The orbital ground state of the azide-substrate complex of human heme oxygenase is an indicator of distal H-bonding: Implications for the enzyme mechanism‡

PubMed Central

Ogura, Hiroshi; Evans, John P.; Peng, Dungeng; Satterlee, James D.; de Montellano, Paul R. Ortiz; Mar, Gerd N. La

2009-01-01

The active site electronic structure of the azide complex of substrate-bound human heme oxygenase-1, (hHO) has been investigated by 1H NMR spectroscopy to shed light on the orbital/spin ground state as an indicator of the unique distal pocket environment of the enzyme. 2D 1H NMR assignments of the substrate and substrate-contact residue signals reveal a pattern of substrate methyl contact shifts, that places the lone iron π-spin in the dxz orbital, rather than the dyz orbital found in the cyanide complex. Comparison of iron spin relaxivity, magnetic anisotropy and magnetic susceptibilities argues for a low-spin, (dxy)2(dyz,dxz)3, ground state in both azide and cyanide complexes. The switch from singly-occupied dyz for the cyanide to dxz for the azide complex of hHO is shown to be consistent with the orbital hole determined by the azide π-plane in the latter complex, which is ∼90° in-plane rotated from that of the imidazole π-plane. The induction of the altered orbital ground state in the azide relative to the cyanide hHO complex, as well as the mean low-field bias of methyl hyperfine shifts and their paramagnetic relaxivity relative to those in globins, indicate that azide exerts a stronger ligand field in hHO than in the globins, or that the distal H-bonding to azide is weaker in hHO than in globins. The Asp140 → Ala hHO mutant that abolishes activity retains the unusual WT azide complex spin/orbital ground state. The relevance of our findings for other HO complexes and the HO mechanism is discussed. PMID:19243105

REVISITING CLASSICAL NUCLEOPHILIC SUBSTITUTIONS IN AQUEOUS MEDIUM: MICROWAVE-ASSISTED SYNTHESIS OF ALKYL AZIDES

EPA Science Inventory

An efficient and clean synthesis of alkyl azides using microwave (MW) radiation is described in aqueous medium by reacting alkyl halides or tosylates with alkali azides. This general and expeditious MW-enhanced approach to nucleophilic substitution reactions is applicable to the ...

Effectiveness of sodium azide alone compared to sodium azide in combination with methyl nitrosurea for rice mutagenesis

USDA-ARS?s Scientific Manuscript database

Rice seeds of the temperate japonica cultivar Kitaake were mutagenized with sodium azide alone and in combination with methyl nitrosourea. Using the reduced representation sequencing method Restriction Enzyme Sequence Comparative Analysis (RESCAN), the mutation densities, types and local sequence co...

Direct Functionalization of an Acid-Terminated Nanodiamond with Azide: Enabling Access to 4-Substituted-1,2,3-Triazole-Functionalized Particles

DOE PAGES

Kennedy, Zachary C.; Barrett, Christopher A.; Warner, Marvin G.

2017-03-01

Azides on the periphery of nanodiamond materials (ND) are of great utility because they have been shown to undergo Cu-catalyzed and Cu-free cycloaddition reactions with structurally diverse alkynes, affording particles tailored for applications in biology and materials science. However, current methods employed to access ND featuring azide groups typically require either harsh pretreatment procedures or multiple synthesis steps and use surface linking groups that may be susceptible to undesirable cleavage. Here in this paper we demonstrate an alternative single-step approach to producing linker-free, azide-functionalized ND. Our method was applied to low-cost, detonation-derived ND powders where surface carbonyl groups undergo silver-mediatedmore » decarboxylation and radical substitution with azide. ND with directly grafted azide groups were then treated with a variety of aliphatic, aromatic, and fluorescent alkynes to afford 1-(ND)-4-substituted-1,2,3-triazole materials under standard copper-catalyzed cycloaddition conditions. Surface modification steps were verified by characteristic infrared absorptions and elemental analyses. High loadings of triazole surface groups (up to 0.85 mmol g –1) were obtained as determined from thermogravimetric analysis. The azidation procedure disclosed is envisioned to become a valuable initial transformation in numerous future applications of ND.« less

Azide functionalized poly(3-hexylthiophene) and method of forming same

DOEpatents

Qin, Yang; Grubbs, Robert B; Park, Young Suk

2014-03-25

The invention relates azide functionalized poly(3-hexylthiophene)s. Various azide functionalized poly(3-hexylthiophene)s and intermediates are disclosed and described, as well as method for making novel monomers that are synthesized and transformed into P3HT-N.sub.mp for use as organic conducting polymers in organic photovoltaic devices.

26. BUILDING NO. 271I, LEAD AZIDE PRIMER BUILDING, WESTERN CORNER ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

26. BUILDING NO. 271-I, LEAD AZIDE PRIMER BUILDING, WESTERN CORNER OF BUILDING SHOWING DOORS TO MIXING ROOM NO. 4. HAND CRANK VISIBLE AT RIGHT ROTATED SMALL POTS (CONTAINING LEAD AZIDE) IN MIXING ROOMS. - Picatinny Arsenal, 200 Area, Shell Component Loading, State Route 15 near I-80, Dover, Morris County, NJ

EPR and pulsed ENDOR study of intermediates from reactions of aromatic azides with group 13 metal trichlorides

PubMed Central

Bencivenni, Giorgio; Cesari, Riccardo; Nanni, Daniele; El Mkami, Hassane

2010-01-01

Summary The reactions of group 13 metal trichlorides with aromatic azides were examined by CW EPR and pulsed ENDOR spectroscopies. Complex EPR spectra were obtained from reactions of aluminium, gallium and indium trichlorides with phenyl azides containing a variety of substituents. Analysis of the spectra showed that 4-methoxy-, 3-methoxy- and 2-methoxyphenyl azides all gave ‘dimer’ radical cations [ArNHC6H4NH2]+• and trimers [ArNHC6H4NHC6H4NH2]+• followed by polymers. 4-Azidobenzonitrile, with its electron-withdrawing substituent, did not react. In general the aromatic azides appeared to react most rapidly with AlCl3 but this reagent tended to generate much polymer. InCl3 was the least reactive group 13 halide. DFT computations of the radical cations provided corroborating evidence and suggested that the unpaired electrons were accommodated in extensive π-delocalised orbitals. A mechanism to account for the reductive conversion of aromatic azides to the corresponding anilines and thence to the dimers and trimers is proposed. PMID:21049080

Determination of insoluble azides by thermometric titrimetry.

PubMed

Chagas, A P; Godinho, O E; Costa, J L

1977-09-01

A method for determination of azide, based on the thermometric titration of this anion with hydrochloric acid, is described. Although this reaction has a large enthalpy change (DeltaH = -3.6 kcal/ mole), sulphate is added as an endothermic thermometric indicator to improve the end-point. The application of the method to the analysis of insoluble azides has been studied.

Biosensor Technology Reveals the Disruption of the Endothelial Barrier Function and the Subsequent Death of Blood Brain Barrier Endothelial Cells to Sodium Azide and Its Gaseous Products.

PubMed

Kho, Dan T; Johnson, Rebecca H; O'Carroll, Simon J; Angel, Catherine E; Graham, E Scott

2017-09-21

Herein we demonstrate the sensitive nature of human blood-brain barrier (BBB) endothelial cells to sodium azide and its gaseous product. Sodium azide is known to be acutely cytotoxic at low millimolar concentrations, hence its use as a biological preservative (e.g., in antibodies). Loss of barrier integrity was noticed in experiments using Electric Cell-substrate Impedance Sensing (ECIS) biosensor technology, to measure endothelial barrier integrity continuously in real-time. Initially the effect of sodium azide was observed as an artefact where it was present in antibodies being employed in neutralisation experiments. This was confirmed where antibody clones that were azide-free did not mediate loss of barrier function. A delayed loss of barrier function in neighbouring wells implied the influence of a liberated gaseous product. ECIS technology demonstrated that the BBB endothelial cells had a lower level of direct sensitivity to sodium azide of ~3 µM. Evidence of gaseous toxicity was consistently observed at 30 µM and above, with disrupted barrier function and cell death in neighbouring wells. We highlight the ability of this cellular biosensor technology to reveal both the direct and gaseous toxicity mediated by sodium azide. The sensitivity and temporal dimension of ECIS technology was instrumental in these observations. These findings have substantial implications for the wide use of sodium azide in biological reagents, raising issues of their application in live-cell assays and with regard to the protection of the user. This research also has wider relevance highlighting the sensitivity of brain endothelial cells to a known mitochondrial disruptor. It is logical to hypothesise that BBB endothelial dysfunction due to mitochondrial dys-regulation could have an important but underappreciated role in a range of neurological diseases.

Copper(II)-Catalyzed Conversion of Aryl/Heteroaryl Boronic Acids, Boronates, and Trifluoroborates into the Corresponding Azides: Substrate Scope and Limitations.

PubMed

Grimes, Kimberly D; Gupte, Amol; Aldrich, Courtney C

2010-05-01

We report the copper(II)-catalyzed conversion of organoboron compounds into the corresponding azide derivatives. A systematic series of phenylboronic acid derivatives is evaluated to examine the importance of steric and electronic effects of the substituents on reaction yield as well as functional group compatibility. Heterocyclic substrates are also shown to participate in this mild reaction while compounds incorporating B-C(sp(3)) bonds are unreactive under the reaction conditions. The copper(II)-catalyzed boronic acid-azide coupling reaction is further extended to both boronate esters and potassium organotrifluoroborate salts. The method described herein complements existing procedures for the preparation of aryl azides from the respective amino, triazene, and halide derivatives and we expect that it will greatly facilitate copper- and ruthenium-catalyzed azide-alkyne cycloaddition reactions for the preparation of diversely functionalized 1-aryl- or 1-heteroaryl-1,2,3-triazoles derivatives.

Metal-Free Poly-Cycloaddition of Activated Azide and Alkynes toward Multifunctional Polytriazoles: Aggregation-Induced Emission, Explosive Detection, Fluorescent Patterning, and Light Refraction.

PubMed

Wu, Yongwei; He, Benzhao; Quan, Changyun; Zheng, Chao; Deng, Haiqin; Hu, Rongrong; Zhao, Zujin; Huang, Fei; Qin, Anjun; Tang, Ben Zhong

2017-09-01

The metal-free click polymerization (MFCP) of activated alkynes and azides or activated azide and alkynes have been developed into powerful techniques for the construction of polytriazoles without the obsession of metallic catalyst residues problem. However, the MFCP of activated azides and alkynes is rarely applied in preparation of functional polytriazoles. In this paper, soluble multifunctional polytriazoles (PIa and PIb) with high weight-average molecular weights (M w up to 32 000) are prepared via the developed metal-free poly-cycloaddition of activated azide and alkynes in high yields (up to 90%). The resultant PIa and PIb are thermally stable, and show aggregation-induced emission characteristics, enabling their aggregates to detect explosives with superamplification effect. Moreover, thanks to their containing aromatic rings and polar moieties, PIa and PIb exhibit high refractive indices. In addition, they can also be cross-linked upon UV irradiation to generate 2D fluorescent patterning due to their remaining azide groups and containing ester groups. Thus, these multifunctional polytriazoles are potentially applicable in the optoelectronic and sensing fields. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bone marrow cells stained by azide-conjugated Alexa fluors in the absence of an alkyne label.

PubMed

Lin, Guiting; Ning, Hongxiu; Banie, Lia; Qiu, Xuefeng; Zhang, Haiyang; Lue, Tom F; Lin, Ching-Shwun

2012-09-01

Thymidine analog 5-ethynyl-2'-deoxyuridine (EdU) has recently been introduced as an alternative to 5-bromo-2-deoxyuridine (BrdU) for cell labeling and tracking. Incorporation of EdU into replicating DNA can be detected by azide-conjugated fluors (eg, Alexa-azide) through a Cu(i)-catalyzed click reaction between EdU's alkyne moiety and azide. While this cell labeling method has proven to be valuable for tracking transplanted stem cells in various tissues, we have found that some bone marrow cells could be stained by Alexa-azide in the absence of EdU label. In intact rat femoral bone marrow, ~3% of nucleated cells were false-positively stained, and in isolated bone marrow cells, ~13%. In contrast to true-positive stains, which localize in the nucleus, the false-positive stains were cytoplasmic. Furthermore, while true-positive staining requires Cu(i), false-positive staining does not. Reducing the click reaction time or reducing the Alexa-azide concentration failed to improve the distinction between true- and false-positive staining. Hematopoietic and mesenchymal stem cell markers CD34 and Stro-1 did not co-localize with the false-positively stained cells, and these cells' identity remains unknown.

Copper-Catalyzed Sulfonyl Azide-Alkyne Cycloaddition Reactions: Simultaneous Generation and Trapping of Copper-Triazoles and -Ketenimines for the Synthesis of Triazolopyrimidines.

PubMed

Nallagangula, Madhu; Namitharan, Kayambu

2017-07-07

First simultaneous generation and utilization of both copper-triazole and -ketenimine intermediates in copper-catalyzed sulfonyl azide-alkyne cycloaddition reactions is achieved for the one-pot synthesis of triazolopyrimidines via a novel copper-catalyzed multicomponent cascade of sulfonyl azides, alkynes, and azirines. Significantly, the reaction proceeds under very mild conditions in good yields.

Synthesis of radiolabelled aryl azides from diazonium salts: experimental and computational results permit the identification of the preferred mechanism.

PubMed

Joshi, Sameer M; de Cózar, Abel; Gómez-Vallejo, Vanessa; Koziorowski, Jacek; Llop, Jordi; Cossío, Fernando P

2015-05-28

Experimental and computational studies on the formation of aryl azides from the corresponding diazonium salts support a stepwise mechanism via acyclic zwitterionic intermediates. The low energy barriers associated with both transition structures are compatible with very fast and efficient processes, thus making this method suitable for the chemical synthesis of radiolabelled aryl azides.

Modification of kanamycin-esculin-azide agar to improve selectivity in the enumeration of fecal streptococci from water samples.

PubMed

Audicana, A; Perales, I; Borrego, J J

1995-12-01

Kanamycin-esculin-azide agar was modified by increasing the concentration of sodium azide to 0.4 g liter-1 and replacing kanamycin sulfate with 5 mg of oxolinic acid liter-1. The modification, named oxolinic acid-esculin-azide (OAA) agar, was compared with Slanetz-Bartley and KF agars by using drinking water and seawater samples. The OAA agar showed higher specificity, selectivity, and recovery efficiencies than those obtained by using the other media. In addition, no confirmation of typical colonies was needed when OAA agar was used, which significantly shortens the time of sample processing and increases the accuracy of the method.

Modification of kanamycin-esculin-azide agar to improve selectivity in the enumeration of fecal streptococci from water samples.

PubMed Central

Audicana, A; Perales, I; Borrego, J J

1995-01-01

Kanamycin-esculin-azide agar was modified by increasing the concentration of sodium azide to 0.4 g liter-1 and replacing kanamycin sulfate with 5 mg of oxolinic acid liter-1. The modification, named oxolinic acid-esculin-azide (OAA) agar, was compared with Slanetz-Bartley and KF agars by using drinking water and seawater samples. The OAA agar showed higher specificity, selectivity, and recovery efficiencies than those obtained by using the other media. In addition, no confirmation of typical colonies was needed when OAA agar was used, which significantly shortens the time of sample processing and increases the accuracy of the method. PMID:8534085

Preparation and Characterization of the Binary Group 13 Azides M(N3)3 and M(N3)3’CH3CN (M = Ga, In, TI), [Ga(N3)5](2-), and [M(N3)6](3-) (M = In, TI) (Preprint)

DTIC Science & Technology

2011-05-24

semiconductor and optoelectronic applications. Although most of these efforts were devoted to gallium azides, aluminium and indium azides were also...their usefulness for semiconductor and optoelectronic applications. Although most of these efforts were devoted to gallium azides,[20,21] aluminium and...57(1) N(7) -152(5) 6417(2) 7317(2) 54(1) N(8) 20(5) 6903(2) 7687(2) 48(1) N(9) 148(4) 7388(3) 8011 (3) 80(2) P(1) 4132(1) 6289(1) 9090(1) 30(1

Exposure to the metabolic inhibitor sodium azide induces stress protein expression and thermotolerance in the nematode Caenorhabditis elegans

PubMed Central

Massie, Michelle R.; Lapoczka, Elizabeth M.; Boggs, Kristy D.; Stine, Karen E.; White, Glenn E.

2003-01-01

Historically, sodium azide has been used to anesthetize the nematode Caenorhabditis elegans; however, the mechanism by which it survives this exposure is not understood. In this study, we report that exposure of wild-type C elegans to 10 mM sodium azide for up to 90 minutes confers thermotolerance (defined as significantly increased survival probability [SP] at 37°C) on the animal. In addition, sodium dodecyl sulfate–polyacrylamide gel electrophoresis revealed enhanced Hsp70 expression, whereas Western blot analysis revealed the induction of Hsp16. We also tested the only known C elegans Hsp mutant daf-21 (codes for Hsp90), which constitutively enters the stress-resistant state known as the dauer larvae. Daf-21 mutants also acquire sodium azide–induced thermotolerance, whereas 3 non-Hsp, constitutive dauer-forming mutants exhibited a variable response to azide exposure. We conclude that the ability of C elegans to survive exposure to azide is associated with the induction of at least 2 stress proteins. PMID:12820649

Improved Synthesis of 5-Substituted 1H-Tetrazoles via the [3+2] Cycloaddition of Nitriles and Sodium Azide Catalyzed by Silica Sulfuric Acid

PubMed Central

Du, Zhenting; Si, Changmei; Li, Youqiang; Wang, Yin; Lu, Jing

2012-01-01

A silica supported sulfuric acid catalyzed [3+2] cycloaddition of nitriles and sodium azide to form 5-substituted 1H-tetrazoles is described. The protocol can provide a series of 5-substituted 1H-tetrazoles using silica sulfuric acid from nitriles and sodium azide in DMF in 72%–95% yield. PMID:22606004

Response of Primary Explosives to Gaseous Discharges in an Improved Approaching-Electrode Electrostatic Sensitivity Apparatus

DTIC Science & Technology

1976-10-01

and Identify by block number) This report describes an improved, approaching-needle electrostatic sensitivity apparatus as well as the...category. Thus, basic lead styphnate, RD1333 lead azide, dextrinated lead azide and tetracene all ignited. But, as expected, tetryl, PETN, superfine PETN... dextrinated lead azide obtained using the same apparatus and procedure and conducted at the same time. Sample Preparation, Electrode Replacement, and

Pyrrole- and Naphthobipyrrole-Strapped Calix[4]pyrroles as Azide Anion Receptors.

PubMed

Kim, Seung Hyeon; Lee, Juhoon; Vargas-Zúñiga, Gabriela I; Lynch, Vincent M; Hay, Benjamin P; Sessler, Jonathan L; Kim, Sung Kuk

2018-03-02

The binding interactions between the azide anion (N 3 - ) and the strapped calix[4]pyrroles 2 and 3 bearing auxiliary hydrogen bonding donors on the bridging moieties, as well as of normal calix[4]pyrrole 1, were investigated via 1 H NMR spectroscopic and isothermal titration calorimetry analyses. The resulting data revealed that receptors 2 and 3 have significantly higher affinities for the azide anion in organic media as compared with the unfunctionalized calix[4]pyrrole 1 and other azide receptors reported to date. Single crystal X-ray diffraction analyses and calculations using density functional theory revealed that receptor 2 binds CsN 3 in two distinct structural forms. As judged from the metric parameters, in the resulting complexes one limiting azide anion resonance contributor is favored over the other, with the specifics depending on the binding mode. In contrast to what is seen for 2, receptor 3 forms a CsN 3 complex in 20% CD 3 OD in CDCl 3 , wherein the azide anion is bound only vertically to the NH protons of the calix[4]pyrrole and the cesium cation is complexed within the cone shaped-calix[4]pyrrole bowl. The bound cesium cation is also in close proximity to a naphthobipyrrole subunit present in a different molecule, forming an apparent cation-π complex.

A highly sensitive protocol for microscopy of alkyne lipids and fluorescently tagged or immunostained proteins[S

PubMed Central

Gaebler, Anne; Penno, Anke; Kuerschner, Lars; Thiele, Christoph

2016-01-01

The demand to study the cellular localization of specific lipids has led to recent advances in lipid probes and microscopy. Alkyne lipids bear a small, noninterfering tag and can be detected upon click reaction with an azide-coupled reporter. Fluorescent alkyne lipid imaging crucially depends on appropriate azide reporters and labeling protocols that allow for an efficient click reaction and therefore a sensitive detection. We synthesized several azide reporters with different spacer components and tested their suitability for alkyne lipid imaging in fixed cells. The implementation of a copper-chelating picolyl moiety into fluorescent or biotin-based azide reagents strongly increased the sensitivity of the imaging routine. We demonstrate the applicability and evaluate the performance of this approach using different lipid classes and experimental setups. As azide picolyl reporters allow for reduced copper catalyst concentrations, they also enable coimaging of alkyne lipids with multiple fluorescent proteins including enhanced green fluorescent protein. Alternatively, and as we also show, microscopy of alkyne lipids can be combined with protein detection by immunocytochemistry. In summary, we present a robust, sensitive, and highly versatile protocol for the labeling of alkyne lipids with azide-coupled reporters for fluorescence microscopy that can be combined with different protein detection and imaging techniques. PMID:27565170

Formation of heterobimetallic zirconium/cobalt diimido complexes via a four-electron transformation.

PubMed

Wu, Bing; Hernández Sánchez, Raúl; Bezpalko, Mark W; Foxman, Bruce M; Thomas, Christine M

2014-10-06

The reactivity of the reduced heterobimetallic complex Zr((i)PrNP(i)Pr2)3CoN2 (1) toward aryl azides was examined, revealing a four-electron redox transformation to afford unusual heterobimetallic zirconium/cobalt diimido complexes. In the case of p-tolyl azide, the diamagnetic C3-symmetric bis(terminal imido) complex 3 is formed, but mesityl azide instead leads to asymmetric complex 4 featuring a bridging imido fragment.

Investigation of induced unimolecular decomposition for development of visible chemical lasers. Quarterly progress report, 1 August 1976--30 October 1976

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

Piper, L G; Taylor, R L

This report summarizes progress during the second quarterly period of the subject contract. The methods available for the production of excited electronic states following azide decomposition are summarized. It is concluded that an experiment designed to study the kinetics of and branching ratios for electronically excited products from azide radicals reactions will be most productive in elucidating excitation mechanisms for potential chemical lasers. A flow reactor is described in which these studies may be undertaken. The major feature of this apparatus is a clean azide radical source based upon the thermal decomposition of solid, ionic azides. The contruction of themore » experimental apparatus has been started.« less

Alkyl Azides, Diazides, Haloazides and Bridged Polycyclic Diazides

DTIC Science & Technology

1991-05-16

temperature. Most of the methyl ether was removed during this process. The ehtyl ether was distilled from the reaction mixture using a water aspirator into a...Street PROGRAM IPROJECT ITASK IWORK li1111? ArliiqIoh, VA 22217-5000 EILIMENT NO I NO. I oACCESSION P10) Alkyl Azides, Dlazides, laloazides and...REPRODUCE LEGIBLY. ALKYL AZIDES, DIAZIDES, HALOAZIDES AND BRIDGED POLYCYCLIC DIAZIDES Final REPORTe July 1, 1989-November 14, 1990 A6jd.%4gi0 F’or

Millimeter-wave spectroscopy of syn formyl azide (HC(O)N3) in seven vibrational states

NASA Astrophysics Data System (ADS)

Walters, Nicholas A.; Amberger, Brent K.; Esselman, Brian J.; Woods, R. Claude; McMahon, Robert J.

2017-01-01

Millimeter-wave spectra for formyl azide (HC(O)N3) were obtained from 240 to 360 GHz at ambient temperature. For the ground state of syn formyl azide, over 1500 independent rotational transitions were measured and least-squares fit to a complete S-reduced 8th order centrifugal distortion/rigid rotor Hamiltonian. The decomposition of formyl azide was monitored over a period of several hours, the half-life (t½ = 30 min) was determined, and its decomposition products were investigated. Transitions from five vibrational satellites of syn formyl azide (ν9, ν12, 2ν9, ν9 + ν12, and ν11) were observed, measured, and least-squares fit to complete or nearly complete octic centrifugally-distorted, single-state S-reduced models. A less complete single-state fit of 3ν9 (509.3 cm-1) was obtained from an unperturbed subset of its assignable transitions. This state is apparently coupled to the fundamental ν8 (489.4 cm-1) and the overtone 2ν12 (503.6 cm-1), but the coupling remains unanalyzed. Anharmonic CCSD(T)/ANO1 estimates of the vibrational frequencies of syn formyl azide were in close agreement with previously published experimental and computational values. Experimentally determined vibration-rotation interaction (αi) values were in excellent agreement with coupled-cluster predicted αi values for the fundamentals ν9, ν12, and ν11.

A highly sensitive protocol for microscopy of alkyne lipids and fluorescently tagged or immunostained proteins.

PubMed

Gaebler, Anne; Penno, Anke; Kuerschner, Lars; Thiele, Christoph

2016-10-01

The demand to study the cellular localization of specific lipids has led to recent advances in lipid probes and microscopy. Alkyne lipids bear a small, noninterfering tag and can be detected upon click reaction with an azide-coupled reporter. Fluorescent alkyne lipid imaging crucially depends on appropriate azide reporters and labeling protocols that allow for an efficient click reaction and therefore a sensitive detection. We synthesized several azide reporters with different spacer components and tested their suitability for alkyne lipid imaging in fixed cells. The implementation of a copper-chelating picolyl moiety into fluorescent or biotin-based azide reagents strongly increased the sensitivity of the imaging routine. We demonstrate the applicability and evaluate the performance of this approach using different lipid classes and experimental setups. As azide picolyl reporters allow for reduced copper catalyst concentrations, they also enable coimaging of alkyne lipids with multiple fluorescent proteins including enhanced green fluorescent protein. Alternatively, and as we also show, microscopy of alkyne lipids can be combined with protein detection by immunocytochemistry. In summary, we present a robust, sensitive, and highly versatile protocol for the labeling of alkyne lipids with azide-coupled reporters for fluorescence microscopy that can be combined with different protein detection and imaging techniques. Copyright © 2016 by the American Society for Biochemistry and Molecular Biology, Inc.

Silicone azide fireproof material

NASA Technical Reports Server (NTRS)

1978-01-01

Finely powdered titanium oxide was added to silicone azide as the sintering agent to produce a nonflammable material. Mixing proportions, physical properties, and chemical composition of the fireproofing material are included.

Highly sensitive fluorescence and SERS detection of azide through a simple click reaction of 8-chloroquinoline and phenylacetylene.

PubMed

Zeng, Qing; Ye, Lingling; Ma, Lu; Yin, Wenqing; Li, Tingsheng; Liang, Aihui; Jiang, Zhiliang

2015-05-01

In 0.19 mol/L acetic acid (HAc), a click reaction of 8-chloroquinoline/azide/phenylacetylene take places in aqueous solution without Cu(I) as a catalyst. 8-Chloroquinoline (CQN) exhibited a strong fluorescence peak at 430 nm that was quenched linearly as the concentration of azide increased from 20 to 1000 ng/mL. This quenching was due to consumption of CQN in the click reaction and a decrease in the number of efficiently excited photons due to the presence of triazole-quinoline ramification molecules with strong hydrophobicity. Using blue nanosilver sol as the substrate, CQN absorbed onto the surface of nanosilver particles, showing a strong surface-enhanced Raman scattering (SERS) peak at 1585 cm(-1) that decreased linearly as the azide concentration increased from 8 to 500 ng/mL; the detection limit was 4 ng/mL. Thus, two new, simple and sensitive fluorescence and SERS methods have been developed for the determination of azide via the click reaction. Copyright © 2014 John Wiley & Sons, Ltd.

Visible-light-driven Efficient Photocatalytic Reduction of Organic Azides to Amines over CdS Sheet-rGO Nanocomposite.

PubMed

Singha, Krishnadipti; Mondal, Aniruddha; Ghosh, Subhash Chandra; Panda, Asit Baran

2018-02-02

CdS sheet-rGO nanocomposite as a heterogeneous photocatalyst enables visible-light-induced photocatalytic reduction of aromatic, heteroaromatic, aliphatic and sulfonyl azides to the corresponding amines using hydrazine hydrate as a reductant. The reaction shows excellent conversion and chemoselectivity towards the formation of the amine without self-photoactivated azo compounds. In the adopted strategy, CdS not only accelerates the formation of nitrene through photoactivation of azide but also enhances the decomposition of azide to a certain extent, which entirely suppressed formation of the azo compound. The developed CdS sheet-rGO nanocomposite catalyst is very active, providing excellent results under irradiation with a 40 W simple household CFL lamp. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigation of Analytical Techniques for the Rapid Determination of the Moisture Content of NOL 130 Primer Mix and Lead Azide

DTIC Science & Technology

1986-05-01

the presence of NOL 130 6 Determination of moisture content of dextrinated lead azide 14 containing known amounts of water, by the Karl Fisher method...maLhiod, extraction mode 8 Determinatiov) of moisture content of special purpose and 16 dextrinated lead atide, containing known amounts of water by the...water in special purpose and dextrinated lead azides were determined by the method described in the experimen- tal section of this report, data shown

Vinyl azides derived from allenes: thermolysis leading to multisubstituted 1,4-pyrazines and Mn(III)-catalyzed photochemical reaction leading to pyrroles.

PubMed

Sajna, K V; Kumara Swamy, K C

2012-10-05

Thermolysis of phosphorus-based vinyl azides under solvent- and catalyst-free conditions furnished a new route for 1,4-pyrazines. A simple one-pot, Mn(III)-catalyzed photochemical route has been developed for multisubstituted pyrroles starting from allenes and 1,3-dicarbonyls via in situ-generated vinyl azides. The utility of new phosphorus-based pyrroles is also demonstrated in the Horner reaction. The structures of key products are unequivocally confirmed by X-ray crystallography.

Visible-light sensitization of vinyl azides by transition-metal photocatalysis.

PubMed

Farney, Elliot P; Yoon, Tehshik P

2014-01-13

Irradiation of vinyl and aryl azides with visible light in the presence of Ru photocatalysts results in the formation of reactive nitrenes, which can undergo a variety of C-N bond-forming reactions. The ability to use low-energy visible light instead of UV in the photochemical activation of azides avoids competitive photodecomposition processes that have long been a significant limitation on the synthetic use of these reactions. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

27. BUILDING NO. 271I, INTERIOR OF LEAD AZIDE MIXING ROOM. ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

27. BUILDING NO. 271-I, INTERIOR OF LEAD AZIDE MIXING ROOM. HERE, TWO POUNDS (MAXIMUM) OF LEAD AZIDE WAS MIXED IN SEVEN SMALL POTS EACH SEPARATED FROM THE OTHERS BY THE STEEL WALLS PICTURED HERE. THE POTS ARE ALL FIXED TO A COMMON SHAFT WHICH IS ROTATED BY A HAND CRANK OUTSIDE OF ROOM (SEE HAER NJ-36A-26). - Picatinny Arsenal, 200 Area, Shell Component Loading, State Route 15 near I-80, Dover, Morris County, NJ

Preparation of a Versatile Bifunctional Zeolite for Targeted Imaging Applications

PubMed Central

Ndiege, Nicholas; Raidoo, Renugan; Schultz, Michael K.; Larsen, Sarah

2011-01-01

Bifunctional zeolite Y was prepared for use in targeted in vivo molecular imaging applications. The strategy involved functionalization of the external surface of zeolite Y with chloropropyltriethoxysilane followed by reaction with sodium azide to form azide-functionalized NaY, which is amenable to copper(1) catalyzed click chemistry. In this study, a model alkyne (4-pentyn-1-ol) was attached to the azide-terminated surface via click chemistry to demonstrate feasibility for attachment of molecular targeting vectors (e.g., peptides, aptamers) to the zeolite surface. The modified particle efficiently incorporates the imaging radioisotope gallium-68 (68Ga) into the pores of the azide-functionalized NaY zeolite to form a stable bifunctional molecular targeting vector. The result is a versatile “clickable” zeolite platform that can be tailored for future in vivo molecular targeting and imaging modalities. PMID:21306141

Hydrothermal synthesis, characterization, and thermal properties of alumino silicate azide sodalite, Na8[AlSiO4]6(N3)2

NASA Astrophysics Data System (ADS)

Borhade, A. V.; Wakchaure, S. G.; Dholi, A. G.; Kshirsagar, T. A.

2017-07-01

First time we report the synthesis, structural characterization and thermal behavior of an unusual N3 - containing alumino-silicate sodalite mineral. Azide sodalite, Na8[AlSiO4]6(N3)2 has been synthesized under hydrothermal conditions at 433 K in steel lined Teflon autoclave. The structural and microstructural properties of azide sodalite mineral was characterized by various methods including FT-IR, XRD, SEM, TGA, and MAS NMR. Crystal structure have been refined by Rietveld method in P\\bar 43n space group, indicating that the N3 - sodalite has cubic in lattice. High temperature study was carried out to see the effect of thermal expansion on cell dimension ( a o) of azide sodalite. Thermal behavior of sodalite was also assessed by thermogravimetric method.

Determination of thiopental in urine sample with high-performance liquid chromatography using iodine-azide reaction as a postcolumn detection system.

PubMed

Zakrzewski, Robert; Ciesielski, Witold

2005-09-25

The reaction between iodine and azide ions induced by thiopental was utilized as a postcolumn reaction for chromatographic determination of thiopental. The method is based on the separation of thiopental on an Nova-Pak CN HP column with an acetonitrile-aqueous solution of sodium azide as a mobile phase, followed by spectrophotometric measurement of the residual iodine (lambda=350 nm) from the postcolumn iodine-azide reaction induced by thiopental after mixing an iodine solution containing iodide ions with the column effluent containing azide ions and thiopental. Chromatograms obtained for thiopental showed negative peaks as a result of the decrease in background absorbance. The detection limit (defined as S/N=3) was 20 nM (0.4 pmol injected amount) for thiopental. Calibration graphs, plotted as peak area versus concentrations, were linear from 40 nM. The elaborated method was applied to determine thiopental in urine samples. The detection limit (defined as S/N=3) was 0.025 nmol/ml urine. Calibration graphs, plotted as peak area versus concentrations, were linear from 0.05 nmol/ml urine. Authentic urine samples were analyzed, thiopental was determined at nmol/ml urine level.

Mutagenesis of Saccharomyces cerevisiae by sodium azide activated in barley.

PubMed

Velemínský, J; Silhánková, L; Smiovská, V; Gichner, T

1979-07-01

Concentrated dialysate of the extract prepared from barley seeds treated with sodium azide increased up to 100--200 times the frequency of forward mutations to cycloheximide resistance in the excision-deficient UV-sensitive heploid strain rad2-5 of Saccharomyces cerevisiae, when applied to growing cells in complete medium at pH 4.2. Only a slight increase of mutation frequency (less than 4 times) was found in the haploid RAD+ strain treated in the same way as well as in haploid RAD+ and rad2-5 strains treated directly by sodium azide. In contrast with the barley-activated sodium azide, UV irradiation was more effective in the induction of cycloheximide resistance in the RAD+ strain than in the RAD2-5 mutant. The dialysate from azide-treated barley seeds, applied at both pH 4.2 and pH 9, also significantly increased the frequency of locus-specific suppressor mutations to isoleucine independence and -- to a lesser extent -- reversions and/or gene conversions in the trp5 locus in growing cells of the diploid strain D7. The dialysate was also mutagenic in resting cells of strains D7 and rad2-5 but with lower effectiveness.

Method for providing adhesion to a metal surface

DOEpatents

Harrah, L.A.; Allred, R.E.; Wilson, K.V. Jr.

1992-02-18

A process for treating metal surfaces to obtain improved susceptibility to bonding with adhesive compositions is disclosed. A metal surface is oxidized with a halogen to form a monolayer of halide ions on the surface. The halide ions are then exchanged with azide ions to form an azide monolayer on the metal surface. Upon contact of the treated surface with an adhesive composition, the azide layer may be thermally or photochemically decomposed to form active nitrene species, which react to bond the adhesive composition to the metal surface.

Method for providing adhesion to a metal surface

DOEpatents

Harrah, Larry A.; Allred, Ronald E.; Wilson, Jr., Kennard V.

1992-01-01

A process for treating metal surfaces to obtain improved susceptibility to bonding with adhesive compositions is disclosed. A metal surface is oxidized with a halogen to form a monolayer of halide ions on the surface. The halide ions are then exchanged with azide ions to form an azide monolayer on the metal surface. Upon contact of the treated surface with an adhesive composition, the azide layer may be thermally or photochemically decomposed to form active nitrene species, which react to bond the adhesive composition to the metal surface.

Synthesis of refractory materials

DOEpatents

Holt, Joseph B.

1984-01-01

Refractory metal nitrides are synthesized during a self-propagating combustion process utilizing a solid source of nitrogren. For this purpose, a metal azide is employed, preferably NaN.sub.3. The azide is combusted with Mg or Ca, and a metal oxide is selected from Groups III-A, IV-A, III-B, IV-B, or a rare earth metal oxide. The mixture of azide, Ca or Mg and metal oxide is heated to the mixture's ignition temperature. At that temperature the mixture is ignited and undergoes self-sustaining combustion until the starter materials are exhausted, producing the metal nitride.

Recent advances in transition metal-catalyzed N -atom transfer reactions of azides

PubMed Central

Driver, Tom G.

2011-01-01

Transition metal-catalyzed N-atom transfer reactions of azides provide efficient ways to construct new carbon–nitrogen and sulfur–nitrogen bonds. These reactions are inherently green: no additive besides catalyst is needed to form the nitrenoid reactive intermediate, and the by-product of the reaction is environmentally benign N2 gas. As such, azides can be useful precursors for transition metal-catalyzed N-atom transfer to sulfides, olefins and C–H bonds. These methods offer competitive selectivities and comparable substrate scope as alternative processes to generate metal nitrenoids. PMID:20617243

The Relevance of the De Broglie Velocity (V sub 1 = h/2md sub 1) to Shock Loading Induced Reactions in Lead Azide

DTIC Science & Technology

1991-09-01

CODES 18. SUBJECT TERMS (Continue on reverse if necessary and identify by block number) FIELD GROUP SUB-GROUP De Broglie Velocity Detonation Particle...Velocity Shock Induced Reaction I Lead Azide 19. ABSTRACT (Continue on reverse if necessary and identify by biock number) Availabl e experimental shock...induced reactive pressure levels for dextrinated and single crystal lead azide are compared to predicted Pv1 magnitudes. PV1 = P. CL V1 where V, = h

Synthesis of refractory materials

DOEpatents

Holt, J.B.

1983-08-16

Refractory metal nitrides are synthesized during a self-propagating combustion process utilizing a solid source of nitrogen. For this purpose, a metal azide is employed, preferably NaN/sub 3/. The azide is combusted with Mg or Ca, and a metal oxide is selected from Groups III-A, IV-A, III-B, IV-B, or a rare earth metal oxide. The mixture of azide, Ca or Mg and metal oxide is heated to the mixture's ignition temperature. At that temperature the mixture is ignited and undergoes self-sustaining combustion until the starter materials are exhausted, producing the metal nitride.

Magnetic equivalence of terminal nuclei in the azide anion broken by nuclear spin relaxation

NASA Astrophysics Data System (ADS)

Bernatowicz, P.; Szymański, S.

NMR spectra of water solution of sodium azide selectively 15N labelled in the central position were studied using an iterative least-squares method. In agreement with predictions based on Bloch-Wangsness-Redfield nuclear spin relaxation theory, it is demonstrated that quadrupolar relaxation of the magnetically equivalent terminal 14N (spin-1) nuclei in the azide anion renders the J coupling between these nuclei an observable quantity. In isotropic fluids, this seems to be the first experimental evidence of relaxation-broken magnetic equivalence symmetry.

Spectroscopic and Computational Investigation of Iron(III) Cysteine Dioxygenase: Implications for the Nature of the Putative Superoxo-Fe(III) Intermediate

PubMed Central

2015-01-01

Cysteine dioxygenase (CDO) is a mononuclear, non-heme iron-dependent enzyme that converts exogenous cysteine (Cys) to cysteine sulfinic acid using molecular oxygen. Although the complete catalytic mechanism is not yet known, several recent reports presented evidence for an Fe(III)-superoxo reaction intermediate. In this work, we have utilized spectroscopic and computational methods to investigate the as-isolated forms of CDO, as well as Cys-bound Fe(III)CDO, both in the absence and presence of azide (a mimic of superoxide). An analysis of our electronic absorption, magnetic circular dichroism, and electron paramagnetic resonance data of the azide-treated as-isolated forms of CDO within the framework of density functional theory (DFT) computations reveals that azide coordinates directly to the Fe(III), but not the Fe(II) center. An analogous analysis carried out for Cys-Fe(III)CDO provides compelling evidence that at physiological pH, the iron center is six coordinate, with hydroxide occupying the sixth coordination site. Upon incubation of this species with azide, the majority of the active sites retain hydroxide at the iron center. Nonetheless, a modest perturbation of the electronic structure of the Fe(III) center is observed, indicating that azide ions bind near the active site. Additionally, for a small fraction of active sites, azide displaces hydroxide and coordinates directly to the Cys-bound Fe(III) center to generate a low-spin (S = 1/2) Fe(III) complex. In the DFT-optimized structure of this complex, the central nitrogen atom of the azide moiety lies within 3.12 Å of the cysteine sulfur. A similar orientation of the superoxide ligand in the putative Fe(III)-superoxo reaction intermediate would promote the attack of the distal oxygen atom on the sulfur of substrate Cys. PMID:25093959

Single-step azide introduction in proteins via an aqueous diazo transfer.

PubMed

van Dongen, Stijn F M; Teeuwen, Rosalie L M; Nallani, Madhavan; van Berkel, Sander S; Cornelissen, Jeroen J L M; Nolte, Roeland J M; van Hest, Jan C M

2009-01-01

The controlled introduction of azides in proteins provides targetable handles for selective protein manipulation. We present here an efficient diazo transfer protocol that can be applied in an aqueous solution, leading to the facile introduction of azides in the side chains of lysine residues and at the N-terminus of enzymes, e.g. horseradish peroxidase (HRP) and the red fluorescent protein DsRed. The effective introduction of azides was verified by mass spectrometry, after which the azido-proteins were used in Cu(I)-catalyzed [3 + 2] cycloaddition reactions. Azido-HRP retained its catalytic activity after conjugation of a small molecule. This modified protein could also be successfully immobilized on the surface of an acetylene-covered polymersome. Azido-DsRed was coupled to an acetylene-bearing protein allowing it to act as a fluorescent label, demonstrating the wide applicability of the diazo transfer procedure.

Site-Selective Copper-Catalyzed Amination and Azidation of Arenes and Heteroarenes via Deprotonative Zincation.

PubMed

Hendrick, Charles E; Bitting, Katie J; Cho, Seoyoung; Wang, Qiu

2017-08-23

Arene amination is achieved by site-selective C-H zincation followed by copper-catalyzed coupling with O-benzoylhydroxylamines under mild conditions. Key to this success is ortho-zincation mediated by lithium amidodiethylzincate base that is effective for a wide range of arenes, including nonactivated arenes bearing simple functionalities such as fluoride, chloride, ester, amide, ether, nitrile, and trifluoromethyl groups as well as heteroarenes including indole, thiophene, pyridine, and isoquinoline. An analogous C-H azidation is also accomplished using azidoiodinane for direct introduction of a useful azide group onto a broad scope of arenes and heteroarenes. These new transformations offer rapid access to valuable and diverse chemical space of aminoarenes. Their broad applications in organic synthesis and drug discovery are demonstrated in the synthesis of novel analogues of natural product (-)-nicotine and antidepressant sertraline by late-stage amination and azidation reactions.

Ionic conduction in sodium azide under high pressure: Experimental and theoretical approaches

NASA Astrophysics Data System (ADS)

Wang, Qinglin; Ma, Yanzhang; Sang, Dandan; Wang, Xiaoli; Liu, Cailong; Hu, Haiquan; Wang, Wenjun; Zhang, Bingyuan; Fan, Quli; Han, Yonghao; Gao, Chunxiao

2018-04-01

Alkali metal azides can be used as starting materials for the synthesis of polymeric nitrogen, a potential material of high energy density. In this letter, we report the ionic transport behavior in sodium azide under high pressure by in situ impedance spectroscopy and density functional theory calculations. The ionic transportation consists of ion transfer and Warburg diffusion processes. The ionic migration channels and barrier energy were given for the high-pressure phases. The enhanced ionic conductivity of the γ phase with pressure is because of the formation of space charge regions in the grain boundaries. This ionic conduction and grain boundary effect in NaN3 under pressures could shed light on the better understanding of the conduction mechanism of alkali azides and open up an area of research for polymeric nitrogen in these compounds and other high-energy-density polynitrides.

Surface grafting of reduced graphene oxide using nanocrystalline cellulose via click reaction

NASA Astrophysics Data System (ADS)

Kabiri, Roya; Namazi, Hassan

2014-07-01

Reduced graphene oxide (RGO) sheet was functionalized with nanocrystalline cellulose (NCC) via click coupling between azide-functionalized graphene oxide (GO-N3) and terminal propargyl-functionalized nanocrystalline cellulose (PG-NCC). First, the reactive azide groups were introduced on the surface of GO with azidation of 2-chloroethyl isocyanate-treated graphene oxide (GO-Cl). Then, the resulted compounds were reacted with PG-NCC utilizing copper-catalyzed azide-alkyne cycloaddition. During the click reaction, GO was simultaneously reduced to graphene. The coupling was confirmed by Fourier transform infrared, Raman, DEPT135, and 13C NMR spectroscopy, and the complete exfoliation of graphene in the NCC matrix was confirmed with X-ray diffraction measurement. The degree of functionalization from the gradual mass loss of RGO-NCC suggests that around 23 mass % has been functionalized covalently. The size of both NCC and GO was found to be in nanometric range, which decreased after click reaction.

Synthesis of fine-grained .alpha.-silicon nitride by a combustion process

DOEpatents

Holt, J. Birch; Kingman, Donald D.; Bianchini, Gregory M.

1990-01-01

A combustion synthesis process for the preparation of .alpha.-silicon nitride and composites thereof is disclosed. Preparation of the .alpha.-silicon nitride comprises the steps of dry mixing silicon powder with an alkali metal azide, such as sodium azide, cold-pressing the mixture into any desired shape, or loading the mixture into a fused, quartz crucible, loading the crucible into a combustion chamber, pressurizing the chamber with nitrogen and igniting the mixture using an igniter pellet. The method for the preparation of the composites comprises dry mixing silicon powder (Si) or SiO.sub.2, with a metal or metal oxide, adding a small amount of an alkali metal azide such as sodium azide, introducing the mixture into a suitable combustion chamber, pressurizing the combustion chamber with nitrogen, igniting the mixture within the combustion chamber, and isolating the .alpha.-silicon nitride formed as a reaction product.

Asymmetric Catalysis with Organic Azides and Diazo Compounds Initiated by Photoinduced Electron Transfer.

PubMed

Huang, Xiaoqiang; Webster, Richard D; Harms, Klaus; Meggers, Eric

2016-09-28

Electron-acceptor-substituted aryl azides and α-diazo carboxylic esters are used as substrates for visible-light-activated asymmetric α-amination and α-alkylation, respectively, of 2-acyl imidazoles catalyzed by a chiral-at-metal rhodium-based Lewis acid in combination with a photoredox sensitizer. This novel proton- and redox-neutral method provides yields of up to 99% and excellent enantioselectivities of up to >99% ee with broad functional group compatibility. Mechanistic investigations suggest that an intermediate rhodium enolate complex acts as a reductive quencher to initiate a radical process with the aryl azides and α-diazo carboxylic esters serving as precursors for nitrogen and carbon-centered radicals, respectively. This is the first report on using aryl azides and α-diazo carboxylic esters as substrates for asymmetric catalysis under photoredox conditions. These reagents have the advantage that molecular nitrogen is the leaving group and sole byproduct in this reaction.

Functionalisation of lanthanide complexes via microwave-enhanced Cu(I)-catalysed azide-alkyne cycloaddition.

PubMed

Szíjjártó, Csongor; Pershagen, Elias; Borbas, K Eszter

2012-07-07

Cu(I)-catalysed azide-alkyne cycloaddition reactions were used to functionalise lanthanide(III)-complexes (Ln; La, Eu and Tb) incorporating alkyne or azide reactive groups. Microwave irradiation significantly accelerated the reactions, enabling full conversion to the triazole products in some cases in 5 min. Alkyl and aryl azides and alkyl and aryl alkynes could all serve as coupling partners. These reaction conditions proved efficient for cyclen-tricarboxylates and previously unreactive cyclen-tris-primary amide chelates. The synthesis of heterobimetallic (Eu/Tb, EuTb17 and Eu/La, EuLa17) and heterotrimetallic (Eu/La/Eu) complexes was achieved in up to 60% isolated yield starting from coumarin 2-appended alkynyl complexes Tb16 or La16 and an azido-Eu complex Eu4, and bis-alkynyl La-complex La5 and Eu4, respectively. EuTb17 displayed dual Eu(III) and Tb(III)-emission upon antenna-centred excitation.

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

PubMed Central

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

2007-01-01

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

Synthesis and luminescence properties of iridium(III) azide- and triazole-bisterpyridine complexes.

PubMed

Goldstein, Daniel C; Peterson, Joshua R; Cheng, Yuen Yap; Clady, Raphael G C; Schmidt, Timothy W; Thordarson, Pall

2013-07-26

We describe here the synthesis of azide-functionalised iridium(III) bisterpyridines using the "chemistry on the complex" strategy. The resulting azide-complexes are then used in the copper(I)-catalysed azide-alkyne Huisgen 1,3-dipolar cycloaddition "click chemistry" reaction to from the corresponding triazole-functionalised iridium(III) bisterpyridines. The photophysical characteristics, including lifetimes, of these compounds were also investigated. Interestingly, oxygen appears to have very little effect on the lifetime of these complexes in aqueous solutions. Unexpectedly, sodium ascorbate acid appears to quench the luminescence of triazole-functionalised iridium(III) bisterpyridines, but this effect can be reversed by the addition of copper(II) sulfate, which is known to oxidize ascorbate under aerobic conditions. The results demonstrate that iridium(III) bisterpyridines can be functionalized for use in "click chemistry" facilitating the use of these photophysically interesting complexes in the modification of polymers or surfaces, to highlight just two possible applications.

Sodium azide

Integrated Risk Information System (IRIS)

Sodium azide ; CASRN 26628 - 22 - 8 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Ef

Functionalization of Mechanochemically Passivated Germanium Nanoparticles via "Click" Chemistry

NASA Astrophysics Data System (ADS)

Purkait, Tapas Kumar

Germanium nanoparticles (Ge NPs) may be fascinating for their electronic and optoelectronic properties, as the band gap of Ge NPs can be tuned from the infrared into the visible range of solar spectru. Further functionalization of those nanoparticles may potentially lead to numerous applications ranging from surface attachment, bioimaging, drug delivery and nanoparticles based devices. Blue luminescent germanium nanoparticles were synthesized from a novel top-down mechanochemical process using high energy ball milling (HEBM) of bulk germanium. Various reactive organic molecules (such as, alkynes, nitriles, azides) were used in this process to react with fresh surface and passivate the surface through Ge-C or Ge-N bond. Various purification process, such as gel permeation chromatography (GPC), Soxhlet dailysis etc. were introduced to purify nanoparticles from molecular impurities. A size separation technique was developed using GPC. The size separated Ge NPs were characterize by TEM, small angle X-ray scattering (SAXS), UV-vis absorption and photoluminescence (PL) emission spectroscopy to investigate their size selective properties. Germanium nanoparticles with alkyne termini group were prepared by HEBM of germanium with a mixture of n-alkynes and alpha, o-diynes. Additional functionalization of those nanoparticles was achieved by copper(I) catalyzed azide-alkyne "click" reaction. A variety of organic and organometallic azides including biologically important glucals have been reacted in this manner resulting in nanopartilces adorned with ferrocenyl, trimethylsilyl, and glucal groups. Additional functionalization of those nanoparticles was achieved by reactions with various azides via a Cu(I) catalyzed azide-alkyne "click" reaction. Various azides, including PEG derivatives and cylcodextrin moiety, were grafted to the initially formed surface. Globular nanoparticle arrays were formed through interparticle linking via "click" chemistry or "host-guest" chemistry. Copper(I) catalyzed "click" chemistry also can be explored with azido-terminated Ge NPs which were synthesized by azidation of chloro-terminated Ge NPs. Water soluble PEGylated Ge NPs were synthesized by "click" reaction for biological application. PEGylated Ge NP clusters were prepared using alpha, o-bis alkyno or bis-azido polyethylene glycol (PEG) derivatives by copper catalyzed "click" reaction via inter-particle linking. These nanoparticles were further functionalized by azido beta-cyclodextrin (beta-CD) and azido adamantane via alkyne-azide "click" reactions. Nanoparticle clusters were made from the functionalized Ge NPs by "host-guest" chemistry of beta-CD functionalized Ge NPs either with adamantane functionalized Ge NPs or fullerene, C60.

Conversion of Azides into Diazo Compounds in Water

PubMed Central

Chou, Ho-Hsuan; Raines, Ronald T.

2013-01-01

Diazo compounds are in widespread use in synthetic organic chemistry, but have untapped potential in chemical biology. We report on the design and optimization of a phosphinoester that mediates the efficient conversion of azides into diazo compounds in phosphate buffer at neutral pH and room temperature. High yields are maintained in the presence of common nucleophilic or electrophilic functional groups, and reaction progress can be monitored by colorimetry. As azido groups are easy to install and maintain in biopolymers or their ligands, this new mode of azide reactivity could have substantial utility in chemical biology. PMID:24053717

Synthesis of RNA 5'-Azides from 2'-O-Pivaloyloxymethyl-Protected RNAs and Their Reactivity in Azide-Alkyne Cycloaddition Reactions.

PubMed

Warminski, Marcin; Kowalska, Joanna; Jemielity, Jacek

2017-07-07

Commercially available 2'-O-pivaloyloxymethyl (PivOM) phosphoramidites were employed in an SPS protocol for RNA 5' azides. The utility of the N 3 -RNAs in CuAAC and SPAAC was demonstrated by RNA 5' labeling, chemical ligation including fragment joining and cyclization, and bioconjugation. As a result, several new RNA conjugates that may be valuable tools for studies on biological events such as innate immune response (cyclic dinucleotides), post-transcriptional gene regulation (circular RNAs), or mRNA turnover (m 7 G capped RNAs) were obtained.

Rhodium/Silver-Cocatalyzed Transannulation of N-Sulfonyl-1,2,3-triazoles with Vinyl Azides: Divergent Synthesis of Pyrroles and 2 H-Pyrazines.

PubMed

Zhang, Lin; Sun, Ge; Bi, Xihe

2016-11-07

The first cyclization reaction between vinyl azides and N-sulfonyl-1,2,3-triazoles is reported. A Rh/Ag binary metal catalyst system proved to be necessary for the successful cyclization. By varying the structure of vinyl azides, such reaction allows the divergent synthesis of pyrroles and 2H-pyrazines. The cyclization reactions feature a broad substrate scope, good functional group tolerance, high reaction efficiency, and good to high product yields. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Metastable Polymeric Nitrogen: The Ultimate Green High-Energy-Density Material

NASA Astrophysics Data System (ADS)

Ciezak, Jennifer

2007-06-01

High-energy-high-density materials offering increased stability, vulnerability, and environmental safety are being aggressively pursued to meet the requirements of the DoD Joint Visions and Future Force. Nearly two decades ago, it was proposed that polymeric nitrogen would exceed all of these requirements and possess nearly five times the energy of any conventional energetic material in use today. The present study details an investigation into nitrogen polymerization using a novel high-pressure approach utilizing sodium azide as the starting material. Due to the weaker bonding structure of the anionic azide chains in comparison to a N-N triple bond, one expects that the azide chains will create single-covalently bonded polymeric networks more easily than diatomic nitrogen. A polymeric form of sodium azide was synthesized at high pressures, but the material was not metastable at ambient conditions, which precluded performance testing. Quantum chemical calculations have indicated stabilization of the polymeric structure at ambient conditions may be possible with the addition of hydrogen. Vibrational spectroscopic characterization suggests that a meta-stable polymeric form of nitrogen has been synthesized under high-pressure using sodium azide/hydrogen as the starting materials. This material remains stable at ambient conditions upwards of two weeks depending on the storage conditions.

40 CFR 721.983 - Sulfonyl azide intermediate (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

...). 721.983 Section 721.983 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.983 Sulfonyl azide intermediate (generic). (a) Chemical substance and significant new uses...

Control of brown stain: in Eastern white pine

Treesearch

Robert E. Stutz; Peter Koch; Millard L. Oldham

1961-01-01

Degrade caused by brown stain and blue stain in eastern white pine was virtually eliminated by the use of sap stain chemicals and sodium azide. Combinations of buffered sodium azide with both sodium pentachlorophenate plus borax and buffered ethyl mercury phosphate were effective.

Solution NMR characterization of magnetic/electronic properties of azide and cyanide-inhibited substrate complexes of human heme oxygenase: implications for steric ligand tilt.

PubMed

Peng, Dungeng; Ogura, Hiroshi; Ma, Li-Hua; Evans, John P; de Montellano, Paul R Ortiz; La Mar, Gerd N

2013-04-01

Solution 2D (1)H NMR was carried out on the azide-ligated substrate complex of human heme oxygenase, hHO, to provide information on the active site molecular structure, chromophore electronic/magnetic properties, and the distal H-bond network linked to the exogenous ligand by catalytically relevant oriented water molecules. While 2D NMR exhibited very similar patterns of two-dimensional nuclear Overhauser spectroscopy cross peaks of residues with substrate and among residues as the previously characterized cyanide complex, significant, broadly distributed chemical shift differences were observed for both labile and non-labile protons. The anisotropy and orientation of the paramagnetic susceptibility tensor, χ, were determined for both the azide and cyanide complexes. The most significant difference observed is the tilt of the major magnetic axes from the heme normal, which is only half as large for the azide than cyanide ligand, with each ligand tilted toward the catalytically cleaved α-meso position. The difference in chemical shifts is quantitatively correlated with differences in dipolar shifts in the respective complexes for all but the distal helix. The necessity of considering dipolar shifts, and hence determination of the orientation/anisotropy of χ, in comparing chemical shifts involving paramagnetic complexes, is emphasized. The analysis shows that the H-bond network cannot detect significant differences in H-bond acceptor properties of cyanide versus azide ligands. Lastly, significant retardation of distal helix labile proton exchange upon replacing cyanide with azide indicates that the dynamic stability of the distal helix is increased upon decreasing the steric interaction of the ligand with the distal helix. Copyright © 2013. Published by Elsevier Inc.

Continuous flow hydrogenation of nitroarenes, azides and alkenes using maghemite-Pd nanocomposites

EPA Science Inventory

Maghemite-supported ultra-fine Pd (1-2 nm) nanoparticles, prepared by a simple co-precipitation method, find application in the catalytic continuous flow hydrogenation of nitroarenes, azides, and alkenes wherein they play an important role in reduction of various functional group...

Synthesis of refractory materials

DOEpatents

Holt, Joseph B.

1984-01-01

Refractory metal nitrides are synthesized during a combustion process utilizing a solid source of nitrogen. For this purpose, a metal azide is employed. The azide is combusted with a transition metal of the IIIB, IVB group, or a rare earth metal, and ignited to produce the refractory material.

Method of preparation of uranium nitride

DOEpatents

Kiplinger, Jaqueline Loetsch; Thomson, Robert Kenneth James

2013-07-09

Method for producing terminal uranium nitride complexes comprising providing a suitable starting material comprising uranium; oxidizing the starting material with a suitable oxidant to produce one or more uranium(IV)-azide complexes; and, sufficiently irradiating the uranium(IV)-azide complexes to produce the terminal uranium nitride complexes.

Synthesis of refractory materials

DOEpatents

Holt, J.B.

Refractory metal nitrides are synthesized during a combustion process utilizing a solid source of nitrogen. For this purpose, a metal azide is employed. The azide is combusted with a transition metal of the IIIB, IVB group, or a rare earth metal, and ignited to produce the refractory material.

REVISITING NUCLEOPHILIC SUBSTITUTION REACTIONS: MICROWAVE-ASSISTED SYNTHESIS OF AZIDES, THIOCYANATES AND SULFONES IN AQUEOUS MEDIUM

EPA Science Inventory

A practical, rapid and efficient microwave (MW) promoted synthesis of various azides, thiocyanates and sulfones, is described in aqueous medium. This general and expeditious MW-enhanced nucleophilic substitution approach uses easily accessible starting materials such as halides o...

Significant rate accelerated synthesis of glycosyl azides and glycosyl 1,2,3-triazole conjugates.

PubMed

Kumar, Rishi; Maulik, Prakas R; Misra, Anup Kumar

2008-10-01

An efficient and significantly rapid access of a series of glycosyl azides and glycosyl 1,2,3-triazole conjugates is reported using modified one-pot reaction conditions. In both cases yields were excellent and single diastereomers were obtained.

Uranium azide photolysis results in C-H bond activation and provides evidence for a terminal uranium nitride

NASA Astrophysics Data System (ADS)

Thomson, Robert K.; Cantat, Thibault; Scott, Brian L.; Morris, David E.; Batista, Enrique R.; Kiplinger, Jaqueline L.

2010-09-01

Uranium nitride [U≡N]x is an alternative nuclear fuel that has great potential in the expanding future of nuclear power; however, very little is known about the U≡N functionality. We show, for the first time, that a terminal uranium nitride complex can be generated by photolysis of an azide (U-N=N=N) precursor. The transient U≡N fragment is reactive and undergoes insertion into a ligand C-H bond to generate new N-H and N-C bonds. The mechanism of this unprecedented reaction has been evaluated through computational and spectroscopic studies, which reveal that the photochemical azide activation pathway can be shut down through coordination of the terminal azide ligand to the Lewis acid B(C6F5)3. These studies demonstrate that photochemistry can be a powerful tool for inducing redox transformations for organometallic actinide complexes, and that the terminal uranium nitride fragment is reactive, cleaving strong C-H bonds.

'Click Chemistry' in the preparation of porous polymer-basedparticulate stationary phases for mu-HPLC separation of peptides andproteins

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

Slater, Michael; Snauko, Marian; Svec, Frantisek

With the use of the copper(I)-catalyzed (3 + 2) azide-alkynecycloaddition, an element of "click chemistry," stationary phasescarrying long alkyl chains or soybean trypsin inhibitor have beenprepared for use in HPLC separations in the reversed-phase and affinitymodes, respectively. The ligands were attached via a triazole ring tosize monodisperse porous beads containing either alkyne or azide pendantfunctionalities. Alkyne-containing beads prepared by directcopolymerization of propargyl acrylate with ethylene dimethacrylate wereallowed to react with azidooctadecane to give a reversed-phase sorbent.Azide-functionalized beads were prepared by chemical modification ofglycidyl methacrylate particles. Subsequent reaction with a terminalaliphatic alkyne produced a reversed-phase sorbent similar to thatobtained from themore » alkyne beads. Soybean trypsin inhibitor wasfunctionalized with N-(4-pentynoyloxy) succinimide to carry alkyne groupsand then allowed to react with the azide-containing beads to produce anaffinity sorbent for trypsin. The performance of these stationary phaseswas demonstrated with the HPLC separations of a variety of peptides andproteins.« less

The Effect of Electric Field on the Explosive Sensitivity of Silver Azide

NASA Astrophysics Data System (ADS)

Rodzevich, A. P.; Gazenaur, E. G.; Kuzmina, L. V.; Krasheninin, V. I.; Gazenaur, N. V.

2017-05-01

The effect of a constant contactless electric field on the rate of a chemical reaction in silver azide is explored in this paper. The technology of growing and processing silver azide whiskers in the constant contactless electric field (field intensity was varied in the range from 10-3 V/m to 100 V/m) allows supervising their explosive sensitivity, therefore, the results of experiments can be relevant for purposeful controlling the resistance of explosive materials. This paper is one of the first attempts to develop efficient methods to affect the explosive sensitivity of energy-related materials in a weak electric field (up to 10-3 V/m).

Generation of hazardous methyl azide and its application to synthesis of a key-intermediate of picarbutrazox, a new potent pesticide in flow.

PubMed

Ichinari, Daisuke; Nagaki, Aiichiro; Yoshida, Jun-Ichi

2017-12-01

Generation and reactions of methyl azide (MeN 3 ) were successfully performed by using a flow reactor system, demonstrating that the flow method serves as a safe method for handling hazardous explosive methyl azide. The reaction of NaN 3 and Me 2 SO 4 in a flow reactor gave a MeN 3 solution, which was used for Huisgen reaction with benzoyl cyanide in a flow reactor after minimal washing. The resulting 1-methyl-5-benzoyltetrazole serves as a key intermediate of picarbutrazox (IX), a new potent pesticide. Copyright © 2017. Published by Elsevier Ltd.

Nano-sized metabolic precursors for heterogeneous tumor-targeting strategy using bioorthogonal click chemistry in vivo.

PubMed

Lee, Sangmin; Jung, Seulhee; Koo, Heebeom; Na, Jin Hee; Yoon, Hong Yeol; Shim, Man Kyu; Park, Jooho; Kim, Jong-Ho; Lee, Seulki; Pomper, Martin G; Kwon, Ick Chan; Ahn, Cheol-Hee; Kim, Kwangmeyung

2017-12-01

Herein, we developed nano-sized metabolic precursors (Nano-MPs) for new tumor-targeting strategy to overcome the intrinsic limitations of biological ligands such as the limited number of biological receptors and the heterogeneity in tumor tissues. We conjugated the azide group-containing metabolic precursors, triacetylated N-azidoacetyl-d-mannosamine to generation 4 poly(amidoamine) dendrimer backbone. The nano-sized dendrimer of Nano-MPs could generate azide groups on the surface of tumor cells homogeneously regardless of cell types via metabolic glycoengineering. Importantly, these exogenously generated 'artificial chemical receptors' containing azide groups could be used for bioorthogonal click chemistry, regardless of phenotypes of different tumor cells. Furthermore, in tumor-bearing mice models, Nano-MPs could be mainly localized at the target tumor tissues by the enhanced permeation and retention (EPR) effect, and they successfully generated azide groups on tumor cells in vivo after an intravenous injection. Finally, we showed that these azide groups on tumor tissues could be used as 'artificial chemical receptors' that were conjugated to bioorthogonal chemical group-containing liposomes via in vivo click chemistry in heterogeneous tumor-bearing mice. Therefore, overall results demonstrated that our nano-sized metabolic precursors could be extensively applied to new alternative tumor-targeting technique for molecular imaging and drug delivery system, regardless of the phenotype of heterogeneous tumor cells. Copyright © 2017 Elsevier Ltd. All rights reserved.

Topological ferrimagnetic behaviours of coordination polymers containing manganese(II) chains with mixed azide and carboxylate bridges and alternating F/AF/AF'/AF'/AF interactions.

PubMed

Wang, Yan-Qin; Liu, Hou-Ting; Qi, Yan; Gao, En-Qing

2014-08-21

Two Mn(ii) complexes with azide and a new zwitterionic tetracarboxylate ligand 1,2,4,5-tetrakis(4-carboxylatopyridinium-1-methylene)benzene (L(1)), {[Mn5(L(1))2(N3)8(OH)2]·12H2O}n () and {[Mn5(L(1))2(N3)8(H2O)2](ClO4)2·6H2O}n (), have been synthesized and characterized crystallographically and magnetically. and contain similar alternating chains constructed by azide and carboxylate bridges. The independent sets of bridges alternate in an ABCCB sequence between adjacent Mn(ii) ions: (EO-N3)2 double bridges (EO = end-on) (denoted as A), [(EO-N3)(OCO)2] triple bridges (denoted as B) and [(EO-N3)(OCO)] double bridges (denoted as C). The alternating chains are interlinked into 2D coordination networks by the tetrapyridinium spacers. Magnetic studies demonstrate that the magnetic coupling through the double EO azide bridges is ferromagnetic and that through mixed azide/carboxylate bridges is antiferromagnetic. The unprecedented F/AF/AF'/AF'/AF coupling sequence along the chain dictates an uncompensated ground spin state (S = 5/2 per Mn5 unit) and leads to one-dimensional topological ferrimagnetism, which features a minimum in the χT versus T plot.

Efficient enzymatic synthesis and dual-colour fluorescent labelling of DNA probes using long chain azido-dUTP and BCN dyes

PubMed Central

Ren, Xiaomei; El-Sagheer, Afaf H.; Brown, Tom

2016-01-01

A sterically undemanding azide analogue of dTTP (AHP dUTP) with an alkyl chain and ethynyl attachment to the nucleobase was designed and incorporated into DNA by primer extension, reverse transcription and polymerase chain reaction (PCR). An azide-modified 523 bp PCR amplicon with all 335 thymidines replaced by AHP dU was shown to be a perfect copy of the template from which it was amplified. Replacement of thymidine with AHP dU increases duplex stability, accounting in part for the high incorporation efficiency of the azide-modified triphosphate. Single-stranded azide-labelled DNA was conveniently prepared from PCR products by λ-exonuclease digestion and streptavidin magnetic bead isolation. Efficient fluorescent labelling of single and double-stranded DNA was carried out using dyes functionalized with bicyclo[6.1.0]non-4-yne (BCN) via the strain-promoted alkyne-azide cycloaddition (SPAAC) reaction. This revealed that the degree of labelling must be carefully controlled to achieve optimum fluorescence and avoid fluorescence quenching. Dual-coloured probes were obtained in a single tube fluorescent labelling reaction; and varying the ratios of the two dyes provides a simple method to prepare DNA probes with unique fluorescent signatures. AHP dUTP is a versatile clickable nucleotide with potentially wide applications in biology and nanotechnology including single molecule studies and synthesis of modified aptamer libraries via SELEX. PMID:26819406

Surface modification of GC and HOPG with diazonium, amine, azide, and olefin derivatives.

PubMed

Tanaka, Mutsuo; Sawaguchi, Takahiro; Sato, Yukari; Yoshioka, Kyoko; Niwa, Osamu

2011-01-04

Surface modification of glassy carbon (GC) and highly oriented pyrolytic graphite (HOPG) was carried out with diazonium, amine, azide, and olefin derivatives bearing ferrocene as an electroactive moiety. Features of the modified surfaces were evaluated by surface concentrations of immobilized molecule, blocking effect of the modified surface against redox reaction, and surface observation using cyclic voltammetry and electrochemical scanning tunneling microscope (EC-STM). The measurement of surface concentrations of immobilized molecule revealed the following three aspects: (i) Diazonium and olefin derivatives could modify substrates with the dense-monolayer concentration. (ii) The surface concentration of immobilized amine derivative did not reach to the dense-monolayer concentration reflecting their low reactivity. (iii) The surface modification with the dense-monolayer concentration was also possible with azide derivative, but the modified surface contained some oligomers produced by the photoreaction of azides. Besides, the blocking effect against redox reaction was observed for GC modified with diazonium derivative and for HOPG modified with diazonium and azide derivatives, suggesting fabrication of a densely modified surface. Finally, the surface observation for HOPG modified with diazonium derivative by EC-STM showed a typical monolayer structure, in which the ferrocene moieties were packed densely at random. On the basis of those results, it was demonstrated that surface modification of carbon substrates with diazonium could afford a dense monolayer similar to the self-assembled monolayer (SAM) formation.

Copper on Chitosan: A Recyclable Heterogeneous Catalyst for Azide-alkyne Cycloaddition Reactions in Water

EPA Science Inventory

Copper sulfate is immobilized over chitosan by simply stirring an aqueous suspension of chitosan in water with copper sulfate; the ensuing catalyst has been utilized for the azide-alkyne cycloaddition in aqueous media and it can be recycled and reused many time without loosing it...

49 CFR 173.182 - Barium azide-50 percent or more water wet.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 2 2014-10-01 2014-10-01 false Barium azide-50 percent or more water wet. 173.182 Section 173.182 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS SHIPPERS-GENERAL REQUIREMENTS FOR SHIPMENTS AND...

49 CFR 173.182 - Barium azide-50 percent or more water wet.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 2 2012-10-01 2012-10-01 false Barium azide-50 percent or more water wet. 173.182 Section 173.182 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS SHIPPERS-GENERAL REQUIREMENTS FOR SHIPMENTS AND...

catena-Poly[[bis­[4-(dimethyl­amino)­pyridine-κN 1]cobalt(II)]-di-μ-azido-κ4 N 1:N 3

PubMed Central

Guenifa, Fatiha; Zeghouan, Ouahida; Hadjadj, Nasreddine; Bendjeddou, Lamia; Merazig, Hocine

2013-01-01

The title layered polymer, [Co(N3)2(C7H10N2)2]n, contains CoII, azide and 4-(dimethyl­amino)­pyridine (4-DMAP) species with site symmetries m2m, 2 and m, respectively. The Co2+ ion adopts an octa­hedral coordination geometry in which four N atoms from azide ligands lie in the equatorial plane and two 4-DMAP N atoms occupy the axial positions. The CoII atoms are connected by two bridging azide ligands, resulting in a chain parallel to the c axis. PMID:23476514

Joint Services Evaluation Plan for Preferred and Alternate Explosive Fills for Principal Munitions. Joint Services Explosive Fill Program (Long Range) Final Report on the Use of Emergency Funds. Volume 4. Joint Service Safety and Performance Manual for Qualification of Explosives for Military Use

DTIC Science & Technology

1972-09-19

Dextrinated Lead Azide. ŕ.4.2 Reports. Applied Mathematic Panel of the National Defense Research Committee (AMP Report No. t01.1R, SRG-P No. 40). 1-2 0D 44811... dextrinated lead azide. (A normal ranae for these compounds shall have been obtained at the time of testing the explosive to be qualified.) 4.3...normal lead styphnate and dextrinated lead azide obtained using the same apparatus and procedure and run at the same time. 4.3.5 Special Requirements

Chemoselective covalent coupling of oligonucleotide probes to self-assembled monolayers.

PubMed

Devaraj, Neal K; Miller, Gregory P; Ebina, Wataru; Kakaradov, Boyko; Collman, James P; Kool, Eric T; Chidsey, Christopher E D

2005-06-22

A chemoselective route to routinely and rapidly attach oligonucleotide probes to well-defined surfaces is presented. Cu(I) tris(benzyltriazolylmethyl)amine-catalyzed coupling of terminal acetylenes to azides on a self-assembled monolayer is used instead of traditional nucleophilic-electrophilic coupling reactions. The reaction proceeds well even in the presence of purposely introduced nucleophilic and electrophilic impurities. The density of oligonucleotide probes can be controlled by controlling the amount of azide functionality. Although most of our work was done on gold surfaces, this technique should be readily applicable to any surface on which an azide-containing monolayer can be assembled as we have preliminarily demonstrated by derivatizing azidotrimethoxysilane-modified glass slides with fluorescein-containing oligonucleotides.

One-pot synthesis of 2,5-dihydropyrroles from terminal alkynes, azides, and propargylic alcohols by relay actions of copper, rhodium, and gold.

PubMed

Miura, Tomoya; Tanaka, Takamasa; Matsumoto, Kohei; Murakami, Masahiro

2014-12-01

Relay actions of copper, rhodium, and gold formulate a one-pot multistep pathway, which directly gives 2,5-dihydropyrroles starting from terminal alkynes, sulfonyl azides, and propargylic alcohols. Initially, copper-catalyzed 1,3-dipolar cycloaddition of terminal alkynes with sulfonyl azides affords 1-sulfonyl-1,2,3-triazoles, which then react with propargylic alcohols under the catalysis of rhodium. The resulting alkenyl propargyl ethers subsequently undergo the thermal Claisen rearrangement to give α-allenyl-α-amino ketones. Finally, a gold catalyst prompts 5-endo cyclization to produce 2,5-dihydropyrroles. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Artificial Chemical Reporter Targeting Strategy Using Bioorthogonal Click Reaction for Improving Active-Targeting Efficiency of Tumor.

PubMed

Yoon, Hong Yeol; Shin, Min Lee; Shim, Man Kyu; Lee, Sangmin; Na, Jin Hee; Koo, Heebeom; Lee, Hyukjin; Kim, Jong-Ho; Lee, Kuen Yong; Kim, Kwangmeyung; Kwon, Ick Chan

2017-05-01

Biological ligands such as aptamer, antibody, glucose, and peptide have been widely used to bind specific surface molecules or receptors in tumor cells or subcellular structures to improve tumor-targeting efficiency of nanoparticles. However, this active-targeting strategy has limitations for tumor targeting due to inter- and intraheterogeneity of tumors. In this study, we demonstrated an alternative active-targeting strategy using metabolic engineering and bioorthogonal click reaction to improve tumor-targeting efficiency of nanoparticles. We observed that azide-containing chemical reporters were successfully generated onto surface glycans of various tumor cells such as lung cancer (A549), brain cancer (U87), and breast cancer (BT-474, MDA-MB231, MCF-7) via metabolic engineering in vitro. In addition, we compared tumor targeting of artificial azide reporter with bicyclononyne (BCN)-conjugated glycol chitosan nanoparticles (BCN-CNPs) and integrin α v β 3 with cyclic RGD-conjugated CNPs (cRGD-CNPs) in vitro and in vivo. Fluorescence intensity of azide-reporter-targeted BCN-CNPs in tumor tissues was 1.6-fold higher and with a more uniform distribution compared to that of cRGD-CNPs. Moreover, even in the isolated heterogeneous U87 cells, BCN-CNPs could bind artificial azide reporters on tumor cells more uniformly (∼92.9%) compared to cRGD-CNPs. Therefore, the artificial azide-reporter-targeting strategy can be utilized for targeting heterogeneous tumor cells via bioorthogonal click reaction and may provide an alternative method of tumor targeting for further investigation in cancer therapy.

New potentiometric transducer based on a Mn(II) [2-formylquinoline thiosemicarbazone] complex for static and hydrodynamic assessment of azides.

PubMed

Kamel, Ayman H

2015-11-01

A new potentiometric transducer for selective recognition of azide is characterized and developed. The PVC plasticized based sensor incorporates Mn(II) [2-formylquinoline thiosemicarbazone] complex in the presence of tri dodecyl methyl ammonium chloride (TDMAC) as a lipophilic cationic additive. The sensor displayed a near-Nernstian response for azide over 1.0×10(-2)-1.0×10(-5) mol L(-1), with an anionic slope of -55.8±0.6 mV decade(-1) and lower limit of detection 0.34 µg mL(-1). The sensor was pH independent in the range 5.5-9 and presented good selectivity features towards several inorganic anions, and it is easily used in a flow injection system and compared with a tubular detector. The intrinsic characteristics of the detector in a low dispersion manifold were determined and compared with data obtained under a hydrodynamic mode of operation. This simple and inexpensive automation, with a good potentiometric detector, enabled the analysis of ~33 samples h(-1) without requiring pre-treatment procedures. The proposed method is also applied to the analysis of trace levels of azide in primer mixtures. Significantly improved accuracy, precision, response time, stability and selectivity were offered by these simple and cost-effective potentiometric sensor compared with other standard techniques. The method has the requisite accuracy, sensitivity and precision to determine azide ions. Copyright © 2015 Elsevier B.V. All rights reserved.

Introduction of sample tubes with sodium azide as a preservative for ethyl glucuronide in urine.

PubMed

Luginbühl, Marc; Weinmann, Wolfgang; Al-Ahmad, Ali

2017-09-01

Ethyl glucuronide (EtG) is a direct alcohol marker, which is widely used for clinical and forensic applications, mainly for abstinence control. However, the instability of EtG in urine against bacterial degradation or the post-collectional synthesis of EtG in contaminated samples may cause false interpretation of EtG results in urine samples. This study evaluates the potential of sodium azide in tubes used for urine collection to hinder degradation of ethyl glucuronide by bacterial metabolism taking place during growth of bacterial colonies. The tubes are part of a commercial oral fluid collection device. The sampling system was tested with different gram-positive and gram-negative bacterial species previously observed in urinary tract infections, such as Escherichia coli, Staphylococcus aureus, Enterecoccus faecalis, Staphylococcus epidermidis, Klebsiella pneumoniae, Enterobacter cloacae, and Pseudomonas aeruginosa. Inhibition of bacterial growth by sodium azide, resulting in lower numbers of colony forming units compared to control samples, was observed for all tested bacterial species. To test the prevention of EtG degradation by the predominant pathogen in urinary tract infection, sterile-filtered urine and deficient medium were spiked with EtG, and inoculated with E. coli prior to incubation for 4 days at 37 °C in tubes with and without sodium azide. Samples were collected every 24 hours, during four consecutive days, whereby the colony forming units (CFU) were counted on Columbia blood agar plates, and EtG was analyzed by LC-MS/MS. As expected, EtG degradation was observed when standard polypropylene tubes were used for the storage of contaminated samples. However, urine specimens collected in sodium azide tubes showed no or very limited bacterial growth and no EtG degradation. As a conclusion, sodium azide is useful to reduce bacterial growth of gram-negative and gram-positive bacteria. It inhibits the degradation of EtG by E. coli and can be used for the stabilization of EtG in urine samples.

Effects of chemical fuel composition on energy generation from thermopower waves

NASA Astrophysics Data System (ADS)

Yeo, Taehan; Hwang, Hayoung; Jeong, Dong-Cheol; Lee, Kang Yeol; Hong, Jongsup; Song, Changsik; Choi, Wonjoon

2014-11-01

Thermopower waves, which occur during combustion within hybrid structures formed from nanomaterials and chemical fuels, result in a self-propagating thermal reaction and concomitantly generate electrical energy from the acceleration of charge carriers along the nanostructures. The hybrid structures for thermopower waves are composed of two primary components: the core thermoelectric material and the combustible fuel. So far, most studies have focused on investigating various nanomaterials for improving energy generation. Herein, we report that the composition of the chemical fuel used has a significant effect on the power generated by thermopower waves. Hybrid nanostructures consisting of mixtures of picric acid and picramide with sodium azide were synthesized and used to generate thermopower waves. A maximum voltage of ˜2 V and an average peak specific power as high as 15 kW kg-1 were obtained using the picric acid/sodium azide/multiwalled carbon nanotubes (MWCNTs) array composite. The average reaction velocity and the output voltage in the case of the picric acid/sodium azide were 25 cm s-1 and 157 mV, while they were 2 cm s-1 and 3 mV, in the case of the picramide/sodium azide. These marked differences are attributable to the chemical and structural differences of the mixtures. Mixing picric acid and sodium azide in deionized water resulted in the formation of 2,4,6-trinitro sodium phenoxide and hydrogen azide (H-N3), owing to the exchange of H+ and Na+ ions, as well as the formation of fiber-like structures, because of benzene π stacking. The negative enthalpy of formation of the new compounds and the fiber-like structures accelerate the reaction and increase the output voltage. Elucidating the effects of the composition of the chemical fuel used in the hybrid nanostructures will allow for the control of the combustion process and help optimize the energy generated from thermopower waves, furthering the development of thermopower waves as an energy source.

Experimental Investigation on the Mechanism of Chelation-Assisted, Copper(II) Acetate-Accelerated Azide-Alkyne Cycloaddition

PubMed Central

Kuang, Gui-Chao; Guha, Pampa M.; Brotherton, Wendy S.; Simmons, J. Tyler; Stankee, Lisa A.; Nguyen, Brian T.; Clark, Ronald J.; Zhu, Lei

2011-01-01

A mechanistic model is formulated to account for the high reactivity of chelating azides (organic azides capable of chelation-assisted metal coordination at the alkylated azido nitrogen position) and copper(II) acetate (Cu(OAc)2) in copper(II)-mediated azide-alkyne cycloaddition (AAC) reactions. Fluorescence and 1H NMR assays are developed for monitoring the reaction progress in two different solvents – methanol and acetonitrile. Solvent kinetic isotopic effect and pre-mixing experiments give credence to the proposed different induction reactions for converting copper(II) to catalytic copper(I) species in methanol (methanol oxidation) and acetonitrile (alkyne oxidative homocoupling), respectively. The kinetic orders of individual components in a chelation-assisted, copper(II)-accelerated AAC reaction are determined in both methanol and acetonitrile. Key conclusions resulting from the kinetic studies include (1) the interaction between copper ion (either in +1 or +2 oxidation state) and a chelating azide occurs in a fast, pre-equilibrium step prior to the formation of the in-cycle copper(I)-acetylide, (2) alkyne deprotonation is involved in several kinetically significant steps, and (3) consistent with prior experimental and computational results by other groups, two copper centers are involved in the catalysis. The X-ray crystal structures of chelating azides with Cu(OAc)2 suggest a mechanistic synergy between alkyne oxidative homocoupling and copper(II)-accelerated AAC reactions, in which both a bimetallic catalytic pathway and a base are involved. The different roles of the two copper centers (a Lewis acid to enhance the electrophilicity of the azido group and a two-electron reducing agent in oxidative metallacycle formation, respectively) in the proposed catalytic cycle suggest that a mixed valency (+2 and +1) dinuclear copper species be a highly efficient catalyst. This proposition is supported by the higher activity of the partially reduced Cu(OAc)2 in mediating a 2-picolylazide-involved AAC reaction than the fully reduced Cu(OAc)2. Finally, the discontinuous kinetic behavior that has been observed by us and others in copper(I/II)-mediated AAC reactions is explained by the likely catalyst disintegration during the course of a relatively slow reaction. Complementing the prior mechanistic conclusions drawn by other investigators which primarily focus on the copper(I)/alkyne interactions, we emphasize the kinetic significance of copper(I/II)/azide interaction. This work not only provides a mechanism accounting for the fast Cu(OAc)2-mediated AAC reactions involving chelating azides, which has apparent practical implications, but suggests the significance of mixed-valency dinuclear copper species in catalytic reactions where two copper centers carry different functions. PMID:21809811

49 CFR 173.182 - Barium azide-50 percent or more water wet.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 2 2013-10-01 2013-10-01 false Barium azide-50 percent or more water wet. 173.182 Section 173.182 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS... Class 1 and Class 7 § 173.182 Barium azide—50 percent or more water wet. Barium azide—50 percent or more...

Rational design of azide-bridged bimetallic complexes. Crystal structure and magnetic properties of Fe(III)MFe(III) (M = Ni(II) and Cu(II)) trinuclear species.

PubMed

Colacio, Enrique; Costes, Jean-Pierre; Domínguez-Vera, José M; Maimoun, Ikram Ben; Suárez-Varela, José

2005-01-28

The first examples of azide-bridged bimetallic trinuclear complexes ([M(cyclam)][FeL(N3)(mu1,5-N3)]2) (H2L = 4,5-dichloro-1,2-bis(pyridine-2-carboxamido) benzene) have been structurally and magnetically characterized.

One-pot synthesis of novel 1-(1H-tetrazol-5-yl)-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine derivatives via an Ugi-azide 4CR process.

PubMed

Ghandi, Mehdi; Salahi, Saleh; Taheri, Abuzar; Abbasi, Alireza

2018-05-01

A facile one-pot method has been developed for the synthesis of novel pyrrolo[2,1-a]pyrazine scaffolds. A variety of 1-(1H-tetrazol-5-yl)-1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazine derivatives were obtained in moderate to high yields in methanol using a one-pot four-component condensation of 1-(2-bromoethyl)-1H-pyrrole-2-carbaldehyde, amine, isocyanide and sodium azide at room temperature. These reactions presumably proceed via a domino imine formation, intramolecular annulation and Ugi-azide reaction. Unambiguous assignment of the molecular structures was carried out by single-crystal X-ray diffraction.

Conjugating folate on superparamagnetic Fe{sub 3}O{sub 4}@Au nanoparticles using click chemistry

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

Shen, Xiaofang, E-mail: xfshen@jiangnan.edu.cn; Ge, Zhaoqiang; Pang, Yuehong

2015-02-15

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

Development of a general methodology for labelling peptide-morpholino oligonucleotide conjugates using alkyne-azide click chemistry.

PubMed

Shabanpoor, Fazel; Gait, Michael J

2013-11-11

We describe a general methodology for fluorescent labelling of peptide conjugates of phosphorodiamidate morpholino oligonucleotides (PMOs) by alkyne functionalization of peptides, subsequent conjugation to PMOs and labelling with a fluorescent compound (Cy5-azide). Two peptide-PMO (PPMO) examples are shown. No detrimental effect of such labelled PMOs was seen in a biological assay.

Synthesis of a D-Glucopyranosyl Azide: Spectroscopic Evidence for Stereochemical Inversion in the S[subscript N]2 Reaction

ERIC Educational Resources Information Center

Adesoye, Olumuyiwa G.; Mills, Isaac N.; Temelkoff, David P.; Jackson, John A.; Norris, Peter

2012-01-01

Stereospecific S[subscript N]2 conversion of configurationally pure acetobromoglucose (2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranosyl bromide) to the corresponding beta-D-glucopyranosyl azide is a useful exercise in the advanced organic undergraduate teaching laboratory. The procedure is safe and suitable for small-scale implementation, and firm…

Exploiting the Reactivity of Actinide Fluoride Bonds for the Synthesis of a New Class of Bis(azide) Uranium Complexes

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

Erickson, Karla A.; Lichtscheidl, Alejandro G.; Monreal, Marisa Jennifer

The terminal actinide fluoride bonds in (C 5Me 5) 2ThF 2(py) (py = pyridine) and (C 5Me 5) 2UF 2(O=PR 3) (R = Me, Ph) react with two equivalents of Me 3SiN 3 in toluene to form the polymeric thorium bis(azide), [(C 5Me 5) 2Th(N 3)2] ∞, and a new class of monometallic uranium bis(azide) complexes, (C 5Me 5) 2U(N 3)2(O=PR 3), respectively. Full characterization of the novel complexes (C 5Me 5) 2ThF 2(py) and (C 5Me 5) 2UF 2(O=PR 3) are reported, including the solid-state structures of (C 5Me 5) 2ThF 2(py) and (C 5Me 5) 2U(N 3) 2(O=PPhmore » 3). Lastly, electronic absorption spectral data are also reported for (C 5Me 5) 2AnF 2(py) (An = Th, U) and (C 5Me 5) 2U(N 3) 2(O=PR 3) to confirm metal oxidation state and enable elucidation of the fluoride and azide ligand bonding in these complexes.« less

Exploiting the Reactivity of Actinide Fluoride Bonds for the Synthesis of a New Class of Bis(azide) Uranium Complexes

DOE PAGES

Erickson, Karla A.; Lichtscheidl, Alejandro G.; Monreal, Marisa Jennifer; ...

2017-11-04

The terminal actinide fluoride bonds in (C 5Me 5) 2ThF 2(py) (py = pyridine) and (C 5Me 5) 2UF 2(O=PR 3) (R = Me, Ph) react with two equivalents of Me 3SiN 3 in toluene to form the polymeric thorium bis(azide), [(C 5Me 5) 2Th(N 3)2] ∞, and a new class of monometallic uranium bis(azide) complexes, (C 5Me 5) 2U(N 3)2(O=PR 3), respectively. Full characterization of the novel complexes (C 5Me 5) 2ThF 2(py) and (C 5Me 5) 2UF 2(O=PR 3) are reported, including the solid-state structures of (C 5Me 5) 2ThF 2(py) and (C 5Me 5) 2U(N 3) 2(O=PPhmore » 3). Lastly, electronic absorption spectral data are also reported for (C 5Me 5) 2AnF 2(py) (An = Th, U) and (C 5Me 5) 2U(N 3) 2(O=PR 3) to confirm metal oxidation state and enable elucidation of the fluoride and azide ligand bonding in these complexes.« less

A new 1D manganese(II) coordination polymer with end-to-end azide bridge and isonicotinoylhydrazone Schiff base ligand: Crystal structure, Hirshfeld surface, NBO and thermal analyses

NASA Astrophysics Data System (ADS)

Khani, S.; Montazerozohori, M.; Masoudiasl, A.; White, J. M.

2018-02-01

A new manganese (II) coordination polymer, [MnL2 (μ-1,3-N3)2]n, with co-ligands including azide anion and Schiff base based on isonicotinoylhydrazone has been synthesized and characterized. The crystal structure determination shows that the azide ligand acts as end-to-end (EE) bridging ligand and generates a one-dimensional coordination polymer. In this compound, each manganes (II) metal center is hexa-coordinated by four azide nitrogens and two pyridinic nitrogens for the formation of octahedral geometry. The analysis of crystal packing indicates that the 1D chain of [MnL2 (μ-1,3-N3)2]n, is stabilized as a 3D supramolecular network by intra- and inter-chain intermolecular interactions of X-H···Y (X = N and C, Y = O and N). Hirshfeld surface analysis and 2D fingerprint plots have been used for a more detailed investigation of intermolecular interactions. Also, natural bond orbital (NBO) analysis was performed to get information about atomic charge distributions, hybridizations and the strength of interactions. Finally, thermal analysis of compound showed its complete decomposition during three thermal steps.

Ethylene formation by polymorphonuclear leukocytes. Role of myeloperoxidase

PubMed Central

1978-01-01

Ethylene formation from the thioethers, beta-methylthiopropionaldehyde (methional) and 2-keto-4-thiomethylbutyric acid by phagocytosing polymorphonuclear leukocytes (PMNs) was found to be largely dependent on myeloperoxidase (MPO). Conversion was less than 10% of normal when MPO-deficient PMNs were employed; formation by normal PMNs was inhibited by the peroxidase inhibitors, azide, and cyanide, and a model system consisting of MPO, H2O2, chloride (or bromide) and EDTA was found which shared many of the properties of the predominant PMN system. MPO-independent mechanisms of ethylene formation were also identified. Ethylene formation from methional by phagocytosing eosinophils and by H2O2 in the presence or absence of catalase was stimulated by azide. The presence of MPO-independent, azide-stimulable systems in the PMN preparations was suggested by the azide stimulation of ethylene formation from methional when MPO-deficient leukocytes were employed. Ethylene formation by dye-sensitized photooxidation was also demonstrated and evidence obtained for the involvement of singlet oxygen (1O2). These findings are discussed in relation to the participation of H2O2, hydroxyl radicals, the superoxide anion and 1O2 in the formation of ethylene by PMNs and by the MPO model system. PMID:212502

Azidoethoxyphenylalanine as a Vibrational Reporter and Click Chemistry Partner in Proteins.

PubMed

Tookmanian, Elise M; Phillips-Piro, Christine M; Fenlon, Edward E; Brewer, Scott H

2015-12-21

An unnatural amino acid, 4-(2-azidoethoxy)-L-phenylalanine (AePhe, 1), was designed and synthesized in three steps from known compounds in 54% overall yield. The sensitivity of the IR absorption of the azide of AePhe was established by comparison of the frequency of the azide asymmetric stretch vibration in water and dimethyl sulfoxide. AePhe was successfully incorporated into superfolder green fluorescent protein (sfGFP) at the 133 and 149 sites by using the amber codon suppression method. The IR spectra of these sfGFP constructs indicated that the azide group at the 149 site was not fully solvated despite the location in sfGFP and the three-atom linker between the azido group and the aromatic ring of AePhe. An X-ray crystal structure of sfGFP-149-AePhe was solved at 1.45 Å resolution and provides an explanation for the IR data as the flexible linker adopts a conformation which partially buries the azide on the protein surface. Both sfGFP-AePhe constructs efficiently undergo a bioorthogonal strain-promoted click cycloaddition with a dibenzocyclooctyne derivative. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bioorthogonal Modification of the Major Sheath Protein of Bacteriophage M13: Extending the Versatility of Bionanomaterial Scaffolds.

PubMed

Urquhart, Taylor; Daub, Elisabeth; Honek, John Frank

2016-10-19

With a mass of ∼1.6 × 10 7 Daltons and composed of approximately 2700 proteins, bacteriophage M13 has been employed as a molecular scaffold in bionanomaterials fabrication. In order to extend the versatility of M13 in this area, residue-specific unnatural amino acid incorporation was employed to successfully display azide functionalities on specific solvent-exposed positions of the pVIII major sheath protein of this bacteriophage. Employing a combination of engineered mutants of the gene coding for the pVIII protein, the methionine (Met) analog, l-azidohomoalanine (Aha), and a suitable Escherichia coli Met auxotroph for phage production, conditions were developed to produce M13 bacteriophage labeled with over 350 active azides (estimated by fluorescent dye labeling utilizing a strain-promoted azide-alkyne cycloaddition) and capable of azide-selective attachment to 5 nm gold nanoparticles as visualized by transmission electron microscopy. The capability of this system to undergo dual labeling utilizing both chemical acylation and bioorthogonal cycloaddition reactions was also verified. The above stratagem should prove particularly advantageous in the preparation of assemblies of larger and more complex molecular architectures based on the M13 building block.

Covalent protein-oligonucleotide conjugates by copper-free click reaction

PubMed Central

Khatwani, Santoshkumar L.; Mullen, Daniel G.; Hast, Michael A.; Beese, Lorena S.; Distefano, Mark D.; Taton, T. Andrew

2013-01-01

Covalent protein-oligodeoxynucleotide (protein-ODN) conjugates are useful in a number of biological applications, but synthesizing discrete conjugates—where the connection between the two components is at a defined location in both the protein and the ODN—under mild conditions with significant yield can be a challenge. In this article, we demonstrate a strategy for synthesizing discrete protein-ODN conjugates using strain-promoted azide-alkyne [3+2] cycloaddition (SPAAC, a copper-free “click” reaction). Azide-functionalized proteins, prepared by enzymatic prenylation of C-terminal CVIA tags with synthetic azidoprenyl diphosphates, were “clicked” to ODNs that had been modified with a strained dibenzocyclooctyne (DIBO-ODN). The resulting protein-ODN conjugates were purified and characterized by size-exclusion chromatography and gel electrophoresis. We find that the yields and reaction times of the SPAAC bioconjugation reactions are comparable to those previously reported for copper-catalyzed azide-alkyne [3+2] cycloaddition (CuAAC) bioconjugation, but require no catalyst. The same SPAAC chemistry was used to immobilize azide-modified proteins onto surfaces, using surface-bound DIBO-ODN as a heterobifunctional linker. Cu-free click bioconjugation of proteins to ODNs is a simple and versatile alternative to Cu-catalyzed click methods. PMID:22682299

From Mechanism to Mouse: A Tale of Two Bioorthogonal Reactions

PubMed Central

2011-01-01

Bioorthogonal reactions are chemical reactions that neither interact with nor interfere with a biological system. The participating functional groups must be inert to biological moieties, must selectively reactive with each other under biocompatible conditions, and, for in vivo applications, must be nontoxic to cells and organisms. Additionally, it is helpful if one reactive group is small and therefore minimally perturbing of a biomolecule into which it has been introduced either chemically or biosynthetically. Examples from the past decade suggest that a promising strategy for bioorthogonal reaction development begins with an analysis of functional group and reactivity space outside those defined by Nature. Issues such as stability of reactants and products (particularly in water), kinetics, and unwanted side reactivity with biofunctionalities must be addressed, ideally guided by detailed mechanistic studies. Finally, the reaction must be tested in a variety of environments, escalating from aqueous media to biomolecule solutions to cultured cells and, for the most optimized transformations, to live organisms. Work in our laboratory led to the development of two bioorthogonal transformations that exploit the azide as a small, abiotic, and bioinert reaction partner: the Staudinger ligation and strain-promoted azide–alkyne cycloaddition. The Staudinger ligation is based on the classic Staudinger reduction of azides with triarylphosphines first reported in 1919. In the ligation reaction, the intermediate aza-ylide undergoes intramolecular reaction with an ester, forming an amide bond faster than aza-ylide hydrolysis would otherwise occur in water. The Staudinger ligation is highly selective and reliably forms its product in environs as demanding as live mice. However, the Staudinger ligation has some liabilities, such as the propensity of phosphine reagents to undergo air oxidation and the relatively slow kinetics of the reaction. The Staudinger ligation takes advantage of the electrophilicity of the azide; however, the azide can also participate in cycloaddition reactions. In 1961, Wittig and Krebs noted that the strained, cyclic alkyne cyclooctyne reacts violently when combined neat with phenyl azide, forming a triazole product by 1,3-dipolar cycloaddition. This observation stood in stark contrast to the slow kinetics associated with 1,3-dipolar cycloaddition of azides with unstrained, linear alkynes, the conventional Huisgen process. Notably, the reaction of azides with terminal alkynes can be accelerated dramatically by copper catalysis (this highly popular Cu-catalyzed azide–alkyne cycloaddition (CuAAC) is a quintessential “click” reaction). However, the copper catalysts are too cytotoxic for long-term exposure with live cells or organisms. Thus, for applications of bioorthogonal chemistry in living systems, we built upon Wittig and Krebs’ observation with the design of cyclooctyne reagents that react rapidly and selectively with biomolecule-associated azides. This strain-promoted azide–alkyne cycloaddition is often referred to as “Cu-free click chemistry”. Mechanistic and theoretical studies inspired the design of a series of cyclooctyne compounds bearing fluorine substituents, fused rings, and judiciously situated heteroatoms, with the goals of optimizing azide cycloaddition kinetics, stability, solubility, and pharmacokinetic properties. Cyclooctyne reagents have now been used for labeling azide-modified biomolecules on cultured cells and in live Caenorhabditis elegans, zebrafish, and mice. As this special issue testifies, the field of bioorthogonal chemistry is firmly established as a challenging frontier of reaction methodology and an important new instrument for biological discovery. The above reactions, as well as several newcomers with bioorthogonal attributes, have enabled the high-precision chemical modification of biomolecules in vitro, as well as real-time visualization of molecules and processes in cells and live organisms. The consequence is an impressive body of new knowledge and technology, amassed using a relatively small bioorthogonal reaction compendium. Expansion of this toolkit, an effort that is already well underway, is an important objective for chemists and biologists alike. PMID:21838330

A Study on the Kinetics of a Disorder-to-Order Transition Induced by Alkyne/Azide Click Reaction

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

X Wei; L Li; J Kalish

2011-12-31

The kinetics of binary blends of poly(ethylene oxide)-block-poly(n-butyl methacrylate-random-propargyl methacrylate) (PEO-b-P(nBMA-r-PgMA)) diblock copolymer and Rhodamine B azide was investigated during a disorder-to-order transition induced by alkyne/azide click reaction. The change in the domain spacing and conversion of reactants as a function of annealing time were investigated by in situ small-angle X-ray scattering (SAXS) and infrared spectroscopy (IR), suggesting several kinetic processes with different time scales during thermal annealing. While a higher conversion can be realized by extending the annealing time, the microphase-separated morphology is independent of the annealing conditions, as long as both the reagents and final products have enoughmore » mobility.« less

Synthesis of geminal bis- and tristriazoles: exploration of unconventional azide chemistry.

PubMed

Erhardt, Hellmuth; Mohr, Fabian; Kirsch, Stefan F

2016-01-11

A range of geminal bis- and tristriazoles are presented. These rare and hardly studied compound classes were easily synthesized using ethyl 2,2-diazido-3-oxobutanoate as the common starting point. Firstly, CuAAC-reaction with an alkyne afforded the corresponding deacetylated bistriazoles. Upon further azidation yielding azidomethylenebistriazoles, a second CuAAC-functionalization then led to the creation of the geminal tristriazole compounds.

Just Click It: Undergraduate Procedures for the Copper(I)-Catalyzed Formation of 1,2,3-Triazoles from Azides and Terminal Acetylenes

ERIC Educational Resources Information Center

Sharpless, William D.; Peng Wu; Hansen, Trond Vidar; Lindberg, James G.

2005-01-01

The click chemistry uses only the most reliable reactions to build complex molecules from olefins, electrophiles and heteroatom linkers. A variation on Huisgen's azide-alkyne 1,2,3-triazole synthesis, the addition of the copper (I), the premium example of the click reaction, catalyst strongly activates terminal acetylenes towards the 1,3-dipole in…

The effects of sodium azide on seed germination and seedling growth of chili pepper (Capsicum annum L. cv. Landung)

NASA Astrophysics Data System (ADS)

Yafizham; Herwibawa, B.

2018-01-01

This study was aimed to determine the effects of sodium azide on the performance of chili pepper. Dry seeds from pure lines of chili pepper cv. Landung were used in this experiment. Each set containing 50 seeds was placed in nylon fishner bags, washed in flowing water and soaked in distilled water for four hours. After soaking, four sets of seeds were dabbed dry with tissue paper and were treated for two hours at 30 0C in appropriate solution of 0, 0.10, 0.20, 0.40, 0.80, 1.60 mM sodium azide with phosphate buffer at pH 3. After treatment, the seeds were germinated in plastic boxes containing sterilized sand and kept under laboratory condition by supplied with water everyday. The seeds for M1 germination percentage, seedling height, plant height and number of leaves were recorded 30 days and 60 days after treatment, respectively. Seeds which radicle emerged were considered germinated, the seedling and plant height were measured from the tip of primary root to the base of the first leaf pair, and the number of leaves were counted for only fully expanded leaves. A completely randomized block design in four replicates was used throughout the experiment. Data obtained were analysed for range, mean, standard of deviation, and percent of control using Microsoft Office Excel 2007 software. It was concluded that different doses of sodium azide influenced the performances of chili pepper cv. Landung. Very low doses of sodium azide (0-1.60 mM) might be used to study the improvement of chili pepper diversity.

N-benzoylimido complexes of palladium. Synthesis, structural characterisation and structure-reactivity relationship.

PubMed

Besenyei, Gábor; Párkányi, László; Szalontai, Gábor; Holly, Sándor; Pápai, Imre; Keresztury, Gábor; Nagy, Andrea

2004-07-07

Benzoyl azides, ArC(O)N3, 2, (Ar = phenyl or substituted phenyl), react with [Pd2Cl2(dppm)2], 1, [dppm = bis(diphenylphosphino)methane] with the formation of novel [Pd2Cl2(mu-NC(O)Ar)(dppm)2], 3, benzoylnitrene complexes that were structurally characterised by multinuclear magnetic resonance and IR spectroscopy and, in several instances, by single crystal X-ray diffraction. As shown by crystallographic studies, the C2P4Pd2 rings adopt extended twist-boat conformations with methylene groups bending towards the bridging benzoylimido moieties. X-ray diffraction studies have revealed the chiral nature of the imido complexes, the chiral element being the propeller-like C2P4Pd2 ring. Structural data accumulated on complexes 3 such as short C-N distances (1.32 A), elongated C=O bonds (1.30 A) as well as the outstandingly high barrier to internal rotation around the N-C(O) linkage (88.3 kJ mol(-1)) are in line with extensive ppi-ppi interaction between the bridging nitrogen and the carbonyl carbon atoms. Theoretical calculations indicate an electron shift from the dimer towards the apical nitrogen atom, which, in turn, facilitates the donation of electrons towards the carbonyl moiety. To elucidate the structure-reactivity relationship of benzoyl azides towards 1, crystallographic and solution IR spectroscopic studies were carried out on a series of para-substituted benzoyl azides. The reaction obeys the Hammett equation. The large positive value of the reaction constant indicates that the azides act as electrophiles in the reaction studied. The enhanced reactivity of 2-nitrobenzoyl azide has been attributed to a decreased conjugation of the phenyl and carbonyl moieties in this reagent.

Catalyst-free room-temperature iClick reaction of molybdenum(ii) and tungsten(ii) azide complexes with electron-poor alkynes: structural preferences and kinetic studies.

PubMed

Schmid, Paul; Maier, Matthias; Pfeiffer, Hendrik; Belz, Anja; Henry, Lucas; Friedrich, Alexandra; Schönfeld, Fabian; Edkins, Katharina; Schatzschneider, Ulrich

2017-10-10

Two isostructural and isoelectronic group VI azide complexes of the general formula [M(η 3 -allyl)(N 3 )(bpy)(CO) 2 ] with M = Mo, W and bpy = 2,2'-bipyridine were prepared and fully characterized, including X-ray structure analysis. Both reacted smoothly with electron-poor alkynes such as dimethyl acetylenedicarboxylate (DMAD) and 4,4,4-trifluoro-2-butynoic acid ethyl ester in a catalyst-free room-temperature iClick [3 + 2] cycloaddition reaction. Reaction with phenyl(trifluoromethyl)acetylene, on the other hand, did not lead to any product formation. X-ray structures of the four triazolate complexes isolated showed the monodentate ligand to be N2-coordinated in all cases, which requires a 1,2-shift of the nitrogen from the terminal azide to the triazolate cycloaddition product. On the other hand, a 19 F NMR spectroscopic study of the reaction of the fluorinated alkyne with the tungsten azide complex at 27 °C allowed detection of the N1-coordinated intermediate. With this method, the second-order rate constant was determined as (7.3 ± 0.1) × 10 -2 M -1 s -1 , which compares favorably with that of first-generation compounds such as difluorocyclooctyne (DIFO) used in the strain-promoted azide-alkyne cycloaddition (SPAAC). In contrast, the reaction of the molybdenum analogue was too fast to be studied with NMR methods. Alternatively, solution IR studies revealed pseudo-first order rate constants of 0.4 to 6.5 × 10 -3 s -1 , which increased in the order of Mo > W and F 3 C-C[triple bond, length as m-dash]C-COOEt > DMAD.

Improved synthesis of [(18)F]FLETT via a fully automated vacuum distillation method for [(18)F]2-fluoroethyl azide purification.

PubMed

Ackermann, Uwe; Plougastel, Lucie; Goh, Yit Wooi; Yeoh, Shinn Dee; Scott, Andrew M

2014-12-01

The synthesis of [(18)F]2-fluoroethyl azide and its subsequent click reaction with 5-ethynyl-2'-deoxyuridine (EDU) to form [(18)F]FLETT was performed using an iPhase FlexLab module. The implementation of a vacuum distillation method afforded [(18)F]2-fluoroethyl azide in 87±5.3% radiochemical yield. The use of Cu(CH3CN)4PF6 and TBTA as catalyst enabled us to fully automate the [(18)F]FLETT synthesis without the need for the operator to enter the radiation field. [(18)F]FLETT was produced in higher overall yield (41.3±6.5%) and shorter synthesis time (67min) than with our previously reported manual method (32.5±2.5% in 130min). Copyright © 2014 Elsevier Ltd. All rights reserved.

Selective Radical Amination of Aldehydic C(sp2)–H Bonds with Fluoroaryl Azides via Co(II)-Based Metalloradical Catalysis: Synthesis of N-Fluoroaryl Amides from Aldehydes under Neutral and Nonoxidative Conditions

PubMed Central

Jin, Li-Mei; Lu, Hongjian; Cui, Yuan; Lizardi, Christopher L.; Arzua, Thiago N.; Wojtas, Lukasz; Cui, Xin

2014-01-01

The Co(II) complex of the D2h-symmetric amidoporphyrin 3,5-DitBu-IbuPhyrin, [Co(P1)], has proven to be an effective metalloradical catalyst for intermolecular amination of C(sp2)–H bonds of aldehydes with fluoroaryl azides. The [Co(P1)]-catalyzed process can employ aldehydes as the limiting reagents and operate under neutral and non-oxidative conditions, generating nitrogen gas as the only byproduct. The metalloradical aldehydic C–H amination is suitable for different combinations of aldehydes and fluoroaryl azides, producing the corresponding N-fluoroaryl amides in good to excellent yields. A series of mechanistic studies support a stepwise radical mechanism for the Co(II)-catalyzed intermolecular C–H amination. PMID:25071929

Selective Radical Amination of Aldehydic C(sp2)-H Bonds with Fluoroaryl Azides via Co(II)-Based Metalloradical Catalysis: Synthesis of N-Fluoroaryl Amides from Aldehydes under Neutral and Nonoxidative Conditions.

PubMed

Jin, Li-Mei; Lu, Hongjian; Cui, Yuan; Lizardi, Christopher L; Arzua, Thiago N; Wojtas, Lukasz; Cui, Xin; Zhang, X Peter

2014-06-01

The Co(II) complex of the D 2h -symmetric amidoporphyrin 3,5-Di t Bu-IbuPhyrin, [Co( P1 )], has proven to be an effective metalloradical catalyst for intermolecular amination of C(sp 2 )-H bonds of aldehydes with fluoroaryl azides. The [Co( P1 )]-catalyzed process can employ aldehydes as the limiting reagents and operate under neutral and non-oxidative conditions, generating nitrogen gas as the only byproduct. The metalloradical aldehydic C-H amination is suitable for different combinations of aldehydes and fluoroaryl azides, producing the corresponding N -fluoroaryl amides in good to excellent yields. A series of mechanistic studies support a stepwise radical mechanism for the Co(II)-catalyzed intermolecular C-H amination.

Decontamination of Casualties from Battlefield Under CW and BW Attack

DTIC Science & Technology

1984-11-15

anion present. Thus the films containing periodide, perbromide, chlorochromate , permanganate, dichromate, and pyridinium azide each had a detectable...38 4. Preparation of Azide Films 38 5. Preparation of Hydroxide Films 39 6. Preparation of Thiosulfate Film 39 7. Preparation of Chlorochromate Films...dichromate, hypochlorite, m-chioroperbenzoaite and related polymers of BD-5-Q film. 𔄁. Preparation of Chlorochromate Films Chromium trioxide (CrO 3 , 9.8 g

Sequential continuous flow processes for the oxidation of amines and azides by using HOF·MeCN.

PubMed

McPake, Christopher B; Murray, Christopher B; Sandford, Graham

2012-02-13

The generation and use of the highly potent oxidising agent HOF·MeCN in a controlled single continuous flow process is described. Oxidations of amines and azides to corresponding nitrated systems by using fluorine gas, water and acetonitrile by sequential gas-liquid/liquid-liquid continuous flow procedures are reported. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pressure-accelerated azide-alkyne cycloaddition: micro capillary versus autoclave reactor performance.

PubMed

Borukhova, Svetlana; Seeger, Andreas D; Noël, Timothy; Wang, Qi; Busch, Markus; Hessel, Volker

2015-02-01

Pressure effects on regioselectivity and yield of cycloaddition reactions have been shown to exist. Nevertheless, high pressure synthetic applications with subsequent benefits in the production of natural products are limited by the general availability of the equipment. In addition, the virtues and limitations of microflow equipment under standard conditions are well established. Herein, we apply novel-process-window (NPWs) principles, such as intensification of intrinsic kinetics of a reaction using high temperature, pressure, and concentration, on azide-alkyne cycloaddition towards synthesis of Rufinamide precursor. We applied three main activation methods (i.e., uncatalyzed batch, uncatalyzed flow, and catalyzed flow) on uncatalyzed and catalyzed azide-alkyne cycloaddition. We compare the performance of two reactors, a specialized autoclave batch reactor for high-pressure operation up to 1800 bar and a capillary flow reactor (up to 400 bar). A differentiated and comprehensive picture is given for the two reactors and the three methods of activation. Reaction speedup and consequent increases in space-time yields is achieved, while the process window for favorable operation to selectively produce Rufinamide precursor in good yields is widened. The best conditions thus determined are applied to several azide-alkyne cycloadditions to widen the scope of the presented methodology. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

1H NMR study of the effect of variable ligand on heme oxygenase electronic and molecular structure

PubMed Central

Ma, Li-Hua; Liu, Yangzhong; Zhang, Xuhong; Yoshida, Tadashi; La Mar, Gerd N.

2009-01-01

Heme oxygenase carries out stereospecific catabolism of protohemin to yield iron, CO and biliverdin. Instability of the physiological oxy complex has necessitated the use of model ligands, of which cyanide and azide are amenable to solution NMR characterization. Since cyanide and azide are contrasting models for bound oxygen, it is of interest to characterize differences in their molecular and/or electronic structures. We report on detailed 2D NMR comparison of the azide and cyanide substrate complexes of heme oxygenase from Neisseria meningitidis, which reveals significant and widespread differences in chemical shifts between the two complexes. To differentiate molecular from electronic structural changes between the two complexes, the anisotropy and orientation of the paramagnetic susceptibility tensor were determined for the azide complex for comparison with those for the cyanide complex. Comparison of the predicted and observed dipolar shifts reveals that shift differences are strongly dominated by differences in electronic structure and do not provide any evidence for detectable differences in molecular structure or hydrogen bonding except in the immediate vicinity of the distal ligand. The readily cleaved C-terminus interacts with the active site and saturation-transfer allows difficult heme assignments in the high-spin aquo complex. PMID:18976815

Sodium azide-associated laryngospasm after air bag deployment.

PubMed

Francis, David; Warren, Samuel A; Warner, Keir J; Harris, William; Copass, Michael K; Bulger, Eileen M

2010-09-01

The advent and incorporation of the air bag into motor vehicles has resulted in the mitigation of many head and truncal injuries in motor vehicle collisions. However, air bag deployment is not risk free. We present a case of sodium azide-induced laryngospasm after air bag deployment. An unrestrained male driver was in a moderate-speed motor vehicle collision with air bag deployment. Medics found him awake, gasping for air with stridorous respirations and guarding his neck. The patient had no external signs of trauma and was presumed to have tracheal injury. The patient was greeted by the Anesthesiology service, which intubated him using glidescope-assisted laryngoscopy. The patient was admitted for overnight observation and treatment of alkaline ocular injury and laryngospasm. Although air bags represent an important advance in automobile safety, their use is not without risk. Bruising and tracheal rupture secondary to air bag deployment have been reported in out-of-position occupants. Additionally, alkaline by-products from the combustion of sodium azide in air bags have been implicated in ocular injury and facial burns. Laryngospasm after sodium azide exposure presents another diagnostic challenge for providers. Therefore, it is incumbent to maintain vigilance in the physical examination and diagnosis of occult injuries after air bag deployment. Copyright © 2010 Elsevier Inc. All rights reserved.

The structure of the Caenorhabditis elegans manganese superoxide dismutase MnSOD-3-azide complex

DOE PAGES

Hunter, Gary J.; Trinh, Chi H.; Bonetta, Rosalin; ...

2015-08-27

C. elegans MnSOD-3 has been implicated in the longevity pathway and its mechanism of catalysis is relevant to the aging process and carcinogenesis. The structures of MnSOD-3 provide unique crystallographic evidence of a dynamic region of the tetrameric interface (residues 41–54). We have determined the structure of the MnSOD-3-azide complex to 1.77-Å resolution. The analysis of this complex shows that the substrate analog, azide, binds end-on to the manganese center as a sixth ligand and that it ligates directly to a third and new solvent molecule also positioned within interacting distance to the His30 and Tyr34 residues of the substratemore » access funnel. This is the first structure of a eukaryotic MnSOD-azide complex that demonstrates the extended, uninterrupted hydrogen-bonded network that forms a proton relay incorporating three outer sphere solvent molecules, the substrate analog, the gateway residues, Gln142, and the solvent ligand. This configuration supports the formation and release of the hydrogen peroxide product in agreement with the 5-6-5 catalytic mechanism for MnSOD. The high product dissociation constant k₄ of MnSOD-3 reflects low product inhibition making this enzyme efficient even at high levels of superoxide.« less

Preparation of the highly dispersed powder of titanium carbonitride by SHS azide technology with previous partial nitriding

NASA Astrophysics Data System (ADS)

Amosov, A. P.; Markov, Yu M.; Dobrovolskaya, R. A.; Nikolaeva, E. N.

2017-02-01

It is shown that the powder of very hard refractory titanium carbonitride (TiC0.5N0.5) is the basis of tungsten-free hard alloys which are prospective for application as inexpensive cutting tools. The finer the powder of titanium carbonitrideis, the moreenhanced properties of hard alloys, sintered from the powder, are. An opportunity to reduce the particle size of the titanium carbonitride powder obtained by energy-saving azide technology of self-propagating high-temperature synthesis at the cost of reducing the particle size of the initial titanium powderwas investigated. To ensure the safety of the grinding process of the initial metal titanium powder, it was offered to nitride a Ti powder partially into a TiN0.2 compound. Such partial nitriding was performed by the azidetechnology with lack of sodium azide (NaN3) as a nitriding reagent. After intensive grinding in the planetary ball mill, the TiN0.2 powder turned into a superfine powder with an ultrafine structure. This powder was capable of nitriding and carburizing in the azide technology with formation of superfine pure powder agglomerates which are composed of ultrafine and nano-particles of TiC0.5N0.5.

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

PubMed Central

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

2009-01-01

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

Comparative DFT study of structure, reactivity and IR spectra of phosphorus-containing dendrons with Pdbnd Nsbnd Pdbnd S linkages, vinyl and azide functional groups

NASA Astrophysics Data System (ADS)

Furer, V. L.; Vandyukov, A. E.; Majoral, J. P.; Caminade, A. M.; Gottis, S.; Laurent, R.; Kovalenko, V. I.

2015-07-01

Fourier transform IR spectra of the first generation dendrons built from thiophosphoryl core with terminal Psbnd Cl groups, vinyl (G1) and azide (G2) functional group at the level of the core have been recorded. The optimized geometries of low energy isomers of G1 and G2 have been calculated by density functional (DFT) method at the PBE/TZ2P level of theory. DFT is used for analyzing the properties of each structural part (core, branches, surface). It was found that the repeated branching units of G1 and G2 contain planar sbnd Osbnd C6H4sbnd CHdbnd Nsbnd N(CH3)sbnd Prbond2 fragments. DFT results for the structure of G1 and G2 are in good agreement with X-ray diffraction measurements. A complete vibrational assignment is proposed for different parts of G1 and G2. The global and local reactivity descriptors have been used to characterize the reactivity pattern of the core functional and terminal groups. Natural bond orbital (NBO) analysis has been applied to comparative study of charge delocalization. Our study reveals why azide group linked to phosphorus has a different reactivity when compared to organic azides.

Steering the azido-tetrazole equilibrium of 4-azidopyrimidines via substituent variation - implications for drug design and azide-alkyne cycloadditions.

PubMed

Thomann, A; Zapp, J; Hutter, M; Empting, M; Hartmann, R W

2015-11-21

This paper focuses on an interesting constitutional isomerism called azido-tetrazole equilibrium which is observed in azido-substituted N-heterocycles. We present a systematic investigation of substituent effects on the isomer ratio within a 2-substituted 4-azidopyrimidine model scaffold. NMR- and IR-spectroscopy as well as X-ray crystallography were employed for thorough analysis and characterization of synthesized derivatives. On the basis of this data, we demonstrate the possibility to steer this valence tautomerism towards the isomer of choice by means of substituent variation. We show that the tetrazole form can act as an efficient disguise for the corresponding azido group masking its well known reactivity in azide-alkyne cycloadditions (ACCs). In copper(I)-catalyzed AAC reactions, substituent-stabilized tetrazoles displayed a highly decreased or even abolished reactivity whereas azides and compounds in the equilibrium were directly converted. By use of an acid sensitive derivative, we provide, to our knowledge, the first experimental basis for a possible exploitation of this dynamic isomerism as a pH-dependent azide-protecting motif for selective SPAAC conjugations in aqueous media. Finally, we demonstrate the applicability and efficiency of stabilized tetrazolo[1,5-c]pyrimidines for Fragment-Based Drug Design (FBDD) in the field of quorum sensing inhibitors.

49 CFR 173.182 - Barium azide-50 percent or more water wet.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 2 2011-10-01 2011-10-01 false Barium azide-50 percent or more water wet. 173.182... Class 1 and Class 7 § 173.182 Barium azide—50 percent or more water wet. Barium azide—50 percent or more water wet, must be packed in wooden boxes (4C1, 4C2, 4D, or 4F) or fiber drums (1G) with inner glass...

49 CFR 173.182 - Barium azide-50 percent or more water wet.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Barium azide-50 percent or more water wet. 173.182... Class 1 and Class 7 § 173.182 Barium azide—50 percent or more water wet. Barium azide—50 percent or more water wet, must be packed in wooden boxes (4C1, 4C2, 4D, or 4F) or fiber drums (1G) with inner glass...

Peptidomimetics via copper-catalyzed azide-alkyne cycloadditions.

PubMed

Angell, Yu L; Burgess, Kevin

2007-10-01

This critical review concerns the impact of copper-mediated alkyne-azide cycloadditions on peptidomimetic studies. It discusses how this reaction has been used to insert triazoles into peptide chains, to link peptides to other functionalities (e.g. carbohydrates, polymers, and labels), and as a basis for evolution of less peptidic compounds as pharmaceutical leads. It will be of interest to those studying this click reaction, peptidomimetic secondary structure and function, and to medicinal chemists.

Design and synthesis of unnatural heparosan and chondroitin building blocks

PubMed Central

Bera, Smritilekha; Linhardt, Robert J.

2011-01-01

Triazole linked heparosan and chondroitin disaccharide and tetrasaccharide building blocks were synthesized in a stereoselective manner by applying a very efficient Copper Catalyzed Azide-Alkyne Cycloadditions (CuAAC) reaction of appropriately substituted azido-glucuronic acid and propargyluted N-acetyl glucosamine and N-acetyl galactosamine derivative respectively. The resulting suitably substituted tetrasaccharide analogs can be easily converted into azide and alkyne unit for further synthesis of higher oligosaccharide analogs. PMID:21438620

[Antimutagenic action of superoxide dismutase on sodium azide- and nitrosoguanidine-induced mutagenesis in Salmonella typhimurium TA 1535].

PubMed

Vorob'eva, L I; Cherdyntseva, T A; Aver'ianov, A A; Abilev, S K

1993-05-01

It was shown that superoxide dismutase (SOD) decreased the mutagenic action of sodium azide (NaN3) and N-methyl-N'-nitro-N-nitrosoguanidine in Salmonella typhimurium TA1535. Catalase and quenchers of hydroxyl radicals showed, unlike SOD no effect on the mutagenicity of NaN3. Cell extract from propionic acid bacteria also possessed the antimutagenic activity, only partially depending on the SOD activity.

Thermodynamic analysis of solid-fuel mixtures glycidyl azide polymer (GAP)/RDX for miniengines of microelectromechanical systems

NASA Astrophysics Data System (ADS)

Fut'ko, S. I.; Ermolaeva, E. M.; Dobrego, K. V.; Bondarenko, V. P.; Dolgii, L. N.

2011-09-01

On the basis of thermodynamic calculations we show that solid-fuel mixtures glycidyl azide polymer/RDX are promising for use in miniengines made on the basis of technologies of microelectromechanical systems of semiconductor microelectronics. It has been shown that small (up to 20 mass percent) additives of RDX to the glycidyl azide polymer markedly increase the values of the theoretical specific impulse and the thermal efficiency of the engine and decrease the quantity of undesirable solid carbon formed in combustion products of the mixed fuel. In so doing, these mixtures provide fairly low combustion temperatures not exceeding the thermostability limit of crystal silicon from which the miniengine case is made. The physicochemical factors influencing the value of the theoretical specific impulse of the mixed solid-fuel charge have been elucidated, and methods for its maximization have been proposed.

Photochemistry of matrix isolated (trifluoromethyl)sulfonyl azide, CF₃SO₂N₃.

PubMed

Zeng, Xiaoqing; Beckers, Helmut; Willner, Helge; Neuhaus, Patrik; Grote, Dirk; Sander, Wolfram

2015-03-19

The photochemistry of matrix isolated (trifluoromethylsulfonyl) azide, CF3SO2N3, has been studied at low temperatures. Upon ArF laser irradiation (λ = 193 nm), the azide eliminates N2 and furnishes triplet [(trifluoromethyl)sulfonyl]nitrene, CF3SO2N, which has been characterized by IR and EPR spectroscopy. Upon subsequent UV light irradiation (λ = 260-400 nm) the nitrene converts to CF3N═SO2 and CF3S(O)NO through a Curtius-type rearrangement. Further two new species CF2N═SO2F and FSNO were identified together with CF2NF, SO2, F2CO, CF3NO, and SO as side products. In addition, triplet nitrene CF3N was detected by its EPR and IR spectra. The complex stepwise photodecomposition of matrix isolated CF3SO2N3 is discussed in terms of the observed photolysis products and quantum chemical calculations.

Surface Functionalization of Exosomes Using Click Chemistry

PubMed Central

2015-01-01

A method for conjugation of ligands to the surface of exosomes was developed using click chemistry. Copper-catalyzed azide alkyne cycloaddition (click chemistry) is ideal for biocojugation of small molecules and macromolecules to the surface of exosomes, due to fast reaction times, high specificity, and compatibility in aqueous buffers. Exosomes cross-linked with alkyne groups using carbodiimide chemistry were conjugated to a model azide, azide-fluor 545. Conjugation had no effect on the size of exosomes, nor was there any change in the extent of exosome adherence/internalization with recipient cells, suggesting the reaction conditions were mild on exosome structure and function. We further investigated the extent of exosomal protein modification with alkyne groups. Using liposomes with surface alkyne groups of a similar size and concentration to exosomes, we estimated that approximately 1.5 alkyne groups were present for every 150 kDa of exosomal protein. PMID:25220352

Discrete Cu(i) complexes for azide-alkyne annulations of small molecules inside mammalian cells.

PubMed

Miguel-Ávila, Joan; Tomás-Gamasa, María; Olmos, Andrea; Pérez, Pedro J; Mascareñas, José L

2018-02-21

The archetype reaction of "click" chemistry, namely, the copper-promoted azide-alkyne cycloaddition (CuAAC), has found an impressive number of applications in biological chemistry. However, methods for promoting intermolecular annulations of exogenous, small azides and alkynes in the complex interior of mammalian cells, are essentially unknown. Herein we demonstrate that isolated, well-defined copper(i)-tris(triazolyl) complexes featuring designed ligands can readily enter mammalian cells and promote intracellular CuAAC annulations of small, freely diffusible molecules. In addition to simplifying protocols and avoiding the addition of "non-innocent" reductants, the use of these premade copper complexes leads to more efficient processes than with the alternative, in situ made copper species prepared from Cu(ii) sources, tris(triazole) ligands and sodium ascorbate. Under the reaction conditions, the well-defined copper complexes exhibit very good cell penetration properties, and do not present significant toxicities.

A general approach to DNA-programmable atom equivalents.

PubMed

Zhang, Chuan; Macfarlane, Robert J; Young, Kaylie L; Choi, Chung Hang J; Hao, Liangliang; Auyeung, Evelyn; Liu, Guoliang; Zhou, Xiaozhu; Mirkin, Chad A

2013-08-01

Nanoparticles can be combined with nucleic acids to programme the formation of three-dimensional colloidal crystals where the particles' size, shape, composition and position can be independently controlled. However, the diversity of the types of material that can be used is limited by the lack of a general method for preparing the basic DNA-functionalized building blocks needed to bond nanoparticles of different chemical compositions into lattices in a controllable manner. Here we show that by coating nanoparticles protected with aliphatic ligands with an azide-bearing amphiphilic polymer, followed by the coupling of DNA to the polymer using strain-promoted azide-alkyne cycloaddition (also known as copper-free azide-alkyne click chemistry), nanoparticles bearing a high-density shell of nucleic acids can be created regardless of nanoparticle composition. This method provides a route to a virtually endless class of programmable atom equivalents for DNA-based colloidal crystallization.

Combining aminocyanine dyes with polyamide dendrons: a promising strategy for imaging in the near-infrared region.

PubMed

Ornelas, Cátia; Lodescar, Rachelle; Durandin, Alexander; Canary, James W; Pennell, Ryan; Liebes, Leonard F; Weck, Marcus

2011-03-21

Cyanine dyes are known for their fluorescence in the near-IR (NIR) region, which is desirable for biological applications. We report the synthesis of a series of aminocyanine dyes containing terminal functional groups such as acid, azide, and cyclooctyne groups for further functionalization through, for example, click chemistry. These aminocyanine dyes can be attached to polyfunctional dendrons by copper-catalyzed azide alkyne cycloaddition (CuAAC), strain-promoted azide alkyne cycloaddition (SPAAC), peptide coupling, or direct S(NR)1 reactions. The resulting dendron-dye conjugates were obtained in high yields and displayed high chemical stability and photostability. The optical properties of the new compounds were studied by UV/Vis and fluorescence spectroscopy. All compounds show large Stokes shifts and strong fluorescence in the NIR region with high quantum yields, which are optimal properties for in vivo optical imaging. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cyclic Multiblock Copolymers via Combination of Iterative Cu(0)-Mediated Radical Polymerization and Cu(I)-Catalyzed Azide-Alkyne Cycloaddition Reaction.

PubMed

Xiao, Lifen; Zhu, Wen; Chen, Jiqiang; Zhang, Ke

2017-02-01

Cyclic multiblock polymers with high-order blocks are synthesized via the combination of single-electron transfer living radical polymerization (SET-LRP) and copper-catalyzed azide-alkyne cycloaddition (CuAAC). The linear α,ω-telechelic multiblock copolymer is prepared via SET-LRP by sequential addition of different monomers. The SET-LRP approach allows well control of the block length and sequence as A-B-C-D-E, etc. The CuAAC is then performed to intramolecularly couple the azide and alkyne end groups of the linear copolymer and produce the corresponding cyclic copolymer. The block sequence and the cyclic topology of the resultant cyclic copolymer are confirmed by the characterization of 1 H nuclear magnetic resonance spectroscopy, gel permeation chromatography, Fourier transform infrared spectroscopy, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pore surface engineering in covalent organic frameworks.

PubMed

Nagai, Atsushi; Guo, Zhaoqi; Feng, Xiao; Jin, Shangbin; Chen, Xiong; Ding, Xuesong; Jiang, Donglin

2011-11-15

Covalent organic frameworks (COFs) are a class of important porous materials that allow atomically precise integration of building blocks to achieve pre-designable pore size and geometry; however, pore surface engineering in COFs remains challenging. Here we introduce pore surface engineering to COF chemistry, which allows the controlled functionalization of COF pore walls with organic groups. This functionalization is made possible by the use of azide-appended building blocks for the synthesis of COFs with walls to which a designable content of azide units is anchored. The azide units can then undergo a quantitative click reaction with alkynes to produce pore surfaces with desired groups and preferred densities. The diversity of click reactions performed shows that the protocol is compatible with the development of various specific surfaces in COFs. Therefore, this methodology constitutes a step in the pore surface engineering of COFs to realize pre-designed compositions, components and functions.

The inhibitory effect of 3-amino-1,2,4-triazole on relaxation induced by hydroxylamine and sodium azide but not hydrogen peroxide or glyceryl trinitrate in rat aorta.

PubMed Central

Mian, K. B.; Martin, W.

1995-01-01

1. In this study we investigated the role of catalase in relaxation induced by hydroxylamine, sodium azide, glyceryl trinitrate and hydrogen peroxide in isolated rings of rat aorta. 2. Hydrogen peroxide (1 microM-1 mM)-induced concentration-dependent relaxation of phenylephrine (PE)-induced tone in endothelium-containing rings. In endothelium-denuded rings, however, higher concentrations (30 microM-1 mM) of hydrogen peroxide were required to produce relaxation. The endothelium-dependent component of hydrogen peroxide-induced relaxation was abolished following pretreatment with N(O)-nitro-L-arginine methyl ester (L-NAME, 30 microM). L-NAME (30 microM) had no effect, however, on hydrogen peroxide-induced relaxation in endothelium-denuded rings. 3. Pretreatment of endothelium-denuded rings with catalase (1000 u ml-1) blocked relaxation induced by hydrogen peroxide (10 microM-1 mM). The ability of catalase to inhibit hydrogen peroxide-induced relaxation was partially blocked following incubation with 3-amino-1,2, 4-triazole (AT, 50 mM) for 30 min and completely blocked at 90 min. 4. Pretreatment of endothelium-denuded rings with methylene blue (MeB, 30 microM) inhibited relaxation induced by hydrogen peroxide (10 microM-1 mM), sodium azide (1-300 nM), hydroxylamine (1-300 nM) and glyceryl trinitrate (1-100 nM) suggesting that each acted by stimulation of soluble guanylate cyclase. 5. Pretreatment of endothelium-denuded rings with AT (1-50 mM, 90 min) to inhibit endogenous catalase blocked relaxation induced by sodium azide (1-300 nM) and hydroxylamine (1-300 nM) but had no effect on relaxation induced by hydrogen peroxide (10 microM-1 mM) or glyceryl trinitrate (1-100 nM). 6. In a cell-free system, incubation of sodium azide (10 microM-3 mM) and hydroxylamine (10 microM-30 mM) but not glyceryl trinitrate (10 microM-1 mM) with catalase (1000 u ml-1) in the presence of hydrogen peroxide (1 mM) led to production of nitrite, a major breakdown product of nitric oxide. AT (1-100 mM) inhibited, in a concentration-dependent manner, the formation of nitrite from azide in the presence of hydrogen peroxide. 7. These data suggest that metabolism by catalase plays an important role in the relaxation induced by hydroxylamine and sodium azide in isolated rings of rat aorta. Relaxation appears to be due to formation of nitric oxide and activation of soluble guanylate cyclase. In contrast, metabolism by catalase does not appear to be involved in the relaxant actions of hydrogen peroxide or glyceryl trinitrate. PMID:8719811

Functionalization of Graphene Nanoplatelets Using Sugar Azide for Graphene/Epoxy Nanocomposites

DTIC Science & Technology

2014-06-20

temperature to 200°C in the single cantilever mode at a heating rate and frequency of 3°C/min and 1 Hz, respectively. Thermogravimetric analysis (TGA) of...14. ABSTRACT We report a covalent functionalization of graphene nanoparticles (GnPs) employing 2,3,4-Tri-O-acetyl-β-D-xylopyranosyl azide...and glass transition temperature (~10C) compared to an un-functionalized GnP based epoxy composite. 15. SUBJECT TERMS Graphene nanoparticles

Reaction of azides and enolisable aldehydes under the catalysis of organic bases and Cinchona based quaternary ammonium salts.

PubMed

Destro, Dario; Sanchez, Sandra; Cortigiani, Mauro; Adamo, Mauro F A

2017-06-21

Herein we report a two-step sequence for the preparation of amides starting from azides and enolisable aldehydes. The reaction proceeded via the formation of triazoline intermediates that were converted into amides via Lewis acid catalysis. Preliminary studies on the preparation of triazolines under chiral phase transfer catalysis are also presented, demonstrating that enantioenriched amides could be prepared from achiral aldehydes in moderate to low enantioselectivity.

Observation of the controlled assembly of preclick components in the in situ click chemistry generation of a chitinase inhibitor

PubMed Central

Hirose, Tomoyasu; Maita, Nobuo; Gouda, Hiroaki; Koseki, Jun; Yamamoto, Tsuyoshi; Sugawara, Akihiro; Nakano, Hirofumi; Hirono, Shuichi; Shiomi, Kazuro; Watanabe, Takeshi; Taniguchi, Hisaaki; Sharpless, K. Barry; Ōmura, Satoshi; Sunazuka, Toshiaki

2013-01-01

The Huisgen cycloaddition of azides and alkynes, accelerated by target biomolecules, termed “in situ click chemistry,” has been successfully exploited to discover highly potent enzyme inhibitors. We have previously reported a specific Serratia marcescens chitinase B (SmChiB)-templated syn-triazole inhibitor generated in situ from an azide-bearing inhibitor and an alkyne fragment. Several in situ click chemistry studies have been reported. Although some mechanistic evidence has been obtained, such as X-ray analysis of [protein]–[“click ligand”] complexes, indicating that proteins act as both mold and template between unique pairs of azide and alkyne fragments, to date, observations have been based solely on “postclick” structural information. Here, we describe crystal structures of SmChiB complexed with an azide ligand and an O-allyl oxime fragment as a mimic of a click partner, revealing a mechanism for accelerating syn-triazole formation, which allows generation of its own distinct inhibitor. We have also performed density functional theory calculations based on the X-ray structure to explore the acceleration of the Huisgen cycloaddition by SmChiB. The density functional theory calculations reasonably support that SmChiB plays a role by the cage effect during the pretranslation and posttranslation states of selective syn-triazole click formation. PMID:24043811

Ultrafast Infrared and UV-vis Studies of the Photochemistry of Methoxycarbonylphenyl Azides in Solution

PubMed Central

Xue, Jiadan; Luk, Hoi Ling; Eswaran, S. V.; Hadad, Christopher M.; Platz, Matthew S.

2012-01-01

The photochemistry of 4-methoxycarbonylphenyl azide (2a), 2-methoxycarbonylphenyl azide (3a) and 2-methoxy-6-methoxycarbonylphenyl azide (4a) were studied by ultrafast time-resolved infrared (IR) and UV-vis spectroscopies in solution. Singlet nitrenes and ketenimines were observed and characterized for all three azides. Isoxazole species 3g and 4g are generated after photolysis of 3a and 4a, respectively, in acetonitrile. Triplet nitrene 4e formation correlated with the decay of singlet nitrene 4b. The presence of water does not change the chemistry or kinetics of singlet nitrenes 2b and 3b, but leads to protonation of 4b to produce nitrenium ion 4f. Singlet nitrenes 2b and 3b have lifetimes of 2 ns and 400 ps, respectively, in solution at ambient temperature. The singlet nitrene 4b in acetonitrile has a lifetime of about 800 ps, and reacts with water with a rate constant of 1.9 × 108 L·mol−1·s−1 at room temperature. These results indicate that a methoxycarbonyl group at either the para or ortho positions has little influence on the ISC rate, but that the presence of a 2-methoxy group dramatically accelerates the ISC rate relative to the unsubstituted phenylnitrene. An ortho methoxy group highly stabilizes the corresponding nitrenium ion and favors its formation in aqueous solvents. This substituent has little influence on the ring-expansion rate. These results are consistent with theoretical calculations for the various intermediates and their transition states. Cyclization from the nitrene to the azirine intermediate is favored to proceed towards the electron-deficient ester group; however, the higher energy barrier is the ring-opening process, that is azirine to ketenimine formation, rendering the formation of the ester-ketenimine to be less favorable than the isomeric MeO-ketenimine. PMID:22568477

Ultrafast infrared and UV-vis studies of the photochemistry of methoxycarbonylphenyl azides in solution.

PubMed

Xue, Jiadan; Luk, Hoi Ling; Eswaran, S V; Hadad, Christopher M; Platz, Matthew S

2012-06-07

The photochemistry of 4-methoxycarbonylphenyl azide (2a), 2-methoxycarbonylphenyl azide (3a), and 2-methoxy-6-methoxycarbonylphenyl azide (4a) were studied by ultrafast time-resolved infrared (IR) and UV-vis spectroscopies in solution. Singlet nitrenes and ketenimines were observed and characterized for all three azides. Isoxazole species 3g and 4g are generated after photolysis of 3a and 4a, respectively, in acetonitrile. Triplet nitrene 4e formation correlated with the decay of singlet nitrene 4b. The presence of water does not change the chemistry or kinetics of singlet nitrenes 2b and 3b, but leads to protonation of 4b to produce nitrenium ion 4f. Singlet nitrenes 2b and 3b have lifetimes of 2 ns and 400 ps, respectively, in solution at ambient temperature. The singlet nitrene 4b in acetonitrile has a lifetime of about 800 ps, and reacts with water with a rate constant of 1.9 × 10(8) L·mol(-1)·s(-1) at room temperature. These results indicate that a methoxycarbonyl group at either the para or ortho positions has little influence on the ISC rate, but that the presence of a 2-methoxy group dramatically accelerates the ISC rate relative to the unsubstituted phenylnitrene. An ortho-methoxy group highly stabilizes the corresponding nitrenium ion and favors its formation in aqueous solvents. This substituent has little influence on the ring-expansion rate. These results are consistent with theoretical calculations for the various intermediates and their transition states. Cyclization from the nitrene to the azirine intermediate is favored to proceed toward the electron-deficient ester group; however, the higher energy barrier is the ring-opening process, that is, azirine to ketenimine formation, rendering the formation of the ester-ketenimine (4d') to be less favorable than the isomeric MeO-ketenimine (4d).

Azide and acetate complexes plus two iron-depleted crystal structures of the di-iron enzyme delta9 stearoyl-acyl carrier protein desaturase. Implications for oxygen activation and catalytic intermediates.

PubMed

Moche, Martin; Shanklin, John; Ghoshal, Alokesh; Lindqvist, Ylva

2003-07-04

Delta9 stearoyl-acyl carrier protein (ACP) desaturase is a mu-oxo-bridged di-iron enzyme, which belongs to the structural class I of large helix bundle proteins and that catalyzes the NADPH and O2-dependent formation of a cis-double bond in stearoyl-ACP. The crystal structures of complexes with azide and acetate, respectively, as well as the apoand single-iron forms of Delta9 stearoyl-ACP desaturase from Ricinus communis have been determined. In the azide complex, the ligand forms a mu-1,3-bridge between the two iron ions in the active site, replacing a loosely bound water molecule. The structure of the acetate complex is similar, with acetate bridging the di-iron center in the same orientation with respect to the di-iron center. However, in this complex, the iron ligand Glu196 has changed its coordination mode from bidentate to monodentate, the first crystallographic observation of a carboxylate shift in Delta9 stearoyl-ACP desaturase. The two complexes are proposed to mimic a mu-1,2 peroxo intermediate present during catalytic turnover. There are striking structural similarities between the di-iron center in the Delta9 stearoyl-ACP desaturase-azide complex and in the reduced rubrerythrin-azide complex. This suggests that Delta9 stearoyl-ACP desaturase might catalyze the formation of water from exogenous hydrogen peroxide at a low rate. From the similarity in iron center structure, we propose that the mu-oxo-bridge in oxidized desaturase is bound to the di-iron center as in rubrerythrin and not as reported for the R2 subunit of ribonucleotide reductase and the hydroxylase subunit of methane monooxygenase. The crystal structure of the one-iron depleted desaturase species demonstrates that the affinities for the two iron ions comprising the di-iron center are not equivalent, Fe1 being the higher affinity site and Fe2 being the lower affinity site.

Comparison of performance of the novel chromogenic spectra VRE agar to that of bile esculin azide and Campylobacter agars for detection of vancomycin-resistant enterococci in fecal samples.

PubMed

Jenkins, S G; Raskoshina, L; Schuetz, A N

2011-11-01

A total of 142 stool specimens were evaluated for vancomycin-resistant enterococcus (VRE). Twenty-four-hour sensitivities and specificities, respectively, were 98% and 95% for Spectra VRE chromogenic agar (Remel, Lenexa, KS), 86% and 92% for bile esculin azide with vancomycin (BEAV; Remel), and 96.5% and 92% for Campylobacter agar (CAMPY; Remel). Spectra VRE and CAMPY are significantly more sensitive at 24 h than BEAV.

Solvent effect on copper-catalyzed azide-alkyne cycloaddition (CuAAC): synthesis of novel triazolyl substituted quinolines as potential anticancer agents.

PubMed

Ellanki, Amarender Reddy; Islam, Aminul; Rama, Veera Swamy; Pulipati, Ranga Prasad; Rambabu, D; Krishna, G Rama; Reddy, C Malla; Mukkanti, K; Vanaja, G R; Kalle, Arunasree M; Kumar, K Shiva; Pal, Manojit

2012-05-15

A regioselective route to novel mono triazolyl substituted quinolines has been developed via copper-catalyzed azide-alkyne cycloaddition (CuAAC) of 2,4-diazidoquinoline with terminal alkynes in DMF. The reaction provided bis triazolyl substituted quinolines when performed in water in the presence of Et(3)N. A number of the compounds synthesized showed promising anti-proliferative properties when tested in vitro especially against breast cancer cells. Copyright © 2012 Elsevier Ltd. All rights reserved.

Development Program of Dual Mode Impact Delay Module for Artillery Fuzes.

DTIC Science & Technology

1979-12-31

analysis phase to demonstrate design confidence and reliability of performance in the artillery firing environment. See Figure I for drawing of the latest...Device P/N KF88590 as proposed by us. This analysis will be based on results of penalty test« in which the test variables will include loading and...istently and unmistakably Dextrinated lead azide was, tent surrogate. On the basis of stab s Id be predicted that any system whi r mated lead azide

Thermal Dissociation of Halogen Azides

DTIC Science & Technology

1994-09-01

Proc. Int. Conf. L.asers 1986. (38) Radimacher, P.; Bittner, A. J.; Schatnc. G.; Wilner, H . Chem. Ber. (43) Hcidner. R. F.; Helvajian . H .; Hollaway. J...Winker, DJ. Bernard and T.A. Seder, H -gh Power Gas Lasers, Proceedings of the SPIE, I= (1990) 543. 6. R.F. Heidner, H . Helvajian , J.S. Holloway and J.B...34Production of NF(a’A) by Dissociation of Fluorine Azide," Journal of Physical Chemistry, vol. 93, pp. 4790-4796, 1989. 3. R.H. Heidner, H . Helvajian , J.S

Thio-phene-2-carbonyl azide.

PubMed

Hsu, Gene C; Singer, Laci M; Cordes, David B; Findlater, Michael

2013-01-01

The title compound, C5H3N3OS, is almost planar (r.m.s. deviation for the ten non-H atoms = 0.018 Å) and forms an extended layer structure in the (100) plane, held together via hydrogen-bonding inter-actions between adjacent mol-ecules. Of particular note is the occurrence of RC-H⋯N(-)=N(+)=NR inter-actions between an aromatic C-H group and an azide moiety which, in conjunction with a complementary C-H⋯O=C inter-action, forms a nine-membered ring.

o-Fluorination of aromatic azides yields improved azido-based fluorescent probes for hydrogen sulfide: synthesis, spectra, and bioimaging.

PubMed

Wei, Chao; Wang, Runyu; Wei, Lv; Cheng, Longhuai; Li, Zhifei; Xi, Zhen; Yi, Long

2014-12-01

Hydrogen sulfide (H2S) is an endogenously produced gaseous signaling molecule with multiple biological functions. To visualize the endogenous in situ production of H2S in real time, new coumarin- and boron-dipyrromethene-based fluorescent turn-on probes were developed for fast sensing of H2S in aqueous buffer and in living cells. Introduction of a fluoro group in the ortho position of the aromatic azide can lead to a greater than twofold increase in the rate of reaction with H2S. On the basis of o-fluorinated aromatic azides, fluorescent probes with high sensitivity and selectivity toward H2S over other biologically relevant species were designed and synthesized. The probes can be used to in situ to visualize exogenous H2S and D-cysteine-dependent endogenously produced H2S in living cells, which makes them promising tools for potential applications in H2S biology. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

One-Step Electrochemical Preparation of Multilayer Graphene Functionalized with Nitrogen

NASA Astrophysics Data System (ADS)

Ustavytska, Olena; Kurys, Yaroslav; Koshechko, Vyacheslav; Pokhodenko, Vitaly

2017-03-01

A new environmentally friendly one-step method for producing multilayer (preferably 7-9 layers) nitrogen-doped graphene (N-MLG) with a slight amount of oxygen-containing defects was developed. The approach is based on the electrochemical exfoliation of graphite electrode in the presence of azide ions under the conditions of electrolysis with pulse changing of the electrode polarization potential. It was found that usage of azide anions lead not only to the exfoliation of graphite but also to the simultaneous functionalization of graphene sheets by nitrogen atoms (as a result of electrochemical decomposition of azide anions with ammonia evolution). Composition, morphology, structure, and electrochemical properties of N-MLG were characterized by C,H,N analysis, transmission electron microscopy, atomic force microscopy, FTIR, UV-Vis, and Raman spectroscopy, as well as cyclic voltammetry. The perspective of using N-MLG as oxygen reduction reaction electrocatalyst and for the electrochemical analysis of biomarkers (dopamine, ascorbic acid, and uric acid) in their mixtures was shown.

Efficient Homodifunctional Bimolecular Ring-Closure Method for Cyclic Polymers by Combining RAFT and Self-Accelerating Click Reaction.

PubMed

Qu, Lin; Sun, Peng; Wu, Ying; Zhang, Ke; Liu, Zhengping

2017-08-01

An efficient metal-free homodifunctional bimolecular ring-closure method is developed for the formation of cyclic polymers by combining reversible addition-fragmentation chain transfer (RAFT) polymerization and self-accelerating click reaction. In this approach, α,ω-homodifunctional linear polymers with azide terminals are prepared by RAFT polymerization and postmodification of polymer chain end groups. By virtue of sym-dibenzo-1,5-cyclooctadiene-3,7-diyne (DBA) as small linkers, well-defined cyclic polymers are then prepared using the self-accelerating double strain-promoted azide-alkyne click (DSPAAC) reaction to ring-close the azide end-functionalized homodifunctional linear polymer precursors. Due to the self-accelerating property of DSPAAC ring-closing reaction, this novel method eliminates the requirement of equimolar amounts of telechelic polymers and small linkers in traditional bimolecular ring-closure methods. It facilitates this method to efficiently and conveniently produce varied pure cyclic polymers by employing an excess molar amount of DBA small linkers. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Attractive Interactions between Heteroallenes and the Cucurbituril Portal.

PubMed

Reany, Ofer; Li, Amanda; Yefet, Maayan; Gilson, Michael K; Keinan, Ehud

2017-06-21

In this paper, we report on the noteworthy attractive interaction between organic azides and the portal carbonyls of cucurbiturils. Five homologous bis-α,ω-azidoethylammonium alkanes were prepared, where the number of methylene groups between the ammonium groups ranges from 4 to 8. Their interactions with cucurbit[6]uril were studied by NMR spectroscopy, IR spectroscopy, X-ray crystallography, and computational methods. Remarkably, while the distance between the portal plane and most atoms at the guest end groups increases progressively with the molecular size, the β-nitrogen atoms maintain a constant distance from the portal plane in all homologues, pointing at a strong attractive interaction between the azide group and the portal. Both crystallography and NMR support a specific electrostatic interaction between the carbonyl and the azide β-nitrogen, which stabilizes the canonical resonance form with positive charge on the β-nitrogen and negative charge on the γ-nitrogen. Quantum computational analyses strongly support electrostatics, in the form of orthogonal dipole-dipole interaction, as the main driver for this attraction. The alternative mechanism of n → π* orbital delocalization does not seem to play a significant role in this interaction. The computational studies also indicate that the interaction is not limited to azides, but generalizes to other isoelectronic heteroallene functions, such as isocyanate and isothiocyanate. This essentially unexploited attractive interaction could be more broadly utilized as a tool not only in relation to cucurbituril chemistry, but also for the design of novel supramolecular architectures.

Comparison of Performance of the Novel Chromogenic Spectra VRE Agar to That of Bile Esculin Azide and Campylobacter Agars for Detection of Vancomycin-Resistant Enterococci in Fecal Samples ▿

PubMed Central

Jenkins, S. G.; Raskoshina, L.; Schuetz, A. N.

2011-01-01

A total of 142 stool specimens were evaluated for vancomycin-resistant enterococcus (VRE). Twenty-four-hour sensitivities and specificities, respectively, were 98% and 95% for Spectra VRE chromogenic agar (Remel, Lenexa, KS), 86% and 92% for bile esculin azide with vancomycin (BEAV; Remel), and 96.5% and 92% for Campylobacter agar (CAMPY; Remel). Spectra VRE and CAMPY are significantly more sensitive at 24 h than BEAV. PMID:21880967

Esculin hydrolysis by Vibrio vulnificus.

PubMed

Tison, D L

1986-01-01

A clinical isolate of Vibrio vulnificus was found to hydrolyze esculin when tested on bile-esculin-azide agar during the initial characterization of the strain. Reports in the literature of esculin hydrolysis by V. vulnificus are conflicting. We tested herein 52 strains of V. vulnificus from clinical and environmental sources for the ability to hydrolyze esculin. Seventy-eight percent of the strains hydrolyzed esculin on bile-esculin-azide agar, whereas all strains of V. vulnificus tested were positive for esculin hydrolysis in a noninhibitory medium, whereas some strains failed to hydrolyze esculin on media containing inhibitory compounds.

Cationic 1,2,3-Triazolium Alkynes: Components To Enhance 1,4-Regioselective Azide-Alkyne Cycloaddition Reactions.

PubMed

Monasterio, Zaira; Sagartzazu-Aizpurua, Maialen; Miranda, José I; Reyes, Yuri; Aizpurua, Jesus M

2016-02-19

4-Alkynyl-1,2,3-triazolium cations undergo thermal [3 + 2] cycloaddition reactions with azides roughly 50- to 100-fold faster than comparable noncharged alkynes. Further, the reaction is highly 1,4-regioselective (dr up to 99:1) owing to the selective stabilization of 1,4-TS transition states via conjugative π-acceptor assistance of the alkyne triazolium ring. The novel cationic triazolium alkynes also accelerate the CuAAC reaction to provide bis(1,2,3-triazoles) in an "ultrafast" way (<5 min).

Non-Catalyzed Click Reactions of ADIBO Derivatives with 5-Methyluridine Azides and Conformational Study of the Resulting Triazoles

PubMed Central

Smyslova, Petra; Popa, Igor; Lyčka, Antonín; Tejral, Gracian; Hlavac, Jan

2015-01-01

Copper-free click reactions between a dibenzoazocine derivative and azides derived from 5-methyluridine were investigated. The non-catalyzed reaction yielded both regioisomers in an approximately equivalent ratio. The NMR spectra of each regioisomer revealed conformational isomery. The ratio of isomers was dependent on the type of regioisomer and the type of solvent. The synthesis of various analogs, a detailed NMR study and computational modeling provided evidence that the isomery was dependent on the interaction of the azocine and pyrimidine parts. PMID:26673606

Processing of energy materials in electromagnetic field

NASA Astrophysics Data System (ADS)

Rodzevich, A. P.; Kuzmina, L. V.; Gazenaur, E. G.; Krasheninin, V. I.

2015-09-01

This paper presents the research results of complex impact of mechanical stress and electromagnetic field on the defect structure of energy materials. As the object of research quite a typical energy material - silver azide was chosen, being a model in chemistry of solids. According to the experiments co-effect of magnetic field and mechanical stress in silver azide crystals furthers multiplication, stopper breakaway, shift of dislocations, and generation of superlattice dislocations - micro-cracks. A method of mechanical and electric strengthening has been developed and involves changing the density of dislocations in whiskers.

AuBr3-catalyzed azidation of per-O-acetylated and per-O-benzoylated sugars.

PubMed

Rajput, Jayashree; Hotha, Srinivas; Vangala, Madhuri

2018-01-01

Herein we report, for the first time, the successful anomeric azidation of per- O -acetylated and per- O -benzoylated sugars by catalytic amounts of oxophilic AuBr 3 in good to excellent yields. The method is applicable to a wide range of easily accessible per- O -acetylated and per- O -benzoylated sugars. While reaction with per- O -acetylated and per- O -benzoylated monosaccharides was complete within 1-3 h at room temperature, the per- O -benzoylated disaccharides needed 2-3 h of heating at 55 °C.

The Electrode as Organolithium Reagent: Catalyst-Free Covalent Attachment of Electrochemically Active Species to an Azide-Terminated Glassy Carbon Electrode Surface

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

Das, Atanu K.; Engelhard, Mark H.; Liu, Fei

2013-12-02

Glassy carbon electrodes have been activated for modification with azide groups and subsequent coupling with ferrocenyl reagents by a catalyst-free route using lithium acetylide-ethylenediamine complex, and also by the more common Cu(I)-catalyzed alkyne-azide coupling (CuAAC) route, both affording high surface coverages. Electrodes were preconditioned at ambient temperature under nitrogen, and ferrocenyl surface coverages obtained by CuAAC were comparable to those reported with preconditioning at 1000 °C under hydrogen/nitrogen. The reaction of lithium acetylide-ethylenediamine with the azide-terminated electrode affords a 1,2,3-triazolyllithium-terminated surface that is active toward covalent C-C coupling reactions including displacement at an aliphatic halide and nucleophilic addition at anmore » aldehyde. For example, surface ferrocenyl groups were introduced by reaction with (6-iodohexyl)ferrocene; the voltammetry shows narrow, symmetric peaks indicating uniform attachment. Coverages are competitive with those obtained by the CuAAC route. X-ray photoelectron spectroscopic data, presented for each synthetic step, are consistent with the proposed reactions. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy. A portion of the research was performed using EMSL, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory.« less

INFRARED AND ULTRAVIOLET SPECTRA OF METHANE DILUTED IN SOLID NITROGEN AND IRRADIATED WITH ELECTRONS DURING DEPOSITION AT VARIOUS TEMPERATURES

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

Chin, Chih-Hao; Chen, Sian-Cong; Liu, Meng-Chen

We recorded the infrared and ultraviolet absorption spectra of CH{sub 4}:N{sub 2} matrix samples that underwent electron bombardment during deposition in the temperature range of 10–44 K. In contrast to a previous experiment on the IR spectroscopy of electron-bombarded icy samples, methyl and azide radicals became the main products upon electron bombardment during deposition; furthermore, reduced production of nitrile species was observed for deposition at 10 and 20 K. On the other hand, for deposition above 33 K, the observed bands of the radical species (such as methyl and azide) decreased, and bands of large nitriles appeared. This observation maymore » suggest that radical species easily diffuse and recombine to form more complex molecules in solid nitrogen at higher temperatures. Further measurements of similar samples at 10–33 K in the UV region revealed the intense band of azide radicals at 272.5 nm and weak, broad, overlapping features of methyl and azide radicals in the 225–197 nm region. For deposition at 44 K, only a broad feature centered at 219.4 nm was observed, and the possible carriers of nitrile species were proposed based on the corresponding IR spectrum and theoretical predictions of excitation energy. This band is similar to the observed absorption feature of Pluto’s surface recorded by the Hubble telescope in terms of both band position and bandwidth. Our findings therefore further support the suggestion that complex nitrile species may exist on the surface of Pluto.« less

Hierachical assembly of collagen mimetic peptides into biofunctional materials

NASA Astrophysics Data System (ADS)

Gleaton, Jeremy W.

Collagen is a remarkably strong and prevalent protein distributed throughout nature and as such, collagen is an ideal material for a variety of medical applications. Research efforts for the development of synthetic collagen biomaterials is an area of rapid growth. Here we present two methods for the assembly of collagen mimetic peptides (CMPs). The initial approach prompts assembly of CMPs which contain modifications for metal ion-triggered assembly. Hierarchical assembly into triple helices, followed by formation of disks via hydrophobic interactions has been demonstrated. Metal-ion mediated assembly of these disks, using iron (II)-bipyrdine interactions, has been shown to form micron-sized cages. The nature of the final structures that form depends on the number of bipyridine moieties incorporated into the CMP. These hollow spheres encapsulate a range of molecular weight fluorescently labeled dextrans. Furthermore, they demonstrate a time dependent release of contents under a variety of thermal conditions. The second approach assembles CMPs via the copper-catalyzed alkyne-azide cycloaddition (CuAAC) and the strain-promoted alkyne-azide cycloaddition (SPAAC) reactions. CMPs that incorporate the unnatural amino acids L-propargylglycine and L-azidolysine form triple helices and demonstrate higher order assembly when reacted via CuAAC. Reaction of the alkyne/azide modified CMPs under CuAAC conditions was found to produce an crosslinked 3-dimensional network. Moreover, we demonstrate that polymers, such as, PEG, can be reacted with alkyne and azide CMP triple helices via CuAAC and SPAAC. This designed covalent CMP chemistry allows for high flexibility in integrating various chemical cues, such as cell growth and differentiation within the higher order structures.

In vivo click reaction between Tc-99m-labeled azadibenzocyclooctyne-MAMA and 2-nitroimidazole-azide for tumor hypoxia targeting.

PubMed

Sun, Wenjing; Chu, Taiwei

2015-10-15

The bioactivity of nitroimidazole in Tc-99m-labeled 2-nitroimidazole, a traditional solid tumor hypoxia-imaging agent for single photon emission computed tomography (SPECT), is reduced by the presence of large ligand and metallic radionuclide, exhibiting lower tumor-to-nontumor ratios. In an effort to solve this general problem, a pretargeting strategy based on click chemistry (strain-promoted cyclooctyne-azide cycloaddition) was applied. The functional click synthons were synthesized as pretargeting components: an azide group linked to 2-nitroimidazole (2NIM-Az) serves for tumor hypoxia-targeting and azadibenzocyclooctyne conjugated with monoamine monoamide dithiol ligand (AM) functions as radiolabeling and binding group to azides in vivo. 2NIM-triazole-MAMA was obtained from in vitro click reaction with a reaction rate constant of 0.98M(-1)s(-1). AM and 2NIM-triazole-MAMA were radiolabeled with Tc-99m. The hypoxia-pretargeting biodistribution was studied in Kunming mice bearing S180 tumor; (99m)Tc-AM and (99m)Tc-triazole-2NIM were used as blank control and conventional control. Compared to the control groups, the pretargeting experiment exhibits the best radio-uptake and retention in tumor, with higher tumor-to-muscle and tumor-to-blood ratios (up to 8.55 and 1.44 at 8h post-(99m)Tc-complex-injection, respectively). To some extent, the pretargeting strategy protects the bioactivity of nitroimidazole and therefore provides an innovative approach for the development of tumor hypoxia-SPECT imaging agents. Copyright © 2015 Elsevier Ltd. All rights reserved.

The concern of emergence of multi-station reaction pathways that might make stepwise the mechanism of the 1,3-dipolar cycloadditions of azides and alkynes

NASA Astrophysics Data System (ADS)

Mohtat, Bita; Siadati, Seyyed Amir; Khalilzadeh, Mohammad Ali; Zareyee, Daryoush

2018-03-01

After hot debates on the concerted or stepwise nature of the mechanism of the catalyst-free 1,3-dipolar cycloadditions (DC)s, nowadays, it is being believed that for the reaction of each dipole and dipolarophile, there is a possibility that the reaction mechanism becomes stepwise, intermediates emerge, and the reaction becomes non-stereospecific. Yield of even minimal amounts of unwanted side products or stereoisomers as impurities could bring many troubles like difficult purification steps. In this project, we have made attempts to study all probable reaction channels of the azide cycloadditions with two functionalized alkynes, in order to answer this question: "is there any possibility that intermediates evolve in the catalyst-free click 1,3-DC reaction of azide-alkynes?". During the calculations, several multi-station reaction pathways supporting the stepwise and concerted mechanisms were detected. Also, the born-oppenheimer molecular dynamic (BOMD) simulation was used to find trustable geometries which could be emerged during the reaction coordinate.

Rapid discovery and structure-activity profiling of novel inhibitors of human immunodeficiency virus type 1 protease enabled by the copper(I)-catalyzed synthesis of 1,2,3-triazoles and their further functionalization.

PubMed

Whiting, Matthew; Tripp, Jonathan C; Lin, Ying-Chuan; Lindstrom, William; Olson, Arthur J; Elder, John H; Sharpless, K Barry; Fokin, Valery V

2006-12-28

Building from the results of a computational screen of a range of triazole-containing compounds for binding efficiency to human immunodeficiency virus type 1 protease (HIV-1-Pr), a novel series of potent inhibitors has been developed. The copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC), which provides ready access to 1,4-disubstituted-1,2,3-triazoles, was used to unite a focused library of azide-containing fragments with a diverse array of functionalized alkyne-containing building blocks. In combination with direct screening of the crude reaction products, this method led to the rapid identification of a lead structure and readily enabled optimization of both azide and alkyne fragments. Replacement of the triazole with a range of alternative linkers led to greatly reduced protease inhibition; however, further functionalization of the triazoles at the 5-position gave a series of compounds with increased activity, exhibiting Ki values as low as 8 nM.

Azide/alkyne-"click"-reactions of encapsulated reagents: toward self-healing materials.

PubMed

Gragert, Maria; Schunack, Marlen; Binder, Wolfgang H

2011-03-02

The successful encapsulation of reactive components for the azide/alkyne-"click"-reaction is reported featuring for the first time the use of a liquid polymer as reactive component. A liquid, azido-telechelic three-arm star poly(isobutylene) (M(n) = 3900 g · mol⁻¹) as well as trivalent alkynes were encapsulated into micron-sized capsules and embedded into a polymer-matrix (high-molecular weight poly(isobutylene), M(n) = 250,000 g · mol⁻¹). Using (Cu(I)Br(PPh₃)₃) as catalyst for the azide/alkyne-"click"-reaction, crosslinking of the two components at 40 °C is observed within 380 min and as fast as 10 min at 80 °C. Significant recovery of the tensile storage modulus was observed in a material containing 10 wt.-% and accordingly 5 wt.-% capsules including the reactive components within 5 d at room temperature, thus proving a new concept for materials with self-healing properties. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Azidoethoxyphenylalanine as a Vibrational Reporter and Click Chemistry Partner in Proteins

PubMed Central

Tookmanian, Elise M.; Phillips-Piro, Christine M.; Fenlon, Edward E.; Brewer, Scott H.

2016-01-01

An unnatural amino acid, 4-(2-azidoethoxy)-l-phenylalanine (AePhe, 1), was designed and synthesized in three steps from known compounds in 54% overall yield. The sensitivity of the IR absorption of the azide of AePhe was established by comparison of the frequency of the asymmetric stretch vibration in water and dimethyl sulfoxide. AePhe was successfully incorporated into superfolder green fluorescent protein (sfGFP) at the 133 and 149 sites using the amber codon suppression method. The IR spectra of these sfGFP constructs indicated that the azide group at the 149 site was not fully solvated despite the location in sfGFP and the three-atom linker between the azido group and the aromatic ring of AePhe. An X-ray crystal structure of sfGFP-149-AePhe was solved at 1.45 Å resolution and provides an explanation for the IR data as the flexible linker adopts a conformation which partially buries the azide on the protein surface. Both sfGFP-AePhe constructs efficiently undergo a bioorthogonal strain-promoted click cycloaddition with a dibenzocyclooctyne derivative. PMID:26608683

Ratiometric Fluorescence Azide-Alkyne Cycloaddition for Live Mammalian Cell Imaging.

PubMed

Fu, Hongxia; Li, Yanru; Sun, Lingbo; He, Pan; Duan, Xinrui

2015-11-17

Click chemistry with metabolic labeling has been widely used for selectively imaging biomacromolecules in cells. The first example of azide-alkyne cycloaddition for ratiometric fluorescent imaging of live cells is reported. The precursor of the azido fluorophore (cresyl violet) has a fluorescence emission peak at 620 nm. The electron-rich nitrogen of the azido group blue-shifts the emission peak to 566 nm. When the click reaction occurs, an emission peak appears at 620 nm due to the lower electronic density of the newly formed triazole ring, which allows us to ratiometrically record fluorescence signals. This emission shift was applied to ratiometric imaging of propargylcholine- and dibenzocyclooctyne-labeled human breast cancer cells MCF-7 under laser confocal microscopy. Two typical triazole compounds were isolated for photophysical parameter measurements. The emission spectra presented a fluorescence emission peak around 620 nm for both click products. The results further confirmed the emission wavelength change was the result of azide-alkyne cycloaddition reaction. Since nearly all biomolecules can be metabolically labeled by reported alkyne-functionalized derivatives of native metabolites, our method can be readily applied to image these biomacromolecules.

Grafting polycaprolactone diol onto cellulose nanocrystals via click chemistry: Enhancing thermal stability and hydrophobic property.

PubMed

Zhou, Ling; He, Hui; Li, Mei-Chun; Huang, Siwei; Mei, Changtong; Wu, Qinglin

2018-06-01

Hydrophobic and thermally-stable cellulose nanocrystals (CNCs) were synthesized by polycarpolactone diol (PCL diol) grafting via click chemistry strategy. The synthesis was designed as a three-step procedure containing azide-modification of CNCs, alkyne-modification of PCL diol and sequent copper(I)-catalyzed azide-alkyne cycloaddition reaction. The structure of azide-modified CNCs and alkyne-modified PCL diol, the structure, hydrophobic ability and thermal stability of click products CNC-PCL were characterized. FTIR, XPS and H 1 NMR results indicated a successful grafting of the N 3 groups onto the CNCs, synthesis of PCL diol-CCH, and formation of the CNC-PCL material. CNC-PCL had enhanced dispersion in the non-polar solvent chloroform owing to the well-maintained microscale size and PCL-induced hydrophobic surface. The thermal stability of CNC-PCL was largely increased due to the grafting of thermally-stable PCL. This work demonstrates that click chemistry is an attractive modification strategy to graft CNCs with polyester chains for further potential application in polymer composites. Copyright © 2018 Elsevier Ltd. All rights reserved.

Synthesis and Biological Evaluation of Non-Hydrolizable 1,2,3-Triazole Linked Sialic Acid Derivatives as Neuraminidase Inhibitors

PubMed Central

Weïwer, Michel; Chen, Chi-Chang; Kemp, Melissa M.; Linhardt, Robert J.

2013-01-01

α-Sialic acid azide 1 has been used as a substrate for the efficient preparation of 1,2,3-triazole derivatives of sialic acid using the copper-catalyzed azide-alkyne Huisgen cycloaddition (“click chemistry”). Our approach is to generate non-natural N-glycosides of sialic acid that are resistant to neuraminidase catalyzed hydrolysis as opposed to the natural O-glycosides. These N-glycosides would act as neuraminidase inhibitors to prevent the release of new virions. As a preliminary study, a small library of 1,2,3-triazole-linked sialic acid derivatives has been synthesized in 71-89% yield. A disaccharide mimic of sialic acid has also been prepared using the α-sialic acid azide 1 and a C-8 propargyl sialic acid acceptor in 68% yield. A model sialic acid coated dendrimer was also synthesized from a per-propargylated pentaerythritol acceptor. These novel sialic acid derivatives were then evaluated as potential neuraminidase inhibitors using a 96-well plate fluorescence assay; micromolar IC50 values were observed, comparable to the known sialidase inhibitor Neu5Ac2en. PMID:24223493

Copper-free click chemistry in living animals

PubMed Central

Chang, Pamela V.; Prescher, Jennifer A.; Sletten, Ellen M.; Baskin, Jeremy M.; Miller, Isaac A.; Agard, Nicholas J.; Lo, Anderson; Bertozzi, Carolyn R.

2010-01-01

Chemical reactions that enable selective biomolecule labeling in living organisms offer a means to probe biological processes in vivo. Very few reactions possess the requisite bioorthogonality, and, among these, only the Staudinger ligation between azides and triarylphosphines has been employed for direct covalent modification of biomolecules with probes in the mouse, an important model organism for studies of human disease. Here we explore an alternative bioorthogonal reaction, the 1,3-dipolar cycloaddition of azides and cyclooctynes, also known as “Cu-free click chemistry,” for labeling biomolecules in live mice. Mice were administered peracetylated N-azidoacetylmannosamine (Ac4ManNAz) to metabolically label cell-surface sialic acids with azides. After subsequent injection with cyclooctyne reagents, glycoconjugate labeling was observed on isolated splenocytes and in a variety of tissues including the intestines, heart, and liver, with no apparent toxicity. The cyclooctynes tested displayed various labeling efficiencies that likely reflect the combined influence of intrinsic reactivity and bioavailability. These studies establish Cu-free click chemistry as a bioorthogonal reaction that can be executed in the physiologically relevant context of a mouse. PMID:20080615

Multiple Click-Selective tRNA Synthetases Expand Mammalian Cell-Specific Proteomics.

PubMed

Yang, Andrew C; du Bois, Haley; Olsson, Niclas; Gate, David; Lehallier, Benoit; Berdnik, Daniela; Brewer, Kyle D; Bertozzi, Carolyn R; Elias, Joshua E; Wyss-Coray, Tony

2018-06-13

Bioorthogonal tools enable cell-type-specific proteomics, a prerequisite to understanding biological processes in multicellular organisms. Here we report two engineered aminoacyl-tRNA synthetases for mammalian bioorthogonal labeling: a tyrosyl ( ScTyr Y43G ) and a phenylalanyl ( MmPhe T413G ) tRNA synthetase that incorporate azide-bearing noncanonical amino acids specifically into the nascent proteomes of host cells. Azide-labeled proteins are chemoselectively tagged via azide-alkyne cycloadditions with fluorophores for imaging or affinity resins for mass spectrometric characterization. Both mutant synthetases label human, hamster, and mouse cell line proteins and selectively activate their azido-bearing amino acids over 10-fold above the canonical. ScTyr Y43G and MmPhe T413G label overlapping but distinct proteomes in human cell lines, with broader proteome coverage upon their coexpression. In mice, ScTyr Y43G and MmPhe T413G label the melanoma tumor proteome and plasma secretome. This work furnishes new tools for mammalian residue-specific bioorthogonal chemistry, and enables more robust and comprehensive cell-type-specific proteomics in live mammals.

Azidoimidazolinium Salts: Safe and Efficient Diazo-transfer Reagents and Unique Azido-donors.

PubMed

Kitamura, Mitsuru

2017-07-01

2-Azido-1,3-dimethylimidazolinium chloride (ADMC) and its corresponding hexafluorophosphate (ADMP) were found to be efficient diazo-transfer reagents to various organic compounds. ADMC was prepared by the reaction of 2-chloro-1,3-dimethylimidazolinium chloride (DMC) and sodium azide. ADMP was isolated as a crystal having good thermal stability and low explosibility. ADMC and ADMP reacted with 1,3-dicarbonyl compounds under mild basic conditions to give 2-diazo-1,3-dicarbonyl compounds in high yields, which were easily isolated in virtue of the high water solubility of the by-products. ADMP showed high diazo-transfer ability to primary amines even in the absence of metal salt such as Cu(II). Using this diazotization approach, various alkyl/aryl azides were directly obtained from their corresponding primary amines in high yields. Furthermore, naphthols reacted with ADMC to give the corresponding diazonaphthoquinones in good to high yields. In addition, 2-azido-1,3-dimethylimidazolinium salts were employed as azide-transfer and migratory amidation reagents. © 2017 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Exploration for the stabilities of CHN7 and CN7-: A theoretical study on the formation and dissociation mechanisms

NASA Astrophysics Data System (ADS)

Yu, Tao; Liu, Ying-Zhe; Lai, Wei-Peng

2018-03-01

CHN7 and CN7- are meta-stable species. In order to study on the relationship between thermodynamic and kinetic stabilities, the potential energy surfaces of CHN7 and CN7- were scanned at the B3LYP/aug-cc-pVDZ level. After the analysis of potential energy surfaces, the optimum pathways were got to conclude the dissociation and formation mechanisms. The dissociation barriers of 5-azido-1H-tetrazole and 5-azido-2H-tetrazole are about 150 kJ mol-1. They are sufficient to keep the two azidotetrazoles stable. The reaction between cyanogen azide and azide anion cannot produce azidotetrazolate anion, but produce the linear CN7- with a lower barrier. The reaction between cyanogen azide and hydrazoic acid preferentially produce 5-azido-1H-tetrazole. The decyclization barriers of 1H-tetrazolo[1,5-d]tetrazole and tetrazolo[1,5-d]tetrazolate anion are 44.7 and 81.6 kJ mol-1, respectively. The deprotoned anion is more available than the neutral compound. Heptaazacubane and heptaazacubanide anion with cubic geometries are highly unstable.

Methods for the selective detection of alkyne-presenting molecules and related compositions and systems

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

Valdez, Carlos A.; Vu, Alexander K.

Provided herein are methods for selectively detecting an alkyne-presenting molecule in a sample and related detection reagents, compositions, methods and systems. The methods include contacting a detection reagent with the sample for a time and under a condition to allow binding of the detection reagent to the one or more alkyne-presenting molecules possibly present in the matrix to the detection reagent. The detection reagent includes an organic label moiety presenting an azide group. The binding of the azide group to the alkyne-presenting molecules results in emission of a signal from the organic label moiety.

Design, synthesis and fluorescence property evaluation of blue emitting triazole-linked chromene peptidomimetics.

PubMed

Mohan, T Jency; Bahulayan, D

2017-08-01

A highly efficient "Click with MCR" strategy for the three-step synthesis of two types of blue emitting chromene peptidomimetics is described. The peptidomimetics were synthesized via a copper-catalyzed [3[Formula: see text]2] azide-alkyne cycloaddition between chromene alkynes obtained from a three-component reaction and the peptide azides obtained from Ugi or Mannich type multicomponent reactions. The photophysical properties of the peptidomimetics are comparable with commercial fluorophores. Computational studies using drug property descriptors support the possibility of using these molecules for modulating difficult target classes having large, flat, and groove-shaped binding sites.

Dense Energetic Compounds of C, H, N, and O Atoms. III. 5-(4-Nitro-(1,2, 5)oxadiazolyl)-5H-(1,2,3)triazolo(4,5-c)(1,2,5)oxadiazole

DTIC Science & Technology

1993-07-21

1,2,5)oxadiazolyl]-5H- [1,2,3]triazolo[4,5-c] [1,2,5]oxadiazole 1. The azide 5 was con- verted to a phosphinimine 9 in a reaction with triphenylphosphine ...and led instead to an intractable mixture in which neither a primary amine nor triphenylphosphine oxide were de- tected. ACKNOWLEDGEMENTS Financial...coi-responding amine 13 was obtained from the azide 5 by reduction with stannous chloride and was oxidized by ammonium persulfate to 5-[4- nitro

Carbohydrate conjugation through microwave-assisted functionalization of single-walled carbon nanotubes using perfluorophenyl azides.

PubMed

Kong, Na; Shimpi, Manishkumar R; Ramström, Olof; Yan, Mingdi

2015-03-20

Carbohydrate-functionalized single-walled carbon nanotubes (SWNTs) were synthesized using microwave-assisted reaction of perfluorophenyl azide with the nanotubes. The results showed that microwave radiation provides a rapid and effective means to covalently attach carbohydrates to SWNTs, producing carbohydrate-SWNT conjugates for biorecognition. The carbohydrate-functionalized SWNTs were furthermore shown to interact specifically with cognate carbohydrate-specific proteins (lectins), resulting in predicted recognition patterns. The carbohydrate-presenting SWNTs constitute a new platform for sensitive protein- or cell recognition, which pave the way for glycoconjugated carbon nanomaterials in biorecognition applications. Copyright © 2014 Elsevier Ltd. All rights reserved.

Synthesis and Thermal Analysis of Nano-Aluminum/Fluorinated Polyurethane Elastomeric Composites for Structural Energetics.

PubMed

Zhang, Xianyu; Kim, Jin Seuk; Kwon, Younghwan

2017-04-01

Here we describe the synthesis of polyurethane (PU)-based energetic nanocomposites loaded with nano-aluminum (n-Al) particles. The energetic nanocomposite was prepared by polyurethane reaction of poly(glycidyl azide-co-tetramethylene glycol) (PGT) prepolymers and IPDI/N-100 isocyanates with simultaneous catalyst-free azide-alkyne Click reaction in the presence of n-Al. Initial study carried out with various n-Al/fluorinated PGT blends and demonstrated the potential of fluorinated PGT prepolymer for an energetic PU matrix. Thermal analysis of n-Al/fluorinated PGT-based PU energetic nanocomposite was performed using DSC and TGA.

Examination of the Mechanism of Rh2(II)-Catalyzed Carbazole Formation Using Intramolecular Competition Experiments

PubMed Central

Stokes, Benjamin J.; Richert, Kathleen J.; Driver, Tom G.

2009-01-01

The use of a rhodium(II) carboxylate catalyst enables the mild and stereoselective formation of carbazoles from biaryl azides. Intramolecular competition experiments of triaryl azides suggested the source of the selectivity. A primary intramolecular kinetic isotope effect was not observed and correlation of the product ratios with Hammett σ+-values produced a plot with two intersecting lines with opposite ρ-values. These data suggest that electronic donation by the biaryl π-system accelerates the formation of rhodium nitrenoid and that C–N bond formation occurs through a 4π-electron-5-atom electrocyclization. PMID:19663433

Selective posttranslational modification of phage-displayed polypeptides

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

Tsao, Meng-Lin; Tian, Feng; Schultz, Peter

The invention relates to posttranslational modification of phage-displayed polypeptides. These displayed polypeptides comprise at least one unnatural amino acid, e.g., an aryl-azide amino acid such as p-azido-L-phenylalanine, or an alkynyl-amino acid such as para-propargyloxyphenylalanine, which are incorporated into the phage-displayed fusion polypeptide at a selected position by using an in vivo orthogonal translation system comprising a suitable orthogonal aminoacyl-tRNA synthetase and a suitable orthogonal tRNA species. These unnatural amino acids advantageously provide targets for posttranslational modifications such as azide-alkyne [3+2] cycloaddition reactions and Staudinger modifications.

Selective posttranslational modification of phage-displayed polypeptides

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

Tsao, Meng-Lin; Tian, Feng; Schultz, Peter

The invention relates to posttranslational modification of phage-displayed polypeptides. These displayed polypeptides comprise at least one unnatural amino acid, e.g., an aryl-azide amino acid such as p-azido-L-phenylalanine, or an alkynyl-amino acid such as para-propargyloxyphenylalanine, which are incorporated into the phage-displayed fusion polypeptide at a selected position by using an in vivo orthogonal translation system comprising a suitable orthogonal aminoacyl-tRNA synthetase and a suitable orthogonal tRNA species. These unnatural amino acids advantageously provide targets for posttranslational modifications such as azide-alkyne [3+2]cycloaddition reactions and Staudinger modifications.

Nitrous oxide-forming codenitrification catalyzed by cytochrome P450nor.

PubMed

Su, Fei; Takaya, Naoki; Shoun, Hirofumi

2004-02-01

Intact cells of the denitrifying fungus Fusarium oxysporum were previously shown to catalyze codenitrification to form a hybrid nitrous oxide (N2O) species from nitrite and other nitrogen compounds such as azide and ammonia. Here we show that cytochrome P450nor can catalyze the codenitrification reaction to form N2O from nitric oxide (NO) but not nitrite, and azide or ammonia. The results show that the direct substrate of the codenitrification by intact cells should not be nitrite but NO, which is formed from nitrite by the reaction of a dissimilatory nitrite reductase.

Creating biomimetic polymeric surfaces by photochemical attachment and patterning of dextran

PubMed Central

Ferrer, M. Carme Coll; Yang, Shu; Eckmann, David M.; Composto, Russell J.

2010-01-01

In this work, we report the preparation of photoactive dextran and demonstrate its utility by photochemically attaching it onto various polymeric substrates. The attachment of homogeneous and patterned dextran films was performed on polyurethane and polystyrene, with detailed analysis of surface morphology, swelling behavior, and the protein resistance of these substrates. The described photoactive dextran and attachment procedure is applicable to a wide variety of substrates while accommodating surfaces with complex surface and geometries. Dextran with azide content between 22 to 0.3 wt% was produced by esterification with p-azidobenzoic acid. Dextran (1.2 wt% azide) was photografted onto plasma oxidized polyurethane and polystyrene and displayed thicknesses of 5 ± 3 nm and 7 ± 3 nm, respectively. The patterned dextran on oxidized polyurethane was patchy with a nominal height difference between dextranized and non-dextranized regions. The azidated dextran on oxidized polystyrene exhibited a distinct step in height. In the presence of PBS buffer, the dextranized regions became smoother and more uniform without affecting the height difference at the oxidized polyurethane boundary. However, the dextranized regions on oxidized polyurethane were observed to swell by a factor of 3 relative to the dried thickness. These dissimilarities were attributed to hydrogen bonding between the dextran and oxidized polyurethane and were confirmed by the photoimmobiliization in the presence of LiCl. The resulting surface was the smoothest of all the azidated dextran samples (RRMS = 1 ± 0.3 nm) and swelled up to 2 times its dried thickness in PBS buffer. The antifouling properties of dextran functionalized surfaces were verified by the selective adsorption of FITC-labeled human albumin only on the non-dextranized regions of the patterned polyurethane and polystyrene substrates. PMID:20712352

Catalytic "active-metal" template synthesis of [2]rotaxanes, [3]rotaxanes, and molecular shuttles, and some observations on the mechanism of the cu(i)-catalyzed azide-alkyne 1,3-cycloaddition.

PubMed

Aucagne, Vincent; Berna, José; Crowley, James D; Goldup, Stephen M; Hänni, Kevin D; Leigh, David A; Lusby, Paul J; Ronaldson, Vicki E; Slawin, Alexandra M Z; Viterisi, Aurélien; Walker, D Barney

2007-10-03

A synthetic approach to rotaxane architectures is described in which metal atoms catalyze covalent bond formation while simultaneously acting as the template for the assembly of the mechanically interlocked structure. This "active-metal" template strategy is exemplified using the Huisgen-Meldal-Fokin Cu(I)-catalyzed 1,3-cycloaddition of azides with terminal alkynes (the CuAAC "click" reaction). Coordination of Cu(I) to an endotopic pyridine-containing macrocycle allows the alkyne and azide to bind to metal atoms in such a way that the metal-mediated bond-forming reaction takes place through the cavity of the macrocycle--or macrocycles--forming a rotaxane. A variety of mono- and bidentate macrocyclic ligands are demonstrated to form [2]rotaxanes in this way, and by adding pyridine, the metal can turn over during the reaction, giving a catalytic active-metal template assembly process. Both the stoichiometric and catalytic versions of the reaction were also used to synthesize more complex two-station molecular shuttles. The dynamics of the translocation of the macrocycle by ligand exchange in these two-station shuttles could be controlled by coordination to different metal ions (rapid shuttling is observed with Cu(I), slow shuttling with Pd(II)). Under active-metal template reaction conditions that feature a high macrocycle:copper ratio, [3]rotaxanes (two macrocycles on a thread containing a single triazole ring) are also produced during the reaction. The latter observation shows that under these conditions the mechanism of the Cu(I)-catalyzed terminal alkyne-azide cycloaddition involves a reactive intermediate that features at least two metal ions.

A chronic Alzheimer's model evoked by mitochondrial poison sodium azide for pharmacological investigations.

PubMed

Szabados, Tamás; Dul, Csaba; Majtényi, Katalin; Hargitai, Judit; Pénzes, Zoltán; Urbanics, Rudolf

2004-09-23

Alzheimer's disease (AD) is a neurodegenerative disorder and accounts for 50-70% of all dementia cases affecting more than 12 million people worldwide. The primary cause of the disease is presently unknown; however, much evidence suggests the involvement of mitochondrial damage. Selective reduction of complex IV activity is present in post-mortem AD brains. Inhibition of this complex could be evoked by chronic sodium azide (NaN(3)) administration in animals. Partial inhibition of the mitochondrial respiratory chain produces free radicals, diminishes aerobic energy metabolism and causes excitotoxic damage creating a deleterious spiral causing neurodegeneration, a pathological process considered to underlie AD. In the present study SPRD rats were treated by various doses of NaN(3) (24-51 mg/kg per day) for 31 days via subcutaneously implanted osmotic minipumps. We have found the proper dose and duration of NaN(3) treatment which was able to cause easily detectable and reproducible cognitive changes. Animals receiving Na-azide doses under 45 mg/kg daily did not show cognitive deficits, but minor histopathological changes were already present. Doses above 45 mg/kg per day proved to be toxic in 4-week-long application causing mortality. NaN(3) dose of 45 mg/kg per day caused cognitive deficit in Morris water maze and passive avoidance tests and a decrease of spontaneous exploratory activity in open field. Histopathological but not biochemical changes were present: dendritic thickening, nerve cell loss, corkscrew-like dendrites and pycnotic nerve cells. The cognitive, behavioural and histopathological features were reproducible. The chronic Na-azide-induced mitochondrial poisoning is suitable for producing AD-like symptoms in rats and testing neuroprotective drug candidates by preventive or curative applications.

Influence of different crosslinking treatments on the physical properties of collagen membranes.

PubMed

Charulatha, V; Rajaram, A

2003-02-01

The physical properties of collagen-based biomaterials are profoundly influenced by the method and extent of crosslinking. In this study, the influence of various crosslinking treatments on the physical properties of reconstituted collagen membranes was assessed. Five crosslinking agents viz., GTA, DMS, DTBP, a combination of DMS and GTA and acyl azide method were used to stabilize collagen matrices. Crosslinking density, swelling ratio, thermo-mechanical properties, stress-strain characteristics and resistance to collagenase digestion were determined to evaluate the physical properties of crosslinked matrices. GTA treatment induced the maximum number of crosslinks (13) while DMS treatment induced the minimum (7). Of the two diimidoesters (DMS and DTBP), DTBP was a more effective crosslinking agent due to the presence of disulphide bonds in the DTBP crosslinks. T(s) for DTBP and DMS crosslinked collagen were 80 degrees C and 70 degrees C, and their HIT values were 5.4 and 2.85MN/m(2), respectively. Low concentration of GTA (0.01%) increased the crosslinking density of an already crosslinked matrix (DMS treated matrix) from 7 to 12. Lowest fracture energy was observed for the acyl azide treated matrix (0.61MJ/m(3)) while the highest was observed for the GTA treated matrix (1.97MJ/m(3)). The tensile strength of GTA treated matrix was maximum (12.4MPa) and that of acyl azide treated matrix was minimum (7.2MPa). GTA, DTBP and acyl azide treated matrices were equally resistant to collagenase degradation with approximately 6% solubilization after 5h while the DMS treated was least stable with 52.4% solubilization after the same time period. The spatial orientation of amino acid side chain residues on collagen plays an important role in determining the crosslinking density and consequent physical properties of the collagen matrix.

Self-assembly of diphenylalanine with preclick components as capping groups.

PubMed

Gemma, Andrea; Mayans, Enric; Ballano, Gema; Torras, Juan; Díaz, Angélica; Jiménez, Ana I; Puiggalí, Jordi; Cativiela, Carlos; Alemán, Carlos

2017-10-11

Alkyne and azide, which are commonly used in the cycloaddition reaction recognized as "click chemistry", have been used as capping groups of two engineered diphenylalanine (FF) derivatives due to their ability to form weak intermolecular interactions (i.e. dipole-π and π-π stacking). In Poc-FF-N 3 , alkyne and azide act as N- and C-terminal capping groups, respectively, while such positions are exchanged in N 3 -FF-OPrp. The self-assembly of such two synthesized peptides has been extensively studied in their "pre-click" state, considering the influence of three different factors: the peptide concentration, the polarity of the medium, and the nature of the substrate. Poc-FF-N 3 assembles into microfibers that, depending on the medium and the substrate, can aggregate hierarchically in supramolecular structures with different morphologies. The most distinctive one corresponds to very stable birefringent dendritic-like microstructures, which are derived from the ordered agglomeration of microfibers. These branched supramolecular structures, which are observed under a variety of conditions, are relatively uncommon in short FF sequences. At the molecular level, Poc-FF-N 3 organizes in antiparallel β-sheets stabilized by N-HO intermolecular hydrogen bonds and re-enforced by weak interactions between the azide and alkyne groups of neighbouring molecules. In contrast, N 3 -FF-OPrp exhibits a very poor tendency to organize into structures with a well-defined morphology. Theoretical calculations on model complexes indicate that the tendency of the latter peptide to organize into small amorphous agglomerates is due to its poor ability to form specific intermolecular interactions in comparison with Poc-FF-N 3 . The implications of the weak interactions induced by the alkyne and azide groups, which strengthen peptidepeptide hydrogen bonds and π-ladders due to the stacked aromatic phenyl side groups, are discussed.

Evidence for the Synthesis of ATP by an F0F1 ATP Synthase in Membrane Vesicles from Halorubrum Saccharovorum

NASA Technical Reports Server (NTRS)

Faguy, David; Lawson, Darion; Hochstein, Lawrence I.; Chang, Sherwood (Technical Monitor)

1996-01-01

Vesicles prepared in a buffer containing ADP, Mg(2+) and Pi synthesized ATP at an initial rate of 2 nmols/min/mg protein after acidification of the bulk medium (pH 8 (right arrow) 4). The intravesicular ATP concentration reached a steady state after about 30 seconds and slowly declined thereafter. ATP synthesis was inhibited by low concentrations of dicyclohexylcarbodiimide and m-chlorophenylhydrazone indicating that synthesis took place in response to the proton gradient. NEM and PCMS, which inhibit vacuolar ATPases and the vacuolar-like ATPases of extreme halophiles, did not affect ATP synthesis, and, in fact, produced higher steady state levels of ATP. This suggested that two ATPase activities were present, one which catalyzed ATP synthesis and one that caused its hydrolysis. Azide, a specific inhibitor of F0F1 ATP Synthases, inhibited halobacterial ATP synthesis. The distribution of acridine orange as imposed by a delta pH demonstrated that azide inhibition was not due to the collapse of the proton gradient due to azide acting as a protonophore. Such an effect was observed, but only at azide concentrations higher than those that inhibited ATP synthesis. These results confirm the earler observations with cells of H. saccharovorum and other extreme halophiles that ATP synthesis is inconsistent with the operation of a vacuolar-like ATPase. Therefore, the observation that a vacuolar-like enzyme is responsible for ATP synthesis (and which serves as the basis for imputing ATP synthesis to the vacuolar-like ATPases of the extreme halophiles, and the Archaea in general) should be taken with some degree of caution.

Diazo Compounds as Highly Tunable Reactants in 1,3-Dipolar Cycloaddition Reactions with Cycloalkynes†

PubMed Central

McGrath, Nicholas A.

2012-01-01

Diazo compounds, which can be accessed directly from azides by deimidogenation, are shown to be extremely versatile dipoles in 1,3-dipolar cycloaddition reactions with a cyclooctyne. The reactivity of a diazo compound can be much greater or much less than its azide analog, and is enhanced markedly in polar-protic solvents. These reactivities are predictable from frontier molecular orbital energies. The most reactive diazo compound exhibited the highest known second-order rate constant to date for a dipolar cycloaddition with a cycloalkyne. These data provide a new modality for effecting chemoselective reactions in a biological context. PMID:23227302

Transition-state structure for the quintessential SN2 reaction of a carbohydrate: reaction of α-glucopyranosyl fluoride with azide ion in water.

PubMed

Chan, Jefferson; Sannikova, Natalia; Tang, Ariel; Bennet, Andrew J

2014-09-03

We report that the SN2 reaction of α-d-glucopyranosyl fluoride with azide ion proceeds through a loose (exploded) transition-state (TS) structure. We reached this conclusion by modeling the TS using a suite of five experimental kinetic isotope effects (KIEs) as constraints for the calculations. We also report that the anomeric (13)C-KIE is not abnormally large (k12/k13 = 1.024 ± 0.006), a finding which is at variance with the previous literature value (Zhang et al. J. Am. Chem. Soc. 1994, 116, 7557).

Phase Transition and Structure of Silver Azide at High Pressure

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

D Hou; F Zhang; C Ji

2011-12-31

Silver azide (AgN{sub 3}) was compressed up to 51.3 GPa. The results reveal a reversible second-order orthorhombic-to-tetragonal phase transformation starting from ambient pressure and completing at 2.7 GPa. The phase transition is accompanied by a proximity of cell parameters a and b, a 3{sup o} rotation of azide anions, and a change of coordination number from 4-4 (four short, four long) to eight fold. The crystal structure of the high pressure phase is determined to be in I4/mcm space group, with Ag at 4a, N{sub 1} at 4d, and N{sub 2} at 8h Wyckoff positions. Both of the two phasesmore » have anisotropic compressibility: the orthorhombic phase exhibits an anomalous expansion under compression along a-axis and is more compressive along b-axis than c-axis; the tetragonal phase is more compressive along the interlayer direction than the intralayer directions. The bulk moduli of the orthorhombic and tetragonal phases are determined to be K{sub OT} = 39{+-}5 GPa with K{sub OT'} = 10{+-}7 and K{sub OT} = 57 {+-}2 GPa with K{sub OT'} = 6.6{+-}0.2, respectively.« less

Site-Specific 64Cu Labeling of the Serine Protease, Active Site Inhibited Factor Seven Azide (FVIIai-N3), Using Copper Free Click Chemistry.

PubMed

Jeppesen, Troels E; Kristensen, Lotte K; Nielsen, Carsten H; Petersen, Lars C; Kristensen, Jesper B; Behrens, Carsten; Madsen, Jacob; Kjaer, Andreas

2018-01-17

A method for site-specific radiolabeling of the serine protease active site inhibited factor seven (FVIIai) with 64 Cu has been applied using a biorthogonal click reaction. FVIIai binds to tissue factor (TF), a trans-membrane protein involved in hemostasis, angiogenesis, proliferation, cell migration, and survival of cancer cells. First a single azide moiety was introduced in the active site of this 50 kDa protease. Then a NOTA moiety was introduced via a strain promoted azide-alkyne reaction and the corresponding conjugate was labeled with 64 Cu. Binding to TF and the stability was evaluated in vitro. TF targeting capability of the radiolabeled conjugate was tested in vivo by positron emission tomography (PET) imaging in pancreatic human xenograft cancer mouse models with various TF expressions. The conjugate showed good stability (>91% at 16 h), an immunoreactivity of 93.5%, and a mean tumor uptake of 2.1 ± 0.2%ID/g at 15 h post injection. In conclusion, FVIIai was radiolabeled with 64 Cu in single well-defined position of the protein. This method can be utilized to prepare conjugates from serine proteases with the label at a specific position.

[Sodium azide poisoning--a rare reason of hospitalization in toxicological units--case report].

PubMed

Kostek, Halina; Sawiniec, Jarosław; Lewandowska-Stanek, Hanna; Kujawa, Anna; Majewska, Magdalena; Szponar, Jarosław

2012-01-01

Sodium azide poisonings are a rare reason for hospitalization in toxicological units. They are observed as rarely as once within a number of years per hospital. Consequently, an algorithm for the optimum procedure of treating such intoxications does not exist and, as a result, there is a need to describe every single clinical case. A female, aged 55, was directed to the toxicological unit from a county hospital after swallowing four tablets of sodium azide, 150 mg each, in the form of preservative for fresh milk samples. Two hours after the incident a gastric lavage was performed and the tableting blend was retrieved. In the clinical examination higher concentration of lactic acid, ALAT and TSH were observed. In the ECG record unspecific aberrations in the ST segment were noticed. Due to the patient's general good condition and the fact that the tableting blend had been retrieved from the gastric rinse, further use of the antidote indicated in the therapy of cyanide intoxications was abandoned. Symptomatic treatment was used along with the patient's eight-day observation. In the described case the early decontamination prevented the development of acute poisoning.

N and O isotope (δ15 Nα , δ15 Nβ , δ18 O, δ17 O) analyses of dissolved NO3- and NO2- by the Cd-azide reduction method and N2 O laser spectrometry.

PubMed

Wassenaar, Leonard I; Douence, Cedric; Altabet, Mark A; Aggarwal, Pradeep K

2018-02-15

The nitrogen and oxygen (δ 15 N, δ 18 O, δ 17 O) isotopic compositions of NO 3 - and NO 2 - are important tracers of nutrient dynamics in soil, rain, groundwater and oceans. The Cd-azide method was used to convert NO 3 - or NO 2 - to N 2 O for N and triple-O isotopic analyses by N 2 O laser spectrometry. A protocol for laser-based headspace isotope analyses was compared with isotope ratio mass spectrometry. Lasers provide the ability to directly measure 17 O anomalies which can help discern atmospheric N sources. δ 15 N, δ 18 O and δ 17 O values were measured on N/O stable isotopic reference materials (IAEA, USGS) by conversion to N 2 O using the Cd-azide method and headspace N 2 O laser spectrometry. A 15 N tracer test assessed the position-specific routing of N to the α or β positions in the N 2 O molecule. A data processing algorithm was used to correct for isotopic dependencies on N 2 O concentration, cavity pressure and water content. NO 3 - /NO 2 - nitrogen is routed to the 15 N α position of N 2 O in the azide reaction; hence the δ 15 N α value should be used for N 2 O laser spectrometry results. With corrections for cavity pressure, N 2 O concentration and water content, the δ 15 N α AIR , δ 18 O VSMOW and δ 17 O VSMOW values (‰) of international reference materials were +4.8 ± 0.1, +25.9 ± 0.3, +12.7 ± 0.2 (IAEA NO 3 ), -1.7 ± 0.1, -26.8 ± 0.8, -14.4 ± 1.1 (USGS34) and +2.6 ± 0.1, +57.6 ± 1.2, +51.2 ± 2.0 (USGS35), in agreement with their values and with the isotope ratio mass spectrometry results. The 17 O excess for USGS35 was +21.2 ± 9‰, in good agreement with previous results. The Cd-azide method yielded excellent results for routine determination of δ 15 N, δ 18 O and δ 17 O values (and the 17 O excess) of nitrate or nitrite by laser spectrometry. Disadvantages are the toxicity of Cd-azide chemicals and the lack of automated sampling devices for N 2 O laser spectrometers. The 15 N-enriched tracer test revealed potential for position-specific experimentation of aqueous nutrient dynamics at high 15 N enrichments by laser spectrometry, but exposed the need for memory corrections and improved spectral deconvolution of 17 O. Copyright © 2017 John Wiley & Sons, Ltd.

Antifungal activity of 1'-homo-N-1,2,3-triazol-bicyclic carbonucleosides: A novel type of compound afforded by azide-enolate (3+2) cycloaddition.

PubMed

González-Calderón, Davir; Mejía-Dionicio, María G; Morales-Reza, Marco A; Aguirre-de Paz, José G; Ramírez-Villalva, Alejandra; Morales-Rodríguez, Macario; Fuentes-Benítes, Aydeé; González-Romero, Carlos

2016-12-01

The first report of 1'-homo-N-1,2,3-triazol-bicyclic carbonucleosides (7a and 7b) is described herein. Azide-enolate (3+2) cycloaddition afforded the synthesis of this novel type of compound. Antifungal activity was evaluated in vitro against four filamentous fungi (Aspergillus fumigatus, Trichosporon cutaneum, Rhizopus oryzae and Mucor hiemalis) as well as nine species of Candida spp. as yeast specimens. These pre-clinical studies suggest that compounds 7a and 7b are promising candidates for complementary biological studies due to their good activity against Candida spp. Copyright © 2016 Elsevier Inc. All rights reserved.

Biocompatible artificial DNA linker that is read through by DNA polymerases and is functional in Escherichia coli

PubMed Central

El-Sagheer, Afaf H.; Sanzone, A. Pia; Gao, Rachel; Tavassoli, Ali; Brown, Tom

2011-01-01

A triazole mimic of a DNA phosphodiester linkage has been produced by templated chemical ligation of oligonucleotides functionalized with 5′-azide and 3′-alkyne. The individual azide and alkyne oligonucleotides were synthesized by standard phosphoramidite methods and assembled using a straightforward ligation procedure. This highly efficient chemical equivalent of enzymatic DNA ligation has been used to assemble a 300-mer from three 100-mer oligonucleotides, demonstrating the total chemical synthesis of very long oligonucleotides. The base sequences of the DNA strands containing this artificial linkage were copied during PCR with high fidelity and a gene containing the triazole linker was functional in Escherichia coli. PMID:21709264

General method for labeling siRNA by click chemistry with fluorine-18 for the purpose of PET imaging.

PubMed

Mercier, Frédéric; Paris, Jérôme; Kaisin, Geoffroy; Thonon, David; Flagothier, Jessica; Teller, Nathalie; Lemaire, Christian; Luxen, André

2011-01-19

The alkyne-azide Cu(I)-catalyzed Huisgen cycloaddition, a click-type reaction, was used to label a double-stranded oligonucleotide (siRNA) with fluorine-18. An alkyne solid support CPG for the preparation of monostranded oligonucleotides functionalized with alkyne has been developed. Two complementary azide labeling agents (1-(azidomethyl)-4-[(18)F]fluorobenzene) and 1-azido-4-(3-[(18)F]fluoropropoxy)benzene have been produced with 41% and 35% radiochemical yields (decay-corrected), respectively. After annealing with the complementary strand, the siRNA was directly labeled by click chemistry with [(18)F]fluoroazide to produce the [(18)F]-radiolabeled siRNA with excellent radiochemical yield and purity.

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

PubMed

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

2010-12-03

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

Reduction and functionalization of graphene oxide sheets using biomimetic dopamine derivatives in one step.

PubMed

Kaminska, Izabela; Das, Manash R; Coffinier, Yannick; Niedziolka-Jonsson, Joanna; Sobczak, Jonusz; Woisel, Patrice; Lyskawa, Joel; Opallo, Marcin; Boukherroub, Rabah; Szunerits, Sabine

2012-02-01

An easy and environmentally friendly chemical method for the simultaneous reduction and noncovalent functionalization of graphene oxide (GO) using dopamine derivatives is described. The reaction takes place at room temperature under ultrasonication of an aqueous suspension of GO and a dopamine derivative. X-ray photoelectron spectroscopy, FT-IR spectroscopy, and cyclic voltammetry characterizations revealed that the resulting material consists of graphene functionalized with the dopamine derivative. This one-step protocol is applied for simultaneous reduction and functionalization of graphene oxide with a dopamine derivative bearing an azide function. The chemical reactivity of the azide function was demonstrated by a postfunctionalization with ethynylferrocene using the Cu(I) catalyzed 1,3-dipolar cyloaddition.

Potentiation of antimicrobial photodynamic inactivation by inorganic salts.

PubMed

Hamblin, Michael R

2017-11-01

Antimicrobial photodynamic inactivation (aPDI) involves the use of non-toxic dyes excited with visible light to produce reactive oxygen species (ROS) that can destroy all classes of microorganisms including bacteria, fungi, parasites, and viruses. Selectivity of killing microbes over host mammalian cells allows this approach (antimicrobial photodynamic therapy, aPDT) to be used in vivo as an alternative therapeutic approach for localized infections especially those that are drug-resistant. Areas covered: We have discovered that aPDI can be potentiated (up to 6 logs of extra killing) by the addition of simple inorganic salts. The most powerful and versatile salt is potassium iodide, but potassium bromide, sodium thiocyanate, sodium azide and sodium nitrite also show potentiation. The mechanism of potentiation with iodide is likely to be singlet oxygen addition to iodide to form iodine radicals, hydrogen peroxide and molecular iodine. Another mechanism involves two-electron oxidation of iodide/bromide to form hypohalites. A third mechanism involves a one-electron oxidation of azide anion to form azide radical. Expert commentary: The addition of iodide has been shown to improve the performance of aPDT in several animal models of localized infection. KI is non-toxic and is an approved drug for antifungal therapy, so its transition to clinical use in aPDT should be straightforward.

Nano/biosensors based on large-area graphene

NASA Astrophysics Data System (ADS)

Ducos, Pedro Jose

Two dimensional materials have properties that make them ideal for applications in chemical and biomolecular sensing. Their high surface/volume ratio implies that all atoms are exposed to the environment, in contrast to three dimensional materials with most atoms shielded from interactions inside the bulk. Graphene additionally has an extremely high carrier mobility, even at ambient temperature and pressure, which makes it ideal as a transduction device. The work presented in this thesis describes large-scale fabrication of Graphene Field Effect Transistors (GFETs), their physical and chemical characterization, and their application as biomolecular sensors. Initially, work was focused on developing an easily scalable fabrication process. A large-area graphene growth, transfer and photolithography process was developed that allowed the scaling of production of devices from a few devices per single transfer in a chip, to over a thousand devices per transfer in a full wafer of fabrication. Two approaches to biomolecules sensing were then investigated, through nanoparticles and through chemical linkers. Gold and platinum Nanoparticles were used as intermediary agents to immobilize a biomolecule. First, gold nanoparticles were monodispersed and functionalized with thiolated probe DNA to yield DNA biosensors with a detection limit of 1 nM and high specificity against noncomplementary DNA. Second, devices are modified with platinum nanoparticles and functionalized with thiolated genetically engineered scFv HER3 antibodies to realize a HER3 biosensor. Sensors retain the high affinity from the scFv fragment and show a detection limit of 300 pM. We then show covalent and non-covalent chemical linkers between graphene and antibodies. The chemical linker 1-pyrenebutanoic acid succinimidyl ester (pyrene) stacks to the graphene by Van der Waals interaction, being a completely non-covalent interaction. The linker 4-Azide-2,3,5,6-tetrafluorobenzoic acid, succinimidyl ester (azide) is a photoactivated perfluorophenyl azide that covalently binds to graphene. A comparison is shown for genetically engineered scFv HER3 antibodies and show a low detection limit of 10 nM and 100 pM for the pyrene and azide, respectively. Finally, we use the azide linker to demonstrate a large-scale fabrication of a multiplexed array for Lyme disease. Simultaneous detection of a mixture of two target proteins of the Lyme disease bacterium (Borrelia burgdorferi), this is done by separating the antibodies corresponding to each target in the mixture to different regions of the chip. We show we can differentiate concentrations of the two targets.

Aryl nitrene rearrangements: spectroscopic observation of a benzazirine and its ring expansion to a ketenimine by heavy-atom tunneling.

PubMed

Inui, Hiroshi; Sawada, Kazuhiro; Oishi, Shigero; Ushida, Kiminori; McMahon, Robert J

2013-07-17

In the photodecompositions of 4-methoxyphenyl azide (1) and 4-methylthiophenyl azide (5) in argon matrixes at cryogenic temperatures, benzazirine intermediates were identified on the basis of IR spectra. As expected, the benzazirines photochemically rearranged to the corresponding ketenimines and triplet nitrenes. Interestingly, with the methylthio substituent, the rearrangement of benzazirine 8 to ketenimine 7 occurred at 1.49 × 10(-5) s(-1) even in the dark at 10 K, despite a computed activation barrier of 3.4 kcal mol(-1). Because this rate is 10(57) times higher than that calculated for passing over the barrier and because it shows no temperature dependence, the rearrangement mechanism is interpreted in terms of heavy-atom tunneling.

A polytriazole synthesized by 1,3-dipolar polycycloaddition showing aggregation-enhanced emission and utility in explosive detection.

PubMed

Wang, Qiang; Chen, Ming; Yao, Bicheng; Wang, Jian; Mei, Ju; Sun, Jing Zhi; Qin, Anjun; Tang, Ben Zhong

2013-05-14

The metal-free click polymerizations (MFCPs) of activated alkynes and azides have become a powerful technique for the preparation of functional polytriazoles. Recently, a new MFCP of activated azide and alkyne has been established, but no functional polytriazole is prepared. In this paper, polytriazole PIa with aggregation-enhanced emission (AEE) characteristics is prepared by this efficient polymerization in excellent yield (97.9%). PIa is thermally stable, with 5% loss of its weight at temperature as high as 440 °C. Thanks to its unique AEE feature of PIa, its nanoaggregates can be used to detect explosives with a superamplification quenching effect. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of C-glycosyl-bis-1,2,3-triazole derivatives from 3,4,6-tri-O-acetyl-D-glucal.

PubMed

Shamim, Anwar; Souza, Frederico B; Trossini, Gustavo H G; Gatti, Fernando M; Stefani, Hélio A

2015-08-01

We have developed an efficient, CuI-catalyzed, microwave-assisted method for the synthesis of bis-1,2,3-triazole derivatives starting from a 3,4,6-tri-O-acetyl-D-glucal-derived mesylate. This mesylate was obtained from 3,4,6-tri-O-acetyl-D-glucal through C-glycosidation, deprotection of acetate groups to alcohols, and selective mesylation of the primary alcohol. This mesylate moiety was then converted to an azide through a microwave-assisted method with good yield. The azide, once synthesized, was then treated with different terminal alkynes in the presence of CuI to synthesize various bis-triazoles in high yields and short reaction times.

Fluorescent and colorimetric molecular recognition probe for hydrogen bond acceptors.

PubMed

Pike, Sarah J; Hunter, Christopher A

2017-11-22

The association constants for formation of 1 : 1 complexes between a H-bond donor, 1-naphthol, and a diverse range of charged and neutral H-bond acceptors have been measured using UV/vis absorption and fluorescence emission titrations. The performance of 1-naphthol as a dual colorimetric and fluorescent molecular recognition probe for determining the H-bond acceptor (HBA) parameters of charged and neutral solutes has been investigated in three solvents. The data were employed to establish self-consistent H-bond acceptor parameters (β) for benzoate, azide, chloride, thiocyanate anions, a series of phosphine oxides, phosphate ester, sulfoxide and a tertiary amide. The results demonstrate both the transferability of H-bond parameters between different solvents and the utility of the naphthol-based dual molecular recognition probe to exploit orthogonal spectroscopic techniques to determine the HBA properties of neutral and charged solutes. The benzoate anion is the strongest HBA studied with a β parameter of 15.4, and the neutral tertiary amide is the weakest H-bond acceptor investigated with a β parameter of 8.5. The H-bond acceptor strength of the azide anion is higher than that of chloride (12.8 and 12.2 respectively), and the thiocyanate anion has a β value of 10.8 and thus is a significantly weaker H-bond acceptor than both the azide and chloride anions.

Branched Polyhedral Oligomeric Silsesquioxane Nanoparticles Prepared via Strain-Promoted 1,3-Dipolar Cycloadditions

PubMed Central

Ledin, Petr A.; Xu, Weinan; Friscourt, Frédéric; Boons, Geert-Jan; Tsukruk, Vladimir V.

2016-01-01

Conjugation of small organic molecules and polymers to polyhedral oligosilsesquioxane (POSS) cores results in novel hybrid materials with unique physical characteristics. We report here an approach in which star-shaped organic–inorganic scaffolds bearing eight cyclooctyne moieties can be rapidly functionalized via strain-promoted azide–alkyne cycloaddition (SPAAC) to synthesize a series of nearly monodisperse branched core–shell nanoparticles with hydrophobic POSS cores and hydrophilic arms. We established that SPAAC is a robust method for POSS core octafunctionalization with the reaction rate constant of 1.9 × 10−2 M−1 s−1. Functionalization with poly(ethylene glycol) (PEG) azide, fluorescein azide, and unprotected lactose azide gave conjugates which represent different classes of compounds: polymer conjugates, fluorescent dots, and bioconjugates. These resulting hybrid compounds were preliminarily tested for their ability to self-assemble in solution and at the air–water interface. We observed the formation of robust smooth Langmuir monolayers with diverse morphologies. We found that polar lactose moieties are completely submerged into the subphase whereas the relatively hydrophobic fluorescein arms had extended conformation at the interface, and PEG arms were partially submerged. Finally, we observed the formation of stable micelles with sizes between 70 and 160 nm in aqueous solutions with size and morphology of the structures dependent on the molecular weight and the type of the peripheral hydrophilic moieties. PMID:26131712

Synthesis of Dendronized Poly(l-Glutamate) via Azide-Alkyne Click Chemistry

PubMed Central

Perdih, Peter; Kržan, Andrej; Žagar, Ema

2016-01-01

Poly(l-glutamate) (PGlu) was modified with a second-generation dendron to obtain the dendronized polyglutamate, P(Glu-D). Synthesized P(Glu-D) exhibited a degree of polymerization (DPn) of 46 and a 43% degree of dendronization. Perfect agreement was found between the P(Glu-D) expected structure and the results of nuclear magnetic resonance spectroscopy (NMR) and size-exclusion chromatography coupled to a multi-angle light-scattering detector (SEC-MALS) analysis. The PGlu precursor was modified by coupling with a bifunctional building block (N3-Pr-NH2) in the presence of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM) coupling reagent. The second-generation polyamide dendron was prepared by a stepwise procedure involving the coupling of propargylamine to the l-lysine carboxyl group, followed by attaching the protected 2,2-bis(methylol)propionic acid (bis-MPA) building block to the l-lysine amino groups. The hydroxyl groups of the resulting second-generation dendron were quantitatively deprotected under mild acidic conditions. The deprotected dendron with an acetylene focal group was coupled to the pendant azide groups of the modified linear copolypeptide, P(Glu-N3), in a Cu(I) catalyzed azide-alkyne cycloaddition reaction to form a 1,4-disubstituted triazole. The dendronization reaction proceeded quantitatively in 48 hours in aqueous medium as confirmed by 1H NMR and Fourier transform infrared spectroscopy (FT-IR) spectroscopy. PMID:28773369

Photolysis of caged calcium in femtoliter volumes using two-photon excitation.

PubMed Central

Brown, E B; Shear, J B; Adams, S R; Tsien, R Y; Webb, W W

1999-01-01

A new technique for the determination of the two-photon uncaging action cross section (deltau) of photolyzable calcium cages is described. This technique is potentially applicable to other caged species that can be chelated by a fluorescent indicator dye, as well as caged fluorescent compounds. The two-photon action cross sections of three calcium cages, DM-nitrophen, NP-EGTA, and azid-1, are studied in the range of excitation wavelengths between 700 and 800 nm. Azid-1 has a maximum deltau of approximately 1.4 GM at 700 nm, DM-nitrophen has a maximum deltau of approximately 0.013 GM at 730 nm, and NP-EGTA has no measurable uncaging yield. The equations necessary to predict the amount of cage photolyzed and the temporal behavior of the liberated calcium distribution under a variety of conditions are derived. These equations predict that by using 700-nm light from a Ti:sapphire laser focused with a 1.3-NA objective, essentially all of the azid-1 within the two-photon focal volume would be photolyzed with a 10-micros pulse train of approximately 7 mW average power. The initially localized distributions of free calcium will dissipate rapidly because of diffusion of free calcium and uptake by buffers. In buffer-free cytoplasm, the elevation of the calcium concentration at the center of the focal volume is expected to last for approximately 165 micros. PMID:9876162

Bio-orthogonal coupling on PEG-modified quantum dots (Conference Presentation)

NASA Astrophysics Data System (ADS)

Zhan, Naiqian; Palui, Goutam; Mattoussi, Hedi

2017-02-01

We have designed two sets of aldehyde- and azide-modified ligands; these ligands also present lipoic acid anchors and PEG hydrophilic moieties (LA-PEG-CHO and LA-PEG-azide). We combined this design with a photoligation strategy to prepare QDs with good control over the fraction of intact reactive groups per nanocrystal. We first applied the extremely efficient hydrazone coupling ligation to react the QD with hydrozinopyridine, which produces a well-defined absorption feature at 354 nm ascribed to the hydrazone chromophore. We exploited this signature to measure the number of aldehyde groups per QD when the fraction of LA-PEG-CHO per nanocrystal was varied, by comparing the optical signature at 354 with the molar extinction coefficient of the chromophore. This allowed us to extract an estimate for the number of LA-PEG ligand per QDs for a few distinct size nanocrystals. We further complemented these findings with the use of NMR spectroscopy to estimate of the ligand density using well defined signatures of the terminal protons of the ligands, and found a good agreement between the two techniques. We then showed that bio-orthogonal reactions based on CLICK and hydrazone coupling can be achieved using QDs presenting a mixture of azide and CHO functions. We anticipate that this strategy could be applied other nanoparticles such as those of Au and metals and semiconductor nanocrystals.

On the vibrational spectra and structural parameters of methyl, silyl, and germyl azide from theoretical predictions and experimental data.

PubMed

Durig, Douglas T; Durig, M S; Durig, James R

2005-05-01

The infrared and Raman spectra of methyl, silyl, and germyl azide (XN3 where X=CH3, SiH3 and GeH3) have been predicted from ab initio calculations with full electron correlation by second order perturbation theory (MP2) and hybrid density function theory (DFT) by the B3LYP method with a variety of basis sets. These predicted data are compared to previously reported experimental data and complete vibrational assignments are provided for all three molecules. It is shown that several of the assignments recently proposed [J. Mol. Struct. (Theochem.) 434 (1998) 1] for methyl azide are not correct. Structural parameters for CH3N3 and GeH3N3 have been obtained by combining the previously reported microwave rotational constants with the ab initio MP2/6-311+G(d,p) predicted values. These "adjusted r0" parameters have very small uncertainties of +/-0.003 A for the XH distances and a maximum of +/-0.005 A for the heavy atom distances and +/-0.5 degrees for the angles. The predicted distance for the terminal NN bond which is nearly a triple bond is much better predicted by the B3LYP calculations, whereas the fundamental frequencies are better predicted by the scaled ab initio calculations. The results are discussed and compared to those obtained for some similar molecules.

Poly(L-lysine) Interfaces via Dual Click Reactions on Surface-Bound Custom-Designed Dithiol Adsorbates.

PubMed

Shakiba, Amin; Jamison, Andrew C; Lee, T Randall

2015-06-09

Surfaces modified with poly(L-lysine) can be used to immobilize selected biomolecules electrostatically. This report describes the preparation of a set of self-assembled monolayers (SAMs) from three different azide-terminated adsorbates as platforms for performing controlled surface attachments and as a means of determining the parameters that afford stable poly(L-lysine)-modified SAM surfaces having controlled packing densities. A maleimide-terminated alkyne linker was "clicked" to the azide-terminated surfaces via a copper-catalyzed cycloaddition reaction to produce the attachment sites for the polypeptides. A thiol-Michael addition was then used to immobilize cysteine-terminated poly(L-lysine) moieties on the gold surface, avoiding adsorbate self-reactions with this two-step procedure. Each step in this process was analyzed by ellipsometry, X-ray photoelectron spectroscopy, polarization modulation infrared reflection-absorption spectroscopy, and contact angle goniometry to determine which adsorbate structure most effectively produced the targeted polypeptide interface. Additionally, a series of mixed SAMs using an azidoalkanethiol in combination with a normal alkanethiol having an equivalent alkyl chain were prepared to provide data to determine how dilution of the azide reactive site on the SAM surface influences the initial click reaction. Overall, the collected data demonstrate the advantages of an appropriately designed bidentate absorbate and its potential to form effective platforms for biomolecule surface attachment via click reactions.

Analysis of enterococci using portable testing equipment for developing countries--variance of Azide NutriDisk medium under variable time and temperature.

PubMed

Godfrey, S; Watkins, J; Toop, K; Francis, C

2006-01-01

This report compares the enterococci count on samples obtained with Azide NutriDisk (AND) (sterile, dehydrated culture medium) and Slanetz and Bartley (SB) medium when exposed to a variable in incubation time and temperature. Three experiments were performed to examine the recovery of enterococci on AND and SB media using membrane filtration with respect to: (a) incubation time; (b) incubation temperature; and (c) a combination of the two. Presumptive counts were observed at 37, 41, 46 and 47 degrees C and at 20, 24, 28 and 48 h. These were compared to AWWA standard method 9230 C (44 degrees C, 44 h). Samples were confirmed using Kanamycin Aesculin Azide (KAA) agar. Friedman's ANOVA and Students t-test analysis indicated higher enumeration of enterococci when grown on AND (p = 0.45) than SB (p = < 0.001) at all temperatures with a survival threshold at 47 degrees C. Significant results for AND medium were noted at 20 h (p = 0.021), 24 h (p = 0.278) and 28 h (p = 0.543). The study concluded that the accuracy of the AND medium at a greater time and temperature range provided flexibility in incubator technology making it an appropriate alternative to SB medium for monitoring drinking water using field testing kits in developing countries.

Electrochemically Protected Copper(I)-Catalyzed Azide-Alkyne Cycloaddition

PubMed Central

Hong, Vu; Udit, Andrew K.; Evans, Richard A.; Finn, M.G.

2012-01-01

The copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction has found broad application in myriad fields. For the most demanding applications requiring high yields at low substrate concentrations, highly active but air-sensitive copper complexes must be used. We describe here the use of an electrochemical potential to maintain catalysts in the active Cu(I) oxidation state in the presence of air. The simple procedure efficiently achieves excellent yields of CuAAC products involving both small molecule and protein substrates without the use of potentially damaging chemical reducing agents. A new water-soluble carboxylated version of the popular tris(benzyltriazolylmethyl)amine (TBTA) ligand is described. Cyclic voltammetry revealed reversible or quasi-reversible electrochemical redox behavior of copper complexes of the TBTA derivative (2; E1/2 = 60 mV vs. Ag/AgCl), sulfonated bathophenanthroline (3; E1/2 = -60 mV), and sulfonated tris(benzimidazoylmethyl)amine (4; E1/2 ~ -70 mV), and showed catalytic turnover to be rapid relative to the voltammetry time scale. Under the influence of a -200 mV potential established using a reticulated vitreous carbon working electrode, CuSO4 and 3 formed a superior catalyst. Electrochemically-protected bioconjugations in air were performed using bacteriophage Qβ derivatized with azide moieties at surface lysine residues. The complete addressing of more than 600 reactive sites per particle was demonstrated within 12 hours of electrolysis with sub-stoichiometric quantities of Cu•3. PMID:18504727

Sodium Azide

MedlinePlus

... Cyanogen chloride (CK) Digitalis Case Definition: Digitalis Poisoning Ethylene glycol Fentanyls and other opioids Case Definition: Opioids ( ... Thallium Toxic alcohols Case Definition: Toxic Alcohol Poisoning Ethylene glycol Trichothecene Case Definition: Trichothecene Mycotoxin Poisoning Unidentified ...

Nitro-Assisted Brønsted Acid Catalysis: Application to a Challenging Catalytic Azidation.

PubMed

Dryzhakov, Marian; Hellal, Malik; Wolf, Eléna; Falk, Florian C; Moran, Joseph

2015-08-05

A cocatalytic effect of nitro compounds is described for the B(C6F5)3·H2O catalyzed azidation of tertiary aliphatic alcohols, enabling catalyst turnover for the first time and with a broad range of substrates. Kinetic investigations into this surprising effect reveal that nitro compounds induce a switch from first order concentration dependence in Brønsted acid to second order concentration dependence in Brønsted acid and second order dependence in the nitro compounds. Kinetic, electronic, and spectroscopic evidence suggests that higher order hydrogen-bonded aggregates of nitro compounds and acids are the kinetically competent Brønsted acid catalysts. Specific weak H-bond accepting additives may offer a new general approach to accelerating Brønsted acid catalysis in solution.

Facile purification and click labeling with 2-[ 18F]fluoroethyl azide using solid phase extraction cartridges

DOE PAGES

Zhou, Dong; Chu, Wenhua; Peng, Xin; ...

2014-11-04

In this paper, a facile method was developed to purify 2-[ 18F]fluoroethyl azide ([ 18F]FEA) using a C18 cartridge and an Oasis® HLB cartridge in series, in which [18F]FEA was exclusively trapped on the HLB cartridge. [ 18F]FEA can be eluted for reactions in solution; alternatively click labeling can be carried out on the HLB cartridge itself by loading an alkyne substrate and copper (I) catalyst dissolved in DMF onto the cartridge. Finally, this solid phase extraction methodology for purification and click labeling with [ 18F]FEA, either in solution or on the cartridge, is safe, simple, reproducible in high yield,more » and compatible with automated synthesis of 18F-labeled PET tracers.« less

I. Synthesis, characterization, and base catalysis of novel zeolite supported super-basic materials II. Oxidative dehydrogenation of ethane over reduced heteropolyanion catalysts

NASA Astrophysics Data System (ADS)

Galownia, Jonathan M.

This thesis is composed of two separate and unrelated projects. The first part of this thesis outlines an investigation into the synthesis and characterization of a novel zeolite supported super-base capable of carbon-carbon olefin addition to alkyl aromatics. A zeolite supported basic material capable of such reactions would benefit many fine chemical syntheses, as well as vastly improve the economics associated with production of the high performance thermoplastic polyester polyethylene naphthalate. The thermal decomposition of alkali---metal azides impregnated in zeolite X is investigated as a novel route to the synthesis of a zeolite supported super-base. Impregnation of the alkali---metal azide precursor is shown to result in azide species occluded within the pores of the zeolite support by using high speed, solid-state 23Na MAS and 2D MQMAS NMR, FTIR, and TGA characterization methods. Addition of alkali---metal azides to the zeolite results in redistribution of the extra-lattice cations in the zeolite framework. Thermal decomposition of impregnated azide species produces further cation redistribution, but no neutral metallic clusters are detected by high speed, solid-state 23Na MAS NMR following thermal activation of the materials. Instead, it is possible that inactive ionic clusters are formed. The thermally activated materials do not promote base catalysis for the isomerization of 1-butene, the ethylation of toluene and o-xylene, and the alkenylation of o-xylene with 1,3-butadiene to produce 5-ortho-tolyl-pent-2-ene (5-OTP). The lack of catalytic activity in the materials is attributed to failure of the materials to form neutral metallic clusters during thermal treatment, possibly due to preferential formation of NMR silent ionic clusters. The formation of neutral metallic clusters is found to be insensitive to synthesis technique and activation procedure. It is concluded that the impregnation of alkali---metal azides in zeolite X does not provide a reliable precursor for the formation of zeolite supported super-basic materials. The second part of this thesis describes the oxidative dehydrogenation of ethane over partially reduced heteropolyanions. Niobium and pyridine exchanged salts of phosphomolybdic (NbPMo12Pyr) and phosphovanadomolybdic (NbPMo11VPyr) acids are investigated as catalyst precursors to prepare materials for catalyzing the oxidative dehydrogenation of ethane to ethylene and acetic acid at atmospheric pressure. The effects of feed composition, steam flow, temperature, and precursor composition on catalytic activity and selectivity are presented for both ethane and ethylene oxidation. Production of ethylene and acetic acid from ethane using the catalytic materials exceeds that reported in the literature for Mo-V-Nb-Ox systems under atmospheric or elevated pressure. Production of acetic acid from ethylene is also greater than that observed for Mo-V-Nb-Ox systems. Addition of vanadium reduces catalytic activity and selectivity to both ethylene and acetic acid while niobium is essential for the formation of acetic acid from ethane. Other metals such as antimony, iron, and gallium do not provide the same beneficial effect as niobium. Molybdenum in close proximity to niobium is the active site for ethane activation while niobium is directly involved in the transformation of ethylene to acetic acid. A balance of niobium and protonated pyridine is required to produce an active catalyst. Water is found to aid in desorption of acetic acid, thereby limiting deep oxidation to carbon oxides. A reaction scheme is proposed for the production of acetic acid from ethane over the catalytic materials.

Curing of polymer thermosets via click reactions and on demand processes

NASA Astrophysics Data System (ADS)

Brei, Mark Richard

In the first project, an azide functional resin and tetra propargyl aromatic diamines were fabricated for use as a composite matrix. These systems take already established epoxy/amine matrices and functionalize them with click moieties. This allows lower temperatures to be used in the production of a thermoset part. These new systems yield many better mechanical properties than their epoxy/amine derivatives, but their Tgs are low in comparison. The second project investigates the characterization of a linear system based off of the above azide functional resin and a difunctional alkyne. Through selectively choosing catalyst, the linear system can show regioselectivity to either a 1,4-disubstituted triazole, or a 1,5-disubstituted triazole. Without the addition of catalyst, the system produces both triazoles in almost an equal ratio. The differently catalyzed systems were cured and then analyzed by 1H and 13C NMR to better understand the structure of the material. The third project builds off of the utility of the aforementioned azide/alkyne system and introduces an on-demand aspect to the curing of the thermoset. With the inclusion of copper(II) within the azide/alkyne system, UV light is able to catalyze said reaction and cure the material. It has been shown that the copper(II) loading levels can be extremely small, which helps in reducing the copper's effect on mechanical properties The fourth project takes a look at polysulfide-based sealants. These sealants are normally cured via an oxidative reaction. This project took thiol-terminated polysulfides and fabricated alkene-terminated polysulfides for use as a thiol-ene cured material. By changing the mechanism for cure, the polysulfide can be cured via UV light with the use of a photoinitiator within the thiol/alkene polysulfide matrix. The final chapter will focus on a characterization technique, MALDI-TOF, which was used to help characterize the above materials as well as many others. By using MALDI-TOF, the researcher is able to elicit the molecular weight of the repeat unit and end group, which allows the determination of the polymer's structure. This technique can also determine the Mn and M w, as well as the PDI for each given polymer.

Rhenium(I) polypyridine dibenzocyclooctyne complexes as phosphorescent bioorthogonal probes: Synthesis, characterization, emissive behavior, and biolabeling properties.

PubMed

Choi, Alex Wing-Tat; Liu, Hua-Wei; Lo, Kenneth Kam-Wing

2015-07-01

We report the development of rhenium(I) polypyridine complexes appended with a dibenzocyclooctyne (DIBO) moiety as bioorthogonal probes for azide-modified biomolecules. Three phosphorescent rhenium(I) polypyridine DIBO complexes [Re(N^N)(CO)3(py-C6-DIBO)][CF3SO3] (py-C6-DIBO=3-(N-(6-(3,4:7,8-dibenzocyclooctyne-5-oxycarbonylamino)hexyl)aminocarbonyl)pyridine; N^N=1,10-phenanthroline (phen) (1a), 3,4,7,8-tetramethyl-1,10-phenanthroline (Me4-phen) (2a), 4,7-diphenyl-1,10-phenanthroline (Ph2-phen) (3a)) and their DIBO-free counterparts [Re(N^N)(CO)3(py-C6-BOC)][CF3SO3] (py-C6-BOC=3-(N-(6-(tert-butoxycarbonylamino)hexyl)aminocarbonyl)pyridine; N^N=phen (1b), Me4-phen (2b), Ph2-phen (3b)) were synthesized and characterized. Upon photoexcitation, all the complexes displayed intense and long-lived yellow triplet metal-to-ligand charge-transfer ((3)MLCT) (dπ(Re)→π*(N^N)) emission. The DIBO complexes underwent facile reactions with benzyl azide in methanol at 298 K with second-order rate constants (k2) in the range of 0.077 to 0.091 M(-1) s(-1). As revealed from SDS-PAGE analysis, the DIBO complexes can selectively label azide-modified proteins and the resulting bioconjugates displayed strong phosphorescence upon photoexcitation. Results of inductively coupled plasma mass spectrometry (ICP-MS) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays indicated that the DIBO complexes accumulated in Chinese Hamster Ovary (CHO) cells with considerable cytotoxic activity. Upon incubation of CHO cells with these complexes, relatively weak intracellular emission was observed. In contrast, upon pretreatment of the cells with 1,3,4,6-tetra-O-acetyl-N-azidoacetyl-D-mannosamine (Ac4ManNAz), intense emission was observed from the cell membrane and some internal compartments. The results suggest that the DIBO complexes are promising candidates for imaging azide-labeled biomolecules. Copyright © 2015 Elsevier Inc. All rights reserved.

Click chemistry reactions in medicinal chemistry: applications of the 1,3-dipolar cycloaddition between azides and alkynes.

PubMed

Tron, Gian Cesare; Pirali, Tracey; Billington, Richard A; Canonico, Pier Luigi; Sorba, Giovanni; Genazzani, Armando A

2008-03-01

In recent years, there has been an ever-increasing need for rapid reactions that meet the three main criteria of an ideal synthesis: efficiency, versatility, and selectivity. Such reactions would allow medicinal chemistry to keep pace with the multitude of information derived from modern biological screening techniques. The present review describes one of these reactions, the 1,3-dipolar cycloaddition ("click-reaction") between azides and alkynes catalyzed by copper (I) salts. The simplicity of this reaction and the ease of purification of the resulting products have opened new opportunities in generating vast arrays of compounds with biological potential. The present review will outline the accomplishments of this strategy achieved so far and outline some of medicinal chemistry applications in which click-chemistry might be relevant in the future. (c) 2007 Wiley Periodicals, Inc.

Transformation of hydrazinium azide to molecular N8 at 40 GPa

NASA Astrophysics Data System (ADS)

Duwal, Sakun; Ryu, Young-Jay; Kim, Minseob; Yoo, Choong-Shik; Bang, Sora; Kim, Kyungtae; Hur, Nam Hwi

2018-04-01

Hydrazinium azide (HA) has been investigated at high pressures to 68 GPa using confocal micro-Raman spectroscopy and synchrotron powder x-ray diffraction. The results show that HA undergoes structural phase transitions from solid HA-I to HA-II at 13 GPa, associated with the strengthening of hydrogen bonding, and then to N8 at 40 GPa. The transformation of HA to recently predicted N8 (N≡N+—N-—N=N—-N—+N≡N) is evident by the emergence of new peaks at 2384 cm-1, 1665 cm-1, and 1165 cm-1, arising from the terminal N≡N stretching, the central N=N stretching, and the N—N stretching, respectively. However, upon decompression, N8 decomposes to ɛ-N2 below 25 GPa, but the remnant can be seen as low as 3 GPa.

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.

A porphyrin complex of Gold(I): (Phosphine)gold(I) azides as cation precursors

PubMed Central

Partyka, David V.; Robilotto, Thomas J.; Zeller, Matthias; Hunter, Allen D.; Gray, Thomas G.

2008-01-01

A silver- and Brönsted acid-free protocol for generating the (tricyclohexylphosphine)gold(I) cation from the corresponding azide complexes is disclosed. The gold(I) cations so liberated are trapped by complexation with octaethylporphyrin. The first structurally authenticated gold(I) porphyrin complex crystallizes with formula C72H112Au2F12N4P2Sb2, space group C2/c, a = 21.388 (4), b = 19.679 (4), c = 19.231 (3) Å; β = 111.030 (3)°. Solution spectroscopic studies indicate that the di-gold complex fragments on dissolution in organic solvents. Approximate density-functional theory calculations find an electrostatic origin for the binding of two gold(I) centers to the unprotonated nitrogen atoms, despite greater orbital density on the porphyrin meso carbons. PMID:18780788

Comparative analysis of mitotic aberrations induced by diethyl sulphate (DES) and sodium azide (SA) in Vicia faba L. (Fabaceae).

PubMed

Bhat, Tariq Ahmad; Sharma, Monika; Anis, M

2007-03-01

The present investigation provides a comparative account of different concentrations (0.01, 0.02, 0.03, 0.04, 0.05 and 0.06%) of diethylsulphate (DES) and Sodium Azide (SA) on mitotic aberrations, seed germination, seedling survival, plant height and mitotic index in Vicia faba L. variety major. The control plants were normal while as treated ones showed significant alterations. The mutagens caused dose dependent decrease in seed germination, seedling survival, plant height and mitotic index. All the parameters were found negatively affected and were positively correlated with mutagenic concentrations. The cytological study revealed various types of mitotic aberrations, among them the dominant were fragments, stickiness, precocious separation, c-metaphase, ring chromosomes, unequal separation, laggards, bridges, micronuclei, disturbed anaphase etc. Stickiness and fragments were more frequent as compared to other types.

An eco-compatible strategy for the diversity-oriented synthesis of macrocycles exploiting carbohydrate-derived building blocks.

PubMed

Maurya, Sushil K; Rana, Rohit

2017-01-01

An efficient, eco-compatible diversity-oriented synthesis (DOS) approach for the generation of library of sugar embedded macrocyclic compounds with various ring size containing 1,2,3-triazole has been developed. This concise strategy involves the iterative use of readily available sugar-derived alkyne/azide-alkene building blocks coupled through copper catalyzed azide-alkyne cycloaddition (CuAAC) reaction followed by pairing of the linear cyclo-adduct using greener reaction conditions. The eco-compatibility, mild reaction conditions, greener solvents, easy purification and avoidance of hazards and toxic solvents are advantages of this protocol to access this important structural class. The diversity of the macrocycles synthesized (in total we have synthesized 13 macrocycles) using a set of standard reaction protocols demonstrate the potential of the new eco-compatible approach for the macrocyclic library generation.

Electron-transporting layer doped with cesium azide for high-performance phosphorescent and tandem white organic light-emitting devices

NASA Astrophysics Data System (ADS)

Yu, Yaoyao; Chen, Xingming; Jin, Yu; Wu, Zhijun; Yu, Ye; Lin, Wenyan; Yang, Huishan

2017-07-01

Cesium azide was employed as an effective n-dopant in the electron-transporting layer (ETL) of organic light-emitting devices (OLEDs) owing to its low deposition temperature and high ambient stability. By doping cesium azide onto 4,7-diphenyl-1,10-phenanthroline, a green phosphorescent OLED having best efficiencies of 66.25 cd A-1, 81.22 lm W-1 and 18.82% was realized. Moreover, the efficiency roll-off from 1000 cd m-2 to 10 000 cd m-2 is only 12.9%, which is comparable with or even lower than that of devices utilizing the co-host system. Physical mechanisms for the improvement of device performance were studied in depth by analyzing the current density-voltage (J-V) characteristics of the electron-only devices. In particular, by comparing the J-V characteristics of the electron-only devices instead of applying the complicated ultraviolet photoelectron spectrometer measurements, we deduced the decrease in barrier height for electron injection at the ETL/cathode contact. Finally, an efficient tandem white OLED utilizing the n-doped layer in the charge generation unit (CGU) was constructed. As far as we know, this is the first report on the application of this CGU for fabricating tandem white OLEDs. The emissions of the tandem device are all in the warm white region from 1213 cd m-2 to 10870 cd m-2, as is beneficial to the lighting application.

The First Molybdenum(VI) and Tungsten(VI) Oxoazides MO2(N3)2, MO2(N3)2⋅2 CH3CN, (bipy)MO2(N3)2, and [MO2(N3)4](2-) (M=Mo, W).

PubMed

Haiges, Ralf; Skotnitzki, Juri; Fang, Zongtang; Dixon, David A; Christe, Karl O

2015-08-10

Molybdenum(VI) and tungsten(VI) dioxodiazide, MO2(N3)2 (M=Mo, W), were prepared through fluoride-azide exchange reactions between MO2F2 and Me3SiN3 in SO2 solution. In acetonitrile solution, the fluoride-azide exchange resulted in the isolation of the adducts MO2(N3)2⋅2 CH3CN. The subsequent reaction of MO2(N3)2 with 2,2'-bipyridine (bipy) gave the bipyridine adducts (bipy)MO2(N3)2. The hydrolysis of (bipy)MoO2(N3)2 resulted in the formation and isolation of [(bipy)MoO2N3]2O. The tetraazido anions [MO2(N3)4](2-) were obtained by the reaction of MO2(N3)2 with two equivalents of ionic azide. Most molybdenum(VI) and tungsten(VI) dioxoazides were fully characterized by their vibrational spectra, impact, friction, and thermal sensitivity data and, in the case of (bipy)MoO2(N3)2, (bipy)WO2(N3)2, [PPh4]2[MoO2(N3)4], [PPh4]2[WO2(N3)4], and [(bipy)MoO2N3]2O by their X-ray crystal structures. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrochemically protected copper(I)-catalyzed azide-alkyne cycloaddition.

PubMed

Hong, Vu; Udit, Andrew K; Evans, Richard A; Finn, M G

2008-06-16

The copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction has found broad application in myriad fields. For the most demanding applications that require high yields at low substrate concentrations, highly active but air-sensitive copper complexes must be used. We describe here the use of an electrochemical potential to maintain catalysts in the active Cu(I) oxidation state in the presence of air. This simple procedure efficiently achieves excellent yields of CuAAC products from both small-molecule and protein substrates without the use of potentially damaging chemical reducing agents. A new water-soluble carboxylated version of the popular tris(benzyltriazolylmethyl)amine (TBTA) ligand is also described. Cyclic voltammetry revealed reversible or quasi-reversible electrochemical redox behavior of copper complexes of the TBTA derivative (2; E(1/2)=60 mV vs. Ag/AgCl), sulfonated bathophenanthroline (3; E(1/2)=-60 mV), and sulfonated tris(benzimidazoylmethyl)amine (4; E(1/2) approximately -70 mV), and showed catalytic turnover to be rapid relative to the voltammetry time scale. Under the influence of a -200 mV potential that was established by using a reticulated vitreous carbon working electrode, CuSO4 and 3 formed a superior catalyst. Electrochemically protected bioconjugations in air were performed by using bacteriophage Qbeta that was derivatized with azide moieties at surface lysine residues. Complete derivatization of more than 600 reactive sites per particle was demonstrated within 12 h of electrolysis with substoichiometric quantities of Cu3.

Functional Group Analysis.

ERIC Educational Resources Information Center

Smith, Walter T., Jr.; Patterson, John M.

1984-01-01

Literature on analytical methods related to the functional groups of 17 chemical compounds is reviewed. These compounds include acids, acid azides, alcohols, aldehydes, ketones, amino acids, aromatic hydrocarbons, carbodiimides, carbohydrates, ethers, nitro compounds, nitrosamines, organometallic compounds, peroxides, phenols, silicon compounds,…

New Methods for the Site-Selective Placement of Peptides on a Microelectrode Array: Probing VEGF-v107 Binding as Proof of Concept.

PubMed

Graaf, Matthew D; Marquez, Bernadette V; Yeh, Nai-Hua; Lapi, Suzanne E; Moeller, Kevin D

2016-10-21

Cu(I)-catalyzed "click" reactions cannot be performed on a borate ester derived polymer coating on a microelectrode array because the Cu(II) precursor for the catalyst triggers background reactions between both acetylene and azide groups with the polymer surface. Fortunately, the Cu(II)-background reaction can itself be used to site-selectively add the acetylene and azide nucleophiles to the surface of the array. In this way, molecules previously functionalized for use in "click" reactions can be added directly to the array. In a similar fashion, activated esters can be added site-selectively to a borate ester coated array. The new chemistry can be used to explore new biological interactions on the arrays. Specifically, the binding of a v107 derived peptide with both human and murine VEGF was probed using a functionalized microelectrode array.

Second-Generation Difluorinated Cyclooctynes for Copper-Free Click Chemistry

PubMed Central

2008-01-01

The 1,3-dipolar cycloaddition of azides and activated alkynes has been used for site-selective labeling of biomolecules in vitro and in vivo. While copper catalysis has been widely employed to activate terminal alkynes for [3 + 2] cycloaddition, this method, often termed “click chemistry”, is currently incompatible with living systems because of the toxicity of the metal. We recently reported a difluorinated cyclooctyne (DIFO) reagent that rapidly reacts with azides in living cells without the need for copper catalysis. Here we report a novel class of DIFO reagents for copper-free click chemistry that are considerably more synthetically tractable. The new analogues maintained the same elevated rates of [3 + 2] cycloaddition as the parent compound and were used for imaging glycans on live cells. These second-generation DIFO reagents should expand the use of copper-free click chemistry in the hands of biologists. PMID:18680289

A General Synthetic Approach for Designing Epitope Targeted Macrocyclic Peptide Ligands.

PubMed

Das, Samir; Nag, Arundhati; Liang, JingXin; Bunck, David N; Umeda, Aiko; Farrow, Blake; Coppock, Matthew B; Sarkes, Deborah A; Finch, Amethist S; Agnew, Heather D; Pitram, Suresh; Lai, Bert; Yu, Mary Beth; Museth, A Katrine; Deyle, Kaycie M; Lepe, Bianca; Rodriguez-Rivera, Frances P; McCarthy, Amy; Alvarez-Villalonga, Belen; Chen, Ann; Heath, John; Stratis-Cullum, Dimitra N; Heath, James R

2015-11-02

We describe a general synthetic strategy for developing high-affinity peptide binders against specific epitopes of challenging protein biomarkers. The epitope of interest is synthesized as a polypeptide, with a detection biotin tag and a strategically placed azide (or alkyne) presenting amino acid. This synthetic epitope (SynEp) is incubated with a library of complementary alkyne or azide presenting peptides. Library elements that bind the SynEp in the correct orientation undergo the Huisgen cycloaddition, and are covalently linked to the SynEp. Hit peptides are tested against the full-length protein to identify the best binder. We describe development of epitope-targeted linear or macrocycle peptide ligands against 12 different diagnostic or therapeutic analytes. The general epitope targeting capability for these low molecular weight synthetic ligands enables a range of therapeutic and diagnostic applications, similar to those of monoclonal antibodies. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Selective chemical labeling reveals the genome-wide distribution of 5-hydroxymethylcytosine.

PubMed

Song, Chun-Xiao; Szulwach, Keith E; Fu, Ye; Dai, Qing; Yi, Chengqi; Li, Xuekun; Li, Yujing; Chen, Chih-Hsin; Zhang, Wen; Jian, Xing; Wang, Jing; Zhang, Li; Looney, Timothy J; Zhang, Baichen; Godley, Lucy A; Hicks, Leslie M; Lahn, Bruce T; Jin, Peng; He, Chuan

2011-01-01

In contrast to 5-methylcytosine (5-mC), which has been studied extensively, little is known about 5-hydroxymethylcytosine (5-hmC), a recently identified epigenetic modification present in substantial amounts in certain mammalian cell types. Here we present a method for determining the genome-wide distribution of 5-hmC. We use the T4 bacteriophage β-glucosyltransferase to transfer an engineered glucose moiety containing an azide group onto the hydroxyl group of 5-hmC. The azide group can be chemically modified with biotin for detection, affinity enrichment and sequencing of 5-hmC-containing DNA fragments in mammalian genomes. Using this method, we demonstrate that 5-hmC is present in human cell lines beyond those previously recognized. We also find a gene expression level-dependent enrichment of intragenic 5-hmC in mouse cerebellum and an age-dependent acquisition of this modification in specific gene bodies linked to neurodegenerative disorders.

Functionalization of multi-walled carbon nanotubes with thermo-responsive azide-terminated poly(N-isopropylacrylamide) via click reactions.

PubMed

Su, Xin; Shuai, Ya; Guo, Zanru; Feng, Yujun

2013-04-18

Covalently functionalized multi-walled carbon nanotubes (MWNTs) were prepared by grafting well-defined thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) via click reactions. First, azide-terminated poly(N-isopropylacrylamide) (N3-PNIPAM) was synthesized by reversible addition fragmentation chain-transfer (RAFT) polymerization, and then the N₃-PNIPAM moiety was connected onto MWNTs by click chemistry. The products were characterized by means of FT-IR, TGA and TEM. The results show that the modification of MWNTs is very successful and MWNTs functionalized by N₃-PNIPAM (MWNTs-PNIPAM) have good solubility and stability in water. TEM images show the functionalized MWNTs are dispersed individually, indicating that the bundles of original MWNTs are separated into individual tubes by surface modification with polymer chains. These MWNTs modified with PNIPAM represent a potential nano-material for preparation of hydrophilic composite materials.

Spectral Studies of Iron Coordination in Hemeprotein Complexes

PubMed Central

Brill, Arthur S.; Sandberg, Howard E.

1968-01-01

In order to evaluate the feasibility of observing the spectral behavior of protein groups in the coordination sphere of the iron in hemeproteins, criteria are developed to determine whether or not the application of difference absorption spectroscopy to the study of complex formation will be successful. Absolute absorption spectra, 300-1100 mμ, from bacterial catalase complexes are displayed, and the infrared bands correlated with magnetic susceptibility values of similar complexes of other hemeproteins. Dissociation constants for the formation of cyanide and azide complexes of metmyoglobin, methemoglobin, bacterial catalase, and horseradish peroxidase are given. Difference spectra, 210-280 mμ, are displayed for cyanide and azide complexes of these hemeproteins. A band at 235-241 mμ is found in the difference spectra of all low-spin vs. high-spin complexes. The factors which favor the assignment of this band to a transition involving a histidine residue are presented. PMID:5699802

Ligands of low electronegativity in the vsepr model: molecular pseudohalides

NASA Astrophysics Data System (ADS)

Glidewell, Christopher; Holden, H. Diane

Equilibrium structures and force constants at linearity, for the skeletal bending mode δ(RNX) have been calculated in the MNDO approximation for 67 isocyanates, isothio-cyanates and azides, RNXY (XY = CO, CS or N 2) and the corresponding structures and force constants, δ(RCN), for 12 fulminates RCNO. Fulminates all have linear skeletons, but for RNXY the molecular skeleton is linear at atom X only if it is linear at N also ; otherwise the skeleton RNXY has a trans planar structure. Bending force constants are large and negative for all azides studied, negative for methyl and substituted methyl isocyanates and isothiocyanates and very small and positive for silyl and substituted silyl isothiocyanates: for silyl and substituted silyl isocyanales, the force constant is small and positive when the R group has effective C2v symmetry, but small and negative when the R group has only effective Cs symmetry.

Cage-like bifunctional chelators, copper-64 radiopharmaceuticals and PET imaging using the same

DOEpatents

Conti, Peter S.; Cai, Hancheng; Li, Zibo; Liu, Shuanglong

2016-08-02

Disclosed is a class of versatile Sarcophagine based bifunctional chelators (BFCs) containing a hexa-aza cage for labeling with metals having either imaging, therapeutic or contrast applications radiolabeling and one or more linkers (A) and (B). The compounds have the general formula ##STR00001## where A is a functional group selected from group consisting of an amine, a carboxylic acid, an ester, a carbonyl, a thiol, an azide and an alkene, and B is a functional group selected from the group consisting of hydrogen, an amine, a carboxylic acid, and ester, a carbonyl, a thiol, an azide and an alkene. Also disclosed are conjugate of the BFC and a targeting moiety, which may be a peptide or antibody. Also disclosed are metal complexes of the BFC/targeting moiety conjugates that are useful as radiopharmaceuticals, imaging agents or contrast agents.

Tricyanomethane and Its Ketenimine Tautomer: Generation from Different Precursors and Analysis in Solution, Argon Matrix, and as a Single Crystal.

PubMed

Banert, Klaus; Chityala, Madhu; Hagedorn, Manfred; Beckers, Helmut; Stüker, Tony; Riedel, Sebastian; Rüffer, Tobias; Lang, Heinrich

2017-08-01

Solutions of azidomethylidenemalononitrile were photolyzed at low temperatures to produce the corresponding 2H-azirine and tricyanomethane, which were analyzed by low-temperature NMR spectroscopy. The latter product was also observed after short thermolysis of the azide precursor in solution whereas irradiation of the azide isolated in an argon matrix did not lead to tricyanomethane, but to unequivocal detection of the tautomeric ketenimine by IR spectroscopy for the first time. When the long-known "aquoethereal" greenish phase generated from potassium tricyanomethanide, dilute sulfuric acid, and diethyl ether was rapidly evaporated and sublimed, a mixture of hydronium tricyanomethanide and tricyanomethane was formed instead of the previously claimed ketenimine tautomer. Under special conditions of sublimation, single crystals of tricyanomethane could be isolated, which enabled the analysis of the molecular structure by X-ray diffraction. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The application of CuAAC 'click' chemistry to catenane and rotaxane synthesis.

PubMed

Hänni, Kevin D; Leigh, David A

2010-04-01

The copper(I)-catalysed azide-alkyne cycloaddition (the CuAAC 'click' reaction) is proving to be a powerful new tool for the construction of mechanically interlocked molecular-level architectures. The reaction is highly selective for the functional groups involved (terminal alkynes and azides) and the experimental conditions are mild and compatible with the weak and reversible intermolecular interactions generally used to template the assembly of interlocked structures. Since the CuAAC reaction was introduced as a means of making rotaxanes by an 'active template' mechanism in 2006, it has proven effective for the synthesis of numerous different types of rotaxanes, catenanes and molecular shuttles by passive as well as active template strategies. Mechanistic insights into the CuAAC reaction itself have been provided by unexpected results encountered during the preparation of rotaxanes. In this tutorial review we highlight the rapidly increasing utility and future potential of the CuAAC reaction in mechanically interlocked molecule synthesis.

Second-generation difluorinated cyclooctynes for copper-free click chemistry.

PubMed

Codelli, Julian A; Baskin, Jeremy M; Agard, Nicholas J; Bertozzi, Carolyn R

2008-08-27

The 1,3-dipolar cycloaddition of azides and activated alkynes has been used for site-selective labeling of biomolecules in vitro and in vivo. While copper catalysis has been widely employed to activate terminal alkynes for [3 + 2] cycloaddition, this method, often termed "click chemistry", is currently incompatible with living systems because of the toxicity of the metal. We recently reported a difluorinated cyclooctyne (DIFO) reagent that rapidly reacts with azides in living cells without the need for copper catalysis. Here we report a novel class of DIFO reagents for copper-free click chemistry that are considerably more synthetically tractable. The new analogues maintained the same elevated rates of [3 + 2] cycloaddition as the parent compound and were used for imaging glycans on live cells. These second-generation DIFO reagents should expand the use of copper-free click chemistry in the hands of biologists.

Azido, triazolyl, and alkynyl complexes of gold(I): syntheses, structures, and ligand effects.

PubMed

Robilotto, Thomas J; Deligonul, Nihal; Updegraff, James B; Gray, Thomas G

2013-08-19

Gold(I) triazolyl complexes are prepared in [3 + 2] cycloaddition reactions of (tertiary phosphine)gold(I) azides with terminal alkynes. Seven such triazolyl complexes, not previously prepared, are described. Reducible functional groups are accommodated. In addition, two new (N-heterocyclic carbene)gold(I) azides and two new gold(I) alkynyls are described. Eight complexes are crystallographically authenticated; aurophilic interactions appear in one structure only. The packing diagrams of gold(I) triazolyls all show intermolecular hydrogen bonding between N-1 of one molecule and N-3 of a neighbor. This hydrogen bonding permeates the crystal lattice. Density-functional theory calculations of (triphenylphosphine)gold(I) triazolyls and the corresponding alkynyls indicate that the triazolyl is a stronger trans-influencer than is the alkynyl, but the alkynyl is more electron-releasing. These results suggest that trans-influences in two-coordinate gold(I) complexes can be more than a simple matter of ligand donicity.

Functionalization of diamond nanoparticles using "click" chemistry.

PubMed

Barras, Alexandre; Szunerits, Sabine; Marcon, Lionel; Monfilliette-Dupont, Nicole; Boukherroub, Rabah

2010-08-17

The paper reports on covalent linking of different alkyne-containing (decyne, ethynylferrocene, and N-propargyl-1-pyrenecarboxamide) compounds to azide-terminated nanodiamond (ND) particles. Azide-terminated particles (ND-N(3)) were obtained from amine-terminated nanodiamond particles (ND-NH(2)) through the reaction with 4-azidobenzoic acid in the presence of a carbodiimide coupling agent. Functionalized ND particles with long alkyl chain groups can be easily dispersed in various organic solvents without any apparent precipitation after several hours. The course of the reaction was followed using Fourier transform infrared (FT-IR) spectroscopy, UV/vis spectroscopy, fluorescence, cyclic voltammetry, thermogravimetric analysis (TGA), and particle size measurements. The surface loading of pyrene bearing a terminal acetylene group was found to be 0.54 mmol/g. Because of its gentle nature and specificity, the chemistry developed in this work can be used as a general platform for the preparation of functional nanoparticles for various applications.

Lithium Azide as an Electrolyte Additive for All-Solid-State Lithium-Sulfur Batteries.

PubMed

Eshetu, Gebrekidan Gebresilassie; Judez, Xabier; Li, Chunmei; Bondarchuk, Oleksandr; Rodriguez-Martinez, Lide M; Zhang, Heng; Armand, Michel

2017-11-27

Of the various beyond-lithium-ion battery technologies, lithium-sulfur (Li-S) batteries have an appealing theoretical energy density and are being intensely investigated as next-generation rechargeable lithium-metal batteries. However, the stability of the lithium-metal (Li°) anode is among the most urgent challenges that need to be addressed to ensure the long-term stability of Li-S batteries. Herein, we report lithium azide (LiN 3 ) as a novel electrolyte additive for all-solid-state Li-S batteries (ASSLSBs). It results in the formation of a thin, compact and highly conductive passivation layer on the Li° anode, thereby avoiding dendrite formation, and polysulfide shuttling. It greatly enhances the cycling performance, Coulombic and energy efficiencies of ASSLSBs, outperforming the state-of-the-art additive lithium nitrate (LiNO 3 ). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Expanding iClick to group 9 metals

DOE PAGES

Beto, Christopher C.; Yang, Xi; Powers, Andrew R.; ...

2015-09-01

In this study, the iClick (inorganic click) reactions between gold-acetylides and group 9 transition metal-azide complexes are presented. Complexes [Rh(CO)(PPh 3) 2][PPh 3Au](μ-N 3C 2C 6H 4NO 2) (3), {[Rh(CO)(PPh 3)][PPh 3Au](μ-N 3C 2C 6H 4NO 2)} 2 (4), and [(CO)(PPh 3) 2IrAuPPh 3](μ-N 3C 2C 6H 4NO 2) (6) have been synthesized via M-azide/M-acetylide cycloaddition reactions between PPh 3Au(Ctriple bond; length of mdashCC 6H 4NO 2) (2) and either Rh(CO)(PPh 3) 2N 3 (1), or Ir(CO)(PPh 3) 2N 3 (5). Complexes 3, 4, and 6 have been characterized by a combination of NMR spectroscopies, crystallography and combustion analysis.

Synthesis, structure and antimicrobial evaluation of a new gossypol triazole conjugates functionalized with aliphatic chains and benzyloxy groups.

PubMed

Pyta, Krystian; Blecha, Marietta; Janas, Anna; Klich, Katarzyna; Pecyna, Paulina; Gajecka, Marzena; Przybylski, Piotr

2016-09-01

Synthetic limitations in the copper-catalyzed azide alkyne cycloaddition (CuAAC) on gossypol's skeleton functionalized with alkyne (2) or azide (3) groups have been indicated. Modified approach to the synthesis of new gossypol-triazole conjugates yielded new compounds (24-31) being potential fungicides. Spectroscopic studies of triazole conjugates 24-31 have revealed their structures in solution, i.e., the presence of enamine-enamine tautomeric forms and π-π stacking intramolecular interactions between triazole arms. Biological evaluation of the new gossypol-triazole conjugates revealed the potency of 30 and 31 derivatives, having triazole-benzyloxy moieties, comparable with that of miconazole against Fusarium oxysporum. The results of HPLC evaluation of ergosterol content in different fungi strains upon treatment of gossypol and its derivatives enabled to propose a mechanism of antifungal activity of these compounds. Copyright © 2016 Elsevier Ltd. All rights reserved.

A recyclable and reusable supported Cu(I) catalyzed azide-alkyne click polymerization

NASA Astrophysics Data System (ADS)

Wu, Haiqiang; Li, Hongkun; Kwok, Ryan T. K.; Zhao, Engui; Sun, Jing Zhi; Qin, Anjun; Tang, Ben Zhong

2014-05-01

The azide-alkyne click polymerization (AACP) has emerged as a powerful tool for the synthesis of functional polytriazoles. While, for the Cu(I)-catalyzed AACP, the removal of the catalytic Cu(I) species from the resulting polytriazoles is difficult, and the research on the recyclability and reusability of the catalyst remains intact. Herein, we reported the first example of using recyclable and reusable supported Cu(I) catalyst of CuI@A-21 for the AACP. CuI@A-21 could not only efficiently catalyze the AACP but also be reused for at least 4 cycles. Moreover, pronounced reduction of copper residues in the products was achieved. Apart from being a green and cost-effective polymer synthesis strategy, this method will also broaden the application of AACP in material and biological sciences and provide guidelines for other polymerizations with metal catalysts.

Concise and diversity-oriented synthesis of ligand arm-functionalized azoamides.

PubMed

Urankar, Damijana; Kosmrlj, Janez

2008-01-01

Azoamides, previously established as bioactive intracellular GSH-depleting agents, were decorated with a terminal alkyne moiety to 4 and then were transformed, by copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC), into different ligand-arm functionalized azoamides 6. Azides 5 having ligand-arms amenable for binding to platinum(II) were selected for this study. Because, for the fragile azoamides 4, the typically employed reaction conditions for CuAAC failed, several alternative solvents and copper catalysts were tested. Excellent results were obtained with copper(II) sulfate pentahydrate/metallic copper and especially with heterogeneous catalysts, such as copper-in-charcoal, cupric oxide, and cuprous oxide. The heterogeneous catalysts were employed to obtain the desired products in almost quantitative yields by a simple three-step "stir-filter-evaporate" protocol with no or negligible contamination with copper impurities. This is of particular importance because compounds 6 have been designed for coordination.

Sensitive, site-specific, and stable vibrational probe of local protein environments: 4-azidomethyl-L-phenylalanine.

PubMed

Bazewicz, Christopher G; Liskov, Melanie T; Hines, Kevin J; Brewer, Scott H

2013-08-01

We have synthesized the unnatural amino acid (UAA), 4-azidomethyl-L-phenylalanine (pN₃CH₂Phe), to serve as an effective vibrational reporter of local protein environments. The position, extinction coefficient, and sensitivity to local environment of the azide asymmetric stretch vibration of pN₃CH₂Phe are compared to the vibrational reporters: 4-cyano-L-phenylalanine (pCNPhe) and 4-azido-L-phenylalanine (pN₃Phe). This UAA was genetically incorporated in a site-specific manner utilizing an engineered, orthogonal aminoacyl-tRNA synthetase in response to an amber codon with high efficiency and fidelity into two distinct sites in superfolder green fluorescent protein (sfGFP). This allowed for the dependence of the azide asymmetric stretch vibration of pN₃CH₂Phe to different protein environments to be measured. The photostability of pN₃CH₂Phe was also measured relative to the photoreactive UAA, pN₃Phe.

Study of monopropellants for electrothermal thrusters

NASA Technical Reports Server (NTRS)

Kuenzly, J. D.

1974-01-01

A 333 mN electrothermal thruster designed to use MIL-grade hydrazine was demonstrated to be suitable for operation with low freezing point monopropellants containing hydrazine azide, monomethylhydrazine, unsymmetrical-dimethylhydrazine and ammonia. The steady-state specific impulse was greater than 200 sec for all propellants. The pulsed-mode specific impulse for an azide blend exceeded 175 sec for pulse widths greater than 50 msec; propellants containing carbonaceous species delivered 175 sec pulsed-mode specific impulses for pulse widths greater than 100 msec. Longer thrust chamber residence times were required for the carbonaceous propellants; the original thruster design was modified by increasing the characteristic chamber length and screen packing density. Specific recommendations were made for the work required to design and develop flight worthy thrusters, including methods to increase propellant dispersal at injection, thruster geometry changes to reduce holding power levels and methods to initiate the rapid decomposition of the carbonaceous propellants.

First synthesis of 2'-deoxyfluoropuromycin analogues: experimental insight into the mechanism of the Staudinger reaction.

PubMed

Charafeddine, Adib; Dayoub, Wissam; Chapuis, Hubert; Strazewski, Peter

2007-01-01

The N(6),N(6)-dedimethyl-2'-deoxyfluoro analogue of puromycin (= 3'-deoxy-N(6),N(6)-dimethyl-3'-[O-methyltyrosylamido]adenosine), its 2',3'-regioisomer and a 3'-cytidyl-5'-(2'-deoxyfluoro)puromycyl dinucleotide analogue were synthesized following an approach involving i) the diastereospecific nitrite-assisted formation of a lyxo nucleosidic 2',3'-epoxide from an adenosine-2',3'-ditriflate derivative in a biphasic solvent mixture; ii) the regio- and stereoselective epoxide ring opening with sodium azide under mildly acidic aqueous conditions, iii) the stereospecific introduction of the fluor atom using DAST and iv) the reaction between the nucleosidyl or dinucleotidyl azide and an active ester of the N-protected amino acid using highly efficient solution conditions for the Staudinger-Vilarrasa coupling, to obtain the corresponding carboxamide directly from the in situ formed iminophosphorane. This coupling reaction furnished sterically quite demanding amides in 94 % isolated yields under very mild conditions and should therefore be of a more general value. Under certain reaction conditions we isolated (amino)acyltriazene derivatives from which dinitrogen was not eliminated. These secondary products are trapped and stabilized witnesses of the first intermediate of the Staudinger reaction, the phosphatriazenes (phosphazides, triazaphosphadienes) which usually eliminate dinitrogen in situ and rapidly rearrange into iminophosphoranes, unless they are derived from conjugated or sterically bulky azides and phosphines. The acyltriazenes could either be thermally decomposed or converted to the corresponding N-alkyl carboxamides through proton-assisted elimination of dinitrogen. All compounds were carefully characterized through MS spectrometry, (1)H, (19)F, (31)P and (13)C NMR spectroscopy.

Ultrafast 25-fs relaxation in highly excited states of methyl azide mediated by strong nonadiabatic coupling.

PubMed

Peters, William K; Couch, David E; Mignolet, Benoit; Shi, Xuetao; Nguyen, Quynh L; Fortenberry, Ryan C; Schlegel, H Bernhard; Remacle, Françoise; Kapteyn, Henry C; Murnane, Margaret M; Li, Wen

2017-12-26

Highly excited electronic states are challenging to explore experimentally and theoretically-due to the large density of states and the fact that small structural changes lead to large changes in electronic character with associated strong nonadiabatic dynamics. They can play a key role in astrophysical and ionospheric chemistry, as well as the detonation chemistry of high-energy density materials. Here, we implement ultrafast vacuum-UV (VUV)-driven electron-ion coincidence imaging spectroscopy to directly probe the reaction pathways of highly excited states of energetic molecules-in this case, methyl azide. Our data, combined with advanced theoretical simulations, show that photoexcitation of methyl azide by a 10-fs UV pulse at 8 eV drives fast structural changes and strong nonadiabatic coupling that leads to relaxation to other excited states on a surprisingly fast timescale of 25 fs. This ultrafast relaxation differs from dynamics occurring on lower excited states, where the timescale required for the wavepacket to reach a region of strong nonadiabatic coupling is typically much longer. Moreover, our theoretical calculations show that ultrafast relaxation of the wavepacket to a lower excited state occurs along one of the conical intersection seams before reaching the minimum energy conical intersection. These findings are important for understanding the unique strongly coupled non-Born-Oppenheimer molecular dynamics of VUV-excited energetic molecules. Although such observations have been predicted for many years, this study represents one of the few where such strongly coupled non-Born-Oppenheimer molecular dynamics of VUV-excited energetic molecules have been conclusively observed directly, making it possible to identify the ultrafast reaction pathways.

RESPIRATORY METABOLISM OF NORMAL AND DIVISIONLESS STRAINS OF CANDIDA ALBICANS

PubMed Central

Ward, John M.; Nickerson, Walter J.

1958-01-01

Respiration of a normal strain of Candida albicans was compared with that of a divisionless mutant which has a biochemical lesion such that metabolically generated hydrogen "spills over," during growth, for non-specific dye reduction. This waste is not at expense of growth, since both strains grow at essentially similar rates, nor at expense of respiration, since the mutant reduces oxygen more rapidly than the normal strain. Respiration in both strains is qualitatively similar, and seemingly unique among highly aerobic organisms in that it is not mediated by cytochrome oxidase. In resting cells of both strains, respiration is not only resistant to, but markedly stimulated by, high concentrations of cyanide, carbon monoxide, and azide. In contrast, growth of these yeasts is inhibited by low concentrations of cyanide and azide. Cytochrome oxidase could not be detected in cell-free preparations; reduced cytochrome c was not oxidized by such preparations. Cytochrome bands could not be observed in thick cell suspensions treated with reducing agents. However, incorporation of superoptimal levels of zinc and iron into the culture medium resulted in growth of cells possessing distinct cytochrome bands; respiration of these cells remained insensitive to cyanide, monoxide, and azide, and the bands were maintained in a reduced form on oxygenation. In the divisionless yeast, tetrazolium dyes compete with oxygen for reduction; this is not the case in the normal strain. The firmness with which hydrogen transfer is channeled in the latter for reduction of disulfide bonds (of importance in the division mechanism) and of oxygen, is contrasted with the lack of such control in the mutant. PMID:13514006

Cell-free identification of novel N-myristoylated proteins from complementary DNA resources using bioorthogonal myristic acid analogues.

PubMed

Takamitsu, Emi; Fukunaga, Kazuki; Iio, Yusuke; Moriya, Koko; Utsumi, Toshihiko

2014-11-01

To establish a non-radioactive, cell-free detection system for protein N-myristoylation, metabolic labeling in a cell-free protein synthesis system using bioorthogonal myristic acid analogues was performed. After Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) with a biotin tag, the tagged proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and blotted on a polyvinylidene fluoride (PVDF) membrane, and then protein N-myristoylation was detected by enhanced chemiluminescence (ECL) using horseradish peroxidase (HRP)-conjugated streptavidin. The results showed that metabolic labeling in an insect cell-free protein synthesis system using an azide analogue of myristic acid followed by CuAAC with alkynyl biotin was the most effective strategy for cell-free detection of protein N-myristoylation. To determine whether the newly developed detection method can be applied for the detection of novel N-myristoylated proteins from complementary DNA (cDNA) resources, four candidate cDNA clones were selected from a human cDNA resource and their susceptibility to protein N-myristoylation was evaluated using the newly developed strategy. As a result, the products of three cDNA clones were found to be novel N-myristoylated protein, and myristoylation-dependent specific intracellular localization was observed for two novel N-myristoylated proteins. Thus, the metabolic labeling in an insect cell-free protein synthesis system using bioorthogonal azide analogue of myristic acid was an effective strategy to identify novel N-myristoylated proteins from cDNA resources. Copyright © 2014 Elsevier Inc. All rights reserved.

Total morphine stability in urine specimens stored under various conditions.

PubMed

Chang, B L; Huang, M K; Tsai, Y Y

2000-09-01

The stability of total morphine in urine stored under various conditions was studied using control and experimental specimens. Samples in the control group were prepared using drug-free urine spiked with morphine at three concentration levels (300, 1000, and 2500 ng/mL), each with the pH adjusted to 5.5, 6.5, and 7.5. Samples in the experimental group came from 20 alleged heroin addicts (provided by Taipei Municipal Psychiatric Hospital). Samples in both groups were divided into two categories--one with and one without the precipitate (formed at 0 degrees C) removed. Samples in each of these two categories were further divided into two sub-groups--one with and one without sodium azide (0.05%) added. Total morphine contents in these samples were first determined by gas chromatography-mass spectrometry prior to storage and at 6, 12, 18, and 24 months following storage at -20, 4, 25, and 35 degrees C. Effects of sample treatment (azide addition and precipitate removal), pH, and storage temperature and length were evaluated by examining the percentage of total morphine remaining at the four time intervals following the initial determination. Major findings were as follows: (1) total morphine decomposition was minimal when stored for 12 months at -20 degrees C, which is a common current practice; (2) samples with lower initial sample pH had slower total morphine decomposition rates; and (3) azide addition appeared to have no detectable effect, whereas precipitate removal appeared to marginally reduce the decomposition rate, especially for samples with lower pH.

Poly(Acrylic Acid-b-Styrene) Amphiphilic Multiblock Copolymers as Building Blocks for the Assembly of Discrete Nanoparticles

PubMed Central

Greene, Anna C.; Zhu, Jiahua; Pochan, Darrin J.; Jia, Xinqiao; Kiick, Kristi L.

2011-01-01

In order to expand the utility of current polymeric micellar systems, we have developed amphiphilic multiblock copolymers containing alternating blocks of poly(acrylic acid) and poly(styrene). Heterotelechelic poly(tert-butyl acrylate-b-styrene) diblock copolymers containing an α-alkyne and an ω-azide were synthesized by atom transfer radical polymerization (ATRP), allowing control over the molecular weight while maintaining narrow polydispersity indices. The multiblock copolymers were constructed by copper-catalyzed azide-alkyne cycloaddition of azide-alkyne end functional diblock copolymers which were then characterized by 1H NMR, FT-IR and SEC. The tert-butyl moieties of the poly(tert-butyl acrylate-b-styrene) multiblock copolymers were easily removed to form the poly(acrylic acid-b-styrene) multiblock copolymer ((PAA-PS)9), which contained up to 9 diblock repeats. The amphiphilic multiblock (PAA-PS)9 (Mn = 73.3 kg/mol) was self-assembled by dissolution into tetrahydrofuran and extensive dialysis against deionized water for 4 days. The critical micelle concentration (CMC) for (PAA-PS)9 was determined by fluorescence spectroscopy using pyrene as a fluorescent probe and was found to be very low at 2 × 10-4 mg/mL. The (PAA-PS)9 multiblock was also analyzed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The hydrodynamic diameter of the particles was found to be 11 nm. Discrete spherical particles were observed by TEM with an average particle diameter of 14 nm. The poly(acrylic acid) periphery of the spherical particles should allow for future conjugation of biomolecules. PMID:21552373

Efficient and Tunable Three-Dimensional Functionalization of Fully Zwitterionic Antifouling Surface Coatings.

PubMed

Lange, Stefanie C; van Andel, Esther; Smulders, Maarten M J; Zuilhof, Han

2016-10-11

To enhance the sensitivity and selectivity of surface-based (bio)sensors, it is of crucial importance to diminish background signals that arise from the nonspecific binding of biomolecules, so-called biofouling. Zwitterionic polymer brushes have been shown to be excellent antifouling materials. However, for sensing purposes, antifouling does not suffice but needs to be combined with the possibility to efficiently modify the brush with recognition units. So far this has been achieved only at the expense of either antifouling properties or binding capacity. Herein we present a conceptually new approach by integrating both characteristics into a single tailor-made monomer: a novel sulfobetaine-based zwitterionic monomer equipped with a clickable azide moiety. Copolymerization of this monomer with a well-established standard sulfobetaine monomer results in highly antifouling surface coatings with a large yet tunable number of clickable groups present throughout the entire brush. Subsequent functionalization of the azido brushes via widely used strain-promoted alkyne azide click reactions yields fully zwitterionic 3D-functionalized coatings with a recognition unit of choice that can be tailored for any specific application. Here we show a proof of principle with biotin-functionalized brushes on Si 3 N 4 that combine excellent antifouling properties with specific avidin binding from a protein mixture. The signal-to-noise ratio is significantly improved over that of traditional chain-end modification of sulfobetaine polymer brushes, even if the azide content is lowered to 1%. This therefore offers a viable approach to the development of biosensors with greatly enhanced performance on any surface.

Relationships between Respiration and Susceptibility to Azole Antifungals in Candida glabrata

PubMed Central

Brun, Sophie; Aubry, Christophe; Lima, Osana; Filmon, Robert; Bergès, Thierry; Chabasse, Dominique; Bouchara, Jean-Philippe

2003-01-01

Over the past two decades, the incidence of infections due to Candida glabrata, a yeast with intrinsic low susceptibility to azole antifungals, has increased markedly. Respiratory deficiency due to mutations in mitochondrial DNA (mtDNA) associated with resistance to azoles frequently occurs in vitro in this species. In order to specify the relationships between respiration and azole susceptibility, the effects of respiratory chain inhibitors on a wild-type isolate of C. glabrata were evaluated. Respiration of blastoconidia was immediately blocked after extemporaneous addition of potassium cyanide, whereas a 4-h preincubation was required for sodium azide. Antifungal susceptibility determined by a disk diffusion method on Casitone agar containing sodium azide showed a significant decrease in the susceptibility to azoles. Biweekly subculturing on Casitone agar supplemented with sodium azide was therefore performed. This resulted after 40 passages in the isolation of a respiration-deficient mutant, as suggested by its lack of growth on glycerol-containing agar. This respiratory deficiency was confirmed by flow cytometric analysis of blastoconidia stained with rhodamine 123 and by oxygraphy. Moreover, transmission electron microscopy and restriction endonuclease analysis of the mtDNA of mutant cells demonstrated the mitochondrial origin of the respiratory deficiency. Finally, this mutant exhibited cross-resistance to all the azoles tested. In conclusion, blockage of respiration in C. glabrata induces decreased susceptibility to azoles, culminating in azole resistance due to the deletion of mtDNA. This mechanism could explain the induction of petite mutations by azole antifungals which have been demonstrated to act directly on the mitochondrial respiratory chain. PMID:12604511

A theoretical DFT study on the structural parameters and azide-tetrazole equilibrium in substituted azidothiazole systems.

PubMed

Abu-Eittah, Rafie H; El-Kelany, Khaled E

2012-12-01

Azido-tetrazole equilibrium is sensitive to: substitution, solvent, temperature and phase. In this work, the effects of the type and position of substitution on the thiazole ring of azidothiazoles on its structural parameters and on the azido-tetrazole equilibrium have been theoretically investigated using the density functional procedures at the B3LYP/6-311G(∗∗) level of theory. This study includes the investigation of the equilibrium geometry, the transformation of the trans-conformer to the cis one then the ring closure to the tetrazole isomer. The transition states of the two steps were located, confirmed and the structural parameters were calculated. In all the steps of calculations, geometry optimization was considered. The results obtained indicate that substitution by: -NO(2) and -CN group shifts the equilibrium to the azide side and in some cases the tetrazole isomer is not obtained. On the other hand, substitution by: -NH(2) and -OH groups shifts the equilibrium to the tetrazole side and in some cases the azide isomer is not obtained and if formed changes spontaneously to the tetrazole isomer. The decisive parameters which determine the position of the equilibrium are: charge density on atoms N3 and N8, rearrangement of bond length and bond angles during the process of cyclization and variation of dipole moment as a result of cyclization. Results of this work indicate that substitution on C5 is more efficient than substitution on C4 of the thiazole ring. Copyright © 2012 Elsevier B.V. All rights reserved.

Degradable polymeric nanoparticles by aggregation of thermoresponsive polymers and ``click'' chemistry

NASA Astrophysics Data System (ADS)

Dworak, Andrzej; Lipowska, Daria; Szweda, Dawid; Suwinski, Jerzy; Trzebicka, Barbara; Szweda, Roza

2015-10-01

This study describes a novel approach to the preparation of crosslinked polymeric nanoparticles of controlled sizes that can be degraded under basic conditions. For this purpose thermoresponsive copolymers containing azide and alkyne functions were obtained by ATRP of di(ethylene glycol) monomethyl ether methacrylate (D) and 2-aminoethyl methacrylate (A) followed by post polymerization modification. The amino groups of A were reacted with propargyl chloroformate or 2-azido-1,3-dimethylimidazolinium hexafluorophosphate, which led to two types of copolymers. Increasing the temperature of aqueous solutions of the mixed copolymers caused their aggregation into spherical nanoparticles composed of both types of chains. Their dimensions could be controlled by changing the concentration and heating rate of the solutions. Covalent stabilization of aggregated chains was performed by a ``click'' reaction between the azide and alkyne groups. Due to the presence of a carbamate bond the nanoparticles undergo pH dependent degradation under mild basic conditions. The proposed procedure opens a route to new carriers for the controlled release of active species.This study describes a novel approach to the preparation of crosslinked polymeric nanoparticles of controlled sizes that can be degraded under basic conditions. For this purpose thermoresponsive copolymers containing azide and alkyne functions were obtained by ATRP of di(ethylene glycol) monomethyl ether methacrylate (D) and 2-aminoethyl methacrylate (A) followed by post polymerization modification. The amino groups of A were reacted with propargyl chloroformate or 2-azido-1,3-dimethylimidazolinium hexafluorophosphate, which led to two types of copolymers. Increasing the temperature of aqueous solutions of the mixed copolymers caused their aggregation into spherical nanoparticles composed of both types of chains. Their dimensions could be controlled by changing the concentration and heating rate of the solutions. Covalent stabilization of aggregated chains was performed by a ``click'' reaction between the azide and alkyne groups. Due to the presence of a carbamate bond the nanoparticles undergo pH dependent degradation under mild basic conditions. The proposed procedure opens a route to new carriers for the controlled release of active species. Electronic supplementary information (ESI) available: GPC-MALLS chromatograms for P(D-co-A)_1 and P(D-co-A)_2 copolymers, absorbance spectra of P(D-co-A)_1, P(D-co-A)_2, P(D-co-A_Pr) and P(D-co-A_Az) after reaction with ninhydrine. See DOI: 10.1039/c5nr04448k

Covalent growth factor tethering to direct neural stem cell differentiation and self-organization.

PubMed

Ham, Trevor R; Farrag, Mahmoud; Leipzig, Nic D

2017-04-15

Tethered growth factors offer exciting new possibilities for guiding stem cell behavior. However, many of the current methods present substantial drawbacks which can limit their application and confound results. In this work, we developed a new method for the site-specific covalent immobilization of azide-tagged growth factors and investigated its utility in a model system for guiding neural stem cell (NSC) behavior. An engineered interferon-γ (IFN-γ) fusion protein was tagged with an N-terminal azide group, and immobilized to two different dibenzocyclooctyne-functionalized biomimetic polysaccharides (chitosan and hyaluronan). We successfully immobilized azide-tagged IFN-γ under a wide variety of reaction conditions, both in solution and to bulk hydrogels. To understand the interplay between surface chemistry and protein immobilization, we cultured primary rat NSCs on both materials and showed pronounced biological effects. Expectedly, immobilized IFN-γ increased neuronal differentiation on both materials. Expression of other lineage markers varied depending on the material, suggesting that the interplay of surface chemistry and protein immobilization plays a large role in nuanced cell behavior. We also investigated the bioactivity of immobilized IFN-γ in a 3D environment in vivo and found that it sparked the robust formation of neural tube-like structures from encapsulated NSCs. These findings support a wide range of potential uses for this approach and provide further evidence that adult NSCs are capable of self-organization when exposed to the proper microenvironment. For stem cells to be used effectively in regenerative medicine applications, they must be provided with the appropriate cues and microenvironment so that they integrate with existing tissue. This study explores a new method for guiding stem cell behavior: covalent growth factor tethering. We found that adding an N-terminal azide-tag to interferon-γ enabled stable and robust Cu-free 'click' immobilization under a variety of physiologic conditions. We showed that the tagged growth factors retained their bioactivity when immobilized and were able to guide neural stem cell lineage commitment in vitro. We also showed self-organization and neurulation from neural stem cells in vivo. This approach will provide another tool for the orchestration of the complex signaling events required to guide stem cell integration. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Effect of Branched Gap Synthesis Parameters on Mechanical Properties of Rocket Propellants

DTIC Science & Technology

1995-12-01

modulus hydroxyl functionality glycidyl azide polymer hexanetriol hydroxy-terminated polybutadiene isophorone diisocyanate hydroxyl equivalent... hexanetriol (HT), glycerol and polyethylene glycol (PEG) with MW 600. The reaction was carried out with one polyol or a blend of two polyols and

Kinetics and mechanics of photo-polymerized triazole-containing thermosetting composites via the copper(I)-catalyzed azide-alkyne cycloaddition

PubMed Central

Song, Han Byul; Wang, Xiance; Patton, James R.; Stansbury, Jeffrey W.; Bowman, Christopher N.

2017-01-01

Objectives Several features necessary for polymer composite materials in practical applications such as dental restorative materials were investigated in photo-curable CuAAC (copper(I)-catalyzed azide-alkyne cycloaddition) thermosetting resin-based composites with varying filler loadings and compared to a conventional BisGMA/TEGDMA based composite. Methods Tri-functional alkyne and di-functional azide monomers were synthesized for CuAAC resins and incorporated with alkyne-functionalized silica microfillers for CuAAC composites. Polymerization kinetics, in situ temperature change, and shrinkage stress were monitored simultaneously with a tensometer coupled with FTIR spectroscopy and a data-logging thermocouple. The glass transition temperature was analyzed by dynamic mechanical analysis. Flexural modulus/strength and flexural toughness were characterized in three-point bending on a universal testing machine. Results The photo-CuAAC polymerization of composites containing between 0 and 60 wt% microfiller achieved ~99% conversion with a dramatic reduction in the maximum heat of reaction (~20 °C decrease) for the 60 wt% filled CuAAC composites as compared with the unfilled CuAAC resin. CuAAC composites with 60 wt% microfiller generated more than twice lower shrinkage stress of 0.43±0.01 MPa, equivalent flexural modulus of 6.1±0.7 GPa, equivalent flexural strength of 107±9 MPa, and more than 10 times higher energy absorption of 10±1 MJ m−3 when strained to 11% relative to BisGMA-based composites at equivalent filler loadings. Significance Mechanically robust and highly tough, photo-polymerized CuAAC composites with reduced shrinkage stress and a modest reaction exotherm were generated and resulted in essentially complete conversion. PMID:28363645

Anaerobic Respiration Using a Complete Oxidative TCA Cycle Drives Multicellular Swarming in Proteus mirabilis

PubMed Central

Alteri, Christopher J.; Himpsl, Stephanie D.; Engstrom, Michael D.; Mobley, Harry L. T.

2012-01-01

ABSTRACT Proteus mirabilis rapidly migrates across surfaces using a periodic developmental process of differentiation alternating between short swimmer cells and elongated hyperflagellated swarmer cells. To undergo this vigorous flagellum-mediated motility, bacteria must generate a substantial proton gradient across their cytoplasmic membranes by using available energy pathways. We sought to identify the link between energy pathways and swarming differentiation by examining the behavior of defined central metabolism mutants. Mutations in the tricarboxylic acid (TCA) cycle (fumC and sdhB mutants) caused altered patterns of swarming periodicity, suggesting an aerobic pathway. Surprisingly, the wild-type strain swarmed on agar containing sodium azide, which poisons aerobic respiration; the fumC TCA cycle mutant, however, was unable to swarm on azide. To identify other contributing energy pathways, we screened transposon mutants for loss of swarming on sodium azide and found insertions in the following genes that involved fumarate metabolism or respiration: hybB, encoding hydrogenase; fumC, encoding fumarase; argH, encoding argininosuccinate lyase (generates fumarate); and a quinone hydroxylase gene. These findings validated the screen and suggested involvement of anaerobic electron transport chain components. Abnormal swarming periodicity of fumC and sdhB mutants was associated with the excretion of reduced acidic fermentation end products. Bacteria lacking SdhB were rescued to wild-type pH and periodicity by providing fumarate, independent of carbon source but dependent on oxygen, while fumC mutants were rescued by glycerol, independent of fumarate only under anaerobic conditions. These findings link multicellular swarming patterns with fumarate metabolism and membrane electron transport using a previously unappreciated configuration of both aerobic and anaerobic respiratory chain components. PMID:23111869

{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.

Kinetics and mechanics of photo-polymerized triazole-containing thermosetting composites via the copper(I)-catalyzed azide-alkyne cycloaddition.

PubMed

Song, Han Byul; Wang, Xiance; Patton, James R; Stansbury, Jeffrey W; Bowman, Christopher N

2017-06-01

Several features necessary for polymer composite materials in practical applications such as dental restorative materials were investigated in photo-curable CuAAC (copper(I)-catalyzed azide-alkyne cycloaddition) thermosetting resin-based composites with varying filler loadings and compared to a conventional BisGMA/TEGDMA based composite. Tri-functional alkyne and di-functional azide monomers were synthesized for CuAAC resins and incorporated with alkyne-functionalized glass microfillers for CuAAC composites. Polymerization kinetics, in situ temperature change, and shrinkage stress were monitored simultaneously with a tensometer coupled with FTIR spectroscopy and a data-logging thermocouple. The glass transition temperature was analyzed by dynamic mechanical analysis. Flexural modulus/strength and flexural toughness were characterized in three-point bending on a universal testing machine. The photo-CuAAC polymerization of composites containing between 0 and 60wt% microfiller achieved ∼99% conversion with a dramatic reduction in the maximum heat of reaction (∼20°C decrease) for the 60wt% filled CuAAC composites as compared with the unfilled CuAAC resin. CuAAC composites with 60wt% microfiller generated more than twice lower shrinkage stress of 0.43±0.01MPa, equivalent flexural modulus of 6.1±0.7GPa, equivalent flexural strength of 107±9MPa, and more than 10 times higher energy absorption of 10±1MJm -3 when strained to 11% relative to BisGMA-based composites at equivalent filler loadings. Mechanically robust and highly tough, photo-polymerized CuAAC composites with reduced shrinkage stress and a modest reaction exotherm were generated and resulted in essentially complete conversion. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Functionalization of surfactant wrapped graphenenanosheets with alkylazides for enhanced dispersibility

NASA Astrophysics Data System (ADS)

Vadukumpully, Sajini; Gupta, Jhinuk; Zhang, Yongping; Xu, Guo Qin; Valiyaveettil, Suresh

2011-01-01

A facile and simple approach for the covalent functionalization of surfactant wrapped graphene sheets is described. The approach involves functionalization of dispersible graphene sheets with various alkylazides and 11-azidoundecanoic acid proved the best azide for enhanced dispersibility. The functionalization was confirmed by infrared spectroscopy and scanning tunneling microscopy. The free carboxylic acidgroups can bind to gold nanoparticles, which were introduced as markers for the reactive sites. The interaction between gold nanoparticles and the graphene sheets was followed by UV-vis spectroscopy. The gold nanoparticle-graphene composite was characterized by transmission electron microscopy and atomic force microscopy, demonstrating the uniform distribution of gold nanoparticles all over the surface. Our results open the possibility to control the functionalization on graphene in the construction of composite nanomaterials.A facile and simple approach for the covalent functionalization of surfactant wrapped graphene sheets is described. The approach involves functionalization of dispersible graphene sheets with various alkylazides and 11-azidoundecanoic acid proved the best azide for enhanced dispersibility. The functionalization was confirmed by infrared spectroscopy and scanning tunneling microscopy. The free carboxylic acidgroups can bind to gold nanoparticles, which were introduced as markers for the reactive sites. The interaction between gold nanoparticles and the graphene sheets was followed by UV-vis spectroscopy. The gold nanoparticle-graphene composite was characterized by transmission electron microscopy and atomic force microscopy, demonstrating the uniform distribution of gold nanoparticles all over the surface. Our results open the possibility to control the functionalization on graphene in the construction of composite nanomaterials. Electronic Supplementary Information (ESI) available: Synthesis and characterization details of dodecylazide, hexylazide, 11-azidoundecanol (AUO), micrographs (SEM and TEM images) of the various azide functionalized samples and the statistical analysis of the graphene thickness. See 10.1039/c0nr00547a.

Enzymatic and structural characterization of hydrolysis of gibberellin A4 glucosyl ester by a rice β-D-glucosidase.

PubMed

Hua, Yanling; Sansenya, Sompong; Saetang, Chiraporn; Wakuta, Shinji; Ketudat Cairns, James R

2013-09-01

In order to identify a rice gibberellin ester β-D-glucosidase, gibberellin A4 β-D-glucosyl ester (GA4-GE) was synthesized and used to screen rice β-glucosidases. Os3BGlu6 was found to have the highest hydrolysis activity to GA4-GE among five recombinantly expressed rice glycoside hydrolase family GH1 enzymes from different phylogenic clusters. The kinetic parameters of Os3BGlu6 and its mutants E178Q, E178A, E394D, E394Q and M251N for hydrolysis of p-nitrophenyl β-D-glucopyranoside (pNPGlc) and GA4-GE confirmed the roles of the catalytic acid/base and nucleophile for hydrolysis of both substrates and suggested M251 contributes to binding hydrophobic aglycones. The activities of the Os3BGlu6 E178Q and E178A acid/base mutants were rescued by azide, which they transglucosylate to produce β-D-glucopyranosyl azide, in a pH-dependent manner, while acetate also rescued Os3BGlu6 E178A at low pH. High concentrations of sodium azide (200-400 mM) inhibited Os3BGlu6 E178Q but not Os3BGlu6 E178A. The structures of Os3BGlu6 E178Q crystallized with either GA4-GE or pNPGlc had a native α-D-glucosyl moiety covalently linked to the catalytic nucleophile, E394, which showed the hydrogen bonding to the 2-hydroxyl in the covalent intermediate. These data suggest that a GH1 β-glucosidase uses the same retaining catalytic mechanism to hydrolyze 1-O-acyl glucose ester and glucoside. Copyright © 2013 Elsevier Inc. All rights reserved.

Kinetics of bulk photo-initiated copper(i)-catalyzed azide-alkyne cycloaddition (CuAAC) polymerizations.

PubMed

Song, Han Byul; Baranek, Austin; Bowman, Christopher N

2016-01-21

Photoinitiation of polymerizations based on the copper(i)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction enables spatio-temporal control and the formation of mechanically robust, highly glassy photopolymers. Here, we investigated several critical factors influencing photo-CuAAC polymerization kinetics via systematic variation of reaction conditions such as the physicochemical nature of the monomers; the copper salt and photoinitiator types and concentrations; light intensity; exposure time and solvent content. Real time Fourier transform infrared spectroscopy (FTIR) was used to monitor the polymerization kinetics in situ . Six different di-functional azide monomers and four different tri-functional alkyne monomers containing either aliphatic, aromatic, ether and/or carbamate substituents were synthesized and polymerized. Replacing carbamate structures with ether moieties in the monomers enabled an increase in conversion from 65% to 90% under similar irradiation conditions. The carbamate results in stiffer monomers and higher viscosity mixtures indicating that chain mobility and diffusion are key factors that determine the CuAAC network formation kinetics. Photoinitiation rates were manipulated by altering various aspects of the photo-reduction step; ultimately, a loading above 3 mol% per functional group for both the copper catalyst and the photoinitiator showed little or no rate dependence on concentration while a loading below 3 mol% exhibited 1 st order rate dependence. Furthermore, a photoinitiating system consisting of camphorquinone resulted in 60% conversion in the dark after only 1 minute of 75 mW cm -2 light exposure at 400-500 nm, highlighting a unique characteristic of the CuAAC photopolymerization enabled by the combination of the copper(i)'s catalytic lifetime and the nature of the step-growth polymerization.

Characterization of Transverse Tubule Vesicles Isolated from Skeletal Muscle

DTIC Science & Technology

1984-08-20

phenylmethylsulfonylfluoride (PMSF), 15 s the Polytron was stopped and the blade quercetin , sodium azide, sodium arsenate, N- cleared of connective tissue...the absence of tors of other ATPase enzymes (oligomycin. ATP. Low-density vesic les (26 pg protein/mi) were incubated ouabain. vanadate. quercetin

Undergraduate Electron-Spin-Resonance Experiment.

ERIC Educational Resources Information Center

Willis, James S.

1980-01-01

Describes the basic procedures for use of an electron-spin resonance spectrometer and potassium azide (KN3) in an experiment which extends from the phase of sample preparation (crystal growth, sample mounting, and orientation) through data taking to the stages of calculation and theoretical explanation. (Author/DS)

Oxidative Hemolysis of Erythrocytes

ERIC Educational Resources Information Center

Wlodek, Lidia; Kusior, Dorota

2006-01-01

This exercise for students will allow them to simultaneously observe lipid peroxidation and consequent hemolysis of rat erythrocytes and the effect of sodium azide, a catalase inhibitor, on these processes. It will also demonstrate a protective action of antioxidants, the therapeutically used N-acetylcysteine and albumins present in plasma.

Evaluation of the oxolinic acid--esculin--azide medium for the isolation and enumeration of faecal streptococci in a routine monitoring programme for bathing waters.

PubMed

Figueras, M J; Inza, I; Polo, F; Guarro, J

1998-10-01

m-Enterococcus agar (m-Ent) has been generally considered the reference medium for faecal streptococci in bathing waters. However, it shows several shortcomings, and therefore it is important to test newly developed media that can guarantee more precise results. In this sense, the recently described oxolinic acid--esculin--azide agar medium (OAA) and m-enterococcus agar (m-Ent) were comparatively evaluated for the detection of faecal streptococci from seawater and fresh water. The OAA medium showed a significantly higher relative recovery percentage and specificity for both types of water than m-Ent. A similar spectrum of species was recorded from both media, Enterococcus faecium being predominant in fresh water and Enterococcus faecalis, in seawater. The superior performance of the OAA medium in both types of bathing waters, added to the fact that it does not require the use of complementary confirmative tests, makes this medium an excellent candidate to be employed for monitoring programmes.

Bifunctional Diaminoterephthalate Fluorescent Dye as Probe for Cross-Linking Proteins.

PubMed

Wallisch, Melanie; Sulmann, Stefan; Koch, Karl-Wilhelm; Christoffers, Jens

2017-05-11

Diaminoterephthalates are fluorescent dyes and define scaffolds, which can be orthogonally functionalized at their two carboxylate residues with functional residues bearing task specific reactive groups. The synthesis of monofunctionalized dyes with thiol groups for surface binding, an azide for click chemistry, and a biotinoylated congener for streptavidin binding is reported. Two bifunctionalized dyes were prepared: One with an azide for click chemistry and a biotin for streptavidin binding, the other with a maleimide for reaction with thiol and a cyclooctyne moiety for ligation with copper-free click chemistry. In general, the compounds are red to orange, fluorescent materials with an absorption at about 450 nm and an emission at 560 nm with quantum yields between 2-41 %. Of particular interest is the maleimide-functionalized compound, which shows low fluorescence quantum yield (2 %) by itself. After addition of a thiol, the fluorescence is "turned on"; quantum yield 41 %. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Process for selection of oxygen-tolerant algal mutants that produce H{sub 2}

DOEpatents

Ghirardi, M.L.; Seibert, M.

1999-02-16

A process for selection of oxygen-tolerant, H{sub 2}-producing algal mutant cells comprises: (a) growing algal cells photoautotrophically under fluorescent light to mid log phase; (b) inducing algal cells grown photoautotrophically under fluorescent light to mid log phase in step (a) anaerobically by (1) resuspending the cells in a buffer solution and making said suspension anaerobic with an inert gas and (2) incubating the suspension in the absence of light at ambient temperature; (c) treating the cells from step (b) with metronidazole, sodium azide, and added oxygen to controlled concentrations in the presence of white light; (d) washing off metronidazole and sodium azide to obtain final cell suspension; (e) plating said final cell suspension on a minimal medium and incubating in light at a temperature sufficient to enable colonies to appear; (f) counting the number of colonies to determine the percent of mutant survivors; and (g) testing survivors to identify oxygen-tolerant H{sub 2}-producing mutants. 5 figs.

Incorporation of Methionine Analogues Into Bombyx mori Silk Fibroin for Click Modifications.

PubMed

Teramoto, Hidetoshi; Kojima, Katsura

2015-05-01

Bombyx mori silk fibroin incorporating three methionine (Met) analogues-homopropargylglycine (Hpg), azidohomoalanine (Aha), and homoallylglycine (Hag)-can be produced simply by adding them to the diet of B. mori larvae. The Met analogues are recognized by methionyl-tRNA synthetase, bound to tRNA(Met), and used for the translation of adenine-uracil-guanine (AUG) codons competitively with Met. In the presence of the standard amount of Met in the diet, incorporation of these analogues remains low. Lowering the amount of Met in the diet drastically improves incorporation efficiencies. Alkyne and azide groups in Hpg and Aha incorporated into silk fibroin can be selectively modified with Cu-catalyzed azide-alkyne cycloaddition reactions (click chemistry). Since Met residues exist only at the N-terminal domain of the fibroin heavy chain and in the fibroin light chain, good access to the reactive sites is expected and domain-selective modifications are possible without perturbing other major domains, including repetitive domains. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Production of Bombyx mori silk fibroin incorporated with unnatural amino acids.

PubMed

Teramoto, Hidetoshi; Kojima, Katsura

2014-07-14

Silk fibroin incorporated with unnatural amino acids was produced by in vivo feeding of p-chloro-, p-bromo-, and p-azido-substituted analogues of L-phenylalanine (Phe) to transgenic silkworms (Bombyx mori) that expressed a mutant of phenylalanyl-tRNA synthetase with expanded substrate recognition capabilities in silk glands. Cutting down the content of Phe in the diet was effective for increasing the incorporation of Phe analogues but simultaneously caused a decrease of fibroin production. The azide groups incorporated in fibroin were active as chemical handles for click chemistry in both the solubilized and the solid (fibrous) states. The azides survived degumming in the boiling alkaline solution that is required for complete removal of the sericin layer, demonstrating that AzPhe-incorporated silk fibroin could be a versatile platform to produce "clickable" silk materials in various forms. This study indicates the huge potential of UAA mutagenesis as a novel methodology to alter the characteristics of B. mori silk.

New AdoMet Analogues as Tools for Enzymatic Transfer of Photo-Cross-Linkers and Capturing RNA-Protein Interactions.

PubMed

Muttach, Fabian; Mäsing, Florian; Studer, Armido; Rentmeister, Andrea

2017-05-02

Elucidation of biomolecular interactions is of utmost importance in biochemistry. Photo-cross-linking offers the possibility to precisely determine RNA-protein interactions. However, despite the inherent specificity of enzymes, approaches for site-specific introduction of photo-cross-linking moieties into nucleic acids are scarce. Methyltransferases in combination with synthetic analogues of their natural cosubstrate S-adenosyl-l-methionine (AdoMet) allow for the post-synthetic site-specific modification of biomolecules. We report on three novel AdoMet analogues bearing the most widespread photo-cross-linking moieties (aryl azide, diazirine, and benzophenone). We show that these photo-cross-linkers can be enzymatically transferred to the methyltransferase target, that is, the mRNA cap, with high efficiency. Photo-cross-linking of the resulting modified mRNAs with the cap interacting protein eIF4E was successful with aryl azide and diazirine but not benzophenone, reflecting the affinity of the modified 5' caps. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Biocompatible click chemistry enabled compartment-specific pH measurement inside E. coli.

PubMed

Yang, Maiyun; Jalloh, Abubakar S; Wei, Wei; Zhao, Jing; Wu, Peng; Chen, Peng R

2014-09-19

Bioorthogonal reactions, especially the Cu(I)-catalysed azide-alkyne cycloaddition, have revolutionized our ability to label and manipulate biomolecules under living conditions. The cytotoxicity of Cu(I) ions, however, has hindered the application of this reaction in the internal space of living cells. By systematically surveying a panel of Cu(I)-stabilizing ligands in promoting protein labelling within the cytoplasm of Escherichia coli, we identify a highly efficient and biocompatible catalyst for intracellular modification of proteins by azide-alkyne cycloaddition. This reaction permits us to conjugate an environment-sensitive fluorophore site specifically onto HdeA, an acid-stress chaperone that adopts pH-dependent conformational changes, in both the periplasm and cytoplasm of E. coli. The resulting protein-fluorophore hybrid pH indicators enable compartment-specific pH measurement to determine the pH gradient across the E. coli cytoplasmic membrane. This construct also allows the measurement of E. coli transmembrane potential, and the determination of the proton motive force across its inner membrane under normal and acid-stress conditions.

General and Facile Route to Isomerically Pure Tricyclic Peptides Based on Templated Tandem CLIPS/CuAAC Cyclizations.

PubMed

Richelle, Gaston J J; Ori, Sumeet; Hiemstra, Henk; van Maarseveen, Jan H; Timmerman, Peter

2018-01-08

We report a one-pot ligation/cyclization technology for the rapid and clean conversion of linear peptides into tricyclic peptides that is based on using tetravalent scaffolds containing two benzyl bromide and two alkyne moieties. These react via CLIPS/CuAAC reactions with cysteines and azides in the peptide. Flexibility in the scaffolds is key to the formation of isomerically pure products as the flexible scaffolds T4 1 and T4 2 mostly promote the formation of single isomeric tricycles while the rigid scaffolds T4 3 and T4 4 do not yield clean products. There seems to be no limitation to the number and types of amino acids present as 18 canonical amino acids were successfully implemented. We also observed that azides at the peptide termini and cysteine residues in the center gave better results than compounds with the functional groups placed the other way round. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermomechanical Formation–Structure–Property Relationships in Photopolymerized Copper-Catalyzed Azide–Alkyne (CuAAC) Networks

PubMed Central

Baranek, Austin; Song, Han Byul; McBride, Mathew; Finnegan, Patricia; Bowman, Christopher N.

2016-01-01

Bulk photopolymerization of a library of synthesized multifunctional azides and alkynes was carried out toward developing structure–property relationships for CuAAC-based polymer networks. Multifunctional azides and alkynes were formulated with a copper catalyst and a photoinitiator, cured, and analyzed for their mechanical properties. Material properties such as the glass transition temperatures (Tg) show a strong dependence on monomer structure with Tg values ranging from 41 to 90 °C for the series of CuAAC monomers synthesized in this study. Compared to the triazoles, analogous thioether-based polymer networks exhibit a 45–49 °C lower Tg whereas analogous monomers composed of ethers in place of carbamates exhibit a 40 °C lower Tg. Here, the formation of the triazole moiety during the polymerization represents a critical component in dictating the material properties of the ultimate polymer network where material properties such as the rubbery modulus, cross-link density, and Tg all exhibit strong dependence on polymerization conversion, monomer composition, and structure postgelation. PMID:27867223

Direct nitration and azidation of aliphatic carbons by an iron-dependent halogenase

PubMed Central

Chang, Wei-chen; Layne, Andrew P; Miles, Linde A; Krebs, Carsten

2014-01-01

Iron-dependent halogenases employ cis-halo-Fe(IV)-oxo (haloferryl) complexes to functionalize unactivated aliphatic carbon centers, a capability elusive to synthetic chemists. Halogenation requires (1) coordination of a halide anion (Cl− or Br−) to the enzyme's Fe(II) cofactor; (2) coupled activation of O2 and decarboxylation of α-ketoglutarate to generate the haloferryl intermediate; (3) abstraction of hydrogen (H•) from the substrate by the ferryl oxo group; and (4) transfer of the cis halogen as Cl• or Br• to the substrate radical. This enzymatic solution to an unsolved chemical challenge is potentially generalizable to installation of other functional groups, provided that the corresponding anions can support the four requisite steps. We show here that the wild-type halogenase SyrB2 can indeed direct aliphatic nitration and azidation reactions by the same chemical logic. The discovery and enhancement by mutagenesis of these previously unknown reaction types suggests unrecognized or untapped versatility in ferryl-mediated enzymatic C–H-bond activation. PMID:24463698

Determination of urinary 6-mercaptopurine and three of its metabolites by HPLC-UV coupled with the iodine-azide reaction.

PubMed

Zakrzewski, Robert; Borowczyk, Kamila; Łuczak, Adam; Młynarski, Wojciech; Trelińska, Joanna

2013-04-01

The presented method is able to determine 6-mercaptopurine (6-MP), 6-thioguanine, 6-mercaptopurine riboside and 6-thioguanine riboside in urine, and is thereby dedicated to control of thiopurine therapy of children with acute lymphoblastic leukemia. Good separation of the mentioned compounds was achieved on a C18 stationary phase with a sodium azide and sodium heptane sulfonate solution, acetonitrile and water at ratio of 50:1:49 (v/v/v). Coefficient of regression is >0.99 for all linearity ranges. LOD and LOQ are 0.3, 0.4, 0.3, 0.8 and 0.4, 0.6, 0.5 and 0.9 nmol/ml of urine for 6-MP, 6-thioguanine, 6-mercaptopurine riboside and 6-thioguanine riboside, respectively. Intra- and inter-day recovery and RSD are close to 100% and less than 10%, respectively, for all investigated thiopurines. The elaborated method was successfully applied for detection and quantitation of 6-MP and its selected metabolites in patients' urine samples.

Process for selection of Oxygen-tolerant algal mutants that produce H.sub.2

DOEpatents

Ghirardi, Maria L.; Seibert, Michael

1999-01-01

A process for selection of oxygen-tolerant, H.sub.2 -producing algal mutant cells comprising: (a) growing algal cells photoautotrophically under fluorescent light to mid log phase; (b) inducing algal cells grown photoautrophically under fluorescent light to mid log phase in step (a) anaerobically by (1) resuspending the cells in a buffer solution and making said suspension anaerobic with an inert gas; (2) incubating the suspension in the absence of light at ambient temperature; (c) treating the cells from step (b) with metronidazole, sodium azide, and added oxygen to controlled concentrations in the presence of white light. (d) washing off metronidazole and sodium azide to obtain final cell suspension; (e) plating said final cell suspension on a minimal medium and incubating in light at a temperature sufficient to enable colonies to appear; (f) counting the number of colonies to determine the percent of mutant survivors; and (g) testing survivors to identify oxygen-tolerant H.sub.2 -producing mutants.

Highly Conductive Aromatic Functionalized Multi-Walled Carbon Nanotube for Inkjet Printable High Performance Supercapacitor Electrodes

PubMed Central

Attri, Pankaj

2015-01-01

We report the functionalization of multiwalled carbon nanotubes (MWCNT) via the 1,3-dipolar [3+2] cycloaddition of aromatic azides, which resulted in a detangled CNT as shown by transmission electron microscopy (TEM). Carboxylic moieties (-COOH) on aromatic azide result in highly stable aqueous dispersion (max. conc. ~ 10 mg/mL H2O), making the suitable for inkjet printing. Printed patterns on polyethylene terephthalate (PET) flexible substrate exhibit low sheet resistivity ~65 Ω. cm, which is attributed to enhanced conductivity. Fabricated Supercapacitors (SC) assembled using these printed substrates exhibit good electrochemical performance in organic as well as aqueous electrolytes. High energy and power density (57.8 Wh/kg and 0.85 kW/kg) in 1M H2SO4 aqueous electrolyte demonstrate the excellent performance of the proposed supercapacitor. Capacitive retention varies from ~85–94% with columbic efficiency ~95% after 1000 charge/discharge cycles in different electrolytes, demonstrating the excellent potential of the device for futuristic power applications. PMID:26153688

Asymmetric homologation of boronic esters bearing azido and silyloxy substituents.

PubMed

Singh, R P; Matteson, D S

2000-10-06

In the asymmetric homologation of boronic esters with a (dihalomethyl)lithium, substituents that can bind metal cations tend to interfere. Accordingly, we undertook the introduction of weakly basic oxygen and nitrogen substituents into boronic esters in order to maximize the efficiency of multistep syntheses utilizing this chemistry. Silyloxy boronic esters cannot be made efficiently by direct substitution, but a (hydroxymethyl)boronic ester has been silylated in the usual manner. Conversion of alpha-halo boronic esters to alpha-azido boronic esters has been carried out with sodium azide and a tetrabutylammonium salt as phase-transfer catalyst in a two-phase system with water and either nitromethane or ethyl acetate. These are safer solvents than the previously used dichloromethane, which can form an explosive byproduct with azide ion. Boronic esters containing silyloxy or alkoxy and azido substituents have been shown to react efficiently with (dihalomethyl)lithiums, resulting in efficient asymmetric insertion of the halomethyl group into the carbon-boron bond.

Dual-Responsive Metabolic Precursor and Light-Up AIEgen for Cancer Cell Bio-orthogonal Labeling and Precise Ablation.

PubMed

Hu, Fang; Yuan, Youyong; Wu, Wenbo; Mao, Duo; Liu, Bin

2018-06-05

Metabolic glycoengineering of unnatural glycans with bio-orthogonal chemical groups and a subsequent click reaction with fluorescent probes have been widely used in monitoring various bioprocesses. Herein, we developed a dual-responsive metabolic precursor that could specifically generate unnatural glycans with azide groups on the membrane of targeted cancer cells with high selectivity. Moreover, a water-soluble fluorescent light-up probe with aggregation-induced emission (AIE) was synthesized, which turned its fluorescence on upon a click reaction with azide groups on the cancer cell surface, enabling special cancer cell imaging with low background signal. Furthermore, the probe can generate 1 O 2 upon light irradiation, fulfilling its dual role as an imaging and therapeutic agent for cancer cells. Therefore, the concepts of the cancer-cell-specific metabolic precursor cRGD-S-Ac 3 ManNAz and the AIE light-up probe are promising in bio-orthogonal labeling and cancer-specific imaging and therapy.

The Dependency in the Elasticity of the Saccharomyces cerevisiae Cell Wall upon Cell Viability and Membrane Integrity

NASA Astrophysics Data System (ADS)

McPherson, Dacia; Zhu, Chenhui; Yi, Youngwoo; Clark, Noel

2007-03-01

In this study the elastic spring constant of the yeast cell wall is probed with the atomic force microscope (AFM) under variable conditions. Cells were sequentially analyzed in rich growth medium (YPD), a 0.8 M NaCl rich growth medium solution and an injection of 0.01% sodium azide solution. Cells in late log phase, which have variable diameters within three to five microns, were immobilized on a patterned silicon substrate with holes approximately 3.8um in diameter and 1.5um deep that was functionalized with polyethylenimine prior to cell application. Force curves were taken moving laterally across the cell in one dimension after exposure to each medium. Spring constants of the cells, calculated from force curves, displayed a positional dependency and marked differences in high osmolarity medium and after the injection of sodium azide. This study demonstrates the ability of the AFM to investigate changes in cell morphology and correlate those findings to underlying physiological processes.

Sensitive, Site-Specific, and Stable Vibrational Probe of Local Protein Environments: 4-Azidomethyl-L-Phenylalanine

PubMed Central

Bazewicz, Christopher G.; Liskov, Melanie T.; Hines, Kevin J.; Brewer, Scott H.

2013-01-01

We have synthesized the unnatural amino acid (UAA), 4-azidomethyl-Lphenylalanine (pN3CH2Phe), to serve as an effective vibrational reporter of local protein environments. The position, extinction coefficient, and sensitivity to local environment of the azide asymmetric stretch vibration of pN3CH2Phe are compared to the vibrational reporters: 4-cyano-L-phenylalanine (pCNPhe) and 4-azido-L-phenylalanine (pN3Phe). This UAA was genetically incorporated in a site-specific manner utilizing an engineered, orthogonal aminoacyl-tRNA synthetase in response to an amber codon with high efficiency and fidelity into two distinct sites in superfolder green fluorescent protein (sfGFP). This allowed for the dependence of the azide asymmetric stretch vibration of pN3CH2Phe to different protein environments to be measured. The photo-stability of pN3CH2Phe was also measured relative to the photoreactive UAA, pN3Phe. PMID:23865850

Divergent Pathways Involving 1,3-Dipolar Addition and N-N Bond Splitting of an Organic Azide across a Zirconium Methylidene.

PubMed

Kurogi, Takashi; Mane, Manoj V; Zheng, Shuai; Carroll, Patrick J; Baik, Mu-Hyun; Mindiola, Daniel J

2018-02-12

The zirconium methylidene (PNP)Zr=CH 2 (OAr) (1) reacts with N 3 Ad to give two products (PNP)Zr=NAd(OAr) (2) and (PNP)Zr(η 2 -N=NAd)(N=CH 2 )(OAr) (3), both resulting from a common cycloaddition intermediate (PNP)Zr(CH 2 N 3 Ad)(OAr) (A). Using a series of control experiments in combination with DFT calculations, it was found that 2 results from a nitrene by a carbene metathesis reaction in which N 2 acts as a delivery vehicle and forms N 2 CH 2 as a side product. In the case of 3, N-N bond splitting of the azide at the α-position allowed the isolation of a rare example of a parent ketimide complex of zirconium. Isotopic labeling studies and solid-state X-ray analysis are presented for 2 and 3, in addition to an independent synthesis for the former. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Decreasing Distortion Energies without Strain: Diazo-Selective 1,3-Dipolar Cycloadditions.

PubMed

Gold, Brian; Aronoff, Matthew R; Raines, Ronald T

2016-07-15

The diazo group has attributes that complement those of the azido group for applications in chemical biology. Here, we use computational analyses to provide insights into the chemoselectivity of the diazo group in 1,3-dipolar cycloadditions. Dipole distortion energies are responsible for ∼80% of the overall energetic barrier for these reactions. Here, we show that diazo compounds, unlike azides, provide an opportunity to decrease that barrier substantially without introducing strain into the dipolarophile. The ensuing rate enhancement is due to the greater nucleophilic character of a diazo group compared to that of an azido group, which can accommodate decreased distortion energies without predistortion. The tuning of distortion energies with substituents in a diazo compound or dipolarophile can enhance reactivity and selectivity in a predictable manner. Notably, these advantages of diazo groups are amplified in water. Our findings provide a theoretical framework that can guide the design and application of both diazo compounds and azides in "orthogonal" contexts, especially for biological investigations.

Investigation of Techniques to Reduce Electrostatic Discharge Susceptibility of Hermetically Sealed EEDS

DTIC Science & Technology

1975-07-03

explosive | output requirement. The substitution of RD 1333 lead azide for dextrinated 1 (Figure 8c) did not improve the output, but the modified charge...Pennsylvania 19112 Library Director Army Material Systems Analysis Agency Aberdeen Proving Ground Aberdeen, Maryland 21005 Technical Library

A regioselective Huisgen reaction inside a Keplerate polyoxomolybdate nanoreactor.

PubMed

Besson, Claire; Schmitz, Sebastian; Capella, Kimberly M; Kopilevich, Sivil; Weinstock, Ira A; Kögerler, Paul

2012-09-07

A 1,3-dipolar cycloaddition reaction taking place quantitatively between propiolic acid "guests" and azide functions previously attached to binding sites within the cavity of a {Mo(132)}-type Keplerate reproducibly gives a 2 : 1 ratio of 1,4- and 1,5-triazoles.

Azide functionalized poly(3-hexylthiophene) and methods of forming same

DOEpatents

Qin, Yang; Grubbs, Robert B; Park, Young Suk

2014-11-18

This disclosure relates to a polymer having the formula: ##STR00001## wherein x is between 1 and about 100 an y is between about 99 and about 1, and x+Y=about 100. The disclosure also includes the use of the polymer in photovoltaic devices.

Targeted Gold Nanoparticle Contrast Agent for Digital Breast Tomosynthesis and Computed Tomography

DTIC Science & Technology

2012-03-01

bromopropionic acid (10 millimolar) was dissolved in acetonitrile (100 mL) , after which sodium azide (50 millimolar) was added to the solution. The mixture was...Transformation of the ionic X-ray contrast agent diatrizoate and related triiodinated benzoates by Trametes versicolor. Appl Environ Microbiol

Direct electrochemical imidation of aliphatic amines via anodic oxidation.

PubMed

Zhang, Li; Su, Ji-Hu; Wang, Sujing; Wan, Changfeng; Zha, Zhenggen; Du, Jiangfeng; Wang, Zhiyong

2011-05-21

Direct electrochemical synthesis of sulfonyl amidines from aliphatic amines and sulfonyl azides was realized with good to excellent yields. Traditional tertiary amine substrates were broadened to secondary and primary amines. The reaction intermediates were observed and a reaction mechanism was proposed and discussed. © The Royal Society of Chemistry 2011

Safety in the Chemical Laboratory: Tested Disposal Methods for Chemical Wastes from Academic Laboratories.

ERIC Educational Resources Information Center

Armour, M. A.; And Others

1985-01-01

Describes procedures for disposing of dichromate cleaning solution, picric acid, organic azides, oxalic acid, chemical spills, and hydroperoxides in ethers and alkenes. These methods have been tested under laboratory conditions and are specific for individual chemicals rather than for groups of chemicals. (JN)

Synthesis of unnatural amino acids via microwave-assisted regio-selective one-pot multi-component reactions of sulfamidates

EPA Science Inventory

Synthesis of triazole-based unnatural amino acids, triazole bisaminoacids and β-amino triazole has been described via stereo and regioselective one-pot multi-component reaction of sulfamidates, sodium azide, and alkynes under MW irradiation conditions. The developed method is app...

Raman spectroscopy - in situ characterization of growth and surface processes

NASA Astrophysics Data System (ADS)

Perkins, James Robert

The goal of this thesis is to expand on the usefulness of Raman spectroscopy as an in situ probe to aid in the growth and implementation of electronic, optical, and biodetection materials. We accomplish this goal by developing two diverse optical characterization projects. In the first project, an autoclave similar to those used in solvothermal growth which has been outfitted with an optical window is used to collect vibrational spectra of solvents and mineralizers commonly used in the ammonothermal growth of gallium nitride. Secondly, novel silver nanowires created by ferroelectric lithography are evaluated by surface enhanced micro-Raman spectroscopy for use as surface enhanced substrates for low detection limit or single molecule bio-detectors. Raman spectroscopy is already a widely accepted method to characterize and identify a wide variety of materials. Vibrational spectra can yield much information on the presence of chemical species as well as information regarding the phase and interactive properties. Because Raman spectroscopy is a generally non-intrusive technique it is ideal for analysis of hazardous or far-from-ambient liquids, gases, or solids. This technique is used in situ to characterize crystal growth and surface enhanced photochemistry. The phenomenon of Surface Enhanced Raman Spectroscopy (SERS) has been observed in many systems but some fundamental understanding is still lacking and the technique has been slow to transition from the laboratory to the industry. Aggregated colloids and lithographically created islands have shown the best success as reproducible substrates for SERS detection. These techniques, however, lack control over shape, size, and position of the metal nanoparticles which leave them reliant on hotspots. Because of the potential for control of the position of aggregates, ferroelectric lithographically created silver nanowires are evaluated as a potential SERS substrate using pyridine, benzoic acid, and Rhodamine 6g. Surface enhancement from these samples varies periodically as excitation light is scanned perpendicular to the wires. The periodicity, however, has the frequency of the positive domains where carbon laser damage is preferentially created. There is a current need for homoepitaxial substrates for gallium nitride devices including light emitting diodes, transistors, and laser diodes. Ammonothermal growth is a promising technique for creating bulk single crystalline GaN, but questions remain concerning the intermediates of reactions in supercritical Ammonia. Neat ammonia and water are monitored by Raman spectroscopy from room temperature to 500°C and 20 kpsi with both UV and visible excitation. In both systems, the amount of hydrogen bonding, which can be determined by O-H and N-H stretch frequency shifts, decreases with increasing temperature. In supercritical ammonia, the degree of Fermi resonance between the nu1 and 2nu4 modes decreases linearly with temperature while a minimum in pyramidal height of the NH3 molecule is reached at moderate pressures. Binary solutions of sodium azide and ammonia are investigated to temperatures which allow observation of the breakdown of the azides. The pressure and N2 Raman signal increase as the azide decomposes to sodium amide and N2 and H2 process gasses. The rate of decrease of the Raman signal of the azide increases as the reaction proceeds suggesting that the reaction rate is proportional to the pressure. The Fermi resonance, hydrogen bonding, and pyramidal height parameters were not affected by the presence of the azide.

Comparison of Types of Cell Death: Apoptosis and Necrosis.

ERIC Educational Resources Information Center

Manning, Francis; Zuzel, Katherine

2003-01-01

Cell death is an essential factor in many biological processes including development. Discusses two types of cell death: (1) necrosis (induced by sodium azide); and (2) apoptosis (induced by sodium chromate). Illustrates key features that differ between these two types of cells death including loss of membrane integrity and internucleosomal DNA…

Polythiophene-block-poly(γ-benzyl L-glutamate): Synthesis and study of a new rod-rod block copolymer

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

Wu, Zong-Quan; Ono, Robert J.; Chen, Zheng

2011-01-01

Coupling of ethynyl terminated poly(3-hexylthiophene) with azide terminated poly(γ-benzyl L-glutamate) afforded the respective block copolymer in good yield and high purity; this material was found to self assemble into hierarchal structures in solution and in the solid state.

Biochemical Oxygen Demand and Dissolved Oxygen. Training Module 5.105.2.77.

ERIC Educational Resources Information Center

Kirkwood Community Coll., Cedar Rapids, IA.

This document is an instructional module package prepared in objective form for use by an instructor familiar with the azide modification of the Winkler dissolved oxygen test and the electronic dissolved oxygen meter test procedures for determining the dissolved oxygen and the biochemical oxygen demand of a wastewater sample. Included are…

Kinetics and Mechanism of the Iodine-Azide Reaction: A Videotaped Experiment.

ERIC Educational Resources Information Center

Haight, Gilbert P.; Jones, Loretta L.

1987-01-01

Discusses some difficulties presented by the use of clock reactions with large numbers of students in illustrating the determination of rate laws and the deduction of a mechanism. Suggests the videotaping of a clock reaction without narration to be used with students in stages so that observations can be recorded. (TW)

Stereo- and regio-selective one-pot synthesis of triazole-based unnatural amino acids and β- amino triazoles

EPA Science Inventory

Synthesis of triazole based unnatural amino acids and β-amino triazole has been described via stereo and regioselective one-pot multi-component reaction of sulfamidates, sodium azide, and alkynes under MW conditions. The developed method is applicable to a broad substrate scope a...

A facile and regioselective synthesis of 1,4-disubstituted 1,2,3-triazoles using click chemistry

EPA Science Inventory

The reaction of α-tosyloxy ketones, sodium azide and terminal alkynes in presence of copper(I) in aqueous polyethylene glycol afforded regioselectively 1,4-disubstituted 1,2,3-triazoles in good yield at ambient temperature. The one-pot exclusive formation of 1,4-disubstituted 1,2...

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

ERIC Educational Resources Information Center

Mendes, Desiree E.; Schoffstall, Allen M.

2011-01-01

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

Biocompatible click chemistry enabled compartment-specific pH measurement inside E. coli

PubMed Central

Yang, Maiyun; Jalloh, Abubakar S.; Wei, Wei

2014-01-01

Bioorthogonal reactions, especially the Cu(I)-catalyzed azide-alkyne cycloaddition, have revolutionized our ability to label and manipulate biomolecules under living conditions. The cytotoxicity of Cu(I) ions, however, has hindered the application of this reaction in the internal space of living cells. By systematically surveying a panel of Cu(I)-stabilizing ligands in promoting protein labeling within the cytoplasm of E. coli, here we identify a highly efficient and biocompatible catalyst for intracellular modification of proteins by azide-alkyne cycloaddition. This reaction permits us to conjugate an environment-sensitive fluorophore site-specifically onto HdeA, an acid-stress chaperone that adopts pH-dependent conformational changes, in both the periplasm and cytoplasm of E. coli. The resulting protein-fluorophore hybrid pH indicators enable compartment-specific pH measurement to determine the pH gradient across the E. coli cytoplasmic membrane. This construct also allows the measurement of E. coli transmembrane potential, and the determination of the proton motive force across its inner membrane under normal and acid-stress conditions. PMID:25236616

N-heterocyclic carbene gold(I) and silver(I) complexes bearing functional groups for bio-conjugation

PubMed Central

Garner, Mary E.; Niu, Weijia; Chen, Xigao; Ghiviriga, Ion; Tan, Weihong; Veige, Adam S.

2015-01-01

This work describes several synthetic approaches to append organic functional groups to gold and silver N-heterocyclic carbene (NHC) complexes suitable for applications in biomolecule conjugation. Carboxylate appended NHC ligands (3) lead to unstable AuI complexes that convert into bis-NHC species (4). A benzyl protected carboxylate NHC-AuI complex 2 was synthesized but deprotection to produce the carboxylic acid functionality could not be achieved. A small library of new alkyne functionalized NHC proligands were synthesized and used for subsequent silver and gold metalation reactions. The alkyne appended NHC gold complex 13 readily react with benzyl azide in a copper catalyzed azide-alkyne cycloaddition reaction to form the triazole appended NHC gold complex 14. Cell cytotoxicity studies were performed on DLD-1 (colorectal adenocarcinoma), Hep-G2 (hepatocellular carcinoma), MCF-7 (breast adenocarcinoma), CCRF-CEM (human T-Cell leukemia), and HEK (human embryonic kidney). Complete spectroscopic characterization of the ligands and complexes was achieved using 1H and 13C NMR, gHMBC, ESI-MS, and combustion analysis. PMID:25490699

Depolarization of the Electrogenic Transmembrane Electropotential of Zea mays L. by Bipolaris (Helminthosporium) maydis Race T Toxin, Azide, Cyanide, Dodecyl Succinic Acid, or Cold Temperature 1

PubMed Central

Mertz, Stuart M.; Arntzen, Charles J.

1978-01-01

The transmembrane electrical potential of root cells of Zea mays L. cv. W64A in a modified 1× Higinbotham solution was partially depolarized by semipurified toxin obtained from Bipolaris (Helminthosporium) maydis race T. At a given toxin concentration depolarization of Texas cytoplasm cells was much greater than for normal cytoplasm cells. This observation correlated directly to the differential host susceptibility to the fungus. The time course and magnitude of depolarization were dependent on toxin concentration; at high concentration the electropotential difference change was rapid. Cortex cells depolarized more slowly than epidermal cells indicating that the toxin slowly permeated intercellular regions. Toxin concentrations which affected electropotential difference were of the same magnitude as those required to inhibit root growth, ion uptake, and mitochondrial processes. Azide, cyanide, and cold temperature (5 C) gave the same partial depolarization as did the toxin. Dodecyl succinic acid caused complete depolarization. These and other data indicate that one of the primary actions of the toxin is to inhibit electrogenic ion pumps in the plasmalemma. PMID:16660605

Selective Inhibition of the Oxidation of Ferrous Iron or Sulfur in Thiobacillus ferrooxidans

PubMed Central

Harahuc, Lesia; Lizama, Hector M.; Suzuki, Isamu

2000-01-01

The oxidation of either ferrous iron or sulfur by Thiobacillus ferrooxidans was selectively inhibited or controlled by various anions, inhibitors, and osmotic pressure. Iron oxidation was more sensitive than sulfur oxidation to inhibition by chloride, phosphate, and nitrate at low concentrations (below 0.1 M) and also to inhibition by azide and cyanide. Sulfur oxidation was more sensitive than iron oxidation to the inhibitory effect of high osmotic pressure. These differences were evident not only between iron oxidation by iron-grown cells and sulfur oxidation by sulfur-grown cells but also between the iron and sulfur oxidation activities of the same iron-grown cells. Growth experiments with ferrous iron or sulfur as an oxidizable substrate confirmed the higher sensitivity of iron oxidation to inhibition by phosphate, chloride, azide, and cyanide. Sulfur oxidation was actually stimulated by 50 mM phosphate or chloride. Leaching of Fe and Zn from pyrite (FeS2) and sphalerite (ZnS) by T. ferrooxidans was differentially affected by phosphate and chloride, which inhibited the solubilization of Fe without significantly affecting the solubilization of Zn. PMID:10698768

Synthesis, Antiviral and Cytotoxic Activity of Novel Terpenyl Hybrid Molecules Prepared by Click Chemistry.

PubMed

Pertino, Mariano Walter; Petrera, Erina; Alché, Laura Edith; Schmeda-Hirschmann, Guillermo

2018-06-03

Naturally occurring terpenes were combined by click reactions to generate sixteen hybrid molecules. The diterpene imbricatolic acid (IA) containing an azide group was used as starting compound for the synthesis of all the derivatives. The alkyne group in the terpenes cyperenoic acid, dehydroabietinol, carnosic acid γ-lactone, ferruginol, oleanolic acid and aleuritolic acid was obtained by esterification using appropriate alcohols or acids. The hybrid compounds were prepared by combining the IA azide function with the different terpene-alkynes under click chemistry conditions. The cytotoxic activity of the terpene hybrids 1 ⁻ 16 was assessed against Vero cells and tumour cell lines (HEP-2, C6 and Raw 264.7). Compounds 1 , 2 , 3 and 7 showed cytotoxic activity against the tested cell lines. The antiviral activity of the compounds was evaluated against HSV-1 KOS, Field and B2006 strain. For the pairs of hybrid compounds formed between IA-diterpene (compounds 3 ⁻ 8 , except for compound 7 ), a moderate activity was observed against the three HSV-1 strains with an interesting selectivity index (SI ≥10, SI = CC 50 /CE 50 ) for some compounds.

Assessment of oxidative stress in serum by d-ROMs test.

PubMed

Kilk, K; Meitern, R; Härmson, O; Soomets, U; Hõrak, P

2014-08-01

Assessment of oxidative stress is an important but technically challenging procedure in medical and biological research. The reactive oxygen metabolites (d-ROMs) test is a simple assay marketed for analyzing the total amount of hydroperoxides in serum via the Fenton's reaction. Earlier reports have raised a suspicion that a part of the signal detected in the assay comes from sources other than metabolites generated by oxidative stress. The aim of this study was to identify which serum components interfere with the d-ROMs signal. By application of sodium azide, ethylenediaminetetraacetic acid, sodium dodecylsulphate, varying temperature, and spiking endogenous substances we demonstrate that in the case of mammalian sera the assay determines ceruloplasmin (CP) activity with potential interferences from hydroperoxides, iron level, thiols, and albumin. In sera of avian species hydroperoxides contribute more to the test outcome, but the CP part is insensitive to inhibition by azide. In conclusion, this assay has deficiencies in terms of detecting realistic concentrations of hydroperoxides, is mostly measuring CP and is also interfered with other serum components, making it very difficult to interpret in most biological systems.

Toward a Molecular Lego Approach for the Diversity-Oriented Synthesis of Cyclodextrin Analogues Designed as Scaffolds for Multivalent Systems.

PubMed

Lepage, Mathieu L; Schneider, Jérémy P; Bodlenner, Anne; Compain, Philippe

2015-11-06

A modular strategy has been developed to access a diversity of cyclic and acyclic oligosaccharide analogues designed as prefunctionalized scaffolds for the synthesis of multivalent ligands. This convergent approach is based on bifunctional sugar building blocks with two temporarily masked functionalities that can be orthogonally activated to perform Cu(I)-catalyzed azide-alkyne cycloaddition reactions (CuAAC). The reducing end is activated as a glycosyl azide and masked as a 1,6-anhydro sugar, while the nonreducing end is activated as a free alkyne and masked as a triethylsilyl-alkyne. Following a cyclooligomerization approach, the first examples of close analogues of cyclodextrins composed of d-glucose residues and triazole units bound together through α-(1,4) linkages were obtained. The cycloglucopyranoside analogue containing four sugar units was used as a template to prepare multivalent systems displaying a protected d-mannose derivative or an iminosugar by way of CuAAC. On the other hand, the modular approach led to acyclic alkyne-functionalized scaffolds of a controlled size that were used to synthesize multivalent iminosugars.

Ultrasonically-enhanced preparation, characterization of CaFe-layered double hydroxides with various interlayer halide, azide and oxo anions (CO32-, NO3-, ClO4-).

PubMed

Szabados, Márton; Varga, Gábor; Kónya, Zoltán; Kukovecz, Ákos; Carlson, Stefan; Sipos, Pál; Pálinkó, István

2018-01-01

An ultrasonically-enhanced mechanochemical method was developed to synthesize CaFe-layered double hydroxides (LDHs) with various interlayer anions (CO 3 2- , NO 3 - , ClO 4 - , N 3 - , F - , Cl - , Br - and I - ). The duration of pre-milling and ultrasonic irradiation and the variation of synthesis temperature in the wet chemical step were investigated to obtain the optimal parameters of preparation. The main method to characterize the products was X-ray diffractometry, but infrared and synchrotron-based X-ray absorption spectroscopies as well as thermogravimetric measurements were also used to learn about fine structural details. The synthesis method afforded successful intercalation of the anions, among others the azide anion, a rarely used counter ion providing a system, which enables safe handling the otherwise highly reactive anion. The X-ray absorption spectroscopic measurements revealed that the quality of the interlayered anions could modulate the spatial arrangement of the calcium ions around the iron(III) ions, but only in the second coordination sphere. Copyright © 2017 Elsevier B.V. All rights reserved.

Bioorthogonal probes for imaging sterols in cells.

PubMed

Jao, Cindy Y; Nedelcu, Daniel; Lopez, Lyle V; Samarakoon, Thilani N; Welti, Ruth; Salic, Adrian

2015-03-02

Cholesterol is a fundamental lipid component of eukaryotic membranes and a precursor of potent signaling molecules, such as oxysterols and steroid hormones. Cholesterol and oxysterols are also essential for Hedgehog signaling, a pathway critical in embryogenesis and cancer. Despite their importance, the use of imaging sterols in cells is currently very limited. We introduce a robust and versatile method for sterol microscopy based on C19 alkyne cholesterol and oxysterol analogues. These sterol analogues are fully functional; they rescue growth of cholesterol auxotrophic cells and faithfully recapitulate the multiple roles that sterols play in Hedgehog signal transduction. Alkyne sterol analogues incorporate efficiently into cellular membranes and can be imaged with high resolution after copper(I)-catalyzed azide-alkyne cycloaddition reaction with fluorescent azides. We demonstrate the use of alkyne sterol probes for visualizing the subcellular distribution of cholesterol and for two-color imaging of sterols and choline phospholipids. Our imaging strategy should be broadly applicable to studying the role of sterols in normal physiology and disease. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Liquid/Liquid Interfacial Synthesis of a Click Nanosheet.

PubMed

Rapakousiou, Amalia; Sakamoto, Ryota; Shiotsuki, Ryo; Matsuoka, Ryota; Nakajima, Ukyo; Pal, Tigmansu; Shimada, Rintaro; Hossain, Amran; Masunaga, Hiroyasu; Horike, Satoshi; Kitagawa, Yasutaka; Sasaki, Sono; Kato, Kenichi; Ozawa, Takeaki; Astruc, Didier; Nishihara, Hiroshi

2017-06-22

A liquid/liquid interfacial synthesis is employed, for the first time, to synthesize a covalent two-dimensional polymer nanosheet. Copper-catalyzed azide-alkyne cycloaddition (CuAAC) between a three-way terminal alkyne and azide at a water/dichloromethane interface generates a 1,2,3-triazole-linked nanosheet. The resultant nanosheet, with a flat and smooth texture, has a maximum domain size of 20 μm and minimum thickness of 5.3 nm. The starting monomers in the organic phase and the copper catalyst in the aqueous phase can only meet at the liquid/liquid interface as a two-dimensional reaction space; this allows them to form the two-dimensional polymer. The robust triazole linkage generated by irreversible covalent-bond formation allows the nanosheet to resist hydrolysis under both acidic and alkaline conditions, and to endure pyrolysis up to more than 300 °C. The coordination ability of the triazolyl group enables the nanosheet to act as a reservoir for metal ions, with an affinity order of Pd 2+ >Au 3+ >Cu 2+ . © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Construction of Nontoxic Polymeric UV-Absorber with Great Resistance to UV-Photoaging

PubMed Central

Huang, Zhong; Ding, Aishun; Guo, Hao; Lu, Guolin; Huang, Xiaoyu

2016-01-01

In this article, we developed a series of new nontoxic polymeric UV-absorbers through covalently attaching a benzophenone derivative onto the main chain of poly(vinyl chloride) (PVC) via mild and quantitative click chemistry. Azide groups were firstly introduced into the backbone of PVC via a nucleophilic reaction without affecting polymeric skeleton. Copper-catalyzed Husigen-Click cycloaddition reaction was performed between the pendant azide groups of PVC and alkynyl of (2-hydroxy-4-(prop-2-ynyloxy)phenyl)(phenyl)methanone at ambient temperature for affording the desired PVC-based UV-absorbers (PVC-UV) with different amounts of benzophenone moieties, which displayed great resistance to photoaging without degradation while exposed to UV irradiation. These polymeric UV-absorbers also showed good solubilities in common organic solvents and no cytotoxicity vs. HaCat cell. Small amounts of PVC-UV were homogeneously mixed with PVC as additive for stabilizing PVC against UV-photoaging without degradation and releasing small molecule even after 200 h while keeping thermal stability. This route of polymeric additive clearly paved an efficient way for solving the puzzle of separation of small molecule additive. PMID:27138547

Genetic Incorporation of Twelve meta-Substituted Phenylalanine Derivatives Using A Single Pyrrolysyl-tRNA Synthetase

PubMed Central

Wang, Yane-Shih; Fang, Xinqiang; Chen, Hsueh-Ying; Wu, Bo; Wang, Zhiyong U.; Hilty, Christian; Liu, Wenshe R.

2012-01-01

When coexpressed with its cognate amber suppressing tRNACUAPyl, a pyrrolysyl-tRNA synthetase mutant N346A/C348A is able to genetically incorporate twelve meta-substituted phenylalanine derivatives into proteins site-specifically at amber mutation sites in Escherichia coli. These genetically encoded noncanonical amino acids resemble phenylalanine in size and contain diverse bioorthogonal functional groups such as halide, trifluoromethyl, nitrile, nitro, ketone, alkyne, and azide moieties. The genetic installation of these functional groups in proteins provides multiple ways to site-selectively label proteins with biophysical and biochemical probes for their functional investigations. We demonstrate that a genetically incorporated trifluoromethyl group can be used as a sensitive 19F NMR probe to study protein folding/unfolding, and that genetically incorporated reactive functional groups such as ketone, alkyne, and azide moieties can be applied to site-specifically label proteins with florescent probes. This critical discovery allows the synthesis of proteins with diverse bioorthogonal functional groups for a variety of basic studies and biotechnology development using a single recombinant expression system. PMID:23138887

α-Conotoxin dendrimers have enhanced potency and selectivity for homomeric nicotinic acetylcholine receptors.

PubMed

Wan, Jingjing; Huang, Johnny X; Vetter, Irina; Mobli, Mehdi; Lawson, Joshua; Tae, Han-Shen; Abraham, Nikita; Paul, Blessy; Cooper, Matthew A; Adams, David J; Lewis, Richard J; Alewood, Paul F

2015-03-11

Covalently attached peptide dendrimers can enhance binding affinity and functional activity. Homogenous di- and tetravalent dendrimers incorporating the α7-nicotinic receptor blocker α-conotoxin ImI (α-ImI) with polyethylene glycol spacers were designed and synthesized via a copper-catalyzed azide-alkyne cycloaddition of azide-modified α-ImI to an alkyne-modified polylysine dendron. NMR and CD structural analysis confirmed that each α-ImI moiety in the dendrimers had the same 3D structure as native α-ImI. The binding of the α-ImI dendrimers to binding protein Ac-AChBP was measured by surface plasmon resonance and revealed enhanced affinity. Quantitative electrophysiology showed that α-ImI dendrimers had ∼100-fold enhanced potency at hα7 nAChRs (IC50 = 4 nM) compared to native α-ImI (IC50 = 440 nM). In contrast, no significant potency enhancement was observed at heteromeric hα3β2 and hα9α10 nAChRs. These findings indicate that multimeric ligands can significantly enhance conotoxin potency and selectivity at homomeric nicotinic ion channels.

Cu-catalyzed multicomponent polymerization to synthesize a library of poly(N-sulfonylamidines).

PubMed

Lee, In-Hwan; Kim, Hyunseok; Choi, Tae-Lim

2013-03-13

We report a versatile Cu-catalyzed multicomponent polymerization (MCP) technique that enables the synthesis of high-molecular-weight, defect-free poly(N-sulfonylamidines) from monomers of diynes, sulfonyl azides, and diamines. Through a series of optimizations, we discovered that the addition of excess triethylamine and the use of N,N'-dimethylformamide as a solvent are key factors to ensure efficient MCP. Formation of cyclic polyamidines was a side reaction during polymerization, but it was readily controlled by using diynes or diamines with long or rigid moieties. In addition, this polymerization is highly selective for three-component reactions over click reactions. The combination of the above factors enables the synthesis of high-molecular-weight polymers, which was challenging in previous MCPs. All three kinds of monomers (diynes, sulfonyl azides, and diamines) are readily accessible and stable under the reaction conditions, with various monomers undergoing successful polymerization regardless of their steric and electronic properties. Thus, we synthesized various high-molecular-weight, defect-free polyamidines from a broad range of monomers while overcoming the limitations of previous MCPs, such as low conversion and defects in the polymer structures.

Copper-free click reactions with polar bicyclononyne derivatives for modulation of cellular imaging.

PubMed

Leunissen, E H P; Meuleners, M H L; Verkade, J M M; Dommerholt, J; Hoenderop, J G J; van Delft, F L

2014-07-07

The ability of cells to incorporate azidosugars metabolically is a useful tool for extracellular glycan labelling. The exposed azide moiety can covalently react with alkynes, such as bicyclo[6.1.0]nonyne (BCN), by strain-promoted alkyne-azide cycloaddition (SPAAC). However, the use of SPAAC can be hampered by low specificity of the cycloalkyne. In this article we describe the synthesis of more polar BCN derivatives and their properties for selective cellular glycan labelling. The new polar derivatives [amino-BCN, glutarylamino-BCN and bis(hydroxymethyl)-BCN] display reaction rates similar to those of BCN and are less cell-permeable. The labelling specificity in HEK293 cells is greater than that of BCN, as determined by confocal microscopy and flow cytometry. Interestingly, amino-BCN appears to be highly specific for the Golgi apparatus. In addition, the polar BCN derivatives label the N-glycan of the membrane calcium channel TRPV5 in HEK293 cells with significantly enhanced signal-to-noise ratios. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of UVA irradiation, aryl azides, and reactive oxygen species on the orthogonal inactivation of the human immunodeficiency virus (HIV-1)

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

Belanger, Julie M.; Raviv, Yossef; Viard, Mathias

2011-08-15

Previously we reported that hydrophobic aryl azides partition into hydrophobic regions of the viral membrane of enveloped viruses and inactivate the virus upon UVA irradiation for 2 min. Prolonged irradiation (15 min) resulted in viral protein aggregation as visualized via Western blot analysis, due to reactive oxygen species (ROS) formation, with preservation of the surface antigenic epitopes. Herein, we demonstrate that these aggregates show detergent resistance and that this property may be useful towards the creation of a novel orthogonal virus inactivation strategy for use in preparing experimental vaccines. When ROS-modified HIV virus preparations were treated with 1% Triton X-100,more » there was an increase in the percent of viral proteins (gp41, p24) in the viral pellet after ultracentrifugation through sucrose. Transmission electron microscopy (TEM) of these detergent-resistant pellets shows some recognizable virus fragments, and immunoprecipitation studies of the gp41 aggregates suggest the aggregation is covalent in nature, involving short-range interactions.« less

Circular DNA by "Bis-Click" Ligation: Template-Independent Intramolecular Circularization of Oligonucleotides with Terminal Alkynyl Groups Utilizing Bifunctional Azides.

PubMed

Yang, Haozhe; Seela, Frank

2016-01-22

A highly effective and convenient "bis-click" strategy was developed for the template-independent circularization of single-stranded oligonucleotides by employing copper(I)-assisted azide-alkyne cycloaddition. Terminal triple bonds were incorporated at both ends of linear oligonucleotides. Alkynylated 7-deaza-2'-deoxyadenosine and 2'-deoxyuridine residues with different side chains were used in solid-phase synthesis with phosphoramidite chemistry. The bis-click ligation of linear 9- to 36-mer oligonucleotides with 1,4-bis(azidomethyl)benzene afforded circular DNA in a simple and selective way; azido modification of the oligonucleotide was not necessary. Short ethynyl side chains were compatible with the circularization of longer oligonucleotides, whereas octadiynyl residues were used for short 9-mers. Compared with linear duplexes, circular bis-click constructs exhibit a significantly increased duplex stability over their linear counterparts. The intramolecular bis-click ligation protocol is not limited to DNA, but may also be suitable for the construction of other macrocycles, such as circular RNAs, peptides, or polysaccharides. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of β-galactosylamides as ligands of the peanut lectin. Insights into the recognition process.

PubMed

Cano, María Emilia; Varela, Oscar; García-Moreno, María Isabel; García Fernández, José Manuel; Kovensky, José; Uhrig, María Laura

2017-04-18

The synthesis of mono and divalent β-galactosylamides linked to a hydroxylated chain having a C2 symmetry axis derived from l-tartaric anhydride is reported. Reference compounds devoid of hydroxyl groups in the linker were also prepared from β-galactosylamine and succinic anhydride. After functionalization with an alkynyl residue, the resulting building blocks were grafted onto different azide-equipped scaffolds through the copper catalyzed azide-alkyne cycloaddition. Thus, a family of structurally related mono and divalent β-N-galactopyranosylamides was obtained and fully characterized. The binding affinities of the ligands towards the model lectin PNA were measured by the enzyme-linked lectin assay (ELLA). The IC 50 values were significantly higher than that of galactose but the presence of hydroxyl groups in the aglycone chain improved lectin recognition. Docking and molecular dynamics experiments were in accordance with the hypothesis that a hydroxyl group properly disposed in the linker could mimic the Glc O3 in the recognition process. On the other hand, divalent presentation of the ligands led to lectin affinity enhancements. Copyright © 2017 Elsevier Ltd. All rights reserved.

Synthesis of novel 13α-18-norandrostane-ferrocene conjugates via homogeneous catalytic methods and their investigation on TRPV1 receptor activation.

PubMed

Szánti-Pintér, Eszter; Wouters, Johan; Gömöry, Ágnes; Sághy, Éva; Szőke, Éva; Helyes, Zsuzsanna; Kollár, László; Skoda-Földes, Rita

2015-12-01

13α-Steroid-ferrocene derivatives were synthesized via two reaction pathways starting from an unnatural 16-keto-18-nor-13α-steroid. The unnatural steroid was converted to ferrocene derivatives via copper-catalyzed azide-alkyne cycloaddition or palladium-catalyzed aminocarbonylation. 16-Azido- and 16-N-(prop-2-ynyl)-carboxamido-steroids were synthesized as starting materials for azide-alkyne cycloaddition with the appropriate ferrocene derivatives. Based on our earlier work, aminocarbonylation of 16-iodo-16-ene and 16-iodo-15-ene derivatives was studied with ferrocenylmethylamine. The new products were obtained in moderate to good yields and were characterized by (1)H and (13)C NMR, IR and MS. The solid state structure of the starting material 13α-18-norandrostan-16-one and two carboxamide products were determined by X-ray crystallography. Evidences were provided that the N-propargyl-carboxamide compound as well as its ferrocenylmethyltriazole derivative are able to decrease the activation of TRPV1 receptor on TRG neurons. Copyright © 2015 Elsevier Inc. All rights reserved.

Proteome-Wide Profiling of Targets of Cysteine reactive Small Molecules by Using Ethynyl Benziodoxolone Reagents.

PubMed

Abegg, Daniel; Frei, Reto; Cerato, Luca; Prasad Hari, Durga; Wang, Chao; Waser, Jerome; Adibekian, Alexander

2015-09-07

In this study, we present a highly efficient method for proteomic profiling of cysteine residues in complex proteomes and in living cells. Our method is based on alkynylation of cysteines in complex proteomes using a "clickable" alkynyl benziodoxolone bearing an azide group. This reaction proceeds fast, under mild physiological conditions, and with a very high degree of chemoselectivity. The formed azide-capped alkynyl-cysteine adducts are readily detectable by LC-MS/MS, and can be further functionalized with TAMRA or biotin alkyne via CuAAC. We demonstrate the utility of alkynyl benziodoxolones for chemical proteomics applications by identifying the proteomic targets of curcumin, a diarylheptanoid natural product that was and still is part of multiple human clinical trials as anticancer agent. Our results demonstrate that curcumin covalently modifies several key players of cellular signaling and metabolism, most notably the enzyme casein kinase I gamma. We anticipate that this new method for cysteine profiling will find broad application in chemical proteomics and drug discovery. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Large-scale separation of single-walled carbon nanotubes by electronic type using click chemistry

NASA Astrophysics Data System (ADS)

Um, Jo-Eun; Song, Sun Gu; Yoo, Pil J.; Song, Changsik; Kim, Woo-Jae

2018-01-01

Single-walled carbon nanotubes (SWCNTs) can be either metallic or semiconducting, making their separation critical for applications in nanoelectronics, biomedical materials, and solar cells. Herein, we investigate a novel solution-phase separation method based on click chemistry (azide-alkyne Huisgen cycloaddition) and determine its efficiency and scalability. In this method, metallic SWCNTs in metallic/semiconducting SWCNT mixtures are selectively functionalized with alkyne groups by being reacted with 4-propargyloxybenezenediazonium tetrafluoroborate. Subsequently, silica nanoparticles are functionalized with azide groups and reacted with alkyne-bearing metallic SWCNTs in the SWCNT mixture in the presence of a Cu catalyst. As a result, metallic SWCNTs are anchored on silica powder, whereas non-functionalized semiconducting SWCNTs remain in solution. Low-speed centrifugation effectively removes the silica powder with attached metallic SWCNTs, furnishing a solution of highly pure semiconducting SWCNTs, as confirmed by Raman and UV-vis/near-infrared absorption measurements. This novel separation scheme exhibits the advantage of simultaneously separating both metallic and semiconducting SWCNTs from their mixtures, being cost-effective and therefore applicable at an industrial scale.

Activity-Based Protein Profiling of Ammonia Monooxygenase in Nitrosomonas europaea

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

Bennett, Kristen; Sadler, Natalie C.; Wright, Aaron T.

Nitrosomonas europaeais an aerobic nitrifying bacterium that oxidizes ammonia (NH 3) to nitrite (NO 2 ₋) through the sequential activities of ammonia monooxygenase (AMO) and hydroxylamine dehydrogenase (HAO). Many alkynes are mechanism-based inactivators of AMO, and here we describe an activity-based protein profiling method for this enzyme using 1,7-octadiyne (17OD) as a probe. Inactivation of NH 4 +-dependent O 2uptake byN. europaeaby 17OD was time- and concentration-dependent. The effects of 17OD were specific for ammonia-oxidizing activity, andde novoprotein synthesis was required to reestablish this activity after cells were exposed to 17OD. Cells were reacted with Alexa Fluor 647 azide usingmore » a copper-catalyzed azide-alkyne cycloaddition (CuAAC) (click) reaction, solubilized, and analyzed by SDS-PAGE and infrared (IR) scanning. A fluorescent 28-kDa polypeptide was observed for cells previously exposed to 17OD but not for cells treated with either allylthiourea or acetylene prior to exposure to 17OD or for cells not previously exposed to 17OD. The fluorescent polypeptide was membrane associated and aggregated when heated with β-mercaptoethanol and SDS. The fluorescent polypeptide was also detected in cells pretreated with other diynes, but not in cells pretreated with structural homologs containing a single ethynyl functional group. The membrane fraction from 17OD-treated cells was conjugated with biotin-azide and solubilized in SDS. Streptavidin affinity-purified polypeptides were on-bead trypsin-digested, and amino acid sequences of the peptide fragments were determined by liquid chromatography-mass spectrometry (LC-MS) analysis. Peptide fragments from AmoA were the predominant peptides detected in 17OD-treated samples. In-gel digestion and matrix-assisted laser desorption ionization–tandem time of flight (MALDI-TOF/TOF) analyses also confirmed that the fluorescent 28-kDa polypeptide was AmoA.« less

An Efficient and Straightforward Method for Radiolabeling of Nanoparticles with {sup 64}Cu via Click Chemistry

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

Lee, Dong-Eun; Kim, Kwangmeyung; Park, Sang Hyun

2015-07-01

Recently, nanoparticles have received a great deal of interest in diagnosis and therapy applications. Since nanoparticles possess intrinsic features that are often required for a drug delivery system and diagnosis, they have potential to be used as platforms for integrating imaging and therapeutic functions, simultaneously. Intrinsic issues that are associated with theranostic nanoparticles, particularly in cancer treatment, include an efficient and straightforward radiolabeling method for understanding the in vivo biodistribution of nanoparticles to reach the tumor region, and monitoring therapeutic responses. Herein, we investigated a facile and highly efficient strategy to prepare radiolabeled nanoparticles with {sup 64}Cu via a strain-promotedmore » azide, i.e., an alkyne cycloaddition strategy, which is often referred to as click chemistry. First, the azide (N3) group, which allows for the preparation of radiolabeled nanoparticles by copper-free click chemistry, was incorporated into glycol chitosan nanoparticles (CNPs). Second, the strained cyclooctyne derivative, dibenzyl cyclooctyne (DBCO) conjugated with a 1,4,7,10-tetraazacyclododecane- 1,4,7,10-tetraacetic acid (DOTA) chelator, was synthesized for preparing the pre-radiolabeled alkyne complex with {sup 64}Cu radionuclide. Following incubation with the {sup 64}Cu-radiolabeled DBCO complex (DBCO-PEG4-Lys-DOTA-{sup 64}Cu with high specific activity, 18.5 GBq/μ mol), the azide-functionalized CNPs were radiolabeled successfully with {sup 64}Cu, with a high radiolabeling efficiency and a high radiolabeling yield (>98%). Importantly, the radiolabeling of CNPs by copper-free click chemistry was accomplished within 30 min, with great efficiency in aqueous conditions. After {sup 64}Cu-CNPs were intravenously administered to tumor-bearing mice, the real time, in vivo biodistribution and tumor-targeting ability of {sup 64}Cu-CNPs were quantitatively evaluated by micro-PET images of tumor-bearing mice. These results demonstrate the benefit of copper-free click chemistry as a facile, pre-radiolabeling approach to Medical sciences conveniently radiolabel nanoparticles for evaluating the real-time in vivo biodistribution of nanoparticles. (authors)« less

Myeloperoxidase potentiates nitric oxide-mediated nitrosation.

PubMed

Lakshmi, Vijaya M; Nauseef, William M; Zenser, Terry V

2005-01-21

Nitrosation is an important reaction elicited by nitric oxide (NO). To better understand how nitrosation occurs in biological systems, we assessed the effect of myeloperoxidase (MPO), a mediator of inflammation, on nitrosation observed during NO autoxidation. Nitrosation of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ; 10 mum) to 2-nitrosoamino-3-methylimidazo[4,5-f]quinoline (N-NO-IQ) was monitored by HPLC. Using the NO donor spermine NONOate at pH 7.4, MPO potentiated N-NO-IQ formation. The minimum effective quantity of necessary components was 8.5 nm MPO, 0.25 mum H(2)O(2)/min, and 0.024 mum NO/min. Autoxidation was only detected at >/=1.2 mum NO/min. MPO potentiation was not affected by a 40-fold excess flux of H(2)O(2) over NO or less than a 2.4-fold excess flux of NO over H(2)O(2). Potentiation was due to an 8.8-fold increased affinity of MPO-derived nitrosating species for IQ. Autoxidation was inhibited by azide, suggesting involvement of the nitrosonium ion, NO(+). MPO potentiation was inhibited by NADH, but not azide, suggesting oxidative nitrosylation with NO(2)(.) or an NO(2)(.)-like species. MPO nonnitrosative oxidation of IQ with 0.3 mm NO(2)(-) at pH 5.5 was inhibited by azide, but not NADH, demonstrating differences between MPO oxidation of IQ with NO compared with NO(2)(-). Using phorbol ester-stimulated human neutrophils, N-NO-IQ formation was increased with superoxide dismutase and inhibited by catalase and NADH, but not NaN(3). This is consistent with nitrosation potentiation by MPO, not peroxynitrite. Increased N-NO-IQ formation was not detected with polymorphonuclear neutrophils from two unrelated MPO-deficient patients. Results suggest that the highly diffusible stable gas NO could initiate nitrosation at sites of neutrophil infiltration.

Mechanisms and kinetic profiles of superoxide-stimulated nitrosative processes in cells using a diaminofluorescein probe.

PubMed

Damasceno, Fernando Cruvinel; Facci, Rômulo Rodrigues; da Silva, Thalita Marques; Toledo, José Carlos

2014-12-01

In this study, we examined the mechanisms and kinetic profiles of intracellular nitrosative processes using diaminofluorescein (DAF-2) as a target in RAW 264.7 cells. The intracellular formation of the fluorescent, nitrosated product diaminofluorescein triazol (DAFT) from both endogenous and exogenous nitric oxide (NO) was prevented by deoxygenation and by cell membrane-permeable superoxide (O2(-)) scavengers but not by extracellular bovine Cu,Zn-SOD. In addition, the DAFT formation rate decreased in the presence of cell membrane-permeable Mn porphyrins that are known to scavenge peroxynitrite (ONOO(-)) but was enhanced by HCO3(-)/CO2. Together, these results indicate that nitrosative processes in RAW 264.7 cells depend on endogenous intracellular O2(-) and are stimulated by ONOO(-)/CO2-derived radical oxidants. The N2O3 scavenger sodium azide (NaN3) only partially attenuated the DAFT formation rate and only with high NO (>120 nM), suggesting that DAFT formation occurs by nitrosation (azide-susceptible DAFT formation) and predominantly by oxidative nitrosylation (azide-resistant DAFT formation). Interestingly, the DAFT formation rate increased linearly with NO concentrations of up to 120-140 nM but thereafter underwent a sharp transition and became insensitive to NO. This behavior indicates the sudden exhaustion of an endogenous cell substrate that reacts rapidly with NO and induces nitrosative processes, consistent with the involvement of intracellular O2(-). On the other hand, intracellular DAFT formation stimulated by a fixed flux of xanthine oxidase-derived extracellular O2(-) that also occurs by nitrosation and oxidative nitrosylation increased, peaked, and then decreased with increasing NO, as previously observed. Thus, our findings complementarily show that intra- and extracellular O2(-)-dependent nitrosative processes occurring by the same chemical mechanisms do not necessarily depend on NO concentration and exhibit different unusual kinetic profiles with NO dynamics, depending on the biological compartment in which NO and O2(-) interact. Copyright © 2014 Elsevier Inc. All rights reserved.

Activity-Based Protein Profiling of Ammonia Monooxygenase in Nitrosomonas europaea

PubMed Central

Bennett, Kristen; Sadler, Natalie C.; Wright, Aaron T.; Yeager, Chris

2016-01-01

Nitrosomonas europaea is an aerobic nitrifying bacterium that oxidizes ammonia (NH3) to nitrite (NO2−) through the sequential activities of ammonia monooxygenase (AMO) and hydroxylamine dehydrogenase (HAO). Many alkynes are mechanism-based inactivators of AMO, and here we describe an activity-based protein profiling method for this enzyme using 1,7-octadiyne (17OD) as a probe. Inactivation of NH4+-dependent O2 uptake by N. europaea by 17OD was time- and concentration-dependent. The effects of 17OD were specific for ammonia-oxidizing activity, and de novo protein synthesis was required to reestablish this activity after cells were exposed to 17OD. Cells were reacted with Alexa Fluor 647 azide using a copper-catalyzed azide-alkyne cycloaddition (CuAAC) (click) reaction, solubilized, and analyzed by SDS-PAGE and infrared (IR) scanning. A fluorescent 28-kDa polypeptide was observed for cells previously exposed to 17OD but not for cells treated with either allylthiourea or acetylene prior to exposure to 17OD or for cells not previously exposed to 17OD. The fluorescent polypeptide was membrane associated and aggregated when heated with β-mercaptoethanol and SDS. The fluorescent polypeptide was also detected in cells pretreated with other diynes, but not in cells pretreated with structural homologs containing a single ethynyl functional group. The membrane fraction from 17OD-treated cells was conjugated with biotin-azide and solubilized in SDS. Streptavidin affinity-purified polypeptides were on-bead trypsin-digested, and amino acid sequences of the peptide fragments were determined by liquid chromatography-mass spectrometry (LC-MS) analysis. Peptide fragments from AmoA were the predominant peptides detected in 17OD-treated samples. In-gel digestion and matrix-assisted laser desorption ionization–tandem time of flight (MALDI-TOF/TOF) analyses also confirmed that the fluorescent 28-kDa polypeptide was AmoA. PMID:26826234

Multifunctional Pt(II) Reagents: Covalent Modifications of Pt Complexes Enable Diverse Structural Variation and In-Cell Detection.

PubMed

White, Jonathan D; Haley, Michael M; DeRose, Victoria J

2016-01-19

To enhance the functionality of Pt-based reagents, several strategies have been developed that utilize Pt compounds modified with small, reactive handles. This Account encapsulates work done by us and other groups regarding the use of Pt(II) compounds with reactive handles for subsequent elaboration with fluorophores or other functional moieties. Described strategies include the incorporation of substituents for well-known condensation or nucleophilic displacement-type reactions and their use, for example, to tether spectroscopic handles to Pt reagents for in vivo investigation. Other chief uses of displacement-type reactions have included tethering various small molecules exhibiting pharmacological activity directly to Pt, thus adding synergistic effects. Click chemistry-based ligation techniques have also been applied, primarily with azide- and alkyne-appended Pt complexes. Orthogonally reactive click chemistry reactions have proven invaluable when more traditional nucleophilic displacement reactions induce side-reactivity with the Pt center or when systematic functionalization of a larger number of Pt complexes is desired. Additionally, a diverse assortment of Pt-fluorophore conjugates have been tethered via click chemistry conjugation. In addition to providing a convenient synthetic path for diversifying Pt compounds, the use of click-capable Pt complexes has proved a powerful strategy for postbinding covalent modification and detection with fluorescent probes. This strategy bypasses undesirable influences of the fluorophore camouflaged as reactivity due to Pt that may be present when detecting preattached Pt-fluorophore conjugates. Using postbinding strategies, Pt reagent distributions in HeLa and lung carcinoma (NCI-H460) cell cultures were observed with two different azide-modified Pt compounds, a monofunctional Pt(II)-acridine type and a difunctional Pt(II)-neutral complex. In addition, cellular distribution was observed with an alkyne-appended difunctional Pt(II)-neutral complex analogous in structure to the aforementioned difunctional azide-Pt(II) reagent. In all cases, significant accumulation of Pt in the nucleolus of cells was observed, in addition to broader localization in the nucleus and cytoplasm of the cell. Using the same strategy of postbinding click modification with fluorescent probes, Pt adducts were detected and roughly quantified on rRNA and tRNA from Pt-treated Saccharomyces cerevisiae; rRNA adducts were found to be relatively long-lived and not targeted for immediate degradation. Finally, the utility and feasibility of the alkyne-appended Pt(II) compound has been further demonstrated with a turn-on fluorophore, dansyl azide, in fluorescent detection of DNA in vitro. In all, these modifications utilizing reactive handles have allowed for the diversification of new Pt reagents, as well as providing cellular localization information on the modified Pt compounds.

Riluzole But Not Melatonin Ameliorates Acute Motor Neuron Degeneration and Moderately Inhibits SOD1-Mediated Excitotoxicity Induced Disrupted Mitochondrial Ca2+ Signaling in Amyotrophic Lateral Sclerosis

PubMed Central

Jaiswal, Manoj Kumar

2017-01-01

Selective motoneurons (MNs) degeneration in the brain stem, hypoglossal motoneurons (HMNs), and the spinal cord resulting in patients paralysis and eventual death are prominent features of amyotrophic lateral sclerosis (ALS). Previous studies have suggested that mitochondrial respiratory impairment, low Ca2+ buffering and homeostasis and excitotoxicity are the pathological phenotypes found in mice, and cell culture models of familial ALS (fALS) linked with Cu/Zn-superoxide dismutase 1 (SOD1) mutation. In our study, we aimed to understand the impact of riluzole and melatonin on excitotoxicity, neuronal protection and Ca2+ signaling in individual HMNs ex vivo in symptomatic adult ALS mouse brain stem slice preparations and in WT and SOD1-G93A transfected SH-SY5Y neuroblastoma cell line using fluorescence microscopy, calcium imaging with high speed charged coupled device camera, together with immunohistochemistry, cell survival assay and histology. In our experiments, riluzole but not melatonin ameliorates MNs degeneration and moderately inhibit excitotoxicity and cell death in SH-SY5YWT or SH-SY5YG93A cell lines induced by complex IV blocker sodium azide. In brain stem slice preparations, riluzole significantly inhibit HMNs cell death induced by inhibiting the mitochondrial electron transport chain by Na-azide. In the HMNs of brainstem slice prepared from adult (14–15 weeks) WT, and corresponding symptomatic SOD1G93A mice, we measured the effect of riluzole and melatonin on [Ca2+]i using fura-2 AM ratiometric calcium imaging in individual MNs. Riluzole caused a significant decrease in [Ca2+]i transients and reversibly inhibited [Ca2+]i transients in Fura-2 AM loaded HMNs exposed to Na-azide in adult symptomatic SOD1G93A mice. On the contrary, melatonin failed to show similar effects in the HMNs of WT and SOD1G93A mice. Intrinsic nicotinamide adenine dinucleotide (NADH) fluorescence, an indicator of mitochondrial metabolism and health in MNs, showed enhanced intrinsic NADH fluorescence in HMNs in presence of riluzole when respiratory chain activity was inhibited by Na-azide. Riluzole’s inhibition of excitability and Ca2+ signaling may be due to its multiple effects on cellular function of mitochondria. Therefore formulating a drug therapy to stabilize mitochondria-related signaling pathways using riluzole might be a valuable approach for cell death protection in ALS. Taken together, the pharmacological profiles of the riluzole and melatonin strengthen the case that riluzole indeed can be used as a therapeutic agent in ALS whereas claims of the efficacy of melatonin alone need further investigation as it fail to show significant neuroprotection efficacy. PMID:28111541

2006 Global Demilitarization Symposium Volume 1 Presentations

DTIC Science & Technology

2006-05-04

produce inorganic crystals in continuous-reaction mode: Continuous synthesis of CdSe–ZnS composite nanoparticles in a microfluidic reactor, Hongzhi...crystallize lead azide nanoparticles , and to grow them into dextrinated microparticles; Point of Application Microfluidic Synthesis of Sensitive...National Laboratory Point of Application Synthesis of Sensitive Explosive Mr. Karl Wally, Sandia National Laboratories Session III- A Session

Formation of N3(-) during interaction of NO with reduced ceria.

PubMed

Mihaylov, Mihail Y; Ivanova, Elena Z; Aleksandrov, Hristiyan A; St Petkov, Petko; Vayssilov, Georgi N; Hadjiivanov, Konstantin I

2015-04-04

We show that the first stages of interaction between NO and reduced ceria comprise the formation of azides, N3(-), with simultaneous oxidation of Ce(3+) to Ce(4+). This finding imposes revision on some current views of catalytic NO conversion and may contribute to design of new deNOx materials and processes.

Synthesis and Explosion Hazards of 4-Azido-l-phenylalanine.

PubMed

Richardson, Mark B; Brown, Derek B; Vasquez, Carlos A; Ziller, Joseph W; Johnston, Kevin M; Weiss, Gregory A

2018-04-20

A reliable, scalable, cost-effective, and chromatography-free synthesis of 4-azido-l-phenylalanine beginning from l-phenylalanine is described. Investigations into the safety of the synthesis reveal that the Ullman-like Cu(I)-catalyzed azidation step does not represent a significant risk. The isolated 4-azido-l-phenylalanine product, however, exhibits previously undocumented explosive characteristics.

1,5 iodonaphthyl Azide Inactivated V3526 Protects against Aerosol Challenge with Virulent Venezuelan Equine Encephalitis Virus.

DTIC Science & Technology

2016-06-02

against VEEV. VEEV is highly infectious in aerosolized form and has been identified as a bio -terrorism agent. The current IND vaccine is poorly...protective response as well as residual virulence associated with the live attenuated vaccine candidates [1]. VEEV is also a bio -threat agent, thereby; any

AN ENZYME LINKED IMMUNOSORBENT ASSAY (ELISA) METHOD FOR THE URINARY BIOMONITORING OF 2,4-DICHLOROPHRENOCYACETIC ACID (2,4-D)

EPA Science Inventory

An enzyme-linked immunosorbent assay (ELISA) method was developed to quantitatively measure 2,4-dichlorophenoyacetic acid (2,4-D) in human urine. Samples were diluted (1:5) with phosphate-buffered saline, 0.05% Tween 20, with 0.02% sodium azide, and analyzed by a 96-microwekk pl...

Undergraduate Organic Experiment: Tetrazole Formation by Microwave Heated (3 + 2) Cycloaddition in Aqueous Solution

ERIC Educational Resources Information Center

DeFrancesco, Heather; Dudley, Joshua; Coca, Adiel

2018-01-01

An undergraduate experiment for the organic laboratory is described that utilizes microwave heating to prepare 5- substituted 1H-tetrazole derivatives through a (3 + 2) cycloaddition between aryl nitriles and sodium azide. The reaction mixture is analyzed by thin layer chromatography. The products are purified through an acid-base extraction and…

A Cu-free clickable fluorescent probe for intracellular targeting of small biomolecules.

PubMed

Yamagishi, Kento; Sawaki, Kazuaki; Murata, Atsushi; Takeoka, Shinji

2015-05-07

We synthesized a novel cyclooctyne-based clickable fluorescent probe with versatile properties such as high cell-membrane permeability and free diffusibility in the cell. Our probe "FC-DBCO" was conjugated to an azide-modified mannose via a Cu-free click reaction in living HeLa cells and displayed intracellular specific fluorescence imaging with low background signals.

In Vivo Test for Chemical Induction of Micronucleated Polychromatic Erythrocytes in Mouse Bone Marrow Cells. Test Article: Dimethylamine-2-2ethyl azide (DMAZ)

DTIC Science & Technology

2008-06-25

Hunched Back Unusual Body Secretions - Nasal Discharge - Lacrimation - Salivation - Bloody Stool - Dianhea Abnormal Behavior - Convulsions...WetGroin - Hunched Back Unusual Body Secretions - Nasal Discharge - Lacrimation - Salivation - Bloody Stool - Diarrhea Abnormal Behavior...Ataxia - Piloerection - WetGrain - Hunched Back Unusual Body Secretions - Nasal Discharge - Lacrimation - Salivation - Bloody Stool

Anti-inflammatory drugs interacting with Zn (II) metal ion based on thiocyanate and azide ligands: synthesis, spectroscopic studies, DFT calculations and antibacterial assays.

PubMed

Chiniforoshan, Hossein; Tabrizi, Leila; Hadizade, Morteza; Sabzalian, Mohammad R; Chermahini, Alireza Najafi; Rezapour, Mehdi

2014-07-15

Zinc (II) complexes with non-steroidal anti-inflammatory drugs (NSAIDs) naproxen (nap) and ibuprofen (ibu) were synthesized in the presence of nitrogen donor ligands (thiocyanate or azide). The complexes were characterized by elemental analysis, FT-IR, (1)H NMR and UV-Vis spectroscopes. The binding modes of the ligands in complexes were established by means of molecular modeling of the complexes, and calculation of their IR, NMR and absorption spectra at DFT (TDDFT)/B3LYP level were studied. The experimental and calculated data verified monodentate binding through the carboxylic oxygen atoms of anti-inflammatory drugs in the zinc complexes. The calculated (1)H, FT-IR and UV-Vis data are in better agreement with the experimental results, and confirm the predicted tetrahedral structures for the Zn (II) complexes. In addition to DFT calculations of complexes, natural bond orbital (NBO) was performed at B3LYP/6-31+G(d,p) level of theory. Biological studies showed the antibacterial activity of zinc complexes against Gram-positive and Gram-negative bacterial strains. Copyright © 2014 Elsevier B.V. All rights reserved.

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

PubMed

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

2011-06-15

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

Towards understanding the kinetic behaviour and limitations in photo-induced copper(i) catalyzed azide-alkyne cycloaddition (CuAAC) reactions.

PubMed

El-Zaatari, Bassil M; Shete, Abhishek U; Adzima, Brian J; Kloxin, Christopher J

2016-09-14

The kinetic behaviour of the photo-induced copper(i) catalyzed azide-alkyne cycloaddition (CuAAC) reaction was studied in detail using real-time Fourier transform infrared (FTIR) spectroscopy on both a solvent-based monofunctional and a neat polymer network forming system. The results in the solvent-based system showed near first-order kinetics on copper and photoinitiator concentrations up to a threshold value in which the kinetics switch to zeroth-order. This kinetic shift shows that the photo-CuAAC reaction is not susceptible from side reactions such as copper disproportionation, copper(i) reduction, and radical termination at the early stages of the reaction. The overall reaction rate and conversion is highly dependent on the initial concentrations of photoinitiator and copper(ii) as well as their relative ratios. The conversion was decreased when an excess of photoinitiator was utilized compared to its threshold value. Interestingly, the reaction showed an induction period at relatively low intensities. The induction period is decreased by increasing light intensity and photoinitiator concentration. The reaction trends and limitations were further observed in a solventless polymer network forming system, exhibiting a similar copper and photoinitiator threshold behaviour.

Tripodal penta(p-phenylene) for the biofunctionalization of alkynyl-modified silicon surfaces

NASA Astrophysics Data System (ADS)

Sánchez-Molina, María; Díaz, Amelia; Valpuesta, María; Contreras-Cáceres, Rafael; López-Romero, J. Manuel; López-Ramírez, M. Rosa

2018-07-01

Here we report the optimization on the covalent grafting methodology of a tripod-shaped penta(p-phenylene), 1, on alkynyl-terminated silicon surfaces, and the incorporation of an active theophylline derivative, 2, for the specific immobilization of proteins. The tripodal molecule presents azide-terminal groups to be attached onto a silicon surface containing an alkynyl monolayer. Initially, compound 1 has been covalently incorporated on alkynyl-terminated Si wafers, by the copper catalyzed alkyne-azide 1,3-dipolar cycloaddition (CuAAC, a click reaction). The tripod density on the silicon surface is tuned by performing the CuAAC reaction at different concentrations of 1, as well as under different experimental conditions (T, base, copper source, shaking). Then, tripod 1-modified surface has also been biofunctionalized with 2. The effective preparation of this silicon-modified surface allowed us to study the streptavidin immobilization on the surface. Characterization of the different surfaces has been carried out by X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and Bright-Field Optical Transmission Microscopy (Confocal) techniques. We also include density functional theory (DFT) analysis of the organic structures to confirm the height-profile and the tripod-surface relative configuration extracted from AFM images.

Ruthenium-Catalyzed Cycloaddition of 1-Haloalkynes with Nitrile Oxides and Organic Azides; Synthesis of 4-Halo Isoxazoles and 5-Halo Triazoles

PubMed Central

Oakdale, James S.; Sit, Rakesh K.

2015-01-01

(Cyclopentadienyl)(cyclooctadiene) ruthenium(II) chloride [CpRuCl(cod)] catalyzes the reaction between nitrile oxides and electronically deficient 1-choro-, 1-bromo- and 1-iodoalkynes leading to 4-haloisoxazoles. Organic azides are also suitable 1,3-dipoles, resulting in 5-halo-1,2,3-triazoles. These air tolerant reactions can be performed at room temperature with 1.25 equiv of the respective 1,3-dipole relative to the alkyne component. Reactive 1-haloalkynes include propiolic amides, esters, ketones and phosphonates. Post-functionalization of the halogenated azole products can be accomplished using palladium-catalyzed cross-coupling reactions as well as via manipulation of reactive amide groups. The lack of catalysis observed with Cp*RuCl(cod) is attributed to steric demands of the Cp* (η5-C5Me5) ligand in comparison to the parent Cp (η5-C5H5). This hypothesis is supported by the poor reactivity of (η5-C5Me4CF3)RuCl(cod), which serves as a an isosteric mimic of Cp* and as an isoelectronic analog of Cp. PMID:25059647

Metal–organic coordination architectures of tetrazole heterocycle ligands bearing acetate groups: Synthesis, characterization and magnetic properties

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

Hu, Bo-Wen, E-mail: bowenhu@hit.edu.cn; Zheng, Xiang-Yu; Ding, Cheng

2015-12-15

Two new coordination complexes with tetrazole heterocycle ligands bearing acetate groups, [Co(L){sub 2}]{sub n} (1) and [Co{sub 3}(L){sub 4}(N{sub 3}){sub 2}·2MeOH]{sub n} (2) (L=tetrazole-1-acetate) have been synthesized and structurally characterized. Single crystal structure analysis shows that the cobalt-complex 1 has the 3D 3,6-connected (4{sup 2}.6){sub 2}(4{sup 4}.6{sup 2}.8{sup 8}.10)-ant topology. By introducing azide in this system, complex 2 forms the 2D network containing the [Co{sub 3}] units. And the magnetic properties of 1 and 2 have been studied. - Graphical abstract: The synthesis, crystal structure, and magnetic properties of the new coordination complexes with tetrazole heterocycle ligands bearing acetate groupsmore » are reported. - Highlights: • Two novel Cobalt(II) complexes with tetrazole acetate ligands were synthesized. • The magnetic properties of two complexes were studied. • Azide as co-ligand resulted in different structures and magnetic properties. • The new coordination mode of tetrazole acetate ligand was obtained.« less

Azide–Alkyne Click Conjugation on Quantum Dots by Selective Copper Coordination

PubMed Central

Mann, Victor R.; Powers, Alexander S.; Tilley, Drew C.; Sack, Jon T.; Cohen, Bruce E.

2018-01-01

Functionalization of nanocrystals is essential for their practical application, but synthesis on nanocrystal surfaces is limited by incompatibilities with certain key reagents. The copper-catalyzed azide-alkyne cycloaddition (CuAAC) is among the most useful methods for ligating molecules to surfaces, but has been largely useless for semiconductor quantum dots (QDs) because Cu+ ions quickly and irreversibly quench QD fluorescence. To discover non-quenching synthetic conditions for Cu-catalyzed click reactions on QD surfaces, we developed a combinatorial fluorescence assay to screen >2000 reaction conditions to maximize cycloaddition efficiency while minimizing QD quenching. We identify conditions for complete coupling without significant quenching, which are compatible with common QD polymer surfaces and various azide/alkyne pairs. Based on insight from the combinatorial screen and mechanistic studies of Cu coordination and quenching, we find that superstoichiometric concentrations of Cu can promote full coupling if accompanied by ligands that selectively compete the Cu from the QD surface but allow it to remain catalytically active. Applied to the conjugation of a K+ channel-specific peptidyl toxin to CdSe/ZnS QDs, we synthesize unquenched QD conjugates and image their specific and voltage-dependent affinity for K+ channels in live cells. PMID:29608274

Discovery of novel anti-HIV agents via Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) click chemistry-based approach.

PubMed

Gao, Ping; Sun, Lin; Zhou, Junsu; Li, Xiao; Zhan, Peng; Liu, Xinyong

2016-09-01

In recent years, a variety of new synthetic methodologies and concepts have been proposed in the search for new pharmaceutical lead structures and optimization. Notably, the Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) click chemistry approach has drawn great attention and has become a powerful tool for the generation of privileged medicinal skeletons in the discovery of anti-HIV agents. This is due to the high degree of reliability, complete specificity (chemoselectivity and regioselectivity), mild conditions, and the biocompatibility of the reactants. Herein, the authors describe the progress thus far on the discovery of novel anti-HIV agents via the CuAAC click chemistry-based approach. CuAAC click chemistry is a proven protocol for synthesizing triazole products which could serve as basic pharmacophores, act as replacements of traditional scaffold or substituent modification, be a linker of dual-target or dual-site inhibitors and more for the discovery of novel anti-HIV agents. What's more, it also provides convenience and feasibility for dynamic combinatorial chemistry and in situ screening. It is envisioned that click chemistry will draw more attention and make more contributions in anti-HIV drug discovery in the future.

RGD-conjugated rod-like viral nanoparticles on 2D scaffold improved bone differentiation of mesenchymal stem cells

NASA Astrophysics Data System (ADS)

Wang, Qian; Pongkwan, Sitasuwan; Lee, L.; Li, Kai; Nguyen, Huong

2014-05-01

Viral nanoparticles have uniform and well-defined nano-structures and can be produced in large quantities. Several plant viral nanoparticles have been tested in biomedical applications due to the lack of mammalian cell infectivity. We are particularly interested in using Tobacco mosaic virus (TMV), which has been demonstrated to enhance bone tissue regeneration, as a tuneable nanoscale building block for biomaterials development. Unmodified TMV particles have been shown to accelerate osteogenic differentiation of adult stem cells by synergistically upregulating BMP2 and IBSP expression with dexamethasone. However, the lack of affinity to mammalian cell surface resulted in low initial cell adhesion. In this study, to increase cell binding capacity of TMV based material the chemical functionalization of TMV with arginine-glycine-aspartic acid (RGD) peptide was explored. An azide-derivatized RGD peptide was “clicked” to tyrosine residues on TMV outer surface via an efficient copper(I) catalysed azide-alkyne cycloaddition reaction. The ligand spacing is calculated to be 2-4 nm, which could offer a polyvalent ligand clustering effect for enhanced cell receptor signalling, further promoting the proliferation and osteogenic differentiation of bone marrow derived mesenchymal stem cells.

ZINClick: a database of 16 million novel, patentable, and readily synthesizable 1,4-disubstituted triazoles.

PubMed

Massarotti, Alberto; Brunco, Angelo; Sorba, Giovanni; Tron, Gian Cesare

2014-02-24

Since Professors Sharpless, Finn, and Kolb first introduced the concept of "click reactions" in 2001 as powerful tools in drug discovery, 1,4-disubstituted-1,2,3-triazoles have become important in medicinal chemistry due to the simultaneous discovery by Sharpless, Fokin, and Meldal of a perfect click 1,3-dipolar cycloaddition reaction between azides and alkynes catalyzed by copper salts. Because of their chemical features, these triazoles are proposed to be aggressive pharmacophores that participate in drug-receptor interactions while maintaining an excellent chemical and metabolic profile. Surprisingly, no virtual libraries of 1,4-disubstituted-1,2,3-triazoles have been generated for the systematic investigation of the click-chemical space. In this manuscript, a database of triazoles called ZINClick is generated from literature-reported alkynes and azides that can be synthesized within three steps from commercially available products. This combinatorial database contains over 16 million 1,4-disubstituted-1,2,3-triazoles that are easily synthesizable, new, and patentable! The structural diversity of ZINClick ( http://www.symech.it/ZINClick ) will be explored. ZINClick will also be compared to other available databases, and its application during the design of novel bioactive molecules containing triazole nuclei will be discussed.

Functionalized Poly(3-hexylthiophene)s via Lithium–Bromine Exchange

PubMed Central

2015-01-01

Poly(3-hexylthiophene) (P3HT) is one of the most extensively investigated conjugated polymers and has been employed as the active material in many devices including field-effect transistors, organic photovoltaics and sensors. As a result, methods to further tune the properties of P3HT are desirable for specific applications. Herein, we report a facile postpolymerization modification strategy to functionalize the 4-position of commercially available P3HT in two simple steps–bromination of the 4-position of P3HT (Br–P3HT) followed by lithium−bromine exchange and quenching with an electrophile. We achieved near quantitative lithium–bromine exchange with Br–P3HT, which requires over 100 thienyl lithiates to be present on a single polymer chain. The lithiated-P3HT is readily combined with functional electrophiles, resulting in P3HT derivatives with ketones, secondary alcohols, trimethylsilyl (TMS) group, fluorine, or an azide at the 4-position. We demonstrated that the azide-modified P3HT could undergo Cu-catalyzed or Cu-free click chemistry, significantly expanding the complexity of the structures that can be appended to P3HT using this method. PMID:25620811

Site-Specific Antibody Labeling by Covalent Photoconjugation of Z Domains Functionalized for Alkyne-Azide Cycloaddition Reactions.

PubMed

Perols, Anna; Arcos Famme, Melina; Eriksson Karlström, Amelie

2015-11-01

Antibodies are extensively used in research, diagnostics, and therapy, and for many applications the antibodies need to be labeled. Labeling is typically performed by using amine-reactive probes that target surface-exposed lysine residues, resulting in heterogeneously labeled antibodies. An alternative labeling strategy is based on the immunoglobulin G (IgG)-binding protein domain Z, which binds to the Fc region of IgG. Introducing the photoactivable amino acid benzoylphenylalanine (BPA) into the Z domain makes it possible for a covalent bond to be be formed between the Z domain and the antibody on UV irradiation, to produce a site-specifically labeled product. Z32 BPA was synthesized by solid-phase peptide synthesis and further functionalized to give alkyne-Z32 BPA and azide-Z32 BPA for Cu(I) -catalyzed cycloaddition, as well as DBCO-Z32 BPA for Cu-free strain-promoted cycloaddition. The Z32 BPA variants were conjugated to the human IgG1 antibody trastuzumab and site-specifically labeled with biotin or fluorescein. The fluorescently labeled trastuzumab showed specific staining of the membranes of HER2-expressing cells in immunofluorescence microscopy. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Click strategy using disodium salts of amino acids improves the water solubility of plinabulin and KPU-300.

PubMed

Yakushiji, Fumika; Muguruma, Kyohei; Hayashi, Yoshiki; Shirasaka, Takuya; Kawamata, Ryosuke; Tanaka, Hironari; Yoshiwaka, Yushi; Taguchi, Akihiro; Takayama, Kentaro; Hayashi, Yoshio

2017-07-15

Plinabulin and KPU-300 are promising anti-microtubule agents; however, the low water solubility of these compounds (<0.1µg/mL) has limited their pharmaceutical advantages. Here, we developed five water-soluble derivatives of plinabulin and KPU-300 with a click strategy using disodium salts of amino acids. The mother skeleton, diketopiperazine (DKP), was transformed into a monolactim-type alkyne and a copper-catalyzed alkyne azide cycloaddition (CuAAC) combined azides that was derived from amino acids as a water-solubilizing moiety. The conversion of carboxyl groups into disodium salts greatly improved the water solubility by 0.8 million times compared to the solubility of the parent molecules. In addition, the α-amino acid side chains of the water-solubilizing moieties affected both the water solubility and the half-lives of the compounds during enzymatic hydrolysis. Our effort to develop a variety of water-soluble derivatives using the click strategy has revealed that the replaceable water-solubilizing moieties can alter molecular solubility and stability under enzymatic hydrolysis. With this flexibility, we are approaching to the in vivo study using water-soluble derivative. Copyright © 2017 Elsevier Ltd. All rights reserved.

Formation of Nitrogen and Hydrogen-bearing Molecules in Solid Ammonia and Implications for Solar System and Interstellar Ices

NASA Astrophysics Data System (ADS)

Zheng, Weijun; Jewitt, David; Osamura, Yoshihiro; Kaiser, Ralf I.

2008-02-01

We irradiated solid ammonia (NH3) in the temperature range of 10-60 K with high-energy electrons to simulate the processing of ammonia-bearing ices in the interstellar medium and in the solar system. By monitoring the newly formed molecules online and in situ, the synthesis of hydrazine (N2H4), diazene (N2H2 isomers), hydrogen azide (HN3), the amino radical (NH2), molecular hydrogen (H2), and molecular nitrogen (N2) has been confirmed. Our results show that the production rates of hydrazine, diazene, hydrogen azide, molecular hydrogen, and molecular nitrogen are higher in amorphous ammonia than those in crystalline ammonia; this behavior is similar to the production of molecular hydrogen, molecular oxygen, and hydrogen peroxide found in electron-irradiated water ices. However, the formation of hydrazine in crystalline ammonia does not show any temperature dependence. Our experimental results give hints to the origin of molecular nitrogen in the Saturnian system and possibly in the atmospheres of proto-Earth and Titan; our research may also guide the search of hitherto unobserved nitrogen-bearing molecules in the interstellar medium and in our solar system.

N-mustard analogs of S-adenosyl-L-methionine as biochemical probes of protein arginine methylation.

PubMed

Hymbaugh Bergman, Sarah J; Comstock, Lindsay R

2015-08-01

Nucleosomes, the fundamental building blocks of eukaryotic chromatin, undergo post-synthetic modifications and play a major role in the regulation of transcriptional processes. Combinations of these modifications, including methylation, regulate chromatin structure, determining its different functional states and playing a central role in differentiation. The biological significance of cellular methylation, particularly on chromatin, is widely recognized, yet we know little about the mechanisms that link biological methylation events. To characterize and fully understand protein methylation, we describe here novel N-mustard analogs of S-adenosyl-l-methionine (SAM) as biochemical tools to better understand protein arginine methylation events using protein arginine methyltransferase 1 (PRMT1). Specifically, azide- and alkyne-functionalized N-mustard analogs serve as cofactor mimics of SAM and are enzymatically transferred to a model peptide substrate in a PRMT1-dependent fashion. Once incorporated, the resulting alkynes and azides can be modified through chemoselective ligations, including click chemistry and the Staudinger ligation. These results readily demonstrate the feasibility of utilizing N-mustard analogs as biochemical tools to site-specifically label substrates of PRMT1 and serve as an alternative approach to study protein methylation events. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

2D polymeric cadmium(II) complexes containing 1,3-imidazolidine-2-thione (Imt) ligand, [Cd(Imt)(H2O)2(SO4)]n and [Cd(Imt)2(N3)2]n

NASA Astrophysics Data System (ADS)

Mahmood, Rashid; Ahmad, Saeed; Fettouhi, Mohammed; Roisnel, Thierry; Gilani, Mazhar Amjad; Mehmood, Kashif; Murtaza, Ghulam; Isab, Anvarhusein A.

2018-03-01

The present study aims at preparing and carrying out the structural investigation of two polymeric cadmium(II) complexes of imidazolidine-2-thione (Imt) based on sulfate or azide ions, [Cd(Imt)(H2O)2(SO4)]n (1) and [Cd(Imt)2(N3)2]n (2). The structures of the complexes were determined by single crystal X-ray analysis. Both compounds, 1 and 2 crystallize in the form of 2D coordination polymers and the cadmium(II) ion is six-coordinate having a distorted octahedral geometry in each compound. In 1, the metal ion is bonded to one sulfur atom of Imt and five oxygen atoms with two from water and three of bridging sulfate ions. In 2, the cadmium coordination sphere is completed by two Imt molecules binding through the sulfur atoms and four nitrogen atoms of bridging azide ions. The crystal structures are stabilized by intra and intermolecular hydrogen bonding interactions. The complexes were also characterized by IR and NMR spectroscopy and the spectroscopic data is consistent with the binding of the ligands.

Crystal structures and DFT calculations of mixed chloride-azide zinc(II) and chloride-isocyanate cadmium(II) complexes with the condensation product of 2-quinolinecarboxaldehyde and Girard's T reagent

NASA Astrophysics Data System (ADS)

Anđelković, Katarina; Pevec, Andrej; Grubišić, Sonja; Turel, Iztok; Čobeljić, Božidar; Milenković, Milica R.; Keškić, Tanja; Radanović, Dušanka

2018-06-01

The mixed chloride-azide [ZnL(N3)1.65Cl0.35] (1) and chloride-isocyanate [CdL(NCO)1.64Cl0.36] (2) complexes with the condensation product of 2-quinolinecarboxaldehyde and trimethylammonium acetohydrazide chloride (Girard's T reagent) (HLCl) have been prepared and characterized by X-ray crystallography. In complexes 1 and 2, Zn1 and Cd1 ions, respectively, are five-coordinated in a distorted square based pyramidal geometry with NNO set of donor atoms of deprotonated hydrazone ligand and two monodentate ligands N3- and/or N3- and Cl- in the case of 1 and OCN- and/or OCN- and Cl- in the case of 2. The structural parameters of 1 and 2 have been discussed in relation to those of previously reported M(II) complexes with the same hydrazone ligand. Density functional theory calculations have been employed to study the interaction between the Zn2+ and Cd2+ ions and ligands. High affinity of ligands towards the Zn2+ and Cd2+ ions are predicted for both complexes.

Structural analysis of NADPH depleted bovine liver catalase and its inhibitor complexes

PubMed Central

Sugadev, Ragumani; Ponnuswamy, M.N.; Sekar, K.

2011-01-01

To study the functional role of NADPH during mammalian catalase inhibition, the X-ray crystal structures of NADPH-depleted bovine liver catalase and its inhibitor complexes, cyanide and azide, determined at 2.8Å resolution. From the complex structures it is observed that subunits with and without an inhibitor/catalytic water molecule are linked by N-terminal domain swapping. Comparing mammalian- and fungal- catalases, we speculate that NADPH-depleted mammalian catalases may function as a domain-swapped dimer of dimers, especially during inactivation by inhibitors like cyanide and azide. We further speculate that in mammalian catalases the N-terminal hinge-loop region and α-helix is the structural element that senses NADPH binding. Although the above arguments are speculative and need further verification, as a whole our studies have opened up a new possibility, viz. that mammalian catalase acts as a domain-swapped dimer of dimers, especially during inhibitor binding. To generalize this concept to the formation of the inactive state in mammalian catalases in the absence of tightly bound NADPH molecules needs further exploration. The present study adds one more intriguing fact to the existing mysteries of mammalian catalases. PMID:21968615

Functional Degradable Polymers by Radical Ring-Opening Copolymerization of MDO and Vinyl Bromobutanoate: Synthesis, Degradability and Post-Polymerization Modification.

PubMed

Hedir, Guillaume G; Bell, Craig A; O'Reilly, Rachel K; Dove, Andrew P

2015-07-13

The synthesis of vinyl bromobutanoate (VBr), a new vinyl acetate monomer derivative obtained by the palladium-catalyzed vinyl exchange reaction between vinyl acetate (VAc) and 4-bromobutyric acid is reported. The homopolymerization of this new monomer using the RAFT/MADIX polymerization technique leads to the formation of novel well-defined and controlled polymers containing pendent bromine functional groups able to be modified via postpolymerization modification. Furthermore, the copolymerization of vinyl bromobutanoate with 2-methylene-1,3-dioxepane (MDO) was also performed to deliver a range of novel functional degradable copolymers, poly(MDO-co-VBr). The copolymer composition was shown to be able to be tuned to vary the amount of ester repeat units in the polymer backbone, and hence determine the degradability, while maintaining a control of the final copolymers' molar masses. The addition of functionalities via simple postpolymerization modifications such as azidation and the 1,3-dipolar cycloaddition of a PEG alkyne to an azide is also reported and proven by (1)H NMR spectroscopy, FTIR spectroscopy, and SEC analyses. These studies enable the formation of a novel class of hydrophilic functional degradable copolymers using versatile radical polymerization methods.

Ultrafast primary processes of an iron-(III) azido complex in solution induced with 266 nm light.

PubMed

Vennekate, Hendrik; Schwarzer, Dirk; Torres-Alacan, Joel; Krahe, Oliver; Filippou, Alexander C; Neese, Frank; Vöhringer, Peter

2012-05-14

The ultrafast photo-induced primary processes of the iron-(III) azido complex, [Fe(III)N(3)(cyclam-acetato)] PF(6) (1), in acetonitrile solution at room temperature were studied using femtosecond spectroscopy with ultraviolet (UV) excitation and mid-infrared (MIR) detection. Following the absorption of a 266 nm photon, the complex undergoes an internal conversion back to the electronic doublet ground state at a time scale below 2 ps. Subsequently, the electronic ground state vibrationally cools with a characteristic time constant of 13 ps. A homolytic bond cleavage was also observed by the appearance of ground state azide radicals, which were identified by their asymmetric stretching vibration at 1659 cm(-1). The azide radical recombines in a geminate fashion with the iron containing fragment within 20 ps. The cage escape leading to well separated fragments after homolytic Fe-N bond breakage was found to occur with a quantum yield of 35%. Finally, non-geminate recombination at nanosecond time scales was seen to further reduce the photolytic quantum yield to below 20% at a wavelength of 266 nm. This journal is © the Owner Societies 2012

After-rinsing hair growth promotion of minoxidil-containing amino alpha-cyclodextrins.

PubMed

Kim, Jin-Chul; Kim, Myoung-Dong

2007-12-01

Triamino alpha-cyclodextrin (CD) was synthesized and the inclusion complex with Minoxidil (MXD) was prepared. alpha-CD was azidated by modifying the 6-hydroxylmethyl CD rim with sodium azide. Then, mono-, di-, tri-, and tetra-azidocyclodextrins were separated by a flash column chromatography and reduced to the corresponding amines by hydrogenation with Pd/C. The substantivities of MXD included in either 2-hydroxypropyl alpha-CD (HP alpha-CD) or triamino alpha-CD were evaluated in vitro using hairless mice skins. After applying the preparations onto the skin and rinsing it, the amount of the drug left on the skin was determined using high-performance liquid chromatography (HPLC). It was the highest when the drug was included in triamino alpha-CD. The electrostatic interaction between the protonated amino CD and the negatively charged skin would be responsible for the relatively high substantivity. The in vivo hair growth promotion effect of each preparation was investigated, where the sample application onto the clipped backs of female mice (C57BL6) and the subsequent rinsing of the backs were done once a day for 30 days. Only MXD in triamino alpha-CD had hair growth promotion effect, possibly due to the significant substantivity.

Click chemistry for the conservation of cellular structures and fluorescent proteins: ClickOx.

PubMed

Löschberger, Anna; Niehörster, Thomas; Sauer, Markus

2014-05-01

Reactive oxygen species (ROS), including hydrogen peroxide, are known to cause structural damage not only in living, but also in fixed, cells. Copper-catalyzed azide-alkyne cycloaddition (click chemistry) is known to produce ROS. Therefore, fluorescence imaging of cellular structures, such as the actin cytoskeleton, remains challenging when combined with click chemistry protocols. In addition, the production of ROS substantially weakens the fluorescence signal of fluorescent proteins. This led us to develop ClickOx, which is a new click chemistry protocol for improved conservation of the actin structure and better conservation of the fluorescence signal of green fluorescent protein (GFP)-fusion proteins. Herein we demonstrate that efficient oxygen removal by addition of an enzymatic oxygen scavenger system (ClickOx) considerably reduces ROS-associated damage during labeling of nascent DNA with ATTO 488 azide by Cu(I)-catalyzed click chemistry. Standard confocal and super-resolution fluorescence images of phalloidin-labeled actin filaments and GFP/yellow fluorescent protein-labeled cells verify the conservation of the cytoskeleton microstructure and fluorescence intensity, respectively. Thus, ClickOx can be used advantageously for structure preservation in conventional and most notably in super-resolution microscopy methods. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermolysis synthesis of pure phase NiO from novel sonochemical synthesized Ni(II) nano metal-organic supramolecular architecture.

PubMed

Hanifehpour, Younes; Morsali, Ali; Mirtamizdoust, Babak; Joo, Sang Woo; Soltani, Behzad

2017-07-01

Nano-structures of a new supramolecular coordination compound of divalent nickel with the pyrazol (pzH) containing the terminal azide anions, [Ni(pzH) 2 (N 3 ) 2 ] (1), with discrete molecular architecture (DMA) in solid state was synthesized via sonochemical method. The new nanostructure was characterized by scanning electron microscopy, X-ray powder diffraction, IR, and elemental analysis. Compound 1 was structurally characterized by single crystal X-ray diffraction and the single-crystal X-ray data shows that the coordination number of Ni (II) ions is six, (NiN 6 ), with four N-donor atoms from neutral "pzH" ligands and two N-donors from two terminal azide anions. The supramolecular features in these complexes are guided and controlled by weak directional intermolecular interactions. The structure of the title complex was optimized by density functional theory calculations. Calculated structural parameters and IR spectra for the title complex are consistent with the crystal structure. The NiO nanoparticles were obtained by thermolysis of 1 at 180°C with oleic acid as a surfactant. Copyright © 2017 Elsevier B.V. All rights reserved.

Fluorine-18 labeling of an anti-HER2 VHH using a residualizing prosthetic group via a strain-promoted click reaction: Chemistry and preliminary evaluation.

PubMed

Zhou, Zhengyuan; Chitneni, Satish K; Devoogdt, Nick; Zalutsky, Michael R; Vaidyanathan, Ganesan

2018-05-01

In a previous study, we evaluated a HER2-specific single domain antibody fragment (sdAb) 2Rs15d labeled with 18 F via conjugation of a residualizing prosthetic agent that was synthesized by copper-catalyzed azide-alkyne cycloaddition (CuAAC). In order to potentially increase overall efficiency and decrease the time required for labeling, we now investigate the use of a strain-promoted azide-alkyne cycloaddition (SPAAC) between the 2Rs15d sdAb, which had been pre-derivatized with an azide-containing residualizing moiety, and an 18 F-labeled aza-dibenzocyclooctyne derivative. The HER2-targeted sdAb 2Rs15d and a nonspecific sdAb R3B23 were pre-conjugated with a moiety containing both azide- and guanidine functionalities. The thus derivatized sdAbs were radiolabeled with 18 F using an 18 F-labeled aza-dibenzocyclooctyne derivative ([ 18 F]F-ADIBO) via SPAAC, generating the desired conjugate ([ 18 F]RL-II-sdAb). For comparison, unmodified 2Rs15d was labeled with N-succinimidyl 4-guanidinomethyl-3-[ 125 I]iodobenzoate ([ 125 I]SGMIB), the prototypical residualizing agent for radioiodination. Radiochemical purity (RCP), immunoreactive fraction (IRF), HER2-binding affinity and cellular uptake of [ 18 F]RL-II-2Rs15d were assessed in vitro. Paired label biodistribution of [ 18 F]RL-II-2Rs15d and [ 125 I]SGMIB-2Rs15d, and microPET/CT imaging of [ 18 F]RL-II-2Rs15d and the [ 18 F]RL-II-R3B23 control sdAb were performed in nude mice bearing HER2-expressing SKOV-3 xenografts. A radiochemical yield of 23.9 ± 6.9% (n = 8) was achieved for the SPAAC reaction between [ 18 F]F-ADIBO and azide-modified 2Rs15d and the RCP of the labeled sdAb was >95%. The affinity (K d ) and IRF for the binding of [ 18 F]RL-II-2Rs15d to HER2 were 5.6 ± 1.3 nM and 73.1 ± 22.5% (n = 3), respectively. The specific uptake of [ 18 F]RL-II-2Rs15d by HER2-expressing BT474M1 breast carcinoma cells in vitro was 14-17% of the input dose at 1, 2, and 4 h, slightly higher than seen for co-incubated [ 125 I]SGMIB-2Rs15d. The uptake of [ 18 F]RL-II-2Rs15d in SKOV-3 xenografts at 1 h and 2 h p.i. were 5.54 ± 0.77% ID/g and 6.42 ± 1.70% ID/g, respectively, slightly higher than those for co-administered [ 125 I]SGMIB-2Rs15d (4.80 ± 0.78% ID/g and 4.78 ± 1.39% ID/g). MicroPET/CT imaging with [ 18 F]RL-II-2Rs15d at 1-3 h p.i. clearly delineated SKOV-3 tumors while no significant accumulation of activity in tumor was seen for [ 18 F]RL-II-R3B23. With the exception of kidneys, normal tissue levels for [ 18 F]RL-II-2Rs15d were low and cleared rapidly. To our knowledge, this is the first time SPAAC method has been used to label an sdAb with 18 F, especially with residualizing functionality. Copyright © 2018 Elsevier Ltd. All rights reserved.

Synthesis, molecular docking and biological evaluation as HDAC inhibitors of cyclopeptide mimetics by a tandem three-component reaction and intramolecular [3+2] cycloaddition.

PubMed

Pirali, Tracey; Faccio, Valeria; Mossetti, Riccardo; Grolla, Ambra A; Di Micco, Simone; Bifulco, Giuseppe; Genazzani, Armando A; Tron, Gian Cesare

2010-02-01

Novel macrocyclic peptide mimetics have been synthesized by exploiting a three-component reaction and an azide-alkyne [3 + 2] cycloaddition. The prepared compounds were screened as HDAC inhibitors allowing us to identify a new compound with promising biological activity. In order to rationalize the biological results, computational studies have also been performed.

Computational Chemistry Toolkit for Energetic Materials Design

DTIC Science & Technology

2006-11-01

industry are aggressively engaged in efforts to develop multiscale modeling and simulation methodologies to model and analyze complex phenomena across...energetic materials design. It is hoped that this toolkit will evolve into a collection of well-integrated multiscale modeling methodologies...Experimenta Theoreticala This Work 1-5-Diamino-4- methyl- tetrazolium nitrate 8.4 41.7 47.5 1-5-Diamino-4- methyl- tetrazolium azide 138.1 161.6

Environmentally Benign Stab Detonators

DTIC Science & Technology

2006-07-11

composition. In addition we will work with our DoD partner TACOM-ARDEC in identifying and testing more environmentally suitable replacement transfer...components identified is shown in Figure 1 below. Figure 1. Photo of M55 stab detonator Al cup with initiation train and components. Common...primer mixes, such as NOL-130, are made up of lead styphnate (basic) 40%, lead azide ( dextrinated ) 20%, barium nitrate 20%, antimony sulfide 15%, and

Novel Energetic Materials for Counter WMD Applications

DTIC Science & Technology

2011-09-01

insensitive dianionic dinitrourea salts: The CN4ol · anion paired with nitrogen-rich cations C. Energetic ionic liquids based on anionic rare earth nitrate ...and their derivatives as energetic materials by click chemistry 1-Pentafluorosulfanyl acetylene and its derivatives react with azide or diazomethane...extended to the syntheses and characterization often DNU dianionic salts by the metathesis oftetrazolium and guanidinium sulfates with in situ

Elimination of Perchlorate Oxidizers from Pyrotechnic Flare Compositions

DTIC Science & Technology

2007-03-09

in candelas ( cd ), where the candela is defined as, 1 cd = 1 lumen /steradian-1. DSC A thermal analysis technique known as Differential...Shorter Wavelength Infrared band routinely monitored in decoy flare performance tests. TGA A thermal analysis technique known as Thermogravimetric ...Scanning Calorimetry DTA A thermal analysis technique known as Differential Thermal Analysis GAP Glycidyl Azide Polymer used as a curable binder in some

Microwave-assisted domino and multicomponent reactions with cyclic acylketenes: expeditious syntheses of oxazinones and oxazindiones.

PubMed

Presset, Marc; Coquerel, Yoann; Rodriguez, Jean

2009-12-17

The microwave-assisted Wolff rearrangement of cyclic 2-diazo-1,3-diketones in the presence of aldehydes and primary amines provides a straightforward access to functionalized bi- and pentacyclic oxazinones following an unprecedented three-component domino reaction. Alternatively, in the presence of acyl azides, an efficient Curtius/Wolff/hetero-Diels-Alder sequence allows the direct synthesis of oxazindiones.

Facile synthesis of unsymmetrical acridines and phenazines by a Rh(III)-catalyzed amination/cyclization/aromatization cascade.

PubMed

Lian, Yajing; Hummel, Joshua R; Bergman, Robert G; Ellman, Jonathan A

2013-08-28

We report formal [3 + 3] annulations of aromatic azides with aromatic imines and azobenzenes to give acridines and phenazines, respectively. These transformations proceed through a cascade process of Rh(III)-catalyzed amination followed by intramolecular electrophilic aromatic substitution and aromatization. Acridines can be directly prepared from aromatic aldehydes by in situ imine formation using catalytic benzylamine.

Liquid Azide Salts and Their Reactions with Common Oxidizers IRFNA and N2O4 (Preprint)

DTIC Science & Technology

2008-02-19

2957(44), 5 2886(13), 2834(7), 1565(4), 1452(7), 1417(19), 1386(8), 1334(21), 1247(3), 1196(1), 1075 (4), 1022(16), 946(2), 874(4), 703(3), 652(1...frames were then processed using the SAINT software16, 17 to give the hkl file corrected for Lp/decay. The absorption correction was performed using

Regioselective Sequential Modification of Chitosan via Azide-Alkyne Click Reaction: Synthesis, Characterization, and Antimicrobial Activity of Chitosan Derivatives and Nanoparticles

PubMed Central

Sarwar, Atif; Katas, Haliza; Samsudin, Siti Noradila; Zin, Noraziah Mohamad

2015-01-01

Recently, the attention of researchers has been drawn toward the synthesis of chitosan derivatives and their nanoparticles with enhanced antimicrobial activities. In this study, chitosan derivatives with different azides and alkyne groups were synthesized using click chemistry, and these were further transformed into nanoparticles by using the ionotropic gelation method. A series of chitosan derivatives was successfully synthesized by regioselective modification of chitosan via an azide-alkyne click reaction. The amino moieties of chitosan were protected during derivatization by pthaloylation and subsequently unblocked at the end to restore their functionality. Nanoparticles of synthesized derivatives were fabricated by ionic gelation to form complexes of polyanionic penta-sodium tripolyphosphate (TPP) and cationic chitosan derivatives. Particle size analysis showed that nanoparticle size ranged from 181.03 ± 12.73 nm to 236.50 ± 14.32 nm and had narrow polydispersity index and positive surface charge. The derivatives and corresponding nanoparticles were evaluated in vitro for antibacterial and antifungal activities against three gram-positive and gram-negative bacteria and three fungal strains, respectively. The minimum inhibitory concentration (MIC) of all derivatives ranged from 31.3 to 250 µg/mL for bacteria and 188 to1500 µg/mL for fungi and was lower than that of native chitosan. The nanoparticles with MIC ranging from 1.56 to 25 µg/mLfor bacteria and 94 to 750 µg/mL for fungi exhibited higher activity than the chitosan derivatives. Chitosan O-(1-methylbenzene) triazolyl carbamate and chitosan O-(1-methyl phenyl sulfide) triazolyl carbamate were the most active against the tested bacterial and fungal strains. The hemolytic assay on erythrocytes and cell viability test on two different cell lines (Chinese hamster lung fibroblast cells V79 and Human hepatic cell line WRL68) demonstrated the safety; suggesting that these derivatives could be used in future medical applications. Chitosan derivatives with triazole functionality, synthesized by Huisgen 1,3-dipolar cycloaddition, and their nanoparticles showed significant enhancement in antibacterial and antifungal activities in comparison to those associated with native, non-altered chitosan. PMID:25928293

Photoelectron Spectroscopy of Nitrogen Containing Molecules of Biological and Industrial Interest

NASA Astrophysics Data System (ADS)

Pinto, Rui Montenegro Val-do-Rio

The work presented herein is based on the gas-phase spectroscopic characterization of several molecules of high nitrogen content which are relevant to organic synthesis, industry and fundamental research on molecular physics. It is mainly an experimental enterprise on selected organic azides and tetrazoles, with heavy support on theoretical results from readily available computational methods. Part of the work relies on the design and construction of scientific apparatus, which substantially improve the existing equipment and extend the limits of the experiment. The electronic structure and gas-phase thermal decomposition of methyl 2-azidopropionate (M2AP, N3CH3CHCO2CH 3), benzyl azide (BA, C6H5CH2N 3), 2-, 3- and 4- methyl benzyl azide (2-, 3- and 4-MBA, CH3C 6H4CH2N3), 5-aminotetrazole (5ATZ, NH2CN4H), and 5-methyltetrazole (5MTZ, CH3CN 4H) are investigated through photoelectron spectroscopy, using either He(I) (21.22 eV) or synchrotron radiation in the Xray range. Relevant information obtained from mass spectrometry and matrix-isolation infrared spectroscopy is used to complement characterization of the samples. Regarding each molecules' thermal decomposition, pathways are proposed which account for the observed end products. Conformational analysis is performed, and the special case of annular tautomerism is addressed in the tetrazole compounds. High-temperature pyrolysis work is performed in collaboration with the University of Southampton, and XPS analysis using synchrotron radiation is performed at Elettra, the multidisciplinary synchrotron light laboratory in Trieste, Italy. Experimental findings are rationalized using different computational methods, based on post-Hartree-Fock approaches: many-body perturbation theory (MPn), configuration interaction (CI) and Green's function methods (OVGF, P3), as well as density functional theory (DFT), are used extensively to obtain optimized molecular geometries, ionization energies, orbital contours, relative energies, vibrational frequencies, and to assess possible pathways for thermal or electron impact fragmentation. Composite methods (G n and CBS) are used to estimate to kcal mol-1 accuracy the energy balance between reactants, transition structures and products in the overall decomposition process of the specified molecules.

Differentiation by hydroquinone of relaxations induced by exogenous and endogenous nitrates in non-vascular smooth muscle: role of superoxide anions.

PubMed Central

Hobbs, A. J.; Tucker, J. F.; Gibson, A.

1991-01-01

1. The influence of hydroquinone on relaxations induced by nitric oxide (NO), nitrovasodilator drugs, and non-adrenergic, non-cholinergic (NANC) field stimulation has been investigated in three tissues in which endogenous nitrates have been implicated in the NANC response; the mechanism of action of hydroquinone was also studied. 2. In mouse anococcygeus, hydroquinone (10-100 microM) produced a concentration-dependent inhibition of relaxations induced by 15 microM NO. Hydroquinone, 100 microM, which reduced responses to NO by 85%, had no effect on relaxations induced by NANC field stimulation (10 Hz; 20s trains), hydroxylamine (10 microM), sodium nitroprusside (1 microM) or sodium azide (20 microM). 3. In guinea-pig trachea, 100 microM hydroquinone reduced relaxations to 150 microM NO by 75%, but had no effect on those to NANC stimulation (10 Hz; 30 s trains) or sodium azide (5 microM). 4. In rat gastric fundus, 100 microM hydroquinone reduced relaxations to 1 microM NO by 85%, but had no effect on those to NANC stimulation (0.5 Hz; 15 s trains) or sodium azide (2 microM). 5. Superoxide dismutase (SOD; 50 u ml-1) had no effect on relaxations of the mouse anococcygeus in response to 15 microM NO or 10 Hz NANC stimulation. Further, the inhibition of responses to NO by hydroquinone was unaffected in the presence of SOD. 6. Hydroquinone (10-100 microM) failed to generate superoxide anions, as detected by a chemiluminescent assay. However, 100 microM hydroquinone, like SOD (50 u ml-1), produced almost complete inhibition of superoxide anion chemiluminescence induced by xanthine (500 microM): xanthine oxidase (0.07 u ml-1). 7. It is concluded that, in our system, hydroquinone inhibits NO by acting as a free radical scavenger rather than by generating superoxide anions. The ability of hydroquinone to block relaxations to NO, but not NANC stimulation, may suggest that the endogenous nitrate substance released by these NANC nerves may not be free NO, but may be an NO-containing, or NO-generating, molecule. PMID:1665746

Carbon Metabolism of Soil microorganisms at Low Temperatures: Position-Specific 13C Labeled Glucose Reveals the Story

NASA Astrophysics Data System (ADS)

Apostel, C.; Bore, E. K.; Halicki, S.; Kuzyakov, Y.; Dippold, M.

2015-12-01

Metabolic pathway activities at low temperature are not well understood, despite the fact that the processes are relevant for many soils globally and seasonally. To analyze soil metabolism at low temperature, isotopomeres of position-specifically 13C labeled glucose were applied at three temperature levels; +5, -5 -20 oC. In additon, one sterilization treatment with sodium azide at +5 oC was also performed. Soils were incubated for 1, 3 and 10 days while soil samples at -20 oC were additionally sampled after 30 days. The 13C from individual molecule position in respired CO2 was quantifed. Incorporation of 13C in bulk soil, extractable microbial biomass by chloroform fumigation extraction (CFE) and cell membranes of different microbial communities classified by 13C phospholipid fatty acid analysis (PLFA) was carried out. Our 13CO2 data showed a dominance of C-1 respiration at +5 °C for treatments with and without sodium azide, but total respiration for sodium azide inhibited treatments increased by 14%. In contrast, at -5 and -20 oC metabolic behavior showed intermingling of preferential respiration of the glucose C-4 and C-1 positions. Therefore, at +5 °C, pentose phosphate pathway activity is a dominant metabolic pathway used by microorganisms to metabolize glucose. The respiration increase due to NaN3 inhibition was attributed to endoenzymes released from dead organisms that are stabilized at the soil matrix and have access to suitable substrate and co-factors to permit their funtions. Our PLFA analysis showed that incorporation of glucose 13C was higher in Gram negative bacteria than other microbial groups as they are most competitive for LMWOS. Only a limited amount of microbial groups maintained their glucose utilizing activity at -5 and -20 °C and they strongly shifted towards a metabolization of glucose via both glycolysis and pentose phosphate pathways indicating both growth and cellular maintenance. This study revealed a remarkable microbial acitivity at low temperatures which differs significantly from our observations at ambient temperature, which could be unraveled based on position-specific labeling.

Synthesis of Polysubstituted Pyridines via a One-Pot Metal-Free Strategy.

PubMed

Wei, Hongbo; Li, Yun; Xiao, Ke; Cheng, Bin; Wang, Huifei; Hu, Lin; Zhai, Hongbin

2015-12-18

An efficient strategy for the one-pot synthesis of polysubstituted pyridines via a cascade reaction from aldehydes, phosphorus ylides, and propargyl azide is reported. The reaction sequence involves a Wittig reaction, a Staudinger reaction, an aza-Wittig reaction, a 6π-3-azatriene electrocyclization, and a 1,3-H shift. This protocol provides quick access to the polysubstituted pyridines from readily available substrates in good to excellent yields.

"Click" saccharide/beta-lactam hybrids for lectin inhibition.

PubMed

Palomo, Claudio; Aizpurua, Jesus M; Balentová, Eva; Azcune, Itxaso; Santos, J Ignacio; Jiménez-Barbero, Jesús; Cañada, Javier; Miranda, José Ignacio

2008-06-05

Hybrid glycopeptide beta-lactam mimetics designed to bind lectins or carbohydrate recognition domains in selectins have been prepared according to a "shape-modulating linker" design. This approach was implemented using the azide-alkyne "click" cycloaddition reaction, and as shown by NMR/MD experiments, binding of the resulting mimetics to Ulex Europaeus Lectin-1 (UEL-1) occurred after a "bent-to-extended" conformational change around a partially rotatable triazolylmethylene moiety.

Facile Synthesis of Unsymmetrical Acridines and Phenazines by a Rhodium(III)-Catalyzed Amination, Cyclization and Aromatization Cascade

PubMed Central

Lian, Yajing; Hummel, Joshua R.; Bergman, Robert G.; Ellman, Jonathan A.

2013-01-01

New formal [3 + 3] annulations have been developed to obtain acridines and phenazines from aromatic azides and aromatic imines and azobenzenes, respectively. These transformations proceed through a cascade process of Rh(III)-catalyzed amination followed by intramolecular electrophilic aromatic substitution and aromatization. Acridines can be directly prepared from aromatic aldehydes by in situ imine formation using catalytic benzylamine. PMID:23957711

The backbone N-(4-azidobutyl) linker for the preparation of peptide chimera.

PubMed

Fernández-Llamazares, Ana I; García, Jesús; Adan, Jaume; Meunier, David; Mitjans, Francesc; Spengler, Jan; Albericio, Fernando

2013-09-06

A robust synthetic strategy for the introduction of the N-(4-azidobutyl) linker into peptides using standard SPPS techniques is described. Based on the example of Cilengitide it is shown that the N-(4-azidobutyl) group exerts similar conformational restraints as a backbone N-Me group and allows conjugation of a desired molecule either via click chemistry or-after azide reduction-via acylation or reductive alkylation.

Liquid Azide Salts and Their Reactions with Common Oxidizers IRFNA and N2O4 (Postprint)

DTIC Science & Technology

2008-01-01

1452(7), 1417(19), 1386(8), 1334(21), 1247(3), 1196(1), 1075 (4), 1022(16), 946(2), 874(4), 703(3), 652(1), 602(7), 495(4), 417(3), 331(2), 279(2), 85...The frames were then processed using the SAINT software16,17 to give the hkl file corrected for Lp/decay. The absorption correction was performed using

- Wave Spectrum of Carbonyl Diazide in Pursuit of Diazirinone

NASA Astrophysics Data System (ADS)

Amberger, Brent K.; Esselman, Brian J.; Woods, R. Claude; McMahon, Robert J.

2013-06-01

Pyrolysis of carbonyl diazide (CO(N_3)_2) has been shown to give diazirinone (CON_2). While diazirione decomposes over the course of a few hours under terrestrial conditions, there is the possibility for it to exist in space. In the pursuit of obtaining a rotational spectrum for diazirinone, we have started with the rotational spectroscopy of its immediate precursor, carbonyl diazide. Carbonyl diazide is highly explosive, and requires careful synthesis. Spectra in the range of 260-360 GHz were collected at room temperature and at -60°C. Ab initio calculations at the CCSD/cc-pVDZ level predict that the conformation where both azide groups are syn to the carbonyl is preferred. A second conformation, where one azide is syn and one is anti, is calculated to lie about 2 kcal/ mol higher in energy. Pure rotational transitions for the ground state and multiple low-lying excited vibrational states of the syn- syn conformation are readily observed and assigned. X. Zeng, H. Beckers, H. Willner and J. F. Stanton, Angew. Chem. Int. Ed. 50 (2011), 1720-1723 A. M. Nolan, B. K. Amberger, B. J. Esselman, V. S. Thimmakondu, J. F. Stanton, R. C. Woods, and R. J. McMahon, Inorg. Chem. 51 (2012), 9846-9851

Fluorescence biosensor for inorganic pyrophosphatase activity.

PubMed

Zhang, Ying; Guo, Yajuan; Zhao, Mengmeng; Lin, Cuiying; Lin, Zhenyu; Luo, Fang; Chen, Guonan

2017-02-01

A highly sensitive and selective fluorescence biosensor for inorganic pyrophosphatase (PPase) activity has been developed based on special click ligation trigger hyperbranched rolling circle amplification (CLT-HRCA). Pyrophosphate ion (PPi) can coordinate with Cu 2+ to form stable PPi/Cu 2+ complex and Cu 2+ in the complex cannot be reduced to Cu + . The addition of PPase causes the hydrolysis of PPi into orthophosphate (Pi) and therefore induces the releasing of Cu 2+ from the stable PPi/Cu 2+ complex, and the free Cu 2+ is easily reduced to Cu + by sodium ascorbate. Then Cu + catalyzes the cyclization reaction between the specially designed 5'-azide and 3'-alkyne tagged padlock probes through Cu + catalyzed azide-alkyne cycloaddition (CuAAC), which in turn initiates the hyperbranched rolling circle amplification (HRCA). Given that the CLT-HRCA products contain large amounts of double-stranded DNAs (dsDNAs), the addition of SYBR Green I resulted in the enhanced fluorescence signal. There was a linear relationship between the enhanced fluorescence intensity and the logarithm PPase activity ranging from 0.05 to 25 mU with a detection limit of 0.02 mU. Such proposed biosensor has been successfully applied to screen the potential PPase inhibitors and has accessed the related inhibit ability with high efficiency.

Fluorescent Labeling of Collagen Production by Cells for Noninvasive Imaging of Extracellular Matrix Deposition.

PubMed

Bardsley, Katie; Yang, Ying; El Haj, Alicia J

2017-04-01

Extracellular matrix (ECM) is an essential component of tissues and provides both integrity and biological cues for cells. Collagen is one of the major proteins found within the ECM and therefore is an essential component of all engineered tissues. Therefore, in this article, we present a method for the online real-time monitoring of collagen deposition in three-dimensional engineered constructs. This method revolves around modification of collagen through the addition of azide-L-proline to cell culture media. The incorporation of azide-L-proline into the neocollagen produced by cells can then be detected by reaction with 10 mM of a Click-IT Alexa Fluor 488 DIBO Alkyne. The reaction was shown as being specific to the collagen as little background staining was observed in cultures, which did not contain the modified proline, and the staining was also depleted after treatment with collagenase and colocalization of collagen type I staining by immunochemistry assay. Real-time online staining of collagen deposition was observed under different culture conditions without affecting proliferation. Collagen deposition was observed to be increased under mechanical stimulation; however, the localization varied across stimulation regimes. This is a new technique for real-time monitoring of cell-produced collagen and will be a valuable addition to the tissue engineering field.

Influence of the Structure of a Solid-Fuel Mixture on the Thermal Efficiency of the Combustion Chamber of an Engine System

NASA Astrophysics Data System (ADS)

Futko, S. I.; Koznacheev, I. A.; Ermolaeva, E. M.

2014-11-01

On the basis of thermodynamic calculations, the features of the combustion of a solid-fuel mixture based on the glycidyl azide polymer were investigated, the thermal cycle of the combustion chamber of a model engine system was analyzed, and the efficiency of this chamber was determined for a wide range of pressures in it and different ratios between the components of the combustible mixture. It was established that, when the pressure in the combustion chamber of an engine system increases, two maxima arise successively on the dependence of the thermal efficiency of the chamber on the weight fractions of the components of the combustible mixture and that the first maximum shifts to the side of smaller concentrations of the glycidyl azide polymer with increase in the pressure in the chamber; the position of the second maximum is independent of this pressure, coincides with the minimum on the dependence of the rate of combustion of the mixture, and corresponds to the point of its structural phase transition at which the mole fractions of the carbon and oxygen atoms in the mixture are equal. The results obtained were interpreted on the basis of the Le-Chatelier principle.

Multicopper Oxidase Involvement in Both Mn(II) and Mn(III) Oxidation during Bacterial Formation of MnO2

PubMed Central

Soldatova, Alexandra V.; Butterfield, Cristina; Oyerinde, Oyeyemi F.; Tebo, Bradley M.; Spiro, Thomas G.

2013-01-01

Global cycling of environmental manganese requires catalysis by bacteria and fungi for MnO2 formation, since abiotic Mn(II) oxidation is slow under ambient conditions. Genetic evidence from several bacteria implicates multicopper oxidases (MCOs) as being required for MnO2 formation. However, MCOs catalyze one-electron oxidations, whereas conversion of Mn(II) to MnO2 is a two-electron process. Trapping experiments with pyrophosphate (PP), a Mn(III) chelator, have demonstrated that Mn(III) is an intermediate in Mn(II) oxidation when mediated by exosporium from the Mn-oxidizing bacterium Bacillus SG-1. The reaction of Mn(II) depends on O2 and is inhibited by azide, consistent with MCO catalysis. We show that the subsequent conversion of Mn(III) to MnO2 also depends on O2 and is inhibited by azide. Thus, both oxidation steps appear to be MCO-mediated, likely by the same enzyme, indicated by genetic evidence to be the MnxG gene product. We propose a model of how the manganese oxidase active site may be organized to couple successive electron transfers to the formation of polynuclear Mn(IV) complexes as precursors to MnO2 formation. PMID:22892957

An Enzyme-Mediated Methodology for the Site-Specific Radiolabeling of Antibodies Based on Catalyst-Free Click Chemistry

PubMed Central

Zeglis, Brian M.; Davis, Charles B.; Aggeler, Robert; Kang, Hee Chol; Chen, Aimei; Agnew, Brian J.; Lewis, Jason S.

2013-01-01

An enzyme- and click chemistry-mediated methodology for the site-selective radiolabeling of antibodies on the heavy chain glycans has been developed and validated. To this end, a model system based on the prostate specific membrane antigen-targeting antibody J591, the positron-emitting radiometal 89Zr, and the chelator desferrioxamine has been employed. The methodology consists of four steps: (1) the removal of sugars on the heavy chain region of the antibody to expose terminal N-acetylglucosamine residues; (2) the incorporation of azide-modified N-acetylgalactosamine monosaccharides into the glycans of the antibody; (3) the catalyst-free click conjugation of desferrioxamine-modified dibenzocyclooctynes to the azide-bearing sugars; and (4) the radiolabeling of the chelator-modified antibody with 89Zr. The site-selective labeling methodology has proven facile, reproducible, and robust, producing 89Zr-labeled radioimmunoconjguates that display high stability and immunoreactivity in vitro (>95%) in addition to high selective tumor uptake (67.5 ± 5.0 %ID/g) and tumor-to-background contrast in athymic nude mice bearing PSMA-expressing subcutaneous LNCaP xenografts. Ultimately, this strategy could play a critical role in the development of novel well-defined and highly immunoreactive radioimmunoconjugates for both the laboratory and clinic. PMID:23688208

N-(3-azidophenyl)-N-methyl-N'-([4-1H]- and [4-3H]-1-naphthyl)guanidine. A potent and selective ligand designed as a photoaffinity label for the phencyclidine site of the N-methyl-D-aspartate receptor.

PubMed

Gee, K R; Durant, G J; Holmes, D L; Magar, S S; Weber, E; Wong, S T; Keana, J F

1993-01-01

A novel radiolabeled photoaffinity ligand has been synthesized for the phencyclidine (PCP) site of the N-methyl-D-aspartate (NMDA) receptor. N-(3-Azidophenyl)-N-methyl-N'-([4-3H]-1-naphthyl)guanidine (13) was prepared with a specific activity of 25 Ci/mmol by diazotization of N-(3-aminophenyl)-N-methyl-N'-([4-3H]-1-naphthyl)guanidine (12) followed by treatment with sodium azide. Guanidine 12 was obtained by catalytic tritiation of N-(4-bromo-1-naphthyl)-N'-methyl-N'-(3-nitrophenyl)guanidine (11). The nontritiated analog 5 of 13 was prepared beginning with N-methyl-N'-1-naphthyl-N-(3-nitrophenyl)guanidine (9). The guanidines 9 and 11 were prepared in moderate yield by the aluminum chloride-catalyzed reaction of N-methyl-3-nitroaniline hydrochloride with 1-naphthylcyanamide and 4-bromo-1-naphthylcyanamide, respectively. Azide 5 showed high selectivity and affinity (IC50 = 100 nM vs [3H]MK801; 3000 nM vs [3H]ditolylguanidine) for the PCP site of the NMDA receptor in guinea pig brain homogenate. Photolabeling experiments with 13, however, failed to radiolabel a significant amount of receptor polypeptide.

Self-interrupted synthesis of sterically hindered aliphatic polyamide dendrimers

PubMed Central

Jishkariani, Davit; Timsina, Yam N.; Grama, Silvia; Gillani, Syeda S.; Divar, Masoumeh; Yadavalli, Srujana S.; Moussodia, Ralph-Olivier; Leowanawat, Pawaret; Berrios Camacho, Angely M.; Walter, Ricardo; Goulian, Mark; Klein, Michael L.; Percec, Virgil

2017-01-01

2,2-Bis(azidomethyl)propionic acid was prepared in four steps and 85% yield from the commercially available 2,2-bis(hydroxymethyl)propionic acid and used as the starting building block for the divergent, convergent, and double-stage convergent–divergent iterative methods for the synthesis of dendrimers and dendrons containing ethylenediamine (EDA), piperazine (PPZ), and methyl 2,2-bis(aminomethyl)propionate (COOMe) cores. These cores have the same multiplicity but different conformations. A diversity of synthetic methods were used for the synthesis of dendrimers and dendrons. Regardless of the method used, a self-interruption of the synthesis was observed at generation 4 for the dendrimer with an EDA core and at generation 5 for the one with a PPZ core, whereas for the COOMe core, self-interruption was observed at generation 6 dendron, which is equivalent to generation 5 dendrimer. Molecular modeling and molecular-dynamics simulations demonstrated that the observed self-interruption is determined by the backfolding of the azide groups at the periphery of the dendrimer. The latter conformation inhibits completely the heterogeneous hydrogenation of the azide groups catalyzed by 10% Pd/carbon as well as homogeneous hydrogenation by the Staudinger method. These self-terminated polyamide dendrimers are enzymatically and hydrolytically stable and also exhibit antimicrobial activity. Thus, these nanoscale constructs open avenues for biomedical applications. PMID:28270599

Improved metal-adhesive polymers from copper(I)-catalyzed azide-alkyne cycloaddition.

PubMed

Accurso, Adrian A; Delaney, Mac; O'Brien, Jeff; Kim, Hyonny; Iovine, Peter M; Díaz Díaz, David; Finn, M G

2014-08-18

Electrically conductive adhesive polymers offer many potential advantages relative to Sn-Pb solders, including reduced toxicity, low cost, low processing temperatures, and the ability to make application-specific formulations. Polymers generated from the copper(I)-catalyzed cycloaddition (CuAAC) reaction between multivalent azides and alkynes have previously been identified as strong metal-binding adhesives. Herein we demonstrate that the performance of these materials can be remarkably improved by the incorporation of a flexibility-inducing difunctionalized component and a tertiary amine additive in optimized concentrations. The best formulations were identified by means of rapid adhesion testing of a library of potential candidates by using a custom-built instrument and validated in an American Society for Testing and Materials (ASTM)-standard lap-shear test. Characteristic phase transitions were identified by differential scanning calorimetry (DSC) for adhesives with and without the additives as a function of curing temperature. The incorporation of flexible components was found to more than double the strength of the adhesive. Moreover, the adhesive was made electrically conductive by the inclusion of 20 wt% silver-coated copper flakes and further improved in this regard by the incorporation of multiwalled carbon nanotubes in the formulation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of Fluorophore-Labeled Thailanstatin Antibody-Drug Conjugates for Cellular Trafficking Studies.

PubMed

Kulkarni, Chethana; Finley, James E; Bessire, Andrew J; Zhong, Xiaotian; Musto, Sylvia; Graziani, Edmund I

2017-04-19

As the antibody-drug conjugate (ADC) field grows increasingly important for cancer treatment, it is vital for researchers to establish a firm understanding of how ADCs function at the molecular level. To gain insight into ADC uptake, trafficking, and catabolism-processes that are critical to ADC efficacy and toxicity-imaging studies have been performed with fluorophore-labeled conjugates. However, such labels may alter the properties and behavior of the ADC under investigation. As an alternative approach, we present here the development of a "clickable" ADC bearing an azide-functionalized linker-payload (LP) poised for "click" reaction with alkyne fluorophores; the azide group represents a significantly smaller structural perturbation to the LP than most fluorophores. Notably, the clickable ADC shows excellent potency in target-expressing cells, whereas the fluorophore-labeled product ADC suffers from a significant loss of activity, underscoring the impact of the label itself on the payload. Live-cell confocal microscopy reveals robust uptake of the clickable ADC, which reacts selectively in situ with a derivatized fluorescent label. Time-course trafficking studies show greater and more rapid net internalization of the ADCs than the parent antibody. More generally, the application of chemical biology tools to the study of ADCs should improve our understanding of how ADCs are processed in biological systems.

Antioxidant capacity of flavanols and gallate esters: pulse radiolysis studies.

PubMed

Bors, W; Michel, C

1999-12-01

Reactivities of several proanthocyanidins (monomers of condensed tannins) and gallate esters (representing hydrolyzable tannins) with hydroxyl radicals, azide radicals, and superoxide anions were investigated using pulse radiolysis combined with kinetic spectroscopy. We determined the scavenging rate constants and the decay kinetics of the aroxyl radicals both at the wavelength of the semiquinone absorption (275 nm) and the absorption band of the gallate ester ketyl radical (400-420 nm). For most compounds second-order decay kinetics were observed, which reflect disproportionation of the semiquinones. In the case of the oligomeric hydrolysable tannins, pentagalloyl glucose and tannic acid, the decay kinetics were more complex involving sequential first-order and second-order reactions, which could only be resolved by kinetic modeling. A correlation of the reaction rates with hydroxyl radicals (k*OH) with the number of adjacent aromatic hydroxyl groups (i.e., representing catechol and/or pyrogallol structures) was obtained for both condensed and hydrolyzable tannins. Similar correlation for the reactions with azide radicals and superoxide anions are less obvious, but exist as well. We consider proanthocyanidins superior radical scavenging agents as compared with the monomeric flavonols and flavones and propose that these substances rather than the flavonoids proper represent the antioxidative principle in red wine and green tea.

Preparation and optical properties of indium tin oxide/epoxy nanocomposites with polyglycidyl methacrylate grafted nanoparticles.

PubMed

Tao, Peng; Viswanath, Anand; Schadler, Linda S; Benicewicz, Brian C; Siegel, Richard W

2011-09-01

Visibly highly transparent indium tin oxide (ITO)/epoxy nanocomposites were prepared by dispersing polyglycidyl methacrylate (PGMA) grafted ITO nanoparticles into a commercial epoxy resin. The oleic acid stabilized, highly crystalline, and near monodisperse ITO nanoparticles were synthesized via a nonaqueous synthetic route with multigram batch quantities. An azido-phosphate ligand was synthesized and used to exchange with oleic acid on the ITO surface. The azide terminal group allows for the grafting of epoxy resin compatible PGMA polymer chains via Cu(I) catalyzed alkyne-azide "click" chemistry. Transmission electron microscopy (TEM) observation shows that PGMA grafted ITO particles were homogeneously dispersed within the epoxy matrix. Optical properties of ITO/epoxy nanocomposites with different ITO concentrations were studied with an ultraviolet-visible-near-infrared (UV-vis-NIR) spectrometer. All the ITO/epoxy nanocomposites show more than 90% optical transparency in the visible light range and absorption of UV light from 300 to 400 nm. In the near-infrared region, ITO/epoxy nanocomposites demonstrate low transmittance and the infrared (IR) transmission cutoff wavelength of the composites shifts toward the lower wavelength with increased ITO concentration. The ITO/epoxy nanocomposites were applied onto both glass and plastic substrates as visibly transparent and UV/IR opaque optical coatings.

Theoretical characterization of stable eta1-N2O-, eta2-N2O-, eta1-N2-, and eta2-N2-bound species: intermediates in the addition reactions of nitrogen hydrides with the pentacyanonitrosylferrate(II) ion.

PubMed

Olabe, José A; Estiú, Guillermina L

2003-08-11

The addition of nitrogen hydrides (hydrazine, hydroxylamine, ammonia, azide) to the pentacyanonitrosylferrate(II) ion has been analyzed by means of density functional calculations, focusing on the identification of stable intermediates along the reaction paths. Initial reversible adduct formation and further decomposition lead to the eta(1)- and eta(2)-linkage isomers of N(2)O and N(2), depending on the nucleophile. The intermediates (adducts and gas-releasing precursors) have been characterized at the B3LYP/6-31G level of theory through the calculation of their structural and spectroscopic properties, modeling the solvent by means of a continuous approach. The eta(2)-N(2)O isomer is formed at an initial stage of adduct decompositions with the hydrazine and azide adducts. Further conversion to the eta(1)-N(2)O isomer is followed by Fe-N(2)O dissociation. Only the eta(1)-N(2)O isomer is predicted for the reaction with hydroxylamine, revealing a kinetically controlled N(2)O formation. eta(1)-N(2) and eta(2)-N(2) isomers are also predicted as stable species.

Structure and evaluation of antibacterial and antitubercular properties of new basic and heterocyclic 3-formylrifamycin SV derivatives obtained via 'click chemistry' approach.

PubMed

Pyta, Krystian; Klich, Katarzyna; Domagalska, Joanna; Przybylski, Piotr

2014-09-12

Thirty four novel derivatives of 3-formylrifamycin SV were synthesized via reductive alkylation and copper(I)-catalysed azide-alkyne cycloaddition. According to the obtained results, 'click chemistry' can be successfully applied for modification of structurally complex antibiotics such as rifamycins, with the formation of desired 1,2,3-triazole products. However, when azide-alkyne cycloaddition on 3-formylrifamycin SV derivatives demanded higher amount of catalyst, lower temperature and longer reaction time because of the high volatility of substrates, an unexpected intramolecular condensation with the formation of 3,4-dihydrobenzo[g]quinazoline heterocyclic system took place. Structures of new derivatives in solution were determined using one- and two-dimensional NMR methods and FT-IR spectroscopy. Computational DFT and PM6 methods were employed to correlate their conformation and acid-base properties to biological activity and establish SAR of the novel compounds. Microbiological, physico-chemical (logP, solubility) and structural studies of newly synthesised rifamycins indicated that for the presence of relatively high antibacterial (MIC ~0.01 nmol/mL) and antitubercular (MIC ~0.006 nmol/mL) activities, a rigid and basic substituent at C(3) arm, containing a protonated nitrogen atom "open" toward intermolecular interactions, is required. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

Inorganic–organic hybrid materials through post-synthesis modification: Impact of the treatment with azides on the mesopore structure

PubMed Central

Keppeler, Miriam; Holzbock, Jürgen; Akbarzadeh, Johanna; Peterlik, Herwig

2011-01-01

Summary Hybrid, hierarchically organized, monolithic silica gels, comprising periodically arranged mesopores and a cellular macroscopic network, have been prepared through a co-condensation reaction of tetrakis(2-hydroxyethyl)orthosilicate with chloromethyl-trimethoxysilane or 3-(chloropropyl)-triethoxysilane. Subsequent conversion of the chloro groups into azido groups, by nucleophilic substitution with NaN3 in N,N-dimethylformamide, was conducted upon preservation of the monolithic structure. However, treatment with NaN3 had a strong influence on the structure in the mesoporous regime, with changes such as an increase of mesopore diameter, pore volume and lattice constants, as well as a concomitant decrease of the pore wall thickness, as confirmed by small angle X-ray scattering, transmission electron microscopy, and nitrogen sorption analysis. Similar effects were observed for unmodified silica gels by simple ageing in azide-containing media, whether a relatively small or a sterically demanding counter ion (Na+ or (H3C)4N+) was used. The structural modification did not seem to depend greatly on whether an organic aprotic solvent (N,N-dimethylformamide, 1,1,3,3-tetramethylurea, 1,3-dimethyl-2-imidazolidinone) or a protic solvent that can form hydrogen bonds, such as water, was used. PMID:22003454

Considerations for conducting incubations to study the mechanisms of As release in reducing groundwater aquifers

PubMed Central

Radloff, Kathleen A.; Manning, Anya R.; Mailloux, Brian; Zheng, Yan; Rahman, M. Moshiur; Huq, M. Rezaul; Ahmed, Kazi M.; van Geen, Alexander

2008-01-01

Microbial Fe reduction is widely believed to be the primary mechanism of As release from aquifer sands in Bangladesh, but alternative explanations have been proposed. Long-term incubation studies using natural aquifer material are one way to address such divergent views. This study addresses two issues related to this approach: (1) the need for suitable abiotic controls and (2) the spatial variability of the composition of aquifer sands. Four sterilization techniques were examined using orange-colored Pleistocene sediment from Bangladesh and artificial groundwater over 8 months. Acetate (10 mM) was added to sacrificial vials before sterilization using either (1) 25 kGy of gamma irradiation, (2) three 1-h autoclave cycles, (3) a single addition of an antibiotic mixture at 1x or (4) 10x the typical dose, and (5) a 10 mM addition of azide. The effectiveness of sterilization was evaluated using two indicators of microbial Fe reduction, changes in diffuse spectral reflectance and leachable Fe(II)/Fe ratios, as well as changes in P-extractable As concentrations in the solid phase. A low dose of antibiotics was ineffective after 70 days, whereas autoclaving significantly altered groundwater composition. Gamma irradiation, a high dose of antibiotics, and azide were effective for the duration of the experiment. PMID:19884962

A Versatile Click-Compatible Monolignol Probe to Study Lignin Deposition in Plant Cell Walls

PubMed Central

Pandey, Jyotsna L.; Wang, Bo; Diehl, Brett G.; Richard, Tom L.; Chen, Gong; Anderson, Charles T.

2015-01-01

Lignin plays important structural and functional roles in plants by forming a hydrophobic matrix in secondary cell walls that enhances mechanical strength and resists microbial decay. While the importance of the lignin matrix is well documented and the biosynthetic pathways for monolignols are known, the process by which lignin precursors or monolignols are transported and polymerized to form this matrix remains a subject of considerable debate. In this study, we have synthesized and tested an analog of coniferyl alcohol that has been modified to contain an ethynyl group at the C-3 position. This modification enables fluorescent tagging and imaging of this molecule after its incorporation into plant tissue by click chemistry-assisted covalent labeling with a fluorescent azide dye, and confers a distinct Raman signature that could be used for Raman imaging. We found that this monolignol analog is incorporated into in vitro-polymerized dehydrogenation polymer (DHP) lignin and into root epidermal cell walls of 4-day-old Arabidopsis seedlings. Incorporation of the analog in stem sections of 6-week-old Arabidopsis thaliana plants and labeling with an Alexa-594 azide dye revealed the precise locations of new lignin polymerization. Results from this study indicate that this molecule can provide high-resolution localization of lignification during plant cell wall maturation and lignin matrix assembly. PMID:25884205

Characterization and purification of polyphenol oxidase from artichoke (Cynara scolymus L.).

PubMed

Dogan, Serap; Turan, Yusuf; Ertürk, Hatibe; Arslan, Oktay

2005-02-09

In this study, the polyphenol oxidase (PPO) of artichoke (Cynara scolymus L.) was first purified by a combination of (NH(4))(2)SO(4) precipitation, dialysis, and a Sepharose 4B-L-tyrosine-p-aminobenzoic acid affinity column. At the end of purification, 43-fold purification was achieved. The purified enzyme migrated as a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Polyacrylamide gel electrophoresis indicated that PPO had a 57 kDa molecular mass. Second, the contents of total phenolic and protein of artichoke head extracts were determined. The total phenolic content of artichoke head was determined spectrophotometrically according to the Folin-Ciocalteu procedure and was found to be 425 mg 100 g(-1) on a fresh weight basis. Protein content was determined according to Bradford method. Third, the effects of substrate specificity, pH, temperature, and heat inactivation were investigated on the activity of PPO purified from artichoke. The enzyme showed activity to 4-methylcatechol, pyrogallol, catechol, and L-dopa. No activity was detected toward L-tyrosine, resorsinol, and p-cresol. According to V(max)/K(m) values, 4-methylcatechol (1393 EU min(-1) mM(-1)) was the best substrate, followed by pyrogallol (1220 EU min(-1) mM(-1)), catechol (697 EU min(-1) mM(-1)), and L-dopa (102 EU min(-1) mM(-1)). The optimum pH values for PPO were 5.0, 8.0, and 7.0 using 4-methylcatechol, pyrogallol, and catechol as substrate, respectively. It was found that optimum temperatures were dependent on the substrates studied. The enzyme activity decreased due to heat denaturation of the enzyme with increasing temperature and inactivation time for 4-methylcatechol and pyrogallol substrates. However, all inactivation experiments for catechol showed that the activity of artichoke PPO increased with mild heating, reached a maximum, and then decreased with time. Finally, inhibition of artichoke PPO was investigated with inhibitors such as L-cysteine, EDTA, ascorbic acid, gallic acid, d,L-dithiothreitol, tropolone, glutathione, sodium azide, benzoic acid, salicylic acid, and 4-aminobenzoic acid using 4-methylcatechol, pyrogallol, and catechol as substrate. The presence of EDTA, 4-aminobenzoic acid, salicylic acid, gallic acid, and benzoic acid did not cause the inhibition of artichoke PPO. A competitive-type inhibition was obtained with sodium azide, L-cysteine, and d,L-dithiothreitol inhibitors using 4-methylcatechol as substrate; with L-cysteine, tropolone, d,L-dithiothreitol, ascorbic acid, and sodium azide inhibitors using pyrogallol as substrate; and with L-cysteine, tropolone, d,L-dithiotreitol, and ascorbic acid inhibitors using catechol as a substrate. A mixed-type inhibition was obtained with glutathione inhibitor using 4-methylcatechol as a substrate. A noncompetitive inhibition was obtained with tropolone and ascorbic acid inhibitors using 4-methylcatechol as substrate, with glutathione inhibitor using pyrogallol as substrate, and with glutathione and sodium azide inhibitors using catechol as substrate. From these results, it can be said that the most effective inhibitor for artichoke PPO is tropolone. Furthermore, it was found that the type of inhibition depended on the origin of the PPO studied and also on the substrate used.

Diversity-oriented synthesis of dihydrobenzoxazepinones by coupling the Ugi multicomponent reaction with a Mitsunobu cyclization

PubMed Central

Moni, Lisa; Banfi, Luca; Basso, Andrea; Brambilla, Alice

2014-01-01

Summary An operationally simple protocol for the synthesis of 2,3-dihydrobenzo[f][1,4]oxazepin-3-ones, based on an Ugi reaction of an ortho-(benzyloxy)benzylamine, glycolic acid, an isocyanide and an aldehyde, followed by an intramolecular Mitsunobu substitution was developed. The required ortho-(benzyloxy)benzylamines have been in situ generated from the corresponding azides, in turn prepared in high yields from salicylic derivatives. PMID:24605140

Demonstration and Validation of a Regenerated Cellulose Dialysis Membrane Diffusion Sampler for Monitoring Groundwater Quality and Remediation Progress at DoD Sites

DTIC Science & Technology

2007-02-01

years if kept refrigerated in its preservative solution of ethanol, sodium benzoate , and ethylene diamine tetra-acetic acid (EDTA). Alternatively... sodium bicarbonate solution, EDTA, and sodium azide solution to remove residual gylcerol, sulfide, cadmium, chromium, copper, iron, nickel, zinc, and lead...Magnesium Cadmium Nickel Potassium Chromium Selenium Sodium Copper Vanadium Aluminum Iron Zinc Arsenic Lead Antimony Manganese Anions (1-3 days

Crystal structures of (Z)-5-[2-(benzo[b]thio-phen-2-yl)-1-(3,5-di-meth-oxy-phen-yl)ethen-yl]-1H-tetra-zole and (Z)-5-[2-(benzo[b]thio-phen-3-yl)-1-(3,4,5-tri-meth-oxy-phen-yl)ethen-yl]-1H-tetra-zole.

PubMed

Penthala, Narsimha Reddy; Yadlapalli, Jaishankar K B; Parkin, Sean; Crooks, Peter A

2016-05-01

(Z)-5-[2-(Benzo[b]thio-phen-2-yl)-1-(3,5-di-meth-oxy-phen-yl)ethen-yl]-1H-tetrazole methanol monosolvate, C19H16N4O2S·CH3OH, (I), was prepared by the reaction of (Z)-3-(benzo[b]thio-phen-2-yl)-2-(3,5-di-meth-oxy-phen-yl)acrylo-nitrile with tri-butyl-tin azide via a [3 + 2]cyclo-addition azide condensation reaction. The structurally related compound (Z)-5-[2-(benzo[b]thio-phen-3-yl)-1-(3,4,5-tri-meth-oxy-phen-yl)ethen-yl]-1H-tetra-zole, C20H18N4O3S, (II), was prepared by the reaction of (Z)-3-(benzo[b]thio-phen-3-yl)-2-(3,4,5-tri-meth-oxy-phen-yl)acrylo-nitrile with tri-butyl-tin azide. Crystals of (I) have two mol-ecules in the asymmetric unit (Z' = 2), whereas crystals of (II) have Z' = 1. The benzo-thio-phene rings in (I) and (II) are almost planar, with r.m.s deviations from the mean plane of 0.0084 and 0.0037 Å in (I) and 0.0084 Å in (II). The tetra-zole rings of (I) and (II) make dihedral angles with the mean planes of the benzo-thio-phene rings of 88.81 (13) and 88.92 (13)° in (I), and 60.94 (6)° in (II). The di-meth-oxy-phenyl and tri-meth-oxy-phenyl rings make dihedral angles with the benzo-thio-phene rings of 23.91 (8) and 24.99 (8)° in (I) and 84.47 (3)° in (II). In both structures, mol-ecules are linked into hydrogen-bonded chains. In (I), these chains involve both tetra-zole and methanol, and are parallel to the b axis. In (II), mol-ecules are linked into chains parallel to the a axis by N-H⋯N hydrogen bonds between adjacent tetra-zole rings.

High-quality uniform dry transfer of graphene to polymers.

PubMed

Lock, Evgeniya H; Baraket, Mira; Laskoski, Matthew; Mulvaney, Shawn P; Lee, Woo K; Sheehan, Paul E; Hines, Daniel R; Robinson, Jeremy T; Tosado, Jacob; Fuhrer, Michael S; Hernández, Sandra C; Walton, Scott G

2012-01-11

In this paper we demonstrate high-quality, uniform dry transfer of graphene grown by chemical vapor deposition on copper foil to polystyrene. The dry transfer exploits an azide linker molecule to establish a covalent bond to graphene and to generate greater graphene-polymer adhesion compared to that of the graphene-metal foil. Thus, this transfer approach provides a novel alternative route for graphene transfer, which allows for the metal foils to be reused. © 2011 American Chemical Society

Demonstration and Validation of a Regenerated-Cellulose Dialysis Membrane Diffusion Sampler for Monitoring Ground Water Quality and Remediation Progress at DoD Sites

DTIC Science & Technology

2007-01-01

ethanol, sodium benzoate , and ethylene diamine tetra-acetic acid (EDTA). Alternatively, the membrane can be purchased dry, but then must be...cleaned in a series of steps that includes soaking and rinsing in deionized water, heated sodium bicarbonate solution, EDTA, and sodium azide solution to...Potassium Chromium Selenium Sodium Copper Vanadium Aluminum Iron Zinc Arsenic Lead Antimony Manganese Anions (1-3 days) Bicarbonate/Alkalinity

Development of Novel Technetium-99m-Labeled Steroids as Estrogen-Responsive Breast Cancer Imaging Agents

DTIC Science & Technology

2007-06-01

alkylation with α,ω-ditosyloxy triethylene glycol, followed by displacement with sodium azide, aromatization and reduction of the 17- keto group give the...17alpha.-E- (trifluoromethylphenyl)vinyl estradiols as novel estrogen receptor ligands. Steroids 2003, 68, 143 -148. 23. Hanson, R.N., Dilis, R...R. N.; Lee, C. Y.; Friel, C.; Hughes, A.; DeSombre, E. R. Steroids 2003, 68, 143 -148. (c) Hanson, R. N.; Tongcharoensirikul, P.; Dilis, R.; Hughes

BACTERIOPHAGE FORMATION WITHOUT BACTERIAL GROWTH

PubMed Central

Price, Winston H.

1947-01-01

1. Iodoacetate, fluoride, and azide have been found to prevent the formation of phage and to inhibit the synthesis of ATP by Staphylococcus muscae. It is suggested that energy-rich phosphate is needed for the synthesis of phage. 2. Gramicidin prevented the formation of phage. 3. No differences were found between normal bacteria and phage-infected bacteria in the inorganic phosphate, adenosinetriphosphate, ribonucleic acid, and desoxyribonucleic acid content of the cells. 4. The mechanism of phage formation is discussed. PMID:18896936

Proceedings of International Pyrotechnics Seminar (4th), Held at Steamboat Village, Colorado, 22-26 July 1974

DTIC Science & Technology

1974-06-17

10-1 I1. Burning Rate Modifiers, D.R. Dillehay ............................. 11-1 12. Spectroscopic Analysis of Azide Decomposition Products for use...solid, and Pit that they ignite a short distance from the surface. Further- more, decomposition of sodium nitrate, which produces the gas to blow the...decreasing U the thermal conductivity of the basic binary. Class 2 compounds, con- sisting of nanganese oxides, catalyze the normal decomposition of

Minutes of the Explosives Safety Seminar (21st) Held at Houston, Texas on 28-30 August 1984. Volume 2

DTIC Science & Technology

1984-01-01

Brigham City, Utah 84302 ERICKSONo Jack A. Federal Cartridge Corp*, Anoka, mi 555303 ERNEST , William F. USA Defense Amo Ctr 6 School, Savanna, IL 61074-9639...Explosives Safety Board, Alex., VA 22331-0600 PRICE, William A. ASD/SEV USAF, Wright- Patterson APB, 0OR 45433 PROHASKA, Frank B. NAVSEACENPAC, San Diego, CA...1103 Paul W. Lurk COMPLEXITIES OF LEA AZIDE.,. ...... ........................ .. ,... 1143 William Shaneyfelt SESSION L--EXPLOSION RESISTANT

trans-Bis(azido-kappaN)bis(pyridine-2-carboxamide-kappa2N1,O2)nickel(II).

PubMed

Daković, Marijana; Popović, Zora

2007-11-01

In the title compound, [Ni(N(3))(2)(C(6)H(6)N(2)O)(2)], the Ni(II) atom lies on an inversion centre. The distorted octahedral nickel(II) coordination environment contains two planar trans-related N,O-chelating picolinamide ligands in one plane and two monodentate azide ligands perpendicular to this plane. Molecules are linked into a three-dimensional framework by N-H...N hydrogen bonds.

Isolating the segment of the mitochondrial electron transport chain responsible for mitochondrial damage during cardiac ischemia

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

Chen, Qun; Yin, Guotian; Stewart, Sarah

2010-07-09

Ischemia damages the mitochondrial electron transport chain (ETC), mediated in part by damage generated by the mitochondria themselves. Mitochondrial damage resulting from ischemia, in turn, leads to cardiac injury during reperfusion. The goal of the present study was to localize the segment of the ETC that produces the ischemic mitochondrial damage. We tested if blockade of the proximal ETC at complex I differed from blockade distal in the chain at cytochrome oxidase. Isolated rabbit hearts were perfused for 15 min followed by 30 min stop-flow ischemia at 37 {sup o}C. Amobarbital (2.5 mM) or azide (5 mM) was used tomore » block proximal (complex I) or distal (cytochrome oxidase) sites in the ETC. Time control hearts were buffer-perfused for 45 min. Subsarcolemmal mitochondria (SSM) and interfibrillar mitochondria (IFM) were isolated. Ischemia decreased cytochrome c content in SSM but not in IFM compared to time control. Blockade of electron transport at complex I preserved the cytochrome c content in SSM. In contrast, blockade of electron transport at cytochrome oxidase with azide did not retain cytochrome c in SSM during ischemia. Since blockade of electron transport at complex III also prevented cytochrome c loss during ischemia, the specific site that elicits mitochondrial damage during ischemia is likely located in the segment between complex III and cytochrome oxidase.« less

Ameliorative effect of vitamin E and selenium against oxidative stress induced by sodium azide in liver, kidney, testis and heart of male mice.

PubMed

Hamza, Reham Z; Al-Harbi, Mohammad S; El-Shenawy, Nahla S

2017-07-01

The study purported to define the effects of daily administration of vitamin E (Vit E) and selenium (Se) on antioxidant enzyme activity in mice treated with high doses of sodium azide (SA). Male mice were randomly split into nine groups. Groups 1, 2 and 3 were injected daily with saline, Vit E, and Se, respectively, while groups 4, 5 and 6 administrated with different doses of SA (low, medium and high, respectively). The mice in groups 7, 8 and 9 received 100mg/kg Vit E, 17.5mg/kg Se, and a combination of Vit E and Se, respectively before the SA-treatment. Hepatic, renal, testis and heart, antioxidant enzymes as well as levels of lipid peroxidation and total antioxidant capacity levels were determined. Vit E alone affected on the antioxidant parameters of the examined tissues. Se had a preventive effect on the decrease of antioxidant parameters caused by SA and improved the diminished activities of all of them. The study demonstrates that a high dose of SA may alter the effects of normal level antioxidant/oxidative status of male mice and that Se is effective in reducing the SA-damage. Se acts as a synergistic agent with the effect of Vit E in various damaged caused by SA. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Development of a novel method for quantification of autophagic protein degradation by AHA labeling.

PubMed

Zhang, Jianbin; Wang, Jigang; Ng, Shukie; Lin, Qingsong; Shen, Han-Ming

2014-05-01

Autophagy is a catabolic process during which cellular components including protein aggregates and organelles are degraded via a lysosome-dependent process to sustain metabolic homeostasis during nutrient or energy deprivation. Measuring the rate of proteolysis of long-lived proteins is a classical assay for measurement of autophagic flux. However, traditional methods, such as a radioisotope labeling assay, are technically tedious and have low sensitivity. Here, we report a novel method for quantification of long-lived protein degradation based on L-azidohomoalanine (AHA) labeling in mouse embryonic fibroblasts (MEFs) and in human cancer cells. AHA is a surrogate for L-methionine, containing a bio-orthogonalazide moiety. When added to cultured cells, AHA is incorporated into proteins during active protein synthesis. After a click reaction between an azide and an alkyne, the azide-containing proteins can be detected with an alkyne-tagged fluorescent dye, coupled with flow cytometry. Induction of autophagy by starvation or mechanistic target of rapamycin (MTOR) inhibitors was able to induce a significant reduction of the fluorescence intensity, consistent with other autophagic markers. Coincidently, inhibition of autophagy by pharmacological agents or by Atg gene deletion abolished the reduction of the fluorescence intensity. Compared with the classical radioisotope pulse-labeling method, we think that our method is sensitive, quantitative, nonradioactive, and easy to perform, and can be applied to both human and animal cell culture systems.

Development of a novel method for quantification of autophagic protein degradation by AHA labeling

PubMed Central

Zhang, Jianbin; Wang, Jigang; Ng, Shukie; Lin, Qingsong; Shen, Han-Ming

2014-01-01

Autophagy is a catabolic process during which cellular components including protein aggregates and organelles are degraded via a lysosome-dependent process to sustain metabolic homeostasis during nutrient or energy deprivation. Measuring the rate of proteolysis of long-lived proteins is a classical assay for measurement of autophagic flux. However, traditional methods, such as a radioisotope labeling assay, are technically tedious and have low sensitivity. Here, we report a novel method for quantification of long-lived protein degradation based on L-azidohomoalanine (AHA) labeling in mouse embryonic fibroblasts (MEFs) and in human cancer cells. AHA is a surrogate for L-methionine, containing a bio-orthogonalazide moiety. When added to cultured cells, AHA is incorporated into proteins during active protein synthesis. After a click reaction between an azide and an alkyne, the azide-containing proteins can be detected with an alkyne-tagged fluorescent dye, coupled with flow cytometry. Induction of autophagy by starvation or mechanistic target of rapamycin (MTOR) inhibitors was able to induce a significant reduction of the fluorescence intensity, consistent with other autophagic markers. Coincidently, inhibition of autophagy by pharmacological agents or by Atg gene deletion abolished the reduction of the fluorescence intensity. Compared with the classical radioisotope pulse-labeling method, we think that our method is sensitive, quantitative, nonradioactive, and easy to perform, and can be applied to both human and animal cell culture systems. PMID:24675368

Fluorometric Measurement of Pyridine Nucleotide Reduction in the Giant Axon of the Squid

PubMed Central

Doane, Marshall G.

1967-01-01

By monitoring the fluorescence of the isolated giant axon of the squid Loligo pealei, it was possible to follow changes in its oxidation-reduction state as caused by the action of anoxia, cyanide, Amytal, and azide. The response to oxygen depletion was very rapid, the NAD within the axon being 90% reduced within 1–2 min. Cyanide and Amytal gave essentially similar results, although somewhat longer periods of time elapsed during their onset and washout periods. The extent of NAD reduction was essentially the same under conditions of anoxia and treatment with cyanide and Amytal. Azide was less effective in this respect, and at comparatively high levels of concentration (25–50 mM) gave values of 40% or less of the reduction observed with the other inhibitors. The application of ouabain and strophanthidin gave no observable NAD reduction. Variations in the time required to consume given quantities of dissolved oxygen before and after stimulation indicated an increase of 10–20% in oxygen uptake rate associated with activity, although this figure appeared to be a function of the surface-to-volume ratio of the axon. A biochemical analysis of axoplasm for oxidized and reduced pyridine nucleotide was made. Fluorometric examination of centrifuged axoplasm indicated that the NAD-NADH was largely confined to the mitochondria of the axon. PMID:4384698

Injectable dextran hydrogels fabricated by metal-free click chemistry for cartilage tissue engineering.

PubMed

Wang, Xiaoyu; Li, Zihan; Shi, Ting; Zhao, Peng; An, Kangkang; Lin, Chao; Liu, Hongwei

2017-04-01

Injectable dextran-based hydrogels were prepared for the first time by bioorthogonal click chemistry for cartilage tissue engineering. Click-crosslinked injectable hydrogels based on cyto-compatible dextran (Mw=10kDa) were successfully fabricated under physiological conditions by metal-free alkyne-azide cycloaddition (click) reaction between azadibenzocyclooctyne-modified dextran (Dex-ADIBO) and azide-modified dextran (Dex-N 3 ). Gelation time of these dextran hydrogels could be regulated in the range of approximately 1.1 to 10.2min, depending on the polymer concentrations (5% or 10%) and ADIBO substitution degree (DS, 5 or 10) of Dex-ADIBO. Rheological analysis indicated that the dextran hydrogels were elastic and had storage moduli from 2.1 to 6.0kPa with increasing DS of ADIBO from 5 to 10. The in vitro tests revealed that the dextran hydrogel crosslinked from Dex-ADIBO DS 10 and Dex-N 3 DS 10 at a polymer concentration of 10% could support high viability of individual rabbit chondrocytes and the chondrocyte spheroids encapsulated in the hydrogel over 21days. Individual chondrocytes and chondrocyte spheroids in the hydrogel could produce cartilage matrices such as collagen and glycosaminoglycans. However, the chondrocyte spheroids produced a higher content of matrices than individual chondrocytes. This study indicates that metal-free click chemistry is effective to produce injectable dextran hydrogels for cartilage tissue engineering. Copyright © 2016 Elsevier B.V. All rights reserved.

Flash Vacuum Pyrolysis of Azides, Triazoles, and Tetrazoles.

PubMed

Wentrup, Curt

2017-03-08

Flash vacuum pyrolysis (FVP) of azides is an extremely valuable method of generating nitrenes and studying their thermal rearrangements. The nitrenes can in many cases be isolated in low-temperature matrices and observed spectroscopically. NH and methyl, alkyl, aralkyl, vinyl, cyano, aryl and N-heteroaryl, acyl, carbamoyl, alkoxycarbonyl, imidoyl, boryl, silyl, phosphonyl, and sulfonyl nitrenes are included. FVP of triazoloazines generates diazomethylazines and azinylcarbenes, which often rearrange to the energetically more stable arylnitrenes. N 2 elimination from monocyclic 1,2,3-triazoles can generate iminocarbenes, 1H-azirines, ketenimines, and cyclization products, and 1,2,4-triazoles are precursors of nitrile ylides. Benzotriazoles are preparatively useful precursors of cyanocyclopentadienes, carbazoles, and aza-analogues. FVP of 5-aryltetrazoles can result in double N 2 elimination with formation of arylcarbenes or of heteroarylcarbenes, which again rearrange to arylnitrenes. Many 5-substituted and 2,5-disubstituted tetrazoles are excellent precursors of nitrile imines (propargylic, allenic, or carbenic), which are isolable at low temperatures in some cases (e.g., aryl- and silylnitrile imines) or rearrange to carbodiimides. 1,5-Disubstituted tetrazoles are precursors of imidoylnitrenes, which also rearrange to carbodiimides or add intramolecularly to aryl substituents to yield indazoles and related compounds. Where relevant for the mechanistic understanding, pyrolysis under flow conditions or in solution or the solid state will be mentioned. Results of photolysis reactions and computational chemistry complementing the FVP results will also be mentioned in several places.

One-pot reaction for the preparation of biofunctionalized self-assembled monolayers on gold surfaces

NASA Astrophysics Data System (ADS)

Raigoza, Annette F.; Fies, Whitney; Lim, Amber; Onyirioha, Kristeen; Webb, Lauren J.

2017-02-01

The Huisgen cycloaddition reaction (;click; chemistry) has been used extensively to functionalize surfaces with macromolecules in a straightforward manner. We have previously developed a procedure using the copper(I)-catalyzed click reaction to tether synthetic α-helical peptides carrying two alkyne groups to a well-ordered azide-terminated alkanethiol self-assembled monolayer (SAM) on a Au(111) surface. While convenient, click-based strategies potentially pose significant problems from reagents, solvents, and reaction temperatures that may irreversibly damage some molecules or substrates. Tuning click chemistry conditions would allow individual optimization of reaction conditions for a wide variety of biomolecules and substrate materials. Here, we explore the utility of simultaneous SAM formation and peptide-attachment chemistry in a one-pot reaction. We demonstrate that a formerly multistep reaction can be successfully carried out concurrently by mixing azide-terminated alkanethiols, CuCl, and a propargylglycine-containing peptide over a bare gold surface in ethanol and reacting at 70 °C. X-ray photoelectron spectroscopy (XPS), surface infrared spectroscopy, surface circular dichroic (CD) spectroscopy, and scanning tunneling microscopy (STM) were used to determine that this one-pot reaction strategy resulted in a high density of surface-bound α-helices without aggregation. This work demonstrates the simplicity and versatility of a SAM-plus-click chemistry strategy for functionalizing Au surfaces with structured biomolecules.

Click chemistry-mediated cyclic cleavage of metal ion-dependent DNAzymes for amplified and colorimetric detection of human serum copper (II).

PubMed

Li, Daxiu; Xie, Jiaqing; Zhou, Wenjiao; Jiang, Bingying; Yuan, Ruo; Xiang, Yun

2017-11-01

The determination of the level of Cu 2+ plays important roles in disease diagnosis and environmental monitoring. By coupling Cu + -catalyzed click chemistry and metal ion-dependent DNAzyme cyclic amplification, we have developed a convenient and sensitive colorimetric sensing method for the detection of Cu 2+ in human serums. The target Cu 2+ can be reduced by ascorbate to form Cu + , which catalyzes the azide-alkyne cycloaddition between the azide- and alkyne-modified DNAs to form Mg 2+ -dependent DNAzymes. Subsequently, the Mg 2+ ions catalyze the cleavage of the hairpin DNA substrate sequences of the DNAzymes and trigger cyclic generation of a large number of free G-quadruplex sequences, which bind hemin to form the G-quadruplex/hemin artificial peroxidase to cause significant color transition of the sensing solution for sensitive colorimetric detection of Cu 2+ . This method shows a dynamic range of 5 to 500 nM and a detection limit of 2 nM for Cu 2+ detection. Besides, the level of Cu 2+ in human serums can also be determined by using this sensing approach. With the advantages of simplicity and high sensitivity, such sensing method thus holds great potential for on-site determination of Cu 2+ in different samples. Graphical abstract Sensitive colorimetric detection of copper (II) by coupling click chemistry with metal ion-dependentDNAzymes.

Preparation of Metalloporphyrin-Bound Superparamagnetic Silica Particles via "Click" Reaction.

PubMed

Hollingsworth, Javoris V; Bhupathiraju, N V S Dinesh K; Sun, Jirun; Lochner, Eric; Vicente, M Graça H; Russo, Paul S

2016-01-13

A facile approach using click chemistry is demonstrated for immobilization of metalloporphyrins onto the surface of silica-coated iron oxide particles. Oleic-acid stabilized iron oxide nanocrystals were prepared by thermal decomposition of iron(III) acetylacetonate. Their crystallinity, morphology, and superparamagnetism were determined using X-ray diffraction, transmission electron microscopy, and a superconducting quantum interference device. Monodisperse core-shell particles were produced in the silica-coating of iron oxide via microemulsion synthesis. Surface modification of these particles was performed in two steps, which included the reaction of silica-coated iron oxide particles with 3-bromopropyltrichlorosilane, followed by azido-functionalization with sodium azide. Monoalkylated porphyrins were prepared using the Williamson ether synthesis of commercially available tetra(4-hydroxyphenyl) porphyrin with propargyl bromide in the presence of a base. (1)H NMR and matrix-assisted laser desorption ionization confirmed the identity of the compounds. The prepared monoalkyne porphyrins were zinc-metalated prior to their introduction to azide-functionalized, silica-coated iron oxide particles in the click reaction. X-ray photoelectron spectroscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy were used to characterize the surface chemistry after each step in the reaction. In addition, particle size was determined using dynamic light scattering and microscopy. The presented methodology is versatile and can be extended to other photoreactive systems, such as phthalocyanines and boron-dipyrromethane, which may lead to new materials for optical, photonic, and biological applications.

PEG-coumarin based biocompatible self-assembled fluorescent nanoaggregates synthesized via click reactions and studies of aggregation behavior.

PubMed

Behl, Gautam; Sikka, Manisha; Chhikara, Aruna; Chopra, Madhu

2014-02-15

Click chemistry has found wide application in drug discovery, bioconjugation reactions, polymer chemistry and synthesis of amphiphilic materials with pharmaceutical and biomedical applications. Triazole substitution via a click reaction alters photophysical properties of coumarin. Both coumarin and triazole moieties participate in π-π stacking interactions. Hence it should be possible to prepare fluorescent self-assembly systems by conjugation of coumarin to poly (ethylene glycol) (PEG) via click reactions exhibiting hydrophilic, hydrophobic and π-π stacking interactions. Moreover, the materials can be suitable platforms to assess fluorescence modulation effect of triazole substitution on coumarins. PEG supported coumarin conjugates were synthesized and the fluorescence modulation effect of the formation of triazole on coumarin was assessed. Their aggregation properties were studied by surface tension measurements, dynamic light scattering (DLS), transmission electron microscopy (TEM), fluorescence and (1)H NMR spectroscopy. The conjugates were found to form nanoaggregates in the size range of 100-120 nm with a negative free energy of micellization (~-27 kJ mol(-1)) confirming aggregation and self-assembly. The Quantum yield of 4-methyl-7-propargylcoumarin (7P4MC) was enhanced after triazole formation with azide functionalized PEG (methoxy-PEG350 azide). The conjugates were found to exhibit π-π stacking interactions in addition to hydrophilic and hydrophobic interactions. They were found to be biocompatible with human pancreatic cancer cells. Copyright © 2013 Elsevier Inc. All rights reserved.

Antimutagenic properties of Mangifera indica L. stem bark extract and evaluation of its effects on hepatic CYP1A1.

PubMed

Morffi, Janet; Rodeiro, Idania; Hernández, Sandra Luz; González, Leonora; Herrera, Jose; Espinosa-Aguirre, J Javier

2012-09-01

Mangifera indica stem bark extract (MSBE) is a Cuban natural product which has shown strong antioxidant properties. In this work, the antimutagenic effect of MSBE was tested against 10 well-known mutagens/carcinogens in the Ames test in the absence or presence of metabolic fraction (S9). The chemical mutagens tested included: cyclophosphamide, mitomycin C, bleomycin, cisplatin, dimethylnitrosamine (DMNA), benzo[a]pyrene (BP), 2-acetylaminofluorene (2-AAF), sodium azide, 1-nitropyrene (1-NP) and picrolonic acid. Protective effects of the extract were also evaluated by comparing the efficiency of S9 fraction obtained from rats treated during 28 days with oral doses of MSBE (50-500 mg/kg) with that obtained from rats treated with vehicle (control) to activate bleomycin and cyclophosphamide in the Ames test. MSBE concentrations between 50 and 500 μg/plate significantly reduced the mutagenicity mediated by all the chemicals tested with the exception of sodium azide. Higher mutagenicity was found when bleomycin and cyclophosphamide (CP) were activated by control S9 than by MSBE S9. In addition, inhibition of CYP1A1 microsomal activity was observed in the presence of MSBE (10-20 μg/ml). We can conclude that besides its potent antioxidant activity previously reported, MSBE may also exert a chemoprotective effect due to its capacity to inhibit CYP activity.

Identifying the Nonradical Mechanism in the Peroxymonosulfate Activation Process: Singlet Oxygenation Versus Mediated Electron Transfer.

PubMed

Yun, Eun-Tae; Lee, Jeong Hoon; Kim, Jaesung; Park, Hee-Deung; Lee, Jaesang

2018-06-01

Select persulfate activation processes were demonstrated to initiate oxidation not reliant on sulfate radicals, although the underlying mechanism has yet to be identified. This study explored singlet oxygenation and mediated electron transfer as plausible nonradical mechanisms for organic degradation by carbon nanotube (CNT)-activated peroxymonosulfate (PMS). The degradation of furfuryl alcohol (FFA) as a singlet oxygen ( 1 O 2 ) indicator and the kinetic retardation of FFA oxidation in the presence of l-histidine and azide as 1 O 2 quenchers apparently supported a role of 1 O 2 in the CNT/PMS system. However, the 1 O 2 scavenging effect was ascribed to a rapid PMS depletion by l-histidine and azide. A comparison of CNT/PMS and photoexcited Rose Bengal (RB) excluded the possibility of singlet oxygenation during heterogeneous persulfate activation. In contrast to the case of excited RB, solvent exchange (H 2 O to D 2 O) did not enhance FFA degradation by CNT/PMS and the pH- and substrate-dependent reactivity of CNT/PMS did not reflect the selective nature of 1 O 2 . Alternatively, concomitant PMS reduction and trichlorophenol oxidation were achieved when PMS and trichlorophenol were physically separated in two chambers using a conductive vertically aligned CNT membrane. This result suggested that CNT-mediated electron transfer from organics to persulfate was primarily responsible for the nonradical degradative route.

One-step ligand exchange reaction as an efficient way for functionalization of magnetic nanoparticles

NASA Astrophysics Data System (ADS)

Mrówczyński, Radosław; Rednic, Lidia; Turcu, Rodica; Liebscher, Jürgen

2012-07-01

Novel magnetic Fe3O4 nanoparticles (NPs) covered by one layer of functionalized fatty acids, bearing entities (Hayashi catalyst, biotin, quinine, proline, and galactose) of high interest for practical application in nanomedicine or organocatalysis, were synthesized. The functionalized fatty acids were obtained by Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) of azido fatty acids with alkynes. All the magnetic NPs show superparamagnetic behavior with high values of magnetization and high colloidal stability in DCM solution.

Insight into Hydrazinium Nitrates, Azides, Dicyanamide, and 5-Azidotetrazolate Ionic Materials from Simulations and Experiments

DTIC Science & Technology

2011-04-04

agreement between simulation and experiment is seen for UDMH , with simulations up to slightly above the boiling point of 336 K falling within a density ...conjunction wi th M05-2X density funct ional. Inclusion of a l one-pair on hydrazinium-based cations significantly improved ion electrostatic description...cation-anion complexes employing aug-cc- pvDz (cc-pvTz) basis functions at MP2 level or in conjunction with M05-2X density functional. Inclusion of

Carbon Dioxide Fixation in Isolated Kalanchoe Chloroplasts 1

PubMed Central

Levi, Carolyn; Gibbs, Martin

1975-01-01

Chloroplasts isolated from Kalanchoe diagremontiana leaves were capable of photosynthesizing at a rate of 5.4 μmoles of CO2 per milligram of chlorophyll per hour. The dark rate of fixation was about 1% of the light rate. A high photosynthetic rate was associated with low starch content of the leaves. Ribose 5-phosphate, fructose 1,6-diphosphate, and dithiothreitol stimulated fixation, whereas phosphoenolpyruvate and azide were inhibitors. The products of CO2 fixation were primarily those of the photosynthetic carbon reduction cycle. PMID:16659249

Explosive nephrolithopaxy: reality or fiction?

PubMed

Miller, R A; Wickham, J E; Reynolds, S E; Westcott, A; Bailey, A

1984-05-01

The use of silver and lead azide explosive charges for the percutaneous distintegration of renal calculi has been investigated. Charges of 10 mg or more reliably reduced calculi to fragments of extractable size; however, the concomitant tissue effects would preclude the use of such charges clinically. Smaller charges require multiple applications. High-speed flash photography demonstrated the unfocussed nature of these discharges. Considerable improvements are anticipated when the shock waves are focused. The use of Nonel tubing is described, and future developments are discussed.

Investigation of Ignition Delay: Novel Beta-Substituted Ethylazide Derivatives as Potential New Liquid Propellant Fuels (Preprint)

DTIC Science & Technology

2007-04-09

Magnetic Resonance (NMR) Spectroscopy and Liquid atography ( LC ). Surprisingly the NMR shifts of the characteristic ethyl peaks were not pronounced .2 ppm...regardless of the conditions, UDMH and 2-chloroethyl azide did not react in H H N3 solven butylhy was re repeat and ch Chrom (only 0 group appear these m...unlike what one might expect from replacing a strong withdrawing group with a donating like an amine. In contrast, the peaks attributed to the

A Comparative Study of Very High Burning Rate Materials - HIVELITE compositions 300511 and 300435

DTIC Science & Technology

1982-08-01

explosives and more or as sensitive as RDX and HMX . Thermal Sensitivity Differential Thermal Analysis/Thermogravimetric Analysis (DTA/TGA) Simultaneous...impact than Comp B end RDX but is less sensitive than lead azide. HIVELITE 30051i on the other hand, is less sensitive than Comp B and RDX on the ERL...represents the alpha to beta phase transition of KNO 3 . This endotherm is followed by four exotherms with peaks at 538 K (265*C), 567 K (2940C), 598 K

3'-End labeling of nucleic acids by a polymerase ribozyme.

PubMed

Samanta, Biswajit; Horning, David P; Joyce, Gerald F

2018-06-13

A polymerase ribozyme can be used to label the 3' end of RNA or DNA molecules by incorporating a variety of functionalized nucleotide analogs. Guided by a complementary template, the ribozyme adds a single nucleotide that may contain a fluorophore, biotin, azide or alkyne moiety, thus enabling the detection and/or capture of selectively labeled materials. Employing a variety of commercially available nucleotide analogs, efficient labeling was demonstrated for model RNAs and DNAs, human microRNAs and natural tRNA.

Isoxazolodihydropyridinones: 1,3-dipolar cycloaddition of nitrile oxides onto 2,4-dioxopiperidines

PubMed Central

Coffman, Keith C.; Hartley, Timothy P.; Dallas, Jerry L.; Kurth, Mark J.

2012-01-01

Practical and efficient methods have been developed for the diversity-oriented synthesis of isoxazolodihydropyridinones via the 1,3-dipolar cycloaddition of nitrile oxides onto 2,4-dioxopiperidines. A select few of these isoxazolodihydropyridinones were further elaborated with triazoles by copper catalyzed azide-alkyne cycloaddition reactions. A total of 70 compounds and intermediates were synthesized and analyzed for drug likeness. Sixty-four of these novel compounds were submitted to the NIH Molecular Libraries Small Molecule Repository for high-throughput biological screening. PMID:22352295

Tandem Cu-catalyzed ketenimine formation and intramolecular nucleophile capture: Synthesis of 1,2-dihydro-2-iminoquinolines from 1-(o-acetamidophenyl)propargyl alcohols

PubMed Central

Kant, Ruchir

2014-01-01

Summary The copper-catalyzed ketenimine formation reaction of 1-(o-acetamidophenyl)propargyl alcohols with various sulfonyl azides is found to undergo a concomitant intramolecular nucleophile attack to generate 1,2-dihydro-2-iminoquinolines after aromatization (via elimination of acetyl and hydroxy groups) and tautomerization. The reaction produces 4-substituted and 3,4-unsubstituted title compounds in moderate to good yields under mild reaction conditions. PMID:24991276

Synthesis of heteroglycoclusters by using orthogonal chemoselective ligations

PubMed Central

Thomas, Baptiste; Fiore, Michele; Bossu, Isabelle; Dumy, Pascal

2012-01-01

Summary Synthetic heteroglycoclusters are being subjected to increasing interest due to their potential to serve as selective ligands for carbohydrate-binding proteins. In this paper, we describe an expedient strategy to prepare cyclopeptides displaying well-defined distributions and combinations of carbohydrates. By using both oxime ligation and copper(I)-catalyzed alkyne–azide cycloaddition, two series of compounds bearing binary combinations of αMan, αFuc or βLac in an overall tetravalent presentation, and either 2:2 or 3:1 relative proportions, have been prepared. PMID:22509212

Copper-catalyzed domino cycloaddition/C-N coupling/cyclization/(C-H arylation): an efficient three-component synthesis of nitrogen polyheterocycles.

PubMed

Qian, Wenyuan; Wang, Hao; Allen, Jennifer

2013-10-11

A cat of all trades: A single copper catalyst promoted up to three reaction steps with separate catalytic cycles in a domino sequence (azide-alkyne cycloaddition/Goldberg amidation/Camps cyclization/(CH arylation)) for the rapid construction of complex heterocycles from three simple components under mild conditions. Facile cleavage of the triazole ring enables further elaboration of the condensation products. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Theory investigation progress of DMAZ

NASA Astrophysics Data System (ADS)

Xie, Hui; Mu, Xiaogang; Zhang, Yue; Wang, Xuanjun

2017-05-01

The recent progress in the theoretical study of N, N-dimethyl-2-azidoethylamine (DMAZ), a new type of azide fuel, is summarized. Thermodynamic Properties (such as Enthalpy-of-Formation, Enthalpy-of-Vaporization, and Enthalpy-of-Sublimation), conformers, Spectrums, the Henry's constant, ignition delay et al. are studied by Density Functional Theory (DFT). It is proved that DMAZ has good performance with a density impulse 2.499 Ns/m3, and has a good application prospect in replacing the traditional hydrazine propellant methyl-hydrazine (MMH).

Synthesis and Properties of N7O+ (PREPRINT)

DTIC Science & Technology

2009-11-23

isolated by pumping off the solvent and gaseous products at low temperature. With an excess of HN3, replacement of the second fluorine atom started to...was analyzed and involves the electrophilic attack of the terminal gamma-N atom of one azide ligand on the electron rich alpha-N atom of the second...Chem. Soc. 1995, 117, 6136. (8) Christe, K. O., Wilson, W. W., Schack, C. J., J. Fluorine . Chem. 1978, 11, 71. (9) Moller, C., Plesset, M. S., Phys

International Symposium on Gas Kinetics (11th) Held in Assisi (Perugia), Italy on 2-7 September 1990. Book of Abstracts

DTIC Science & Technology

1990-09-07

as traditional, themes in Gas Phase Kinetics. Highlighted topics include: A) Atmospheric Chemistry; B) Theory of Reactive, Inelastic, and...KINETICS AND SPECTROSCOPY OF EXCITED SPECIES OBTAINED VIA DETONATION OF LEAD AZIDE 0-20 C.Nyeland (Copenhagen, Denmark) COLLISION THEORY OF "FALL-OF...J.P.Burrows, and G.K.Moortgat (Mainz, W.Germany) POSSIBLE ABIOTIC SOURCES OF N2 0 B - THEORY OF REACTIVE, INELASTIC, AND PHODISSOCIATIVE PROCESSES B-i

Performance characteristics of a laser initiated microdetonator

NASA Technical Reports Server (NTRS)

Yang, L. C.

1981-01-01

The test results of 320 units of a laser initiated microdetonator are summarized. The commercially fabricated units used a lead styphnate/lead azide/HMX (1 mg/13.5 mg) explosive train design contained in a miniature aluminum can that was capped with a glass-metal seal window. The test parameters were the laser energy, temperature, laser pulse duration, laser wavelength and nuclear radiation (5,000,000 rad of 1 MeV gamma rays). The performance parameters were the laser energy for ignition and the actuation response time.

Liquid Azide Salts (Preprint)

DTIC Science & Technology

2007-09-13

the SAINT software52, 53 to give the hkl file corrected for Lp/decay. The absorption correction was performed using the SADABS54 program. The...4), 3060(5), 3021(4), 2952(12), 2821(4), 1621(4), 1573(5), 1539(2), 1433(4), 1405(44), 1330(77), 1262(1), 1244(9), 1226(5), 1177(4), 1093(7), 1075 ...Geissler, P.; Klapötke, T.M.; Kroth, H.-J.; Spectrochim. Acta, Part A 1995, 51A, 1075 . [31] Johnson, J.P.; MacLean, G.K.; Passmore, J.; White, P.S

Liquid Azide Salts

DTIC Science & Technology

2007-09-13

M.; Kroth, H.-J. Spectrochim. Acta, Part A 1995, 51A, 1075 . (31) Johnson, J. P.; MacLean, G. K.; Passmore, J.; White, P. S. Can. J. Chem. 1989, 67...were then processed using the SAINT software52,53 to give the hkl file corrected for Lp/decay. For the structure of 4, the absorption correction was...1244(9), 1226(5), 1177(4), 1093(7), 1075 (19), 1029(3), 984(16), 914(0+), 891(0+), 740(2), 657(1), 617(11), 455(7), 332(6), 303(6), 123(100), 102(84

Imaging spectroscopy of polymer ablation plasmas for laser propulsion applications

NASA Astrophysics Data System (ADS)

Jiao, Long; Truscott, Benjamin S.; Liu, Hao; Ashfold, Michael N. R.; Ma, Honghao

2017-01-01

A number of polymers have been proposed for use as propellants in space launch and thruster applications based on laser ablation, although few prior studies have either evaluated their performance at background pressures representative of the upper atmosphere or investigated interactions with ambient gases other than air. Here, we use spatially and temporally resolved optical emission spectroscopy to compare three polymers, poly(ethylene), poly(oxymethylene), and glycidyl azide polymer, ablated using a 532 nm, nanosecond pulsed laser under Ar and O2 at pressures below 1 Torr. Emission lines from neutrally and positively charged atoms are observed in each case, along with the recombination radiation at the interaction front between the plasma plume and the background gas. C2 radicals arise either as a direct fragmentation product or by a three-body recombination of C atoms, depending on the structure of the polymer backbone, and exhibit a rotational temperature of ≈5000 K. The Sedov-Taylor point blast model is used to infer the energy release relative to the incident laser energy, which for all polymers is greater in the presence of O2, as to be expected based on their negative oxygen balance. Under Ar, plume confinement is seen to enhance the self-reactivity of the ejecta from poly(oxymethylene) and glycidyl azide polymer, with maximum exothermicity close to 0.5 Torr. However, little advantage of the latter, widely considered one of the most promising energetic polymers, is apparent under the present conditions over the former, a common engineering plastic.

Assessment of sample preservation techniques for pharmaceuticals, personal care products, and steroids in surface and drinking water.

PubMed

Vanderford, Brett J; Mawhinney, Douglas B; Trenholm, Rebecca A; Zeigler-Holady, Janie C; Snyder, Shane A

2011-02-01

Proper collection and preservation techniques are necessary to ensure sample integrity and maintain the stability of analytes until analysis. Data from improperly collected and preserved samples could lead to faulty conclusions and misinterpretation of the occurrence and fate of the compounds being studied. Because contaminants of emerging concern, such as pharmaceuticals and personal care products (PPCPs) and steroids, generally occur in surface and drinking water at ng/L levels, these compounds in particular require such protocols to accurately assess their concentrations. In this study, sample bottle types, residual oxidant quenching agents, preservation agents, and hold times were assessed for 21 PPCPs and steroids in surface water and finished drinking water. Amber glass bottles were found to have the least effect on target analyte concentrations, while high-density polyethylene bottles had the most impact. Ascorbic acid, sodium thiosulfate, and sodium sulfite were determined to be acceptable quenching agents and preservation with sodium azide at 4 °C led to the stability of the most target compounds. A combination of amber glass bottles, ascorbic acid, and sodium azide preserved analyte concentrations for 28 days in the tested matrices when held at 4 °C. Samples without a preservation agent were determined to be stable for all but two of the analytes when stored in amber glass bottles at 4 °C for 72 h. Results suggest that if improper protocols are utilized, reported concentrations of target PPCPs and steroids may be inaccurate.

Intracellular in situ labeling of TiO2 nanoparticles for fluorescence microscopy detection

PubMed Central

Brown, Koshonna; Thurn, Ted; Xin, Lun; Liu, William; Bazak, Remon; Chen, Si; Lai, Barry; Vogt, Stefan; Jacobsen, Chris; Paunesku, Tatjana; Woloschak, Gayle E.

2018-01-01

Titanium dioxide (TiO2) nanoparticles are produced for many different purposes, including development of therapeutic and diagnostic nanoparticles for cancer detection and treatment, drug delivery, induction of DNA double-strand breaks, and imaging of specific cells and subcellular structures. Currently, the use of optical microscopy, an imaging technique most accessible to biology and medical pathology, to detect TiO2 nanoparticles in cells and tissues ex vivo is limited with low detection limits, while more sensitive imaging methods (transmission electron microscopy, X-ray fluorescence microscopy, etc.) have low throughput and technical and operational complications. Herein, we describe two in situ post-treatment labeling approaches to stain TiO2 nanoparticles taken up by the cells. The first approach utilizes fluorescent biotin and fluorescent streptavidin to label the nanoparticles before and after cellular uptake; the second approach is based on the copper-catalyzed azide-alkyne cycloaddition, the so-called Click chemistry, for labeling and detection of azide-conjugated TiO2 nanoparticles with alkyne-conjugated fluorescent dyes such as Alexa Fluor 488. To confirm that optical fluorescence signals of these nanoparticles match the distribution of the Ti element, we used synchrotron X-ray fluorescence microscopy (XFM) at the Advanced Photon Source at Argonne National Laboratory. Titanium-specific XFM showed excellent overlap with the location of optical fluorescence detected by confocal microscopy. Therefore, future experiments with TiO2 nanoparticles may safely rely on confocal microscopy after in situ nanoparticle labeling using approaches described here. PMID:29541425

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

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

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

2011-01-01

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

Dehydrophenylnitrenes: matrix isolation and photochemical rearrangements.

PubMed

Sander, Wolfram; Winkler, Michael; Cakir, Bayram; Grote, Dirk; Bettinger, Holger F

2007-02-02

The photochemistry of 3-iodo-2,4,5,6-tetrafluorophenyl azide 8 and 3,5-diiodo-2,4,6-trifluorophenyl azide 9 was studied by IR and EPR spectroscopy in cryogenic argon and neon matrices. Both compounds form the corresponding nitrenes as primary photoproducts in photostationary equilibria with their azirine and ketenimine isomers. In contrast to fluorinated phenylnitrenes, ring-opened products are obtained upon short-wavelength irradiation of the iodine-containing systems, indicative of C-I bond cleavage in the nitrenes or didehydroazepines under these conditions. Neither 3-dehydrophenylnitrene 6 nor 3,5-didehydrophenylnitrene 7 could be detected directly. The structures of the acyclic photoproducts were identified by extensive comparison with DFT calculated spectra. Mechanistic aspects of the rearrangements leading to the observed products and the electronic properties of the title intermediates are discussed on the basis of DFT as well as high-level ab initio calculations. The computations indicate strong through-bond coupling of the exocyclic orbital in the meta position with the singly occupied in-plane nitrene orbital in the monoradical nitrenes. In contrast to the ortho or para isomers, this interaction results in low-spin ground states for meta nitrene radicals and a weakening of the C1-C2 bond causing the kinetic instability of these species even under low-temperature conditions. 3,5-Didehydrophenylnitrenes, on the other hand, in which a strong C3-C5 interaction reduces coupling of the radical sites with the nitrene unit, might be accessible synthetic targets if the intermediate formation of labile monoradicals could be circumvented.

Applications of Shock Wave Research to Developments of Therapeutic Devices.

NASA Astrophysics Data System (ADS)

Takayama, Kazuyoshi

2007-06-01

Underwater shock wave research applied to medicine started in 1980 by exploding micro lead azide pellets in water. Collaboration with urologists in the School of Medicine, Tohoku University at the same time was directed to disintegration of kidney stones by controlling shock waves. We initially proposed a miniature truncated ellipsoidal cavity for generating high-pressures enough to disintegrate the stone but gave up the idea, when encountering the Dornie Systems' invention of an extracorporeal shock wave lithotripter (ESWL). Then we confirmed its effectiveness by using 10 mg silver azide pellets and constructed our own lithotripter, which was officially approved for a clinical use in 1987. Tissue damage during ESWL was attributable to bubble collapse and we convinced it could be done in a controlled fashion. In 1996, we used 160 mJ pulsed Ho:YAG laser beam focusing inside a catheter for shock generation and applied it to the revascularization of cerebral embolism, which is recently expanded to the treatment of pulmonary infarction. Micro water jets discharged in air were so effective to dissect soft tissues preserving small blood vessels. Animal experiments are successfully performed with high frequency water jets driven by an actuator-assisted micro-pump. A metal foil is deformed at high speed by a Q-switched Nd:YAG laser beam loading. We used this technique to project micro-particles or dry drugs attached on its reverse side and extended it to a laser ablation assisted dry drug delivery or DNA introductory system.

Design and characterization of a phantom that simultaneously simulates tissue optical properties between 400 and 650 nm

NASA Astrophysics Data System (ADS)

Wagnieres, Georges A.; Cheng, Shangguan; Zellweger, Matthieu; Doegnitz-Utke, Nora; Braichotte, Daniel; Ballini, Jean-Pierre; van den Bergh, Hubert

1996-12-01

The design and characterization of optical phantoms which have the same absorption and scattering characteristics as biological tissues in a broad spectral window (between 400 and 650 nm) are presented. These low cost phantoms use agarose dissolved in water as the transparent matrix. The latter is loaded with various amounts of silicon dioxide, intralipid, ink, bovine serum, blood, azide, penicillin and fluorochromes. The silicon dioxide and intralipid particles are responsible for the light scattering whereas the ink and blood are the absorbers. The penicillin and the azide are used to insure the conservation of such phantoms when stored at 4 degrees Celsius. The serum and fluorochromes, such as Coumarin 30, produce an autofluorescence similar to human tissues. Various fluorochromes or photosensitizers can be added to these phantoms to simulate a photodetection procedure. The absorption and fluorescence spectroscopy of the dyes tested was not different in these phantoms than in live tissues. The mechanical properties of these gelatinous phantoms are also of interest as they can easily be molded and reshaped with a conventional cutter, so that for instance layered structures, with different optical properties in each layer, can be designed. The optical properties of these phantoms were determined between 400 and 650 nm by measuring their effective attenuation coefficient ((mu) eff) and total reflectance (Rd). The microscopic absorption and reduced scattering coefficients ((mu) a, (mu) s') were deduced from (mu) eff and Rd using a Monte-Carlo simulation.

pH responsive label-assisted click chemistry triggered sensitivity amplification for ultrasensitive electrochemical detection of carbohydrate antigen 24-2.

PubMed

Zheng, Yun; Zhao, Lihua; Ma, Zhanfang

2018-05-15

Sensitivity amplification strategy by implementing click chemistry in the construction of biosensing interface can efficiently improve the performance of immunosensor. Herein, we developed a sandwich-type amperometric immunosensor for ultrasensitive detection of carbohydrate antigen 24-2 (CA 242) based on pH responsive label-assisted click chemistry triggered sensitivity amplification strategy. The sensitivity of amperometric immunosensor relies on the current response differences (ΔI) caused by per unit concentration target analyte. The pH responsive Cu 2+ -loaded polydopamine (CuPDA) particles conjugated with detection antibodies were employed as labels, which can release Cu(II) ions by regulating pH. In the presence of ascorbic acid (reductant), Cu(II) ions were reduced to Cu(I) ions. Azide-functionalized double-stranded DNA (dsDNA) as signal enhancer was immobilized on the substrate through Cu + -catalyzed azide/alkyne cycloaddition reaction. With the help of the click reaction, the ΔI caused by target was elevated prominently, resulting in sensitivity amplification of the immunosensor. Under optimal condition, the proposed immunosensor exhibited excellent performance with linear range from 0.0001 to 100 U mL -1 and ultralow detection limit of 20.74 μU mL -1 . This work successfully combines click chemistry with pH-responsive labels in sandwich-type amperometric immunosensor, providing a promising sensitivity amplification strategy to construct immunosensing platform for analysis of other tumor marker. Copyright © 2018 Elsevier B.V. All rights reserved.

Chemical proteomics approaches for identifying the cellular targets of natural products.

PubMed

Wright, M H; Sieber, S A

2016-05-04

Covering: 2010 up to 2016Deconvoluting the mode of action of natural products and drugs remains one of the biggest challenges in chemistry and biology today. Chemical proteomics is a growing area of chemical biology that seeks to design small molecule probes to understand protein function. In the context of natural products, chemical proteomics can be used to identify the protein binding partners or targets of small molecules in live cells. Here, we highlight recent examples of chemical probes based on natural products and their application for target identification. The review focuses on probes that can be covalently linked to their target proteins (either via intrinsic chemical reactivity or via the introduction of photocrosslinkers), and can be applied "in situ" - in living systems rather than cell lysates. We also focus here on strategies that employ a click reaction, the copper-catalysed azide-alkyne cycloaddition reaction (CuAAC), to allow minimal functionalisation of natural product scaffolds with an alkyne or azide tag. We also discuss 'competitive mode' approaches that screen for natural products that compete with a well-characterised chemical probe for binding to a particular set of protein targets. Fuelled by advances in mass spectrometry instrumentation and bioinformatics, many modern strategies are now embracing quantitative proteomics to help define the true interacting partners of probes, and we highlight the opportunities this rapidly evolving technology provides in chemical proteomics. Finally, some of the limitations and challenges of chemical proteomics approaches are discussed.

Intracellular in situ labeling of TiO2 nanoparticles for fluorescence microscopy detection.

PubMed

Brown, Koshonna; Thurn, Ted; Xin, Lun; Liu, William; Bazak, Remon; Chen, Si; Lai, Barry; Vogt, Stefan; Jacobsen, Chris; Paunesku, Tatjana; Woloschak, Gayle E

2018-01-01

Titanium dioxide (TiO 2 ) nanoparticles are produced for many different purposes, including development of therapeutic and diagnostic nanoparticles for cancer detection and treatment, drug delivery, induction of DNA double-strand breaks, and imaging of specific cells and subcellular structures. Currently, the use of optical microscopy, an imaging technique most accessible to biology and medical pathology, to detect TiO 2 nanoparticles in cells and tissues ex vivo is limited with low detection limits, while more sensitive imaging methods (transmission electron microscopy, X-ray fluorescence microscopy, etc.) have low throughput and technical and operational complications. Herein, we describe two in situ post-treatment labeling approaches to stain TiO 2 nanoparticles taken up by the cells. The first approach utilizes fluorescent biotin and fluorescent streptavidin to label the nanoparticles before and after cellular uptake; the second approach is based on the copper-catalyzed azide-alkyne cycloaddition, the so-called Click chemistry, for labeling and detection of azide-conjugated TiO 2 nanoparticles with alkyne-conjugated fluorescent dyes such as Alexa Fluor 488. To confirm that optical fluorescence signals of these nanoparticles match the distribution of the Ti element, we used synchrotron X-ray fluorescence microscopy (XFM) at the Advanced Photon Source at Argonne National Laboratory. Titanium-specific XFM showed excellent overlap with the location of optical fluorescence detected by confocal microscopy. Therefore, future experiments with TiO 2 nanoparticles may safely rely on confocal microscopy after in situ nanoparticle labeling using approaches described here.

Reticulation des fibres lignocellulosiques

NASA Astrophysics Data System (ADS)

Landrevy, Christel

Pour faire face à la crise économique la conception de papier à valeur ajoutée est développée par les industries papetières. Le but de se projet est l'amélioration des techniques actuelles de réticulation des fibres lignocellulosiques de la pâte à papier visant à produire un papier plus résistant. En effet, lors des réactions de réticulation traditionnelles, de nombreuses liaisons intra-fibres se forment ce qui affecte négativement l'amélioration anticipée des propriétés physiques du papier ou du matériau produit. Pour éviter la formation de ces liaisons intra-fibres, un greffage sur les fibres de groupements ne pouvant pas réagir entre eux est nécessaire. La réticulation des fibres par une réaction de « click chemistry » appelée cycloaddition de Huisgen entre un azide et un alcyne vrai, catalysée par du cuivre (CuAAC) a été l'une des solutions trouvée pour remédier à ce problème. De plus, une adaptation de cette réaction en milieux aqueux pourrait favoriser son utilisation en milieu industriel. L'étude que nous désirons entreprendre lors de ce projet vise à optimiser la réaction de CuAAC et les réactions intermédiaires (propargylation, tosylation et azidation) sur la pâte kraft, en milieu aqueux. Pour cela, les réactions ont été adaptées en milieu aqueux sur la cellulose microcristalline afin de vérifier sa faisabilité, puis transférée à la pâte kraft et l'influence de différents paramètres comme le temps de réaction ou la quantité de réactifs utilisée a été étudiée. Dans un second temps, une étude des différentes propriétés conférées au papier par les réactions a été réalisée à partir d'une série de tests papetiers optiques et physiques. Mots Clés Click chemistry, Huisgen, CuAAC, propargylation, tosylation, azidation, cellulose, pâte kraft, milieu aqueux, papier.

Bifunctional Catalysts for CO2 Reduction

DTIC Science & Technology

2014-09-30

hexane soluble material was crystallized at –35 ºC permitting characterization by X-ray diffraction to identify [(tbsL) Co3 (µ 3- N)]NBu4 as the product...of the trinuclear core and make atom and group-transfer processes even more facile. To probe this we investigated the reactivity of (tbsL) Co3 (py...Reaction of (tbsL) Co3 (py) with with Bu4N[N3] yields the azide adduct Bu4N[( tbsL) Co3 (µ 3-N3)] which features a C3-symmetric, paramagnetically shifted

Design and synthesis via click chemistry of 8,9-anhydroerythromycin A 6,9-hemiketal analogues with anti-MRSA and -VRE activity.

PubMed

Sugawara, Akihiro; Sunazuka, Toshiaki; Hirose, Tomoyasu; Nagai, Kenichiro; Yamaguchi, Yukie; Hanaki, Hideaki; Sharpless, K Barry; Omura, Satoshi

2007-11-15

An erythromycin analogue, 11,12-di-O-iso-butyryl-8,9-anhydroerythromycin A 6,9-hemiketal (1b), was found to be a potential anti-MRSA and anti-VRE agent. The use of copper catalyzed azide-acetylene cycloaddition, and click chemistry, readily provided 10 types of triazole analogues of 1b in good to nearly quantitative yield. Among the library, 5b exhibited activity against MRSA and VRE bacterial strains, representing more than twice the potency of 1b.

Diazido­bis(5,5′-dimethyl-2,2′-bipyridyl-κ2 N,N′)nickel(II) monohydrate

PubMed Central

Phatchimkun, Jaturong; Kongsaeree, Palangpon; Suchaichit, Nattawut; Chaichit, Narongsak

2009-01-01

In the crystal structure of the title compound, [Ni(N3)2(C12H12N2)2]·H2O, the NiII atom is situated on a twofold axis and adopts a distorted octa­hedral geometry with the two 5,5′-dimethyl-2,2′-bipyridyl (dmbpy) and the two azide ligands in a cis arrangement. The water solvent mol­ecule is disordered over two positions in a 1:1 ratio. PMID:21577389

A Thermal Stability Test for Primary Explosive Stab Sensitizers: Study of the Thermal and Hydrolytic Stability of 2-Picryl-5-Nitrotetrazole,

DTIC Science & Technology

1984-02-01

have been described previously (2]. The actual batch used was designated Batch D and was identical to that referred to as Batch C in Reference [2...Tetrazene was type RD1357 prepared at Materials Research Laboratories. The batch used was designated Batch 10/83(A). Lead Azide was type RD1343 and was...Preparation of Experimental Detonators Eperimental detonators were prepared in mild steel tubes, 6 mm o.d., 3.2 mm i.d., length 6 mm, prepared from

Amphoteric Borylketenimines: Versatile Intermediates in the Synthesis of Borylated Heterocycles.

PubMed

Kaldas, Sherif J; O'Keefe, Kowan T V; Mendoza-Sanchez, Rodrigo; Yudin, Andrei K

2017-07-21

We report the first synthesis of amphoteric borylketenimines from ethynyl N-methyliminodiacetic acid (MIDA) boronate and sulfonyl azides via copper catalysis. In situ trapping of these intermediates with various nucleophiles provided access to novel borylated azetidimines, iminocoumarins, amides, iminooxetanes, and amidines. The described strategy based on borylketenimines offers high levels of chemo- and regioselectivity, enabling the synthesis of unprecedented borylated molecules. This work highlights the unexplored utility of borylketenimines in the synthesis of potentially bioactive molecules. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sequential Multicomponent Strategy for the Diastereoselective Synthesis of Densely Functionalized Spirooxindole-Fused Thiazolidines.

PubMed

Rainoldi, Giulia; Begnini, Fabio; de Munnik, Mariska; Lo Presti, Leonardo; Vande Velde, Christophe M L; Orru, Romano; Lesma, Giordano; Ruijter, Eelco; Silvani, Alessandra

2018-02-12

We developed two Ugi-type three-component reactions of spirooxindole-fused 3-thiazolines, isocyanides, and either carboxylic acids or trimethylsilyl azide, to give highly functionalized spirooxindole-fused thiazolidines. Two diverse libraries were generated using practical and robust procedures affording the products in typically good yields. The obtained thiazolidines proved to be suitable substrates for further transformations. Notably, both the Ugi-Joullié and the azido-Ugi reactions resulted highly diastereoselective, affording predominantly the trans-configured products, as confirmed by X-ray crystallographic analysis.

Test for Chemical Induction of Chromosome Aberrations in Cultured Chinese Hamster Ovary (CHO) Cells With and Without Metabolic Activation. Test Article: Dimethylamine-2-2ethyl azide (DMAZ)

DTIC Science & Technology

2008-07-26

cultures at each concentration level were treated for 3 hours in serum-free medium containing phenobarbital !B-naphthoflavone-induced rat liver S-9...Research Laboratories and it consisted of phenobarbital -S,6-Benzoflavone (phenobarbitallB-naphthoflavone) -induced rat liver homogenate (S-9 fraction...Content: 4. Inducing Agent: S. Storage Condition: 6. Expiration Date: Moltox 2147 31.0 mg/rnL Phenobarbital -S,6-Benzoflavone < -70°C April

Informal Conference on the Chemistry of Energetic Azides, Isocyanates, and Related Species Held in Denver, Colorado on 27-28th April 1989

DTIC Science & Technology

1990-02-16

radiation has a bent configuration. From the internal energy distributions in the CN fragment, a lower limit for the heat of formation of NCO, 40.7 kcal/mole...Physics, Ben-Gurion University of the Negev Beer-Sheva 84105, Israel Abstract The electronic excitation of Pb atoms in the gas phase, following the...and the calculations indicate that high concentrations of excited, effectively long-lived Pb states are maintained as a result of radiation -trapping

Ion Cloud Modeling

DTIC Science & Technology

1977-11-11

neutral collision time is discussed in Section 4.4. The chemical formulation for the barium thermite is based on the reaction of 2.5 moles of barium...per mole of cupric oxide according to the formula 2.5Ba + CuO - BaO + Cu + 1.5Ba. 23 In addition, 1.8% of the thermite weight was barium azide. 5 As a...constant value, tf . Generally at? 1 but if VD1 >> U 2 ,the value of atf * can be much less than 1 . In this case of rapid descent of the ion cloud, its

Mechanical Properties of Titanium and Aluminum Alloys at Cryogenic Temperatures

DTIC Science & Technology

1962-03-01

aluminum alloys. Table I is a tabulation of the chemical composition of the tita - nium alloys. The bar was 5/8 inch in diameter and the sheet 0.060 inch...Ti-6AI-4V Tensile azid yield strength data for both bar and sheet of this tita - nium alloy are shown in Figure A-3. Bar and sheet data show approxi...not recommended for low temperature applications. The remainder of the tita - nium alloys were tested from room temperature to -452 F. In general, Ti

Aromatic Chlorosulfonylation by Photoredox Catalysis.

PubMed

Májek, Michal; Neumeier, Michael; Jacobi von Wangelin, Axel

2017-01-10

Visible-light photoredox catalysis enables the efficient synthesis of arenesulfonyl chlorides from anilines. The new protocol involves the convenient in situ preparation of arenediazonium salts (from anilines) and the reactive gases SO 2 and HCl (from aqueous SOCl 2 ). The photocatalytic chlorosulfonylation operates at mild conditions (room temperature, acetonitrile/water) with low catalyst loading. Various functional groups are tolerated (e.g., halides, azides, nitro groups, CF 3 , SF 5 , esters, heteroarenes). Theoretical and experimental studies support a photoredox-catalysis mechanism. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mercuric 5-Nitrotetrazole, a Possible Replacement for Lead Azide in Australian Ordnance. Part 1. An Assessment of Preparation Methods

DTIC Science & Technology

1983-08-01

nitrotetrazole) (Cuen2 (NT)2 ) [7) A solution of sodium nitrite (26 g) and cupric sulfate pentahydrate (13.75 g) in water (75 ml) was placed in the 600 ml...pan and cooled to 50C. To this stirred solution was added a solution of 5-aminotetrazole monohydrate (12.9 g), cupric sulfate pentahydrate (1.0 g) and...stirring then a solution of cupric sulfate pentahydrate (5.25 q) and ethylenediamine (11.25 ml) in water (20 ml) was added. Stirring and heating were

International Symposium on Special Topics in Chemical Propulsion (8th): Advancements in Energetic Materials and Chemical Propulsion Held in Cape Town, South Africa on 2-6 November 2009

DTIC Science & Technology

2009-11-06

Hydrogen azide is well-known as an endothermic explosion gas for a long time, but there is a lack of understanding about the detailed kinetics of its...Martin, K.K. Kuo, R. Houim, and M. Degges Lidar Detection of Explosives Vapors Using Excimer Laser (Log #127) S. Bobrovnikov, E. Gorlov, G...Agents for High Energy Propellants (Log #190) B.M. Kosowski, J. Consaga, and A. Condo Formulation & Development of an Explosive that Allows

1,3-Dipolar Cycloadditions of Diazo Compounds in the Presence of Azides.

PubMed

Aronoff, Matthew R; Gold, Brian; Raines, Ronald T

2016-04-01

The diazo group has untapped utility in chemical biology. The tolerance of stabilized diazo groups to cellular metabolism is comparable to that of azido groups. However, chemoselectivity has been elusive, as both groups undergo 1,3-dipolar cycloadditions with strained alkynes. Removing strain and tuning dipolarophile electronics yields diazo group selective 1,3-dipolar cycloadditions that can be performed in the presence of an azido group. For example, diazoacetamide but not its azido congener react with dehydroalanine residues, as in the natural product nisin.

Guidance Document: Surface Soils Sampling for Munitions Residues in Military Live Fire Training Ranges: Canadian Protocol

DTIC Science & Technology

2012-12-01

NA Boron B 0.5 NA Cadmium Cd 0.3 22 Calcium Ca 4.0 NA Chromium Cr 0.5 87 Cobalt Co 0.5 300 Copper Cu 0.4 91 Iron Fe 0.6 NA Lead Pb 2.5 600...on their susceptibility to initiation. Primary explosives, which include lead azide, lead styphnate, and mercury fulminate, are highly susceptible...ballistic properties. The degradation of NC leads to substances which speed up the degradation process, or else an autocatalytic reaction. To counteract

Bioorthogonal Noncanonical Amino Acid Tagging (BONCAT) Enables Time-Resolved Analysis of Protein Synthesis in Native Plant Tissue1[OPEN

PubMed Central

Moradian, Annie

2017-01-01

Proteomic plasticity undergirds stress responses in plants, and understanding such responses requires accurate measurement of the extent to which proteins levels are adjusted to counter external stimuli. Here, we adapt bioorthogonal noncanonical amino acid tagging (BONCAT) to interrogate protein synthesis in vegetative Arabidopsis (Arabidopsis thaliana) seedlings. BONCAT relies on the translational incorporation of a noncanonical amino acid probe into cellular proteins. In this study, the probe is the Met surrogate azidohomoalanine (Aha), which carries a reactive azide moiety in its amino acid side chain. The azide handle in Aha can be selectively conjugated to dyes and functionalized beads to enable visualization and enrichment of newly synthesized proteins. We show that BONCAT is sensitive enough to detect Arabidopsis proteins synthesized within a 30-min interval defined by an Aha pulse and that the method can be used to detect proteins made under conditions of light stress, osmotic shock, salt stress, heat stress, and recovery from heat stress. We further establish that BONCAT can be coupled to tandem liquid chromatography-mass spectrometry to identify and quantify proteins synthesized during heat stress and recovery from heat stress. Our results are consistent with a model in which, upon the onset of heat stress, translation is rapidly reprogrammed to enhance the synthesis of stress mitigators and is again altered during recovery. All experiments were carried out with commercially available reagents, highlighting the accessibility of the BONCAT method to researchers interested in stress responses as well as translational and posttranslational regulation in plants. PMID:28104718

Labeling proteins on live mammalian cells using click chemistry.

PubMed

Nikić, Ivana; Kang, Jun Hee; Girona, Gemma Estrada; Aramburu, Iker Valle; Lemke, Edward A

2015-05-01

We describe a protocol for the rapid labeling of cell-surface proteins in living mammalian cells using click chemistry. The labeling method is based on strain-promoted alkyne-azide cycloaddition (SPAAC) and strain-promoted inverse-electron-demand Diels-Alder cycloaddition (SPIEDAC) reactions, in which noncanonical amino acids (ncAAs) bearing ring-strained alkynes or alkenes react, respectively, with dyes containing azide or tetrazine groups. To introduce ncAAs site specifically into a protein of interest (POI), we use genetic code expansion technology. The protocol can be described as comprising two steps. In the first step, an Amber stop codon is introduced--by site-directed mutagenesis--at the desired site on the gene encoding the POI. This plasmid is then transfected into mammalian cells, along with another plasmid that encodes an aminoacyl-tRNA synthetase/tRNA (RS/tRNA) pair that is orthogonal to the host's translational machinery. In the presence of the ncAA, the orthogonal RS/tRNA pair specifically suppresses the Amber codon by incorporating the ncAA into the polypeptide chain of the POI. In the second step, the expressed POI is labeled with a suitably reactive dye derivative that is directly supplied to the growth medium. We provide a detailed protocol for using commercially available ncAAs and dyes for labeling the insulin receptor, and we discuss the optimal surface-labeling conditions and the limitations of labeling living mammalian cells. The protocol involves an initial cloning step that can take 4-7 d, followed by the described transfections and labeling reaction steps, which can take 3-4 d.

Effect of vitamin E and selenium separately and in combination on biochemical, immunological and histological changes induced by sodium azide in male mice.

PubMed

El-Shenawy, Nahla S; AL-Harbi, Mohammad S; Hamza, Reham Z

2015-01-01

Sodium azide (SA) is used as an active ingredient to control a broad spectrum of soil borne pathogens including insects, weeds, nematodes, fungi, and bacteria. The purpose of this study was to evaluate the ameliorator property of vitamin E (Vit E) or/and selenium (Se) against SA-induced injury in male mice at the biochemical, immunological and histological levels. The mice were divided into nine groups (10/group). The first three groups were served as control, Vit E and Se while, the second three groups were treated with three different doses of SA. The last three groups were treated with high dose of SA with Vit E or Se or Vit E and Se and all animals were treated for a period of 30 days. Exposure to SA at the three doses to mice led to an alternation of liver and kidney functions, decrease the testosterone concentration, decreased IgG and IgM levels as well as the increasing the TNF-α. The effects of SA on the biochemical parameters of mice were dose-dependent. Administration of Se or/and Vit E to SA-treated mice attenuates the toxicity of this compound, objectified by biochemical and histological improvement of liver, kidney and testis. But, the alleviation is more pronounced with the both antioxidants. Thus, the synergistic effect of Se and Vit E is most powerful in reducing the toxicity induced by SA and improving the humoral immune response of mice. Copyright © 2014 Elsevier GmbH. All rights reserved.

Improving TCO-Conjugated Antibody Reactivity for Bioorthogonal Pretargeting

NASA Astrophysics Data System (ADS)

Chu, Tina Tingyi

Cancer remains a major cause of death because of its unpredictable progression. Utilizing bioorthogonal chemistry between trans-cyclooctene (TCO) and tetrazine to target imaging agents to tumors in two subsequent steps offers a more versatile platform for molecular imaging. This is accomplished by pretargeting TCO-modified primary antibody to cell surface biomarkers, followed by delivery of tetrazine-modified imaging probes. In previous work, it has been established that TCO-tetrazine chemistry can be applied to in vivo imaging, resulting in precise tumor detection. However, most TCO modifications on an antibody are not reactive because they are buried within hydrophobic domains. To expose and improve the reactivity, Rahim et al. incorporated a polyethylene glycol (PEG) linker through a two-step reaction with DBCO-azide, which successfully maintained 100% TCO functionality. In this project, various types of linkers were studied to improve the reactivity in a single step. Three primary types of linkers were studied: hydrophilic PEG chains, hydrophobic short linkers, and amphiphilic linkers. Our results show that PEG chain alone can only maintain 40% TCO reactivity. Unexpectedly, a short alkyl chain (valeric acid) provided superior results, with 60% TCO reactivity. Lengthening the alkyl chain did not improve results further. Finally, an amphiphilic linker containing valeric acid and PEG performed worse than either linker type alone, at ˜30% functionality. We conclude that our previous 100% functional TCO result obtained with the two-step coupling may have stemmed from generation of the DBCO/azide cycloaddition product. Future work will explore factors such as rigidity of linker structure, polarity, or charges.

Oligonucleotide Sensor Based on Selective Capture of Upconversion Nanoparticles Triggered by Target-Induced DNA Interstrand Ligand Reaction

PubMed Central

2017-01-01

We present a sensor that exploits the phenomenon of upconversion luminescence to detect the presence of specific sequences of small oligonucleotides such as miRNAs among others. The sensor is based on NaYF4:Yb,Er@SiO2 nanoparticles functionalized with ssDNA that contain azide groups on the 3′ ends. In the presence of a target sequence, interstrand ligation is possible via the click-reaction between one azide of the upconversion probe and a DBCO-ssDNA-biotin probe present in the solution. As a result of this specific and selective process, biotin is covalently attached to the surface of the upconversion nanoparticles. The presence of biotin on the surface of the nanoparticles allows their selective capture on a streptavidin-coated support, giving a luminescent signal proportional to the amount of target strands present in the test samples. With the aim of studying the analytical properties of the sensor, total RNA samples were extracted from healthy mosquitoes and were spiked-in with a specific target sequence at different concentrations. The result of these experiments revealed that the sensor was able to detect 10–17 moles per well (100 fM) of the target sequence in mixtures containing 100 ng of total RNA per well. A similar limit of detection was found for spiked human serum samples, demonstrating the suitability of the sensor for detecting specific sequences of small oligonucleotides under real conditions. In contrast, in the presence of noncomplementary sequences or sequences having mismatches, the luminescent signal was negligible or conspicuously reduced. PMID:28332400

Exploration Of `Click' Chemistry For Microelectronic Applications

NASA Astrophysics Data System (ADS)

Musa, Osama M.; Sridhar, Laxmisha M.

The ‘Click’ chemistry was explored for low temperature snap cure and for possible use as an adhesion promoter in electronic applications. Several azide and alkyne resins were synthesized and their curing potential was evaluated with a special emphasis on exploring Cu(I) catalyst effect. The preliminary curing study in the absence of catalysts showed a strong dependence of cure temperatures on the electronic nature of alkynes. The cure temperatures showed a tendency to increase with decreasing electronegativity of the substituent on alkynes. The capability of Cu(I) catalysts to accelerate the ‘Click’ chemistry was demonstrated for the first time in bulk phase. Using several Cu(I) catalysts, the cure temperatures could be lowered by as much as 40-100°C compared to the control, depending on the nature of catalyst and the catalyst loading. We discovered a novel synergistic effect between Cu(I) and silver filler in lowering the cure temperatures. Using this combination, lower cure temperatures could be obtained than using either alone. Among several resins screened, one resin system has shown promise for 80°C snap-cure in which the aforementioned synergistic effect is operative. Solution phase ‘Click’ chemistry was employed for the synthesis of a hybrid triazole-epoxy resin system. This system was found to cure without added amine curative. The triazole group here serves as a linker as well as an internal adhesion promoter. To address the incompatibility and volatility issues, which arose during evaluation, a controlled oligomerization method has been developed using controlled heating of azides and alkynes in solution phase.

Identification of an intracellular protein that specifically interacts with photoaffinity-labeled oncogenic p21 protein.

PubMed

Lee, G; Ronai, Z A; Pincus, M R; Brandt-Rauf, P W; Murphy, R B; Delohery, T M; Nishimura, S; Yamaizumi, Z; Weinstein, I B

1989-11-01

An oncogenic 21-kDa (p21) protein (Harvey RAS protein with Val-12) has been covalently modified with a functional reagent that contains a photoactivatable aromatic azide group. This modified p21 protein has been introduced quantitatively into NIH 3T3 cells using an erythrocyte-mediated fusion technique. The introduced p21 protein was capable of inducing enhanced pinocytosis and DNA synthesis in the recipient cells. To identify the putative intracellular protein(s) that specifically interact with the modified p21 protein, the cells were pulsed with [35S]methionine at selected times after fusion and then UV-irradiated to activate the azide group. The resulting nitrene covalently binds to amino acid residues in adjacent proteins, thus linking the p21 protein to these proteins. The cells were then lysed, and the lysate was immunoprecipitated with the anti-p21 monoclonal antibody Y13-259. The immunoprecipitate was analyzed by SDS/PAGE to identify p21-protein complexes. By using this technique, we found that three protein complexes of 51, 64, and 82 kDa were labeled specifically and reproducibly. The most prominent band is the 64-kDa protein complex that shows a time-dependent rise and fall, peaking within a 5-hr period after introduction of the p21 protein into the cells. These studies provide evidence that in vitro the p21 protein becomes associated with a protein whose mass is about 43 kDa. We suggest that the formation of this complex may play a role in mediating early events involved with cell transformation induced by RAS oncogenes.

Intracellular in situ labeling of TiO 2 nanoparticles for fluorescence microscopy detection

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

Brown, Koshonna; Thurn, Ted; Xin, Lun

Titanium dioxide (TiO 2) nanoparticles are produced for many different purposes, including development of therapeutic and diagnostic nanoparticles for cancer detection and treatment, drug delivery, induction of DNA double-strand breaks, and imaging of specific cells and subcellular structures. Currently, the use of optical microscopy, an imaging technique most accessible to biology and medical pathology, to detect TiO 2 nanoparticles in cells and tissues ex vivo is limited with low detection limits, while more sensitive imaging methods (transmission electron microscopy, X-ray fluorescence microscopy, etc.) have low throughput and technical and operational complications. In this paper, we describe two in situ posttreatmentmore » labeling approaches to stain TiO 2 nanoparticles taken up by the cells. The first approach utilizes fluorescent biotin and fluorescent streptavidin to label the nanoparticles before and after cellular uptake; the second approach is based on the copper-catalyzed azide-alkyne cycloaddition, the so-called Click chemistry, for labeling and detection of azide-conjugated TiO 2 nanoparticles with alkyneconjugated fluorescent dyes such as Alexa Fluor 488. To confirm that optical fluorescence signals of these nanoparticles match the distribution of the Ti element, we used synchrotron X-ray fluorescence microscopy (XFM) at the Advanced Photon Source at Argonne National Laboratory. Titanium-specific XFM showed excellent overlap with the location of optical fluorescence detected by confocal microscopy. Finally and therefore, future experiments with TiO 2 nanoparticles may safely rely on confocal microscopy after in situ nanoparticle labeling using approaches described here.« less

Click Chemistry and Radiochemistry: The First 10 Years.

PubMed

Meyer, Jan-Philip; Adumeau, Pierre; Lewis, Jason S; Zeglis, Brian M

2016-12-21

The advent of click chemistry has had a profound influence on almost all branches of chemical science. This is particularly true of radiochemistry and the synthesis of agents for positron emission tomography (PET), single photon emission computed tomography (SPECT), and targeted radiotherapy. The selectivity, ease, rapidity, and modularity of click ligations make them nearly ideally suited for the construction of radiotracers, a process that often involves working with biomolecules in aqueous conditions with inexorably decaying radioisotopes. In the following pages, our goal is to provide a broad overview of the first 10 years of research at the intersection of click chemistry and radiochemistry. The discussion will focus on four areas that we believe underscore the critical advantages provided by click chemistry: (i) the use of prosthetic groups for radiolabeling reactions, (ii) the creation of coordination scaffolds for radiometals, (iii) the site-specific radiolabeling of proteins and peptides, and (iv) the development of strategies for in vivo pretargeting. Particular emphasis will be placed on the four most prevalent click reactions-the Cu-catalyzed azide-alkyne cycloaddition (CuAAC), the strain-promoted azide-alkyne cycloaddition (SPAAC), the inverse electron demand Diels-Alder reaction (IEDDA), and the Staudinger ligation-although less well-known click ligations will be discussed as well. Ultimately, it is our hope that this review will not only serve to educate readers but will also act as a springboard, inspiring synthetic chemists and radiochemists alike to harness click chemistry in even more innovative and ambitious ways as we embark upon the second decade of this fruitful collaboration.

Photo-induced bleaching of sensory rhodopsin II (phoborhodopsin) from Halobacterium salinarum by hydroxylamine: identification of the responsible intermediates.

PubMed

Tamogami, Jun; Kikukawa, Takashi; Ikeda, Yoichi; Demura, Makoto; Nara, Toshifumi; Kamo, Naoki

2012-01-05

Sensory rhodopsin II from Halobacterium salinarum (HsSRII) is a retinal protein in which retinal binds to a specific lysine residue through a Schiff base. Here, we investigated the photobleaching of HsSRII in the presence of hydroxylamine. For identification of intermediate(s) attacked by hydroxylamine, we employed the flash-induced bleaching method. In order to change the concentration of intermediates, such as M- and O-intermediates, experiments were performed under varying flashlight intensities and concentrations of azide that accelerated only the M-decay. We found the proportional relationship between the bleaching rate and area under the concentration-time curve of M, indicating a preferential attack of hydroxylamine on M. Since hydroxylamine is a water-soluble reagent, we hypothesize that for M, hydrophilicity or water-accessibility increases specifically in the moiety of Schiff base. Thus, hydroxylamine bleaching rates may be an indication of conformational changes near the Schiff base. We also considered the possibility that azide may induce a small conformational change around the Schiff base. We compared the hydroxylamine susceptibility between HsSRII and NpSRII (SRII from Natronomonas pharaonis) and found that the M of HsSRII is about three times more susceptible than that of the stable NpSRII. In addition, long illumination to HsSRII easily produced M-like photoproduct, P370. We thus infer that the instability of HsSRII under illumination may be related to this increase of hydrophilicity at M and P370. Copyright © 2011 Elsevier B.V. All rights reserved.

Acidification of rabbit corneal endothelium during contact lens wear in vitro.

PubMed

Giasson, C; Bonanno, J A

1995-04-01

Contact lens wear causes significant epithelial and stromal acidosis. In this study, we tested whether lens wear can cause endothelial acidosis as well. Rabbit corneas were isolated and perfused in vitro. The endothelial intracellular pH (pHi) was measured with a pH sensitive fluorescent probe (BCECF). Three conditions were examined: 1) Polymethylmethacrylate (PMMA) and rigid gas-permeable (RGP) contact lens wear using a range of oxygen transmissibility (Dk/L) from 0 to 121, 2) epithelial hypoxia produced by exposure to oligomycin/sodium azide solution or epithelial perfusion with 100% N2 equilibrated Ringer's solution, and 3) epithelial exposure to Ringer's equilibrated with 5% CO2, balance air. PMMA and RGP contact lens wear acidified endothelial cells by 0.23 +/- 0.01 (n = 23) and 0.11 +/- 0.01 pH units (n = 23), respectively, within twenty min of lens insertion. Epithelial hypoxia, induced by sodium azide and oligomycin, reversibly acidified the endothelium by 0.04 +/- 0.01 pH units (n = 4). However, epithelial hypoxia induced by perfusion with 100% N2 equilibrated Ringer's did not have a significant effect on endothelial pHi. Introduction of 5% CO2 to the epithelium, acidified the endothelium by 0.15 +/- 0.02 pH units (n = 7) within 10 min. We conclude that contact lens wear can significantly acidify corneal endothelial cells. The endothelial pHi change is caused almost exclusively by a build up of CO2 behind the lens; hypoxia having very little contribution. As expected, RGP contact lenses induced less endothelial acidosis than PMMA controls.

Synthesis of linear and cyclic peptide-PEG-lipids for stabilization and targeting of cationic liposome-DNA complexes.

PubMed

Ewert, Kai K; Kotamraju, Venkata Ramana; Majzoub, Ramsey N; Steffes, Victoria M; Wonder, Emily A; Teesalu, Tambet; Ruoslahti, Erkki; Safinya, Cyrus R

2016-03-15

Because nucleic acids (NAs) have immense potential value as therapeutics, the development of safe and effective synthetic NA vectors continues to attract much attention. In vivo applications of NA vectors require stabilized, nanometer-scale particles, but the commonly used approaches of steric stabilization with a polymer coat (e.g., PEGylation; PEG=poly(ethylene glycol)) interfere with attachment to cells, uptake, and endosomal escape. Conjugation of peptides to PEG-lipids can improve cell attachment and uptake for cationic liposome-DNA (CL-DNA) complexes. We present several synthetic approaches to peptide-PEG-lipids and discuss their merits and drawbacks. A lipid-PEG-amine building block served as the common key intermediate in all synthetic routes. Assembling the entire peptide-PEG-lipid by manual solid phase peptide synthesis (employing a lipid-PEG-carboxylic acid) allowed gram-scale synthesis but is mostly applicable to linear peptides connected via their N-terminus. Conjugation via thiol-maleimide or strain-promoted (copper-free) azide-alkyne cycloaddition chemistry is highly amenable to on-demand preparation of peptide-PEG-lipids, and the appropriate PEG-lipid precursors are available in a single chemical step from the lipid-PEG-amine building block. Azide-alkyne cycloaddition is especially suitable for disulfide-bridged peptides such as iRGD (cyclic CRGDKGPDC). Added at 10 mol% of a cationic/neutral lipid mixture, the peptide-PEG-lipids stabilize the size of CL-DNA complexes. They also affect cell attachment and uptake of nanoparticles in a peptide-dependent manner, thereby providing a platform for preparing stabilized, affinity-targeted CL-DNA nanoparticles. Copyright © 2016 Elsevier Ltd. All rights reserved.

Intracellular in situ labeling of TiO 2 nanoparticles for fluorescence microscopy detection

DOE PAGES

Brown, Koshonna; Thurn, Ted; Xin, Lun; ...

2017-07-19

Titanium dioxide (TiO 2) nanoparticles are produced for many different purposes, including development of therapeutic and diagnostic nanoparticles for cancer detection and treatment, drug delivery, induction of DNA double-strand breaks, and imaging of specific cells and subcellular structures. Currently, the use of optical microscopy, an imaging technique most accessible to biology and medical pathology, to detect TiO 2 nanoparticles in cells and tissues ex vivo is limited with low detection limits, while more sensitive imaging methods (transmission electron microscopy, X-ray fluorescence microscopy, etc.) have low throughput and technical and operational complications. In this paper, we describe two in situ posttreatmentmore » labeling approaches to stain TiO 2 nanoparticles taken up by the cells. The first approach utilizes fluorescent biotin and fluorescent streptavidin to label the nanoparticles before and after cellular uptake; the second approach is based on the copper-catalyzed azide-alkyne cycloaddition, the so-called Click chemistry, for labeling and detection of azide-conjugated TiO 2 nanoparticles with alkyneconjugated fluorescent dyes such as Alexa Fluor 488. To confirm that optical fluorescence signals of these nanoparticles match the distribution of the Ti element, we used synchrotron X-ray fluorescence microscopy (XFM) at the Advanced Photon Source at Argonne National Laboratory. Titanium-specific XFM showed excellent overlap with the location of optical fluorescence detected by confocal microscopy. Finally and therefore, future experiments with TiO 2 nanoparticles may safely rely on confocal microscopy after in situ nanoparticle labeling using approaches described here.« less

Green primaries: Environmentally friendly energetic complexes

PubMed Central

Huynh, My Hang V.; Hiskey, Michael A.; Meyer, Thomas J.; Wetzler, Modi

2006-01-01

Primary explosives are used in small quantities to generate a detonation wave when subjected to a flame, heat, impact, electric spark, or friction. Detonation of the primary explosive initiates the secondary booster or main-charge explosive or propellant. Long-term use of lead azide and lead styphnate as primary explosives has resulted in lead contamination at artillery and firing ranges and become a major health hazard and environmental problem for both military and civilian personnel. Devices using lead primary explosives are manufactured by the tens of millions every year in the United States from primers for bullets to detonators for mining. Although substantial synthetic efforts have long been focused on the search for greener primary explosives, this unresolved problem has become a “holy grail” of energetic materials research. Existing candidates suffer from instability or excessive sensitivity, or they possess toxic metals or perchlorate. We report here four previously undescribed green primary explosives based on complex metal dianions and environmentally benign cations, (cat)2[MII(NT)4(H2O)2] (where cat is NH4+ or Na+, M is Fe2+ or Cu2+, and NT− is 5-nitrotetrazolato-N2). They are safer to prepare, handle, and transport than lead compounds, have comparable initiation efficiencies to lead azide, and offer rapid reliable detonation comparable with lead styphnate. Remarkably, they possess all current requirements for green primary explosives and are suitable to replace lead primary explosives in detonators. More importantly, they can be synthesized more safely, do not pose health risks to personnel, and cause much less pollution to the environment. PMID:16567623