Respiratory quinones in Archaea: phylogenetic distribution and application as biomarkers in the marine environment.

Science.gov (United States)

Elling, Felix J; Becker, Kevin W; Könneke, Martin; Schröder, Jan M; Kellermann, Matthias Y; Thomm, Michael; Hinrichs, Kai-Uwe

2016-02-01

The distribution of respiratory quinone electron carriers among cultivated organisms provides clues on both the taxonomy of their producers and the redox processes these are mediating. Our study of the quinone inventories of 25 archaeal species belonging to the phyla Eury-, Cren- and Thaumarchaeota facilitates their use as chemotaxonomic markers for ecologically important archaeal clades. Saturated and monounsaturated menaquinones with six isoprenoid units forming the alkyl chain may serve as chemotaxonomic markers for Thaumarchaeota. Other diagnostic biomarkers are thiophene-bearing quinones for Sulfolobales and methanophenazines as functional quinone analogues of the Methanosarcinales. The ubiquity of saturated menaquinones in the Archaea in comparison to Bacteria suggests that these compounds may represent an ancestral and diagnostic feature of the Archaea. Overlap between quinone compositions of distinct thermophilic and halophilic archaea and bacteria may indicate lateral gene transfer. The biomarker potential of thaumarchaeal quinones was exemplarily demonstrated on a water column profile of the Black Sea. Both, thaumarchaeal quinones and membrane lipids showed similar distributions with maxima at the chemocline. Quinone distributions indicate that Thaumarchaeota dominate respiratory activity at a narrow interval in the chemocline, while they contribute only 9% to the microbial biomass at this depth, as determined by membrane lipid analysis. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.

Production of quinones by in vitro cultures of Dionaea and Streptocarpus species

OpenAIRE

Nestor, Cora

2006-01-01

Quinones are a class of oxygen-containing secondary metabolites found chiefly in higher plants, fungi, bacteria and restricted in the animal kingdom to arthropods and echinoderms (Thompson 1971). In the plant, quinones, especially naphthoquinones, have been shown to function in allelopathy (juglone; Binder et al 1989), plant-insect interactions and plant-plant interactions (plumbagin; Kubo et al 1986, 1998, Spencer et al 1986, Ganapaty et al 2004). These quinones also have significant in vitr...

Quinones from Heliotropium ovalifolium.

Science.gov (United States)

Guntern, A; Ioset, J R; Queiroz, E F; Foggin, C M; Hostettmann, K

2001-10-01

Two new benzoquinones, heliotropinones A and B, have been isolated from the aerial parts of Heliotropium ovalifolium. Their structures were elucidated by spectrometric methods including high resolution electrospray ionization (ESI-HR), EI mass spectrometry, 1H, 13C and 2D NMR experiments. The two quinones demonstrated antifungal activities against Cladosporium cucumerinum and Candida albicans as well as antibacterial activity against Bacillus subtilis.

Catalytic asymmetric diels-alder reaction of quinone imine ketals: a site-divergent approach.

Science.gov (United States)

Hashimoto, Takuya; Nakatsu, Hiroki; Maruoka, Keiji

2015-04-07

The catalytic asymmetric Diels-Alder reaction of quinone imine ketals with diene carbamates catalyzed by axially chiral dicarboxylic acids is reported herein. A variety of primary and secondary alkyl-substituted quinone derivatives which have not been applied in previous asymmetric quinone Diels-Alder reactions could be employed using this method. More importantly, we succeeded in developing a strategy to divert the reaction site in unsymmetrical 3-alkyl quinone imine ketals from the inherently favored unsubstituted C=C bond to the disfavored alkyl-substituted C=C bond. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chemical modification of b-lactoglobulin by quinones

Directory of Open Access Journals (Sweden)

DUSAN SLADIC

2003-05-01

Full Text Available The avarone/avarol quinone/hydroquinone couple, as well as their derivatives show considerable antitumor activity. In this work, covalent modifications of b-lactoglobulin, isolated from cow milk, by avarone, its model compound 2-tert-butyl-1,4-benzoquinone, and several of their alkylthio derivatives were studied. The techniques applied for assaying the modifications were: UV/VIS spectrophotometry, SDS PAGE and isoelectrofocusing. The results of the SDS PAGE suggest that polymerisation of the protein occurs. The shift of the pI of the protein upon modification toward lower values indicates that lysine amino groups are the principal site of the reaction of b-lactoglobulin with the quinones.

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

High-capacity aqueous zinc batteries using sustainable quinone electrodes

Science.gov (United States)

Zhao, Qing; Huang, Weiwei; Luo, Zhiqiang; Liu, Luojia; Lu, Yong; Li, Yixin; Li, Lin; Hu, Jinyan; Ma, Hua; Chen, Jun

2018-01-01

Quinones, which are ubiquitous in nature, can act as sustainable and green electrode materials but face dissolution in organic electrolytes, resulting in fast fading of capacity and short cycle life. We report that quinone electrodes, especially calix[4]quinone (C4Q) in rechargeable metal zinc batteries coupled with a cation-selective membrane using an aqueous electrolyte, exhibit a high capacity of 335 mA h g−1 with an energy efficiency of 93% at 20 mA g−1 and a long life of 1000 cycles with a capacity retention of 87% at 500 mA g−1. The pouch zinc batteries with a respective depth of discharge of 89% (C4Q) and 49% (zinc anode) can deliver an energy density of 220 Wh kg−1 by mass of both a C4Q cathode and a theoretical Zn anode. We also develop an electrostatic potential computing method to demonstrate that carbonyl groups are active centers of electrochemistry. Moreover, the structural evolution and dissolution behavior of active materials during discharge and charge processes are investigated by operando spectral techniques such as IR, Raman, and ultraviolet-visible spectroscopies. Our results show that batteries using quinone cathodes and metal anodes in aqueous electrolyte are reliable approaches for mass energy storage. PMID:29511734

Interaction of quinones with three pyrimidine bases: A laser flash photolysis study

Energy Technology Data Exchange (ETDEWEB)

Bose, Adity [Chemical Sciences Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Basu, Samita, E-mail: samita.basu@saha.ac.i [Chemical Sciences Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India)

2009-11-15

The interaction between three different pyrimidine bases, uracil (U), cytosine (C) and thymine (T) and two quinones, 2-methyl-1,4-naphthoquinone or menadione (MQ) and 9,10-anthraquinone (AQ) have been studied using laser flash photolysis technique in organic homogeneous medium. The three pyrimidines have revealed a difference in their extent of reactivity towards the quinones, which has been attributed to their structural difference. Our works have revealed that the difference in structural dimension of the quinones is also responsible for affecting the reactivity of these pyrimidines in homogeneous medium.

Interaction of quinones with three pyrimidine bases: A laser flash photolysis study

International Nuclear Information System (INIS)

Bose, Adity; Basu, Samita

2009-01-01

The interaction between three different pyrimidine bases, uracil (U), cytosine (C) and thymine (T) and two quinones, 2-methyl-1,4-naphthoquinone or menadione (MQ) and 9,10-anthraquinone (AQ) have been studied using laser flash photolysis technique in organic homogeneous medium. The three pyrimidines have revealed a difference in their extent of reactivity towards the quinones, which has been attributed to their structural difference. Our works have revealed that the difference in structural dimension of the quinones is also responsible for affecting the reactivity of these pyrimidines in homogeneous medium.

Antitrypanosomal isoflavan quinones from Abrus precatorius

CSIR Research Space (South Africa)

Hata, Y

2014-03-01

Full Text Available Fitoterapia Vol. 93, pp 81-87 Antitrypanosomal isoflavan quinones from Abrus precatorius Yoshie Hata a,d, Samad Nejad Ebrahimi a,e, Maria De Mieri a, Stefanie Zimmermann a, Tsholofelo Mokoka c, Dashnie Naidoo c, Gerda Fouche c, Vinesh Maharaj c...

Quinones: reactions with hemoglobin, effects within erythrocytes and potential for antimalarial development

International Nuclear Information System (INIS)

Denny, B.J.

1986-01-01

The focus of this research was to characterize the interactions of some simple quinone like compounds with purified hemoglobin and to study the effects of these compounds within erythrocytes. It is proposed that these sorts of agents can have an antimalarial effect. The simplest compounds chosen for study were benzoquinone, methylquinone (toluquinone) and hydroquinone. When 14 C-quinone was reacted with purified hemoglobin (Hb) there was rapid binding of the first two moles of substrate per Hb molecule. An unusual property of the modified Hb's is that in the presence of a redox sensitive agent such as cytochrome c they are capable of generating superoxide anions. Within erythrocytes, quinone and toluquinone which differ only by a single methyl group have completely different effects. Toluquinone causes the cells to hemolyse and the effect was enhanced when the erythrocyte superoxide dismutase was inhibited; the effect was diminished when scavengers of activated oxygen such as histidine, mannitol and vital E were present. Benzoquinone on the other hand did not cause the cells to hemolyse and instead appeared to protect the cells from certain hemolytic stresses. Growth of malaria parasites in erythrocytes has been shown to be inhibited by activated forms of oxygen, also some quinone like agents in the past have been shown to inhibit the parasite's metabolism. An initial experiment with erythrocytes infected with malaria parasites showed that quinone and toluquinone could both inhibit the growth rate of parasites

Bioinspired aerobic oxidation of secondary amines and nitrogen heterocycles with a bifunctional quinone catalyst.

Science.gov (United States)

Wendlandt, Alison E; Stahl, Shannon S

2014-01-08

Copper amine oxidases are a family of enzymes with quinone cofactors that oxidize primary amines to aldehydes. The native mechanism proceeds via an iminoquinone intermediate that promotes high selectivity for reactions with primary amines, thereby constraining the scope of potential biomimetic synthetic applications. Here we report a novel bioinspired quinone catalyst system consisting of 1,10-phenanthroline-5,6-dione/ZnI2 that bypasses these constraints via an abiological pathway involving a hemiaminal intermediate. Efficient aerobic dehydrogenation of non-native secondary amine substrates, including pharmaceutically relevant nitrogen heterocycles, is demonstrated. The ZnI2 cocatalyst activates the quinone toward amine oxidation and provides a source of iodide, which plays an important redox-mediator role to promote aerobic catalytic turnover. These findings provide a valuable foundation for broader development of aerobic oxidation reactions employing quinone-based catalysts.

Enhanced bio-decolorization of azo dyes by co-immobilized quinone-reducing consortium and anthraquinone

DEFF Research Database (Denmark)

Su, YY; Zhang, Yifeng; Wang, J

2009-01-01

In the present study, the accelerating effect of co-immobilized anthraquinone and quinone-reducing consortium was investigated in the bio-decolorization process. The anthraquinone and quinone-reducing consortium were co-immobilized by entrapment in calcium alginate. The co-immobilized beads...

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.

Preliminary X-ray crystallographic analysis of sulfide:quinone oxidoreductase from Acidithiobacillus ferrooxidans

International Nuclear Information System (INIS)

Zhang, Yanfei; Cherney, Maia M.; Solomonson, Matthew; Liu, Jianshe; James, Michael N. G.; Weiner, Joel H.

2009-01-01

The sulfide:quinone oxidoreductase from A. ferrooxidans ATCC 23270 was overexpressed in E. coli and purified. Crystallization and preliminarily X-ray crystallographic analysis were performed for the recombinant enzyme. The gene product of open reading frame AFE-1293 from Acidithiobacillus ferrooxidans ATCC 23270 is annotated as encoding a sulfide:quinone oxidoreductase, an enzyme that catalyses electron transfer from sulfide to quinone. Following overexpression in Escherichia coli, the enzyme was purified and crystallized using the hanging-drop vapour-diffusion method. The native crystals belonged to the tetragonal space group P4 2 2 1 2, with unit-cell parameters a = b = 131.7, c = 208.8 Å, and diffracted to 2.3 Å resolution. Preliminary crystallographic analysis indicated the presence of a dimer in the asymmetric unit, with an extreme value of the Matthews coefficient (V M ) of 4.53 Å 3 Da −1 and a solvent content of 72.9%

Redox potential tuning through differential quinone binding in the photosynthetic reaction center of Rhodobacter sphaeroides.

Science.gov (United States)

Vermaas, Josh V; Taguchi, Alexander T; Dikanov, Sergei A; Wraight, Colin A; Tajkhorshid, Emad

2015-03-31

Ubiquinone forms an integral part of the electron transport chain in cellular respiration and photosynthesis across a vast number of organisms. Prior experimental results have shown that the photosynthetic reaction center (RC) from Rhodobacter sphaeroides is only fully functional with a limited set of methoxy-bearing quinones, suggesting that specific interactions with this substituent are required to drive electron transport and the formation of quinol. The nature of these interactions has yet to be determined. Through parameterization of a CHARMM-compatible quinone force field and subsequent molecular dynamics simulations of the quinone-bound RC, we have investigated and characterized the interactions of the protein with the quinones in the Q(A) and Q(B) sites using both equilibrium simulation and thermodynamic integration. In particular, we identify a specific interaction between the 2-methoxy group of ubiquinone in the Q(B) site and the amide nitrogen of GlyL225 that we implicate in locking the orientation of the 2-methoxy group, thereby tuning the redox potential difference between the quinones occupying the Q(A) and Q(B) sites. Disruption of this interaction leads to weaker binding in a ubiquinone analogue that lacks a 2-methoxy group, a finding supported by reverse electron transfer electron paramagnetic resonance experiments of the Q(A)⁻Q(B)⁻ biradical and competitive binding assays.

Quinone-Enriched Gold Nanoparticles in Bioelectrochemistry and Charge Storage

DEFF Research Database (Denmark)

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

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...

Identification of Carotenoids and Isoprenoid Quinones from Asaia lannensis and Asaia bogorensis

Directory of Open Access Journals (Sweden)

Hubert Antolak

2017-09-01

Full Text Available The aim of the study was to identify and quantitatively assess of carotenoids and isoprenoid quinones biosynthesized by six different strains of acetic acid bacteria, belonging to genus Asaia, that are common beverage-spoiling bacteria in Europe. Bacterial cultures were conducted in a laboratory liquid culture minimal medium with 2% sucrose. Carotenoids and isoprenoid quinones were investigated using UHPLC-DAD-ESI-MS analysis. In general, tested strains of Asaia spp. were able to produce 10 carotenoids and 3 isoprenoid quinones: menaquinone-7, menaquinone-8, and ubiquinone-10. The main identified carotenoids in Asaia lannensis strains were phytofluene, neurosporene, α-carotene, while for Asaia bogorensis, neurosporene, canthaxanthin, and zeaxanthin were noted. What is more, tested Asaia spp. were able to produce myxoxanthophyll, which has so far been identified primarily in cyanobacteria. The results show that A. lannensis are characterized by statistically higher concentrations of produced carotenoids, as well as a greater variety of these compounds. We have noted that carotenoids were not only accumulated by bacterial cells, but also some strains of A. lannensis produced extracellular carotenoids.

Computational design of molecules for an all-quinone redox flow battery† †Electronic supplementary information (ESI) available: The list of computationally predicted candidate quinone molecules with interesting redox properties. See DOI: 10.1039/c4sc03030c Click here for additional data file.

Science.gov (United States)

Er, Süleyman; Suh, Changwon; Marshak, Michael P.

2015-01-01

Inspired by the electron transfer properties of quinones in biological systems, we recently showed that quinones are also very promising electroactive materials for stationary energy storage applications. Due to the practically infinite chemical space of organic molecules, the discovery of additional quinones or other redox-active organic molecules for energy storage applications is an open field of inquiry. Here, we introduce a high-throughput computational screening approach that we applied to an accelerated study of a total of 1710 quinone (Q) and hydroquinone (QH2) (i.e., two-electron two-proton) redox couples. We identified the promising candidates for both the negative and positive sides of organic-based aqueous flow batteries, thus enabling an all-quinone battery. To further aid the development of additional interesting electroactive small molecules we also provide emerging quantitative structure-property relationships. PMID:29560173

Post-translational modifications near the quinone binding site of mammalian complex I.

Science.gov (United States)

Carroll, Joe; Ding, Shujing; Fearnley, Ian M; Walker, John E

2013-08-23

Complex I (NADH:ubiquinone oxidoreductase) in mammalian mitochondria is an L-shaped assembly of 44 protein subunits with one arm buried in the inner membrane of the mitochondrion and the orthogonal arm protruding about 100 Å into the matrix. The protruding arm contains the binding sites for NADH, the primary acceptor of electrons flavin mononucleotide (FMN), and a chain of seven iron-sulfur clusters that carries the electrons one at a time from FMN to a coenzyme Q molecule bound in the vicinity of the junction between the two arms. In the structure of the closely related bacterial enzyme from Thermus thermophilus, the quinone is thought to bind in a tunnel that spans the interface between the two arms, with the quinone head group close to the terminal iron-sulfur cluster, N2. The tail of the bound quinone is thought to extend from the tunnel into the lipid bilayer. In the mammalian enzyme, it is likely that this tunnel involves three of the subunits of the complex, ND1, PSST, and the 49-kDa subunit. An arginine residue in the 49-kDa subunit is symmetrically dimethylated on the ω-N(G) and ω-N(G') nitrogen atoms of the guanidino group and is likely to be close to cluster N2 and to influence its properties. Another arginine residue in the PSST subunit is hydroxylated and probably lies near to the quinone. Both modifications are conserved in mammalian enzymes, and the former is additionally conserved in Pichia pastoris and Paracoccus denitrificans, suggesting that they are functionally significant.

Toxicity to sea urchin egg development of the quinone fraction obtained from Auxemma oncocalyx

Directory of Open Access Journals (Sweden)

Costa-Lotufo L.V.

2002-01-01

Full Text Available Auxemma oncocalyx Taub. belongs to the Boraginaceae family and is native to the Brazilian northeast where it is known as "pau-branco". We investigated the ability of the water soluble fraction isolated from the heartwood of A. oncocalyx to inhibit sea urchin egg development. This fraction contains about 80% oncocalyxone A (quinone fraction, a compound known to possess strong cytotoxic and antitumor activities. In fact, the quinone fraction inhibited cleavage in a dose-dependent manner [IC50 of 18.4 (12.4-27.2 µg/ml, N = 6], and destroyed the embryos in the blastula stage [IC50 of 16.2 (13.7-19.2 µg/ml, N = 6]. We suggest that this activity is due to the presence of oncocalyxone A. In fact, these quinones present in A. oncocalyx extract have strong toxicity related to their antimitotic activity.

Photo-bleaching of polymer discoloration caused by quinone methides

Czech Academy of Sciences Publication Activity Database

Pospíšil, Jan; Nešpůrek, Stanislav; Zweifel, H.; Kuthan, J.

2002-01-01

Roč. 78, č. 2 (2002), s. 251-255 ISSN 0141-3910 R&D Projects: GA AV ČR IAA1050901 Institutional research plan: CEZ:AV0Z4050913 Keywords : quinone methide * photo- bleaching * polymer discoloration Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.145, year: 2002

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

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.

Studies on the mechanism of quinone action on hormonal regulation of metabolism in the rat liver

International Nuclear Information System (INIS)

Cheng, E.Y.

1989-01-01

The mechanism of quinone actions in liver cell metabolism had been investigated using menadione as a model compound. Previous reports suggested that quinones and free radicals could produce perturbations in cellular calcium homeostasis. Since calcium plays an important role in the regulation of cellular metabolic processes, then regulation of cytosolic calcium concentrations, and thus of cellular metabolism, by calcium-mobilizing hormones such as phenylephrine and vasopressin could possibly be modified by quinones such as menadione. Methods used to approach this hypothesis included the assay for activation of glycogen phosphorylase, an indirect index of calcium mobilization; the determination of calcium mobilization with 45 Ca efflux exchange and with fluorescent calcium indicator fura-2; and the measurement of phosphatidylinositides, an important link in the membrane-associated receptor-mediated signal transduction mechanism

The inhibition mechanisms of quinones and phenols present in wood for the vinyl polymerization

International Nuclear Information System (INIS)

Nobashi, Kenzo; Yokota, Tokuo

1977-01-01

The inhibitory effects and mechanisms of the quinones and phenols present in wood for the vinyl polymerization initiated with γ-rays and other initiation systems were investigated. The results obtained are summarized as follows; (1) Although phenolic compounds like isotaxiresinol inhibit the γ-ray initiated polymerization of methyl methacrylate (MMA) under the presence of air, they have no inhibitory effects in vacuo. On the other hand, o-benzoquinone and mansonones show strong inhibitory or retarding effects in vacuo. These facts indicate that oxygen may be important for the phenols to inhibit the vinyl polymerization. (2) It is shown qualitatively that there is a relationship between the strength of inhibitory action of quinones and their normal redox potentials. (3) PMMA produced under the presence of o-benzoquinone is found to include the fraction having extremely large chain length based on gel permeation chromatogram. (4) Based on the reaction products of orthoquinones and azobisisobutyronitrile, which was assumed as a model of polymer radicals, the inhibition reaction with polymer chain radical is concluded to take place upon the oxygen atoms of the quinones. (auth.)

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.

Comparative evaluation of the acceptor properties of quinone derivatized polypyridinic ligands

International Nuclear Information System (INIS)

Norambuena, Ester; Olea-Azar, Claudio; Delgadillo, Alvaro; Barrera, Mauricio; Loeb, Barbara

2009-01-01

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.

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. Copyright © 2015 Elsevier Ltd. All rights reserved.

UV-Vis spectrophotometry of quinone flow battery electrolyte for in situ monitoring and improved electrochemical modeling of potential and quinhydrone formation.

Science.gov (United States)

Tong, Liuchuan; Chen, Qing; Wong, Andrew A; Gómez-Bombarelli, Rafael; Aspuru-Guzik, Alán; Gordon, Roy G; Aziz, Michael J

2017-12-06

Quinone-based aqueous flow batteries provide a potential opportunity for large-scale, low-cost energy storage due to their composition from earth abundant elements, high aqueous solubility, reversible redox kinetics and their chemical tunability such as reduction potential. In an operating flow battery utilizing 9,10-anthraquinone-2,7-disulfonic acid, the aggregation of an oxidized quinone and a reduced hydroquinone to form a quinhydrone dimer causes significant variations from ideal solution behavior and of optical absorption from the Beer-Lambert law. We utilize in situ UV-Vis spectrophotometry to establish (a), quinone, hydroquinone and quinhydrone molar attenuation profiles and (b), an equilibrium constant for formation of the quinhydrone dimer (K QHQ ) ∼ 80 M -1 . We use the molar optical attenuation profiles to identify the total molecular concentration and state of charge at arbitrary mixtures of quinone and hydroquinone. We report density functional theory calculations to support the quinhydrone UV-Vis measurements and to provide insight into the dimerization conformations. We instrument a quinone-bromine flow battery with a Pd-H reference electrode in order to demonstrate how complexation in both the negative (quinone) and positive (bromine) electrolytes directly impacts measured half-cell and full-cell voltages. This work shows how accounting for electrolyte complexation improves the accuracy of electrochemical modeling of flow battery electrolytes.

Quinone-fused porphyrins as contrast agents for photoacoustic imaging

KAUST Repository

Banala, Srinivas

2017-06-27

Photoacoustic (PA) imaging is an emerging non-invasive diagnostic modality with many potential clinical applications in oncology, rheumatology and the cardiovascular field. For this purpose, there is a high demand for exogenous contrast agents with high absorption coefficients in the optical window for tissue imaging, i.e. the near infrared (NIR) range between 680 and 950 nm. We herein report the photoacoustic properties of quinone-fused porphyrins inserted with different transition metals as new highly promising candidates. These dyes exhibit intense NIR absorption, a lack of fluorescence emission, and PA sensitivity in concentrations below 3 nmol mL. In this context, the highest PA signal was obtained with a Zn(ii) inserted dye. Furthermore, this dye was stable in blood serum and free thiol solution and exhibited negligible cell toxicity. Additionally, the Zn(ii) probe could be detected with an up to 3.2 fold higher PA intensity compared to the clinically most commonly used PA agent, ICG. Thus, further exploration of the \\'quinone-fusing\\' approach to other chromophores may be an efficient way to generate highly potent PA agents that do not fluoresce and shift their absorption into the NIR range.

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.

All three quinone species play distinct roles in ensuring optimal growth under aerobic and fermentative conditions in E. coli K12

Science.gov (United States)

Nitzschke, Annika

2018-01-01

The electron transport chain of E. coli contains three different quinone species, ubiquinone (UQ), menaquinone (MK) and demethylmenaquinone (DMK). The content and ratio of the different quinone species vary depending on the external conditions. To study the function of the different quinone species in more detail, strains with deletions preventing UQ synthesis, as well as MK and/or DMK synthesis were cultured under aerobic and anaerobic conditions. The strains were characterized with respect to growth and product synthesis. As quinones are also involved in the control of ArcB/A activity, we analyzed the phosphorylation state of the response regulator as well as the expression of selected genes.The data show reduced aerobic growth coupled to lactate production in the mutants defective in ubiquinone synthesis. This confirms the current assumption that ubiquinone is the main quinone under aerobic growth conditions. In the UQ mutant strains the amount of MK and DMK is significantly elevated. The strain synthesizing only DMK is less affected in growth than the strain synthesizing MK as well as DMK. An inhibitory effect of MK on aerobic growth due to increased oxidative stress is postulated.Under fermentative growth conditions the mutant synthesizing only UQ is severely impaired in growth. Obviously, UQ is not able to replace MK and DMK during anaerobic growth. Mutations affecting quinone synthesis have an impact on ArcA phosphorylation only under anaerobic conditions. ArcA phosphorylation is reduced in strains synthesizing only MK or MK plus DMK. PMID:29614086

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.

Isoprenoid quinones resolve the stratification of microbial redox processes in a biogeochemical continuum from the photic zone to deep anoxic sediments of the Black Sea.

Science.gov (United States)

Becker, Kevin W; Elling, Felix J; Schröder, Jan M; Lipp, Julius S; Goldhammer, Tobias; Zabel, Matthias; Elvert, Marcus; Overmann, Jörg; Hinrichs, Kai-Uwe

2018-03-09

The stratified water column of the Black Sea serves as a model ecosystem for studying the interactions of microorganisms with major biogeochemical cycles. Here we provide detailed analysis of isoprenoid quinones to study microbial redox processes in the ocean. In a continuum from the photic zone through the chemocline into deep anoxic sediments of the southern Black Sea, diagnostic quinones and inorganic geochemical parameters indicate niche segregation between redox processes and corresponding shifts in microbial community composition. Quinones specific for oxygenic photosynthesis and aerobic respiration dominate oxic waters, while quinones associated with thaumarchaeal ammonia-oxidation and bacterial methanotrophy, respectively, dominate a narrow interval in suboxic waters. Quinone distributions indicate highest metabolic diversity within the anoxic zone, with anoxygenic photosynthesis being a major process in its photic layer. In the dark anoxic layer, quinone profiles indicate occurrence of bacterial sulfur and nitrogen cycling, archaeal methanogenesis, and archaeal methanotrophy. Multiple novel ubiquinone isomers, possibly originating from unidentified intra-aerobic anaerobes, occur in this zone. The respiration modes found in the anoxic zone continue into shallow subsurface sediments, but quinone abundances rapidly decrease within the upper 50 cm below sea floor, reflecting the transition to lower energy availability. In the deep subseafloor sediments, quinone distributions and geochemical profiles indicate archaeal methanogenesis/methanotrophy and potentially bacterial fermentative metabolisms. We observed that sedimentary quinone distributions track lithology, which supports prior hypotheses that deep biosphere community composition and metabolisms are determined by environmental conditions during sediment deposition. Importance Microorganisms play crucial roles in global biogeochemical cycles. Yet, we have only a fragmentary understanding of the diversity

Quenching of bacteriochlorophyll fluorescence in chlorosomes from Chloroflexus aurantiacus by exogenous quinones

DEFF Research Database (Denmark)

Tokita, S; Frigaard, N-U; Hirota, M

2000-01-01

The quenching of bacteriochlorophyll (BChl) c fluorescence in chlorosomes isolated from Chloroflexus aurantiacus was examined by the addition of various benzoquinones, naphthoquinones (NQ), and anthraquinones (AQ). Many quinones showed strong quenching in the micromolar or submicromolar range. Th...

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.

Effects of oxygen radical scavengers on the inactivation of SS phi X174 DNA by the semi-quinone free radical of the antitumor agent etoposide

NARCIS (Netherlands)

van Maanen, M.J.; Mans, D.R.A.; Lafleur, M.V.M.; Van Schaik, M A; de Vries, J; Vermeulen, N P; Retèl, J.; Lankelma, J

1990-01-01

We have studied the effects of oxygen radical scavengers on the inactivation of ss phi X174 DNA by the semi-quinone free radical of the antitumor agent etoposide (VP 16-213), which was generated from the ortho-quinone of etoposide at pH greater than or equal to 7.4. A semi-quinone free radical of

Menadione enhances oxyradical formation in earthworm extracts: vulnerability of earthworms to quinone toxicity

International Nuclear Information System (INIS)

Osman, A.M.; Besten, P.J. den; Noort, P.C.M. van

2003-01-01

NAD(P)H-cytochrome c reductase activities have been determined in the earthworms, L. rubellus and A. chlorotica, extracts. Menadione (0.35 mM, maximum concentration tested) was found to stimulate the rates of NADPH- and NADH-dependent cytochrome c reduction by three- and twofold, respectively. Superoxide dismutase (SOD) inhibited completely this menadione-mediated stimulation, suggesting that ·O 2 - is involved in the redox cycling of menadione. However, SOD had no effect on the basal activity (activity in the absence of quinone) in the case of NADH-dependent cytochrome c reduction, whereas it partially inhibited the basal activity of NADPH-cytochrome c reduction. This indicates direct electron transfer in the former case and the formation of superoxide anion in the latter. DT-diaphorase, measured as the dicumarol-inhibitable part of menadione reductase activity, was not detectable in the earthworms' extracts. In contrast, it was found that DT-diaphorase represents about 70% of the menadione reductase activities in the freshwater mussel, Dreissena polymorpha. The results of this work suggest that earthworms, compared with mussels, could be more vulnerable to oxidative stress from quinones due to lack, or very low level of DT-diaphorase, an enzyme considered to play a significant role in the detoxification of quinones. On the contrary, mussels have efficient DT-diaphorase, which catalyzes two-electron reduction of menadione directly to hydroquinone, thus circumventing the formation of semiquinone

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. PMID:23162467

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. Copyright © 2014 Elsevier Ltd. All rights reserved.

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.

Quinones are growth factors for the human gut microbiota.

Science.gov (United States)

Fenn, Kathrin; Strandwitz, Philip; Stewart, Eric J; Dimise, Eric; Rubin, Sarah; Gurubacharya, Shreya; Clardy, Jon; Lewis, Kim

2017-12-20

The human gut microbiome has been linked to numerous components of health and disease. However, approximately 25% of the bacterial species in the gut remain uncultured, which limits our ability to properly understand, and exploit, the human microbiome. Previously, we found that growing environmental bacteria in situ in a diffusion chamber enables growth of uncultured species, suggesting the existence of growth factors in the natural environment not found in traditional cultivation media. One source of growth factors proved to be neighboring bacteria, and by using co-culture, we isolated previously uncultured organisms from the marine environment and identified siderophores as a major class of bacterial growth factors. Here, we employ similar co-culture techniques to grow bacteria from the human gut microbiome and identify novel growth factors. By testing dependence of slow-growing colonies on faster-growing neighboring bacteria in a co-culture assay, eight taxonomically diverse pairs of bacteria were identified, in which an "induced" isolate formed a gradient of growth around a cultivatable "helper." This set included two novel species Faecalibacterium sp. KLE1255-belonging to the anti-inflammatory Faecalibacterium genus-and Sutterella sp. KLE1607. While multiple helper strains were identified, Escherichia coli was also capable of promoting growth of all induced isolates. Screening a knockout library of E. coli showed that a menaquinone biosynthesis pathway was required for growth induction of Faecalibacterium sp. KLE1255 and other induced isolates. Purified menaquinones induced growth of 7/8 of the isolated strains, quinone specificity profiles for individual bacteria were identified, and genome analysis suggests an incomplete menaquinone biosynthetic capability yet the presence of anaerobic terminal reductases in the induced strains, indicating an ability to respire anaerobically. Our data show that menaquinones are a major class of growth factors for bacteria

Menadione enhances oxyradical formation in earthworm extracts: vulnerability of earthworms to quinone toxicity

Energy Technology Data Exchange (ETDEWEB)

Osman, A.M.; Besten, P.J. den; Noort, P.C.M. van

2003-10-08

NAD(P)H-cytochrome c reductase activities have been determined in the earthworms, L. rubellus and A. chlorotica, extracts. Menadione (0.35 mM, maximum concentration tested) was found to stimulate the rates of NADPH- and NADH-dependent cytochrome c reduction by three- and twofold, respectively. Superoxide dismutase (SOD) inhibited completely this menadione-mediated stimulation, suggesting that {center_dot}O{sub 2}{sup -} is involved in the redox cycling of menadione. However, SOD had no effect on the basal activity (activity in the absence of quinone) in the case of NADH-dependent cytochrome c reduction, whereas it partially inhibited the basal activity of NADPH-cytochrome c reduction. This indicates direct electron transfer in the former case and the formation of superoxide anion in the latter. DT-diaphorase, measured as the dicumarol-inhibitable part of menadione reductase activity, was not detectable in the earthworms' extracts. In contrast, it was found that DT-diaphorase represents about 70% of the menadione reductase activities in the freshwater mussel, Dreissena polymorpha. The results of this work suggest that earthworms, compared with mussels, could be more vulnerable to oxidative stress from quinones due to lack, or very low level of DT-diaphorase, an enzyme considered to play a significant role in the detoxification of quinones. On the contrary, mussels have efficient DT-diaphorase, which catalyzes two-electron reduction of menadione directly to hydroquinone, thus circumventing the formation of semiquinone.

Quinone methides tethered to naphthalene diimides as selective G-quadruplex alkylating agents.

Science.gov (United States)

Di Antonio, Marco; Doria, Filippo; Richter, Sara N; Bertipaglia, Carolina; Mella, Mariella; Sissi, Claudia; Palumbo, Manlio; Freccero, Mauro

2009-09-16

We have developed novel G-quadruplex (G-4) ligand/alkylating hybrid structures, tethering the naphthalene diimide moiety to quaternary ammonium salts of Mannich bases, as quinone-methide precursors, activatable by mild thermal digestion (40 degrees C). The bis-substituted naphthalene diimides were efficiently synthesized, and their reactivity as activatable bis-alkylating agents was investigated in the presence of thiols and amines in aqueous buffered solutions. The electrophilic intermediate, quinone-methide, involved in the alkylation process was trapped, in the presence of ethyl vinyl ether, in a hetero Diels-Alder [4 + 2] cycloaddition reaction, yielding a substituted 2-ethoxychroman. The DNA recognition and alkylation properties of these new derivatives were investigated by gel electrophoresis, circular dichroism, and enzymatic assays. The alkylation process occurred preferentially on the G-4 structure in comparison to other DNA conformations. By dissecting reversible recognition and alkylation events, we found that the reversible process is a prerequisite to DNA alkylation, which in turn reinforces the G-quadruplex structural rearrangement.

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.

Enzyme-Initiated Quinone-Chitosan Conjugation Chemistry: Toward A General in Situ Strategy for High-Throughput Photoelectrochemical Enzymatic Bioanalysis.

Science.gov (United States)

Wang, Guang-Li; Yuan, Fang; Gu, Tiantian; Dong, Yuming; Wang, Qian; Zhao, Wei-Wei

2018-02-06

Herein we report a general and novel strategy for high-throughput photoelectrochemical (PEC) enzymatic bioanalysis on the basis of enzyme-initiated quinone-chitosan conjugation chemistry (QCCC). Specifically, the strategy was illustrated by using a model quinones-generating oxidase of tyrosinase (Tyr) to catalytically produce 1,2-bezoquinone or its derivative, which can easily and selectively be conjugated onto the surface of the chitosan deposited PbS/NiO/FTO photocathode via the QCCC. Upon illumination, the covalently attached quinones could act as electron acceptors of PbS quantum dots (QDs), improving the photocurrent generation and thus allowing the elegant probing of Tyr activity. Enzyme cascades, such as alkaline phosphatase (ALP)/Tyr and β-galactosidase (Gal)/Tyr, were further introduced into the system for the successful probing of the corresponding targets. This work features not only the first use of QCCC in PEC bioanalysis but also the separation of enzymatic reaction from the photoelectrode as well as the direct signal recording in a split-type protocol, which enables quite convenient and high-throughput detection as compared to previous formats. More importantly, by using numerous other oxidoreductases that involve quinones as reactants/products, this protocol could serve as a common basis for the development of a new class of QCCC-based PEC enzymatic bioanalysis and further extended for general enzyme-labeled PEC bioanalysis of versatile targets.

An Inverse Electron Demand Azo-Diels-Alder Reaction of o-Quinone Methides and Imino Ethers: Synthesis of Benzocondensed 1,3-Oxazines.

Science.gov (United States)

Osipov, Dmitry V; Osyanin, Vitaly A; Khaysanova, Guzel' D; Masterova, Elvira R; Krasnikov, Pavel E; Klimochkin, Yuri N

2018-04-20

We have studied the reactions of o-quinone methide precursors with imino ethers. The reaction provides a versatile route to substituted 1,3-benzoxazines. The proposed reaction mechanism involves the generation of the o-quinone methide intermediates, imino-Diels-Alder reaction, and elimination. This cascade process is a rare example of the participation of imino ethers as dienophiles.

Chemical proprieties of the iron-quinone complex in mutated reaction centers of Rb. sphaeroides

International Nuclear Information System (INIS)

Hałas, Agnieszka; Derrien, Valerie; Sebban, Pierre; Matlak, Krzysztof; Korecki, Józef; Kruk, Jerzy; Burda, Kvĕtoslava

2012-01-01

We investigated type II bacterial photosynthetic reaction centers, which contain a quinone - iron complex (Q A -Fe-Q B ) on their acceptor side. Under physiological conditions it was observed mainly in a reduced high spin state but its low spin ferrous states were also observed. Therefore, it was suggested that it might regulate the dynamical properties of the iron–quinone complex and the protonation and deprotonation events in its neighbourhood. In order to get insight into the molecular mechanism of the NHFe low spin state formation, we preformed Mössbauer studies of a wild type of Rb. sphaeroides and its two mutated forms. Our Mössbauer measurements show that the hydrophobicity of the Q A binding site can be crucial for stabilization of the high spin ferrous state of NHFe.

Are the reactions of quinones on graphite adiabatic?

International Nuclear Information System (INIS)

Luque, N.B.; Schmickler, W.

2013-01-01

Outer sphere electron transfer reactions on pure metal electrodes are often adiabatic and hence independent of the electrode material. Since it is not clear, whether adiabatic electron transfer can also occur on a semi-metal like graphite, we have re-investigated experimental data presented in a recent communication by Nissim et al. [Chemical Communications 48 (2012) 3294] on the reactions of quinones on graphite. We have supplemented their work by DFT calculations and conclude, that these reactions are indeed adiabatic. This contradicts the assertion of Nissim et al. that the rates are proportional to the density of states at the Fermi level

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

2017-11-01

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 LiBF 4 /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.

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.

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)

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

International Nuclear Information System (INIS)

Hashemi, Mohammed M.; Eftekhari-Sis, Bagher; Khalili, Behzad; Karimi-Jaberi, Zahed

2005-01-01

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)

A prototype hybrid 7π quinone-fused 1,3,2-dithiazolyl radical.

Science.gov (United States)

Decken, A; Mailman, A; Passmore, J; Rautiainen, J M; Scherer, W; Scheidt, E-W

2011-01-28

Reaction of 1,4-naphthoquinone and SNSMF(6) (M = As, Sb) in SO(2) solution in a 1 : 2 molar ratio led to the naphthoquinone fused 1,3,2-dithiazolylium salts, 3MF(6) quantitatively by multinuclear NMR (87% isolated yield of 3SbF(6)) via the cycloaddition and oxidative dehydrogenation chemistry of SNS(+) with formation of NH(4)SbF(6) and S(8). The product 3SbF(6) was fully characterized by IR, Raman, multinuclear {(1)H, (13)C, (14)N} NMR, elemental analysis, cyclic voltammetry and single crystal X-ray crystallography. The reduction of 3SbF(6) with ferrocene (Cp(2)Fe) in refluxing acetonitrile (CH(3)CN) led to the first isolation of a fused quinone-thiazyl radical, 3˙ in 73% yield. The prototype hybrid quinone-thiazyl radical 3˙ was fully characterized by IR, Raman microscopy, EI-MS, elemental analysis, solution and solid state EPR, magnetic susceptibility (2-370 K) and was found to form π*-π* dimers in the solid state as determined by single crystal X-ray crystallography. Furthermore, the thermal decomposition of 3˙ led to a novel quinone-fused 1,2,3,4-tetrathiine, 10 (x = 2) and the known 1,2,5-thiadiazole, 11. The energetics of the cycloadditon and oxidative dehydrogenation chemistry of SNS(+) and 1,4-naphthoquinone leading to 3SbF(6) were estimated in the gas phase and SO(2) solution by DFT calculations (PBE0/6-311G(d)) and lattice enthalpies obtained by the volume based thermodynamic (VBT) approach in the solid state. The gas phase ion energetics (ionization potential (IP) and electron affinity (EA)) of 3˙ are compared to related 1,3,2- and 1,2,3-dithiazolyl radicals.

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

Quinones as dienophiles in the Diels-Alder reaction: history and applications in total synthesis.

Science.gov (United States)

Nawrat, Christopher C; Moody, Christopher J

2014-02-17

In the canon of reactions available to the organic chemist engaged in total synthesis, the Diels-Alder reaction is among the most powerful and well understood. Its ability to rapidly generate molecular complexity through the simultaneous formation of two carbon-carbon bonds is almost unrivalled, and this is reflected in the great number of reported applications of this reaction. Historically, the use of quinones as dienophiles is highly significant, being the very first example investigated by Diels and Alder. Herein, we review the application of the Diels-Alder reaction of quinones in the total synthesis of natural products. The highlighted examples span some 60 years from the landmark syntheses of morphine (1952) and reserpine (1956) by Gates and Woodward, respectively, through to the present day examples, such as the tetracyclines. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrochemistry of potentially bioreductive alkylating quinones. Part 3. Quantitative structure-electrochemistry relationships of aziridinylquinones

NARCIS (Netherlands)

Driebergen, R.J.; Moret, E.E.; Janssen, L.H.M.; Blauw, J.S.; Holthuis, J.J.M.; Postma kelder, S.J.; Verboom, Willem; Reinhoudt, David; van der Linden, W.E.

1992-01-01

The concept of bioreductive alkylation as a mechanism of action of aziridinylquinoid anticancer agents has been investigated by the use of electrochemical techniques. Properly substituted aziridinylquinones are activated by an electrochemical step (reduction of the quinone function), followed by

Comparison of calculated and experimental isotope edited FTIR difference spectra for purple bacterial photosynthetic reaction centers with different quinones incorporated into the QA binding site.

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Nan eZhao

2013-08-01

Full Text Available Previously we have shown that ONIOM type (QM/MM calculations can be used to simulate isotope edited FTIR difference spectra for neutral ubiquinone in the QA binding site in Rhodobacter sphaeroides photosynthetic reaction centers. Here we considerably extend upon this previous work by calculating isotope edited FTIR difference spectra for reaction centers with a variety of unlabeled and 18O labeled foreign quinones incorporated into the QA binding site. Isotope edited spectra were calculated for reaction centers with 2,3-dimethoxy-5,6-dimethyl-1,4-benzoquinone (MQ0, 2,3,5,6-tetramethyl-1,4-benzoquinone (duroquinone, DQ, and 2,3-dimethyl-l,4-naphthoquinone (DMNQ incorporated, and compared to corresponding experimental spectra. The calculated and experimental spectra agree well, further demonstrating the utility and applicability of our ONIOM approach for calculating the vibrational properties of pigments in protein binding sites.The normal modes that contribute to the bands in the calculated spectra, their composition, frequency and intensity, and how these quantities are modified upon 18O labeling, are presented. This computed information leads to a new and more detailed understanding/interpretation of the experimental FTIR difference spectra. Hydrogen bonding to the carbonyl groups of the incorporated quinones is shown to be relatively weak. It is also shown that there is some asymmetry in hydrogen bonding, accounting for 10-13 cm-1 separation in the frequencies of the carbonyl vibrational modes of the incorporated quinones. The extent of asymmetry H-bonding could only be established by considering the spectra for various types of quinones incorporated into the QA binding site. The quinones listed above are tail-less. Spectra were also calculated for reaction centers with corresponding tail containing quinones incorporated, and it is found that replacement of the quinone methyl group by a phytyl or prenyl chain does not alter ONIOM calculated s

In vivo relevance of two critical levels for NAD(P)H:quinone oxidoreductase (NQO1)-mediated cellular protection against electrophile toxicity found in vitro

NARCIS (Netherlands)

Haan, de L.H.J.; Pot, G.K.; Aarts, J.M.M.J.G.; Rietjens, I.M.C.M.; Alink, G.M.

2006-01-01

NAD(P)H:quinone oxidoreductase (NQO1)-mediated detoxification of quinones is suggested to be involved in cancer prevention. In the present study, using transfected CHO cells, it was demonstrated that the relation between NQO1 activity and the resulting protection against the cytotoxicity of

Atmospheric Distribution of PAHs and Quinones in the Gas and PM1 Phases in the Guadalajara Metropolitan Area, Mexico: Sources and Health Risk

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Valeria Ojeda-Castillo

2018-04-01

Full Text Available Polycyclic aromatic hydrocarbons (PAHs and quinones in the gas phase and as submicron particles raise concerns due to their potentially carcinogenic and mutagenic properties. The majority of existing studies have investigated the formation of quinones, but it is also important to consider both the primary and secondary sources to estimate their contributions. The objectives of this study were to characterize PAHs and quinones in the gas and particulate matter (PM1 phases in order to identify phase distributions, sources, and cancer risk at two urban monitoring sites in the Guadalajara Metropolitan Area (GMA in Mexico. The simultaneous gas and PM1 phases samples were analyzed using a gas chromatography–mass spectrometer. The lifetime lung cancer risk (LCR due to PAH exposure was calculated to be 1.7 × 10−3, higher than the recommended risk value of 10−6, indicating a potential health hazard. Correlations between parent PAHs, criteria pollutants, and meteorological parameters suggest that primary sources are the main contributors to the Σ8 Quinones concentrations in PM1, while the secondary formation of 5,12-naphthacenequinone and 9,10-anthraquinone may contribute less to the observed concentration of quinones. Additionally, naphthalene, acenaphthene, fluorene, phenanthrene, and anthracene in PM1, suggest photochemical degradation into unidentified species. Further research is needed to determine how these compounds are formed.

Selective Alkylation of C-Rich Bulge Motifs in Nucleic Acids by Quinone Methide Derivatives.

Science.gov (United States)

Lönnberg, Tuomas; Hutchinson, Mark; Rokita, Steven

2015-09-07

A quinone methide precursor featuring a bis-cyclen anchoring moiety has been synthesized and its capacity to alkylate oligonucleotide targets quantified in the presence and absence of divalent metal ions (Zn(2+) , Ni(2+) and Cd(2+) ). The oligonucleotides were designed for testing the sequence and secondary structure specificity of the reaction. Gel electrophoretic analysis revealed predominant alkylation of C-rich bulges, regardless of the presence of divalent metal ions or even the bis-cyclen anchor. This C-selectivity appears to be an intrinsic property of the quinone methide electrophile as reflected by its reaction with an equimolar mixture of the 2'-deoxynucleosides. Only dA-N1 and dC-N3 alkylation products were detected initially and only the dC adduct persisted for detection under conditions of the gel electrophoretic analysis. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Beneficial synergistic effects of microdose lithium with pyrroloquinoline quinone in an Alzheimer's disease mouse model.

Science.gov (United States)

Zhao, Lei; Gong, Neng; Liu, Meng; Pan, Xiaoli; Sang, Shaoming; Sun, Xiaojing; Yu, Zhe; Fang, Qi; Zhao, Na; Fei, Guoqiang; Jin, Lirong; Zhong, Chunjiu; Xu, Tianle

2014-12-01

Alzheimer's disease (AD) is a complicated, neurodegenerative disorder involving multifactorial pathogeneses and still lacks effective clinical treatment. Recent studies show that lithium exerts disease-modifying effects against AD. However, the intolerant side effects at conventional effective dosage limit the clinical use of lithium in treating AD. To explore a novel AD treatment strategy with microdose lithium, we designed and synthesized a new chemical, tri-lithium pyrroloquinoline quinone (Li3PQQ), to study the synergistic effects of low-dose lithium and pyrroloquinoline quinone, a native compound with powerful antioxidation and mitochondrial amelioration. The results showed that Li3PQQ at a relative low dose (6 and 12 mg/kg) exhibited more powerful effects in restoring the impairment of learning and memory, facilitating hippocampal long-term potentiation, and reducing cerebral amyloid deposition and phosphorylated tau level in APP/PS1 transgenic mice than that of lithium chloride at both low and high dose (5 and 100 mg/kg). We further found that Li3PQQ inhibited the activity of glycogen synthase kinase-3 and increased the activity of β-amyloid-binding alcohol dehydrogenase, which might underlie the beneficial effects of Li3PQQ on APP/PS1 transgenic mice. Our study demonstrated the efficacy of a novel AD therapeutic strategy targeting at multiple disease-causing mechanisms through the synergistic effects of microdose lithium and pyrroloquinoline quinone. Copyright © 2014 Elsevier Inc. All rights reserved.

Immunomodulatory Effects of Diterpene Quinone Derivatives from the Roots of Horminum pyrenaicum in Human PBMC

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K. Becker

2018-01-01

Full Text Available Several phytochemicals were shown to interfere with redox biology in the human system. Moreover, redox biochemistry is crucially involved in the orchestration of immunological cascades. When screening for immunomodulatory compounds, the two interferon gamma- (IFN-γ- dependent immunometabolic pathways of tryptophan breakdown via indoleamine 2,3-dioxygenase-1 (IDO-1 and neopterin formation by GTP-cyclohydrolase 1 (GTP-CH-I represent prominent targets, as IFN-γ-related signaling is strongly sensitive to oxidative triggers. Herein, the analysis of these pathway activities in human peripheral mononuclear cells was successfully applied in a bioactivity-guided fractionation strategy to screen for anti-inflammatory substances contained in the root of Horminum (H. pyrenaicum L. (syn. Dragon’s mouth, the only representative of the monophyletic genus Horminum. Four abietane diterpene quinone derivatives (horminone, 7-O-acetylhorminone, inuroyleanol and its 15,16-dehydro-derivative, a novel natural product, two nor-abietane diterpene quinones (agastaquinone and 3-deoxyagastaquinone and two abeo 18 (4 → 3 abietane diterpene quinones (agastol and its 15,16-dehydro-derivative could be identified. These compounds were able to dose-dependently suppress the above mentioned pathways with different potency. Beside the description of new active compounds, this study demonstrates the feasibility of integrating IDO-1 and GTP-CH-I activity in the search for novel anti-inflammatory compounds, which can then be directed towards a more detailed mode of action analysis.

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....... and on flash-induced cytochrome c oxidation were studied in whole cells under aerobic conditions. BChl c fluorescence in a cell suspension with 5.4 microM BChl c was quenched to 50% by addition of 0.6 microM shikonin ((R)-2-(1-hydroxy-4-methyl-3-pentenyl)-5,8-dihydroxy-1, 4-naphthoquinone), 0.9 microM 5......-hydroxy-1,4-naphthoquinone, or 4 microM 2-acetyl-3-methyl-1,4-naphthoquinone. Between 25 and 100 times higher quinone concentrations were needed to quench BChl a fluorescence to a similar extent. These quinones also efficiently inhibited flash-induced cytochrome c oxidation when BChl c was excited...

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

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

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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.

Electronic Connection Between the Quinone and Cytochrome c Redox Pools and Its Role in Regulation of Mitochondrial Electron Transport and Redox Signaling

Science.gov (United States)

Sarewicz, Marcin; Osyczka, Artur

2015-01-01

Mitochondrial respiration, an important bioenergetic process, relies on operation of four membranous enzymatic complexes linked functionally by mobile, freely diffusible elements: quinone molecules in the membrane and water-soluble cytochromes c in the intermembrane space. One of the mitochondrial complexes, complex III (cytochrome bc1 or ubiquinol:cytochrome c oxidoreductase), provides an electronic connection between these two diffusible redox pools linking in a fully reversible manner two-electron quinone oxidation/reduction with one-electron cytochrome c reduction/oxidation. Several features of this homodimeric enzyme implicate that in addition to its well-defined function of contributing to generation of proton-motive force, cytochrome bc1 may be a physiologically important point of regulation of electron flow acting as a sensor of the redox state of mitochondria that actively responds to changes in bioenergetic conditions. These features include the following: the opposing redox reactions at quinone catalytic sites located on the opposite sides of the membrane, the inter-monomer electronic connection that functionally links four quinone binding sites of a dimer into an H-shaped electron transfer system, as well as the potential to generate superoxide and release it to the intermembrane space where it can be engaged in redox signaling pathways. Here we highlight recent advances in understanding how cytochrome bc1 may accomplish this regulatory physiological function, what is known and remains unknown about catalytic and side reactions within the quinone binding sites and electron transfers through the cofactor chains connecting those sites with the substrate redox pools. We also discuss the developed molecular mechanisms in the context of physiology of mitochondria. PMID:25540143

Energetic change of the primary quinone in photosynthetic reaction center. Mutation, delayed fluorescence and model calculations (Theses of the Ph.D. dissertation)

International Nuclear Information System (INIS)

Rinyu, L.

2007-01-01

Complete text of publication follows. Photosynthesis is one of the basic metabolic processes of living organisms. Photosynthesizing species (bacteria, algae and higher class plants) convert the energy of light into other forms of free energy (redox potential, electro- chemical potential of ions and protons and phosphate-potential) which are directly suit- able either to cover the energy need of the vital processes of the cell or to storage. In reaction center (RC) protein of photo- synthetic bacteria, electron transfer is initiated upon light excitation from the excited bacteriochlorophyll dimer (P) to the secondary quinone (Q B ) via bacteriopheophytine (Bph) and the primary quinone (Q A ). In Rhodobacter sphaeroides purple bacteria, both quinones are ubiquinone-10, but due to the different protein environment, their electrochemical properties is highly different. Whereas Q A makes one-electron chemistry, Q B can be doubly reduced to form hydroquinone, Q B H 2 by uptake of two protons. Q B H 2 subsequently leaves the RC and is replaced by an oxidized quinone from to membrane pool. The semiquinones are important intermediates in the quinone reduction cycle of the RC. The redox midpoint potentials of the Q/Q - redox pairs (E m ) are also different: the Q A /Q A - has 60 mV more negative potential than the Q B /Q B - couple (pH 8) to make the (interquinone) electron transfer favorable. For fine tuning of the midpoint redox potentials of the quinones, the protein assures appropriate steric and electrostatic environment. The most important aim of this study was the design and production of reaction center mutants in the binding pocket of the primary quinone to investigate the effect of the amino acids of the protein and lipids of the membrane on the thermodynamics of the primary quinone. The first priority was the determination of the absolute free energy gap between the P* and the P + Q A - states in wild type and mutant reaction centers by comparison of the

Mechanisms of action of quinone-containing alkylating agents: DNA alkylation by aziridinylquinones.

Science.gov (United States)

Hargreaves, R H; Hartley, J A; Butler, J

2000-11-01

Aziridinyl quinones can be activated by cellular reductases eg. DT-diaphorase and cytochrome P450 reductase to form highly reactive DNA alkylating agents. The mechanisms by which this activation and alkylation take place are many and varied. Using clinically relevant and experimental agents this review will describe many of these mechanisms. The agents discussed are Mitomycin C, EO9 and analogues, diaziridinylbenzoquinones and the pyrrolo[1, 2-alpha]benzimidazolequinones.

Quinones from plants of northeastern Brazil: structural diversity, chemical transformations, NMR data and biological activities.

Science.gov (United States)

Lemos, Telma L G; Monte, Francisco J Q; Santos, Allana Kellen L; Fonseca, Aluisio M; Santos, Hélcio S; Oliveira, Mailcar F; Costa, Sonia M O; Pessoa, Otilia D L; Braz-Filho, Raimundo

2007-05-20

The present review focus in quinones found in species of Brazilian northeastern Capraria biflora, Lippia sidoides, Lippia microphylla and Tabebuia serratifolia. The review cover ethnopharmacological aspects including photography of species, chemical structure feature, NMR datea and biological properties. Chemical transformations of lapachol to form enamine derivatives and biological activities are discussed.

Enhanced biotic and abiotic transformation of Cr(vi) by quinone-reducing bacteria/dissolved organic matter/Fe(iii) in anaerobic environment.

Science.gov (United States)

Huang, Bin; Gu, Lipeng; He, Huan; Xu, Zhixiang; Pan, Xuejun

2016-09-14

This study investigated the simultaneous transformation of Cr(vi) via a closely coupled biotic and abiotic pathway in an anaerobic system of quinone-reducing bacteria/dissolved organic matters (DOM)/Fe(iii). Batch studies were conducted with quinone-reducing bacteria to assess the influences of sodium formate (NaFc), electron shuttling compounds (DOM) and the Fe(iii) on Cr(vi) reduction rates as these chemical species are likely to be present in the environment during in situ bioremediation. Results indicated that the concentration of sodium formate and anthraquinone-2-sodium sulfonate (AQS) had apparently an effect on Cr(vi) reduction. The fastest decrease in rate for incubation supplemented with 5 mM sodium formate and 0.8 mM AQS showed that Fe(iii)/DOM significantly promoted the reduction of Cr(vi). Presumably due to the presence of more easily utilizable sodium formate, DOM and Fe(iii) have indirect Cr(vi) reduction capability. The coexisting cycles of Fe(ii)/Fe(iii) and DOM(ox)/DOM(red) exhibited a higher redox function than the individual cycle, and their abiotic coupling action can significantly enhance Cr(vi) reduction by quinone-reducing bacteria.

Dicumarol inhibition of NADPH:quinone oxidoreductase induces growth inhibition of pancreatic cancer via a superoxide-mediated mechanism.

Science.gov (United States)

Cullen, Joseph J; Hinkhouse, Marilyn M; Grady, Matthew; Gaut, Andrew W; Liu, Jingru; Zhang, Yu Ping; Weydert, Christine J Darby; Domann, Frederick E; Oberley, Larry W

2003-09-01

NADPH:quinone oxidoreductase (NQO(1)), a homodimeric, ubiquitous, flavoprotein, catalyzes the two-electron reduction of quinones to hydroquinones. This reaction prevents the one-electron reduction of quinones by cytochrome P450 reductase and other flavoproteins that would result in oxidative cycling with generation of superoxide (O(2)(.-)). NQO(1) gene regulation may be up-regulated in some tumors to accommodate the needs of rapidly metabolizing cells to regenerate NAD(+). We hypothesized that pancreatic cancer cells would exhibit high levels of this enzyme, and inhibiting it would suppress the malignant phenotype. Reverse transcription-PCR, Western blots, and activity assays demonstrated that NQO(1) was up-regulated in the pancreatic cancer cell lines tested but present in very low amounts in the normal human pancreas. To determine whether inhibition of NQO(1) would alter the malignant phenotype, MIA PaCa-2 pancreatic cancer cells were treated with a selective inhibitor of NQO(1), dicumarol. Dicumarol increased intracellular production of O(2)(.-), as measured by hydroethidine staining, and inhibited cell growth. Both of these effects were blunted with infection of an adenoviral vector containing the cDNA for manganese superoxide dismutase. Dicumarol also inhibited cell growth, plating efficiency, and growth in soft agar. We conclude that inhibition of NQO(1) increases intracellular O(2)(.-) production and inhibits the in vitro malignant phenotype of pancreatic cancer. These mechanisms suggest that altering the intracellular redox environment of pancreatic cancer cells may inhibit growth and delineate a potential strategy directed against pancreatic cancer.

Differential stress-induced regulation of two quinone reductases in the brown rot Basidiomycete Gloeophyllum trabeum

Science.gov (United States)

Roni Cohen; Melissa R. Suzuki; Kenneth E. Hammel

2004-01-01

Quinone reductases (QRDs) have two important functions in the basidiomycete Gloeophyllum trabeum, which causes brown rot of wood. First, a QRD is required to generate biodegradative hydroxyl radicals via redox cycling between two G. trabeum extracellular metabolites, 2,5-dimethoxyhydroquinone (2,5-DMHQ) and 2,5-dimethoxy-1,4-benzoquinone (2,5- DMBQ). Second, because 2,...

Calcium mobilization by quinones and other free radical generating systems in rat hepatocytes

International Nuclear Information System (INIS)

Chen, E.C.; Chan, T.M.

1987-01-01

Using isolated rat hepatocytes, sublethal concentrations of quinones and other free radical generating systems were used to test the role of extracellular calcium (Ca) in activating glycogen phosphorylase and intracellular Ca mobilization. The α-agonist phenylephrine (Phe) was used for comparison. The EC50's were: Phe = 2.6 x 10 -7 M, menadione (K 3 ) = 4.5 x 10 -5 M, dicumarol = 2 x 10 -5 M. In normal Ca buffer, activation by K 3 was slower than Phe, being maximal at 2' but more sustained. Dicumarol and tert-butyl hydroperoxide (t-BH) activated phosphorylase similarly. The xanthine-xanthine oxidase (X-XO) system stimulated activation similar to K 3 . Dicumarol greatly augmented phosphorylase activation by K 3 but had no effect on Phe action. Depletion of extracellular Ca abolished Phe action, markedly diminished t-BH and dicumarol, but had no effect on K 3 or X-XO activation of phosphorylase. Ca efflux exchange measured in 45 Ca preloaded cells were stimulated equally by Phe, K 3 , dicumarol, or K 3 + dicumarol in the presence of extracellular Ca. Absence of extracellular Ca abolished Phe effect but minimally affected stimulation by K 3 or K 3 + dicumarol. These data suggest that activation of glycogen phosphorylase by sublethal doses of quinones may not reflect the degree and the mechanism of intracellular Ca mobilization

Redox-active quinones induces genome-wide DNA methylation changes by an iron-mediated and Tet-dependent mechanism

DEFF Research Database (Denmark)

Zhao, Bailin; Yang, Ying; Wang, Xiaoli

2014-01-01

DNA methylation has been proven to be a critical epigenetic mark important for various cellular processes. Here, we report that redox-active quinones, a ubiquitous class of chemicals found in natural products, cancer therapeutics and environment, stimulate the conversion of 5 mC to 5 hmC in vivo,...

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.

Vitamin E and vitamin E-quinone levels in red blood cells and plasma of newborn infants and their mothers.

Science.gov (United States)

Jain, S K; Wise, R; Bocchini, J J

1996-02-01

Vitamin E is a physiological antioxidant and protects cell membranes from oxidative damage. This study has determined whether vitamin E level in RBC of newborns has any relationship with its level in their mothers. We have also examined levels of vitamin E and vitamin E-quinone, an oxidized product of vitamin E, in paired samples of red blood cells (RBC) and plasma of newborns and their mothers. Blood was collected from 26 mothers and their full-term placental cords at delivery. Vitamin E and vitamin E-quinone levels were determined in RBC and plasma by HPLC. Newborn-plasma had significantly lower vitamin E levels compared with maternal-plasma both when expressed as nmole/ml (5.5+/-0.4 vs 26.1+/-1.1, p = 0.0001) or nmole/mumole total lipids (1.9+/-0.1 vs 2.6+/-0.1, p = 0.0001). Vitamin E level in the newborn-RBC was similar to that of maternal-RBC when expressed as nmole/ml packed cells (2.77+/-0.14 vs 2.95+/-0.13), but was significantly lower when expressed as nmole/mumole total lipids (0.56+/-0.03 vs 0.64+/-0.04, p = 0.03) from that of maternal-RBC. Vitamin E-quinone levels are significantly elevated in newborns compared with their mothers both in RBC (29.4+/-2.1 vs 24.1+/-1.2, p = 0.04) and plasma (39.9+/-5.3 vs 25.3+/-4.2, p = 0.006) when expressed as nmole/mmole total lipids but not when expressed as nmole/ml. There was a significant correlation of vitamin E between newborn-plasma and newborn-RBC (r = 0.65, p = 0.0002 for nmole per ml packed RBC;r = 0.63, p = 0.0007 for nmole per mumole total lipids). The relationship between maternal plasma and newborn plasma was significant when vitamin E was normalized with nmole/mumole total lipid (r = 0.54, p = 0.007 but not when expressed as nmole/ml (r = 0.09, p = 0.64). However, vitamin E in the RBC of maternal and newborn had significant correlation when expressed as per ml packed cells (r = 0.61, p = 0.001) and per total lipid (r = 0.46, p = 0.02). There was no relationship of vitamin E-quinone levels between RBC and

Identification of a multi-protein reductive dehalogenase complex in Dehalococcoides mccartyi strain CBDB1 suggests a protein-dependent respiratory electron transport chain obviating quinone involvement

DEFF Research Database (Denmark)

Kublik, Anja; Deobald, Darja; Hartwig, Stefanie

2016-01-01

electrophoresis (BN-PAGE), gel filtration and ultrafiltration an active dehalogenating protein complex with a molecular mass of 250–270 kDa was identified. The active subunit of reductive dehalogenase (RdhA) colocalised with a complex iron-sulfur molybdoenzyme (CISM) subunit (CbdbA195) and an iron-sulfur cluster...... of the dehalogenating complex prior to membrane solubilisation. Taken together, the identification of the respiratory dehalogenase protein complex and the absence of indications for quinone participation in the respiration suggest a quinone-independent protein-based respiratory electron transfer chain in D. mccartyi....

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.

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

Synthesis of α- and β-lapachone derivatives from hetero diels-alder trapping of alkyl and aryl o-quinone methides

International Nuclear Information System (INIS)

Silva, Fernando de C. da; Ferreira, Sabrina B.; Ferreira, Vitor F.; Kaiser, Carlos R.; Pinto, Angelo C.

2009-01-01

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 α- and β-lapachone (author)

Biosynthesis of actinorhodin and related antibiotics: discovery of alternative routes for quinone formation encoded in the act gene cluster.

Science.gov (United States)

Okamoto, Susumu; Taguchi, Takaaki; Ochi, Kozo; Ichinose, Koji

2009-02-27

All known benzoisochromanequinone (BIQ) biosynthetic gene clusters carry a set of genes encoding a two-component monooxygenase homologous to the ActVA-ORF5/ActVB system for actinorhodin biosynthesis in Streptomyces coelicolor A3(2). Here, we conducted molecular genetic and biochemical studies of this enzyme system. Inactivation of actVA-ORF5 yielded a shunt product, actinoperylone (ACPL), apparently derived from 6-deoxy-dihydrokalafungin. Similarly, deletion of actVB resulted in accumulation of ACPL, indicating a critical role for the monooxygenase system in C-6 oxygenation, a biosynthetic step common to all BIQ biosyntheses. Furthermore, in vitro, we showed a quinone-forming activity of the ActVA-ORF5/ActVB system in addition to that of a known C-6 monooxygenase, ActVA-ORF6, by using emodinanthrone as a model substrate. Our results demonstrate that the act gene cluster encodes two alternative routes for quinone formation by C-6 oxygenation in BIQ biosynthesis.

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

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.

Photocleavage of DNA: irradiation of quinone-containing reagents converts supercoiled to linear DNA

International Nuclear Information System (INIS)

Kock, T.; Schuster, G.B.; Ropp, J.D.; Sligar, S.G.

1993-01-01

Irradiation (350 nm) of air-saturated solutions of reagents containing an anthraquinone group linked to quaternary alkyl ammonium groups converts supercoiled DNA to circular and to linear DNA. Generation of linear DNA does not occur by accumulation of numerous single-strand cuts but by coincident-site double-strand cleavage of DNA. Irradiation forms the triplet state of the anthraquinone, which reacts either by hydrogen atom abstraction from a sugar of DNA or by electron transfer from a base of the DNA. Subsequent reactions result in chain scission. The quinone is apparently reformed after this sequence and reirradiation leads to double-strand cleavage. (Author)

Constituents of Musa x paradisiaca cultivar with the potential to induce the phase II enzyme, quinone reductase.

Science.gov (United States)

Jang, Dae Sik; Park, Eun Jung; Hawthorne, Michael E; Vigo, Jose Schunke; Graham, James G; Cabieses, Fernando; Santarsiero, Bernard D; Mesecar, Andrew D; Fong, Harry H S; Mehta, Rajendra G; Pezzuto, John M; Kinghorn, A Douglas

2002-10-23

A new bicyclic diarylheptanoid, rel-(3S,4aR,10bR)-8-hydroxy-3-(4-hydroxyphenyl)-9-methoxy-4a,5,6,10b-tetrahydro-3H-naphtho[2,1-b]pyran (1), as well as four known compounds, 1,2-dihydro-1,2,3-trihydroxy-9-(4-methoxyphenyl)phenalene (2), hydroxyanigorufone (3), 2-(4-hydroxyphenyl)naphthalic anhydride (4), and 1,7-bis(4-hydroxyphenyl)hepta-4(E),6(E)-dien-3-one (5), were isolated from an ethyl acetate-soluble fraction of the methanol extract of the fruits of Musa x paradisiaca cultivar, using a bioassay based on the induction of quinone reductase (QR) in cultured Hepa1c1c7 mouse hepatoma cells to monitor chromatographic fractionation. The structure and relative stereochemistry of compound 1 were elucidated unambiguously by one- and two-dimensional NMR experiments ((1)H NMR, (13)C NMR, DEPT, COSY, HMQC, HMBC, and NOESY) and single-crystal X-ray diffraction analysis. Isolates 1-5 were evaluated for their potential cancer chemopreventive properties utilizing an in vitro assay to determine quinone reductase induction and a mouse mammary organ culture assay.

Kinetic modeling of electron transfer reactions in photosystem I complexes of various structures with substituted quinone acceptors.

Science.gov (United States)

Milanovsky, Georgy E; Petrova, Anastasia A; Cherepanov, Dmitry A; Semenov, Alexey Yu

2017-09-01

The reduction kinetics of the photo-oxidized primary electron donor P 700 in photosystem I (PS I) complexes from cyanobacteria Synechocystis sp. PCC 6803 were analyzed within the kinetic model, which considers electron transfer (ET) reactions between P 700 , secondary quinone acceptor A 1 , iron-sulfur clusters and external electron donor and acceptors - methylviologen (MV), 2,3-dichloro-naphthoquinone (Cl 2 NQ) and oxygen. PS I complexes containing various quinones in the A 1 -binding site (phylloquinone PhQ, plastoquinone-9 PQ and Cl 2 NQ) as well as F X -core complexes, depleted of terminal iron-sulfur F A /F B clusters, were studied. The acceleration of charge recombination in F X -core complexes by PhQ/PQ substitution indicates that backward ET from the iron-sulfur clusters involves quinone in the A 1 -binding site. The kinetic parameters of ET reactions were obtained by global fitting of the P 700 + reduction with the kinetic model. The free energy gap ΔG 0 between F X and F A /F B clusters was estimated as -130 meV. The driving force of ET from A 1 to F X was determined as -50 and -220 meV for PhQ in the A and B cofactor branches, respectively. For PQ in A 1A -site, this reaction was found to be endergonic (ΔG 0  = +75 meV). The interaction of PS I with external acceptors was quantitatively described in terms of Michaelis-Menten kinetics. The second-order rate constants of ET from F A /F B , F X and Cl 2 NQ in the A 1 -site of PS I to external acceptors were estimated. The side production of superoxide radical in the A 1 -site by oxygen reduction via the Mehler reaction might comprise ≥0.3% of the total electron flow in PS I.

Electrochemical study of quinone redox cycling: A novel application of DNA-based biosensors for monitoring biochemical reactions.

Science.gov (United States)

Ensafi, Ali A; Jamei, Hamid Reza; Heydari-Bafrooei, Esmaeil; Rezaei, B

2016-10-01

This paper presents the results of an experimental investigation of voltammetric and impedimetric DNA-based biosensors for monitoring biological and chemical redox cycling reactions involving free radical intermediates. The concept is based on associating the amounts of radicals generated with the electrochemical signals produced, using differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). For this purpose, a pencil graphite electrode (PGE) modified with multiwall carbon nanotubes and poly-diallydimethlammonium chloride decorated with double stranded fish sperm DNA was prepared to detect DNA damage induced by the radicals generated from a redox cycling quinone (i.e., menadione (MD; 2-methyl-1,4-naphthoquinone)). Menadione was employed as a model compound to study the redox cycling of quinones. A direct relationship was found between free radical production and DNA damage. The relationship between MD-induced DNA damage and free radical generation was investigated in an attempt to identify the possible mechanism(s) involved in the action of MD. Results showed that DPV and EIS were appropriate, simple and inexpensive techniques for the quantitative and qualitative comparisons of different reducing reagents. These techniques may be recommended for monitoring DNA damages and investigating the mechanisms involved in the production of redox cycling compounds. Copyright © 2016 Elsevier B.V. All rights reserved.

Pulse radiolytic and electrochemical investigations of intramolecular electron transfer in carotenoporphyrins and carotenoporphyrin-quinone triads

International Nuclear Information System (INIS)

Land, E.J.; Lexa, D.; Bensasson, R.V.; Gust, D.; Moore, T.A.; Moore, A.L.; Liddell, P.A.; Nemeth, G.A.

1987-01-01

Thermodynamic and kinetic aspects of intramolecular electron-transfer reactions in carotenoporphyrin dyads and carotenoid-porphyrin-quinone triads have been studied by using pulse radiolysis and cyclic voltammetry. Rapid (<1 μs) electron transfer from carotenoid radical anions to attached porphyrins has been inferred. Carotenoid cations, on the other hand, do not readily accept electrons from attached porphyrins or pyropheophorbides. Electrochemical studies provide the thermodynamic basis for these observations and also allow estimation of the energetics of photoinitiated two-step electron transfer and two-step charge recombination in triad models for photosynthetic charge separation

LC/MSMS STUDY OF BENZO[A]PYRENE-7,8-QUINONE ADDUCTION TO GLOBIN TRYPTIC PEPTIDES AND N-ACETYLAMINO ACIDS

Science.gov (United States)

Benzo[a]pyrene-7,8-quinone (BPQ) is regarded as a reactive genotoxic compound enzymatically formed from a xenobiotic precursor benzo[a]pyrene-7,8-diol by aldo-keto-reductase family of enzymes. Because BPQ, a Michael electrophile, was previously shown to react with oligonucleotide...

Role of thiol homeostasis and adenine nucleotide metabolism in the protective effects of fructose in quinone-induced cytotoxicity in rat hepatocytes

NARCIS (Netherlands)

Toxopeus, C.; van Holsteijn, I.; de Winther, M. P.; van den Dobbelsteen, D.; Horbach, G. J.; Blaauboer, B. J.; Noordhoek, J.

1994-01-01

Freshly-isolated rat hepatocytes were exposed in glucose (15 mM) or fructose (5 mM) medium to menadione (2-methyl-1,4-naphthoquinone) (85 microM) or 1,4-naphthoquinone (NQ) (50 microM). Menadione and NQ are closely related quinones and have an approximately equal potential to induce redox cycling.

Chemical modification of the lectin of the marine coral Gerardia savaglia by marine quinone avarone

Directory of Open Access Journals (Sweden)

IVANA PAJIC

2007-12-01

Full Text Available The quinone avarone, isolated from the marine sponge Dysidea avara, possesses the ability to chemically modify proteins. In this work, modification of lectin isolated from the coral Gerardia savaglia by avarone was examined. The techniques used for studying the modification were: SDS PAGE, isoelectric focusing and hemagglutination testing. The results of the SDS PAGE indicate dimerization of the protein. A shift of the pI toward lower value occurs upon modification. The change of the hemagglutination activity of the protein confirms that chemical modification of G. savaglia lectin by avarone changes its ability to interact with the membrane of erythrocytes.

Chemoselective Methylation of Phenolic Hydroxyl Group Prevents Quinone Methide Formation and Repolymerization During Lignin Depolymerization

Energy Technology Data Exchange (ETDEWEB)

Kim, Kwang Ho; Dutta, Tanmoy; Walter, Eric D.; Isern, Nancy G.; Cort, John R.; Simmons, Blake A.; Singh, Seema

2017-03-30

Chemoselective blocking of the phenolic hydroxyl (Ar-OH) group by methylation was found to suppress secondary repolymerization and charring during lignin depolymerization. Methylation of Ar-OH prevents formation of reactive quinone methide intermediates, which are partly responsible for undesirable secondary repolymerization reactions. Instead, this structurally modified lignin produces more relatively low molecular weight products from lignin depolymerization compared to unmodified lignin. This result demonstrates that structural modification of lignin is desirable for production of low molecular weight phenolic products. This approach could be directed toward alteration of natural lignification processes to produce biomass more amenable to chemical depolymerization.

Role of NAD(P)H:quinone oxidoreductase 1 in clofibrate-mediated hepatoprotection from acetaminophen

International Nuclear Information System (INIS)

Moffit, Jeffrey S.; Aleksunes, Lauren M.; Kardas, Michael J.; Slitt, Angela L.; Klaassen, Curtis D.; Manautou, Jose E.

2007-01-01

Mice pretreated with the peroxisome proliferator clofibrate (CFB) are resistant to acetaminophen (APAP) hepatotoxicity. Whereas the mechanism of protection is not entirely known, CFB decreases protein adducts formed by the reactive metabolite of APAP, N-acetyl-p-benzoquinone imine (NAPQI). NAD(P)H:quinone oxidoreductase 1 (NQO1) is an enzyme with antioxidant properties that is responsible for the reduction of cellular quinones. We hypothesized that CFB increases NQO1 activity, which in turn enhances the conversion of NAPQI back to the parent APAP. This could explain the decreases in APAP covalent binding and glutathione depletion produced by CFB without affecting APAP bioactivation to NAPQI. Administration of CFB (500 mg/kg, i.p.) to male CD-1 mice for 5 or 10 days increased NQO1 protein and activity levels. To evaluate the capacity of NQO1 to reduce NAPQI back to APAP, we utilized a microsomal activating system. Cytochrome P450 enzymes present in microsomes bioactivate APAP to NAPQI, which binds the electrophile trapping agent, N-acetyl cysteine (NAC). We analyzed the formation of APAP-NAC metabolite in the presence of human recombinant NQO1. Results indicate that NQO1 is capable of reducing NAPQI. The capacity of NQO1 to amelioriate APAP toxicity was then evaluated in primary hepatocytes. Primary hepatocytes isolated from mice dosed with CFB are resistant to APAP toxicity. These hepatocytes were also exposed to ES936, a high affinity, and irreversible inhibitor of NQO1 in the presence of APAP. Concentrations of ES936 that resulted in over 94% inhibition of NQO1 activity did not increase the susceptibility of hepatocytes from CFB treated mice to APAP. Whereas NQO1 is mechanistically capable of reducing NAPQI, CFB-mediated hepatoprotection does not appear to be dependent upon enhanced expression of NQO1

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).

Reduction of quinones and phenoxy radicals by extracellular glucose dehydrogenase from Glomerella cingulata suggests a role in plant pathogenicity.

Science.gov (United States)

Sygmund, Christoph; Klausberger, Miriam; Felice, Alfons K; Ludwig, Roland

2011-11-01

The plant-pathogenic fungus Glomerella cingulata (anamorph Colletotrichum gloeosporoides) secretes high levels of an FAD-dependent glucose dehydrogenase (GDH) when grown on tomato juice-supplemented media. To elucidate its molecular and catalytic properties, GDH was produced in submerged culture. The highest volumetric activity was obtained in shaking flasks after 6 days of cultivation (3400 U l⁻¹, 4.2 % of total extracellular protein). GDH is a monomeric protein with an isoelectric point of 5.6. The molecular masses of the glycoforms ranged from 95 to 135 kDa, but after deglycosylation, a single 68 kDa band was obtained. The absorption spectrum is typical for an FAD-containing enzyme with maxima at 370 and 458 nm and the cofactor is non-covalently bound. The preferred substrates are glucose and xylose. Suitable electron acceptors are quinones, phenoxy radicals, 2,6-dichloroindophenol, ferricyanide and ferrocenium hexafluorophosphate. In contrast, oxygen turnover is very low. The GDH-encoding gene was cloned and phylogenetic analysis of the translated protein reveals its affiliation to the GMC family of oxidoreductases. The proposed function of this quinone and phenoxy radical reducing enzyme is to neutralize the action of plant laccase, phenoloxidase or peroxidase activities, which are increased in infected plants to evade fungal attack.

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

OpenAIRE

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

2012-01-01

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 analysi...

A Hierarchically Porous Hypercrosslinked and Novel Quinone based Stable Organic Polymer Electrode for Lithium-Ion Batteries

International Nuclear Information System (INIS)

Ahmad, Aziz; Meng, Qinghai; Melhi, Saad; Mao, Lijuan; Zhang, Miao; Han, Bao-Hang; Lu, Kun; Wei, Zhixiang

2017-01-01

Highlights: •A novel hypercrosslinked Poly-Pillar[5]quinone (Poly-P5Q) polymer has been prepared and applied as electrode material in Li-ion batteries. •The novel synthetic route of Poly-P5Q was introduced by the oxidation of Poly-Dimethoxypillar[5]arene. •A Friedel-Crafts reaction was employed to prepare a novel Poly-P5Q as organic cathode material for lithium-ion batteries. -- Abstract: In the recent years, organic electrode materials have attracted tremendous attention and becoming promising electrode candidates for the green and sustainable lithium-ion batteries. A novel hypercrosslinked Poly-Pillar[5]quinone (Poly-P5Q) polymer was prepared and applied as electrode material in Li-ion batteries. Poly-P5Q is the oxidized form of Poly-Dimethoxypillar[5]arene (Poly-DMP5A) which was obtained from the condensation of dimethoxypillar[5]arene and formaldehyde dimethyl acetal using Friedel-Crafts reaction. The prepared materials were characterized by 13 C solid state NMR, FTIR, SEM, EDX and TGA analysis. The Poly-P5Q cathode showed an initial discharge capacity up to 105 mAh g −1 whereas it retained 82.3% of its initial discharge capacity after 100 charge-discharge cycles at a current speed of 100 mA g −1 in the potential window between 1.75 to 3.25 V. In future, research in this direction will provide great insight for the development of novel polymers from various small organic molecules as a stable and high performance electrode materials for green lithium-ion batteries.

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.

Comparative toxicity of eugenol and its quinone methide metabolite in cultured liver cells using kinetic fluorescence bioassays.

Science.gov (United States)

Thompson, D C; Barhoumi, R; Burghardt, R C

1998-03-01

Comparative kinetic analyses of the mechanisms of toxicity of the alkylphenol eugenol and its putative toxic metabolite (quinone methide, EQM) were carried out in cultured rat liver cells (Clone 9, ATCC) using a variety of vital fluorescence bioassays with a Meridian Ultima laser cytometer. Parameters monitored included intracellular GSH and calcium levels ([Ca2+]i), mitochondrial and plasma membrane potentials (MMP and PMP), intracellular pH, reactive oxygen species (ROS) generation, and gap junction-mediated intercellular communication (GJIC). Cells were exposed to various concentrations of test compounds (1 to 1000 microM) and all parameters monitored directly after addition at 15 s intervals for at least 10 min. Eugenol depleted intracellular GSH, inhibited GJIC and generation of ROS, and had a modest effect on MMP at concentrations of 10 to 100 microM. At high concentrations (1000 microM), eugenol also affected [Ca2+]i, PMP, and pH. Effects of EQM were seen at lower concentrations (1 to 10 microM). The earliest and most potent effects of either eugenol or EQM were seen on GSH levels and GJIC. Coadministration of glutathione ethyl ester enhanced intracellular GSH levels by almost 100% and completely protected cells from cell death caused by eugenol and EQM. These results suggest that eugenol mediates its hepatotoxic effects primarily through depletion of cytoprotective thiols and interference in thiol-dependent processes such as GJIC. Furthermore, our results support the hypothesis that the toxic effects of eugenol are mediated through its quinone methide metabolite.

Channelling phenomenon in the gamma irradiated Benzo-quinone and other compounds observed under the scanning electron microscope

International Nuclear Information System (INIS)

Suleiman, Y.M.

1984-01-01

Scanning Electron Microscope (S.E.M.), has been used to examine the gamma irradiated pure crystals of Benzo-quinone and other compounds in the polycrystaline form. After gamma irradiation, shallow lines (channels) were observed on the crystal's surfaces when the crystal layers arrangements are parallel to the photons beam direction. Holes were also observed when those layers of the crystals are in the nonparallel case. The phenomenon has been studied and analysed in connected with the H-atom bonds disruption, and H-atoms migration through the crystal's layers. (author)

NAD(P)H-dependent quinone oxidoreductase 1 (NQO1) and cytochrome P450 oxidoreductase (CYP450OR) differentially regulate menadione-mediated alterations in redox status, survival and metabolism in pancreatic β-cells.

Science.gov (United States)

Gray, Joshua P; Karandrea, Shpetim; Burgos, Delaine Zayasbazan; Jaiswal, Anil A; Heart, Emma A

2016-11-16

NQO1 (NAD(P)H-quinone oxidoreductase 1) reduces quinones and xenobiotics to less-reactive compounds via 2-electron reduction, one feature responsible for the role of NQO1 in antioxidant defense in several tissues. In contrast, NADPH cytochrome P450 oxidoreductase (CYP450OR), catalyzes the 1-electron reduction of quinones and xenobiotics, resulting in enhanced superoxide formation. However, to date, the roles of NQO1 and CYP450OR in pancreatic β-cell metabolism under basal conditions and oxidant challenge have not been characterized. Using NQO1 inhibition, over-expression and knock out, we have demonstrated that, in addition to protection of β-cells from toxic concentrations of the redox cycling quinone menadione, NQO1 also regulates the basal level of reduced-to-oxidized nucleotides, suggesting other role(s) beside that of an antioxidant enzyme. In contrast, over-expression of NADPH cytochrome P450 oxidoreductase (CYP450OR) resulted in enhanced redox cycling activity and decreased cellular viability, consistent with the enhanced generation of superoxide and H 2 O 2 . Basal expression of NQO1 and CYP450OR was comparable in isolated islets and liver. However, NQO1, but not CYP450OR, was strongly induced in β-cells exposed to menadione. NQO1 and CYP450OR exhibited a reciprocal preference for reducing equivalents in β-cells: while CYP450OR preferentially utilized NADPH, NQO1 primarily utilized NADH. Together, these results demonstrate that NQO1 and CYP450OR reciprocally regulate oxidant metabolism in pancreatic β-cells. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

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.

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.

Ebselen: A thioredoxin reductase-dependent catalyst for α-tocopherol quinone reduction

International Nuclear Information System (INIS)

Fang Jianguo; Zhong Liangwei; Zhao Rong; Holmgren, Arne

2005-01-01

The thioredoxin system, composed of thioredoxin (Trx), thioredoxin reductase (TrxR), and NADPH, is a powerful protein disulfide reductase system with a broad substrate specificity. Recently the selenazol drug ebselen was shown to be a substrate for both mammalian TrxR and Trx. We examined if α-tocopherol quinone (TQ), a product of α-tocopherol oxidation, is reduced by ebselen in the presence of TrxR, since TQ was not a substrate for the enzyme itself. Ebselen reduction of TQ in the presence of TrxR was caused by ebselen selenol, generated from fast reduction of ebselen by the enzyme. TQ has no intrinsic antioxidant activity, while the product of reduction of TQ, α-tocopherolhydroquinone (TQH 2 ), is a potent antioxidant. The thioredoxin system dependence of ebselen to catalyze reduction of other oxidized species, such as hydrogen peroxide, dehydroascorbate, and peroxynitrite, is discussed. The ability of ebselen to reduce TQ via the thioredoxin system is a novel mechanism to explain the effects of the drug as an antioxidant in vivo

Regulation of expression of Na+ -translocating NADH:quinone oxidoreductase genes in Vibrio harveyi and Klebsiella pneumoniae.

Science.gov (United States)

Fadeeva, Maria S; Yakovtseva, Evgenia A; Belevich, Galina A; Bertsova, Yulia V; Bogachev, Alexander V

2007-10-01

The expression of genes encoding sodium-translocating NADH:quinone oxidoreductase (Na(+)-NQR) was studied in the marine bacterium Vibrio harveyi and in the enterobacterium Klebsiella pneumoniae. It has been shown that such parameters as NaCl concentration, pH value, and presence of an uncoupler in the growth media do not influence significantly the level of nqr expression. However, nqr expression depends on the growth substrates used by these bacteria. Na(+)-NQR is highly repressed in V. harveyi during anaerobic growth, and nqr expression is modulated by electron acceptors and values of their redox potentials. The latter effect was shown to be independent of the ArcAB regulatory system.

Quinone reduction via secondary B-branch electron transfer in mutant bacterial reaction centers.

Science.gov (United States)

Laible, Philip D; Kirmaier, Christine; Udawatte, Chandani S M; Hofman, Samuel J; Holten, Dewey; Hanson, Deborah K

2003-02-18

Symmetry-related branches of electron-transfer cofactors-initiating with a primary electron donor (P) and terminating in quinone acceptors (Q)-are common features of photosynthetic reaction centers (RC). Experimental observations show activity of only one of them-the A branch-in wild-type bacterial RCs. In a mutant RC, we now demonstrate that electron transfer can occur along the entire, normally inactive B-branch pathway to reduce the terminal acceptor Q(B) on the time scale of nanoseconds. The transmembrane charge-separated state P(+)Q(B)(-) is created in this manner in a Rhodobacter capsulatus RC containing the F(L181)Y-Y(M208)F-L(M212)H-W(M250)V mutations (YFHV). The W(M250)V mutation quantitatively blocks binding of Q(A), thereby eliminating Q(B) reduction via the normal A-branch pathway. Full occupancy of the Q(B) site by the native UQ(10) is ensured (without the necessity of reconstitution by exogenous quinone) by purification of RCs with the mild detergent, Deriphat 160-C. The lifetime of P(+)Q(B)(-) in the YFHV mutant RC is >6 s (at pH 8.0, 298 K). This charge-separated state is not formed upon addition of competitive inhibitors of Q(B) binding (terbutryn or stigmatellin). Furthermore, this lifetime is much longer than the value of approximately 1-1.5 s found when P(+)Q(B)(-) is produced in the wild-type RC by A-side activity alone. Collectively, these results demonstrate that P(+)Q(B)(-) is formed solely by activity of the B-branch carriers in the YFHV RC. In comparison, P(+)Q(B)(-) can form by either the A or B branches in the YFH RC, as indicated by the biexponential lifetimes of approximately 1 and approximately 6-10 s. These findings suggest that P(+)Q(B)(-) states formed via the two branches are distinct and that P(+)Q(B)(-) formed by the B side does not decay via the normal (indirect) pathway that utilizes the A-side cofactors when present. These differences may report on structural and energetic factors that further distinguish the functional

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.

Characterization of PEDOT-Quinone Conducting Redox Polymers for Water Based Secondary Batteries

International Nuclear Information System (INIS)

Sterby, Mia; Emanuelsson, Rikard; Huang, Xiao; Gogoll, Adolf; Strømme, Maria; Sjödin, Martin

2017-01-01

Lithium-ion technologies show great promise to meet the demands that the transition towards renewable energy sources and the electrification of the transport sector put forward. However, concerns regarding lithium-ion batteries, including limited material resources, high energy consumption during production, and flammable electrolytes, necessitate research on alternative technologies for electrochemical energy storage. Organic materials derived from abundant building blocks and with tunable properties, together with water based electrolytes, could provide safe, inexpensive and sustainable alternatives. In this study, two conducting redox polymers based on poly(3,4-ethylenedioxythiophene) (PEDOT) and a hydroquinone pendant group have been synthesized and characterized in an acidic aqueous electrolyte. The polymers were characterized with regards to kinetics, pH dependence, and mass changes during oxidation and reduction, as well as their conductance. Both polymers show redox matching, i.e. the quinone redox reaction occurs within the potential region where the polymer is conducting, and fast redox conversion that involves proton cycling during pendant group redox conversion. These properties make the presented materials promising candidates as electrode materials for water based all-organic batteries.

Expression of NAD(P)H quinone dehydrogenase 1 (NQO1) is increased in the endometrium of women with endometrial cancer and women with polycystic ovary syndrome

DEFF Research Database (Denmark)

Atiomo, William; Shafiee, Mohamad Nasir; Chapman, Caroline

2017-01-01

of differentially expressed genes identified by RNA sequencing, including NAD(P)H quinone dehydrogenase 1 (NQO1), was validated by quantitative reverse transcriptase PCR validation (n = 76) and in the cancer genome atlas UCEC (uterine corpus endometrioid carcinoma) RNA sequencing data set (n = 381). The expression...

Oxadiazole-substituted naphtho[2,3-b]thiophene-4,9-diones as potent inhibitors of keratinocyte hyperproliferation. Structure-activity relationships of the tricyclic quinone skeleton and the oxadiazole substituent

DEFF Research Database (Denmark)

Basoglu, Atila; Dirkmann, Simone; Zahedi Golpayegani, Nader

2017-01-01

Novel analogues of oxadiazole-substituted naphtho[2,3-b]thiophene-4,9-diones were synthesized in which the tricyclic quinone skeleton was systematically replaced with simpler moieties, such as structures with fewer rings and open-chain forms, while the oxadiazole ring was maintained. In addition...

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.

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

Bioorthogonal Metabolic DNA Labelling using Vinyl Thioether-Modified Thymidine and o-Quinolinone Quinone Methide.

Science.gov (United States)

Gubu, Amu; Li, Long; Ning, Yan; Zhang, Xiaoyun; Lee, Seonghyun; Feng, Mengke; Li, Qiang; Lei, Xiaoguang; Jo, Kyubong; Tang, Xinjing

2018-04-17

Bioorthogonal metabolic DNA labeling with fluorochromes is a powerful strategy to visualize DNA molecules and their functions. Here, we report the development of a new DNA metabolic labeling strategy enabled by the catalyst-free bioorthogonal ligation using vinyl thioether modified thymidine and o-quinolinone quinone methide. With the newly designed vinyl thioether-modified thymidine (VTdT), we added labeling tags on cellular DNA, which could further be linked to fluorochromes in cells. Therefore, we successfully visualized the DNA localization within cells as well as single DNA molecules without other staining reagents. In addition, we further characterized this bioorthogonal DNA metabolic labeling using DNase I digestion, MS characterization of VTdT as well as VTdT-oQQF conjugate in cell nuclei or mitochondria. This technique provides a powerful strategy to study DNA in cells, which paves the way to achieve future spatiotemporal deciphering of DNA synthesis and functions. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Inducible Alkylation of DNA by a Quinone Methide-Peptide Nucleic Acid Conjugate†

Science.gov (United States)

Liu, Yang; Rokita, Steven E.

2012-01-01

The reversibility of alkylation by a quinone methide intermediate (QM) avoids the irreversible consumption that plagues most reagents based on covalent chemistry and allows for site specific reaction that is controlled by the thermodynamics rather than kinetics of target association. This characteristic was originally examined with an oligonucleotide QM conjugate but broad application depends on alternative derivatives that are compatible with a cellular environment. Now, a peptide nucleic acid (PNA) derivative has been constructed and shown to exhibit an equivalent ability to delivery the reactive QM in a controlled manner. This new conjugate demonstrates high selectivity for a complementary sequence of DNA even when challenged with an alternative sequence containing a single T/T mismatch. Alkylation of non-complementary sequences is only possible when a template strand is present to co-localize the conjugate and its target. For efficient alkylation in this example, a single-stranded region of the target is required adjacent to the QM conjugate. Most importantly, the intrastrand self adducts formed between the PNA and its attached QM remained active and reversible over more than eight days in aqueous solution prior to reaction with a chosen target added subsequently. PMID:22243337

Carbon nanotube-supported Au-Pd alloy with cooperative effect of metal nanoparticles and organic ketone/quinone groups as a highly efficient catalyst for aerobic oxidation of amines.

Science.gov (United States)

Deng, Weiping; Chen, Jiashu; Kang, Jincan; Zhang, Qinghong; Wang, Ye

2016-05-21

Functionalised carbon nanotube (CNT)-supported Au-Pd alloy nanoparticles were highly efficient catalysts for the aerobic oxidation of amines. We achieved the highest turnover frequencies (>1000 h(-1)) for the oxidative homocoupling of benzylamine and the oxidative dehydrogenation of dibenzylamine. We discovered a cooperative effect between Au-Pd nanoparticles and ketone/quinone groups on CNTs.

Spectroscopic and molecular docking studies on the charge transfer complex of bovine serum albumin with quinone in aqueous medium and its influence on the ligand binding property of the protein

Science.gov (United States)

Satheshkumar, Angupillai; Elango, Kuppanagounder P.

2014-09-01

The spectral techniques such as UV-Vis, 1H NMR and fluorescence and electrochemical experiments have been employed to investigate the interaction between 2-methoxy-3,5,6-trichloro-1,4-benzoquinone (MQ; a water soluble quinone) and bovine serum albumin (BSA) in aqueous medium. The fluorescence of BSA was quenched by MQ via formation of a 1:1 BSA-MQ charge transfer adduct with a formation constant of 3.3 × 108 L mol-1. Based on the Forster’s theory the binding distance between them is calculated as 2.65 nm indicating high probability of binding. For the first time, influence of quinone on the binding property of various types of ligands such as aspirin, ascorbic acid, nicotinimide and sodium stearate has also been investigated. The results indicated that the strong and spontaneous binding existing between BSA and MQ, decreased the intensity of binding of these ligands with BSA. Since Tryptophan (Trp) is the basic residue present in BSA, a comparison between binding property of Trp-MQ adduct with that of BSA-MQ with these ligands has also been attempted. 1H NMR titration study indicated that the Trp forms a charge transfer complex with MQ, which reduces the interaction of Trp with the ligands. Molecular docking study supported the fact that the quinone interacts with the Trp212 unit of the BSA and the free energy change of binding (ΔG) for the BSA-MQ complex was found to be -46 kJ mol-1, which is comparable to our experimental free energy of binding (-49 kJ mol-1) obtained from fluorescence study.

Substrate-bound tyrosinase electrode using gold nanoparticles anchored to pyrroloquinoline quinone for a pesticide biosensor

Energy Technology Data Exchange (ETDEWEB)

Kim, G.Y.; Kang, M.S.; Shim, J.; Moon, S.H. [Gwangju Inst. of Science and Technology (Korea, Republic of). Dept. of Environmental Science and Engineering

2008-07-01

Enzyme electrodes are now being considered for use in the detection of pesticides. However, the electrodes do not have the sensitivity to detect low concentration pesticides, and external substrates are needed to measure changes in enzyme activity. This study discussed a chemical species designed to mimic a substrate in the preparation of a tyrosinase (TYR) electrode for use without substrate standard solutions. Pyrroloquinolone quinone (PQQ) was integrated within the tyrosinase electrode and used as an assimilated substrate for measuring the pesticide. Gold (Au) nanoparticles were also used to detect low concentration pesticides. The TYR was immobilized on the PQQ-anchored Au nanoparticles by a covalent bond. The tethered PQQ was then reduced by obtaining 2-electrons from the electrode. The study showed that the substrate-bound enzyme electrode can be used to detect pesticide without a substrate standard solution through the immobilization of the enzyme and the substrate on the Au nanoparticles.

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.

Membrane protein damage and repair: selective loss of a quinone-protein function in chloroplast membranes

International Nuclear Information System (INIS)

Kyle, D.J.; Ohad, I.; Arntzen, C.J.

1984-01-01

A loss of electron transport capacity in chloroplast membranes was induced by high-light intensities (photoinhibition). The primary site of inhibition was at the reducing side of photosystem II (PSII) with little damage to the oxidizing side or to the reaction center core of PSII. Addition of herbicides (atrazine or diuron) partially protected the membrane from photoinhibition; these compounds displace the bound plastoquinone (designated as Q/sub B/), which functions as the secondary electron acceptor on the reducing side of PSII. Loss of function of the 32-kilodalton Q/sub B/ apoprotein was demonstrated by a loss of binding sites for [ 14 C]atraazine. We suggest that quinone anions, which may interact with molecular oxygen to produce an oxygen radical, selectively damage the apoprotein of the secondary acceptor of PSII, thus rendering it inactive and thereby blocking photosynthetic electron flow under conditions of high photon flux densities. 21 references, 4 figures, 2 tables

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. Copyright © 2014 John Wiley & Sons, Ltd.

Cranberry extract-enriched diets increase NAD(P)H:quinone oxidoreductase and catalase activities in obese but not in nonobese mice.

Science.gov (United States)

Boušová, Iva; Bártíková, Hana; Matoušková, Petra; Lněničková, Kateřina; Zappe, Lukáš; Valentová, Kateřina; Szotáková, Barbora; Martin, Jan; Skálová, Lenka

2015-10-01

Consumption of antioxidant-enriched diets is 1 method of addressing obesity, which is associated with chronic oxidative stress and changes in the activity/expression of various enzymes. In this study, we hypothesized that the modulation of antioxidant enzymes and redox status through a cranberry extract (CBE)-enriched diet would differ between obese and nonobese mice. The CBE used in this study was obtained from the American cranberry (Vaccinium macrocarpon, Ericaceae), a popular constituent of dietary supplements that is a particularly rich source of (poly)phenols and has strong antioxidant properties. The present study was designed to test and compare the in vivo effects of 28-day consumption of a CBE-enriched diet (2%) on the antioxidant status of nonobese mice and mice with monosodium glutamate-induced obesity. Plasma, erythrocytes, liver, and small intestine were studied concurrently to obtain more complex information. The specific activities, protein, and messenger RNA expression levels of antioxidant enzymes as well as the levels of malondialdehyde and thiol (SH) groups were analyzed. Cranberry extract treatment increased the SH group content in plasma and the glutathione S-transferase activity in the erythrocytes of the obese and nonobese mice. In addition, in the obese animals, the CBE treatment reduced the malondialdehyde content in erythrocytes and increased quinone oxidoreductase (liver) and catalase (erythrocytes and small intestine) activities. The elevation of hepatic quinone oxidoreductase activity was accompanied by an increase in the corresponding messenger RNA levels. The effects of CBE on the activity of antioxidant enzymes and redox status were more pronounced in the obese mice compared with the nonobese mice. Copyright © 2015 Elsevier Inc. All rights reserved.

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.

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

International Nuclear Information System (INIS)

Dai, Xi; Du, Zhi-Fang; Wang, Li-Hong; Miao, Jun-Ying; Zhao, Bao-Xiang

2016-01-01

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.

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

Formation of quinones by one-electron oxidation in the metabolism of benzo[a]pyrene and 6-fluorobenzo[a]pyrene

International Nuclear Information System (INIS)

Cavalieri, E.; Wong, A.; Cremonesi, P.; Warner, C.; Rogan, E.

1986-01-01

Metabolic activation of polycyclic aromatic hydrocarbons (PAH), as well as other chemical carcinogens, occurs by two major pathways: One-electron oxidation and two-electron oxidation, or monooxygenation. One-electron oxidation generates radical cations or radicals, depending on the molecule in which the oxidation occurs, whereas two-electron oxidation produces oxygenated metabolites. Radical cations of PAH are ultimate electrophilic metabolites capable of binding to cellular macromolecules to initiate the tumor process. In this paper the authors will provide evidence that one-electron oxidation is involved not only in PAH carcinogenesis, but also in the formation of certain metabolites. Metabolism of benzo[a]pyrene (BP) by cytochrome P-450 monooxygenase yields three classes of products: phenols, dihydrodiols and the quinones, 1,6-, 3,6- and 6,12- dione

A cannabigerol quinone alleviates neuroinflammation in a chronic model of multiple sclerosis.

Science.gov (United States)

Granja, Aitor G; Carrillo-Salinas, Francisco; Pagani, Alberto; Gómez-Cañas, María; Negri, Roberto; Navarrete, Carmen; Mecha, Miriam; Mestre, Leyre; Fiebich, Bend L; Cantarero, Irene; Calzado, Marco A; Bellido, Maria L; Fernandez-Ruiz, Javier; Appendino, Giovanni; Guaza, Carmen; Muñoz, Eduardo

2012-12-01

Phytocannabinoids like ∆(9)-tetrahydrocannabinol (THC) and cannabidiol (CBD) show a beneficial effect on neuroinflammatory and neurodegenerative processes through cell membrane cannabinoid receptor (CBr)-dependent and -independent mechanisms. Natural and synthetic cannabinoids also target the nuclear receptor peroxisome proliferator-activated receptor-gamma (PPARγ), an attractive molecular target for the treatment of neuroinflammation. As part of a study on the SAR of phytocannabinoids, we have investigated the effect of the oxidation modification in the resorcinol moiety of cannabigerol (CBG) on CB(1), CB(2) and PPARγ binding affinities, identifying cannabigerol quinone (VCE-003) as a potent anti-inflammatory agent. VCE-003 protected neuronal cells from excitotoxicity, activated PPARγ transcriptional activity and inhibited the release of pro-inflammatory mediators in LPS-stimulated microglial cells. Theiler's murine encephalomyelitis virus (TMEV) model of multiple sclerosis (MS) was used to investigate the anti-inflammatory activity of this compound in vivo. Motor function performance was evaluated and the neuroinflammatory response and gene expression pattern in brain and spinal cord were studied by immunostaining and qRT-PCR. We found that VCE-003 ameliorated the symptoms associated to TMEV infection, decreased microglia reactivity and modulated the expression of genes involved in MS pathophysiology. These data lead us to consider VCE-003 to have high potential for drug development against MS and perhaps other neuroinflammatory diseases.

Comparison of the Biological Properties of Several Marine Sponge-Derived Sesquiterpenoid Quinones

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Ping Yin

2007-07-01

Full Text Available Eight naturally occurring marine-sponge derived sesquiterpenoid quinones wereevaluated as potential inhibitors of pyruvate phosphate dikinase (PPDK, a C4 plantregulatory enzyme. Of these, the hydroxyquinones ilimaquinone, ethylsmenoquinone andsmenoquinone inhibited PPDK activity with IC50’s (reported with 95% confidenceintervals of 285.4 (256.4 – 317.7, 316.2 (279.2 – 358.1 and 556.0 (505.9 – 611.0 μM,respectively, as well as being phytotoxic to the C4 plant Digitaria ciliaris. The potentialanti-inflammatory activity of these compounds, using bee venom phospholipase A2(PLA2, was also evaluated. Ethylsmenoquinone, smenospongiarine, smenospongidine andilimaquinone inhibited PLA2 activity (% inhibition of 73.2 + 4.8 at 269 μM, 61.5 + 6.1 at242 μM, 41.0 + 0.6 at 224 μM and 36.4 + 8.2 at 279 μM, respectively. SAR analysesindicate that a hydroxyquinone functionality and a short, hydroxide/alkoxide side-chain atC-20 is preferred for inhibition of PPDK activity, and that a larger amine side-chain at C-20 is tolerated for PLA2 inhibitory activity.

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

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Ruphin, Fatiany Pierre; Baholy, Robijaona; Emmanue, Andrianarivo; Amelie, Raharisololalao; Martin, Marie-Therese; Koto-te-Nyiwa, Ngbolua

2013-10-01

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. 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. 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. The results suggest that furthers studies involving antineoplastic activity is needed for the development of this lead compound as anticancer drug. Copyright © 2013 Asian Pacific Tropical Biomedical Magazine. Published by Elsevier B.V. All rights reserved.

Safety of pyrroloquinoline quinone disodium salt as a novel food pursuant to Regulation (EC) No 258/97

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Sjödin, Anders Mikael

2017-01-01

Following a request from the European Commission, the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to deliver an opinion on pyrroloquinoline quinone disodium salt (PQQ), trade name BioPQQTM, as a novel food pursuant to Regulation (EC) No 258/97. PQQ is produced...... by fermentation using Hyphomicrobium denitrificans CK-275 and purification process. PQQ has a minimum purity of 99.0%. The information provided on the composition, specifications, batch-to-batch variability, stability and production process of PQQ is sufficient and does not raise safety concerns. The applicant...... intends to market PQQ for use in food supplements for healthy adults, except pregnant and lactating women, at a maximum proposed level of consumption of 20 mg/day (corresponding to 0.29 mg/kg bw per day for a 70-kg person). The proposed level of consumption is at least 250 times higher than the estimated...

Cyanide as a copper and quinone-directed inhibitor of amine oxidases from pea seedlings ( Pisum sativum) and Arthrobacter globiformis: evidence for both copper coordination and cyanohydrin derivatization of the quinone cofactor.

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Shepard, Eric M; Juda, Gregory A; Ling, Ke-Qing; Sayre, Lawrence M; Dooley, David M

2004-04-01

The interactions of cyanide with two copper-containing amine oxidases (CuAOs) from pea seedlings (PSAO) and the soil bacterium Arthrobacter globiformis (AGAO) have been investigated by spectroscopic and kinetic techniques. Previously, we rationalized the effects of azide and cyanide for several CuAOs in terms of copper coordination by these exogenous ligands and their effects on the internal redox equilibrium TPQ(amr)-Cu(II) right harpoon over left harpoon TPQ(sq)-Cu(I). The mechanism of cyanide inhibition was proposed to occur through complexation to Cu(I), thereby directly competing with O(2) for reoxidation of TPQ. Although cyanide readily and reversibly reacts with quinones, no direct spectroscopic evidence for cyanohydrin derivatization of TPQ has been previously documented for CuAOs. This work describes the first direct spectroscopic evidence, using both model and enzyme systems, for cyanohydrin derivatization of TPQ. K(d) values for Cu(II)-CN(-) and Cu(I)-CN(-), as well as the K(i) for cyanide inhibition versus substrate amine, are reported for PSAO and AGAO. In spite of cyanohydrin derivatization of the TPQ cofactor in these enzymes, the uncompetitive inhibition of amine oxidation is determined to arise almost exclusively through CN(-) complexation of Cu(I).

A new cytotoxic sesquiterpene quinone produced by Penicillium sp. F00120 isolated from a deep sea sediment sample.

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Lin, Xiuping; Zhou, Xuefeng; Wang, Fazuo; Liu, Kaisheng; Yang, Bin; Yang, Xianwen; Peng, Yan; Liu, Juan; Ren, Zhe; Liu, Yonghong

2012-01-01

A new fungal strain, displaying strong toxic activity against brine shrimp larvae, was isolated from a deep sea sediment sample collected at a depth of 1300 m. The strain, designated as F00120, was identified as a member of the genus Penicillium on the basis of morphology and ITS sequence analysis. One new sesquiterpene quinone, named penicilliumin A (1), along with two known compounds ergosterol (2) and ergosterol peroxide (3), were isolated and purified from the cultures of F00120 by silica gel column, Sephadex LH-20 column, and preparative thin layer chromatography. Their structures were elucidated by detailed nuclear magnetic resonance (NMR) and mass spectroscopic (MS) analysis as well as comparison with literature data. The new compound penicilliumin A inhibited in vitro proliferation of mouse melanoma (B16), human melanoma (A375), and human cervical carcinoma (Hela) cell lines moderately.

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.

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

International Nuclear Information System (INIS)

Levova, Katerina; Moserova, Michaela; Nebert, Daniel W.; Phillips, David H.; Frei, Eva; Schmeiser, Heinz H.; Arlt, Volker M.; Stiborova, Marie

2012-01-01

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.

Ultrafast Adiabatic Photodehydration of 2-Hydroxymethylphenol and the Formation of Quinone Methide.

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Škalamera, Đani; Antol, Ivana; Mlinarić-Majerski, Kata; Vančik, Hrvoj; Phillips, David Lee; Ma, Jiani; Basarić, Nikola

2018-04-20

The photochemical reactivity of 2-hydroxymethylphenol (1) was investigated experimentally by photochemistry under cryogenic conditions, by detecting reactive intermediates by IR spectroscopy, and by using nanosecond and femtosecond transient absorption spectroscopic methods in solution at room temperature. In addition, theoretical studies were performed to facilitate the interpretation of the experimental results and also to simulate the reaction pathway to obtain a better understanding of the reaction mechanism. The main finding of this work is that photodehydration of 1 takes place in an ultrafast adiabatic photochemical reaction without any clear intermediate, delivering quinone methide (QM) in the excited state. Upon photoexcitation to a higher vibrational level of the singlet excited state, 1 undergoes vibrational relaxation leading to two photochemical pathways, one by which synchronous elimination of H 2 O gives QM 2 in its S 1 state and the other by which homolytic cleavage of the phenolic O-H bond produces a phenoxyl radical (S 0 ). Both are ultrafast processes that occur within a picosecond. The excited state of QM 2 (S 1 ) probably deactivates to S 0 through a conical intersection to give QM 2 (S 0 ), which subsequently delivers benzoxete 4. Elucidation of the reaction mechanisms for the photodehydration of phenols by which QMs are formed is important to tune the reactivity of QMs with DNA and proteins for the potential application of QMs in medicine as therapeutic agents. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Correlation of quinone reductase activity and allyl isothiocyanate formation among different genotypes and grades of horseradish roots.

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

2015-03-25

Horseradish (Armoracia rusticana) is a perennial crop and its ground root tissue is used in condiments because of the pungency of the glucosinolate (GS)-hydrolysis products allyl isothiocyanate (AITC) and phenethyl isothiocyanate (PEITC) derived from sinigrin and gluconasturtiin, respectively. Horseradish roots are sold in three grades: U.S. Fancy, U.S. No. 1, and U.S. No. 2 according to the USDA standards. These grading standards are primarily based on root diameter and length. There is little information on whether root grades vary in their phytochemical content or potential health promoting properties. This study measured GS, GS-hydrolysis products, potential anticancer activity (as quinone reductase inducing activity), total phenolic content, and antioxidant activities from different grades of horseradish accessions. U.S. Fancy showed significantly higher sinigrin and AITC concentrations than U.S. No. 1 ,whereas U.S. No. 1 showed significantly higher concentrations of 1-cyano 2,3-epithiopropane, the epithionitrile hydrolysis product of sinigrin, and significantly higher total phenolic concentrations than U.S. Fancy.

In vivo relevance of two critical levels for NAD(P)H:quinone oxidoreductase (NQO1)-mediated cellular protection against electrophile toxicity found in vitro.

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de Haan, Laura H J; Pot, Gerda K; Aarts, Jac M M J G; Rietjens, Ivonne M C M; Alink, Gerrit M

2006-08-01

NAD(P)H:quinone oxidoreductase (NQO1)-mediated detoxification of quinones is suggested to be involved in cancer prevention. In the present study, using transfected CHO cells, it was demonstrated that the relation between NQO1 activity and the resulting protection against the cytotoxicity of menadione shows a steep dose-response curve revealing a 'lower protection threshold' of 0.5mumol DCPIP/min/mg protein and an 'upper protection threshold' at 1mumol DCPIP/min/mg protein. In an additional in vivo experiment it was investigated how both in vitro critical activity levels of NQO1, relate to NQO1 activities in mice and man, either without or upon induction of the enzyme by butylated hydroxyanisol (BHA) or indole-3-carbinol (I(3)C). Data from an experiment with CD1 mice revealed that base-line NQO1 levels in liver, kidney, small intestine, colon and lung are generally below the observed 'lower protection threshold' in vitro, this also holds for most human tissue S-9 samples. To achieve NQO1 levels above this 'lower protection threshold' will require 5-20 fold NQO1 induction. Discussion focuses on the relevance of the in vitro NQO1 activity thresholds for the in vivo situation. We conclude that increased protection against menadione toxicity can probably not be achieved by NQO1 induction but should be achieved by other mechanisms. Whether this conclusion also holds for other electrophiles and the in vivo situation awaits further definition of their NQO1 protection thresholds.

Heritable Variation in Quinone-Induced Haustorium Development in the Parasitic Plant Triphysaria1

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Jamison, Denneal S.; Yoder, John I.

2001-01-01

We are using the facultative hemiparasite, Triphysaria, as a model for studying host-parasite signaling in the Scrophulariaceae. Parasitic members of this family form subterranean connections, or haustoria, on neighboring host roots to access host water and nutrients. These parasitic organs develop in response to haustorial-inducing factors contained in host root exudates. A well-characterized inducing factor, 2, 6-dimethoxy-p-benzoquinone (DMBQ), can be used to trigger in vitro haustorium formation in the roots of Triphysaria. We have assayed three species, Triphysaria eriantha (Benth.) Chuang and Heckard, Triphysaria pusilla (Benth.) Chuang and Heckard, and Triphysaria versicolor Fischer and C. Meyer, for haustorium development in response to DMBQ. There were significant differences between the species in their ability to recognize and respond to this quinone. Ninety percent of T. versicolor individuals responded, whereas only 40% of T. pusilla and less than 10% of T. eriantha formed haustoria. Within field collections of self-pollinating T. pusilla, differential responsiveness to DMBQ was seen in distinct maternal families. Assaying haustorium development in subsequent generations of self-pollinated T. pusilla showed that DMBQ responsiveness was heritable. Reciprocal crosses between T. eriantha and T. versicolor demonstrated that DMBQ responsiveness was influenced by maternal factors. These results demonstrate heritable, natural variation in the recognition of a haustorial-inducing factor by a parasitic member of the Scrophulariaceae. PMID:11299366

H32, a non-quinone sulfone analog of vitamin K3, inhibits human hepatoma cell growth by inhibiting Cdc25 and activating ERK.

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Kar, Siddhartha; Wang, Meifang; Ham, Seung Wook; Carr, Brian I

2006-10-01

We previously synthesized a K-vitamin derivative, Cpd 5, which was a potent growth inhibitor of human tumor cells, including Hep3B hepatoma cells. However, being a quinone compound, Cpd 5 has the potential for generating toxic reactive oxygen species (ROS). We therefore synthesized a nonquinone sulfone derivative, H32, which has a sufone group substituting the quinone. The IC50 of H32 for Hep3B cells was found to be 2.5 microM, which was 2.5 and 3.2 times more potent than Cpd 5 and vitamin K3 respectively. It induced apoptosis in Hep3B cells but did not generate ROS when compared to Cpd 5. Interestingly, under similar culture conditions, normal rat hepatocytes were 14-fold more and 7-fold more resistant to the growth inhibitory effects of H32 than Hep3B and PLC/PRF5 cells respectively. H32 preferentially inhibited the activities of the cell cycle controlling Cdc25A phosphatase likely by binding to its catalytic cysteine. As a consequence, it induced inhibitory tyrosine phosphorylation of the Cdc25 substrate kinases Cdk2 and Cdk4 in Hep3B cells and the cells undergo an arrest in the G1 phase of the cell cycle. H32 also induced persistent phosphorylation of the MAPK protein ERK1/2, but marginal JNK1/2 and p38 phosphorylation. The ERK inhibitor U0126, added at least 30 min prior to H32, antagonized the growth inhibition induced by H32. However, the JNK and p38 inhibitors, JNKI-II and SB203580, were not able to antagonize H32 induced growth inhibition. Thus, H32 differentially inhibited growth of normal and liver tumor cells by preferentially inhibiting the actions of Cdc25 phosphatases and inducing persistent ERK phosphorylation.

Role of Quinone Reductase 2 in the Antimalarial Properties of Indolone-Type Derivatives

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Laure-Estelle Cassagnes

2017-01-01

Full Text Available Indolone-N-oxides have antiplasmodial properties against Plasmodium falciparum at the erythrocytic stage, with IC50 values in the nanomolar range. The mechanism of action of indolone derivatives involves the production of free radicals, which follows their bioreduction by an unknown mechanism. In this study, we hypothesized that human quinone reductase 2 (hQR2, known to act as a flavin redox switch upon binding to the broadly used antimalarial chloroquine, could be involved in the activity of the redox-active indolone derivatives. Therefore, we investigated the role of hQR2 in the reduction of indolone derivatives. We analyzed the interaction between hQR2 and several indolone-type derivatives by examining enzymatic kinetics, the substrate/protein complex structure with X-ray diffraction analysis, and the production of free radicals with electron paramagnetic resonance. The reduction of each compound in cells overexpressing hQR2 was compared to its reduction in naïve cells. This process could be inhibited by the specific hQR2 inhibitor, S29434. These results confirmed that the anti-malarial activity of indolone-type derivatives was linked to their ability to serve as hQR2 substrates and not as hQR2 inhibitors as reported for chloroquine, leading to the possibility that substrate of hQR2 could be considered as a new avenue for the design of new antimalarial compounds.

The pea SAD short-chain dehydrogenase/reductase: quinone reduction, tissue distribution, and heterologous expression.

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Scherbak, Nikolai; Ala-Häivälä, Anneli; Brosché, Mikael; Böwer, Nathalie; Strid, Hilja; Gittins, John R; Grahn, Elin; Eriksson, Leif A; Strid, Åke

2011-04-01

The pea (Pisum sativum) tetrameric short-chain alcohol dehydrogenase-like protein (SAD) family consists of at least three highly similar members (SAD-A, -B, and -C). According to mRNA data, environmental stimuli induce SAD expression. The aim of this study was to characterize the SAD proteins by examining their catalytic function, distribution in pea, and induction in different tissues. In enzyme activity assays using a range of potential substrates, the SAD-C enzyme was shown to reduce one- or two-ring-membered quinones lacking long hydrophobic hydrocarbon tails. Immunological assays using a specific antiserum against the protein demonstrated that different tissues and cell types contain small amounts of SAD protein that was predominantly located within epidermal or subepidermal cells and around vascular tissue. Particularly high local concentrations were observed in the protoderm of the seed cotyledonary axis. Two bow-shaped rows of cells in the ovary and the placental surface facing the ovule also exhibited considerable SAD staining. Ultraviolet-B irradiation led to increased staining in epidermal and subepidermal cells of leaves and stems. The different localization patterns of SAD suggest functions both in development and in responses to environmental stimuli. Finally, the pea SAD-C promoter was shown to confer heterologous wound-induced expression in Arabidopsis (Arabidopsis thaliana), which confirmed that the inducibility of its expression is regulated at the transcriptional level.

Spectrofluorimetric determination of gemifloxacin mesylate and linezolid in pharmaceutical formulations: Application of quinone-based fluorophores and enhanced native fluorescence

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Moussa Bahia Abbas

2014-03-01

Full Text Available Quinone-based fluorophores and enhanced native fluorescence techniques were applied for a fast quantitative analysis of gemifloxacin mesylate (GEM and linezolid (LIN in pharmaceutical formulations. For this purpose, three sensitive, accurate and precise spectrofluorimetric methods were developed. GEM, as an n-electron donor, reacts with 7,7,8,8-tetracyanoquinodimethane (method A and 2,5-dichloro-3,6-dihydroxy-p-benzoquinone (method B as п-electron acceptors, forming charge transfer complexes that exhibit high fluorescence intensity at 441 and 390 nm upon excitation at 260 and 339 nm, respectively. Method C depends on measurement of enhanced native fluorescence of LIN in phosphate buffer (pH 5 at 380 nm upon excitation at 260 nm. Experimental factors affecting fluorescence intensity were optimized. Linearity was obtained over concentration ranges 50-500, 10-60 and 20-400 ng mL-1 for methods A, B and C, respectively. The developed methods were validated and successfully applied for determination of the cited drugs in tablets.

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

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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.

Transient Kinetic Analysis of Hydrogen Sulfide Oxidation Catalyzed by Human Sulfide Quinone Oxidoreductase*

Science.gov (United States)

Mishanina, Tatiana V.; Yadav, Pramod K.; Ballou, David P.; Banerjee, Ruma

2015-01-01

The first step in the mitochondrial sulfide oxidation pathway is catalyzed by sulfide quinone oxidoreductase (SQR), which belongs to the family of flavoprotein disulfide oxidoreductases. During the catalytic cycle, the flavin cofactor is intermittently reduced by sulfide and oxidized by ubiquinone, linking H2S oxidation to the electron transfer chain and to energy metabolism. Human SQR can use multiple thiophilic acceptors, including sulfide, sulfite, and glutathione, to form as products, hydrodisulfide, thiosulfate, and glutathione persulfide, respectively. In this study, we have used transient kinetics to examine the mechanism of the flavin reductive half-reaction and have determined the redox potential of the bound flavin to be −123 ± 7 mV. We observe formation of an unusually intense charge-transfer (CT) complex when the enzyme is exposed to sulfide and unexpectedly, when it is exposed to sulfite. In the canonical reaction, sulfide serves as the sulfur donor and sulfite serves as the acceptor, forming thiosulfate. We show that thiosulfate is also formed when sulfide is added to the sulfite-induced CT intermediate, representing a new mechanism for thiosulfate formation. The CT complex is formed at a kinetically competent rate by reaction with sulfide but not with sulfite. Our study indicates that sulfide addition to the active site disulfide is preferred under normal turnover conditions. However, under pathological conditions when sulfite concentrations are high, sulfite could compete with sulfide for addition to the active site disulfide, leading to attenuation of SQR activity and to an alternate route for thiosulfate formation. PMID:26318450

Transient Kinetic Analysis of Hydrogen Sulfide Oxidation Catalyzed by Human Sulfide Quinone Oxidoreductase.

Science.gov (United States)

Mishanina, Tatiana V; Yadav, Pramod K; Ballou, David P; Banerjee, Ruma

2015-10-09

The first step in the mitochondrial sulfide oxidation pathway is catalyzed by sulfide quinone oxidoreductase (SQR), which belongs to the family of flavoprotein disulfide oxidoreductases. During the catalytic cycle, the flavin cofactor is intermittently reduced by sulfide and oxidized by ubiquinone, linking H2S oxidation to the electron transfer chain and to energy metabolism. Human SQR can use multiple thiophilic acceptors, including sulfide, sulfite, and glutathione, to form as products, hydrodisulfide, thiosulfate, and glutathione persulfide, respectively. In this study, we have used transient kinetics to examine the mechanism of the flavin reductive half-reaction and have determined the redox potential of the bound flavin to be -123 ± 7 mV. We observe formation of an unusually intense charge-transfer (CT) complex when the enzyme is exposed to sulfide and unexpectedly, when it is exposed to sulfite. In the canonical reaction, sulfide serves as the sulfur donor and sulfite serves as the acceptor, forming thiosulfate. We show that thiosulfate is also formed when sulfide is added to the sulfite-induced CT intermediate, representing a new mechanism for thiosulfate formation. The CT complex is formed at a kinetically competent rate by reaction with sulfide but not with sulfite. Our study indicates that sulfide addition to the active site disulfide is preferred under normal turnover conditions. However, under pathological conditions when sulfite concentrations are high, sulfite could compete with sulfide for addition to the active site disulfide, leading to attenuation of SQR activity and to an alternate route for thiosulfate formation. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Rhodium-catalyzed C-H bond activation for the synthesis of quinonoid compounds: Significant Anti-Trypanosoma cruzi activities and electrochemical studies of functionalized quinones.

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Jardim, Guilherme A M; Silva, Thaissa L; Goulart, Marilia O F; de Simone, Carlos A; Barbosa, Juliana M C; Salomão, Kelly; de Castro, Solange L; Bower, John F; da Silva Júnior, Eufrânio N

2017-08-18

Thirty four halogen and selenium-containing quinones, synthesized by rhodium-catalyzed C-H bond activation and palladium-catalyzed cross-coupling reactions, were evaluated against bloodstream trypomastigotes of T. cruzi. We have identified fifteen compounds with IC 50 /24 h values of less than 2 μM. Electrochemical studies on A-ring functionalized naphthoquinones were also performed aiming to correlate redox properties with trypanocidal activity. For instance, (E)-5-styryl-1,4-naphthoquinone 59 and 5,8-diiodo-1,4-naphthoquinone 3, which are around fifty fold more active than the standard drug benznidazole, are potential derivatives for further investigation. These compounds represent powerful new agents useful in Chagas disease therapy. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

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

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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.

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

International Nuclear Information System (INIS)

Maeda, Tomoji; Tanabe-Fujimura, Chiaki; Fujita, Yu; Abe, Chihiro; Nanakida, Yoshino; Zou, Kun; Liu, Junjun; Liu, Shuyu; Nakajima, Toshihiro; Komano, Hiroto

2016-01-01

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.

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

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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. Copyright © 2014 Elsevier Ltd. All rights reserved.

Whole cell Deinococcus radiodurans ameliorates salt stress in Indian mustard through pyrroloquinoline quinone

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Srivastava, A.K.; Jadhav, P.; Suprasanna, P.; Rajpurohit, Y.S.; Misra, H.S.

2015-01-01

Salinity stress is considered as one of the major abiotic stresses limiting crop productivity. A variety of symbiotic and non-symbiotic bacteria are currently being used worldwide with the aim to boost built-in defense system in plants. Deinococcus radiodurans is a highly desiccation and radiation tolerant bacterium which synthesizes PQQ (pyrroloquinoline quinone) that has been shown to have a versatile role in crop productivity and as a general stress response regulator in bacteria and mammals. PQQ also acts as scavenger of reactive oxygen species and hence, can module redox signaling, one of the major regulator of stress tolerance in plants. In view of this, present research was conducted to evaluate the potential of whole cell D. radiodurans for ameliorating salt stress in plants. The soil colonization with wild-type cells led to partial amelioration of salt stress. The PQQ mutant showed an intermediate phenotype between wild-type seedlings and those grown on non-colonized soils which confirmed that the effects are largely associated with PQQ. The differential phenotype was also correlated with ROS level and ABA accumulation. The flame photometry data showed that there was no significant reduction in water soluble Na + level in control plant and those treated with either wild-type or PQQ mutant. Further, the elevated levels of antioxidant enzymes and reduced ascorbate in the plants treated with bacterial cells indicated its positive role in oxidative stress management. Although, the exact molecular basis to these effects is yet to be understood, present findings support the use of whole cell D. radiodurans for managing the growth and productivity of Indian mustard in salt affected fields. (author)

On the Catalytic Effect of Water in the Intramolecular Diels–Alder Reaction of Quinone Systems: A Theoretical Study

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Renato Contreras

2012-11-01

Full Text Available The mechanism of the intramolecular Diels–Alder (IMDA reaction of benzoquinone 1, in the absence and in the presence of three water molecules, 1w, has been studied by means of density functional theory (DFT methods, using the M05-2X and B3LYP functionals for exploration of the potential energy surface (PES. The energy and geometrical results obtained are complemented with a population analysis using the NBO method, and an analysis based on the global, local and group electrophilicity and nucleophilicity indices. Both implicit and explicit solvation emphasize the increase of the polarity of the reaction and the reduction of activation free energies associated with the transition states (TSs of this IMDA process. These results are reinforced by the analysis of the reactivity indices derived from the conceptual DFT, which show that the increase of the electrophilicity of the quinone framework by the hydrogen-bond formation correctly explains the high polar character of this intramolecular process. Large polarization at the TSs promoted by hydrogen-bonds and implicit solvation by water together with a high electrophilicity-nucleophilicity difference consistently explains the catalytic effects of water molecules.

A self-powered glucose biosensor based on pyrolloquinoline quinone glucose dehydrogenase and bilirubin oxidase operating under physiological conditions.

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Kulkarni, Tanmay; Slaughter, Gymama

2017-07-01

A novel biosensing system capable of simultaneously sensing glucose and powering portable electronic devices such as a digital glucometer is described. The biosensing system consists of enzymatic glucose biofuel cell bioelectrodes functionalized with pyrolloquinoline quinone glucose dehydrogenase (PQQ-GDH) and bilirubin oxidase (BOD) at the bioanode and biocathode, respectively. A dual-stage power amplification circuit is integrated with the single biofuel cell to amplify the electrical power generated. In addition, a capacitor circuit was incorporated to serve as the transducer for sensing glucose. The open circuit voltage of the optimized biofuel cell reached 0.55 V, and the maximum power density achieved was 0.23 mW/ cm 2 at 0.29 V. The biofuel cell exhibited a sensitivity of 0.312 mW/mM.cm 2 with a linear dynamic range of 3 mM - 20 mM glucose. The overall self-powered glucose biosensor is capable of selectively screening against common interfering species, such as ascorbate and urate and exhibited an operational stability of over 53 days, while maintaining 90 % of its activity. These results demonstrate the system's potential to replace the current glucose monitoring devices that rely on external power supply, such as a battery.

Altering pyrroloquinoline quinone nutritional status modulates mitochondrial, lipid, and energy metabolism in rats.

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Kathryn Bauerly

Full Text Available We have reported that pyrroloquinoline quinone (PQQ improves reproduction, neonatal development, and mitochondrial function in animals by mechanisms that involve mitochondrial related cell signaling pathways. To extend these observations, the influence of PQQ on energy and lipid relationships and apparent protection against ischemia reperfusion injury are described herein. Sprague-Dawley rats were fed a nutritionally complete diet with PQQ added at either 0 (PQQ- or 2 mg PQQ/Kg diet (PQQ+. Measurements included: 1 serum glucose and insulin, 2 total energy expenditure per metabolic body size (Wt(3/4, 3 respiratory quotients (in the fed and fasted states, 4 changes in plasma lipids, 5 the relative mitochondrial amount in liver and heart, and 6 indices related to cardiac ischemia. For the latter, rats (PQQ- or PQQ+ were subjected to left anterior descending occlusions followed by 2 h of reperfusion to determine PQQ's influence on infarct size and myocardial tissue levels of malondialdehyde, an indicator of lipid peroxidation. Although no striking differences in serum glucose, insulin, and free fatty acid levels were observed, energy expenditure was lower in PQQ- vs. PQQ+ rats and energy expenditure (fed state was correlated with the hepatic mitochondrial content. Elevations in plasma di- and triacylglyceride and β-hydroxybutryic acid concentrations were also observed in PQQ- rats vs. PQQ+ rats. Moreover, PQQ administration (i.p. at 4.5 mg/kg BW for 3 days resulted in a greater than 2-fold decrease in plasma triglycerides during a 6-hour fast than saline administration in a rat model of type 2 diabetes. Cardiac injury resulting from ischemia/reperfusion was more pronounced in PQQ- rats than in PQQ+ rats. Collectively, these data demonstrate that PQQ deficiency impacts a number of parameters related to normal mitochondrial function.

Influence of adding pyrroloquinoline quinone to parenteral nutrition on gut-associated lymphoid tissue.

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Omata, Jiro; Fukatsu, Kazuhiko; Murakoshi, Satoshi; Moriya, Tomoyuki; Ueno, Chikara; Maeshima, Yoshinori; Okamoto, Koichi; Saitoh, Daizoh; Yamamoto, Junji; Hase, Kazuo

2011-09-01

Experimental intravenous (IV) parenteral nutrition (PN) diminishes gut-associated lymphoid tissue (GALT) cell number and function. PN solution cannot maintain GALT at the same level as a normal diet, even when delivered intragastrically (IG). Previous studies demonstrated pyrroloquinoline quinone (PQQ)-deficient mice to be less immunologically responsive. Because standard (STD) PN solution lacks PQQ, PQQ supplementation may prevent PN-induced GALT changes. This study was designed to determine the influence of adding PQQ to PN on GALT. In experiment 1, mice (n = 32) were randomized to chow, IV-STD-PN, and IV-PQQ-PN groups. The chow group was fed chow with the same caloric content as PN. The IV-STD-PN group received STD-PN solution, whereas the IV-PQQ-PN group was given PQQ (3 mcg/d)-enriched PN by the IV route. After 5 days of feeding, lymphocytes were isolated from the Peyer's patch (PPs), intraepithelial space (IE), and lamina propria (LP) of the small intestine. GALT lymphocyte number and phenotype (αβTCR+, γδTCR+, CD4+, CD8+, B220+ cells) and intestinal immunoglobulin A (IgA) level were determined. In experiment 2, mice (n = 28) were randomized to IG-STD-PN or IG-PQQ-PN group. After IG nutrition supports, GALT mass and function were determined as in experiment 1. The IV-PQQ-PN group showed increased PP lymphocyte number and PP CD8+ cell number compared with the IV-STD PN group. The IG-PQQ-PN group had significantly greater PP lymphocyte number and PP CD4+ cell numbers than the IG-STD-PN group. Neither IV nor IG PQQ treatment raised IgA level. PQQ added to PN partly restores GALT mass, although its effects on GALT function remain unclear.

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

International Nuclear Information System (INIS)

Sun, Bin; Hoshino, Juma; Jermihov, Katie; Marler, Laura; Pezzuto, John M.; Mesecar, Andrew D.; Cushman, Mark

2010-01-01

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 50 0.59 μM) 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 50 70 nM) and 84 (IC 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 50 of 80 μM. In addition to aromatase inhibitory activity, compounds 32 and 44 also displayed potent QR2 inhibitory activity (IC 50 1.7 μM and 0.27 μM, 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.

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

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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.

The Pea SAD Short-Chain Dehydrogenase/Reductase: Quinone Reduction, Tissue Distribution, and Heterologous Expression1[W][OA

Science.gov (United States)

Scherbak, Nikolai; Ala-Häivälä, Anneli; Brosché, Mikael; Böwer, Nathalie; Strid, Hilja; Gittins, John R.; Grahn, Elin; Eriksson, Leif A.; Strid, Åke

2011-01-01

The pea (Pisum sativum) tetrameric short-chain alcohol dehydrogenase-like protein (SAD) family consists of at least three highly similar members (SAD-A, -B, and -C). According to mRNA data, environmental stimuli induce SAD expression. The aim of this study was to characterize the SAD proteins by examining their catalytic function, distribution in pea, and induction in different tissues. In enzyme activity assays using a range of potential substrates, the SAD-C enzyme was shown to reduce one- or two-ring-membered quinones lacking long hydrophobic hydrocarbon tails. Immunological assays using a specific antiserum against the protein demonstrated that different tissues and cell types contain small amounts of SAD protein that was predominantly located within epidermal or subepidermal cells and around vascular tissue. Particularly high local concentrations were observed in the protoderm of the seed cotyledonary axis. Two bow-shaped rows of cells in the ovary and the placental surface facing the ovule also exhibited considerable SAD staining. Ultraviolet-B irradiation led to increased staining in epidermal and subepidermal cells of leaves and stems. The different localization patterns of SAD suggest functions both in development and in responses to environmental stimuli. Finally, the pea SAD-C promoter was shown to confer heterologous wound-induced expression in Arabidopsis (Arabidopsis thaliana), which confirmed that the inducibility of its expression is regulated at the transcriptional level. PMID:21343423

Sensitivity of hiPSC-derived neural stem cells (NSC) to Pyrroloquinoline quinone depends on their developmental stage.

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Augustyniak, J; Lenart, J; Zychowicz, M; Lipka, G; Gaj, P; Kolanowska, M; Stepien, P P; Buzanska, L

2017-12-01

Pyrroloquinoline quinone (PQQ) is a factor influencing on the mitochondrial biogenesis. In this study the PQQ effect on viability, total cell number, antioxidant capacity, mitochondrial biogenesis and differentiation potential was investigated in human induced Pluripotent Stem Cells (iPSC) - derived: neural stem cells (NSC), early neural progenitors (eNP) and neural progenitors (NP). Here we demonstrated that sensitivity to PQQ is dependent upon its dose and neural stage of development. Induction of the mitochondrial biogenesis by PQQ at three stages of neural differentiation was evaluated at mtDNA, mRNA and protein level. Changes in NRF1, TFAM and PPARGC1A gene expression were observed at all developmental stages, but only at eNP were correlated with the statistically significant increase in the mtDNA copy numbers and enhancement of SDHA, COX-1 protein level. Thus, the "developmental window" of eNP for PQQ-evoked mitochondrial biogenesis is proposed. This effect was independent of high antioxidant capacity of PQQ, which was confirmed in all tested cell populations, regardless of the stage of hiPSC neural differentiation. Furthermore, a strong induction of GFAP, with down regulation of MAP2 gene expression upon PQQ treatment was observed. This indicates a possibility of shifting the balance of cell differentiation in the favor of astroglia, but more research is needed at this point. Copyright © 2017 Elsevier Ltd. All rights reserved.

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

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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·.

Exogenous Methyl Jasmonate Treatment Increases Glucosinolate Biosynthesis and Quinone Reductase Activity in Kale Leaf Tissue

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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. PMID:25084454

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

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Zhang, Shaojie; Patel, Ananddeep; Moorthy, Bhagavatula; Shivanna, Binoy, E-mail: shivanna@bcm.edu

2015-11-13

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. - Highlights: • We investigated whether omeprazole induces NQO1 in human fetal lung cells. • Omeprazole induces the phase II enzyme, NQO1, in human fetal lung cells. • AhR deficiency fails to abrogate omeprazole-mediated induction of NQO1. • Omeprazole increases phosphoNrf2 (S40) protein expression in human fetal lung cells. • Nrf2 knockdown abrogates the induction of NQO1 by omeprazole in human lung cells.

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.

Radioprotection on nucleated and anucleated erythrocytes by oxide-reduction coenzymes

International Nuclear Information System (INIS)

Fernandez, M.; Tomicic, I.; Rojo, I.

1981-01-01

The protective effects of NAD, FAD and quinone and mixtures of these compounds were studied on gamma irradiated rabbit and chicken erythrocytes. The dose relative factor (DRF 37) was evaluated by visible absorbancy measurements of liberated hemoglobin. The DRF 37 obtained on rabbit erythrocytes were: NAD+FAD+quinone mixture: 11,1; NAD+ quinone mixture: 6,1; FAD+quinone mixture: 6,1; NAD: 1,6; FAD: 5,5; quinone: 5,1. The DRF 37 obtained with the mixture NAD+FAD+quinone on chicken erythrocytes was 3,9. The high efficiency of the radioprotective mixture NAD+FAD+ quinone is discussed. (author)

Heterologous expression of pyrroloquinoline quinone (pqq) gene cluster confers mineral phosphate solubilization ability to Herbaspirillum seropedicae Z67.

Science.gov (United States)

Wagh, Jitendra; Shah, Sonal; Bhandari, Praveena; Archana, G; Kumar, G Naresh

2014-06-01

Gluconic acid secretion mediated by the direct oxidation of glucose by pyrroloquinoline quinone (PQQ)-dependent glucose dehydrogenase (GDH) is responsible for mineral phosphate solubilization in Gram-negative bacteria. Herbaspirillum seropedicae Z67 (ATCC 35892) genome encodes GDH apoprotein but lacks genes for the biosynthesis of its cofactor PQQ. In this study, pqqE of Erwinia herbicola (in plasmid pJNK1) and pqq gene clusters of Pseudomonas fluorescens B16 (pOK53) and Acinetobacter calcoaceticus (pSS2) were over-expressed in H. seropedicae Z67. Transformants Hs (pSS2) and Hs (pOK53) secreted micromolar levels of PQQ and attained high GDH activity leading to secretion of 33.46 mM gluconic acid when grown on 50 mM glucose while Hs (pJNK1) was ineffective. Hs (pJNK1) failed to solubilize rock phosphate, while Hs (pSS2) and Hs (pOK53) liberated 125.47 μM and 168.07 μM P, respectively, in minimal medium containing 50 mM glucose under aerobic conditions. Moreover, under N-free minimal medium, Hs (pSS2) and Hs (pOK53) not only released significant P but also showed enhanced growth, biofilm formation, and exopolysaccharide (EPS) secretion. However, indole acetic acid (IAA) production was suppressed. Thus, the addition of the pqq gene cluster, but not pqqE alone, is sufficient for engineering phosphate solubilization in H. seropedicae Z67 without compromising growth under nitrogen-fixing conditions.

Energy of Intramolecular Hydrogen Bonding in ortho-Hydroxybenzaldehydes, Phenones and Quinones. Transfer of Aromaticity from ipso-Benzene Ring to the Enol System(s

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Danuta Rusinska-Roszak

2017-03-01

Full Text Available Intramolecular hydrogen bonding (HB is one of the most studied noncovalent interactions of molecules. Many physical, spectral, and topological properties of compounds are under the influence of HB, and there are many parameters used to notice and to describe these changes. Hitherto, no general method of measurement of the energy of intramolecular hydrogen bond (EHB has been put into effect. We propose the molecular tailoring approach (MTA for EHB calculation, modified to apply it to Ar-O-H∙∙∙O=C systems. The method, based on quantum calculations, was checked earlier for hydroxycarbonyl-saturated compounds, and for structures with resonance-assisted hydrogen bonding (RAHB. For phenolic compounds, the accuracy, repeatability, and applicability of the method is now confirmed for nearly 140 structures. For each structure its aromaticity HOMA indices were calculated for the central (ipso ring and for the quasiaromatic rings given by intramolecular HB. The comparison of calculated HB energies and values of estimated aromaticity indices allowed us to observe, in some substituted phenols and quinones, the phenomenon of transfer of aromaticity from the ipso-ring to the H-bonded ring via the effect of electron delocalization.

Tuning cofactor redox potentials: the 2-methoxy dihedral angle generates a redox potential difference of >160 mV between the primary (Q(A)) and secondary (Q(B)) quinones of the bacterial photosynthetic reaction center.

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

2013-10-15

Only quinones with a 2-methoxy group can act simultaneously as the primary (QA) and secondary (QB) electron acceptors in photosynthetic reaction centers from Rhodobacter sphaeroides. (13)C hyperfine sublevel correlation measurements of the 2-methoxy in the semiquinone states, SQA and SQB, were compared with quantum mechanics calculations of the (13)C couplings as a function of the 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 analogue lacking the 2-methoxy to function as QB in mutant reaction centers with a ΔEm of ≈160-195 mV.

Quinone-functionalized activated carbon improves the reduction of congo red coupled to the removal of p-cresol in a UASB reactor.

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Alvarez, Luis H; Arvizu, Iris C; García-Reyes, Refugio Bernardo; Martinez, Claudia M; Olivo-Alanis, Daniel; Del Angel, Yair A

2017-09-15

In this research was immobilized anthraquinone-2-sulfonate (AQS) on granular activated carbon (GAC) to evaluate its capacity to reduce congo red (CR) in batch reactor and continuous UASB reactors. The removal of p-cresol coupled to the reduction of CR was also evaluated. Results show that the immobilization of AQS on GAC (GAC-AQS) achieved 0.469mmol/g, improving 2.85-times the electron-transferring capacity compared to unmodified GAC. In batch, incubations with GAC-AQS achieved a rate of decolorization of 2.64-fold higher than the observed with GAC. Decolorization efficiencies in UASB reactor with GAC-AQS were 83.9, 82, and 79.9% for periods I, II, and III; these values were 14.9-22.8% higher than the obtained by reactor with unmodified GAC using glucose as energy source. In the fourth period, glucose and p-cresol were simultaneously fed, increasing the decolorization efficiency to 87% for GAC-AQS and 72% for GAC. Finally, reactors efficiency decreased when p-cresol was the only energy source, but systems gradually recovered the decolorization efficiency up to 84% (GAC-AQS) and 71% (GAC) after 250 d. This study demonstrates the longest and efficient continuous UASB reactor operation for the reduction of electron-accepting contaminant in presence of quinone-functionalized GAC, but also using a recalcitrant pollutant as electron donor. Copyright © 2017 Elsevier B.V. All rights reserved.

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

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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

Inhibition of melanoma cell proliferation by resveratrol is correlated with upregulation of quinone reductase 2 and p53

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Hsieh Tzechen; Wang Zhirong; Hamby, Carl V.; Wu, Joseph M.

2005-01-01

Resveratrol (trans-3,4',5-trihydroxystilbene) is a grape-derived polyphenol under intensive study for its potential in cancer prevention. In the case of cultured human melanoma cells, no one to our knowledge has investigated whether resveratrol exerts similar anti-proliferative activities in cells with different metastatic potential. Therefore, we examined the effects of this polyphenol on the growth of weakly metastatic Line IV clone 3 and on autologous, highly metastatic Line IV clone 1 cultured melanoma cells. Comparable inhibition of growth and colony formation resulted from treatment by resveratrol in both cell lines. Flow cytometric analysis revealed that resveratrol-treated clone 1 cells had a dose-dependent increase in S phase and a concomitant reduction in the G 1 phase. No detectable change in cell cycle phase distribution was found in similarly treated clone 3 cells. Western blots demonstrated a significant increase in the expression of the tumor suppressor gene p53, without a commensurate change in p21 and several other cell cycle regulatory proteins in both cell types. Chromatography of Line IV clone 3 and clone 1 cell extracts on resveratrol affinity columns revealed that the basal expression of dihydronicotinamide riboside quinone reductase 2 (NQO2) was higher in Line IV clone 1 than clone 3 cells. Levels of NQO2 but not its structural analog NQO1 were dose-dependently increased by resveratrol in both cell lines. We propose that induction of NQO2 may relate to the observed increased expression of p53 that, in turn, contributes to the observed suppression of cell growth in both melanoma cell lines

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

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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. CoCl 2  · 6H 2 O, ρ-amino benzoic acid, and MgSO 4  · 7H 2 O 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.

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

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

2010-04-09

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. Copyright 2009 Elsevier Inc. All rights reserved.

Methyl Jasmonate and 1-Methylcyclopropene Treatment Effects on Quinone Reductase Inducing Activity and Post-Harvest Quality of Broccoli

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Ku, Kang Mo; Choi, Jeong Hee; Kim, Hyoung Seok; Kushad, Mosbah M.; Jeffery, Elizabeth H.; Juvik, John A.

2013-01-01

Effect of pre-harvest methyl jasmonate (MeJA) and post-harvest 1-methylcyclopropene (1-MCP) treatments on broccoli floret glucosinolate (GS) concentrations and quinone reductase (QR, an in vitro anti-cancer biomarker) inducing activity were evaluated two days prior to harvest, at harvest and at 10, 20, and 30 days of post-harvest storage at 4 °C. MeJA treatments four days prior to harvest of broccoli heads was observed to significantly increase floret ethylene biosynthesis resulting in chlorophyll catabolism during post-harvest storage and reduced product quality. Post-harvest treatment with 1-methylcyclopropene (1-MCP), which competitively binds to protein ethylene receptors, maintained post-harvest floret chlorophyll concentrations and product visual quality in both control and MeJA-treated broccoli. Transcript abundance of BoPPH, a gene which is responsible for the synthesis of pheophytinase, the primary enzyme associated with chlorophyll catabolism in broccoli, was reduced by 1-MCP treatment and showed a significant, negative correlation with floret chlorophyll concentrations. The GS, glucobrassicin, neoglucobrassicin, and gluconasturtiin were significantly increased by MeJA treatments. The products of some of the GS from endogenous myrosinase hydrolysis [sulforaphane (SF), neoascorbigen (NeoASG), N-methoxyindole-3-carbinol (NI3C), and phenethyl isothiocyanate (PEITC)] were also quantified and found to be significantly correlated with QR. Sulforaphane, the isothiocyanate hydrolysis product of the GS glucoraphanin, was found to be the most potent QR induction agent. Increased sulforaphane formation from the hydrolysis of glucoraphanin was associated with up-regulated gene expression of myrosinase (BoMyo) and the myrosinase enzyme co-factor gene, epithiospecifier modifier1 (BoESM1). This study demonstrates the combined treatment of MeJA and 1-MCP increased QR activity without post-harvest quality loss. PMID:24146962

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.

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Paz, Tiago Antunes; dos Santos, Vânia A F F M; Inácio, Marielle Cascaes; Pina, Edieidia Souza; Pereira, Ana Maria Soares; Furlan, Maysa

2013-01-01

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  μ g·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.

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

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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.

Anticancer activity of Nigella sativa (black seed) and its relationship with the thermal processing and quinone composition of the seed.

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Agbaria, Riad; Gabarin, Adi; Dahan, Arik; Ben-Shabat, Shimon

2015-01-01

The traditional preparation process of Nigella sativa (NS) oil starts with roasting of the seeds, an allegedly unnecessary step that was never skipped. The aims of this study were to investigate the role and boundaries of thermal processing of NS seeds in the preparation of therapeutic extracts and to elucidate the underlying mechanism. NS extracts obtained by various seed thermal processing methods were investigated in vitro for their antiproliferative activity in mouse colon carcinoma (MC38) cells and for their thymoquinone content. The effect of the different methods of thermal processing on the ability of the obtained NS oil to inhibit the nuclear factor kappa B (NF-κB) pathway was then investigated in Hodgkin's lymphoma (L428) cells. The different thermal processing protocols yielded three distinct patterns: heating the NS seeds to 50°C, 100°C, or 150°C produced oil with a strong ability to inhibit tumor cell growth; no heating or heating to 25°C had a mild antiproliferative effect; and heating to 200°C or 250°C had no effect. Similar patterns were obtained for the thymoquinone content of the corresponding oils, which showed an excellent correlation with the antiproliferative data. It is proposed that there is an oxidative transition mechanism between quinones after controlled thermal processing of the seeds. While NS oil from heated seeds delayed the expression of NF-κB transcription, non-heated seeds resulted in only 50% inhibition. The data indicate that controlled thermal processing of NS seeds (at 50°C-150°C) produces significantly higher anticancer activity associated with a higher thymoquinone oil content, and inhibits the NF-κB signaling pathway.

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

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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.

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

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Li, Shenghong; Qiu, Shengxiang; Yao, Ping; Sun, Handong; Fong, Harry H S; Zhang, Hongjie

2013-01-01

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 9 α -hydroxy-13(14)-labden-16,15-amide (2) and 6 β -acetoxy-9 α -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.

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

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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.

Understanding the mechanism of direct electrochemistry of mitochondria-modified electrodes from yeast, potato and bovine sources at carbon paper electrodes

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Giroud, Fabien; Nicolo, Tera A.; Koepke, Sara J.; Minteer, Shelley D.

2013-01-01

Although mitochondria have been used for bio-electrochemistry for over 5 years, little is known about their direct electrochemistry mechanism. This paper focuses on developing a better understanding of the electron transfer mechanism of mitochondria from three different organisms at carbon electrodes. Yeast, potato and bovine mitochondria have been successfully isolated and immobilized onto Toray paper electrodes via vapor deposited silica. Organelle-modified electrodes were first characterized using cyclic voltammetry. Similar electrochemical signals were obtained for all organisms. Direct electron transfer was observed when a metabolite of the Krebs cycle was present in the buffer solution. Control experiments based on the immobilization of two electron carriers contained in mitochondria, cytochrome c and a quinone (coenzyme Q 10 ), tend to show the electron transfer mechanism to the carbon material comes from the quinone pool of the organelles. As quinones are known to be pH-dependent, we further investigated the response of the electrochemical signal of the three isolated mitochondria and the two electron carriers separately. The half wave potentials obtained from the organelles appeared to be pH-dependent and their variations are comparable to coenzyme Q 10 rather than cytochrome c. Finally, extraction of both the cytochrome c and the quinone pool from intact mitochondria was performed to validate our hypothesis that direct electrochemistry of mitochondria happens via the quinone pool. Electrochemistry of immobilized quinone-depleted mitochondria validated the hypothesis that the mitochondria are communicating with the electrodes through the quinone pool

The quinone methide aurin is a heat shock response inducer that causes proteotoxic stress and Noxa-dependent apoptosis in malignant melanoma cells.

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Davis, Angela L; Qiao, Shuxi; Lesson, Jessica L; Rojo de la Vega, Montserrat; Park, Sophia L; Seanez, Carol M; Gokhale, Vijay; Cabello, Christopher M; Wondrak, Georg T

2015-01-16

Pharmacological induction of proteotoxic stress is rapidly emerging as a promising strategy for cancer cell-directed chemotherapeutic intervention. Here, we describe the identification of a novel drug-like heat shock response inducer for the therapeutic induction of proteotoxic stress targeting malignant human melanoma cells. Screening a focused library of compounds containing redox-directed electrophilic pharmacophores employing the Stress & Toxicity PathwayFinder(TM) PCR Array technology as a discovery tool, a drug-like triphenylmethane-derivative (aurin; 4-[bis(p-hydroxyphenyl)methylene]-2,5-cyclohexadien-1-one) was identified as an experimental cell stress modulator that causes (i) heat shock factor transcriptional activation, (ii) up-regulation of heat shock response gene expression (HSPA6, HSPA1A, DNAJB4, HMOX1), (iii) early unfolded protein response signaling (phospho-PERK, phospho-eIF2α, CHOP (CCAAT/enhancer-binding protein homologous protein)), (iv) proteasome impairment with increased protein-ubiquitination, and (v) oxidative stress with glutathione depletion. Fluorescence polarization-based experiments revealed that aurin displays activity as a geldanamycin-competitive Hsp90α-antagonist, a finding further substantiated by molecular docking and ATPase inhibition analysis. Aurin exposure caused caspase-dependent cell death in a panel of human malignant melanoma cells (A375, G361, LOX-IMVI) but not in non-malignant human skin cells (Hs27 fibroblasts, HaCaT keratinocytes, primary melanocytes) undergoing the aurin-induced heat shock response without impairment of viability. Aurin-induced melanoma cell apoptosis depends on Noxa up-regulation as confirmed by siRNA rescue experiments demonstrating that siPMAIP1-based target down-regulation suppresses aurin-induced cell death. Taken together, our data suggest feasibility of apoptotic elimination of malignant melanoma cells using the quinone methide-derived heat shock response inducer aurin. © 2015 by The

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.

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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. Copyright © 2013 Elsevier Ltd. All rights reserved.

NQO1-dependent redox cycling of idebenone: effects on cellular redox potential and energy levels.

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Roman H Haefeli

Full Text Available Short-chain quinones are described as potent antioxidants and in the case of idebenone have already been under clinical investigation for the treatment of neuromuscular disorders. Due to their analogy to coenzyme Q10 (CoQ10, a long-chain quinone, they are widely regarded as a substitute for CoQ10. However, apart from their antioxidant function, this provides no clear rationale for their use in disorders with normal CoQ10 levels. Using recombinant NAD(PH:quinone oxidoreductase (NQO enzymes, we observed that contrary to CoQ10 short-chain quinones such as idebenone are good substrates for both NQO1 and NQO2. Furthermore, the reduction of short-chain quinones by NQOs enabled an antimycin A-sensitive transfer of electrons from cytosolic NAD(PH to the mitochondrial respiratory chain in both human hepatoma cells (HepG2 and freshly isolated mouse hepatocytes. Consistent with the substrate selectivity of NQOs, both idebenone and CoQ1, but not CoQ10, partially restored cellular ATP levels under conditions of impaired complex I function. The observed cytosolic-mitochondrial shuttling of idebenone and CoQ1 was also associated with reduced lactate production by cybrid cells from mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS patients. Thus, the observed activities separate the effectiveness of short-chain quinones from the related long-chain CoQ10 and provide the rationale for the use of short-chain quinones such as idebenone for the treatment of mitochondrial disorders.

The neuroprotective action of pyrroloquinoline quinone against glutamate-induced apoptosis in hippocampal neurons is mediated through the activation of PI3K/Akt pathway

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Zhang Qi; Shen Mi; Ding Mei; Shen Dingding; Ding Fei

2011-01-01

Pyrroloquinoline quinone (PQQ), a cofactor in several enzyme-catalyzed redox reactions, possesses a potential capability of scavenging reactive oxygen species (ROS) and inhibiting cell apoptosis. In this study, we investigated the effects of PQQ on glutamate-induced cell death in primary cultured hippocampal neurons and the possible underlying mechanisms. We found that glutamate-induced apoptosis in cultured hippocampal neurons was significantly attenuated by the ensuing PQQ treatment, which also inhibited the glutamate-induced increase in Ca2+ influx, caspase-3 activity, and ROS production, and reversed the glutamate-induced decrease in Bcl-2/Bax ratio. The examination of signaling pathways revealed that PQQ treatment activated the phosphorylation of Akt and suppressed the glutamate-induced phosphorylation of c-Jun N-terminal protein kinase (JNK). And inhibition of phosphatidylinositol-3-kinase (PI3K)/Akt cascade by LY294002 and wortmannin significantly blocked the protective effects of PQQ, and alleviated the increase in Bcl-2/Bax ratio. Taken together, our results indicated that PQQ could protect primary cultured hippocampal neurons against glutamate-induced cell damage by scavenging ROS, reducing Ca2+ influx, and caspase-3 activity, and suggested that PQQ-activated PI3K/Akt signaling might be responsible for its neuroprotective action through modulation of glutamate-induced imbalance between Bcl-2 and Bax. - Research Highlights: →PQQ attenuated glutamate-induced cell apoptosis of cultured hippocampal neurons. →PQQ inhibited glutamate-induced Ca 2+ influx and caspase-3 activity. →PQQ reduced glutamate-induced increase in ROS production. →PQQ affected phosphorylation of Akt and JNK signalings after glutamate injury. →PI3K/Akt was required for neuroprotection of PQQ by modulating Bcl-2/Bax ratio.

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.

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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.

Lack of association between NADPH quinone oxidoreductase 1 (NQO1 gene C609T polymorphism and lung cancer: a case-control study and a meta-analysis.

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Shujie Guo

Full Text Available BACKGROUND: The association between NAD(PH:quinone oxidoreductase 1 (NQO1 gene C609T polymorphism (rs1800566 and lung cancer has been widely evaluated, and a definitive answer so far is lacking. We first conducted a case-control study to assess this association in northeastern Han Chinese, and then performed a meta-analysis to further address this issue. METHODOLOGY/PRINCIPAL FINDINGS: This case-control study involved 684 patients clinically diagnosed as lung cancer and 602 age-matched cancer-free controls from Harbin city, Heilongjiang province, China. Genotyping was conducted using the PCR-LDR (ligase detection reactions method. Meta-analysis was managed by STATA software. Data and study quality were assessed in duplicate. Our case-control association study indicated no significant difference in the genotype and allele distributions of C609T polymorphism between lung cancer patients and controls, consistent with the results of the further meta-analysis involving 7286 patients and 9167 controls under both allelic (odds ratio (OR = 0.99; 95% confidence interval (CI: 0.92-1.06; P = 0.692 and dominant (OR = 0.98; 95% CI: 0.89-1.08; P = 0.637 models. However, there was moderate evidence of between-study heterogeneity and low probability of publication bias. Further subgroup analyses by ethnicity, source of controls and sample size detected no positive associations in this meta-analysis. CONCLUSIONS: Our study in northeastern Han Chinese, along with the meta-analysis, failed to confirm the association of NQO1 gene C609T polymorphism with lung cancer risk, even across different ethnic populations.

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.

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

2013-10-25

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).

On dithiothreitol (DTT as a measure of oxidative potential for ambient particles: evidence for the importance of soluble ewline transition metals

Directory of Open Access Journals (Sweden)

J. G. Charrier

2012-10-01

Full Text Available The rate of consumption of dithiothreitol (DTT is increasingly used to measure the oxidative potential of particulate matter (PM, which has been linked to the adverse health effects of PM. While several quinones are known to be very reactive in the DTT assay, it is unclear what other chemical species might contribute to the loss of DTT in PM extracts. To address this question, we quantify the rate of DTT loss from individual redox-active species that are common in ambient particulate matter. While most past research has indicated that the DTT assay is not sensitive to metals, our results show that seven out of the ten transition metals tested do oxidize DTT, as do three out of the five quinones tested. While metals are less efficient at oxidizing DTT compared to the most reactive quinones, concentrations of soluble transition metals in fine particulate matter are generally much higher than those of quinones. The net result is that metals appear to dominate the DTT response for typical ambient PM_2.5 samples. Based on particulate concentrations of quinones and soluble metals from the literature, and our measured DTT responses for these species, we estimate that for typical PM_2.5 samples approximately 80% of DTT loss is from transition metals (especially copper and manganese, while quinones account for approximately 20%. We find a similar result for DTT loss measured in a small set of PM_2.5 samples from the San Joaquin Valley of California. Because of the important contribution from metals, we also tested how the DTT assay is affected by EDTA, a chelator that is sometimes used in the assay. EDTA significantly suppresses the response from both metals and quinones; we therefore recommend that EDTA should not be included in the DTT assay.

Photoproduction of hydrogen peroxide in aqueous solution from model compounds for chromophoric dissolved organic matter (CDOM)

International Nuclear Information System (INIS)

Clark, Catherine D.; Bruyn, Warren de; Jones, Joshua G.

2014-01-01

Highlights: • CDOM produces hydrogen peroxide in sunlit surface waters. • Quinone moieties have been proposed as the photo-active chromophore in CDOM. • Hydrogen peroxide is produced in irradiated aqueous quinone solutions. • Concentrations and production rates are comparable to humic and fulvic acids. • Optical properties post-irradiation were similar to CDOM. - Abstract: To explore whether quinone moieties are important in chromophoric dissolved organic matter (CDOM) photochemistry in natural waters, hydrogen peroxide (H 2 O 2 ) 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 H 2 O 2 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

Genomic phenotyping by barcode sequencing broadly distinguishes between alkylating agents, oxidizing agents, and non-genotoxic agents, and reveals a role for aromatic amino acids in cellular recovery after quinone exposure.

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Svensson, J Peter; Quirós Pesudo, Laia; McRee, Siobhan K; Adeleye, Yeyejide; Carmichael, Paul; Samson, Leona D

2013-01-01

Toxicity screening of compounds provides a means to identify compounds harmful for human health and the environment. Here, we further develop the technique of genomic phenotyping to improve throughput while maintaining specificity. We exposed cells to eight different compounds that rely on different modes of action: four genotoxic alkylating (methyl methanesulfonate (MMS), N-Methyl-N-nitrosourea (MNU), N,N'-bis(2-chloroethyl)-N-nitroso-urea (BCNU), N-ethylnitrosourea (ENU)), two oxidizing (2-methylnaphthalene-1,4-dione (menadione, MEN), benzene-1,4-diol (hydroquinone, HYQ)), and two non-genotoxic (methyl carbamate (MC) and dimethyl sulfoxide (DMSO)) compounds. A library of S. cerevisiae 4,852 deletion strains, each identifiable by a unique genetic 'barcode', were grown in competition; at different time points the ratio between the strains was assessed by quantitative high throughput 'barcode' sequencing. The method was validated by comparison to previous genomic phenotyping studies and 90% of the strains identified as MMS-sensitive here were also identified as MMS-sensitive in a much lower throughput solid agar screen. The data provide profiles of proteins and pathways needed for recovery after both genotoxic and non-genotoxic compounds. In addition, a novel role for aromatic amino acids in the recovery after treatment with oxidizing agents was suggested. The role of aromatic acids was further validated; the quinone subgroup of oxidizing agents were extremely toxic in cells where tryptophan biosynthesis was compromised.

The correlation of cathodic peak potentials of vitamin K(3) derivatives and their calculated electron affinities. The role of hydrogen bonding and conformational changes.

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Nasiri, Hamid Reza; Panisch, Robin; Madej, M Gregor; Bats, Jan W; Lancaster, C Roy D; Schwalbe, Harald

2009-06-01

2-methyl-1,4-naphtoquinone 1 (vitamin K(3), menadione) derivatives with different substituents at the 3-position were synthesized to tune their electrochemical properties. The thermodynamic midpoint potential (E(1/2)) of the naphthoquinone derivatives yielding a semi radical naphthoquinone anion were measured by cyclic voltammetry in the aprotic solvent dimethoxyethane (DME). Using quantum chemical methods, a clear correlation was found between the thermodynamic midpoint potentials and the calculated electron affinities (E(A)). Comparison of calculated and experimental values allowed delineation of additional factors such as the conformational dependence of quinone substituents and hydrogen bonding which can influence the electron affinities (E(A)) of the quinone. This information can be used as a model to gain insight into enzyme-cofactor interactions, particularly for enzyme quinone binding modes and the electrochemical adjustment of the quinone motif.

Fabricated catecholic films are capable of redox-cycling and H2O2-generation in the absence of enzymes

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The redox activity of quinones is integral to their physiological function in the electron transfer pathways of respiration and photosynthesis. Quinones and phenolic radicals are also intermediates in the biosynthesis of macromolecular structures (lignins and melanins) generated by plants and insec...

Expression of NAD(P)H quinone dehydrogenase 1 (NQO1) is increased in the endometrium of women with endometrial cancer and women with polycystic ovary syndrome.

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Atiomo, William; Shafiee, Mohamad Nasir; Chapman, Caroline; Metzler, Veronika M; Abouzeid, Jad; Latif, Ayşe; Chadwick, Amy; Kitson, Sarah; Sivalingam, Vanitha N; Stratford, Ian J; Rutland, Catrin S; Persson, Jenny L; Ødum, Niels; Fuentes-Utrilla, Pablo; Jeyapalan, Jennie N; Heery, David M; Crosbie, Emma J; Mongan, Nigel P

2017-11-01

Women with a prior history of polycystic ovary syndrome (PCOS) have an increased risk of endometrial cancer (EC). To investigate whether the endometrium of women with PCOS possesses gene expression changes similar to those found in EC. Patients with EC, PCOS and control women unaffected by either PCOS or EC were recruited into a cross-sectional study at the Nottingham University Hospital, UK. For RNA sequencing, representative individual endometrial biopsies were obtained from women with EC, PCOS and a woman unaffected by PCOS or EC. Expression of a subset of differentially expressed genes identified by RNA sequencing, including NAD(P)H quinone dehydrogenase 1 (NQO1), was validated by quantitative reverse transcriptase PCR validation (n = 76) and in the cancer genome atlas UCEC (uterine corpus endometrioid carcinoma) RNA sequencing data set (n = 381). The expression of NQO1 was validated by immunohistochemistry in EC samples from a separate cohort (n = 91) comprised of consecutive patients who underwent hysterectomy at St Mary's Hospital, Manchester, between 2011 and 2013. A further 6 postmenopausal women with histologically normal endometrium who underwent hysterectomy for genital prolapse were also included. Informed consent and local ethics approval were obtained for the study. We show for the first that NQO1 expression is significantly increased in the endometrium of women with PCOS and EC. Immunohistochemistry confirms significantly increased NQO1 protein expression in EC relative to nonmalignant endometrial tissue (P < .0001). The results obtained here support a previously unrecognized molecular link between PCOS and EC involving NQO1. © 2017 The Authors. Clinical Endocrinology Published by John Wiley & Sons Ltd.

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

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African Journals Online (AJOL)

The electrochemical properties of quinones make them a promising class of compounds to be utilized as active matter in secondary batteries. Quinones incorporated in carbon paste electrodes. (CPE) have been frequently employed to investigate their electrochemical behavior [1,2,3]. The redox couple ...

Electrochemistry coupled to (LC-)MS for the simulation of oxidative biotransformation reactions of PAHs.

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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/H 2 , 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.

Journal of Chemical Sciences | Indian Academy of Sciences

Indian Academy of Sciences (India)

Activation of molecular oxygen has also been observed and has been used for oxidative dealkylation of a hindered phenol, producing di-butyl quinones with yields of 20-25% and 10-12 fold catalytic turnover. Dihydroxybenzenes and substituted catechols are also readily oxidized to the corresponding quinones, ...

Electrically Reversible Redox-Switchable Polydopamine Films for Regulating Cell Behavior

International Nuclear Information System (INIS)

Tan, Guoxin; Liu, Yan; Wu, Yuxuan; Ouyang, Kongyou; Zhou, Lei; Yu, Peng; Liao, Jinwen; Ning, Chengyun

2017-01-01

Highlights: • The phenolic/quinone groups on polydopamine can redox-switchable reversible under electrical stimulation. • The quinone groups on PDA (oxidized PDA) enhanced cell spreading and proliferation. • The phenolic groups on PDA (reduced PDA) induced cell differentiation. - Abstract: Switchable surfaces that respond to external stimuli are important for regulating cell behavior. The results herein suggest that the redox process of polydopamine (PDA) is a switching reaction between oxidized polydopamine and reduced polydopamine, involving an interconversion of coupled two-proton (2H + ) and two-electron (2e − ) processes. The redox-switchable reversible surface potential arising from the potential-tunable redox reaction of the phenolic and quinone groups on PDA on titanium induced both cell adhesion and spreading. In vitro experiments demonstrated that the quinone groups on PDA greatly enhanced pre-osteoblasts MC3T3-E1 cell spreading and proliferation. Phenolic groups enhanced the induction of differentiation. The proposed methodology may allow further investigation of switchable surfaces for biological and medical applications.

Lipoquinones of some spore-forming rods, lactic-acid bacteria and actinomycetes.

Science.gov (United States)

Hess, A; Holländer, R; Mannheim, W

1979-11-01

The respiratory quinones of 73 strains of Gram-positive bacteria including spore-forming rods, lactic-acid bacteria and actinomyctes were examined. Menaquinones with seven isoprenoid units (MK-7) were the main quinone type found in representatives of the genus Bacillus and in Sporolactobacillus inulinus. However, a strain of B. thuringiensis produced MK-8 in addition to MK-7, and strains of B. lentus and B. pantothenticus appeared to produce MK-9 and MK-8, respectively, with no MK-7. In the clostridia and lactic-acid bacteria, no quinones were found, except in Pediococcus cerevisiae NCTC 8066 and Lactobacillus casei subsp. rhamnosus ATCC 7469, which contained menaquinones, and Streptococcus faecalis NCTC 775 and HIM 478-1, which contained demethylmenaquinones, in relatively low concentrations. Menaquinones were also found in the actinomycetes (except Actinomyces odontolyticus and Bifidobacterium bifidum which did not produce any quinones) and in Protaminobacter alboflavus ATCC 8458, the so-called Actinobacillus actinoides ATCC 15900 and Noguchia granulosis NCTC 10559.

Genomic phenotyping by barcode sequencing broadly distinguishes between alkylating agents, oxidizing agents, and non-genotoxic agents, and reveals a role for aromatic amino acids in cellular recovery after quinone exposure.

Directory of Open Access Journals (Sweden)

J Peter Svensson

Full Text Available Toxicity screening of compounds provides a means to identify compounds harmful for human health and the environment. Here, we further develop the technique of genomic phenotyping to improve throughput while maintaining specificity. We exposed cells to eight different compounds that rely on different modes of action: four genotoxic alkylating (methyl methanesulfonate (MMS, N-Methyl-N-nitrosourea (MNU, N,N'-bis(2-chloroethyl-N-nitroso-urea (BCNU, N-ethylnitrosourea (ENU, two oxidizing (2-methylnaphthalene-1,4-dione (menadione, MEN, benzene-1,4-diol (hydroquinone, HYQ, and two non-genotoxic (methyl carbamate (MC and dimethyl sulfoxide (DMSO compounds. A library of S. cerevisiae 4,852 deletion strains, each identifiable by a unique genetic 'barcode', were grown in competition; at different time points the ratio between the strains was assessed by quantitative high throughput 'barcode' sequencing. The method was validated by comparison to previous genomic phenotyping studies and 90% of the strains identified as MMS-sensitive here were also identified as MMS-sensitive in a much lower throughput solid agar screen. The data provide profiles of proteins and pathways needed for recovery after both genotoxic and non-genotoxic compounds. In addition, a novel role for aromatic amino acids in the recovery after treatment with oxidizing agents was suggested. The role of aromatic acids was further validated; the quinone subgroup of oxidizing agents were extremely toxic in cells where tryptophan biosynthesis was compromised.

Amelioration of cadmium- and mercury-induced liver and kidney damage in rats by genetically engineered probiotic Escherichia coli Nissle 1917 producing pyrroloquinoline quinone with oral supplementation of citric acid.

Science.gov (United States)

Raghuvanshi, Ruma; Chaudhari, Archana; Kumar, G Naresh

2016-01-01

Antioxidants, chelating agents, and probiotics are used to manage the toxic effects of cadmium (Cd) and mercury (Hg). The aim of this study was to investigate the combined effects of antioxidants, chelating agents, and probiotics against heavy metal toxicity. Genetically modified probiotic Escherichia coli Nissle 1917 (EcN-20) producing a potent water soluble antioxidant pyrroloquinoline quinone (PQQ) was supplemented with oral citric acid and compared with another genetically modified probiotic EcN-21 producing PQQ and citric acid against oxidative stress induced by Cd and Hg. Rats were independently given 100 ppm Cd and 80 ppm Hg in drinking water for 4 wk. EcN-20 was found to be more effective than EcN-2 (EcN strain with genomic integration of vgb and gfp genes) with orally given PQQ against oxidative stress induced by Cd and Hg. EcN-20 supplemented with oral citric acid was more effective against Cd and Hg toxicity compared with EcN-2+citric acid (oral), EcN-2+PQQ (oral), EcN-2+PQQ (oral)+citric acid (oral), EcN-20, and EcN-21. However, protection shown by EcN-21 was similar to EcN-20. The combination therapy involving probiotic EcN-20 producing PQQ with citric acid given orally was found to be a moderately effective strategy against toxicity induced by Cd and Hg, whereas the protective effect of EcN-21 was the same as EcN-20. Copyright © 2016 Elsevier Inc. All rights reserved.

The effects of protein crowding in bacterial photosynthetic membranes on the flow of quinone redox species between the photochemical reaction center and the ubiquinol-cytochrome c2 oxidoreductase.

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Woronowicz, Kamil; Sha, Daniel; Frese, Raoul N; Sturgis, James N; Nanda, Vikas; Niederman, Robert A

2011-08-01

Atomic force microscopy (AFM) of the native architecture of the intracytoplasmic membrane (ICM) of a variety of species of purple photosynthetic bacteria, obtained at submolecular resolution, shows a tightly packed arrangement of light harvesting (LH) and reaction center (RC) complexes. Since there are no unattributed structures or gaps with space sufficient for the cytochrome bc(1) or ATPase complexes, they are localized in membrane domains distinct from the flat regions imaged by AFM. This has generated a renewed interest in possible long-range pathways for lateral diffusion of UQ redox species that functionally link the RC and the bc(1) complexes. Recent proposals to account for UQ flow in the membrane bilayer are reviewed, along with new experimental evidence provided from an analysis of intrinsic near-IR fluorescence emission that has served to test these hypotheses. The results suggest that different mechanism of UQ flow exist between species such as Rhodobacter sphaeroides, with a highly organized arrangement of LH and RC complexes and fast RC electron transfer turnover, and Phaeospirillum molischianum with a more random organization and slower RC turnover. It is concluded that packing density of the peripheral LH2 antenna in the Rba. sphaeroides ICM imposes constraints that significantly slow the diffusion of UQ redox species between the RC and cytochrome bc(1) complex, while in Phs. molischianum, the crowding of the ICM with LH3 has little effect upon UQ diffusion. This supports the proposal that in this type of ICM, a network of RC-LH1 core complexes observed in AFM provides a pathway for long-range quinone diffusion that is unaffected by differences in LH complex composition or organization.

Chemical compounds in teak

Directory of Open Access Journals (Sweden)

Fernanda Viana da Silva Leonardo

2015-09-01

Full Text Available Quinone compounds are largely generated at extractive fraction of the woods in a complex and variable biological system. The literature has indications for many segments from food industry to pharmaceutical industry. Within the field of industrial use of wood, they are less desirable since they are treated only as incidental substances in production strings of pulp, paper, charcoal, and sawmill. In spite of its small amount, compared to other chemical compounds called essential, these substances have received special attention from researchers revealing a diverse range of offerings to market products textiles, pharmaceuticals, colorants, and other polymers, for which are being tested and employed. Quinones are found in fungi, lichens, and mostly in higher plants. Tectona grandis, usually called teak, is able to biosynthesize anthraquinones, which is a quinone compound, byproduct of secondary metabolism. This species provides wood that is much prized in the furniture sector and can also be exploited for metabolites to supply the market in quinone compounds and commercial development of new technologies, adding value to the plantations of this species within our country.

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

Strecker Aldehyde Formation in Wine: New Insights into the Role of Gallic Acid, Glucose, and Metals in Phenylacetaldehyde Formation.

Science.gov (United States)

Monforte, Ana Rita; Martins, Sara I F S; Silva Ferreira, Antonio C

2018-03-14

Strecker degradation (SD) leading to the formation of phenylacetaldehyde (PA) was studied in wine systems. New insights were gained by using two full factorial designs focusing on the effects of (1) pH and (2) temperature. In each design of experiments (DoE) three factors, glucose, gallic acid, and metals at two levels (present or absence), were varied while phenylalanine was kept constant. The obtained results gave a clear indication, with statistical significance, that in wine conditions, the SD occurs in the presence of metals preferentially via the phenolic oxidation independent of the temperature (40 or 80 °C). The reaction of the amino acid with the o-quinone formed by the oxidation of the gallic acid seems to be favored when compared with the SD promoted by the reaction with α-dicarbonyls formed by MR between glucose and phenylalanine. In fact, kinetics results showed that the presence of glucose had an inhibitory effect on PA rate of formation. PA formation was 4 times higher in the control wine when compared to the same wine with 10 g/L glucose added. By gallic acid quinone quantitation it is shown that glucose affects directly the concentration of the quinone. decreasing the rate of quinone formation. This highlights the role of sugar in o-quinone concentration and consequently in the impact on Strecker aldehyde formation, a promising new perspective regarding wine shelf-life understanding.

pH-Dependent Regulation of the Relaxation Rate of the Radical Anion of the Secondary Quinone Electron Acceptor QB in Photosystem II As Revealed by Fourier Transform Infrared Spectroscopy.

Science.gov (United States)

Nozawa, Yosuke; Noguchi, Takumi

2018-05-15

Photosystem II (PSII) is a protein complex that performs water oxidation using light energy during photosynthesis. In PSII, electrons abstracted from water are eventually transferred to the secondary quinone electron acceptor, Q B , and upon double reduction, Q B is converted to quinol by binding two protons. Thus, excess electron transfer in PSII increases the pH of the stroma. In this study, to investigate the pH-dependent regulation of the electron flow in PSII, we have estimated the relaxation rate of the Q B - radical anion in the pH region between 5 and 8 by direct monitoring of its population using light-induced Fourier transform infrared difference spectroscopy. The decay of Q B - by charge recombination with the S 2 state of the water oxidation center in PSII membranes was shown to be accelerated at higher pH, whereas that of Q A - examined in the presence of a herbicide was virtually unaffected at pH ≤7.5 and slightly slowed at pH 8. These observations were consistent with the previous studies that included rather indirect monitoring of the Q B - and Q A - decays using fluorescence detection. The accelerated relaxation of Q B - was explained by the shift of a redox equilibrium between Q A - and Q B - to the Q A - side due to the decrease in the redox potential of Q B at higher pH, which is induced by deprotonation of a single amino acid residue near Q B . It is proposed that this pH-dependent Q B - relaxation is one of the mechanisms of electron flow regulation in PSII for its photoprotection.

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. Copyright © 2014 Elsevier Ltd. All rights reserved.

Cytotoxicity mechanism of two naphthoquinones (menadione and plumbagin in Saccharomyces cerevisiae.

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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

Cytotoxicity Mechanism of Two Naphthoquinones (Menadione and Plumbagin) in Saccharomyces cerevisiae

Science.gov (United States)

Castro, Frederico Augusto Vieira; Mariani, Diana; Panek, Anita Dolly; Eleutherio, Elis Cristina Araújo; Pereira, Marcos Dias

2008-01-01

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 (gtt1Δ and gtt2Δ) 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 these compounds use different

Diels-Alder Reactions of 12-Hydroxy-9(10®20-5aH-abeo-abieta-1(10,8(9,12(13-triene-11,14-dione

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Shougang Hu

2013-06-01

Full Text Available 12-Hydroxy-9(10®20-5aH-abeo-abieta-1(10,8(9,12(13-triene-11,14-dione (quinone 2 served as the dienophile in numerous intermolecular Diels-Alder reactions. These cycloadditions were conducted either thermally (including microwave heating or with Lewis acid activation. While most dienes reacted with quinone 2 in good chemical yield, others were incompatible under the experimental conditions used.

Chloroanthraquinone as a grafted probe molecule to investigate grafting yield on carbon powder

International Nuclear Information System (INIS)

Le Comte, Annaïg; Brousse, Thierry; Bélanger, Daniel

2016-01-01

Spontaneous grafting of chloroanthraquinone (ClAQ) groups on Black Pearls carbon by reduction of the corresponding in-situ generated diazonium cations was successfully achieved. The presence of an halogen atom on the quinone molecule allowed the use of different spectroscopic characterization techniques to determine the accurate quinone content of the modified carbon. Electrochemical characterization highlighted that the presence of chlorine atom on the grafted molecule did not affect the electrochemical response or the grafting reaction efficiency. The amount of ClAQ molecules at the carbon surface after grafting was determined by cyclic voltammetry, together with thermogravimetric analysis coupled mass spectroscopy, X-ray photoelectron spectroscopy and elemental analysis. The ClAQ mass loadings estimated from the four techniques are in very good agreement and confirm that the grafted moieties are all electrochemically active and accessible. Finally, the grafting of quinone-type molecule using the reduction of diazonium cations does not affect the electroactivity of the grafted groups and cyclic voltammetry can be considered as a reliable technique to evaluate the mass loading of grafted quinone groups on porous carbon. Thus ClAQ can be used as a grafted probe molecule to investigate grafting yield on carbon powder, and this approach can be extended to functionalized electrodes used in an increasing number of electrochemical energy storage devices.

Optical properties of humic substances and CDOM: effects of borohydride reduction.

Science.gov (United States)

Ma, Jiahai; Del Vecchio, Rossana; Golanoski, Kelli S; Boyle, Erin S; Blough, Neil V

2010-07-15

Treatment of Suwanee River humic (SRHA) and fulvic (SRFA) acids, a commercial lignin (LAC), and a series of solid phase extracts (C18) from the Middle Atlantic Bight (MAB extracts) with sodium borohydride (NaBH(4)), a selective reductant of carbonyl-containing compounds including quinones and aromatic ketones, produces a preferential loss of visible absorption (> or = 50% for SRFA) and substantially enhanced, blue-shifted fluorescence emission (2- to 3-fold increase). Comparison of the results with those obtained from a series of model quinones and hydroquinones demonstrates that these spectral changes cannot be assigned directly to the absorption and emission of visible light by quinones/hydroquinones. Instead, these results are consistent with a charge transfer model in which the visible absorption is due primarily to charge transfer transitions arising among hydroxy- (methoxy-) aromatic donors and carbonyl-containing acceptors. Unlike most of the model hydroquinones, the changes in optical properties of the natural samples following NaBH(4) reduction were largely irreversible in the presence of air and following addition of a Cu(2+) catalyst, providing tentative evidence that aromatic ketones (or other similar carbonyl-containing structures) may play a more important role than quinones in the optical properties of these materials.

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

International Nuclear Information System (INIS)

Stiborova, Marie; Dracinska, Helena; Mizerovska, Jana; Frei, Eva; Schmeiser, Heinz H.; Hudecek, Jiri; Hodek, Petr; Phillips, David H.; Arlt, Volker M.

2008-01-01

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 40 mg/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

One-electron oxidation of the hydroquinonic form of vitamin K by OH· and N3· free radicals. A steady-state gamma radiolysis study

International Nuclear Information System (INIS)

Nguyen Van Binh, E.; Gardes-Albert, M.; Ferradini, C.; Acher, F.; Azerad, R.

1991-01-01

The oxidation of a water-soluble model of vitamin K hydroquinone, symbolised by KH 2 p, has been studied by γ radiolysis using OH· or N 3 · free radicals as oxidants. Irradiation doses were up to 300 Gy. The analysis of final products by spectrophotometric absorption and HPLC allowed to characterize the formation of the quinone K and to estimate the initial yield of KH 2 p-disappearance and K-formation. N 3 · radicals led selectively to the formation of the quinone K with a G-value of (3.0 ± 0.3) x 10 -7 mol/J, thus involving a simple one-electron oxidation mechanism. On the contrary, when OH· radicals oxidized KH 2 p, in addition to the quinone, other non identified species were simultaneously produced during the radiolysis, thus requiring a more complex oxidation mechanism [fr

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.

Study of the interactions between naphthoquinone and protein

International Nuclear Information System (INIS)

Zhang Zhaoxia; Zhao Hongwei; Zhu Hongping; Ge Min; Hao Shumei; Wang Wenfeng; Li Wenxin

2006-01-01

Quinones are found in probably all respiring animal and plant cells. They are widely used as anticancer, antibacterial or antimalarial drugs and as fungicides. Over the last several decades, much attention has been paid to quinone compounds since they play important roles as electron and hydrogen atom acceptors in both chemistry and biochemistry. It has been known that the reactive states for the photoreduction of quinones are triplets. As for the photochemistry of simple quinones, such as benzoquinones (BQ), anthraquinones (AQ) and naphthoquinone (NQ), a large number of studies on their photochemical properties and elementary photoreactions. However little research on the protein electron transfer of triplet naphthoquinones ( 3 NQ * ) in organic solvents has been reported using laser flash photolysis. We have studied interactions between 3 NQ * and lysozyme in a mixture solution of acetonitrile and H 2 O (3:1, v/v) using 355 nm laser flash photolysis technique combined with the sample being irradiated in steady-state. Electron transfer reaction between 3 NQ * and lysozyme was found, and the rate constant was determined. On the other hand, the results of electrophoresis suggested that protein can be damaged induced by NQ irradiated with UVA light. It was indicated that the mechanisms and products of oxidative damage were relative to the concentration of riboflavin, the time of irradiation and the ambience. Mechanisms of photosensitive damage of protein were proposed. (authors)

Bimolecular Rate Constants for FAD-Dependent Glucose Dehydrogenase from Aspergillus terreus and Organic Electron Acceptors.

Science.gov (United States)

Tsuruoka, Nozomu; Sadakane, Takuya; Hayashi, Rika; Tsujimura, Seiya

2017-03-10

The flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH) from Aspergillus species require suitable redox mediators to transfer electrons from the enzyme to the electrode surface for the application of bioelectrical devices. Although several mediators for FAD-GDH are already in use, they are still far from optimum in view of potential, kinetics, sustainability, and cost-effectiveness. Herein, we investigated the efficiency of various phenothiazines and quinones in the electrochemical oxidation of FAD-GDH from Aspergillus terreus . At pH 7.0, the logarithm of the bimolecular oxidation rate constants appeared to depend on the redox potentials of all the mediators tested. Notably, the rate constant of each molecule for FAD-GDH was approximately 2.5 orders of magnitude higher than that for glucose oxidase from Aspergillus sp. The results suggest that the electron transfer kinetics is mainly determined by the formal potential of the mediator, the driving force of electron transfer, and the electron transfer distance between the redox active site of the mediator and the FAD, affected by the steric or chemical interactions. Higher k ₂ values were found for ortho-quinones than for para-quinones in the reactions with FAD-GDH and glucose oxidase, which was likely due to less steric hindrance in the active site in the case of the ortho-quinones.

Bimolecular Rate Constants for FAD-Dependent Glucose Dehydrogenase from Aspergillus terreus and Organic Electron Acceptors

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Nozomu Tsuruoka

2017-03-01

Full Text Available The flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH from Aspergillus species require suitable redox mediators to transfer electrons from the enzyme to the electrode surface for the application of bioelectrical devices. Although several mediators for FAD-GDH are already in use, they are still far from optimum in view of potential, kinetics, sustainability, and cost-effectiveness. Herein, we investigated the efficiency of various phenothiazines and quinones in the electrochemical oxidation of FAD-GDH from Aspergillus terreus. At pH 7.0, the logarithm of the bimolecular oxidation rate constants appeared to depend on the redox potentials of all the mediators tested. Notably, the rate constant of each molecule for FAD-GDH was approximately 2.5 orders of magnitude higher than that for glucose oxidase from Aspergillus sp. The results suggest that the electron transfer kinetics is mainly determined by the formal potential of the mediator, the driving force of electron transfer, and the electron transfer distance between the redox active site of the mediator and the FAD, affected by the steric or chemical interactions. Higher k2 values were found for ortho-quinones than for para-quinones in the reactions with FAD-GDH and glucose oxidase, which was likely due to less steric hindrance in the active site in the case of the ortho-quinones.

Synergistic electron transfer effect-based signal amplification strategy for the ultrasensitive detection of dopamine.

Science.gov (United States)

Lu, Qiujun; Chen, Xiaogen; Liu, Dan; Wu, Cuiyan; Liu, Meiling; Li, Haitao; Zhang, Youyu; Yao, Shouzhuo

2018-05-15

The selective and sensitive detection of dopamine (DA) is of great significance for the identification of schizophrenia, Huntington's disease, and Parkinson's disease from the perspective of molecular diagnostics. So far, most of DA fluorescence sensors are based on the electron transfer from the fluorescence nanomaterials to DA-quinone. However, the limited electron transfer ability of the DA-quinone affects the level of detection sensitivity of these sensors. In this work, based on the DA can reduce Ag + into AgNPs followed by oxidized to DA-quinone, we developed a novel silicon nanoparticles-based electron transfer fluorescent sensor for the detection of DA. As electron transfer acceptor, the AgNPs and DA-quinone can quench the fluorescence of silicon nanoparticles effectively through the synergistic electron transfer effect. Compared with traditional fluorescence DA sensors, the proposed synergistic electron transfer-based sensor improves the detection sensitivity to a great extent (at least 10-fold improvement). The proposed sensor shows a low detection limit of DA, which is as low as 0.1 nM under the optimal conditions. This sensor has potential applicability for the detection of DA in practical sample. This work has been demonstrated to contribute to a substantial improvement in the sensitivity of the sensors. It also gives new insight into design electron transfer-based sensors. Copyright © 2018. Published by Elsevier B.V.

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)

Menaquinone-7 in the reaction center complex of the green sulfur bacterium Chlorobium vibrioforme functions as the electron acceptor A1

DEFF Research Database (Denmark)

Kjaer, B; Frigaard, N-U; Yang, F

1998-01-01

Photosynthetically active reaction center complexes were prepared from the green sulfur bacterium Chlorobium vibrioforme NCIMB 8327, and the content of quinones was determined by extraction and high-performance liquid chromatography. The analysis showed a stoichiometry of 1.7 molecules of menaqui......Photosynthetically active reaction center complexes were prepared from the green sulfur bacterium Chlorobium vibrioforme NCIMB 8327, and the content of quinones was determined by extraction and high-performance liquid chromatography. The analysis showed a stoichiometry of 1.7 molecules...

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

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. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Catalytic oxidation of 2-aminophenols and ortho hydroxylation of aromatic amines by tyrosinase

International Nuclear Information System (INIS)

Toussaint, O.; Lerch, K.

1987-01-01

The usual substrates of tyrosinase, a copper-containing monooxygenase (EC 1.14.18.1), are monophenols and o-diphenols which are both converted to o-quinones. In this paper, the authors studied the reaction of this enzyme with two new classes of substrates: aromatic amines and o-aminophenols, structural analogues of monophenols and o-diphenols, respectively. They undergo the same catalytic reactions (ortho hydroxylation and oxidation), as documented by product analysis and kinetic studies. In the presence of tyrosinase, arylamines and o-aminophenols are converted to o-quinone imines, which are isolated as quinone anils or phenoxazones. As an example, in the presence of tyrosinase, 2-amino-3-hydroxybenzoic acid (an o-aminophenol) is converted to cinnabarinic acid, a well-known phenoxazone, while p-aminotoluene (an aromatic amine) gives rise to the formation of 5-amino-2-methyl-1,4-benzoquinone 1-(4-methylanil). Kinetic studies using an oxygen electrode show that arylamines and the corresponding monophenols exhibit similar Michaelis constants. In contrast, the reaction rates observed for aromatic amines are relatively slow as compared to monophenols. The enzymatic conversion of arylamines by tryosinase is different from the typical ones: N-oxidation and ring hydroxylation without further oxidation. This difference originates from the regiospecific hydroxylation (ortho position) and subsequent oxidation of the intermediate o-aminophenol to the corresponding o-quinone imine. Finally, the well-know monooxygenase activity of tyrosinase was also confirmed for the aromatic amine p-aminotoluene, with 18 O 2

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

Radioprotection of DNA molecule by oxido-reduction's coenzymes

International Nuclear Information System (INIS)

Araos, M.S.; Fernandez, M.; Tomicic, I.; Toha, J.C.

1978-01-01

The radio protective action of respiratory coenzymes on DNA-water solutions is studied after irradiation with a 60 Co source. Coenzymes were used separately or in mixtures of their oxidized and reduced forms. The dose relative factor (DRF) values evaluated by uv absorbancy measurements of DNA damage were high: 18.03 for the (NAD-FAD-quinone) mixture (a respiratory chain model); 14.91 for (quinone-hydroquinone) mixtures; 14.46 for quinone; 14.27 for hydroquinone; 12.49 for FAD; 7.21 for the (NAD-NADH) mixture; 6.48 for NADH and 3.79 for NAD. No parallelism was found between the DNA coenzymes strong interactions and their protective action, performed by overcoming the indirect radiation damage. Besides, uv irradiation studies give no support to protection through direct energy transfer processes from excited DNA to coenzymes. The high efficiency of the mixtures of oxidized-reduced respiratory coenzymes is discussed in terms of simultaneous and equivalent trapping of recombinable radicals. The high tolerance of these protectors in living cells is emphasized. (author)

Ligninolytic basidiomycetes as promising organisms for the mycoremediation of PAH-contaminated Environments

Science.gov (United States)

Pozdnyakova, N. N.; Balandina, S. A.; Dubrovskaya, E. V.; Golubev, C. N.; Turkovskaya, O. V.

2018-01-01

Primary screening of ligninolytic fungi belonging to wood- and soil-inhabiting basidiomycetes revealed their ability to degrade three-ringed PAHs with formation of quinone metabolites at the first stage. The degradative activity was both species and strain specific, and some differences in the “chances” for the formed quinones were found. They were the main end metabolites in the degradation of PAHs by Stropharia rugosoannulata and Agaricus bisporus. During PAH degradation by strains of Trametes versicolor, Pleurotus ostreatus, Schizophyllum commune, and Bjerkandera adusta similar metabolites were detected during the cultivation, but they were utilized further. The results supported the hypothesis that the degree of PAH degradation may depend on the composition of the extracellular ligninolytic complex of the fungi: in the presence of a single ligninolytic enzyme, laccase, the accumulation of quinone metabolites takes place; their further utilization is possible with the participation of ligninolytic peroxidases. The data obtained showed the necessity not only to identify the metabolites formed, but also to study the activity of the basic ligninolytic enzymes. It is important for the correct selection of fungal strains for mycoremediation.

Does menaquinone participate in brain astrocyte electron transport?

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Lovern, Douglas; Marbois, Beth

2013-10-01

Quinone compounds act as membrane resident carriers of electrons between components of the electron transport chain in the periplasmic space of prokaryotes and in the mitochondria of eukaryotes. Vitamin K is a quinone compound in the human body in a storage form as menaquinone (MK); distribution includes regulated amounts in mitochondrial membranes. The human brain, which has low amounts of typical vitamin K dependent function (e.g., gamma carboxylase) has relatively high levels of MK, and different regions of brain have different amounts. Coenzyme Q (Q), is a quinone synthesized de novo, and the levels of synthesis decline with age. The levels of MK are dependent on dietary intake and generally increase with age. MK has a characterized role in the transfer of electrons to fumarate in prokaryotes. A newly recognized fumarate cycle has been identified in brain astrocytes. The MK precursor menadione has been shown to donate electrons directly to mitochondrial complex III. Vitamin K compounds function in the electron transport chain of human brain astrocytes. Copyright © 2013 Elsevier Ltd. All rights reserved.

The study of redox mechanism of dobutamine at different pH media by electrochemical and in situ spectroelectrochemical methods

International Nuclear Information System (INIS)

Yang Gongjun; Xu Jingjuan; Chen Hongyuan

2004-01-01

Based on the comprehensive analyses of the experimental results of the electrochemical methods, in situ UV-Vis absorption spectra, in situ electron spin resonance (ESR), and attenuated total-internal reflection (ATR) as well as the calculation of UV-Vis absorption data by PM3 Semi-Empirical method, a reaction mechanism for the redox processes of dobutamine was presented. When the anodic sweep is carried out, dobutamine firstly undergoes a free radical reaction with one-electron and one-proton to form semi-quinone free radicals, which will continuously convert to its corresponding quinone form by further electrochemical oxidation reaction. The formed quinone cannot only undergo a cyclization process by chemical reaction to produce a new compound, which can be reduced at more negative potential, but also be reduced to form dobutamine again when subsequent cathodic sweep is followed. The cyclization rate is depended upon pH values, and it increases with the increase of pH. In neutral medium, the corresponding oxidation form of the cyclization reaction product is easy to convert to melanin

Electron Shuttling by Dissolved Humic Substances: Using Fluorescence Spectroscopy to Move Beyond the Laboratory to Natural Lakes, Streams and Groundwaters

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McKnight, D. M.

2017-12-01

Humic substances are an important class of reactive chemical species in natural waters, and one important role is their capacity to as an electron acceptor and/or electron shuttle to ferric iron present as solid phase ferric oxides. Several lines of evidence point to quinone-like moieties being the main redox active moieties that can be used by microbes in respiration. Concomitantly, the humic fraction of dissolved organic mater (DOM) contains the dominant fluorophores in many natural waters. Examination of excitation emission matrices (EEMs) across redox gradients in diverse aquatic systems show that the EEMs are generally red-shifted under reducing conditions, such as anoxic bottom waters in lakes and hypoxic waters in riparian wetlands. Furthermore, there is striking similarity between the humic fluorophores that are resolved by statistical analysis and the fluorescence spectra of model quinone compounds, with the more reduced species having red-shifted fluorescence spectra. This apparent red-shift can be quantified based on the distribution of apparently "quinone-like", "semi-quinone-like" and "hydroquinone-like" fluorophores determined by the PARAFAC statistical analysis. Because fluorescence spectroscopy can be applied at ambient DOM concentrations for samples that have been maintained in an anoxic condition, fluorescence spectroscopy can provide insight into the role of humic electron shuttling in natural systems. Examples are presented demosntrating the changing EEMs in anoxic bottomwaters in a lake in the McMurdo Dry Valleys following a major flood event and the role of organic material in the mobilization of arsenic in shallow groundwater in South East Asia.

Photoinduced electron transfer interaction of anthraquinones with aniline quenchers: Influence of methyl substitution in aniline donors

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Sivakumar, V.; Ponnamma, Deepalekshmi; Hussein, Yasser H. A.

2017-02-01

Photoinduced electron transfer between triplet state of 9,10-anthraquinone (AQ) and its two derivatives: 2-chloro-9,10-anthraquinone (CAQ) and sodium anthraquinone-2-sulfonate (AQS) and ground state aniline (AN) and its dimethyl substitutions: 2,3-dimethylaniline (2,3-DMA), 2,6-dimethylaniline (2,6-DMA), 3,5-dimethylaniline (3,5-DMA) and N,N-dimethylaniline (N,N-DMA) is studied using nanosecond laser flash photolysis at room temperature. Detection of radical bands of quinone anions and aniline cations along with their formation and/or decay kinetics are used to confirm the electron transfer (ET) process. In MeCN medium, AN quenches the triplet state of CAQ (CAQT) but not the triplets AQT or AQST. However in aqueous medium, AN quenches AQST and forms radical ion pair. All the DMAs can react through ET with all the triplet quinones at different degrees of efficiency in MeCN medium. Noticeably, the ring substituted DMAs are less efficient in electron donation to AQT or AQST while the N,N-DMA shows high efficiency in donating electron to all triplet quinones in MeCN medium. Charge distribution of donor molecules, in MeCN medium is calculated using density functional theory (DFT), and shows an enhancement of electron density of the ring of N,N-DMA, making it an ideal electron donor for ET studies compared to other DMAs. This systematic selection and usage of anilines with electrochemically tunable quinones can be viewed as a working model of donor-acceptor system that can be utilized in photoinduced ET applications.

Physiological Evidence for Isopotential Tunneling in the Electron Transport Chain of Methane-Producing Archaea.

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Duszenko, Nikolas; Buan, Nicole R

2017-09-15

Many, but not all, organisms use quinones to conserve energy in their electron transport chains. Fermentative bacteria and methane-producing archaea (methanogens) do not produce quinones but have devised other ways to generate ATP. Methanophenazine (MPh) is a unique membrane electron carrier found in Methanosarcina species that plays the same role as quinones in the electron transport chain. To extend the analogy between quinones and MPh, we compared the MPh pool sizes between two well-studied Methanosarcina species, Methanosarcina acetivorans C2A and Methanosarcina barkeri Fusaro, to the quinone pool size in the bacterium Escherichia coli We found the quantity of MPh per cell increases as cultures transition from exponential growth to stationary phase, and absolute quantities of MPh were 3-fold higher in M. acetivorans than in M. barkeri The concentration of MPh suggests the cell membrane of M. acetivorans , but not of M. barkeri , is electrically quantized as if it were a single conductive metal sheet and near optimal for rate of electron transport. Similarly, stationary (but not exponentially growing) E. coli cells also have electrically quantized membranes on the basis of quinone content. Consistent with our hypothesis, we demonstrated that the exogenous addition of phenazine increases the growth rate of M. barkeri three times that of M. acetivorans Our work suggests electron flux through MPh is naturally higher in M. acetivorans than in M. barkeri and that hydrogen cycling is less efficient at conserving energy than scalar proton translocation using MPh. IMPORTANCE Can we grow more from less? The ability to optimize and manipulate metabolic efficiency in cells is the difference between commercially viable and nonviable renewable technologies. Much can be learned from methane-producing archaea (methanogens) which evolved a successful metabolic lifestyle under extreme thermodynamic constraints. Methanogens use highly efficient electron transport systems and

Requirement of histidine 217 for ubiquinone reductase activity (Qi site) in the cytochrome bc1 complex.

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Gray, K A; Dutton, P L; Daldal, F

1994-01-25

Folding models suggest that the highly conserved histidine 217 of the cytochrome b subunit from the cytochrome bc1 complex is close to the quinone reductase (Qi) site. This histidine (bH217) in the cytochrome b polypeptide of the photosynthetic bacterium Rhodobacter capsulatus has been replaced with three other residues, aspartate (D), arginine (R), and leucine (L). bH217D and bH217R are able to grow photoheterotrophically and contain active cytochrome bc1 complexes (60% of wild-type activity), whereas the bH217L mutant is photosynthetically incompetent and contains a cytochrome bc1 complex that has only 10% of the wild-type activity. Single-turnover flash-activated electron transfer experiments show that cytochrome bH is reduced via the Qo site with near native rates in the mutant strains but that electron transfer between cytochrome bH and quinone bound at the Qi site is greatly slowed. These results are consistent with redox midpoint potential (Em) measurements of the cytochrome b subunit hemes and the Qi site quinone. The Em values of cyt bL and bH are approximately the same in the mutants and wild type, although the mutant strains have a larger relative concentration of what may be the high-potential form of cytochrome bH, called cytochrome b150. However, the redox properties of the semiquinone at the Qi site are altered significantly. The Qi site semiquinone stability constant of bH217R is 10 times higher than in the wild type, while in the other two strains (bH217D and bH217L) the stability constant is much lower than in the wild type. Thus H217 appears to have major effects on the redox properties of the quinone bound at the Qi site. These data are incorporated into a suggestion that H217 forms part of the binding pocket of the Qi site in a manner reminiscent of the interaction between quinone bound at the Qb site and H190 of the L subunit of the bacterial photosynthetic reaction center.

Laccase-catalyzed oxidation and intramolecular cyclization of dopamine: A new method for selective determination of dopamine with laccase/carbon nanotube-based electrochemical biosensors

International Nuclear Information System (INIS)

Xiang, Ling; Lin, Yuqing; Yu, Ping; Su, Lei; Mao, Lanqun

2007-01-01

This study demonstrates a new electrochemical method for the selective determination of dopamine (DA) with the coexistence of ascorbic acid (AA) and 3,4-dihydroxyphenylacetic acid (DOPAC) with laccase/multi-walled carbon nanotube (MWNT)-based biosensors prepared by cross-linking laccase into MWNT layer confined onto glassy carbon electrodes. The method described here is essentially based on the chemical reaction properties of DA including oxidation, intramolecular cyclization and disproportionation reactions to finally give 5,6-dihydroxyindoline quinone and on the uses of the two-electron and two-proton reduction of the formed 5,6-dihydroxyindoline quinone to constitute a method for the selective determination of DA at a negative potential that is totally separated from those for the redox processes of AA and DOPAC. Instead of the ECE reactions of DA with the first oxidation of DA being driven electrochemically, laccase is used here as the biocatalyst to drive the first oxidation of DA into its quinone form and thus initialize the sequential reactions of DA finally into 5,6-dihydroxyindoline quinone. In addition, laccase also catalyzes the oxidation of AA and DOPAC into electroinactive species with the concomitant reduction of O 2 . As a consequence, a combinational exploitation of the chemical properties inherent in DA and the multifunctional catalytic properties of laccase as well as the excellent electrochemical properties of carbon nanotubes substantially enables the prepared laccase/MWNT-based biosensors to be well competent for the selective determination of DA with the coexistence of physiological levels of AA and DOPAC. This demonstration offers a new method for the selective determination of DA, which could be potentially employed for the determination of DA in biological systems

Enhancement of anti-inflammatory activity of Aloe vera adventitious root extracts through the alteration of primary and secondary metabolites via salicylic acid elicitation.

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Yun Sun Lee

Full Text Available Aloe vera (Asphodeloideae is a medicinal plant in which useful secondary metabolites are plentiful. Among the representative secondary metabolites of Aloe vera are the anthraquinones including aloe emodin and chrysophanol, which are tricyclic aromatic quinones synthesized via a plant-specific type III polyketide biosynthesis pathway. However, it is not yet clear which cellular responses can induce the pathway, leading to production of tricyclic aromatic quinones. In this study, we examined the effect of endogenous elicitors on the type III polyketide biosynthesis pathway and identified the metabolic changes induced in elicitor-treated Aloe vera adventitious roots. Salicylic acid, methyl jasmonate, and ethephon were used to treat Aloe vera adventitious roots cultured on MS liquid media with 0.3 mg/L IBA for 35 days. Aloe emodin and chrysophanol were remarkably increased by the SA treatment, more than 10-11 and 5-13 fold as compared with untreated control, respectively. Ultra-performance liquid chromatography-electrospray ionization mass spectrometry analysis identified a total of 37 SA-induced compounds, including aloe emodin and chrysophanol, and 3 of the compounds were tentatively identified as tricyclic aromatic quinones. Transcript accumulation analysis of polyketide synthase genes and gas chromatography mass spectrometry showed that these secondary metabolic changes resulted from increased expression of octaketide synthase genes and decreases in malonyl-CoA, which is the precursor for the tricyclic aromatic quinone biosynthesis pathway. In addition, anti-inflammatory activity was enhanced in extracts of SA-treated adventitious roots. Our results suggest that SA has an important role in activation of the plant specific-type III polyketide biosynthetic pathway, and therefore that the efficacy of Aloe vera as medicinal agent can be improved through SA treatment.

Enhancement of anti-inflammatory activity of Aloe vera adventitious root extracts through the alteration of primary and secondary metabolites via salicylic acid elicitation.

Science.gov (United States)

Lee, Yun Sun; Ju, Hyun Kyoung; Kim, Yeon Jeong; Lim, Tae-Gyu; Uddin, Md Romij; Kim, Yeon Bok; Baek, Jin Hong; Kwon, Sung Won; Lee, Ki Won; Seo, Hak Soo; Park, Sang Un; Yang, Tae-Jin

2013-01-01

Aloe vera (Asphodeloideae) is a medicinal plant in which useful secondary metabolites are plentiful. Among the representative secondary metabolites of Aloe vera are the anthraquinones including aloe emodin and chrysophanol, which are tricyclic aromatic quinones synthesized via a plant-specific type III polyketide biosynthesis pathway. However, it is not yet clear which cellular responses can induce the pathway, leading to production of tricyclic aromatic quinones. In this study, we examined the effect of endogenous elicitors on the type III polyketide biosynthesis pathway and identified the metabolic changes induced in elicitor-treated Aloe vera adventitious roots. Salicylic acid, methyl jasmonate, and ethephon were used to treat Aloe vera adventitious roots cultured on MS liquid media with 0.3 mg/L IBA for 35 days. Aloe emodin and chrysophanol were remarkably increased by the SA treatment, more than 10-11 and 5-13 fold as compared with untreated control, respectively. Ultra-performance liquid chromatography-electrospray ionization mass spectrometry analysis identified a total of 37 SA-induced compounds, including aloe emodin and chrysophanol, and 3 of the compounds were tentatively identified as tricyclic aromatic quinones. Transcript accumulation analysis of polyketide synthase genes and gas chromatography mass spectrometry showed that these secondary metabolic changes resulted from increased expression of octaketide synthase genes and decreases in malonyl-CoA, which is the precursor for the tricyclic aromatic quinone biosynthesis pathway. In addition, anti-inflammatory activity was enhanced in extracts of SA-treated adventitious roots. Our results suggest that SA has an important role in activation of the plant specific-type III polyketide biosynthetic pathway, and therefore that the efficacy of Aloe vera as medicinal agent can be improved through SA treatment.

Partitioning of electron flux between the respiratory chains of the yeast Candida parapsilosis: parallel working of the two chains.

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Guerin, M G; Camougrand, N M

1994-02-08

Partitioning of the electron flux between the classical and the alternative respiratory chains of the yeast Candida parapsilosis, was measured as a function of the oxidation rate and of the Q-pool redox poise. At low respiration rate, electrons from external NADH travelled preferentially through the alternative pathway as indicated by the antimycin A-insensitivity of electron flow. Inhibition of the alternative pathway by SHAM restored full antimycin A-sensitivity to the remaining electro flow. The dependence of the respiratory rate on the redox poise of the quinone pool was investigated when the electron flux was mediated either by the main respiratory chain (growth in the absence of antimycin A) or by the second respiratory chain (growth in the presence of antimycin A). In the former case, a linear relationship was found between these two parameters. In contrast, in the latter case, the relationship between Q-pool reduction level and electron flux was non-linear, but it could be resolved into two distinct curves. This second quinone is not reducible in the presence of antimycin A but only in the presence of high concentrations of myxothiazol or cyanide. Since two quinone species exist in C. parapsilosis, UQ9 and Qx (C33H54O4), we hypothesized that these two curves could correspond to the functioning of the second quinone engaged during the alternative pathway activity. Partitioning of electrons between both respiratory chains could occur upstream of complex III with the second chain functioning in parallel to the main one, and with the additional possibility of merging into the main one at the complex IV level.

Oxidation of atenolol, propranolol, carbamazepine and clofibric acid by a biological Fenton-like system mediated by the white-rot fungus Trametes versicolor.

Science.gov (United States)

Marco-Urrea, Ernest; Radjenović, Jelena; Caminal, Gloria; Petrović, Mira; Vicent, Teresa; Barceló, Damià

2010-01-01

Biological advanced oxidation of the pharmaceuticals clofibric acid (CA), carbamazepine (CBZP), atenolol (ATL) and propranolol (PPL) is reported for the first time. Extracellular oxidizing species were produced through a quinone redox cycling mechanism catalyzed by an intracellular quinone reductase and any of the ligninolytic enzymes of Trametes versicolor after addition of the lignin-derived quinone 2,6-dimethoxy-1,4-benzoquinone (DBQ) and Fe(3+)-oxalate in the medium. Time-course experiments with approximately 10mg L(-1) of initial pharmaceutical concentration resulted in percent degradations above 80% after 6h of incubation. Oxidation of pharmaceuticals was only observed under DBQ redox cycling conditions. A similar degradation pattern was observed when CBZP was added at the environmentally relevant concentration of 50 microg L(-1). Depletion of DBQ due to the attack of oxidizing agents was assumed to be the main limiting factor of pharmaceutical degradation. The main degradation products, that resulted to be pharmaceutical hydroxylated derivatives, were structurally elucidated. The detected 4- and 7-hydroxycarbamazepine intermediates of CBZP degradation were not reported to date. Total disappearance of intermediates was observed in all the experiments at the end of the incubation period. (c) 2009 Elsevier Ltd. All rights reserved.

Synthesis of New 4-Aminoquinolines and Evaluation of Their In Vitro Activity against Chloroquine-Sensitive and Chloroquine-Resistant Plasmodium falciparum.

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Chandima S K Rajapakse

Full Text Available The efficacy of chloroquine, once the drug of choice in the fight against Plasmodium falciparum, is now severely limited due to widespread resistance. Amodiaquine is one of the most potent antimalarial 4-aminoquinolines known and remains effective against chloroquine-resistant parasites, but toxicity issues linked to a quinone-imine metabolite limit its clinical use. In search of new compounds able to retain the antimalarial activity of amodiaquine while circumventing quinone-imine metabolite toxicity, we have synthesized five 4-aminoquinolines that feature rings lacking hydroxyl groups in the side chain of the molecules and are thus incapable of generating toxic quinone-imines. The new compounds displayed high in vitro potency (low nanomolar IC50, markedly superior to chloroquine and comparable to amodiaquine, against chloroquine-sensitive and chloroquine-resistant strains of P. falciparum, accompanied by low toxicity to L6 rat fibroblasts and MRC5 human lung cells, and metabolic stability comparable or higher than that of amodiaquine. Computational studies indicate a unique mode of binding of compound 4 to heme through the HOMO located on a biphenyl moeity, which may partly explain the high antiplasmodial activity observed for this compound.

Pyrroloquinoline-quinone suppresses liver fibrogenesis in mice.

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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.

CHARACTERIZATION OF STABLE BENZO(A)PYRENE-7,8-QUINONE-DNA ADDUCTS IN CALF THYMUS DNA

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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...

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...

FY 1974 report on the results of the Sunshine Project. Comprehensive study of hydrogen use subsystem and study on the periphery technology (Investigational study on the hydrogen production method by the quinone method); 1974 nendo suiso riyo subsystem no sogoteki kento to shuhen gijutsu ni kansuru kenkyu seika hokokusho. Kinonho ni yoru suiso seizoho ni kansuru chosa kenkyu

Energy Technology Data Exchange (ETDEWEB)

NONE

1975-05-01

This is aimed at making an investigational study on the hydrogen production from water by means of quinone compounds. The paper studied a preparation method in case of using n-TiO2 photosemiconductor and p-GaAs and Gap photosemiconductor to photoelectrode as catalysts of this reaction. The reaction from p-benzoquinone to p-hydroquinone by reaction with H2O were studied in terms of photochemical reaction, and light reaction/dark reaction of photosemiconductor electrode. As a result, it was found out that this reaction easily advances by the photochemical reaction by solar light, and also that it advances by the counter electrode Pt electrode reaction in the water electrolysis of n-TiO2 photosemiconductor electrode. The H2 production reaction from p-hydrogquinone was studied in terms of the photochemical reaction, photosemiconductor electrode reaction, and effects of the catalysis of electron transport of metal salts, methylviologen, etc. As a result, in the n-TiO2 photosemiconductor electrode reaction, H2 formation was not as great as it can be confirmed. However, it was found that p-hydroquinone can produce H2 under the existence of methylviologen or Fe salts. (NEDO)

A new look on protein-polyphenol complexation during honey storage: is this a random or organized event with the help of dirigent-like proteins?

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Katrina Brudzynski

Full Text Available Honey storage initiates melanoidin formation that involves a cascade of seemingly unguided redox reactions between amino acids/proteins, reducing sugars and polyphenols. In the process, high molecular weight protein-polyphenol complexes are formed, but the mechanism involved remains unknown. The objective of this study was twofold: to determine quantitative and qualitative changes in proteins in honeys stored for prolonged times and in different temperatures and to relate these changes to the formation of protein-polyphenol complexes. Six -month storage decreased the protein content by 46.7% in all tested honeys (t-test, p<0.002 with the rapid reduction occurring during the first three month. The changes in protein levels coincided with alterations in molecular size and net charge of proteins on SDS -PAGE. Electro-blotted proteins reacted with a quinone-specific nitro blue tetrazolium (NBT on nitrocellulose membranes indicating that quinones derived from oxidized polyphenols formed covalent bonds with proteins. Protein-polyphenol complexes isolated by size-exclusion chromatography differed in size and stoichiometry and fall into two categories: (a high molecular weight complexes (230-180 kDa enriched in proteins but possessing a limited reducing activity toward the NBT and (b lower molecular size complexes (110-85 kDa enriched in polyphenols but strongly reducing the dye. The variable stoichiometry suggest that the large, "protein-type" complexes were formed by protein cross-linking, while in the smaller, "polyphenol-type" complexes polyphenols were first polymerized prior to protein binding. Quinones preferentially bound a 31 kDa protein which, by the electrospray quadrupole time of flight mass spectrometry (ESI-Qtof-MS analysis, showed homology to dirigent-like proteins known for assisting in radical coupling and polymerization of phenolic compounds. These findings provide a new look on protein-polyphenol interaction in honey where the

Physiological responses of emerald ash borer larvae to feeding on different ash species reveal putative resistance mechanisms and insect counter-adaptations.

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Rigsby, C M; Showalter, D N; Herms, D A; Koch, J L; Bonello, P; Cipollini, D

2015-07-01

Emerald ash borer, Agrilus planipennis Fairmaire, an Asian wood-boring beetle, has devastated ash (Fraxinus spp.) trees in North American forests and landscapes since its discovery there in 2002. In this study, we collected living larvae from EAB-resistant Manchurian ash (Fraxinus mandschurica), and susceptible white (Fraxinus americana) and green (Fraxinus pennsylvanica) ash hosts, and quantified the activity and production of selected detoxification, digestive, and antioxidant enzymes. We hypothesized that differences in larval physiology could be used to infer resistance mechanisms of ash. We found no differences in cytochrome P450, glutathione-S-transferase, carboxylesterase, sulfotransferase, and tryptic BApNAase activities between larvae feeding on different hosts. Despite this, Manchurian ash-fed larvae produced a single isozyme of low electrophoretic mobility that was not produced in white or green ash-fed larvae. Additionally, larvae feeding on white and green ash produced two serine protease isozymes of high electrophoretic mobility that were not observed in Manchurian ash-fed larvae. We also found lower activity of β-glucosidase and higher activities of monoamine oxidase, ortho-quinone reductase, catalase, superoxide dismutase, and glutathione reductase in Manchurian ash-fed larvae compared to larvae that had fed on susceptible ash. A single isozyme was detected for both catalase and superoxide dismutase in all larval groups. The activities of the quinone-protective and antioxidant enzymes are consistent with the resistance phenotype of the host species, with the highest activities measured in larvae feeding on resistant Manchurian ash. We conclude that larvae feeding on Manchurian ash could be under quinone and oxidative stress, suggesting these may be potential mechanisms of resistance of Manchurian ash to EAB larvae, and that quinone-protective and antioxidant enzymes are important counter-adaptations of larvae for dealing with these resistance

Insights into the importance of oxygen functional groups in carbon reactions with oxygen containing gases

International Nuclear Information System (INIS)

John Zhu, Max Lu

2005-01-01

The role of pore structure of carbon in carbon-related adsorptions and reactions has been extensively investigated. However the studies on the role of surface chemistry of carbon are limited. In this paper, we present the importance of oxygen functional groups in carbon reactions with oxygen-containing gases. It is found that there is a good correlation between the electronic structures and reactivities of carbon edge sites. Zigzag sites are more active in oxygen adsorption because of the unpaired electrons and armchair sites are less active in oxygen adsorption due to the triple character. However, the desorption of semi-quinone oxygen from zigzag sites needs a bond energy ca. 30% higher than that of o-quinone oxygen from armchair edge sites. CO 2 and H 2 O adsorb on carbon surface much less favorably than O 2 . H 2 O is first physically adsorbed on the virgin graphite surface followed by chemisorption through oxygen atom approaching the carbon edge site and the movements of two hydrogen atoms to produce H 2 . The adsorption mechanism of H 2 O is different from that for CO 2 , but the final result is quite similar, i.e. producing only semi-quinone oxygen. Based upon the above studies, a new generalized mechanism, as shown in Fig. 1, is developed and can account for all the important kinetic phenomena of carbon-gas reactions. The key point is that in CO 2 /H 2 O-carbon reaction only semi-quinone formed; while, in O 2 -carbon reaction, semi-quinone, o-quinone (at lower pressure), and off-plane epoxy oxygen (at relatively higher pressure) can be formed. This is the main reason for the different reaction kinetics of O 2 -carbon reaction and CO 2 /H 2 O-carbon reactions as observed experimentally. The oxygen functional groups of carbon can be characterized by XPS, PZC (point of zero charge), IEP (isoelectric point) and TPD (temperature-programmed desorption), which were used in our previous studies. We treated the carbon surface with different acids, finding that HNO 3

Total Synthesis of (+)-Cytosporolide A via a Biomimetic Hetero-Diels-Alder Reaction.

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Takao, Ken-Ichi; Noguchi, Shuji; Sakamoto, Shu; Kimura, Mizuki; Yoshida, Keisuke; Tadano, Kin-Ichi

2015-12-23

The first total synthesis of (+)-cytosporolide A was achieved by a biomimetic hetero-Diels-Alder reaction of (-)-fuscoatrol A with o-quinone methide generated from (+)-CJ-12,373. The dienophile, highly oxygenated caryophyllene sesquiterpenoid (-)-fuscoatrol A, was synthesized from the synthetic intermediate in our previous total synthesis of (+)-pestalotiopsin A. The o-quinone methide precursor, isochroman carboxylic acid (+)-CJ-12,373, was synthesized through a Kolbe-Schmitt reaction and an oxa-Pictet-Spengler reaction. The hetero-Diels-Alder reaction of these two compounds proceeded with complete chemo-, regio-, and stereoselectivity to produce the complicated pentacyclic ring system of the cytosporolide skeleton. This total synthesis unambiguously demonstrates that natural cytosporolide A has the structure previously suggested.

Sodium dodecyl benzene sulphonate mediated tautomerism of Eriochrome Black-T: Effect of charge transfer interaction

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Ghosh, Sumit

2010-11-01

Interaction between anionic surfactant, sodium dodecyl benzene sulphonate, (SDBS) and an anionic dye Eriochrome Black-T, (EBT) has been investigated by visible spectroscopy, conductometry, dynamic light scattering and zeta potential measurements. Spectral changes of EBT observed on addition of SDBS indicate formation of quinone-hydrazone tautomer at pH 7.0, whereas in absence of SDBS this change appears at pH ˜ 9.45. However, at pH 7.0 this change in tautomerism is not observed in presence of sodium dodecyl sulphate (SDS). Experimental results indicate presence of charge transfer interaction between less stable quinone-hydrazone tautomer of EBT and SDBS molecules, which is confirmed using Benesi-Hildebrand and Scott equations.

Electrochemical analysis in a liposome suspension using lapachol as a hydrophobic electro active species.

Science.gov (United States)

Okumura, Noriko; Wakamatsu, Shiori; Uno, Bunji

2014-01-01

This study demonstrated that the electro-chemical analysis of hydrophobic quinones can be performed in liposome suspension systems. We prepared and analyzed liposome suspensions containing lapachol, which is a quinone-based anti-tumor activity compound. In this suspension system, a simple one redox couple of lapachol is observed. These results are quite different from those obtained in organic solvents. In addition, the pH dependence of redox behaviors of lapachol could be observed in multilamellar vesicle (MLV) suspension system. This MLV suspension system method may approximate the electrochemical behavior of hydrophobic compounds in aqueous conditions. A benefit of this liposome suspension system for electrochemical analysis is that it enables to observe water-insoluble compounds without using organic solvents.

Electron transfer pathways in microbial oxygen biocathodes

Energy Technology Data Exchange (ETDEWEB)

Freguia, Stefano, E-mail: stefano@kais.kyoto-u.ac.j [Bio-analytical and Physical Chemistry Laboratory, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8205 (Japan); Tsujimura, Seiya, E-mail: seiya@kais.kyoto-u.ac.j [Bio-analytical and Physical Chemistry Laboratory, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8205 (Japan); Kano, Kenji, E-mail: kkano@kais.kyoto-u.ac.j [Bio-analytical and Physical Chemistry Laboratory, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8205 (Japan)

2010-01-01

The ability of some bacteria to enhance the rate of cathodic oxygen reduction to water has been recently discovered, opening the way to an entirely renewable and environmentally friendly concept of biocathode. In this study we reveal that several mechanisms may induce catalytic effects by bacteria. These comprise mechanisms that are putatively beneficial to the bacteria as well as mechanisms which are merely side effects, including quinone autoxidation and direct O{sub 2} reduction by heme compounds. Here we showed that 1 muM of ACNQ is able to generate a significant catalytic wave for oxygen reduction, with onset at approximately 0 V vs. SHE. Similarly, adsorption of hemin on a carbon surface catalyses O{sub 2} reduction to H{sub 2}O{sub 2} with an onset of +0.2 V vs. SHE. To evaluate the catalytic pathways of live cells on cathodic oxygen reduction, two species of electrochemically active bacteria were selected as pure cultures, namely Acinetobacter calcoaceticus and Shewanella putrefaciens. The former appears to exploit a self-excreted redox compound with redox characteristics matching those of pyrroloquinoline quinone (PQQ) for extracellular electron transfer. The latter appears to utilise outer membrane-bound redox compounds. Interaction of quinones and cytochromes with the membrane-bound electron transfer chain is yet to be proven.

Simulation of the oxidative metabolism of diclofenac by electrochemistry/(liquid chromatography/)mass spectrometry.

Science.gov (United States)

Faber, Helene; Melles, Daniel; Brauckmann, Christine; Wehe, Christoph Alexander; Wentker, Kristina; Karst, Uwe

2012-04-01

Diclofenac is a frequently prescribed drug for rheumatic diseases and muscle pain. In rare cases, it may be associated with a severe hepatotoxicity. In literature, it is discussed whether this toxicity is related to the oxidative phase I metabolism, resulting in electrophilic quinone imines, which can subsequently react with nucleophiles present in the liver in form of glutathione or proteins. In this work, electrochemistry coupled to mass spectrometry is used as a tool for the simulation of the oxidative pathway of diclofenac. Using this purely instrumental approach, diclofenac was oxidized in a thin layer cell equipped with a boron doped diamond working electrode. Sum formulae of generated oxidation products were calculated based on accurate mass measurements with deviations below 2 ppm. Quinone imines from diclofenac were detected using this approach. It could be shown for the first time that these quinone imines do not react with glutathione exclusively but also with larger molecules such as the model protein β-lactoglobulin A. A tryptic digest of the generated drug-protein adduct confirms that the protein is modified at the only free thiol-containing peptide. This simple and purely instrumental set-up offers the possibility of generating reactive metabolites of diclofenac and to assess their reactivity rapidly and easily.

Electrochemical studies of redox probes in self-organized lyotropic ...

Indian Academy of Sciences (India)

Administrator

quinone|hydroquinone, methyl viologen and ferrocenemethanol probes in a lyotropic hexagonal columnar phase (H1 phase) using cyclic voltammetry and electrochemical impedance ..... hydrogen bond of hydroquinone during oxidation is.

Biochemistry of Catabolic Reductive Dehalogenation.

Science.gov (United States)

Fincker, Maeva; Spormann, Alfred M

2017-06-20

A wide range of phylogenetically diverse microorganisms couple the reductive dehalogenation of organohalides to energy conservation. Key enzymes of such anaerobic catabolic pathways are corrinoid and Fe-S cluster-containing, membrane-associated reductive dehalogenases. These enzymes catalyze the reductive elimination of a halide and constitute the terminal reductases of a short electron transfer chain. Enzymatic and physiological studies revealed the existence of quinone-dependent and quinone-independent reductive dehalogenases that are distinguishable at the amino acid sequence level, implying different modes of energy conservation in the respective microorganisms. In this review, we summarize current knowledge about catabolic reductive dehalogenases and the electron transfer chain they are part of. We review reaction mechanisms and the role of the corrinoid and Fe-S cluster cofactors and discuss physiological implications.

Pulse radiolytic one-electron reduction of 1,4-amino and hydroxy disubstituted 9,10-anthraquinones

International Nuclear Information System (INIS)

Pal, H.; Palit, D.K.; Mukherjee, T.; Mittal, J.P.

1992-01-01

The semiquinone radicals produced by one-electron reduction of 1-amino-4-hydroxy-9,10-anthraquinone and 1,4-diamino-9,10-anthraquinone have been studied in aqueous-organic mixed solvent using pulse radiolysis technique. Spectroscopic characteristics, kinetic characteristics of formation and decay, acid/base behaviour and redox characteristics of the semiquinones have been investigated and compared with those of some similar systems studied earlier. It has been shown that the variation of the disproportionation equilibria involving the reduced semiquinone radicals, the parent quinone and the fully reduced hydroquinone with pH of the solutions follow a similar trend as observed in the case of other dihydroxy quinones. Stability of the semiquinones over a broad pH range and their thermodynamic properties have been correlated. (Author)

Visual sensing of fluoride ions by dipyrrolyl derivatives bearing

Indian Academy of Sciences (India)

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.

A cytogenetic methodology to evaluate in vitro the G2-chromosomal ...

Indian Academy of Sciences (India)

2National School of Public Health, Department of Occupational and Industrial Hygiene, 196 Alexandras Avenue, ... In this work, we propose an experimental methodol- ... quinone affects the cell-cycle proliferation kinetics inducing.

21 CFR 177.2600 - Rubber articles intended for repeated use.

Science.gov (United States)

2010-04-01

...) of this chapter. Sodium decylbenzenesulfonate Sodium dodecylbenzenesulfonate Sodium lauryl sulfate.... Piperidinium pentamethylenedithiocarba-mate. Potassium pentamethylenedithiocarbamate. p-Quinone dioxime. Sodium dibutyldithiocarbamate. Sodium dimethyldithiocarbamate. Stannous oleate for use only as an accelerator for silicone...

Identification of the quinolinedione inhibitor binding site in Cdc25 phosphatase B through docking and molecular dynamics simulations

Science.gov (United States)

Ge, Yushu; van der Kamp, Marc; Malaisree, Maturos; Liu, Dan; Liu, Yi; Mulholland, Adrian J.

2017-11-01

Cdc25 phosphatase B, a potential target for cancer therapy, is inhibited by a series of quinones. The binding site and mode of quinone inhibitors to Cdc25B remains unclear, whereas this information is important for structure-based drug design. We investigated the potential binding site of NSC663284 [DA3003-1 or 6-chloro-7-(2-morpholin-4-yl-ethylamino)-quinoline-5, 8-dione] through docking and molecular dynamics simulations. Of the two main binding sites suggested by docking, the molecular dynamics simulations only support one site for stable binding of the inhibitor. Binding sites in and near the Cdc25B catalytic site that have been suggested previously do not lead to stable binding in 50 ns molecular dynamics (MD) simulations. In contrast, a shallow pocket between the C-terminal helix and the catalytic site provides a favourable binding site that shows high stability. Two similar binding modes featuring protein-inhibitor interactions involving Tyr428, Arg482, Thr547 and Ser549 are identified by clustering analysis of all stable MD trajectories. The relatively flexible C-terminal region of Cdc25B contributes to inhibitor binding. The binding mode of NSC663284, identified through MD simulation, likely prevents the binding of protein substrates to Cdc25B. The present results provide useful information for the design of quinone inhibitors and their mechanism of inhibition.

Identification of the quinolinedione inhibitor binding site in Cdc25 phosphatase B through docking and molecular dynamics simulations.

Science.gov (United States)

Ge, Yushu; van der Kamp, Marc; Malaisree, Maturos; Liu, Dan; Liu, Yi; Mulholland, Adrian J

2017-11-01

Cdc25 phosphatase B, a potential target for cancer therapy, is inhibited by a series of quinones. The binding site and mode of quinone inhibitors to Cdc25B remains unclear, whereas this information is important for structure-based drug design. We investigated the potential binding site of NSC663284 [DA3003-1 or 6-chloro-7-(2-morpholin-4-yl-ethylamino)-quinoline-5, 8-dione] through docking and molecular dynamics simulations. Of the two main binding sites suggested by docking, the molecular dynamics simulations only support one site for stable binding of the inhibitor. Binding sites in and near the Cdc25B catalytic site that have been suggested previously do not lead to stable binding in 50 ns molecular dynamics (MD) simulations. In contrast, a shallow pocket between the C-terminal helix and the catalytic site provides a favourable binding site that shows high stability. Two similar binding modes featuring protein-inhibitor interactions involving Tyr428, Arg482, Thr547 and Ser549 are identified by clustering analysis of all stable MD trajectories. The relatively flexible C-terminal region of Cdc25B contributes to inhibitor binding. The binding mode of NSC663284, identified through MD simulation, likely prevents the binding of protein substrates to Cdc25B. The present results provide useful information for the design of quinone inhibitors and their mechanism of inhibition.

A review on toxicological properties of thymoquinone a natural broad spectrum ingredient

Directory of Open Access Journals (Sweden)

2017-11-01

Full Text Available Background and objectives: Nigella sativa is a delicate floral vegetable belonging to Ranunculaceae family. Thymoquinone (TQ is the dominant active component in Nigella sativa seed oil which has a variety of pharmacological properties such as antioxidant, anticancer, anti-inflammatory and analgesic activities. However, TQ is a quinone derivative, which may lead to the generation of reactive oxygen species and resulting intermediate toxicity with various adverse effects in vivo, including acute cytotoxicity, genotoxicity, immunotoxicity, and carcinogenesis. In this review we have mentioned several studies on the toxicity properties of thymoquinone and Nigella sativa. Methods: A literature search was conducted using the Web of Science, PubMed, MEDLINE and Scopus. The search included the following keywords: "thymoquinone", "hydroquinone"," quinone" and "Nigella sativa". Citations within articles were also reviewed to identify the relevant sources. We studied about 170 articles and put aside the articles that were performed on the effect of Nigella sativa and thymoquinone on cancer cell lines. Results:  Since TQ is a quinone derivative, we observed the generation of reactive oxygen species and the toxicity of this substance in some studies. LD50 of Thymoquinone was very higher than Nigella sativa and also LD50 of this substance in oral route was higher than intrapritoneal route of administration. Conclusion: The findings have provided approximate safety information for TQ, which will further help researchers.

Download this PDF file

African Journals Online (AJOL)

Elamin

274-7. 14. Wright RS, Quinones-Baldrich WJ, Anders AJ,. Danovitch GM. Pleural effusion associated withipsilateral breast and arm edema as a complication of subclavian vein catheterization and arteriovenous fistula formation for hemodialysis.

Antiprotozoal Isoflavan Quinones from Abrus precatorius ssp. africanus

CSIR Research Space (South Africa)

Hata, Y

2013-04-01

Full Text Available and semipreparative RPHPLC chromatography. Structures were established by HR-ESIMS, and 1D and 2D NMR ((sup)1H, (sup)13C, COSY, HMBC, HSQC, and NOE difference spectroscopy). Five compounds were obtained and identified as two isoflavan hydroquinones, abruquinone H (1...

Condensed tannins: Quinone methide intermediates in procyanidin synthesis

Science.gov (United States)

Richard W. Hemingway; L. Y. Foo

1983-01-01

Proanthocyanidins (condensed tanruns) are widely distributed in plants and are found in sufficiently high concentration in some tree barks to encourage their industrial utilization. These polymers consist of flavanoid units linked through the C-4 of the pyran ring to the C-6 or C-8 carbons of the aromatic A-ring. Recent advances in the chemistry of condensed tannins...

Magnetic, catalytic, EPR and electrochemical studies on binuclear ...

Indian Academy of Sciences (India)

Magnetic, catalytic, EPR and electrochemical studies on binuclear copper(II) complexes ... to the oxidation of 3,5-di--butylcatechol to the corresponding quinone. ... EPR spectral studies in methanol solvent show welldefined four hyperfine ...

One electron transfer redox potentials of free radicals. I. The oxygen-superoxide system. Progress report, September 1, 1975--July 1, 1976

International Nuclear Information System (INIS)

Ilan, Y.A.; Czapski, G.; Meisel, D.

1976-01-01

The method of determination of Redox potentials of radicals, using the pulse radiolysis technique, is outlined. The method is based on the determination of equilibria constants of electron transfer reactions between the radicals and appropriate acceptors. The limitations of this technique are discussed. The redox potentials of several quinones--semi-quinones are calculated, as well as the standard redox potential of the peroxy radical. E 0 /sub O 2 /O 2 /sup -/ = -0.33 V and the redox oxidation properties of the peroxy radical in various systems and pH are discussed. The value determined for the redox potentials of O 2 /O 2 - is higher by more than 0.2 volts than earlier estimates, which has important implications on the possible role of O 2 - in biological processes of O 2 fixation

The immune enhancer, thymoquinone, and the hope of utilizing the ...

African Journals Online (AJOL)

USER

2010-05-24

May 24, 2010 ... in the immuno-control strategy against mosquito-borne diseases. Key words: .... quinone (Tq) in the dengue fever vector Aedes aegypti. (Ahmed ...... expression profiling of apoptosis-related genes in the yellow fever mosquito ...

Waste to wealth: Production of oxytetracycline using streptomyces ...

African Journals Online (AJOL)

Yomi

2012-05-29

May 29, 2012 ... used due to high risk of sensitization (Archer et al., 2001). However, ocular ... degree of aeration at the surface favours the production of antibiotics ... the near absence of water. Oxytetracycline, a quinone antibiotic commonly.

Journal of Biosciences | Indian Academy of Sciences

Indian Academy of Sciences (India)

Keywords. Antioxidant; biofertilizer and biocontrol agent; biosensor; pharmacological agent; protein kinase inducer; pyrroloquinoline-quinone. Abstract. Pyrroloquinoline-quinine (PQQ) was initially characterized as a redox cofactor for membrane-bound dehydrogenases in the bacterial system. Subsequently, PQQ was ...

YNL134C from Saccharomyces cerevisiae encodes a novel protein with aldehyde reductase activity for detoxification of furfural derived from lignocellulosic biomass.

Science.gov (United States)

Zhao, Xianxian; Tang, Juan; Wang, Xu; Yang, Ruoheng; Zhang, Xiaoping; Gu, Yunfu; Li, Xi; Ma, Menggen

2015-05-01

Furfural and 5-hydroxymethylfurfural (HMF) are the two main aldehyde compounds derived from pentoses and hexoses, respectively, during lignocellulosic biomass pretreatment. These two compounds inhibit microbial growth and interfere with subsequent alcohol fermentation. Saccharomyces cerevisiae has the in situ ability to detoxify furfural and HMF to the less toxic 2-furanmethanol (FM) and furan-2,5-dimethanol (FDM), respectively. Herein, we report that an uncharacterized gene, YNL134C, was highly up-regulated under furfural or HMF stress and Yap1p and Msn2/4p transcription factors likely controlled its up-regulated expression. Enzyme activity assays showed that YNL134C is an NADH-dependent aldehyde reductase, which plays a role in detoxification of furfural to FM. However, no NADH- or NADPH-dependent enzyme activity was observed for detoxification of HMF to FDM. This enzyme did not catalyse the reverse reaction of FM to furfural or FDM to HMF. Further studies showed that YNL134C is a broad-substrate aldehyde reductase, which can reduce multiple aldehydes to their corresponding alcohols. Although YNL134C is grouped into the quinone oxidoreductase family, no quinone reductase activity was observed using 1,2-naphthoquinone or 9,10-phenanthrenequinone as a substrate, and phylogenetic analysis indicates that it is genetically distant to quinone reductases. Proteins similar to YNL134C in sequence from S. cerevisiae and other microorganisms were phylogenetically analysed. Copyright © 2015 John Wiley & Sons, Ltd.

The electronic and solvatochromic properties of [Co(L)(bipyridine)2]+ (L = o-catecholato, o-benzenedithiolato) species: a combined experimental and computational study.

Science.gov (United States)

Cioncoloni, Giacomo; Senn, Hans M; Sproules, Stephen; Wilson, Claire; Symes, Mark D

2016-10-04

Complexes of Co(iii) containing mixed chelating diimine and o-quinone ligand sets are of fundamental interest on account of their fascinating magnetic and electronic properties. Whilst complexes of this type containing one diimine and two o-quinone ligands have been studied extensively, those with the reverse stoichiometry (two diimines and one o-quinone) are much rarer. Herein, we describe a ready route to the synthesis of the complex [Co III (o-catecholate) (2,2'-bipyridine) 2 ] + (1), and also report the synthesis of [Co III (o-catecholate)(5,5'-dimethyl-2,2'-bipyridine) 2 ] + (2) and [Co III (o-benezenedithiolate)(5,5'-dimethyl-2,2'-bipyridine) 2 ] + (3) for the first time. Spectroscopic studies show that complex 2 displays intriguing solvatochromic behaviour as a function of solvent hydrogen bond donation ability, a property of this type of complex which has hitherto not been reported. Time-dependent density function theory (TD-DFT) shows that this effect arises as a result of hydrogen bonding between the solvent and the oxygen atoms of the catecholate ligand. In contrast, the sulfur atoms in the benzenedithiolate analogue 3 are much weaker acceptors of hydrogen bonds from the solvent, meaning that complex 3 is only very weakly solvatochromic. Finally, we show that complex 2 has some potential as a molecular probe that can report on the composition of mixed solvent systems as a function of its absorbance spectrum.

Isolation and partial characterization of pigment-like antibiotics produced by a new strain of Streptosporangium isolated from an Algerian soil.

Science.gov (United States)

Boudjella, H; Bouti, K; Zitouni, A; Mathieu, F; Lebrihi, A; Sabaou, N

2007-07-01

Identification of a new actinomycete strain Sg3, belonging to the genus Streptosporangium and partial characterization of the produced antibacterial activities. The strain Sg3 was isolated from an Algerian Saharan soil and identified by morphological, chemotaxonomic and phylogenetic analyses to the genus Streptosporangium. The comparison of its physiological characteristics with those of known species of Streptosporangium showed significant differences with the nearest species Streptosporangium carneum. Analysis of the 16S rDNA sequence of strain Sg3 showed a similarity level ranging between 97% and 98.8% within Streptosporangium species, with S. carneum the most closely related. Strain Sg3 showed a red coloured antibacterial activity against gram-positive bacteria on several culture media. The purification of the red pigment by chromatographic methods led to the isolation of three active products. The (1)H nuclear magnetic resonance (NMR), mass, infrared (IR) and ultraviolet-visible (UV-VIS) data of these molecules strongly suggested that they belonged to the quinone-anthracycline group with three or more rings. Strain Sg3 represents a distinct phyletic line suggesting a new genomic species. It produces antibacterial activities identified as quinone-anthracycline aromatics. The quinone-anthracycline antibiotics are known for their antimicrobial and antineoplastic activities and are used in chemotherapy for the treatment of many cancer diseases. The present work constitutes the first stage of a whole series of studies to be realized on these antibiotics before arriving at a possible application.

Structural and Biochemical Characterization of Chlamydia trachomatis Hypothetical Protein CT263 Supports That Menaquinone Synthesis Occurs through the Futalosine Pathway*

Science.gov (United States)

Barta, Michael L.; Thomas, Keisha; Yuan, Hongling; Lovell, Scott; Battaile, Kevin P.; Schramm, Vern L.; Hefty, P. Scott

2014-01-01

The obligate intracellular human pathogen Chlamydia trachomatis is the etiological agent of blinding trachoma and sexually transmitted disease. Genomic sequencing of Chlamydia indicated this medically important bacterium was not exclusively dependent on the host cell for energy. In order for the electron transport chain to function, electron shuttling between membrane-embedded complexes requires lipid-soluble quinones (e.g. menaquionone or ubiquinone). The sources or biosynthetic pathways required to obtain these electron carriers within C. trachomatis are poorly understood. The 1.58Å crystal structure of C. trachomatis hypothetical protein CT263 presented here supports a role in quinone biosynthesis. Although CT263 lacks sequence-based functional annotation, the crystal structure of CT263 displays striking structural similarity to 5′-methylthioadenosine nucleosidase (MTAN) enzymes. Although CT263 lacks the active site-associated dimer interface found in prototypical MTANs, co-crystal structures with product (adenine) or substrate (5′-methylthioadenosine) indicate that the canonical active site residues are conserved. Enzymatic characterization of CT263 indicates that the futalosine pathway intermediate 6-amino-6-deoxyfutalosine (kcat/Km = 1.8 × 103 m−1 s−1), but not the prototypical MTAN substrates (e.g. S-adenosylhomocysteine and 5′-methylthioadenosine), is hydrolyzed. Bioinformatic analyses of the chlamydial proteome also support the futalosine pathway toward the synthesis of menaquinone in Chlamydiaceae. This report provides the first experimental support for quinone synthesis in Chlamydia. Menaquinone synthesis provides another target for agents to combat C. trachomatis infection. PMID:25253688

Oxidative Metabolites of Curcumin Poison Human Type II Topoisomerases†

Science.gov (United States)

Ketron, Adam C.; Gordon, Odaine N.; Schneider, Claus; Osheroff, Neil

2013-01-01

The polyphenol curcumin is the principal flavor and color component of the spice turmeric. Beyond its culinary uses, curcumin is believed to positively impact human health and displays antioxidant, anti-inflammatory, antibacterial, and chemopreventive properties. It also is in clinical trials as an anticancer agent. In aqueous solution at physiological pH, curcumin undergoes spontaneous autoxidation that is enhanced by oxidizing agents. The reaction proceeds through a series of quinone methide and other reactive intermediates to form a final dioxygenated bicyclopentadione product. Several naturally occurring polyphenols that can form quinones have been shown to act as topoisomerase II poisons (i.e., increase levels of topoisomerase II-mediated DNA cleavage). Because several of these compounds have chemopreventive properties, we determined the effects of curcumin, its oxidative metabolites, and structurally related degradation products (vanillin, ferulic acid, and feruloylmethane), on the DNA cleavage activities of human topoisomerase IIα and IIβ. Intermediates in the curcumin oxidation pathway increased DNA scission mediated by both enzymes ~4-5–fold. In contrast, curcumin and the bicyclopentadione, as well as vanillin, ferulic acid, and feruloylmethane, had no effect on DNA cleavage. As found for other quinone-based compounds, curcumin oxidation intermediates acted as redox-dependent (as opposed to interfacial) topoisomerase II poisons. Finally, under conditions that promote oxidation, the dietary spice turmeric enhanced topoisomerase II-mediated DNA cleavage. Thus, even within the more complex spice formulation, oxidized curcumin intermediates appear to function as topoisomerase II poisons. PMID:23253398

ELECTROCHEMICAL SYNTHESIS AND CHARACTERIZATION OF ...

African Journals Online (AJOL)

Using simple electrosynthesis methods a single and bilayer of conducting ... metal oxides [5-8], carbon nanomaterials [5-8], polyoxometalates [9-12], and quinone .... where C is the specific capacitance in farads per grams (F/g), i is current ...

Agaricus bisporus browning: a review

NARCIS (Netherlands)

Jolivet, S.; Arpin, N.; Wichers, H.J.; Pellon, G.

1998-01-01

Agaricus bisporus browning is a common and economically detrimental phenomenon, in which melanogenic phenols are enzymically processed into quinones, which evolve eventually to melanins. This review deals with the two fundamental sides of this process, enzyme(s) and phenolic substrates. Mushroom

Dithiothreitol activity by particulate oxidizers of SOA produced from photooxidation of hydrocarbons under varied NOx levels

Science.gov (United States)

Jiang, Huanhuan; Jang, Myoseon; Yu, Zechen

2017-08-01

When hydrocarbons (HCs) are atmospherically oxidized, they form particulate oxidizers, including quinones, organic hydroperoxides, and peroxyacyl nitrates (PANs). These particulate oxidizers can modify cellular materials (e.g., proteins and enzymes) and adversely modulate cell functions. In this study, the contribution of particulate oxidizers in secondary organic aerosols (SOAs) to the oxidative potential was investigated. SOAs were generated from the photooxidation of toluene, 1,3,5-trimethylbenzene, isoprene, and α-pinene under varied NOx levels. Oxidative potential was determined from the typical mass-normalized consumption rate (reaction time t = 30 min) of dithiothreitol (DTTt), a surrogate for biological reducing agents. Under high-NOx conditions, the DTTt of toluene SOA was 2-5 times higher than that of the other types of SOA. Isoprene DTTt significantly decreased with increasing NOx (up to 69 % reduction by changing the HC / NOx ratio from 30 to 5). The DTTt of 1,3,5-trimethylbenzene and α-pinene SOA was insensitive to NOx under the experimental conditions of this study. The significance of quinones to the oxidative potential of SOA was tested through the enhancement of DTT consumption in the presence of 2,4-dimethylimidazole, a co-catalyst for the redox cycling of quinones; however, no significant effect of 2,4-dimethylimidazole on modulation of DTT consumption was observed for all SOA, suggesting that a negligible amount of quinones was present in the SOA of this study. For toluene and isoprene, mass-normalized DTT consumption (DTTm) was determined over an extended period of reaction time (t = 2 h) to quantify their maximum capacity to consume DTT. The total quantities of PANs and organic hydroperoxides in toluene SOA and isoprene SOA were also measured using the Griess assay and the 4-nitrophenylboronic acid assay, respectively. Under the NOx conditions (HC / NOx ratio: 5-36 ppbC ppb-1) applied in this study, the amount of organic hydroperoxides was

p53 Mutagenesis by Benzo[a]pyrene derived Radical Cations

Science.gov (United States)

Sen, Sushmita; Bhojnagarwala, Pratik; Francey, Lauren; Lu, Ding; Jeffrey Field, Trevor M. Penning

2013-01-01

Benzo[a]pyrene (B[a]P), a major human carcinogen in combustion products such as cigarette smoke and diesel exhaust, is metabolically activated into DNA-reactive metabolites via three different enzymatic pathways. The pathways are the anti-(+)-benzo[a]pyrene 7,8-diol 9, 10-epoxide pathway (P450/ epoxide hydrolase catalyzed) (B[a]PDE), the benzo[a]pyrene o-quinone pathway (aldo ketose reductase (AKR) catalyzed) and the B[a]P radical cation pathway (P450 peroxidase catalyzed). We used a yeast p53 mutagenesis system to assess mutagenesis by B[a]P radical cations. Because radical cations are short-lived, they were generated in situ by reacting B[a]P with cumene hydroperoxide (CuOOH) and horse radish peroxidase (HRP) and then monitoring the generation of the more stable downstream products, B[a]P-1,6-dione and B[a]P-3,6-dione. Based on the B[a]P-1,6 and 3,6-dione formation, approximately 4µM of radical cation was generated. In the mutagenesis assays, the radical cations produced in situ showed a dose-dependent increase in mutagenicity from 0.25 µM to 10 µM B[a]P with no significant increase seen with further escalation to 50 µM B[a]P. However, mutagenesis was 200-fold less than with the AKR pathway derived B[a]P, 7–8 dione. Mutant p53 plasmids, which yield red colonies, were recovered from the yeast to study the pattern and spectrum of mutations. The mutation pattern observed was G to T (31%) > G to C (29%) > G to A (14%). The frequency of codons mutated by the B[a]P radical cations was essentially random and not enriched at known cancer hotspots. The quinone products of radical cations, B[a]P-1,6-dione and B[a]P-3,6-dione were more mutagenic than the radical cation reactions, but still less mutagenic than AKR derived B[a]P-7,8-dione. We conclude that B[a]P radical cations and their quinone products are weakly mutagenic in this yeast-based system compared to redox cycling PAH o-quinones. PMID:22768918

Short Communication: Studies of antimicrobial activity and chemical ...

African Journals Online (AJOL)

Chemical constituents of the extract were also determined. The extract of was active against the test organisms including Escherischia coli, Pseudomonas aeruginosa and Candida albicans. Tannins, flavonoids, alkaloids, saponins, anthrax-quinones, starch, general glycosides and bitter principles were found to be present ...

Asymmetric Brønsted Acid Catalyzed Substitution of Diaryl Methanols with Thiols and Alcohols for the Synthesis of Chiral Thioethers and Ethers

KAUST Repository

Chatupheeraphat, Adisak; Liao, Hsuan-Hung; Mader, Steffen; Sako, Makoto; Sasai, Hiroaki; Atodiresei, Iuliana; Rueping, Magnus

2016-01-01

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.

Phytochemical Screening, Proximate and Mineral Composition of ...

African Journals Online (AJOL)

Leaves of sweet potato (Ipomoea batatas) grown in Tepi area was studied for their class of phytochemicals, mineral and proximate composition using standard analytical methods. The phytochemical screening revealed the presence of alkaloids, flavonoid, terpenoids, saponins, quinones, phenol, tannins, amino acid and ...

NQO1 and NFE2L2 polymorphisms, fruit and vegetable intake and smoking and the risk of colorectal adenomas in an endoscopy-based population.

NARCIS (Netherlands)

Tijhuis, M.J.; Visker, M.H.P.W.; Aarts, J.M.G.A.; Laan, W.; Boer, S.Y. de; Kok, F.J.; Kampman, E.

2008-01-01

Both environment and genetics contribute to the pathogenesis and prevention of colorectal neoplasia. NAD(P)H:quinone oxidoreductase (NQO1) is a detoxification enzyme that is polymorphic and inducible. We investigated interactions between lifestyle factors and polymorphisms in NQO1 and its key

NQO1 and NFE2L2 polymorphisms, fruit and vegetable intake and smoking, and the risk of colorectal adenomas in an endoscopy-based population.

NARCIS (Netherlands)

Tijhuis, M.J.; Visker, M.H.P.W.; Aarts, J.M.M.J.G.; Laan, van der A.; Boer, van S.Y.; Kok, F.J.; Kampman, E.

2008-01-01

Both environment and genetics contribute to the pathogenesis and prevention of colorectal neoplasia. NAD(P)H:quinone oxidoreductase (NQO1) is a detoxification enzyme that is polymorphic and inducible. We investigated interactions between lifestyle factors and polymorphisms in NQO1 and its key

Research Paper ISSN 0189-6016©2009

African Journals Online (AJOL)

Sapogenins. Antimony chloride in concentrated hydrochloric acid. Violet. Terpenoids. Antimony chloride in chloroform. Green. Quinones. Exposure to ammonia fumes. Red, orange, yellow, brown. (Adapted from Chowdhury et al., 2008.) Table 2: % mean Inhibition zones of the extracts/drugs. Extract/ drug. % mean inhibition.

Molecular aspects of herbicide binding in chloroplasts = [Molekulaire aspekten van herbicide binding in chloroplasten

NARCIS (Netherlands)

Naber, D.

1989-01-01

Many weed-controlling agents act by inhibiting the process of photosynthesis. Their mode of action is a displacement of the secondary quinone electron acceptor of photosystem II from its proteinaceous binding environment. This results in a blocking of the electron transport. Consequently

Measuring the Bioenergetic Effects of 1,2-Naphthoquinone Exposure on Human Lung Macrophages Using Seahorse Extracellular Flux Analyses

Science.gov (United States)

Exposure to ambient particulate matter (PM) is one of the leading causes of morbidity and mortality in humans. Quinones are organic PM components that induce inflammatory responses through redox cycling and electrophilic attack. 1,2-naphthoquinone (1,2-NQ) has previously been sho...

77 FR 51957 - Defense Federal Acquisition Regulation Supplement: Clarification of “F” Orders in the Procurement...

Science.gov (United States)

2012-08-28

... multi-agency contracts, or basic ordering agreements. The proposed text also directs that a... agreements, or blanket purchase agreements. As a result of the proposed rule, new awards under the AbilityOne... Part 204 Government procurement. Manuel Quinones, Editor, Defense Acquisition Regulations System...

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.

Untitled

African Journals Online (AJOL)

properties of p-aminophenol on a polyaniline modified carbon electrode. Surface. The results reveal reversible redox waves. The quinone derivatives formed from p-aminopheno! (PAP) oxidation seem to depress the rate of degradation of polyaniline (PAN) at positive potentials. INTRODUCTION. Electronically conducting ...

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...

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

Biosynthesis of hydroxycinnamoyl esters and amides in legume species

Science.gov (United States)

In forage crops, protein that is degraded following harvest is poorly utilized by ruminant animals, resulting in both economic and environmental consequences. In red clover, secondary reactions of quinones resulting from polyphenol oxidase (PPO)-mediated oxidation of the caffeic acid derivatives pha...

USING STRUCTURAL EFFECTS ON THE ORGANIZATION OF THE CYTOSKELETON OF RAINBOW TROUT HEPATOCYTES TO SORT PATHWAYS OF REACTIVE TOXICITY

Science.gov (United States)

Quinones have been shown to be more acutely toxic to aquatic organisms than chemicals that are not capable of either direct interaction with cellular nucleophiles or potentially metabolized free radicals. For the development of accurate QSAR models, in vitro toxicity assays are n...

Asp170 is crucial for the redox properties of vanillyl-alcohol oxidase

NARCIS (Netherlands)

Heuvel, van den R.H.H.; Fraaije, M.W.; Mattevi, A.; Berkel, van W.J.H.

2000-01-01

Vanillyl-alcohol oxidase is a flavoprotein containing a covalent flavin that catalyzes the oxidation of 4-(methoxymethyl)phenol to 4-hydroxybenzaldehyde. The reaction proceeds through the formation of a p-quinone methide intermediate, after which, water addition takes place. Asp-170, located near

Asp-170 Is Crucial for the Redox Properties of Vanillyl-alcohol Oxidase

NARCIS (Netherlands)

Heuvel, Robert H.H. van den; Fraaije, Marco W.; Mattevi, Andrea; Berkel, Willem J.H. van

2000-01-01

Vanillyl-alcohol oxidase is a flavoprotein containing a covalent flavin that catalyzes the oxidation of 4-(methoxymethyl)phenol to 4-hydroxybenzaldehyde. The reaction proceeds through the formation of a p-quinone methide intermediate, after which, water addition takes place. Asp-170, located near

Crystal Structure of Agaricus bisporus Mushroom Tyrosinase : Identity of the Tetramer Subunits and Interaction with Tropolone

NARCIS (Netherlands)

Ismaya, Wangsa T.; Rozeboom, Henriette J.; Weijn, Amrah; Mes, Jurriaan J.; Fusetti, Fabrizia; Wichers, Harry J.; Dijkstra, Bauke W.

2011-01-01

Tyrosinase catalyzes the conversion of phenolic compounds into their quinone derivatives, which are precursors for the formation of melanin, a ubiquitous pigment in living organisms. Because of its importance for browning reactions in the food industry, the tyrosinase from the mushroom Agaricus

Crystal Structure of Agaricus bisporus Mushroom Tyrosinase: Identity of the Tetramer Subunits and Interaction with Tropolone

NARCIS (Netherlands)

Ismaya, W.T.; Rozeboom, H.J.; Weijn, A.; Mes, J.J.; Fusetti, F.; Wichers, H.J.; Dijkstra, B.W.

2011-01-01

Tyrosinase catalyzes the conversion of phenolic compounds into their quinone derivatives, which are precursors for the formation of melanin, a ubiquitous pigment in living organisms. Because of its importance for browning reactions in the food industry, the tyrosinase from the mushroom Agaricus

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)

Amperometric micro pH measurements in oxygenated saliva.

Science.gov (United States)

Chaisiwamongkhol, Korbua; Batchelor-McAuley, Christopher; Compton, Richard G

2017-07-24

An amperometric micro pH sensor has been developed based on the chemical oxidation of carbon fibre surfaces (diameter of 9 μm and length of ca. 1 mm) to enhance the population of surface quinone groups for the measurement of salivary pH. The pH analysis utilises the electrochemically reversible two-electron, two-proton behaviour of surface quinone groups on the micro-wire electrodes. A Nernstian response is observed across the pH range 2-8 which is the pH range of many biological fluids. We highlight the measurement of pH in small volumes of biological fluids without the need for oxygen removal and specifically the micro pH electrode is examined by measuring the pH of commercial synthetic saliva and authentic human saliva samples. The results correspond well with those obtained by using commercial glass pH electrodes on large volume samples.

A rhodium(III) complex for high-affinity DNA base-pair mismatch recognition

Science.gov (United States)

Junicke, Henrik; Hart, Jonathan R.; Kisko, Jennifer; Glebov, Oleg; Kirsch, Ilan R.; Barton, Jacqueline K.

2003-01-01

A rhodium(III) complex, rac-[Rh(bpy)2phzi]3+ (bpy, 2,2′-bipyridine; phzi, benzo[a]phenazine-5,6-quinone diimine) has been designed as a sterically demanding intercalator targeted to destabilized mismatched sites in double-helical DNA. The complex is readily synthesized by condensation of the phenazine quinone with the corresponding diammine complex. Upon photoactivation, the complex promotes direct strand scission at single-base mismatch sites within the DNA duplex. As with the parent mismatch-specific reagent, [Rh(bpy)2(chrysi)]3+ [chrysene-5,6-quinone diimine (chrysi)], mismatch selectivity depends on the helix destabilization associated with mispairing. Unlike the parent chrysi complex, the phzi analogue binds and cleaves with high affinity and efficiency. The specific binding constants for CA, CC, and CT mismatches within a 31-mer oligonucleotide duplex are 0.3, 1, and 6 × 107 M−1, respectively; site-specific photocleavage is evident at nanomolar concentrations. Moreover, the specificity, defined as the ratio in binding affinities for mispaired vs. well paired sites, is maintained. The increase in affinity is attributed to greater stability in the mismatched site associated with stacking by the heterocyclic aromatic ligand. The high-affinity complex is also applied in the differential cleavage of DNA obtained from cell lines deficient in mismatch repair vs. those proficient in mismatch repair. Agreement is found between photocleavage by the mismatch-specific probes and deficiency in mismatch repair. This mismatch-specific targeting, therefore, offers a potential strategy for new chemotherapeutic design. PMID:12610209

Multilayer models of photosynthetic membranes. Final report

Energy Technology Data Exchange (ETDEWEB)

Brocklehurst, J R; Flanagan, M T

1982-01-01

The primary aim of this project has been to build an artificial membrane in which is incorporated, in a functional state, the protein bacteriorhodopsin responsible for generating an electrical potential difference across the membrane of the photosynthetic bacterium, halobacterium halobium, and to investigate the use of this artificial system as the basis of a solar cell. the bacteriorhodopsin has been incorporated into Langmuir-Blodgett multilayers. If ths supporting filter is then illuminated, a potential difference is generated between the two compartments. The lipid in the filter appears to act as a charge carrier for protons, the charge species that forms the electrochemical gradient generated by the bacteriorhodopsin when this molecule absorbs light. The internal resistances of such solar cells were determined and found to be so high that the cells could not be seriously considered as competitors with classical semiconductor cells. Multilayerswere deposited onto filters in which ion carriers that make the filters permeable to sodium ions had been dissolved in the paraffin. The photovoltage obtained indicated that protons transferred from one side of the filter to the other by the action of the bacteriorhodopsin were bing exchanged for sodium ions. A secondary aim of the project has been to examine the possibility of depositing mixed multilayers of a dye and a long chain quinone onto a semiconductor surface. A sensitizing multilayer has been prepared and the mobility of long chain quinones within the layers is high enough to warrant further research. However, it was found that, with the dyes and quinones used, quenched complexes were formed which would not act as sensitizers.

Quinone-fused porphyrins as contrast agents for photoacoustic imaging

KAUST Repository

Banala, Srinivas; Fokong, Stanley; Brand, Christian; Andreou, Chrysafis; Krä utler, Bernhard; Rueping, Magnus; Kiessling, Fabian

2017-01-01

Photoacoustic (PA) imaging is an emerging non-invasive diagnostic modality with many potential clinical applications in oncology, rheumatology and the cardiovascular field. For this purpose, there is a high demand for exogenous contrast agents

In vitro Investigation of the Antimicrobial Activity of a Series of ...

African Journals Online (AJOL)

NICOLAAS

aCatalysis and Peptide Research Unit, School of Health Sciences, University of KwaZulu-Natal, Durban, South Africa. ... coli and Klebsiella pneumoniae, and the fungus Candida albicans. ... Antimicrobial activity, phenols, naphthols, quinone methides. 1. ... associated with the inhibition of RNA and protein synthesis.11.

Phytochemical composition and antioxidant capacity of whole wheat products

Science.gov (United States)

Whole wheat contains an array of phytochemicals. We quantified alkylresorcinols (AR), phenolic acids, phytosterols, and tocols in six whole wheat products and characterized their antioxidant capacity and ability to induce quinone reductase activity (QR). Total AR content ranged from 136.8 to 233.9 m...

Production of jet fuel precursor monoterpenoids from engineered Escherichia coli

DEFF Research Database (Denmark)

Mendez-Perez, Daniel; Alonso-Gutierrez, Jorge; Hu, Qijun

2017-01-01

). FPP biosynthesis diverts the carbon flux from monoterpene production to C15 products and quinone biosynthesis. In this study, we tested a chromosomal mutation of Escherichia coli's native FPP synthase (IspA) to improve GPP availability for the production of monoterpenes using a heterologous mevalonate...

Analysis of Chlorogenic Acid Oxidation Pathway in Simulated ...

African Journals Online (AJOL)

Keywords: Honeysuckle, Chlorogenic acid, Enzymatic browning, Mimic system, Oxidation pathway, ... enzymatic oxidation of CA is the major cause of ..... to the concentration of catechol, o-quinone and current at PPO-modified microcylinder biosensor for diffusion- kinetic model. J Electroanal Chem 2011; 660: 200-208.

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

-solution interface. A reagentless and direct electrochemical detection was obtained by detection of the electrochemical changes using square wave voltammetry (SWV). An increase in the peak current of quinone was observed upon hybridization of probe on the target, whereas no change is observed with non...

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...

Synthesis of extended bifunctional triptycenes

Czech Academy of Sciences Publication Activity Database

Rybáček, Jiří; Závada, Jiří; Holý, Petr

-, č. 22 (2008), s. 3615-3618 ISSN 0039-7881 R&D Projects: GA ČR GA203/03/0087 Institutional research plan: CEZ:AV0Z40550506 Keywords : anthracenes * arynes * Diels - Alder reaction * quinones * triptycenes Subject RIV: CC - Organic Chemistry Impact factor: 2.470, year: 2008

a comparative study of two agricultural extension approaches in ...

African Journals Online (AJOL)

each approach are described and their strengths and weaknesses are revealed including the implications of having two extension ... line of technical support and administrative control, b) to change the multi-purpose role ... evaluation and training plots called Management Training Plots (MTPs). According to Quinones et al; ...

PBT,PBO-Based Hybrid Polymers with Nonlinear Optical Properties or High Electrical Conductivity

Science.gov (United States)

1988-08-29

standing. Experiments with stronger oxidizing agents such as nitrosonium salts (e.g., NO+Br4, NO+PF6) and high-potential quinones (e.g., DDQ...several unique possibilities. First, the ionic structure should raise Tg. Second, electrophoretic ion migration under the influence of the poling field

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

Role of a novel dual flavin reductase (NR1) and an associated histidine triad protein (DCS-1) in menadione-induced cytotoxicity

International Nuclear Information System (INIS)

Kwasnicka-Crawford, Dorota A.; Vincent, Steven R.

2005-01-01

Microsomal cytochrome P450 reductase catalyzes the one-electron transfer from NADPH via FAD and FMN to various electron acceptors, such as cytochrome P450s or to some anti-cancer quinone drugs. This results in generation of free radicals and toxic oxygen metabolites, which can contribute to the cytotoxicity of these compounds. Recently, a cytosolic NADPH-dependent flavin reductase, NR1, has been described which is highly homologous to the microsomal cytochrome P450 reductase. In this study, we show that over-expression of NR1 in human embryonic kidney cells enhances the cytotoxic action of the model quinone, menadione. Furthermore, we show that a novel human histidine triad protein DCS-1, which is expressed together with NR1 in many tissues, can significantly reduce menadione-induced cytotoxicity in these cells. We also show that DCS-1 binds NF1 and directly modulates its activity. These results suggest that NR1 may play a role in carcinogenicity and cell death associated with one-electron reductions

Utilizing a CdTe quantum dots-enzyme hybrid system for the determination of both phenolic compounds and hydrogen peroxide.

Science.gov (United States)

Yuan, Jipei; Guo, Weiwei; Wang, Erkang

2008-02-15

In this paper, we attempt to construct a simple and sensitive detection method for both phenolic compounds and hydrogen peroxide, with the successful combination of the unique property of quantum dots and the specificity of enzymatic reactions. In the presence of H2O2 and horseradish peroxidase, phenolic compounds can quench quantum dots' photoluminescence efficiently, and the extent of quenching is severalfold to more than 100-fold increase. Quinone intermediates produced from the enzymatic catalyzed oxidation of phenolic compounds were believed to play the main role in the photoluminescence quenching. Using a quantum dots-enzyme system, the detection limits for phenolic compounds and hydrogen peroxide were detected to be approximately 10(-7) mol L(-1). The coupling of efficient quenching of quantum dot photoluminescence by quinone and the effective enzymatic reactions make this a simple and sensitive method for phenolic compound detection and great potential in the development of H2O2 biosensors for various analytes.

Allyl isothiocyanate enhances shelf life of minimally processed shredded cabbage.

Science.gov (United States)

Banerjee, Aparajita; Penna, Suprasanna; Variyar, Prasad S

2015-09-15

The effect of allyl isothiocyanate (AITC), in combination with low temperature (10°C) storage on post harvest quality of minimally processed shredded cabbage was investigated. An optimum concentration of 0.05μL/mL AITC was found to be effective in maintaining the microbial and sensory quality of the product for a period of 12days. Inhibition of browning was shown to result from a down-regulation (1.4-fold) of phenylalanine ammonia lyase (PAL) gene expression and a consequent decrease in PAL enzyme activity and o-quinone content. In the untreated control samples, PAL activity increased following up-regulation in PAL gene expression that could be linearly correlated with enhanced o-quinone formation and browning. The efficacy of AITC in extending the shelf life of minimally processed shredded cabbage and its role in down-regulation of PAL gene expression resulting in browning inhibition in the product is reported here for the first time. Copyright © 2015 Elsevier Ltd. All rights reserved.

Comparison of epoxide and free-radical mechanisms for activation of benzo[a]pyrene by Sprague-Dawley rat liver microsomes

International Nuclear Information System (INIS)

Selkirk, J.K.

1980-01-01

Coincubation of [6- 3 H]benzo[a]pyrene ([6- 3 H]BP) and [ 14 C]BP with SD rat liver microsomes produced metabolic profiles that showed that the C-6 of BP was not affected by formation of 4,5-dihydro-4,5-dihydroxy-BP, 7,8-dihydro-7,8-dihydroxy-BP, and 9,10-dihydro-9,10-dihydroxy-BP nor the 3- and 9-phenols of BP. Complete retention of tritium at C-6, except in the three quinones, confirmed the radical-cation model for formation of the 6-oxo-radical followed by oxidation to quinone. Epoxide formation at the carcinogenically active regions of BP appeared to biochemically isolate from 6-position activation and suggested that the microsomal epoxide pathway is unrelated to the radicalcation scheme. These molar ratios derived from double-label experiments reinforced the current literature that indicates the epoxide mechanism as the major pathway toward carcinogenic forms of BP

Effects of ozonation on disinfection and microbial activity in waste activated sludge for land application

Energy Technology Data Exchange (ETDEWEB)

Ahn, Kyu-Hong; Maeng, Sung Kyu; Hong, Jun-Seok; Lim, Byung-Ran

2003-07-01

Effects of ozonation on microbial biomass activity and community structure in waste activated sludges from various treatment plants were investigated. The densities of viable cells and microbial community structure in the sludges treated with ozone at 0.1, 0.2 and 0.4 gO{sub 3}/gDS were measured on the basis of the respiratory quinone profile and LIVE/DEAD Backlight(TM). The results from the bacterial concentration and quinone profiles of the waste activated sludge showed that respiratory activities of microorganisms were detected at the ozone dose of 0.4 gO{sub 3}/gDS. However, fecal coliform, fecal streptococcus and Salmonella sp. in the ozonized sludge were not detected. This result implies that some microorganisms might be more tolerant to ozonation than the pathogenic indicators. The pathogens reduction requirements for Class A biosolids were still met by the ozonation at 0.4 gO{sub 3}/gDS.

Towards an improved prediction of the free radical scavenging potency of flavonoids: the significance of double PCET mechanisms.

Science.gov (United States)

Amić, Ana; Marković, Zoran; Dimitrić Marković, Jasmina M; Stepanić, Višnja; Lučić, Bono; Amić, Dragan

2014-01-01

The 1H(+)/1e(-) and 2H(+)/2e(-) proton-coupled electron transfer (PCET) processes of free radical scavenging by flavonoids were theoretically studied for aqueous and lipid environments using the PM6 and PM7 methods. The results reported here indicate that the significant contribution of the second PCET mechanism, resulting in the formation of a quinone/quinone methide, effectively discriminates the active from inactive flavonoids. The predictive potency of descriptors related to the energetics of second PCET mechanisms (the second O-H bond dissociation enthalpy (BDE2) related to hydrogen atom transfer (HAT) mechanism, and the second electron transfer enthalpy (ETE2) related to sequential proton loss electron transfer (SPLET) mechanism) are superior to the currently used indices, which are related to the first 1H(+)/1e(-) processes, and could serve as primary descriptors in development of the QSAR (quantitative structure-activity relationships) of flavonoids. Copyright © 2013 Elsevier Ltd. All rights reserved.

Molecular complexes of L-phenylalanine with substituted 1,4-benzoquinones in aqueous medium: Spectral and theoretical investigations

Science.gov (United States)

Ganesh, K.; El-Mossalamy, E. H.; Satheshkumar, A.; Balraj, C.; Elango, K. P.

2013-12-01

Various spectral techniques such as UV-Vis, FT-IR, and fluorescence have been employed to investigate the charge transfer interaction of L-phenylalanine (LPA) with substituted 1,4-benzoquinones (MQ1-4). Kinetic and thermodynamic properties of the complexes were determined in aqueous medium at physiological condition (pH = 7). The interaction of MQ1-4 with L-phenylalanine (LPA) was found to proceed through the formation of donor-acceptor complex, yielding a radical anion. The stoichiometry of the complexes was determined by Jobs continuous variation method and was found to be 1:1 in all the cases. Fluorescence quenching studies showed that the interaction between the donor and the acceptors is spontaneous. The results indicated that the progressive replacement of chlorine atom (-I effect) by methoxy group (+M effect) in the quinone decreased the electron acceptor property of the quinone. The order of the experimentally measured association constant of these complexes was well supported by DFT/B3LYP calculations.

A fluorescence-based rapid screening assay for cytotoxic compounds

International Nuclear Information System (INIS)

Montoya, Jessica; Varela-Ramirez, Armando; Estrada, Abril; Martinez, Luis E.; Garza, Kristine; Aguilera, Renato J.

2004-01-01

A simple fluorescence-based assay was developed for the rapid screening of potential cytotoxic compounds generated by combinatorial chemistry. The assay is based on detection of nuclear green fluorescent protein (GFP) staining of a human cervical cancer cell line (HeLa) carrying an integrated histone H2B-GFP fusion gene. Addition of a cytotoxic compound to the HeLa-GFP cells results in the eventual degradation of DNA and loss of the GFP nuclear fluorescence. Using this assay, we screened 11 distinct quinone derivatives and found that several of these compounds were cytotoxic. These compounds are structurally related to plumbagin an apoptosis-inducing naphthoquinone isolated from Black Walnut. In order to determine the mechanism by which cell death was induced, we performed additional experiments with the most cytotoxic quinones. These compounds were found to induce morphological changes (blebbing and nuclear condensation) consistent with induction of apoptosis. Additional tests revealed that the cytotoxic compounds induce both necrotic and apoptotic modes of death

Pulse radiolytic one-electron oxidation of some dihydroxy-substituted anthraquinones

International Nuclear Information System (INIS)

Pal, H.; Palit, D.K.; Mukherjee, T.; Mittal, J.P.

1992-01-01

The spectroscopic characteristics and the kinetic parameters associated with the transients formed on one-electron oxidation of quinizarin (1,4-dihydroxy-9,10-anthraquinone), quinizarin 2- and 6-sulfonates, 1,5-dihydroxy-9,10-anthraquinone and 1,8-dihydroxy-9,10-anthraquinone have been studied by pulse radiolysis and kinetic spectrophotometric techniques, using OH . , O .- , N 3 . , Br 2 .- and . CH 2 CHO as the oxidising radicals. The pK a and the disproportionation equilibria of the semi-oxidised quinones have been studied for the water-soluble sulfonates. In contrast to the complex decay of the semi-oxidised naphthazarin (5,8-dihydroxy-1,4-naphtho-quinone), the semi-oxidised anthraquinone derivatives decay by simple second-order kinetics. The pK a values of the latter are also much higher (ca. 8) compared to the former (ca. <4). The differences observed are attributed to the loss in symmetry in the free radical structures of the semi-oxidised anthraquinone derivatives. (author)

Pre-harvest methyl jasmonate treatment enhances cauliflower chemoprotective attributes without a loss in postharvest quality.

Science.gov (United States)

Ku, Kang Mo; Choi, Jeong-Hee; Kushad, Mosbah M; Jeffery, Elizabeth H; Juvik, John A

2013-06-01

Methyl jasmonate (MeJA) treatment can significantly increase glucosinolate (GS) concentrations in Brassica vegetables and potentially enhance anticancer bioactivity. Although MeJA treatment may promote ethylene biosynthesis, which can be detrimental to postharvest quality, there are no previous reports of its effect on cauliflower postharvest quality. To address this, cauliflower curds in field plots were sprayed with either 0.1 % Triton X-100 (control) or 500 μM MeJA solutions four days prior to harvest, then stored at 4 °C. Tissue subsamples were collected after 0, 10, 20, and 30 days of postharvest storage and assayed for visual color change, ethylene production, GS concentrations, and extract quinone reductase inductive activity. MeJA treatment increased curd GS concentrations of glucoraphanin, glucobrassicin, and neoglucobrassicin by 1.5, 2.4, and 4.6-fold over controls, respectively. MeJA treated cauliflower showed significantly higher quinone reductase activity, a biomarker for anticancer bioactivity, without reducing visual color and postharvest quality for 10 days at 4 °C storage.

Isolation and Purification of Complex II from Proteus Mirabilis Strain ATCC 29245

Science.gov (United States)

Shabbiri, Khadija; Ahmad, Waqar; Syed, Quratulain; Adnan, Ahmad

2010-01-01

A respiratory complex was isolated from plasma membrane of pathogenic Proteus mirabilis strain ATCC 29245. It was identified as complex II consisting of succinate:quinone oxidoreductase (EC 1.3.5.1) containing single heme b. The complex II was purified by ion-exchange chromatography and gel filtration. The molecular weight of purified complex was 116.5 kDa and it was composed of three subunits with molecular weights of 19 kDa, 29 kDa and 68.5 kDa. The complex II contained 9.5 nmoles of cytochrome b per mg protein. Heme staining indicated that the 19 kDa subunit was cytochrome b. Its reduced form showed absorptions peaks at 557.0, 524.8 and 424.4 nm. The α-band was shifted from 557.0 nm to 556.8 nm in pyridine ferrohemochrome spectrum. The succinate: quinone oxidoreductase activity was found to be high in this microorganism. PMID:24031557

β-Lapachone attenuates mitochondrial dysfunction in MELAS cybrid cells.

Science.gov (United States)

Jeong, Moon Hee; Kim, Jin Hwan; Seo, Kang-Sik; Kwak, Tae Hwan; Park, Woo Jin

2014-11-21

Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) is a mitochondrial disease caused by mutations in the mitochondrial genome. This study investigated the efficacy of β-lapachone (β-lap), a natural quinone compound, in rescuing mitochondrial dysfunction in MELAS cybrid cells. β-Lap significantly restored energy production and mitochondrial membrane potential as well as normalized the elevated ROS level in MELAS cybrid cells. Additionally, β-lap reduced lactic acidosis and restored glucose uptake in the MELAS cybrid cells. Finally, β-lap activated Sirt1 by increasing the intracellular NAD(+)/NADH ratio, which was accompanied by increased mtDNA content. Two other quinone compounds (idebenone and CoQ10) that have rescued mitochondrial dysfunction in previous studies of MELAS cybrid cells had a minimal effect in the current study. Taken together, these results demonstrated that β-lap may provide a novel therapeutic modality for the treatment of MELAS. Copyright © 2014 Elsevier Inc. All rights reserved.

Production, purification and detergent exchange of isotopically labeled Bacillussubtilis cytochrome b₅₅₈ (SdhC).

Science.gov (United States)

Baureder, Michael; Hederstedt, Lars

2011-11-01

Cytochrome b₅₅₈ of the gram-positive bacterium Bacillussubtilis is the membrane anchor subunit of the succinate:quinone oxidoreductase of the citric acid cycle. The cytochrome consists of the SdhC polypeptide (202 residues) and two protoheme IX groups that function in transmembrane electron transfer to menaquinone. The general structure of the cytochrome is known from extensive experimental studies and by comparison to Wolinellasuccinogenes fumarate reductase for which the X-ray crystal structure has been determined. Solution state NMR can potentially be used to identify the quinone binding site(s) and study, e.g. redox-linked, dynamics of cytochrome b₅₅₈. In this work we present an efficient procedure for the isolation of preparative amounts of isotopically labeled B. subtilis cytochrome b₅₅₈ produced in Escherichia coli. We have also evaluated several detergents suitable for NMR for their effectiveness in maintaining the cytochrome solubilized and intact for days at room temperature. Copyright © 2011 Elsevier Inc. All rights reserved.

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…

Fitness and competition studies of QoI resistant and sensitive Cercospora sojina isolates, the causal agent of frogeye leaf spot

Science.gov (United States)

Frogeye leaf spot (FLS), caused by Cercospora sojina, is a yearly foliar disease of soybean in Tennessee and causes substantial economic losses if not properly managed. Quinone outside inhibitor (QoI) fungicides are often used to manage FLS, but C. sojina isolates have developed resistance to this c...

The End of the Six-Party Talks?

Science.gov (United States)

2007-01-01

Pyongyang is wary of Beijing’s international influence, its ability to collaborate with the United States and South Korea, its willingness to foster ...Kenneth Quinones, “ Dualism in the Bush Administration’s North Korea Policy,” Asian Perspective, XXVII, no. 1, 2003, 197-224; Karin Lee and Adam Miles

Copper Complexes with Non-innocent Ligands: Probing Cu-II/catecholato-Cu-I/o-Semiquinonato Redox Isomer Equilibria with EPR Spectroscopy

Czech Academy of Sciences Publication Activity Database

Kaim, W.; Wanner, M.; Knödler, A.; Záliš, Stanislav

2002-01-01

Roč. 337, - (2002), s. 163-172 ISSN 0020-1693 R&D Projects: GA MŠk OC D14.20 Institutional research plan: CEZ:AV0Z4040901 Keywords : copper compounds * EPR spectroscopy * quinone ligand s Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.566, year: 2002

78 FR 13543 - Defense Federal Acquisition Regulation Supplement; Technical Amendments

Science.gov (United States)

2013-02-28

..., 204, 215, 225, 227, 242, 245 and 252 Government procurement. Manuel Quinones, Editor, Defense...) shall be conducted only when-- (i) A contractor has $50 million of qualifying sales to the Government... circumstance(s) may result in a material impact on Government contract costs: (1) Information or data reveals a...

Valence-State Analysis through Spectroelectrochemistry in a Series of Quinonoid-Bridged Diruthenium Complexes [(acac)(2)Ru(mu-L)Ru(acac)(2)](n) (n =+2,+1, 0,-1,-2)

Czech Academy of Sciences Publication Activity Database

Ghumaan, S.; Sarkar, B.; Maji, S.; Puranik, V. G.; Fiedler, Jan; Urbanos, F. A.; Jimenez-Aparicio, R.; Kaim, W.; Lahiri, G. K.

2008-01-01

Roč. 14, č. 34 (2008), s. 10816-10828 ISSN 0947-6539 R&D Projects: GA MŠk OC 140; GA MŠk LC510 Institutional research plan: CEZ:AV0Z40400503 Keywords : magnetic properties * quinones * ruthenium * spectroelectrochemistry Subject RIV: CG - Electrochemistry Impact factor: 5.454, year: 2008

Electrochemical monitoring of intracellular enzyme activity of single living mammalian cells by using a double-mediator system

International Nuclear Information System (INIS)

Matsumae, Yoshiharu; Takahashi, Yasufumi; Ino, Kosuke; Shiku, Hitoshi; Matsue, Tomokazu

2014-01-01

Graphical abstract: NAD(P)H:quinone oxidoreductase (NQO) activity of single HeLa cells were evaluated by using the menadione–ferrocyanide double mediator system combined with scanning electrochemical microscopy (SECM). - Highlights: • NAD(P)H:quinone oxidoreductase activity of single cells were evaluated with SECM. • Fe(CN) 6 3− /menadione concentrations were optimized for long-term SECM monitoring. • Menadione affect the intracellular levels of reactive oxygen species and GSH. • At 100 μM menadione, the Fe(CN) 6 3− generation rate decreased rapidly within 30 min. - Abstract: We evaluated the intracellular NAD(P)H:quinone oxidoreductase (NQO) activity of single HeLa cells by using the menadione–ferrocyanide double-mediator system combined with scanning electrochemical microscopy (SECM). The double-mediator system was used to amplify the current response from the intracellular NQO activity and to reduce menadione-induced cell damage. The electron shuttle between the electrode and menadione was mediated by the ferrocyanide/ferricyanide redox couple. Generation of ferrocyanide was observed immediately after the addition of a lower concentration (10 μM) of menadione. The ferrocyanide generation rate was constant for 120 min. At a higher menadione concentration (100 μM), the ferrocyanide generation rate decreased within 30 min because of the cytotoxic effect of menadione. We also investigated the relationship between intracellular reactive oxygen species or glutathione levels and exposure to different menadione concentrations to determine the optimal condition for SECM with minimal invasiveness. The present study clearly demonstrates that SECM is useful for the analysis of intracellular enzymatic activities in single cells with a double-mediator system

Electrochemical monitoring of intracellular enzyme activity of single living mammalian cells by using a double-mediator system

Energy Technology Data Exchange (ETDEWEB)

Matsumae, Yoshiharu [Graduate School of Environmental Studies, Tohoku University, Aramaki 6-6-11-605, Aoba, Sendai 980-8579 (Japan); Takahashi, Yasufumi [Advanced Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba, Sendai 980-8577 (Japan); Ino, Kosuke [Graduate School of Environmental Studies, Tohoku University, Aramaki 6-6-11-605, Aoba, Sendai 980-8579 (Japan); Shiku, Hitoshi, E-mail: shiku@bioinfo.che.tohoku.ac.jp [Graduate School of Environmental Studies, Tohoku University, Aramaki 6-6-11-605, Aoba, Sendai 980-8579 (Japan); Matsue, Tomokazu, E-mail: matsue@bioinfo.che.tohoku.ac.jp [Graduate School of Environmental Studies, Tohoku University, Aramaki 6-6-11-605, Aoba, Sendai 980-8579 (Japan); Advanced Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba, Sendai 980-8577 (Japan)

2014-09-09

Graphical abstract: NAD(P)H:quinone oxidoreductase (NQO) activity of single HeLa cells were evaluated by using the menadione–ferrocyanide double mediator system combined with scanning electrochemical microscopy (SECM). - Highlights: • NAD(P)H:quinone oxidoreductase activity of single cells were evaluated with SECM. • Fe(CN){sub 6}{sup 3−}/menadione concentrations were optimized for long-term SECM monitoring. • Menadione affect the intracellular levels of reactive oxygen species and GSH. • At 100 μM menadione, the Fe(CN){sub 6}{sup 3−} generation rate decreased rapidly within 30 min. - Abstract: We evaluated the intracellular NAD(P)H:quinone oxidoreductase (NQO) activity of single HeLa cells by using the menadione–ferrocyanide double-mediator system combined with scanning electrochemical microscopy (SECM). The double-mediator system was used to amplify the current response from the intracellular NQO activity and to reduce menadione-induced cell damage. The electron shuttle between the electrode and menadione was mediated by the ferrocyanide/ferricyanide redox couple. Generation of ferrocyanide was observed immediately after the addition of a lower concentration (10 μM) of menadione. The ferrocyanide generation rate was constant for 120 min. At a higher menadione concentration (100 μM), the ferrocyanide generation rate decreased within 30 min because of the cytotoxic effect of menadione. We also investigated the relationship between intracellular reactive oxygen species or glutathione levels and exposure to different menadione concentrations to determine the optimal condition for SECM with minimal invasiveness. The present study clearly demonstrates that SECM is useful for the analysis of intracellular enzymatic activities in single cells with a double-mediator system.

Effect of phytotoxic secondary metabolites and semisynthetic compounds from endophytic fungus Xylaria feejeensis strain SM3e-1b on spinach chloroplast photosynthesis.

Science.gov (United States)

Macías-Rubalcava, Martha Lydia; García-Méndez, Marbella Claudia; King-Díaz, Beatriz; Macías-Ruvalcaba, Norma Angélica

2017-01-01

We investigated the mechanism of action on the photosynthesis light reactions of three major secondary metabolites produced by the endophytic fungus Xylaria feejeensis strain SM3e-1b, isolated from Sapium macrocarpum; and four novel derivatives of coriloxine, a major compound produced by X. feejeensis. The natural phytotoxins include one epoxycyclohexenone derivative, coriloxine (1), and two quinone derivatives (2-3). The semisynthetic derivatives of coriloxine are two cyclohexenone (4-6) and two quinone compounds (5-7). Cyclohexenone (4), (4R,5S,6R)-6-chloro-4,5-dihydroxy-3-methoxy-5-methylcyclohex-2-enone, inhibited ATP synthesis in freshly lysed spinach chloroplasts from water to MV; it also partly inhibited the basal and uncoupled photosynthetic electron transport, and significantly enhanced the phosphorylating electron transport and Mg 2+ -ATPase activity, thus demonstrating its action as an uncoupler agent. On the other hand, quinone (7), 2-((4-butylphenyl)amino)-5-methoxy-3-methylcyclohexa-2,5-diene-1,4-dione, inhibited ATP synthesis, and non-cyclic electron transport from water to MV in basal, phosphorylating and uncoupled conditions in a concentration-dependent manner. Hence, (7) behaves as a Hill reaction inhibitor at the PSII electron transport on the water splitting enzyme (OEC), and on the acceptor side between P 680 and Q A . This mechanism of action was confirmed by chlorophyll a fluorescence measurements. These results indicate that coriloxine derivatives 4 and 7 could work as prototype structures for the development of new herbicides. Contrastingly, natural products 1-3, and derivatives 5 and 6 did not show a significant inhibitory effect on ATP synthesis. Copyright © 2016 Elsevier B.V. All rights reserved.

Chemistry of superoxide radical in seawater: CDOM associated sink of superoxide in coastal waters

Energy Technology Data Exchange (ETDEWEB)

Goldstone, J.V.; Voelker, B.M.

2000-03-15

Colored dissolved organic matter (CDOM) and humic substances contain a nonmetallic redox-cycling component capable of catalyzing superoxide (O{sub 2}{sup {minus}}) dismutation. First-order rate coefficients (k{sub pseudo}) measured for this O{sub 2}{sup {minus}} sink in a number of coastal and Chesapeake Bay water samples range up to 1.4s{sup {minus}1}, comparable in magnitude to catalyzed dismutation by Cu species. A significant (r{sup 2}=0.73) correlation is observed between k{sub pseudo} and the optical absorption and salinity of individual coastal water samples, suggesting an association with non-marine-derived CDOM. The activity of this sink is not changed by acidification or boiling of samples but is removed by photooxidation, indicating that it is an organic compound, but that it is neither enzymatic nor likely to consist of tightly bound metals. The stoichiometry of hydrogen peroxide formation from O{sub 2}{sup {minus}} decay indicates that this sink is capable of a redox cycle catalyzing the dismutation of O{sub 2}{sup {minus}}. This CDOM sink combined with the organic copper sink previously described will produce a steady-state superoxide concentration in coastal waters that is 100--1000-fold lower than that predicted from bimolecular dismutation alone. Catalyzed O{sub 2}{sup {minus}} decay was also observed in a variety of humic and fulvic acid samples, possibly occurring through quinone functionalities. Although the presence of quinone moieties in humic and fulvic acids has been demonstrated, there do not appear to be good correlations between several measures of quinone content and the O{sub 2}{sup {minus}} dismutation rates of these samples.

Border between natural product and drug: Comparison of the related benzoquinones idebenone and coenzyme Q10

Directory of Open Access Journals (Sweden)

Nuri Gueven

2015-04-01

Full Text Available Coenzyme Q10 is a ubiquitous component of cellular membranes and belongs to the class of benzoquinones that mainly differ with regards to the length and composition of their hydrophobic tail. The characteristic quinone group can accept electrons from various biological sources and is converted by a one electron transfer to the unstable semiquinone or by a two electron transfer to the more stable hydroquinone. This feature makes CoQ10 the bona fide cellular electron transfer molecule within the mitochondrial respiratory chain and also makes it a potent cellular antioxidant. These activities serve as justification for its popular use as food supplement. Another quinone with similarities to the naturally occurring CoQ10 is idebenone, which shares its quinone moiety with CoQ10, but at the same time differs from CoQ10 by the presence of a much shorter, less lipophilic tail. However, despite its similarity to CoQ10, idebenone cannot be isolated from any natural sources but instead was synthesized and selected as a pharmacologically active compound in the 1980s by Takeda Pharmaceuticals purely based on its pharmacological properties. Several recent clinical trials demonstrated some therapeutic efficacy of idebenone in different indications and as a consequence, many practitioners question if the freely available CoQ10 could not be used instead. Here, we describe the molecular and pharmacological features of both molecules that arise from their structural differences to answer the question if idebenone is merely a CoQ10 analogue as frequently perpetuated in the literature or a pharmaceutical drug with entirely different features.

Electrochemistry of potentially bioreductive alkylating quinones : Part 1. Electrochemical properties of relatively simple quinones, as model compounds of mitomycin- and aziridinylquinone-type antitumour agents

NARCIS (Netherlands)

Driebergen, R.J.; den Hartigh, J.; Holthuis, J.J.M.; Hulshoff, A.; van Oort, W.J.; Postma kelder, S.J.; Verboom, Willem; Reinhoudt, David; Bos, M.; van der Linden, W.E.

1990-01-01

The influence of methyl-, hydroxy and amino substituents on the electrochemical behaviour of simple 1,4-naphtho-and 1,4-benzoquinones, model compounds of many quinoid antitumour agents, in aqueous media was studied. Significant changes in electrochemical behaviour were observed, potentially the

Dithiothreitol activity by particulate oxidizers of SOA produced from photooxidation of hydrocarbons under varied NOx levels

Directory of Open Access Journals (Sweden)

H. Jiang

2017-08-01

Full Text Available When hydrocarbons (HCs are atmospherically oxidized, they form particulate oxidizers, including quinones, organic hydroperoxides, and peroxyacyl nitrates (PANs. These particulate oxidizers can modify cellular materials (e.g., proteins and enzymes and adversely modulate cell functions. In this study, the contribution of particulate oxidizers in secondary organic aerosols (SOAs to the oxidative potential was investigated. SOAs were generated from the photooxidation of toluene, 1,3,5-trimethylbenzene, isoprene, and α-pinene under varied NOx levels. Oxidative potential was determined from the typical mass-normalized consumption rate (reaction time t =  30 min of dithiothreitol (DTTt, a surrogate for biological reducing agents. Under high-NOx conditions, the DTTt of toluene SOA was 2–5 times higher than that of the other types of SOA. Isoprene DTTt significantly decreased with increasing NOx (up to 69 % reduction by changing the HC ∕ NOx ratio from 30 to 5. The DTTt of 1,3,5-trimethylbenzene and α-pinene SOA was insensitive to NOx under the experimental conditions of this study. The significance of quinones to the oxidative potential of SOA was tested through the enhancement of DTT consumption in the presence of 2,4-dimethylimidazole, a co-catalyst for the redox cycling of quinones; however, no significant effect of 2,4-dimethylimidazole on modulation of DTT consumption was observed for all SOA, suggesting that a negligible amount of quinones was present in the SOA of this study. For toluene and isoprene, mass-normalized DTT consumption (DTTm was determined over an extended period of reaction time (t =  2 h to quantify their maximum capacity to consume DTT. The total quantities of PANs and organic hydroperoxides in toluene SOA and isoprene SOA were also measured using the Griess assay and the 4-nitrophenylboronic acid assay, respectively. Under the NOx conditions (HC ∕ NOx ratio: 5–36 ppbC ppb−1 applied in

Invariant Oxidation State of Copper but not of Ruthenium in Complexes with Noninnocent N-(2-Methyl-5,8-dioxo-5,8-dihydroquinolin-7-yl)acetamide: A Combined Structural, Electrochemical and Spectroelectrochemical Investigation

Czech Academy of Sciences Publication Activity Database

Paretzki, A.; Das, H. S.; Weisser, F.; Scherer, T.; Bubrin, D.; Fiedler, Jan; Nycz, J. E.; Sarkar, B.

-, č. 15 (2011), s. 2413-2421 ISSN 1434-1948 R&D Projects: GA ČR GA203/09/0705; GA ČR GA203/08/1157 Institutional research plan: CEZ:AV0Z40400503 Keywords : copper * ruthenium * quinones Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.049, year: 2011

On the chlorophill a fluorescence yield in chloroplasts upon excitation with twin turnover flashes (TTF) and high frequency flash trains

NARCIS (Netherlands)

Vredenberg, W.J.; Prasil, O.; Durchan, M.

2007-01-01

Chlorophyll fluorescence is routinely taken as a quantifiable measure of the redox state of the primary quinone acceptor QA of PSII. The variable fluorescence in thylakoids increases in a single turnover flash (STF) from its low dark level F o towards a maximum F mSTF when QA becomes reduced. We

Nitration of phenolic compounds and oxidation of hydroquinones ...

Indian Academy of Sciences (India)

Abstract. 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 ...

Ranking mechanical pulps for their potential to photoyellow

Science.gov (United States)

Umesh P. Agarwal

2000-01-01

Recently found experimental evidence has provided strong support for an alternative photoyellowing mechanism that suggests that pulp- photoyellowing occurs due to direct photooxidation of hydroquinones (present in mechanical pulps) top-quinones. Because hydroquinones were found to be present in pulps, it may be possible to quantify them. Quantification of mechanical-...

Towards a New Russia Policy

Science.gov (United States)

2008-02-01

Johnson’s Russia List, February 27, 2006, available at www.cdi.org. On Korea, see C. Kenneth Quinones, “ Dualism in the Bush Administration’s North... Foster -Carter, “Pyongyang Watch: Six-Party Glacier: Did the US Melt?” Asia Times Online, June 28, 2004, www.atimes.com. The author can attest to

Impedance Spectroscopy as a Tool for Non-Intrusive Detection of Extracellular Mediators in Microbial Fuel Cells

Science.gov (United States)

2009-12-01

2005; Marsili et al., 2008; Myers and Myers, 2004; Newman and Kolter , 2000; Rosso et al., 2003; vonCanstein et al., 2008; Ward et al., 2004). In an... Kolter R. 2000. A role for excreted quinones in extracellular electron transfer. Nature 405:94. Rabaey K, Boon N, Siciliano SD, Verhaege M, Verstraete W

Investigating the use of endogenous quinoid moieties on carbon fibre as means of developing micro pH sensors

International Nuclear Information System (INIS)

Anderson, Ashleigh; Phair, Jolene; Benson, John; Meenan, Brian; Davis, James

2014-01-01

The redox profile obtained from electrochemically oxidised carbon fibre was exploited as a foundation from which to design a reusable pH probe. X-ray photoelectron spectroscopy of the surface after anodisation revealed an increase in the population of endogenous quinone moieties. Square wave voltammograms recorded in various buffer solutions (pH 3–9) yielded a distinct and unambiguous oxidation process through which to ascribe the peak potential — with the latter found to shift in a sub-Nernstian (− 0.052 V/pH) manner. The design of a discrete 2-electrode reusable probe which provides a rapid assessment of pH is described and a preliminary characterisation of the electrochemical performance is critically assessed. - Graphical abstract: The redox profile obtained from electrochemically oxidised carbon fibre was exploited as a foundation from which to design a reusable pH probe. X-ray photoelectron spectroscopy of the surface after anodisation revealed an increase in the population endogenous quinone moieties. Square wave voltammograms recorded in various buffer solutions (pH 3–9) yielded a distinct and unambiguous oxidation process through which to ascribe the peak potential — with the latter found to shift in a sub-Nernstian (− 0.052 V/pH) manner. The design of a discrete 2-electrode reusable probe which provides a rapid assessment of pH is described and a preliminary characterisation of the electrochemical performance is critically assessed. - Highlights: • In situ creation of pH sensitive quinone groups on carbon fibre • Versatile and accessible approach to manufacturing disposable pH sensors • Miniature probe design enables monitoring pH in small volumes. • Detailed surface characterisation of electrochemically modified carbon fibre

The uptake of tocopherols by RAW 264.7 macrophages

Directory of Open Access Journals (Sweden)

Papas Andreas M

2002-10-01

Full Text Available Abstract Background Alpha-Tocopherol and gamma-tocopherol are the two major forms of vitamin E in human plasma and the primary lipid soluble antioxidants. The dietary intake of gamma-tocopherol is generally higher than that of alpha-tocopherol. However, alpha-tocopherol plasma levels are about four fold higher than those of gamma-tocopherol. Among other factors, a preferential cellular uptake of gamma-tocopherol over alpha-tocopherol could contribute to the observed higher plasma alpha-tocopherol levels. In this investigation, we studied the uptake and depletion of both alpha-tocopherol and gamma-tocopherol (separately and together in cultured RAW 264.7 macrophages. Similar studies were performed with alpha-tocopheryl quinone and gamma-tocopheryl quinone, which are oxidation products of tocopherols. Results RAW 264.7 macrophages showed a greater uptake of gamma-tocopherol compared to alpha-tocopherol (with uptake being defined as the net difference between tocopherol transported into the cells and loss due to catabolism and/or in vitro oxidation. Surprisingly, we also found that the presence of gamma-tocopherol promoted the cellular uptake of alpha-tocopherol. Mass balance considerations suggest that products other than quinone were formed during the incubation of tocopherols with macrophages. Conclusion Our data suggests that gamma-tocopherol could play a significant role in modulating intracellular antioxidant defence mechanisms. Moreover, we found the presence of gamma-tocopherol dramatically influenced the cellular accumulation of alpha-tocopherol, i.e., gamma-tocopherol promoted the accumulation of alpha-tocopherol. If these results could be extrapolated to in vivo conditions they suggest that gamma-tocopherol is selectively taken up by cells and removed from plasma more rapidly than alpha-tocopherol. This could, in part, contribute to the selective maintenance of alpha-tocopherol in plasma compared to gamma-tocopherol.

Investigating the use of endogenous quinoid moieties on carbon fibre as means of developing micro pH sensors

Energy Technology Data Exchange (ETDEWEB)

Anderson, Ashleigh; Phair, Jolene; Benson, John; Meenan, Brian; Davis, James, E-mail: james.davis@ulster.ac.uk

2014-10-01

The redox profile obtained from electrochemically oxidised carbon fibre was exploited as a foundation from which to design a reusable pH probe. X-ray photoelectron spectroscopy of the surface after anodisation revealed an increase in the population of endogenous quinone moieties. Square wave voltammograms recorded in various buffer solutions (pH 3–9) yielded a distinct and unambiguous oxidation process through which to ascribe the peak potential — with the latter found to shift in a sub-Nernstian (− 0.052 V/pH) manner. The design of a discrete 2-electrode reusable probe which provides a rapid assessment of pH is described and a preliminary characterisation of the electrochemical performance is critically assessed. - Graphical abstract: The redox profile obtained from electrochemically oxidised carbon fibre was exploited as a foundation from which to design a reusable pH probe. X-ray photoelectron spectroscopy of the surface after anodisation revealed an increase in the population endogenous quinone moieties. Square wave voltammograms recorded in various buffer solutions (pH 3–9) yielded a distinct and unambiguous oxidation process through which to ascribe the peak potential — with the latter found to shift in a sub-Nernstian (− 0.052 V/pH) manner. The design of a discrete 2-electrode reusable probe which provides a rapid assessment of pH is described and a preliminary characterisation of the electrochemical performance is critically assessed. - Highlights: • In situ creation of pH sensitive quinone groups on carbon fibre • Versatile and accessible approach to manufacturing disposable pH sensors • Miniature probe design enables monitoring pH in small volumes. • Detailed surface characterisation of electrochemically modified carbon fibre.

Reengineered glucose oxidase for amperometric glucose determination in diabetes analytics.

Science.gov (United States)

Arango Gutierrez, Erik; Mundhada, Hemanshu; Meier, Thomas; Duefel, Hartmut; Bocola, Marco; Schwaneberg, Ulrich

2013-12-15

Glucose oxidase is an oxidoreductase exhibiting a high β-D-glucose specificity and high stability which renders glucose oxidase well-suited for applications in diabetes care. Nevertheless, GOx activity is highly oxygen dependent which can lead to inaccuracies in amperometric β-D-glucose determinations. Therefore a directed evolution campaign with two rounds of random mutagenesis (SeSaM followed by epPCR), site saturation mutagenesis studies on individual positions, and one simultaneous site saturation library (OmniChange; 4 positions) was performed. A diabetes care well suited mediator (quinone diimine) was selected and the GOx variant (T30V I94V) served as starting point. For directed GOx evolution a microtiter plate detection system based on the quinone diimine mediator was developed and the well-known ABTS-assay was applied in microtiter plate format to validate oxygen independency of improved GOx variants. Two iterative rounds of random diversity generation and screening yielded to two subsets of amino acid positions which mainly improved activity (A173, A332) and oxygen independency (F414, V560). Simultaneous site saturation of all four positions with a reduced subset of amino acids using the OmniChange method yielded finally variant V7 with a 37-fold decreased oxygen dependency (mediator activity: 7.4 U/mg WT, 47.5 U/mg V7; oxygen activity: 172.3 U/mg WT, 30.1 U/mg V7). V7 is still highly β-D-glucose specific, highly active with the quinone diimine mediator and thermal resistance is retained (prerequisite for GOx coating of diabetes test stripes). The latter properties and V7's oxygen insensitivity make V7 a very promising candidate to replace standard GOx in diabetes care applications. Copyright © 2013 Elsevier B.V. All rights reserved.

Effects of juglone and lawsone on oxidative stress in maize coleoptile cells treated with IAA.

Science.gov (United States)

Kurtyka, Renata; Pokora, Wojciech; Tukaj, Zbigniew; Karcz, Waldemar

2016-01-01

Naphthoquinones are secondary metabolites widely distributed in nature and produced by bacteria, fungi and higher plants. Their biological activity may result from induction of oxidative stress, caused by redox cycling or direct interaction with cellular macromolecules, in which quinones act as electrophiles. The redox homeostasis is known as one of factors involved in auxin-mediated plant growth regulation. To date, however, little is known about the crosstalk between reactive oxygen species (ROS) produced by quinones and the plant growth hormone auxin (IAA). In this study, redox cycling properties of two naphthoquinones, juglone (5-hydroxy-1,4-naphthoquinone) and lawsone (2-hydroxy-1,4-naphthoquinone), were compared in experiments performed on maize coleoptile segments incubated with or without the addition of IAA. It was found that lawsone was much more effective than juglone in increasing both H 2 O 2 production and the activity of antioxidative enzymes (SOD, POX and CAT) in coleoptile cells, regardless of the presence of IAA. An increase in the activity of Cu/Zn-SOD isoenzymes induced by both naphthoquinones suggests that juglone- and lawsone-generated H 2 O 2 was primarily produced in the cytosolic and cell wall spaces. The cell potential to neutralize hydrogen peroxide, determined by POX and CAT activity, pointed to activity of catalase as the main enzymatic mechanism responsible for degradation of H 2 O 2 Therefore, we assumed that generation of H 2 O 2 , induced more efficiently by LW than JG, was the major factor accounting for differences in the toxicity of naphthoquinones in maize coleoptiles. The role of auxin in the process appeared negligible. Moreover, the results suggested that oxidative stress imposed by JG and LW was one of mechanisms of allelopathic action of the studied quinones in plants. © The Authors 2016. Published by Oxford University Press on behalf of the Annals of Botany Company.

Functions of NQO1 in Cellular Protection and CoQ10 Metabolism and its Potential Role as a Redox Sensitive Molecular Switch

Directory of Open Access Journals (Sweden)

David Ross

2017-08-01

Full Text Available NQO1 is one of the two major quinone reductases in mammalian systems. It is highly inducible and plays multiple roles in cellular adaptation to stress. A prevalent polymorphic form of NQO1 results in an absence of NQO1 protein and activity so it is important to elucidate the specific cellular functions of NQO1. Established roles of NQO1 include its ability to prevent certain quinones from one electron redox cycling but its role in quinone detoxification is dependent on the redox stability of the hydroquinone generated by two-electron reduction. Other documented roles of NQO1 include its ability to function as a component of the plasma membrane redox system generating antioxidant forms of ubiquinone and vitamin E and at high levels, as a direct superoxide reductase. Emerging roles of NQO1 include its function as an efficient intracellular generator of NAD+ for enzymes including PARP and sirtuins which has gained particular attention with respect to metabolic syndrome. NQO1 interacts with a growing list of proteins, including intrinsically disordered proteins, protecting them from 20S proteasomal degradation. The interactions of NQO1 also extend to mRNA. Recent identification of NQO1 as a mRNA binding protein have been investigated in more detail using SERPIN1A1 (which encodes the serine protease inhibitor α-1-antitrypsin as a target mRNA and indicate a role of NQO1 in control of translation of α-1-antitrypsin, an important modulator of COPD and obesity related metabolic syndrome. NQO1 undergoes structural changes and alterations in its ability to bind other proteins as a result of the cellular reduced/oxidized pyridine nucleotide ratio. This suggests NQO1 may act as a cellular redox switch potentially altering its interactions with other proteins and mRNA as a result of the prevailing redox environment.

Understanding the Etiology of Tuberous Sclerosis Complex

Science.gov (United States)

2012-07-01

catalog #4856), mouse anti-NeuN (1:500; Millipore), GFAP (1:100, DAKO) and DCX (1:500, Santa Cruz Biotechnology). Each staining was replicated in slices...Tramontin, A.D., Quinones-Hinojosa, A., Barbaro, N.M., Gupta, N., Kunwar, S., Lawton, M.T., McDermott, M.W., Parsa, A.T., Manuel -Garcia, V.J. et al

Cell protein cross-linking by erbstatin and related compounds | Center for Cancer Research

Science.gov (United States)

The scheme depicts a possible mechanism of cross-linking by erbstatin and related analogues. A mechanism of action is proposed which involves initial oxidation to reactive quinone intermediates that subsequently cross-link protein nucleophiles via multiple 1,4-Michael-type additions. Similar alkylation of protein by protein-tyrosine kinase inhibitors, such as herbimycin A, has

Journal of Chemical Sciences | Indian Academy of Sciences

Indian Academy of Sciences (India)

... behaves as an effective catalyst towards oxidation of 3,5-ditertiarybutyl catechol (3,5-DTBC) in acetonitrile to its corresponding quinone derivative in air. The reaction follows first-order reaction kinetics with rate constant 4.28 × 10−5 min-1. The reaction follows Michaelis-Menten enzymatic kinetics with a turnover number of ...

Molecular dynamics comparison of E. coli WrbA apoprotein and holoprotein

Czech Academy of Sciences Publication Activity Database

Řeha, David; Balasubramanian, H.; Sinha, Dhiraj; Kukačka, Zdeněk; McSally, J.; Ettrichová, Olga; Novák, Petr; Carey, J.; Ettrich, Rüdiger

2014-01-01

Roč. 20, č. 9 (2014), s. 2400 ISSN 1610-2940 R&D Projects: GA ČR GAP207/10/1934 Institutional support: RVO:67179843 ; RVO:61388971 Keywords : global motions * force field parametrization * binding site volume * electrostatic potential surface * NAD(P)H:quinone oxidoreductase Subject RIV: EH - Ecology, Behaviour Impact factor: 1.736, year: 2014

Drug: D02894 [KEGG MEDICUS

Lifescience Database Archive (English)

Full Text Available D02894 Drug Ametantrone acetate (USAN) ... C22H28N4O4. (C2H4O2)2 D02894.gif ... Antineoplastic ... DG01727 ... Anthra...quinone antineoplastic ... anthraquinone derivative ... CAS: 70711-40-9 PubChem: 17397051 ChEMBL: CHEMBL2104059 LigandBox: D02894 NIKKAJI: J395.653I ...

Biological Reactive Intermediates (BRIs) Formed from Botanical Dietary Supplements

Science.gov (United States)

Dietz, Birgit M.; Bolton, Judy L.

2013-01-01

The use of botanical dietary supplements is increasingly popular, due to their natural origin and the perceived assumption that they are safer than prescription drugs. While most botanical dietary supplements can be considered safe, a few contain compounds, which can be converted to reactive biological reactive intermediates (BRIs) causing toxicity. For example, sassafras oil contains safrole, which can be converted to a reactive carbocation forming genotoxic DNA adducts. Alternatively, some botanical dietary supplements contain stable BRIs such as simple Michael acceptors that react with chemosensor proteins such as Keap1 resulting in induction of protective detoxification enzymes. Examples include curcumin from turmeric, xanthohumol from hops, and Z-ligustilide from dang gui. Quinones (sassafras, kava, black cohosh), quinone methides (sassafras), and epoxides (pennyroyal oil) represent BRIs of intermediate reactivity, which could generate both genotoxic and/or chemopreventive effects. The biological targets of BRIs formed from botanical dietary supplements and their resulting toxic and/or chemopreventive effects are closely linked to the reactivity of BRIs as well as dose and time of exposure. PMID:20970412

Hydroxynaphthoquinone ultrathin films obtained by diazonium electroreduction: toward design of biosensitive electroactive interfaces.

Science.gov (United States)

March, Gregory; Reisberg, Steeve; Piro, Benoit; Pham, Minh-Chau; Fave, Claire; Noel, Vincent

2010-05-01

Electroactive 2-(phenylsulfanyl)-8-hydroxy-1,4-naphthoquinone has been electrodeposited via the reduction of the corresponding diazonium salt on Au electrodes. Surface characterizations by X-ray photoelectron spectroscopy (XPS) and infrared reflection-absorption spectroscopy (IRRAS) reveal that the mechanism of film deposition follows an aryl radical formation and its immobilization on the electrode surface. Electrochemical study shows that the surface coverage can be finely tuned (thickness between one and four layers) by adjusting the potential and the deposition time. By managing the potential applied when reducing diazonium in potentiostatic mode, the formed layer could mediate or not charge transfer. This is the first time that the films obtained by diazonium process are demonstrated to act as mediators in the growth process. Hence, with potentials higher than the formal potential of quinone group, very thin and homogeneous layers are obtained, whereas thicker films are formed when more cathodic potentials than that of quinone are applied. The possibility to manage the charge-transfer kinetics, the thickness, and the homogeneity of electroactive deposits is interesting in the scope of designing electrochemical transducers.

Voltammetric pH sensing using carbon electrodes: glassy carbon behaves similarly to EPPG.

Science.gov (United States)

Lu, Min; Compton, Richard G

2014-09-21

Developing and building on recent work based on a simple sensor for pH determination using unmodified edge plane pyrolytic graphite (EPPG) electrodes, we present a voltammetric method for pH determination using a bare unmodified glassy carbon (GC) electrode. By exploiting the pH sensitive nature of quinones present on carbon edge-plane like sites within the GC, we show how GC electrodes can be used to measure pH. The electro-reduction of surface quinone groups on the glassy carbon electrode was characterised using cyclic voltammetry (CV) and optimised with square-wave voltammetry (SWV) at 298 K and 310 K. At both temperatures, a linear correlation was observed, corresponding to a 2 electron, 2 proton Nernstian response over the aqueous pH range 1.0 to 13.1. As such, unmodified glassy carbon electrodes are seen to be pH dependent, and the Nernstian response suggests its facile use for pH sensing. Given the widespread use of glassy carbon electrodes in electroanalysis, the approach offers a method for the near-simultaneous measurement and monitoring of pH during such analyses.

A single use electrochemical sensor based on biomimetic nanoceria for the detection of wine antioxidants.

Science.gov (United States)

Andrei, Veronica; Sharpe, Erica; Vasilescu, Alina; Andreescu, Silvana

2016-08-15

We report the development and characterization of a disposable single use electrochemical sensor based on the oxidase-like activity of nanoceria particles for the detection of phenolic antioxidants. The use of nanoceria in the sensor design enables oxidation of phenolic compounds, particularly those with ortho-dihydroxybenzene functionality, to their corresponding quinones at the surface of a screen printed carbon electrode. Detection is carried out by electrochemical reduction of the resulting quinone at a low applied potential of -0.1V vs the Ag/AgCl electrode. The sensor was optimized and characterized with respect to particle loading, applied potential, response time, detection limit, linear concentration range and sensitivity. The method enabled rapid detection of common phenolic antioxidants including caffeic acid, gallic acid and quercetin in the µM concentration range, and demonstrated good functionality for the analysis of antioxidant content in several wine samples. The intrinsic oxidase-like activity of nanoceria shows promise as a robust tool for sensitive and cost effective analysis of antioxidants using electrochemical detection. Copyright © 2016 Elsevier B.V. All rights reserved.

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.

Thermal behavior of biflorin by beans TG and a DSC photovisual system

Directory of Open Access Journals (Sweden)

C. F. S. Aragão

Full Text Available This work proposes thermal characterization, of the biflorine, orto-quinon of Capraria biflora L., through the TG and DSC photovisual data. The thermogravimetric results showed that the decomposition reaction biflorine occurs three steps under air atmosphere, The DSC of biflorin presented five peaks relating to phase transitions. The DSC photovisual system demonstrated changes in biflorin.

Mixed-Valent Metals Bridged by a Radical Ligand: Fact, or Fiction Based on Structure-Oxidation State Correlations

Czech Academy of Sciences Publication Activity Database

Sarkar, B.; Patra, S.; Fiedler, Jan; Sunoj, R. B.; Janardanan, D.; Lahiri, G. K.; Kaim, W.

2008-01-01

Roč. 130, č. 11 (2008), s. 3532-3542 ISSN 0002-7863 R&D Projects: GA MŠk 1P05OC068; GA MŠk OC 140 Institutional research plan: CEZ:AV0Z40400503 Keywords : electron transfer series * quinone-related ligand s * ruthenium complexes Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 8.091, year: 2008

Antinociceptive Activity of Thymoquinone and its Structural Analogues

African Journals Online (AJOL)

Methods: The quinones were prepared by an oxidation procedure using molecular oxygen and catalysis with [CoII(salen)] from ... mg/kg, ip) was evaluated using formalin test in mice. Vehicle (5 % Tween ... oxidation reactions. ... with 0.1 mol∙L-1 HCl (2 × 10 mL), water and brine. .... antinociceptive effect in the acetic acid and.

Enhancement of radiation effect using beta-lapachone and underlying mechanism

International Nuclear Information System (INIS)

Ahn, Ki Jung; Lee, Hyung Sik; Bai, Se Kyung; Song, Chang Won

2013-01-01

Beta-lapachone (β-Lap; 3,4-dihydro-2, 2-dimethyl-2H-naphthol[1, 2-b]pyran-5,6-dione) is a novel anti-cancer drug under phase I/II clinical trials. (β-Lap has been demonstrated to cause apoptotic and necrotic death in a variety of human cancer cells in vitro and in vivo. The mechanisms underlying the (β-Lap toxicity against cancer cells has been controversial. The most recent view is that (β-Lap, which is a quinone compound, undergoes two-electron reduction to hydroquinone form utilizing NAD(P)H or NADH as electron source. This two-electron reduction of (β-Lap is mediated by NAD(P)H:quinone oxidoreductase (NQO1), which is known to mediate the reduction of many quinone compounds. The hydroquinone forms of (β-Lap then spontaneously oxidizes back to the original oxidized (β-Lap, creating futile cycling between the oxidized and reduced forms of (β-Lap. It is proposed that the futile recycling between oxidized and reduced forms of (β-Lap leads to two distinct cell death pathways. First one is that the two-electron reduced (β-Lap is converted first to one-electron reduced (β-Lap, i.e., semiquinone (β-Lap (SQ)- causing production of reactive oxygen species (ROS), which then causes apoptotic cell death. The second mechanism is that severe depletion of NAD(P)H and NADH as a result of futile cycling between the quinone and hydroquinone forms of β- p causes severe disturbance in cellular metabolism leading to apoptosis and necrosis. The relative importance of the aforementioned two mechanisms, i.e., generation of ROS or depletion of NAD(P)H/NADH, may vary depending on cell type and environment. Importantly, the NQO1 level in cancer cells has been found to be higher than that in normal cells indicating that β-Lap may be preferentially toxic to cancer cells relative to non-cancer cells. The cellular level of NQO1 has been found to be significantly increased by divergent physical and chemical stresses including ionizing radiation. Recent reports clearly demonstrated

Kinetics and mechanism of auto- and copper-catalyzed oxidation of 1,4-naphthohydroquinone.

Science.gov (United States)

Yuan, Xiu; Miller, Christopher J; Pham, A Ninh; Waite, T David

2014-06-01

Although quinones represent a class of organic compounds that may exert toxic effects both in vitro and in vivo, the molecular mechanisms involved in quinone species toxicity are still largely unknown, especially in the presence of transition metals, which may both induce the transformation of the various quinone species and result in generation of harmful reactive oxygen species. In this study, the oxidation of 1,4-naphthohydroquinone (NH2Q) in the absence and presence of nanomolar concentrations of Cu(II) in 10 mM NaCl solution over a pH range of 6.5-7.5 has been investigated, with detailed kinetic models developed to describe the predominant mechanisms operative in these systems. In the absence of copper, the apparent oxidation rate of NH2Q increased with increasing pH and initial NH2Q concentration, with concomitant oxygen consumption and peroxide generation. The doubly dissociated species, NQ(2-), has been shown to be the reactive species with regard to the one-electron oxidation by O2 and comproportionation with the quinone species, both generating the semiquinone radical (NSQ(·-)). The oxidation of NSQ(·-) by O2 is shown to be the most important pathway for superoxide (O2(·-)) generation with a high intrinsic rate constant of 1.0×10(8)M(-1)s(-1). Both NSQ(·-) and O2(·-) served as chain-propagating species in the autoxidation of NH2Q. Cu(II) is capable of catalyzing the oxidation of NH2Q in the presence of O2 with the oxidation also accelerated by increasing the pH. Both the uncharged (NH2Q(0)) and the mono-anionic (NHQ(-)) species were found to be the kinetically active forms, reducing Cu(II) with an intrinsic rate constant of 4.0×10(4) and 1.2×10(7)M(-1)s(-1), respectively. The presence of O2 facilitated the catalytic role of Cu(II) by rapidly regenerating Cu(II) via continuous oxidation of Cu(I) and also by efficient removal of NSQ(·-) resulting in the generation of O2(·-). The half-cell reduction potentials of various redox couples at neutral p

Paracoccus niistensis sp. nov., isolated from forest soil, India

Digital Repository Service at National Institute of Oceanography (India)

Dastager, S.G.; Deepa, C; Li, Wen-Jun; Tang, Shu-Kun; Pandey, A.

acids of strain NII-0918 sup(T) were summed feature 7 (C18:1 ω7c/ω 9t/ω 12t) (83.0%) and C18:0 (12.5%). Ubiquinone Q-10 was detected as the major respiratory quinone. The G+C content of genomic DNA of NII-0918 sup(T) was 66.6 mol%. On the basis...

Condensed tannins: Base-catalysed reactions of polymeric procyanidins with toluene-α-thiol, liability of the interflavanoid bond and pyran ring

Science.gov (United States)

Peter E. Laks; Richard W. Hemingway

1987-01-01

Reaction of polymeric procyanidins (condensed tannins) with toluene-α-thiol at pH 12.0 and 23°C gave predominantly one stereoisomer of 1.3-bisbenzylthio-1-(3,4-dihydroxyphenyl)-3-(2,4,6-trihydroxyphenyl) propan-2-ol (10) by stereoselective reaction at C-4 and C-2 of the Quinone methide derived from the upper 2,3-cis procyanidin units....

Screening and antibacterial activity analysis of some important medicinal plants

OpenAIRE

G. Senthilmurugan Viji; B. Vasanthe; Kuru Suresh

2013-01-01

The screening and study of five different plant specimens belonging to different families for phytochemical constituents was performed using generally accepted laboratory technique for qualitative determinations. The constituents screened were saponins, combined anthraquinones, terpenoids, flavonoids, carotenoids, steroids, xantho proteins, couramins, alkaloids, quinones, vitamin C. The distribution of these constituents in the plant specimens were assessed and compared. The medicinal plant s...

Uji Aktivitas Antioksidan Ekstrak Air dan Ekstrak Etanol Daun Kelor (Moringa Oleifera LAM)

OpenAIRE

Rizkayanti, Rizkayanti; Diah, Anang Wahid M; Jura, Minarni Rama

2017-01-01

Moringa (moringa oleifera Lam) leaves contains many molecules as inhibitors for free radicals such as phenolic compounds (phenolic acids, flavonoids, quinones, coumarins, lignans, stilbenes, tannins), nitrogen compounds (alkaloids, amines, betalain), vitamins, terpenoids (including carotenoids), and several other endogenous metabolites as antioxidants. This study aimed to determine the antioxidant potency of water and ethanol extracts of moringa (moringa oleifera Lam) leave obtained by macera...

Chemoselective organocatalytic aerobic oxidation of primary amines to secondary imines.

Science.gov (United States)

Wendlandt, Alison E; Stahl, Shannon S

2012-06-01

Biomimetic aerobic oxidation of primary benzylic amines has been achieved by using a quinone catalyst. Excellent selectivity is observed for primary, unbranched benzylic amines relative to secondary/tertiary amines, branched benzylic amines, and aliphatic amines. The exquisite selectivity for benzylic amines enables oxidative self-sorting within dynamic mixtures of amines and imines to afford high yields of cross-coupled imine products.

Free radical-mediated stimulation of tyrosine-specific protein kinase in rat liver plasma membrane

International Nuclear Information System (INIS)

Chan, T.M.; Tatoyan, A.; Cheng, E.; Shargill, N.S.; Pleta, M.

1986-01-01

Incorporation of 32 P from (γ- 32 P)-ATP into endogenous proteins of plasma membranes isolated from rat liver was significantly increased by several naphthoquinones including menadione. This apparent stimulation of membrane-associated protein kinase activity by these compounds was most striking (up to 6-7 fold) when the synthetic copolymers containing glutamate and tyrosine residues (4:1) was used as substrate. Since tyrosine residues are the only possible phosphate acceptor in the copolymers, the quinone-stimulated liver membrane protein kinase is most likely tyrosine specific. Although not required for protein kinase activity, dithiothreitol (DTT) was necessary for its stimulation by these quinonoid compounds. Hydrolysis of ATP was not significantly affected by quinones under the experimental conditions. Both menadione and vitamin k 5 increased phosphorylation of plasma membrane proteins of molecular weight 45 and 60 kd. The stimulatory effect of menadione on protein phosphorylation was prevented by the addition of superoxide dismutase. Dihydroxyfumerate, which spontaneously produces various radical species, and H 2 O 2 , also stimulated tyrosine-specific protein phosphorylation. DTT was also required for their full effect. It, therefore, appears that quinonone stimulation of tyrosine-specific protein phosphorylation is mediated by oxygen radicals

Um panorama atual da química e da farmacologia de naftoquinonas, com ênfase na beta-lapachona e derivados An overview of the chemistry and pharmacology of naphthoquinones with emphasis on beta-lapachone and derivatives

Directory of Open Access Journals (Sweden)

Milton N. da Silva

2003-05-01

Full Text Available Naphthoquinones have been extensively studied due to their activity as topoisomerase inhibitors. These enzymes are critical to DNA replication in cells. In addition, naphthoquinones have been shown to induce what are known as "reactive oxygen species" that can cause damage to cells. beta-Lapachone is a very important pyranaphthoquinone obtained from the heartwood of the lapacho tree, Tabebuia avellanedae Lorentz ex. Griseb. (Bignoniaceae, and other Tabebuia trees native to Central and South America and chemically from lapachol. beta-Lapachone has a diversity of useful biological activities against various cancer cell lines such as human ovarian and prostate tumors and, at lower doses is a radiosensitizer of several human cancer cell lines. It gives rise to a variety of effects in vitro including the inhibition or activation of topoisomerase I an II in a distinct manner from that of other topoisomerase inhibitors. This review intend to discuss some details of the mechanisms of quinone-induced cell damage and death, and we also summarize results of the literature indicating that b-Lapachone may take part in quinone-elicited apoptosis despite the fact that its mechanism of action in vivo and its targets are still unknown.

Alcohol dehydrogenase of acetic acid bacteria: structure, mode of action, and applications in biotechnology.

Science.gov (United States)

Yakushi, Toshiharu; Matsushita, Kazunobu

2010-05-01

Pyrroquinoline quinone-dependent alcohol dehydrogenase (PQQ-ADH) of acetic acid bacteria is a membrane-bound enzyme involved in the acetic acid fermentation by oxidizing ethanol to acetaldehyde coupling with reduction of membranous ubiquinone (Q), which is, in turn, re-oxidized by ubiquinol oxidase, reducing oxygen to water. PQQ-ADHs seem to have co-evolved with the organisms fitting to their own habitats. The enzyme consists of three subunits and has a pyrroloquinoline quinone, 4 heme c moieties, and a tightly bound Q as the electron transfer mediators. Biochemical, genetic, and electrochemical studies have revealed the unique properties of PQQ-ADH since it was purified in 1978. The enzyme is unique to have ubiquinol oxidation activity in addition to Q reduction. This mini-review focuses on the molecular properties of PQQ-ADH, such as the roles of the subunits and the cofactors, particularly in intramolecular electron transport of the enzyme from ethanol to Q. Also, we summarize biotechnological applications of PQQ-ADH as to enantiospecific oxidations for production of the valuable chemicals and bioelectrocatalysis for sensors and fuel cells using indirect and direct electron transfer technologies and discuss unsolved issues and future prospects related to this elaborate enzyme.

Cytochrome b 6 f function and localization, phosphorylation state of thylakoid membrane proteins and consequences on cyclic electron flow.

Science.gov (United States)

Dumas, Louis; Chazaux, Marie; Peltier, Gilles; Johnson, Xenie; Alric, Jean

2016-09-01

Both the structure and the protein composition of thylakoid membranes have an impact on light harvesting and electron transfer in the photosynthetic chain. Thylakoid membranes form stacks and lamellae where photosystem II and photosystem I localize, respectively. Light-harvesting complexes II can be associated to either PSII or PSI depending on the redox state of the plastoquinone pool, and their distribution is governed by state transitions. Upon state transitions, the thylakoid ultrastructure and lateral distribution of proteins along the membrane are subject to significant rearrangements. In addition, quinone diffusion is limited to membrane microdomains and the cytochrome b 6 f complex localizes either to PSII-containing grana stacks or PSI-containing stroma lamellae. Here, we discuss possible similarities or differences between green algae and C3 plants on the functional consequences of such heterogeneities in the photosynthetic electron transport chain and propose a model in which quinones, accepting electrons either from PSII (linear flow) or NDH/PGR pathways (cyclic flow), represent a crucial control point. Our aim is to give an integrated description of these processes and discuss their potential roles in the balance between linear and cyclic electron flows.

Low-energy electron interaction with retusin extracted from Maackia amurensis: towards a molecular mechanism of the biological activity of flavonoids.

Science.gov (United States)

Pshenichnyuk, Stanislav A; Elkin, Yury N; Kulesh, Nadezda I; Lazneva, Eleonora F; Komolov, Alexei S

2015-07-14

The antioxidant isoflavone retusin efficiently attaches low-energy electrons in vacuo, generating fragment species via dissociative electron attachment (DEA), as has been shown by DEA spectroscopy. According to in silico results obtained by means of density functional theory, retusin is able to attach solvated electrons and could be decomposed under reductive conditions in vivo, for instance, near the mitochondrial electron transport chain, analogous to gas-phase DEA. The most intense decay channels of retusin temporary negative ions were found to be associated with the elimination of H atoms and H2 molecules. Doubly dehydrogenated fragment anions were predicted to possess a quinone structure. It is thought that molecular hydrogen, known for its selective antioxidant properties, can be efficiently generated via electron attachment to retusin in mitochondria and may be responsible for its antioxidant activity. The second abundant species, i.e., quinone bearing an excess negative charge, can serve as an electron carrier and can return the captured electron back to the respiration cycle. The number of OH substituents and their relative positions are crucial for the present molecular mechanism, which can explain the radical scavenging activity of polyphenolic compounds.

Quantum dots as optical labels for ultrasensitive detection of polyphenols.

Science.gov (United States)

Akshath, Uchangi Satyaprasad; Shubha, Likitha R; Bhatt, Praveena; Thakur, Munna Singh

2014-07-15

Considering the fact that polyphenols have versatile activity in-vivo, its detection and quantification is very much important for a healthy diet. Laccase enzyme can convert polyphenols to yield mono/polyquinones which can quench Quantum dots fluorescence. This phenomenon of charge transfer from quinones to QDs was exploited as optical labels to detect polyphenols. CdTe QD may undergo dipolar interaction with quinones as a result of broad spectral absorption due to multiple excitonic states resulting from quantum confinement effects. Thus, "turn-off" fluorescence method was applied for ultrasensitive detection of polyphenols by using laccase. We observed proportionate quenching of QDs fluorescence with respect to polyphenol concentration in the range of 100 µg to 1 ng/mL. Also, quenching of the photoluminescence was highly efficient and stable and could detect individual and total polyphenols with high sensitivity (LOD-1 ng/mL). Moreover, proposed method was highly efficient than any other reported methods in terms of sensitivity, specificity and selectivity. Therefore, a novel optical sensor was developed for the detection of polyphenols at a sensitive level based on the charge transfer mechanism. Copyright © 2014 Elsevier B.V. All rights reserved.

Dye-sensitized photopolymerization of N,N ...

Indian Academy of Sciences (India)

Unknown

and a primary radical derived from the reducing agent. This radical initiates the vinyl polymerization. (scheme 1). In scheme 1, D is the dye, 1D the first excited singlet state, 3D the triplet state, DH. • the semi- quinone dye, DH2 the leuco dye, RH the reducing agent and R. • the initiating radical. Similar schemes. 1D → 3D,.

Larvicidal activity of Cybistax antisyphilitica against Aedes aegypti larvae.

Science.gov (United States)

Rodrigues, A M S; de Paula, J E; Roblot, F; Fournet, A; Espíndola, L S

2005-12-01

The larvicidal activity against Aedes aegypti larvae of a stem wood hexane extract of Cybistax antisyphilitica was evaluated. Bioassay-guided fractionation of the crude extract, monitored by larvicidal assay, led to the isolation of a natural quinone identified as 2-hydroxy-3-(3-methyl-2-butenyl)-1.4-naphthoquinone (lapachol). This compound was quite potent against A. aegypti larvae (LC50 26.3 microg/ml).

Frederiksenia canicola gen. nov., sp. nov. isolated from dogs and human dog-bite wounds

DEFF Research Database (Denmark)

Korczak, Bożena M.; Bisgaard, Magne; Christensen, Henrik

2014-01-01

below the genus level. Major whole cell fatty acids for the strain HPA 21(T) are C14:0, C16:0, C18:0 and C16:1 ω7c/C15:0 iso 2OH. Major respiratory quinones are menaquinone-8, ubiquinone-8 and demethylmenaquinone-8. We propose to classify these organisms as a novel genus and species within the family...

Penicillipyrones A and B, meroterpenoids from a marine-derived Penicillium sp. fungus.

Science.gov (United States)

Liao, Lijuan; Lee, Jung-Ho; You, Minjung; Choi, Tae Joon; Park, Wanki; Lee, Sang Kook; Oh, Dong-Chan; Oh, Ki-Bong; Shin, Jongheon

2014-02-28

Penicillipyrones A (1) and B (2), two novel meroterpenoids, were isolated from the marine-derived fungus Penicillium sp. On the basis of the results of combined spectroscopic analyses, these compounds were structurally elucidated to be sesquiterpene γ-pyrones from a new skeletal class derived from a unique linkage pattern between the drimane sesquiterpene and pyrone moieties. Compound 2 elicited significant induction of quinone reductase.

A dual Lewis base activation strategy for enantioselective carbene-catalyzed annulations.

Science.gov (United States)

Izquierdo, Javier; Orue, Ane; Scheidt, Karl A

2013-07-24

A dual activation strategy integrating N-heterocyclic carbene (NHC) catalysis and a second Lewis base has been developed. NHC-bound homoenolate equivalents derived from α,β-unsaturated aldehydes combine with transient reactive o-quinone methides in an enantioselective formal [4 + 3] fashion to access 2-benzoxopinones. The overall approach provides a general blueprint for the integration of carbene catalysis with additional Lewis base activation modes.

Study of dopamine reactivity on platinum single crystal electrode surfaces

International Nuclear Information System (INIS)

Chumillas, Sara; Figueiredo, Marta C.; Climent, Víctor; Feliu, Juan M.

2013-01-01

Dopamine is the biological molecule responsible, among other functions, of the heart beat and blood pressure regulation. Its loss, in the human body, can result in serious diseases such as Parkinson's, schizophrenia or depression. Structurally, this molecule belongs to the group of catecholamines, together with epinephrine (adrenaline) and norepinephrine (noradrenaline). The hydroquinone moiety of the molecule can be easily oxidized to quinone, rendering the electrochemical methods a convenient approach for the development of dopamine biosensors. The reactivity of similar aromatic molecules, such as catechol and hydroquinone, at well-ordered platinum surfaces, has recently been investigated in our group. In this paper, we extend these studies to the structurally related molecule dopamine. The study has been performed in neutral pH, since this is closer to the natural conditions for these molecules in biological media. Cyclic voltammetry and in situ infra-red spectroscopy have been combined to extract information about the behavior of this molecule on well-defined platinum surfaces. Dopamine appears to be electrochemically active and reveals interesting adsorption phenomena at low potentials (0.15–0.25 V vs RHE), sensitive to the single crystal orientation. The adsorption of dopamine on these surfaces is very strong, taking place at much lower potentials than the electron transfer from solution species. Specifically, the voltammetry of Pt(1 1 1) and Pt(1 0 0) in dopamine solutions shows an oxidation peak at potentials close to the onset of hydrogen evolution, which is related to the desorption of hydrogen and the adsorption of dopamine. On the other hand, adsorption on Pt(1 1 0) is irreversible and the surface appears totally blocked. Spectroscopic results indicate that dopamine is adsorbed flat on the surface. At potentials higher than 0.6 V vs RHE the three basal planes show a common redox process. The initial formation of the quinone moiety is followed by a

A metal-free organic-inorganic aqueous flow battery

Energy Technology Data Exchange (ETDEWEB)

Huskinson, B; Marshak, MP; Suh, C; Er, S; Gerhardt, MR; Galvin, CJ; Chen, XD; Aspuru-Guzik, A; Gordon, RG; Aziz, MJ

2014-01-08

As the fraction of electricity generation from intermittent renewable sources-such as solar or wind-grows, the ability to store large amounts of electrical energy is of increasing importance. Solid-electrode batteries maintain discharge at peak power for far too short a time to fully regulate wind or solar power output(1,2). In contrast, flow batteries can independently scale the power (electrode area) and energy (arbitrarily large storage volume) components of the system by maintaining all of the electro-active species in fluid form(3-5). Wide-scale utilization of flow batteries is, however, limited by the abundance and cost of these materials, particularly those using redox-active metals and precious-metal electrocatalysts(6,7). Here we describe a class of energy storage materials that exploits the favourable chemical and electro-chemical properties of a family of molecules known as quinones. The example we demonstrate is ametal-free flow battery based on the redox chemistry of 9,10-anthraquinone-2,7-disulphonic acid (AQDS). AQDS undergoes extremely rapid and reversible two-electron two-proton reduction on a glassy carbon electrode in sulphuric acid. An aqueous flow battery with inexpensive carbon electrodes, combining the quinone/hydroquinone couple with the Br-2/Br- redox couple, yields a peak galvanic power density exceeding 0.6 W cm(-2) at 1.3 A cm(-2). Cycling of this quinone-bromide flow battery showed >99 per cent storage capacity retention per cycle. The organic anthraquinone species can be synthesized from inexpensive commodity chemicals(8). This organic approach permits tuning of important properties such as the reduction potential and solubility by adding functional groups: for example, we demonstrate that the addition of two hydroxy groups to AQDS increases the open circuit potential of the cell by 11% and we describe a pathway for further increases in cell voltage. The use of p-aromatic redox-active organic molecules instead of redox-active metals

Mutagenicity studies on alcohol extracts from gamma-irradiated potatoes

International Nuclear Information System (INIS)

Shinozaki, Yoshiharu; Hogetsu, Daisuke; Okuyama, Norio; Manabe, Takashi; Sasagawa, Tatsuru.

1981-01-01

The preparation of alcohol extracts from gamma-irradiated potatoes of the ''Danshaku'' variety and their chemical aspects were studied. The final concentrate of alcohol extracts from potatoes showed pH values of 3 -- 4. The o-quinones or ''radiotoxins'' reported by Kuzin, et al. were not detected in the alcohol extracts from potatoes of this variety by high performance liquid chromatography (HPLC) analysis, paper chromatography and the model enzymatic experiment. (author)

Effect of physisorbed molecules and an external external fields on the metallic Shockley surface state of Cu(111): A density functional theory study

Science.gov (United States)

Berland, Kristian; Einstein, T. L.; Hyldgaard, Per

2012-02-01

To manipulate the Cu(111) partially-filled Shockley surface state, we study its response to an external fieldootnotetextKB, TLE, PH; arXiv 1109:6706 E and physisorbed PAHs and quinone molecules. We use density-functional theory calculations with periodic-boundary conditions. The van der Waals density functional version vdW-DF2 accounts for the molecular adsorption. The issue that the Kohn-Sham wave functions couple to both sides of the Cu slab is handled with a decoupling scheme based on a rotation in Hilbert space. A convergence study reveals that to obtain a proper Shockley surface state, 6 Cu layers is sufficient, while 15 is optimal. We use 6 layers for the response to the molecules and 15 to external field. We find that the surface state displays isotropic dispersion (up to order k^6), free-electron like until the Fermi wave vector but with a significant quartic component beyond. The shift in band minimum and effective mass depend linearly on E, with a smaller fractional change in the latter. Charge transfer occurs beyond the outermost copper atoms, and most of the screening is due to bulk electrons. We find that the molecular physisorption increases the band minimum, with the effect the of a quinone being much stronger than the corresponding PAH.

Schistosome and liver fluke derived catechol-estrogens and helminth associated cancers

Directory of Open Access Journals (Sweden)

José M Correia da Costa

2014-12-01

Full Text Available Infection with helminth parasites remains a persistent public health problem in developing countries. Three of these pathogens, the liver flukes Clonorchis sinensis, Opisthorchis viverrini and the blood fluke Schistosoma haematobium, are of particular concern due to their classification as Group 1 carcinogens: infection with these worms is carcinogenic. Using liquid chromatography-mass spectrometry (LC-MS/MS approaches, we identified steroid hormone like (e.g. oxysterol-like, catechol estrogen quinone-like, etc. metabolites and related DNA-adducts, apparently of parasite origin, in developmental stages including eggs of S. haematobium, in urine of people with urogenital schistosomiasis, and in the adult stage of Opisthorchis viverrini. Since these kinds of sterol derivatives are metabolized to active quinones that can modify DNA, which in other contexts can lead to breast and other cancers, helminth parasite associated sterols might induce tumor-like phenotypes in the target cells susceptible to helminth parasite associated cancers, i.e. urothelial cells of the bladder in the case of urogenital schistosomiasis and the bile duct epithelia or cholangiocytes, in the case of O. viverrini and C. sinensis. Indeed we postulate that helminth induced cancers originate from parasite estrogen-host epithelial/urothelial cell chromosomal DNA adducts, and here we review recent findings that support this conjecture.

Modulatory Effect of 2-(4-Hydroxyphenylamino-1,4-naphthoquinone on Endothelial Vasodilation in Rat Aorta

Directory of Open Access Journals (Sweden)

Javier Palacios

2016-01-01

Full Text Available The vascular endothelium plays an essential role in the control of the blood flow. Pharmacological agents like quinone (menadione at various doses modulate this process in a variety of ways. In this study, Q7, a 2-phenylamino-1,4-naphthoquinone derivative, significantly increased oxidative stress and induced vascular dysfunction at concentrations that were not cytotoxic to endothelial or vascular smooth muscle cells. Q7 reduced nitric oxide (NO levels and endothelial vasodilation to acetylcholine in rat aorta. It also blunted the calcium release from intracellular stores by increasing the phenylephrine-induced vasoconstriction when CaCl2 was added to a calcium-free medium but did not affect the influx of calcium from extracellular space. Q7 increased the vasoconstriction to BaCl2 (10−3 M, an inward rectifying K+ channels blocker, and blocked the vasodilation to KCl (10−2 M in aortic rings precontracted with BaCl2. This was recovered with sodium nitroprusside (10−8 M, a NO donor. In conclusion, Q7 induced vasoconstriction was through a modulation of cellular mechanisms involving calcium fluxes through K+ channels, and oxidative stress induced endothelium damage. These findings contribute to the characterization of new quinone derivatives with low cytotoxicity able to pharmacologically modulate vasodilation.

A rapid method for the extraction and analysis of carotenoids and other hydrophobic substances suitable for systems biology studies with photosynthetic bacteria.

Science.gov (United States)

Bóna-Lovász, Judit; Bóna, Aron; Ederer, Michael; Sawodny, Oliver; Ghosh, Robin

2013-10-11

A simple, rapid, and inexpensive extraction method for carotenoids and other non-polar compounds present in phototrophic bacteria has been developed. The method, which has been extensively tested on the phototrophic purple non-sulphur bacterium Rhodospirillum rubrum, is suitable for extracting large numbers of samples, which is common in systems biology studies, and yields material suitable for subsequent analysis using HPLC and mass spectroscopy. The procedure is particularly suitable for carotenoids and other terpenoids, including quinones, bacteriochlorophyll a and bacteriopheophytin a, and is also useful for the analysis of polar phospholipids. The extraction procedure requires only a single step extraction with a hexane/methanol/water mixture, followed by HPLC using a Spherisorb C18 column, with a mobile phase consisting of acetone-water and a non-linear gradient of 50%-100% acetone. The method was employed for examining the carotenoid composition observed during microaerophilic growth of R. rubrum strains, and was able to determine 18 carotenoids, 4 isoprenoid-quinones, bacteriochlorophyll a and bacteriopheophytin a as well as four different phosphatidylglycerol species of different acyl chain compositions. The analytical procedure was used to examine the dynamics of carotenoid biosynthesis in the major and minor pathways operating simultaneously in a carotenoid biosynthesis mutant of R. rubrum.

A Rapid Method for the Extraction and Analysis of Carotenoids and Other Hydrophobic Substances Suitable for Systems Biology Studies with Photosynthetic Bacteria

Directory of Open Access Journals (Sweden)

Oliver Sawodny

2013-10-01

Full Text Available A simple, rapid, and inexpensive extraction method for carotenoids and other non-polar compounds present in phototrophic bacteria has been developed. The method, which has been extensively tested on the phototrophic purple non-sulphur bacterium Rhodospirillum rubrum, is suitable for extracting large numbers of samples, which is common in systems biology studies, and yields material suitable for subsequent analysis using HPLC and mass spectroscopy. The procedure is particularly suitable for carotenoids and other terpenoids, including quinones, bacteriochlorophyll a and bacteriopheophytin a, and is also useful for the analysis of polar phospholipids. The extraction procedure requires only a single step extraction with a hexane/methanol/water mixture, followed by HPLC using a Spherisorb C18 column, with a mobile phase consisting of acetone-water and a non-linear gradient of 50%–100% acetone. The method was employed for examining the carotenoid composition observed during microaerophilic growth of R. rubrum strains, and was able to determine 18 carotenoids, 4 isoprenoid-quinones, bacteriochlorophyll a and bacteriopheophytin a as well as four different phosphatidylglycerol species of different acyl chain compositions. The analytical procedure was used to examine the dynamics of carotenoid biosynthesis in the major and minor pathways operating simultaneously in a carotenoid biosynthesis mutant of R. rubrum.

A spectroelectrochemical and chemical study on oxidation of hydroxycinnamic acids in aprotic medium

Energy Technology Data Exchange (ETDEWEB)

Petrucci, Rita [Dipartimento di Ingegneria Chimica M.M.P.M., Universita di Roma ' La Sapienza' , via del Castro Laurenziano 7, I-00161 Rome (Italy)]. E-mail: rita.petrucci@uniroma1.it; Astolfi, Paola [Dipartimento di Scienze dei Materiali e della Terra, Universita Politecnica delle Marche, via Brecce Bianche, I-60131 Ancona (Italy); Greci, Lucedio [Dipartimento di Scienze dei Materiali e della Terra, Universita Politecnica delle Marche, via Brecce Bianche, I-60131 Ancona (Italy); Firuzi, Omidreza [Dipartimento di Farmacologia delle Sostanze Naturali e Fisiologia Generale, Universita di Roma ' La Sapienza' , p.le Aldo Moro 5, I-00185 Rome (Italy); Saso, Luciano [Dipartimento di Farmacologia delle Sostanze Naturali e Fisiologia Generale, Universita di Roma ' La Sapienza' , p.le Aldo Moro 5, I-00185 Rome (Italy); Marrosu, Giancarlo [Dipartimento di Ingegneria Chimica M.M.P.M., Universita di Roma ' La Sapienza' , via del Castro Laurenziano 7, I-00161 Rome (Italy)

2007-02-01

Electrochemical and chemical oxidation of hydroxycinnamic acids (HCAs) was studied to investigate the mechanisms occurring in their antioxidant activities in a protons poor medium. Electrolyses and chemical reactions were followed on-line by monitoring the UV-spectral changes with time; final solutions were analysed by HPLC-MS. Anodic oxidation of mono- and di-HCAs, studied by cyclic voltammetry and controlled potential electrolyses, occurs via a reversible one-step two-electrons process, yielding the corresponding stable phenoxonium cation. A cyclization product was also proposed, as supported by ESR studies. Chemical oxidation with lead dioxide leads to different oxidation products according to the starting substrate. Di-HCAs like chlorogenic and rosmarinic acids and the ethyl ester of caffeic acid gave the corresponding neutral o-quinones, while mono-HCAs like cumaric, ferulic and sinapinic acids yielded the corresponding unstable neutral phenoxyl radical, as supported by the formation of dimerization products evidenced by HPLC-MS. In the case of caffeic acid, traces of the dimerization product suggest that the neutral phenoxyl radical may competitively undergo dimerization or decomposition of the neutral quinone. Chemical oxidation of HCAs was also followed by ESR spectroscopy: the di-HCAs radical anions were generated and detected, whereas among the mono-HCAs only the phenoxyl radical of the sinapinic acid was recorded.

Crystallization of the NADH-oxidizing domain of the Na+-translocating NADH:ubiquinone oxidoreductase from Vibrio cholerae

International Nuclear Information System (INIS)

Tao, Minli; Türk, Karin; Diez, Joachim; Grütter, Markus G.; Fritz, Günter; Steuber, Julia

2006-01-01

The FAD domain of the NqrF subunit from the Na + -translocating NADH dehydrogenase from V. cholerae has been purified and crystallized. A complete data set was recorded at 3.1 Å. The Na + -translocating NADH:quinone oxidoreductase (Na + -NQR) from pathogenic and marine bacteria is a respiratory complex that couples the exergonic oxidation of NADH by quinone to the transport of Na + across the membrane. The NqrF subunit oxidizes NADH and transfers the electrons to other redox cofactors in the enzyme. The FAD-containing domain of NqrF has been expressed, purified and crystallized. The purified NqrF FAD domain exhibited high rates of NADH oxidation and contained stoichiometric amounts of the FAD cofactor. Initial crystallization of the flavin domain was achieved by the sitting-drop technique using a Cartesian MicroSys4000 robot. Optimization of the crystallization conditions yielded yellow hexagonal crystals with dimensions of 30 × 30 × 70 µm. The protein mainly crystallizes in long hexagonal needles with a diameter of up to 30 µm. Crystals diffract to 2.8 Å and belong to space group P622, with unit-cell parameters a = b = 145.3, c = 90.2 Å, α = β = 90, γ = 120°

Transcriptional Responses in the Hemiparasitic Plant Triphysaria versicolor to Host Plant Signals1[w

Science.gov (United States)

Matvienko, Marta; Torres, Manuel J.; Yoder, John I.

2001-01-01

Parasitic plants in the Scrophulariaceae use chemicals released by host plant roots to signal developmental processes critical for heterotrophy. Haustoria, parasitic plant structures that attach to and invade host roots, develop on roots of the hemiparasitic plant Triphysaria versicolor within a few hours of exposure to either maize (Zea mays) root exudate or purified haustoria-inducing factors. We prepared a normalized, subtractive cDNA library enriched for transcripts differentially abundant in T. versicolor root tips treated with the allelopathic quinone 2,6-dimethoxybenzoquinone (DMBQ). Northern analyses estimated that about 10% of the cDNAs represent transcripts strongly up-regulated in roots exposed to DMBQ. Northern and reverse northern analyses demonstrated that most DMBQ-responsive messages were similarly up-regulated in T. versicolor roots exposed to maize root exudates. From the cDNA sequences we assembled a unigene set of 137 distinct transcripts and assigned functions by homology comparisons. Many of the proteins encoded by the transcripts are predicted to function in quinone detoxification, whereas others are more likely associated with haustorium development. The identification of genes transcriptionally regulated by haustorium-inducing factors provides a framework for dissecting genetic pathways recruited by parasitic plants during the transition to heterotrophic growth. PMID:11553755

Modulatory Effect of 2-(4-Hydroxyphenyl)amino-1,4-naphthoquinone on Endothelial Vasodilation in Rat Aorta.

Science.gov (United States)

Palacios, Javier; Cifuentes, Fredi; Valderrama, Jaime A; Benites, Julio; Ríos, David; González, Constanza; Chiong, Mario; Cartes-Saavedra, Benjamín; Lafourcade, Carlos; Wyneken, Ursula; González, Pamela; Owen, Gareth I; Pardo, Fabián; Sobrevia, Luis; Buc Calderon, Pedro

The vascular endothelium plays an essential role in the control of the blood flow. Pharmacological agents like quinone (menadione) at various doses modulate this process in a variety of ways. In this study, Q7 , a 2-phenylamino-1,4-naphthoquinone derivative, significantly increased oxidative stress and induced vascular dysfunction at concentrations that were not cytotoxic to endothelial or vascular smooth muscle cells. Q7 reduced nitric oxide (NO) levels and endothelial vasodilation to acetylcholine in rat aorta. It also blunted the calcium release from intracellular stores by increasing the phenylephrine-induced vasoconstriction when CaCl 2 was added to a calcium-free medium but did not affect the influx of calcium from extracellular space. Q7 increased the vasoconstriction to BaCl 2 (10 -3  M), an inward rectifying K + channels blocker, and blocked the vasodilation to KCl (10 -2  M) in aortic rings precontracted with BaCl 2 . This was recovered with sodium nitroprusside (10 -8  M), a NO donor. In conclusion, Q7 induced vasoconstriction was through a modulation of cellular mechanisms involving calcium fluxes through K + channels, and oxidative stress induced endothelium damage. These findings contribute to the characterization of new quinone derivatives with low cytotoxicity able to pharmacologically modulate vasodilation.

Triplet state and semiquinone free radical of 5-methoxyquinizarin : a laser flash photolysis and pulse radiolysis study

International Nuclear Information System (INIS)

Pal, H.; Patil, D.K.; Mukherjee, T.; Mittal, J.P.

1992-01-01

The triplet(T) state properties like T-T absorption spectra, quantum yield, energy level and decay kinetics of 5-methoxyquinizarin (5-methoxy-1, 4-dihydroxy-9, 10-anthraquinone; MQZ) have been investigated in cyclohexane, acetonitrile and isopropyl alcohol using nanosecond laser flash photolysis technique. In isopropylalcohol, a neutral semiquinone radical is also formed which has been characterised by comparing the long lived transient spectra with the MQZ-semiquinone spectra obtained by pulse radiolysis of MQZ in the same solvent. A relatively small amount of a long lived transient formed in cyclohexane and acetonitrile, along with the triplet state of MQZ, could not be characterised unambiguously, but has been attributed to the semiquinone radical of MQZ, produced by the reaction of the excited states of the quinone with the solvent. The quantum yield of the semiquinone radical in isopropyl alcohol is considerably higher than the triplet quantum yield, showing that both the excited singlet and the triplet states of the quinone probably react with the solvent molecules to form the semiquinone radical. The photophysical properties of the triplet and the semiquinone radical of MQZ have been compared with those of simple 1,4-disubstituted anthraquinones. (author). 23 refs., 5 figs., 1 tab

THERMOMECHANICAL PROPERTIES OF JUTE/BAGASSE HYBRID FIBRE REINFORCED EPOXY THERMOSET COMPOSITES

OpenAIRE

Sudhir Kumar Saw; Chandan Datta

2009-01-01

Natural fibres are partly replacing currently used synthetic fibres as reinforcement for polymer composites. Jute fibre bundles were high-cellulose-content modified by alkali treatment, while the bagasse fibre bundles were modified by creating quinones in the lignin portions of fibre surfaces and reacting them with furfuryl alcohol (FA) to increase their adhesiveness. The effects of different fibre bundle loading and modification of bagasse fibre surfaces in hybrid fibre reinforced epoxy comp...

Évaluation de la valeur nutritive et recherche des substances ...

African Journals Online (AJOL)

SARAH

30 juin 2016 ... et des lipides. Puis, l'évaluation a été effectuée sur ces échantillons pour rechercher la présence des alcaloïdes, des saponines, des quinones, des stéroïdes, des terpenoïdes, des flavonoïdes, des leucoanthocyanes, des tannoïdes et des hétérosides cyanogénétiques. Les teneurs moyennes en humidité ...

Method of protecting human skin from actinic radiation

International Nuclear Information System (INIS)

Fusaro, R.M.

1975-01-01

Enhanced protection from sunlight is achieved by applying to human skin beforehand separate, time-spaced applications of (1) a carbonyl compound which is reactive with amino groups in human skin, for example dihydroxyacetone, and (2) a benzo- or naptho-quinone such as lawsone. Preferably several sequential applications of each active component in a separate carrier are made the evening before the first exposure, and protection is thereafter maintained by applying each component separately each evening

Characterization of bisphenol A metabolites produced by Portulaca oleracea cv. by liquid chromatography coupled with tandem mass spectrometry.

Science.gov (United States)

Watanabe, Ippei; Harada, Kazuo; Matsui, Takeshi; Miyasaka, Hitoshi; Okuhata, Hiroshi; Tanaka, Satoshi; Nakayama, Hideki; Kato, Ko; Bamba, Takeshi; Hirata, Kazumasa

2012-01-01

The garden plant portulaca (Portulaca oleracea cv.) efficiently removes bisphenol A (BPA), an endocrine-disrupting chemical, from a hydroponic solution, but the molecular mechanisms underlying BPA metabolism by portulaca remain unclear. In this study, BPA metabolites converted by portulaca were analyzed by liquid chromatography coupled with tandem mass spectrometry. We observed the hydroxylation of BPA and the oxidization of it to quinone. Polyphenol oxidases are likely to contribute to BPA degradation by portulaca.

NATURAL PESTICIDES FROM SEEDS OF CHIRIMOYA (Annona cherimolia Mill.) AND GUANABANA (Annona muricata L.)

OpenAIRE

Rivera C., D.; Ale B., N.; Huamán M., J.; Muñoz H., P.; Rodríguez B., M.; Bravo A., M.; Delmás R., D.

2014-01-01

Seeds of chirimoya and guanabana from the communities of Cumbe and Callahuanca - Yauyos, Lima were analyzed. The extraction of natural toxic was realized using ethanol as the optimal solvent, after several solvent tests, phytochemicals analysis identified :saponins, coumarins, tannins, quinones and essential oils, mostly castor oil which was confirmed by FTIR spectra. Qualitative analysis results identified: PO4(3-), AsO4(3-) and others. Toxicological tests extracts applied on larvae and frui...

Pulse radiolysis study of the reduction mechanism of an antitumor antibiotic, mitomycin C

International Nuclear Information System (INIS)

Machtalere, G.; Houee-Levin, C.; Gardes-Albert, M.; Ferradini, C.; Hickel, B.

1988-01-01

Mitomycin C is a quinonic antitumor metabolized in vivo by one-electron reduction. We have studied the mechanism of the one-electron reduction of this drug by pulse radiolysis using C00 .- free radicals as reductants. Semiquinonic and hydroquinonic intermediates are formed. The hydroquinonic form undergoes a methanol elimination leading to a transient which can disappear in one of two ways: by either internal redox reaction or hydrolysis of the aziridine. 17 refs [fr

Investigation and computer modeling of radiation and thermal decomposition of polystyrene scintillators

Science.gov (United States)

Sakhno, Tamara V.; Pustovit, Sergey V.; Borisenko, Artem Y.; Senchishin, Vitaliy G.; Barashkov, Nikolay N.

2003-12-01

This paper is devoted to the investigation and computer modeling of radiation and thermal decomposition of luminescent polystyrene compositions. It has been shown, that the stability of the optical properties of luminescent polymer composition depends on its material structure. On the basis of quantum-chemical calculation has been obtained the possible products of PS gamma-radiolysis and the effect of formation of fragments with conjugated double bonds and products with quinone structure has been investigated.

Electrochemistry of acid-base reactions in anhydrous hydrogen fluoride

International Nuclear Information System (INIS)

Masson, J.P.; Devynck, J.; Tremillon, B.

1975-01-01

Electrochemical studies were made in following media: water-HF mixtures, anhydrous HF and KF solutions in HF, solutions of the SbF5 type in HF. The acidity level of these solutions was evaluated using the R(H) functions based on the strehlow hypotheses. From the pH measurement in anhydrous HF, it was possible to get acid-base titration curves and pH buffers. The behavior of quinones in anhydrous HF is presented [fr

Organic Redox Species in Aqueous Flow Batteries: Redox Potentials, Chemical Stability and Solubility

OpenAIRE

Kristina Wedege; Emil Dražević; Denes Konya; Anders Bentien

2016-01-01

Organic molecules are currently investigated as redox species for aqueous low-cost redox flow batteries (RFBs). The envisioned features of using organic redox species are low cost and increased flexibility with respect to tailoring redox potential and solubility from molecular engineering of side groups on the organic redox-active species. In this paper 33, mainly quinone-based, compounds are studied experimentially in terms of pH dependent redox potential, solubility and stability, combined ...

Property and quinone profile analysis of the compost made in Kuriyama town

OpenAIRE

森本, 正則; 桑原, 直美; 田中, 尚道; 駒井, 功一郎

2006-01-01

[Synopsis] Application of compost made from garbage and bio-sludge show crop growth promoting effect in the field. We have evaluated to a property of the compost made in Kuriyama town (Hokkaido). Kuriyama town have a compost producing facility established in 2004. Mainly, we have evaluated suppression of the plant disease and plant growth promotion by using this compost. Application of this compost had promoted the cucumber growth in dose dependent manner. Application of native compost ...

New degraded quinone diterpenoid from the stems of Byrsonima coccolobifolia Kunt (Malpighiaceae)

International Nuclear Information System (INIS)

Sousa, Lorena R.F. de; Santos, Marcos H.F.; Severino, Vanessa G.P.; Severino, Richele P.; Vieira, Paulo C.

2018-01-01

A chemical investigation of two specimens of Byrsonima coccolobifolia collected in the southeast cerrado and from central Brazil was performed. A new degraded diterpenoid, byrsonimaquinone, was isolated from the stems along with known compounds. This is the first study on the roots of B. coccolobifolia, and several triterpenes, such as α-amyrin, β-amyrin, oleanolic acid, and glochidonol, along with a mixture of stigmasterol, β-sitosterol and campesterol, were identified. These compounds were identified by spectroscopic analysis techniques, including 1D and 2D NMR, GC-MS and high-resolution mass spectrometry. (author)

New degraded quinone diterpenoid from the stems of Byrsonima coccolobifolia Kunt (Malpighiaceae)

Energy Technology Data Exchange (ETDEWEB)

Sousa, Lorena R.F. de; Santos, Marcos H.F.; Severino, Vanessa G.P.; Severino, Richele P. [Universidade Federal de Goiás (UFG), GO (Brazil). Unidade Acadêmica Especial de Química; Vieira, Paulo C., E-mail: dpcv@ufscar.br [Universidade Federal de São Carlos (UFSCar), SP (Brazil). Departamehnto de Quimica

2018-02-15

A chemical investigation of two specimens of Byrsonima coccolobifolia collected in the southeast cerrado and from central Brazil was performed. A new degraded diterpenoid, byrsonimaquinone, was isolated from the stems along with known compounds. This is the first study on the roots of B. coccolobifolia, and several triterpenes, such as α-amyrin, β-amyrin, oleanolic acid, and glochidonol, along with a mixture of stigmasterol, β-sitosterol and campesterol, were identified. These compounds were identified by spectroscopic analysis techniques, including 1D and 2D NMR, GC-MS and high-resolution mass spectrometry. (author)

WrbA bridges bacterial flavonoids and eukaryotic NAD(P)H:quinone oxidoreductases

Czech Academy of Sciences Publication Activity Database

Carey, J.; Brynda, Jiří; Wolfová, Julie; Grandori, R.; Gustavsson, T.; Ettrich, Rüdiger; Kutá-Smatanová, Ivana

2007-01-01

Roč. 16, č. 10 (2007), s. 2301-2305 ISSN 0961-8368 Institutional research plan: CEZ:AV0Z50520514; CEZ:AV0Z60870520 Keywords : WrbA * crystal structure * Nqo1 * oxidoreductases Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.135, year: 2007

Exploiting the oxidizing capabilities of laccases exploiting the oxidizing capabilities of laccases for sustainable chemistry

Energy Technology Data Exchange (ETDEWEB)

Cannatelli, Mark D. [Georgia Inst. of Technology, Atlanta, GA (United States)

2017-05-01

Part one of this dissertation research has focused on harnessing the ability of laccases to generate reactive para-quinones in situ from the corresponding hydroquinones, followed by reaction with a variety of nucleophiles to perform novel carbon-carbon, carbon-nitrogen, and carbon-sulfur bond forming reactions for the synthesis of new and existing compounds. In part two of this dissertation, the fundamental laccase-catalyzed coupling chemistry developed in part one was applied to functionalize the surface of kraft lignin.

Biological effects of menadione photochemistry: effects of menadione on biological systems may not involve classical oxidant production.

OpenAIRE

McCormick, M L; Denning, G M; Reszka, K J; Bilski, P; Buettner, G R; Rasmussen, G T; Railsback, M A; Britigan, B E

2000-01-01

Because cell-mediated reduction of menadione leads to the generation of reactive oxygen species (ROS), this quinone is widely used to investigate the effects of ROS on cellular functions. We report that A549 human lung epithelial cells exposed to menadione demonstrate a dose-dependent increase in both intracellular calcium ([Ca(2+)](i)) and ROS formation. The concentrations of menadione required to initiate these two events are markedly different, with ROS detection requiring higher levels of...

Novel Biocatalysts Combining the Special Assembly Properties of S-Layer Proteins and the Functionality of Enzymes of Extremophiles (BIOCAT)

Science.gov (United States)

2010-04-14

recrystallization properties of rSbpA/LamAAs shown by transmission electron microscopy of negatively stained preparations. rSbpA/LamA had the capability...the restriction sites BamHl and Noll were introduced at the 5’ and 3’ ends, respectively. For expression, all recombinant plasm ids were established...Laccase oxidizes hydroquinone to quinone by releasing two protons and two electrons . In the presence of oxygen, the enzyme forms water. First of all the

Screening phytochimique et identification spectroscopique des ...

African Journals Online (AJOL)

Origin

plante, effectuée pour la première fois, a révélé la présence des alcaloïdes, des flavonoïdes, des tanins catéchiques, des terpènes, des coumarines et des composés cyanogénétiques. Quant aux saponines et les quinones libres, ils sont présents chez les fleurs et absents chez les feuilles. La caractérisation des molécules.

Determination of trace amounts of lead by chelating ion exchange and on-line preconcentration in flow-injection atomic absorption spectrometry

International Nuclear Information System (INIS)

Purohit, Rajesh; Devi, Surekha

1992-01-01

Resins synthesized from quinolin-8-ol and resorcinol or hydro-quinone, with furfuraldehyde, formaldehyde or benzaldehyde as cross-linking agent, were used for the preconcentration of nanogram amounts of lead. The rate of exchange and activation energy of lead exchange were calculated. Column separations of lead-copper and lead-zinc did not show any cross-contamination. A continuous flow manifold using resin microcolumns was developed for the preconcentration and determination of lead. (author). 24 refs.; 5 figs.; 3 tabs

UDP-glucuronosyltransferases 1A6 and 1A10 catalyze reduced menadione glucuronidation

International Nuclear Information System (INIS)

Nishiyama, Takahito; Ohnuma, Tomokazu; Inoue, Yuu; Kishi, Takehiko; Ogura, Kenichiro; Hiratsuka, Akira

2008-01-01

Menadione (2-methyl-1,4-naphthoquine), also known as vitamin K3, has been widely used as a model compound in the field of oxidative stress-related research. The metabolism of menadione has been studied, and it is known that menadione undergoes a two-electron reduction by NAD(P)H:Quinone oxidoreductase 1 (NQO1) after which the reduced form of menadione (2-methyl-1,4-naphthalenediol, menadiol) is glucuronidated and excreted in urine. To investigate which human UDP-glucuronosyltransferase (UGT) isoforms participate in the glucuronidation of menadiol reduced by NQO1 from menadione, we first constructed heterologously expressed NQO1 in Sf9 cells and tested the menadiol glucuronidating activity of 16 human recombinant UGT isoforms. Of the 16 UGT isoforms, UGTs 1A6, 1A7, 1A8, 1A9, and 1A10 catalyzed menadiol glucuronidation, and, of these, UGTs 1A6 and 1A10 catalyzed menadiol glucuronidation at much higher rates than the other UGTs. Menadiol was regioselectively glucuronidated in the manner of 4-position > 1-position by UGTs 1A7, 1A8, 1A9, and 1A10. In contrast to these UGTs, only UGT1A6 exhibited 1-menadiol-preferential glucuronidating activity. The results suggest possible detoxification pathways for quinones via NQO1 reduction followed by UGT glucuronidation

Mechanism of pyrogallol red oxidation induced by free radicals and reactive oxidant species. A kinetic and spectroelectrochemistry study.

Science.gov (United States)

Atala, E; Velásquez, G; Vergara, C; Mardones, C; Reyes, J; Tapia, R A; Quina, F; Mendes, M A; Speisky, H; Lissi, E; Ureta-Zañartu, M S; Aspée, A; López-Alarcón, C

2013-05-02

Pyrogallol red (PGR) presents high reactivity toward reactive (radical and nonradical) species (RS). This property of PGR, together with its characteristic spectroscopic absorption in the visible region, has allowed developing methodologies aimed at evaluating the antioxidant capacity of foods, beverages, and human fluids. These methods are based on the evaluation of the consumption of PGR induced by RS and its inhibition by antioxidants. However, at present, there are no reports regarding the degradation mechanism of PGR, limiting the extrapolation to how antioxidants behave in different systems comprising different RS. In the present study, we evaluate the kinetics of PGR consumption promoted by different RS (peroxyl radicals, peroxynitrite, nitrogen dioxide, and hypochlorite) using spectroscopic techniques and detection of product by HPLC mass spectrometry. The same pattern of oxidation and spectroscopic properties of the products is observed, independently of the RS employed. Mass analysis indicates the formation of only one product identified as a quinone derivative, excluding the formation of peroxides or hydroperoxides and/or chlorinated compounds, in agreement with FOX's assays and oxygen consumption experiments. Cyclic voltammetry, carried out at different pH's, shows an irreversible oxidation of PGR, indicating the initial formation of a phenoxy radical and a second charge transfer reaction generating an ortho-quinone derivative. Spectroelectrochemical oxidation of PGR shows oxidation products with identical UV-visible absorption properties to those observed in RS-induced oxidation.

The oxidation of luteolin, the natural flavonoid dye

International Nuclear Information System (INIS)

Ramešová, Šárka; Sokolová, Romana; Tarábek, Ján; Degano, Ilaria

2013-01-01

The oxidation of natural flavonoid luteolin in aqueous solution is studied by electrochemical methods, electron paramagnetic resonance (EPR), spectroelectrochemistry and separation techniques HPLC-DAD and HPLC–MS/MS. The number of electrons involved in the oxidation of luteolin depends on the presence of its dissociation forms in solution. The study explains the differences in the number of electrons presented in the literature. The overall one electron oxidation mechanism of luteolin in alkaline solution is explained by the comproportionation reaction of resulting quinone, despite the fact that quinone is formed by two electron oxidation. Then a hydroxylation takes place. The EPR spectroelectrochemical study of the semiquinone radical anion formation as well as of the reaction steps following the electron transfer during the oxidation is presented. The novelty of this contribution consists in the additional temperature controlled semi-quantitative in situ EPR spectroelectrochemical experiment of the flavonoid oxidation. The data acquired by temperature controlled in situ EPR spectroelectrochemistry supports the comproportionation/disproportionation equilibria as well as the oxidative decomposition of luteolin and shows that the formation of a pi-dimer is less probable. The oxidation products hydroxy-luteolin and 3,5-dihydroxy-2-(2-oxoacetyl)phenyl-3,4-dihydroxybenzoate are not stable under ambient conditions and decompose to low molecular hydroxycompounds such as 3,4-dihydroxybenzoic acid and 2,5,7-trihydroxy-4H-1-benzopyran-4-one

Humic acids: Structural properties and multiple functionalities for novel technological developments.

Science.gov (United States)

de Melo, Bruna Alice Gomes; Motta, Fernanda Lopes; Santana, Maria Helena Andrade

2016-05-01

Humic acids (HAs) are macromolecules that comprise humic substances (HS), which are organic matter distributed in terrestrial soil, natural water, and sediment. HAs differ from the other HS fractions (fulvic acid and humins) in that they are soluble in alkaline media, partially soluble in water, and insoluble in acidic media. Due to their amphiphilic character, HAs form micelle-like structures in neutral to acidic conditions, which are useful in agriculture, pollution remediation, medicine and pharmaceuticals. HAs have undefined compositions that vary according to the origin, process of obtainment, and functional groups present in their structures, such as quinones, phenols, and carboxylic acids. Quinones are responsible for the formation of reactive oxygen species (ROS) in HAs, which are useful for wound healing and have fungicidal/bactericidal properties. Phenols and carboxylic acids deprotonate in neutral and alkaline media and are responsible for various other functions, such as the antioxidant and anti-inflammatory properties of HAs. In particular, the presence of phenolic groups in HAs provides antioxidant properties due to their free radical scavenging capacity. This paper describes the main multifunctionalities of HAs associated with their structures and properties, focusing on human health applications, and we note perspectives that may lead to novel technological developments. To the best of our knowledge, this is the first review to address this topic from this approach. Copyright © 2015 Elsevier B.V. All rights reserved.

Urinary biomarkers of trimethoprim bioactivation in vivo following therapeutic dosing in children.

Science.gov (United States)

van Haandel, Leon; Goldman, Jennifer L; Pearce, Robin E; Leeder, J Steven

2014-02-17

The antimicrobial trimethoprim-sulfamethoxazole (TMP-SMX) is widely used for the treatment of skin and soft-tissue infections in the outpatient setting. Despite its therapeutic benefits, TMP-SMX has been associated with a number of adverse drug reactions, which have been primarily attributed to the formation of reactive metabolites from SMX. Recently, in vitro experiments have demonstrated that TMP may form reactive intermediates as well. However, evidence of TMP bioactivation in patients has not yet been demonstrated. In this study, we performed in vitro trapping experiments with N-acetyl-l-cysteine (NAC) to determine stable markers of reactive TMP intermediates, focusing on eight potential markers (NAC-TMP adducts), some of which were previously identified in vitro. We developed a specific and sensitive assay involving liquid chromatography followed by tandem mass spectrometry for measurement of these adducts in human liver microsomal samples and expanded the methodology toward the detection of these analytes in human urine. Urine samples from four patients receiving TMP-SMX treatment were analyzed, and all samples demonstrated the presence of six NAC-TMP adducts, which were also detected in vitro. These adducts are consistent with the formation of imino-quinone-methide and para-quinone-methide reactive intermediates in vivo. As a result, the TMP component of TMP-SMX should be considered as well when evaluating adverse drug reactions to TMP-SMX.

Electron transfer reactions involving porphyrins and chlorophyll a

International Nuclear Information System (INIS)

Neta, P.; Scherz, A.; Levanon, H.

1979-01-01

Electron transfer reactions involving porphyrins (P) and quinones (Q) have been studied by pulse radiolysis. The porphyrins used were tetraphenylporphyrin (H 2 TPP), its tetracarboxy derivative (H 2 TCPP), the sodium and zinc compounds (Na 2 TPP and ZnTPP), and chlorophyll a (Chl a). These compounds were found to be rapidly reduced by electron transfer from (CH 3 ) 2 CO - . Reduction by (CH 3 ) 2 COH was rapid in aqueous solutions but relatively slow in i-PrOH solutions. Transient spectra of the anion radicals were determined and, in the case of H 2 TCPP - ., a pK = 9.7 was derived for its protonation. Electron-transfer reactions from the anion radical of H 2 TCPP to benzoquinone, duroquinone, 9,10-anthraquinone 2-sulfonate, and methylviologen occur in aqueous solutions with rate constants approx. 10 7 -10 9 M -1 s -1 which depend on the pH and the quinone reduction potential. Reactions of Na 2 TPP - ., ZnTPP - ., and Chl a - . with anthraquinone in basic i-PrOH solutions occur with rate constants approx. 10 9 M -1 s -1 . The spectral changes associated with these electron-transfer reactions as observed over a period of approx. 1 ms indicated, in some cases, the formation of an intermediate complex [P...Q - .]. 8 figures, 2 tables

EPR identification of irradiated Monascus purpureus red pigment

International Nuclear Information System (INIS)

Duliu, Octavian G.; Ferdes, Mariana; Ferdes, Ovidiu S.

2000-01-01

Fresh red alimentary pigment extracted from Monascus purpureus fungus exhibits an intense EPR line consisting of a single, narrow line, attributed to a quinone radical. When irradiated with 7 MeV electrons or 60 Co γ-rays, the amplitude of this line increased with the absorbed dose following a saturation exponential dependency up to 10 kGy. During annealing treatment (isothermal heating at 100 deg. C) the irradiation centers decay exponentially with a half-life time of 2.30 min

BINDING OF THE RESPIRATORY CHAIN INHIBITOR ANTIMYCIN TO THE MITOCHONDRIAL bc1 COMPLEX: A NEW CRYSTAL STRUCTURE REVEALS AN ALTERED INTRAMOLECULAR HYDROGEN-BONDING PATTERN.

OpenAIRE

Huang, Li-shar; Cobessi, David; Tung, Eric Y.; Berry, Edward A.

2005-01-01

Antimycin A (antimycin), one of the first known and most potent inhibitors of the mitochondrial respiratory chain, binds to the quinone reduction site of the cytochrome bc1 complex. Structure-activity-relationship studies have shown that the N-formylamino-salicyl-amide group is responsible for most of the binding specificity, and suggested that a low pKa for the phenolic OH group and an intramolecular H-bond between that OH and the carbonyl O of the salicylamide linkage are important. Tw...

PHYTOCHEMICAL STUDY OF A TINCTORIAL PLANT OF BENIN TRADITIONAL PHARMACOPOEIA: THE RED SORGHUM (Sorghum caudatum) OF BENIN

OpenAIRE

PASCAL D. C. AGBANGNAN; CHRISTINE TACHON; HELENE BONIN; ANNA CHROSTOWKA; ERIC FOUQUET; DOMINIQUE C. K. SOHOUNHLOUE

2012-01-01

The full phytochemical screening of red sorghum from Benin (Sorghum caudatum) achieved in this work reveals the presence of leucoanthocyanins, flavonoides, free quinones, combined anthracene derivatives, sterols and terpenes in higher concentration in the leaf sheath and marrow of stem than in the seed. Catechin tannin content is 11.4% in the leaf sheath (slightly higher than that of red wine), 5.8% in the marrow and 2.8% in the seed. Gallic tannins, saponins and the mucilage present in the l...

Resistance to the photosystem II herbicide diuron is dominant to sensitivity in the cyanobacterium Synechococcus sp. PCC7942

OpenAIRE

Brusslan, Judy; Haselkorn, Robert

1989-01-01

The transformable cyanobacterium, Synechococcus sp. PCC7942, was used to study the genetics of resistance to the herbicide diuron. In wild-type cells, diuron binds to one of the core proteins, called D1, of photosystem II reaction centres. This binding prevents the transfer of electrons from QA, the primary quinone acceptor, to QB, which is necessary to create the charge separation that drives ATP synthesis. A single amino acid substitution in the D1 protein reduces diuron binding and confers...

The radiation chemistry of aqueous solutions of sodium 9,10-anthraquinone-2-sulfonate

International Nuclear Information System (INIS)

Burchill, C.E.; Smith, D.M.; Charlton, J.L.

1976-01-01

The 60 Co γ-radiolysis of aqueous solutions of sodium 9,10-anthraquinone-2-sulfonate has been studied in acidic, unbuffered, and alkaline conditions and with addition of N 2 O and 2-propanol. Mechanisms are proposed to account for the yields of H 2 O 2 and hydroxylated anthraquinone sulfonates. In neutral solution, in the absence of O 2 , the OH and e - adducts undergo preferential cross termination. Reduction of the OH adduct leads to dehydration and regeneration of the quinone. (author)

Radiation-induced O-glycoside bond scission in carbohydrates

International Nuclear Information System (INIS)

Kisel', R.M.

2005-01-01

Regularities in formation of products resulting from O-glycoside bond cleavage on radiolysis of aqueous solutions of (-methyl-D-glucopyranoside (I), 3-O-methylglucopyranose (II), maltose and lactose were studied. Oxygen and quinones were shown to inhibit radiation-induced homolytic destruction processes taking place in glycosides. The data obtained in this study enabled the authors to demonstrate an important role played by fragmentation reaction of C-2 radicals generated from the starting substances in formation of final radiolysis products. (authors)

Redox and Non-Redox Mechanism of In Vitro Cyclooxygenase Inhibition by Natural Quinones

Czech Academy of Sciences Publication Activity Database

Landa, Přemysl; Kutil, Zsófia; Tremml, V.; Vuorien, A.; Malík, J.; Dvořáková, Marcela; Maršík, Petr; Kokoška, L.; Přibylová, Marie; Schuster, D.; Vaněk, Tomáš

2012-01-01

Roč. 78, č. 4 (2012), s. 326-333 ISSN 0032-0943 R&D Projects: GA ČR GP525/09/P528; GA MŠk ME08070 Grant - others:GA ČR(CZ) GA525/08/1179 Program:GA Institutional research plan: CEZ:AV0Z50380511 Keywords : inflammation * prostaglandin synthase * structure-activity relationship Subject RIV: GM - Food Processing Impact factor: 2.348, year: 2012

A review on the study of bioreductive drugs

International Nuclear Information System (INIS)

Chen Xiaojing; Jin Yizun

2003-01-01

Hypoxia is a feature that exists in most solid tumors. Bio-reductive drugs are pro-drugs that can selectively target the hypoxia cells in tumors. In reductive environment, they are reductively metabolized to generate toxic species. There are 3 main classes of bio-reductive drugs: the nitro-aromatics, N-oxides and quinones. Recently, bio-reductive drugs were combined with GDEPT for the treatment of cancer, in addition to radiation and the chemotherapeutic agents. Bio-reductive drugs will play a significant role in future cancer therapy

Proton conduction within the reaction centers of Rhodobacter capsulatus: the electrostatic role of the protein.

OpenAIRE

Maróti, P; Hanson, D K; Baciou, L; Schiffer, M; Sebban, P

1994-01-01

Light-induced charge separation in the photosynthetic reaction center results in delivery of two electrons and two protons to the terminal quinone acceptor QB. In this paper, we have used flash-induced absorbance spectroscopy to study three strains that share identical amino acid sequences in the QB binding site, all of which lack the protonatable amino acids Glu-L212 and Asp-L213. These strains are the photosynthetically incompetent site-specific mutant Glu-L212/Asp-L213-->Ala-L212/Ala-L213 ...

Isometachromin, a new cytotoxic sesquiterpenoid from a deep water sponge of the family Spongiidae.

Science.gov (United States)

McConnell, O J; Longley, R; Gunasekera, M

1992-09-15

Isometachromin (1), a new sesquiterpene-quinone that is related structurally to metachromin C (2), and the known compounds ilimaquinone (3) and 5-epi-ilimaquinone (4), were isolated from a deep water sponge in the family Spongiidae; the structure of isometachromin was elucidated by spectral methods. Isometachromin exhibits in vitro cytotoxicity against the human lung cancer cell line A549 (IC50 = 2.6 micrograms/ml), but not against P388 murine leukemia (IC 50 > or equal to 10 micrograms/ml) and also exhibits antimicrobial activity.

Reactivity and selectivity of arenes in reactions with ozone

International Nuclear Information System (INIS)

Vysotskii, Yu.B.; Mestechkin, M.M.; Sivyakova, L.N.; Tyupalo, N.F.

1987-01-01

The reactions of arenes with ozone, distinguished by the variety of products (quinones, aldehydes, acids), are of interest not only from the theoretical standpoint but also are of preparative value in the case of polycyclic hydrocarbons. In this work a quantitative treatment of this reaction is given on the basis of direct kinetic measurements and simple quantum chemical means, permitting its rate constants and the yield of the products to be related to the elements of electronic structure readily subject to quantum mechanical calculation

Mechanism and kinetics in reactions of caffeic acid with radicals by pulse radiolysis and calculation

International Nuclear Information System (INIS)

Li, Xifeng; Cai, Zhongli; Katsumura, Yosuke

2000-01-01

The interaction of caffeic acid with e aq - , (CH 3 ) 2 (OH) CCH 2 · , CO 2 ·- , H · , ·OH and N 3 · radicals were studied by γ-, pulse radiolysis and molecular orbital calculation. UV-visible spectra of electron/·OH adducts, semi-quinone radicals of caffeic ions, and the stable products from the reactions were derived. The rate constants were determined. The attacked sites and the most favorable structures of the transient radicals were predicted. Reaction mechanisms were proposed. (author)

Traditional usages, botany, phytochemistry, pharmacology and toxicology of Polygonum multiflorum Thunb.: a review.

Science.gov (United States)

Lin, Longfei; Ni, Boran; Lin, Hongmei; Zhang, Miao; Li, Xuechun; Yin, Xingbin; Qu, Changhai; Ni, Jian

2015-01-15

Polygonum multiflorum Thunb., which is known as Heshouwu ( in Chinese) in China. It is traditionally valued and reported for hair-blacking, liver and kidney-tonifying and anti-aging effects as well as low toxicity. The aim of this review is to provide comprehensive information on the botany, traditional uses, phytochemistry, pharmacological research and toxicology of Polygonum multiflorum, based on the scientific literature. Moreover, trends and perspectives for future investigation of this plant are discussed. It will build up a new foundation for further study on Polygonum multiflorum. A systematic review of the literature on Polygonum multiflorum was performed using several resources, including classic books on Chinese herbal medicine and various scientific databases, such as PubMed, SciFinder, the Web of Science, Science Direct, China Knowledge Resource Integrated (CNKI). Polygonum multiflorum is widely distributed throughout the world and has been used as a traditional medicine for centuries in China. The ethnomedical uses of Polygonum multiflorum have been recorded in many provinces of China and Japan for nine species of adulterants in six families. More than 100 chemical compounds have been isolated from this plant, and the major components have been determined to be stilbenes, quinones, flavonoids and others. Crude extracts and pure compounds of this plant are used as effective agents in pre-clinical and clinical practice due to their anti-aging, anti-hyperlipidaemia, anti-cancer and anti-inflammatory effects and to promote immunomodulation, neuroprotection, and the curing of other diseases. However, these extracts can also lead to hepatotoxicity, nephrotoxicity and embryonic toxicity. Pharmacokinetic studies have demonstrated that the main components of Polygonum multiflorum, such as 2,3,5,4'-tetrahydroxystilbene-2-O-β-d-glucopyranoside and emodin are distributed among many organs and tissues. Therapeutic potential of Polygonum multiflorum has been

A combination of electro-enzymatic catalysis and electrocoagulation for the removal of endocrine disrupting chemicals from water.

Science.gov (United States)

Zhao, He; Zhang, Di; Du, Penghui; Li, Haitao; Liu, Chenming; Li, Yuping; Cao, Hongbin; Crittenden, John C; Huang, Qingguo

2015-10-30

We in this study investigated a novel electrochemical approach combining electro-enzyme and electrocoagulation to precipitate bisphenol A (BPA) from water containing humic acid (HA). Horseradish peroxidase was immobilized on the graphite felt of Ti electrode as HRP-GF/Ti cathode, with aluminum plate anode establishing a pair of working electrodes. BPA was 100% removed and the reduction of total organic carbon (TOC) reached 95.1% after 20-min sequencing treatment with the current density of 2.3 mA/cm(2). Real wastewater (TOC=28.76 mg/L, BPA=4.1 μg/L) also can achieve 94% BPA removal and 52% TOC reduction after sequencing treatment. Additionally, coupled electro-system with continuous flow only required energy of 0.016 kWh/m(3) to achieve simultaneous 90% BPA and 85% TOC removal. As indicated in the time-of-flight mass spectrometry and FTIR spectra, the electro-enzymatic process not only oxidized BPA into dimer and BPA-3,4-quinone, but also greatly altered the chemical and structural features of HA, where hydrophilic moieties (phenolic and alcohols) transformed into hydrophobic forms (ethers, quinone and aliphatic). These polymerized products were effectively separated from aquous solution during anodic electrocoagulation, leading to significant removal of BPA and TOC. Thus, the coupled process may provide a faster and less energy strategy to control certain emerging contaminants in water/wastewater treatment. Copyright © 2015 Elsevier B.V. All rights reserved.

Evaluation of Antitrypanosomal Dihydroquinolines for Hepatotoxicity, Mutagenicity, and Methemoglobin Formation In Vitro.

Science.gov (United States)

Werbovetz, Karl A; Riccio, Edward S; Furimsky, Anna; Richard, Julian V; He, Shanshan; Iyer, Lalitha; Mirsalis, Jon

2014-07-01

N1-Benzylated dihydroquinolin-6-ols and their corresponding esters display exceptional activity against African trypanosomes in vitro, and administration of members of this class of compounds to trypanosome-infected mice results in cures in a first-stage African trypanosomiasis model. Since a quinone imine intermediate has been implicated in the antiparasitic mechanism of action of these compounds, evaluation of the hepatotoxic, mutagenic, and methemoglobin-promoting effects of these agents was performed. 1-Benzyl-1,2-dihydro-2,2,4-trimethylquinolin-6-ol hydrochloride and 1-benzyl-1,2-dihydro-2,2,4-trimethylquinolin-6-yl acetate showed outstanding in vitro selectivity for Trypanosoma brucei compared to the HepG2, Hep3B, Huh7, and PLC5 hepatocyte cell lines. 1-Benzyl-1,2-dihydro-2,2,4-trimethylquinolin-6-ol hydrochloride and 1-(2-methoxybenzyl)-1,2-dihydro-2,2,4-trimethylquinolin-6-yl acetate were not mutagenic when screened in the Ames assay, with or without metabolic activation. The latter 2 compounds promoted time- and dose-dependent formation of methemoglobin when incubated in whole human blood, but such levels were below those typically required to produce symptoms of methemoglobinemia in humans. Although compounds capable of quinone imine formation require careful evaluation, these in vitro studies indicate that antitrypanosomal dihydroquinolines merit further study as drug candidates against the neglected tropical disease human African trypanosomiasis. © The Author(s) 2014.

One electron transfer equilibria and redox potentials of radicals studies by pulse radiolysis. Progress report, September 1, 1975--July 1, 1976

International Nuclear Information System (INIS)

Meisel, D.; Czapski, G.

1976-01-01

The pulse radiolysis technique is utilized for measurements of the equilibrium constants for electron transfer between the durosemiquinone radical anion and oxygen, menadione and indigo disulfonate. These equilibrium constants are in turn used for calculations of one-electron redox potentials for these systems. Each of these equilibrium constants was determined experimentally and independently and found to be self consistent. Only for the reactions of the semiquinones with oxygen could the electron transfer reaction be followed directly. For the reactions between the various quinone/semiquinone systems substantial indirect evidence is presented that these equilibria are achieved rapidly. In those cases equilibrium constants were determined from studies of the effect of quinone concentrations on the relative yields of the semiquinones. A method for distinguishing between kinetic competition and equilibrium is outlined and its usefulness is emphasized. The DQ/DQ - (DQ = duroquinone) and IDS/IDS - (IDS = indigo disulfonate) systems were employed as reference couples as the redox potentials for those systems are either available in the literature (IDS/IDS - ) or may be calculated from available data (DQ/DQ - ). Taking E 7 1 , the redox potential for the first one-electron reduction step at pH 7, of DQ/DQ - as -0.235 volts or of IDS/IDS - as -0.125 volts, both yield E 7 1 = -0.325 V for the O 2 /O 2 - system (1 atm O 2 ) and E 7 1 = -0.20 for the menadione system

Effect of release of dopamine on iron transformations and reactive oxygen species (ROS) generation under conditions typical of coastal waters.

Science.gov (United States)

Sun, Yingying; Pham, A Ninh; Waite, T David

2018-01-24

Seasonally persistent blooms of Ulvaria obscura var. blyttii, the prominent species present in green tides in the northern Pacific and Atlantic, have been well documented in recent decades. The synthesis and release of dopamine (DA) by Ulvaria obscura var. blyttii has been proposed to be associated with the suppression and inhibition of the growth of other organisms competing for limited resources. To better understand the potential benefits obtained from the release of DA, the transformation of DA as well its concomitant impact on the local seawater environment are investigated in this study. The results show that, despite several toxic quinones being produced during the oxidation of DA, aminochrome (DAC) is likely to be the only quinone playing an allelopathic role in view of its expected accumulation in the surrounding environment. As a consequence of the direct oxidation of DA and DA induced generation of 5,6-dihydroxyindole (DHI), high concentrations of H 2 O 2 accumulate over time, especially in the presence of elements including iron, calcium and magnesium. The oxidative stress to other organisms induced by the release of DA may be particularly detrimental as a result of H 2 O 2 induced reduction in photosynthesis, inactivation of antioxidant systems or even the generation of ˙OH. DA induced iron mobilization may benefit the continuously persistent blooms of Ulvaria obscura var. blyttii or even the whole community via alleviation in iron deficiency within the bloom region.

15N NMR investigation of the covalent binding of reduced TNT amines to soil humic acid, model compounds, and lignocellulose

Science.gov (United States)

Thorn, K.A.; Kennedy, K.R.

2002-01-01

The five major reductive degradation products of TNT-4ADNT (4-amino-2,6-dinitrotoluene), 2ADNT (2-amino-4,6-dinitrotoluene), 2,4DANT (2,4-diamino-6-nitrotoluene), 2,6DANT (2,6-diamino-4-nitrotoluene), and TAT (2,4,6-triaminotoluene)-labeled with 15N in the amine positions, were reacted with the IHSS soil humic acid and analyzed by 15N NMR spectrometry. In the absence of catalysts, all five amines underwent nucleophilic addition reactions with quinone and other carbonyl groups in the soil humic acid to form both heterocyclic and nonheterocyclic condensation products. Imine formation via 1,2-addition of the amines to quinone groups in the soil humic acid was significant with the diamines and TAT but not the monoamines. Horseradish peroxidase (HRP) catalyzed an increase in the incorporation of all five amines into the humic acid. In the case of the diamines and TAT, HRP also shifted the binding away from heterocyclic condensation product toward imine formation. A comparison of quantitative liquid phase with solid-state CP/MAS 15N NMR indicated that the CP experiment underestimated imine and heterocyclic nitrogens in humic acid, even with contact times optimal for observation of these nitrogens. Covalent binding of the mono- and diamines to 4-methylcatechol, the HRP catalyzed condensation of 4ADNT and 2,4DANT to coniferyl alcohol, and the binding of 2,4DANT to lignocellulose with and without birnessite were also examined.

Cytotoxic, trypanocidal activities and physicochemical parameters of nor-beta-lapachone-based 1,2,3-triazoles

Energy Technology Data Exchange (ETDEWEB)

Silva Junior, Eufranio N. da [Universidade Federal Fluminense (UFF), Niteroi , RJ (Brazil). Inst. de Quimica. Dept. de Quimica Organica; Moura, Maria Aline B. F. de [Universidade Federal de Alagoas (UFAL), Maceio, AL (Brazil). Inst. de Quimica e Biotecnologia; Pinto, Antonio V. [Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ (Brazil). Nucleo de Pesquisas de Produtos Naturais] (and others)

2009-07-01

The cytotoxicities of five nor-{beta}-lapachone-based 1,2,3-triazoles and the precursor azidonaphthoquinone were assayed against six neoplasic cancer cell lines: SF-295 (central nervous system), HCT-8 (colon), MDAMB-435 (melanoma), HL-60 (leukaemia), PC-3 (prostate) and B-16 (murine melanoma). IC{sub 50} values ranging from 0.43 to 9.48 {mu}M were obtained. 3-(4-(1-hydroxycyclohexyl)-{sup 1}H-1,2,3-triazol-1- yl)-2,2-dimethylnaphtho[1,2-b]furan-4,5-dione proved highly cytotoxic to MDAMB-435, with IC{sub 50} even lower than the one from doxorubicin (positive control). In an attempt to correlate physicochemical parameters (reduction potentials and calculated log P) with cytotoxic activity, electrochemical studies were conducted in acetate buffer, pH 4.5, using a vitreous carbon electrode and calculated log P values were obtained. Despite the absence of a structural conjugative interaction between the two systems (quinone and triazole), the heterocyclic group was found to influence the voltammetric behaviour, as indicated by anodic shifts in the reduction potentials. No correlation was found between Ep{sub Ic} and cytotoxicity. In contrast, a comparison of Ep{sub Ic} with previously reported trypanocidal activities reconfirmed the trend for higher activity coupled with better quinone electrophilicity (> Ep{sub Ic}). A leading term in the correlation of cytoxicity, despite the absence of a linear correlation, was the calculated log P: the lower the lipophilicity, the lower the cytoxicity (> IC{sub 50}). (author)

Novel 1,4-naphthoquinone-based sulfonamides: Synthesis, QSAR, anticancer and antimalarial studies.

Science.gov (United States)

Pingaew, Ratchanok; Prachayasittikul, Veda; Worachartcheewan, Apilak; Nantasenamat, Chanin; Prachayasittikul, Supaluk; Ruchirawat, Somsak; Prachayasittikul, Virapong

2015-10-20

A novel series of 1,4-naphthoquinones (33-44) tethered by open and closed chain sulfonamide moieties were designed, synthesized and evaluated for their cytotoxic and antimalarial activities. All quinone-sulfonamide derivatives displayed a broad spectrum of cytotoxic activities against all of the tested cancer cell lines including HuCCA-1, HepG2, A549 and MOLT-3. Most quinones (33-36 and 38-43) exerted higher anticancer activity against HepG2 cell than that of the etoposide. The open chain analogs 36 and 42 were shown to be the most potent compounds. Notably, the restricted sulfonamide analog 38 with 6,7-dimethoxy groups exhibited the most potent antimalarial activity (IC₅₀ = 2.8 μM). Quantitative structure-activity relationships (QSAR) study was performed to reveal important chemical features governing the biological activities. Five constructed QSAR models provided acceptable predictive performance (Rcv 0.5647-0.9317 and RMSEcv 0.1231-0.2825). Four additional sets of structurally modified compounds were generated in silico (34a-34d, 36a-36k, 40a-40d and 42a-42k) in which their activities were predicted using the constructed QSAR models. A comprehensive discussion of the structure-activity relationships was made and a set of promising compounds (i.e., 33, 36, 38, 42, 36d, 36f, 42e, 42g and 42f) was suggested for further development as anticancer and antimalarial agents. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Kaxiras’s Porphyrin: DFT Modeling of Redox-Tuned Optical and Electronic Properties in a Theoretically Designed Catechol-Based Bioinspired Platform

Directory of Open Access Journals (Sweden)

Orlando Crescenzi

2017-11-01

Full Text Available A detailed computational investigation of the 5,6-dihydroxyindole (DHI-based porphyrin-type tetramer first described by Kaxiras as a theoretical structural model for eumelanin biopolymers is reported herein, with a view to predicting the technological potential of this unique bioinspired tetracatechol system. All possible tautomers/conformers, as well as alternative protonation states, were explored for the species at various degrees of oxidation and all structures were geometry optimized at the density functional theory (DFT level. Comparison of energy levels for each oxidized species indicated a marked instability of most oxidation states except the six-electron level, and an unexpected resilience to disproportionation of the one-electron oxidation free radical species. Changes in the highest energy occupied molecular orbital (HOMO–lowest energy unoccupied molecular orbital (LUMO gaps with oxidation state and tautomerism were determined along with the main electronic transitions: more or less intense absorption in the visible region is predicted for most oxidized species. Data indicated that the peculiar symmetry of the oxygenation pattern pertaining to the four catechol/quinone/quinone methide moieties, in concert with the NH centers, fine-tunes the optical and electronic properties of the porphyrin system. For several oxidation levels, conjugated systems extending over two or more indole units play a major role in determining the preferred tautomeric state: thus, the highest stability of the six-electron oxidation state reflects porphyrin-type aromaticity. These results provide new clues for the design of innovative bioinspired optoelectronic materials.

Podocyte specific knock out of selenoproteins does not enhance nephropathy in streptozotocin diabetic C57BL/6 mice

Directory of Open Access Journals (Sweden)

Carlson Bradley A

2008-07-01

Full Text Available Abstract Background Selenoproteins contain selenocysteine (Sec, commonly considered the 21st genetically encoded amino acid. Many selenoproteins, such as the glutathione peroxidases and thioredoxin reductases, protect cells against oxidative stress by functioning as antioxidants and/or through their roles in the maintenance of intracellular redox balance. Since oxidative stress has been implicated in the pathogenesis of diabetic nephropathy, we hypothesized that selenoproteins protect against this complication of diabetes. Methods C57BL/6 mice that have a podocyte-specific inability to incorporate Sec into proteins (denoted in this paper as PodoTrsp-/- and control mice were made diabetic by intraperitoneal injection of streptozotocin, or were injected with vehicle. Blood glucose, body weight, microalbuminuria, glomerular mesangial matrix expansion, and immunohistochemical markers of oxidative stress were assessed. Results After 3 and 6 months of diabetes, control and PodoTrsp-/- mice had similar levels of blood glucose. There were no differences in urinary albumin/creatinine ratios. Periodic acid-Schiff staining to examine mesangial matrix expansion also demonstrated no difference between control and PodoTrsp-/- mice after 6 months of diabetes, and there were no differences in immunohistochemical stainings for nitrotyrosine or NAD(PH dehydrogenase, quinone 1. Conclusion Loss of podocyte selenoproteins in streptozotocin diabetic C57BL/6 mice does not lead to increased oxidative stress as assessed by nitrotyrosine and NAD(PH dehydrogenase, quinone 1 immunostaining, nor does it lead to worsening nephropathy.

Social dilemma in the external immune system of the red flour beetle? It is a matter of time.

Science.gov (United States)

Gokhale, Chaitanya S; Traulsen, Arne; Joop, Gerrit

2017-09-01

Sociobiology has revolutionized our understanding of interactions between organisms. Interactions may present a social dilemma where the interests of individual actors do not align with those of the group as a whole. Viewed through a sociobiological lens, nearly all interactions can be described regarding their costs and benefits, and a number of them then resemble a social dilemma. Numerous experimental systems, from bacteria to mammals, have been proposed as models for studying such dilemmas. Here, we make use of the external immune system of the red flour beetle, Tribolium castaneum , to investigate how the experimental duration can affect whether the external secretion comprises a social dilemma or not. Some beetles (secretors) produce a costly quinone-rich external secretion that inhibits microbial growth in the surrounding environment, providing the secretors with direct personal benefits. However, as the antimicrobial secretion acts in the environment of the beetle, it is potentially also advantageous to other beetles (nonsecretors), who avoid the cost of producing the secretion. We test experimentally if the secretion qualifies as a public good. We find that in the short term, costly quinone secretion can be interpreted as a public good presenting a social dilemma where the presence of secretors increases the fitness of the group. In the long run, the benefit to the group of having more secretors vanishes and becomes detrimental to the group. Therefore, in such seminatural environmental conditions, it turns out that qualifying a trait as social can be a matter of timing.

Chemical constituents of soft coral Sarcophyton infundibuliforme from the South China Sea

KAUST Repository

Wang, Chang Yun; Chen, An Na; Shao, Chang Lun; Li, Liang; Xu, Ying; Qian, Pei Yuan

2011-01-01

Chemical investigation on soft coral Sarcophyton infundibuliforme collected from the South China Sea led to the isolation and identification of 14 secondary metabolites, including ten cembrene diterpenoids (1-10), one α-tocopheryl quinone derivative (11), one prostaglandin (12), one lipid (13) and one carotinoid (14). Their structures were determined by extensive analysis of their spectroscopic data. All of these metabolites were isolated from this species for the first time. Diterpenoids 1, 2, 7 and 10 showed potent antifouling activity against the larval settlement of barnacle Balanus amphitrite. © 2011 Elsevier Ltd.

Redox enzymes in the plant plasma membrane and their possible roles

DEFF Research Database (Denmark)

Berczi, A.; Møller, I.M.

2000-01-01

Purified plasma membrane (PM) vesicles from higher plants contain redox proteins with low-molecular-mass prosthetic groups such as flavins (both FMN and FAD), hemes, metals (Cu, Fe and Mn), thiol groups and possibly naphthoquinone (vitamin K-1), all of which are likely to participate in redox...... protein which has been partially purified from plant PM so far is a high-potential and ascorbate-reducible b-type cytochrome. In co-operation with vitamin K-1 and an NAD(P)H-quinone oxidoreductase, it may participate in trans-PM electron transport....

Ketopantoyl lactone reductase is a conjugated polyketone reductase.

Science.gov (United States)

Hata, H; Shimizu, S; Hattori, S; Yamada, H

1989-03-01

Ketopantoyl lactone reductase (EC 1.1.1.168) of Saccharomyces cerevisiae was found to catalyze the reduction of a variety of natural and unnatural conjugated polyketone compounds and quinones, such as isatin, ninhydrin, camphorquinone and beta-naphthoquinone in the presence of NADPH. 5-Bromoisatin is the best substrate for the enzyme (Km = 3.1 mM; Vmax = 650 mumol/min/mg). The enzyme is inhibited by quercetin, and several polyketones. These results suggest that ketopantoyl lactone reductase is a carbonyl reductase which specifically catalyzes the reduction of conjugated polyketones.

Chemical constituents of soft coral Sarcophyton infundibuliforme from the South China Sea

KAUST Repository

Wang, Chang Yun

2011-08-01

Chemical investigation on soft coral Sarcophyton infundibuliforme collected from the South China Sea led to the isolation and identification of 14 secondary metabolites, including ten cembrene diterpenoids (1-10), one α-tocopheryl quinone derivative (11), one prostaglandin (12), one lipid (13) and one carotinoid (14). Their structures were determined by extensive analysis of their spectroscopic data. All of these metabolites were isolated from this species for the first time. Diterpenoids 1, 2, 7 and 10 showed potent antifouling activity against the larval settlement of barnacle Balanus amphitrite. © 2011 Elsevier Ltd.

Carbon material for hydrogen storage

Science.gov (United States)

Bourlinos, Athanasios; Steriotis, Theodore; Stubos, Athanasios; Miller, Michael A

2016-09-13

The present invention relates to carbon based materials that are employed for hydrogen storage applications. The material may be described as the pyrolysis product of a molecular precursor such as a cyclic quinone compound. The pyrolysis product may then be combined with selected transition metal atoms which may be in nanoparticulate form, where the metals may be dispersed on the material surface. Such product may then provide for the reversible storage of hydrogen. The metallic nanoparticles may also be combined with a second metal as an alloy to further improve hydrogen storage performance.

Development of assembly techniques for fire resistant aircraft interior panels

Science.gov (United States)

Lee, S. C. S.

1978-01-01

Ten NASA Type A fire resistant aircraft interior panels were fabricated and tested to develop assembly techniques. These techiques were used in the construction of a full scale lavatory test structure for flame propagation testing. The Type A panel is of sandwich construction consisting of Nomex honeycomb filled with quinone dioxime foam, and bismaleimide/glass face sheets bonded to the core with polyimide film adhesive. The materials selected and the assembly techniques developed for the lavatory test structure were designed for obtaining maximum fire containment with minimum smoke and toxic emission.

HS-SPME-GC-MS analysis of antioxidant degradation products migrating to drinking water from PE materials and PEX pipes

DEFF Research Database (Denmark)

Lützhøft, Hans-Christian Holten; Waul, Christopher Kevin; Andersen, Henrik Rasmus

2013-01-01

degradation products may leach and enter drinking water. The aim of this investigation was to develop a method for measuring these degradation products with a performance meeting the drinking water quality criteria of 20 µg L−1. Using headspace solid phase microextraction coupled to a gas chromatograph......Polyethylene (PE) and cross-linked polyethylene (PEX) pipes are frequently used in water supply systems. Such pipes contain added antioxidants with phenolic structures, e.g. Irgafos 168, Irganox 1010 and 1076, in order to improve durability. However, phenol, ketone and quinone antioxidant...

Geranylfarnesyl diphosphate synthase from Methanosarcina mazei: Different role, different evolution

International Nuclear Information System (INIS)

Ogawa, Takuya; Yoshimura, Tohru; Hemmi, Hisashi

2010-01-01

The gene of (all-E) geranylfarnesyl diphosphate synthase that is responsible for the biosynthesis of methanophenazine, an electron carrier utilized for methanogenesis, was cloned from a methanogenic archaeon Methanosarcina mazei Goe1. The properties of the recombinant enzyme and the results of phylogenetic analysis suggest that the enzyme is closely related to (all-E) prenyl diphosphate synthases that are responsible for the biosynthesis of respiratory quinones, rather than to the enzymes involved in the biosynthesis of archaeal membrane lipids, including (all-E) geranylfarnesyl diphosphate synthase from a thermophilic archaeon.

Implicações químicas na sistemática e filogenia de Bignoniaceae

Directory of Open Access Journals (Sweden)

Franciane Auxiliadora Cipriani

2012-01-01

Full Text Available Our solemn homage to the great Master Otto R. Gottlieb who knew how to teach the mystery of evolutionary relationships between chemistry and its natural sources. The micromolecular chemical study of the family Bignoniaceae shows a profile predominantly characterized by the occurrence of metabolites derived from acetic acid biosynthetic pathways such as terpenoids, quinones, flavonoids and special aromatic derivatives. Analysis of different chemosystematic parameters for the metabolite data collected, provided valuable information for the systematic characterization of the Bignoniaceae family within the Angiosperm derived taxa.

A review of the chrome mordant dyeing of wool with special reference to the afterchrome process

CSIR Research Space (South Africa)

Maasdorp, APB

1983-11-01

Full Text Available a -~min*o'- Hydroxyaw Dycs Salicylic Acid Dyes Azo dyes oxidkd to Quinone form when complexed (C.I. Mordant Black 3) e Chrome Fast Brow TV (C.I. Mordant Brow 33) Flavine A (C.I. Mordant Yellow 5) e Solochrome Rcd (C.I. Mordant..., it was decided that they should bedescribed in more detail. In 1858, Peter Greiss, a chemist at a Burton-on-Trent brewery produced the first diizonium salts by treating primary aromatic amines with nitrous acid produced from hydrochloric acid and sodium...

Magterpenoids A-C, Three Polycyclic Meroterpenoids with PTP1B Inhibitory Activity from the Bark of Magnolia officinalis var. biloba.

Science.gov (United States)

Li, Chuan; Li, Chuang-Jun; Ma, Jie; Chen, Fang-You; Li, Li; Wang, Xiao-Liang; Ye, Fei; Zhang, Dong-Ming

2018-06-15

Magterpenoid A (1), possessing a rare 4,6,11-trioxatricyclo[5.3.1.0 1,5 ]undecane framework with an irregular monoterpenoid moiety, magterpenoid B (2), with an unprecedented 6/6/6/6 polycyclic skeleton, and magterpenoid C (3), a novel terpenoid quinone with a C6-C3 unit, were isolated from the bark of Magnolia officinalis var. biloba. Plausible biogenetic pathways of 1-3 are presented. Compounds 1 and 3 exhibited significant PTP1B inhibitory activities with IC 50 values of 1.44 and 0.81 μM, respectively.

Small organic molecule based flow battery

Science.gov (United States)

Huskinson, Brian; Marshak, Michael; Aziz, Michael J.; Gordon, Roy G.; Betley, Theodore A.; Aspuru-Guzik, Alan; Er, Suleyman; Suh, Changwon

2018-05-08

The invention provides an electrochemical cell based on a new chemistry for a flow battery for large scale, e.g., gridscale, electrical energy storage. Electrical energy is stored chemically at an electrochemical electrode by the protonation of small organic molecules called quinones to hydroquinones. The proton is provided by a complementary electrochemical reaction at the other electrode. These reactions are reversed to deliver electrical energy. A flow battery based on this concept can operate as a closed system. The flow battery architecture has scaling advantages over solid electrode batteries for large scale energy storage.

The Use of Copper- 64 in the Investigation of Reaction Mechanisms of Enzymes, Particularly as Related to Food Processing; Emploi de Cuivre-64 dans l'Etude des Mecanismes de Reaction des Enzymes, Notamment en Ce Qui Concerne la Preparation des Denrees Alimentaires; ПРИМЕНЕНИЕ МЕДИ-64 ДЛЯ ИССЛЕДОВАНИЯ МЕХАНИЗМОВ ФЕРМЕНТАТИВНЫХ РЕАКЦИЙ, СВЯЗАННЫХ С ОБРАБОТКОЙ ПИЛИ; Empleo de Cobre-64 en el Estudio de los Mecanismos de Reacciones Enzima Ticas de Interes para la Elaboracion de Alimentos

Energy Technology Data Exchange (ETDEWEB)

Arthur, Jr., J. C.; McLemore, T. A. [Southern Regional Research Laboratory, New Orleans, LA (United States)

1963-03-15

The oxidative enzymes of plant tissues are often dormant or only slightly active during the resting state, becoming active on the injury of the tissue or on separation from the tissue. During food processing this results in an acceleration of the oxidation of the natural substrates and polymerization of the products, which discolour the tissue. Copper oxidases are the principal enzymes involved in catalysing these reactions. The activation of the enzyme also leads to its reaction inactivation. One of the causes of the phenomenon of reaction inactivation is the decrease in the effective concentration of the enzyme, probably by the removal or binding of its metal prosthetic group copper. By using copper- 64, in vitro, it was shown that, in a resting solution, cupric ion can complex and/or exchange with the copper of the enzyme and that, in oxidizing solutions, an additional amount of cupric ion can be complexed. Cu-o-quinone- type complexes have higher formation constants than Cu-p-quinone- type complexes. The amount of cupric ion complexed was decreased, if the ion was added in an oxidizing solution after the initiation of polymerization of the o-quinone type reaction products. The kinetics of the exchange and complexing processes for cupric ions with enzyme and reaction products are discussed mathematically. (author) [French] Les enzymes oxydants des tissus vegetaux sont souvent inactifs ou tres peu actifs a l'etat de repos et ne deviennent actifs qu'en cas de lesion du tissu ou lorsqu'ils sont separes de celui-ci. Lors de la preparation des denrees alimentaires, ce phenomene a pour effet d'accelerer l'oxydation des substrats naturels et de polymeriser les produits, ce qui donne lieu a une decoloration du tissu. Les oxydases de cuivre sont les principaux enzymes qui interviennent comme catalyseurs dans ces reactions. L'activation de l'enzyme entraine en outre une inhibition de la reaction qu'il subit. Une des causes de ce phenomene est la diminution de la

Determination of Oxygen Radical Absorbance Capacity of Black Cumin (Nigella sativa) Seed Quinone Compounds

Czech Academy of Sciences Publication Activity Database

Tesařová, H.; Svobodová, B.; Kokoška, L.; Maršík, Petr; Přibylová, Marie; Landa, Přemysl; Vadlejch, J.

2011-01-01

Roč. 6, č. 2 (2011), s. 213-216 ISSN 1934-578X R&D Projects: GA ČR GA525/08/1179 Institutional research plan: CEZ:AV0Z50380511 Keywords : Antioxidative activity * Dihydrothymoquinone * Thymoquinone Subject RIV: GM - Food Processing Impact factor: 1.242, year: 2011

UV irradiation of polycyclic aromatic hydrocarbons in ices: production of alcohols, quinones, and ethers

Science.gov (United States)

Bernstein, M. P.; Sandford, S. A.; Allamandola, L. J.; Gillette, J. S.; Clemett, S. J.; Zare, R. N.

1999-01-01

Polycyclic aromatic hydrocarbons (PAHs) in water ice were exposed to ultraviolet (UV) radiation under astrophysical conditions, and the products were analyzed by infrared spectroscopy and mass spectrometry. Peripheral carbon atoms were oxidized, producing aromatic alcohols, ketones, and ethers, and reduced, producing partially hydrogenated aromatic hydrocarbons, molecules that account for the interstellar 3.4-micrometer emission feature. These classes of compounds are all present in carbonaceous meteorites. Hydrogen and deuterium atoms exchange readily between the PAHs and the ice, which may explain the deuterium enrichments found in certain meteoritic molecules. This work has important implications for extraterrestrial organics in biogenesis.

Controlled sp(2) Functionalization of Boron Doped Diamond as a Route for the Fabrication of Robust and Nernstian pH Electrodes.

Science.gov (United States)

Ayres, Zoë J; Borrill, Alexandra J; Newland, Jonathan C; Newton, Mark E; Macpherson, Julie V

2016-01-05

The development of a voltammetric boron doped diamond (BDD) pH sensor is described. To obtain pH sensitivity, laser micromachining (ablation) is utilized to introduce controlled regions of sp(2) carbon into a high quality polycrystalline BDD electrode. The resulting sp(2) carbon is activated to produce electrochemically reducible quinone groups using a high temperature acid treatment, followed by anodic polarization. Once activated, no further treatment is required. The quinone groups show a linear (R(2) = 0.999) and Nernstian (59 mV/(pH unit)) pH-dependent reductive current-voltage response over a large analyzable pH range, from pH 2 to pH 12. Using the laser approach, it is possible to optimize sp(2) coverage on the BDD surface, such that a measurable pH response is recorded, while minimizing background currents arising from oxygen reduction reactions on sp(2) carbon in the potential region of interest. This enables the sensor to be used in aerated solutions, boding well for in situ analysis. The voltammetric response of the electrode is not compromised by the presence of excess metal ions such as Pb(2+), Cd(2+), Cu(2+), and Zn(2+). Furthermore, the pH sensor is stable over a 3 month period (the current time period of testing), can be stored in air between measurements, requires no reactivation of the surface between measurements, and can be reproducibly fabricated using the proposed approach. The efficacy of this pH sensor in a real-world sample is demonstrated with pH measurements in U.K. seawater.

Nitrates and NO-NSAIDs in cancer chemoprevention and therapy: in vitro evidence querying the NO donor functionality.

Science.gov (United States)

Dunlap, Tareisha; Abdul-Hay, Samer O; Chandrasena, R Esala P; Hagos, Ghenet K; Sinha, Vaishali; Wang, Zhiqiang; Wang, Huali; Thatcher, Gregory R J

2008-09-01

Properties of the NO-ASA family of NO-donating NSAIDs (NO-NSAIDs), notably NCX 4016 (mNO-ASA) and NCX 4040 (pNO-ASA), reported in more than one hundred publications, have included positive preclinical data in cancer chemoprevention and therapy. Evidence is presented that the antiproliferative, the chemopreventive (antioxidant/electrophile response element (ARE) activation), and the anti-inflammatory activity of NO-ASA in cell cultures is replicated by X-ASA derivatives that are incapable of acting as NO donors. pBr-ASA and mBr-ASA are conisogenic with NO-ASA, but are not NO donors. The biological activity of pNO-ASA is replicated by pBr-ASA; and both pNO-ASA and pBr-ASA are bioactivated to the same quinone methide electrophile. The biological activity of mNO-ASA is replicated by mBr-ASA; mNO-ASA and mBr-ASA are bioactivated to different benzyl electrophiles. The observed activity is likely initiated by trapping of thiol biomolecules by the quinone and benzyl electrophiles, leading to depletion of GSH and modification of Cys-containing sensor proteins. Whereas all NO-NSAIDs containing the same structural "linker" as NCX 4040 and NCX 4016 are anticipated to possess activity resulting from bioactivation to electrophilic metabolites, this expectation does not extend to other linker structures. Nitrates require metabolic bioactivation to liberate NO bioactivity, which is often poorly replicated in vitro, and NO bioactivity provided by NO-NSAIDs in vivo provides proven therapeutic benefits in mitigation of NSAID gastrotoxicity. The in vivo properties of X-ASA drugs await discovery.

Nitrates and NO-NSAIDs in Cancer Chemoprevention & Therapy: In Vitro Evidence Querying the NO Donor Functionality

Science.gov (United States)

Dunlap, Tareisha; Abdul-Hay, Samer; Chandrasena, R. Esala P.; Hagos, Ghenet K; Sinha, Vaishali; Wang, Zhiqiang; Wang, Huali; Thatcher, Gregory R. J.

2008-01-01

Properties of the NO-ASA family of NO-donating NSAIDs (NO-NSAIDs), notably NCX 4016 (mNO-ASA) and NCX 4040 (pNO-ASA), reported in more than a hundred publications, have included positive preclinical data in cancer chemoprevention and therapy. Evidence is presented that the antiproliferative, the chemopreventive (antioxidant/electrophile response element (ARE) activation), and the anti-inflammatory activity of NO-ASA in cell cultures is replicated by X-ASA derivatives that are incapable of acting as NO donors. pBr-ASA and mBr-ASA are conisogenic with NO-ASA, but are not NO donors. The biological activity of pNO-ASA is replicated by pBr-ASA; and both pNO-ASA and pBr-ASA are bioactivated to the same quinone methide electrophile. The biological activity of mNO-ASA is replicated by mBr-ASA; mNO-ASA and mBr-ASA are bioactivated to different benzyl electrophiles. The observed activity is likely initiated by trapping of thiol biomolecules by the quinone and benzyl electrophiles, leading to depletion of GSH and modification of Cys-containing sensor proteins. Whereas all NO-NSAIDs containing the same structural “linker” as NCX 4040 and NCX 4016 are anticipated to possess activity resulting from bioactivation to electrophilic metabolites, this expectation does not extend to other linker structures. Nitrates require metabolic bioactivation to liberate NO bioactivity, which is often poorly replicated in vitro, and NO bioactivity provided by NO-NSAIDs in vivo provides proven therapeutic benefits in mitigation of NSAID gastrotoxicity. The in vivo properties of X-ASA drugs await discovery. PMID:18485921

Glutathione maintenance mitigates age-related susceptibility to redox cycling agents

Directory of Open Access Journals (Sweden)

Nicholas O. Thomas

2016-12-01

Full Text Available Isolated hepatocytes from young (4–6 mo and old (24–26 mo F344 rats were exposed to increasing concentrations of menadione, a vitamin K derivative and redox cycling agent, to determine whether the age-related decline in Nrf2-mediated detoxification defenses resulted in heightened susceptibility to xenobiotic insult. An LC50 for each age group was established, which showed that aging resulted in a nearly 2-fold increase in susceptibility to menadione (LC50 for young: 405 μM; LC50 for old: 275 μM. Examination of the known Nrf2-regulated pathways associated with menadione detoxification revealed, surprisingly, that NAD(PH: quinone oxido-reductase 1 (NQO1 protein levels and activity were induced 9-fold and 4-fold with age, respectively (p=0.0019 and p=0.018; N=3, but glutathione peroxidase 4 (GPX4 declined by 70% (p=0.0043; N=3. These results indicate toxicity may stem from vulnerability to lipid peroxidation instead of inadequate reduction of menadione semi-quinone. Lipid peroxidation was 2-fold higher, and GSH declined by a 3-fold greater margin in old versus young rat cells given 300 µM menadione (p2-fold reduction in cell death, suggesting that the age-related increase in menadione susceptibility likely stems from attenuated GSH-dependent defenses. This data identifies cellular targets for intervention in order to limit age-related toxicological insults to menadione and potentially other redox cycling compounds.

One-electron transfer equilibria and redox potentials of radicals studied by pulse radiolysis

International Nuclear Information System (INIS)

Meisel, D.; Czapski, G.

1975-01-01

The pulse radiolysis technique is utilized for measurements of the equilibrium constants for electron transfer between the durosemiquinone radical anion and oxygen, menadione, and indigodisulfonate. These equilibrium constants are in turn used for calculations of one-electron redox potentials for these systems. Each of these equilibrium constants was determined experimentally and independently and found to be self-consistent. Only for the reactions of the semiquinone radical ions with oxygen could the electron transfer reaction be followed directly. For the reactions between the various quinone-semiquinone systems substantial indirect evidence is presented that these equilibria are achieved rapidly. In those cases equilibrium constants were determined from studies of the effect of quinone concentrations on the relative yields of the semiquinones. A method for distinguishing between kinetic competition and equilibrium is outlined and its usefulness is emphasized. The DQ parallel DQ - (DQ = duroquinone) and IDS parallel IDS - (IDS = indigodisulfonate) systems were employed as reference couples as the redox potentials for those systems are either available in the literature (IDS parallel IDS - ) or may be calculated from available data (DQ parallel DQ - ). Taking E 7 1 , the redox potential for the first one-electron reduction step at pH 7, of DQ parallel DQ - as -0.235 V or of IDS parallelIDS - as -0.247 V both yield E 7 1 = -0.325 V for the O 2 parallel O 2 - system (1 atm of O 2 ) and E 2 1 = -0.20 V for the menadione system. (U.S.)

FaQR, required for the biosynthesis of the strawberry flavor compound 4-hydroxy-2,5-dimethyl-3(2H)-furanone, encodes an enone oxidoreductase.

Science.gov (United States)

Raab, Thomas; López-Ráez, Juan Antonio; Klein, Dorothée; Caballero, Jose Luis; Moyano, Enriqueta; Schwab, Wilfried; Muñoz-Blanco, Juan

2006-04-01

The flavor of strawberry (Fragaria x ananassa) fruit is dominated by an uncommon group of aroma compounds with a 2,5-dimethyl-3(H)-furanone structure. We report the characterization of an enzyme involved in the biosynthesis of 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF; Furaneol), the key flavor compound in strawberries. Protein extracts were partially purified, and the observed distribution of enzymatic activity correlated with the presence of a single polypeptide of approximately 37 kD. Sequence analysis of two peptide fragments showed total identity with the protein sequence of a strongly ripening-induced, auxin-dependent putative quinone oxidoreductase, Fragaria x ananassa quinone oxidoreductase (FaQR). The open reading frame of the FaQR cDNA consists of 969 bp encoding a 322-amino acid protein with a calculated molecular mass of 34.3 kD. Laser capture microdissection followed by RNA extraction and amplification demonstrated the presence of FaQR mRNA in parenchyma tissue of the strawberry fruit. The FaQR protein was functionally expressed in Escherichia coli, and the monomer catalyzed the formation of HDMF. After chemical synthesis and liquid chromatography-tandem mass spectrometry analysis, 4-hydroxy-5-methyl-2-methylene-3(2H)-furanone was confirmed as a substrate of FaQR and the natural precursor of HDMF. This study demonstrates the function of the FaQR enzyme in the biosynthesis of HDMF as enone oxidoreductase and provides a foundation for the improvement of strawberry flavor and the biotechnological production of HDMF.

Protein profiling of plastoglobules in chloroplasts and chromoplasts. A surprising site for differential accumulation of metabolic enzymes.

Science.gov (United States)

Ytterberg, A Jimmy; Peltier, Jean-Benoit; van Wijk, Klaas J

2006-03-01

Plastoglobules (PGs) are oval or tubular lipid-rich structures present in all plastid types, but their specific functions are unclear. PGs contain quinones, alpha-tocopherol, and lipids and, in chromoplasts, carotenoids as well. It is not known whether PGs contain any enzymes or regulatory proteins. Here, we determined the proteome of PGs from chloroplasts of stressed and unstressed leaves of Arabidopsis (Arabidopsis thaliana) as well as from pepper (Capsicum annuum) fruit chromoplasts using mass spectrometry. Together, this showed that the proteome of chloroplast PGs consists of seven fibrillins, providing a protein coat and preventing coalescence of the PGs, and an additional 25 proteins likely involved in metabolism of isoprenoid-derived molecules (quinines and tocochromanols), lipids, and carotenoid cleavage. Four unknown ABC1 kinases were identified, possibly involved in regulation of quinone monooxygenases. Most proteins have not been observed earlier but have predicted N-terminal chloroplast transit peptides and lack transmembrane domains, consistent with localization in the PG lipid monolayer particles. Quantitative differences in PG composition in response to high light stress and degreening were determined by differential stable-isotope labeling using formaldehyde. More than 20 proteins were identified in the PG proteome of pepper chromoplasts, including four enzymes of carotenoid biosynthesis and several homologs of proteins observed in the chloroplast PGs. Our data strongly suggest that PGs in chloroplasts form a functional metabolic link between the inner envelope and thylakoid membranes and play a role in breakdown of carotenoids and oxidative stress defense, whereas PGs in chromoplasts are also an active site for carotenoid conversions.

Protein Profiling of Plastoglobules in Chloroplasts and Chromoplasts. A Surprising Site for Differential Accumulation of Metabolic Enzymes1[W

Science.gov (United States)

Ytterberg, A. Jimmy; Peltier, Jean-Benoit; van Wijk, Klaas J.

2006-01-01

Plastoglobules (PGs) are oval or tubular lipid-rich structures present in all plastid types, but their specific functions are unclear. PGs contain quinones, α-tocopherol, and lipids and, in chromoplasts, carotenoids as well. It is not known whether PGs contain any enzymes or regulatory proteins. Here, we determined the proteome of PGs from chloroplasts of stressed and unstressed leaves of Arabidopsis (Arabidopsis thaliana) as well as from pepper (Capsicum annuum) fruit chromoplasts using mass spectrometry. Together, this showed that the proteome of chloroplast PGs consists of seven fibrillins, providing a protein coat and preventing coalescence of the PGs, and an additional 25 proteins likely involved in metabolism of isoprenoid-derived molecules (quinines and tocochromanols), lipids, and carotenoid cleavage. Four unknown ABC1 kinases were identified, possibly involved in regulation of quinone monooxygenases. Most proteins have not been observed earlier but have predicted N-terminal chloroplast transit peptides and lack transmembrane domains, consistent with localization in the PG lipid monolayer particles. Quantitative differences in PG composition in response to high light stress and degreening were determined by differential stable-isotope labeling using formaldehyde. More than 20 proteins were identified in the PG proteome of pepper chromoplasts, including four enzymes of carotenoid biosynthesis and several homologs of proteins observed in the chloroplast PGs. Our data strongly suggest that PGs in chloroplasts form a functional metabolic link between the inner envelope and thylakoid membranes and play a role in breakdown of carotenoids and oxidative stress defense, whereas PGs in chromoplasts are also an active site for carotenoid conversions. PMID:16461379

Calcium binding and transport by coenzyme Q.

Science.gov (United States)

Bogeski, Ivan; Gulaboski, Rubin; Kappl, Reinhard; Mirceski, Valentin; Stefova, Marina; Petreska, Jasmina; Hoth, Markus

2011-06-22

Coenzyme Q10 (CoQ10) is one of the essential components of the mitochondrial electron-transport chain (ETC) with the primary function to transfer electrons along and protons across the inner mitochondrial membrane (IMM). The concomitant proton gradient across the IMM is essential for the process of oxidative phosphorylation and consequently ATP production. Cytochrome P450 (CYP450) monoxygenase enzymes are known to induce structural changes in a variety of compounds and are expressed in the IMM. However, it is unknown if CYP450 interacts with CoQ10 and how such an interaction would affect mitochondrial function. Using voltammetry, UV-vis spectrometry, electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), fluorescence microscopy and high performance liquid chromatography-mass spectrometry (HPLC-MS), we show that both CoQ10 and its analogue CoQ1, when exposed to CYP450 or alkaline media, undergo structural changes through a complex reaction pathway and form quinone structures with distinct properties. Hereby, one or both methoxy groups at positions 2 and 3 on the quinone ring are replaced by hydroxyl groups in a time-dependent manner. In comparison with the native forms, the electrochemically reduced forms of the new hydroxylated CoQs have higher antioxidative potential and are also now able to bind and transport Ca(2+) across artificial biomimetic membranes. Our results open new perspectives on the physiological importance of CoQ10 and its analogues, not only as electron and proton transporters, but also as potential regulators of mitochondrial Ca(2+) and redox homeostasis.

Identification of anthraquinone-degrading bacteria in soil contaminated with polycyclic aromatic hydrocarbons.

Science.gov (United States)

Rodgers-Vieira, Elyse A; Zhang, Zhenfa; Adrion, Alden C; Gold, Avram; Aitken, Michael D

2015-06-01

Quinones and other oxygenated polycyclic aromatic hydrocarbons (oxy-PAHs) are toxic and/or genotoxic compounds observed to be cocontaminants at PAH-contaminated sites, but their formation and fate in contaminated environmental systems have not been well studied. Anthracene-9,10-dione (anthraquinone) has been found in most PAH-contaminated soils and sediments that have been analyzed for oxy-PAHs. However, little is known about the biodegradation of oxy-PAHs, and no bacterial isolates have been described that are capable of growing on or degrading anthraquinone. PAH-degrading Mycobacterium spp. are the only organisms that have been investigated to date for metabolism of a PAH quinone, 4,5-pyrenequinone. We utilized DNA-based stable-isotope probing (SIP) with [U-(13)C]anthraquinone to identify bacteria associated with anthraquinone degradation in PAH-contaminated soil from a former manufactured-gas plant site both before and after treatment in a laboratory-scale bioreactor. SIP with [U-(13)C]anthracene was also performed to assess whether bacteria capable of growing on anthracene are the same as those identified to grow on anthraquinone. Organisms closely related to Sphingomonas were the most predominant among the organisms associated with anthraquinone degradation in bioreactor-treated soil, while organisms in the genus Phenylobacterium comprised the majority of anthraquinone degraders in the untreated soil. Bacteria associated with anthracene degradation differed from those responsible for anthraquinone degradation. These results suggest that Sphingomonas and Phenylobacterium species are associated with anthraquinone degradation and that anthracene-degrading organisms may not possess mechanisms to grow on anthraquinone. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Exciplex formation and excited state deactivation of difluoroborondipyrromethene (Bodipy) dyads.

Science.gov (United States)

Benniston, Andrew C; Copley, Graeme; Lemmetyinen, Helge; Tkachenko, Nikolai V

2010-06-07

Two series of geometrically-related dyads are discussed based on the difluoroborondipyrromethene (Bodipy) unit, and incorporating covalently attached hydroquinone/quinone groups. These units are anchored directly, or via a phenylene spacer, to the Bodipy core at the meso position in one series (BD-MHQ, BD-MQ, BD-MPHQ, BD-MPQ), but for the second series the attachment site is the 2-position (BD-SHQ, BD-SQ, BD-SPHQ, BD-SPQ). The compounds show various levels of fluorescence depending on the oxidation state of the appended group and the substitution pattern. In non-polar solvents such as toluene, diethyl ether and dichlorobenzene, the S(1) state deactivation of the Bodipy unit in BD-SPQ and BD-MPQ is dominated by (1, 3)exciplex formation, which has not been reported for Bodipy derivatives so far. In the latter molecule, the decay of the exciplex is divided between population of the Bodipy triplet state (13 %-21 %) and ground state reformation. This partitioning is not seen for the side-on substituted derivative, BD-SPQ, and only ground state reformation is observed following decay of the exciplex. This difference in behavior is explained by the radical-pair inter-system-crossing mechanism, which more effectively operates in BD-MPQ because of the orthogonality of the donor-acceptor units. In the more polar solvent CH(3)CN all the quinone derivatives show fast formation of the charge-separated state (k(CS)) followed by slower charge recombination (k(CR)). The ratio k(CS)/k(CR)

New light on a dark subject: On the use of fluorescence data to deduce redox states of natural organic matter (NOM)

Science.gov (United States)

Macalady, Donald L.; Walton-Day, Katherine

2009-01-01

This paper reports the use of excitation-emission matrix fluorescence spectroscopy (EEMS), parallel factor statistical analysis (PARAFAC), and oxidation-reduction experiments to examine the effect of redox conditions on PARAFAC model results for aqueous samples rich in natural organic matter. Fifty-four aqueous samples from 11 different geographic locations and two plant extracts were analyzed untreated and after chemical treatments or irradiation were used in attempts to change the redox status of the natural organic matter. The EEMS spectra were generated and modeled using a PARAFAC package developed by Cory and McKnight (2005). The PARAFAC model output was examined for consistency with previously reported relations and with changes expected to occur upon experimental oxidation and reduction of aqueous samples. Results indicate the implied fraction of total sample fluorescence attributed to quinone-like moieties was consistent (0.64 to 0.78) and greater than that observed by Cory and McKnight (2005). The fraction of the quinone-like moieties that was reduced (the reducing index, RI) showed relatively little variation (0.46 to 0.71) despite attempts to alter the redox status of the natural organic matter. The RI changed little after reducing samples using zinc metal, oxidizing at high pH with air, or irradiating with a Xenon lamp. Our results, however, are consistent with the correlations between the fluorescence indices (FI) of samples and the ratio of PARAFAC fitting parameters suggested by Cory and McKnight (2005), though we used samples with a much narrower range of FI values.

The Inverse Demand Oxa-Diels-Alder Reaction of Resorcinarenes: An Experimental and Theoretical Analysis of Regioselectivity and Diastereoselectivity.

Science.gov (United States)

Stefańska, Karolina; Jędrzejewska, Hanna; Wierzbicki, Michał; Szumna, Agnieszka; Iwanek, Waldemar

2016-07-15

The Diels-Alder reaction enables introduction of new functionalities onto the resorcinarene skeleton with simultaneous generation of new stereogenic centers and expansion of the internal cavity. We present highly regio- and diastereoselective inverse electron demand oxa-Diels-Alder reactions of resorcinarene ortho-quinone methide with benzofuran and indene, each generating 12 new stereogenic centers. The mechanism and reasons for regioselectivity and diastereoselectivity were analyzed using theoretical calculations (NBO charges, Fukui functions, transition state energies, and thermodynamic stability of the products). Enantiomers were separated, and their configurations were determined by comparison of experimental and theoretical electronic circular dichroism spectra.

Magnetic Field Effect: An Efficient Tool To Investigate The Mechanism Of Reactions Using Laser Flash Photolysis Technique

International Nuclear Information System (INIS)

Basu, Samita; Bose, Adity; Dey, Debarati

2008-01-01

Magnetic field effect combined with laser flash photolysis technique have been used to study the mechanism of interactions between two drug-like quinone molecules, Menadione (1,4-naphthoquinone, MQ) and 9, 10 Anthraquinone (AQ) with one of the DNA bases, Adenine in homogeneous acetonitrile/water and heterogeneous micellar media. A switchover in reaction mode from electron transfer to hydrogen abstraction is observed with MQ on changing the solvent from acetonitrile/water to micelle; whereas, AQ retains its mode of interaction towards Adenine as electron transfer in both the media due to its bulky structure compared to MQ

Copolymerization of carbon monoxide and styrene catalyzed by resin-supported palladium polymer

Directory of Open Access Journals (Sweden)

2007-02-01

Full Text Available Polyketone was prepared by the copolymerization of carbon monoxide (CO and styrene (ST catalyzed by o-phenylenediamine resin-supported palladium acetate. Effects of each catalytic system component such as 2,2’-bipyridine, 1,4-quinone and p-toluene-sulphonate on the copolymerization were investigated. The resin-supported catalyst and the copolymerization product were characterized by infrared spectroscopy (IR, differential scanning calorimetry (DSC, thermogravimetry (TG, X-ray photoelectron spectroscopy (XPS, Scanning Electron Microscopy (SEM. Results indicated that the resin-supported catalyst has excellent catalytic property. Furthermore, partial catalytic activity was maintained after the catalyst was used for five times.

New isoflavone derivative and other flavonoids from the resin of Amburana cearensis

International Nuclear Information System (INIS)

Bandeira, Paulo N.; Farias, Silvana S. de; Santos, Helcio S.; Albuquerque, Maria R.J.R.; Lemos, Telma L.G.; Braz-Filho, Raimundo; Costa, Sonia M.O.

2011-01-01

Phytochemical investigation of the resin of Amburana cearensis A. C. Smith allowed the isolation of a new compound: 3',4'-dimethoxy-1'-(7-methoxy-4-oxo-4Hcromen-3-yl)benzo-2',5'-quinone (1), together with six known compounds identified as: 4,2',4'-trihydroxychalcone (2), 7,8,3',4'-tetramethoxyisoflavone (3), 4,2',4'-trihydroxy-3-methoxychalcone (4), 3,4,5-trimethoxycinnamaldehyde (5), 3',4'-dimethoxy-7-hydroxyisoflavone (6) and 6,7,4'-trimethoxy-3'-hydroxyisoflavone (7). The structures were established from the IR, HR.ESI.MS and NMR spectral data, including 2D-NMR experiments. (author)

Mechanism and kinetics in reactions of caffeic acid with radicals by pulse radiolysis and calculation

Energy Technology Data Exchange (ETDEWEB)

Li, Xifeng; Cai, Zhongli; Katsumura, Yosuke [Tokyo Univ., Tokai, Ibaraki (Japan). Nuclear Engineering Research Lab

2000-03-01

The interaction of caffeic acid with e{sub aq}{sup -}, (CH{sub 3}){sub 2}(OH) CCH{sub 2}{sup {center_dot}}, CO{sub 2}{sup {center_dot}}{sup -}, H{sup {center_dot}}, {center_dot}OH and N{sub 3}{sup {center_dot}} radicals were studied by {gamma}-, pulse radiolysis and molecular orbital calculation. UV-visible spectra of electron/{center_dot}OH adducts, semi-quinone radicals of caffeic ions, and the stable products from the reactions were derived. The rate constants were determined. The attacked sites and the most favorable structures of the transient radicals were predicted. Reaction mechanisms were proposed. (author)

Mechanistic aspects of biosynthesis of silver nanoparticles by several Fusarium oxysporum strains

Directory of Open Access Journals (Sweden)

De Souza Gabriel IH

2005-07-01

Full Text Available Abstract Extracellular production of metal nanoparticles by several strains of the fungus Fusarium oxysporum was carried out. It was found that aqueous silver ions when exposed to several Fusarium oxysporum strains are reduced in solution, thereby leading to the formation of silver hydrosol. The silver nanoparticles were in the range of 20–50 nm in dimensions. The reduction of the metal ions occurs by a nitrate-dependent reductase and a shuttle quinone extracellular process. The potentialities of this nanotechnological design based in fugal biosynthesis of nanoparticles for several technical applications are important, including their high potential as antibacterial material.

Oxidative protein modification as predigestive mechanism of the carnivorous plant Dionaea muscipula: an hypothesis based on in vitro experiments.

Science.gov (United States)

Galek, H; Osswald, W F; Elstner, E F

1990-01-01

Aqueous leaf extracts from Dionaea muscipula contain quinones such as the naphthoquinone plumbagin that couple to different NADH-dependent diaphorases, producing superoxide and hydrogen peroxide upon autoxidation. Upon preincubation of Dionaea extracts with certain diaphorases and NADH in the presence of serumalbumin (SA), subsequent tryptic digestion of SA is facilitated. Since the secretroy glands of Droseracea contain proteases and possibly other degradative enzymes it is suggested that the presence of oxygen-activating redox cofactors in the extracts function as extracellular predigestive oxidants which render membrane-bound proteins of the prey (insects) more susceptible to proteolytic attacks.

Redox properties of free radicals

International Nuclear Information System (INIS)

Neta, P.

1981-01-01

Results of electron transfer reactions observed and monitored by pulse radiolysis are reported. This technique allows determination of the first one-electron reduction or oxidation of a compound rather than the overall two-electron transfer usually reported. Pulse radiolysis allows the determination of absolute rate constants for reactions of free radicals and helps elucidate the mechanisms involved. Studies using this technique to study radicals derived from quinones, nitro compounds, pyridines, phenols, and anilines are reported. Radicals of biochemical interest arising from riboflavin, ascorbic acid, vitamin K 3 , vitamin E, MAD + , porphyrins, etc. have also been studied

Electrochemical Study of Esculetin Nitration by Digital Simulation of Cyclic Voltammograms

Directory of Open Access Journals (Sweden)

Lida Khalafi

2013-01-01

Full Text Available The reaction of electrochemically generated o-quinones from oxidation of esculetin as Michael acceptor with nitrite ion as nucleophile has been studied using cyclic voltammetry. The reaction mechanism is believed to be EC, including oxidation of catechol moiety of esculetin followed by Michael addition of nitrite ion. The observed homogeneous rate constants (obs for reactions were estimated by comparing the experimental voltammetric responses with the digitally simulated results based on the proposed mechanism. Also the effects of pH and nucleophile concentration on voltammetric behavior and the rate constants of chemical reactions were described.

In-situ quartz crystal microgravimetric studies of molecular adsorbates containing thiol and hydroquinone moieties bound to Au(111) surfaces in aqueous electrolytes

Energy Technology Data Exchange (ETDEWEB)

Mo, Y.; Sukenik, C.; Sandifer, M. [Case Western Univ., Cleveland, OH (United States); Barriga, R.J.; Soriaga, M.P.; Scherson, D. [Texas A& M Univ., College Station, TX (United States)

1995-12-01

The microgravimetric properties of monolayers of 2, 5-dihydroxythiophenol, 2,5-dihydroxybenzyl mercaptan, and 2, 5-dihydroxy-4-methylbenzyl mercaptan adsorbed on Au(111) single crystal electrodes were examined by in situ quartz crystal microbalance techniques in aqueous perchloric acid electrolytes. The results obtained are consistent with the reversible loss of an average of about three waters per adsorbed molecule as the layers are oxidized and subsequently reduced. These observations provide evidence for discrete changes in the extent of bound water within the hydroquinone/quinone layer as the oxidation state of the monolayer is changed. 9 refs., 4 figs.

PoC, LGBTQ, and gender: The intersectionality of America Chavez.

Science.gov (United States)

Jiménez, Laura M

2018-05-04

The Life and Times of America Chavez was a comic book series eventually published in trade form. Written by Gabby Rivera, queer Latinx young adult literature author, this iteration of Marvel Comic's Miss America (America Chavez) possesses an awareness and authenticity of Latinx culture and lesbian identity that was nothing less than revolutionary. Joe Quinones's artwork, rich in color, spirit, and pride, underscored the need for Latinx voices (both visual and verbal) to tell our stories. In this essay, I provide both a scholarly view of AMERICA as a superhero tale and illuminate the experience of reading her as a Latina lesbian.

Key role of water in proton transfer at the Q(o)-site of the cytochrome bc(1) complex predicted by atomistic molecular dynamics simulations

DEFF Research Database (Denmark)

Postila, P. A.; Kaszuba, K.; Sarewicz, M.

2013-01-01

of the cyt bc(1) function have remained unclear especially regarding the substrate binding at the Q(o)-site. In this work we address this issue by performing extensive atomistic molecular dynamics simulations with the cyt bc(1) complex of Rhodobacter capsulatus embedded in a lipid bilayer. Based...... on the simulations we are able to show the atom-level binding modes of two substrate forms: quinol (QH(2)) and quinone (Q). The QH(2) binding at the Q(o)-site involves a coordinated water arrangement that produces an exceptionally close and stable interaction between the cyt b and iron sulfur protein subunits...

WrpA Is an Atypical Flavodoxin Family Protein under Regulatory Control of the Brucella abortus General Stress Response System.

Science.gov (United States)

Herrou, Julien; Czyż, Daniel M; Willett, Jonathan W; Kim, Hye-Sook; Chhor, Gekleng; Babnigg, Gyorgy; Kim, Youngchang; Crosson, Sean

2016-04-01

The general stress response (GSR) system of the intracellular pathogen Brucella abortus controls the transcription of approximately 100 genes in response to a range of stress cues. The core genetic regulatory components of the GSR are required for B. abortus survival under nonoptimal growth conditions in vitro and for maintenance of chronic infection in an in vivo mouse model. The functions of the majority of the genes in the GSR transcriptional regulon remain undefined. bab1_1070 is among the most highly regulated genes in this regulon: its transcription is activated 20- to 30-fold by the GSR system under oxidative conditions in vitro. We have solved crystal structures of Bab1_1070 and demonstrate that it forms a homotetrameric complex that resembles those of WrbA-type NADH:quinone oxidoreductases, which are members of the flavodoxin protein family. However, B. abortus WrbA-related protein (WrpA) does not bind flavin cofactors with a high affinity and does not function as an NADH:quinone oxidoreductase in vitro. Soaking crystals with flavin mononucleotide (FMN) revealed a likely low-affinity binding site adjacent to the canonical WrbA flavin binding site. Deletion of wrpA (ΔwrpA) does not compromise cell survival under acute oxidative stress in vitro or attenuate infection in cell-based or mouse models. However, a ΔwrpA strain does elicit increased splenomegaly in a mouse model, suggesting that WrpA modulates B. abortus interaction with its mammalian host. Despite high structural homology with canonical WrbA proteins, we propose that B. abortus WrpA represents a functionally distinct member of the diverse flavodoxin family. Brucella abortus is an etiological agent of brucellosis, which is among the most common zoonotic diseases worldwide. The general stress response (GSR) regulatory system of B. abortus controls the transcription of approximately 100 genes and is required for maintenance of chronic infection in a murine model; the majority of GSR-regulated genes