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.

Chemically Modified Bacteriophage as a Streamlined Approach to Noninvasive Breast Cancer Imaging

DTIC Science & Technology

2013-12-01

between the two major MALDI peaks is 245 Da, which is presumably an aldol addition of the ketone group to the PLP aldehyde (expected change: 248 Da...of the pVIII coat proteins lining the filamentous phage are converted to ketone groups, which can be subsequently modified with small molecule...chemistry to convert the N-terminal amines of the ∼4200 coat proteins into ketone groups. These sites can then serve as chemospecific handles for the

DFT investigation of the interaction of gold nanoclusters with poly(amidoamine) PAMAM G0 dendrimer

NASA Astrophysics Data System (ADS)

Camarada, M. B.

2016-06-01

The interaction between PAMAM G0 and gold nanoclusters Aun (n = 2, 4, 6, and 8) was studied theoretically at DFT level. Different coordination sites were explored, including internal and superficial coordination. All stable complexes exhibited external interaction with the amine or carbonyl site, while the core site coordination was not favored. The more stable binding of Aun was registered with the terminal amine group, while the binding at the amide site was relatively weaker. The vertical first ionization potential, electron affinity, Fermi level, and the HOMO-LUMO gap of PAMAM and Aun-PAMAM G0 complexes were also analyzed.

Activity of select dehydrogenases with sepharose-immobilized N(6)-carboxymethyl-NAD.

PubMed

Beauchamp, Justin; Vieille, Claire

2015-01-01

N(6)-carboxymethyl-NAD (N(6)-CM-NAD) can be used to immobilize NAD onto a substrate containing terminal primary amines. We previously immobilized N(6)-CM-NAD onto sepharose beads and showed that Thermotoga maritima glycerol dehydrogenase could use the immobilized cofactor with cofactor recycling. We now show that Saccharomyces cerevisiae alcohol dehydrogenase, rabbit muscle L-lactate dehydrogenase (type XI), bovine liver L-glutamic dehydrogenase (type III), Leuconostoc mesenteroides glucose-6-phosphate dehydro-genase, and Thermotoga maritima mannitol dehydrogenase are active with soluble N(6)-CM-NAD. The products of all enzymes but 6-phospho-D-glucono-1,5-lactone were formed when sepharose-immobilized N(6)-CM-NAD was recycled by T. maritima glycerol dehydrogenase, indicating that N(6)-immobilized NAD is suitable for use by a variety of different dehydrogenases. Observations of the enzyme active sites suggest that steric hindrance plays a greater role in limiting or allowing activity with the modified cofactor than do polarity and charge of the residues surrounding the N(6)-amine group on NAD.

Poly(ethylene oxide) surfactant polymers.

PubMed

Vacheethasanee, Katanchalee; Wang, Shuwu; Qiu, Yongxing; Marchant, Roger E

2004-01-01

We report on a series of structurally well-defined surfactant polymers that undergo surface-induced self-assembly on hydrophobic biomaterial surfaces. The surfactant polymers consist of a poly(vinyl amine) backbone with poly(ethylene oxide) and hexanal pendant groups. The poly(vinyl amine) (PVAm) was synthesized by hydrolysis of poly(N-vinyl formamide) following free radical polymerization of N-vinyl formamide. Hexanal and aldehyde-terminated poly(ethylene oxide) (PEO) were simultaneously attached to PVAm via reductive amination. Surfactant polymers with different PEO:hexanal ratios and hydrophilic/hydrophobic balances were prepared, and characterized by FT-IR, 1H-NMR and XPS spectroscopies. Surface active properties at the air/water interface were determined by surface tension measurements. Surface activity at a solid surface/water interface was demonstrated by atomic force microscopy, showing epitaxially molecular alignment for surfactant polymers adsorbed on highly oriented pyrolytic graphite. The surfactant polymers described in this report can be adapted for simple non-covalent surface modification of biomaterials and hydrophobic surfaces to provide highly hydrated interfaces.

Isomer-sensitive deboronation in reductive aminations of aryl boronic acids

DOE PAGES

Jones, Brad Howard; Wheeler, David R.; Wheeler, Jill S.; ...

2015-09-05

Deboronation is observed during the reductive amination of formylphenylboronic acid (FPBA) to the amine termini and side chains of peptides. This deboronation is sensitive to the isomerism of the boronic acid (BA), with ortho-FPBA yielding complete deboronation in the preparation of an N-terminally-modified dipeptide. The observed behavior is also clearly mediated by the chemical identity of the amine substrate. These results reveal a previously undocumented subtlety of BA functionalization and highlight the importance of thorough spectroscopic characterization in the preparation of peptide and small molecule BAs.

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.

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.

Synthesis of γ-Phosphate-Labeled and Doubly Labeled Adenosine Triphosphate Analogs.

PubMed

Hacker, Stephan M; Welter, Moritz; Marx, Andreas

2015-03-09

This unit describes the synthesis of γ-phosphate-labeled and doubly labeled adenosine triphosphate (ATP) analogs and their characterization using the phosphodiesterase I from Crotalus adamanteus (snake venom phosphodiesterase; SVPD). In the key step of the synthesis, ATP or an ATP analog, bearing a linker containing a trifluoroacetamide group attached to the nucleoside, are modified with an azide-containing linker at the terminal phosphate using an alkylation reaction. Subsequently, different labels are introduced to the linkers by transformation of one functional group to an amine and coupling to an N-hydroxysuccinimide ester. Specifically, the Staudinger reaction of the azide is employed as a straightforward means to obtain an amine in the presence of various labels. Furthermore, the fluorescence characteristics of a fluorogenic, doubly labeled ATP analog are investigated following enzymatic cleavage by SVPD. Copyright © 2015 John Wiley & Sons, Inc.

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

{μ-2-[(3-Amino-2,2-dimethyl-prop-yl)imino-meth-yl]-6-meth-oxy-phenolato-1:2κ(5)O(1),O(6):N,N',O(1)}{2-[(3-amino-2,2-dimethyl-prop-yl)imino-meth-yl]-6-meth-oxy-phenolato-1κ(3)N,N',O(1)}-μ-azido-1:2κ(2)N:N-azido-2κN-methanol-2κO-dinickel(II).

PubMed

Ghaemi, Akbar; Rayati, Saeed; Fayyazi, Kazem; Ng, Seik Weng; Tiekink, Edward R T

2012-08-01

Two distinct coordination geometries are found in the binuclear title complex, [Ni(2)(C(13)H(19)N(2)O(2))(2)(N(3))(2)(CH(3)OH)], as one Schiff base ligand is penta-dentate, coordinating via the anti-cipated oxide O, imine N and amine N atoms (as for the second, tridentate, ligand) but the oxide O is bridging and coordination also occurs through the meth-oxy O atom. The Ni(II) atoms are linked by a μ(2)-oxide atom and one end of a μ(2)-azide ligand, forming an Ni(2)ON core. The coordination geometry for the Ni(II) atom coordinated by the tridentate ligand is completed by the meth-oxy O atom derived from the penta-dentate ligand, with the resulting N(3)O(3) donor set defining a fac octa-hedron. The second Ni(II) atom has its cis-octa-hedral N(4)O(2) coordination geometry completed by the imine N and amine N atoms of the penta-dentate Schiff base ligand, a terminally coordinated azide N and a methanol O atom. The arrangement is stabilized by an intra-molecular hydrogen bond between the methanol H and the oxide O atom. Linear supra-molecular chains along the a axis are formed in the crystal packing whereby two amine H atoms from different amine atoms hydrogen bond to the terminal N atom of the monodentate azide ligand.

Carbon Dioxide Transformation in Imidazolium Salts: Hydroaminomethylation Catalyzed by Ru-Complexes.

PubMed

Ali, Meher; Gual, Aitor; Ebeling, Gunter; Dupont, Jairton

2016-08-23

The catalytic species generated by dissolving Ru3 (CO)12 in the ionic liquids 1-n-butyl-3-methyl-imidazolium chloride or 1-n-butyl-2,3-dimethyl-imidazolium chloride are efficient multifunctional catalysts for: (a) reverse water-gas shift, (b) hydroformylation of alkenes, and (c) reductive amination of aldehydes. Thus the reaction of alkenes with primary or secondary amines (alkene/amine, 1:1) under CO2 /H2 (1:1) affords the hydroaminomethylations products in high alkene conversions (up to 99 %) and selectivities (up to 96 %). The reaction proceeds under relatively mild reaction conditions (120 °C, 60 bar=6 MPa) and affords selectively secondary and tertiary amines. The presence of amine strongly reduces the alkene hydrogenation competitive pathway usually observed in the hydroformylation of terminal alkenes by Ru complexes. The catalytic system is also highly active for the reductive amination of aldehydes and ketones yielding amines in high yields (>90 %). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

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.

Alkyne- and 1,6-elimination- succinimidyl carbonate - terminated heterobifunctional poly(ethylene glycol) for reversible "Click" PEGylation.

PubMed

Xie, Yumei; Duan, Shaofeng; Forrest, M Laird

2010-01-01

A new heterobifunctional (succinimidyl carbonate, SC)-activated poly(ethylene glycol) (PEG) with a reversible 1,6-elimination linker and a terminal alkyne for "click" chemistry was synthesized with high efficiency and low polydispersity. The α-alkyne-ω-hydroxyl PEG was first prepared using trimethylsilyl-2-propargyl alcohol as an initiator for ring-opening polymerization of ethylene oxide followed by mild deprotection with tetrabutylammonium fluoride. The hydroxy end was then modified with diglycolic anhydride to generate α-alkyne-ω-carboxylic acid PEG. The reversible 1, 6-elimination linker was introduced by conjugation of a hydroxymethyl phenol followed by activation with N,N'-disuccinimidyl carbonate to generate the heterobifunctional α-alkyne-ω-SC PEG. The terminal alkyne is available for "click" conjugation to azido ligands via 1,3-dipolar cycloaddition, and the succinimidyl carbonate will form a reversible conjugate to amines (e.g. in proteins) that can release the unaltered amine after base or enzyme catalyzed cleavage of the 1,6-linker.

Nickel Ligation of the N-Terminal Amine of HypA Is Required for Urease Maturation in Helicobacter pylori.

PubMed

Hu, Heidi Q; Johnson, Ryan C; Merrell, D Scott; Maroney, Michael J

2017-02-28

The human pathogen Helicobacter pylori requires nickel for colonization of the acidic environment of the stomach. HypA, a Ni metallochaperone that is typically associated with hydrogenase maturation, is also required for urease maturation and acid survival of H. pylori. There are two proposed Ni site structures for HypA; one is a paramagnetic six-coordinate site characterized by X-ray absorption spectroscopy (XAS) in unmodified HypA, while another is a diamagnetic four-coordinate planar site characterized by solution nuclear magnetic resonance in an N-terminally modified HypA construct. To determine the role of the N-terminal amine in Ni binding of HypA, an N-terminal extension variant, L2*-HypA, in which a leucine residue was inserted into the second position of the amino acid sequence in the proposed Ni-binding motif, was characterized in vitro and in vivo. Structural characterization of the Ni site using XAS showed a coordination change from six-coordinate in wild-type HypA (WT-HypA) to five-coordinate pyramidal in L2*-HypA, which was accompanied by the loss of two N/O donor protein ligands and the addition of an exogenous bromide ligand from the buffer. The magnetic properties of the Ni sites in WT-HypA compared to those of the Ni sites in L2*-HypA confirmed that a spin-state change from high to low spin accompanied this change in structure. The L2*-HypA H. pylori strain was shown to be acid sensitive and deficient in urease activity in vivo. In vitro characterization showed that L2*-HypA did not disrupt the HypA-UreE interaction that is essential for urease maturation but was at least 20-fold weaker in Ni binding than WT-HypA. Characterization of the L2*-HypA variant clearly demonstrates that the N-terminal amine of HypA is involved in proper Ni coordination and is necessary for urease activity and acid survival.

Nickel Ligation of the N-Terminal Amine of HypA Is Required for Urease Maturation in Helicobacter pylori

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

Hu, Heidi Q.; Johnson, Ryan C.; Merrell, D. Scott

The human pathogen Helicobacter pylori requires nickel for colonization of the acidic environment of the stomach. HypA, a Ni metallochaperone that is typically associated with hydrogenase maturation, is also required for urease maturation and acid survival of H. pylori. There are two proposed Ni site structures for HypA; one is a paramagnetic six-coordinate site characterized by X-ray absorption spectroscopy (XAS) in unmodified HypA, while another is a diamagnetic four-coordinate planar site characterized by solution nuclear magnetic resonance in an N-terminally modified HypA construct. To determine the role of the N-terminal amine in Ni binding of HypA, an N-terminal extension variant,more » L2*-HypA, in which a leucine residue was inserted into the second position of the amino acid sequence in the proposed Ni-binding motif, was characterized in vitro and in vivo. Structural characterization of the Ni site using XAS showed a coordination change from six-coordinate in wild-type HypA (WT-HypA) to five-coordinate pyramidal in L2*-HypA, which was accompanied by the loss of two N/O donor protein ligands and the addition of an exogenous bromide ligand from the buffer. The magnetic properties of the Ni sites in WT-HypA compared to those of the Ni sites in L2*-HypA confirmed that a spin-state change from high to low spin accompanied this change in structure. The L2*-HypA H. pylori strain was shown to be acid sensitive and deficient in urease activity in vivo. In vitro characterization showed that L2*-HypA did not disrupt the HypA–UreE interaction that is essential for urease maturation but was at least 20-fold weaker in Ni binding than WT-HypA. Characterization of the L2*-HypA variant clearly demonstrates that the N-terminal amine of HypA is involved in proper Ni coordination and is necessary for urease activity and acid survival.« less

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.

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.

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.

Porous Cross-Linked Polyimide-Urea Networks

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B. (Inventor); Nguyen, Baochau N. (Inventor)

2015-01-01

Porous cross-linked polyimide-urea networks are provided. The networks comprise a subunit comprising two anhydride end-capped polyamic acid oligomers in direct connection via a urea linkage. The oligomers (a) each comprise a repeating unit of a dianhydride and a diamine and a terminal anhydride group and (b) are formulated with 2 to 15 of the repeating units. The subunit was formed by reaction of the diamine and a diisocyanate to form a diamine-urea linkage-diamine group, followed by reaction of the diamine-urea linkage-diamine group with the dianhydride and the diamine to form the subunit. The subunit has been cross-linked via a cross-linking agent, comprising three or more amine groups, at a balanced stoichiometry of the amine groups to the terminal anhydride groups. The subunit has been chemically imidized to yield the porous cross-linked polyimide-urea network. Also provided are wet gels, aerogels, and thin films comprising the networks, and methods of making the networks.

Protein immobilization onto electrochemically synthesized CoFe nanowires

PubMed Central

Torati, Sri Ramulu; Reddy, Venu; Yoon, Seok Soo; Kim, CheolGi

2015-01-01

CoFe nanowires have been synthesized by the electrodeposition technique into the pores of a polycarbonate membrane with a nominal pore diameter of 50 nm, and the composition of CoFe nanowires varying by changing the source concentration of iron. The synthesized nanowire surfaces were functionalized with amine groups by treatment with aminopropyltriethoxysilane (APTES) linker, and then conjugated with streptavidin-Cy3 protein via ethyl (dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide coupling chemistry. The oxide surface of CoFe nanowire is easily modified with aminopropyltriethoxysilane to form an amine terminating group, which is covalently bonded to streptavidin-Cy3 protein. The physicochemical properties of the nanowires were analyzed through different characterization techniques such as scanning electron microscope, energy dispersive spectroscopy, and vibrating sample magnetometer. Fluorescence microscopic studies and Fourier transform infrared studies confirmed the immobilization of protein on the nanowire surface. In addition, the transmission electron microscope analysis reveals the thin protein layer which is around 12–15 nm on the nanowire surfaces. PMID:25609966

Morphology and properties of amine terminated poly(arylene ether ketone) and poly(arylene ether sulfone) modified epoxy resin systems

NASA Technical Reports Server (NTRS)

Cecere, J. A.; Mcgrath, J. E.; Hedrick, J. L.

1986-01-01

Epoxy resin networks cured with DDS were modified by incorporating tough ductile thermoplastics such as the amine terminated polyether sulfones and amine terminated polyether ketones. Both linear copolymers were able to significantly improve the fracture toughness values at the 15 and 30 weight percent concentrations examined. These improvements in fracture toughness were achieved without any significant change in the flexural modulus.

Amide or Amine: Determining the Origin of the 3300 cm−1 NH Mode in Protein SFG Spectra Using 15N Isotope Labels

PubMed Central

Weidner, Tobias; Breen, Nicholas F.; Drobny, Gary P.; Castner, David G.

2009-01-01

Sum frequency generation (SFG) vibrational spectroscopy has been employed in biomaterials research and protein adsorption studies with growing success in recent years. A number of studies focusing on understanding SFG spectra of proteins and peptides at different interfaces have laid the foundation for future, more complex studies. In many cases a strong NH mode near 3300 cm−1 is observed in the SFG spectra, but the relationship of this mode to the peptide structure is uncertain since it has been assigned to either a backbone amide mode or a side chain related amine resonance. A thorough understanding of the SFG spectra of these first model systems is an important first step for future experiments. To clarify the origin of the NH SFG mode we studied 15N isotopically labeled 14-amino acid amphiphilic model peptides composed of lysine (K) and leucine (L) in an α-helical secondary structure (LKα14) that were adsorbed onto charged surfaces in situ at the solid-liquid interface. 15N substitution at the terminal amine group of the lysine side chains resulted in a red-shift of the NH mode of 9 cm−1 on SiO2 and 13 cm−1 on CaF2. This clearly shows the 3300 cm−1 NH feature is associated with side chain NH stretches and not with backbone amide modes. PMID:19873996

Amide or amine: determining the origin of the 3300 cm(-1) NH mode in protein SFG spectra using 15N isotope labels.

PubMed

Weidner, Tobias; Breen, Nicholas F; Drobny, Gary P; Castner, David G

2009-11-26

Sum frequency generation (SFG) vibrational spectroscopy has been employed in biomaterials research and protein adsorption studies with growing success in recent years. A number of studies focusing on understanding SFG spectra of proteins and peptides at different interfaces have laid the foundation for future, more complex studies. In many cases, a strong NH mode near 3300 cm(-1) is observed in the SFG spectra, but the relationship of this mode to the peptide structure is uncertain, since it has been assigned to either a backbone amide mode or a side chain related amine resonance. A thorough understanding of the SFG spectra of these first model systems is an important first step for future experiments. To clarify the origin of the NH SFG mode, we studied (15)N isotopically labeled 14-amino acid amphiphilic model peptides composed of lysine (K) and leucine (L) in an alpha-helical secondary structure (LKalpha14) that were adsorbed onto charged surfaces in situ at the solid-liquid interface. (15)N substitution at the terminal amine group of the lysine side chains resulted in a red-shift of the NH mode of 9 cm(-1) on SiO(2) and 13 cm(-1) on CaF(2). This clearly shows the 3300 cm(-1) NH feature is associated with side chain NH stretches and not with backbone amide modes.

Tailoring Enzyme-Like Activities of Gold Nanoclusters by Polymeric Tertiary Amines for Protecting Neurons Against Oxidative Stress.

PubMed

Liu, Ching-Ping; Wu, Te-Haw; Lin, Yu-Lung; Liu, Chia-Yeh; Wang, Sabrina; Lin, Shu-Yi

2016-08-01

The cytotoxicity of nanozymes has drawn much attention recently because their peroxidase-like activity can decompose hydrogen peroxide (H2 O2 ) to produce highly toxic hydroxyl radicals (•OH) under acidic conditions. Although catalytic activities of nanozymes are highly associated with their surface properties, little is known about the mechanism underlying the surface coating-mediated enzyme-like activities. Herein, it is reported for the first time that amine-terminated PAMAM dendrimer-entrapped gold nanoclusters (AuNCs-NH2 ) unexpectedly lose their peroxidase-like activity while still retaining their catalase-like activity in physiological conditions. Surprisingly, the methylated form of AuNCs-NH2 (i.e., MAuNCs-N(+) R3 , where R = H or CH3 ) results in a dramatic recovery of the intrinsic peroxidase-like activity while blocking most primary and tertiary amines (1°- and 3°-amines) of dendrimers to form quaternary ammonium ions (4°-amines). However, the hidden peroxidase-like activity is also found in hydroxyl-terminated dendrimer-encapsulated AuNCs (AuNCs-OH, inside backbone with 3°-amines), indicating that 3°-amines are dominant in mediating the peroxidase-like activity. The possible mechanism is further confirmed that the enrichment of polymeric 3°-amines on the surface of dendrimer-encapsulated AuNCs provides sufficient suppression of the critical mediator •OH for the peroxidase-like activity. Finally, it is demonstrated that AuNCs-NH2 with diminished cytotoxicity have great potential for use in primary neuronal protection against oxidative damage. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Fluorescence Studies of Protein Crystallization Interactions

NASA Technical Reports Server (NTRS)

Pusey, Marc L.; Smith, Lori; Forsythe, Elizabeth

1999-01-01

We are investigating protein-protein interactions in under- and over-saturated crystallization solution conditions using fluorescence methods. The use of fluorescence requires fluorescent derivatives where the probe does not markedly affect the crystal packing. A number of chicken egg white lysozyme (CEWL) derivatives have been prepared, with the probes covalently attached to one of two different sites on the protein molecule; the side chain carboxyl of ASP 101, within the active site cleft, and the N-terminal amine. The ASP 101 derivatives crystallize while the N-terminal amine derivatives do not. However, the N-terminal amine is part of the contact region between adjacent 43 helix chains, and blocking this site does would not interfere with formation of these structures in solution. Preliminary FRET data have been obtained at pH 4.6, 0.1M NaAc buffer, at 5 and 7% NaCl, 4 C, using the N-terminal bound pyrene acetic acid (PAA, Ex 340 nm, Em 376 nm) and ASP 101 bound Lucifer Yellow (LY, Ex 425 nm, Em 525 nm) probe combination. The corresponding Csat values are 0.471 and 0.362 mg/ml (approximately 3.3 and approximately 2.5 x 10 (exp 5) M respectively), and all experiments were carried out at approximately Csat or lower total protein concentration. The data at both salt concentrations show a consistent trend of decreasing fluorescence yield of the donor species (PAA) with increasing total protein concentration. This decrease is apparently more pronounced at 7% NaCl, consistent with the expected increased intermolecular interactions at higher salt concentrations (reflected in the lower solubility). The estimated average distance between protein molecules at 5 x 10 (exp 6) M is approximately 70 nm, well beyond the range where any FRET can be expected. The calculated RO, where 50% of the donor energy is transferred to the acceptor, for the PAA-CEWL * LY-CEWL system is 3.28 nm, based upon a PAA-CEWL quantum efficiency of 0.41.

Charge reversible gold nanoparticles for high efficient absorption and desorption of DNA

NASA Astrophysics Data System (ADS)

Wang, Can; Zhuang, Jiaqi; Jiang, Shan; Li, Jun; Yang, Wensheng

2012-10-01

Mercaptoundecylamine and mercaptoundecanoic acid co-modified Au nanoparticles were prepared by two-step ligand exchange of 6-mercaptohexanoic acid modified gold nanoparticles. Such particles terminated by appropriate ratios of the amine and carboxyl groups ( R N/C) were identified to show reversible charge on their surface, which were switchable by pH of the solution. The isoelectric point (IEP) of the particles is tunable by changing the ratios of the amine and carboxyl groups on the particle surfaces. The particles can absorb DNA effectively at pH lower than the IEP driven by the direct electrostatic interactions between DNA and the particle surface. When pH of the solutions was elevated to be higher than the IEP, the absorbed DNA can be released almost completely due to the electrostatic repulsion between the particle surface and DNA. With appropriate R N/C ratios of 0.8, the absorption and desorption efficiencies of DNA were 97 and 98 %, respectively, corresponding an extraction efficiency of 95 %. Such particles with reversible surface charges allow the high efficient extraction of DNA by simply changing pH instead of by changing salt concentration in the conventional salt bridge method.

Method for forming pyrrone molding powders and products of said method

NASA Technical Reports Server (NTRS)

Hughes, C. T.; Mchenry, R. J. (Inventor)

1972-01-01

The formation of pyrrone resins of the ladder or semiladder structure is described. The technique involves initial formation of fully cyclized prepolymers having an average degree of polymerization of about 1.5, one with acidic terminal groups, another with amine terminal groups. Thereafter the prepolymers are intimately admixed on a 1:1 stoichiometric basis. The resulting powder mixture is molded at elevated pressures and temperatures to form a fully cyclized resin.

Structure-activity relationships of lipopolysaccharide sequestration in guanylhydrazone-bearing lipopolyamines.

PubMed

Wu, Wenyan; Sil, Diptesh; Szostak, Michal L; Malladi, Subbalakshmi S; Warshakoon, Hemamali J; Kimbrell, Matthew R; Cromer, Jens R; David, Sunil A

2009-01-15

The toxicity of gram-negative bacterial endotoxin (lipopolysaccharide, LPS) resides in its structurally highly conserved glycolipid component called lipid A. Our major goal has been to develop small-molecules that would sequester LPS by binding to the lipid A moiety, so that it could be useful for the prophylaxis or adjunctive therapy of gram-negative sepsis. We had previously identified in rapid-throughput screens several guanylhydrazones as potent LPS binders. We were desirous of examining if the presence of the guanylhydrazone (rather than an amine) functionality would afford greater LPS sequestration potency. In evaluating a congeneric set of guanylhydrazone analogues, we find that C(16) alkyl substitution is optimal in the N-alkylguanylhydrazone series; a homospermine analogue with the terminal amine N-alkylated with a C(16) chain with the other terminus of the molecule bearing an unsubstituted guanylhydrazone moiety is marginally more active, suggesting very slight, if any, steric effects. Neither C(16) analogue is significantly more active than the N-C(16)-alkyl or N-C(16)-acyl compounds that we had characterized earlier, indicating that basicity of the phosphate-recognizing cationic group, is not a determinant of LPS sequestration activity.

Porous Cross-Linked Polyimide Networks

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B. (Inventor); Guo, Haiquan (Inventor)

2015-01-01

Porous cross-linked polyimide networks are provided. The networks comprise an anhydride end-capped polyamic acid oligomer. The oligomer (i) comprises a repeating unit of a dianhydride and a diamine and terminal anhydride groups, (ii) has an average degree of polymerization of 10 to 50, (iii) has been cross-linked via a cross-linking agent, comprising three or more amine groups, at a balanced stoichiometry of the amine groups to the terminal anhydride groups, and (iv) has been chemically imidized to yield the porous cross-linked polyimide network. Also provided are porous cross-linked polyimide aerogels comprising a cross-linked and imidized anhydride end-capped polyamic acid oligomer, wherein the oligomer comprises a repeating unit of a dianhydride and a diamine, and the aerogel has a density of 0.10 to 0.333 g/cm.sup.3 and a Young's modulus of 1.7 to 102 MPa. Also provided are thin films comprising aerogels, and methods of making porous cross-linked polyimide networks.

Blocking an N-terminal acetylation–dependent protein interaction inhibits an E3 ligase

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

Scott, Daniel C.; Hammill, Jared T.; Min, Jaeki

N-terminal acetylation is an abundant modification influencing protein functions. Because ~80% of mammalian cytosolic proteins are N-terminally acetylated, this modification is potentially an untapped target for chemical control of their functions. Structural studies have revealed that, like lysine acetylation, N-terminal acetylation converts a positively charged amine into a hydrophobic handle that mediates protein interactions; hence, this modification may be a druggable target. We report the development of chemical probes targeting the N-terminal acetylation–dependent interaction between an E2 conjugating enzyme (UBE2M or UBC12) and DCN1 (DCUN1D1), a subunit of a multiprotein E3 ligase for the ubiquitin-like protein NEDD8. The inhibitors aremore » highly selective with respect to other protein acetyl-amide–binding sites, inhibit NEDD8 ligation in vitro and in cells, and suppress anchorage-independent growth of a cell line with DCN1 amplification. Overall, our data demonstrate that N-terminal acetyl-dependent protein interactions are druggable targets and provide insights into targeting multiprotein E2–E3 ligases.« less

Linker Dependent Bond Rupture Force Measurements in Single-Molecule Junctions

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

Frei M.; Hybertsen M.; Aradhya S.V.

We use a modified conducting atomic force microscope to simultaneously probe the conductance of a single-molecule junction and the force required to rupture the junction formed by alkanes terminated with four different chemical link groups which vary in binding strength and mechanism to the gold electrodes. Molecular junctions with amine, methylsulfide, and diphenylphosphine terminated molecules show clear conductance signatures and rupture at a force that is significantly smaller than the measured 1.4 nN force required to rupture the single-atomic gold contact. In contrast, measurements with a thiol terminated alkane which can bind covalently to the gold electrode show conductance andmore » force features unlike those of the other molecules studied. Specifically, the strong Au-S bond can cause structural rearrangements in the electrodes, which are accompanied by substantial conductance changes. Despite the strong Au-S bond and the evidence for disruption of the Au structure, the experiments show that on average these junctions also rupture at a smaller force than that measured for pristine single-atom gold contacts.« less

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

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.

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.

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.

Hydrophobic benzyl amines as supports for liquid-phase C-terminal amidated peptide synthesis: application to the preparation of ABT-510.

PubMed

Matsumoto, Emiko; Fujita, Yuko; Okada, Yohei; Kauppinen, Esko I; Kamiya, Hidehiro; Chiba, Kazuhiro

2015-09-01

C-terminal amidation is one of the most common modification of peptides and frequently found in bioactive peptides. However, the C-terminal modification must be creative, because current chemical synthetic techniques of peptides are dominated by the use of C-terminal protecting supports. Therefore, it must be carried out after the removal of such supports, complicating reaction work-up and product isolation. In this context, hydrophobic benzyl amines were successfully added to the growing toolbox of soluble tag-assisted liquid-phase peptide synthesis as supports, leading to the total synthesis of ABT-510 (2). Although an ethyl amide-forming type was used in the present work, different types of hydrophobic benzyl amines could also be simply designed and prepared through versatile reductive aminations in one step. The standard acidic treatment used in the final deprotection step for peptide synthesis gave the desired C-terminal secondary amidated peptide with no epimerization. Copyright © 2015 European Peptide Society and John Wiley & Sons, Ltd.

Characterization of labelling and de-labelling reagents for detection and recovery of tyrosine residue in peptide.

PubMed

Toyo'oka, Toshimasa; Mantani, Tomomi; Kato, Masaru

2003-01-01

This paper characterized the labelling and de-labelling reagents for reversible labelling of tyrosine (Tyr)-containing peptide, which involves detection and recovery. The phenolic hydroxyl group (-OH) in Tyr structure reacted with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F), 4-(N,N-dimethylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (DBD-F), and 1-fluoro-2,4-dinitrobenzene (DNFB) under mild conditions at room temperature at pH 9.3. The labels in the resulting derivatives were removed with the treatment of nucleophiles, such as thiols (cysteine, N-acetyl-L-cysteine and dithiothreitol) and amines (dimethylamine, methylamine, diethylamine, ethylamine and pyrrolidine). The de-labelling reactions of NBD-labelled N-acetyl-L-tyrosine (N-AcTyr) with the nucleophiles produced N-AcTyr, accompanied by NBD-nucleophile. Although DBD-F and DNFB also successfully labeled the -OH group in N-AcTyr, the efficiency of Cbond;O bond cleavage and recovery of N-AcTyr by the nucleophiles was relatively low compared with NBD-label. Among the de-labelling reagents, N-acetyl-L-cysteine and dimethylamine were recommended for the elimination of NBD moiety, with respect to the reaction rate, the side reaction, and the yield of recovery. The proposed procedure, which includes the labelling with NBD-F and the removal of NBD moiety by the nucleophiles, was successfully applied to the reversible labelling of N-terminal amine-blocked peptides, i.e. N-AcTyr-Val-Gly, Z-Glu-Tyr, Z-Phe-Tyr, N-Formyl-Met-Leu-Tyr, and N-AcArg-Pro-Pro-Gly-Phe-Ser-Pro-Tyr-Arg. Copyright 2003 John Wiley & Sons, Ltd.

Paramagnetic NMR Investigation of Dendrimer-Based Host-Guest Interactions

PubMed Central

Wang, Fei; Shao, Naimin; Cheng, Yiyun

2013-01-01

In this study, the host-guest behavior of poly(amidoamine) (PAMAM) dendrimers bearing amine, hydroxyl, or carboxylate surface functionalities were investigated by paramagnetic NMR studies. 2,2,6,6-Tetramethylpiperidinyloxy (TEMPO) derivatives were used as paramagnetic guest molecules. The results showed that TEMPO-COOH significantly broaden the 1H NMR peaks of amine- and hydroxyl-terminated PAMAM dendrimers. In comparison, no paramagnetic relaxation enhancement (PRE) was observed between TEMPO-NH2, TEMPO-OH and the three types of PAMAM dendrimers. The PRE phenomenon observed is correlated with the encapsulation of TEMPO-COOH within dendrimer pockets. Protonation of the tertiary amine groups within PAMAM dendrimers plays an important role during this process. Interestingly, the absence of TEMPO-COOH encapsulation within carboxylate-terminated PAMAM dendrimer is observed due to the repulsion of TEMPO-COO- anion and anionic dendrimer surface. The combination of paramagnetic probes and 1H NMR linewidth analysis can be used as a powerful tool in the analysis of dendrimer-based host-guest systems. PMID:23762249

Ruthenium-catalyzed regioselective allylic amination of 2,3,3-trifluoroallylic carbonates.

PubMed

Isobe, Shin-Ichi; Terasaki, Shou; Hanakawa, Taisyun; Mizuno, Shota; Kawatsura, Motoi

2017-04-05

We demonstrated the ruthenium-catalyzed allylic amination of 2,3,3-trifluoroallylic carbonates with several types of amines. The reactions proceeded with several types of amines, and succeeded in obtaining polyfluorinated terminal alkenes possessing branched allylic amines as a single regioisomer.

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.

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

Metal-Free Oxidation of Primary Amines to Nitriles through Coupled Catalytic Cycles.

PubMed

Lambert, Kyle M; Bobbitt, James M; Eldirany, Sherif A; Kissane, Liam E; Sheridan, Rose K; Stempel, Zachary D; Sternberg, Francis H; Bailey, William F

2016-04-04

Synergism among several intertwined catalytic cycles allows for selective, room temperature oxidation of primary amines to the corresponding nitriles in 85-98% isolated yield. This metal-free, scalable, operationally simple method employs a catalytic quantity of 4-acetamido-TEMPO (ACT; TEMPO=2,2,6,6-tetramethylpiperidine N-oxide) radical and the inexpensive, environmentally benign triple salt oxone as the terminal oxidant under mild conditions. Simple filtration of the reaction mixture through silica gel affords pure nitrile products. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

1-{(E)-[(2E)-3-(4-Meth-oxy-phen-yl)-1-phenyl-prop-2-en-1-yl-idene]amino}-3-phenyl-urea: crystal structure and Hirshfeld surface analysis.

PubMed

Tan, Ming Yueh; Crouse, Karen A; Ravoof, Thahira B S A; Jotani, Mukesh M; Tiekink, Edward R T

2017-11-01

The title compound, C 23 H 21 N 3 O 2 , is constructed about an almost planar disubstituted amino-urea residue (r.m.s. deviation = 0.0201 Å), which features an intra-molecular amine-N-H⋯N(imine) hydrogen bond. In the 'all- trans ' chain connecting this to the terminal meth-oxy-benzene residue, the conformation about each of the imine and ethyl-ene double bonds is E . In the crystal, amide-N-H⋯O(carbon-yl) hydrogen bonds connect centrosymmetrically related mol-ecules into dimeric aggregates, which also incorporate ethyl-ene-C-H⋯O(amide) inter-actions. The dimers are linked by amine-phenyl-C-H⋯π(imine-phen-yl) and meth-oxy-benzene-C-H⋯π(amine-phen-yl) inter-actions to generate a three-dimensional network. The importance of C-H⋯π inter-actions in the mol-ecular packing is reflected in the relatively high contributions made by C⋯H/H⋯C contacts to the Hirshfeld surface, i.e . 31.6%.

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.

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.

Molecularly imprinted electrochemical sensor based on amine group modified graphene covalently linked electrode for 4-nonylphenol detection.

PubMed

Chen, Hong-Jun; Zhang, Zhao-Hui; Cai, Rong; Chen, Xing; Liu, Yu-Nan; Rao, Wei; Yao, Shou-Zhuo

2013-10-15

In this work, an imprinted electrochemical sensor based on electrochemical reduced graphene covalently modified carbon electrode was developed for the determination of 4-nonylphenol (NP). An amine-terminated functional graphene oxide was covalently modified onto the electrode surface with diazonium salt reactions to improve the stability and reproducibility of the imprinted sensor. The electrochemical properties of each modified electrodes were investigated with differential pulse voltammetry (DPV). The electrochemical characteristic of the imprinted sensor was also investigated using electrochemical impedance spectroscopy (EIS) in detail. The response currents of the imprinted electrode exhibited a linear relationship toward 4-nonylphenol concentration ranging from 1.0 × 10(-11) to 1.0 × 10(-8) gm L(-1) with the detection limit of 3.5 × 10(-12) gm L(-1) (S/N=3). The fabricated electrochemical imprinted sensor was successfully applied to the detection of 4-nonylphenol in rain and lake water samples. Crown Copyright © 2013 Published by Elsevier B.V. All rights reserved.

A Blocking Group Scan Using a Spherical Organometallic Complex Identifies an Unprecedented Binding Mode with Potent Activity In Vitro and In Vivo for the Opioid Peptide Dermorphin.

PubMed

Strack, Martin; Bedini, Andrea; Yip, King T; Lombardi, Sara; Siegmund, Daniel; Stoll, Raphael; Spampinato, Santi M; Metzler-Nolte, Nils

2016-10-04

Herein, the selective enforcement of one particular receptor-ligand interaction between specific domains of the μ-selective opioid peptide dermorphin and the μ opioid receptor is presented. For this, a blocking group scan is described which exploits the steric demand of a bis(quinolinylmethyl)amine rhenium(I) tricarbonyl complex conjugated to a number of different, strategically chosen positions of dermorphin. The prepared peptide conjugates lead to the discovery of two different binding modes: An expected N-terminal binding mode corresponds to the established view of opioid peptide binding, whereas an unexpected C-terminal binding mode is newly discovered. Surprisingly, both binding modes provide high affinity and agonistic activity at the μ opioid receptor in vitro. Furthermore, the unprecedented C-terminal binding mode shows potent dose-dependent antinociception in vivo. Finally, in silico docking studies support receptor activation by both dermorphin binding modes and suggest a biological relevance for dermorphin itself. Relevant ligand-protein interactions are similar for both binding modes, which is in line with previous protein mutation studies. © 2016 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.

40 CFR 721.10017 - Amine terminated bisphenol A diglycidyl ether polymer (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... diglycidyl ether polymer (generic). 721.10017 Section 721.10017 Protection of Environment ENVIRONMENTAL... ether polymer (generic). (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substances identified generically as amine terminated bisphenol A diglycidyl ether polymer (PMNs P...

40 CFR 721.10017 - Amine terminated bisphenol A diglycidyl ether polymer (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... diglycidyl ether polymer (generic). 721.10017 Section 721.10017 Protection of Environment ENVIRONMENTAL... ether polymer (generic). (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substances identified generically as amine terminated bisphenol A diglycidyl ether polymer (PMNs P...

40 CFR 721.10017 - Amine terminated bisphenol A diglycidyl ether polymer (generic).

Code of Federal Regulations, 2013 CFR

2013-07-01

... diglycidyl ether polymer (generic). 721.10017 Section 721.10017 Protection of Environment ENVIRONMENTAL... ether polymer (generic). (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substances identified generically as amine terminated bisphenol A diglycidyl ether polymer (PMNs P...

40 CFR 721.10017 - Amine terminated bisphenol A diglycidyl ether polymer (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... diglycidyl ether polymer (generic). 721.10017 Section 721.10017 Protection of Environment ENVIRONMENTAL... ether polymer (generic). (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substances identified generically as amine terminated bisphenol A diglycidyl ether polymer (PMNs P...

40 CFR 721.10017 - Amine terminated bisphenol A diglycidyl ether polymer (generic).

Code of Federal Regulations, 2012 CFR

2012-07-01

... diglycidyl ether polymer (generic). 721.10017 Section 721.10017 Protection of Environment ENVIRONMENTAL... ether polymer (generic). (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substances identified generically as amine terminated bisphenol A diglycidyl ether polymer (PMNs P...

Tandem Carbocupration/Oxygenation of Terminal Alkynes

PubMed Central

Zhang, Donghui; Ready, Joseph M.

2008-01-01

A direct and general synthesis of α-branched aldehydes and their enol derivatives is described. Carbocupration of terminal alkynes and subsequent oxygenation with lithium tert-butyl peroxide generates a metallo-enolate. Trapping with various electrophiles provides α-branched aldehydes or stereo-defined trisubstituted enol esters or silyl ethers. The tandem carbocupration/oxygenation tolerates alkyl and silyl ethers, esters and tertiary amines. The reaction is effective with organocopper complexes derived from primary, secondary and tertiary Grignard reagents and from n-butyllithium. PMID:16321021

Solid-Phase Synthesis of Diverse Peptide Tertiary Amides By Reductive Amination

PubMed Central

Pels, Kevin; Kodadek, Thomas

2015-01-01

The synthesis of libraries of conformationally-constrained peptide-like oligomers is an important goal in combinatorial chemistry. In this regard an attractive building block is the N-alkylated peptide, also known as peptide tertiary amide (PTA). PTAs are strongly biased conformationally due to allylic 1,3 strain interactions. We report here an improved synthesis of these species on solid supports through the use of reductive amination chemistry using amino acid-terminated, bead-displayed oligomers and diverse aldehydes. The utility of this chemistry is demonstrated by the synthesis of a library of 10,000 mixed peptoid-PTA oligomers. PMID:25695359

Solid-phase synthesis of diverse peptide tertiary amides by reductive amination.

PubMed

Pels, Kevin; Kodadek, Thomas

2015-03-09

The synthesis of libraries of conformationally constrained peptide-like oligomers is an important goal in combinatorial chemistry. In this regard an attractive building block is the N-alkylated peptide, also known as a peptide tertiary amide (PTA). PTAs are conformationally constrained because of allylic 1,3 strain interactions. We report here an improved synthesis of these species on solid supports through the use of reductive amination chemistry using amino acid-terminated, bead-displayed oligomers and diverse aldehydes. The utility of this chemistry is demonstrated by the synthesis of a library of 10,000 mixed peptoid-PTA oligomers.

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.

Crosslinked Aspartic Acids as Helix-Nucleating Templates.

PubMed

Zhao, Hui; Liu, Qi-Song; Geng, Hao; Tian, Yuan; Cheng, Min; Jiang, Yan-Hong; Xie, Ming-Sheng; Niu, Xiao-Gang; Jiang, Fan; Zhang, Ya-Ou; Lao, Yuan-Zhi; Wu, Yun-Dong; Xu, Nai-Han; Li, Zi-Gang

2016-09-19

Described is a facile helix-nucleating template based on a tethered aspartic acid at the N-terminus [terminal aspartic acid (TD)]. The nucleating effect of the template is subtly influenced by the substituent at the end of the side-chain-end tether as indicated by circular dichroism, nuclear magnetic resonance, and molecular dynamics simulations. Unlike most nucleating strategies, the N-terminal amine is preserved, thus enabling further modification. Peptidomimetic estrogen receptor modulators (PERMs) constructed using this strategy show improved therapeutic properties. The current strategy can be regarded as a good complement to existing helix-stabilizing methods. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Structural analysis of N-glycans by the glycan-labeling method using 3-aminoquinoline-based liquid matrix in negative-ion MALDI-MS.

PubMed

Nishikaze, Takashi; Kaneshiro, Kaoru; Kawabata, Shin-ichirou; Tanaka, Koichi

2012-11-06

Negative-ion fragmentation of underivatized N-glycans has been proven to be more informative than positive-ion fragmentation. Fluorescent labeling via reductive amination is often employed for glycan analysis, but little is known about the influence of the labeling group on negative-ion fragmentation. We previously demonstrated that the on-target glycan-labeling method using 3-aminoquinoline/α-cyano-4-hydroxycinnamic acid (3AQ/CHCA) liquid matrix enables highly sensitive, rapid, and quantitative N-glycan profiling analysis. The current study investigates the suitability of 3AQ-labeled N-glycans for structural analysis based on negative-ion collision-induced dissociation (CID) spectra. 3AQ-labeled N-glycans exhibited simple and informative CID spectra similar to those of underivatized N-glycans, with product ions due to cross-ring cleavages of the chitobiose core and ions specific to two antennae (D and E ions). The interpretation of diagnostic fragment ions suggested for underivatized N-glycans could be directly applied to the 3AQ-labeled N-glycans. However, fluorescently labeled N-glycans by conventional reductive amination, such as 2-aminobenzamide (2AB)- and 2-pyrydilamine (2PA)-labeled N-glycans, exhibited complicated CID spectra consisting of numerous signals formed by dehydration and multiple cleavages. The complicated spectra of 2AB- and 2PA-labeled N-glycans was found to be due to their open reducing-terminal N-acetylglucosamine (GlcNAc) ring, rather than structural differences in the labeling group in the N-glycan derivative. Finally, as an example, the on-target 3AQ labeling method followed by negative-ion CID was applied to structurally analyze neutral N-glycans released from human epidermal growth factor receptor type 2 (HER2) protein. The glycan-labeling method using 3AQ-based liquid matrix should facilitate highly sensitive quantitative and qualitative analyses of glycans.

LANL Virtual Center for Chemical Hydrogen Storage: Chemical Hydrogen Storage Using Ultra-high Surface Area Main Group Materials

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

Susan M. Kauzlarich; Phillip P. Power; Doinita Neiner

The focus of the project was to design and synthesize light element compounds and nanomaterials that will reversibly store molecular hydrogen for hydrogen storage materials. The primary targets investigated during the last year were amine and hydrogen terminated silicon (Si) nanoparticles, Si alloyed with lighter elements (carbon (C) and boron (B)) and boron nanoparticles. The large surface area of nanoparticles should facilitate a favorable weight to volume ratio, while the low molecular weight elements such as B, nitrogen (N), and Si exist in a variety of inexpensive and readily available precursors. Furthermore, small NPs of Si are nontoxic and non-corrosive.more » Insights gained from these studies will be applied toward the design and synthesis of hydrogen storage materials that meet the DOE 2010 hydrogen storage targets: cost, hydrogen capacity and reversibility. Two primary routes were explored for the production of nanoparticles smaller than 10 nm in diameter. The first was the reduction of the elemental halides to achieve nanomaterials with chloride surface termination that could subsequently be replaced with amine or hydrogen. The second was the reaction of alkali metal Si or Si alloys with ammonium halides to produce hydrogen capped nanomaterials. These materials were characterized via X-ray powder diffraction, TEM, FTIR, TG/DSC, and NMR spectroscopy.« less

PRINT: A Protein Bioconjugation Method with Exquisite N-terminal Specificity

PubMed Central

Sur, Surojit; Qiao, Yuan; Fries, Anja; O’Meally, Robert N.; Cole, Robert N.; Kinzler, Kenneth W.; Vogelstein, Bert; Zhou, Shibin

2015-01-01

Chemical conjugation is commonly used to enhance the pharmacokinetics, biodistribution, and potency of protein therapeutics, but often leads to non-specific modification or loss of bioactivity. Here, we present a simple, versatile and widely applicable method that allows exquisite N-terminal specific modification of proteins. Combining reversible side-chain blocking and protease mediated cleavage of a commonly used HIS tag appended to a protein, we generate with high yield and purity exquisitely site specific and selective bio-conjugates of TNF-α by using amine reactive NHS ester chemistry. We confirm the N terminal selectivity and specificity using mass spectral analyses and show near complete retention of the biological activity of our model protein both in vitro and in vivo murine models. We believe that this methodology would be applicable to a variety of potentially therapeutic proteins and the specificity afforded by this technique would allow for rapid generation of novel biologics. PMID:26678960

Copper-Catalyzed Chan-Lam Cyclopropylation of Phenols and Azaheterocycles.

PubMed

Derosa, Joseph; O'Duill, Miriam L; Holcomb, Matthew; Boulous, Mark N; Patman, Ryan L; Wang, Fen; Tran-Dubé, Michelle; McAlpine, Indrawan; Engle, Keary M

2018-04-06

Small molecules containing cyclopropane-heteroatom linkages are commonly needed in medicinal chemistry campaigns yet are problematic to prepare using existing methods. To address this issue, a scalable Chan-Lam cyclopropylation reaction using potassium cyclopropyl trifluoroborate has been developed. With phenol nucleophiles, the reaction effects O-cyclopropylation, whereas with 2-pyridones, 2-hydroxybenzimidazoles, and 2-aminopyridines the reaction brings about N-cyclopropylation. The transformation is catalyzed by Cu(OAc) 2 and 1,10-phenanthroline and employs 1 atm of O 2 as the terminal oxidant. This method is operationally convenient to perform and provides a simple, strategic disconnection toward the synthesis of cyclopropyl aryl ethers and cyclopropyl amine derivatives bearing an array of functional groups.

Atomistic computer simulations on multi-loaded PAMAM dendrimers: a comparison of amine- and hydroxyl-terminated dendrimers

NASA Astrophysics Data System (ADS)

Badalkhani-Khamseh, Farideh; Ebrahim-Habibi, Azadeh; Hadipour, Nasser L.

2017-12-01

Poly(amidoamine) (PAMAM) dendrimers have been extensively studied as delivery vectors in biomedical applications. A limited number of molecular dynamics (MD) simulation studies have investigated the effect of surface chemistry on therapeutic molecules loading, with the aim of providing insights for biocompatibility improvement and increase in drug loading capacity of PAMAM dendrimers. In this work, fully atomistic MD simulations were employed to study the association of 5-Fluorouracil (5-FU) with amine (NH2)- and hydroxyl (OH)-terminated PAMAM dendrimers of generations 3 and 4 (G3 and G4). MD results show a 1:12, 1:1, 1:27, and 1:4 stoichiometry, respectively, for G3NH2-FU, G3OH-FU, G4NH2-FU, and G4OH-FU complexes, which is in good agreement with the isothermal titration calorimetry results. The results obtained showed that NH2-terminated dendrimers assume segmented open structures with large cavities and more drug molecules can encapsulate inside the dendritic cavities of amine terminated dendrimers. However, OH-terminated have a densely packed structure and therefore, 5-FU drug molecules are more stable to locate close to the surface of the dendrimers. Intermolecular hydrogen bonding analysis showed that 5-FU drug molecules have more tendency to form hydrogen bonds with terminal monomers of OH-terminated dendrimers, while in NH2-terminated these occur both in the inner region and the surface. Furthermore, MM-PBSA analysis revealed that van der Waals and electrostatic energies are both important to stabilize the complexes. We found that drug molecules are distributed uniformly inside the amine and hydroxyl terminated dendrimers and therefore, both dendrimers are promising candidates as drug delivery systems for 5-FU drug molecules.

Multiplex N-terminome analysis of MMP-2 and MMP-9 substrate degradomes by iTRAQ-TAILS quantitative proteomics.

PubMed

Prudova, Anna; auf dem Keller, Ulrich; Butler, Georgina S; Overall, Christopher M

2010-05-01

Proteolysis is a major protein posttranslational modification that, by altering protein structure, affects protein function and, by truncating the protein sequence, alters peptide signatures of proteins analyzed by proteomics. To identify such modified and shortened protease-generated neo-N-termini on a proteome-wide basis, we developed a whole protein isobaric tag for relative and absolute quantitation (iTRAQ) labeling method that simultaneously labels and blocks all primary amines including protein N- termini and lysine side chains. Blocking lysines limits trypsin cleavage to arginine, which effectively elongates the proteolytically truncated peptides for improved MS/MS analysis and peptide identification. Incorporating iTRAQ whole protein labeling with terminal amine isotopic labeling of substrates (iTRAQ-TAILS) to enrich the N-terminome by negative selection of the blocked mature original N-termini and neo-N-termini has many advantages. It enables simultaneous characterization of the natural N-termini of proteins, their N-terminal modifications, and proteolysis product and cleavage site identification. Furthermore, iTRAQ-TAILS also enables multiplex N-terminomics analysis of up to eight samples and allows for quantification in MS2 mode, thus preventing an increase in spectral complexity and extending proteome coverage by signal amplification of low abundance proteins. We compared the substrate degradomes of two closely related matrix metalloproteinases, MMP-2 (gelatinase A) and MMP-9 (gelatinase B), in fibroblast secreted proteins. Among 3,152 unique N-terminal peptides identified corresponding to 1,054 proteins, we detected 201 cleavage products for MMP-2 and unexpectedly only 19 for the homologous MMP-9 under identical conditions. Novel substrates identified and biochemically validated include insulin-like growth factor binding protein-4, complement C1r component A, galectin-1, dickkopf-related protein-3, and thrombospondin-2. Hence, N-terminomics analyses using iTRAQ-TAILS links gelatinases with new mechanisms of action in angiogenesis and reveals unpredicted restrictions in substrate repertoires for these two very similar proteases.

Multiplex N-terminome Analysis of MMP-2 and MMP-9 Substrate Degradomes by iTRAQ-TAILS Quantitative Proteomics*

PubMed Central

Prudova, Anna; auf dem Keller, Ulrich; Butler, Georgina S.; Overall, Christopher M.

2010-01-01

Proteolysis is a major protein posttranslational modification that, by altering protein structure, affects protein function and, by truncating the protein sequence, alters peptide signatures of proteins analyzed by proteomics. To identify such modified and shortened protease-generated neo-N-termini on a proteome-wide basis, we developed a whole protein isobaric tag for relative and absolute quantitation (iTRAQ) labeling method that simultaneously labels and blocks all primary amines including protein N- termini and lysine side chains. Blocking lysines limits trypsin cleavage to arginine, which effectively elongates the proteolytically truncated peptides for improved MS/MS analysis and peptide identification. Incorporating iTRAQ whole protein labeling with terminal amine isotopic labeling of substrates (iTRAQ-TAILS) to enrich the N-terminome by negative selection of the blocked mature original N-termini and neo-N-termini has many advantages. It enables simultaneous characterization of the natural N-termini of proteins, their N-terminal modifications, and proteolysis product and cleavage site identification. Furthermore, iTRAQ-TAILS also enables multiplex N-terminomics analysis of up to eight samples and allows for quantification in MS2 mode, thus preventing an increase in spectral complexity and extending proteome coverage by signal amplification of low abundance proteins. We compared the substrate degradomes of two closely related matrix metalloproteinases, MMP-2 (gelatinase A) and MMP-9 (gelatinase B), in fibroblast secreted proteins. Among 3,152 unique N-terminal peptides identified corresponding to 1,054 proteins, we detected 201 cleavage products for MMP-2 and unexpectedly only 19 for the homologous MMP-9 under identical conditions. Novel substrates identified and biochemically validated include insulin-like growth factor binding protein-4, complement C1r component A, galectin-1, dickkopf-related protein-3, and thrombospondin-2. Hence, N-terminomics analyses using iTRAQ-TAILS links gelatinases with new mechanisms of action in angiogenesis and reveals unpredicted restrictions in substrate repertoires for these two very similar proteases. PMID:20305284

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

Syntheses, structures, and properties of trinuclear complexes [M(bpca)(2)(M'(hfac)(2))(2)], constructed with the complexed bridging ligand [M(bpca)(2)] [M, M' = Ni(II), Mn(II); Cu(II), Mn(II); Fe(II), Mn(II); Ni(II), Fe(II); and Fe(II), Fe(II); Hbpca = Bis(2-pyridylcarbonyl)amine, Hhfac = Hexafluoroacetylacetone].

PubMed

Kamiyama, Asako; Noguchi, Tomoko; Kajiwara, Takashi; Ito, Tasuku

2002-02-11

Five trinuclear complexes [M(bpca)(2)(M'(hfac)(2))(2)] (where MM'(2) = NiMn(2), CuMn(2), FeMn(2), NiFe(2), and FeFe(2); Hbpca = bis(2-pyridylcarbonyl)amine; and Hhfac = hexafluoroacetylacetone) were synthesized almost quantitatively by the reaction of [M(bpca)(2)] and [M'(hfac)(2)] in 1:2 molar ratio, and their structures and magnetic properties were investigated. Three complexes, with M' = Mn, crystallize in the same space group, Pna2(1), whereas two complexes, with M' = Fe, crystallize in P4(1), and complexes within each set are isostructural to one another. In all complexes, [M(bpca)(2)] acts as a bis-bidentate bridging ligand to form a linear trinuclear complex in which three metal ions are arranged in the manner M'-M-M'. The central metal ion is in a strong ligand field created by the N(6) donor set, and hence the Fe(II) in the [Fe(bpca)(2)] moiety is in a low-spin state. The terminal metal ions (M') are surrounded by O(6) donor sets with a moderate ligand field, which leads to the high-spin configuration of Fe(II). Three metal ions in all complexes are almost collinear, and metal-metal distances are ca. 5.5 A. The magnetic behavior of NiMn(2) and NiFe(2) shows a weak ferromagnetic interaction between the central Ni(II) ion and the terminal Mn(II) or Fe(II) ions. In these complexes, sigma-spin orbitals of the central Ni(II) ion and those of terminal metal ions have different symmetry about a 2-fold rotation axis through the Ni-N(amide)-M'(terminal) atoms, and this results in orthogonality between the neighboring sigma-spin orbitals and thus ferromagnetic interactions.

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.

Phenylethynyl amine

NASA Technical Reports Server (NTRS)

Hergenrother, Paul M. (Inventor); Bryant, Robert G. (Inventor); Jensen, Brian J. (Inventor); Havens, Stephen J. (Inventor)

1997-01-01

Four phenylethynyl amine compounds--3 and 4-aminophenoxy-4'-phenylethynylbenzophenone, and 3 and 4-amino-4'-phenylethynylbenzophenone--were readily prepared and were used to endcap imide oligomers. Phenylethynyl-terminated amide acid oligomers and phenylethynyl-terminated imide oligomers with various molecular weights and compositions were prepared and characterized. These oligomers were cured at 300.degree. C. to 400.degree. C. to provide crosslinked polyimides with excellent solvent resistance, high strength and modulus and good high temperature properties. Adhesive panels, composites, films and moldings from these phenylethynyl terminated imide oligomers gave excellent mechanical performance.

Ketimine modifications as a route to novel amorphous and derived semicrystalline poly(arylene ether ketone) homo- and copolymers

NASA Technical Reports Server (NTRS)

Mohanty, D. K.; Lowery, R. C.; Lyle, G. D.; Mcgrath, J. E.

1987-01-01

A series of amine terminal amorphous poly(arylene ether ketone) oligomers of controlled molecular weights (2-15 K) were synthesized. These oligomers have been found to undergo 'self-crosslinking' reactions upon heating above 220 C, via the reaction of the terminal amine groups with the in-chain keto carbonyl functionalities. The resulting networks are ductile, chemically resistant, and nonporous. The networks obtained via generated ketimine functionality were characterized by solid state NMR. They have also been found to be remarkably stable toward hydrolysis. Ketimine functional bishalide monomers have also been synthesized. Such monomers have been utilized to synthesize a wide variety of amorphous poly(arylene ether) ketimine polymers. A high molecular weight hydroquinone functional poly(arylene ether) ketimine has been acid treated to regenerate a poly(arylene ether ketone) backbone in solution. This novel procedure thus allows for the synthesis of important matrix resins under relatively mild conditions.

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.

Preventive effects of fermented brown rice and rice bran against N-nitrosobis (2-oxopropyl) amine-induced pancreatic tumorigenesis in male hamsters.

PubMed

Kuno, Toshiya; Takahashi, Satoru; Tomita, Hiroyuki; Hisamatsu, Kenji; Hara, Akira; Hirata, Akihiro; Kobayashi, Hiroshi; Mori, Hideki

2015-12-01

Fermented brown rice by Aspergillus oryzae (FBRA) is known to have the potential to prevent chemical carcinogenesis of the colon, liver, esophagus, urinary bladder, stomach and lungs in rodents. The present study examined the possible chemopreventive effects of FBRA on N-nitrosobis(2-oxopropyl)amine (BOP)-induced pancreatic tumorigenesis in hamsters. Five-week-old male Syrian golden hamsters were divided into seven groups. Groups 1-5 were subcutaneously injected with BOP (10 mg/kg body weight) four times during week 6 to induce pancreatic tumors, while groups 6 and 7 were injected with saline. Groups 2 and 3 were fed diets containing 5 and 10% FBRA, respectively, during the initiation phase. By contrast, groups 4 and 5 were fed diets containing 5 and 10% FBRA, respectively, during the post-initiation phase. Group 6 received a diet containing 10% FBRA throughout the experiment, and group 7 was kept on the basal diet alone and served as the untreated control. At the termination of the study (week 22), oral intake of 10% FBRA (group 5) during the post-initiation phase was identified to have significantly reduced the multiplicity (number of lesions/animal) of ductal adenocarcinoma [pancreatic intraepithelial neoplasia 3 (PanIN3); carcinoma in situ and invasive carcinoma] in comparison with group 1 control hamsters (0.24±0.44 vs. 0.71±0.72; P<0.05). Treatment with 10% FBRA in the post-initiation phase inhibited the progression of normal/precancerous lesions (PanIN1, mild hyperplastic lesions; and PanIN2, papillary hyperplasia) to ductal adenocarcinomas. Furthermore, dietary exposure to 10% FBRA during the initiation (group 3) and post-initiation phases (group 5) significantly reduced the multiplicity of PanIN2 (group 3, 0.55±0.69; group 5, 0.45±0.69; versus group 1, 1.26±1.24; P<0.05 and P<0.01, respectively). A significant reduction of Ki-67 positivity of PanIN2 in group 5 was also confirmed (group 5, 0.05±0.03; group 1, 0.22±0.12; P<0.01). Using terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling, augmentation of apoptosis by FBRA exposure in the non-lesional ductal epithelium and proliferative lesions was not evident. These findings indicate that FBRA exhibits inhibitory effects on BOP-induced pancreatic tumorigenesis in hamsters due to the reduced proliferation rate of tumor cells. Thus, FBRA may be a promising chemopreventive agent in human pancreatic cancer.

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.

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.

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.

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.

A Convenient Approach to Synthesizing Peptide C-Terminal N-Alkyl Amides

PubMed Central

Fang, Wei-Jie; Yakovleva, Tatyana; Aldrich, Jane V.

2014-01-01

Peptide C-terminal N-alkyl amides have gained more attention over the past decade due to their biological properties, including improved pharmacokinetic and pharmacodynamic profiles. However, the synthesis of this type of peptide on solid phase by current available methods can be challenging. Here we report a convenient method to synthesize peptide C-terminal N-alkyl amides using the well-known Fukuyama N-alkylation reaction on a standard resin commonly used for the synthesis of peptide C-terminal primary amides, the PAL-PEG-PS (Peptide Amide Linker-polyethylene glycol-polystyrene) resin. The alkylation and oNBS deprotection were conducted under basic conditions and were therefore compatible with this acid labile resin. The alkylation reaction was very efficient on this resin with a number of different alkyl iodides or bromides, and the synthesis of model enkephalin N-alkyl amide analogs using this method gave consistently high yields and purities, demonstrating the applicability of this methodology. The synthesis of N-alkyl amides was more difficult on a Rink amide resin, especially the coupling of the first amino acid to the N-alkyl amine, resulting in lower yields for loading the first amino acid onto the resin. This method can be widely applied in the synthesis of peptide N-alkyl amides. PMID:22252422

Saturated amine oxides: Part 8. Hydroacridines: Part 27. Effects of N-oxidation and of N-quaternization on the 15N NMR chemical shifts of N-methylpiperidine-derived mono-, bi-, and tricycloaliphatic tertiary amines.

PubMed

Potmischil, Francisc; Duddeck, Helmut; Nicolescu, Alina; Deleanu, Calin

2007-03-01

The (15)N chemical shifts of 13 N-methylpiperidine-derived mono-, bi- and tricycloaliphatic tertiary amines, their methiodides and their N-epimeric pairs of N-oxides were measured, and the contributions of specific structural parameters to the chemical shifts were determined by multilinear regression analysis. Within the examined compounds, the effects of N-oxidation upon the (15)N chemical shifts of the amines vary from +56 ppm to +90 ppm (deshielding), of which approx. +67.7 ppm is due to the inductive effect of the incoming N(+)--O(-) oxygen atom, whereas the rest is due to the additive shift effects of the various C-alkyl substituents of the piperidine ring. The effects of quaternization vary from -3.1 ppm to +29.3 ppm, of which approx. +8.9 ppm is due to the inductive effect of the incoming N(+)--CH(3) methyl group, and the rest is due to the additive shift effects of the various C-alkyl substituents of the piperidine ring. The shift effects of the C-alkyl substituents in the amines, the N-oxides and the methiodides are discussed. Copyright (c) 2007 John Wiley & Sons, Ltd.

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.

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

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.

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.

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.

Labelling Polymers and Micellar Nanoparticles via Initiation, Propagation and Termination with ROMP

PubMed Central

Thompson, Matthew P.; Randolph, Lyndsay M.; James, Carrie R.; Davalos, Ashley N.; Hahn, Michael E.

2014-01-01

In this paper we compare and contrast three approaches for labelling polymers with functional groups via ring-opening metathesis polymerization (ROMP). We explored the incorporation of functionality via initiation, termination and propagation employing an array of novel initiators, termination agents and monomers. The goal was to allow the generation of selectively labelled and well-defined polymers that would in turn lead to the formation of labelled nanomaterials. Norbornene analogues, prepared as functionalized monomers for ROMP, included fluorescent dyes (rhodamine, fluorescein, EDANS, and coumarin), quenchers (DABCYL), conjugatable moieties (NHS esters, pentafluorophenyl esters), and protected amines. In addition, a set of symmetrical olefins for terminally labelling polymers, and for the generation of initiators in situ is described. PMID:24855496

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.

A method for the 32P labeling of peptides or peptide nucleic acid oligomers

NASA Technical Reports Server (NTRS)

Kozlov, I. A.; Nielsen, P. E.; Orgel, L. E.; Bada, J. L. (Principal Investigator)

1998-01-01

A novel approach to the radioactive labeling of peptides and PNA oligomers is described. It is based on the conjugation of a deoxynucleoside 3'-phosphate with the terminal amine of the substrate, followed by phosphorylation of the 5'-hydroxyl group of the nucleotide using T4 polynucleotide kinase and [gamma-32P]ATP.

Solution structure of Mycobacterium tuberculosis NmtR in the apo-state: Insights into Ni(II)-mediated allostery

PubMed Central

Lee, Chul Won; Chakravorty, Dhruva K.; Chang, Feng-Ming James; Reyes-Caballero, Hermes; Ye, Yuzhen; Merz, Kenneth M.; Giedroc, David P.

2012-01-01

Mycobacterium tuberculosis is an obligate human respiratory pathogen that encodes approximately ten arsenic repressor (ArsR) family regulatory proteins that allow the organism to respond to a wide range of changes in its immediate microenvironment. How individual ArsR repressors have evolved to respond to selective stimuli is of intrinsic interest. The Ni(II)/Co(II)-specific repressor NmtR and related actinomycete nickel sensors harbor a conserved N-terminal αNH2-Gly2-His3-Gly4 sequence. Here, we present the solution structure of homodimeric apo-NmtR and show that the core of the molecule adopts a typical winged-helix ArsR repressor (α1-α2-α3-αR-β1-β2-α5) “open conformation” that is similar to the related zinc sensor Staphylococcus aureus CzrA, but harboring long, flexible N-terminal (residues 2-16) and C-terminal (residues 109-120) extensions. Ni(II) binding to the regulatory sites induces strong paramagnetic broadening of the α5 helical region and the extreme N-terminal tail to residue 10. Ratiometric pulse chase amidination mass spectrometry reveals that the rate of amidination of the Gly2 α-amino group is strongly attenuated in the Ni(II) complex relative to the apo-state and non-cognate Zn(II) complex. Ni(II) binding also induces dynamic disorder in the μs-ms timescale of key DNA interacting regions that likely contributes to the negative regulation of DNA binding by Ni(II). Molecular dynamics simulations and quantum chemical calculations reveal that NmtR readily accommodates a distal Ni(II) hexacoordination model involving the α-amine and His3 of the N-terminal region and α5 residues Asp91′, His93′, His104 and His107, which collectively define a new metal sensing site configuration in ArsR family regulators. PMID:22394357

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

Graphite-supported gold nanoparticles as efficient catalyst for aerobic oxidation of benzylic amines to imines and N-substituted 1,2,3,4-tetrahydroisoquinolines to amides: synthetic applications and mechanistic study.

PubMed

So, Man-Ho; Liu, Yungen; Ho, Chi-Ming; Che, Chi-Ming

2009-10-05

Selective oxidation of amines using oxygen as terminal oxidant is an important area in green chemistry. In this work, we describe the use of graphite-supported gold nanoparticles (AuNPs/C) to catalyze aerobic oxidation of cyclic and acyclic benzylic amines to the corresponding imines with moderate-to-excellent substrate conversions (43-100%) and product yields (66-99%) (19 examples). Oxidation of N-substituted 1,2,3,4-tetrahydroisoquinolines in the presence of aqueous NaHCO3 solution gave the corresponding amides in good yields (83-93%) with high selectivity (up to amide/enamide=93:4) (6 examples). The same protocol can be applied to the synthesis of benzimidazoles from the reaction of o-phenylenediamines with benzaldehydes under aerobic conditions (8 examples). By simple centrifugation, AuNPs/C can be recovered and reused for ten consecutive runs for the oxidation of dibenzylamine to N-benzylidene(phenyl)methanamine without significant loss of catalytic activity and selectivity. This protocol "AuNPs/C+O2" can be scaled to the gram scale, and 8.9 g (84 % isolated yield) of 3,4-dihydroisoquinoline can be obtained from the oxidation of 10 g 1,2,3,4-tetrahydroisoquinoline in a one-pot reaction. Based on the results of kinetic studies, radical traps experiment, and Hammett plot, a mechanism involving the hydrogen-transfer reaction from amine to metal and oxidation of M-H is proposed.

[Effect of Long-Term Fertilization on Organic Nitrogen Functional Groups in Black Soil as Revealed by Synchrotron-Based X-Ray Absorption Near-Edge Structure Spectroscopy].

PubMed

Li, Hui; Gao, Qiang; Wang, Shuai; Zhu, Ping; Zhang, Jin-jing; Zhao, Yi-dong

2015-07-01

Nitrogen (N) is a common limiting nutrient in crop production. The N content of soil has been used as an important soil fertility index. Organic N is the major form of N in soil. In most agricultural surface soils, more than 90% of total N occurs in organic forms. Therefore, understanding the compositional characteristics of soil organic N functional groups can provide the scientific basis for formulating the reasonable farmland management strategies. Synchrotron radiation soft X-ray absorption near-edge structure (N K-edge XANES) spectroscopy is the most powerful tool to characterize in situ organic N functional groups compositions in soil. However, to our most knowledge, no studies have been conducted to examine the organic N functional groups compositions of soil using N K-edge XANES spectroscopy under long-term fertilization practices. Based on a long-term field experiment (started in 1990) in a black soil (Gongzhuling, Northeast China), we investigated the differences in organic N functional groups compositions in bulk soil and clay-size soil fraction among fertilization patterns using synchrotron-based N K- edge XANES spectroscopy. Composite soil samples (0-20 cm) were collected in 2008. The present study included six treatments: farmland fallow (FALL), no-fertilization control (CK), chemical nitrogen, phosphorus, and potassium fertilization (NPK), NPK in combination with organic manure (NPKM), 1.5 times of NPKM (1.5 NPKM), and NPK in combination with maize straw (NPKS). The results showed that N K-edge XANES spectra of all the treatments under study exhibited characteristic absorption peaks in the ranges of 401.2-401.6 and 402.7-403.1 eV, which were assigned as amides/amine-N and pyrrole-N, respectively. These characteristic absorption peaks were more obvious in clay-size soil fraction than in bulk soil. The results obtained from the semi-quantitative analysis of N K-edge XANES spectra indicated that the relative proportion of amides/amine-N was the highest in both bulk soil and clay-size soil fraction, and it was the most major forms in soil organic nitrogen functional groups. Compared with the FALL treatment, the relative proportion of amide/amine-N was lower whereas that of Pyrrole-N was higher in the CK treatment. In the treatments with combined chemical fertilizers and organic manure, the relative proportion of amide/amine-N decreased with increasing application rates of organic manure, while that of Pyrrole-N had an opposite trend. In bulk soil, the relative proportion of amide/amine-N was the highest for the NPKS treatment than for the other treatments. On the other hand, the relative proportion of nitrile/aromatic-N was the highest for the Fallow treatment than for the other treatments in clay-size soil fraction. It is feasible to use N K-edge XANES spectroscopy for characterizing in situ the changes of organic N functional groups in soil under different fertilization practices.

Syntheses, structures and properties of homo- and heterobimetallic complexes of the type [Zn(tren)NCS] 2[M(NCS) 4] [tren = tris(2-aminoethyl)amine; M = Zn, Cu

NASA Astrophysics Data System (ADS)

Chattopadhyay, Soumi; Bhar, Kishalay; Das, Sumitra; Chantrapromma, Suchada; Fun, Hoong-Kun; Ghosh, Barindra Kumar

2010-04-01

A 2:2:1:6 molar ratio of Zn(ClO 4) 2·6H 2O, tris(2-aminoethyl)amine (tren), Zn(ClO 4) 2·6H 2O/Cu(ClO 4) 2·6H 2O and NH 4NCS in methanol-water solution mixtures affords homo-/heterobimetallic compounds of the type [Zn(tren)NCS] 2[M(NCS) 4] (M = Zn, 1; M = Cu, 2) which have been characterized using microanalytical, spectroscopic, magnetic and other physicochemical results. The structures of the compounds are determined by X-ray diffraction measurements. Structural analyses reveal that 1 and 2 are isomorphous and consist of two discrete [Zn(tren)NCS] + cations and a [M(NCS) 4] 2- (M = Zn/Cu) anion. Zinc(II) centers in the [Zn(tren)NCS] + units adopt distorted trigonal bipyramidal geometry with ZnN 5 chromophores coordinated through four N atoms of tren and one N atom of terminal thiocyanate. Each metal(II) center in [M(NCS) 4] 2- has a distorted tetrahedral coordination environment with an MN 4 chromophore ligated by four N atoms of the terminal thiocyanates. In solid state, doubly N-H…S hydrogen bonded 1D chains of [Zn(tren)NCS] + cations are interconnected by tetrahedral [Zn(NCS) 4] 2-/[Cu(NCS) 4] 2- anions through cooperative N-H…S and N-H…N (in 1) and N-H…S and C-H…S (in 2) hydrogen bonds resulting in 3D network structures. Establishment of such networks seems to be aiding the crystallization.

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.

Elastomer Reinforced with Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Hudson, Jared L.; Krishnamoorti, Ramanan

2009-01-01

Elastomers are reinforced with functionalized, single-walled carbon nanotubes (SWNTs) giving them high-breaking strain levels and low densities. Cross-linked elastomers are prepared using amine-terminated, poly(dimethylsiloxane) (PDMS), with an average molecular weight of 5,000 daltons, and a functionalized SWNT. Cross-link densities, estimated on the basis of swelling data in toluene (a dispersing solvent) indicated that the polymer underwent cross-linking at the ends of the chains. This thermally initiated cross-linking was found to occur only in the presence of the aryl alcohol functionalized SWNTs. The cross-link could have been via a hydrogen-bonding mechanism between the amine and the free hydroxyl group, or via attack of the amine on the ester linage to form an amide. Tensile properties examined at room temperature indicate a three-fold increase in the tensile modulus of the elastomer, with rupture and failure of the elastomer occurring at a strain of 6.5.

Star-shaped azomethines based on tris(2-aminoethyl)amine. Characterization, thermal and optical study.

PubMed

Iwan, Agnieszka; Janeczek, Henryk; Kaczmarczyk, Bozena; Jarzabek, Bozena; Sobota, Michal; Rannou, Patrice

2010-02-01

The synthesis and detailed (physico)-chemical ((1)H/(13)C NMR, FTIR, UV-vis and elemental analysis) characterizations of new star-shaped compounds based on tris(2-aminoethyl)amine, including in their structure an azomethine function (HCN-) and alkoxysemiperfluorinated (-O-(CH(2))(3)-(CF(2))(7)-CF(3)), octadecyloxy aliphatic (-O-(CH(2))(17)-CH(3)) chain or two phenyl rings (-Ph-Ph-) as a terminal group, were reported. The mesomorphic behavior was investigated by means of differential scanning calorimetry (DSC), polarized optical microscopy (POM) and additionally by FTIR(T) and UV-vis(T) spectroscopy. Wide-angle X-ray diffraction (WAXD) technique was used to probe the structural properties of the azomethines. Moreover, the azomethine A1 was electro-spun to prepare fibers with poly(methyl methacrylate) (PMMA) and investigated by DSC and POM. Additionally, a film of the A1 with PMMA was cast from chloroform and the thermal properties of the film were compared with the thermal properties of the fiber and powder. It was showed that terminal groups dramatically influence the thermal and optical properties of the star-shaped azomethines. Copyright (c) 2009 Elsevier B.V. All rights reserved.

In vitro effects of benzimidazole/thioether-copper complexes with antitumor activity on human erythrocytes.

PubMed

Suwalsky, Mario; Castillo, Ivan; Sánchez-Eguía, Brenda N; Gallardo, María José; Dukes, Nathan; Santiago-Osorio, Edelmiro; Aguiñiga, Itzen; Rivera-Martínez, Ana R

2018-01-01

Two cytotoxic copper(II) complexes with N-H and N-methylated benzimidazole-derived ligands (Cu-L 1 and Cu-L 1Me ; L 1 =bis(2-methylbenzimidazolyl)(2-methylthioethyl)amine, L 1Me =bis(1-methyl-2-methylbenzimidazolyl)(2-methylthioethyl)amine) were synthesized and exposed to human erythrocytes and molecular models of its membrane. The latter were bilayers built-up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), classes of lipids present in the external and internal moieties of the human red cell membrane, respectively. Scanning electron microscopy (SEM) of erythrocytes incubated with solutions of both Cu(II) complexes showed that they induced morphological changes to the normal cells to echinocytes, and hemolysis at higher concentrations. Real-time observation of the dose-dependent effects of the complexes on live erythrocytes by defocusing microscopy (DM) confirmed SEM results. The formation of echinocytes implied that complex molecules inserted into the outer moiety of the red cell membrane. X-ray diffraction studies on DMPC and DMPE showed that none of these complexes interacted with DMPE and only Cu-L 1 interacted with DMPC. This difference was explained by the fact that Cu-L 1Me complex is more voluminous than Cu-L 1 because it has two additional methyl groups; on the other hand, DMPC molecule has three methyl groups in its bulky terminal amino end. Thus, by steric hindrance Cu-L 1Me molecules cannot intercalate into DMPC bilayer, which besides is present in the gel phase. These results, together with the increased antiproliferative capacity of the N-methylated complex Cu-L 1Me over that of Cu-L 1 are rationalized mainly based on its higher lipophilicity. Copyright © 2017 Elsevier Inc. All rights reserved.

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.

Ozone Promotes Chloropicrin Formation by Oxidizing Amines to Nitro Compounds.

PubMed

McCurry, Daniel L; Quay, Amanda N; Mitch, William A

2016-02-02

Chloropicrin formation has been associated with ozonation followed by chlorination, but the reaction pathway and precursors have been poorly characterized. Experiments with methylamine demonstrated that ozonation converts methylamine to nitromethane at ∼100% yield. Subsequent chlorination converts nitromethane to chloropicrin at ∼50% yield under the conditions evaluated. Similarly high yields from other primary amines were limited to those with functional groups on the β-carbon (e.g., the carboxylic acid in glycine) that facilitate carbon-carbon bond cleavage to release nitromethyl anion. Secondary amines featuring these reactive primary amines as functional groups (e.g., secondary N-methylamines) formed chloropicrin at high yields, likely by facile dealkylation to release the primary nitro compound. Chloropicrin yields from tertiary amines were low. Natural water experiments, including derivatization to transform primary and secondary amines to less reactive carbamate functional groups, indicated that primary and secondary amines were the dominant chloropicrin precursors during ozonation/chlorination. Ozonation followed by chlorination of the primary amine side chain of lysine demonstrated low yields (∼0.2%) of chloropicrin, but high yields (∼17%) of dichloronitrolysine, a halonitroalkane structural analogue to chloropicrin. However, chloropicrin yields increased and dichloronitrolysine yields decreased in the absence of hydroxyl radical scavengers, suggesting that future research should characterize the potential occurrence of such halonitroalkane analogues relative to natural radical scavenger (e.g., carbonate) concentrations.

Coordination modes of multidentate ligands in fac-[Re(CO)(3)(polyaminocarboxylate)] analogues of (99m)Tc radiopharmaceuticals. dependence on aqueous solution reaction conditions.

PubMed

Lipowska, Malgorzata; He, Haiyang; Xu, Xiaolong; Taylor, Andrew T; Marzilli, Patricia A; Marzilli, Luigi G

2010-04-05

We study Re analogues of (99m)Tc renal agents to interpret previous results at the (99m)Tc tracer level. The relative propensities of amine donors versus carboxylate oxygen donors of four L = polyaminocarboxylate ligands to coordinate in fac-[Re(I)(CO)(3)L](n) complexes were assessed by examining the reaction of fac-[Re(I)(CO)(3)(H(2)O)(3)](+) under conditions differing in acidity and temperature. All four L [N,N-bis-(2-aminoethyl)glycine (DTGH), N,N-ethylenediaminediacetic acid, diethylenetriamine-N-malonic acid, and diethylenetriamine-N-acetic acid] can coordinate as tridentate ligands while creating a dangling chain terminated in a carboxyl group. Dangling carboxyl groups facilitate renal clearance in fac-[(99m)Tc(I)(CO)(3)L](n) agents. Under neutral conditions, the four ligands each gave two fac-[Re(I)(CO)(3)L](n) products with HPLC traces correlating well with known traces of the fac-[(99m)Tc(I)(CO)(3)L](n) mixtures. Such mixtures are common in renal agents because the needed dangling carboxyl group can compete for a coordination site. However, the HPLC separations needed to assess the biodistribution of a single tracer are impractical in a clinical setting. One goal in investigating this Re chemistry is to identify conditions for avoiding this problem of mixtures in preparations of fac-[(99m)Tc(I)(CO)(3)L](n) renal tracers. After separation and isolation of the fac-[Re(I)(CO)(3)L](n) products, NMR analysis of all products and single crystal X-ray crystallographic analysis of both DTGH products, as well as one product each from the other L, allowed us to establish coordination mode unambiguously. The product favored in acidic conditions has a dangling amine chain and more bound oxygen. The product favored in basic conditions has a dangling carboxyl chain and more bound nitrogen. At the elevated temperatures used for simulating tracer preparation, equilibration was facile (ca. 1 h or less), allowing selective formation of one product by utilizing acidic or basic conditions. The results of this fundamental study offer protocols and guidance useful for the design and preparation of fac-[(99m)Tc(I)(CO)(3)L](n) agents consisting of a single tracer.

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.

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.

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.

Fabrication and characterization of amine terminated poly(arylene ether sulfone) modified epoxy-carbon fiber composites

NASA Technical Reports Server (NTRS)

Cecere, James A.; Senger, James S.; Mcgrath, James E.; Steiner, Paul A.; Wong, Raymond S.

1987-01-01

Multifunctional epoxy resin networks were chemically modified with thermoplastic amine terminated poly(arylene ether sulfones) of controlled molecular weights. This system was then examined as both neat resin and as a matrix resin for carbon fiber composites. The neat resin displayed a significant increase in both fracture toughness and energy release rate values. This was attributed to the altered morphology, which could be varied from particles of polysulfone in an epoxy matrix to that of a quasi-continuous polysulfone phase.

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

Detection of nitroaromatics in the solid, solution, and vapor phases using silicon quantum dot sensors

NASA Astrophysics Data System (ADS)

Nguyen, An; Gonzalez, Christina M.; Sinelnikov, Regina; Newman, W.; Sun, Sarah; Lockwood, Ross; Veinot, Jonathan G. C.; Meldrum, Al

2016-03-01

Silicon quantum dots (Si-QDs) represent a well-known QD fluorophore that can emit throughout the visible spectrum depending on the interface structure and surface functional group. Detection of nitroaromatic compounds by monitoring the luminescence response of the sensor material (typically fluorescent polymers) currently forms the basis of new explosives sensing technologies. Freestanding silicon QDs may represent a benign alternative with a high degree of chemical and physical versatility. Here, we investigate dodecyl and amine-terminated Si-QD luminescence response to the presence of nitrobenzene and dinitrotoluene (DNT) in various solid, solution, and vapor forms. For dinitrotoluene vapor the 3σ detection limit was 6 ppb for monomer-terminated QDs. For nitroaromatics dissolved in toluene the detection limit was on the order of 400 nM, corresponding to ∼100 pg of material distributed over ∼1 cm2 on the sensor surface. Solid traces of nitroaromatics were also easily detectable via a simple ‘touch test’. The samples showed minimal interference effects from common contaminants such as water, ethanol, and acetonitrile. The sensor can be as simple and inexpensive as a small circle of filter paper dipped into a QD solution, with a single vial of QDs able to make hundreds of these sensors. Additionally, a trial fiber-optic sensor device was tested by applying the QDs to one end of a 2 × 2 fiber coupler and exposing them to controlled DNT vapor. Finally, the quenching mechanism was explored via luminescence dynamics measurements and is different for blue (amine) and red (dodecyl) fluorescent silicon QDs.

Impacts of Different Functional Groups on the Kinetic Rates of α-Amine Ketoximesilanes Hydrolysis in the Preparation of Room Temperature Vulcanized Silicone Rubber

PubMed Central

Xu, Huihui; Liu, Zihou; Liu, Qingyang; Bei, Yiling; Zhu, Qingzeng

2018-01-01

α-Amine ketoximesilanes are proven to be effective crosslinkers in the preparation of ketone-oxime one-component room temperature vulcanized (RTV) silicone rubber without the use of toxic metal catalyst. This work aimed to investigate the hydrolysis kinetic of α-amine ketoximesilanes, which is vitally important for the preparation of RTV silicone rubber. Five kinds of α-amine ketoximesilanes, namely α-(N,N-diethyl)aminomethyltri(methylethylketoxime)silane (DEMOS), α-(N,N-di-n-butyl)aminomethyltri(methylethylketoxime)silane (DBMOS), α-(N-n-butyl)aminomethyltri(methylethylketoxime)silane (n-BMOS), α-(N-cyclohexyl)aminomethyltri(methylethylketoxime)silane (CMOS) and α-(β-aminomethyl)aminomethyltri(methylethylketoxime)silane (AEMOS), were successfully obtained and confirmed using Fourier transform infrared spectrometer (FT-IR) and hydrogen-1 nuclear magnetic resonance ( 1H NMR). Kinetics of hydrolysis reactions were measured by FT-IR and conductivity. Our results illustrated that the kinetic constant rates ranged from 12.2 × 10−4 s−1 to 7.6 × 10−4 s−1, with the decreasing order of DEMOS > n-BMOS > DBMOS > CMOS > AEMOS at the given temperature and humidity. Better performances of thermal stability could be achieved when using the α-amine ketoximesilanes as crosslinkers in the preparation of RTV silicon rubber than that of RTV silicone rubber with the use of methyltri(methylethylketoxime)silane (MOS) as a crosslinker and organic tin as a catalyst. PMID:29757263

Impacts of Different Functional Groups on the Kinetic Rates of α-Amine Ketoximesilanes Hydrolysis in the Preparation of Room Temperature Vulcanized Silicone Rubber.

PubMed

Xu, Huihui; Liu, Zihou; Liu, Qingyang; Bei, Yiling; Zhu, Qingzeng

2018-05-13

α-Amine ketoximesilanes are proven to be effective crosslinkers in the preparation of ketone-oxime one-component room temperature vulcanized (RTV) silicone rubber without the use of toxic metal catalyst. This work aimed to investigate the hydrolysis kinetic of α-amine ketoximesilanes, which is vitally important for the preparation of RTV silicone rubber. Five kinds of α-amine ketoximesilanes, namely α-(N,N-diethyl)aminomethyltri(methylethylketoxime)silane (DEMOS), α-(N,N-di-n-butyl)aminomethyltri(methylethylketoxime)silane (DBMOS), α-(N-n-butyl)aminomethyltri(methylethylketoxime)silane (n-BMOS), α-(N-cyclohexyl)aminomethyltri(methylethylketoxime)silane (CMOS) and α-(β-aminomethyl)aminomethyltri(methylethylketoxime)silane (AEMOS), were successfully obtained and confirmed using Fourier transform infrared spectrometer (FT-IR) and hydrogen-1 nuclear magnetic resonance ( ¹H NMR). Kinetics of hydrolysis reactions were measured by FT-IR and conductivity. Our results illustrated that the kinetic constant rates ranged from 12.2 × 10 −4 s −1 to 7.6 × 10 −4 s −1 , with the decreasing order of DEMOS > n-BMOS > DBMOS > CMOS > AEMOS at the given temperature and humidity. Better performances of thermal stability could be achieved when using the α-amine ketoximesilanes as crosslinkers in the preparation of RTV silicon rubber than that of RTV silicone rubber with the use of methyltri(methylethylketoxime)silane (MOS) as a crosslinker and organic tin as a catalyst.

(Carbonato-κO,O')bis-(di-2-pyridyl-amine-κN,N')cobalt(III) bromide.

PubMed

Czapik, Agnieszka; Papadopoulos, Christos; Lalia-Kantouri, Maria; Gdaniec, Maria

2011-04-01

In the title compound, [Co(CO(3))(C(10)H(9)N(3))(2)]Br, a distorted octa-hedral coordination of the Co(III) atom is completed by four N atoms of the two chelating di-2-pyridyl-amine ligands and two O atoms of the chelating carbonate anion. The di-2-pyridyl-amine ligands are nonplanar and the dihedral angles between the 2-pyridyl groups are 29.11 (9) and 37.15 (12)°. The coordination cation, which has approximate C(2) symmetry, is connected to the bromide ion via an N-H⋯Br(-) hydrogen bond. The ionic pair thus formed is further assembled into a dimer via N-H⋯O inter-actions about an inversion centre. A set of weaker C-H⋯O and C-H⋯Br(-) inter-actions connect the dimers into a three-dimensional network.

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.

Carbonic anhydrase inhibitors. Inhibition of human cytosolic isoforms I and II with (reduced) Schiff's bases incorporating sulfonamide, carboxylate and carboxymethyl moieties.

PubMed

Nasr, Gihane; Cristian, Alina; Barboiu, Mihail; Vullo, Daniella; Winum, Jean-Yves; Supuran, Claudiu T

2014-05-15

A library of Schiff bases was synthesized by condensation of aromatic amines incorporating sulfonamide, carboxylic acid or carboxymethyl functionalities as Zn(2+)-binding groups, with aromatic aldehydes incorporating tert-butyl, hydroxy and/or methoxy groups. The corresponding amines were thereafter obtained by reduction of the imines. These compounds were assayed for the inhibition of two cytosolic human carbonic anhydrase (hCA, EC 4.2.1.1) isoenzymes, hCA I and II. The Ki values of the Schiff bases were in the range of 7.0-21,400nM against hCA II and of 52-8600nM against hCA I, respectively. The corresponding amines showed Ki values in the range of 8.6nM-5.3μM against hCA II, and of 18.7-251nM against hCA I, respectively. Unlike the imines, the reduced Schiff bases are stable to hydrolysis and several low-nanomolar inhibitors were detected, most of them incorporating sulfonamide groups. Some carboxylates also showed interesting CA inhibitory properties. Such hydrosoluble derivatives may show pharmacologic applications. Copyright © 2014 Elsevier Ltd. All rights reserved.

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.

Sequential Metabolism of Secondary Alkyl Amines to Metabolic-Intermediate Complexes: Opposing Roles for the Secondary Hydroxylamine and Primary Amine Metabolites of Desipramine, (S)-Fluoxetine, and N-Desmethyldiltiazem

PubMed Central

Hanson, Kelsey L.; VandenBrink, Brooke M.; Babu, Kantipudi N.; Allen, Kyle E.; Nelson, Wendel L.

2010-01-01

Three secondary amines desipramine (DES), (S)-fluoxetine [(S)-FLX], and N-desmethyldiltiazem (MA) undergo N-hydroxylation to the corresponding secondary hydroxylamines [N-hydroxydesipramine, (S)-N-hydroxyfluoxetine, and N-hydroxy-N-desmethyldiltiazem] by cytochromes P450 2C11, 2C19, and 3A4, respectively. The expected primary amine products, N-desmethyldesipramine, (S)-norfluoxetine, and N,N-didesmethyldiltiazem, are also observed. The formation of metabolic-intermediate (MI) complexes from these substrates and metabolites was examined. In each example, the initial rates of MI complex accumulation followed the order secondary hydroxylamine > secondary amine ≫ primary amine, suggesting that the primary amine metabolites do not contribute to formation of MI complexes from these secondary amines. Furthermore, the primary amine metabolites, which accumulate in incubations of the secondary amines, inhibit MI complex formation. Mass balance studies provided estimates of the product ratios of N-dealkylation to N-hydroxylation. The ratios were 2.9 (DES-CYP2C11), 3.6 [(S)-FLX-CYP2C19], and 0.8 (MA-CYP3A4), indicating that secondary hydroxylamines are significant metabolites of the P450-mediated metabolism of secondary alkyl amines. Parallel studies with N-methyl-d3-desipramine and CYP2C11 demonstrated significant isotopically sensitive switching from N-demethylation to N-hydroxylation. These findings demonstrate that the major pathway to MI complex formation from these secondary amines arises from N-hydroxylation rather than N-dealkylation and that the primary amines are significant competitive inhibitors of MI complex formation. PMID:20200233

Sequential metabolism of secondary alkyl amines to metabolic-intermediate complexes: opposing roles for the secondary hydroxylamine and primary amine metabolites of desipramine, (s)-fluoxetine, and N-desmethyldiltiazem.

PubMed

Hanson, Kelsey L; VandenBrink, Brooke M; Babu, Kantipudi N; Allen, Kyle E; Nelson, Wendel L; Kunze, Kent L

2010-06-01

Three secondary amines desipramine (DES), (S)-fluoxetine [(S)-FLX], and N-desmethyldiltiazem (MA) undergo N-hydroxylation to the corresponding secondary hydroxylamines [N-hydroxydesipramine, (S)-N-hydroxyfluoxetine, and N-hydroxy-N-desmethyldiltiazem] by cytochromes P450 2C11, 2C19, and 3A4, respectively. The expected primary amine products, N-desmethyldesipramine, (S)-norfluoxetine, and N,N-didesmethyldiltiazem, are also observed. The formation of metabolic-intermediate (MI) complexes from these substrates and metabolites was examined. In each example, the initial rates of MI complex accumulation followed the order secondary hydroxylamine > secondary amine > primary amine, suggesting that the primary amine metabolites do not contribute to formation of MI complexes from these secondary amines. Furthermore, the primary amine metabolites, which accumulate in incubations of the secondary amines, inhibit MI complex formation. Mass balance studies provided estimates of the product ratios of N-dealkylation to N-hydroxylation. The ratios were 2.9 (DES-CYP2C11), 3.6 [(S)-FLX-CYP2C19], and 0.8 (MA-CYP3A4), indicating that secondary hydroxylamines are significant metabolites of the P450-mediated metabolism of secondary alkyl amines. Parallel studies with N-methyl-d(3)-desipramine and CYP2C11 demonstrated significant isotopically sensitive switching from N-demethylation to N-hydroxylation. These findings demonstrate that the major pathway to MI complex formation from these secondary amines arises from N-hydroxylation rather than N-dealkylation and that the primary amines are significant competitive inhibitors of MI complex formation.

Efficient Intracellular siRNA Delivery by Ethyleneimine-Modified Amphiphilic Macromolecules

PubMed Central

Sparks, Sarah M.; Waite, Carolyn L.; Harmon, Alexander M.; Nusblat, Leora M.; Roth, Charles M.; Uhrich, Kathryn E.

2013-01-01

Summary New materials that can bind and deliver oligonucleotides such as short interfering RNA (siRNA) without toxicity are greatly needed to fulfill the promise of therapeutic gene silencing. Amphiphilic macromolecules (AMs) were functionalized with linear ethyleneimines to create cationic AMs capable of complexing with siRNA. Structurally, the parent AM is formed from a mucic acid backbone whose tetra-hydroxy groups are alkylated with 12-carbon aliphatic chains to form the hydrophobic component of the macromolecule. This alkylated mucic acid is then mono-functionalized with poly(ethylene glycol) (PEG) as a hydrophilic component. The resulting AM contains a free carboxylic acid within the hydrophobic domain. In this work, linear ethyleneimines were conjugated to the free carboxylic acid to produce an AM with one primary amine (1N) or one primary amine and four secondary amines (5N). Further, an AM with amine substitution both to the free carboxylic acid in the hydrophobic domain and also to the adjacent PEG was synthesized to produce a polymer with one primary amine and eight secondary amines (9N), four located on each side of the AM hydrophobic domain. All amine-functionalized AMs formed nanoscale micelles but only the 5N and 9N AMs had cationic zeta potentials, which increased with increasing number of amines. All AMs exhibited less inherent cytotoxicity than linear polyethyleneimine (L-PEI) at concentrations of 10 µM and above. By increasing the length of the cationic ethyleneimine chain and the total number of amines, successful siRNA complexation and cellular siRNA delivery was achieved in a malignant glioma cell line. In addition, siRNA-induced silencing of firefly luciferase was observed using complexes of siRNA with the 9N AM and comparable to L-PEI, yet showed better cell viability at higher concentrations (above 10 µM). This work highlights the promise of cationic AMs as safe and efficient synthetic vectors for siRNA delivery. Specifically, a novel polymer (9N) was identified for efficient siRNA delivery to cancer cells and will be further evaluated. PMID:21793212

Gas-phase kinetics study of reaction of OH radical with CH3NHNH2 by second-order multireference perturbation theory.

PubMed

Sun, Hongyan; Zhang, Peng; Law, Chung K

2012-05-31

The gas-phase kinetics of H-abstraction reactions of monomethylhydrazine (MMH) by OH radical was investigated by second-order multireference perturbation theory and two-transition-state kinetic model. It was found that the abstractions of the central and terminal amine H atoms by the OH radical proceed through the formation of two hydrogen bonded preactivated complexes with energies of 6.16 and 5.90 kcal mol(-1) lower than that of the reactants, whereas the abstraction of methyl H atom is direct. Due to the multireference characters of the transition states, the geometries and ro-vibrational frequencies of the reactant, transition states, reactant complexes, and product complexes were optimized by the multireference CASPT2/aug-cc-pVTZ method, and the energies of the stationary points of the potential energy surface were refined at the QCISD(T)/CBS level via extrapolation of the QCISD(T)/cc-pVTZ and QCISD(T)/cc-pVQZ energies. It was found that the abstraction reactions of the central and two terminal amine H atoms of MMH have the submerged energy barriers with energies of 2.95, 2.12, and 1.24 kcal mol(-1) lower than that that of the reactants respectively, and the abstraction of methyl H atom has a real energy barrier of 3.09 kcal mol(-1). Furthermore, four MMH radical-H(2)O complexes were found to connect with product channels and the corresponding transition states. Consequently, the rate coefficients of MMH + OH for the H-abstraction of the amine H atoms were determined on the basis of a two-transition-state model, with the total energy E and angular momentum J conserved between the two transition-state regions. In units of cm(3) molecule(-1) s(-1), the rate coefficient was found to be k(1) = 3.37 × 10(-16)T(1.295) exp(1126.17/T) for the abstraction of the central amine H to form the CH(3)N(•)NH(2) radical, k(2) = 2.34 × 10(-17)T(1.907) exp(1052.26/T) for the abstraction of the terminal amine H to form the trans-CH(3)NHN(•)H radical, k(3) = 7.41 × 10(-20)T(2.428) exp(1343.20/T) for the abstraction of the terminal amine H to form the cis-CH(3)NHN(•)H radical, and k(4) = 9.13 × 10(-21)T(2.964) exp(-114.09/T) for the abstraction of the methyl H atom to form the C(•)H(2)NHNH(2) radical, respectively. Assuming that the rate coefficients are additive, the total rate coefficient of these theoretical predictions quantitatively agrees with the measured rate constant at temperatures of 200-650 K, with no adjustable parameters.

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.

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.

Thermometric titrations of amines with nitrosyl perchlorate in acetonitrile solvent.

PubMed

Gündüz, T; Kiliç, E; Cakirer, O

1996-05-01

Thirteen aliphatic and four aromatic amines, namely diethylamine, triethylamine, n-propylamine, di-n-propylamine, tri-n-butylamine, isopropylamine, di-isopropylamine, n-butylamine, di-n-butylamine, tri-n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, aniline, N,N-dimethylaniline, 2-nitroaniline and 4-nitroaniline were titrated thermometrically with nitrosyl perchlorate in acetonitrile solvent. All the aliphatic amines gave very well-shaped thermometric titration curves. The calculated recovery values of the amines were very good. In comparison, the aromatic amines, aniline and N,N-dimethylaniline gave rather well-shaped titration curves, but the recovery values were fairly low. 2-Nitro- and 4-nitro anilines gave no thermometric response at all. The heats of reaction of the amines with nitrosyl perchlorate are rather high. However, the average heat of reaction of the aromatic amines is approximately two-thirds that of the average heat of the aliphatic amines. To support this method all the amines were also titrated potentiometrically and very similar results to those obtained with the thermometric method are seen. The nitrosyl ion is a Lewis acid, strong enough to titrate quantitatively aliphatic amines in acetonitrile solvent, but not strong enough to titrate aromatic amines at the required level in the same solvent.

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.

Impact behavior of f-silica and amine terminated polybutadiene co-acrylonitrile rubber modified novolac epoxy/Kevlar nanocomposites

NASA Astrophysics Data System (ADS)

Kavita, Pal, Vijayeta; Tiwari, R. K.

2018-05-01

In the present work, nano-fumed silica treated with 3-Glycidoxypropyl trimethoxy silane (f-silica) was used as a nanoreinforcement in the fabrication of amine terminated polybutadiene co-acrylonitrile rubber (ATBN) modified Kevlar/epoxy based nanocomposites. Nanocomposites with different f-silica loading (0, 0.5, 1.0 and 2.0 wt. %) and having same ATBN (10 wt. %) were made and characterized by Izod impact test for evaluating impact strength values. All the nanocomposites showed better impact strength than neat Kevlar/novolac epoxy based composite.

Palladium-catalysed anti-Markovnikov selective oxidative amination

NASA Astrophysics Data System (ADS)

Kohler, Daniel G.; Gockel, Samuel N.; Kennemur, Jennifer L.; Waller, Peter J.; Hull, Kami L.

2018-03-01

In recent years, the synthesis of amines and other nitrogen-containing motifs has been a major area of research in organic chemistry because they are widely represented in biologically active molecules. Current strategies rely on a multistep approach and require one reactant to be activated prior to the carbon-nitrogen bond formation. This leads to a reaction inefficiency and functional group intolerance. As such, a general approach to the synthesis of nitrogen-containing compounds from readily available and benign starting materials is highly desirable. Here we present a palladium-catalysed oxidative amination reaction in which the addition of the nitrogen occurs at the less-substituted carbon of a double bond, in what is known as anti-Markovnikov selectivity. Alkenes are shown to react with imides in the presence of a palladate catalyst to generate the terminal imide through trans-aminopalladation. Subsequently, olefin isomerization occurs to afford the thermodynamically favoured products. Both the scope of the transformation and mechanistic investigations are reported.

Simple diazonium chemistry to develop specific gene sensing platforms.

PubMed

Revenga-Parra, M; García-Mendiola, T; González-Costas, J; González-Romero, E; Marín, A García; Pau, J L; Pariente, F; Lorenzo, E

2014-02-27

A simple strategy for covalent immobilizing DNA sequences, based on the formation of stable diazonized conducting platforms, is described. The electrochemical reduction of 4-nitrobenzenediazonium salt onto screen-printed carbon electrodes (SPCE) in aqueous media gives rise to terminal grafted amino groups. The presence of primary aromatic amines allows the formation of diazonium cations capable to react with the amines present at the DNA capture probe. As a comparison a second strategy based on the binding of aminated DNA capture probes to the developed diazonized conducting platforms through a crosslinking agent was also employed. The resulting DNA sensing platforms were characterized by cyclic voltammetry, electrochemical impedance spectroscopy and spectroscopic ellipsometry. The hybridization event with the complementary sequence was detected using hexaamineruthenium (III) chloride as electrochemical indicator. Finally, they were applied to the analysis of a 145-bp sequence from the human gene MRP3, reaching a detection limit of 210 pg μL(-1). Copyright © 2014 Elsevier B.V. All rights reserved.

Benzoisothiazolone Organo/Copper-Cocatalyzed Redox Dehydrative Construction of Amides and Peptides from Carboxylic Acids using (EtO)3P as the Reductant and O2 in Air as the Terminal Oxidant.

PubMed

Liebeskind, Lanny S; Gangireddy, Pavankumar; Lindale, Matthew G

2016-06-01

Carboxylic acids and amine/amino acid reactants can be converted to amides and peptides at neutral pH within 5-36 h at 50 °C using catalytic quantities of a redox-active benzoisothiazolone and a copper complex. These catalytic "oxidation-reduction condensation" reactions are carried out open to dry air using O2 as the terminal oxidant and a slight excess of triethyl phosphite as the reductant. Triethyl phosphate is the easily removed byproduct. These simple-to-run catalytic reactions provide practical and economical procedures for the acylative construction of C-N bonds.

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.

Robust forests of vertically aligned carbon nanotubes chemically assembled on carbon substrates.

PubMed

Garrett, David J; Flavel, Benjamin S; Shapter, Joseph G; Baronian, Keith H R; Downard, Alison J

2010-02-02

Forests of vertically aligned carbon nanotubes (VACNTs) have been chemically assembled on carbon surfaces. The structures show excellent stability over a wide potential range and are resistant to degradation from sonication in acid, base, and organic solvent. Acid-treated single-walled carbon nanotubes (SWCNTs) were assembled on amine-terminated tether layers covalently attached to pyrolyzed photoresist films. Tether layers were electrografted to the carbon substrate by reduction of the p-aminobenzenediazonium cation and oxidation of ethylenediamine. The amine-modified surfaces were incubated with cut SWCNTs in the presence of N,N'-dicyclohexylcarbodiimide (DCC), giving forests of vertically aligned carbon nanotubes (VACNTs). The SWCNT assemblies were characterized by scanning electron microscopy, atomic force microscopy, and electrochemistry. Under conditions where the tether layers slow electron transfer between solution-based redox probes and the underlying electrode, the assembly of VACNTs on the tether layer dramatically increases the electron-transfer rate at the surface. The grafting procedure, and hence the preparation of VACNTs, is applicable to a wide range of materials including metals and semiconductors.

Facile N-Arylation of Amines and Sulfonamides and O-Arylation of Phenols and Arenecarboxylic Acids

PubMed Central

Liu, Zhijian; Larock, Richard C.

2008-01-01

An efficient, transition-metal free procedure for the N-arylation of amines, sulfonamides and carbamates and O-arylation of phenols and carboxylic acids has been achieved by allowing these substrates to react with a variety of o-silylaryl triflates in the presence of CsF. Good to excellent yields of arylated products are obtained under very mild reaction conditions. This chemistry readily tolerates a variety of functional groups. PMID:16599619

Development of a general non-noble metal catalyst for the benign amination of alcohols with amines and ammonia.

PubMed

Cui, Xinjiang; Dai, Xingchao; Deng, Youquan; Shi, Feng

2013-03-11

The N-alkylation of amines or ammonia with alcohols is a valuable route for the synthesis of N-alkyl amines. However, as a potentially clean and economic choice for N-alkyl amine synthesis, non-noble metal catalysts with high activity and good selectivity are rarely reported. Normally, they are severely limited due to low activity and poor generality. Herein, a simple NiCuFeOx catalyst was designed and prepared for the N-alkylation of ammonia or amines with alcohol or primary amines. N-alkyl amines with various structures were successfully synthesized in moderate to excellent yields in the absence of organic ligands and bases. Typically, primary amines could be efficiently transformed into secondary amines and N-heterocyclic compounds, and secondary amines could be N-alkylated to synthesize tertiary amines. Note that primary and secondary amines could be produced through a one-pot reaction of ammonia and alcohols. In addition to excellent catalytic performance, the catalyst itself possesses outstanding superiority, that is, it is air and moisture stable. Moreover, the magnetic property of this catalyst makes it easily separable from the reaction mixture and it could be recovered and reused for several runs without obvious deactivation. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

MICROWAVE-ASSISTED CU (I) CATALYZED SOLVENT-FREE THREE COMPONENT COUPLING OF ALDEHYDE, ALKYNE AND AMINE

EPA Science Inventory

Direct Grignard type addition of terminal alkynes to in situ generated imines, from aldehydes and amines, occurs under microwave irradiation using CuBr alone in a one-pot operation. This solventless approach provides ready access to propargylamines and is applicable both...

pH-Responsive Dimeric Zinc(II) Phthalocyanine in Mesoporous Silica Nanoparticles as an Activatable Nanophotosensitizing System for Photodynamic Therapy.

PubMed

Wong, Roy C H; Chow, Sun Y S; Zhao, Shirui; Fong, Wing-Ping; Ng, Dennis K P; Lo, Pui-Chi

2017-07-19

An acid-cleavable acetal-linked zinc(II) phthalocyanine dimer with an azido terminal group (cPc) was prepared and conjugated to alkyne-modified mesoporous silica nanoparticles via copper(I)-catalyzed alkyne-azide cycloaddition reaction. For comparison, an amine-linked analogue (nPc) was also prepared as a non-acid-cleavable counterpart. These dimeric phthalocyanines were significantly self-quenched due to the close proximity of the phthalocyanine units inside the mesopores, resulting in much weaker fluorescence emission and singlet oxygen generation, both in N,N-dimethylformamide and in phosphate-buffered saline (PBS), compared with the free molecular counterparts. Under acidic conditions in PBS, the cPc-encapsulated nanosystem was activated in terms of fluorescence emission and singlet oxygen production. After internalization into human colon adenocarcinoma HT29 cells, it exhibited much higher intracellular fluorescence and photocytotoxicity compared to the nanosystem entrapped with nPc. The activation of this nanosystem was also demonstrated in tumor-bearing nude mice. The intratumoral fluorescence intensity increased gradually over 24 h, while for the nPc counterpart the fluorescence remained very weak. The results suggest that this nanosystem serves as a promising activatable nanophotosensitizing agent for photodynamic therapy.

Cell surface acid-base properties of Escherichia coli and Bacillus brevis and variation as a function of growth phase, nitrogen source and C:N ratio.

PubMed

Hong, Yongsuk; Brown, Derick G

2006-07-01

Potentiometric titration has been conducted to systematically examine the acid-base properties of the cell surfaces of Escherichia coli K-12 and Bacillus brevis as a function of growth phase, nitrogen source (ammonium or nitrate), and carbon to nitrogen (C:N) ratio of the growth substrate. The two bacterial species revealed four distinct proton binding sites, with pK(a) values in the range of 3.08-4.05 (pK(1)), 4.62-5.57 (pK(2)), 6.47-7.30 (pK(3)), and 9.68-10.89 (pK(4)) corresponding to phosphoric/carboxylic, carboxylic, phosphoric, and hydroxyl/amine groups, respectively. Two general observations in the data are that for B. brevis the first site concentration (N(1)), corresponding to phosphoric/carboxylic groups (pK(1)), varied as a function of nitrogen source, while for E. coli the fourth site concentration (N(4)), corresponding to hydroxyl/amine groups (pK(4)), varied as a function of C:N ratio. Correspondingly, it was found that N(1) was the highest of the four site concentrations for B. brevis and N(4) was the highest for E. coli. The concentrations of the remaining sites showed little variation. Finally, comparison between the titration data and a number of cell surface compositional studies in the literature indicates one distinct difference between the two bacteria is that pK(4) of the Gram-negative E. coli can be attributed to hydroxyl groups while that of the Gram-positive B. brevis can be attributed to amine groups.

Assembly of acid-functionalized single-walled carbon nanotubes at oil/water interfaces.

PubMed

Feng, Tao; Hoagland, David A; Russell, Thomas P

2014-02-04

The efficient segregation of water-soluble, acid-functionalized, single-walled carbon nanotubes (SWCNTs) at the oil/water interface was induced by dissolving low-molecular-weight amine-terminated polystyrene (PS-NH2) in the oil phase. Salt-bridge interactions between carboxylic acid groups of SWCNTs and amine groups of PS drove the assembly of SWCNTs at the interface, monitored by pendant drop tensiometry and laser scanning confocal microscopy. The impact of PS end-group functionality, PS and SWCNT concentrations, and the degree of SWCNT acid modification on the interfacial activity was assessed, and a sharp drop in interfacial tension was observed above a critical SWCNT concentration. Interfacial tensions were low enough to support stable oil/water emulsions. Further experiments, including potentiometric titrations and the replacement of SWCNTs by other carboxyl-containing species, demonstrated that the interfacial tension drop reflects the loss of SWCNT charge as the pH falls near/below the intrinsic carboxyl dissociation constant; species lacking multivalent carboxylic acid groups are inactive. The trapped SWCNTs appear to be neither ordered nor oriented.

Crystal structures of two mixed-valence copper cyanide complexes with N-methyl­ethylenedi­amine

PubMed Central

Sabatino, Alexander

2017-01-01

The crystal structures of two mixed-valence copper cyanide compounds involving N-methyl­ethylenedi­amine (meen), are described. In compound (I), poly[bis(μ3-cyanido-κ3 C:C:N)tris(μ2-cyanido-κ2 C:N)bis(N-methylethane-1,2-di­amine-κ2 N,N′)tricopper(I)copper(II)], [Cu4(CN)5(C3H10N2)2] or Cu4(CN)5meen2, cyanide groups link CuI atoms into a three-dimensional network containing open channels parallel to the b axis. In the network, two tetra­hedrally bound CuI atoms are bonded by the C atoms of two end-on bridging CN groups to form Cu2(CN)6 moieties with the Cu atoms in close contact at 2.560 (1) Å. Other trigonally bound CuI atoms link these units together to form the network. The CuII atoms, coordinated by two meen units, are covalently linked to the network via a cyanide bridge, and project into the open network channels. In the mol­ecular compound (II), [(N-methylethylenediamine-κ2 N,N′)copper(II)]-μ2-cyanido-κ2 C:N-[bis(cyanido-κC)copper(I)] monohydrate, [Cu2(CN)3(C3H10N2)2]·H2O or Cu2(CN)3meen2·H2O, a CN group connects a CuII atom coordinated by two meen groups with a trigonal–planar CuI atom coordinated by CN groups. The mol­ecules are linked into centrosymmetric dimers via hydrogen bonds to two water mol­ecules. In both compounds, the bridging cyanide between the CuII and CuI atoms has the N atom bonded to CuII and the C atom bonded to CuI, and the CuII atoms are in a square-pyramidal coordination. PMID:28217329

Covalent binding of reduced metabolites of [{sup 15}N{sub 3}]TNT to soil organic matter during a bioremediation process analyzed by {sup 15}N NMR spectroscopy

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

Achtnich, C.; Fernandes, E.; Bollag, J.M.

1999-12-15

Evidence is presented for the covalent binding of biologically reduced metabolites of 2,4,6-{sup 15}N{sub 3}-trinitrotoluene (TNT) to different soil fractions, using liquid {sup 15}N NMR spectroscopy. A silylation procedure was used to release soil organic matter from humin and whole soil for spectroscopic measurements. TNT-contaminated soil was spiked with 2,4,6-{sup 15}N{sub 3}-trinitrotoluene and {sup 14}C-ring labeled TNT, before treatment in a soil slurry reactor. During the anaerobic/aerobic incubation the amount of radioactivity detected in the fulvic and humic acid fractions did not change significantly whereas the radioactivity bound to humin increased to 71%. The {sup 15}N NMR spectra of themore » fulvic acid samples were dominated by a large peak that corresponded to aliphatic amines or ammonia. In the early stages of incubation, {sup 15}N NMR analysis of the humic acids indicated bound azoxy compounds. The signals arising from nitro and azoxy groups disappeared with further anaerobic treatment. At the end of incubation, the NMR shifts showed that nitrogen was covalently bound to humic acid as substituted amines and amides. The NMR spectra of the silylated humin suggest formation of azoxy compounds and imine linkages. Bound metabolites possessing nitro groups were also detected. Primary amines formed during the anaerobic incubation disappeared during the aerobic treatment. Simultaneously, the amount of amides and tertiary amines increased. Nitro and azoxy groups of bound molecules were still present in humin at the end of the incubation period. Formation of azoxy compounds from partially reduced TNT followed by binding and further reduction appears to be an important mechanism for the immobilization of metabolites of TNT to soil.« less

40 CFR 721.7285 - Amines, N-cocoalkyltrimethylenedi-, citrates.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Amines, N-cocoalkyltrimethylenedi... Specific Chemical Substances § 721.7285 Amines, N-cocoalkyltrimethylenedi-, citrates. (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified as amines, N...

40 CFR 721.7286 - Amines, N-tallowalkyltripropylenetetra-, citrates.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Amines, N-tallowalkyltripropylenetetra... Specific Chemical Substances § 721.7286 Amines, N-tallowalkyltripropylenetetra-, citrates. (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified as amines, N...

40 CFR 721.7285 - Amines, N-cocoalkyltrimethylenedi-, citrates.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Amines, N-cocoalkyltrimethylenedi... Specific Chemical Substances § 721.7285 Amines, N-cocoalkyltrimethylenedi-, citrates. (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified as amines, N...

40 CFR 721.7286 - Amines, N-tallowalkyltripropylenetetra-, citrates.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Amines, N-tallowalkyltripropylenetetra... Specific Chemical Substances § 721.7286 Amines, N-tallowalkyltripropylenetetra-, citrates. (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified as amines, N...

CH stretching overtone spectra of trimethyl amine and dimethyl sulfide

NASA Astrophysics Data System (ADS)

Billinghurst, Brant E.; Gough, Kathleen M.; Low, Geoffrey R.; Kjaergaard, Henrik G.

2004-01-01

Trimethyl amine (TMA) exhibits the largest known difference in CH bond lengths within a methyl group, due to what is known as the lone pair trans effect. Dimethyl sulfide also exhibits this effect, but to a far lesser extent, making it ideal for comparison to TMA. In this paper, the first through fourth overtone spectra of N(CH3)3, N(CD3)3, N(CD2H)(CD3)2, N(CH3)(CD3)2, N(CD3)(CH3)2 and S(CH3)2 are reported and all major bands are assigned. The intensities of the observed bands are compared to intensities predicted by the harmonically coupled anharmonic oscillator local mode model. Good correlation is found between the experimental intensities and those predicted with the local mode model and HF/6-311++G(2d,2p) calculated dipole moment functions. An increase in the ability to resolve peaks as methyl groups are deuterated suggests that the lone pair mediates increased coupling between methyl groups.

Targeting Cancer Protein Profiles with Split-Enzyme Reporter Fragments to Achieve Chemical Resolution for Molecular Imaging

DTIC Science & Technology

2014-11-01

near-infrared fluorophore, Cy5.5, linked with up to three units of amino-ethoxy-ethoxy- acid (AEEA) at the N-terminal amine of the peptide. Table 1...RPMI or Dulbecco’s Modified Eagle’s Medium (DMEM; Gibco), respectively, and supplemented with 10% FBS and 1% penicillin–streptomycin. The cells were...peptide, compound 6, using the amino acid residues of the parent peptide (compound 5) in random order. Compound 2 targeted the tumor efficiently

Micropatterned ferrocenyl monolayers covalently bound to hydrogen-terminated silicon surfaces: effects of pattern size on the cyclic voltammetry and capacitance characteristics.

PubMed

Fabre, Bruno; Pujari, Sidharam P; Scheres, Luc; Zuilhof, Han

2014-06-24

The effect of the size of patterns of micropatterned ferrocene (Fc)-functionalized, oxide-free n-type Si(111) surfaces was systematically investigated by electrochemical methods. Microcontact printing with amine-functionalized Fc derivatives was performed on a homogeneous acid fluoride-terminated alkenyl monolayer covalently bound to n-type H-terminated Si surfaces to give Fc patterns of different sizes (5 × 5, 10 × 10, and 20 × 20 μm(2)), followed by backfilling with n-butylamine. These Fc-micropatterned surfaces were characterized by static water contact angle measurements, ellipsometry, X-ray photoelectron spectroscopy (XPS), infrared reflection-absorption spectroscopy (IRRAS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The charge-transfer process between the Fc-micropatterned and underlying Si interface was subsequently studied by cyclic voltammetry and capacitance. By electrochemical studies, it is evident that the smallest electroactive ferrocenyl patterns (i.e., 5 × 5 μm(2) squares) show ideal surface electrochemistry, which is characterized by narrow, perfectly symmetric, and intense cyclic voltammetry and capacitance peaks. In this respect, strategies are briefly discussed to further improve the development of photoswitchable charge storage microcells using the produced redox-active monolayers.

Reductive amination-assisted quantitation of tamoxifen and its metabolites by liquid phase chromatography tandem mass spectrometry.

PubMed

Liang, Shih-Shin; Wang, Tsu-Nai; Chiu, Chien-Chih; Kuo, Po-Lin; Huang, Mei-Fang; Liu, Meng-Chieh; Tsai, Eing-Mei

2016-02-19

Tamoxifen, a hormonal therapy drug against estrogen receptor-positive breast cancer, can be metabolized by cytochrome P450 enzymes such as CYP3A4 and CYP3A5, and converted to N-desmethyltamoxifen, which is subsequently, metabolized by CYP2D6 and inverted to form 4-hydroxy-N-desmethyltamoxifen (endoxifen). Conventional mass spectrometry (MS) analyses of tamoxifen and its metabolites require isotopic internal standards (ISs). In this study, endoxifen and N-desmethyltamoxifen amine groups were modified by reductive amination with formaldehyde-D2 to produce new metabolite molecules. Both endoxifen and N-desmethyltamoxifen generated their corresponding D2-methyl modified analogs. This method is expected to simplify MS detection and overcome the difficulty in selecting adequate ISs when tamoxifen metabolites are analyzed by absolute quantification. It identified tamoxifen, D2-methyl modified endoxifen, and D2-methyl modified N-desmethyltamoxifen with a linearity ranging from 2 to 5000 ng/mL with correlation coefficient (R(2)) values of 0.9868, 0.9849, and 0.9880, respectively. Furthermore, this reductive amination-based method may enhance the signal intensities of D2-methyl modified N-desmethyltamoxifen and endoxifen, thus facilitating the MS detection. Copyright © 2016 Elsevier B.V. All rights reserved.

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

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.

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

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

Young, D.A.; Smith, C.H.

A carboxyl-terminated butadiene/acrylonitrile (CTBN)/epoxy resin adduct, used to encapsulate electronic devices, was studied to improve its quality and reliability. The average physical and mechanical properties of the amine-cured product were obtained by testing 16 batches of adduct prepared from 13 separate lots of CTBN. It was found that by using a CTBN with a higher acrylonitrile content (or one in which the chemical structure includes carboxyl groups in the chain backbone, in addition to end termination), a clear, soluble liquid adduct that does not separate in storage or transit could be prepared. These materials also produced clear epoxy castings andmore » filled potting compounds with improved impact, flexural, compressive, and tensile strengths.« less

Connections from the rat dorsal column nuclei (DCN) to the periaqueductal gray matter (PAG).

PubMed

Barbaresi, Paolo; Mensà, Emanuela

2016-08-01

Electrical stimulation of the dorsal columns (DCs; spinal cord stimulation; SCS) has been proposed to treat chronic neuropathic pain. SCS may activate a dual mechanism that would affect both the spinal cord and supraspinal levels. Stimulation of DCs or DC nuclei (DCN) in animals where neuropathic pain has been induced causes activation of brainstem centers including the periaqueductal gray (PAG), which is involved in the endogenous pain suppression system. Biotinylated dextran-amine (BDA) was iontophoretically injected into the DCN to analyze the ascending projection directed to the PAG. Separate injections into the gracile nucleus (GrN) and the cuneate nucleus (CunN) showed BDA-positive fibers terminating in different regions of the contralateral PAG. GrN-PAG afferents terminated in the caudal and middle portions of PAG-l, whereas CunN-PAG fibers terminated in the middle and rostral portions of PAG-l. Based on the DCN somatotopic map, the GrN sends information to the PAG from the contralateral hindlimb and the tail and the CunN from the contralateral forelimb, shoulder, neck and ear. This somatotopic organization is consistent with earlier electrophysiological and PAG stimulation studies. These fibers could form part of the DCs-brainstem-spinal cord loop, which may be involved in the inhibitory effects of SCS on neuropathic pain. Copyright © 2016. Published by Elsevier Ireland Ltd.

Probing the effect of charge transfer enhancement in off resonance mode SERS via conjugation of the probe dye between silver nanoparticles and metal substrates.

PubMed

Selvakannan, Pr; Ramanathan, Rajesh; Plowman, Blake J; Sabri, Ylias M; Daima, Hemant K; O'Mullane, Anthony P; Bansal, Vipul; Bhargava, Suresh K

2013-08-21

The charge transfer-mediated surface enhanced Raman scattering (SERS) of crystal violet (CV) molecules that were chemically conjugated between partially polarized silver nanoparticles and optically smooth gold and silver substrates has been studied under off-resonant conditions. Tyrosine molecules were used as a reducing agent to convert silver ions into silver nanoparticles where oxidised tyrosine caps the silver nanoparticle surface with its semiquinone group. This binding through the quinone group facilitates charge transfer and results in partially oxidised silver. This establishes a chemical link between the silver nanoparticles and the CV molecules, where the positively charged central carbon of CV molecules can bind to the terminal carboxylate anion of the oxidised tyrosine molecules. After drop casting Ag nanoparticles bound with CV molecules it was found that the free terminal amine groups tend to bind with the underlying substrates. Significantly, only those CV molecules that were chemically conjugated between the partially polarised silver nanoparticles and the underlying gold or silver substrates were found to show SERS under off-resonant conditions. The importance of partial charge transfer at the nanoparticle/capping agent interface and the resultant conjugation of CV molecules to off resonant SERS effects was confirmed by using gold nanoparticles prepared in a similar manner. In this case the capping agent binds to the nanoparticle through the amine group which does not facilitate charge transfer from the gold nanoparticle and under these conditions SERS enhancement in the sandwich configuration was not observed.

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.

Gallium compounds for the design of (nano)radiophamarceuticals

NASA Astrophysics Data System (ADS)

Silva, Francisco Franca A. C.

The work presented in this thesis focus on the design of targeted nanosized and molecular tools, for the design of gallium radiopharmaceuticals with potential application in cancer theranostics. The first part describes gold nanoparticles (AuNPs) stabilized with thiolated derivatives of acyclic and macrocyclic chelators, and functionalized with bioactive peptides for specific targeting of Gastrin Releasing Peptide (GRP) and Epidermal Growth Factor (EGF) receptors. For GRPr targeting, the AuNPs were decorated with a bombesin (BBN) analog and stabilized with derivatives of diethylene triamine pentaacetic acid (DTPA) or 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) chelators for 67Ga complexation. From the evaluated radiolabeled nanoconstructs, the ones containing a dithioctic derivative of BBN and a thiolated DOTA chelator is the most promising one for the design of 67Ga (nano)radiopharmaceuticals, due to its high in vitro/in vivo stability, high cellular internalization in GRPr-positive PC3 cells, and significant tumor uptake in prostate cancer tumor xenografts. For EGFr targeting, the AuNPs were decorated with GE-11 peptide that was incorporated in a thiolated DOTA derivative. The resulting AuNPs were labeled with 67Ga using pre- and post-labeling approaches. Those obtained based on the pre-labeling approach showed an enhanced in vitro stability towards release of 67Ga while maintaining a high cellular internalization in A431 cells overexpressing EGFr. The second part describes new N4O2-donor acyclic chelators of the Schiff base type and the respective reduced amines, which contain pyridyl or pyrazolyl coordinating units at the central nitrogen atom of diethylenetriamine and phenol groups introduced at the terminal amines. The Schiff bases undergo decomposition reactions, while the corresponding amine derivatives give well defined monocationic Ga(III) complexes. However, only a pyridyl-containing amine derivative was able to effectively coordinate 67Ga. Biodistribution studies in mice showed that the corresponding radiocomplex displays a high in vivo stability and favourable pharmacokinetics, being a good candidate for further evaluation in radiopharmaceutical research.

Polyethylene glycol grafted polyethylene: a versatile platform for nonmigratory active packaging applications.

PubMed

Barish, Jeffrey A; Goddard, Julie M

2011-01-01

Nonmigratory active packaging, in which bioactive components are tethered to the package, offers the potential to reduce the need for additives in food products while maintaining safety and quality. A challenge in developing nonmigratory active packaging materials is the loss of biomolecular activity that can occur when biomolecules are immobilized. In this work, we describe a method in which a biocompatible polymer (polyethylene glycol, PEG) is grafted from the surface of ozone-treated low-density polyethylene (LDPE) resulting in a surface functionalized polyethylene to which a range of amine-terminated bioactive molecules can be immobilized. Free radical graft polymerization is used to graft PEG onto the LDPE surface, followed by immobilization of ethylenediamine onto the PEG tether. Ethylenediamine was used to demonstrate that amine-terminated molecules could be covalently attached to the PEG-grafted film. Changes in surface chemistry and topography were measured by attenuated total reflectance Fourier transform infrared spectroscopy, contact angle, atomic force microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. We demonstrate the ability to graft PEG onto the surface of polymer packaging films by free radical graft polymerization, and to covalently link an amine-terminated molecule to the PEG tether, demonstrating that amine-terminated bioactive compounds (such as peptides, enzymes, and some antimicrobials) can be immobilized onto PEG-grafted LDPE in the development of nonmigratory active packaging.   Nonmigratory active packaging offers the potential for improving food safety and quality while minimizing the migration of the active agent into food. In this paper, we describe a technique to modify polyethylene packaging films such that active agents can be covalently immobilized by a biocompatible tether. Such a technique can be adapted to a number of applications such as antimicrobial, antioxidant, or immobilized enzyme active packaging. © 2011 Institute of Food Technologists®

Suppressing interfacial water signals to assist the peak assignment of the N⁺-H stretching mode in sum frequency generation vibrational spectroscopy.

PubMed

Nguyen, Khoi Tan; Nguyen, Anh V

2015-11-21

Amines are one of the common functional groups of interest due to their abundant presence in natural proteins, surfactants and other chemicals. However, their accurate spectral assignment of vibrational modes, critical to interpreting SFG signals for characterizing various bio-interfaces such as protein-membrane interaction and surfactant adsorption, still remains elusive. Herein we present a systematic study to identify and justify the correct peak assignment of the N(+)-H stretching mode at the air-water interface. We used three special surfactants: hexadecylamine (a primary amine without counterions), dodecylamine hydrochloride (a primary amine with counterions) and hexadecyltrimethylammonium bromide as a control (the N(+)-H stretching mode is absent in this quarternary amine). We suppressed the SFG interfacial water signals using saturated NaCl solutions. Our designed experiments resolved the current controversy and concluded that the 3080 cm(-1) peak is from the N(+)-H vibrations, while the 3330 cm(-1) peak is not due to ammonium species but rather originates from the interfacial water vibrational modes or the backbone amide modes.

Preparation of fluorescent-dye-labeled cDNA from RNA for microarray hybridization.

PubMed

Ares, Manuel

2014-01-01

This protocol describes how to prepare fluorescently labeled cDNA for hybridization to microarrays. It consists of two steps: first, a mixture of anchored oligo(dT) and random hexamers is used to prime amine-modified cDNA synthesis by reverse transcriptase using a modified deoxynucleotide with a reactive amine group (aminoallyl-dUTP) and an RNA sample as a template. Second, the cDNA is purified and exchanged into bicarbonate buffer so that the amine groups in the cDNA react with the dye N-hydroxysuccinimide (NHS) esters, covalently joining the dye to the cDNA. The dye-coupled cDNA is purified again, and the amount of dye incorporated per microgram of cDNA is determined.

(Carbonato-κ2 O,O′)bis­(di-2-pyridyl­amine-κ2 N,N′)cobalt(III) bromide

PubMed Central

Czapik, Agnieszka; Papadopoulos, Christos; Lalia-Kantouri, Maria; Gdaniec, Maria

2011-01-01

In the title compound, [Co(CO3)(C10H9N3)2]Br, a distorted octa­hedral coordination of the CoIII atom is completed by four N atoms of the two chelating di-2-pyridyl­amine ligands and two O atoms of the chelating carbonate anion. The di-2-pyridyl­amine ligands are nonplanar and the dihedral angles between the 2-pyridyl groups are 29.11 (9) and 37.15 (12)°. The coordination cation, which has approximate C 2 symmetry, is connected to the bromide ion via an N—H⋯Br− hydrogen bond. The ionic pair thus formed is further assembled into a dimer via N—H⋯O inter­actions about an inversion centre. A set of weaker C—H⋯O and C—H⋯Br− inter­actions connect the dimers into a three-dimensional network. PMID:21753946

Transition Metal Free C-N Bond Forming Dearomatizations and Aryl C-H Aminations by in Situ Release of a Hydroxylamine-Based Aminating Agent.

PubMed

Farndon, Joshua J; Ma, Xiaofeng; Bower, John F

2017-10-11

We outline a simple protocol that accesses directly unprotected secondary amines by intramolecular C-N bond forming dearomatization or aryl C-H amination. The method is dependent on the generation of a potent electrophilic aminating agent released by in situ deprotection of O-Ts activated N-Boc hydroxylamines.

Functional PEG-PAMAM-tetraphosphonate capped NaLnF₄ nanoparticles and their colloidal stability in phosphate buffer.

PubMed

Zhao, Guangyao; Tong, Lemuel; Cao, Pengpeng; Nitz, Mark; Winnik, Mitchell A

2014-06-17

Developing surface coatings for NaLnF4 nanoparticles (NPs) that provide long-term stability in solutions containing competitive ions such as phosphate remains challenging. An amine-functional polyamidoamine tetraphosphonate (NH2-PAMAM-4P) as a multidentate ligand for these NPs has been synthesized and characterized as a ligand for the surface of NaGdF4 and NaTbF4 nanoparticles. A two-step ligand exchange protocol was developed for introduction of the NH2-PAMAM-4P ligand on oleate-capped NaLnF4 NPs. The NPs were first treated with methoxy-poly(ethylene glycol)-monophosphoric acid (M(n) = 750) in tetrahydrofuran. The mPEG750-OPO3-capped NPs were stable colloidal solutions in water, where they could be ligand-exchanged with NH2-PAMAM-4P. The surface amine groups on the NPs were available for derivatization to attach methoxy-PEG (M(n) = 2000) and biotin-terminated PEG (M(n) = 2000) chains. The surface coverage of ligands on the NPs was examined by thermal gravimetric analysis, and by a HABA analysis for biotin-containing NPs. Colloidal stability of the NPs was examined by dynamic light scattering. NaGdF4 and NaTbF4 NPs capped with mPEG2000-PAMAM-4P showed colloidal stability in DI water and in phosphate buffer (10 mM, pH 7.4). A direct comparison with NaTbF4 NPs capped with a mPEG2000-lysine-based tetradentate ligand that we reported previously (Langmuir 2012, 28, 12861-12870) showed that both ligands provided long-term stability in phosphate buffer, but that the lysine-based ligand provided better stability in phosphate-buffered saline.

Photocatalytic organic transformation by layered double hydroxides: highly efficient and selective oxidation of primary aromatic amines to their imines under ambient aerobic conditions.

PubMed

Yang, Xiu-Jie; Chen, Bin; Li, Xu-Bing; Zheng, Li-Qiang; Wu, Li-Zhu; Tung, Chen-Ho

2014-06-25

We report the first application of layered double hydroxide as a photocatalyst in the transformation of primary aromatic amines to their corresponding imines with high efficiency and selectivity by using oxygen in an air atmosphere as a terminal oxidant under light irradiation.

Crystal Structure and Magnetic Behavior of Two New Dinuclear Carbonato-Bridged Copper(II) Compounds. Superexchange Pathway for the Different Coordination Modes of the Carbonato Bridge in Polynuclear Copper(II) Compounds.

PubMed

Escuer, Albert; Mautner, Franz A.; Peñalba, Evaristo; Vicente, Ramon

1998-08-24

Four new &mgr;-CO(3)(2-) copper(II) complexes with different coordination modes for the carbonato bridge have been obtained by fixation of atmospheric CO(2): {(&mgr;(3)-CO(3))[Cu(3)(ClO(4))(3)(Et(3)dien)(3)]}(ClO(4)) (1), Et(3)dien = N,N',N"-triethylbis(2-aminoethane)amine; {(&mgr;-CO(3))[Cu(2)(H(2)O)(Et(4)dien)(2)]}(ClO(4))(2).H(2)O (2), Et(4)dien = N,N,N",N"-tetraethyl-bis(2-aminoethane)amine; {(&mgr;-CO(3))[Cu(2)(H(2)O)(2)(EtMe(4)dien)(2)]} (ClO(4))(2).2H(2)O (3), EtMe(4)dien = N'-ethyl-N,N,N",N"-tetramethylbis(2-aminoethane)amine; and {(&mgr;-CO(3))[Cu(2)(H(2)O)(Me(5)dien)(2)]}(ClO(4))(2).H(2)O (4), Me(5)dien = N,N,N',N",N"-pentamethylbis(2-aminoethane)amine. The crystal structures have been solved for 2, monoclinic system, space group P2(1)/n, formula [C(25)H(62)Cl(2)Cu(2)N(6)O(13)] with a = 12.763(6) Å, b = 25.125(8) Å, c = 13.261(4) Å, beta = 111.85(3) degrees, Z = 4, and for 3, triclinic system, space group P&onemacr;, formula [C(21)H(58)Cl(2)Cu(2)N(6)O(15)] with a = 8.412(3) Å, b = 14.667(4) Å, c = 16.555(5) Å, alpha = 99.66(2) degrees, beta = 102.14(2) degrees, gamma = 104.72(2) degrees, Z = 2. Susceptibility measurements show ferromagnetic behavior (J = +6.7(6) cm(-)(1)) for the trinuclear compound 1 whereas 2-4 are antiferromagnetically coupled with J = -17.8(8), -125.5(9), and -21.2(3) cm(-)(1) respectively. Certain synthetic aspects that may be related to the nuclearity of the copper(II) &mgr;-CO(3)(2-) compounds and the superexchange pathway for the different coordination modes of the carbonato bridge are discussed.

Fragmentation Patterns and Mechanisms of Singly and Doubly Protonated Peptoids Studied by Collision Induced Dissociation

NASA Astrophysics Data System (ADS)

Ren, Jianhua; Tian, Yuan; Hossain, Ekram; Connolly, Michael D.

2016-04-01

Peptoids are peptide-mimicking oligomers consisting of N-alkylated glycine units. The fragmentation patterns for six singly and doubly protonated model peptoids were studied via collision-induced dissociation tandem mass spectrometry. The experiments were carried out on a triple quadrupole mass spectrometer with an electrospray ionization source. Both singly and doubly protonated peptoids were found to fragment mainly at the backbone amide bonds to produce peptoid B-type N-terminal fragment ions and Y-type C-terminal fragment ions. However, the relative abundances of B- versus Y-ions were significantly different. The singly protonated peptoids fragmented by producing highly abundant Y-ions and lesser abundant B-ions. The Y-ion formation mechanism was studied through calculating the energetics of truncated peptoid fragment ions using density functional theory and by controlled experiments. The results indicated that Y-ions were likely formed by transferring a proton from the C-H bond of the N-terminal fragments to the secondary amine of the C-terminal fragments. This proton transfer is energetically favored, and is in accord with the observation of abundant Y-ions. The calculations also indicated that doubly protonated peptoids would fragment at an amide bond close to the N-terminus to yield a high abundance of low-mass B-ions and high-mass Y-ions. The results of this study provide further understanding of the mechanisms of peptoid fragmentation and, therefore, are a valuable guide for de novo sequencing of peptoid libraries synthesized via combinatorial chemistry.

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.

fac-[Re(CO)(3)L](+) complexes with N-CH(2)-CH(2)-X-CH(2)-CH(2)-N tridentate ligands. synthetic, X-ray crystallographic, and NMR spectroscopic investigations.

PubMed

Christoforou, Anna Maria; Marzilli, Patricia A; Fronczek, Frank R; Marzilli, Luigi G

2007-12-24

Polyamine ligands (L) have excellent binding characteristics for the formation of fac-99mTc(CO)3-based radiopharmaceuticals. Normally, these L are elaborated so as to leave pendant groups designed to impart useful biodistribution characteristics to the fac-[99mTc(CO)3L] imaging agent. Our goal is to lay a foundation for understanding the features of the bound elaborated ligands by using the fac-[Re(CO)3L]-analogue approach with the minimal prototypical ligands, diethylenetriamine (dien) or simple dien-related derivatives. Treatment of the fac-[Re(CO)3(H2O)3]+ cation with such triamine (NNN) ligands afforded fac-[Re(CO)3L]+ complexes. Ligand variations included having a central amine thioether donor, thus allowing X-ray crystallographic and NMR spectroscopic comparisons of fac-[Re(CO)3L]+ complexes with NNN and NSN ligands. fac-[Re(CO)3L]+ complexes with two terminal exo-NH groups exhibit unusually far upfield exo-NH NMR signals in DMSO-d6. Upon the addition of Cl-, these exo-NH signals move downfield, while the signals of any endo-NH or central NH groups move very little. This behavior is attributed to the formation of 1:1 ion pairs having selective Cl- hydrogen bonding to both exo-NH groups. Base addition to a DMSO-d6 solution of meso-exo-[Re(CO)3(N,N',N''-Me3dien)]PF6 led to isomerization of only one NHMe group, producing the chiral isomer. The meso isomer did not form. The [Re(CO)3(N,N,N',N'',N''-pentamethyldiethylenetriamine)]triflate.[Re(CO)3(mu3-OH)]4.3.35H2O crystal, the first structure with a fac-[Re(CO)3L] complex cocrystallized with this well-known cluster, provided parameters for a bulky NNN ligand and also reveals CO-CO interlocking intermolecular interactions that could stabilize the crystal.

Tunable synthesis and acetylation of dendrimer-entrapped or dendrimer-stabilized gold-silver alloy nanoparticles.

PubMed

Liu, Hui; Shen, Mingwu; Zhao, Jinglong; Guo, Rui; Cao, Xueyan; Zhang, Guixiang; Shi, Xiangyang

2012-06-01

In this study, amine-terminated generation 5 poly(amidoamine) dendrimers were used as templates or stabilizers to synthesize dendrimer-entrapped or dendrimer-stabilized Au-Ag alloy nanoparticles (NPs) with different gold atom/silver atom/dendrimer molar ratios with the assistance of sodium borohydride reduction chemistry. Following a one-step acetylation reaction to transform the dendrimer terminal amines to acetyl groups, a series of dendrimer-entrapped or dendrimer-stabilized Au-Ag alloy NPs with terminal acetyl groups were formed. The formed Au-Ag alloy NPs before and after acetylation reaction were characterized using different techniques. We showed that the optical property and the size of the bimetallic NPs were greatly affected by the metal composition. At the constant total metal atom/dendrimer molar ratio, the size of the alloy NPs decreased with the gold content. The formed Au-Ag alloy NPs were stable at different pH (pH 5-8) and temperature (4-50°C) conditions. X-ray absorption coefficient measurements showed that the attenuation of the binary NPs was dependent on both the gold content and the surface modification. With the increase of gold content in the binary NPs, their X-ray attenuation intensity was significantly enhanced. At a given metal composition, the X-ray attenuation intensity of the binary NPs was enhanced after acetylation. Cytotoxicity assays showed that after acetylation, the cytocompatibility of Au-Ag alloy NPs was significantly improved. With the controllable particle size and optical property, metal composition-dependent X-ray attenuation characteristics, and improved cytocompatibility after acetylation, these dendrimer-entrapped or dendrimer-stabilized Au-Ag alloy NPs should have a promising potential for CT imaging and other biomedical applications. Copyright © 2012 Elsevier B.V. All rights reserved.

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.

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

Purification and characterization of the amine dehydrogenase from a facultative methylotroph.

PubMed

Coleman, J P; Perry, J J

1984-01-01

Strain RA-6 is a pink-pigmented organism which can grow on a variety of substrates including methylamine. It can utilize methylamine as sole source of carbon via an isocitrate lyase negative serine pathway. Methylamine grown cells contain an inducible primary amine dehydrogenase [primary amine: (acceptor) oxidoreductase (deaminating)] which is not present in succinate grown cells. The amine dehydrogenase was purified to over 90% homogeneity. It is an acidic protein (isoelectric point of 5.37) with a molecular weight of 118,000 containing subunits with approximate molecular weights of 16,500 and 46,000. It is active on an array of primary terminal amines and is strongly inhibited by carbonyl reagents. Cytochrome c or artificial electron acceptors are required for activity; neither NAD nor NADP can serve as primary electron acceptor.

Fullerol ionic fluids.

PubMed

Fernandes, Nikhil; Dallas, Panagiotis; Rodriguez, Robert; Bourlinos, Athanasios B; Georgakilas, Vasilios; Giannelis, Emmanuel P

2010-09-01

We report for the first time an ionic fluid based on hydroxylated fullerenes (fullerols). The ionic fluid was synthesized by neutralizing the fully protonated fullerol with an amine terminated polyethylene/polypropylene oxide oligomer (Jeffamine). The ionic fluid was compared to a control synthesized by mixing the partially protonated form (sodium form) of the fullerols with the same oligomeric amine in the same ratio as in the ionic fluids (20 wt% fullerol). In the fullerol fluid the ionic bonding significantly perturbs the thermal transitions and melting/crystallization behavior of the amine. In contrast, both the normalized heat of fusion and crystallization of the amine in the control are similar to those of the neat amine consistent with a physical mixture of the fullerols/amine with minimal interactions. In addition to differences in thermal behavior, the fullerol ionic fluid exhibits a complex viscoelastic behavior intermediate between the neat Jeffamine (liquid-like) and the control (solid-like).

Fullerol ionic fluids

NASA Astrophysics Data System (ADS)

Fernandes, Nikhil; Dallas, Panagiotis; Rodriguez, Robert; Bourlinos, Athanasios B.; Georgakilas, Vasilios; Giannelis, Emmanuel P.

2010-09-01

We report for the first time an ionic fluid based on hydroxylated fullerenes (fullerols). The ionic fluid was synthesized by neutralizing the fully protonated fullerol with an amine terminated polyethylene/polypropylene oxide oligomer (Jeffamine®). The ionic fluid was compared to a control synthesized by mixing the partially protonated form (sodium form) of the fullerols with the same oligomeric amine in the same ratio as in the ionic fluids (20 wt% fullerol). In the fullerol fluid the ionic bonding significantly perturbs the thermal transitions and melting/crystallization behavior of the amine. In contrast, both the normalized heat of fusion and crystallization of the amine in the control are similar to those of the neat amine consistent with a physical mixture of the fullerols/amine with minimal interactions. In addition to differences in thermal behavior, the fullerol ionic fluid exhibits a complex viscoelastic behavior intermediate between the neat Jeffamine® (liquid-like) and the control (solid-like).

A polyethylenimine-mimetic biodegradable polycation gene vector and the effect of amine composition in transfection efficiency.

PubMed

Shen, J; Zhao, D J; Li, W; Hu, Q L; Wang, Q W; Xu, F J; Tang, G P

2013-06-01

The low toxicity and efficient gene delivery of polymeric vectors remain the major barrier to the clinical application of non-viral gene therapy. Here, we present a poly-D, L-succinimide (PSI)-based biodegradable cationic polymer which mimicked the golden standard, branched polyethylenimine (PEI, ~25 kDa). To investigate the influence of 1°, 2°, 3° amine group ratio in the polymer, a series of PSI-based vectors (PSI-NN'x-NNy) grafted with different amine side chains of N,N-dimethyldipropylenetriamine (NN') and bis(3-aminopropyl)amine (NN) were first characterized and contrasted by biophysical measurements. The in vitro and in vivo biological assay demonstrated that PSI-NN'0.85-NN1 exhibited better transfection ability and biocompatibility than PEI. The present results suggest that such PEI-mimic biodegradable PSI-NN'0.85-NN1 possesses a good potential application for clinical gene delivery. Copyright © 2013 Elsevier Ltd. All rights reserved.

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.

Preparation of sulfonic-functionalized graphene oxide as ion-exchange material and its application into electrochemiluminescence analysis.

PubMed

Chen, Guifen; Zhai, Shengyong; Zhai, Yanling; Zhang, Ke; Yue, Qiaoli; Wang, Lei; Zhao, Jinsheng; Wang, Huaisheng; Liu, Jifeng; Jia, Jianbo

2011-03-15

Graphene oxide (GO) obtained from chemical oxidation of flake graphite was derivatized with sulfonic groups to form sulfonic-functionalized GO (GO-SO(3)(-)) through four sulfonation routes: through amide formation between the carboxylic group of GO and amine of sulfanilic acid (AA-GO-SO(3)(-)), aryl diazonium reaction of sulfanilic acid (AD-GO-SO(3)(-)), amide formation between the carboxylic group of GO and amine of cysteamine and oxidation by H(2)O(2) (CA-GO-SO(3)(-)), and alkyl diazonium reaction of cysteamine and oxidation by H(2)O(2) (CD-GO-SO(3)(-)). Results of Fourier transform infrared spectroscopy and X-ray photoelectrospectrocopy showed that -SO(3)(-) groups were attached onto GO. Thermo gravimetric analysis showed that derivatization with sulfonic groups improved thermo stability of GO. X-ray diffraction results indicated that GO-SO(3)(-) had more ordered π-π stacking structure than the original GO. GO-SO(3)(-) and cationic polyelectrote, poly (diallyldimethylammoniumchloride) (PDDA) were adsorbed at indium tin oxide (ITO) glass surface through layer-by-layer assembling to form (GO-SO(3)(-)/PDDA)(n)/ITO multilayers. After tris-(2,2'-bipyridyl) ruthenium (II) dichloride (Ru(bpy)(3)(2+)) was incorporated into the multilayers, the obtained Ru(bpy)(3)(2+)/(GO-SO(3)(-)/PDDA)(n)/ITO electrodes can be used as electrochemiluminescence sensors for detection of organic amine with high sensitivity (limit of detection of 1 nM) and stability. Copyright © 2010 Elsevier B.V. All rights reserved.

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

5-Bromo-N-methyl­pyrimidin-2-amine

PubMed Central

Yang, Qi; Xu, Ning; Zhu, Kai; Lv, Xiaoping; Han, Ping-fang

2012-01-01

In the title mol­ecule, C5H6BrN3, the pyrimidine ring is essentially planar, with an r.m.s. deviation of 0.007 Å. The Br and N atoms substituted to the pyrimidine ring are coplanar with the ring [displacements = 0.032 (1) and 0.009 (5) Å, respectively], while the methyl C atom lies 0.100 (15) Å from this plane with a dihedral angle between the pyrimidine ring and the methyl­amine group of 4.5 (3)°. In the crystal, C—H⋯N, C—H⋯Br and N—H⋯N hydrogen bonds link the mol­ecules into a two-dimensional network in the (011) plane. PMID:22259398

Facile preparation of well-defined AB2 Y-shaped miktoarm star polypeptide copolymer via the combination of ring-opening polymerization and click chemistry.

PubMed

Rao, Jingyi; Zhang, Yanfeng; Zhang, Jingyan; Liu, Shiyong

2008-10-01

Well-defined AB2 Y-shaped miktoarm star polypeptide copolymer, PZLL-b-(PBLG)2, was synthesized via a combination of ring-opening polymerization (ROP) of alpha-amino acid N-carboxyanhydride (NCA) and click chemistry, where PZLL is poly(epsilon-benzyloxycarbonyl-L-lysine) and PBLG is poly(gamma-benzyl-L-glutamate). First, two types of primary-amine-containing initiators, N-aminoethyl 3,5-bis(propargyloxyl)-benzamide and 3-azidopropylamine, were synthesized and employed for the ROP of NCA, leading to the formation of dialkynyl-terminated PZLL and azide-terminated PBLG, dialkynyl-PZLL and PBLG-N3, respectively. The subsequent copper(I)-catalyzed cycloaddition reaction between dialkynyl-PZLL and slightly excess PBLG-N3 led to facile preparation of PZLL-b-(PBLG)2 Y-shaped miktoarm star polypeptide copolymer. The excess PBLG-N3 was scavenged off by reacting with alkynyl-functionalized Wang resin. The obtained Y-shaped miktoarm star polypeptide copolymer was characterized by gel permeation chromatograph (GPC), Fourier transform-infrared spectroscopy (FT-IR), and (1)H NMR. Moreover, after the hydrolysis of protecting benzyl and benzyloxycarbonyl groups of PZLL-b-(PBLG)2, water-soluble pH-responsive Y-shaped miktoarm star polypeptide copolymer, PLL-b-(PLGA)2, was obtained, where PLL is poly(L-lysine) and PLGA is poly(L-glutamic acid). It can self-assemble into PLGA-core micelles at acidic pH and PLL-core micelles at alkaline pH, accompanied with the coil-to-helix transition of PLGA and PLL sequences, respectively. The spontaneous pH-responsive supramolecular assembly of PLL-b-(PLGA)2 miktoarm star polypeptide copolymer has been investigated via a combination of (1)H NMR, laser light scattering (LLS), transmission electron microscopy (TEM), and circular dichroism (CD) spectroscopy.

Identification of amines in wintertime ambient particulate material using high resolution aerosol mass spectrometry

NASA Astrophysics Data System (ADS)

Bottenus, Courtney L. H.; Massoli, Paola; Sueper, Donna; Canagaratna, Manjula R.; VanderSchelden, Graham; Jobson, B. Thomas; VanReken, Timothy M.

2018-05-01

Significant amounts of amines were detected in fine particulate matter (PM) during ambient wintertime conditions in Yakima, WA, using a high resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). Positive matrix factorization (PMF) of the organic aerosol (OA) signal resulted in a six-factor solution that included two previously unreported amine OA factors. The contributions of the amine factors were strongly episodic, but the concentration of the combined amine factors was as high as 10-15 μg m-3 (2-min average) during those episodes. In one occasion, the Amine-II component was 45% of total OA signal. The Amine-I factor was dominated by spectral peaks at m/z 86 (C5H12N+) and m/z 100 (C6H14N+), while the Amine-II factor was dominated by spectral peaks at m/z 58 (C3H8N+ and C2H6N2+) and m/z 72 (C4H10N+ and C3H8N2+). The ions dominating each amine factor showed distinct time traces, suggesting different sources or formation processes. Investigation into the chemistry of the amine factors suggests a correlation with inorganic anions for Amine-I, but no evidence that the Amine-II was being neutralized by the same inorganic ions. We also excluded the presence of organonitrates (ON) in the OA. The presence of C2H4O2+ at m/z 60 (a levoglucosan fragment) in the Amine-I spectrum suggests some influence of biomass burning emissions (more specifically residential wood combustion) in this PMF factor, but wind direction suggested that the most likely sources of these amines were agricultural activities and feedlots to the S-SW of the site.

The Analysis of AGEs and ALEs by Mass Spectrometry: What does the Future Hold?

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

Metz, Thomas O.

2009-09-15

In 1912, Louis-Camille Maillard described a reaction between amino acids and reducing sugars that produced a discolored (brown) reaction mixture in the presence of heat [1]. This complex network of reactions between reducing sugars and free amine groups on amino acids or proteins came to be known as the Maillard reaction and was the domain of food chemists for the next 50 years. Work in the 1960s began a very exciting era in the field. A few years earlier, several groups [2-5] reported on the heterogeneity of normal human adult hemoglobin (HbA) as determined chromatographically, and Allen et al weremore » the first to use cation-exchange chromatography to separate a previously observed fast moving component (HbAI) into three fractions that they termed AIa, AIb, and AIc. An increase in the fast moving HbAI of four diabetic patients was subsequently reported by Huisman and Dozy in 1962 [6], and the link between diabetes and increased HbAI was later strengthened by Rahbar’s observation of increased HbAI – the majority of which is HbAIc – in 47 cases of diabetes [7]. Bookchin and Gallop determined that HbAIc consisted of a hexose bound to both β-chains [8], and Bunn and colleagues subsequently proposed that glucose binds to the N-terminal amine groups of the β-chain valine residues in the form of a Schiff base, which then rearranges to form an Amadori compound [9]. Thus, while Maillard chemistry was known to occur during the heating and processing of food, the identification of Amadori-modified hemoglobin proved that it also occurred in vivo (after all, as John Baynes likes to point out, humans are essentially low temperature ovens with long cooking cycles!).« less

Fabrication of nanometer- and micrometer-scale protein structures by site-specific immobilization of histidine-tagged proteins to aminosiloxane films with photoremovable protein-resistant protecting groups

DOE PAGES

Xia, Sijing; Cartron, Michael; Morby, James; ...

2016-01-28

The site-specific immobilization of histidine-tagged proteins to patterns formed by far-field and near-field exposure of films of aminosilanes with protein-resistant photolabile protecting groups is demonstrated. After deprotection of the aminosilane, either through a mask or using a scanning near-field optical microscope, the amine terminal groups are derivatized first with glutaraldehyde and then with N-(5-amino-1-carboxypentyl)iminodiacetic acid to yield a nitrilo-triacetic-acid-terminated surface. After complexation with Ni 2+, this surface binds histidine-tagged GFP and CpcA-PEB in a site-specific fashion. The chemistry is simple and reliable and leads to extensive surface functionalization. Bright fluorescence is observed in fluorescence microscopy images of micrometer- and nanometer-scalemore » patterns. X-ray photoelectron spectroscopy is used to study quantitatively the efficiency of photodeprotection and the reactivity of the modified surfaces. The efficiency of the protein binding process is investigated quantitatively by ellipsometry and by fluorescence microscopy. We find that regions of the surface not exposed to UV light bind negligible amounts of His-tagged proteins, indicating that the oligo(ethylene glycol) adduct on the nitrophenyl protecting group confers excellent protein resistance; in contrast, exposed regions bind His-GFP very effectively, yielding strong fluorescence that is almost completely removed on treatment of the surface with imidazole, confirming a degree of site-specific binding in excess of 90%. As a result, this simple strategy offers a versatile generic route to the spatially selective site-specific immobilization of proteins at surfaces.« less

Fabrication of Nanometer- and Micrometer-Scale Protein Structures by Site-Specific Immobilization of Histidine-Tagged Proteins to Aminosiloxane Films with Photoremovable Protein-Resistant Protecting Groups

PubMed Central

2016-01-01

The site-specific immobilization of histidine-tagged proteins to patterns formed by far-field and near-field exposure of films of aminosilanes with protein-resistant photolabile protecting groups is demonstrated. After deprotection of the aminosilane, either through a mask or using a scanning near-field optical microscope, the amine terminal groups are derivatized first with glutaraldehyde and then with N-(5-amino-1-carboxypentyl)iminodiacetic acid to yield a nitrilo-triacetic-acid-terminated surface. After complexation with Ni2+, this surface binds histidine-tagged GFP and CpcA-PEB in a site-specific fashion. The chemistry is simple and reliable and leads to extensive surface functionalization. Bright fluorescence is observed in fluorescence microscopy images of micrometer- and nanometer-scale patterns. X-ray photoelectron spectroscopy is used to study quantitatively the efficiency of photodeprotection and the reactivity of the modified surfaces. The efficiency of the protein binding process is investigated quantitatively by ellipsometry and by fluorescence microscopy. We find that regions of the surface not exposed to UV light bind negligible amounts of His-tagged proteins, indicating that the oligo(ethylene glycol) adduct on the nitrophenyl protecting group confers excellent protein resistance; in contrast, exposed regions bind His-GFP very effectively, yielding strong fluorescence that is almost completely removed on treatment of the surface with imidazole, confirming a degree of site-specific binding in excess of 90%. This simple strategy offers a versatile generic route to the spatially selective site-specific immobilization of proteins at surfaces. PMID:26820378

Metal and base free synthesis of primary amines via ipso amination of organoboronic acids mediated by [bis(trifluoroacetoxy)iodo]benzene (PIFA).

PubMed

Chatterjee, Nachiketa; Goswami, Avijit

2015-08-07

A metal and base free synthesis of primary amines has been developed at ambient temperature through ipso amination of diversely functionalized organoboronic acids, employing a combination of [bis(trifluoroacetoxy)iodo]benzene (PIFA)-N-bromosuccinimide (NBS) and methoxyamine hydrochloride as the aminating reagent. The amines were primarily obtained as their trifluoroacetate salts which on subsequent aqueous alkaline work up provided the corresponding free amines. The combination of PIFA-NBS is found to be the mildest choice compared to the commonly used strong bases (e.g. n-BuLi, Cs2CO3) for activating the aminating agent. The reaction is expected to proceed via activation of the aminating reagent followed by B-N 1,2-aryl migration.

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.

40 CFR 721.642 - Amines, N-(C14-18 and C16-16 unsaturated alkyl)] dipropylene-tri-, tripropylenetetra-, and...

Code of Federal Regulations, 2010 CFR

2010-07-01

... substances amines, N-(C14-18 and C16-18 unsaturated alkyl)] dipropylenetri-, (PMN P-94-1244... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Amines, N-(C14-18 and C16-16... Amines, N-(C14-18 and C16-16 unsaturated alkyl)] dipropylene-tri-, tripropylenetetra-, and...

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.

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.

Nanosized zinc oxide particles do not promote DHPN-induced lung carcinogenesis but cause reversible epithelial hyperplasia of terminal bronchioles.

PubMed

Xu, Jiegou; Futakuchi, Mitsuru; Alexander, David B; Fukamachi, Katsumi; Numano, Takamasa; Suzui, Masumi; Shimizu, Hideo; Omori, Toyonori; Kanno, Jun; Hirose, Akihiko; Tsuda, Hiroyuki

2014-01-01

Zinc oxide (ZnO) is known to induce lung toxicity, including terminal bronchiolar epithelial hyperplasia, which gives rise to concerns that nanosized ZnO (nZnO) might lead to lung carcinogenesis. We studied the tumor promoting activity of nZnO by an initiation-promotion protocol using human c-Ha-ras proto-oncogene transgenic rats (Hras128 rats). The rats were given 0.2 % N-nitrosobis(2-hydroxypropyl)amine (DHPN) in the drinking water for 2 weeks and then treated with 0.5 ml of 250 or 500 μg/ml nZnO suspension by intra-pulmonary spraying once every 2 weeks for a total of 7 times. Treatment with nZnO particles did not promote DHPN-induced lung carcinogenesis. However, nZnO dose-dependently caused epithelial hyperplasia of terminal bronchioles (EHTB) and fibrosis-associated interstitial pneumonitis (FAIP) that were independent of DHPN treatment. Tracing the fate of EHTB lesions in wild-type rats indicated that the hyperplastic lesions almost completely disappeared within 12 weeks after the last nZnO treatment. Since nZnO particles were not found in the lung and ZnCl2 solution induced similar lung lesions and gene expression profiles, the observed lesions were most likely caused by dissolved Zn(2+). In summary, nZnO did not promote carcinogenesis in the lung and induced EHTB and FAIP lesions that regressed rapidly, probably due to clearance of surplus Zn(2+) from the lung.

Occurrence of aromatic amines and N-nitrosamines in the different steps of a drinking water treatment plant.

PubMed

Jurado-Sánchez, Beatriz; Ballesteros, Evaristo; Gallego, Mercedes

2012-09-15

The occurrence of 24 amines within a full scale drinking water treatment plant that used chlorinated agents as disinfectants was evaluated for the first time in this research. Prior to any treatment (raw water), aniline, 3-chloroaniline, 3,4-dichloroaniline and N-nitrosodimethylamine were detected at low levels (up to 18 ng/L) but their concentration increased ∼10 times after chloramination while 9 new amines were produced (4 aromatic amines and 5 N-nitrosamines). Within subsequent treatments, there were no significant changes in the amine levels, although the concentrations of 2-nitroaniline, N-nitrosodimethylamine and N-nitrosodiethylamine increased slightly within the distribution system. Eleven of the 24 amines studied were undetected either in the raw and in the treatment plant samples analysed. There is an important difference in the behaviour of the aromatic amines and N-nitrosamines with respect to water temperature and rainfall events. Amine concentrations were higher in winter due to low water temperatures, this effect being more noticeable for N-nitrosamines. Aromatic amines were detected at their highest concentrations (especially 3,4-dichloroaniline and 2-nitroaniline) in treated water after rainfall events. These results may be explained by the increase in the levels of amine precursors (pesticides and their degradation products) in raw water since the rainfall facilitated the transport of these compounds from soil which was previously contaminated as a result of intensive agricultural practices. Copyright © 2012 Elsevier Ltd. All rights reserved.

Mechanistic insights into the one-pot synthesis of propargylamines from terminal alkynes and amines in chlorinated solvents catalyzed by gold compounds and nanoparticles.

PubMed

Aguilar, David; Contel, Maria; Urriolabeitia, Esteban P

2010-08-09

Propargylamines can be obtained from secondary amines and terminal alkynes in chlorinated solvents by a three- and two-component synthesis catalyzed by gold compounds and nanoparticles (Au-NP) under mild conditions. The use of dichloromethane allows for the activation of two C-Cl bonds and a clean transfer of the methylene fragment to the final product. The scope of the reaction as well as the influence of different gold(III) cycloaurated complexes and salts has been investigated. The involvement of gold nanoparticles generated in situ in the process is discussed and a plausible reaction mechanism is proposed on the basis of the data obtained.

Crystal structures of three lead(II) acetate-bridged di-amino-benzene coordination polymers.

PubMed

Geiger, David K; Parsons, Dylan E; Zick, Patricia L

2014-12-01

Poly[tris-(acetato-κ(2) O,O')(μ2-acetato-κ(3) O,O':O)tetra-kis-(μ3-acetato-κ(4) O,O':O:O')bis-(benzene-1,2-di-amine-κN)tetra-lead(II)], [Pb4(CH3COO)8(C6H8N2)2] n , (I), poly[(acetato-κ(2) O,O')(μ3-acetato-κ(4) O,O':O:O')(4-chloro-benzene-1,2-diamine-κN)lead(II)], [Pb(CH3COO)2(C6H7ClN2)] n , (II), and poly[(κ(2) O,O')(μ3-acetato-κ(4) O,O':O:O')(3,4-di-amino-benzo-nitrile-κN)lead(II)], [Pb(CH3COO)2(C7H7N3)] n , (III), have polymeric structures in which monomeric units are joined by bridging acetate ligands. All of the Pb(II) ions exhibit hemidirected coordination. The repeating unit in (I) is composed of four Pb(II) ions having O6, O6N, O7 and O6N coordination spheres, respectively, where N represents a monodentate benzene-1,2-di-amine ligand and O acetate O atoms. Chains along [010] are joined by bridging acetate ligands to form planes parallel to (10-1). (II) and (III) are isotypic and have one Pb(II) ion in the asymmetric unit that has an O6N coordination sphere. Pb2O2 units result from a symmetry-imposed inversion center. Polymeric chains parallel to [100] exhibit hydrogen bonding between the amine and acetate ligands. In (III), additional hydrogen bonds between cyano groups and non-coordinating amines join the chains by forming R 2 (2)(14) rings.

X-ray crystal structure and theoretical study of a new dinuclear Cu(II) complex with two different geometry centers bridged with an oxo group

NASA Astrophysics Data System (ADS)

Golbedaghi, Reza; Azimi, Saeid; Molaei, Atefeh; Hatami, Masoud; Notash, Behrouz

2017-10-01

A new Schiff base ligand HL, 1,3-bis(2-((Z)-(2-aminoethylimino)methyl)phenoxy)ethylene di amine, has been synthesized from the reaction of a new aldehyde and ethylenediamine. After preparation the Schiff base, a new dinuclear Cu(II) complex with two different geometry for each metal ion was synthesized. Single crystal X-ray structure analysis of the complex Cu(II) showed that the complex is binuclear and all nitrogen and oxygen atoms of ligand (N4O3) are coordinated to two Cu(II) center ions. The crystal structure studying shows, a perchlorate ion has been coordinated to the two Cu(II) metal centers as bridged and another perchlorate coordinated to the one of Cu(II) ion as terminal. However, two interesting structures square pyramidal and distorted octahedral Cu(II) ions are bridged asymmetrically by a perchlorate ion and oxygen of hydroxyl group of Schiff base ligand. In addition, we had a theoretical study to have a comparison of experimental and theoretical results we determined the HOMO and LUMO orbitals.

Versatile On-Resin Synthesis of High Mannose Glycosylated Asparagine with Functional Handles

PubMed Central

Chen, Rui; Pawlicki, Mark A.; Tolbert, Thomas J.

2013-01-01

Here we present a synthetic route for solid phase synthesis of N-linked glycoconjugates containing high mannose oligosaccharides which allows the incorporation of useful functional handles on the N-terminus of asparagine. In this strategy, the C-terminus of an Fmoc protected aspartic acid residue is first attached to a solid phase support. The side chain of aspartic acid is protected by a 2-phenylisopropyl protecting group, which allows selective deprotection for the introduction of glycosylation. By using a convergent on-resin glycosylamine coupling strategy, an N-glycosidic linkage is successfully formed on the free side chain of the resin bound aspartic acid with a large high mannose oligosaccharide, Man8GlcNAc2, to yield N-linked high mannose glycosylated asparagine. The use of on-resin glycosylamine coupling provides excellent glycosylation yield, can be applied to couple other types of oligosaccharides, and also makes it possible to recover excess oligosaccharides conveniently after the on-resin coupling reaction. Useful functional handles including an alkene (p-vinylbenzoic acid), an alkyne (4-pentynoic acid), biotin, and 5-carboxyfluorescein are then conjugated onto the N-terminal amine of asparagine on-resin after the removal of the Fmoc protecting group. In this way, useful functional handles are introduced onto the glycosylated asparagine while maintaining the structural integrity of the reducing end of the oligosaccharide. The asparagine side chain also serves as a linker between the glycan and the functional group and preserves the native presentation of N-linked glycan which may aid in biochemical and structural studies. As an example of a biochemical study using functionalized high mannose glycosylated asparagine, a fluorescence polarization assay has been utilized to study the binding of the lectin Concanavalin A (ConA) using 5-carboxyfluorescein labeled high mannose glycosylated asparagine. PMID:24326091

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.

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

Molecular structure, proton affinity and hydrogen bonds of (2-hydroxyethyl)amine-N-oxides: DFT, MP2 and FTIR study

NASA Astrophysics Data System (ADS)

Aksamentova, Tamara N.; Chipanina, Nina N.; Oznobikhina, Larisa P.; Adamovich, Sergei N.; Smirnov, Vladimir I.

2018-01-01

Tris- 1, bis- 2, and mono- 3 (2-hydroxyethyl)amine-N-oxides isomers, their protonated forms, and H-complexes with acids have been studied in gas phase and DMSO solution by the quantum chemical calculations using DFT and MP2 methods. It is found that the proton affinity of the endo isomers 1a-3a, exo isomers 1b-3b and epi isomer 1c depends on the number of the hydroxyethyl groups, steric factors and strengths of the intramolecular H-bonds OHṡṡṡON in 1a-3a and OHṡṡṡOH in 1b-3b. The peculiarities of formation of the hydrogen bonded and proton transfer complexes of tris(2-hydroxyethyl)amine-N-oxide with trifluoroacetic and 2-methylphenyloxyacetic acids are defined by 1 configuration, acid strength and solvent polarity. The structure of 1 and its complexes upon transition to solution was determined using FTIR spectroscopy.

Influence of the Terminal Electron Donor in D-D-π-A Organic Dye-Sensitized Solar Cells: Dithieno[3,2-b:2',3'-d]pyrrole versus Bis(amine).

PubMed

Dai, Panpan; Yang, Lin; Liang, Mao; Dong, Huanhuan; Wang, Peng; Zhang, Chunyao; Sun, Zhe; Xue, Song

2015-10-14

With respect to the electron-withdrawing acceptors of D-A-π-A organic dyes, reports on the second electron-donating donors for D-D-π-A organic dyes are very limited. Both of the dyes have attracted significant attention in the field of dye-sensitized solar cells (DSCs). In this work, four new D-D-π-A organic dyes with dithieno[3,2-b:2',3'-d]pyrrole (DTP) or bis(amine) donor have been designed and synthesized for a investigation of the influence of the terminal electron donor in D-D-π-A organic dye-sensitized solar cells. It is found that DTP is a promising building block as the terminal electron donor when introduced in the dithiophenepyrrole direction, but not just a good bridge, which exhibits several characteristics: (i) efficiently increasing the maximum molar absorption coefficient and extending the absorption bands; (ii) showing stronger charge transfer interaction as compared with the pyrrole direction; (iii) beneficial to photocurrent generation of DSCs employing cobalt electrolytes. DSCs based on M45 with the Co-phen electrolyte exhibit good light-to-electric energy conversion efficiencies as high as 9.02%, with a short circuit current density (JSC) of 15.3 mA cm(-2), open circuit voltage (VOC) of 867 mV and fill factor (FF) of 0.68 under AM 1.5 illumination (100 mW cm(-2)). The results demonstrate that N,S-heterocycles such as DTP unit could be promising candidates for application in highly efficient DSCs employing cobalt electrolyte.

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.

Retrospective evaluation of ProcalAmine administration in a population of hospitalized ICU dogs: 36 cases (2010-2013).

PubMed

Olan, Natasha V; Prittie, Jennifer

2015-01-01

To describe the use of ProcalAmine as a source of parenteral nutrition in hospitalized dogs and to report complications possibly referable to its use. Retrospective study. Private veterinary teaching hospital. Thirty-six dogs hospitalized in ICU receiving ProcalAmine between October 2010 and March 2013. None. The most common underlying disease process in this population of dogs was trauma (n = 8). Median duration of administration was 4 days and median resting energy requirement provided via ProcalAmine was 33%. ProcalAmine was administered via central catheters in 86% of cases and via peripheral catheters in 14% of cases. The overall mechanical complication rate was 19%. Metabolic complications possibly associated with ProcalAmine administration were documented in 12/36 dogs. Hyponatremia was most commonly identified (n = 6) followed by hyperglycemia (n = 4), hypochloremia (n = 2), azotemia (n = 2), metabolic alkalosis (n = 2), hyperchloremia (n = 1), and metabolic acidosis (n = 1). ProcalAmine appears to be relatively safe and a viable option for parenteral nutrition in ill and injured dogs. Due to the potential for electrolyte derangements and other metabolic complications, daily monitoring of these parameters is advisable. © Veterinary Emergency and Critical Care Society 2015.

Phenylethynyl terminated imide oligomers

NASA Technical Reports Server (NTRS)

Hergenrother, Paul M. (Inventor); Bryant, Robert G. (Inventor); Jensen, Brian J. (Inventor); Havens, Stephen J. (Inventor)

1994-01-01

Four phenylethynyl amine compounds - 3 and 4-aminophenoxy-4'-phenylethynylbenzophenone, and 3 and 4-amino-4'-phenylethynylbenzophenone - were readily prepared and were used to endcap imide oligomers. Phenylethynyl-terminated amide acid oligomers and phenylethynyl-terminated imide oligomers with various molecular weights and compositions were prepared and characterized. These oligomers were cured at 300 to 400 C to provide crosslinked polyimides with excellent solvent resistance, high strength and modulus, and good high temperature properties. Adhesive panels, composites, films, and moldings from these phenylethynyl terminated imide oligomers gave excellent mechanical performance.

Phenylethynyl terminated imide oligomers

NASA Technical Reports Server (NTRS)

Hergenrother, Paul M. (Inventor); Bryant, Robert G. (Inventor); Jensen, Brian J. (Inventor); Havens, Stephen J. (Inventor)

1995-01-01

Four phenylethynyl amine compounds - 3 and 4-aminophenoxy-4'-phenylethynylbenzophenone, and 3 and 4-amino-4'-phenylethynylbenzophenone - were readily prepared and were used to endcap imide oligomers. Phenylethynyl-terminated amide acid oligomers and phenylethynyl-terminated imide oligomers with various molecular weights and compositions were prepared and characterized. These oligomers were cured at 300 to 400 C to provide crosslinked polyimides with excellent solvent resistance, high strength and modulus, and good high temperature properties. Adhesive panels, composites, films, and moldings from these phenylethynyl terminated imide oligomers gave excellent mechanical performance.

Regulation of the catalytic behavior of pullulanases chelated onto nickel (II)-modified magnetic nanoparticles.

PubMed

Wang, Jianfeng; Liu, Zhongmei; Zhou, Zhemin

2017-06-01

Chelating of pullulanases onto nickel (II)-modified magnetic nanoparticles results in one-step purification and immobilization of pullulanase, and facilitates the commercial application of pullulanase in industrial scale. To improve the catalytic behavior, especially the operational stability, of the nanocatalyst in consecutive batch reactions, we prepared various iminodiacetic acid-modified magnetic nanoparticles differed in surface polarity and spacer length, on which the His6-tagged pullulanases were chelated via nickel ions, and then studied the correlation between the MNPs surface property and the corresponding catalyst behavior. When pullulanases were chelated onto the surface-modified MNPs, the thermostability of all pullulanase derivatives were lower than that of free counterpart, being not relevant to the protein orientation guided by the locality of the His6-tag, but related to the MNPs basal surface polarity and the grafted spacer length. After chelating of pullulanases onto MNPs, there were changes observed in the pH-activity profile and the apparent Michaelis constant toward pullulan. The changing tendencies were mainly dependent on the His6-tagged pullulanase orientation, and the changing extents were tuned by the spacer length. The reusability of pullulanase immobilized by N-terminal His6-tag was higher than that of pullulanase immobilized by C-terminal His6-tag. Moreover, the reusability of the immobilized pullulanase tested increased till grafting polyether amine-400 as spacer-arm, therefore the N-terminal His6-tagged pullulanase chelating MNPs grafted polyether amine-400 gave the best reusability, which retained 60% of initial activity after 18 consecutive cycles with a total reaction time of 9h. Additionally, the correlation analysis of the catalyst behaviors indicated that the reusability was independent from other catalytic properties such as thermostability and substrate affinity. All the results revealed that the catalyst behavior can be mainly controlled by the His6-tagged pullulanase orientation than by the MNPs surface property which can tune the catalyst function. Copyright © 2017. Published by Elsevier Inc.

Tethered tertiary amines as solid-state n-type dopants for solution-processable organic semiconductors

DOE PAGES

Russ, Boris; Robb, Maxwell J.; Popere, Bhooshan C.; ...

2015-12-09

A scarcity of stable n-type doping strategies compatible with facile processing has been a major impediment to the advancement of organic electronic devices. Localizing dopants near the cores of conductive molecules can lead to improved efficacy of doping. We and others recently showed the effectiveness of tethering dopants covalently to an electron-deficient aromatic molecule using trimethylammonium functionalization with hydroxide counterions linked to a perylene diimide core by alkyl spacers. In this work, we demonstrate that, contrary to previous hypotheses, the main driver responsible for the highly effective doping observed in thin films is the formation of tethered tertiary amine moietiesmore » during thin film processing. Furthermore, we demonstrate that tethered tertiary amine groups are powerful and general n-doping motifs for the successful generation of free electron carriers in the solid-state, not only when coupled to the perylene diimide molecular core, but also when linked with other small molecule systems including naphthalene diimide, diketopyrrolopyrrole, and fullerene derivatives. Our findings help expand a promising molecular design strategy for future enhancements of n-type organic electronic materials.« less

Tethered tertiary amines as solid-state n-type dopants for solution-processable organic semiconductors

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

Russ, Boris; Robb, Maxwell J.; Popere, Bhooshan C.

A scarcity of stable n-type doping strategies compatible with facile processing has been a major impediment to the advancement of organic electronic devices. Localizing dopants near the cores of conductive molecules can lead to improved efficacy of doping. We and others recently showed the effectiveness of tethering dopants covalently to an electron-deficient aromatic molecule using trimethylammonium functionalization with hydroxide counterions linked to a perylene diimide core by alkyl spacers. In this work, we demonstrate that, contrary to previous hypotheses, the main driver responsible for the highly effective doping observed in thin films is the formation of tethered tertiary amine moietiesmore » during thin film processing. Furthermore, we demonstrate that tethered tertiary amine groups are powerful and general n-doping motifs for the successful generation of free electron carriers in the solid-state, not only when coupled to the perylene diimide molecular core, but also when linked with other small molecule systems including naphthalene diimide, diketopyrrolopyrrole, and fullerene derivatives. Our findings help expand a promising molecular design strategy for future enhancements of n-type organic electronic materials.« less

Synthesis and anti-HIV activity of novel N-1 side chain-modified analogs of 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (HEPT).

PubMed

Pontikis, R; Benhida, R; Aubertin, A M; Grierson, D S; Monneret, C

1997-06-06

A series of 33 N-1 side chain-modified analogs of 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (1, HEPT) were synthesized and evaluated for their anti-HIV-1 activity. In particular, the influence of substitution of the terminal hydroxy group of the acyclic structure of HEPT and the structural rigidity of this side chain were investigated. Halo (7, 8), azido (9), and amino (10-15) derivatives were synthesized from HEPT via the p-tosylate derivative 6. Acylation of the primary amine 15 afforded the amido analogs 16-20. The diaryl derivatives 26-29 were prepared by reaction of HEPT, or of the 6-(2-pyridylthio) analog 23, with diaryl disulfides in the presence of tri-n-butylphosphine. Compounds 39-41, in which the N-1 side chain is rigidified by incorporation of an E-configured double bond, were obtained by palladium(0)-catalyzed coupling of several different 6-(arylthio)uracil derivatives (37, 38) with allyl acetates 33. Compounds 13, 40a,c,d,f, and 41, incorporating an aromatic ring at the end of the acyclic side chain, were found to be more potent than the known diphenyl-substituted HEPT analog BPT (2), two of them, 40c,d, being 10-fold more active.

Oxidations of N-(3-indoleethyl) cyclic aliphatic amines by horseradish peroxidase: the indole ring binds to the enzyme and mediates electron-transfer amine oxidation.

PubMed

Ling, Ke-Qing; Li, Wen-Shan; Sayre, Lawrence M

2008-01-23

Although oxidations of aromatic amines by horseradish peroxidase (HRP) are well-known, typical aliphatic amines are not substrates of HRP. In this study, the reactions of N-benzyl and N-methyl cyclic amines with HRP were found to be slow, but reactions of N-(3-indoleethyl) cyclic amines were 2-3 orders of magnitude faster. Analyses of pH-rate profiles revealed a dominant contribution to reaction by the amine-free base forms, the only species found to bind to the enzyme. A metabolic study on a family of congeneric N-(3-indoleethyl) cyclic amines indicated competition between amine and indole oxidation pathways. Amine oxidation dominated for the seven- and eight-membered azacycles, where ring size supports the change in hybridization from sp3 to sp2 that occurs upon one-electron amine nitrogen oxidation, whereas only indole oxidation was observed for the six-membered ring congener. Optical difference spectroscopic binding data and computational docking simulations suggest that all the arylalkylamine substrates bind to the enzyme through their aromatic termini with similar binding modes and binding affinities. Kinetic saturation was observed for a particularly soluble substrate, consistent with an obligatory role of an enzyme-substrate complexation preceding electron transfer. The significant rate enhancements seen for the indoleethylamine substrates suggest the ability of the bound indole ring to mediate what amounts to medium long-range electron-transfer oxidation of the tertiary amine center by the HRP oxidants. This is the first systematic investigation to document aliphatic amine oxidation by HRP at rates consistent with normal metabolic turnover, and the demonstration that this is facilitated by an auxiliary electron-rich aromatic ring.

Chlorotoxin-Conjugated Multifunctional Dendrimers Labeled with Radionuclide 131I for Single Photon Emission Computed Tomography Imaging and Radiotherapy of Gliomas.

PubMed

Zhao, Lingzhou; Zhu, Jingyi; Cheng, Yongjun; Xiong, Zhijuan; Tang, Yueqin; Guo, Lilei; Shi, Xiangyang; Zhao, Jinhua

2015-09-09

Chlorotoxin-conjugated multifunctional dendrimers labeled with radionuclide 131I were synthesized and utilized for targeted single photon emission computed tomography (SPECT) imaging and radiotherapy of cancer. In this study, generation five amine-terminated poly(amidoamine) dendrimers were used as a platform to be sequentially conjugated with polyethylene glycol (PEG), targeting agent chlorotoxin (CTX), and 3-(4'-hydroxyphenyl)propionic acid-OSu (HPAO). This was followed by acetylation of the remaining dendrimer terminal amines and radiolabeling with 131I to form the targeted theranostic dendrimeric nanoplatform. We show that the dendrimer platform possessing approximately 7.7 CTX and 21.1 HPAO moieties on each dendrimer displays excellent cytocompatibility in a given concentration range (0-20 μM) and can specifically target cancer cells overexpressing matrix metallopeptidase 2 (MMP2) due to the attached CTX. With the attached HPAO moiety having the phenol group, the dendrimer platform can be effectively labeled with radioactive 131I with good stability and high radiochemical purity. Importantly, the 131I labeling renders the dendrimer platform with an ability to be used for targeted SPECT imaging and radiotherapy of an MMP2-overexpressing glioma model in vivo. The developed radiolabeled multifunctional dendrimeric nanoplatform may hold great promise to be used for targeted theranostics of human gliomas.

Comparative distribution of misonidazole and its amine metabolite in female Swiss Webster mice

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

Born, J.L.; Hadley, W.M.

1985-06-01

The distribution of misonidazole and its terminal reduction product 1-(2-amino-1-imidazolyl)-3-methoxy-2-propanol (misoamine) were compared in female Swiss Webster mice to determine if either misonidazole or misoamine is distributed to peripheral nerves. Female Swiss Webster mice received a 100 mg/kg (5 ..mu..Ci/..mu..mole) i.p. dose of either /sup 3/H-misonidazole or /sup 3/H-miso-amine and the distribution of radioactivity was determined in various tissues including sciatic nerves and other myelinated nerves. Misonidazole produced higher initial tissue concentrations of radioactivity than did miso-amine. The relative tissue concentrations of radioactivity produced by misonidazole or miso-amine were similar, although not identical, 48 hours after administration of the drugs.more » Both sciatic and other myelinated nerves were found to retain radioactivity following the administration of either misonidazole or miso-amine.« less

Free terminal amines in DNA-binding peptides alter the product distribution from guanine radicals produced by single electron oxidation.

PubMed

Konigsfeld, Katie M; Lee, Melissa; Urata, Sarah M; Aguilera, Joe A; Milligan, Jamie R

2012-03-01

Electron deficient guanine radical species are major intermediates produced in DNA by the direct effect of ionizing irradiation. There is evidence that they react with amine groups in closely bound ligands to form covalent crosslinks. Crosslink formation is very poorly characterized in terms of quantitative rate and yield data. We sought to address this issue by using oligo-arginine ligands to model the close association of DNA and its binding proteins in chromatin. Guanine radicals were prepared in plasmid DNA by single electron oxidation. The product distribution derived from them was assayed by strand break formation after four different post-irradiation incubations. We compared the yields of DNA damage produced in the presence of four ligands in which neither, one, or both of the amino and carboxylate termini were blocked with amides. Free carboxylate groups were unreactive. Significantly higher yields of heat labile sites were observed when the amino terminus was unblocked. The rate of the reaction was characterized by diluting the unblocked amino group with its amide blocked derivative. These observations provide a means to develop quantitative estimates for the yields in which these labile sites are formed in chromatin by exposure to ionizing irradiation.

A Statistics-based Platform for Quantitative N-terminome Analysis and Identification of Protease Cleavage Products*

PubMed Central

auf dem Keller, Ulrich; Prudova, Anna; Gioia, Magda; Butler, Georgina S.; Overall, Christopher M.

2010-01-01

Terminal amine isotopic labeling of substrates (TAILS), our recently introduced platform for quantitative N-terminome analysis, enables wide dynamic range identification of original mature protein N-termini and protease cleavage products. Modifying TAILS by use of isobaric tag for relative and absolute quantification (iTRAQ)-like labels for quantification together with a robust statistical classifier derived from experimental protease cleavage data, we report reliable and statistically valid identification of proteolytic events in complex biological systems in MS2 mode. The statistical classifier is supported by a novel parameter evaluating ion intensity-dependent quantification confidences of single peptide quantifications, the quantification confidence factor (QCF). Furthermore, the isoform assignment score (IAS) is introduced, a new scoring system for the evaluation of single peptide-to-protein assignments based on high confidence protein identifications in the same sample prior to negative selection enrichment of N-terminal peptides. By these approaches, we identified and validated, in addition to known substrates, low abundance novel bioactive MMP-2 targets including the plasminogen receptor S100A10 (p11) and the proinflammatory cytokine proEMAP/p43 that were previously undescribed. PMID:20305283

Poly-l-Lactic Acid Nanofiber-Polyamidoamine Hydrogel Composites: Preparation, Properties, and Preliminary Evaluation as Scaffolds for Human Pluripotent Stem Cell Culturing.

PubMed

Gualandi, Chiara; Bloise, Nora; Mauro, Nicolò; Ferruti, Paolo; Manfredi, Amedea; Sampaolesi, Maurilio; Liguori, Anna; Laurita, Romolo; Gherardi, Matteo; Colombo, Vittorio; Visai, Livia; Focarete, Maria Letizia; Ranucci, Elisabetta

2016-10-01

Electrospun poly-l-lactic acid (PLLA) nanofiber mats carrying surface amine groups, previously introduced by nitrogen atmospheric pressure nonequilibrium plasma, are embedded into aqueous solutions of oligomeric acrylamide-end capped AGMA1, a biocompatible polyamidoamine with arg-gly-asp (RGD)-reminiscent repeating units. The resultant mixture is finally cured giving PLLA-AGMA1 hydrogel composites that absorb large amounts of water and, in the swollen state, are translucent, soft, and pliable, yet as strong as the parent PLLA mat. They do not split apart from each other when swollen in water and remain highly flexible and resistant, since the hydrogel portion is covalently grafted onto the PLLA nanofibers via the addition reaction of the surface amine groups to a part of the terminal acrylic double bonds of AGMA1 oligomers. Preliminary tested as scaffolds, the composites prove capable of maintaining short-term undifferentiated cultures of human pluripotent stem cells in feeder-free conditions. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Controlled Interactions between Two Dimensional Layered Inorganic Nanosheets and Polymers

DTIC Science & Technology

2016-06-15

transition metal and non- pair electrons of amine allows us to develop scalable, stable and uniform composite films with numerous combinations of TMD...modification of TMDs sheets with amine-terminated polymers is introduced and the strong Lewis acid-base interaction between transition metal and non- pair ...can be readily entangled with other chains of the matrix polymer, thereby ensuring homogeneous PNC formation. The solvent medium offers an extra

Copper(II)-catalyzed electrophilic amination of quinoline N-oxides with O-benzoyl hydroxylamines.

PubMed

Li, Gang; Jia, Chunqi; Sun, Kai; Lv, Yunhe; Zhao, Feng; Zhou, Kexiao; Wu, Hankui

2015-03-21

Copper acetate-catalyzed C-H bond functionalization amination of quinoline N-oxides was achieved using O-benzoyl hydroxylamine as an electrophilic amination reagent, thereby affording the desired products in moderate to excellent yields. Electrophilic amination can also be performed in good yield on a gram scale.

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

USGS Publications Warehouse

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

1996-01-01

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

Successful Conversion of the Bacillus subtilis BirA Group II Biotin Protein Ligase into a Group I Ligase

PubMed Central

Henke, Sarah K.; Cronan, John E.

2014-01-01

Group II biotin protein ligases (BPLs) are characterized by the presence of an N-terminal DNA binding domain that allows transcriptional regulation of biotin biosynthetic and transport genes whereas Group I BPLs lack this N-terminal domain. The Bacillus subtilis BPL, BirA, is classified as a Group II BPL based on sequence predictions of an N-terminal helix-turn-helix motif and mutational alteration of its regulatory properties. We report evidence that B. subtilis BirA is a Group II BPL that regulates transcription at three genomic sites: bioWAFDBI, yuiG and yhfUTS. Moreover, unlike the paradigm Group II BPL, E. coli BirA, the N-terminal DNA binding domain can be deleted from Bacillus subtilis BirA without adverse effects on its ligase function. This is the first example of successful conversion of a Group II BPL to a Group I BPL with retention of full ligase activity. PMID:24816803

Naphthalene Diimide Based n-Type Conjugated Polymers as Efficient Cathode Interfacial Materials for Polymer and Perovskite Solar Cells.

PubMed

Jia, Tao; Sun, Chen; Xu, Rongguo; Chen, Zhiming; Yin, Qingwu; Jin, Yaocheng; Yip, Hin-Lap; Huang, Fei; Cao, Yong

2017-10-18

A series of naphthalene diimide (NDI) based n-type conjugated polymers with amino-functionalized side groups and backbones were synthesized and used as cathode interlayers (CILs) in polymer and perovskite solar cells. Because of controllable amine side groups, all the resulting polymers exhibited distinct electronic properties such as oxidation potential of side chains, charge carrier mobilities, self-doping behaviors, and interfacial dipoles. The influences of the chemical variation of amine groups on the cathode interfacial effects were further investigated in both polymer and perovskite solar cells. We found that the decreased electron-donating property and enhanced steric hindrance of amine side groups substantially weaken the capacities of altering the work function of the cathode and trap passivation of the perovskite film, which induced ineffective interfacial modifications and declining device performance. Moreover, with further improvement of the backbone design through the incorporation of a rigid acetylene spacer, the resulting polymers substantially exhibited an enhanced electron-transporting property. Upon use as CILs, high power conversion efficiencies (PCEs) of 10.1% and 15.2% were, respectively, achieved in polymer and perovskite solar cells. Importantly, these newly developed n-type polymers were allowed to be processed over a broad thickness range of CILs in photovoltaic devices, and a prominent PCE of over 8% for polymer solar cells and 13.5% for perovskite solar cells can be achieved with the thick interlayers over 100 nm, which is beneficial for roll-to-roll coating processes. Our findings contribute toward a better understanding of the structure-performance relationship between CIL material design and solar cell performance, and provide important insights and guidelines for the design of high-performance n-type CIL materials for organic and perovskite optoelectronic devices.

Histamine and tele-methylhistamine quantification in cerebrospinal fluid from narcoleptic subjects by liquid chromatography tandem mass spectrometry with precolumn derivatization.

PubMed

Croyal, Mikaël; Dauvilliers, Yves; Labeeuw, Olivier; Capet, Marc; Schwartz, Jean-Charles; Robert, Philippe

2011-02-01

An ultra-performance liquid chromatography tandem mass spectrometry (UPLC™-MS/MS) assay was developed for the simultaneous analysis of histamine, its major metabolite tele-methylhistamine, and an internal standard (N-tele-(R)-α-dimethylhistamine) from human cerebrospinal fluid (CSF) samples. The method involves derivatization of primary amines with 4-bromobenzenesulfonyl chloride and subsequent analysis by reversed phase liquid chromatography with mass spectrometry detection and positive electrospray ionization. The separation of derivatized biogenic amines was achieved within 3.5 min on an Acquity® BEH C(18) column by elution with a linear gradient of acetonitrile/water/formic acid (0.1%). The assay was linear in the concentration range of 50-5000 pM for each amine (5.5-555 pg/ml for histamine and 6.25-625 pg/ml for tele-methylhistamine). For repeatability and precision determination, coefficients of variation (CVs) were less than 11.0% over the tested concentration ranges, within acceptance criteria. Thus, the developed method provides the rapid, easy, highly sensitive, and selective requirement to quantify these amines in human CSF. No significant difference was found in the mean ± standard error levels of these amines between a group of narcoleptic patients (histamine=392 ± 64 pM, tele-methylhistamine=2431 ± 461 pM, n=7) and of neurological control subjects (histamine=402 ± 72 pM, tele-methylhistamine=2209 ± 463 pM, n=32). Copyright © 2010 Elsevier Inc. All rights reserved.

Chirality sensing with stereodynamic biphenolate zinc complexes.

PubMed

Bentley, Keith W; de Los Santos, Zeus A; Weiss, Mary J; Wolf, Christian

2015-10-01

Two bidentate ligands consisting of a fluxional polyarylacetylene framework with terminal phenol groups were synthesized. Reaction with diethylzinc gives stereodynamic complexes that undergo distinct asymmetric transformation of the first kind upon binding of chiral amines and amino alcohols. The substrate-to-ligand chirality imprinting at the zinc coordination sphere results in characteristic circular dichroism signals that can be used for direct enantiomeric excess (ee) analysis. This chemosensing approach bears potential for high-throughput ee screening with small sample amounts and reduced solvent waste compared to traditional high-performance liquid chromatography methods. © 2015 Wiley Periodicals, Inc.

Structure of β- N-dimethylamino-4-dodecyloxypropiophenone complexes with di- and polycarboxylic acids

NASA Astrophysics Data System (ADS)

Lebedeva, Tamara L.; Shandryuk, George A.; Sycheva, Tatyana I.; Bezborodov, Vladimir S.; Talroze, Raissa V.; Platé, Nicolai A.

1995-07-01

The type of bonds responsible for the complexation of di- and polyacids with the tertiary amine β- N-dimethylamino-4-dodecyloxypropiophenone is studied by means of FTIR spectroscopy. The complexes are shown to be stable due to strong H-bonding with partial charge transfer. The characteristic composition for complexes of polyacrylic, polymethacrylic and malonic acids is calculated as 2:1 (number of carboxylic groups per number of amine molecules) whereas glutaric acid forms complexes of different composition including 1:1. The characteristic composition results from the structure of the initial acid. The structures of both the characteristic complex and "excess" acid are also discussed.

Aqua[bis(pyrimidin-2-yl-kappa N)amine](carbonato-kappa 2O,O')copper(II) dihydrate.

PubMed

van Albada, Gerard A; Mutikainen, Ilpo; Turpeinen, Urho; Reedijk, Jan

2002-03-01

The title mononuclear complex, [Cu(CO(3))(C(8)H(7)N(5))(H(2)O)] x 2H(2)O, was obtained by fixation of CO(2) by a mixture of copper(II) tetrafluoroborate and the ligand bis(pyrimidin-2-yl)amine in ethanol/water. The Cu(II) ion of the complex has a distorted square-pyramidal environment, with a basal plane formed by two N atoms of the ligand and two chelating O atoms of the carbonate group, while the apical position is occupied by the O atom of the coordinating water molecule. In the solid state, hydrogen-bonding interactions are dominant, the most unusual being the Watson-Crick-type coplanar ligand pairing through two N--H...N bonds. Lattice water molecules also participate in hydrogen bonding.

Pyrylium Salts as Reactive Matrices for MALDI-MS Imaging of Biologically Active Primary Amines

NASA Astrophysics Data System (ADS)

Shariatgorji, Mohammadreza; Nilsson, Anna; Källback, Patrik; Karlsson, Oskar; Zhang, Xiaoqun; Svenningsson, Per; Andren, Per E.

2015-06-01

Many neuroactive substances, including endogenous biomolecules, environmental compounds, and pharmaceuticals possess primary amine functional groups. Among these are catecholamine neurotransmitters (e.g., dopamine), many substituted phenethylamines (e.g., amphetamine), as well as amino acids and neuropeptides. In most cases, mass spectrometric (ESI and MALDI) analyses of trace amounts of such compounds are challenging because of their poor ionization properties. We present a method for chemical derivatization of primary amines by reaction with pyrylium salts that facilitates their detection by MALDI-MS and enables the imaging of primary amines in brain tissue sections. A screen of pyrylium salts revealed that the 2,4-diphenyl-pyranylium ion efficiently derivatizes primary amines and can be used as a reactive MALDI-MS matrix that induces both derivatization and desorption. MALDI-MS imaging with such matrix was used to map the localization of dopamine and amphetamine in brain tissue sections and to quantitatively map the distribution of the neurotoxin β- N-methylamino-L-alanine.

Redox inactive metal ion triggered N-dealkylation by an iron catalyst with dioxygen activation: a lesson from lipoxygenases.

PubMed

Zhang, Jisheng; Wang, Yujuan; Luo, Nengchao; Chen, Zhuqi; Wu, Kangbing; Yin, Guochuan

2015-06-07

Utilization of dioxygen as the terminal oxidant at ambient temperature is always a challenge in redox chemistry, because it is hard to oxidize a stable redox metal ion like iron(III) to its high oxidation state to initialize the catalytic cycle. Inspired by the dioxygenation and co-oxidase activity of lipoxygenases, herein, we introduce an alternative protocol to activate the sluggish iron(III) species with non-redox metal ions, which can promote its oxidizing power to facilitate substrate oxidation with dioxygen, thus initializing the catalytic cycle. In oxidations of N,N-dimethylaniline and its analogues, adding Zn(OTf)2 to the [Fe(TPA)Cl2]Cl catalyst can trigger the amine oxidation with dioxygen, whereas [Fe(TPA)Cl2]Cl alone is very sluggish. In stoichiometric oxidations, it has also been confirmed that the presence of Zn(OTf)2 can apparently improve the electron transfer capability of the [Fe(TPA)Cl2]Cl complex. Experiments using different types of substrates as trapping reagents disclosed that the iron(IV) species does not occur in the catalytic cycle, suggesting that oxidation of amines is initialized by electron transfer rather than hydrogen abstraction. Combined experiments from UV-Vis, high resolution mass spectrometry, electrochemistry, EPR and oxidation kinetics support that the improved electron transfer ability of iron(III) species originates from its interaction with added Lewis acids like Zn(2+) through a plausible chloride or OTf(-) bridge, which has promoted the redox potential of iron(III) species. The amine oxidation mechanism was also discussed based on the available data, which resembles the co-oxidase activity of lipoxygenases in oxidative dealkylation of xenobiotic metabolisms where an external electron donor is not essential for dioxygen activation.

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

Tsuji-Trost N-allylation with allylic acetates using cellulose-Pd catalyst

EPA Science Inventory

Allylic amines are synthesized using heterogeneous cellulose-Pd catalyst via N-allylation of amines; aliphatic and benzyl amines undergo facile reaction with substituted and unsubstituted allyl acetates in high yields.

Enzymes immobilized on amine-terminated ionic liquid-functionalized carbon nanotube for hydrogen peroxide determination.

PubMed

Liu, Xiuhui; Bu, Caihong; Nan, Zhihan; Zheng, Lichun; Qiu, Yu; Lu, Xiaoquan

2013-02-15

We report on a new approach for the electrochemical detection of hydrogen peroxide (H2O2) based on Cytochrome C (Cyt c) immobilized ionic liquid (IL)-functionalized multi-walled carbon nanotubes (MWCNTs) modified glass carbon electrode (GCE). Functionalization of multi-walled carbon nanotube with amine-terminated ionic liquid materials was characterized using fourier transform infrared spectroscopy (FTIR), UV-vis spectra, and electrochemical impedance spectroscopy (EIS), and the results showed that the covalent modification of MWCNTs with ILs exhibited a high surface area for enzyme immobilization and provided a good microenvironment for Cyt c to retain its bioelectrocatalytic activity toward H2O2. Amperometry was used to evaluate the catalytic activity of the cyt c towards H2O2. The proposed biosensor exhibited a wide linear response range nearly 4 orders of magnitude of H2O2 (4.0 × 10(-8)M-1.0 × 10(-4)M) with a good linearity (0.9980) and a low detection limit of 1.3 × 10(-8)M (based on S/N=3). Furthermore, the biosensor also displays some other excellent characteristics such as high selectivity, good reproducibility and long-term stability. Thus, the biosensor constructed in this study has great potential for detecting H2O2 in the complex biosystems. Copyright © 2012 Elsevier B.V. All rights reserved.

Crystal structure and electrochemical properties of [Ni(bztmpen)(CH3CN)](BF4)2 {bztmpen is N-benzyl-N,N',N'-tris-[(6-methyl-pyridin-2-yl)meth-yl]ethane-1,2-di-amine}.

PubMed

Chen, Lin; Ren, Gan; Guo, Yakun; Sang, Ge

2017-06-01

The mononuclear nickel title complex (acetonitrile-κ N ){ N -benzyl- N , N ', N '-tris-[(6-methyl-pyridin-2-yl)meth-yl]ethane-1,2-di-amine}-nickel(II) bis-(tetra-fluor-ido-borate), [Ni(C 30 H 35 N 5 )(CH 3 CN)](BF 4 ) 2 , was prepared from the reaction of Ni(BF 4 ) 2 ·6H 2 O with N -benzyl- N , N ', N '-tris-[(6-methyl-pyridin-2-yl)meth-yl]ethane-1,2-di-amine ( bztmpen ) in aceto-nitrile at room temperature. With an open site occupied by the aceto-nitrile mol-ecule, the nickel(II) atom is chelated by five N-atom sites from the ligand and one N atom from the ligand, showing an overall octa-hedral coordination environment. Compared with analogues where the 6-methyl substituent is absent, the bond length around the Ni 2+ cation are evidently longer. Upon reductive dissociation of the acetro-nitrile mol-ecule, the title complex has an open site for a catalytic reaction. The title complex has two redox couples at -1.50 and -1.80 V ( versus F c +/0 ) based on nickel. The F atoms of the two BF 4 - counter-anions are split into two groups and the occupancy ratios refined to 0.611 (18):0.389 (18) and 0.71 (2):0.29 (2).

The occurrence of N-nitrosamines, residual nitrite and biogenic amines in commercial dry fermented sausages and evaluation of their occasional relation.

PubMed

De Mey, Eveline; De Klerck, Katrijn; De Maere, Hannelore; Dewulf, Lore; Derdelinckx, Guy; Peeters, Marie-Christine; Fraeye, Ilse; Vander Heyden, Yvan; Paelinck, Hubert

2014-02-01

Regarding food borne intoxications, the accumulation of biogenic amines must be avoided in all kinds of food products. Moreover, biogenic amines can function as precursors for the formation of carcinogenic N-nitrosamines when nitrite is present. To estimate the food safety of the dry fermented sausages available on the Belgian market, a screening of the residual sodium nitrite and nitrate contents, biogenic amines and volatile N-nitrosamine concentrations was performed on 101 samples. The median concentrations of residual NaNO2 and NaNO3 were each individually lower than 20mg/kg. In general, the biogenic amine accumulation remained low at the end of shelf life. Only in one product the amounts of cadaverine and putrescine reached intoxicating levels. Concerning the occurrence of N-nitrosamines, only N-nitrosopiperidine and N-nitrosomorpholine were detected in a high number of samples (resp. 22% and 28%). No correlation between the presence of N-nitrosamines and the biogenic amines content was observed. Although the N-nitrosamines could not been linked to specific product categories, the occurrence of N-nitrosopiperidine could probably be attributed to the use of pepper. © 2013.

Origin of fast catalysis in allylic amination reactions catalyzed by Pd-Ti heterobimetallic complexes.

PubMed

Walker, Whitney K; Kay, Benjamin M; Michaelis, Scott A; Anderson, Diana L; Smith, Stacey J; Ess, Daniel H; Michaelis, David J

2015-06-17

Experiments and density functional calculations were used to quantify the impact of the Pd-Ti interaction in the cationic heterobimetallic Cl2Ti(N(t)BuPPh2)2Pd(η(3)-methallyl) catalyst 1 used for allylic aminations. The catalytic significance of the Pd-Ti interaction was evaluated computationally by examining the catalytic cycle for catalyst 1 with a conformation where the Pd-Ti interaction is intact versus one where the Pd-Ti interaction is severed. Studies were also performed on the relative reactivity of the cationic monometallic (CH2)2(N(t)BuPPh2)2Pd(η(3)-methallyl) catalyst 2 where the Ti from catalyst 1 was replaced by an ethylene group. These computational and experimental studies revealed that the Pd-Ti interaction lowers the activation barrier for turnover-limiting amine reductive addition and accelerates catalysis up to 10(5). The Pd-Ti distance in 1 is the result of the N(t)Bu groups enforcing a boat conformation that brings the two metals into close proximity, especially in the transition state. The turnover frequency of classic Pd π allyl complexes was compared to that of 1 to determine the impact of P-Pd-P coordination angle and ligand electronic properties on catalysis. These experiments identified that cationic (PPh3)2Pd(η(3)-CH2C(CH3)CH2) catalyst 3 performs similarly to 1 for allylic aminations with diethylamine. However, computations and experiment reveal that the apparent similarity in reactivity is due to very fast reaction kinetics. The higher reactivity of 1 versus 3 was confirmed in the reaction of methallyl chloride and 2,2,6,6-tetramethylpiperidine (TMP). Overall, experiments and calculations demonstrate that the Pd-Ti interaction induces and is responsible for significantly lower barriers and faster catalysis for allylic aminations.

Synthesis, structure, properties and immobilization on a gold surface of the monoribbed-functionalized tris-dioximate cobalt(II) clathrochelates and an electrocatalytic hydrogen production from H+ ions.

PubMed

Voloshin, Y Z; Belov, A S; Vologzhanina, A V; Aleksandrov, G G; Dolganov, A V; Novikov, V V; Varzatskii, O A; Bubnov, Y N

2012-05-28

The cycloaddition of the mono- and dichloroglyoximes to the cobalt(II) bis-α-benzyldioximate afforded the cobalt(II) mono- and dichloroclathrochelates in moderate yields (40-60%). These complexes undergo nucleophilic substitution of their reactive chlorine atoms with aliphatic amines, alcohols and thiolate anions. In the case of ethylenediamine and 1,2-ethanedithiol, only the macrobicyclic products with α,α'-N(2)- and α,α'-S(2)-alicyclic six-numbered ribbed fragments were obtained. The cobalt(II) cage complexes with terminal mercapto groups were synthesized using aliphatic dithiols. The crystal and molecular structures of the six cobalt(II) clathrochelates were obtained by X-ray diffraction. Their CoN(6)-coordination polyhedra possess a geometry intermediate between a trigonal prism and a trigonal antiprism, and the encapsulated cobalt(II) ions are shifted from their centres due to the structural Jahn-Teller effect with the Co-N distances varying significantly (by 0.10-0.26 Å). The electrochemistry of the complexes obtained was studied by cyclic voltammetry (CV). The anodic waves correspond to the quasi-reversible Co(2+/3+) oxidations, whereas the cathodic ranges contain the quasi-reversibile waves assigned to the Co(2+/+) reductions; all the cobalt(i)-containing clathrochelate anions formed are stable in the CV time scale. The electrocatalytic properties of the cobalt complexes obtained were studied in the production of hydrogen from H(+) ions: the addition of HClO(4) resulted in the formation of the same catalytic cathodic reduction Co(2+/+) waves. The controlled-potential electrolysis with gas chromatography analysis confirmed the production of H(2) in high Faraday yields. The efficiency of this electrocatalytic process was enhanced by an immobilization of the complexes with terminal mercapto groups on a surface of the working gold electrode.

N6-Trimethyl-lysine metabolism. Structural identification of the metabolite 3-hydroxy-N6-trimethyl-lysine

PubMed Central

Novak, Raymond F.; Swift, Terrence J.; Hoppel, Charles L.

1980-01-01

1H and 13C nuclear-magnetic-resonance spectroscopy and functional-group analysis were used to determine the molecular structure of an isolated metabolite (IIb) of trimethyl-lysine as 3-hydroxy-N6-trimethyl-lysine, an important intermediate in the conversion of trimethyl-lysine into trimethylammoniobutyrate and carnitine [Hoppel, Cox & Novak (1980) Biochem. J. 188, 509–519]. Functional-group analysis revealed the presence of a primary amine and reaction of metabolite (IIb) with periodate yielded 4-N-trimethylammoniobutyrate as a product, showing 2,3-substitution on the molecule and suggesting that the 3-substitution on the molecule may be an alcohol ([unk]CH–OH), amine ([unk]CH[unk]–NH2) or carbonyl ([unk]C=O) functional group. 1H integration ratios, 1H and 13C chemical-shift data and 1H and 13C signal multiplicities from the sample (IIb) were used to complete the identification of metabolite (IIb) as 3-hydroxy-N6-trimethyl-lysine. For example, the proton multiplet at δ 4.2p.p.m. and doublet at δ 4.1p.p.m., positions representative of amine or alcohol substitution on methylene carbon atoms, integration ratios of 1:1:2:9:4 and a positive ninhydrin test suggest 3-hydroxy-N6-trimethyl-lysine as the molecular structure for metabolite (IIb). 13C chemical-shift data obtained from the sample (IIb) and compared with several model compounds (trimethylammoniohexanoate, trimethyl-lysine and 3-hydroxylysine) resulted in generation of the spectrum of the metabolite and allowed independent identification of metabolite (IIb) as 3-hydroxy-N6-trimethyl-lysine. The 1H spectrum of erythro- and threo-3-hydroxylysine are presented for comparison, and the 1H and 13C n.m.r. spectra of the erythro-isomer support this analysis. PMID:6772169

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.

Ligand- and base-free copper(II)-catalyzed C-N bond formation: cross-coupling reactions of organoboron compounds with aliphatic amines and anilines.

PubMed

Quach, Tan D; Batey, Robert A

2003-11-13

[reaction: see text] A ligandless and base-free Cu-catalyzed protocol for the cross-coupling of arylboronic acids and potassium aryltrifluoroborate salts with primary and secondary aliphatic amines and anilines is described. The process utilizes catalytic copper(II) acetate monohydrate and 4 A molecular sieves in dichloromethane at slightly elevated temperatures under an atmosphere of oxygen. A broad range of functional groups are tolerated on both of the cross-coupling partners.

Thermal properties of wood reacted with a phosphorus pentoxide–amine system

Treesearch

Hong-Lin Lee; George C. Chen; Roger M. Rowell

2004-01-01

The objective of this research was to improve the fire-retardant properties of wood in one treatment using a phosphorus pentoxide–amine system. Phosphorus pentoxide and 16 amines including alkyl, halophenyl, and phenyl amines were compounded in N,N-dimethylformamide and the resulting solutions containing phosphoramides were reacted with wood. The characteristics of...

Mediated Electron Transfer at Vertically Aligned Single-Walled Carbon Nanotube Electrodes During Detection of DNA Hybridization.

PubMed

Wallen, Rachel; Gokarn, Nirmal; Bercea, Priscila; Grzincic, Elissa; Bandyopadhyay, Krisanu

2015-12-01

Vertically aligned single-walled carbon nanotube (VASWCNT) assemblies are generated on cysteamine and 2-mercaptoethanol (2-ME)-functionalized gold surfaces through amide bond formation between carboxylic groups generated at the end of acid-shortened single-walled carbon nanotubes (SWCNTs) and amine groups present on the gold surfaces. Atomic force microscopy (AFM) imaging confirms the vertical alignment mode of SWCNT attachment through significant changes in surface roughness compared to bare gold surfaces and the lack of any horizontally aligned SWCNTs present. These SWCNT assemblies are further modified with an amine-terminated single-stranded probe-DNA. Subsequent hybridization of the surface-bound probe-DNA in the presence of complementary strands in solution is followed using impedance measurements in the presence of Fe(CN)6 (3-/4-) as the redox probe in solution, which show changes in the interfacial electrochemical properties, specifically the charge-transfer resistance, due to hybridization. In addition, hybridization of the probe-DNA is also compared when it is attached directly to the gold surfaces without any intermediary SWCNTs. Contrary to our expectations, impedance measurements show a decrease in charge-transfer resistance with time due to hybridization with 300 nM complementary DNA in solution with the probe-DNA attached to SWCNTs. In contrast, an increase in charge-transfer resistance is observed with time during hybridization when the probe-DNA is attached directly to the gold surfaces. The decrease in charge-transfer resistance during hybridization in the presence of VASWCNTs indicates an enhancement in the electron transfer process of the redox probe at the VASWCNT-modified electrode. The results suggest that VASWCNTs are acting as mediators of electron transfer, which facilitate the charge transfer of the redox probe at the electrode-solution interface.

Mediated Electron Transfer at Vertically Aligned Single-Walled Carbon Nanotube Electrodes During Detection of DNA Hybridization

NASA Astrophysics Data System (ADS)

Wallen, Rachel; Gokarn, Nirmal; Bercea, Priscila; Grzincic, Elissa; Bandyopadhyay, Krisanu

2015-06-01

Vertically aligned single-walled carbon nanotube (VASWCNT) assemblies are generated on cysteamine and 2-mercaptoethanol (2-ME)-functionalized gold surfaces through amide bond formation between carboxylic groups generated at the end of acid-shortened single-walled carbon nanotubes (SWCNTs) and amine groups present on the gold surfaces. Atomic force microscopy (AFM) imaging confirms the vertical alignment mode of SWCNT attachment through significant changes in surface roughness compared to bare gold surfaces and the lack of any horizontally aligned SWCNTs present. These SWCNT assemblies are further modified with an amine-terminated single-stranded probe-DNA. Subsequent hybridization of the surface-bound probe-DNA in the presence of complementary strands in solution is followed using impedance measurements in the presence of Fe(CN)6 3-/4- as the redox probe in solution, which show changes in the interfacial electrochemical properties, specifically the charge-transfer resistance, due to hybridization. In addition, hybridization of the probe-DNA is also compared when it is attached directly to the gold surfaces without any intermediary SWCNTs. Contrary to our expectations, impedance measurements show a decrease in charge-transfer resistance with time due to hybridization with 300 nM complementary DNA in solution with the probe-DNA attached to SWCNTs. In contrast, an increase in charge-transfer resistance is observed with time during hybridization when the probe-DNA is attached directly to the gold surfaces. The decrease in charge-transfer resistance during hybridization in the presence of VASWCNTs indicates an enhancement in the electron transfer process of the redox probe at the VASWCNT-modified electrode. The results suggest that VASWCNTs are acting as mediators of electron transfer, which facilitate the charge transfer of the redox probe at the electrode-solution interface.

Synthesis and Preclinical Evaluation of QS-21 Variants Leading to Simplified Vaccine Adjuvants and Mechanistic Probes

PubMed Central

Chea, Eric K.; Fernández-Tejada, Alberto; Damani, Payal; Adams, Michelle M.; Gardner, Jeffrey R.; Livingston, Philip O.; Ragupathi, Govind; Gin, David Y.

2012-01-01

QS-21 is a potent immunostimulatory saponin that is currently under clinical investigation as an adjuvant in various vaccines to treat infectious diseases, cancers, and congnitive disorders. Herein we report the design, synthesis, and preclinical evaluation of simplified QS-21 congeners to define key structural features that are critical for adjuvant activity. Truncation of the linear tetrasaccharide domain revealed that a trisaccharide variant is equipotent to QS-21 while the corresponding disaccharide and monosaccharide congeners are more toxic or less potent, respectively. Modification of the acyl domain in the trisaccharide series revealed that a terminal carboxylic acid is well-tolerated while a terminal amine results in reduced adjuvant activity. Acylation of the terminal amine can restore adjuvant activity and enables the synthesis of fluorescently-labeled QS-21 variants. Cellular studies with these probes revealed that, contrary to conventional wisdom, the most highly adjuvant active of these fluorescently-labeled saponins does not simply associate with the plasma membrane, but rather is internalized by dendritic cells. PMID:22866694

Adsorption of CO2 on amine-functionalised MCM-41: experimental and theoretical studies.

PubMed

dos Santos, Thiago Custódio; Bourrelly, Sandrine; Llewellyn, Philip L; Carneiro, José Walkimar de M; Ronconi, Célia Machado

2015-04-28

Adsorption of CO2 on MCM-41 functionalised with [3-(2-aminoethylamino)propyl]trimethoxysilane (MCM-41-N2), N(1)-(3-trimethoxysilylpropyl)diethylenetriamine (MCM-41-N3), 4-aminopyridine (MCM-41-aminopyridine), 4-(methylamino)pyridine (MCM-41-methylaminopyridine) and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (MCM-41-guanidine) was investigated. The amine-functionalised materials were characterised by (29)Si and (13)C solid-state nuclear magnetic resonance, N2 adsorption/desorption isotherms, X-ray diffraction and transmission electron microscopy. CO2 adsorption at 1.0 bar and 30 °C showed that the amount of CO2 (nads/mmol g(-1)) adsorbed on MCM-41-N2 and MCM-41-N3 is approximately twice the amount adsorbed on MCM-41. For MCM-41-aminopyridine, MCM-41-methylaminopyridine and MCM-41-guanidine, the CO2 adsorption capacity was smaller than that of MCM-41 at the same conditions. The proton affinity (computed with wB97x-D/6-311++G(d,p)) of the secondary amino groups is higher than that of the primary amino groups; however, the relative stabilities of the primary and secondary carbamates are similar. The differential heat of adsorption decreases as the number of secondary amino groups increases.

Tissue Permeability Effects Associated with the Use of Mucoadhesive Cationic Nanoformulations of Docetaxel in the Bladder.

PubMed

Pandey, Rakhi; Jackson, John K; Mugabe, Clement; Liggins, Richard; Burt, Helen M

2016-08-01

Recently, efficacy studies in mice have shown that amine-terminated cationic (CNP) nanoparticulate carriers of DTX offer an improved formulation of the drug for intravesical delivery. It is hypothesized that this improved efficacy may arise from a carrier mediated bladder exfoliation process that removes the urothelial barrier allowing for increased drug uptake into bladder tissue. The objective of this study was to investigate exfoliation processes in fresh pig's bladders (ex vivo) exposed to three cationic polyglycerols with increasing degrees of amination (denoted 350, 580 and 780). The study also compared the tissue depth profile of DTX uptake into these tissues using these different carriers. Aminated polyglycerols were synthesized and characterized in the laboratory with low (CNP-360), medium (CNP-580) and high (CNP-780) levels of amine content. CNP-based DTX solutions and commercial DTX solutions in polysorbate 80 (Taxotere®) were doped with (3)H-radiolabeled DTX and prepared by solvent evaporation from acetonitrile, followed by drying and reconstitution in pH 6.4 buffer. Sections of fresh pig's bladder tissue were clamped into Franz diffusion cells and the urothelial side was exposed to the DTX solutions for 2 h. Tissue sections were then frozen for sectioning by cryotome sectioning and subsequently processed for drug analysis by liquid scintillation counting. Alternatively tissue sections were fixed in 2% glutaraldehyde and 2% paraformaldehyde in 0.1 M sodium cacodylate buffer for the purposes of scanning electron microscopy (SEM). Exposure of the urothelial surface to the amine-terminated polyglycerol solutions resulted in the exfoliation of bladder tissues in a time- and concentration-dependent manner. Exfoliation was significantly more pronounced when using CNPs with a medium or high levels of amination whereas only minor levels of exfoliation were seen with low levels. Following incubation of tissues in Tween-based commercial formulations (Taxotere) of DTX (0.5 mg/mL) the drug was detectable at low levels (10-40 μg/g tissue) in all depths of tissue. Similar drug uptake was observed using the CNP-360 formulation. However drug uptake levels were increased to 60-100 μg/g tissue when samples were incubated with either the CNP-580 or CNP-780 formulations. The use of cationic polyglycerols with higher levels of amine termination allows for an enhanced uptake of DTX into bladder tissues as compared to commercial (Taxotere) formulations. These increased drug levels probably arise from exfoliation processes resulting in a temporary elimination of the urothelial permeability barrier and increased drug penetration into the tissue.

Selective reduction of N-oxides to amines: application to drug metabolism.

PubMed

Kulanthaivel, Palaniappan; Barbuch, Robert J; Davidson, Rita S; Yi, Ping; Rener, Gregory A; Mattiuz, Edward L; Hadden, Chad E; Goodwin, Lawrence A; Ehlhardt, William J

2004-09-01

Phase I oxidative metabolism of nitrogen-containing drug molecules to their corresponding N-oxides is a common occurrence. There are instances where liquid chromatography/tandem mass spectometry techniques are inadequate to distinguish this pathway from other oxidation processes, including C-hydroxylations and other heteroatom oxidations, such as sulfur to sulfoxide. Therefore, the purpose of the present study was to develop and optimize an efficient and practical chemical method to selectively convert N-oxides to their corresponding amines suitable for drug metabolism applications. Our results indicated that efficient conversion of N-oxides to amines could be achieved with TiCl(3) and poly(methylhydrosiloxane). Among them, we found TiCl(3) to be a facile and easy-to-use reagent, specifically applicable to drug metabolism. There are a few reports describing the use of TiCl(3) to reduce N-O bonds in drug metabolism studies, but this methodology has not been widely used. Our results indicated that TiCl(3) is nearly as efficient when the reductions were carried out in the presence of biological matrices, including plasma and urine. Finally, we have shown a number of examples where TiCl(3) can be successfully used to selectively reduce N-oxides in the presence of sulfoxides and other labile groups.

Micelles of enzymatically synthesized PEG-poly(amine-co-ester) block copolymers as pH-responsive nanocarriers for docetaxel delivery.

PubMed

Zhang, Xiaofang; Liu, Bo; Yang, Zhe; Zhang, Chao; Li, Hao; Luo, Xingen; Luo, Huiyan; Gao, Di; Jiang, Qing; Liu, Jie; Jiang, Zhaozhong

2014-03-01

A series of PEGylated poly(amine-co-ester) terpolymers were successfully synthesized in one step via lipase-catalyzed copolymerization of ω-pentadecalactone (PDL), diethyl sebacate (DES), and N-methyldiethanolamine (MDEA) comonomers in the presence of poly(ethylene glycol) methyl ether as a chain-terminating agent. The resultant amphiphilic poly(ethylene glycol)-poly(PDL-co-MDEA-co-sebacate) (PEG-PPMS) block copolymers consisted of hydrophilic PEG chain segments and hydrophobic random PPMS chain segments, which self-assembled in aqueous medium to form stable, nanosized micelles at physiological pH of 7.4. Upon decreasing the medium pH from 7.4 to 5.0, the copolymer micelles swell significantly due to protonation of the amino groups in the micelle PPMS cores. Correspondingly, docetaxel (DTX)-encapsulated PEG2K-PPMS copolymer micelles showed gradual sustained drug release at pH of 7.4, but remarkably accelerated DTX release at acidic pH of 5.0. The drug-loaded micelle particles were readily internalized by SK-BR-3 cancer cells and, compared to free DTX drug, DTX-loaded micelles of the copolymers with optimal compositions exhibited enhanced potency against the cells. Biodegradable PEG-PPMS copolymer micelles represent a new type of promising, pH-responsive nanocarriers for anticancer drug delivery, and the drug release rate from the micelles can be systematically controlled by both pH and the copolymer composition. Copyright © 2013 Elsevier B.V. All rights reserved.

Copper-catalyzed three- five- or seven-component coupling reactions: the selective synthesis of cyanomethylamines, N,N-bis(cyanomethyl)amines and N,N'-bis(cyanomethyl)methylenediamines based on a Strecker-type synthesis.

PubMed

Sakai, Norio; Takahashi, Nobuaki; Inoda, Daiki; Ikeda, Reiko; Konakahara, Takeo

2013-10-10

We have demonstrated that a cooperative catalytic system comprised of CuCl and Cu(OTf)(2) could be used to effectively catalyse the three-, five- and seven-component coupling reactions of aliphatic or aromatic amines, formaldehyde, and trimethylsilyl cyanide (TMSCN), and selectively produce in good yields the corresponding cyanomethylamines, N,N-bis(cyanomethyl)amines and N,N'-bis(cyanomethyl)methylenediamines.

The Cu(II) affinity of the N-terminus of human copper transporter CTR1: Comparison of human and mouse sequences.

PubMed

Bossak, Karolina; Drew, Simon C; Stefaniak, Ewelina; Płonka, Dawid; Bonna, Arkadiusz; Bal, Wojciech

2018-05-01

Copper Transporter 1 (CTR1) is a homotrimeric membrane protein providing the main route of copper transport into eukaryotic cells from the extracellular milieu. Its N-terminal extracellular domain, rich in His and Met residues, is considered responsible for directing copper into the transmembrane channel. Most of vertebrate CTR1 proteins contain the His residue in position three from N-terminus, creating a well-known Amino Terminal Cu(II)- and Ni(II)-Binding (ATCUN) site. CTR1 from humans, primates and many other species contains the Met-Asp-His (MDH) sequence, while some rodents including mouse have the Met-Asn-His (MNH) N-terminal sequence. CTR1 is thought to collect Cu(II) ions from blood copper transport proteins, including albumin, but previous reports indicated that the affinity of N-terminal peptide/domain of CTR1 is significantly lower than that of albumin, casting serious doubt on this aspect of CTR1 function. Using potentiometry and spectroscopic techniques we demonstrated that MDH-amide, a tripeptide model of human CTR1 N-terminus, binds Cu(II) with K of 1.3 × 10 13  M -1 at pH 7.4, ~13 times stronger than Human Serum Albumin (HSA), and MNH-amide is even stronger, K of 3.2 × 10 14  M -1 at pH 7.4. These results indicate that the N-terminus of CTR1 may serve as intermediate binding site during Cu(II) transfer from blood copper carriers to the transporter. MDH-amide, but not MNH-amide also forms a low abundance complex with non-ATCUN coordination involving the Met amine, His imidazole and Asp carboxylate. This species might assist Cu(II) relay down the peptide chain or its reduction to Cu(I), both steps necessary for the CTR1 function. Copyright © 2018 Elsevier Inc. All rights reserved.

Experimental investigation and DFT calculation of different amine/ammonium salts adsorption on kaolinite

NASA Astrophysics Data System (ADS)

Chen, Jun; Min, Fan-fei; Liu, Lingyun; Liu, Chunfu; Lu, Fangqin

2017-10-01

The adsorption of four different amine/ammonium salts of DDA (Dodecyl amine), MDA (N-methyldodecyl amine), DMDA (N,N-dimethyldodecyl amine) and DTAC (Dodecyl trimethyl ammonium chloride) on kaolinite particles was investigated in the study through the measurement of contact angles, zeta potentials, aggregation observation, adsorption and sedimentation. The results show that different amine/ammonium salts can adsorb on the kaolinite surface to enhance the hydrophobicity and reduce the electronegativity of kaolinite particle surface, and thus induce a strong hydrophobic aggregation of kaolinite particles which promotes the settlement of kaolinite. To explore the adsorption mechanism of these four amine/ammonium salts on kaolinite surfaces, the adsorptions of DDA+, MDA+, DMDA+ and DTAC+ on kaolinite (001) surface and (00 1 bar) surface are calculated with DFT (Density functional theory). The DFT calculation results indicate that different amine/ammonium cations can strongly adsorbed on kaolinite (001) surface and (00 1 bar) surface by forming Nsbnd H⋯O strong hydrogen bonds or Csbnd H⋯O weak hydrogen bonds, and there are strongly electrostatic attractions between different amine/ammonium cations and kaolinite surfaces. The main adsorption mechanism of amine/ammonium cations on kaolinite is hydrogen-bond interaction and electrostatic attraction.

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.

Aryl triolborates: novel reagent for copper-catalyzed N arylation of amines, anilines, and imidazoles.

PubMed

Yu, Xiao-Qiang; Yamamoto, Yasunori; Miyaura, Norio

2008-09-01

The N arylation of primary and secondary aliphatic amines, anilines, and imidazoles with novel potassium aryl triolborates was carried out in the presence of a reoxidant and a catalytic amount of Cu(OAc)(2) (10 mol %). Aryl triolborates were found to be better reagents than aryl boronic acids or potassium aryl trifluoroborates as the former achieved high yields under mild conditions. Coupling of primary and secondary aliphatic amines to give N-aryl amines in excellent yields was performed under oxygen atmosphere. The reactions of anilines and imidazoles to provide N-aryl anilines and N-aryl imidazoles in good yields proceeded smoothly when trimethylamine N-oxide was used as an oxidant.

Study of Adsorption Mechanism of Congo Red on Graphene Oxide/PAMAM Nanocomposite

PubMed Central

Rafi, Mohammad; Samiey, Babak; Cheng, Chil-Hung

2018-01-01

Graphene oxide/poly(amidoamine) (GO/PAMAM) nanocomposite adsorbed high quantities of congo red (CR) anionic dye in 0.1 M NaCl solution, with the maximum adsorption capacity of 198 mg·g−1. The kinetics and thermodynamics of adsorption were investigated to elucidate the effects of pH, temperature, shaking rate, ionic strength, and contact time. Kinetic data were analyzed by the KASRA model and the KASRA, ISO, and pore-diffusion equations. Adsorption adsorption isotherms were studied by the ARIAN model and the Henry, Langmuir, and Temkin equations. It was shown that adsorption sites of GO/PAMAM at experimental conditions were phenolic hydroxyl groups of GO sheets and terminal amine groups of PAMAM dendrimer. Analysis of kinetic data indicated that amine sites were located on the surface, and that hydroxyl sites were placed in the pores of adsorbent. CR molecules interacted with the adsorption sites via hydrogen bonds. The molecules were adsorbed firstly on the amine sites, and then on the internal hydroxyl sites. Adsorption kinetic parameters indicated that the interaction of CR to the –NH3+ sites was the rate-controlling step of adsorption of CR on this site and adsorption activation energies calculated for different parts of this step. On the other hand, kinetic parameters showed that the intraparticle diffusion was the rate-controlling step during the interaction of CR molecules to –OH sites and activation energy of this step was not calculable. Finally, the used GO/PAMAM was completely regenerated by using ethylenediamine. PMID:29587463

Synthesis and biological evaluation of radio and dye labeled amino functionalized dendritic polyglycerol sulfates as multivalent anti-inflammatory compounds.

PubMed

Gröger, Dominic; Paulus, Florian; Licha, Kai; Welker, Pia; Weinhart, Marie; Holzhausen, Cornelia; Mundhenk, Lars; Gruber, Achim D; Abram, Ulrich; Haag, Rainer

2013-09-18

Herein we describe a platform technology for the synthesis and characterization of partially aminated, (35)S-labeled, dendritic polyglycerol sulfate (dPG(35)S amine) and fluorescent dPGS indocarbocyanine (ICC) dye conjugates. These polymer conjugates, based on a biocompatible dendritic polyglycerol scaffold, exhibit a high affinity to inflamed tissue in vivo and represent promising candidates for therapeutic and diagnostic applications. By utilizing a one-step sequential copolymerization approach, dendritic polyglycerol (Mn ≈ 4.5 kDa) containing 9.4% N-phthalimide protected amine functionalities was prepared on a large scale. Sulfation and simultaneous radio labeling with (35)SO3 pyridine complex, followed by cleavage of the N-phthalimide protecting groups, yielded dPG(35)S amine as a beta emitting, inflammation specific probe with free amino functionalities for conjugation. Furthermore, efficient labeling procedures with ICC via iminothiolane modification and subsequent "Michael" addition of the maleimide functionalized ICC dye, as well as by amide formation via NHS derivatized ICC on a dPGS amine scaffold, are described. The dPGS-ICC conjugates were investigated with respect to their photophysical properties, and both the radiolabeled and fluorescent compounds were comparatively visualized in histological tissue sections (radio detection and fluorescence microscopy) of animals treated with dPGS. Furthermore, cellular uptake of dPGS-ICC was found in endothelial cord blood (HUVEC) and the epithelial lung cells (A549). The presented synthetic routes allow a reproducible, controlled synthesis of dPGS amine on kilogram scale applying a one-pot batch reaction process. dPGS amine can be used for analysis via radioactivity or fluorescence, thereby creating a new platform for inflammation specific, multimodal imaging purposes using other attachable probes or contrast agents.

The fabrication of porous N-doped carbon from widely available urea formaldehyde resin for carbon dioxide adsorption.

PubMed

Liu, Zhen; Du, Zhenyu; Song, Hao; Wang, Chuangye; Subhan, Fazle; Xing, Wei; Yan, Zifeng

2014-02-15

N-doped carbon material constitutes abundant of micropores and basic nitrogen species that have potential implementation for CO2 capture. In this paper, porous carbon material with high nitrogen content was simply fabricated by carbonizing low cost and widely available urea formaldehyde resin, and then followed by KOH activation. CO2 capture experiment showed high adsorption capacity of 3.21 mmol g(-1) at 25 °C under 1 atm for UFCA-2-600. XRD, SEM, XPS and FT-IR analysis confirmed that a graphitic-like structure was retained even after high temperature carbonization and strong base activation. Textural property analysis revealed that narrow micropores, especially below 0.8 nm, were effective for CO2 adsorption by physical adsorption mechanism. Chemical evolved investigation revealed that graphitic-like embedded basic nitrogen groups are generated from bridged and terminal amines of urea formaldehyde resin from thermal carbonization and KOH activation treatment, which is responsible for the enrichment of CO2 capacity by chemical adsorption mechanism. The relationship between CO2 adsorption capacity and pore size or basic N species was also studied, which turned out that both of them played crucial role by physical and chemical adsorption mechanism, respectively. Copyright © 2013 Elsevier Inc. All rights reserved.

Influence on wine biogenic amine composition of modifications to soil N availability and grapevine N by cover crops.

PubMed

Pérez-Álvarez, Eva P; Garde-Cerdán, Teresa; Cabrita, Maria João; García-Escudero, Enrique; Peregrina, Fernando

2017-11-01

Vineyard soil management can modify the nitrogen soil availability and, therefore, grape amino acid content. These compounds are precursors of biogenic amines, which have negative effects on wine quality and human health. The objective was to study whether the effect of conventional tillage and two cover crops (barley and clover) on grapevine nitrogen status could be related to wine biogenic amines. Over 4 years, soil NO 3 - -N, nitrogen content in leaf and wine biogenic amine concentration were determined. Barley reduced soil NO 3 - -N availability and clover increased it. In 2011, at bloom, nitrogen content decreased with barley treatment in both blade and petiole. In 2012, nitrogen content in both leaf tissues at bloom was greater with clover than with tillage and barley treatments. Also, total biogenic amines decreased in barley with respect to tillage and clover treatments. There were correlations between some individual and total biogenic amine concentrations with respect to nitrogen content in leaf tissues. Wine biogenic amine concentration can be affected by the grapevine nitrogen status, provoked by changes in the soil NO 3 - -N availability with both cover crop treatments. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Identification and characterization of glycation adducts on osteocalcin

PubMed Central

Thomas, Corinne J.; Cleland, Timothy P.; Zhang, Sheng; Gundberg, Caren M.; Vashishth, Deepak

2017-01-01

Osteocalcin is an important extracellular matrix bone protein that contributes to the structural properties of bone through its interactions with hydroxyapatite mineral and with collagen I. This role may be affected by glycation, a labile modification the levels of which has been shown to correlate with bone fragility. Glycation starts with the spontaneous addition of a sugar onto a free amine group on a protein, forming an Amadori product, and then proceeds through several environment-dependent stages resulting in the formation of an advanced glycation end product. Here, we induce the first step of this modification on synthetic osteocalcin, and then use multiple mass spectrometry fragmentation techniques to determine the location of this modification. Collision-induced dissociation resulted in spectra dominated by neutral loss, and was unable to identify Amadori products. Electron-transfer dissociation showed that the Amadori product formed solely on osteocalcin’s N-terminus. This suggests that the glycation of osteocalcin is unlikely to interfere with osteocalcin’s interaction with hydroxyapatite. Instead, glycation may interfere with its interaction with collagen I or another bone protein, osteopontin. Potentially, the levels of glycated osteocalcin fragments released from bone during bone resorption could be used to assess bone quality, should the N-terminal fragments be targeted. PMID:28237256

Non-covalent and coordination interactions in Cu(II) systems with uridine, uridine 5'-monophosphate and triamine or tetramine as biogenic amine analogues in aqueous solutions.

PubMed

Łomozik, Lechosław; Jastrzab, Renata

2003-10-01

Reactions of metallation and non-covalent interactions have been studied in ternary systems of Cu(II) ions with uridine, uridine 5'-monophosphate and diamines or triamines. It has been found that in metal-free systems the reaction centres of the nucleoside with the polyamine are the donor nitrogen atoms N(3) and protonated -NH(x) groups of the amines. In comparison to systems with adenosine or cytidine, the pH range of complex formation is shifted towards higher values. It is a consequence of significantly higher basicity of uridine and in agreement with the ion-ion, ion-dipole interaction model assumed. Formation of molecular complexes of uridine 5'-monophosphate with polyamines at a low pH is the result of activity of the phosphate group which plays the role of a negatively charged reaction site. Non-covalent interactions interfere in processes of bioligand metallation. Centres of weak interactions are simultaneously binding sites of metal ions. In protonated Cu(Urd)(PA)H(x) complexes, coordination has been found to involve the N(3) atom from the nucleoside and two donor nitrogen atoms from the polyamine (PA). In the heteroligand species Cu(Urd)(PA), despite deprotonation of all amine groups, one of these groups is located outside the inner coordination sphere. In complexes with uridine-5'-monophosphate, the phosphate group is active in metallation. Moreover, in certain coordination compounds this group is engaged in non-covalent interactions with PA molecules, despite binding Cu ions, as has been shown on the basis of equilibrium and spectral studies.

Interaction between the Staphylococcus aureus extracellular adherence protein Eap and its subdomains with platelets.

PubMed

Palankar, Raghavendra; Binsker, Ulrike; Haracska, Bianca; Wesche, Jan; Greinacher, Andreas; Hammerschmidt, Sven

2018-04-18

S. aureus associated bacteremia can lead to severe infections with high risk of mortality (e.g. sepsis, infective endocarditis). Many virulence factors and adhesins of S. aureus are known to directly interact with platelets. Extracellular adherence protein, Eap, one of the most important virulence factors in S. aureus mediated infections is a multi-tandem domain protein and has been shown to interact with almost all cell types in the human circulatory system. By using amine reactive fluorescent N-hydroxysuccinimidyl (NHS)-ester dyes and by direct detection with primary fluorescently conjugated anti-histidine (His-tag) antibodies against detect N-terminal His6, we show Eap subdomain Eap D 3 D 4 specifically interacts and rapidly activates human platelets. Furthermore, we validate our finding by using site directed directional immobilization of Eap D 3 D 4 through N-terminal His 6 on nickel (II)-nitrilotriacetic acid (Ni-NTA) functionalized bacteriomimetic microbead arrays to visualize real-time platelet activation through calcium release assay. These methods offer an easily adoptable protocols for screening of S.aureus derived virulence factors and adhesins with platelets. Copyright © 2018 Elsevier GmbH. All rights reserved.

Bulk gold catalyzed oxidation reactions of amines and isocyanides and iron porphyrin catalyzed N-H and O-H bond insertion/cyclization reactions of diamines and aminoalcohols

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

Klobukowski, Erik

2011-01-01

This work involves two projects. The first project entails the study of bulk gold as a catalyst in oxidation reactions of isocyanides and amines. The main goal of this project was to study the activation and reactions of molecules at metal surfaces in order to assess how organometallic principles for homogeneous processes apply to heterogeneous catalysis. Since previous work had used oxygen as an oxidant in bulk gold catalyzed reactions, the generality of gold catalysis with other oxidants was examined. Amine N-oxides were chosen for study, due to their properties and use in the oxidation of carbonyl ligands in organometallicmore » complexes. When amine N-oxides were used as an oxidant in the reaction of isocyanides with amines, the system was able to produce ureas from a variety of isocyanides, amines, and amine N-oxides. In addition, the rate was found to generally increase as the amine N-oxide concentration increased, and decrease with increased concentrations of the amine. Mechanistic studies revealed that the reaction likely involves transfer of an oxygen atom from the amine N-oxide to the adsorbed isocyanide to generate an isocyanate intermediate. Subsequent nucleophilic attack by the amine yields the urea. This is in contrast to the bulk gold-catalyzed reaction mechanism of isocyanides with amines and oxygen. Formation of urea in this case was proposed to proceed through a diaminocarbene intermediate. Moreover, formation of the proposed isocyanate intermediate is consistent with the reactions of metal carbonyl ligands, which are isoelectronic to isocyanides. Nucleophilic attack at coordinated CO by amine N-oxides produces CO{sub 2} and is analogous to the production of an isocyanate in this gold system. When the bulk gold-catalyzed oxidative dehydrogenation of amines was examined with amine N-oxides, the same products were afforded as when O{sub 2} was used as the oxidant. When the two types of oxidants were directly compared using the same reaction system and conditions, it was found that the oxidative dehydrogenation of dibenzylamine to Nbenzylidenebenzylamine, with N-methylmorpholine N-oxide (NMMO), was nearly quantitative (96%) within 24 h. However, the reaction with oxygen was much slower, with only a 52% yield of imine product over the same time period. Moreover, the rate of reaction was found to be influenced by the nature of the amine N-oxide. For example, the use of the weakly basic pyridine N-oxide (PyNO) led to an imine yield of only 6% after 24 h. A comparison of amine N-oxide and O2 was also examined in the oxidation of PhCH{sub 2}OH to PhCHO catalyzed by bulk gold. In this reaction, a 52% yield of the aldehyde was achieved when NMMO was used, while only a 7% product yield was afforded when O{sub 2} was the oxidant after 48 h. The bulk gold-catalyzed oxidative dehydrogenation of cyclic amines generates amidines, which upon treatment with Aerosil and water were found to undergo hydrolysis to produce lactams. Moreover, 5-, 6-, and 7-membered lactams could be prepared through a one-pot reaction of cyclic amines by treatment with oxygen, water, bulk gold, and Aerosil. This method is much more atom economical than industrial processes, does not require corrosive acids, and does not generate undesired byproducts. Additionally, the gold and Aerosil catalysts can be readily separated from the reaction mixture. The second project involved studying iron(III) tetraphenylporphyrin chloride, Fe(TPP)Cl, as a homogeneous catalyst for the generation of carbenes from diazo reagents and their reaction with heteroatom compounds. Fe(TPP)Cl, efficiently catalyzed the insertion of carbenes derived from methyl 2-phenyldiazoacetates into O-H bonds of aliphatic and aromatic alcohols. Fe(TPP)Cl was also found to be an effective catalyst for tandem N-H and O-H insertion/cyclization reactions when 1,2-diamines and 1,2-alcoholamines were treated with diazo reagents. This approach provides a one-pot process for synthesizing piperazinones and morpholinones and related analogues such as quinoxalinones and benzoxazin-2-ones.« less

The C- and N-Terminal Residues of Synthetic Heptapeptide Ion Channels Influence Transport Efficacy Through Phospholipid Bilayers

PubMed Central

Djedovič, Natasha; Ferdani, Riccardo; Harder, Egan; Pajewska, Jolanta; Pajewski, Robert; Weber, Michelle E.; Schlesinger, Paul H.; Gokel, George W.

2008-01-01

The synthetic peptide, R2N-COCH2OCH2CO-Gly-Gly-Gly-Pro-Gly-Gly-Gly-OR’, was shown to be selective for Cl- over K+ when R is n-octadecyl and R’ is benzyl. Nineteen heptapeptides have now been prepared in which the N-terminal and C-terminal residues have been varied. All of the N-terminal residues are dialkyl but the C-terminal chains are esters, 2° amides, or 3° amides. The compounds having varied N-terminal anchors and C-terminal benzyl groups are as follows: 1, R = n-propyl; 2, R = n-hexyl; 3, R = n-octyl; 4, R = n-decyl; 5, R = n-dodecyl; 6, R = n-tetradecyl; 7, R = n-hexadecyl; 8, R = n-octadecyl. Compounds 9-19 have R = n-octadecyl and C-terminal residues as follows: 9, OR’ = OCH2CH3; 10, OR’ = OCH(CH3)2; 11, OR’ = O(CH2)6CH3; 12, OR’ = OCH2-c-C6H11; 13, OR’ = O(CH2)9CH3; 14, OR’ = O (CH2)17CH3; 15, NR’2 = N[(CH2)6CH3]2; 16, NHR’ = NH(CH2)9CH3; 17, NR’2 = N[(CH2)9CH3]2; 18, NHR’ = NH(CH2)17CH3; 19, NR’2 = N[(CH2)17CH3]2. The highest anion transport activities were observed as follows. For the benzyl esters whose N-terminal residues were varied, i.e. 1-8, compound 3 was most active. For the C18 anchored esters 10-14, n-heptyl ester 11 was most active. For the C18 anchored, C-terminal amides 15-19, di-n-decylamide 17 was most active. It was concluded that both the C- and N-terminal anchors were important for channel function in the bilayer but that activity was lost unless only one of the two anchoring groups was dominant. PMID:19633728

Concentration Dependent Speciation and Mass Transport Properties of Switchable Polarity Solvents

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

Aaron D. Wilson; Christopher J. Orme

2014-12-01

Tertiary amine switchable polarity solvents (SPS) consisting of predominantly water, tertiary amine, and tertiary ammonium and bicarbonate ions were produced at various concentrations for three different amines: N,N-dimethylcyclohexylamine, N,N-dimethyloctylamine, and 1 cyclohexylpiperidine. For all concentrations, physical properties were measured including viscosity, molecular diffusion coefficients, freezing point depression, and density. Based on these measurements a variation on the Mark Houwink equation was developed to predict the viscosity of any tertiary amine SPS as a function of concentration using the amine’s molecular mass. The observed physical properties allowed the identification of solution state speciation of non-osmotic SPS, where the amine to carbonicmore » acid ratio is significantly greater than one. These results indicate that at most concentrations the stoichiometric excess amine is involved in solvating a proton with two amines. The physical properties of osmotic SPS have consistent concentration dependence behavior over a wide range of concentrations; this consistence suggests osmotic pressures based on low concentrations freezing point studies can be reliably extrapolated to higher concentrations.« less

Hollow Cathode Plasma-Enhanced Atomic Layer Deposition of Silicon Nitride Using Pentachlorodisilane.

PubMed

Meng, Xin; Kim, Harrison Sejoon; Lucero, Antonio T; Hwang, Su Min; Lee, Joy S; Byun, Young-Chul; Kim, Jiyoung; Hwang, Byung Keun; Zhou, Xiaobing; Young, Jeanette; Telgenhoff, Michael

2018-04-25

In this work, a novel chlorodisilane precursor, pentachlorodisilane (PCDS, HSi 2 Cl 5 ), was investigated for the growth of silicon nitride (SiN x ) via hollow cathode plasma-enhanced atomic layer deposition (PEALD). A well-defined self-limiting growth behavior was successfully demonstrated over the growth temperature range of 270-360 °C. At identical process conditions, PCDS not only demonstrated approximately >20% higher growth per cycle than that of a commercially available chlorodisilane precursor, hexachlorodisilane (Si 2 Cl 6 ), but also delivered a better or at least comparable film quality determined by characterizing the refractive index, wet etch rate, and density of the films. The composition of the SiN x films grown at 360 °C using PCDS, as determined by X-ray photoelectron spectroscopy, showed low O content (∼2 at. %) and Cl content (<1 at. %; below the detection limit). Fourier transform infrared spectroscopy spectra suggested that N-H bonds were the dominant hydrogen-containing bonds in the SiN x films without a significant amount of Si-H bonds originating from the precursor molecules. The possible surface reaction pathways of the PEALD SiN x using PCDS on the surface terminated with amine groups (-NH 2 and -NH-) are proposed. The PEALD SiN x films grown using PCDS also exhibited a leakage current density as low as 1-2 nA/cm 2 at 2 MV/cm and a breakdown electric field as high as ∼12 MV/cm.

Dual C-H functionalization of N-aryl amines: synthesis of polycyclic amines via an oxidative Povarov approach.

PubMed

Min, Chang; Sanchawala, Abbas; Seidel, Daniel

2014-05-16

Iminium ions generated in situ via copper(I) bromide catalyzed oxidation of N-aryl amines readily undergo [4 + 2] cycloadditions with a range of dienophiles. This method involves the functionalization of both a C(sp(3))-H and a C(sp(2))-H bond and enables the rapid construction of polycyclic amines under relatively mild conditions.

Design, synthesis and in vitro kinetic study of tranexamic acid prodrugs for the treatment of bleeding conditions

NASA Astrophysics Data System (ADS)

Karaman, Rafik; Ghareeb, Hiba; Dajani, Khuloud Kamal; Scrano, Laura; Hallak, Hussein; Abu-Lafi, Saleh; Mecca, Gennaro; Bufo, Sabino A.

2013-07-01

Based on density functional theory (DFT) calculations for the acid-catalyzed hydrolysis of several maleamic acid amide derivatives four tranexamic acid prodrugs were designed. The DFT results on the acid catalyzed hydrolysis revealed that the reaction rate-limiting step is determined on the nature of the amine leaving group. When the amine leaving group was a primary amine or tranexamic acid moiety, the tetrahedral intermediate collapse was the rate-limiting step, whereas in the cases by which the amine leaving group was aciclovir or cefuroxime the rate-limiting step was the tetrahedral intermediate formation. The linear correlation between the calculated DFT and experimental rates for N-methylmaleamic acids 1- 7 provided a credible basis for designing tranexamic acid prodrugs that have the potential to release the parent drug in a sustained release fashion. For example, based on the calculated B3LYP/6-31G(d,p) rates the predicted t1/2 (a time needed for 50 % of the prodrug to be converted into drug) values for tranexamic acid prodrugs ProD 1- ProD 4 at pH 2 were 556 h [50.5 h as calculated by B3LYP/311+G(d,p)] and 6.2 h as calculated by GGA: MPW1K), 253 h, 70 s and 1.7 h, respectively. Kinetic study on the interconversion of the newly synthesized tranexamic acid prodrug ProD 1 revealed that the t1/2 for its conversion to the parent drug was largely affected by the pH of the medium. The experimental t1/2 values in 1 N HCl, buffer pH 2 and buffer pH 5 were 54 min, 23.9 and 270 h, respectively.

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

Application of ultraviolet, ozone, and advanced oxidation treatments to washwaters to destroy nitrosamines, nitramines, amines, and aldehydes formed during amine-based carbon capture.

PubMed

Shah, Amisha D; Dai, Ning; Mitch, William A

2013-03-19

Although amine-based CO(2) absorption is a leading contender for full-scale postcombustion CO(2) capture at power plants, concerns have been raised about the potential release of carcinogenic N-nitrosamines and N-nitramines formed by reaction of exhaust gas NO(x) with the amines. Experiments with a laboratory-scale pilot unit suggested that washwater units meant to scrub contaminants from absorber unit exhaust could potentially serve as a source of N-nitrosamines via reactions of residual NO(x) with amines accumulating in the washwater. Dosage requirements for the continuous treatment of the washwater recycle line with ultraviolet (UV) light for destruction of N-nitrosamines and N-nitramines, and with ozone or hydroxyl radical-based advanced oxidation processes (AOPs) for destruction of amines and aldehydes, were evaluated. Although <1000 mJ/cm(2) UV fluence was generally needed for 90% removal of a series of model N-nitrosamines and N-nitramines, 280-1000 mJ/cm(2) average fluence was needed for 90% removal of total N-nitrosamines in pilot washwaters associated with two different solvents. While AOPs were somewhat more efficient than ozone for acetaldehyde destruction, ozone was more efficient for amine destruction. Ozone achieved 90% amine removal in washwaters at 5-12 molar excess of ozone, indicating transferred dosage levels of ∼100 mg/L for 90% removal in a first-stage washwater unit, but likely only ∼10 mg/L if applied to a second-stage washwater. Accurate dosage and cost estimates would require pilot testing to capture synergies between UV and ozone treatments.

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.

Silane surface modification for improved bioadhesion of esophageal stents

NASA Astrophysics Data System (ADS)

Karakoy, Mert; Gultepe, Evin; Pandey, Shivendra; Khashab, Mouen A.; Gracias, David H.

2014-08-01

Stent migration occurs in 10-40% of patients who undergo placement of esophageal stents, with higher migration rates seen in those treated for benign esophageal disorders. This remains a major drawback of esophageal stent therapy. In this paper, we propose a new surface modification method to increase the adhesion between self-expandable metallic stents (SEMS) and tissue while preserving their removability. Taking advantage of the well-known affinity between epoxide and amine terminated silane coupling agents with amine and carboxyl groups that are abundant in proteins and related molecules in the human body; we modified the surfaces of silicone coated esophageal SEMS with these adhesive self-assembled monolayers (SAMs). We utilized vapor phase silanization to modify the surfaces of different substrates including PDMS strips and SEMS, and measured the force required to slide these substrates on a tissue piece. Our results suggest that surface modification of esophageal SEMS via covalent attachment of protein-binding coupling agents improves adhesion to tissue and could offer a solution to reduce SEMS migration while preserving their removability.

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

DNA sequencing using fluorescence background electroblotting membrane

DOEpatents

Caldwell, Karin D.; Chu, Tun-Jen; Pitt, William G.

1992-01-01

A method for the multiplex sequencing on DNA is disclosed which comprises the electroblotting or specific base terminated DNA fragments, which have been resolved by gel electrophoresis, onto the surface of a neutral non-aromatic polymeric microporous membrane exhibiting low background fluorescence which has been surface modified to contain amino groups. Polypropylene membranes are preferably and the introduction of amino groups is accomplished by subjecting the membrane to radio or microwave frequency plasma discharge in the presence of an aminating agent, preferably ammonia. The membrane, containing physically adsorbed DNA fragments on its surface after the electroblotting, is then treated with crosslinking means such as UV radiation or a glutaraldehyde spray to chemically bind the DNA fragments to the membrane through said smino groups contained on the surface thereof. The DNA fragments chemically bound to the membrane are subjected to hybridization probing with a tagged probe specific to the sequence of the DNA fragments. The tagging may be by either fluorophores or radioisotopes. The tagged probes hybridized to said target DNA fragments are detected and read by laser induced fluorescence detection or autoradiograms. The use of aminated low fluorescent background membranes allows the use of fluorescent detection and reading even when the available amount of DNA to be sequenced is small. The DNA bound to the membrances may be reprobed numerous times.

DNA sequencing using fluorescence background electroblotting membrane

DOEpatents

Caldwell, K.D.; Chu, T.J.; Pitt, W.G.

1992-05-12

A method for the multiplex sequencing on DNA is disclosed which comprises the electroblotting or specific base terminated DNA fragments, which have been resolved by gel electrophoresis, onto the surface of a neutral non-aromatic polymeric microporous membrane exhibiting low background fluorescence which has been surface modified to contain amino groups. Polypropylene membranes are preferably and the introduction of amino groups is accomplished by subjecting the membrane to radio or microwave frequency plasma discharge in the presence of an aminating agent, preferably ammonia. The membrane, containing physically adsorbed DNA fragments on its surface after the electroblotting, is then treated with crosslinking means such as UV radiation or a glutaraldehyde spray to chemically bind the DNA fragments to the membrane through amino groups contained on the surface. The DNA fragments chemically bound to the membrane are subjected to hybridization probing with a tagged probe specific to the sequence of the DNA fragments. The tagging may be by either fluorophores or radioisotopes. The tagged probes hybridized to the target DNA fragments are detected and read by laser induced fluorescence detection or autoradiograms. The use of aminated low fluorescent background membranes allows the use of fluorescent detection and reading even when the available amount of DNA to be sequenced is small. The DNA bound to the membranes may be reprobed numerous times. No Drawings

The biosynthesis of nitrogen-, sulfur-, and high-carbon chain-containing sugars.

PubMed

Lin, Chia-I; McCarty, Reid M; Liu, Hung-wen

2013-05-21

Carbohydrates serve many structural and functional roles in biology. While the majority of monosaccharides are characterized by the chemical composition (CH2O)n, modifications including deoxygenation, C-alkylation, amination, O- and N-methylation, which are characteristic of many sugar appendages of secondary metabolites, are not uncommon. Interestingly, some sugar molecules are formed via modifications including amine oxidation, sulfur incorporation, and "high-carbon" chain attachment. Most of these unusual sugars have been identified over the past several decades as components of microbially produced natural products, although a few high-carbon sugars are also found in the lipooligosaccharides of the outer cell walls of Gram-negative bacteria. Despite their broad distribution in nature, these sugars are considered "rare" due to their relative scarcity. The biosynthetic steps that underlie their formation continue to perplex researchers to this day and many questions regarding key transformations remain unanswered. This review will focus on our current understanding of the biosynthesis of unusual sugars bearing oxidized amine substituents, thio-functional groups, and high-carbon chains.

Carbon Dioxide Absorbents

DTIC Science & Technology

1950-05-17

boiling points should be investigated to dotermine the effect of certain structures on the behavior of amines. Only amines which are commercially...ALKANOL ALIPHATIC AMINIES (Contd.) Alkanol Tertiary Amines 141 2-Dinaethylethanolamine (CH3 )2N02 1401 142 2- Diethylethanolamine (02115) 2N0C2 40 143... Diethylethanolamine (C2115)2NC2 1401 143 Triethanolamine (C211401),3N- 144 Ethyl Diethanolamine C2H5N(C2 1401)2 145 Methyl Diethanolamine CH3N(C H401)9

Preparation of silica coated cobalt ferrite magnetic nanoparticles for the purification of histidine-tagged proteins

NASA Astrophysics Data System (ADS)

Aygar, Gülfem; Kaya, Murat; Özkan, Necati; Kocabıyık, Semra; Volkan, Mürvet

2015-12-01

Surface modified cobalt ferrite (CoFe2O4) nanoparticles containing Ni-NTA affinity group were synthesized and used for the separation of histidine tag proteins from the complex matrices through the use of imidazole side chains of histidine molecules. Firstly, CoFe2O4 nanoparticles with a narrow size distribution were prepared in an aqueous solution using the controlled co-precipitation method. In order to obtain small CoFe2O4 agglomerates, oleic acid and sodium chloride were used as dispersants. The CoFe2O4 particles were coated with silica and subsequently the surface of these silica coated particles (SiO2-CoFe2O4) was modified by amine (NH2) groups in order to add further functional groups on the silica shell. Then, carboxyl (-COOH) functional groups were added to the SiO2-CoFe2O4 magnetic nanoparticles through the NH2 groups. After that Nα,Nα-Bis(carboxymethyl)-L-lysine hydrate (NTA) was attached to carboxyl ends of the structure. Finally, the surface modified nanoparticles were labeled with nickel (Ni) (II) ions. Furthermore, the modified SiO2-CoFe2O4 magnetic nanoparticles were utilized as a new system that allows purification of the N-terminal His-tagged recombinant small heat shock protein, Tpv-sHSP 14.3.

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.

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.

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.

The rate of charge tunneling is insensitive to polar terminal groups in self-assembled monolayers in Ag(TS)S(CH2)(n)M(CH2)(m)T//Ga2O3/EGaIn junctions.

PubMed

Yoon, Hyo Jae; Bowers, Carleen M; Baghbanzadeh, Mostafa; Whitesides, George M

2014-01-08

This paper describes a physical-organic study of the effect of uncharged, polar, functional groups on the rate of charge transport by tunneling across self-assembled monolayer (SAM)-based large-area junctions of the form Ag(TS)S(CH2)(n)M(CH2)(m)T//Ga2O3/EGaIn. Here Ag(TS) is a template-stripped silver substrate, -M- and -T are "middle" and "terminal" functional groups, and EGaIn is eutectic gallium-indium alloy. Twelve uncharged polar groups (-T = CN, CO2CH3, CF3, OCH3, N(CH3)2, CON(CH3)2, SCH3, SO2CH3, Br, P(O)(OEt)2, NHCOCH3, OSi(OCH3)3), having permanent dipole moments in the range 0.5 < μ < 4.5, were incorporated into the SAM. A comparison of the electrical characteristics of these junctions with those of junctions formed from n-alkanethiolates led to the conclusion that the rates of charge tunneling are insensitive to the replacement of terminal alkyl groups with the terminal polar groups in this set. The current densities measured in this work suggest that the tunneling decay parameter and injection current for SAMs terminated in nonpolar n-alkyl groups, and polar groups selected from common polar organic groups, are statistically indistinguishable.

Polypeptide Grafted Hyaluronan: Synthesis and Characterization

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

Wang, Xiaojun; Messman, Jamie M; Mays, Jimmy

2010-01-01

Poly(L-leucine) grafted hyaluronan (HA-g-PLeu) has been synthesized via a Michael addition reaction between primary amine terminated poly(L-leucine) and acrylate-functionalized HA (TBAHA-acrylate). The precursor hyaluronan was first functionalized with acrylate groups by reaction with acryloyl chloride in the presence of triethylamine in N,N-dimethylformamide. 1H NMR analysis of the resulting product indicated that an increase in the concentration of acryloylchoride with respect to hydroxyl groups on HA has only a moderate effect on functionalization efficiency, f. A precise control of stoichiometry was not achieved, which could be attributed to partial solubility of intermolecular aggregates and the hygroscopic nature of HA. Michael additionmore » at high [PLeu- NH2]/[acrylate]TBAHA ratios gave a molar grafting ratio of only 0.20 with respect to the repeat unit of HA, indicating grafting limitation due to insolubility of the grafted HA-g-PLeu. Soluble HA-g-PLeu graft copolymers were obtained for low grafting ratios (<0.039) with <8.6% by mass of PLeu and were characterized thoroughly using light scattering, 1H NMR, FT-IR, and AFM techniques. Light scattering experiments showed a strong hydrophobic interaction between PLeu chains, resulting in aggregates with segregated nongrafted HA segments. This yields local networks of aggregates, as demonstrated by atomic force microscopy. Circular dichroism spectroscopy showed a -sheet conformation for aggregates of poly(L-leucine).« less

Constructing polyamidoamine dendrons from poly(poly(ethylene glycol) monomethacrylate) brushes grafted from planar silicon hydride surfaces for biomedical applications

NASA Astrophysics Data System (ADS)

Liu, Xiang; Zheng, Hong-Ning; Yan, Qin; Wang, Cuie; Ma, Yin-Zhou; Tang, Yan-Chun; Xiao, Shou-Jun

2011-06-01

A facile approach was established to construct polyamidoamine (PAMAM) dendrons from polymer brushes of poly(poly(ethylene glycol) monomethacrylate) (Si-g-P(PEGMA-OH)) grafted from a planar silicon hydride surface. First the Si-g-P(PEGMA-OH) brushes were grown via surface-initiated atom transfer radical polymerization with robust Si-C links on silicon surfaces. The side-chain hydroxyl groups of Si-g-P(PEGMA-OH) were chlorinated with thionyl chloride and further chlorines were substituted with amino groups of ethylenediamine, giving terminal primary amines. Borrowing the solution synthesis approach, we constructed second and third generations of PAMAM dendrons on-chip by surface-initiated alternative growth of two monomers, methyl acrylate and ethylenediamine. Two applications of silicon-based PAMAM dendrons were shown: the dense amino groups were activated via a cross-linker, N-succinimidyl-6-maleimidylhexanoate, to capture a free-thiol-carrying peptide of oxytocin and the third generation of PAMAM dendrons was used as a platform to on-chip synthesize a three amino acid peptide of Arg-Gly-Asp (RGD). The above conclusions were mainly derived from a home-built multiple transmission-reflection infrared spectroscopy, and complemented by X-ray photoelectron spectroscopy, UV-Vis spectroscopy and matrix-assisted laser desorption/ionization-time of flight-mass spectrometry.

Cu(I)-catalyzed transannulation of N-heteroaryl aldehydes or ketones with alkylamines via C(sp3)-H amination.

PubMed

Li, Mingyang; Xie, Ying; Ye, Yong; Zou, Yong; Jiang, Huanfeng; Zeng, Wei

2014-12-05

A copper(I)-catalyzed direct transannulation of N-heteroaryl aldehydes or ketones with alkylamines via Csp(3)-H amination has been achieved using molecular oxygen as a sole oxidant. N-Heteroarenes are employed as the amine source. This transformation provides a rapid and concise access to multifunctional imidazo[1,5-a]pyridines.

Poly(amido)amine (PAMAM) dendrimer-cisplatin complexes for chemotherapy of cisplatin-resistant ovarian cancer cells

NASA Astrophysics Data System (ADS)

Yellepeddi, Venkata Kashyap; Vangara, Kiran Kumar; Palakurthi, Srinath

2013-09-01

Dendrimer-cisplatin complexes were prepared using PAMAM dendrimers with terminal -NH2 and -COOH groups as well as biotin-conjugated dendrimers. Preformulation parameters of dendrimer-cisplatin complexes were studied using differential scanning calorimetry (DSC) and inductively coupled plasma-mass spectrometry (ICP-MS). Cytotoxicity and mechanism of cytotoxicity of dendrimer-cisplatin complexes was investigated in OVCAR-3, SKOV, A2780 and cisplatin-resistant CP70 human ovarian cancer cell lines. The loading of cisplatin in dendrimers was 11 % (w/w). PAMAM G4 dendrimers with amine surface groups (biotinylated and native) have shown 2.5- to 3.0-fold reduction in IC50 values in ovarian cancer cells when compared with carboxylate surface dendrimers ( p < 0.05). A correlation was observed among cytotoxicity of the complexes, cellular uptake, and platinum-DNA adduct formation. Treatment with dendrimer-cisplatin complexes resulted in a 7.0-fold increase ( p < 0.05) in expression of apoptotic genes ( Bcl2, Bax, p53) and 13.2- to 27.1-fold increase ( p < 0.05) in the activity of caspases 3, 8, and 9 in vitro. Results suggest that PAMAM dendrimers can be used as potential carrier for cisplatin chemotherapy of ovarian cancer.

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

Determination of Aromatic Amines Using Solid-Phase Microextraction Based on an Ionic Liquid-Mediated Sol–Gel Technique

PubMed Central

Abbasi, Vajihe; Sarafraz-Yazdi, Ali; Amiri, Amirhassan; Vatani, Hossein

2016-01-01

A headspace solid-phase microextraction (HS-SPME) method was developed for isolation of monocyclic aromatic amines from water samples followed by gas chromatography–flame ionization detector (GC–FID). In this work, the effect of the presence of ionic liquid (namely, 1-hexyl-3-methyl-imidazolium hexafluorophosphate [C6MIM][PF6]) was investigated in the sol–gel coating solutions on the morphology and extraction behavior of the resulting hybrid organic–inorganic sol–gel sorbents utilized in SPME. Hydroxy-terminated poly(dimethylsiloxane) (PDMS) was used as the sol–gel active organic component for sol–gel hybrid coatings. Two different coated fibers that were prepared are PDMS and PDMS-IL ([C6MIM][PF6]) fibers. Under the optimal conditions, the method detection limits (S/N = 3) with PDMS-IL were in the range of 0.001–0.1 ng/mL and the limits of quantification (S/N = 10) between 0.005 and 0.5 ng/mL. The relative standard deviations for one fiber (n = 5) were obtained from 3.1 up to 8.5% and between fibers or batch to batch (n = 3) in the range of 5.3–10.1%. The developed method was successfully applied to real water and juice fruits samples while the relative recovery percentages obtained for the spiked water samples at 0.1 ng/mL were from 83.3 to 95.0%. PMID:26759488

Stabilization of polyaniline solutions through additives

DOEpatents

Wrobleski, D.A.; Benicewicz, B.C.

1996-12-10

A stabilized non-conductive polyaniline solution comprising from about 1 to about 10 percent by weight polyaniline or a polyaniline derivative, from about 90 to about 99 percent by weight N-methylpyrrolidone, and from about 0.5 percent by weight to about 15 percent by weight of a solution stabilizing additive selected from the group consisting of hindered amine light stabilizers, polymeric amines, and dialkylamines, percent by weight of additive based on the total weight of polyaniline or polyaniline derivative is provided together with a method for stabilizing a polyaniline solution. 4 figs.

Stabilization of polyaniline solutions through additives

DOEpatents

Wrobleski, Debra A.; Benicewicz, Brian C.

1996-01-01

A stabilized non-conductive polyaniline solution comprising from about 1 to bout 10 percent by weight polyaniline or a polyaniline derivative, from about 90 to about 99 percent by weight N-methylpyrrolidone, and from about 0.5 percent by weight to about 15 percent by weight of a solution stabilizing additive selected from the group consisting of hindered amine light stabilizers, polymeric amines, and dialkylamines, percent by weight of additive based on the total weight of polyaniline or polyaniline derivative is provided together with a method for stabilizing a polyaniline solution.

Preparation and Characterization of Fluorescent Derivatives of Lysozyme

NASA Technical Reports Server (NTRS)

Smith, Lori; Pusey, Marc

1998-01-01

Fluorescence is one of the most versatile and powerful tools for the study of macromolecules. However, its use in macromolecular crystal growth studies is hampered by the necessity of preparing fluorescent derivatives where the probe does not markedly affect the crystal packing. Alternatively, one can prepare derivatives of limited utility if it is known that they will not affect the specific goals of a given study. We have prepared a number of fluorescent derivatives of chicken egg white lysozyme, covalently attaching fluorescent probes to two different sites on the protein molecule. The first site is the side chain carboxyl group of ASP 101. Amine containing probes such as lucifer yellow, cascade blue, and 5- (2-aminoethyl) aminonapthalene-l-sulfonic acid (EDANS) have been attached using a carbodiimide coupling procedure. ASP 101 lies within the active site cleft, and it is believed that the probes are "buried" within that cleft. This is supported by the fact that all such derivatives have been found to crystallize, with the crystals being fluorescent. Tetragonal crystals of the lucifer yellow derivative have been found to diffract to at least 1.9 A resolution. X-ray diffraction data has been acquired and we are now working on the structure of this derivative. The second group of derivatives is to the N-terminal amine group. The derivatization reaction is performed by using a succinimidyl ester of the probe to be attached. Fluorescent probes such as pyrene acetic acid, 5-carboxyfluorescein, and Oregon green have been attached to this site. We have had little success in crystallizing these derivatives, probably because this site is part of the contact region between the 43 helix chains. However, these sites do not interfere with formation of the 43 helices and the derivatives are suitable for study of their formation in solution. The derivatives are being characterized by steady state and lifetime fluorescence methods, and the presentation will discuss these results.

Geometric isomerism in pentacoordinate Cu2+ complexes: equilibrium, kinetic, and density functional theory studies reveal the existence of equilibrium between square pyramidal and trigonal bipyramidal forms for a tren-derived ligand.

PubMed

Algarra, Andrés G; Basallote, Manuel G; Castillo, Carmen E; Clares, M Paz; Ferrer, Armando; García-España, Enrique; Llinares, José M; Máñez, M Angeles; Soriano, Conxa

2009-02-02

A ligand (L1) (bis(aminoethyl)[2-(4-quinolylmethyl)aminoethyl]amine) containing a 4-quinolylmethyl group attached to one of the terminal amino groups of tris(2-aminoethyl)amine (tren) has been prepared, and its protonation constants and stability constants for the formation of Cu(2+) complexes have been determined. Kinetic studies on the formation of Cu(2+) complexes in slightly acidic solutions and on the acid-promoted complex decomposition strongly suggest that the Cu(2+)-L1 complex exists in solution as a mixture of two species, one of them showing a trigonal bipyramidal (tbp) coordination environment with an absorption maximum at 890 nm in the electronic spectrum, and the other one being square pyramidal (sp) with a maximum at 660 nm. In acidic solution only a species with tbp geometry is formed, whereas in neutral and basic solutions a mixture of species with tbp and sp geometries is formed. The results of density functional theory (DFT) calculations indicate that these results can be rationalized by invoking the existence of an equilibrium of hydrolysis of the Cu-N bond with the amino group supporting the quinoline ring so that CuL1(2+) would be actually a mixture of tbp [CuL1(H(2)O)](2+) and sp [CuL1(H(2)O)(2)](2+). As there are many Cu(2+)-polyamine complexes with electronic spectra that show two overlapping bands at wavelengths close to those observed for the Cu(2+)-L1 complex, the existence of this kind of equilibrium between species with two different geometries can be quite common in the chemistry of these compounds. A correlation found between the position of the absorption maximum and the tau parameter measuring the distortion from the idealized tbp and sp geometries can be used to estimate the actual geometry in solution of this kind of complex.

Amine templating effect absent in uranyl sulfates synthesized with 1,4-n-butyldiamine

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

Jouffret, Laurent J., E-mail: ljouffret@nd.edu; Wylie, Ernest M.; Burns, Peter C.

2013-01-15

Two new uranyl sulfates, (C{sub 4}H{sub 14}N{sub 2})[(UO{sub 2}){sub 2}(SO{sub 4}){sub 3}(H{sub 2}O)]{center_dot}2H{sub 2}O (NDUS2) and (C{sub 4}H{sub 14}N{sub 2})[(UO{sub 2})(SO{sub 4}){sub 2}(H{sub 2}O)]{center_dot}2H{sub 2}O (NDUS3), were synthesized and their crystal structures determined. NDUS2 was obtained in highly acidic media heat-treated at 373 K and subsequently maintained at 278 K until crystals formed after two months. NDUS3 results from the degradation of NDUS2 over the course of a few days. NDUS2 and NDUS3 crystallize in the monoclinic space group P2{sub 1}/n, a=10.9075(4) A, b=10.4513(4) A, c=17.7881(7) A, {beta}=97.908(2) Degree-Sign , V=2008.52(13) A{sup 3}, Z=4, at 140 K and a=8.8570(4) A,more » b=7.3299(3) A, c=20.4260(9) A, {beta}=95.140(2) Degree-Sign , V=1320.74(10) A{sup 3}, Z=4, at 140 K, respectively. The compounds contain interlayer 1,4-n-butyldiammonium cations that charge-balance the anionic structural units. - Graphical abstract: Amine templating effect absent in uranyl sulfates synthesized with 1,4-diaminobutane, as shown by the synthesis of two new uranyl sulfates, (C{sub 4}H{sub 14}N{sub 2})[(UO{sub 2}){sub 2}(SO{sub 4}){sub 3}(H{sub 2}O)]{center_dot}2H{sub 2}O (NDUS2) and (C{sub 4}H{sub 14}N{sub 2})[(UO{sub 2})(SO{sub 4}){sub 2}(H{sub 2}O)]{center_dot}2H{sub 2}O (NDUS3). Highlights: Black-Right-Pointing-Pointer Two layered uranyl sulfates were synthesized. Black-Right-Pointing-Pointer Amine molecules are located in the interlayers of the compounds. Black-Right-Pointing-Pointer No templating effect of the amine was observed. Black-Right-Pointing-Pointer Amine molecules are only charge balancing cations in the structures.« less

Cationic PAMAM Dendrimers Aggressively Initiate Blood Clot Formation

PubMed Central

Jones, Clinton F.; Campbell, Robert A.; Brooks, Amanda E.; Assemi, Shoeleh; Tadjiki, Soheyl; Thiagarajan, Giridhar; Mulcock, Cheyanne; Weyrich, Andrew S.; Brooks, Benjamin D.; Ghandehari, Hamidreza; Grainger, David W.

2012-01-01

Poly(amidoamine) (PAMAM) dendrimers are increasingly studied as model nanoparticles for a variety of biomedical applications, notably in systemic administrations. However, with respect to blood contacting applications, amine-terminated dendrimers have recently been shown to activate platelets and cause a fatal, disseminated intravascular coagulation (DIC)-like condition in mice and rats. We here demonstrate that, upon addition to blood, cationic G7 PAMAM dendrimers induce fibrinogen aggregation, which may contribute to the in vivo DIC-like phenomenon. We demonstrate that amine-terminated dendrimers act directly on fibrinogen in a thrombin-independent manner to generate dense, high-molecular-weight fibrinogen aggregates with minimal fibrin fibril formation. In addition, we hypothesize this clot-like behavior is likely mediated through electrostatic interactions between the densely charged cationic dendrimer surface and negatively charged fibrinogen domains. Interestingly, cationic dendrimers also induced aggregation of albumin, suggesting that many negatively charged blood proteins may be affected by cationic dendrimers. To investigate this further, zebrafish embryos (ZFE) were employed to more specifically determine the speed of this phenomenon and the pathway- and dose-dependency of the resulting vascular occlusion phenotype. These novel findings show that G7 PAMAM dendrimers significantly and adversely impact many blood components to produce rapid coagulation and strongly suggest that these effects are independent of classic coagulation mechanisms. These results also strongly suggest the need to fully characterize amine-terminated PAMAM dendrimers in regards to their adverse effects on both coagulation and platelets, which may contribute to blood toxicity. PMID:23062017

Relating Trp-Glu dipeptide fluorescence to molecular conformation: the role of the discrete Chi 1 and Chi 2 angles.

PubMed

Eisenberg, Azaria Solomon; Juszczak, Laura J

2013-07-05

Molecular dynamics (MD), coupled with fluorescence data for charged dipeptides of tryptophanyl glutamic acid (Trp-Glu), reveal a detailed picture of how specific conformation affects fluorescence. Fluorescence emission spectra and time-resolved emission measurements have been collected for all four charged species. MD simulations 20 to 30 ns in length have also been carried out for the Trp-Glu species, as simulation provides aqueous phase conformational data that can be correlated with the fluorescence data. The calculations show that each dipeptide species is characterized by a similar set of six, discrete Chi 1, Chi 2 dihedral angle pairs. The preferred Chi 1 angles--60°, 180°, and 300°--play the significant role in positioning the terminal amine relative to the indole ring. A Chi 1 angle of 60° results in the arching of the backbone over the indole ring and no interaction of the ring with the terminal amine. Chi 1 values of 180° and 300° result in an extension of the backbone away from the indole ring and a NH3 cation-π interaction with indole. This interaction is believed responsible for charge transfer quenching. Two fluorescence lifetimes and their corresponding amplitudes correlate with the Chi 1 angle probability distribution for all four charged Trp-Glu dipeptides. Fluorescence emission band maxima are also consistent with the proposed pattern of terminal amine cation quenching of fluorescence. Copyright © 2013 Wiley Periodicals, Inc.

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

Molecular electrocatalysts for oxidation of hydrogen using earth-abundant metals: shoving protons around with proton relays.

PubMed

Bullock, R Morris; Helm, Monte L

2015-07-21

Sustainable, carbon-neutral energy is needed to supplant the worldwide reliance on fossil fuels in order to address the persistent problem of increasing emissions of CO2. Solar and wind energy are intermittent, highlighting the need to develop energy storage on a huge scale. Electrocatalysts provide a way to convert between electrical energy generated by renewable energy sources and chemical energy in the form of chemical bonds. Oxidation of hydrogen to give two electrons and two protons is carried out in fuel cells, but the typical catalyst is platinum, a precious metal of low earth abundance and high cost. In nature, hydrogenases based on iron or iron/nickel reversibly oxidize hydrogen with remarkable efficiencies and rates. Functional models of these enzymes have been synthesized with the goal of achieving electrocatalytic H2 oxidation using inexpensive, earth-abundant metals along with a key feature identified in the [FeFe]-hydrogenase: an amine base positioned near the metal. The diphosphine ligands P(R)2N(R')2 (1,5-diaza-3,7-diphosphacyclooctane with alkyl or aryl groups on the P and N atoms) are used as ligands in Ni, Fe, and Mn complexes. The pendant amines facilitate binding and heterolytic cleavage of H2, placing the hydride on the metal and the proton on the amine. The pendant amines also serve as proton relays, accelerating intramolecular and intermolecular proton transfers. Electrochemical oxidations and deprotonations by an exogeneous amine base lead to catalytic cycles for oxidation of H2 (1 atm) at room temperature for catalysts derived from [Ni(P(Cy)2N(R')2)2](2+), Cp(C6F5)Fe(P(tBu)2N(Bn)2)H, and MnH(P(Ph)2N(Bn)2)(bppm)(CO) [bppm = (PAr(F)2)2CH2]. In the oxidation of H2 catalyzed by [Ni(P(Cy)2N(R')2)2](2+), the initial product observed experimentally is a Ni(0) complex in which two of the pendant amines are protonated. Two different pathways can occur from this intermediate; deprotonation followed by oxidation occurs with a lower overpotential than the alternate pathway involving oxidation followed by deprotonation. The Mn cation [Mn(P(Ph)2N(Bn)2)(bppm)(CO)](+) mediates the rapid (>10(4) s(-1) at -95 °C), reversible heterolytic cleavage of H2. Obtaining the optimal benefit of pendant amines incorporated into the ligand requires that the pendant amine be properly positioned to interact with a M-H or M(H2) bond. In addition, ligands are ideally selected such that the hydride-acceptor ability of the metal and the basicity of a pendant are tuned to give low barriers for heterolytic cleavage of the H-H bond and subsequent proton transfer reactions. Using these principles allows the rational design of electrocatalysts for H2 oxidation using earth-abundant metals.

PAMAM dendrimers as a carbamazepine delivery system for neurodegenerative diseases: A biophysical and nanotoxicological characterization.

PubMed

Igartúa, Daniela E; Martinez, Carolina S; Temprana, C Facundo; Alonso, Silvia Del V; Prieto, M Jimena

2018-06-10

Carbamazepine (CBZ) is an antiepileptic drug, which also could be used in the treatment of neurodegenerative diseases, such as the Alzheimer's disease. However, its use has been limited due to its low solubility, inefficient pharmacokinetic profiles, and multiple side effects. PAMAM dendrimers, ethylenediamine core, generation 4.0 (amine terminal groups) and 4.5 (carboxylate terminal groups) (DG4.0 and DG4.5 respectively) are polymers that can increase drug solubility through complexation. Thus, the aim of this work was to obtain and characterize complexes between CBZ and dendrimers. Both DG4.0 and DG4.5 allowed the incorporation of ∼20 molecules of CBZ per dendrimer, into their hydrophobic pockets. DG4.0-CBZ and DG4.5-CBZ complexes were found to be stable for 90 days at 37 °C and resistant to a lyophilization process, presenting controlled drug release. Also, the complexes nanotoxicity was tested ex vivo (human red blood cells), in vitro (N2a cell line), and in vivo (zebrafish). No hemolytic effect was observed in the ex vivo model. As regards in vitro toxicity, the DG4.5-CBZ complexes significantly reduced the toxicity caused by the free drug. Moreover, the DG4.5-CBZ did not cause neurotoxicity or cardiotoxicity in zebrafish larvae. In conclusion, a stable and biocompatible drug delivery system based on the DG4.5 capable of complex the CBZ has been developed. This achievement highlights the advantages of using negatively charged dendrimers for nanomedicine. Copyright © 2018 Elsevier B.V. All rights reserved.

Amphiphilic, cross-linkable diblock copolymers for multifunctionalized nanoparticles as biological probes

NASA Astrophysics Data System (ADS)

Schmidtke, Christian; Pöselt, Elmar; Ostermann, Johannes; Pietsch, Andrea; Kloust, Hauke; Tran, Huong; Schotten, Theo; Bastús, Neus G.; Eggers, Robin; Weller, Horst

2013-07-01

Nanoparticles (NPs) play an increasingly important role in biological labeling and imaging applications. However, preserving their useful properties in an aqueous biological environment remains challenging, even more as NPs therein have to be long-time stable, biocompatible and nontoxic. For in vivo applications, size control is crucial in order to route excretion pathways, e.g. renal clearance vs. hepato-biliary accumulation. Equally necessary, cellular and tissue specific targeting demands suitable linker chemistry for surface functionalization with affinity molecules, like peptides, proteins, carbohydrates and nucleotides. Herein, we report a three stage encapsulation process for NPs comprised of (1) a partial ligand exchange by a multidentate polyolefinic amine ligand, PI-N3, (2) micellar encapsulation with a precisely tuned amphiphilic diblock PI-b-PEG copolymer, in which the PI chains intercalate to the PI-N3 prepolymer and (3) radical cross-linking of the adjacent alkenyl bonds. As a result, water-soluble NPs were obtained, which virtually maintained their primal physical properties and were exceptionally stable in biological media. PEG-terminal functionalization of the diblock PI-b-PEG copolymer with numerous functional groups was mostly straightforward by chain termination of the living anionic polymerization (LAP) with the respective reagents. More complex affinity ligands, e.g. carbohydrates or biotin, were introduced in a two-step process, prior to micellar encapsulation. Advantageously, this pre-assembly approach opens up rapid access to precisely tuned multifunctional NPs, just by using mixtures of diverse functional PI-b-PEG polymers in a combinatorial manner. All constructs showed no toxicity from 0.001 to 1 μM (particle concentration) in standard WST and LDH assays on A549 cells, as well as only marginal unspecific cellular uptake, even in serum-free medium.Nanoparticles (NPs) play an increasingly important role in biological labeling and imaging applications. However, preserving their useful properties in an aqueous biological environment remains challenging, even more as NPs therein have to be long-time stable, biocompatible and nontoxic. For in vivo applications, size control is crucial in order to route excretion pathways, e.g. renal clearance vs. hepato-biliary accumulation. Equally necessary, cellular and tissue specific targeting demands suitable linker chemistry for surface functionalization with affinity molecules, like peptides, proteins, carbohydrates and nucleotides. Herein, we report a three stage encapsulation process for NPs comprised of (1) a partial ligand exchange by a multidentate polyolefinic amine ligand, PI-N3, (2) micellar encapsulation with a precisely tuned amphiphilic diblock PI-b-PEG copolymer, in which the PI chains intercalate to the PI-N3 prepolymer and (3) radical cross-linking of the adjacent alkenyl bonds. As a result, water-soluble NPs were obtained, which virtually maintained their primal physical properties and were exceptionally stable in biological media. PEG-terminal functionalization of the diblock PI-b-PEG copolymer with numerous functional groups was mostly straightforward by chain termination of the living anionic polymerization (LAP) with the respective reagents. More complex affinity ligands, e.g. carbohydrates or biotin, were introduced in a two-step process, prior to micellar encapsulation. Advantageously, this pre-assembly approach opens up rapid access to precisely tuned multifunctional NPs, just by using mixtures of diverse functional PI-b-PEG polymers in a combinatorial manner. All constructs showed no toxicity from 0.001 to 1 μM (particle concentration) in standard WST and LDH assays on A549 cells, as well as only marginal unspecific cellular uptake, even in serum-free medium. Electronic supplementary information (ESI) available: Images of the QDs, toxicity data and NMR spectra. See DOI: 10.1039/c3nr01520c

N-formylation of amines via the aerobic oxidation of methanol over supported gold nanoparticles.

PubMed

Ishida, Tamao; Haruta, Masatake

2009-01-01

Dress code: formyl. Gold nanoparticles supported on NiO catalyze the one-pot N-formylation of amines with methanol and molecular oxygen to produce formamide at a selectivity of 90 %. This process generates methyl formate in situ, followed by reaction with amines.

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.

The Effect of Aptamer Concetration towards Reduced Graphene Oxide-Field Effect Transistor Surface Channel for Biosensor Application

NASA Astrophysics Data System (ADS)

Syafiq Zainol Abidin, Azrul; Rahim, Ruslinda Abdul; Huan, Chow Yong; Maidin, Nur Nasyifa Mohd; Atiqah Ahmad, Nurul; Hashwan, Saeed S. Ba; Faudzi, Fatin Nabilah Mohd; Hong, Voon Chun

2018-03-01

Aptamer are artificially produce bioreceptor that has been developed to bind with various target biomolecules such as ion, cells, protein and small molecules. In this research, an aptamer concentration of 0.5 nM, 1 nM, 5 nM, 10 nM, and 50 nM were immobilized on reduced graphene oxide (rGO) integrated with field effect transistor (FET) respectively to study the effect of aptamer concentration toward rGO surface for stable biosensing platform. The 0.5 nM concentration of aptamer shows the highest current result of 84.3 µA at 1 V applied through the source and drain. After immobilized with aminated aptamer, the conductivity shows significant reduction due to the formation of amide bond on rGO surface between aminated aptamer and carboxyl group on rGO. The electrical performance of FET integrated with rGO shows stable electrical performance suitable to be used in the biosensing application.

Distribution of Aliphatic Amines in CO, CV, and CK Carbonaceous Chondrites and Relation to Mineralogy and Processing History

NASA Technical Reports Server (NTRS)

Aponte, Jose C.; Abreu, Neyda M.; Glavin, Daniel P.; Dworkin, Jason P.; Elsila, Jamie E.

2017-01-01

The analysis of water-soluble organic compounds in meteorites provides valuable insights into the prebiotic synthesis of organic matter and the processes that occurred during the formation of the solar system. We investigated the concentration of aliphatic monoamines present in hot acid water extracts of the unaltered Antarctic carbonaceous chondrites, Dominion Range (DOM) 08006 (CO3) and Miller Range (MIL) 05013 (CO3), and the thermally altered meteorites, Allende (CV3), LAP 02206 (CV3), GRA 06101 (CV3), Allan Hills (ALH) 85002 (CK4), and EET 92002 (CK5). We have also reviewed and assessed the petrologic characteristics of the meteorites studied here to evaluate the effects of asteroidal processing on the abundance and molecular distributions of monoamines. The CO3, CV3, CK4, and CK5 meteorites studied here contain total concentrations of amines ranging from 1.2 to 4.0 nmol/g of meteorite; these amounts are 1-3 orders of magnitude below those observed in carbonaceous chondrites from the CI, CM, and CR groups. The low-amine abundances for CV and CK chondrites may be related to their extensive degree of thermal metamorphism and/or to their low original amine content. Although the CO3 meteorites, DOM 08006 and MIL 05013, do not show signs of thermal and aqueous alteration, their monoamine contents are comparable to those observed in moderately/extensively thermally altered CV3, CK4, and CK5 carbonaceous chondrites. The low content of monoamines in pristine CO carbonaceous chondrites suggests that the initial amounts, and not asteroidal processes, play a dominant role in the content of monoamines in carbonaceous chondrites. The primary monoamines, methylamine, ethylamine, and n-propylamine constitute the most abundant amines in the CO3, CV3, CK4, and CK5 meteorites studied here. Contrary to the predominance of n-x-amino acid isomers in CO3 and thermally altered meteorites, there appears to be no preference for the larger n-amines.

Determination of the pKa of the N-terminal amino group of ubiquitin by NMR

PubMed Central

Oregioni, Alain; Stieglitz, Benjamin; Kelly, Geoffrey; Rittinger, Katrin; Frenkiel, Tom

2017-01-01

Ubiquitination regulates nearly every aspect of cellular life. It is catalysed by a cascade of three enzymes and results in the attachment of the C-terminal carboxylate of ubiquitin to a lysine side chain in the protein substrate. Chain extension occurs via addition of subsequent ubiquitin molecules to either one of the seven lysine residues of ubiquitin, or via its N-terminal α-amino group to build linear ubiquitin chains. The pKa of lysine side chains is around 10.5 and hence E3 ligases require a mechanism to deprotonate the amino group at physiological pH to produce an effective nucleophile. In contrast, the pKa of N-terminal α-amino groups of proteins can vary significantly, with reported values between 6.8 and 9.1, raising the possibility that linear chain synthesis may not require a general base. In this study we use NMR spectroscopy to determine the pKa for the N-terminal α-amino group of methionine1 of ubiquitin for the first time. We show that it is 9.14, one of the highest pKa values ever reported for this amino group, providing a rational for the observed need for a general base in the E3 ligase HOIP, which synthesizes linear ubiquitin chains. PMID:28252051

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

Nitrosamine formation in amine scrubbing at desorber temperatures.

PubMed

Fine, Nathan A; Goldman, Mark J; Rochelle, Gary T

2014-01-01

Amine scrubbing is a thermodynamically efficient and industrially proven method for carbon capture, but amine solvents can nitrosate in the desorber, forming potentially carcinogenic nitrosamines. The kinetics of reactions involving nitrite and monoethanolamine (MEA), diethanolamine (DEA), methylethanolamine (MMEA), and methyldiethanolamine (MDEA) were determined under desorber conditions. The nitrosations of MEA, DEA, and MMEA are first order in nitrite, carbamate species, and hydronium ion. Nitrosation of MDEA, a tertiary amine, is not catalyzed by the addition of CO2 since it cannot form a stable carbamate. Concentrated and CO2 loaded MEA was blended with low concentrations of N-(2-hydroxyethyl) glycine (HeGly), hydroxyethyl-ethylenediamine (HEEDA), and DEA, secondary amines common in MEA degradation. Nitrosamine yield was proportional to the concentration of secondary amine and was a function of CO2 loading and temperature. Blends of tertiary amines with piperazine (PZ) showed n-nitrosopiperazine (MNPZ) yields close to unity, validating the slow nitrosation rates hypothesized for tertiary amines. These results provide a useful tool for estimating nitrosamine accumulation over a range of amine solvents.

Strain Release Amination

PubMed Central

Gianatassio, Ryan; Lopchuk, Justin M.; Wang, Jie; Pan, Chung-Mao; Malins, Lara R.; Prieto, Liher; Brandt, Thomas A.; Collins, Michael R.; Gallego, Gary M.; Sach, Neal W.; Spangler, Jillian E.; Zhu, Huichin; Zhu, Jinjiang; Baran, Phil S.

2015-01-01

To optimize drug candidates, modern medicinal chemists are increasingly turning to an unconventional structural motif: small, strained ring systems. However, the difficulty of introducing substituents such as bicyclo[1.1.1]pentanes, azetidines, or cyclobutanes often outweighs the challenge of synthesizing the parent scaffold itself. Thus, there is an urgent need for general methods to rapidly and directly append such groups onto core scaffolds. Here we report a general strategy to harness the embedded potential energy of effectively spring-loaded C–C and C–N bonds with the most oft-encountered nucleophiles in pharmaceutical chemistry, amines. Strain release amination can diversify a range of substrates with a multitude of desirable bioisosteres at both the early and late-stages of a synthesis. The technique has also been applied to peptide labeling and bioconjugation. PMID:26816372

Using liquid and solid state NMR and photoluminescence to study the synthesis and solubility properties of amine capped silicon nanoparticles.

PubMed

Giuliani, J R; Harley, S J; Carter, R S; Power, P P; Augustine, M P

2007-08-01

Water soluble silicon nanoparticles were prepared by the reaction of bromine terminated silicon nanoparticles with 3-(dimethylamino)propyl lithium and characterized with liquid and solid state nuclear magnetic resonance (NMR) and photoluminescence (PL) spectroscopies. The surface site dependent 29Si chemical shifts and the nuclear spin relaxation rates from an assortment of 1H-29Si heteronuclear solid state NMR experiments for the amine coated reaction product are consistent with both the 1H and 13C liquid state NMR results and routine transmission electron microscopy, ultra-violet/visible, and Fourier transform infrared measurements. PL was used to demonstrate the pH dependent solubility properties of the amine passivated silicon nanoparticles.

Oxyfunctionalization of the Remote C-H Bonds of Aliphatic Amines by Decatungstate Photocatalysis.

PubMed

Schultz, Danielle M; Lévesque, François; DiRocco, Daniel A; Reibarkh, Mikhail; Ji, Yining; Joyce, Leo A; Dropinski, James F; Sheng, Huaming; Sherry, Benjamin D; Davies, Ian W

2017-11-27

Aliphatic amines, oxygenated at remote positions within the molecule, represent an important class of synthetic building blocks to which there are currently no direct means of access. Reported herein is an efficient and scalable solution that relies upon decatungstate photocatalysis under acidic conditions using either H 2 O 2 or O 2 as the terminal oxidant. By using these reaction conditions a series of simple and unbiased aliphatic amine starting materials can be oxidized to value-added ketone products. Lastly, NMR spectroscopy using in situ LED-irradiated samples was utilized to monitor the kinetics of the reaction, thus enabling direct translation of the reaction into flow. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

CO2 Biofixation of Actinobacillus succinogenes Through Novel Amine-Functionalized Polystyrene Microsphere Materials.

PubMed

Zhu, Wenhao; Li, Qiang; Dai, Ning

2017-02-01

CO 2 -derived succinate production was enhanced by Actinobacillus succinogenes through polystyrene (PSt) microsphere materials for CO 2 adsorption in bioreactor, and the adhesion forces between A. succinogenes bacteria and PSt materials were characterized. Synthesized uniformly sized and highly cross-linked PSt microspheres had high specific surface areas. After modification with amine functional groups, the novel amine-functionalized PSt microspheres exhibited a high adsorption capacity of 25.3 mg CO 2 /g materials. After addition with the functionalized microspheres into the culture broth, CO 2 supply to the cells increased. Succinate production by A. succinogenes can be enhanced from 29.6 to 48.1 g L -1 . Moreover, the characterization of interaction forces between A. succinogenes cells and the microspheres indicated that the maximal adhesive force was about 250 pN. The amine-functionalized PSt microspheres can adsorb a large amount of CO 2 and be employed for A. succinogenes anaerobic cultivation in bioreactor for high-efficiency production of CO 2 -derived succinate.

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.

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.

Copper(II)-catalyzed oxidative N-nitrosation of secondary and tertiary amines with nitromethane under an oxygen atmosphere.

PubMed

Sakai, Norio; Sasaki, Minoru; Ogiwara, Yohei

2015-07-25

The combination of a catalytic amount of Cu(OTf)2 and less than a stoichiometric amount of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) under an O2 atmosphere effectively promoted the N-nitrosation of both secondary aromatic/aliphatic amines and tertiary aromatic amines with nitromethane (CH3NO2) leading to the preparation of N-nitrosamine derivatives.

Nitric Oxide-Releasing Chitosan Oligosaccharides as Antibacterial Agents

PubMed Central

Lu, Yuan; Slomberg, Danielle L.; Schoenfisch, Mark H.

2014-01-01

Secondary amine-functionalized chitosan oligosaccharides of different molecular weights (i.e., ~2500, 5000, 10000) were synthesized by grafting 2-methyl aziridine from the primary amines on chitosan oligosaccharides, followed by reaction with nitric oxide (NO) gas under basic conditions to yield N-diazeniumdiolate NO donors. The total NO storage, maximum NO flux, and half-life of the resulting NO-releasing chitosan oligosaccharides were controlled by the molar ratio of 2-methyl aziridine to primary amines (e.g., 1:1, 2:1) and the functional group surrounding the N-diazeniumdiolates (e.g., polyethylene glycol (PEG) chains), respectively. The secondary amine-modified chitosan oligosaccharides greatly increased the NO payload over existing biodegradable macromolecular NO donors. In addition, the water-solubility of the chitosan oligosaccharides enabled their penetration across the extracellular polysaccharides matrix of Pseudomonas aeruginosa biofilms and association with embedded bacteria. The effectiveness of these chitosan oligosaccharides at biofilm eradication was shown to depend on both the molecular weight and ionic characteristics. Low molecular weight and cationic chitosan oligosaccharides exhibited rapid association with bacteria throughout the entire biofilm, leading to enhanced biofilm killing. At concentrations resulting in 5-log killing of bacteria in Pseudomonas aeruginosa biofilms, the NO-releasing and control chitosan oligosaccharides elicited no significant cytotoxicity to mouse fibroblast L929 cells in vitro. PMID:24268196

Polyisobutylene chain end transformations: Block copolymer synthesis and click chemistry functionalizations

NASA Astrophysics Data System (ADS)

Magenau, Andrew Jackson David

The primary objectives of this research were twofold: (1) development of synthetic procedures for combining quasiliving carbocationic polymerization (QLCCP) of isobutylene (IB) and reversible addition fragmentation chain transfer (RAFT) polymerization for block copolymer synthesis; (2) utilization of efficient, robust, and modular chemistries for facile functionalization of polyisobutylene (PIB). In the first study block copolymers consisting of PIB, and either PMMA or PS block segments, were synthesized by a site transformation approach combining living cationic and reversible addition-fragmentation chain transfer (RAFT) polymerizations. The initial PIB block was synthesized via quasiliving cationic polymerization using the TMPCl/TiCl4 initiation system and was subsequently converted into a hydroxylterminated PIB. Site transformation of the hydroxyl-terminated PIB into a macro chain transfer agent (PIB-CTA) was accomplished by N,N'-dicyclohexylcarbodiimide/dimethylaminopyridine-catalyzed esterification with 4-cyano-4-(dodecylsulfanylthiocarbonylsulfanyl)pentanoic acid. In the second study another site transformation approach was developed to synthesize a novel block copolymer, composed of PIB and PNIPAM segments. The PIB block was prepared via quasiliving cationic polymerization and end functionalized by in-situ quenching to yield telechelic halogen-terminated PIB. Azido functionality was obtained by displacement of the terminal halogen through nucleophilic substitution, which was confirmed by both 1H and 13C NMR. Coupling of an alkyne-functional chain transfer agent (CTA) to azido PIB was successfully accomplished through a copper catalyzed click reaction. Structure of the resulting PIB-based macro-CTA was verified with 1H NMR, FTIR, and GPC; whereas coupling reaction kinetics were monitored by real time variable temperature (VT) 1H NMR. In a third study, a click chemistry functionalization procedure was developed based upon the azide-alkyne 1,3-dipolar cycloaddition reaction. 1-(o-Azidoalkyl)pyrrolyl-terminated PIB was successfully synthesized both by substitution of the terminal halide of 1-(o-haloalkyl)pyrrolyl-terminated PIB with sodium azide and by in situ quenching of quasiliving PIB with a 1-(o-azidoalkyl)pyrrole. GPC indicated the absence of coupled PIB under optimized conditions, confirming exclusive mono-substitution on each pyrrole ring. In a fourth study, radical thiol-ene hydrothiolation "Click" chemistry was explored and adapted to easily and rapidly modify exo -olefin PIB with an array of thiol compounds bearing useful functionalities, including primary halogen, primary amine, primary hydroxyl, and carboxylic acid. The thiol-ene "click" procedure was shown to be applicable to both mono and difunctional exo-olefin polyisobutylene. Telechelic mono- and difunctional exo-olefin PIBs were synthesized via quasiliving cationic polymerization followed by quenching with the hindered amine, 1,2,2,6,6-pentamethylpiperidine. Lower reaction temperatures were found to increase exo-olefin conversion to near quantitative amounts. In the fifth study, thiol-terminated polyisobutylene (PIB-SH) was synthesized by reaction of thiourea with alpha,o-bromine-terminated PIB in a three step one-pot procedure. First the alkylisothiouronium salt was produced using a 1:1 (v:v) DMF:heptane cosolvent mixture at 90°C. Hydrolysis of the salt by aqueous base produced thiolate chain ends, which were then acidified to form the desired thiol functional group. An extension of this reaction was performed by a sequential thiol-ene/thiol-yne procedure to produce tetra-hydroxy functionalized PIB. 1H NMR was used to confirm formation of both alkyne and tetrahydroxyl functional species. Further utility of PIB-SH was demonstrated by base catalyzed thiol-isocyanate reactions. A model reaction was conducted with phenyl isocyanate in THF using triethylamine as the catalyst. Last, conversion of PIB-SH directly into a RAFT macro-CTA was accomplished, as shown by 1H NMR, by treatment of PIB-SH with triethylamine in carbon disulfide and subsequent alkylation with 2-bromopropionic acid. (Abstract shortened by UMI.)

MICROWAVE-ASSISTED CHEMISTRY: SYNTHESIS OF AMINES AND HETEROCYCLES VIA CARBON-NITROGEN BOND FORMATION IN AQUEOUS MEDIA

EPA Science Inventory

Improved C-N bond formation under MW influence is demonstrated by a) solventless three-component coupling reaction to generate propargyl amines that uses only Cu (I); b) aqueous N-alkylation of amines by alkyl halides that proceeds expeditiously in the presence of NaOH to deliver...

Synthesis of 2‐Alkynoates by Palladium(II)‐Catalyzed Oxidative Carbonylation of Terminal Alkynes and Alcohols

PubMed Central

Cao, Qun; Hughes, N. Louise

2016-01-01

Abstract A homogeneous PdII catalyst, utilizing a simple and inexpensive amine ligand (TMEDA), allows 2‐alkynoates to be prepared in high yields by an oxidative carbonylation of terminal alkynes and alcohols. The catalyst system overcomes many of the limitations of previous palladium carbonylation catalysts. It has an increased substrate scope, avoids large excesses of alcohol substrate and uses a desirable solvent. The catalyst employs oxygen as the terminal oxidant and can be operated under safer gas mixtures. PMID:27305489

Covalent Co–O–V and Sb–N Bonds Enable Polyoxovanadate Charge Control

PubMed Central

2017-01-01

The formation of [{CoII(teta)2}{CoII2(tren)(teta)2}VIV15SbIII6O42(H2O)]·ca.9H2O [teta = triethylenetetraamine; tren = tris(2-aminoethyl)amine] illustrates a strategy toward reducing the molecular charge of polyoxovanadates, a key challenge in their use as components in single-molecule electronics. Here, a V–O–Co bond to a binuclear Co2+-centered complex and a Sb–N bond to the terminal N atom of a teta ligand of a mononuclear Co2+ complex allow for full charge compensation of the archetypal molecular magnet [V15Sb6O42(H2O)]6–. Density functional theory based electron localization function analysis demonstrates that the Sb–N bond has an electron density similar to that of a Sb–O bond. Magnetic exchange coupling between the VIV and CoII spin centers mediated via the Sb–N bridge is comparably weakly antiferromagnetic. PMID:28541697

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.

Dehydrogenation of secondary amines: synthesis, and characterization of rare-earth metal complexes incorporating imino- or amido-functionalized pyrrolyl ligands.

PubMed

Li, Qinghai; Zhou, Shuangliu; Wang, Shaowu; Zhu, Xiancui; Zhang, Lijun; Feng, Zhijun; Guo, Liping; Wang, Fenhua; Wei, Yun

2013-02-28

The dehydrogenation of pyrrolyl-functionalized secondary amines initiated by rare-earth metal amides was systematically studied. Reactions of the rare-earth metal amides [(Me(3)Si)(2)N](3)RE(μ-Cl)Li(THF)(3) with pyrrolyl-functionalized secondary amines 2-(t)BuNHCH(2)-5-R-C(4)H(2)NH (R = H (1), R = (t)Bu (2)) led to dehydrogenation of the secondary amines with isolation of imino-functionalized pyrrolyl rare-earth metal complexes [2-(t)BuN=CH-5-R-C(4)H(2)N](2)REN(SiMe(3))(2) (R = H, RE = Y (3a), Dy (3b), Yb (3c), Eu (3d); R = (t)Bu, RE = Y (4a), Dy (4b), Er (4c)). The mixed ligands erbium complex [2-(t)BuNCH(2)-5-(t)Bu-C(4)H(2)N]Er[2-(t)BuN=CH-5-(t)BuC(4)H(2)N](2)ClLi(2)(THF) (4c') was isolated in a short reaction time for the synthesis of complex 4c. Reaction of the deuterated pyrrolyl-functionalized secondary amine 2-((t)BuNHCHD)C(4)H(3)NH with yttrium amide [(Me(3)Si)(2)N](3)Y(μ-Cl)Li(THF)(3) further proved that pyrrolyl-amino ligands were transferred to pyrrolyl-imino ligands. Treatment of 2-((t)BuNHCH(2))C(4)H(3)NH (1) with excess (Me(3)Si)(2)NLi gave the only pyrrole deprotonated product {[η(5):η(2):η(1)-2-((t)BuNHCH(2))C(4)H(3)N]Li(2)N(SiMe(3))(2)}(2) (5), indicating that LiN(SiMe(3))(2) could not dehydrogenate the secondary amines to imines and rare-earth metal ions had a decisive effect on the dehydrogenation. The reaction of the rare-earth metal amides [(Me(3)Si)(2)N](3)RE(μ-Cl)Li(THF)(3) with 1 equiv. of more bulky pyrrolyl-functionalized secondary amine 2-[(2,6-(i)Pr(2)C(6)H(3))NHCH(2)](C(4)H(3)NH) (6) in toluene afforded the only amine and pyrrole deprotonated dinuclear rare-earth metal amido complexes {(μ-η(5):η(1)):η(1)-2-[(2,6-(i)Pr(2)C(6)H(3))NCH(2)]C(4)H(3)N]LnN(SiMe(3))(2)}(2) (RE = Nd (7a), Sm (7b), Er (7c)), no dehydrogenation of secondary amine to imine products were observed. On the basis of experimental results, a plausible mechanism for the dehydrogenation of secondary amines to imines was proposed.

Imide/arylene ether copolymers

NASA Technical Reports Server (NTRS)

Jensen, Brian J. (Inventor); Hergenrother, Paul M. (Inventor); Bass, Robert G. (Inventor)

1992-01-01

Imide/arylene ether block copolymers are prepared by reacting anhydride terminated poly(amic acids) with amine terminated poly(arylene ethers) in polar aprotic solvents and by chemically or thermally cyclodehydrating the resulting intermediate poly(amic acids). The resulting block copolymers have one glass transition temperature or two, depending upon the particular structure and/or the compatibility of the block units. Most of these block copolymers form tough, solvent resistant films with high tensile properties.

Capturing Labile Sulfenamide and Sulfinamide Serum Albumin Adducts of Carcinogenic Arylamines by Chemical Oxidation

PubMed Central

Peng, Lijuan; Turesky, Robert J.

2013-01-01

Aromatic amines and heterocyclic aromatic amines (HAAs) are a class of structurally related carcinogens that are formed during the combustion of tobacco or during the high temperature cooking of meats. These procarcinogens undergo metabolic activation by N-oxidation of the exocyclic amine group to produce N-hydroxylated metabolites, which are critical intermediates implicated in toxicity and DNA damage. The arylhydroxylamines and their oxidized arylnitroso derivatives can also react with cysteine (Cys) residues of glutathione or proteins to form, respectively, sulfenamide and sulfinamide adducts. However, sulfur-nitrogen linked adducted proteins are often difficult to detect because they are unstable and undergo hydrolysis during proteolytic digestion. Synthetic N-oxidized intermediates of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), a carcinogenic HAA produced in cooked meats, and 4-aminobiphenyl, a carcinogenic aromatic amine present in tobacco smoke were reacted with human serum albumin (SA) and formed labile sulfenamide or sulfinamide adducts at the Cys34 residue. Oxidation of the carcinogen-modified SA with m-chloroperoxybenzoic acid (m-CPBA) produced the arylsulfonamide adducts, which were stable to heat and the chemical reduction conditions employed to denature SA. The sulfonamide adducts of PhIP and 4-ABP were identified, by liquid chromatography/mass spectrometry, in proteolytic digests of denatured SA. Thus, selective oxidation of arylamine-modified SA produces stable arylsulfonamide-SA adducts, which may serve as biomarkers of these tobacco and dietary carcinogens. PMID:23240913

A simple synthesis of N-perfluoroacylated and N-acylated glycals of neuraminic acid with a cyclic aminic substituent at the 4α position as possible inhibitors of sialidases.

PubMed

Rota, Paola; Allevi, Pietro; Agnolin, Irene S; Mattina, Roberto; Papini, Nadia; Anastasia, Mario

2012-04-14

A simple protocol for the synthesis of N-perfluoroacylated and N-acylated glycals of neuraminic acid, with a secondary cyclic amine (morpholine or piperidine) at the 4α position, has been set-up, starting from peracetylated N-acetylneuraminic acid methyl ester that undergoes, sequentially to its direct N-transacylation followed by a C-4 amination, a β-elimination, and a selective hydrolysis of the ester functions, without affecting the sensitive perfluorinated amide. This journal is © The Royal Society of Chemistry 2012

(E)-α,β-unsaturated amides from tertiary amines, olefins and CO via Pd/Cu-catalyzed aerobic oxidative N-dealkylation.

PubMed

Shi, Renyi; Zhang, Hua; Lu, Lijun; Gan, Pei; Sha, Yuchen; Zhang, Heng; Liu, Qiang; Beller, Matthias; Lei, Aiwen

2015-02-21

A novel Pd/Cu-catalyzed chemoselective aerobic oxidative N-dealkylation/carbonylation reaction has been developed. Tertiary amines are utilized as a "reservoir" of "active" secondary amines in this transformation, which inhibits the formation of undesired by-products and the deactivation of the catalysts. This protocol allows for an efficient and straightforward construction of synthetically useful and bioactive (E)-α,β-unsaturated amide derivatives from easily available tertiary amines, olefins and CO.

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.

Vibrational spectroscopic study of cationic phosphorus dendrimers with aminoethylpiperidine terminal groups

NASA Astrophysics Data System (ADS)

Furer, V. L.; Vandyukov, A. E.; Tripathi, V.; Majoral, J. P.; Caminade, A. M.; Kovalenko, V. I.

2018-04-01

Two generations of phosphoric dendrimers with piperidine functional groups were synthesized for use in biology and medicine. Neutral samples are soluble in organic solvents but after protonation these dendrimers become water soluble and can be used for biological experiments. The FTIR and FT Raman spectra of two generations of dendrimers Gi constructed from the cyclotriphosphazene core, repeating units sbnd Osbnd C6H4sbnd CHdbnd Nsbnd N(CH3)sbnd P(S)< and aminoethylpiperidine end groups sbnd NHsbnd (CH2)2sbnd C5NH11 were recorded. The study of the IR spectra shows that the NH groups form hydrogen bonds. The calculation of the molecular structure and vibrational spectra of the first generation dendrimer was performed by the method of DFT. This molecule has flat, repeating units and a plane of symmetry passing through the core. The calculation of the distribution of potential energy made it possible to classify the bands in the experimental spectra of dendrimers. Amine groups are manifested in the form of a band of NH stretching vibrations at 3389 cm-1 in the IR spectrum of G1. NH+ stretching bands located at 2646 and 2540 cm-1 in the IR spectrum of G2. The stretching vibrations of NH+ groups are noticeably shifted to low frequencies due to the formation of a hydrogen bond with the chlorine atom. The line at 1575 cm-1 in the Raman spectrum of G1 is characteristic for repeating units.

Diffusivity of nitrous oxide in N-methyldiethanolamine + diethanolamine + water

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

Rinker, E.B.; Russell, J.W.; Tamimi, A.

1995-05-01

The tertiary amine N-methyldiethanolamine and the secondary amine diethanolamine are commonly used in the gas-treating industry as chemical solvents for the removal of acid gases such as CO{sub 2} and H{sub 2}S. The diffusion coefficients for nitrous oxide in aqueous solutions consisting of N-methyldiethanolamine (MDEA) and diethanolamine (DEA) were measured over the temperature range 293--353 K for a total amine concentration of 50 mass % and for the mass ratio of DEA to MDEA varying from 0.0441 to 0.588. The experimental diffusion coefficients were found to be relatively insensitive to the mass ratio of amines.

Plasmatic levels of N-terminal pro-atrial natriuretic peptide in preeclamptic patients and healthy normotensive pregnant women.

PubMed

Reyna-Villasmil, Eduardo; Mejia-Montilla, Jorly; Reyna-Villasmil, Nadia; Mayner-Tresol, Gabriel; Herrera-Moya, Pedro; Fernández-Ramírez, Andreina; Rondón-Tapía, Marta

2018-05-11

To compare plasma N-terminal pro-atrial natriuretic peptide concentrations in preeclamptic patients and healthy normotensive pregnant women. A cases-controls study was done with 180 patients at Hospital Central Dr. Urquinaona, Maracaibo, Venezuela, that included 90 preeclamptic patients (group A; cases) and 90 healthy normotensive pregnant women selected with the same age and body mass index similar to group A (group B; controls). Blood samples were collected one hour after admission and prior to administration of any medication in group A to determine plasma N-terminal pro-atrial natriuretic peptide and other laboratory parameters. Plasma N-terminal pro-atrial natriuretic peptide concentrations in group A (mean 1.01 [0.26] pg/mL) showed a significant difference when compared with patients in group B (mean 0.55 [0.07] pg/mL; P<.001]. There was no significant correlation with systolic and diastolic blood pressure values in preeclamptic patients (P=ns). A cut-off value of 0.66ng/mL had an area under the curve of 0.93, sensitivity of 87.8%, specificity of 83.3%, a positive predictive value of 84.0% and a negative predictive value of 87.2%, with a diagnostic accuracy of 85.6%. Preeclamptic patients have significantly higher concentrations of plasma N-terminal pro-atrial natriuretic peptide compared with healthy normotensive pregnant women, with high predictive values for diagnosis. Copyright © 2017 Elsevier España, S.L.U. All rights reserved.

High selectivity of colorimetric detection of p-nitrophenol based on Ag nanoclusters

NASA Astrophysics Data System (ADS)

Qu, Fei; Chen, Ping; Zhu, Shuyun; You, Jinmao

2017-01-01

Ag nanoclusters (Ag NCs) templated by hyperbranched polyethyleneimine (PEI) with different terminal groups and molecular weights had been developed as a special optical sensor for detecting p-nitrophenol (p-NP). When adding p-NP into Ag NCs, an obvious color change from pale yellow to deep yellow could be observed by naked eyes, accompanying with an apparent red-shift of absorption peak, and the reason was attributed to the formation of oxygen anion of p-NP based on the transfer of H+ from p-NP to amine groups of PEI. The molecular weights of template would greatly affect the sensitivity of p-NP. Ag NCs capped by PEI terminated ethylenediamine (EDA) possessed better sensitivity than other Ag NCs, showing good linear range from 5 to 140 μM with the limit of detection as low as 1.28 μM. Most importantly, this present system displayed high selectivity toward p-NP even in the presence of other nitrophenols and nitrotoluenes. This reliable method had been successfully applied for the detection of p-NP in real water and soil samples.

Palladium-catalyzed three-component reaction of N-tosyl hydrazones, isonitriles and amines leading to amidines.

PubMed

Dai, Qiang; Jiang, Yan; Yu, Jin-Tao; Cheng, Jiang

2015-12-04

A palladium-catalyzed three-component reaction between N-tosyl hydrazones, aryl isonitriles and amines was developed, leading to amidines in moderate to good yields. This procedure features the rapid construction of amidine frameworks with high diversity and complexity. Ketenimines serve as intermediates, which encounter nucleophilic attack by amines to produce amidines.

Synthesis and evaluation of biaryl derivatives for structural characterization of selective monoamine oxidase B inhibitors toward Parkinson's disease therapy.

PubMed

Yeon, Seul Ki; Choi, Ji Won; Park, Jong-Hyun; Lee, Ye Rim; Kim, Hyeon Jeong; Shin, Su Jeong; Jang, Bo Ko; Kim, Siwon; Bahn, Yong-Sun; Han, Gyoonhee; Lee, Yong Sup; Pae, Ae Nim; Park, Ki Duk

2018-01-01

Benzyloxyphenyl moiety is a common structure of highly potent, selective and reversible inhibitors of monoamine oxidase B (MAO-B), safinamide and sembragiline. We synthesized 4-(benzyloxy)phenyl and biphenyl-4-yl derivatives including halogen substituents on the terminal aryl unit. In addition, we modified the carbon linker between amine group and the biaryl linked unit. Among synthesized compounds, 12c exhibited the most potent and selective MAO-B inhibitory effect (hMAO-B IC 50 : 8.9 nM; >10,000-fold selectivity over MAO-A) as a competitive inhibitor. In addition, 12c showed greater MAO-B inhibitory activity and selectivity compared to well-known MAO-B inhibitors such as selegiline, safinamide and sembragiline. In the MPTP-induced mouse model of Parkinson's disease (PD), 12c significantly protected the tyrosine hydroxylase (TH)-immunopositive DAergic neurons and attenuated the PD-associated behavioral deficits. This study suggests characteristic structures as a MAO-B inhibitor that may provide a good insight for the development of therapeutic agents for PD. Copyright © 2017 Elsevier Ltd. All rights reserved.

Different types of degradable vectors from low-molecular-weight polycation-functionalized poly(aspartic acid) for efficient gene delivery.

PubMed

Dou, X B; Hu, Y; Zhao, N N; Xu, F J

2014-03-01

Poly(aspartic acid) (PAsp) has been employed as the potential backbone for the preparation of efficient gene carriers, due to its low cytotoxicity, good biodegradability and excellent biocompatibility. In this work, the degradable linear or star-shaped PBLA was first prepared via ring-opining polymerization of β-benzyl-L-aspartate N-carboxy anhydride (BLA-NCA) initiated by ethylenediamine (ED) or ED-functionalized cyclodextrin cores. Then, PBLA was functionalized via aminolysis reaction with low-molecular-weight poly(2-(dimethylamino)ethyl methacrylate) with one terminal primary amine group (PDMAEMA-NH2), followed by addition of excess ED or ethanolamine (EA) to complete the aminolysis process. The obtained different types of cationic PAsp-based vectors including linear or star PAsp-PDM-NH2 and PAsp-PDM-OH exhibited good condensation capability and degradability, benefiting gene delivery process. In comparison with gold standard polyethylenimine (PEI, ∼ 25 kDa), the cationic PAsp-based vectors, particularly star-shaped ones, exhibited much better transfection performances. Copyright © 2013 Elsevier Ltd. All rights reserved.

Niaspan increases axonal remodeling after stroke in type 1 diabetes rats✩

PubMed Central

Yan, Tao; Chopp, Michael; Ye, Xinchun; Liu, Zhongwu; Zacharek, Alex; Cui, Yisheng; Roberts, Cynthia; Buller, Ben; Chen, Jieli

2012-01-01

Background and objective We investigated axonal plasticity in the bilateral motor cortices and the long term therapeutic effect of Niaspan on axonal remodeling after stroke in type-1 diabetic (T1DM) rats. Experimental approaches T1DM was induced in young adult male Wistar rats via injection of streptozotocin. T1DM rats were subjected to 2 h transient middle cerebral artery occlusion (MCAo) and were treated with 40 mg/kg Niaspan or saline starting 24 h after MCAo and daily for 28 days. Anterograde tracing using biotinylated dextran amine (BDA) injected into the contralateral motor cortex was performed to assess axonal sprouting in the ipsilateral motor cortex area. Functional outcome, SMI-31 (a pan-axonal microfilament marker), Bielschowsky silver and synaptophysin expression were measured. In vitro studies using primary cortical neuron (PCN) cultures and in vivo BDA injection into the brain to anterogradely label axons and terminals were employed. Results Niaspan treatment of stroke in T1DM–MCAo rats significantly improved functional outcome after stroke and increased SMI-31, Bielschowsky silver and synaptophysin expression in the ischemic brain compared to saline treated T1DM–MCAo rats (p<0.05). Using BDA to anterograde label axons and terminals, Niaspan treatment significantly increased axonal density in ipsilateral motor cortex in T1DM–MCAo rats (p<0.05, n=7/group). Niacin treatment of PCN significantly increased Ang1 expression under high glucose condition. Niacin and Ang1 significantly increased neurite outgrowth, and anti-Ang1 antibody marginally attenuated Niacin induced neurite outgrowth (p=0.06, n=6/group) in cultured PCN under high glucose condition. Conclusion Niaspan treatment increased ischemic brain Ang1 expression and promoted axonal remodeling in the ischemic brain as well as improved functional outcome after stroke. Ang1 may partially contribute to Niaspan-induced axonal remodeling after stroke in T1DM-rats. PMID:22266016

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.

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.

An exploration of pregnant teenagers' views of the future and their decisions to continue or terminate their pregnancy: implications for nursing care.

PubMed

Bell, Emily R; Glover, Lesley; Alexander, Tim

2014-09-01

To explore teenagers' views of the future in relation to their choices to continue or terminate pregnancy. Despite recent decreases in the numbers of teenage pregnancies, across the world, the teenage pregnancy rate remains high. Consideration of views of the future (future orientation) appears to play an important part in teenage girls' decisions to continue with pregnancy. To date, no study has explored this in teenage pregnant girls at the time they make their decision to continue with or terminate their pregnancy. Cross-sectional mixed methods design. Three groups were included: termination of pregnancy (n = 19), antenatal (n = 9) and never pregnant (n = 23). Participants were 13-18 years old. The termination of pregnancy and antenatal groups were interviewed, and the never pregnant group completed postal questionnaires. Groups differed in individual aspects of future orientation, that is, education, career and family, and reasons for pregnancy resolution choice. The termination group had more clearly developed and longer-term plans for the future with a focus on career. The never pregnant group shared aspects of their future orientation with both the antenatal and termination of pregnancy groups. The impact of negative discourses about teenage pregnancy from others was identified as a significant issue. How pregnant teenage girls view the future has a relationship with their decision to terminate or continue with their pregnancy. The findings suggest that working with teenage girls to clarify their views of the future may be useful both in preventing future unwanted pregnancy and in supporting teenagers in making pregnancy decisions. Supporting pregnant teenagers in distancing themselves from negative stereotypes of teenage mothers may also be beneficial. © 2013 John Wiley & Sons Ltd.

X-ray photoelectron spectroscopy characterization of gold nanoparticles functionalized with amine-terminated alkanethiols

PubMed Central

Techane, Sirnegeda D.; Gamble, Lara J.; Castner, David G.

2011-01-01

Gold nanoparticles (AuNPs) functionalized with a short chain amine-terminated alkanethiol (HS-(CH2)2NH2 or C2 NH2-thiol) are prepared via a direct synthesis method and then ligand-exchanged with a long chain amine-terminated alkanethiol (HS-(CH2)11NH2 or C11 NH2-thiol). Transmission electron microscopy analysis showed the AuNPs were relatively spherical with a median diameter of 24.2±4.3 nm. X-ray photoelectron spectroscopy was used to determine surface chemistry of the functionalized and purified AuNPs. The ligand-exchange process was monitored within the time range from 30 min to 61 days. By the fourth day of exchange all the C2 NH2-thiol molecules had been replaced by C11 NH2-thiol molecules. C11 NH2-thiol molecules continued to be incorporated into the C11 NH2 self-assembled monolayer between days 4 and 14 of ligand-exchange. As the length of the exchange time increased, the functionalized AuNPs became more stable against aggregation. The samples were purified by a centrifugation and resuspension method. The C2 NH2 covered AuNPs aggregated immediately when purification was attempted. The C11 NH2 covered AuNPs could be purified with minimal or no aggregation. Small amounts of unbound thiol (∼15%) and oxidized sulfur (∼20%) species were detected on the ligand-exchanged AuNPs. Some of the unbound thiol and all of the oxidized sulfur could be removed by treating the functionalized AuNPs with HCl. PMID:21974680

Stille coupling via C-N bond cleavage

NASA Astrophysics Data System (ADS)

Wang, Dong-Yu; Kawahata, Masatoshi; Yang, Ze-Kun; Miyamoto, Kazunori; Komagawa, Shinsuke; Yamaguchi, Kentaro; Wang, Chao; Uchiyama, Masanobu

2016-09-01

Cross-coupling is a fundamental reaction in the synthesis of functional molecules, and has been widely applied, for example, to phenols, anilines, alcohols, amines and their derivatives. Here we report the Ni-catalysed Stille cross-coupling reaction of quaternary ammonium salts via C-N bond cleavage. Aryl/alkyl-trimethylammonium salts [Ar/R-NMe3]+ react smoothly with arylstannanes in 1:1 molar ratio in the presence of a catalytic amount of commercially available Ni(cod)2 and imidazole ligand together with 3.0 equivalents of CsF, affording the corresponding biaryl with broad functional group compatibility. The reaction pathway, including C-N bond cleavage step, is proposed based on the experimental and computational findings, as well as isolation and single-crystal X-ray diffraction analysis of Ni-containing intermediates. This reaction should be widely applicable for transformation of amines/quaternary ammonium salts into multi-aromatics.

The Biosynthesis of Nitrogen-, Sulfur-, and High-carbon Chain-containing Sugars†

PubMed Central

Lin, Chia-I; McCarty, Reid M.; Liu, Hung-wen

2013-01-01

Carbohydrates serve many structural and functional roles in biology. While the majority of monosaccharides are characterized by the chemical composition: (CH2O)n, modifications including deoxygenation, C-alkylation, amination, O- and N-methylation, which are characteristic of many sugar appendages of secondary metabolites, are not uncommon. Interestingly, some sugar molecules are formed via modifications including amine oxidation, sulfur incorporation, and “high-carbon” chain attachment. Most of these unusual sugars have been identified over the past several decades as components of microbially produced natural products, although a few high-carbon sugars are also found in the lipooligosaccharides of the outer cell walls of Gram-negative bacteria. Despite their broad distribution in nature, these sugars are considered “rare” due to their relative scarcity. The biosynthetic steps that underlie their formation continue to perplex researchers to this day and many questions regarding key transformations remain unanswered. This review will focus on our current understanding of the biosynthesis of unusual sugars bearing oxidized amine substituents, thio-functional groups, and high-carbon chains. PMID:23348524

Solution-phase synthesis of a hindered N-methylated tetrapeptide using Bts-protected amino acid chlorides: efficient coupling and methylation steps allow purification by extraction.

PubMed

Vedejs, E; Kongkittingam, C

2000-04-21

N-Benzothiazole-2-sulfonyl (Bts)-protected amino acid chlorides were used to prepare the hindered cyclosporin 8-11 tetrapeptide subunit 1. The synthesis was performed via 3a and the deprotected amines 5a, 13, and 19, including three repeated cycles involving N-methylation using iodomethane/potassium carbonate, deprotection of the Bts group, and N-acylation with a N-Bts-amino acid chloride such as 9b or 9c. Among three Bts cleavage methods compared (H3PO2/THF; NaBH4/EtOH; PhSH/K2CO3), the third gave somewhat higher overall yields. N-Acylation of 5a with the Bts-protected N-methylamino acid chloride 10b followed by deprotection was also highly efficient and could be used as an alternative route to 11. Each of the deprotected amines was isolated without chromatography using simple extraction methods to remove neutral byproducts. The tetrapeptide 1 was obtained in analytically pure form as the monohydrate.

Crystal structure of bis-[(phenyl-methanamine-κN)(phthalocyaninato-κ(4) N)zinc] phenyl-methan-amine tris-olvate.

PubMed

Shamsudin, Norzianah; Tan, Ai Ling; Wimmer, Franz L; Young, David J; Tiekink, Edward R T

2015-09-01

The asymmetric unit of the title compound, 2[Zn(C32H16N8)(C7H9N)]·3C7H9N, comprises two independent complex mol-ecules and three benzyl-amine solvent mol-ecules. Each complex mol-ecule features a penta-coordinated Zn(2+) ion within a square-pyramidal geometry, whereby the N5 donor set is defined by four atoms of the phthalocyaninate dianion (PC) and an N-bound benzyl-amine mol-ecule; it is the relative orientations of the latter that differentiate between the independent complex mol-ecules. The uncoordinated benzyl-amine mol-ecules display different conformations in the structure, with syn-Car-Car-Cm-N (ar = aromatic, m = methyl-ene) torsion angles spanning the range -28.7 (10) to 35.1 (14)°. In the crystal, N-H⋯N and N-H⋯π inter-actions lead to supra-molecular layers in the ab plane. The layers have a zigzag topology, have the coordinating and non-coordinating benzyl-amine mol-ecules directed to the inside, and present the essentially flat PC resides to the outside. This arrangement enables adjacent layers to associate via π-π inter-actions [inter-centroid distance between pyrrolyl and fused-benzene rings = 3.593 (2) Å] so that a three-dimensional architecture is formed.

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

Cooperative Light-Activated Iodine and Photoredox Catalysis for the Amination of Csp3 -H Bonds.

PubMed

Becker, Peter; Duhamel, Thomas; Stein, Christopher J; Reiher, Markus; Muñiz, Kilian

2017-06-26

An unprecedented method that makes use of the cooperative interplay between molecular iodine and photoredox catalysis has been developed for dual light-activated intramolecular benzylic C-H amination. Iodine serves as the catalyst for the formation of a new C-N bond by activating a remote Csp3 -H bond (1,5-HAT process) under visible-light irradiation while the organic photoredox catalyst TPT effects the reoxidation of the molecular iodine catalyst. To explain the compatibility of the two involved photochemical steps, the key N-I bond activation was elucidated by computational methods. The new cooperative catalysis has important implications for the combination of non-metallic main-group catalysis with photocatalysis. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Nitrite ion mitigates the formation of N-nitrosodimethylamine (NDMA) during chloramination of ranitidine.

PubMed

Seid, Mingizem Gashaw; Cho, Kangwoo; Lee, Changha; Park, Hyun-Mee; Hong, Seok Won

2018-08-15

Ranitidine (RNT) has been an important tertiary amine precursor of N-nitrosodimethylamine (NDMA) in chlorine-based water treatment, due to reaction with monochloramine (NH 2 Cl) with exceptionally high molar yields up to 90%. This study examined the effects of nitrite ions (NO 2 - ) on the kinetics of NDMA formation during the chloramination of RNT under variable concentrations of dissolved oxygen (DO, 0.7-7.5mg/L), RNT (5-30μM), NH 2 Cl (5-20mM), NO 2 - or NO 3 - (0-2mM) and pH (5.6-8.6). In the absence of the NO 2 - , the ultimate molar yield of NDMA after 6h of reaction was primarily influenced by [DO] and pH, while marginally affected by initial [RNT] and [NH 2 Cl]. A kinetic model, prepared in accordance with the reaction sequence of NDMA formation, suggested that the rate determining step was accelerated with increasing [NH 2 Cl] 0 , [DO], and pH. A Kinetic study together with ultra-performance liquid chromatography-quadrupole-time of flight mass spectrometer (UPLC-Q-TOF MS) and gas chromatography (GC)/TOF MS analyses in parallel demonstrated that the nitrite ion inhibited the nucleophilic substitution of the terminal amine on NH 2 Cl, and reduced the pseudo-steady state concentration of N-peroxyl radicals, significantly decreasing the ultimate yields of NDMA. Copyright © 2018 Elsevier B.V. All rights reserved.

Reduction of aromatic and heterocyclic aromatic N-hydroxylamines by human cytochrome P450 2S1.

PubMed

Wang, Kai; Guengerich, F Peter

2013-06-17

Many aromatic amines and heterocyclic aromatic amines (HAAs) are known carcinogens for animals, and there is also strong evidence of some in human cancer. The activation of these compounds, including some arylamine drugs, involves N-hydroxylation, usually by cytochrome P450 enzymes (P450) in Family 1 (1A2, 1A1, and 1B1). We previously demonstrated that the bioactivation product of the anticancer agent 2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole (5F 203), an N-hydroxylamine, can be reduced by P450 2S1 to its amine precursor under anaerobic conditions and, to a lesser extent, under aerobic conditions [Wang, K., and Guengerich, F. P. (2012) Chem. Res. Toxicol. 25, 1740-1751]. In the study presented here, we tested the hypothesis that P450 2S1 is involved in the reductive biotransformation of known carcinogenic aromatic amines and HAAs. The N-hydroxylamines of 4-aminobiphenyl (4-ABP), 2-naphthylamine (2-NA), and 2-aminofluorene (2-AF) were synthesized and found to be reduced by P450 2S1 under both anaerobic and aerobic conditions. The formation of amines due to P450 2S1 reduction also occurred under aerobic conditions but was less apparent because the competitive disproportionation reactions (of the N-hydroxylamines) also yielded amines. Further, some nitroso and nitro derivatives of the arylamines could also be reduced by P450 2S1. None of the amines tested were oxidized by P450 2S1. These results suggest that P450 2S1 may be involved in the reductive detoxication of several of the activated products of carcinogenic aromatic amines and HAAs.

Reduction of Aromatic and Heterocyclic Aromatic N-Hydroxylamines by Human Cytochrome P450 2S1

PubMed Central

Wang, Kai; Guengerich, F. Peter

2013-01-01

Many aromatic amines and heterocyclic aromatic amines (HAAs) are known carcinogens for animals and there is also strong evidence for some in human cancer. The activation of these compounds, including some arylamine drugs, involves N-hydroxylation, usually by cytochrome P450 enzymes (P450) in Family 1 (1A2, 1A1, and 1B1). We previously demonstrated that the bioactivation product of the anti-cancer agent 2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole (5F 203), an N-hydroxylamine, can be reduced by P450 2S1 to its amine precursor under anaerobic conditions and, to a lesser extent, under aerobic conditions (Wang, K., and Guengerich, F. P. (2012) Chem. Res. Toxicol. 25, 1740–1751). In the present study, we tested the hypothesis that P450 2S1 is involved in the reductive biotransformation of known carcinogenic aromatic amines and HAAs. The N-hydroxylamines of 4-aminobiphenyl (4-ABP), 2-naphthylamine (2-NA), and 2-aminofluorene (2-AF) were synthesized and found to be reduced by P450 2S1 under both anaerobic and aerobic conditions. The formation of amines due to P450 2S1 reduction also occurred under aerobic conditions but was less apparent because the competitive disproportionation reactions (of the N-hydroxylamines) also yielded amines. Further, some nitroso and nitro derivatives of the arylamines could also be reduced by P450 2S1. None of the amines tested were oxidized by P450 2S1. These results suggest that P450 2S1 may be involved in the reductive detoxication of several of the activated products of carcinogenic aromatic amines and HAAs. PMID:23682735

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.

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

Wilfong, Walter Christopher; Kail, Brian W.; Bank, Tracy L.

Recovering aqueous rare earth elements (REEs) from domestic water sources is one key strategy to diminish the U.S.’s foreign reliance of these precious commodities. Herein, we synthesized an array of porous, amine–epoxy monolith and particle REE recovery sorbents from different polyamine, namely tetraethylenepentamine, and diepoxide (E2), triepoxide (E3), and tetra-epoxide (E4) monomer combinations via a polymer-induced phase separation (PIPS) method. The polyamines provided -NH 2 (primary amine) plus -NH (secondary amine) REE adsorption sites, which were partially reacted with C–O–C (epoxide) groups at different amine/epoxide ratios to precipitate porous materials that exhibited a wide range of apparent porosities and REEmore » recoveries/affinities. Specifically, polymer particles (ground monoliths) were tested for their recovery of La 3+, Nd 3+, Eu 3+, Dy 3+, and Yb 3+ (Ln 3+) species from ppm-level, model REE solutions (pH ≈ 2.4, 5.5, and 6.4) and a ppb-level, simulated acid mine drainage (AMD) solution (pH ≈ 2.6). Screening the sorbents revealed that E3/TEPA-88 (88% theoretical reaction of -NH 2 plus -NH) recovered, overall, the highest percentage of Ln 3+ species of all particles from model 100 ppm- and 500 ppm-concentrated REE solutions. Water swelling (monoliths) and ex situ, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) (ground monoliths/particles) data revealed the high REE uptake by the optimized particles was facilitated by effective distribution of amine and hydroxyl groups within a porous, phase-separated polymer network. In situ DRIFTS results clarified that phase separation, in part, resulted from polymerization of the TEPA-E3 (N-N-diglycidyl-4-glycidyloxyaniline) species in the porogen via C–N bond formation, especially at higher temperatures. Most importantly, the E3/TEPA-88 material cyclically recovered >93% of ppb-level Ln 3+ species from AMD solution in a recovery–strip–recovery scheme, highlighting the efficacy of these materials for practical applications.« less

Recovering Rare Earth Elements from Aqueous Solution with Porous Amine–Epoxy Networks

DOE PAGES

Wilfong, Walter Christopher; Kail, Brian W.; Bank, Tracy L.; ...

2017-05-12

Recovering aqueous rare earth elements (REEs) from domestic water sources is one key strategy to diminish the U.S.’s foreign reliance of these precious commodities. Herein, we synthesized an array of porous, amine–epoxy monolith and particle REE recovery sorbents from different polyamine, namely tetraethylenepentamine, and diepoxide (E2), triepoxide (E3), and tetra-epoxide (E4) monomer combinations via a polymer-induced phase separation (PIPS) method. The polyamines provided -NH 2 (primary amine) plus -NH (secondary amine) REE adsorption sites, which were partially reacted with C–O–C (epoxide) groups at different amine/epoxide ratios to precipitate porous materials that exhibited a wide range of apparent porosities and REEmore » recoveries/affinities. Specifically, polymer particles (ground monoliths) were tested for their recovery of La 3+, Nd 3+, Eu 3+, Dy 3+, and Yb 3+ (Ln 3+) species from ppm-level, model REE solutions (pH ≈ 2.4, 5.5, and 6.4) and a ppb-level, simulated acid mine drainage (AMD) solution (pH ≈ 2.6). Screening the sorbents revealed that E3/TEPA-88 (88% theoretical reaction of -NH 2 plus -NH) recovered, overall, the highest percentage of Ln 3+ species of all particles from model 100 ppm- and 500 ppm-concentrated REE solutions. Water swelling (monoliths) and ex situ, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) (ground monoliths/particles) data revealed the high REE uptake by the optimized particles was facilitated by effective distribution of amine and hydroxyl groups within a porous, phase-separated polymer network. In situ DRIFTS results clarified that phase separation, in part, resulted from polymerization of the TEPA-E3 (N-N-diglycidyl-4-glycidyloxyaniline) species in the porogen via C–N bond formation, especially at higher temperatures. Most importantly, the E3/TEPA-88 material cyclically recovered >93% of ppb-level Ln 3+ species from AMD solution in a recovery–strip–recovery scheme, highlighting the efficacy of these materials for practical applications.« less

Determination of Aromatic Amines Using Solid-Phase Microextraction Based on an Ionic Liquid-Mediated Sol-Gel Technique.

PubMed

Abbasi, Vajihe; Sarafraz-Yazdi, Ali; Amiri, Amirhassan; Vatani, Hossein

2016-04-01

A headspace solid-phase microextraction (HS-SPME) method was developed for isolation of monocyclic aromatic amines from water samples followed by gas chromatography-flame ionization detector (GC-FID). In this work, the effect of the presence of ionic liquid (namely, 1-hexyl-3-methyl-imidazolium hexafluorophosphate [C6MIM][PF6]) was investigated in the sol-gel coating solutions on the morphology and extraction behavior of the resulting hybrid organic-inorganic sol-gel sorbents utilized in SPME. Hydroxy-terminated poly(dimethylsiloxane) (PDMS) was used as the sol-gel active organic component for sol-gel hybrid coatings. Two different coated fibers that were prepared are PDMS and PDMS-IL ([C6MIM][PF6]) fibers. Under the optimal conditions, the method detection limits (S/N = 3) with PDMS-IL were in the range of 0.001-0.1 ng/mL and the limits of quantification (S/N = 10) between 0.005 and 0.5 ng/mL. The relative standard deviations for one fiber (n = 5) were obtained from 3.1 up to 8.5% and between fibers or batch to batch (n = 3) in the range of 5.3-10.1%. The developed method was successfully applied to real water and juice fruits samples while the relative recovery percentages obtained for the spiked water samples at 0.1 ng/mL were from 83.3 to 95.0%. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

New sulfenamide accelerators derived from 'safe' amines for the rubber and tyre industry.

PubMed

Wacker, C D; Spiegelhalder, B; Preussmann, R

1991-01-01

A reduction of the high exposures to N-nitrosamines in the rubber and tyre industry is possible using the concept of 'safe' amines, in which vulcanization accelerators contain amine moieties that are both difficult to nitrosate and, on nitrosation, yield noncarcinogenic N-nitroso compounds. The toxicological and technological properties of more than 50 benzothiazole sulfenamides derived from 'safe' amines have been evaluated. Some of the new compounds show excellent vulcanization properties and seem suitable as replacements for traditional accelerators in this class of compounds.

Direct peptide bioconjugation/PEGylation at tyrosine with linear and branched polymeric diazonium salts.

PubMed

Jones, Mathew W; Mantovani, Giuseppe; Blindauer, Claudia A; Ryan, Sinead M; Wang, Xuexuan; Brayden, David J; Haddleton, David M

2012-05-02

Direct polymer conjugation at peptide tyrosine residues is described. In this study Tyr residues of both leucine enkephalin and salmon calcitonin (sCT) were targeted using appropriate diazonium salt-terminated linear monomethoxy poly(ethylene glycol)s (mPEGs) and poly(mPEG) methacrylate prepared by atom transfer radical polymerization. Judicious choice of the reaction conditions-pH, stoichiometry, and chemical structure of diazonium salt-led to a high degree of site-specificity in the conjugation reaction, even in the presence of competitive peptide amino acid targets such as histidine, lysines, and N-terminal amine. In vitro studies showed that conjugation of mPEG(2000) to sCT did not affect the peptide's ability to increase intracellular cAMP induced in T47D human breast cancer cells bearing sCT receptors. Preliminary in vivo investigation showed preserved ability to reduce [Ca(2+)] plasma levels by mPEG(2000)-sCT conjugate in rat animal models. © 2012 American Chemical Society

Novel Cobalt(II) complexes containing N,N-di(2-picolyl)amine based ligands; Synthesis, characterization and application towards methyl methacrylate polymerisation

NASA Astrophysics Data System (ADS)

Ahn, Seoung Hyun; Choi, Sang-Il; Jung, Maeng Joon; Nayab, Saira; Lee, Hyosun

2016-06-01

The reaction of [CoCl2·6H2O] with N‧-substituted N,N-di(2-picolyl)amine ligands such as 1-cyclohexyl-N,N-bis(pyridin-2-ylmethyl)methanamine (LA), 2-methoxy-N,N-bis(pyridin-2-ylmethyl)ethan-1-amine (LB), and 3-methoxy-N,N-bis(pyridin-2-ylmethyl)propan-1-amine (LC), yielded [LnCoCl2] (Ln = LA, LB and LC), respectively. The Co(II) centre in [LnCoCl2] (Ln = LA, and LC) adopted distorted bipyramidal geometries through coordination of nitrogen atoms of di(2-picolyl)amine moiety to the Co(II) centre along with two chloro ligands. The 6-coordinated [LBCoCl2] showed a distorted octahedral geometry, achieved through coordination of the two pyridyl units, two chloro units, and bidentate coordination of nitrogen and oxygen in the N‧-methoxyethylamine to the Co(II) centre. [LCCoCl2] (6.70 × 104 gPMMA/molCo h) exhibited higher catalytic activity for the polymerisation of methyl methacrylate (MMA) in the presence of modified methylaluminoxane (MMAO) compared to rest of Co(II) complexes. The catalytic activity was considered as a function of steric properties of ligand architecture and increased steric bulk around the metal centre resulted in the decrease catalytic activity. All Co(II) initiators yielded syndiotactic poly(methylmethacrylate) (PMMA).

Efficient SO2 capture by amine functionalized PEG.

PubMed

Yang, Dezhong; Hou, Minqiang; Ning, Hui; Zhang, Jianling; Ma, Jun; Han, Buxing

2013-11-07

Polyethylene glycols (PEGs) are a class of non-toxic, non-volatile, biocompatible, and widely available polymers. In this work, we synthesized N-ethyl-N-(2-(2-(2-methoxyethoxy)ethoxy)ethyl)-2-aminoethanol (EE3AE) that combines the properties of PEG and amines, and N-decyl-N-ethyl-2-aminoethanol (DEAE). Their performances to capture SO2 were studied at different temperatures, pressures, and absorption times. The interaction between the absorbents and SO2 were characterized by NMR and FTIR techniques. It was demonstrated that both EE3AE and DEAE could absorb SO2 efficiently, and there existed chemical and physical interactions between the absorbents and SO2. In particular, the absorption capacity of EE3AE could be as high as 1.09 g SO2 per g EE3AE at 1 atm. The absorption capacity of EE3AE was much larger than that of DEAE because the ether group in the EE3AE interacted with SO2 more strongly than the alkyl group in the DEAE. The SO2 absorbed by EE3AE could be stripped out by bubbling N2 or by applying a vacuum and the EE3AE could be reused. Moreover, both absorbents exhibited a high SO2-CO2 selectivity.

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.

Asymmetric NHC-catalyzed redox α-amination of α-aroyloxyaldehydes.

PubMed

Taylor, James E; Daniels, David S B; Smith, Andrew D

2013-12-06

Asymmetric α-amination through an N-heterocyclic carbene (NHC)-catalyzed redox reaction of α-aroyloxyaldehydes with N-aryl-N-aroyldiazenes to form α-hydrazino esters with high enantioselectivity (up to 99% ee) is reported. The hydrazide products are readily converted into enantioenriched N-aryl amino esters through samarium(II) iodide mediated N-N bond cleavage.

Chloridobis(ethyl­enediamine-κ2 N,N′)(n-pentyl­amine-κN)cobalt(III) dichloride monhydrate

PubMed Central

Anbalagan, K.; Tamilselvan, M.; Nirmala, S.; Sudha, L.

2009-01-01

The title complex, [CoCl(C5H13N)(C2H8N2)2]Cl2·H2O, comprises one chloridobis(ethyl­enediamine)(n-pentyl­amine)cobalt(III) cation, two chloride counter-anions and a water mol­ecule. The CoIII atom of the complex is hexa­coordinated by five N and one Cl atoms. The five N atoms are from two chelating ethyl­enediamine and one n-pentyl­amine ligands. Neighbouring cations and anions are connected by N—H⋯Cl and N—H⋯O hydrogen bonds to each other and also to the water mol­ecule. PMID:21582753

Spectroscopic, DFT, and XRD Studies of Hydrogen Bonds in N-Unsubstituted 2-Aminobenzamides.

PubMed

Mphahlele, Malose Jack; Maluleka, Marole Maria; Rhyman, Lydia; Ramasami, Ponnadurai; Mampa, Richard Mokome

2017-01-04

The structures of the mono- and the dihalogenated N -unsubstituted 2-aminobenzamides were characterized by means of the spectroscopic (¹H-NMR, UV-Vis, FT-IR, and FT-Raman) and X-ray crystallographic techniques complemented with a density functional theory (DFT) method. The hindered rotation of the C(O)-NH₂ single bond resulted in non-equivalence of the amide protons and therefore two distinct resonances of different chemical shift values in the ¹H-NMR spectra of these compounds were observed. 2-Amino-5-bromobenzamide ( ABB ) as a model confirmed the presence of strong intramolecular hydrogen bonds between oxygen and the amine hydrogen. However, intramolecular hydrogen bonding between the carbonyl oxygen and the amine protons was not observed in the solution phase due to a rapid exchange of these two protons with the solvent and fast rotation of the Ar-NH₂ single bond. XRD also revealed the ability of the amide unit of these compounds to function as a hydrogen bond donor and acceptor simultaneously to form strong intermolecular hydrogen bonding between oxygen of one molecule and the NH moiety of the amine or amide group of the other molecule and between the amine nitrogen and the amide hydrogen of different molecules. DFT calculations using the B3LYP/6-311++G(d,p) basis set revealed that the conformer ( A ) with oxygen and 2-amine on the same side predominates possibly due to the formation of a six-membered intramolecular ring, which is assisted by hydrogen bonding as observed in the single crystal XRD structure.

Base metal dehydrogenation of amine-boranes

DOEpatents

Blacquiere, Johanna Marie [Ottawa, CA; Keaton, Richard Jeffrey [Pearland, TX; Baker, Ralph Thomas [Los Alamos, NM

2009-06-09

A method of dehydrogenating an amine-borane having the formula R.sup.1H.sub.2N--BH.sub.2R.sup.2 using base metal catalyst. The method generates hydrogen and produces at least one of a [R.sup.1HN--BHR.sup.2].sub.m oligomer and a [R.sup.1N--BR.sup.2].sub.n oligomer. The method of dehydrogenating amine-boranes may be used to generate H.sub.2 for portable power sources, such as, but not limited to, fuel cells.

Structure-Function Study of Tertiary Amines as Switchable Polarity Solvents

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

Aaron D. Wilson; Frederick F. Stewart

2014-02-01

A series of tertiary amines have been screened for their function as switchable polarity solvents (SPS). The relative ratios of tertiary amine and carbonate species as well as maximum possible concentration were determined through quantitative 1H and 13C NMR spectroscopy. The viscosities of the polar SPS solutions were measured and ranged from near water in dilute systems through to gel formation at high concentrations. The van't Hoff indices for SPS solutions were measured through freezing point depression studies as a proxy for osmotic pressures. A new form of SPS with an amine : carbonate ratio significantly greater than unity hasmore » been identified. Tertiary amines that function as SPS at ambient pressures appear to be limited to molecules with fewer than 12 carbons. The N,N-dimethyl-n-alkylamine structure has been identified as important to the function of an SPS.« less

Silane surface modification for improved bioadhesion of esophageal stents

PubMed Central

Karakoy, Mert; Gultepe, Evin; Pandey, Shivendra; Khashab, Mouen A.; Gracias, David H.

2014-01-01

Stent migration occurs in 10-40% of patients who undergo placement of esophageal stents, with higher migration rates seen in those treated for benign esophageal disorders. This remains a major drawback of esophageal stent therapy. In this paper, we propose a new surface modification method to increase the adhesion between self-expandable metallic stents (SEMS) and tissue while preserving their removability. Taking advantage of the well-known affinity between epoxide and amine terminated silane coupling agents with amine and carboxyl groups that are abundant in proteins and related molecules in the human body; we modified the surfaces of silicone coated esophageal SEMS with these adhesive self-assembled monolayers (SAMs). We utilized vapor phase silanization to modify the surfaces of different substrates including PDMS strips and SEMS, and measured the force required to slide these substrates on a tissue piece. Our results suggest that surface modification of esophageal SEMS via covalent attachment of protein-binding coupling agents improves adhesion to tissue and could offer a solution to reduce SEMS migration while preserving their removability. PMID:25663731

Phenylethylamine N-methylation by human brain preparations

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

Mosnaim, A.D.; Callaghan, O.H.; Wolf, M.E.

Alterations in the brain metabolism of biogenic amines has been postulated to play a role in the pathophysiology of several psychiatric disorders. There is some evidence suggesting schizogenic properties for some abnormal neuroamine methylated derivatives. The authors now report that postmortem human brain preparations, obtained from the putamen and thalamus, convert phenylethylamine (PEA) to its behaviorally active derivative N-methyl PEA, a reaction which is carried out by the 100,000 xg supernatant (in presence of 1 x 10 /sup -5/M pargyline) and enhanced by the addition of NADPH. PEA N-methylation occurred in schizophrenics as well as in sex and age matchedmore » controls. The formation of increased amounts of (/sup 3/H-) or (/sup 14/C-) N-methyl PEA when incubating either cold amine and /sup 3/H-SAM or 1-/sup 14/C PEA and cold SAM, respectively, indicates that SAM is a methyl group donor in this reaction. They will discuss the physiological and pharmacological implications of these results.« less

Molecular structure of tris(cyclopropylsilyl)amine as determined by gas electron diffraction and quantum-chemical calculations

NASA Astrophysics Data System (ADS)

Vishnevskiy, Yuri V.; Abaev, Maxim A.; Ivanov, Arkadii A.; Vilkov, Lev V.; Dakkouri, Marwan

2008-10-01

The molecular structure and conformation of tris(cyclopropylsilyl)amine (TCPSA) has been studied by means of gas-phase electron diffraction at 338 K and quantum-chemical calculations. A total of 12 relatively stable conformations of TCPSA molecule were considered. According to the experimental results and the DFT calculations the most stable conformer corresponds to a configuration (according to the Prelog-Klyne notation) of the type (-ac)(-ac)(+ac)-(-ac)(-ac)(+ac), where the first three parentheses describe the three different Si-N-Si-C torsional angles and the latter ones depict the rotation of the three cyclopropyl groups about the C ring-Si axes, respectively. The quantum-mechanical calculations were performed using various density functional (B3LYP, X3LYP and O3LYP) and perturbation MP2 methods in combination with double- and triple- ζ basis sets plus polarization and diffuse functions. The most important experimental geometrical parameters of TCPSA ( ra Å, ∠ h1 degrees) are: (Si-N) av = 1.741(3), (Si-C) av = 1.866(4), (C-C) av = 1.510(3), (C-C(Si)) av = 1.535(3), (N-Si-C) av = 115.1(18)°. For the purpose of comparison and searching for reasons leading to the planarity of the Si 3N moiety in trisilylated amines we carried out NBO analysis and optimized the geometries of numerous silylamines. Among these compounds was tris(allylsilyl)amine (TASA), which is isovalent and isoelectronic to TCPSA. Utilizing the structural results we obtained we could show that Si +⋯Si + electrostatic repulsive interaction is predominantly responsible for the planarity of the Si 3N skeleton in TCPSA and in all other trisilylamines we considered. We also found that regardless the size and partial charges of the substituents the Si-N-Si bond angle in various disilylamines amounts to 130 ± 2°.

Formation of N-alkylpyrroles via intermolecular redox amination.

PubMed

Pahadi, Nirmal K; Paley, Miranda; Jana, Ranjan; Waetzig, Shelli R; Tunge, Jon A

2009-11-25

A wide variety of aldehydes, ketones, and lactols undergo redox amination when allowed to react with 3-pyrroline in the presence of a mild Brønsted acid catalyst. This reaction utilizes the inherent reducing power of 3-pyrroline to perform the equivalent of a reductive amination to form alkyl pyrroles. In doing so, the reaction avoids stoichiometric reducing agents that are typically associated with reductive aminations. Moreover, the redox amination protocol allows access to alkyl pyrroles that cannot be made via standard reductive amination.

Path Integral Simulation of the H/D Kinetic Isotope Effect in Monoamine Oxidase B Catalyzed Decomposition of Dopamine.

PubMed

Mavri, Janez; Matute, Ricardo A; Chu, Zhen T; Vianello, Robert

2016-04-14

Brain monoamines regulate many centrally mediated body functions, and can cause adverse symptoms when they are out of balance. A starting point to address challenges raised by the increasing burden of brain diseases is to understand, at atomistic level, the catalytic mechanism of an essential amine metabolic enzyme-monoamine oxidase B (MAO B). Recently, we demonstrated that the rate-limiting step of MAO B catalyzed conversion of amines into imines represents the hydride anion transfer from the substrate α-CH2 group to the N5 atom of the flavin cofactor moiety. In this article we simulated for MAO B catalyzed dopamine decomposition the effects of nuclear tunneling by the calculation of the H/D kinetic isotope effect. We applied path integral quantization of the nuclear motion for the methylene group and the N5 atom of the flavin moiety in conjunction with the QM/MM treatment on the empirical valence bond (EVB) level for the rest of the enzyme. The calculated H/D kinetic isotope effect of 12.8 ± 0.3 is in a reasonable agreement with the available experimental data for closely related biogenic amines, which gives strong support for the proposed hydride mechanism. The results are discussed in the context of tunneling in enzyme centers and advent of deuterated drugs into clinical practice.

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.

N-Iodosuccinimide-Promoted Hofmann-Löffler Reactions of Sulfonimides under Visible Light.

PubMed

O'Broin, Calvin Q; Fernández, Patricia; Martínez, Claudio; Muñiz, Kilian

2016-02-05

Conditions for an attractive and productive protocol for the position-selective intramolecular C-H amination of aliphatic groups (Hofmann-Löffler reaction) are reported employing sulfonimides as nitrogen sources. N-Iodosuccinimide is the only required promoter for this transformation, which is conveniently initiated by visible light. The overall transformation provides pyrrolidines under mild and selective conditions as demonstrated for 17 different substrates.

Convergent Synthesis of N-Linked Glycopeptides via Aminolysis of ω-Asp p-Nitrophenyl Thioesters in Solution.

PubMed

Du, Jing-Jing; Gao, Xiao-Fei; Xin, Ling-Ming; Lei, Ze; Liu, Zheng; Guo, Jun

2016-10-07

An efficient N-linked glycosylation reaction between glycosylamines and p-nitrophenyl thioester peptides has been developed. The reaction conditions are mild and compatible with the C-terminal free carboxylic acid group and the unprotected N-linked sialyloligosaccharide. By means of this convergent strategy, a versatile N-glycopeptide fragment containing an N-terminal Thz and a C-terminal thioester was readily prepared, which is available for the synthesis of long glycopeptides and glycoproteins using the protocol of native chemical ligation.

New ultra deep blue emitters based on chrysene chromophores

NASA Astrophysics Data System (ADS)

Shin, Hwangyu; Kang, Seokwoo; Jung, Hyocheol; Lee, Hayoon; Lee, Jaehyun; Kim, Beomjin; Park, Jongwook

2016-09-01

Chrysene, which has a wide band gap, was selected as an emission core to develop and study new materials that emit ultra-deep-blue light with high efficiency. Six compounds introducing various side groups were designed and synthesized: 6, 12-bis(30,50-diphenylphenyl)chrysene (TP-C-TP), 6-(30,50-diphenylphenyl)-12-(3,5-diphenylbiphenyl-400-yl)chrysene (TP-C-TPB) and 6,12-bis(300,500-diphenylbiphenyl-40-yl)chrysene (TPB-C-TPB), which contained bulky aromatic si de groups; and N,N,N0 ,N0-tetraphenyl-chrysene-6,12-diamine (DPA-C-DPA), [12-(4-diphenylamino-phenyl)-chrysene-6-yl]-diphenylamine(DPA-C-TPA) and 6,12-bis[4-(diphenylamino)phenyl]chrysene (TPA-C-TPA), which contained aromatic amine groups, were designed to afford improved hole injection properties. The synthesized materials showed maxi mum absorption wavelengths at 342-402 nm in the film state and exhibited deep-blue photoluminescence (PL) emission s at 417-464 nm. The use of TP-C-TPB in a non-doped organic light emitting diode (OLED) device resulted in ultra-deep-blue emission with an external quantum efficiency (EQE) of 4.02% and Commission Internationale de L'Eclairage coo rdinates (CIE x, y) of (0.154, 0.042) through effective control of the internal conjugation length and suppression of the p -p* stacking. The use of TPA-C-TPA, which includes an aromatic amine side group, afforded an excellent EQE of 4.83 % and excellent color coordinates CIE x, y of (0.147, 0.077).

Copper-Catalyzed Electrophilic Amination of Organoaluminum Nucleophiles with O-Benzoyl Hydroxylamines.

PubMed

Zhou, Shuangliu; Yang, Zhiyong; Chen, Xu; Li, Yimei; Zhang, Lijun; Fang, Hong; Wang, Wei; Zhu, Xiancui; Wang, Shaowu

2015-06-19

A copper-catalyzed electrophilic amination of aryl and heteroaryl aluminums with N,N-dialkyl-O-benzoyl hydroxylamines that affords the corresponding anilines in good yields has been developed. The catalytic reaction proceeds very smoothly under mild conditions and exhibits good substrate scope. Moreover, the developed catalytic system is also well suited for heteroaryl aluminum nucleophiles, providing facile access to heteroaryl amines.

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.

Crystal structure of bis­[trans-di­chlorido­bis(propane-1,3-di­amine-κ2 N,N′)chromium(III)] dichromate from synchrotron data

PubMed Central

Moon, Dohyun; Ryoo, Keon Sang; Choi, Jong-Ha

2016-01-01

The structure of the title compound, [CrCl2(tn)2]2[Cr2O7] (tn = propane-1,3-di­amine; C3H10N2), has been determined from synchrotron data. The asymmetric unit contains one CrIII complex cation and half a [Cr2O7]2− anion. In the complex cation, the CrIII ion is coordinated by the four N atoms of two propane-1,3-di­amine (tn) ligands in the equatorial plane and by two Cl atoms in a trans configuration, displaying a distorted octa­hedral coordination sphere. The two six-membered rings in the complex cation have an anti chair–chair conformation with respect to each other. The mean Cr—N(tn) and Cr—Cl bond lengths are 2.09 (1) and 2.320 (2) Å, respectively. The slightly bent dichromate anion is disordered over two sets of sites (occupancy ratio = 0.7:0.3) and has a staggered conformation. The crystal structure is stabilized by inter­molecular hydrogen bonds involving the NH2 groups of the tn ligands as donors and the O atoms of the [Cr2O7]2− anion and chlorido ligands as acceptors. PMID:27920920

Graphene/multi-walled carbon nanotubes functionalized with an amine-terminated ionic liquid for determination of (Z)-3-(chloromethylene)-6-fluorothiochroman-4-one in urine.

PubMed

Chen, Huanhuan; Yuan, Yanan; Xiang, Can; Yan, Hongyuan; Han, Yehong; Qiao, Fengxia

2016-11-25

A new type of amine-terminated-ionic-liquid-functionalized graphene/multi-walled carbon nanotubes hybrid material (IL-G/MWCNTs) was synthesized and used as an adsorbent in miniaturized pipette tip solid-phase extraction (PT-SPE) coupled with liquid chromatography for the isolation and determination of (Z)-3-(chloromethylene)-6-fluorothiochroman-4-one (CMFT) in urine. Parameters for the preparation of IL-G/MWCNTs and the PT-SPE procedure, including the mass ratio of graphene oxide and oxidized multi-walled carbon nanotubes, the mass ratio of graphene oxide and the ionic liquid, and the type and volume of washing and elution solvents were optimized to achieve higher extraction efficiency. Good linearity of the method was achieved in the range 0.03-5.0μgmL -1 with a coefficient of determination (r 2 ) of 0.9999. The limits of detection and quantification were 0.009 and 0.030μgmL -1 , respectively. The intra- and inter-day precisions, expressed as relative standard deviations (RSDs), were evaluated by performing replicate analyses of samples spiked at 0.1μgmL -1 on the same day (n=6) and over three consecutive days, and were 4.8 and 5.5%, respectively. Recoveries between 73.9 and 93.9% were obtained at three spiking levels, with RSDs≤7.9%. Five batches of the adsorbent were investigated to confirm the reliability of the preparation method. Copyright © 2016 Elsevier B.V. All rights reserved.

Group A Streptococcal vaccine candidate: contribution of epitope to size, antigen presenting cell interaction and immunogenicity.

PubMed

Zaman, Mehfuz; Chandrudu, Saranya; Giddam, Ashwini K; Reiman, Jennifer; Skwarczynski, Mariusz; McPhun, Virginia; Moyle, Peter M; Batzloff, Michael R; Good, Michael F; Toth, Istvan

2014-12-01

Utilize lipopeptide vaccine delivery system to develop a vaccine candidate against Group A Streptococcus. Lipopeptides synthesized by solid-phase peptide synthesis-bearing carboxyl (C)-terminal and amino (N)-terminal Group A Streptococcus peptide epitopes. Nanoparticles formed were evaluated in vivo. Immune responses were induced in mice without additional adjuvant. We demonstrated for the first time that incorporation of the C-terminal epitope significantly enhanced the N-terminal epitope-specific antibody response and correlated with forming smaller nanoparticles. Antigen-presenting cells had increased uptake and maturation by smaller, more immunogenic nanoparticles. Antibodies raised by vaccination recognized isolates. Demonstrated the lipopeptidic nanoparticles to induce an immune response which can be influenced by the combined effect of epitope choice and size.

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.

Utilization of peptide carrier system to improve intestinal absorption: targeting prolidase as a prodrug-converting enzyme

NASA Technical Reports Server (NTRS)

Bai, J. P.; Hu, M.; Subramanian, P.; Mosberg, H. I.; Amidon, G. L.

1992-01-01

The feasibility of targeting prolidase as a peptide prodrug-converting enzyme has been examined. The enzymatic hydrolysis by prolidase of substrates for the peptide transporter L-alpha-methyldopa-pro and several dipeptide analogues without an N-terminal alpha-amino group (phenylpropionylproline, phenylacetylproline, N-benzoylproline, and N-acetylproline) was investigated. The Michaelis-Menten parameters Km and Vmax for L-alpha-methyldopa-pro are 0.09 +/- 0.02 mM and 3.98 +/- 0.25 mumol/min/mg protein, respectively. However, no hydrolysis of the dipeptide analogues without an N-terminal alpha-amino group is observed, suggesting that an N-terminal alpha-amino group is required for prolidase activity. These results demonstrate that prolidase may serve as a prodrug-converting enzyme for the dipeptide-type prodrugs, utilizing the peptide carrier for transport of prodrugs into the mucosal cells and prolidase, a cytosolic enzyme, to release the drug. However, a free alpha-amino group appears to be necessary for prolidase hydrolysis.

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.

Comparative analysis of the effects combined physical procedures and alpha-lipoic acid on the electroneurographic parameters of patients with distal sensorimotor diabetic polyneuropathy

PubMed Central

Grbovic, Vesna; Jurisic-Skevin, Aleksandra; Djukic, Svetlana; Stefanović, Srdjan; Nurkovic, Jasmin

2016-01-01

[Purpose] Painful diabetic polyneuropathy occurs as a complication in 16% of all patients with diabetes mellitus. [Subjects and Methods] A clinical, prospective open-label randomized intervention study was conducted of 60 adult patients, with distal sensorimotor diabetic neuropathy two groups of 30 patients, with diabetes mellitus type 2 with distal sensorimotor diabetic neuropathy. Patients in group A were treated with combined physical procedures, and patients in group B were treated with alpha lipoic acid. [Results] There where a statistically significant improvements in terminal latency and the amplitude of the action potential in group A patients, while group B patients showed a statistically significant improvements in conduction velocity and terminal latency of n. peroneus. Group A patients showed a statistically significant improvements in conduction velocity and terminal latency, while group B patients also showed a statistically significant improvements in conduction velocity and terminal latency. This was reflected in a significant improvements in electrophysiological parameters (conduction velocity, amplitude and latency) of the motor and sensory nerves (n. peroneus, n. suralis). [Conclusion] These results present further evidence justifying of the use of physical agents in the treatment of diabetic sensorimotor polyneuropathy. PMID:27065527

Highly porous organic polymers bearing tertiary amine group and their exceptionally high CO{sub 2} uptake capacities

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

Gomes, Ruth; Bhaumik, Asim, E-mail: msab@iacs.res.in

2015-02-15

We report a very simple and unique strategy for synthesis of a tertiary amine functionalized high surface area porous organic polymer (POP) PDVTA-1 through the co-polymerization of monomers divinylbenzene (DVB) and triallylamine (TAA) under solvothermal reaction conditions. Two different PDVTA-1 samples have been synthesized by varying the molar ratio of the monomers. The porous polymeric materials have been thoroughly characterized by solid state {sup 13}C CP MAS-NMR, FT-IR and UV–vis spectroscopy, N{sub 2} sorption, HR TEM and FE SEM to understand its chemical environment, nanostructure, bonding, morphology and related surface properties. PDVTA-1 with higher amine content (DVB/TAA=4.0) showed exceptionally highmore » CO{sub 2} uptake capacity of 85.8 wt% (19.5 mmol g{sup −1}) at 273 K and 43.69 wt% (9.93 mmol g{sup −1}) at 298 K under 3 bar pressure, whereas relatively low amine loaded material (DVB/TAA=7.0) shows uptake capacity of 59.2 wt% (13.45 mmol g{sup −1}) at 273 K and 34.36 wt% (7.81 mmol g{sup −1}) at 298 K. Highly porous nanostructure together with very high surface area and basicity at the surface due to the presence of abundant basic tertiary amine N-sites in the framework of PDVTA-1 could be responsible for very high CO{sub 2} adsorption. - Graphical abstract: Exceptionally high CO2 uptake (85.8 wt % at 273 K) has been observed over a high surface area porous organic polymer PDVTA-1 synthesized through copolymerization of divinylbenzene and triallyl amine. - Highlights: • Designing the synthesis of a new N-rich cross-linked porous organic polymer PDVTA-1. • PDVTA-1 showed mesoporosity with very high surface area of 903 m{sup 2} g{sup −1}. • High surface area and presence of basic sites facilitates the CO{sub 2} uptake. • PDVTA-1 showed exceptionally high CO{sub 2} adsorption capacity of 85.8 wt% at 273 K, 3 bar pressure.« less

Polymeric Coatings that Mimic the Endothelium: Combining Nitric Oxide Release with Surface-Bound Active Thrombomodulin and Heparin

PubMed Central

Wu, Biyun; Gerlitz, Bruce; Grinnell, Brian W.; Meyerhoff, Mark E.

2007-01-01

Multi-functional bilayer polymeric coatings are prepared with both controlled nitric oxide (NO) release and surface-bound active thrombomodulin (TM) alone or in combination with immobilized heparin. The outer-layer is made of CarboSil, a commercially available copolymer of silicone rubber (SR) and polyurethane (PU). The CarboSil is either carboxylated or aminated via an allophanate reaction with a diisocyanate compound followed by a urea-forming reaction between the generated isocyanate group of the polymer and the amine group of an amino acid (glycine), an oligopeptide (triglycine) or a diamine. The carboxylated CarboSil can then be used to immobilize TM through the formation of an amide bond between the surface carboxylic acid groups and the lysine residues of TM. Aminated CarboSil can also be employed to initially couple heparin to the surface, and then the carboxylic acid groups on heparin can be further used to anchor TM. Both surface-bound TM and heparin’s activity are evaluated by chromogenic assays and found to be at clinically significant levels. The underlying NO release layer is made with another commercial SR-PU copolymer (PurSil) mixed with a lipophilic NO donor (N-diazeniumdiolated dibutylhexanediamine (DBHD/N2O2)). The NO release rate can be tuned by changing the thickness of top coatings, and the duration of NO release at physiologically relevant levels can be as long as 2 weeks. The combination of controlled NO release as well as immobilized active TM and heparin from/on the same polymeric surface mimics the highly thromboresistant endothelium layer. Hence, such multifunctional polymer coatings should provide more blood-compatible surfaces for biomedical devices. PMID:17597201

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.

Aerobic biodegradation of amines in industrial saline wastewaters.

PubMed

Campo, Pablo; Platten, William; Suidan, Makram T; Chai, Yunzhou; Davis, John W

2011-11-01

The treatment of hypersaline wastewaters represents a challenge since high salt concentrations disrupt bacteria present in normal biological treatments. This study was conducted to determine the fate of amines in two hypersaline wastewaters obtained from an industrial treatment plant processing influents with 3% and 7% of NaCl. The compounds were aniline (ANL), 4,4'-methylenedianiline (4,4'-MDA), cyclohexylamine (CHA), N-(2-aminoethyl)ethanolamine (AEA), N,N-diethylethanolamine (DEA), N,N-bis(2-hydroxyethyl)methylamine (MDEA), and tris(2-hydroxyethyl)amine (TEA). Mixtures of these chemicals with a mixed liquor suspended solids concentration of 1000 mg L(-1) were prepared at two salinities (3% and 7% NaCl). Ethanolamines were readily biodegraded at both salinities, following first-order kinetics with half-lives ranging between 10 and 58 h. Hydroxyl groups present in the ethanolamines had a positive impact on the biodegradation. Salinity did not affect the biodegradation rate of TEA and MDEA, whereas AEA and DEA degraded faster in 3% NaCl. After 48h, CHA was metabolized within a 24-h period in 3% NaCl, while no degradation was observed in 7% NaCl. ANL exhibited lag phases in both salinities and, in the following 24-h period, ANL concentrations dropped 40% and disappeared after 48 h. 4,4'-MDA degraded in 3% NaCl (half-life of 123 h) and remained unaltered after 120 h in 7% NaCl. Copyright © 2011 Elsevier Ltd. All rights reserved.

Controlling the oxidation of bis-tridentate cobalt(ii) complexes having bis(2-pyridylalkyl)amines: ligand vs. metal oxidation.

PubMed

Anjana, S; Donring, S; Sanjib, P; Varghese, B; Murthy, Narasimha N

2017-08-22

Two bis-tridentate chelated cobalt(ii) complexes, which differ in the ligand structure by a methylene group, activate molecular oxygen (O 2 ), and give different oxidation products. The O 2 reaction of [Co II (pepma) 2 ] 2+ (1) with unsymmetrical 2-(2-pyridyl)-N-(2-pyridylmethyl)ethanamine (pepma) results in ligand oxidation, to the corresponding Co(ii) imine complex [Co II (pepmi) 2 ] 2+ (2). Contrastingly, the Co(ii) complex [Co II (bpma) 2 ] 2+ (3) of similar symmetrical bis(2-pyridylmethyl)amine (bpma), undergoes metal oxidation, yielding a cobalt(iii) complex, [Co III (bpma) 2 ] 2+ (4). The reversibility of the amine to imine conversion and the stability of the Co(ii) imine complex (2) are investigated. Furthermore, the solution dynamics of Co(ii) complexes are highlighted with the help of paramagnetic 1 H-NMR spectroscopy.

Effects of porcine pancreatic enzymes on the pancreas of hamsters. Part 2: carcinogenesis studies.

PubMed

Nozawa, Fumiaki; Yalniz, Mehmet; Saruc, Murat; Standop, Jens; Egami, Hiroshi; Pour, Parviz M

2012-09-10

Our previous study suggested that porcine pancreatic extract in hamsters with peripheral insulin resistance, normalizes insulin output, islet size and pancreatic DNA synthetic rate. It also inhibited the growth of human pancreatic cancer cells in nude mice. To examine the potential value of the porcine pancreatic extract in controlling pancreatic carcinogenesis in this model, the present experiment was performed. Hamsters were fed a high fat diet and four weeks later when insulin resistance emerges, they were divided into two groups. One group received 1 g/kg BW of porcine pancreatic extract in drinking water and the other group received tap water. One week later, when insulin output normalizes in porcine pancreatic extract-treated hamsters, a single subcutaneous injection of N-nitrosobis-(2-oxopropyl) amine (BOP) at a dose of 40 mg/kg BW was given to all hamsters. The experiment was terminated at 43 weeks after the porcine pancreatic extract treatment. The number and size of pancreatic tumors, blood glucose, insulin, amylase and lipase levels, the average size of islets and the number of insulin cells/islets were determined. The incidence of pancreatic cancer was significantly lower in the porcine pancreatic extract group (P=0.043), as well as the plasma insulin level and the size of the islets in the porcine pancreatic extract group were significantly lower (P<0.001) than in the control group. No significantly differences were found in the glucose level between the groups. These results show that porcine pancreatic extract has a potential to inhibit pancreatic cancer growth.

Photochemical key steps in the synthesis of surfactants from furfural-derived intermediates.

PubMed

Gassama, Abdoulaye; Ernenwein, Cédric; Hoffmann, Norbert

2009-01-01

Furfural is oxidized to 2[5H]-furanone by using hydrogen peroxide or to 5-hydroxy-2[5H]-furanone by using photo-oxygenation. An amine function is introduced by photochemically induced radical addition of tertiairy amines, some of which carry an n-alkyl side chain as hydrophobic moiety. These amines are produced from fatty aldehydes and cyclic secondary amines. The resulting adducts are transformed into amphoteric surfactants possessing an ammonium and a carboxylate function. Amphoteric (pK(N) and isoelectric point) and surfactant properties such as the critical micelle concentration and the adsorption efficiency are determined.

Synthesis of an N-aminopyrazinonium analogue of cytidine.

PubMed

Lee, T C; Chello, P L; Chou, T C; Templeton, M A; Parham, J C

1983-02-01

An N-aminated pyrazine analogue of cytidine, in which the pyrimidine N(3) ring nitrogen and C(4) amino group were replaced by a C-amino and an N-amino function, respectively, was prepared as a potential deaminase-resistant cytidine antimetabolite. The nucleoside 1,2-diamino-4-beta-D-ribofuranosylpyrazin-2-onium chloride (6) was a mild cytostatic agent but was neither a substrate for nor an inhibitor of mouse kidney cytidine deaminase. It ionized with a lower pKa than expected. The anion did not undergo the dimerization usually observed with N-imino heterocyclic ylides but unerwent hydrolysis of the 2-amino group to yield a 1-aminopyrazine-2,3-dione nucleoside.

Microwave assisted IMDAF# reaction: microwave irradiation applied with success to cycloaddition reaction of N-propargyl-N-p-tolyl-N-2-furfurylamines.

PubMed

Mance, Ana Dunja; Jakopcić, Kresimir

2005-01-01

The new tertiary furfurylamine with triple bond as a dienophylic part i.e. N-(5-methyl-2-furfuryl)-N-prop-2-ynyl-p-toluidine (1) was prepared and the intramolecular Diels-Alder reaction of the amine (1) was performed under microwave irradiation conditions and by heating a benzene solution of the amine under nitrogen. Comparing the results of the usual thermal and the MAOS reaction, we confirmed our expectations that MAOS could promote the outcome of IMDA reaction of the suitably N-substituted tertiary 2-furfuryl-amines. In the present example, N-p-tolyl-5-methyl-5,7a-dihydro-5,7a-epoxyisoindoline was obtained in much better yield and of higher purity.

Design and synthesis of dihydroisoquinolones for fragment-based drug discovery (FBDD).

PubMed

Palmer, Nick; Peakman, Torren M; Norton, David; Rees, David C

2016-02-07

This study describes general synthesis aspects of fragments for FBDD, as illustrated by the dihydroisoquinolones 1-3. Previous Rh(III) methodology is extended to incorporate amines, heteroatoms (N and S), and substituents (halogen, ester) as potential binding groups and/or synthetic growth points for fragment-to-lead elaboration.

Copper/amino acid catalyzed cross-couplings of aryl and vinyl halides with nucleophiles.

PubMed

Ma, Dawei; Cai, Qian

2008-11-18

Copper-assisted Ullmann-type coupling reactions are valuable transformations for organic synthesis. Researchers have extensively applied these reactions in both academic and industrial settings. However, two important issues, the high reaction temperatures (normally above 150 degrees C) and the stoichiometric amounts of copper necessary, have greatly limited the reaction scope. To solve these problems, we and other groups have recently explored the use of special ligands to promote these coupling reactions. We first showed that the structure of alpha-amino acids can accelerate Cu-assisted Ullmann reactions, leading to the coupling reactions of aryl halides and alpha-amino acids at 80-90 degrees C. In response to these encouraging results, we also discovered that an l-proline ligand facilitated the following transformations: (1) coupling of aryl halides with primary amines, cyclic secondary amines, and N-containing heterocycles at 40-90 degrees C; (2) coupling of aryl halides with sulfinic acid salts at 80-95 degrees C; (3) azidation of aryl halides and vinyl halides with sodium azide at 40-95 degrees C; (4) coupling of aryl halides with activated methylene compounds at 25-50 degrees C. In addition, we found that N,N-dimethylglycine as a ligand facilitated Cu-catalyzed biaryl ether formation at 90 degrees C. Moreover, Sonogashira reactions worked in the absence of palladium and phosphine ligands, forming enamides from vinyl halides and amides at temperatures ranging from ambient temperature up to 80 degrees C. Furthermore, we discovered that an ortho-amide group can accelerate some Ullmann-type reactions. This functional group in combination with other ligand effects allowed for aryl amination or biaryl ether formation at ambient temperature. The coupling between aryl halides and activated methylene compounds even proceeded at -45 degrees C to enantioselectively form a quaternary carbon center. Taking advantage of these results, we developed several novel approaches for the synthesis of pharmaceutically important heterocycles: 1,2-disubstituted benzimidazoles, polysubstituted indoles, N-substituted 1,3-dihydrobenzimidazol-2-ones, and substituted 3-acyl oxindoles. Our results demonstrate that an l-proline or N,N-dimethylglycine ligand can facilitate most typical Ullmann-type reactions, with reactions occurring under relatively mild conditions and using only 2-20 mol % copper catalysts. These conveniently available and inexpensive catalytic systems not only accelerate the reactions but also tolerate many more functional groups. Thus, they should find considerable application in organic synthesis.

Practical Aerobic Oxidations of Alcohols and Amines with Homogeneous Cu/TEMPO and Related Catalyst Systems

PubMed Central

Ryland, Bradford L.; Stahl, Shannon S.

2014-01-01

Alcohol and amine oxidations are common reactions in laboratory and industrial synthesis of organic molecules. Aerobic oxidation methods have long been sought for these transformations, but few practical methods exist that offer advantages over traditional oxidation methods. Recently developed homogeneous Cu/TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidinyl-N-oxyl) and related catalyst systems appear to fill this void. The reactions exhibit high levels of chemoselectivity and broad functional-group tolerance, and they often operate efficiently at room temperature with ambient air as the oxidant. These advances, together with their historical context and recent applications, are highlighted in this minireview. PMID:25044821

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.

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

A novel route to recognizing quaternary ammonium cations using electrospray mass spectrometry.

PubMed

Shackman, Holly M; Ding, Wei; Bolgar, Mark S

2015-01-01

Characterizing and elucidating structures is a commonplace and necessary activity in the pharmaceutical industry with mass spectrometry and NMR being the primary tools for analysis. Although many functional groups are readily identifiable, quaternary ammonium cations have proven to be difficult to unequivocally identify using these techniques. Due to the lack of an N-H bond, quaternary ammonium groups can only be detected in the (1)H NMR spectra by weak signals generated from long-range (14)N-H coupling, which by themselves are inconclusive evidence of a quaternary ammonium functional group. Due to their low intensity, these signals are frequently not detected. Additionally, ions cannot be differentiated in a mass spectrum as an M(+) or [M + H](+) ion without prior knowledge of the compound's structure. In order to utilize mass spectrometry as a tool for determining this functionality, ion cluster formation of quaternary ammonium cations and non-quaternary amines was studied using electrospray ionization. Several mobile phase modifiers were compared; however, the addition of small amounts of trifluoroacetic acid proved superior in producing characteristic and intense [M +2TFA](-) clusters for compounds containing quaternary ammonium cations when using negative electrospray. By fragmenting this characteristic ion using CID, nearly all compounds studied could be unambiguously identified as containing a quaternary ammonium cation or a non-quaternary amine attributable to the presence (non-quaternary amine) or absence (quaternary ammonium cation) of the resulting [2TFA + H](-) ion in the product spectra. This method of analysis provides a rapid, novel, and reliable technique for indicating the presence of quaternary ammonium cations in order to aid in structural elucidation.

NO3 and OH initiated secondary aerosol formation from aliphatic amines - salt formation and effect of water vapor

USDA-ARS?s Scientific Manuscript database

Aliphatic amines enter the atmosphere from a variety of sources, and have been detected existing in gas and particle phases in the atmosphere. Similar to ammonia, amines can form inorganic salt through acid-base reactions. However, the atmospheric behavior of amines with atmospheric oxidants (e.g. n...

Tertiary-amine-containing thermo- and pH-sensitive hydrophilic ABA triblock copolymers: effect of different tertiary amines on thermally induced sol-gel transitions.

PubMed

Henn, Daniel M; Wright, Roger A E; Woodcock, Jeremiah W; Hu, Bin; Zhao, Bin

2014-03-11

This Article reports on the synthesis of a series of well-defined, tertiary-amine-containing ABA triblock copolymers, composed of a poly(ethylene oxide) (PEO) central block and thermo- and pH-sensitive outer blocks, and the study of the effect of different tertiary amines on thermally induced sol-gel transition temperatures (T(sol-gel)) of their 10 wt % aqueous solutions. The doubly responsive ABA triblock copolymers were prepared from a difunctional PEO macroinitiator by atom transfer radical polymerization of methoxydi(ethylene glycol) methacrylate and ethoxydi(ethylene glycol) methacrylate at a feed molar ratio of 30:70 with ∼5 mol % of either N,N-diethylaminoethyl methacrylate (DEAEMA), N,N-diisopropylaminoethyl methacrylate, or N,N-di(n-butyl)aminoethyl methacrylate. The chain lengths of thermosensitive outer blocks and the molar contents of tertiary amines were very similar for all copolymers. Using rheological measurements, we determined the pH dependences of T(sol-gel) of 10 wt % aqueous solutions of these copolymers in a phosphate buffer. The T(sol-gel) versus pH curves of all polymers exhibited a sigmoidal shape. The T(sol-gel) increased with decreasing pH; the changes were small on both high and low pH sides. At a specific pH, the T(sol-gel) decreased with increasing the hydrophobicity of the tertiary amine, and upon decreasing pH the onset pH value for the T(sol-gel) to begin to increase noticeably was lower for the more hydrophobic tertiary amine-containing copolymer. In addition, we studied the effect of different tertiary amines on the release behavior of FITC-dextran from 10 wt % micellar gels in an acidic medium at 37 and 27 °C. The release profiles for three studied hydrogels at 37 °C were essentially the same, suggesting that the release was dominated by the diffusion of FITC-dextran. At 27 °C, the release was significantly faster for the DEAEMA-containing copolymer, indicating that both diffusion and gel dissolution contributed to the release at this temperature.

Doping Level of Boron-Doped Diamond Electrodes Controls the Grafting Density of Functional Groups for DNA Assays.

PubMed

Švorc, Ĺubomír; Jambrec, Daliborka; Vojs, Marian; Barwe, Stefan; Clausmeyer, Jan; Michniak, Pavol; Marton, Marián; Schuhmann, Wolfgang

2015-09-02

The impact of different doping levels of boron-doped diamond on the surface functionalization was investigated by means of electrochemical reduction of aryldiazonium salts. The grafting efficiency of 4-nitrophenyl groups increased with the boron levels (B/C ratio from 0 to 20,000 ppm). Controlled grafting of nitrophenyldiazonium was used to adjust the amount of immobilized single-stranded DNA strands at the surface and further on the hybridization yield in dependence on the boron doping level. The grafted nitro functions were electrochemically reduced to the amine moieties. Subsequent functionalization with a succinic acid introduced carboxyl groups for subsequent binding of an amino-terminated DNA probe. DNA hybridization significantly depends on the probe density which is in turn dependent on the boron doping level. The proposed approach opens new insights for the design and control of doped diamond surface functionalization for the construction of DNA hybridization assays.

New recombinant cyclohexylamine oxidase variants for deracemization of secondary amines by orthogonally assaying designed mutants with structurally diverse substrates

NASA Astrophysics Data System (ADS)

Li, Guangyue; Yao, Peiyuan; Cong, Peiqian; Ren, Jie; Wang, Lei; Feng, Jinhui; Lau, Peter C. K.; Wu, Qiaqing; Zhu, Dunming

2016-05-01

To further expand the substrate range of the cyclohexylamine oxidase (CHAO) from Brevibacterium oxydans, a library of diverse mutants was created and assayed toward a group of structurally diverse substrates. Among them, mutants T198A and M226A exhibited enhanced activity relative to wt CHAO for most (S)-enantiomers of primary amines and some secondary amines. While mutants T198I, L199I, L199F, M226I and M226T were more active than wt CHAO toward the primary amines, mutants T198F, L199T, Y321A, Y321T, Y321I and Y321F enhanced the enzyme activity toward the secondary amines. In particular, mutant Y321I displayed an enhanced catalytic efficiency toward 1-(4-methoxybenzyl)-1, 2, 3, 4, 5, 6, 7, 8-octahydroisoquinoline (13). Whereas a double mutant, Y321I/M226T, acted on (S)-N-(prop-2-yn-1-yl)-2, 3-dihydro-1H-inden-1-amine [(S)-8]. Since (R)-8 is an irreversible inhibitor of monoamine oxidase and (S)-13 is an intermediate of dextromethorphan, a cough suppressant drug, deracemizations of 8 and 13 were carried out with crude enzyme extracts of the respective mutants. This resulted in 51% and 78% isolated yields of (R)-8 and (S)-13, respectively, each with high enantiomeric excess (93% and 99% ee). The results demonstrated the application potential of the evolved CHAO mutants in drug synthesis requiring chiral secondary amines.

New recombinant cyclohexylamine oxidase variants for deracemization of secondary amines by orthogonally assaying designed mutants with structurally diverse substrates

PubMed Central

Li, Guangyue; Yao, Peiyuan; Cong, Peiqian; Ren, Jie; Wang, Lei; Feng, Jinhui; Lau, Peter C.K.; Wu, Qiaqing; Zhu, Dunming

2016-01-01

To further expand the substrate range of the cyclohexylamine oxidase (CHAO) from Brevibacterium oxydans, a library of diverse mutants was created and assayed toward a group of structurally diverse substrates. Among them, mutants T198A and M226A exhibited enhanced activity relative to wt CHAO for most (S)-enantiomers of primary amines and some secondary amines. While mutants T198I, L199I, L199F, M226I and M226T were more active than wt CHAO toward the primary amines, mutants T198F, L199T, Y321A, Y321T, Y321I and Y321F enhanced the enzyme activity toward the secondary amines. In particular, mutant Y321I displayed an enhanced catalytic efficiency toward 1-(4-methoxybenzyl)-1, 2, 3, 4, 5, 6, 7, 8-octahydroisoquinoline (13). Whereas a double mutant, Y321I/M226T, acted on (S)-N-(prop-2-yn-1-yl)-2, 3-dihydro-1H-inden-1-amine [(S)-8]. Since (R)-8 is an irreversible inhibitor of monoamine oxidase and (S)-13 is an intermediate of dextromethorphan, a cough suppressant drug, deracemizations of 8 and 13 were carried out with crude enzyme extracts of the respective mutants. This resulted in 51% and 78% isolated yields of (R)-8 and (S)-13, respectively, each with high enantiomeric excess (93% and 99% ee). The results demonstrated the application potential of the evolved CHAO mutants in drug synthesis requiring chiral secondary amines. PMID:27138090

PEGylated dendrimer-entrapped gold nanoparticles for in vivo blood pool and tumor imaging by computed tomography.

PubMed

Peng, Chen; Zheng, Linfeng; Chen, Qian; Shen, Mingwu; Guo, Rui; Wang, Han; Cao, Xueyan; Zhang, Guixiang; Shi, Xiangyang

2012-02-01

We report the synthesis and characterization of dendrimer-entrapped gold nanoparticles (Au DENPs) modified by polyethylene glycol (PEG) with enhanced biocompatibility for computed tomography (CT) imaging applications. In this study, amine-terminated poly(amidoamine) dendrimers of generation 5 (G5.NH(2)) modified by PEG monomethyl ether (G5.NH(2)-mPEG(20)) were used as templates to synthesize Au DENPs, followed by acetylation of the remaining dendrimer terminal amines to generate PEGylated Au DENPs. The partial PEGylation modification of dendrimer terminal amines allows high loading of Au within the dendrimer interior, and consequently by simply varying the Au salt/dendrimer molar ratio, the size of the PEGylated Au DENPs can be controlled at a range of 2-4 nm with a narrow size distribution. The formed PEGylated Au DENPs are water-dispersible, stable in a pH range of 5-8 and a temperature range of 0-50 °C, and non-cytotoxic at a concentration as high as 100 μm. X-ray absorption coefficient measurements show that the attenuation intensity of the PEGylated Au DENPs is much higher than that of Omnipaque with iodine concentration similar to Au. With the sufficiently long half-decay time demonstrated by pharmacokinetics studies, the PEGylated Au DENPs enabled not only X-ray CT blood pool imaging of mice and rats after intravenous injection of the particles, but also effective CT imaging of a xenograft tumor model in nude mice. These findings suggest that the designed PEGylated Au DENPs can be used as a promising contrast agent with enhanced biocompatibility for CT imaging of various biological systems, especially in cancer diagnosis. Copyright © 2011 Elsevier Ltd. All rights reserved.

New pyrrole inhibitors of monoamine oxidase: synthesis, biological evaluation, and structural determinants of MAO-A and MAO-B selectivity.

PubMed

La Regina, Giuseppe; Silvestri, Romano; Artico, Marino; Lavecchia, Antonio; Novellino, Ettore; Befani, Olivia; Turini, Paola; Agostinelli, Enzo

2007-03-08

A series of new pyrrole derivatives have been synthesized and evaluated for their monoamine oxidase (MAO) A and B inhibitory activity and selectivity. N-Methyl,N-(benzyl),N-(pyrrol-2-ylmethyl)amine (7) and N-(2-benzyl),N-(1-methylpyrrol-2-ylmethyl)amine (18) were the most selective MAO-B (7, SI = 0.0057) and MAO-A (18, SI = 12500) inhibitors, respectively. Docking and molecular dynamics simulations gave structural insights into the MAO-A and MAO-B selectivity. Compound 18 forms an H-bond with Gln215 through its protonated amino group into the MAO-A binding site. This H-bond is absent in the 7/MAO-A complex. In contrast, compound 7 places its phenyl ring into an aromatic cage of the MAO-B binding pocket, where it forms charge-transfer interactions. The slightly different binding pose of 18 into the MAO-B active site seems to be forced by a bulkier Tyr residue, which replaces a smaller Ile residue present in MAO-A.

Interactions and encapsulation of vitamins C, B3, and B6 with dendrimers in water.

PubMed

Boisselier, Elodie; Liang, Liyuan; Dalko-Csiba, Maria; Ruiz, Jaime; Astruc, Didier

2010-05-25

Titrations of commercial diaminobutane (DAB) and polyamidoamine (PAMAM) dendrimers by vitamins C (ascorbic acid, AA), B(3) (nicotinic acid), and B(6) (pyridoxine) were monitored by (1)H NMR spectroscopy using the chemical shifts of both dendrimer and vitamin protons and analyzed by comparison with the titration of propylamine. Quaternarizations of the terminal primary amino groups and intradendritic tertiary amino groups, which are nearly quantitative with vitamin C, were characterized by more or less sharp variations (Deltadelta) of the (1)H chemical shift (delta) at the equivalence points. The peripheral primary amino groups of the DAB dendrimers were quaternarized first, but not selectively, whereas a sharp chemical-shift variation was recorded for the inner methylene protons near the tertiary amines, thereby indicating encapsulation, when all the dendritic amines were quaternarized. With DAB-G5-64-NH(2), some excess acid is required to protonate the inner amino groups, presumably because of basicity decrease due to excess charge repulsion. On the other hand, this selectivity was not observed with PAMAM dendrimers. The special case of the titration of the dendrimers by vitamin B(6) indicates only dominant supramolecular hydrogen-bonding interactions and no quaternarization, with core amino groups being privileged, which indicates the strong tendency to encapsulate vitamins. With vitamin B(3), a carboxylic acid, titration of DAB-G3-16-NH(2) shows that only six peripheral amino groups are protonated on average, even with excess vitamin B(3), because protonation is all the more difficult due to increased charge repulsion, as positive charges accumulate around the dendrimer. Inner amino groups interact with this vitamin, however, thus indicating encapsulation presumably with supramolecular hydrogen bonding without much charge transfer.

The Surface Chemistry of Metal Chalcogenide Nanocrystals

NASA Astrophysics Data System (ADS)

Anderson, Nicholas Charles

The surface chemistry of metal chalcogenide nanocrystals is explored through several interrelated analytical investigations. After a brief discussion of the nanocrystal history and applications, molecular orbital theory is used to describe the electronic properties of semiconductors, and how these materials behave on the nanoscale. Quantum confinement plays a major role in dictating the optical properties of metal chalcogenide nanocrystals, however surface states also have an equally significant contribution to the electronic properties of nanocrystals due to the high surface area to volume ratio of nanoscale semiconductors. Controlling surface chemistry is essential to functionalizing these materials for biological imaging and photovoltaic device applications. To better understand the surface chemistry of semiconducting nanocrystals, three competing surface chemistry models are presented: 1.) The TOPO model, 2.) the Non-stoichiometric model, and 3.) the Neutral Fragment model. Both the non-stoichiometric and neutral fragment models accurately describe the behavior of metal chalcogenide nanocrystals. These models rely on the covalent bond classification system, which divides ligands into three classes: 1.) X-type, 1-electron donating ligands that balance charge with excess metal at the nanocrystal surface, 2.) L-type, 2-electron donors that bind metal sites, and 3.) Z-type, 2-electron acceptors that bind chalcogenide sites. Each of these ligand classes is explored in detail to better understand the surface chemistry of metal chalcogenide nanocrystals. First, chloride-terminated, tri-n-butylphosphine (Bu 3P) bound CdSe nanocrystals were prepared by cleaving carboxylate ligands from CdSe nanocrystals with chlorotrimethylsilane in Bu3P solution. 1H and 31P{1H} nuclear magnetic resonance spectra of the isolated nanocrystals allowed assignment of distinct signals from several free and bound species, including surface-bound Bu3P and [Bu3P-H]+[Cl]- ligands as well as a Bu3P complex of cadmium chloride. Nuclear magnetic resonance spectroscopy supports complete cleavage of the X-type carboxylate ligands. Combined with measurements of the Se:Cd:Cl ratio using Rutherford backscattering spectrometry, these studies support a structural model of nanocrystals where chloride ligands terminate the crystal lattice by balancing the charges of excess Cd2+ ions. The adsorption of dative phosphine ligands leads to nanocrystals who's solubility is afforded by reversibly bound and readily exchanged L-type ligands, e.g. primary amines and phosphines. The other halides (Br and I) can also be used to prepare Bu 3P-bound, halide-terminated CdSe nanocrystals, however these nanocrystals are not soluble after exchange. The change in binding affinity of Bu 3P over the halide series is briefly discussed. Next, we report a series of L-type ligand exchanges using Bu3P-bound, chloride-terminated CdSe nanocrystals with several Lewis bases, including aromatic, cyclic, and non-cyclic sulfides, and ethers; primary, secondary, and tertiary amines and phosphines; tertiary phosphine chalcogenides; primary alcohols, isocyanides, and isothiocyanides. Using 31P nuclear magnetic resonance spectroscopy, we establish a relative binding affinity for these ligands that reflects electronic considerations but is dominated primarily by steric interactions, as determined by comparing binding affinity to Tolmann cone angles. We also used chloride-terminated CdSe nanocrystals to explore the reactivity of ionic salts at nanocrystal surfaces. These salts, particularly [Bu3P-H]+[Cl]-, bind nanocrystals surfaces as L-type ligands, making them soluble in polar solvents such as acetonitrile. This information should provide insight for rational ligand design for future applications involving metal chalcogenide nanocrystals. The strongest ligand, primary n-alkylamine, rapidly displace the Bu3P from halide-terminated CdSe nanocrystals, leading to amine-bound nanocrystals with higher dative ligand coverages and greatly increased photoluminescence quantum yields. The importance of ligand coverage to both the UV-visible absorption and photoluminescence spectra are discussed. (Abstract shortened by UMI.).

Synthesis of a Potent Aminopyridine-Based nNOS-Inhibitor by Two Recent No-Carrier-Added (18)F-Labelling Methods.

PubMed

Drerup, Christian; Ermert, Johannes; Coenen, Heinz H

2016-09-01

Nitric oxide (NO), an important multifunctional signaling molecule, is produced by three isoforms of NO-synthase (NOS) and has been associated with neurodegenerative disorders. Selective inhibitors of the subtypes iNOS (inducible) or nNOS (neuronal) are of great interest for decoding neurodestructive key factors, and (18)F-labelled analogues would allow investigating the NOS-function by molecular imaging with positron emission tomography. Especially, the highly selective nNOS inhibitor 6-((3-((3-fluorophenethylamino)methyl)phenoxy)methyl)-4-methylpyridin-2-amine (10) lends itself as suitable compound to be (18)F-labelled in no-carrier-added (n.c.a.) form. For preparation of the (18)F-labelled nNOS-Inhibitor [(18)F]10 a "build-up" radiosynthesis was developed based on a corresponding iodonium ylide as labelling precursor. The such activated phenethyl group of the compound was efficiently and regioselectively labelled with n.c.a. [(18)F]fluoride in 79% radiochemical yield (RCY). After conversion by reductive amination and microwave assisted displacement of the protecting groups, the desired nNOS-inhibitor was obtained in about 15% total RCY. Alternatively, for a simplified "late-stage" (18)F-labelling procedure a corresponding boronic ester precursor was synthesized and successfully used in a newer, copper(II) mediated n.c.a. (18)F-fluoro-deboroniation reaction, achieving the same total RCY. Thus, both methods proved comparatively suited to provide the highly selective NOS-inhibitor [(18)F]10 as probe for preclinical in vivo studies.

Medical expenditure and family satisfaction between hospice and general care in terminal cancer patients in Taiwan.

PubMed

Lin, Wen-Yuan; Chiu, Tai-Yuan; Hsu, Hua-Shai; Davidson, Lance E; Lin, Tsann; Cheng, Kao-Chi; Chiu, Chang-Fang; Li, Chia-Ing; Chiu, Yi-Wen; Lin, Cheng-Chieh; Liu, Chiu-Shong

2009-10-01

As the number of terminal cancer patients increases, several care models have been adopted to provide better care quality and reduce medical expenditure. This study compared inpatient medical expenditure and family satisfaction in a hospice ward (HW) and general ward (GW) for terminal cancer patients in Taiwan. We enrolled terminal cancer patients who were admitted and died during the same admission period in a tertiary care hospital in Taiwan from January 2003 to December 2005. These patients were allocated into three groups: inpatient care in HW alone; inpatient care in GW alone; and inpatient care in mixed group (initially in GW, then transferred to HW). Inpatient medical expenditure and family satisfaction were compared between the three groups. A total of 1942 patients were recruited and allocated into HW (n = 292), GW (n = 1511) and mixed (n = 139) groups. The average medical expenditure per person or per inpatient day was lower in the HW than the GW or mixed group. Subjects who had ever been admitted to the intensive care unit or received cardiopulmonary resuscitation in the GW or mixed groups required more expenditure on medical care than that in the HW group. Daily medical expenditure in the HW group also was much lower than that in the GW and mixed groups, based on length of stay and cancer type. The family satisfaction score was significantly higher in the mixed and/or HW group than the GW group. For terminal cancer patients, hospice care can improve family satisfaction while reducing medical expenditure in Taiwan.

Mechanistic and Structural Analysis of a Drosophila melanogaster Enzyme, Arylalkylamine N-Acetyltransferase Like 7, an Enzyme That Catalyzes the Formation of N-Acetylarylalkylamides and N-Acetylhistamine.

PubMed

Dempsey, Daniel R; Jeffries, Kristen A; Handa, Sumit; Carpenter, Anne-Marie; Rodriguez-Ospina, Santiago; Breydo, Leonid; Merkler, David J

2015-04-28

Arylalkylamine N-acetyltransferase like 7 (AANATL7) catalyzes the formation of N-acetylarylalkylamides and N-acetylhistamine from acetyl-CoA and the corresponding amine substrate. AANATL7 is a member of the GNAT superfamily of >10000 GCN5-related N-acetyltransferases, many members being linked to important roles in both human metabolism and disease. Drosophila melanogaster utilizes the N-acetylation of biogenic amines for the inactivation of neurotransmitters, the biosynthesis of melatonin, and the sclerotization of the cuticle. We have expressed and purified D. melanogaster AANATL7 in Escherichia coli and used the purified enzyme to define the substrate specificity for acyl-CoA and amine substrates. Information about the substrate specificity provides insight into the potential contribution made by AANATL7 to fatty acid amide biosynthesis because D. melanogaster has emerged as an important model system contributing to our understanding of fatty acid amide metabolism. Characterization of the kinetic mechanism of AANATL7 identified an ordered sequential mechanism, with acetyl-CoA binding first followed by histamine to generate an AANATL7·acetyl-CoA·histamine ternary complex prior to catalysis. Successive pH-activity profiling and site-directed mutagenesis experiments identified two ionizable groups: one with a pKa of 7.1 that is assigned to Glu-26 as a general base and a second pKa of 9.5 that is assigned to the protonation of the thiolate of the coenzyme A product. Using the data generated herein, we propose a chemical mechanism for AANATL7 and define functions for other important amino acid residues involved in substrate binding and regulation of catalysis.

N-propargylbenzylamine, a major metabolite of pargyline, is a potent inhibitor of monoamine oxidase type B in rats in vivo: a comparison with deprenyl.

PubMed Central

Karoum, F.

1987-01-01

In an effort to explore the contribution of the metabolites of pargyline towards the in vivo inhibition of monoamine oxidase (MAO), the effects of pargyline and its major metabolites on the production and metabolism of a number of biogenic amines were studied in rats. The administration of pargyline gave rise to three major ethyl acetate extractable metabolites: benzylamine, N-methylbenzylamine and N-propargylbenzylamine (NPB). Only NPB demonstrated in vivo monoamine oxidase inhibitory properties at an acute dose of 30 mg kg-1. The acute effects of pargyline, NPB, and deprenyl on urine and brain concentrations of a number of biogenic amines (phenylethylamine (PEA), m- and p-tyramine, noradrenaline (NA), dopamine, and 5-hydroxytryptamine (5-HT) and their metabolites were evaluated. Increased urine and brain concentrations of PEA were considered to represent in vivo inhibition of type B MAO while decreased concentrations of NA and 5-HT metabolites were regarded as indicators of an in vivo inhibition of MAO type A. NPB, like deprenyl and pargyline, significantly increased urine and brain PEA while only pargyline reduced 5-HT metabolism, suggesting that the metabolism of pargyline to NPB may contribute towards the MAO type B inhibitory effects of pargyline in vivo. Since the therapeutic benefits of MAO inhibitors in clinical practice usually require some period of chronic treatment, the chronic effects of repeated 14 daily doses of the above MAO inhibitors on central and peripheral biogenic amines were evaluated at the following times: during treatment, one day and five days after termination of treatment. The biochemical changes observed during the course of chronic NPB, pargyline and deprenyl treatments generally follow the expected in vitro characteristics of these drugs, but the detailed changes observed suggest clear differences. For example, the in vivo effect of pargyline on urine 5-hydroxyindoleacetic acid excretion was considerably weaker than its effect on the excretion of NA and dopamine metabolites. These changes are opposite to the in vitro effects of pargyline on 5-HT, dopamine and NA oxidative deamination. Inhibitions of the metabolism of all the amines studied were clearly observed during chronic MAOI treatments, but these effects were less evident five days after the end of treatment, suggesting an almost normal metabolism of biogenic amines. It is concluded that while MAO inhibitors may be the primary compound responsible for MAO inhibition, the effects of their metabolites in some cases may also play equally important roles in the regulation of monoamines both in the periphery and the brain.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:3103805

Nuclear Magnetic Resonance Shift Reagents: Abnormal 13C Shifts Produced by Complexation of Lanthanide Chelates with Saturated Amines and n-Butyl Isocyanide

PubMed Central

Marzin, Claude; Leibfritz, Dieter; Hawkes, Geoffrey E.; Roberts, John D.

1973-01-01

Lanthanide-induced shfits of 13C nuclear magnetic resonances are reported for several amines and n-butyl isocyanide. Contact contributions to such shifts, especially of β carbons, are clearly important for the chelates of Eu+3 and Pr+3. The importance of contact terms is shown to change in a rather predictable manner with the structure of the amine. PMID:16592062

Allylic Amination and N-Arylation-Based Domino Reactions Providing Rapid Three-Component Strategies to Fused Pyrroles with Different Substituted Patterns

PubMed Central

Jiang, Bo; Li, Ying; Tu, Man-Su; Wang, Shu-Liang; Tu, Shu-Jiang; Li, Guigen

2012-01-01

New three-component domino reaction providing divergent approaches to multi-functionalized fused pyrroles with different substituted patterns have been established (40 examples). The direct C(sp3)–N bond formation was achieved through intermolecular allylic amination in a one-pot operation; and N-arylation of amines was realized by varying N-amino acid enaminones. The reaction is easy to perform simply by mixing three common reactants in acetic acid under microwave heating. The reaction proceeds at fast rates and can be finished within 30 min, which makes workup convenient to give good chemical yields. PMID:22852549

Effect of nutritional support on terminally ill patients with cancer in a palliative care unit.

PubMed

Amano, Koji; Morita, Tatsuya; Baba, Mika; Kawasaki, Muneyoshi; Nakajima, Shinichiro; Uemura, Minako; Kobayashi, Yuka; Hori, Moeko; Wakayama, Hiroshi

2013-11-01

The role of nutritional support on terminally ill patients with cancer in a palliative care unit has not been clarified. A total of 63 patients were retrospectively investigated; the patients receiving individualized nutritional support (intervention group [n = 22]) were compared to the others (control group [n = 41]). The intervention group received individualized nutritional support. There were no significant differences in the characteristics of patients between the groups. The prevalence of bedsores was significantly lower in the intervention group (14% vs 46%, P = .012). The prevalence of edema and the use of antibiotic therapies tended to be lower in the intervention group than in the control group (36% vs 54%, P = .19; 14% vs 27%, P = .34, respectively). Some terminally ill patients with cancer in a palliative care unit might benefit from nutritional support.

Coupling Reagent for UV/vis Absorbing Azobenzene-Based Quantitative Analysis of the Extent of Functional Group Immobilization on Silica.

PubMed

Choi, Ra-Young; Lee, Chang-Hee; Jun, Chul-Ho

2018-05-18

A methallylsilane coupling reagent, containing both a N-hydroxysuccinimidyl(NHS)-ester group and a UV/vis absorbing azobenzene linker undergoes acid-catalyzed immobilization on silica. Analysis of the UV/vis absorption band associated with the azobenzene group in the adduct enables facile quantitative determination of the extent of loading of the NHS groups. Reaction of NHS-groups on the silica surface with amine groups of GOx and rhodamine can be employed to generate enzyme or dye-immobilized silica for quantitative analysis.

A general method for N-methylation of amines and nitro compounds with dimethylsulfoxide.

PubMed

Jiang, Xue; Wang, Chao; Wei, Yawen; Xue, Dong; Liu, Zhaotie; Xiao, Jianliang

2014-01-03

DMSO methylates a broad range of amines in the presence of formic acid, providing a novel, green and practical method for amine methylation. The protocol also allows the one-pot transformation of aromatic nitro compounds into dimethylated amines in the presence of a simple iron catalyst. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Rare Terminal Dinitrogen Complex of Chromium

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

Mock, Michael T.; Chen, Shentan; Rousseau, Roger J.

The reduction of dinitrogen to ammonia from N2 and H2 is currently carried out by the Haber-Bosch process, an energy intensive process that requires high pressures and high temperatures and accounts for the production of millions of tons of ammonia per year. The development of a catalytic, energy-efficient process for N2 reduction is of great interest and remains a formidable challenge. In this communication, we are reporting the preparation, characterization and computational electronic structure analysis of a rare 'Chatt-type' ((P-P)2M(N2)2, P-P = diphosphine ligand) complex of chromium, cis-[Cr(N2)2(PPh2NBn2)2] and its reactivity with CO. This complex is supported by the diphosphinemore » ligand PPh2NBn2, containing non-coordinating pendant amine bases, to serve as proton relays. Future studies for this complex are aimed at answering fundamental questions regarding the role of proton relays in the second coordination sphere in their ability to facilitate proton movement from an external acid to metal-bound dinitrogen ligands in the challenging multi-proton/electron reduction of N2 to ammonia.« less

Functionalized Congeners of P2Y1 Receptor Antagonists:

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

de Castro, Sonia; Maruoka, Hiroshi; Hong, Kunlun

2010-01-01

The P2Y{sub 1} receptor is a prothrombotic G protein-coupled receptor (GPCR) activated by ADP. Preference for the North (N) ring conformation of the ribose moiety of adenine nucleotide 3',5'-bisphosphate antagonists of the P2Y{sub 1} receptor was established by using a ring-constrained methanocarba (a bicyclo[3.1.0]hexane) ring as a ribose substitute. A series of covalently linkable N{sup 6}-methyl-(N)-methanocarba-2'-deoxyadenosine-3',5'-bisphosphates containing extended 2-alkynyl chains was designed, and binding affinity at the human (h) P2Y{sub 1} receptor determined. The chain of these functionalized congeners contained hydrophilic moieties, a reactive substituent, or biotin, linked via an amide. Variation of the chain length and position of anmore » intermediate amide group revealed high affinity of carboxylic congener 8 (K{sub i} 23 nM) and extended amine congener 15 (K{sub i} 132 nM), both having a 2-(1-pentynoyl) group. A biotin conjugate 18 containing an extended {epsilon}-aminocaproyl spacer chain exhibited higher affinity than a shorter biotinylated analogue. Alternatively, click coupling of terminal alkynes of homologous 2-dialkynyl nucleotide derivatives to alkyl azido groups produced triazole derivatives that bound to the P2Y{sub 1} receptor following deprotection of the bisphosphate groups. The preservation of receptor affinity of the functionalized congeners was consistent with new P2Y{sub 1} receptor modeling and ligand docking. Attempted P2Y{sub 1} antagonist conjugation to PAMAM dendrimer carriers by amide formation or palladium-catalyzed reaction between an alkyne on the dendrimer and a 2-iodopurine-derivatized nucleotide was unsuccessful. A dialkynyl intermediate containing the chain length favored in receptor binding was conjugated to an azide-derivatized dendrimer, and the conjugate inhibited ADP-promoted human platelet aggregation. This is the first example of attaching a strategically functionalized P2Y receptor antagonist to a PAMAM dendrimer to produce a multivalent conjugate exhibiting a desired biological effect, i.e., antithrombotic action.« less

DIRECT SYNTHESIS OF TERTIARY AMINES IN WATER USING MICROWAVES

EPA Science Inventory

A direct synthesis of tertiary amines is presented that proceeds expeditiously via N-alkylation of amines using alkyl halides in alkaline aqueous medium. This environmentally benign reaction is accelerated upon exposure to microwave irradiation resulting in shortened reaction tim...

Biocompatible silicon quantum dots by ultrasound-induced solution route

NASA Astrophysics Data System (ADS)

Lee, Soojin; Cho, Woon-Jo

2004-10-01

The water-soluble silicon quantum dots (QDs) of average diameter ~3 nm were prepared in organic solvent by ultrasound-induced solution route. This speedy rout produces the silicon QDs in the size range from 2 nm to 4 nm at room temperature and ambient pressure. The product yield of QDs was estimated to be higher than 60 % based on the initial NaSi weight. The surfaces of QDs were terminated with organic molecules including biocompatible ending groups (hydroxyl, amine and carboxyl) during simple preparation. Covalent attached molecules were characterized by FT-IR spectroscopy. These water-soluble passivation of QDs has just a little effect on the optical properties of original QDs.

Poly(amidoamine) dendrimers on lipid bilayers II: Effects of bilayer phase and dendrimer termination.

PubMed

Kelly, Christopher V; Leroueil, Pascale R; Orr, Bradford G; Banaszak Holl, Mark M; Andricioaei, Ioan

2008-08-07

The molecular structures and enthalpy release of poly(amidoamine) (PAMAM) dendrimers binding to 1,2-dimyristoyl- sn-glycero-3-phosphocholine (DMPC) bilayers were explored through atomistic molecular dynamics. Three PAMAM dendrimer terminations were examined: protonated primary amine, neutral acetamide, and deprotonated carboxylic acid. Fluid and gel lipid phases were examined to extract the effects of lipid tail mobility on the binding of generation-3 dendrimers, which are directly relevant to the nanoparticle interactions involving lipid rafts, endocytosis, lipid removal, and/or membrane pores. Upon binding to gel phase lipids, dendrimers remained spherical, had a constant radius of gyration, and approximately one-quarter of the terminal groups were in close proximity to the lipids. In contrast, upon binding to fluid phase bilayers, dendrimers flattened out with a large increase in their asphericity and radii of gyration. Although over twice as many dendrimer-lipid contacts were formed on fluid versus gel phase lipids, the dendrimer-lipid interaction energy was only 20% stronger. The greatest enthalpy release upon binding was between the charged dendrimers and the lipid bilayer. However, the stronger binding to fluid versus gel phase lipids was driven by the hydrophobic interactions between the inner dendrimer and lipid tails.

Crystal structure of bis-(benzyl-amine-κN)[5,10,15,20-tetra-kis-(4-chloro-phen-yl)porphyrinato-κ(4) N]iron(II) n-hexane monosolvate.

PubMed

Dhifaoui, Selma; Harhouri, Wafa; Bujacz, Anna; Nasri, Habib

2016-01-01

In the title compound, [Fe(II)(C44H24Cl4N4)(C6H5CH2NH2)2]·C6H14 or [Fe(II)(TPP-Cl)(BzNH2)2]·n-hexane [where TPP-Cl and BzNH2 are 5,10,15,20-tetra-kis-(4-chloro-phen-yl)porphyrinate and benzyl-amine ligands, respectively], the Fe(II) cation lies on an inversion centre and is octa-hedrally coordinated by the four pyrrole N atoms of the porphyrin ligand in the equatorial plane and by two amine N atoms of the benzyl-amine ligand in the axial sites. The crystal structure also contains one inversion-symmetric n-hexane solvent mol-ecule per complex mol-ecule. The average Fe-Npyrrole bond length [1.994 (3) Å] indicates a low-spin complex. The crystal packing is sustained by N-H⋯Cl and C-H⋯Cl hydrogen-bonding inter-actions and by C-H⋯π inter-molecular inter-actions, leading to a three-dimensional network structure.

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

Wang, Hua; Zhou, Feng; Ren, Gerui

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-(L-2-aminopentanoyl)-L-phenylalanine dihydrate, a hydrophobic dipeptide with a nonproteinogenic residue.

PubMed

Görbitz, Carl Henrik; Yadav, Vitthal N

2013-09-01

The title dipeptide, better known as L-norvalyl-L-phenylalanine {systematic name: (S)-2-[(S)-2-aminopentanamido]-3-phenylpropanoic acid dihydrate}, C14H20N2O3·2H2O, has a nonproteinogenic N-terminal residue. In the solid state, it takes on a molecular conformation typical for one of the three classes of nanoporous dipeptides, but like two related compounds with a hydrophobic N-terminal residue and a C-terminal L-phenylalanine, it fails to form channels or pores. Instead, the crystal structure is divided into distinct hydrophobic and hydrophilic layers, the latter encompassing cocrystallized water molecules connecting the charged N- and C-terminal groups.

Computational Design of Iron Diphosphine Complexes with Pendant Amines for Hydrogenation of CO2 to Methanol: A Mimic of [NiFe] Hydrogenase.

PubMed

Chen, Xiangyang; Jing, Yuanyuan; Yang, Xinzheng

2016-06-20

Inspired by the active-site structure of the [NiFe] hydrogenase, we have computationally designed the iron complex [P(tBu) 2 N(tBu) 2 )Fe(CN)2 CO] by using an experimentally ready-made diphosphine ligand with pendant amines for the hydrogenation of CO2 to methanol. Density functional theory calculations indicate that the rate-determining step in the whole catalytic reaction is the direct hydride transfer from the Fe center to the carbon atom in the formic acid with a total free energy barrier of 28.4 kcal mol(-1) in aqueous solution. Such a barrier indicates that the designed iron complex is a promising low-cost catalyst for the formation of methanol from CO2 and H2 under mild conditions. The key role of the diphosphine ligand with pendent amine groups in the reaction is the assistance of the cleavage of H2 by forming a Fe-H(δ-) ⋅⋅⋅H(δ+) -N dihydrogen bond in a fashion of frustrated Lewis pairs. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Target Specificity of the E3 Ligase LUBAC for Ubiquitin and NEMO Relies on Different Minimal Requirements*

PubMed Central

Smit, Judith J.; van Dijk, Willem J.; El Atmioui, Dris; Merkx, Remco; Ovaa, Huib; Sixma, Titia K.

2013-01-01

The ubiquitination of NEMO with linear ubiquitin chains by the E3-ligase LUBAC is important for the activation of the canonical NF-κB pathway. NEMO ubiquitination requires a dual target specificity of LUBAC, priming on a lysine on NEMO and chain elongation on the N terminus of the priming ubiquitin. Here we explore the minimal requirements for these specificities. Effective linear chain formation requires a precise positioning of the ubiquitin N-terminal amine in a negatively charged environment on the top of ubiquitin. Whereas the RBR-LDD region on HOIP is sufficient for targeting the ubiquitin N terminus, the priming lysine modification on NEMO requires catalysis by the RBR domain of HOIL-1L as well as the catalytic machinery of the RBR-LDD domains of HOIP. Consequently, target specificity toward NEMO is determined by multiple LUBAC components, whereas linear ubiquitin chain elongation is realized by a specific interplay between HOIP and ubiquitin. PMID:24030825

Synthesis and Structure of Hypervalent Iodine(III) Reagents Containing Phthalimidate and Application to Oxidative Amination Reactions.

PubMed

Kiyokawa, Kensuke; Kosaka, Tomoki; Kojima, Takumi; Minakata, Satoshi

2015-11-09

A new class of hypervalent iodine reagents containing phthalimidate was synthesized, and structurally characterized by X-ray analysis. The benziodoxole-based reagent displays satisfactory solubility in common organic solvents and is reasonably stable in solution as well as in the solid state. The reagent was used for the oxidative amination of the C(sp(3))-H bond of N,N-dimethylanilines. In addition, the reagent was also applicable to oxidative amination with rearrangement of trialkylamines as well as enamines that were prepared in situ from secondary amines and aldehydes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

NH NMR shifts of new structurally characterized fac-[Re(CO)3(polyamine)]n+ complexes probed via outer-sphere hydrogen-bonding interactions to anions, including the paramagnetic [Re(IV)Br6]2- anion.

PubMed

Perera, Theshini; Marzilli, Patricia A; Fronczek, Frank R; Marzilli, Luigi G

2010-06-21

fac-[Re(I)(CO)(3)L](n) complexes serve as models for short-lived fac-[(99m)Tc(I)(CO)(3)L](n) imaging tracers (L = tridentate ligands forming two five-membered chelate rings defining the L face). Dangling groups on L, needed to achieve desirable biodistribution, complicate the NMR spectra, which are not readily understood. Using less complicated L, we found that NH groups (exo-NH) projecting toward the L face sometimes showed an upfield shift attributable to steric shielding of the exo-NH group from the solvent by the chelate rings. Our goal is to advance our ability to relate these spectral features to structure and solution properties. To investigate whether exo-NH groups in six-membered rings exhibit the same effect and whether the presence of dangling groups alters the effect, we prepared new fac-[Re(CO)(3)L](n+) complexes that allow direct comparisons of exo-NH shifts for six-membered versus five-membered chelate rings. New complexes were structurally characterized with the following L: dipn [N-3-(aminopropyl)-1,3-propanediamine], N'-Medipn (3,3'-diamino-N-methyldipropylamine), N,N-Me(2)dipn (N,N-dimethyldipropylenetriamine), aepn [N-2-(aminoethyl)-1,3-propanediamine], trpn [tris-(3-aminopropyl)amine], and tren [tris-(2-aminoethyl)amine]. In DMSO-d(6), the upfield exo-NH signals were exhibited by all complexes, indicating that the rings sterically shield the exo-NH groups from bulky solvent molecules. This interpretation was supported by exo-NH signal shift changes caused by added halide and [ReBr(6)](2-) anions, consistent with outer-sphere hydrogen-bond interactions between these anions and the exo-NH groups. For fac-[Re(CO)(3)(dipn)]PF(6) in acetonitrile-d(3), the exo-NH signal shifted further downfield in the series, Cl(-) > Br(-) > I(-), and the plateau in the shift change required a lower concentration for smaller anions. These results are consistent with steric shielding of the exo-NH groups by the chelate rings. Nevertheless, despite its size, the shape and charge of [ReBr(6)](2-) allowed the dianion to induce large upfield paramagnetic shifts of the exo-NH signal of fac-[Re(CO)(3)(dipn)]PF(6). This dianion shows promise as an outer-sphere hydrogen-bonding paramagnetic shift reagent.

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

Environmentally friendly chemoselective oxidation of primary aliphatic amines by using a biomimetic electrocatalytic system.

PubMed

Largeron, Martine; Chiaroni, Angèle; Fleury, Maurice-Bernard

2008-01-01

Environmentally friendly oxidation of primary aliphatic amines to imines has been successfully achieved, under metal-free conditions, by the use of diverse electrogenerated o-azaquinone mediators. High catalytic performance, together with high chemoselectivity, were observed with electron-poor o-azaquinone catalysts generated from 2-aminoresorcinol derivatives. Similar to copper amine oxidase enzymes, these mediators exhibited lower reactivity toward alpha-branched primary amines and no reactivity toward secondary amines. In the case of 3,4-aminophenol derivatives lacking a 2-hydroxy group, the generated o-azaquinone species failed to catalyze the oxidation of the amine to the corresponding imine. Further mechanistic considerations allowed a rationalization of the crucial role of the 2-hydroxy group in converting a catalytically inert species into a highly effective biomimetic catalyst.

Oxidative condensation reactions of (diethylenetriamine)cobalt(III) complexes with substituted bis(pyridin-2-yl)methane ligands

NASA Astrophysics Data System (ADS)

Zhou, Xiangting; Hockless, David C. R.; Willis, Anthony C.; Jackson, W. Gregory

2005-04-01

The synthesis and characterisation of Co(III) complexes derived from a condensation reaction with a central or terminal nitrogen of a dien ligand and the α-carbon of a range of substituted bis(pyridin-2-yl)methane ligands are described. Aerial oxidation of bpm {bis(pyridin-2-yl)methane with Co(II)/dien or direct reaction with Co(dien)Cl 3 provided in low yield a single C-N condensation product 1 (at the primary terminal NH 2) after the pyridyl -CH 2- is formally oxidised to -CH +-. The methyl substituted ligand bpe {1,1-bis(pyridin-2-yl)ethane} behaves likewise, except both terminal (prim) and central (sec) amines condense to yield isomeric products 2 and 3. Two of these three materials have been characterised by single crystal X-ray crystallography. The corresponding reactions for the bis(pyridyl) ligand bpk {bis(pyridin-2-yl)ketone} provided C-N condensation products without the requirement for oxidation at the α-C center; two carbinolamine complexes in different geometrical configurations resulted, mer-anti-[Co(dienbpc)Cl]ZnCl 4, 5, and unsym- fac-[Co(dienbpc)Cl]ZnCl 4, 6, {dienbpc=[2-(2-aminoethylamino)-ethylamino]-di-pyridin-2-yl-methanol}. In addition, a novel complex, [Co(bpk)(bpd-OH)Cl]ZnCl 4, 4, in which one bidentate N, N-bonded bpk ligand and one tridentate N, O, N-bonded bpd (the diol from bpk+OH -) were coordinated, was obtained via the Co(II)/O 2 synthetic route. When the bpc ligand (bpc=bis(pyridin-2-yl)methanol) was employed directly as a reagent along with dien, no condensation reactions were observed, but rather a single isomeric complex [Co(dien)(bpc)]Cl.ZnCl 4, 7, in which the ligand bpc acted as a N,N,O-bonded tridentate ligand rather than as a N,N-bidentate ligand was isolated. 13C, 1D and 2D 1H NMR studies are reported for all the complexes; they establish the structures unambiguously.

Enhancement of carcinogenesis and fatty infiltration in the pancreas in N-nitrosobis(2-oxopropyl)amine-treated hamsters by high-fat diet.

PubMed

Hori, Mika; Kitahashi, Tsukasa; Imai, Toshio; Ishigamori, Rikako; Takasu, Shinji; Mutoh, Michihiro; Sugimura, Takashi; Wakabayashi, Keiji; Takahashi, Mami

2011-11-01

Obesity is associated with increased pancreatic cancer risk, although the mechanisms have yet to be detailed. This study aimed to elucidate promotion of pancreatic cancer by obesity and hyperlipidemia. Six-week-old female Syrian golden hamsters were treated with N-nitrosobis(2-oxopropyl)amine (BOP) and after 1 week were fed a high-fat diet (HFD) or standard diet (STD) for 6 or 17 weeks. Body weight and serum levels of lipids and leptin were significantly higher in the HFD than the STD group at 14 weeks of age. Pancreatic ductal adenocarcinomas developed only in the BOP + HFD group, with an incidence of 67% (P < 0.01) at 14 weeks of age. In addition, the multiplicity was 2-fold greater in the BOP + HFD group than in the BOP + STD group (P < 0.05) at 25 weeks of age. Pancreatic fatty infiltration was increased by BOP treatment and further enhanced by the HFD, correlating with progression of BOP-induced pancreatic ductal adenocarcinoma and up-regulated expression of adipocytokines and cell proliferation-related genes in the pancreas. High-fat diet is shown to increase serum lipid levels and enhance fatty infiltration in the pancreas with abnormal adipocytokine production, which may accelerate and enhance pancreatic cancer.

75 FR 50891 - N-alkyl (C8-C18) Primary Amines and Acetate Salts; Exemption from the Requirement of a Tolerance

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-18

... alcohols and hydrocarbons; surfactants such as polyoxyethylene polymers and fatty acids; carriers such as... NAPAAS primary amines and primary amine acetate salt may also be conjugated, whether by glucuronidation...

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.

A novel, colorimetric method for biogenic amine detection based on arylalkylamine N-acetyltransferase.

PubMed

Leng, Pei-Qiang; Zhao, Feng-Lan; Yin, Bin-Cheng; Ye, Bang-Ce

2015-05-21

We developed a novel colorimetric method for rapid detection of biogenic amines based on arylalkylamine N-acetyltransferase (aaNAT). The proposed method offers distinct advantages including simple handling, high speed, low cost, good sensitivity and selectivity.

'GREENER' CHEMICAL SYNTHESES USING ALTERNATE REACTION CONDITIONS

EPA Science Inventory

Microwave (MW) irradiation in conjunction with water as reaction media has proven to be a greener chemical approach for expeditious N-alkylation reactions of amines and hydrazines wherein the reactions under mildly basic conditions afford tertiary amines and double N-alkylation t...

Reversible formation of aminals: a new strategy to control the release of bioactive volatiles from dynamic mixtures.

PubMed

Godin, Guillaume; Levrand, Barbara; Trachsel, Alain; Lehn, Jean-Marie; Herrmann, Andreas

2010-05-14

Dynamic mixtures generated by reversible aminal formation of fragrance aldehydes with N,N-dibenzyl alkyldiamines in aqueous systems were found to be suitable delivery systems for the controlled release of bioactive volatiles.

Quantum-chemical studies on the favored and rare tautomers of neutral and redox adenine.

PubMed

Raczyńska, Ewa D; Makowski, Mariusz; Zientara-Rytter, Katarzyna; Kolczyńska, Katarzyna; Stępniewski, Tomasz M; Hallmann, Małgorzata

2013-02-21

All possible twenty-three prototropic tautomers of neutral and redox adenine (nine amine and fourteen imine forms, including geometric isomerism of the exo ═NH group) were examined in vacuo {DFT(B3LYP)/6-311+G(d,p)}. The NH → NH conversions as well as those usually omitted, NH → CH and CH → CH, were considered. An interesting change of the tautomeric preference occurs when proceeding from neutral to reduced adenine. One-electron reduction favors the nonaromatic amine C8H-N10H tautomer. This tautomeric preference is similar to that (C2H) for reduced imidazole. Water molecules (PCM model) seem to not change this trend. They influence solely the relative energies. The DFT vertical detachment energy in the gas phase is positive for each tautomer, e.g., 0.03 eV for N9H-N10H and 1.84 eV for C8H-N10H. The DFT adiabatic electron affinity for the favored process, neutral N9H-N10H → reduced C8H-N10H (ground states), is equal to 0.18 eV at 0 K (ZPE included). One-electron oxidation does not change the tautomeric preference in the gas phase. The aromatic amine N9H-N10H tautomer is favored for the oxidized molecule similarly as for the neutral one. The DFT adiabatic ionization potential for the favored process, neutral N9H-N10H → oxidized N9H-N10H (ground states), is equal to 8.12 eV at 0 K (ZPE included). Water molecules (PCM model) seem to influence solely the composition of the tautomeric mixture and the relative energies. They change the energies of the oxidation and reduction processes by ca. 2 eV.

An accessible protocol for solid-phase extraction of N-linked glycopeptides through reductive amination by amine-functionalized magnetic nanoparticles.

PubMed

Zhang, Ying; Kuang, Min; Zhang, Lijuan; Yang, Pengyuan; Lu, Haojie

2013-06-04

In light of the significance of glycosylation for wealthy biological events, it is important to prefractionate glycoproteins/glycopeptides from complex biological samples. Herein, we reported a novel protocol of solid-phase extraction of glycopeptides through a reductive amination reaction by employing the easily accessible 3-aminopropyltriethoxysilane (APTES)-functionalized magnetic nanoparticles. The amino groups from APTES, which were assembled onto the surface of the nanoparticles through a one-step silanization reaction, could conjugate with the aldehydes from oxidized glycopeptides and, therefore, completed the extraction. To the best of our knowledge, this is the first example of applying the reductive amination reaction into the isolation of glycopeptides. Due to the elimination of the desalting step, the detection limit of glycopeptides was improved by 2 orders of magnitude, compared to the traditional hydrazide chemistry-based solid phase extraction, while the extraction time was shortened to 4 h, suggesting the high sensitivity, specificity, and efficiency for the extraction of N-linked glycopeptides by this method. In the meantime, high selectivity toward glycoproteins was also observed in the separation of Ribonuclease B from the mixtures contaminated with bovine serum albumin. What's more, this technique required significantly less sample volume, as demonstrated in the successful mapping of glycosylation of human colorectal cancer serum with the sample volume as little as 5 μL. Because of all these attractive features, we believe that the innovative protocol proposed here will shed new light on the research of glycosylation profiling.

Emulsification Of Eutectic Salt Mixtures In Fluid Vehicles

NASA Astrophysics Data System (ADS)

Vanderhoff, J. W.; El-Aasser, M. S.; Hawkins, T. W.

1988-05-01

High-internal-phase-volume emulsions of 75 volt 3/18/79 potassium iodide/sodium iodide/ urea model eutectic salt mixture in 83.5/16.5 Sartomer R-45HT hydroxy-terminated polybutadi-ene/Nujol mineral oil binder mixture were prepared at 60°C using water-in-oil emulsifiers and cured with isophorone diisocyanate or Desmodur N-100. The Nujol mineral oil enhanced the emulsification with a negligible reduction in the tensile properties of the cured elastomer. The average emulsion droplet sizes were ca. 200 nm initially, but increased slowly during curing to 500-1000 nm. The coalescence of the emulsion droplets followed the second-order dependence predicted by the von Smoluchowski diffusion-controlled flocculation; the rate constants were 1.05x10-18 and 9.58x10-18 cc/droplet-sec for dirnethyldioctadecylammonium bromide and Span 85 sorbitan trioleate, respectively. The isophorone diisocyanate reacted with emulsifiers containing primary hydroxyl or amine groups, to give unstable emulsions or no emulsions at all. Dimethyldioctadecylammonium bromide with no primary hydroxyl or amine groups, however, did not react with isocyanates and gave stable emulsions. The reaction of the R-45HT hydroxy-terminated polybutadiene with isophorone diisocyanate followed the expec-ted second-order kinetics with a rate constant of 3.42x10-4 liters/mole-sec at 60°C. The tensile properties of the cured elastomers and emulsions generally increased with increasing NCO/OH ratio up to 1.6/1.0. With increasing volume fraction of dispersed phase, the maximum stress (tensile strength) decreased, the maximum strain (percent elongation) increased, and the initial modulus (tensile modulus) decreased, in contrast to the behavior of conventional filled polymer systems; however, the maximum stresses were in accord with theoretical values for a filled polymer in which the filler particles bear no load, the initial moduli were in accord with the predictions of an isostrain model, and the maximum strain increased with in-creasing volume fraction of dispersed phase; these unusual variations, which were attributed to the liquid nature of the emulsion droplets, were used to estimate the elastomer proper-ties required to give the desired properties: 60-100 psi maximum stress, 80-150% maximum strain, and 500-2000 psi initial modulus for an 88/12 eutectic salt/crosslinked polybutadi-ene composite containing 20% aluminum particles. The addition of 20% aluminum particles gave a modest improvement in tensile properties, and the addition of 2.5% or 3.5% submicroscopic carbon black particles gave a greater improvement; however, the tensile properties were still slightly short of the desired properties.

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.

Modification of the effects of guanethidine on cardiac catechol amines by various agents

PubMed Central

Bhagat, B.

1964-01-01

A study has been made of the effect of injections of guanethidine in rats, in depleting catechol amines from the whole cardiac ventricles and from various subcellular fractions. Unlike reserpine, guanethidine first affected the concentration of the amines in the soluble fraction of the cell. Neither [2-(2,6-dimethylphenoxy)-propyl]trimethylammonium chloride monohydrate (β-methyl xylocholine) nor hemicholinium affected the endogenous catechol amines or the uptake of injected noradrenaline, but each significantly reduced the action of guanethidine in depleting catechol amines. Administration of choline chloride after hemicholinium reversed its influence on guanethidine depletion. In cats, cocaine potentiated the pressor response to noradrenaline, but antagonized the response to tyramine and guanethidine, while bretylium and N-o-chlorobenzyl-N'N”-dimethylguanidine sulphate (BW392C60) potentiated the responses to noradrenaline, tyramine and guanethidine. PMID:14190459

Single molecule junction conductance and binding geometry

NASA Astrophysics Data System (ADS)

Kamenetska, Maria

This Thesis addresses the fundamental problem of controlling transport through a metal-organic interface by studying electronic and mechanical properties of single organic molecule-metal junctions. Using a Scanning Tunneling Microscope (STM) we image, probe energy-level alignment and perform STM-based break junction (BJ) measurements on molecules bound to a gold surface. Using Scanning Tunneling Microscope-based break-junction (STM-BJ) techniques, we explore the effect of binding geometry on single-molecule conductance by varying the structure of the molecules, metal-molecule binding chemistry and by applying sub-nanometer manipulation control to the junction. These experiments are performed both in ambient conditions and in ultra high vacuum (UHV) at cryogenic temperatures. First, using STM imaging and scanning tunneling spectroscopy (STS) measurements we explore binding configurations and electronic properties of an amine-terminated benzene derivative on gold. We find that details of metal-molecule binding affect energy-level alignment at the interface. Next, using the STM-BJ technique, we form and rupture metal-molecule-metal junctions ˜104 times to obtain conductance-vs-extension curves and extract most likely conductance values for each molecule. With these measurements, we demonstrated that the control of junction conductance is possible through a choice of metal-molecule binding chemistry and sub-nanometer positioning. First, we show that molecules terminated with amines, sulfides and phosphines bind selectively on gold and therefore demonstrate constant conductance levels even as the junction is elongated and the metal-molecule attachment point is modified. Such well-defined conductance is also obtained with paracyclophane molecules which bind to gold directly through the pi system. Next, we are able to create metal-molecule-metal junctions with more than one reproducible conductance signatures that can be accessed by changing junction geometry. In the case of pyridine-linked molecules, conductance can be reliably switched between two distinct conductance states using sub-nanometer mechanical manipulation. Using a methyl sulfide linker attached to an oligoene backbone, we are able to create a 3-nm-long molecular potentiometer, whose resistance can be tuned exponentially with Angstom-scale modulations in metal-molecule configuration. These experiments points to a new paradigm for attaining reproducible electrical characteristics of metal-organic devices which involves controlling linker-metal chemistry rather than fabricating identically structured metal-molecule interfaces. By choosing a linker group which is either insensitive to or responds reproducibly to changes in metal-molecule configuration, one can design single molecule devices with functionality more complex than a simple resistor. These ambient temperature experiments were combined with UHV conductance measurements performed in a commercial STM on amine-terminated benzene derivatives which conduct through a non-resonant tunneling mechanism, at temperatures varying from 5 to 300 Kelvin. Our results indicate that while amine-gold binding remains selective irrespective of environment, conductance is not temperature independent, in contrast to what is expected for a tunneling mechanism. Furthermore, using temperature-dependent measurements in ambient conditions we find that HOMO-conducting amines and LUMO-conducting pyridines show opposite dependence of conductance on temperature. These results indicate that energy-level alignment between the molecule and the electrodes changes as a result of varying electrode structure at different temperatures. We find that temperature can serve as a knob with which to tune transport properties of single molecule-metal junctions.

A Central Mesencephalic Reticular Formation Projection to the Supraoculomotor Area in Macaque Monkeys

PubMed Central

Bohlen, Martin O.; Warren, Susan; May, Paul J.

2015-01-01

The central mesencephalic reticular formation is physiologically implicated in oculomotor function and anatomically interwoven with many parts of the oculomotor system’s premotor circuitry. This study in Macaca fascicularis monkeys investigates the pattern of central mesencephalic reticular formation projections to the area in and around the extraocular motor nuclei, with special emphasis on the supraoculomotor area. It also examines the location of the cells responsible for this projection. Injections of biotinylated dextran amine were stereotaxically placed within the central mesencephalic reticular formation to anterogradely label axons and terminals. These revealed bilateral terminal fields in the supraoculomotor area. In addition, dense terminations were found in both the preganglionic Edinger-Westphal nuclei. The dense terminations just dorsal to the oculomotor nucleus overlap with the location of the C-group medial rectus motoneurons projecting to multiply innervated muscle fibers suggesting they may be targeted. Minor terminal fields were observed bilaterally within the borders of the oculomotor and abducens nuclei. Injections including the supraoculomotor area and oculomotor nucleus retrogradely labeled a tight band of neurons crossing the central third of the central mesencephalic reticular formation at all rostrocaudal levels, indicating a subregion of the nucleus provides this projection. Thus, these experiments reveal that a subregion of the central mesencephalic reticular formation may directly project to motoneurons in the oculomotor and abducens nuclei, as well as to preganglionic neurons controlling the tone of intraocular muscles. This pattern of projections suggests an as yet undetermined role in regulating the near triad. PMID:25859632

A central mesencephalic reticular formation projection to the supraoculomotor area in macaque monkeys.

PubMed

Bohlen, Martin O; Warren, Susan; May, Paul J

2016-05-01

The central mesencephalic reticular formation is physiologically implicated in oculomotor function and anatomically interwoven with many parts of the oculomotor system's premotor circuitry. This study in Macaca fascicularis monkeys investigates the pattern of central mesencephalic reticular formation projections to the area in and around the extraocular motor nuclei, with special emphasis on the supraoculomotor area. It also examines the location of the cells responsible for this projection. Injections of biotinylated dextran amine were stereotaxically placed within the central mesencephalic reticular formation to anterogradely label axons and terminals. These revealed bilateral terminal fields in the supraoculomotor area. In addition, dense terminations were found in both the preganglionic Edinger-Westphal nuclei. The dense terminations just dorsal to the oculomotor nucleus overlap with the location of the C-group medial rectus motoneurons projecting to multiply innervated muscle fibers suggesting they may be targeted. Minor terminal fields were observed bilaterally within the borders of the oculomotor and abducens nuclei. Injections including the supraoculomotor area and oculomotor nucleus retrogradely labeled a tight band of neurons crossing the central third of the central mesencephalic reticular formation at all rostrocaudal levels, indicating a subregion of the nucleus provides this projection. Thus, these experiments reveal that a subregion of the central mesencephalic reticular formation may directly project to motoneurons in the oculomotor and abducens nuclei, as well as to preganglionic neurons controlling the tone of intraocular muscles. This pattern of projections suggests an as yet undetermined role in regulating the near triad.

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.

Glycerol as a Building Block for Prochiral Aminoketone, N-Formamide, and N-Methyl Amine Synthesis.

PubMed

Dai, Xingchao; Rabeah, Jabor; Yuan, Hangkong; Brückner, Angelika; Cui, Xinjiang; Shi, Feng

2016-11-23

Prochiral aminoketones are key intermediates for the synthesis of optically active amino alcohols, and glycerol is one of the main biomass-based alcohols available in industry. In this work, glycerol was catalytically activated and purposefully converted with amines to generate highly valuable prochiral aminoketones, as well as N-formamides and N-methyl amines, over CuNiAlO x catalyst. The catalyst structure can be anticipated as nano-Ni species on or in CuAlO x via the formation of nano- Cu-Ni alloy particles. This concept may present a novel and valuable methodology for glycerol utilization. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A novel assay to measure tertiary and quaternary amines in wastewater: An indicator for NDMA wastewater precursors.

PubMed

Woods-Chabane, Gwen C; Glover, Caitlin M; Marti, Erica J; Dickenson, Eric R V

2017-07-01

This study examined the potential of using a novel bulk amine assay as an approximation for the tertiary and quaternary amine load in wastewaters and surface water samples, and this approximation was compared to N-nitrosodimethylamine (NDMA) formation potential using chloramines. An existing colorimetric method was examined and optimized for the detection of amines in environmental water samples. The method consists of liquid-liquid extraction followed by a catalyzed reaction to form a yet-undefined product that is known to be both a strong chromophore and fluorophore. Previous work verified that this reaction was effectively catalyzed by a number of compounds containing tertiary and quaternary amine moieties. Many tertiary and quaternary compounds are also efficient producers of NDMA under chloramination conditions, and a linear correlation was consequently derived from the bulk amine signals vs. NDMA formation potential in various wastewater samples (R 2  = 0.74; n = 24; p-value < 0.05). The results provide evidence that approximately 2% of the tertiary and quaternary amines measured can form NDMA and an estimated 0.01-1.3% of nitrogen in dissolved organic nitrogen originates from these bulk amines. The normalization of NDMA concentration by the amine measurement revealed that ozone effectively destroyed those tertiary and quaternary amine structures more likely to form NDMA in treated wastewater samples. This bulk amine assay illustrates that proxy measurements of tertiary and quaternary amines can be linked to the NDMA formation potential of a given sample, and this approach may prove useful as a characterizing tool for NDMA precursors in wastewater. Copyright © 2017 Elsevier Ltd. All rights reserved.

Tandem mass spectrometry of isomeric aniline-labeled N-glycans separated on porous graphitic carbon: Revealing the attachment position of terminal sialic acids and structures of neutral glycans.

PubMed

Michael, Claudia; Rizzi, Andreas M

2015-07-15

Quantitative monitoring of changes in the N-glycome upon disease has gained significance in the context of biomarker discovery. Separation and quantification of isobaric glycan isomers can be attained by using high-performance liquid chromatography/electrospray ionization mass spectrometry (HPLC/ESI-MS). Collision-induced dissociation (CID)-based fragmentation of separated isobaric glycans is evaluated in respect to its potential of providing fragment ions specific for the linkage positions of terminal sialic acids and the presence of intersecting GlcNAc moieties, respectively. N-Glycans were labeled via reductive amination using (12)C6-aniline and (13)C6-aniline as isotope-coded labeling reagents. The differently labeled glycans were merged and separated into various species using a porous graphitic carbon (PGC) stationary phase. Identification of structural features of separated isobaric isomers was performed by CID-based tandem mass spectrometry (MS/MS) carried out in a quadrupole time-of-flight (QqTOF) or a quadrupole ion-trap (IT) mass spectrometer. Working in the negative ion mode, new diagnostic CID fragment ions could be found that are indicative for the α2,6-type linkage of sialic acids. Other diagnostic ions, identified before as being indicative for the substitution of the 6-antenna, could be confirmed as being of relevance also in the case of aniline labeling. In the positive ion mode, CID fragment ions indicative for the structure of short neutral N-glycans were identified. One new diagnostic ion specific for the linkage position of the terminal sialic acids and one for the presence of bisecting GlcNAc in N-glycans were identified. The aniline label introduced for improved relative quantitation in MS(1) was found not to significantly alter the CID fragmentation patterns that were reported previously by other authors for unlabeled/reduced glycans or for glycans with more polar labels. Copyright © 2015 John Wiley & Sons, Ltd.

Design and synthesis of novel diphenyl oxalamide and diphenyl acetamide derivatives as anticonvulsants.

PubMed

Nikalje, Anna Pratima G; Ghodke, Mangesh; Girbane, Amol

2012-01-01

A series of novel N(1) -substituted-N(2) ,N(2) -diphenyl oxalamides 3a-l were synthesized in good yield by stirring diphenylcarbamoyl formyl chloride (2) and various substituted aliphatic, alicyclic, aromatic, heterocyclic amines in DMF and K(2) CO(3) . Also 2-substituted amino-N,N-diphenylacetamides 5a-m were designed by pharmacophore generation and synthesized by stirring 2-chloro-N,N-diphenylacetamide (4) and various substituted amines in acetone using triethyl amine as a catalyst. All the synthesized compounds were screened for anticonvulsant activity in Swiss albino mice by MES and ScPTZ induced seizure tests. Neurotoxicity screening and behavioral testing was also carried out. Some of the synthesized test compounds were found to be more potent than the standard drug. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of non-cytotoxic poly(ester-amine) dendrimers as potential solubility enhancers for drugs: methotrexate as a case study.

PubMed

Soto-Castro, Delia; Cruz-Morales, Jorge A; Ramírez Apan, María Teresa; Guadarrama, Patricia

2010-11-09

This study describes the synthesis of two new families of dendrimers based on the esterification of N-alkylated 3-amine-1-propanol with two different cores, adipic acid (1st and 2nd generations) and ethylenediamine (generation 1.5), both with carboxylic acid end groups, offering a wide variety of further modifications at the periphery. According to the cytotoxic evaluation of the dendrimers and their possible degradation products within cell lines, these materials could be considered as innocuous. In preliminary studies, the synthesized dendrimers proved to be potential enhancers of solubility of highly hydrophobic drugs, like methotrexate, widely used in chemotherapy.

DFT studies of the effectiveness of p-substituted diphenyl amine antioxidants in styrene-butadiene rubber through their Cu(II) coordination ability

NASA Astrophysics Data System (ADS)

Puškárová, Ingrid; Breza, Martin

2017-07-01

Structures of a series of diphenyl amine (DPA) antioxidants and of their complexes with Cu2+ were optimized at B3LYP level of theory. DPAs may be divided into two groups according to their molar antioxidant effectiveness (AEM). The effectiveness of high-AEM DPA antioxidants at 130 °C rises with decreasing spin densities at Cu atoms and with the increasing electron density Laplacian at Cu-N bond critical points in the 2[DPA…Cu]2+ complexes similarly as in the case of p-phenylene diamine antioxidants. No such trends are observed at 25 °C and for low- AEM DPA antioxidants.

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.

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.

Non-amine-based dopamine transporter (reuptake) inhibitors retain properties of amine-based progenitors.

PubMed

Madras, Bertha K; Fahey, Michele A; Miller, Gregory M; De La Garza, Richard; Goulet, Martin; Spealman, Roger D; Meltzer, Peter C; George, Susan R; O'Dowd, Brian F; Bonab, Ali A; Livni, Eli; Fischman, Alan J

2003-10-31

Without exception, therapeutic and addictive drugs that produce their primary effects by blocking monoamine transporters in brain contain an amine nitrogen in their structure. This fundamental canon of drug design was based on a prevailing premise that an amine nitrogen is required to mimic the structures of monoamine neurotransmitters and other natural products. Non-amines, a novel class of compounds that contain no amine nitrogen, block monoamine transporters in the nM range and display markedly high selectivity for monoamine transporters, but not for receptors. Non-amines retain the spectrum of biochemical and pharmacological properties characteristic of amine-bearing counterparts. These novel drugs compel a revision of current concepts of drug-monoamine transporter complex formation and open avenues for discovery of a new generation of therapeutic drugs.

White polymer light-emitting electrochemical cells using emission from exciplexes with long intermolecular distances formed between polyfluorene and π-conjugated amine molecules

NASA Astrophysics Data System (ADS)

Nishikitani, Y.; Takeuchi, H.; Nishide, H.; Uchida, S.; Yazaki, S.; Nishimura, S.

2015-12-01

The authors present white polymer light-emitting electrochemical cells (PLECs) fabricated with polymer blend films of poly(9,9-di-n-dodecylfluorenyl-2,7-diyl) (PFD) and π-conjugated triphenylamine molecules. The PLECs have bulk heterojunction structures composed of van der Waals interfaces between the PFD segments and the amine molecules. White-light electroluminescence (EL) can be achieved via light-mixing of the blue exciton emission from PFD and long-wavelength exciplex emission from excited complexes consisting of PFD segments (acceptors (As)) and the amine molecules (donors (Ds)). Precise control of the distances between the PFD and the amine molecules, affected through proper choice of the concentrations of PFD, amine molecules, and polymeric solid electrolytes, is critical to realizing white emission. White PLECs can be fabricated with PFD and amine molecules whose highest occupied molecular orbital (HOMO) levels range from -5.3 eV to -5.0 eV. Meanwhile, PLECs fabricated with amine molecules whose HOMO levels are lower than -5.6 eV cannot produce exciplex emission. The distances between the PFD and amine molecules of the exciplexes appear to be larger than 0.4 nm. These experimental data are explained by perturbation theory using the charge-transfer state ( A - D + ), the locally excited state ( A * D ), which is assumed to be the locally excited acceptor state in which there is no interaction with the donor molecule; and the energy gap between the HOMO levels of the PFD and the amine molecules. Color-stable white PLECs were fabricated using 4,4',4″-tris[N-(2-naphthyl)-N-phenylamino]-triphenylamine, which has a HOMO level of -5.2 eV, as the amine molecule, and the color stability of the device is a function of the fact that PFD forms exciplexes with these molecules.

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…

One-Pot Two-Step Multicomponent Process of Indole and Other Nitrogenous Heterocycles or Amines toward α-Oxo-acetamidines.

PubMed

Martinez-Ariza, Guillermo; McConnell, Nicholas; Hulme, Christopher

2016-04-15

A cesium carbonate promoted three-component reaction of N-H containing heterocycles, primary or secondary amines, arylglyoxaldehydes, and anilines is reported. The key step involves a tandem sequence of N-1 addition of a heterocycle or an amine to preformed α-iminoketones, followed by an air- or oxygen-mediated oxidation to form α-oxo-acetamidines. The scope of the reaction is enticingly broad, and this novel methodology is applied toward the synthesis of various polycyclic heterocycles.

AN EFFICIENT AND CHEMOSELECTIVE CBZ-PROTECTION OF AMINES USING SILICA-SULFURIC ACID AT ROOM TEMPERATURE

EPA Science Inventory

A simple, facile, and chemoselective N-benzyloxycarbonylation of amines using silica-sulfuric acid that proceeds under solvent-free conditions at room temperature has been achieved. These reactions are applicable to a wide variety of primary (aliphatic, cyclic) secondary amines, ...

Influence of various cooking methods on the concentrations of volatile N-nitrosamines and biogenic amines in dry-cured sausages.

PubMed

Li, Ling; Wang, Peng; Xu, Xinglian; Zhou, Guanghong

2012-05-01

N-nitrosamines, biogenic amines, and residual nitrites are harmful substances and are often present in cured meats. The effects of different cooking methods (boiling, pan-frying, deep-frying, and microwave) were investigated on their contents in dry-cured sausage. The various N-nitrosamines were isolated by a steam distillation method and analyzed by gas chromatography mass spectrometry (GC-MS). The biogenic amines were determined after extraction with perchloric acid as dansyl derivatives by high-performance liquid chromatography (HPLC) method. The results showed that initial dry-cured raw sausage contained 5.31 μg/kg of total N-nitrosamines. Cooking by deep-frying or pan-frying resulted in products having the highest (P < 0.05) contents, compared with boiling or microwave treatments, which were not different from the raw. Although frying increased the content of N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), and N-nitrosopyrrolidine (NPYR), it decreased the contents of histamine and cadaverine. Boiling and microwave treatments decreased the total biogenic amines significantly (P < 0.05). Residual nitrite was significantly reduced by cooking treatments. The results suggest that boiling and microwave treatments were more suitable methods for cured meat. © 2012 Institute of Food Technologists®

The role of brain biogenic amines in the control of pituitary-adrenocortical activity

NASA Technical Reports Server (NTRS)

Maickel, R. P.

1975-01-01

It was found that pretreatment of animals with desmethyl imipramine antagonized the reserpine-induced sedation without preventing the decline in brain amines or the hypersecretion of adrenocorticotropic hormone (ACTH). The antagonism of reserpine-induced ACTH hypersecretion by the monoamine oxidose (MAO) inhibitor pargyline (MO 911, N-methyl-N-benzyl-2-propynylamine) was studied. Evidence is presented that this antagonism is related to the level of brain biogenic amines maintained during the course of action of the drug. Pretreatment with MAO inhibitors does not affect the ACTH hypersecretion evoked by exposure to cold or chlorpromazine, lending further support to the hypothesis that reserpine-induced ACTH hypersecretion is related to brain amine changes.

Integrated on-chip derivatization and electrophoresis for the rapid analysis of biogenic amines.

PubMed

Beard, Nigel P; Edel, Joshua B; deMello, Andrew J

2004-07-01

We demonstrate the monolithic integration of a chemical reactor with a capillary electrophoresis device for the rapid and sensitive analysis of biogenic amines. Fluorescein isothiocyanate (FITC) is widely employed for the analysis of amino-group containing analytes. However, the slow reaction kinetics hinders the use of this dye for on-chip labeling applications. Other alternatives are available such as o-phthaldehyde (OPA), however, the inferior photophysical properties and the UV lambdamax present difficulties when using common excitation sources leading to a disparity in sensitivity. Consequently, we present for the first time the use of dichlorotriazine fluorescein (DTAF) as a superior in situ derivatizing agent for biogenic amines in microfluidic devices. The developed microdevice employs both hydrodynamic and electroosmotic flow, facilitating the creation of a polymeric microchip to perform both precolumn derivatization and electrophoretic analysis. The favorable photophysical properties of the DTAF and its fast reaction kinetics provide detection limits down to 1 nM and total analysis times (including on-chip mixing and reaction) of <60 s. The detection limits are two orders of magnitude lower than current limits obtained with both FITC and OPA. The optimized microdevice is also employed to probe biogenic amines in real samples.

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.

Nitrogen fertilisation increases biogenic amines and amino acid concentrations in Vitis vinifera var. Riesling musts and wines.

PubMed

Smit, Inga; Pfliehinger, Marco; Binner, Antonie; Großmann, Manfred; Horst, Walter J; Löhnertz, Otmar

2014-08-01

Wines rich in biogenic amines can cause adverse health effects to the consumer. Being nitrogen-containing substances, the amount of amines in wines might be strongly influenced by the rate of nitrogen fertiliser application during grape production. The aim of this work was to evaluate the effect of nitrogen fertilisation in the vineyard on the formation of biogenic amines in musts and wines. In a field experiment which compared unfertilised and fertilised (60 and 150 kg N ha(-1)) vines over two separate years, the total amine concentrations in must and wine increased. The latter was due to an increase of individual amines such as ethylamine, histamine, isopentylamine, phenylethylamine and spermidine in the musts and wines with the nitrogen application. Furthermore, the fermentation process increased the concentration of histamine and ethylamine in most of the treatments, while spermidine, spermine and isopentylamine concentrations generally decreased. Throughout both vintages, the concentrations of tyramine and histamine of the investigated musts and wines never reached detrimental levels to the health of non-allergenic people. Nitrogen fertilisation has a significant effect on amines formation in musts and wines. Furthermore, during fermentation, ethylamine and histamine increased while other amines were presumably serving as N sources during fermentation. © 2013 Society of Chemical Industry.

Brønsted acid-catalyzed decarboxylative redox amination: formation of N-alkylindoles from azomethine ylides by isomerization.

PubMed

Mao, Hui; Wang, Sichang; Yu, Peng; Lv, Huiqing; Xu, Runsheng; Pan, Yuanjiang

2011-02-18

A Brønsted acid-catalyzed decarboxylative redox amination involving aldehydes with 2-carboxyindoline for the synthesis of N-alkylindoles is described. The decarboxylative condensations of aldehydes with 2-carboxyindoline produce azomethine ylides in situ, which then transform into N-alkylindoles by isomerization. © 2011 American Chemical Society

Syntheses and structure characterization of ten acid-base hybrid crystals based on N-containing aromatic brønsted bases and mineral acids

NASA Astrophysics Data System (ADS)

Lin, Zhihao; Jin, Shouwen; Li, Xiaoliang; Xiao, Xiao; Hu, Kaikai; Guo, Ming; Chi, Xinchen; Liu, Hui; Wang, Daqi

2017-10-01

Cocrystallization of the aromatic brønsted bases with a series of mineral acids gave a total of ten hybrid salts with the compositions: (2-methylquinoline)2: (hydrochloride acid): 3H2O [(HL1)+. (L1)·· (Cl-) · (H2O)3] (1), (6-bromobenzo[d]thiazol-2-amine): (hydrochloride acid) [(HL2)+. (Cl-)] (2), (6-bromobenzo[d]thiazol-2-amine): (nitric acid) [(HL2)+. (NO3-)] (3), (6-bromobenzo[d]thiazol-2-amine): (sulfuric acid) [(HL2)+ · (HSO4)-] (4), (6-bromobenzo[d]thiazol-2-amine): (phosphoric acid) [(HL2)+ · (H2PO4)-] (5), (5,7-dimethyl-1,8-naphthyridine-2-amine): (hydrochloride acid): 3H2O [(HL3)+ · (Cl-) (H2O)3] (6), (5,7-dimethyl-1,8-naphthyridine-2-amine): (hydrobromic acid): CH3OH [(HL3)+ · (Br)- · CH3OH] (7), (5,7-dimethyl-1,8-naphthyridine-2-amine): (sulfuric acid): H2O [(HL3)+ · (HSO4)- · H2O] (8), (2-aminophenol): (phosphoric acid) [(HL4)+ · (H2PO4)-] (9), and (2-amino-4-chlorophenol): (phosphoric acid) [(HL5)+ · (H2PO4)-] (10). The ten salts have been characterized by X-ray diffraction analysis, IR, and elemental analysis, and the melting points of all the salts were also reported. And their structural and supramolecular aspects are fully analyzed. The result reveals that among the ten investigated crystals the ring N of the heterocycle or the NH2 in the aminophenol are protonated when the acids are deprotonated, and the crystal packing is interpreted in terms of the strong charge-assisted classical hydrogen bonds between the NH+/NH3+ and deprotonated acidic groups. Further analysis of the crystal packing of the salts indicated that a different family of additional CHsbnd O, CHsbnd Cl, CH3sbnd N, CH3sbnd O, CHsbnd Br, CH3sbnd Br, Brsbnd Cl, Clsbnd S, Osbnd S, Osbnd O, Brsbnd S, Hsbnd H, and π-π associations contribute to the stabilization and expansion of the total high-dimensional frameworks. For the coexistence of the various weak nonbonding interactions these structures adopted homo or hetero supramolecular synthons or both. Some classical supramolecular synthons, such as R22(8), R42(8), R43(10) and R44(12), usually observed in the organic solids, were again shown to be involved in constructing most of these H-bonding networks.

Reversibly extracellular pH controlled cellular uptake and photothermal therapy by PEGylated mixed-charge gold nanostars.

PubMed

Wang, Shouju; Teng, Zhaogang; Huang, Peng; Liu, Dingbin; Liu, Ying; Tian, Ying; Sun, Jing; Li, Yanjun; Ju, Huangxian; Chen, Xiaoyuan; Lu, Guangming

2015-04-17

Shielding nanoparticles from nonspecific interactions with normal cells/tissues before they reach and after they leave tumors is crucial for the selective delivery of NPs into tumor cells. By utilizing the reversible protonation of weak electrolytic groups to pH changes, long-chain amine/carboxyl-terminated polyethylene glycol (PEG) decorated gold nanostars (GNSs) are designed, exhibiting reversible, significant, and sensitive response in cell affinity and therapeutic efficacy to the extracellular pH (pHe) gradient between normal tissues and tumors. This smart nanosystem shows good dispersity and unimpaired photothermal efficacy in complex bioenvironment at pH 6.4 and 7.4 even when their surface charge is neutral. One PEGylated mixed-charge GNSs with certain surface composition, GNS-N/C 4, exhibits high cell affinity and therapeutic efficacy at pH 6.4, and low affinity and almost "zero" damage to cells at pH 7.4. Remarkably, this significant and sensitive response in cell affinity and therapeutic efficacy is reversible as local pH alternated. In vivo, GNS-N/C 4 shows higher accumulation in tumors and improved photothermal therapeutic efficacy than pH-insensitive GNSs. This newly developed smart nanosystem, whose cell affinity reversibly transforms in response to pHe gradient with unimpaired biostability, provides a novel effective means of tumor-selective therapy. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Facile and Efficient Preparation of Tri-component Fluorescent Glycopolymers via RAFT-controlled Polymerization.

PubMed

Wang, Wei; Lester, John M; Amorosa, Anthony E; Chance, Deborah L; Mossine, Valeri V; Mawhinney, Thomas P

2015-06-19

Synthetic glycopolymers are instrumental and versatile tools used in various biochemical and biomedical research fields. An example of a facile and efficient synthesis of well-controlled fluorescent statistical glycopolymers using reversible addition-fragmentation chain-transfer (RAFT)-based polymerization is demonstrated. The synthesis starts with the preparation of β-galactose-containing glycomonomer 2-lactobionamidoethyl methacrylamide obtained by reaction of lactobionolactone and N-(2-aminoethyl) methacrylamide (AEMA). 2-Gluconamidoethyl methacrylamide (GAEMA) is used as a structural analog lacking a terminal β-galactoside. The following RAFT-mediated copolymerization reaction involves three different monomers: N-(2-hydroxyethyl) acrylamide as spacer, AEMA as target for further fluorescence labeling, and the glycomonomers. Tolerant of aqueous systems, the RAFT agent used in the reaction is (4-cyanopentanoic acid)-4-dithiobenzoate. Low dispersities (≤1.32), predictable copolymer compositions, and high reproducibility of the polymerizations were observed among the products. Fluorescent polymers are obtained by modifying the glycopolymers with carboxyfluorescein succinimidyl ester targeting the primary amine functional groups on AEMA. Lectin-binding specificities of the resulting glycopolymers are verified by testing with corresponding agarose beads coated with specific glycoepitope recognizing lectins. Because of the ease of the synthesis, the tight control of the product compositions and the good reproducibility of the reaction, this protocol can be translated towards preparation of other RAFT-based glycopolymers with specific structures and compositions, as desired.

Solubility and diffusivity of N{sub 2}O and CO{sub 2} in (monoethanolamine + N-methyldiethanolamine + water) and in (monoethanolamine + 2-amino-2-methyl-1-propanol + water)

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

Li, M.H.; Lai, M.D.

1995-03-01

Solutions of amines are frequently used in gas-treating processes to remove acid gases, such as CO{sub 2} and H{sub 2}S, from gas streams in the natural gas and synthetic ammonia industries and petroleum chemical plants. The solubility and diffusivity of N{sub 2}O in (monoethanolamine + N-methyldiethanolamine + water) and in (monoethanolamine + 2-amino-2-methyl-l-propanol + water) were measured at 30, 35, and 40 C and at atmospheric pressure. Six (monoethanolamine + N-methyldiethanolamine + water) and five (monoethanolamine + 2-amino-2-methyl-l-propanol + water) systems were studied. The total amine mass percent in all cases was 30. The solubilities were measured by a solubilitymore » apparatus similar to that of Haimour and Sandall (1984). A wetted wall column absorber was used to obtain the diffusivity of N{sub 2}O in amines. The N{sub 2}O solubilities in amine solutions have been correlated on the basis of the excess Henry constant correlation of Wang et al. (1992). The N{sub 2}O analogy was used to estimate the solubility and diffusivity of CO{sub 2} in (monoethanolamine + N-methyldiethanolamine + water) and in (monoethanolamine + 2-amino-2-methyl-l-propanol + water).« less

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.

Structures of potent selective peptide mimetics bound to carboxypeptidase B.

PubMed

Adler, Marc; Buckman, Brad; Bryant, Judi; Chang, Zheng; Chu, Kieu; Emayan, Kumar; Hrvatin, Paul; Islam, Imadul; Morser, John; Sukovich, Drew; West, Christopher; Yuan, Shendong; Whitlow, Marc

2008-02-01

This article reports the crystal structures of inhibitors of the functional form of thrombin-activatable fibrinolysis inhibitor (TAFIa). In vivo experiments indicate that selective inhibitors of TAFIa would be useful in the treatment of heart attacks. Since TAFIa rapidly degrades in solution, the homologous protein porcine pancreatic carboxypeptidase B (pp-CpB) was used in these crystallography studies. Both TAFIa and pp-CpB are zinc-based exopeptidases that are specific for basic residues. The final development candidate, BX 528, is a potent inhibitor of TAFIa (2 nM) and has almost no measurable effect on the major selectivity target, carboxypeptidase N. BX 528 was designed to mimic the tripeptide Phe-Val-Lys. A sulfonamide replaces the Phe-Val amide bond and a phosphinate connects the Val and Lys groups. The phosphinate also chelates the active-site zinc. The electrostatic interactions with the protein mimic those of the natural substrate. The primary amine in BX 528 forms a salt bridge to Asp255 at the base of the S1' pocket. The carboxylic acid interacts with Arg145 and the sulfonamide is hydrogen bonded to Arg71. Isopropyl and phenyl groups replace the side chains of Val and Phe, respectively. A series of structures are presented here that illustrate the evolution of BX 528 from thiol-based inhibitors that mimic a free C-terminal arginine. The first step in development was the replacement of the thiol with a phosphinate. This caused a precipitous drop in binding affinity. Potency was reclaimed by extending the inhibitors into the downstream binding sites for the natural substrate.

Determination of airborne, volatile amines from polyurethane foams by sorption onto a high-capacity cation-exchange resin based on poly(succinic acid).

PubMed

Seeber, G; Buchmeiser, M R; Bonn, G K; Bertsch, T

1998-06-05

A high-capacity carboxylic acid-functionalized resin prepared by ring-opening metathesis polymerization based on cross-linked endo,endo-poly(norborn-2-ene-5,6-dicarboxylic acid) was used for the sampling of volatile, airborne amines from polyurethane (PU) foams. Six tertiary amines which represent commonly used promotors for the formation of PUs from diisocyanates and polyols, namely pentamethyldiethylenetriamine, diazabicyclooctane, N-methylmorpholine, N-ethylmorphine, 1,4-dimethylpiperazine and N,N-dimethylethanolamine, were sorbed onto the new resin. The sorption behavior of the new material was investigated in terms of loading capacities, the influence of concentration, flow-rate as well as of the amount of resin. Breakthrough curves were recorded from each single component as well as of mixtures thereof. Finally, the resin was used for the sampling of amines evaporating from PU foams applied in buildings. Further information about time dependent concentration profiles were obtained using a combination of GC-MS and Fourier transform IR spectroscopy.

Teaching Old Compounds New Tricks: DDQ-Photocatalyzed C-H Amination of Arenes with Carbamates, Urea, and N-Heterocycles.

PubMed

Das, Somnath; Natarajan, Palani; König, Burkhard

2017-12-22

The C-H amination of benzene derivatives was achieved using DDQ as photocatalyst and BocNH 2 as the amine source under aerobic conditions and visible light irradiation. Electron-deficient and electron-rich benzenes react as substrates with moderate to good product yields. The amine scope of the reaction comprises Boc-amine, carbamates, pyrazoles, sulfonimides and urea. Preliminary mechanistic investigations indicate arene oxidation by the triplet of DDQ to radical cations with different electrophilicity and a charge transfer complex between the amine and DDQ as intermediate of the reaction. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cloning, expression, purification, crystallization and preliminary X-ray diffraction analysis of variants of monoamine oxidase from Aspergillus niger

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

Atkin, Kate E.; Reiss, Renate; Turner, Nicholas J.

2008-03-01

Crystals of A. niger monoamine oxidase variants display P2{sub 1} or P4{sub 1}2{sub 1}2/P4{sub 3}2{sub 1}2 symmetry, with eight or two molecules in the asymmetric unit, respectively. Monoamine oxidase from Aspergillus niger (MAO-N) is an FAD-dependent enzyme that catalyses the conversion of terminal amines to their corresponding aldehydes. Variants of MAO-N produced by directed evolution have been shown to possess altered substrate specificity. Crystals of two of these variants (MAO-N-3 and MAO-N-5) have been obtained; the former displays P2{sub 1} symmetry with eight molecules per asymmetric unit and the latter has P4{sub 1}2{sub 1}2 or P4{sub 3}2{sub 1}2 symmetry andmore » two molecules per asymmetric unit. Solution of these structures will help shed light on the molecular determinants of improved activity and high enantioselectivity towards a broad range of substrates.« less

A Catalyst-Free Amination of Functional Organolithium Reagents by Flow Chemistry.

PubMed

Kim, Heejin; Yonekura, Yuya; Yoshida, Jun-Ichi

2018-04-03

Reported is the electrophilic amination of functional organolithium intermediates with well-designed aminating reagents under mild reaction conditions using flow microreactors. The aminating reagents were optimized to achieve efficient C-N bond formation without using any catalyst. The electrophilic amination reactions of functionalized aryllithiums were successfully conducted under mild reaction conditions, within 1 minute, by using flow microreactors. The aminating reagent was also prepared by the flow method. Based on stopped-flow NMR analysis, the reaction time for the preparation of the aminating reagent was quickly optimized without the necessity of work-up. Integrated one-flow synthesis consisting of the generation of an aryllithium, the preparation of an aminating reagent, and their combined reaction was successfully achieved to give the desired amine within 5 minutes of total reaction time. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The antiproliferative effect of acridone alkaloids on several cancer cell lines.

PubMed

Kawaii, S; Tomono, Y; Katase, E; Ogawa, K; Yano, M; Takemura, Y; Ju-ichi, M; Ito, C; Furukawa, H

1999-04-01

Fifteen acridone alkaloids were examined for their antiproliferative activity toward monolayers and suspension of several types of cancer and normal human cell lines. As a result, atalaphyllidine (9), 5-hydroxy-N-methylseverifoline (11), atalaphyllinine (12), and des-N-methylnoracronycine (13) showed potent antiproliferative activity against tumor cell lines, whereas they have weak cytotoxicity on normal human cell lines. The structure-activity relationship established from the results revealed that a secondary amine, hydroxyl groups at C-1 and C-5, and a prenyl group at C-2 played an important role for antiproliferative activities of the tetracyclic acridones.

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.

Stable, concentrated solutions of polyaniline using amines as gel inhibitors

DOEpatents

Wang, Hsing-Lin; Mattes, Benjamin R.

2002-01-01

Stable, concentrated solutions of high-molecular weight polyaniline using amines as gel inhibitors. Certain amine compounds (gel inhibitors) are used to form highly concentrated, stable solutions of the emeraldine base form of polyaniline in numerous organic solvents from which coatings, films and fibers are readily prepared without problems associated with rapid gelation which occurs when concentrated solutions are attempted without the use of the gel inhibitors of the present invention. Tertiary amines are used to solubilize low-molecular weight fractions (M.sub.w <120,000, M.sub.n <30,000) of the pernigraniline, emeraldine, and leucoemeraldine oxidation states of polyaniline as concentrated (>20 wt. %) polyaniline solutions, while primary and secondary amines are used to produce solutions having 15-40 wt % of high-molecular weight polyaniline [M.sub.w.gtoreq.120,000, M.sub.n.gtoreq.30,000]. Concentrated solutions of polyaniline co-polymers or ring and/or nitrogen-substituted polyanilines may also be prepared.

Ultrafast relaxation dynamics of amine-substituted bipyridyl ruthenium(II) complexes

NASA Astrophysics Data System (ADS)

Song, Hongwei; Wang, Xian; Yang, WenWen; He, Guiying; Kuang, Zhuoran; Li, Yang; Xia, Andong; Zhong, Yu-Wu; Kong, Fan'ao

2017-09-01

The excited state properties of a series of ruthenium(II) amine-substituted bipyridyl complexes, [Ru(bpy)n(NNbpy)3-n]2+, were investigated by steady-state and transient absorption spectroscopy, as well as quantum chemical calculations. The steady-state absorption spectra of these complexes in CH3CN show a distinct red-shift of the 1MLCT absorption with increasing numbers of amine substituent, whereas the emission spectra indicate an energy gap order of [Ru(bpy)3]2+ > [Ru(bpy)2(NNbpy)]2+ > [Ru(NNbpy)3]2+ > [Ru(bpy)(NNbpy)2]2+. Nanosecond, femtosecond transient absorption and electrochemical measurements suggest that NNbpy ligand has a strong influence on the electronic and emission properties of these complexes, due to electron-rich amine substituent. We illustrate how the numbers of amine substituent modulate the spectroscopic properties of transition metal complexes, which is related to the design of new electro-active systems with novel photoelectrochemical properties.

Amines as occupational hazards for visual disturbance

PubMed Central

JANG, Jae-Kil

2015-01-01

Various amines, such as triethylamine and N,N-dimethylethylamine, have been reported to cause glaucopsia in workers employed in epoxy, foundry, and polyurethane foam industries. This symptom has been related to corneal edema and vesicular collection of fluid within the corneal subepithelial cells. Exposure to amine vapors for 30 min to several hours leads to blurring of vision, a blue-grey appearance of objects, and halos around lights, that are probably reversible. Concentration-effect relationships have been established. The visual disturbance is considered a nuisance, as it could cause onsite accidents, impair work efficiency, and create difficulties in driving back home. Occupational exposure limits have been established for some amines, but there is shortage of criteria. Volatility factors, such as vapor pressure, should be considered in industrial settings to prevent human ocular risks, while trying to reduce levels of hazardous amines in the atmosphere. PMID:26538000

Diffusivity of nitrous oxide in aqueous solutions of N-methyldiethanolamine and diethanolamine from 293 to 368 K

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

Tamimi, A.; Rinker, E.B.; Sandall, O.C.

1994-04-01

The diffusion coefficients for nitrous oxide in aqueous solutions of diethanolamine (DEA) and N-methyldiethanolamine (MDEA) were determined using a wetted-sphere absorber over the temperature range 293--368 K. The ranges of amine concentrations covered in the experiments were 10--30 mass % for DEA and 10--50 mass % for MDEA. The diffusion coefficients indicated a linear dependence on amine concentration, but the temperature dependence was nonlinear. It was found that the diffusivity of N[sub 2]O in aqueous DEA is always less than that in aqueous MDEA under equivalent conditions of amine concentration and temperature.

A Review of Aspects of Oxidative Hair Dye Chemistry with Special Reference to N-Nitrosamine Formation

PubMed Central

Lewis, David; Mama, John; Hawkes, Jamie

2013-01-01

This review discusses a new aspect to the safety profile of oxidative hair dyes using data already in the public domain. These dyes contain secondary amines that are capable of forming potentially carcinogenic nitrosamine derivatives when exposed to atmospheric pollution. Numerous scientific articles confirm the existence of secondary amines in hair dyes (and their intermediates), the possibility of nitrosation by atmospheric NOx of secondary amines to give the N-nitrosamines, and the significant safety risks on N-nitrosamines. It is believed that such nitrosamine derivatives should be investigated more fully in the interests of consumer safety. PMID:28809322

Interaction of protonated merocyanine dyes with amines in organic solvents.

PubMed

Ribeiro, Eduardo Alberton; Sidooski, Thiago; Nandi, Leandro Guarezi; Machado, Vanderlei Gageiro

2011-10-15

2,6-Diphenyl-4-(2,4,6-triphenylpyridinium-1-yl)phenolate (1a) and 4-[(1-methyl-4(1H)-pyridinylidene)-ethylidene]-2,5-cyclohexadien-1-one (2a) were protonated in organic solvents (dichloromethane, acetonitrile, and DMSO) to form 1b and 2b, respectively. The appearance of the solvatochromic bands of 1a and 2a was studied UV-vis spectrophotometrically by deprotonation of 1b and 2b in solution in the presence of the following amines: aniline (AN), N-methylaniline (NMAN), N,N-dimethylaniline (NDAN), n-butylamine (BA), diethylamine (DEA), and triethylamine (TEA). Titrations of 1b and 2b with the amines were carried out and the binding constants were determined from the titration curves in each solvent, using a mathematical model adapted from the literature which considers the simultaneous participation of two dye: amine stoichiometries, 1:1 and 1:2. The data obtained showed the following base order for the two compounds in DMSO: BA>DEA>TEA, while aromatic amines did not cause any effect. In dichloromethane, the following base order for 1b was verified: TEA>DEA>BA≫NDAN, while for 2b the order was: TEA>DEA>BA, suggesting that 1b is more acidic than 2b. The data in acetonitrile indicated for 1b and 2b the following order for the amines: DEA>TEA>BA. The diversity of the experimental data were explained based on a model that considers the level of interaction of the protonated dyes with the amines to be dependent on three aspects: (a) the basicity of the amine, which varies according to their molecular structure and the solvent in which it is dissolved, (b) the molecular structure of the dye, and (c) the solvent used to study the system. Copyright © 2011 Elsevier B.V. All rights reserved.

Fetal intracardiac potassium chloride injection to expedite second-trimester dilation and evacuation.

PubMed

Singh, Sareena; Seligman, Neil S; Jackson, Brittany; Berghella, Vincenzo

2012-01-01

To determine whether potassium chloride (KCl)-induced feticide prior to termination by dilation and evacuation (D&E) improves surgical outcome. We conducted a retrospective study of women who underwent second-trimester (13 0/7 to 23 6/7 weeks) D&E at an urban university-based hospital between January 2000 and July 2010. Women were divided into 3 cohorts: (1) D&E for termination of pregnancy after feticide, (2) D&E without feticide, and (3) D&E for spontaneous pregnancy loss. We compared maternal characteristics, various perioperative variables, and surgical outcomes for all 3 groups. Anesthesia time was used as a surrogate for operative time in the primary outcome. We analyzed 128 pregnancies (group 1: n = 23, group 2: n = 53, group 3: n = 52). Baseline maternal characteristics did not differ among the 3 groups. Anesthesia time was longest in the termination with KCl group (group 1: 116.9 min vs. group 2: 94.5 min and group 3: 90.3 min, p = 0.004), however, the effect was mitigated after controlling for fetal size (p = 0.176). There was no difference in blood loss (p = 0.968). Complications were uncommon, however, cervical lacerations were more common in the termination with KCl group (2 vs. 0 and 0, p = 0.010). Presurgical feticide with KCl was not associated with shorter anesthesia time. The decision to perform feticide should be based on other considerations, such as patient preference. Copyright © 2011 S. Karger AG, Basel.

Unexpected role of activated carbon in promoting transformation of secondary amines to N-nitrosamines.

PubMed

Padhye, Lokesh; Wang, Pei; Karanfil, Tanju; Huang, Ching-Hua

2010-06-01

Activated carbon (AC) is the most common solid phase extraction material used for analysis of nitrosamines in water. It is also widely used for the removal of organics in water treatment and as a catalyst or catalyst support in some industrial applications. In this study, it was discovered that AC materials can catalyze transformation of secondary amines to yield trace levels of N-nitrosamines under ambient aerobic conditions. All 11 commercial ACs tested in the study formed nitrosamines from secondary amines. Among the different ACs, the N-nitrosodimethylamine (NDMA) yield at pH 7.5 ranged from 0.001% to 0.01% of initial amount of aqueous dimethylamine (DMA) concentration, but at 0.05-0.29% of the amount of adsorbed DMA by AC. Nitrosamine yield increased with higher pH and for higher molecular weight secondary amines, probably because of increased adsorption of amines. Presence of oxygen was a critical factor in the transformation of secondary amines, since ACs with adsorbed secondary amines dried under air for longer period of time exhibited significantly higher nitrosamine yields. The AC-catalyzed nitrosamine formation was also observed in surface water and wastewater effluent samples. Properties of AC play an important role in the nitrosamine yields. Preliminary evaluation indicated that nitrosamine formation was higher on reduced than oxidized AC surfaces. Overall, the study results show that selecting ACs and reaction conditions are important to minimize analytical errors and undesirable formation associated with nitrosamines in water samples.

Conformational study of 2-phenylethylamine by molecular-beam Fourier transform microwave spectroscopy.

PubMed

López, Juan C; Cortijo, Vanessa; Blanco, Susana; Alonso, Jose L

2007-08-28

The conformational preferences of the simplest amine neurotransmitter 2-phenylethylamine have been investigated using molecular beam Fourier transform microwave (MB-FTMW) spectroscopy. Two new conformers have been observed together with the two previously reported by Godfrey et al. [J. Am. Chem. Soc., 1995, 117, 8204]. The (14)N nuclear quadrupole hyperfine structure has been resolved for all four conformers. Comparison of the experimental rotational and quadrupole coupling constants with those calculated theoretically provides a conclusive test for the identification of all conformers. The two most stable conformers present a gauche (folded) disposition of the alkyl-amine chain and are stabilised by a weak NH...pi interaction between the amino group and the aromatic ring. The other two conformers show an anti (extended) arrangement of the alkyl-amine chain. Tunnelling splittings have been observed in the spectrum of one of the anti conformers. The post expansion relative abundances in the supersonic jet have been also investigated and related to the conformer energies.

Odd-Even Alternation in Tautomeric Porous Organic Cages with Exceptional Chemical Stability.

PubMed

Bera, Saibal; Basu, Arghya; Tothadi, Srinu; Garai, Bikash; Banerjee, Subhrashis; Vanka, Kumar; Banerjee, Rahul

2017-02-13

Amine-linked (C-NH) porous organic cages (POCs) are preferred over the imine-linked (C=N) POCs owing to their enhanced chemical stability. In general, amine-linked cages, obtained by the reduction of corresponding imines, are not shape-persistent in the crystalline form. Moreover, they require multistep synthesis. Herein, a one-pot synthesis of four new amine-linked organic cages by the reaction of 1,3,5-triformylphloroglucinol (Tp) with different analogues of alkanediamine is reported. The POCs resulting from the odd diamine (having an odd number of -CH 2 groups) is conformationally eclipsed, while the POCs constructed from even diamines adopt a gauche conformation. This odd-even alternation in the conformation of POCs has been supported by computational calculations. The synthetic strategy hinges on the concept of Schiff base condensation reaction followed by keto-enol tautomerization. This mechanism is the key for the exceptional chemical stability of cages and facilitates their resistance towards acids and bases. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Grafting of Ring-Opened Cyclopropylamine Thin Films on Silicon (100) Hydride via UV Photoionization.

PubMed

Tung, J; Ching, J Y; Ng, Y M; Tew, L S; Khung, Y L

2017-09-13

The grafting of cyclopropylamine onto a silicon (100) hydride (Si-H) surface via a ring-opening mechanism using UV photoionization is described here. In brief, radicals generated from the Si-H surface upon UV irradiation were found to behave in classical hydrogen abstraction theory manner by which the distal amine group was first hydrogen abstracted and the radical propagated down to the cyclopropane moiety. This subsequently liberated the strained bonds of the cyclopropane group and initiated the surface grafting process, producing a thin film approximately 10-15 nm in height. Contact angle measurements also showed that such photoionization irradiation had yielded an extremely hydrophilic surface (∼21.3°) and X-ray photoelectron spectroscopy also confirmed the coupling was through the Si-C linkage. However, when the surface underwent high-temperature hydrosilylation (>160 °C), the reaction proceeded predominantly through the nucleophilic NH 2 group to form a Si-N linkage to the surface. This rendered the surface hydrophobic and hence suggested that the Si-H homolysis model may not be the main process. To the best of our knowledge, this was the first attempt reported in the literature to use photoionization to directly graft cyclopropylamine onto a silicon surface and in due course generate a highly rich NH-terminated surface that was found to be highly bioactive in promoting cell viability on the basis of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide studies.

Metal vinylidenes and allenylidenes in catalysis: applications in anti-Markovnikov additions to terminal alkynes and alkene metathesis.

PubMed

Bruneau, Christian; Dixneuf, Pierre H

2006-03-27

The involvement of a catalytic metal vinylidene species was proposed for the first time in 1986 to explain the regioselective formation of vinyl carbamates directly from terminal alkynes, carbon dioxide, and amines. Since this initial report, various metal vinylidenes and allenylidenes, which are key activation intermediates, have proved extremely useful for many alkyne transformations. They have contributed to the rational design of new catalytic reactions. This 20th anniversary is a suitable occasion to present the advancement of organometallic vinylidenes and allenylidenes in catalysis.

Three-dimensional analysis of vestibular efferent neurons innervating semicircular canals of the gerbil

NASA Technical Reports Server (NTRS)

Purcell, I. M.; Perachio, A. A.

1997-01-01

Anterograde labeling techniques were used to examine peripheral innervation patterns of vestibular efferent neurons in the crista ampullares of the gerbil. Vestibular efferent neurons were labeled by extracellular injections of biocytin or biotinylated dextran amine into the contralateral or ipsilateral dorsal subgroup of efferent cell bodies (group e) located dorsolateral to the facial nerve genu. Anterogradely labeled efferent terminal field varicosities consist mainly of boutons en passant with fewer of the terminal type. The bouton swellings are located predominately in apposition to the basolateral borders of the afferent calyces and type II hair cells, but several boutons were identified close to the hair cell apical border on both types. Three-dimensional reconstruction and morphological analysis of the terminal fields from these cells located in the sensory neuroepithelium of the anterior, horizontal, and posterior cristae were performed. We show that efferent neurons densely innervate each end organ in widespread terminal fields. Subepithelial bifurcations of parent axons were minimal, with extensive collateralization occurring after the axons penetrated the basement membrane of the neuroepithelium. Axonal branching ranged between the 6th and 27th orders and terminal field collecting area far exceeds that of the peripheral terminals of primary afferent neurons. The terminal fields of the efferent neurons display three morphologically heterogeneous types: central, peripheral, and planum. All cell types possess terminal fields displaying a high degree of anisotropy with orientations typically parallel to or within +/-45 degrees of the longitudinal axis if the crista. Terminal fields of the central and planum zones predominately project medially toward the transverse axis from the more laterally located penetration of the basement membrane by the parent axon. Peripheral zone terminal fields extend predominately toward the planum semilunatum. The innervation areas of efferent terminal fields display a trend from smallest to largest for the central, peripheral, and planum types, respectively. Neurons that innervate the central zone of the crista do not extend into the peripheral or planum regions. Conversely, those neurons with terminal fields in the peripheral or planum regions do not innervate the central zone of the sensory neuroepithelium. The central zone of the crista is innervated preferentially by efferent neurons with cell bodies located in the ipsilateral group e. The peripheral and planum zones of the crista are innervated preferentially by efferent neurons with cell bodies located in the contralateral group e. A model incorporating our anatomic observations is presented describing an ipsilateral closed-loop feedback between ipsilateral efferent neurons and the periphery and an open-loop feed-forward innervation from contralateral efferent neurons. A possible role for the vestibular efferent neurons in the modulation of semicircular canal afferent response dynamics is proposed.

Determination of secondary and tertiary amines as N-nitrosamine precursors in drinking water system using ultra-fast liquid chromatography-tandem mass spectrometry.

PubMed

Wu, Qihua; Shi, Honglan; Ma, Yinfa; Adams, Craig; Eichholz, Todd; Timmons, Terry; Jiang, Hua

2015-01-01

N-Nitrosamines are potent mutagenic and carcinogenic emerging water disinfection by-products (DBPs). The most effective strategy to control the formation of these DBPs is minimizing their precursors from source water. Secondary and tertiary amines are dominating precursors of N-nitrosamines formation during drinking water disinfection process. Therefore, the screening and removal of these amines in source water are very essential for preventing the formation of N-nitrosamines. A rapid, simple, and sensitive ultrafast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS) method has been developed in this study to determine seven amines, including dimethylamine, ethylmethylamine, diethylamine, dipropylamine, trimethylamine, 3-(dimethylaminomethyl)indole, and 4-dimethylaminoantipyrine, as major precursors of N-nitrosamines in drinking water system. No sample preparation process is needed except a simple filtration. Separation and detection can be achieved in 11 min per sample. The method detection limits of selected amines are ranging from 0.02 μg/L to 1 μg/L except EMA (5 μg/L), and good calibration linearity was achieved. The developed method was applied to determine the selected precursors in source water and drinking water samples collected from Midwest area of the United States. In most of water samples, the concentrations of selected precursors of N-nitrosamines were below their method detection limits. Dimethylamine was detected in some of water samples at the concentration up to 25.4 μg/L. Copyright © 2014 Elsevier B.V. All rights reserved.

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...

Metal-free, mild, nonepimerizing, chemo- and enantio- or diastereoselective N-alkylation of amines by alcohols via oxidation/imine-iminium formation/reductive amination: a pragmatic synthesis of octahydropyrazinopyridoindoles and higher ring analogues.

PubMed

Khan, Imran A; Saxena, Anil K

2013-12-06

A mild step and atom-economical nonepimerizing chemo- and enantioselective N-alkylating procedure has been developed via oxidation/imine-iminium formation/reduction cascade using TEMPO-BAIB-HEH-Brønsted acid catalysis in DMPU as solvent and a stoichiometric amount of amine. The optimized conditions were further extended for the nonenzymatic kinetic resolution of the chiral amine thus formed under nonenzymatic in situ hydrogen-transfer conditions using VAPOL-derived phosphoric acid (VAPOL-PA) as the Brønsted acid catalyst. The enantioselective cascade of the presented reaction was successfully utilized in the synthesis of octahydropyrazinopyridoindole and its higher ring analogues.