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Sample records for quinones

  1. Electrocoagulation of Quinone Pigments

    Directory of Open Access Journals (Sweden)

    Duang Buddhasukh

    2006-07-01

    Full Text Available Some representative quinones, viz. one naphthoquinone (plumbagin and five anthraquinones (alizarin, purpurin, chrysazin, emodin, and anthrarufin, were subjected to electrocoagulation. It was found that the rate and extent of coagulation of these compounds appears to correlate with the number and relative position of their phenolic substituent groups, and that all of the coagulated quinones could be recovered. Attempts were then made to electrochemically isolate three quinones, namely plumbagin, morindone and erythrolaccin, from natural sources.

  2. Quinone Reductase 2 Is a Catechol Quinone Reductase

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Yue; Buryanovskyy, Leonid; Zhang, Zhongtao (NYMEDCO)

    2008-09-05

    The functions of quinone reductase 2 have eluded researchers for decades even though a genetic polymorphism is associated with various neurological disorders. Employing enzymatic studies using adrenochrome as a substrate, we show that quinone reductase 2 is specific for the reduction of adrenochrome, whereas quinone reductase 1 shows no activity. We also solved the crystal structure of quinone reductase 2 in complexes with dopamine and adrenochrome, two compounds that are structurally related to catecholamine quinones. Detailed structural analyses delineate the mechanism of quinone reductase 2 specificity toward catechol quinones in comparison with quinone reductase 1; a side-chain rotational difference between quinone reductase 1 and quinone reductase 2 of a single residue, phenylalanine 106, determines the specificity of enzymatic activities. These results infer functional differences between two homologous enzymes and indicate that quinone reductase 2 could play important roles in the regulation of catecholamine oxidation processes that may be involved in the etiology of Parkinson disease.

  3. Quinone diazides for olefin functionalization.

    Science.gov (United States)

    Dao, Hai T; Baran, Phil S

    2014-12-22

    The utility of quinone diazides in materials science is vast and well-documented, yet this potentially useful motif has languished in the annals of organic synthesis. Herein we show that modern tools of catalysis can be employed with free or suitably masked quinone diazides to unleash the power of these classic diazo compounds in the context of both inter- and intramolecular olefin cyclopropanation.

  4. Antitermitic quinones from Diospyros sylvatica.

    Science.gov (United States)

    Ganapaty, Seru; Thomas, Pannakal Steve; Fotso, Serge; Laatsch, Hartmut

    2004-05-01

    Six quinones were isolated from the chloroform extract of the roots of Diospyros sylvatica and identified as 2-methyl-anthraquinone, plumbagin, diosindigo, diospyrin, isodiospyrin and microphyllone. The effect of the root extract on the orientation and survival of the subterranean termite, Odontotermes obesus was tested. In addition, four of these quinones were tested on the survival of the subterranean termite. In a direct-choice experiment, exposure to an extract-treated filter disc had a significantly repellent effect over the solvent-treated filter disc. The no-choice experiment revealed the toxic property of the extract as well as the tested quinones and showed high mortality of the O. obesus workers after 48 h on forced exposure. The major termiticidal components identified were plumbagin, isodiospyrin and microphyllone while diospyrin was not toxic to termites at the concentration tested. All the quinones are reported for the first time from D. sylvatica.

  5. Structure activity study on the quinone/quinone methide chemistry of flavonoids

    NARCIS (Netherlands)

    Awad, H.M.; Boersma, M.G.; Boeren, S.; Bladeren, van P.J.; Vervoort, J.; Rietjens, I.M.C.M.

    2001-01-01

    A structure-activity study on the quinone/quinone methide chemistry of a series of 3',4'-dihydroxyflavonoids was performed. Using the glutathione trapping method followed by HPLC, 1H NMR, MALDI-TOF, and LC/MS analysis to identify the glutathionyl adducts, the chemical behavior of the quinones/quinon

  6. Abietane Quinones from Rabdosia serra

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A new abietane quinone diterpenoid was isolated, together with horminone, 16-acetoxy-7-0-acetylhorminone, β-sitosterol, stigmasterol, ursolic acid and palmitic acid from the leaves of Rabdosia Serra (MAXIM) Hara. The new compound was elucidated as 16-acetoxy-7α-ethoxyroyleanone.

  7. Quinones in aerobic and anaerobic mitochondria

    NARCIS (Netherlands)

    van der Klei, S.A.

    2009-01-01

    Ubiquinone (UQ), also known as coenzyme Q, is a ubiquitous quinone and is known to have several functions. One of these functions is electron carrier in the mitochondrial electron transport chain of aerobically functioning bacteria and eukaryotes. In contrast to this aerobically functioning quinone,

  8. Quinones in aerobic and anaerobic mitochondria

    NARCIS (Netherlands)

    van der Klei, S.A.

    2009-01-01

    Ubiquinone (UQ), also known as coenzyme Q, is a ubiquitous quinone and is known to have several functions. One of these functions is electron carrier in the mitochondrial electron transport chain of aerobically functioning bacteria and eukaryotes. In contrast to this aerobically functioning quinone,

  9. Structure activity study on the quinone/quinone methide chemistry of flavonoids

    NARCIS (Netherlands)

    Awad, H.M.; Boersma, M.G.; Boeren, S.; Bladeren, van P.J.; Vervoort, J.; Rietjens, I.M.C.M.

    2001-01-01

    A structure-activity study on the quinone/quinone methide chemistry of a series of 3',4'-dihydroxyflavonoids was performed. Using the glutathione trapping method followed by HPLC, 1H NMR, MALDI-TOF, and LC/MS analysis to identify the glutathionyl adducts, the chemical behavior of the

  10. Quinones and Sulfhydryl-Dependent Immunotoxicity

    Science.gov (United States)

    1983-08-01

    Research Triangle Park, North Carolina 7 INTRODUCTION_ The work to be described is based on the use of immunologic models to understand mec-4tnisms of...and o-quinone metabolites of immunotoxic xenobiotics or analogous resonance struc- tures that possess SH-alkylating activity. Potency differences are...1765-1769. Lane, M. A. (1978)t Muscarinic cholinergic activation of mouse spleen cells cytotoxic to tumor cells in vitro, J. Natl. Cancer Inst., 61:923

  11. Quinone emissions from gasoline and diesel motor vehicles.

    Science.gov (United States)

    Jakober, Chris A; Riddle, Sarah G; Robert, Michael A; Destaillats, Hugo; Charles, M Judith; Green, Peter G; Kleeman, Michael J

    2007-07-01

    Gas- and particle-phase emissions from gasoline and diesel vehicles operated on chassis dynamometers were collected using annular denuders, quartz filters, and PUF substrates. Quinone species were measured using O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine derivatization in conjunction with gas chromatography-mass spectrometry and high-performance liquid chromatography-mass spectrometry. Nine quinones were observed, ranging from C6 to C16. New species identified in motor vehicle exhaust include methyl-1,4-benzoquinone, 2-methyl-1,4-naphthoquinone (MNQN), and aceanthrenequinone. Gas-phase motor vehicle emissions of quinones are also reported for the first time. Six gas-phase quinones were quantified with emission rates of 2-28 000 microg L(-1) fuel consumed. The most abundant gas-phase quinones were 1,4-benzoquinone (BON) and MNQN. The gas-phase fraction was > or = 69% of quinone mass for light-duty gasoline emissions, and > or = 84% for heavy-duty diesel emissions. Eight particle-phase quinones were observed between 2 and 1600 microg L(-1), with BQN the most abundant species followed by 9,10-phenanthrenequinone and 1,2-naphthoquinone. Current particle-phase quinone measurements agree well with the few available previous results. Further research is needed concerning the gas-particle partitioning behavior of quinones in ambient and combustion source conditions.

  12. Reactivities of Quinone Methides versus o-Quinones in Catecholamine Metabolism and Eumelanin Biosynthesis

    Directory of Open Access Journals (Sweden)

    Manickam Sugumaran

    2016-09-01

    Full Text Available Melanin is an important biopolymeric pigment produced in a vast majority of organisms. Tyrosine and its hydroxylated product, dopa, form the starting material for melanin biosynthesis. Earlier studies by Raper and Mason resulted in the identification of dopachrome and dihydroxyindoles as important intermediates and paved way for the establishment of well-known Raper–Mason pathway for the biogenesis of brown to black eumelanins. Tyrosinase catalyzes the oxidation of tyrosine as well as dopa to dopaquinone. Dopaquinone thus formed, undergoes intramolecular cyclization to form leucochrome, which is further oxidized to dopachrome. Dopachrome is either converted into 5,6-dihydroxyindole by decarboxylative aromatization or isomerized into 5,6-dihydroxyindole-2-carboxylic acid. Oxidative polymerization of these two dihydroxyindoles eventually produces eumelanin pigments via melanochrome. While the role of quinones in the biosynthetic pathway is very well acknowledged, that of isomeric quinone methides, however, remained marginalized. This review article summarizes the key role of quinone methides during the oxidative transformation of a vast array of catecholamine derivatives and brings out the importance of these transient reactive species during the melanogenic process. In addition, possible reactions of quinone methides at various stages of melanogenesis are discussed.

  13. The Diterpenoid Quinones from Coleus forskohlii

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Two new diterpenoid quinones, coleon S and T were isolated from the chloroform extract of the leaves of Coleus forskohlii, and based on spectroscopic data, their structures were identified as 1,4-phenathrenedione-4b,5,6,8a,9,10-hexahydro-3,9b,10a-trihydroxy-4b,7,8-rimethyl -2-(2-ethoxypropyl)(1) and 1,4-phenathrenedione-2,3,4b,5,6, 8a,9,10-octahydro-3,9b,10a- tri-hydroxy-4b,7,8-trimethyl-2-propylene(2), respectively.

  14. Reversible redox chemistry of quinones: impact on biogeochemical cycles.

    Science.gov (United States)

    Uchimiya, Minori; Stone, Alan T

    2009-10-01

    The role of quinone biomolecules and quinone moieties of natural organic matter (NOM) as the electron transfer mediator in essential biogeochemical processes such as iron bioreduction and contaminant degradation has received considerable interests in the past decade. Hypothesized electron shuttling mechanism must be evaluated based on the availability and stability of quinones under a given environmental setting. The goal of this review is to examine the source, reactivity, and fate of potential quinone catalysts with respect to chemical interactions (e.g., with other quinones and nucleophiles) that will inevitably occur in complex environmental media. We will first discuss natural and anthropogenic sources of quinones in aqueous environments, and fundamental transformation pathways including cross reaction, autoxidation, and addition reactions. We will then assess how the described sources (molecular structure) and transformation pathways (stability) will impact the ability of a quinone molecule to catalyze a biogeochemical process. Thermodynamics and kinetics of electron transfer reactions with both the electron donor (e.g., hydrogen sulfide as a bulk reductant) and the terminal electron acceptor (e.g., nitroaromatic explosives in contaminant degradation), and stability towards irreversible side reactions are the key factors determining the geochemical conditions under which the catalysis by a quinone molecule will be operative.

  15. Antiprotozoal Isoflavan Quinones from Abrus precatorius ssp. africanus

    CSIR Research Space (South Africa)

    Hata, Y

    2013-04-01

    Full Text Available ) and abruquinone G (2), and three isoflavan quinones, abruquinone I (3), abruquinone B (4), and 7, 8, 3′‚5′- tetramethoxyisoflavan-1′,4′- quinone (5). Compounds 1 and 3 were new natural products. The absolute configuration of compounds was determined by comparison...

  16. Production and Radioprotective Effects of Pyrroloquinoline Quinone

    Directory of Open Access Journals (Sweden)

    De-Xuan Yang

    2011-12-01

    Full Text Available Pyrroloquinoline quinone (PQQ was produced by fermentation of the Methylovorus sp. MP688 strain and purified by ion-exchange chromatography, crystallization and recrystallization. The yield of PQQ reached approximately 125 mg/L and highly pure PQQ was obtained. To determine the optimum dose of PQQ for radioprotection, three doses (2 mg/kg, 4 mg/kg, 8 mg/kg of PQQ were orally administrated to the experimental animals subjected to a lethal dose of 8.0 Gy in survival test. Survival of mice in the irradiation + PQQ (4 mg/kg group was found to be significantly higher in comparison with the irradiation and irradiation + nilestriol (10 mg/kg groups. The numbers of hematocytes and bone marrow cells were measured for 21 days after sublethal 4 Gy gamma-ray irradiation with per os of 4 mg/kg of PQQ. The recovery of white blood cells, reticulocytes and bone marrow cells in the irradiation + PQQ group was faster than that in the irradiation group. Furthermore, the recovery of bone marrow cell in the irradiation + PQQ group was superior to that in irradiation + nilestriol group. Our results clearly indicate favourable effects on survival under higher lethal radiation doses and the ability of pyrroloquinoline quinine to enhance haemopoietic recovery after sublethal radiation exposure.

  17. Quinone-induced protein handling changes: Implications for major protein handling systems in quinone-mediated toxicity

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, Rui; Siegel, David; Ross, David, E-mail: david.ross@ucdenver.edu

    2014-10-15

    Para-quinones such as 1,4-Benzoquinone (BQ) and menadione (MD) and ortho-quinones including the oxidation products of catecholamines, are derived from xenobiotics as well as endogenous molecules. The effects of quinones on major protein handling systems in cells; the 20/26S proteasome, the ER stress response, autophagy, chaperone proteins and aggresome formation, have not been investigated in a systematic manner. Both BQ and aminochrome (AC) inhibited proteasomal activity and activated the ER stress response and autophagy in rat dopaminergic N27 cells. AC also induced aggresome formation while MD had little effect on any protein handling systems in N27 cells. The effect of NQO1 on quinone induced protein handling changes and toxicity was examined using N27 cells stably transfected with NQO1 to generate an isogenic NQO1-overexpressing line. NQO1 protected against BQ–induced apoptosis but led to a potentiation of AC- and MD-induced apoptosis. Modulation of quinone-induced apoptosis in N27 and NQO1-overexpressing cells correlated only with changes in the ER stress response and not with changes in other protein handling systems. These data suggested that NQO1 modulated the ER stress response to potentiate toxicity of AC and MD, but protected against BQ toxicity. We further demonstrated that NQO1 mediated reduction to unstable hydroquinones and subsequent redox cycling was important for the activation of the ER stress response and toxicity for both AC and MD. In summary, our data demonstrate that quinone-specific changes in protein handling are evident in N27 cells and the induction of the ER stress response is associated with quinone-mediated toxicity. - Highlights: • Unstable hydroquinones contributed to quinone-induced ER stress and toxicity.

  18. Electronic transport properties of a quinone-based molecular switch

    Science.gov (United States)

    Zheng, Ya-Peng; Bian, Bao-An; Yuan, Pei-Pei

    2016-09-01

    In this paper, we carried out first-principles calculations based on density functional theory and non-equilibrium Green's function to investigate the electronic transport properties of a quinone-based molecule sandwiched between two Au electrodes. The molecular switch can be reversibly switched between the reduced hydroquinone (HQ) and oxidized quinone (Q) states via redox reactions. The switching behavior of two forms is analyzed through their I- V curves, transmission spectra and molecular projected self-consistent Hamiltonian at zero bias. Then we discuss the transmission spectra of the HQ and Q forms at different bias, and explain the oscillation of current according to the transmission eigenstates of LUMO energy level for Q form. The results suggest that this kind of a quinone-based molecule is usable as one of the good candidates for redox-controlled molecular switches.

  19. Quinones as Strecker degradation reagents in wine oxidation processes.

    Science.gov (United States)

    Oliveira, Carla Maria; Santos, Sónia A O; Silvestre, Armando J D; Barros, António S; Ferreira, António César Silva; Silva, Artur M S

    2017-08-01

    The Strecker aldehydes formed during the reaction between α-amino acids (phenylalanine or methionine) and either gallic acid, caffeic acid or (+)-catechin ortho-quinones were evaluated in wine-model systems. It was demonstrated that phenylacetaldehyde was formed by quinone intermediates at wine pH. The highest amounts of phenylacetaldehyde during the 10days of experiment (69±5µg/L/day; 7x>Control) were obtained from (+) catechin, followed by gallic acid (61±4µg/L/day; 6x>Control) and caffeic acid (41±4µg/L/day; 4x>Control). The intermediate structures delivered from the reaction of ortho-quinones with α-amino acids were demonstrated by MS(n). Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Terahertz time-domain spectroscopic investigation on quinones

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Well resolved far-infrared spectra of 1,4-benzoquinone, 1,4-naphthoquinone, and 9, 10-anthraquinonme in polycrystalline form have been measured with terahertz time domain spectroscopy at room tem- perature. The characterizations of power absorption and index of refraction in the frequency range 0.3 -2.0 THz are presented. Theoretical calculation is applied to assist the analysis and assignment of individual THz absorption spectra of the p-quinones with semiempirical AM1, Hartree-Fock (HF), and density functional theory (DFT) method. Observed THz responses are assigned to the translational and torsional vibrations of p-quinone dimer held together by weak hydrogen bonds.

  1. Terahertz time-domain spectroscopic investigation on quinones

    Institute of Scientific and Technical Information of China (English)

    GE Min; ZHAO HongWei; WANG WenFeng; YU XiaoHan; LI WenXin

    2008-01-01

    Well resolved far-infrared spectra of 1,4-benzoquinone, 1,4-naphthoquinone, and 9, 10-anthraquinonme in polycrystalline form have been measured with terahertz time domain spectroscopy at room tem-perature. The characterizations of power absorption and index of refraction in the frequency range 0.3 -2.0 THz are presented. Theoretical calculation is applied to assist the analysis and assignment of individual THz absorption spectra of the p-quinones with semiempirical AM1, Hartree-Fock (HF), and density functional theory (DFT) method. Observed THz responses are assigned to the translational and torsional vibrations of p-quinone dimer held together by weak hydrogen bonds.

  2. The regioselectivity of glutathione adduct formation with flavonoid quinone methides is pH-dependent

    NARCIS (Netherlands)

    Awad, H.M.; Boersma, M.G.; Boeren, S.; Vervoort, J.; Bladeren, van P.J.; Rietjens, I.M.C.M.

    2002-01-01

    In the present study, the formation of glutathionyl adducts from a series of 3',4'-dihydroxy flavonoid o-quinone/p-quinone methides was investigated with special emphasis on the regioselectivity of the glutathione addition as a function of pH. The flavonoid o-quinones were generated using

  3. The regioselectivity of glutathione adduct formation with flavonoid quinone methides is pH-dependent

    NARCIS (Netherlands)

    Awad, H.M.; Boersma, M.G.; Boeren, S.; Vervoort, J.; Bladeren, van P.J.; Rietjens, I.M.C.M.

    2002-01-01

    In the present study, the formation of glutathionyl adducts from a series of 3',4'-dihydroxy flavonoid o-quinone/p-quinone methides was investigated with special emphasis on the regioselectivity of the glutathione addition as a function of pH. The flavonoid o-quinones were generated using horseradis

  4. Two New Abietane Quinones from Isodon lophanthoides var. Micranthus

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The structures of two new abietane quinones, named micranthins A and B, weredetermined to be 7α-methoxy-14, 16-epoxy-8, 13-abietadiene-11, 12-dione (1) and 16-acetoxy-6,7-dehydroroyleanone (2) respectively, which were isolated from Isodon lophanthoides var.micranthus.

  5. Structural requirements of pyrroloquinoline quinone dependent enzymatic reactions

    NARCIS (Netherlands)

    Oubrie, Arthur; Dijkstra, Bauke W.

    2000-01-01

    On the basis of crystal structures of the pyrroloquinoline quinone (PQQ) dependent enzymes methanol dehydrogenase (MDH) and soluble glucose dehydrogenase (s-GDH), different catalytic mechanisms have been proposed. However, several lines of biochemical and kinetic evidence are strikingly similar for

  6. Removal of bisphenol derivatives through quinone oxidation by polyphenol oxidase and subsequent quinone adsorption on chitosan in the heterogeneous system.

    Science.gov (United States)

    Kimura, Yuji; Takahashi, Ayumi; Kashiwada, Ayumi; Yamada, Kazunori

    2015-01-01

    In this study, the combined use of a biopolymer chitosan and an oxidoreductase polyphenol oxidase (PPO) was systematically investigated for the removal of bisphenol derivatives from aqueous medium. The process parameters, such as the pH value, temperature, and PPO concentration, were estimated to conduct the enzymatic quinone oxidation of bisphenol derivatives by as little enzyme as possible. Bisphenol derivatives effectively underwent PPO-catalysed quinone oxidation without H2O2 unlike other oxidoreductases, such as peroxidase and tyrosinase, and the optimum conditions were determined to be pH 7.0 and 40°C for bisphenol B, bisphenol E, bisphenol O, and bisphenol Z; pH 7.0 and 30°C for bisphenol C and bisphenol F; and pH 8.0 and 40°C for bisphenol T. They were completely removed through adsorption of enzymatically generated quinone derivatives on chitosan beads or chitosan powders. Quinone adsorption on chitosan beads or chitosan powders in the heterogeneous system was found to be a more effective procedure than generation of aggregates in the homogeneous system with chitosan solution. The removal time was shortened by increasing the amount of chitosan beads or decreasing the size of the chitosan powders.

  7. Study of quinones reactions with wine nucleophiles by cyclic voltammetry.

    Science.gov (United States)

    Oliveira, Carla M; Barros, António S; Ferreira, António C S; Silva, Artur M S

    2016-11-15

    Quinones are electrophilic species which can react with various nucleophiles, like wine antioxidants, such as sulfur dioxide or ascorbic acid, thiols, amino acids, and numerous polyphenols. These reactions are very important in wine aging because they mediate oxygen reactions during both production and bottle aging phases. In this work, the major challenge was to determine the interaction between ortho-quinones and wine nucleophiles (amino acids, thiols, and the antioxidants SO2 and ascorbic acid), by cyclic voltammetry. Wine-model solutions with gallic acid, caffeic acid, or (+)-catechin and nucleophilic compounds were used. To understand the effect of nucleophilic addition in wine, a white wine with the same added nucleophiles was also analysed. Cyclic voltammograms were taken with glassy carbon electrode or screen-printed carbon electrodes, respectively, for wine-model and white wines solutions, in the absence and in the presence of nucleophiles. A nucleophilic order profile related to the cathodic current intensity decrease was observed.

  8. Quinone-Enriched Gold Nanoparticles in Bioelectrochemistry and Charge Storage

    DEFF Research Database (Denmark)

    Wagner, Michal; Qvortrup, Katrine; Tanner, David Ackland

    We are aiming at the development of a general electrochemical platform suitable for multifarious investigations of biogenic materials. The new platform can be attained by grafting organic/metal hybrids with quinone functionality. In-house made and customized anthraquinone derivatives (with linking...... groups ranging from thiophenes to thiols) were chosen as model compounds for linking together bulk quantities of gold nanoparticles and providing desired functionality. Anthraquinone thiophene and thiol derivatives were synthetized via Sonogashira coupling-type reactions. The synthetic pathways...... for merging gold nanoparticles with resultant anthraquinones include one-pot microwave assisted synthesis or after-mixing of separately prepared gold nanoparticles with selected compounds. The quinone-enriched gold nanoparticles can be transferred onto different electrode surfaces, thus enabling facile...

  9. Two new quinones from the roots of Juglans mandshurica.

    Science.gov (United States)

    Jin, Mei; Sun, Jinfeng; Li, Ren; Diao, Shengbao; Zhang, Changhao; Cui, Jiongmo; Son, Jong-Keun; Zhou, Wei; Li, Gao

    2016-09-01

    Two new quinones, 1-hydroxy-5-pentyl-anthraquinone (1) and 4-(5-hydroxy-1,4-dioxo-1,4-dihydro-naphthalen-2-ylamino)-butyric acid methyl ester (2), together with two known quinones, 5-hydroxy-2-(2-hydroxy-ethylamino)-(1,4) naphthoquinone (3) and juglone (4) were isolated from the roots of Juglans mandshurica (Juglandaceae). Their structures were elucidated on the basis of spectral data. Compound 3 was isolated from the Juglans genus for the first time. Compounds 1-4 exhibited significant cytotoxicity towards cultured MDA-MB231, HepG2 and SNU638 cells with IC50 values ranging from 4.46 to 88.47 μM.

  10. Selective synthesis of the para-quinone region of geldanamycin.

    Science.gov (United States)

    Andrus, Merritt B; Hicken, Erik J; Meredith, Erik L; Simmons, Bryon L; Cannon, John F

    2003-10-16

    [structure: see text] The quinone portion of the ansamycin geldanamycin was made with complete selectivity from the 1,4-dihydroquinone generated from a 1,4-bis-methoxymethyl (MOM) ether intermediate. Palladium catalysis with air gave the desired product in 98% isolated yield. The structure was established using NMR, UV, and X-ray analysis with comparisons to geldanamycin, ortho-quino-geldanamycin and a model compound.

  11. Soluble and stable zethrenebis(dicarboximide) and its quinone

    KAUST Repository

    Sun, Zhe

    2010-10-15

    Soluble and stable zethrenebis(dicarboximide) (1) was synthesized by an in situ Stille cross coupling/transannular cyclization reaction. 1 showed largely improved photostability and solubility compared with the very unstable zethrene and it also exhibited far-red absorption and emission with high photoluminescence quantum yield. Bromination of 1 with NBS/DMF gave its quinone form 2 via an unusual pathway. © 2010 American Chemical Society.

  12. Design and Synthesis of Novel Isoxazole Tethered Quinone-Amino Acid Hybrids

    Directory of Open Access Journals (Sweden)

    P. Ravi Kumar

    2014-01-01

    Full Text Available A new series of isoxazole tethered quinone-amino acid hybrids has been designed and synthesized involving 1,3-dipolar cycloaddition reaction followed by an oxidation reaction using cerium ammonium nitrate (CAN. Using this method, for the first time various isoxazole tethered quinone-phenyl alanine and quinone-alanine hybrids were synthesized from simple commercially available 4-bromobenzyl bromide, propargyl bromide, and 2,5-dimethoxybenzaldehyde in good yield.

  13. Compositions comprising a polypeptide having cellulolytic enhancing activity and a quinone compound and uses thereof

    Energy Technology Data Exchange (ETDEWEB)

    Quinlan, Jason; Xu, Feng; Sweeney, Matthew

    2017-09-05

    The present invention relates to compositions comprising: a polypeptide having cellulolytic enhancing activity and a quinone compound. The present invention also relates to methods of using the compositions.

  14. Liquid Quinones for Solvent-Free Redox Flow Batteries.

    Science.gov (United States)

    Shimizu, Akihiro; Takenaka, Keisuke; Handa, Naoyuki; Nokami, Toshiki; Itoh, Toshiyuki; Yoshida, Jun-Ichi

    2017-09-08

    Liquid benzoquinone and naphthoquinone having diethylene glycol monomethyl ether groups are designed and synthesized as redox active materials that dissolve supporting electrolytes. The Li-ion batteries based on the liquid quinones using LiBF4 /PC show good performance in terms of voltage, capacity, energy efficiency, and cyclability in both static and flow modes. A battery is constructed without using intentionally added organic solvent, and its high energy density (264 W h L(-1) ) demonstrates the potential of solvent-free organic redox flow batteries using liquid active materials. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Terpenoids from Diplophyllum taxifolium with quinone reductase-inducing activity.

    Science.gov (United States)

    Wang, Xiao; Zhang, Jiao-Zhen; Zhou, Jin-Chuan; Shen, Tao; Lou, Hong-Xiang

    2016-03-01

    Two new ent-prenylaromadendrane-type diterpenoids, diplotaxifols A (1) and B (2), a new ent-eudesmol, ent-eudesma-4(15),11(13)-dien-6α,12-diol (3), eight new eudesmanolides enantiomers (4-11) of the corresponding compounds from higher plants along with four known ent-eudesmanolides (12-15) were isolated from the 95% EtOH extract of Chinese liverwort Diplophyllum taxifolium. Their structures were elucidated on the basis of MS, NMR and IR spectral data, and confirmed by single-crystal X-ray diffraction analysis. The quinone reductase-inducing activity of the compounds was evaluated.

  16. Carbons, ionic liquids and quinones for electrochemical capacitors

    Directory of Open Access Journals (Sweden)

    Raul eDiaz

    2016-04-01

    Full Text Available Carbons are the main electrode materials used in electrochemical capacitors, which are electrochemical energy storage devices with high power densities and long cycling lifetimes. However, increasing their energy density will improve their potential for commercial implementation. In this regard, the use of high surface area carbons and high voltage electrolytes are well known strategies to increase the attainable energy density, and lately ionic liquids have been explored as promising alternatives to current state of the art acetonitrile-based electrolytes. Also, in terms of safety and sustainability ionic liquids are attractive electrolyte materials for electrochemical capacitors. In addition, it has been shown that the matching of the carbon pore size with the electrolyte ion size further increases the attainable electric double layer (EDL capacitance and energy density.The use of pseudocapacitive reactions can significantly increase the attainable energy density, and quinonic-based materials offer a potentially sustainable and cost effective research avenue for both the electrode and the electrolyte. This perspective will provide an overview of the current state of the art research on electrochemical capacitors based on combinations of carbons, ionic liquids and quinonic compounds, highlighting performances and challenges and discussing possible future research avenues. In this regard, current interest is mainly focused on strategies which may ultimately lead to commercially competitive sustainable high performance electrochemical capacitors for different applications including those requiring mechanical flexibility and biocompatibility.

  17. Carbons, ionic liquids and quinones for electrochemical capacitors

    Science.gov (United States)

    Diaz, Raul; Doherty, Andrew

    2016-04-01

    Carbons are the main electrode materials used in electrochemical capacitors, which are electrochemical energy storage devices with high power densities and long cycling lifetimes. However, increasing their energy density will improve their potential for commercial implementation. In this regard, the use of high surface area carbons and high voltage electrolytes are well known strategies to increase the attainable energy density, and lately ionic liquids have been explored as promising alternatives to current state of the art acetonitrile-based electrolytes. Also, in terms of safety and sustainability ionic liquids are attractive electrolyte materials for electrochemical capacitors. In addition, it has been shown that the matching of the carbon pore size with the electrolyte ion size further increases the attainable electric double layer (EDL) capacitance and energy density. The use of pseudocapacitive reactions can significantly increase the attainable energy density, and quinonic-based materials offer a potentially sustainable and cost effective research avenue for both the electrode and the electrolyte. This perspective will provide an overview of the current state of the art research on electrochemical capacitors based on combinations of carbons, ionic liquids and quinonic compounds, highlighting performances and challenges and discussing possible future research avenues. In this regard, current interest is mainly focused on strategies which may ultimately lead to commercially competitive sustainable high performance electrochemical capacitors for different applications including those requiring mechanical flexibility and biocompatibility.

  18. Universal quinone electrodes for long cycle life aqueous rechargeable batteries

    Science.gov (United States)

    Liang, Yanliang; Jing, Yan; Gheytani, Saman; Lee, Kuan-Yi; Liu, Ping; Facchetti, Antonio; Yao, Yan

    2017-08-01

    Aqueous rechargeable batteries provide the safety, robustness, affordability, and environmental friendliness necessary for grid storage and electric vehicle operations, but their adoption is plagued by poor cycle life due to the structural and chemical instability of the anode materials. Here we report quinones as stable anode materials by exploiting their structurally stable ion-coordination charge storage mechanism and chemical inertness towards aqueous electrolytes. Upon rational selection/design of quinone structures, we demonstrate three systems that coupled with industrially established cathodes and electrolytes exhibit long cycle life (up to 3,000 cycles/3,500 h), fast kinetics (>=20C), high anode specific capacity (up to 200-395 mAh g-1), and several examples of state-of-the-art specific energy/energy density (up to 76-92 Wh kg-1/ 161-208 Wh l-1) for several operational pH values (-1 to 15), charge carrier species (H+, Li+, Na+, K+, Mg2+), temperature (-35 to 25 °C), and atmosphere (with/without O2), making them a universal anode approach for any aqueous battery technology.

  19. Phospholipid and Respiratory Quinone Analyses From Extreme Environments

    Science.gov (United States)

    Pfiffner, S. M.

    2008-12-01

    Extreme environments on Earth have been chosen as surrogate sites to test methods and strategies for the deployment of space craft in the search for extraterrestrial life. Surrogate sites for many of the NASA astrobiology institutes include the South African gold mines, Canadian subpermafrost, Atacama Desert, and acid rock drainage. Soils, sediments, rock cores, fracture waters, biofilms, and service and drill waters represent the types of samples collected from these sites. These samples were analyzed by gas chromatography mass spectrometry for phospholipid fatty acid methyl esters and by high performance liquid chromatography atmospheric pressure chemical ionization tandem mass spectrometry for respiratory quinones. Phospholipid analyses provided estimates of biomass, community composition, and compositional changes related to nutritional limitations or exposure to toxic conditions. Similar to phospholipid analyses, respiratory quinone analyses afforded identification of certain types of microorganisms in the community based on respiration and offered clues to in situ redox conditions. Depending on the number of samples analyzed, selected multivariate statistical methods were applied to relate membrane lipid results with site biogeochemical parameters. Successful detection of life signatures and refinement of methodologies at surrogate sites on Earth will be critical for the recognition of extraterrestrial life. At this time, membrane lipid analyses provide useful information not easily obtained by other molecular techniques.

  20. Crystal structure and characterization of pyrroloquinoline quinone disodium trihydrate

    Directory of Open Access Journals (Sweden)

    Ikemoto Kazuto

    2012-06-01

    Full Text Available Abstract Background Pyrroloquinoline quinone (PQQ, a tricarboxylic acid, has attracted attention as a growth factor, and its application to supplements and cosmetics is underway. The product used for these purposes is a water-soluble salt of PQQ disodium. Although in the past, PQQ disodiumpentahydrates with a high water concentration were used, currently, low hydration crystals of PQQ disodiumpentahydrates are preferred. Results We prepared a crystal of PQQ disodium trihydrate in a solution of ethanol and water, studied its structure, and analyzed its properties. In the prepared crystal, the sodium atom interacted with the oxygen atom of two carboxylic acids as well as two quinones of the PQQ disodium trihydrate. In addition, the hydration water of the prepared crystal was less than that of the conventional PQQ disodium crystal. From the results of this study, it was found that the color and the near-infrared (NIR spectrum of the prepared crystal changed depending on the water content in the dried samples. Conclusions The water content in the dried samples was restored to that in the trihydrate crystal by placing the samples in a humid environment. In addition, the results of X-ray diffraction (XRD and X-ray diffraction-differential calorimetry (XRD-DSC analyses show that the phase of the trihydrate crystal changed when the crystallization water was eliminated. The dried crystal has two crystalline forms that are restored to the original trihydrate crystals in 20% relative humidity (RH. This crystalline (PQQ disodium trihydrate is stable under normal environment.

  1. Supercritical Fluid Extraction of Quinones from Compost for Microbial Community Analysis

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    Ni Luh Gede Ratna Juliasih

    2015-01-01

    Full Text Available Supercritical fluid extraction (SFE was used to extract quinones from compost to monitor the microbial community dynamics during composting. The 0.3 g of dried compost was extracted using 3 mL min−1 of carbon dioxide (90% and methanol (10% at 45°C and 25 MPa for a 30 min extraction time. The extracted quinones were analysed using ultra performance liquid chromatography (UPLC with 0.3 mL min−1 of methanol mobile phase for a 50 min chromatographic run time. A comparable detected amount of quinones was obtained using the developed method and an organic solvent extraction method, being 36.06 μmol kg−1 and 34.54 μmol kg−1, respectively. Significantly low value of dissimilarity index (D between the two methods (0.05 indicated that the quinone profile obtained by both methods was considered identical. The developed method was then applied to determine the maturity of the compost by monitoring the change of quinone during composting. The UQ-9 and MK-7 were predominant quinones in the initial stage of composting. The diversity of quinone became more complex during the cooling and maturation stages. This study showed that SFE had successfully extracted quinones from a complex matrix with simplification and rapidity of the analysis that is beneficial for routine analysis.

  2. Electron affinity of p-quinones. Improved method of electrochemical estimation

    Science.gov (United States)

    Jaworski, Jan S.

    1986-06-01

    Electron affinities of four p-quinones are estimated from enthalpy changes obtained on the basis of measured formal potentials and reaction entropies in the electroreduction process. A linear correlation between electron affinities of p-quinones and parent hydrocarbons is found.

  3. Quinone-based stable isotope probing for assessment of 13C substrate-utilizing bacteria

    Science.gov (United States)

    Kunihiro, Tadao; Katayama, Arata; Demachi, Toyoko; Veuger, Bart; Boschker, Henricus T. S.; van Oevelen, Dick

    2015-04-01

    In this study, we attempted to establish quinone-stable-isotope probing (SIP) technique to link substrate-utilizing bacterial group to chemotaxonomic group in bacterial community. To identify metabolically active bacterial group in various environments, SIP techniques combined with biomarkers have been widely utilized as an attractive method for environmental study. Quantitative approaches of the SIP technique have unique advantage to assess substrate-incorporation into bacteria. As a most major quantitative approach, SIP technique based on phospholipid-derived fatty acids (PLFA) have been applied to simultaneously assess substrate-incorporation rate into bacteria and microbial community structure. This approach is powerful to estimate the incorporation rate because of the high sensitivity due to the detection by a gas chromatograph-combustion interface-isotope ratio mass spectrometer (GC-c-IRMS). However, its phylogenetic resolution is limited by specificity of a compound-specific marker. We focused on respiratory quinone as a biomarker. Our previous study found a good correlation between concentrations of bacteria-specific PLFAs and quinones over several orders of magnitude in various marine sediments, and the quinone method has a higher resolution (bacterial phylum level) for resolving differences in bacterial community composition more than that of bacterial PLFA. Therefore, respiratory quinones are potentially good biomarkers for quantitative approaches of the SIP technique. The LC-APCI-MS method as molecular-mass based detection method for quinone was developed and provides useful structural information for identifying quinone molecular species in environmental samples. LC-MS/MS on hybrid triple quadrupole/linear ion trap, which enables to simultaneously identify and quantify compounds in a single analysis, can detect high molecular compounds with their isotope ions. Use of LC-MS/MS allows us to develop quinone-SIP based on molecular mass differences due to

  4. Activation of Electron-Deficient Quinones through Hydrogen-Bond-Donor-Coupled Electron Transfer.

    Science.gov (United States)

    Turek, Amanda K; Hardee, David J; Ullman, Andrew M; Nocera, Daniel G; Jacobsen, Eric N

    2016-01-11

    Quinones are important organic oxidants in a variety of synthetic and biological contexts, and they are susceptible to activation towards electron transfer through hydrogen bonding. Whereas this effect of hydrogen bond donors (HBDs) has been observed for Lewis basic, weakly oxidizing quinones, comparable activation is not readily achieved when more reactive and synthetically useful electron-deficient quinones are used. We have successfully employed HBD-coupled electron transfer as a strategy to activate electron-deficient quinones. A systematic investigation of HBDs has led to the discovery that certain dicationic HBDs have an exceptionally large effect on the rate and thermodynamics of electron transfer. We further demonstrate that these HBDs can be used as catalysts in a quinone-mediated model synthetic transformation. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Cytotoxic Quinones from the Roots of Aloe dawei

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    Negera Abdissa

    2014-03-01

    Full Text Available Seven naphthoquinones and nine anthraquinones were isolated from the roots of Aloe dawei by chromatographic separation. The purified metabolites were identified by NMR and MS analyses. Out of the sixteen quinones, 6-hydroxy-3,5-dimethoxy-2-methyl-1,4-naphthoquinone is a new compound. Two of the isolates, 5,8-dihydroxy-3-methoxy-2-methylnaphthalene-1,4-dione and 1-hydroxy-8-methoxy-3-methylanthraquinone showed high cytotoxic activity (IC50 1.15 and 4.85 µM on MCF-7 breast cancer cells, whereas the others showed moderate to low cytotoxic activity against MDA-MB-231 (ER Negative and MCF-7 (ER Positive cancer cells.

  6. Identification of quinone imine containing glutathione conjugates of diclofenac in rat bile.

    Science.gov (United States)

    Waldon, Daniel J; Teffera, Yohannes; Colletti, Adria E; Liu, Jingzhou; Zurcher, Danielle; Copeland, Katrina W; Zhao, Zhiyang

    2010-12-20

    High-resolution accurate MS with an LTQ-Orbitrap was used to identify quinone imine metabolites derived from the 5-hydroxy (5-OH) and 4 prime-hydroxy (4'-OH) glutathione conjugates of diclofenac in rat bile. The initial quinone imine metabolites formed by oxidation of diclofenac have been postulated to be reactive intermediates potentially involved in diclofenac-mediated hepatotoxicity; while these metabolites could be formed using in vitro systems, they have never been detected in vivo. This report describes the identification of secondary quinone imine metabolites derived from 5-OH and 4'-OH diclofenac glutathione conjugates in rat bile. To verify the proposed structures, the diclofenac quinone imine GSH conjugate standards were prepared synthetically and enzymatically. The novel metabolite peaks displayed the identical retention times, accurate mass MS/MS spectra, and the fragmentation patterns as the corresponding authentic standards. The formation of these secondary quinone metabolites occurs only under conditions where bile salt homeostasis was experimentally altered. Standard practice in biliary excretion experiments using bile duct-cannulated rats includes infusion of taurocholic acid and/or other bile acids to replace those lost due to continuous collection of bile; for this experiment, the rats received no replacement bile acid infusion. High-resolution accurate mass spectrometry data and comparison with chemically and enzymatically prepared quinone imines of diclofenac glutathione conjugates support the identification of these metabolites. A mechanism for the formation of these reactive quinone imine containing glutathione conjugates of diclofenac is proposed.

  7. Monitoring Dopamine Quinone-Induced Dopaminergic Neurotoxicity Using Dopamine Functionalized Quantum Dots.

    Science.gov (United States)

    Ma, Wei; Liu, Hui-Ting; Long, Yi-Tao

    2015-07-08

    Dopamine (DA) quinone-induced dopaminergic neurotoxicity is known to occur due to the interaction between DA quinone and cysteine (Cys) residue, and it may play an important a role in pathological processes associated with neurodegeneration. In this study, we monitored the interaction process of DA to form DA quinone and the subsequent Cys residue using dopamine functionalized quantum dots (QDs). The fluorescence (FL) of the QD bioconjugates changes as a function of the structure transformation during the interaction process, providing a potential FL tool for monitoring dopaminergic neurotoxicity.

  8. Solid state oxidation of phenols to quinones with sodium perborate on wet montmorillonite K10

    Energy Technology Data Exchange (ETDEWEB)

    Hashemi, Mohammed M.; Eftekhari-Sis, Bagher; Khalili, Behzad; Karimi-Jaberi, Zahed [Sharif University of Technology, Tehran (Iran, Islamic Republic of). Dept. of Chemistry]. E-mail: mhashemi@sharif.edu

    2005-09-15

    Phenols were oxidized to quinones using sodium perborate (SPB) on wet montmorillonite as oxidant. The reaction was carried out at ambient temperature on the solid phase under solvent free conditions. (author)

  9. Transimination of quinone imines: a mechanism for embedding exogenous redox activity into the nucleosome.

    Science.gov (United States)

    Ye, Wenjie; Seneviratne, Uthpala I; Chao, Ming-Wei; Ravindra, Kodihalli C; Wogan, Gerald N; Tannenbaum, Steven R; Skipper, Paul L

    2012-12-17

    Aminophenols can redox cycle through the corresponding quinone imines to generate ROS. The electrophilic quinone imine intermediate can react with protein thiols as a mechanism of immobilization in vivo. Here, we describe the previously unkown transimination of a quinone imine by lysine as an alternative anchoring mechanism. The redox properties of the condensation product remain largely unchanged because the only structural change to the redox nucleus is the addition of an alkyl substituent to the imine nitrogen. Transimination enables targeting of histone proteins since histones are lysine-rich but nearly devoid of cysteines. Consequently, quinone imines can be embedded in the nucleosome and may be expected to produce ROS in maximal proximity to the genome.

  10. Porphyrin-quinone compounds as synthetic models of the reaction centre in photosynthesis

    Science.gov (United States)

    Borovkov, V. V.; Evstigneeva, Rima P.; Strekova, L. N.; Filippovich, E. I.

    1989-06-01

    Data on the synthesis, steric structure, and photochemical properties of porphyrin-quinone compounds as synthetic models of the reaction centre in photosynthesis are examined and described systematically. The bibliography includes 113 references.

  11. Mild and rapid method for the generation of ortho-(naphtho)quinone methide intermediates.

    Science.gov (United States)

    Shaikh, Abdul kadar; Cobb, Alexander J A; Varvounis, George

    2012-01-20

    A new mild method has been devised for generating o-(naphtho)quinone methides via fluoride-induced desilylation of silyl derivatives of o-hydroxybenzyl(or 1-naphthylmethyl) nitrate. The reactive o-(naphtho)quinone methide intermediates were trapped by C, O, N, and S nucleophiles and underwent "inverse electron-demand" hetero-Diels-Alder reaction with dienophiles to give stable adducts. The method has useful potential application in natural product synthesis and drug research.

  12. Semiquinone formation and DNA base damage by toxic quinones and inhibition by N-acetylcysteine (NAC)

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, D.C.; Shibamoto, T.

    1986-03-05

    Toxic, mutagenic, carcinogenic, and teratogenic effects have been reported for some quinones as well as compounds metabolized to quinones. Semiquinone radical formation, thymidine degradation, and protection by NAC were studied in a hypoxanthine/xanthine oxidase (HX/XO) system. Quinone, benzo(a)pyrene-3,6-quinone, danthron, doxorubicin, emodin, juglone, menadione, and moniliformin were tested. Diethylstilbestrolquinone, N-acetylquinoneimine, and benzoquinonediimine, hypothesized toxic metabolites of diethylstilbestrol, acetaminophen and p-phenylenediamine, respectively, were synthesized and studied. Semiquinone radical formation was assessed in a HX/XO system monitoring cytochrome C reduction. Large differences in rates of semiquinone radical formation were noted for different quinones, with V/Vo values ranging from 1.2 to 10.6. DNA base degradation, thymine or thymidine glycol formation, and thiobarbituric acid reactive substance (TBARS) production were measured in a similar system containing thymine, thymidine, calf thymus DNA, or deoxyribose. TBARS formation was observed with deoxyribose, but thymidine degradation without TBARS formation was noted with thymidine. NAC (0.5 to 10 mM) caused dose-dependent inhibition of quinone-induced cytochrome C reduction.

  13. Terreic Acid, a Quinone Epoxide Inhibitor of Bruton's Tyrosine Kinase

    Science.gov (United States)

    Kawakami, Yuko; Hartman, Stephen E.; Kinoshita, Eiji; Suzuki, Hidefumi; Kitaura, Jiro; Yao, Libo; Inagaki, Naoki; Franco, Alessandra; Hata, Daisuke; Maeda-Yamamoto, Mari; Fukamachi, Hiromi; Nagai, Hiroichi; Kawakami, Toshiaki

    1999-03-01

    Bruton's tyrosine kinase (Btk) plays pivotal roles in mast cell activation as well as in B cell development. Btk mutations lead to severe impairments in proinflammatory cytokine production induced by cross-linking of high-affinity IgE receptor on mast cells. By using an in vitro assay to measure the activity that blocks the interaction between protein kinase C and the pleckstrin homology domain of Btk, terreic acid (TA) was identified and characterized in this study. This quinone epoxide specifically inhibited the enzymatic activity of Btk in mast cells and cell-free assays. TA faithfully recapitulated the phenotypic defects of btk mutant mast cells in high-affinity IgE receptor-stimulated wild-type mast cells without affecting the enzymatic activities and expressions of many other signaling molecules, including those of protein kinase C. Therefore, this study confirmed the important roles of Btk in mast cell functions and showed the usefulness of TA in probing into the functions of Btk in mast cells and other immune cell systems. Another insight obtained from this study is that the screening method used to identify TA is a useful approach to finding more efficacious Btk inhibitors.

  14. Syntrophic Growth via Quinone-Mediated Interspecies Electron Transfer

    Directory of Open Access Journals (Sweden)

    Jessica A Smith

    2015-02-01

    Full Text Available The mechanisms by which microbial species exchange electrons are of interest because interspecies electron transfer can expand the metabolic capabilities of microbial communities. Previous studies with the humic substance analog anthraquinone-2,6-disulfonate (AQDS suggested that quinone-mediated interspecies electron transfer (QUIET is feasible, but it was not determined if sufficient energy is available from QUIET to support the growth of both species. Furthermore, there have been no previous studies on the mechanisms for the oxidation of anthrahydroquinone-2,6-disulfonate (AHQDS. A co-culture of Geobacter metallireducens and Geobacter sulfurreducens metabolized ethanol with the reduction of fumarate much faster in the presence of AQDS, and there was an increase in cell protein. G. sulfurreducens was more abundant, consistent with G. sulfurreducens obtaining electrons from acetate that G. metallireducens produced from ethanol, as well as from AHQDS. Cocultures initiated with a citrate synthase-deficient strain of G. sulfurreducens that was unable to use acetate as an electron donor also metabolized ethanol with the reduction of fumarate and cell growth, but acetate accumulated over time. G. sulfurreducens and G. metallireducens were equally abundant in these co-cultures reflecting the inability of the citrate synthase-deficient strain of G. sulfurreducens to metabolize acetate. Evaluation of the mechanisms by which G. sulfurreducens accepts electrons from AHQDS demonstrated that a strain deficient in outer-surface c-type cytochromes that are required for AQDS reduction was as effective at QUIET as the wild-type strain. Deletion of additional genes previously implicated in extracellular electron transfer also had no impact on QUIET. These results demonstrate that QUIET can yield sufficient energy to support the growth of both syntrophic partners, but that the mechanisms by which electrons are derived from extracellular hydroquinones require

  15. Biotransformation of lepidocrocite in the presence of quinones and flavins

    Science.gov (United States)

    Bae, Sungjun; Lee, Woojin

    2013-08-01

    This study investigated the bioreduction of lepidocrocite (γ-FeIIIOOH) and its mineral transformation in the presence of exogenous (quinones) and endogenous (flavins) electron transfer mediators (ETMs) at low concentrations of the ETMs and bacterial cells (Shewanella putrefaciens CN32). It is very important to investigate the bioreduction of lepidocrocite in the presence of different ETMs because biotransformation of Fe(III)-containing minerals can be stimulated by ETMs and affect fate and transport of contaminants in contaminated environments. In the absence of phosphate, green rust formation was observed with fast Fe(II) production rate (0.44-0.56 mM d-1) during the bioreduction of lepidocrocite with exogenous ETMs, while goethite formed at slow Fe(II) production rate (0.24-0.29 mM d-1) with endogenous ETMs. In the presence of phosphate, formation of green rust and vivianite was observed with fast Fe(II) production rate (0.54-0.74 mM d-1) during the bioreduction of lepidocrocite with exogenous ETMs, while vivianite formed at moderate Fe(II) production rate (0.36-0.40 mM d-1) with endogenous ETMs. Vivianite formed in all experimental cases with phosphate in a broad range of Fe(II) production rates (0.23-0.74 mM d-1). Our results (1) suggest that exogenous and endogenous ETMs can significantly but differently affect the biotransformation of lepidocrocite, especially at low concentrations of the ETMs and bacterial cells, (2) highlight the importance of Fe(II) production rate to determine the formation of specific biogenic minerals, (3) provide additional evidence that phosphate can significantly affect the bioreduction rate and the mineral transformation, and (4) help to understand the basic knowledge about complex interactions among microbial cell, soil mineral, and ETM in natural environments and engineered systems.

  16. Structural Changes of Water Molecules Upon the Reduction of Quinones in The Reaction Center from Rhodobactery Sphaeroides

    Institute of Scientific and Technical Information of China (English)

    T.Iwata; M.L.Paddock; M.Y.Okamura; H.Kandori

    2007-01-01

    1 Results The photosynthetic bacterial reaction center (RC) is a membrane protein complex.The RC is composed of three protein subunits and redox components such as bacteriochlorophylls, bacteriopheophytins,and quinones.The RC performs the photochemical electron transfer from the bacteriochlorophyll dimer through a series of electron donor and acceptor molecules to a secondary quinone,QB.QB accepts electrons from a primary quinone,QA,in two sequential electron transfer reactions.The second electron trans...

  17. Chlorophyll-quinone photochemistry in liposomes: mechanisms of radical formation and decay

    Energy Technology Data Exchange (ETDEWEB)

    Hurley, J.K.; Tollin, G.

    1980-01-01

    Laser flash photolysis has been used to investigate the mechanism of formation and decay of the radical species generated by light induced electron transfer from chlorophyll a triplet to quinone in egg phosphatidyl choline bilayer vesicles. Chlorophyll triplet quenching by quinone is controlled by diffusion occurring within the bilayer membrane and reflects bilayer viscosity. Radical formation via separation of the intermediate ion pair is also inhibited by increased bilayer viscosity. Cooperativity is observed in this process due to an enhancement of radical separation by electron transfer from semiquinone anion radical to a neighboring quinone molecule. Two modes of radical decay are observed, a rapid recombination occurring within the bilayer and a much slower recombination occurring across the bilayer. The slow decay is only observed with quinones which are not tightly anchored into the bilayer, and is probably the result of electron transfer from semiquinone anion radical formed within the bilayer to a quinone molecule residing at the bilayer-water interface. With benzoquinone, approximately 60% of the radical decay occurs via the slow mode. Triplet to radical conversion efficiencies in the bilayer systems are comparable to those obtained in fluid solution (approx. 60%). However, radical recombination, at least for the slow decay mechanism, is considerably retarded.

  18. Photoinduced electron transfer reactions of ruthenium(II)-complexes containing amino acid with quinones.

    Science.gov (United States)

    Eswaran, Rajkumar; Kalayar, Swarnalatha; Paulpandian, Muthu Mareeswaran; Seenivasan, Rajagopal

    2014-05-01

    With the aim of mimicking, at basic level the photoinduced electron transfer process in the reaction center of photosystem II, ruthenium(II)-polypyridyl complexes, carrying amino acids were synthesized and studied their photoinduced electron transfer reactions with quinones by steady state and time resolved measurements. The reaction of quinones with excited state of ruthenium(II)-complexes, I-V in acetonitrile has been studied by luminescence quenching technique and the rate constant, k(q), values are close to the diffusion controlled rate. The detection of the semiquinone anion radical in this system using time-resolved transient absorption spectroscopy confirms the electron transfer nature of the reaction. The semiclassical theory of electron transfer has been successfully applied to the photoluminescence quenching of Ru(II)-complexes with quinones.

  19. NAD(PH:quinone oxidoreductase 1 (NQO1 localizes to the mitotic spindle in human cells.

    Directory of Open Access Journals (Sweden)

    David Siegel

    Full Text Available NAD(PH:quinone oxidoreductase 1 (NQO1 is an FAD containing quinone reductase that catalyzes the 2-electron reduction of a broad range of quinones. The 2-electron reduction of quinones to hydroquinones by NQO1 is believed to be a detoxification process since this reaction bypasses the formation of the highly reactive semiquinone. NQO1 is expressed at high levels in normal epithelium, endothelium and adipocytes as well as in many human solid tumors. In addition to its function as a quinone reductase NQO1 has been shown to reduce superoxide and regulate the 20 S proteasomal degradation of proteins including p53. Biochemical studies have indicated that NQO1 is primarily located in the cytosol, however, lower levels of NQO1 have also been found in the nucleus. In these studies we demonstrate using immunocytochemistry and confocal imaging that NQO1 was found associated with mitotic spindles in cells undergoing division. The association of NQO1 with the mitotic spindles was observed in many different human cell lines including nontransformed cells (astrocytes, HUVEC immortalized cell lines (HBMEC, 16HBE and cancer (pancreatic adenocarcinoma, BXPC3. Confocal analysis of double-labeling experiments demonstrated co-localization of NQO1with alpha-tubulin in mitotic spindles. In studies with BxPc-3 human pancreatic cancer cells the association of NQO1 with mitotic spindles appeared to be unchanged in the presence of NQO1 inhibitors ES936 or dicoumarol suggesting that NQO1 can associate with the mitotic spindle and still retain catalytic activity. Analysis of archival human squamous lung carcinoma tissue immunostained for NQO1 demonstrated positive staining for NQO1 in the spindles of mitotic cells. The purpose of this study is to demonstrate for the first time the association of the quinone reductase NQO1 with the mitotic spindle in human cells.

  20. Quinone-mediated decolorization of sulfonated azo dyes by cells and cell extracts from Sphingomonas xenophaga

    Institute of Scientific and Technical Information of China (English)

    JIAO Ling; LU Hong; ZHOU Jiti; WANG Jing

    2009-01-01

    The effects of various quinone compounds on the decolorization rates of sulfonated azo dyes by Sphingomonas xenophaga QYY were investigated. The results showed that anthraquinone-2-sulfonate (AQS) was the most effective redox mediator and AQS reduction was the rate-limited step of AQS-mediated decolorization of sulfonated azo dyes. Based on AQS biological toxicity tests, it was assumed that AQS might enter the cells to kill them. In the cytoplasmic extracts from strain QYY, AQS effectively increased decolorization rates of sulfonated azo dyes than other quinone compounds. In addition, we found a NADH/FMN-dependent AQS reductase using nondenaturing polyacrylamide gel electrophoresis (Native-PAGE).

  1. Substituent effects on carbocation stability: the pK(R) for p-quinone methide.

    Science.gov (United States)

    Toteva, Maria M; Moran, Michael; Amyes, Tina L; Richard, John P

    2003-07-23

    A value of k(H) = 1.5 x 10(-)(3) M(-)(1) s(-)(1) has been determined for the generation of simple p-quinone methide by the acid-catalyzed cleavage of 4-hydroxybenzyl alcohol in water at 25 degrees C and I = 1.0 (NaClO(4)). This was combined with k(s) = 5.8 x 10(6) s(-)(1) for the reverse addition of solvent water to the 4-hydroxybenzyl carbocation [J. Am. Chem. Soc. 2002, 124, 6349-6356] to give pK(R) = -9.6 as the Lewis acidity constant of O-protonated p-quinone methide. Values of pK(R) = 2.3 for the Lewis acidity constant of neutral p-quinone methide and pK(add) = -7.6 for the overall addition of solvent water to p-quinone methide to form 4-hydroxybenzyl alcohol are also reported. The thermodynamic driving force for transfer of the elements of water from formaldehyde hydrate to p-quinone methide to form formaldehyde and p-(hydroxymethyl)phenol (4-hydroxybenzyl alcohol) is determined as 6 kcal/mol. This relatively small driving force represents the balance between the much stronger chemical bonds to oxygen at the reactant formaldehyde hydrate than at the product p-(hydroxymethyl)phenol and the large stabilization of product arising from the aromatization that accompanies solvent addition to p-quinone methide. The Marcus intrinsic barrier for nucleophilic addition of solvent water to the "extended" carbonyl group at p-quinone methide is estimated to be 4.5 kcal/mol larger than that for the addition of water to the simple carbonyl group of formaldehyde. O-Alkylation of p-quinone methide to give the 4-methoxybenzyl carbocation and of formaldehyde to give a simple oxocarbenium ion results in very little change in the relative Marcus intrinsic barriers for the addition of solvent water to these electrophiles.

  2. New roles of flavoproteins in molecular cell biology: an unexpected role for quinone reductases as regulators of proteasomal degradation.

    Science.gov (United States)

    Sollner, Sonja; Macheroux, Peter

    2009-08-01

    Quinone reductases are ubiquitous soluble enzymes found in bacteria, fungi, plants and animals. These enzymes utilize a reduced nicotinamide such as NADH or NADPH to reduce the flavin cofactor (either FMN or FAD), which then affords two-electron reduction of cellular quinones. Although the chemical nature of the quinone substrate is still a matter of debate, the reaction appears to play a pivotal role in quinone detoxification by preventing the generation of potentially harmful semiquinones. In recent years, an additional role of quinone reductases as regulators of proteasomal degradation of transcription factors and possibly intrinsically unstructured protein has emerged. To fulfil this role, quinone reductase binds to the core particle of the proteasome and recruits certain transcription factors such as p53 and p73alpha to the complex. The latter process appears to be governed by the redox state of the flavin cofactor of the quinone reductase, thus linking the stability of transcription factors to cellular events such as oxidative stress. Here, we review the current evidence for protein complex formation between quinone reductase and the 20S proteasome in eukaryotic cells and describe the regulatory role of this complex in stabilizing transcription factors by acting as inhibitors of their proteasomal degradation.

  3. Protonated paramagnetic redox forms of di-o-quinone bridged with p-phenylene-extended TTF: A EPR spectroscopy study

    Directory of Open Access Journals (Sweden)

    Nikolay O. Chalkov

    2016-11-01

    Full Text Available The chemical oxidation and reduction processes of deprotonated, direduced o-quinone-exTTF-o-quinone in protic solvents were studied by EPR spectroscopy. The formation of relatively stable paramagnetic protonated redox forms of the parent triad was very surprising. The character of spin-density distribution in the semiquinone–quinone and semiquinone–catechol redox forms indicates that the p-phenylene-extended tetrathiafulvalene connector provides a quite effective electronic communication channel between dioxolene coordination sites. It was found that the deprotonated, direduced o-quinone-exTTF-o-quinone is capable to reduction of the metal copper in solution. The radical anion species formed in this reaction exists in solution as a solvent-separated ion pair with a copper cation. A character of spin-density distribution in a radical anion species leads to the conclusion that the ligand corresponds to type III of the Robin–Day classification.

  4. Spare quinones in the QB cavity of crystallized photosystem II from Thermosynechococcus elongatus.

    Science.gov (United States)

    Krivanek, Roland; Kern, Jan; Zouni, Athina; Dau, Holger; Haumann, Michael

    2007-06-01

    The recent crystallographic structure at 3.0 A resolution of PSII from Thermosynechococcus elongatus has revealed a cavity in the protein which connects the membrane phase to the binding pocket of the secondary plastoquinone Q(B). The cavity may serve as a quinone diffusion pathway. By fluorescence methods, electron transfer at the donor and acceptor sides was investigated in the same membrane-free PSII core particle preparation from T. elongatus prior to and after crystallization; PSII membrane fragments from spinach were studied as a reference. The data suggest selective enrichment of those PSII centers in the crystal that are intact with respect to O(2) evolution at the manganese-calcium complex of water oxidation and with respect to the integrity of the quinone binding site. One and more functional quinone molecules (per PSII monomer) besides of Q(A) and Q(B) were found in the crystallized PSII. We propose that the extra quinones are located in the Q(B) cavity and serve as a PSII intrinsic pool of electron acceptors.

  5. Anaerobic mineralization of toluene by enriched sediments with quinones and humus as terminal electron acceptors

    NARCIS (Netherlands)

    Cervantes, F.J.; Dijksma, W.; Duong-Dac, T.; Ivanova, A.; Lettinga, G.; Field, J.A.

    2001-01-01

    The anaerobic microbial oxidation of toluene to CO2 coupled to humus respiration was demonstrated by use of enriched anaerobic sediments from the Amsterdam petroleum harbor (APH) and the Rhine River. Both highly purified soil humic acids (HPSHA) and the humic quinone moiety model compound anthraquin

  6. Anaerobic mineralization of toluene by enriched sediments with quinones and humus as terminal electron acceptors

    NARCIS (Netherlands)

    Cervantes, F.J.; Dijksma, W.; Duong-Dac, T.; Ivanova, A.; Lettinga, G.; Field, J.A.

    2001-01-01

    The anaerobic microbial oxidation of toluene to CO2 coupled to humus respiration was demonstrated by use of enriched anaerobic sediments from the Amsterdam petroleum harbor (APH) and the Rhine River. Both highly purified soil humic acids (HPSHA) and the humic quinone moiety model compound

  7. Selective enrichment of Geobacter sulfurreducens from anaerobic granular sludge with quinones as terminal electron acceptors

    NARCIS (Netherlands)

    Cervantes-Carillo, F.J.; Duong Dac, T.; Ivanova, A.E.; Roest, de K.; Akkermans, A.D.L.; Lettinga, G.; Field, J.A.

    2003-01-01

    A quinone-respiring, enrichment culture derived from methanogenic granular sludge was phylogenetically characterized by using a combined cloning-denaturing gradient gel electrophoresis (DGGE) method, which revealed that the consortium developed was dominated by a single microorganism: 97% related, i

  8. Induction of micronuclei and aneuploidy by the quinone-forming agents benzene and o-phenylphenol.

    Science.gov (United States)

    Eastmond, D A

    1993-04-01

    A number of carcinogens appear to exert their tumorigenic effects through the formation of quinone metabolites. These quinone-forming carcinogens are generally inactive or weakly active in standard gene mutation assays. Accumulating evidence indicates that this class of compounds may exert their genotoxic and carcinogenic effects through the induction of large-scale gene alterations. This article presents an overview of work that has been performed using recently developed molecular cytogenic techniques to investigate the aneuploidy-inducing and clastogenic properties of the major quinone-forming metabolites of benzene, a widely used industrial chemical, and o-phenylphenol, a fungicide and disinfectant. These metabolites of benzene (hydroquinone, catechol, and benzenetriol) and o-phenylphenol (phenylhydroquinone) have each been shown to be capable of interfering with chromosome segregation and inducing chromosomal breakage. These results indicate that both numerical and structural chromosomal aberrations induced by the quinone metabolites of benzene and o-phenylphenol may play a role in the carcinogenic effects of these two agents.

  9. Role of Catechin Quinones in the Induction of EpRE-Mediated Gene Expression

    NARCIS (Netherlands)

    Muzolf-Panek, M.; Gliszczynska-Swiglo, A.; Haan, de L.H.J.; Aarts, J.M.M.J.G.; Szymusiak, H.; Vervoort, J.J.M.; Tyrakowska, B.; Rietjens, I.M.C.M.

    2008-01-01

    In the present study, the ability of green tea catechins to induce electrophile-responsive element (EpRE)-mediated gene expression and the role of their quinones in the mechanism of this induction were investigated. To this end, Hepa1c1c7 mouse hepatoma cells were used, stably transfected with a luc

  10. Catalytic aerobic oxidation of phenols to ortho-quinones with air-stable copper precatalysts.

    Science.gov (United States)

    Askari, M S; Rodríguez-Solano, L A; Proppe, A; McAllister, B; Lumb, J-P; Ottenwaelder, X

    2015-07-21

    A range of air-stable copper species was examined for catalytic activity in the catalytic aerobic transformation of phenols into ortho-quinones. Efficient catalysis was obtained with commercially available copper(II) acetate. The stability of all constituents before mixing makes for a practical process that advances previously reported copper(I)-based oxygenations.

  11. EXAMINATION OF QUINONE TOXICITY USING YEAST SACCHAROMYCES CEREVISIAE MODEL SYSTEM. (R827352C007)

    Science.gov (United States)

    The toxicity of quinones is generally thought to occur by two mechanisms: the formation of covalent bonds with biological molecules by Michael addition chemistry and the catalytic reduction of oxygen to superoxide and other reactive oxygen species (ROS) (redox cycling). In an ...

  12. Preserving the adhesion of catechol-conjugated hydrogels by thiourea-quinone coupling.

    Science.gov (United States)

    Xu, Yang J; Wei, Kongchang; Zhao, Pengchao; Feng, Qian; Choi, Chun Kit K; Bian, Liming

    2016-11-15

    Mussel adhesion has inspired the development of catechol-based adhesive polymers. However, conventional strategies require basic pH conditions and lead to the loss of adhesion. To solve the problem, we report the first attempt to use thiourea-functionalized polymers for preserving hydrogel adhesion. We believe that this simple thiourea-quinone coupling chemistry is instrumental to synthetic adhesive materials.

  13. Studies on Antibacterial QSAR of Diterpene Quinones from Sclvic Przewalskii Maxim

    Institute of Scientific and Technical Information of China (English)

    XUE Ming; SHI Yan-bin; CUI Yin; ZHOU Zong-tian; ZHANG Bin; LUO Yong-jiang; XIA Wen-jiang; ZHAO Rong-cai; WANG Han-qing

    2001-01-01

    The antibacierial (staphylococcus aureus) activities of 23 diterpene quinones from the Salvia przewalskii Maxim, the artificial synthesis ones and that of the metabolism in pigs were examined in an effort to study the quantitative structure activity relationship with the Free-Wilson method. With the application of the multipiy regression, the Free-Wilson pattern was established by the dummy (indicator) variable of the structural fragments or substituents. The results showed: (1) The diketone moiety played the fundamental role in antibacterial activities, ortho-quinones was higher active than para-quinones. (2) The single bond existed between the C15 and the C16 at D-ring led to higher activity. (3) The saturation at the A-ring led to higher activity. (4) The components adjacent to nitrogen substituents at C15 led to higher activity. (5)The hydroxylation or dehydrogenation at A-ring led to less activity. The research results can provide the theoretical basis for developing a new antibacterial drug from the Salvia diterpene quinones.

  14. Genomic Analysis of the Human Gut Microbiome Suggests Novel Enzymes Involved in Quinone Biosynthesis

    Science.gov (United States)

    Ravcheev, Dmitry A.; Thiele, Ines

    2016-01-01

    Ubiquinone and menaquinone are membrane lipid-soluble carriers of electrons that are essential for cellular respiration. Eukaryotic cells can synthesize ubiquinone but not menaquinone, whereas prokaryotes can synthesize both quinones. So far, most of the human gut microbiome (HGM) studies have been based on metagenomic analysis. Here, we applied an analysis of individual HGM genomes to the identification of ubiquinone and menaquinone biosynthetic pathways. In our opinion, the shift from metagenomics to analysis of individual genomes is a pivotal milestone in investigation of bacterial communities, including the HGM. The key results of this study are as follows. (i) The distribution of the canonical pathways in the HGM genomes was consistent with previous reports and with the distribution of the quinone-dependent reductases for electron acceptors. (ii) The comparative genomics analysis identified four alternative forms of the previously known enzymes for quinone biosynthesis. (iii) Genes for the previously unknown part of the futalosine pathway were identified, and the corresponding biochemical reactions were proposed. We discuss the remaining gaps in the menaquinone and ubiquinone pathways in some of the microbes, which indicate the existence of further alternate genes or routes. Together, these findings provide further insight into the biosynthesis of quinones in bacteria and the physiology of the HGM. PMID:26904004

  15. Theoretical investigation of pillar[4]quinone as a cathode active material for lithium-ion batteries.

    Science.gov (United States)

    Huan, Long; Xie, Ju; Chen, Ming; Diao, Guowang; Zhao, Rongfang; Zuo, Tongfei

    2017-04-01

    The applicability of a novel macrocyclic multi-carbonyl compound, pillar[4]quinone (P4Q), as the cathode active material for lithium-ion batteries (LIBs) was assessed theoretically. The molecular geometry, electronic structure, Li-binding thermodynamic properties, and the redox potential of P4Q were obtained using density functional theory (DFT) at the M06-2X/6-31G(d,p) level of theory. The results of the calculations indicated that P4Q interacts with Li atoms via three binding modes: Li-O ionic bonding, O-Li···O bridge bonding, and Li···phenyl noncovalent interactions. Calculations also indicated that, during the LIB discharging process, P4Q could yield a specific capacity of 446 mAh g(-1) through the utilization of its many carbonyl groups. Compared with pillar[5]quinone and pillar[6]quinone, the redox potential of P4Q is enhanced by its high structural stability as well as the effect of the solvent. These results should provide the theoretical foundations for the design, synthesis, and application of novel macrocyclic carbonyl compounds as electrode materials in LIBs in the future. Graphical Abstract Schematic representation of the proposed charge-discharge mechanism of Pillar[4]quinone as cathode for lithium-ion batteries.

  16. Identification of NAD(PH quinone oxidoreductase activity in azoreductases from P. aeruginosa: azoreductases and NAD(PH quinone oxidoreductases belong to the same FMN-dependent superfamily of enzymes.

    Directory of Open Access Journals (Sweden)

    Ali Ryan

    Full Text Available Water soluble quinones are a group of cytotoxic anti-bacterial compounds that are secreted by many species of plants, invertebrates, fungi and bacteria. Studies in a number of species have shown the importance of quinones in response to pathogenic bacteria of the genus Pseudomonas. Two electron reduction is an important mechanism of quinone detoxification as it generates the less toxic quinol. In most organisms this reaction is carried out by a group of flavoenzymes known as NAD(PH quinone oxidoreductases. Azoreductases have previously been separate from this group, however using azoreductases from Pseudomonas aeruginosa we show that they can rapidly reduce quinones. Azoreductases from the same organism are also shown to have distinct substrate specificity profiles allowing them to reduce a wide range of quinones. The azoreductase family is also shown to be more extensive than originally thought, due to the large sequence divergence amongst its members. As both NAD(PH quinone oxidoreductases and azoreductases have related reaction mechanisms it is proposed that they form an enzyme superfamily. The ubiquitous and diverse nature of azoreductases alongside their broad substrate specificity, indicates they play a wide role in cellular survival under adverse conditions.

  17. Update of the NAD(PH:quinone oxidoreductase (NQO gene family

    Directory of Open Access Journals (Sweden)

    Vasiliou Vasilis

    2006-03-01

    Full Text Available Abstract The NAD(PH:quinone acceptor oxidoreductase (NQO gene family belongs to the flavoprotein clan and, in the human genome, consists of two genes (NQO1 and NQO2. These two genes encode cytosolic flavoenzymes that catalyse the beneficial two-electron reduction of quinones to hydroquinones. This reaction prevents the unwanted one-electron reduction of quinones by other quinone reductases; one-electron reduction results in the formation of reactive oxygen species, generated by redox cycling of semiquinones in the presence of molecular oxygen. Both the mammalian NQO1 and NQO2 genes are upregulated as a part of the oxidative stress response and are inexplicably overexpressed in particular types of tumours. A non-synonymous mutation in the NQO1 gene, leading to absence of enzyme activity, has been associated with an increased risk of myeloid leukaemia and other types of blood dyscrasia in workers exposed to benzene. NQO2 has a melatonin-binding site, which may explain the anti-oxidant role of melatonin. An ancient NQO3 subfamily exists in eubacteria and the authors suggest that there should be additional divisions of the NQO family to include the NQO4 subfamily in fungi and NQO5 subfamily in archaebacteria. Interestingly, no NQO genes could be identified in the worm, fly, sea squirt or plants; because these taxa carry quinone reductases capable of one- and two-electron reductions, there has been either convergent evolution or redundancy to account for the appearance of these enzyme functions whenever they have been needed during evolution.

  18. X-ray structural studies of quinone reductase 2 nanomolar range inhibitors

    Energy Technology Data Exchange (ETDEWEB)

    Pegan, Scott D.; Sturdy, Megan; Ferry, Gilles; Delagrange, Philippe; Boutin, Jean A.; Mesecar, Andrew D. (IdRS); (Purdue); (Colorado); (UIC)

    2011-09-06

    Quinone reductase 2 (QR2) is one of two members comprising the mammalian quinone reductase family of enzymes responsible for performing FAD mediated reductions of quinone substrates. In contrast to quinone reductase 1 (QR1) which uses NAD(P)H as its co-substrate, QR2 utilizes a rare group of hydride donors, N-methyl or N-ribosyl nicotinamide. Several studies have linked QR2 to the generation of quinone free radicals, several neuronal degenerative diseases, and cancer. QR2 has been also identified as the third melatonin receptor (MT3) through in cellulo and in vitro inhibition of QR2 by traditional MT3 ligands, and through recent X-ray structures of human QR2 (hQR2) in complex with melatonin and 2-iodomelatonin. Several MT3 specific ligands have been developed that exhibit both potent in cellulo inhibition of hQR2 nanomolar, affinity for MT3. The potency of these ligands suggest their use as molecular probes for hQR2. However, no definitive correlation between traditionally obtained MT3 ligand affinity and hQR2 inhibition exists limiting our understanding of how these ligands are accommodated in the hQR2 active site. To obtain a clearer relationship between the structures of developed MT3 ligands and their inhibitory properties, in cellulo and in vitro IC{sub 50} values were determined for a representative set of MT3 ligands (MCA-NAT, 2-I-MCANAT, prazosin, S26695, S32797, and S29434). Furthermore, X-ray structures for each of these ligands in complex with hQR2 were determined allowing for a structural evaluation of the binding modes of these ligands in relation to the potency of MT3 ligands.

  19. Taming reactive phenol tautomers and o-quinone methides with transition metals: a structure-reactivity relationship.

    Science.gov (United States)

    Amouri, Hani; Le Bras, Jean

    2002-07-01

    Quinone methides act as important intermediates in organic syntheses, as well as in chemical and biological processes; however, examples of such isolated species are scarce as a result of their high reactivity. Phenol tautomers (keto form of phenol) are also important intermediates in several organic and organometallic reactions; nevertheless, isolated complexes are rare. This Account reviews the recent progress on the synthesis and reactivity of iridium and rhodium o-quinone methide complexes as well as on iridium-mediated ortho functionalization of phenols. This reaction was at the origin of the discovery of a general synthetic procedure to prepare the first metal-stabilized o-quinone methide.

  20. Heats of formation and protonation thermochemistry of gaseous benzaldehyde, tropone and quinone methides

    Science.gov (United States)

    Bouchoux, Guy

    2010-08-01

    Quantum chemistry calculations using composite G3B3, G3MP2B3 and CBS-QB3 methods were performed for benzaldehyde, 1, tropone, 2, ortho-quinone methide, 3, para-quinone methide, 4, their protonated forms 1H+- 4H+ and the isomeric meta-hydroxybenzyl cation 5H+. The G3B3 298 K heats of formation values obtained in this work are: -39, 61, 52, 39, 661, 679, 699, 680 and 733 kJ mol -1 for 1- 4, 1H+- 5H+, respectively. At the same level of theory, computed proton affinities are equal to 834, 916, 887 and 892 kJ mol -1 for molecules 1- 4. These results allow to correct discrepancies on the previously reported thermochemistry of molecules 2- 4 and cations 2H+- 5H+.

  1. Quinone exchange at the A{sub 1} site in photosystem I [PSI

    Energy Technology Data Exchange (ETDEWEB)

    Barkoff, A.; Brunkan, N.; Snyder, S.W.; Ostafin, A.; Werst, M.; Thurnauer, M.C. [Argonne National Lab., IL (United States); Biggins, J. [Brown Univ., Providence, RI (United States)

    1995-12-31

    Quinones play an essential role in light-induced electron transport in photosynthetic reaction centers (RC). Study of quinone binding within the protein matrix of the RC is a focal point of understanding the biological optimization of photosynthesis. In plant and cyanobacterial PSI, phylloquinone (K{sub 1}) is believed to be the secondary electron acceptor, A{sub 1}, similar to Q{sub a} in the purple bacterial RC. Photoinduced electron transfer is initiated by reduction of the electron acceptor (A{sub 0}), a chlorophyll species, by the photoexcited primary donor *P{sub 700}. A{sub 1} acts as a transient redox intermediate between A{sub 0} and the iron-sulfur centers (FeS). We have examined the characteristic PSI electron spin polarized (ESP) electron paramagnetic resonance (EPR) signal as a marker of the interacting radical pairs developed during electron transfer.

  2. Induction of quinone reductase (QR) by withanolides isolated from Physalis pubescens L. (Solanaceae).

    Science.gov (United States)

    Ji, Long; Yuan, Yonglei; Ma, Zhongjun; Chen, Zhe; Gan, Lishe; Ma, Xiaoqiong; Huang, Dongsheng

    2013-09-01

    In the present study, it was demonstrated that the dichloromethane extract of Physalis pubescens L. (DEPP) had weak potential quinone reductase (QR) inducing activity, but an UPLC-ESI-MS method with glutathione (GSH) as the substrate revealed that the DEPP had electrophiles (with an α,β-unsaturated ketone moiety). These electrophiles could induce quinone reductase (QR) activity, which might be attributed to the modification of the highly reactive cysteine residues in Keap1. Herein, four withanolides, including three new compounds physapubescin B (2), physapubescin C (3), physapubescin D (4), together with one known steroidal compound physapubescin (1) were isolated. Structures of these compounds were determined by spectroscopic analysis and that of physapubescin C (3) was confirmed by a combination of molecular modeling and quantum chemical DFT-GIAO calculations. Evaluation of the QR inducing activities of all withanolides indicated potent activities of compounds 1 and 2, which had a common α,β-unsaturated ketone moiety.

  3. An antibacterial ortho-quinone diterpenoid and its derivatives from Caryopteris mongolica.

    Science.gov (United States)

    Saruul, Erdenebileg; Murata, Toshihiro; Selenge, Erdenechimeg; Sasaki, Kenroh; Yoshizaki, Fumihiko; Batkhuu, Javzan

    2015-06-15

    To identify antibacterial components in traditional Mongolian medicinal plant Caryopteris mongolica, an ortho-quinone abietane caryopteron A (1) and three its derivatives caryopteron B-D (2-4) were isolated from the roots of the plant together with three known abietanes demethylcryptojaponol (5), 6α-hydroxydemethyl cryptojaponol (6), and 14-deoxycoleon U (7). The chemical structures of these abietane derivatives were elucidated on the basis of spectroscopic data. Compounds 1-4 had C-13 methylcyclopropane substructures, and 2-4 had a hexanedioic anhydride ring C instead of ortho-quinone in 1. The stereochemistry of these compound was assumed from NOE spectra and ECD Cotton effects. Compounds 1 and 5-7 showed antibacterial activities against the Gram-positive bacteria Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, and Micrococcus luteus, being 1 the more potent.

  4. Synthesis and properties of polycyclic quinones condensed with 1,6-methano[10]annulene

    Directory of Open Access Journals (Sweden)

    Shigeyasu Kuroda et al

    2007-01-01

    Full Text Available Two types of polycyclic quinones condensed with 1,6-methano[10]annulenes as type A: 1,6-methanonaphtho[2,3-c][10]annulene-7,12-dione 5a, and type B: 1,6-methanonaphtho[2,3-c][10]annulene-5,14-dione 18, bis(1,6-methano[10]annuleno[3,4-b; 3,4-g]anthracene-10,21-dione 20, 1,6-methanoanthraceno[2,3-c][10]annulene-5,16-dione 22, 1,6-methanotetraceno[2,3-c][10]annulene-6,17-dione 23, and 1,6-methano phenanthreno[2,3-c][10]annulene-5,6-dione 24 have been synthesized. The acene derivative 6 corresponding to that of 5a was synthesized by the reduction of quinone 5a. The physical, spectral, and chemical properties of these new compounds have been investigated.

  5. Comparative evaluation of the acceptor properties of quinone derivatized polypyridinic ligands

    Energy Technology Data Exchange (ETDEWEB)

    Norambuena, Ester [Departamento de Quimica, Facultad de Ciencias Basicas, Universidad Metropolitana de Ciencias de la Educacion, Santiago (Chile); Olea-Azar, Claudio [Facultad de Ciencias Quimicas y Farmaceuticas, Universidad de Chile, Santiago (Chile); Delgadillo, Alvaro [Departamento de Quimica, Facultad de Ciencias, Universidad de La Serena, Casilla 599, La Serena (Chile); Barrera, Mauricio [Facultad de Quimica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago (Chile); Loeb, Barbara, E-mail: bloeb@puc.cl [Facultad de Quimica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago (Chile)

    2009-05-18

    The reduction properties of four acceptor polipyridyl ligands modified with quinones were studied by different experimental methods, as cyclic voltammetry and ESR spectroscopy, and by theoretical calculations. ESR spectra for the reduced ligands show different patterns among them, suggesting that the quinone moiety plays an important role in the delocalization of the received electron. The hyperfine coupling constants calculated for the magnetic nucleus were in good agreement with experimental data. The results were additionally interpreted with the help of two theoretical predictors: the electrophilicity index and the Fukui function obtained through the spin density. The results suggest that 12,17-dihydronaphtho-[2,3-h]dipyrido[3,2-a:2',3'-c]-phenazine-12,17-dione, Aqphen, shows the most promising behavior to be employed as an acceptor ligand in complexes with potential application in NLO devices.

  6. Ruthenium(II) complexes containing quinone based ligands: Synthesis, characterization, catalytic applications and DNA interaction

    Science.gov (United States)

    Anitha, P.; Manikandan, R.; Endo, A.; Hashimoto, T.; Viswanathamurthi, P.

    2012-12-01

    1,2-Naphthaquinone reacts with amines such as semicarbazide, isonicotinylhydrazide and thiosemicarbazide in high yield procedure with the formation of tridentate ligands HLn (n = 1-3). By reaction of ruthenium(II) starting complexes and quinone based ligands HLn (n = 1-3), a series of ruthenium complexes were synthesized and characterized by elemental and spectroscopic methods (FT-IR, electronic, 1H, 13C, 31P NMR and ESI-MS). The ligands were coordinated to ruthenium through quinone oxygen, imine nitrogen and enolate oxygen/thiolato sulfur. On the basis of spectral studies an octahedral geometry may be assigned for all the complexes. Further, the catalytic oxidation of primary, secondary alcohol and transfer hydrogenation of ketone was carried out. The DNA cleavage efficiency of new complexes has also been tested.

  7. New method for spectrophotometric determination of quinones and barbituric acid through their reaction. A kinetic study

    Science.gov (United States)

    Medien, H. A. A.

    1996-11-01

    A new and sensitive spectrophotometric method is described for the determination of p-benzoquinone, p-chloranil and 1.4-naphthoquinone. The method is based on the reaction between quinones and barbituric acid, by which a color is developed with maximum absorption between 485 and 555 nm in 50% methyl alcohol-water mixture. The absorption of the product obeys Beer's law within the concentration range 0.025-05 mM of orginal quinone. The kinetics of the reaction between p-benzoquinone and barbituric acid was studied in a range of methyl alcohol-water mixtures. The reaction follows overall second order kinetics, first order in each of the reactants. The rate increases with increasing dielectric constant. The method was applied for determination of barbituric acid with p-benzoquinone in the concentration range of 0.025-0.345 mM. Other barbiturates do not interfere.

  8. Copper Toxicity Affects Photosystem II Electron Transport at the Secondary Quinone Acceptor, QB1

    Science.gov (United States)

    Mohanty, Narendranath; Vass, Imre; Demeter, Sándor

    1989-01-01

    The nature of Cu2+ inhibition of photosystem II (PSII) photochemistry in pea (Pisum sativum L.) thylakoids was investigated monitoring Hill activity and light emission properties of photosystem II. In Cu2+-inhibited thylakoids, diphenyl carbazide addition does not relieve the loss of Hill activity. The maximum yield of fluorescence induction restored by hydroxylamine in Tris-inactivated thylakoids is markedly reduced by Cu2+. This suggests that Cu2+ does not act on the donor side of PSII but on the reaction center of PSII or on components beyond. Thermoluminescence and delayed luminescence studies show that charge recombination between the positively charged intermediate in water oxidation cycle (S2) and negatively charged primary quinone acceptor of pSII (QA−) is largely unaffected by Cu2+. The S2QB− charge recombination, however, is drastically inhibited which parallels the loss of Hill activity. This indicates that Cu2+ inhibits photosystem II photochemistry primarily affecting the function of the secondary quinone electron acceptor, QB. We suggest that Cu2+ does not block electron flow between the primary and secondary quinone acceptor but modifies the QB site in such a way that it becomes unsuitable for further photosystem II photochemistry. PMID:16666731

  9. Comparative Studies on Plastoquinones: V. Changes in Lipophilic Chloroplast Quinones during Development.

    Science.gov (United States)

    Barr, R; Crane, F L; Peak, S M

    1970-01-01

    Changes of lipophilic chloroplast quinones in corn, oats, peas, and Vicia faba are reported after 0, 4, 8, 12, 16, 20, 24, 48, 72, or 96 hours of exposure to light. There is a pronounced increase in plastoquinone A and chlorophyll levels and slight increase, in plastoquinone C(1-6), vitamin K(1), and alpha-tocopherylquinone content. Coenzyme Q levels, on the other hand, show little change upon exposure to light.THE SEQUENCE IN WHICH INDIVIDUAL QUINONES APPEAR DURING DEVELOPMENT IS AS FOLLOWS: plastoquinone A instantaneously after exposure to light, plastoquinone C(1-6) from 4 to 24 hours, vitamin K(1) from 12 to 24 hours, alpha-tocopherylquinone from 0 to 24 hours of illumination. Small amounts (<0.01 mumole/g, dry wt) of plastoquinone A and plastoquinone B are found in seeds and etiolated tissues. After exposure to light, the quinone tentatively identified as a member of the plastoquinone B series by reverse phase thin layer chromatography disappears and can be detected again in small amounts during maturity and toward senescence of the leaf.

  10. Crystal structures of Pseudomonas syringae pv. tomato DC3000 quinone oxidoreductase and its complex with NADPH

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Xiaowei [National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing 100101 (China); Graduate University of the Chinese Academy of Sciences, Beijing 100049 (China); Zhang, Hongmei; Gao, Yu; Li, Mei [National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing 100101 (China); Chang, Wenrui, E-mail: wrchang@sun5.ibp.ac.cn [National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing 100101 (China)

    2009-12-18

    Zeta-crystallin-like quinone oxidoreductase is NAD(P)H-dependent and catalyzes one-electron reduction of certain quinones to generate semiquinone. Here we present the crystal structures of zeta-crystallin-like quinone oxidoreductase from Pseudomonas syringae pv. tomato DC3000 (PtoQOR) and its complexes with NADPH determined at 2.4 and 2.01 A resolutions, respectively. PtoQOR forms as a homologous dimer, each monomer containing two domains. In the structure of the PtoQOR-NADPH complex, NADPH locates in the groove between the two domains. NADPH binding causes obvious conformational changes in the structure of PtoQOR. The putative substrate-binding site of PtoQOR is wider than that of Escherichia coli and Thermus thermophilus HB8. Activity assays show that PtoQOR has weak 1,4-benzoquinone catalytic activity, and very strong reduction activity towards large substrates such as 9,10-phenanthrenequinone. We propose a model to explain the conformational changes which take place during reduction reactions catalyzed by PtoQOR.

  11. Widespread ability of fungi to drive quinone redox cycling for biodegradation.

    Science.gov (United States)

    Krueger, Martin C; Bergmann, Michael; Schlosser, Dietmar

    2016-06-01

    Wood-rotting fungi possess remarkably diverse extracellular oxidation mechanisms, including enzymes, such as laccase and peroxidases, and Fenton chemistry. The ability to biologically drive Fenton chemistry by the redox cycling of quinones has previously been reported to be present in both ecologically diverging main groups of wood-rotting basidiomycetes. Therefore, we investigated whether it is even more widespread among fungal organisms. Screening of a diverse selection of a total of 18 ascomycetes and basidiomycetes for reduction of the model compound 2,6-dimethoxy benzoquinone revealed that all investigated strains were capable of reducing it to its corresponding hydroquinone. In a second step, depolymerization of the synthetic polymer polystyrene sulfonate was used as a proxy for quinone-dependent Fenton-based biodegradation capabilities. A diverse subset of the strains, including environmentally ubiquitous molds, white-rot fungi, as well as peatland and aquatic isolates, caused substantial depolymerization indicative for the effective employment of quinone redox cycling as biodegradation tool. Our results may also open up new paths to utilize diverse fungi for the bioremediation of recalcitrant organic pollutants.

  12. Occurrence and Potential Sources of Quinones Associated with PM2.5 in Guadalajara, Mexico

    Directory of Open Access Journals (Sweden)

    Adriana Barradas-Gimate

    2017-07-01

    Full Text Available This study aims to establish the influence of primary emission sources and atmospheric transformation process contributing to the concentrations of quinones associated to particulate matter of less than 2.5 µm (PM2.5 in three sites within the Metropolitan Area of Guadalajara (MAG, namely Centro (CEN, Tlaquepaque (TLA and Las Águilas (AGU. Environmental levels of quinones extracted from PM2.5 filters were analyzed using Gas Chromatography coupled to Mass Spectrometry (GC-MS. Overall, primary emissions in combination with photochemical and oxidation reactions contribute to the presence of quinones in the urban atmosphere of MAG. It was found that quinones in PM2.5 result from the contributions from direct emission sources by incomplete combustion of fossil fuels such as diesel and gasoline that relate mainly to vehicular activity intensity in the three sampling sites selected. However, this also suggests that the occurrence of quinones in MAG can be related to photochemical transformation of the parent Polycyclic Aromatic Hydrocarbons (PAHs, to chemical reactions with oxygenated species, or a combination of both routes. The higher concentration of 1,4-Chrysenequinone during the rainy season compared to the warm-dry season indicates chemical oxidation of chrysene, since the humidity could favor singlet oxygen collision with parent PAH present in the particle phase. On the contrary, 9,10-Anthraquinone/Anthracene and 1,4-Naftoquinone/Naphthalene ratios were higher during the warm-dry season compared to the rainy season, which might indicate a prevalence of the photochemical formation during the warm-dry season favored by the large solar radiation typical of the season. In addition, the estimated percentage of photochemical formation of 9,10-Phenanthrenequinone showed that the occurrence of this compound in Tlaquepaque (TLA and Las Águilas (AGU sites is mainly propagated by conditions of high solar radiation such as in the warm-dry season and

  13. Electron transfer capacity dependence of quinone-mediated Fe(III) reduction and current generation by Klebsiella pneumoniae L17.

    Science.gov (United States)

    Li, Xiaomin; Liu, Liang; Liu, Tongxu; Yuan, Tian; Zhang, Wei; Li, Fangbai; Zhou, Shungui; Li, Yongtao

    2013-06-01

    Quinone groups in exogenous electron shuttles can accelerate extracellular electron transfer (EET) from bacteria to insoluble terminal electron acceptors, such as Fe(III) oxides and electrodes, which are important in biogeochemical redox processes and microbial electricity generation. However, the relationship between quinone-mediated EET performance and electron-shuttling properties of the quinones remains incompletely characterized. This study investigates the effects of a series of synthetic quinones (SQs) on goethite reduction and current generation by a fermenting bacterium Klebsiella pneumoniae L17. In addition, the voltammetric behavior and electron transfer capacities (ETCs) of SQ, including electron accepting (EAC) and donating (EDC) capacities, is also examined using electrochemical methods. The results showed that SQ can significantly increase both the Fe(III) reduction rates and current outputs of L17. Each tested SQ reversibly accepted and donated electrons as indicated by the cyclic voltammograms. The EAC and EDC results showed that Carmine and Alizarin had low relative capacities of electron transfer, whereas 9,10-anthraquinone-2,6-disulfonic acid (AQDS), 2-hydroxy-1,4-naphthoquinone (2-HNQ), and 5-hydroxy-1,4-naphthoquinone (5-HNQ) showed stronger relative ETC, and 9,10-anthraquinone-2-carboxylic acid (AQC) and 9,10-anthraquinone-2-sulfonic acid (AQS) had high relative ETC. Enhancement of microbial goethite reduction kinetics and current outputs by SQ had a good linear relationship with their ETC, indicating that the effectiveness of quinone-mediated EET may be strongly dependent on the ETC of the quinones. Therefore, the presence of quinone compounds and fermenting microorganisms may increase the diversity of microbial populations that contribute to element transformation in natural environments. Moreover, ETC determination of different SQ would help to evaluate their performance for microbial EET under anoxic conditions. Copyright © 2013 Elsevier

  14. The Role of Human Aldo-Keto Reductases in the Metabolic Activation and Detoxication of Polycyclic Aromatic Hydrocarbons: Interconversion of PAH Catechols and PAH o-Quinones

    OpenAIRE

    Li eZhang; Yi eJin; Meng eHuang; Penning, Trevor M.

    2012-01-01

    Polycyclic aromatic hydrocarbons (PAH) are ubiquitous environmental pollutants. They are procarcinogens requiring metabolic activation to elicit their deleterious effects. Aldo-keto reductases (AKR) catalyze the oxidation of proximate carcinogenic PAH trans-dihydrodiols to yield electrophilic and redox-active PAH o-quinones. AKRs are also found to be capable of reducing PAH o-quinones to form PAH catechols. The interconversion of o-quinones and catechols results in the redox-cycling of PAH o-...

  15. FAD semiquinone stability regulates single- and two-electron reduction of quinones by Anabaena PCC7119 ferredoxin:NADP+ reductase and its Glu301Ala mutant.

    Science.gov (United States)

    Anusevicius, Zilvinas; Miseviciene, Lina; Medina, Milagros; Martinez-Julvez, Marta; Gomez-Moreno, Carlos; Cenas, Narimantas

    2005-05-15

    Flavoenzymes may reduce quinones in a single-electron, mixed single- and two-electron, and two-electron way. The mechanisms of two-electron reduction of quinones are insufficiently understood. To get an insight into the role of flavin semiquinone stability in the regulation of single- vs. two-electron reduction of quinones, we studied the reactions of wild type Anabaena ferredoxin:NADP(+)reductase (FNR) with 48% FAD semiquinone (FADH*) stabilized at the equilibrium (pH 7.0), and its Glu301Ala mutant (8% FADH* at the equilibrium). We found that Glu301Ala substitution does not change the quinone substrate specificity of FNR. However, it confers the mixed single- and two-electron mechanism of quinone reduction (50% single-electron flux), whereas the wild type FNR reduces quinones in a single-electron way. During the oxidation of fully reduced wild type FNR by tetramethyl-1,4-benzoquinone, the first electron transfer (formation of FADH*) is about 40 times faster than the second one (oxidation of FADH*). In contrast, the first and second electron transfer proceeded at similar rates in Glu301Ala FNR. Thus, the change in the quinone reduction mechanism may be explained by the relative increase in the rate of second electron transfer. This enabled us to propose the unified scheme of single-, two- and mixed single- and two-electron reduction of quinones by flavoenzymes with the central role of the stability of flavin/quinone ion-radical pair.

  16. Directly probing redox-linked quinones in photosystem II membrane fragments via UV resonance Raman scattering.

    Science.gov (United States)

    Chen, Jun; Yao, Mingdong; Pagba, Cynthia V; Zheng, Yang; Fei, Liping; Feng, Zhaochi; Barry, Bridgette A

    2015-01-01

    In photosynthesis, photosystem II (PSII) harvests sunlight with bound pigments to oxidize water and reduce quinone to quinol, which serves as electron and proton mediators for solar-to-chemical energy conversion. At least two types of quinone cofactors in PSII are redox-linked: QA, and QB. Here, we for the first time apply 257-nm ultraviolet resonance Raman (UVRR) spectroscopy to acquire the molecular vibrations of plastoquinone (PQ) in PSII membranes. Owing to the resonance enhancement effect, the vibrational signal of PQ in PSII membranes is prominent. A strong band at 1661 cm(-1) is assigned to ring CC/CO symmetric stretch mode (ν8a mode) of PQ, and a weak band at 469 cm(-1) to ring stretch mode. By using a pump-probe difference UVRR method and a sample jet technique, the signals of QA and QB can be distinguished. A frequency difference of 1.4 cm(-1) in ν8a vibrational mode between QA and QB is observed, corresponding to ~86 mV redox potential difference imposed by their protein environment. In addition, there are other PQs in the PSII membranes. A negligible anharmonicity effect on their combination band at 2130 cm(-1) suggests that the 'other PQs' are situated in a hydrophobic environment. The detection of the 'other PQs' might be consistent with the view that another functional PQ cofactor (not QA or QB) exists in PSII. This UVRR approach will be useful to the study of quinone molecules in photosynthesis or other biological systems.

  17. Complete phenotypic recovery of an Alzheimer's disease model by a quinone-tryptophan hybrid aggregation inhibitor.

    Directory of Open Access Journals (Sweden)

    Roni Scherzer-Attali

    Full Text Available The rational design of amyloid oligomer inhibitors is yet an unmet drug development need. Previous studies have identified the role of tryptophan in amyloid recognition, association and inhibition. Furthermore, tryptophan was ranked as the residue with highest amyloidogenic propensity. Other studies have demonstrated that quinones, specifically anthraquinones, can serve as aggregation inhibitors probably due to the dipole interaction of the quinonic ring with aromatic recognition sites within the amyloidogenic proteins. Here, using in vitro, in vivo and in silico tools we describe the synthesis and functional characterization of a rationally designed inhibitor of the Alzheimer's disease-associated beta-amyloid. This compound, 1,4-naphthoquinon-2-yl-L-tryptophan (NQTrp, combines the recognition capacities of both quinone and tryptophan moieties and completely inhibited Abeta oligomerization and fibrillization, as well as the cytotoxic effect of Abeta oligomers towards cultured neuronal cell line. Furthermore, when fed to transgenic Alzheimer's disease Drosophila model it prolonged their life span and completely abolished their defective locomotion. Analysis of the brains of these flies showed a significant reduction in oligomeric species of Abeta while immuno-staining of the 3(rd instar larval brains showed a significant reduction in Abeta accumulation. Computational studies, as well as NMR and CD spectroscopy provide mechanistic insight into the activity of the compound which is most likely mediated by clamping of the aromatic recognition interface in the central segment of Abeta. Our results demonstrate that interfering with the aromatic core of amyloidogenic peptides is a promising approach for inhibiting various pathogenic species associated with amyloidogenic diseases. The compound NQTrp can serve as a lead for developing a new class of disease modifying drugs for Alzheimer's disease.

  18. High On/Off Conductance Switching Ratio via H-Tautomerization in Quinone.

    Science.gov (United States)

    Tawfik, Sherif Abdulkader; Cui, X Y; Ringer, S P; Stampfl, C

    2015-09-01

    Through first-principles electron transport simulations using the nonequilibrium Green's function formalism together with density functional theory, we show that, upon H-tautomerization, a simple derivative of quinone can act as a molecular switch with high ON/OFF ratio, up to 70 at low bias voltage. This switching behavior is explained by the quantum interference effect, where the positional change of hydrogen atoms causes the energies of the transmission channels to overlap. Our results suggest that this molecule could have potential applications as an effective switching device.

  19. THz-Raman Identification of labile products in the system "phenol-semiquinone-quinone"

    CERN Document Server

    Polubotko, E A Iasenko V P Chelibanov A M

    2016-01-01

    The paper presents the results of SERS studies of the dynamic behavior of "phenol-semiquinone-quinone" system. This system is a key part of chemiluminescent sensors for reactive oxygen species. The dynamics of the system seems to be very important in the processes that determine the secondary metabolism at the cellular level in molecular biology. THz Raman spectra were recorded for the labile products formed in the processes initiated by proton transfer. A mechanism of the proton-transfer-initiated reaction is proposed.

  20. Homologation of α-aryl amino acids through quinone-catalyzed decarboxylation/Mukaiyama-Mannich addition.

    Science.gov (United States)

    Haugeberg, Benjamin J; Phan, Johnny H; Liu, Xinyun; O'Connor, Thomas J; Clift, Michael D

    2017-03-09

    A new method for amino acid homologation by way of formal C-C bond functionalization is reported. This method utilizes a 2-step/1-pot protocol to convert α-amino acids to their corresponding N-protected β-amino esters through quinone-catalyzed oxidative decarboxylation/in situ Mukaiyama-Mannich addition. The scope and limitations of this chemistry are presented. This methodology provides an alternative to the classical Arndt-Eistert homologation for accessing β-amino acid derivatives. The resulting N-protected amine products can be easily deprotected to afford the corresponding free amines.

  1. Measuring protection of aromatic wine thiols from oxidation by competitive reactions vs wine preservatives with ortho-quinones.

    Science.gov (United States)

    Nikolantonaki, Maria; Magiatis, Prokopios; Waterhouse, Andrew L

    2014-11-15

    Quinones are central intermediates in wine oxidation that can degrade the quality of wine by reactions with varietal thiols, such as 3-sulfanylhexanol, decreasing desirable aroma. Protection by wine preservatives (sulphur dioxide, glutathione, ascorbic acid and model tannin, phloroglucinol) was assessed by competitive sacrificial reactions with 4-methyl-1,2-benzoquinone, quantifying products and ratios by HPLC-UV-MS. Regioselectivity was assessed by product isolation and identification by NMR spectroscopy. Nucleophilic addition reactions compete with two electron reduction of quinones by sulphur dioxide or ascorbic acid, and both routes serve as effective quenching pathways, but minor secondary products from coupled redox reactions between the products and reactants are also observed. The wine preservatives were all highly reactive and thus all very protective against 3-sulfanylhexanol loss to the quinone, but showed only additive antioxidant effects. Confirmation of these reaction rates and pathways in wine is needed to assess the actual protective action of each tested preservative.

  2. Xanthones with quinone reductase-inducing activity from the fruits of Garcinia mangostana (Mangosteen).

    Science.gov (United States)

    Chin, Young-Won; Jung, Hyun-Ah; Chai, Heebyung; Keller, William J; Kinghorn, A Douglas

    2008-02-01

    Bioactivity-guided fractionation of a dichloromethane-soluble extract of Garcinia mangostana fruits has led to the isolation and identification of five compounds, including two xanthones, 1,2-dihydro-1,8,10-trihydroxy-2-(2-hydroxypropan-2-yl)-9-(3-methylbut-2-enyl)furo[3,2-a]xanthen-11-one (1) and 6-deoxy-7-demethylmangostanin (2), along with three known compounds, 1,3,7-trihydroxy-2,8-di-(3-methylbut-2-enyl)xanthone (3), mangostanin (4), and alpha-mangostin (5). The structures of compounds 1 and 2 were determined from analysis of their spectroscopic data. All isolated compounds in the present study together with eleven other compounds previously isolated from the pericarp of mangosteen, were tested in an in vitro quinone reductase-induction assay using murine hepatoma cells (Hepa 1c1c7) and an in vitro hydroxyl radical antioxidant assay. Of these, compounds 1-4 induced quinone reductase (concentration to double enzyme induction, 0.68-2.2microg/mL) in Hepa 1c1c7 cells and gamma-mangostin (6) exhibited hydroxyl radical-scavenging activity (IC50, 0.20microg/mL).

  3. Absence of large-scale displacement of quinone QB in bacterial photosynthetic reaction centers.

    Science.gov (United States)

    Breton, Jacques

    2004-03-30

    Photosynthesis transforms light into chemical energy by coupling electron transfer to proton uptake at the quinone Q(B). The possibility of initiating this process with a brief pulse of light and the known X-ray structure makes the photosynthetic bacterial reaction center a paradigm for studying coupled electron-proton transfer in biology. It has been established that electron transfer from the primary quinone Q(A) to Q(B) is gated by a protein conformational change. On the basis of a dramatic difference in the location of Q(B) in structures derived from crystals cooled to 90 K either under illumination or in the dark, a functional model for the gating mechanism was proposed whereby neutral Q(B) moves 4.5 A before receiving the electron from Q(A)(-) [Stowell, M. H. B., McPhillips, T. M., Rees, D. C., Soltis, S. M., Abresch, E., and Feher, G. (1997) Science 276, 812-816]. Isotope-edited FTIR difference spectroscopy of Q(B) photoreduction at 290 and 85 K is used to investigate whether Q(B) moves upon reduction. We show that the specific interactions of the carbonyl groups of Q(B) and Q(B)(-) with the protein at a single binding site remain identical at both temperatures. Therefore, the different locations of Q(B) reported in many X-ray crystal structures probably are unrelated to functional electron transfer from Q(A)(-) to Q(B).

  4. Identification of lactate dehydrogenase as a mammalian pyrroloquinoline quinone (PQQ)-binding protein

    Science.gov (United States)

    Akagawa, Mitsugu; Minematsu, Kenji; Shibata, Takahiro; Kondo, Tatsuhiko; Ishii, Takeshi; Uchida, Koji

    2016-01-01

    Pyrroloquinoline quinone (PQQ), a redox-active o-quinone, is an important nutrient involved in numerous physiological and biochemical processes in mammals. Despite such beneficial functions, the underlying molecular mechanisms remain to be established. In the present study, using PQQ-immobilized Sepharose beads as a probe, we examined the presence of protein(s) that are capable of binding PQQ in mouse NIH/3T3 fibroblasts and identified five cellular proteins, including l-lactate dehydrogenase (LDH) A chain, as potential mammalian PQQ-binding proteins. In vitro studies using a purified rabbit muscle LDH show that PQQ inhibits the formation of lactate from pyruvate in the presence of NADH (forward reaction), whereas it enhances the conversion of lactate to pyruvate in the presence of NAD+ (reverse reaction). The molecular mechanism underlying PQQ-mediated regulation of LDH activity is attributed to the oxidation of NADH to NAD+ by PQQ. Indeed, the PQQ-bound LDH oxidizes NADH, generating NAD+, and significantly catalyzes the conversion of lactate to pyruvate. Furthermore, PQQ attenuates cellular lactate release and increases intracellular ATP levels in the NIH/3T3 fibroblasts. Our results suggest that PQQ, modulating LDH activity to facilitate pyruvate formation through its redox-cycling activity, may be involved in the enhanced energy production via mitochondrial TCA cycle and oxidative phosphorylation. PMID:27230956

  5. Direct and quinone-mediated palladium reduction by Geobacter sulfurreducens: mechanisms and modeling.

    Science.gov (United States)

    Pat-Espadas, Aurora M; Razo-Flores, Elías; Rangel-Mendez, J Rene; Cervantes, Francisco J

    2014-01-01

    Palladium(II) reduction to Pd(0) nanoparticles by Geobacter sulfurreducens was explored under conditions of neutral pH, 30 °C and concentrations of 25, 50, and 100 mg of Pd(II)/L aiming to investigate the effect of solid species of palladium on their microbial reduction. The influence of anthraquinone-2,6-disulfonate was reported to enhance the palladium reaction rate in an average of 1.7-fold and its addition is determining to achieve the reduction of solid species of palladium. Based on the obtained results two mechanisms are proposed: (1) direct, which is fully described considering interactions of amide, sulfur, and phosphoryl groups associated to proteins from bacteria on palladium reduction reaction, and (2) quinone-mediated, which implies multiheme c-type cytochromes participation. Speciation analysis and kinetic results were considered and integrated into a model to fit the experimental data that explain both mechanisms. This work provides elements for a better understanding of direct and quinone-mediated palladium reduction by G. sulfurreducens, which could facilitate metal recovery with concomitant formation of valuable palladium nanoparticles in industrial processes.

  6. Another unusual type of citric acid cycle enzyme in Helicobacter pylori: the malate:quinone oxidoreductase.

    Science.gov (United States)

    Kather, B; Stingl, K; van der Rest, M E; Altendorf, K; Molenaar, D

    2000-06-01

    The only enzyme of the citric acid cycle for which no open reading frame (ORF) was found in the Helicobacter pylori genome is the NAD-dependent malate dehydrogenase. Here, it is shown that in this organism the oxidation of malate to oxaloacetate is catalyzed by a malate:quinone oxidoreductase (MQO). This flavin adenine dinucleotide-dependent membrane-associated enzyme donates electrons to quinones of the electron transfer chain. Similar to succinate dehydrogenase, it is part of both the electron transfer chain and the citric acid cycle. MQO activity was demonstrated in isolated membranes of H. pylori. The enzyme is encoded by the ORF HP0086, which is shown by the fact that expression of the HP0086 sequence from a plasmid induces high MQO activity in mqo deletion mutants of Escherichia coli or Corynebacterium glutamicum. Furthermore, this plasmid was able to complement the phenotype of the C. glutamicum mqo deletion mutant. Interestingly, the protein predicted to be encoded by this ORF is only distantly related to known or postulated MQO sequences from other bacteria. The presence of an MQO shown here and the previously demonstrated presence of a 2-ketoglutarate:ferredoxin oxidoreductase and a succinyl-coenzyme A (CoA):acetoacetyl-CoA transferase indicate that H. pylori possesses a complete citric acid cycle, but one which deviates from the standard textbook example in three steps.

  7. Monitoring of BHT-quinone and BHT-CHO in the gas of capsules of Asclepias physocarpa.

    Science.gov (United States)

    Ma, Bing-Ji; Peng, Hua; Liu, Ji-Kai

    2006-01-01

    Three volatile components, namely benzoic acid ethyl ester (1), 2,6-di-tert-butyl-p-benzoquinone (BHT-quinone) (2), and 3,5-di-tert-butyl-4-hydroxybenzaldehyde (BHT-CHO) (3), were detected from the gas in the capsules of Asclepias physocarpa by means of GC/MS analysis. BHT-quinone and BHT-CHO as organic pollutants are the degradation products of the antioxidant 2,6-di-tert-butyl-4-methylphenol (BHT). Ground water, lake water and/or rain water are a source of BHT metabolites in the plant Asclepias physocarpa.

  8. A physiological threshold for protection against menadione toxicity by human NAD(P)H : quinone oxidoreductase (NQO1) in Chinese hamster ovary (CHO) cells

    NARCIS (Netherlands)

    Haan, de L.H.J.; Boerboom, A.M.J.F.; Rietjens, I.M.C.M.; Capelle, van D.; Ruijter, de A.J.M.; Jaiswal, A.K.; Aarts, J.M.M.J.G.

    2002-01-01

    NAD(P)H:quinone oxidoreductase 1 (NQO1) has often been suggested to be involved in cancer prevention by means of detoxification of electrophilic quinones. In the present study, a series of Chinese hamster ovary (CHO) cell lines expressing various elevated levels of human NQO1 were generated by stabl

  9. The Role of Human Aldo-Keto Reductases in the Metabolic Activation and Detoxication of Polycyclic Aromatic Hydrocarbons: Interconversion of PAH Catechols and PAH o-Quinones.

    Science.gov (United States)

    Zhang, Li; Jin, Yi; Huang, Meng; Penning, Trevor M

    2012-01-01

    Polycyclic aromatic hydrocarbons (PAH) are ubiquitous environmental pollutants. They are procarcinogens requiring metabolic activation to elicit their deleterious effects. Aldo-keto reductases (AKR) catalyze the oxidation of proximate carcinogenic PAH trans-dihydrodiols to yield electrophilic and redox-active PAH o-quinones. AKRs are also found to be capable of reducing PAH o-quinones to form PAH catechols. The interconversion of o-quinones and catechols results in the redox-cycling of PAH o-quinones to give rise to the generation of reactive oxygen species and subsequent oxidative DNA damage. On the other hand, PAH catechols can be intercepted through phase II metabolism by which PAH o-quinones could be detoxified and eliminated. The aim of the present review is to summarize the role of human AKRs in the metabolic activation/detoxication of PAH and the relevance of phase II conjugation reactions to human lung carcinogenesis.

  10. Time-Resolved Electron Paramagnetic Resonance Study of Photoinduced Electron Transfer in Pd Porphyrin-Quinone and Zn Porphyrin-Quinone Dyads with a Cyclohexylene Spacer.

    Science.gov (United States)

    Perchanova, Maya; Kurreck, Harry; Berg, Alexander

    2015-07-23

    Peculiarities of the light induced intramolecular electron transfer processes in two ensembles where Pd porphyrin and Zn porphyrin donors with similar peripheral substituents are covalently linked via cyclohexylene spacer with a quinone acceptor, were studied by time-resolved electron paramagnetic resonance spectroscopy in different phases of the magnetically oriented nematic liquid crystal E-7. In the photoexcited PdP-Q the net absorptive signal was observed and ascribed to the thermally equilibrated spectrum of (3)*(PdP(•+)-Q(•-)). In ZnP-Q photoinduced intramolecular electron transfer was also found. It was demonstrated that the multiplet spectrum of the charge-separated state (3)*(ZnP(•+)-Q(•-)) consists of two signals with different widths and decay times. The signals were assigned to two spin-polarized triplets of the radical pairs formed in "stretched" and "folded" ensemble conformers, corresponding to different configurations of the cyclohexylene spacer. These findings were discussed in terms of differences in the properties of the porphyrin metal cores, macrocycle peripheral substituents and geometry of the donor-acceptor cyclohexylene spacer.

  11. Crystal structure of quinone-dependent alcohol dehydrogenase from Pseudogluconobacter saccharoketogenes. A versatile dehydrogenase oxidizing alcohols and carbohydrates

    NARCIS (Netherlands)

    Rozeboom, Henriette J.; Yu, Shukun; Mikkelsen, Rene; Nikolaev, Igor; Mulder, Harm J.; Dijkstra, Bauke W.

    2015-01-01

    The quinone-dependent alcohol dehydrogenase (PQQ-ADH, E.C. 1.1.5.2) from the Gram-negative bacterium Pseudogluconobacter saccharoketogenes IFO 14464 oxidizes primary alcohols (e.g. ethanol, butanol), secondary alcohols (monosaccharides), as well as aldehydes, polysaccharides, and cyclodextrins. The

  12. The interaction of quinones, herbicides and bicarbonate with their binding environment and the acceptor side of photosystem II in photosynthesis

    NARCIS (Netherlands)

    Vermaas, W.

    1984-01-01

    In this thesis experiments are described which are directed towards a further characterization of the interaction of the native bound plastoquinone Q B , artificial quinones, herbicides and bicarbonate with their binding environment at the acceptor side of Photosystem II in the thylakoid

  13. Hydroquinone and quinone-grafted porous carbons for highly selective CO2 capture from flue gases and natural gas upgrading

    NARCIS (Netherlands)

    Wang, J.; Krishna, R.; Yang, J.; Deng, S.

    2015-01-01

    Hydroquinone and quinone functional groups were grafted onto a hierarchical porous carbon framework via the Friedel-Crafts reaction to develop more efficient adsorbents for the selective capture and removal of carbon dioxide from flue gases and natural gas. The oxygen-doped porous carbons were

  14. Contribution of quinone-reducing microorganisms to the anaerobic biodegradation of organic compounds under different redox conditions

    Energy Technology Data Exchange (ETDEWEB)

    Cervantes, F. J.; Gutierrez, C. H.; Lopez, K. Y.; Estrada-Alvarodo, M. I.; Meza-Escalante, E. R.; Texier, A. C.; Cuervo, F.; Gomez, J.

    2009-07-01

    Reduction of humic substances (HS) has recently been recognized as a microbial respiratory process supporting growth of several distinct microorganisms. Quinone moieties, which are very abundant in the humic acid fraction of humus, are the main functional groups conferring electron-accepting capacity to HS. The capacity to reduce HS has been reported in anaerobic consortia from a wide diversity of environments. (Author)

  15. Cathodic Voltammetric Behavior of Pillar[5]quinone in Nonaqueous Media. Symmetry Effects on the Electron Uptake Sequence.

    Science.gov (United States)

    Cheng, Beijun; Kaifer, Angel E

    2015-08-12

    The cathodic voltammetric behavior of pillar[5]quinone was investigated in dichloromethane solution. Our data show that the symmetry of the macrocycle has a pronounced effect on the electron uptake sequence. The uptake of the first five electrons follows a 2-1-2 pattern, and only a total of eight electrons could be injected into the macrocycle under our experimental conditions.

  16. The effect of glassy carbon surface oxides in non-aqueous voltammetry: the case of quinones in acetonitrile.

    Science.gov (United States)

    Staley, Patrick A; Newell, Christina M; Pullman, David P; Smith, Diane K

    2014-11-04

    Glassy carbon (GC) electrodes are well-known to contain oxygenated functional groups such as phenols, carbonyls, and carboxylic acids on their surface. The effects of these groups on voltammetry in aqueous solution are well-studied, but there has been little discussion of their possible effects in nonaqueous solution. In this study, we show that the acidic functional groups, particularly phenols, are likely causes of anomalous features often seen in the voltammetry of quinones in nonaqueous solution. These features, a too small second cyclic voltammetric wave and extra current between the two waves that sometimes appears to be a small, broad third voltammetric wave, have previously been attributed to different types of dimerization. In this work, concentration-dependent voltammetry in acetonitrile rules out dimerization with a series of alkyl-benzoquinones because the anomalous features get larger as the concentration decreases. At low concentrations, solution bimolecular reactions will be relatively less important than reactions with surface groups. Addition of substoichiometric amounts of naphthol at higher quinone concentrations produces almost identical behavior as seen at low quinone concentrations with no added naphthol. This implicates hydrogen bonding and proton transfer from the surface phenolic groups as the cause of the anomalous features in quinone voltammetry at GC electrodes. This conclusion is supported by the perturbation of surface oxide coverage on GC electrodes through different electrode pretreatments.

  17. The interaction of quinones, herbicides and bicarbonate with their binding environment at the acceptor side of photosystem II in photosynthesis

    NARCIS (Netherlands)

    Vermaas, W.F.J.

    1984-01-01

    In this thesis experiments are described which are directed towards a further characterization of the interaction of the native bound plastoquinone Q B , artificial quinones, herbicides and bicarbonate with their binding environment at the acceptor side of Photosystem II in

  18. Peltomexicanin, a Peltogynoid Quinone Methide from Peltogyne Mexicana Martínez Purple Heartwood

    Directory of Open Access Journals (Sweden)

    Paulina Gutiérrez-Macías

    2016-02-01

    Full Text Available Peltomexicanin (7,10-dihydroxy-6,12-dioxa-5H-tetraphen-3-one is a new peltogynoid quinone methide isolated from Palo Morado (Peltogyne mexicana Martínez heartwood by column chromatography. Its chemical structure was elucidated by IR, NMR (1H, 13C, 2D NMR experiments (COSY, NOESY, HMQC, and HSQC, ESI-MS, and UV-Vis spectroscopic analysis. According to HPLC quantification, this compound is the main pigment and accounts for 1.21% of Palo Morado heartwood material. The antioxidant activity of peltomexicanin and dried methanolic extract (DEx of purple heartwood was evaluated using the radical of 2,2’-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid (ABTS assay, and the corresponding values expressed as Trolox equivalents (µmol TE/mg sample were 4.25 and 4.57, respectively.

  19. Anti-inflammatory and Quinone Reductase Inducing Compounds from Fermented Noni (Morinda citrifolia) Juice Exudates.

    Science.gov (United States)

    Youn, Ui Joung; Park, Eun-Jung; Kondratyuk, Tamara P; Sang-Ngern, Mayuramas; Wall, Marisa M; Wei, Yanzhang; Pezzuto, John M; Chang, Leng Chee

    2016-06-24

    A new fatty acid ester disaccharide, 2-O-(β-d-glucopyranosyl)-1-O-(2E,4Z,7Z)-deca-2,4,7-trienoyl-β-d-glucopyranose (1), a new ascorbic acid derivative, 2-caffeoyl-3-ketohexulofuranosonic acid γ-lactone (2), and a new iridoid glycoside, 10-dimethoxyfermiloside (3), were isolated along with 13 known compounds (4-16) from fermented noni fruit juice (Morinda citrifolia). The structures of the new compounds, together with 4 and 5, were determined by 1D and 2D NMR experiments, as well as comparison with published values. Compounds 2 and 7 showed moderate inhibitory activities in a TNF-α-induced NF-κB assay, and compounds 4 and 6 exhibited considerable quinone reductase-1 (QR1) inducing effects.

  20. Photochemical formation and chemistry of long-lived adamantylidene-quinone methides and 2-adamantyl cations.

    Science.gov (United States)

    Basarić, Nikola; Zabcić, Ivana; Mlinarić-Majerski, Kata; Wan, Peter

    2010-01-01

    Hydroxymethylphenols strategically substituted with the 2-hydroxy-2-adamantyl moiety, AdPh 8-10, were synthesized, and their photochemical reactivity was investigated. On excitation to the singlet excited state, AdPh 8 undergoes intramolecular proton transfer coupled with a loss of H(2)O giving quinone methide 8QM. The presence of 8QM has been detected by laser flash photolysis (CH(3)CN-H(2)O 1:1, tau = 0.55 s) and UV-vis spectroscopy. Singlet excited states of AdPh 9 and 10 in the presence of H(2)O dehydrate giving 9QM and 10QM. Photochemically formed QMs are trapped by nucleophiles giving the addition products (e.g., Phi for methanolysis of 8 is 0.55). In addition, the zwitterionic 9QM undergoes an unexpected rearrangement involving transformation of the 2-phenyl-2-adamantyl cation into the 4-phenyl-2-adamantyl cation (Phi approximately 0.03). An analogous rearrangement was observed with methoxy derivatives 9a and 10a. Zwitterionic 9QM was characterized by LFP in 2,2,2-trifluoroethanol (tau = 1 mus). In TFE, in the ground state, AdPh 10 is in equilibrium with 10QM, which allowed for recording the (1)H and (13)C NMR spectra of the QM. Introduction of the adamantyl substituent into the o-hydroxymethylphenol moiety increased the quantum yield of the associated QM formation by up to 3-fold and significantly prolonged their lifetimes. Furthermore, adamantyl substituent made the study of the alkyl-substituted quinone methides easier by LFP by prolonging their lifetimes and increasing the quantum yields of formation.

  1. Quinones and aromatic chemical compounds in particulate matter induce mitochondrial dysfunction: implications for ultrafine particle toxicity.

    Science.gov (United States)

    Xia, Tian; Korge, Paavo; Weiss, James N; Li, Ning; Venkatesen, M Indira; Sioutas, Constantinos; Nel, Andre

    2004-10-01

    Particulate pollutants cause adverse health effects through the generation of oxidative stress. A key question is whether these effects are mediated by the particles or their chemical compounds. In this article we show that aliphatic, aromatic, and polar organic compounds, fractionated from diesel exhaust particles (DEPs), exert differential toxic effects in RAW 264.7 cells. Cellular analyses showed that the quinone-enriched polar fraction was more potent than the polycyclic aromatic hydrocarbon (PAH)-enriched aromatic fraction in O2 .- generation, decrease of membrane potential (Delta-Psi m), loss of mitochondrial membrane mass, and induction of apoptosis. A major effect of the polar fraction was to promote cyclosporin A (CsA)-sensitive permeability transition pore (PTP) opening in isolated liver mitochondria. This opening effect is dependent on a direct effect on the PTP at low doses as well as on an effect on Delta-Psi m at high doses in calcium (Ca2+)-loaded mitochondria. The direct PTP effect was mimicked by redox-cycling DEP quinones. Although the aliphatic fraction failed to perturb mitochondrial function, the aromatic fraction increased the Ca2+ retention capacity at low doses and induced mitochondrial swelling and a decrease in Delta-Psi m at high doses. This swelling effect was mostly CsA insensitive and could be reproduced by a mixture of PAHs present in DEPs. These chemical effects on isolated mitochondria could be reproduced by intact DEPs as well as ambient ultrafine particles (UFPs). In contrast, commercial polystyrene nanoparticles failed to exert mitochondrial effects. These results suggest that DEP and UFP effects on the PTP and Delta-Psi m are mediated by adsorbed chemicals rather than the particles themselves.

  2. Metabolomic profiling unravels DNA adducts in human breast that are formed from peroxidase mediated activation of estrogens to quinone methides.

    Directory of Open Access Journals (Sweden)

    Nilesh W Gaikwad

    Full Text Available Currently there are three major hypotheses that have been proposed for estrogen induced carcinogenicity, however exact etiology remains unknown. Based on the chemical logic, studies were undertaken to investigate if estrogens could generate quinone methides in an oxidative environment which then could cause DNA damage in humans. In presence of MnO2 estrogens were oxidized to quinone methides. Surprisingly quinone methides were found to be stable with t1/2 of 20.8 and 4.5 min respectively. Incubation of estrogens with lactoperoxidase (LPO and H2O2 resulted in formation of respective quinone methides (E1(E2-QM. Subsequent addition of adenine to the assay mixture lead to trapping of E1(E2-QM, resulting in formation of adenine adducts of estrogens, E1(E2-9-N-Ade. Targeted ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS based metabolomic analysis of the breast tissue extracts showed the presence of adenine adducts of estrogens, E1(E2-9-N-Ade, along with other estrogen related metabolites. Identity of E1(E2-N-Ade in LPO assay extracts and breast tissue extracts were confirmed by comparing them to pure synthesized E1(E2-9-N-Ade standards. From these results, it is evident that peroxidase enzymes or peroxidase-like activity in human breast tissue could oxidize estrogens to electrophilic and stable quinone methides in a single step that covalently bind to DNA to form adducts. The error prone repair of the damaged DNA can result in mutation of critical genes and subsequently cancer. This article reports evidence for hitherto unknown estrogen metabolic pathway in human breast, catalyzed by peroxidase, which could initiate cancer.

  3. Studies using structural analogs and inbred strain differences to support a role for quinone methide metabolites of butylated hydroxytoluene (BHT) in mouse lung tumor promotion.

    Science.gov (United States)

    Thompson, J A; Carlson, T J; Sun, Y; Dwyer-Nield, L D; Malkinson, A M

    2001-03-07

    Chronic treatment of BALB and GRS mice with BHT (2,6-di-tert-butyl-4-methylphenol) following a single urethane injection increases lung tumor multiplicity, but this does not occur in CXB4 mice. Previous data suggest that promotion requires the conversion of BHT to a tert-butyl-hydroxylated metabolite (BHTOH) in lung and the subsequent oxidation of this species to an electrophilic quinone methide. To obtain additional evidence for the importance of quinone methide formation, structural analogs that form less reactive quinone methides were tested and found to lack promoting activity in BHT-responsive mice. The possibility that promotion-unresponsive strains are unable to form BHTOH was tested by substituting this compound for BHT in the promotion protocol using CXB4 mice. No promotion occurred, and in-vitro work demonstrated that CXB4 mice are, in fact, capable of producing BHTOH and its quinone methide, albeit in smaller quantities. Incubations with BALB lung microsomes and radiolabeled substrates confirmed that more covalent binding to protein occurs with BHTOH than with BHT and, in addition, BHTOH quinone methide is considerably more toxic to mouse lung epithelial cells than BHT quinone methide. These data are consistent with the hypothesis that a two-step oxidation process, i.e. hydroxylation and quinone methide formation, is required for the promotion of mouse lung tumors by BHT.

  4. Quinone-induced inhibition of urease: elucidation of its mechanisms by probing thiol groups of the enzyme.

    Science.gov (United States)

    Zaborska, Wiesława; Krajewska, Barbara; Kot, Mirosława; Karcz, Waldemar

    2007-06-01

    In this work we studied the reaction of four quinones, 1,4-benzoquinone (1,4-BQ), 2,5-dimethyl-1,4-benzoquinone (2,5-DM-1,4-BQ), tetrachloro-1,4-benzoquinone (TC-1,4-BQ) and 1,4-naphthoquinone (1,4-NQ) with jack bean urease in phosphate buffer, pH 7.8. The enzyme was allowed to react with different concentrations of the quinones during different incubation times in aerobic conditions. Upon incubation the samples had their residual activities assayed and their thiol content titrated. The titration carried out with use of 5,5'-di-thiobis(2-nitrobenzoic) acid was done to examine the involvement of urease thiol groups in the quinone-induced inhibition. The quinones under investigation showed two distinct patterns of behaviour, one by 1,4-BQ, 2,5-DM-1,4-BQ and TC-1,4-BQ, and the other by 1,4-NQ. The former consisted of a concentration-dependent inactivation of urease where the enzyme-inhibitor equilibrium was achieved in no longer than 10min, and of the residual activity of the enzyme being linearly correlated with the number of modified thiols in urease. We concluded that arylation of the thiols in urease by these quinones resulting in conformational changes in the enzyme molecule is responsible for the inhibition. The other pattern of behaviour observed for 1,4-NQ consisted of time- and concentration-dependent inactivation of urease with a nonlinear residual activity-modified thiols dependence. This suggests that in 1,4-NQ inhibition, in addition to the arylation of thiols, operative are other reactions, most likely oxidations of thiols provoked by 1,4-NQ-catalyzed redox cycling. In terms of the inhibitory strength, the quinones studied formed a series: 1,4-NQ approximately 2,5-DM-1,4-BQ<1,4-BQ

  5. In vivo induction of phase II detoxifying enzymes, glutathione transferase and quinone reductase by citrus triterpenoids

    Directory of Open Access Journals (Sweden)

    Ahmad Hassan

    2010-09-01

    Full Text Available Abstract Background Several cell culture and animal studies demonstrated that citrus bioactive compounds have protective effects against certain types of cancer. Among several classes of citrus bioactive compounds, limonoids were reported to prevent different types of cancer. Furthermore, the structures of citrus limonoids were reported to influence the activity of phase II detoxifying enzymes. The purpose of the study was to evaluate how variations in the structures of citrus limonoids (namely nomilin, deacetyl nomilin, and isoobacunoic acid and a mixture of limonoids would influence phase II enzyme activity in excised tissues from a mouse model. Methods In the current study, defatted sour orange seed powder was extracted with ethyl acetate and subjected to silica gel chromatography. The HPLC, NMR and mass spectra were used to elucidate the purity and structure of compounds. Female A/J mice were treated with three limonoids and a mixture in order to evaluate their effect on phase II enzymes in four different tissues. Assays for glutathione S-transferase and NAD(PH: quinone reductase (QR were used to evaluate induction of phase II enzymatic activity. Results The highest induction of GST against 1-chloro-2,4-dinitrobenzene (CDNB was observed in stomach (whole, 58% by nomilin, followed by 25% isoobacunoic acid and 19% deacetyl nomilin. Deacetyl nomilin in intestine (small as well as liver significantly reduced GST activity against CDNB. Additionally isoobacunoic acid and the limonoid mixture in liver demonstrated a significant reduction of GST activity against CDNB. Nomilin significantly induced GST activity against 4-nitroquinoline 1-oxide (4NQO, intestine (280% and stomach (75% while deacetyl nomilin showed significant induction only in intestine (73%. Induction of GST activity was also observed in intestine (93% and stomach (45% treated with the limonoid mixture. Finally, a significant induction of NAD(PH: quinone reductase (QR activity was

  6. Successful removal of p-quinone with chitosan in an aqueous phase in relation to degree of deacetylation.

    Science.gov (United States)

    Takahashi, Tomoki; Imai, Masanao; Suzuki, Isao

    2004-01-01

    Phenol oxidant is successfully removed by using chitosan particles in the aqueous phase. Removal of p-quinone by chitosan from crab shells was investigated kinetically from molecular weight (MW) of chitosan, deacetylation degree (DD) and reaction temperature. The rate constant assuming first-ordered reaction on removal of p-quinone in aqueous phase primarily depended on the MW of chitosan, not on the DD. Quantities of chitosan exceeding 5 x 10(5) MW are able to obtain a sufficiently high rate constant (10(-3) s(-1)). At higher temperatures, higher rate constants were obtained in the entire experimental MW and DD. The activation energy obtained was 43.8 kJ x mol(-1).

  7. The sodium pumping NADH:quinone oxidoreductase (Na⁺-NQR), a unique redox-driven ion pump.

    Science.gov (United States)

    Barquera, Blanca

    2014-08-01

    The Na(+)-translocating NADH:quinone oxidoreductase (Na(+)-NQR) is a unique Na(+) pumping respiratory complex found only in prokaryotes, that plays a key role in the metabolism of marine and pathogenic bacteria, including Vibrio cholerae and other human pathogens. Na(+)-NQR is the main entrance for reducing equivalents into the respiratory chain of these bacteria, catalyzing the oxidation of NADH and the reduction of quinone, the free energy of this redox reaction drives the selective translocation of Na(+) across the cell membrane, which energizes key cellular processes. In this review we summarize the unique properties of Na(+)-NQR in terms of its redox cofactor composition, electron transfer reactions and a possible mechanism of coupling and pumping.

  8. Selective, nontoxic CB(2) cannabinoid o-quinone with in vivo activity against triple-negative breast cancer.

    Science.gov (United States)

    Morales, Paula; Blasco-Benito, Sandra; Andradas, Clara; Gómez-Cañas, María; Flores, Juana María; Goya, Pilar; Fernández-Ruiz, Javier; Sánchez, Cristina; Jagerovic, Nadine

    2015-03-12

    Triple-negative breast cancer (TNBC) represents a subtype of breast cancer characterized by high aggressiveness. There is no current targeted therapy for these patients whose prognosis, as a group, is very poor. Here, we report the synthesis and evaluation of a potent antitumor agent in vivo for this type of breast cancer designed as a combination of quinone/cannabinoid pharmacophores. This new compound (10) has been selected from a series of chromenopyrazolediones with full selectivity for the nonpsychotropic CB2 cannabinoid receptor and with efficacy in inducing death of human TNBC cell lines. The dual concept quinone/cannabinoid was supported by the fact that compound 10 exerts antitumor effect by inducing cell apoptosis through activation of CB2 receptors and through oxidative stress. Notably, it did not show either cytotoxicity on noncancerous human mammary epithelial cells nor toxic effects in vivo, suggesting that it may be a new therapeutic tool for the management of TNBC.

  9. 3-Methoxy-2-methyl-carbazole-1,4-quinone, carbazomycins D and F from Streptomyces sp. CMU-JT005.

    Science.gov (United States)

    Ruanpanun, Pornthip; Dame, Zerihun Teklemariam; Laatsch, Hartmut; Lumyong, Saisamorn

    2011-09-01

    3-Methoxy-2-methyl-carbazole-1,4-quinone (1) together with carbazomycins D (2) and F (3) were isolated from the crude extract of Streptomyces CMU-JT005, an actinomycete with nematicidal activity. 3-Methoxy-2-methyl-carbazole-1,4-quinone is reported here for the first time from nature. In this paper, we describe the isolation and structure elucidation of the compounds together with the characterization of the Streptomyces strain CMU-JT005.

  10. Novel synthesis of 3-substituted 2,3-dihydrobenzofurans via ortho-quinone methide intermediates generated in situ.

    Science.gov (United States)

    Shaikh, Abdul kadar; Varvounis, George

    2014-03-01

    A new method is presented for the regioselective one-pot synthesis of 3-substituted 2,3-dihydrobenzofurans from 2-bromo-1-{2-[(triisopropylsilyl)oxy]phenyl}ethyl nitrate by fluoride-induced desilylation leading to o-quinone methide generation, Michael addition of different C, N, O, and S nucleophiles, and intramolecular 5-exo-tet elimination of a bromide anion. The method has potential synthetic applications in drug discovery.

  11. The key role of glutamate 172 in the mechanism of type II NADH:quinone oxidoreductase of Staphylococcus aureus.

    Science.gov (United States)

    Sousa, Filipe M; Sena, Filipa V; Batista, Ana P; Athayde, Diogo; Brito, José A; Archer, Margarida; Oliveira, A Sofia F; Soares, Cláudio M; Catarino, Teresa; Pereira, Manuela M

    2017-10-01

    Type II NADH:quinone oxidoreductases (NDH-2s) are membrane bound enzymes that deliver electrons to the respiratory chain by oxidation of NADH and reduction of quinones. In this way, these enzymes also contribute to the regeneration of NAD(+), allowing several metabolic pathways to proceed. As for the other members of the two-Dinucleotide Binding Domains Flavoprotein (tDBDF) superfamily, the enzymatic mechanism of NDH-2s is still little explored and elusive. In this work we addressed the role of the conserved glutamate 172 (E172) residue in the enzymatic mechanism of NDH-2 from Staphylococcus aureus. We aimed to test our earlier hypothesis that E172 plays a key role in proton transfer to allow the protonation of the quinone. For this we performed a complete biochemical characterization of the enzyme's variants E172A, E172Q and E172S. Our steady state kinetic measurements show a clear decrease in the overall reaction rate, and our substrate interaction studies indicate the binding of the two substrates is also affected by these mutations. Interestingly our fast kinetic results show quinone reduction is more affected than NADH oxidation. We have also determined the X-ray crystal structure of the E172S mutant (2.55Ǻ) and compared it with the structure of the wild type (2.32Ǻ). Together these results support our hypothesis for E172 being of central importance in the catalytic mechanism of NDH-2, which may be extended to other members of the tDBDF superfamily. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Insight into the kinetics and thermodynamics of the hydride transfer reactions between quinones and lumiflavin: a density functional theory study.

    Science.gov (United States)

    Reinhardt, Clorice R; Jaglinski, Tanner C; Kastenschmidt, Ashly M; Song, Eun H; Gross, Adam K; Krause, Alyssa J; Gollmar, Jonathan M; Meise, Kristin J; Stenerson, Zachary S; Weibel, Tyler J; Dison, Andrew; Finnegan, Mackenzie R; Griesi, Daniel S; Heltne, Michael D; Hughes, Tom G; Hunt, Connor D; Jansen, Kayla A; Xiong, Adam H; Hati, Sanchita; Bhattacharyya, Sudeep

    2016-09-01

    The kinetics and equilibrium of the hydride transfer reaction between lumiflavin and a number of substituted quinones was studied using density functional theory. The impact of electron withdrawing/donating substituents on the redox potentials of quinones was studied. In addition, the role of these substituents on the kinetics of the hydride transfer reaction with lumiflavin was investigated in detail under the transition state (TS) theory assumption. The hydride transfer reactions were found to be more favorable for an electron-withdrawing substituent. The activation barrier exhibited a quadratic relationship with the driving force of these reactions as derived under the formalism of modified Marcus theory. The present study found a significant extent of electron delocalization in the TS that is stabilized by enhanced electrostatic, polarization, and exchange interactions. Analysis of geometry, bond-orders, and energetics revealed a predominant parallel (Leffler-Hammond) effect on the TS. Closer scrutiny reveals that electron-withdrawing substituents, although located on the acceptor ring, reduce the N-H bond order of the donor fragment in the precursor complex. Carried out in the gas-phase, this is the first ever report of a theoretical study of flavin's hydride transfer reactions with quinones, providing an unfiltered view of the electronic effect on the nuclear reorganization of donor-acceptor complexes.

  13. Enhanced dechlorination of carbon tetrachloride by Geobacter sulfurreducens in the presence of naturally occurring quinones and ferrihydrite.

    Science.gov (United States)

    Doong, Ruey-an; Lee, Chun-chi; Lien, Chia-min

    2014-02-01

    The effect of naturally occurring quinones including lawsone (LQ), ubiquinone (UQ), juglone (JQ), and 1,4-naphthoquinone (NQ) on the biotransformation of carbon tetrachloride (CT) in the presence of Geobacter sulfurreducens and ferrihydrite was investigated. AQDS was used as the model compound for comparison. The reductive dissolution of ferrihydrite by G. sulfurreducens was enhanced by AQDS, NQ, and LQ. However, addition of UQ and JQ had little enhancement effect on Fe(II) production. The bioreduction efficiency and rate of ferrihydrite was highly dependent on the natural property and concentration of quinone compounds and the addition of low concentrations of LQ and NQ significantly accelerated the biotransformation rate of CT. The pseudo-first-order rate constants for CT dechlorination (kobsCT) in AQDS-, LQ- and NQ-amended batches were 5.4-5.8, 4.6-7.4 and 2.4-5.8 times, respectively, higher than those in the absence of quinone. A good relationship between kobsCT for CT dechlorination and bioreduction ratio of ferrihydrite was observed, indicating the important role of biogenic Fe(II) in dechlorination of CT under iron-reducing conditions. Spectroscopic analysis showed that AQDS and NQ could be reduced to semiquinones and hydroquinones, while only hydroquinones were generated in LQ-amended batches.

  14. Modification of quinone electrochemistry by the proteins in the biological electron transfer chains: examples from photosynthetic reaction centers

    Science.gov (United States)

    Gunner, M. R.; Madeo, Jennifer; Zhu, Zhenyu

    2009-01-01

    Quinones such as ubiquinone are the lipid soluble electron and proton carriers in the membranes of mitochondria, chloroplasts and oxygenic bacteria. Quinones undergo controlled redox reactions bound to specific sites in integral membrane proteins such as the cytochrome bc1 oxidoreductase. The quinone reactions in bacterial photosynthesis are amongst the best characterized, presenting a model to understand how proteins modulate cofactor chemistry. The free energy of ubiquinone redox reactions in aqueous solution and in the QA and QB sites of the bacterial photosynthetic reaction centers (RCs) are compared. In the primary QA site ubiquinone is reduced only to the anionic semiquinone (Q•−) while in the secondary QB site the product is the doubly reduced, doubly protonated quinol (QH2). The ways in which the protein modifies the relative energy of each reduced and protonated intermediate are described. For example, the protein stabilizes Q•− while destabilizing Q= relative to aqueous solution through electrostatic interactions. In addition, kinetic and thermodynamic mechanisms for stabilizing the intermediate semiquinones are compared. Evidence for the protein sequestering anionic compounds by slowing both on and off rates as well as by binding the anion more tightly is reviewed. PMID:18979192

  15. A new approach to evaluating the extent of Michael adduct formation to PAH quinones: tetramethylammonium hydroxide (TMAH) thermochemolysis with GC/MS.

    Science.gov (United States)

    Briggs, Mary K; Desavis, Emmanuel; Mazzer, Paula A; Sunoj, R B; Hatcher, Susan A; Hadad, Christopher M; Hatcher, Patrick G

    2003-11-01

    Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants that are converted to cytotoxic and carcinogenic metabolites, quinones, by detoxifying enzyme systems in animals. PAH metabolites such as the quinones can form Michael adducts with biological macromolecules containing reactive nucleophiles, making detection of exposure to PAHs difficult using conventional techniques. A technique has been developed for detecting exposure to PAHs. Tetramethylammonium hydroxide (TMAH) thermochemolysis coupled with GC/MS is proposed as an assay method for PAH quinones that have formed Michael adducts with biological molecules. Three PAH quinones (1,4-naphthoquinone, 1,2-naphthoquinone, and 1,4-anthraquinone) and 1,4-benzoquinone were reacted with cysteine, and the TMAH thermochemolysis method was used to assay for both thiol and amine adduction between the quinones and the cysteine. Additional studies with 1,4-naphthoquinone adducts to glutathione and bovine serum albumin showed the same thiol and amine TMAH thermochemolysis products with larger peptides as was observed with cysteine adducts. The TMAH GC/MS method clearly shows great promise for detecting PAH quinones, produced by enzymatic conversion of PAHs in biological systems, that have been converted to respective Michael adducts.

  16. Lipoprotein-like particles in a prokaryote: quinone droplets of Thermoplasma acidophilum.

    Science.gov (United States)

    Nagy, István; Knispel, Roland Wilhelm; Kofler, Christine; Orsini, Massimiliano; Boicu, Marius; Varga, Sándor; Weyher-Stingl, Elisabeth; Sun, Na; Fernandez-Busnadiego, Ruben; Kukolya, József; Nickell, Stephan; Baumeister, Wolfgang

    2016-09-01

    Cytosolic, globular droplets with an average diameter of 50 nm were observed in vitrified Thermoplasma acidophilum cells by means of cryo-electron tomography. These droplets were isolated by column chromatography and immunoprecipitation protein purification methods. Subsequent chemical and biochemical analyses identified lipid and protein components, respectively. Two major lipid components, comigrating menaquinones at the solvent front and the slower migrating Thermoplasma polar lipid U4, were detected by TLC experiments. The major protein component was identified as the 153 amino acid long Ta0547 vitellogenin-N domain protein. This domain has been found so far exclusively in large lipid transport proteins of vertebrates and non-vertebrates. Blast protein database homology searches with Ta0547 did not return any eukaryal hits; homologous sequences were found only in thermo-acidophilic archaeons. However, a profile-sequence domain search performed with the vitellogenin-N domain (PF01347) hmm-profile against the T. acidophilum proteome returned Ta0547 as hit. Electron microscopy appearance of isolated droplets resembled to lipoprotein particles. However, no (tetraether) lipid layer could be detected on the droplets surface, rather hydrophobic compounds of the electron dense lumen were surrounded by a denser discontinuous protein boundary. Based on described features, these particles qualify for a novel lipoprotein particle category, what we nominated Thermoplasma Quinone Droplet.

  17. Quinone-formaldehyde polymer as an active material in Li-ion batteries

    Science.gov (United States)

    Pirnat, Klemen; Mali, Gregor; Gaberscek, Miran; Dominko, Robert

    2016-05-01

    A benzoquinone polymer is synthesized by the polymerisation of hydrobenzoquinone and formaldehyde, followed by oxidation process using a hydrogen peroxide to convert hydroquinone to quinone. As prepared materials are characterized with FTIR, 1H-13C CPMAS NMR, pyrolysis coupled with gas chromatography (GC) and mass spectrometer (MS), TGA-MS analysis, EDX, elemental analysis, XRD, SEM and TEM microscopies and BET nitrogen adsorption. The benzoquinone polymer shows an excellent electrochemical performance when used as a positive electrode material in Li-ion secondary batteries. Using an electrolyte consisting 1 M bis(trifluoromethane)-sulfonimide lithium salt dissolved in 1,3-dioxolane and dimethoxyethane in a vol. ratio 1:1 (1 M LiTFSI/DOL + DME = 1:1) a stable capacity close to 150 mAh/g can be obtained. Compared to other electroactive materials based on benzoquinones it has a supreme capacity stability and is prepared by a simple synthesis using easily accessible starting materials. Further improvements in the capacity value (up to the theoretical value of 406 mAh/g) can be foreseen by achieving a higher degree of oxidation and by modification of polymerization process to enhance the electronic and ionic conductivity.

  18. Flavin adenine dinucleotide content of quinone reductase 2: analysis and optimization for structure-function studies.

    Science.gov (United States)

    Leung, Kevin Ka Ki; Litchfield, David W; Shilton, Brian H

    2012-01-01

    Quinone reductase 2 (NQO2) is a broadly expressed enzyme implicated in responses to a number of compounds, including protein kinase inhibitors, resveratrol, and antimalarial drugs. NQO2 includes a flavin adenine dinucleotide (FAD) cofactor, but X-ray crystallographic analysis of human NQO2 expressed in Escherichia coli showed that electron density for the isoalloxazine ring of FAD was weak and there was no electron density for the adenine mononucleotide moiety. Reversed-phase high-performance liquid chromatography (HPLC) of the NQO2 preparation indicated that FAD was not present and only 38% of the protomers contained flavin mononucleotide (FMN), explaining the weak electron density for FAD in the crystallographic analysis. A method for purifying NQO2 and reconstituting with FAD such that the final content approaches 100% occupancy with FAD is presented here. The enzyme prepared in this manner has a high specific activity, and there is strong electron density for the FAD cofactor in the crystal structure. Analysis of NQO2 crystal structures present in the Protein Data Bank indicates that many may have sub-stoichiometric cofactor content and/or contain FMN rather than FAD. This method of purification and reconstitution will help to optimize structural and functional studies of NQO2 and possibly other flavoproteins.

  19. Pyrroloquinoline quinone ameliorates l-thyroxine-induced hyperthyroidism and associated problems in rats.

    Science.gov (United States)

    Kumar, Narendra; Kar, Anand; Panda, Sunanda

    2014-08-01

    Pyrroloquinoline quinone (PQQ) is believed to be a strong antioxidant. In this study, we have evaluated its hitherto unknown role in l-thyroxin (L-T4 )-induced hyperthyroidism considering laboratory rat as a model. Alterations in the serum concentration of thyroxin (T4 ) and triiodothyronine (T3 ); lipid peroxidation (LPO) of liver, kidney, heart, muscles and brain; in the endogenous antioxidants such as superoxide dismutase, catalase and glutathione and in serum total cholesterol, high-density lipoprotien, triglycerides, serum glutamate pyruvate transaminase (SGPT), serum glutamate oxaloacetate transaminase (SGOT) and urea were evaluated. Administration of l-T4 (500-µg kg(-1) body weight) enhanced not only the serum T3 and T4 levels but also the tissue LPO, serum SGOT, SGPT and urea with a parallel decrease in the levels of antioxidants and serum lipids. However, on simultaneous administration of PQQ (5 mg kg(-1) for 6 days), all these adverse effects were ameliorated, indicating the potential of PQQ in the amelioration of hyperthyroidism and associated problems. Possibly, the curative effects were mediated through inhibition of oxidative stress. We suggest that PQQ may be considered for therapeutic use for hyperthyroidism after dose standardization.

  20. Glycosylation of quinone-fused polythiophene for reagentless and label-free detection of E. coli.

    Science.gov (United States)

    Ma, Fen; Rehman, Abdul; Liu, Haiying; Zhang, Jingtuo; Zhu, Shilei; Zeng, Xiangqun

    2015-02-03

    In this report, a new polythiophene interface is fabricated containing fused quinone moieties which are then glycosylated to form a carbohydrate platform for bacterial detection. Very importantly, this interface can be used for label-free and reagentless detection, both by electrochemical and Quartz Crystal Microbalance (QCM) transducers and by using the direct pili-mannose binding as well as Concanavalin A (Con A) mediated lipopolysaccharides (LPS)-mannose binding. The conductive polymer's unique collective properties are very sensitive to very minor perturbations, which result in significant changes of electrical conductivity and providing amplified sensitivity and improved limits of detection (i.e., 25 cell/mL for electrochemical sensor and 50 cells/mL for QCM sensor), a widened logarithmic range of detection (i.e., 3-7 for pili-mannose binding and 2-8 for Con A mediated binding), high specificity and selectivity, and an extraordinary reliability by a mechanism of internal validation. With these analytical performances, the described biosensor is envisaged for being capable of differentiating Gram-negative bacterial strain and species, for many important applications.

  1. Origin of the Giant Honeycomb Network of Quinones on Cu(111)

    Science.gov (United States)

    Einstein, T. L.; Kim, Kwangmoo; Wyrick, Jon; Cheng, Zhihai; Bartels, Ludwig; Berland, Kristian; Hyldgaard, Per

    2011-03-01

    We discuss the factors that lead to the amazing regular giant honeycomb network formed by quinones on Cu(111). Using a related lattice gas model with many characteristic energies, we can reproduce many experimental features. These models require a long-range attraction, which can be attributed to indirect interactions mediated by the Shockley surface state of Cu(111). However, Wyrick's preceding talk gave evidence that the network self-selects for the size of the pore rather than for the periodicity of the superstructure, suggesting that confined states are the key ingredient. We discuss this phenomenon in terms of the magic numbers of 2D quantum dots. We also report calculations of the effects of anthraquinones (AQ) in modifying the surface states by considering a superlattice of AQ chains with various separations. We discuss implications of these results for tuning the electronic states and, thence, superstructures. Supported by (TLE) NSF CHE 07-50334 & UMD MRSEC DMR 05-20471, (JW & LB) NSF CHE NSF CHE 07-49949, (KB & PH) Swedish Vetenskapsrådet VR 621-2008-4346.

  2. All-solid-state lithium organic battery with composite polymer electrolyte and pillar[5]quinone cathode.

    Science.gov (United States)

    Zhu, Zhiqiang; Hong, Meiling; Guo, Dongsheng; Shi, Jifu; Tao, Zhanliang; Chen, Jun

    2014-11-26

    The cathode capacity of common lithium ion batteries (LIBs) using inorganic electrodes and liquid electrolytes must be further improved. Alternatively, all-solid-state lithium batteries comprising the electrode of organic compounds can offer much higher capacity. Herein, we successfully fabricated an all-solid-state lithium battery based on organic pillar[5]quinone (C35H20O10) cathode and composite polymer electrolyte (CPE). The poly(methacrylate) (PMA)/poly(ethylene glycol) (PEG)-LiClO4-3 wt % SiO2 CPE has an optimum ionic conductivity of 0.26 mS cm(-1) at room temperature. Furthermore, pillar[5]quinine cathode in all-solid-state battery rendered an average operation voltage of ∼2.6 V and a high initial capacity of 418 mAh g(-1) with a stable cyclability (94.7% capacity retention after 50 cycles at 0.2C rate) through the reversible redox reactions of enolate/quinonid carbonyl groups, showing favorable prospect for the device application with high capacity.

  3. Hydrolysis of the quinone methide of butylated hydroxytoluene in aqueous solutions.

    Science.gov (United States)

    Willcockson, Maren Gulsrud; Toteva, Maria M; Stella, Valentino J

    2013-10-01

    Butylated hydroxytoluene or BHT is an antioxidant commonly used in pharmaceutical formulations. BHT upon oxidation forms a quinone methide (QM). QM is a highly reactive electrophilic species that can undergo nucleophilic addition. Here, the kinetic reactivity of QM with water at various apparent pH values in a 50% (v/v) water-acetonitrile solution at constant ionic strength of I = 0.5 (NaCl)4 , was studied. The hydrolysis of QM in the presence of added acid, base, sodium chloride, and phosphate buffer resulted in the formation of only one product--the corresponding 3,5-di-tert-butyl-4-hydroxybenzyl alcohol (BA). The rate of BA formation was catalyzed by the addition of acid and base, but not chloride and phosphate species. Nucleophilic excipients, used in the pharmaceutical formulation, or nucleophilic groups on active pharmaceutical ingredient molecule may form adducts with QM, the immediate oxidative product of BHT degradation, thus having implications for drug product impurity profiles. Because of these considerations, BHT should be used with caution in formulations containing drugs or excipients capable of acting as nucleophiles.

  4. NAD(P)H:quinone oxidoreductase 1 inducer activity of some novel anilinoquinazoline derivatives

    Science.gov (United States)

    Ghorab, Mostafa M; Alsaid, Mansour S; Higgins, Maureen; Dinkova-Kostova, Albena T; Shahat, Abdelaaty A; Elghazawy, Nehal H; Arafa, Reem K

    2016-01-01

    The Kelch-like ECH-associated protein 1 (Keap1)/nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response elements pathway enables cells to survive oxidative stress conditions through regulating the expression of cytoprotective enzymes such as NAD(P)H:quinone oxidoreductase 1 (NQO1). This work presents the design and synthesis of novel anilinoquinazoline derivatives (2–16a) and evaluation of their NQO1 inducer activity in murine cells. Molecular docking of the new compounds was performed to assess their ability to inhibit Keap1–Nrf2 protein–protein interaction through occupying the Keap1–Nrf2-binding domain, which leads to Nrf2 accumulation and enhanced gene expression of NQO1. Docking results showed that all compounds can potentially interact with Keap1; however, 1,5-dimethyl-2-phenyl-4-(2-phenylquinazolin-4-ylamino)-1,2-dihydropyrazol-3-one (9), the most potent inducer, showed the largest number of interactions with key amino acids in the binding pocket (Arg483, Tyr525, and Phe478) compared to the native ligand or any other compound in this series. PMID:27540279

  5. Quinone molecules encapsulated in SWCNTs for low-temperature Na ion batteries

    Science.gov (United States)

    Li, Canghao; Ishii, Yosuke; Inayama, Shunya; Kawasaki, Shinji

    2017-09-01

    We have performed Li and Na ion charge-discharge experiments of 9,10-phenanthrene quinone (PhQ) molecules encapsulated in single-walled carbon nanotubes (SWCNTs) with mean tube diameters of 1.5 and 2.5 nm at room temperature and also at low temperatures. The Na ion reversible capacity of PhQ encapsulated in the larger diameter SWCNTs, measured at a low temperature of 0 °C, remained as high as that measured at room temperature (RT), while the capacity of PhQ in the smaller diameter SWCNTs at 0 °C was about a half of that at RT. The diameter dependence of the capacity should be attributed to the difference in the interactions between the encapsulated PhQ molecules and the host SWCNTs, which was revealed by Raman peak profile analysis. Charge-transfer reaction from metallic tubes to PhQ molecules encapsulated in the smaller diameter SWCNTs was detected by Raman measurements. The electrostatic interaction between charged SWCNTs and PhQ molecules, induced by the charge-transfer reaction, would partly contribute to the stabilization of PhQ molecules in the smaller diameter SWCNTs, while only van der Waals interaction stabilizes PhQ molecules in the larger diameter SWCNTs. The difference in stability was confirmed by thermogravimetric, x-ray photoelectron spectroscopy, and Raman measurements. Charge-discharge curves of PhQ encapsulated in SWCNTs were also discussed based on the stability difference.

  6. Up-regulation of NAD(P)H quinone oxidoreductase 1 during human liver injury

    Institute of Scientific and Technical Information of China (English)

    Lauren M Aleksunes; Michael Goedken; José E Manautou

    2006-01-01

    AIM: To investigate the expression and activity of NAD(P)H quinone oxidoreductase 1 (NQO1) in human liver specimens obtained from patients with liver damage due to acetaminophen (APAP) overdose or primary biliary cirrhosis (PBC).METHODS: NQO1 activity was determined in cytosol from normal, APAP and PBC liver specimens. Western blot and immunohistochemical staining were used to determine patterns of NQO1 expression using a specific antibody against NQO1.RESULTS: NQO1 protein was very low in normal human livers. In both APAP and PBC livers, there was strong induction of NQO1 protein levels on Western blot.Correspondingly, significant up-regulation of enzyme activity (16- and 22-fold, P< 0.05) was also observed in APAP and PBC livers, respectively. Immunohistochemical analysis highlighted injury-specific patterns of NQO1 staining in both APAP and PBC livers.CONCLUSION: These data demonstrate that NQO1 protein and activity are markedly induced in human livers during both APAP overdose and PBC. Up-regulation of this cytoprotective enzyme may represent an adaptive stress response to limit further disease progression by detoxifying reactive species.

  7. Bisphenol A 3,4-quinone induces the conversion of xanthine dehydrogenase into oxidase in vitro.

    Science.gov (United States)

    Sakuma, Satoru; Nakanishi, Masahiko; Morinaga, Kazuhiro; Fujitake, Mihoyo; Wada, Shun-ichi; Fujimoto, Yohko

    2010-01-01

    In the present study, we assessed the influence of bisphenol A (BPA) and bisphenol A 3,4-quinone (BPAQ) on the conversion of xanthine dehydrogenase (XD) into xanthine oxidase (XO) in the rat liver in vitro. BPA up to 100 micromol/L did not affect the XO and XD activities in the partially purified cytosolic fraction from rat liver, whereas BPAQ (2-10 micromol/L) dose-dependently enhanced the XO activity concomitant with a decrease in the XD activity, implying that BPAQ, but not BPA, can convert XD into the reactive oxygen species (ROS) producing the form XO. Furthermore, it was found that BPAQ could increase the generation of ROS and oxidize the guanine moiety of deoxyguanosine in the DNA of primary rat hepatocyte cultures. These results suggest that BPAQ has the potential to convert XD into XO in the liver, which in turn may lead to ROS generation and oxidative DNA damage in this region. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

  8. Identification of a lactate-quinone oxidoreductase (Lqo in staphylococcus aureus that is essential for virulence

    Directory of Open Access Journals (Sweden)

    James R Fuller

    2011-12-01

    Full Text Available Staphylococcus aureus is an important human pathogen commonly infecting nearly every host tissue. The ability of S. aureus to resist innate immunity is critical to its success as a pathogen, including its propensity to grow in the presence of host nitric oxide (NO·. Upon exogenous NO· exposure, S. aureus immediately excretes copious amounts of L-lactate to maintain redox balance. However, after prolonged NO·-exposure, S. aureus reassimilates L-lactate specifically and in this work, we identify the enzyme responsible for this L-lactate consumption as a L-lactate-quinone oxidoreductase (Lqo, SACOL2623. Originally annotated as Mqo2 and thought to oxidize malate, we show that this enzyme exhibits no affinity for malate but reacts specifically with L-lactate (KM = ~330 µM. In addition to its requirement for reassimilation of L-lactate during NO·-stress, Lqo is also critical to respiratory growth on L-lactate as a sole carbon source. Moreover, ∆lqo mutants exhibit attenuation in a murine model of sepsis, particularly in their ability to cause myocarditis. Interestingly, this cardiac-specific attenuation is completely abrogated in mice unable to synthesize inflammatory NO· (iNOS-/-. We demonstrate that S. aureus NO·-resistance is highly dependent on the availability of a glycolytic carbon sources. However, S. aureus can utilize the combination of peptides and L-lactate as carbon sources during NO·-stress in an Lqo-dependent fashion. Murine cardiac tissue has markedly high levels of L-lactate in comparison to renal or hepatic tissue consistent with the NO·-dependent requirement for Lqo in S. aureus myocarditis. Thus, Lqo provides S. aureus with yet another means of replicating in the presence of host NO·.

  9. Binding of DNA-Intercalating Agents to Oxidized and Reduced Quinone Reductase 2.

    Science.gov (United States)

    Leung, Kevin K K; Shilton, Brian H

    2015-12-29

    Quinone reductase 2 (NQO2) is an enzyme that might have intracellular signaling functions. NQO2 can exist in either an oxidized state or a reduced state, and binding of compounds to one or both of these states inhibits enzymatic activity and could also affect intracellular signaling. A wide range of planar aromatic compounds bind NQO2, and we have identified three DNA-intercalating agents [ethidium bromide, acridine orange (AO), and doxorubicin] as novel nanomolar inhibitors of NQO2. Ethidium and AO, which carry a positive charge in their aromatic ring systems, bound reduced NQO2 with an affinity 50-fold higher than that of oxidized NQO2, while doxorubicin bound only oxidized NQO2. Crystallographic analyses of oxidized NQO2 in complex with the inhibitors indicated that the inhibitors were situated deep in the active site. The aromatic faces were sandwiched between the isoalloxazine ring of FAD and the phenyl ring of F178, with their edges making direct contact with residues lining the active site. In reduced NQO2, ethidium and AO occupied a more peripheral position in the active site, allowing several water molecules to interact with the polar end of the negatively charged isoalloxazine ring. We also showed that AO inhibited NQO2 at a nontoxic concentration in cells while ethidium was less effective at inhibiting NQO2 in cells. Together, this study shows that reduced NQO2 has structural and electrostatic properties that yield a preference for binding of planar, aromatic, and positively charged molecules that can also function as DNA-intercalating agents.

  10. Water oxidation chemistry of a synthetic dinuclear ruthenium complex containing redox-active quinone ligands.

    Science.gov (United States)

    Isobe, Hiroshi; Tanaka, Koji; Shen, Jian-Ren; Yamaguchi, Kizashi

    2014-04-21

    We investigated theoretically the catalytic mechanism of electrochemical water oxidation in aqueous solution by a dinuclear ruthenium complex containing redox-active quinone ligands, [Ru2(X)(Y)(3,6-tBu2Q)2(btpyan)](m+) [X, Y = H2O, OH, O, O2; 3,6-tBu2Q = 3,6-di-tert-butyl-1,2-benzoquinone; btpyan =1,8-bis(2,2':6',2″-terpyrid-4'-yl)anthracene] (m = 2, 3, 4) (1). The reaction involves a series of electron and proton transfers to achieve redox leveling, with intervening chemical transformations in a mesh scheme, and the entire molecular structure and motion of the catalyst 1 work together to drive the catalytic cycle for water oxidation. Two substrate water molecules can bind to 1 with simultaneous loss of one or two proton(s), which allows pH-dependent variability in the proportion of substrate-bound structures and following pathways for oxidative activation of the aqua/hydroxo ligands at low thermodynamic and kinetic costs. The resulting bis-oxo intermediates then undergo endothermic O-O radical coupling between two Ru(III)-O(•) units in an anti-coplanar conformation leading to bridged μ-peroxo or μ-superoxo intermediates. The μ-superoxo species can liberate oxygen with the necessity for the preceding binding of a water molecule, which is possible only after four-electron oxidation is completed. The magnitude of catalytic current would be limited by the inherent sluggishness of the hinge-like bending motion of the bridged μ-superoxo complex that opens up the compact, hydrophobic active site of the catalyst and thereby allows water entry under dynamic conditions. On the basis of a newly proposed mechanism, we rationalize the experimentally observed behavior of electrode kinetics with respect to potential and discuss what causes a high overpotential for water oxidation by 1.

  11. Crystal Structure and Function of PqqF Protein in the Pyrroloquinoline Quinone Biosynthetic Pathway.

    Science.gov (United States)

    Wei, Qiaoe; Ran, Tingting; Ma, Chencui; He, Jianhua; Xu, Dongqing; Wang, Weiwu

    2016-07-22

    Pyrroloquinoline quinone (PQQ) has received considerable attention due to its numerous important physiological functions. PqqA is a precursor peptide of PQQ with two conserved residues: glutamate and tyrosine. After linkage of the Cγ of glutamate and Cϵ of tyrosine by PqqE, these two residues are hypothesized to be cleaved from PqqA by PqqF. The linked glutamate and tyrosine residues are then used to synthesize PQQ. Here, we demonstrated that the pqqF gene is essential for PQQ biosynthesis as deletion of it eliminated the inhibition of prodigiosin production by glucose. We further determined the crystal structure of PqqF, which has a closed clamshell-like shape. The PqqF consists of two halves composed of an N- and a C-terminal lobe. The PqqF-N and PqqF-C lobes form a chamber with the volume of the cavity of ∼9400 Å(3) The PqqF structure conforms to the general structure of inverzincins. Compared with the most thoroughly characterized inverzincin insulin-degrading enzyme, the size of PqqF chamber is markedly smaller, which may define the specificity for its substrate PqqA. Furthermore, the 14-amino acid-residue-long tag formed by the N-terminal tag from expression vector precisely protrudes into the counterpart active site; this N-terminal tag occupies the active site and stabilizes the closed, inactive conformation. His-48, His-52, Glu-129 and His-14 from the N-terminal tag coordinate with the zinc ion. Glu-51 acts as a base catalyst. The observed histidine residue-mediated inhibition may be applicable for the design of a peptide for the inhibition of M16 metalloproteases.

  12. Exogenous methyl jasmonate treatment increases glucosinolate biosynthesis and quinone reductase activity in kale leaf tissue.

    Science.gov (United States)

    Ku, Kang-Mo; Jeffery, Elizabeth H; Juvik, John A

    2014-01-01

    Methyl jasmonate (MeJA) spray treatments were applied to the kale varieties 'Dwarf Blue Curled Vates' and 'Red Winter' in replicated field plantings in 2010 and 2011 to investigate alteration of glucosinolate (GS) composition in harvested leaf tissue. Aqueous solutions of 250 µM MeJA were sprayed to saturation on aerial plant tissues four days prior to harvest at commercial maturity. The MeJA treatment significantly increased gluconasturtiin (56%), glucobrassicin (98%), and neoglucobrassicin (150%) concentrations in the apical leaf tissue of these genotypes over two seasons. Induction of quinone reductase (QR) activity, a biomarker for anti-carcinogenesis, was significantly increased by the extracts from the leaf tissue of these two cultivars. Extracts of apical leaf tissues had greater MeJA mediated increases in phenolics, glucosinolate concentrations, GS hydrolysis products, and QR activity than extracts from basal leaf tissue samples. The concentration of the hydrolysis product of glucoraphanin, sulforphane was significantly increased in apical leaf tissue of the cultivar 'Red Winter' in both 2010 and 2011. There was interaction between exogenous MeJA treatment and environmental conditions to induce endogenous JA. Correlation analysis revealed that indole-3-carbanol (I3C) generated from the hydrolysis of glucobrassicin significantly correlated with QR activity (r = 0.800, Pkale leaf tissues of both cultivars in 2011. Correlation analysis of these results indicated that sulforaphane, NI3C, neoascorbigen, I3C, and diindolylmethane were all significantly correlated with QR activity. Thus, increased QR activity may be due to combined increases in phenolics (quercetin and kaempferol) and GS hydrolysis product concentrations rather than by individual products alone.

  13. The binding of quinone to the photosynthetic reaction centers: kinetics and thermodynamics of reactions occurring at the QB-site in zwitterionic and anionic liposomes.

    Science.gov (United States)

    Mavelli, Fabio; Trotta, Massimo; Ciriaco, Fulvio; Agostiano, Angela; Giotta, Livia; Italiano, Francesca; Milano, Francesco

    2014-07-01

    Liposomes represent a versatile biomimetic environment for studying the interaction between integral membrane proteins and hydrophobic ligands. In this paper, the quinone binding to the QB-site of the photosynthetic reaction centers (RC) from Rhodobacter sphaeroides has been investigated in liposomes prepared with either the zwitterionic phosphatidylcholine (PC) or the negatively charged phosphatidylglycerol (PG) to highlight the role of the different phospholipid polar heads. Quinone binding (K Q) and interquinone electron transfer (L AB) equilibrium constants in the two type of liposomes were obtained by charge recombination reaction of QB-depleted RC in the presence of increasing amounts of ubiquinone-10 over the temperature interval 6-35 °C. The kinetic of the charge recombination reactions has been fitted by numerically solving the ordinary differential equations set associated with a detailed kinetic scheme involving electron transfer reactions coupled with quinone release and uptake. The entire set of traces at each temperature was accurately fitted using the sole quinone release constants (both in a neutral and a charge separated state) as adjustable parameters. The temperature dependence of the quinone exchange rate at the QB-site was, hence, obtained. It was found that the quinone exchange regime was always fast for PC while it switched from slow to fast in PG as the temperature rose above 20 °C. A new method was introduced in this paper for the evaluation of constant K Q using the area underneath the charge recombination traces as the indicator of the amount of quinone bound to the QB-site.

  14. Affinity and activity of non-native quinones at the QB site of bacterial photosynthetic reaction centers

    Science.gov (United States)

    Zhang, Xinyu; Gunner, M. R.

    2014-01-01

    Purple, photosynthetic reaction centers (RCs) from Rb. sphaeroides bacteria use UQ10 as primary (QA) and secondary (QB) electron acceptors. Many quinones reconstitute QA function, while few will act as QB. Nine quinones were tested for their ability to bind and reconstitute QA and QB function. Only ubiquinone (UQ) reconstitutes both QA and QB function in the same protein. The affinities of the non-native quinones for the QB site were determined by a competitive inhibition assay. The affinities of benzoquinones (BQ), napthoquinone (NQ) and 2-methyl-NQ for the QB site are 7±3 times weaker than for the QA site. However, di-ortho substituted NQs and anthraquinone bind tightly to the QA site (Kd ≤200 nM) and ≥1000 times more weakly to the QB site, perhaps setting a limit on the size of the site. With a low potential electron donor (2-methyl, 3-dimethylamino-1,4-Napthoquinone (Me-diMeAm-NQ)) at QA, QB reduction is 260 meV more favorable than with UQ as QA. Electron transfer from Me-diMeAm-NQ at the QA site to NQ at the QB site can be detected. In the QB site the NQ semiquinone is estimated to be ≈ 60–100 meV higher in energy than the UQ semiquinone, while in the QA site the semiquinone energy level is similar or lower with NQ than with UQ. Thus, the NQ semiquinone is more stable in the QA than QB site. In contrast, the native UQ semiquinone is ≈ 60 meV lower in energy in the QB than the QA site, stabilizing forward electron transfer from QA to QB. PMID:23715773

  15. A sesquiterpene quinone, dysidine, from the sponge Dysidea villosa, activates the insulin pathway through inhibition of PTPases

    Institute of Scientific and Technical Information of China (English)

    Yu ZHANG; Yan LI; Yue-wei GUO; Hua-liang JIANG; Xu SHEN

    2009-01-01

    Aim: The sesquiterpene hydroquinones/quinones belong to one class of marine sponge metabolites, and they have Accepted considerable attention due to their varied biological activities, including anti-tumor, anti-HIV, and anti-inflammatory action. In order to probe the potential anti-diabetic effect of the sesquiterpene hydroquinones/quinones, the effect of dysi-dine on the insulin pathway was studied.Methods: The promotion of glucose uptake by dysidine was studied in differentiated 3T3-L1 cells. The increase in membrane-located GLUT4 by dysidine was studied in CHO-K1/GLUT4 and 3T3-L1 cells by immuno-staining. The activation of the insulin signaling pathway by dysidine was probed by Western blotting. The inhibition of PTPases by dysidine was detected in vitro.Results: Dysidine, found in the Hainan sponge Dysidea villosa in the Chinese South Sea, effectively activated the insulin signaling pathway, greatly promoted glucose uptake in 3T3-L1 ceils, and showed strong insulin-sensitizing activities. The potential targets of action for dysidine were probed, and the results indicated that dysidine exhibited its cellular effects through activation of the insulin pathway, possibly through the inhibition of protein tyrosine phosphatases, with more specific inhibition against protein tyrosine phosphatase 1B (PTPIB). Conclusion: Our findings are expected to expand understanding of the biological activities of sesquiterpene hydroquino-nes/quinones, and they show that dysidine could be a potential lead compound in the development of an alternative adju-vant in insulin therapy.

  16. Kinetic, thermodynamic and X-ray structural insights into the interaction of melatonin and analogues with quinone reductase 2

    Energy Technology Data Exchange (ETDEWEB)

    Calamini, Barbara; Santarsiero, Bernard D.; Boutin, Jean A.; Mesecar, Andrew D. (IdRS); (UIC)

    2008-09-12

    Melatonin exerts its biological effects through at least two transmembrane G-protein-coupled receptors, MT1 and MT2, and a lower-affinity cytosolic binding site, designated MT3. MT3 has recently been identified as QR2 (quinone reductase 2) (EC 1.10.99.2) which is of significance since it links the antioxidant effects of melatonin to a mechanism of action. Initially, QR2 was believed to function analogously to QR1 in protecting cells from highly reactive quinones. However, recent studies indicate that QR2 may actually transform certain quinone substrates into more highly reactive compounds capable of causing cellular damage. Therefore it is hypothesized that inhibition of QR2 in certain cases may lead to protection of cells against these highly reactive species. Since melatonin is known to inhibit QR2 activity, but its binding site and mode of inhibition are not known, we determined the mechanism of inhibition of QR2 by melatonin and a series of melatonin and 5-hydroxytryptamine (serotonin) analogues, and we determined the X-ray structures of melatonin and 2-iodomelatonin in complex with QR2 to between 1.5 and 1.8 {angstrom} (1 {angstrom} = 0.1 nm) resolution. Finally, the thermodynamic binding constants for melatonin and 2-iodomelatonin were determined by ITC (isothermal titration calorimetry). The kinetic results indicate that melatonin is a competitive inhibitor against N-methyldihydronicotinamide (K{sub i} = 7.2 {mu}M) and uncompetitive against menadione (K{sub i} = 92 {mu}M), and the X-ray structures shows that melatonin binds in multiple orientations within the active sites of the QR2 dimer as opposed to an allosteric site. These results provide new insights into the binding mechanisms of melatonin and analogues to QR2.

  17. The Three-Dimensional Structure of NAD(P)H:Quinone Reductase, a Flavoprotein Involved in Cancer Chemoprotection and Chemotherapy: Mechanism of the Two-Electron Reduction

    Science.gov (United States)

    Li, Rongbao; Bianchet, Mario A.; Talalay, Paul; Amzel, L. Mario

    1995-09-01

    Quinone reductase [NAD(P)H:(quinone acceptor) oxidoreductase, EC 1.6.99.2], also called DT diaphorase, is a homodimeric FAD-containing enzyme that catalyzes obligatory NAD(P)H-dependent two-electron reductions of quinones and protects cells against the toxic and neoplastic effects of free radicals and reactive oxygen species arising from one-electron reductions. These two-electron reductions participate in the reductive bioactivation of cancer chemotherapeutic agents such as mitomycin C in tumor cells. Thus, surprisingly, the same enzymatic reaction that protects normal cells activates cytotoxic drugs used in cancer chemotherapy. The 2.1-Å crystal structure of rat liver quinone reductase reveals that the folding of a portion of each monomer is similar to that of flavodoxin, a bacterial FMN-containing protein. Two additional portions of the polypeptide chains are involved in dimerization and in formation of the two identical catalytic sites to which both monomers contribute. The crystallographic structures of two FAD-containing enzyme complexes (one containing NADP^+, the other containing duroquinone) suggest that direct hydride transfers from NAD(P)H to FAD and from FADH_2 to the quinone [which occupies the site vacated by NAD(P)H] provide a simple rationale for the obligatory two-electron reductions involving a ping-pong mechanism.

  18. Computation of the Redox and Protonation Properties of Quinones: Towards the Prediction of Redox Cycling Natural Products.

    Energy Technology Data Exchange (ETDEWEB)

    Cape, Jonathan L.; Bowman, Michael K.; Kramer, David M.

    2006-08-01

    Quinone metabolites perform a variety of key functions in plants, including pathogen protection, oxidative phosphorylation, and redox signaling. Many of these structurally diverse compounds have been shown to exhibit potent antimicrobial, anticancer, and anti-inflammatory properties, although the exact mechanisms of action are far from understood. Redox cycling has been proposed as a possible mechanism of action for many quinine species. Experimental determination of the essential thermodynamic data (i.e. electrochemical and pKa values) required to predict the propensity towards redox cycling is often difficult or impossible to obtain due to the experimental limitations. We demonstrate a practical computational approach to obtain reasonable estimates of these parameters.

  19. Exogenous quinones inhibit photosynthetic electron transfer in Chloroflexus aurantiacus by specific quenching of the excited bacteriochlorophyll c antenna

    DEFF Research Database (Denmark)

    Frigaard, N-U; Tokita, S; Matsuura, K

    1999-01-01

    In the photosynthetic green filamentous bacterium Chloroflexus aurantiacus, excitation energy is transferred from a large bacteriochlorophyll (BChl) c antenna via smaller BChl a antennas to the reaction center. The effects of substituted 1,4-naphthoquinones on BChl c and BChl a fluorescence and o...... antenna. Our results provide a model system for studying the redox-dependent antenna quenching in green sulfur bacteria because the antennas in these bacteria inherently exhibit a sensitivity to O(2) similar to the quinone-supplemented cells of Cfx. aurantiacus....

  20. Pyrroloquinoline Quinone-Dependent Cytochrome Reduction in Polyvinyl Alcohol-Degrading Pseudomonas sp. Strain VM15C

    OpenAIRE

    1989-01-01

    A polyvinyl alcohol (PVA) oxidase-deficient mutant of Pseudomonas sp. strain VM15C, strain ND1, was shown to possess PVA dehydrogenase, in which pyrroloquinoline quinone (PQQ) functions as a coenzyme. The mutant grew on PVA and required PQQ for utilization of PVA as an essential growth factor. Incubation of the membrane fraction of the mutant with PVA caused cytochrome reduction of the fraction. Furthermore, it was found that in spite of the presence of PVA oxidase, the membrane fraction of s...

  1. Biphasic kinetic behavior of E. coli WrbA, an FMN-dependent NAD(PH:quinone oxidoreductase.

    Directory of Open Access Journals (Sweden)

    Iryna Kishko

    Full Text Available The E. coli protein WrbA is an FMN-dependent NAD(PH:quinone oxidoreductase that has been implicated in oxidative defense. Three subunits of the tetrameric enzyme contribute to each of four identical, cavernous active sites that appear to accommodate NAD(PH or various quinones, but not simultaneously, suggesting an obligate tetramer with a ping-pong mechanism in which NAD departs before oxidized quinone binds. The present work was undertaken to evaluate these suggestions and to characterize the kinetic behavior of WrbA. Steady-state kinetics results reveal that WrbA conforms to a ping-pong mechanism with respect to the constancy of the apparent Vmax to Km ratio with substrate concentration. However, the competitive/non-competitive patterns of product inhibition, though consistent with the general class of bi-substrate reactions, do not exclude a minor contribution from additional forms of the enzyme. NMR results support the presence of additional enzyme forms. Docking and energy calculations find that electron-transfer-competent binding sites for NADH and benzoquinone present severe steric overlap, consistent with the ping-pong mechanism. Unexpectedly, plots of initial velocity as a function of either NADH or benzoquinone concentration present one or two Michaelis-Menten phases depending on the temperature at which the enzyme is held prior to assay. The effect of temperature is reversible, suggesting an intramolecular conformational process. WrbA shares these and other details of its kinetic behavior with mammalian DT-diaphorase, an FAD-dependent NAD(PH:quinone oxidoreductase. An extensive literature review reveals several other enzymes with two-plateau kinetic plots, but in no case has a molecular explanation been elucidated. Preliminary sedimentation velocity analysis of WrbA indicates a large shift in size of the multimer with temperature, suggesting that subunit assembly coupled to substrate binding may underlie the two-plateau behavior. An

  2. Pyrroloquinoline quinone prevents oxidative stress-induced neuronal death probably through changes in oxidative status of DJ-1.

    OpenAIRE

    Nunome, Kana; Miyazaki, Shin; Nakano, Masahiko; Iguchi-Ariga, Sanae; Ariga, Hiroyoshi

    2008-01-01

    Pyrroloquinoline quinone (PQQ) has been shown to play a role as an anti-oxidant in neuronal cells and prevent neuronal cell death in a rodent stroke model. DJ-1, a causative gene product for a familial form of Parkinson's disease, plays a role in anti-oxidative stress function by self-oxidation of DJ-1. In this study, the expression level and oxidation status of DJ-1 were examined in SHSY-5Y cells and primary cultured neurons treated with 6-hydroxydopamine (6-OHDA) or H(2)O(2) in the presence...

  3. Regional NAD(P)H:quinone oxidoreductase activity in Alzheimer's disease.

    Science.gov (United States)

    SantaCruz, Karen S; Yazlovitskaya, Eugenia; Collins, Julie; Johnson, Jeff; DeCarli, Charles

    2004-01-01

    Converging evidence supports the role of oxidative stress in the pathology of Alzheimer's disease (AD). This notion is further supported by recent findings of increased NAD(P)H:quinone oxidodreductase (NQO1) activity, a potent antioxidant system, in association with hippocampal AD pathology. If increased NQO1 activity is truly related to the AD process, however, we would expect to see regional co-localization of NQO1 activity with AD pathology throughout affected brain regions and the absence of NQO1 activity in regions unaffected by AD. We examined this hypothesis by measuring NQO1 enzymatic activity and NQO1 immunohistochemical staining in regions commonly affected by the AD process such as frontal cortex and compared this to regions generally unaffected by the AD process such as occipital cortex, cerebellum, and substantia nigra for a group of AD patients and controls. The ratio of frontal to cerebellar NQO1 enzymatic activity was significantly increased in patients with AD (2.07 +/- 1.90) versus controls (0.60 +/- 0.31; P < 0.03). Moreover, regional immunohistochemical staining revealed specific localization of NQO1 staining to astrocytes and neurites surrounding senile plaques. The extent of immunohistochemical staining also closely correlated with the extent of local AD pathology across the various brain regions examined. Neuronal NQO1 staining seen in frontal cortex of AD patients was absent in frontal cortex of controls, but was found to the same extent in neurons of the substantia nigra of both AD patients and controls. We conclude that NQO1 activity co-localizes closely with AD pathology supporting a presumed role as an antioxidant system upregulated in response to the oxidative stress of the AD process. The antioxidant role for NQO1 is further supported by finding increased neuronal NQO1 activity in substantia nigra neurons of both AD patients and controls as this neuronal population is known to be under constant oxidative stress. While requiring further

  4. Polychlorinated biphenyl quinone induces oxidative DNA damage and repair responses: The activations of NHEJ, BER and NER via ATM-p53 signaling axis

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Hui; Shi, Qiong; Song, Xiufang; Fu, Juanli; Hu, Lihua; Xu, Demei; Su, Chuanyang; Xia, Xiaomin; Song, Erqun; Song, Yang, E-mail: songyangwenrong@hotmail.com

    2015-07-01

    Our previous studies demonstrated that polychlorinated biphenyl (PCB) quinone induced oxidative DNA damage in HepG2 cells. To promote genomic integrity, DNA damage response (DDR) coordinates cell-cycle transitions, DNA repair and apoptosis. PCB quinone-induced cell cycle arrest and apoptosis have been documented, however, whether PCB quinone insult induce DNA repair signaling is still unknown. In this study, we identified the activation of DDR and corresponding signaling events in HepG2 cells upon the exposure to a synthetic PCB quinone, PCB29-pQ. Our data illustrated that PCB29-pQ induces the phosphorylation of p53, which was mediated by ataxia telangiectasia mutated (ATM) protein kinase. The observed phosphorylated histone H2AX (γ-H2AX) foci and the elevation of 8-hydroxy-2′-deoxyguanosine (8-OHdG) indicated that DDR was stimulated by PCB29-pQ treatment. Additionally, we found PCB29-pQ activates non-homologous end joining (NHEJ), base excision repair (BER) and nucleotide excision repair (NER) signalings. However, these repair pathways are not error-free processes and aberrant repair of DNA damage may cause the potential risk of carcinogenesis and mutagenesis. - Highlights: • Polychlorinated biphenyl quinone induces oxidative DNA damage in HepG2 cells. • The elevation of γ-H2AX and 8-OHdG indicates the activation of DNA damage response. • ATM-p53 signaling acts as the DNA damage sensor and effector. • Polychlorinated biphenyl quinone activates NHEJ, BER and NER signalings.

  5. In vitro antifungal effect of black cumin seed quinones against dairy spoilage yeasts at different acidity levels.

    Science.gov (United States)

    Halamova, Katerina; Kokoska, Ladislav; Flesar, Jaroslav; Sklenickova, Olga; Svobodova, Blanka; Marsik, Petr

    2010-12-01

    The antiyeast activity of the black cumin seed (Nigella sativa) quinones dithymoquinone, thymohydroquinone (THQ), and thymoquinone (TQ) were evaluated in vitro with a broth microdilution method against six dairy spoilage yeast species. Antifungal effects of the quinones were compared with those of preservatives commonly used in milk products (calcium propionate, natamycin, and potassium sorbate) at two pH levels (4.0 and 5.5). THQ and TQ possessed significant antiyeast activity and affected the growth of all strains tested at both pH levels, with MICs ranging from 8 to 128 μg/ml. With the exception of the antibiotic natamycin, the inhibitory effects of all food preservatives against the yeast strains tested in this study were strongly affected by differences in pH, with MICs of ≥16 and ≥512 μg/ml at pH 4.0 and 5.5, respectively. These findings suggest that HQ and TQ are effective antiyeast agents that could be used in the dairy industry as chemical preservatives of natural origin.

  6. Crystal structure of quinone-dependent alcohol dehydrogenase from Pseudogluconobacter saccharoketogenes. A versatile dehydrogenase oxidizing alcohols and carbohydrates.

    Science.gov (United States)

    Rozeboom, Henriëtte J; Yu, Shukun; Mikkelsen, Rene; Nikolaev, Igor; Mulder, Harm J; Dijkstra, Bauke W

    2015-12-01

    The quinone-dependent alcohol dehydrogenase (PQQ-ADH, E.C. 1.1.5.2) from the Gram-negative bacterium Pseudogluconobacter saccharoketogenes IFO 14464 oxidizes primary alcohols (e.g. ethanol, butanol), secondary alcohols (monosaccharides), as well as aldehydes, polysaccharides, and cyclodextrins. The recombinant protein, expressed in Pichia pastoris, was crystallized, and three-dimensional (3D) structures of the native form, with PQQ and a Ca(2+) ion, and of the enzyme in complex with a Zn(2+) ion and a bound substrate mimic were determined at 1.72 Å and 1.84 Å resolution, respectively. PQQ-ADH displays an eight-bladed β-propeller fold, characteristic of Type I quinone-dependent methanol dehydrogenases. However, three of the four ligands of the Ca(2+) ion differ from those of related dehydrogenases and they come from different parts of the polypeptide chain. These differences result in a more open, easily accessible active site, which explains why PQQ-ADH can oxidize a broad range of substrates. The bound substrate mimic suggests Asp333 as the catalytic base. Remarkably, no vicinal disulfide bridge is present near the PQQ, which in other PQQ-dependent alcohol dehydrogenases has been proposed to be necessary for electron transfer. Instead an associated cytochrome c can approach the PQQ for direct electron transfer. © 2015 The Protein Society.

  7. Quinone-rich polydopamine functionalization of yttria stabilized zirconia for apatite biomineralization: The effects of coating temperature

    Science.gov (United States)

    Zain, Norhidayu Muhamad; Hussain, Rafaqat; Abdul Kadir, Mohammed Rafiq

    2015-08-01

    The use of yttria stabilized zirconia (YSZ) as biomedical implants is often offset by its bioinert nature that prevents its osseointegration to occur. Therefore, the functionalization of YSZ surface by polydopamine to facilitate the biomineralization of apatite layer on top of the coated film has incessantly been studied. In this study YSZ discs were first immersed in 2 mg/mL of stirred dopamine solution at coating temperatures between 25 and 80 °C. The specimens were then incubated for 7d in 1.5 SBF. The effect of coating temperature on the properties (chemical compositions and wettability) and the apatite mineralization on top of the generated films was investigated. It was found that at 50 °C, the specimen displayed the highest intensity of Ca 2p peak (1.55 ± 0.42 cps) with Ca/P ratio of 1.67 due to the presence of abundant quinone groups (Cdbnd O). However, the hydrophilicity (40.9 ± 01.7°) was greatly improved at 60 °C accompanied by the highest film thickness of 306 nm. Therefore, it was concluded that the presence of high intensity of quinone groups (Cdbnd O) in polydopamine film at elevated temperature affects the chelation of Ca2+ ions and thus enhance the growth of apatite layer on top of the functionalized YSZ surface.

  8. Redox potential of the terminal quinone electron acceptor QB in photosystem II reveals the mechanism of electron transfer regulation.

    Science.gov (United States)

    Kato, Yuki; Nagao, Ryo; Noguchi, Takumi

    2016-01-19

    Photosystem II (PSII) extracts electrons from water at a Mn4CaO5 cluster using light energy and then transfers them to two plastoquinones, the primary quinone electron acceptor QA and the secondary quinone electron acceptor QB. This forward electron transfer is an essential process in light energy conversion. Meanwhile, backward electron transfer is also significant in photoprotection of PSII proteins. Modulation of the redox potential (Em) gap of QA and QB mainly regulates the forward and backward electron transfers in PSII. However, the full scheme of electron transfer regulation remains unresolved due to the unknown Em value of QB. Here, for the first time (to our knowledge), the Em value of QB reduction was measured directly using spectroelectrochemistry in combination with light-induced Fourier transform infrared difference spectroscopy. The Em(QB (-)/QB) was determined to be approximately +90 mV and was virtually unaffected by depletion of the Mn4CaO5 cluster. This insensitivity of Em(QB (-)/QB), in combination with the known large upshift of Em(QA (-)/QA), explains the mechanism of PSII photoprotection with an impaired Mn4CaO5 cluster, in which a large decrease in the Em gap between QA and QB promotes rapid charge recombination via QA (-).

  9. Redox potential of the terminal quinone electron acceptor QB in photosystem II reveals the mechanism of electron transfer regulation

    Science.gov (United States)

    Kato, Yuki; Nagao, Ryo; Noguchi, Takumi

    2016-01-01

    Photosystem II (PSII) extracts electrons from water at a Mn4CaO5 cluster using light energy and then transfers them to two plastoquinones, the primary quinone electron acceptor QA and the secondary quinone electron acceptor QB. This forward electron transfer is an essential process in light energy conversion. Meanwhile, backward electron transfer is also significant in photoprotection of PSII proteins. Modulation of the redox potential (Em) gap of QA and QB mainly regulates the forward and backward electron transfers in PSII. However, the full scheme of electron transfer regulation remains unresolved due to the unknown Em value of QB. Here, for the first time (to our knowledge), the Em value of QB reduction was measured directly using spectroelectrochemistry in combination with light-induced Fourier transform infrared difference spectroscopy. The Em(QB−/QB) was determined to be approximately +90 mV and was virtually unaffected by depletion of the Mn4CaO5 cluster. This insensitivity of Em(QB−/QB), in combination with the known large upshift of Em(QA−/QA), explains the mechanism of PSII photoprotection with an impaired Mn4CaO5 cluster, in which a large decrease in the Em gap between QA and QB promotes rapid charge recombination via QA−. PMID:26715751

  10. A novel coumarin-quinone derivative SV37 inhibits CDC25 phosphatases, impairs proliferation, and induces cell death.

    Science.gov (United States)

    Bana, Emilie; Sibille, Estelle; Valente, Sergio; Cerella, Claudia; Chaimbault, Patrick; Kirsch, Gilbert; Dicato, Mario; Diederich, Marc; Bagrel, Denyse

    2015-03-01

    Cell division cycle (CDC) 25 proteins are key phosphatases regulating cell cycle transition and proliferation by regulating CDK/cyclin complexes. Overexpression of these enzymes is frequently observed in cancer and is related to aggressiveness, high-grade tumors and poor prognosis. Thus, targeting CDC25 by compounds, able to inhibit their activity, appears a good therapeutic approach. Here, we describe the synthesis of a new inhibitor (SV37) whose structure is based on both coumarin and quinone moieties. An analytical in vitro approach shows that this compound efficiently inhibits all three purified human CDC25 isoforms (IC50 1-9 µM) in a mixed-type mode. Moreover, SV37 inhibits growth of breast cancer cell lines. In MDA-MB-231 cells, reactive oxygen species generation is followed by pCDK accumulation, a mark of CDC25 dysfunction. Eventually, SV37 treatment leads to activation of apoptosis and DNA cleavage, underlining the potential of this new type of coumarin-quinone structure.

  11. Hydroquinone and Quinone-Grafted Porous Carbons for Highly Selective CO2 Capture from Flue Gases and Natural Gas Upgrading.

    Science.gov (United States)

    Wang, Jun; Krishna, Rajamani; Yang, Jiangfeng; Deng, Shuguang

    2015-08-04

    Hydroquinone and quinone functional groups were grafted onto a hierarchical porous carbon framework via the Friedel-Crafts reaction to develop more efficient adsorbents for the selective capture and removal of carbon dioxide from flue gases and natural gas. The oxygen-doped porous carbons were characterized with scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. CO2, CH4, and N2 adsorption isotherms were measured and correlated with the Langmuir model. An ideal adsorbed solution theory (IAST) selectivity for the CO2/N2 separation of 26.5 (298 K, 1 atm) was obtained on the hydroquinone-grafted carbon, which is 58.7% higher than that of the pristine porous carbon, and a CO2/CH4 selectivity value of 4.6 (298 K, 1 atm) was obtained on the quinone-grafted carbon (OAC-2), which represents a 28.4% improvement over the pristine porous carbon. The highest CO2 adsorption capacity on the oxygen-doped carbon adsorbents is 3.46 mmol g(-1) at 298 K and 1 atm. In addition, transient breakthrough simulations for CO2/CH4/N2 mixture separation were conducted to demonstrate the good separation performance of the oxygen-doped carbons in fixed bed adsorbers. Combining excellent adsorption separation properties and low heats of adsorption, the oxygen-doped carbons developed in this work appear to be very promising for flue gas treatment and natural gas upgrading.

  12. Supercritical Fluid Extraction and Ultra Performance Liquid Chromatography of Respiratory Quinones for Microbial Community Analysis in Environmental and Biological Samples

    Directory of Open Access Journals (Sweden)

    Koichi Fujie

    2012-03-01

    Full Text Available Microbial community structure plays a significant role in environmental assessment and animal health management. The development of a superior analytical strategy for the characterization of microbial community structure is an ongoing challenge. In this study, we developed an effective supercritical fluid extraction (SFE and ultra performance liquid chromatography (UPLC method for the analysis of bacterial respiratory quinones (RQ in environmental and biological samples. RQ profile analysis is one of the most widely used culture-independent tools for characterizing microbial community structure. A UPLC equipped with a photo diode array (PDA detector was successfully applied to the simultaneous determination of ubiquinones (UQ and menaquinones (MK without tedious pretreatment. Supercritical carbon dioxide (scCO2 extraction with the solid-phase cartridge trap proved to be a more effective and rapid method for extracting respiratory quinones, compared to a conventional organic solvent extraction method. This methodology leads to a successful analytical procedure that involves a significant reduction in the complexity and sample preparation time. Application of the optimized methodology to characterize microbial communities based on the RQ profile was demonstrated for a variety of environmental samples (activated sludge, digested sludge, and compost and biological samples (swine and Japanese quail feces.

  13. Supercritical fluid extraction and ultra performance liquid chromatography of respiratory quinones for microbial community analysis in environmental and biological samples.

    Science.gov (United States)

    Hanif, Muhammad; Atsuta, Yoichi; Fujie, Koichi; Daimon, Hiroyuki

    2012-03-05

    Microbial community structure plays a significant role in environmental assessment and animal health management. The development of a superior analytical strategy for the characterization of microbial community structure is an ongoing challenge. In this study, we developed an effective supercritical fluid extraction (SFE) and ultra performance liquid chromatography (UPLC) method for the analysis of bacterial respiratory quinones (RQ) in environmental and biological samples. RQ profile analysis is one of the most widely used culture-independent tools for characterizing microbial community structure. A UPLC equipped with a photo diode array (PDA) detector was successfully applied to the simultaneous determination of ubiquinones (UQ) and menaquinones (MK) without tedious pretreatment. Supercritical carbon dioxide (scCO(2)) extraction with the solid-phase cartridge trap proved to be a more effective and rapid method for extracting respiratory quinones, compared to a conventional organic solvent extraction method. This methodology leads to a successful analytical procedure that involves a significant reduction in the complexity and sample preparation time. Application of the optimized methodology to characterize microbial communities based on the RQ profile was demonstrated for a variety of environmental samples (activated sludge, digested sludge, and compost) and biological samples (swine and Japanese quail feces).

  14. Photochemistry of free and bound Zn-chlorophyll analogues to synthetic peptides depend on the quinone and pH.

    Science.gov (United States)

    Razeghifard, Reza

    2015-11-01

    A synthetic peptide was used as a scaffold to bind Zn-Chlorophyll (ZnChl) analogues through histidine ligation to study their photochemistry in the presence of different type of quinones. The Chl analogues were chlorin e6 (Ce6), chlorin e6 trimethyl ester, pyropheophorbide a, and pheophorbide a while the quinones were PPBQ, DMBQ, NPHQ, DBTQ, DCBQ and PBQ. The binding of each ZnChl analogue to the peptide was verified by native gel electrophoresis. First the photo-stability of the ZnChl analogues were tested under continuous light. The ZnCe6 and ZnCe6TM analogues showed the least stability judged by the loss of optical signal intensity at their Qy band. The photoactivity of each ZnChl analogue was measured in the presence of each of the six quinones using time-resolved EPR spectroscopy. DMBQ was found to be the most efficient electron acceptor when all four ZnChl analogues were compared. The light-induced electron transfer between the ZnChl analogues complexed with the peptide and DMBQ were also measured using time-resolved EPR spectroscopy. The ZnCe6-peptide complex exhibited the highest photoactivity. The electron transfer in the complex was faster and the photoactivity yield was higher than those values obtained for free ZnCe6 and DMBQ. The fast phase of kinetics can be attributed to intra-protein electron transfer in the complex since it was not observed in the presence of DMBQ-glutathione adduct. Unlike free ZnCe6, the ZnCe6-peptide complex was robust and demonstrated very similar photoactivity efficiency in pH values 10, 8.0 and 5.0. The electron transfer kinetics were pH dependent and appeared to be modulated by the peptide charge and possibly fold. The charge recombination rate was slowed by an order of magnitude when the pH value was changed from 10.0 to 5.0. The implications of constructing the photoactive peptide complexes in terms of artificial photosynthesis are discussed.

  15. REACTIONS OF BENZO[A]PYRENE-7,8-QUINONE WITH DEOXYGUANOSINE AND DEOXYADENOSINE AT PHYSIOLOGICAL pH: IDENTIFICATION AND CHARACTERIZATION OF STABLE ADDUCTS

    Science.gov (United States)

    Reactions of Benzo[a]pyrene-7,8-quinone with Deoxyguanosine and Deoxyadenosine at Physiological pH: Identification and Characterization of Stable AdductsNarayanan Balu, William T. Padgett, Guy Lambert, Adam E. Swank,Ann M. Richard, and Stephen NesnowEnvironmen...

  16. Synthesis of {alpha}- and {beta}-lapachone derivatives from hetero diels-alder trapping of alkyl and aryl o-quinone methides

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Fernando de C. da; Ferreira, Sabrina B.; Ferreira, Vitor F. [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Inst. de Quimica. Dept. de Quimica Organica], e-mail: cegvito@vm.uff.br; Kaiser, Carlos R.; Pinto, Angelo C. [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Inst. de Quimica

    2009-07-01

    Methylene and aryl o-quinone methides (o-QMs) generated by Knoevenagel condensation of 2-hydroxy-1,4-naphthoquinone with formaldehyde and arylaldehydes, undergo facile hetero Diels-Alder reaction with some substituted styrenes (as dienophiles) in aqueous ethanol media providing derivatives of {alpha}- and {beta}-lapachone (author)

  17. Chlorinated biphenyl quinones and phenyl-2,5-benzoquinone differentially modify the catalytic activity of human hydroxysteroid sulfotransferase hSULT2A1.

    Science.gov (United States)

    Qin, Xiaoyan; Lehmler, Hans-Joachim; Teesch, Lynn M; Robertson, Larry W; Duffel, Michael W

    2013-10-21

    Human hydroxysteroid sulfotransferase (hSULT2A1) catalyzes the sulfation of a broad range of environmental chemicals, drugs, and other xenobiotics in addition to endogenous compounds that include hydroxysteroids and bile acids. Polychlorinated biphenyls (PCBs) are persistent environmental contaminants, and oxidized metabolites of PCBs may play significant roles in the etiology of their adverse health effects. Quinones derived from the oxidative metabolism of PCBs (PCB-quinones) react with nucleophilic sites in proteins and also undergo redox cycling to generate reactive oxygen species. This, along with the sensitivity of hSULT2A1 to oxidative modification at cysteine residues, led us to hypothesize that electrophilic PCB-quinones react with hSULT2A1 to alter its catalytic function. Thus, we examined the effects of four phenylbenzoquinones on the ability of hSULT2A1 to catalyze the sulfation of the endogenous substrate, dehydroepiandrosterone (DHEA). The quinones studied were 2'-chlorophenyl-2,5-benzoquinone (2'-Cl-BQ), 4'-chlorophenyl-2,5-benzoquinone (4'-Cl-BQ), 4'-chlorophenyl-3,6-dichloro-2,5-benzoquinone (3,6,4'-triCl-BQ), and phenyl-2,5-benzoquinone (PBQ). At all concentrations examined, pretreatment of hSULT2A1 with the PCB-quinones decreased the catalytic activity of hSULT2A1. Pretreatment with low concentrations of PBQ, however, increased the catalytic activity of the enzyme, while higher concentrations inhibited catalysis. A decrease in substrate inhibition with DHEA was seen following preincubation of hSULT2A1 with all of the quinones. Proteolytic digestion of the enzyme followed by LC/MS analysis indicated PCB-quinone- and PBQ-adducts at Cys55 and Cys199, as well as oxidation products at methionines in the protein. Equilibrium binding experiments and molecular modeling suggested that changes due to these modifications may affect the nucleotide binding site and the entrance to the sulfuryl acceptor binding site of hSULT2A1.

  18. Inhibition of photosynthetic oxygen evolution and electron transfer from the quinone acceptor QA- to QB by iron deficiency.

    Science.gov (United States)

    Msilini, Najoua; Zaghdoudi, Maha; Govindachary, Sridharan; Lachaâl, Mokhtar; Ouerghi, Zeineb; Carpentier, Robert

    2011-03-01

    The effect of iron deficiency on photosynthetic electron transport in Photosystem II (PS II) was studied in leaves and thylakoid membranes of lettuce (Lactuca sativa, Romaine variety) plants. PS II electron transport was characterized by oxygen evolution and chlorophyll fluorescence parameters. Iron deficiency in the culture medium was shown to affect water oxidation and the advancement of the S-states. A decrease of maximal quantum yield of PS II and an increase of fluorescence intensity at step J and I of OJIP kinetics were also observed. Thermoluminescence measurements revealed that charge recombination between the quinone acceptor of PS II, Q(B), and the S(2) state of the Mn-cluster was strongly perturbed. Also the dark decay of Chl fluorescence after a single turnover white flash was greatly retarded indicating a slower rate of Q(A)(-) reoxidation.

  19. Dielectric studies on the heterogeneity and interfacial property of composites made of polyacene quinone radical polymers and sulfonated polyurethanes.

    Science.gov (United States)

    Zhu, Dan; Zhang, Juan; Bin, Yuezhen; Xu, Chunye; Shen, Jian; Matsuo, Masaru

    2012-03-01

    Sulfonated polyurethane (PUI, matrix) is synthesized and composited with polyacene quinone radical polymers (PAQRs, filler). The polarization mechanism of these polymers and composites were investigated in terms of their frequency, temperature, and filler-concentration-dependent dielectric properties. We found that PUI/PAQR composites have a high permittivity, which is attributed to the filler-matrix interfacial polarization and the contact effect. The PAQR-concentration-dependent permittivity of different PUI/PAQR composites reveals a percolation threshold at 20-30 wt % with scaling exponents that indicate the intercluster polarization. The frequency dependence of dielectric response is well-fitted by using the Debye and Cole-Cole functions on the basis of the structural diagrams and equivalent circuit, leading to a detailed evaluation on heterogeneous structures of different PUI/PAQR composites.

  20. Generalized Mulliken-Hush analysis of electronic coupling interactions in compressed pi-stacked porphyrin-bridge-quinone systems.

    Science.gov (United States)

    Zheng, Jieru; Kang, Youn K; Therien, Michael J; Beratan, David N

    2005-08-17

    Donor-acceptor interactions were investigated in a series of unusually rigid, cofacially compressed pi-stacked porphyrin-bridge-quinone systems. The two-state generalized Mulliken-Hush (GMH) approach was used to compute the coupling matrix elements. The theoretical coupling values evaluated with the GMH method were obtained from configuration interaction calculations using the INDO/S method. The results of this analysis are consistent with the comparatively soft distance dependences observed for both the charge separation and charge recombination reactions. Theoretical studies of model structures indicate that the phenyl units dominate the mediation of the donor-acceptor coupling and that the relatively weak exponential decay of rate with distance arises from the compression of this pi-electron stack.

  1. A quick response fluorescent probe based on coumarin and quinone for glutathione and its application in living cells

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Xi [Institute of Organic Chemistry, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China); Du, Zhi-Fang [Taishan College, Shandong University, Jinan 250100 (China); Wang, Li-Hong; Miao, Jun-Ying [Institute of Developmental Biology, School of Life Science, Shandong University, Jinan 250100 (China); Zhao, Bao-Xiang, E-mail: bxzhao@sdu.edu.cn [Institute of Organic Chemistry, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China)

    2016-05-30

    We have designed and synthesized a simple but effective fluorescent probe for sensing glutathione (GSH) by PET process based on coumarin and quinone, which worked as fluorophore and reaction site, respectively. The probe could discriminate GSH from cysteine and homocysteine within 1 min in PBS-buffered solution. The sensing mechanism was confirmed by density functional theory (DFT), viscosity test, fluorescence spectrum analysis and HRMS, respectively. The probe has a low limit of detection (0.1 μM) and finally been used in cell imaging successfully. - Highlights: • This probe can discriminate glutathione from sulfhydryl compound by PET process. • This probe can be used to determine glutathione in aqueous solution within 1 min. • This probe has been successfully applied in living cell image.

  2. Simultaneous Synthesis of both Rings of Chromenes via a Benzannulation/o-Quinone Methide Formation/Electrocyclization Cascade

    Science.gov (United States)

    Majumdar, Nilanjana; Korthals, Keith A.; Wulff, William D.

    2011-01-01

    A new route to the chromene ring system has been developed which involves the reaction of an α,β-unsaturated Fischer carbene complex of chromium with a propargyl ether bearing an alkenyl group on the propargylic carbon. This transformation involves a cascade of reactions that begins with a benzannulation reaction and is followed by the formation of an o-quinone methide and finally, results in the emergence of a chromene upon an electrocyclization. This reaction was extended to the provide access to by employing an aryl carbene complex. This constitutes the first synthesis of chromenes in which both rings of the chromene system are generated in a single step and is highlighted in the synthesis of lapachenole and Vitamin E. PMID:22176537

  3. Pyrroloquinoline quinone from Gluconobacter oxydans fermentation broth enhances superoxide anion-scavenging capacity of Cu/Zn-SOD.

    Science.gov (United States)

    Ma, Ke; Cui, Jun-Zhu; Ye, Jian-Bin; Hu, Xian-Mei; Ma, Ge-Li; Yang, Xue-Peng

    2017-09-01

    A bioassay-guided fractionation of extract from Gluconobacter oxydans fermentation broth afforded Compound 1, which was identified as pyrroloquinoline quinone (PQQ) by spectroscopic methods. PQQ has been shown to enhance the superoxide anion-scavenging capacity significantly for Cu/Zn-SOD. To illustrate the mechanism, the interaction between PQQ and Cu/Zn-SOD was investigated. The multiple binding sites involving hydrogen bonds and van der Waals force between PQQ and Cu/Zn-SOD were revealed by isothermal titration calorimetry. The α-helix content was increased in the Cu/Zn-SOD structure with the addition of PQQ into the solution through ultraviolet (UV) spectroscopy. These results indicated that PQQ could change the conformation of Cu/Zn-SOD through interaction, which could enhance its superoxide anion-scavenging capacity. Therefore, PQQ is a potential natural antioxidant. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Activity-guided isolation of constituents of Tephrosia purpurea with the potential to induce the phase II enzyme, quinone reductase.

    Science.gov (United States)

    Chang, L C; Gerhäuser, C; Song, L; Farnsworth, N R; Pezzuto, J M; Kinghorn, A D

    1997-09-01

    An isoflavone, 7,4'-dihydroxy-3',5'-dimethoxyisoflavone (1), and a chalcone, (+)-tephropurpurin (2), both novel compounds, as well as six constituents of known structure, (+)-purpurin (3), pongamol (4), lanceolatin B (5), (-)-maackiain (6), (-)-3-hydroxy-4-methoxy-8,9-methylene-dioxypterocarpan (7), and (-)-medicarpin (8), were obtained as active compounds from Tephrosia purpurea, using a bioassay based on the induction of quinone reductase (QR) activity with cultured Hepa 1c1c7 mouse hepatoma cells. Additionally, three inactive compounds of known structure, 3'-methoxydaidzein, desmoxyphyllin B, and 3,9-dihydroxy-8-methoxycoumestan, were isolated and identified. The structure elucidation of compounds 1 and 2 was carried out by spectral data interpretation.

  5. Variation of glucosinolates and quinone reductase activity among different varieties of Chinese kale and improvement of glucoraphanin by metabolic engineering.

    Science.gov (United States)

    Qian, Hongmei; Sun, Bo; Miao, Huiying; Cai, Congxi; Xu, Chaojiong; Wang, Qiaomei

    2015-02-01

    The variation of glucosinolates and quinone reductase (QR) activity in fourteen varieties of Chinese kale (Brassica oleracea var. alboglabra Bailey) was investigated in the present study. Results showed that gluconapin (GNA), instead of glucoraphanin (GRA), was the most predominant glucosinolate in all varieties, and QR activity was remarkably positively correlated with the glucoraphanin level. AOP2, a tandem 2-oxoglutarate-dependent dioxygenase, catalyzes the conversion of glucoraphanin to gluconapin in glucosinolate biosynthesis. Here, antisense AOP2 was transformed into Gailan-04, the variety with the highest gluconapin content and ratio of GNA/GRA. The glucoraphanin content and corresponding QR activity were notably increased in transgenic plants, while no significant difference at the level of other main nutritional compounds (total phenolics, vitamin C, carotenoids and chlorophyll) was observed between the transgenic lines and the wide-type plants. Taken together, metabolic engineering is a good practice for improvement of glucoraphanin in Chinese kale.

  6. Odoriferous Defensive stink gland transcriptome to identify novel genes necessary for quinone synthesis in the red flour beetle, Tribolium castaneum.

    Directory of Open Access Journals (Sweden)

    Jianwei Li

    Full Text Available Chemical defense is one of the most important traits, which endow insects the ability to conquer a most diverse set of ecological environments. Chemical secretions are used for defense against anything from vertebrate or invertebrate predators to prokaryotic or eukaryotic parasites or food competitors. Tenebrionid beetles are especially prolific in this category, producing several varieties of substituted benzoquinone compounds. In order to get a better understanding of the genetic and molecular basis of defensive secretions, we performed RNA sequencing in a newly emerging insect model, the red flour beetle Tribolium castaneum (Coleoptera: Tenebrionidae. To detect genes that are highly and specifically expressed in the odoriferous gland tissues that secret defensive chemical compounds, we compared them to a control tissue, the anterior abdomen. 511 genes were identified in different subtraction groups. Of these, 77 genes were functionally analyzed by RNA interference (RNAi to recognize induced gland alterations morphologically or changes in gland volatiles by gas chromatography-mass spectrometry. 29 genes (38% presented strong visible phenotypes, while 67 genes (87% showed alterations of at least one gland content. Three of these genes showing quinone-less (ql phenotypes - Tcas-ql VTGl; Tcas-ql ARSB; Tcas-ql MRP - were isolated, molecularly characterized, their expression identified in both types of the secretory glandular cells, and their function determined by quantification of all main components after RNAi. In addition, microbe inhibition assays revealed that a quinone-free status is unable to impede bacterial or fungal growth. Phylogenetic analyses of these three genes indicate that they have evolved independently and specifically for chemical defense in beetles.

  7. Activities of Secreted Aryl Alcohol Quinone Oxidoreductases from Pycnoporus cinnabarinus Provide Insights into Fungal Degradation of Plant Biomass.

    Science.gov (United States)

    Mathieu, Yann; Piumi, Francois; Valli, Richard; Aramburu, Juan Carro; Ferreira, Patricia; Faulds, Craig B; Record, Eric

    2016-04-01

    Auxiliary activities family 3 subfamily 2 (AA3_2) from the CAZy database comprises various functions related to ligninolytic enzymes, such as fungal aryl alcohol oxidases (AAO) and glucose oxidases, both of which are flavoenzymes. The recent study of the Pycnoporus cinnabarinus CIRM BRFM 137 genome combined with its secretome revealed that four AA3_2 enzymes are secreted during biomass degradation. One of these AA3_2 enzymes, scf184803.g17, has recently been produced heterologously in Aspergillus niger Based on the enzyme's activity and specificity, it was assigned to the glucose dehydrogenases (PcinnabarinusGDH [PcGDH]). Here, we analyze the distribution of the other three AA3_2 enzymes (scf185002.g8, scf184611.g7, and scf184746.g13) to assess their putative functions. These proteins showed the highest homology with aryl alcohol oxidase from Pleurotus eryngii Biochemical characterization demonstrated that they were also flavoenzymes harboring flavin adenine dinucleotide (FAD) as a cofactor and able to oxidize a wide variety of phenolic and nonphenolic aryl alcohols and one aliphatic polyunsaturated primary alcohol. Though presenting homology with fungal AAOs, these enzymes exhibited greater efficiency in reducing electron acceptors (quinones and one artificial acceptor) than molecular oxygen and so were defined as aryl-alcohol:quinone oxidoreductases (AAQOs) with two enzymes possessing residual oxidase activity (PcAAQO2 and PcAAQO3). Structural comparison of PcAAQO homology models with P. eryngii AAO demonstrated a wider substrate access channel connecting the active-site cavity to the solvent, explaining the absence of activity with molecular oxygen. Finally, the ability of PcAAQOs to reduce radical intermediates generated by laccase from P. cinnabarinus was demonstrated, shedding light on the ligninolytic system of this fungus.

  8. Quinone-induced activation of Keap1/Nrf2 signaling by aspirin prodrugs masquerading as nitric oxide.

    Science.gov (United States)

    Dunlap, Tareisha; Piyankarage, Sujeewa C; Wijewickrama, Gihani T; Abdul-Hay, Samer; Vanni, Michael; Litosh, Vladislav; Luo, Jia; Thatcher, Gregory R J

    2012-12-17

    The promising therapeutic potential of the NO-donating hybrid aspirin prodrugs (NO-ASA) includes induction of chemopreventive mechanisms and has been reported in almost 100 publications. One example, NCX-4040 (pNO-ASA), is bioactivated by esterase to a quinone methide (QM) electrophile. In cell cultures, pNO-ASA and QM-donating X-ASA prodrugs that cannot release NO rapidly depleted intracellular GSH and caused DNA damage; however, induction of Nrf2 signaling elicited cellular defense mechanisms including upregulation of NAD(P)H:quinone oxidoreductase-1 (NQO1) and glutamate-cysteine ligase (GCL). In HepG2 cells, the "NO-specific" 4,5-diaminofluorescein reporter, DAF-DA, responded to NO-ASA and X-ASA, with QM-induced oxidative stress masquerading as NO. LC-MS/MS analysis demonstrated efficient alkylation of Cys residues of proteins including glutathione-S-transferase-P1 (GST-P1) and Kelch-like ECH-associated protein 1 (Keap1). Evidence was obtained for alkylation of Keap1 Cys residues associated with Nrf2 translocation to the nucleus, nuclear translocation of Nrf2, activation of antioxidant response element (ARE), and upregulation of cytoprotective target genes. At least in cell culture, pNO-ASA acts as a QM donor, bioactivated by cellular esterase activity to release salicylates, NO(3)(-), and an electrophilic QM. Finally, two novel aspirin prodrugs were synthesized, both potent activators of ARE, designed to release only the QM and salicylates on bioactivation. Current interest in electrophilic drugs acting via Nrf2 signaling suggests that QM-donating hybrid drugs can be designed as informative chemical probes in drug discovery.

  9. The Na+-Translocating NADH:Quinone Oxidoreductase Enhances Oxidative Stress in the Cytoplasm of Vibrio cholerae.

    Science.gov (United States)

    Muras, Valentin; Dogaru-Kinn, Paul; Minato, Yusuke; Häse, Claudia C; Steuber, Julia

    2016-09-01

    We searched for a source of reactive oxygen species (ROS) in the cytoplasm of the human pathogen Vibrio cholerae and addressed the mechanism of ROS formation using the dye 2',7'-dichlorofluorescein diacetate (DCFH-DA) in respiring cells. By comparing V. cholerae strains with or without active Na(+)-translocating NADH:quinone oxidoreductase (Na(+)-NQR), this respiratory sodium ion redox pump was identified as a producer of ROS in vivo The amount of cytoplasmic ROS detected in V. cholerae cells producing variants of Na(+)-NQR correlated well with rates of superoxide formation by the corresponding membrane fractions. Membranes from wild-type V. cholerae showed increased superoxide production activity (9.8 ± 0.6 μmol superoxide min(-1) mg(-1) membrane protein) compared to membranes from the mutant lacking Na(+)-NQR (0.18 ± 0.01 μmol min(-1) mg(-1)). Overexpression of plasmid-encoded Na(+)-NQR in the nqr deletion strain resulted in a drastic increase in the formation of superoxide (42.6 ± 2.8 μmol min(-1) mg(-1)). By analyzing a variant of Na(+)-NQR devoid of quinone reduction activity, we identified the reduced flavin adenine dinucleotide (FAD) cofactor of cytoplasmic NqrF subunit as the site for intracellular superoxide formation in V. cholerae The impact of superoxide formation by the Na(+)-NQR on the virulence of V. cholerae is discussed. In several studies, it was demonstrated that the Na(+)-NQR in V. cholerae affects virulence in a yet unknown manner. We identified the reduced FAD cofactor in the NADH-oxidizing NqrF subunit of the Na(+)-NQR as the site of superoxide formation in the cytoplasm of V. cholerae Our study provides the framework to understand how reactive oxygen species formed during respiration could participate in the regulated expression of virulence factors during the transition from aerobic to microaerophilic (intestinal) habitats. This hypothesis may turn out to be right for many other pathogens which, like V. cholerae, depend on the Na

  10. The Role of Human Aldo-Keto Reductases (AKRs in the Metabolic Activation and Detoxication of Polycyclic Aromatic Hydrocarbons: Interconversion of PAH-catechols and PAH o-Quinones

    Directory of Open Access Journals (Sweden)

    Li eZhang

    2012-11-01

    Full Text Available Polycyclic aromatic hydrocarbons (PAH are ubiquitous environmental pollutants. They are procarcinogens requiring metabolic activation to elicit their deleterious effects. Aldo-keto reductases (AKR catalyze the oxidation of proximate carcinogenic PAH trans-dihydrodiols to yield electrophilic and redox-active PAH o-quiniones. AKRs are also found to be capable of reducing PAH o-quinones to form PAH catechols. The interconversion of o-quinones and catechols results in the redox cycling of PAH o-quinones to give rise to the generation of reactive oxygen species and subsequent oxidative DNA damage. On the other hand, PAH catechols can be intercepted through phase II metabolism by which PAH o-quinones could be detoxified and eliminated. The aim of the present review is to summarize the role of human AKRs in the metabolic activation/detoxication of PAH and the relevance of phase II conjugation reactions to human lung carcinogenesis.

  11. QSAR studies on 1,2-dithiole-3-thiones: modeling of lipophilicity, quinone reductase specific activity, and production of growth hormone.

    Science.gov (United States)

    Khadikar, Padmakar; Jaiswal, Mona; Gupta, Madhu; Mandloi, Dheeraj; Sisodia, Raj Singh

    2005-02-15

    Studies on modeling of lipophilicity (logP) quinone reductase specific activity (logCDQR) and production of growth hormone (logCDGH) of 1,2-dithiole-3-thiones have been carried out using distance-based topological indices. The regression analysis of the data has shown that the set of compounds exhibit 'familial' relationships in that excellent results are obtained by dividing the data set into two or more classes (families).

  12. Quinone (QB) reduction by B-branch electron transfer in mutant bacterial reaction centers from Rhodobacter sphaeroides: quantum efficiency and X-ray structure.

    Science.gov (United States)

    Paddock, M L; Chang, C; Xu, Q; Abresch, E C; Axelrod, H L; Feher, G; Okamura, M Y

    2005-05-10

    The photosynthetic reaction center (RC) from purple bacteria converts light into chemical energy. Although the RC shows two nearly structurally symmetric branches, A and B, light-induced electron transfer in the native RC occurs almost exclusively along the A-branch to a primary quinone electron acceptor Q(A). Subsequent electron and proton transfer to a mobile quinone molecule Q(B) converts it to a quinol, Q(B)H(2). We report the construction and characterization of a series of mutants in Rhodobacter sphaeroides designed to reduce Q(B) via the B-branch. The quantum efficiency to Q(B) via the B-branch Phi(B) ranged from 0.4% in an RC containing the single mutation Ala-M260 --> Trp to 5% in a quintuple mutant which includes in addition three mutations to inhibit transfer along the A-branch (Gly-M203 --> Asp, Tyr-M210 --> Phe, Leu-M214 --> His) and one to promote transfer along the B-branch (Phe-L181 --> Tyr). Comparing the value of 0.4% for Phi(B) obtained in the AW(M260) mutant, which lacks Q(A), to the 100% quantum efficiency for Phi(A) along the A-branch in the native RC, we obtain a ratio for A-branch to B-branch electron transfer of 250:1. We determined the structure of the most effective (quintuple) mutant RC at 2.25 A (R-factor = 19.6%). The Q(A) site did not contain a quinone but was occupied by the side chain of Trp-M260 and a Cl(-). In this structure a nonfunctional quinone was found to occupy a new site near M258 and M268. The implications of this work to trap intermediate states are discussed.

  13. Free radical-derived quinone methide mediates skin tumor promotion by butylated hydroxytoluene hydroperoxide: expanded role for electrophiles in multistage carcinogenesis.

    Science.gov (United States)

    Guyton, K Z; Bhan, P; Kuppusamy, P; Zweier, J L; Trush, M A; Kensler, T W

    1991-01-01

    Free radical derivatives of peroxides, hydroperoxides, and anthrones are thought to mediate tumor promotion by these compounds. Further, the promoting activity of phorbol esters is attributed, in part, to their ability to stimulate the cellular generation of oxygen radicals. A hydroperoxide metabolite of butylated hydroxytoluene, 2,6-di-tert-butyl-4-hydroperoxyl-4-methyl-2,5-cyclohexadienone (BHTOOH), has previously been shown to be a tumor promoter in mouse skin. BHTOOH is extensively metabolized by murine keratinocytes to several radical species. The primary radical generated from BHTOOH is a phenoxyl radical that can disproportionate to form butylated hydroxytoluene quinone methide, a reactive electrophile. Since electrophilic species have not been previously postulated to mediate tumor promotion, the present study was undertaken to examine the role of this electrophile in the promoting activity of BHTOOH. The biological activities of two chemical analogs of BHTOOH, 4-trideuteromethyl-BHTOOH and 4-tert-butyl-BHTOOH, were compared with that of the parent compound. 4-Trideuteromethyl-BHTOOH and 4-tert-butyl-BHTOOH have a reduced ability or inability, respectively, to form a quinone methide; however, like the parent compound, they both generate a phenoxyl radical when incubated with keratinocyte cytosol. The potency of BHTOOH, 4-trideuteromethyl-BHTOOH, and 4-tert-butyl-BHTOOH as inducers of ornithine decarboxylase, a marker of tumor promotion, was commensurate with their capacity for generating butylated hydroxytoluene quinone methide. These initial results were confirmed in a two-stage tumor promotion protocol in female SENCAR mice. Together, these data indicate that a quinone methide is mediating tumor promotion by BHTOOH, providing direct evidence that an electrophilic intermediate can elicit this stage of carcinogenesis. PMID:1846971

  14. [3+2] versus [4+2] cycloadditions of quinone monoimide with azadienes: a Lewis acid-free access to 5-amino-2,3-dihydrobenzofuranes.

    Science.gov (United States)

    Lomberget, Thierry; Baragona, Fabien; Fenet, Bernard; Barret, Roland

    2006-08-31

    The reaction between p-quinone monoimide 1a and various azadienes 2 is described in the absence of a Lewis acid promoter. When alpha,beta-unsaturated hydrazones are substituted by proton or alkyl groups, 2,3-dihydrobenzofuranes 4, a motif that is present in numerous biologically active products, are obtained in moderate to excellent yields. The regio- and stereoselectivity of this reaction has been proved by a complete NMR study, including 1H-15N correlations.

  15. Polymyxin B identified as an inhibitor of alternative NADH dehydrogenase and malate: quinone oxidoreductase from the Gram-positive bacterium Mycobacterium smegmatis.

    Science.gov (United States)

    Mogi, Tatsushi; Murase, Yoshiro; Mori, Mihoko; Shiomi, Kazuro; Omura, Satoshi; Paranagama, Madhavi P; Kita, Kiyoshi

    2009-10-01

    Tuberculosis is the leading cause of death due to a single infectious agent in the world and the emergence of multidrug-resistant strains prompted us to develop new drugs with novel targets and mechanism. Here, we screened a natural antibiotics library with Mycobacterium smegmatis membrane-bound dehydrogenases and identified polymyxin B (cationic decapeptide) and nanaomycin A (naphtoquinone derivative) as inhibitors of alternative NADH dehydrogenase [50% inhibitory concentration (IC(50)) values of 1.6 and 31 microg/ml, respectively] and malate: quinone oxidoreductase (IC(50) values of 4.2 and 49 microg/ml, respectively). Kinetic analysis on inhibition by polymyxin B showed that the primary site of action was the quinone-binding site. Because of the similarity in K(m) value for ubiquinone-1 and inhibitor sensitivity, we examined amino acid sequences of actinobacterial enzymes and found possible binding sites for L-malate and quinones. Proposed mechanisms of polymyxin B and nanaomycin A for the bacteriocidal activity were the destruction of bacterial membranes and production of reactive oxygen species, respectively, while this study revealed their inhibitory activity on bacterial membrane-bound dehydrogenases. Screening of the library with bacterial respiratory enzymes resulted in unprecedented findings, so we are hoping that continuing efforts could identify lead compounds for new drugs targeting to mycobacterial respiratory enzymes.

  16. Vitamins K interact with N-terminus α-synuclein and modulate the protein fibrillization in vitro. Exploring the interaction between quinones and α-synuclein.

    Science.gov (United States)

    da Silva, Fernanda Luna; Coelho Cerqueira, Eduardo; de Freitas, Mônica Santos; Gonçalves, Daniela Leão; Costa, Lilian Terezinha; Follmer, Cristian

    2013-01-01

    In the last decades, a series of compounds, including quinones and polyphenols, has been described as having anti-fibrillogenic action on α-synuclein (α-syn) whose aggregation is associated to the pathogenesis of Parkinson's disease (PD). Most of these molecules act as promiscuous anti-amyloidogenic agents, interacting with the diverse amyloidogenic proteins (mostly unfolded) through non-specific hydrophobic interactions. Herein we investigated the effect of the vitamins K (phylloquinone, menaquinone and menadione), which are 1,4-naphthoquinone (1,4-NQ) derivatives, on α-syn aggregation, comparing them with other anti-fibrillogenic molecules such as quinones, polyphenols and lipophilic vitamins. Vitamins K delayed α-syn fibrillization in substoichiometric concentrations, leading to the formation of short, sheared fibrils and amorphous aggregates, which are less prone to produce leakage of synthetic vesicles. In seeding conditions, menadione and 1,4-NQ significantly inhibited fibrils elongation, which could be explained by their ability to destabilize preformed fibrils of α-syn. Bidimensional NMR experiments indicate that a specific site at the N-terminal α-syn (Gly31/Lys32) is involved in the interaction with vitamins K, which is corroborated by previous studies suggesting that Lys is a key residue in the interaction with quinones. Together, our data suggest that 1,4-NQ, recently showed up by our group as a potential scaffold for designing new monoamine oxidase inhibitors, is also capable to modulate α-syn fibrillization in vitro.

  17. The structure and function of quinones in biological solar energy transduction: a cyclic voltammetry, EPR, and hyperfine sub-level correlation (HYSCORE) spectroscopy study of model naphthoquinones.

    Science.gov (United States)

    Coates, Christopher S; Ziegler, Jessica; Manz, Katherine; Good, Jacob; Kang, Bernard; Milikisiyants, Sergey; Chatterjee, Ruchira; Hao, Sijie; Golbeck, John H; Lakshmi, K V

    2013-06-20

    Quinones function as electron transport cofactors in photosynthesis and cellular respiration. The versatility and functional diversity of quinones is primarily due to the diverse midpoint potentials that are tuned by the substituent effects and interactions with surrounding amino acid residues in the binding site in the protein. In the present study, a library of substituted 1,4-naphthoquinones are analyzed by cyclic voltammetry in both protic and aprotic solvents to determine effects of substituent groups and hydrogen bonds on the midpoint potential. We use continuous-wave electron paramagnetic resonance (EPR) spectroscopy to determine the influence of substituent groups on the electronic properties of the 1,4-naphthoquinone models in an aprotic solvent. The results establish a correlation between the presence of substituent group(s) and the modification of electronic properties and a corresponding shift in the midpoint potential of the naphthoquinone models. Further, we use pulsed EPR spectroscopy to determine the effect of substituent groups on the strength and planarity of the hydrogen bonds of naphthoquinone models in a protic solvent. This study provides support for the tuning of the electronic properties of quinone cofactors by the influence of substituent groups and hydrogen bonding interactions.

  18. Regiospecific attack of nitrogen and sulfur nucleophiles on quinones derived from poison oak/ivy catechols (urushiols) and analogues as models for urushiol-protein conjugate formation.

    Science.gov (United States)

    Liberato, D J; Byers, V S; Dennick, R G; Castagnoli, N

    1981-01-01

    Attempts to characterize potential biologically important covalent interactions between electrophilic quinones derived from catechols present in poison oak/ivy (urushiol) and biomacromolecules have led to the analysis of model reactions involving sulfur and amino nucleophiles with 3-heptadecylbenzoquinone. Characterization of the reaction products indicates that this quinone undergoes regiospecific attack by (S)-N-acetylcysteine at C-6 and by 1-aminopentane at C-5. The red solid obtained with 1-aminopentane proved to be 3-heptadecyl-5-(pentylamino)-1,2-benzoquinone. Analogous aminobenzoquinones were obtained with the quinones derived from the 4- and 6-methyl analogues of 3-pentadecylcatechol. All three adducts absorbed visible light at different wavelengths. When the starting catechols were incubated with human serum albumin almost identical chromophores were formed. These results establish that cathechols responsible for the production of the poison oak/ivy contact dermatitis in humans undergo a sequence of reactions in the presence of human serum albumin that lead to covalent attachment of the catechols to the protein via carbon-nitrogen bonds. Estimations of the extent of this binding indicate that, at least with human serum albumin, the reaction is quantitative.

  19. Quinone 1 e and 2 e /2 H + Reduction Potentials: Identification and Analysis of Deviations from Systematic Scaling Relationships

    Energy Technology Data Exchange (ETDEWEB)

    Huynh, Mioy T.; Anson, Colin W.; Cavell, Andrew C.; Stahl, Shannon S.; Hammes-Schiffer, Sharon

    2016-11-10

    Quinones participate in diverse electron transfer and proton-coupled electron transfer processes in chemistry and biology. An experimental study of common quinones reveals a non-linear correlation between the 1 e and 2 e/2 H+ reduction potentials. This unexpected observation prompted a computational study of 128 different quinones, probing their 1 e reduction potentials, pKa values, and 2 e/2 H+ reduction potentials. The density functional theory calculations reveal an approximately linear correlation between these three properties and an effective Hammett constant associated with the quinone substituent(s). However, deviations from this linear scaling relationship are evident for quinones that feature halogen substituents, charged substituents, intramolecular hydrogen bonding in the hydroquinone, and/or sterically bulky substituents. These results, particularly the different substituent effects on the 1 e versus 2 e /2 H+ reduction potentials, have important implications for designing quinones with tailored redox properties.

  20. Investigations on some metabolites of Tecoma stans Juss. callus tissue. Part II. Chromatographical analysis of alkaloid and quinone compounds

    Directory of Open Access Journals (Sweden)

    Barbara Dohnal

    2015-01-01

    Full Text Available Tecoma stans Juss. callus tissue grown on Murashige-Mei Lie Lin (M-L and Murashige-Skoog (RT-k medium supplemented with Tecoma alkaloid precursors like lysine, mevalonic acid lactone and quinolinic acid, were investigated for their alkaloid content by thin-layer (TLC and paper (PC chromatography methods. The results were compared with those obtained by parallel analysis of greenhouse plant leaves. Seven alkaloid spots were detected in the leaf extracts, namely: actinidine, 4-noractinidine, boschniakine, tecomanine, two spots of skytanthine derivatives and one unidentified spot. Only l spot corresponding to skytanthine derivatives appeard in the extracts of callus tissues cultured on basal M-L medium or supplemented with lysine or mevalonic acid lactone. However, 3 alkaloid spots were revealed in extracts of homogeneous parenchyma-like callus tissues obtained o-n, RT-k medium. Beside the skytanthine derivatives rnentioned above, actinidine and tecomanine were identified, and moreover, in callus tissues growing on the same medium (RT-k supplemented with quinolinic acid, boschniakine was found. It was found that T. stans leaves as well as callus tissues cultured on RT-k medium contained traces of lapachol and another quinone-type compound.

  1. Pyrroloquinoline quinone increases the expression and activity of Sirt1 and -3 genes in HepG2 cells.

    Science.gov (United States)

    Zhang, Jian; Meruvu, Sunitha; Bedi, Yudhishtar Singh; Chau, Jason; Arguelles, Andrix; Rucker, Robert; Choudhury, Mahua

    2015-09-01

    Sirtuin (Sirt) 1 and Sirt 3 are nicotinamide adenine dinucleotide ((+))-dependent protein deacetylases that are important to a number of mitochondrial-related functions; thus, identification of sirtuin activators is important. Herein, we hypothesize that pyrroloquinoline quinone (PQQ) can act as a Sirt1/Sirt3 activator. In HepG2 cell cultures, PQQ increased the expression of Sirt1 and Sirt3 gene, protein, and activity levels (P < .05). We also observed a significant increase in nicotinamide phosphoribosyltransferase gene expression (as early as 18 hours) and increased NAD(+) activity at 24 hours. In addition, targets of Sirt1 and Sirt3 (peroxisome proliferator-activated receptor γ coactivator 1α, nuclear respiratory factor 1 and 2, and mitochondrial transcription factor A) were increased at 48 hours. This is the first report that demonstrates PQQ as an activator of Sirt1 and Sirt3 expression and activity, making it an attractive therapeutic agent for the treatment of metabolic diseases and for healthy aging. Based on our study and the available data in vivo, PQQ has the potential to serve as a therapeutic nutraceutical, when enhancing mitochondrial function.

  2. Quinone-modified NH2-MIL-101(Fe) composite as a redox mediator for improved degradation of bisphenol A.

    Science.gov (United States)

    Li, Xianghui; Guo, Weilin; Liu, Zhonghua; Wang, Ruiqin; Liu, Hua

    2017-02-15

    A novel quinone-modified metal-organic frameworks NH2-MIL-101(Fe) was synthesized using a simple chemical method under mild condition. The introduced 2-anthraquinone sulfonate (AQS) can be covalently modified with NH2-MIL-101(Fe) and acts as a redox mediator to enhance the degradation of bisphenol A (BPA) via persulfate activation. The obtained AQS-NH-MIL-101(Fe) was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectra, cyclic voltammetry and electrochemical impedance spectroscopy. AQS-NH-MIL-101(Fe) exhibited better catalytic performance compared with NH2-MIL-101(Fe) and NH2-MIL-101(Fe) with free AQS (NH2-MIL-101(Fe)/AQS). That is, AQS-NH-MIL-101(Fe) was proved to be the most effective in that more than 97.7% of BPA was removed. The degradation rate constants (k) of AQS-NH-MIL-101(Fe) was 9-fold higher than that of NH2-MIL-101(Fe) and 7-fold higher than NH2-MIL-101(Fe)/AQS, indicating that AQS is a great electron-transfer mediator when modified with NH2-MIL-101(Fe). Based on the above results, the possible mechanism of catalytic reaction has been investigated in view of the trapping experiments. In addition, the AQS-NH-MIL-101(Fe) catalyst exhibited excellent stability and can be used several times without significant deterioration in performance.

  3. Role of Quinones in Electron Transfer of PQQ–Glucose Dehydrogenase Anodes—Mediation or Orientation Effect

    Energy Technology Data Exchange (ETDEWEB)

    Babanova, Sofia; Matanovic, Ivana; Chavez, Madelaine Seow; Atanassov, Plamen

    2015-06-24

    In this study, the influence of two quinones (1,2- and 1,4-benzoquinone) on the operation and mechanism of electron transfer in PQQ-dependent glucose dehydrogenase (PQQ–sGDH) anodes has been determined. Benzoquinones were experimentally explored as mediators present in the electrolyte. The electrochemical performance of the PQQ–sGDH anodes with and without the mediators was examined and for the first time molecular docking simulations were used to gain a fundamental understanding to explain the role of the mediator molecules in the design and operation of the enzymatic electrodes. It was proposed that the higher performance of the PQQ–sGDH anodes in the presence of 1,2- and 1,4-benzoquinones introduced in the solution is due to the shorter distance between these molecules and PQQ in the enzymatic molecule. It was also hypothesized that when 1,4-benzoquinone is adsorbed on a carbon support, it would play the dual role of a mediator and an orienting agent. At the same time, when 1,2-benzoquinone and ubiquinone are adsorbed on the electrode surface, the enzyme would transfer the electrons directly to the support, and these molecules would primarily play the role of an orienting agent.

  4. Profiles of Glucosinolates, Their Hydrolysis Products, and Quinone Reductase Inducing Activity from 39 Arugula (Eruca sativa Mill.) Accessions.

    Science.gov (United States)

    Ku, Kang-Mo; Kim, Moo Jung; Jeffery, Elizabeth H; Kang, Young-Hwa; Juvik, John A

    2016-08-31

    Glucosinolates, their hydrolysis product concentrations, and the quinone reductase (QR) inducing activity of extracts of leaf tissue were assayed from 39 arugula (Eruca sativa Mill.) accessions. Arugula accessions from Mediterranean countries (n = 16; Egypt, Greece, Italy, Libya, Spain, and Turkey) and Northern Europe (n = 2; Poland and United Kingdom) were higher in glucosinolates and their hydrolysis products, especially glucoraphanin and sulforaphane, compared to those from Asia (n = 13; China, India, and Pakistan) and Middle East Asia (n = 8; Afghanistan, Iran, and Israel). The QR inducing activity was also the highest in Mediterranean and Northern European arugula accessions, possibly due to a significant positive correlation between sulforaphane and QR inducing activity (r = 0.54). No nitrile hydrolysis products were found, suggesting very low or no epithiospecifier protein activity from these arugula accessions. Broad sense heritability (H(2)) was estimated to be 0.91-0.98 for glucoinolates, 0.55-0.83 for their hydrolysis products, and 0.90 for QR inducing activity.

  5. Synthesis, spectral characterization, molecular structure and pharmacological studies of N'-(1, 4-naphtho-quinone-2yl) isonicotinohyWdrazide

    Science.gov (United States)

    Kavitha Rani, P. R.; Fernandez, Annette; George, Annie; Remadevi, V. K.; Sudarsanakumar, M. R.; Laila, Shiny P.; Arif, Muhammed

    2015-01-01

    A simple and efficient procedure was employed for the synthesis of N'-(1,4-naphtho-quinone-2-yl) isonicotinohydrazide (NIH) by the reaction of 2-hydroxy-1,4-naphthaquinone (lawsone) and isonicotinoyl hydrazine in methanol using ultrasonic irradiation. Lawsone is the principal dye, isolated from the leaves of henna (Lawsonia inermis). Structural modification was done on the molecule aiming to get a more active derivative. The structure of the parent compound and the derivative was characterized by elemental analyses, infrared, electronic, 1H, 13C NMR and GC-MS spectra. The fluorescence spectral investigation of the compound was studied in DMSO and ethanol. Single crystal X-ray diffraction studies reveal that NIH crystallizes in monoclinic space group. The DNA cleavage study was monitored by gel electrophoresis method. The synthesized compound was found to have significant antioxidant activity against DPPH radical (IC50 = 58 μM). The in vitro cytotoxic studies of the derivative against two human cancer cell lines MCF-7 (human breast cancer) and HCT-15 (human colon carcinoma cells) using MTT assay revealed that the compound exhibited higher cytotoxic activity with a lower IC50 value indicating its efficiency in killing the cancer cells even at low concentrations. These results suggest that the structural modifications performed on lawsone could be considered a good strategy to obtain a more active drug.

  6. A Sulfur Heterocyclic Quinone Cathode and a Multifunctional Binder for a High-Performance Rechargeable Lithium-Ion Battery.

    Science.gov (United States)

    Ma, Ting; Zhao, Qing; Wang, Jianbin; Pan, Zeng; Chen, Jun

    2016-05-23

    We report a rational design of a sulfur heterocyclic quinone (dibenzo[b,i]thianthrene-5,7,12,14-tetraone=DTT) used as a cathode (uptake of four lithium ions to form Li4 DTT) and a conductive polymer [poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)= PSS) used as a binder for a high-performance rechargeable lithium-ion battery. Because of the reduced energy level of the lowest unoccupied molecular orbital (LUMO) caused by the introduced S atoms, the initial Li-ion intercalation potential of DTT is 2.89 V, which is 0.3 V higher than that of its carbon analog. Meanwhile, there is a noncovalent interaction between DTT and PSS, which remarkably suppressed the dissolution and enhanced the conductivity of DTT, thus leading to the great improvement of the electrochemical performance. The DTT cathode with the PSS binder displays a long-term cycling stability (292 mAh g(-1) for the first cycle, 266 mAh g(-1) after 200 cycles at 0.1 C) and a high rate capability (220 mAh g(-1) at 1 C). This design strategy based on a noncovalent interaction is very effective for the application of small organic molecules as the cathode of rechargeable lithium-ion batteries. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. NAD(P)H quinone oxidoreductase 1 inhibits the proteasomal degradation of homocysteine-induced endoplasmic reticulum protein

    Energy Technology Data Exchange (ETDEWEB)

    Maeda, Tomoji, E-mail: t-maeda@nichiyaku.ac.jp [Department of Neuroscience, School of Pharmacy, Iwate Medical University, 2-1-1 Nishitokuta, Yahaba-Cho, Shiwagun, Iwate, 028-3603 (Japan); Tanabe-Fujimura, Chiaki; Fujita, Yu; Abe, Chihiro; Nanakida, Yoshino; Zou, Kun; Liu, Junjun; Liu, Shuyu [Department of Neuroscience, School of Pharmacy, Iwate Medical University, 2-1-1 Nishitokuta, Yahaba-Cho, Shiwagun, Iwate, 028-3603 (Japan); Nakajima, Toshihiro [Institute of Medical Science, Tokyo Medical University, 6-1-1 Shinjyuku, Shinjyuku, Tokyo, Tokyo, 160-8402 (Japan); Komano, Hiroto, E-mail: hkomano@iwate-med.ac.jp [Department of Neuroscience, School of Pharmacy, Iwate Medical University, 2-1-1 Nishitokuta, Yahaba-Cho, Shiwagun, Iwate, 028-3603 (Japan)

    2016-05-13

    Homocysteine-induced endoplasmic reticulum (ER) protein (Herp) is an ER stress-inducible key regulatory component of ER-associated degradation (ERAD) that has been implicated in insulin hypersecretion in diabetic mouse models. Herp expression is tightly regulated. Additionally, Herp is a highly labile protein and interacts with various proteins, which are characteristic features of ubiquitinated protein. Previously, we reported that ubiquitination is not required for Herp degradation. In addition, we found that the lysine residues of Herp (which are ubiquitinated by E3 ubiquitin ligase) are not sufficient for regulation of Herp degradation. In this study, we found that NAD(P)H quinone oxidoreductase 1 (NQO1)-mediated targeting of Herp to the proteasome was involved in Herp degradation. In addition, we found that Herp protein levels were markedly elevated in synoviolin-null cells. The E3 ubiquitin ligase synoviolin is a central component of ERAD and is involved in the degradation of nuclear factor E2-related factor-2 (Nrf2), which regulates cellular reactive oxygen species. Additionally, NQO1 is a target of Nrf2. Thus, our findings indicated that NQO1 could stabilize Herp protein expression via indirect regulation of synoviolin. -- Highlights: •Herp interacts with NQO1. •NQO1 regulates Herp degradation.

  8. Structure-based de novo design, molecular docking and molecular dynamics of primaquine analogues acting as quinone reductase II inhibitors.

    Science.gov (United States)

    Murce, Erika; Cuya-Guizado, Teobaldo Ricardo; Padilla-Chavarria, Helmut Isaac; França, Tanos Celmar Costa; Pimentel, Andre Silva

    2015-11-01

    Primaquine is a traditional antimalarial drug with low parasitic resistance and generally good acceptance at higher doses, which has been used for over 60 years in malaria treatment. However, several limitations related to its hematotoxicity have been reported. It is believed that this toxicity comes from the hydroxylation of the C-5 and C-6 positions of its 8-aminoquinoline ring before binding to the molecular target: the quinone reductase II (NQO2) human protein. In this study we propose primaquine derivatives, with substitution at position C-6 of the 8-aminoquinoline ring, planned to have better binding to NQO2, compared to primaquine, but with a reduced toxicity related to the C-5 position being possible to be oxidized. On this sense the proposed analogues were suggested in order to reduce or inhibit hydroxylation and further oxidation to hemotoxic metabolites. Five C-6 substituted primaquine analogues were selected by de novo design and further submitted to docking and molecular dynamics simulations. Our results suggest that all analogues bind better to NQO2 than primaquine and may become better antimalarials. However, the analogues 3 and 4 are predicted to have a better activity/toxicity balance.

  9. Design, synthesis, and biological evaluation of resveratrol analogues as aromatase and quinone reductase 2 inhibitors for chemoprevention of cancer

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Bin; Hoshino, Juma; Jermihov, Katie; Marler, Laura; Pezzuto, John M.; Mesecar, Andrew D.; Cushman, Mark (Hawaii); (Purdue); (UIC)

    2012-07-11

    A series of new resveratrol analogues were designed and synthesized and their inhibitory activities against aromatase were evaluated. The crystal structure of human aromatase (PDB 3eqm) was used to rationalize the mechanism of action of the aromatase inhibitor 32 (IC{sub 50} 0.59 {mu}M) through docking, molecular mechanics energy minimization, and computer graphics molecular modeling, and the information was utilized to design several very potent inhibitors, including compounds 82 (IC{sub 50} 70 nM) and 84 (IC{sub 50} 36 nM). The aromatase inhibitory activities of these compounds are much more potent than that for the lead compound resveratrol, which has an IC{sub 50} of 80 {mu}M. In addition to aromatase inhibitory activity, compounds 32 and 44 also displayed potent QR2 inhibitory activity (IC{sub 50} 1.7 {mu}M and 0.27 {mu}M, respectively) and the high-resolution X-ray structures of QR2 in complex with these two compounds provide insight into their mechanism of QR2 inhibition. The aromatase and quinone reductase inhibitors resulting from these studies have potential value in the treatment and prevention of cancer.

  10. Central role of the Na(+)-translocating NADH:quinone oxidoreductase (Na(+)-NQR) in sodium bioenergetics of Vibrio cholerae.

    Science.gov (United States)

    Steuber, Julia; Halang, Petra; Vorburger, Thomas; Steffen, Wojtek; Vohl, Georg; Fritz, Günter

    2014-12-01

    Vibrio cholerae is a Gram-negative bacterium that lives in brackish or sea water environments. Strains of V. cholerae carrying the pathogenicity islands infect the human gut and cause the fatal disease cholera. Vibrio cholerae maintains a Na(+) gradient at its cytoplasmic membrane that drives substrate uptake, motility, and efflux of antibiotics. Here, we summarize the major Na(+)-dependent transport processes and describe the central role of the Na(+)-translocating NADH:quinone oxidoreductase (Na(+)-NQR), a primary Na(+) pump, in maintaining a Na(+)-motive force. The Na(+)-NQR is a membrane protein complex with a mass of about 220 kDa that couples the exergonic oxidation of NADH to the transport of Na(+) across the cytoplasmic membrane. We describe the molecular architecture of this respiratory complex and summarize the findings how electron transport might be coupled to Na(+)-translocation. Moreover, recent advances in the determination of the three-dimensional structure of this complex are reported.

  11. Pyrroloquinoline quinone and a quinoprotein kinase support γ-radiation resistance in Deinococcus radiodurans and regulate gene expression.

    Science.gov (United States)

    Rajpurohit, Yogendra Singh; Desai, Shruti Sumeet; Misra, Hari Sharan

    2013-06-01

    Deinococcus radiodurans is known for its extraordinary resistance to various DNA damaging agents including γ-radiation and desiccation. The pqqE:cat and Δdr2518 mutants making these cells devoid of pyrroloquinoline quinone (PQQ) and a PQQ inducible Ser/Thr protein kinase, respectively, became sensitive to γ-radiation. Transcriptome analysis of these mutants showed differential expression of the genes including those play roles in oxidative stress tolerance and (DSB) repair in D. radiodurans and in genome maintenance and stress response in other bacteria. Escherichia coli cells expressing DR2518 and PQQ showed improved resistance to γ-radiation, which increased further when both DR2518 and PQQ were present together. Although, profiles of genes getting affected in these mutants were different, there were still a few common genes showing similar expression trends in both the mutants and some others as reported earlier in oxyR and pprI mutant of this bacterium. These results suggested that PQQ and DR2518 have independent roles in γ-radiation resistance of D. radiodurans but their co-existence improves radioresistance further, possibly by regulating differential expression of the genes important for bacterial response to oxidative stress and DNA damage. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Leflunomide induces NAD(P)H quinone dehydrogenase 1 enzyme via the aryl hydrocarbon receptor in neonatal mice.

    Science.gov (United States)

    Shrestha, Amrit Kumar; Patel, Ananddeep; Menon, Renuka T; Jiang, Weiwu; Wang, Lihua; Moorthy, Bhagavatula; Shivanna, Binoy

    2017-03-25

    Aryl hydrocarbon receptor (AhR) has been increasingly recognized to play a crucial role in normal physiological homeostasis. Additionally, disrupted AhR signaling leads to several pathological states in the lung and liver. AhR activation transcriptionally induces detoxifying enzymes such as cytochrome P450 (CYP) 1A and NAD(P)H quinone dehydrogenase 1 (NQO1). The toxicity profiles of the classical AhR ligands such as 3-methylcholanthrene and dioxins limit their use as a therapeutic agent in humans. Hence, there is a need to identify nontoxic AhR ligands to develop AhR as a clinically relevant druggable target. Recently, we demonstrated that leflunomide, a FDA approved drug, used to treat rheumatoid arthritis in humans, induces CYP1A enzymes in adult mice via the AhR. However, the mechanisms by which this drug induces NQO1 in vivo are unknown. Therefore, we tested the hypothesis that leflunomide will induce pulmonary and hepatic NQO1 enzyme in neonatal mice via AhR-dependent mechanism(s). Leflunomide elicited significant induction of pulmonary CYP1A1 and NQO1 expression in neonatal mice. Interestingly, the dose at which leflunomide increased NQO1 was significantly higher than that required to induce CYP1A1 enzyme. Likewise, it also enhanced hepatic CYP1A1, 1A2 and NQO1 expression in WT mice. In contrast, leflunomide failed to induce these enzymes in AhR-null mice. Our results indicate that leflunomide induces pulmonary and hepatic CYP1A and NQO1 enzymes via the AhR in neonatal mice. These findings have important implications to prevent and/or treat disorders such as bronchopulmonary dysplasia in human infants where AhR may play a crucial role in the disease pathogenesis.

  13. Inhibitory effects of different forms of tocopherols, tocopherol phosphates, and tocopherol quinones on growth of colon cancer cells.

    Science.gov (United States)

    Dolfi, Sonia C; Yang, Zhihong; Lee, Mao-Jung; Guan, Fei; Hong, Jungil; Yang, Chung S

    2013-09-11

    Tocopherols are the major source of dietary vitamin E. In this study, the growth inhibitory effects of different forms of tocopherols (T), tocopheryl phosphates (TP), and tocopherol quinones (TQ) on human colon cancer HCT116 and HT29 cells were investigated. δ-T was more active than γ-T in inhibiting colon cancer cell growth, decreasing cancer cell colony formation, and inducing apoptosis; however, α-T was rather ineffective. Similarly, the rate of cellular uptake also followed the ranking order δ-T > γ-T ≫ α-T. TP and TQ generally had higher inhibitory activities than their parent compounds. Interestingly, the γ forms of TP and TQ were more active than the δ forms in inhibiting cancer cell growth, whereas the α forms were the least effective. The potencies of γ-TQ and δ-TQ (showing IC50 values of ∼0.8 and ∼2 μM on HCT116 cells after a 72 h incubation, respectively) were greater than 100-fold and greater than 20-fold higher, respectively, than those of their parent tocopherols. Induction of cancer cell apoptosis by δ-T, γ-TP, and γ-TQ was characterized by the cleavage of caspase 3 and PARP1 and DNA fragmentation. These studies demonstrated the higher growth inhibitory activity of δ-T than γ-T, the even higher activities of the γ forms of TP and TQ, and the ineffectiveness of the α forms of tocopherol and their metabolites against colon cancer cells.

  14. Effects of dietary pyrroloquinoline quinone disodium on growth performance, carcass yield and antioxidant status of broiler chicks.

    Science.gov (United States)

    Samuel, K G; Zhang, H J; Wang, J; Wu, S G; Yue, H Y; Sun, L L; Qi, G H

    2015-03-01

    Pyrroloquinoline quinone (PQQ), a putative essential nutrient and redox modulator in microorganisms, cell and animal models, has been recognized as a growth promoter in rodents. Growth performance, carcass yield and antioxidant status were evaluated on broiler chickens fed different levels of PQQ disodium (PQQ.Na2). A total of 784 day-old male Arbor Acres (AA) broilers were randomly allotted into seven dietary groups: negative control group (NC) fed a basal diet without virginiamycin (VIR) or PQQ.Na2; a positive control group (PC) fed a diet with 15 mg of VIR/kg diet; and PQQ.Na2 groups fed with 0.05, 0.10, 0.20, 0.40 or 0.80 mg PQQ.Na2/kg diet. Each treatment contained eight replicates with 14 birds each. The feeding trial lasted for 6 weeks. The results showed that chicks fed 0.2 mg PQQ.Na2/kg diet significantly improved growth performance comparable to those in PC group, and the feed efficiency enhancement effects of dietary PQQ.Na2 was more apparent in grower phase. Dietary addition of PQQ.Na2 had the potential to stimulate immune organs development, and low level dietary addition (<0.1 mg/kg) increased plasma lysozyme level. Broilers fed 0.2 mg PQQ.Na2/kg diet gained more carcasses at day 42, and had lower lipid peroxide malondialdehyde content and higher total antioxidant power in plasma. The results indicated that dietary PQQ.Na2 (0.2 mg/kg diet) had the potential to act as a growth promoter comparable to antibiotic in broiler chicks.

  15. Residue-free wines: fate of some quinone outside inhibitor (QoI) fungicides in the winemaking process.

    Science.gov (United States)

    Garau, Vincenzo Luigi; De Melo Abreu, Susana; Caboni, Pierluigi; Angioni, Alberto; Alves, Arminda; Cabras, Paolo

    2009-03-25

    The fate of three fungicide residues (fenamidone, pyraclostrobin, and trifloxystrobin) from vine to wine was studied to evaluate the decay ratio and the influence of the technological process. The aim of this work was to identify pesticides that can degrade rapidly or be eliminated together with byproduct (lees and cake) of the winemaking process to obtain wine free of residues. The disappearance rate on grapes was calculated as pseudo-first-order kinetics, and the half-life (t(1/2)) was in the range from 5.4 +/- 1.9 to 12.2 +/- 1.2 days. The mechanism of dissipation of the three quinone outside inhibitor (QoI) fungicides was studied using different model systems. It was observed that the main mechanism responsible for disappearance was photodegradation. For active ingredients (ai) the half-lives of fenamidone, pyraclostrobin, and trifloxystrobin were 10.2 +/- 0.8, 20.1 +/- 0.1, and 8.6 +/- 1.0 h, respectively, whereas for formulation higher half-lives were observed when epicuticular waxes were present (from 13.8 +/- 0.2 to 26.6 +/- 0.1 h). After winemaking, fenamidone, pyraclostrobin, and trifloxystrobin residues were not detected in the wine, but they were present in the cake and lees. This was due to the adsorption of pesticide residues to the solid parts, which are always eliminated at the end of the alcoholic fermentation. The data obtained in these experiments suggest that these three active ingredients could be used in a planning process to obtain residue-free wines.

  16. Cooperation of NAD(P)H:quinone oxidoreductase 1 and UDP-glucuronosyltransferases reduces menadione cytotoxicity in HEK293 cells.

    Science.gov (United States)

    Nishiyama, Takahito; Izawa, Tadashi; Usami, Mami; Ohnuma, Tomokazu; Ogura, Kenichiro; Hiratsuka, Akira

    2010-04-01

    Previous studies have shown that NAD(P)H:quinone oxidoreductase 1 (NQO1) plays an important role in the detoxification of menadione (2-methyl-1,4-naphthoquinone, also known as vitamin K3). However, menadiol (2-methyl-1,4-naphthalenediol) formed from menadione by NQO1-mediated reduction continues to be an unstable substance, which undergoes the reformation of menadione with concomitant formation of reactive oxygen species (ROS). Hence, we focused on the roles of phase II enzymes, with particular attention to UDP-glucuronosyltransferases (UGTs), in the detoxification process of menadione. In this study, we established an HEK293 cell line stably expressing NQO1 (HEK293/NQO1) and HEK293/NQO1 cell lines with doxycycline (DOX)-regulated expression of UGT1A6 (HEK293/NQO1/UGT1A6) and UGT1A10 (HEK293/NQO1/UGT1A10), and evaluated the role of NQO1 and UGTs against menadione-induced cytotoxicity. Our results differed from those of previous studies. HEK293/NQO1 was the most sensitive cell line to menadione cytotoxicity among cell lines established in this study. These phenomena were also observed in HEK293/NQO1/UGT1A6 and HEK293/NQO1/UGT1A10 cells in which the expression of UGT was suppressed by DOX treatment. On the contrary, HEK293/NQO1/UGT1A6 and HEK293/NQO1/UGT1A10 cells without DOX treatment were resistant to menadione-induced cytotoxicity. These results demonstrated that NQO1 is not a detoxification enzyme for menadione and that UGT-mediated glucuronidation of menadiol is the most important detoxification process.

  17. Riboflavin is an active redox cofactor in the Na+-pumping NADH: quinone oxidoreductase (Na+-NQR) from Vibrio cholerae.

    Science.gov (United States)

    Juárez, Oscar; Nilges, Mark J; Gillespie, Portia; Cotton, Jennifer; Barquera, Blanca

    2008-11-28

    Here we present new evidence that riboflavin is present as one of four flavins in Na+-NQR. In particular, we present conclusive evidence that the source of the neutral radical is not one of the FMNs and that riboflavin is the center that gives rise to the neutral flavosemiquinone. The riboflavin is a bona fide redox cofactor and is likely to be the last redox carrier of the enzyme, from which electrons are donated to quinone. We have constructed a double mutant that lacks both covalently bound FMN cofactors (NqrB-T236Y/NqrC-T225Y) and have studied this mutant together with the two single mutants (NqrB-T236Y and NqrC-T225Y) and a mutant that lacks the noncovalently bound FAD in NqrF (NqrF-S246A). The double mutant contains riboflavin and FAD in a 0.6:1 ratio, as the only flavins in the enzyme; noncovalently bound flavins were detected. In the oxidized form, the double mutant exhibits an EPR signal consistent with a neutral flavosemiquinone radical, which is abolished on reduction of the enzyme. The same radical can be observed in the FAD deletion mutant. Furthermore, when the oxidized enzyme reacts with ubiquinol (the reduced form of the usual electron acceptor) in a process that reverses the physiological direction of the electron flow, a single kinetic phase is observed. The kinetic difference spectrum of this process is consistent with one-electron reduction of a neutral flavosemiquinone. The presence of riboflavin in the role of a redox cofactor is thus far unique to Na+-NQR.

  18. Prodrugs Bioactivated to Quinones Target NF-κB and Multiple Protein Networks: Identification of the Quinonome.

    Science.gov (United States)

    Pierce, Emily N; Piyankarage, Sujeewa C; Dunlap, Tareisha; Litosh, Vladislav; Siklos, Marton I; Wang, Yue-Ting; Thatcher, Gregory R J

    2016-07-18

    Electrophilic reactive intermediates resulting from drug metabolism have been associated with toxicity and off-target effects and in some drug discovery programs trigger NO-GO decisions. Many botanicals and dietary supplements are replete with such reactive electrophiles, notably Michael acceptors, which have been demonstrated to elicit chemopreventive mechanisms; and Michael acceptors are gaining regulatory approval as contemporary cancer therapeutics. Identifying protein targets of these electrophiles is central to understanding potential therapeutic benefit and toxicity risk. NO-donating NSAID prodrugs (NO-NSAIDs) have been the focus of extensive clinical and preclinical studies in inflammation and cancer chemoprevention and therapy: a subset exemplified by pNO-ASA, induces chemopreventive mechanisms following bioactivation to an electrophilic quinone methide (QM) Michael acceptor. Having previously shown that these NO-independent, QM-donors activated Nrf2 via covalent modification of Keap-1, we demonstrate that components of canonical NF-κB signaling are also targets, leading to the inhibition of NF-κB signaling. Combining bio-orthogonal probes of QM-donor ASA prodrugs with mass spectrometric proteomics and pathway analysis, we proceeded to characterize the quinonome: the protein cellular targets of QM-modification by pNO-ASA and its ASA pro-drug congeners. Further comparison was made using a biorthogonal probe of the "bare-bones", Michael acceptor, and clinical anti-inflammatory agent, dimethyl fumarate, which we have shown to inhibit NF-κB signaling. Identified quinonome pathways include post-translational protein folding, cell-death regulation, protein transport, and glycolysis; and identified proteins included multiple heat shock elements, the latter functionally confirmed by demonstrating activation of heat shock response.

  19. Quercetin 7-O-glucoside suppresses nitrite-induced formation of dinitrosocatechins and their quinones in catechin/nitrite systems under stomach simulating conditions.

    Science.gov (United States)

    Morina, Filis; Takahama, Umeo; Yamauchi, Ryo; Hirota, Sachiko; Veljovic-Jovanovic, Sonja

    2015-01-01

    Foods of plant origin contain flavonoids. In the adzuki bean, (+)-catechin, quercetin 3-O-rutinoside (rutin), and quercetin 7-O-β-D-glucopyranoside (Q7G) are the major flavonoids. During mastication of foods prepared from the adzuki bean, the flavonoids are mixed with saliva and swallowed into the stomach. Here we investigated the interactions between Q7G and (+)-catechin at pH 2, which may proceed in the stomach after the ingestion of foods prepared from the adzuki bean. Q7G reacted with nitrous acid producing nitric oxide (˙NO) and a glucoside of 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxy-3(2H)-benzofuranone. (+)-Catechin reacted with nitrous acid producing ˙NO and 6,8-dinitrosocatechin. The production of the dinitrosocatechin was partly suppressed by Q7G, and the suppression resulted in the enhancement of Q7G oxidation. 6,8-Dinitrosocatechin reacted further with nitrous acid generating the o-quinone, and the quinone formation was effectively suppressed by Q7G. In the flavonoids investigated, the suppressive effect decreased in the order Q7G≈quercetin>kaempferol>quercetin 4'-O-glucoside>rutin. Essentially the same results were obtained when (-)-epicatechin was used instead of (+)-catechin. The results indicate that nitrous acid-induced formation of 6,8-dinitrosocatechins and the o-quinones can be suppressed by flavonols in the stomach, and that both a hydroxyl group at C3 and ortho-hydroxyl groups in the B-ring are required for efficient suppression.

  20. An isotope-edited FTIR investigation of the role of Ser-L223 in binding quinone (QB) and semiquinone (QB-) in the reaction center from Rhodobacter sphaeroides.

    Science.gov (United States)

    Nabedryk, Eliane; Paddock, Mark L; Okamura, Melvin Y; Breton, Jacques

    2005-11-08

    In the photosynthetic reaction center (RC) from the purple bacterium Rhodobacter sphaeroides, proton-coupled electron-transfer reactions occur at the secondary quinone (Q(B)) site. Several nearby residues are important for both binding and redox chemistry involved in the light-induced conversion from Q(B) to quinol Q(B)H(2). Ser-L223 is one of the functionally important residues located near Q(B). To obtain information on the interaction between Ser-L223 and Q(B) and Q(B)(-), isotope-edited Q(B)(-)/Q(B) FTIR difference spectra were measured in a mutant RC in which Ser-L223 is replaced with Ala and compared to the native RC. The isotope-edited IR fingerprint spectra for the C=O [see text] and C=C [see text] modes of Q(B) (Q(B)(-)) in the mutant are essentially the same as those of the native RC. These findings indicate that highly equivalent interactions of Q(B) and Q(B)(-) with the protein occur in both native and mutant RCs. The simplest explanation of these results is that Ser-L223 is not hydrogen bonded to Q(B) or Q(B)(-) but presumably forms a hydrogen bond to a nearby acid group, preferentially Asp-L213. The rotation of the Ser OH proton from Asp-L213 to Q(B)(-) is expected to be an important step in the proton transfer to the reduced quinone. In addition, the reduced quinone remains firmly bound, indicating that other distinct hydrogen bonds are more important for stabilizing Q(B)(-). Implications on the design features of the Q(B) binding site are discussed.

  1. Dopamine as a potent inducer of cellular glutathione and NAD(P)H:quinone oxidoreductase 1 in PC12 neuronal cells: a potential adaptive mechanism for dopaminergic neuroprotection.

    Science.gov (United States)

    Jia, Zhenquan; Zhu, Hong; Misra, Bhaba R; Li, Yunbo; Misra, Hara P

    2008-11-01

    Dopamine auto-oxidation and the consequent formation of reactive oxygen species and electrophilic quinone molecules have been implicated in dopaminergic neuronal cell death in Parkinson's disease. We reported here that in PC12 dopaminergic neuronal cells dopamine at noncytotoxic concentrations (50-150 muM) potently induced cellular glutathione (GSH) and the phase 2 enzyme NAD(P)H:quinone oxidoreductase 1 (NQO1), two critical cellular defenses in detoxification of ROS and electrophilic quinone molecules. Incubation of PC12 cells with dopamine also led to a marked increase in the mRNA levels for gamma-glutamylcysteine ligase catalytic subunit (GCLC) and NQO1. In addition, treatment of PC12 cells with dopamine resulted in a significant elevation of GSH content in the mitochondrial compartment. To determine whether treatment with dopamine at noncytotoxic concentrations, which upregulated the cellular defenses could protect the neuronal cells against subsequent lethal oxidative and electrophilic injury, PC12 cells were pretreated with dopamine (150 muM) for 24 h and then exposed to various cytotoxic concentrations of dopamine or 6-hydroxydopamine (6-OHDA). We found that pretreatment of PC12 cells with dopamine at a noncytotoxic concentration led to a remarkable protection against cytotoxicity caused by dopamine or 6-OHDA at lethal concentrations, as detected by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium reduction assay. In view of the critical roles of GSH and NQO1 in protecting against dopaminergic neuron degeneration, the above findings implicate that upregulation of both GSH and NQO1 by dopamine at noncytotoxic concentrations may serve as an important adaptive mechanism for dopaminergic neuroprotection.

  2. Role of the NAD(P)H quinone oxidoreductase NQR and the cytochrome b AIR12 in controlling superoxide generation at the plasma membrane.

    Science.gov (United States)

    Biniek, Catherine; Heyno, Eiri; Kruk, Jerzy; Sparla, Francesca; Trost, Paolo; Krieger-Liszkay, Anja

    2017-04-01

    The quinone reductase NQR and the b-type cytochrome AIR12 of the plasma membrane are important for the control of reactive oxygen species in the apoplast. AIR12 and NQR are two proteins attached to the plant plasma membrane which may be important for generating and controlling levels of reactive oxygen species in the apoplast. AIR12 (Auxin Induced in Root culture) is a single gene of Arabidopsis that codes for a mono-heme cytochrome b. The NADPH quinone oxidoreductase NQR is a two-electron-transferring flavoenzyme that contributes to the generation of O 2(•-) in isolated plasma membranes. A. thaliana double knockout plants of both NQR and AIR12 generated more O 2(•-) and germinated faster than the single mutant affected in AIR12. To test whether NQR and AIR12 are able to interact functionally, recombinant purified proteins were added to plasma membranes isolated from soybean hypocotyls. In vitro NADH-dependent O 2(•-) production at the plasma membrane in the presence of NQR was reduced upon addition of AIR12. Electron donation from semi-reduced menadione to AIR12 was shown to take place. Biochemical analysis showed that purified plasma membrane from soybean hypocotyls or roots contained phylloquinone and menaquinone-4 as redox carriers. This is the first report on the occurrence of menaquinone-4 in eukaryotic photosynthetic organisms. We propose that NQR and AIR12 interact via the quinone, allowing an electron transfer from cytosolic NAD(P)H to apoplastic monodehydroascorbate and control thereby the level of reactive oxygen production and the redox state of the apoplast.

  3. Investigation of the cumulative body burden of estrogen-3,4-quinone in breast cancer patients and controls using albumin adducts as biomarkers.

    Science.gov (United States)

    Lin, Che; Chen, Dar-Ren; Hsieh, Wei-Chung; Yu, Wen-Fa; Lin, Ching-Chiuan; Ko, Mao-Huei; Juan, Chang-Hsin; Tsuang, Ben-Jei; Lin, Po-Hsiung

    2013-04-26

    Both 17β-estradiol-2,3-quinone (E2-2,3-Q) and 17β-estradiol-3,4-quinone (E2-3,4-Q) are reactive metabolites of estrogen. Elevation of E2-3,4-Q to E2-2,3-Q ratio is thought to be an important indicator of estrogen-induced carcinogenesis. Our current study compared the cumulative body burden of these estrogen quinones in serum samples taken from Taiwanese women with breast cancer (n=152) vs healthy controls (n=75) by using albumin (Alb) adducts as biomarkers. Results clearly demonstrated the presence of cysteinyl adducts of E2-2,3-Q-4-S-Alb and E2-3,4-Q-2-S-Alb in all study population at levels ranging from 61.7-1330 to 66.6-1,590 pmol/g, respectively. Correlation coefficient between E2-2,3-Q-4-S-Alb and E2-3,4-Q-2-S-Alb was 0.610 for controls and 0.767 for breast cancer patients (pQ-2-S-Alb was inversely proportional to BMI with about 25% increase in E2-3,4-Q-2-S-Alb per 5 kg/m(2) decrease in BMI (pQ-2-S-Alb in breast cancer patients were ∼5-fold greater than in those of controls (pQ may play a role in the development of breast cancer.

  4. Quinone-dependent D-lactate dehydrogenase Dld (Cg1027 is essential for growth of Corynebacterium glutamicum on D-lactate

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    Oikawa Tadao

    2010-12-01

    Full Text Available Abstract Background Corynebacterium glutamicum is able to grow with lactate as sole or combined carbon and energy source. Quinone-dependent L-lactate dehydrogenase LldD is known to be essential for utilization of L-lactate by C. glutamicum. D-lactate also serves as sole carbon source for C. glutamicum ATCC 13032. Results Here, the gene cg1027 was shown to encode the quinone-dependent D-lactate dehydrogenase (Dld by enzymatic analysis of the protein purified from recombinant E. coli. The absorption spectrum of purified Dld indicated the presence of FAD as bound cofactor. Inactivation of dld resulted in the loss of the ability to grow with D-lactate, which could be restored by plasmid-borne expression of dld. Heterologous expression of dld from C. glutamicum ATCC 13032 in C. efficiens enabled this species to grow with D-lactate as sole carbon source. Homologs of dld of C. glutamicum ATCC 13032 are not encoded in the sequenced genomes of other corynebacteria and mycobacteria. However, the dld locus of C. glutamicum ATCC 13032 shares 2367 bp of 2372 bp identical nucleotides with the dld locus of Propionibacterium freudenreichii subsp. shermanii, a bacterium used in Swiss-type cheese making. Both loci are flanked by insertion sequences of the same family suggesting a possible event of horizontal gene transfer. Conclusions Cg1067 encodes quinone-dependent D-lactate dehydrogenase Dld of Corynebacterium glutamicum. Dld is essential for growth with D-lactate as sole carbon source. The genomic region of dld likely has been acquired by horizontal gene transfer.

  5. Rh(III)-Catalyzed Diastereoselective Annulation of Amides with Quinone Monoacetals: Access to Bridged Nine-Membered Heterocycles via C-H Activation.

    Science.gov (United States)

    Yang, Wei; Dong, Jinhuan; Wang, Jingyi; Xu, Xianxiu

    2017-02-03

    An unprecedented Rh(III)-catalyzed annulation of various benzamides and acrylamides with quinone monoacetals was developed for the facile and efficient one-pot synthesis of bridged nine-membered benzo[c]azonine-1,5(2H)-diones and 2-azabicyclo[4.3.1]dec-4-ene-3,8-diones. It is the first example of synthesis of nine-membered heterocycles through Rh(III)-catalyzed C-H bond functionalization, and both aryl and vinyl C-H bonds are tolerant in this reaction. A plausible mechanism is proposed on the basis of control experiments.

  6. Pyrroloquinoline Quinone Ethanol Dehydrogenase in Methylobacterium extorquens AM1 Extends Lanthanide-Dependent Metabolism to Multicarbon Substrates.

    Science.gov (United States)

    Good, Nathan M; Vu, Huong N; Suriano, Carly J; Subuyuj, Gabriel A; Skovran, Elizabeth; Martinez-Gomez, N Cecilia

    2016-11-15

    Lanthanides are utilized by microbial methanol dehydrogenases, and it has been proposed that lanthanides may be important for other type I alcohol dehydrogenases. A triple mutant strain (mxaF xoxF1 xoxF2; named MDH-3), deficient in the three known methanol dehydrogenases of the model methylotroph Methylobacterium extorquens AM1, is able to grow poorly with methanol if exogenous lanthanides are added to the growth medium. When the gene encoding a putative quinoprotein ethanol dehydrogenase, exaF, was mutated in the MDH-3 background, the quadruple mutant strain could no longer grow on methanol in minimal medium with added lanthanum (La(3+)). ExaF was purified from cells grown with both calcium (Ca(2+)) and La(3+) and with Ca(2+) only, and the protein species were studied biochemically. Purified ExaF is a 126-kDa homodimer that preferentially binds La(3+) over Ca(2+) in the active site. UV-visible spectroscopy indicates the presence of pyrroloquinoline quinone (PQQ) as a cofactor. ExaF purified from the Ca(2+)-plus-La(3+) condition readily oxidizes ethanol and has secondary activities with formaldehyde, acetaldehyde, and methanol, whereas ExaF purified from the Ca(2+)-only condition has minimal activity with ethanol as the substrate and activity with methanol is not detectable. The exaF mutant is not affected for growth with ethanol; however, kinetic and in vivo data show that ExaF contributes to ethanol metabolism when La(3+) is present, expanding the role of lanthanides to multicarbon metabolism. ExaF is the most efficient PQQ-dependent ethanol dehydrogenase reported to date and, to our knowledge, the first non-XoxF-type alcohol oxidation system reported to use lanthanides as a cofactor, expanding the importance of lanthanides in biochemistry and bacterial metabolism beyond methanol dehydrogenases to multicarbon metabolism. These results support an earlier proposal that an aspartate residue near the catalytic aspartate residue may be an indicator of rare

  7. The 2-Methoxy Group Orientation Regulates the Redox Potential Difference between the Primary (QA) and Secondary (QB) Quinones of Type II Bacterial Photosynthetic Reaction Centers

    Science.gov (United States)

    2015-01-01

    Recent studies have shown that only quinones with a 2-methoxy group can act simultaneously as the primary (QA) and secondary (QB) electron acceptors in photosynthetic reaction centers from purple bacteria such as Rb. sphaeroides. 13C HYSCORE measurements of the 2-methoxy group in the semiquinone states, SQA and SQB, were compared with DFT calculations of the 13C hyperfine couplings as a function of the 2-methoxy dihedral angle. X-ray structure comparisons support 2-methoxy dihedral angle assignments corresponding to a redox potential gap (ΔEm) between QA and QB of 175–193 mV. A model having a methyl group substituted for the 2-methoxy group exhibits no electron affinity difference. This is consistent with the failure of a 2-methyl ubiquinone analogue to function as QB in mutant reaction centers with a ΔEm of ∼160–195 mV. The conclusion reached is that the 2-methoxy group is the principal determinant of electron transfer from QA to QB in type II photosynthetic reaction centers with ubiquinone serving as both acceptor quinones. PMID:25126386

  8. The 2-Methoxy Group Orientation Regulates the Redox Potential Difference between the Primary (QA) and Secondary (QB) Quinones of Type II Bacterial Photosynthetic Reaction Centers.

    Science.gov (United States)

    de Almeida, Wagner B; Taguchi, Alexander T; Dikanov, Sergei A; Wraight, Colin A; O'Malley, Patrick J

    2014-08-07

    Recent studies have shown that only quinones with a 2-methoxy group can act simultaneously as the primary (QA) and secondary (QB) electron acceptors in photosynthetic reaction centers from purple bacteria such as Rb. sphaeroides. (13)C HYSCORE measurements of the 2-methoxy group in the semiquinone states, SQA and SQB, were compared with DFT calculations of the (13)C hyperfine couplings as a function of the 2-methoxy dihedral angle. X-ray structure comparisons support 2-methoxy dihedral angle assignments corresponding to a redox potential gap (ΔEm) between QA and QB of 175-193 mV. A model having a methyl group substituted for the 2-methoxy group exhibits no electron affinity difference. This is consistent with the failure of a 2-methyl ubiquinone analogue to function as QB in mutant reaction centers with a ΔEm of ∼160-195 mV. The conclusion reached is that the 2-methoxy group is the principal determinant of electron transfer from QA to QB in type II photosynthetic reaction centers with ubiquinone serving as both acceptor quinones.

  9. Fluorescence quenching studies on the interaction of catechin-quinone with CdTe quantum dots. Mechanism elucidation and feasibility studies.

    Science.gov (United States)

    Dwiecki, Krzysztof; Neunert, Grażyna; Nogala-Kałucka, Małgorzata; Polewski, Krzysztof

    2015-01-01

    Changes of the photoluminescent properties of QD in the presence of oxidized catechin (CQ) were investigated by absorption, steady-state fluorescence, fluorescence lifetime and dynamic light scattering measurements. Photoluminescence intensity and fluorescence lifetime was decreasing with increasing CQ concentration. Dynamic light scattering technique found the hydrodynamic diameter of QD suspension in water is in range of 45 nm, whereas in presence of CQ increased to mean values of 67 nm. Calculated from absorption peak position of excition band indicated on average QD size of 3.2 nm. Emission spectroscopy and time-resolved emission studies confirmed preservation of electronic band structure in QD-CQ aggregates. On basis of the presented results, the elucidated mechanism of QD fluorescence quenching is a result of the interaction between QD and CQ due to electron transfer and electrostatic attraction. The results of fluorescence quenching of water-soluble CdTe quantum dot (QD) capped with thiocarboxylic acid were used to implement a simple and fast method to determine the presence of native antioxidant quinones in aqueous solutions. Feasibility studies on this method carried out with oxidized catechin showed a linear relation between the QD emission and quencher concentration, in range from 1 up to 200 μM. The wide linear range of concentration dependence makes it possible to apply this method for the fast and sensitive detection of quinones in solutions.

  10. Antiplasmodial, cytotoxic activities and characterization of a new naturally occurring quinone methide pentacyclic triterpenoid derivative isolated from Salacia leptoclada Tul. (Celastraceae) originated from Madagascar

    Institute of Scientific and Technical Information of China (English)

    Fatiany Pierre Ruphin; Robijaona Baholy; Randrianarivo Emmanuel; Raharisololalao Amelie; Marie-Therese Martin; Ngbolua Koto-te-Nyiwa

    2013-01-01

    Objective:To validate scientifically the traditional use of Salacia leptoclada Tul. (Celastraceae) (S. leptoclada) and to isolate and elucidate the structure of the biologically active compound. Methods:Bioassay-guided fractionation of the acetonic extract of the stem barks of S. leptoclada was carried out by a combination of chromatography technique and biological experiments in viro using Plasmodium falciparum and P388 leukemia cell lines as models. The structure of the biologically active pure compound was elucidated by 1D and 2D NMR spectroscopy and mass spectrometry. Results:Biological screening of S. leptoclada extracts resulted in the isolation of a pentacyclic triterpenic quinone methide. The pure compound exhibited both in vitro a cytotoxic effect on murine P388 leukemia cells with IC50 value of (0.041±0.020) µg/mL and an antiplasmodial activity against the chloroquine-resistant strain FC29 of Plasmodium falciparum with an IC50 value of (0.052±0.030) µg/mL. Despite this interesting anti-malarial property of the lead compound, the therapeutic index was weak (0.788). In the best of our knowledge, the quinone methide pentacyclic triterpenoid derivative compound is reported for the first time in S. leptoclada. Conclusions:The results suggest that furthers studies involving antineoplastic activity is needed for the development of this lead compound as anticancer drug.

  11. Quinone/hydroquinone meroterpenoids with antitubercular and cytotoxic activities produced by the sponge-derived fungus Gliomastix sp. ZSDS1-F7.

    Science.gov (United States)

    He, Wei-Jun; Zhou, Xiao-Jiang; Qin, Xiao-Chu; Mai, Yong-Xin; Lin, Xiu-Ping; Liao, Sheng-Rong; Yang, Bin; Zhang, Tianyu; Tu, Zheng-Chao; Wang, Jun-Feng; Liu, Yonghong

    2017-03-01

    Fifteen compounds, including six quinone/hydroquinone meroterpenoids, purpurogemutantin (1), macrophorin A (2), 4'-oxomacrophorin (3), 7-deacetoxyyanuthone A (4), 2,3-hydro-deacetoxyyanuthone A (5), 22-deacetylyanuthone A (6), anicequol (7), three roquefortine derivatives, roquefortine C (8), (16S)-hydroxyroquefortine C (9), (16R)-hydroxyroquefortine C (10), dihydroresorcylide (11), nectriapyrone (12), together with three fatty acid derivatives, methyl linoleate (13), phospholipase A2 (14), methyl elaidate (15), were isolated from the sponge-derived fungus Gliomastix sp. ZSDS1-F7 isolated from the sponge Phakellia fusca Thiele collected in the Yongxing island of Xisha. Their structures were elucidated mainly by extensive NMR spectroscopic and mass spectrometric analyses. Among these compounds, compounds 1-3 and 5-7 showed significant in vitro cytotoxicities against the K562, MCF-7, Hela, DU145, U937, H1975, SGC-7901, A549, MOLT-4 and HL60 cell lines, with IC50 values ranging from 0.19 to 35.4 μM. And compounds 2-4 exhibited antitubercular activity with IC50 values of 22.1, 2.44 and 17.5 μM, respectively. Furthermore, compound 7 had anti-enterovirus 71 activity with MIC value of 17.8 μM. To the best of our knowledge, this is the first report to product two quinone/hydroquinone meroterpenoids skeletons (linear skeleton and drimane skeleton) from the same fungal strain.

  12. Distribution in Different Organisms of Amino Acid Oxidases with FAD or a Quinone As Cofactor and Their Role as Antimicrobial Proteins in Marine Bacteria

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    Jonatan C. Campillo-Brocal

    2015-12-01

    Full Text Available Amino acid oxidases (AAOs catalyze the oxidative deamination of amino acids releasing ammonium and hydrogen peroxide. Several kinds of these enzymes have been reported. Depending on the amino acid isomer used as a substrate, it is possible to differentiate between l-amino acid oxidases and d-amino acid oxidases. Both use FAD as cofactor and oxidize the amino acid in the alpha position releasing the corresponding keto acid. Recently, a novel class of AAOs has been described that does not contain FAD as cofactor, but a quinone generated by post-translational modification of residues in the same protein. These proteins are named as LodA-like proteins, after the first member of this group described, LodA, a lysine epsilon oxidase synthesized by the marine bacterium Marinomonas mediterranea. In this review, a phylogenetic analysis of all the enzymes described with AAO activity has been performed. It is shown that it is possible to recognize different groups of these enzymes and those containing the quinone cofactor are clearly differentiated. In marine bacteria, particularly in the genus Pseudoalteromonas, most of the proteins described as antimicrobial because of their capacity to generate hydrogen peroxide belong to the group of LodA-like proteins.

  13. Distribution in Different Organisms of Amino Acid Oxidases with FAD or a Quinone As Cofactor and Their Role as Antimicrobial Proteins in Marine Bacteria.

    Science.gov (United States)

    Campillo-Brocal, Jonatan C; Lucas-Elío, Patricia; Sanchez-Amat, Antonio

    2015-12-16

    Amino acid oxidases (AAOs) catalyze the oxidative deamination of amino acids releasing ammonium and hydrogen peroxide. Several kinds of these enzymes have been reported. Depending on the amino acid isomer used as a substrate, it is possible to differentiate between l-amino acid oxidases and d-amino acid oxidases. Both use FAD as cofactor and oxidize the amino acid in the alpha position releasing the corresponding keto acid. Recently, a novel class of AAOs has been described that does not contain FAD as cofactor, but a quinone generated by post-translational modification of residues in the same protein. These proteins are named as LodA-like proteins, after the first member of this group described, LodA, a lysine epsilon oxidase synthesized by the marine bacterium Marinomonas mediterranea. In this review, a phylogenetic analysis of all the enzymes described with AAO activity has been performed. It is shown that it is possible to recognize different groups of these enzymes and those containing the quinone cofactor are clearly differentiated. In marine bacteria, particularly in the genus Pseudoalteromonas, most of the proteins described as antimicrobial because of their capacity to generate hydrogen peroxide belong to the group of LodA-like proteins.

  14. Oxygen control of nif gene expression in Klebsiella pneumoniae depends on NifL reduction at the cytoplasmic membrane by electrons derived from the reduced quinone pool.

    Science.gov (United States)

    Grabbe, Roman; Schmitz, Ruth A

    2003-04-01

    In Klebsiella pneumoniae, the flavoprotein, NifL regulates NifA mediated transcriptional activation of the N2-fixation (nif) genes in response to molecular O2 and ammonium. We investigated the influence of membrane-bound oxidoreductases on nif-regulation by biochemical analysis of purified NifL and by monitoring NifA-mediated expression of nifH'-'lacZ reporter fusions in different mutant backgrounds. NifL-bound FAD-cofactor was reduced by NADH only in the presence of a redox-mediator or inside-out vesicles derived from anaerobically grown K. pneumoniae cells, indicating that in vivo NifL is reduced by electrons derived from membrane-bound oxidoreductases of the anaerobic respiratory chain. This mechanism is further supported by three lines of evidence: First, K. pneumoniae strains carrying null mutations of fdnG or nuoCD showed significantly reduced nif-induction under derepressing conditions, indicating that NifL inhibition of NifA was not relieved in the absence of formate dehydrogenase-N or NADH:ubiquinone oxidoreductase. The same effect was observed in a heterologous Escherichia coli system carrying a ndh null allele (coding for NADH dehydrogenaseII). Second, studying nif-induction in K. pneumoniae revealed that during anaerobic growth in glycerol, under nitrogen-limitation, the presence of the terminal electron acceptor nitrate resulted in a significant decrease of nif-induction. The final line of evidence is that reduced quinone derivatives, dimethylnaphthoquinol and menadiol, are able to transfer electrons to the FAD-moiety of purified NifL. On the basis of these data, we postulate that under anaerobic and nitrogen-limited conditions, NifL inhibition of NifA activity is relieved by reduction of the FAD-cofactor by electrons derived from the reduced quinone pool, generated by anaerobic respiration, that favours membrane association of NifL. We further hypothesize that the quinol/quinone ratio is important for providing the signal to NifL.

  15. 8-Methoxy-naphtho[2,3-b]thiophen-4,9-quinone, a non-competitive inhibitor of trypanothione reductase

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    Zani Carlos L

    2003-01-01

    Full Text Available The enzyme trypanothione reductase is a recognised drug target in trypanosomatids and has been used in the search of new compounds with potential activity against diseases such as leishmaniasis, Chagas disease and African trypanosomiasis. 8-Methoxy-naphtho [2,3-b] thiophen-4,9-quinone was selected in a screening of natural and synthetic compounds using an in vitro assay with the recombinant enzyme from Trypanosoma cruzi. Its mode of inhibition fits a non-competitive model with respect to the substrate (trypanothione and to the co-factor (NADPH, with Ki-values of 5 and 3.6 µM, respectively. When tested against human glutathione reductase, this compound did not display any significant inhibition at 100 µM, indicating a good selectivity against the parasite enzyme.

  16. Determination of the absolute configuration of perylene quinone-derived mycotoxins by measurement and calculation of electronic circular dichroism spectra and specific rotations.

    Science.gov (United States)

    Podlech, Joachim; Fleck, Stefanie C; Metzler, Manfred; Bürck, Jochen; Ulrich, Anne S

    2014-09-01

    Altertoxins I-III, alterlosins I and II, alteichin (alterperylenol), stemphyltoxins I-IV, stemphyperylenol, stemphytriol, 7-epi-8-hydroxyaltertoxin I, and 6-epi-stemphytriol are mycotoxins derived from perylene quinone, for which the absolute configuration was not known. Electronic circular dichroism (ECD) spectra were calculated for these compounds and compared with measured spectra of altertoxins I-III, alteichin, and stemphyltoxin III and with reported Cotton effects. Specific rotations were calculated and compared with reported specific rotations. The absolute configuration of all the toxins, except for stemphyltoxin IV, could thus be determined. The validity of the assignment was high whenever reported ECD data were available for comparison, and the validity was lower when the assignment was based only on the comparison of calculated and reported specific rotations. ECD spectra are intrinsically different for toxins with a biphenyl substructure and for toxins derived from dihydroanthracene.

  17. Roles of the sodium-translocating NADH:quinone oxidoreductase (Na+-NQR) on vibrio cholerae metabolism, motility and osmotic stress resistance.

    Science.gov (United States)

    Minato, Yusuke; Fassio, Sara R; Kirkwood, Jay S; Halang, Petra; Quinn, Matthew J; Faulkner, Wyatt J; Aagesen, Alisha M; Steuber, Julia; Stevens, Jan F; Häse, Claudia C

    2014-01-01

    The Na+ translocating NADH:quinone oxidoreductase (Na+-NQR) is a unique respiratory enzyme catalyzing the electron transfer from NADH to quinone coupled with the translocation of sodium ions across the membrane. Typically, Vibrio spp., including Vibrio cholerae, have this enzyme but lack the proton-pumping NADH:ubiquinone oxidoreductase (Complex I). Thus, Na+-NQR should significantly contribute to multiple aspects of V. cholerae physiology; however, no detailed characterization of this aspect has been reported so far. In this study, we broadly investigated the effects of loss of Na+-NQR on V. cholerae physiology by using Phenotype Microarray (Biolog), transcriptome and metabolomics analyses. We found that the V. cholerae ΔnqrA-F mutant showed multiple defects in metabolism detected by Phenotype Microarray. Transcriptome analysis revealed that the V. cholerae ΔnqrA-F mutant up-regulates 31 genes and down-regulates 55 genes in both early and mid-growth phases. The most up-regulated genes included the cadA and cadB genes, encoding a lysine decarboxylase and a lysine/cadaverine antiporter, respectively. Increased CadAB activity was further suggested by the metabolomics analysis. The down-regulated genes include sialic acid catabolism genes. Metabolomic analysis also suggested increased reductive pathway of TCA cycle and decreased purine metabolism in the V. cholerae ΔnqrA-F mutant. Lack of Na+-NQR did not affect any of the Na+ pumping-related phenotypes of V. cholerae suggesting that other secondary Na+ pump(s) can compensate for Na+ pumping activity of Na+-NQR. Overall, our study provides important insights into the contribution of Na+-NQR to V. cholerae physiology.

  18. Roles of the sodium-translocating NADH:quinone oxidoreductase (Na+-NQR on vibrio cholerae metabolism, motility and osmotic stress resistance.

    Directory of Open Access Journals (Sweden)

    Yusuke Minato

    Full Text Available The Na+ translocating NADH:quinone oxidoreductase (Na+-NQR is a unique respiratory enzyme catalyzing the electron transfer from NADH to quinone coupled with the translocation of sodium ions across the membrane. Typically, Vibrio spp., including Vibrio cholerae, have this enzyme but lack the proton-pumping NADH:ubiquinone oxidoreductase (Complex I. Thus, Na+-NQR should significantly contribute to multiple aspects of V. cholerae physiology; however, no detailed characterization of this aspect has been reported so far. In this study, we broadly investigated the effects of loss of Na+-NQR on V. cholerae physiology by using Phenotype Microarray (Biolog, transcriptome and metabolomics analyses. We found that the V. cholerae ΔnqrA-F mutant showed multiple defects in metabolism detected by Phenotype Microarray. Transcriptome analysis revealed that the V. cholerae ΔnqrA-F mutant up-regulates 31 genes and down-regulates 55 genes in both early and mid-growth phases. The most up-regulated genes included the cadA and cadB genes, encoding a lysine decarboxylase and a lysine/cadaverine antiporter, respectively. Increased CadAB activity was further suggested by the metabolomics analysis. The down-regulated genes include sialic acid catabolism genes. Metabolomic analysis also suggested increased reductive pathway of TCA cycle and decreased purine metabolism in the V. cholerae ΔnqrA-F mutant. Lack of Na+-NQR did not affect any of the Na+ pumping-related phenotypes of V. cholerae suggesting that other secondary Na+ pump(s can compensate for Na+ pumping activity of Na+-NQR. Overall, our study provides important insights into the contribution of Na+-NQR to V. cholerae physiology.

  19. An NAD(P)H:quinone oxidoreductase 1 (NQO1) enzyme responsive nanocarrier based on mesoporous silica nanoparticles for tumor targeted drug delivery in vitro and in vivo

    Science.gov (United States)

    Gayam, Srivardhan Reddy; Venkatesan, Parthiban; Sung, Yi-Ming; Sung, Shuo-Yuan; Hu, Shang-Hsiu; Hsu, Hsin-Yun; Wu, Shu-Pao

    2016-06-01

    The synthesis and characterization of an NAD(P)H:quinone oxidoreductase 1 (NQO1) enzyme responsive nanocarrier based on mesoporous silica nanoparticles (MSNPs) for on-command delivery applications has been described in this paper. Gatekeeping of MSNPs is achieved by the integration of mechanically interlocked rotaxane nanovalves on the surface of MSNPs. The rotaxane nanovalve system is composed of a linear stalk anchoring on the surface of MSNPs, an α-cyclodextrin ring that encircles it and locks the payload ``cargo'' molecules in the mesopores, and a benzoquinone stopper incorporated at the end of the stalk. The gate opening and controlled release of the cargo are triggered by cleavage of the benzoquinone stopper using an endogenous NQO1 enzyme. In addition to having efficient drug loading and controlled release mechanisms, this smart biocompatible carrier system showed obvious uptake and consequent release of the drug in tumor cells, could selectively induce the tumor cell death and enhance the capability of inhibition of tumor growth in vivo. The controlled drug delivery system demonstrated its use as a potential theranostic material.The synthesis and characterization of an NAD(P)H:quinone oxidoreductase 1 (NQO1) enzyme responsive nanocarrier based on mesoporous silica nanoparticles (MSNPs) for on-command delivery applications has been described in this paper. Gatekeeping of MSNPs is achieved by the integration of mechanically interlocked rotaxane nanovalves on the surface of MSNPs. The rotaxane nanovalve system is composed of a linear stalk anchoring on the surface of MSNPs, an α-cyclodextrin ring that encircles it and locks the payload ``cargo'' molecules in the mesopores, and a benzoquinone stopper incorporated at the end of the stalk. The gate opening and controlled release of the cargo are triggered by cleavage of the benzoquinone stopper using an endogenous NQO1 enzyme. In addition to having efficient drug loading and controlled release mechanisms, this

  20. Evidence for the formation of a quinone methide during the oxidation of the insect cuticular sclerotizing precursor 1,2-dehydro-N-acetyldopamine.

    Science.gov (United States)

    Sugumaran, M; Semensi, V; Kalyanaraman, B; Bruce, J M; Land, E J

    1992-05-25

    properties of the two-electron oxidized species derived from dehydro-NADA and from 1,2-dehydro-N-acetyldopa methyl ester, it is concluded that the transient intermediate exhibiting absorbance at 485 nm is the quinone methide tautomer of the o-quinone of dehydro-NADA. Sclerotization of insect cuticle is discussed in the light of these findings.

  1. Molecular and Catalytic Properties of the Aldehyde Dehydrogenase of Gluconacetobacter diazotrophicus, a Quinoheme Protein Containing Pyrroloquinoline Quinone, Cytochrome b, and Cytochrome c▿

    Science.gov (United States)

    Gómez-Manzo, S.; Chavez-Pacheco, J. L.; Contreras-Zentella, M.; Sosa-Torres, M. E.; Arreguín-Espinosa, R.; Pérez de la Mora, M.; Membrillo-Hernández, J.; Escamilla, J. E.

    2010-01-01

    Several aldehyde dehydrogenase (ALDH) complexes have been purified from the membranes of acetic acid bacteria. The enzyme structures and the chemical nature of the prosthetic groups associated with these enzymes remain a matter of debate. We report here on the molecular and catalytic properties of the membrane-bound ALDH complex of the diazotrophic bacterium Gluconacetobacter diazotrophicus. The purified ALDH complex is a heterodimer comprising two subunits of 79.7 and 50 kDa, respectively. Reversed-phase high-pressure liquid chromatography (HPLC) and electron paramagnetic resonance spectroscopy led us to demonstrate, for the first time, the unequivocal presence of a pyrroloquinoline quinone prosthetic group associated with an ALDH complex from acetic acid bacteria. In addition, heme b was detected by UV-visible light (UV-Vis) spectroscopy and confirmed by reversed-phase HPLC. The smaller subunit bears three cytochromes c. Aliphatic aldehydes, but not formaldehyde, were suitable substrates. Using ferricyanide as an electron acceptor, the enzyme showed an optimum pH of 3.5 that shifted to pH 7.0 when phenazine methosulfate plus 2,6-dichlorophenolindophenol were the electron acceptors. Acetaldehyde did not reduce measurable levels of the cytochrome b and c centers; however, the dithionite-reduced hemes were conveniently oxidized by ubiquinone-1; this finding suggests that cytochrome b and the cytochromes c constitute an intramolecular redox sequence that delivers electrons to the membrane ubiquinone. PMID:20802042

  2. Cyanide degradation by Pseudomonas pseudoalcaligenes CECT5344 involves a malate:quinone oxidoreductase and an associated cyanide-insensitive electron transfer chain.

    Science.gov (United States)

    Luque-Almagro, Victor M; Merchán, Faustino; Blasco, Rafael; Igeño, M Isabel; Martínez-Luque, Manuel; Moreno-Vivián, Conrado; Castillo, Francisco; Roldán, M Dolores

    2011-03-01

    The alkaliphilic bacterium Pseudomonas pseudoalcaligenes CECT5344 is able to grow with cyanide as the sole nitrogen source. Membrane fractions from cells grown under cyanotrophic conditions catalysed the production of oxaloacetate from L-malate. Several enzymic activities of the tricarboxylic acid and glyoxylate cycles in association with the cyanide-insensitive respiratory pathway seem to be responsible for the oxaloacetate formation in vivo. Thus, in cyanide-grown cells, citrate synthase and isocitrate lyase activities were significantly higher than those observed with other nitrogen sources. Malate dehydrogenase activity was undetectable, but a malate:quinone oxidoreductase activity coupled to the cyanide-insensitive alternative oxidase was found in membrane fractions from cyanide-grown cells. Therefore, oxaloacetate production was linked to the cyanide-insensitive respiration in P. pseudoalcaligenes CECT5344. Cyanide and oxaloacetate reacted chemically inside the cells to produce a cyanohydrin (2-hydroxynitrile), which was further converted to ammonium. In addition to cyanide, strain CECT5344 was able to grow with several cyano derivatives, such as 2- and 3-hydroxynitriles. The specific system required for uptake and metabolization of cyanohydrins was induced by cyanide and by 2-hydroxynitriles, such as the cyanohydrins of oxaloacetate and 2-oxoglutarate.

  3. Pro187Ser Polymorphism of NAD(P)H:quinone oxidoreductase 1 and Prognosis of Non-small Cell Lung Cancer after Radiation Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Song, Si Yeol; Yoon, Sang Min; Shin, Seong Soo; Ahn, Seung Do; Lee, Jung Shin; Choi, Eun Kyung [University of Ulsan, Seoul (Korea, Republic of); Park, Heon Joo [Inha University, Incheon (Korea, Republic of); Hong, Yun Chul; Kim, Jin Hee; Park, Charn Il and others [Seoul National University, Seoul (Korea, Republic of)

    2005-07-01

    NAD(P)H:quinone oxidoreductase 1 (NQO1) has been known to function on reduction of oxidative status as a cytosolic flavoenzyme that catalyzes the electron reduction of substrates. It was reported to play a role in the prognosis of lung cancer patients treated with chemotherapy. Single nucleotide polymorphisms (SNPs) make up about ninety percent of human DNA polymorphisms, and they are a major focus of study about the individual differences for the risk of cancer and for anti-cancer treatment. A point mutation in exon 6 of the NQO1 gene is a C-to-T base pair substitution at position 609 of the NQO1 cDNA, and this codes for a proline-to-serine change at position 187 in the amino acid sequence of the protein. We hypothesized that NQO1 polymorphism could have an adverse influence on the survival of NSCLC patients treated with radiation therapy and/or surgery, and so we tried to discover whether the NQO1 polymorphism could be a predictive or prognostic marker for determining treatment outcome of radiotherapy in nonsmall cell lung cancer (NSCLC) patients.

  4. Sulindac compounds facilitate the cytotoxicity of β-lapachone by up-regulation of NAD(P)H quinone oxidoreductase in human lung cancer cells.

    Science.gov (United States)

    Kung, Hsiu-Ni; Weng, Tsai-Yun; Liu, Yu-Lin; Lu, Kuo-Shyan; Chau, Yat-Pang

    2014-01-01

    β-lapachone, a major component in an ethanol extract of Tabebuia avellanedae bark, is a promising potential therapeutic drug for various tumors, including lung cancer, the leading cause of cancer-related deaths worldwide. In the first part of this study, we found that apoptotic cell death induced in lung cancer cells by high concentrations of β-lapachone was mediated by increased activation of the pro-apoptotic factor JNK and decreased activation of the cell survival/proliferation factors PI3K, AKT, and ERK. In addition, β-lapachone toxicity was positively correlated with the expression and activity of NAD(P)H quinone oxidoreductase 1 (NQO1) in the tumor cells. In the second part, we found that the FDA-approved non-steroidal anti-inflammatory drug sulindac and its metabolites, sulindac sulfide and sulindac sulfone, increased NQO1 expression and activity in the lung adenocarcinoma cell lines CL1-1 and CL1-5, which have lower NQO1 levels and lower sensitivity to β-lapachone treatment than the A549 cell lines, and that inhibition of NQO1 by either dicoumarol treatment or NQO1 siRNA knockdown inhibited this sulindac-induced increase in β-lapachone cytotoxicity. In conclusion, sulindac and its metabolites synergistically increase the anticancer effects of β-lapachone primarily by increasing NQO1 activity and expression, and these two drugs may provide a novel combination therapy for lung cancers.

  5. Sulindac compounds facilitate the cytotoxicity of β-lapachone by up-regulation of NAD(PH quinone oxidoreductase in human lung cancer cells.

    Directory of Open Access Journals (Sweden)

    Hsiu-Ni Kung

    Full Text Available β-lapachone, a major component in an ethanol extract of Tabebuia avellanedae bark, is a promising potential therapeutic drug for various tumors, including lung cancer, the leading cause of cancer-related deaths worldwide. In the first part of this study, we found that apoptotic cell death induced in lung cancer cells by high concentrations of β-lapachone was mediated by increased activation of the pro-apoptotic factor JNK and decreased activation of the cell survival/proliferation factors PI3K, AKT, and ERK. In addition, β-lapachone toxicity was positively correlated with the expression and activity of NAD(PH quinone oxidoreductase 1 (NQO1 in the tumor cells. In the second part, we found that the FDA-approved non-steroidal anti-inflammatory drug sulindac and its metabolites, sulindac sulfide and sulindac sulfone, increased NQO1 expression and activity in the lung adenocarcinoma cell lines CL1-1 and CL1-5, which have lower NQO1 levels and lower sensitivity to β-lapachone treatment than the A549 cell lines, and that inhibition of NQO1 by either dicoumarol treatment or NQO1 siRNA knockdown inhibited this sulindac-induced increase in β-lapachone cytotoxicity. In conclusion, sulindac and its metabolites synergistically increase the anticancer effects of β-lapachone primarily by increasing NQO1 activity and expression, and these two drugs may provide a novel combination therapy for lung cancers.

  6. Molecular and catalytic properties of the aldehyde dehydrogenase of Gluconacetobacter diazotrophicus, a quinoheme protein containing pyrroloquinoline quinone, cytochrome b, and cytochrome c.

    Science.gov (United States)

    Gómez-Manzo, S; Chavez-Pacheco, J L; Contreras-Zentella, M; Sosa-Torres, M E; Arreguín-Espinosa, R; Pérez de la Mora, M; Membrillo-Hernández, J; Escamilla, J E

    2010-11-01

    Several aldehyde dehydrogenase (ALDH) complexes have been purified from the membranes of acetic acid bacteria. The enzyme structures and the chemical nature of the prosthetic groups associated with these enzymes remain a matter of debate. We report here on the molecular and catalytic properties of the membrane-bound ALDH complex of the diazotrophic bacterium Gluconacetobacter diazotrophicus. The purified ALDH complex is a heterodimer comprising two subunits of 79.7 and 50 kDa, respectively. Reversed-phase high-pressure liquid chromatography (HPLC) and electron paramagnetic resonance spectroscopy led us to demonstrate, for the first time, the unequivocal presence of a pyrroloquinoline quinone prosthetic group associated with an ALDH complex from acetic acid bacteria. In addition, heme b was detected by UV-visible light (UV-Vis) spectroscopy and confirmed by reversed-phase HPLC. The smaller subunit bears three cytochromes c. Aliphatic aldehydes, but not formaldehyde, were suitable substrates. Using ferricyanide as an electron acceptor, the enzyme showed an optimum pH of 3.5 that shifted to pH 7.0 when phenazine methosulfate plus 2,6-dichlorophenolindophenol were the electron acceptors. Acetaldehyde did not reduce measurable levels of the cytochrome b and c centers; however, the dithionite-reduced hemes were conveniently oxidized by ubiquinone-1; this finding suggests that cytochrome b and the cytochromes c constitute an intramolecular redox sequence that delivers electrons to the membrane ubiquinone.

  7. Towards a novel bioelectrocatalytic platform based on “wiring” of pyrroloquinoline quinone-dependent glucose dehydrogenase with an electrospun conductive polymeric fiber architecture

    Science.gov (United States)

    Gladisch, Johannes; Sarauli, David; Schäfer, Daniel; Dietzel, Birgit; Schulz, Burkhard; Lisdat, Fred

    2016-01-01

    Electrospinning is known as a fabrication technique for electrode architectures that serve as immobilization matrices for biomolecules. The current work demonstrates a novel approach to construct a conductive polymeric platform, capable not only of immobilization, but also of electrical connection of the biomolecule with the electrode. It is produced upon electrospinning from mixtures of three different highly conductive sulfonated polyanilines and polyacrylonitrile on ITO electrodes. The resulting fiber mats are with a well-retained conductivity. After coupling the enzyme pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH) to polymeric structures and addition of the substrate glucose an efficient bioelectrocatalysis is demonstrated. Depending on the choice of the sulfonated polyanilline mediatorless bioelectrocatalysis starts at low potentials; no large overpotential is needed to drive the reaction. Thus, the electrospun conductive immobilization matrix acts here as a transducing element, representing a promising strategy to use 3D polymeric scaffolds as wiring agents for active enzymes. In addition, the mild and well reproducible fabrication process and the active role of the polymer film in withdrawing electrons from the reduced PQQ-GDH lead to a system with high stability. This could provide access to a larger group of enzymes for bioelectrochemical applications including biosensors and biofuel cells.

  8. The PufX quinone channel enables the light-harvesting 1 antenna to bind more carotenoids for light collection and photoprotection.

    Science.gov (United States)

    Olsen, John D; Martin, Elizabeth C; Hunter, C Neil

    2017-02-01

    Photosynthesis in some phototrophic bacteria requires the PufX component of the reaction centre-light-harvesting 1-PufX (RC-LH1-PufX) complex, which creates a pore for quinone/quinol (Q/QH2 ) exchange across the LH1 barrier surrounding the RC. However, photosynthetic bacteria such as Thermochromatium (T.) tepidum do not require PufX because there are fewer carotenoid binding sites, which creates multiple pores in the LH1 ring for Q/QH2 exchange. We show that an αTrp-24 →Phe alteration of the Rhodobacter (Rba.) sphaeroides LH1 antenna impairs carotenoid binding and allows photosynthetic growth in the absence of PufX. We propose that acquisition of PufX and confining Q/QH2 traffic to a pore adjacent to the RC QB site is an evolutionary upgrade that allows increased LH1 carotenoid content for enhanced light absorption and photoprotection. © 2017 The Authors. FEBS Letters published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.

  9. Time-resolved visible and infrared absorption spectroscopy data obtained using photosystem I particles with non-native quinones incorporated into the A1 binding site.

    Science.gov (United States)

    Makita, Hiroki; Hastings, Gary

    2016-06-01

    Time-resolved visible and infrared absorption difference spectroscopy data at both 298 and 77 K were obtained using cyanobacterial menB (-) mutant photosystem I particles with several non-native quinones incorporated into the A1 binding site. Data was obtained for photosystem I particles with phylloquinone (2-methyl-3-phytyl-1,4-naphthoquinone), 2-bromo-1,4-naphthoquinone, 2-chloro-1,4-naphthoquinone, 2-methyl-1,4-naphthoquinone, 2,3-dibromo-1,4-naphthoquinone, 2,3-dichloro-1,4-naphthoquinone, and 9,10-anthraquinone incorporated. Transient absorption data were obtained at 487 and 703 nm in the visible spectral range, and 1950-1100 cm(-1) in the infrared region. Time constants obtained from fitting the time-resolved infrared and visible data are in good agreement. The measured time constants are crucial for the development of appropriate kinetic models that can describe electron transfer processes in photosystem I, "Modeling Electron Transfer in Photosystem I" Makita and Hastings (2016) [1].

  10. Medium optimization for pyrroloquinoline quinone (PQQ) production by Methylobacillus sp. zju323 using response surface methodology and artificial neural network-genetic algorithm.

    Science.gov (United States)

    Wei, Peilian; Si, Zhenjun; Lu, Yao; Yu, Qingfei; Huang, Lei; Xu, Zhinan

    2017-08-09

    Methylobacillus sp. zju323 was adopted to improve the biosynthesis of pyrroloquinoline quinone (PQQ) by systematic optimization of the fermentation medium. The Plackett-Burman design was implemented to screen for the key medium components for the PQQ production. CoCl2 · 6H2O, ρ-amino benzoic acid, and MgSO4 · 7H2O were found capable of enhancing the PQQ production most significantly. A five-level three-factor central composite design was used to investigate the direct and interactive effects of these variables. Both response surface methodology (RSM) and artificial neural network-genetic algorithm (ANN-GA) were used to predict the PQQ production and to optimize the medium composition. The results showed that the medium optimized by ANN-GA was better than that by RSM in maximizing PQQ production and the experimental PQQ concentration in the ANN-GA-optimized medium was improved by 44.3% compared with that in the unoptimized medium. Further study showed that this ANN-GA-optimized medium was also effective in improving PQQ production by fed-batch mode, reaching the highest PQQ accumulation of 232.0 mg/L, which was about 47.6% increase relative to that in the original medium. The present work provided an optimized medium and developed a fed-batch strategy which might be potentially applicable in industrial PQQ production.

  11. Oxidant-induced formation of a neutral flavosemiquinone in the Na+-translocating NADH:Quinone oxidoreductase (Na+-NQR) from Vibrio cholerae.

    Science.gov (United States)

    Tao, Minli; Casutt, Marco S; Fritz, Günter; Steuber, Julia

    2008-01-01

    The Na(+)-translocating NADH:quinone oxidoreductase (Na(+)-NQR) from the human pathogen Vibrio cholerae is a respiratory flavo-FeS complex composed of the six subunits NqrA-F. The Na(+)-NQR was produced as His(6)-tagged protein by homologous expression in V. cholerae. The isolated complex contained near-stoichiometric amounts of non-covalently bound FAD (0.78 mol/mol Na(+)-NQR) and riboflavin (0.70 mol/mol Na(+)-NQR), catalyzed NADH-driven Na(+) transport (40 nmol Na(+)min(-1) mg(-1)), and was inhibited by 2-n-heptyl-4-hydroxyquinoline-N-oxide. EPR spectroscopy showed that Na(+)-NQR as isolated contained very low amounts of a neutral flavosemiquinone (10(-3) mol/mol Na(+)-NQR). Reduction with NADH resulted in the formation of an anionic flavosemiquinone (0.10 mol/mol Na(+)-NQR). Subsequent oxidation of the Na(+)-NQR with ubiquinone-1 or O(2) led to the formation of a neutral flavosemiquinone (0.24 mol/mol Na(+)-NQR). We propose that the Na(+)-NQR is fully oxidized in its resting state, and discuss putative schemes of NADH-triggered redox transitions.

  12. The Na+-translocating NADH:quinone oxidoreductase (Na+-NQR) from Vibrio cholerae enhances insertion of FeS in overproduced NqrF subunit.

    Science.gov (United States)

    Tao, Minli; Fritz, Günter; Steuber, Julia

    2008-01-01

    The Na+-translocating NADH:quinone oxidoreductase (Na+-NQR) from Vibrio cholerae is a membrane-bound, respiratory Na+ pump. Its NqrF subunit contains one FAD and a [2Fe-2S] cluster and catalyzes the initial oxidation of NADH. A soluble variant of NqrF lacking its hydrophobic, N-terminal helix (NqrF') was produced in V. cholerae wild type and nqr deletion strain. Under identical conditions of growth and induction, the yield of NqrF' increased by 30% in the presence of the Na+-NQR. FAD-containing NqrF' species with or without the FeS cluster were observed, indicating that assembly of the FeS center, but not insertion of the flavin cofactor, was limited during overproduction in V. cholerae. A comparison of these distinct NqrF' species with regard to specific NADH dehydrogenase activity, pH dependence of activity and thermal inactivation showed that NqrF' lacking the [2Fe-2S] cluster was less stable, partially unfolded, and therefore prone to proteolytic degradation in V. cholerae. We conclude that the overall yield of NqrF' critically depends on the amount of fully assembled, FeS-containing NqrF' in the V. cholerae host cells. The Na+-NQR is proposed to increase the stability of NqrF' by stimulating the maturation of FeS centers.

  13. Localization and function of the membrane-bound riboflavin in the Na+-translocating NADH:quinone oxidoreductase (Na+-NQR) from Vibrio cholerae.

    Science.gov (United States)

    Casutt, Marco S; Huber, Tamara; Brunisholz, René; Tao, Minli; Fritz, Günter; Steuber, Julia

    2010-08-27

    The sodium ion-translocating NADH:quinone oxidoreductase (Na(+)-NQR) from the human pathogen Vibrio cholerae is a respiratory membrane protein complex that couples the oxidation of NADH to the transport of Na(+) across the bacterial membrane. The Na(+)-NQR comprises the six subunits NqrABCDEF, but the stoichiometry and arrangement of these subunits are unknown. Redox-active cofactors are FAD and a 2Fe-2S cluster on NqrF, covalently attached FMNs on NqrB and NqrC, and riboflavin and ubiquinone-8 with unknown localization in the complex. By analyzing the cofactor content and NADH oxidation activity of subcomplexes of the Na(+)-NQR lacking individual subunits, the riboflavin cofactor was unequivocally assigned to the membrane-bound NqrB subunit. Quantitative analysis of the N-terminal amino acids of the holo-complex revealed that NqrB is present in a single copy in the holo-complex. It is concluded that the hydrophobic NqrB harbors one riboflavin in addition to its covalently attached FMN. The catalytic role of two flavins in subunit NqrB during the reduction of ubiquinone to ubiquinol by the Na(+)-NQR is discussed.

  14. Novel lavendamycin analogues as antitumor agents: synthesis, in vitro cytotoxicity, structure-metabolism, and computational molecular modeling studies with NAD(P)H:quinone oxidoreductase 1.

    Science.gov (United States)

    Hassani, Mary; Cai, Wen; Holley, David C; Lineswala, Jayana P; Maharjan, Babu R; Ebrahimian, G Reza; Seradj, Hassan; Stocksdale, Mark G; Mohammadi, Farahnaz; Marvin, Christopher C; Gerdes, John M; Beall, Howard D; Behforouz, Mohammad

    2005-12-01

    Novel lavendamycin analogues with various substituents were synthesized and evaluated as potential NAD(P)H:quinone oxidoreductase (NQO1)-directed antitumor agents. Pictet-Spengler condensation of quinoline- or quninoline-5,8-dione aldehydes with tryptamine or tryptophans yielded the lavendamycins. Metabolism studies with recombinant human NQO1 revealed that addition of NH2 and CH2OH groups at the quinolinedione-7-position and indolopyridine-2'-position had the greatest positive impact on substrate specificity. The best and poorest substrates were 37 (2'-CH2OH-7-NH2 derivative) and 31 (2'-CONH2-7-NHCOC3H7-n derivative) with reduction rates of 263 +/- 30 and 0.1 +/- 0.1 micromol/min/mg NQO1, respectively. Cytotoxicity toward human colon adenocarcinoma cells was determined for the lavendamycins. The best substrates for NQO1 were also the most selectively toxic to the NQO1-rich BE-NQ cells compared to NQO1-deficient BE-WT cells with 37 as the most selective. Molecular docking supported a model in which the best substrates were capable of efficient hydrogen-bonding interactions with key residues of the active site along with hydride ion reception.

  15. Time-resolved visible and infrared absorption spectroscopy data obtained using photosystem I particles with non-native quinones incorporated into the A1 binding site

    Directory of Open Access Journals (Sweden)

    Hiroki Makita

    2016-06-01

    Full Text Available Time-resolved visible and infrared absorption difference spectroscopy data at both 298 and 77 K were obtained using cyanobacterial menB− mutant photosystem I particles with several non-native quinones incorporated into the A1 binding site. Data was obtained for photosystem I particles with phylloquinone (2-methyl-3-phytyl-1,4-naphthoquinone, 2-bromo-1,4-naphthoquinone, 2-chloro-1,4-naphthoquinone, 2-methyl-1,4-naphthoquinone, 2,3-dibromo-1,4-naphthoquinone, 2,3-dichloro-1,4-naphthoquinone, and 9,10-anthraquinone incorporated. Transient absorption data were obtained at 487 and 703 nm in the visible spectral range, and 1950–1100 cm−1 in the infrared region. Time constants obtained from fitting the time-resolved infrared and visible data are in good agreement. The measured time constants are crucial for the development of appropriate kinetic models that can describe electron transfer processes in photosystem I, “Modeling Electron Transfer in Photosystem I” Makita and Hastings (2016 [1].

  16. Nuclear Magnetic Resonance Structure and Binding Studies of PqqD, a Chaperone Required in the Biosynthesis of the Bacterial Dehydrogenase Cofactor Pyrroloquinoline Quinone.

    Science.gov (United States)

    Evans, Robert L; Latham, John A; Xia, Youlin; Klinman, Judith P; Wilmot, Carrie M

    2017-05-30

    Biosynthesis of the ribosomally synthesized and post-translationally modified peptide (RiPP), pyrroloquinoline quinone (PQQ), is initiated when the precursor peptide, PqqA, is recognized and bound by the RiPP precursor peptide recognition element (RRE), PqqD, for presentation to the first enzyme in the pathway, PqqE. Unlike other RiPP-producing, postribosomal peptide synthesis (PRPS) pathways in which the RRE is a component domain of the first enzyme, PqqD is predominantly a separate scaffolding protein that forms a ternary complex with the precursor peptide and first tailoring enzyme. As PqqD is a stable, independent RRE, this makes the PQQ pathway an ideal PRPS model system for probing RRE interactions using nuclear magnetic resonance (NMR). Herein, we present both the solution NMR structure of Methylobacterium extorquens PqqD and results of (1)H-(15)N HSQC binding experiments that identify the PqqD residues involved in binding the precursor peptide, PqqA, and the enzyme, PqqE. The reported structural model for an independent RRE, along with the mapped binding surfaces, will inform future efforts both to understand and to manipulate PRPS pathways.

  17. Lung toxicity and tumor promotion by hydroxylated derivatives of 2,6-di-tert-butyl-4-methylphenol (BHT) and 2-tert-butyl-4-methyl-6-iso-propylphenol: correlation with quinone methide reactivity.

    Science.gov (United States)

    Kupfer, Rene; Dwyer-Nield, Lori D; Malkinson, Alvin M; Thompson, John A

    2002-08-01

    Acute pulmonary toxicity and tumor promotion by the food additive 2,6-di-tert-butyl-4-methylphenol (BHT) in mice are well documented. These effects have been attributed to either of two quinone methides, 2,6-di-tert-butyl-4-methylenecyclohexa-2,5-dienone (BHT-QM) formed through direct oxidation of BHT by pulmonary cytochrome P450 or a quinone methide formed by hydroxylation of a tert-butyl group of BHT (to form BHTOH) followed by oxidation of this metabolite to BHTOH-QM. BHTOH-QM is a more reactive electrophile compared to BHT-QM due to intramolecular interactions of the side-chain hydroxyl with the carbonyl oxygen. To further examine this bioactivation pathway, an analogue of BHTOH was prepared, 2-tert-butyl-6-(1'-hydroxy-1'-methyl)ethyl-4-methylphenol (BPPOH), that is structurally very similar to BHTOH but forms a quinone methide (BPPOH-QM) capable of more efficient intramolecular hydrogen bonding and, therefore, higher electrophilicity than BHTOH-QM. BPPOH-QM was synthesized and its reactivity with water, methanol, and glutathione determined to be >10-fold higher than that of BHTOH-QM. The conversions of BPPOH and BHTOH to quinone methides in lung microsomes from male BALB/cByJ mice were quantitatively similar, but in vivo the former was pneumotoxic at one-half of the dose required for the latter and one-eighth of the dose required for BHT, as determined by increased lung weight:body weight ratios following a single i.p. injection. Similar differences were found in the doses of BHT, BHTOH, or BPPOH required for tumor promotion after a single initiating dose of 3-methylcholanthrene followed by three weekly injections of the phenol. The downregulaton of calpain II, previously shown to accompany lung tumor promotion by BHT and BHTOH, also occurred with BPPOH. The correlation between biologic activities of these phenols and the reactivities of their corresponding quinone methides provides additional support for the role of BHTOH-QM as the principal metabolite

  18. Cr(VI) reduction and Cr(III) immobilization by Acinetobacter sp. HK-1 with the assistance of a novel quinone/graphene oxide composite.

    Science.gov (United States)

    Zhang, Hai-Kun; Lu, Hong; Wang, Jing; Zhou, Ji-Ti; Sui, Meng

    2014-11-04

    Cr(VI) biotreatment has attracted a substantial amount of interest due to its cost effectiveness and environmental friendliness. However, the slow Cr(VI) bioreduction rate and the formed organo-Cr(III) in solution are bottlenecks for biotechnology application. In this study, a novel strain, Acinetobacter sp. HK-1, capable of reducing Cr(VI) and immobilizing Cr(III) was isolated. Under optimal conditions, the Cr(VI) reduction rate could reach 3.82 mg h(-1) g cell(-1). To improve the Cr(VI) reduction rate, two quinone/graphene oxide composites (Q-GOs) were first prepared via a one-step covalent chemical reaction. The results showed that 2-amino-3-chloro-1,4-naphthoquinone-GO (NQ-GO) exhibited a better catalytic performance in Cr(VI) reduction compared to 2-aminoanthraquinone-GO. Specifically, in the presence of 50 mg L(-1) NQ-GO, a Cr(VI) removal rate of 190 mg h(-1) g cell(-1), which was the highest rate obtained, was achieved. The increased Cr(VI) reduction rate is mainly the result of NQ-GO significantly increasing the Cr(VI) reduction activity of cell membrane proteins containing dominant Cr(VI) reductases. X-ray photoelectron spectroscopy analysis found that Cr(VI) was reduced to insoluble Cr(III), which was immobilized by glycolipids secreted by strain HK-1. These findings indicate that the application of strain HK-1 and NQ-GO is a promising strategy for enhancing the treatment of Cr(VI)-containing wastewater.

  19. Protection against 1,2-di-methylhydrazine-induced systemic oxidative stress and altered brain neurotransmitter status by probiotic Escherichia coli CFR 16 secreting pyrroloquinoline quinone.

    Science.gov (United States)

    Pandey, Sumeet; Singh, Ashish; Chaudhari, Nirja; Nampoothiri, Laxmipriya P; Kumar, G Naresh

    2015-05-01

    Exposure to environmental pollutant 1,2-dimethylhydrazine (DMH) is attributed to systemic oxidative stress and is known to cause neurotropic effect by altering brain neurotransmitter status. Probiotics are opted as natural therapeutic against oxidative stress and also have the ability to modulate gut-brain axis. Pyrroloquinoline quinone (PQQ) is water-soluble, heat-stable antioxidant molecule. Aim of the present study was to evaluate the antioxidant efficacy of PQQ-producing probiotic E. coli CFR 16 on DMH-induced systemic oxidative damage and altered neurotransmitter status in rat brain. Adult virgin Charles Forster rats (200-250 g) were given DMH dose (25 mg/kg body weight, s.c.) for 8 weeks. Blood lipid peroxidation levels exhibited a marked increase while antioxidant enzyme activities of superoxide dismutase, catalase, glucose-6-phosphate dehydrogenase and glutathione peroxidase were found to be reduced in DMH-treated rats. Likewise, brain serotonin and norepinephrine levels displayed a significant decrease, whereas epinephrine levels demonstrated a marked increase in brain of these rats. PQQ-producing E. coli CFR 16 supplementation reduced systemic oxidative stress and also restored brain neurotransmitter status. However, E. coli CFR 16 did not show any effect on these parameters. In contrast, E. coli CFR 16:: vgb-gfp and E. coli CFR 16:: vgb-gfp vector exhibited some degree of protection again oxidative stress but they were not able to modulate neurotransmitter levels. In conclusion, continuous and sustained release of PQQ by probiotic E. coli in rat intestine ameliorates systemic oxidative stress and restored brain neurotransmitter levels.

  20. Selective activation of mitomycin A by thiols to form DNA cross-links and monoadducts: biochemical basis for the modulation of mitomycin cytotoxicity by the quinone redox potential.

    Science.gov (United States)

    Paz, M M; Das, A; Palom, Y; He, Q Y; Tomasz, M

    2001-08-16

    Mitomycin A (MA) but not mitomycin C (MC) cross-linked linearized (32)P-pBR322 DNA in the presence of dithiothreitol (DTT) or glutathione (GSH), as shown by a sensitive DNA cross-link assay. Incubation of calf-thymus DNA with MA and DTT or mercaptoethanol (MER) resulted in the formation of MA-DNA adducts, which were isolated from nuclease digests of the drug-DNA complexes by HPLC. The adducts were characterized by their UV absorption spectra, electrospray ionization mass spectrometry (ESIMS), and facile conversion from 7-methoxy- to 7-amino-substituted mitosene type adducts upon 10% NH(4)OH treatment, which were identical with known adducts of MC. Both DNA interstrand and intrastrand cross-link adducts, linking two deoxyguanosine residues at N(2), as well as several deoxyguanosine-N(2) monoadducts of MA, were identified. No DNA adducts were formed with MC under the same conditions. A specificity of DNA cross-link formation for the CpG sequence was observed using 12-mer synthetic oligodeoxyribonucleotides as substrates and as DNA sequence models, in analogy to the known CpG sequence specificity of MC-induced DNA cross-links. MA is known to be more cytotoxic by 2-3 orders of magnitude than MC, and this property correlates with redox potentials of MA (-0.19 V) and MA analogues that are higher than those of MC (-0.40 V) and its analogues. It is suggested that the biochemical basis for the higher cytotoxic potency of MA is MA's propensity to be reductively activated by cellular thiols while MC is resistant to thiol activation. This distinction is probably derived from the large difference between the quinone redox potentials of the two drugs.

  1. Electron transfer between iron minerals and quinones: estimating the reduction potential of the Fe(II)-goethite surface from AQDS speciation.

    Science.gov (United States)

    Orsetti, Silvia; Laskov, Christine; Haderlein, Stefan B

    2013-12-17

    Redox reactions at iron mineral surfaces play an important role in controlling biogeochemical processes of natural porous media such as sediments, soils and aquifers, especially in the presence of recurrent variations in redox conditions. Ferrous iron associated with iron mineral phases forms highly reactive species and is regarded as a key factor in determining pathways, rates, and extent of chemically and microbially driven electron transfer processes across the iron mineral-water interface. Due to their transient nature and heterogeneity a detailed characterization of such surface bound Fe(II) species in terms of redox potential is still missing. To this end, we used the nonsorbing anthraquinone-2,6-disulfonate (AQDS) as a redox probe and studied the thermodynamics of its redox reactions in heterogeneous iron systems, namely goethite-Fe(II). Our results provide a thermodynamic basis for and are consistent with earlier observations on the ability of AQDS to "shuttle" electrons between microbes and iron oxide minerals. On the basis of equilibrium AQDS speciation we reported for the first time robust reduction potential measurements of reactive iron species present at goethite in aqueous systems (EH,Fe-GT ≈ -170 mV). Due to the high redox buffer intensity of heterogeneous mixed valent iron systems, this value might be characteristic for many iron-reducing environments in the subsurface at circumneutral pH. Our results corroborate the picture of a dynamic remodelling of Fe(II)/Fe(III) surface sites at goethite in response to oxidation/reduction events. As quinones play an essential role in the electron transport systems of microbes, the proposed method can be considered as a biomimetic approach to determine "effective" biogeochemical reduction potentials in heterogeneous iron systems.

  2. Structural and functional investigation of flavin binding center of the NqrC subunit of sodium-translocating NADH:quinone oxidoreductase from Vibrio harveyi.

    Directory of Open Access Journals (Sweden)

    Valentin Borshchevskiy

    Full Text Available Na+-translocating NADH:quinone oxidoreductase (NQR is a redox-driven sodium pump operating in the respiratory chain of various bacteria, including pathogenic species. The enzyme has a unique set of redox active prosthetic groups, which includes two covalently bound flavin mononucleotide (FMN residues attached to threonine residues in subunits NqrB and NqrC. The reason of FMN covalent bonding in the subunits has not been established yet. In the current work, binding of free FMN to the apo-form of NqrC from Vibrio harveyi was studied showing very low affinity of NqrC to FMN in the absence of its covalent bonding. To study structural aspects of flavin binding in NqrC, its holo-form was crystallized and its 3D structure was solved at 1.56 Å resolution. It was found that the isoalloxazine moiety of the FMN residue is buried in a hydrophobic cavity and that its pyrimidine ring is squeezed between hydrophobic amino acid residues while its benzene ring is extended from the protein surroundings. This structure of the flavin-binding pocket appears to provide flexibility of the benzene ring, which can help the FMN residue to take the bended conformation and thus to stabilize the one-electron reduced form of the prosthetic group. These properties may also lead to relatively weak noncovalent binding of the flavin. This fact along with periplasmic location of the FMN-binding domains in the vast majority of NqrC-like proteins may explain the necessity of the covalent bonding of this prosthetic group to prevent its loss to the external medium.

  3. Structural and functional investigation of flavin binding center of the NqrC subunit of sodium-translocating NADH:quinone oxidoreductase from Vibrio harveyi.

    Science.gov (United States)

    Borshchevskiy, Valentin; Round, Ekaterina; Bertsova, Yulia; Polovinkin, Vitaly; Gushchin, Ivan; Ishchenko, Andrii; Kovalev, Kirill; Mishin, Alexey; Kachalova, Galina; Popov, Alexander; Bogachev, Alexander; Gordeliy, Valentin

    2015-01-01

    Na+-translocating NADH:quinone oxidoreductase (NQR) is a redox-driven sodium pump operating in the respiratory chain of various bacteria, including pathogenic species. The enzyme has a unique set of redox active prosthetic groups, which includes two covalently bound flavin mononucleotide (FMN) residues attached to threonine residues in subunits NqrB and NqrC. The reason of FMN covalent bonding in the subunits has not been established yet. In the current work, binding of free FMN to the apo-form of NqrC from Vibrio harveyi was studied showing very low affinity of NqrC to FMN in the absence of its covalent bonding. To study structural aspects of flavin binding in NqrC, its holo-form was crystallized and its 3D structure was solved at 1.56 Å resolution. It was found that the isoalloxazine moiety of the FMN residue is buried in a hydrophobic cavity and that its pyrimidine ring is squeezed between hydrophobic amino acid residues while its benzene ring is extended from the protein surroundings. This structure of the flavin-binding pocket appears to provide flexibility of the benzene ring, which can help the FMN residue to take the bended conformation and thus to stabilize the one-electron reduced form of the prosthetic group. These properties may also lead to relatively weak noncovalent binding of the flavin. This fact along with periplasmic location of the FMN-binding domains in the vast majority of NqrC-like proteins may explain the necessity of the covalent bonding of this prosthetic group to prevent its loss to the external medium.

  4. Synthesis of Polyacene Quinone Radical Polymers with the New Method of Molten Salt%新型熔盐法合成多省并醌

    Institute of Scientific and Technical Information of China (English)

    汪云龙; 唐先忠; 赵波; 张怡

    2011-01-01

    PAQRs (Polyacene quinone radical polymers) with certain dielectr/c constant were synthesized by anthraquinone (AQ) and pyromellitic dianhydride (PMA) with the aluminum chloride as catalyst, compared with the solution (nitrobenzene) method and the molten salt ( NaCl - AlCl3 ) method. The structures of products were identified by Fourier transform infrared spectroscopy ( FTIR) , and Thermo Gravimetric (TG) Analysis were done, finally the dielectrle constant of the PAQRs were tested. Results showed the thermal properties of both kind of PAQRs was good, and the dielectric constant was 4350 at 20 Hz with the molten salt method, while the dielectric constant was only 48.5.%以蒽醌(AQ)和均苯四甲酸酐(PMA)为原料在三氯化铝的催化作用下,对比采用溶液(硝基苯)法和熔盐(NaCl-AlCl3)法合成了具有一定介电常数的多省并醌聚合物(PAQR)。通过红外对产物进行结构表征,然后对产物进行热失重(TC)分析测试,最后测量两种方岳PAQR的介电常数。结果显示两种方法合成的PAQR热稳定性均良好:采用熔盐法得到了在20Hz频率下,介电常数为4350的PAQR,而溶液法的介电常数仅为48.5。

  5. Covalent modification of a melanoma-derived antigenic peptide with a natural quinone methide. Preliminary chemical, molecular modelling and immunological evaluation studies.

    Science.gov (United States)

    Douat-Casassus, Céline; Marchand-Geneste, Nathalie; Diez, Elisabeth; Aznar, Céline; Picard, Philippe; Geoffre, Serge; Huet, Aline; Bourguet-Kondracki, Marie-Lise; Gervois, Nadine; Jotereau, Francine; Quideau, Stéphane

    2006-05-01

    A LigandFit shape-directed docking methodology was used to identify the best position at which the melanoma-derived MHC class-I HLA-A2-binding antigenic peptide ELAGIGILTV could be modified by attaching a small molecule capable of fitting at the interface of complementary determining regional (CDR) loops of a T-cell receptor (TCR) while triggering T-cell responses. The small molecule selected here for determining the feasibility of this alternative track to chemical alteration of antigenic peptides was the electrophilic quinone methide (+)-puupehenone (), a natural product that belongs to a family of marine metabolites capable of expressing immunomodulatory activities. A preliminary chemical reactivity model study revealed the efficacy of the thiol group of a cysteine (C) side-chain in its nucleophilic addition reaction with in a regio- and diastereoselective manner. The best TCR/HLA-A2 ligand [i.e., ELAGCGILTV-S-puupehenol ()] then identified by the LigandFit docking procedure was synthesized and used to pulse HLA-A2(+) T2 cells for T-cell stimulation. Among the ELAGIGILTV-specific T-cell clones we tested, five of them recognized the conjugate in spite of its low binding affinity for the HLA-A2 molecules. The resulting T-cell stimulation was determined through the intracytoplasmic secretion of IFN-gamma and the percentage of T-cells thus activated. These highly encouraging results indicate that small non-peptidic natural product-derived molecules attached onto the central part of an antigenic peptide can fit at the TCR/HLA-A2 interface with induction of T-cell responses.

  6. Construction of nerve guide conduits from cellulose/soy protein composite membranes combined with Schwann cells and pyrroloquinoline quinone for the repair of peripheral nerve defect.

    Science.gov (United States)

    Luo, Lihua; Gan, Li; Liu, Yongming; Tian, Weiqun; Tong, Zan; Wang, Xiong; Huselstein, Celine; Chen, Yun

    2015-02-20

    Regeneration and functional reconstruction of peripheral nerve defects remained a significant clinical challenge. Nerve guide conduits, with seed cells or neurotrophic factors (NTFs), had been widely used to improve the repair and regeneration of injured peripheral nerve. Pyrroloquinoline quinone (PQQ) was an antioxidant that can stimulate nerve growth factors (NGFs) synthesis and accelerate the Schwann cells (SCs) proliferation and growth. In present study, three kinds of nerve guide conduits were constructed: one from cellulose/SPI hollow tube (CSC), another from CSC combined with SCs (CSSC), and the third one from CSSC combined with PQQ (CSSPC), respectively. And then they were applied to bridge and repair the sciatic nerve defect in rats, using autograft as control. Effects of different nerve guide conduits on the nerve regeneration were comparatively evaluated by general analysis, sciatic function index (SFI) and histological analysis (HE and TEM). Newly-formed regenerative nerve fibers were observed and running through the transparent nerve guide conduits 12 weeks after surgery. SFI results indicated that the reconstruction of motor function in CSSPC group was better than that in CSSC and CSC groups. HE images from the cross-sections and longitudinal-sections of the harvested regenerative nerve indicated that regenerative nerve fibers had been formed and accompanied with new blood vessels and matrix materials in the conduits. TEM images also showed that lots of fresh myelinated and non-myelinated nerve fibers had been formed. Parts of vacuolar, swollen and abnormal axons occurred in CSC and CSSC groups, while the vacuolization and swell of axons was the least serious in CSSPC group. These results indicated that CSSPC group had the most ability to repair and reconstruct the nerve structure and functions due to the comprehensive contributions from hollow CSC tube, SCs and PQQ. As a result, the CSSPC may have the potential for the applications as nerve guide

  7. Compounds from the Fruits of the Popular European Medicinal Plant Vitex agnus-castus in Chemoprevention via NADP(H:Quinone Oxidoreductase Type 1 Induction

    Directory of Open Access Journals (Sweden)

    Shenghong Li

    2013-01-01

    Full Text Available As part of our continuing efforts in the search for potential biologically active compounds from medicinal plants, we have isolated 18 compounds including two novel nitrogen containing diterpenes from extracts of the fruits of Vitex agnus-castus. These isolates, along with our previously obtained novel compound vitexlactam A (1, were evaluated for potential biological effects, including cancer chemoprevention. Chemically, the nitrogenous isolates were found to be two labdane diterpene alkaloids, each containing an α, β-unsaturated γ-lactam moiety. Structurally, they were elucidated to be 9α-hydroxy-13(14-labden-16,15-amide (2 and 6β-acetoxy-9α-hydroxy-13(14-labden-15,16-amide (3, which were named vitexlactams B and C, respectively. The 15 known isolates were identified as vitexilactone (4, rotundifuran (5, 8-epi-manoyl oxide (6, vitetrifolin D (7, spathulenol (8, cis-dihydro-dehydro-diconiferylalcohol-9-O-β-D-glucoside (9, luteolin-7-O-glucoside (10, 5-hydroxy-3,6,7,4′-tetramethoxyflavone (11, casticin (12, artemetin (13, aucubin (14, agnuside (15, β-sitosterol (16, p-hydroxybenzoic acid (17, and p-hydroxybenzoic acid glucose ester (18. All compound structures were determined/identified on the basis of 1D and/or 2D NMR and mass spectrometry techniques. Compounds 6, 8, 9, and 18 were reported from a Vitex spieces for the first time. The cancer chemopreventive potentials of these isolates were evaluated for NADP(H:quinone oxidoreductase type 1 (QR1 induction activity. Compound 7 demonstrated promising QR1 induction effect, while the new compound vitexlactam (3 was only slightly active.

  8. NAD(P)H:quinone oxidoreductase expression in Cyp1a-knockout and CYP1A-humanized mouse lines and its effect on bioactivation of the carcinogen aristolochic acid I

    Energy Technology Data Exchange (ETDEWEB)

    Levova, Katerina; Moserova, Michaela [Department of Biochemistry, Faculty of Science, Charles University, Prague (Czech Republic); Nebert, Daniel W. [Department of Environmental Health, University of Cincinnati Medical Center, Cincinnati (United States); Phillips, David H. [Analytical and Environmental Sciences Division, MRC-HPA Centre for Environment and Health, King' s College London, London (United Kingdom); Frei, Eva [Division of Preventive Oncology, National Center for Tumor Diseases, German Cancer Research Center (DKFZ), Heidelberg (Germany); Schmeiser, Heinz H. [Research Group Genetic Alterations in Carcinogenesis, German Cancer Research Center (DKFZ), Heidelberg (Germany); Arlt, Volker M. [Analytical and Environmental Sciences Division, MRC-HPA Centre for Environment and Health, King' s College London, London (United Kingdom); Stiborova, Marie, E-mail: stiborov@natur.cuni.cz [Department of Biochemistry, Faculty of Science, Charles University, Prague (Czech Republic)

    2012-12-15

    Aristolochic acid causes a specific nephropathy (AAN), Balkan endemic nephropathy, and urothelial malignancies. Using Western blotting suitable to determine protein expression, we investigated in several transgenic mouse lines expression of NAD(P)H:quinone oxidoreductase (NQO1)—the most efficient cytosolic enzyme that reductively activates aristolochic acid I (AAI). The mouse tissues used were from previous studies [Arlt et al., Chem. Res. Toxicol. 24 (2011) 1710; Stiborova et al., Toxicol. Sci. 125 (2012) 345], in which the role of microsomal cytochrome P450 (CYP) enzymes in AAI metabolism in vivo had been determined. We found that NQO1 levels in liver, kidney and lung of Cyp1a1(−/−), Cyp1a2(−/−) and Cyp1a1/1a2(−/−) knockout mouse lines, as well as in two CYP1A-humanized mouse lines harboring functional human CYP1A1 and CYP1A2 and lacking the mouse Cyp1a1/1a2 orthologs, differed from NQO1 levels in wild-type mice. NQO1 protein and enzymic activity were induced in hepatic and renal cytosolic fractions isolated from AAI-pretreated mice, compared with those in untreated mice. Furthermore, this increase in hepatic NQO1 enzyme activity was associated with bioactivation of AAI and elevated AAI-DNA adduct levels in ex vivo incubations of cytosolic fractions with DNA and AAI. In conclusion, AAI appears to increase its own metabolic activation by inducing NQO1, thereby enhancing its own genotoxic potential. Highlights: ► NAD(P)H:quinone oxidoreductase expression in Cyp1a knockout and humanized CYP1A mice ► Reductive activation of the nephrotoxic and carcinogenic aristolochic acid I (AAI) ► NAD(P)H:quinone oxidoreductase is induced in mice treated with AAI. ► Induced hepatic enzyme activity resulted in elevated AAI-DNA adduct levels.

  9. Calcium and calcium sensing receptor modulates the expression of thymidylate synthase, NAD(P)H:quinone oxidoreductase 1 and survivin in human colon carcinoma cells: promotion of cytotoxic response to mitomycin C and fluorouracil

    OpenAIRE

    Liu, Guangming; Hu, Xin; Varani, James; Chakrabarty, Subhas

    2009-01-01

    Ca2+ and the cell-surface calcium sensing receptor (CaSR) constitute a novel and robust ligand/receptor system in regulating the proliferation and differentiation of colonic epithelial cells. Here we show that activation of CaSR by extracellular Ca2+ (or CaSR agonists) enhanced the sensitivity of human colon carcinoma cells to mitomycin C (MMC) and fluorouracil (5-FU). Activation of CaSR up-regulated the expression of MMC activating enzyme, NAD(P)H:quinone oxidoreductase 1 (NQO-1) and down-re...

  10. Pyrroloquinoline Quinone Resists Denervation-Induced Skeletal Muscle Atrophy by Activating PGC-1α and Integrating Mitochondrial Electron Transport Chain Complexes.

    Directory of Open Access Journals (Sweden)

    Yung-Ting Kuo

    Full Text Available Denervation-mediated skeletal muscle atrophy results from the loss of electric stimulation and leads to protein degradation, which is critically regulated by the well-confirmed transcriptional co-activator peroxisome proliferator co-activator 1 alpha (PGC-1α. No adequate treatments of muscle wasting are available. Pyrroloquinoline quinone (PQQ, a naturally occurring antioxidant component with multiple functions including mitochondrial modulation, demonstrates the ability to protect against muscle dysfunction. However, it remains unclear whether PQQ enhances PGC-1α activation and resists skeletal muscle atrophy in mice subjected to a denervation operation. This work investigates the expression of PGC-1α and mitochondrial function in the skeletal muscle of denervated mice administered PQQ. The C57BL6/J mouse was subjected to a hindlimb sciatic axotomy. A PQQ-containing ALZET® osmotic pump (equivalent to 4.5 mg/day/kg b.w. was implanted subcutaneously into the right lower abdomen of the mouse. In the time course study, the mouse was sacrificed and the gastrocnemius muscle was prepared for further myopathological staining, energy metabolism analysis, western blotting, and real-time quantitative PCR studies. We observed that PQQ administration abolished the denervation-induced decrease in muscle mass and reduced mitochondrial activities, as evidenced by the reduced fiber size and the decreased expression of cytochrome c oxidase and NADH-tetrazolium reductase. Bioenergetic analysis demonstrated that PQQ reprogrammed the denervation-induced increase in the mitochondrial oxygen consumption rate (OCR and led to an increase in the extracellular acidification rate (ECAR, a measurement of the glycolytic metabolism. The protein levels of PGC-1α and the electron transport chain (ETC complexes were also increased by treatment with PQQ. Furthermore, PQQ administration highly enhanced the expression of oxidative fibers and maintained the type II glycolytic

  11. Induction of NAD(P)H:quinone oxidoreductase 1 (NQO1) by Glycyrrhiza species used for women's health: differential effects of the Michael acceptors isoliquiritigenin and licochalcone A

    Science.gov (United States)

    Hajirahimkhan, Atieh; Simmler, Charlotte; Dong, Huali; Lantvit, Daniel D.; Li, Guannan; Chen, Shao-Nong; Nikolić, Dejan; Pauli, Guido F.; van Breemen, Richard B.; Dietz, Birgit M.; Bolton, Judy L.

    2016-01-01

    For the alleviation of menopausal symptoms, women frequently turn to botanical dietary supplements, such as licorice and hops. In addition to estrogenic properties, these botanicals could also have chemopreventive effects. We have previously shown that hops and its Michael acceptor xanthohumol (XH) induced the chemoprevention enzyme, NAD(P)H:quinone oxidoreductase 1 (NQO1), in vitro and in vivo. Licorice species could also induce NQO1, as they contain the Michael acceptors isoliquiritigenin (LigC) found in Glycyrrhiza glabra (GG), G. uralensis (GU), and G. inflata (GI) and licochalcone A (LicA) which is only found in GI. These licorice species and hops induced NQO1 activity in murine hepatoma (Hepa1c1c7) cells; hops >> GI > GG ≅ GU. Similar to the known chemopreventive compounds curcumin (turmeric), sulforaphane (broccoli), and XH, LigC and LicA were active dose-dependently; sulforaphane >> XH > LigC > LicA ≅ curcumin >> LigF. Induction of the antioxidant response element-luciferase in human hepatoma (Hep-G2-ARE-C8) cells suggested involvement of the Keap1-Nrf2 pathway. GG, GU, and LigC also induced NQO1 in non-tumorigenic breast epithelial MCF-10A cells. In female Sprague-Dawley rats treated with GG and GU, LigC and LigF were detected in the liver and mammary gland. GG weakly enhanced NQO1 activity in the mammary tissue but not in the liver. Treatment with LigC alone did not induce NQO1 in vivo most likely due to its conversion to LigF, extensive metabolism, and its low bioavailability in vivo. These data show the chemopreventive potential of licorice species in vitro could be due to LigC and LicA and emphasize the importance of chemical and biological standardization of botanicals used as dietary supplements. Although the in vivo effects in the rat model after four day treatment are minimal, it must be emphasized that menopausal women take these supplements for extended periods of time and long-term beneficial effects are quite possible. PMID:26473469

  12. Construction of nerve guide conduits from cellulose/soy protein composite membranes combined with Schwann cells and pyrroloquinoline quinone for the repair of peripheral nerve defect

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Lihua [Department of Biomedical Engineering, School of Basic Medical Sciences, Wuhan University, Wuhan 430071 (China); Center of Molecular Medicine, School of Medicine, Hubei University of Arts and Sciences, Xiangyang 441053 (China); Gan, Li; Liu, Yongming; Tian, Weiqun; Tong, Zan [Department of Biomedical Engineering, School of Basic Medical Sciences, Wuhan University, Wuhan 430071 (China); Wang, Xiong; Huselstein, Celine [Ingénierie Moléculaire et Physiopathologie Articulaire (IMoPA), UMR 7365 CNRS – Université de Lorraine, Biopôle, 54500 Vandoeuvre-lès-Nancy (France); Chen, Yun, E-mail: yunchen@whu.edu.cn [Department of Biomedical Engineering, School of Basic Medical Sciences, Wuhan University, Wuhan 430071 (China)

    2015-02-20

    Regeneration and functional reconstruction of peripheral nerve defects remained a significant clinical challenge. Nerve guide conduits, with seed cells or neurotrophic factors (NTFs), had been widely used to improve the repair and regeneration of injured peripheral nerve. Pyrroloquinoline quinone (PQQ) was an antioxidant that can stimulate nerve growth factors (NGFs) synthesis and accelerate the Schwann cells (SCs) proliferation and growth. In present study, three kinds of nerve guide conduits were constructed: one from cellulose/SPI hollow tube (CSC), another from CSC combined with SCs (CSSC), and the third one from CSSC combined with PQQ (CSSPC), respectively. And then they were applied to bridge and repair the sciatic nerve defect in rats, using autograft as control. Effects of different nerve guide conduits on the nerve regeneration were comparatively evaluated by general analysis, sciatic function index (SFI) and histological analysis (HE and TEM). Newly-formed regenerative nerve fibers were observed and running through the transparent nerve guide conduits 12 weeks after surgery. SFI results indicated that the reconstruction of motor function in CSSPC group was better than that in CSSC and CSC groups. HE images from the cross-sections and longitudinal-sections of the harvested regenerative nerve indicated that regenerative nerve fibers had been formed and accompanied with new blood vessels and matrix materials in the conduits. TEM images also showed that lots of fresh myelinated and non-myelinated nerve fibers had been formed. Parts of vacuolar, swollen and abnormal axons occurred in CSC and CSSC groups, while the vacuolization and swell of axons was the least serious in CSSPC group. These results indicated that CSSPC group had the most ability to repair and reconstruct the nerve structure and functions due to the comprehensive contributions from hollow CSC tube, SCs and PQQ. As a result, the CSSPC may have the potential for the applications as nerve guide

  13. Dietary supplementation of pyrroloquinoline quinone disodium protects against oxidative stress and liver damage in laying hens fed an oxidized sunflower oil-added diet.

    Science.gov (United States)

    Wang, J; Zhang, H J; Xu, L; Long, C; Samuel, K G; Yue, H Y; Sun, L L; Wu, S G; Qi, G H

    2016-07-01

    The protective effects of dietary pyrroloquinoline quinone disodium (PQQ.Na2) supplementation against oxidized sunflower oil-induced oxidative stress and liver injury in laying hens were examined. Three hundred and sixty 53-week-old Hy-Line Gray laying hens were randomly allocated into one of the five dietary treatments. The treatments included: (1) a diet containing 2% fresh sunflower oil; (2) a diet containing 2% thermally oxidized sunflower oil; (3) an oxidized sunflower oil diet with 100 mg/kg of added vitamin E; (4) an oxidized sunflower oil diet with 0.08 mg/kg of PQQ.Na2; and (5) an oxidized sunflower oil diet with 0.12 mg/kg of PQQ.Na2. Birds fed the oxidized sunflower oil diet showed a lower feed intake compared to birds fed the fresh oil diet or oxidized oil diet supplemented with vitamin E (P=0.009). Exposure to oxidized sunflower oil increased plasma malondialdehyde (Pdiet were modulated by dietary vitamin E or PQQ.Na2 supplementation to levels comparable to the fresh oil group. Dietary supplementation with PQQ.Na2 or vitamin E increased the activities of total superoxide dismutase and glutathione peroxidase in plasma and the liver, when compared with the oxidized sunflower oil group (Pdiet induced elevation of liver weight (P=0.026), liver to BW ratio (P=0.001) and plasma activities of alanine aminotransferase (P=0.001) and aspartate aminotransferase (Pdiet. Furthermore, oxidized sunflower oil increased hepatic DNA tail length (Pdiet induced DNA tail length and tail moment to the basal levels in fresh oil diet. These results indicate that PQQ.Na2 is a potential antioxidant and is as effective against oxidized oil-related liver injury in laying hens as vitamin E. The protective effects of PQQ.Na2 against liver damage induced by oxidized oil may be partially due to its role in the scavenging of free radicals, inhibiting of lipid peroxidation and enhancing of antioxidant defense systems.

  14. 31. Antioxidant and hypoxia induce the human antioxidant response element-mediated expression of NAD(P) H: quinone oxidoreductase1 gene

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Background: NAD(P)H: quinone oxidoreductase 1 (NQO1) is an obligate two-electron reductase that is involved in protection of cells against redox cycling, oxidative stress, and neoplasia. and can also bioactivate certain antitumor quinones. Many antioxidants are cancer chemopreventive agents, and tumour hypoxia are now being exploited in cancer treatment which shows considerable promise to overcome the resistance to cancer chemotherapy. Antioxidant response element (ARE) is sensitive to perturbations of cellular redox states. Our previous studies have shown that β-tyrosol (β-TY), as a phenolic antioxidant, can protects cells against DNA damage resulting from toxic H2O2. Aim: We take the present study with the goal of whether antioxidants such as β-tyrosol, butylated hydroxyanisole(BHA) and β-Naphthooflavone(β-NF) and hypoxia (pO2 0.1% -0.5%) can induce gene expression of NQO1, inhibit proliferation of human hepatoma cells SMMC-7721 and the relationship between them; whether ARE can mediate gene expression in response to antioxidans and hypoxia. Methods: SMMC-7721 human hepatoma cells are planted in plates, grown for 24h. and exposed to antioxidants and hypoxia, each alone or in combination for another 24h. The enzyme activity was determinied by spectrophotometric assay using direct measurement of NQO1 from cells cultured in Microtiter wells. Semi-quantitative reverse transcription-PCR (RT-PCR) technique was used to measure NQO1 mRNA levets. Proliferation was estimated using the crystal violet staining technique. Electrophoretic mobility shift assay (EMSA) was employed to assess protein binding to the ARE under all of These conditions. Hypoxia cells were harvested in an anaerobic chamber at the end of the incubation period. Results: Antioxidant (90ug/ml β-TY、60μmol/L BHA、80μmol/L β-NF) potently induce an increase in the activity of NQO1. From 60μg/ml to 90μg/ml, β-TY caused NQO1 activity enhancement in a dose-dependent manner The NQO1 activity induced

  15. Effects of aqueous extract of Ruta graveolens and its ingredients on cytochrome P450, uridine diphosphate (UDP-glucuronosyltransferase, and reduced nicotinamide adenine dinucleotide (phosphate (NAD(PH-quinone oxidoreductase in mice

    Directory of Open Access Journals (Sweden)

    Yune-Fang Ueng

    2015-09-01

    Full Text Available Ruta graveolens (the common rue has been used for various therapeutic purposes, including relief of rheumatism and treatment of circulatory disorder. To elucidate the effects of rue on main drug-metabolizing enzymes, effects of an aqueous extract of the aerial part of rue and its ingredients on cytochrome P450 (P450/CYP, uridine diphosphate (UDP-glucuronosyltransferase, and reduced nicotinamide adenine dinucleotide (phosphate (NAD(PH:quinone oxidoreductase were studied in C57BL/6JNarl mice. Oral administration of rue extract to males increased hepatic Cyp1a and Cyp2b activities in a dose-dependent manner. Under a 7-day treatment regimen, rue extract (0.5 g/kg induced hepatic Cyp1a and Cyp2b activities and protein levels in males and females. This treatment increased hepatic UDP-glucuronosyltransferase activity only in males. However, NAD(PH:quinone oxidoreductase activity remained unchanged. Based on the contents of rutin and furanocoumarins of mouse dose of rue extract, rutin increased hepatic Cyp1a activity and the mixture of furanocoumarins (Fmix increased Cyp2b activities in males. The mixture of rutin and Fmix increased Cyp1a and Cyp2b activities. These results revealed that rutin and Fmix contributed at least in part to the P450 induction by rue.

  16. Assignment of quinone derivatives as the main compound class composing 'interstellar' grains based on both polarity ions detected by the 'Cometary and Interstellar Dust Analyser' (CIDA) onboard the spacecraft STARDUST.

    Science.gov (United States)

    Krueger, Franz R; Werther, Wolfgang; Kissel, Jochen; Schmid, Erich R

    2004-01-01

    The 'Cometary and Interstellar Dust Analyser' (CIDA) is a particle impact time-of-flight mass spectrometer onboard the NASA spacecraft STARDUST. A series of positive and negative ion mass spectra from the impact of (apparently) interstellar dust particles has been collected since 1999. In the meantime laboratory work has been performed to better understand the ion formation processes of organic grains impacting at those speeds (>15 km/s) and to relate them to some other ion formation methods. The key ion types were the negative ions, with some additional information from the positive ions. Here, first the principal ion formation rules are briefly reviewed. Secondly, the common substance class is inferred mainly by the application of exclusion principles, and appears to be partly condensed aromatic and quinonoid compounds with high oxygen and low nitrogen content. Oxygen appears to be present in quinone-type structures with condensed aromatic rings, possibly with furan substructures and some hydroxyl moieties. Some nitrogen may be present in pyrrole- or quinoline-type structures. Considerations of thermodynamics and radiation physics of these dust particles within the solar system are consistent with this interpretation. Quinoenzyme cofactors such as the known compound pyrroloquinoline-quinone (PQQ) and its subconstituents would be expected to yield similar mass spectra.

  17. Pyrroloquinoline quinone inhibits oxygen/glucose deprivation-induced apoptosis by activating the PI3K/AKT pathway in cardiomyocytes.

    Science.gov (United States)

    Xu, Feng; Yu, Haixia; Liu, Jinyao; Cheng, Lu

    2014-01-01

    The purposes of this study were to examine the protective effect of pyrroloquinoline quinone (PQQ) on oxygen/glucose deprivation (OGD)-induced injury to H9C2 rat cardiomyocytes and to investigate the mechanism. Using H9C2 cells cultured in vitro, we examined changes in cell viability with an MTT assay at 12, 24, and 48 h after injury induced by OGD. Various concentrations of PQQ (1, 10, and 100 μM) were added, and the effect of PQQ on cell viability after OGD was assessed using the MTT assay. Thus, the optimal concentration of PQQ for the protection of cardiomyocytes against oxygen and glucose deprivation injury was determined. We also used flow cytometry analysis to examine the effect of PQQ on H9C2 cells with OGD-induced injury. The molecular probe 2',7'-dichlorofluorescin diacetate was used to label the H9C2 cells, and flow cytometry was used to detect the effect of PQQ on reactive oxygen species (ROS) content. After labeling the H9C2 cells using a mitochondrial green fluorescent probe (Mito-Tracker Green), we measured the change in the mitochondrial content of PQQ-treated H9C2 cells. Western blotting was used to examine the effect of PQQ on the phosphatidylinositol 3-kinase (PI3K)/Akt pathway in the H9C2 cells. The results of the MTT assay showed that 48 h of OGD significantly injured the H9C2 cells (p < 0.01) and that treatment with 100 μM PQQ effectively decreased the level of OGD-induced injury (p < 0.01). The results of the flow cytometry analysis showed that PQQ significantly reduced apoptosis in H9C2 cells subjected to OGD (p < 0.05). In addition, OGD significantly increased the ROS level in H9C2 cells (p < 0.01), and PQQ significantly inhibited this increase (p < 0.05). The results of the Mito-Tracker Green staining suggested that PQQ effectively inhibited the decrease in mitochondrial content caused by OGD (p < 0.05). Western blot analysis showed that PQQ partially reversed the decrease in Akt phosphorylation that was caused by OGD (p

  18. Análise sazonal do potencial antimicrobiano e teores de flavonoides e quinonas de extratos foliares de Aloe arborescens Mill., Xanthorrhoeaceae Seasonal analysis from the antimicrobial potency and flavonoid and quinone content from Aloe arborescens Mill., Xanthorrhoeaceae, leaf extracts

    Directory of Open Access Journals (Sweden)

    Fernando Leite Cardoso

    2010-03-01

    Full Text Available Este trabalho teve como objetivos avaliar o potencial antimicrobiano e os teores de flavonoides e quinonas de extratos foliares de Aloe arborescens Mill., Xanthorrhoeaceae, produzidos em diferentes épocas do ano. Extratos etanólicos e clorofórmicos foram preparados a partir de folhas, os bioensaios de atividade antimicrobiana foram desenvolvidos pelo método de macrodiluição em caldo, e dosagens de flavonoides e quinonas foram realizadas nos extratos. Todos os extratos apresentaram ação inibitória sobre os microrganismos testados. O extrato clorofórmico de inverno apresentou a menor CIM (128 µg/mL sobre B. subtilis. Os extratos clorofórmicos de inverno, primavera e verão apresentaram maior atividade antimicrobiana em relação ao extrato clorofórmico de outono. O extrato etanólico de inverno apresentou a menor CIM (256 µg/mL e a menor CMM (512 µg/mL sobre K. pneumoniae. Os extratos etanólicos de verão e outono mostraram baixa atividade antimicrobiana. Os teores de quinonas das folhas foram maiores nos períodos mais quentes de coleta (verão e outono, enquanto os teores de flavonoides foram semelhantes nos quatro períodos de coleta.This work has the objective of evaluate the antimicrobial potency and the content of flavonoids and quinones from the Aloe arborescens Mill., Xanthorrhoeaceae, leaf extracts produced in the four seasons of the year. Ethanol and chloroform extracts were prepared from the leaves, the bioassays from antimicrobial activity were developed by the macrodilution method in broth, and dosages of flavonoids and quinones were performed in the extracts. The winter chloroform extract showed the lowest CIM (128 µg/mL on B. subtilis. The ethanol extract showed the lowest CIM (256 µg/mL and the lowest CMM (512 µg/mL on K. pneumoniae. The summer and fall ethanol extracts showed low antimicrobial activity. The quinones extracts showed inhibitory activity on the tested microorganisms. The winter, spring and summer

  19. Tuning cofactor redox potentials: the 2-methoxy dihedral angle generates a redox potential difference greater than 160 mV between the primary (QA) and secondary (QB) quinones of the photosynthetic reaction center

    Science.gov (United States)

    Taguchi, Alexander T.; Mattis, Aidas J.; O'Malley, Patrick J.; Dikanov, Sergei A.; Wraight, Colin A.

    2013-01-01

    Only quinones with a 2-methoxy group can act simultaneously as the primary (QA) and secondary (QB) electron acceptors in photosynthetic reaction centers from Rb. sphaeroides. 13C HYSCORE measurements of the 2-methoxy in the semiquinone states, SQA and SQB, were compared with QM calculations of the 13C couplings as a function of dihedral angle. X-ray structures support dihedral angle assignments corresponding to a redox potential gap (ΔEm) between QA and QB of ~180 mV. This is consistent with the failure of a ubiquinone analog lacking the 2-methoxy to function as QB in mutant reaction centers with a ΔEm ≈ 160–195 mV. PMID:24079813

  20. Spermine and spermidine inhibition of photosystem II: Disassembly of the oxygen evolving complex and consequent perturbation in electron donation from TyrZ to P680+ and the quinone acceptors QA- to QB.

    Science.gov (United States)

    Beauchemin, Rémy; Gauthier, Alain; Harnois, Johanne; Boisvert, Steve; Govindachary, Sridharan; Carpentier, Robert

    2007-07-01

    Polyamines are implicated in plant growth and stress response. However, the polyamines spermine and spermidine were shown to elicit strong inhibitory effects in photosystem II (PSII) submembrane fractions. We have studied the mechanism of this inhibitory action in detail. The inhibition of electron transport in PSII submembrane fractions treated with millimolar concentrations of spermine or spermidine led to the decline of plastoquinone reduction, which was reversed by the artificial electron donor diphenylcarbazide. The above inhibition was due to the loss of the extrinsic polypeptides associated with the oxygen evolving complex. Thermoluminescence measurements revealed that charge recombination between the quinone acceptors of PSII, QA and QB, and the S2 state of the Mn-cluster was abolished. Also, the dark decay of chlorophyll fluorescence after a single turn-over white flash was greatly retarded indicating a slower rate of QA- reoxidation.

  1. Solid phase extraction and determination of ultra trace amounts of copper(II) using octadecyl silica membrane disks modified by 11-hydroxynaphthacene-5,12-quinone and flame atomic absorption spectrometry.

    Science.gov (United States)

    Shamsipur, M; Avanes, A; Rofouei, M K; Sharghi, H; Aghapour, G

    2001-06-21

    A simple and selective method for rapid extraction and determination of trace amounts of copper(II) ions using octadecyl-bonded silica membrane disks modified with 11-hydroxynaphthacene-5,12-quinone and flame atomic absorption spectrometry is presented. Extraction efficiency and the influence of pH, flow rates, amount of ligand and type and least amount of stripping acid were evaluated. Maximum capacity of the membrane disks modified by 5 mg of the ligand was found to be 360 mug of Cu(2+) ion. The break through volume is larger than 2000 ml. The limit of detection of the proposed method is 0.2 ng ml(-1). The effects of various cationic interferences on the percent recovery of copper in binary mixtures were studied. The method was applied to the recovery of Cu(2+) ions from four different water samples and a synthetic sample.

  2. Molecular mechanism of metal-independent decomposition of lipid hydroperoxide by the carcinogenic halogenated quinones%致癌性卤代醌介导的脂质氢过氧化物分解的分子机制

    Institute of Scientific and Technical Information of China (English)

    刘庆林; 覃浩; 黄春华; 刘蒲; 朱本占

    2014-01-01

    Halogenated quinones are a class of carcinogenic intermediates and newly identified chlorination disinfection byproducts in drinking water. 13-Hydroperoxy-9, 11-octadecadienoic acid (13-HPODE) is the most extensively studied endogenous lipid hydroperoxide. Although it is well known that the decomposition of 13-HPODE can be catalyzed by transition metal ions, it is not clear whether halogenated quinones could enhance its decomposition independent of metal ions, and if so, what are the unique characteristics and similarities? We found that halogenated quinones such as 2,5-dichloro-1,4-benzoquinone ( DCBQ) could markedly enhance the decomposition of 13-HPODE and formation of the reactive lipid alkyl radicals such as pentyl and 7-carboxyheptyl radicals, and the genotoxic 4-hydroxy-2-nonenal ( HNE ) , through the complementary application of ESR spin-trapping, HPLC-MS and GC-MS methods. Interestingly, two chloroquinone-lipid alkoxyl conjugates were also detected and identified from the reaction between DCBQ and 13-HPODE. We propose that the enhanced decomposition of the endogenous lipid hydroperoxide 13-HPODE by halogenated quinones and formation of reactive lipid alkyl radicals and genotoxic HNE is through a novel metal-independent nucelophilic substitution coupled with homolytic decomposition mechanism, which may partly explain their potential genotoxicity and carcinogenicity.%卤代醌是许多卤芳香持久有机污染物的致癌代谢产物和饮用水消毒副产物.13-过氧羟基-9,11-十八碳二烯酸(13-HPODE)是最为广泛研究的内源性脂质过氧化物.众所周知,过渡金属离子可以催化分解13-HPODE,但尚不清楚卤代醌是否可以通过不依赖金属离子的途径促进其分解;若是如此,又有什么特异性和相似性?我们发现卤化醌如2,5-二氯-1,4-苯醌( DCBQ)可显著促进13-HPODE的分解.综合采用电子自旋共振-自旋捕获、HPLC-MS和GC-MS等分析方法,可检测到反

  3. FMN is covalently attached to a threonine residue in the NqrB and NqrC subunits of Na(+)-translocating NADH-quinone reductase from Vibrio alginolyticus.

    Science.gov (United States)

    Hayashi, M; Nakayama, Y; Yasui, M; Maeda, M; Furuishi, K; Unemoto, T

    2001-01-12

    The Na(+)-translocating NADH-quinone reductase (NQR) from Vibrio alginolyticus is composed of six subunits (NqrA to NqrF). We previously demonstrated that both NqrB and NqrC subunits contain a flavin cofactor covalently attached to a threonine residue. Fluorescent peptide fragments derived from the NqrB and NqrC subunits were applied to a matrix-assisted laser desorption ionization time-of-flight mass spectrometer, and covalently attached flavin was identified as FMN in both subunits. From post-source decay fragmentation analysis, it was concluded that FMN is attached by a phosphate group to Thr-235 in the NqrB subunit and to Thr-223 in the NqrC subunit. The phosphoester binding of FMN to a threonine residue reported here is a new type of flavin attachment to a polypeptide.

  4. Omeprazole Induces NAD(P)H Quinone Oxidoreductase 1 via Aryl Hydrocarbon Receptor-Independent Mechanisms: Role of the Transcription Factor Nuclear Factor Erythroid 2–Related Factor 2

    Science.gov (United States)

    Zhang, Shaojie; Patel, Ananddeep; Moorthy, Bhagavatula; Shivanna, Binoy

    2015-01-01

    Activation of the aryl hydrocarbon receptor (AhR) transcriptionally induces phase I (cytochrome P450 (CYP) 1A1) and phase II (NAD(P)H quinone oxidoreductase 1 (NQO1) detoxifying enzymes. The effects of the classical and nonclassical AhR ligands on phase I and II enzymes are well studied in human hepatocytes. Additionally, we observed that the proton pump inhibitor, omeprazole (OM), transcriptionally induces CYP1A1 in the human adenocarcinoma cell line, H441 cells via AhR. Whether OM activates AhR and induces the phase II enzyme, NAD(P)H quinone oxidoreductase 1 (NQO1), in fetal primary human pulmonary microvascular endothelial cells (HPMEC) is unknown. Therefore, we tested the hypothesis that OM will induce NQO1 in HPMEC via the AhR. The concentrations of OM used in our experiments did not result in cytotoxicity. OM activated AhR as evident by increased CYP1A1 mRNA expression. However, contrary to our hypothesis, OM increased NQO1 mRNA and protein via an AhR-independent mechanism as AhR knockdown failed to abrogate OM-mediated increase in NQO1 expression. Interestingly, OM activated Nrf2 as evident by increased phosphoNrf2 (S40) expression in OM-treated compared to vehicle-treated cells. Furthermore, Nrf2 knockdown abrogated OM-mediated increase in NQO1 expression. In conclusion, we provide evidence that OM induces NQO1 via AhR-independent, but Nrf2-dependent mechanisms. PMID:26441083

  5. Soy isoflavones increase quinone reductase in hepa-1c1c7 cells via estrogen receptor beta and nuclear factor erythroid 2-related factor 2 binding to the antioxidant response element.

    Science.gov (United States)

    Froyen, Erik B; Steinberg, Francene M

    2011-09-01

    Soy protein and isoflavones (genistein and daidzein) have been demonstrated to increase quinone reductase (QR) activity, protein, and mRNA in animal and cell culture models. However, their mechanism of action has not been completely characterized. Additionally, it has not been determined if equol, a daidzein metabolite, can modulate QR activity and expression. Estrogen receptor beta (ERβ) is thought to be involved in stimulating QR gene transcription by anti-estrogens and phytoestrogens, along with nuclear factor erythroid 2-related factor 2 (Nrf2). This study tested the hypothesis that genistein, daidzein and equol increase quinone reductase activity, protein and mRNA via ERβ and Nrf2 binding to the QR antioxidant response element (ARE). QR expression and activity were determined using TaqMan polymerase chain reaction, protein immunoblots and activity assays. Molecular events were investigated using luciferase reporter gene assays and chromatin immunoprecipitation (ChIP). Hepa-1c1c7 cells were treated with control [0.1% (v:v) dimethyl sulfoxide (DMSO)]; 1 μmol/L β-naphthoflavone (positive control); 5 μmol/L resveratrol (ChIP positive control for ERβ binding) and 1, 5 and 25 μmol/L genistein, daidzein or equol. Treatment durations were 1 h (ChIP), 24 h (mRNA and luciferase assays) and 24 and 48 h (protein and activity). Genistein, daidzein and equol increased QR activity, protein and mRNA, with daidzein and equol having more of an impact at physiologic concentrations (1 and 5 μmol/L) compared to genistein. Furthermore, the study results demonstrate that genistein, daidzein and equol interact with the QR ARE and that daidzein and equol act via both ERβ and Nrf2 binding strongly to the QR ARE.

  6. Acid/base and hydrogen bonding effects on the proton-coupled electron transfer of quinones and hydroquinones in acetonitrile: Mechanistic investigation by voltammetry, {sup 1}H NMR and computation

    Energy Technology Data Exchange (ETDEWEB)

    Alligrant, Timothy M. [Department of Chemistry, Virginia Commonwealth University, 1001 West Main St., P.O. Box 842006, Richmond, VA 23284 (United States); Hackett, John C. [Institute for Structural Biology and Drug Discovery, Virginia Commonwealth University, P.O. Box 980133, Richmond, VA 23219 (United States); Alvarez, Julio C., E-mail: jcalvarez2@vcu.ed [Department of Chemistry, Virginia Commonwealth University, 1001 West Main St., P.O. Box 842006, Richmond, VA 23284 (United States)

    2010-09-01

    This report seeks to address the role of hydrogen bonding with Bronsted acids and bases in proton-coupled electron transfer (PCET) as it pertains to concerted or stepwise pathways of quinone (Q) and hydroquinone (QH{sub 2}) electrochemistry. This study was performed using a series of techniques that included cyclic voltammetry (CV), digital simulations, computational chemistry and {sup 1}H NMR. Hydrogen bonding was inferred by a decrease in diffusion coefficient (D) values measured using a pulsed gradient echo- (PGE-) {sup 1}H NMR technique. Changes of 40.8% and 37.9% in D values were only noted after the addition of two equivalents of acetate to 1,4-hydroquinone (1,4-QH{sub 2}) and catechol (1,2-QH{sub 2}), respectively. In contrast, the D values for the addition of selected amines (pyridine, N,N-diisopropylethylamine and triethylamine) changed only 3.2% on average. Quantum mechanical calculations were conducted to determine the pK{sub a} of all quinoid species to serve as a starting point for the determination of equilibrium constants in voltammetric simulations. Simulations indicate that 1,4-benzoquinone undergoes stepwise electron-proton transfer upon addition of acetic acid, N-ethyldiisopropylammonium perchlorate and pyridinium nitrate and were simulated without the presence of hydrogen bonds. The QH{sub 2} compounds show stepwise proton-electron transfers after addition of the both the conjugate amines and acetate.

  7. Pyrroloquinoline quinone (PQQ inhibits lipopolysaccharide induced inflammation in part via downregulated NF-κB and p38/JNK activation in microglial and attenuates microglia activation in lipopolysaccharide treatment mice.

    Directory of Open Access Journals (Sweden)

    Chongfei Yang

    Full Text Available Therapeutic strategies designed to inhibit the activation of microglia may lead to significant advancement in the treatment of most neurodegenerative diseases. Pyrroloquinoline quinone (PQQ is a naturally occurring redox cofactor that acts as an essential nutrient, antioxidant, and has been reported to exert potent immunosuppressive effects. In the present study, the anti-inflammatory effects of PQQ was investigated in LPS treated primary microglia cells. Our observations showed that pretreatment with PQQ significantly inhibited the production of NO and PGE2 and suppressed the expression of pro-inflammatory mediators such as iNOS, COX-2, TNF-a, IL-1b, IL-6, MCP-1 and MIP-1a in LPS treated primary microglia cells. The nuclear translocation of NF-κB and the phosphorylation level of p65, p38 and JNK MAP kinase pathways were also inhibited by PQQ in LPS stimulated primary microglia cells. Further a systemic LPS treatment acute inflammation murine brain model was used to study the suppressive effects of PQQ against neuroinflammation in vivo. Mice treated with PQQ demonstrated marked attenuation of neuroinflammation based on Western blotting and immunohistochemistry analysis of Iba1-against antibody in the brain tissue. Indicated that PQQ protected primary cortical neurons against microglia-mediated neurotoxicity. These results collectively suggested that PQQ might be a promising therapeutic agent for alleviating the progress of neurodegenerative diseases associated with microglia activation.

  8. Pyrroloquinoline quinone (PQQ) inhibits lipopolysaccharide induced inflammation in part via downregulated NF-κB and p38/JNK activation in microglial and attenuates microglia activation in lipopolysaccharide treatment mice.

    Science.gov (United States)

    Yang, Chongfei; Yu, Lifeng; Kong, Lingbo; Ma, Rui; Zhang, Juliang; Zhu, Qingsheng; Zhu, Jinyu; Hao, Dingjun

    2014-01-01

    Therapeutic strategies designed to inhibit the activation of microglia may lead to significant advancement in the treatment of most neurodegenerative diseases. Pyrroloquinoline quinone (PQQ) is a naturally occurring redox cofactor that acts as an essential nutrient, antioxidant, and has been reported to exert potent immunosuppressive effects. In the present study, the anti-inflammatory effects of PQQ was investigated in LPS treated primary microglia cells. Our observations showed that pretreatment with PQQ significantly inhibited the production of NO and PGE2 and suppressed the expression of pro-inflammatory mediators such as iNOS, COX-2, TNF-a, IL-1b, IL-6, MCP-1 and MIP-1a in LPS treated primary microglia cells. The nuclear translocation of NF-κB and the phosphorylation level of p65, p38 and JNK MAP kinase pathways were also inhibited by PQQ in LPS stimulated primary microglia cells. Further a systemic LPS treatment acute inflammation murine brain model was used to study the suppressive effects of PQQ against neuroinflammation in vivo. Mice treated with PQQ demonstrated marked attenuation of neuroinflammation based on Western blotting and immunohistochemistry analysis of Iba1-against antibody in the brain tissue. Indicated that PQQ protected primary cortical neurons against microglia-mediated neurotoxicity. These results collectively suggested that PQQ might be a promising therapeutic agent for alleviating the progress of neurodegenerative diseases associated with microglia activation.

  9. Aspartic Acid 397 in Subunit B of the Na+-pumping NADH:Quinone Oxidoreductase from Vibrio cholerae Forms Part of a Sodium-binding Site, Is Involved in Cation Selectivity, and Affects Cation-binding Site Cooperativity

    Science.gov (United States)

    Shea, Michael E.; Juárez, Oscar; Cho, Jonathan; Barquera, Blanca

    2013-01-01

    The Na+-pumping NADH:quinone complex is found in Vibrio cholerae and other marine and pathogenic bacteria. NADH:ubiquinone oxidoreductase oxidizes NADH and reduces ubiquinone, using the free energy released by this reaction to pump sodium ions across the cell membrane. In a previous report, a conserved aspartic acid residue in the NqrB subunit at position 397, located in the cytosolic face of this protein, was proposed to be involved in the capture of sodium. Here, we studied the role of this residue through the characterization of mutant enzymes in which this aspartic acid was substituted by other residues that change charge and size, such as arginine, serine, lysine, glutamic acid, and cysteine. Our results indicate that NqrB-Asp-397 forms part of one of the at least two sodium-binding sites and that both size and charge at this position are critical for the function of the enzyme. Moreover, we demonstrate that this residue is involved in cation selectivity, has a critical role in the communication between sodium-binding sites, by promoting cooperativity, and controls the electron transfer step involved in sodium uptake (2Fe-2S → FMNC). PMID:24030824

  10. 2,3-Dichloro-1,4-hydro-quinone 2,3-dichloro-1,4-benzoquinone monohydrate: a quinhydrone-type 1:1 donor-acceptor [D-A] charge-transfer complex.

    Science.gov (United States)

    Guégano, Xavier; Hauser, Jürg; Liu, Shi-Xia; Decurtins, Silvio

    2011-11-01

    IN THE CRYSTAL STRUCTURE OF THE TITLE COMPOUND (SYSTEMATIC NAME: 2,3-dichloro-benzene-1,4-diol 2,3-dichloro-cyclo-hexa-2,5-diene-1,4-dione monohydrate), C(6)H(4)Cl(2)O(2)·C(6)H(2)Cl(2)O(2)·H(2)O, the 2,3-dichloro-1,4-hydro-quinone donor (D) and the 2,3-dichloro-1,4-benzoquinone acceptor (A) mol-ecules form alternating stacks along [100]. Their mol-ecular planes [maximum deviations for non-H atoms: 0.0133 (14) (D) and 0.0763 (14) Å (A)] are inclined to one another by 1.45 (3)° and are thus almost parallel. There are π-π inter-actions involving the D and A mol-ecules, with centroid-centroid distances of 3.5043 (9) and 3.9548 (9) Å. Inter-molecular O-H⋯O hydrogen bonds involving the water mol-ecule and the hy-droxy and ketone groups lead to the formation of two-dimensional networks lying parallel to (001). These networks are linked by C-H⋯O inter-actions, forming a three-dimensional structure.

  11. 2,3-Dichloro-1,4-hydro­quinone 2,3-dichloro-1,4-benzoquinone monohydrate: a quinhydrone-type 1:1 donor-acceptor [D—A] charge-transfer complex

    Science.gov (United States)

    Guégano, Xavier; Hauser, Jürg; Liu, Shi-Xia; Decurtins, Silvio

    2011-01-01

    In the crystal structure of the title compound (systematic name: 2,3-dichloro­benzene-1,4-diol 2,3-dichloro­cyclo­hexa-2,5-diene-1,4-dione monohydrate), C6H4Cl2O2·C6H2Cl2O2·H2O, the 2,3-dichloro-1,4-hydro­quinone donor (D) and the 2,3-dichloro-1,4-benzoquinone acceptor (A) mol­ecules form alternating stacks along [100]. Their mol­ecular planes [maximum deviations for non-H atoms: 0.0133 (14) (D) and 0.0763 (14) Å (A)] are inclined to one another by 1.45 (3)° and are thus almost parallel. There are π–π inter­actions involving the D and A mol­ecules, with centroid–centroid distances of 3.5043 (9) and 3.9548 (9) Å. Inter­molecular O—H⋯O hydrogen bonds involving the water mol­ecule and the hy­droxy and ketone groups lead to the formation of two-dimensional networks lying parallel to (001). These networks are linked by C—H⋯O inter­actions, forming a three-dimensional structure. PMID:22219991

  12. Indigofera suffruticosa Mill extracts up-regulate the expression of the π class of glutathione S-transferase and NAD(P)H: quinone oxidoreductase 1 in rat Clone 9 liver cells.

    Science.gov (United States)

    Chen, Chun-Chieh; Liu, Chin-San; Li, Chien-Chun; Tsai, Chia-Wen; Yao, Hsien-Tsung; Liu, Te-Chung; Chen, Haw-Wen; Chen, Pei-Yin; Wu, Yu-Ling; Lii, Chong-Kuei; Liu, Kai-Li

    2013-09-01

    Because induction of phase II detoxification enzyme is important for chemoprevention, we study the effects of Indigofera suffruticosa Mill, a medicinal herb, on the expression of π class of glutathione S-transferase (GSTP) and NAD(P)H: quinone oxidoreductase 1 (NQO1) in rat Clone 9 liver cells. Both water and ethanolic extracts of I. suffruticosa significantly increased the expression and enzyme activities of GSTP and NQO1. I. suffruticosa extracts up-regulated GSTP promoter activity and the binding affinity of nuclear factor erythroid 2-related factor 2 (Nrf2) with the GSTP enhancer I oligonucleotide. Moreover, I. suffruticosa extracts increased nuclear Nrf2 accumulation as well as ARE transcriptional activity. The level of phospho-ERK was augmented by I. suffruticosa extracts, and the ERK inhibitor PD98059 abolished the I. suffruticosa extract-induced ERK activation and GSTP and NQO-1 expression. Moreover, I. suffruticosa extracts, especially the ethanolic extract increased the glutathione level in mouse liver and red blood cells as well as Clone 9 liver cells. The efficacy of I. suffruticosa extracts in induction of phase II detoxification enzymes and glutathione content implies that I. suffruticosa could be considered as a potential chemopreventive agent.

  13. Production of the Quinone-Methide Triterpene Maytenin by In Vitro Adventitious Roots of Peritassa campestris (Cambess. A.C.Sm. (Celastraceae and Rapid Detection and Identification by APCI-IT-MS/MS

    Directory of Open Access Journals (Sweden)

    Tiago Antunes Paz

    2013-01-01

    Full Text Available Establishment of adventitious root cultures of Peritassa campestris (Celastraceae was achieved from seed cotyledons cultured in semisolid Woody Plant Medium (WPM supplemented with 2% sucrose, 0.01% PVP, and 4.0 mg L−1 IBA. Culture period on accumulation of biomass and quinone-methide triterpene maytenin in adventitious root were investigated. The accumulation of maytenin in these roots was compared with its accumulation in the roots of seedlings grown in a greenhouse (one year old. A rapid detection and identification of maytenin by direct injection into an atmospheric-pressure chemical ionization ion trap tandem mass spectrometer (APCI-IT-MS/MS were performed without prior chromatographic separation. In vitro, the greatest accumulation of biomass occurred within 60 days of culture. The highest level of maytenin—972.11 μg·g−1 dry weight—was detected at seven days of cultivation; this value was 5.55-fold higher than that found in the roots of seedlings grown in a greenhouse.

  14. Induction of NAD(P)H-quinone oxidoreductase 1 by antioxidants in female ACI rats is associated with decrease in oxidative DNA damage and inhibition of estrogen-induced breast cancer

    Science.gov (United States)

    Singh, Bhupendra; Bhat, Hari K.

    2012-01-01

    Exact mechanisms underlying the initiation and progression of estrogen-related cancers are not clear. Literature, evidence and our studies strongly support the role of estrogen metabolism-mediated oxidative stress in estrogen-induced breast carcinogenesis. We have recently demonstrated that antioxidants vitamin C and butylated hydroxyanisole (BHA) or estrogen metabolism inhibitor α-naphthoflavone (ANF) inhibit 17β-estradiol (E2)-induced mammary tumorigenesis in female ACI rats. The objective of the current study was to identify the mechanism of antioxidant-mediated protection against E2-induced DNA damage and mammary tumorigenesis. Female ACI rats were treated with E2 in the presence or absence of vitamin C or BHA or ANF for up to 240 days. Nuclear factor erythroid 2-related factor 2 (NRF2) and NAD(P)H-quinone oxidoreductase 1 (NQO1) were suppressed in E2-exposed mammary tissue and in mammary tumors after treatment of rats with E2 for 240 days. This suppression was overcome by co-treatment of rats with E2 and vitamin C or BHA. Time course studies indicate that NQO1 levels tend to increase after 4 months of E2 treatment but decrease on chronic exposure to E2 for 8 months. Vitamin C and BHA significantly increased NQO1 levels after 120 days. 8-Hydroxydeoxyguanosine (8-OHdG) levels were higher in E2-exposed mammary tissue and in mammary tumors compared with age-matched controls. Vitamin C or BHA treatment significantly decreased E2-mediated increase in 8-OHdG levels in the mammary tissue. In vitro studies using silencer RNA confirmed the role of NQO1 in prevention of oxidative DNA damage. Our studies further demonstrate that NQO1 upregulation by antioxidants is mediated through NRF2. PMID:22072621

  15. Cloning of an Erwinia herbicola gene necessary for gluconic acid production and enhanced mineral phosphate solubilization in Escherichia coli HB101: nucleotide sequence and probable involvement in biosynthesis of the coenzyme pyrroloquinoline quinone.

    Science.gov (United States)

    Liu, S T; Lee, L Y; Tai, C Y; Hung, C H; Chang, Y S; Wolfram, J H; Rogers, R; Goldstein, A H

    1992-09-01

    Escherichia coli is capable of synthesizing the apo-glucose dehydrogenase enzyme (GDH) but not the cofactor pyrroloquinoline quinone (PQQ), which is essential for formation of the holoenzyme. Therefore, in the absence of exogenous PQQ, E. coli does not produce gluconic acid. Evidence is presented to show that the expression of an Erwinia herbicola gene in E. coli HB101(pMCG898) resulted in the production of gluconic acid, which, in turn, implied PQQ biosynthesis. Transposon mutagenesis showed that the essential gene or locus was within a 1.8-kb region of a 4.5-kb insert of the plasmid pMCG898. This 1.8-kb region contained only one apparent open reading frame. In this paper, we present the nucleotide sequence of this open reading frame, a 1,134-bp DNA fragment coding for a protein with an M(r) of 42,160. The deduced sequence of this protein had a high degree of homology with that of gene III (M(r), 43,600) of a PQQ synthase gene complex from Acinetobacter calcoaceticus previously identified by Goosen et al. (J. Bacteriol. 171:447-455, 1989). In minicell analysis, pMCG898 encoded a protein with an M(r) of 41,000. These data indicate that E. coli HB101(pMCG898) produced the GDH-PQQ holoenzyme, which, in turn, catalyzed the oxidation of glucose to gluconic acid in the periplasmic space. As a result of the gluconic acid production, E. coli HB101(pMCG898) showed an enhanced mineral phosphate-solubilizing phenotype due to acid dissolution of the hydroxyapatite substrate.

  16. The environmental pollutant and carcinogen 3-nitrobenzanthrone induces cytochrome P450 1A1 and NAD(P)H:quinone oxidoreductase in rat lung and kidney, thereby enhancing its own genotoxicity.

    Science.gov (United States)

    Stiborová, Marie; Dracínská, Helena; Mizerovská, Jana; Frei, Eva; Schmeiser, Heinz H; Hudecek, Jirí; Hodek, Petr; Phillips, David H; Arlt, Volker M

    2008-05-02

    3-Nitrobenzanthrone (3-NBA) is a carcinogen occurring in diesel exhaust and air pollution. Using the (32)P-postlabelling method, we found that 3-NBA and its human metabolite, 3-aminobenzanthrone (3-ABA), are activated to species forming DNA adducts by cytosols and/or microsomes isolated from rat lung, the target organ for 3-NBA carcinogenicity, and kidney. Each compound generated identical five DNA adducts. We have demonstrated the importance of pulmonary and renal NAD(P)H:quinone oxidoreductase (NQO1) to reduce 3-NBA to species that are further activated by N,O-acetyltransferases and sulfotransferases. Cytochrome P450 (CYP) 1A1 is the essential enzyme for oxidative activation of 3-ABA in microsomes of both organs, while cyclooxygenase plays a minor role. 3-NBA was also investigated for its ability to induce NQO1 and CYP1A1 in lungs and kidneys, and for the influence of such induction on DNA adduct formation by 3-NBA and 3-ABA. When cytosols from rats treated i.p. with 40mg/kg bw of 3-NBA were incubated with 3-NBA, DNA adduct formation was up to 2.1-fold higher than in incubations with cytosols from control animals. This increase corresponded to an increase in protein level and enzymatic activity of NQO1. Incubations of 3-ABA with microsomes of 3-NBA-treated rats led to up to a fivefold increase in DNA adduct formation relative to controls. The stimulation of DNA adduct formation correlated with the potential of 3-NBA to induce protein expression and activity of CYP1A1. These results demonstrate that 3-NBA is capable to induce NQO1 and CYP1A1 in lungs and kidney of rats thereby enhancing its own genotoxic and carcinogenic potential.

  17. The single NqrB and NqrC subunits in the Na(+)-translocating NADH: quinone oxidoreductase (Na(+)-NQR) from Vibrio cholerae each carry one covalently attached FMN.

    Science.gov (United States)

    Casutt, Marco S; Schlosser, Andreas; Buckel, Wolfgang; Steuber, Julia

    2012-10-01

    The Na(+)-translocating NADH:quinone oxidoreductase (Na(+)-NQR) is the prototype of a novel class of flavoproteins carrying a riboflavin phosphate bound to serine or threonine by a phosphodiester bond to the ribityl side chain. This membrane-bound, respiratory complex also contains one non-covalently bound FAD, one non-covalently bound riboflavin, ubiquinone-8 and a [2Fe-2S] cluster. Here, we report the quantitative analysis of the full set of flavin cofactors in the Na(+)-NQR and characterize the mode of linkage of the riboflavin phosphate to the membrane-bound NqrB and NqrC subunits. Release of the flavin by β-elimination and analysis of the cofactor demonstrates that the phosphate group is attached at the 5'-position of the ribityl as in authentic FMN and that the Na(+)-NQR contains approximately 1.7mol covalently bound FMN per mol non-covalently bound FAD. Therefore, each of the single NqrB and NqrC subunits in the Na(+)-NQR carries a single FMN. Elimination of the phosphodiester bond yields a dehydro-2-aminobutyrate residue, which is modified with β-mercaptoethanol by Michael addition. Proteolytic digestion followed by mass determination of peptide fragments reveals exclusive modification of threonine residues, which carry FMN in the native enzyme. The described reactions allow quantification and localization of the covalently attached FMNs in the Na(+)-NQR and in related proteins belonging to the Rhodobacter nitrogen fixation (RNF) family of enzymes. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012).

  18. Effects of Low to Intermediate Water Concentrations on Proton-Coupled Electron Transfer (PCET) Reactions of Flavins in Aprotic Solvents and a Comparison with the PCET Reactions of Quinones.

    Science.gov (United States)

    Tan, Serena L J; Novianti, Maria L; Webster, Richard D

    2015-11-05

    The electrochemical reduction mechanisms of 2 synthesized flavins (Flox) were examined in detail in deoxygenated solutions of DMSO containing varying amounts of water, utilizing variable scan rate cyclic voltammetry (ν = 0.1-20 V s(-1)), controlled-potential bulk electrolysis, and UV-vis spectroscopy. Flavin 1, which contains a hydrogen atom at N(3), is capable of donating its proton to other reduced flavin species. After 1e(-) reduction, the initially formed Fl(•-) receives a proton from another Flox to form FlH(•) (and concomitantly produce the deprotonated flavin, Fl(-)), although the equilibrium constant for this process favors the back reaction. Any FlH(•) formed at the electrode surface immediately undergoes another 1e(-) reduction to form FlH(-), which reacts with Fl(-) to form 2 molecules of Fl(•-). Further 1e(-) reduction of Fl(•-) at more negative potentials produces the dianion, Fl(2-), which can also be protonated by another Flox to form FlH(-) and Fl(-). Flavin 2, which is methylated at N(3) (and therefore has no acidic proton), undergoes a simple chemically reversible 1e(-) reduction process in DMSO provided the water content is low (solvents results in protonation of the anion radical species, Fl(•-), for both flavins, causing an increase in the amount of FlH(-) in solution. This behavior contrasts with what is observed for quinones, which are also reduced in two 1e(-) steps in aprotic organic solvents to form the radical anions and dianions, but are able to exist in hydrogen-bonded forms (with trace or added water) without undergoing protonation.

  19. A Novel Mechanism for Halogenated Quinone- Mediated and Metal-Independent Organic Fenton-Like Reaction%不依赖于过渡金属离子的卤代醌介导的新型有机类Fenton反应机理

    Institute of Scientific and Technical Information of China (English)

    朱本占; 任福荣; 夏海英; 邵杰

    2012-01-01

    卤代醌是许多卤芳香持久有机污染物的致癌代谢产物和饮用水消毒副产物.羟基自由基(OH)被公认为生物系统中最具活性的活性氧物种,能导致生物体内DNA等生物大分子的氧化损伤.目前,最被广泛接受的OH产生机理是过渡金属离子催化的Fenton反应.综合采用电子自旋共振二级自旋捕获和其他分析方法,发现四氯苯醌和其它卤代醌皆可通过不依赖于过渡金属离子的途径,显著促进氢过氧化物(H2O2或有机氢过氧化物)的分解而产生OH或烷氧自由基,并首次检测到一种新型的、以碳为中心的醌自由基.基于以上研究,提出一类不依赖于过渡金属离子的卤代醌介导的新型有机类Fenton反应机理.%Halogenated quinones are a class of carcinogenic metabolites of many halogenated persistent organic pollutants and new chlorination disinfection byproducts in drinking water. The hydroxyl radical ("OH) has been considered to be one of the most reactive oxygen species produced in biological systems. It has been shown that 'OH can cause oxidative damage to DNA and other macromolecuies. One of the most widely accepted mechanisms for OH production is through the transition metal-catalyzed Fenton reaction. Through the complementary application of electron spin resonance (ESR) secondary spin-trapping and other analytical methods, we found that tetrachloro-1,4-benzoquinone (TCBQ) and other halogenated quinones could markedly enhance the decomposition of hydroperoxides (H2O2 and organic hydroperoxides) and formation of "OH and alkoxyl radicals independent of transition metal ions. A novel carbon-centered quinone ketoxy radical was also detected and identified for the first time. Based on these data, we proposed a novel mechanism for metal-independent and halogenated quinone-mediated organic Fenton-like reaction.

  20. Aqueous extracts of selenium-fertilized broccoli increase selenoprotein activity and inhibit DNA single-strand breaks, but decrease the activity of quinone reductase in Hepa 1c1c7 cells.

    Science.gov (United States)

    Keck, Anna-Sigrid; Finley, John W

    2006-05-01

    Depending on growth conditions, broccoli may be enriched in the isothiocyanate sulforaphane and/or the mineral selenium (Se); both compounds may play an important role in the reduction of intracellular oxidative stress and chronic disease prevention. Sulforaphane up-regulates transcription of Phase II detoxification proteins (e.g. quinone reductase [QR]), whereas Se is needed for the production of thioredoxin reductase (TR) and glutathione peroxidase-1 (GPx1), both of which exhibit antioxidant activity. The objective of the present study was to determine whether the fertilization of broccoli with Se increases the antioxidant ability of broccoli. Hydrogen peroxide-induced DNA single-strand breaks (measured by single cell electrophoresis, Comet assay) and activity of antioxidant enzymes (GPx, TR and QR) were measured in mouse hepatoma cells (Hepa 1c1c7 cells) treated with purified sulforaphane, sodium selenite or extracts of selenized broccoli. When supplied separately as chemically pure substances, sodium selenite was more effective than sulforaphane for reduction of single-strand breaks. Se-fertilized broccoli extracts were the most effective for reduction of DNA single-strand breaks, and extracts that contained 0.71 microM Se and 0.08 microM sulforaphane inhibited 94% of DNA single-strand breaks. A significant positive association (r = 0.81, p = 0.009) between GPx1 activity and inhibition of DNA single-strand breaks as well as a 24h lag time between addition of Se, sulforaphane or broccoli extract and inhibition of single-strand breaks suggests that some of the antioxidant protection is mediated through selenoproteins. Conversely, fertilization of broccoli with Se decreased the ability of broccoli extract to induce QR activity. These results demonstrate that Se and sulforaphane, alone or as a component of broccoli, may help decrease oxidative stress. They further suggest that Se is the most important for decreasing oxidative stress, but maximizing the Se content

  1. Absolute quantification of NAD(P)H:quinone oxidoreductase 1 in human tumor cell lines and tissues by liquid chromatography–mass spectrometry/mass spectrometry using both isotopic and non-isotopic internal standards

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Zhiyuan; Wu, Mengqiu; Li, Yingchun; Zheng, Xiao; Liu, Huiying; Cheng, Xuefang [State Key Laboratory of Natural Medicines, Key Lab of Drug Metabolism and Pharmacokinetics, China Pharmaceutical University, Nanjing 210009 (China); Xu, Lin [Department of Thoracic Surgery, Jiangsu Cancer Hospital, Nanjing 210009 (China); Wang, Guangji, E-mail: guangjiwang@hotmail.com [State Key Laboratory of Natural Medicines, Key Lab of Drug Metabolism and Pharmacokinetics, China Pharmaceutical University, Nanjing 210009 (China); Hao, Haiping, E-mail: hhp_770505@yahoo.com.cn [State Key Laboratory of Natural Medicines, Key Lab of Drug Metabolism and Pharmacokinetics, China Pharmaceutical University, Nanjing 210009 (China)

    2013-04-15

    Highlights: ► The peptide fingerprint map of NQO1 has been defined by using TripleTOF. ► Signature peptide of NQO1 can be quickly quantified within 10 min. ► Analysis is performed with non-isotopic analog and compared with isotopic method. ► This method is adequate for NQO1 quantitation from human cancer cells and tissues. -- Abstract: NAD(P)H:quinone oxidoreductase 1 (NQO1, DT-diaphorase) is a prognostic biomarker and a potential therapeutic target for various tumors. Therefore, it is of significance to develop a robust method for the absolute quantification of NQO1. This study aimed to develop and validate a LC–MS/MS based method and to test the appropriateness of using non-isotopic analog peptide as the internal standard (IS) by comparing with a stable isotope labeled (SIL) peptide. The chromatographic performance and mass spectra between the selected signature peptide of NQO1 and the non-isotopic peptide were observed to be very similar. The use of the two internal standards was validated appropriate for the absolute quantification of NQO1, as evidenced by satisfactory validation results over a concentration range of 1.62–162 fmol μL{sup −1}. This method has been successfully applied to the absolute quantification of NQO1 expression in various tumor cell lines and tissues. NQO1 expression in human tumor tissues is much higher than that in the neighboring normal tissues in both the cases of lung and colon cancer. The quantitative results obtained from the isotopic and non-isotopic methods are quite similar, further supporting that the use of non-isotopic analog peptide as internal standard is appropriate and feasible for the quantification of NQO1. By comparing with a classical isotopic IS, the present study indicates that the use of a non-isotopic peptide analog to the proteotypic peptide as the internal standard can get equal accuracy and preciseness in measuring NQO1. The universal applicability of the non-isotopic IS approach for the

  2. Bioactivation of 5-(aziridin-1-yl)-2,4-dinitrobenzamide (CB 1954) by human NAD(P)H quinone oxidoreductase 2: a novel co-substrate-mediated antitumor prodrug therapy.

    Science.gov (United States)

    Knox, R J; Jenkins, T C; Hobbs, S M; Chen, S; Melton, R G; Burke, P J

    2000-08-01

    A novel prodrug activation system, endogenous in human tumor cells, is described. A latent enzyme-prodrug system is switched on by a simple synthetic, small molecule co-substrate. This ternary system is inactive if any one of the components is absent. CB 1954 [5-(aziridin-1-yl)-2,4-dinitrobenzamide] is an antitumor prodrug that is activated in certain rat tumors via its 4-hydroxylamine derivative to a potent bifunctional alkylating agent. However, human tumor cells are resistant to CB 1954 because they are unable to catalyze this bioactivation efficiently. A human enzyme has been discovered that can activate CB 1954, and it has been shown to be commonly present in human tumor cells. The enzyme is NQO2 [NAD(P)H quinone oxidoreductase 2], but its activity is normally latent, and a nonbiogenic co-substrate such as NRH [nicotinamide riboside (reduced)] is required for enzymatic activity. There is a very large (100-3000-fold) increase in CB 1954 cytotoxicity toward either NQO2-transfected rodent or nontransfected human tumor cell lines in the presence of NRH. Other reduced pyridinium compounds can also act as co-substrates for NQO2. Thus, the simplest quaternary salt of nicotinamide, 1-methyl-3-carboxamidopyridinium iodide, was a co-substrate for NQO2 when reduced to the corresponding 1,4-dihydropyridine derivative. Increased chain length and/or alkyl load at the 1-position of the dihydropyridine ring improved specific activity, and compounds more active than NRH were found. However, little activity was seen with either the 1-benzyl or 1-(2-phenylethyl) derivatives. A negatively charged substituent at the 3-position of the reduced pyridine ring also negated the ability of these compounds to act as cosubstrates for NQO2. In particular, 1-carbamoylmethyl-3-carbamoyl-1,4dihydropyridine was shown to be a co-substrate for NQO2 with greater stability than NRH, with the ability to enter cells and potentiate the cytotoxicity of CB 1954. Furthermore, this agent is synthetically

  3. Response of Chloroplast NAD(P)H Dehydrogenase-Mediated Cyclic Electron Flow to a Shortage or Lack in Ferredoxin-Quinone Oxidoreductase-Dependent Pathway in Rice Following Short-Term Heat Stress.

    Science.gov (United States)

    Essemine, Jemaa; Qu, Mingnan; Mi, Hualing; Zhu, Xin-Guang

    2016-01-01

    Cyclic electron flow (CEF) around photosystem I (PSI) can protect photosynthetic electron carriers under conditions of stromal over-reduction. The goal of the research reported in this paper was to investigate the responses of both PSI and photosystem II (PSII) to a short-term heat stress in two rice lines with different capacities of cyclic electron transfer, i.e., Q4149 with a high capacity (hcef) and C4023 with a low capacity (lcef). The absorbance change at 820 nm (ΔA820) was used here to assess the charge separation in the PSI reaction center (P700). The results obtained show that short-term heat stress abolishes the ferredoxin-quinone oxidoreductase (FQR)-dependent CEF in rice and accelerates the initial rate of P700 (+) re-reduction. The P700 (+) amplitude was slightly increased at a moderate heat-stress (35°C) because of a partial restriction of FQR but it was decreased following high heat-stress (42°C). Assessment of PSI and PSII activities shows that PSI is more susceptible to heat stress than PSII. Under high temperature, FQR-dependent CEF was completely removed and NDH-dependent CEF was up-regulated and strengthened to a higher extent in C4023 than in Q4149. Specifically, under normal growth temperature, hcef (Q4149) was characterized by higher FQR- and chloroplast NAD(P)H dehydrogenase (NDH)-dependent CEF rates than lcef (C4023). Following thermal stress, the activation of NDH-pathway was 130 and 10% for C4023 and Q4149, respectively. Thus, the NDH-dependent CEF may constitute the second layer of plant protection and defense against heat stress after the main route, i.e., FQR-dependent CEF, reaches its capacity. We discuss the possibility that under high heat stress, the NDH pathway serves as a safety valve to dissipate excess energy by cyclic photophosphorylation and overcome the stroma over-reduction following inhibition of CO2 assimilation and any shortage or lack in the FQR pathway. The potential role of the NDH-dependent pathway during the

  4. Antitrypanosomal isoflavan quinones from Abrus precatorius

    CSIR Research Space (South Africa)

    Hata, Y

    2014-03-01

    Full Text Available known from the first batch of plant material. The absolute configuration of compounds 1 to 3was determined by comparison of electronic circular dichroism (ECD) spectra with calculated ECD data. Compounds 2 to 5 showed high in vitro activity against T. b...

  5. Expression of sulfide-quinone reductase (SQR) in Escherichia coli and Lactic acid bacteria%SQR基因在大肠杆菌和乳酸菌中的表达

    Institute of Scientific and Technical Information of China (English)

    潘伟芹; 于建宁; 王公金; 徐小波; 于峰祥; 李燕

    2012-01-01

    To study the construction of lactococcal expression vector pMG36e-SQR-Myc and its expression in Esche-richia coli and Lactococcus lactis MG1363, the expression vector pMG36e and the gene (SQR-Myc) were digested by two restriction endonucleases. SQR-Myc gene was ligated with expression vector pMG36e by T4 DNA ligase, and the Iigation products were transferred into Escherichia coli by KCM to get the recombinant vector. The recombinant vector pMG36e-SQR-Myc were verified by double enzyme digestion and PCR amplification. pMG36e-SQR-Myc were transferred into Lactococcus lactis MG1363 by eletroporation. The expression of SQR in Lactococcus lactis MG1363 was detected by SDS-PAGE and Western-blotting. The results showed that the recombinant plasmid pMG36e-SQR-Myc was successfully constructed, and the SQR expression in Escherichia coli and Lactococcus lactis MG1363 were successfully detected. Lactococcus lactis MG1363 could be used for the expression of sulfide-quinone reductase (SQR).%为了研究硫化物-醌氧化还原酶( SQR)基因的乳酸菌表达载体pMG36e-SQR-Myc的构建及其在大肠杆菌DH5a和乳酸菌MG1363中的表达,通过限制性内切酶酶切大肠杆菌-乳酸菌穿梭表达载体pMG36e与目的片段SQR-Myc,回收纯化并用T4连接酶进行连接,连接产物通过KCM法转化到大肠杆菌DH5a中,提取所得到阳性大肠杆菌菌株质粒pMG36e-SQR-Myc进行双酶切鉴定与普通PCR鉴定;并通过电转化将重组质粒导入乳酸菌MG1363中,采用SDS-PAGE电泳和Western-blotting检测SQR蛋白质在其中的表达情况.结果显示,SQR乳酸菌重组表达载体pMG36e-SQR-Myc被成功构建,目的蛋白质SQR在大肠杆菌和乳酸菌MG1363中被成功检测到.因此,乳酸菌MG1363可以用来表达硫化物-醌氧化还原酶(SQR).

  6. 精神分裂症患者醌氧化还原酶1 C609T 多态性与血脂水平相关性研究%The correlation of quinone oxidoreductase 1 gene C609T poly-morphism and blood lipid levels of schizophrenia patients

    Institute of Scientific and Technical Information of China (English)

    张炳奎; 杨保春; 赵若莲

    2014-01-01

    目的:探讨醌氧化还原酶1 C609 T 基因多态性与精神分裂症患者血脂水平的相关性。方法对328例精神分裂症患者血脂水平及醌氧化还原酶1 C609 T基因多态性进行检测分析。结果本组患者醌氧化还原酶1 C609T位点CC、CT 和 T T基因型频率分别为43.9%、42.1%和14.0%;C和T等位基因频率分别为66.3%和33.7%。醌氧化还原酶1 C609T基因型频率、等位基因频率与患者血脂水平均无显著相关性(P>0.05)。结论醌氧化还原酶1基因C609T位点在精神分裂症患者中存在多态性,其基因型频率、等位基因频率与患者的血脂水平无显著相关性。%Objective To explore the correlation of quinone oxidoreductase 1 (NAD (P) H :quinone oxidoreductase l ,NQO1) gene C609T polymorphism and blood lipid levels of schizophrenia patients .Methods Blood lipid levels and NQO1 gene C609T polymor-phism were detected and analyzed in 328 schizophrenia patients .Results The frequency of genotype CC , CT and TT at NQO1 locus C609T was 43 .9% ,42 .1% and 14 .0% respectively ;C and T allele frequency were 66 .3% and 33 .7% respectively .Both NQO1 C609T genotype and allele frequency had no obvious cor-relation to blood lipid levels (P> 0 .05) .Conclusion Schizophrenia patients have NQO1 gene C609T pol-ymorphisms ,its genotype and allele frequency had no obvious correlation to blood lipid levels .

  7. 正常培养的人类前列腺癌细胞对白藜芦醇的吸收及白藜芦醇对靶向蛋白醌还原酶2QR2的作用%Uptake of resveratrol and role of resveratrol-targeting protein, quinone reductase 2, in normally cultured human prostate cells

    Institute of Scientific and Technical Information of China (English)

    Tze-Chen Hsieh

    2009-01-01

    Resveratrol is a dietary polyphenol espoused to have chemopreventive activity against a variety of human cancer types. We first reported that resveratrol significantly decreases the proliferation of both androgen-dependent and hormone-refractory prostate cancer cells. However, the effects of resveratrol in normal prostate epithelial and stromal cells, particularly with regard to its uptake, subcellular distribution and intracellular targets, have not been investigated. To advance the knowledge on accessibility and cellular disposition of resveratrol in prostate cells, [3H] resveratrol, fractionation of cell extracts into subcellular compartments, Western blot analysis, resveratrol affinity column chromatography and flow cytometry were used to study the uptake and intracellular distribution of resveratrol in normally cultured prostate stromal (PrSCs) and epithelial cells (PrECs). Pretreatment of both PrSCs and PrECs for 2 days with resveratrol modulated its uptake and selectively increased its distribution to the membrane and organelle compartments. Resveratrol affinity column chromatography studies showed differential expression of a previously identified resveratrol-targeting protein, quinone reductase 2 (QR2), in PrSCs and PrECs. Flow cytometric analysis comparing resveratrol-treated and untreated PrSCs showed a large decrease in G1-phase and a concomitant increase in S and G2/M-phases of the cell cycle. These results suggest that resveratrol suppresses PrSC proliferation by affecting cell cycle phase distribution, which may involve the participation by QR2.

  8. Inhibition of glutathione S-transferase P1-1 in mouse lung epithelial cells by the tumor promoter 2,6-di-tert-butyl-4-methylene-2,5-cyclohexadienone (BHT-quinone methide): protein adducts investigated by electrospray mass spectrometry.

    Science.gov (United States)

    Lemercier, Jean-Noël; Meier, Brent W; Gomez, Jose D; Thompson, John A

    2004-12-01

    Oxidation of the food preservative 2,6-di-tert-butyl-4-methylphenol (BHT) by mouse lung cytochrome P450 produces electrophilic quinone methides thought to promote lung tumors in mice by covalent binding to critical proteins. Specific pulmonary targets of 2,6-di-tert-butyl-4-methylenecyclohexa-2,5-dienone (BHT-QM) have not been identified, however. The present work was undertaken to determine if glutathione S-transferase P1-1 (GSTP1-1) is alkylated by BHT-QM, as this protein is overexpressed in tumors and has important roles in protecting cells from electrophiles and oxidants and in regulating stress kinases. This work was conducted with cell lines C10 and E10 derived from mouse lung epithelia and their spontaneous transformants, the tumorigenic cell lines A5 and E9. Cytosolic GSTs were isolated by affinity chromatography and analyzed by ESI-LC/MS. Ion current chromatograms indicated that GSTP1 predominates over the other isoforms, especially in tumorigenic cells. Treatment with BHT-QM inhibited cytosolic GST activity by 28-44%, and inhibition was exacerbated by depleting intracellular GSH. Alkylation of GSTP1 by BHT-QM was investigated by separating cytosolic proteins with two-dimensional SDS-PAGE and detecting adducts by Western blotting with polyclonal antibodies that recognize the BHT group. The identity of GSTP1 comigrating with immunoreactive material was confirmed by in-gel proteolysis and LC/MS/MS analysis. Human GSTP1 was utilized to investigate the specific residues involved in QM binding. The only peptide adduct detected in digests of monoadducted GSTP1 corresponded to Cys101, whereas adducts at Cys14, Cys47, and Cys101 were identified from the trialkylated protein. Losses of transferase activity were most influenced by alkylation at Cys47, but binding to Cys14 appeared to inhibit the activity further. These findings demonstrate that cytosolic GSTP1 may be a target for BHT-QM resulting in decreased cellular protection from electrophiles and oxidants

  9. Pyrroloquinoline-quinone and its versatile roles in biological processes

    Indian Academy of Sciences (India)

    H S Misra; Y S Rajpurohit; N P Khairnar

    2012-06-01

    Pyrroloquinoline-quinine (PQQ) was initially characterized as a redox cofactor for membrane-bound dehydrogenases in the bacterial system. Subsequently, PQQ was shown to be an antioxidant protecting the living cells from oxidative damage in vivo and the biomolecules from artificially produced reaction oxygen species in vitro. The presence of PQQ has been documented from different biological samples. It functions as a nutrient and vitamin for supporting the growth and protection of living cells under stress. Recently, the role of PQQ has also been shown as a bio-control agent for plant fungal pathogens, an inducer for proteins kinases involved in cellular differentiation of mammalian cells and as a redox sensor leading to development of biosensor. Recent reviews published on PQQ and enzymes requiring this cofactor have brought forth the case specific roles of PQQ. This review covers the comprehensive information on various aspects of PQQ known till date. These include the roles of PQQ in the regulation of cellular growth and differentiation in mammalian system, as a nutrient and vitamin in stress tolerance, in crop productivity through increasing the availability of insoluble phosphate and as a bio-control agent, and as a redox agent leading to the biosensor development. Most recent findings correlating the exceptionally high redox recycling ability of PQQ to its potential as anti-neurodegenerative, anticancer and pharmacological agents, and as a signalling molecule have been distinctly brought out. This review discusses different findings suggesting the versatility in PQQ functions and provides the most plausible intellectual basis to the ubiquitous roles of this compound in a large number of biological processes, as a nutrient and a perspective vitamin.

  10. Pyrroloquinoline-quinone suppresses liver fibrogenesis in mice.

    Directory of Open Access Journals (Sweden)

    Dongwei Jia

    Full Text Available Liver fibrosis represents the consequences of a sustained wound healing response to chronic liver injuries, and its progression toward cirrhosis is the major cause of liver-related morbidity and mortality worldwide. However, anti-fibrotic treatment remains an unconquered area for drug development. Accumulating evidence indicate that oxidative stress plays a critical role in liver fibrogenesis. In this study, we found that PQQ, a natural anti-oxidant present in a wide variety of human foods, exerted potent anti-fibrotic and ROS-scavenging activity in Balb/C mouse models of liver fibrosis. The antioxidant activity of PQQ was involved in the modulation of multiple steps during liver fibrogenesis, including chronic liver injury, hepatic inflammation, as well as activation of hepatic stellate cells and production of extracellular matrix. PQQ also suppressed the up-regulation of RACK1 in activated HSCs in vivo and in vitro. Our data suggest that PQQ suppresses oxidative stress and liver fibrogenesis in mice, and provide rationale for the clinical application of PQQ in the prevention and treatment of liver fibrosis.

  11. On the Origin of Photodynamic activity of Perylene Quinone Framework

    Science.gov (United States)

    Parida, Dibyajyoti; Pancharatna, Pattath D.; Balakrishnarajan, Musiri M.

    2016-10-01

    The basic skeleton of perylenequinone is surprisingly ubiquitous in several naturally occurring pigments, such as Hypocrellins, Cercosporin, etc. to name a few. Several of these molecules and their derivatives are also experimentally characterized as potent candidates for photodynamic therapy and are predicted to be aiding the formation singlet Oxygen. Theoretical calculations that unravel the mystery behind the perylenequinone motif in these bio-molecules. Perylenequinone framework has a unique frontier MOs that aid in facile intersystem crossing of the π-π* excitation. The resulting triplet state remarkably resists phosphorescence that presumably leads to high quantum yield of singlet oxygen production. The excitation assisted change in the nature of conjugation and the attendant out-of-plane distortion of the perylene framework is found to be the general characteristic of all these systems and the substituents at the bay region favourably assist the excited state behavior as shown by time dependent/ independent DFT calculations.

  12. CHARACTERIZATION OF STABLE BENZOLALPYRENE-7,8-QUINONE-DNA ADDUCTS IN CALF THYMUS DNA AND POLYDEOXYNUCLEOTIDES

    Science.gov (United States)

    Bcnzo[a]pyrene-7,8-dione (BPQ) is a reactive aldo-keto reductase-mediated product of B[a]P-7,8-diol, a major P450/epoxide hydrolase metabolite of the multi-species carcinogen, B[a]P. The role of BPQ in B[a]P's genotoxicity and carcinogenesis is evolving. Toxicity pathways involvi...

  13. CHARACTERIZATION OF STABLE BENZO(A)PYRENE-7,8-QUINONE-DNA ADDUCTS IN CALF THYMUS DNA

    Science.gov (United States)

    Benzo[alpyrene-7,8-dione (BPQ) is a reactive aldo-keto reductase-mediated product of B[a]P-7,8-diol, a major P450/epoxide hydrolase metabolite of the multi-species carcinogen, B[a]P. The role of BPQ in B[a]P's genotoxicity and carcinogenesis is evolving. Toxicity pathways involvi...

  14. The Control of Orbital Mixing in Ruthenium Complexes Containing Quinone Related Ligands

    Science.gov (United States)

    1991-04-04

    F D’rN MiTcr) F1 S.-’-’ -5 i"’C .1sktuInii 2a A EOP 5 EP0N6 ic %-𔃻,10AL ’ -:- 0 1 IoilouoC Area coce) 22C ;"C;- 3yMBOL Dr Roald A.De Mrc 110 FORM...Liaw, D.-S.; Chen, CA-.; Wang , Y. Inorg. China. Acta 1985, Ji(3, L31.. 28. Christoph, G. G.; Goedken, V. L. J. Am. Chem. Soc. 1973, 25, 3869. 29. Hall

  15. Anti-inflammatory and quinone reductase inducing compounds from fermented noni exudates

    Science.gov (United States)

    A new fatty acid ester disaccharide, 2-O-(ß-D-glucopyranosyl)-1-O- (2E,4Z,7Z)-deca-2,4,7-trienoyl-ß-D-glucopyranose (1), a new ascorbic acid derivative, 2-caffeyl-3-ketohexulofuranosonic acid '-lactone (2), and a new iridoid glycoside, 10-dimethoxyfermiloside (5), were isolated along with thirteen k...

  16. Quinones as Electron Acceptors and Redox Mediators for the Anaerobic Biotransformation of Priority Pollutants

    NARCIS (Netherlands)

    Cervantes-Carillo, F.J.

    2002-01-01

    Humus is the most abundant organic fraction in the biosphere. It is composed of a complex structure in which recalcitrant polymers prevail with a residence time lasting decades or even centuries. Despite the recalcitrance of humic substances, they have recently been recognized to play an important r

  17. Quinone-respiration improves dechlorination of carbon tetrachloride by anaerobic sludge

    NARCIS (Netherlands)

    Cervantes, F.J.; Vu-Thi-Thu, L.; Lettinga, G.; Field, J.A.

    2004-01-01

    The impact of humic acids and the humic model compound, anthraquinone-2,6-disulfonate (AQDS), on the biodegradation of carbon tetrachloride (CT) by anaerobic granular sludge was studied. Addition of both humic acids and AQDS at sub-stoichiometric levels increased the first-order rate of conversion o

  18. First total synthesis of justicidone, a p-quinone-lignan derivative from Justicia hyssopifolia.

    Science.gov (United States)

    Boluda, Carlos J; López, Hermelo; Pérez, José A; Trujillo, Juan M

    2005-08-01

    The first synthesis of justicidone (4-(1',3'-Benzodioxol-5'-yl)-6-methoxynaphtho[2,3-c]furan-1,5,8(3H)-trione) was carried out from piperonal, as a starting compound, through a lineal process using well known reactions.

  19. Catalytic reaction of cytokinin dehydrogenase : preference for quinones as electron acceptors

    NARCIS (Netherlands)

    Frébortová, Jitka; Fraaije, Marco W.; Galuszka, Petr; Šebela, Marek; Peč, Pavel; Hrbáč, Jan; Novák, Ondřej; Bilyeu, Kristin D.; English, James T.; Frébort, Ivo; Sebela, M.; Pec, P.; Hrbac, J.; Frebort, [No Value

    2004-01-01

    The catalytic reaction of cytokinin oxidase/dehydrogenase (EC 1.5.99.12) was studied in detail using the recombinant flavoenzyme from maize. Determination of the redox potential of the covalently linked flavin cofactor revealed a relatively high potential dictating the type of electron acceptor that

  20. Investigation of the charge effect on the electrochemical transduction in a quinone-based DNA sensor

    DEFF Research Database (Denmark)

    Reisberg, S.; Piro, B.; Noel, V.

    2008-01-01

    To elucidate the mechanism involved in the electrochemical transduction process of a conducting polymer-based DNA sensor, peptide nucleic acids (PNA) were used. PNA are DNA analogues having similar hybridization properties but are neutral. This allows to discriminate the electrostatic effect of D...

  1. In vitro activity of almond skin polyphenols for scavenging free radicals and inducing quinone reductase

    Science.gov (United States)

    Observational studies and clinical trials suggest nut intake, including almonds, is associated with an enhancement in antioxidant defense and a reduction in risk of cancer and cardiovascular disease. Almond skins are rich in polyphenols (ASP) that may contribute to these putative benefits. To assess...

  2. Gac-mediated changes in pyrroloquinoline quinone biosynthesis enhance the antimicrobial activity of Pseudomonas fluorescens SBW25

    NARCIS (Netherlands)

    Cheng, X.; Voort, van der M.; Raaijmakers, J.M.

    2015-01-01

    In Pseudomonas species, production of secondary metabolites and exoenzymes is regulated by the GacS/GacA two-component regulatory system. In P. fluorescens SBW25, mutations in the Gac-system cause major transcriptional changes and abolished production of the lipopeptide viscosin and of an exoproteas

  3. Interaction of Herbicides and Quinone with the QB-Protein of the Diuron-Resistant Chlamydomonas reinhardtii Mutant Dr2

    Science.gov (United States)

    Haworth, Philip; Steinback, Katherine E.

    1987-01-01

    We have used the diuron-resistant Dr2 mutant of Chlamydomonas reinhardtii which is altered in the 32 kilodalton QB-protein at amino acid 219 (valine to isoleucine), to investigate the interactions of herbicides and plastoquinone with the 32 kilodalton QB-protein. The data contained in this report demonstrate that the effects of this mutation are different from those of the more completely characterized mutant which confers extreme resistance to triazines in higher plants. The mutation in C. reinhardtii Dr2 confers only slight resistance to a number of inhibitors of photosynthetic electron transport. Extreme triazine resistance results from an increase in the binding constant of the herbicide with the 32 kilodalton QB-protein, in contrast the diuron binding constant for chloroplasts isolated from wild-type (sensitive) Chlamydomonas and the resistant Dr2 are indistinguishable. We conclude that the altered structure in the 32 kilodalton QB-protein of Dr2 does not directly affect the diuron binding site. This mutation appears to alter the steric properties of the binding protein in such a way that diuron and plastoquinone do not directly compete for binding. This steric perturbation confers mild resistance to other herbicidal inhibitors of photosynthesis and alters the kinetics of QA to QB electron transfer. PMID:16665318

  4. Functions of Flavin Reductase and Quinone Reductase in 2,4,6-Trichlorophenol Degradation by Cupriavidus necator JMP134▿

    OpenAIRE

    Belchik, Sara Mae; Xun, Luying

    2007-01-01

    The tcpRXABCYD operon of Cupriavidus necator JMP134 is involved in the degradation of 2,4,6-trichlorophenol (2,4,6-TCP), a toxic pollutant. TcpA is a reduced flavin adenine dinucleotide (FADH2)-dependent monooxygenase that converts 2,4,6-TCP to 6-chlorohydroxyquinone. It has been implied via genetic analysis that TcpX acts as an FAD reductase to supply TcpA with FADH2, whereas the function of TcpB in 2,4,6-TCP degradation is still unclear. In order to provide direct biochemical evidence for t...

  5. Dopamine inhibits lipopolysaccharide-induced nitric oxide production through the formation of dopamine quinone in murine microglia BV-2 cells

    Directory of Open Access Journals (Sweden)

    Yasuhiro Yoshioka

    2016-02-01

    Full Text Available Dopamine (DA has been suggested to modulate functions of glial cells including microglial cells. To reveal the regulatory role of DA in microglial function, in the present study, we investigated the effect of DA on lipopolysaccharide (LPS-induced nitric oxide (NO production in murine microglial cell line BV-2. Pretreatment with DA for 24 h concentration-dependently attenuated LPS-induced NO production in BV-2 cells. The inhibitory effect of DA on LPS-induced NO production was not inhibited by SCH-23390 and sulpiride, D1-like and D2-like DA receptor antagonists, respectively. In addition, pretreatment with (−-(6aR,12bR-4,6,6a,7,8,12b-Hexahydro-7-methylindolo[4,3-a]phenanthridin (CY 208–243 and bromocriptine, D1-like and D2-like DA receptor agonists, respectively, did not affect the LPS-induced NO production. N-Acetylcysteine, which inhibits DA oxidation, completely inhibited the effect of DA. Tyrosinase, which catalyzes the oxidation of DA to DA quionone (DAQ, accelerated the inhibitory effect of DA on LPS-induced NO production. These results suggest that DA attenuates LPS-induced NO production through the formation of DAQ in BV-2 cells.

  6. NAD(P)H:quinone oxidoreductase 1 activity reduces hypertrophy in 3T3-L1 adipocytes

    Science.gov (United States)

    The nuclear factor E2-related factor 2 (Nrf2)/Kelch-like ECH-associated protein 1 (Keap1) pathway responds to oxidative stress via control of the expression of several antioxidant genes. Recent efforts demonstrate that Nrf2 modulates development of adiposity and adipogenesis. However little is kno...

  7. Cyanobacterial photosystem II at 2.9-A resolution and the role of quinones, lipids, channels and chloride

    NARCIS (Netherlands)

    Guskov, Albert; Kern, Jan; Gabdulkhakov, Azat; Broser, Matthias; Zouni, Athina; Saenger, Wolfram

    2009-01-01

    Photosystem II (PSII) is a large homodimeric protein-cofactor complex located in the photosynthetic thylakoid membrane that acts as light-driven water:plastoquinone oxidoreductase. The crystal structure of PSII from Thermosynechococcus elongatus at 2.9-A resolution allowed the unambiguous assignment

  8. Dopamine inhibits lipopolysaccharide-induced nitric oxide production through the formation of dopamine quinone in murine microglia BV-2 cells.

    Science.gov (United States)

    Yoshioka, Yasuhiro; Sugino, Yuta; Tozawa, Azusa; Yamamuro, Akiko; Kasai, Atsushi; Ishimaru, Yuki; Maeda, Sadaaki

    2016-02-01

    Dopamine (DA) has been suggested to modulate functions of glial cells including microglial cells. To reveal the regulatory role of DA in microglial function, in the present study, we investigated the effect of DA on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in murine microglial cell line BV-2. Pretreatment with DA for 24 h concentration-dependently attenuated LPS-induced NO production in BV-2 cells. The inhibitory effect of DA on LPS-induced NO production was not inhibited by SCH-23390 and sulpiride, D1-like and D2-like DA receptor antagonists, respectively. In addition, pretreatment with (-)-(6aR,12bR)-4,6,6a,7,8,12b-Hexahydro-7-methylindolo[4,3-a]phenanthridin (CY 208-243) and bromocriptine, D1-like and D2-like DA receptor agonists, respectively, did not affect the LPS-induced NO production. N-Acetylcysteine, which inhibits DA oxidation, completely inhibited the effect of DA. Tyrosinase, which catalyzes the oxidation of DA to DA quionone (DAQ), accelerated the inhibitory effect of DA on LPS-induced NO production. These results suggest that DA attenuates LPS-induced NO production through the formation of DAQ in BV-2 cells.

  9. Crystal Structure of Saccharomyces cerevisiae ECM4, a Xi-Class Glutathione Transferase that Reacts with Glutathionyl-(hydro)quinones

    Science.gov (United States)

    Schwartz, Mathieu; Didierjean, Claude; Hecker, Arnaud; Girardet, Jean-Michel; Morel-Rouhier, Mélanie; Gelhaye, Eric; Favier, Frédérique

    2016-01-01

    Glutathionyl-hydroquinone reductases (GHRs) belong to the recently characterized Xi-class of glutathione transferases (GSTXs) according to unique structural properties and are present in all but animal kingdoms. The GHR ScECM4 from the yeast Saccharomyces cerevisiae has been studied since 1997 when it was found to be potentially involved in cell-wall biosynthesis. Up to now and in spite of biological studies made on this enzyme, its physiological role remains challenging. The work here reports its crystallographic study. In addition to exhibiting the general GSTX structural features, ScECM4 shows extensions including a huge loop which contributes to the quaternary assembly. These structural extensions are probably specific to Saccharomycetaceae. Soaking of ScECM4 crystals with GS-menadione results in a structure where glutathione forms a mixed disulfide bond with the cysteine 46. Solution studies confirm that ScECM4 has reductase activity for GS-menadione in presence of glutathione. Moreover, the high resolution structures allowed us to propose new roles of conserved residues of the active site to assist the cysteine 46 during the catalytic act. PMID:27736955

  10. Correlation of the aquarium goldfish toxicities of some phenols, quinones, and other benzene derivatives with their inhibition of autooxidative reactions.

    Science.gov (United States)

    SOLLMANN, T

    1949-07-01

    Hydroquinone when added to the aquarium water was found to be about a hundred times more toxic than phenol, to goldfish (and to Daphnia magna), but is only about twice as toxic when injected into fish or mammals. Tertiarybutyl catechol shows a similar high toxicity in the aquarium, while the toxicity of catechol, resorcinol, and pyrogallol approaches more closely that of phenol. As the substances of high aquarium toxicity are known to inhibit many oxidative and polymerizing autocatalytic "chain reactions," rank correlations were tabulated between the recorded inhibitory potency of various substances in these processes, and their aquarium toxicity for goldfish. The correlation between aquarium fish toxicity and electric oxidation potential (P 0.09) is more than suggestive, and becomes still more so if explainable discrepancies are excluded. Antioxidant fat stabilizers show suggestive correlation with fish toxicity (0.20), and better with electric oxidation potential (0.10). The photographic reduction potential gives suggestive correlation with fish toxicity (0.20) and somewhat better with the oxidation potential (0.15). The gasoline induction period correlation is more than suggestive with the oxidation potential (0.099), but rather poor for fish toxicity (0.265). The rubber anti-aging potency gives only poor correlation (0.39) with fish toxicity. The reasons for these divergencies are not clear; they may perhaps be connected with the solvent properties of the substrate. As an example, Lea (p. 175) cites that 0.01 per cent of maleic acid prevents rancidity of fats, but is rendered ineffective by the presence of water. Taken by themselves, no one of the P values is entirely convincing of the relationships stressed in this paper. However, the consistent finding of relatively small values of P lends considerable weight to the hypothesis that these chemicals act in a related manner; and that the chemical activity of a substance may furnish useful suggestions of its biologic potency, perhaps more so than the chemical constitution as such. The aquarium toxicity, for goldfish is a convenient means of classifying the biologic potency.

  11. Environmental friendly alkaline sulfite anthra quinone-methonal (ASAM) pulping with Rumex crispus plant extract of woody materials.

    Science.gov (United States)

    Mertoglu-Elmas, Gulnur; Gunaydin, Keriman; Ozden, Oznur

    2012-09-01

    ASAM with Rumex crispus extract organosolv pulping was developed by using 1,5-dihydroxy-3-methoxy-7-methyl-anthraquinone from Rumex crispus root, instead of anthraquinone. ASAM was also produced as a control pulping. Both pulps were made by handsheets from fast growing P. deltoides clone (Samsun p. clone), Robinia pseudoacacia L. and Pinus pinaster grown in Turkey for wood fibrous raw materials. The mechanical consisting tensile, bursting and tear values and optical values of ASAM handsheets yellowness, brightness and whiteness were compared to ASAM with Rumex crispus L. extracted. It is concluded that ASAM with Rumex crispus extract pulping suits well in the manufacturing of special papers.

  12. Quinone-Based Polymers for Label-Free and Reagentless Electrochemical Immunosensors: Application to Proteins, Antibodies and Pesticides Detection

    Directory of Open Access Journals (Sweden)

    Minh-Chau Pham

    2013-01-01

    Full Text Available Polyquinone derivatives are widely recognized in the literature for their remarkable properties, their biocompatibility, simple synthesis, and easy bio-functionalization. We have shown that polyquinones present very stable electroactivity in neutral aqueous medium within the cathodic potential domain avoiding side oxidation of interfering species. Besides, they can act as immobilized redox transducers for probing biomolecular interactions in sensors. Our group has been working on devices based on such modified electrodes with a view to applications for proteins, antibodies and organic pollutants using a reagentless label-free electrochemical immunosensor format. Herein, these developments are briefly reviewed and put into perspective.

  13. A partial metabolic pathway enables group b streptococcus to overcome quinone deficiency in a host bacterial community.

    Science.gov (United States)

    Franza, Thierry; Delavenne, Emilie; Derré-Bobillot, Aurélie; Juillard, Vincent; Boulay, Mylène; Demey, Emmanuelle; Vinh, Joelle; Lamberet, Gilles; Gaudu, Philippe

    2016-10-01

    Aerobic respiration metabolism in Group B Streptococcus (GBS) is activated by exogenous heme and menaquinone. This capacity enhances resistance of GBS to acid and oxidative stress and improves its survival. In this work, we discovered that GBS is able to respire in the presence of heme and 1,4-dihydroxy-2-naphthoic acid (DHNA). DHNA is a biosynthetic precursor of demethylmenaquinone (DMK) in many bacterial species. A GBS gene (gbs1789) encodes a homolog of the MenA 1,4-dihydroxy-2-naphthoate prenyltransferase enzyme, involved in the synthesis of demethylmenaquinone. In this study, we showed that gbs1789 is involved in the biosynthesis of long-chain demethylmenaquinones (DMK-10). The Δgbs1789 mutant cannot respire in the presence of heme and DHNA, indicating that endogenously synthesized DMKs are cofactors of the GBS respiratory chain. We also found that isoprenoid side chains from GBS DMKs are produced by the protein encoded by the gbs1783 gene, since this gene can complement an Escherichia coli ispB mutant defective for isoprenoids chain synthesis. In the gut or vaginal microbiote, where interspecies metabolite exchanges occur, this partial DMK biosynthetic pathway can be important for GBS respiration and survival in different niches. © 2016 John Wiley & Sons Ltd.

  14. Label-free and reagentless electrochemical detection of PCR fragments using self-assembled quinone derivative monolayer: Application to Mycobacterium tuberculosis

    DEFF Research Database (Denmark)

    Zhang, Q D; March, G; Noel, V;

    2012-01-01

    ), as well as with polymerase chain reaction (PCR) products related to different lineages of Mycobacterium tuberculosis strains. With pure oligonucleotides, this system achieves high sensitivity (~300pM of DNA target, i.e. 30fmol in a 100µL sample) and excellent selectivity, allowing to detect a single...

  15. Electrocatalytic Mechanism Involving Michaelis-Menten Kinetics at the Preparative Scale: Theory and Applicability to Photocurrents from a Photosynthetic Algae Suspension With Quinones.

    Science.gov (United States)

    Longatte, Guillaume; Guille-Collignon, Manon; Lemaître, Frédéric

    2017-06-15

    In the past years, many strategies have been implemented to benefit from oxygenic photosynthesis to harvest photosynthetic electrons and produce a significant photocurrent. Therefore, electrochemical tools were considered and have globally relied on the electron transfer(s) between the photosynthetic chain and a collecting electrode. In this context, we recently reported the implementation of an electrochemical set-up at the preparative scale to produce photocurrents from a Chlamydomonas reinhardtii algae suspension with an appropriate mediator (2,6-DCBQ) and a carbon gauze as the working electrode. In the present work, we wish to describe a mathematical modeling of the recorded photocurrents to better understand the effects of the experimental conditions on the photosynthetic extraction of electrons. In that way, we established a general model of an electrocatalytic mechanism at the preparative scale (that is, assuming a homogenous bulk solution at any time and a constant diffusion layer, both assumptions being valid under forced convection) in which the chemical step involves a Michaelis-Menten-like behaviour. Dependences of transient and steady-state corresponding currents were analysed as a function of different parameters by means of zone diagrams. This model was tested to our experimental data related to photosynthesis. The corresponding results suggest that competitive pathways beyond photosynthetic harvesting alone should be taken into account. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Evidence for the semireduced primary quinone electron acceptor of photosystem II being a photosensitizer for UVB damage to the photosynthetic apparatus

    NARCIS (Netherlands)

    Rodrigues, G.C.; Jansen, M.A.K.; Noort, van den M.E.; Rensen, van J.J.S.

    2006-01-01

    Exposure to ultraviolet-B radiation (UVB) radiation affects plants in multiple ways, including effects on the photosynthetic apparatus. The carbon dioxide reduction reactions are affected as well as the light reactions, especially those of photosystem II. In the literature several UVB chromophores a

  17. High performance liquid chromatographic analysis of the pharmacologically active quinones and related compounds in the oil of the black seed (Nigella sativa L.).

    Science.gov (United States)

    Ghosheh, O A; Houdi, A A; Crooks, P A

    1999-04-01

    An HPLC method for quantifying the putative pharmacologically active constituents: thymoquinone (TQ), dithymoquinone (DTQ), thymohydroquinone (THQ), and thymol (THY), in the oil of Nigella sativa seed is described. Extraction of the constituents from the oil was carried out using C18 PrepSep mini columns followed by quantification of the recovered constituents by HPLC on a reversed-phase muBondapak C18 analytical column, using an isocratic mobile phase of water:methanol:2-propanol (50:45:5% v/v) at a flow rate of 2 ml min(-1). UV detection was at 254 nm for TQ, DTQ, and THY, and at 294 nm for THQ. The above four compounds were separated with good resolution, reproducibility, and sensitivity under these conditions. This analytical method was used to quantify the above four constituents in a commercial sample of N. sativa seed oil, and provides a good quality control methodology for the pharmacologically active components in this widely used natural remedy.

  18. Identification, design and biological evaluation of heterocyclic quinolones targeting Plasmodium falciparum type II NADH:quinone oxidoreductase (PfNDH2).

    Science.gov (United States)

    Leung, Suet C; Gibbons, Peter; Amewu, Richard; Nixon, Gemma L; Pidathala, Chandrakala; Hong, W David; Pacorel, Bénédicte; Berry, Neil G; Sharma, Raman; Stocks, Paul A; Srivastava, Abhishek; Shone, Alison E; Charoensutthivarakul, Sitthivut; Taylor, Lee; Berger, Olivier; Mbekeani, Alison; Hill, Alasdair; Fisher, Nicholas E; Warman, Ashley J; Biagini, Giancarlo A; Ward, Stephen A; O'Neill, Paul M

    2012-03-08

    Following a program undertaken to identify hit compounds against NADH:ubiquinone oxidoreductase (PfNDH2), a novel enzyme target within the malaria parasite Plasmodium falciparum, hit to lead optimization led to identification of CK-2-68, a molecule suitable for further development. In order to reduce ClogP and improve solubility of CK-2-68 incorporation of a variety of heterocycles, within the side chain of the quinolone core, was carried out, and this approach led to a lead compound SL-2-25 (8b). 8b has IC(50)s in the nanomolar range versus both the enzyme and whole cell P. falciparum (IC(50) = 15 nM PfNDH2; IC(50) = 54 nM (3D7 strain of P. falciparum) with notable oral activity of ED(50)/ED(90) of 1.87/4.72 mg/kg versus Plasmodium berghei (NS Strain) in a murine model of malaria when formulated as a phosphate salt. Analogues in this series also demonstrate nanomolar activity against the bc(1) complex of P. falciparum providing the potential added benefit of a dual mechanism of action. The potent oral activity of 2-pyridyl quinolones underlines the potential of this template for further lead optimization studies.

  19. Identification, design and biological evaluation of bisaryl quinolones targeting Plasmodium falciparum type II NADH:quinone oxidoreductase (PfNDH2).

    Science.gov (United States)

    Pidathala, Chandrakala; Amewu, Richard; Pacorel, Bénédicte; Nixon, Gemma L; Gibbons, Peter; Hong, W David; Leung, Suet C; Berry, Neil G; Sharma, Raman; Stocks, Paul A; Srivastava, Abhishek; Shone, Alison E; Charoensutthivarakul, Sitthivut; Taylor, Lee; Berger, Olivier; Mbekeani, Alison; Hill, Alasdair; Fisher, Nicholas E; Warman, Ashley J; Biagini, Giancarlo A; Ward, Stephen A; O'Neill, Paul M

    2012-03-08

    A program was undertaken to identify hit compounds against NADH:ubiquinone oxidoreductase (PfNDH2), a dehydrogenase of the mitochondrial electron transport chain of the malaria parasite Plasmodium falciparum. PfNDH2 has only one known inhibitor, hydroxy-2-dodecyl-4-(1H)-quinolone (HDQ), and this was used along with a range of chemoinformatics methods in the rational selection of 17 000 compounds for high-throughput screening. Twelve distinct chemotypes were identified and briefly examined leading to the selection of the quinolone core as the key target for structure-activity relationship (SAR) development. Extensive structural exploration led to the selection of 2-bisaryl 3-methyl quinolones as a series for further biological evaluation. The lead compound within this series 7-chloro-3-methyl-2-(4-(4-(trifluoromethoxy)benzyl)phenyl)quinolin-4(1H)-one (CK-2-68) has antimalarial activity against the 3D7 strain of P. falciparum of 36 nM, is selective for PfNDH2 over other respiratory enzymes (inhibitory IC(50) against PfNDH2 of 16 nM), and demonstrates low cytotoxicity and high metabolic stability in the presence of human liver microsomes. This lead compound and its phosphate pro-drug have potent in vivo antimalarial activity after oral administration, consistent with the target product profile of a drug for the treatment of uncomplicated malaria. Other quinolones presented (e.g., 6d, 6f, 14e) have the capacity to inhibit both PfNDH2 and P. falciparum cytochrome bc(1), and studies to determine the potential advantage of this dual-targeting effect are in progress.

  20. Leishmanicidal, antiplasmodial, and cytotoxic activity of novel diterpenoid 1,2-quinones from Perovskia abrotanoides: new source of tanshinones

    DEFF Research Database (Denmark)

    Sairafianpour, M; Christensen, J; Staerk, D

    2001-01-01

    provide a rationale for traditional use of the roots in Iran as a constituent of poultices for treatment of cutaneous leishmaniasis. The isolated tanshinones also inhibited growth of cultured malaria parasites (3D7 strain of Plasmodium falciparum), drug-sensitive KB-3-1 human carcinoma cell line...

  1. Lack of contribution of covalent benzo[a]pyrene-7,8-quinone-DNA adducts in benzo[a]pyrene-induced mouse lung tumorigenesis

    Science.gov (United States)

    Benzo[a]pyrene (B[a]P) is a potent human and rodent lung carcinogen. This activity has been ascribed in part to the formation of anti-trans-B[a]P-7,8-diol-9,10-epoxide (BPDE)-DNA adducts. Other carcinogenic mechanisms have been proposed: 1.] The induction of apurinic sites from r...

  2. EFFECTS OF NATURAL ORGANIC MATTER, ANTHROPOGENIC SURFACTANTS, AND MODEL QUINONES ON THE REDUCTION OF CONTAMINANTS BY ZERO-VALENT IRON. (R827117)

    Science.gov (United States)

    Recent studies of contaminant reduction by zero-valent iron metal (Fe0) have highlighted the role of iron oxides at the metal–water interface and the effect that sorption has at the oxide–water interface on contaminant reduction kinetics. The results s...

  3. Photographic fixative poisoning

    Science.gov (United States)

    Photographic developer poisoning; Hydroquinone poisoning; Quinone poisoning; Sulfite poisoning ... Quinones Sodium thiosulfate Sodium sulfite/bisulfite Boric acid Photographic fixative can also break down (decompose) to form ...

  4. Protein (Cyanobacteria): 493214371 [PGDBj - Ortholog DB

    Lifescience Database Archive (English)

    Full Text Available P)H-quinone oxidoreductase subunit 4 Nodularia spumigena MKIFPSLKKFVVYSLVLLVSVCSLLFTAPTAIAAVDVSTQYIAFDTSTGSIDEAVASYRSLKGKVAKQQSLSIDE...IKQALGVINDKINTLVQEKKDLLAADSNASTDNLDSSIASYRSLKGKVAKQQSLSIDEIKQALGVINAKINSLT

  5. 吡咯喹啉醌对雪旺细胞增殖及NF-κB表达的影响%Effects of pyrroloquinoline quinone on proliferation and expression of NF-κB in cultured Schwann cells

    Institute of Scientific and Technical Information of China (English)

    贺斌; 刘世清; 李皓桓

    2009-01-01

    [Objective] To investigate the effects of pyrroloquinoline quinine (PQQ) on proliferation and expression of NF - kB of Schwann cells. [Methods] Schwann cells were cultured from sciatic nerves of SD rats in vitro. The Schwann cells were identified and purified by immunofluorescence of S-100 and Ara-C. Experimental group with was 100 nmol/L of PQQ and control group were set up. The expression of NF-kB in Schwann cells was determined by RT-PCR and Western blotting. [ Results] The expression of NF - kB were up - ragulated by PQQ in cultured Schwann cells (P<0.05).[Conclusion ] PQQ could promote the proliferation of Schwann cells and up-regulation of NF-rd3 play an important role in this process.%[目的]观察吡咯喹啉醌对雪旺细胞的增殖作用及其对体外培养雪旺细胞NF-κB表达的影响.[方法]新生鼠雪旺细胞体外原代培养及纯化,S-100免疫荧光标记鉴定雪旺细胞,设实验组与对照组,实验组吡咯喹啉醌的浓度为100 nmol/L;加药72 h后提取总mRNA及总蛋白进行RT-PCR和Western blot分析.[结果]采用RT-PCR和Western blot检测NF-κB的表达,结果均表明实验组表达较对照组高(P<0.05).[结论]吡咯喹啉醌可促进雪旺细胞增殖,NF-κB上调在吡咯喹啉醌促雪旺细胞增殖中起作用.

  6. Steady-state FTIR spectra of the photoreduction of QA and QB in Rhodobacter sphaeroides reaction centers provide evidence against the presence of a proposed transient electron acceptor X between the two quinones.

    Science.gov (United States)

    Breton, Jacques

    2007-04-17

    In the reaction center (RC) of the photosynthetic bacterium Rhodobacter sphaeroides, two ubiquinone molecules, QA and QB, play a pivotal role in the conversion of light energy into chemical free energy by coupling electron transfer to proton uptake. In native RCs, the transfer of an electron from QA to QB takes place in the time range of 5-200 micros. On the basis of time-resolved FTIR step-scan measurements in native RCs, a new and unconventional mechanism has been proposed in which QB- formation precedes QA- oxidation [Remy, A., and Gerwert, K. (2003) Nat. Struct. Biol. 10, 637-644]. The IR signature of the proposed transient intermediary electron acceptor (denoted X) operating between QA and QB has been recently measured by the rapid-scan technique in the DN(L210) mutant RCs, in which the QA to QB electron transfer is slowed 8-fold compared to that in native RCs. This IR signature has been reported as a difference spectrum involving states X+, X, QA, and QA- [Hermes, S., et al. (2006) Biochemistry 45, 13741-13749]. Here, we report the steady-state FTIR difference spectra of the photoreduction of either QA or QB measured in both native and DN(L210) mutant RCs in the presence of potassium ferrocyanide. In these spectra, the CN stretching marker modes of ferrocyanide and ferricyanide allow the extent of the redox reactions to be quantitatively compared and are used for a precise normalization of the QA-/QA and QB-/QB difference spectra. The calculated QA- QB/QA QB- double-difference spectrum in DN(L210) mutant RCs is closely equivalent to the reported QA- X+/QA X spectrum in the rapid-scan measurement. We therefore conclude that species X+ and X are spectrally indistinguishable from QB and QB-, respectively. Further comparison of the QA- QB/QA QB- double-difference spectra in native and DN(L210) RCs also allows the possibility that QB- formation precedes QA- reoxidation to be ruled out for native RCs.

  7. Response of Chloroplast NAD(PH Dehydrogenase-Mediated Cyclic Electron Flow to a Shortage or Lack in Ferredoxin-Quinone Oxidoreductase-Dependent Pathway in Rice Following Short-Term Heat Stress

    Directory of Open Access Journals (Sweden)

    Jemaa eEssemine

    2016-03-01

    Full Text Available Cyclic electron flow around PSI can protect photosynthetic electron carriers under conditions of stromal over-reduction. The goal of the research reported in this paper was to investigate the responses of both PSI and PSII to a short-term heat stress in two rice lines with different capacities of cyclic electron transfer, i.e. Q4149 with a high capacity (hcef and C4023 with a low capacity (lcef. The absorbance change at 820 nm (ΔA820 was used here to assess the charge separation in the photosystem I (PSI reaction center (P700. The results obtained show that short-term heat stress abolishes the FQR-dependent CEF in rice and accelerates the initial rate of P700+ re-reduction. The P700+ amplitude was slightly increased at a moderate heat-stress (35°C because of a partial restriction of FQR but it was decreased following high heat-stress (42°C. Assessment of PSI and PSII activities shows that PSI is more susceptible to heat stress than photosystem II (PSII. Under high temperature, FQR-dependent CEF was completely removed and NDH-dependent CEF was up-regulated and strengthened to a higher extent in C4023 than in Q4149. Specifically, under normal growth temperature, hcef (Q4149 was characterized by higher FQR- and NDH-dependent CEF rates than lcef (C4023. Following thermal stress, the activation of NDH-pathway was 130% and 10% for C4023 and Q4149, respectively. Thus, the NDH-dependent CEF may constitute the second layer of plant protection and defence against heat stress after the main route, i.e. FQR-dependent CEF, reaches its capacity. We discuss the possibility that under high heat stress, the NDH pathway serves as a safety valve to dissipate excess energy by cyclic photophosphorylation and overcome the stroma over-reduction following inhibition of CO2 assimilation and any shortage or lack in the FQR pathway. The potential role of the NDH-dependent pathway during the evolution of C4 photosynthesis is briefly discussed.

  8. 丹参醌类抗氧化剂的结构特征与活性关联(Ⅰ)%Structural Features and Antioxidative Activities on Quinone Antioxidants (Ⅰ)

    Institute of Scientific and Technical Information of China (English)

    宫宝安; 程建波; 姜忠民; 郑秋生

    2001-01-01

    对双氢丹参醌Ⅰ和丹参醌Ⅱ在油脂中的抗氧化作用及构效关联进行了量子化学研究.结果表明,抗氧化剂与油脂中碳中心自由基(R*)复合成稳定自由基(AH-R*),可能是丹参醌抑制或阻止油脂氧化酸败的主要途径,双氢丹参醌Ⅰ也可借助释放活泼H(本身转化成稳定自由基A*)有效清除R*.丹参醌分子本身的化学活性和对应的AH-R*与A*的稳定性对此类抗氧化作用有重要影响.AH-R*和A*中自旋集居分布,特别是释放H处C原子的自旋集居数,对比较抗氧化剂的相对活性可能是一个有价值的电子结构参数.%The antioxidation of dihydrotanshinone I and tanshinone II in fat and the relationship between the structures of dihydrotanshinone I and tanshinone II and their antioxidative activities in fat are studied by quantum chemical calculation. The results show that the formation of stable radical AH-R*between the antioxidant and the carbon-centred free radical R*from fat may be a main mechanism of the antioxidation to retard lipid rancid, and dihydrotanshinone I can also act as an antioxidant by donating a hydrogenatom to R*, becoming themselves an unreactive radical A*. The chemical activities of tanshinone molecule and the stabilities of AH-R*and A* have an important effect on the antioxidation. The distribution of spin populations in AH-R*and A*, specially the spin population of C atom at donating H, may be a valuable parameter of electric structure to compare the relative activity of antioxidants.

  9. 化学発光法に基づく生体内活性酸素産生物質の解析

    OpenAIRE

    2015-01-01

    Quinones play critical roles in biological systems, but are also regarded as a class of toxins that can cause oxidative stress in living cells, and the involvement of quinone-based reactive oxygen species in oxidative stress has been reported. In biological systems, quinones are reduced to semiquinone radicals by the enzyme NADPH:quinone reductase. Next, semiquinone radicals react with dissolved oxygen to form superoxide anion, which reacts with biological molecules to cause oxidative stress....

  10. Protein (Cyanobacteria): 465666 [PGDBj - Ortholog DB

    Lifescience Database Archive (English)

    Full Text Available (P)H-quinone oxidoreductase subunit 4 Nodularia spumigena CCY9414 MKIFPSLKKFVVYSLVLLVSVCSLLFTAPTAIAAVDVSTQYIAFDTSTGSIDE...AVASYRSLKGKVAKQQSLSIDEIKQALGVINDKINTLVQEKKDLLAADSNASTDNLDSSIASYRSLKGKVAKQQSLSIDEIKQALGVINAKINSLT ...

  11. 酪醇诱导肝癌细胞NQO1酶基因表达增加及细胞增殖的抑制%Enhancement of NADPH: quinone oxidoreductase 1 (NQO1) gene expression and inhibition of cell proliferation induced by β-tyrosol in human hepatoma SMMC-7721 cells

    Institute of Scientific and Technical Information of China (English)

    薛丽君; 金中初

    2002-01-01

    目的:研究酪醇诱导肝癌细胞Ⅱ相脱毒酶NAD(P)H:醌氧化还原酶-1(NQO1)基因表达情况和对细胞增殖的影响以及两者之间的关系.方法: 肝癌细胞SMMC-7721接种后24 h经β-酪醇处理24 h,分别测定NQO1酶活性,mRNA表达和细胞增殖情况.NQO1酶活性采用微孔板直接测定法,诱导结果用NQO1酶比活性=NQO1酶活性/细胞数;mRNA水平的变化采用定量RT-PCR;细胞增殖采用结晶紫显色法. 结果:NQO1酶活性诱导上,酪醇大于60 mg/L时有明显的剂量效应关系,且每一浓度点(60 mg/L, 70 mg/L, 80 mg/L, 90 mg/L)与空白组比较均有显著差异(P<0.05),80 mg/L的酪醇与80 μmol/L的β-NF(阳性对照)诱导的酶比活性相当;mRNA表达量存在剂量依赖性增加(r=0.824,P<0.05),且与酶比活性存在明显的相关性(r=0.951, P<0.01);酪醇在70 mg/L-100 mg/L范围内,其抑制细胞增殖的能力随着浓度的增加而增加.另外,细胞增殖与酶比活性呈负相关(r=-0.410,P<0.01). 结论: 酪醇在培养肝癌细胞SMMC-7721上能使NQO1酶活性与mRNA表达量诱导性增加,同时酪醇能抑制细胞的增殖,这种增殖抑制与酶活性诱导增加有关.

  12. X-ray crystallographic studies of two bacterial quinoproteins. Methylamine Dehydrogenase and Quinohaemoprotein Alcohol Dehydrogenase

    NARCIS (Netherlands)

    Huizinga, Eric Geert

    1994-01-01

    For the catalysis of reactions involving the transfer of electrons enzymes utilize either metal ions or special organic compounds called cofactors. A group of enzymes, known as quinoproteins, makes use of cofactors that contain a quinone function. This quinone function enables quinoproteins to

  13. Engineering alfalfa to accumulate useful caffeic acid derivatives and characterization of hydroxycinnamoyl-CoA transferases from legumes

    Science.gov (United States)

    Some forages crops, such as red clover, accumulate high levels of caffeic acid derivatives. Oxidation of these o-diphenols to quinones by endogenous polyphenol oxidases (PPOs) and the subsequent reactions of these quinones (probably with endogenous plant proteases) result in a significant reduction ...

  14. NCBI nr-aa BLAST: CBRC-ETEL-01-1273 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-ETEL-01-1273 ref|ZP_01554688.1| NADH-quinone oxidoreductase, chain G [Burkholder...ia ambifaria MC40-6] gb|EAV52269.1| NADH-quinone oxidoreductase, chain G [Burkholderia ambifaria MC40-6] ZP_01554688.1 2.1 23% ...

  15. PHYTOCHEMICAL STUDIES OF THE GENUS ZINGIBER FROM FAMILY ZINGIBERACEAE

    Directory of Open Access Journals (Sweden)

    Kasarkar A. R.

    2011-02-01

    Full Text Available Phytochemical analysis of three Zingiber species (Zingiberaceae revealed presence of phenols and phenolic compounds, acicubin, cyanogenic glycosides, flavonoid and lignins leucoanthocyanis, catechol, tannins, quinone, naptho-quinones and coumarin are absence in all the species. The chemical compounds like syringin glycosides, saponin are doubtful in these species.

  16. Dose-dependent kinetics and metabolism of 1,2-dichlorobenzene in rat : effect of pretreatment with phenobarbital

    NARCIS (Netherlands)

    Hissink, A.M.; Ommen, B. van; Bladeren, P.J. van

    1996-01-01

    Toxicity of halobenzenes has been ascribed mainly to their epoxides, but recent studies with bromobenzene have shown that secondary quinone metabolites are also involved in the alkylation of hepatic proteins. However, the relative contribution of the quinones and the epoxides to the toxicity of

  17. NCBI nr-aa BLAST: CBRC-ACAR-01-1002 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-ACAR-01-1002 ref|YP_534416.1| NADH dehydrogenase (quinone) [Rhodopseudomonas p...alustris BisB18] gb|ABD90097.1| NADH dehydrogenase (quinone) [Rhodopseudomonas palustris BisB18] YP_534416.1 0.56 28% ...

  18. NCBI nr-aa BLAST: CBRC-MDOM-06-0011 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-MDOM-06-0011 ref|YP_197376.1| NADH-quinone oxidoreductase chain L [Ehrlichia ruminant...ium str. Welgevonden] emb|CAI26994.1| NADH-quinone oxidoreductase chain L [Ehrlichia ruminantium str. Welgevonden] YP_197376.1 0.039 24% ...

  19. NCBI nr-aa BLAST: CBRC-MDOM-06-0011 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-MDOM-06-0011 ref|YP_196416.1| NADH-quinone oxidoreductase chain L [Ehrlichia ruminant...ium str. Gardel] emb|CAI27942.1| NADH-quinone oxidoreductase chain L [Ehrlichia ruminantium str. Gardel] YP_196416.1 0.039 24% ...

  20. NCBI nr-aa BLAST: CBRC-MDOM-06-0011 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-MDOM-06-0011 ref|YP_180342.1| NADH-quinone oxidoreductase chain L [Ehrlichia ruminant...ium str. Welgevonden] emb|CAH58206.1| NADH-quinone oxidoreductase chain L [Ehrlichia ruminantium str. Welgevonden] YP_180342.1 0.039 24% ...

  1. NCBI nr-aa BLAST: CBRC-SARA-01-0415 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-SARA-01-0415 ref|YP_547770.1| NADH dehydrogenase (quinone) [Polaromonas sp. JS...666] gb|ABE42872.1| NADH dehydrogenase (quinone) [Polaromonas sp. JS666] YP_547770.1 4.6 26% ...

  2. Dose-dependent kinetics and metabolism of 1,2-dichlorobenzene in rat : effect of pretreatment with phenobarbital

    NARCIS (Netherlands)

    Hissink, A.M.; Ommen, B. van; Bladeren, P.J. van

    1996-01-01

    Toxicity of halobenzenes has been ascribed mainly to their epoxides, but recent studies with bromobenzene have shown that secondary quinone metabolites are also involved in the alkylation of hepatic proteins. However, the relative contribution of the quinones and the epoxides to the toxicity of halo

  3. Polarographic methods of investigation of radiochemical transformations of phenol compounds induced by gamma radiation

    Energy Technology Data Exchange (ETDEWEB)

    Norbaev, N.

    1977-01-01

    Electron polarography was used for studies on radiochemical changes in phenol compounds following exposure to gamma radiation. The amount of quinones 3 to 4 h after irradiation increased in chlorogenic acid, pyrocatechol, and quercetin; the amount of quinones decreased 24 h after irradiation. (HLW)

  4. NCBI nr-aa BLAST: CBRC-ACAR-01-1198 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-ACAR-01-1198 ref|YP_001280665.1| Pyrrolo-quinoline quinone [Psychrobacter sp. ...PRwf-1] gb|ABQ94715.1| Pyrrolo-quinoline quinone [Psychrobacter sp. PRwf-1] YP_001280665.1 6.8 30% ...

  5. NCBI nr-aa BLAST: CBRC-ETEL-01-1222 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-ETEL-01-1222 ref|ZP_01637373.1| Pyrrolo-quinoline quinone [Pseudomonas putida ...W619] gb|EAX20318.1| Pyrrolo-quinoline quinone [Pseudomonas putida W619] ZP_01637373.1 3.9 47% ...

  6. NCBI nr-aa BLAST: CBRC-FCAT-01-1212 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-FCAT-01-1212 ref|YP_001379363.1| Pyrrolo-quinoline quinone [Anaeromyxobacter s...p. Fw109-5] gb|ABS26379.1| Pyrrolo-quinoline quinone [Anaeromyxobacter sp. Fw109-5] YP_001379363.1 0.041 27% ...

  7. NCBI nr-aa BLAST: CBRC-ETEL-01-1222 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-ETEL-01-1222 ref|ZP_01712850.1| Quinate dehydrogenase (pyrroloquinoline-quinon...e) [Pseudomonas putida GB-1] gb|EAZ71206.1| Quinate dehydrogenase (pyrroloquinoline-quinone) [Pseudomonas putida GB-1] ZP_01712850.1 3.0 43% ...

  8. NCBI nr-aa BLAST: CBRC-ETEL-01-1222 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-ETEL-01-1222 ref|YP_608486.1| quinate dehydrogenase (pyrroloquinoline-quinone)... [Pseudomonas entomophila L48] emb|CAK15693.1| quinate dehydrogenase (pyrroloquinoline-quinone) [Pseudomonas] YP_608486.1 3.0 43% ...

  9. Kinetics and mechanism of the chain reaction between N-phenyl-1,4-benzoquinone monoimine and thiophenol

    Science.gov (United States)

    Varlamov, V. T.; Gadomsky, S. Ya.

    2017-05-01

    The kinetics of the reaction between N-phenyl-1,4-benzoquinone monoimine (quinone monoimine) and thiophenol is studied in chlorobenzene at 343 K. The reaction has the same mechanism proposed earlier for a similar reaction involving N,N'-diphenyl-1,4-benzoquinone diimine (quinone diimine). This mechanism has two paths: chain and nonchain. An important difference between the kinetics of the two reactions is the apparent reversible nature of the chain reaction in the quinone monoimine + thiophenol system. This nature reveals itself when the concentrations of thiophenol are comparable to or slightly higher than the concentrations of quinone imine. In light of this, kinetic research is conducted under conditions where the concentrations of thiophenol are significantly higher than those of quinone monoimine, allowing us to simplify the kinetic features and obtain interpretable data. The rate constants of the reaction's elementary steps are estimated and found to be three to five times lower for the reaction involving quinone monoamine than for the one involving quinone diimine. Both reactions have relatively short chains whose lengths do not exceed several tens of units.

  10. Novel Roles for the Polyphenol Oxidase Enzyme in Secondary Metabolism and the Regulation of Cell Death in Walnut

    National Research Council Canada - National Science Library

    Soha Araji; Theresa A. Grammer; Ross Gertzen; Stephen D. Anderson; Maja Mikulic-Petkovsek; Robert Veberic; My L. Phu; Anita Solar; Charles A. Leslie; Abhaya M. Dandekar; Matthew A. Escobar

    2014-01-01

    .... Polymerization of PPO-derived quinones causes the postharvest browning of cut or bruised fruit, but the native physiological functions of PPOs in undamaged, intact plant cells are not well understood. Walnut (Juglans regia...

  11. 78 FR 14792 - Ocean Transportation Intermediary License Applicants

    Science.gov (United States)

    2013-03-07

    ..., Secaucus, NJ 07094. Officer: Cesar E. Quinones, Sole Proprietor (QI). Application Type: New NVO License Denizabel Shipping, Inc. (OFF), 19558 NW 50th Court, Miami, FL 33055. Officer: Isabel Ramirez, President...

  12. Computational Electrochemistry Study of Derivatives of Anthraquinone and Phenanthraquinone Analogues

    DEFF Research Database (Denmark)

    Wang, Zhen; Li, Anyang; Gou, Lei

    2016-01-01

    The substituent effect on fused heteroaromatic anthraquinone and phenanthraquinone are investigated by density functional calculations to determine some guidelines for designing potential cathode materials for rechargeable Li-ion batteries. The calculated redox potentials of the quinone derivativ...

  13. Main: ARE1 [PLACE

    Lifescience Database Archive (English)

    Full Text Available ARE1 S000022 16-Jan-1998 (last modified) kehi ARE (antioxidant response element); antioxidant... response element of rat glutathione S-transferase Ya subunit, and rat NAD(P)H:quinone reductase genes; antioxidant

  14. Label-free DNA electrochemical sensor based on a PNA-functionalized conductive polymer

    DEFF Research Database (Denmark)

    Reisberg, S; Dang, L A; Nguyen, Q A;

    2008-01-01

    An electrochemical hybridization biosensor based on peptide nucleic acid (PNA) probe is presented. PNA were attached covalently onto a quinone-based electroactive polymer. Changes in flexibility of the PNA probe strand upon hybridization generates electrochemical changes at the polymer...

  15. Pigments in Thermophilic fungi

    OpenAIRE

    Somasundaram, T.; Rao, Sanjay SR; Maheshwari,R.

    1986-01-01

    UV and visible absorption spectra of thermophilic fungi were obtained by photoacoustic spectroscopy. Based on these data as well as on the chem. properties and IR spectra, it is suggested that the pigments may be hydroxylated polycyclic quinones.

  16. Dependence of the rate of an interfacial Diels-Alder reaction on the steric environment of the immobilized dienophile: an example of enthalpy-entropy compensation.

    Science.gov (United States)

    Kwon, Youngeun; Mrksich, Milan

    2002-02-06

    This paper describes a physical organic study of the relationship between the rate for an interfacial Diels-Alder reaction and the steric environment around the reacting molecules. The study used as a model reaction the cycloaddition of cyclopentadiene with a self-assembled monolayer (SAM) presenting benzoquinone groups surrounded by hydroxyl-terminated alkanethiolates. The accessibility of the quinone was varied by preparing monolayers from hydroquinone-terminated alkanethiols of different lengths [HS(CH(2))(n)-HQ, n = 6-14] and a hydroxyl-terminated alkanethiol [HS(CH(2))(11)-OH] of constant length. Cyclic voltammetry was used to measure the rate of the reaction by monitoring the decay of the redox-active quinone. The second-order rate constant showed a modest change as the position of quinone was varied relative to the hydroxyl groups of the monolayer. For monolayers wherein the quinone groups were extended from the interface, the rate constants oscillated near 0.20 M(-1) s(-1) with an even-odd dependence on the length of the alkanethiol. For monolayers that positioned the quinone groups below the surrounding hydroxyl groups, the rate constants decreased by approximately 8-fold. Examination of the activation parameters revealed that the quinone groups that were positioned below the interface (and in a crowded environment) reacted with an enthalpy of activation that was 4 kcal/mol greater than did the quinones that were accessible at the interface. The reaction of the buried quinone, however, proceeded with an entropy of activation that was more favorable by 13 eu, and therefore with a similar free energy of activation. The combination of SAMs for preparing model interfaces and cyclic voltammetry for measuring rates provides a new opportunity for physical organic studies of interfacial reactions.

  17. Nitration of phenolic compounds and oxidation of hydroquinones using tetrabutylammonium chromate and dichromate under aprotic conditions

    Indian Academy of Sciences (India)

    Ali Reza Pourali; Arezou Goli

    2011-01-01

    In this work, we have reported a mild, efficient and selective method for the mononitration of phenolic compounds using sodium nitrite in the presence of tetrabutylammonium dichromate (TBAD) and oxidation of hydroquinones to quinones with TBAD in CH2Cl2. Using this method, high yields of nitrophenols and quinones were obtained under neutral aprotic conditions. Tetrabutylammonium chromate (TBAC) can also be used as oxidant at same conditions.

  18. In situ FTIR Investigation of Magnetic Field Effect on Heterogeneous Photocatalytic Degradation of Benzene over Pt/TiO2

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    In situ FTIR spectroscopy was utlized to investigate the magnetic field effect on the heterogeneous photocatalytic degradation of benzene over platinized titania (Pt/TiO2). The results revealed that the employment of magnetic field may not change the mechanism of photocatalytic degradation of benzene, however, it greatly facilitate the conversion of benzene to phenol and quinone, as well as the transformation from phenol to quinone, resulting in opening the benzene ring easily and promoting the production of CO2.

  19. Potent Methyl Oxidation of 5-Methyl-2′-deoxycytidine by Halogenated Quinoid Carcinogens and Hydrogen Peroxide via a Metal-independent Mechanism

    OpenAIRE

    Shao, Jie; Huang, Chun-Hua; Kalyanaraman, Balaraman; Zhu, Ben-Zhan

    2013-01-01

    Halogenated quinones are a class of carcinogenic intermediates and newly identified chlorination disinfection byproducts in drinking water. We found recently that the highly reactive and biologically important hydroxyl radical (•OH) can be produced by halogenated quinones and H2O2 independent of transition metal ions. However, it is not clear whether these quinoid carcinogens and H2O2 can oxidize the nucleoside 5-methyl-2′-deoxycytidine (5mdC) to its methyl oxidation prod...

  20. Chemical, pulse radiolysis and density functional studies of a new, labile 5,6-indolequinone and its semiquinone.

    Science.gov (United States)

    Pezzella, Alessandro; Crescenzi, Orlando; Natangelo, Anna; Panzella, Lucia; Napolitano, Alessandra; Navaratnam, Suppiah; Edge, Ruth; Land, Edward J; Barone, Vincenzo; d'Ischia, Marco

    2007-03-02

    The chemical and spectroscopic characterization of 5,6-indolequinones and their semiquinones, key transient intermediates in the oxidative conversion of 5,6-dihydroxyindoles to eumelanin biopolymers, is a most challenging task. In the present paper, we report the characterization of a novel, relatively long-lived 5,6-indolequinone along with its semiquinone using an integrated chemical, pulse radiolytic, and computational approach. The quinone was obtained by oxidation of 5,6-dihydroxy-3-iodoindole (1a) with o-chloranil in cold ethyl acetate or aqueous buffer: it displayed electronic absorption bands around 400 and 600 nm, was reduced to 1a with Na2S2O4, and reacted with o-phenylenediamine to give small amounts of 3-iodo-1H-pyrrolo[2,3-b]phenazine (2). The semiquinone exhibited absorption maxima at 380 nm (sh) and 520 nm and was detected as the initial species produced by pulse radiolytic oxidation of 1a at pH 7.0. DFT investigations indicated the 6-phenoxyl radical and the N-protonated radical anion as the most stable tautomers for the neutral and anion forms of the semiquinone, respectively. Calculated absorption spectra in water gave bands at 350 (sh) and 500 nm for the neutral form and at 310 and 360 (sh) nm for the anion. Disproportionation of the semiquinone with fast second-order kinetics (2k = 1.1 x 1010 M-1 s-1) gave a chromophore with absorption bands resembling those of chemically generated 1a quinone. Computational analysis predicted 1a quinone to exist in vacuo as the quinone-methide tautomer, displaying low energy transitions at 380 and 710 nm, and in water as the o-quinone, with calculated absorption bands around 400 and 820 nm. A strong participation of a p orbital on the iodine atom in the 360-380 nm electronic transitions of the o-quinone and quinone-methide was highlighted. The satisfactory agreement between computational and experimental electronic absorption data would suggest partitioning of 1a quinone between the o-quinone and quinone

  1. Electrochemistry coupled to (LC-)MS for the simulation of oxidative biotransformation reactions of PAHs.

    Science.gov (United States)

    Wigger, Tina; Seidel, Albrecht; Karst, Uwe

    2017-06-01

    Electrochemistry coupled to liquid chromatography and mass spectrometry was used for simulating the biological and environmental fate of polycyclic aromatic hydrocarbons (PAHs) as well as for studying the PAH degradation behavior during electrochemical remediation. Pyrene and benzo[a]pyrene were selected as model compounds and oxidized within an electrochemical thin-layer cell equipped with boron-doped diamond electrode. At potentials of 1.2 and 1.6 V vs. Pd/H2, quinones were found to be the major oxidation products for both investigated PAHs. These quinones belong to a large group of PAH derivatives referred to as oxygenated PAHs, which have gained increasing attention in recent years due to their high abundance in the environment and their significant toxicity. Separation of oxidation products allowed the identification of two pyrene quinone and three benzo[a]pyrene quinone isomers, all of which are known to be formed via photooxidation and during mammalian metabolism. The good correlation between electrochemically generated PAH quinones and those formed in natural processes was also confirmed by UV irradiation experiments and microsomal incubations. At potentials higher than 2.0 V, further degradation of the initial oxidation products was observed which highlights the capability of electrochemistry to be used as remediation technique. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Reassessment of the active site quino-cofactor proposed to occur in the Aspergillus niger amine oxidase AO-I from the properties of model compounds.

    Science.gov (United States)

    Melville, C R; Green, E L; Sanders-Loehr, J; Klinman, J P

    2000-06-27

    Quino-cofactors have been found in a wide variety of prokaryotic and eukaryotic organisms. Two variants have, thus far, been demonstrated to derive from tyrosine precursors: these are the 2,4, 5-trihydroxyphenylalanine quinone (topa quinone or TPQ) [Janes, S. M. , et al. (1990) Science 248, 98] and an o-quinone analogue containing the side chain of a lysine residue (lysyltyrosine quinone or LTQ) [Wang, S. Z., et al. (1996) Science 273, 1078]. Additionally, a third variant of the family of tyrosine-derived cofactors has been reported to exist in an Aspergillus niger amine oxidase AO-I. This was described as an o-quinone cross-linked to the side chain of a glutamate residue [Frebort, I. (1996) Biochim. Biophys. Acta 1295, 59]. We have synthesized model compounds related to the proposed structure. Characterization of the redox properties for the model compound and spectral properties of its 4-nitrophenylhydrazine derivative lead us to conclude that the cofactor in A. niger amine oxidase AO-I has been misidentified. A TPQ carboxylate ester is considered an unlikely candidate for a biologically functional quino-cofactor.

  3. Unprecedent aminophysalin from Physalis angulata.

    Science.gov (United States)

    Men, Rui-Zhi; Li, Ning; Ding, Wan-Jing; Hu, Zhi-Juan; Ma, Zhong-Jun; Cheng, Lin

    2014-10-01

    The 95% ethanol extract of the whole plant of Physalis angulata Linn. afforded one new skeletal physalin named aminophysalin A (1) and one new naturally occurring 5β-hydroxy-6a-chloro-5,6-dihydrophysalin B (2), together with five known physalins (3-7). Their structures were elucidated through MS, IR, NMR spectroscopy analyses and X-ray crystallography. Aminophysalin A (1) had an absolutely unusual structural feature in the chemistry of physalins with a nitrogen atom. Compounds 1-7 were evaluated for quinone reductase activities in hepa 1c1c7 cells. Physalin H (6) showed strong quinone reductase induction activity with IR (Induction ratio, QR induction activity) value of 3.74±0.02, using 4-bromoflavone as a positive control substance (2.17±0.01, 10 μg/mL), while compounds 1, 2, 3, 5 showed weak quinone reductase induction activity.

  4. Lignin Modification for Biopolymer/Conjugated Polymer Hybrids as Renewable Energy Storage Materials.

    Science.gov (United States)

    Nilsson, Ting Yang; Wagner, Michal; Inganäs, Olle

    2015-12-07

    Lignin derivatives, which arise as waste products from the pulp and paper industry and are mainly used for heating, can be used as charge storage materials. The charge storage function is a result of the quinone groups formed in the lignin derivative. Herein, we modified lignins to enhance the density of such quinone groups by covalently linking monolignols and quinones through phenolation. The extra guaiacyl, syringyl, and hydroquinone groups introduced by phenolation of kraft lignin derivatives were monitored by (31) P nuclear magnetic resonance and size exclusion chromatography. Electropolymerization in ethylene glycol/tetraethylammonium tosylate electrolyte was used to synthesize the kraft lignin/polypyrrole hybrid films. These modifications changed the phenolic content of the kraft lignin with attachment of hydroquinone units yielding the highest specific capacity (around 70 mA h g(-1) ). The modification of softwood and hardwood lignin derivatives yielded 50 % and 23 % higher charge capacity than the original lignin, respectively.

  5. Preparation and phytotoxicity of sorgoleone analogues

    Directory of Open Access Journals (Sweden)

    Luiz Cláudio de Almeida Barbosa

    2001-12-01

    Full Text Available 3,5-Dimethoxybenzylic alcohol was converted into the 2-acetoxy-5-methoxy-3-(pent-1-yl-1,4-benzoquinone (12, in seven steps, with an overall yield of 14.6%. The natural quinone sorgoleone (1 was isolated from Sorghum bicolor and converted into the corresponding quinone (13 having a saturated side chain. The selective effects of these compounds (1, 12 and 13, at the dose of 5.6 mug of a.i./ g of substrate, on the growth of Cucumis sativus, Lactuca sativa, Desmodium tortuosum, Hyptis suaveolens and Euphorbia heterophylla were evaluated. All three compounds caused some inhibition on the root growth of the test plants (0.0-69.19% with the aerial parts less affected. The results showed that the triene unit of the sorgoleone side chain is not essential for the phytotoxicity and also the synthetic quinone was as active as the natural product.

  6. Electrochemical oxidation of wine polyphenols in the presence of sulfur dioxide.

    Science.gov (United States)

    Makhotkina, Olga; Kilmartin, Paul A

    2013-06-12

    Electrochemical oxidation of three representative wine polyphenols (catechin, caffeic acid, and quercetin) in the presence of sulfur dioxide in a model wine solution (pH = 3.3) was investigated. The oxidation was undertaken using chronoamperometry at a rotating glassy carbon rod electrode, and the reaction products were characterized by HPLC-MS. The mechanism of electrochemical oxidation of polyphenols in the presence of sulfur dioxide was proposed to be an ECEC mechanism. The polyphenols first underwent a one-electron oxidation to a semiquinone radical, which can be reduced back to the original polyphenol by sulfur dioxide, or further oxidized to the quinone form. In the cases of caffeic acid and catechin, the quinone combined with sulfur dioxide and produced new derivatives. The quercetin quinone underwent further chemical transformations, producing several new compounds. The proposed mechanisms were confirmed by digital simulation of cyclic voltammograms.

  7. The Staphylococcus aureus NuoL-like protein MpsA contributes to the generation of membrane potential.

    Science.gov (United States)

    Mayer, Sonja; Steffen, Wojtek; Steuber, Julia; Götz, Friedrich

    2015-03-01

    In aerobic microorganisms, the entry point of respiratory electron transfer is represented by the NADH:quinone oxidoreductase. The enzyme couples the oxidation of NADH with the reduction of quinone. In the type 1 NADH:quinone oxidoreductase (Ndh1), this reaction is accompanied by the translocation of cations, such as H(+) or Na(+). In Escherichia coli, cation translocation is accomplished by the subunit NuoL, thus generating membrane potential (Δψ). Some microorganisms achieve NADH oxidation by the alternative, nonelectrogenic type 2 NADH:quinone oxidoreductase (Ndh2), which is not cation translocating. Since these enzymes had not been described in Staphylococcus aureus, the goal of this study was to identify proteins operating in the NADH:quinone segment of its respiratory chain. We demonstrated that Ndh2 represents a NADH:quinone oxidoreductase in S. aureus. Additionally, we identified a hypothetical protein in S. aureus showing sequence similarity to the proton-translocating subunit NuoL of complex I in E. coli: the NuoL-like protein MpsA. Mutants with deletion of the nuoL-like gene mpsA and its corresponding operon, mpsABC (mps for membrane potential-generating system), exhibited a small-colony-variant-like phenotype and were severely affected in Δψ and oxygen consumption rates. The MpsABC proteins did not confer NADH oxidation activity. Using an Na(+)/H(+) antiporter-deficient E. coli strain, we could show that MpsABC constitute a cation-translocating system capable of Na(+) transport. Our study demonstrates that MpsABC represent an important functional system of the respiratory chain of S. aureus that acts as an electrogenic unit responsible for the generation of Δψ.

  8. Short-lived quinonoid species from 5,6-dihydroxyindole dimers en route to eumelanin polymers: integrated chemical, pulse radiolytic, and quantum mechanical investigation.

    Science.gov (United States)

    Pezzella, Alessandro; Panzella, Lucia; Crescenzi, Orlando; Napolitano, Alessandra; Navaratman, Suppiah; Edge, Ruth; Land, Edward J; Barone, Vincenzo; d'Ischia, Marco

    2006-12-06

    The transient species formed by oxidation of three dimers of 5,6-dihydroxyindole (1), a major building block of the natural biopolymer eumelanin, have been investigated. Pulse radiolytic oxidation of 5,5',6,6'-tetrahydroxy-2,4'-biindolyl (3) and 5,5',6,6'-tetrahydroxy-2,7'-biindolyl (4) led to semiquinones absorbing around 450 nm, which decayed with second-order kinetics (2k=2.8x10(9) and 1.4x10(9) M-1 s-1, respectively) to give the corresponding quinones (500-550 nm). 5,5',6, 6'-Tetrahydroxy-2,2'-biindolyl (2), on the other hand, furnished a semiquinone (lamdamax=480 nm) which disproportionated at a comparable rate (2k=3x10(9) M-1 s-1) to give a relatively stable quinone (lamdamax=570 nm). A quantum mechanical investigation of o-quinone, quinonimine, and quinone methide structures of 2-4 suggested that oxidized 2-4 exist mainly as 2-substituted extended quinone methide tautomers. Finally, an oxidation product of 3 was isolated for the first time and was formulated as the hydroxylated derivative 5 arising conceivably by the addition of water to the quinone methide intermediate predicted by theoretical analysis. Overall, these results suggest that the oxidation chemistry of biindolyls 2-4 differs significantly from that of the parent 1, whereby caution must be exercised before concepts that apply strictly to the mode of coupling of 1 are extended to higher oligomers.

  9. Humic substance-mediated reduction of iron(III) oxides and degradation of 2,4-D by an alkaliphilic bacterium, Corynebacterium humireducens MFC-5.

    Science.gov (United States)

    Wu, Chun-yuan; Zhuang, Li; Zhou, Shun-gui; Yuan, Yong; Yuan, Tian; Li, Fang-bai

    2013-03-01

    With the use of an alkaliphilic bacterium, Corynebacterium humireducens MFC-5, this study investigated the reduction of goethite (α-FeOOH) and degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) mediated by different humic substances (humics) and quinones in alkaline conditions (pH of 9.0). The results indicated that (i) using sucrose as the electron donor, the strain MFC-5 was capable of reducing anthraquinone-2,6-disulfonic acid (AQDS), anthraquinone-2-disulfonic acid (AQS), anthraquinone-2-carboxylic acid (AQC), humic acid (HA) and fulvic acid (FA), and its reducing capability ranked as AQC > AQS > AQDS > FA > HA; (ii) the anaerobic reduction of α-FeOOH and 2,4-D by the strain was insignificant, while the reductions were greatly enhanced by the addition of quinones/humics serving as redox mediators; (iii) the Fe(III) reduction rate was positively related to the content of quinone functional groups and the electron-accepting capacities (EAC) of quinones/humics based on fourier-transform infrared spectroscopy (FT-IR) and electrochemical analyses; however, such a relationship was not found in 2,4-D degradation probably because quinone reduction was not the rate-limiting step of quinone-mediated reduction of 2,4-D. Using the example of α-FeOOH and 2,4-D, this study well demonstrated the important role of humics reduction on the Fe(III)/Fe(II) biogeochemical cycle and chlorinated organic compounds degradation in alkaline reducing environments. © 2012 The Authors. Published by Society for Applied Microbiology and Blackwell Publishing Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

  10. Cytotoxicity mechanism of two naphthoquinones (menadione and plumbagin in Saccharomyces cerevisiae.

    Directory of Open Access Journals (Sweden)

    Frederico Augusto Vieira Castro

    Full Text Available BACKGROUND: Quinones are compounds extensively used in studies of oxidative stress due to their role in plants as chemicals for defense. These compounds are of great interest for pharmacologists and scientists, in general, because several cancer chemotherapeutic agents contain the quinone nucleus. However, due to differences in structures and diverse pharmacological effects, the exact toxicity mechanisms exerted by quinones are far from elucidatation. METHODOLOGY/PRINCIPAL FINDINGS: Using Saccharomyces cerevisiae, we evaluated the main mechanisms of toxicity of two naphthoquinones, menadione and plumbagin, by determining tolerance and oxidative stress biomarkers such as GSH and GSSG, lipid peroxidation levels, as well as aconitase activity. The importance of glutathione transferases (GST in quinone detoxification was also addressed. The GSSG/GSH ratio showed that menadione seemed to exert its toxicity mainly through the generation of ROS while plumbagin acted as an electrophile reacting with GSH. However, the results showed that, even by different pathways, both drugs were capable of generating oxidative stress through their toxic effects. Our results showed that the control strain, BY4741, and the glutathione transferase deficient strains (gtt1Delta and gtt2Delta were sensitive to both compounds. With respect to the role of GST isoforms in cellular protection against quinone toxicity, we observed that the Gtt2 deficient strain was unable to overcome lipid peroxidation, even after a plumbagin pre-treatment, indicating that this treatment did not improve tolerance when compared with the wild type strain. Cross-tolerance experiments confirmed distinct cytotoxicity mechanisms for these naphthoquinones since only a pre-treatment with menadione was able to induce acquisition of tolerance against stress with plumbagin. CONCLUSIONS/SIGNIFICANCE: These results suggest different responses to menadione and plumbagin which could be due to the fact that

  11. Evaluation of photosynthetic electrons derivation by exogenous redox mediators.

    Science.gov (United States)

    Longatte, Guillaume; Fu, Han-Yi; Buriez, Olivier; Labbé, Eric; Wollman, Francis-André; Amatore, Christian; Rappaport, Fabrice; Guille-Collignon, Manon; Lemaître, Frédéric

    2015-10-01

    Oxygenic photosynthesis is the complex process that occurs in plants or algae by which the energy from the sun is converted into an electrochemical potential that drives the assimilation of carbon dioxide and the synthesis of carbohydrates. Quinones belong to a family of species commonly found in key processes of the Living, like photosynthesis or respiration, in which they act as electron transporters. This makes this class of molecules a popular candidate for biofuel cell and bioenergy applications insofar as they can be used as cargo to ship electrons to an electrode immersed in the cellular suspension. Nevertheless, such electron carriers are mostly selected empirically. This is why we report on a method involving fluorescence measurements to estimate the ability of seven different quinones to accept photosynthetic electrons downstream of photosystem II, the first protein complex in the light-dependent reactions of oxygenic photosynthesis. To this aim we use a mutant of Chlamydomonas reinhardtii, a unicellular green alga, impaired in electron downstream of photosystem II and assess the ability of quinones to restore electron flow by fluorescence. In this work, we defined and extracted a "derivation parameter" D that indicates the derivation efficiency of the exogenous quinones investigated. D then allows electing 2,6-dichlorobenzoquinone, 2,5-dichlorobenzoquinone and p-phenylbenzoquinone as good candidates. More particularly, our investigations suggested that other key parameters like the partition of quinones between different cellular compartments and their propensity to saturate these various compartments should also be taken into account in the process of selecting exogenous quinones for the purpose of deriving photoelectrons from intact algae. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. A Novel Dimer of α-Tocopherol

    Directory of Open Access Journals (Sweden)

    Anjan Patel

    2008-01-01

    Full Text Available Decomposition of the complex 4, formed between the α-tocopherol ortho-quinone methide (2 and NMMO, by fast heating from −78∘C to 70∘C in inert solvents produces a novel α-tocopherol dimer with 6H,12H-dibenzo[b,f][1,5]dioxocine structure (5 which—in contrast to the well-known spiro-dimer of α-tocopherol (3—is symmetrical. This is the first example of a direct reaction of the highly transient zwitterionic, aromatic precursor 2a in the formation of the ortho-quinone methide 2.

  13. AcEST: DK943990 [AcEST

    Lifescience Database Archive (English)

    Full Text Available producing significant alignments: (bits) Value sp|Q85FH3|NU4LC_ADICA NAD(P)H-quinone oxidoreductase subunit...V=3 Length = 99 Score = 162 bits (410), Expect = 1e-39 Identities = 85/99 (85%), ...Positives = 85/99 (85%) Frame = +3 Query: 72 MFEQGLILSAYLLCVGFFGLITSRNMVRALMSLELIFNAITLNFITLSNLFDNRETGEIF 251 MFEQGLILSAYLLCVGFFGLITS...RNMVRALMSLELIFNAITLNFITLSNLFDNRETGEIF Sbjct: 1 MFEQGLILSAYLLCVGFFGLITSRNMVRALMSLELI...(P)H-quinone oxidoreductase subunit 4L, chloroplastic OS=Angiopteris evecta GN=ndhE PE=3 SV=1 Length = 100 Score = 117 bits

  14. A bio-inspired, small molecule electron-coupled-proton buffer for decoupling the half-reactions of electrolytic water splitting.

    Science.gov (United States)

    Rausch, Benjamin; Symes, Mark D; Cronin, Leroy

    2013-09-18

    Electron-coupled-proton buffers (ECPBs) allow H2 and O2 evolution to be separated from each other in time during the electrolysis of water. Natural photosynthetic systems achieve an analogous feat during water splitting and employ a range of intermediate redox mediators such as quinone derivatives to aid this process. Drawing on this natural example, we show that a low molecular weight quinone derivative is capable of decoupling H2 evolution from O2 evolution at scale during electrochemical water splitting. This work could significantly lower the cost of ECPBs, paving the way for their more widespread adoption in water splitting.

  15. Total synthesis of (+)-geldanamycin and (-)-o-quinogeldanamycin with use of asymmetric anti- and syn-glycolate aldol reactions.

    Science.gov (United States)

    Andrus, Merritt B; Meredith, Erik L; Simmons, Bryon L; Soma Sekhar, B B V; Hicken, Erik J

    2002-10-03

    Geldanamycin (GA), an antitumor Hsp90 inhibitor, was made for the first time by using an oxidative demethylation reaction as the final step. A biaryldioxanone auxiliary set the anti C11-12 hydroxy-methoxy functionality and a methylglycolate auxiliary based on norephedrine was used for the syn C6-7 methoxy-urethane. p-Quinone-forming oxidants, CAN and AgO, produced an unusual aza-quinone product. Nitric acid gave GA from a trimethoxy precursor in 55% yield as a 1:10 mixture with nonnatural o-quino-GA. [structure: see text

  16. Atomistic simulations indicate cardiolipin to have an integral role in the structure of the cytochrome bc(1) complex

    DEFF Research Database (Denmark)

    Poyry, S.; Cramariuc, O.; Postila, P. A.

    2013-01-01

    The reaction mechanism of the cytochrome (cyt) bc(1) complex relies on proton and electron transfer to/from the substrate quinone/quinol, which in turn generate a proton gradient across the mitochondrial membrane. Cardiolipin (CL) have been suggested to play an important role in cyt bc(1) functio...

  17. Role of Geobacter sulfurreducens Outer Surface c-Type Cytochromes in Reduction of Soil Humic Acid and Anthraquinone-2,6-Disulfonate▿

    Science.gov (United States)

    Voordeckers, James W.; Kim, Byoung-Chan; Izallalen, Mounir; Lovley, Derek R.

    2010-01-01

    Deleting individual genes for outer surface c-type cytochromes in Geobacter sulfurreducens partially inhibited the reduction of humic substances and anthraquinone-2,6,-disulfonate. Complete inhibition was obtained only when five of these genes were simultaneously deleted, suggesting that diverse outer surface cytochromes can contribute to the reduction of humic substances and other extracellular quinones. PMID:20154112

  18. Role of Geobacter sulfurreducens outer surface c-type cytochromes in reduction of soil humic acid and anthraquinone-2,6-disulfonate.

    Science.gov (United States)

    Voordeckers, James W; Kim, Byoung-Chan; Izallalen, Mounir; Lovley, Derek R

    2010-04-01

    Deleting individual genes for outer surface c-type cytochromes in Geobacter sulfurreducens partially inhibited the reduction of humic substances and anthraquinone-2,6,-disulfonate. Complete inhibition was obtained only when five of these genes were simultaneously deleted, suggesting that diverse outer surface cytochromes can contribute to the reduction of humic substances and other extracellular quinones.

  19. Effect of Michael adduction on peptide preservation in natural waters.

    Science.gov (United States)

    McKee, G A; Kobiela, M E; Hatcher, P G

    2014-09-20

    The reaction of peptides with chemicals already present in natural waters (such as polycyclic aromatic hydrocarbons) is one method that has been suggested to preserve peptides for the longer term. In this study we test whether the reaction of tetrapeptides with a model quinone can help stabilise the peptide in one polluted riverine system, Elizabeth River in Virginia, USA. We found that there is almost no difference in rate constants between the peptide and its quinone adduct (e.g. 6.62 versus 6.86 per day for AVFA and its respective adduct). However, when monitoring the removal of the adduct from natural water, we identified two new compounds that are formed as a result of its decomposition. Using tandem mass spectrometry we identified potential structures and mechanisms for the formation of these new compounds. These new compounds are more recalcitrant than their parent peptide-quinone adduct, since they remain in solution for 3-10 times longer. Based on our findings we postulate that the reaction of peptides with quinones can help preserve sections of the original peptide following an initial rearrangement of the original adduct, potentially explaining why seemingly labile peptides are observed in most natural waters.

  20. Bio-antioxidant of Anthraquinone Derivatives

    Institute of Scientific and Technical Information of China (English)

    CUI,Jian; LI,Zhao-Long; HONG,Xiao-Yin

    2004-01-01

    @@ The Rubiaceae family is well known for containing anthraquinones. More specifically, lapachol and its analogues are known to possess antitumor, antibiotic, antimalarial and antiulceric activities.[1] Several report indicated that some quinones containing OH in its structure were found to have higher bio-activity than quinines lacking the OH group.

  1. Biodegradation of RDX by Stimulating Humic Substance- and Fe(III) - Reduction

    Science.gov (United States)

    2007-06-19

    167. 57. Stevenson , F. J. 1982. Humus chemistry genesis, composition, reactions. Wiley Interscience, New York. 58. Stolz, J. F., D. R. Lovley, and...Sediments with Quinones and Humus as Terminal Electron Acceptors. Appl. Environ. Microbiol. 67:4471-4478. 10. Coates, J. D., D. J. Ellis, E. L

  2. Decrease of the IgE-binding by Mal d 1, the major apple allergen, by means of polyphenol oxidase and peroxidase treatments

    NARCIS (Netherlands)

    Garcia-Borrego, A.; Wichers, J.H.; Wichers, H.J.

    2007-01-01

    Mal d 1, the major apple allergen, is heat labile and easily oxidized. Oxidative reactions catalyzed by polyphenol oxidase (PPO) and/or peroxidase (POD), present in apple, may be involved in decreasing its allergenicity. PPO and POD convert phenolic compounds into o-quinones. In this study the effec

  3. InterProScan Result: BY943640 [KAIKOcDNA[Archive

    Lifescience Database Archive (English)

    Full Text Available BY943640 BY943640_3_ORF2 1A5A29DABF684387 PFAM PF00420 Oxidored_q2 1.3e-14 T IPR001...133 NADH:ubiquinone/quinone oxidoreductase, chain 4L Biological Process: ATP synthesis coupled electron transport (GO:0042773)|Biological Process: oxidation reduction (GO:0055114) ...

  4. InterProScan Result: FS817035 [KAIKOcDNA[Archive

    Lifescience Database Archive (English)

    Full Text Available FS817035 FS817035_1_ORF2 B027832D7CA10145 PFAM PF00420 Oxidored_q2 6.7e-13 T IPR001...133 NADH:ubiquinone/quinone oxidoreductase, chain 4L Biological Process: ATP synthesis coupled electron transport (GO:0042773)|Biological Process: oxidation reduction (GO:0055114) ...

  5. InterProScan Result: BB988450 [KAIKOcDNA[Archive

    Lifescience Database Archive (English)

    Full Text Available BB988450 BB988450_1_ORF2 3834FAB5D3F21F02 PFAM PF00420 Oxidored_q2 7e-10 T IPR00113...3 NADH:ubiquinone/quinone oxidoreductase, chain 4L Biological Process: ATP synthesis coupled electron transport (GO:0042773)|Biological Process: oxidation reduction (GO:0055114) ...

  6. InterProScan Result: FS872940 [KAIKOcDNA[Archive

    Lifescience Database Archive (English)

    Full Text Available FS872940 FS872940_6_ORF2 F693A02F4F60091F PFAM PF00420 Oxidored_q2 5.6e-10 T IPR001...133 NADH:ubiquinone/quinone oxidoreductase, chain 4L Biological Process: ATP synthesis coupled electron transport (GO:0042773)|Biological Process: oxidation reduction (GO:0055114) ...

  7. InterProScan Result: FY028411 [KAIKOcDNA[Archive

    Lifescience Database Archive (English)

    Full Text Available FY028411 FY028411_1_ORF2 F006CE54DB614664 PFAM PF00420 Oxidored_q2 9.3e-10 T IPR001...133 NADH:ubiquinone/quinone oxidoreductase, chain 4L Biological Process: ATP synthesis coupled electron transport (GO:0042773)|Biological Process: oxidation reduction (GO:0055114) ...

  8. Enantioselective synthesis of helicenequinones and -bisquinones.

    Science.gov (United States)

    Urbano, Antonio; Carreño, M Carmen

    2013-02-07

    A convergent approach based on Diels-Alder reactions between polycyclic dienes and benzoquinones has emerged as a powerful tool for the construction of helicenequinones and bisquinones. Chemical resolution and asymmetric Diels-Alder reactions with sulfinyl quinones provide direct access to enantiopure derivatives. Biaryl or ferrocenyl dienes can be resolved leading to helicenequinones having additional axial or planar chirality.

  9. Visual sensing of fluoride ions by dipyrrolyl derivatives bearing electron-withdrawing groups

    Indian Academy of Sciences (India)

    Tamal Ghosh; Bhaskar G Maiya

    2004-01-01

    Two new, easy-to-prepare dipyrrolyl derivatives endowed with electron-withdrawing quinone or dicyano functionalities in their architecture permit the detection of fluoride ions under visual (naked-eye) as well as optical (absorption and fluorescence) and electrochemical conditions in organic solvents.

  10. Synthesis and structural elucidation of glutathione and N-aceyl-cysteine conjugates of 5-aminosalicylic acid

    DEFF Research Database (Denmark)

    Jensen, J.; Cornett, Claus; Olsen, C. E.

    1993-01-01

    The ability of 5-aminosalicylic acid (5-ASA) to be oxidized to a quinone monoimine compound capable of conjugating with nucleophilic compounds such as N-acetyl-cysteine (NAC) and glutathione (GSH) has been investigated in vitro. Three isomeric conjugates of 5-ASA and NAC as well as three isomeric...

  11. Application and progress of coenzyme Q10 in statin myopathy

    Directory of Open Access Journals (Sweden)

    Bo LI

    2013-11-01

    Full Text Available Statins have been widely used, however, the reports of muscle toxicity caused by statins are increasing. Coenzyme Q10 is a quinone substance which is in the cell membrane, and it is important material of intercellular signaling, mitochondrial respiratory chain and muscle activity energy. The myopathic symptoms can be significantly improved by taking coenzyme Q10.

  12. Genomic plasticity of the rrn-nqrF intergenic segment in the Chlamydiaceae

    NARCIS (Netherlands)

    Liu, Zhi; Rank, Roger; Kaltenboeck, Bernhard; Magnino, Simone; Dean, Deborah; Burall, Laurel; Plaut, Roger D.; Read, Timothy D.; Myers, Garry; Bavoil, Patrik M.

    2007-01-01

    In Chlamydiaceae, the nucleotide sequence between the 5S rRNA gene and the gene for subunit F of the Na+-translocating NADH-quinone reductase (nqrF or dmpP) has varied lengths and gene contents. We analyzed this site in 45 Chlamydiaceae strains having diverse geographical and pathological origins an

  13. AcEST: DK960210 [AcEST

    Lifescience Database Archive (English)

    Full Text Available ng NADH-quinone reductase ... 29 7.5 sp|Q9XPN6|MATK_HELBU Maturase K OS=Helonias bulla...WSINYQDV-VAIGKL 249 >sp|Q9XPN6|MATK_HELBU Maturase K OS=Helonias bullata GN=matK PE=3 SV=1 Length = 515 Scor

  14. 2- Materials and methods

    African Journals Online (AJOL)

    Unicornis

    2012-05-01

    May 1, 2012 ... Quinones are subjected to further reactions leading to the formation of .... distilled water), 500 µL of sodium bicarbonate 20% and 1.745 ml of distilled water ... acetic acid-water (2:98, v/v) (solvent A) and acetonitrile (solvent B).

  15. ROLE OF RED CLOVER PPO IN PATHOGEN RESISTANCE

    Science.gov (United States)

    Higher plant polyphenol oxidases (PPO) are copper-containing enzymes which catalyse both hydroxylation of monophenols to o-diphenols and oxidation of o- diphenols to o-quinones. While PPO is widespread in the plant kingdom, its role in plants has not been unequivocally determined; however, evidence ...

  16. Immunogold Labelling to Localize Polyphenol Oxidase (PPO) During Wilting of Red Clover Leaf Tissue and the Effect of Removing Cellular Matrices on PPO Protection of Glycerol-Based Lipid in the Rumen

    Science.gov (United States)

    The enzyme polyphenol oxidase (PPO) reduces the extent of proteolysis and lipolysis within red clover fed to ruminants. PPO catalyses the conversion of phenols to quinones which can react with nucleophilic cellular constituents (e.g. proteins), forming protein-phenol complexes that may reduce protei...

  17. In vitro Investigation of the Antimicrobial Activity of a Series of ...

    African Journals Online (AJOL)

    NICOLAAS

    bDepartment of Organic Chemistry and Biochemistry, Ruder Boskovic Institute, Bijenicka cesta ... phenolic compounds inhibit DNA synthesis, due to an effect ... during metabolic processes. ...... tified in wild mushrooms, SAR analysis and docking studies. ... aza-quinone methides as latent alkylating species in the design of.

  18. Dasycarine, a New Quinoline Alkaloid from Dictamnus dasycarpus

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Dasycarine, a new quinoline alkaloid along with five known compounds, dictamine, dihydroobacunone, obacunone, fraxinellone and b -sitosterol, were isolated from Dictamnus dasycarpus. The structure of dasycarine was identified as 4, 5, 8- trimethoxyl -3- (3- methyl -2- butenyl)- 2- quinone by 1D and 2D NMR techniques.

  19. Albirhodobacter marinus gen. nov., sp. nov., a member of the family Rhodobacteraceae isolated from sea shore water of Visakhapatnam, India

    Digital Repository Service at National Institute of Oceanography (India)

    Nupur; Bhumika, V.; Srinivas, T.N.R.; AnilKumar, P.

    activities. The fatty acids were found to be dominated by C sub(16:0),C sub(18:1) omega7c and summed in feature 3 (C sub(16:1) omega 7c and/or C sub(16:1) omega 6c). Strain N9 sup(T) was determined to contain Q-10 as the major respiratory quinone...

  20. Iron-catalyzed Rearrangements and Cycloaddition Reactions of 2H-Chromenes

    Science.gov (United States)

    Luan, Yi; Sun, Huan

    2014-01-01

    Iron(III) salts catalyse the tandem rearrangement/hetero-Diels—Alder reaction of 2H-chromenes to yield tetrahydrochromeno heterocycles. The process can occur as a homodimerization and cycloaddition process using electron rich dienophiles. Deuterium labeling and mechanistic studies revealed a hydride shift and ortho-quinone methide cycloaddition reaction pathway. PMID:22098535

  1. The Synthesis of a Cockroach Pheromone: An Experiment for the Second-Year Organic Chemistry Laboratory

    Science.gov (United States)

    Feist, Patty L.

    2008-01-01

    This experiment describes the synthesis of gentisyl quinone isovalerate, or blattellaquinone, a sex pheromone of the German cockroach that was isolated and identified in 2005. The synthesis is appropriate for the second semester of a second-year organic chemistry laboratory course. It can be completed in two, three-hour laboratory periods and uses…

  2. The Synthesis of a Cockroach Pheromone: An Experiment for the Second-Year Organic Chemistry Laboratory

    Science.gov (United States)

    Feist, Patty L.

    2008-01-01

    This experiment describes the synthesis of gentisyl quinone isovalerate, or blattellaquinone, a sex pheromone of the German cockroach that was isolated and identified in 2005. The synthesis is appropriate for the second semester of a second-year organic chemistry laboratory course. It can be completed in two, three-hour laboratory periods and uses…

  3. Asymmetric Brønsted Acid Catalyzed Substitution of Diaryl Methanols with Thiols and Alcohols for the Synthesis of Chiral Thioethers and Ethers

    KAUST Repository

    Chatupheeraphat, Adisak

    2016-03-08

    An enantioselective addition of thiols and alcohols to aza-ortho-quinone methides, starting from diaryl methanols, was developed. The asymmetric additions occur under mild reaction conditions in the presence of chiral phosphoric acids and furnish the corresponding adducts with excellent yields and enantioselectivities.

  4. Contaminant immobilization and nutrient release by carbonized biomass in water and soils

    Science.gov (United States)

    Chars contain functional surface groups such as carboxylic, phenolic, hydroxyl, carbonyl, and quinones, in addition to porous structures that can impact essential soil properties such as cation exchange capacity (CEC), pH, and retention of water, nutrients, and pesticides. Physical and chemical pro...

  5. Richard Willstätter and the 1915 Nobel Prize in chemistry.

    Science.gov (United States)

    Trauner, Dirk

    2015-10-01

    One hundred years after his Nobel Prize, Richard Willstätter's achievements and the fascinating role he played in 20th century chemistry are discussed in this Essay. Several of his discoveries, such as the anthocyanidins, cyclooctatetraene, the ortho-quinones, and the structure of cocaine, will forever be associated with his name.

  6. Unique proline-benzoquinone pigment from the colored nectar of "bird's Coca cola tree" functions in bird attractions.

    Science.gov (United States)

    Luo, Shi-Hong; Liu, Yan; Hua, Juan; Niu, Xue-Mei; Jing, Shu-Xi; Zhao, Xu; Schneider, Bernd; Gershenzon, Jonathan; Li, Sheng-Hong

    2012-08-17

    The major pigment responsible for the dark brown nectar of the "bird's Coca cola tree", Leucosceptrum canum (Labiatae), was isolated and identified as a unique symmetric proline-quinone conjugate, 2,5-di-(N-(-)-prolyl)-para-benzoquinone (DPBQ). Behavioral experiments with both isolated and synthetic authentic samples indicated that DPBQ functions mainly as a color attractant to bird pollinators.

  7. Microbial community changes in biological phosphate-removal systems on altering sludge phosphorus content

    NARCIS (Netherlands)

    Liu, WT; Linning, KD; Nakamura, K; Mino, T; Matsuo, T; Forney, LJ

    Biomarkers (respiratory quinones and cellular fatty acids) and denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA genes were used to characterize the microbial community structure of lab-scale enhanced biological phosphate-removal (EBPR) systems in response to altering sludge

  8. Use of PCR-RFLP analysis to monitor fungicide resistance in Cercospora beticola populations from sugarbeet (Beta vulgaris) in Michigan, United States

    Science.gov (United States)

    Genetic resistance to Quinone outside inhibitor (QoI) and benzimidazole fungicides may be responsible for a recent decline in efficacy of chemical control management strategies for Cercospora leaf spot (CLS) caused by Cercospora beticola (Sacc.) in Michigan sugarbeet (Beta vulgaris L.) fields. The t...

  9. Microsomal superoxide anion production and NADPH-oxidation in a series of 22 aziridinylbenzoquinones

    NARCIS (Netherlands)

    Prins, Bram; Koster, Andries Sj.; Verboom, Willem; Reinhoudt, David N.

    1989-01-01

    Several 2,5-bis(1-aziridinyl)-1,4-benzoquinones (BABQs) can be activated to alkylating species by reduction of the quinone moiety. On the other hand, cytotoxicity of these compounds can be induced by redox cycling. A series of BABQs and their methylated analogues (BMABQs) with different substituents

  10. Inhibition of tyrosinase-mediated enzymatic browning by sulfite and natural alternatives

    NARCIS (Netherlands)

    Kuijpers, T.F.M.; Vincken, J.P.

    2013-01-01

    Although sulfite is widely used to counteract enzymatic browning, its mechanism has remained largely unknown. We describe a double inhibitory mechanism of sulfite on enzymatic browning, affecting both the enzymatic oxidation of phenols into o‑quinones, as well as the non‑enzymatic reactions of these

  11. Genomic plasticity of the rrn-nqrF intergenic segment in the Chlamydiaceae

    NARCIS (Netherlands)

    Liu, Zhi; Rank, Roger; Kaltenboeck, Bernhard; Magnino, Simone; Dean, Deborah; Burall, Laurel; Plaut, Roger D.; Read, Timothy D.; Myers, Garry; Bavoil, Patrik M.

    2007-01-01

    In Chlamydiaceae, the nucleotide sequence between the 5S rRNA gene and the gene for subunit F of the Na+-translocating NADH-quinone reductase (nqrF or dmpP) has varied lengths and gene contents. We analyzed this site in 45 Chlamydiaceae strains having diverse geographical and pathological origins an

  12. Pro-Oxidant Activity of Flavonoids Induces EpRE-Mediated Gene Expression.

    NARCIS (Netherlands)

    Lee-Hilz, Y.Y.; Boerboom, A.M.J.F.; Westphal, A.H.; Berkel, van W.J.H.; Aarts, J.M.M.J.G.; Rietjens, I.M.C.M.

    2006-01-01

    Flavonoids are important bioactive dietary compounds. They induce electrophile-responsive element (EpRE)-mediated expression of enzymes, such as NAD(P)H-quinone oxidoreductase (NQO1) and glutathione S-transferases (GSTs), which are major defense enzymes against electrophilic toxicants and oxidative

  13. PH-Sensitive Ni(OH)2-Based Microelectrochemical Transistors.

    Science.gov (United States)

    1986-11-24

    including those based on W0 3 , 13 on platinized poly(3- methylthiophene),2 1 on ferrocyanide-loaded, protonated poly(4- ,V. vinylpyridine),2 2 and on...a viologen /quinone-based polymer.2 3 One important difference between Ni(OH)2 and the other active materials in pH-sensitive transistors is that Ni

  14. Chemical Defence in a Millipede: Evaluation and Characterization of Antimicrobial Activity of the Defensive Secretion from Pachyiulus hungaricus (Karsch, 1881) (Diplopoda, Julida, Julidae).

    Science.gov (United States)

    Stanković, Slaviša; Dimkić, Ivica; Vujisić, Ljubodrag; Pavković-Lučić, Sofija; Jovanović, Zvezdana; Stević, Tatjana; Sofrenić, Ivana; Mitić, Bojan; Tomić, Vladimir

    2016-01-01

    The chemical defence of the millipede Pachyiulus hungaricus is reported in the present paper, in which a chemical characterization is given and antimicrobial activity is determined. In total, independently of sex, 44 compounds were identified. All compounds belong to two groups: quinones and pentyl and hexyl esters of long-chain fatty acids. The relative abundances of quinones and non-quinones were 94.7% vs. 5.3% (males) and 87.3% vs. 12.7% (females), respectively. The two dominant quinones in both sexes were 2-methyl-1,4,-benzoquinone and 2-methoxy-3-methyl-1,4-benzoquinone. Antibacterial and antifungal activity of the defensive secretion was evaluated in vitro against seven bacterial strains and eight fungal species. With the aid of a dilution technique, the antimicrobial potential of the secretion and high sensitivity of all tested strains were confirmed. The lowest minimum concentrations of these compounds (0.20-0.25 mg/mL) were sufficient for inhibition of Aeromonas hydrophila, Listeria monocytogenes and Methicillin resistant Staphylococcus aureus (MRSA). The growth of eight tested fungal species was inhibited by slightly lower concentrations of the secretion, with Fusarium equiseti as the most sensitive fungus and Aspergillus flavus as the most resistant. Values of MIC and MFC in the employed microdilution assay ranged from 0.10 to above 0.35 mg/mL. The given extract contains antimicrobial components potentially useful as therapeutic agents in the pharmaceutical and agricultural industries.

  15. Dicty_cDB: Contig-U15227-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available RecName: Full=NADH-quinone oxidoreductase subunit H; ... 129 8e-29 EU237487_4( EU237487 |pid:none) Plakortis angulo...ia natans mitochondrion,... 124 3e-27 DQ643834_2( DQ643834 |pid:none) Mussa angulosa mitochondrion, comp...

  16. Human carbonyl reductase (CBR) localized to band 21q22. 1 by high-resolution fluorescence in situ hybridization displays gene dosage effects in trisomy 21 cells

    Energy Technology Data Exchange (ETDEWEB)

    Lemieux, N. (Universite de Montreal (Canada)); Malfoy, B. (Institut Curie Section de Biologie, Paris (France)); Forrest, G.L. (Beckman Research Institute at the City of Hope, Duarte, CA (United States))

    1993-01-01

    Human carbonyl reductase (CBR) belongs to a group of NADPH-dependent enzymes called aldo-keto reductases. The enzyme can function as an aldo-keto reductase or as a quinone reductase with potential for modulating quinone-mediated oxygen free radicals. The CBR gene was mapped by high-resolution fluorescence in situ hybridization to band 21q22.12, very close to the SOD1 locus at position 2lq22.11. CBR displayed gene dosage effects in trisomy 21 human lymphoblasts at the DNA and mRNA levels. Lymphoblasts with increasing chromosome 21 ploidy also showed increased aldo-keto reductase activity and increased quinone reductase activity. Both aldo-keto reductase activity and quinone reductase activity have been shown to be associated with carbonyl reductase. The location of CBR near SOD1 and the increased enzyme activity and potential for free radical modulation in trisomy 21 cells implicate CBR as a candidate for contributing to the pathology of certain diseases such as Down syndrome and Alzheimer disease. 28 refs., 1 fig., 1 tab.

  17. Domain Modeling: NP_067022.1 [SAHG[Archive

    Lifescience Database Archive (English)

    Full Text Available NP_067022.1 chr15 The first X-ray structure of a sulfide:quinone oxidoreductase: in...sights into sulfide oxidation mechanism p3h8lb_ chr15/NP_067022.1/NP_067022.1_holo_44-383.pdb psi-blast 50G,

  18. Photoproduction of hydrogen peroxide in aqueous solution from model compounds for chromophoric dissolved organic matter (CDOM).

    Science.gov (United States)

    Clark, Catherine D; de Bruyn, Warren; Jones, Joshua G

    2014-02-15

    To explore whether quinone moieties are important in chromophoric dissolved organic matter (CDOM) photochemistry in natural waters, hydrogen peroxide (H2O2) production and associated optical property changes were measured in aqueous solutions irradiated with a Xenon lamp for CDOM model compounds (dihydroquinone, benzoquinone, anthraquinone, napthoquinone, ubiquinone, humic acid HA, fulvic acid FA). All compounds produced H2O2 with concentrations ranging from 15 to 500 μM. Production rates were higher for HA vs. FA (1.32 vs. 0.176 mM h(-1)); values ranged from 6.99 to 0.137 mM h(-1) for quinones. Apparent quantum yields (Θ app; measure of photochemical production efficiency) were higher for HA vs. FA (0.113 vs. 0.016) and ranged from 0.0018 to 0.083 for quinones. Dihydroquinone, the reduced form of benzoquinone, had a higher production rate and efficiency than its oxidized form. Post-irradiation, quinone compounds had absorption spectra similar to HA and FA and 3D-excitation-emission matrix fluorescence spectra (EEMs) with fluorescent peaks in regions associated with CDOM.

  19. Kinetic and chemical analyses of the cytokinin dehydrogenase-catalysed reaction : correlations with the crystal structure

    NARCIS (Netherlands)

    Popelková, Hana; Fraaije, Marco W.; Novák, Ondřej; Frébortová, Jitka; Bilyeu, Kristin D.; Frébort, Ivo

    2006-01-01

    CKX (cytokinin dehydrogenase) is a flavoprotein that cleaves cytokinins to adenine and the corresponding side-chain aldehyde using a quinone-type electron acceptor. In the present study, reactions of maize (Zea mays) CKX with five different substrates (N6-isopentenyladenine, trans-zeatin, kinetin, p

  20. Studies on Synthetic and Natural Melanin and Its Affinity for Fe(III Ion

    Directory of Open Access Journals (Sweden)

    T. G. Costa

    2012-01-01

    Full Text Available In this work, we measured the metal-binding sites of natural and synthetic dihydroxyindole (DHI melanins and their respective interactions with Fe(III ions. Besides the two acid groups detected for the DHI system: catechol (Cat and quinone-imine (QI, acetate groups were detected in the natural oligomer by potentiometric titrations. At acidic pH values, Fe(III complexation with synthetic melanin was detected in an Fe(OH(CatH2Cat interaction. With an increase of pH, three new interactions occurred: dihydroxide diprotonated catechol, Fe(OH2(CatH2Cat−, dihydroxide monoprotonated catechol, [Fe(OH2(CatHCat]2−, and an interaction resulting from the association of one quinone-imine and a catechol group, [Fe(OH2(Qi−(CatHCat]3−. In the natural melanin system, we detected the same interactions involving catechol and quinone-imine groups but also the metal interacts with acetate group at pH values lower than 4.0. Furthermore, interactions in the synthetic system were also characterized by infrared spectroscopy by using the characteristic vibrations of catechol and quinone-imine groups. Finally, scanning electronic microscopy (SEM and energy-dispersive X-ray (EDS analysis were used to examine the differences in morphology of these two systems in the absence and presence of Fe(III ions. The mole ratio of metal and donor atoms was obtained by the EDS analysis.

  1. Biogenesis of membrane bound respiratory complexes in Escherichia coli

    NARCIS (Netherlands)

    Price, Claire E.; Driessen, Arnold J. M.

    2010-01-01

    Escherichia colt is one of the preferred bacteria for studies on the energetics and regulation of respiration Respiratory chains consist of primary dehydrogenases and terminal reductases or oxidases linked by quinones. In order to assemble this complex arrangement of protein complexes, synthesis of

  2. Hemoglobin adducts as biomarkers of estrogen homeostasis: elevation of estrogenquinones as a risk factor for developing breast cancer in Taiwanese women.

    Science.gov (United States)

    Lin, Che; Hsieh, Wei-Chung; Chen, Dar-Ren; Kuo, Shou-Jen; Yu, Wen-Fa; Hu, Suh-Woan; Sue, Hung-Jie; Ko, Mao-Hui; Juan, Chang-Hsin; Chung, Kuo-Suan; Lin, Po-Hsiung

    2014-03-21

    The aim of this study was to establish a methodology to analyze estrogen quinone-derived adducts, including 17β-estradiol-2,3-quinone (E2-2,3-Q) and 17β-estradiol-3,4-quinone (E2-3,4-Q), in human hemoglobin (Hb). The methodology was then used to measure the levels of these adducts in Hb derived from female breast cancer patients (n=143) as well as controls (n=147) in Taiwan. Our result confirmed that both E2-2,3-Q- and E2-3,4-Q-derived adducts, including E2-2,3-Q-4-S-Hb and E2-3,4-Q-2-S-Hb, were detected in all breast cancer patients with median levels at 434 (215-1472) and 913 (559-2384) (pmol/g), respectively. Levels of E2-2,3-Q-4-S-Hb correlated significantly with those of E2-3,4-Q-2-S-Hb (r=0.622-0.628, pQ-4-S-Hb and E2-3,4-Q-2-S-Hb in breast cancer patients compared to those in the controls (pbreast cancer risk. We hypothesize that combination of genetic events and environmental factors may modulate estrogen homeostasis and enhance the production of estrogen quinones which lead to subsequent generation of pro-mutagenic DNA lesions in breast cancer patients.

  3. Sequence Classification: 389518 [

    Lifescience Database Archive (English)

    Full Text Available Non-TMB Non-TMH TMB Non-TMB Non-TMB TMB >gi|31794029|ref|NP_856522.1| PROBABLE MALA...TE:QUINONE OXIDOREDUCTASE MQO (MALATE DEHYDROGENASE || http://www.ncbi.nlm.nih.gov/protein/31794029 ...

  4. Sequence Classification: 399279 [

    Lifescience Database Archive (English)

    Full Text Available Non-TMB Non-TMH TMB Non-TMB Non-TMB TMB >gi|15609989|ref|NP_217368.1| PROBABLE MALA...TE:QUINONE OXIDOREDUCTASE MQO (MALATE DEHYDROGENASE || http://www.ncbi.nlm.nih.gov/protein/15609989 ...

  5. Molecular basis of fungicide resistance in Cercospora beticola

    Science.gov (United States)

    Cercospora leaf spot (CLS), caused by the fungus Cercospora beticola, is the most important foliar disease of sugarbeet. Control measures include the application of sterol demethylation inhibitor (DMI) and quinone outside inhibitor (QoI) fungicides. Understanding the molecular mechanism of fungici...

  6. Kinetic and chemical analyses of the cytokinin dehydrogenase-catalysed reaction : correlations with the crystal structure

    NARCIS (Netherlands)

    Popelková, Hana; Fraaije, Marco W.; Novák, Ondřej; Frébortová, Jitka; Bilyeu, Kristin D.; Frébort, Ivo

    2006-01-01

    CKX (cytokinin dehydrogenase) is a flavoprotein that cleaves cytokinins to adenine and the corresponding side-chain aldehyde using a quinone-type electron acceptor. In the present study, reactions of maize (Zea mays) CKX with five different substrates (N6-isopentenyladenine, trans-zeatin, kinetin,

  7. 78 FR 48397 - Defense Federal Acquisition Regulation Supplement: Clauses With Alternates-Transportation (DFARS...

    Science.gov (United States)

    2013-08-08

    .... Manuel Quinones, Editor, Defense Acquisition Regulations System. Therefore, 48 CRF parts 212, 216, 247..., subassemblies, accessories, and equipment; machine tools; material; equipment; stores of all kinds; end items...; equipment; stores of all kinds; end items; construction materials; and components of the foregoing. (7)...

  8. Flash Photolysis and Its Applications: Meeting in Honour of Sir George Porter, P.R.S. held in London, England on 14-16 July 1986,

    Science.gov (United States)

    1986-07-16

    dopachrome and reform dopa. By contrast, the cysteinyldopa quinones decayed via an acid-catalysed unimolecular cyclisation involving the cysteine side chain...porphyrin -dianion). Aeration of the photolysed solution causesimmediate reformation of the original porphyrin, with very little <%/ byproduct formation... ESTRUTURAL , COMPLEXO I INSTITUTO SUPERIOR TECNICO AV. ROVISCO PATS, 1096 LISBOA CODEX, PORTUGAL Reversed micelles have been used to mimic membrane

  9. A rapid procedure for the in situ assay of periplasmic, PQQ-dependent methanol dehydrogenase in intact single bacterial colonies.

    Science.gov (United States)

    Vemuluri, Venkata Ramana; Shaw, Shreya; Autenrieth, Caroline; Ghosh, Robin

    2017-03-23

    Mechanistic details of methanol oxidation catalyzed by the periplasmically-located pyrroloquinoline quinone-dependent methanol dehydrogenase of methylotrophs can be elucidated using site-directed mutants. Here, we present an in situ colony assay of methanol dehydrogenase, which allows robotic screening of large populations of intact small colonies, and regrowth of colonies for subsequent analysis.

  10. Active-site structure of the soluble quinoprotein glucose dehydrogenase complexed with methylhydrazine : A covalent cofactor-inhibitor complex

    NARCIS (Netherlands)

    Oubrie, Arthur; Rozeboom, Henriëtte J.; Dijkstra, Bauke W.

    1999-01-01

    Soluble glucose dehydrogenase (s-GDH) from the bacterium Acinetobacter calcoaceticus is a classical quinoprotein. It requires the cofactor pyrroloquinoline quinone (PQQ) to catalyze the oxidation of glucose to gluconolactone, The precise catalytic role of PQQ in s-GDH and several other PQQ-dependent

  11. Feasibility study on the application of rhizosphere microflora of rice for the biohydrogen production from wasted bread

    Energy Technology Data Exchange (ETDEWEB)

    Doi, Tetsuya [Field Production Science Center, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Nishitokyo, Tokyo 188-0002 (Japan); Nishihara Environment Technology Inc., Tokyo 108-0023 (Japan); Matsumoto, Hisami [Nishihara Environment Technology Inc., Tokyo 108-0023 (Japan); Abe, Jun [AE-Bio, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo 113-8657 (Japan); Morita, Shigenori [Field Production Science Center, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Nishitokyo, Tokyo 188-0002 (Japan)

    2009-02-15

    We performed an experiment of continuous anaerobic hydrogen fermentation as a pilot-plant-scale test, in which waste from a bread factory was fermented by microflora of rice rhizosphere origin. The community structure of microflora during anaerobic hydrogen fermentation was analyzed using PCR-DGGE, FISH, and quinone profiles. The relation of those results to hydrogen generation was discussed. Results show that a suitable condition was a reactor temperature of 35 C, with HRT 12-36 h, volume load of 30-70 kg-COD{sub Cr}/m{sup 3} day, and maximum hydrogen production rate of 1.30 mol-H{sub 2}/mol-hexose. Regarding characteristics of microflora during fermentation, PCR-DGGE results show specific 16S rDNA band patterns; Megasphaera elsdenii and Clostridium sp. of the hydrogen-producing bacteria were identified. M. elsdenii was detected throughout the fermentation period, while Clostridium sp. of hydrogen-producing bacteria was detected on the 46th day. Furthermore, FISH revealed large amounts of Clostridium spp. in the sample. The quinone profile showed that the dominant molecular species of quinone is MK-7. Because Clostridium spp. belong to MK-7, results suggest that the quinone profile result agrees with the results of PCR-DGGE and FISH. Microflora in the rhizosphere of rice plants can be a possible resource for effective bacteria of biohydrogen production. (author)

  12. Application of redox mediators to accelerate the transformation of reactive azo dyes in anaerobic bioreactors.

    NARCIS (Netherlands)

    Zee, van der F.P.; Bouwman, R.H.M.; Strik, D.P.B.T.B.; Lettinga, G.; Field, J.A.

    2001-01-01

    Azo dyes are nonspecifically reduced under anaerobic conditions but the slow rates at which reactive azo dyes are converted presents a serious problem for the application of anaerobic technology as a first stage in the complete biodegradation of these compounds. As quinones have been found to cataly

  13. Evaluation of various strategies to formation of pH responsive hydroquinone-terminated films on carbon electrodes

    DEFF Research Database (Denmark)

    Holm, A.H.; Vase, K.H.; Winther-Jensen, Bjørn;

    2007-01-01

    The hydroquinone/quinone (H(2)Q/Q) redox system was tethered to glassy carbon surfaces using first an electrochemical pre-oxidation treatment to afford carboxylic acid functionalities followed by immobilizing the H(2)Q Precursor, n-(2,5-dimethoxyphenyl)alkan-1-amine (general structure: H2N-(CH2)(...

  14. Mushroom Tyrosinase: A Model System to Combine Experimental Investigation of Enzyme-Catalyzed Reactions, Data Handling Using R, and Enzyme-Inhibitor Structural Studies

    Science.gov (United States)

    Nairn, Robert; Cresswell, Will; Nairn, Jacqueline

    2015-01-01

    The activity of mushroom tyrosinase can be measured by monitoring the conversion of phenolic compounds into quinone derivatives using spectrophotometry. This article describes a series of experiments which characterize the functional properties of tyrosinase, the analysis of the resulting data using R to determine the kinetic parameters, and the…

  15. [Preparation and application of the quinonyl chloromethylation polystyrene in biological treatment of wastewater].

    Science.gov (United States)

    Zhang, Hua-Yu; Xu, Qing; Niu, Chun-Mei; Wang, Ya-Jun; Hou, Zheng-Hao; Li, Shao-Ying; Chen, Yan-Ming; Lian, Jing; Wu, Shi-Bin; Guo, Jian-Bo

    2014-05-01

    The technology of non-water-soluble mediator anaerobic biological catalysis has attracted more and more attention in the field of environment technology. In this study, five kinds of quinonly compounds were grafted on the chloromethylation polystyrene macromolecular carrier by Friedel-Crafts reaction. Reaction factors of temperature and molar ratio for the 1,4-naphthoquinone grafting carrier were optimized, and the optimal temperature was 78 degreesC while the optimal molar ratio of 1, 4-naphthoquinone and chloromethylation polystyrene was 2: 1. Fourier infrared spectrum analysis confirmed that the quinone groups were successfully grafted on the macromolecular backbone chloromethylation polystyrene. Catalysis using the five kinds of quinonly materials as non-water-soluble redox mediators enhanced the biological denitrification rate and the decoloration of azo dyes, meanwhile these materials showed good reusability in the biodegradation of azo dye. This study developed a new method for the preparation of quinonly materials and revealed a new field in the technology of mediator catalysis.

  16. Study on Nitrogen Forms in Phenolic Polymers Incorporating Protien by 15N CP—MAS NMR

    Institute of Scientific and Technical Information of China (English)

    CHENGLILI; WENQIXIAO; 等

    1996-01-01

    Phenolic polymers synthesized by reactions by reactions of p-benzoquinone with 15N-labelled protein or (15NH4)2SO4 were studied by using 15N CP-MAS NMR technique in combination with chemical approaches.Results showed that more than 80% of nitrogen in quinone-protein polymers was in the form of amide with some present as aromatic and /or aliphatic amine and less than 10% of nitrogen occurred as heterocyclic N.The nitrogen distribution in the non-hydrolyzable residue of the quinone-protein polymers was basically similar to that of soil humic acid reported in literature with the exception that a higher proportion of N as heterocyclic N and aromatic amine and a lower proportion of N as amide and aliphatic amine were found in the former than in the latter,More than 70% of total nitrogen in quinone-(NH4)2OS4 polymer was acid resistant ,of which about 53% occurred as pyrrole,nitrile and imion type N.The possible roles of the reactions of phenols or quinones with proteins in the formation of humic acid.especially the non-hydrolyzable nitrogen in humicacid,are discussed.

  17. Reactivity of an o-indoloquinone to 1- and 2-azadienes.

    Science.gov (United States)

    Bernardes Génisson, V; Nebois, P; Domard, M; Fillion, H

    2000-06-01

    The cycloaddition reactions of o-indoloquinone 4 to azadienes are described. With 1-azadiene 2, quinone 4 works as a dienophile to give the directly aromatized cycloadduct 6. In contrast, when 2-azadiene 3 is used, the cycloaddition occurs with CO-4, indicating that this system functions as a heterodienophile.

  18. AcEST: DK952776 [AcEST

    Lifescience Database Archive (English)

    Full Text Available ase subunit 5, chromatophore 2 OS=Paulinella chromatophora Align length 67 Score (bit) 31.2 E-value 4.5 Repo...S=Escheric... 30 9.9 >sp|B1X5V5|NU5C2_PAUCH NAD(P)H-quinone oxidoreductase subunit 5, chromatophore 2 OS=Pauline

  19. AcEST: DK961411 [AcEST

    Lifescience Database Archive (English)

    Full Text Available 2 2.9 sp|Q6N1Z5|NUOI2_RHOPA NADH-quinone oxidoreductase subunit I 2 OS... 32 3.8 sp|P97588|SMAD1_RAT Mothers...LISGEGKVRGYRYWSVAGKAIPGKDKGE---AEHEAPP 165 >sp|P97588|SMAD1_RAT Mothers against decapentaplegic homolog 1 OS

  20. Conformational differences between the methoxy groups of QA and QB site ubisemiquinones in bacterial reaction centers: a key role for methoxy group orientation in modulating ubiquinone redox potential.

    Science.gov (United States)

    Taguchi, Alexander T; O'Malley, Patrick J; Wraight, Colin A; Dikanov, Sergei A

    2013-07-09

    Ubiquinone is an almost universal, membrane-associated redox mediator. Its ability to accept either one or two electrons allows it to function in critical roles in biological electron transport. The redox properties of ubiquinone in vivo are determined by its environment in the binding sites of proteins and by the dihedral angle of each methoxy group relative to the ring plane. This is an attribute unique to ubiquinone among natural quinones and could account for its widespread function with many different redox complexes. In this work, we use the photosynthetic reaction center as a model system for understanding the role of methoxy conformations in determining the redox potential of the ubiquinone/semiquinone couple. Despite the abundance of X-ray crystal structures for the reaction center, quinone site resolution has thus far been too low to provide a reliable measure of the methoxy dihedral angles of the primary and secondary quinones, QA and QB. We performed 2D ESEEM (HYSCORE) on isolated reaction centers with ubiquinones (13)C-labeled at the headgroup methyl and methoxy substituents, and have measured the (13)C isotropic and anisotropic components of the hyperfine tensors. Hyperfine couplings were compared to those derived by DFT calculations as a function of methoxy torsional angle allowing estimation of the methoxy dihedral angles for the semiquinones in the QA and QB sites. Based on this analysis, the orientation of the 2-methoxy groups are distinct in the two sites, with QB more out of plane by 20-25°. This corresponds to an ≈50 meV larger electron affinity for the QB quinone, indicating a substantial contribution to the experimental difference in redox potentials (60-75 mV) of the two quinones. The methods developed here can be readily extended to ubiquinone-binding sites in other protein complexes.

  1. Conformational differences between the methoxy groups of QA and QB site ubisemiquinones in bacterial reaction centers: a key role for methoxy group orientation in modulating ubiquinone redox potential†

    Science.gov (United States)

    Taguchi, Alexander T.; O'Malley, Patrick J.; Wraight, Colin A.; Dikanov, Sergei A.

    2013-01-01

    Ubiquinone is an almost universal, membrane-associated redox mediator. Its ability to accept either one or two electrons allows it to function in critical roles in biological electron transport. The redox properties of ubiquinone in vivo are determined by its environment in the binding sites of proteins and by the dihedral angle of each methoxy group relative to the ring plane. This is an attribute unique to ubiquinone among natural quinones and could account for its widespread function with many different redox complexes. In this work, we use the photosynthetic reaction center as a model system for understanding the role of methoxy conformations in determining the redox potential of the ubiquinone/semiquinone couple. Despite the abundance of X-ray crystal structures for the reaction center, quinone site resolution has thus far been too low to provide a reliable measure of the methoxy dihedral angles of the primary and secondary quinones, QA and QB. We performed 2D ESEEM (HYSCORE) on isolated reaction centers with ubiquinones 13C-labeled at the headgroup methyl and methoxy substituents, and have measured the 13C isotropic and anisotropic components of the hyperfine tensors. Hyperfine couplings were compared to those derived by DFT calculations as a function of methoxy torsional angle allowing estimation of the methoxy dihedral angles for the semiquinones in the QA and QB sites. Based on this analysis, the orientation of the 2-methoxy groups are distinct in the two sites, with QB more out of plane by 20-30°. This corresponds to an ≈50 meV larger electron affinity for the QB quinone, indicating a substantial contribution to the experimental difference in redox potentials (60-75 mV) of the two quinones. The methods developed here can be readily extended to ubiquinone-binding sites in other protein complexes. PMID:23745576

  2. New functional sulfide oxidase-oxygen reductase supercomplex in the membrane of the hyperthermophilic bacterium Aquifex aeolicus.

    Science.gov (United States)

    Prunetti, Laurence; Infossi, Pascale; Brugna, Myriam; Ebel, Christine; Giudici-Orticoni, Marie-Thérèse; Guiral, Marianne

    2010-12-31

    Aquifex aeolicus, a hyperthermophilic and microaerophilic bacterium, obtains energy for growth from inorganic compounds alone. It was previously proposed that one of the respiratory pathways in this organism consists of the electron transfer from hydrogen sulfide (H(2)S) to molecular oxygen. H(2)S is oxidized by the sulfide quinone reductase, a membrane-bound flavoenzyme, which reduces the quinone pool. We have purified and characterized a novel membrane-bound multienzyme supercomplex that brings together all the molecular components involved in this bioenergetic chain. Our results indicate that this purified structure consists of one dimeric bc(1) complex (complex III), one cytochrome c oxidase (complex IV), and one or two sulfide quinone reductases as well as traces of the monoheme cytochrome c(555) and quinone molecules. In addition, this work strongly suggests that the cytochrome c oxidase in the supercomplex is a ba(3)-type enzyme. The supercomplex has a molecular mass of about 350 kDa and is enzymatically functional, reducing O(2) in the presence of the electron donor, H(2)S. This is the first demonstration of the existence of such a respirasome carrying a sulfide oxidase-oxygen reductase activity. Moreover, the kinetic properties of the sulfide quinone reductase change slightly when integrated in the supercomplex, compared with the free enzyme. We previously purified a complete respirasome involved in hydrogen oxidation and sulfur reduction from Aquifex aeolicus. Thus, two different bioenergetic pathways (sulfur reduction and sulfur oxidation) are organized in this bacterium as supramolecular structures in the membrane. A model for the energetic sulfur metabolism of Aquifex aeolicus is proposed.

  3. Three enzymatic activities catalyze the oxidation of sulfide to thiosulfate in mammalian and invertebrate mitochondria.

    Science.gov (United States)

    Hildebrandt, Tatjana M; Grieshaber, Manfred K

    2008-07-01

    Hydrogen sulfide is a potent toxin of aerobic respiration, but also has physiological functions as a signalling molecule and as a substrate for ATP production. A mitochondrial pathway catalyzing sulfide oxidation to thiosulfate in three consecutive reactions has been identified in rat liver as well as in the body-wall tissue of the lugworm, Arenicola marina. A membrane-bound sulfide : quinone oxidoreductase converts sulfide to persulfides and transfers the electrons to the ubiquinone pool. Subsequently, a putative sulfur dioxygenase in the mitochondrial matrix oxidizes one persulfide molecule to sulfite, consuming molecular oxygen. The final reaction is catalyzed by a sulfur transferase, which adds a second persulfide from the sulfide : quinone oxidoreductase to sulfite, resulting in the final product thiosulfate. This role in sulfide oxidation is an additional physiological function of the mitochondrial sulfur transferase, rhodanese.

  4. Microbe inhibition by Tribolium flour beetles varies with beetle species, strain, sex, and microbe group.

    Science.gov (United States)

    Prendeville, Holly R; Stevens, Lori

    2002-06-01

    Tribolium flour beetles produce defensive compounds, including quinones, putatively aimed at deterring predators and inhibiting microbes. Here we examine how effective the defensive secretions of Tribolium confusum and T. castaneum are at inhibiting growth of various microbes and how this varies with species, geographic strain, and sex of the beetles. We explore differences at both the kingdom and species level of common flour microbes in their susceptibility to defensive compounds. Beetle species and strains vary in their ability to inhibit microbial growth. In addition, microbes vary in their sensitivity to the beetles' defense compounds. The capability to suppress microbial growth is likely under stabilizing selection with optimum quinone production varying among populations and may be dependent on several environmental factors including temperature, humidity, and predators.

  5. [Reaction of 3-aryl-2-nitroacrylates with titanium tetrachloride. Formation of 4H-1,2-oxazines and hydroxy-arylaldehydes].

    Science.gov (United States)

    Hirotani, S; Zen, S

    1994-04-01

    The reaction of ethyl 3-aryl-2-nitroacrylate (1a: aryl = 3-methoxyphenyl) with toluene in the presence of titanium tetrachloride gave 4-(4'-methyl-phenyl)-4H-1,2-benzoxazine (3) in a 44.2% yield. The acrylate 1a reacted with dichloromethane in the presence of titanium tetrachloride to give 5-methoxy-salicylaldehyde (2a) in a 61.8% yield. Therefore, 2a was presumed to be formed via an intermediate 4H-1,2-benzoxazine (3'), followed by ring opening to quinone methide and cyano formate. In a similar reaction using both toluene and dichloromethane, 1 bearing a 2-naphthyl group gave a dimer of quinone methide and 1-hydroxy-2-naphthaldehyde via 4H-naphth[2,1-e]-1,2-oxazine, respectively.

  6. Kinetic Study of the Oxidation of Catechols in the Presence of N-Methylaniline

    Directory of Open Access Journals (Sweden)

    Lida Khalafi

    2013-01-01

    Full Text Available The reactions of electrochemically generated o-quinones from oxidation of catechol and 4-methylcatechol as Michael acceptors with N-methylaniline as nucleophile have been studied using cyclic voltammetry. Voltammetric responses show that oxidation of catechols is followed by Michael addition of N-methylaniline. The reaction products are believed to be diphenylamine derivatives of catechols that undergo electron transfer at more negative potentials than the catechols. The observed homogeneous rate constants for Michael addition were estimated by digital simulation and show that the reactivity of 4-methyluinone is considerably less than o-quinone. The oxidation potentials of the desired products drastically depend on the solution pH and their structures.

  7. Effects of commonly consumed fruit juices and carbohydrates on redox status and anticancer biomarkers in female rats

    DEFF Research Database (Denmark)

    Breinholt, Vibeke M.; Nielsen, Salka E.; Knuthsen, Pia

    2003-01-01

    the average carbohydrate levels in the employed fruit juices. None of the fruit juices were found to affect the activities of antioxidant enzymes in red blood cells or hepatic glutathione S-transferase. Hepatic quinone reductase activity, on the other hand, was significantly increased by grape-fruit juice....../kg of diet. However, no effects were observed on hepatic glutathione S-transferase or quinone reductase activities, plasma redox status, or the activity of red blood cell antioxidant enzymes. Overall, the results of the present study suggest that commonly consumed fruit juices can alter lipid and protein......Administration of apple juice, black currant juice, ora 1:1 combination of the two juices significantly decreased the level of the lipid peroxidation biomarker malondialdehyde in plasma of female rats, whereas the protein oxidation biomarker 2-amino-adipic semialdehyde, was significantly increased...

  8. Synthesis and Cytotoxic Activity on Human Cancer Cells of Novel Isoquinolinequinone-Amino Acid Derivatives.

    Science.gov (United States)

    Valderrama, Jaime A; Delgado, Virginia; Sepúlveda, Sandra; Benites, Julio; Theoduloz, Cristina; Buc Calderon, Pedro; Muccioli, Giulio G

    2016-09-08

    A variety of aminoisoquinoline-5,8-quinones bearing α-amino acids moieties were synthesized from 3-methyl-4-methoxycarbonylisoquinoline-5,8-quinone and diverse l- and d-α-amino acid methyl esters. The members of the series were evaluated for their cytotoxic activity against normal and cancer cell lines by using the (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) (MTT) assay. From the current investigation, structure-activity relationships demonstrate that the location and structure of the amino acid fragment plays a significant role in the cytotoxic effects. Moderate to high cytotoxic activity was observed and four members, derived from l-alanine, l-leucine, l-phenylalanine, and d-phenylalanine, were selected as promising compounds by their IC50 ranging from 0.5 to 6.25 μM and also by their good selectivity indexes (≥2.24).

  9. Parkinson's disease and mitochondrial complex I: a perspective on the Ndi1 therapy.

    Science.gov (United States)

    Marella, Mathieu; Seo, Byoung Boo; Yagi, Takao; Matsuno-Yagi, Akemi

    2009-12-01

    Mitochondrial impairment has been collecting more and more attention as a contributing factor to the etiology of Parkinson's disease. Above all, the NADH-quinone oxidoreductase, complex I, of the respiratory chain seems to be most culpable. Complex I dysfunction is translated to an increased production of reactive oxygen species and a decreased energy supply. In the brain, the dopaminergic neurons are one of the most susceptible cells. Their death is directly linked to the disease apparition. Developing an effective gene therapy is challenged by harmful actions of reactive oxygen species. To overcome this problem a therapeutic candidate must be able to restore the NADH-quinone oxidoreductase activity regardless of how complex I is impaired. Here we discuss the potency of the yeast alternative NADH dehydrogenase, the Ndi1 protein, to reinstate the mitochondrial respiratory chain compensating for disabled complex I and the benefit Ndi1 brings toward retardation of Parkinson's disease.

  10. Inhibition of enzymatic browning and protection of sulfhydryl enzymes by thiol compounds.

    Science.gov (United States)

    Negishi, O; Ozawa, T

    2000-06-01

    In a reaction between (-)-epicatechin (EC) and 2-mercaptoethanol (2ME), catalyzed by partially purified polyphenol oxidase (PPO) extracted from the style of Rhododendron mucronatum, 2'-(2-hydroxyethylthio)-(-)-epicatechin (2'-HETEC), 5'-(2-hydroxyethylthio)-(-)-epicatechin (5'-HETEC), and 2',5'-bis(2-hydroxyethylthio)-(-)-epicatechin (2',5'-HETEC) were formed. The rate of formation of 2',5'-HETEC from 5'-HETEC was faster than that from 2'-HETEC. In the absence of 2ME, the concentration of EC decreased rapidly and the reaction mixture turned brown; 2'-, 5'-, and 2',5'-HETEC, especially 2'-substituted HETECs. reacted more slowly. These data indicate that 2ME acts both as an inhibitor of the polymerization of O-quinone, presumably by binding to it and as a reductant involved in the conversion of O-quinone to O-dihydroxyphenol, Inhibition of enzymatic browning by other thiol compounds such as cysteine and dithiothreitol was also investigated.

  11. Controlling mechanical properties of bio-inspired hydrogels by modulating nano-scale, inter-polymeric junctions

    Directory of Open Access Journals (Sweden)

    Seonki Hong

    2014-06-01

    Full Text Available Quinone tanning is a well-characterized biochemical process found in invertebrates, which produce diverse materials from extremely hard tissues to soft water-resistant adhesives. Herein, we report new types of catecholamine PEG derivatives, PEG-NH-catechols that can utilize an expanded spectrum of catecholamine chemistry. The PEGs enable simultaneous participation of amine and catechol in quinone tanning crosslinking. The intermolecular reaction between PEG-NH-catechols forms a dramatic nano-scale junction resulting in enhancement of gelation kinetics and mechanical properties of PEG hydrogels compared to results obtained by using PEGs in the absence of amine groups. Therefore, the study provides new insight into designing new crosslinking chemistry for controlling nano-scale chemical reactions that can broaden unique properties of bulk hydrogels.

  12. AcEST: DK958895 [AcEST

    Lifescience Database Archive (English)

    Full Text Available tr|Q38M75|Q38M75_SOLTU Ripening regulated protein-like OS=Solanu... 144 7e-45 tr|B6T2P8|B6T2P8_MAIZE Chloroplastic...ncharacterized protein OS=Oryza... 140 5e-42 tr|B6SZC2|B6SZC2_MAIZE Chloroplastic quinone-oxidoreductase OS=...t: 116 TVSRPAEVSAAEGAGLLIAGLTALQALVNPAEVKLDGTGPRKNILVTAASGGVGHY 171 >tr|B6T2P8|B6T2P8_MAIZE Chloroplastic qu...tr|B6TE27|B6TE27_MAIZE Chloroplastic quinone-oxidoreductase OS=Z... 135 2e-39 tr|...icum monococcum ... 129 2e-40 tr|A3ASY6|A3ASY6_ORYSJ Putative uncharacterized protein OS=Oryza... 130 4e-40

  13. Characteristics and Kinetic Analysis of AQS Transformation and Microbial Goethite Reduction:Insight into "Redox mediator-Microbe-Iron oxide" Interaction Process.

    Science.gov (United States)

    Zhu, Weihuang; Shi, Mengran; Yu, Dan; Liu, Chongxuan; Huang, Tinglin; Wu, Fengchang

    2016-01-01

    The characteristics and kinetics of redox transformation of a redox mediator, anthraquinone-2-sulfonate (AQS), during microbial goethite reduction by Shewanella decolorationis S12, a dissimilatory iron reduction bacterium (DIRB), were investigated to provide insights into "redox mediator-iron oxide" interaction in the presence of DIRB. Two pre-incubation reaction systems of the "strain S12- goethite" and the "strain S12-AQS" were used to investigate the dynamics of goethite reduction and AQS redox transformation. Results show that the concentrations of goethite and redox mediator, and the inoculation cell density all affect the characteristics of microbial goethite reduction, kinetic transformation between oxidized and reduced species of the redox mediator. Both abiotic and biotic reactions and their coupling regulate the kinetic process for "Quinone-Iron" interaction in the presence of DIRB. Our results provide some new insights into the characteristics and mechanisms of interaction among "quinone-DIRB- goethite" under biotic/abiotic driven.

  14. Phytochemistry, Bioactivity and Potential Impact on Health of Juglans: the Original Plant of Walnut.

    Science.gov (United States)

    Bi, Dongdong; Zhao, Yicheng; Jiang, Rui; Wang, Yan; Tian, Yuxin; Chen, Xiaoyi; Bai, Shaojuan; She, Gaimei

    2016-06-01

    Walnuts are seeds with a hard shell from the genus Juglans (J. mandshurica, J. regia, J. sinensis, J. cathayensis, J. nigra and J. sigillata). Walnuts can nourish brain cells to improve human memory. Other parts of the plant are also employed as traditional Chinese medicines. Modern research on Juglans species has been mostly focused on the above-mentioned species, the seeds of which are all called walnuts. Juglans species have diverse chemical constituents, including diarylheptanoids, quinones, polyphenols, flavones and terpenes. The diarylheptanoids and quinones have notable antitumor activity, supplying new lead compounds for preparing antitumor drugs. The potent pain-relieving, antioxidant, antibacterial and antitumor activities of these plants are significant. In the review, comprehensive information on the nutritional characteristics, traditional functions, chemical constituents, and biological activities of the Juglans species, together with the seeds used as walnuts is provided to explore their potential and to advance research.

  15. Crystallization and preliminary X-ray crystallographic analysis of latent isoform PPO4 mushroom (Agaricus bisporus) tyrosinase.

    Science.gov (United States)

    Mauracher, Stephan Gerhard; Molitor, Christian; Al-Oweini, Rami; Kortz, Ulrich; Rompel, Annette

    2014-02-01

    Tyrosinase exhibits catalytic activity for the ortho-hydroxylation of monophenols to diphenols as well as their subsequent oxidation to quinones. Owing to polymerization of these quinones, brown-coloured high-molecular-weight compounds called melanins are generated. The latent precursor form of polyphenol oxidase 4, one of the six tyrosinase isoforms from Agaricus bisporus, was purified to homogeneity and crystallized. The obtained crystals belonged to space group C121 (two molecules per asymmetric unit) and diffracted to 2.78 Å resolution. The protein only formed crystals under low-salt conditions using the 6-tungstotellurate(VI) salt Na6[TeW6O24] · 22H2O as a co-crystallization agent.

  16. Structure of a bacterial homologue of vitamin K epoxide reductase

    Energy Technology Data Exchange (ETDEWEB)

    Li, Weikai; Schulman, Sol; Dutton, Rachel J.; Boyd, Dana; Beckwith, Jon; Rapoport, Tom A. (Harvard-Med); (HHMI)

    2010-03-19

    Vitamin K epoxide reductase (VKOR) generates vitamin K hydroquinone to sustain {gamma}-carboxylation of many blood coagulation factors. Here, we report the 3.6 {angstrom} crystal structure of a bacterial homologue of VKOR from Synechococcus sp. The structure shows VKOR in complex with its naturally fused redox partner, a thioredoxin-like domain, and corresponds to an arrested state of electron transfer. The catalytic core of VKOR is a four transmembrane helix bundle that surrounds a quinone, connected through an additional transmembrane segment with the periplasmic thioredoxin-like domain. We propose a pathway for how VKOR uses electrons from cysteines of newly synthesized proteins to reduce a quinone, a mechanism confirmed by in vitro reconstitution of vitamin K-dependent disulphide bridge formation. Our results have implications for the mechanism of the mammalian VKOR and explain how mutations can cause resistance to the VKOR inhibitor warfarin, the most commonly used oral anticoagulant.

  17. Kinetic characterization of oxyresveratrol as a tyrosinase substrate.

    Science.gov (United States)

    Ortiz-Ruiz, Carmen Vanessa; Ballesta de Los Santos, Manuel; Berna, Jose; Fenoll, Jose; Garcia-Ruiz, Pedro Antonio; Tudela, Jose; Garcia-Canovas, Francisco

    2015-11-01

    Oxyresveratrol is a stilbenoid described as a powerful inhibitor of tyrosinase and proposed as skin-whitening and anti-browning agent. However, the enzyme is capable of acting on it, considering it as a substrate, as it has been proved in the case of its analogous resveratrol. Tyrosinase hydroxylates the oxyresveratrol to an o-diphenol and oxidizes the latter to an o-quinone, which finally isomerizes to p-quinone. For these reactions to take place the presence of the Eox (oxy-tyrosinase) form is necessary. The kinetic analysis of the proposed mechanism has allowed the kinetic characterization of this molecule as a substrate of tyrosinase, affording a catalytic constant of 5.39 ± 0.21 sec(-1) and a Michaelis constant of 8.65 ± 0.73 µM.

  18. Tyrosinase-Catalyzed Hydroxylation of 4-Hexylresorcinol, an Antibrowning and Depigmenting Agent: A Kinetic Study.

    Science.gov (United States)

    Ortiz-Ruiz, Carmen Vanessa; Berna, Jose; Rodriguez-Lopez, Jose Neptuno; Tomas, Virginia; Garcia-Canovas, Francisco

    2015-08-12

    4-Hexylresorcinol (HR) is a compound used in the food and cosmetic industries as an antibrowning and lightening agent. Its use is mainly attributed to its inhibitory effect on the enzyme tyrosinase. However, the enzyme hydroxylates HR to an o-diphenol, which it then oxidizes to an o-quinone, which rapidly isomerizes to p-quinone. For tyrosinase to act in this way, the Eox form (oxy-tyrosinase) must be present in the reaction medium, which can be brought about by (a) hydrogen peroxide, (b) ascorbic acid, or (c) catalytic concentrations of o-diphenol and a reductant (NADH) to maintain it constant. This work demonstrates that HR is a substrate of tyrosinase and proposes a mechanism for its action. Its kinetic characterization provides a catalytic constant of 0.85 ± 0.04 s(-1) and a Michaelis constant of 60.31 ± 6.73 μM.

  19. Electrochemical study of 7{alpha},12,20-O-trimethyl-conacytone in acetonitrile

    Energy Technology Data Exchange (ETDEWEB)

    Frontana, Carlos; Frontana-Uribe, Bernardo A.; Gonzalez, Ignacio

    2003-10-30

    An electrochemical study of the electroreduction in anhydrous acetonitrile of 7{alpha},12,20-O-trimethyl-conacytone, an abietane quinoid diterpene derivative from the natural product 7{alpha}-O-methyl-conacytone, showed two reduction signals. At the first reduction step, fast chemical reactions involving the loss of the methoxyl group located at C-7 with simultaneous regeneration of the quinoid moiety were observed. This electrogenerated quinone is reduced again, at the same potential used with the former quinone, resulting in a two-electron peak. These results were obtained by cyclic voltammetry and double-step chronoamperometry experiments. The electrolysis under methylating conditions of 7{alpha}-O-methyl-conacytone, at potential values of the second electron transfer, generates as major products, methoxy-hydroquinone, where the methoxy group at C-7 is lost, which is in agreement with the proposed mechanism. Therefore, the second reduction signal was attributed to the reduction of semiquinone intermediates by a mechanism not elucidated.

  20. Total synthesis of (+)-geldanamycin and (-)-o-quinogeldanamycin: asymmetric glycolate aldol reactions and biological evaluation.

    Science.gov (United States)

    Andrus, Merritt B; Meredith, Erik L; Hicken, Erik J; Simmons, Bryon L; Glancey, Russell R; Ma, Wei

    2003-10-17

    The total synthesis of (+)-geldanamycin (GA), following a linear route, has been completed using a demethylative quinone-forming reaction as the last step. Key steps include the use of two new asymmetric boron glycolate aldol reactions. To set the anti-C11,12 hydroxymethoxy functionality, (S,S)-5,6-bis-4-methoxyphenyldioxanone 8 was used. Methylglycolate derived from norephedrine 5 set the C6,7 methoxyurethane stereochemistry. The quinone formation step using nitric acid gave the non-natural o-quino-GA product 55 10:1 over geldanamycin. Other known oxidants gave an unusual azaquinone product 49. o-Quino-GA 55 binds Hsp90 with good affinity but is less cytotoxic compared to GA.

  1. AcEST: BP913213 [AcEST

    Lifescience Database Archive (English)

    Full Text Available YMU001_000027_G05 514 Adiantum capillus-veneris mRNA. clone: YMU001_000027_G05. BP913213 - Show BP913213...is mRNA. clone: YMU001_000027_G05. Accession BP913213 Tissue type prothallium Developmental stage - Contig I.... 25:3389-3402. Query= BP913213|Adiantum capillus-veneris mRNA, clone: YMU001_000027_G05. (514 letters) Data...0 5e-09 sp|O07948|NUOF_RHOCA NADH-quinone oxidoreductase subunit F OS=Rh... 60 5e-09 sp|P29913... OS=My... 34 0.35 sp|P65568|NUOF_MYCBO NADH-quinone oxidoreductase subunit F OS=My... 34 0.35 sp|P56913

  2. Aquifex aeolicus membrane hydrogenase for hydrogen biooxidation: Role of lipids and physiological partners in enzyme stability and activity

    Energy Technology Data Exchange (ETDEWEB)

    Infossi, Pascale; Lojou, Elisabeth; Giudici-Orticoni, Marie-Therese [Unite de Bioenergetique et Ingenierie des Proteines, UPR 9036, Institut de Microbiologie de la Mediterranee - CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20 (France); Chauvin, Jean-Paul [Institut de Biologie du developpement de Marseille Luminy, UMR 6216, Parc Scientifique de Luminy, 163 Avenue de Luminy, BP 907, 13009 Marseille (France); Herbette, Gaetan [Spectropole FI 1739, Aix-Marseille Universite case 511, Faculte de St Jerome Avenue Escadrille Normandie Niemen, 13397 Marseille Cedex 20 (France); Brugna, Myriam [Unite de Bioenergetique et Ingenierie des Proteines, UPR 9036, Institut de Microbiologie de la Mediterranee - CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20 (France); Universite de Provence, 3 Place Victor Hugo, 13331 Marseille Cedex 03 (France)

    2010-10-15

    Hydrogenase I from the hyperthermophilic bacterium Aquifex aeolicus is a good candidate for biotechnological devices thanks to its ability to oxidize hydrogen at high temperature, even in the presence of oxygen and CO. In order to enhance the enzyme stability and the catalytic efficiency, we investigated the hydrogen oxidation process with hydrogenase I embedded in a physiological-like environment. Hydrogenase I partners in the metabolic chain, namely membrane quinone and cytochrome b, were purified and fully characterized. The complex hydrogenase I-cytochrome b was inserted into liposomes. Surface Plasmon Resonance revealed that quinone took part in the stabilization of the complex. By use of molecular modelization and electrochemistry analysis, enzyme stability has been demonstrated to be stronger and enzymatic efficiency to be five times higher when hydrogenase is embedded into the liposomes. This result raises the possibility of using hydrogenases as biocatalysts in fuel cells. (author)

  3. Mechanism of Anesthetic Toxicity: Metabolism, Reactive Oxygen Species, Oxidative Stress, and Electron Transfer

    OpenAIRE

    2011-01-01

    There is much literature on the toxic effects of anesthetics. This paper deals with both the volatiles and locals. Adverse effects appear to be multifaceted, with the focus on radicals, oxidative stress (OS), and electron transfer (ET). ET functionalities involved are quinone, iminoquinone, conjugated iminium, and nitrone. The non-ET routes involving radicals and OS apparently pertain to haloalkanes and ethers. Beneficial effects of antioxidants, evidently countering OS, are reported. Knowled...

  4. Modification of Microelectrode Arrays: New Microelectrochemical Devices for Sensor Applications.

    Science.gov (United States)

    1986-08-22

    oxides. W03 is known to be such a redox active material and has been widely studied in connection with electrochromic display devices (Dautremont... devices . Quinone- Viologen Connected Microelectrodes: Use of an Electroactive Molecular Material With An Intrinsic pH Dependence. W03 is an example of an...REPORT & PERIOD COVERED Modification of Microelectrode Arrays: New Interim Technical Report Microelectrochemical Devices for Sensor Applications 6

  5. Synthesis and spectroscopic characterization of high-spin mononuclear iron(II) p-semiquinonate complexes.

    Science.gov (United States)

    Baum, Amanda E; Park, Heaweon; Lindeman, Sergey V; Fiedler, Adam T

    2014-12-01

    Two mononuclear iron(II) p-semiquinonate (pSQ) complexes have been generated via one-electron reduction of precursor complexes containing a substituted 1,4-naphthoquinone ligand. Detailed spectroscopic and computational analysis confirmed the presence of a coordinated pSQ radical ferromagnetically coupled to the high-spin Fe(II) center. The complexes are intended to model electronic interactions between (semi)quinone and iron cofactors in biology.

  6. Synthesis and Spectroscopic Characterization of High-Spin Mononuclear Iron(II) p-Semiquinonate Complexes

    OpenAIRE

    Baum, Amanda E.; Park, Heaweon; Lindeman, Sergey V.; Fiedler, Adam T.

    2014-01-01

    Two mononuclear iron(II) p-semiquinonate (pSQ) complexes have been generated via one-electron reduction of precursor complexes containing a substituted 1,4-naphthoquinone ligand. Detailed spectroscopic and computational analysis confirmed the presence of a coordinated pSQ radical ferromagnetically coupled to the high-spin FeII center. The complexes are intended to model electronic interactions between (semi)quinone and iron cofactors in biology.

  7. Development of a laccase biosensor for determination of Phenolic micropollutants in surface waters

    OpenAIRE

    Souza Gil, Eric de; Rezende, Stefani Garcia; Júnior, Eli José Miranda Ribeiro; Barcelos, Hernane Toledo; Scalize,Paulo Sérgio; Santiago, Mariangela Fontes; Quintino, Michelle Pereira; Somerset, Vernon Sydwill

    2014-01-01

    Laccase is a poliphenoloxidase enzyme that catalyzes the oxidation of phenolic compounds in the corresponding quinones. The current obtained in this redox process can be used for quantitative analysis. In this work, a carbon paste biosensor modified gluteraldehyde functionalized silica and an enzymatic extract of the Pycnoporus sanguineus fungi as a lacase source is proposed for phenol determination. The effect of carbon paste and electrolyte composition, pH from 3.0 to 8.0, start potentia...

  8. Polyaniline: Synthesis, Chemistry and Processing

    Science.gov (United States)

    1992-06-19

    1990 to June 3, 1991 (289). These figures are due in large part to the very considerable industrial interest in the polyanilines as evidenced by, for...e.g., E4i shieldina. These materials are now ccmmerciallv available in large quantitifs. 2. THE CONCEPT OF DOPING Until the discovery of the novel...protonation of the imine nitrogen atoms in emeraldine base by, e.g. aqueous HCI, results in the formation of a delocalized polysemi -quinone radical

  9. Dicty_cDB: Contig-U10239-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available lkic**iiefgnkd**ile**aqkkp*tmdlqdhy*eeqgsymilekiihmmtmin milks**ekkiihiqdl**e*kkcikvyp**nkh*iiydpv**n*ke*i*l...is NAD(P)H-quin... 132 3e-50 (Q6MIR5) RecName: Full=NADH-quinone oxidoreductase subunit C/D; ... 144 6e-50 F...5569 Start point 30294 End point 32015 Strand (PLUS/MINUS) PLUS Number of clones 8 Number of EST 10 Link to ...MD VGALTPFLWAFEEREKLMEFYERVSGARMHAAYIRPGGVAFDLPMNISEDIYKFVIQYRK RLEEIEDMLINNRIWKQRLVDIGIVSAEEALNYGFTGPLLRGAGIVYDIR...KNYPYDDYDK YDFKIIIGEENNSYTRFIIRMKEMYQSLSIIEQALNNLRPGLIKLEGVNITAPDRAFVKK DMESCINHFKFFFRRIYNTSK*klydcrst

  10. Etude des interactions des protéines dans la chaîne respiratoire par spectroscopie IR et par électrochimie

    OpenAIRE

    Neehaul, Yashvin

    2012-01-01

    The field of molecular bioenergetics deals with the energy transduction in biological cells. In this project, respiration and more specifically proton and sodium pumping enzymes and their coupling to electron transfer have been in focus. First we have been interested in the Na+-pumping NADH:quinone reductase from Vibrio cholerae which is the entry site of electrons in the respiratory chain of several pathogens. The role of specific flavin cofactors and amino acids involved in Na+ transfer has...

  11. A Selective Colorimetric Anion Sensor Based on Di(hydroxymethyl) Di-(2-pyrrolyl)methane -TCBQ System

    Institute of Scientific and Technical Information of China (English)

    Yong GUO; Shi Jun SHAO; Jian XU; Yan Pin SHI; Sheng Xiang JIANG

    2004-01-01

    A new class of non-covalent charge-transfer complex for anion sensing, consisting of di(hydroxymethyl) di-(2-pyrrolyl) methane and chloranil (TCBQ) is characterized. The new colorimetric anion sensors can generate visual color change against PO43- and HPO42- anions in EtOH/H2O (1:1 v/v) mixture solution. The dipyrromethane-quinone aggregations may be used for higher selective detection of PO43- than other inorganic anions in water solution.

  12. UV Irradiation Chlorine Dioxide Photocatalytic Oxidation of Simulated Fuchsine Wastewater by UV-Vis and Online FTIR Spectrophotometric Method

    OpenAIRE

    Jie Liu; Chunlei Huai; Na Li; Xiaomei Wang; Laishun Shi

    2012-01-01

    The photocatalyst TiO2/SiO2 was prepared and used for chlorine dioxide photocatalytic oxidation of simulated fuchsine wastewater under UV irradiation. The removal efficiency of fuchsine treated by photocatalytic oxidation process is higher than that of chemical oxidation process. By using UV-Vis and online FTIR analysis technique, the intermediates during the degradation process were obtained. The benzene ring in fuchsine was degraded into quinone and carboxylic acid and finally changed into ...

  13. Production of hydrogen by electron transfer catalysis using conventional and photochemical means

    Science.gov (United States)

    Rillema, D. P.

    1981-01-01

    Alternate methods of generating hydrogen from the sulfuric acid thermal or electrochemical cycles are presented. A number of processes requiring chemical, electrochemical or photochemical methods are also presented. These include the design of potential photoelectrodes and photocatalytic membranes using Ru impregnated nafion tubing, and the design of experiments to study the catalyzed electrolytic formation of hydrogen and sulfuric acid from sulfur dioxide and water using quinones as catalysts. Experiments are carried out to determine the value of these approaches to energy conversion.

  14. Protective effect of ghrelin against paraquatinduced acute lung injury in mice

    Institute of Scientific and Technical Information of China (English)

    刘瑶

    2014-01-01

    Objective To measure the levels of ghrelin-induced expression or activation of nuclear factor erythroid 2-re-lated factor 2(Nrf2),heme oxygenase-1(HO-1),and NAD(P)H:quinone oxidoreductase 1(NQO1)in the PQ-injured lungs of mice and to evaluate the protective effect of ghrelin against paraquat(PQ)-induced acute lung injury in mice.Methods According to the random number table method,50 ICR mice of clean grade were

  15. Synthesis and Charge Transport Properties of Polymers Derived from Oxidation of 1-H-1’(6-pyrrol-1-yl)-hexyl-4,4’-bipyridinium Bis-hexafluorophosphate and Demonstration of a pH Sensitive Microelectrochemical Transistor Derived from the Redox Properties of a Conventional Redox Center.

    Science.gov (United States)

    1988-08-15

    platinized poly(3- methylthiophene), 7b a viologen /quinone polymer, 9 ferrocyanide-loaded protonated poly(4-vinylpyridine),10 and electroactive metal...number) FiELD GROUP SUB-GROUP Microelectrode array, redox polymer, polypyrrole, viologen 19. ABSTRACT (Continue on reverse if necessary and identify by...electrochemical properties of redox polymers, having a poly- pyrrole backbone and viologen subunits, derived from oxidative electropolymerization of l

  16. Synthesis and Charge Transport Properties of Polymers Derived from Oxidation of 1-H-1’(6-pyrrol-1-yl)-hexyl-4,4’-bipyridinium

    Science.gov (United States)

    1988-08-15

    platinized poly(3- methylthiophene),7b a viologen /quinone polymer, 9 ferrocyanide-loaded protonated poly(4-vinylpyridine),l 0 and electroactive metal oxides...article describes the synthesis and electrochemical properties of redox polymers, having a poly- pyrrole backbone and viologen subunits, derived from...study aspects of the charge transport behavior of the viologen redox system. Poly(P-V-Me2 ) and poly(P-V-H2+ ) have been used to investigate the

  17. Oceanospirillum nioense sp. nov., a marine bacterium isolated from sediment sample of Palk bay, India

    Digital Repository Service at National Institute of Oceanography (India)

    Krishna, K.K.; Bhumika, V.; Thomas, M.; AnilKumar, P.; Srinivas, T.N.R.

    (18:1). Strain NIO-S6 sup(T) contains Q-8 as the major respiratory quinone. The DNA G+C content of the strain NIO-S6 sup(T) was determined to be 49.5 plus or minus 0.6 mol percent. Phylogenetic analysis based on 16S rRNA gene sequence of strain NIO-S6...

  18. Molecular aspects of allergic contact dermatitis to plants. Recent progress in phytodermatochemistry.

    Science.gov (United States)

    Benezra, C; Ducombs, G

    1987-01-01

    A classification of plants based on the chemical structures of their skin sensitizers is presented. A whole range of chemical structures of contact sensitizers exists in plants containing sesquiterpene lactones (Compositae, Frullania, Lauraceae etc.), tulipalin (Tulipa, Alstroemeria etc.), quinones (Primula and tropical woods), long chain phenols (Anacardiaceae, Ginkgoaceae) and miscellaneous structures such as aldehydes, ketones, terpene hydrocarbons etc. Knowledge of allergens in various plants allows prediction of cross-reactivity.

  19. Dynamical theory of primary processes of charge separation in the photosynthetic reaction center.

    Science.gov (United States)

    Lakhno, Victor D

    2005-05-01

    A dynamical theory has been developed for primary separation of charges in the course of photosynthesis. The theory deals with both hopping and superexchange transfer mechanisms. Dynamics of electron transfer from dimeric bacteriochlorophyll to quinone has been calculated. The results obtained agree with experimental data and provide a unified explanation of both the hierarchy of the transfer time in the photosynthetic reaction center and the phenomenon of coherent oscillations accompanying the transfer process.

  20. Redox-promoted associative assembly of metal–organic materials† †Electronic supplementary information (ESI) available: Experimental procedures, compound characterization data, and X-ray crystallographic data for compounds 3–7 and 9–11. CCDC 1405641–1405645, 1429643, 1405647 and 1405648. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5sc02214b Click here for additional data file. Click here for additional data file.

    Science.gov (United States)

    Glavinović, Martin; Qi, Feng; Katsenis, Athanassios D.

    2016-01-01

    We develop an associative synthesis of metal–organic materials that combines solid-state metal oxidation and coordination-driven self-assembly into a one-step, waste-free transformation. The methodology hinges on the unique reactivity of ortho-quinones, which we introduce as versatile oxidants for mechanochemical synthesis. Our strategy opens a previously unexplored route to paramagnetic metal–organic materials from elementary metals. PMID:28791114