thin film shows p-type semiconducting property. On the basis of TGA and FT-IR analysis, tert-butoxycarboxyl groups can be transformed into the -COOH ones by eliminating gaseous isobutylene after thermal annealing of pDPPBu-BT thin film at 240 °C. The FET with the thermally treated thin film of pDPPBu-BT displays remarkably sensitive and selective response toward ammonia and volatile amines. This can be attributed to the fact that the elimination of gaseous isobutylene accompanies the formation of nanopores with the thin film, which will facilitate the diffusion and interaction of ammonia and other amines with the semiconducting layer, leading to high sensitivity and fast response for this FET sensor. This FET sensor can detect ammonia down to 10 ppb and the interferences from other volatile analytes except amines can be negligible.

Naked eye and spectrophotometric detection of chromogenic insecticide in aquaculture using amine functionalized gold nanoparticles in the presence of major interferents

NASA Astrophysics Data System (ADS)

Loganathan, C.; John, S. Abraham

2017-02-01

Detection of a chromogenic insecticide, malachite green (MG) using 3,5-diamino-1,2,4-triazole capped gold nanoparticles (DAT-AuNPs) by both naked eye and spectrophotometry was described in this paper. The DAT-AuNPs were prepared by wet chemical method and show absorption maximum at 518 nm. The zeta potential of DAT-AuNPs was found to be - 39.9 mV, suggesting that one of the amine groups of DAT adsorbed on the surface of AuNPs and the other amine group stabilizes the AuNPs from aggregation. The wine red color DAT-AuNPs changes to violet while adding 25 μM MG whereas the absorption band at 518 nm was increased and shifted towards longer wavelength. However, addition of 70 μM MG leads to the aggregation of DAT-AuNPs. This is due to strong electrostatic interaction between ammonium ion of MG and the free amine group of DAT. Based on the color change and shift in SPR band, 25 and 5 μM MG can be easily detected by naked eye and spectrophotometry. The DAT-AuNPs show high selectivity towards MG even in the presence of 5000-fold higher concentrations of common interferents. The practical application was successfully demonstrated by determining MG in fish farm water.

Amine-functionalized, multi-arm star polymers: A novel platform for removing glyphosate from aqueous media.

PubMed

Samuel, Lianna; Wang, Ran; Dubois, Geraud; Allen, Robert; Wojtecki, Rudy; La, Young-Hye

2017-02-01

We describe a novel method for efficiently removing glyphosate from aqueous media via adsorption onto highly functionalized star-shaped polymeric particles. These particles have a polystyrene core with more than 35 attached methacrylate polymer arms, each containing a plurality of pendant amines (poly(dimethylamino ethyl methacrylate): PDMAEMA) that are partially protonated in water. Kinetic studies demonstrate that these star-polymers successfully remove up to 93% of glyphosate present in aqueous solution (feed concentration: 5 ppm), within 10 min contact time, outperforming activated carbon, which removed 33% after 20 min. On these star-polymers, glyphosate adsorption closely follows the Langmuir model indicating monolayer coverage at most. Ionic interaction between the protonated amines and glyphosate's dissociated carboxylic and phosphoric acid groups lead to effective glyphosate capture even at feed concentrations below 1 ppm. Surface charge of these star polymers and dissociation of glyphosate are both influenced by pH, thus glyphosate removal efficiency increases from 63% to 93% when pH increases from 4.2 to 7.7. NMR studies conducted with butylamine as a proxy for these polymeric particles confirm that the amine group binds with both glyphosate's carboxylic and phosphoric acid groups when its concentrations are in a 2:1 or higher molar ratio with glyphosate. Copyright © 2016 Elsevier Ltd. All rights reserved.

Catalyst–Controlled C–O versus C–N Allylic Functionalization of Terminal Olefins

PubMed Central

Strambeanu, Iulia I.; White, M. Christina

2014-01-01

The divergent synthesis of syn-1, 2-aminoalcohol or syn-1,2-diamine precursors from a common terminal olefin has been accomplished using a combination of palladium(II) catalysis with Lewis acid co-catalysis. Palladium(II)/bis-sulfoxide catalysis with a silver triflate co-catalyst leads for the first time to anti-2-aminooxazolines (C—O) in good to excellent yields. Simple removal of the bis-sulfoxide ligand from this reaction results in a complete switch in reactivity to afford anti-imidazolidinone products (C—N) in good yields and excellent diastereoselectivities. Mechanistic studies suggest the divergent C—O versus C—N reactivity from a common ambident nucleophile arises due to a switch in mechanism from allylic C—H cleavage/functionalization to olefin isomerization/oxidative amination. PMID:23855956

Chemical Modeling for Predicting the Abundances of Certain Aldimines and Amines in Hot Cores

NASA Astrophysics Data System (ADS)

Sil, Milan; Gorai, Prasanta; Das, Ankan; Bhat, Bratati; Etim, Emmanuel E.; Chakrabarti, Sandip K.

2018-02-01

We consider six isomeric groups ({{CH}}3{{N}}, {{CH}}5{{N}}, {{{C}}}2{{{H}}}5{{N}}, {{{C}}}2{{{H}}}7{{N}}, {{{C}}}3{{{H}}}7{{N}}, and {{{C}}}3{{{H}}}9{{N}}) to review the presence of amines and aldimines within the interstellar medium (ISM). Each of these groups contains at least one aldimine or amine. Methanimine ({{CH}}2{NH}) from {{CH}}3{{N}} and methylamine ({{CH}}3{{NH}}2) from {{CH}}5{{N}} isomeric group were detected a few decades ago. Recently, the presence of ethanimine ({{CH}}3{CHNH}) from {{{C}}}2{{{H}}}5{{N}} isomeric group has been discovered in the ISM. This prompted us to investigate the possibility of detecting any aldimine or amine from the very next three isomeric groups in this sequence: {{{C}}}2{{{H}}}7{{N}}, {{{C}}}3{{{H}}}7{{N}}, and {{{C}}}3{{{H}}}9{{N}}. We employ high-level quantum chemical calculations to estimate accurate energies of all the species. According to enthalpies of formation, optimized energies, and expected intensity ratio, we found that ethylamine (precursor of glycine) from {{{C}}}2{{{H}}}7{{N}} isomeric group, (1Z)-1-propanimine from {{{C}}}3{{{H}}}7{{N}} isomeric group, and trimethylamine from {{{C}}}3{{{H}}}9{{N}} isomeric group are the most viable candidates for the future astronomical detection. Based on our quantum chemical calculations and from other approximations (from prevailing similar types of reactions), a complete set of reaction pathways to the synthesis of ethylamine and (1Z)-1-propanimine is prepared. Moreover, a large gas-grain chemical model is employed to study the presence of these species in the ISM. Our modeling results suggest that ethylamine and (1Z)-1-propanimine could efficiently be formed in hot-core regions and could be observed with present astronomical facilities. Radiative transfer modeling is also implemented to additionally aid their discovery in interstellar space.

Rapid fixation of methylene chloride by a macrocyclic amine.

PubMed

Lee, Jung-Jae; Stanger, Keith J; Noll, Bruce C; Gonzalez, Carlos; Marquez, Manuel; Smith, Bradley D

2005-03-30

A simple macrocyclic amine is alkylated by methylene chloride to give a quaternary ammonium chloride salt. When methylene chloride is the solvent, the reaction exhibits pseudo-first-order kinetics, and the reaction half-life at 25.0 degrees C is 2.0 min. The reaction half-life for a structurally related, acyclic amine is approximately 50 000 times longer. Detailed calculations favor a mechanism where the methylene chloride associates with the macrocycle to form an activated prereaction complex. The macrocyclic nitrogen subsequently attacks the methylene chloride with a classic SN2 trajectory, and although the carbon-chlorine bond breaks, the chloride leaving group does not separate from the newly formed cationic macrocycle, such that the product is a tightly associated ion-pair. X-ray crystal structures of the starting amine and the product salt, as well as kinetic data, support this mechanism.

Structure-Activity Relationships for Rates of Aromatic Amine Oxidation by Manganese Dioxide.

PubMed

Salter-Blanc, Alexandra J; Bylaska, Eric J; Lyon, Molly A; Ness, Stuart C; Tratnyek, Paul G

2016-05-17

New energetic compounds are designed to minimize their potential environmental impacts, which includes their transformation and the fate and effects of their transformation products. The nitro groups of energetic compounds are readily reduced to amines, and the resulting aromatic amines are subject to oxidation and coupling reactions. Manganese dioxide (MnO2) is a common environmental oxidant and model system for kinetic studies of aromatic amine oxidation. In this study, a training set of new and previously reported kinetic data for the oxidation of model and energetic-derived aromatic amines was assembled and subjected to correlation analysis against descriptor variables that ranged from general purpose [Hammett σ constants (σ(-)), pKas of the amines, and energies of the highest occupied molecular orbital (EHOMO)] to specific for the likely rate-limiting step [one-electron oxidation potentials (Eox)]. The selection of calculated descriptors (pKa, EHOMO, and Eox) was based on validation with experimental data. All of the correlations gave satisfactory quantitative structure-activity relationships (QSARs), but they improved with the specificity of the descriptor. The scope of correlation analysis was extended beyond MnO2 to include literature data on aromatic amine oxidation by other environmentally relevant oxidants (ozone, chlorine dioxide, and phosphate and carbonate radicals) by correlating relative rate constants (normalized to 4-chloroaniline) to EHOMO (calculated with a modest level of theory).

Synergistic antioxidant activity of milk sphingomyeline and its sphingoid base with α-tocopherol on fish oil triacylglycerol.

PubMed

Shimajiri, Junki; Shiota, Makoto; Hosokawa, Masashi; Miyashita, Kazuo

2013-08-21

The effects of milk phospholipids (PLs), sphingolipids (SLs), and their sphingoid backbone on the oxidation of fish oil triacylglycerol (TAG) were examined with or without α-tocopherol. All compounds had little effect on the TAG oxidation in the absence of α-tocopherol. On the other hand, they could act synergistically with α-tocopherol. The highest synergistic activity was shown by sphingoid bases, followed by sphingomyelin (SPM) and other amine-containing PLs and SLs. This result showed that the synergistic activity increased with an increasing concentration of amine group of PLs, SLs, or sphingoid bases in the reaction mixture. The comparison of changes in α-tocopherol content in fish oil TAG and tricaprylin suggested that antioxidant compounds would be formed from the amine group and the lipid oxidation products in a mild oxidation condition controlled by α-tocopherol.

Site-Selective Copper-Catalyzed Amination and Azidation of Arenes and Heteroarenes via Deprotonative Zincation.

PubMed

Hendrick, Charles E; Bitting, Katie J; Cho, Seoyoung; Wang, Qiu

2017-08-23

Arene amination is achieved by site-selective C-H zincation followed by copper-catalyzed coupling with O-benzoylhydroxylamines under mild conditions. Key to this success is ortho-zincation mediated by lithium amidodiethylzincate base that is effective for a wide range of arenes, including nonactivated arenes bearing simple functionalities such as fluoride, chloride, ester, amide, ether, nitrile, and trifluoromethyl groups as well as heteroarenes including indole, thiophene, pyridine, and isoquinoline. An analogous C-H azidation is also accomplished using azidoiodinane for direct introduction of a useful azide group onto a broad scope of arenes and heteroarenes. These new transformations offer rapid access to valuable and diverse chemical space of aminoarenes. Their broad applications in organic synthesis and drug discovery are demonstrated in the synthesis of novel analogues of natural product (-)-nicotine and antidepressant sertraline by late-stage amination and azidation reactions.

SuFEx-Based Polysulfonate Formation from Ethenesulfonyl Fluoride-Amine Adducts

DOE PAGES

Wang, Hua; Zhou, Feng; Ren, Gerui; ...

2017-05-18

In this article, the SuFEx-based polycondensation between bisalkylsulfonyl fluorides (AA monomers) and bisphenol bis(t-butyldimethylsilyl) ethers (BB monomers) using [Ph 3P=N-PPh 3] +[HF 2] - as the catalyst is described. The AA monomers were prepared via the highly reliable Michael addition of ethenesulfonyl fluoride and amines/anilines while the BB monomers were obtained from silylation of bisphenols by t-butyldimethylsilyl chloride. With these reactions, a remarkable diversity of monomeric building blocks was achieved by exploiting readily available amines, anilines, and bisphenols as starting materials. The SuFEx-based polysulfonate formation reaction exhibited excellent efficiency and functional group tolerance, producing polysulfonates with a variety of sidemore » chain functionalities in >99 % conversion within 10 min to 1 h. When bearing an orthogonal group on the side chain, the polysulfonates can be further functionalized via click-chemistry-based post-polymerization modification.« less

N-substituted imidazolines and ethylenediamines and their action on alpha- and beta-adrenergic receptors.

PubMed

Hamada, A; Yaden, E L; Horng, J S; Ruffolo, R R; Patil, P N; Miller, D D

1985-09-01

A series of N-substituted imidazolines and ethylenediamines were synthesized and examined for their activity in alpha- and beta-adrenergic systems. The length of the intermediate side chain between the catechol and imidazoline ring or the amine of the ethylenediamine segment was shown to affect the adrenergic activity. N-[2-(3,4-Dihydroxyphenyl)ethyl]imidazoline hydrochloride (2) and N-[2-(3,4-dihydroxyphenyl)ethyl]ethylenediamine dihydrochloride (4), both with two methylene groups between the catechol and amine segment, were found to be somewhat selective for alpha 2-adrenergic receptors while 1-(3,4-dihydroxybenzyl)imidazoline hydrochloride (1) and N-2-(3,4-dihydroxybenzyl)ethylenediamine dihydrochloride (3), both with one methylene group between the catechol and amine segment, were more selective for alpha1-adrenergic receptors in a pithed rat model. Of the four compounds examined, only compound 2 showed significant direct activity on beta1- and beta2-adrenergic receptors.

Pd-catalyzed intramolecular oxidative C-H amination: synthesis of carbazoles.

PubMed

Youn, So Won; Bihn, Joon Hyung; Kim, Byung Seok

2011-07-15

A Pd-catalyzed oxidative C-H amination of N-Ts-2-arylanilines under ambient temperature using Oxone as an inexpensive, safe, and easy-to-handle oxidant has been developed. This process represents a green and practical method for the facile construction of carbazoles with a broad substrate scope and wide functional group tolerance. © 2011 American Chemical Society

Monitoring of biogenic amines and drugs of various therapeutic groups in urine samples with use of HPLC.

PubMed

Baranowska, Irena; Płonka, Joanna

2016-04-01

A high-performance liquid chromatography method for simultaneous separation and determination of biogenic amines [dopamine, epinephrine, serotonin and its six metabolites (normetanephrine, metanephrine, 3,4-dihydroxyphenylacetic acid, 4-hydroxy-3-methoxyphenylglycol, homovanilic acid and 5-hydroxyindoloacetic acid)] with drugs from different therapeutically groups [analgesics (paracetamol, metamizol), diuretics (furosemide) and antibiotics (cefazolin, fluconazole)] was developed. A chromatographic column with pre-column with octadecylsilane phase (C18e ) and two detectors - diode array serial connected and fluorescence - was used. Gradient elution of mixture of acetate buffer (pH 4.66) and methanol as a mobile phase was applied. The limit of detection (LOD) of 8-10 ng/mL and limit of quantitation (LOQ) of 24-30 ng/mL for biogenic amines, as well as the LOD of 50-100 ng/mL and the LOQ of 150-300 ng/mL for drugs, were determined. The applied sample preparation method allowed recoveries of 93% for the biogenic amines and 92% for the drugs to be achieved. The developed procedure has been applied to simultaneous determination of the examined compounds in urine samples and could be used in clinical analysis. Copyright © 2015 John Wiley & Sons, Ltd.

Amination of nitroazoles--a comparative study of structural and energetic properties.

PubMed

Zhao, Xiuxiu; Qi, Cai; Zhang, Lubo; Wang, Yuan; Li, Shenghua; Zhao, Fengqi; Pang, Siping

2014-01-14

In this work, 3-nitro-1H-1,2,4-triazole (1) and 3,5-dinitro-1H-pyrazole (2) were C-aminated and N-aminated using different amination agents, yielding their respective C-amino and N-amino products. All compounds were fully characterized by NMR (1H, 13C, 15N), IR spectroscopy, differential scanning calorimetry (DSC). X-ray crystallographic measurements were performed and delivered insight into structural characteristics as well as inter- and intramolecular interactions of the products. Their impact sensitivities were measured by using standard BAM fallhammer techniques and their explosive performances were computed using the EXPLO 5.05 program. A comparative study on the influence of those different amino substituents on the structural and energetic properties (such as density, stability, heat of formation, detonation performance) is presented. The results showed that the incorporation of an N-amino group into a nitroazole ring can improve nitrogen content, heat of formation and impact sensitivity, while the introduction of a C-amino group can enhance density, detonation velocity and pressure. The potential of N-amino and C-amino moieties for the design of next generation energetic materials is explored.

Room-Temperature, Ambient-Pressure Chemical Synthesis of Amine-Functionalized Hierarchical Carbon-Sulfur Composites for Lithium-Sulfur Battery Cathodes.

PubMed

Chae, Changju; Kim, Jinmin; Kim, Ju Young; Ji, Seulgi; Lee, Sun Sook; Kang, Yongku; Choi, Youngmin; Suk, Jungdon; Jeong, Sunho

2018-02-07

Recently, the achievement of newly designed carbon-sulfur composite materials has attracted a tremendous amount of attention as high-performance cathode materials for lithium-sulfur batteries. To date, sulfur materials have been generally synthesized by a sublimation technique in sealed containers. This is a well-developed technique for the synthesizing of well-ordered sulfur materials, but it is limited when used to scale up synthetic procedures for practical applications. In this study, we suggest an easily scalable, room-temperature/ambient-pressure chemical pathway for the synthesis of highly functioning cathode materials using electrostatically assembled, amine-terminated carbon materials. It is demonstrated that stable cycling performance outcomes are achievable with a capacity of 730 mAhg -1 at a current density of 1 C with good cycling stability by a virtue of the characteristic chemical/physical properties (a high conductivity for efficient charge conduction and the presence of a number of amine groups that can interact with sulfur atoms during electrochemical reactions) of composite materials. The critical roles of conductive carbon moieties and amine functional groups inside composite materials are clarified with combinatorial analyses by X-ray photoelectron spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy.

Tertiary amine derivatives of chlorochalcone as acetylcholinesterase (AChE) and buthylcholinesterase (BuChE) inhibitors: the influence of chlorine, alkyl amine side chain and α,β-unsaturated ketone group.

PubMed

Gao, Xiao-Hui; Zhou, Chao; Liu, Hao-Ran; Liu, Lin-Bo; Tang, Jing-Jing; Xia, Xin-Hua

2017-12-01

A new series of tertiary amine derivatives of chlorochalcone (4a∼4l) were designed, synthesized and evaluated for the effect on acetylcholinesterase (AChE) and buthylcholinesterase (BuChE). The results indicated that all compounds revealed moderate or potent inhibitory activity against AChE, and some possessed high selectivity for AChE over BuChE. The structure-activity investigation showed that the substituted position of chlorine significantly influenced the activity and selectivity. The alteration of tertiary amine group also leads to obvious change in bioactivity. Among them, IC 50 of compound 4l against AChE was 0.17 ± 0.06 µmol/L, and the selectivity was 667.2 fold for AChE over BuChE. Molecular docking and enzyme kinetic study on compound 4l suggested that it simultaneously binds to the catalytic active site (CAS) and peripheral anionic site (PAS) of AChE. Further study showed that the pyrazoline derivatives synthesized from chlorochalcones had weaker activity and lower selectivity in inhibiting AChE compared to that of chlorochalcone derivatives.

Dangerous liaisons: anion-induced protonation in phosphate-polyamine interactions and their implications for the charge states of biologically relevant surfaces.

PubMed

Laucirica, Gregorio; Marmisollé, Waldemar A; Azzaroni, Omar

2017-03-22

Although not always considered a preponderant interaction, amine-phosphate interactions are omnipresent in multiple chemical and biological systems. This study aims to answer questions that are still pending about their nature and consequences. We focus on the description of the charge state as surface charges constitute directing agents of the interaction of amine groups with either natural or synthetic counterparts. Our results allow us to quantitatively determine the relative affinities of HPO 4 2- and H 2 PO 4 - from the analysis of the influence of phosphates on the zeta-potential of amino-functionalized surfaces in a broad pH range. We show that phosphate anions enhance the protonation of amino groups and, conversely, charged amines induce further proton dissociation of phosphates, yielding a complex dependence of the surface effective charge on the pH and phosphate concentration. We also demonstrate that phosphate-amine interaction is specific and the modulation of surface charge occurs in the physiological phosphate concentration range, emphasizing its biochemical and biotechnological relevance and the importance of considering this veiled association in both in vivo and in vitro studies.

Influence of ultrasonic and sonic activation of epoxy-amine resin-based sealer on penetration of sealer into lateral canals.

PubMed

Arslan, Hakan; Abbas, Aneesh; Karatas, Ertugrul

2016-11-01

The aim of this study was to evaluate the efficacy of sonic and ultrasonic activation of epoxy-amine resin-based root canal sealer (2Seal; VDW GmbH, München, Germany) on penetration of the sealer into lateral canals compared to non-activated filling. Thirty-six single-rooted human anterior teeth were decoronated and prepared, using the ProTaper rotary system (Dentsply Maillefer, Ballaigues, Switzerland) to F4. After the completion of the clearing procedures, lateral canals were created at 2, 4, and 6 mm from the working length. The specimens were randomly divided into a control group (non-activated sealer application) and two experimental groups that received a sealer application with either sonic or ultrasonic activation. The root canals were filled using cold lateral compaction and images were obtained from each lateral canals at 40× magnification using a stereomicroscope. The sealer penetration was evaluated using a four-grade scoring system. The data were evaluated statistically using the Kruskal-Wallis and Mann-Whitney U tests with a 95 % confidence level (P = 0.05). The ultrasonic activation resulted in a better sealer penetration compared with the non-activated and sonically activated groups (P < 0.001). Sonic activation also resulted in better sealer penetration compared to the non-activated group (P < 0.001). The use of the ultrasonic activation of an epoxy-amine resin-based sealer promoted greater sealer penetration into the lateral canals. Sonic activation was not effective as ultrasonic activation, but was more effective than the non-activated group. The ultrasonic activation of an epoxy-amine resin-based sealer could be beneficial in filling procedures.

Novel Aryne Chemistry in Organic Synthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Zhijian

2006-12-12

Arynes are among the most intensively studied systems in chemistry. However, many aspects of the chemistry of these reactive intermediates are not well understood yet and their use as reagents in synthetic organic chemistry has been somewhat limited, due to the harsh conditions needed to generate arynes and the often uncontrolled reactivity exhibited by these species. Recently, o-silylaryl triflates, which can generate the corresponding arynes under very mild reaction conditions, have been found very useful in organic synthesis. This thesis describes several novel and useful methodologies by employing arynes, which generate from o-silylaryl triflates, in organic synthesis. An efficient, reliablemore » method for the N-arylation of amines, sulfonamides and carbamates, and the O-arylation of phenols and carboxylic acids is described in Chapter 1. Amines, sulfonamides, phenols, and carboxylic acids are good nucleophiles, which can react with arynes generated from a-silylaryl triflates to afford the corresponding N- and O-arylated products in very high yields. The regioselectivity of unsymmetrical arynes has also been studied. A lot of useful, functional groups can tolerate our reaction conditions. Carbazoles and dibenzofurans are important heteroaromatic compounds, which have a variety of biological activities. A variety of substituted carbazoles and dibenzofwans are readily prepared in good to excellent yields starting with the corresponding o-iodoanilines or o-iodophenols and o-silylaryl triflates by a treatment with CsF, followed by a Pd-catalyzed cyclization, which overall provides a one-pot, two-step process. By using this methodology, the carbazole alkaloid mukonine has been concisely synthesized in a very good yield. Insertion of an aryne into a σ-bond between a nucleophile and an electrophile (Nu-E) should potentially be a very beneficial process from the standpoint of organic synthesis. A variety of substituted ketones and sulfoxides have been synthesized in good yields via the intermolecular C-N σ-bond addition of amides and S-N σ-bond addition of sulfinamides to arynes under mild reaction conditions. The indazole moiety is a frequently found subunit in drug substances with important biological activities. Indazole analogues have been readily synthesized under mild reaction conditions by the [3+2] cycloaddition of a variety of diazo compounds with o-silylaryl triflates in the presence of CsF or TBAF. Polycyclic aromatic and heteroaromatic hydrocarbons have been synthesized in high yields by two different processes involving the Pd-catalyzed annulation of arynes. Both processes appear to involve the catalytic, stepwise coupling of two very reactive substrates, an aryne and an organopalladium species, to generate excellent yields of cross-coupled products.« less

Computational Investigation of Amine–Oxygen Exciplex Formation

PubMed Central

Haupert, Levi M.; Simpson, Garth J.; Slipchenko, Lyudmila V.

2012-01-01

It has been suggested that fluorescence from amine-containing dendrimer compounds could be the result of a charge transfer between amine groups and molecular oxygen [Chu, C.-C.; Imae, T. Macromol. Rapid Commun. 2009, 30, 89.]. In this paper we employ equation-of-motion coupled cluster computational methods to study the electronic structure of an ammonia–oxygen model complex to examine this possibility. The results reveal several bound electronic states with charge transfer character with emission energies generally consistent with previous observations. However, further work involving confinement, solvent, and amine structure effects will be necessary for more rigorous examination of the charge transfer fluorescence hypothesis. PMID:21812447

15N NMR investigation of the covalent binding of reduced TNT amines to soil humic acid, model compounds, and lignocellulose

USGS Publications Warehouse

Thorn, K.A.; Kennedy, K.R.

2002-01-01

The five major reductive degradation products of TNT-4ADNT (4-amino-2,6-dinitrotoluene), 2ADNT (2-amino-4,6-dinitrotoluene), 2,4DANT (2,4-diamino-6-nitrotoluene), 2,6DANT (2,6-diamino-4-nitrotoluene), and TAT (2,4,6-triaminotoluene)-labeled with 15N in the amine positions, were reacted with the IHSS soil humic acid and analyzed by 15N NMR spectrometry. In the absence of catalysts, all five amines underwent nucleophilic addition reactions with quinone and other carbonyl groups in the soil humic acid to form both heterocyclic and nonheterocyclic condensation products. Imine formation via 1,2-addition of the amines to quinone groups in the soil humic acid was significant with the diamines and TAT but not the monoamines. Horseradish peroxidase (HRP) catalyzed an increase in the incorporation of all five amines into the humic acid. In the case of the diamines and TAT, HRP also shifted the binding away from heterocyclic condensation product toward imine formation. A comparison of quantitative liquid phase with solid-state CP/MAS 15N NMR indicated that the CP experiment underestimated imine and heterocyclic nitrogens in humic acid, even with contact times optimal for observation of these nitrogens. Covalent binding of the mono- and diamines to 4-methylcatechol, the HRP catalyzed condensation of 4ADNT and 2,4DANT to coniferyl alcohol, and the binding of 2,4DANT to lignocellulose with and without birnessite were also examined.

Adducts of nitrogenous ligands with rhodium(II) tetracarboxylates and tetraformamidinate: NMR spectroscopy and density functional theory calculations.

PubMed

Cmoch, Piotr; Głaszczka, Rafał; Jaźwiński, Jarosław; Kamieński, Bohdan; Senkara, Elżbieta

2014-03-01

Complexation of tetrakis(μ2-N,N'-diphenylformamidinato-N,N')-di-rhodium(II) with ligands containing nitrile, isonitrile, amine, hydroxyl, sulfhydryl, isocyanate, and isothiocyanate functional groups has been studied in liquid and solid phases using (1)H, (13)C and (15)N NMR, (13)C and (15)N cross polarisation-magic angle spinning NMR, and absorption spectroscopy in the visible range. The complexation was monitored using various NMR physicochemical parameters, such as chemical shifts, longitudinal relaxation times T1 , and NOE enhancements. Rhodium(II) tetraformamidinate selectively bonded only unbranched amine (propan-1-amine), pentanenitrile, and (1-isocyanoethyl)benzene. No complexation occurred in the case of ligands having hydroxyl, sulfhydryl, isocyanate, and isothiocyanate functional groups, and more expanded amine molecules such as butan-2-amine and 1-azabicyclo[2.2.2]octane. Such features were opposite to those observed in rhodium(II) tetracarboxylates, forming adducts with all kind of ligands. Special attention was focused on the analysis of Δδ parameters, defined as a chemical shift difference between signal in adduct and corresponding signal in free ligand. In the case of (1)H NMR, Δδ values were either negative in adducts of rhodium(II) tetraformamidinate or positive in adducts of rhodium(II) tetracarboxylates. Experimental findings were supported by density functional theory molecular modelling and gauge independent atomic orbitals chemical shift calculations. The calculation of chemical shifts combined with scaling procedure allowed to reproduce qualitatively Δδ parameters. Copyright © 2013 John Wiley & Sons, Ltd.

Biotransformation and bioactivation reactions of alicyclic amines in drug molecules.

PubMed

Bolleddula, Jayaprakasam; DeMent, Kevin; Driscoll, James P; Worboys, Philip; Brassil, Patrick J; Bourdet, David L

2014-08-01

Aliphatic nitrogen heterocycles such as piperazine, piperidine, pyrrolidine, morpholine, aziridine, azetidine, and azepane are well known building blocks in drug design and important core structures in approved drug therapies. These core units have been targets for metabolic attack by P450s and other drug metabolizing enzymes such as aldehyde oxidase and monoamine oxidase (MAOs). The electron rich nitrogen and/or α-carbons are often major sites of metabolism of alicyclic amines. The most common biotransformations include N-oxidation, N-conjugation, oxidative N-dealkylation, ring oxidation, and ring opening. In some instances, the metabolic pathways generate electrophilic reactive intermediates and cause bioactivation. However, potential bioactivation related adverse events can be attenuated by structural modifications. Hence it is important to understand the biotransformation pathways to design stable drug candidates that are devoid of metabolic liabilities early in the discovery stage. The current review provides a comprehensive summary of biotransformation and bioactivation pathways of aliphatic nitrogen containing heterocycles and strategies to mitigate metabolic liabilities.

DNA-Templated Introduction of an Aldehyde Handle in Proteins.

PubMed

Kodal, Anne Louise B; Rosen, Christian B; Mortensen, Michael R; Tørring, Thomas; Gothelf, Kurt V

2016-07-15

Many medical and biotechnological applications rely on protein labeling, but a key challenge is the production of homogeneous and site-specific conjugates. This can rarely be achieved by simple residue-specific random labeling, but generally requires genetic engineering. Using site-selective DNA-templated reductive amination, we created DNA-protein conjugates with control over labeling stoichiometry and without genetic engineering. A guiding DNA strand with a metal-binding functionality facilitates site-selectivity by directing the coupling of a second reactive DNA strand in the vicinity of a protein metal-binding site. We demonstrate DNA-templated reductive amination for His6 -tagged proteins and metal-binding proteins, including IgG1 antibodies. We also used a cleavable linker between the DNA and the protein to remove the DNA and introduce a single aldehyde on the protein. This functions as a handle for further modifications with desired labels. In addition to directing the aldehyde positioning, the DNA provides a straightforward route for purification between reaction steps. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enzyme-like catalysis via ternary complex mechanism: alkoxy-bridged dinuclear cobalt complex mediates chemoselective O-esterification over N-amidation.

PubMed

Hayashi, Yukiko; Santoro, Stefano; Azuma, Yuki; Himo, Fahmi; Ohshima, Takashi; Mashima, Kazushi

2013-04-24

Hydroxy group-selective acylation in the presence of more nucleophilic amines was achieved using acetates of first-row late transition metals, such as Mn, Fe, Co, Cu, and Zn. Among them, cobalt(II) acetate was the best catalyst in terms of reactivity and selectivity. The combination of an octanuclear cobalt carboxylate cluster [Co4(OCOR)6O]2 (2a: R = CF3, 2b: R = CH3, 2c: R = (t)Bu) with nitrogen-containing ligands, such as 2,2'-bipyridine, provided an efficient catalytic system for transesterification, in which an alkoxide-bridged dinuclear complex, Co2(OCO(t)Bu)2(bpy)2(μ2-OCH2-C6H4-4-CH3)2 (10), was successfully isolated as a key intermediate. Kinetic studies and density functional theory calculations revealed Michaelis-Menten behavior of the complex 10 through an ordered ternary complex mechanism similar to dinuclear metallo-enzymes, suggesting the formation of alkoxides followed by coordination of the ester.

Template-constrained macrocyclic peptides prepared from native, unprotected precursors

PubMed Central

Lawson, Kenneth V.; Rose, Tristan E.; Harran, Patrick G.

2013-01-01

Peptide–protein interactions are important mediators of cellular-signaling events. Consensus binding motifs (also known as short linear motifs) within these contacts underpin molecular recognition, yet have poor pharmacological properties as discrete species. Here, we present methods to transform intact peptides into stable, templated macrocycles. Two simple steps install the template. The key reaction is a palladium-catalyzed macrocyclization. The catalysis has broad scope and efficiently forms large rings by engaging native peptide functionality including phenols, imidazoles, amines, and carboxylic acids without the necessity of protecting groups. The tunable reactivity of the template gives the process special utility. Defined changes in reaction conditions markedly alter chemoselectivity. In all cases examined, cyclization occurs rapidly and in high yield at room temperature, regardless of peptide composition or chain length. We show that conformational restraints imparted by the template stabilize secondary structure and enhance proteolytic stability in vitro. Palladium-catalyzed internal cinnamylation is a strong complement to existing methods for peptide modification. PMID:24043790

Z-Selective iridium-catalyzed cross-coupling of allylic carbonates and α-diazo esters† †Electronic supplementary information (ESI) available: Full procedures, computational details and characterization data. See DOI: 10.1039/c7sc04283c

PubMed Central

Thomas, Bryce N.; Moon, Patrick J.; Yin, Shengkang; Brown, Alex

2017-01-01

A well-defined Ir–allyl complex catalyzes the Z-selective cross-coupling of allyl carbonates with α-aryl diazo esters. The process overrides the large thermodynamic preference for E-products typically observed in metal-mediated coupling reactions to enable the synthesis of Z,E-dieneoates in good yield with selectivities consistently approaching or greater than 90 : 10. This transformation represents the first productive merger of Ir–carbene and Ir–allyl species, which are commonly encountered intermediates in allylation and cyclopropanation/E–H insertion catalysis. Potentially reactive functional groups (aryl halides, ketones, nitriles, olefins, amines) are tolerated owing to the mildness of reaction conditions. Kinetic analysis of the reaction suggests oxidative addition of the allyl carbonate to an Ir-species is rate-determining. Mechanistic studies uncovered a pathway for catalyst activation mediated by NEt3. PMID:29629093

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

PubMed

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.

Selective collision-induced fragmentation of ortho-hydroxybenzyl-aminated lysyl-containing tryptic peptides.

PubMed

Simon, E S; Papoulias, P G; Andrews, P C

2013-07-30

In protein studies that employ tandem mass spectrometry the manipulation of protonated peptide fragmentation through exclusive dissociation pathways may be preferred in some applications over the comprehensive amide backbone fragmentation that is typically observed. In this study, we characterized the selective cleavage of the side-chain Cζ-Nε bond of peptides with ortho-hydroxybenzyl-aminated lysine residues. Internal lysyl residues of representative peptides were derivatized via reductive amination with ortho-hydroxybenzaldehyde. The modified peptides were analyzed using collision-induced dissociation (CID) on an Orbitrap tandem mass spectrometer. Theoretical calculations using computational methods (density functional theory) were performed to investigate the potential dissociation mechanisms for the Cζ-Nε bond of the derivatized lysyl residue resulting in the formation of the observed product ions. Tandem mass spectra of the derivatized peptide ions exhibit product peaks corresponding to selective cleavage of the side-chain Cζ-Nε bond that links the derivative to lysine. The ortho-hydroxybenzyl derivative is released either as a neutral moiety [C7H6O1] or as a carbocation [C7H7O1](+) through competing pathways (retro-Michael versus Carbocation Elimination (CCE), respectively). The calculated transition state activation barriers indicate that the retro-Michael pathway is kinetically favored over CCE and both are favored over amide cleavage. The application of ortho-hydroxybenzyl amination is a promising peptide derivatization scheme for promoting selective dissociation pathways in the tandem mass spectrometry of protonated peptides. This can be implemented in the rational development of peptide reactive reagents for applications that may benefit from selective fragmentation paths (including crosslinking or MRM reagents). Copyright © 2013 John Wiley & Sons, Ltd.

Synthesis of galactosyl compounds for targeted gene delivery.

PubMed

Ren, T; Zhang, G; Liu, D

2001-11-01

Cell-specific DNA delivery offers a great potential for targeted gene therapy. Toward this end, we have synthesized a series of compounds carrying galactose residues as a targeting ligand for asialoglycoprotein receptors of hepatocytes and primary amine groups as a functional domain for DNA binding. Biological activity of these galactosyl compounds in DNA delivery was evaluated in HepG2 and BL-6 cells and compared with respect to the number of galactose residues as well as primary amine groups in each molecule. Transfection experiments using a firefly luciferase gene as a reporter revealed that compounds with multivalent binding properties were more active in DNA delivery. An optimal transfection activity in HepG2 cells requires seven primary amine groups and a minimum of two galactose residues in each molecule. The transfection activity of compounds carrying multi-galactose residues can be inhibited by asialofetuin, a natural substrate for asialoglycoprotein receptors of hepatocytes, suggesting that gene transfer by these galactosyl compounds is asialoglycoprotein receptor-mediated. These results provide direct evidence in support of our new strategy for the use of small and synthetic compounds for cell specific and targeted gene delivery.

Further studies on the effect of lysine at the C-terminus of the Dmt-Tic opioid pharmacophore.

PubMed

Balboni, Gianfranco; Onnis, Valentina; Congiu, Cenzo; Zotti, Margherita; Sasaki, Yusuke; Ambo, Akihiro; Bryant, Sharon D; Jinsmaa, Yunden; Lazarus, Lawrence H; Lazzari, Ilaria; Trapella, Claudio; Salvadori, Severo

2007-05-01

A wide range of activities are induced by Lys when introduced at C-terminus of the delta-opioid Dmt-Tic pharmacophore through the alpha-amine group, including: improved delta-antagonism, mu-agonism and mu-antagonism. Here we report the synthesis of a new series of compounds with the general formula H-Dmt-Tic-NH-(CH(2))(4)-CH(R)-R' (R=-NH(2), -NH-Ac, -NH-Z; R'=CO-NH-Ph, -CO-NH-CH(2)-Ph, -Bid) in which Lys is linked to Dmt-Tic through its side-chain amine group. All new compounds (1-9) displayed potent and selective delta-antagonism (MVD, pA(2)=7.81-8.27), which was independent of the functionalized alpha-amine and carboxylic groups of C-terminal Lys. This behaviour suggests a direct application as a prototype intermediate, such as Boc-Dmt-Tic-epsilon-Lys(Z)-OMe, which could be successfully applied in the synthesis (after Z or methyl ester removal) of unique designed multiple ligands containing the pharmacophore of the quintessential delta-antagonist Dmt-Tic and another opioid or biologically active non-opioid ligand.

A potential nanobiotechnology platform based on infectious bursal disease subviral particles.

PubMed

Taghavian, Omid; Mandal, Manoj K; Steinmetz, Nicole F; Rasche, Stefan; Spiegel, Holger; Fischer, Rainer; Schillberg, Stefan

2012-03-07

We describe a novel nanobiotechnology platform based on subviral particles derived from infectious bursal disease virus (IBD-SVPs). The major virus coat protein VP2 assembles into spherical, 23 nm SVPs when expressed as a heterologous protein in the yeast Pichia pastoris . We recovered up to 38 mg of IBD-SVPs at > 95% purity from 1 L of recombinant yeast culture. The purified particles were able to tolerate organic solvents up to 20% concentration (ethanol or dimethylsulfoxide), they resisted temperatures up to 65 °C and remained stable over a wide pH range (2.5-9.0). We achieved bioconjugation to the amine groups of lysine residues and to the carboxyl groups of aspartic and glutamic acid residues, allowing the functionalization of IBD-SVPs with biotin. The accessibility of surface amine groups was measured using Alexa Fluor 488 N -hydroxysuccinimide (NHS) ester, an amine-selective fluorescent dye, revealing that approximately 60 dye molecules were attached to the surface of each particle. IBD-SVPs can therefore be exploited as a robust and versatile nanoscaffold to display diverse functional ligands.

Modulation of biogenic amines content by poly(propylene imine) dendrimers in rats.

PubMed

Ciepluch, Karol; Ziemba, Barbara; Janaszewska, Anna; Appelhans, Dietmar; Klajnert, Barbara; Bryszewska, Maria; Fogel, Wiesława Agnieszka

2012-09-01

Biogenic amines and polyamines participate in all vital organism functions, their levels being important function determinants. Studies were performed to check whether repeated administration of poly(propylene imine) (PPI) dendrimers, synthetic macromolecules with diaminobutane core, and peripheral primary amine groups, may influence the endogenous level of amines, as represented by the two of them: spermidine, a natural derivative of diaminobutane, and histamine. The experiment was carried out on Wistar rats. Fourth generation PPI dendrimer, as well as maltotriose-modified fourth generation PPI dendrimers with (a) cationic open sugar shell and (b) neutral dense sugar shell that possess a higher biocompatibility, was used. Applying the combination of column chromatography on Cellex P and spectrofluorimetric assays of o-phthaldialdehyde, the final amine condensation products were employed to analyze tissue spermidine and histamine outside the central nervous system. Furthermore, radioenzymatic assay was used to measure histamine levels in the brain. The obtained results indicate that in some tissues, the endogenous concentrations of histamine and spermidine may be affected by dendrimers depending on their dose and type of dendrimers.

Experimental design to optimize an Haemophilus influenzae type b conjugate vaccine made with hydrazide-derivatized tetanus toxoid.

PubMed

Laferriere, Craig; Ravenscroft, Neil; Wilson, Seanette; Combrink, Jill; Gordon, Lizelle; Petre, Jean

2011-10-01

The introduction of type b Haemophilus influenzae conjugate vaccines into routine vaccination schedules has significantly reduced the burden of this disease; however, widespread use in developing countries is constrained by vaccine costs, and there is a need for a simple and high-yielding manufacturing process. The vaccine is composed of purified capsular polysaccharide conjugated to an immunogenic carrier protein. To improve the yield and rate of the reductive amination conjugation reaction used to make this vaccine, some of the carboxyl groups of the carrier protein, tetanus toxoid, were modified to hydrazides, which are more reactive than the ε -amine of lysine. Other reaction parameters, including the ratio of the reactants, the size of the polysaccharide, the temperature and the salt concentration, were also investigated. Experimental design was used to minimize the number of experiments required to optimize all these parameters to obtain conjugate in high yield with target characteristics. It was found that increasing the reactant ratio and decreasing the size of the polysaccharide increased the polysaccharide:protein mass ratio in the product. Temperature and salt concentration did not improve this ratio. These results are consistent with a diffusion controlled rate limiting step in the conjugation reaction. Excessive modification of tetanus toxoid with hydrazide was correlated with reduced yield and lower free polysaccharide. This was attributed to a greater tendency for precipitation, possibly due to changes in the isoelectric point. Experimental design and multiple regression helped identify key parameters to control and thereby optimize this conjugation reaction.

Amine terminated bisaspartimide polymer

NASA Technical Reports Server (NTRS)

Kumar, D. (Inventor); Fohlen, G. M. (Inventor); Parker, J. A. (Inventor)

1986-01-01

Novel amine terminated bisaspartimides are prepared by a Michael-type reaction of an aromatic bismalteimide and an aromatic diamine in an aprotic solvent. These bisaspartimides are thermally polymerized to yield tough, resinous polymers cross-lined through -NH- groups. Such polymers are useful in applications requiring materials with resistance to change at elevated temperatures, e.g., as lightweight laminates with graphite cloth, molding material prepregs, adhesives and insulating material.

Oligonucleotides Containing Aminated 2'-Amino-LNA Nucleotides: Synthesis and Strong Binding to Complementary DNA and RNA.

PubMed

Lou, Chenguang; Samuelsen, Simone V; Christensen, Niels Johan; Vester, Birte; Wengel, Jesper

2017-04-19

Mono- and diaminated 2'-amino-LNA monomers were synthesized and introduced into oligonucleotides. Each modification imparts significant stabilization of nucleic acid duplexes and triplexes, excellent sequence selectivity, and significant nuclease resistance. Molecular modeling suggested that structural stabilization occurs via intrastrand electrostatic attraction between the protonated amino groups of the aminated 2'-amino-LNA monomers and the host oligonucleotide backbone.

Zero VOC, Coal Tar Free Splash Zone Coating (SZC)

DTIC Science & Technology

2010-12-01

polymer became commercially available in 1943, thirteen years after the Thiokol Corporation developed and marketed a millable gum polysulfide known...overall solvent resistance properties as the millable gum polysulfides. However, the liquid polysulfides have the advantage of being room temperature...amine to form a covalent sulfur-carbon bond. The tertiary amine is regenerated and is then available to react with another oxirane group. These

Zero VOC, Coal Tar Free Splash Zone Coating (SZC)

DTIC Science & Technology

2011-09-01

marketed a millable gum polysulfide known as the first synthetic rubber commercially made in the United States. Today, there are several liquid...polysulfide polymers have the same excellent overall solvent resistance properties as the millable gum polysulfides. However, the liquid polysulfides...to the epoxide group and displaces the tertiary amine to form a covalent sulfur-carbon bond. The tertiary amine is regenerated and is then available

Organoselenium-catalyzed, hydroxy-controlled regio- and stereoselective amination of terminal alkenes: efficient synthesis of 3-amino allylic alcohols.

PubMed

Deng, Zhimin; Wei, Jialiang; Liao, Lihao; Huang, Haiyan; Zhao, Xiaodan

2015-04-17

An efficient route to prepare 3-amino allylic alcohols in excellent regio- and stereoselectivity in the presence of bases by orangoselenium catalysis has been developed. In the absence of bases α,β-unsaturated aldehydes were formed in up to 97% yield. Control experiments reveal that the hydroxy group is crucial for the direct amination.

A one-pot radioiodination of aryl amines via stable diazonium salts: preparation of 125I-imaging agents.

PubMed

Sloan, Nikki L; Luthra, Sajinder K; McRobbie, Graeme; Pimlott, Sally L; Sutherland, Andrew

2017-10-05

An operationally simple, one-pot, two-step tandem procedure that allows the incorporation of radioactive iodine into aryl amines via stable diazonium salts is described. The mild conditions are tolerant of various functional groups and substitution patterns, allowing late-stage, rapid access to a wide range of 125 I-labelled aryl compounds and SPECT radiotracers.

Self-healable interfaces based on thermo-reversible Diels-Alder reactions in carbon fiber reinforced composites.

PubMed

Zhang, W; Duchet, J; Gérard, J F

2014-09-15

Thermo-reversible Diels-Alder (DA) bonds formed between maleimide and furan groups have been used to generate an interphase between carbon fiber surface and an epoxy matrix leading to the ability of interfacial self-healing in carbon:epoxy composite materials. The maleimide groups were grafted on an untreated T700 carbon fiber from a three step surface treatment: (i) nitric acid oxidization, (ii) tetraethylenepentamine amination, and (iii) bismaleimide grafting. The furan groups were introduced in the reactive epoxy system from furfuryl glycidyl ether. The interface between untreated carbon fiber and epoxy matrix was considered as a reference. The interfacial shear strength (IFSS) was evaluated by single fiber micro-debonding test. The debonding force was shown to have a linear dependence with embedded length. The highest healing efficiency calculated from the debonding force was found to be about 82% more compared to the value for the reference interface. All the interphases designed with reversible DA bonds have a repeatable self-healing ability. As after the fourth healing, they can recover a relatively high healing efficiency (58% for the interphase formed by T700-BMI which is oxidized for 60 min during the first treatment step). Copyright © 2014 Elsevier Inc. All rights reserved.

Selective and eco-friendly procedures for the synthesis of benzimidazole derivatives. The role of the Er(OTf)3 catalyst in the reaction selectivity

PubMed Central

Herrera Cano, Natividad; Uranga, Jorge G; Nardi, Mónica; Procopio, Antonio; Wunderlin, Daniel A

2016-01-01

An improved and greener protocol for the synthesis of benzimidazole derivatives, starting from o-phenylenediamine, with different aldehydes is reported. Double-condensation products were selectively obtained when Er(OTf)3 was used as the catalyst in the presence of electron-rich aldehydes. Conversely, the formation of mono-condensation products was the preferred path in absence of this catalyst. One of the major advantages of these reactions was the formation of a single product, avoiding extensive isolation and purification of products, which is frequently associated with these reactions. Theoretical calculations helped to understand the different reactivity established for these reactions. Thus, we found that the charge density on the oxygen of the carbonyl group has a significant impact on the reaction pathway. For instance, electron-rich aldehydes better coordinate to the catalyst, which favours the addition of the amine group to the carbonyl group, therefore facilitating the formation of double-condensation products. Reactions with aliphatic or aromatic aldehydes were possible, without using organic solvents and in a one-pot procedure with short reaction time (2–5 min), affording single products in excellent yields (75–99%). This convenient and eco-friendly methodology offers numerous benefits with respect to other protocols reported for similar compounds. PMID:28144309

Selective and eco-friendly procedures for the synthesis of benzimidazole derivatives. The role of the Er(OTf)3 catalyst in the reaction selectivity.

PubMed

Herrera Cano, Natividad; Uranga, Jorge G; Nardi, Mónica; Procopio, Antonio; Wunderlin, Daniel A; Santiago, Ana N

2016-01-01

An improved and greener protocol for the synthesis of benzimidazole derivatives, starting from o -phenylenediamine, with different aldehydes is reported. Double-condensation products were selectively obtained when Er(OTf) 3 was used as the catalyst in the presence of electron-rich aldehydes. Conversely, the formation of mono-condensation products was the preferred path in absence of this catalyst. One of the major advantages of these reactions was the formation of a single product, avoiding extensive isolation and purification of products, which is frequently associated with these reactions. Theoretical calculations helped to understand the different reactivity established for these reactions. Thus, we found that the charge density on the oxygen of the carbonyl group has a significant impact on the reaction pathway. For instance, electron-rich aldehydes better coordinate to the catalyst, which favours the addition of the amine group to the carbonyl group, therefore facilitating the formation of double-condensation products. Reactions with aliphatic or aromatic aldehydes were possible, without using organic solvents and in a one-pot procedure with short reaction time (2-5 min), affording single products in excellent yields (75-99%). This convenient and eco-friendly methodology offers numerous benefits with respect to other protocols reported for similar compounds.

Comparative Metabolism of Furan in Rodent and Human Cryopreserved Hepatocytes

PubMed Central

Gates, Leah A.; Phillips, Martin B.; Matter, Brock A.

2014-01-01

Furan is a liver toxicant and carcinogen in rodents. Although humans are most likely exposed to furan through a variety of sources, the effect of furan exposure on human health is still unknown. In rodents, furan requires metabolism to exert its toxic effects. The initial product of the cytochrome P450 2E1-catalyzed oxidation is a reactive α,β-unsaturated dialdehyde, cis-2-butene-1,4-dial (BDA). BDA is toxic and mutagenic and consequently is considered responsible for the toxic effects of furan. The urinary metabolites of furan in rats are derived from the reaction of BDA with cellular nucleophiles, and precursors to these metabolites are detected in furan-exposed hepatocytes. Many of these precursors are 2-(S-glutathionyl)butanedial-amine cross-links in which the amines are amino acids and polyamines. Because these metabolites are derived from the reaction of BDA with cellular nucleophiles, their levels are a measure of the internal dose of this reactive metabolite. To compare the ability of human hepatocytes to convert furan to the same metabolites as rodent hepatocytes, furan was incubated with cryopreserved human and rodent hepatocytes. A semiquantitative liquid chromatography with tandem mass spectrometry assay was developed for a number of the previously characterized furan metabolites. Qualitative and semiquantitative analysis of the metabolites demonstrated that furan is metabolized in a similar manner in all three species. These results indicate that humans may be susceptible to the toxic effects of furan. PMID:24751574

Facile synthesis of amine-functional reduced graphene oxides as modified quick, easy, cheap, effective, rugged and safe adsorbent for multi-pesticide residues analysis of tea.

PubMed

Ma, Guicen; Zhang, Minglu; Zhu, Li; Chen, Hongping; Liu, Xin; Lu, Chengyin

2018-01-05

Amine-functional reduced graphene oxide (amine-rGO) with different carbon chain length amino groups were successfully synthesized. The graphene oxides (GO) reduction as well as amino grafting were achieved simultaneously in one step via a facile solvothermal synthetic strategy. The obtained materials were characterized by X-ray diffraction, Raman spectroscopy, Fourier-transform infrared spectrometry and X-ray photoelectron spectroscopy to confirm the modification of GO with different amino groups. The adsorption performance of catechins and caffeine from tea acetonitrile extracts on different amine functional rGO samples were evaluated. It was found that tributylamine-functional rGO (tri-BuA-rGO) exhibited the highest adsorption ability for catechins and caffeine compared to GO and other amino group functional rGO samples. It was worth to note that the adsorption capacity of catechins on tri-BuA-rGO was 11 times higher than that of GO (203.7mgg -1 vs 18.7mgg -1 ). Electrostatic interaction, π-π interaction and surface hydrophilic-hydrophobic properties of tri-BuA-rGO played important roles in the adsorption of catechins as well as caffeine. The gravimetric analysis confirmed that the tri-BuA-rGO achieved the highest efficient cleanup preformance compared with traditional dispersive solid phase extraction (dSPE) adsorbents like primary-secondary amine (PSA), graphitized carbon black (GCB) or C18. A multi-pesticides analysis method based on tri-BuA-rGO is validated on 33 representative pesticides in tea using gas chromatography coupled to tandem mass spectrometry or high-performance liquid chromatography coupled with tandem mass spectrometry. The analysis method gave a high coefficient of determination (r 2 >0.99) for each pesticide and satisfactory recoveries in a range of 72.1-120.5%. Our study demonstrated that amine functional rGO as a new type of QuEChERS adsorbent is expected to be widely applied for analysis of pesticides at trace levels. Copyright © 2017 Elsevier B.V. All rights reserved.

Unlocking the Potential of Phenacyl Protecting Groups: CO2-Based Formation and Photocatalytic Release of Caged Amines.

PubMed

Speckmeier, Elisabeth; Klimkait, Michael; Zeitler, Kirsten

2018-04-06

Orthogonal protection and deprotection of amines remain important tools in synthetic design as well as in chemical biology and material research applications. A robust, highly efficient, and sustainable method for the formation of phenacyl-based carbamate esters was developed using CO 2 for the in situ preparation of the intermediate carbamates. Our mild and broadly applicable protocol allows for the formation of phenacyl urethanes of anilines, primary amines, including amino acids, and secondary amines in high to excellent yields. Moreover, we demonstrate the utility by a mild and convenient photocatalytic deprotection protocol using visible light. A key feature of the [Ru(bpy) 3 ](PF 6 ) 2 -catalyzed method is the use of ascorbic acid as reductive quencher in a neutral, buffered, two-phase acetonitrile/water mixture, granting fast and highly selective deprotection for all presented examples.

Photoimageable composition

DOEpatents

Simison, Kelby Liv; Dentinger, Paul

2003-11-11

The use of selected buffering amines in a photoimageable composition prevents process bias which with conventional photoresists causes designed features to be distorted, especially in corners and high resolution features. It is believed that the amines react with the catalysts, e.g., photoacids, generated to create an inert salt. The presence of the amines also increases resolution. Suitable photoimageable compositions includes: (a) a multifunctional polymeric epoxy resin that is dissolved in an organic solvent wherein the epoxy resin comprises oligomers of bisphenol A that is quantitatively protected by glycidyl ether and wherein the oligomers have an average functionality that ranges from about 3 to 12; (b) a photoactive compound; and (c) an amine that is selected from the group consisting of triisobutylamine, 1,8-bis(dimethylamino)naphthalene (also known as PROTON SPONGET.TM.), 2,2'-diazabicyclo[2.2.2] octane and mixtures thereof. The photoimageable composition is particularly suited for producing high aspect ratio metal microstructures.

Palladium(II) complexes bearing di-(2-picolyl)amine functionalized chrysin fragments. An experimental and theoretical study

NASA Astrophysics Data System (ADS)

González-Montiel, Simplicio; Valdez-Calderón, Alejandro; Vásquez-Pérez, J. Manuel; Torres-Valencia, J. Martín; Martínez-Otero, Diego; López, Jorge A.; Cruz-Borbolla, Julián

2017-10-01

A new series of chrysin derivatives containing the di-(2-picolyl)amine (2a-d) moiety have been designed, synthesized, and treated with PdCl2·2CH3CN allowing the preparation of new cationic Palladium(II) complexes (3a-d). Solution-phase studies by 1H NMR spectroscopy of 3a-d revealed that the protons of the methylene groups of the di(2-picolyl)amine fragment are diasterotopic. GIAO/DFT studies were performed to predict the molecular structures of 3a-d by comparing the experimental and theoretical 1H-NMR chemical shifts. The molecular structure of 3c was determined by X-ray crystallographic analysis revealing that di-(2-picolyl)amine fragment is coordinated to the palladium center in a κ3-N,N,N-tridentate fashion in an overall square-planar geometry completed with a chloride atom.

Production of Primary Amines by Reductive Amination of Biomass-Derived Aldehydes/Ketones.

PubMed

Liang, Guanfeng; Wang, Aiqin; Li, Lin; Xu, Gang; Yan, Ning; Zhang, Tao

2017-03-06

Transformation of biomass into valuable nitrogen-containing compounds is highly desired, yet limited success has been achieved. Here we report an efficient catalyst system, partially reduced Ru/ZrO 2 , which could catalyze the reductive amination of a variety of biomass-derived aldehydes/ketones in aqueous ammonia. With this approach, a spectrum of renewable primary amines was produced in good to excellent yields. Moreover, we have demonstrated a two-step approach for production of ethanolamine, a large-market nitrogen-containing chemical, from lignocellulose in an overall yield of 10 %. Extensive characterizations showed that Ru/ZrO 2 -containing multivalence Ru association species worked as a bifunctional catalyst, with RuO 2 as acidic promoter to facilitate the activation of carbonyl groups and Ru as active sites for the subsequent imine hydrogenation. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spectroscopic investigation and direct comparison of the reactivities of iron pyridyl oxidation catalysts

NASA Astrophysics Data System (ADS)

Song, Yang; Mayes, Howard G.; Queensen, Matthew J.; Bauer, Eike B.; Dupureur, Cynthia M.

2017-03-01

The growing interest in green chemistry has fueled attention to the development and characterization of effective iron complex oxidation catalysts. A number of iron complexes are known to catalyze the oxidation of organic substrates utilizing peroxides as the oxidant. Their development is complicated by a lack of direct comparison of the reactivities of the iron complexes. To begin to correlate reactivity with structural elements, we compare the reactivities of a series of iron pyridyl complexes toward a single dye substrate, malachite green (MG), for which colorless oxidation products are established. Complexes with tetradentate, nitrogen-based ligands with cis open coordination sites were found to be the most reactive. While some complexes reflect sensitivity to different peroxides, others are similarly reactive with either H2O2 or tBuOOH, which suggests some mechanistic distinctions. [Fe(S,S-PDP)(CH3CN)2](SbF6)2 and [Fe(OTf)2(tpa)] transition under the oxidative reaction conditions to a single intermediate at a rate that exceeds dye degradation (PDP = bis(pyridin-2-ylmethyl) bipyrrolidine; tpa = tris(2-pyridylmethyl)amine). For the less reactive [Fe(OTf)2(dpa)] (dpa = dipicolylamine), this reaction occurs on a timescale similar to that of MG oxidation. Thus, the spectroscopic method presented herein provides information about the efficiency and mechanism of iron catalyzed oxidation reactions as well as about potential oxidative catalyst decomposition and chemical changes of the catalyst before or during the oxidation reaction.

Detection of Amines and Ammonia with an Ambient Pressure Mass Spectrometer using a Corona Discharge Ion Source, in an Urban Atmosphere and in a Teflon Film Chamber

NASA Astrophysics Data System (ADS)

Alves, M.; Hanson, D. R.; Grieves, C.; Ortega, J. V.

2015-12-01

Amines and ammonia are an important group of molecules that can greatly affect atmospheric particle formation that can go on to impact cloud formation and their scattering of thermal and solar radiation, and as a result human health and ecosystems. In this study, an Ambient Pressure Mass Spectrometer (AmPMS) that is selective and sensitive to molecules with a high proton affinity, such as amines, was coupled with a newly built corona discharge ion source. AmPMS was used to monitor many different nitrogenous compound that are found in an urban atmosphere (July 2015, Minneapolis), down to the single digit pmol/mol level. Simultaneous to this, a proton transfer mass spectrometer also sampled the atmosphere through an inlet within 20 m of the AmPMS inlet. In another set of studies, a similar AmPMS was attached to a large Teflon film chamber at the Atmospheric Chemistry Division at NCAR (August 2015, Boulder). Exploratory studies are planned on the sticking of amines to the chamber walls as well as oxidizing the amine and monitoring products. Depending on the success of these studies, results will be presented on the reversability of amine partitioning and mass balance for these species in the chamber.

Discovery and structural characterisation of new fold type IV-transaminases exemplify the diversity of this enzyme fold

PubMed Central

Pavkov-Keller, Tea; Strohmeier, Gernot A.; Diepold, Matthias; Peeters, Wilco; Smeets, Natascha; Schürmann, Martin; Gruber, Karl; Schwab, Helmut; Steiner, Kerstin

2016-01-01

Transaminases are useful biocatalysts for the production of amino acids and chiral amines as intermediates for a broad range of drugs and fine chemicals. Here, we describe the discovery and characterisation of new transaminases from microorganisms which were enriched in selective media containing (R)-amines as sole nitrogen source. While most of the candidate proteins were clearly assigned to known subgroups of the fold IV family of PLP-dependent enzymes by sequence analysis and characterisation of their substrate specificity, some of them did not fit to any of these groups. The structure of one of these enzymes from Curtobacterium pusillum, which can convert d-amino acids and various (R)-amines with high enantioselectivity, was solved at a resolution of 2.4 Å. It shows significant differences especially in the active site compared to other transaminases of the fold IV family and thus indicates the existence of a new subgroup within this family. Although the discovered transaminases were not able to convert ketones in a reasonable time frame, overall, the enrichment-based approach was successful, as we identified two amine transaminases, which convert (R)-amines with high enantioselectivity, and can be used for a kinetic resolution of 1-phenylethylamine and analogues to obtain the (S)-amines with e.e.s >99%. PMID:27905516

Surface modification of GC and HOPG with diazonium, amine, azide, and olefin derivatives.

PubMed

Tanaka, Mutsuo; Sawaguchi, Takahiro; Sato, Yukari; Yoshioka, Kyoko; Niwa, Osamu

2011-01-04

Surface modification of glassy carbon (GC) and highly oriented pyrolytic graphite (HOPG) was carried out with diazonium, amine, azide, and olefin derivatives bearing ferrocene as an electroactive moiety. Features of the modified surfaces were evaluated by surface concentrations of immobilized molecule, blocking effect of the modified surface against redox reaction, and surface observation using cyclic voltammetry and electrochemical scanning tunneling microscope (EC-STM). The measurement of surface concentrations of immobilized molecule revealed the following three aspects: (i) Diazonium and olefin derivatives could modify substrates with the dense-monolayer concentration. (ii) The surface concentration of immobilized amine derivative did not reach to the dense-monolayer concentration reflecting their low reactivity. (iii) The surface modification with the dense-monolayer concentration was also possible with azide derivative, but the modified surface contained some oligomers produced by the photoreaction of azides. Besides, the blocking effect against redox reaction was observed for GC modified with diazonium derivative and for HOPG modified with diazonium and azide derivatives, suggesting fabrication of a densely modified surface. Finally, the surface observation for HOPG modified with diazonium derivative by EC-STM showed a typical monolayer structure, in which the ferrocene moieties were packed densely at random. On the basis of those results, it was demonstrated that surface modification of carbon substrates with diazonium could afford a dense monolayer similar to the self-assembled monolayer (SAM) formation.

Biofunctionalized silicon nitride platform for sensing applications.

PubMed

Hoi, Hiofan; Rezaie, Salva S; Gong, Lu; Sen, Payel; Zeng, Hongbo; Montemagno, Carlo; Gupta, Manisha

2018-04-15

Silicon nitride (SiN x ) based biosensors have the potential to converge on the technological achievements of semiconductor microfabrication and biotechnology. Development of biofunctionalized SiN x surface and its integration with other devices will allow us to integrate the biosensing capability with probe control, data acquisition and data processing. Here we use the hydrogen plasma generated by inductively coupled plasma-reactive ion etching (ICP-RIE) technique to produce amino-functionality on the surface of SiN x which can then be readily used for biomolecule immobilization. ICP-RIE produces high-density hydrogen ions/radicals at low energy, which produces high-density amino group on the SiN x surface within a short duration of time and with minimal surface damage. In this work, we have demonstrated selective amination of SiN x surface as compared to Si surface. The as-activated SiN x surface can be readily biofunctionalized with both protein and oligonucleotide through covalent immobilization. N-5-azido-2-nitrobenzoyloxysuccinimide, a photoactivable amino reactive bifunctional crosslinker, was used and greater than 90% surface coverage was achieved for protein immobilization. In addition, ssDNA immobilization and hybridization with its complemented strand was shown. Thus, we demonstrate a uniform, reliable, fast and economical technique for creating biofunctionalized SiN x surface that can be used for developing compact high-sensitivity biosensors. Copyright © 2017 Elsevier B.V. All rights reserved.

[Contact allergy to epoxy resins plastics based on materials collected by the Nofer Institute of Occupational Medicine].

PubMed

Kieć-Swierczyńska, Marta; Krecisz, Beata

2003-01-01

Of the 5604 patients examined in 1984-2001 for suspected occupational dermatitis, 160 persons (2.8%) showed allergy to epoxy resins plastics. Allergy was more frequent in men (4.9%) than in women (1.2%); in 154 persons, allergy was of occupational etiology (in a group of 160 patients with allergy to epoxy resins, the following proportions were observed: bricklayers, platelayers--17.5%; fitters, turners, machinist millers--13.8%; plastics molders--13.1%; laminators--11.3%; electrical equipment assemblers--10.6%; painters--10.0%). Having compared the frequency of allergy to components of epoxy resins in the years 1984-1993 and 1994-2001, it was found that allergy to resin, reactive diluents and plasticizers was on increase, whereas allergy to amines and acid anhydrides hardeners was on decrease. In a group of 13 chemical compounds entering into the composition of epoxy resins, epoxy resin contributed to the largest number of positive patch tests (77.5% of epoxy-allergic persons). This was followed by triethylenetetramine (23.1%), ethylenediamine (13.1%), phthalic anhydride (8.1%), diethylenetetramine (6.9%) and phenylglycidylether (6.2%). In addition, three patients reacted to both epoxy resin and cycloaliphatic resin.

Structure-Activity Relationships for Rates of Aromatic Amine Oxidation by Manganese Dioxide

DOE PAGES

Salter-Blanc, Alexandra J.; Bylaska, Eric J.; Lyon, Molly A.; ...

2016-04-13

New energetic compounds are designed to minimize their potential environmental impacts, which includes their transformation and the fate and effects of their transformation products. The nitro groups of energetic compounds are readily reduced to amines, and the resulting aromatic amines are subject to oxidation and coupling reactions. Manganese dioxide (MnO 2) is a common environmental oxidant and model system for kinetic studies of aromatic amine oxidation. Here in this study, a training set of new and previously reported kinetic data for the oxidation of model and energetic-derived aromatic amines was assembled and subjected to correlation analysis against descriptor variables that ranged from general purpose [Hammettmore » $$\\sigma$$ constants ($$\\sigma^-$$), pK as of the amines, and energies of the highest occupied molecular orbital (E HOMO)] to specific for the likely rate-limiting step [one-electron oxidation potentials (E ox)]. The selection of calculated descriptors (pK a), E HOMO, and E ox) was based on validation with experimental data. All of the correlations gave satisfactory quantitative structure-activity relationships (QSARs), but they improved with the specificity of the descriptor. The scope of correlation analysis was extended beyond MnO 2 to include literature data on aromatic amine oxidation by other environmentally relevant oxidants (ozone, chlorine dioxide, and phosphate and carbonate radicals) by correlating relative rate constants (normalized to 4-chloroaniline) to E HOMO (calculated with a modest level of theory).« less

Structure-Activity Relationships for Rates of Aromatic Amine Oxidation by Manganese Dioxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salter-Blanc, Alexandra J.; Bylaska, Eric J.; Lyon, Molly A.

New energetic compounds are designed to minimize their potential environmental impacts, which includes their transformation and the fate and effects of their transformation products. The nitro groups of energetic compounds are readily reduced to amines, and the resulting aromatic amines are subject to oxidation and coupling reactions. Manganese dioxide (MnO 2) is a common environmental oxidant and model system for kinetic studies of aromatic amine oxidation. Here in this study, a training set of new and previously reported kinetic data for the oxidation of model and energetic-derived aromatic amines was assembled and subjected to correlation analysis against descriptor variables that ranged from general purpose [Hammettmore » $$\\sigma$$ constants ($$\\sigma^-$$), pK as of the amines, and energies of the highest occupied molecular orbital (E HOMO)] to specific for the likely rate-limiting step [one-electron oxidation potentials (E ox)]. The selection of calculated descriptors (pK a), E HOMO, and E ox) was based on validation with experimental data. All of the correlations gave satisfactory quantitative structure-activity relationships (QSARs), but they improved with the specificity of the descriptor. The scope of correlation analysis was extended beyond MnO 2 to include literature data on aromatic amine oxidation by other environmentally relevant oxidants (ozone, chlorine dioxide, and phosphate and carbonate radicals) by correlating relative rate constants (normalized to 4-chloroaniline) to E HOMO (calculated with a modest level of theory).« less

Hydrolysis of aspartic acid phosphoramidate nucleotides: a comparative quantum chemical study.

PubMed

Michielssens, Servaas; Tien Trung, Nguyen; Froeyen, Matheus; Herdewijn, Piet; Tho Nguyen, Minh; Ceulemans, Arnout

2009-09-07

L-Aspartic acid has recently been found to be a good leaving group during HIV reverse transcriptase catalyzed incorporation of deoxyadenosine monophosphate (dAMP) in DNA. This showed that L-Asp is a good mimic for the pyrophosphate moiety of deoxyadenosine triphosphate. The present work explores the thermochemistry and mechanism for hydrolysis of several models for L-aspartic-dAMP using B3LYP/DGDZVP, MP2/6-311++G** and G3MP2 level of theory. The effect of the new compound is gradually investigated: starting from a simple methyl amine leaving group up to the aspartic acid leaving group. The enzymatic environment was mimicked by involving two Mg(2+) ions and some important active site residues in the reaction. All reactions are compared to the corresponding O-coupled leaving group, which is methanol for methyl amine and malic acid for aspartic acid. With methyl amine as a leaving group a tautomeric associative or tautomeric dissociative mechanism is preferred and the barrier is lower than the comparable mechanism with methanol as a leaving group. The calculations on the aspartic acid in the enzymatic environment show that qualitatively the mechanism is the same as for triphosphate but the barrier for hydrolysis by the associative mechanism is higher for L-aspartic-dAMP than for L-malic-dAMP and pyrophosphate.

Comparison of analytical protein separation characteristics for three amine-based capillary-channeled polymer (C-CP) stationary phases.

PubMed

Jiang, Liuwei; Marcus, R Kenneth

2016-02-01

Capillary-channeled polymer (C-CP) fiber stationary phases are finding utility in the realms of protein analytics as well as downstream processing. We have recently described the modification of poly(ethylene terephthalate) (PET) C-CP fibers to affect amine-rich phases for the weak anion-exchange (WAX) separation of proteins. Polyethylenimine (PEI) is covalently coupled to the PET surface, with subsequent cross-linking imparted by treatment with 1,4-butanediol diglycidyl ether (BUDGE). These modifications yield vastly improved dynamic binding capacities over the unmodified fibers. We have also previously employed native (unmodified) nylon 6 C-CP fibers as weak anion/cation-exchange (mixed-mode) and hydrophobic interaction chromatography (HIC) phases for protein separations. Polyamide, nylon 6, consists of amide groups along the polymer backbone, with primary amines and carboxylic acid end groups. The analytical separation characteristics of these three amine-based C-CP fiber phases are compared here. Each of the C-CP fiber columns in this study was shown to be able to separate a bovine serum albumin/hemoglobin/lysozyme mixture at high mobile phase linear velocity (∼70 mm s(-1)) but with different elution characteristics. These differences reflect the types of protein-surface interactions that are occurring, based on the active group composition of the fiber surfaces. This study provides important fundamental understanding for the development of surface-modified C-CP fiber columns for protein separation.

Selective Adsorption of Pb(II) from Aqueous Solution by Triethylenetetramine-Grafted Polyacrylamide/Vermiculite

PubMed Central

Gu, Shiqing; Wang, Lan; Mao, Xinyou; Yang, Liping; Wang, Chuanyi

2018-01-01

Amine groups play significant roles in polymeric composites for heavy metals removal. However, generating a composite with a large number of functional and stable amine groups based on clay is still a challenge. In this work, a new amine-functionalized adsorbent based on acid-activated vermiculite (a-Verm) was prepared by organic modification of silane coupling agent as bridge, followed by in situ polymerization of acrylamide (AM) and further grafting of triethylene tetramine (TETA). The obtained polymeric composite g-PAM/OVerm was characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), Fourier transform infrared (FTIR), thermal analysis (TG/DTG), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) analyses, confirming that amine groups were successfully grafted onto the surface of Verm. The efficacy g-PAM/OVerm for removing Pb(II) was tested. The adsorption equilibrium data on g-PAM/OVerm was in good accordance with the Langmuir adsorption isotherms, and the adsorption maximal value of Pb(II) was 219.4 mg·g−1. The adsorption kinetic data fit the pseudo-second-order kinetic model well. Additionally, g-PAM/OVerm has better selectivity for Pb(II) ion in comparison with Zn(II), Cd(II) and Cu(II) ions. The present work shows that g-PAM/OVerm holds great potential for removing Pb(II) from wastewater, and provides a new and efficient method for the removal of heavy metal ions from industrial wastewater. PMID:29597288

Real-Time In Vivo Monitoring of Reactive Oxygen Species in Guard Cells.

PubMed

Park, Ky Young; Roubelakis-Angelakis, Kalliopi A

2018-01-01

The intra-/intercellular homeostasis of reactive oxygen species (ROS), and especially of superoxides (O 2 .- ) and hydrogen peroxide (O 2 .- ) participate in signalling cascades which dictate developmental processes and reactions to biotic/abiotic stresses. Polyamine oxidases terminally oxidize/back convert polyamines generating H 2 O 2 . Recently, an NADPH-oxidase/Polyamine oxidase feedback loop was identified to control oxidative burst under salinity. Thus, the real-time localization/monitoring of ROS in specific cells, such as the guard cells, can be of great interest. Here we present a detailed description of the real-time in vivo monitoring of ROS in the guard cells using H 2 O 2 - and O 2 .- specific fluorescing probes, which can be used for studying ROS accumulation generated from any source, including the amine oxidases-dependent pathway, during development and stress.

Water-soluble polymers and compositions thereof

DOEpatents

Smith, B.F.; Robison, T.W.; Gohdes, J.W.

1999-04-06

Water-soluble polymers including functionalization from the group of amino groups, carboxylic acid groups, phosphonic acid groups, phosphonic ester groups, acylpyrazolone groups, hydroxamic acid groups, aza crown ether groups, oxy crown ethers groups, guanidinium groups, amide groups, ester groups, aminodicarboxylic groups, permethylated polyvinylpyridine groups, permethylated amine groups, mercaptosuccinic acid groups, alkyl thiol groups, and N-alkylthiourea groups are disclosed.

Water-soluble polymers and compositions thereof

DOEpatents

Smith, Barbara F.; Robison, Thomas W.; Gohdes, Joel W.

2002-01-01

Water-soluble polymers including functionalization from the group of amino groups, carboxylic acid groups, phosphonic acid groups, phosphonic ester groups, acylpyrazolone groups, hydroxamic acid groups, aza crown ether groups, oxy crown ethers groups, guanidinium groups, amide groups, ester groups, aminodicarboxylic groups, permethylated polvinylpyridine groups, permethylated amine groups, mercaptosuccinic acid groups, alkyl thiol groups, and N-alkylthiourea groups are disclosed.

Water-soluble polymers and compositions thereof

DOEpatents

Smith, Barbara F.; Robison, Thomas W.; Gohdes, Joel W.

1999-01-01

Water-soluble polymers including functionalization from the group of amino groups, carboxylic acid groups, phosphonic acid groups, phosphonic ester groups, acylpyrazolone groups, hydroxamic acid groups, aza crown ether groups, oxy crown ethers groups, guanidinium groups, amide groups, ester groups, aminodicarboxylic groups, permethylated polyvinylpyridine groups, permethylated amine groups, mercaptosuccinic acid groups, alkyl thiol groups, and N-alkylthiourea groups are disclosed.

Rapid Asymmetric Synthesis of Disubstituted Allenes by Coupling of Flow‐Generated Diazo Compounds and Propargylated Amines

PubMed Central

Poh, Jian‐Siang; Makai, Szabolcs; von Keutz, Timo; Tran, Duc N.; Battilocchio, Claudio; Pasau, Patrick

2017-01-01

Abstract We report herein the asymmetric coupling of flow‐generated unstabilized diazo compounds and propargylated amine derivatives, using a new pyridinebis(imidazoline) ligand, a copper catalyst and base. The reaction proceeds rapidly, generating chiral allenes in 10–20 minutes with high enantioselectivity (89–98 % de/ee), moderate yields and a wide functional group tolerance. PMID:28075518

Mono-Amine Functionalized Phthalocyanines: Mwave-Assisted Solid-Phase Synthesis and Bioconjugation Strategies

PubMed Central

Erdem, S. Sibel; Nesterova, Irina V.; Soper, Steven A.; Hammer, Robert P.

2009-01-01

Phthalocyanines (Pcs) are excellent candidates for use as fluors for near-infrared (near-IR) fluorescent tagging of biomolecules for a wide variety of bioanalytical applications. Mono-functionalized Pcs, having two different types of peripheral substitutents; one for covalent conjugation of the Pc to biomolecules and others to improve the solubility of the macrocycle, ideally suit for the desired applications. To date, difficulties faced during the purification of the mono-functionalized Pcs limited their usage in various types of applications. Herein are reported a new synthetic method for rapid synthesis of the target Pcs and bioconjugation techniques for labeling of the oligonucleotides with the near-IR flours. A novel synthetic route was developed utilizing a hydrophilic, polyethylene glycol-based (PEG) support with an acid labile Rink Amide linker. The Pcs were functionalized with an amine group for covalent conjugation purposes and were decorated with short PEG chains, serving as solubilizing groups. Mwave-assisted solid-phase synthetic method was successfully applied to obtain pure asymmetrically-substituted mono-amine functionalized Pcs in a short period of time. Three different bioconjugation techniques, reductive amination, amidation and Huisgen cycloaddition, were employed for covalent conjugation of Pcs to oligonucleotides. The described μwave-assisted bioconjugation methods give an opportunity to synthesize and isolate the Pc-oligonucleotide conjugate in a few hours. PMID:19911767

Fine-Tuning of the Carbon Dioxide Capture Capability of Diamine-Grafted Metal-Organic Framework Adsorbents Through Amine Functionalization.

PubMed

Jo, Hyuna; Lee, Woo Ram; Kim, Nam Woo; Jung, Hyun; Lim, Kwang Soo; Kim, Jeong Eun; Kang, Dong Won; Lee, Hanyeong; Hiremath, Vishwanath; Seo, Jeong Gil; Jin, Hailian; Moon, Dohyun; Han, Sang Soo; Hong, Chang Seop

2017-02-08

A combined sonication and microwave irradiation procedure provides the most effective functionalization of ethylenediamine (en) and branched primary diamines of 1-methylethylenediamine (men) and 1,1-dimethylethylenediamine (den) onto the open metal sites of Mg 2 (dobpdc) (1). The CO 2 capacities of the advanced adsorbents 1-en and 1-men under simulated flue gas conditions are 19 wt % and 17.4 wt %, respectively, which are the highest values reported among amine-functionalized metal-organic frameworks (MOFs) to date. Moreover, 1-den exhibits both a significant working capacity (12.2 wt %) and superb CO 2 uptake (11 wt %) at 3 % CO 2 . Additionally, this framework showcases the superior recyclability; ultrahigh stability after exposure to O 2 , moisture, and SO 2 ; and exceptional CO 2 adsorption capacity under humid conditions, which are unprecedented among MOFs. We also elucidate that the performance of CO 2 adsorption can be controlled by the structure of the diamine ligands grafted such as the number of amine end groups or the presence of side groups, which provides the first systematic and comprehensive demonstration of fine-tuning of CO 2 uptake capability using different amines. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Maximizing the reactivity of phenolic and aminic radical-trapping antioxidants: just add nitrogen!

PubMed

Valgimigli, Luca; Pratt, Derek A

2015-04-21

Hydrocarbon autoxidation, the archetype free radical chain reaction, challenges the longevity of both living organisms and petroleum-derived products. The most important strategy in slowing this process is via the intervention of radical-trapping antioxidants (RTAs), which are abundant in nature and included as additives to almost every petroleum-derived product as well as several other commercial products. Accordingly, a longstanding objective of many academic and industrial scientists has been the design and development of novel RTAs that can outperform natural and industrial standards, such as α-tocopherol, the most biologically active form of vitamin E, and dialkylated diphenylamines, respectively. Some time ago we recognized that attempts to maximize the reactivity of phenolic RTAs had largely failed because substitution of the phenolic ring with electron-donating groups to weaken the O-H bond and accelerate the rate of H atom transfer to radicals leads to compounds that are unstable in air. We surmised that incorporating nitrogen into the phenolic ring would render them more stable to one-electron oxidation, enabling their substitution with strong electron-donating groups. Guided by computational chemistry, we demonstrated that replacing the phenyl ring in very electron-rich phenols with either 3-pyridyl or 5-pyrimidyl rings leads to phenolic-like RTAs with good air stability and great reactivity. In fact, rate constants determined for the reactions of some compounds with peroxyl radicals were almost 2 orders of magnitude greater than those for α-tocopherol and implied that the reactions proceeded without an enthalpic barrier. Following extensive thermochemical and kinetic characterization, we took our studies of these compounds to more physiologically relevant media, such as lipid bilayers and human low density lipoproteins, where the heterocyclic analogues of vitamin E shone, displaying unparalleled abilities to inhibit lipid peroxidation and prompting their current investigation in animal models of degenerative disease. Moreover, we carried out studies of these compounds in several industrially relevant contexts and in particular demonstrated that they could be used synergistically with less reactive, less expensive, phenolic RTAs. More recently, our attention has turned to the application of these ideas to maximizing the reactivity of diarylamine RTAs that are common in additives to petroleum-derived products, such as lubricating oils, transmission and hydraulic fluids, and rubber. In doing so, we have developed the most reactive diarylamines ever reported. The 3-pyridyl- and 5-pyrimidyl-containing diarylamines are easily accessed using Pd- and/or Cu-catalyzed cross-coupling reactions, and display an ideal compromise between reactivity and stability. The most reactive compounds are characterized by rate constants for reactions with peroxyl radicals that are independent of temperature, implying that-as for the most reactive heterocyclic phenols-these reactions proceed without an enthalpic barrier. Unprecedented reactivity was also observed when hydrocarbon autoxidations were carried out at elevated temperatures, real-world conditions where diarylamines are uniquely effective because of a catalytic RTA activity that makes use of the hydrocarbon substrate as a sacrificial reductant. Our studies to date suggest that heterocyclic diarylamines have real potential to increase the longevity of petroleum-derived products in a variety of applications where diphenylamines are currently used.

Metabolism and Biomarkers of Heterocyclic Aromatic Amines in Molecular Epidemiology Studies: Lessons Learned from Aromatic Amines

PubMed Central

2011-01-01

Aromatic amines and heterocyclic aromatic amines (HAAs) are structurally related classes of carcinogens that are formed during the combustion of tobacco or during the high-temperature cooking of meats. Both classes of procarcinogens undergo metabolic activation by N-hydroxylation of the exocyclic amine group, to produce a common proposed intermediate, the arylnitrenium ion, which is the critical metabolite implicated in toxicity and DNA damage. However, the biochemistry and chemical properties of these compounds are distinct and different biomarkers of aromatic amines and HAAs have been developed for human biomonitoring studies. Hemoglobin adducts have been extensively used as biomarkers to monitor occupational and environmental exposures to a number of aromatic amines; however, HAAs do not form hemoglobin adducts at appreciable levels and other biomarkers have been sought. A number of epidemiologic studies that have investigated dietary consumption of well-done meat in relation to various tumor sites reported a positive association between cancer risk and well-done meat consumption, although some studies have shown no associations between well-done meat and cancer risk. A major limiting factor in most epidemiological studies is the uncertainty in quantitative estimates of chronic exposure to HAAs and, thus, the association of HAAs formed in cooked meat and cancer risk has been difficult to establish. There is a critical need to establish long-term biomarkers of HAAs that can be implemented in molecular epidemioIogy studies. In this review article, we highlight and contrast the biochemistry of several prototypical carcinogenic aromatic amines and HAAs to which humans are chronically exposed. The biochemical properties and the impact of polymorphisms of the major xenobiotic-metabolizing enzymes on the biological effects of these chemicals are examined. Lastly, the analytical approaches that have been successfully employed to biomonitor aromatic amines and HAAs, and emerging biomarkers of HAAs that may be implemented in molecular epidemiology studies are discussed. PMID:21688801

The synthesis of α-aryl-α-aminophosphonates and α-aryl-α-aminophosphine oxides by the microwave-assisted Pudovik reaction

PubMed Central

Tajti, Ádám; Ádám, Anna; Csontos, István; Karaghiosoff, Konstantin; Czugler, Mátyás; Ábrányi-Balogh, Péter

2017-01-01

A family of α-aryl-α-aminophosphonates and α-aryl-α-aminophosphine oxides was synthesized by the microwave-assisted solvent-free addition of dialkyl phosphites and diphenylphosphine oxide, respectively, to imines formed from benzaldehyde derivatives and primary amines. After optimization, the reactivity was mapped, and the fine mechanism was evaluated by DFT calculations. Two α-aminophosphonates were subjected to an X-ray study revealing a racemic dimer formation made through a N–H···O=P intermolecular hydrogen bridges pair. PMID:28179951

A Protocol for Safe Lithiation Reactions Using Organolithium Reagents

PubMed Central

Gau, Michael R.; Zdilla, Michael J.

2016-01-01

Organolithium reagents are powerful tools in the synthetic chemist's toolbox. However, the extreme pyrophoric nature of the most reactive reagents warrants proper technique, thorough training, and proper personal protective equipment. To aid in the training of researchers using organolithium reagents, a thorough, step-by-step protocol for the safe and effective use of tert-butyllithium on an inert gas line or within a glovebox is described. As a model reaction, preparation of lithium tert-butyl amide by the reaction of tert-butyl amine with one equivalent of tert-butyl lithium is presented. PMID:27911386

Metallo‐Supramolecular Gels that are Photocleavable with Visible and Near‐Infrared Irradiation

PubMed Central

Theis, Sabrina; Iturmendi, Aitziber; Gorsche, Christian; Orthofer, Marco; Lunzer, Markus; Baudis, Stefan; Ovsianikov, Aleksandr; Liska, Robert

2017-01-01

Abstract A photolabile ruthenium‐based complex, [Ru(bpy)2(4AMP)2](PF6)2, (4AMP=4‐(aminomethyl)pyridine) is incorporated into polyurea organo‐ and hydrogels via the reactive amine moieties on the photocleavable 4AMP ligands. While showing long‐term stability in the dark, cleavage of the pyridine–ruthenium bond upon irradiation with visible or near‐infrared irradiation (in a two‐photon process) leads to rapid de‐gelation of the supramolecular gels, thus enabling spatiotemporal micropatterning by photomasking or pulsed NIR‐laser irradiation PMID:28941025

Elastomer toughened polyimide adhesives. [bonding metal and composite material structures for aircraft and spacecraft

NASA Technical Reports Server (NTRS)

St.clair, A. K.; St.clair, T. L. (Inventor)

1985-01-01

A rubber-toughened, addition-type polyimide composition is disclosed which has excellent high temperature bonding characteristics in the fully cured state and improved peel strength and adhesive fracture resistance physical property characteristics. The process for making the improved adhesive involves preparing the rubber-containing amic acid prepolymer by chemically reacting an amine-terminated elastomer and an aromatic diamine with an aromatic dianhydride with which a reactive chain stopper anhydride has been mixed, and utilizing solvent or mixture of solvents for the reaction.

Cyclization Cascades Initiated by 1,6-Conjugate Addition

PubMed Central

Brooks, Joshua L.; Frontier, Alison J.

2012-01-01

Dienyl diketones containing tethered acetates selectively undergo two different 1,6-conjugate addition-initiated cyclization cascades. One is a 1,6-conjugate addition/cyclization sequence with incorporation of the nucleophile, and the other is catalyzed by DABCO and is thought to proceed via a cyclic acetoxonium intermediate. The reaction behavior of substrates lacking the tethered acetate was also studied. The scope of both types of cyclization cascades, the role of the amine additive, and the factors controlling reactivity and selectivity in the two different reaction pathways is discussed. PMID:23004564

OMS-2-Supported Cu Hydroxide-Catalyzed Benzoxazoles Synthesis from Catechols and Amines via Domino Oxidation Process at Room Temperature.

PubMed

Meng, Xu; Wang, Yanmin; Wang, Yuanguang; Chen, Baohua; Jing, Zhenqiang; Chen, Gexin; Zhao, Peiqing

2017-07-07

In the presence of manganese oxide octahedral molecular sieve (OMS-2) supported copper hydroxide Cu(OH) x /OMS-2, aerobic synthesis of benzoxazoles from catechols and amines via domino oxidation/cyclization at room temperature is achieved. This heterogeneous benzoxazoles synthesis initiated by the efficient oxidation of catechols over Cu(OH) x /OMS-2 tolerates a variety of substrates, especially amines containing sensitive groups (hydroxyl, cyano, amino, vinyl, ethynyl, ester, and even acetyl groups) and heterocycles, which affords functionalized benzoxazoles in good to excellent yields by employing low catalyst loading (2 mol % Cu). The characterization and plausible catalytic mechanism of Cu(OH) x /OMS-2 are described. The notable features of our catalytic protocol such as the use of air as the benign oxidant and EtOH as the solvent, mild conditions, ease of product separation, being scalable up to the gram level, and superior reusability of catalyst (up to 10 cycles) make it more practical and environmentally friendly for organic synthesis.

Comparison of polymer induced and solvent induced trypsin denaturation: the role of hydrophobicity.

PubMed

Jasti, Lakshmi S; Fadnavis, Nitin W; Addepally, Uma; Daniels, Siona; Deokar, Sarika; Ponrathnam, Surendra

2014-04-01

Trypsin adsorption from aqueous buffer by various copolymers of allyl glycidyl ether-ethylene glycol dimethacrylate (AGE-EGDM) copolymer with varying crosslink density increases with increasing crosslink density and the effect slowly wears off after reaching a plateau at 50% crosslink density. The copolymer with 25% crosslink density was reacted with different amines with alkyl/aryl side chains to obtain a series of copolymers with 1,2-amino alcohol functional groups and varying hydrophobicity. Trypsin binding capacity again increases with hydrophobicity of the reacting amine and a good correlation between logPoctanol of the amine and protein binding is observed. The bound trypsin is denatured to the extent of 90% in spite of the presence of hydrophilic hydroxyl and amino groups. The behavior was comparable to that in mixtures of aqueous buffer and water-miscible organic co-solvents where the solvent concentration required to deactivate 50% of the enzyme (C50) is dependent on logPoctanol of the co-solvent. Copyright © 2014 Elsevier B.V. All rights reserved.

Quinone-induced protein modifications: Kinetic preference for reaction of 1,2-benzoquinones with thiol groups in proteins.

PubMed

Li, Yuting; Jongberg, Sisse; Andersen, Mogens L; Davies, Michael J; Lund, Marianne N

2016-08-01

Oxidation of polyphenols to quinones serves as an antioxidative mechanism, but the resulting quinones may induce damage to proteins as they react through a Michael addition with nucleophilic groups, such as thiols and amines to give protein adducts. In this study, rate constants for the reaction of 4-methylbenzoquinone (4MBQ) with proteins, thiol and amine compounds were determined under pseudo first-order conditions by UV-vis stopped-flow spectrophotometry. The chemical structures of the adducts were identified by LC-ESI-MS/MS. Proteins with free thiols were rapidly modified by 4MBQ with apparent second order rate constants, k2 of (3.1±0.2)×10(4)M(-1)s(-1) for bovine serum albumin (BSA) and (4.8±0.2)×10(3)M(-1)s(-1) for human serum albumin at pH 7.0. These values are at least 12-fold greater than that for α-lactalbumin (4.0±0.2)×10(2)M(-1)s(-1), which does not contain any free thiols. Reaction of Cys-34 of BSA with N-ethylmaleimide reduced the thiol concentration by ~59%, which resulted in a decrease in k2 by a similar percentage, consistent with rapid adduction at Cys-34. Reaction of 4MBQ with amines (Gly, Nα-acetyl-l-Lys, Nε-acetyl-l-Lys and l-Lys) and the guanidine group of Nα-acetyl-l-Arg was at least 5×10(5) slower than with low-molecular-mass thiols (l-Cys, Nα-acetyl-l-Cys, glutathione). The thiol-quinone interactions formed colorless thiol-phenol products via an intermediate adduct, while the amine-quinone interactions generated colored amine-quinone products that require oxygen involvement. These data provide strong evidence for rapid modification of protein thiols by quinone species which may be of considerable significance for biological and food systems. Copyright © 2016 Elsevier Inc. All rights reserved.

Biodegradation and detoxification of textile azo dyes by bacterial consortium under sequential microaerophilic/aerobic processes

PubMed Central

Lade, Harshad; Kadam, Avinash; Paul, Diby; Govindwar, Sanjay

2015-01-01

Release of textile azo dyes to the environment is an issue of health concern while the use of microorganisms has proved to be the best option for remediation. Thus, in the present study, a bacterial consortium consisting of Providencia rettgeri strain HSL1 and Pseudomonas sp. SUK1 has been investigated for degradation and detoxification of structurally different azo dyes. The consortium showed 98-99 % decolorization of all the selected azo dyes viz. Reactive Black 5 (RB 5), Reactive Orange 16 (RO 16), Disperse Red 78 (DR 78) and Direct Red 81 (DR 81) within 12 to 30 h at 100 mg L-1 concentration at 30 ± 0.2 °C under microaerophilic, sequential aerobic/microaerophilic and microaerophilic/aerobic processes. However, decolorization under microaerophilic conditions viz. RB 5 (0.26 mM), RO 16 (0.18 mM), DR 78 (0.20 mM) and DR 81 (0.23 mM) and sequential aerobic/microaerophilic processes viz. RB 5 (0.08 mM), RO 16 (0.06 mM), DR 78 (0.07 mM) and DR 81 (0.09 mM) resulted into the formation of aromatic amines. In distinction, sequential microaerophilic/ aerobic process doesn’t show the formation of amines. Additionally, 62-72 % reduction in total organic carbon content was observed in all the dyes decolorized broths under sequential microaerophilic/aerobic processes suggesting the efficacy of method in mineralization of dyes. Notable induction within the levels of azoreductase and NADH-DCIP reductase (97 and 229 % for RB 5, 55 and 160 % for RO 16, 63 and 196 % for DR 78, 108 and 258 % for DR 81) observed under sequential microaerophilic/aerobic processes suggested their critical involvements in the initial breakdown of azo bonds, whereas, a slight increase in the levels of laccase and veratryl alcohol oxidase confirmed subsequent oxidation of formed amines. Also, the acute toxicity assay with Daphnia magna revealed the nontoxic nature of the dye-degraded metabolites under sequential microaerophilic/aerobic processes. As biodegradation under sequential microaerophilic/aerobic process completely detoxified all the selected textile azo dyes, further efforts should be made to implement such methods for large scale dye wastewater treatment technologies. PMID:26417357