Property Predictions for Nitrate Salts with Nitroxy-Functionalized Cations

DTIC Science & Technology

2011-05-01

Imidazole, Indazole, and Benzimidazole . Journal of Chemical Thermodynamics, 1987, 19, 985–992. Jocelyn, P. C. Some Derivatives of 2-2...Enthalpies of Formation of Pyrazole, Imidazole, Indazole, and Benzimidazole . Journal of Chemical Thermodynamics 1987, 19, 985–992. pA B3LYP/6-31+G(d,p

Comparative pharmacodynamic analysis of imidazoline compounds using rat model of ocular mydriasis with a test of quantitative structure-activity relationships.

PubMed

Raczak-Gutknecht, Joanna; Nasal, Antoni; Frąckowiak, Teresa; Kornicka, Anita; Sączewski, Franciszek; Wawrzyniak, Renata; Kubik, Łukasz; Kaliszan, Roman

2017-09-10

Imidazol(in)e derivatives, having the chemical structure similar to clonidine, exert diverse pharmacological activities connected with their interactions with alpha2-adrenergic receptors, e.g. hypotension, bradycardia, sedation as well as antinociceptive, anxiolytic, antiarrhythmic, muscle relaxant and mydriatic effects. The mechanism of pupillary dilation observed after systemic administration of imidazol(in)es to rats, mice and cats depends on the stimulation of postsynaptic alpha2-adrenoceptors within the brain. It was proved that the central nervous system (CNS)-localized I1-imidazoline receptors are not engaged in those effects. It appeared interesting to analyze the CNS-mediated pharmacodynamics of imidazole(in)e agents in terms of their chromatographic and calculation chemistry-derived parameters. In the present study a systematic determination and comparative pharmacometric analysis of mydriatic effects in rats were performed on a series of 20 imidazol(in)e agents, composed of the well-known drugs and of the substances used in experimental pharmacology. The eye pupil dilatory activities of the compounds were assessed in anesthetized Wistar rats according to the established Koss method. Among twenty imidazol(in)e derivatives studied, 18 produced diverse dose-dependent mydriatic effects. In the quantitative structure-activity relationships (QSAR) analysis, the pharmacological data (half maximum mydriatic effect - ED 50 in μmol/kg) were considered along with the structural parameters of the agents from molecular modeling. The theoretically calculated lipophilicity parameters, CLOGP, of imidazol(in)es, as well as their lipophilicity parameters from HPLC, logk w , were also considered. The attempts to derive statistically significant QSAR equations for a full series of the agents under study were unsuccessful. However, for a subgroup of eight apparently structurally related imidazol(in)es a significant relationship between log(1/ED 50 ) and logk w values was obtained. The lack of "predictive" QSAR for the whole series of the structurally diverse agents is probably due to a complex mechanism of the ligand-alpha2-adrenergic receptor interactions, which are predominantly of a highly structurally specific polar nature. Such interactions are difficult to quantify with the established chemical structural descriptors, contrary to the less specific, molecular bulkiness-related interactions. Copyright © 2017 Elsevier B.V. All rights reserved.

New Imidazole-based High Nitrogen Energetic Materials

NASA Astrophysics Data System (ADS)

Windler, G. Kenneth; Leonard, Philip; Schulze, Maxwell; Hartline, Ernest

2017-06-01

Energetic materials derive their power from energy release, usually in the form of gaseous products. The type and quantity of these products contribute to performance and detonation parameters. In particular, high-nitrogen materials produce large quantities of elemental nitrogen, and can be tuned via molecular structure for suitability as propellants (gas generators) or explosives. In this work, the five-membered nitrogen heterocycle imidazole is used as a substrate for a variety of high-nitrogen materials. Substitution of the imidazole ring directly with nitro-, azido-, diazo-, and tetrazole moieties allows for tunable properties of the resultant energetic material. Properties can be further tailored by salt formation at the acidic proton(s) on the molecules. The various combinations of these derivatives are presented, along with the substitution effects on physical, chemical, and explosive properties.

1-[(3-Aryloxy-3-aryl)propyl]-1H-imidazoles, new imidazoles with potent activity against Candida albicans and dermatophytes. Synthesis, structure-activity relationship, and molecular modeling studies.

PubMed

La Regina, Giuseppe; D'Auria, Felicia Diodata; Tafi, Andrea; Piscitelli, Francesco; Olla, Stefania; Caporuscio, Fabiana; Nencioni, Lucia; Cirilli, Roberto; La Torre, Francesco; De Melo, Nadja Rodrigues; Kelly, Steven L; Lamb, David C; Artico, Marino; Botta, Maurizio; Palamara, Anna Teresa; Silvestri, Romano

2008-07-10

New 1-[(3-aryloxy-3-aryl)propyl]-1 H-imidazoles were synthesized and evaluated against Candida albicans and dermatophytes in order to develop structure-activity relationships (SARs). Against C. albicans the new imidazoles showed minimal inhibitory concentrations (MICs) comparable to those of ketoconazole, miconazole, and econazole, and were more potent than fluconazole. Several derivatives ( 10, 12, 14, 18- 20, 24, 28, 29, 30, and 34) turned out to be potent inhibitors of C. albicans strains resistant to fluconazole, with MIC values less than 10 microg/mL. Against dermatophytes strains, compounds 20, 25, and 33 (MIC

Visible-light-driven Photocatalytic N-arylation of Imidazole Derivatives and Arylboronic Acids on Cu/graphene catalyst

PubMed Central

Cui, Yan-Li; Guo, Xiao-Ning; Wang, Ying-Yong; Guo, Xiang-Yun

2015-01-01

N-aryl imidazoles play an important role as structural and functional units in many natural products and biologically active compounds. Herein, we report a photocatalytic route for the C-N cross-coupling reactions over a Cu/graphene catalyst, which can effectively catalyze N-arylation of imidazole and phenylboronic acid, and achieve a turnover frequency of 25.4 h−1 at 25 oC and the irradiation of visible light. The enhanced catalytic activity of the Cu/graphene under the light irradiation results from the localized surface plasmon resonance of copper nanoparticles. The Cu/graphene photocatalyst has a general applicability for photocatalytic C-N, C-O and C-S cross-coupling of arylboronic acids with imidazoles, phenols and thiophenols. This study provides a green photocatalytic route for the production of N-aryl imidazoles. PMID:26189944

Antimycobacterial activity of new N(1)-[1-[1-aryl-3-[4-(1H-imidazol-1-yl)phenyl]-3-oxo]propyl]-pyridine-2-carboxamidrazone derivatives.

PubMed

Zampieri, Daniele; Mamolo, Maria Grazia; Vio, Luciano; Romano, Maurizio; Skoko, Nataša; Baralle, Marco; Pau, Valentina; De Logu, Alessandro

2016-07-15

N(1)-[1-[1-aryl-3-[4-(1H-imidazol-1-yl)phenyl]-3-oxo]propyl]-pyridine-2-carboxamidrazone derivatives were design, synthesized and tested for their in vitro antimycobacterial activity. The new compounds showed a moderate antimycobacterial activity against the tested strain of Mycobacterium tuberculosis H37Ra and a significant antimycobacterial activity against several mycobacteria other than tuberculosis strains. Copyright © 2016 Elsevier Ltd. All rights reserved.

Halogenated boron-dipyrromethenes: synthesis, properties and applications.

PubMed

Lakshmi, Vellanki; Rao, Malakalapalli Rajeswara; Ravikanth, Mangalampalli

2015-03-07

Boron-dipyrromethene dyes (BODIPYs) containing halogens at pyrrole carbons are very useful synthons for the synthesis of a variety of BOIDPYs for a wide range of applications. Among the functional groups, halogens are the functional groups which can be regiospecifically introduced at any desired pyrrole carbon of the BODIPY framework by adopting appropriate synthetic strategies. The halogenated BODIPYs can undergo facile nucleophilic substitution reactions to prepare several interesting BODIPY based compounds. This review describes the synthesis, properties and potential applications of halogenated BODIPYs containing one to six halogens at the pyrrole carbons of the BODIPY core as well as properties and applications of some of the substituted BODIPYs derived from halogenated BODIPYs.

Imidazoles and benzimidazoles as tubulin-modulators for anti-cancer therapy.

PubMed

Torres, Fernando C; García-Rubiño, M Eugenia; Lozano-López, César; Kawano, Daniel F; Eifler-Lima, Vera L; von Poser, Gilsane L; Campos, Joaquín M

2015-01-01

Imidazoles and benzimidazoles are privileged heterocyclic bioactive compounds used with success in the clinical practice of innumerous diseases. Although there are many advancements in cancer therapy, microtubules remain as one of the few macromolecular targets validated for planning active anti-cancer compounds, and the design of drugs that modulate microtubule dynamics in unknown sites of tubulin is one of the goals of the medicinal chemistry. The discussion of the role of new and commercially available imidazole and benzimidazole derivatives as tubulin modulators is scattered throughout scientific literature, and indicates that these compounds have a tubulin modulation mechanism different from that of tubulin modulators clinically available, such as paclitaxel, docetaxel, vincristine and vinblastine. In fact, recent literature indicates that these derivatives inhibit microtubule formation binding to the colchicine site, present good pharmacokinetic properties and are capable of overcoming multidrug resistance in many cell lines. The understanding of the mechanisms involved in the imidazoles/benzimidazoles modulation of microtubule dynamics is very important to develop new strategies to overcome the resistance to anti-cancer drugs and to discover new biomarkers and targets for cancer chemotherapy.

Development of Highly Fluorescent Materials Based on Thiophenylimidazole Dyes

NASA Technical Reports Server (NTRS)

Santos, Javier; Bu, Xiu R.; Mintz, Eric A.; Meador, Michael A. (Technical Monitor)

2000-01-01

Organic fluorescent materials are expected to find many potential applications in optical devices and photo-functionalized materials. Although many investigations have been focused on heterocyclic compounds such as coumarins, bipyridines, rhodamines, and pyrrole derivatives, little is known for fluorescent imidazole materials. We discovered that one particular class of imidazole derivatives is highly fluorescent. A series of monomeric and polymeric based fluorescent dyes were prepared containing a thiophene unit at the second position of the imidazole ring. Dependence of fluorescence efficiency on parameters such as solvent polarity and substituent groups has been investigated. It was found that a formyl group at the 2-position of the thiophene ring dramatically enhance fluorescence properties. Ion recognition probes indicated their potential as sensor materials. These fluorophores have flexibility for introduction of versatile substituent groups that could improve the fluorescence efficiency and sensor properties.

Fine tuning of graphene properties by modification with aryl halogens

NASA Astrophysics Data System (ADS)

Bouša, D.; Pumera, M.; Sedmidubský, D.; Šturala, J.; Luxa, J.; Mazánek, V.; Sofer, Z.

2016-01-01

Graphene and its derivatives belong to one of the most intensively studied materials. The radical reaction using halogen derivatives of arene-diazonium salts can be used for effective control of graphene's electronic properties. In our work we investigated the influence of halogen atoms (fluorine, chlorine, bromine and iodine) as well as their position on the benzene ring towards the electronic and electrochemical properties of modified graphenes. The electronegativity as well as the position of the halogen atoms on the benzene ring has crucial influence on graphene's properties due to the inductive and mesomeric effects. The results of resistivity measurement are in good agreement with the theoretical calculations of electron density within chemically modified graphene sheets. Such simple chemical modifications of graphene can be used for controllable and scalable synthesis of graphene with tunable transport properties.Graphene and its derivatives belong to one of the most intensively studied materials. The radical reaction using halogen derivatives of arene-diazonium salts can be used for effective control of graphene's electronic properties. In our work we investigated the influence of halogen atoms (fluorine, chlorine, bromine and iodine) as well as their position on the benzene ring towards the electronic and electrochemical properties of modified graphenes. The electronegativity as well as the position of the halogen atoms on the benzene ring has crucial influence on graphene's properties due to the inductive and mesomeric effects. The results of resistivity measurement are in good agreement with the theoretical calculations of electron density within chemically modified graphene sheets. Such simple chemical modifications of graphene can be used for controllable and scalable synthesis of graphene with tunable transport properties. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06295k

Effect of halogenated substituents on the metabolism and estrogenic effects of the equine estrogen, equilenin.

PubMed

Liu, Xuemei; Zhang, Fagen; Liu, Hong; Burdette, Joanna E; Li, Yan; Overk, Cassia R; Pisha, Emily; Yao, Jiaqin; van Breemen, Richard B; Swanson, Steven M; Bolton, Judy L

2003-06-01

Estrogen replacement therapy has been correlated with an increased risk for developing breast and endometrial cancers. One potential mechanism of estrogen carcinogenesis involves metabolism of estrogens to 2- and 4-hydroxylated catechols, which are further oxidized to electrophilic/redox active o-quinones that have the potential to both initiate and promote the carcinogenic process. Previously, we showed that the equine estrogens, equilin and equilenin, which are major components of the estrogen replacement formulation Premarin (Wyeth-Ayerst), are primarily metabolized to the catechol, 4-hydroxyequilenin. This catechol was found to autoxidize to an o-quinone causing oxidation and alkylation of DNA in vitro and in vivo. To block catechol formation from equilenin, 4-halogenated equilenin derivatives were synthesized. These derivatives were tested for their ability to bind to the estrogen receptor, induce estrogen sensitive genes, and their potential to form catechol metabolites. We found that the 4-fluoro derivatives were more estrogenic than the 4-chloro and 4-bromo derivatives as demonstrated by a higher binding affinity for estrogen receptors alpha and beta, an enhanced induction of alkaline phosphatase activity in Ishikawa cells, pS2 expression in S30 cells, and PR expression in Ishikawa cells. Incubation of these compounds with tyrosinase in the presence of GSH showed that the halogenated equilenin compounds formed less catechol GSH conjugates than the parent compounds, equilenin and 17beta-hydroxyequilenin. In addition, these halogenated compounds showed less cytotoxicity in the presence of tyrosinase than the parent compounds in S30 cells. Also, as stated above, the 4-fluoro derivatives showed similar estrogenic effects as compared with parent compounds; however, they were less toxic in S30 cells as compared to equilenin and 17beta-equilenin. Because 17beta-hydroxy-4-halogenated equilenin derivatives showed higher estrogenic effects than the halogenated equilenin derivatives in vitro, we studied the relative ability of the 17beta-hydroxy-4-halogenated equilenin derivatives to induce estrogenic effects in the ovariectomized rat model. The 4-fluoro derivative showed higher activity than 4-chloro and 4-bromo derivatives as demonstrated by inducing higher vaginal cellular differentiation, uterine growth, and mammary gland branching. However, 17beta-hydroxy-4-fluoroequilenin showed a lower estrogenic activity than 17beta-hydroxyequilenin and estradiol, which could be due to alternative pharmacokinetic properties for these compounds. These data suggest that the 4-fluoroequilenin derivatives have promise as alternatives to traditional estrogen replacement therapy due to their similar estrogenic properties with less overall toxicity.

Syntheses of halogen derivatives of L-tryptophan, L-tyrosine and L-phenylalanine labeled with hydrogen isotopes.

PubMed

Pająk, Małgorzata; Pałka, Katarzyna; Winnicka, Elżbieta; Kańska, Marianna

2016-01-01

Halogenated, labeled with tritium and doubly with deuterium and tritium, derivatives of L-tryptophan, i.e. 5'-bromo-[2-(3)H]-, 5'-bromo-[2-(2)H/(3)H]-, 5'-fluoro-[2-(3)H]-5'-fluoro-[2-(2)H/(3)H]-, 6'-fluoro-[2-(3)H]-, 6'-fluoro-[2-(2)H/(3)H]-L-tryptophan, as well as, L-tyrosine, i.e. 3'-fluoro-[2-(3)H]-, 3'-fluoro-[2-(2)H/(3)H]-, 3'-chloro-[2-(3)H]-, and 3'-chloro-[2-(2)H/(3)H]-L-tyrosine, and also L-phenylalanine, i.e. 2'-fluoro-[(3S)-(3)H]-, 2'-fluoro-[(3S)-(2)H/(3) H]-, 2'-chloro-[(3S)-(3)H]-, 2'-chloro-[(3S)-(2)H/(3)H]-, 4'-chloro-[(3S)-(3)H]-, and 4'-chloro-[(3S)-(2)H/(3)H]-L-phenylalanine were synthesized using enzymatic methods. Isotopomers of L-tryptophan were synthesized by coupling of halogenated indoles with S-methyl-L-cysteine carried out in deuteriated or tritiated incubation media. Labeled halogenated derivatives of L-tyrosine were obtained by the enzymatically supported exchange between halogenated L-tyrosine and isotopic water. Labeled halogenated isotopologues of L-Phe were synthesized by the enzymatic addition of ammonia to halogenated cinnamic acid. As a source of hydrogen tritiated water (HTO) and heavy water (D2O) with addition of HTO were used. Copyright © 2015 John Wiley & Sons, Ltd.

Nanomolar Inhibitors of Glycogen Phosphorylase Based on β-d-Glucosaminyl Heterocycles: A Combined Synthetic, Enzyme Kinetic, and Protein Crystallography Study.

PubMed

Bokor, Éva; Kyriakis, Efthimios; Solovou, Theodora G A; Koppány, Csenge; Kantsadi, Anastassia L; Szabó, Katalin E; Szakács, Andrea; Stravodimos, George A; Docsa, Tibor; Skamnaki, Vassiliki T; Zographos, Spyros E; Gergely, Pál; Leonidas, Demetres D; Somsák, László

2017-11-22

Aryl substituted 1-(β-d-glucosaminyl)-1,2,3-triazoles as well as C-β-d-glucosaminyl 1,2,4-triazoles and imidazoles were synthesized and tested as inhibitors against muscle and liver isoforms of glycogen phosphorylase (GP). While the N-β-d-glucosaminyl 1,2,3-triazoles showed weak or no inhibition, the C-β-d-glucosaminyl derivatives had potent activity, and the best inhibitor was the 2-(β-d-glucosaminyl)-4(5)-(2-naphthyl)-imidazole with a K i value of 143 nM against human liver GPa. An X-ray crystallography study of the rabbit muscle GPb inhibitor complexes revealed structural features of the strong binding and offered an explanation for the differences in inhibitory potency between glucosyl and glucosaminyl derivatives and also for the differences between imidazole and 1,2,4-triazole analogues.

Quantitative structure-activity relationships of selective antagonists of glucagon receptor using QuaSAR descriptors.

PubMed

Manoj Kumar, Palanivelu; Karthikeyan, Chandrabose; Hari Narayana Moorthy, Narayana Subbiah; Trivedi, Piyush

2006-11-01

In the present paper, quantitative structure activity relationship (QSAR) approach was applied to understand the affinity and selectivity of a novel series of triaryl imidazole derivatives towards glucagon receptor. Statistically significant and highly predictive QSARs were derived for glucagon receptor inhibition by triaryl imidazoles using QuaSAR descriptors of molecular operating environment (MOE) employing computer-assisted multiple regression procedure. The generated QSAR models revealed that factors related to hydrophobicity, molecular shape and geometry predominantly influences glucagon receptor binding affinity of the triaryl imidazoles indicating the relevance of shape specific steric interactions between the molecule and the receptor. Further, QSAR models formulated for selective inhibition of glucagon receptor over p38 mitogen activated protein (MAP) kinase of the compounds in the series highlights that the same structural features, which influence the glucagon receptor affinity, also contribute to their selective inhibition.

Concentration-dependent multiple chirality transition in halogen-bond-driven 2D self-assembly process

NASA Astrophysics Data System (ADS)

Miao, Xinrui; Li, Jinxing; Zha, Bao; Miao, Kai; Dong, Meiqiu; Wu, Juntian; Deng, Wenli

2018-03-01

The concentration-dependent self-assembly of iodine substituted thienophenanthrene derivative (5,10-DITD) is investigated at the 1-octanic acid/graphite interface using scanning tunneling microscopy. Three kinds of chiral arrangement and transition of 2D molecular assembly mainly driven by halogen bonding is clearly revealed. At high concentration the molecules self-assembled into a honeycomb-like chiral network. Except for the interchain van der Waals forces, this pattern is stabilized by intermolecular continuous Cdbnd O⋯I⋯S halogen bonds in each zigzag line. At moderate concentration, a chiral kite-like nanoarchitecture are observed, in which the Cdbnd O⋯I⋯S and I⋯Odbnd C halogen bonds, along with the molecule-solvent Cdbnd O⋯I⋯H halogen bonds are the dominated forces to determine the structural formation. At low concentration, the molecules form a chiral cyclic network resulting from the solvent coadsorption mainly by molecule-molecule Cdbnd O⋯I⋯S halogen bonds and molecule-solvent Cdbnd O⋯I⋯H halogen bonds. The density of molecular packing becomes lower with the decreasing of the solution concentration. The solution-concentration dependent self-assembly of thienophenanthrene derivative with iodine and ester chain moieties reveals that the type of intermolecular halogen bond and the number of the co-adsorbing 1-octanic acids by molecule-solvent Cdbnd O⋯I⋯H halogen bonds determine the formation and transformation of chirality. This research emphasizes the role of different types of halogen (I) bonds in the controllable supramolecular structures and provides an approach for the fabrication of chirality.

Halogen bond: a long overlooked interaction.

PubMed

Cavallo, Gabriella; Metrangolo, Pierangelo; Pilati, Tullio; Resnati, Giuseppe; Terraneo, Giancarlo

2015-01-01

Because of their high electronegativity, halogen atoms are typically considered, in most of their derivatives, as sites of high electron density and it is commonly accepted that they can form attractive interactions by functioning as the electron donor site (nucleophilic site). This is the case when they work as hydrogen bond acceptor sites. However, the electron density in covalently bound halogens is anisotropically distributed. There is a region of higher electron density, accounting for the ability of halogens to function as electron donor sites in attractive interactions, and a region of lower electron density where the electrostatic potential is frequently positive (mainly in the heavier halogens). This latter region is responsible for the ability of halogen atoms to function as the electron-acceptor site (electrophilic site) in attractive interactions formed with a variety of lone pair-possessing atoms, anions, and π-systems. This ability is quite general and is shown by a wide diversity of halogenated compounds (e.g., organohalogen derivatives and dihalogens). According to the definition proposed by the International Union of Pure and Applied Chemistry, any attractive interactions wherein the halogen atom is the electrophile is named halogen bond (XB). In this chapter, it is discussed how the practice and the concept of XB developed and a brief history of the interaction is presented. Papers (either from the primary or secondary literature) which have reported major experimental findings in the field or which have given important theoretical contributions for the development of the concept are recollected in order to trace how a unifying and comprehensive categorization emerged encompassing all interactions wherein halogen atoms function as the electrophilic site.

Graph theoretical analysis, insilico modeling, design, and synthesis of compounds containing benzimidazole skeleton as antidepressant agents.

PubMed

Theivendren, Panneerselvam; Subramanian, Arumugam; Murugan, Indhumathy; Joshi, Shrinivas D; More, Uttam A

2017-05-01

In this study, drug target was identified using KEGG database and network analysis through Cytoscape software. Designed series of novel benzimidazoles were taken along with reference standard Flibanserin for insilico modeling. The novel 4-(1H-benzo[d]imidazol-2-yl)-N-(substituted phenyl)-4-oxobutanamide (3a-j) analogs were synthesized and evaluated for their antidepressant activity. Reaction of 4-(1H-benzo[d]imidazol-2-yl)-4-oxobutanoic acid (1) with 4-(1H-benzo [d] imidazol-2-yl)-4-oxobutanoyl chloride (2) furnished novel 4-(1H-benzo [d] imidazol-2-yl)-N-(substituted phenyl)-4-oxobutanamide (3a-j). All the newly synthesized compounds were characterized by IR, 1 H-NMR, and mass spectral analysis. The antidepressant activities of synthesized derivatives were compared with standard drug clomipramine at a dose level of 20 mg/kg. Among the derivatives tested, most of the compounds were found to have potent activity against depression. The high level of activity was shown by the compounds 3d, 3e, 3i, and it significantly reduced the duration of immobility time at the dose level of 50 mg/kg. © 2016 John Wiley & Sons A/S.

Spectroscopic analysis and molecular docking of imidazole derivatives and investigation of its reactive properties by DFT and molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Thomas, Renjith; Hossain, Mossaraf; Mary, Y. Sheena; Resmi, K. S.; Armaković, Stevan; Armaković, Sanja J.; Nanda, Ashis Kumar; Ranjan, Vivek Kumar; Vijayakumar, G.; Van Alsenoy, C.

2018-04-01

Solvent-free synthesis pathway for obtaining two imidazole derivatives (2-chloro-1-(4-methoxyphenyl)-4,5-dimethyl-1H-imidazole (CLMPDI) and 1-(4-bromophenyl)-2-chloro-4,5-dimethyl-1H-imidazole (BPCLDI) has been reported in this work, followed by detailed experimental and computational spectroscopic characterization and reactivity study. Spectroscopic methods encompassed IR, FT-Raman and NMR techniques, with the mutual comparison of experimentally and computationally obtained results at DFT/B3LYP level of theory. Reactivity study based on DFT calculations encompassed molecular orbitals analysis, followed by calculations of molecular electrostatic potential (MEP) and average local ionization energy (ALIE) values, Fukui functions and bond dissociation energies (BDE). Additionally, the stability of title molecules in water has been investigated via molecular dynamics (MD) simulations, while interactivity with aspulvinonedimethylallyl transferase protein has been evaluated by molecular docking procedure. CLMPDI compound showed antimicrobial activity against all four bacterial strain in both gram positive and gram negative bacteria while, BPCLDI showed only in gram positive bacteria, Staphylococcus Aureus (MTCC1144). The first order hyperpolarizability of CLMPDI and BPCLDI are 20.15 and 6.10 times that of the standard NLO material urea.

Evaluating the potential for halogen bonding in ketosteroid isomerase’s oxyanion hole using unnatural amino acid mutagenesis

PubMed Central

Kraut, Daniel A; Churchil, Michael J; Dawson, Phillip E

2009-01-01

There has recently been an increasing interest in controlling macromolecular conformations and interactions through halogen bonding. Halogen bonds are favorable electrostatic interactions between polarized, electropositive chlorine, bromine or iodine atoms and electronegative atoms such as oxygen or nitrogen. These interactions have been likened to hydrogen bonds both in terms of their favored acceptor molecules, their geometries, and their energetics. We asked whether a halogen bond could replace a hydrogen bond in the oxyanion hole of ketosteroid isomerase, using semi-synthetic enzyme containing para-halogenated phenylalanine derivatives to replace the tyrosine hydrogen bond donor. Formation of a halogen bond to the oxyanion in the transition state would be expected to rescue the effects of mutation to phenylalanine, but all of the halogenated enzymes were comparable in activity to the phenylalanine mutant. We conclude that, at least in this active site, a halogen bond cannot functionally replace a hydrogen bond. PMID:19260691

A Halogen-Containing Stilbene Derivative from the Leaves of Cajanus cajan that Induces Osteogenic Differentiation of Human Mesenchymal Stem Cells.

PubMed

Cai, Jia-Zhong; Tang, Rong; Ye, Gui-Fu; Qiu, Sheng-Xiang; Zhang, Nen-Ling; Hu, Ying-Jie; Shen, Xiao-Ling

2015-06-11

A new natural halogen-containing stilbene derivative was isolated from the leaves of Cajanus cajan (L.) Millsp. and identified as 3-O-(3-chloro-2-hydroxyl-propanyl)-longistylin A by comprehensive spectroscopic and chemical analysis, and named cajanstilbene H (1). It is the first halogen-containing stilbene derivative found from plants. In human mesenchymal stem cells (hMSC) from bone marrow, 1 did not promote cell proliferation, but distinctly enhanced osteogenic differentiation of hMSC in time- and dose-dependent manners. In six human cancer cell lines, 1 showed a moderate inhibitory effect on cell proliferation, with IC50 values of 21.42-25.85 μmol·L(-1).

Histidine-functionalized water-soluble nanoparticles for biomimetic nucleophilic/general-base catalysis under acidic conditions.

PubMed

Chadha, Geetika; Zhao, Yan

2013-10-21

Cross-linking the micelles of 4-dodecyloxybenzyltripropargylammonium bromide by 1,4-diazidobutane-2,3-diol in the presence of azide-functionalized imidazole derivatives yielded surface-cross-linked micelles (SCMs) with imidazole groups on the surface. The resulting water-soluble nanoparticles were found, by fluorescence spectroscopy, to contain hydrophobic binding sites. The imidazole groups promoted the photo-deprotonation of 2-naphthol at pH 6 and catalyzed the hydrolysis of p-nitrophenylacetate (PNPA) in aqueous solution at pH ≥ 4. Although the overall hydrolysis rate slowed down with decreasing solution pH, the catalytic effect of the imidazole became stronger because the reactions catalyzed by unfunctionalized SCMs slowed down much more. The unusual ability of the imidazole–SCMs to catalyze the hydrolysis of PNPA under acidic conditions was attributed to the local hydrophobicity and the positive nature of the SCMs.

Binding interactions of halogenated bisphenol A with mouse PPARα: In vitro investigation and molecular dynamics simulation.

PubMed

Zhang, Jie; Li, Tiezhu; Wang, Tuoyi; Guan, Tianzhu; Yu, Hansong; Li, Zhuolin; Wang, Yongzhi; Wang, Yongjun; Zhang, Tiehua

2018-02-01

The binding of bisphenol A (BPA) and its halogenated derivatives (halogenated BPAs) to mouse peroxisome proliferator-activated receptor α ligand binding domain (mPPARα-LBD) was examined by a combination of in vitro investigation and in silico simulation. Fluorescence polarization (FP) assay showed that halogenated BPAs could bind to mPPARα-LBD* as the affinity ligands. The calculated electrostatic potential (ESP) illustrated the different charge distributions of halogenated BPAs with altered halogenation patterns. As electron-attracting substituents, halogens decrease the positive electrostatic potential and thereby have a significant influence on the electrostatic interactions of halogenated BPAs with mPPARα-LBD*. The docking results elucidated that hydrophobic and hydrogen-bonding interactions may also contribute to stabilize the binding of the halogenated BPAs to their receptor molecule. Comparison of the calculated binding energies with the experimentally determined affinities yielded a good correlation (R 2 =0.6659) that could provide a rational basis for designing environmentally benign chemicals with reduced toxicities. This work can potentially be used for preliminary screening of halogenated BPAs. Copyright © 2017 Elsevier B.V. All rights reserved.

Adsorbed States of phosphonate derivatives of N-heterocyclic aromatic compounds, imidazole, thiazole, and pyridine on colloidal silver: comparison with a silver electrode.

PubMed

Podstawka, Edyta; Olszewski, Tomasz K; Boduszek, Bogdan; Proniewicz, Leonard M

2009-09-03

Here, we report a systematic surface-enhanced Raman spectroscopy (SERS) study of the structures of phosphonate derivatives of the N-heterocyclic aromatic compounds imidazole (ImMeP ([hydroxy(1H-imidazol-5-yl)methyl]phosphonic acid) and (ImMe)(2)P (bis[hydroxy-(1H-imidazol-4-yl)-methyl]phosphinic acid)), thiazole (BAThMeP (butylaminothiazol-2-yl-methyl)phosphonic acid) and BzAThMeP (benzylaminothiazol-2-yl-methyl)phosphonic acid)), and pyridine ((PyMe)(2)P (bis[(hydroxypyridin-3-yl-methyl)]phosphinic acid)) adsorbed on nanometer-sized colloidal particles. We compared these structures to those on a roughened silver electrode surface to determine the relationship between the adsorption strength and the geometry. For example, we showed that all of these biomolecules interact with the colloidal surface through aromatic rings. However, for BzAThMeP, a preferential interaction between the benzene ring and the colloidal silver surface is observed more so than that between the thiazole ring and this substrate. The PC(OH)C fragment does not take part in the adsorption process, and the phosphonate moiety of ImMeP and (ImMe)(2)P, being removed from the surface, only assists in this process.

Synthesis, spectroscopic, computational (DFT/B3LYP), AChE inhibition and antioxidant studies of imidazole derivative

NASA Astrophysics Data System (ADS)

Ahmad, Faheem; Alam, Mohammad Jane; Alam, Mahboob; Azaz, Shaista; Parveen, Mehtab; Park, Soonheum; Ahmad, Shabbir

2018-01-01

The present study reports the synthesis and evaluation of biological properties of 3a,8a-dihydroxy-8-oxo-1,3,3a,8a-tetrahydroindeno[1,2-d]imidazol-2(1H)-iminium chloride (3). The structure was confirmed by the FTIR, NMR, MS, CHN microanalysis and X-ray crystallographic analysis. Quantum chemical calculations have been performed at B3LYP-D3/6-311++G(d,p) level of theory to study the molecular geometry, IR, (1H and 13C) NMR, UV/Vis spectra and other molecular parameters of the asymmetric unit of crystal of imidazole compound (3). An empirical dispersion correction to hybrid functional (B3LYP-D3) has been incorporated in the present calculations due to presence of non-covalent interaction, Cl⋯H-O, in the present compound. The remarkable agreement has been observed between theoretical data and those measured experimentally. Moreover, the Hirshfeld analysis was carried out to ascertain the secondary interactions and associated 2D fingerprint plots. The synthesized imidazole derivative showed promising antioxidant property and inhibitory activity against acetylcholinesterase (AChE). Molecular docking was also performed in order to explain in silico antioxidant studies and to ascertain the probable binding mode of compound with the amino acid residues of protein.

α-Halogenated oxaphosphinanes: Synthesis, unexpected reactions and evaluation as inhibitors of cancer cell proliferation.

PubMed

Babouri, Rachida; Rolland, Marc; Sainte-Catherine, Odile; Kabouche, Zahia; Lecouvey, Marc; Bakalara, Norbert; Volle, Jean-Noël; Virieux, David; Pirat, Jean-Luc

2015-11-02

This paper describes the preparation and the biological evaluation of α-halogenated oxaphosphinanes. These halogen derivatives were synthetized from a short and stereoselective synthetic sequence starting by previously described hydroxy-precursors 1 and 2 with respectively a glucose and mannose-like configuration. The in vitro biological tests of these unnatural halogenated phosphinosugars, on several cell lines, highlighted, for some of them, their antiproliferative and anti migration and invasion properties at nanomolar concentration. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Experimental and computational evidence of halogen bonds involving astatine

NASA Astrophysics Data System (ADS)

Guo, Ning; Maurice, Rémi; Teze, David; Graton, Jérôme; Champion, Julie; Montavon, Gilles; Galland, Nicolas

2018-03-01

The importance of halogen bonds—highly directional interactions between an electron-deficient σ-hole moiety in a halogenated compound and an acceptor such as a Lewis base—is being increasingly recognized in a wide variety of fields from biomedicinal chemistry to materials science. The heaviest halogens are known to form stronger halogen bonds, implying that if this trend continues down the periodic table, astatine should exhibit the highest halogen-bond donating ability. This may be mitigated, however, by the relativistic effects undergone by heavy elements, as illustrated by the metallic character of astatine. Here, the occurrence of halogen-bonding interactions involving astatine is experimentally evidenced. The complexation constants of astatine monoiodide with a series of organic ligands in cyclohexane solution were derived from distribution coefficient measurements and supported by relativistic quantum mechanical calculations. Taken together, the results show that astatine indeed behaves as a halogen-bond donor—a stronger one than iodine—owing to its much more electrophilic σ-hole.

Determination of imidazole derivatives by micellar electrokinetic chromatography combined with solid-phase microextraction using activated carbon-polymer monolith as adsorbent.

PubMed

Shih, Yung-Han; Lirio, Stephen; Li, Chih-Keng; Liu, Wan-Ling; Huang, Hsi-Ya

2016-01-08

In this study, an effective method for the separation of imidazole derivatives 2-methylimidazole (2-MEI), 4- methylimidazole (4-MEI) and 2-acetyl-4-tetrahydroxybutylimidazole (THI) in caramel colors using cation-selective exhaustive injection and sweeping micellar electrokinetic chromatography (CSEI-sweeping-MEKC) was developed. The limits of detection (LOD) and quantitation (LOQ) for the CSEI-sweeping-MEKC method were in the range of 4.3-80μgL(-1) and 14-270μgL(-1), respectively. Meanwhile, a rapid fabrication activated carbon-polymer (AC-polymer) monolithic column as adsorbent for solid-phase microextraction (SPME) of imidazole colors was developed. Under the optimized SPME condition, the extraction recoveries for intra-day, inter-day and column-to-column were in the range of 84.5-95.1% (<6.3% RSDs), 85.6-96.1% (<4.9% RSDs), and 81.3-96.1% (<7.1% RSDs), respectively. The LODs and LOQs of AC-polymer monolithic column combined with CSEI-sweeping-MEKC method were in the range of 33.4-60.4μgL(-1) and 111.7-201.2μgL(-1), respectively. The use of AC-polymer as SPME adsorbent demonstrated the reduction of matrix effect in food samples such as soft drink and alcoholic beverage thereby benefiting successful determination of trace-level caramel colors residues using CSEI-sweeping-MEKC method. The developed AC-polymer monolithic column can be reused for more than 30 times without any significant loss in the extraction recovery for imidazole derivatives. Copyright © 2015 Elsevier B.V. All rights reserved.

A Selective Organic-Based Corrosion Inhibitors Containing Iodide Ion as Enhancer for Protection of Carbon Steel: A Review

NASA Astrophysics Data System (ADS)

Ibrahim, I. M.; Kassim, E. S. Mohd; Husin, H.; Jai, J.; Daud, M.; Hashim, M. A.

2018-05-01

This paper contains a review on the effect of halide ion with a selected inhibitor which is imidazole derivatives on the efficiency of corrosion inhibition. The paper first describes the mechanism of synergistic inhibition effect among halide ions enhancer with inhibitor on the steel surface. Then the paper describes the measured inhibition efficiency and summarizes the synergistic inhibition condition of imidazoline derivatives inhibitor with iodide ions. The characteristic of synergistic inhibition effect and the relationship between the amount of iodide ion consumption and the amount of organic inhibitor consumption are also discussed. It has been shown that, the synergistic effect between imidazole derivative and iodide ion is an effective method to improve the inhibitive performance in different aqueous media.

Effect of Fatty Acyl Group and Sterol Composition on Sensitivity of Lecithin Liposomes to Imidazole Antimycotics

PubMed Central

Yamaguchi, Hideyo; Iwata, Kazuo

1979-01-01

The specific affinity for membrane lipids and the membrane selectivity of three imidazole derivatives, clotrimazole, miconazole, and econazole, were studied using various types of liposomes with respect to the lecithin fatty acyl group composition and the liposome content and composition of sterol as membrane models. The sensitivity of liposomes to these drugs was primarily dependent upon the lecithin fatty acyl group composition. With sterol-free liposome systems, each imidazole induced maximum release of trapped glucose as a marker from the unsaturated dioleoyl lecithin liposomes, minimum release from the saturated dipalmitoyl lecithin liposomes, and intermediate release from egg lecithin liposomes. The sensitivity of the dipalmitoyl lecithin liposomes to any imidazole drug was not influenced by the incorporation of cholesterol or ergosterol. On the other hand, clotrimazole-induced permeability changes of liposomes prepared from unsaturated dioleoyl lecithin or egg lecithin were greatly enhanced by the incorporation of ergosterol, whereas they were suppressed by cholesterol incorporation. The sensitivity of liposomes prepared from these unsaturated lecithins to miconazole and econazole was also augmented by ergosterol incorporation, although it was scarcely altered by cholesterol incorporation. Negatively charged liposomes were more sensitive to the three imidazole drugs than positively charged liposomes. PMID:525988

Effect of fatty acyl group and sterol composition on sensitivity of lecithin liposomes to imidazole antimycotics.

PubMed

Yamaguchi, H; Iwata, K

1979-05-01

The specific affinity for membrane lipids and the membrane selectivity of three imidazole derivatives, clotrimazole, miconazole, and econazole, were studied using various types of liposomes with respect to the lecithin fatty acyl group composition and the liposome content and composition of sterol as membrane models. The sensitivity of liposomes to these drugs was primarily dependent upon the lecithin fatty acyl group composition. With sterol-free liposome systems, each imidazole induced maximum release of trapped glucose as a marker from the unsaturated dioleoyl lecithin liposomes, minimum release from the saturated dipalmitoyl lecithin liposomes, and intermediate release from egg lecithin liposomes. The sensitivity of the dipalmitoyl lecithin liposomes to any imidazole drug was not influenced by the incorporation of cholesterol or ergosterol. On the other hand, clotrimazole-induced permeability changes of liposomes prepared from unsaturated dioleoyl lecithin or egg lecithin were greatly enhanced by the incorporation of ergosterol, whereas they were suppressed by cholesterol incorporation. The sensitivity of liposomes prepared from these unsaturated lecithins to miconazole and econazole was also augmented by ergosterol incorporation, although it was scarcely altered by cholesterol incorporation. Negatively charged liposomes were more sensitive to the three imidazole drugs than positively charged liposomes.

A mushroom-derived amino acid, ergothioneine, is a potential inhibitor of inflammation-related DNA halogenation.

PubMed

Asahi, Takashi; Wu, Xiaohong; Shimoda, Hiroshi; Hisaka, Shinsuke; Harada, Etsuko; Kanno, Tomomi; Nakamura, Yoshimasa; Kato, Yoji; Osawa, Toshihiko

2016-01-01

Myeloperoxidase (MPO)-generated halogenating molecules, such as hypochlorous acid and hypobromous acid (HOBr), in inflammatory regions are postulated to contribute to disease progression. In this study, we showed that ergothioneine (EGT), derived from an edible mushroom, inhibited MPO activity as well as the formation of 8-bromo-2'-deoxyguanosine in vitro. The HOBr scavenging effect of EGT is higher than those of ascorbic acid and glutathione. We initially observed that the administration of Coprinus comatus, an edible mushroom containing a high amount of EGT, inhibited the UV-B-induced inflammatory responses and DNA halogenation, suggesting that EGT is a promising anti-inflammatory agent from mushrooms.

Radical production from photosensitization of imidazoles

NASA Astrophysics Data System (ADS)

Corral Arroyo, P.; Gonzalez, L.; Steimer, S.; Aellig, R.; Volkamer, R. M.; George, C.; Bartels-Rausch, T.; Ammann, M.

2015-12-01

Reactions promoted by light are key in atmospheric chemistry. Some of them occur in the condensed phase of aerosols containing light absorbing organic compounds (George et al., 2015). This work explores the radical reactions initiated by near-UV light in mixtures of citric acid (CA) and imidazole-2-carboxaldehyde (IC) using NO as a probe molecule for HO2, by means of coated wall flow tube experiments. Citric acid may act as H atom or electron donor in condensed phase radical cycles. IC may act as a photosensitizer. The loss of NO was measured by a chemiluminescence detector. The dependence of the NO loss on the NO concentration, the IC/CA ratio in the film, relative humidity, light intensity, oxygen molar fraction were investigated as well as the HONO and NO2 yields. We also added halide salts to investigate the effect of a competing electron donor in the system and the output of halogens to the gas phase. We found a correlation between the loss of NO above the film and the molar ratio of IC/CA and the light intensity. The variation of the NO loss with oxygen corroborates a mechanism, in which the triplet excited state of IC is reduced by citric acid, to a reduced ketyl radical that transfers an electron to molecular oxygen, which in turn leads to production of HO2 radicals. Therefore, the NO loss in the gas phase is related to the production of HO2 radicals. Relative humidity had a strong impact on the HO2 output, which shows a maximum production rate at around 30%. The addition of halide ions (X- = Cl-, Br-, I-) increases the HO2 output at low concentration and decrease it at higher concentration when X2- radical ions likely scavenge HO2. We could preliminarily quantify for the first time the contribution of these processes to the oxidative capacity in the atmosphere and conclude that their role is significant for aerosol aging and potentially a significant source of halogen compounds to the gas phase.

Imidazole catalyzes chlorination by unreactive primary chloramines

PubMed Central

Roemeling, Margo D.; Williams, Jared; Beckman, Joseph S.; Hurst, James K.

2015-01-01

Hypochlorous acid and simple chloramines (RNHCl) are stable biologically-derived chlorinating agents. In general, the chlorination potential of HOCl is much greater than that of RNHCl, allowing it to oxidize or chlorinate a much wider variety of reaction partners. However, in this study we demonstrate by kinetic analysis that the reactivity of RNHCl can be dramatically promoted by imidazole and histidyl model compounds via intermediary formation of the corresponding imidazole chloramines. Two biologically relevant reactions were investigated—loss of imidazole-catalyzed chlorinating capacity and phenolic ring chlorination using fluorescein and the tyrosine analog, 4-hydroxyphenylacetic acid (HPA). HOCl reacted stoichiometrically with imidazole, N-acetylhistidine (NAH), or imidazoleacetic acid to generate the corresponding imidazole chloramines which subsequently decomposed. Chloramine (NH2Cl) also underwent a markedly accelerated loss in chlorinating capacity when NAH was present, although in this case NAHCl did not accumulate, indicating that the catalytic intermediate must be highly reactive. Mixing HOCl with 1-methylimidazole (MeIm) led to very rapid loss in chlorinating capacity via formation of a highly reactive chlorinium ion (MeImCl+) intermediate; this behavior suggests that the reactive forms of the analogous imidazole chloramines are their conjugate acids, e.g., the imidazolechlorinium ion (HImCl+). HOCl-generated imidazole chloramine (ImCl) reacted rapidly with fluorescein in a specific acid-catalyzed second order reaction to give 3′-monochloro and 3′,5′-dichloro products. Equilibrium constants for the transchlorination reactions: HOCl + HIm = H2O + ImCl and NH2Cl + HIm = NH3 + ImCl were estimated from the dependence of the rate constants upon [HIm]/[HOCl] and literature data. Acid catalysis again suggests that the actual chlorinating agent is HImCl+; consistent with this interpretation, MeIm markedly catalyzed fluorescein chlorination by HOCl. Time-dependent imidazole-catalyzed HPA chlorination by NH2Cl was also demonstrated by product analyses. Quantitative assessment of the data suggests that physiological levels of histidyl groups will react with primary chloramines to generate a flux of imidazole chloramine sufficient to catalyze biological chlorination via HImCl+, particularly in environments that generate high concentrations of HOCl such as the neutrophil phagosome. PMID:25660996

Understanding reactivity of two newly synthetized imidazole derivatives by spectroscopic characterization and computational study

NASA Astrophysics Data System (ADS)

Hossain, Mossaraf; Thomas, Renjith; Mary, Y. Sheena; Resmi, K. S.; Armaković, Stevan; Armaković, Sanja J.; Nanda, Ashis Kumar; Vijayakumar, G.; Van Alsenoy, C.

2018-04-01

Two newly synthetized imidazole derivatives (1-(4-methoxyphenyl)-4,5-dimethyl-1H-imidazole-2-yl acetate (MPDIA) and 1-(4-bromophenyl)-4,5-dimethyl-1H-imidazole-2-yl acetate (BPDIA)) have been prepared by solvent-free synthesis pathway and their specific spectroscopic and reactive properties have been discussed based on combined experimental and computational approaches. Aside of synthesis, experimental part of this work included measurements of IR, FT-Raman and NMR spectra. All of the aforementioned spectra were also obtained computationally, within the framework of density functional theory (DFT) approach. Additionally, DFT calculations have been used in order to investigate local reactivity properties based on molecular orbital theory, molecular electrostatic potential (MEP), average local ionization energy (ALIE), Fukui functions and bond dissociation energy (BDE). Molecular dynamics (MD) simulations have been used in order to obtain radial distribution functions (RDF), which were used for identification of the atoms with pronounced interactions with water molecules. MEP showed negative regions are mainly localized over N28, O29, O35 atoms, it is represent with red colour in rainbow color scheme for MPDIA and BPDIA (which are most reactive sites for electrophilic attack). The first order hyperpolarizabilities of MPDIA and BPDIA are 20.15 and 6.10 times that of the standard NLO material urea. Potential interaction with antihypertensive protein hydrolase.

Thermodynamics parameters for binding of halogenated benzotriazole inhibitors of human protein kinase CK2α.

PubMed

Winiewska, Maria; Kucińska, Katarzyna; Makowska, Małgorzata; Poznański, Jarosław; Shugar, David

2015-10-01

The interaction of human CK2α (hCK2α) with nine halogenated benzotriazoles, TBBt and its analogues representing all possible patterns of halogenation on the benzene ring of benzotriazole, was studied by biophysical methods. Thermal stability of protein-ligand complexes, monitored by calorimetric (DSC) and optical (DSF) methods, showed that the increase in the mid-point temperature for unfolding of protein-ligand complexes (i.e. potency of ligand binding to hCK2α) follow the inhibitory activities determined by biochemical assays. The dissociation constant for the ATP-hCK2α complex was estimated with the aid of microscale thermophoresis (MST) as 4.3±1.8 μM, and MST-derived dissociation constants determined for halogenated benzotriazoles, when converted according to known ATP concentrations, perfectly reconstruct IC50 values determined by the biochemical assays. Ligand-dependent quenching of tyrosine fluorescence, together with molecular modeling and DSC-derived heats of unfolding, support the hypothesis that halogenated benzotriazoles bind in at least two alternative orientations, and those that are efficient hCK2α inhibitors bind in the orientation which TBBt adopts in its complex with maize CK2α. DSC-derived apparent heat for ligand binding (ΔΔHbind) is driven by intermolecular electrostatic interactions between Lys68 and the triazole ring of the ligand, as indicated by a good correlation between ΔΔHbind and ligand pKa. Overall results, additionally supported by molecular modeling, confirm that a balance of hydrophobic and electrostatic interactions contribute predominantly (~40 kJ/mol), relative to possible intermolecular halogen/hydrogen bonding (less than 10 kJ/mol), in binding of halogenated benzotriazoles to the ATP-binding site of hCK2α. This article is part of a Special Issue entitled: Inhibitors of Protein Kinases. Copyright © 2015 Elsevier B.V. All rights reserved.

Metalloporphyrins and their uses as imageable tumor-targeting agents for radiation therapy

DOEpatents

Miura, Michiko; Slatkin, Daniel N.

2003-05-20

The present invention covers halogenated derivatives of boronated porphyrins containing multiple carborane cages having the formula ##STR1## which selectively accumulate in neoplastic tissue within the irradiation volume and thus can be used in cancer therapies including, but not limited to, boron neutron- capture therapy and photodynamic therapy. The present invention also covers methods for using these halogenated derivatives of boronated porphyrins in tumor imaging and cancer treatment.

Use of novel metalloporphyrins as imageable tumor-targeting agents for radiation therapy

DOEpatents

Miura, Michiko; Slatkin, Daniel N.

2005-10-04

The present invention covers halogenated derivatives of boronated phorphyrins containing multiple carborane cages having the formula ##STR1## which selectively accumulate in neoplastic tissue within the irradiation volume and thus can be used in cancer therapies including, but not limited to, boron neutron-capture therapy and photodynamic therapy. The present invention also covers methods for using these halogenated derivatives of boronated porphyrins in tumor imaging and cancer treatment.

Iodine(III) Derivatives as Halogen Bonding Organocatalysts.

PubMed

Heinen, Flemming; Engelage, Elric; Dreger, Alexander; Weiss, Robert; Huber, Stefan M

2018-03-26

Hypervalent iodine(III) derivatives are known as versatile reagents in organic synthesis, but there is only one previous report on their use as Lewis acidic organocatalysts. Herein, we present first strong indications for the crucial role of halogen bonding in this kind of catalyses. To this end, the solvolysis of benzhydryl chloride and the Diels-Alder reaction of cyclopentadiene with methyl vinyl ketone served as benchmark reactions for halide abstraction and the activation of neutral compounds. Iodolium compounds (cyclic diaryl iodonium species) were used as activators or catalysts, and we were able to markedly reduce or completely switch off their activity by sterically blocking one or two of their electrophilic axes. Compared with previously established bidentate cationic halogen bond donors, the monodentate organoiodine derivatives used herein are at least similarly active (in the Diels-Alder reaction) or even decidedly more active (in benzhydryl chloride solvolysis). © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

CNTs grown on nanoporous carbon from zeolitic imidazolate frameworks for supercapacitors.

PubMed

Kim, Jeonghun; Young, Christine; Lee, Jaewoo; Park, Min-Sik; Shahabuddin, Mohammed; Yamauchi, Yusuke; Kim, Jung Ho

2016-10-27

Carbon nanotubes (CNT) grown on nanoporous carbon (NPC), which yields coexisting amorphous and graphitic nanoarchitectures, have been prepared on a large scale from zeolitic imidazolate framework (ZIF) by introducing bimetallic ions (Co 2+ and Zn 2+ ). Interestingly, the hybrid Co/Zn-ZIF-derived NPC showed rich graphitic CNTs on the surface. This NPC was utilized for a coin-type supercapacitor cell with an aqueous electrolyte, which showed enhanced retention at high current density and good stability over 10 000 cycles.

The pharmacological actions of some murexine-like substances

PubMed Central

Erspamer, V.; Glässer, A.

1958-01-01

Four choline esters of imidazole acids, two imidazole ethers of choline and thirteen ringsubstituted murexine-like compounds were compared with murexine for their muscle-paralysing and their nicotine-like effects. Dihydromurexine appeared, in animal experiments, to be the most potent derivative, but it was shown to be less effective than murexine in man. Among the other compounds, imidazolebutyrylcholine and imidazolepropoxycholine appeared to be worthy of particular consideration. The relation between the chemical structure of the murexine-like substances studied and their pharmacological effects is discussed. PMID:13618539

Strong coupling effects in the polarized IR spectra of the chain hydrogen bond systems in imidazole crystals: H/D isotopic ?self-organization? effects in the IR spectra of isotopically diluted imidazole single crystals

NASA Astrophysics Data System (ADS)

Flakus, Henryk T.; Michta, Anna

2004-11-01

This paper presents the investigation results of the polarized IR spectra of H1245 imidazole crystals and of D1H245, D1245 and H1D245 imidazole deuterium derivative crystals. The spectra were measured using polarized light at the room temperature and at 77 K by a transmission method, for two different crystalline faces. Theoretical analysis of the results concerned linear dichroic effects, H/D isotopic and temperature effects, observed in the spectra of the hydrogen and of the deuterium bonds in imidazole crystals, at the frequency ranges of νN-H and νN-D bands. The basic crystal spectral properties can be satisfactorily interpreted in a quantitative way for a hydrogen bond linear dimer model. Such a model explains not only a two-branch structure of the νN-H and νN-D bands in crystalline spectra, but also some essential linear dichroic effects in the band frequency ranges, for isotopically diluted crystals. Model calculations, performed within the limits of the strong-coupling model, allowed for quantitative interpretation and for understanding of the basic properties of the hydrogen bond IR spectra of imidazole crystals, H/D isotopic, temperature and dichroic effects included. The results allowed verification of theoretical models proposed recently for the imidazole crystal spectra generation mechanisms. In the scope of our studies, the mechanism of H/D isotopic self-organization processes, taking place in the crystal hydrogen bond lattices, was also recognized. It was proved that for isotopically diluted crystalline samples of imidazole, a non-random distribution of protons and deuterons exclusively occurs in some restricted fragments (domains) of open chains of the hydrogen-bonded molecules. Nevertheless, these co-operative interactions between the hydrogen bonds do not concern adjacent fragments of neighboring hydrogen bond chains in the lattice. Analysis of the isotopic self-organization effects in the spectra of imidazole crystals delivered crucial arguments for understanding of the nature of the hydrogen bond spectra generation mechanisms.

Synthesis and antimalarial evaluation of novel isocryptolepine derivatives.

PubMed

Whittell, Louise R; Batty, Kevin T; Wong, Rina P M; Bolitho, Erin M; Fox, Simon A; Davis, Timothy M E; Murray, Paul E

2011-12-15

A series of mono- and di-substituted analogues of isocryptolepine have been synthesized and evaluated for in vitro antimalarial activity against chloroquine sensitive (3D7) and resistant (W2mef) Plasmodium falciparum and for cytotoxicity (3T3 cells). Di-halogenated compounds were the most potent derivatives and 8-bromo-2-chloroisocryptolepine displayed the highest selectivity index (106; the ratio of cytotoxicity (IC(50)=9005 nM) to antimalarial activity (IC(50)=85 nM)). Our evaluation of novel isocryptolepine compounds has demonstrated that di-halogenated derivatives are promising antimalarial lead compounds. Copyright © 2011 Elsevier Ltd. All rights reserved.

New benzimidazoles and their antitumor effects with Aurora A kinase and KSP inhibitory activities.

PubMed

Abd El-All, Amira S; Magd-El-Din, Asmaa A; Ragab, Fatma A F; ElHefnawi, Mahmoud; Abdalla, Mohamed M; Galal, Shadia A; El-Rashedy, Ahmed A

2015-07-01

A newly synthesized series of anticancer compounds comprising thiazolo[3,2-a]pyrimidine derivatives 6a-q bearing a benzimidazole moiety was produced via a one-pot reaction of N-(4-(1H-benzo[d]imidazol-2-yl)phenyl)-2-cyanoacetamide 5 with 2-aminothiazole and an appropriate aromatic aldehyde. Compound 7 was obtained via the reaction of 4-(1H-benzo[d]imidazol-2yl)benzenamide 1 with carbon disulphide and methyl iodide in the presence of concentrated aqueous solution of NaOH, then treated with o-phenylenediamine to give N-(4-1H-benzo[d]imidazol-2-yl)phenyl)-1H-benzo[d]imidazol-2-amine 8. The structures of the newly synthesized compounds were confirmed by analytical and spectroscopic measurements (IR, MS, and (1) H NMR). The synthesized products were screened and studied for their in vitro antitumor activity against three human cancer cell lines (namely colorectal cancer cell line HCT116, human liver cancer cell line HepG2, and human ovarian cancer cell line A2780) and their Aurora A kinase and KSP inhibitory activities. All newly synthesized compounds revealed marked results comparable with the standard drug CK0106023. The compounds 6e and 6k of the thiazolopyrimidine derivatives were the most active compounds when tested against the three cell lines in comparison with the standard drug CK0106023, and showed potent dual KSP and Aurora A kinase inhibition. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of new derivatives of 21-imidazolyl-16-dehydropregnenolone as inhibitors of 5α-reductase 2 and with cytotoxic activity in cancer cells.

PubMed

Silva-Ortiz, Aylin Viviana; Bratoeff, Eugene; Ramírez-Apan, Teresa; Heuze, Yvonne; Soriano, Juan; Moreno, Isabel; Bravo, Marisol; Bautista, Lucero; Cabeza, Marisa

2017-03-01

The aim of this study was to synthesize several 16-dehydropregnenolone derivatives containing an imidazole ring at C-21 and a different ester moiety at C-3 as inhibitors of 5α-reductase 1 and 2 isoenzymes. Their binding capacity to the androgen receptor (AR) was also studied. Additionally, we evaluated their pharmacological effect in a castrated hamster model and their cytotoxic activity on a panel of cancer cells (PC-3, MCF7, SK-LU-1). The results showed that only the derivatives with an alicyclic ester at C-3 showed 5α-R2 enzyme inhibition activity, the most potent of them being 21-(1H-imidazol-1-yl)-20-oxopregna-5,16-dien-3β-yl-cyclohexanecarboxylate with an IC 50 of 29nM. This is important because prostatic benign hyperplasia is directly associated with the presence of 5α-R2. However, all the derivatives failed to inhibit 5α-R1 or bind to the AR. These alicyclic ester derivatives decreased the weight and size of androgen-dependent glands in the hamster, indicating they are very active in vivo and are not toxic. In addition, the 21-(1H-imidazol-1-yl)-20-oxopregna-5,16-dien-3β-yl-acetate derivative showed the highest cytotoxic activity on the three cancer cell lines studied. It is therefore important in the synthesis of steroidal compounds to consider the size of the ester moiety at C-3 of the steroid skeleton, which is key in obtaining biological activity, as observed in this experiment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Prediction of enthalpy and standard Gibbs energy of vaporization of haloaromatics from atomic properties.

PubMed

Monte, M J S; Almeida, A R R P; Liebman, J F

2015-11-01

Halogenated benzenes form a class of pollutants with a huge number of members - 1504 distinct benzene compounds, where one or more hydrogen atoms are replaced by halogens, may exist theoretically. This study presents a user friendly method for accurate prediction of vapor pressures and enthalpies of vaporization, at 298.15 K, of any mono or poly halobenzene compound. The derived equations for the prediction of those vaporization properties depend just on the number of each constituent halogen atom. This is a consequence of the absence of intramolecular interactions between the halogen atoms, revealed after examining vaporization results of ca. 40 halogenated benzenes. In order to rationalize the estimation equations, the contribution of the halogen atoms for the referred to above properties of vaporization was decomposed into two atomic properties - the volume and electron affinity. Extension of the applicability of the estimation method to substituted benzenes containing other substituent groups beyond halogen atoms as well as to some polycyclic aromatic species was tested with success. Copyright © 2015 Elsevier Ltd. All rights reserved.

Synthesis and antimicrobial properties of 3-aryl-1-(1,1'-biphenyl-4-yl)-2-(1H-imidazol-1-yl)propanes as 'carba-analogues' of the N-arylmethyl-N-[(1,1'-biphenyl)-4-ylmethyl])-1H-imidazol-1-amines, a new class of antifungal agents.

PubMed

Castellano, Sabrina; Stefancich, Giorgio; Chillotti, Annalisa; Poni, Graziella

2003-08-01

A new series of 3-phenyl-1-(1,1'-biphenyl-4-yl)-2-(1H-imidazol-1-yl)propane derivatives 2a-l (related to the antifungal bifonazole) was synthesized and tested for antimicrobial activity. A number of substituents on the phenyl ring were chosen to compare the relative biological properties with those of corresponding aza-analogues, previously described by us. The in vitro antifungal activities of the newly synthesized azoles were tested against several pathogenic fungi responsible for human disease. Test pathogens included representatives of yeasts (Candida albicans, Candida parapsilosis, Criptococcus neoformans), dermathophytes (Tricophyton verrucosum, Tricophyton rubrum, Microsporum gypseum) and moulds (Aspergillus fumigatus). Bifonazole and miconazole were used as reference drugs. Title compounds were prepared by alkylation of 1-biphenyl-4-yl-2-imidazol-1-yl-ethanone with the proper arylmethyl halide and subsequent reduction of corresponding ketones applying the Huang-Minlon modification of the Wolff-Kishner reaction.

Competition of hydrogen bonds and halogen bonds in complexes of hypohalous acids with nitrogenated bases.

PubMed

Alkorta, Ibon; Blanco, Fernando; Solimannejad, Mohammad; Elguero, Jose

2008-10-30

A theoretical study of the complexes formed by hypohalous acids (HOX, X = F, Cl, Br, I, and At) with three nitrogenated bases (NH 3, N 2, and NCH) has been carried out by means of ab initio methods, up to MP2/aug-cc-pVTZ computational method. In general, two minima complexes are found, one with an OH...N hydrogen bond and the other one with a X...N halogen bond. While the first one is more stable for the smallest halogen derivatives, the two complexes present similar stabilities for the iodine case and the halogen-bonded structure is the most stable one for the hypoastatous acid complexes.

Metal-Mediated Halogen Exchange in Aryl and Vinyl Halides: A Review

PubMed Central

Evano, Gwilherm; Nitelet, Antoine; Thilmany, Pierre; Dewez, Damien F.

2018-01-01

Halogenated arenes and alkenes are of prime importance in many areas of science, especially in the pharmaceutical, agrochemical, and chemical industries. While the simplest ones are commercially available, some of them are still hardly accessible depending on their substitution patterns and the nature of the halogen atom. Reactions enabling the selective and efficient replacement of the halogen atom of an aryl or alkenyl halide by another one, lighter, or heavier, are therefore of major importance since they can be used for example to turn a less reactive aryl/alkenyl chloride into the more reactive iodinated derivatives or, in a reversed sense, to block an undesired reactivity, for late-stage modifications or for the introduction of a radionuclide. If some halogen exchange reactions are possible with activated substrates, they usually require catalysis with metal complexes. Remarkably efficient processes have been developed for metal-mediated halogen exchange in aryl and vinyl halides: they are overviewed, in a comprehensive manner, in this review article. PMID:29755967

Metal-Mediated Halogen Exchange in Aryl and Vinyl Halides: a Review

NASA Astrophysics Data System (ADS)

Evano, Gwilherm; Nitelet, Antoine; Thilmany, Pierre; Dewez, Damien F.

2018-04-01

Halogenated arenes and alkenes are of prime importance in many areas of science, especially in the pharmaceutical, agrochemical and chemical industries. While the simplest ones are commercially available, some of them are still hardly accessible depending on their substitution patterns and the nature of the halogen atom. Reactions enabling the selective and efficient replacement of the halogen atom of an aryl or alkenyl halide by another one, lighter or heavier, are therefore of major importance since they can be used for example to turn a less reactive aryl/alkenyl chloride into the more reactive iodinated derivatives or, in a reversed sense, to block an undesired reactivity, for late-stage modifications or for the introduction of a radionuclide. If some halogen exchange reactions are possible with activated substrates, they usually require catalysis with metal complexes. Remarkably efficient processes have been developed for metal-mediated halogen exchange in aryl and vinyl halides: they are overviewed, in a comprehensive manner, in this review article.

2-(4-Meth-oxy-phen-yl)-1-pentyl-4,5-di-phenyl-1H-imidazole.

PubMed

Simpson, Jim; Mohamed, Shaaban K; Marzouk, Adel A; Talybov, Avtandil H; Abdelhamid, Antar A

2013-01-01

The title compound, C27H28N2O, is a lophine (2,4,5-triphenyl-1H-imidazole) derivative with an n-pentyl chain on the amine N atom and a 4-meth-oxy substituent on the benzene ring. The two phenyl and meth-oxy-benzene rings are inclined to the imidazole ring at angles of 25.32 (7), 76.79 (5) and 35.42 (7)°, respectively, while the meth-oxy substituent lies close to the plane of its benzene ring, with a maximum deviation of 0.126 (3) Å for the meth-oxy C atom. In the crystal, inversion dimers linked by pairs of C-H⋯O hydrogen bonds generate R2(2)(22) loops. These dimers are stacked along the a-axis direction.

Conjugates of 18β-glycyrrhetinic acid derivatives with 3-(1H-benzo[d]imidazol-2-yl)propanoic acid as Pin1 inhibitors displaying anti-prostate cancer ability.

PubMed

Li, Kun; Ma, Tianyi; Cai, Jingjing; Huang, Min; Guo, Hongye; Zhou, Di; Luan, Shenglin; Yang, Jinyu; Liu, Dan; Jing, Yongkui; Zhao, Linxiang

2017-10-15

Twenty-six conjugates of 18β-glycyrrhetinic acid derivatives with 3-(1H-benzo[d]imidazol-2-yl)propanoic acid were designed and synthesized as Pin1 inhibitors. Most of these semi-synthetic compounds showed improved Pin1 inhibitory activity and anti-proliferative effects against prostate cancer cells as compared to 3-(1H-benzo[d]imidazol-2-yl)propanoic acid and GA. Compounds 10a and 12i were the most potent to inhibit growth of prostate cancer PC-3 with GI 50 values of 7.80μM and 3.52μM, respectively. The enzyme inhibition ratio of nine compounds at 10μM was over 90%. Structure-activity relationships indicated that both appropriate structure at ring C of GA and suitable length of linker between GA skeleton and benzimidazole moiety had significant impact on improving activity. Western blot assay revealed that 10a decreased the level of cell cycle regulating protein cyclin D1. Thus, these compounds might represent a novel anti-proliferative agent working through Pin1 inhibition. Copyright © 2017. Published by Elsevier Ltd.

Phosphorylated lignin as a halogen-free flame retardant additive for epoxy composites

Treesearch

Gamini P. Mendis; Sydney G. Weiss; Matthew Korey; Charles R. Boardman; Mark Dietenberger; Jeffrey P. Youngblood; John A. Howarter

2016-01-01

Sustainable, non-halogenated flame retardants are desired for a variety of industry applications. Lignin, as an industrially processed wood derivative, has been examined as a potential sustainable flame retardant additive to polymer systems. Here, the lignin is phosphorylated using a pyridine-catalysed esterification reaction with diphenyl phosphoryl chloride to...

Tuning the electronic structure of graphene through alkali metal and halogen atom intercalation

NASA Astrophysics Data System (ADS)

Ahmad, Sohail; Miró, Pere; Audiffred, Martha; Heine, Thomas

2018-04-01

The deposition, intercalation and co-intercalation of heavy alkali metals and light halogens atoms in graphene mono- and bilayers have been studied using first principles density-functional calculations. Both the deposition and the intercalation of alkali metals gives rise to n-type doping due to the formation of M+-C- pairs. The co-intercalation of a 1:1 ratio of alkali metals and halogens derives into the formation of ionic pairs among the intercalated species, unaltering the electronic structure of the layered material.

Development and application of a sampling method for the determination of reactive halogen species in volcanic gas emissions.

PubMed

Rüdiger, Julian; Bobrowski, Nicole; Liotta, Marcello; Hoffmann, Thorsten

2017-10-01

Volcanoes release large amounts of reactive trace gases including sulfur and halogen-containing species into the atmosphere. The knowledge of halogen chemistry in volcanic plumes can deliver information about subsurface processes and is relevant for the understanding of the impact of volcanoes on atmospheric chemistry. In this study, a gas diffusion denuder sampling method using 1,3,5-trimethoxybenzene (1,3,5-TMB)-coated glass tubes for the in situ derivatization of reactive halogen species (RHS) was characterized by a series of laboratory experiments. The coating proved to be applicable to collect selectively gaseous bromine species with oxidation states (OS) of +1 or 0 (such as Br 2 , BrCl, HOBr, BrO, and BrONO 2 ) while being unreactive to HBr (OS -1). The reaction of 1,3,5-TMB with reactive bromine species forms 1-bromo-2,4,6-TMB-other halogens give corresponding derivatives. Solvent elution of the derivatives followed by analysis with GC-MS results in absolute detection limits of a few nanograms for Br 2 , Cl 2 , and I 2 . In 2015, the technique was applied on volcanic gas plumes at Mt. Etna (Italy) measuring reactive bromine mixing ratios between 0.8 and 7.0 ppbv. Total bromine mixing ratios between 4.7 and 27.5 ppbv were derived from alkaline trap samples, simultaneously taken by a Raschig tube and analyzed with IC and ICP-MS. This leads to the first results of the reactive bromine contribution to total bromine in volcanic emissions, spanning over a range between 12% (±1) and 36% (±2). Our finding is in an agreement with previous model studies, which imply values <44% for plume ages <1 min, which is consistent with the assumed plume age at the sampling sites. Graphical abstract Illustration of the measurement procedure for the determination of reactive halogen species in volcanic plumes.

Low-basicity 5-HT7 Receptor Agonists Synthesized Using the van Leusen Multicomponent Protocol.

PubMed

Hogendorf, Adam S; Hogendorf, Agata; Kurczab, Rafał; Satała, Grzegorz; Lenda, Tomasz; Walczak, Maria; Latacz, Gniewomir; Handzlik, Jadwiga; Kieć-Kononowicz, Katarzyna; Wierońska, Joanna M; Woźniak, Monika; Cieślik, Paulina; Bugno, Ryszard; Staroń, Jakub; Bojarski, Andrzej J

2017-05-04

A series of 5-aryl-1-alkylimidazole derivatives was synthesized using the van Leusen multicomponent reaction. The chemotype is the first example of low-basicity scaffolds exhibiting high affinity for 5-HT 7 receptor together with agonist function. The chosen lead compounds 3-(1-ethyl-1H-imidazol-5-yl)-5-iodo-1H-indole (AGH-107, 1o, K i 5-HT7  = 6 nM, EC 50  = 19 nM, 176-fold selectivity over 5-HT 1A R) and 1e (5-methoxy analogue, K i 5-HT7  = 30 nM, EC 50  = 60 nM) exhibited high selectivity over related CNS targets, high metabolic stability and low toxicity in HEK-293 and HepG2 cell cultures. A rapid absorption to the blood, high blood-brain barrier permeation and a very high peak concentration in the brain (C max  = 2723 ng/g) were found for 1o after i.p. (5 mg/kg) administration in mice. The compound was found active in novel object recognition test in mice, at 0.5, 1 and 5 mg/kg. Docking to 5-HT 7 R homology models indicated a plausible binding mode which explain the unusually high selectivity over the related CNS targets. Halogen bond formation between the most potent derivatives and the receptor is consistent with both the docking results and SAR. 5-Chlorine, bromine and iodine substitution resulted in a 13, 27 and 89-fold increase in binding affinities, respectively, and in enhanced 5-HT 1A R selectivity.

[4-t-butylphenyl]-N-(4-imidazol-1-yl phenyl)sulfonamide (ISCK03) inhibits SCF/c-kit signaling in 501mel human melanoma cells and abolishes melanin production in mice and brownish guinea pigs.

PubMed

Na, Yong Joo; Baek, Heung Su; Ahn, Soo Mi; Shin, Hyun Jung; Chang, Ih-Seop; Hwang, Jae Sung

2007-09-01

It is well known that c-kit is related to pigmentation as well as to the oncology target protein. The objective of this study was to discover a skin-whitening agent that regulates c-kit activity. We have developed a high-throughput screening system using recombinant human c-kit protein. Approximately 10,000 synthetic compounds were screened for their effect on c-kit activity. Phenyl-imidazole sulfonamide derivatives showed inhibitory activity on c-kit phosphorylation in vitro. The effects of one derivative, [4-t-butylphenyl]-N-(4-imidazol-1-yl phenyl)sulfonamide (ISCK03), on stem-cell factor (SCF)/c-kit cellular signaling in 501mel human melanoma cells were examined further. Pretreatment of 501mel cells with ISCK03 inhibited SCF-induced c-kit phosphorylation dose dependently. ISCK03 also inhibited p44/42 ERK mitogen-activated protein kinase (MAPK) phosphorylation, which is known to be involved in SCF/c-kit downstream signaling. However ISCK03 did not inhibit hepatocyte growth factor (HGF)-induced phosphorylation of p44/42 ERK proteins. To determine the in vivo potency of ISCK03, it was orally administered to depilated C57BL/6 mice. Interestingly, oral administration of ISCK03 induced the dose-dependent depigmentation of newly regrown hair, and this was reversed with cessation of ISCK03 treatment. Finally, to investigate whether the inhibitory effect of ISCK03 on SCF/c-kit signaling abolished UV-induced pigmentation, ISCK03 was applied to UV-induced pigmented spots on brownish guinea pig skin. The topical application of ISCK03 promoted the depigmentation of UV-induced hyperpigmented spots. Fontana-Masson staining analysis showed epidermal melanin was diminished in spots treated with ISCK03. These results indicate that phenyl-imidazole sulfonamide derivatives are potent c-kit inhibitors and might be used as skin-whitening agents.

Non-Doped Sky-Blue OLEDs Based on Simple Structured AIE Emitters with High Efficiencies at Low Driven Voltages.

PubMed

Islam, Amjad; Zhang, Dongdong; Peng, Ruixiang; Yang, Rongjuan; Hong, Ling; Song, Wei; Wei, Qiang; Duan, Lian; Ge, Ziyi

2017-09-05

Blue organic light-emitting diodes (OLEDs) are necessary for flat-panel display technologies and lighting applications. To make more energy-saving, low-cost and long-lasting OLEDs, efficient materials as well as simple structured devices are in high demand. However, a very limited number of blue OLEDs achieving high stability and color purity have been reported. Herein, three new sky-blue emitters, 1,4,5-triphenyl-2-(4-(1,2,2-triphenylvinyl)phenyl)-1H-imidazole (TPEI), 1-(4-methoxyphenyl)-4,5-diphenyl-2-(4-(1,2,2-triphenylvinyl)phenyl)-1H-imidazole (TPEMeOPhI) and 1-phenyl-2,4,5-tris(4-(1,2,2-triphenylvinyl)phenyl)-1H-imidazole (3TPEI), with a combination of imidazole and tetraphenylethene groups, have been developed. High photoluminescence quantum yields are obtained for these materials. All derivatives have demonstrated aggregation-induced emission (AIE) behavior, excellent thermal stability with high decomposition and glass transition temperatures. Non-doped sky-blue OLEDs with simple structure have been fabricated employing these materials as emitters and realized high efficiencies of 2.41 % (4.92 cd A -1 , 2.70 lm W -1 ), 2.16 (4.33 cd A -1 , 2.59 lm W -1 ) and 3.13 % (6.97 cd A -1 , 4.74 lm W -1 ) for TPEI, TPEMeOPhI and 3TPEI, with small efficiency roll-off. These are among excellent results for molecules constructed from the combination of imidazole and TPE reported so far. The high performance of a 3TPEI-based device shows the promising potential of the combination of imidazole and AIEgen for synthesizing efficient electroluminescent materials for OLED devices. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Alkylating Derivatives of Vitamin D Hormone for Prostate Cancer

DTIC Science & Technology

2006-10-01

Acetic Anhydride / Pyridine/ 40C 1. UV / Toluene 2. EtOH - Reflux TBDMSCl / Imidazole /DMF BrCH2COOH / DCC / DMAP / CH2Cl2 1,25(OH)2D3-3-BE Figure 1...BE OH SO2 OTBDMS OH OTBDMS 1. Liq. SO2 / Reflux 2. TBDMSCl / Imidazole /DMF NaHCO3 / EtOH / Reflux NMO / SeO2 / CH2Cl2 / Reflux OH OTBDMSHO OTHP...containing 200 mg of 25-hydroxyvitamin D3 in a flask fitted with a trap that was cooled with dry ice-acetone (-780C). The yellow solution was refluxed

Pyrazolylbenzo[d]imidazoles as new potent and selective inhibitors of carbonic anhydrase isoforms hCA IX and XII.

PubMed

Kumar, Satish; Ceruso, Mariangela; Tuccinardi, Tiziano; Supuran, Claudiu T; Sharma, Pawan K

2016-07-01

Novel pyrazolylbenzo[d]imidazole derivatives (2a-2f) were designed, synthesized and evaluated against four human carbonic anhydrase isoforms belonging to α family comprising of two cytosolic isoforms hCA I and II as well as two transmembrane tumor associated isoforms hCA IX and XII. Starting from these derivatives that showed high potency but low selectivity in favor of tumor associated isoforms hCA IX and XII, we investigated the impact of removing the sulfonamide group. Thus, analogs 3a-3f without sulfonamide moiety were synthesized and biological assay revealed a good activity as well as an excellent selectivity as inhibitors for tumor associated hCA IX and hCA XII and the same was analyzed by molecular docking studies. Copyright © 2016 Elsevier Ltd. All rights reserved.

GC-MS Study of Mono- and Bishaloethylphosphonates Related to Schedule 2.B.04 of the Chemical Weapons Convention: The Discovery of a New Intramolecular Halogen Transfer

NASA Astrophysics Data System (ADS)

Picazas-Márquez, Nerea; Sierra, María; Nova, Clara; Moreno, Juan Manuel; Aboitiz, Nuria; de Rivas, Gema; Sierra, Miguel A.; Martínez-Álvarez, Roberto; Gómez-Caballero, Esther

2016-09-01

A new class of compounds, mono- and bis-haloethylphosphonates (HAPs and bisHAPs, respectively), listed in Schedule 2.B.04 of the Chemical Weapons Convention (CWC), has been synthesized and studied by GC-MS with two aims. First, to improve the identification of this type of chemicals by the Organization for the Prohibition of Chemical Weapons, (OPCW). Second, to study the synergistic effect of halogen and silicon atoms in molecules undergoing mass spectrometry. Fragmentation patterns of trimethylsilyl derivatives of HAPs were found to depend on the nature of the halogen atom; this was in agreement with DFT-calculations. The data suggest that a novel intramolecular halogen transfer takes place during the fragmentation process.

GC-MS Study of Mono- and Bishaloethylphosphonates Related to Schedule 2.B.04 of the Chemical Weapons Convention: The Discovery of a New Intramolecular Halogen Transfer.

PubMed

Picazas-Márquez, Nerea; Sierra, María; Nova, Clara; Moreno, Juan Manuel; Aboitiz, Nuria; de Rivas, Gema; Sierra, Miguel A; Martínez-Álvarez, Roberto; Gómez-Caballero, Esther

2016-09-01

A new class of compounds, mono- and bis-haloethylphosphonates (HAPs and bisHAPs, respectively), listed in Schedule 2.B.04 of the Chemical Weapons Convention (CWC), has been synthesized and studied by GC-MS with two aims. First, to improve the identification of this type of chemicals by the Organization for the Prohibition of Chemical Weapons, (OPCW). Second, to study the synergistic effect of halogen and silicon atoms in molecules undergoing mass spectrometry. Fragmentation patterns of trimethylsilyl derivatives of HAPs were found to depend on the nature of the halogen atom; this was in agreement with DFT-calculations. The data suggest that a novel intramolecular halogen transfer takes place during the fragmentation process. Graphical Abstract ᅟ.

Discovery of a tetrahydropyrimidin-2(1H)-one derivative (TAK-442) as a potent, selective, and orally active factor Xa inhibitor.

PubMed

Fujimoto, Takuya; Imaeda, Yasuhiro; Konishi, Noriko; Hiroe, Katsuhiko; Kawamura, Masaki; Textor, Garret P; Aertgeerts, Kathleen; Kubo, Keiji

2010-05-13

Coagulation enzyme factor Xa (FXa) is a particularly promising target for the development of new anticoagulant agents. We previously reported the imidazo[1,5-c]imidazol-3-one derivative 1 as a potent and orally active FXa inhibitor. However, it was found that 1 predominantly undergoes hydrolysis upon incubation with human liver microsomes, and the human specific metabolic pathway made it difficult to predict the human pharmacokinetics. To address this issue, our synthetic efforts were focused on modification of the imidazo[1,5-c]imidazol-3-one moiety of the active metabolite 3a, derived from 1, which resulted in the discovery of the tetrahydropyrimidin-2(1H)-one derivative 5k as a highly potent and selective FXa inhibitor. Compound 5k showed no detectable amide bond cleavage in human liver microsomes, exhibited a good pharmacokinetic profile in monkeys, and had a potent antithrombotic efficacy in a rabbit model without prolongation of bleeding time. Compound 5k is currently under clinical development with the code name TAK-442.

Prebiotic synthesis of imidazole-4-acetaldehyde and histidine

NASA Astrophysics Data System (ADS)

Shen, Chun; Yang, Lily; Miller, Stanley L.; Oró, J.

1987-09-01

The prebiotic synthesis of imidazole-4-acetaldehyde and imidazole-4-glycol from erythrose and formamidine has been demonstrated as well as the prebiotic synthesis of imidazole-4-ethanol and imidazole-4-glycol from erythrose, formaldehyde and ammonia. The products were identified by TLC, HPLC, and LC-MS by comparison with authentic samples. The maximum yields of imidazole-4-acetaldehyde, imidazole-4-ethanol, and imidazole-4-glycol obtained in these reactions are 1.6, 5.4, 6.8% respectively, based on the erythrose. Imidazole-4-acetaldehyde would have been converted to histidine on the primitive earth by a Strecker synthesis, and several prebiotic reactions would convert imidazole-4-glycol and imidazole-4-ethanol to imidazole-4-acetaldehyde.

Substituent and ring effects on enthalpies of formation: 2-methyl- and 2-ethylbenzimidazoles versus benzene- and imidazole-derivatives

NASA Astrophysics Data System (ADS)

Jiménez, Pilar; Roux, María Victoria; Dávalos, Juan Z.; Temprado, Manuel; Ribeiro da Silva, Manuel A. V.; Ribeiro da Silva, Maria Das Dores M. C.; Amaral, Luísa M. P. F.; Cabildo, Pilar; Claramunt, Rosa M.; Mó, Otilia; Yáñez, Manuel; Elguero, José

The enthalpies of combustion, heat capacities, enthalpies of sublimation and enthalpies of formation of 2-methylbenzimidazole (2MeBIM) and 2-ethylbenzimidazole (2EtBIM) are reported and the results compared with those of benzimidazole itself (BIM). Theoretical estimates of the enthalpies of formation were obtained through the use of atom equivalent schemes. The necessary energies were obtained in single-point calculations at the B3LYP/6-311+G(d,p) on B3LYP/6-31G* optimized geometries. The comparison of experimental and calculated values of benzenes, imidazoles and benzimidazoles bearing H (unsubstituted), methyl and ethyl groups shows remarkable homogeneity. The energetic group contribution transferability is not followed, but either using it or adding an empirical interaction term, it is possible to generate an enormous collection of reasonably accurate data for different substituted heterocycles (pyrazole-derivatives, pyridine-derivatives, etc.) from the large amount of values available for substituted benzenes and those of the parent (pyrazole, pyridine) heterocycles.

Hybrid imidazole (benzimidazole)/pyridine (quinoline) derivatives and evaluation of their anticancer and antimycobacterial activity.

PubMed

Mantu, Dorina; Antoci, Vasilichia; Moldoveanu, Costel; Zbancioc, Gheorghita; Mangalagiu, Ionel I

2016-01-01

The design, synthesis, structure, and in vitro anticancer and antimycobacterial activity of new hybrid imidazole (benzimidazole)/pyridine (quinoline) derivatives are described. The strategy adopted for synthesis is straight and efficient, involving a three-step setup procedure: N-acylation, N-alkylation, and quaternization of nitrogen heterocycle. The solubility in microbiological medium and anticancer and antimycobacterial activity of a selection of new synthesized compounds were evaluated. The hybrid derivatives have an excellent solubility in microbiological medium, which make them promising from the pharmacological properties point of view. One of the hybrid compounds, 9 (with a benzimidazole and 8-aminoquinoline skeleton), exhibits a very good and selective antitumor activity against Renal Cancer A498 and Breast Cancer MDA-MB-468. Moreover, the anticancer assay suggests that the hybrid Imz (Bimz)/2-AP (8-AQ) compounds present a specific affinity to Renal Cancer A498. Concerning the antimycobacterial activity, only the hybrid compound, 9, has a significant activity. SAR correlations have been performed.

Tannins and Tannin-Related Derivatives Enhance the (Pseudo-)Halogenating Activity of Lactoperoxidase.

PubMed

Gau, Jana; Prévost, Martine; Van Antwerpen, Pierre; Sarosi, Menyhárt-Botond; Rodewald, Steffen; Arnhold, Jürgen; Flemmig, Jörg

2017-05-26

Several hydrolyzable tannins, proanthocyanidins, tannin derivatives, and a tannin-rich plant extract of tormentil rhizome were tested for their potential to regenerate the (pseudo-)halogenating activity, i.e., the oxidation of SCN - to hypothiocyanite - OSCN, of lactoperoxidase (LPO) after hydrogen peroxide-mediated enzyme inactivation. Measurements were performed using 5-thio-2-nitrobenzoic acid in the presence of tannins and related substances in order to determine kinetic parameters and to trace the LPO-mediated - OSCN formation. The results were combined with docking studies and molecular orbital analysis. The - OSCN-regenerating effect of tannin derivatives relates well with their binding properties toward LPO as well as their occupied molecular orbitals. Especially simple compounds like ellagic acid or methyl gallate and the complex plant extract were found as potent enzyme-regenerating compounds. As the (pseudo-)halogenating activity of LPO contributes to the maintenance of oral bacterial homeostasis, the results provide new insights into the antibacterial mode of action of tannins and related compounds. Furthermore, chemical properties of the tested compounds that are important for efficient enzyme-substrate interaction and regeneration of the - OSCN formation by LPO were identified.

Directly oxidized chemiluminescence of 2-substituted-4,5-di(2-furyl)-1H -imidazole by acidic potassium permanganate and its analytical application for determination of albumin.

PubMed

Kang, Jing; Zhang, Yumin; Huang, Zhongxiu; Han, Lu; Tang, Jieli; Wang, Shuaijun; Zhang, Yihua

2011-07-01

In the paper, 2,4,5-tri(2-furyl)-1H-imidazole (TFI) and 2-phenyl-4,5-di(2-furyl)-1H-imidazole (PDFI), were chosen to investigate chemiluminescence (CL) properties of 2-substituted-4,5-di(2-furyl)-1H-imidazoles. The directly oxidized CL of analytes by potassium permanganate (KMnO(4)) was in detail studied. The KMnO(4) could directly oxidize TFI/PDFI to produce strong CL emission in acidic solution. The effects of experimental conditions were investigated. Under the optimal conditions, the effect of albumin on the TFI/PDFI-KMnO(4) system was investigated. It was found that the addition of albumin into the system could induce enhancement of CL signal, and the enhanced CL intensity is linearly related to the logarithm of concentration of albumin. Based on this study, a novel CL method has been developed for the determination of albumin with high sensitivity and good selectivity. The method was applied to the determination of albumin in human serum samples, and the results were in agreement with those obtained by the bromcresol green (BCG) method. The relative errors for the analytical results were from -5.8% to 4.2%. These new phenomena would further enable people to exploit more CL analytical application of the heterocyclic imidazole derivatives. © Springer Science+Business Media, LLC 2011

Remarkable effect of halogenation of aromatic compounds on efficiency of nanowire formation through polymerization/crosslinking by high-energy single particle irradiation

NASA Astrophysics Data System (ADS)

Horio, Akifumi; Sakurai, Tsuneaki; Kayama, Kazuto; Lakshmi, G. B. V. S.; Kumar Avasthi, Devesh; Sugimoto, Masaki; Yamaki, Tetsuya; Chiba, Atsuya; Saito, Yuichi; Seki, Shu

2018-01-01

Irradiation of high-energy ion particles on organic films induced solid-state polymerization and crosslinking reactions of the materials along the ion trajectories, resulting in the formation of insoluble uniform nanowires with a precise diameter. The nanowires were isolated by the development process i.e. the irradiated film was immersed in organic solvents, and their morphology was visualized by atomic force microscopy. The target organic materials are 4-vinyltriphenylamine, poly(4-vinyltriphenylamine), and polystyrene derivatives with/without the partial substitutions by halogen atoms. It was found that 4-vinyltriphenylamines, in spite of their small molecular sizes, afforded nanowires more clearly than poly(4-vinyltriphenylamine)s. Moreover, the efficiency of demonstrated polymerization/crosslinking reactions obviously depends on the substituted halogen atom species. The averaged diameters of nanowires from bromo- or iodo- substituted 4-vinyltriphenylamine (9.3 and 9.4 nm, respectively) were larger than that obtained from simple 4-vinyltriphenylamine (6.8 nm). The remarkable effect of halogenation of aromatic compounds on the efficiency of the radiation-induced reactions was also observed for polystyrene derivatives. This contrast was considered to originate from the sum of the efficiency of elementary reactions including dissociative electron attachment.

Characterization, photophysical and DFT calculation study on 2-(2,4-difluorophenyl)-1-(4-methoxyphenyl)-1H-imidazo[4,5-f][1,10]phenanthroline ligand.

PubMed

Jayabharathi, Jayaraman; Thanikachalam, Venugopal; Venkatesh Perumal, Marimuthu

2012-09-01

The synthesized imidazole derivative 2-(2,4-difluorophenyl)-1-(4-methoxyphenyl)-1H-imidazo[4,5-f][1,10] phenanthroline (dfpmpip) has been characterized using IR, mass, (1)H, (13)C NMR and elemental analysis. The photophysical properties of dfpmpip have been studied using UV-visible and fluorescence spectroscopy in different solvents. The solvent effect on the absorption and fluorescence bands has been analyzed by a multi-component linear regression. Theoretically calculated bond lengths, bond angles and dihedral angles are found to be slightly higher than that of X-ray Diffraction (XRD) values of its parent compound. The charge distribution has been calculated from the atomic charges by non-linear optical (NLO) and natural bond orbital (NBO) analysis. Since the synthesized imidazole derivative has the largest μ(g)β(0) value, the reported imidazole can be used as potential NLO material. The energies of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels and the molecular electrostatic potential (MEP) energy surface studies evidenced the existence of intramolecular charge transfer (ICT) within the molecule. Theoretical calculations regarding the chemical potential (μ), hardness (η) and electrophilicity index (ω) have also been calculated. Copyright © 2012 Elsevier B.V. All rights reserved.

Modulation of the fibrillogenesis inhibition properties of two transthyretin ligands by halogenation.

PubMed

Cotrina, Ellen Y; Pinto, Marta; Bosch, Lluís; Vilà, Marta; Blasi, Daniel; Quintana, Jordi; Centeno, Nuria B; Arsequell, Gemma; Planas, Antoni; Valencia, Gregorio

2013-11-27

The amyloidogenic protein transthyretin (TTR) is thought to aggregate into amyloid fibrils by tetramer dissociation which can be inhibited by a number of small molecule compounds. Our analysis of a series of crystallographic protein-inhibitor complexes has shown no clear correlation between the observed molecular interactions and the in vitro activity of the inhibitors. From this analysis, it emerged that halogen bonding (XB) could be mediating some key interactions. Analysis of the halogenated derivatives of two well-known TTR inhibitors has shown that while flufenamic acid affinity for TTR was unchanged by halogenation, diflunisal gradually improves binding up to 1 order of magnitude after iodination through interactions that can be interpreted as a suboptimal XB (carbonyl Thr106: I...O distance 3.96-4.05 Å; C-I...O angle 152-156°) or as rather optimized van der Waals contacts or as a mixture of both. These results illustrate the potential of halogenation strategies in designing and optimizing TTR fibrillogenesis inhibitors.

Structure of five molecular salts assembled from noncovalent associations between organic acids, imidazole, benzimidazole, and 1-(2-(1H-benzimidazol-1-yl)ethyl)-1H-benzimidazole

NASA Astrophysics Data System (ADS)

Chen, Xuchong; Jin, Shouwen; Zhang, Huan; Xiao, Xiao; Liu, Bin; Wang, Daqi

2017-09-01

Cocrystallization of the imidazole derivatives, L1-L3, with a series of organic acids gave a total of five molecular salts with the compositions: (imidazole): (DL-10-camphorsulfonic acid) [(HL1+)·(cpsa-), cpsa- = DL-10-camphorsulfonate] (1), (imidazole): (3,5-dihydroxybenzoic acid) [(HL1+) · (3,5-dba-), 3,5-dba- = 3,5-dihydroxybenzoate] (2), (imidazole): (isophthalic acid): H2O [(HL1)+·(Hmpa)-·H2O, Hmpa- = hydrogenisophthalate] (3), (benzimidazole): (butane-1,2,3,4-tetracarboxylic acid) [(HL2+)·(H3bta -), H3bta- = trihydrogen butane-1,2,3,4-tetracarboxylate] (4), and (benzimidazole)2: 1-(2-(1H-benzimidazol-1-yl)ethyl)-1H-benzimidazole: (5-nitrosalicylic acid)2 [(L2)2·(H2L3)2+·(5-nsa-)2, 5-nsa- = 5-nitrosalicylate], (5). The five salts have been characterized by XRD technique, IR, and EA, and the melting points of all the salts were also reported. And their structural and supramolecular aspects are fully analyzed. The result reveals that among the five investigated crystals the ring N in the imidazole moieties are protonated when the organic acids are ionized, and the crystal packing is interpreted in terms of the strong Nsbnd H⋯O H-bond from the imidazole and the ionized acids. In addition to the Nsbnd H⋯O H-bond, the Osbnd H⋯O H-bonds were also established at the salts 2-5, compound 1 has the additional Nsbnd H⋯S H-bonds. Further analysis of the crystal packing of the salts displayed that a different family of additional CHsbnd O/CH2sbnd O/CH3sbnd O, CHsbnd S, CHsbnd π, NHsbnd π, and πsbnd π associations contribute to the stabilization and expansion of the total 3D framework structures. For the coexistence of the various weak interactions these structures had homo or hetero supramolecular synthons or both. Some classical supramolecular synthons, such as R12(4), R22(7), and R22(8) usually observed in crystals of organic acids with imidazole, were again shown to be involved in constructing most of these hydrogen bonding networks.

[Anti-amebic effect of polyenic antibiotics].

PubMed

Liubimova, L K; Ovnanian, K O; Ivanova, L N

1985-03-01

All-Union Research technological Institute of Antibiotics and Medical Enzymes, Leningrad. Institute of Epidemiology, Virology and medical parasitology, Ministry of Health of the Armenian SSR. The effect of polyenic antibiotics made in the USSR on development of E. histolytica and E. moshkovski was studied. The following antibiotics were used: levorin and its derivatives, mycoheptin, amphotericin B, amphoglucamine and nystatin. The antibiotics were compared with emetine and metronidazole. Some drugs of the imidazole group were also included into the study. On the whole 15 drugs were tested for their antiamebic activity. All the polyenic antibiotics showed a high antiamebic activity. Levorin and its derivatives were the most active. Their MICs ranged from 0.1 to 5.38 micrograms/ml. The most active of the new imidazoles was 100 times less effective than sodium levorin. The studies show that the polyenic antibiotics have an antiamebic activity and a broad antiprotozoal spectrum.

A new fluorogenic sensing platform for salicylic acid derivatives based on π-π and NH-π interactions between electron-deficient and electron-rich aromatics.

PubMed

Pandith, Anup; Hazra, Giridhari; Kim, Hong-Seok

2017-05-05

A novel simple fluorescent probe was designed for the recognition of electron-rich salicylic acid derivatives (SAs). The imidazole-appended aminomethyl perylene probe 1 selectively differentiated between electron-rich amino-SAs and electron-deficient nitro-SAs in EtOH, exhibiting the highest selectivity and sensitivity toward 5-aminosalicylic acid (5-ASA) and showing strong 1:1 binding (K a =1.37×10 7 M -1 ). This high selectivity and sensitivity resulted from the synergistic multiple hydrogen bonding interactions of secondary amine and imidazole units and π-π interactions between electron-rich and electron-deficient rings, along with the unusual NH-π interactions between 5-ASA and the perylene moiety of 1. The limit of detection (LOD) for 5-ASA in EtOH was 0.012ppb. Copyright © 2017 Elsevier B.V. All rights reserved.

Formation and antimicrobial activity of complexes of beta-cyclodextrin and some antimycotic imidazole derivatives.

PubMed

Van Doorne, H; Bosch, E H; Lerk, C F

1988-04-22

Complex formation between beta-cyclodextrin and six antimycotic imidazole derivatives has been studied. The solubility of all drugs was increased in the presence of beta-cyclodextrin. The smallest increase (approx. 5-fold) was observed for miconazol, and the largest increase (approx. 160-fold) was observed for bifonazol. Apparent 1:1-complex constants were measured and found to decrease in the order: bifonazol greater than ketoconazol greater than tioconazol greater than miconazol greater than itraconazol greater than clotrimazol. The complexes appeared to possess a low, if any, antimicrobial activity. Measurement of inhibition zone sizes, with four test organisms was used to study the release of the antimycotic drugs from topical preparations. The antimycotic drugs were more readily released from topical preparations containing beta-cyclodextrin than from the same vehicles without beta-cyclodextrin. The rationale of beta-cyclodextrin addition to antimycotic topical preparations is discussed.

Synthesis and biological evaluation of new 2-(4,5-dihydro-1H-imidazol-2-yl)-3,4-dihydro-2H-1,4-benzoxazine derivatives.

PubMed

Touzeau, Frédérique; Arrault, Axelle; Guillaumet, Gérald; Scalbert, Elizabeth; Pfeiffer, Bruno; Rettori, Marie-Claire; Renard, Pierre; Mérour, Jean-Yves

2003-05-08

2-(4,5-Dihydro-1H-imidazol-2-yl)-3,4-dihydro-2H-1,4-benzoxazine derivatives and tricyclic analogues with a fused additional ring on the nitrogen atom of the benzoxazine moiety have been prepared and evaluated for their cardiovascular effects as potential antihypertensive agents. The imidazoline ring was generated by reaction of the corresponding ethyl ester with ethylenediamine. Affinities for imidazoline binding sites (IBS) I(1) and I(2) and alpha(1) and alpha(2) adrenergic receptors were evaluated as well as the effects on mean arterial blood pressure (MAP) and heart rate (HR) of spontaneously hypertensive rats. With few exceptions the most active compounds on MAP were those with high affinities for IBS and alpha(2) receptor. Among these, compound 4h was the most interesting and is now, together with its enantiomers, under complementary pharmacological evaluation.

Novel Halogenated Pyrazine-Based Chalcones as Potential Antimicrobial Drugs.

PubMed

Kucerova-Chlupacova, Marta; Vyskovska-Tyllova, Veronika; Richterova-Finkova, Lenka; Kunes, Jiri; Buchta, Vladimir; Vejsova, Marcela; Paterova, Pavla; Semelkova, Lucia; Jandourek, Ondrej; Opletalova, Veronika

2016-10-27

Chalcones, i.e., compounds with the chemical pattern of 1,3-diphenylprop-2-en-1-ones, exert a wide range of bio-activities, e.g., antioxidant, anti-inflammatory, anticancer, anti-infective etc. Our research group has been focused on pyrazine analogues of chalcones; several series have been synthesized and tested in vitro on antifungal and antimycobacterial activity. The highest potency was exhibited by derivatives with electron withdrawing groups (EWG) in positions 2 and 4 of the ring B. As halogens also have electron withdrawing properties, novel halogenated derivatives were prepared by Claisen-Schmidt condensation. All compounds were submitted for evaluation of their antifungal and antibacterial activity, including their antimycobacterial effect. In the antifungal assay against eight strains of selected fungi, growth inhibition of Candida glabrata and Trichophyton interdigitale (formerly T. mentagrophytes ) was shown by non-alkylated derivatives with 2-bromo or 2-chloro substitution. In the panel of selected bacteria, 2-chloro derivatives showed the highest inhibitory effect on Staphylococcus sp. In addition, all products were also screened for their antimycobacterial activity against Mycobacterium tuberculosis H37RV My 331/88, M. kansasii My 235/80, M. avium 152/80 and M. smegmatis CCM 4622. Some of the examined compounds, inhibited growth of M. kansasii and M. smegmatis with minimum inhibitory concentrations (MICs) comparable with those of isoniazid.

Studies on the synthesis, spectroscopic analysis, molecular docking and DFT calculations on 1-hydroxy-2-(4-hydroxyphenyl)-4,5-dimethyl-imidazol 3-oxide

NASA Astrophysics Data System (ADS)

Benzon, K. B.; Sheena, Mary Y.; Panicker, C. Yohannan; Armaković, Stevan; Armaković, Sanja J.; Pradhan, Kiran; Nanda, Ashis Kumar; Van Alsenoy, C.

2017-02-01

In this work we have investigated in details the spectroscopic and reactive properties of newly synthesized imidazole derivative, namely the 1-hydroxy-2-(4-hydroxyphenyl)-4,5-dimethyl-imidazole 3-oxide (HHPDI). FT-IR and NMR spectra were measured and compared with theoretically obtained data provided by calculations of potential energy distribution and chemical shifts, respectively. Insight into the global reactivity properties has been obtained by analysis of frontier molecular orbitals, while local reactivity properties have been investigated by analysis of charge distribution, ionization energies and Fukui functions. NBO analysis was also employed to understand the stability of molecule, while hyperpolarizability has been calculated in order to assess the nonlinear optical properties of title molecule. Sensitivity towards autoxidation and hydrolysis mechanisms has been investigated by calculations of bond dissociation energies and radial distribution functions, respectively. Molecular docking study was also performed, in order to determine the pharmaceutical potential of the investigated molecule.

Imidazole incorporated semicarbazone derivatives as a new class of anticonvulsants: design, synthesis and in-vivo screening.

PubMed

Amir, Mohammad; Ali, Israr; Hassan, Mohd Zaheen

2013-06-01

A series of novel imidazole incorporated semicarbazones was synthesized using an appropriate synthetic route and characterized by spectral analysis (IR, 1H NMR, 13C NMR and Mass). The anticonvulsant activity of the synthesized compounds was determined using doses of 30, 100, and 300 mg kg-1 against maximal electroshock seizure (MES), subcutaneous pentylenetetrazole (scPTZ) induced seizure and minimal neurotoxicity test. Six compounds exhibited protection in both models and 2-(1-(4-chlorophenyl)-2-(1H-imidazol-1-yl)ethylidene)-N-p-tolylsemicarbazone emerged as the most active compound of the series without any neurotoxicity and significant CNS depressant effect. Liver enzyme estimations (SGOT, SGPT, Alkaline phosphatase) of the compound also showed no significant change in the enzymes levels. Moreover, it caused 80% elevation of γ-amino butyric acid (GABA) levels in the whole mice brain, thus indicating that it could be a promising candidate in designing of a potent anticonvulsant drug.

A Survey of Electron Impact Cross-Sections for Halogens and Halogen Compounds of Interest to Plasma Processing

NASA Technical Reports Server (NTRS)

Sharma, S. P.; Rao, M. V. V. S.; Arnold, James O. (Technical Monitor)

1998-01-01

Published electron impact cross section data on halogens Cl2, F2, and halogen containing compounds such as Cx Fy, HCl, Cx Cly Fz are reviewed and critically evaluated based on the information provided by various researchers. The present work reports data on electron impact excitation, ionization, dissociation, electron attachment, electron detachment, and photo detachment. Elastic scattering cross sections and data on bulk properties such as diffusion coefficients in various background gases are also evaluated. Since some of the cross sectional data is derived from indirect measurements such as drift velocity, care has been taken to reconcile the differences among the reported data with due attention to the measurement technique. In conclusion, the processes with no or very limited amount of data and questionable set of data are identified and recommendation for further research direction is made.

Synthesis and biological evaluation of 2-arylimino-3-pyridin-thiazolineone derivatives as antibacterial agents.

PubMed

Cai, Ming-Guang; Wu, Yang; Chang, Jun

2016-05-15

With an intention to find more potent antibacterial agents, four halogen disubstituted thiazolineone derivatives (2a-d), five halogen monosubstituted thiazolineone derivatives (2e-i), and eleven 2-arylimino-3-pyridin-thiazolineone derivatives (2j-t) were synthesized and screened for their antibacterial activity, bactericidal activity, cytotoxicity, and erythrocyte hemolysis. Most of the synthesized derivatives showed antibacterial activity in inhibiting the growth of S. epidermidis and MRSA, and exhibited safety in the cytotoxicity study on the Vero cells and hemolytic activities test on healthy human erythrocytes. 2-Arylimino-3-pyridin-thiazolineone derivatives not only improved the clog P, but also showed potent antibacterial activity in inhibiting the growth of S. epidermidis and MRSA. In particularly, several compounds (2f, 2i, 2r and 2t) showed bactericidal activity, in which compound 2r displayed the best inhibitory capacity among the synthesized compounds, and further druggability research is on going. Copyright © 2016 Elsevier Ltd. All rights reserved.

Some reactions of the hydroxyl adduct of adenine

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

Vanhemmen, J.J.

1975-01-01

The chemical reactions of purine derivatives resulting from pulse radiolysis were studied. Some reactions of the hydroxyl adduct of adenine are described and one of these reactions was compared with similar reactions of hydroxyl adducts of other purine derivatives. Evidence is given that in various purines opening of the imidazole ring is due to unimolecular rearrangements of the hydroxyl adducts. (GRA)

Synthesis and anthelmintic activity of arctigenin derivatives against Dactylogyrus intermedius in goldfish.

PubMed

Hu, Yang; Liu, Lei; Liu, Guang-Lu; Tu, Xiao; Wang, Gao-Xue; Ling, Fei

2017-08-01

To control the parasitic disease of Dactylogyrus intermedius, a series of new arctigenin derivatives were designed, synthesized and tested in our study. The anthelmintic activity of most of the derivatives ranged from 1 to 10mg/L. Compared to traditional drug praziquantel (EC 50 =2.69mg/L), ether derivatives 2g and 2h exhibited slightly higher anti-parasitic activity, with the EC 50 values of 2.48 and 1.52mg/L, respectively. Furthermore, the arctigenin-imidazole hybrids 4a and 4b also removed D. intermedius effectively, with the EC 50 values of 2.13 and 2.07mg/L, respectively. The structure-activity relationship analysis indicated that four carbon atoms length of linker and imidazole substitute group could significantly increase the anthelmintic activity, and reduced the toxicity. Through the scanning electron microscope observation, compounds 4a and 4b caused the D. intermedius tegumental damage such as intensive wrinkles, holes and nodular structures. Overall, the structural optimization analysis of arctigenin suggested that 4a and 4b can be used for preventing and controlling Dactylogyrus infections and considered as promising lead compounds for the development of commercial drugs. Copyright © 2017 Elsevier Ltd. All rights reserved.

Spectroscopic study of 2-, 4- and 5-substituents on p Ka values of imidazole heterocycles prone to intramolecular proton-electrons transfer

NASA Astrophysics Data System (ADS)

Eseola, Abiodun O.; Obi-Egbedi, Nelson O.

2010-02-01

New 2-(1H-imidazol-2-yl)phenols ( L1Et- L8tBuPt) bearing a phenolic proton in the vicinity of the imidazole base were prepared and characterized. Experimental studies of the dependence of their protonation/deprotonation equilibrium on substituent identities and intramolecular hydrogen bonding tendencies were carried out using electronic absorption spectroscopy at varying pH values. In order to make comparison, 2-(anthracen-10-yl)-4,5-diphenyl-1H-imidazole ( L9Anthr) bearing no phenolic proton and 4,5-diphenyl-2-(4,5-diphenyl-1H-imidazol-2-yl)-1H-imidazole ( L10BisIm) bearing two symmetrical imidazole base fragments were also prepared and experimentally investigated. DFT calculations were carried out to study frontier orbitals of the investigated molecules. While electron-releasing substituents produced increase in protonation-deprotonation p Kas for the hydroxyl group, values for the imidazole base were mainly affected by polarization of the imidazole ring aromaticity across the 2-imidazole carbon and the 4,5-imidazole carbons axis of the imidazole ring. It was concluded that electron-releasing substituents on the phenol ring and/or electron-withdrawing substituents on 4,5-imidazole carbons negatively affects donor strengths/coordination chemistries of 2-(1H-imidazol-2-yl)phenols, and vice versa. Change of substituents on the phenol ring significantly altered the donor strength of the imidazole base. The understanding of p Ka variation on account of electronic effects of substituents in this work should aid the understanding of biochemical properties and substituent environments of imidazole-containing biomacromolecules.

Dehalogenases: From Improved Performance to Potential Microbial Dehalogenation Applications.

PubMed

Ang, Thiau-Fu; Maiangwa, Jonathan; Salleh, Abu Bakar; Normi, Yahaya M; Leow, Thean Chor

2018-05-07

The variety of halogenated substances and their derivatives widely used as pesticides, herbicides and other industrial products is of great concern due to the hazardous nature of these compounds owing to their toxicity, and persistent environmental pollution. Therefore, from the viewpoint of environmental technology, the need for environmentally relevant enzymes involved in biodegradation of these pollutants has received a great boost. One result of this great deal of attention has been the identification of environmentally relevant bacteria that produce hydrolytic dehalogenases—key enzymes which are considered cost-effective and eco-friendly in the removal and detoxification of these pollutants. These group of enzymes catalyzing the cleavage of the carbon-halogen bond of organohalogen compounds have potential applications in the chemical industry and bioremediation. The dehalogenases make use of fundamentally different strategies with a common mechanism to cleave carbon-halogen bonds whereby, an active-site carboxylate group attacks the substrate C atom bound to the halogen atom to form an ester intermediate and a halide ion with subsequent hydrolysis of the intermediate. Structurally, these dehalogenases have been characterized and shown to use substitution mechanisms that proceed via a covalent aspartyl intermediate. More so, the widest dehalogenation spectrum of electron acceptors tested with bacterial strains which could dehalogenate recalcitrant organohalides has further proven the versatility of bacterial dehalogenators to be considered when determining the fate of halogenated organics at contaminated sites. In this review, the general features of most widely studied bacterial dehalogenases, their structural properties, basis of the degradation of organohalides and their derivatives and how they have been improved for various applications is discussed.

OH Radical Reactions with Nitroimidazole and Nitrotriazole Derivatives

NASA Astrophysics Data System (ADS)

Gümüş, Selçuk

2012-04-01

The reactions between hydroxyl radical and 5-nitro-1H-imidazole (A), 2-nitro-1H-imidazole (B), and 3-nitro-4H-1,2,4-triazole (C) were theoretically investigated using B3LYP/6-31G(d,p) level of theory. The OH radical additions to double bonds were explored in bulk solvent (water). The data presented show that the barriers to reaction were very low, 3-7 kcal/mol, indicating fast reactions. Thermodynamically, OH addition to position 2 of structure A leads to the most stable radical product. The main geometrical parameters are reported for reactants, transition states, and radical products together with some energetic data of the nitro-imidazolone-type final compounds.

A facile approach towards increasing the nitrogen-content in nitrogen-doped carbon nanotubes via halogenated catalysts

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

Ombaka, L.M.; Ndungu, P.G.; Department of Applied Chemistry, Doornfontein Campus, University of Johannesburg, P.O. Box 17011, Johannesburg 2028

Nitrogen-doped carbon nanotubes (N-CNTs) have been synthesized at 850 °C via a CVD deposition technique by use of three ferrocenyl derivative catalysts, i.e. para-CN, -CF{sub 3} and -Cl substituted-phenyl rings. The synthesized catalysts have been characterized by NMR, IR, HR-MS and XRD. The XRD analysis of the para-CF{sub 3} catalyst indicates that steric factors influence the X-ray structure of 1,1′-ferrocenylphenyldiacrylonitriles. Acetonitrile or pyridine was used as carbon and nitrogen sources to yield mixtures of N-CNTs and carbon spheres (CS). The N-CNTs obtained from the para-CF{sub 3} catalysts, in pyridine, have the highest nitrogen-doping level, show a helical morphology and aremore » less thermally stable compared with those synthesized by use of the para-CN and -Cl as catalyst. This suggests that fluorine heteroatoms enhance nitrogen-doping in N-CNTs and formation of helical-N-CNTs (H-N-CNTs). The para-CF{sub 3} and para-Cl catalysts in acetonitrile yielded iron-filled N-CNTs, indicating that halogens promote encapsulation of iron into the cavity of N-CNT. The use of acetonitrile, as carbon and nitrogen source, with the para-CN and -Cl as catalysts also yielded a mixture of N-CNTs and carbon nanofibres (CNFs), with less abundance of CNFs in the products obtained using para-Cl catalysts. However, para-CF{sub 3} catalyst in acetonitrile gave N-CNTs as the only shaped carbon nanomaterials. - Graphical abstract: Graphical abstract showing the synthesis of N-CNTs using halogenated-ferrocenyl derivatives as catalyst with pyridine or acetonitrile as nitrogen and carbon sources via the chemical vapour deposition technique. - Highlights: • N-CNTs were synthesized from halogenated ferrocenyl catalysts. • Halogenated catalysts promote nitrogen-doping and pyridinic nitrogen in N-CNTs. • Halogenated catalysts facilitate iron filling of N-CNTs.« less

Important role of phosphoramido linkage in imidazole-based dioleyl helper lipids for liposome stability and primary cell transfection.

PubMed

Mével, Mathieu; Haudebourg, Thomas; Colombani, Thibault; Peuziat, Pauline; Dallet, Laurence; Chatin, Benoît; Lambert, Olivier; Berchel, Mathieu; Montier, Tristan; Jaffrès, Paul-Alain; Lehn, Pierre; Pitard, Bruno

2016-01-01

To optimize synthetic gene delivery systems, there is a need to develop more efficient lipid formulations. Most cationic lipid formulations contain 'helper' neutral lipids because of their ability to increase DNA delivery, in particular by improving endosomal escape of DNA molecules via the pH-buffering effect of protonatable groups and/or fusion with the lipid bilayer of endosomes. We evaluated the influence of the linker structure between the two oleyl chains in the helper lipid on transfection efficiency in cell lines, as well as in primary cells (hepatocytes/cardiomyocytes). We reported the synthesis of two new pH-buffering imidazole helper lipids characterized by a polar headgroup containing one (compound 6) or two (compound 5) imidazole groups and two oleyl chains linked by an amide group. We studied their association with the aminoglycoside lipidic derivative dioleylsuccinylparomomycin (DOSP), which contains two oleyl chains linked to the aminoglycoside polar headgroup via an amide function. We compared the morphology and transfection properties of such binary liposomes of DOSP/5 and DOSP/6 with those of liposomes combining DOSP with another imidazole-based dioleyl helper lipid (MM27) in which a phosphoramido group acts as a linker between the two oleyl chains and imidazole function. The phosphoramido linker in the helper lipid induces a major difference in terms of morphology and resistance to decomplexation at physical pH for DOSP/helper lipid complexes. This hybrid dioleyl linker composition of DOSP/MM27 led to higher transfection efficiency in cell lines and in primary cells compared to complexes with homogeneous dioleyl linker. Copyright © 2015 John Wiley & Sons, Ltd.

Halogens, Barium and Uranium in Mantle Fluid Inclusions

NASA Astrophysics Data System (ADS)

Villa, I. M.; Peverelli, V.; Oglialoro, E.; Pettke, D. T.; Frezzotti, M. L.

2016-12-01

Halogens are an underexplored geochemical marker. A way to measure halogens at ng/g levels is measuring Ar, Kr and Xe in irradiated samples [1,2]. We derive absolute halogen amounts from rare gas amounts via scapolite monitor SY [2]. Kr-Xe systematics also yield Ba and U concentrations. We combined irradiation with stepheating on carbonate-sulfate-rich fluid inclusions (FI)-bearing xe­no­liths from El Hierro, Canarias: spinel harzburgite XML-7 and spinel dunite XML-1 [3]. Three components are recognized in the rare gas release. (1) Atmospheric surface contamination occurs up to 1000 °C. (2) FI decrepitation by laboratory heating occurs above 1200 °C [4], corresponding to the release of 80,82Kr and 128Xe in the 1200 and 1400 °C steps. Br whole-rock concentrations are 3-8 ng/g; the molar Br/Cl and I/Cl ratios in the harzburgite FI, 9 E-4 resp. 2 E-4, are identical to those in the dunite FI. This sets the halogens in our FI apart from MORB [2]. Halogen-derived rare gases are closely associated to artificial 131Xe from Ba; Ba has a high affinity of for CO2-rich fluids. Daughter minerals in multiphase FI were identified by Raman micro­spectroscopy [4]. The calculated Ba concentrations are 2-6 µg/g. (3) The third component is U-derived 134,136Xe and 86Kr released in a spike at 1000 °C, decoupled from FI. This requires a different carrier than FI, e.g. Ti oxides. As U concentrations are 10-20 pg/g, the U-bearing phase needs to be below a ppm, invisible by petro­graphy. The 136Xe/134Xe ratio > 1 suggests retention of radio­genic Xe. However, analysis of an unirradiated sample detected no radiogenic Xe. It is likely that Xe-U produced in the core of the McMaster reactor (thermal, epithermal and fast neutrons) has a different isotopic composition from that in textbooks, as proposed by [2].[1] Jeffery & Reynolds (1961) J.Geophys. Res. 66, 3582 [2] Kendrick (2012) Chem. Geol. 292, 116 [3] Oglialoro et al (2015) AGU Fall Meeting abstract V21C-3046 [4] Roedder (1965) Am. Min. 50, 1746

Discovery, SAR, and Radiolabeling of Halogenated Benzimidazole Carboxamide Antagonists as Useful Tools for (alpha)4(beta)1 Integrin Expressed on T- and B-cell Lymphomas

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

Carpenter, R D; Natarajan, A; Lau, E Y

2010-02-08

The cell surface receptor {alpha}{sub 4}{beta}{sub 1} integrin is an attractive yet poorly understood target for selective diagnosis and treatment of T- and B-cell lymphomas. This report focuses on the rapid microwave preparation of medicinally pertinent benzimidazole heterocycles, structure-activity relationships (SAR) of novel halobenzimidazole carboxamide antagonists 3-6, and preliminary biological evaluation of radioiodinated agents 7, 8, and 18. The I-125 derivative 18 had good tumor uptake (12 {+-} 1% ID/g at 24 h; 4.5 {+-} 1% ID/g at 48 h) and tumor:kidney ratio ({approx}4:1 at 24 h; 2.5:1 at 48 h) in xenograft murine models of B-cell lymphoma. Molecular homologymore » models of {alpha}{sub 4}{beta}{sub 1} integrin have predicted that docked halobenzimidazole carboxamides have the halogen atom in a suitable orientation for halogen-hydrogen bonding. These high affinity ({approx} pM binding) halogenated ligands are attractive tools for medicinal and biological use; the fluoro and iodo derivatives are potential radiodiagnostic ({sup 18}F) or radiotherapeutic ({sup 131}I) agents, whereas the chloro and bromo analogues could provide structural insight into integrin-ligand interactions through photoaffinity cross-linking/mass spectroscopy experiments, as well as co-crystallization X-ray studies.« less

Syntheses and structure characterization of ten acid-base hybrid crystals based on imidazole derivatives and mineral acids

NASA Astrophysics Data System (ADS)

Hu, Kaikai; Deng, Bowen; Jin, Shouwen; Ding, Aihua; Jin, Shide; Zhu, Jin; Zhang, Huan; Wang, Daqi

2018-04-01

Cocrystallization of the imidazole derivatives with a series of mineral acids gave a total of ten hybrid salts with the compositions: [(H2bzm)(Cl)2·3H2O] (1), [(H2bzm)(ClO4)2] (2), [(H2bze)(Cl)2·2H2O] (3), [(H2bze)(Br)2·2H2O] (4), [(H2bzp)(Cl)2·4H2O] (5), [(H2bzp)(Br)2·4H2O] (6), (2-(imidazol-1-yl)-1-phenylethanone): (phosphoric acid) [(Himpeta)+(H2PO4)-] (7), [(H2impd)(Br)2] (8), [(H2impd)(ClO4)2] (9), and [(Hbzml)(Cl)] (10). The ten salts have been characterised by X-ray diffraction analysis, IR, and elemental analysis, and the melting points of all the salts were also reported. And their structural and supramolecular aspects are fully analyzed. The result reveals that among the ten investigated crystals the ring N atoms of the imidazole are protonated when the acids are deprotonated, and the crystal packing is interpreted in terms of the strong charge-assisted classical H-bonds between the NH+ and deprotonated acidic groups. Further analysis of the crystal packing of the salts indicated that a different set of additional CHsbnd O, CH2sbnd O, CHsbnd Cl, CH2sbnd Cl, CHsbnd N, CHsbnd Br, CH2sbnd Br, Osbnd O, O-π, Br-π, CH-π, and π-π associations contribute to the stabilization and expansion of the total high-dimensional frameworks. For the coexistence of the various weak nonbonding interactions these structures adopted homo or hetero supramolecular synthons or both. Some classical supramolecular synthons, such as R21(7), R22(7), R22(8), and R42(8), usually observed in the organic solids, were again shown to be involved in constructing some of these H-bonding networks.

Effect of leaving group on the oligomerization of 5'-AMP on montmorillonite. [Abstract only

NASA Technical Reports Server (NTRS)

Prabahar, K. Joseph; Ferris, James P.

1994-01-01

The oligomerization of imidazole derivative of 5'-AMP (ImpA) in the presence of montmorillonite clay yields oligomers containing up to 10 monomer units. In these reactions, the heterocyclic base, imidazole is the leaving group. In our present study, we synthesized a series of activated nucleotides of 5'AMP using other leaving groups such as pyrazole, 1,2,4-triazole, piperidine, morpholine, 4-aminopyridine, 4-methylaminopyridine, 4-dimethylaminopyridine, 2-aminobenzimidazole etc. to determine the effect of amine leaving group on the products of the oligomerization reaction. Earlier results from our laboratory showed that the presence AppA in the clay reaction of ImpA enhances the oligomerization reaction to yield higher oligomers. We also studied the effect of AppA in the clay mediated oligomerization reaction of the activated nucleotides. Oligomerization of 2-amino-benzimidazole derivative of 5'-AMP gave higher oligomers containing up to nine monomer units in the presence of AppA.

Partition coefficients of some purine derivatives and its application to pharmacokinetics.

PubMed

Chrzanowska, M; Sobiak, J; Kuehn, M; Dorawa, E; Hermann, T

2009-12-01

Metazathioprine (MAZA), a methylated derivative of azathioprine (AZA), demonstrated the greatest values of apparent and specific partition coefficients in n-octanol/phosphate buffer at pH 5.7 and pH 7.4 among purine derivatives such as 6-mercaptopurine (6-MP), 6-thioguanine (6-TG) and AZA. Introduction of a methyl group into the imidazole ring of AZA increases lipophilic properties of MAZA compared to AZA. Mass balance of purine derivatives in n-octanol and in phosphate buffer indicated their chemical stability in those media.

Photolytic dehalogenation of disinfection byproducts in water by natural sunlight irradiation.

PubMed

Abusallout, Ibrahim; Hua, Guanghui

2016-09-01

The aqueous photolysis of halogenated disinfection byproducts (DBPs) by natural sunlight irradiation was studied to determine their photolytic dehalogenation kinetics. Total organic halogen analysis was used to quantify the dehalogenation extents of DBPs during outdoor photolysis experiments. Dichloroacetamide, chloral hydrate, chloroform, dichloroacetonitrile, monochloro-, monobromo-, dichloro-, dibromo-, and trichloroacetic acids were generally resistant to photolytic dehalogenation and showed less than 10% reduction after 6 h sunlight irradiation. Monoiodoacetic acid, tribromoacetic acid, bromoform, dibromoacetonitrile, and trichloronitromethane showed moderate to high dehalogenation degrees with half-lives of 4.0-19.3 h. Diiodoacetic acid, triiodoacetic acid, and iodoform degraded rapidly under the sunlight irradiation and exhibited half-lives of 5.3-10.2 min. In general, the photosensitive cleavage of carbon-halogen bonds of DBPs increased with increasing number of halogens (tri- > di- > mono-halogenated) and size of the substituted halogens (I > Br > Cl). Nitrate, nitrite, and pH had little impact on the photodehalogenation of DBPs under typical levels in surface waters. The presence of natural organic matter (NOM) inhibited the photodehalogenation of DBPs by light screening. The NOM inhibiting effects were more pronounced for the fast degrading iodinated DBPs. The results of this study improve our understanding about the photolytic dehalogenation of wastewater-derived DBPs in surface waters during water reuse. Published by Elsevier Ltd.

Structure and biocatalytic scope of thermophilic flavin-dependent halogenase and flavin reductase enzymes.

PubMed

Menon, Binuraj R K; Latham, Jonathan; Dunstan, Mark S; Brandenburger, Eileen; Klemstein, Ulrike; Leys, David; Karthikeyan, Chinnan; Greaney, Michael F; Shepherd, Sarah A; Micklefield, Jason

2016-10-04

Flavin-dependent halogenase (Fl-Hal) enzymes have been shown to halogenate a range of synthetic as well as natural aromatic compounds. The exquisite regioselectively of Fl-Hal enzymes can provide halogenated building blocks which are inaccessible using standard halogenation chemistries. Consequently, Fl-Hal are potentially useful biocatalysts for the chemoenzymatic synthesis of pharmaceuticals and other valuable products, which are derived from haloaromatic precursors. However, the application of Fl-Hal enzymes, in vitro, has been hampered by their poor catalytic activity and lack of stability. To overcome these issues, we identified a thermophilic tryptophan halogenase (Th-Hal), which has significantly improved catalytic activity and stability, compared with other Fl-Hal characterised to date. When used in combination with a thermostable flavin reductase, Th-Hal can efficiently halogenate a number of aromatic substrates. X-ray crystal structures of Th-Hal, and the reductase partner (Th-Fre), provide insights into the factors that contribute to enzyme stability, which could guide the discovery and engineering of more robust and productive halogenase biocatalysts.

Regional atmospheric emissions determined from measurements at Jeju Island, Korea: Halogenated compounds from China

NASA Astrophysics Data System (ADS)

Kim, Jooil; Li, Shanlan; Kim, Kyung-Ryul; Stohl, Andreas; Mühle, Jens; Kim, Seung-Kyu; Park, Mi-Kyung; Kang, Dong-Jin; Lee, Gangwoong; Harth, Christina M.; Salameh, Peter K.; Weiss, Ray F.

2010-06-01

High-frequency in-situ measurements of a wide range of halogenated compounds including chlorofluorocarbons (CFCs), halons, hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), perfluorinated compounds (PFCs), sulfur hexafluoride (SF6), and other chlorinated and brominated compounds have been made at Gosan (Jeju Island, Korea). Regional emissions of HCFC-22 (CHClF2) calculated from inverse modeling were combined with interspecies correlation methods to estimate national emissions for China, a major emitter of industrial halogenated gases. Our results confirm the signs of successful phase-out of primary ozone-depleting species such as CFCs, halons and many chlorinated or brominated compounds, along with substantial emissions of replacement HCFCs. Emissions derived for HFCs, PFCs, and SF6 were compared to published estimates and found to be a significant fraction of global totals. Overall, Chinese emissions of the halogenated compounds discussed here represent 19(14-17)% and 20(15-26)% of global emissions when evaluated in terms of their Ozone Depletion Potentials and 100-year Global Warming Potentials, respectively.

Aminopiperidine-Fused Imidazoles as Dipeptidyl Peptidase-IV Inhibitors

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

Edmondson, S.; Mastracchio, A; Cox, J

2009-01-01

A new series of DPP-4 inhibitors derived from piperidine-fused benzimidazoles and imidazopyridines is described. Optimization of this class of DPP-4 inhibitors led to the discovery of imidazopyridine 34. The potency, selectivity, cross-species DMPK profiles, and in vivo efficacy of 34 is reported.

pH-Dependent Optical Properties of Synthetic Fluorescent Imidazoles

PubMed Central

Berezin, Mikhail Y.; Kao, Jeff; Achilefu, Samuel

2010-01-01

An imidazole moiety is often found as an integral part of fluorophores in a variety of fluorescent proteins and many such proteins possess pH dependent light emission. In contrast, synthetic fluorescent compounds with incorporated imidazoles are rare and have not been studied as pH probes. In this report, the richness of imidazole optical properties, including pH sensitivity, was demonstrated via a novel imidazole-based fluorophore 1H-imidazol-5-yl-vinyl-benz[e]indolium. Three species corresponding to protonated, neutral and deprotonated imidazoles were identified in the broad range of pH 1-12. The absorption and emission bands of each species were assigned by comparative spectral analysis with synthesized mono- and di-N-methylated fluorescent imidazole analogues. pKa analysis in the ground and the excited states showed photoacidic properties of the fluorescent imidazoles due to the excited state proton transfer (ESPT). This effect was negligible for substituted imidazoles. The assessment of a pH sensitive center in the imidazole ring revealed the switching of the pH sensitive centers from 1-N in the ground state to 3-N in the excited state. The effect was attributed to the unique kind of the excited state charge transfer (ESCT) resulting in a positive charge swapping between two nitrogens. PMID:19212987

Metronidazole within phosphatidylcholine lipid membranes: new insights to improve the design of imidazole derivatives.

PubMed

Lopes-de-Campos, Daniela; Nunes, Cláudia; Sarmento, Bruno; Jakobtorweihen, Sven; Reis, Salette

2018-05-30

Metronidazole is a benzimidazole derivative with antibacterial and antiprotozoal activity. Despite its therapeutic efficacy, several studies have been developing new imidazole derivatives with lower toxicity. Considering that drug-membrane interactions are key factors for drugs pharmacokinetic and pharmacodynamic properties, the aim of this work is to provide new insights into the structure-toxicity relationships of metronidazole within phosphatidylcholine membranes. For that purpose, lipid membrane models (liposomes and monolayers) composed of dipalmitoylphosphatidylcholine were used. Experimental techniques (determination of partition coefficients and Langmuir isotherm measurements) were combined with molecular dynamics simulations. Different pHs and lipid phases were evaluated to enable a better extrapolation for in vivo conditions. The partition of metronidazole depends on the pH and on the biphasic system (octanol/water or DPPC/water system). At pH 1.2, metronidazole is hydrophilic. At pH 7.4, metronidazole disturbs the order and the packing of phospholipids. For this toxic effect, the hydroxyl group of the side chain of metronidazole is a key by interacting with the water embedded in the membrane and with the phosphate group and the apolar chains of phospholipids. Copyright © 2018. Published by Elsevier B.V.

Imidazole-containing phthalazine derivatives inhibit Fe-SOD performance in Leishmania species and are active in vitro against visceral and mucosal leishmaniasis.

PubMed

Sánchez-Moreno, M; Gómez-Contreras, F; Navarro, P; Marín, C; Ramírez-Macías, I; Rosales, M J; Campayo, L; Cano, C; Sanz, A M; Yunta, M J R

2015-07-01

The in vitro leishmanicidal activity of a series of imidazole-containing phthalazine derivatives 1-4 was tested on Leishmania infantum, Leishmania braziliensis and Leishmania donovani parasites, and their cytotoxicity on J774·2 macrophage cells was also measured. All compounds tested showed selectivity indexes higher than that of the reference drug glucantime for the three Leishmania species, and the less bulky monoalkylamino substituted derivatives 2 and 4 were clearly more effective than their bisalkylamino substituted counterparts 1 and 3. Both infection rate measures and ultrastructural alterations studies confirmed that 2 and 4 were highly leishmanicidal and induced extensive parasite cell damage. Modifications to the excretion products of parasites treated with 2 and 4 were also consistent with substantial cytoplasmic alterations. On the other hand, the most active compounds 2 and 4 were potent inhibitors of iron superoxide dismutase enzyme (Fe-SOD) in the three species considered, whereas their impact on human CuZn-SOD was low. Molecular modelling suggests that 2 and 4 could deactivate Fe-SOD due to a sterically favoured enhanced ability to interact with the H-bonding net that supports the antioxidant features of the enzyme.

Halogen atom effect on the photophysical properties of substituted aza-BODIPY derivatives.

PubMed

De Simone, B C; Mazzone, G; Pirillo, J; Russo, N; Sicilia, E

2017-01-18

The influence of halogen atom substitution (Br and I), in different amounts and positions in an aza-BODIPY skeleton, on the photophysical properties of some aza-BODIPY derivatives has been investigated by using density functional theory and its time-dependent extension. The heavy atom effect on excitation energies, singlet-triplet energy gaps and spin-orbit matrix elements has been considered. The maximum absorption within the therapeutic window has been confirmed for all the aza-BODIPY derivatives. The feasible intersystem spin crossing pathways for the population of the lowest triplet state, that will depend on the values of the spin-orbit matrix elements, the energy gap as well as the orbital composition of the involved states have been found to most likely involve the S 1 and T 1 or T 2 states. The outcomes of computations support the potential therapeutic use of these compounds as photosensitizers in photodynamic therapy.

First Quantification of Imidazoles in Ambient Aerosol Particles: Potential Photosensitizers, Brown Carbon Constituents, and Hazardous Components.

PubMed

Teich, Monique; van Pinxteren, Dominik; Kecorius, Simonas; Wang, Zhibin; Herrmann, Hartmut

2016-02-02

Imidazoles are widely discussed in recent literature. They have been studied as a secondary product of the reaction of dicarbonyls with nitrogen containing compounds in a number of laboratory studies, potentially acting as photosensitizers triggering secondary organic aerosol growth and are forming constituents of light absorbing brown carbon. Despite the knowledge from laboratory studies, no quantitative information about imidazoles in ambient aerosol particles is available. Within the present study, five imidazoles (1-butylimidazole, 1-ethylimidazole, 2-ethylimidazole, imidazol-2-carboxaldehyde, and 4(5)-methylimidazole) were successfully identified and quantified for the first time in ambient aerosol samples from different environments in Europe and China. Their concentrations range between 0.2 and 14 ng/m(3). 4(5)-Methylimidazole was found to be the most abundant imidazole. The occurrence of imidazoles seems to be favored at sites with strong biomass burning influence or connected to more polluted air masses. No connection was found between aerosol particle pH and imidazole concentration. Our work corroborates the laboratory studies by showing that imidazoles are present in ambient aerosol samples in measurable amounts. Moreover, it further motivates to explore the potential photosensitizing properties of small alkyl-substituted imidazoles.

Estrogenicity of halogenated bisphenol A: in vitro and in silico investigations.

PubMed

Zhang, Jie; Li, Tiezhu; Wang, Tuoyi; Yuan, Cuiping; Zhong, Shuning; Guan, Tianzhu; Li, Zhuolin; Wang, Yongzhi; Yu, Hansong; Luo, Quan; Wang, Yongjun; Zhang, Tiehua

2018-03-01

The binding interactions of bisphenol A (BPA) and its halogenated derivatives (halogenated BPAs) to human estrogen receptor α ligand binding domain (hERα-LBD) was investigated using a combined in vitro and in silico approach. First, the recombinant hERα-LBD was prepared as a soluble protein in Escherichia coli BL21(DE3)pLysS. A native fluorescent phytoestrogen, coumestrol, was employed as tracer for the fluorescence polarization assay. The results of the in vitro binding assay showed that bisphenol compounds could bind to hERα-LBD as the affinity ligands. All the tested halogenated BPAs exhibited weaker receptor binding than BPA, which might be explained by the steric effect of substituents. Molecular docking studies elucidated that the halogenated BPAs adopted different conformations in the flexible hydrophobic ligand binding pocket (LBP), which is mainly dependent on their distinct halogenation patterns. The compounds with halogen substituents on the phenolic rings and on the bridging alkyl moiety acted as agonists and antagonists for hERα, respectively. Interestingly, all the compounds in the agonist conformation of hERα formed a hydrogen bond with His524, while the compounds in the antagonist conformation formed a hydrogen bond with Thr347. These docking results suggested a pivotal role of His524/Thr347 in maintaining the hERα structure in the biologically active agonist/antagonist conformation. Comparison of the calculated binding energies vs. experimental binding affinities yielded a good correlation, which might be applicable for the structure-based design of novel bisphenol compounds with reduced toxicities and for environmental risk assessment. In addition, based on hERα-LBD as a recognition element, the proposed fluorescence polarization assay may offer an alternative to chromatographic techniques for the multi-residue determination of bisphenol compounds.

MISTRA mechanism development: A new mechanism focused on marine environments

NASA Astrophysics Data System (ADS)

Bräuer, Peter; Sommariva, Roberto; von Glasow, Roland

2015-04-01

The tropospheric multiphase chemistry of halogen compounds plays a key role in marine environments. Moreover, halogen compounds have an impact on the tropospheric oxidation capacity and climate. With more than two thirds of the Earth's surface covered with oceans, effects are of global importance. Various conditions are found in marine environments ranging from pristine regions to polluted regimes in the continental outflow. Furthermore, there are important sources for halogen compounds over land, such as volcanoes, salt lakes, or emissions from industrial processes. To assess the impact of halogen chemistry with numerical models under these distinct conditions, a multiphase mechanism has been developed in the last decades and applied successfully in numerous box and 1D model studies. Contributions from these model studies helped to identify important chemical cycles affecting the composition and chemistry of the troposphere. However, several discrepancies between model results and field measurements remain. Therefore, a major revision of the chemical mechanism has been performed including an update of the kinetic data and the addition of new reaction cycles. The extended mechansims have been evaluated in several model studies with the 1D model MISTRA. Current work focuses at the identification of the most important reaction cycles, which led to significant changes in the concentration-time profiles of several halogen species. Subsequently, the mechanism will be reduced to the most imporatant reactions, which are currently investigated. As regional and global model studies become more important to identify the importance of tropospheric halogen multiphase chemistry, the goal is to derive parameterisations for the most important halogen chemistry cycles, which can than be implemented in regional and global 3D models. In the reduction process, the extented MISTRA version will serve as a benchmark to assess the quality and accuracy of the reduced mechansim versions.

A DFT investigation of a bulky biomimetic model catalyzing the 5'-outer ring deiodination of thyroxine.

PubMed

Fortino, Mariagrazia; Marino, Tiziana; Russo, Nino; Sicilia, Emilia

2016-12-01

This paper illustrates the outcomes of a density functional theory investigation aimed at unraveling mechanistic aspects of the 5'-outer ring deiodination process of thyroxine (T4) assisted by the sterically protected organoselenol compound BpqSeH. BpqSeH, which was previously synthesized and tested for its deiodinase activity, is able to afford the active hormone 3,5,3'-tetraiodothyronine (T3) by selective outer-ring deiodination of T4, and to protect the SeH moiety inside the nano-sized molecular cavity from further reactivity, allowing its isolation and characterization. Calculations were also performed including an imidazole ring that, mimicking a His residue in the active site of the original enzyme, plays an crucial role in deprotonating the selenol moiety. Both the suggested enol/keto tautomerization and the previously proven formation of an intermediate whose main characteristic is the presence of a Se⋯I⋯C halogen bond, were examined along the pathway leading to 5'-outer ring deiodination. The calculated potential energy surface showed that neither the pathway encompassing enol/keto tautomerism nor the formation of a halogen bond paving the way to C-I bond breaking and chalcogen-I bond forming is viable. The exergonic formation of the final selenenyl iodide product confirms the stabilization effect of the molecular cavity. Graphical Abstract Computed free energy profile describing the 5'-outer deiodination of thyroxine assisted by the steric hindered organoselenol BpqSH compound. The molecular electrostatic potential map reoported for the INT1 intermediate shows the non-covalent Se-I interaction, due to the attraction between charges of opposite sign, that weakens the C-I bond and prepares the formation of the new Se-I bond.

Discovery of novel 2-aryl-4-benzoyl-imidazoles targeting the colchicines binding site in tubulin as potential anticancer agents

PubMed Central

Chen, Jianjun; Wang, Zhao; Li, Chien-Ming; Lu, Yan; Vaddady, Pavan K.; Meibohm, Bernd; Dalton, James T.; Miller, Duane D.; Li, Wei

2010-01-01

A series of 2-aryl-4-benzoyl-imidazoles (ABI) was synthesized as a result of structural modifications based on the previous set of 2-aryl-imidazole-4-carboxylic amide (AICA) derivatives and 4-substituted methoxylbenzoyl-aryl-thiazoles (SMART). The average IC50 of the most active compound (5da) was 15.7 nM. ABI analogs have substantially improved aqueous solubility (48.9 μg/mL for 5ga vs. 0.909 μg/mL for SMART-1, 0.137 μg/mL for paclitaxel, and 1.04 μg/mL for Combretastatin A4). Mechanism of action studies indicate that the anticancer activity of ABI analogs is through inhibition of tubulin polymerization by interacting with the colchicine binding site. Unlike paclitaxel and colchicine, the ABI compounds were equally potent against multidrug resistant cancer cells and the sensitive parental melanoma cancer cells. In vivo results indicated that 5cb was more effective than DTIC in inhibiting melanoma xenograph tumor growth. Our results suggest that the novel ABI compounds may be developed to effectively treat drug-resistant tumors. PMID:20919720

Novel fluorescent pH sensor based on coumarin with piperazine and imidazole substituents.

PubMed

Saleh, Na'il; Al-Soud, Yaseen A; Nau, Werner M

2008-12-01

A new coumarin derivative containing piperazine and imidazole moieties is reported as a fluorophore for hydrogen ions sensing. The fluorescence enhancement of the studied sensor with an increase in hydrogen ions concentration is based on the hindering of photoinduced electron transfer from the piperazinyl amine and the imidazolyl amine to the coumarin fluorophore by protonation. The presented sensor has a novel design of fluorophore-spacer-receptor(1)-receptor(2) format, which is proposed to sense two ranges of pH (from 2.5 to 5.5) and (from 10 to 12) instead of sensing one pH range. A model compound, in which the piperazinyl ring is absent, was synthesized as well to confirm the novel pH sensing of the proposed sensor.

Synthesis and biological evaluation of some novel thiazole compounds as potential anti-inflammatory agents.

PubMed

Helal, M H M; Salem, M A; El-Gaby, M S A; Aljahdali, M

2013-07-01

In the present investigation, furo[2,3-d]thiazol-5(2H)-one 5 was obtained from reaction of thiosemicarbazone derivative 2 with diethyl acetylene dicarboxylate. A series of newly synthesized 2-(hydrazinyl)thiazol-4(5H)-one 6, 7 &8 and 2-(4-(substituted)-thiazol-2-yl)hydrazono derivatives 9a, b &10 were synthesized from treatment of thiosemicarbazone derivative 2 with appropriate α-halogenated compounds. Also, a one pot synthesis of thiazole derivatives 13 &15 was achieved from three components reaction of hydrazone derivative 11 with phenyl isothiocyanate and α-halogenated compounds catalyzed by DMF/KOH. 4-(4-Morpholino phenyl) thiazol-2-amino 17 was obtained via the reaction of acetophenone derivative 1 with thiourea in presence of iodine. The reactivity of 2-aminothiazole 17 toward some electrophilic reagents was investigated. The structure of the newly compounds was confirmed on the basis of elemental analysis and spectral data. The antibacterial activity towards two Gram negative (Proteus mirabilis &Serratia marcesens) and two Gram positive (Staphylococcus aureus &Bacillus cereus) bacteria was investigated. The anti-inflammatory activity was also investigated and the inhibition of the carrageenin-induced oedema by these compounds was established. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

Transition-metal chromophore as a new, sensitive spectroscopic tag for proteins. Selective covalent labeling of histidine residues in cytochromes c with chloro(2,2':6',2''-terpyridine)platinum(II) chloride

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

Ratilla, E.M.A.; Brothers, H.M. II; Kostic, N.M.

1987-07-22

Reactivity and selectivity of Pt(trpy)Cl/sup +/ toward proteins are studied with cytochromes c from horse and tuna as examples. The new transition-metal reagent is specific for histidine residues at pH 5. The reaction, facile one-step displacement of the Cl/sup -/ ligand by imidazole, produces good yield. The binding sites, His 26 and His 33 in the horse protein and His 26 in the tuna protein, are identified by UV-vis spectrophotometry and by peptide-mapping experiments. Model complexes with imidazole, histidine, histidine derivatives, and histidine-containing peptides are prepared and characterized. The covalently attached Pt(trpy)/sup 2 +/ labels allow easy separation of themore » protein derivatives by cation-exchange chromatography. The labels do not perturb the conformation and reduction potential of cytochrome c, as shown by UV-vis spectrophotometry, cyclic voltammetry, differential-pulse voltammetry, EPR spectroscopy, and /sup 1/H NMR spectroscopy. The selectivity of Pt(trpy)Cl/sup +/ is entirely opposite from that of PtCl/sub 4//sup 2 -/ although both of them are platinum(II)-chloro complexes. Owing to an interplay between the steric and electronic effects of the terpyridyl ligand, the new reagent is unreactive toward methionine (a thio ether) and cystine (a disulfide), which are otherwise highly nucleophilic ligands, but very reactive toward imidazole, which is otherwise a relatively weak ligand. Unusual and useful selectivity of preformed transition-metal complexes toward proteins evidently can be achieved by a judicious choice of ancillary ligands.« less

Synthesis and XRD, FT-IR vibrational, UV-vis, and nonlinear optical exploration of novel tetra substituted imidazole derivatives: A synergistic experimental-computational analysis

NASA Astrophysics Data System (ADS)

Ahmad, Muhammad Saeed; Khalid, Muhammad; Shaheen, Muhammad Ashraf; Tahir, Muhammad Nawaz; Khan, Muhammad Usman; Braga, Ataualpa Albert Carmo; Shad, Hazoor Ahmad

2018-04-01

Heterocyclic compounds have potential applications in many fields of life. We synthesized novel tetra substituted imidazoles by four-component condensation of benzil, substituted aldehydes, substituted anilines and ammonium acetate as a source of ammonia and acetic acid as the solvent. Their chemical structures were resolved through X-ray crystallographic and spectroscopic (Fourier transform IR and UV-vis) techniques. In addition to experimental analysis, density functional theory (DFT) calculations at the B3LYP/6-311 + G(d,p) level were performed on 4-bromo-2-(1-(4-methoxyphenyl)-4,5-diphenyl-1H-imidazole-2-yl)phenol (1), 4-bromo-2-(1-(1-naphthalen-yl)-4,5-diphenyl-1H-imidazole-2-yl)phenol (2), and 2-(1-(2-chlorophenyl)-4,5-diphenyl-1-H-imidazole-2-yl)-6-methoxyphenol (3) to obtain the optimized geometry and spectroscopic (Fourier transform IR and UV-vis) and non-linear optical properties. Frontier molecular orbital analysis was performed at the Hartee-Fock/6-311+g(d,p) and DFT/B3LYP/6-311+G(d,p) levels of theory. Natural bond orbital (NBO) and UV-vis spectral analyses were performed at the M06-2X/6-31+G(d,p) and time-dependent DFT/B3LYP/6-311+G(d,p) levels, respectively. Overall, the DFT findings show good agreement with the experimental data. The hyper conjugative interaction network, which is responsible for the stability of compounds 1, 2 and 3 was explored by the NBO approach. The global reactivity parameters were explored with use of the energy of the frontier molecular orbitals. DFT calculations predict the first-order hyperpolarizabilities of compounds 1, 2 and 3 are 294.89 × 10-30, 219.45 × 10-30 and 146.77 × 10-30 esu, respectively. A two-state model was used to describe the non-linear optical properties of the compounds investigated.

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

PubMed

Hayashi, Yuki; Okano, Kentaro; Mori, Atsunori

2018-02-16

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

Synthesis and biological evaluation of coumarin derivatives containing imidazole skeleton as potential antibacterial agents.

PubMed

Hu, Yang; Shen, Yufeng; Wu, Xiaohu; Tu, Xiao; Wang, Gao-Xue

2018-01-01

Emergence of multidrug-resistant bacteria causes an urgent need for new generation of antibiotics, which may have a different mechanism of inhibition or killing action from the existing. Here, we report on the design, synthesis, and biological evaluation of thirty-nine coumarin derivatives in order to solve the antibacterial resistance by targeting at the inhibition of biosynthesis pathway of fatty acids. Their antibacterial activities against Escherichia coli, Staphylococcus aureus, Streptococcus agalactiae, and Flavobacterium cloumnare are tested and action mechanism against the key enzyme in bacterial fatty acid synthesis pathway are studied. The results show that compounds 13 and 18 have potent and broad spectrum antimicrobial activity. In addition, 9, 14 and 19 show eminent antimicrobial efficacy toward S. aureus, S. agalactiae, and F. cloumnare. Mechanistically, coumarin derivatives display the antibacterial activity via the control of FabI and FabK function. The structure-activity relationship analysis indicate that the length of linker and imidazole substitute group could significantly influence the antimicrobial activity, as well as the inhibitory activity against FabI and FabK. The structural optimization analysis of coumarin suggest that derivatives 9, 13, 14, 18 and 19 could be a viable way of preventing and controlling bacteria and considered as promising lead compounds for the development of commercial drugs. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Studies on the π-π stacking features of imidazole units present in a series of 5-amino-1-alkylimidazole-4-carboxamides

NASA Astrophysics Data System (ADS)

Ray, Sibdas; Das, Aniruddha

2015-06-01

Reaction of 2-ethoxymethyleneamino-2-cyanoacetamide with primary alkyl amines in acetonitrile solvent affords 1-substituted-5-aminoimidazole-4-carboxamides. Single crystal X-ray diffraction studies of these imidazole compounds show that there are both anti-parallel and syn-parallel π-π stackings between two imidazole units in parallel-displaced (PD) conformations and the distance between two π-π stacked imidazole units depends mainly on the anti/ syn-parallel nature and to some extent on the alkyl group attached to N-1 of imidazole; molecules with anti-parallel PD-stacking arrangements of the imidazole units have got vertical π-π stacking distance short enough to impart stabilization whereas the imidazole unit having syn-parallel stacking arrangement have got much larger π-π stacking distances. DFT studies on a pair of anti-parallel imidazole units of such an AICA lead to curves for 'π-π stacking stabilization energy vs. π-π stacking distance' which have got similarity with the 'Morse potential energy diagram for a diatomic molecule' and this affords to find out a minimum π-π stacking distance corresponding to the maximum stacking stabilization energy between the pair of imidazole units. On the other hand, a DFT calculation based curve for 'π-π stacking stabilization energy vs. π-π stacking distance' of a pair of syn-parallel imidazole units is shown to have an exponential nature.

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

PubMed

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

2016-10-10

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

Investigating Planetary Volatile Accretion Mechanisms Using the Halogens

NASA Astrophysics Data System (ADS)

Ballentine, C. J.; Clay, P. L.; Burgess, R.; Busemann, H.; Ruzié, L.; Joachim, B.; Day, J. M.

2014-12-01

Depletion of the volatile elements in the Earth relative to the CI chondrites is roughly correlated with volatility, or decreasing condensation temperature. For the heavy halogen group elements (Cl, Br and I), volatility alone does not account for their apparent depletion, which early data has suggested is far greater than predicted [1-2]. Such depletion has been used to argue for the preferential loss of halogens by, amongst other processes, impact-driven erosive loss from Earth's surface [2]. Little consensus exists as to why the halogens should exhibit such preferential behavior during accretionary processes. Early efforts to constrain halogen abundance and understand their behavior in both Earth and planetary materials [3-6] have been hampered by their typically low abundance (ppb level) in most geologic materials. We present the results of halogen analysis of 23 chondrite samples, selected to represent diverse groups and petrologic type. Halogen abundances were measured by neutron irradiation noble gas mass spectrometry (NI-NGMS). Significant concentration heterogeneity is observed within some samples. However, a single Br/Cl and I/Cl ratio of 1.9 ± 0.2 (x 10-3) and 335 ± 10 (x 10-6) can be defined for carbonaceous chondrites with a good correlation between Br and Cl (R2 = 0.97) and between I and Cl (R2 = 0.84). Ratios of I/Cl overlap with terrestrial estimates of Bulk Silicate Earth and Mid Ocean Ridge Basalts. Similarly, good correlations are derived for enstatite (E) chondrites and a sulfide- and halogen- rich subset of E-chondrites. Chlorine abundances of CI (Orgueil) in this study are lower by factor of ~ 3 than the value of ~ 700 ppm Cl (compilation in [1]). Our results are similar to early discarded low values for Ivuna and Orgueil from [5,6] and agree more closely with values for CM chondrites. Halogens may not be as depleted in Earth as previously suggested, or a high degree of heterogeneity in the abundance of these volatile elements in carbonaceous chondrites should be considered when we assess Earth's halogen abundance relative to CI. [1] Lodders (2003) Astr J 591:1220-47. [2] Sharp et al. (2013) EPSL 369/70: 71-7. [3] Dreibus et al. (1979) Phys Chem Earth 11:33-8. [4] Goles et al. (1967) GCA 31: 1771-7. [5] Reed and Allen (1966) GCA 30: 779-800. [6] Greenland & Lovering (1965) GCA 29: 821-58.

QSAR by LFER model of cytotoxicity data of anti-HIV 5-phenyl-1-phenylamino-1H-imidazole derivatives using principal component factor analysis and genetic function approximation.

PubMed

Roy, Kunal; Leonard, J Thomas

2005-04-15

Cytotoxicity data of anti-HIV 5-phenyl-1-phenylamino-1H-imidazole derivatives were subjected to quantitative structure-activity relationship (QSAR) study using linear free energy related (LFER) model of Hansch using electronic (Hammett sigma), hydrophobicity (pi) and steric (molar refractivity and STERIMOL L, B1, B2, B3 and B4) parameters of phenyl ring substituents of the compounds, along with appropriate indicator variables. Principal component factor analysis (FA) was used as the data-preprocessing step to identify the important predictor variables contributing to the response variable and to avoid collinearities among them. The generated multiple linear regression (MLR) equations were statistically validated using leave-one-out technique. Genetic function approximation (GFA) was also used on the same data set to develop QSAR equations, which produced the same best equation as obtained with FA-MLR. The final equation is of acceptable statistical quality (explained variance 80.2%) and predictive potential (leave-one-out predicted variance 74%). The analysis explores the structural and physicochemical contributions of the compounds for cytotoxicity. A thiol substituent at 2 position of the imidazole nucleus decreases cytotoxicity when compared to the corresponding unsubstituted congener. Presence of hydrogen bond donor group at meta position of the phenyl ring present at 5 position of the imidazole nucleus also reduces cytotoxicity. Additionally, absence of any substituent at 2 and 3 positions of the phenyl ring of 1-phenylamino fragment reduces the cytotoxicity. The negative coefficient of sigmap indicates that presence of electron-withdrawing substituents at the para position of the phenyl ring of the 1-phenylamino fragment is not favourable for the cytotoxicity. Again, lipophilicity of meta substituents of the 5-phenyl ring increases cytotoxicity. The coefficients of molar refractivity (MRm) and STERIMOL parameters for meta substituents (Lm, B1m and B4m) of the phenyl ring of 1-phenylamino fragment indicate that the length, width and overall size of meta substituents are conducive factors for the cytotoxicity.

Rational design of an orthogonal noncovalent interaction system at the MUPP1 PDZ11 complex interface with CaMKIIα-derived peptides in human fertilization.

PubMed

Zhang, Yi-Le; Han, Zhao-Feng

2017-09-26

The recognition and association between the Ca 2+ /calmodulin-activated protein kinase II-α (CaMKIIα) and the multi-PDZ domain protein 1 (MUPP1) plays an important role in the sperm acrosome reaction and human fertilization. Previously, we have demonstrated that the MUPP1 PDZ11 domain is the primary binding partner of the CaMKIIα C-terminal tail, which can be targeted by a rationally designed sia peptide with nanomolar affinity. Here, we further introduced an orthogonal noncovalent interaction (ONI) system between a native hydrogen bond and a designed halogen bond across the complex interface of the PDZ11 domain with the sia [Asn-1Phe] peptide mutant, where the halogen bond was formed by substituting the o-hydrogen atom of the benzene ring of the peptide Phe-1 residue with a halogen atom (F, Cl, Br or I). Molecular dynamics simulations and high-level theoretical calculations suggested that bromine (Br) is a good compromise between the halogen-bonding strength and steric hindrance effect due to introduction of a bulkier halogen atom into the tightly packed complex interface. Fluorescence spectroscopy assays revealed that the resulting o-Br-substituted peptide (K d = 18 nM) exhibited an ∼7.6-fold affinity increase relative to its native counterpart (K d = 137 nM). In contrast, the p-Br-substituted peptide, a negative control that is unable to establish the ONI according to structure-based analysis, has decreased affinity (K d = 210 nM) upon halogenation.

Cytokinin oxidase from Phaseolus vulgaris callus tissues. Enhanced in vitro activity of the enzyme in the presence of copper-imidazole complexes

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

Chatfield, J.M.; Armstrong, D.J.

1987-07-01

The effects of metal ions on cytokinin oxidase activity extracted from callus tissues of Phaseolus vulgaris L. cv Great Northern have been examined using an assay based on the oxidation of N/sup 6/-(..delta../sup 2/-isopentenyl)-adenine-2,8-/sup 3/H (i/sup 6/ Ade) to adenine (Ade). The addition of cupric ions to reaction mixtures containing imidazole buffer markedly enhanced cytokinin oxidase activity. In the presence of optimal concentrations of copper and imidazole, cytokinin oxidase activity was stimulated more than 20-fold. The effect was enzyme dependent, specific for copper, and observed only in the presence of imidazole. The substrate specificity of the copper-imidazole enhanced reaction, asmore » judged by substrate competition tests, was the same as that observed in the absence of copper and imidazole. Similarly, in tests involving DEAE-cellulose chromatography, elution profiles of cytokinin oxidase activity determined using a copper-imidazole enhanced assay were identical to those obtained using an assay without copper and imidazole. On the basis of these results, the addition of copper and imidazole to reaction mixtures used to assay for cytokinin oxidase activity is judged to provide a reliable and specific assay of greatly enhanced sensitivity for the enzyme. The mechanism by which copper and imidazole enhance cytokinin oxidase activity is not certain, but the reaction catalyzed by the enzyme was not inhibited by anaerobic conditions when these reagents were present. This observation suggests that copper-imidazole complexes are substituting for oxygen in the reaction mechanism by which cytokinin oxidase effects cleavage of the N/sup 6/-side chain of i/sup 6/ Ade.« less

Structure and nature of manganese(II) imidazole complexes in frozen aqueous solutions.

PubMed

Un, Sun

2013-04-01

A common feature of a large majority of the manganese metalloenzymes, as well as many synthetic biomimetic complexes, is the bonding between the manganese ion and imidazoles. This interaction was studied by examining the nature and structure of manganese(II) imidazole complexes in frozen aqueous solutions using 285 GHz high magnet-field continuous-wave electron paramagnetic resonance (cw-HFEPR) and 95 GHz pulsed electron-nuclear double resonance (ENDOR) and pulsed electron-double resonance detected nuclear magnetic resonance (PELDOR-NMR). The (55)Mn hyperfine coupling and isotropic g values of Mn(II) in frozen imidazole solutions continuously decreased with increasing imidazole concentration. ENDOR and PELDOR-NMR measurements demonstrated that the structural basis for this behavior arose from the imidazole concentration-dependent distribution of three six-coordinate and two four-coordinate species: [Mn(H2O)6](2+), [Mn(imidazole)(H2O)5](2+), [Mn(imidazole)2(H2O)4](2+), [Mn(imidazole)3(H2O)](2+), and [Mn(imidazole)4](2+). The hyperfine and g values of manganese proteins were also fully consistent with this imidazole effect. Density functional theory methods were used to calculate the structures, spin and charge densities, and hyperfine couplings of a number of different manganese imidazole complexes. The use of density functional theory with large exact-exchange admixture calculations gave isotropic (55)Mn hyperfine couplings that were semiquantitative and of predictive value. The results show that the covalency of the Mn-N bonds play an important role in determining not only magnetic spin parameters but also the structure of the metal binding site. The relationship between the isotropic (55)Mn hyperfine value and the number of imidazole ligands provides a quick and easy test for determining whether a protein binds an Mn(II) ion using histidine residues and, if so, how many are involved. Application of this method shows that as much as 40% of the Mn(II) ions in Deinococcus radiodurans are ligated to two histidines (Tabares, L. C.; Un, S. J. Biol. Chem 2013, in press).

Carbide-derived carbons - From porous networks to nanotubes and graphene

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

Presser, V.; Heon, M.; Gogotsi, Y.

2011-02-09

Carbide-derived carbons (CDCs) are a large family of carbon materials derived from carbide precursors that are transformed into pure carbon via physical (e.g., thermal decomposition) or chemical (e.g., halogenation) processes. Structurally, CDC ranges from amorphous carbon to graphite, carbon nanotubes or graphene. For halogenated carbides, a high level of control over the resulting amorphous porous carbon structure is possible by changing the synthesis conditions and carbide precursor. The large number of resulting carbon structures and their tunability enables a wide range of applications, from tribological coatings for ceramics, or selective sorbents, to gas and electrical energy storage. In particular, themore » application of CDC in supercapacitors has recently attracted much attention. This review paper summarizes key aspects of CDC synthesis, properties, and applications. It is shown that the CDC structure and properties are sensitive to changes of the synthesis parameters. Understanding of processing–structure–properties relationships facilitates tuning of the carbon material to the requirements of a certain application.« less

Influence of the chemical structure on odor qualities and odor thresholds of halogenated guaiacol-derived odorants

NASA Astrophysics Data System (ADS)

Juhlke, Florian; Lorber, Katja; Wagenstaller, Maria; Buettner, Andrea

2017-12-01

Chlorinated guaiacol derivatives are found in waste water of pulp mills using chlorine in the bleaching process of wood pulp. They can also be detected in fish tissue, possibly causing off-odors. To date, there is no systematic investigation on the odor properties of halogenated guaiacol derivatives. To close this gap, odor thresholds in air and odor qualities of 14 compounds were determined by gas chromatography-olfactometry. Overall, the investigated compounds elicited smells that are characteristic for guaiacol, namely smoky, sweet, vanilla-like, but also medicinal and plaster-like. Their odor thresholds in air were, however, very low, ranging from 0.00072 to 23 ng/Lair. The lowest thresholds were found for 5-chloro- and 5-bromoguaiacol, followed by 4,5-dichloro- and 6-chloroguaiacol. Moreover, some inter-individual differences in odor threshold values could be observed, with the highest variations having been recorded for the individual values of 5-iodo- and 4-bromoguaiacol.

Synthesis of Bisimidazole Derivatives for Selective Sensing of Fluoride Ion.

PubMed

Zhang, Liang; Liu, Fang

2017-09-11

Rapid and efficient analysis of fluoride ion is crucial to providing key information for fluoride ion hazard assessment and pollution management. In this study, we synthesized one symmetrical structure called 1,4-bis(4,5-diphenyl-1 H -imidazol-2-yl)benzene ( 1a ) and two asymmetrical structures, namely 2-(4-(4,5-diphenyl-1 H -imidazol-2-yl)phenyl)-1 H -phenanthro(9,10- d )imidazole ( 1b ) and 2-(4-(4,5-diphenyl-1 H -imidazol-2-yl)phenyl)-1 H -imidazo(4,5- f )(1,10)phenanthroline ( 1c ), which served as an efficient anion sensor for fluoride ion over a wide range of other anions (Cl - , Br - , I - , NO₃ - , ClO₄ - , HSO₄ - , BF₄ - , and PF₆ - ) owing to imidazole group in the main backbone. The absorption intensity of compound 1a at λ max 358 nm slightly decreased; however, a new band at λ max 414 nm appeared upon the addition of fluoride ion, while no evident change occurred upon the addition of eight other anions. The photoluminescence intensity of compound 1a at λ max 426 nm was nearly quenched and fluorescence emission spectra were broadened when fluoride ion was added into dimethyl sulfoxide (DMSO) solution of compound 1a . Compared with the optical behaviors of the DMSO solution of compound 1a in the presence of Bu₄N⁺F - , compounds 1b and 1c exhibited considerable sensitivity to fluoride ion due to the increase in coplanarity. Furthermore, compared with the fluorescence emission behaviors of the DMSO solutions of compounds 1a and 1b in the presence of Bu₄N⁺F - , compound 1c exhibited the most significant sensitivity to fluoride ion due to the charge transfer enhancement. Consequently, the detection limits of compounds 1a - 1 c increased from 5.47 × 10 -6 M to 4.21 × 10 -6 M to 9.12 × 10 -7 M. Furthermore, the largest red shift (75 nm) of the DMSO solution compound 1c in the presence of fluoride ion can be observed. Our results suggest that the increase in coplanarity and the introduction of electron-withdrawing groups to the imidazole backbone can improve the performance in detecting fluoride ion.

3D-QSAR based on quantum-chemical molecular fields: toward an improved description of halogen interactions.

PubMed

Güssregen, Stefan; Matter, Hans; Hessler, Gerhard; Müller, Marco; Schmidt, Friedemann; Clark, Timothy

2012-09-24

Current 3D-QSAR methods such as CoMFA or CoMSIA make use of classical force-field approaches for calculating molecular fields. Thus, they can not adequately account for noncovalent interactions involving halogen atoms like halogen bonds or halogen-π interactions. These deficiencies in the underlying force fields result from the lack of treatment of the anisotropy of the electron density distribution of those atoms, known as the "σ-hole", although recent developments have begun to take specific interactions such as halogen bonding into account. We have now replaced classical force field derived molecular fields by local properties such as the local ionization energy, local electron affinity, or local polarizability, calculated using quantum-mechanical (QM) techniques that do not suffer from the above limitation for 3D-QSAR. We first investigate the characteristics of QM-based local property fields to show that they are suitable for statistical analyses after suitable pretreatment. We then analyze these property fields with partial least-squares (PLS) regression to predict biological affinities of two data sets comprising factor Xa and GABA-A/benzodiazepine receptor ligands. While the resulting models perform equally well or even slightly better in terms of consistency and predictivity than the classical CoMFA fields, the most important aspect of these augmented field-types is that the chemical interpretation of resulting QM-based property field models reveals unique SAR trends driven by electrostatic and polarizability effects, which cannot be extracted directly from CoMFA electrostatic maps. Within the factor Xa set, the interaction of chlorine and bromine atoms with a tyrosine side chain in the protease S1 pocket are correctly predicted. Within the GABA-A/benzodiazepine ligand data set, PLS models of high predictivity resulted for our QM-based property fields, providing novel insights into key features of the SAR for two receptor subtypes and cross-receptor selectivity of the ligands. The detailed interpretation of regression models derived using improved QM-derived property fields thus provides a significant advantage by revealing chemically meaningful correlations with biological activity and helps in understanding novel structure-activity relationship features. This will allow such knowledge to be used to design novel molecules on the basis of interactions additional to steric and hydrogen-bonding features.

Single step signal group-imidazole labeling of organic phosphate groups under aqueous conditions

DOEpatents

Giese, Roger W.; Wang, Poguang

1996-01-01

Compounds and methods for single step, covalent labeling of the phosphate group of an organic substance under aqueous conditions are described. The labeling compound includes any kind of detectable signal group covalently bound to an imidazole moiety, which can be imidazole or a substituted imidazole. A preferred labeling compound has the formula ##STR1##

Conformational equilibrium of phenylacetic acid and its halogenated analogues through theoretical studies, NMR and IR spectroscopy

NASA Astrophysics Data System (ADS)

Levandowski, Mariana N.; Rozada, Thiago C.; Melo, Ulisses Z.; Basso, Ernani A.; Fiorin, Barbara C.

2017-03-01

This paper presents a study on the conformational preferences of phenylacetic acid (PA) and its halogenated analogues (FPA, CPA, BPA). To clarify the effects that rule these molecules' behaviour, theoretical calculations were used, for both the isolated phase and solution, combined with nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy. Most conformations of phenylacetic acid and its halogenated derivatives are stabilized through the hyperconjugative effect, which rules the conformational preference. NMR analyses showed that even with the variation in medium polarity, there was no significant change in the conformation population. Infrared spectroscopy showed similar results for all compounds under study. In most spectra, two bands were found through the carbonyl deconvolution, which is in accordance with the theoretical data. It was possible to prove that variation in the nature of the substituent in the ortho position had no significant influence on the conformational equilibrium.

Fluoroalkenylphosphonates

NASA Astrophysics Data System (ADS)

Kadyrov, A. A.; Rokhlin, E. M.

1988-09-01

In this review we survey the methods for the preparation of derivatives of fluoroalkenylphosphonic acid and their reactions. The main methods for obtaining these compounds are based on the reactions of fluoroolefins with phosphites and also on the elimination of halogens, hydrogen halides and alkyl halides from fluoroalkylphosphonates or fluorine-containing phosphorus ylides. The chemical properties of fluoroalkenylphosphonates are due to the combined effect of the fluorine atoms and the phosphonate group. Their reactions with different reagents leads to modifications of the phosphonate group, addition to the C=C bond, replacement of the vinyl halogen atom, and cleavage of the C-P bond. The bibliography includes 96 references.

40 CFR 721.4468 - 1H-Imidazole, 2-ethyl-4,5-dihydro-4-methyl-.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false 1H-Imidazole, 2-ethyl-4,5-dihydro-4... Specific Chemical Substances § 721.4468 1H-Imidazole, 2-ethyl-4,5-dihydro-4-methyl-. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as 1H-imidazole...

Evaluation of lophine derivatives as L-012 (luminol analog)-dependent chemiluminescence enhancers for measuring horseradish peroxidase and H2O2.

PubMed

Ichibangase, T; Ohba, Y; Kishikawa, N; Nakashima, K; Kuroda, N

2014-03-01

8-Amino-5-chloro-7-phenylpyrido[3,4-d]pyridazine-1,4(2H,3H)dione (L-012) was recently synthesized as a new chemiluminescence (CL) probe; the light intensity and the sensitivity of L-012 are higher than those of other CL probes such as luminol. Previously, our group developed four lophine-based CL enhancers of the horseradish peroxidase (HRP)-catalyzed CL oxidation of luminol, namely 2-(4-hydroxyphenyl)-4,5-diphenylimidazole (HDI), 2-(4-hydroxyphenyl)-4,5-di(2-pyridyl)imidazole (HPI), 4-(4,5-diphenyl-1H-imidazol-2-yl)phenylboronic acid (DPA), and 4-[4,5-di(2-pyridyl)-1H-imidazol-2-yl]phenylboronic acid (DPPA), and showed that DPPA was suitable for the photographic detection of HRP. In this study, we replaced luminol with L-012 and evaluated these as L-012-dependent CL enhancers. In addition, to detect HRP and/or H2O2 with higher sensitivity, each detection condition for the L-012-HRP-H2O2 enhanced CL was optimized. All the derivatives enhanced the L-012-dependent CL as well as luminol CL; HPI generated the highest enhanced luminescence. Under optimized conditions for HRP detection, the detection limit of HRP was 0.08 fmol. By contrast, the detection limit of HRP with the enhanced L-012-dependent CL using 4-iodophenol, which is a common enhancer of luminol CL, was 1.1 fmol. With regard to H2O2 detection, the detection limits for enhanced CL with HPI and 4-iodophenol were 0.29 and 1.5 pmol, respectively. Therefore, it is demonstrated that HPI is the most superior L-012-dependent CL enhancer. Copyright © 2013 John Wiley & Sons, Ltd.

Diazole-based powdered cocrystal featuring a helical hydrogen-bonded network: structure determination from PXRD, solid-state NMR and computer modeling.

PubMed

Sardo, Mariana; Santos, Sérgio M; Babaryk, Artem A; López, Concepción; Alkorta, Ibon; Elguero, José; Claramunt, Rosa M; Mafra, Luís

2015-02-01

We present the structure of a new equimolar 1:1 cocrystal formed by 3,5-dimethyl-1H-pyrazole (dmpz) and 4,5-dimethyl-1H-imidazole (dmim), determined by means of powder X-ray diffraction data combined with solid-state NMR that provided insight into topological details of hydrogen bonding connectivities and weak interactions such as CH···π contacts. The use of various 1D/2D (13)C, (15)N and (1)H high-resolution solid-state NMR techniques provided structural insight on local length scales revealing internuclear proximities and relative orientations between the dmim and dmpz molecular building blocks of the studied cocrystal. Molecular modeling and DFT calculations were also employed to generate meaningful structures. DFT refinement was able to decrease the figure of merit R(F(2)) from ~11% (PXRD only) to 5.4%. An attempt was made to rationalize the role of NH···N and CH···π contacts in stabilizing the reported cocrystal. For this purpose four imidazole derivatives with distinct placement of methyl substituents were reacted with dmpz to understand the effect of methylation in blocking or enabling certain intermolecular contacts. Only one imidazole derivative (dmim) was able to incorporate into the dmpz trimeric motif thus resulting in a cocrystal, which contains both hydrophobic (methyl groups) and hydrophilic components that self-assemble to form an atypical 1D network of helicoidal hydrogen bonded pattern, featuring structural similarities with alpha-helix arrangements in proteins. The 1:1 dmpz···dmim compound I is the first example of a cocrystal formed by two different azoles. Copyright © 2014 Elsevier Inc. All rights reserved.

Development of a pair of differential H/D isotope-coded derivatization reagents d(0)/d(3)-4-(1-methyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenlamine and its application for determination of aldehydes in selected aquatic products by liquid chromatography-tandem mass spectrometry.

PubMed

Sun, Zhiwei; Wang, Xiaoxiang; Cai, Yiping; Fu, Junqing; You, Jinmao

2014-03-01

A new pair of derivatization reagents, d0-4-(1-methyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenlamine (d0-MPIA) and d3-4-(1-methyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenlamine (d3-MPIA) have been designed and synthesized. It was successfully used to label aliphatic aldehydes and the aldehyde derivatives were analyzed by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The new isotope-coded reagents could easily label aldehydes under acidic conditions in the presence of NaCNBH3. The target derivatives exhibited intense [M+H](+) and regular product ions with electrospray ionization source in positive mode. The d0/d3-MPIA-aldehydes were monitored by the transitions of [M+H](+)→m/z 322 and [M+H](+)→m/z 165, and the obtained detection limits were in the range of 0.18-15.9 pg/mL at signal to noise ratio of 3. The global isotope internal standard technology was employed for quantification analysis with d3-MPIA-aldehyde as internal standard for corresponding d0-MPIA-aldehyde. Excellent linear responses for relative quantification were observed in the range of 1/10-10/1 with coefficients >0.998. The developed method has been applied to the quantification of aliphatic aldehydes in selected aquatic products with RSD<3.6% and recoveries >85.2%. © 2013 Elsevier B.V. All rights reserved.

Room-Temperature Phosphorescence in Pure Organic Materials: Halogen Bonding Switching Effects.

PubMed

Xiao, Lu; Wu, Yishi; Yu, Zhenyi; Xu, Zhenzhen; Li, Jinbiao; Liu, Yanping; Yao, Jiannian; Fu, Hongbing

2018-02-06

Organic room-temperature phosphorescence (ORTP), when combined with external stimuli-responsive capability, is very attractive for sensors and bio-imaging devices, but remains challenging. Herein, by doping two β-iminoenamine-BF 2 derivatives (S-2CN and S-2I) into a 4-iodoaniline (I-Ph-NH 2 ) crystalline matrix, the formation of S-2CN⋅⋅⋅I-Ph-NH 2 and S-2I⋅⋅⋅I-Ph-NH 2 halogen bonds leads to bright-red RTP emissions from these two host-guest doped crystals (hgDCs) with quantum efficiencies up to 13.43 % and 15.96 %, respectively. Upon treatment with HCl, the competition of I-Ph-NH 2 ⋅HCl formation against S-2I⋅⋅⋅I-Ph-NH 2 halogen bonding switches off the red RTP from S-2I/I-Ph-NH 2 hgDCs, whereas the stable halogen-bonded S-2CN⋅⋅⋅I-Ph-NH 2 ensures red RTP from S-2CN/I-Ph-NH 2 hgDCs remains unchanged. A security protection luminescence pattern by using these different HCl-responsive RTP behaviors was designed. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

QSPR models of n-octanol/water partition coefficients and aqueous solubility of halogenated methyl-phenyl ethers by DFT method.

PubMed

Zeng, Xiao-Lan; Wang, Hong-Jun; Wang, Yan

2012-02-01

The possible molecular geometries of 134 halogenated methyl-phenyl ethers were optimized at B3LYP/6-31G(*) level with Gaussian 98 program. The calculated structural parameters were taken as theoretical descriptors to establish two new novel QSPR models for predicting aqueous solubility (-lgS(w,l)) and n-octanol/water partition coefficient (lgK(ow)) of halogenated methyl-phenyl ethers. The two models achieved in this work both contain three variables: energy of the lowest unoccupied molecular orbital (E(LUMO)), most positive atomic partial charge in molecule (q(+)), and quadrupole moment (Q(yy) or Q(zz)), of which R values are 0.992 and 0.970 respectively, their standard errors of estimate in modeling (SD) are 0.132 and 0.178, respectively. The results of leave-one-out (LOO) cross-validation for training set and validation with external test sets both show that the models obtained exhibited optimum stability and good predictive power. We suggests that two QSPR models derived here can be used to predict S(w,l) and K(ow) accurately for non-tested halogenated methyl-phenyl ethers congeners. Copyright © 2011 Elsevier Ltd. All rights reserved.

Spectroscopic investigations and molecular docking study of 3-(1H-imidazol-1-yl)-1-phenylpropan-1-one, a potential precursor to bioactive agents

NASA Astrophysics Data System (ADS)

Al-Alshaikh, Monirah A.; Mary Y, Sheena; Panicker, C. Yohannan; Attia, Mohamed I.; El-Emam, Ali A.; Alsenoy, C. Van

2016-04-01

The optimized molecular structure, vibrational wavenumbers, corresponding vibrational assignments of 3-(1H-imidazol-1-yl)-1-phenylpropan-1-one have been investigated theoretically and experimentally. The calculated geometrical parameters of the title compound are in agreement with the reported XRD data. The HOMO and LUMO analysis is used to determine the charge transfer within the molecule. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis. Molecular electrostatic potential was performed by the DFT method and from the MEP plot, it is evident that the negative charge covers the carbonyl group and the nitrogen atom N3 of the imidazole ring and the positive region is over the remaining portions of the molecule. The first and second hyperpolarizabilities are calculated and the first hyperpolarizability of the title compound is 16.99 times that of standard NLO material urea and the title compound and its derivatives are good object for further studies in nonlinear optics. The docked ligand title compound forms a stable complex with plasmodium falciparum and gives a binding affinity value of -5.5 kcal/mol and the preliminary results suggest that the compound might exhibit antimalarial activity against plasmodium falciparum.

Singlet versus Triplet Excited State Mediated Photoinduced Dehalogenation Reactions of Itraconazole in Acetonitrile and Aqueous Solutions.

PubMed

Zhu, Ruixue; Li, Ming-de; Du, Lili; Phillips, David Lee

2017-04-06

Photoinduced dehalogenation of the antifungal drug itraconazole (ITR) in acetonitrile (ACN) and ACN/water mixed solutions was investigated using femtosecond and nanosecond time-resolved transient absorption (fs-TA and ns-TA, respectively) and nanosecond time-resolved resonance Raman spectroscopy (ns-TR 3 ) experiments. An excited resonance energy transfer is found to take place from the 4-phenyl-4,5-dihydro-3H-1,2,4-triazol-3-one part of the molecule to the 1,3-dichlorobenzene part of the molecule when ITR is excited by ultraviolet light. This photoexcitation is followed by a fast carbon-halogen bond cleavage that leads to the generation of radical intermediates via either triplet and/or singlet excited states. It is found that the singlet excited state-mediated carbon-halogen cleavage is the predominant dehalogenation process in ACN solvent, whereas a triplet state-mediated carbon-halogen cleavage prefers to occur in the ACN/water mixed solutions. The singlet-to-triplet energy gap is decreased in the ACN/water mixed solvents and this helps facilitate an intersystem crossing process, and thus, the carbon-halogen bond cleavage happens mostly through an excited triplet state in the aqueous solutions examined. The ns-TA and ns-TR 3 results also provide some evidence that radical intermediates are generated through a homolytic carbon-halogen bond cleavage via predominantly the singlet excited state pathway in ACN but via mainly the triplet state pathway in the aqueous solutions. In strong acidic solutions, protonation at the oxygen and/or nitrogen atoms of the 1,2,4-triazole-3-one group appears to hinder the dehalogenation reactions. This may offer the possibility that the phototoxicity of ITR due to the generation of aryl or halogen radicals can be reduced by protonation of certain moieties in suitably designed ITR halogen-containing derivatives.

Acidity of a Cu-bound histidine in the binuclear center of cytochrome C oxidase.

PubMed

Fadda, Elisa; Chakrabarti, Nilmadhab; Pomès, Régis

2005-12-01

Cytochrome c oxidase (CcO) is a crucial enzyme in the respiratory chain. Its function is to couple the reduction of molecular oxygen, which takes place in the Fea3-CuB binuclear center, to proton translocation across the mitochondrial membrane. Although several high-resolution structures of the enzyme are known, the molecular basis of proton pumping activation and its mechanism remain to be elucidated. We examine a recently proposed scheme (J. Am. Chem. Soc. 2004, 126, 1858; FEBS Lett. 2004, 566, 126) that involves the deprotonation of the CuB-bound imidazole ring of a histidine (H291 in mammalian CcO) as a key element in the proton pumping mechanism. The central feature of that proposed mechanism is that the pKa values of the imidazole vary significantly depending on the redox state of the metals in the binuclear center. We use density functional theory in combination with continuum electrostatics to calculate the pKa values, successively in bulk water and within the protein, of the Cu-bound imidazole in various Cu- and Cu-Fe complexes. From pKas in bulk water, we derived a value of -266.34 kcal.mol(-1) for the proton solvation free energy (Delta). This estimate is in close agreement with the experimental value of -264.61 kcal.mol(-1) (J. Am. Chem. Soc. 2001, 123, 7314), which reinforces the conclusion that Delta is more negative than previous values used for pKa calculations. Our approach, on the basis of the study of increasingly more detailed models of the CcO binuclear center at different stages of the catalysis, allows us to examine successively the effect of each of the two metals' redox states and of solvation on the acidity of imidazole, whose pKa is approximately 14 in bulk water. This analysis leads to the following conclusions: first, the effect of Cu ligation on the imidazole acidity is negligible regardless of the redox state of the metal. Second, results obtained for Cu-Fe complexes in bulk water indicate that Cu-bound imidazole pKa values lie within the range of 14.8-16.6 throughout binuclear redox states corresponding to the catalytic cycle, demonstrating that the effect of the Fe oxidation states is also negligible. Finally, the low-dielectric CcO proteic environment shifts the acid-base equilibrium toward a neutral imidazole, further increasing the corresponding pKa values. These results are inconsistent with the proposed role of the Cu-bound histidine as a key element in the pumping mechanism. Limitations of continuum solvation models in pKa calculations are discussed.

Single step signal group-imidazole labeling of organic phosphate groups under aqueous conditions

DOEpatents

Giese, R.W.; Wang, P.

1996-04-30

Compounds and methods for single step, covalent labeling of the phosphate group of an organic substance under aqueous conditions are described. The labeling compound includes any kind of detectable signal group covalently bound to an imidazole moiety, which can be imidazole or a substituted imidazole. A preferred labeling compound has the formula shown in the accompanying diagram. 4 figs.

Impacts of halogen additions on mercury oxidation, in a slipstream selective catalyst reduction (SCR), reactor when burning sub-bituminous coal.

PubMed

Cao, Yan; Gao, Zhengyang; Zhu, Jiashun; Wang, Quanhai; Huang, Yaji; Chiu, Chengchung; Parker, Bruce; Chu, Paul; Pant, Wei-Ping

2008-01-01

This paper presents a comparison of impacts of halogen species on the elemental mercury (Hg(0)) oxidation in a real coal-derived flue gas atmosphere. It is reported there is a higher percentage of Hg(0) in the flue gas when burning sub-bituminous coal (herein Powder River Basin (PRB) coal) and lignite, even with the use of selective catalytic reduction (SCR). The higher Hg(0)concentration in the flue gas makes it difficult to use the wet-FGD process for the mercury emission control in coal-fired utility boilers. Investigation of enhanced Hg(0) oxidation by addition of hydrogen halogens (HF, HCl, HBr, and HI) was conducted in a slipstream reactor with and without SCR catalysts when burning PRB coal. Two commercial SCR catalysts were evaluated. SCR catalyst no. 1 showed higher efficiencies of both NO reduction and Hg(0) oxidation than those of SCR catalyst no. 2. NH3 addition seemed to inhibit the Hg(0) oxidation, which indicated competitive processes between NH3 reduction and Hg(0) oxidation on the surface of SCR catalysts. The hydrogen halogens, in the order of impact on Hg(0) oxidation, were HBr, HI, and HCl or HF. Addition of HBr at approximately 3 ppm could achieve 80% Hg(0) oxidation. Addition of HI at approximately 5 ppm could achieve 40% Hg(0) oxidation. In comparison to the empty reactor, 40% Hg(0) oxidation could be achieved when HCl addition was up to 300 ppm. The enhanced Hg(0) oxidation by addition of HBr and HI seemed not to be correlated to the catalytic effects by both evaluated SCR catalysts. The effectiveness of conversion of hydrogen halogens to halogen molecules or interhalogens seemed to be attributed to their impacts on Hg(0) oxidation.

Functional and structural analysis of AT-specific minor groove binders that disrupt DNA–protein interactions and cause disintegration of the Trypanosoma brucei kinetoplast

PubMed Central

Millan, Cinthia R.; Acosta-Reyes, Francisco J.; Lagartera, Laura; Ebiloma, Godwin U.; Lemgruber, Leandro; Nué Martínez, J. Jonathan; Saperas, Núria

2017-01-01

Abstract Trypanosoma brucei, the causative agent of sleeping sickness (Human African Trypanosomiasis, HAT), contains a kinetoplast with the mitochondrial DNA (kDNA), comprising of >70% AT base pairs. This has prompted studies of drugs interacting with AT-rich DNA, such as the N-phenylbenzamide bis(2-aminoimidazoline) derivatives 1 [4-((4,5-dihydro-1H-imidazol-2-yl)amino)-N-(4-((4,5-dihydro-1H-imidazol-2-yl)amino)phenyl)benzamide dihydrochloride] and 2 [N-(3-chloro-4-((4,5-dihydro-1H-imidazol-2-yl)amino)phenyl)-4-((4,5-dihydro-1H-imidazol-2-yl)amino)benzamide] as potential drugs for HAT. Both compounds show in vitro effects against T. brucei and in vivo curative activity in a mouse model of HAT. The main objective was to identify their cellular target inside the parasite. We were able to demonstrate that the compounds have a clear effect on the S-phase of T. brucei cell cycle by inflicting specific damage on the kinetoplast. Surface plasmon resonance (SPR)–biosensor experiments show that the drug can displace HMG box-containing proteins essential for kDNA function from their kDNA binding sites. The crystal structure of the complex of the oligonucleotide d[AAATTT]2 with compound 1 solved at 1.25 Å (PDB-ID: 5LIT) shows that the drug covers the minor groove of DNA, displaces bound water and interacts with neighbouring DNA molecules as a cross-linking agent. We conclude that 1 and 2 are powerful trypanocides that act directly on the kinetoplast, a structure unique to the order Kinetoplastida. PMID:28637278

Gold(I) and Gold(III) Complexes of Cyclic (Alkyl)(amino)carbenes

PubMed Central

2016-01-01

The chemistry of Au(I) complexes with two types of cyclic (alkyl)(amino)carbene (CAAC) ligands has been explored, using the sterically less demanding dimethyl derivative Me2CAAC and the 2-adamantyl ligand AdCAAC. The conversion of (AdCAAC)AuCl into (AdCAAC)AuOH by treatment with KOH is significantly accelerated by the addition of tBuOH. (AdCAAC)AuOH is a convenient starting material for the high-yield syntheses of (AdCAAC)AuX complexes by acid/base and C–H activation reactions (X = OAryl, CF3CO2, N(Tf)2, C2Ph, C6F5, C6HF4, C6H2F3, CH2C(O)C6H4OMe, CH(Ph)C(O)Ph, CH2SO2Ph), while the cationic complexes [(AdCAAC)AuL]+ (L = CO, CNtBu) and (AdCAAC)AuCN were obtained by chloride substitution from (AdCAAC)AuCl. The reactivity toward variously substituted fluoroarenes suggests that (AdCAAC)AuOH is able to react with C–H bonds with pKa values lower than about 31.5. This, together with the spectroscopic data, confirm the somewhat stronger electron-donor properties of CAAC ligands in comparison to imidazolylidene-type N-heterocyclic carbenes (NHCs). In spite of this, the oxidation of Me2CAAC and AdCAAC gold compounds is much less facile. Oxidations proceed with C–Au cleavage by halogens unless light is strictly excluded. The oxidation of (AdCAAC)AuCl with PhICl2 in the dark gives near-quantitative yields of (AdCAAC)AuCl3, while [Au(Me2CAAC)2]Cl leads to trans-[AuCl2(Me2CAAC)2]Cl. In contrast to the chemistry of imidazolylidene-type gold NHC complexes, oxidation products containing Au–Br or Au–I bonds could not be obtained; whereas the reaction with CsBr3 cleaves the Au–C bond to give mixtures of [AdCAAC-Br]+[AuBr2]− and [(AdCAAC-Br)]+ [AuBr4]−, the oxidation of (AdCAAC)AuI with I2 leads to the adduct (AdCAAC)AuI·I2. Irrespective of the steric demands of the CAAC ligands, their gold complexes proved more resistant to oxidation and more prone to halogen cleavage of the Au–C bonds than gold(I) complexes of imidazole-based NHC ligands. PMID:26146436

Dual role of imidazole as activator/inhibitor of sweet almond (Prunus dulcis) β-glucosidase.

PubMed

Caramia, Sara; Gatius, Angela Gala Morena; Dal Piaz, Fabrizio; Gaja, Denis; Hochkoeppler, Alejandro

2017-07-01

The activity of Prunus dulcis (sweet almond) β-glucosidase at the expense of p -nitrophenyl-β-d-glucopyranoside at pH 6 was determined, both under steady-state and pre-steady-state conditions. Using crude enzyme preparations, competitive inhibition by 1-5 mM imidazole was observed under both kinetic conditions tested. However, when imidazole was added to reaction mixtures at 0.125-0.250 mM, we detected a significant enzyme activation. To further inspect this effect exerted by imidazole, β-glucosidase was purified to homogeneity. Two enzyme isoforms were isolated, i.e. a full-length monomer, and a dimer containing a full-length and a truncated subunit. Dimeric β-glucosidase was found to perform much better than the monomeric enzyme, independently of the kinetic conditions used to assay enzyme activity. In addition, the sensitivity towards imidazole was found to differ between the two isoforms. While monomeric enzyme was indeed found to be relatively insensitive to imidazole, dimeric β-glucosidase was observed to be significantly activated by 0.125-0.250 mM imidazole under pre-steady-state conditions. Further, steady-state assays revealed that the addition of 0.125 mM imidazole to reaction mixtures increases the K m of dimeric enzyme from 2.3 to 6.7 mM. The activation of β-glucosidase dimer by imidazole is proposed to be exerted via a conformational transition poising the enzyme towards proficient catalysis.

Effects on transport of rapidly penetrating, competing substrates: activation and inhibition of the choline carrier in erythrocytes by imidazole.

PubMed

Devés, R; Krupka, R M

1987-01-01

The properties of the choline transport system are fundamentally altered in saline solution containing 5 mM imidazole buffer instead of 5 mM phosphate: (i) The system no longer exhibits accelerated exchange. (ii) Choline in the external compartment fails to increase the rate of inactivation of the carrier by N-ethylmaleimide. (iii) Depending on the relative concentrations of choline and imidazole, transport may be activated or inhibited. The maximum rates are increased more than fivefold by imidazole, but at moderate substrate concentrations activation is observed with low concentrations of imidazole and inhibition with high concentrations. (iv) The imidazole effect is asymmetric, there being a greater tendency to activate exit than entry. All this behavior is predicted by the carrier model if imidazole is a substrate of the choline carrier having a high maximum transport rate but a relatively low affinity, and if imidazole rapidly enters the cell by simple diffusion, so that it can add to carrier sites on both sides of the membrane. Addition at the cis side inhibits, and at the trans side activates. According to the carrier model, asymmetry is a necessary consequence of the potassium ion gradient in red cells, potassium ion being another substrate of the choline system.

Imidazole modified g-C3N4 photocatalyst: Structural characterization and versatile energy applications

NASA Astrophysics Data System (ADS)

Zhang, Lu; Liu, Qianqian; Chai, Yuanyuan; Ren, Jia; Dai, Wei-Lin

2018-02-01

Novel imidazole modified g-C3N4 were firstly synthesized via a facile one-pot thermo-induced co-condensation method. Characterization results showed that imidazole modification can improve the visible light harvesting, interfacial charge transfer and separation of g-C3N4, without destroying its pristine framework structure. The as-obtained imidazole modified g-C3N4 showed remarkably enhanced and rather stable photocatalytic performance in H2 evolution, photo-degradation of water contaminants and selective photo-oxidation of benzyl alcohol, demonstrating its all-round applications as a versatile photocatalyst. The weight ratio between imidazole and urea was well tuned and the optimal photocatalytic activity was obtained, which shows CNU-I50 sample (50 mg imidazole in 15 g urea) possesses the highest hydrogen evolution rate of 2150 μmol g-1 h-1, superior to most of the previous reported g-C3N4 materials. These results suggest that those imidazole modified g-C3N4 materials are potential photocatalyst when applied to solar energy conversion, water purification and selective photosynthesis reactions.

4-([1,2,4]Triazolo[1,5-a]pyridin-6-yl)-5(3)-(6-methylpyridin-2-yl)imidazole and -pyrazole derivatives as potent and selective inhibitors of transforming growth factor-β type I receptor kinase.

PubMed

Jin, Cheng Hua; Krishnaiah, Maddeboina; Sreenu, Domalapally; Subrahmanyam, Vura Bala; Park, Hyun-Ju; Park, So-Jung; Sheen, Yhun Yhong; Kim, Dae-Kee

2014-05-01

A series of 4-([1,2,4]triazolo[1,5-a]pyridin-6-yl)-5(3)-(6-methylpyridin-2-yl)imidazoles and -pyrazoles 14a-c, 15a-c, 16a, 16b, 19a-d, 21a, and 21b has been synthesized and evaluated for their ALK5 inhibitory activity in an enzyme assay and in a cell-based luciferase reporter assay. Among them, the pyrazole derivative 21b inhibited ALK5 phosphorylation with an IC50 value of 0.018 μM and showed 95% inhibition at 0.03 μM in a luciferase reporter assay using HaCaT cells permanently transfected with p3TP-luc reporter construct. The 21b showed a high selectivity index of 284 against p38α MAP kinase. The binding pose of 21b generated by docking analysis reveals that it fits well into the ATP binding cavity of ALK5 by forming several hydrogen bond interactions. Copyright © 2014 Elsevier Ltd. All rights reserved.

A NEW COPPER (II)-IMIDAZOLE DERIVATIVE EFFECTIVELY INHIBITS REPLICATION OF DENV-2 IN VERO CELL

PubMed Central

Sucipto, Teguh Hari; Churrotin, Siti; Setyawati, Harsasi; Martak, Fahimah; Mulyatno, Kris Cahyo; Amarullah, Ilham Harlan; Kotaki, Tomohiro; Kameoka, Masanori; Yotopranoto, Subagyo; Soegijanto, and Soegeng

2018-01-01

Background: Dengue is a kind of infectious disease that was distributed in the tropical and sub-tropical areas. To date, there is no clinically approved dengue vaccine or antiviral for humans, even though there have been great efforts towards this end. Therefore, finding the effective compound against dengue virus (DENV) replication is very important. Among the complex compounds, copper(II)-imidazole derivatives are of interest because of their biological and medicinal benefits. Materials and Methods: In the present study, antiviral activity of [Cu(2,4,5-triphenylimidazole)2]n, was evaluated against different stages of dengue virus type 2 (DENV-2) replication in Vero cell using focus forming unit reduction assay and quantitative ELISA. Results: [Cu(2,4,5-triphenylimidazole)2]n inhibited DENV-2 replication in Vero cells with IC50 = 2.3 μg/ml and SI= 19.42 when cells were treated 2 days after virus infection, whereas its CC50 for cytotoxicity to Vero cells was 44.174 μg/ml. Conclusion: The compound has high anti-DENV2 activity, less toxicity, and a high possibility to be considered a drug candidate. PMID:29619441

Effect of halogenated impurities on lifetime of organic light emitting diode

NASA Astrophysics Data System (ADS)

Yamawaki, Hayato; Suzuki, Kunihiko; Kubota, Tomohiro; Watabe, Takeyoshi; Ishigaki, Ayumi; Nakamura, Rina; Inoue, Hideko; Nakashima, Harue; Horikoshi, Nozomi; Nowatari, Hiromi; Kataishi, Riho; Hamada, Toshiki; Sasaki, Toshiki; Suzuki, Tsunenori; Seo, Satoshi

2016-09-01

We investigated a correlation between lifetime and the halogen element concentration in an organic light-emitting diode (OLED) and conducted experiments and simulations to discuss degradation mechanisms due to the halogen. OELD is generally formed of high-purity materials. Since the synthesis of high-purity materials takes time and cost, quantitative understanding of the kind, amount, and influence of impurities in OLED devices is expected. The results of combustion ion chromatography show that, if the chlorine concentration in the host material is more than several parts per million, the lifetime of the device is drastically reduced. The chlorine element, which is derived from the chlorinated by-product of the host material, is found to be transferred from the chloride to other materials (e.g., an emissive dopant) according to the results of LC-MS analysis. In addition, the electron transport layer including such impurities is also found to adversely affect the lifetime. The results of TOF-SIMS analysis suggest that the dissociated chlorine element diffuse to the light-emitting layer side when the device is driven. The results of simulations (Gaussian 09) and electrochemical analyses (cyclic voltammetry and electrolysis) reveal that the halogen element is easy to dissociate from halide by excitation or reduction. The halogen element can repeat reactions with the peripheral materials by excitation or reduction and cause damages, e.g., generate radicals or further reaction products due to the radicals. The results of simulation suggest that, such compounds have low energy level and become quenchers.

Synthesis, characterization, and molecular docking analysis of novel benzimidazole derivatives as cholinesterase inhibitors.

PubMed

Yoon, Yeong Keng; Ali, Mohamed Ashraf; Wei, Ang Chee; Choon, Tan Soo; Khaw, Kooi-Yeong; Murugaiyah, Vikneswaran; Osman, Hasnah; Masand, Vijay H

2013-08-01

Two series of novel acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitors containing benzimidazole core structure were synthesized by a four-step reaction pathway starting from 4-fluoro-3-nitrobenzoic acid as the basic compound. The structure of the novel benzimidazoles was characterized and confirmed by the elemental and mass spectral analyses as well as (1)H NMR spectroscopic data. Of the 34 novel synthesized compounds, three benzimidazoles revealed AChE inhibition with IC50<10 μM. The highest inhibitory activity (IC50=5.12 μM for AChE and IC50=8.63 μM for BChE) corresponds to the compound 5IIc (ethyl 1-(3-(1H-imidazol-1-yl)propyl)-2-(4-nitrophenyl)-1H-benzo[d]imidazole-5-carboxylate). The relationship between lipophilicity and the chemical structures as well as their limited structure-activity relationship was discussed. Copyright © 2013 Elsevier Inc. All rights reserved.

Sulfur-containing compounds quench 3,7-dihydro-2-methyl-6-(4-methoxyphenyl)imidazol[1,2-a]pyrazine-3-one chemiluminescence: Discrimination between true antioxidants and quenchers using xanthine oxidase.

PubMed

Kruglov, Alexey G; Nikiforova, Anna B; Shatalin, Yuri V; Shubina, Viktoria V; Fisyuk, Alexander S; Akatov, Vladimir S

2010-11-15

The probe 3,7-dihydro-2-methyl-6-(4-methoxyphenyl)imidazol[1,2-a]pyrazine-3-one (MCLA) is widely used for studying the superoxide anion production and the efficiency of antioxidants in biological systems. Here we report that a number of sulfur-containing compounds applied in biochemical and cytological studies are able to suppress MCLA-derived chemiluminescence (MDCL) independent of their capability to scavenge superoxide anion. The most effective MDCL quenchers appeared to be the substances with thiocarbamoyl and thiocarbonyl groups coupled to cyclic molecules and several thiol- and disulfide-containing compounds. The analysis of MDCL kinetics in a xanthine oxidase system allows one to rapidly discriminate between true antioxidants and the quenchers of chemiluminescence. Copyright 2010 Elsevier Inc. All rights reserved.

40 CFR 180.426 - 2-[4,5-Dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-quinoline carboxylic acid...

Code of Federal Regulations, 2010 CFR

2010-07-01

...-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-quinoline carboxylic acid; tolerance for residues. 180.426 Section 180...-Dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-quinoline carboxylic acid; tolerance for...)-5-oxo-1H-imidazol-2-yl]-3-quinoline carboxylic acid, in or on the raw agricultural commodity soybean...

Proton transfer from imidazole to chloranil studied by FTIR spectroscopy

NASA Astrophysics Data System (ADS)

Sharma, Amit

2018-05-01

Imidazole is incorporated into many important biological molecules. The most obvious is the amino acid histidine, which has an imidazole side chain. Histidine is present in many proteins and enzymes and plays a vital part in the structure and binding functions of hemoglobin. Therefore it is important to study its proton transfer property. In the present work proton transfer from imidazole to chloranil is investigated by Fourier Transform Infra red Spectroscopy.

15N Hyperpolarization of Imidazole-15N2 for Magnetic Resonance pH Sensing via SABRE-SHEATH

PubMed Central

2016-01-01

15N nuclear spins of imidazole-15N2 were hyperpolarized using NMR signal amplification by reversible exchange in shield enables alignment transfer to heteronuclei (SABRE-SHEATH). A 15N NMR signal enhancement of ∼2000-fold at 9.4 T is reported using parahydrogen gas (∼50% para-) and ∼0.1 M imidazole-15N2 in methanol:aqueous buffer (∼1:1). Proton binding to a 15N site of imidazole occurs at physiological pH (pKa ∼ 7.0), and the binding event changes the 15N isotropic chemical shift by ∼30 ppm. These properties are ideal for in vivo pH sensing. Additionally, imidazoles have low toxicity and are readily incorporated into a wide range of biomolecules. 15N-Imidazole SABRE-SHEATH hyperpolarization potentially enables pH sensing on scales ranging from peptide and protein molecules to living organisms. PMID:27379344

15N Hyperpolarization of Imidazole-15N2 for Magnetic Resonance pH Sensing via SABRE-SHEATH.

PubMed

Shchepin, Roman V; Barskiy, Danila A; Coffey, Aaron M; Theis, Thomas; Shi, Fan; Warren, Warren S; Goodson, Boyd M; Chekmenev, Eduard Y

2016-06-24

15 N nuclear spins of imidazole- 15 N 2 were hyperpolarized using NMR signal amplification by reversible exchange in shield enables alignment transfer to heteronuclei (SABRE-SHEATH). A 15 N NMR signal enhancement of ∼2000-fold at 9.4 T is reported using parahydrogen gas (∼50% para-) and ∼0.1 M imidazole- 15 N 2 in methanol:aqueous buffer (∼1:1). Proton binding to a 15 N site of imidazole occurs at physiological pH (p K a ∼ 7.0), and the binding event changes the 15 N isotropic chemical shift by ∼30 ppm. These properties are ideal for in vivo pH sensing. Additionally, imidazoles have low toxicity and are readily incorporated into a wide range of biomolecules. 15 N-Imidazole SABRE-SHEATH hyperpolarization potentially enables pH sensing on scales ranging from peptide and protein molecules to living organisms.

Halogens in normal- and enriched-basalts from Central Indian Ridge (18-20°S): Testing the E-MORB subduction origin hypothesis

NASA Astrophysics Data System (ADS)

Ruzie, L.; Burgess, R.; Hilton, D. R.; Ballentine, C. J.

2012-12-01

Basalts emitted along oceanic ridges have often been subdivided into two categories: the Normal-MORB and the Enriched-MORB, anomalously enriched in highly incompatible elements. Donnelly et al. (2004) proposed that the formation of enriched sources is related to two stages of melting. The first one occurs in subduction zones where the mantle wedge is enriched by the addition of low-degree melts of subducted slab. The second stage of melting occurs beneath ocean ridges. Because of their incompatibility, relatively high concentrations and distinct elemental compositions in surface reservoirs, the heavy halogens (Cl, Br, I) are good tracers to detect the slab contribution in E-MORB sources. However, the halogen systematics in mantle reservoirs remains poorly constrained mainly because of their very low abundance in materials of interest. An innovative halogen analytical technique, developed at the University of Manchester, involving neutron irradiation of samples to convert halogens to noble gases provides detection limits unmatched by any other technique studies [Johnson et al. 2000]. For the first time Cl, Br and I can now be determined in appropriate samples. We focus on the content of halogens in the glassy margins of basalts erupted along the CIR from 18-20°S and the off-axis Gasitao Ridge. Our set of samples contains both N- and E-MORB and is fully described in terms of major and trace elements, as well as 3He/4He ratios and water concentrations [Murton et al., 2005; Nauret et al., 2006; Füri et al., 2011; Barry et al., in prep.]. The halogen concentration range is between 10 and 140 ppm for Cl, 30 and 500 ppb for Br and 0.8 and 10 ppb for I. The higher concentrations are found in E-MORB samples from the northern part of ridge axis. Comparing our data with previous halogen studies, our sample suites fall within the range of N-MORB from East Pacific Ridge (EPR) and Mid-Atlantic Ridge (MAR) [Jambon et al. 1995; Deruelle et al. 1992] and in the lower range of E-MORB from Macquarie Island [Kendrick et al., 2012]. The concentrations are not related to superficial processes. The on-axis samples display a relatively restricted range (6.9-8.6wt%) of MgO contents, suggesting no control of the crystallisation processes. The basalts were erupted between 3900-2000 m bsl, so no appreciable degassing of halogens would be expected. The strong correlation, which exists between the halogens and other incompatible elements (e.g., Rb, La), also rules out seawater assimilation. Therefore, concentrations and elemental ratios can be directly linked to melting and source features. Estimates of halogens abundances in the depleted-mantle source are 4 ppm Cl, 14 ppb Br and 0.3 ppb I. These low abundances, which are in agreement with values derived for sub-continental mantle from coated diamonds [Burgess et al., 2002], suggest that, like noble gases, the upper mantle is degassed of its halogens. Critically, the halogen elemental ratios show no significant variations along the axial ridge and off-axis ridge or between N-MORB and E-MORB: Br/Cl=0.00147±0.00014, I/Cl=0.000021±0.000005; I/Br=0.0142±0.0036. These ratios are similar to E-MORB from Macquarie Island [Kendrick et al., 2012]. This observation is thus not consistent with subduction as a source of halogen enrichment in E-MORB.

Benzimidazole derivatives: selective fluorescent chemosensors for the picogram detection of picric acid.

PubMed

Xiong, Jin-Feng; Li, Jian-Xiao; Mo, Guang-Zhen; Huo, Jing-Pei; Liu, Jin-Yan; Chen, Xiao-Yun; Wang, Zhao-Yang

2014-12-05

1,3,5-Tri(1H-benzo[d]imidazol-2-yl)benzene derivatives, as a new kind of fluorescent chemosensor for the detection of nitroaromatic explosives, are designed and synthesized by simple N-hydrocarbylation. Among 16 obtained compounds, compound 4g has the best capability for detection of picric acid (PA), having good selectivity and high sensitivity. The detection of PA with 4g solution-coated paper strips at the picogram level is developed. A simple, portable, and low-cost method is provided for detecting PA in solution and contact mode.

Atmosphere-Ocean Coupling through Trace Gases

NASA Astrophysics Data System (ADS)

Tegtmeier, S.; Atlas, E. L.; Krüger, K.; Lennartz, S. T.; Marandino, C. A.; Patra, P. K.; Quack, B.; Schlundt, C.

2017-12-01

Halogen- and sulfur-containing trace gases, as well as other volatile organic compounds (VOCs, such as isoprene) from biogeochemical marine sources are important constituents of the ocean and the atmosphere. These compounds exert wide-ranging influence on atmospheric chemical processes and climate interactions, as well as on human health in coastal regions. In their reactive form, they can affect the oxidizing capacity of the air and lead to the formation of new particles or the growth of existing ones. In this contribution, marine derived halogen-, sulfur-, and oxygen-containing compounds will be discussed. Their net flux into the atmosphere and their impact on atmospheric processes is analyzed based on observations and model simulations.

The Suzuki-Miyaura Cross-Coupling Reaction of Halogenated Aminopyrazoles: Method Development, Scope, and Mechanism of Dehalogenation Side Reaction.

PubMed

Jedinák, Lukáš; Zátopková, Renáta; Zemánková, Hana; Šustková, Alena; Cankař, Petr

2017-01-06

The efficient Suzuki-Miyaura cross-coupling reaction of halogenated aminopyrazoles and their amides or ureas with a range of aryl, heteroaryl, and styryl boronic acids or esters has been developed. The method allowed incorporation of problematic substrates: aminopyrazoles bearing protected or unprotected pyrazole NH, as well as the free amino or N-amide group. Direct comparison of the chloro, bromo, and iodopyrazoles in the Suzuki-Miyaura reaction revealed that Br and Cl derivatives were superior to iodopyrazoles, as a result of reduced propensity to dehalogenation. Moreover, the mechanism and factors affecting the undesired dehalogenation side reaction were revealed.

Nonthmicin, a Polyether Polyketide Bearing a Halogen-Modified Tetronate with Neuroprotective and Antiinvasive Activity from Actinomadura sp.

PubMed

Igarashi, Yasuhiro; Matsuoka, Noriaki; In, Yasuko; Kataura, Tetsushi; Tashiro, Etsu; Saiki, Ikuo; Sudoh, Yuri; Duangmal, Kannika; Thamchaipenet, Arinthip

2017-03-17

Nonthmicin (1), a new polyether polyketide bearing a chlorinated tetronic acid, was isolated from the culture extract of a soil-derived Actinomadura strain. The structure of 1 was elucidated by interpretation of NMR and MS spectroscopic data, and the absolute configuration of 1 was proposed on the basis of the crystal structure of its dechloro congener ecteinamycin (2) also isolated from the same strain. Tetronic acids modified by halogenation have never been reported from natural products. Compounds 1 and 2 were found to have neuroprotective activity and antimetastatic properties at submicromolar concentrations in addition to antibacterial activity.

Engineering of new-to-nature halogenated indigo precursors in plants.

PubMed

Fräbel, Sabine; Wagner, Bastian; Krischke, Markus; Schmidts, Volker; Thiele, Christina M; Staniek, Agata; Warzecha, Heribert

2018-03-01

Plants are versatile chemists producing a tremendous variety of specialized compounds. Here, we describe the engineering of entirely novel metabolic pathways in planta enabling generation of halogenated indigo precursors as non-natural plant products. Indican (indolyl-β-D-glucopyranoside) is a secondary metabolite characteristic of a number of dyers plants. Its deglucosylation and subsequent oxidative dimerization leads to the blue dye, indigo. Halogenated indican derivatives are commonly used as detection reagents in histochemical and molecular biology applications; their production, however, relies largely on chemical synthesis. To attain the de novo biosynthesis in a plant-based system devoid of indican, we employed a sequence of enzymes from diverse sources, including three microbial tryptophan halogenases substituting the amino acid at either C5, C6, or C7 of the indole moiety. Subsequent processing of the halotryptophan by bacterial tryptophanase TnaA in concert with a mutant of the human cytochrome P450 monooxygenase 2A6 and glycosylation of the resulting indoxyl derivatives by an endogenous tobacco glucosyltransferase yielded corresponding haloindican variants in transiently transformed Nicotiana benthamiana plants. Accumulation levels were highest when the 5-halogenase PyrH was utilized, reaching 0.93 ± 0.089 mg/g dry weight of 5-chloroindican. The identity of the latter was unambiguously confirmed by NMR analysis. Moreover, our combinatorial approach, facilitated by the modular assembly capabilities of the GoldenBraid cloning system and inspired by the unique compartmentation of plant cells, afforded testing a number of alternative subcellular localizations for pathway design. In consequence, chloroplasts were validated as functional biosynthetic venues for haloindican, with the requisite reducing augmentation of the halogenases as well as the cytochrome P450 monooxygenase fulfilled by catalytic systems native to the organelle. Thus, our study puts forward a viable alternative production platform for halogenated fine chemicals, eschewing reliance on fossil fuel resources and toxic chemicals. We further contend that in planta generation of halogenated indigoid precursors previously unknown to nature offers an extended view on and, indeed, pushes forward the established frontiers of biosynthetic capacity of plants. Copyright © 2018 International Metabolic Engineering Society. Published by Elsevier Inc. All rights reserved.

Loading Ag nanoparticles on Cd(II) boron imidazolate framework for photocatalysis

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

Liu, Min; State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002; Zhang, De-Xiang

2016-05-15

An amine-functionalized Cd(II) boron imidazolate framework (BIF-77) with three-dimensional open structure has been successfully synthesized, which can load Ag nanoparticles (NPs) for photocatalytic degradation of methylene blue (MB). - Graphical abstract: An amine-functionalized neutral Cd(II) boron imidazolate framework can load Ag NPs and show excellent photocatalytic degradation behavious for MB. - Highlights: • Amine-functionalization. • Neutral boron imidazolate framework. • Loading Ag nanoparticles (NPs). • Photocatalytic degradation of methylene blue.

Chemistry and Biology of the Pyrrole-Imidazole Alkaloids.

PubMed

Lindel, Thomas

More than a decade after our last review on the chemistry of the pyrrole-imidazole alkaloids, it was time to analyze once more the developments in that field. The comprehensive article focusses on the total syntheses of pyrrole-imidazole alkaloids that have appeared since 2005. The classic monomeric pyrrole-imidazole alkaloids have all been synthesized, sometimes primarily to demonstrate the usefulness of a new method, as in the case of the related molecules agelastatin A and cyclooroidin with more than 15 syntheses altogether. The phakellin skeleton has been made more than 10 times, too, with a focus on the target structure itself. Thus, some of the pyrrole-imidazole alkaloids are now available in gram amounts, and the supply problem has been solved. The total synthesis of the dimeric pyrrole-imidazole alkaloids is still mostly in its pioneering phase with two routes to palau'amine and massadine discovered and three routes to the axinellamines and ageliferin. In addition, the review summarizes recent discoveries regarding the biological activity of the pyrrole-imidazole alkaloids. Regarding the biosynthesis of sceptrin, a pathway is proposed that starts from nagelamide I and proceeds via two electrocyclizations and reduction. Copyright © 2017 Elsevier Inc. All rights reserved.

Source regions of stratospheric VSLS in the Indian Ocean

NASA Astrophysics Data System (ADS)

Quack, Birgit; Hepach, Helmke; Atlas, Elliot; Bracher, Astrid; Endres, Sonja; Arevalo-Martinez, Damian; Bange, Hermann; Lennartz, Sinikka; Steinhoff, Tobias; Booge, Dennis; Zarvasky, Alexander; Marandino, Christa; Patey, Matt; Achterberg, Eric; Dengler, Markus; Fiehn, Alina; Tegtmeier, Susann; Krüger, Kirstin

2016-04-01

Halogenated very-short-lived substances (VSLS), which are naturally produced in the ocean, play a significant role in present day ozone depletion, in particular in combination with enhanced stratospheric sulfate aerosol, which is also partly derived from oceanic VSLS. The decline of anthropogenic chlorine in the stratosphere within the 21st century will increase the relative importance of the natural emissions on stratospheric ozone destruction. Especially, oceanic sources and source regions of the compounds need to be better constrained, in order to improve the future prediction. During boreal summer the Asian monsoon circulation transports air masses from the Indian Ocean to the stratosphere, while the contribution of VSLS from this ocean to stratospheric halogen and sulfur is unknown. During the research cruises SO 234/2 and SO 235 in July-August 2014 onboard RV SONNE oceanic and atmospheric halogenated VSLS such as bromoform (CHBr3), dibromomethane (CH2Br2) and methyl iodide (CH3I) were measured in the subtropical and tropical West Indian Ocean for the first time. Here we present the oceanic sources of the halogenated compounds and their relation to other biogeochemical parameters (short- and longlived trace gases, phytoplankton and nutrients) along the cruise track, which covered coastal, upwelling and open ocean regimes and the Seychelles-Chagos thermocline ridge as important source region for stratospheric bromine.

Force Field Model of Periodic Trends in Biomolecular Halogen Bonds

PubMed Central

Scholfield, Matthew R.; Ford, Melissa Coates; Vander Zanden, Crystal M.; Billman, M. Marie; Ho, P. Shing; Rappé, Anthony K.

2016-01-01

The study of the noncovalent interaction now defined as a halogen bond (X-bond) has become one of the fastest growing areas in experimental and theoretical chemistry—its applications as a design tool are highly extensive. The significance of the interaction in biology has only recently been recognized, but has now become important in medicinal chemistry. We had previously derived a set of empirical potential energy functions to model the structure-energy relationships for bromines in biomolecular X-bonds (BXBs). Here, we have extended this force field for BXBs (ffBXB) to the halogens (Cl, Br, and I) that are commonly seen to form stable X-bonds. The ffBXB calculated energies show a remarkable one-to-one linear relationship to explicit BXB energies determined from an experimental DNA junction system, thereby validating the approach and the model. The resulting parameters allow us to interpret the stabilizing effects of BXBs in terms of well-defined physical properties of the halogen atoms, including their size, shape, and charge, showing periodic trends that are predictable along the Group VII column of elements. Consequently, we have established the ffBXB as accurate computational tool that can be applied to, for example, for the design of new therapeutic compounds against clinically important targets and new biomolecular based materials. PMID:25338128

Synthesis, Physicochemical Properties, and Hydrogen Bonding of 4(5)-Substituted 1-H-Imidazole-2-carboxamide, A Potential Universal Reader for DNA Sequencing by Recognition Tunneling

PubMed Central

Liang, Feng; Li, Shengqing

2012-01-01

We have developed a chemical reagent that recognizes all naturally occurring DNA bases, a so called universal reader, for DNA sequencing by recognition tunnelling in nanopores.[1] The primary requirements for this type of molecules are the ability to form non-covalent complexes with individual DNA bases and to generate recognizable electronic signatures under an electrical bias. 1-H-imidazole-2-carboxamide was designed as such a recognition moiety to interact with the DNA bases through hydrogen bonding. In the present study, we first furnished a synthetic route to 1-H-imidazole-2-carboxamide containing a short ω-functionalized alkyl chain at its 4(5) position for its attachment to metal and carbon electrodes. The acid dissociation constants of the imidazole-2-carboxamide were then determined by UV spectroscopy. The data show that the 1-H-imidazole-2-carboxamide exists in a neutral form between pH 6–10. Density functional theory (DFT) and NMR studies indicate that the imidazole ring exists in prototropic tautomers. We propose an intramolecular mechanism for tautomerization of 1-H-imidazole-2-carboxamide. In addition, the imidazole-2-carboxamide can self-associate to form hydrogen bonded dimers. NMR titration found that naturally occurring nucleosides interacted with 1-H-imidazole-2-carboxamide through hydrogen bonding in a tendency of dG>dC≫dT> dA. These studies are indispensable to assisting us in understanding the molecular recognition that takes place in the nanopore where routinely used analytical tools such as NMR and FTIR cannot be conveniently applied. PMID:22461259

Biology-oriented drug synthesis (BIODS): In vitro β-glucuronidase inhibitory and in silico studies on 2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl aryl carboxylate derivatives.

PubMed

Salar, Uzma; Khan, Khalid Mohammed; Taha, Muhammad; Ismail, Nor Hadiani; Ali, Basharat; Qurat-Ul-Ain; Perveen, Shahnaz; Ghufran, Mehreen; Wadood, Abdul

2017-01-05

Current study is based on the biology-oriented drug synthesis (BIODS) of 2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl aryl carboxylate derivatives 1-26, by treating metronidazole with different aryl and hetero-aryl carboxylic acids in the presence of 1,1'-carbonyl diimidazole (CDI) as a coupling agent. Structures of all synthetic derivatives were confirmed with the help of various spectroscopic techniques such as EI-MS, 1 H -NMR and 13 C NMR. CHN elemental analyses were also found in agreement with the calculated values. Synthetic derivatives were evaluated to check their β-glucuronidase inhibitory activity which revealed that except few derivatives, all demonstrated good inhibition in the range of IC 50  = 1.20 ± 0.01-60.30 ± 1.40 μM as compared to the standard d-saccharic acid 1,4-lactone (IC 50  = 48.38 ± 1.05 μM). Compounds 1, 3, 4, 6, 9-19, and 21-24 were found to be potent analogs and showed superior activity than standard. Limited structure-activity relationship is suggested that the molecules having electron withdrawing groups like NO 2 , F, Cl, and Br, were displayed better activity than the compounds with electron donating groups such as Me, OMe and BuO. To verify these interpretations, in silico study was also performed, a good correlation was observed between bioactivities and docking studies. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

On the organocatalytic activity of N-heterocyclic carbenes: role of sulfur in thiamine.

PubMed

Hollóczki, Oldamur; Kelemen, Zsolt; Nyulászi, László

2012-07-20

The reaction energy profiles of the benzoin condensation from three aldehydes catalyzed by imidazol-2-ylidene, triazol-3-ylidene, and thiazol-2-ylidene have been investigated computationally. The barriers for all steps of all investigated reactions have been found to be low enough to indicate the viability of the mechanism proposed by Breslow in the 1950s. The most remarkable difference in the catalytic cycles has been the increased stability of the Breslow intermediate in case of thiazol-2-ylidene (by ca. 10 kcal/mol) compared to the other two carbenes, which results in lower energy for the coupling of the second aldehyde molecule, thus, increasing the reversibility of the reaction. Since the analogous transketolase reaction, being involved in the carbohydrate metabolism of many organisms, requires an initial decoupling-a reverse benzoin condensation-this difference provides a reasonable explanation for the presence of a thiazolium ring in thiamine instead of the otherwise generally more available imidazole derivatives. The "resting intermediate" found by Berkessel and co-workers for a triazole-based catalyst was found more stable than the Breslow intermediate for all of the systems investigated. The (gas phase) proton affinities of several carbenes were compared, the relative trends being in agreement with the available (in aqueous solution) data. The hydrolytic ring-opening reaction of the thiazole-based carbene was shown to be different from that of imidazole-2-ylidenes.

An ab initio MO study of heavy atom effects on the zero-field splitting tensors of high-spin nitrenes: how the spin-orbit contributions are affected.

PubMed

Sugisaki, Kenji; Toyota, Kazuo; Sato, Kazunobu; Shiomi, Daisuke; Kitagawa, Masahiro; Takui, Takeji

2014-05-21

The CASSCF and the hybrid CASSCF-MRMP2 methods are applied to the calculations of spin-spin and spin-orbit contributions to the zero-field splitting tensors (D tensors) of the halogen-substituted spin-septet 2,4,6-trinitrenopyridines, focusing on the heavy atom effects on the spin-orbit term of the D tensors (D(SO) tensors). The calculations reproduced experimentally determined |D| values within an error of 15%. Halogen substitutions at the 3,5-positions are less influential in the spin-spin dipolar (D(SS)) term of 2,4,6-trinitrenopyridines, although the D(SO) terms are strongly affected by the introduction of heavier halogens. The absolute sign of the D(SO) value (D = D(ZZ) - (D(XX) + D(YY))/2) of 3,5-dibromo derivative 3 is predicted to be negative, which contradicts the Pederson-Khanna (PK) DFT result previously reported. The large negative contributions to the D(SO) value of 3 arise from the excited spin-septet states ascribed mainly to the excitations of in-plane lone pair of bromine atoms → SOMO of π nature. The importance of the excited states involving electron transitions from the lone pair orbital of the halogen atom is also confirmed in the D(SO) tensors of halogen-substituted para-phenylnitrenes. A new scheme based on the orbital region partitioning is proposed for the analysis of the D(SO) tensors as calculated by means of the PK-DFT approach.

A refined method for calculating equivalent effective stratospheric chlorine

NASA Astrophysics Data System (ADS)

Engel, Andreas; Bönisch, Harald; Ostermöller, Jennifer; Chipperfield, Martyn P.; Dhomse, Sandip; Jöckel, Patrick

2018-01-01

Chlorine and bromine atoms lead to catalytic depletion of ozone in the stratosphere. Therefore the use and production of ozone-depleting substances (ODSs) containing chlorine and bromine is regulated by the Montreal Protocol to protect the ozone layer. Equivalent effective stratospheric chlorine (EESC) has been adopted as an appropriate metric to describe the combined effects of chlorine and bromine released from halocarbons on stratospheric ozone. Here we revisit the concept of calculating EESC. We derive a refined formulation of EESC based on an advanced concept of ODS propagation into the stratosphere and reactive halogen release. A new transit time distribution is introduced in which the age spectrum for an inert tracer is weighted with the release function for inorganic halogen from the source gases. This distribution is termed the release time distribution. We show that a much better agreement with inorganic halogen loading from the chemistry transport model TOMCAT is achieved compared with using the current formulation. The refined formulation shows EESC levels in the year 1980 for the mid-latitude lower stratosphere, which are significantly lower than previously calculated. The year 1980 is commonly used as a benchmark to which EESC must return in order to reach significant progress towards halogen and ozone recovery. Assuming that - under otherwise unchanged conditions - the EESC value must return to the same level in order for ozone to fully recover, we show that it will take more than 10 years longer than estimated in this region of the stratosphere with the current method for calculation of EESC. We also present a range of sensitivity studies to investigate the effect of changes and uncertainties in the fractional release factors and in the assumptions on the shape of the release time distributions. We further discuss the value of EESC as a proxy for future evolution of inorganic halogen loading under changing atmospheric dynamics using simulations from the EMAC model. We show that while the expected changes in stratospheric transport lead to significant differences between EESC and modelled inorganic halogen loading at constant mean age, EESC is a reasonable proxy for modelled inorganic halogen on a constant pressure level.

40 CFR 65.154 - Halogen scrubbers and other halogen reduction devices.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 15 2011-07-01 2011-07-01 false Halogen scrubbers and other halogen... Routing to a Fuel Gas System or a Process § 65.154 Halogen scrubbers and other halogen reduction devices. (a) Halogen scrubber and other halogen reduction device equipment and operating requirements. (1) An...

Zeolitic imidazolate frameworks for kinetic separation of propane and propene

DOEpatents

Li, Jing; Li, Kunhao; Olson, David H.

2014-08-05

Zeolitic Imidazolate Frameworks (ZIFs) characterized by organic ligands consisting of imidazole ligands that are either essentially all 2-chloroimidazole ligands or essentially all 2-bromoimidazole ligands are disclosed. Methods for separating propane and propene with the ZIFs of the present invention, as well as other ZIFs, are also disclosed.

High-Resolution Infrared Spectroscopy of Imidazole Clusters in Helium Droplets Using Quantum Cascade Lasers

NASA Astrophysics Data System (ADS)

Mani, Devendra; Can, Cihad; Pal, Nitish; Schwaab, Gerhard; Havenith, Martina

2017-06-01

Imidazole ring is a part of many biologically important molecules and drugs. Imidazole monomer, dimer and its complexes with water have earlier been studied using infrared spectroscopy in helium droplets^{1,2} and molecular beams^{3}. These studies were focussed on the N-H and O-H stretch regions, covering the spectral region of 3200-3800 \\wn. We have extended the studies on imidazole clusters into the ring vibration region. The imidazole clusters were isolated in helium droplets and were probed using a combination of infrared spectroscopy and mass spectrometry. The spectra in the region of 1000-1100 \\wn and 1300-1460 \\wn were recorded using quantum cascade lasers. Some of the observed bands could be assigned to imidazole monomer and higher order imidazole clusters, using pickup curve analysis and ab initio calculations. Work is still in progress. The results will be discussed in detail in the talk. References: 1) M.Y. Choi and R.E. Miller, J. Phys. Chem. A, 110, 9344 (2006). 2) M.Y. Choi and R.E. Miller, Chem. Phys. Lett., 477, 276 (2009). 3) J. Zischang, J. J. Lee and M. Suhm, J. Chem. Phys., 135, 061102 (2011). Note: This work was supported by the Cluster of Excellence RESOLV (Ruhr-Universitat EXC1069) funded by the Deutsche Forschungsgemeinschaft.

Absolute configuration and crystal packing chirality for three conglomerate-forming ortho-halogen substituted phenyl glycerol ethers

NASA Astrophysics Data System (ADS)

Bredikhin, Alexander A.; Gubaidullin, Aidar T.; Bredikhina, Zemfira A.

2010-06-01

Three conglomerate-forming ortho-Hal (Hal = Cl, Br, I) substituted phenyl glycerol ethers 1- 3 were investigated by single-crystal X-ray analysis, and the absolute configuration for all substances was established. The molecular structures and crystal packing details for halogen derivatives were compared with the same characteristics for ortho-OCH 3 and ortho-CH 3 analogues. Two different types of crystal packing were evaluated for these very much alike compounds. The interplay of the supramolecular crystal organization chirality sense and the single molecule absolute configuration was demonstrated. Some stabilizing and destabilizing interactions involving the ortho-substituents were revealed. The resolution of rac-2 by entrainment procedure was successfully realized.

Volatile composition of microinclusions in diamonds from the Panda kimberlite, Canada: Implications for chemical and isotopic heterogeneity in the mantle

NASA Astrophysics Data System (ADS)

Burgess, Ray; Cartigny, Pierre; Harrison, Darrell; Hobson, Emily; Harris, Jeff

2009-03-01

In order to better investigate the compositions and the origins of fluids associated with diamond growth, we have carried-out combined noble gas (He and Ar), C and N isotope, K, Ca and halogen (Cl, Br, I) determinations on fragments of individual microinclusion-bearing diamonds from the Panda kimberlite, North West Territories, Canada. The fluid concentrations of halogens and noble gases in Panda diamonds are enriched by several orders of magnitude over typical upper mantle abundances. However, noble gas, C and N isotopic ratios ( 3He/ 4He = 4-6 Ra, 40Ar/ 36Ar = 20,000-30,000, δ 13C = -4.5‰ to -6.9‰ and δ 15N = -1.2‰ to -8.8‰) are within the worldwide range determined for fibrous diamonds and similar to the mid ocean ridge basalt (MORB) source value. The high 36Ar content of the diamonds (>1 × 10 -9 cm 3/g) is at least an order of magnitude higher than any previously reported mantle sample and enables the 36Ar content of the subcontinental lithospheric mantle to be estimated at ˜0.6 × 10 -12 cm 3/g, again similar to estimates for the MORB source. Three fluid types distinguished on the basis of Ca-K-Cl compositions are consistent with carbonatitic, silicic and saline end-members identified in previous studies of diamonds from worldwide sources. These fluid end-members also have distinct halogen ratios (Br/Cl and I/Cl). The role of subducted seawater-derived halogens, originally invoked to explain some of the halogen ratio variations in diamonds, is not considered an essential component in the formation of the fluids. In contrast, it is considered that large halogen fractionation of a primitive mantle ratio occurs during fluid-melt partitioning in forming silicic fluids, and during separation of an immiscible saline fluid.

Cytoprotection of Human Endothelial Cells Against Oxidative Stress by 1-[2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]imidazole (CDDO-Im): Application of Systems Biology to Understand the Mechanism of Action

DTIC Science & Technology

2014-04-03

and exogenous oxidants, electrophiles , and toxicants. Activation of this pathway was reported to facilitate the induction of HMOX1 (Heiss et al., 2009...cytoprotective effect of caffeic acid phenethyl ester (CAPE) and fluorinated derivatives: effects on heme oxygenase-1 induction and antioxidant

Controllable Construction of Core-Shell Polymer@Zeolitic Imidazolate Frameworks Fiber Derived Heteroatom-Doped Carbon Nanofiber Network for Efficient Oxygen Electrocatalysis.

PubMed

Zhao, Yingxuan; Lai, Qingxue; Zhu, Junjie; Zhong, Jia; Tang, Zeming; Luo, Yan; Liang, Yanyu

2018-05-01

Designing rational nanostructures of metal-organic frameworks based carbon materials to promote the bifunctional catalytic activity of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is highly desired but still remains a great challenge. Herein, an in situ growth method to achieve 1D structure-controllable zeolitic imidazolate frameworks (ZIFs)/polyacrylonitrile (PAN) core/shell fiber (PAN@ZIFs) is developed. Subsequent pyrolysis of this precursor can obtain a heteroatom-doped carbon nanofiber network as an efficient bifunctional oxygen electrocatalyst. The electrocatalytic performance of derived carbon nanofiber is dominated by the structures of PAN@ZIFs fiber, which is facilely regulated by efficiently controlling the nucleation and growth process of ZIFs on the surface of polymer fiber as well as optimizing the components of ZIFs. Benefiting from the core-shell structures with appropriate dopants and porosity, as-prepared catalysts show brilliant bifunctional ORR/OER catalytic activity and durability. Finally, the rechargeable Zn-air battery assembled from the optimized catalyst (CNF@Zn/CoNC) displays a peak power density of 140.1 mW cm -2 , energy density of 878.9 Wh kg Zn -1 , and excellent cyclic stability over 150 h, giving a promising performance in realistic application. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and characterization of tetra phenoxy-substituted halogen-rich metallophthalocyanine derivatives: A study on their LCD color filter requirements

NASA Astrophysics Data System (ADS)

Muthukumar, Palanisamy; Kim, Hak-Soo; Jeong, Jong Woo; Son, Young-A.

2016-09-01

This study addresses the synthesis and characterization of new tetra phenoxy-substituted halogen-rich metallophthalocyanine derivatives (MPcs) 4-7 (M = Co, Ni, Cu and Zn). The synthesized new compounds were characterized using UV-Vis, FT-IR, MALDI-TOF, 1H NMR and elemental analyses. In addition, the basic requirements such as aggregation behavior, thermal stability, transmittance and solubility in propylene glycol monomethyl ether acetate (PGMEA) of MPcs 4-7 were investigated for their usage as a green color filter in Liquid Crystal Displays (LCDs). All of the MPcs showed thermal stability and sufficient solubility in PGMEA. However, the addition of binder into PGMEA solution of MPcs 5 and 6 leads to precipitation. Among the four MPcs, zinc phthalocyanine (7) showed higher transmittance. The higher transmittance of zinc phthalocyanine (7) along with its thermal stability and sufficient solubility in PGMEA are promising for its application as a green color filter in LCDs.

40 CFR 63.994 - Halogen scrubbers and other halogen reduction devices.

Code of Federal Regulations, 2012 CFR

2012-07-01

... halogen scrubber or other halogen reduction technique used to reduce the vent stream halogen atom mass... subpart shall determine the halogen atom mass emission rate prior to the combustion device according to...

40 CFR 63.994 - Halogen scrubbers and other halogen reduction devices.

Code of Federal Regulations, 2014 CFR

2014-07-01

... halogen scrubber or other halogen reduction technique used to reduce the vent stream halogen atom mass... subpart shall determine the halogen atom mass emission rate prior to the combustion device according to...

40 CFR 63.994 - Halogen scrubbers and other halogen reduction devices.

Code of Federal Regulations, 2010 CFR

2010-07-01

... halogen scrubber or other halogen reduction technique used to reduce the vent stream halogen atom mass... subpart shall determine the halogen atom mass emission rate prior to the combustion device according to...

40 CFR 63.994 - Halogen scrubbers and other halogen reduction devices.

Code of Federal Regulations, 2013 CFR

2013-07-01

... halogen scrubber or other halogen reduction technique used to reduce the vent stream halogen atom mass... subpart shall determine the halogen atom mass emission rate prior to the combustion device according to...

40 CFR 63.994 - Halogen scrubbers and other halogen reduction devices.

Code of Federal Regulations, 2011 CFR

2011-07-01

... halogen scrubber or other halogen reduction technique used to reduce the vent stream halogen atom mass... subpart shall determine the halogen atom mass emission rate prior to the combustion device according to...

A single amino acid substitution makes ERK2 susceptible to pyridinyl imidazole inhibitors of p38 MAP kinase.

PubMed Central

Fox, T.; Coll, J. T.; Xie, X.; Ford, P. J.; Germann, U. A.; Porter, M. D.; Pazhanisamy, S.; Fleming, M. A.; Galullo, V.; Su, M. S.; Wilson, K. P.

1998-01-01

Mitogen-activated protein (MAP) kinases are serine/threonine kinases that mediate intracellular signal transduction pathways. Pyridinyl imidazole compounds block pro-inflammatory cytokine production and are specific p38 kinase inhibitors. ERK2 is related to p38 in sequence and structure, but is not inhibited by pyridinyl imidazole inhibitors. Crystal structures of two pyridinyl imidazoles complexed with p38 revealed these compounds bind in the ATP site. Mutagenesis data suggested a single residue difference at threonine 106 between p38 and other MAP kinases is sufficient to confer selectivity of pyridinyl imidazoles. We have changed the equivalent residue in human ERK2, Q105, into threonine and alanine, and substituted four additional ATP binding site residues. The single residue change Q105A in ERK2 enhances the binding of SB202190 at least 25,000-fold compared to wild-type ERK2. We report enzymatic analyses of wild-type ERK2 and the mutant proteins, and the crystal structure of a pyridinyl imidazole, SB203580, bound to an ERK2 pentamutant, I103L, Q105T, D106H, E109G. T110A. These ATP binding site substitutions induce low nanomolar sensitivity to pyridinyl imidazoles. Furthermore, we identified 5-iodotubercidin as a potent ERK2 inhibitor, which may help reveal the role of ERK2 in cell proliferation. PMID:9827991

Donor impurity incorporation during layer growth of Zn II-VI semiconductors

NASA Astrophysics Data System (ADS)

Barlow, D. A.

2017-12-01

The maximum halogen donor concentration in Zn II-VI semiconductors during layer growth is studied using a standard model from statistical mechanics. Here the driving force for incorporation is an increase in entropy upon mixing of the donor impurity into the available anion lattice sites in the host binary. A formation energy opposes this increase and thus equilibrium is attained at some maximum concentration. Considering the halogen donor impurities within the Zn II-VI binary semiconductors ZnO, ZnS, ZnSe and ZnTe, a heat of reaction obtained from reported diatomic bond strengths is shown to be directly proportional to the log of maximum donor concentration. The formation energy can then be estimated and an expression for maximum donor concentration derived. Values for the maximum donor concentration with each of the halogen impurities, within the Zn II-VI compounds, are computed. This model predicts that the halogens will serve as electron donors in these compounds in order of increasing effectiveness as: F, Br, I, Cl. Finally, this result is taken to be equivalent to an alternative model where donor concentration depends upon impurity diffusion and the conduction band energy shift due to a depletion region at the growing crystal's surface. From this, we are able to estimate the diffusion activation energy for each of the impurities mentioned above. Comparisons are made with reported values and relevant conclusions presented.

Highly nitrogen-doped porous carbon derived from zeolitic imidazolate framework-8 for CO2 capture.

PubMed

Ma, Xiancheng; Li, Liqing; Chen, Ruofei; Wang, Chunhao; Li, Haoyang; Li, Hailong

2018-05-18

CO2 adsorption capacity of nitrogen-doped porous carbon depends to a large nitrogen doping levels and high surface area in previous studies. However, it seems difficult to incorporate large amounts of nitrogen while maintaining a high surface area and pore structure. Here we have reported porous carbon having a nitrogen content of up to 25.52% and specific surface area of 948 m2 g-1, which is prepared by pyrolyzing the nitrogen-containing zeolite imidazole framework-8 and urea composite at 650 °C under a nitrogen atmosphere. ZNC650 exhibits a superior CO2 uptake of 3.7 mmol g-1 at 25 ℃ and 1 bar. Experimental and theoretical results indicate that the nitrogen-containing functional groups can enhance CO2 uptake electrostatic interactions, Lewis acid-base interactions and hydrogen-bonding interactions, which are elucidated by density functional theory calculations. As CO2 adsorbent materials, these carbons have excellent adsorption capacity. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electron spin echo envelope modulation studies of the Cu(II)-substituted derivative of isopenicillin N synthase: A structural and spectroscopic model

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

Feng Jiang; Peisach, J.; Lijune Ming

Electron spin echo envelope modulation spectroscopy (ESEEM) was used to study the active site structure of isopenicillin N synthase (IPNS) from Cephalosporium acremonium with Cu(II) as a spectroscopic probe. Fourier transform of the simulated electron spin-echo envelope for the Cu(II)-substituted enzyme, Cu(II)IPNS, revealed two nearly magnetically equivalent, equatorially coordinated His imidazoles. The superhyperfine coupling constant, A{sub iso}, for the remote {sup 14}N of each imidazole was 1.65 MHz. The binding of substrate to the enzyme altered the magnetic coupling so that A{sub iso} is 1.30 MHz for one nitrogen and 2.16 MHz for the other. From a comparison of themore » ESSEM of Cu(II)IPNS in D{sub 2}O and H{sub 2}O, it is suggested that water is a ligand of Cu(II) and this is displaced upon the addition of substrate.« less

AzaHx, a novel fluorescent, DNA minor groove and G·C recognition element: Synthesis and DNA binding properties of a p-anisyl-4-aza-benzimidazole-pyrrole-imidazole (azaHx-PI) polyamide.

PubMed

Satam, Vijay; Babu, Balaji; Patil, Pravin; Brien, Kimberly A; Olson, Kevin; Savagian, Mia; Lee, Megan; Mepham, Andrew; Jobe, Laura Beth; Bingham, John P; Pett, Luke; Wang, Shuo; Ferrara, Maddi; Bruce, Chrystal D; Wilson, W David; Lee, Moses; Hartley, John A; Kiakos, Konstantinos

2015-09-01

The design, synthesis, and DNA binding properties of azaHx-PI or p-anisyl-4-aza-benzimidazole-pyrrole-imidazole (5) are described. AzaHx, 2-(p-anisyl)-4-aza-benzimidazole-5-carboxamide, is a novel, fluorescent DNA recognition element, derived from Hoechst 33258 to recognize G·C base pairs. Supported by theoretical data, the results from DNase I footprinting, CD, ΔT(M), and SPR studies provided evidence that an azaHx/IP pairing, formed from antiparallel stacking of two azaHx-PI molecules in a side-by-side manner in the minor groove, selectively recognized a C-G doublet. AzaHx-PI was found to target 5'-ACGCGT-3', the Mlu1 Cell Cycle Box (MCB) promoter sequence with specificity and significant affinity (K(eq) 4.0±0.2×10(7) M(-1)). Copyright © 2015 Elsevier Ltd. All rights reserved.

Theoretical studies of weak interactions of formamide with methanol and its derivates

NASA Astrophysics Data System (ADS)

Zheng, Xiao-Wen; Wang, Lu; Han, Shu-Min; Cui, Xiang-Yang; Du, Chong-Yang; Liu, Tao

2015-08-01

Theoretical calculations have been performed for the complexes of formamide (FA) with methanol and its derivates (MAX, X = F, Cl, Br, NO2, H, OH, CH3, and NH2) to study their structures and properties. Substituent effects on the hydrogen bond (H-bond) strength and cooperative effect by using water and its derivatives (HOZ, Z = H, NH2, and Br) as weak interaction probe were also explored. The calculation results show that electron-donating groups strengthen the weak interaction between formamide with methanol whereas electron-withdrawing groups weaken it. The cooperativity is present for the N-HïO H-bond in MAX-FA-HOZ and the cooperative effect increases in a series HONH2, HOH, and HOBr. In addition, we investigated the interaction between FA with hypohalous acids HOY (Y = F, Cl, and Br). It was found that the weak interaction between FA and HOY became stronger with the increase of the size of halogen atom. The nature of the halogen atom has negligible impact on the strength of the H-bond in MAX-FA (X = F, Cl, and Br), whereas it has an obvious influence on the strength of the H-bond in HOY-FA (Y = F, Cl, and Br).

Synthesis and in vitro biological evaluation of novel coumarin derivatives containing isoxazole moieties on melanin synthesis in B16 cells and inhibition on bacteria.

PubMed

Pang, Guang Xian; Niu, Chao; Mamat, Nuramina; Aisa, Haji Akber

2017-06-15

A novel series of coumarin derivatives 6a-o, bearing isoxazole moieties were designed and synthesized. After that, they were evaluated for melanin synthesis in murine B16 cells and inhibitory effect on the growth of CA (Candida albicans), EC (Escherichia coli), SA (Staphylococcus aureus). It was found that eleven compounds (6b-f, 6j-o) showed a better activity on melanin synthesis than positive control (8-MOP). Among them, compounds 6d (242%) and 6f (390%), with nearly 1.6 and 2.6-fold potency compared with 8-MOP (149%) respectively, were recognized as the most promising candidate hits for further pharmacological study of anti-vitiligo. Seven halogen substituted compounds exhibited moderate antimicrobial activity against CA. It is interesting that 6e-f and 6l-m, which had two halogens on the benzene showed a comparable activity with Amphotericin B against CA. The evaluation of melanin synthesis in B16 cells and inhibitory effect on bacteria of above structurally diverse derivatives had also led to an outline of structure-activity relationship. Copyright © 2017 Elsevier Ltd. All rights reserved.

Development of Enabling Chemical Technologies for Power from Green Sources

DTIC Science & Technology

2013-11-18

structurally analogous polymers based on N-heterocycles (triazole, imidazole and pyrazole) and benz-N-heterocycles (benzotriazole, benzimidazole ...found that triazole (benzotriazole) and imidazole ( benzimidazole ) containing polymers exhibit similar proton conductivities, about 4 orders of...magnitude higher than those with pyrazole (benzopyrazole) (Figure 6b). The similar behavior of triazole and imidazole (benzotriazole and benzimidazole

Kinetic Studies of Imidazoles in Tropospheric Aqueous-Phase Chemistry: Photochemistry of Imidazole-2-carboxaldehyde and Oxidation Reaction with Hydroxyl Radicals

NASA Astrophysics Data System (ADS)

Felber, T.; Otto, T.; Herrmann, H.

2017-12-01

The formation of imidazoles via the reaction of dicarbonyls with nitrogen containing compounds in the atmosphere and their potential to act as photosensitizers possibly initiating secondary organic aerosol (SOA) growth is a field of increasing activity. A recent field study quantified and qualified imidazoles in ambient aerosol samples from Europe and China. However, kinetic data and mechanisms of particle-phase reactions involving imidazoles are still scarce. In this study, kinetic measurements were investigated using laser flash photolysis-laser long path absorption (LFP-LLPA). Quenching rate constants for the reactions of the excited triplet state of imidazole-2-carboxaldehyde (IC) with bromide anion (kq = (1.6 ± 0.3) × 107 L mol-1 s-1), oxygen (kq = (2.5 ± 0.07) × 109 L mol-1 s-1), and formic acid (kq = (8.8 ± 0.5) × 109 L mol-1 s-1) are determined. IC is efficiently quenched by oxygen and formic acid. Furthermore, the quenching reaction of IC with isopropanol is investigated and compared to the reaction with formic acid to propose a preliminary mechanism of photosensitized reactions of IC with organic compounds. It is suggested that an electron transfer occurs, as it is the case for inorganics. Furthermore, rate constants of hydroxyl (OH) radical oxidation reactions with different imidazoles were determined. Following rate constants are obtained at a temperature of 298 K: k(imidazole-2-carboxaldehyde) = (3.3 ± 1.3) × 109 L mol-1 s-1, k(1-methylimidazolium hydrogen sulfate) = (2.7 ± 0.2) × 109 L mol-1 s-1, k(2-methylimidazole) = (5.4 ± 0.2) × 109 L mol-1 s-1, k(4(5)-methylimidazole) = (5.1 ± 0.3) × 109 L mol-1 s-1, k(1-ethylimidazole) = (3.0 ± 0.3) × 109 L mol-1 s-1, k(2-ethylimidazole) = (5.0 ± 0.2) × 109 L mol-1 s-1. The OH radical reaction rate constants of imidazoles are in the same range as for non-heteroaromatic compounds. Therefore, imidazoles can be expected to exist just for a limited time in the atmosphere (τ = 16 - 29 hours) after their formation. The received kinetic data will be added into model studies to evaluate the importance of aqueous-phase chemistry of imidazoles for atmospheric processes as well as the impact of photosensitized reactions on atmospheric particles possibly contributing to SOA formation.

Monohalogenated maleimides as potential agents for the inhibition of Pseudomonas aeruginosa biofilm.

PubMed

Carteau, David; Soum-Soutéra, Emmanuelle; Faÿ, Fabienne; Dufau, Chrystèle; Cérantola, Stéphane; Vallée-Réhel, Karine

2010-01-01

New monohalogenated maleimide derivatives (with bromine, chlorine or iodine) were synthesized to test the effect of halogen atoms in inhibiting the formation of Pseudomonas aeruginosa biofilm. The evaluation of their biological activities clearly defines a structure-activity relationship. In this study, the bactericidal action of the three compounds was observed at the concentration range 0.3-5.0 mM on Luria-Bertani agar plates. The halogen atom of these molecules was critical in modulating the antibacterial activity, with a slightly higher effectiveness for chlorine. Confocal laser scanning microscopy was used to examine P. aeruginosa biofilms cultivated in flow cells. At concentration as low as 40 microM, the bromine and iodine compounds displayed a total inhibition towards the formation of bacterial biofilm. At this concentration, the bacterial attachment to glass surfaces was strongly affected by the presence of bromine and iodine whereas the chlorine derivative behaved as a bactericidal compound. A bioluminescent reporter strain was then used to detect the effect of the chemically synthesized maleimides on quorum sensing (QS) in P. aeruginosa. At the concentration range 10-100 microM, bioluminescence assays reveal that halogenated maleimides were able to interfere with the QS of the bacterium. Although the relationship between the weak inhibition of cell-to-cell communication (15-55% of the signal) and the high inhibition of biofilm formation has not been elucidated clearly, the results demonstrate that bromo- and iodo-N-substituted maleimides bromine and iodine may be used as new potent inhibitors that control bacterial biofilms.

Abrupt spin transition with thermal hysteresis of iron(III) complex [Fe(III)(Him)2(hapen)]AsF6 (Him = imidazole, H2hapen = N,N'-bis(2-hydroxyacetophenylidene)ethylenediamine).

PubMed

Fujinami, Takeshi; Koike, Masataka; Matsumoto, Naohide; Sunatsuki, Yukinari; Okazawa, Atsushi; Kojima, Norimichi

2014-02-17

The solvent-free spin crossover iron(III) complex [Fe(III)(Him)2(hapen)]AsF6 (Him = imidazole, H2hapen = N,N'-bis(2-hydroxyacetophenylidene)ethylenediamine), exhibiting thermal hysteresis, was synthesized and characterized. The Fe(III) ion has an octahedral coordination geometry, with N2O2 donor atoms of the planar tetradentate ligand (hapen) and two nitrogen atoms of two imidazoles at the axial positions. One of two imidazoles is hydrogen-bonded to the phenoxo oxygen atom of hapen of the adjacent unit to give a hydrogen-bonded one-dimensional chain, while the other imidazole group is free from hydrogen bonding. The temperature dependencies of the magnetic susceptibilities and Mössbauer spectra revealed an abrupt spin transition between the high-spin (S = 5/2) and low-spin (S = 1/2) states, with thermal hysteresis.

Synthesis and Characterization of New Poly(alkyl/arylphosphazenes)

DTIC Science & Technology

1991-11-26

substituted (silylamino) phosphines , 7, (eq 4) in good yields as thermally stable, distillable liquids. Subsequent oxidative halogenation to 8a, followed by...have been prepared simply by treating the anion with aldehydes or ketones, including those with potentially electroactive groups such as ferrocene 2 1...i.e., x:y = 2:1), but is as high as 45% for the ferrocene and thiophene derivatives. The T values of the alcohol derivatives show the expected

Crystal structures of eight 3D molecular adducts derived from bis-imidazole, bis(benzimidazole), and organic acids

NASA Astrophysics Data System (ADS)

Ding, Aihua; Jin, Shouwen; Jin, Shide; Hu, KaiKai; Lin, Zhihao; Liu, Hui; Wang, Daqi

2018-01-01

Cocrystallization of the bis(imidazole)/bis(benzimidazole) with a series of organic acids gave a total of eight molecular adducts with the compositions: (3,6-bis(imidazole-1-yl)pyridazine): (trichloroacetic acid)2(1) [(H2L1)2+ · (tca-)2, L1 = 3,6-bis(imidazole-1-yl)pyridazine, tca- = trichloroacetate], (bis(N-imidazolyl)methane): (suberic acid) (2) [(L2) · (H2suba), L2 = bis(N-imidazolyl)methane, H2suba = suberic acid], bis(N-imidazolyl)methane: (3-nitrophthalic acid): 3H2O (3) [(H2L2)2+ · (3-Hnpa-)2 · 3H2O, 3-Hnpa- = 3-nitro hydrogenphthalate], (bis(N-imidazolyl)butane)0.5: (4-nitrophthalic acid): H2O (4) [(H2L3)0.5+ · (4-Hnpa-)- · H2O, L3 = bis(N-imidazolyl)butane, 4-Hnpa- = 4-nitro hydrogenphthalate], (1-(3-(1H-benzimidazol-1-yl)propyl)-1H-benzimidazole): (3,5-dinitrosalicylic acid) (5) [(HL4) · (3,5-dns-), L4 = 1-(3-(1H-benzimidazol-1-yl)propyl)-1H-benzimidazole, 3,5-dns- = 3,5-dinitrosalicylate], (1-(3-(1H-benzimidazol-1-yl)propyl)-1H-benzimidazole): (3-nitrophthalic acid) (6) [(H2L4) · (3-npa2-), L4 = 1-(3-(1H-benzimidazol-1-yl)propyl)-1H-benzimidazole, 3-npa2-=3-nitrogenphthalate], (bis(N-imidazolyl)butane): (pamoic acid) (7) [(H2L3) · (pam), pam = pamoate], and (3,6-bis(imidazole-1-yl)pyridazine): (1,5-naphthalenedisulfonic acid) [(H2L1)2+ · (npda)2- = 1,5-naphthalenedisulfonate] (8). The eight adducts have been characterized by X-ray diffraction technique, infrared spectrum, and elemental analysis, and the melting points of all adducts were also reported. And their structural and supramolecular aspects are fully analyzed. The result reveals that among the eight investigated crystals both the end ring N in the bis(imidazole) moieties are protonated when the organic acids are deprotonated except 2, and 5, and the crystal packing is interpreted in terms of the strong ionic Nsbnd H⋯O H-bond between the imidazolium and the deprotonated acidic groups. Except the Nsbnd H⋯O H-bond, the Osbnd H⋯O H-bonds were also found at the salts 3, 4, 5, and 7, salt 5 has the additional Nsbnd H⋯N H-bond, the Nsbnd H⋯S H-bond was established at 8. Further analysis of the crystal packing of the adducts indicated that a different set of additional CHsbnd O/CH2sbnd O, CHsbnd Cl, CH-π/CH2-π, Clsbnd C, Clsbnd N, Osbnd O, O-π, OH-π, and π-π associations contribute to the stabilization and expansion of the total 3D frameworks. For the coexistence of the various weak interactions these structures had homo or hetero supramolecular synthons or both. Some supramolecular synthons, such as R12(4), R22(7), and R22(8) usually found in crystals of organic acids with imidazole unit, were again shown to be appeared in constructing most of these H-bond networks.

2-(2-Hydroxyphenyl)imidazole-based four-coordinate organoboron compounds with efficient deep blue photoluminescence and electroluminescence.

PubMed

Zhang, Zhenyu; Zhang, Zuolun; Zhang, Hongyu; Wang, Yue

2017-12-19

Two new four-coordinate organoboron compounds with 2-(2-hydroxyphenyl)imidazole derivatives as the chelating ligands have been synthesized. They possess high thermal stability and are able to form an amorphous glass state. Crystallographic analyses indicate that the differences in ligand structure cause the change of ππ stacking character. The CH 2 Cl 2 solutions and thin films of these compounds display bright blue emission, and these compounds have appropriate HOMO and LUMO energy levels for carrier injection in OLEDs. By utilizing the good thermal and luminescent properties, as well as the proper frontier orbital energy levels, bright non-doped OLEDs with a simple structure have been realized. Notably, these simple devices show deep blue electroluminescence with the Commission Internationale de l'Éclairage (CIE) coordinate of ca. (0.16, 0.08), which is close to the CIE coordinate of (0.14, 0.08) for standard blue defined by the National Television System Committee. In addition, one of the devices exhibits good performance, showing brightness, current efficiency, power efficiency and external quantum efficiency up to 2692 cd m -2 , 2.50 cd A -1 , 1.81 lm W -1 and 3.63%, respectively. This study not only provides good deep-blue emitting OLED materials that are rarely achieved by using four-coordinate organoboron compounds, but also allows a deeper understanding of the structure-property relationship of 2-(2-hydroxyphenyl)imidazole-based boron complexes, which benefits the further structural design of this type of material.

Method and apparatus for vapor detection

NASA Technical Reports Server (NTRS)

Lerner, Melvin (Inventor); Hood, Lyal V. (Inventor); Rommel, Marjorie A. (Inventor); Pettitt, Bruce C. (Inventor); Erikson, Charles M. (Inventor)

1980-01-01

The method disclosed herein may be practiced by passing the vapors to be sampled along a path with halogen vapor, preferably chlorine vapor, heating the mixed vapors to halogenate those of the sampled vapors subject to halogenation, removing unreacted halogen vapor, and then sensing the vapors for organic halogenated compounds. The apparatus disclosed herein comprises means for flowing the vapors, both sample and halogen vapors, into a common path, means for heating the mixed vapors to effect the halogenation reaction, means for removing unreacted halogen vapor, and a sensing device for sensing halogenated compounds. By such a method and means, the vapors of low molecular weight hydrocarbons, ketones and alcohols, when present, such as methane, ethane, acetone, ethanol, and the like are converted, at least in part, to halogenated compounds, then the excess halogen removed or trapped, and the resultant vapors of the halogenated compounds sensed or detected. The system is highly sensitive. For example, acetone in a concentration of 30 parts per billion (volume) is readily detected.

Designing Polyamide Inhibitors of TWIST 1 for Prosenescence Therapy

DTIC Science & Technology

2014-09-01

Pyrrole -Imidazole Polyamides; TWIST1; KRAS; non-small cell lung cancer (NSCLC); senescence 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF... Pyrrole -Imidazole Polyamides (PIP) are a class of cell permeable programmable small-molecule heterocyclic amino acid oligomers that can be designed...The original specific aims are below: Specific Aim#1. Design and synthesize a TWIST1-inhibitory specific Pyrrole -Imidazole Polyamides (PIP

Synthesis, structure, photoluminescence and antitumour activity of zinc complex based on 2-(2-(1H-benzo-[d]imidazol-2-yl)benzyl)-1H-benzo-[d]imidazole

NASA Astrophysics Data System (ADS)

Che, Zhijian; Wang, Shaoxiang; Liu, Shenggui; Li, Guobi; Wu, Qiting; Lin, Chunyu; Kong, Linglang; Wang, Sheng

2015-01-01

A new complex [Zn(bbb)Cl2]·DMF, where bbb is 2-(2-(1H-benzo[d]imidazol-2-yl)benzyl)-1H-benzo[d]imidazole, was synthesized and characterized by element analysis, 1H NMR and X-ray single crystal structure analyses. For complex: crystal system, triclinic, space group, P-1, a = 9.4661(13), b = 10.3534(14), c = 13.0025(18) Å, α = 73.477(2), β = 80.743(2), γ = 88.658(2)°, V = 1205.5(3) Å3, Z = 2. In this complex, the Zn2+ distorted tetrahedron geometry is coordinated by two nitrogen atoms from 2-(2-(1H-benzo[d]imidazol-2-yl)benzyl)-1H-benzo[d]imidazole and two Cl-. The complex emits yellow green luminescence with the maximal emission peak at 550 nm in DMF solution. The complex exhibits inhibition on the growth of Eca109 cancer cell with IC50 value of 8.9 ± 1.1 μM, which was lower than that of cisplatin (14.3 ± 1.4 μM). This complex has potential application in treatment of esophageal cancer.

Halogen speciation in volcanic plumes - Development of compact denuder sampling techniques with in-situ derivatization followed by gas chromatography-mass spectrometry and their application at Mt. Etna, Mt. Nyiragongo and Mt. Nyamulagira in 2015.

NASA Astrophysics Data System (ADS)

Rüdiger, Julian; Bobrowski, Nicole; Hoffmann, Thorsten

2016-04-01

Volcanoes are a large source for several reactive atmospheric trace gases including sulfur and halogen containing species. The detailed knowledge of volcanic plume chemistry can give insights into subsurface processes and can be considered as a useful geochemical tool for monitoring of volcanic activity, especially halogen to sulfur ratios (e.g. Bobrowski and Giuffrida, 2012; Donovan et al., 2014). The reactive bromine species bromine monoxide (BrO) is of particular interest, because BrO as well as SO2 are readily measurable by UV spectrometer at a safe distance. Furthermore it is formed in the plume by a multiphase reaction mechanism under depletion of ozone in the plume. The abundance of BrO changes as a function of the reaction time and therefore distance from the vent as well as the spatial position in the plume. The precursor substance for the formation of BrO is HBr with Br2as an intermediate product. The reaction of HBr to BrO involves heterogeneous reactions involving aerosol particles, while Br2 reacts directly with O3 to form BrO in a UV radiation induced mechanism. Due to the lack of analytical approaches for the species analysis of halogens (HBr, Br2, Br, BrCl, HOBr) there are still uncertainties about the magnitude of volcanic halogen emissions and in particular their speciation and therefore also in the understanding of the bromine chemistry in volcanic plumes (Bobrowski et al., 2007). In this study a gas diffusion denuder sampling method using a 1,3,5-trimethoxybenzene (1,3,5-TMB) coating for the derivatization of reactive halogen species (Rüdiger et al., 2015) was characterized by reaction chamber experiments. The coating proved to be suitable to collect selectively gaseous bromine species with oxidation states of +1 or 0 (such as Br2, BrCl, BrO(H) and BrONO2), while being ignorant to HBr (OS -1). The reaction of 1,3,5-TMB with reactive bromine species gives 1-bromo-2,4,6-trimethoxybenzene (1-bromo-2,4,6-TMB) - other halogens give corresponding products. The diffusion denuder technique allows sampling of gaseous compounds exclusively without collecting particulate matter. Solvent elution of the derivatized analytes and subsequent analysis with gas chromatography-mass spectrometry gives a limit of detection below 1 ng of bromine. The method was applied in 2015 on volcanic gas plumes at Mt. Etna (Italy), Mt. Nyiragongo and Mt. Nyamulagira (DR Congo) giving reactive bromine mixing ratios from 0.3 ppb (Nyiragongo) up to 22 ppb (Etna, NEC). Compared with total halogen data derived by alkaline trap sampling (Raschig-tube) and ion-chromatography analysis the reactive bromine mixing ratios allow the investigation of the conversion of HBr into reactive species due to plume chemistry with progressing plume age. The new method will be described in detail and the first results on the reactive halogen to total halogen output will be discussed (for bromine and chlorine) and compared to earlier volcanic plume chemistry model studies. References Bobrowski, N. and G. Giuffrida: Bromine monoxide / sulphur dioxide ratios in relation to volcanological observations at Mt. Etna 2006-2009. Solid Earth, 3, 433-445, 2012 Bobrowski, N., R. von Glasow, A. Aiuppa, S. Inguaggiato, I. Louban, O. W. Ibrahim and U. Platt: Reactive halogen chemistry in volcanic plumes. J. Geophys. Res., 112, 2007 Donovan A., V. Tsanev, C. Oppenheimer and M. Edmonds: Reactive halogens (BrO and OClO) detected in the plume of Soufrière Hills Volcano during an eruption hiatus. Geochem. Geophys. Geosyst., 15, 3346-3363, 2014 Rüdiger, J., N. Bobrowski, T. Hoffmann (2015), Development and application of compact denuder sampling techniques with in situ derivatization followed by gas chromatography-mass spectrometry for halogen speciation in volcanic plumes (EGU2015-2392-2), EGU General Assembly 2015

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

PubMed

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

2008-09-01

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

Gas-phase behaviour of Ru(II) cyclopentadienyl-derived complexes with N-coordinated ligands by electrospray ionization mass spectrometry: fragmentation pathways and energetics.

PubMed

Madeira, Paulo J Amorim; Morais, Tânia S; Silva, Tiago J L; Florindo, Pedro; Garcia, M Helena

2012-08-15

The gas-phase behaviour of six Ru(II) cyclopentadienyl-derived complexes with N-coordinated ligands, compounds with antitumor activities against several cancer lines, was studied. This was performed with the intent of establishing fragmentation pathways and to determine the Ru-L(N) and Ru-L(P) ligand bond dissociation energies. Such knowledge can be an important tool for the postulation of the mechanisms of action of these anticancer drugs. Two types of instruments equipped with electrospray ionisation were used (ion trap and a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer). The dissociation energies were determined using energy-variable collision-induced dissociation measurements in the ion trap. The FTICR instrument was used to perform MS(n) experiments on one of the compounds and to obtain accurate mass measurements. Theoretical calculations were performed at the density functional theory (DFT) level using two different functionals (B3LYP and M06L) to estimate the dissociation energies of the complexes under study. The influence of the L(N) on the bond dissociation energy (D) of RuCp compounds with different nitrogen ligands was studied. The lability order of L(N) was: imidazole<1-butylimidazole<5-phenyl-1H-tetrazole<1-benzylimidazole. Both the functionals used gave the following ligand lability order: imidazole<1-benzylimidazole<5-phenyl-1H-tetrazole<1-butylimidazole. It is clear that there is an inversion between 1-benzylimidazole and 1-butylimidazole for the experimental and theoretical lability orders. The M06L functional afforded values of D closer to the experimental values. The type of phosphane (L(P) ) influenced the dissociation energies, with values of D being higher for Ru-L(N) with 1-butylimidazole when the phosphane was 1,2-bis(diphenylphosphino)ethane. The Ru-L(P) bond dissociation energy for triphenylphosphane was independent of the type of complex. The D values of Ru-L(N) and Ru-L(P) were determined for all six compounds and compared with the values calculated by the DFT method. For the imidazole-derived ligands the energy trend was rationalized in terms of the increasing extension of the σ-donation/π-backdonation effect. The bond dissociation energy of Ru-PPh(3) was independent of the fragmentations. Copyright © 2012 John Wiley & Sons, Ltd.

Synthesis and potential cytotoxic activity of some new benzoxazoles, imidazoles, benzimidazoles and tetrazoles.

PubMed

Arulmurugan, Subramaniyan; Kavitha, Helen P

2013-06-01

2 The present work deals with the synthesis of some novel heterocyclic compounds such as benzoxazoles , 7, 13 and 19, imidazoles 3, 8, 14 and 20, benzimidazoles 4, 9, 15 and 21, and tetrazoles 10, 16, and 22. The synthesized compounds were characterized by IR, 1H NMR, mass spectrometry and elemental analysis. The compounds were evaluated for cytotoxicity against human cancer cell lines such as MCF-7 (breast cancer) and HT-29 (colon cancer) by the MTT assay method. Among the tested compounds, 4,4'-sulfonylbis(N-(2-(1H-benzo[d]imidazol- -2-yl)ethyl)aniline (9), N-bis(2-(benzo[d]oxazol-2-yl)-ethyl)- 6-phenyl-1,3,5-triazine-2,4-diamine (13), N-bis(2-(1H-benzo[ d]imidazol-2-yl)ethyl)-6-phenyl-1,3,5-triazine-2,4-diamine (15) and N-tris(2-1H-benzo[d]imidazol-2-yl)ethyl)- 1,3,5-triazine-2,4,6-triamine (21) showed potent cytotoxicity.

An efficient synthesis of a rationally designed 1,5 disubstituted imidazole AT(1) angiotensin II receptor antagonist: reorientation of imidazole pharmacophore groups in losartan reserves high receptor affinity and confirms docking studies.

PubMed

Agelis, George; Roumelioti, Panagiota; Resvani, Amalia; Durdagi, Serdar; Androutsou, Maria-Eleni; Kelaidonis, Konstantinos; Vlahakos, Demetrios; Mavromoustakos, Thomas; Matsoukas, John

2010-09-01

A new 1,5 disubstituted imidazole AT(1) Angiotensin II (AII) receptor antagonist related to losartan with reversion of butyl and hydroxymethyl groups at the 2-, 5-positions of the imidazole ring was synthesized and evaluated for its antagonist activity (V8). In vitro results indicated that the reorientation of butyl and hydroxymethyl groups on the imidazole template of losartan retained high binding affinity to the AT(1) receptor concluding that the spacing of the substituents at the 2,5- positions is of primary importance. The docking studies are confirmed by binding assay results which clearly show a comparable binding score of the designed compound V8 with that of the prototype losartan. An efficient, regioselective and cost effective synthesis renders the new compound as an attractive candidate for advanced toxicological evaluation and a drug against hypertension.

An efficient synthesis of a rationally designed 1,5 disubstituted imidazole AT1 Angiotensin II receptor antagonist: reorientation of imidazole pharmacophore groups in losartan reserves high receptor affinity and confirms docking studies

NASA Astrophysics Data System (ADS)

Agelis, George; Roumelioti, Panagiota; Resvani, Amalia; Durdagi, Serdar; Androutsou, Maria-Eleni; Kelaidonis, Konstantinos; Vlahakos, Demetrios; Mavromoustakos, Thomas; Matsoukas, John

2010-09-01

A new 1,5 disubstituted imidazole AT1 Angiotensin II (AII) receptor antagonist related to losartan with reversion of butyl and hydroxymethyl groups at the 2-, 5-positions of the imidazole ring was synthesized and evaluated for its antagonist activity ( V8). In vitro results indicated that the reorientation of butyl and hydroxymethyl groups on the imidazole template of losartan retained high binding affinity to the AT1 receptor concluding that the spacing of the substituents at the 2,5- positions is of primary importance. The docking studies are confirmed by binding assay results which clearly show a comparable binding score of the designed compound V8 with that of the prototype losartan. An efficient, regioselective and cost effective synthesis renders the new compound as an attractive candidate for advanced toxicological evaluation and a drug against hypertension.

Geometry of AN Isolated Dimer of Imidazole Characterised by Rotational Spectroscopy and AB Initio Calculations

NASA Astrophysics Data System (ADS)

Mullaney, John C.; Zaleski, Daniel P.; Tew, David Peter; Walker, Nick; Legon, Anthony

2016-06-01

An isolated, gas-phase dimer of imidazole is generated through laser vaporisation of a solid rod containing a 1:1 mixture of imidazole and copper in the presence of an argon buffer gas undergoing supersonic expansion. The complex is characterised through broadband rotational spectroscopy and is shown to have a twisted, hydrogen-bonded geometry. Calculations at the CCSD(T)(F12*)/cc-pVDZ-F12 level of theory confirm this to be the lowest-energy conformer of the imidazole dimer. The distance between the respective centres of mass of the imidazole monomer subunits is determined to be 5.2751(1) Å, and the twist angle γ describing rotation of one monomer with respect to the other about a line connecting the centres of mass of the monomers is determined to be 87.9(4)o. Four out of six intermolecular parameters in the model geometry are precisely determined from the experimental rotational constants and are consistent with results calculated ab initio.

Characterization of particulate products for aging of ethylbenzene secondary organic aerosol in the presence of ammonium sulfate seed aerosol.

PubMed

Huang, Mingqiang; Zhang, Jiahui; Cai, Shunyou; Liao, Yingmin; Zhao, Weixiong; Hu, Changjin; Gu, Xuejun; Fang, Li; Zhang, Weijun

2016-09-01

Aging of secondary organic aerosol (SOA) particles formed from OH- initiated oxidation of ethylbenzene in the presence of high mass (100-300μg/m(3)) concentrations of (NH4)2SO4 seed aerosol was investigated in a home-made smog chamber in this study. The chemical composition of aged ethylbenzene SOA particles was measured using an aerosol laser time-of-flight mass spectrometer (ALTOFMS) coupled with a Fuzzy C-Means (FCM) clustering algorithm. Experimental results showed that nitrophenol, ethyl-nitrophenol, 2,4-dinitrophenol, methyl glyoxylic acid, 5-ethyl-6-oxo-2,4-hexadienoic acid, 2-ethyl-2,4-hexadiendioic acid, 2,3-dihydroxy-5-ethyl-6-oxo-4-hexenoic acid, 1H-imidazole, hydrated N-glyoxal substituted 1H-imidazole, hydrated glyoxal dimer substituted imidazole, 1H-imidazole-2-carbaldehyde, N-glyoxal substituted hydrated 1H-imidazole-2-carbaldehyde and high-molecular-weight (HMW) components were the predominant products in the aged particles. Compared to the previous aromatic SOA aging studies, imidazole compounds, which can absorb solar radiation effectively, were newly detected in aged ethylbenzene SOA in the presence of high concentrations of (NH4)2SO4 seed aerosol. These findings provide new information for discussing aromatic SOA aging mechanisms. Copyright © 2016. Published by Elsevier B.V.

Comparative toxicity of pristine graphene oxide and its carboxyl, imidazole or polyethylene glycol functionalized products to Daphnia magna: A two generation study.

PubMed

Liu, Yingying; Han, Wenli; Xu, Zhizhen; Fan, Wenhong; Peng, Weihua; Luo, Shenglian

2018-06-01

To investigate the chronic toxicity of graphene oxide (GO) and its functionalized products (GO-carboxyl, GO-imidazole and GO-polyethylene glycol), a two-generation study was conducted using the aquatic model species Daphnia magna. Each generation of daphnids were exposed for 21 days to 1.0 mg L -1 graphene material, with body length, neonate number, time of first brood and the intrinsic rate of natural increase (r) assessed as endpoints. Chronic exposure to GO, GO-carboxyl, and GO-imidazole had no adverse effect on body length or offspring number in the daphnid F0 generation, however, this exposure paradigm led to significant growth or reproduction inhibition in the following generation. Meanwhile, GO was found to show the strongest inhibitory effect, sequentially followed by GO-carboxyl and GO-imidazole. With exposure to GO-polyethylene glycol, no significant effects on growth or reproduction were observed for both F0 and F1 generation daphnids. These results reveal that carboxyl, imidazole and polyethylene glycol functional attachments alleviate the bio-toxicity of GO, especially polyethylene glycol. The increased C/O atomic ratio present in GO-carboxyl, GO-imidazole and GO-polyethylene glycol due to functionalization may mainly explain the reduced toxicity. Copyright © 2018 Elsevier Ltd. All rights reserved.

Structure-toxicity relationship study of para-halogenated styrene analogues in CYP2E1 transgenic cells

PubMed Central

Chung, Jou-Ku; Shen, Shuijie; Jiang, Zhiteng; Yuan, Wei; Zheng, Jiang

2012-01-01

Styrene is one of the most important industrial intermediates consumed in the world and is mainly used as a monomer for reinforced plastics and rubber. Styrene has been found to be hepatotoxic and pneumotoxic in humans and experimental animals. The toxicity of styrene is suggested to be metabolism-dependent. Styrene-7,8-oxide has been considered as the major metabolite responsible for styrene-induced cytotoxicity. The objective of the study was to investigate the correlation between cytotoxicity of styrene and chemical and biochemical properties of the vinyl group of styrene by development of structure activity relationships (SAR). 4-Fluorostyrene, 4-chlorostyrene and 4-bromostyrene were selected for the SAR study. Cytotoxicity of styrene and the halogenated styrene derivatives with an order of 4-bromostyrene > 4-chlorostyrene > 4-fluorostyrene ≈ styrene was observed in CYP2E1 transgenic cells. Similar orders in the efficiency of the metabolism of styrene and the halogenated styrene analogues to their oxides and in the electrophilicity of the corresponding oxides were observed. Additionally, the order of the potency of cellular glutathione depletion and the degree of protein adduction induced by styrene and the halogenated styrenes were consistent with that of their cytotoxicities. The wild-type cells were less susceptible to the toxicity of the corresponding model compounds than CYP2E1 cells. The present study provided insight into the roles of the biochemical and chemical properties of styrene in its cytotoxicity. PMID:22366341

Structural characterization of two tetra­chlorido­zincate salts of 4-carb­oxy-1H-imidazol-3-ium: a salt hydrate and a co-crystal salt hydrate

PubMed Central

Martens, Sean J.

2017-01-01

Imidazole-containing compounds exhibit a myriad of pharmacological activities. Two tetra­chlorido­zincate salts of 4-carb­oxy-1H-imidazol-3-ium, ImHCO2H+, are reported. Bis(4-carb­oxy-1H-imidazol-3-ium) tetra­chlorido­zincate monohydrate, (C4H5N2O2)2[ZnCl4]·H2O, (I), crystallizes as a monohydrate salt, while bis­(4-carb­oxy-1H-imidazol-3-ium) tetra­chlorido­zincate bis­(1H-imidazol-3-ium-4-carboxyl­ato) monohydrate, (C4H5N2O2)2[ZnCl4]·2C4H4N2O2·H2O, (II), is a co-crystal salt with six residues: two ImHCO2H+ cations, two formula units of the zwitterionic 1H-imidazol-3-ium-4-carboxyl­ate, ImHCO2, one tetra­chlorido­zincate anion and one water mol­ecule disordered over two sites in a 0.60 (4):0.40 (4) ratio. The geometric parameters of the ImHCO2H+ and the ImHCO2 moieties are the same within the standard uncertainties of the measurements. Both compounds exhibit extensive hydrogen bonding, including involvement of the tetra­chlorido­zincate anion, resulting in inter­connected chains of anions joined by water mol­ecules. PMID:28217334

Synthesis of backbone P-functionalized imidazol-2-ylidene complexes: en route to novel functional ionic liquids.

PubMed

Majhi, Paresh Kumar; Sauerbrey, Susanne; Schnakenburg, Gregor; Arduengo, Anthony J; Streubel, Rainer

2012-10-01

1-Alkyl-3-methyl-4-diphenylphosphoryl-imidazolium hydrogensulfate (4a,b) (a: R(1) = R(2) = Me; b: R(1) = (i)Pr, R(2) = Me) and 1-alkyl-3-methyl-4,5-bis(diphenylphosphoryl)imidazolium hydrogensulfate (6a,c) (c: R(1) = (n)Bu, R(2) = Me) were obtained selectively and in good yields by oxidative desulfurization of 1-alkyl-3-methyl-4-diphenylphosphino-imidazole-2-thiones (2a,b) and 1-n-butyl-3-methyl-4,5-bis(diphenylphosphoryl)imidazole-2-thione (3c) or 1,3-dimethyl-4-diphenylthiophosphoryl-5-diphenylphosphino-imidazole-2-thione (5a), respectively, with hydrogen peroxide. Synthesis of phosphoryl functionalized imidazol-2-ylidene complexes of group VI metal pentacarbonyls (7a-9a) and (10b-12b) and bis(phosphoryl) functionalized imidazol-2-ylidene complexes of group VI metal pentacarbonyls (13c-15c) and (16a) with low steric demand (methyl, isopropyl, n-butyl) at both N-centers was achieved through deprotonation of imidazolium salts (4a,b) and (6a,c), respectively,-having HSO(4)(-) as a counterion-with potassium tert-butoxide followed by rapid addition of metal pentacarbonyl acetonitrile complexes [M(CO)(5)(CH(3)CN)] (M = Cr, Mo, W). The products were unambiguously characterized by elemental analyses, spectroscopic and spectrometric methods, and in addition, by single-crystal X-ray structure studies in the cases of 4b, 8a, 15c, and 16a; the latter two reveal imidazole ring bond distance alternation in contrast to 8a.

Importance of surface modification of γ-alumina in creating its nanostructured composites with zeolitic imidazolate framework ZIF-67.

PubMed

Liu, Yuanyuan; Gonçalves, Alexandre A S; Zhou, Yang; Jaroniec, Mietek

2018-05-07

Application of zeolitic imidazolate framework-67 (ZIF-67) as an adsorbent has been greatly hindered by slow mass transfer of adsorbate molecules due to its inherent microporosity. To address this limitation, we have developed binary nanostructures composed of ZIF-67 and γ-alumina (GA) containing respectively micropores and large mesopores. The nanostructured composites were successfully prepared by coupling ZIF-67 and GA with and without surface modification with imidazole silane that mimics the building blocks of ZIF-67 to obtain GA-Im-ZIF-67 (with imidazole silane) and GA-ZIF-67 (without imidazole silane). The sizes of ZIF-67 crystals in these composites were smaller as compared to those of pure ZIF-67, and the textural properties of these composites with and without surface modification were quite similar. However, the surface grafting of alumina with imidazole silane played an important role in improving interfacial coupling between GA and ZIF-67, which resulted in significant changes in the dispersion of ZIF-67 crystals and better adsorption properties. The presence of large mesopores in the alumina-based composites containing smaller ZIF-67 crystals improved their adsorption properties toward dyes such as Rhodamine B (RhB). The RhB adsorption capacity of GA-Im-ZIF-67 was much higher than that of GA-ZIF-67, suggesting that the imidazole silane modification of GA before its coupling with ZIF-67 and the GA mesoporosity were essential for a substantial increase in the adsorption capacity of RhB. Copyright © 2018 Elsevier Inc. All rights reserved.

Combretastatin A-4 derived 5-(1-methyl-4-phenyl-imidazol-5-yl)indoles with superior cytotoxic and anti-vascular effects on chemoresistant cancer cells and tumors.

PubMed

Mahal, Katharina; Biersack, Bernhard; Schruefer, Sebastian; Resch, Marcus; Ficner, Ralf; Schobert, Rainer; Mueller, Thomas

2016-08-08

5-(1-Methyl-4-phenyl-imidazol-5-yl)indoles 5 were prepared and tested as analogs of the natural vascular-disrupting agent combretastatin A-4 (CA-4). The 3-bromo-4,5-dimethoxyphenyl derivative 5c was far more active than CA-4 with low nanomolar IC50 concentrations against multidrug-resistant KB-V1/Vbl cervix and MCF-7/Topo mamma carcinoma cells, and also against CA-4-resistant HT-29 colon carcinoma cells. While not interfering markedly with the polymerization of tubulin in vitro, indole 5c completely disrupted the microtubule cytoskeleton of cancer cells at low concentrations. It also destroyed real blood vessels, both in the chorioallantoic membrane (CAM) of fertilized chicken eggs and within tumor xenografts in mice, without harming embryo or mouse, respectively. Indole 5c was less toxic than CA-4 to endothelial cells, fibroblasts, and cardiomyocytes. In highly vascularized xenograft tumors 5c induced distinct discolorations and histological features typical of vascular-disrupting agents, such as disrupted vessel structures, hemorrhages, and extensive necrosis. In a first preliminary therapy trial, indole 5c retarded the growth of resistant xenograft tumors in mice. © 2016 Elsevier Science Ltd. All rights reserved. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

High performance liquid chromatography with UV detection for the simultaneous determination of sympathomimetic amines using 4-(4,5-diphenyl-1H-imidazole-2-yl)benzoyl chloride as a label.

PubMed

Kaddoumi, A; Kubota, A; Nakashima, M N; Takahashi, M; Nakashima, K

2001-10-01

A high performance liquid chromatographic method has been developed for the simultaneous determination of (+/-) fenfluramine (Fen) and phentermine (Phen) in addition to three other sympathomimetic amines-ephedrine (E), norephedrine (NE) and 2-phenylethylamine (2-PEA), using cyclohexylamine (CX) as an internal standard in plasma. The compounds were derivatized with 4-(4,5-diphenyl-1H-imidazole-2-yl)benzoyl chloride (DIB-Cl) to give the DIB-derivatives. The derivatives were then separated using an isocratic HPLC system with UV detection. The limits of detection for Fen, Phen, E, NE and 2-PEA in plasma ranged from 0.32 to 22.9 pmol on column at a signal-to-noise ratio of 3. The recoveries following alkaline extraction from plasma samples of known concentrations were found to be more than 94% for the studied compounds. This method might be useful for the screening of the studied sympathomimetic amines in human plasma samples in forensic as well as toxicological studies. Furthermore, the developed method was modified for the simultaneous determination of Fen and Phen in human and rat plasma using fluoxetine as an internal standard. The methods are reproducible and precise. Finally, the two drugs were administered intraperitoneally to rats in combination, and their plasma levels over the investigated time course were successfully determined. Copyright 2001 John Wiley & Sons, Ltd.

Process for removal of hydrogen halides or halogens from incinerator gas

DOEpatents

Huang, Hann S.; Sather, Norman F.

1988-01-01

A process for reducing the amount of halogens and halogen acids in high temperature combustion gases and through their removal, the formation of halogenated organics at lower temperatures, with the reduction being carried out electrochemically by contacting the combustion gas with the negative electrode of an electrochemical cell and with the halogen and/or halogen acid being recovered at the positive electrode.

Process for removal of hydrogen halides or halogens from incinerator gas

DOEpatents

Huang, H.S.; Sather, N.F.

1987-08-21

A process for reducing the amount of halogens and halogen acids in high temperature combustion gas and through their removal, the formation of halogenated organics at lower temperatures, with the reduction being carried out electrochemically by contacting the combustion gas with the negative electrode of an electrochemical cell and with the halogen and/or halogen acid being recovered at the positive electrode.

Prebiotic condensation reactions using cyanamide

NASA Technical Reports Server (NTRS)

Sherwood, E.; Nooner, D. W.; Eichberg, J.; Epps, D. E.; Oro, J.

1978-01-01

Condensation reactions in cyanamide, 4-amino-5-imidazole-carboxamide and cyanamide, imidazole systems under dehydrating conditions at moderate temperatures (60 to 100 deg C) were investigated. The cyanamide, imidazole system was used for synthesis of palmitoylglycerols from ammonium palmitate and glycerol. With the addition of deoxythymidine to the former system, P1, P2-dideoxythymidine 5 prime-phosphate was obtained; the same cyanamide, 4-amino-5-imidazole-carboxamide system was used to synthesize deoxythymidine oligonucleotides using deoxythymidine 5 prime-phosphate and deoxythymidine 5 prime-triphosphate, and peptides using glycine, phenylalanine or isoleucine with adenosine 5 prime-triphosphate. The pH requirements for these reactions make their prebiotic significance questionable; however, it is conceivable that they could occur in stable pockets of low interlayer acidity in a clay such as montmorillonite.

Is halogen content the most important factor in the removal of halogenated trace organics by MBR treatment?

PubMed

Hai, Faisal I; Tadkaew, Nichanan; McDonald, James A; Khan, Stuart J; Nghiem, Long D

2011-05-01

This study investigated the relationship between physicochemical properties (namely halogen content and hydrophobicity) of halogenated trace organics and their removal efficiencies by a laboratory scale membrane bioreactor (MBR) under stable operating conditions. The reported results demonstrated a combined effect of halogen content and hydrophobicity on the removal. Compounds with high halogen content (>0.3) were well removed (>85%) when they possessed high hydrophobicity (Log D>3.2), while those with lower Log D values were also well removed if they had low halogen content (<0.1). General indices such as the BIOWIN index (which is based on only biodegradation) or a more specific index such as the halogen content (which captures a chemical aspect) appeared insufficient to predict the removal efficiency of halogenated compounds in MBR. Experimental data confirmed that the ratio of halogen content and Log D, which incorporates two important physico-chemical properties, is comparatively more suitable. Copyright © 2011 Elsevier Ltd. All rights reserved.

Indomethacin Analogs: Synthesis and Anti-inflammatory and Analgesic Activities of Indoline Derivatives.

PubMed

Amin, Mohamed M; Shaaban, Mohamed R; Al-Qurashi, Nadia T; Mahmoud, Huda K; Farghaly, Thoraya A

2018-03-29

Short reaction time and high yield was achieved for the synthesis of new hydrazonoindolines having thiazole moiety under microwave irradiation via the reaction of hydrazonoyl chlorides or halogenated activemethylene derivatives with thiosemicarbazone derivatives. Also, the utility of the versatile indoline-2,3-dione derivatives in the design of new multifunctional building blocks using condensation with hydrazine derivatives was demonstrated. The information derived from the spectral data of the formed compounds were confirmed their structures. Also, the analgesic and anti-inflammatory activities of the designed derivatives were screened and the results obtained indicated that six derivatives 4g, 9b, 4c, 10b, 4d and 11a revealed the highest anti-inflammatory and analgesic effects. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Click Chemistry-Facilitated Structural Diversification of Nitrothiazoles, Nitrofurans, and Nitropyrroles Enhances Antimicrobial Activity against Giardia lamblia

PubMed Central

Kim, Wan Jung; Korthals, Keith A.; Li, Suhua; Le, Christine; Kalisiak, Jarosław; Sharpless, K. Barry; Fokin, Valery V.; Miyamoto, Yukiko

2017-01-01

ABSTRACT Giardia lamblia is an important and ubiquitous cause of diarrheal disease. The primary agents in the treatment of giardiasis are nitroheterocyclic drugs, particularly the imidazoles metronidazole and tinidazole and the thiazole nitazoxanide. Although these drugs are generally effective, treatment failures occur in up to 20% of cases, and resistance has been demonstrated in vivo and in vitro. Prior work had suggested that side chain modifications of the imidazole core can lead to new effective 5-nitroimidazole drugs that can combat nitro drug resistance, but the full potential of nitroheterocycles other than imidazole to yield effective new antigiardial agents has not been explored. Here, we generated derivatives of two clinically utilized nitroheterocycles, nitrothiazole and nitrofuran, as well as a third heterocycle, nitropyrrole, which is related to nitroimidazole but has not been systematically investigated as an antimicrobial drug scaffold. Click chemistry was employed to synthesize 442 novel nitroheterocyclic compounds with extensive side chain modifications. Screening of this library against representative G. lamblia strains showed a wide spectrum of in vitro activities, with many of the compounds exhibiting superior activity relative to reference drugs and several showing >100-fold increase in potency and the ability to overcome existing forms of metronidazole resistance. The majority of new compounds displayed no cytotoxicity against human cells, and several compounds were orally active against murine giardiasis in vivo. These findings provide additional impetus for the systematic development of nitroheterocyclic compounds with nonimidazole cores as alternative and improved agents for the treatment of giardiasis and potentially other infectious agents. PMID:28396548

Hydrogen bonded binary molecular adducts derived from exobidentate N-donor ligand with dicarboxylic acids: Acid⋯imidazole hydrogen-bonding interactions in neutral and ionic heterosynthons

NASA Astrophysics Data System (ADS)

Kathalikkattil, Amal Cherian; Damodaran, Subin; Bisht, Kamal Kumar; Suresh, Eringathodi

2011-01-01

Four new binary molecular compounds between a flexible exobidentate N-heterocycle and a series of dicarboxylic acids have been synthesized. The N-donor 1,4-bis(imidazol-1-ylmethyl)benzene (bix) was reacted with flexible and rigid dicarboxylic acids viz., cyclohexane-1,4-dicarboxylic acid (H 2chdc), naphthalene-1,4-dicarboxylic acid (H 2npdc) and 1H-pyrazole-3,5-dicarboxylic acid (H 2pzdc), generating four binary molecular complexes. X-ray crystallographic investigation of the molecular adducts revealed the primary intermolecular interactions carboxylic acid⋯amine (via O-H⋯N) as well as carboxylate⋯protonated amine (via N-H +⋯O -) within the binary compounds, generating layered and two-dimensional sheet type H-bonded networks involving secondary weak interactions (C-H⋯O) including the solvent of crystallization. Depending on the differences in p Ka values of the selected base/acid (Δp Ka), diverse H-bonded supramolecular assemblies could be premeditated. This study demonstrates the H-bonding interactions between imidazole/imidazolium cation and carboxylic acid/carboxylate anion in providing sufficient driving force for the directed assembly of binary molecular complexes. In the two-component solid form of hetero synthons involving bix and dicarboxylic acid, only H 2chdc exist as cocrystal with bix, while all the other three compounds crystallized exclusively as salt, in agreement with the Δp Ka values predicted for the formation of salts/cocrystals from the base and acid used in the synthesis of supramolecular solids.

Click Chemistry-Facilitated Structural Diversification of Nitrothiazoles, Nitrofurans, and Nitropyrroles Enhances Antimicrobial Activity against Giardia lamblia.

PubMed

Kim, Wan Jung; Korthals, Keith A; Li, Suhua; Le, Christine; Kalisiak, Jarosław; Sharpless, K Barry; Fokin, Valery V; Miyamoto, Yukiko; Eckmann, Lars

2017-06-01

Giardia lamblia is an important and ubiquitous cause of diarrheal disease. The primary agents in the treatment of giardiasis are nitroheterocyclic drugs, particularly the imidazoles metronidazole and tinidazole and the thiazole nitazoxanide. Although these drugs are generally effective, treatment failures occur in up to 20% of cases, and resistance has been demonstrated in vivo and in vitro Prior work had suggested that side chain modifications of the imidazole core can lead to new effective 5-nitroimidazole drugs that can combat nitro drug resistance, but the full potential of nitroheterocycles other than imidazole to yield effective new antigiardial agents has not been explored. Here, we generated derivatives of two clinically utilized nitroheterocycles, nitrothiazole and nitrofuran, as well as a third heterocycle, nitropyrrole, which is related to nitroimidazole but has not been systematically investigated as an antimicrobial drug scaffold. Click chemistry was employed to synthesize 442 novel nitroheterocyclic compounds with extensive side chain modifications. Screening of this library against representative G. lamblia strains showed a wide spectrum of in vitro activities, with many of the compounds exhibiting superior activity relative to reference drugs and several showing >100-fold increase in potency and the ability to overcome existing forms of metronidazole resistance. The majority of new compounds displayed no cytotoxicity against human cells, and several compounds were orally active against murine giardiasis in vivo These findings provide additional impetus for the systematic development of nitroheterocyclic compounds with nonimidazole cores as alternative and improved agents for the treatment of giardiasis and potentially other infectious agents. Copyright © 2017 American Society for Microbiology.

Electrochemical oxidation of tramadol in low-salinity reverse osmosis concentrates using boron-doped diamond anodes.

PubMed

Lütke Eversloh, Christian; Schulz, Manoj; Wagner, Manfred; Ternes, Thomas A

2015-04-01

The electrochemical treatment of low-salinity reverse osmosis (RO) concentrates was investigated using tramadol (100 μM) as a model substance for persistent organic contaminants. Galvanostatic degradation experiments using boron-doped diamond electrodes at different applied currents were conducted in RO concentrates as well as in ultra-pure water containing either sodium chloride or sodium sulfate. Kinetic investigations revealed a significant influence of in-situ generated active chlorine besides direct anodic oxidation. Therefore, tramadol concentrations decreased more rapidly at elevated chloride content. Nevertheless, reduction of total organic carbon (TOC) was found to be comparatively low, demonstrating that transformation rather than mineralization was taking place. Early stage product formation could be attributed to both direct and indirect processes, including demethylation, hydroxylation, dehydration, oxidative aromatic ring cleavage and halogenation reactions. The latter led to various halogenated derivatives and resulted in AOX (adsorbable organic halogens) formation in the lower mg/L-range depending on the treatment conditions. Characterisation of transformation products (TPs) was achieved via MS(n) experiments and additional NMR measurements. Based on identification and quantification of the main TPs in different matrices and on additional potentiostatic electrolysis, a transformation pathway was proposed. Copyright © 2014 Elsevier Ltd. All rights reserved.

Transition from metal-ligand bonding to halogen bonding involving a metal as halogen acceptor a study of Cu, Ag, Au, Pt, and Hg complexes

NASA Astrophysics Data System (ADS)

Oliveira, Vytor; Cremer, Dieter

2017-08-01

Utilizing all-electron Dirac-exact relativistic calculations with the Normalized Elimination of the Small Component (NESC) method and the local vibrational mode approach, the transition from metal-halide to metal halogen bonding is determined for Au-complexes interacting with halogen-donors. The local stretching force constants of the metal-halogen interactions reveal a smooth transition from weak non-covalent halogen bonding to non-classical 3-center-4-electron bonding and finally covalent metal-halide bonding. The strongest halogen bonds are found for dialkylaurates interacting with Cl2 or FCl. Differing trends in the intrinsic halogen-metal bond strength, the binding energy, and the electrostatic potential are explained.

Oxidative polycondensation of benzimidazole using NaOCl: Synthesis, characterization, optical, thermal and electrical properties of polybenzimidazoles

NASA Astrophysics Data System (ADS)

Anand, Siddeswaran; Muthusamy, Athianna; Dineshkumar, Sengottuvelu; Chandrasekaran, J.

2017-11-01

A series of polybenzimidazole polymers, poly-2-(1H-benzo[d] imidazole-2-yl) phenol (PBIP2), poly-3-(1H-benzo[d] imidazole-2-yl) phenol (PBIP3) and poly-4-(1H-benzo[d] imidazole-2-yl) phenol (PBIP4) were synthesized by oxidative polycondensation of benzimidazole monomers 2-(1H-benzo [d] imidazole-2-yl) phenol (BIP2), 3-(1H-benzo [d] imidazole-2-yl) phenol (BIP3) and 4-(1H-benzo [d] imidazole-2-yl) phenol (BIP4). The structure of benzimidazoles monomers and polybenzimidazoles (PBI) were confirmed by various spectroscopic techniques. The quantum theoretical calculations of band gap energy values of monomers were done with DFT and are compared with its optical band gap energy values. Fluorescence spectra of these compounds showed maximum emission in blue region. The electrical conductivity of PBIs was measured by four-point probe technique and showed good electrical response on iodine doping and conductivity increases with increase iodine doping time. The differences in conductivities among the three PBIs are in accordance with the charge density on imidazole nitrogens calculated by Huckel method. The high carbines residue (∼40%) at 500 °C in thermo gravimetric analysis shows that the PBIs are having reasonably good thermal stability. Polymers have recorded high dielectric constant at low applied frequency of 50 Hz at 393 K. The I-V characteristics of polybenzimidazoles p-n diodes showed rectifying nature with a typical forward to reverse current in the range -4 to 4 V. The high n values are caused by non homogeneities and effect of series resistance.

A Novel Tetrasubstituted Imidazole as a Prototype for the Development of Anti-inflammatory Drugs.

PubMed

Nascimento, Marcus Vinicius P S; Munhoz, Antonio C M; Theindl, Lais C; Mohr, Eduarda Talita B; Saleh, Najla; Parisotto, Eduardo B; Rossa, Thaís A; Zamoner, Ariane; Creczynski-Pasa, Tania B; Filippin-Monteiro, Fabíola B; Sá, Marcus M; Dalmarco, Eduardo Monguilhott

2018-04-14

Although inflammation is a biological phenomenon that exists to protect the host against infections and/or related problems, its unceasing activation results in the aggravation of several medical conditions. Imidazoles, whether natural or synthetic, are molecules related to a broad spectrum of biological effects, including anti-inflammatory properties. In this study, we screened eight novel small molecules of the imidazole class synthesized by our research group for their in vitro anti-inflammatory activity. The effect of the selected molecules was confirmed in an in vivo inflammatory model. We also analyzed whether the effects were caused by inhibition of nuclear factor kappa B (NF-κB) transcription factor transmigration. Of the eight imidazoles tested, methyl 1-allyl-2-(4-fluorophenyl)-5-phenyl-1H-imidazole-4-acetate (8) inhibited nitric oxide metabolites and pro-inflammatory cytokine (TNF-α, IL-6, and IL-1β) secretion in J774 macrophages stimulated with LPS. It also attenuated leukocyte migration and exudate formation in the pleural cavity of mice challenged with carrageenan. Furthermore, imidazole 8 reverted the oxidative stress pattern triggered by carrageenan in the pleural cavity by diminishing myeloperoxidase, superoxide dismutase, catalase, and glutathione S-transferase activities and reducing the production of nitric oxide metabolites and thiobarbituric acid-reactive substances. Finally, these effects can be attributed, at least in part, to the ability of this compound to prevent NF-κB transmigration. In this context, our results demonstrate that imidazole 8 has promising potential as a prototype for the development of a new anti-inflammatory drug to treat inflammatory conditions in which NF-κB and oxidative stress play a prominent role. Graphical Abstract ᅟ.

Synthesis, biological evaluation and structure-activity correlation study of a series of imidazol-based compounds as Candida albicans inhibitors.

PubMed

Moraca, Francesca; De Vita, Daniela; Pandolfi, Fabiana; Di Santo, Roberto; Costi, Roberta; Cirilli, Roberto; D'Auria, Felicia Diodata; Panella, Simona; Palamara, Anna Teresa; Simonetti, Giovanna; Botta, Maurizio; Scipione, Luigi

2014-08-18

A new series of 2-(1H-imidazol-1-yl)-1-phenylethanol derivatives was synthesized. The antifungal activity was evaluated in vitro against different fungal species. The biological results show that the most active compounds possess an antifungal activity comparable or higher than Fluconazole against Candida albicans, non-albicans Candida species, Cryptococcus neoformans and dermathophytes. Because of their racemic nature, the most active compounds 5f and 6c were tested as pure enantiomers. For 6c the (R)-enantiomer resulted more active than the (S)-one, otherwise for 5f the (S)-enantiomer resulted the most active. To rationalize the experimental data, a ligand-based computational study was carried out; the results of the modelling study show that (S)-5f and (R)-6c perfectly align to the ligand-based model, showing the same relative configuration. Preliminary studies on the human lung adenocarcinoma epithelial cells (A549) have shown that 6c, 5e and 5f possess a low cytotoxicity. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

The Activity-Related Ionization in Carbonic Anhydrase

PubMed Central

Appleton, David W.; Sarkar, Bibudhendra

1974-01-01

The catalytic activity of carbonic anhydrase (EC 4.2.1.1) is linked to the ionization of a group in close proximity to the essential zinc ion. Studies have been undertaken to delineate the ionizations germane to the active-site chelate system. Several imidazole ligand systems were studied in order to approach a representative chelate. The simplest involved the complexation of Zn(II) by imidazole and by N-methylimidazole. As well, two bidentate systems, Zn(II)-4,4′-bis-imidazoylmethane and Co(II)-cyclic-L-histidyl-L-histidine were investigated. It was found that in a species containing metal-bound water and imidazole coordinated by means of the pyridinium nitrogen, the most acidic group was the pyrrole N-H in the imidazole ring. By the use of N-methylimidazole, the pKa of a metal-bound water molecule in a tri-imidazole ligand field was found to be 9.1. Noting the preference for labilization of the pyrrole hydrogen, the catalytic features of carbonic anhydrase are reexamined assuming that the pKenz is associated with the N-H ionization, and not with the ionization of metal-bound water. PMID:4209558

A new route to the imidazole-2-thiones from 2-thiohydantoins. Implications in the study of ergothioneine

PubMed Central

Scott, J. E.; Henderson, Gillian

1968-01-01

1. 2-Thiohydantoins are reduced by borohydrides to 4(5)-hydroxyimidazolidine-2-thiones, which eliminate water in acid to form imidazole-2-thiones. Both steps take place in mild conditions, in high yield. A number of imidazole-2-thiones have been synthesized by this sequence of steps, with one, two or three substituents in the 1-, 3- and 4(5)-positions. 2. 4(5)-Hydroxyimidazolidine-2-thiones are ammonium pseudo-bases, giving rise to an equilibrium mixture of amino aldehyde, carbinolamine and mesomeric ammonium cationic forms. The elimination of water is suggested to be a property of the mesomeric ammonium cation. 3. The mild conditions in which imidazole-2-thiones are formed from 4(5)-hydroxyimidazolidine-2-thiones are similar to those in which ergothioneine, a naturally occurring imidazole-2-thione of uncertain function, is normally released and measured. It is suggested that the occurrence in vivo of a precursor to ergothioneine, in the form of a 4(5)-hydroxyimidazolidine-2-thione, would explain many otherwise conflicting published data. PMID:5679364

A Metal-Organic Framework Approach toward Highly Nitrogen-Doped Graphitic Carbon as a Metal-Free Photocatalyst for Hydrogen Evolution.

PubMed

Zhao, Xiuxia; Yang, Hao; Jing, Peng; Shi, Wei; Yang, Guangming; Cheng, Peng

2017-03-01

Zeolitic imidazolate framework-8 (ZIF-8)-derived N-doped graphene analogous polyhedrons (ZNGs) obtained via the direct carbonation of ZIF-8 are applied to photocatalytic hydrogen evolution for the first time. The contents of different types of nitrogen atoms in ZNGs can be fine-tuned via the calcination temperature, which significantly influences the hydrogen evolution rate of the ZNGs. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reversible uptake of molecular oxygen by heteroligand Co(II)-L-α-amino acid-imidazole systems: equilibrium models at full mass balance.

PubMed

Pająk, Marek; Woźniczka, Magdalena; Vogt, Andrzej; Kufelnicki, Aleksander

2017-09-19

The paper examines Co(II)-amino acid-imidazole systems (where amino acid = L-α-amino acid: alanine, asparagine, histidine) which, when in aqueous solutions, activate and reversibly take up dioxygen, while maintaining the structural scheme of the heme group (imidazole as axial ligand and O 2 uptake at the sixth, trans position) thus imitating natural respiratory pigments such as myoglobin and hemoglobin. The oxygenated reaction shows higher reversibility than for Co(II)-amac systems with analogous amino acids without imidazole. Unlike previous investigations of the heteroligand Co(II)-amino acid-imidazole systems, the present study accurately calculates all equilibrium forms present in solution and determines the [Formula: see text]equilibrium constants without using any simplified approximations. The equilibrium concentrations of Co(II), amino acid, imidazole and the formed complex species were calculated using constant data obtained for analogous systems under oxygen-free conditions. Pehametric and volumetric (oxygenation) studies allowed the stoichiometry of O 2 uptake reaction and coordination mode of the central ion in the forming oxygen adduct to be determined. The values of dioxygen uptake equilibrium constants [Formula: see text] were evaluated by applying the full mass balance equations. Investigations of oxygenation of the Co(II)-amino acid-imidazole systems indicated that dioxygen uptake proceeds along with a rise in pH to 9-10. The percentage of reversibility noted after acidification of the solution to the initial pH ranged within ca 30-60% for alanine, 40-70% for asparagine and 50-90% for histidine, with a rising tendency along with the increasing share of amino acid in the Co(II): amino acid: imidazole ratio. Calculations of the share of the free Co(II) ion as well as of the particular complex species existing in solution beside the oxygen adduct (regarding dioxygen bound both reversibly and irreversibly) indicated quite significant values for the systems with alanine and asparagine-in those cases the of oxygenation reaction is right shifted to a relatively lower extent. The experimental results indicate that the "active" complex, able to take up dioxygen, is a heteroligand CoL 2 L'complex, where L = amac (an amino acid with a non-protonated amine group) while L' = Himid, with the N1 nitrogen protonated within the entire pH range under study. Moreover, the corresponding log  [Formula: see text] value at various initial total Co(II), amino acid and imidazole concentrations was found to be constant within the limits of error, which confirms those results. The highest log [Formula: see text] value, 14.9, occurs for the histidine system; in comparison, asparagine is 7.8 and alanine is 9.7. This high value is most likely due to the participation of the additional effective N3 donor of the imidazole side group of histidine. The Co(II)-amac-Himid systems formed by using a [Co(imid) 2 ] n polymer as starting material demonstrate that the reversible uptake of molecular oxygen occurs by forming dimeric μ-peroxy adducts. The essential impact on the electron structure of the dioxygen bridge, and therefore, on the reversibility of O 2 uptake, is due to the imidazole group at axial position (trans towards O 2 ). However, the results of reversibility measurements of O 2 uptake, unequivocally indicate a much higher effectiveness of dioxygenation than in systems in which the oxygen adducts are formed in equilibrium mixtures during titration of solutions containing Co(II) ions, the amino acid and imidazole, separately.

Part 1. Synthetic approaches to indole/imidazole marine alkaloids. Part 2. 1-cyanobenzotriazole as a cyanating agent. Part 3. Synthesis of potential molecular rectifiers

NASA Astrophysics Data System (ADS)

Hughes, Terry Vincent

1999-12-01

This dissertation consists of four chapters. The first chapter details the progress toward a total synthesis of securine A (1). Securine A is an indole/imidazole containing marine alkaloid which contains a 2,3-disubstituted indole ring and a 4,5- disubstituted imidazole ring with a 12-membered lactam connecting the two. The approach into the securine A ring system utilized the opening of a pyrano[3,4-b]indol-3-one ring system with a modified histamine derivative. Efforts in the synthesis of securine A were not successful, but the synthesis of a similar analogue, compound 53, which contained a 13-membered ring was achieved. Chapter two deals with the total synthesis of the indole/maleimide/imidazole containing marine alkaloids: the didemnimides A-D (84- 87). The total syntheses of didemnimide A-D were successful and utilized a base catalyzed condensation reaction of methyl indolyl-3-glyoxylate (102) and 1-trityl-4-imidazoleacetamide (104). Chapter three details a new and convenient synthesis of 1-cyanobenzotriazole (123) and efforts to use it as a source of +CN in carbon-carbon forming reactions. The synthesis is safer than previously reported methods and allows for 123 to be made in multi-gram scale rather inexpensively. It was demonstrated that 1-cyanobenzotriazole (123) is a good source of +CN in carbon-carbon forming reactions by reacting with a variety of sp3, Sp 2, and sp carbanions. Chapter four details a new synthesis of hexadecylquinolinium tricyanoquinodimethanide (171) which has been shown to be a molecular rectifier. In search of additional molecular rectifiers, this new methodology was applied to the synthesis of Z- β-(N-n -hexadecyl-2-benzothiazolium)-α-cyano-4-styryldicyanomethanide (181) as well as its selenium and tellurium analogues 190 and 200; respectively. Additionally, the synthesis of other T- D+-π-A- types of molecules was explored in search for other molecular rectifiers. However, of all the compounds synthesized herein, only 171 has been shown to rectify.

Treatment System for Removing Halogenated Compounds from Contaminated Sources

NASA Technical Reports Server (NTRS)

Clausen, Christian A. (Inventor); Yestrebsky, Cherie L. (Inventor); Quinn, Jacqueline W. (Inventor)

2015-01-01

A treatment system and a method for removal of at least one halogenated compound, such as PCBs, found in contaminated systems are provided. The treatment system includes a polymer blanket for receiving at least one non-polar solvent. The halogenated compound permeates into or through a wall of the polymer blanket where it is solubilized with at least one non-polar solvent received by said polymer blanket forming a halogenated solvent mixture. This treatment system and method provides for the in situ removal of halogenated compounds from the contaminated system. In one embodiment, the halogenated solvent mixture is subjected to subsequent processes which destroy and/or degrade the halogenated compound.

Effect of halogen dopants on the properties of Li2O2: is chloride special?

PubMed

Cortes, Henry A; Vildosola, Verónica L; Barral, María Andrea; Corti, Horacio R

2018-05-18

There is consensus on the fact that one of the main limitations of Li air batteries (LABs) is the insulating character of Li2O2 and that it becomes crucial to explore new conduction paths. Recent studies indicate that doping with chloride increases the ion conductivity of Li2O2, although to a much lesser extent than expected if chloride is assumed to be a donor dopant [Gerbig et al., Adv. Mater., 2013, 25, 3129]. Subsequently, it has been shown that the addition of lithium chloride, LiCl, to the battery electrolyte increases its discharge capacity, while this effect is not observed with other halogens [Matsuda et al., J. Phys. Chem. C, 2016, 120, 13360]. This fact was attributed to an increase in the conductivity of Cl-doped Li2O2, but still the responsible mechanism is not clear. In this work, we have performed first principle calculations to study the effect of the different halogens (F, Cl, Br, I) as substitutional defects on the electronic and transport properties of Li2O2. We have calculated the formation energies of the different defects and impurities and we analysed how they affect the activation barriers and diffusion coefficients. We have demonstrated that the chloride does not behave like a donor dopant, thus explaining the meager increase of the ionic conductivity experimentally observed, and neither does it promote polaron formation and mobility. We have also found that chloride does not present any special behaviour among the halogen series. Our results reveal that all the studied configurations associated with the halogen defects do not derive metallic states nor extra polarons that would increase considerably the electronic conductivity. This is mainly due to the ionic characteristics of the Li2O2 crystal and the capability of the oxygen dimers to adapt its valence rather than to the nature of the dopant itself.

Comment on "Cosmic-ray-driven reaction and greenhouse effect of halogenated molecules: Culprits for atmospheric ozone depletion and global climate change"

NASA Astrophysics Data System (ADS)

Müller, Rolf; Grooß, Jens-Uwe

2014-04-01

Lu's "cosmic-ray-driven electron-induced reaction (CRE) theory" is based on the assumption that the CRE reaction of halogenated molecules (e.g., chlorofluorocarbons (CFCs), HCl, ClONO2) adsorbed or trapped in polar stratospheric clouds in the winter polar stratosphere is the key step in forming photoactive halogen species that are the cause of the springtime ozone hole. This theory has been extended to a warming theory of halogenated molecules for climate change. In this comment, we discuss the chemical and physical foundations of these theories and the conclusions derived from the theories. First, it is unclear whether the loss rates of halogenated molecules induced by dissociative electron attachment (DEA) observed in the laboratory can also be interpreted as atmospheric loss rates, but even if this were the case, the impact of DEA-induced reactions on polar chlorine activation and ozone loss in the stratosphere is limited. Second, we falsify several conclusions that are reported on the basis of the CRE theory: There is no polar ozone loss in darkness, there is no apparent 11-year periodicity in polar total ozone measurements, the age of air in the polar lower stratosphere is much older than 1-2 years, and the reported detection of a pronounced recovery (by about 20-25%) in Antarctic total ozone measurements by the year 2010 is in error. There are also conclusions about the future development of sea ice and global sea level which are fundamentally flawed because Archimedes' principle is neglected. Many elements of the CRE theory are based solely on correlations between certain datasets which are no substitute for providing physical and chemical mechanisms causing a particular behavior noticeable in observations. In summary, the CRE theory cannot be considered as an independent, alternative mechanism for polar stratospheric ozone loss and the conclusions on recent and future surface temperature and global sea level change do not have a physical basis.

Anti-human immunodeficiency virus (HIV) activities of halogenated gomisin J derivatives, new nonnucleoside inhibitors of HIV type 1 reverse transcriptase.

PubMed

Fujihashi, T; Hara, H; Sakata, T; Mori, K; Higuchi, H; Tanaka, A; Kaji, H; Kaji, A

1995-09-01

Halogenated gomisin J (a derivative of lignan compound), represented by the bromine derivative 1506 [(6R, 7S, S-biar)-4,9-dibromo-3,10-dihydroxy-1,2,11,12-tetramethoxy-6, 7-dimethyl-5,6,7,8- tetrahydrodibenzo[a,c]cyclo-octene], was found to be a potent inhibitor of the cytopathic effects of human immunodeficiency virus type 1 (HIV-1) on MT-4 human T cells (50% effective dose, 0.1 to 0.5 microM). Gomisin J derivatives were active in preventing p24 production from acutely HIV-1-infected H9 cells. The selective indices (toxic dose/effective dose) of these compounds were as high as > 300 in some systems. 1506 was active against 3'-azido-3'-deoxythymidine-resistant HIV-1 and acted synergistically with AZT and 2',3'-ddC. 1506 inhibited HIV-1 reverse transcriptase (RT) in vitro but not HIV-1 protease. From the time-of-addition experiment, 1506 was found to inhibit the early phase of the HIV life cycle. A 1506-resistant HIV mutant was selected and shown to possess a mutation within the RT-coding region (at position 188 [Tyr to Leu]). The mutant RT expressed in Escherichia coli was resistant to 1506 in the in vitro RT assay. Some of the HIV strains resistant to other nonnucleoside HIV-1 RT inhibitors were also resistant to 1506. Comparison of various gomisin J derivatives with gomisin J showed that iodine, bromine, and chlorine in the fourth and ninth positions increased RT inhibitory activity as well as cytoprotective activity.

Detection of Aryl Hydrocarbon Receptor Activation by Some Chemicals in Food Using a Reporter Gene Assay

PubMed Central

Amakura, Yoshiaki; Tsutsumi, Tomoaki; Yoshimura, Morio; Nakamura, Masafumi; Handa, Hiroshi; Matsuda, Rieko; Teshima, Reiko; Watanabe, Takahiro

2016-01-01

The purpose of this study was to examine whether a simple bioassay used for the detection of dioxins (DXNs) could be applied to detect trace amounts of harmful DXN-like substances in food products. To identify substances with possible DXN-like activity, we assessed the ability of various compounds in the environment to bind the aryl hydrocarbon receptor (AhR) that binds specifically to DXNs. The compounds tested included 19 polycyclic aromatic hydrocarbons (PAHs), 20 PAH derivatives (nitrated, halogenated, and aminated derivatives), 23 pesticides, six amino acids, and eight amino acid metabolites. The AhR binding activities (AhR activity) of these compounds were measured using the chemical activated luciferase gene expression (CALUX) reporter gene assay system. The majority of the PAHs exhibited marked AhR activity that increased in a concentration-dependent manner. Furthermore, there was a positive link between AhR activity and the number of aromatic rings in the PAH derivatives. Conversely, there appeared to be a negative correlation between AhR activity and the number of chlorine residues present on halogenated PAH derivatives. However, there was no correlation between AhR activity and the number and position of substituents among nitrated and aminated derivatives. Among the pesticides tested, the indole-type compounds carbendazim and thiabendazole showed high levels of activity. Similarly, the indole compound tryptamine was the only amino acid metabolite to induce AhR activity. The results are useful in understanding the identification and characterization of AhR ligands in the CALUX assay. PMID:28231110

Spectral properties and structure of unsymmetrical diarylethenes based on thiazole ring with hydrogen at the reactive carbon.

PubMed

Lvov, Andrey G; Alexeeva, Anna M; Lvova, Evgeniya A; Krayushkin, Mikhail M; Shirinian, Valerii Z

2018-05-31

Six new photoactive unsymmetrical diarylethenes bearing thiazole ring with hydrogen at the reactive carbon atom have been synthesized. Their structures have been studied by DFT calculations and X-ray crystallography. All compounds undergo irreversible photochemical transformations under irradiation with ultraviolet light, proceeding through the photocyclization stage. It has been found that only some normal (thiophene, imidazole and pyrazole derivatives) and inverse type (oxazole derivative) diarylethenes form colored photoinduced isomers under UV. In polar acetonitrile these intermediates show relatively fast irreversible thermal reaction, while in nonpolar toluene slow cycloreversion to initial diarylethenes is the predominant process of these species. Copyright © 2018 Elsevier B.V. All rights reserved.

Epoxy Nanocomposites Containing Zeolitic Imidazolate Framework-8.

PubMed

Liu, Cong; Mullins, Michael; Hawkins, Spencer; Kotaki, Masaya; Sue, Hung-Jue

2018-01-10

Zeolitic imidazole framework-8 (ZIF-8) is utilized as a functional filler and a curing agent in the preparation of epoxy nanocomposites. The imidazole group on the surface of the ZIF-8 initiates epoxy curing, resulting in covalent bonding between the ZIF-8 crystals and epoxy matrix. A substantial reduction in dielectric constant and increase in tensile modulus were observed. The implication of the present study for utilization of metal-organic framework to improve physical and mechanical properties of polymeric matrixes is discussed.

Synthesis, characterization and biological approach of metal chelates of some first row transition metal ions with halogenated bidentate coumarin Schiff bases containing N and O donor atoms.

PubMed

Prabhakara, Chetan T; Patil, Sangamesh A; Toragalmath, Shivakumar S; Kinnal, Shivashankar M; Badami, Prema S

2016-04-01

The impregnation of halogen atoms in a molecule is an emerging trend in pharmaceutical chemistry. The presence of halogens (Cl, Br, I and F) increases the lipophilic nature of molecule and improves the penetration of lipid membrane. The presence of electronegative halogen atoms increases the bio- activity of core moiety. In the present study, Co(II), Ni(II) and Cu(II) complexes are synthesised using Schiff bases (HL(I) and HL(II)), derived from 8-formyl-7-hydroxy-4-methylcoumarin/3-chloro-8-formyl-7-hydroxy-4-methylcoumarin with 2,4-difluoroaniline/o-toluidine respectively. The synthesized compounds were characterized by spectral (IR, NMR, UV-visible, Mass, ESI-MS, ESR), thermal, fluorescence and molar conductivity studies. All the synthesized metal complexes are completely soluble in DMF and DMSO. The non-electrolytic nature of the metal complexes was confirmed by molar conductance studies. Elemental analysis study suggest [ML2(H2O)2] stoichiometry, here M=Co(II), Ni(II) and Cu(II), L=deprotonated ligand. The obtained IR data supports the binding of metal ion to Schiff base. Thermal study suggests the presence of coordinated water molecules. Electronic spectral results reveal six coordinated geometry for the synthesized metal complexes. The Schiff bases and their metal complexes were evaluated for antibacterial (Pseudomonas aureginosa and Proteus mirabilis), antifungal (Aspergillus niger and Rhizopus oryzae), anthelmintic (Pheretima posthuma) and DNA cleavage (Calf Thymus DNA) activities. Copyright © 2016 Elsevier B.V. All rights reserved.

A 4-term energy level scheme for the high-spin ferrous hemoproteins: evidence for the 5E eta, and 5B2 terms as the ground multiplets in hemoproteins with a histidine and a cysteine protein-derived heme ligand, respectively.

PubMed

Oganesyan, V S; Sharonov, Y A

1997-03-01

We have carried out analysis of the electronic level scheme of the high-spin ferrous hemoproteins by simultaneous fit of the adjustable parameters of a 4-term theoretical model to low-temperature magnetic circular dichroism (MCD), room temperature absorption spectra and available magnetic susceptibility and or Mössbauer data of myoglobin, horseradish peroxidase and cytochrome P450. The high reliability of the ligand field parameter values obtained for deoxymyoglobin is confirmed by good agreement between the predicted and observed magnetic field dependences of MCD and magnetization not used in the fit procedure. In addition, an energy gap between the ground and first excited singlets, estimated to be 4.2 cm-1, agrees well with the value of approximately 4 cm-1 derived from the far-infrared magnetic resonance. Our computer and explicit theoretical analyses give strong evidence that large distinctions in the shape, intensity and temperature behaviour of the MCD of Mb and HRP from those of cytochrome P450 can be described only if the ground manifold in these proteins is 5E eta and 5B2, respectively. The changes in relative energies of the one-electron 3d-orbitals on substitution of an imidazole of histidine for a sulphur anion of cysteine as a protein-derived heme iron ligand are rationalized by the lower ionization potential of the negatively charged sulphur ligand and the higher pi-orbital overlap of its lone pair orbitals with the iron d pi-orbitals compared to the imidazole ligand.

Synthesis, molecular modelling, and preliminary anticonvulsant activity evaluation of novel naphthalen-2-yl acetate and 1,6-dithia-4,9-diazaspiro [4.4] nonane-3,8-dione derivatives.

PubMed

Ghareb, Nagat; Abdel Daim, Mohamed M; El-Sayed, Norhan M; Elgawish, Mohamed Saleh

2017-04-01

The synthesis, pharmacological evaluation and molecular modelling study of novel naphthalen-2-yl acetate and 1,6-dithia-4,9-diazaspiro [4.4]nonane-3,8-dione derivatives as potential anticonvulsant agents are described. The newly synthesized compounds were characterized by both analytical and spectral data. Alkylation of 1H-imidazole or substituted piperazine with 1-(2-naphthyl)-2-bromoethanone (2) gave naphthalen-2-yl 2-(1H-imidazol-1-yl) acetate (3) and naphthalen-2-yl 2-(substituted piperazin-1-yl) acetate (4-8). Moreover, condensation of naphthalen-2-yl 2-bromoacetate or 2-bromo-1-(naphthalen-2-yl) ethanone with hydrazine hydrate and acetylacetone resulted in the formation of the cyclic pyrazole products 9 and 13. Sonication of naphthalen-2-yl acetate (1) with 2-chloropyridine, 2-chloropyrimidine and 2-(chloromethyl) oxirane gave naphthalen-2-yl 2-(pyridin-2-yl) acetate (10), naphthalen-2-yl 2-(pyrimidin-2-yl) acetate (11) and naphthalen-2-yl-3-(oxiran-2-yl) propanoate (12) respectively. Cyclocondensation reaction of 2-iminothiazolidin-4-one (14) with thioglycolic acid, thiolactic acid and thiomalic acid gave 1,6-dithia-4,9-diazaspiro [4.4]nonane-3,8-dione derivatives (15-17). The compounds were testedin vivofor the anticonvulsant activity by delaying strychnine-induced seizures. The diazaspirononane (17) and 1-(2-naphthyl)-2-bromoethanone (2) showed a high significant delay in the onset of convulsion and prolongation of survival time compared to phenobarbital. The molecular modelling study of anticonvulsant activity of synthesized compounds showed a CNS depressant activity via modulation of benzodiazepine allosteric site in GABA-A receptors. Copyright © 2017 Elsevier Inc. All rights reserved.

Quantum mechanical/molecular mechanical and docking study of the novel analogues based on hybridization of common pharmacophores as potential anti-breast cancer agents

PubMed Central

Asadi, Parvin; Khodarahmi, Ghadamali; Farrokhpour, Hossein; Hassanzadeh, Farshid; Saghaei, Lotfollah

2017-01-01

In an attempt to identify some new potential leads as anti-breast cancer agents, novel hybrid compounds were designed by molecular hybridization approach. These derivatives were structurally derived from hybrid benzofuran–imidazole and quinazolinone derivatives, which had shown good cytotoxicity against the breast cancer cell line (MCF-7). Since aromatase enzyme (CYP19) is highly expressed in the MCF-7 cell line, the binding of these novel hybrid compounds to aromatase was investigated using the docking method. In this study, due to the positive charge on the imidazole ring of the designed ligands and also, the presence of heme iron in the active site of the enzyme, it was decided to optimize the ligand inside the protein to obtain more realistic atomic charges for it. Quantum mechanical/molecular mechanical (QM/MM) method was used to obtain more accurate atomic charges of ligand for docking calculations by considering the polarization effects of CYP19 on ligands. It was observed that the refitted charge improved the binding energy of the docked compounds. Also, the results showed that these novel hybrid compounds were adopted properly within the aromatase binding site, thereby suggesting that they could be potential inhibitors of aromatase. The main binding modes in these complexes were through hydrophobic and H bond interactions showing agreement with the basic physicochemical features of known anti aromatase compounds. Finally, the complex structures obtained from the docking study were used for single point QM/MM calculations to obtain more accurate electronic interaction energy, considering the electronic polarization of the ligand by its protein environment. PMID:28626481

A new class of halogen bonds that avoids the σ-hole

NASA Astrophysics Data System (ADS)

Zhang, Yu; Ma, Ning; Wang, Weizhou

2012-04-01

A new class of halogen bonds of the type X = Hal⋯Y has been investigated by using the density functional theory calculations. The strength of this new class of halogen bonds is in the range of 90-120 kcal/mol, which is greatly larger than that of the conventional halogen bond of the type X-Hal⋯Y. The geometry of this new class of halogen bonds is not determined by the halogen's positive σ-hole. Natural bond orbital analysis shows it is the n → π∗ interaction that determines the geometry of this new class of halogen bonds. Experimental results are in good agreement with the theoretical predictions.

The Halogen Bond in the Design of Functional Supramolecular Materials: Recent Advances

PubMed Central

2013-01-01

Halogen bonding is an emerging noncovalent interaction for constructing supramolecular assemblies. Though similar to the more familiar hydrogen bonding, four primary differences between these two interactions make halogen bonding a unique tool for molecular recognition and the design of functional materials. First, halogen bonds tend to be much more directional than (single) hydrogen bonds. Second, the interaction strength scales with the polarizability of the bond-donor atom, a feature that researchers can tune through single-atom mutation. In addition, halogen bonds are hydrophobic whereas hydrogen bonds are hydrophilic. Lastly, the size of the bond-donor atom (halogen) is significantly larger than hydrogen. As a result, halogen bonding provides supramolecular chemists with design tools that cannot be easily met with other types of noncovalent interactions and opens up unprecedented possibilities in the design of smart functional materials. This Account highlights the recent advances in the design of halogen-bond-based functional materials. Each of the unique features of halogen bonding, directionality, tunable interaction strength, hydrophobicity, and large donor atom size, makes a difference. Taking advantage of the hydrophobicity, researchers have designed small-size ion transporters. The large halogen atom size provided a platform for constructing all-organic light-emitting crystals that efficiently generate triplet electrons and have a high phosphorescence quantum yield. The tunable interaction strengths provide tools for understanding light-induced macroscopic motions in photoresponsive azobenzene-containing polymers, and the directionality renders halogen bonding useful in the design on functional supramolecular liquid crystals and gel-phase materials. Although halogen bond based functional materials design is still in its infancy, we foresee a bright future for this field. We expect that materials designed based on halogen bonding could lead to applications in biomimetics, optics/photonics, functional surfaces, and photoswitchable supramolecules. PMID:23805801

Halogen Chemistry in the CMAQ Model

EPA Science Inventory

Halogens (iodine and bromine) emitted from oceans alter atmospheric chemistry and influence atmospheric ozone mixing ratio. We previously incorporated a representation of detailed halogen chemistry and emissions of organic and inorganic halogen species into the hemispheric Commun...

Method of dehalogenation using diamonds

DOEpatents

Farcasiu, Malvina; Kaufman, Phillip B.; Ladner, Edward P.; Anderson, Richard R.

2000-01-01

A method for preparing olefins and halogenated olefins is provided comprising contacting halogenated compounds with diamonds for a sufficient time and at a sufficient temperature to convert the halogenated compounds to olefins and halogenated olefins via elimination reactions.

Regio- and Enantioselective N-Allylations of Imidazole, Benzimidazole, and Purine Heterocycles Catalyzed by Single-Component Metallacyclic Iridium Complexes

PubMed Central

Stanley, Levi M.

2010-01-01

Highly regio- and enantioselective iridium-catalyzed N-allylations of benzimidazoles, imidazoles, and purines have been developed. N-Allylated benzimidazoles and imidazoles were isolated in high yields (up to 97%) with high branched-to-linear selectivity (up to 99:1) and enantioselectivity (up to 98% ee) from the reactions of benzimidazole and imidazole nucleophiles with unsymmetrical allylic carbonates in the presence of single component, ethylene-bound, metallacyclic iridium catalysts. N-Allylated purines were also obtained in high yields (up to 91%) with high N9:N7 selectivity (up to 96:4), high branched-to-linear selectivity (98:2), and high enantioselectivity (up to 98% ee) under similar conditions. The reactions encompass a range of benzimidazole, imidazole, and purine nucleophiles, as well as a variety of unsymmetrical aryl, heteroaryl, and aliphatic allylic carbonates. Competition experiments between common amine nucleophiles and the heterocyclic nitrogen nucleophiles studied in this work illustrate the effect of nucleophile pKa on the rate of iridium-catalyzed N-allylation reactions. Kinetic studies on the allylation of benzimidazole catalyzed by metallacyclic iridium-phosphoramidite complexes, in combination with studies on the deactivation of these catalysts in the presence of heterocyclic nucleophiles, provide insight into the effects of the structure of the phosphoramidite ligands on the stability of the metallacyclic catalysts. The data obtained from these studies has led to the development of N-allylations of benzimidazoles and imidazoles in the absence of an exogenous base. PMID:19480431

Cd(II)-coordination polymers based on tetracarboxylic acid and diverse bis(imidazole) ligands: Synthesis, structural diversity and photoluminescence properties

NASA Astrophysics Data System (ADS)

Arıcı, Mürsel; Yeşilel, Okan Zafer; Taş, Murat

2017-01-01

Three new Cd(II)-coordination polymers, namely, {[Cd2(μ6-ao2btc)(μ-1,5-bipe)2]·2H2O}n (1), {[Cd2(μ6-ao2btc)(μ-1,4-bix)2]n·2DMF} (2) and {[Cd2(μ8-abtc)(μ-1,4-betix)]·DMF·H2O}n (3) (ao2btc=di-oxygenated form of 3,3‧,5,5‧-azobenzenetetracarboxylate, 1,5-bipe: 1,5-bis(imidazol-1yl)pentane, 1,4-bix=1,4-bis(imidazol-1ylmethyl)benzene, 1,4-betix=1,4-bis(2-ethylimidazol-1ylmethyl)benzene) were synthesized with 3,3‧,5,5‧-azobenzenetetracarboxylic acid and flexible, semi-flexible and semi-flexible substituted bis(imidazole) linkers. They were characterized by IR spectroscopy, elemental analysis, single-crystal X-ray diffraction, powder X-ray diffractions (PXRD) and thermal analyses (TG/DTA). Complexes 1-3 exhibited structural diversities depending on flexible, semi-flexible and semi-flexible substituted bis(imidazole) ligands. Complex 1 was 2D structure with 3,6L18 topology. Complex 2 had a 3D pillar-layered framework with the rare sqc27 topology. When semi-flexible substituted bis(imidazole) linker was used, 3D framework of complex 3 was obtained with the paddlewheel Cd2(CO2)4-type binuclear SBU. Moreover, thermal and photoluminescence properties of the complexes were determined in detailed.

Method of producing nano-scaled graphene and inorganic platelets and their nanocomposites

DOEpatents

Jang, Bor Z [Centerville, OH; Zhamu, Aruna [Centerville, OH

2011-02-22

Disclosed is a method of exfoliating a layered material (e.g., graphite and graphite oxide) to produce nano-scaled platelets having a thickness smaller than 100 nm, typically smaller than 10 nm, and often between 0.34 nm and 1.02 nm. The method comprises: (a) subjecting the layered material in a powder form to a halogen vapor at a first temperature above the melting point or sublimation point of the halogen at a sufficient vapor pressure and for a duration of time sufficient to cause the halogen molecules to penetrate an interlayer space of the layered material, forming a stable halogen-intercalated compound; and (b) heating the halogen-intercalated compound at a second temperature above the boiling point of the halogen, allowing halogen atoms or molecules residing in the interlayer space to exfoliate the layered material to produce the platelets. Alternatively, rather than heating, step (a) is followed by a step of dispersing the halogen-intercalated compound in a liquid medium which is subjected to ultrasonication for exfoliating the halogen-intercalated compound to produce the platelets, which are dispersed in the liquid medium. The halogen can be readily captured and re-used, thereby significantly reducing the impact of halogen to the environment. The method can further include a step of dispersing the platelets in a polymer or monomer solution or suspension as a precursor step to nanocomposite fabrication.

Method of producing nano-scaled graphene and inorganic platelets and their nanocomposites

DOEpatents

Jang, Bor Z [Centerville, OH; Zhamu, Aruna [Centerville, OH

2012-02-14

Disclosed is a method of exfoliating a layered material (e.g., graphite and graphite oxide) to produce nano-scaled platelets having a thickness smaller than 100 nm, typically smaller than 10 nm, and often between 0.34 nm and 1.02 nm. The method comprises: (a) subjecting the layered material in a powder form to a halogen vapor at a first temperature above the melting point or sublimation point of the halogen at a sufficient vapor pressure and for a duration of time sufficient to cause the halogen molecules to penetrate an interlayer space of the layered material, forming a stable halogen-intercalated compound; and (b) heating the halogen-intercalated compound at a second temperature above the boiling point of the halogen, allowing halogen atoms or molecules residing in the interlayer space to exfoliate the layered material to produce the platelets. Alternatively, rather than heating, step (a) is followed by a step of dispersing the halogen-intercalated compound in a liquid medium which is subjected to ultrasonication for exfoliating the halogen-intercalated compound to produce the platelets, which are dispersed in the liquid medium. The halogen can be readily captured and re-used, thereby significantly reducing the impact of halogen to the environment. The method can further include a step of dispersing the platelets in a polymer or monomer solution or suspension as a precursor step to nanocomposite fabrication.

Biosynthesis of coral settlement cue tetrabromopyrrole in marine bacteria by a uniquely adapted brominase–thioesterase enzyme pair

PubMed Central

El Gamal, Abrahim; Agarwal, Vinayak; Diethelm, Stefan; Rahman, Imran; Schorn, Michelle A.; Sneed, Jennifer M.; Louie, Gordon V.; Whalen, Kristen E.; Mincer, Tracy J.; Noel, Joseph P.; Paul, Valerie J.; Moore, Bradley S.

2016-01-01

Halogenated pyrroles (halopyrroles) are common chemical moieties found in bioactive bacterial natural products. The halopyrrole moieties of mono- and dihalopyrrole-containing compounds arise from a conserved mechanism in which a proline-derived pyrrolyl group bound to a carrier protein is first halogenated and then elaborated by peptidic or polyketide extensions. This paradigm is broken during the marine pseudoalteromonad bacterial biosynthesis of the coral larval settlement cue tetrabromopyrrole (1), which arises from the substitution of the proline-derived carboxylate by a bromine atom. To understand the molecular basis for decarboxylative bromination in the biosynthesis of 1, we sequenced two Pseudoalteromonas genomes and identified a conserved four-gene locus encoding the enzymes involved in its complete biosynthesis. Through total in vitro reconstitution of the biosynthesis of 1 using purified enzymes and biochemical interrogation of individual biochemical steps, we show that all four bromine atoms in 1 are installed by the action of a single flavin-dependent halogenase: Bmp2. Tetrabromination of the pyrrole induces a thioesterase-mediated offloading reaction from the carrier protein and activates the biosynthetic intermediate for decarboxylation. Insights into the tetrabrominating activity of Bmp2 were obtained from the high-resolution crystal structure of the halogenase contrasted against structurally homologous halogenase Mpy16 that forms only a dihalogenated pyrrole in marinopyrrole biosynthesis. Structure-guided mutagenesis of the proposed substrate-binding pocket of Bmp2 led to a reduction in the degree of halogenation catalyzed. Our study provides a biogenetic basis for the biosynthesis of 1 and sets a firm foundation for querying the biosynthetic potential for the production of 1 in marine (meta)genomes. PMID:27001835

Independent Evolution of Six Families of Halogenating Enzymes.

PubMed

Xu, Gangming; Wang, Bin-Gui

2016-01-01

Halogenated natural products are widespread in the environment, and the halogen atoms are typically vital to their bioactivities. Thus far, six families of halogenating enzymes have been identified: cofactor-free haloperoxidases (HPO), vanadium-dependent haloperoxidases (V-HPO), heme iron-dependent haloperoxidases (HI-HPO), non-heme iron-dependent halogenases (NI-HG), flavin-dependent halogenases (F-HG), and S-adenosyl-L-methionine (SAM)-dependent halogenases (S-HG). However, these halogenating enzymes with similar biological functions but distinct structures might have evolved independently. Phylogenetic and structural analyses suggest that the HPO, V-HPO, HI-HPO, NI-HG, F-HG, and S-HG enzyme families may have evolutionary relationships to the α/β hydrolases, acid phosphatases, peroxidases, chemotaxis phosphatases, oxidoreductases, and SAM hydroxide adenosyltransferases, respectively. These halogenating enzymes have established sequence homology, structural conservation, and mechanistic features within each family. Understanding the distinct evolutionary history of these halogenating enzymes will provide further insights into the study of their catalytic mechanisms and halogenation specificity.

Synthesis and evaluation of in vitro and in vivo trypanocidal properties of a new imidazole-containing nitrophthalazine derivative.

PubMed

Olmo, Francisco; Gómez-Contreras, Fernando; Navarro, Pilar; Marín, Clotilde; Yunta, María J R; Cano, Carmen; Campayo, Lucrecia; Martín-Oliva, David; Rosales, María José; Sánchez-Moreno, Manuel

2015-12-01

A series of new phthalazine derivatives (1-4) containing imidazole rings and functionalized with nitro groups in the benzene ring of the phthalazine moiety were prepared and identified on the basis of their MS, elemental analyses and bidimensional (1)H and (13)C NMR data, and their trypanocidal activity was tested. The 8-nitrosubstituted compound (3) was more active in vitro against Trypanosoma cruzi and less toxic against Vero cells than the reference drug benznidazole, and showed a SI value that was 47-fold better than the reference drug in amastigote forms. It also remarkably reduced the infectivity rate in Vero cells and decreased the reactivation of parasitemia in immunodeficient mice. Ultrastructural alterations found in epimastigotes treated with 3 confirmed extensive cytoplasm destruction in the parasites, whereas histopathological analysis of the hearts of mice infected and treated with 3 resulted in a decrease in cardiac damage. Biochemical markers showed that livers, hearts, and kidneys of treated mice were substantially unaffected by the administration of 3, despite the presence of the potentially toxic nitro group. It was also found that this compound selectively inhibited the antioxidant parasite enzyme Fe-superoxide dismutase (Fe-SOD) in comparison with human CuZn-SOD, and molecular modeling suggested interaction with the H-bonding system of the iron-based moiety as a feasible mechanism of action against the enzyme. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

A new synthesis of certain 7-(beta-D-ribofuranosyl) and 7-(2-deoxy-beta-D-ribofuranosyl) derivatives of 3-deazaguanine via the sodium salt glycosylation procedure.

PubMed Central

Gupta, P K; Robins, R K; Revankar, G R

1985-01-01

A facile synthesis of 7-beta-D-ribofuranosyl-3-deazaguanine (1) and certain 8-substituted derivatives of 1 via the sodium salt glycosylation method has been developed. Glycosylation of the sodium salt of methyl 2-chloro(or methylthio)-4(5)-cyanomethylimidazole-5(4)-carboxylate (5 and 13b) with 2,3,5-tri-O-benzoyl-D-ribofuranosyl bromide (6) gave exclusively methyl 2-chloro(or methylthio)-4-cyanomethyl-1-(2,3, 5-tri-O-benzoyl-beta-D-ribofuranosyl)imidazole-5-carboxylate (7 and 14a), respectively. Ammonolysis of 7 and 14a provided 6-amino-2-chloro(or methylthio)-3-beta-D-ribofuranosylimidazo-[4,5-c]pyridin-4(5H)-one (11 and 17), which on subsequent dehalogenation (or dethiation) gave 1. Similarly, reaction of the sodium salt of 5 and 13b with 1-chloro-2-deoxy-3,5-di-O-p-toluoyl-alpha-D-erythro-pentofuranose (8), and ammonolysis of the glycosylated imidazole precursors (9 and 16) gave 6-amino-2-chloro(or methylthio)-3-(2-deoxy-beta-D-erythro-pentofuranosyl) imidazo[4,5-c]-pyridin-4(5H)-one (10a and 15), respectively. Dehalogenation of 10a or dethiation of 15 gave 2'-deoxy-7-beta-D-ribofuranosyl-3-deazaguanine (10b). This procedure provided a direct method of obtaining 10b without the contaminating 9-glycosyl isomer 4. PMID:4022783

Carbon materials derived from chitosan/cellulose cryogel-supported zeolite imidazole frameworks for potential supercapacitor application.

PubMed

Li, Zehui; Yang, Lan; Cao, Hongbin; Chang, Yu; Tang, Kexin; Cao, Zhiqin; Chang, Junjun; Cao, Youpeng; Wang, Wenbo; Gao, Meng; Liu, Chenming; Liu, Dagang; Zhao, He; Zhang, Yi; Li, Mingjie

2017-11-01

In order to promote sustainable development, green and renewable clean energy technologies continue to be developed to meet the growing demand for energy, such as supercapacitor, fuel cells and lithium-ion battery. It is urgent to develop appropriate nanomaterials for these energy technologies to reduce the volume of the device, improve the efficiency of energy conversion and enlarge the energy storage capacity. Here, chitosan/cellulose carbon cryogel (CCS/CCL) were designed and synthesized. Through the introduction of zeolite imidazole frameworks (ZIFs) into the chitosan/cellulose cryogels, the obtained materials showed a microstructure of ZIF-7 (a kind of ZIFs) coated chitosan/cellulose fibers (CS/CL). After carbonizing, the as-prepared carbonized ZIF-7@cellulose cryogel (NC@CCL, NC is carbonized ZIF-7) and carbonized ZIF-7@chitosan cryogel (NC@CCS) exhibited suitable microspore contents of 34.37% and 30%, respectively, and they both showed an internal resistance lower than 2Ω. Thereby, NC@CCL and NC@CCS exhibited a high specific capacitance of 150.4Fg -1 and 173.1Fg -1 , respectively, which were much higher than those of the original materials. This approach offers a facile method for improving the strength and electronic conductivity of carbon cryogel derived from nature polymers, and also efficiently inhibits the agglomeration of cryogel during carbonization in high temperature, which opens a novel avenue for the development of carbon cryogel materials for application in energy conversion systems. Copyright © 2017 Elsevier Ltd. All rights reserved.

Titanium-based zeolitic imidazolate framework for chemical fixation of carbon dioxide

EPA Science Inventory

A titanium-based zeolitic imidazolate framework (Ti-ZIF) with high surface area and porous morphology was synthesized and itsefficacy was demonstrated in the synthesis of cyclic carbonates from epoxides and carbon dioxide.

Impacts of bromine and iodine chemistry on tropospheric OH and HO2: comparing observations with box and global model perspectives

NASA Astrophysics Data System (ADS)

Stone, Daniel; Sherwen, Tomás; Evans, Mathew J.; Vaughan, Stewart; Ingham, Trevor; Whalley, Lisa K.; Edwards, Peter M.; Read, Katie A.; Lee, James D.; Moller, Sarah J.; Carpenter, Lucy J.; Lewis, Alastair C.; Heard, Dwayne E.

2018-03-01

The chemistry of the halogen species bromine and iodine has a range of impacts on tropospheric composition, and can affect oxidising capacity in a number of ways. However, recent studies disagree on the overall sign of the impacts of halogens on the oxidising capacity of the troposphere. We present simulations of OH and HO2 radicals for comparison with observations made in the remote tropical ocean boundary layer during the Seasonal Oxidant Study at the Cape Verde Atmospheric Observatory in 2009. We use both a constrained box model, using detailed chemistry derived from the Master Chemical Mechanism (v3.2), and the three-dimensional global chemistry transport model GEOS-Chem. Both model approaches reproduce the diurnal trends in OH and HO2. Absolute observed concentrations are well reproduced by the box model but are overpredicted by the global model, potentially owing to incomplete consideration of oceanic sourced radical sinks. The two models, however, differ in the impacts of halogen chemistry. In the box model, halogen chemistry acts to increase OH concentrations (by 9.8 % at midday at the Cape Verde Atmospheric Observatory), while the global model exhibits a small increase in OH at the Cape Verde Atmospheric Observatory (by 0.6 % at midday) but overall shows a decrease in the global annual mass-weighted mean OH of 4.5 %. These differences reflect the variety of timescales through which the halogens impact the chemical system. On short timescales, photolysis of HOBr and HOI, produced by reactions of HO2 with BrO and IO, respectively, increases the OH concentration. On longer timescales, halogen-catalysed ozone destruction cycles lead to lower primary production of OH radicals through ozone photolysis, and thus to lower OH concentrations. The global model includes more of the longer timescale responses than the constrained box model, and overall the global impact of the longer timescale response (reduced primary production due to lower O3 concentrations) overwhelms the shorter timescale response (enhanced cycling from HO2 to OH), and thus the global OH concentration decreases. The Earth system contains many such responses on a large range of timescales. This work highlights the care that needs to be taken to understand the full impact of any one process on the system as a whole.

Passivation of quartz for halogen-containing light sources

DOEpatents

Falkenstein, Zoran

1999-01-01

Lifetime of halogen containing VUV, UV, visible or IR light sources can be extended by passivating the quartz or glass gas containers with halogens prior to filling the quartz with the halogen and rare gas mixtures used to produce the light.

Method and apparatus for low temperature destruction of halogenated hydrocarbons

DOEpatents

Reagen, William Kevin; Janikowski, Stuart Kevin

1999-01-01

A method and apparatus for decomposing halogenated hydrocarbons are provided. The halogenated hydrocarbon is mixed with solvating agents and maintained in a predetermined atmosphere and at a predetermined temperature. The mixture is contacted with recyclable reactive material for chemically reacting with the recyclable material to create dehalogenated hydrocarbons and halogenated inorganic compounds. A feature of the invention is that the process enables low temperature destruction of halogenated hydrocarbons.

Halogen lamp experiment, HALEX

NASA Technical Reports Server (NTRS)

Schmitt, G.; Stapelmann, J.

1986-01-01

The main purpose of the Halogen Lamp Experiment (HALEX) was to investigate the operation of a halogen lamp during an extended period in a microgravity environment and to prove its behavior in space. The Mirror Heating Facilities for Crystal Growth and Material Science Experiments in space relies on one or two halogen lamps as a furnace to melt the specimens. The HALEX aim is to verify: full power operation of a halogen lamp for a period of about 60 hours; achievement of about 10% of its terrestrial life span; and operation of the halogen lamp under conditions similar to furnace operation.

The Important Role of Halogen Bond in Substrate Selectivity of Enzymatic Catalysis

NASA Astrophysics Data System (ADS)

Jiang, Shuiqin; Zhang, Lujia; Cui, Dongbin; Yao, Zhiqiang; Gao, Bei; Lin, Jinping; Wei, Dongzhi

2016-10-01

The use of halogen bond is widespread in drug discovery, design, and clinical trials, but is overlooked in drug biosynthesis. Here, the role of halogen bond in the nitrilase-catalyzed synthesis of ortho-, meta-, and para-chlorophenylacetic acid was investigated. Different distributions of halogen bond induced changes of substrate binding conformation and affected substrate selectivity. By engineering the halogen interaction, the substrate selectivity of the enzyme changed, with the implication that halogen bond plays an important role in biosynthesis and should be used as an efficient and reliable tool in enzymatic drug synthesis.

Halogen bonding in solution: thermodynamics and applications.

PubMed

Beale, Thomas M; Chudzinski, Michael G; Sarwar, Mohammed G; Taylor, Mark S

2013-02-21

Halogen bonds are noncovalent interactions in which covalently bound halogens act as electrophilic species. The utility of halogen bonding for controlling self-assembly in the solid state is evident from a broad spectrum of applications in crystal engineering and materials science. Until recently, it has been less clear whether, and to what extent, halogen bonding could be employed to influence conformation, binding or reactivity in the solution phase. This tutorial review summarizes and interprets solution-phase thermodynamic data for halogen bonding interactions obtained over the past six decades and highlights emerging applications in molecular recognition, medicinal chemistry and catalysis.

Comparison of stratospheric NO2 profiles above Kiruna, Sweden retrieved from ground-based zenith sky DOAS measurements, SAOZ balloon measurements and SCIAMACHY limb observations

NASA Astrophysics Data System (ADS)

Gu, Myojeong; Enell, Carl-Fredrik; Hendrick, François; Pukite, Janis; Van Roozendael, Michel; Platt, Ulrich; Raffalski, Uwe; Wagner, Thomas

2015-04-01

Stratospheric NO2 not only destroys ozone but acts as a buffer against halogen catalyzed ozone loss by converting halogen species into stable nitrates. These two roles of stratospheric NO2 depend on the altitude. Hence, the objective of this study is to investigate the vertical distribution of stratospheric NO2. We compare the NO2 profiles derived from the zenith sky DOAS with those obtained from, SAOZ balloon measurements and satellite limb observations. Vertical profiles of stratospheric NO2 are retrieved from ground-based zenith sky DOAS observations operated at Kiruna, Sweden (68.84°N, 20.41°E) since 1996. To determine the profile of stratospheric NO2 measured from ground-based zenith sky DOAS, we apply the Optimal Estimation Method (OEM) to retrieval of vertical profiles of stratospheric NO2 which has been developed by IASB-BIRA. The basic principle behind this profiling approach is the dependence of the mean scattering height on solar zenith angle (SZA). We compare the retrieved profiles to two additional datasets of stratospheric NO2 profile. The first one is derived from satellite limb observations by SCIAMACHY (Scanning Imaging Absorption spectrometer for Atmospheric CHartographY) on EnviSAT. The second is derived from the SAOZ balloon measurements (using a UV/Visible spectrometer) performed at Kiruna in Sweden.

Tests of halogen photochemistry using in situ measurements of ClO and BrO in the lower polar stratosphere

NASA Astrophysics Data System (ADS)

Avallone, Linnea M.; Toohey, Darin W.

2001-05-01

In situ observations of the halogen oxides ClO and BrO made from the NASA ER-2 during the Airborne Arctic Stratospheric Expedition (AASE) I and II missions are used to test current understanding of photochemical parameters. Measurements of ClO obtained during AASE I in the dark perturbed polar vortex are analyzed with respect to temperature to derive the equilibrium expression for the ClO/Cl2O2 system. Assuming photochemical steady state and complete activation of chlorine (ClO + 2Cl2O2 = Cly), observations of ClO made during AASE II are used to derive the photolysis rate of Cl2O2. The photolysis rate derived from atmospheric observations is compared to J values calculated with a photochemical model and various values for the absorption cross section of Cl2O2. The photolysis rate calculated with the cross section of Huder and DeMore [1995] is shown to be systematically too small, while those of Burkholder et al. [1990] and Cox and Hayman [1988] are too large to be consistent with atmospheric observations. Observations of BrO made during AASE II indicate that our understanding of the inorganic bromine budget in the polar regions is incomplete. A possible role for the adduct BrOOCl is investigated.

Complementary π-π interactions induce multicomponent coassembly into functional fibrils.

PubMed

Ryan, Derek M; Doran, Todd M; Nilsson, Bradley L

2011-09-06

Noncovalent self-assembled materials inspired by amyloid architectures are useful for biomedical applications ranging from regenerative medicine to drug delivery. The selective coassembly of complementary monomeric units to provide ordered multicomponent fibrils is a possible strategy for enhancing the sophistication of these noncovalent materials. Herein we report that complementary π-π interactions can be exploited to promote the coassembly of phenylalanine (Phe) derivatives that possess complementary aromatic side-chain functionality. Specifically, equimolar mixtures of Fmoc-Phe and Fmoc-F(5)-Phe, which possess side-chain groups with complementary quadrupole electronics, readily coassemble to form two-component fibrils and hydrogels under conditions where Fmoc-Phe alone fails to self-assemble. In addition, it was found that equimolar mixtures of Fmoc-Phe with monohalogenated (F, Cl, and Br) Fmoc-Phe derivatives also coassembled into two-component fibrils. These results collectively indicate that face-to-face quadrupole stacking between benzyl side-chain groups does not account for the molecular recognition between Phe and halogenated Phe derivatives that promote cofibrillization but that coassembly is mediated by more subtle π-π effects arising from the halogenation of the benzyl side chain. The use of complementary π-π interactions to promote the coassembly of two distinct monomeric units into ordered two-component fibrils dramatically expands the repertoire of noncovalent interactions that can be used in the development of sophisticated noncovalent materials. © 2011 American Chemical Society

Dibromotyrosine and histamine derivatives from the tropical marine sponge Aplysina sp.

PubMed

Santalova, Elena A; Denisenko, Vladimir A; Stonik, Valentin A

2010-03-01

Two new compounds, 3-amino-7,8-dihydroimidazo-[1,5-c]-pyrimidin-5(6H)-one (1) and ethyl 3-(2-amino-1H-imidazol-4-yl)propylcarbamate (2), along with the previously known 7,8-dihydroimidazo-[1,5-c]-pyrimidin-5(6H)-one (3), aeroplysinin-1 (4), dibromoverongiaquinol (5), bisoxazolidinone derivative (6), aerophobins-1 (7) and -2 (8), purealidins J (9) and L, have been isolated from Aplysina sp. from the South China Sea. The structures were elucidated on the basis of 1H, 13C NMR, MS and IR analyses. The histamine-derived alkaloids 1-3 may be unknown bioconversion products of purealidin J (9), aerophobin-2 (8) and aerophobin-1 (7), respectively, when 7-9 are cleaved at C-8-C-9 in reactions of activated chemical defense in Aplysina sponge.

Cd(II)-coordination polymers based on tetracarboxylic acid and diverse bis(imidazole) ligands: Synthesis, structural diversity and photoluminescence properties

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

Arıcı, Mürsel, E-mail: marici@ogu.edu.tr; Yeşilel, Okan Zafer; Taş, Murat

Three new Cd(II)-coordination polymers, namely, ([Cd{sub 2}(μ{sub 6}-ao{sub 2}btc)(μ-1,5-bipe){sub 2}]·2H{sub 2}O){sub n} (1), ([Cd{sub 2}(μ{sub 6}-ao{sub 2}btc)(μ-1,4-bix){sub 2}]{sub n}·2DMF) (2) and ([Cd{sub 2}(μ{sub 8}-abtc)(μ-1,4-betix)]·DMF·H{sub 2}O){sub n} (3) (ao{sub 2}btc=di-oxygenated form of 3,3′,5,5′-azobenzenetetracarboxylate, 1,5-bipe: 1,5-bis(imidazol-1yl)pentane, 1,4-bix=1,4-bis(imidazol-1ylmethyl)benzene, 1,4-betix=1,4-bis(2-ethylimidazol-1ylmethyl)benzene) were synthesized with 3,3′,5,5′-azobenzenetetracarboxylic acid and flexible, semi-flexible and semi-flexible substituted bis(imidazole) linkers. They were characterized by IR spectroscopy, elemental analysis, single-crystal X-ray diffraction, powder X-ray diffractions (PXRD) and thermal analyses (TG/DTA). Complexes 1–3 exhibited structural diversities depending on flexible, semi-flexible and semi-flexible substituted bis(imidazole) ligands. Complex 1 was 2D structure with 3,6L18 topology. Complex 2 had a 3D pillar-layered framework with the raremore » sqc27 topology. When semi-flexible substituted bis(imidazole) linker was used, 3D framework of complex 3 was obtained with the paddlewheel Cd{sub 2}(CO{sub 2}){sub 4}-type binuclear SBU. Moreover, thermal and photoluminescence properties of the complexes were determined in detailed. - Graphical abstract: In this study, three novel Cd(II)-coordination polymers were synthesized with 3,3′,5,5′-azobenzenetetracarboxylic acid and flexible, semi-flexible and semi-flexible substituted bis(imidazole) linkers. They were characterized by IR spectroscopy, elemental analysis, single-crystal X-ray diffraction, powder X-ray diffractions (PXRD) and thermal analyses (TG/DTA). Complexes 1–3 exhibited structural diversities depending on flexible, semi-flexible and semi-flexible substituted bis(imidazole) ligands. Complex 1 was 2D structure with 3,6L18 topology. Complex 2 had a 3D pillar-layered framework with the rare sqc27 topology. When semi-flexible substituted bis(imidazole) linker was used, 3D framework of complex 3 was obtained with the paddlewheel Cd{sub 2}(CO{sub 2}){sub 4}-type binuclear SBU. - Highlights: • Three new Cd(II)-coordination polymers with azobenzenetetracarboxylic acid and diverse bis(imidazole) linkers. • Complex 1 is 2D structure with 3,6L18 topology. • 3D pillar-layered framework of 2 with the rare sqc27 topology. • 3D framework of 3 with the paddlewheel Cd{sub 2}(CO{sub 2}){sub 4}-type SBU.« less

Catalytic soman scavenging by Y337A/F338A acetylcholinesterase mutant assisted with novel site-directed aldoximes

PubMed Central

Kovarik, Zrinka; Hrvat, Nikolina Maček; Katalinić, Maja; Sit, Rakesh K.; Paradyse, Alexander; Žunec, Suzana; Musilek, Kamil; Fokin, Valery V.; Taylor, Palmer; Radić, Zoran

2016-01-01

Exposure to the nerve agent soman is difficult to treat due to the rapid dealkylation of soman-acetylcholinesterase (AChE) conjugate known as aging. Oxime antidotes commonly used to reactivate organophosphate inhibited AChE are ineffective against soman, while the efficacy of the recommended nerve agent bioscavenger butyrylcholinesterase is limited by strictly stoichiometric scavenging. To overcome this limitation, we tested ex vivo, in human blood, and in vivo, in soman exposed mice, the capacity of aging-resistant human AChE mutant Y337A/F338A in combination with oxime HI-6 to act as a catalytic bioscavenger of soman. HI-6 was previously shown in vitro to efficiently reactivate this mutant upon soman, as well as VX, cyclosarin, sarin and paraoxon inhibition. We here demonstrate that ex vivo, in whole human blood, 1 μM soman was detoxified within 30 minutes when supplemented with 0.5 μM Y337A/F338A AChE and 100 μM HI-6. This combination was further tested in vivo. Catalytic scavenging of soman in mice improved the therapeutic outcome and resulted in the delayed onset of toxicity symptoms. Furthermore, in a preliminary in vitro screen we identified an even more efficacious oxime than HI-6, in a series of forty-two pyridinium aldoximes, and five imidazole 2-aldoxime N-propyl pyridinium derivatives. One of the later imidazole aldoximes, RS-170B, was a 2–3 –fold more effective reactivator of Y337A/F338A AChE than HI-6 due to the smaller imidazole ring, as indicated by computational molecular models, that affords a more productive angle of nucleophilic attack. PMID:25835984

Mechanism of Inducible Nitric-oxide Synthase Dimerization Inhibition by Novel Pyrimidine Imidazoles*

PubMed Central

Nagpal, Latika; Haque, Mohammad M.; Saha, Amit; Mukherjee, Nirmalya; Ghosh, Arnab; Ranu, Brindaban C.; Stuehr, Dennis J.; Panda, Koustubh

2013-01-01

Overproduction of nitric oxide (NO) by inducible nitric-oxide synthase (iNOS) has been etiologically linked to several inflammatory, immunological, and neurodegenerative diseases. As dimerization of NOS is required for its activity, several dimerization inhibitors, including pyrimidine imidazoles, are being evaluated for therapeutic inhibition of iNOS. However, the precise mechanism of their action is still unclear. Here, we examined the mechanism of iNOS inhibition by a pyrimidine imidazole core compound and its derivative (PID), having low cellular toxicity and high affinity for iNOS, using rapid stopped-flow kinetic, gel filtration, and spectrophotometric analysis. PID bound to iNOS heme to generate an irreversible PID-iNOS monomer complex that could not be converted to active dimers by tetrahydrobiopterin (H4B) and l-arginine (Arg). We utilized the iNOS oxygenase domain (iNOSoxy) and two monomeric mutants whose dimerization could be induced (K82AiNOSoxy) or not induced (D92AiNOSoxy) with H4B to elucidate the kinetics of PID binding to the iNOS monomer and dimer. We observed that the apparent PID affinity for the monomer was 11 times higher than the dimer. PID binding rate was also sensitive to H4B and Arg site occupancy. PID could also interact with nascent iNOS monomers in iNOS-synthesizing RAW cells, to prevent their post-translational dimerization, and it also caused irreversible monomerization of active iNOS dimers thereby accomplishing complete physiological inhibition of iNOS. Thus, our study establishes PID as a versatile iNOS inhibitor and therefore a potential in vivo tool for examining the causal role of iNOS in diseases associated with its overexpression as well as therapeutic control of such diseases. PMID:23696643

White Light Emission from Planar Remote Phosphor Based on NHC Cycloplatinated Complexes.

PubMed

Fuertes, Sara; Chueca, Andrés J; Perálvarez, Mariano; Borja, Pilar; Torrell, Marc; Carreras, Josep; Sicilia, Violeta

2016-06-29

We report on the generation of bright white luminescence through solid-state illumination of remote phosphors based on novel cycloplatinated N-heterocyclic carbene (NHC) compounds. Following a stepwise protocol we got the new NHC compound [{Pt(μ-Cl)(C(∧)C*)}2] (4) (HC(∧)C*-κC* = 1-(4-(ethoxycarbonyl)phenyl)-3-methyl-1H-imidazol-2-ylidene), which was used together with the related ones 4a (HC(∧)C*-κC*= 1-(4-cyanophenyl)-3-methyl-1H-imidazol-2-ylidene) and 4b (HC(∧)C*-κC*= 3-methyl-1-(naphthalen-2-yl)-1H-imidazol-2-ylidene) as starting materials for the synthesis of the new ionic derivatives [Pt(R-C(∧)C*) (CNR')2]PF6 (R = -COOEt, R' = t-Bu (5), Xyl (6); R = -CN, R' = t-Bu (7), Xyl (8); R(∧)C = Naph, R' = t-Bu (9), Xyl (10)). The X-ray structures of 6 and 8-10 have been determined. The photophysical properties of these cationic compounds have been studied and supported by the time-dependent-density functional theory (TD-DFT) calculations. The compounds 5, 8, and 9 have been revealed as the most efficient emitters in the solid state with quantum yields of 41%, 21%, and 40%, respectively. White-light remote-phosphors have been prepared just by stacking different combinations of these compounds and [Pt(bzq) (CN) (CN(t)Bu)] (R1) as blue (5, 8), yellow (9), and red (R1) components onto the same substrate. The CCT (correlated color temperature) and the CRI (color rendering index) of the emitted white-light have been tuned by accurately controlling the individual contributions.

The Influence of a Presence of a Heavy Atom on (13)C Shielding Constants in Organomercury Compounds and Halogen Derivatives.

PubMed

Wodyński, Artur; Gryff-Keller, Adam; Pecul, Magdalena

2013-04-09

(13)C nuclear magnetic resonance shielding constants have been calculated by means of density functional theory (DFT) for several organomercury compounds and halogen derivatives of aliphatic and aromatic compounds. Relativistic effects have been included through the four-component Dirac-Kohn-Sham (DKS) method, two-component Zeroth Order Regular Approximation (ZORA) DFT, and DFT with scalar effective core potentials (ECPs). The relative shieldings have been analyzed in terms of the position of carbon atoms with respect to the heavy atom and their hybridization. The results have been compared with the experimental values, some newly measured and some found in the literature. The main aim of the calculations has been to evaluate the magnitude of heavy atom effects on the (13)C shielding constants and to check what are the relative contributions of scalar relativistic effects and spin-orbit coupling. Another object has been to compare the DKS and ZORA results and to check how the approximate method of accounting for the heavy-atom-on-light-atom (HALA) relativistic effect by means of scalar effective core potentials on heavy atoms performs in comparison with the more rigorous two- and four-component treatment.

Squaraine dyes for photodynamic therapy: study of their cytotoxicity and genotoxicity in bacteria and mammalian cells.

PubMed

Ramaiah, Danaboyina; Eckert, Inge; Arun, Kalliat T; Weidenfeller, Lydia; Epe, Bernd

2002-12-01

Halogenated squaraine dyes are characterized by long wavelength absorption (>600 nm) and high triplet yields and therefore represent new types of photosensitizers that could be useful for photodynamic therapy. We have analyzed the cytotoxicity and genotoxicity of the bromo derivative 1, the iodo derivative 2 and the corresponding nonhalogenated dye 3 in the absence and presence of visible light. At concentrations of 1-2 microM, 1 and 2 reduced the cloning efficiency of AS52 Chinese hamster ovary cells to less than 1% under conditions that were well tolerated in the dark. Similarly, the proliferation of L5178Y mouse lymphoma cells was inhibited by photoexcited 1 and 2 with high selectivity. The squaraine 3 was much less efficient. Both 1 and 2 induced only few mutations in the gpt locus of the AS52 cells in the presence of light and were not mutagenic in the dark. No mutagenicity with and without irradiation was observed in Salmonella typhimurium TA100 and TA2638. However, both 1 and 2 plus light increased the frequency of micronuclei in AS52 cells. The results indicate that halogenated squaraines exhibit photobiological properties in vitro that are favorable for photodynamic therapeutical applications.

Polyimidazoles via aromatic nucleophilic displacement

NASA Technical Reports Server (NTRS)

Connell, John W. (Inventor); Hergenrother, Paul M. (Inventor)

1992-01-01

Polyimidazoles (PI) are prepared by the aromatic nucleophilic displacement reaction of di(hydroxyphenyl) imidazole monomers with activated aromatic dihalides or activated aromatic dinitro compounds. The reactions are carried out in polar aprotic solvents such as N,N-dimethyl acetamide, sulfolane, N-methylpyrrolidinone, dimethylsulfoxide, or diphenylsulfone using alkali metal bases such as potassium carbonate at elevated temperatures under nitrogen. The di(hydroxyphenyl) imidazole monomers are prepared by reacting an aromatic aldehyde with a dimethoxybenzil or by reacting an aromatic dialdehyde with a methoxybenzil in the presence of ammonium acetate. The di(methoxyphenyl) imidazole is subsequently treated with aqueous hydrobromic acid to give the di(hydroxphenyl) imidazole monomer. This synthetic route has provided high molecular weight PI of new chemical structure, is economically and synthetically more favorable than other routes, and allows for facile chemical structure variation due to the availability of a large variety of activated aromatic dihalides and dinitro compounds.

Polyimidazoles via aromatic nucleophilic displacement

NASA Technical Reports Server (NTRS)

Hergenrother, Paul M. (Inventor); Connell, John W. (Inventor)

1991-01-01

Polyimidazoles (Pl) are prepared by the aromatic nucleophilic displacement reaction of di(hydroxyphenyl)imidazole monomers with activated aromatic dihalides or activated aromatic dinitro compounds. The reactions are carried out in polar aprotic solvents such as N,N-dimethylacetamide, sulfolane, N-methylpyrroldinone, dimethylsulfoxide, or diphenylsulfone using alkali metal bases such as potassium carbonate at elevated temperature under nitrogen. The di(hydroxyphenyl)imidazole monomers are prepared by reacting an aromatic aldehyde with a dimethoxybenzil or by reacting an aromatic dialdehyde with a methoxybenzil in the presence of ammonium acetate. The di(methoxyphenyl)imidazole is subsequently treated with aqueous hydrobromic acid to give the di(hydroxyphenyl)imidazole monomer. This synthetic route has provided high molecular weight Pl of new chemical structure, is economically and synthetically more favorable than other routes, and allows for facile chemical structure variation due to the availability of a large variety of activated aromatic dihalides and dinitro compounds.

Implementation of marine halogen chemistry into the Community Multiscale Air Quality (CMAQ) model

NASA Astrophysics Data System (ADS)

Gantt, B.; Sarwar, G.

2017-12-01

In two recent studies (Sarwar et al, 2015 and Gantt et al., 2017), the impact of marine halogen (bromine and iodine) chemistry on air quality has been evaluated using the Community Multiscale Air Quality (CMAQ) model. We found that marine halogen chemistry not only has the expected effect of reducing marine boundary layer ozone concentrations, but also reduces ozone in the free troposphere and inland from the coast. In Sarwar et al. (2015), the impact of the halogen chemistry without and with photochemical reactions of higher iodine oxides over the Northern Hemisphere was examined using the coarse horizontal grids of a hemispheric domain. Halogen chemistry without and with the photochemical reactions of higher iodine oxides reduces ozone over seawater by 15% and 48%, respectively. Using the results of the chemistry without the photochemical reactions of higher iodine oxides, we developed a simple first order ozone loss rate and implemented it into the public version of CMAQv52. In Gantt et al. (2017), the impact of the simple first order loss rate as well as the full halogen chemistry without photochemical reactions of higher iodine oxides over the continental United States was examined using finer horizontal grids of the regional domain and boundary conditions from the hemispheric domain with and without marine halogen chemistry. The boundary conditions obtained with the halogen chemistry as well as the simple halogen chemistry reduces ozone along the coast where CMAQ typically overpredicts the concentrations. Development of halogen chemistry in CMAQ has continued with the implementation of several heterogeneous reactions of bromine and iodine species, revised reactions of higher iodine oxides, and a refined marine halogen emissions inventory. Our latest version of halogen chemistry with photochemical reactions of higher iodine oxides reduces ozone by 23% over the seawater. This presentation will discuss the previous and ongoing implementation of revised halogen chemistry in CMAQ and its impacts on air quality.

Technology for radiation efficiency measurement of high-power halogen tungsten lamp used in calibration of high-energy laser energy meter.

PubMed

Wei, Ji Feng; Hu, Xiao Yang; Sun, Li Qun; Zhang, Kai; Chang, Yan

2015-03-20

The calibration method using a high-power halogen tungsten lamp as a calibration source has many advantages such as strong equivalence and high power, so it is very fit for the calibration of high-energy laser energy meters. However, high-power halogen tungsten lamps after power-off still reserve much residual energy and continually radiate energy, which is difficult to be measured. Two measuring systems were found to solve the problems. One system is composed of an integrating sphere and two optical spectrometers, which can accurately characterize the radiative spectra and power-time variation of the halogen tungsten lamp. This measuring system was then calibrated using a normal halogen tungsten lamp made of the same material as the high-power halogen tungsten lamp. In this way, the radiation efficiency of the halogen tungsten lamp after power-off can be quantitatively measured. In the other measuring system, a wide-spectrum power meter was installed far away from the halogen tungsten lamp; thus, the lamp can be regarded as a point light source. The radiation efficiency of residual energy from the halogen tungsten lamp was computed on the basis of geometrical relations. The results show that the halogen tungsten lamp's radiation efficiency was improved with power-on time but did not change under constant power-on time/energy. All the tested halogen tungsten lamps reached 89.3% of radiation efficiency at 50 s after power-on. After power-off, the residual energy in the halogen tungsten lamp gradually dropped to less than 10% of the initial radiation power, and the radiation efficiency changed with time. The final total radiation energy was decided by the halogen tungsten lamp's radiation efficiency, the radiation efficiency of residual energy, and the total power consumption. The measuring uncertainty of total radiation energy was 2.4% (here, the confidence factor is two).

Enzymatic Halogenation and Dehalogenation Reactions: Pervasive and Mechanistically Diverse.

PubMed

Agarwal, Vinayak; Miles, Zachary D; Winter, Jaclyn M; Eustáquio, Alessandra S; El Gamal, Abrahim A; Moore, Bradley S

2017-04-26

Naturally produced halogenated compounds are ubiquitous across all domains of life where they perform a multitude of biological functions and adopt a diversity of chemical structures. Accordingly, a diverse collection of enzyme catalysts to install and remove halogens from organic scaffolds has evolved in nature. Accounting for the different chemical properties of the four halogen atoms (fluorine, chlorine, bromine, and iodine) and the diversity and chemical reactivity of their organic substrates, enzymes performing biosynthetic and degradative halogenation chemistry utilize numerous mechanistic strategies involving oxidation, reduction, and substitution. Biosynthetic halogenation reactions range from simple aromatic substitutions to stereoselective C-H functionalizations on remote carbon centers and can initiate the formation of simple to complex ring structures. Dehalogenating enzymes, on the other hand, are best known for removing halogen atoms from man-made organohalogens, yet also function naturally, albeit rarely, in metabolic pathways. This review details the scope and mechanism of nature's halogenation and dehalogenation enzymatic strategies, highlights gaps in our understanding, and posits where new advances in the field might arise in the near future.

Independent Evolution of Six Families of Halogenating Enzymes

PubMed Central

Xu, Gangming; Wang, Bin-Gui

2016-01-01

Halogenated natural products are widespread in the environment, and the halogen atoms are typically vital to their bioactivities. Thus far, six families of halogenating enzymes have been identified: cofactor-free haloperoxidases (HPO), vanadium-dependent haloperoxidases (V-HPO), heme iron-dependent haloperoxidases (HI-HPO), non-heme iron-dependent halogenases (NI-HG), flavin-dependent halogenases (F-HG), and S-adenosyl-L-methionine (SAM)-dependent halogenases (S-HG). However, these halogenating enzymes with similar biological functions but distinct structures might have evolved independently. Phylogenetic and structural analyses suggest that the HPO, V-HPO, HI-HPO, NI-HG, F-HG, and S-HG enzyme families may have evolutionary relationships to the α/β hydrolases, acid phosphatases, peroxidases, chemotaxis phosphatases, oxidoreductases, and SAM hydroxide adenosyltransferases, respectively. These halogenating enzymes have established sequence homology, structural conservation, and mechanistic features within each family. Understanding the distinct evolutionary history of these halogenating enzymes will provide further insights into the study of their catalytic mechanisms and halogenation specificity. PMID:27153321

Heterobimetallic thiocyanato-bridged coordination polymers based on [Hg(SCN){sub 4}]{sup 2-}: Synthesis, crystal structure, magnetic properties and ESR studies

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

Jian Fangfang; Xiao Hailian; Liu Faqian

2006-12-15

Three new M/Hg bimetallic thiocyanato-bridged coordination polymers; [Hg(SCN){sub 4}Ni(Im){sub 3}] {sub {infinity}} 1, [Hg(SCN){sub 4}Mn(Im){sub 2}] {sub {infinity}} 2, and [Hg(SCN){sub 4}Cu(Me-Im){sub 2} Hg(SCN){sub 4}Cu(Me-Im){sub 4}] {sub {infinity}} 3, (Im=imidazole, Me-Im=N-methyl-imidazole), have been synthesized and characterized by means of elemental analysis, ESR, and single-crystal X-ray. X-ray diffraction analysis reveals that these three complexes all form 3D network structure, and their structures all contain a thiocyanato-bridged Hg...Hg chain (M=Mn, Ni, Cu) in which the metal and mercury centers exhibit different coordination environments. In complex 1, the [Hg(SCN){sub 4}]{sup 2-} anion connects three [Ni(Im){sub 3}]{sup 2+} using three SCN ligands giving risemore » to a 3D structure, and in complex 2, four SCN ligands bridge [Hg(SCN){sub 4}]{sup 2-} and [Mn(Im){sub 2}]{sup 2+} to form a 3D structure. The structure of 3 contains two copper atoms with distinct coordination environment; one is coordinated by four N-methyl-imidazole ligands and two axially elongated SCN groups, and another by four SCN groups (two elongated) and two N-methyl-imidazole ligands. The magnetic property of complex 1 has been investigated. The spin state structure in hetermetallic NiHgNi systems of complex 1 is irregular. The ESR spectra results of complex 3 demonstrate Cu{sup 2+} ion lie on octahedral environment. -- Graphical abstract: Three new M/Hg bimetallic thiocyanato-bridged coordination polymers; [Hg(SCN){sub 4}Ni(Im){sub 3}] {sub {infinity}} 1, [Hg(SCN){sub 4}Mn(Im){sub 2}] {sub {infinity}} 2, and [Hg(SCN){sub 4}Cu(Me-Im){sub 2} Hg(SCN){sub 4}Cu(Me-Im){sub 4}] {sub {infinity}} 3, (Im=imidazole, Me-Im=N-methyl-imidazole), have been synthesized and characterized by single-crystal X-ray. All coordination polymers possess 3-D structures, and consist of organic base neutral ligands (imidazole and N-methyl-imidazole) and SCN{sup -1} anions. Their structural difference is maicaused by the role of the organic base and metal ions. The complex 1 shows the irregular spin state structure.« less

Halogenation of microcapsule walls

NASA Technical Reports Server (NTRS)

Davis, T. R.; Schaab, C. K.; Scott, J. C.

1972-01-01

Procedure for halogenation of confining walls of both gelatin and gelatin-phenolic resin capsules is similar to that used for microencapsulation. Ten percent halogen content renders capsule wall nonburning; any higher content enhances flame-retardant properties of selected internal phase material. Halogenation decreases permeability of wall material to encapsulated materials.

Halogens are key cofactors in building of collagen IV scaffolds outside the cell.

PubMed

Brown, Kyle L; Hudson, Billy G; Voziyan, Paul A

2018-05-01

The purpose of this review is to highlight recent advances in understanding the molecular assembly of basement membranes, as exemplified by the glomerular basement membrane (GBM) of the kidney filtration apparatus. In particular, an essential role of halogens in the basement membrane formation has been discovered. Extracellular chloride triggers a molecular switch within non collagenous domains of collagen IV that induces protomer oligomerization and scaffold assembly outside the cell. Moreover, bromide is an essential cofactor in enzymatic cross-linking that reinforces the stability of scaffolds. Halogenation and halogen-induced oxidation of the collagen IV scaffold in disease states damage scaffold function. Halogens play an essential role in the formation of collagen IV scaffolds of basement membranes. Pathogenic damage of these scaffolds by halogenation and halogen-induced oxidation is a potential target for therapeutic interventions.

Structure–efficiency relationships of cyclodextrin scavengers in the hydrolytic degradation of organophosphorus compounds

PubMed Central

Letort, Sophie; Bosco, Michaël; Cornelio, Benedetta; Brégier, Frédérique; Daulon, Sébastien; Gouhier, Géraldine

2017-01-01

New derivatives of cyclodextrins were prepared in order to determine the relative importance of the structural key elements involved in the degradation of organophosphorus nerve agents. To avoid a competitive inclusion between the organophosphorus substrate and the iodosobenzoate group, responsible for its degradation, the latter group had to be covalently bound to the cyclodextrin scaffold. Although the presence of the α nucleophile iodosobenzoate was a determinant in the hydrolysis process, an imidazole group was added to get a synergistic effect towards the degradation of the agents. The degradation efficiency was found to be dependent on the relative position of the heterocycle towards the reactive group as well as on the nature of the organophosphorus derivative. PMID:28382180

Structure-efficiency relationships of cyclodextrin scavengers in the hydrolytic degradation of organophosphorus compounds.

PubMed

Letort, Sophie; Bosco, Michaël; Cornelio, Benedetta; Brégier, Frédérique; Daulon, Sébastien; Gouhier, Géraldine; Estour, François

2017-01-01

New derivatives of cyclodextrins were prepared in order to determine the relative importance of the structural key elements involved in the degradation of organophosphorus nerve agents. To avoid a competitive inclusion between the organophosphorus substrate and the iodosobenzoate group, responsible for its degradation, the latter group had to be covalently bound to the cyclodextrin scaffold. Although the presence of the α nucleophile iodosobenzoate was a determinant in the hydrolysis process, an imidazole group was added to get a synergistic effect towards the degradation of the agents. The degradation efficiency was found to be dependent on the relative position of the heterocycle towards the reactive group as well as on the nature of the organophosphorus derivative.

Design and verification of halogen-bonding system at the complex interface of human fertilization-related MUP PDZ5 domain with CAMK's C-terminal peptide.

PubMed

Wang, Juan; Guo, Yunjie; Zhang, Xue

2018-02-01

Calmodulin-dependent protein kinase (CAMK) is physiologically activated in fertilized human oocytes and is involved in the Ca 2+ response pathways that link the fertilization calmodulin signal to meiosis resumption and cortical granule exocytosis. The kinase has an unstructured C-terminal tail that can be recognized and bound by the PDZ5 domain of its cognate partner, the multi-PDZ domain protein (MUP). In the current study, we reported a rational biomolecular design of halogen-bonding system at the complex interface of CAMK's C-terminal peptide with MUP PDZ5 domain by using high-level computational approaches. Four organic halogens were employed as atom probes to explore the structural geometry and energetic property of designed halogen bonds in the PDZ5-peptide complex. It was found that the heavier halogen elements such as bromine Br and iodine I can confer stronger halogen bond but would cause bad atomic contacts and overlaps at the complex interface, while fluorine F cannot form effective halogen bond in the complex. In addition, the halogen substitution at different positions of peptide's aromatic ring would result in distinct effects on the halogen-bonding system. The computational findings were then verified by using fluorescence analysis; it is indicated that the halogen type and substitution position play critical role in the interaction strength of halogen bonds, and thus the PDZ5-peptide binding affinity can be improved considerably by optimizing their combination. Copyright © 2017 Elsevier Ltd. All rights reserved.

Atomic resolution ADF-STEM imaging of organic molecular crystal of halogenated copper phthalocyanine.

PubMed

Haruta, Mitsutaka; Yoshida, Kaname; Kurata, Hiroki; Isoda, Seiji

2008-05-01

Annular dark-field (ADF) scanning transmission electron microscopy (STEM) measurements are demonstrated for the first time to be applicable for acquiring Z-contrast images of organic molecules at atomic resolution. High-angle ADF imaging by STEM is a new technique that provides incoherent high-resolution Z-contrast images for organic molecules. In the present study, low-angle ADF-STEM is successfully employed to image the molecular crystal structure of hexadecachloro-Cu-phthalocyanine (Cl16-CuPc), an organic molecule. The structures of CuPc derivatives (polyhalogenated CuPc with Br and Cl) are determined quantitatively using the same technique to determine the occupancy of halogens at each chemical site. By comparing the image contrasts of atomic columns, the occupancy of Br is found to be ca. 56% at the inner position, slightly higher than that for random substitution and in good agreement with previous TEM results.

Supramolecular amplification of amyloid self-assembly by iodination

NASA Astrophysics Data System (ADS)

Bertolani, Arianna; Pirrie, Lisa; Stefan, Loic; Houbenov, Nikolay; Haataja, Johannes S.; Catalano, Luca; Terraneo, Giancarlo; Giancane, Gabriele; Valli, Ludovico; Milani, Roberto; Ikkala, Olli; Resnati, Giuseppe; Metrangolo, Pierangelo

2015-06-01

Amyloid supramolecular assemblies have found widespread exploitation as ordered nanomaterials in a range of applications from materials science to biotechnology. New strategies are, however, required for understanding and promoting mature fibril formation from simple monomer motifs through easy and scalable processes. Noncovalent interactions are key to forming and holding the amyloid structure together. On the other hand, the halogen bond has never been used purposefully to achieve control over amyloid self-assembly. Here we show that single atom replacement of hydrogen with iodine, a halogen-bond donor, in the human calcitonin-derived amyloidogenic fragment DFNKF results in a super-gelator peptide, which forms a strong and shape-persistent hydrogel at 30-fold lower concentration than the wild-type pentapeptide. This is remarkable for such a modest perturbation in structure. Iodination of aromatic amino acids may thus develop as a general strategy for the design of new hydrogels from unprotected peptides and without using organic solvents.

Molecular association via halogen bonding and other weak interactions in the crystal structures of 11-bromo-12-oxo-5β-cholan derivatives

NASA Astrophysics Data System (ADS)

Salunke, Deepak B.; Hazra, Braja G.; Gonnade, Rajesh G.; Pore, Vandana S.; Bhadbhade, Mohan M.

2008-12-01

Methyl 3α,7α-diacetoxy-12-oxo-5β-cholan-24-oate 2, methyl 11α-bromo-3α,7α-diacetoxy-12-oxo-5β-cholan-24-oate 3, methyl 11β-bromo-3α,7α-diacetoxy-12-oxo-5β-cholan-24-oate 4 and methyl 11,11-dibromo-3α,7α-diacetoxy-12-oxo-5β-cholan-24-oate 5 were synthesized. The crystal structures of these molecules were resolved to study the effect of bulky bromine atom in the steroid skeleton of cholic acid with different stereo-chemical orientations at C-11 on the two-dimensional arrangement of molecules and solid-state properties. All the molecules associate only via weak intermolecular interactions in their crystal structures, notable one being the Halogen Bonded assembly (C-Br…O) in 5.

Enantioselective decarboxylative chlorination of β-ketocarboxylic acids

PubMed Central

Shibatomi, Kazutaka; Kitahara, Kazumasa; Sasaki, Nozomi; Kawasaki, Yohei; Fujisawa, Ikuhide; Iwasa, Seiji

2017-01-01

Stereoselective halogenation is a highly useful organic transformation for multistep syntheses because the resulting chiral organohalides can serve as precursors for various medicinally relevant derivatives. Even though decarboxylative halogenation of aliphatic carboxylic acids is a useful and fundamental synthetic method for the preparation of a variety of organohalides, an enantioselective version of this reaction has not been reported. Here we report a highly enantioselective decarboxylative chlorination of β-ketocarboxylic acids to obtain α-chloroketones under mild organocatalytic conditions. The present method is also applicable for the enantioselective synthesis of tertiary α-chloroketones. The conversions of the resulting α-chloroketones into α-aminoketones and α-thio-substituted ketones via SN2 reactions at the tertiary carbon centres are also demonstrated. These results constitute an efficient approach for the synthesis of chiral organohalides and are expected to enhance the availability of enantiomerically enriched chiral compounds with heteroatom-substituted chiral stereogenic centres. PMID:28580951

Anaerobic biodegradation of halogenated and nonhalogenated N-, s-, and o-heterocyclic compounds in aquifer slurries

USGS Publications Warehouse

Adrian, Neal R.; Suflita, Joseph M.

1994-01-01

The fate of several halogenated and nonhalogenated heterocyclic compounds in anoxic aquifer slurries was investigated Substrate depletion and methane formation were monitored in serum bottle incubations by HPLC and GC, respectively Pyridine, pyrimidine, thiophene, and furan were not mineralized following an 11-month incubation, but the corresponding carboxylated or oxygenated compounds were That is, >74% of the theoretically expected amount of methane was recovered from nicotinic acid, uracil, or 2-furoic acid Chlorinated derivatives, like 2 chloro- or 6-chloronicotinic acid, as well as 4 chloro- and 5-chlorouracil resisted mineralization However, 5-bromouracil was reductively dehalogenated to stoichiometric amounts of uracil, whereas 2-chloropyrimidine was metabolized to a more polar unidentified compound that resisted further anaerobic biodegradation Microorganisms acclimated to 5-bromouracil were unable to transform 4 chloro or 5 chlorouracil These findings illustrate how the structure of heterocyclic contaminants influences their susceptibility to anaerobic decay

Enantioselective decarboxylative chlorination of β-ketocarboxylic acids

NASA Astrophysics Data System (ADS)

Shibatomi, Kazutaka; Kitahara, Kazumasa; Sasaki, Nozomi; Kawasaki, Yohei; Fujisawa, Ikuhide; Iwasa, Seiji

2017-06-01

Stereoselective halogenation is a highly useful organic transformation for multistep syntheses because the resulting chiral organohalides can serve as precursors for various medicinally relevant derivatives. Even though decarboxylative halogenation of aliphatic carboxylic acids is a useful and fundamental synthetic method for the preparation of a variety of organohalides, an enantioselective version of this reaction has not been reported. Here we report a highly enantioselective decarboxylative chlorination of β-ketocarboxylic acids to obtain α-chloroketones under mild organocatalytic conditions. The present method is also applicable for the enantioselective synthesis of tertiary α-chloroketones. The conversions of the resulting α-chloroketones into α-aminoketones and α-thio-substituted ketones via SN2 reactions at the tertiary carbon centres are also demonstrated. These results constitute an efficient approach for the synthesis of chiral organohalides and are expected to enhance the availability of enantiomerically enriched chiral compounds with heteroatom-substituted chiral stereogenic centres.

40 CFR 721.5452 - Alkali metal salt of halogenated organoborate (generic).

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Alkali metal salt of halogenated... Specific Chemical Substances § 721.5452 Alkali metal salt of halogenated organoborate (generic). (a... generically as alkali metal salt of halogenated organoborate (PMN P-00-0638) is subject to reporting under...

40 CFR 721.5452 - Alkali metal salt of halogenated organoborate (generic).

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkali metal salt of halogenated... Specific Chemical Substances § 721.5452 Alkali metal salt of halogenated organoborate (generic). (a... generically as alkali metal salt of halogenated organoborate (PMN P-00-0638) is subject to reporting under...

Vibrational investigation on the copper(II) binding mode of carcinine and its pH dependence

NASA Astrophysics Data System (ADS)

Torreggiani, Armida; Reggiani, Matteo; Manco, Immacolata; Tinti, Anna

2007-05-01

A comparative FT-Raman and FT-IR study of Carcinine (Carc), a natural imidazole dipeptide, and its complexes with Cu(II) ions was performed at different pH's. Both Raman and IR spectra present marker bands useful for the identification of the predominant complexes; in particular, Raman spectroscopy appears useful for identifying the metal-coordination site of the imidazole ring (N π or N τ atoms) of Carc. Free Carc shows a strong network of H-bonds and tautomer I (N τ-H) is the preferred form of the imidazolic ring (bands at 1578, 1292 and 988 cm -1). The presence of Cu(II) does not affect the tautomeric equilibrium at pH 7, whereas the deprotonation of both N-imidazolic nitrogens is strongly induced at higher pH. Under neutral and alkaline conditions the primary amino group takes part to the Cu(II) chelation, whereas all the peptidic moieties are involved in coordination only at pH 7. Thus, Carc acts as a tri-dentate ligand at neutral pH, mainly giving a monomeric complex, [CuLH -1], containing tautomer I, whereas an oligonuclear complex, probably [Cu 4L 4H -8], where metal-imidazolate ions connect different ligand molecules, predominates at alkaline pH.

Interaction of dopamine beta-mono-oxygenase with substituted imidazoles and pyrazoles. Catalysis and inhibition.

PubMed Central

Sirimanne, S R; Herman, H H; May, S W

1987-01-01

The interaction of dopamine beta-mono-oxygenase (DBM) with substrate analogues possessing either imidazole or pyrazole functionalities at the alkyl chain terminus was investigated. 1-(4-Hydroxybenzyl)imidazole (4-HOBI) is an active substrate for DBM, and it exhibits the expected ascorbate- and fumarate-dependencies and normal kinetic behaviour at concentrations up to 10 mM. 4-Hydroxybenzaldehyde was identified as the product formed from 4-HOBI on the basis of h.p.l.c. and g.c.-m.s. analysis, and its formation exhibits the expected 1:1 stoichiometry with O2 consumption. The 4-HOBI/DBM reaction is kinetically comparable with other DBM activities, and 4-HOBI is the first substrate analogue yet reported that exhibits substantial activity though lacking a terminal amino group. Introduction of a methyl substituent at the 2-position of the imidazole ring abolishes substrate activity, probably through a steric effect. 1-(4-Hydroxybenzyl)pyrazole, where imidazole is replaced by the isomeric pyrazole moiety, is a potent DBM inhibitor, and not a substrate. These results represent the first report of an active heterocyclic substrate or inhibitor for this enzyme, and establish the basis for the design of new classes of DBM substrates and inhibitors. PMID:3593236

Magnetic graphene oxide modified by imidazole-based ionic liquids for the magnetic-based solid-phase extraction of polysaccharides from brown alga.

PubMed

Wang, Xiaoqin; Li, Guizhen; Row, Kyung Ho

2017-08-01

Magnetic graphene oxide was modified by four imidazole-based ionic liquids to synthesize materials for the extraction of polysaccharides by magnetic solid-phase extraction. Fucoidan and laminarin were chosen as the representative polysaccharides owing to their excellent pharmaceutical value and availability. Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, and thermogravimetric analysis were applied to characterize the synthesized materials. Single-factor experiments showed that the extraction efficiency of polysaccharides was affected by the amount of ionic liquids for modification, solid-liquid ratio of brown alga and ethanol, the stirring time of brown alga and ionic liquid-modified magnetic graphene oxide materials, and amount of 1-(3-aminopropyl)imidazole chloride modified magnetic graphene oxide materials added to the brown alga sample solution. The results indicated that 1-(3-aminopropyl)imidazole chloride modified magnetic graphene oxide possessed better extraction ability than graphene oxide, magnetic graphene oxide, and other three ionic-liquid-modified magnetic graphene oxide materials. The highest extraction recoveries of fucoidan and laminarin extracted by 1-(3-aminopropyl)imidazole chloride modified magnetic graphene oxide were 93.3 and 87.2%, respectively. In addition, solid materials could be separated and reused easily owing to their magnetic properties. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cu(II) coordination polymers constructed by tetrafluoroterephthalic acid and varied imidazole-containing ligands: Syntheses, structures and properties

NASA Astrophysics Data System (ADS)

Liu, Kang; Sun, Yayong; Deng, Liming; Cao, Fan; Han, Jishu; Wang, Lei

2018-02-01

Six new copper(II) coordination polymers combining 2,3,5,6-tetrafluoroterephthalatic acid (H2tfBDC) and diverse imidazole-containing ligands, {[Cu(tfBDC)(1,2-bix)2]·2(H2O)}n (1), {Cu(tfBDC)(Im)2}n (2), {[Cu(1,4-bmimb)2(H2O)]·(tfBDC)·2(H2O)}n (3), {Cu(1,4-bimb)2(H2O)2·(tfBDC)}n (4), {[Cu(1,3-bix)2(H2O)2]·(tfBDC)·6(H2O)}n (5) and {[Cu(1,4-bix)2(H2O)2]·(tfBDC)·(1,4-bix)·4(H2O)}n (6) (1,2-bix = 1,2-bis(imidazole-1-ylmethyl)-benzene, Im = imidazole, 1,4-bmimb = 1,4-bis((2-methyl-1H-imidazol-1-yl)methyl)benzene, 1,4-bimb = 1,4-bis(imidazol-1-yl)-butane, 1,3-bix = 1,3-bis(imidazole-1-ylmethyl)-benzene, 1,4-bix = 1,4-bis(imidazole-1-ylmethyl)-benzene), have been obtained and structurally verified by single-crystal X-ray diffraction analyses and further characterized by powder X-ray diffraction (PXRD), elemental analyses and infrared spectroscopy (IR). Single crystal X-ray diffraction analysis revealed that 1 is 2D 4-connected sql topology (point symbol: {44·62}) based on a single metal ion node. Compound 2 is characterized as an infinite 1D chain structure, which is further extended into a 2D layer through N-H···O hydrogen bonds and then a 3D supramolecular architecture via π···π stacking interactions. Note that 2 was prepared through an in situ ligand reaction in which N,N'-carbonyldiimidazole (cdi) broke up into imidazole ligand. Compound 3 possesses a 3D 4-fold interpenetrated architecture with 4-connected dia topology (Schläfli symbol: {66}) in which tfBDC2- is stabilized in the channel by hydrogen bonds. Compounds 4-6 are all linear 1D coordination polymers. In 4, the free tfBDC2- ligand acts as a μ4-bridge to link four coordinated water molecules from the chain to construct a 2D structure via hydrogen bonds. While in 5 and 6, the uncoordinated tfBDC2- ligands and multimeric water clusters is responsible for the conversion of these 1D coordination polymers into 3D supramolecular assemblies through O-H⋯O hydrogen bonding interactions. Moreover, the UV-vis spectra and thermal stability of 1-6 are discussed in detail.

Halogen bonding based recognition processes: a world parallel to hydrogen bonding.

PubMed

Metrangolo, Pierangelo; Neukirch, Hannes; Pilati, Tullio; Resnati, Giuseppe

2005-05-01

Halogen bonding is the noncovalent interaction between halogen atoms (Lewis acids) and neutral or anionic Lewis bases. The main features of the interaction are given, and the close similarity with the hydrogen bonding will become apparent. Some heuristic principles are presented to develop a rational crystal engineering based on halogen bonding. The focus is on halogen-bonded supramolecular architectures given by halocarbons. The potential of the interaction is shown by useful applications in the field of synthetic chemistry, material science, and bioorganic chemistry.

Systematic and Automated Development of Quantum Mechanically Derived Force Fields: The Challenging Case of Halogenated Hydrocarbons.

PubMed

Prampolini, Giacomo; Campetella, Marco; De Mitri, Nicola; Livotto, Paolo Roberto; Cacelli, Ivo

2016-11-08

A robust and automated protocol for the derivation of sound force field parameters, suitable for condensed-phase classical simulations, is here tested and validated on several halogenated hydrocarbons, a class of compounds for which standard force fields have often been reported to deliver rather inaccurate performances. The major strength of the proposed protocol is that all of the parameters are derived only from first principles because all of the information required is retrieved from quantum mechanical data, purposely computed for the investigated molecule. This a priori parametrization is carried out separately for the intra- and intermolecular contributions to the force fields, respectively exploiting the Joyce and Picky programs, previously developed in our group. To avoid high computational costs, all quantum mechanical calculations were performed exploiting the density functional theory. Because the choice of the functional is known to be crucial for the description of the intermolecular interactions, a specific procedure is proposed, which allows for a reliable benchmark of different functionals against higher-level data. The intramolecular and intermolecular contribution are eventually joined together, and the resulting quantum mechanically derived force field is thereafter employed in lengthy molecular dynamics simulations to compute several thermodynamic properties that characterize the resulting bulk phase. The accuracy of the proposed parametrization protocol is finally validated by comparing the computed macroscopic observables with the available experimental counterparts. It is found that, on average, the proposed approach is capable of yielding a consistent description of the investigated set, often outperforming the literature standard force fields, or at least delivering results of similar accuracy.

The evolution of histamine H₃ antagonists/inverse agonists.

PubMed

Lebois, Evan P; Jones, Carrie K; Lindsley, Craig W

2011-01-01

This article describes our efforts along with recent advances in the development, biological evaluation and clinical proof of concept of small molecule histamine H₃ antagonists/inverse agonists. The H3 receptor is a presynaptic autoreceptor within the Class A GPCR family, but also functions as a heteroreceptor modulating levels of neurotransmitters such as dopamine, acetylcholine, norepinephrine, serotonin, GABA and glutamate. Thus, H₃R has garnered a great deal of interest from the pharmaceutical industry for the possible treatment of obesity, epilepsy, sleep/wake, schizophrenia, Alzheimer's disease, neuropathic pain and ADHD. Within the two main classes of H₃ ligands, both imidazole and non-imidazole derived, have shown sufficient potency and specificity which culminated with efficacy in preclinical models for various CNS disorders. Importantly, conserved elements have been identified within the small molecule H₃ ligand scaffolds that resulted in a highly predictive pharmacophore model. Understanding of the pharmacophore model has allowed several groups to dial H₃R activity into scaffolds designed for other CNS targets, and engender directed polypharmacology. Moreover, Abbott, GSK, Pfizer and several others have reported positive Phase I and/or Phase II data with structurally diverse H₃R antagonists/inverse agonists.

Structure–activity relationships of imidazole-derived 2-[N-carbamoylmethyl-alkylamino]acetic acids, dual binders of human insulin-degrading enzyme

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

Charton, Julie; Gauriot, Marion; Totobenazara, Jane

Insulin degrading enzyme (IDE) is a zinc metalloprotease that degrades small amyloid peptides such as amyloid-â and insulin. So far the dearth of IDE-specific pharmacological inhibitors impacts the understanding of its role in the physiopathology of Alzheimer's disease, amyloid-â clearance, and its validation as a potential therapeutic target. Hit 1 was previously discovered by high-throughput screening. Here we describe the structure-activity study, that required the synthesis of 48 analogues. We found that while the carboxylic acid, the imidazole and the tertiary amine were critical for activity, the methyl ester was successfully optimized to an amide or a 1,2,4-oxadiazole. Along withmore » improving their activity, compounds were optimized for solubility, lipophilicity and stability in plasma and microsomes. The docking or co-crystallization of some compounds at the exosite or the catalytic site of IDE provided the structural basis for IDE inhibition. The pharmacokinetic properties of best compounds 44 and 46 were measured in vivo. As a result, 44 (BDM43079) and its methyl ester precursor 48 (BDM43124) are useful chemical probes for the exploration of IDE's role.« less

Mono- and bimetallic zwitterionic chromium(0) and tungsten(0) allenyls.

PubMed

Giner, Elena A; Santiago, Alicia; Gómez-Gallego, Mar; Ramírez de Arellano, Carmen; Poulten, Rebecca C; Whittlesey, Michael K; Sierra, Miguel A

2015-06-01

A series of stable chiral (racemic), formally neutral, zwitterionic mono- and bimetallic M(CO)5[C(OEt)═C═CR(NHC)] (M = Cr, W) σ-allenyls are ready available by the addition of N-heterocyclic carbenes (NHCs) to Cr(0) and W(0) alkynyl Fischer carbene complexes. Different classes of NHCs, (e.g., 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene, 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene, and their six- and seven-membered analogues and 1,3-bis(dimethyl)imidazol-2-ylidene) were employed as nucleophiles in these C-C bond-forming reactions yielding the novel complexes in essentially quantitative yields. A systematic experimental and computational study of the electronic properties of the Cr- and W-allenyls shows that their UV-vis spectra are directly influenced by the structure of the heterocyclic moiety derived from the NHC (ring size, substituents on the N atoms) and by the nature of the metal fragment (Cr/W). The electron-releasing nature of these complexes allows them to participate in electron-transfer reactions in the ground state, leading to a type of charged α,β-unsaturated Fischer carbenes that incorporate an NHC fragment in their structure.

Interaction of fluorescently labeled pyrrole-imidazole polyamide probes with fixed and living murine and human cells.

PubMed

Nozeret, Karine; Loll, François; Cardoso, Gildas Mouta; Escudé, Christophe; Boutorine, Alexandre S

2018-06-01

Pericentromeric heterochromatin plays important roles in controlling gene expression and cellular differentiation. Fluorescent pyrrole-imidazole polyamides targeting murine pericentromeric DNA (major satellites) can be used for the visualization of pericentromeric heterochromatin foci in live mouse cells. New derivatives targeting human repeated DNA sequences (α-satellites) were synthesized and their interaction with target DNA was characterized. The possibility to use major satellite and α -satellite binding polyamides as tools for staining pericentromeric heterochromatin was further investigated in fixed and living mouse and human cells. The staining that was previously observed using the mouse model was further characterized and optimized, but remained limited regarding the fluorophores that can be used. The promising results regarding the staining in the mouse model could not be extended to the human model. Experiments performed in human cells showed chromosomal DNA staining without selectivity. Factors limiting the use of fluorescent polyamides, in particular probe aggregation in the cytoplasm, were investigated. Results are discussed with regards to structure and affinity of probes, density of target sites and chromatin accessibility in both models. Copyright © 2018 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.

Structure-activity relationships of Imidazole-derived 2-[N-carbamoylmethyl-alkylamino]acetic acids, dual binders of human Insulin-Degrading Enzyme

PubMed Central

Charton, Julie; Gauriot, Marion; Totobenazara, Jane; Hennuyer, Nathalie; Dumont, Julie; Bosc, Damien; Marechal, Xavier; Elbakali, Jamal; Herledan, Adrien; Wen, Xiaoan; Ronco, Cyril; Gras-Masse, Helene; Heninot, Antoine; Pottiez, Virginie; Landry, Valerie; Staels, Bart; Liang, Wenguang G.; Leroux, Florence; Tang, Wei-Jen; Deprez, Benoit; Deprez-Poulain, Rebecca

2015-01-01

Insulin degrading enzyme (IDE) is a zinc metalloprotease that degrades small amyloid peptides such as amyloid-β and insulin. So far the dearth of IDE-specific pharmacological inhibitors impacts the understanding of its role in the physiopathology of Alzheimer’s disease, amyloid-β clearance, and its validation as a potential therapeutic target. Hit 1 was previously discovered by high-throughput screening. Here we describe the structure-activity study, that required the synthesis of 48 analogues. We found that while the carboxylic acid, the imidazole and the tertiary amine were critical for activity, the methyl ester was successfully optimized to an amide or a 1,2,4-oxadiazole. Along with improving their activity, compounds were optimized for solubility, lipophilicity and stability in plasma and microsomes. The docking or co-crystallization of some compounds at the exosite or the catalytic site of IDE provided the structural basis for IDE inhibition. The pharmacokinetic properties of best compounds 44 and 46 were measured in vivo. As a result, 44 (BDM43079) and its methyl ester precursor 48 (BDM43124) are useful chemical probes for the exploration of IDE’s role. PMID:25489670

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

Osiry, H.; Cano, A.; Lemus-Santana, A.A.

This contribution discusses the intercalation of imidazole and its 2-ethyl derivative, and pyridine in 2D copper nitroprusside. In the interlayer region, neighboring molecules remain interacting throu gh their dipole and quadrupole moments, which supports the solid 3D crystal structure. The crystal structure of this series of intercalation compounds was solved and refined from powder X-ray diffraction patterns complemented with spectroscopic information. The intermolecular interactions were studied from the refined crystal structures and low temperature magnetic measurements. Due to strong attractive forces between neighboring molecules, the resulting π–π cloud overlapping enables the ferromagnetic coupling between metal centers on neighboring layers, which wasmore » actually observed for the solids containing imidazole and pyridine as intercalated molecules. For these two solids, the magnetic data were properly described with a model of six neighbors. For the solid containing 2-ethylimidazole and for 2D copper nitroprusside, a model of four neighbors in a plane is sufficient to obtain a reliable data fitting. - Highlights: • Intercalation of organic molecules in 2D copper (II) nitroprusside. • Molecular properties of intercalation compounds of 2D copper (II) nitroprusside. • Magnetic properties of hybrid inorganic–organic solids. • Hybrid inorganic–organic 3D framework.« less

Quantitative analysis of polypeptide pharmaceuticals by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

PubMed

Amini, Ahmad; Nilsson, Elin

2008-02-13

An accurate method based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) has been developed for quantitative analysis of calcitonin and insulin in different commercially available pharmaceutical products. Tryptic peptides derived from these polypeptides were chemically modified at their C-terminal lysine-residues with 2-methoxy-4,5-dihydro-imidazole (light tagging) as standard and deuterated 2-methoxy-4,5-dihydro-imidazole (heavy tagging) as internal standard (IS). The heavy modified tryptic peptides (4D-Lys tag), differed by four atomic mass units from the corresponding light labelled counterparts (4H-Lys tag). The normalized peak areas (the ratio between the light and heavy tagged peptides) were used to construct a standard curve to determine the concentration of the analytes. The concentrations of calcitonin and insulin content of the analyzed pharmaceutical products were accurately determined, and less than 5% error was obtained between the present method and the manufacturer specified values. It was also found that the cysteine residues in CSNLSTCVLGK from tryptic calcitonin were converted to lanthionine by the loss of one sulfhydryl group during the labelling procedure.

Theoretical understanding of ruthenium(II) based fluoride sensor derived from 4,5-bis(benzimidazol-2-yl)imidazole (H3ImBzim) and bipyridine: electronic structure and binding nature.

PubMed

Wang, Jian; Bai, Fu-Quan; Xia, Bao-Hui; Sun, Lei; Zhang, Hong-Xing

2011-03-17

Using density functional theory (DFT) approach, we assessed the newly developed fluoride sensor: [(bpy)(2)Ru(H(3)ImBzim)](2+) (denoted as 1, where H(3)ImBzim = 4,5-bis(benzimidazol-2-yl)imidazole and byp = 2,2'-bipyridine). On the basis of our benchmark test, a PBE0 functional with a LanL2DZ basis set was chosen to explore the electronic structure of 1 in both ground and singlet excited states in acetonitrile solution. Both absorption bands at 426 and 352 nm are assigned as metal-to-ligand charge-transfer transition characters. By analyzing the difference of absorption spectrum between the binding adducts and the experimental measurement, the fluoride detection process was found to be driven by the proton transfer model, which makes 1 not only capable of detecting fluoride, but also for other Bønster base anions. And the result is in general accordance with the experimental observations. We hope the current exploration can give some knowledge about the detection mechanism of the F(-) anion sensor and provide some inspiration for the design of functional molecular detectors for F(-) anion.

Peroxyoxalate chemiluminescence detection for the highly sensitive determination of fluorescence-labeled chlorpheniramine with Suzuki coupling reaction.

PubMed

Adutwum, Lawrence Asamoah; Kishikawa, Naoya; Ohyama, Kaname; Harada, Shiro; Nakashima, Kenichiro; Kuroda, Naotaka

2010-09-01

A sensitive and selective high performance liquid chromatography-peroxyoxalate chemiluminescence (PO-CL) method has been developed for the simultaneous determination of chlorpheniramine (CPA) and monodesmethyl chlorpheniramine (MDCPA) in human serum. The method combines fluorescent labeling with 4-(4,5-diphenyl-1H-imidazole-2-yl)phenyl boronic acid using Suzuki coupling reaction with PO-CL detection. CPA and MDCPA were extracted from human serum by liquid-liquid extraction with n-hexane. Excess labeling reagent, which interfered with trace level determination of analytes, was removed by solid-phase extraction using a C18 cartridge. Separation of derivatives of both analytes was achieved isocratically on a silica column with a mixture of acetonitrile and 60 mM imidazole-HNO(3) buffer (pH 7.2; 85:15, v/v) containing 0.015% triethylamine. The proposed method exhibited a good linearity with a correlation coefficient of 0.999 for CPA and MDCPA within the concentration range of 0.5-100 ng/mL. The limits of detection (S/N = 3) were 0.14 and 0.16 ng/mL for CPA and MDCPA, respectively. Using the proposed method, CPA could be selectively determined in human serum after oral administration.

Pyrrolo isoquinolines

DOEpatents

Goodman, Mark M.; Shi, Bing Z.

2000-01-01

Compounds of the formula: ##STR1## wherein X, Y, and R, independently of one another, is each a H; halogen, wherein said halogen is selected from the group consisting of .sup.123 I, .sup.124 I, .sup.125 I, .sup.131 I, .sup.75 Br, .sup.76 Br, .sup.77 Br, .sup.82 Br, .sup.18 F, or .sup.210 At; small alkyl, small alkenyl, or small alkynyl, any of which contains from one to about six carbon atoms and optionally having a carbon atom replaced by an O or S; or halogen substituted-small alkyl, halogen substituted-small alkenyl, or halogen substituted-small alkynyl wherein said compound contains at least one radioacitve halogen. The compounds bind to the serotonin transporter. Depending upon the choice of halogen substituent, the compounds are useful for PET or SPECT imaging, diagnosis and treatment of psychiatric disorders such as depression, anxiety, obsessive-compulsive disorder, and other conditions associated with defects of serotonin transporter function.

40 CFR 721.275 - Halogenated-N-(2-propenyl)-N-(substituted phenyl) acetamide.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Halogenated-N-(2-propenyl)-N... New Uses for Specific Chemical Substances § 721.275 Halogenated-N-(2-propenyl)-N-(substituted phenyl... identified generically as halogenated-N-(2-propenyl)-N-(substituted phenyl) acetamide (P-83-1085) is subject...

40 CFR 721.275 - Halogenated-N-(2-propenyl)-N-(substituted phenyl) acetamide.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Halogenated-N-(2-propenyl)-N... New Uses for Specific Chemical Substances § 721.275 Halogenated-N-(2-propenyl)-N-(substituted phenyl... identified generically as halogenated-N-(2-propenyl)-N-(substituted phenyl) acetamide (P-83-1085) is subject...

Do Halogen–Hydrogen Bond Donor Interactions Dominate the Favorable Contribution of Halogens to Ligand–Protein Binding?

PubMed Central

2017-01-01

Halogens are present in a significant number of drugs, contributing favorably to ligand–protein binding. Currently, the contribution of halogens, most notably chlorine and bromine, is largely attributed to halogen bonds involving favorable interactions with hydrogen bond acceptors. However, we show that halogens acting as hydrogen bond acceptors potentially make a more favorable contribution to ligand binding than halogen bonds based on quantum mechanical calculations. In addition, bioinformatics analysis of ligand–protein crystal structures shows the presence of significant numbers of such interactions. It is shown that interactions between halogens and hydrogen bond donors (HBDs) are dominated by perpendicular C–X···HBD orientations. Notably, the orientation dependence of the halogen–HBD (X–HBD) interactions is minimal over greater than 100° with favorable interaction energies ranging from −2 to −14 kcal/mol. This contrasts halogen bonds in that X–HBD interactions are substantially more favorable, being comparable to canonical hydrogen bonds, with a smaller orientation dependence, such that they make significant, favorable contributions to ligand–protein binding and, therefore, should be actively considered during rational ligand design. PMID:28657759

Kinetics and mechanisms of some atomic oxygen reactions

NASA Technical Reports Server (NTRS)

Cvetanovic, R. J.

1987-01-01

Mechanisms and kinetics of some reactions of the ground state of oxygen atoms, O(3P), are briefly summarized. Attention is given to reactions of oxygen atoms with several different types of organic and inorganic compounds such as alkanes, alkenes, alkynes, aromatics, and some oxygen, nitrogen, halogen and sulfur derivatives of these compounds. References to some recent compilations and critical evaluations of reaction rate constants are given.

Likelihood of atom-atom contacts in crystal structures of halogenated organic compounds.

PubMed

Jelsch, Christian; Soudani, Sarra; Ben Nasr, Cherif

2015-05-01

The likelihood of occurrence of intermolecular contacts in crystals of halogenated organic compounds has been analysed statistically using tools based on the Hirshfeld surface. Several families of small halogenated molecules (containing organic F, Cl, Br or I atoms) were analysed, based on chemical composition and aromatic or aliphatic character. The behaviour of crystal contacts was also probed for molecules containing O or N. So-called halogen bonding (a halogen making short interactions with O or N, or a π interaction with C) is generally disfavoured, except when H is scarce on the molecular surface. Similarly, halogen⋯halogen contacts are more rare than expected, except for molecules that are poor in H. In general, the H atom is found to be the preferred partner of organic halogen atoms in crystal structures. On the other hand, C⋯C interactions in parallel π-stacking have a high propensity to occur in halogenated aromatic molecules. The behaviour of the four different halogen species (F, Cl, Br, I) is compared in several chemical composition contexts. The analysis tool can be refined by distinguishing several types for a given chemical species, such as H atoms bound to O or C. Such distinction shows, for instance, that C-H⋯Cl and O-H⋯O are the preferred interactions in compounds containing both O and Cl.

New Polybenzimidazole Architectures by Diels Alder Polymerization

DTIC Science & Technology

2012-02-14

stable organic polymers known.9 This class of polymers is aromatic with the heterocyclic benzimidazole group, a five membered imidazole ring...will allow benzimidazole ring systems to be prepared from the cycloaddition with an imidazole diene. The goals of the project included synthesis

Hydrogen bond and halogen bond inside the carbon nanotube

NASA Astrophysics Data System (ADS)

Wang, Weizhou; Wang, Donglai; Zhang, Yu; Ji, Baoming; Tian, Anmin

2011-02-01

The hydrogen bond and halogen bond inside the open-ended single-walled carbon nanotubes have been investigated theoretically employing the newly developed density functional M06 with the suitable basis set and the natural bond orbital analysis. Comparing with the hydrogen or halogen bond in the gas phase, we find that the strength of the hydrogen or halogen bond inside the carbon nanotube will become weaker if there is a larger intramolecular electron-density transfer from the electron-rich region of the hydrogen or halogen atom donor to the antibonding orbital of the X-H or X-Hal bond involved in the formation of the hydrogen or halogen bond and will become stronger if there is a larger intermolecular electron-density transfer from the electron-rich region of the hydrogen or halogen atom acceptor to the antibonding orbital of the X-H or X-Hal bond. According to the analysis of the molecular electrostatic potential of the carbon nanotube, the driving force for the electron-density transfer is found to be the negative electric field formed in the carbon nanotube inner phase. Our results also show that the X-H bond involved in the formation of the hydrogen bond and the X-Hal bond involved in the formation of the halogen bond are all elongated when encapsulating the hydrogen bond and halogen bond within the carbon nanotube, so the carbon nanotube confinement may change the blue-shifting hydrogen bond and the blue-shifting halogen bond into the red-shifting hydrogen bond and the red-shifting halogen bond. The possibility to replace the all electron nanotube-confined calculation by the simple polarizable continuum model is also evaluated.

On the ultrafast charge migration and subsequent charge directed reactivity in Cl⋯N halogen-bonded clusters following vertical ionization

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

Chandra, Sankhabrata; Bhattacharya, Atanu, E-mail: atanub@ipc.iisc.ernet.in; Periyasamy, Ganga

2015-06-28

In this article, we have presented ultrafast charge transfer dynamics through halogen bonds following vertical ionization of representative halogen bonded clusters. Subsequent hole directed reactivity of the radical cations of halogen bonded clusters is also discussed. Furthermore, we have examined effect of the halogen bond strength on the electron-electron correlation- and relaxation-driven charge migration in halogen bonded complexes. For this study, we have selected A-Cl (A represents F, OH, CN, NH{sub 2}, CF{sub 3}, and COOH substituents) molecules paired with NH{sub 3} (referred as ACl:NH{sub 3} complex): these complexes exhibit halogen bonds. To the best of our knowledge, this ismore » the first report on purely electron correlation- and relaxation-driven ultrafast (attosecond) charge migration dynamics through halogen bonds. Both density functional theory and complete active space self-consistent field theory with 6-31 + G(d, p) basis set are employed for this work. Upon vertical ionization of NCCl⋯NH{sub 3} complex, the hole is predicted to migrate from the NH{sub 3}-end to the ClCN-end of the NCCl⋯NH{sub 3} complex in approximately 0.5 fs on the D{sub 0} cationic surface. This hole migration leads to structural rearrangement of the halogen bonded complex, yielding hydrogen bonding interaction stronger than the halogen bonding interaction on the same cationic surface. Other halogen bonded complexes, such as H{sub 2}NCl:NH{sub 3}, F{sub 3}CCl:NH{sub 3}, and HOOCCl:NH{sub 3}, exhibit similar charge migration following vertical ionization. On the contrary, FCl:NH{sub 3} and HOCl:NH{sub 3} complexes do not exhibit any charge migration following vertical ionization to the D{sub 0} cation state, pointing to interesting halogen bond strength-dependent charge migration.« less

Model studies of the Cu(B) site of cytochrome c oxidase utilizing a Zn(II) complex containing an imidazole-phenol cross-linked ligand.

PubMed

Pesavento, Russell P; Pratt, Derek A; Jeffers, Jerry; van der Donk, Wilfred A

2006-07-21

Cytochrome c oxidase, the enzyme complex responsible for the four-electron reduction of O2 to H2O, contains an unusual histidine-tyrosine cross-link in its bimetallic heme a3-CuB active site. We have synthesised an unhindered, tripodal chelating ligand, BPAIP, containing the unusual ortho-imidazole-phenol linkage, which mimics the coordination environment of the CuB center. The ligand was used to investigate the physicochemical (pKa, oxidation potential) and coordination properties of the imidazole-phenol linkage when bound to a dication. Zn(II) coordination lowers the pKa of the phenol by 0.6 log units, and increases the potential of the phenolate/phenoxyl radical couple by approximately 50 mV. These results are consistent with inductive withdrawal of electron density from the phenolic ring. Spectroscopic data and theoretical calculations (DFT) were used to establish that the cationic complex [Zn(BPAIP)Br]+ has an axially distorted trigonal bipyramidal structure, with three coordinating nitrogen ligands (two pyridine and one imidazole) occupying the equatorial plane and the bromide and the tertiary amine nitrogen of the tripod in the axial positions. Interestingly, the Zn-Namine bonding interaction is weak or absent in [Zn(BPAIP)Br]+ and the complex gains stability in basic solutions, as indicated by 1H NMR spectroscopy. These observations are supported by theoretical calculations (DFT), which suggest that the electron-donating capacity of the equatorial imidazole ligand can be varied by modulation of the protonation and/or redox state of the cross-linked phenol. Deprotonation of the phenol makes the equatorial imidazole a stronger sigma-donor, resulting in an increased Zn-Nimd interaction and thereby leading to distortion of the axial ligand axis toward a more tetrahedral geometry.

Adsorption of 1- and 2-butylimidazoles at the copper/air and steel/air interfaces studied by sum frequency generation vibrational spectroscopy.

PubMed

Casford, Michael T L; Davies, Paul B

2012-07-24

The structure of thin films of 1- and 2-butylimidazoles adsorbed on copper and steel surfaces under air was examined using sum frequency generation (SFG) vibrational spectroscopy in the ppp and ssp polarizations. Additionally, the SFG spectra of both isomers were recorded at 55 °C at the liquid imidazole/air interface for reference. Complementary bulk infrared, reflection-absorption infrared spectroscopy (RAIRS), and Raman spectra of both imidazoles were recorded for assignment purposes. The SFG spectra in the C-H stretching region at the liquid/air interface are dominated by resonances from the methyl end group of the butyl side chain of the imidazoles, indicating that they are aligned parallel or closely parallel to the surface normal. These are also the most prominent features in the SFG spectra on copper and steel. In addition, both the ppp and ssp spectra on copper show resonances from the C-H stretching modes of the imidazole ring for both isomers. The ring C-H resonances are completely absent from the spectra on steel and at the liquid/air interface. The relative intensities of the SFG spectra can be interpreted as showing that, on copper, under air, both butylimidazoles are adsorbed with their butyl side chains perpendicular to the interface and with the ring significantly inclined away from the surface plane and toward the surface normal. The SFG spectra of both imidazoles on steel indicate an orientation where the imidazole rings are parallel or nearly parallel to the surface. The weak C-H resonances from the ring at the liquid/air interface suggest that the tilt angle of the ring from the surface normal at this interface is significantly greater than it is on copper.

Sub-50 fs excited state dynamics of 6-chloroguanine upon deep ultraviolet excitation.

PubMed

Mondal, Sayan; Puranik, Mrinalini

2016-05-18

The photophysical properties of natural nucleobases and their respective nucleotides are ascribed to the sub-picosecond lifetime of their first singlet states in the UV-B region (260-350 nm). Electronic transitions of the ππ* type, which are stronger than those in the UV-B region, lie at the red edge of the UV-C range (100-260 nm) in all isolated nucleobases. The lowest energetic excited states in the UV-B region of nucleobases have been investigated using a plethora of experimental and theoretical methods in gas and solution phases. The sub-picosecond lifetime of these molecules is not a general attribute of all nucleobases but specific to the five primary nucleobases and a few xanthine and methylated derivatives. To determine the overall UV photostability, we aim to understand the effect of more energetic photons lying in the UV-C region on nucleobases. To determine the UV-C initiated photophysics of a nucleobase system, we chose a halogen substituted purine, 6-chloroguanine (6-ClG), that we had investigated previously using resonance Raman spectroscopy. We have performed quantitative measurements of the resonance Raman cross-section across the Bb absorption band (210-230 nm) and constructed the Raman excitation profiles. We modeled the excitation profiles using Lee and Heller's time-dependent theory of resonance Raman intensities to extract the initial excited state dynamics of 6-ClG within 30-50 fs after photoexcitation. We found that imidazole and pyrimidine rings of 6-ClG undergo expansion and contraction, respectively, following photoexcitation to the Bb state. The amount of distortions of the excited state structure from that of the ground state structure is reflected by the total internal reorganization energy that is determined at 112 cm(-1). The contribution of the inertial component of the solvent response towards the total reorganization energy was obtained at 1220 cm(-1). In addition, our simulation also yields an instantaneous response of the first solvation shell within an ultrafast timescale of less than 30 fs following photoexcitation.

Imidazole as a pH Probe: An NMR Experiment for the General Chemistry Laboratory

ERIC Educational Resources Information Center

Hagan, William J., Jr.; Edie, Dennis L.; Cooley, Linda B.

2007-01-01

The analysis describes an NMR experiment for the general chemistry laboratory, which employs an unknown imidazole solution to measure the pH values. The described mechanism can also be used for measuring the acidity within the isolated cells.

An imidazole functionalized pentameric thiophene displays different staining patterns in normal and malignant cells

NASA Astrophysics Data System (ADS)

Nilsson, Peter; Magnusson, Karin; Appelqvist, Hanna; Cieslar-Pobuda, Artur; Bäck, Marcus; Kågedal, Bertil; Jonasson, Jon; Los, Marek

2015-10-01

Molecular tools for fluorescent imaging of cells and their components are vital for understanding the function and activity of cells. Here, we report an imidazole functionalized pentameric oligothiophene, p-HTIm, that can be utilized for fluorescent imaging of cells. p-HTIm fluorescence in normal cells appeared in a peripheral punctate pattern partially co-localized with lysosomes, whereas a one-sided perinuclear Golgi associated localization of the dye was observed in malignant cells. The uptake of p-HTIm was temperature dependent and the intracellular target was reached within 1 h after staining. The ability of p-HTIm to stain cells was reduced when the imidazole side chain was chemically altered, verifying that specific imidazole side-chain functionalities are necessary for achieving the observed cellular staining. Our findings confirm that properly functionalized oligothiophenes can be utilized as fluorescent tools for vital staining of cells and that the selectivity towards distinct intracellular targets are highly dependent on the side-chain functionalities along the conjugated thiophene backbone.

Di-μ3-chlorido-tetra-μ2-chlorido-dichloridobis(dimethyl­formamide-κO)hexa­kis­(1H-imidazole-κN 3)tetra­cadmium

PubMed Central

Zhu, Run-Qiang

2011-01-01

The centrosymmetric mol­ecule of the title complex, [Cd4Cl8(C3H4N2)6(C3H7NO)2], contains four CdII atoms, six imidazole, two dimethyl­formamide and eight chloride ligands. The structure shows a novel chloride-bridged tetra­nuclear cadmium quasi-cubane cluster. The coordination geometry of all CdII atoms is distorted octa­hedral, with the two metal atoms in the asymmetric unit in different coordination environments. One of the Cd2+ ions is coordinated by five Cl− ions and by one N atom from an imidazole ligand, while the second is coordinated by three chloride ligands, two N atoms from two imidazole ligands and one O atom from a dimethyl­formamide mol­ecule. Inter­molecular N—H⋯Cl hydrogen bonds link the mol­ecules into a two-dimensional polymeric structure parallel to the ab plane. PMID:22058708

Effect of 1-(4-phenoxyphenoxypropyl)imidazole (KS-175) on larval growth in the silkworm Bombyx mori.

PubMed

Shiotsuki, T; Yukuhiro, F; Kiuchi, M; Kuwano, E

1999-12-01

1-(4-Phenoxyphenoxypropyl)imidazole (KS-175), which has two types of characteristic moieties of insect growth regulators (IGRs), the phenoxyphenoxyalkyl group of juvenile hormone analogs (JHAs) and imidazole of 1,5-disubstituted imidazole such as KK-42, was tested for its biological activity on the silkworm, Bombyx mori. Penultimate (4th) instar larvae topically treated with KS-175 did not molt for more than 20 days. This activity was different from that reported for any IGRs. After the treatment, ecdysteroid levels in the hemolymph did not increase and the cells of the prothoracic gland had shrunk. When the treated penultimate larvae were fed an artificial diet supplemented with 20 ppm of 20-hydroxyecdysone, the larvae molted to the ultimate (5th) instar with a timing similar to that of control larvae fed a diet with or without 20-hydroxyecdysone. These results suggest that topical application of KS-175 irreversibly damages ecdysone biosynthesis in the prothoracic glands.

Diaqua­bis{5-carboxy-2-[(1H-1,2,4-triazol-1-yl)­meth­yl]-1H-imidazole-4-carboxyl­ato}­manganese(II)

PubMed Central

Ding, De-Gang; Tong, Yan

2010-01-01

In the title compound, [Mn(C8H6N5O4)2(H2O)2], the MnII ion is situated on an inversion center and is six-coordinated by two N and two O atoms from two L ligands (HL = 2-[(1H-1,2,4-triazol-1-yl)meth­yl]-1H-imidazole-4,5-dicarboxylic acid) and two water mol­ecules in a distorted octa­hedral geometry. In ligand L, the imidazole and triazole rings form a dihedral angle of 74.25 (8)°. Mol­ecules are assembled into a three-dimensional structure via inter­molecular O—H⋯O, O—H⋯N and N—H⋯N hydrogen-bonds, and π–π inter­actions with a short distance of 3.665 (2) Å between the centroids of the imidazole and triazole rings of neighbouring mol­ecules. PMID:21579014

{pi}-{pi} Interactions and magnetic properties in a series of hybrid inorganic-organic crystals

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

Gonzalez, M.; Lemus-Santana, A.A.; Rodriguez-Hernandez, J.

The series of hybrid inorganic-organic solids T(Im){sub 2}[Ni(CN){sub 4}] with T=Fe, Co, Ni and Im=imidazole were prepared by soft chemical routes from aqueous solutions of the involved building units: imidazole, T{sup 2+} metal and the [Ni(CN){sub 4}]{sup 2-} anionic block. The obtained samples were characterized from infrared and UV-vis spectroscopies, and thermogravimetric, X-ray diffraction and magnetic measurements. Anhydrous solids which crystallize with a monoclinic unit cell, in the I2/a space group with four formula units per cell (Z=4) were obtained. Their crystal structure was solved ab initio from the recorded X-ray powder patterns and then refined by the Rietveld method.more » The metal T is found with octahedral coordination to four N ends of CN groups and two imidazole molecules while the inner Ni atom preserves its planar coordination. The system of layers remains stacked in an ordered 3D structure through dipole-dipole and {pi}-{pi} interactions between imidazole rings from neighboring layers. In this way, a pillared structure is achieved without requiring the coordination of both nitrogen atoms from imidazole ring. The recorded magnetic data indicate the occurrence of a predominant ferromagnetic interaction at low temperature for Co and Ni but not for Fe. Such magnetic ordering is more favorable for Ni with transition temperature of 14.67 K, which was ascribed to the relatively high polarizing power for this metal. Within the considered T metals, to nickel the highest electron-withdrawing ability corresponds and this leads to an increase for the metal-ligand electron clouds overlapping and to a stronger {pi}-{pi} attractive interaction, two factors that result into a higher magnetic ordering temperature. - Graphical Abstract: Magnetic ordering through the {pi}-{pi} interaction between the imidazole rings. Highlights: Black-Right-Pointing-Pointer Hybrid inorganic-organic solids. Black-Right-Pointing-Pointer Hybrid inorganic-organic molecular based magnets. Black-Right-Pointing-Pointer Ferromagnetic interaction through {pi}-{pi} stacking of imidazole rings. Black-Right-Pointing-Pointer Organic pillars formed through {pi}-{pi} stacking.« less

Novel synthetic kojic acid-methimazole derivatives inhibit mushroom tyrosinase and melanogenesis.

PubMed

Chen, Ming-Jen; Hung, Chih-Chuan; Chen, Yan-Ru; Lai, Shih-Ting; Chan, Chin-Feng

2016-12-01

In this study, two kojic acid-methimazole (2-mercapto-1-methylimidazole, MMI, 1) derivatives, 5-hydroxy-2-{[(1-methyl-1H-imidazol-2-yl)thio]methyl}-4H-pyran-4-one (compound 4) and 5-methoxy-2-{[(1-methyl-1H-imidazol-2-yl)thio]methyl}-4H-pyran-4-one (compound 5), were synthesized to examine their inhibitory kinetics on mushroom tyrosinase. Compound 4 exhibited a potent inhibitory effect on monophenolase activity in a dose-dependent manner, with an IC 50 value of 0.03 mM. On diphenolase activity, compound 4 exhibited a less inhibitory effect (IC 50  = 1.29 mM) but was stronger than kojic acid (IC 50  = 1.80 mM). Kinetic analysis indicated that compound 4 was both as a noncompetitive monophenolase and diphenolase inhibitor. By contrast, compound 5 exhibited no inhibitory effects on mushroom tyrosinase activity. The IC 50 value of compound 4 for the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity was 4.09 mM, being much higher than the IC 50 of compound 4 for inhibiting the tyrosinase activity. The results indicated that the antioxidant activity of compound 4 may be partly related to the potent inhibitory effect on mushroom tyrosinase. Compound 4 also exerted a potent inhibitory effect on intracellular melanin formation in B16/F10 murine melanoma cells, and caused no cytotoxicity. Furthermore, compound 4 induced no adverse effects on the Hen's egg test-chorioallantoic membrane (HET-CAM). Copyright © 2016 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Cosmic-Ray Reaction and Greenhouse Effect of Halogenated Molecules: Culprits for Atmospheric Ozone Depletion and Global Climate Change

NASA Astrophysics Data System (ADS)

Lu, Q.-B.

2013-07-01

This study is focused on the effects of cosmic rays (solar activity) and halogen-containing molecules (mainly chlorofluorocarbons — CFCs) on atmospheric ozone depletion and global climate change. Brief reviews are first given on the cosmic-ray-driven electron-induced-reaction (CRE) theory for O3 depletion and the warming theory of halogenated molecules for climate change. Then natural and anthropogenic contributions to these phenomena are examined in detail and separated well through in-depth statistical analyses of comprehensive measured datasets of quantities, including cosmic rays (CRs), total solar irradiance, sunspot number, halogenated gases (CFCs, CCl4 and HCFCs), CO2, total O3, lower stratospheric temperatures and global surface temperatures. For O3 depletion, it is shown that an analytical equation derived from the CRE theory reproduces well 11-year cyclic variations of both polar O3 loss and stratospheric cooling, and new statistical analyses of the CRE equation with observed data of total O3 and stratospheric temperature give high linear correlation coefficients ≥ 0.92. After the removal of the CR effect, a pronounced recovery by 20 25 % of the Antarctic O3 hole is found, while no recovery of O3 loss in mid-latitudes has been observed. These results show both the correctness and dominance of the CRE mechanism and the success of the Montreal Protocol. For global climate change, in-depth analyses of the observed data clearly show that the solar effect and human-made halogenated gases played the dominant role in Earth's climate change prior to and after 1970, respectively. Remarkably, a statistical analysis gives a nearly zero correlation coefficient (R = -0.05) between corrected global surface temperature data by removing the solar effect and CO2 concentration during 1850-1970. In striking contrast, a nearly perfect linear correlation with coefficients as high as 0.96-0.97 is found between corrected or uncorrected global surface temperature and total amount of stratospheric halogenated gases during 1970-2012. Furthermore, a new theoretical calculation on the greenhouse effect of halogenated gases shows that they (mainly CFCs) could alone result in the global surface temperature rise of 0.6°C in 1970-2002. These results provide solid evidence that recent global warming was indeed caused by the greenhouse effect of anthropogenic halogenated gases. Thus, a slow reversal of global temperature to the 1950 value is predicted for coming 5 7 decades. It is also expected that the global sea level will continue to rise in coming 1 2 decades until the effect of the global temperature recovery dominates over that of the polar O3 hole recovery; after that, both will drop concurrently. All the observed, analytical and theoretical results presented lead to a convincing conclusion that both the CRE mechanism and the CFC-warming mechanism not only provide new fundamental understandings of the O3 hole and global climate change but have superior predictive capabilities, compared with the conventional models.

Model Studies of the Histidine-Tyrosine Cross-Link in Cytochrome c Oxidase Reveal the Flexible Substituent Effect of the Imidazole Moiety

PubMed Central

Pratt, Derek A.; Pesavento, Russell P.; van der Donk, Wilfred A.

2010-01-01

Experimental and theoretical studies were carried out to interrogate the effect of an imidazole substituent in each of the ortho, meta, and para positions on the pKa, E°, and O–H BDE of phenol. The results reveal that imidazole substitution lowers the pKa of phenol and increases the E° of phenoxide due to its σ-electron withdrawing ability (σp− = +0.21, σm− = +0.45) but decreases the O–H BDE and E° of phenol due to its σ-electron-donating ability (σp+ = −0.45). PMID:15957934

Oleanolic acid and its synthetic derivatives for the prevention and therapy of cancer: Preclinical and clinical evidence

PubMed Central

Shanmugam, Muthu K.; Dai, Xiaoyun; Kumar, Alan Prem; Tan, Benny KH; Sethi, Gautam; Bishayee, Anupam

2014-01-01

Oleanolic acid (OA, 3β-hydroxyolean-12-en-28-oic acid) is a ubiquitous pentacyclic multifunctional triterpenoid, widely found in several dietary and medicinal plants. Natural and synthetic OA derivatives can modulate multiple signaling pathways including nuclear factor-κB, AKT, signal transducer and activator of transcription 3, mammalian target of rapamycin, caspases, intercellular adhesion molecule 1, vascular endothelial growth factor, and poly (ADP-ribose) polymerase in a variety of tumor cells. Importantly, synthetic derivative of OA, 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO), and its C-28 methyl ester (CDDO-Me) and C28 imidazole (CDDO-Im) have demonstrated potent antiangiogenic and antitumor activities in rodent cancer models. These agents are presently under evaluation in phase I studies in cancer patients. This review summarizes the diverse molecular targets of OA and its derivatives and also provides clear evidence on their promising potential in preclinical and clinical situations. PMID:24486850

The unique role of halogen substituents in the design of modern agrochemicals.

PubMed

Jeschke, Peter

2010-01-01

The past 30 years have witnessed a period of significant expansion in the use of halogenated compounds in the field of agrochemical research and development. The introduction of halogens into active ingredients has become an important concept in the quest for a modern agrochemical with optimal efficacy, environmental safety, user friendliness and economic viability. Outstanding progress has been made, especially in synthetic methods for particular halogen-substituted key intermediates that were previously prohibitively expensive. Interestingly, there has been a rise in the number of commercial products containing 'mixed' halogens, e.g. one or more fluorine, chlorine, bromine or iodine atoms in addition to one or more further halogen atoms. Extrapolation of the current trend indicates that a definite growth is to be expected in fluorine-substituted agrochemicals throughout the twenty-first century. A number of these recently developed agrochemical candidates containing halogen substituents represent novel classes of chemical compounds with new modes of action. However, the complex structure-activity relationships associated with biologically active molecules mean that the introduction of halogens can lead to either an increase or a decrease in the efficacy of a compound, depending on its changed mode of action, physicochemical properties, target interaction or metabolic susceptibility and transformation. In spite of modern design concepts, it is still difficult to predict the sites in a molecule at which halogen substitution will result in optimal desired effects. This review describes comprehensively the successful utilisation of halogens and their unique role in the design of modern agrochemicals, exemplified by various commercial products from Bayer CropScience coming from different agrochemical areas.

Removal of Intermediate Aromatic Halogenated DBPs by Activated Carbon Adsorption: A New Approach to Controlling Halogenated DBPs in Chlorinated Drinking Water.

PubMed

Jiang, Jingyi; Zhang, Xiangru; Zhu, Xiaohu; Li, Yu

2017-03-21

During chlorine disinfection of drinking water, chlorine may react with natural organic matter (NOM) and bromide ion in raw water to generate halogenated disinfection byproducts (DBPs). To mitigate adverse effects from DBP exposure, granular activated carbon (GAC) adsorption has been considered as one of the best available technologies for removing NOM (DBP precursor) in drinking water treatment. Recently, we have found that many aromatic halogenated DBPs form in chlorination, and they act as intermediate DBPs to decompose and form commonly known DBPs including trihalomethanes and haloacetic acids. In this work, we proposed a new approach to controlling drinking water halogenated DBPs by GAC adsorption of intermediate aromatic halogenated DBPs during chlorination, rather than by GAC adsorption of NOM prior to chlorination (i.e., traditional approach). Rapid small-scale column tests were used to simulate GAC adsorption in the new and traditional approaches. Significant reductions of aromatic halogenated DBPs were observed in the effluents with the new approach; the removals of total organic halogen, trihalomethanes, and haloacetic acids by the new approach always exceeded those by the traditional approach; and the effluents with the new approach were considerably less developmentally toxic than those with the traditional approach. Our findings indicate that the new approach is substantially more effective in controlling halogenated DBPs than the traditional approach.

Halogenated solvent interactions with N,N-dimethyltryptamine: formation of quaternary ammonium salts and their artificially induced rearrangements during analysis.

PubMed

Brandt, Simon D; Martins, Cláudia P B; Freeman, Sally; Dempster, Nicola; Riby, Philip G; Gartz, Jochen; Alder, John F

2008-07-04

The psychoactive properties of N,N-dimethyltryptamine (DMT) 1a are known to induce altered states of consciousness in humans. This particular attribute attracts great interest from a variety of scientific and also clandestine communities. Our recent research has confirmed that DMT reacts with dichloromethane (DCM), either as a result of work-up or storage to give a quaternary N-chloromethyl ammonium salt 2a. Furthermore, this was observed to undergo rearrangement during analysis using gas chromatography-mass spectrometry (GC-MS) with products including 3-(2-chloroethyl)indole 3 and 2-methyltetrahydro-beta-carboline 4 (2-Me-THBC). This study further investigates this so far unexplored area of solvent interactions by the exposure of DMT to other halogenated solvents including dibromomethane and 1,2-dichloroethane (DCE). The N-bromomethyl- and N-chloroethyl quaternary ammonium derivatives were subsequently characterised by ion trap GC-MS in electron and chemical ionisation tandem MS mode and by NMR spectroscopy. The DCE-derived derivative formed at least six rearrangement products in the total ion chromatogram. Identification of mass spectrometry generated by-products was verified by conventional or microwave-accelerated synthesis. The use of deuterated DCM and deuterated DMT 1b provided insights into the mechanism of the rearrangements. The presence of potentially characteristic marker molecules may allow the identification of solvents used during the manufacture of controlled substances, which is often neglected since these are considered inert.

Boiling points of halogenated ethanes: an explanatory model implicating weak intermolecular hydrogen-halogen bonding.

PubMed

Beauchamp, Guy

2008-10-23

This study explores via structural clues the influence of weak intermolecular hydrogen-halogen bonds on the boiling point of halogenated ethanes. The plot of boiling points of 86 halogenated ethanes versus the molar refraction (linked to polarizability) reveals a series of straight lines, each corresponding to one of nine possible arrangements of hydrogen and halogen atoms on the two-carbon skeleton. A multiple linear regression model of the boiling points could be designed based on molar refraction and subgroup structure as independent variables (R(2) = 0.995, standard error of boiling point 4.2 degrees C). The model is discussed in view of the fact that molar refraction can account for approximately 83.0% of the observed variation in boiling point, while 16.5% could be ascribed to weak C-X...H-C intermolecular interactions. The difference in the observed boiling point of molecules having similar molar refraction values but differing in hydrogen-halogen intermolecular bonds can reach as much as 90 degrees C.

Halogen-free boron based electrolyte solution for rechargeable magnesium batteries

NASA Astrophysics Data System (ADS)

Zhu, Jinjie; Guo, Yongsheng; Yang, Jun; Nuli, Yanna; Zhang, Fan; Wang, Jiulin; Hirano, Shin-ichi

2014-02-01

All halogen containing electrolytes for Mg battery are apt to corrode conventional metal current collectors. In this paper, a new type of halogen-free boron based electrolyte (Mg[Mes3BPh]2/THF) is designed and prepared. Electrochemical tests show that this electrolyte system possesses high ion conductivity (1.5 × 10-3 S cm-1) and good Mg deposition-dissolution reversibility. More importantly, the same electrochemical window (2.6 V vs. Mg RE) of the electrolyte on Pt and stainless steel electrodes indicates that halogen-free electrolyte indeed lessens the corrosion to conventional metal current collectors. The surface morphologies of stainless steel, aluminum and copper are further observed after their anodic potentiostatic polarization in 0.25 mol L-1 Mg[Mes3BPh]2/THF electrolyte solution for 2 days. A comparison with halogen containing electrolytes proves that the presence of halogen in electrolyte is the reason for corrosion. This work provides a stepping stone for developing new halogen-free electrolyte systems for rechargeable Mg batteries.

Structural, photophysical, and theoretical studies of imidazole-based excited-state intramolecular proton transfer molecules

NASA Astrophysics Data System (ADS)

Somasundaram, Sivaraman; Kamaraj, Eswaran; Hwang, Su Jin; Park, Sanghyuk

2018-02-01

Imidazole-based excited state intramolecular proton transfer (ESIPT) blue fluorescent molecules, 2-(1-(4-chlorophenyl)-4,5-diphenyl-1H-imidazol-2-yl)phenol (BHPI-Cl) and 2-(1-(4-bromophenyl)-4,5-diphenyl-1H-imidazol-2-yl)phenol (BHPI-Br) were designed and synthesized by Debus-Radziszewski method through a one-pot multicomponent reaction in high yield. The synthesized compounds were fully characterized by 1H NMR, 13C NMR, FT-IR, FT-Raman, GC-Mass, and elemental analysis. The molecular structures in single crystal lattice were studied by X-ray crystallographic analysis. Because of the intramolecular hydrogen bonding, hydroxyphenyl group is planar to the central imidazole ring, while the other phenyl rings gave distorted conformations to the central heterocyclic ring. BHPI-Cl and BHPI-Br molecules showed intense ESIPT fluorescence at 480 nm, because the two twisted phenyl rings on 4- and 5-positions have reduced intermolecular interaction between adjacent molecules in each crystal through a head-to-tail packing manner. Quantum chemical calculations of energies were carried out by (TD-)DFT using B3LYP/6-31G(d, p) basis set to predict the electronic absorption spectra of the compounds, and they showed good agreement between the computational and the experimental values. The thermal analyses of the synthesized molecules were also carried out by TGA/DSC method.

Volatile (Li, B, F and Cl) mobility during amphibole breakdown in subduction zones

NASA Astrophysics Data System (ADS)

Debret, Baptiste; Koga, Kenneth T.; Cattani, Fanny; Nicollet, Christian; Van den Bleeken, Greg; Schwartz, Stephane

2016-02-01

Amphiboles are ubiquitous minerals in the altered oceanic crust. During subduction, their breakdown is governed by continuous reactions up to eclogitic facies conditions. Amphiboles thus contribute to slab-derived fluid throughout prograde metamorphism and continuously record information about volatile exchanges occurring between the slab and the mantle wedge. However, the fate of volatile elements and especially halogens, such as F and Cl, in amphibole during subduction is poorly constrained. We studied metagabbros from three different localities in the Western Alps: the Chenaillet ophiolite, the Queyras Schistes Lustrés and the Monviso meta-ophiolitic complexes. These samples record different metamorphic conditions, from greenschist to eclogite facies, and have interacted with different lithologies (e.g. sedimentary rocks, serpentinites) from their formation at mid-oceanic ridge, up to their devolatilization during subduction. In the oceanic crust, the initial halogen budget is mostly stored in magmatic amphibole (F = 300-7000 ppm; Cl = 20-1200 ppm) or in amphibole corona (F = 100-7000 ppm; Cl = 80-2000 ppm) and titanite (F = 200-1500 ppm; Cl < 200 ppm) formed during hydrothermal seafloor alteration. It is thus the fate of these phases that govern the halogen fluxes between the crust and the overlying mantle and/or the plate interface in subduction zones. Li and B are poorly stored in the oceanic crust (< 5 ppm). In subduction zones, prograde metamorphism of metagabbros is first marked by the crystallization of glaucophane at the expense of magmatic and amphibole coronas. This episode is accompanied with a decrease of halogen concentrations in amphiboles (< 200 ppm of F and Cl) suggesting that these elements can be transferred to the mantle wedge by fluids. In the Queyras Schistes Lustrés complex, the intense deformation and the abundant devolatilization of metasedimentary rocks produce large fluid flows that promote rock chemical hybridization (metasomatic mixing with hybrid composition between metasedimentary rock and metagabbro) at the metasedimentary rock/metagabbro contacts. Such fluid/rock interactions result in a strong addition of Li in glaucophane (up to 600 ppm) whereas halogen concentrations are unaffected. At eclogite facies conditions, metagabbros display low halogens concentrations (< 20 ppm of F and < 100 ppm of Cl) relative to altered oceanic crust (F = 40-650 ppm; Cl = 40-1400 ppm) suggesting that these elements are continuously released by fluids during the first 30-80 km of subduction whatever the tectonic environment (e.g. slab, plate interface) and the considered fluid/rock interactions.

The Halogen Bond

PubMed Central

2016-01-01

The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design. PMID:26812185

Adsorption of halogens on metal surfaces

NASA Astrophysics Data System (ADS)

Andryushechkin, B. V.; Pavlova, T. V.; Eltsov, K. N.

2018-06-01

This paper presents a review of the experimental and theoretical investigations of halogen interaction with metal surfaces. The emphasis was placed on the recent measurements performed with a scanning tunneling microscope in combination with density functional theory calculations. The surface structures formed on metal surface after halogen interaction are classified into three groups: chemisorbed monolayer, surface halide, bulk-like halide. Formation of monolayer structures is described in terms of surface phase transitions. Surface halide phases are considered to be intermediates between chemisorbed halogen and bulk halide. The modern theoretical approaches in studying the dynamics of metal halogenation reactions are also presented.

What’s New in Enzymatic Halogenations

PubMed Central

Fujimori, Danica Galoniæ; Walsh, Christopher T.

2007-01-01

Summary The halogenation of thousands of natural products occurs during biosynthesis and often confers important functional properties. While haloperoxidases had been the default paradigm for enzymatic incorporation of halogens, via X+ equivalents into organic scaffolds, a combination of microbial genome sequencing, enzymatic studies and structural biology have provided deep new insights into enzymatic transfer of halide equivalents in three oxidation states. These are: (1) the halide ions (X−) abundant in nature, (2) halogen atoms (X•), and (3) the X+ equivalents. The mechanism of halogen incorporation is tailored to the electronic demands of specific substrates and involves enzymes with distinct redox coenzyme requirements. PMID:17881282

Evaluation of carbon isotope fractionation during anaerobic reductive dehalogenation of chlorinated and brominated benzenes.

PubMed

Sohn, Seo Yean; Kuntze, Kevin; Nijenhuis, Ivonne; Häggblom, Max M

2018-02-01

Compound specific stable isotope analysis (CSIA) has been established as a useful tool to evaluate in situ biodegradation. Here, CSIA was used to determine microbial dehalogenation of chloro- and bromobenzenes in microcosms derived from Hackensack River sediments. Gas chromatography-isotope ratio mass spectrometry (GC-IRMS) was used to measure carbon isotope fractionation during reductive dehalogenation of hexachlorobenzene (HCB), pentachlorobenzene (PeCB), 1,2,3,5-tetrachlorobenzene (TeCB), 1,2,3,5-tetrabromobenzene (TeBB), and 1,3,5-tribromobenzene (TriBB). Strong evidence of isotope fractionation coupled to dehalogenation was not observed in the substrate, possibly due to the low solubilities of the highly halogenated benzene substrates and a dilution of the isotope signal. Nonetheless, we could measure a depletion of the δ 13 C value in the dichlorobenzene product during dechlorination of HCB, the sequential depletion and enrichment of δ 13 C value for trichlorobenzene in TeCB dechlorinating cultures, and the enrichment of δ 13 C during debromination of TriBB. This indicates that a measurable isotope fractionation occurred during reductive dehalogenation of highly halogenated chloro- and bromobenzenes in aquatic sediments. Thus, although more quantitative measurements will be needed, the data suggests that CSIA may have application for monitoring in situ microbial reductive dehalogenation of highly halogenated benzenes. Copyright © 2017. Published by Elsevier Ltd.

Effective binding of perhalogenated closo-borates to serum albumins revealed by spectroscopic and ITC studies

NASA Astrophysics Data System (ADS)

Kuperman, Marina V.; Losytskyy, Mykhaylo Yu.; Bykov, Alexander Yu.; Yarmoluk, Sergiy M.; Zhizhin, Konstantin Yu.; Kuznetsov, Nikolay T.; Varzatskii, Oleg A.; Gumienna-Kontecka, Elzbieta; Kovalska, Vladyslava B.

2017-08-01

The interactions of boron cluster compounds closo-borates with biomolecules are widely studied due to their efficiency as agents for boron neutron capture therapy of cancer. In present work the binding abilities of anionic halogen closo-borates [B10Hal10]2- (Hal = Cl, Br, I) and [B12Hal12]2- (Hal = Cl, I) towards bovine and human serum albumins were investigated by spectroscopic and isothermal titration calorimetry (ITC) methods. The protein fluorescence quenching method and ITC studies confirmed the complex formation. The degree of protein fluorescence quenching increased from chlorine to iodine boron derivatives that is attributed to external heavy atom effect. The ITC data point on the existence in the protein structure of two types of binding sites: with higher and lower affinity to closo-borates. Albumin-closo-borate complex binding ratio, n (4-5 anions per protein molecule) is higher than for the parent hydrogen closo-borates (2 anions per protein molecule). Binding constants estimated by fluorescent and ITC methods indicate higher affinity of halogen closo-borates to albumins (K in the range of 104-106 M-1) comparing to that of the hydrogen closo-borate (K about 103 M-1). Due to their high affinity and high binding ratio to albumins halogen closo-borates are proposed for further studies as agents for boron neutron capture therapy.

Hydrogen bonded C-H···Y (Y = O, S, Hal) molecular complexes: A natural bond orbital analysis

NASA Astrophysics Data System (ADS)

Isaev, A. N.

2016-03-01

Hydrogen bonded C-H···Y complexes formed by H2O, H2S molecules, hydrogen halides, and halogen-ions with methane, halogen substituted methane as well as with the C2H2 and NCH molecules were studied at the MP2/aug-cc-pVDZ level. The structure of NBOs corresponding to lone pair of acceptor Y, n Y, and vacant anti-σ-bond C-H of proton donor was analyzed and estimates of second order perturbation energy E(2) characterizing donor-acceptor n Y → σ C-H * charge-transfer interaction were obtained. Computational results for complexes of methane and its halogen substituted derivatives show that for each set of analogous structures, the EnY→σ*C-H (2) energy tends to grow with an increase in the s-component percentage in the lone pair NBO of acceptor Y. Calculations for different C···Y distances show that the equilibrium geometries of complexes lie in the region where the E(2) energy is highest and it changes symbatically with the length of the covalent E-H bond when the R(C···Y) distance is varied. The performed analysis allows us to divide the hydrogen bonded complexes into two groups, depending on the pattern of overlapping for NBOs of the hydrogen bridge.

Characterization of non-classical Csbnd Br⋯π interactions in (E)-1,3-dibromo-5-(2-(ferrocenyl)vinyl)benzene and related derivatives of ferrocene

NASA Astrophysics Data System (ADS)

Shukla, Rahul; Panini, Piyush; McAdam, C. John; Robinson, Brian H.; Simpson, Jim; Tagg, Tei; Chopra, Deepak

2017-03-01

Amongst the halogens, the involvement of bromine atoms in various types of intermolecular interactions is comparatively the least studied. In this manuscript, we report the formation of Csbnd Br⋯π interactions, with the π-rings being the cyclopentadienyl (Cp) rings of a ferrocene molecule in a newly synthesized compound (E)-1,3-dibromo-5-(2-(ferrocenyl)vinyl)benzene. We have also performed a detailed quantitative analysis on Csbnd Br⋯π interactions observed in the synthesized molecule and in several related molecules found in the Cambridge Structure Database (CSD) showing the presence of these interactions. A topological analysis based upon QTAIM theory and electrostatic potential ESP mapped on the Hirshfeld surface of these molecules confirm that these interactions are better described as "halogen bonds" wherein the electropositive region (σ-hole) on the Br-atom interacts with the electronegative region over the Cp-ring of the ferrocene. Further, the electronegative region on the bromine atom (perpendicular to the Csbnd Br bond) was observed to be involved in the formation of highly directional Csbnd H⋯Br interactions with the ∠Csbnd Br⋯H close to 90°. Thus the bromine atom is acting as both a "halogen bond donor" and "hydrogen bond acceptor" in the crystal packing with the two interactions being mutually orthogonal.

Metalloporphyrins and their uses as radiosensitizers for radiation therapy

DOEpatents

Miura, Michiko; Slatkin, Daniel N.

2004-07-06

The present invention covers radiosensitizers containing as an active ingredient halogenated derivatives of boronated porphyrins containing multiple carborane cages having the structure ##STR1## which selectively accumulate in neoplastic tissue within the irradiation volume and thus can be used in cancer therapies including, but not limited to, boron neutron--capture therapy and photodynamic therapy. The present invention also covers methods for using these radiosensitizers in tumor imaging and cancer treatment.

Arylthioindole inhibitors of tubulin polymerization. 3. Biological evaluation, structure-activity relationships and molecular modeling studies.

PubMed

La Regina, Giuseppe; Edler, Michael C; Brancale, Andrea; Kandil, Sahar; Coluccia, Antonio; Piscitelli, Francesco; Hamel, Ernest; De Martino, Gabriella; Matesanz, Ruth; Díaz, José Fernando; Scovassi, Anna Ivana; Prosperi, Ennio; Lavecchia, Antonio; Novellino, Ettore; Artico, Marino; Silvestri, Romano

2007-06-14

The new arylthioindole (ATI) derivatives 10, 14-18, and 21-24, which bear a halogen atom or a small size ether group at position 5 of the indole moiety, were compared with the reference compounds colchicine and combretastatin A-4 for biological activity. Derivatives 10, 11, 16, and 21-24 inhibited MCF-7 cell growth with IC50 values <50 nM. A halogen atom (14-17) at position 5 caused a significant reduction in the free energy of binding of compound to tubulin, with a concomitant reduction in cytotoxicity. In contrast, methyl (21) and methoxy (22) substituents at position 5 caused an increase in cytotoxicity. Compound 16, the most potent antitubulin agent, led to a large increase (56%) in HeLa cells in the G2/M phase at 24 h, and at 48 h, 26% of the cells were hyperploid. Molecular modeling studies showed that, despite the absence of the ester moiety present in the previously examined analogues, most of the compounds bind in the colchicine site in the same orientation as the previously studied ATIs. Binding to beta-tubulin involved formation of a hydrogen bond between the indole and Thr179 and positioning of the trimethoxy phenyl group in a hydrophobic pocket near Cys241.

Carbazole ligands as c-myc G-quadruplex binders.

PubMed

Głuszyńska, Agata; Juskowiak, Bernard; Kuta-Siejkowska, Martyna; Hoffmann, Marcin; Haider, Shozeb

2018-07-15

The interactions of c-myc G-quadruplex with three carbazole derivatives were investigated by UV-Vis spectrophotometry, fluorescence, CD spectroscopy, and molecular modeling. The results showed that a combination of carbazole scaffold functionalized with ethyl, triazole and imidazole groups resulted in stabilization of the intramolecular G-quadruplex formed by the DNA sequence derived from the NHE III 1 region of c-myc oncogene (Pu22). Binding to the G-quadruplex Pu22 resulted in the significant increase in fluorescence intensity of complexed ligands 1-3. All ligands were capable of interacting with G4 DNA with binding stoichiometry indicating that two ligand molecules bind to G-quadruplex with comparable affinity, which agrees with binding model of end-stacking on terminal G-tetrads. Copyright © 2018 Elsevier B.V. All rights reserved.

40 CFR 63.2465 - What requirements must I meet for process vents that emit hydrogen halide and halogen HAP or HAP...

Code of Federal Regulations, 2014 CFR

2014-07-01

... process vents that emit hydrogen halide and halogen HAP or HAP metals? 63.2465 Section 63.2465 Protection... hydrogen halide and halogen HAP or HAP metals? (a) You must meet each emission limit in Table 3 to this...) of this section. (b) If any process vents within a process emit hydrogen halide and halogen HAP, you...

40 CFR 63.2465 - What requirements must I meet for process vents that emit hydrogen halide and halogen HAP or HAP...

Code of Federal Regulations, 2013 CFR

2013-07-01

... process vents that emit hydrogen halide and halogen HAP or HAP metals? 63.2465 Section 63.2465 Protection... hydrogen halide and halogen HAP or HAP metals? (a) You must meet each emission limit in Table 3 to this...) of this section. (b) If any process vents within a process emit hydrogen halide and halogen HAP, you...

40 CFR 63.2465 - What requirements must I meet for process vents that emit hydrogen halide and halogen HAP or HAP...

Code of Federal Regulations, 2012 CFR

2012-07-01

... process vents that emit hydrogen halide and halogen HAP or HAP metals? 63.2465 Section 63.2465 Protection... hydrogen halide and halogen HAP or HAP metals? (a) You must meet each emission limit in Table 3 to this...) of this section. (b) If any process vents within a process emit hydrogen halide and halogen HAP, you...

A metagenomic-based survey of microbial (de)halogenation potential in a German forest soil

PubMed Central

Weigold, Pascal; El-Hadidi, Mohamed; Ruecker, Alexander; Huson, Daniel H.; Scholten, Thomas; Jochmann, Maik; Kappler, Andreas; Behrens, Sebastian

2016-01-01

In soils halogens (fluorine, chlorine, bromine, iodine) are cycled through the transformation of inorganic halides into organohalogen compounds and vice versa. There is evidence that these reactions are microbially driven but the key enzymes and groups of microorganisms involved are largely unknown. Our aim was to uncover the diversity, abundance and distribution of genes encoding for halogenating and dehalogenating enzymes in a German forest soil by shotgun metagenomic sequencing. Metagenomic libraries of three soil horizons revealed the presence of genera known to be involved in halogenation and dehalogenation processes such as Bradyrhizobium or Pseudomonas. We detected a so far unknown diversity of genes encoding for (de)halogenating enzymes in the soil metagenome including specific and unspecific halogenases as well as metabolic and cometabolic dehalogenases. Genes for non-heme, no-metal chloroperoxidases and haloalkane dehalogenases were the most abundant halogenase and dehalogenase genes, respectively. The high diversity and abundance of (de)halogenating enzymes suggests a strong microbial contribution to natural halogen cycling. This was also confirmed in microcosm experiments in which we quantified the biotic formation of chloroform and bromoform. Knowledge on microorganisms and genes that catalyze (de)halogenation reactions is critical because they are highly relevant to industrial biotechnologies and bioremediation applications. PMID:27353292

Pyrrole-Imidazole Polyamides: Manual Solid-Phase Synthesis.

PubMed

Pauff, Steven M; Fallows, Andrew J; Mackay, Simon P; Su, Wu; Cullis, Paul M; Burley, Glenn A

2015-12-01

Pyrrole-imidazole polyamides (PAs) are a family of DNA-binding peptides that bind in the minor groove of double-stranded DNA (dsDNA) in a sequence-selective, programmable fashion. This protocol describes a detailed manual procedure for the solid-phase synthesis of this family of compounds. The protocol entails solution-phase synthesis of the Boc-protected pyrrole (Py) and imidazole (Im) carboxylic acid building blocks. This unit also describes the importance of choosing the appropriate condensing agent to form the amide linkages between each building block. Finally, a monomeric coupling protocol and a fragment-based approach are described that delivers PAs in 13% to 30% yield in 8 days. Copyright © 2015 John Wiley & Sons, Inc.

Oligoglyceric acid synthesis by autocondensation of glyceroyl thioester

NASA Technical Reports Server (NTRS)

Weber, A. L.

1986-01-01

The autocondensation of the glyceroyl thioester, S-glyceroyl-ethane-thiol, yielded olioglyceric acid. The rates of autocondensation and hydrolysis of the thioester increased from pH 6.5 to pH 7.5 in 2,6-lutidine and imidazole buffers. Autocondensation and hydrolysis were much more rapid in imidazole buffers as compared to 2,6-lutidine and phosphate buffers. The efficiency of ester bond synthesis was about 20% for 40 mM S-glyceroyl-ethane-thiol in 2,6-lutidine and imidazole buffers near neutral pH. The size and yield of the olioglyceric acid products increased when the concentration of the thioester was increased. The relationship of these results to prebiotic polymer synthesis is discussed.

Poly(arylene ether-co-imidazole)s as toughness modifiers for epoxy resins

NASA Technical Reports Server (NTRS)

Mcdaniel, Patricia D. (Inventor); Connell, John W. (Inventor)

1994-01-01

A toughened epoxy was prepared by reacting an epoxy resin with a poly(arylene ether-co-imidazole)s (PAEI). The epoxy resin comprises N,N,N',N'tetraglycidyl-4,4'- methylenebisbenzenamine and 4-aminophenyl sulfone. The PAEI was prepared by reacting an aromatic bisphenol, a bisphenol imidazole, and an activated aromatic dihalide or dinitro compound in the presence of potassium carbonate in a polar aprotic solvent at an elevated temperature. The epoxies which were modified with these particular PAEI's showed a significant increase in toughness with only a 10 weight percent loading of the PAEI into the epoxy. These toughened epoxies were used to prepare composites and molded parts.

Stabilities of nitrogen containing heterocyclic radicals and geometrical influences on non-radiative processes in organic molecules

NASA Technical Reports Server (NTRS)

Evleth, E. M.

1971-01-01

Theoretical and experimental work on generating radicals by removal of a hydrogen atom from pyrrole, imidazole, indole, and carbazole is reported. Photophysical studies on indolizine and related aza-derivatives show that materials having large S2-S1 energy gaps might exhibit upper state fluorescence. Photodecomposition quantum yields of a series of sterically hindered p-aminobenzene diazonium cations in water were found structurally and wavelength dependent and unquenched in aqueous sodium bromide solutions. Photodecomposition of diazonium materials did not produce a metastable species with a longer lifetime than 1 msec.

Platinum-free catalysts for low temperature fuel cells

NASA Astrophysics Data System (ADS)

Lastovina, Tatiana; Pimonova, Julia; Budnyk, Andriy

2017-04-01

In this work, we have successfully prepared Zn/Co-N/C and Zn/Co-Fe/N/C composites, both derived from single zeolitic imidazolate framework (ZIF) precursor Zn/Co-ZIF containing equivalent quantities of Zn and Co metal sites. The composites were formed by pyrolysis of the precursor at 700 °C in inert gas atmosphere as such and after mixing it with Fe(II) salt and 1,10-phenontraline in ethanol. Catalytic tests for oxygen reduction reaction (ORR) in electrochemical cell demonstrated promising results allowing us to consider these composites as potential Pt-free catalysts for low temperature fuel cells.

Structures and electronic states of halogen-terminated graphene nano-flakes

NASA Astrophysics Data System (ADS)

Tachikawa, Hiroto; Iyama, Tetsuji

2015-12-01

Halogen-functionalized graphenes are utilized as electronic devices and energy materials. In the present paper, the effects of halogen-termination of graphene edge on the structures and electronic states of graphene flakes have been investigated by means of density functional theory (DFT) method. It was found that the ionization potential (Ip) and electron affinity of graphene (EA) are blue-shifted by the halogen termination, while the excitation energy is red-shifted. The drastic change showed a possibility as electronic devices such as field-effect transistors. The change of electronic states caused by the halogen termination of graphene edge was discussed on the basis of the theoretical results.

Deriving an atmospheric budget of total organic bromine using airborne in-situ measurements from the Western Pacific during SHIVA

NASA Astrophysics Data System (ADS)

Sala, S.; Bönisch, H.; Keber, T.; Oram, D. E.; Mills, G.; Engel, A.

2014-02-01

During the SHIVA (Stratospheric Ozone: Halogen Impacts in a Varying Atmosphere) project an extensive dataset of all halogen species relevant for the atmospheric budget of total organic bromine has been collected in the West Pacific region using the FALCON aircraft operated by the German Aerospace agency DLR (Deutsches Zentrum für Luft- und Raumfahrt) covering a vertical range from the planetary boundary layer up to the ceiling altitude of the aircraft of 13 km. In total, more than 700 measurements were performed with the newly developed fully-automated in-situ instrument GHOST-MS (Gas cHromatograph for the Observation of Tracers - coupled with a Mass Spectrometer) by the Goethe University of Frankfurt (GUF) and with the onboard whole-air sampler WASP with subsequent ground based state-of-the-art GC/MS analysis by the University of East Anglia (UEA). Both instruments yield good agreement for all major (CHBr3 and CH2Br2) and minor (CHBrCl, CHBrCl2 and CHBr2Cl) VSLS (very short-lived substances), at least at the level of their 2 σ measurement uncertainties. In contrast to the suggestion that the Western Pacific could be a major source region for VSLS (Pyle et al., 2011), we found only slightly enhanced mixing ratios of brominated halogen source gases relative to the levels reported in Montzka et al. (2011) for other tropical regions. A budget for total organic bromine, including all four halons,CH3Br and the VSLS, is derived for the upper troposphere, the input region for the TTL and thus also for the stratosphere, compiled from the SHIVA dataset. With exception of the two minor VSLS CHBrCl2 and CHBr2Cl, excellent agreement with the values reported in Montzka et al. (2011) is found, while being slightly higher than previous studies from our group based on balloon-borne measurements.

The relation between molecular structure and biological activity among mononitrophenols containing halogens

USGS Publications Warehouse

Applegate, Vernon C.; Johnson, B.G.H.; Smith, Manning A.

1966-01-01

The results of tests of the biological activity of certain nitrophenols containing halogen are reported. Some of these are shown to be significantly more toxic to larvae of the sea lamprey (Petromyzon marinus L.) than to fishes. It is proposed that the death of lamprey larvae exposed to these compounds results from an acute hypotension (shock) with concomitant circulatory and respiratory failure. Rainbow trout (Salmo gairdneri), on the other hand, appear to die, at higher concentrations of the toxin, due to a chemically-caused mechanical interference with respiration through the gills. A systematic series of studies of mononitrophenols containing halogens disclosed that those phenols having the nitro group in the para-position and a halogen atom or group in the meta-position are generally more toxic to lampreys than to fish. The halogens or halogen groups used in this study were fluorine, chlorine, bromine, and trifluormethyl. The same substituents in other positions only occasionally gave rise to selectively toxic compounds. The relationship between the selectively active class of nitrophenols containing halogens and other related structures is discussed.

Reversible capture and release of Cl 2 and Br 2 with a redox-active metal–organic framework

DOE PAGES

Tulchinsky, Yuri; Hendon, Christopher H.; Lomachenko, Kirill A.; ...

2017-03-28

Extreme toxicity, corrosiveness, and volatility pose serious challenges for the safe storage and transportation of elemental chlorine and bromine, which play critical roles in the chemical industry. Solid materials capable of forming stable nonvolatile compounds upon reaction with elemental halogens may partially mitigate these challenges by allowing safe halogen release on demand. Here we demonstrate that elemental halogens quantitatively oxidize coordinatively unsaturated Co(II) ions in a robust azolate metal-organic framework (MOF) to produce stable and safe-to-handle Co(III) materials featuring terminal Co(III)-halogen bonds. Thermal treatment of the oxidized MOF causes homolytic cleavage of the Co(III)-halogen bonds, reduction to Co(II), and concomitantmore » release of elemental halogens. The reversible chemical storage and thermal release of elemental halogens occur with no significant losses of structural integrity, as the parent cobaltous MOF retains its crystallinity and porosity even after three oxidation/reduction cycles. Finally, these results highlight a material operating via redox mechanism that may find utility in the storage and capture of other noxious and corrosive gases.« less

40 CFR 180.601 - Cyazofamid; tolerances for residues.

Code of Federal Regulations, 2010 CFR

2010-07-01

... residues of cyazofamid, 4-chloro-2-cyano-N,N-dimethyl-5-(4-methylphenyl)-1H-imidazole-1-sulfonamide, and its metabolite CCIM, 4-chloro-5-(4-methylphenyl)-1H-imidazole-2-carbonitrile, expressed as cyazofamid... established for the combined residues of cyazofamid, 4-chloro-2-cyano- N,N-dimethyl-5-(4-methylphenyl)-1H...

Model studies in cytochrome P-450-mediated toxicity of halogenated compounds: radical processes involving iron porphyrins.

PubMed Central

Brault, D

1985-01-01

Haloalkane toxicity originates from attack on biological targets by reactive intermediates derived from haloalkane metabolism by a hemoprotein, cytochrome P-450. Carbon-centered radicals and their peroxyl derivatives are most likely involved. The reactions of iron porphyrin--a model for cytochrome P-450--with various carbon-centered and peroxyl radicals generated by pulse radiolysis are examined. Competition between iron porphyrin and unsaturated fatty acids for attack by peroxyl radicals is pointed out. These kinetic data are used to derive a model for toxicity of haloalkanes with particular attention to carbon tetrachloride and halothane. The importance of local oxygen concentration and structural arrangement of fatty acids around cytochrome P-450 is emphasized. PMID:3007100

E.S.R., magnetic, electronic and superoxide dismutase studies of imidazolate-bridged Cu(II)-Cu(II) complexes with ethylenediamine as capping ligand.

PubMed

Patel, R N; Singh, Nripendra; Shukla, K K; Gundla, V L N

2005-06-01

X-band E.S.R., magnetic and electronic spectra of some imidazolate-bridged homometallic complexes [(en)2Cu-R-Im-Cu(en)2](ClO4)3 where en, ethylenediamine; R-ImH, R = H imidazole (ImH); if R = CH3, 2-methylimidazole (M-ImH) and if R = C2H5, 2-ethylimidazole (E-ImH), and mononuclear complexes [(en)Cu-dien](ClO4)2 and [(en)Cu-PMDT](ClO4)2 where dien, diethylenetriamine; PMDT, pentamethyldiethylenetriamine have been described. Superoxide dismutase (SOD) activity has also been measured and compared with earlier reported complexes. In frozen solution at 77 K, the spectra show axial symmetry with a d(x2-y2) ground state. Difference in lambda(max) between mononuclear and binuclear complexes was found to be approximately 65-75 nm. Magnetic susceptibility and E.S.R. spectral measurements for all these binuclear complexes revealed that the copper(II) ions are involved in antiferromagnetic exchange interactions propagated by the imidazolate bridge.

Construction, Structural Diversity and Properties of Five Coordination Polymers Based on 5-Nitroisophthalate and Bis(imidazole) Linkers

NASA Astrophysics Data System (ADS)

Arıcı, Mürsel

2018-06-01

Five coordination polymers, namely, [Cd(μ3-5-nip)(μ-obix)]n (1), [Co(μ3-5-nip)(μ-obix)]n (2), [Zn(μ-5-nip)(μ-obix)]n (3 and 4) and [Cd(μ-5-nip)(μ-bisobix)]n (5) (5-nip: 5-nitroisophthalate, obix: 1,2-bis(imidazol-1ylmethyl)benzene, bisobix: 1,2-bis(2-isopropylimidazol-1ylmethyl)benzene) were hydrothermally synthesized and characterized by IR spectroscopy, elemental analysis, single crystal and powder X-ray diffraction and thermal analysis (TG/DTA). X-ray results showed that the complexes displayed structural diversity depending on metal ions and conformations of bis(imidazole) linkers. Complexes 1 and 2 were 1D structures and obix ligand displayed cis-conformation. Complexes 3 and 4 exhibited 2D and 3D structures with same components depending on obix conformation. In complex 5, 3D+3D→3D interpenetrated structure was obtained with dia topology when bisobix having sterically hindered groups on imidazole rings was used. Moreover, thermal, photoluminescence and optical properties of the complexes were also investigated.

Continuous synthesis of peralkylated imidazoles and their transformation into ionic liquids with improved (electro)chemical stabilities.

PubMed

Maton, Cedric; De Vos, Nils; Roman, Bart I; Vanecht, Evert; Brooks, Neil R; Binnemans, Koen; Schaltin, Stijn; Fransaer, Jan; Stevens, Christian V

2012-09-17

A versatile and efficient method to synthesize tetrasubstituted imidazoles via a one-pot modified Debus-Radziszewski reaction and their subsequent transformation into the corresponding imidazolium ionic liquids is reported. The tetrasubstituted imidazoles were also synthesized by means of a continuous flow process. This straightforward synthetic procedure allows for a fast and selective synthesis of tetrasubstituted imidazoles on a large scale. The completely substituted imidazolium dicyanamide and bis(trifluoromethylsulfonyl)imide salts were obtained via a metathesis reaction of the imidazolium iodide salts. The melting points and viscosities are of the same order of magnitude as for their non-substituted analogues. In addition to the superior chemical stability of these novel ionic liquids, which allows them to be applied in strong alkaline media, the improved thermal and electrochemical stabilities of these compounds compared with conventional imidazolium ionic liquids is also demonstrated by thermogravimetrical analysis (TGA) and cyclic voltammetry (CV). Although increased substitution of the ionic liquids does not further increase thermal stability, a definite increase in cathodic stability is observable. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Trapped in imidazole: how to accumulate multiple photoelectrons on a black-absorbing ruthenium complex.

PubMed

Zedler, Linda; Kupfer, Stephan; de Moraes, Inês Rabelo; Wächtler, Maria; Beckert, Rainer; Schmitt, Michael; Popp, Jürgen; Rau, Sven; Dietzek, Benjamin

2014-03-24

Ruthenium dyes incorporating a 4H-imidazole chromophore as a ligand exhibit a spectrally broad absorption in the UV/Vis region. Furthermore, they show the ability to store two electrons within the 4H-imidazole ligand. These features render them promising molecular systems, for example, as inter- or intramolecular electron relays. To optimize the structures with respect to their electron-storage capability, it is crucial to understand the impact of structural changes accompanying photoinduced charge transfer in the electronic intermediates of multistep electron-transfer processes. The photophysical properties of these (reactive) intermediates might impact the function of the molecular systems quite substantially. However, the spectroscopic study of short-lived intermediates in stepwise multielectron-transfer processes is experimentally challenging. To this end, this contribution reports on the electrochemical generation of anions identical to intermediate structures and their spectroscopic characterization by in situ resonance Raman and UV/Vis spectroelectrochemistry and computational methods. Thereby, an efficient two-electron pathway to the 4H-imidazole electron-accepting ligand is identified. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In-situ complex with by-product HCl and release chloride ions to dissolve aramid.

PubMed

Dai, Yu; Cheng, Zheng; Yuan, Yihao; Meng, Chenbo; Qin, Jiaqiang; Liu, Xiangyang

2018-06-20

Because of the strong hydrogen-bond interaction among macromolecular chains, addition of chloride salts is generally needed to offer Cl- ions for dissolution of aromatic polyamides. In this paper, poly-(benzimidazole-terephthalamide) which complexed with by-product HCl during polymerization (PABI-HCl) was prepared and imidazole compound as cosolvent was added into dimethylacetamide (DMAc) to dissolve PABI-HCl. Due to stronger affinity to protons, imidazole compound could in-situ complex with HCl of PABI-HCl and form imidazolium hydrochloride. Then imidazolium hydrochloride would ionize and produce much free Cl- ions which acted as stronger hydrogen-bond acceptor to disrupt interaction among macromolecular chains. As a result, solubility of PABI-HCl in DMAc was improved significantly in existence of small amount of imidazole compound. Moreover, DMAc-imidazole mixture was utlized for synthesis of different kinds of aramids and no precipitation was observed with progress of the reaction. So the mixture was suitable to be utlized as solvent for polymerization of aramid. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

40 CFR 63.128 - Transfer operations provisions-test methods and procedures.

Code of Federal Regulations, 2013 CFR

2013-07-01

... using a scrubber or other halogen reduction device to reduce the vent stream halogen atom mass emission...)(2) shall determine the halogen atom mass emission rate prior to the combustor according to the...

40 CFR 63.128 - Transfer operations provisions-test methods and procedures.

Code of Federal Regulations, 2011 CFR

2011-07-01

... using a scrubber or other halogen reduction device to reduce the vent stream halogen atom mass emission...)(2) shall determine the halogen atom mass emission rate prior to the combustor according to the...

40 CFR 63.128 - Transfer operations provisions-test methods and procedures.

Code of Federal Regulations, 2010 CFR

2010-07-01

... using a scrubber or other halogen reduction device to reduce the vent stream halogen atom mass emission...)(2) shall determine the halogen atom mass emission rate prior to the combustor according to the...

40 CFR 63.128 - Transfer operations provisions-test methods and procedures.

Code of Federal Regulations, 2014 CFR

2014-07-01

... using a scrubber or other halogen reduction device to reduce the vent stream halogen atom mass emission...)(2) shall determine the halogen atom mass emission rate prior to the combustor according to the...

40 CFR 63.128 - Transfer operations provisions-test methods and procedures.

Code of Federal Regulations, 2012 CFR

2012-07-01

... using a scrubber or other halogen reduction device to reduce the vent stream halogen atom mass emission...)(2) shall determine the halogen atom mass emission rate prior to the combustor according to the...

Magnesium Bisamide-Mediated Halogen Dance of Bromothiophenes.

PubMed

Yamane, Yoshiki; Sunahara, Kazuhiro; Okano, Kentaro; Mori, Atsunori

2018-03-16

A magnesium bisamide-mediated halogen dance of bromothiophenes is described. The thienylmagnesium species generated in situ is more stable than the corresponding thienyllithium species, which was applied to trap the transient anion species with several electrophiles, such as allyl iodide, phenyl isocyanate, and tributylstannyl chloride. The utility of the magnesium bisamide-mediated halogen dance is useful in the concise synthesis of a medicinally advantageous compound via a one-pot, ester-directed halogen dance/Negishi cross coupling.

Degradation of halogenated aliphatic compounds by Xanthobacter autotrophicus GJ10.

PubMed Central

Janssen, D B; Scheper, A; Dijkhuizen, L; Witholt, B

1985-01-01

A bacterium that is able to utilize a number of halogenated short-chain hydrocarbons and halogenated carboxylic acids as sole carbon source for growth was identified as a strain of Xanthobacter autotrophicus. The organism constitutively produces two different dehalogenases. One enzyme is specific for halogenated alkanes, whereas the other, which is more heat stable and has a higher pH optimum, is specific for halogenated carboxylic acids. Haloalkanes were hydrolyzed in cell extracts to produce alcohols and halide ions, and a route for the metabolism of 1,2-dichlorethane is proposed. Both dehalogenases show a broad substrate specificity, allowing the degradation of bromine- and chlorine-substituted organic compounds. The results show that X. autotrophicus may play a role in the degradation of organochlorine compounds and that hydrolytic dehalogenases may be involved in the microbial metabolism of short-chain halogenated hydrocarbons in microorganisms. Images PMID:3994371

Evidence for Interfacial Halogen Bonding.

PubMed

Swords, Wesley B; Simon, Sarah J C; Parlane, Fraser G L; Dean, Rebecca K; Kellett, Cameron W; Hu, Ke; Meyer, Gerald J; Berlinguette, Curtis P

2016-05-10

A homologous series of donor-π-acceptor dyes was synthesized, differing only in the identity of the halogen substituents about the triphenylamine (TPA; donor) portion of each molecule. Each Dye-X (X=F, Cl, Br, and I) was immobilized on a TiO2 surface to investigate how the halogen substituents affect the reaction between the light-induced charge-separated state, TiO2 (e(-) )/Dye-X(+) , with iodide in solution. Transient absorption spectroscopy showed progressively faster reactivity towards nucleophilic iodide with more polarizable halogen substituents: Dye-F < Dye-Cl < Dye-Br < Dye-I. Given that all other structural and electronic properties for the series are held at parity, with the exception of an increasingly larger electropositive σ-hole on the heavier halogens, the differences in dye regeneration kinetics for Dye-Cl, Dye-Br, and Dye-I are ascribed to the extent of halogen bonding with the nucleophilic solution species. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electron-paramagnetic-resonance studies of leghaemoglobins from soya-bean and cowpea root nodules. Identification of nitrosyl-leghaemoglobin in crude leghaemoglobin preparations

PubMed Central

Maskall, C. Sidney; Gibson, John F.; Dart, Peter J.

1977-01-01

1. Leghaemoglobins from soya-bean (Glycine max) and cowpea (Vigna unguiculata) root nodules were purified by chromatography on DEAE-cellulose phosphate columns at pH8.0 and pH5.8, to avoid the relatively low pH (5.2) commonly used to purify these proteins. 2. E.p.r. (electron-paramagnetic-resonance) spectra of the fluoride, azide, hydroxide and cyanide complexes of these ferric leghaemoglobins were very similar to the spectra of the corresponding myoglobin derivatives, indicating that the immediate environment of the iron in leghaemoglobin and myoglobin is similar, an imidazole moiety of histidine being the proximal ligand to the haem iron [cf. Appleby, Blumberg, Peisach, Wittenberg & Wittenberg (1976) J. Biol. Chem. 251, 6090–6096]. 3. E.p.r. spectra of the acid-metleghaemoglobins showed prominent high-spin features very near g=6 and g=2 and, unlike myoglobin, small low-spin absorptions near g=2.26, 2.72 and 3.14. The width of the g=6 absorption derivative at 10–20K was about 4–4.5mT, similar to the value for acid-methaemoglobin. In contrast, a recently published (Appleby et al., 1976) spectrum of acid-metleghaemoglobin a had less high-spin character and a much broader absorption derivative around g=6. 4. E.p.r. spectra of ferric leghaemoglobin nicotinate and imidazole complexes suggest that the low-spin absorption near g=3.14 can be attributed to a trace of ferric leghaemoglobin nicotinate, and those near g=2.26 and 2.72 are from an endogenous dihistidyl haemichrome. 5. A large e.p.r. signal at g=2 in all samples of crude leghaemoglobin was shown to be from nitrosyl-leghaemoglobin. A soya-bean sample contained 27±3% of the latter. A previously unidentified form of soya-bean ferrous leghaemoglobin a was shown to be its nitrosyl derivative. If this is not an artifact, and occurs in the root nodule, the nitrosyl radical may interfere with the function of leghaemoglobin. PMID:23110

Preparation of an aminopropyl imidazole-modified silica gel as a sorbent for solid-phase extraction of carboxylic acid compounds and polycyclic aromatic hydrocarbons.

PubMed

Wang, Na; Guo, Yong; Wang, Licheng; Liang, Xiaojing; Liu, Shujuan; Jiang, Shengxiang

2014-05-21

In this paper, a kind of aminopropyl imidazole-modified silica sorbent was synthesized and used as a solid-phase extraction (SPE) sorbent for the determination of carboxylic acid compounds and polycyclic aromatic hydrocarbons (PAHs). The resultant aminopropyl imidazole-modified silica sorbent was characterized by Fourier transform infrared spectroscopy (FT-IR) and elemental analysis (EA) to ensure the successful binding of aminopropyl imidazole on the surface of silica gel. Then the aminopropyl imidazole-modified silica sorbent served as a SPE sorbent for the enrichment of carboxylic acid compounds and PAHs. The new sorbent exhibited high extraction efficiency towards the tested compounds and the results show that such a sorbent can offer multiple intermolecular interactions: electrostatic, π-π, and hydrophobic interactions. Several parameters affecting the extraction recovery, such as the pH of sample solution, the pH of eluent, the solubility of eluent, the volume of eluent, and sample loading, were also investigated. Under the optimized conditions, the proposed method was applied to the analysis of four carboxylic acid compounds and four PAHs in environmental water samples. Good linearities were obtained for all the tested compounds with R(2) larger than 0.9903. The limits of detection were found to be in the range of 0.0065-0.5 μg L(-1). The recovery values of spiked river water samples were from 63.2% to 112.3% with relative standard deviations (RSDs) less than 10.1% (n = 4).

Aerosol-halogen interaction: Change of physico-chemical properties of SOA by naturally released halogen species

NASA Astrophysics Data System (ADS)

Ofner, J.; Balzer, N.; Buxmann, J.; Grothe, H.; Krüger, H.; Platt, U.; Schmitt-Kopplin, P.; Zetzsch, C.

2011-12-01

Reactive halogen species are released by various sources like photo-activated sea-salt aerosol or salt pans and salt lakes. These heterogeneous release mechanisms have been overlooked so far, although their potential of interaction with organic aerosols like Secondary Organic Aerosol (SOA), Biomass Burning Organic Aerosol (BBOA) or Atmospheric Humic LIke Substances (HULIS) is completely unknown. Such reactions can constitute sources of gaseous organo-halogen compounds or halogenated organic particles in the atmospheric boundary layer. To study the interaction of organic aerosols with reactive halogen species (RHS), SOA was produced from α-pinene, catechol and guaiacol using an aerosol smog-chamber. The model SOAs were characterized in detail using a variety of physico-chemical methods (Ofner et al., 2011). Those aerosols were exposed to molecular halogens in the presence of UV/VIS irradiation and to halogens, released from simulated natural halogen sources like salt pans, in order to study the complex aerosol-halogen interaction. The heterogeneous reaction of RHS with those model aerosols leads to different gaseous species like CO2, CO and small reactive/toxic molecules like phosgene (COCl2). Hydrogen containing groups on the aerosol particles are destroyed to form HCl or HBr, and a significant formation of C-Br bonds could be verified in the particle phase. Carbonyl containing functional groups of the aerosol are strongly affected by the halogenation process. While changes of functional groups and gaseous species were visible using FTIR spectroscopy, optical properties were studied using Diffuse Reflectance UV/VIS spectroscopy. Overall, the optical properties of the processed organic aerosols are significantly changed. While chlorine causes a "bleaching" of the aerosol particles, bromine shifts the maximum of UV/VIS absorption to the red end of the UV/VIS spectrum. Further physico-chemical changes were recognized according to the aerosol size-distributions or the averaged carbon oxidation state (OSc). The heterogeneous reaction of SOA with molecular halogens released from the simulated salt-pan at different simulated environmental conditions leads to changes of several physico-chemical features of the aerosol. However, the halogen release mechanisms are also affected by the presence of organic aerosols. One order of magnitude less BrO was detected by an active Differential Optical Absorption Spectroscopy (DOAS) instrument in the presence of SOA compared to experiments without SOA. This work was supported by the German Research Foundation within the HALOPROC project. Ofner, J., Krüger, H.-U., Grothe, H., Schmitt-Kopplin, P., Whitmore, K., and Zetzsch, C. (2011), Atmos. Chem. Phys., 11, 1-15.

The metabolic response in fish to mildly elevated water temperature relates to species-dependent muscular concentrations of imidazole compounds and free amino acids.

PubMed

Geda, Fikremariam; Declercq, Annelies M; Remø, Sofie C; Waagbø, Rune; Lourenço, Marta; Janssens, Geert P J

2017-04-01

Fish species show distinct differences in their muscular concentrations of imidazoles and free amino acids (FAA). This study was conducted to investigate whether metabolic response to mildly elevated water temperature (MEWT) relates to species-dependent muscular concentrations of imidazoles and FAA. Thirteen carp and 17 Nile tilapia, housed one per aquarium, were randomly assigned to either acclimation (25°C) or MEWT (30°C) for 14 days. Main muscular concentrations were histidine (HIS; P<0.001) in carp versus N-α-acetylhistidine (NAH; P<0.001) and taurine (TAU; P=0.001) in tilapia. Although the sum of imidazole (HIS+NAH) and TAU in muscle remained constant over species and temperatures (P>0.05), (NAH+HIS)/TAU ratio was markedly higher in carp versus tilapia, and decreased with MEWT only in carp (P<0.05). Many of the muscular FAA concentrations were higher in carp than in tilapia (P<0.05). Plasma acylcarnitine profile suggested a higher use of AA and fatty acids in carp metabolism (P<0.05). On the contrary, the concentration of 3-hydroxyisovalerylcarnitine, a sink of leucine catabolism, (P=0.009) pointed to avoidance of leucine use in tilapia metabolism. Despite a further increase of plasma longer-chain acylcarnitines in tilapia at MEWT (P=0.009), their corresponding beta-oxidation products (3-hydroxy-longer-chain acylcarnitines) remained constant. Together with higher plasma non-esterified fatty acids (NEFA) in carp (P=0.001), the latter shows that carp, being a fatter fish, more readily mobilises fat than tilapia at MEWT, which coincides with more intensive muscular mobilization of imidazoles. This study demonstrates that fish species differ in their metabolic response to MEWT, which is associated with species-dependent changes in muscle imidazole to taurine ratio. Copyright © 2017 Elsevier Ltd. All rights reserved.

Organic Halogen and Related Trace Gases in the Tropical Atmosphere: Results from Recent Airborne Campaigns Over the Pacific

NASA Astrophysics Data System (ADS)

Atlas, E. L.; Navarro, M. A.; Donets, V.; Schauffler, S.; Lueb, R.; Hendershot, R.; Gabbard, S.; Hornbrook, R. S.; Apel, E. C.; Riemer, D. D.; Pan, L.; Salawitch, R. J.; Nicely, J. M.; Montzka, S. A.; Miller, B.; Moore, F. L.; Elkins, J. W.; Hintsa, E. J.; Campos, T. L.; Quack, B.; Zhu, X.; Pope, L.

2014-12-01

Organic halogen gases, especially containing bromine and iodine, play a significant role as precursors to active halogen chemistry and ozone catalytic loss. Much of the reactive organic halogen originates from biological processes in the surface ocean, which can be quite variable by season and location. The tropics and coastal margins are potentially important sources that are being examined. The recent coordinated CONTRAST/ATTREX/CAST missions were conducted in the Western Tropical Pacific, a region that is a major transport pathway for tropospheric air entering the stratosphere. One of the goals of the missions was to identify sources, distributions, and transport of organic halogens from the ocean surface into the tropical lower stratosphere. The missions were conducted during the NH winter season, Jan-Feb, 2014. In this presentation, we will discuss the distributions and variability of organic halogen gases in the study region and will examine the input of organic halogen species into the Tropical Tropopause Layer (TTL). Comparison with other tracers, such as methyl nitrate and NMHC, will help identify source regions for these gases. We will focus on the measurements obtained in the CONTRAST and ATTREX missions with data from in-situ GC/MS measurements and whole air samples collected on the NSF GV and NASA Global Hawk aircraft. Comparisons with other recent airborne campaigns, such as HIPPO and TC4, and with several ship-based studies will provide an additional context for evaluating the variability of organic halogen species in the tropical atmosphere and their role in transporting reactive halogen compounds into the UT/LS.

Angles between orthogonal spd bond orbitals with maximum strength.

PubMed

Pauling, L

1976-05-01

An equation is derived for values of bond angles for two equivalent best spd hybrid bond orbitals with given amounts of s, p, and d character, and is applied in the discussion of structures of transargononic compounds, including the xenon and halogen fluorides. Bond orbitals with a rather small amount of d character tend to lie at angles 90 degrees and 180 degrees , and those with a larger amount, at somewhat smaller angles.

Survey of less-inflammable hydraulic fluids for aircraft

NASA Technical Reports Server (NTRS)

Drake, Wray V; Drell, I L

1950-01-01

A survey of current information on civil and military development of less-inflammable hydraulic fluids for aircraft is presented. Types of less-inflammable fluid reported include: glycol derivative, water base, silicone, ester, and halogenated compound. Specification requirements, physical and chemical properties, hydraulic-system test results, and advantages and disadvantages of various hydraulic fluids are discussed. For completely satisfactory service, some modification of currently available fluids or of present hydraulic-system parts still appears necessary.

(2E)-3-[4-(Benz-yloxy)phen-yl]-1-(2,6-dichloro-3-fluoro-phen-yl)prop-2-en-1-one.

PubMed

Praveen, Aletti S; Yathirajan, Hemmige S; Gerber, Thomas; van Brecht, Benjamin; Betz, Richard

2012-12-01

In the title compound, C22H15Cl2FO2, a chalcone derivative featuring a threefold-halogenated aromatic substituent, the conformation about the C=C bond is E. In the crystal C-H⋯F and C-H⋯Cl contacts connect the mol-ecules into undulating sheets parallel to (101). In addition, C-H⋯π inter-actions are also present.

Asymmetric Synthesis of 1,2,9,9a-Tetrahydrocyclopropa[c]benzo[e]indol-4-one (CBI)

PubMed Central

Lajiness, James P.; Boger, Dale L.

2011-01-01

A short, asymmetric synthesis of the 1,2,9,9a-tetrahydrocyclopropa[c]benzo[e]indol-4-one (CBI) analogue of the CC-1065 and duocarmycin DNA alkylation subunits is described. Treatment of iodo-epoxide 5, prepared by late-stage alkylation of 4 with (S)-glycidal-3-nosylate, with EtMgBr at room temperature directly provides the optically pure alcohol 6 in 87% yield (99% ee) derived from selective metal–halogen exchange and subsequent regioselective intramolecular 6-endo-tet cyclization. The use of MeMgBr or i-PrMgBr also provides the product in high yields (82–87%), but requires larger amounts of the Grignard reagent to effect metal–halogen exchange and cyclization. Direct transannular spirocyclization of 7 following O-debenzylation of 6 provides N-Boc-CBI. This approach represents the most efficient (9-steps, 31% overall) and effective (99% ee) route to the optically pure CBI alkylation subunit yet described. PMID:21192653

Development of a flameproof elastic elastomeric fiber

NASA Technical Reports Server (NTRS)

Howarth, J. T.; Nilgrom, J.; Massucco, A.; Sheth, S. G.; Dawn, F. S.

1971-01-01

Various flexible polyurethane structures containing halogen were synthesized from polyesters derived from aliphatic or aromatic polyols and dibasic acids. Aliphatic halide structures could not be used because they are unstable at the required reaction temperatures, giving of hydrogen halide which hydrolyzes the ester linkages. In contract, halogen-containing aromatic polyols were stable and satisfactory products were made. The most promising composition, a brominated neopentyl glycol capped with toluene disocyanate, was used as a conventional diisocyanate, in conjunction with hydroxy-terminated polyethers or polyesters to form elastomeric urethanes containing about 10% bromine with weight. Products made in this manner will not burn in air, have an oxygen index value of about 25, and have tensile strength values of about 5,000 psi at 450% elongation. The most efficient additives for imparting flame retardancy to Spandex urethanes are aromatic halides and the most effective of these are the bromide compounds. Various levels of flame retardancy have been achieved depending on the levels of additives used.

Photocrystallographic observation of halide-bridged intermediates in halogen photoeliminations.

PubMed

Powers, David C; Anderson, Bryce L; Hwang, Seung Jun; Powers, Tamara M; Pérez, Lisa M; Hall, Michael B; Zheng, Shao-Liang; Chen, Yu-Sheng; Nocera, Daniel G

2014-10-29

Polynuclear transition metal complexes, which frequently constitute the active sites of both biological and chemical catalysts, provide access to unique chemical transformations that are derived from metal-metal cooperation. Reductive elimination via ligand-bridged binuclear intermediates from bimetallic cores is one mechanism by which metals may cooperate during catalysis. We have established families of Rh2 complexes that participate in HX-splitting photocatalysis in which metal-metal cooperation is credited with the ability to achieve multielectron photochemical reactions in preference to single-electron transformations. Nanosecond-resolved transient absorption spectroscopy, steady-state photocrystallography, and computational modeling have allowed direct observation and characterization of Cl-bridged intermediates (intramolecular analogues of classical ligand-bridged intermediates in binuclear eliminations) in halogen elimination reactions. On the basis of these observations, a new class of Rh2 complexes, supported by CO ligands, has been prepared, allowing for the isolation and independent characterization of the proposed halide-bridged intermediates. Direct observation of halide-bridged structures establishes binuclear reductive elimination as a viable mechanism for photogenerating energetic bonds.

Ultrafast Solvation Dynamics and Vibrational Coherences of Halogenated Boron-Dipyrromethene Derivatives Revealed through Two-Dimensional Electronic Spectroscopy.

PubMed

Lee, Yumin; Das, Saptaparna; Malamakal, Roy M; Meloni, Stephen; Chenoweth, David M; Anna, Jessica M

2017-10-18

Boron-dipyrromethene (BODIPY) chromophores have a wide range of applications, spanning areas from biological imaging to solar energy conversion. Understanding the ultrafast dynamics of electronically excited BODIPY chromophores could lead to further advances in these areas. In this work, we characterize and compare the ultrafast dynamics of halogenated BODIPY chromophores through applying two-dimensional electronic spectroscopy (2DES). Through our studies, we demonstrate a new data analysis procedure for extracting the dynamic Stokes shift from 2DES spectra revealing an ultrafast solvent relaxation. In addition, we extract the frequency of the vibrational modes that are strongly coupled to the electronic excitation, and compare the results of structurally different BODIPY chromophores. We interpret our results with the aid of DFT calculations, finding that structural modifications lead to changes in the frequency, identity, and magnitude of Franck-Condon active vibrational modes. We attribute these changes to differences in the electron density of the electronic states of the structurally different BODIPY chromophores.

Blue-light emitting electrochemical cells comprising pyrene-imidazole derivatives

NASA Astrophysics Data System (ADS)

Lee, Hyeonji; Sunesh, Chozhidakath Damodharan; Subeesh, Madayanad Suresh; Choe, Youngson

2018-04-01

Light-emitting electrochemical cells (LECs), the next-generation lighting sources are the potential replacements for organic light-emitting diodes (OLEDs). In recent years, organic small molecules (SMs) have established the applicability in solid-state lighting, and considered as prospective active materials for LECs with higher device performance. Here, we describe the synthesis of pyrene-imidazole based SMs, PYR1, and PYR2 that differ by one pyrene unit and their characterization by various spectroscopic methods. To investigate the thermal, photophysical, and electrochemical properties of the two synthesized compounds, we performed thermogravimetric, UV-visible, photoluminescence (PL), and voltammetric measurements. The photoluminescence (PL) emission spectra of PYR1 and PYR2 measured in the acetonitrile solution, where PYR1 and PYR2 emit in the blue spectral region with peaks aligned at 383 nm and 389 nm, respectively. The fabricated LEC devices exhibited broader electroluminescence (EL) spectra with a significant red shift of the emission maxima to 446 nm and 487 nm, with CIE coordinates of (0.17, 0.18) and (0.18, 0.25) for PYR1 and PYR2, respectively. The LECs based on PYR1 and PYR2 produced maximum brightness values of 180 and 72 cd m-2 and current densities of 55 and 27 mA cm-2, respectively.

Design of Zeolitic Imidazolate Framework Derived Nitrogen-Doped Nanoporous Carbons Containing Metal Species for Carbon Dioxide Fixation Reactions.

PubMed

Toyao, Takashi; Fujiwaki, Mika; Miyahara, Kenta; Kim, Tae-Ho; Horiuchi, Yu; Matsuoka, Masaya

2015-11-01

Various N-doped nanoporous carbons containing metal species were prepared by direct thermal conversion of zeolitic imidazolate frameworks (ZIFs; ZIF-7, -8, -9, and -67) at different temperatures (600, 800, and 1000 °C). These materials were utilized as bifunctional acid-base catalysts to promote the reaction of CO2 with epoxides to form cyclic carbonates under 0.6 MPa of CO2 at 80 °C. The catalyst generated by thermal conversion of ZIF-9 at 600 °C (C600-ZIF-9) was found to exhibit a higher catalytic activity than the other ZIFs, other conventional catalysts, and other metal-organic framework catalysts. The results of various characterization techniques including elemental analysis, X-ray diffraction, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and transmission electron microscopy show that C600-ZIF-9 contains partly oxidized Co nanoparticles and N species. Temperature-programmed desorption measurements by using CO2 and NH3 as probe molecules revealed that C600-ZIF-9 has both Lewis acid and Lewis base catalytic sites. Finally, the substrate scope was extended to seven other kinds of epoxides. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Porous CNTs/Co Composite Derived from Zeolitic Imidazolate Framework: A Lightweight, Ultrathin, and Highly Efficient Electromagnetic Wave Absorber.

PubMed

Yin, Yichao; Liu, Xiaofang; Wei, Xiaojun; Yu, Ronghai; Shui, Jianglan

2016-12-21

Porous carbon nanotubes/cobalt nanoparticles (CNTs/Co) composite with dodecahedron morphology was synthesized by in situ pyrolysis of the Co-based zeolitic imidazolate framework in a reducing atmosphere. The morphology and microstructure of the composite can be well tuned by controlling the pyrolysis conditions. At lower pyrolysis temperature, the CNTs/Co composite is composed of well-dispersed Co nanoparticles and short CNT clusters with low graphitic degree. The increase of pyrolysis temperature/time promotes the growth and graphitization of CNTs and leads to the aggregation of Co nanoparticles. The optimized CNTs/Co composite exhibits strong dielectric and magnetic losses as well as a good impedance matching property. Interestingly, the CNTs/Co composite displays extremely strong electromagnetic wave absorption with a maximum reflection loss of -60.4 dB. More importantly, the matching thickness of the absorber is as thin as 1.81 mm, and the filler loading of composite in the matrix is only 20 wt %. The highly efficient absorption is closely related to the well-designed structure and the synergistic effect between CNTs and Co nanoparticles. The excellent absorbing performance together with lightweight and ultrathin thickness endows the CNTs/Co composite with the potential for application in the electromagnetic wave absorbing field.

Peptide selectivity between the PDZ domains of human pregnancy-related serine proteases (HtrA1, HtrA2, HtrA3, and HtrA4) can be reshaped by different halogen probes.

PubMed

Sun, Mei-Ling; Sun, Li-Mei; Wang, Yong-Qing

2018-06-01

The human HtrA family of serine proteases (HtrA1, HtrA2, HtrA3, and HtrA4) are the key enzymes associated with pregnancy and closely related to the development and progression of many pathological events. Previously, it was found that halogen substitution at the indole moiety of peptide Trp-1 residue can form a geometrically satisfactory halogen bond with the Drosophila discs large, zona occludens-1 (PDZ) domain of HtrA proteases. Here, we attempt to systematically investigate the effect of substitution with 4 halogen types and 2 indole positions on the binding affinity and specificity of peptide ligands to the 4 HtrA PDZ domains. The complex structures, interaction energies, halogen-bonding strength, and binding affinity of domain-peptide systems were modeled, analyzed, and measured via computational modeling and fluorescence-based assay. It is revealed that there is a compromise between the local rearrangement of halogen bond involving different halogen atoms and the global optimization of domain-peptide interaction; the substitution position is fundamentally important for peptide-binding affinity, while the halogen type can effectively shift peptide selectivity between the 4 domains. The HtrA1-PDZ and HtrA4-PDZ as well as HtrA2-PDZ and HtrA3-PDZ respond similarly to different halogen substitutions of peptide; -Br substitution at R2-position and -I substitution at R4-position are most effective in improving peptide selectivity for HtrA1-PDZ/HtrA4-PDZ and HtrA2-PDZ/HtrA3-PDZ, respectively; -F substitution would not address substantial effect on peptide selectivity for all the 4 domains. Consequently, the binding affinities of a native peptide ligand DSRIWWV -COOH as well as its 4 R2-halogenated counterparts were determined as 1.9, 1.4, 0.5, 0.27, and 0.92 μM, which are basically consistent with computational analysis. This study would help to rationally design selective peptide inhibitors of HtrA family members by using different halogen substitutions. Copyright © 2017 John Wiley & Sons, Ltd.

Derivatization in gas chromatographic determination of phenol and aniline traces in aqueous media

NASA Astrophysics Data System (ADS)

Gruzdev, I. V.; Zenkevich, I. G.; Kondratenok, B. M.

2015-06-01

Substituted anilines and phenols are the most common hydrophilic organic environmental toxicants. The principles of gas chromatographic determination of trace amounts of these compounds in aqueous media at concentrations <=0.1 μg litre-1 based on synthesis of their derivatives (derivatization) directly in the aqueous phase are considered. Conversion of relatively hydrophilic analytes into more hydrophobic derivatives makes it possible to achieve such low detection limits and optimize the protocols of extractive preconcentration and selective chromatographic detection. Among the known reactions, this condition is best met by electrophilic halogenation of compounds at the aromatic moiety. The bibliography includes 177 references.

Deriving an atmospheric budget of total organic bromine using airborne in-situ measurements of brominated hydrocarbons in the Western Pacific during SHIVA

NASA Astrophysics Data System (ADS)

Sala, Stephan; Bönisch, Harald; Keber, Timo; Oram, Dave; Mills, Graham; Engel, Andreas

2014-05-01

Halogenated hydrocarbons play a major role as precursors for stratospheric ozone depletion. Released from the surface in the troposphere, the halocarbons reach the stratosphere via transport through the tropical tropopause layer. The contribution of the so called very short lived species (VSLS), having atmospheric lifetimes of less than half a year as sources gases for stratospheric bromine is significant. Source gas observations of long-lived bromine compounds and VSLS have so far not been able to explain the amount of bromine derived in the stratosphere from observations of BrO and modeling of the ratio of BrO to total bromine. Due to the short lifetimes and the high atmospheric variability, the representativeness of the available observations of VSLS source gases remains unclear, as these may vary with region and display seasonal variability. During the SHIVA (Stratospheric Ozone: Halogen Impacts in a Varying Atmosphere) project an extensive dataset with over 700 samples of ambient air of all halogen species relevant for the atmospheric budget of total organic bromine (long lived halocarbons: H-1301, H-1211, H-1202, H-2402 and CH3Br, very short lived substances: CHBr3, CH2Br2, CHBr2Cl, CHBrCl2 and CHBrCl) have been collected from onboard the FALCON aircraft in the West Pacific region. Measurements were performed with the newly developed fully-automated in-situ instrument GHOST-MS (Gas chromatograph for the Observation of Tracers - coupled with a Mass Spectrometer) by the Goethe University of Frankfurt and with the onboard whole-air sampler WASP with subsequent ground based state-of-the-art GC/MS analysis by the University of East Anglia. We will present the datasets, compare these to other observation, derive a bromine budget for the West Pacific and derive an estimate of the amount of bromine from VSLS reaching the stratosphere. Using the mean mixing ratios in the upper troposphere of the halocarbons mentioned above, the calculated budget of the total organic bromine is (20.01 ± 1.77) ppt and the total amount from VSLS is (4.35 ± 0.59) ppt. Regarding the entry of bromine in the stratosphere, the estimation of the bromine content at the LZRH gives a value of (18.54 ± 1.78) ppt and a value of (2.88 ± 0.60) ppt from VSLS, reflecting a fraction of 16% of the total bromine budget.

Synthesis and evaluation of 2-halogenated-1,1-bis(4-hydroxyphenyl)-2-(3-hydroxyphenyl)-ethylenes as potential estrogen receptor-targeted radiodiagnostic and radiotherapeutic agents.

PubMed

Hanson, Robert N; Tongcharoensirikul, Pakamas; Barnsley, Kelton; Ondrechen, Mary Jo; Hughes, Alun; DeSombre, Eugene R

2015-04-01

A series of three 1,1-bis(4-hydroxyphenyl)-2-(3-hydroxyphenyl)-ethylene derivatives was prepared and evaluated as potential estrogen receptor imaging agents. The compounds display high binding affinity compared to estradiol, with the 2-iodo and 2-bromo-derivatives expressing higher affinity than the parent 2-nonhalogenated derivative. Evaluation in immature female rats also indicate that the compounds were all full estrogenic agonists with potencies in the same order of activity (I∼Br>H). Computational analysis of the interactions between the ligands and ERα-LBD demonstrated positive contribution of halide to binding properties. In preparation for studies using the radiohalogenated analogs, the corresponding protected 2-(tributylstannyl) derivative was prepared and converted to the corresponding 2-iodo-product. Copyright © 2015 Elsevier Inc. All rights reserved.

Metal-containing Complexes of Lactams, Imidazoles, and Benzimidazoles and Their Biological Activity

NASA Astrophysics Data System (ADS)

Kukalenko, S. S.; Bovykin, B. A.; Shestakova, S. I.; Omel'chenko, A. M.

1985-07-01

The results of the latest investigations of the problem of the synthesis of metal-containing complexes of lactams, imidazoles, and benzimidazoles, their structure, and their stability in solutions are surveyed. Some data on their biological activity (pesticide and pharmacological) and the mechanism of their physiological action are presented. The bibliography includes 190 references.

Amorphization of the prototypical zeolitic imidazolate framework ZIF-8 by ball-milling.

PubMed

Cao, Shuai; Bennett, Thomas D; Keen, David A; Goodwin, Andrew L; Cheetham, Anthony K

2012-08-14

We report the rapid amorphization of the prototypical substituted zeolitic imidazolate framework, ZIF-8, by ball-milling. The resultant amorphous ZIF-8 (a(m)ZIF-8) possesses a continuous random network (CRN) topology with a higher density and a lower porosity than its crystalline counterpart. A decrease in thermal stability upon amorphization is also evident.

Tracking thermal-induced amorphization of a zeolitic imidazolate framework via synchrotron in situ far-infrared spectroscopy.

PubMed

Ryder, Matthew R; Bennett, Thomas D; Kelley, Chris S; Frogley, Mark D; Cinque, Gianfelice; Tan, Jin-Chong

2017-06-27

We present the first use of in situ far-infrared spectroscopy to analyze the thermal amorphization of a zeolitic imidazolate framework material. We explain the nature of vibrational motion changes during the amorphization process and reveal new insights into the effect that temperature has on the Zn-N tetrahedra.

Water-based synthesis of zeolitic imidazolate framework-90 (ZIF-90) with a controllable particle size.

PubMed

Shieh, Fa-Kuen; Wang, Shao-Chun; Leo, Sin-Yen; Wu, Kevin C-W

2013-08-19

The ZIF code: ZIF-90 materials were successfully synthesized in an optimized water-based system. The particle size, ranging from micro- to nanoscales, could be controlled by different amounts of polyvinylpyrrolidone (PVP), Zn/imidazole-2-carboxaldehyde ratio and alcohol. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Porous Metal Carboxylate Boron Imidazolate Frameworks (MC-BIFs)

PubMed Central

Zheng, Shoutian; Wu, Tao; Zhang, Jian; Chow, Mina; Nieto, Ruben A.

2011-01-01

Integrated Material for Efficient CO2 Storage A new family of porous materials with tunable gas sorption properties have been made by integrating metal carboxylates and boron imidazolates under hydro- or solvothermal conditions. One hydrothermally synthesized phase exhibits a very high volumetric CO2 storage capacity at 81 L/L (273K, 1atm). PMID:20583020

Disrupting the PCSK9/LDLR protein-protein interaction by an imidazole-based minimalist peptidomimetic.

PubMed

Stucchi, Mattia; Grazioso, Giovanni; Lammi, Carmen; Manara, Silvia; Zanoni, Chiara; Arnoldi, Anna; Lesma, Giordano; Silvani, Alessandra

2016-10-18

Herein we report on the multicomponent synthesis of a novel imidazole-based compound, able to act efficiently as a minimalist β-strand mimic. Biological evaluation proved its ability to impair the LDLR-PCSK9 protein-protein interaction, disclosing it as the first small molecule exerting a PCSK9-mediated hypocholesterolemic effect.

Synthesis and characterization of new N-heterocyclic carbene ligands: 1,3-Bis(acetamide)imidazol-3-ium bromide and 3-(acetamide)-1-(3-aminopropyl)-1H-imidazol-3-ium bromide

NASA Astrophysics Data System (ADS)

Turkyilmaz, Murat; Uluçam, Gühergül; Aktaş, Şaban; Okan, S. Erol

2017-05-01

Two new pincer type N-heterocyclic carbene ligands were synthesized. The compounds were characterized by FTIR, NMR (1H, 13C) GC-MS and elemental analyses. They were also both modelled by DFT calculations as the crystal structure of 1,3-bis(acetamide)imidazol-3-ium bromide was determined by XRD which is an orthorhombic system with space group P21212. The structural analyses in gas phase were realized by comparing the experimental NMR and IR spectra with those of the theoretical calculations. In vitro biological activities of the molecules were determined and found that one of them exhibits significant cytotoxic activity.

Bromidotetra-kis-(1H-2-ethyl-5-methyl-imidazole-κN)copper(II) bromide.

PubMed

Godlewska, Sylwia; Baranowska, Katarzyna; Socha, Joanna; Dołęga, Anna

2011-12-01

The Cu(II) ion in the title compound, [CuBr(C(6)H(10)N(2))(4)]Br, is coordinated in a square-based-pyramidal geometry by the N atoms of four imidazole ligands and a bromide anion in the apical site. Both the Cu(II) and Br(-) atoms lie on a crystallographic fourfold axis. In the crystal, the [CuBr(C(6)H(10)N(2))(4)](+) complex cations are linked to the uncoordinated Br(-) anions (site symmetry [Formula: see text]) by N-H⋯Br hydrogen bonds, generating a three-dimensional network. The ethyl group of the imidazole ligand was modelled as disordered over two orientations with occupancies of 0.620 (8) and 0.380 (8).

Shear bond strength of a bracket-bonding system cured with a light-emitting diode or halogen-based light-curing unit at various polymerization times

PubMed Central

Gupta, Sanjay Prasad; Shrestha, Basanta Kumar

2018-01-01

Purpose To determine and compare the shear bond strength (SBS) of bracket-bonding system cured with light-emitting diode (LED) and halogen-based light-curing unit at various polymerization times. Materials and methods Ninety six human maxillary premolar teeth extracted for orthodontic purpose were divided into four groups, according to the light-curing unit and exposure times used. In the halogen group, the specimens were light cured for 20 and 40 seconds. In the LED group, the specimens were light cured for 5 and 10 seconds. Stainless steel brackets were bonded with Enlight bonding system, stored in distilled water at 37°C for 24 hours and then submitted to SBS testing in a universal testing machine at a crosshead speed of 0.5 mm/minute. Adhesive remnant index (ARI) was used to evaluate the amount of adhesive remaining on the teeth determined by stereomicroscope at 10× magnification. Results The highest mean SBS was obtained with the halogen 40 seconds (18.27 MPa) followed by halogen 20 seconds (15.36 MPa), LED 10 seconds (14.60 MPa) and least with LED 5 seconds (12.49 MPa) group. According to analysis of variance (ANOVA) and Tukey’s multiple-comparison test, SBS of halogen 20 seconds group was not significantly different from halogen 40 seconds group, LED 5 seconds group and LED 10 seconds group, whereas halogen 40 seconds group was significantly different from LED 5 seconds and LED 10 seconds group. The method of light curing did not influence the ARI, with score 2 being predominant. Conclusion Polymerization with both halogen and LED resulted in SBS values that were clinically acceptable for orthodontic treatment in all groups. Hence, for bonding orthodontic brackets, photoactivation with halogen for 20 seconds and LED for 5 seconds is suggested. PMID:29692633

Treatment of halogen-containing waste and other waste materials

DOEpatents

Forsberg, Charles W.; Beahm, Edward C.; Parker, George W.

1997-01-01

A process for treating a halogen-containing waste material. The process provides a bath of molten glass containing a sacrificial metal oxide capable of reacting with a halogen in the waste material. The sacrificial metal oxide is present in the molten glass in at least a stoichiometric amount with respect to the halogen in the waste material. The waste material is introduced into the bath of molten glass to cause a reaction between the halogen in the waste material and the sacrificial metal oxide to yield a metal halide. The metal halide is a gas at the temperature of the molten glass. The gaseous metal halide is separated from the molten glass and contacted with an aqueous scrubber solution of an alkali metal hydroxide to yield a metal hydroxide or metal oxide-containing precipitate and a soluble alkali metal halide. The precipitate is then separated from the aqueous scrubber solution. The molten glass containing the treated waste material is removed from the bath as a waste glass. The process of the invention can be used to treat all types of waste material including radioactive wastes. The process is particularly suited for separating halogens from halogen-containing wastes.

Treatment of halogen-containing waste and other waste materials

DOEpatents

Forsberg, C.W.; Beahm, E.C.; Parker, G.W.

1997-03-18

A process is described for treating a halogen-containing waste material. The process provides a bath of molten glass containing a sacrificial metal oxide capable of reacting with a halogen in the waste material. The sacrificial metal oxide is present in the molten glass in at least a stoichiometric amount with respect to the halogen in the waste material. The waste material is introduced into the bath of molten glass to cause a reaction between the halogen in the waste material and the sacrificial metal oxide to yield a metal halide. The metal halide is a gas at the temperature of the molten glass. The gaseous metal halide is separated from the molten glass and contacted with an aqueous scrubber solution of an alkali metal hydroxide to yield a metal hydroxide or metal oxide-containing precipitate and a soluble alkali metal halide. The precipitate is then separated from the aqueous scrubber solution. The molten glass containing the treated waste material is removed from the bath as a waste glass. The process of the invention can be used to treat all types of waste material including radioactive wastes. The process is particularly suited for separating halogens from halogen-containing wastes. 3 figs.

Metal halogen battery system with multiple outlet nozzle for hydrate

DOEpatents

Bjorkman, Jr., Harry K.

1983-06-21

A metal halogen battery system, including at least one cell having a positive electrode and a negative electrode contacted by aqueous electrolyte containing the material of said metal and halogen, store means whereby halogen hydrate is formed and stored as part of an aqueous material, means for circulating electrolyte through the cell and to the store means, and conduit means for transmitting halogen gas formed in the cell to a hydrate former whereby the hydrate is formed in association with the store means, said store means being constructed in the form of a container which includes a filter means, said filter means being inoperative to separate the hydrate formed from the electrolyte, said system having, a hydrate former pump means associated with the store means and being operative to intermix halogen gas with aqueous electrolyte to form halogen hydrate, said hydrate former means including, multiple outlet nozzle means connected with the outlet side of said pump means and being operative to minimize plugging, said nozzle means being comprised of at least one divider means which is generally perpendicular to the rotational axes of gears within the pump means, said divider means acting to divide the flow from the pump means into multiple outlet flow paths.

Flavonol and imidazole derivatives block HPV16 E6 activities and reactivate apoptotic pathways in HPV+ cells

PubMed Central

Yuan, C-H; Filippova, M; Krstenansky, J L; Duerksen-Hughes, P J

2016-01-01

High-risk human papillomaviruses (HR-HPVs) cause nearly all cases of cervical cancer, as well as approximately 30% of head and neck cancers. HPV 16 E6, one of two major viral oncogenes, protects cells from apoptosis by binding to and accelerating the degradation of several proteins important in apoptotic signaling, including caspase 8 and p53. We proposed that blocking the interactions between HPV E6 and its partners using small molecules had the potential to re-sensitize HPV+ cells to apoptosis. To test this idea, we screened libraries of small molecules for candidates that could block E6/caspase 8 binding and identified several candidates from different chemical classes. We tested hits for dose-dependency and specificity in vitro and for toxicity in a cell-based assay and then used this information to select the two best candidates for further testing: myricetin, a flavonol, and spinacine, an imidazole amino-acid derivative of histidine. Both compounds clearly inhibited the ability of E6 to bind in vitro to both caspase 8 and E6AP, the protein that mediates p53 degradation. In addition, both compounds were able to increase the level of caspase 8 and p53 in SiHa cervical cancer cells, resulting in an increase of caspase 3/7 activity. Finally, both myricetin and spinacine sensitized HPV+ cervical and oral cancer cells, but not HPV− cervical and oral cancer cells, to apoptosis induced by the cancer-specific ligand TRAIL, as well as the chemotherapeutic agents doxorubicin and cisplatin. New therapies based on this work may improve treatment for HPV+ cancer patients. PMID:26794656

Method for halogenating or radiohalogenating a chemical compound

DOEpatents

Kabalka, George W.

2006-05-09

A method for obtaining a halogenated organic compound, whereby an organotrifluoroborate compound is reacted with a halide ion in the presence of an oxidizing agent to produce the corresponding halogenated organic compound. The method may be used for producing radiohalogenated organic compounds.

Double-chamber electrode for spectrochemical determination of chlorine and other halogens

USGS Publications Warehouse

de Paiva, Azevedo; Specht, A.W.; Harner, R.S.

1954-01-01

A double-chamber, graphite electrode, suitable for d.c. arc determination of halogens by means of the alkaline earth halide bands, is described. An upper chamber holds the alkaline earth compound and an interconnected, lower chamber holds the halogen compound. This arrangement assures that there will be an abundance of alkaline earths in the arc by the time the halogen is volatilized from the lower chamber, and thereby promotes maximum emission of the alkaline earth halide bands. ?? 1954.

Four groups of new aromatic halogenated disinfection byproducts: effect of bromide concentration on their formation and speciation in chlorinated drinking water.

PubMed

Pan, Yang; Zhang, Xiangru

2013-02-05

Bromide is naturally present in source waters worldwide. Chlorination of drinking water can generate a variety of chlorinated and brominated disinfection byproducts (DBPs). Although substantial efforts have been made to examine the effect of bromide concentration on the formation and speciation of halogenated DBPs, almost all previous studies have focused on trihalomethanes and haloacetic acids. Given that about 50% of total organic halogen formed in chlorination remains unknown, it is still unclear how bromide concentration affects the formation and speciation of the new/unknown halogenated DBPs. In this study, chlorinated drinking water samples with different bromide concentrations were prepared, and a novel approach-precursor ion scan using ultra performance liquid chromatography/electrospray ionization-triple quadrupole mass spectrometry-was adopted for the detection and identification of polar halogenated DBPs in these water samples. With this approach, 11 new putative aromatic halogenated DBPs were identified, and they were classified into four groups: dihalo-4-hydroxybenzaldehydes, dihalo-4-hydroxybenzoic acids, dihalo-salicylic acids, and trihalo-phenols. A mechanism for the formation of the four groups of new aromatic halogenated DBPs was proposed. It was found that increasing the bromide concentration shifted the entire polar halogenated DBPs as well as the four groups of new DBPs from being less brominated to being more brominated; these new aromatic halogenated DBPs might be important intermediate DBPs formed in drinking water chlorination. Moreover, the speciation of the four groups of new DBPs was modeled: the speciation patterns of the four groups of new DBPs well matched those determined from the model equations, and the reactivity differences between HOBr and HOCl in reactions forming the four groups of new DBPs were larger than those in reactions forming trihalomethanes and haloacetic acids.

Sedimentary halogens and noble gases within Western Antarctic xenoliths: Implications of extensive volatile recycling to the sub continental lithospheric mantle

NASA Astrophysics Data System (ADS)

Broadley, Michael W.; Ballentine, Chris J.; Chavrit, Déborah; Dallai, Luigi; Burgess, Ray

2016-03-01

Recycling of marine volatiles back into the mantle at subduction zones has a profound, yet poorly constrained impact on the geochemical evolution of the Earth's mantle. Here we present a combined noble gas and halogen study on mantle xenoliths from the Western Antarctic Rift System (WARS) to better understand the flux of subducted volatiles to the sub continental lithospheric mantle (SCLM) and assess the impact this has on mantle chemistry. The xenoliths are extremely enriched in the heavy halogens (Br and I), with I concentrations up to 1 ppm and maximum measured I/Cl ratios (85.2 × 10-3) being ∼2000 times greater than mid ocean ridge basalts (MORB). The Br/Cl and I/Cl ratios of the xenoliths span a range from MORB-like ratios to values similar to marine pore fluids and serpentinites, whilst the 84Kr/36Ar and 130Xe/36Ar ratios range from modern atmosphere to oceanic sediments. This indicates that marine derived volatiles have been incorporated into the SCLM during an episode of subduction related metasomatism. Helium isotopic analysis of the xenoliths show average 3He/4He ratios of 7.5 ± 0.5 RA (where RA is the 3He/4He ratio of air = 1.39 × 10-6), similar to that of MORB. The 3He/4He ratios within the xenoliths are higher than expected for the xenoliths originating from the SCLM which has been extensively modified by the addition of subducted volatiles, indicating that the SCLM beneath the WARS must have seen a secondary alteration from the infiltration and rise of asthenospheric fluids/melts as a consequence of rifting and lithospheric thinning. Noble gases and halogens within these xenoliths have recorded past episodes of volatile interaction within the SCLM and can be used to reconstruct a tectonic history of the WARS. Marine halogen and noble gas signatures within the SCLM xenoliths provide evidence for the introduction and retention of recycled volatiles within the SCLM by subduction related metasomatism, signifying that not all volatiles that survive subduction are mixed efficiently through the convecting mantle. The global SCLM therefore represents a potentially important reservoir for the long term residence of subducted volatiles.

Martian fluid and Martian weathering signatures identified in Nakhla, NWA 998 and MIL 03346 by halogen and noble gas analysis

NASA Astrophysics Data System (ADS)

Cartwright, J. A.; Gilmour, J. D.; Burgess, R.

2013-03-01

We report argon (Ar) noble gas, Ar-Ar ages and halogen abundances (Cl, Br, I) of Martian nakhlites Nakhla, NWA 998 and MIL 03346 to determine the presence of Martian hydrous fluids and weathering products. Neutron-irradiated samples were either crushed and step-heated (Nakhla only), or simply step-heated using a laser or furnace, and analysed for noble gases using an extension of the 40Ar-39Ar technique to determine halogen abundances. The data obtained provide the first isotopic evidence for a trapped fluid that is Cl-rich, has a strong correlation with 40ArXS (40ArXS = 40Armeasured - 40Arradiogenic) and displays 40ArXS/36Ar of ˜1000 - consistent with the Martian atmosphere. This component was released predominantly in the low temperature and crush experiments, which may suggest a fluid inclusion host. For the halogens, we observe similar Br/Cl and I/Cl ratios between the nakhlites and terrestrial reservoirs, which is surprising given the absence of crustal recycling, organic matter and frequent fluid activity on Mars. In particular, Br/Cl ratios in our Nakhla samples (especially olivine) are consistent with previously analysed Martian weathering products, and both low temperature and crush analyses show a similar trend to the evaporation of seawater. This may indicate that surface brines play an important role on Mars and on halogen assemblages within Martian meteorites and rocks. Elevated I/Cl ratios in the low temperature NWA 998 and MIL 03346 releases may relate to in situ terrestrial contamination, though we are unable to distinguish between low temperature terrestrial or Martian components. Whilst estimates of the amount of water present based on the 36Ar concentrations are too high to be explained by a fluid component alone, they are consistent with a mixed-phase inclusion (gas and fluid) or with shock-implanted Martian atmospheric argon. The observed fluid is dilute (low salinity, but high Br/Cl and I/Cl ratios), contains a Martian atmospheric component, and may represent a mixture of a shallow fluid with one derived from fluid circulation within the nakhlite cumulate pile - with heat for fluid circulation supplied by either the igneous intrusion or by an impact event.

Assembling supramolecular networks by halogen bonding in coordination polymers driven by 5-bromonicotinic acid

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

Gu, Jin-Zhong, E-mail: gujzh@lzu.edu.cn; Wu, Jiang; Kirillov, Alexander M.

2014-05-01

A series of six coordination compounds ([Zn(5-Brnic){sub 2}]·1.5H{sub 2}O){sub n} (1), [Cd(5-Brnic){sub 2}]{sub n} (2), [Co(5-Brnic){sub 2}(H{sub 2}O){sub 2}]{sub n} (3), [Zn(5-Brnic){sub 2}(H{sub 2}biim)]{sub n} (4), ([Cd(5-Brnic){sub 2}(phen)]·H{sub 2}O){sub n} (5), and [Pb(5-Brnic){sub 2}(phen)] (6) have been generated by the hydrothermal method from the metal(II) nitrates, 5-bromonicotinic acid (5-BrnicH), and an optional ancillary 1,10-phenanthroline (phen) or 2,2′-biimidazole (H{sub 2}biim) ligand. All the products 1–6 have been characterized by IR spectroscopy, elemental, thermal, powder and single-crystal X-ray diffraction analyses. Their 5-bromonicotinate-driven structures vary from the 3D metal-organic framework with the seh-3,5-P21/c topology (in 2) and the 2D interdigitated layers with themore » sql topology (in 1 and 3), to the 1D chains (in 4 and 5) and the 0D discrete monomers (in 6). The 5-bromonicotinate moiety acts as a versatile building block and its tethered bromine atom plays a key role in reinforcing and extending the structures into diverse 3D supramolecular networks via the various halogen bonding Br⋯O, Br⋯Br, and Br⋯π interactions, as well as the N–H⋯O and C–H⋯O hydrogen bonds. The obtained results demonstrate a useful guideline toward engineering the supramolecular architectures in the coordination network assembly under the influence of various halogen bonding interactions. The luminescent (for 1, 2, 4, 5, and 6) and magnetic (for 3) properties have also been studied and discussed in detail. - Graphical abstract: Six coordination compounds driven by 5-bromonicotinic acid have been generated and structurally characterized, revealing diverse metal-organic networks that are further reinforced and extended via various halogen bonding interactions. - Highlights: • 5-Bromonicotinic acid is a versatile ligand for Zn, Cd, Co and Pb derivatives. • Careful selection of co-ligands and metals resulted in different network structures. • Halogen and hydrogen bonding interactions lead to various supramolecular networks. • Luminescent and magnetic properties were studied and discussed in detail.« less

Scientific conferences: A big hello to halogen bonding

NASA Astrophysics Data System (ADS)

Erdelyi, Mate

2014-09-01

Halogen bonding connects a wide range of subjects -- from materials science to structural biology, from computation to crystal engineering, and from synthesis to spectroscopy. The 1st International Symposium on Halogen Bonding explored the state of the art in this fast-growing field of research.

DESTRUCTION OF HALOGENATED HYDROCARBONS WITH SOLVATED ELECTRONS IN THE PRESENCE OF WATER. (R826180)

EPA Science Inventory

Model halogenated aromatic and aliphatic hydrocarbons and halogenated phenols were dehalogenated in seconds by solvated electrons generated from sodium in both anhydrous liquid ammonia and ammonia/water solutions. The minimum sodium required to completely dehalogenate these mo...

Halogen-bonding-triggered supramolecular gel formation

NASA Astrophysics Data System (ADS)

Meazza, Lorenzo; Foster, Jonathan A.; Fucke, Katharina; Metrangolo, Pierangelo; Resnati, Giuseppe; Steed, Jonathan W.

2013-01-01

Supramolecular gels are topical soft materials involving the reversible formation of fibrous aggregates using non-covalent interactions. There is significant interest in controlling the properties of such materials by the formation of multicomponent systems, which exhibit non-additive properties emerging from interaction of the components. The use of hydrogen bonding to assemble supramolecular gels in organic solvents is well established. In contrast, the use of halogen bonding to trigger supramolecular gel formation in a two-component gel (‘co-gel’) is essentially unexplored, and forms the basis for this study. Here, we show that halogen bonding between a pyridyl substituent in a bis(pyridyl urea) and 1,4-diiodotetrafluorobenzene brings about gelation, even in polar media such as aqueous methanol and aqueous dimethylsulfoxide. This demonstrates that halogen bonding is sufficiently strong to interfere with competing gel-inhibitory interactions and create a ‘tipping point’ in gel assembly. Using this concept, we have prepared a halogen bond donor bis(urea) gelator that forms co-gels with halogen bond acceptors.

79/81Br nuclear quadrupole resonance spectroscopic characterization of halogen bonds in supramolecular assemblies.

PubMed

Cerreia Vioglio, P; Szell, P M J; Chierotti, M R; Gobetto, R; Bryce, D L

2018-05-28

Despite the applicability of solid-state NMR to study the halogen bond, the direct NMR detection of 79/81 Br covalently bonded to carbon remains impractical due to extremely large spectral widths, even at ultra-high magnetic fields. In contrast, nuclear quadrupole resonance (NQR) offers comparatively sharp resonances. Here, we demonstrate the abilities of 79/81 Br NQR to characterize the electronic changes in the C-Br···N halogen bonding motifs found in supramolecular assemblies constructed from 1,4-dibromotetrafluorobenzene and nitrogen-containing heterocycles. An increase in the bromine quadrupolar coupling constant is observed, which correlates linearly with the halogen bond distance ( d Br···N ). Notably, 79/81 Br NQR is able to distinguish between two symmetry-independent halogen bonds in the same crystal structure. This approach offers a rapid and reliable indication for the occurrence of a halogen bond, with experimental times limited only by the observation of 79/81 Br NQR resonances.

Modulation of persistent organic pollutant toxicity through nutritional intervention: emerging opportunities in biomedicine and environmental remediation.

PubMed

Petriello, Michael C; Newsome, Bradley J; Dziubla, Thomas D; Hilt, J Zach; Bhattacharyya, Dibakar; Hennig, Bernhard

2014-09-01

Environmental pollution is increasing worldwide, and there is evidence that exposure to halogenated persistent organic pollutants (POPs) such as polychlorinated biphenyls can contribute to the pathology of inflammatory diseases such as atherosclerosis, diabetes, and cancer. Pollutant removal from contaminated sites and subsequent pollutant degradation are critical for reducing the long-term health risks associated with exposure. However, complete remediation of a toxicant from the environment is very difficult and cost-prohibitive. Furthermore, remediation technologies often result in the generation of secondary toxicants. Considering these circumstances, environmentally-friendly and sustainable remediation technologies and biomedical solutions to reduce vulnerability to environmental chemical insults need to be explored to reduce the overall health risks associated with exposure to environmental pollutants. We propose that positive lifestyle changes such as healthful nutrition and consumption of diets rich in fruits and vegetables or bioactive nutrients with antioxidant and/or anti-inflammatory properties will reduce the body's vulnerability to environmental stressors and thus reduce toxicant-mediated disease pathologies. Interestingly, emerging evidence now implicates the incorporation of bioactive nutrients, such as plant-derived polyphenols, in technologies focused on the capture, sensing and remediation of halogenated POPs. We propose that human nutritional intervention in concert with the use of natural polyphenol sensing and remediation platforms may provide a sensible means to develop primary and long-term prevention strategies of diseases associated with many environmental toxic insults including halogenated POPs. Copyright © 2014 Elsevier B.V. All rights reserved.

Modulation of persistent organic pollutant toxicity through nutritional intervention: emerging opportunities in biomedicine and environmental remediation

PubMed Central

Petriello, Michael C.; Newsome, Bradley J.; Dziubla, Thomas D.; Hilt, J. Zach; Bhattacharyya, Dibakar; Hennig, Bernhard

2014-01-01

Environmental pollution is increasing worldwide, and there is evidence that exposure to halogenated persistent organic pollutants (POPs) such as polychlorinated biphenyls can contribute to the pathology of inflammatory diseases such as atherosclerosis, diabetes, and cancer. Pollutant removal from contaminated sites and subsequent pollutant degradation are critical for reducing the long-term health risks associated with exposure. However, complete remediation of a toxicant from the environment is very difficult and cost-prohibitive. Furthermore, remediation technologies often result in the generation of secondary toxicants. Considering these circumstances, environmentally-friendly and sustainable remediation technologies and biomedical solutions to reduce vulnerability to environmental chemical insults need to be explored to reduce the overall health risks associate with exposure to environmental pollutants. We propose that positive lifestyle changes such as healthful nutrition and consumption of diets rich in fruits and vegetables or bioactive nutrients with antioxidant and/or anti-inflammatory properties will reduce the body’s vulnerability to environmental stressors and thus reduce toxicant-mediated disease pathologies. Interestingly, emerging evidence now implicates the incorporation of bioactive nutrients, such as plant-derived polyphenols, in technologies focused on the capture, sensing and remediation of halogenated POPs. We propose that human nutritional intervention in concert with the use of natural polyphenol sensing and remediation platforms may provide a sensible means to develop primary and long-term prevention strategies of diseases associated with many environmental toxic insults including halogenated POPs. PMID:24530186

Sources of volcanic aerosols: Petrologic and volcanological constraints

NASA Technical Reports Server (NTRS)

Sigurdsson, Haraldur

1991-01-01

Global climatic effects brought about by volcanism are related to the impact of volcanic gases and their derivative aerosols on the atmosphere, rather than the effects of volcanic ash. Evidence from both historic eruptions and polar ice cores indicate that volcanic sulfur gases are the dominant aerosol-forming component, resulting in produciton of a sulfuric acid-rich stratosphere aerosol that can have profound effects on the earth radiation budget over periods of a few years. Due to highly variable sulfur content of different magma types, the climatic effects do not relate simply to total erupted mass. There is a close relationship between volcanic sulfur yield to the atmospheric and hemispheric surface temperature decrease following an eruption, with up to 1 C surface temperature decrease indicated following a major volcanic event such as the 1815 Tambora eruption. While the erupted mass of HCl and HF is equal to or greater than that of sulfur gases in some volcanic events, the halogens do not form known aerosols nor are they abundant in ice core acidity layers. The early removal of halogens from eruption columns occurs by rain flushing and adsorption onto tephra particles, but the fate of halogens in the atmosphere following very large explosive eruptions is unknown. The CO2 flux to the atmosphere from volcanic eruptions is volumetrically one of the most important of the gas species, but owing to the huge size of the atmospheric reservoir of this gas, the volcanic contribution is likely to have negligible effects.

The contribution of hydrothermally altered ocean crust to the mantle halogen and noble gas cycles

NASA Astrophysics Data System (ADS)

Chavrit, Déborah; Burgess, Ray; Sumino, Hirochika; Teagle, Damon A. H.; Droop, Giles; Shimizu, Aya; Ballentine, Chris J.

2016-06-01

Recent studies suggest that seawater-derived noble gases and halogens are recycled into the deep mantle by the subduction of oceanic crust. To understand the processes controlling the availability of halogens and noble gases for subduction, we determined the noble gas elemental and isotopic ratios and halogen (Cl, Br, I) concentrations in 28 igneous samples from the altered oceanic crust (AOC) from 5 ODP sites in the Eastern and Western Pacific Ocean. Crushing followed by heating experiments enabled determination of noble gases and halogens in fluid inclusions and mineral phases respectively. Except for He and Ar, Ne, Kr and Xe isotopic ratios were all air-like suggesting that primary MORB signatures have been completely overprinted by air and/or seawater interaction. In contrast, 3He/4He ratios obtained by crushing indicate that a mantle helium component is still preserved, and 40Ar/36Ar values are affected by radiogenic decay in the mineral phases. The 130Xe/36Ar and 84Kr/36Ar ratios are respectively up to 15 times and 5 times higher than those of seawater and the highest ratios are found in samples affected by low temperature alteration (shallower than 800-900 m sub-basement). We consider three possible processes: (i) adsorption onto the clays present in the samples; (ii) fluid inclusions with a marine pore fluid composition; and (iii) fractionation of seawater through phase separation caused by boiling. Ninety percent of the Cl, Br and I were released during the heating experiments, showing that halogens are dominantly held in mineral phases prior to subduction. I/Cl ratios vary by 4 orders of magnitude, from 3 × 10-6 to 2 × 10-2. The mean Br/Cl ratio is 30% lower than in MORB and seawater. I/Cl ratios lower than MORB values are attributed to Cl-rich amphibole formation caused by hydrothermal alteration at depths greater than 800-900 m sub-basement together with different extents of I loss during low and high temperature alteration. At shallower depths, I/Cl ratios higher than MORB values can be explained by the addition of organic-rich sediments or the presence of organic detritus, both known to efficiently sequester I. Concentrations of 36Ar of the pre-subducting materials are sufficient to account for the 36Ar and composition of the mantle in the context of existing subduction-flux models. We find the Cl subduction flux of the oceanic crust to be about three times higher than the previous estimates and that sufficient Cl and Br can potentially be delivered by subduction over the last 3 Ga to account for mantle source compositions.

Asymmetric supercapacitors utilizing highly porous metal-organic framework derived Co3O4 nanosheets grown on Ni foam and polyaniline hydrogel derived N-doped nanocarbon electrode materials

NASA Astrophysics Data System (ADS)

Fan, Xin; Chen, Weiliang; Pang, Shuhua; Lu, Wei; Zhao, Yu; Liu, Zheng; Fang, Dong

2017-12-01

In the present work, asymmetric supercapacitors (ASCs) are assembled using a highly conductive N-doped nanocarbon (NDC) material derived from a polyaniline hydrogel as a cathode, and Ni foam covered with flower-like Co3O4 nanosheets (Co3O4-Ni) prepared from a zeolitic imidazolate metal-organic framework as a single precursor serves as a high gravimetric capacitance anode. At a current of 0.2 A g-1, the Co3O4-Ni electrode provides a gravimetric capacitance of 637.7 F g-1, and the NDC electrode provides a gravimetric capacitance of 359.6 F g-1. The ASC assembled with an optimal active material loading operates within a wide potential window of 0-1.1 V, and provides a high areal capacitance of 25.7 mF cm-2. The proposed ASC represents a promising strategy for designing high-performance supercapacitors.

High performance capacitive deionization using modified ZIF-8-derived, N-doped porous carbon with improved conductivity.

PubMed

Li, Yang; Kim, Jeonghun; Wang, Jie; Liu, Nei-Ling; Bando, Yoshio; Alshehri, Abdulmohsen Ali; Yamauchi, Yusuke; Hou, Chia-Hung; Wu, Kevin C-W

2018-06-05

Zeolitic imidazolate framework (ZIF) composite-derived carbon exhibiting large surface area and high micropore volume is demonstrated to be a promising electrode material for the capacitive deionization (CDI) application. However, some inherent serious issues (e.g., low electrical conductivity, narrow pore size, relatively low pore volume, etc.) are still observed for nitrogen-doped porous carbon particles, which restrict their CDI performance. To solve the above-mentioned problems, herein, we prepared gold-nanoparticle-embedded ZIF-8-derived nitrogen-doped carbon calcined at 800 °C (Au@NC800) and PEDOT doped-NC-800 (NC800-PEDOT). The newly generated NC800-PEDOT and Au@NC800 electrodes exhibited notably increased conductivity, and they also achieved high electrosorption capacities of 16.18 mg g-1 and 14.31 mg g-1, respectively, which were much higher than that of NC800 (8.36 mg g-1). Au@NC800 and NC800-PEDOT can be promisingly applicable as highly efficient CDI electrode materials.

ZIF-Derived Nitrogen-Doped Porous Carbons for Xe Adsorption and Separation

NASA Astrophysics Data System (ADS)

Zhong, Shan; Wang, Qian; Cao, Dapeng

2016-02-01

Currently, finding high capacity adsorbents with large selectivity to capture Xe is still a great challenge. In this work, nitrogen-doped porous carbons were prepared by programmable temperature carbonization of zeolitic imidazolate framework-8 (ZIF-8) and ZIF-8/xylitol composite precursors and the resultant samples are marked as Carbon-Z and Carbon-ZX, respectively. Further adsorption measurements indicate that ZIF-derived nitrogen-doped Carbon-ZX exhibits extremely high Xe capacity of 4.42 mmol g-1 at 298 K and 1 bar, which is higher than almost all other pristine MOFs such as CuBTC, Ni/DOBDC, MOF-5 and Al-MIL-53, and even more than three times of the matrix ZIF-8 at similar conditions. Moreover, Carbon-ZX also shows the highest Xe/N2 selectivity about ~120, which is much larger than all other reported MOFs. These remarkable features illustrate that ZIF-derived nitrogen-doped porous carbon is an excellent adsorbent for Xe adsorption and separation at room temperature.

40 CFR 180.447 - Imazethapyr; tolerances for residues.

Code of Federal Regulations, 2012 CFR

2012-07-01

... of the herbicide imazethapyr, 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo- 1H-imidazol-2-yl]-5... established for the sum of the residues of the herbicide imazethapyr, 2-[4,5-dihydro-4-methyl-4-(1-methylethyl... of the herbicide imazethapyr, 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo- 1H-imidazol-2-yl]-5...

40 CFR 180.447 - Imazethapyr; tolerances for residues.

Code of Federal Regulations, 2011 CFR

2011-07-01

... of the herbicide imazethapyr, 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo- 1H-imidazol-2-yl]-5... established for the sum of the residues of the herbicide imazethapyr, 2-[4,5-dihydro-4-methyl-4-(1-methylethyl... of the herbicide imazethapyr, 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo- 1H-imidazol-2-yl]-5...

40 CFR 180.447 - Imazethapyr; tolerances for residues.

Code of Federal Regulations, 2010 CFR

2010-07-01

... of the herbicide imazethapyr, 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo- 1H-imidazol-2-yl]-5... established for the sum of the residues of the herbicide imazethapyr, 2-[4,5-dihydro-4-methyl-4-(1-methylethyl... of the herbicide imazethapyr, 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo- 1H-imidazol-2-yl]-5...

40 CFR 180.447 - Imazethapyr; tolerances for residues.

Code of Federal Regulations, 2013 CFR

2013-07-01

... of the herbicide imazethapyr, 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo- 1H-imidazol-2-yl]-5... established for the sum of the residues of the herbicide imazethapyr, 2-[4,5-dihydro-4-methyl-4-(1-methylethyl... of the herbicide imazethapyr, 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo- 1H-imidazol-2-yl]-5...

40 CFR 180.447 - Imazethapyr; tolerances for residues.

Code of Federal Regulations, 2014 CFR

2014-07-01

... of the herbicide imazethapyr, 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo- 1H-imidazol-2-yl]-5... established for the sum of the residues of the herbicide imazethapyr, 2-[4,5-dihydro-4-methyl-4-(1-methylethyl... of the herbicide imazethapyr, 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo- 1H-imidazol-2-yl]-5...

Contract W911NF-07-1-0139 (Massachusetts Institute of Technology)

DTIC Science & Technology

2013-07-09

materials were effective in nucleophilic degradation of organophosphorous (OP) esters represented by CWA simulants and pesticides. Studies demonstrated...separate the cells effectively from suspension using a magnet. A fluorescence dye displacement assay shows strong affinities of the nanoparticles...as other imidazole groups, in its proximity. In that regard, we were interested in potential neighboring effects of the imidazole groups concentrated

γ-Alumina Nanoparticle Catalyzed Efficient Synthesis of Highly Substituted Imidazoles.

PubMed

Reddy, Bandapalli Palakshi; Vijayakumar, Vijayaparthasarathi; Arasu, Mariadhas Valan; Al-Dhabi, Naif Abdullah

2015-10-21

γ-Alumina nano particle catalyzed multi component reaction of benzil, arylaldehyde and aryl amines afforded the highly substituted 1,2,4,5-tetraaryl imidazoles with good to excellent yield in less reaction time under the sonication as well as the conventional methods. Convenient operational simplicity, mild conditions and the reusability of catalyst were the other advantages of this developed protocol.

Multi-wall carbon nanotube@zeolite imidazolate framework composite from a nanoscale zinc oxide precursor

DOE PAGES

Yue, Yanfeng; Guo, Bingkun; Qiao, Zhenan; ...

2014-07-24

Nanocomposite of multi-walled carbon nanotube@zeolite imidazolate frameworks (MWNT@ZIF) was prepared through a nanotube-facilitated growth based on a nanosized ZnO precursor. The electrically conductive nanocomposite displays a capacity of 380 mAh/g at 0.1 °C in Li–sulfur battery, transforming electrically inactive ZIF into the active one for battery applications.

Protonation-dissociation reactions of imazamethabenz-methyl and imazamethabenz-Acid in relation to their soil sorption and abiotic degradation.

PubMed

Pintado, Sara; Montoya, Mercedes Ruiz; Mellado, José Miguel Rodríguez

2009-12-09

This paper present ultraviolet-visible absorption spectra of imazamethabenz-methyl (IMBM) (mixture of the isomers methyl 6-[(RS)-4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl]-m-toluate, m-imazamethabenz, and methyl 2-[(RS)-4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl]-p-toluate, p-imazamethabenz) and the corresponding carboxylic acid, imazamethabenz-acid (IMBA). The spectral characteristics are determined as functions of the pH. The appreciable absorbance in the visible (or near-ultraviolet) region of the spectra indicates that the natural photolytic degradation is possible. From variations of the maximum absorbances of the bands, the pK values of 3.4 +/- 0.2 and 9.4 +/- 0.2 were obtained for protonation of the imidazol (=N-) nitrogen and dissociation of the NH imidazol nitrogen of IMBM, respectively. For IMBA, the dissociation pK of the carboxylic group is very close to that of the imidazol (=N-) nitrogen, both being close to 3.3. The dissociation pK of the NH imidazol nitrogen for IMBA is 9.6 +/- 0.2. The role of the acid-base reactions on the sorption on soils of these herbicides is discussed.

Spectral, biological screening of metal chelates of chalcone based Schiff bases of N-(3-aminopropyl) imidazole.

PubMed

Kalanithi, M; Rajarajan, M; Tharmaraj, P; Sheela, C D

2012-02-15

Tridentate chelate complexes of Co(II), Ni(II), Cu(II) and Zn(II) have been synthesized from the chalcone based ligands 2-[1-(3-(1H-imidazol-1-yl)propylimino)-3-(phenylallyl)]phenol(HL(1)), 2-[1-(3-(1H-imidazol-1-yl)propylimino)-3-p-tolylallyl]phenol(HL(2)), 2-[1-(3-(1H-imidazol-1-yl)propylimino)-3-4-nitrophenylallyl]phenol(HL(3)). Microanalytical data, UV-vis spectrophotometric method, magnetic susceptibility measurements, IR, 1H NMR, Mass, and EPR techniques were used to characterize the structure of chelates. The electronic absorption spectra and magnetic susceptibility measurements suggest a distorted square planar geometry for the copper(II) ion. The other metal complexes show distorted tetrahedral geometry. The coordination of the ligands with metal(II) ions was further confirmed by solution fluorescence spectrum. The antimicrobial activity of the ligands and metal(II) complexes against the species Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Candida albigans and Aspergillus niger has been carried out and compared. The electrochemical behavior of copper(II) complex is studied by cyclic voltammetry. Copyright © 2011 Elsevier B.V. All rights reserved.

Synthesis and characterization of (cryptand-222)potassium (2-methylimidazolato)(meso-tetraphenylporphinato)ferrate(II)-2-methylimidazole-tetrahydrofuran (1/1/2).

PubMed

Wu, Qi; Yao, Zhen; Li, Jianfeng

2017-09-01

Metalloporphyrin complexes containing an additional imidazole ligand can provide information about the effect of deprotonation or hydrogen bonding on the axial histidine unit in heme proteins. The title high-spin five-coordinate imidazolate-ligated iron(II) porphyrinate, [K(C 18 H 36 N 2 O 6 )][Fe(C 4 H 5 N 2 )(C 44 H 28 N 4 )]·C 4 H 6 N 2 ·2C 4 H 8 O, has been synthesized and investigated. The solvated salt crystallizes with one 2-methylimidazole molecule, two tetrahydrofuran solvent molecules and a potassium cation chelated inside a cryptand-222 (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane) molecule. The imidazolate ligand is ordered. The average Fe-Np (Np is a porphyrin N atom) bond length is 2.113 (11) Å and the axial Fe-N Im (N Im is an imidazolate N atom) is 2.0739 (13) Å. The out-of-plane displacement of the Fe II atom from the 24-atom mean plane is 0.6098 (5) Å, indicating an apparent doming of the porphyrin core.

Angles between orthogonal spd bond orbitals with maximum strength*

PubMed Central

Pauling, Linus

1976-01-01

An equation is derived for values of bond angles for two equivalent best spd hybrid bond orbitals with given amounts of s, p, and d character, and is applied in the discussion of structures of transargononic compounds, including the xenon and halogen fluorides. Bond orbitals with a rather small amount of d character tend to lie at angles 90° and 180°, and those with a larger amount, at somewhat smaller angles. PMID:16592315

Reactions of Trimethylsilyl Fluorosulfonyldifluoroacetate with Purine and Pyrimidine Nucleosides

PubMed Central

Rapp, Magdalena; Cai, Xiaohong; Xu, Wei; Dolbier, William R.; Wnuk, Stanislaw F.

2008-01-01

Difluorocarbene, generated from trimethylsilyl fluorosulfonyldifluoroacetate (TFDA), reacts with the uridine and adenosine substrates preferentially at the enolizable amide moiety of the uracil ring and the 6-amino group of the purine ring. 2',3'-Di-O-acetyl-3'-deoxy-3'-methyleneuridine reacts with TFDA to produce 4-O-difluoromethyl product derived from an insertion of difluorocarbene into the 4-hydroxyl group of the enolizable uracil ring. Reaction of the difluorocarbene with the adenosine substrates having the unprotected 6-amino group in the purine ring produced the 6-N-difluoromethyl derivative, while reaction with 6-N-benzoyl protected adenosine analogues gave the difluoromethyl ether product derived from the insertion of difluorocarbene into the enol form of the 6-benzamido group. Treatment of the 6-N-phthaloyl protected adenosine analogues with TFDA resulted in the unexpected one-pot conversion of the imidazole ring of the purine into the corresponding N-difluoromethylthiourea derivatives. Treatment of the suitably protected pyrimidine and purine nucleosides bearing an exomethylene group at carbons 2', 3' or 4' of the sugar rings with TFDA afforded the corresponding spirodifluorocyclopropyl analogues but in low yields. PMID:20160856

Affinity of guanosine derivatives for polycytidylate revisited

NASA Technical Reports Server (NTRS)

Kanavarioti, A.; Hurley, T. B.; Baird, E. E.

1995-01-01

Evidence is presented for complexation of guanosine 5'-monophosphate 2-methylimidazolide (2-MeImpG) with polycytidylate (poly(C)) at pH 8.0 and 23 degrees C in the presence of 1.0 M NaCl2 and 0.2 M MgCl2 in water. The association of 2-MeImpG with poly(C) was investigated using UV-vis spectroscopy as well as by monitoring the kinetics of the nucleophilic substitution reaction of the imidazole moiety by amines. The results of both methods are consistent with moderately strong poly(C) 2-MeImpG complexation and the spectrophotometric measurements allowed the construction of a binding isotherm with a concentration of 2-MeImpG equal to 5.55 +/- 0.15 mM at half occupancy. UV spectroscopy was employed to establish the binding of other guanosine derivatives on poly(C). These derivatives are guanosine 5'-monophosphate (5'GMP), guanosine 5'-monophosphate imidazolide (ImpG), and guanosine 5'-monophosphate morpholidate (morpG). Within experimental error these guanosine derivatives exhibit the same affinity for poly(C) as 2-MeImpG.

2-(4-aminophenyl) benzothiazole: a potent and selective pharmacophore with novel mechanistic action towards various tumour cell lines.

PubMed

Dubey, Raghvendra; Shrivastava, Prabhat K; Basniwal, Pawan K; Bhattacharya, Snehendu; Moorthy, Narayana S Hari Narayana

2006-06-01

2-(4-aminophenyl) benzothiazole (CJM -126) (Table 1 (1) and its analogues represent a potent and highly selective class of antitumor agents. These compounds in nanomolar range elicit potent growth inhibition in human-derived breast, colon, ovarian and renal tumour cell lines. Metabolism of benzothiazole plays a central role in its mode of action. Cytocrome P450 isoform, CYP1A1, biotransforms benzothiazoles, to active, as well as inactive metabolites. In vitro studies had confirmed that N-oxidation and N-acetylation (only 3' halogen congener) as main active metabolic transformation (generating cytotoxic electrophilic species), while C-6 oxidation and N-acetylation (except 3' halogen congener) as inactive metabolic transformation pathway. Generation of an inactive metabolite 2-(4-aminophenyl)-6-hydoxybenzothiazole [6-OH 126, (Table 1) (10)] is blocked by fluorinated analogue, substituted around benzothiazole nucleus, especially at 5-position. National Cancer Institute (NCI), USA, confirms this series as a unique mechanistic class distinct from clinically used chemotherapeutic agents. Benzothiazoles are potent aryl hydrocarbon receptor (AhR) agonists, binding to AhR results in induction of CYP1A1, causes generation of electrophilic reactive species which forms DNA adduct, ultimately resulting in cell death by activation of apoptotic machinery. To overcome the poor physiochemical and pharmaceutical properties (bioavailability problem) of this compounds, prodrug of benzothiazole derivatives were synthesized, which are introduced in clinical trails.

Benzene-1,4-diol–5-(1H-imidazol-1-yl)pyrimidine (1/1)

PubMed Central

Jiang, Yan-Ke; Hou, Gui-Ge

2011-01-01

The asymmetric unit of title compound, C7H6N4·C6H6O2, contains one 5-(1H-imidazol-1-yl)pyrimidine mol­ecule and two half benzene-1,4-diol mol­ecules; the benzene-1,4-diol mol­ecules are located on individual inversion centers. In the pyrimidine mol­ecule, the imidazole ring is twisted with respect to the pyrimidine ring at a dihedral angle of 25.73 (7)°. In the crystal, O—H⋯N hydrogen bonds link the mol­ecules to form supra­molecular chains. π–π stacking is also observed in the crystal, the centroid–centroid distance between parallel imdazole rings being 3.5543 (16) Å. PMID:22220081

Aminoacyl transfer from an adenylate anhydride to polyribonucleotides

NASA Technical Reports Server (NTRS)

Weber, A. L.; Lacey, J. C., Jr.

1975-01-01

Imidazole catalysis of phenylalanyl transfer from phenylalanine adenylate to hydroxyl groups of homopolyribonucleotides is studied as a possible chemical model of biochemical aminoacylation of transfer RNA (tRNA). The effect of pH on imidazole-catalyzed transfer of phenylalanyl residues to poly(U) and poly(A) double helix strands, the number of peptide linkages and their lability to base and neutral hydroxylamine, and the nature of adenylate condensation products are investigated. The chemical model entertained exhibits a constraint by not acylating the hydroxyl groups of polyribonucleotides in a double helix. The constraint is consistent with selective biochemical aminoacylation at the tRNA terminus. Interest in imidazole as a model of histidine residue in protoenzymes participating in prebiotic aminoacyl transfer to polyribonucleotides, and in rendering the tRNA a more efficient adaptor, is indicated.

Bromidotetra­kis­(1H-2-ethyl-5-methyl­imidazole-κN 3)copper(II) bromide

PubMed Central

Godlewska, Sylwia; Baranowska, Katarzyna; Socha, Joanna; Dołęga, Anna

2011-01-01

The CuII ion in the title compound, [CuBr(C6H10N2)4]Br, is coordinated in a square-based-pyramidal geometry by the N atoms of four imidazole ligands and a bromide anion in the apical site. Both the CuII and Br− atoms lie on a crystallographic fourfold axis. In the crystal, the [CuBr(C6H10N2)4]+ complex cations are linked to the uncoordinated Br− anions (site symmetry ) by N—H⋯Br hydrogen bonds, generating a three-dimensional network. The ethyl group of the imidazole ligand was modelled as disordered over two orientations with occupancies of 0.620 (8) and 0.380 (8). PMID:22199662

Intramolecular inverse-electron-demand Diels-Alder reactions of imidazoles with 1,2,4-triazines: a new route to 1,2,3,4-tetrahydro-1,5-naphthyridines and related heterocycles.

PubMed

Lahue, Brian R; Lo, Sie-Mun; Wan, Zhao-Kui; Woo, Grace H C; Snyder, John K

2004-10-15

The intramolecular inverse-electron-demand Diels-Alder reaction between imidazoles and 1,2,4-triazines linked by a trimethylene tether from the imidazole N1 position to the triazine C3 proceed in excellent yields to produce 1,2,3,4-tetrahydro-1,5-naphthyridines. The reaction proceeds by a cycloaddition with subsequent loss of nitrogen, followed by a presumed stepwise loss of a nitrile. The analogous intramolecular cycloadditions employing a tetramethylene tether also proceeded to give 2,3,4,5-tetrahydro-1H-pyrido[3,2-b]azepines in acceptable yields. The reaction to produce the tetrahydro-1,5-naphthyridines can also be promoted with microwave irradiation.

Impact of enhanced ozone deposition and halogen chemistry on tropospheric ozone over the Northern Hemisphere

EPA Science Inventory

Fate of ozone in marine environments has been receiving increased attention due to the tightening of ambient air quality standards. The role of deposition and halogen chemistry is examined through incorporation of an enhanced ozone deposition algorithm and inclusion of halogen ch...

40 CFR 721.10145 - Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino...

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Modified reaction products of alkyl... Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino compound... identified generically as modified reaction products of alkyl alcohol, halogenated alkane, substituted...

40 CFR 721.10145 - Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino...

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Modified reaction products of alkyl... Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino compound... identified generically as modified reaction products of alkyl alcohol, halogenated alkane, substituted...

Halogenated arsenenes as Dirac materials

NASA Astrophysics Data System (ADS)

Tang, Wencheng; Sun, Minglei; Ren, Qingqiang; Wang, Sake; Yu, Jin

2016-07-01

Arsenene is the graphene-like arsenic nanosheet, which has been predicted very recently [S. Zhang, Z. Yan, Y. Li, Z. Chen, and H. Zeng, Angewandte Chemie, 127 (2015) 3155-3158]. Using first-principles calculations, we systematically investigate the structures and electronic properties of fully-halogenated arsenenes. Formation energy analysis reveals that all the fully-halogenated arsenenes except iodinated arsenene are energetically favorable and could be synthesized. We have revealed the presence of Dirac cone in fully-halogenated arsenene compounds. They may have great potential applications in next generation of high-performance devices.

Density functional IR, Raman, and VCD spectra of halogen substituted β-lactams

NASA Astrophysics Data System (ADS)

Rode, Joanna E.; Dobrowolski, Jan Cz.

2003-06-01

Halogenoazetidinones are important as synthetic intermediates for preparation of halogen β-lactam (2-azetidinone) antibiotics and as building blocks for carbohydrates and amino acids. In this paper, we consider the influence of the halogen atom, substituted at the C4 position of the 2-azetidinone ring, on the geometry, IR, Raman, and vibrational circular dichroism spectra. The vibrational spectra were calculated for the chiral 4-( R)-X-2-azetidinone (X=F, Cl or Br) molecules at the B3PW91/aug-cc-pVTZ level. It was shown that the geometry of the molecules studied do not change much upon the change of the halogen atom. In case of the vibrational spectra, the position but even more the intensities depend strongly on the kind of halogen substituent.

Abnormal synergistic effects between Lewis acid-base interaction and halogen bond in F3B···NCX···NCM

NASA Astrophysics Data System (ADS)

Tang, Qingjie; Li, Qingzhong

2015-12-01

An abnormal synergistic effect was found between the Lewis acid-base interaction and halogen bond in triads F3B···NCX···NCM (X and M are halogen atoms), where the strong Lewis acid-base interaction between F3B and NCX has a larger enhancement than the weak halogen bond between NCX and NCM. This is in contrast with the traditional cooperative effect. It is interesting that the alkali-metal substituent as well as the heavier halogen atom play a more remarkable role in the enhancement of the interaction F3B···NCX than that of NCX···NCM, particularly, the alkali-metal substituent makes the abnormal synergistic effect be the traditional cooperative one.

Competition between Halogen, Hydrogen and Dihydrogen Bonding in Brominated Carboranes.

PubMed

Fanfrlík, Jindřich; Holub, Josef; Růžičková, Zdeňka; Řezáč, Jan; Lane, Paul D; Wann, Derek A; Hnyk, Drahomír; Růžička, Aleš; Hobza, Pavel

2016-11-04

Halogen bonds are a subset of noncovalent interactions with rapidly expanding applications in materials and medicinal chemistry. While halogen bonding is well known in organic compounds, it is new in the field of boron cluster chemistry. We have synthesized and crystallized carboranes containing Br atoms in two different positions, namely, bound to C- and B-vertices. The Br atoms bound to the C-vertices have been found to form halogen bonds in the crystal structures. In contrast, Br atoms bound to B-vertices formed hydrogen bonds. Quantum chemical calculations have revealed that halogen bonding in carboranes can be much stronger than in organic architectures. These findings open new possibilities for applications of carboranes, both in materials and medicinal chemistry. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigation of reactive halogens in the Arctic using a mobile instrumental laboratory

NASA Astrophysics Data System (ADS)

Custard, K.; Shepson, P. B.; Stephens, C. R.

2011-12-01

Custard, K kcustard@purdue.edu Chemistry Department, Purdue University, West Lafayette, IN, USA Shepson, P pshepson@purdue.edu Chemistry Department, Purdue University, West Lafayette, IN, USA Stephens, C thompscr@purdue.edu Chemistry Department, Purdue University, West Lafayette, IN, USA Investigation of the chemistry of reactive halogens in ice-covered regions is important because of its significant impact on atmospheric composition. Halogens in the Arctic react with ozone and gaseous elemental mercury to sometimes completely deplete them from the ambient atmosphere, at least during polar springtime. There is much uncertainty about the sources and concentrations of these atmospheric halogens in the Arctic, particularly with respect to chlorine. To gain a better understanding of them, we have developed a method to simultaneously measure the concentrations of BrOx and ClOx radicals using a flowtube method. The method involves reaction of the halogen atom with a halogenated alkene, to produce a multiply halogenated characteristic ketone product, which is then detected via GC/ECD. The system was deployed at Barrow, AK, using a mobile instrumental laboratory so that measurements could be made from multiple locations along the sea ice. In this paper we will discuss laboratory evaluation of the flowtube method, and present preliminary data from Barrow, AK, during the spring 2011 deployment.

Impact of Enhanced Ozone Deposition and Halogen Chemistry on Tropospheric Ozone over the Northern Hemisphere.

PubMed

Sarwar, Golam; Gantt, Brett; Schwede, Donna; Foley, Kristen; Mathur, Rohit; Saiz-Lopez, Alfonso

2015-08-04

Fate of ozone in marine environments has been receiving increased attention due to the tightening of ambient air quality standards. The role of deposition and halogen chemistry is examined through incorporation of an enhanced ozone deposition algorithm and inclusion of halogen chemistry in a comprehensive atmospheric modeling system. The enhanced ozone deposition treatment accounts for the interaction of iodide in seawater with ozone and increases deposition velocities by 1 order of magnitude. Halogen chemistry includes detailed chemical reactions of organic and inorganic bromine and iodine species. Two different simulations are completed with the halogen chemistry: without and with photochemical reactions of higher iodine oxides. Enhanced deposition reduces mean summer-time surface ozone by ∼3% over marine regions in the Northern Hemisphere. Halogen chemistry without the photochemical reactions of higher iodine oxides reduces surface ozone by ∼15% whereas simulations with the photochemical reactions of higher iodine oxides indicate ozone reductions of ∼48%. The model without these processes overpredicts ozone compared to observations whereas the inclusion of these processes improves predictions. The inclusion of photochemical reactions for higher iodine oxides leads to ozone predictions that are lower than observations, underscoring the need for further refinement of the halogen emissions and chemistry scheme in the model.

Ketoconazole in paracoccidioidomycosis: efficacy of prolonged oral therapy.

PubMed

Restrepo, A; Stevens, D A; Leiderman, E; Fuentes, J; Arana, A; Angel, R; Mejía, G; Gómez, I

1980-08-29

Ketoconazole, a new oral imidazole derivative, was employed for the treatment of five patients with paracoccidioidomycosis. The response was excellent, with objective clinical improvement and healing of both mucocutaneous and pulmonary lesions. Mycological and serological tests, as well as delayed hypersensitivity, were assessed and found to correlate with clinical improvement. Therapy was conducted for 12 months with a dose of 200 mg day in 2 patients; in the remainder the dose was reduced (100 mg day) after the first 6 months and maintained as such for an equal period. No side-effects or toxicity were noted despite prolonged treatment. The advantages of the new therapeutic approach are discussed.

A Fast and Effective Pyridine-Free Method for the Determination of Hydroxyl Value of Hydroxyl-Terminated Polybutadiene and Other Hydroxy Compounds

NASA Astrophysics Data System (ADS)

Alex, Ancy Smitha; Kumar, Vijendra; Sekkar, V.; Bandyopadhyay, G. G.

2017-07-01

Hydroxyl-terminated polybutadiene (HTPB) is the workhorse propellant binder for launch vehicle and missile applications. Accurate determination of the hydroxyl value (OHV) of HTPB is crucial for tailoring the ultimate mechanical and ballistic properties of the propellant derived. This article describes a fast and effective methodology free of pyridine based on acetic anhydride, N-methyl imidazole, and toluene for the determination of OHV of nonpolar polymers like HTPB and other hydroxyl compounds. This method gives accurate and reproducible results comparable to standard methods and is superior to existing methods in terms of user friendliness, efficiency, and time requirement.

Smooth transition between SMM and SCM-type slow relaxing dynamics for a 1-D assemblage of {Dy(nitronyl nitroxide)2} units.

PubMed

Liu, Ruina; Li, Licun; Wang, Xiaoling; Yang, Peipei; Wang, Chao; Liao, Daizheng; Sutter, Jean-Pascal

2010-04-21

A model example for size effects on the dynamic susceptibility behavior is provided by the chain compound [{Dy(hfac)(3)NitPhIm(2)}Dy(hfac)(3)] (NitPhIm = 2-[4-(1-imidazole)phenyl]nitronyl nitroxide radical). The Arrhenius plot reveals two relaxation regimes attributed to SMM (Delta = 17.1 K and tau(0) = 17.5 x 10(-6) s) and SCM (Delta = 82.7 K and tau(0) = 8.8 x 10(-8) s) behaviors. The ferromagnetic exchange among the spin carriers has been established for the corresponding Gd derivative.

Copper(II) imidazolate frameworks as highly efficient photocatalysts for reduction of CO{sub 2} into methanol under visible light irradiation

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

Li, Jingtian; Luo, Deliang; Yang, Chengju

2013-07-15

Three copper(II) imidazolate frameworks were synthesized by a hydrothermal (or precipitation) reaction. The catalysts were characterized by X-ray diffraction (XRD), nitrogen adsorption, transmission electron microscopy (TEM), ultraviolet–visible spectroscopy (UV–vis), Fourier transform infrared spectra (FTIR), thermogravimetry (TG). Meanwhile, the photocatalytic activities of the samples for reduction of CO{sub 2} into methanol and degradation of methylene blue (MB) under visible light irradiation were also investigated. The results show that the as-prepared samples exhibit better photocatalytic activities for the reduction of carbon dioxide into methanol with water and degradation of MB under visible light irradiation. The orthorhombic copper(II) imidazolate frameworks with a bandmore » gap of 2.49 eV and green (G) color has the best photocatalytic activity for reduction of CO{sub 2} into methanol, 1712.7 μmol/g over 5 h, which is about three times as large as that of monoclinic copper(II) imidazolate frameworks with a band gap 2.70 eV and blue (J) color. The degradation kinetics of MB over three photocatalysts fitted well to the apparent first-order rate equation and the apparent rate constants for the degradation of MB over G, J and P (with pink color) are 0.0038, 0.0013 and 0.0016 min{sup −1}, respectively. The synergistic effects of smallest band gap and orthorhombic crystal phase structure are the critical factors for the better photocatalytic activities of G. Moreover, three frameworks can also be stable up to 250 °C. The investigation of Cu-based zeolitic imidazolate frameworks maybe provide a design strategy for a new class of photocatalysts applied in degradation of contaminations, reduction of CO{sub 2}, and even water splitting into hydrogen and oxygen under visible light. - Graphical abstract: Carbon dioxide was reduced into methanol with water over copper(II) imidazolate frameworks under visible light irradiation. - Highlights: • Three copper(II) imidazolate frameworks were first applied in the photo-reduction of CO{sub 2}. • The photocatalytic activities of the frameworks depend on their band gap and phase structures. • The photocatalytic activity of orthorhombic frameworks is 3 times that of monoclinic frameworks. • The degradation kinetics of MB over three photocatalysts followed the first-order rate equation. • The largest yield for reduction of CO{sub 2} into methanol on green framworks was 1712.7 μmol/g over 5 h.« less

Characterization of halogenated DBPs and identification of new DBPs trihalomethanols in chlorine dioxide treated drinking water with multiple extractions.

PubMed

Han, Jiarui; Zhang, Xiangru; Liu, Jiaqi; Zhu, Xiaohu; Gong, Tingting

2017-08-01

Chlorine dioxide (ClO 2 ) is a widely used alternative disinfectant due to its high biocidal efficiency and low-level formation of trihalomethanes and haloacetic acids. A major portion of total organic halogen (TOX), a collective parameter for all halogenated DBPs, formed in ClO 2 -treated drinking water is still unknown. A commonly used pretreatment method for analyzing halogenated DBPs in drinking water is one-time liquid-liquid extraction (LLE), which may lead to a substantial loss of DBPs prior to analysis. In this study, characterization and identification of polar halogenated DBPs in a ClO 2 -treated drinking water sample were conducted by pretreating the sample with multiple extractions. Compared to one-time LLE, the combined four-time LLEs improved the recovery of TOX by 2.3 times. The developmental toxicity of the drinking water sample pretreated with the combined four-time LLEs was 1.67 times higher than that pretreated with one-time LLE. With the aid of ultra-performance liquid chromatography/electrospray ionization-triple quadrupole mass spectrometry, a new group of polar halogenated DBPs, trihalomethanols, were detected in the drinking water sample pretreated with multiple extractions; two of them, trichloromethanol and bromodichloromethanol, were identified with synthesized standard compounds. Moreover, these trihalomethanols were found to be the transformation products of trihalomethanes formed during ClO 2 disinfection. The results indicate that multiple LLEs can significantly improve extraction efficiencies of polar halogenated DBPs and is a better pretreatment method for characterizing and identifying new polar halogenated DBPs in drinking water. Copyright © 2017. Published by Elsevier B.V.

Singlet oxygen production by combining erythrosine and halogen light for photodynamic inactivation of Streptococcus mutans.

PubMed

Fracalossi, Camila; Nagata, Juliana Yuri; Pellosi, Diogo Silva; Terada, Raquel Sano Suga; Hioka, Noboru; Baesso, Mauro Luciano; Sato, Francielle; Rosalen, Pedro Luiz; Caetano, Wilker; Fujimaki, Mitsue

2016-09-01

Photodynamic inactivation of microorganisms is based on a photosensitizing substance which, in the presence of light and molecular oxygen, produces singlet oxygen, a toxic agent to microorganisms and tumor cells. This study aimed to evaluate singlet oxygen quantum yield of erythrosine solutions illuminated with a halogen light source in comparison to a LED array (control), and the photodynamic effect of erythrosine dye in association with the halogen light source on Streptococcus mutans. Singlet oxygen quantum yield of erythrosine solutions was quantified using uric acid as a chemical-probe in an aqueous solution. The in vitro effect of the photodynamic antimicrobial activity of erythrosine in association with the halogen photopolimerizing light on Streptococcus mutans (UA 159) was assessed during one minute. Bacterial cultures treated with erythrosine alone served as negative control. Singlet oxygen with 24% and 2.8% degradation of uric acid in one minute and a quantum yield of 0.59 and 0.63 was obtained for the erythrosine samples illuminated with the halogen light and the LED array, respectively. The bacterial cultures with erythrosine illuminated with the halogen light presented a decreased number of CFU mL(-1) in comparison with the negative control, with minimal inhibitory concentrations between 0.312 and 0.156mgmL(-1). The photodynamic response of erythrosine induced by the halogen light was capable of killing S. mutans. Clinical trials should be conducted to better ascertain the use of erythrosine in association with halogen light source for the treatment of dental caries. Copyright © 2016 Elsevier B.V. All rights reserved.

Role of halogen and hydrogen bonds for stabilization of antithyroid drugs with hypohalous acids (HOX, X = I, Br, and Cl) adducts

NASA Astrophysics Data System (ADS)

El-Sheshtawy, Hamdy S.; El-Mehasseb, Ibrahim

2017-11-01

The mechanism for the inhibition of thyroid hormones by the thioamide-like antithyroid drug is a key process in the thyroid gland function. Therefore, in this study theoretical investigation of the molecular interaction between two antithyroid drugs, namely methimazol (MMI) and thiazoline-2-thione (T2T), with the hypohalous acids (HOX, X = I, Br, and Cl), which act as heme-linked halogenated species to tyrosine residue was discussed. The calculations were performed by M06-2X and MP2 using aug-cc-pVDZ level of theory. In addition, wB97xd/6-31G* level of theory was used in order to account for the dispersion forces. The results show the possible formation of three adducts, which is stabilized by halogen bond (I), both halogen and hydrogen bonds (II), two hydrogen bonds (III). The binding energies of the complexes reveals stabilization in the order III > II > I. The binding energies of the complexes was increased with increasing the electron affinity and polarizability of halogen atom, the dipole moment of the complexes (I and II), the electrostatic potential on halogen atom (Vmax:i.e σ-hole), and the charge-transfer process through the halogen bond in I. On the other hand, the binding energies of the complexes decreased with increasing the halogen atom electronegativity and the dipole moment of complex III. Natural bond orbital (NBO) analysis was used to investigate the molecular orbital interactions and the charge transfer process upon complexation.

Pure white OLED based on an organic small molecule: 2,6-Di(1H-benzo[d]imidazol-2-yl)pyridine

NASA Astrophysics Data System (ADS)

Liu, Jian

2015-10-01

2,6-Di(1H-benzo[d]imidazol-2-yl)pyridine (DBIP) was synthesized. The single-crystal structure of DBIP was resolved. DBIP-based OLED was fabricated. The electroluminescence for the device corresponds to a pure white emission. In addition, thermal stability, UV-vis, photoluminescence and electrochemical behaviors of DBIP were investigated as well.

Polyacrylic acid@zeolitic imidazolate framework-8 nanoparticles with ultrahigh drug loading capability for pH-sensitive drug release.

PubMed

Ren, Hong; Zhang, Lingyu; An, Jiping; Wang, Tingting; Li, Lu; Si, Xiaoyan; He, Liu; Wu, Xiaotong; Wang, Chungang; Su, Zhongmin

2014-01-28

The polyacrylic acid@zeolitic imidazolate framework-8 (PAA@ZIF-8) nanoparticles (NPs) were first fabricated using a facile and simple route. It is worthwhile noting that the as-fabricated PAA@ZIF-8 NPs possessed ultrahigh doxorubicin (DOX) loading capability (1.9 g DOX g(-1) NPs), which were employed as pH-dependent drug delivery vehicles.

Bromidotetra-kis-(2-isopropyl-1H-imidazole-κN)copper(II) bromide.

PubMed

Godlewska, Sylwia; Socha, Joanna; Baranowska, Katarzyna; Dołęga, Anna

2011-10-01

The Cu(II) atom in the title salt, [CuBr(C(6)H(10)N(2))(4)]Br, is coordinated in a square-pyramidal geometry by four imidazole N atoms and one bromide anion that is located at the apex of the pyramid. The cations and the anions form a two-dimensional network parallel to (001) through N-H⋯Br hydrogen bonds.

A tailored biocatalyst achieved by the rational anchoring of imidazole groups on a natural polymer: furnishing a potential artificial nuclease by sustainable materials engineering.

PubMed

Ferreira, José G L; Grein-Iankovski, Aline; Oliveira, Marco A S; Simas-Tosin, Fernanda F; Riegel-Vidotti, Izabel C; Orth, Elisa S

2015-04-11

Foreseeing the development of artificial enzymes by sustainable materials engineering, we rationally anchored reactive imidazole groups on gum arabic, a natural biocompatible polymer. The tailored biocatalyst GAIMZ demonstrated catalytic activity (>10(5)-fold) in dephosphorylation reactions with recyclable features and was effective in cleaving plasmid DNA, comprising a potential artificial nuclease.

Discovery of novel histidine-derived lipo-amino acids: applied in the synthesis of ultra-short antimicrobial peptidomimetics having potent antimicrobial activity, salt resistance and protease stability.

PubMed

Ahn, Mija; Murugan, Ravichandran N; Jacob, Binu; Hyun, Jae-Kyung; Cheong, Chaejoon; Hwang, Eunha; Park, Hyo-Nam; Seo, Ji-Hyung; Srinivasrao, G; Lee, Kyung S; Shin, Song Yub; Bang, Jeong Kyu

2013-10-01

Here we report for the first time the synthesis of Histidine (His) derived lipo-amino acids having pendant lipid tails at N(τ)- and N(π)-positions on imidazole group of His and applied it into synthesis of lipo-peptides. The attachment of His-derived lipo-amino acid into the very short inactive cationic peptides endows potent antimicrobial activity against Gram-positive and Gram-negative bacteria without hemolytic activity. Furthermore, our designed His-derived lipo-peptidomimetics (HDLPs) consisting of two or three residues displayed strong anti-MRSA activity and protease stability as well as retained potent antimicrobial activity under high salt concentration. Our results demonstrate that the novel lipo-amino acid is highly flexible to synthesize and carry out the extensive structure-activity relationship (SAR) on lipo-antimicrobial peptidomimetics and represents a unique amenable platform for modifying parameters important for antimicrobial activity. Through this study, we proved that the discovery of His-derived lipo-amino acid and the corresponding HDLPs are an excellent candidate as a lead compound for the development of novel antimicrobial agents. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

79/81Br nuclear quadrupole resonance spectroscopic characterization of halogen bonds in supramolecular assemblies† †Electronic supplementary information (ESI) available: 13C SSNMR spectra, powder X-ray diffractograms. See DOI: 10.1039/c8sc01094c

PubMed Central

Cerreia Vioglio, P.; Szell, P. M. J.; Chierotti, M. R.; Gobetto, R.

2018-01-01

Despite the applicability of solid-state NMR to study the halogen bond, the direct NMR detection of 79/81Br covalently bonded to carbon remains impractical due to extremely large spectral widths, even at ultra-high magnetic fields. In contrast, nuclear quadrupole resonance (NQR) offers comparatively sharp resonances. Here, we demonstrate the abilities of 79/81Br NQR to characterize the electronic changes in the C–Br···N halogen bonding motifs found in supramolecular assemblies constructed from 1,4-dibromotetrafluorobenzene and nitrogen-containing heterocycles. An increase in the bromine quadrupolar coupling constant is observed, which correlates linearly with the halogen bond distance (dBr···N). Notably, 79/81Br NQR is able to distinguish between two symmetry-independent halogen bonds in the same crystal structure. This approach offers a rapid and reliable indication for the occurrence of a halogen bond, with experimental times limited only by the observation of 79/81Br NQR resonances. PMID:29899948

Degree of conversion of two lingual retainer adhesives cured with different light sources.

PubMed

Usümez, Serdar; Büyükyilmaz, Tamer; Karaman, Ali Ihya; Gündüz, Beniz

2005-04-01

The aim of this study was to evaluate the degree of conversion (DC) of two lingual retainer adhesives, Transbond Lingual Retainer (TLR) and Light Cure Retainer (LCR), cured with a fast halogen light, a plasma arc light and a light-emitting diode (LED) at various curing times. A conventional halogen light served as the control. One hundred adhesive samples (five per group) were cured for 5, 10 or 15 seconds with an Optilux 501 (fast halogen light), for 3, 6 or 9 seconds with a Power Pac (plasma arc light), or for 10, 20 or 40 seconds with an Elipar Freelight (LED). Samples cured for 40 seconds with the conventional halogen lamp were used as the controls. Absorbance peaks were recorded using Fourier transform infrared (FT-IR) spectroscopy. DC values were calculated. Data were analysed using Kruskal-Wallis and Mann-Whitney U-tests. For the TLR, the highest DC values were achieved in 6 and 9 seconds with the plasma arc light. Curing with the fast halogen light for 15 seconds and with the LED for 40 seconds produced statistically similar DC values, but these were lower than those with the plasma arc light. All of these light exposures yielded a statistically significantly higher DC than 40 seconds of conventional halogen light curing. The highest DC value for the LCR was achieved in 15 seconds with the fast halogen light, then the plasma arc light curing for 6 seconds. These two combinations produced a statistically significantly higher DC when compared with the 40 seconds of conventional halogen light curing. The lowest DC for the LCR was achieved with 10 seconds of LED curing. The overall DC of the LCR was significantly higher than that of the TLR. The results suggest that a similar or higher DC than the control values could be achieved in 6-9 seconds by plasma arc curing, in 10-15 seconds by fast halogen curing or in 20 seconds by LED curing.

Halogens in chondritic meteorites and terrestrial accretion

NASA Astrophysics Data System (ADS)

Clay, Patricia L.; Burgess, Ray; Busemann, Henner; Ruzié-Hamilton, Lorraine; Joachim, Bastian; Day, James M. D.; Ballentine, Christopher J.

2017-11-01

Volatile element delivery and retention played a fundamental part in Earth’s formation and subsequent chemical differentiation. The heavy halogens—chlorine (Cl), bromine (Br) and iodine (I)—are key tracers of accretionary processes owing to their high volatility and incompatibility, but have low abundances in most geological and planetary materials. However, noble gas proxy isotopes produced during neutron irradiation provide a high-sensitivity tool for the determination of heavy halogen abundances. Using such isotopes, here we show that Cl, Br and I abundances in carbonaceous, enstatite, Rumuruti and primitive ordinary chondrites are about 6 times, 9 times and 15-37 times lower, respectively, than previously reported and usually accepted estimates. This is independent of the oxidation state or petrological type of the chondrites. The ratios Br/Cl and I/Cl in all studied chondrites show a limited range, indistinguishable from bulk silicate Earth estimates. Our results demonstrate that the halogen depletion of bulk silicate Earth relative to primitive meteorites is consistent with the depletion of lithophile elements of similar volatility. These results for carbonaceous chondrites reveal that late accretion, constrained to a maximum of 0.5 ± 0.2 per cent of Earth’s silicate mass, cannot solely account for present-day terrestrial halogen inventories. It is estimated that 80-90 per cent of heavy halogens are concentrated in Earth’s surface reservoirs and have not undergone the extreme early loss observed in atmosphere-forming elements. Therefore, in addition to late-stage terrestrial accretion of halogens and mantle degassing, which has removed less than half of Earth’s dissolved mantle gases, the efficient extraction of halogen-rich fluids from the solid Earth during the earliest stages of terrestrial differentiation is also required to explain the presence of these heavy halogens at the surface. The hydropilic nature of halogens, whereby they track with water, supports this requirement, and is consistent with volatile-rich or water-rich late-stage terrestrial accretion.

Fluorescence spectroscopy and amplified spontaneous emission (ASE) of phenylimidazoles: predicted vibronic coupling along the excited-state intramolecular proton transfer in 2-(2'-hydroxyphenyl)imidazoles.

PubMed

del Valle, Juan Carlos; Claramunt, R M; Catalán, J

2008-06-26

Methylation at the 1N position of 2-phenylimidazole provides the shortest wavelength for a liquid-state laser dye reported to date; that is, the 1-methyl-2-phenylimidazole molecule in cyclohexane solution yields amplified spontaneous emission (ASE) with a peak wavelength at 314.5 nm and a constant laser gain value of 5 cm(-1) from 310 to 317 nm. Methyl substitution in this case favors the appearance of laser action (owing to a torsion-vibrational mechanism) in cyclohexane as compared with the nonmethylated species which does not exhibit ASE in this solvent. The 2-(2'-hydroxyphenyl)imidazole molecules give rise to ASE with high gain values (ca. 9 cm(-1)) at 450 and 466 nm. The mechanism of population inversion is understood in terms of a vibronic coupling between the hydroxyl stretching motion and the torsional vibration of the phenyl and imidazole rings. The proton-transfer spectroscopy of 2-(2'-hydroxyphenyl)imidazoles is studied in dioxane, cyclohexane, dimethyl sulfoxide, methanol, and water. The greater the acidity of the solvent the greater the disruption of the intramolecular hydrogen bond; solvent acidity is the main parameter which favors formation of the open-form species in the ground electronic state. Methyl substitution at the 1N position favors formation of the open species for 2-hydroxyphenylimidazoles in the ground electronic state, which decreases their own capacity to undergo ASE. Low-temperature absorption spectroscopy confirms aggregation processes for 2-(2'-hydroxyphenyl)imidazoles in solution. In accordance with X-ray analyses in the solid phase, these molecules form associations through intermolecular chains of the type N-H...O or O-H...N.

Recognition of T·G mismatched base pairs in DNA by stacked imidazole-containing polyamides: surface plasmon resonance and circular dichroism studies

PubMed Central

Lacy, Eilyn R.; Cox, Kari K.; Wilson, W. David; Lee, Moses

2002-01-01

An imidazole-containing polyamide trimer, f-ImImIm, where f is a formamido group, was recently found using NMR methods to recognize T·G mismatched base pairs. In order to characterize in detail the T·G recognition affinity and specificity of imidazole-containing polyamides, f-ImIm, f-ImImIm and f-PyImIm were synthesized. The kinetics and thermodynamics for the polyamides binding to Watson–Crick and mismatched (containing one or two T·G, A·G or G·G mismatched base pairs) hairpin oligonucleotides were determined by surface plasmon resonance and circular dichroism (CD) methods. f-ImImIm binds significantly more strongly to the T·G mismatch-containing oligonucleotides than to the sequences with other mismatched or with Watson–Crick base pairs. Compared with the Watson–Crick CCGG sequence, f-ImImIm associates more slowly with DNAs containing T·G mismatches in place of one or two C·G base pairs and, more importantly, the dissociation rate from the T·G oligonucleotides is very slow (small kd). These results clearly demonstrate the binding selectivity and enhanced affinity of side-by-side imidazole/imidazole pairings for T·G mismatches and show that the affinity and specificity increase arise from much lower kd values with the T·G mismatched duplexes. CD titration studies of f-ImImIm complexes with T·G mismatched sequences produce strong induced bands at ∼330 nm with clear isodichroic points, in support of a single minor groove complex. CD DNA bands suggest that the complexes remain in the B conformation. PMID:11937638

C-I···π Halogen Bonding Driven Supramolecular Helix of Bilateral N-Amidothioureas Bearing β-Turns.

PubMed

Cao, Jinlian; Yan, Xiaosheng; He, Wenbin; Li, Xiaorui; Li, Zhao; Mo, Yirong; Liu, Maili; Jiang, Yun-Bao

2017-05-17

We report the first example of C-I···π halogen bonding driven supramolecular helix in highly dilute solution of micromolar concentration, using alanine based bilateral I-substituted N-amidothioureas that contain helical fragments, the β-turn structures. The halogen bonding interactions afford head-to-tail linkages that help to propagate the helicity of the helical fragments. In support of this action of the halogen bonding, chiral amplification was observed in the supramolecular helix formed in acetonitrile solution. The present finding provides alternative tools in the design of self-assembling macromolecules.

Aromatic fluorine compounds. XI. Replacement of chlorine by fluorine in halopyridines

USGS Publications Warehouse

Finger, G.C.; Starr, L.D.; Dickerson, D.R.; Gutowsky, H.S.; Hamer, J.

1963-01-01

The ??-halogenated pyridines react with potassium fluoride in various solvents to give replacement of the ??-halogen by fluorine. A 50% yield of 2-fluoropyridine was obtained from 2-chloropyridine by heating with potassium fluoride in dimethyl sulfone or tetramethylene sulfone for twenty-one days; 2-bromopyridine gave a similar yield with a heating period of only seven days. The ??-halogens of the polyhalopyridines undergo the exchange reaction more readily than do the halogens of the ??-monohalopyridines. The proposed structures of the fluoropyridines are supported by alternate syntheses and by n.m.r. studies.

New halogenated phenylcoumarins as tyrosinase inhibitors.

PubMed

Matos, Maria João; Santana, Lourdes; Uriarte, Eugenio; Delogu, Giovanna; Corda, Marcella; Fadda, Maria Benedetta; Era, Benedetta; Fais, Antonella

2011-06-01

With the aim to find out structural features for the tyrosinase inhibitory activity, in the present communication we report the synthesis and pharmacological evaluation of a new series of phenylcoumarin derivatives with different number of hydroxyl or ether groups and bromo substituent in the scaffold. The synthesized compounds 5-12 were evaluated as mushroom tyrosinase inhibitors showing, two of them, lower IC(50) than the umbelliferone. Compound 12 (IC(50)=215 μM) is the best tyrosinase inhibitor of this series. Copyright © 2011 Elsevier Ltd. All rights reserved.

Electronic and Ionic Transport in Processable Conducting Polymers. Symmetry Effects on the Physical and Electrically Conducting, Substituted Poly(di-2-thienylphenylenes)

DTIC Science & Technology

1991-10-21

incorporated using a Grignard coupling reaction. 19 The derivatives with long alkoxy side groups were successfully halogenated with elemental bromine in CC14...transmetallation reaction of 2-thienyllithium with 7 anhydrous zinc chloride. This reagent was treated with the 1,4-dibromo-2,5- disubstitutedbenzene...were attributed to the steric effects in polymer 7c and the regiospecificity in the alkoxy substituted polymers. Experimental Section Reagents and

Palladium-catalyzed cross coupling reactions of 4-bromo-6H-1,2-oxazines

PubMed Central

Schmidt, Elmar; Andrä, Michal; Duhs, Marcel-Antoine; Linder, Igor

2009-01-01

Summary A number of 4-aryl- and 4-alkynyl-substituted 6H-1,2-oxazines 8 and 9 have been prepared in good yields via cross coupling reactions of halogenated precursors 2, which in turn are easily accessible by bromination of 6H-1,2-oxazines 1. Lewis-acid promoted reaction of 1,2-oxazine 9c with 1-hexyne provided alkynyl-substituted pyridine derivative 12 thus demonstrating the potential of this approach for the synthesis of pyridines. PMID:19936264

A Rapid, One-Pot Synthesis of β-Siloxy-α-Haloaldehydes

PubMed Central

Saadi, Jakub; Akakura, Matsujiro

2011-01-01

The Mukaiyama cross aldol reaction of α-fluoro-, α-chloro-, and α-bromoacetaldehyde-derived (Z)-tris(trimethylsilyl)- silyl enol ethers furnishing anti-β-siloxy-α-haloaldehydes is described. A highly diastereoselective, one-pot, sequential double aldol process, affording novel β,δ-bissiloxy-α,γ-bishaloaldehydes is developed. Reactions are catalyzed by C6F5CHTf2 and C6F5CTf2AlMe2 (0.5–1.5 mol%) and provide access to halogenated polyketide fragments. PMID:21815682

Halogen Bonding: A Powerful Tool for Modulation of Peptide Conformation

PubMed Central

2017-01-01

Halogen bonding is a weak chemical force that has so far mostly found applications in crystal engineering. Despite its potential for use in drug discovery, as a new molecular tool in the direction of molecular recognition events, it has rarely been assessed in biopolymers. Motivated by this fact, we have developed a peptide model system that permits the quantitative evaluation of weak forces in a biologically relevant proteinlike environment and have applied it for the assessment of a halogen bond formed between two amino acid side chains. The influence of a single weak force is measured by detection of the extent to which it modulates the conformation of a cooperatively folding system. We have optimized the amino acid sequence of the model peptide on analogues with a hydrogen bond-forming site as a model for the intramolecular halogen bond to be studied, demonstrating the ability of the technique to provide information about any type of weak secondary interaction. A combined solution nuclear magnetic resonance spectroscopic and computational investigation demonstrates that an interstrand halogen bond is capable of conformational stabilization of a β-hairpin foldamer comparable to an analogous hydrogen bond. This is the first report of incorporation of a conformation-stabilizing halogen bond into a peptide/protein system, and the first quantification of a chlorine-centered halogen bond in a biologically relevant system in solution. PMID:28581720

Tropospheric Halogen Chemistry

NASA Astrophysics Data System (ADS)

von Glasow, R.; Crutzen, P. J.

2003-12-01

Halogens are very reactive chemicals that are known to play an important role in anthropogenic stratospheric ozone depletion chemistry, first recognized by Molina and Rowland (1974). However, they also affect the chemistry of the troposphere. They are of special interest because they are involved in many reaction cycles that can affect the oxidation power of the atmosphere indirectly by influencing the main oxidants O3 and its photolysis product OH and directly, e.g., by reactions of the Cl radical with hydrocarbons (e.g., CH4).Already by the middle of the nineteenth century, Marchand (1852) reported the presence of bromine and iodine in rain and other natural waters. He also mentions the benefits of iodine in drinking water through the prevention of goitres and cretinism. In a prophetic monograph "Air and Rain: The Beginnings of a Chemical Climatology," Smith (1872) describes measurements of chloride in rain water, which he states to originate partly from the oceans by a process that he compares with the bursting of "soap bubbles" which produces "small vehicles" that transfer small spray droplets of seawater to the air. From deviations of the sulfate-to-chloride ratio in coastal rain compared to seawater, Smith concluded that chemical processes occur once the particles are airborne.For almost a century thereafter, however, atmospheric halogens received little attention. One exception was the work by Cauer (1939), who reported that iodine pollution has been significant in Western and Central Europe due to the inefficient burning of seaweed, causing mean gas phase atmospheric concentrations as high as or greater than 0.5 μg m-3. In his classical textbook Air Chemistry and Radioactivity, Junge (1963) devoted less than three pages to halogen gas phase chemistry, discussing chlorine and iodine. As reviewed by Eriksson (1959a, b), the main atmospheric source of halogens is sea salt, derived from the bursting of bubbles of air which are produced by ocean waves and other processes. Early work by Cauer (1951) had shown that Cl/Na and Cl/Mg ratios were lower in air than in seawater, indicating loss of chlorine by "acid displacement" from sea salt by the strong acids, H2SO4 (Eriksson (1959a, b) and HNO3 (Robbins et al., 1959). Already the first measurements of bromine in aerosols by Duce et al. (1963) showed that bromine, like chlorine, was lost from the sea salt particles, whereas iodine was strongly enriched ( Duce et al., 1965). Research since the early 1980s has shown that photochemical processes are actively involved.Interest in the chemistry of atmospheric halogens took a steep upward surge after it was postulated that the release of industrially produced halocarbons, in particular the chlorofluorocarbons (CFCs), CFCl3, and CF2Cl2, could cause severe depletions in stratospheric ozone (Molina and Rowland, 1974) by the reactions involving the CFC photolytic product radicals, Cl and ClO, as catalysts. The first stratospheric measurements of ClO did indeed show its presence in significant quantities in the stratosphere so that by the end of the 1970s USA, Canada, and the Scandinavian countries issued laws against the use of CFC gases as propellants in spray cans. In the mid-1980s the springtime stratospheric ozone hole over Antarctica was discovered by Farman et al. (1985), involving heterogeneous reactions on polar stratospheric clouds that lead to chlorine activation ( Solomon et al., 1986). Ten years later, in 1996, a complete phaseout ofthe production of the CFCs and a number of other chlorine- or bromine-containing chemicals came into effect for all nations in the developed world. In this contribution we will, however, concentrate on the impact of reactive chlorine, bromine, and iodine on tropospheric ozone chemistry.Halogens have the potential to be important in many facets of tropospheric chemistry. A multitude of gas phase reactions and gas-particle interactions occur that include coupling with the sulfur cycle and reactions with hydrocarbons. Loss of ozone by catalytic reactions involving halogen radicals lowers the concentrations of the hydroxyl radical OH and thus the oxidation power of the atmosphere. Figure 1 shows these and other relevant halogen-related processes schematically. The sum of particulate and gaseous halogen concentrations maximize in the marine troposphere. Important for our climate - via feedback with cloud microphysics mainly in the large regions of marine stratocumulus - are links between halogen chemistry and the sulfur cycle. HOBraq and HOClaq can increase the liquid phase oxidation of S(IV) to S(VI), while BrO can decrease the most important in situ source for SO2 in the marine troposphere, namely, the oxidation of DMS to SO2 by reaction with OH by providing an alternate pathway (BrO+DMS) that reduces the yield of SO2 from DMS oxidation. Thus, the presence of bromine and chlorine in the troposphere lowers gas phase SO2 concentrations and thus the formation of new sulfate particles via the reaction sequence SO2+OH→H2SO4. (17K)Figure 1. Schematic depiction of the most important halogen-related processes in the troposphere. High mixing ratios of iodine oxide at a coastal site indicate a potentially significant role of iodine for the destruction of O3 and new particle embryo formation (Alicke et al., 1999; O'Dowd et al., 1998). Almost 20 years earlier, Chameides and Davis (1980) suggested that open ocean iodine chemistry would be initiated by the photolysis of CH3I. This was based on the measurements of Lovelock et al. (1973) and Singh et al. (1979), who found volume mixing ratios of CH3I of 1-5 pmol mol-1 over the ocean.The potentially strong involvement of halogens in tropospheric chemistry was first observed in the Arctic, where strong ozone depletion events were found to coincide with high levels of bromine (Barrie et al., 1988).The first mid-latitude demonstration of reactive halogen chemistry in the troposphere was made downwind of salt pans in the Dead Sea area, where the so far highest atmospheric mixing ratios of BrO were measured (Hebestreit et al., 1999). Volcanoes are sources of halogens as well, mainly in the form of HCl. Biomass burning releases halogens as do industrial processes.So far we have only mentioned chlorine, bromine, and iodine. This is justified because chemistry of fluorine is of no consequence, as very unreactive HF is efficiently formed in the atmosphere, e.g., via the reaction F+H2O→HF+OH. However, several fluorine-containing gases of anthropogenic origin are potentially powerful greenhouse gases, because they absorb strongly in the infrared atmospheric window region near 10 μm. Fully fluorinated gases - such as SF6, CF4, and C2F6 - have atmospheric lifetimes of the order of thousands of years and thus possess very high global warming potential (GWP). Although their abundance in the atmosphere has not yet grown large enough to be of concern for Earth's climate, their production must ultimately be curtailed in the future. The most abundant fully fluorinated gas, CF4, had an atmospheric volume mixing ratio of ˜75 pmol mol-1 in 1995 (Warneck, 1999). Because of their higher concentrations in the atmosphere, about 270 pmol mol-1 and 530 pmol mol-1, respectively, the CFC gases, CFCl3 and CF2Cl2, already exert a significant radiative greenhouse forcing (Ramanathan, 1975) on Earth's climate. For further discussion about atmospheric fluorine, the reader is referred to a thorough review article by Harnisch (1999).Several overview articles have been published on tropospheric halogen chemistry since the early 1980s, starting with Cicerone (1981). Wayne et al. (1995) list in great detail reaction paths, laboratory data, and atmospheric implications of halogen oxides. A good overview on laboratory measurements was also given by de Haan et al. (1999). Reaction cycles involved in tropospheric halogen chemistry and measurements are also thoroughly discussed by Platt (2000) and Platt and Hönninger (2003). Important compilations of laboratory studies that were made to elucidate chemical reaction paths are given by, e.g., DeMore et al. (1997), Sander et al. (2000), and Atkinson et al. (1999, 2000). Emission inventories for chlorine were compiled by Graedel and Keene (1995) and Keene et al. (1999).In Section 4.02.2 of this overview we will first describe the main halogen reaction mechanisms and then discuss, in Section 4.02.3, the springtime surface ozone depletion events in high latitudes that were first observed in the Arctic. Another main part of this chapter is concerned with halogens in the marine boundary layer ( Section 4.02.4). In Section 4.02.5 we describe interactions of halogens with some other elements of atmospheric importance. A very recently discovered environment where halogen chemistry plays a large role are salt lakes ( Section 4.02.6). There the chemistry bears similarity to that of the high-latitude ozone depletion events. This is followed in Section 4.02.7 by a discussion of halogen chemistry in the free troposphere and in Section 4.02.8 by other sources of halogens such as industry and biomass burning.

Polymeric medium

DOEpatents

Klaehn, John R [Idaho Falls, ID; Peterson, Eric S [Idaho Falls, ID; Orme, Christopher J [Shelley, ID; Jones, Michael G [Chubbuck, ID; Wertsching, Alan K [Idaho Falls, ID; Luther, Thomas A [Idaho Falls, ID; Trowbridge, Tammy L [Idaho Falls, ID

2012-03-06

A PBI compound includes imidazole nitrogens at least a portion of which are substituted with a moiety containing a carbonyl group, the substituted imidazole nitrogens being bonded to carbon of the carbonyl group. At least 85% of the nitrogens may be substituted. The carbonyl-containing moiety may include RCO--, where R is alkoxy or haloalkyl. The PBI compound may exhibit a first temperature marking an onset of weight loss corresponding to reversion of the substituted PBI that is less than a second temperature marking an onset of decomposition of an otherwise identical PBI compound without the substituted moiety. The PBI compound may be included in separatory media. A substituted PBI synthesis method may include providing a parent PBI in a less than 5 wt % solvent solution. Substituting may use more than 5 equivalents in relation to the imidazole nitrogens to be substituted.

Polybenzimidazole compounds

DOEpatents

Klaehn, John R [Idaho Falls, ID; Peterson, Eric S [Idaho Falls, ID; Orme, Christopher J [Shelley, ID; Jones, Michael G [Chubbuck, ID; Wertsching, Alan K [Idaho Falls, ID; Luther, Thomas A [Idaho Falls, ID; Trowbridge, Tammy L [Idaho Falls, ID

2011-11-22

A PBI compound includes imidazole nitrogens at least a portion of which are substituted with a moiety containing a carbonyl group, the substituted imidazole nitrogens being bonded to carbon of the carbonyl group. At least 85% of the nitrogens may be substituted. The carbonyl-containing moiety may include RCO--, where R is alkoxy or haloalkyl. The PBI compound may exhibit a first temperature marking an onset of weight loss corresponding to reversion of the substituted PBI that is less than a second temperature marking an onset of decomposition of an otherwise identical PBI compound without the substituted moiety. The PBI compound may be included in separatory media. A substituted PBI synthesis method may include providing a parent PBI in a less than 5 wt % solvent solution. Substituting may use more than 5 equivalents in relation to the imidazole nitrogens to be substituted.

Characterization of newly synthesized pyrimidine derivatives for corrosion inhibition as inferred from computational chemical analysis

NASA Astrophysics Data System (ADS)

El-Taib Heakal, F.; Rizk, S. A.; Elkholy, A. E.

2018-01-01

Corrosion of metallic constructions is a serious problem in most industries worldwide that can be controlled via addition of special chemicals having adsorption capability on metal surfaces and hence isolating it from the aggressive environment. These chemicals are characterized by being rich in functional groups containing free lone pairs of electrons and/or π-electrons. In the present study four newly imidazole-pyrimidine based ionic derivatives have been synthesized and their structures were characterized by means of elemental analysis and different spectroscopic techniques. Quantum chemical calculations were carried out to give insights into the structural and electronic characteristics of these fabricated compounds. Monte Carlo simulation was also applied to shed the light on our prepared corrosion inhibitor molecules by examining their aptitude to adsorb on iron surface. Our ultimate goal is to help industries in fighting corrosion by providing them with a cheap and efficient anti-corrosion molecules.

Evaluation of readily accessible azoles as mimics of the aromatic ring of D-phenylalanine in the turn region of gramicidin S.

PubMed

van der Knaap, Matthijs; Lageveen, Lianne T; Busscher, Henk J; Mars-Groenendijk, Roos; Noort, Daan; Otero, José M; Llamas-Saiz, Antonio L; van Raaij, Mark J; van der Marel, Gijsbert A; Overkleeft, Herman S; Overhand, Mark

2011-05-02

The influence of replacing the d-phenylalanine residue with substituted and unsubstituted azoles on the structure and biological activity of the antibiotic gramicidin S was investigated against a representative panel of Gram-positive and Gram-negative bacteria strains. Substituted triazole derivatives, obtained using a convergent synthetic strategy, are as active as gramicidin S, provided that any substituent on the triazole moiety is not too large. The unsubstituted triazole derivative was biologically less active than the parent natural product, gramicidin S. In general for the triazole series, the hemolytic activity could be correlated with the antibacterial activity, that is, the higher the antibacterial activity, the higher the toxicity towards blood cells. Interestingly, its imidazole counterpart showed high antibacterial activity, combined with significantly diminished hemolytic activity. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Heavy metal coordination chemistry in mercaptides and enzymes studied by TDPAC

NASA Astrophysics Data System (ADS)

Butz, T.

1993-03-01

Time differential perturbed angular correlation (TDPAC) studies of the coordination chemistry of the heavy metal atoms Cd and Hg via the nuclear quadrupole interaction are presented for the following systems; (i) mercury complexes with mercaptides, polymers with thiol groups, and ferrocenethiols. Mercury has a strong tendency to form linear or almost linear bonds with sulfur ligands. Evidence for 1,3-dithia-2-mercura[3]ferrocenophane formation is presented. (ii)111mCd-derivatives of the small electron transport proteins azurin, including a his 117gly mutant, and stellacyanin. The titration of the his 117gly mutant of azurin with imidazole was monitored in situ. (iii)111mCd- and199mHg-derivatives of the multi-Cu enzymes ascorbate oxidase and laccase. Reconstitution probabilities for Hg-reconstitution will be given as well as information on selective depletion and blocking of Cu-sites.

The influence of ocean halogen and sulfur emissions in the air quality of a coastal megacity: The case of Los Angeles

EPA Science Inventory

The oceans are the main source of natural halogen and sulfur compounds, which have a significant influence on the oxidizing capacity of the marine atmosphere; however, their impact on the air quality of coastal cities is currently unknown. We explore the effect of marine halogens...

Halogen-free benzoxazine based curable compositions for high TG applications

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

Tietze, Roger; Nguyen, Yen-Loan

The present invention provides a halogen-free curable composition including a benzoxazine monomer, at least one epoxy resin, a catalyst, a toughening agent and a solvent. The halogen-free curable composition is especially suited for use in automobile and aerospace applications since the composition, upon curing, produces a composite having a high glass transition temperature.