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Sample records for additional hydroxyl group

  1. Anaerobic Activation of p-Cymene in Denitrifying Betaproteobacteria: Methyl Group Hydroxylation versus Addition to Fumarate

    PubMed Central

    Strijkstra, Annemieke; Trautwein, Kathleen; Jarling, René; Wöhlbrand, Lars; Dörries, Marvin; Reinhardt, Richard; Drozdowska, Marta; Golding, Bernard T.; Wilkes, Heinz

    2014-01-01

    The betaproteobacteria “Aromatoleum aromaticum” pCyN1 and “Thauera” sp. strain pCyN2 anaerobically degrade the plant-derived aromatic hydrocarbon p-cymene (4-isopropyltoluene) under nitrate-reducing conditions. Metabolite analysis of p-cymene-adapted “A. aromaticum” pCyN1 cells demonstrated the specific formation of 4-isopropylbenzyl alcohol and 4-isopropylbenzaldehyde, whereas with “Thauera” sp. pCyN2, exclusively 4-isopropylbenzylsuccinate and tentatively identified (4-isopropylphenyl)itaconate were observed. 4-Isopropylbenzoate in contrast was detected with both strains. Proteogenomic investigation of p-cymene- versus succinate-adapted cells of the two strains revealed distinct protein profiles agreeing with the different metabolites formed from p-cymene. “A. aromaticum” pCyN1 specifically produced (i) a putative p-cymene dehydrogenase (CmdABC) expected to hydroxylate the benzylic methyl group of p-cymene, (ii) two dehydrogenases putatively oxidizing 4-isopropylbenzyl alcohol (Iod) and 4-isopropylbenzaldehyde (Iad), and (iii) the putative 4-isopropylbenzoate-coenzyme A (CoA) ligase (Ibl). The p-cymene-specific protein profile of “Thauera” sp. pCyN2, on the other hand, encompassed proteins homologous to subunits of toluene-activating benzylsuccinate synthase (termed [4-isopropylbenzyl]succinate synthase IbsABCDEF; identified subunits, IbsAE) and protein homologs of the benzylsuccinate β-oxidation (Bbs) pathway (termed BisABCDEFGH; all identified except for BisEF). This study reveals that two related denitrifying bacteria employ fundamentally different peripheral degradation routes for one and the same substrate, p-cymene, with the two pathways apparently converging at the level of 4-isopropylbenzoyl-CoA. PMID:25261521

  2. Chemoselective Hydroxyl Group Transformation: An Elusive Target‡

    PubMed Central

    Trader, Darci J.; Carlson, Erin E.

    2012-01-01

    The selective reaction of one functional group in the presence of others is not a trivial task. A noteworthy amount of research has been dedicated to the chemoselective reaction of the hydroxyl moiety. This group is prevalent in many biologically important molecules including natural products and proteins. However, targeting the hydroxyl group is difficult for many reasons including its relatively low nucleophilicity in comparison to other ubiquitous functional groups such as amines and thiols. Additionally, many of the developed chemoselective reactions cannot be used in the presence of water. Despite these complications, chemoselective transformation of the hydroxyl moiety has been utilized in the synthesis of complex natural product derivatives, the reaction of tyrosine residues in proteins, the isolation of natural products and is the mechanism of action of myriad drugs. Here, methods for selective targeting of this group, as well as applications of several devised methods, are described. PMID:22695722

  3. Group Sparse Additive Models

    PubMed Central

    Yin, Junming; Chen, Xi; Xing, Eric P.

    2016-01-01

    We consider the problem of sparse variable selection in nonparametric additive models, with the prior knowledge of the structure among the covariates to encourage those variables within a group to be selected jointly. Previous works either study the group sparsity in the parametric setting (e.g., group lasso), or address the problem in the nonparametric setting without exploiting the structural information (e.g., sparse additive models). In this paper, we present a new method, called group sparse additive models (GroupSpAM), which can handle group sparsity in additive models. We generalize the ℓ1/ℓ2 norm to Hilbert spaces as the sparsity-inducing penalty in GroupSpAM. Moreover, we derive a novel thresholding condition for identifying the functional sparsity at the group level, and propose an efficient block coordinate descent algorithm for constructing the estimate. We demonstrate by simulation that GroupSpAM substantially outperforms the competing methods in terms of support recovery and prediction accuracy in additive models, and also conduct a comparative experiment on a real breast cancer dataset.

  4. A ribozyme that triphosphorylates RNA 5′-hydroxyl groups

    PubMed Central

    Moretti, Janina E.; Müller, Ulrich F.

    2014-01-01

    The RNA world hypothesis describes a stage in the early evolution of life in which RNA served as genome and as the only genome-encoded catalyst. To test whether RNA world organisms could have used cyclic trimetaphosphate as an energy source, we developed an in vitro selection strategy for isolating ribozymes that catalyze the triphosphorylation of RNA 5′-hydroxyl groups with trimetaphosphate. Several active sequences were isolated, and one ribozyme was analyzed in more detail. The ribozyme was truncated to 96 nt, while retaining full activity. It was converted to a trans-format and reacted with rates of 0.16 min−1 under optimal conditions. The secondary structure appears to contain a four-helical junction motif. This study showed that ribozymes can use trimetaphosphate to triphosphorylate RNA 5′-hydroxyl groups and suggested that RNA world organisms could have used trimetaphosphate as their energy source. PMID:24452796

  5. Identification and quantification of aerosol polar oxygenated compounds bearing carboxylic or hydroxyl groups. 1. Method development.

    PubMed

    Jaoui, M; Kleindienst, T E; Lewandowski, M; Edney, E O

    2004-08-15

    In this study, a new analytical technique was developed for the identification and quantification of multifunctional compounds containing simultaneously at least one hydroxyl or one carboxylic group, or both. This technique is based on derivatizing first the carboxylic group(s) of the multifunctional compound using an alcohol (e.g., methanol, 1-butanol) in the presence of a relatively strong Lewis acid (BF3) as a catalyst. This esterification reaction quickly and quantitatively converts carboxylic acids to their ester forms. The second step is based on silylation of the ester compounds using bis(trimethylsilyl) trifluoroacetamide (BSTFA) as the derivatizing agent. For compounds bearing ketone groups in addition to carboxylic and hydroxyl groups, a third step was used based on PFBHA derivatization of the carbonyls. Different parameters including temperature, reaction time, and effect due to artifacts were optimized. A GC/MS in EI and in methane-CI mode was used for the analysis of these compounds. The new approach was tested on a number of multifunctional compounds. The interpretation of their EI (70 eV) and CI mass spectra shows that critical information is gained leading to unambiguous identification of unknown compounds. For example, when derivatized only with BF(3)-methanol, their mass spectra comprise primary ions at m/z M.+ + 1, M.+ + 29, and M.+ - 31 for compounds bearing only carboxylic groups and M.+ + 1, M.+ + 29, M.+ - 31, and M+. - 17 for those bearing hydroxyl and carboxylic groups. However, when a second derivatization (BSTFA) was used, compounds bearing hydroxyl and carboxylic groups simultaneously show, in addition to the ions observed before, ions at m/z M.+ + 73, M.+ - 15, M.+ - 59, M.+ - 75, M.+ - 89, and 73. To the best of our knowledge, this technique describes systematically for the first time a method for identifying multifunctional oxygenated compounds containing simultaneously one or more hydroxyl and carboxylic acid groups.

  6. The Juxtaposition of Ribose Hydroxyl Groups: The Root of Biological Catalysis and the RNA World?

    NASA Astrophysics Data System (ADS)

    Bernhardt, Harold S.

    2015-06-01

    We normally think of enzymes as being proteins; however, the RNA world hypothesis suggests that the earliest biological catalysts may have been composed of RNA. One of the oldest surviving RNA enzymes we are aware of is the peptidyl transferase centre (PTC) of the large ribosomal RNA, which joins amino acids together to form proteins. Recent evidence indicates that the enzymatic activity of the PTC is principally due to ribose 2 '-OHs. Many other reactions catalyzed by RNA and/or in which RNA is a substrate similarly utilize ribose 2 '-OHs, including phosphoryl transfer reactions that involve the cleavage and/or ligation of the ribose-phosphate backbone. It has recently been proposed by Yakhnin (2013) that phosphoryl transfer reactions were important in the prebiotic chemical evolution of RNA, by enabling macromolecules composed of polyols joined by phosphodiester linkages to undergo recombination reactions, with the reaction energy supplied by the phosphodiester bond itself. The almost unique juxtaposition of the ribose 2'-hydroxyl and 3'-oxygen in ribose-containing polymers such as RNA, which gives ribose the ability to catalyze such reactions, may have been an important factor in the selection of ribose as a component of the first biopolymer. In addition, the juxtaposition of hydroxyl groups in free ribose: (i) allows coordination of borate ions, which could have provided significant and preferential stabilization of ribose in a prebiotic environment; and (ii) enhances the rate of permeation by ribose into a variety of lipid membrane systems, possibly favouring its incorporation into early metabolic pathways and an ancestral ribose-phosphate polymer. Somewhat more speculatively, hydrogen bonds formed by juxtaposed ribose hydroxyl groups may have stabilized an ancestral ribose-phosphate polymer against degradation (Bernhardt and Sandwick 2014). I propose that the almost unique juxtaposition of ribose hydroxyl groups constitutes the root of both biological

  7. Effect of liquefaction temperature on hydroxyl groups of bio-oil from loblolly pine (Pinus taeda).

    PubMed

    Celikbag, Yusuf; Via, Brian K; Adhikari, Sushil; Wu, Yonnie

    2014-10-01

    Loblolly pine was liquefied with ethylene glycol at 100, 150, 200 and 250 °C in order to analyze the effect of liquefaction temperature on hydroxyl groups of bio-oil, and to determine the source and variation of hydroxyl groups. The optimum temperature was found to be 150-200 °C. Hydroxyl number (OHN) of the bio-oil was ranged from 632 to 1430 mg KOH/g. GC-MS analysis showed that 70-90% of OHN was generated from unreacted EG. (31)P NMR analysis showed that the majority of hydroxyl groups were aliphatic, and none of the bio-oil exhibited any detectable hydroxyl groups from phenolic sources. Finally, it was found that all bio-oils were stable in terms of OHN for 2 months when stored at -10 °C.

  8. Non-exchanging hydroxyl groups on the surface of cellulose fibrils: The role of interaction with water.

    PubMed

    Lindh, Erik L; Bergenstråhle-Wohlert, Malin; Terenzi, Camilla; Salmén, Lennart; Furó, István

    2016-11-03

    The interaction of water with cellulose stages many unresolved questions. Here (2)H MAS NMR and IR spectra recorded under carefully selected conditions in (1)H-(2)H exchanged, and re-exchanged, cellulose samples are presented. It is shown here, by a quantitative and robust approach, that only two of the three available hydroxyl groups on the surface of cellulose fibrils are exchanging their hydrogen with the surrounding water molecules. This finding is additionally verified and explained by MD simulations which demonstrate that the (1)HO(2) and (1)HO(6) hydroxyl groups of the constituting glucose units act as hydrogen-bond donors to water, while the (1)HO(3) groups behave exclusively as hydrogen-bond acceptors from water and donate hydrogen to their intra-chain neighbors O(5). We conclude that such a behavior makes the latter hydroxyl group unreactive to hydrogen exchange with water.

  9. Coumestan inhibits radical-induced oxidation of DNA: is hydroxyl a necessary functional group?

    PubMed

    Xi, Gao-Lei; Liu, Zai-Qun

    2014-06-18

    Coumestan is a natural tetracycle with a C═C bond shared by a coumarin moiety and a benzofuran moiety. In addition to the function of the hydroxyl group on the antioxidant activity of coumestan, it is worth exploring the influence of the oxygen-abundant scaffold on the antioxidant activity as well. In this work, seven coumestans containing electron-withdrawing and electron-donating groups were synthesized to evaluate the abilities to trap 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) cationic radical (ABTS(•+)), 2,2'-diphenyl-1-picrylhydrazyl radical (DPPH), and galvinoxyl radical, respectively, and to inhibit the oxidations of DNA mediated by (•)OH, Cu(2+)/glutathione (GSH), and 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH), respectively. It was found that all of the coumestans used herein can quench the aforementioned radicals and can inhibit (•)OH-, Cu(2+)/GSH-, and AAPH-induced oxidations of DNA. In particular, substituent-free coumestan exhibits higher ability to quench DPPH and to inhibit AAPH-induced oxidation of DNA than Trolox. In addition, nonsubstituted coumestan shows a similar ability to inhibit (•)OH- and Cu(2+)/GSH-induced oxidations of DNA relative to that of Trolox. The antioxidant effectiveness of the coumestan can be attributed to the lactone in the coumarin moiety and, therefore, a hydroxyl group may not be a necessary functional group for coumestan to be an antioxidant.

  10. Coumarin-fused coumarin: antioxidant story from N,N-dimethylamino and hydroxyl groups.

    PubMed

    Xi, Gao-Lei; Liu, Zai-Qun

    2015-04-08

    Two coumarin skeletons can form chromeno[3,4-c]chromene-6,7-dione by sharing with the C ═ C in lactone. The aim of the present work was to explore the antioxidant effectiveness of the coumarin-fused coumarin via six synthetic compounds containing hydroxyl and N,N-dimethylamino as the functional groups. The abilities to quench 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) cationic radical (ABTS(+•)), 2,2'-diphenyl-1-picrylhydrazyl radical (DPPH), and galvinoxyl radical revealed that the rate constant for scavenging radicals was related to the amount of hydroxyl group in the scaffold of coumarin-fused coumarin. But coumarin-fused coumarin was able to inhibit DNA oxidations caused by (•)OH, Cu(2+)/glutathione (GSH), and 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH) even in the absence of hydroxyl group. In particular, a hydroxyl and an N,N-dimethylamino group locating at different benzene rings increased the inhibitory effect of coumarin-fused coumarin on AAPH-induced oxidation of DNA about 3 times higher than a single hydroxyl group, whereas N,N-dimethylamino-substituted coumarin-fused coumarin possessed high activity toward (•)OH-induced oxidation of DNA without the hydroxyl group contained. Therefore, the hydroxyl group together with N,N-dimethylamino group may be a novel combination for the design of coumarin-fused heterocyclic antioxidants.

  11. Antioxidant effectiveness generated by one or two phenolic hydroxyl groups in coumarin-substituted dihydropyrazoles.

    PubMed

    Xi, Gao-Lei; Liu, Zai-Qun

    2013-10-01

    A cascade operation was designed to synthesize nine coumarin-substituted dihydropyrazoles with only one or two phenolic hydroxyl groups contained. Antioxidant abilities of the obtained compounds were evaluated by inhibiting 2,2'-azobis(2-amidinopropanehydrochloride) (AAPH)-, Cu2+/glutathione (GSH)-, and .OH-induced oxidation of DNA. It was found that less phenolic hydroxyl groups can enhance the abilities of coumarin-substituted dihydropyrazoles to protect DNA against the oxidation. Moreover, these coumarin-substituted dihydropyrazoles were employed to scavenge 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) cationic radical (ABTS+.), 2,2'-diphenyl-1-picrylhydrazyl radical (DPPH), and galvinoxyl radical, respectively. It was found that double phenolic hydroxyl groups were more beneficial for enhancing the abilities of coumarin-substituted dihydropyrazoles to quench the aforementioned radicals. Therefore, dihydropyrazole linked with coumarin exhibited powerful antioxidant effectiveness even in the case of less phenolic hydroxyl groups involved.

  12. Inhibition of Pseudomonas aeruginosa Swarming Motility by 1-Naphthol and Other Bicyclic Compounds Bearing Hydroxyl Groups

    PubMed Central

    Oura, Hiromu; Tashiro, Yosuke; Toyofuku, Masanori; Ueda, Kousetsu; Kiyokawa, Tatsunori; Ito, Satoshi; Takahashi, Yurika; Lee, Seunguk; Nojiri, Hideaki; Nakajima-Kambe, Toshiaki; Uchiyama, Hiroo; Futamata, Hiroyuki

    2015-01-01

    Many bacteria convert bicyclic compounds, such as indole and naphthalene, to oxidized compounds, including hydroxyindoles and naphthols. Pseudomonas aeruginosa, a ubiquitous bacterium that inhabits diverse environments, shows pathogenicity against animals, plants, and other microorganisms, and increasing evidence has shown that several bicyclic compounds alter the virulence-related phenotypes of P. aeruginosa. Here, we revealed that hydroxyindoles (4- and 5-hydroxyindoles) and naphthalene derivatives bearing hydroxyl groups specifically inhibit swarming motility but have minor effects on other motilities, including swimming and twitching, in P. aeruginosa. Further analyses using 1-naphthol showed that this effect is also associated with clinically isolated hyperswarming P. aeruginosa cells. Swarming motility is associated with the dispersion of cells from biofilms, and the addition of 1-naphthol maintained biofilm biomass without cell dispersion. We showed that this 1-naphthol-dependent swarming inhibition is independent of changes of rhamnolipid production and the intracellular level of signaling molecule cyclic-di-GMP (c-di-GMP). Transcriptome analyses revealed that 1-naphthol increases gene expression associated with multidrug efflux and represses gene expression associated with aerotaxis and with pyochelin, flagellar, and pilus synthesis. In the present study, we showed that several bicyclic compounds bearing hydroxyl groups inhibit the swarming motility of P. aeruginosa, and these results provide new insight into the chemical structures that inhibit the specific phenotypes of P. aeruginosa. PMID:25681177

  13. Oxidoreduction of different hydroxyl groups in bile acids during their enterohepatic circulation in man

    SciTech Connect

    Bjoerkhem, I.L.; Liljeqvist, L.; Nilsell, K.; Einarsson, K.

    1986-02-01

    The extent of oxidoreduction of the 3 alpha-, 7 alpha- and 12 alpha-hydroxyl groups in bile acids during the enterohepatic circulation in man was studied with the use of (3 beta-/sup 3/H)-labeled deoxycholic acid and cholic acid, (7 beta-/sup 3/H)-labeled cholic acid, and (12 beta-/sup 3/H)-labeled deoxycholic acid and cholic acid. Each (/sup 3/H)-labeled bile acid was given per os to healthy volunteers, together with the corresponding (24-/sup 14/C)-labeled bile acid. The rate of oxidoreduction was calculated from the decrease in the ratio between /sup 3/H and /sup 14/C in the respective bile acid isolated from duodenal contents collected at different time intervals after administration of the labeled bile acids. The mean fractional conversion rate was found to be 0.29 day-1 for the 3 alpha-hydroxyl group in deoxycholic acid (n = 2), 0.18 day-1 for the 12 alpha-hydroxyl group in deoxycholic acid (n = 6), 0.09 day-1 for the 3 alpha-hydroxyl group in cholic acid (n = 3), 0.05 day-1 for the 7 alpha-hydroxyl group in cholic acid (n = 2), and 0.03 day-1 for the 12 alpha-hydroxyl group in cholic acid (n = 2). The extent of oxidoreduction of the 12 alpha-hydroxyl group in (12 beta-/sup 3/H)-labeled deoxycholic acid given to two patients operated with subtotal colectomy and ileostomy was markedly reduced (less than 20% of normal).

  14. Entropy Loss of Hydroxyl Groups of Balanol upon Binding to Protein Kinase A

    NASA Astrophysics Data System (ADS)

    Gidofalvi, Gergely; Wong, Chung F.; McCammon, J. Andrew

    2002-09-01

    This article describes a short project for an undergraduate to learn several techniques for computer-aided drug design. The project involves estimating the loss of the rotational entropy of the hydroxyl groups of balanol upon its binding to the enzyme protein kinase A (PKA), as the entropy loss can significantly influence PKA balanol binding affinity. This work employs semiempirical quantum mechanical techniques for estimating the potential energy curves for the rotation of the hydroxyl groups of balanol in vacuum and in PKA, and solves the Poisson equation to correct the potential energy curves for hydration effects. Statistical mechanical principles are then applied to estimate the desired entropy loss from the potential energy curves. The analysis examines the influence of hydration effects on the rotational preference of the hydroxyl groups and the significance of the rotational entropy in determining binding affinity.

  15. Relative impact of 3- and 5-hydroxyl groups of cytosporone B on cancer cell viability.

    PubMed

    Xia, Zebin; Cao, Xihua; Rico-Bautista, Elizabeth; Yu, Jinghua; Chen, Liqun; Chen, Jiebo; Bobkov, Andrey; Wolf, Dieter A; Zhang, Xiao-Kun; Dawson, Marcia I

    2013-02-01

    A novel and the shortest route, thus far, for preparing cytosporone B (Csn-B) is reported. Csn-B and two analogs were used to probe the importance of hydroxyl groups at the 3- and 5-positions of the Csn-B benzene ring in inhibiting the viability of human H460 lung cancer and LNCaP prostate cancer cells, inducing H460 cell apoptosis, and interacting with the NR4A1 (TR3) ligand-binding domain (LBD). These studies indicate that Csn-B and 5-Me-Csn-B, having a phenolic hydroxyl at the 3-position of their aromatic rings, had similar activities in inhibiting cancer cell viability and in inducing apoptosis, whereas 3,5-(Me)2-Csn-B was unable to do so. These results are in agreement with ligand-binding experiments showing that the interaction with the NR4A1 LBD required the presence of the 3-hydroxyl group.

  16. Use of molecular dynamics to assess the biophysiological role of hydroxyl groups in glycerol dyalkyl glycerol teraethers

    NASA Astrophysics Data System (ADS)

    Huguet, Carme; Costenaro, Lionel; Fietz, Susanne; Daura, Xavier

    2015-04-01

    The cell membrane of some Archaea is constituted by lipids that span the whole membrane width and contain two alkyl chains bound by two glycerol groups (glycerol dyalkyl glycerol teraethers or GDGTs). These lipids confer stability to the membrane in mesophile to extremophile environments. Besides the more frequently studied isoprenoid archaeal lipids, both mono- and dihydroxy-GDGTs (OH-GDGT) have been recently reported to occur in marine sediments (1). OH-GDGTs contain up to two cyclopentane moieties and have been identified in both core and intact forms. In 2013, a correlation between OH-GDGTs and temperature was reported, with higher relative OH-GDGT abundances at high latitudes (2,3). The physiological function of the hydroxyl group in a GDGT is not yet known, but given the field results, it could be linked to an adaptation of the membrane to changes in temperature. For hydroxydiether lipid cores in methanogenic bacteria, it has been postulated that the hydroxyl group may alter the cell membrane properties: either extending the polar head group region or creating a hydrophilic pocket (4). It has also been suggested that the hydroxylation of the biphytany (l) moiety may result in enhanced membrane rigidity (1). To improve our understanding of the effect of the hydroxylation on physical properties of membranes, we performed molecular-dynamics simulations of GDGT membranes presenting and lacking these additional OH groups. This is an approach with a great development potential in the archaea lipid field, especially in relation to proxy validation. Our results indicate that the addition of an OH increases the membrane fluidity, thus providing an advantage in cold environments. We also observe a widening of the polar head group area, which could enhance transport. 1. Liu et al. 2012, GCA 2. Huguet et al. 2013, Org. Geochem 3. Fietz et al. 2013 4. Sprott et al. 1990. J. Biol. Chem. 265, 13735-13740.

  17. Conformational influence of the ribose 2'-hydroxyl group: crystal structures of DNA-RNA chimeric duplexes

    NASA Technical Reports Server (NTRS)

    Egli, M.; Usman, N.; Rich, A.

    1993-01-01

    We have crystallized three double-helical DNA-RNA chimeric duplexes and determined their structures by X-ray crystallography at resolutions between 2 and 2.25 A. The two self-complementary duplexes [r(G)d(CGTATACGC)]2 and [d(GCGT)r(A)d(TACGC)]2, as well as the Okazaki fragment d(GGGTATACGC).r(GCG)d(TATACCC), were found to adopt A-type conformations. The crystal structures are non-isomorphous, and the crystallographic environments for the three chimeras are different. A number of intramolecular interactions of the ribose 2'-hydroxyl groups contribute to the stabilization of the A-conformation. Hydrogen bonds between 2'-hydroxyls and 5'-oxygens or phosphate oxygens, in addition to the previously observed hydrogen bonds to 1'-oxygens of adjacent riboses and deoxyriboses, are observed in the DNA-RNA chimeric duplexes. The crystalline chimeric duplexes do not show a transition between the DNA A- and B-conformations. CD spectra suggest that the Okazaki fragment assumes an A-conformation in solution as well. In this molecule the three RNA residues may therefore lock the complete decamer in the A-conformation. Crystals of an all-DNA strand with the same sequence as the self-complementary chimeras show a morphology which is different from those of the chimera crystals. Moreover, the oligonucleotide does not match any of the sequence characteristics of DNAs usually adopting the A-conformation in the crystalline state (e.g., octamers with short alternating stretches of purines and pyrimidines). In DNA-RNA chimeric duplexes, it is therefore possible that a single RNA residue can drive the conformational equilibrium toward the A-conformation.

  18. Predicting the acidity constant of a goethite hydroxyl group from first principles

    NASA Astrophysics Data System (ADS)

    Leung, Kevin; Criscenti, Louise J.

    2012-03-01

    Accurate predictions of the acid-base behavior of hydroxyl groups at mineral surfaces are critical for understanding the trapping of toxic and radioactive ions in soil samples. In this work, we apply ab initio molecular dynamics (AIMD) simulations and potential-of-mean-force techniques to calculate the pKa of a doubly protonated oxygen atom bonded to a single Fe atom (FeIOH2) on the goethite (101) surface. Using formic acid as a reference system, pKa = 7.0 is predicted, suggesting that isolated, positively charged groups of this type are marginally stable at neutral pH. Similarities and differences between AIMD and the more empirical multi-site complexation methodology are highlighted, particularly with respect to the treatment of hydrogen bonding with water and proton sharing among surface hydroxyl groups. We also highlight the importance of an electronic structure method that can accurately predict transition metal ion properties for goethite pKa calculations.

  19. XPS study of PBO fiber surface modified by incorporation of hydroxyl polar groups in main chains

    NASA Astrophysics Data System (ADS)

    Zhang, Tao; Hu, Dayong; Jin, Junhong; Yang, Shenglin; Li, Guang; Jiang, Jianming

    2010-01-01

    Dihydroxy poly(p-phenylene benzobisoxazole) (DHPBO), a modified poly(p-phenylene benzoxazole) (PBO) polymer containing double hydroxyl groups in polymer chains, was synthesized by copolymerization of 4,6-diamino resorcinol dihydrochloride (DAR), purified terephthalic acid (TA) and 2,5-dihydroxyterephthalic acid (DHTA). DHPBO fibers were prepared by dry-jet wet-spinning method. The effects of hydroxyl polar groups on the surface elemental compositions of PBO fiber were investigated by X-ray photoelectron spectroscopy (XPS). The results show that the ratio of oxygen/carbon on the surface of DHPBO fibers is higher than that on the surface of PBO fibers, which indicates the content of polar groups on the surface of DHPBO fiber increase compared with PBO fiber.

  20. Relative impact of 3- and 5-hydroxyl groups of cytosporone B on cancer cell viability†

    PubMed Central

    Rico-Bautista, Elizabeth; Yu, Jinghua; Chen, Liqun; Chen, Jiebo; Bobkov, Andrey; Wolf, Dieter A.; Zhang, Xiao-Kun; Dawson, Marcia I.

    2014-01-01

    A novel and the shortest route, thus far, for preparing cytosporone B (Csn-B) is reported. Csn-B and two analogs were used to probe the importance of hydroxyl groups at the 3- and 5-positions of the Csn-B benzene ring in inhibiting the viability of human H460 lung cancer and LNCaP prostate cancer cells, inducing H460 cell apoptosis, and interacting with the NR4A1 (TR3) ligand-binding domain (LBD). These studies indicate that Csn-B and 5-Me-Csn-B, having a phenolic hydroxyl at the 3-position of their aromatic rings, had similar activities in inhibiting cancer cell viability and in inducing apoptosis, whereas 3,5-(Me)2-Csn-B was unable to do so. These results are in agreement with ligand-binding experiments showing that the interaction with the NR4A1 LBD required the presence of the 3-hydroxyl group. PMID:24795803

  1. Structure-affinity relationship of flavones on binding to serum albumins: effect of hydroxyl groups on ring A.

    PubMed

    Xiao, Jianbo; Cao, Hui; Wang, Yuanfeng; Yamamoto, Koichiro; Wei, Xinlin

    2010-07-01

    Four flavones (flavone, 7-hydroxyflavone, chrysin, and baicalein) sharing the same B- and C-ring structure but a different numbers of hydroxyl groups on the A-ring were studied for their affinities for BSA and HSA. The hydroxylation on ring A of flavones increased the binding constants (K(a)) and the number of binding sites (n) between flavones and serum albumins. The affinities of 7-hydroxyflavone for BSA and HSA were about 800 times and 40 times higher than that of flavone, respectively. It appears that the optimal number of hydroxyl groups introduced to the ring A of flavones is one. As more hydroxyl groups were introduced to positions at C-5, C-6, and/or C-7 of flavones, the affinities for serum albumins decrease. The critical energy transfer distances (R(0)) between the hydroxylated flavones (1-3 OH on the ring A) and serum albumins decreased with the increasing affinities for serum albumins.

  2. Smart materials behavior in phosphates: Role of hydroxyl groups and relevance to antiwear films

    NASA Astrophysics Data System (ADS)

    Shakhvorostov, Dmitry; Müser, Martin H.; Song, Yang; Norton, Peter R.

    2009-07-01

    The elastic properties of materials under high pressure are relevant to the understanding and performance of many systems of current interest, for example, in geology and tribology. Of particular interest is the origin of the dramatic increase in modulus with increasing pressure, a response which is also called "smart materials behavior." In this context, simple phosphate-containing materials have been studied experimentally and theoretically, and the origins of this behavior have been associated with factors such as coordination of the cations and changes in the degree of polymerization and hydrogenation of the phosphate units. In the present paper we extend the former analysis on simple metal phosphate model compounds to so-called thermal films, an intermediate stage in the formation of effective antiwear films. The material was produced by heating a commercial zinc dialkyldithiophosphate (ZDDP), a common antiwear additive in lubricating oils, in poly-α-olefin base oil solutions to 150 °C, a process known to produce the thermal films. Its structure and equation of state were studied by means of x-ray diffraction and IR synchrotron radiation techniques during compression up to 25 GPa in a diamond anvil cell as well as during the subsequent decompression. As is the case for the simple metal phosphates, we find that the thermal films are relatively soft at low pressures but stiffen rapidly and ultimately amorphize irreversibly at high pressure. However, in addition to phase transformations involving cation sites occurring in the metal phosphates studied previously, thermal films undergo displacive transitions associated with instabilities of the hydroxyl groups. These results may imply that ZDDP ligands and those of the transformed materials not only affect ZDDP decomposition rate in engines but also the mechanical properties of the resulting antiwear films.

  3. Smart materials behavior in phosphates: role of hydroxyl groups and relevance to antiwear films.

    PubMed

    Shakhvorostov, Dmitry; Müser, Martin H; Song, Yang; Norton, Peter R

    2009-07-28

    The elastic properties of materials under high pressure are relevant to the understanding and performance of many systems of current interest, for example, in geology and tribology. Of particular interest is the origin of the dramatic increase in modulus with increasing pressure, a response which is also called "smart materials behavior." In this context, simple phosphate-containing materials have been studied experimentally and theoretically, and the origins of this behavior have been associated with factors such as coordination of the cations and changes in the degree of polymerization and hydrogenation of the phosphate units. In the present paper we extend the former analysis on simple metal phosphate model compounds to so-called thermal films, an intermediate stage in the formation of effective antiwear films. The material was produced by heating a commercial zinc dialkyldithiophosphate (ZDDP), a common antiwear additive in lubricating oils, in poly-alpha-olefin base oil solutions to 150 degrees C, a process known to produce the thermal films. Its structure and equation of state were studied by means of x-ray diffraction and IR synchrotron radiation techniques during compression up to 25 GPa in a diamond anvil cell as well as during the subsequent decompression. As is the case for the simple metal phosphates, we find that the thermal films are relatively soft at low pressures but stiffen rapidly and ultimately amorphize irreversibly at high pressure. However, in addition to phase transformations involving cation sites occurring in the metal phosphates studied previously, thermal films undergo displacive transitions associated with instabilities of the hydroxyl groups. These results may imply that ZDDP ligands and those of the transformed materials not only affect ZDDP decomposition rate in engines but also the mechanical properties of the resulting antiwear films.

  4. Crystalline structures and mesomorphic properties of gemini diammonium surfactants with a pendant hydroxyl group.

    PubMed

    Wei, Zengbin; Wei, Xilian; Sun, Dezhi; Liu, Jiuqiang; Tang, Xiaojuan

    2011-02-15

    A series of homologous crystals of gemini diammonium surfactants (GDAS) containing one hydroxyl substituted methylene spacer are prepared. The crystal structures of these compounds, namely [C(n)H(2)(n)(+1)-N(+) (CH(3))(2)-CH(2)CH(OH)CH(2)-N(+)(CH(3))(2)-C(n)H(2)(n)(+1)], are determined by single-crystal X-ray diffraction techniques, in order to have a better understanding of the structure relation between the solid and the mesophase. The hydroxyl groups enhance the hydrogen bonding interaction between neighboring compounds, and therefore the packing of GDAS in the solid state is arranged to form a herringbone-like mode. To the best of our knowledge, this is the first GDAS crystal with a herringbone-like structure. Their mesomorphic properties are investigated by differential scanning calorimetry, polarizing optical microscopy, X-ray powder diffraction, and rheological measurement. These compounds have relatively low melting points and form thermotropic mesophases over a broad temperature range, as compared to those without a hydroxyl substituted at the spacer. The rheological behavior of the smectic phases clearly reveals that hydrogen bonds exert a significant effect on the high values of moduli and viscosity. Moreover, the melting point and rheological parameters increase, conforming to the length of alkyl chains.

  5. A first principle study of graphene functionalized with hydroxyl, nitrile, or methyl groups

    NASA Astrophysics Data System (ADS)

    Barhoumi, M.; Rocca, D.; Said, M.; Lebègue, S.

    2017-01-01

    By means of ab initio calculations, we study the functionalization of graphene by different chemical groups such as hydroxyl, nitrile, or methyl. Two extreme cases of functionalization are considered: a single group on a supercell of graphene and a sheet of graphene fully functionalized. Once the equilibrium geometry is obtained by density functional theory, we found that the systems are metallic when a single group is attached to the sheet of graphene. With the exception of the nitrile functionalized boat configuration, a large bandgap is obtained at full coverage. Specifically, by using the GW approximation, our calculated bandgaps are direct and range between 5.0 and 5.5 eV for different configurations of hydroxyl functionalized graphene. An indirect GW bandgap of 6.50 eV was found in nitrile functionalized graphene while the methyl group functionalization leads to a direct bandgap with a value of 4.50 eV. Since in the two limiting cases of minimal and full coverage, the electronic structure changes drastically from a metal to a wide bandgap semiconductor, a series of intermediate states might be expected by tuning the amount of functionalization with these different groups.

  6. Chemoselective methylation of phenolic hydroxyl group prevents quinone methide formation and repolymerization during lignin depolymerization

    DOE PAGES

    Kim, Kwang Ho; Dutta, Tanmoy; Walter, Eric D.; ...

    2017-03-22

    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. Finally, this approach could be directed toward alteration of natural lignification processes to produce biomass that is more amenable to chemical depolymerization.

  7. Exchange of carbon-bound hydrogen atoms ortho to the hydroxyl group in tyrosine.

    PubMed

    Martin, R B; Morlino, V J

    1965-10-22

    The carbon-bound hydrogen atoms of tyrosine that exchange with solvent protons in strongly acid solutions at about 100 degrees C are not the methylene hydrogen atoms but a pair on the aromatic ring. Of the two pairs of protons on the aromatic ring, observed in the proton magnetic resonance spectra, the pair at higher field undergoes exchange in 2.4N DCI at 100 degrees C. Other hydrogen atoms, attached either to aliphatic or aromatic carbon atoms, exhibit no noticeable exchange under the same conditions. From a chemicalshift analysis the exchanging protons are assigned as those ortho to the hydroxyl group on the aromatic ring.

  8. A functionalizable polyester with free hydroxyl groups and tunable physiochemical and biological properties

    PubMed Central

    You, Zhengwei; Cao, Haiping; Gao, Jin; Shin, Paul H.; Day, Billy W.; Wang, Yadong

    2010-01-01

    Polyesters with free functional groups allow facile modifications with biomolecules, which can lead to versatile biomaterials that afford controlled interactions with cells and tissues. Efficient synthesis of functionalizable polyesters is still a challenge that greatly limits the availability and widespread applications of biofunctionalized synthetic polymers. Here we report a simple route to prepare a functionalizable polyester, poly(sebacoyl diglyceride) (PSeD) bearing free hydroxyl groups. The key synthetic step is an epoxide ring-opening polymerization, instead of the traditional polycondensation, that produces poly(glycerol sebacate) (PGS) [1]. PSeD has a more defined structure with mostly linear backbone, more free hydroxyl groups, higher molecular weight, and lower polydispersity than PGS. Crosslinking PSeD with sebacic acid yields a polymer five times tougher and more elastic than cured PGS. PSeD exhibits good cytocompatibility in vitro. Furthermore, functionalization by glycine proceeds with high efficiency. This versatile synthetic platform can offer a large family of biodegradable, functionalized polymers with tunable physiochemical and biological properties useful for a wide range of biomedical applications. PMID:20149441

  9. Niosomes containing hydroxyl additives as percutaneous penetration enhancers: effect on the transdermal delivery of sulfadiazine sodium salt.

    PubMed

    Muzzalupo, Rita; Tavano, Lorena; Lai, Francesco; Picci, Nevio

    2014-11-01

    The aim of this study was to improve the transdermal permeation of sulfadiazine sodium, employing synergistic combination of surfactants (in the form of niosomes) and additives with different number of hydroxylic groups, (following referred to as "alcohol"), as component of the bilayer. In particular the effect of different concentration of each alcohol (ethanol, propylene glycol or glycerol, from 5%, to 40% v/v) on niosomes size and distribution, drug entrapment efficiencies and ex vivo drug percutaneous permeation were evaluated, identifying formulations giving the best performances. The findings revealed that the presence of alcohol critically affect the physico-chemical properties of niosomes, with regards to dimensions, drug encapsulation and permeation. Vesicular size increased with the amount of alcohol and at the same alcohol concentration, follow the sequence ethanol>propylene glycol>glycerol. Loaded niosomes were larger than empty ones. Low E% values were found for ethanol, even less in propylene glycol and glycerol based samples, confirming that the chemical structure of the alcohol and its physico-chemical properties, affected the sulfadiazine entrapment efficiency. The comparative evaluation of percutaneous permeation profiles showed that the cumulative amount of permeated drug increases with alcohol concentration up to 20% v/v. Higher concentration (40% v/v) resulted in a strong decrease of the potential skin permeation. Best performances were obtained with glycerol. In all cases ex vivo sulfadiazine percutaneous permeations are controlled and improved respect to the corresponding free drug solutions and traditional niosomes used as controls.

  10. Comparison of Polyurethanes with Polyhydroxyurethanes: Effect of the Hydroxyl Group on Structure-Property Relationships

    NASA Astrophysics Data System (ADS)

    Leitsch, Emily K.; Lombardo, Vince M.; Scheidt, Karl A.; Torkelson, John M.

    2014-03-01

    Polyurethanes (PUs) are commonly synthesized by rapid step-growth polymerization through the reaction of a multifunctional alcohol with a polyisocyanate. PUs can be prepared at ambient conditions utilizing a variety of starting material molecular weights and backbones, resulting in highly tunable thermal and physical properties. The urethane linkages as well as the nanophase separated morphology attainable in PU materials lead to desirable properties including elastomeric character and adhesion. The isocyanate-based monomers used in the synthesis of traditional PUs have come under increasing regulatory pressure and thus inspired the investigation of alternative routes for the formation of PU materials. We examine an alternative route to synthesize PU- the reaction of five-membered cyclic carbonate with amines. This reaction results in the formation of a urethane linkage with an adjacent alcohol group. The effects of this hydroxyl group on the thermal and mechanical properties of the resulting polymer are investigated and compared with an analogous traditional PU system.

  11. Water growth on metals and oxides: binding, dissociation and role of hydroxyl groups

    SciTech Connect

    Salmeron, M.; Bluhm, H.; Tatarkhanov, M.; Ketteler, G.; Shimizu, T.K.; Mugarza, A.; Deng, Xingyi; Herranz, T.; Yamamoto, S.; Nilsson, A.

    2008-09-01

    The authors discuss the role of the presence of dangling H bonds from water or from surface hydroxyl species on the wetting behavior of surfaces. Using Scanning Tunneling and Atomic Force Microscopies, and Photoelectron Spectroscopy, they have examined a variety of surfaces, including mica, oxides, and pure metals. They find that in all cases, the availability of free, dangling H-bonds at the surface is crucial for the subsequent growth of wetting water films. In the case of mica electrostatic forces and H-bonding to surface O atoms determine the water orientation in the first layer and also in subsequent layers with a strong influence in its wetting characteristics. In the case of oxides like TiO{sub 2}, Cu{sub 2}O, SiO{sub 2} and Al{sub 2}O{sub 3}, surface hydroxyls form readily on defects upon exposure to water vapor and help nucleate the subsequent growth of molecular water films. On pure metals, such as Pt, Pd, and Ru, the structure of the first water layer and whether or not it exhibits dangling H bonds is again crucial. Dangling H-bonds are provided by molecules with their plane oriented vertically, or by OH groups formed by the partial dissociation of water. By tying the two II atoms of the water molecules into strong H-bonds with pre-adsorbed O on Ru can also quench the wettability of the surface.

  12. Influence of Molecular Hydrogen Diffusion on Concentration and Distribution of Hydroxyl Groups in Silica Fibers

    NASA Astrophysics Data System (ADS)

    Plotnichenko, Victor G.; Ivanov, Gennadii A.; Kryukova, Elena B.; Aksenov, Vyacheslav A.; Sokolov, Vyacheslav O.; Isaev, Victor A.

    2005-01-01

    To study the hydroxyl (OH)-group contamination mechanisms in silica-based optical fibers, the transmission spectra of substrate tubes and fiber preforms made from various types of silica glasses ("Suprasil F-300," KS-4V, and KUVI) are measured by the method of infrared Fourier spectroscopy in a wavelength region of 2-5 μm. Due to the intensity of the fundamental OH stretching vibration band, the absorption coefficient, concentration, and a distribution profile of OH groups across the aforesaid samples are calculated. It is found that using an oxyhydrogen burner in the modified chemical vapor deposition (MCVD) process of manufacturing preforms and fiber drawing, the main source of impurity OH groups can be the molecular hydrogen H2 penetrating into glass much deeper than the OH groups diffusing from the substrate tube surface. A simple model explaining the formation and diffusion of OH groups into a fiber core and cladding is proposed. It is shown that heating tubes and preforms in a flame of oxyhydrogen burner during fiber fabrication causes a significant OH-group content growth (almost by two orders of magnitude) near to the outer preform surface. Using substrate tubes made from Suprasil F-300 glass, optical fibers are fabricated having a silica core and fluorosilicate reflecting cladding with optical losses of 0.3 dB/km at 1.55 μm and a refractive-index difference between core and cladding ~ 1 . 10^-2.

  13. IDENTIFICATION AND QUANTIFICATION OF AEROSOL POLAR OXYGENATED COMPOUNDS BEARING CARBOXYLIC AND/OR HYDROXYL GROUPS. 1. METHOD DEVELOPMENT

    EPA Science Inventory

    In this study, a new analytical technique was developed for the identification and quantification of multi-functional compounds containing simultaneously at least one hydroxyl or one carboxylic group, or both. This technique is based on derivatizing first the carboxylic group(s) ...

  14. Water Contact Angle Dependence with Hydroxyl Functional Groups on Silica Surfaces under CO2 Sequestration Conditions.

    PubMed

    Chen, Cong; Zhang, Ning; Li, Weizhong; Song, Yongchen

    2015-12-15

    Functional groups on silica surfaces under CO2 sequestration conditions are complex due to reactions among supercritical CO2, brine and silica. Molecular dynamics simulations have been performed to investigate the effects of hydroxyl functional groups on wettability. It has been found that wettability shows a strong dependence on functional groups on silica surfaces: silanol number density, space distribution, and deprotonation/protonation degree. For neutral silica surfaces with crystalline structure (Q(3), Q(3)/Q(4), Q(4)), as silanol number density decreases, contact angle increases from 33.5° to 146.7° at 10.5 MPa and 318 K. When Q(3) surface changes to an amorphous structure, water contact angle increases 20°. Water contact angle decreases about 12° when 9% of silanol groups on Q(3) surface are deprotonated. When the deprotonation degree increases to 50%, water contact angle decreases to 0. The dependence of wettability on silica surface functional groups was used to analyze contact angle measurement ambiguity in literature. The composition of silica surfaces is complicated under CO2 sequestration conditions, the results found in this study may help to better understand wettability of CO2/brine/silica system.

  15. Addition polyimide adhesives containing various end groups

    NASA Technical Reports Server (NTRS)

    Saint Clair, A. K.; Saint Clair, T. L.

    1982-01-01

    Addition polyimode oligomers have been synthesized from 3,3 prime, 4,4 prime-benzophenone tetracarboxylic acid dianhydride and 3,3 prime-methylenedianiline using a variety of latent crosslinking groups as end-caps. The nominal 1300 molecular weight imide prepolymers were isolated and characterized for solubility in amide, chlorinated and ether solvents, melt-flow and cure properties, glass transition temperature, and thermal stability on heating in an air atmosphere. Adhesive strengths of the polyimides were obtained both at ambient and elevated temperatures before and after aging at 232 C. Properties of the novel addition polyimides were compared to a known nadic end-capped adhesive, LARC-13.

  16. Regioselective inversion of the hydroxyl group in D-ribo-phytosphingosine via a cyclic sulfate and bis-sulfonate intermediate.

    PubMed

    Lee, Yun Mi; Baek, Dong Jae; Lee, Seokwoo; Kim, Deukjoon; Kim, Sanghee

    2011-01-21

    The selective synthesis of D-xylo- and D-lyxo-phytosphingosines from commercially available D-ribo-phytosphingosine is described. Thermolysis of the N-carbonyl protected cyclic sulfate led to an inversion of configuration of the proximal hydroxyl group to give the xylo-isomer, whereas the corresponding bis-sulfonate resulted in an inversion of configuration of the distal hydroxyl group to give the lyxo-isomer. This study allowed the comparison between a cyclic sulfate and a bis-sulfonate in an intramolecular substitution reaction involving a carbonyl oxygen nucleophile.

  17. Unique lead adsorption behavior of activated hydroxyl group in two-dimensional titanium carbide.

    PubMed

    Peng, Qiuming; Guo, Jianxin; Zhang, Qingrui; Xiang, Jianyong; Liu, Baozhong; Zhou, Aiguo; Liu, Riping; Tian, Yongjun

    2014-03-19

    The functional groups and site interactions on the surfaces of two-dimensional (2D) layered titanium carbide can be tailored to attain some extraordinary physical properties. Herein a 2D alk-MXene (Ti3C2(OH/ONa)(x)F(2-x)) material, prepared by chemical exfoliation followed by alkalization intercalation, exhibits preferential Pb(II) sorption behavior when competing cations (Ca(II)/Mg(II)) coexisted at high levels. Kinetic tests show that the sorption equilibrium is achieved in as short a time as 120 s. Attractively, the alk-MXene presents efficient Pb(II) uptake performance with the applied sorption capacities of 4500 kg water per alk-MXene, and the effluent Pb(II) contents are below the drinking water standard recommended by the World Health Organization (10 μg/L). Experimental and computational studies suggest that the sorption behavior is related to the hydroxyl groups in activated Ti sites, where Pb(II) ion exchange is facilitated by the formation of a hexagonal potential trap.

  18. Curable liquid hydrocarbon prepolymers containing hydroxyl groups and process for producing same

    NASA Technical Reports Server (NTRS)

    Rhein, R. A.; Ingham, J. D. (Inventor)

    1978-01-01

    Production of hydroxyl containing curable liquid hydrocarbon prepolymers by ozonizing a high molecular weight saturated hydrocarbon polymer such as polyisobutylene or ethylene propylene rubber is discussed. The ozonized material is reduced using reducing agents, preferably diisobutyl aluminum hydride, to form the hydroxyl containing liquid prepolymers having a substantially lower molecular weight than the parent polymer. The resulting curable liquid hydroxyl containing prepolymers can be poured into a mold and readily cured, with reactants such as toluene diisocyanate, to produce highly stable elastomers having a variety of uses such as binders for solid propellants.

  19. Enumeration of sugars and sugar alcohols hydroxyl groups by aqueous-based acetylation and MALDI-TOF mass spectrometry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A method is described for enumerating hydroxyl groups on analytes in aqueous media is described, and applied to some common polyalcohols (erythritol, mannitol, and xylitol) and selected carbohydrates. The analytes were derivatized in water with vinyl acetate in presence of sodium phosphate buffer. ...

  20. Distribution of Hydroxyl Groups in Kukersite Shale Oil: Quantitative Determination Using Fourier Transform Infrared (FT-IR) Spectroscopy.

    PubMed

    Baird, Zachariah Steven; Oja, Vahur; Järvik, Oliver

    2015-05-01

    This article describes the use of Fourier transform infrared (FT-IR) spectroscopy to quantitatively measure the hydroxyl concentrations among narrow boiling shale oil cuts. Shale oil samples were from an industrial solid heat carrier retort. Reference values were measured by titration and were used to create a partial least squares regression model from FT-IR data. The model had a root mean squared error (RMSE) of 0.44 wt% OH. This method was then used to study the distribution of hydroxyl groups among more than 100 shale oil cuts, which showed that hydroxyl content increased with the average boiling point of the cut up to about 350 °C and then leveled off and decreased.

  1. Role of hydroxyl groups on the stability and catalytic activity of Au clusters on rutile surface

    SciTech Connect

    Kent, Paul R

    2011-01-01

    Hydroxyls are present as surface terminations of transition metal oxides under ambient conditions and may modify the properties of supported catalysts. We perform first-principles density functional theory calculations to investigate the role of hydroxyls on the catalytic activity of supported gold clusters on TiO{sub 2} (rutile). We find that they have a long-range effect increasing the adhesion of gold clusters on rutile. While hydroxyls make one gold atom more electronegative, a more complex charge-transfer scenario is observed on larger clusters which are important for catalytic applications. This enhances the molecular adsorption and coadsorption energies of CO and O{sub 2}, thereby increasing the catalytic activity of gold clusters for CO oxidation, consistent with reported experiments. Hydroxyls at the interface between gold and rutile surface are most important to this process, even when not directly bound to gold. As such, accurate models of catalytic processes on gold and other catalysts should include the effect of surface hydroxyls.

  2. Edge-Hydroxylated Boron Nitride Nanosheets as an Effective Additive to Improve the Thermal Response of Hydrogels.

    PubMed

    Xiao, Feng; Naficy, Sina; Casillas, Gilberto; Khan, Majharul H; Katkus, Tomas; Jiang, Lei; Liu, Huakun; Li, Huijun; Huang, Zhenguo

    2015-11-25

    Upon flowing hot steam over hexagonal boron nitride (h-BN) bulk powder, efficient exfoliation and hydroxylation of BN occur simultaneously. Through effective hydrogen bonding with water and N-isopropylacrylamide, edge-hydroxylated BN nanosheets dramatically improve the dimensional change and dye release of this temperature-sensitive hydrogel and thereby enhance its efficacy in bionic, soft robotic, and drug-delivery applications.

  3. Synthesis and biological activities of NB-506 analogues: Effects of the positions of two hydroxyl groups at the indole rings.

    PubMed

    Ohkubo, M; Nishimura, T; Honma, T; Nishimura, I; Ito, S; Yoshinari, T; Suda, H A; Morishima, H; Nishimura, S

    1999-12-06

    In the course of a study of 6-N-amino-substituted analogues of NB-506 (1), a more potent anticancer drug, J-109,404 (2), in which the formyl group of NB-506 was replaced with a 1,3-dihydroxypropane group, was reported. A study of further modification in the positions of two hydroxyl groups at the indole rings of 2 resulted in the discovery of a 2,10-dihydroxy analogue, J-107,088 (3), which is a promising anticancer agent with a broader therapeutic window than J-109,404.

  4. Theoretical study of the hydroxyl radical addition to uracil and photochemistry of the formed U6OH• adduct.

    PubMed

    Francés-Monerris, Antonio; Merchán, Manuela; Roca-Sanjuán, Daniel

    2014-03-20

    Hydroxyl radical ((•)OH) is produced in biological systems by external or endogenous agents. It can damage DNA/RNA by attacking pyrimidine nucleobases through the addition to the C5═C6 double bond. The adduct resulting from the attachment at the C5 position prevails in the experimental measurements, although the reasons for this preference remain unclear. The first aim of this work is therefore to shed light on the comprehension of this important process. Thus, the thermal (•)OH addition to the C5═C6 double bond of uracil has been studied theoretically by using DFT, MP2, and the multiconfigurational CASPT2//CASSCF methodologies. The in-vacuo results obtained with the latter protocol plus the analysis of solvent effects support the experimental observation. A significant lower barrier height is predicted for the C5 pathway with respect to that of the C6 route. In contrast to the C5 adduct, the C6 adduct is able to absorb visible light. Hence, the second aim of the work is to study the photochemistry of this species using the CASPT2//CASSCF methodology within the framework of the photochemical reaction path approach (PRPA). The nonradiative decay to the ground state of this compound has been characterized. A photoreactive character is predicted for the C6 adduct in the excited states according to the presence of excited-state minima along the main decay channel. Finally, a new mechanism of photodissociation has been explored, which implies the photoinduced regeneration of the canonical nucleobase by irradiating with visible light, being therefore relevant in RNA protection against damage by reactive oxygen species.

  5. Role of diaxial versus diequatorial hydroxyl groups in the tumorigenic activity of a benzo[a]pyrene bay-region diol epoxide.

    PubMed Central

    Chang, R L; Wood, A W; Conney, A H; Yagi, H; Sayer, J M; Thakker, D R; Jerina, D M; Levin, W

    1987-01-01

    Tumorigenic activities of the (7R,8S,9S,10R)-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydro derivatives of benzo[a]pyrene [(+)-B[a]P diol epoxide-2] and 6-fluorobenzo[a]pyrene (6-FB[a]P diol epoxide-2) were evaluated in newborn CD-1 mice. A total dose of 14 nmol of either diol epoxide was administered to preweanling mice, and tumorigenic activity was determined when the mice were 32 to 36 weeks old. At the termination of the study, 13% of solvent-treated control mice had developed lung tumors with an average of 0.19 tumor per mouse. No other tumors were observed in control animals. (+)-B[a]P diol epoxide-2 induced pulmonary tumors in 60% of the mice with an average of 1.9 tumors per mouse, and 14% of the male mice developed hepatic tumors with an average of 0.18 tumor per mouse. In contrast, 6-FB[a]P diol epoxide-2 had no significant tumorigenic activity at the 14-nmol dose. Although both bay-region diol epoxides have the same absolute configuration, (7R,8S,9S,10R), the hydroxyl groups of (+)-B[a]P diol epoxide-2 prefer the pseudoequatorial conformation whereas the hydroxyl groups of 6-FB[a]P diol epoxide-2 prefer the pseudoaxial conformation. The tumorigenicity results reported here are the first direct demonstration that conformation of the hydroxyl groups in a bay-region diol epoxide, in addition to the documented effect of absolute configuration, is an important determinant in the tumorigenic activity of these ultimate carcinogens. PMID:3479808

  6. Structure-activity relationships of nonisomerizable derivatives of tamoxifen: importance of hydroxyl group and side chain positioning for biological activity.

    PubMed

    Murphy, C S; Parker, C J; McCague, R; Jordan, V C

    1991-03-01

    other substitutions produced either estrogenic compounds or less potent antiestrogens. The hydroxyl group appears to be critical to locate the alkyl aminoethoxy side chain in the correct position in the steroid-binding site to block estrogen action. Novel antiestrogens were identified that could have been predicted based upon earlier drug-receptor models for the ER.

  7. Chain structures of surface hydroxyl groups formed via line oxygen vacancies on TiO2(110) surfaces studied using noncontact atomic force microscopy.

    PubMed

    Namai, Yoshimichi; Matsuoka, Osamu

    2005-12-22

    Structures of surface hydroxyl groups arranged on a reduced TiO2(110) surface that had line oxygen vacancies were studied using noncontact atomic force microscopy (NC-AFM). NC-AFM results revealed that by increasing the density of oxygen vacancies on the TiO2(110) surface, line oxygen vacancies were formed by removal of oxygen atoms in a bridge oxygen row on the TiO2(110) surface. After the TiO2(110) surface with the line oxygen vacancies was exposed to water, the surface showed hydroxyl chain structures that were composed of hydroxyl groups linearly arranged in a form of two rows on the line oxygen vacancies and on a neighboring bridge oxygen row. In-situ NC-AFM measurements of these surfaces exposed to water at room temperature revealed that hydroxyl chain structures were formed at the line oxygen vacancy. Annealing above 500 K was sufficient to remove the hydroxyl chain structures on the TiO2(110) surface and allowed line oxygen vacancies to reappear on the surface. The line oxygen vacancies are active sites for water dissociation. In conclusion, the formation of the hydroxyl chain structure suggests that the surface hydroxyl groups on a TiO2(110) surface can be controlled by preparing oxygen vacancy structures on the surface.

  8. Effect of alkyl chain length and hydroxyl group functionalization on the surface properties of imidazolium ionic liquids.

    PubMed

    Pensado, Alfonso S; Costa Gomes, Margarida F; Canongia Lopes, José N; Malfreyt, Patrice; Pádua, Agílio A H

    2011-08-14

    Properties of the surface of ionic liquids, such as surface tension, ordering, and charge and density profiles, were studied using molecular simulation. Two types of modification in the molecular structure of imidazolium cations were studied: the length of the alkyl side chain and the presence of a polar hydroxyl group at the end of the side chain. Four ionic liquids were considered: 1-ethyl-3-methylimidazolium tetrafluoroborate, [C(2)C(1)im][BF(4)]; 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate, [C(2)OHC(1)im][BF(4)]; 1-octyl-3-methylimidazolium tetrafluoroborate, [C(8)C(1)im][BF(4)] and 1-(8-hydroxyoctyl)-3-methylimidazolium tetrafluoroborate, [C(8)OHC(1)im][BF(4)]. The surface tension was calculated using both mechanical and thermodynamic definitions, with consistent treatment of the long-range corrections. The simulations reproduce the available experimental values of surface tension with a maximum deviation of ±10%. This energetic characterization of the interface is completed by microscopic structural analysis of orientational ordering at the interface and density profiles along the direction normal to the interface. The presence of the hydroxyl group modifies the local structure at the interface, leading to a less organized liquid phase. The results allow us to relate the surface tension to the structural ordering at the liquid-vacuum interface.

  9. Number of free hydroxyl groups on bile acid phospholipids determines the fluidity and hydration of model membranes.

    PubMed

    Sreekanth, Vedagopuram; Bajaj, Avinash

    2013-10-10

    Interactions of synthetic phospholipids with model membranes determines the drug release capabilities of phospholipid vesicles at diseased sites. We performed 1,6-diphenyl-1,3,5-hexatriene (DPH)-based fluorescence anisotropy, Laurdan-based membrane hydration, and differential scanning calorimetry (DSC) studies to cognize the interactions of three bile acid phospholipids, lithocholic acid-phosphocholine (LCA-PC), deoxycholic acid-phosphocholine (DCA-PC), and cholic acid-phosphocholine (CA-PC) with model membranes. These studies revealed that bile acid phospholipids increases membrane fluidity in DCA-PC > CA-PC > LCA-PC order, indicating that induction of membrane fluidity is contingent on the number and positioning of free hydroxyl groups on bile acids. Similarly, DCA-PC causes maximum membrane perturbations due to the presence of a free hydroxyl group, whereas LCA-PC induces gel phase in membranes due to hydrophobic bile acid acyl chain interactions. These DCA-PC-induced membrane perturbations induce a drastic decrease in phase transition temperature (Tm) as determined by calorimetric studies, whereas doping of LCA-PC causes phase transition broadening without change in Tm. Doping of CA-PC induces membrane perturbations and membrane hydration like DCA-PC but sharpening of phase transition at higher doping suggests self-association of CA-PC molecules. Therefore these differential mode of interactions between bile acid phospholipids and model membranes would help in the future for their use in drug delivery.

  10. Fluoride removal mechanism of bayerite/boehmite nanocomposites: roles of the surface hydroxyl groups and the nitrate anions.

    PubMed

    Jia, Yong; Zhu, Bai-Sheng; Jin, Zhen; Sun, Bai; Luo, Tao; Yu, Xin-Yao; Kong, Ling-Tao; Liu, Jin-Huai

    2015-02-15

    Three-dimensional feather like bayerite/boehmite nanocomposites were synthesized by a facile one-pot hydrothermal method. The obtained nanocomposites were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption-desorption isotherms. The removal properties toward fluoride were investigated, including adsorption kinetics, adsorption isotherm, and influences of pH and coexisting anions. The maximal adsorption capacity was 56.80 mg g(-1) at pH 7.0, which is favorable compared to those reported in the literature using other adsorbents. The coexisting of sulfate and bicarbonate inhibited the fluoride removal especially at high concentrations. Furthermore, the removal mechanism was revealed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The results suggest that both of the surface hydroxyl groups and the nitrate anions were participated in the ion-exchange process.

  11. Highly Active Supported Pt Nanocatalysts Synthesized by Alcohol Reduction towards Hydrogenation of Cinnamaldehyde: Synergy of Metal Valence and Hydroxyl Groups.

    PubMed

    Wang, Yanyan; He, Wanhong; Wang, Liren; Yang, Junjiao; Xiang, Xu; Zhang, Bing; Li, Feng

    2015-07-01

    The hydrogenation of α,β-unsaturated aldehydes to allylic alcohols or saturated aldehydes provides a typical example to study the catalytic effect on structure-sensitive reactions. In this work, supported platinum nanocatalysts over hydrotalcite were synthesized by an alcohol reduction method. The Pt catalyst prepared by the reduction with a polyol (ethylene glycol) outperforms those prepared with ethanol and methanol in the hydrogenation of cinnamaldehyde. The selectivity towards the C=O bond is the highest over the former, although its mean size of Pt particles is the smallest. The hydroxyl groups on hydrotalcite could act as an internally accessible promoter to enhance the selectivity towards the C=O bond. The optimal Pt catalyst showed a high activity with an initial turnover frequency (TOF) of 2.314 s(-1). This work unveils the synergic effect of metal valence and in situ promoter on the chemoselective hydrogenation, which could open up a new direction in designing hydrogenation catalysts.

  12. Influence of Hydroxyl Group Position and Temperature on Thermophysical Properties of Tetraalkylammonium Hydroxide Ionic Liquids with Alcohols

    PubMed Central

    Attri, Pankaj; Baik, Ku Youn.; Venkatesu, Pannuru; Kim, In Tae; Choi, Eun Ha

    2014-01-01

    In this work, we have explored the thermophysical properties of tetraalkylammonium hydroxide ionic liquids (ILs) such as tetrapropylammonium hydroxide (TPAH) and tetrabutylammonium hydroxide (TBAH) with isomers of butanol (1-butanol, 2-butanol and 2-methyl-2-propanol) within the temperature range 293.15–313.15 K, with interval of 5 K and over the varied concentration range of ILs. The molecular interactions between ILs and butanol isomers are essential for understanding the function of ILs in related measures and excess functions are sensitive probe for the molecular interactions. Therefore, we calculated the excess molar volume (VE) and the deviation in isentropic compressibility (Δκs) using the experimental values such as densities (ρ) and ultrasonic sound velocities (u) that are measured over the whole compositions range at five different temperatures (293.15, 298.15, 303.15, 308.15 and 313.15 K) and atmospheric pressure. These excess functions were adequately correlated by using the Redlich–Kister polynomial equation. It was observed that for all studied systems, the VE and Δκs values are negative for the whole composition range at 293.15 K. And, the excess function follows the sequence: 2-butanol>1-butanol>2-methyl-2-propanol, which reveals that (primary or secondary or tertiary) position of hydroxyl group influence the magnitude of interactions with ILs. The negative values of excess functions are contributions from the ion-dipole interaction, hydrogen bonding and packing efficiency between the ILs and butanol isomers. Hence, the position of hydroxyl group plays an important role in the interactions with ILs. The hydrogen bonding features between ILs and alcohols were analysed using molecular modelling program by using HyperChem 7. PMID:24489741

  13. Structure-activity relationships among the kanamycin aminoglycosides: role of ring I hydroxyl and amino groups.

    PubMed

    Salian, Sumantha; Matt, Tanja; Akbergenov, Rashid; Harish, Shinde; Meyer, Martin; Duscha, Stefan; Shcherbakov, Dmitri; Bernet, Bruno B; Vasella, Andrea; Westhof, Eric; Böttger, Erik C

    2012-12-01

    The kanamycins form an important subgroup of the 4,6-disubstituted 2-deoxystreptamine aminoglycoside antibiotics, comprising kanamycin A, kanamycin B, tobramycin, and dibekacin. These compounds interfere with protein synthesis by targeting the ribosomal decoding A site, and they differ in the numbers and locations of amino and hydroxy groups of the glucopyranosyl moiety (ring I). We synthesized kanamycin analogues characterized by subtle variations of the 2' and 6' substituents of ring I. The functional activities of the kanamycins and the synthesized analogues were investigated (i) in cell-free translation assays on wild-type and mutant bacterial ribosomes to study drug-target interaction, (ii) in MIC assays to assess antibacterial activity, and (iii) in rabbit reticulocyte translation assays to determine activity on eukaryotic ribosomes. Position 2' forms an intramolecular H bond with O5 of ring II, helping the relative orientations of the two rings with respect to each other. This bond becomes critical for drug activity when a 6'-OH substituent is present.

  14. Additive Bilingualism, Schooling, and Special Education: A Minority Group Perspective.

    ERIC Educational Resources Information Center

    Landry, R.

    1987-01-01

    The effect of schooling on the acquisition of an additive type of bilingualism is examined, focusing on additive bilingualism's relation to the ethnolinguistic vitality of linguistic groups and contributions of individual networks of linguistic contacts. A special and regular education merger without domination by a single cultural perspective is…

  15. Hydroxyl ion addition to one-electron oxidized thymine: Unimolecular interconversion of C5 to C6 OH-adducts

    PubMed Central

    Adhikary, Amitava; Kumar, Anil; Heizer, Alicia N.; Palmer, Brian J.; Pottiboyina, Venkata; Liang, Yong; Wnuk, Stanislaw F.; Sevilla, Michael D.

    2013-01-01

    In this work, addition of OH− to one-electron oxidized thymidine (dThd) and thymine nucleotides in basic aqueous glasses is investigated. At pHs ca. 9–10 where the thymine base is largely deprotonated at N3, one-electron oxidation of the thymine base by Cl2•− at ca. 155 K results in formation of a neutral thyminyl radical, T(−H)•. Assignment to T(−H)• is confirmed by employing 15N substituted 5'-TMP. At pH ≥ ca. 11.5, formation of the 5-hydroxythymin-6-yl radical, T(5OH)•, is identified as a metastable intermediate produced by OH− addition to T(−H)• at C5 at ca. 155 K. Upon further annealing to ca. 170 K, T(5OH)• readily converts to the 6-hydroxythymin-5-yl radical, T(6OH)•. One-electron oxidation of N3-methyl-thymidine (N3-Me-dThd) by Cl2•− at ca. 155 K produces the cation radical (N3-Me-dThd•+) for which we find a pH dependent competition between deprotonation from the methyl group at C5 and addition of OH− to C5. At pH 7 the 5-methyl deprotonated species is found; however, at pH ca. 9, N3-Me-dThd•+ produces T(5OH)• that on annealing up to 180 K forms T(6OH)•. Through use of deuterium substitution at C5' and on the thymine base, i.e., specifically employing [5',5”-D,D]-5'-dThd, [5',5”-D,D]-5'-TMP, [CD3]-dThd and [CD3,6D]-dThd, we find unequivocal evidence for T(5OH)• formation and its conversion to T(6OH)•. The addition of OH− to the C5 position in T(−H)• and N3-Me-dThd•+ is governed by spin and charge localization. DFT calculations predict that the conversion of the “reducing” T(5OH)• to the “oxidizing” T(6OH)• occurs by a unimolecular OH group transfer from C5 to C6 in the thymine base. The T(5OH)• to T(6OH)• conversion is found to occur more readily for deprotonated dThd and its nucleotides than for N3-Me-dThd. In agreement, calculations predict that the deprotonated thymine base has a lower energy barrier (ca. 6 kcal/mol) for OH transfer than its corresponding N3-protonated thymine

  16. Stabilization of hydroxyl-group-terminated SERS-marker molecules on microAg particles by silanization.

    PubMed

    Xia, Lixin; Kim, Nam Hoon; Kim, Kwan

    2007-02-01

    Micrometer-sized Ag (microAg) powders are very efficient substrates for both the infrared and Raman spectroscopic characterization of molecular adsorbates assembled on silver. In particular, the Raman spectrum of organic monolayers on microAg powders is a surface-enhanced Raman scattering (SERS) spectrum. To use microAg powders as a core material for constructing molecular sensing/recognition units operating via SERS, it is first necessary to stabilize the SERS-marker molecules that are directly in contact with the microAg powders. One promising strategy is the fabrication of silica shells onto SERS-marker molecules, and herein we demonstrate its feasibility by choosing 4-mercaptophenol (4-MPH) as a model SERS-marker molecule. Due to the presence of the hydroxyl group of 4-MPH, silica was readily deposited onto microAg particles by the base-catalyzed hydrolysis of tetraethyl orthosilicate, and its subsequent condensation, to form a cagelike structure. The formation of silica shells was confirmed with infrared, Raman, and X-ray photoelectron spectroscopy, coupled with field emission scanning electron microscopy. We were able to tune the thickness of silica shells simply by varying the silanization reaction time.

  17. Horseradish peroxidase-catalyzed formation of hydrogels from chitosan and poly(vinyl alcohol) derivatives both possessing phenolic hydroxyl groups.

    PubMed

    Sakai, Shinji; Khanmohammadi, Mehdi; Khoshfetrat, Ali Baradar; Taya, Masahito

    2014-10-13

    Horseradish peroxidase-catalyzed cross-linking was applied to prepare hydrogels from aqueous solutions containing chitosan and poly(vinyl alcohol) derivatives both possessing phenolic hydroxyl groups (denoted as Ph-chitosan and Ph-PVA, respectively). Comparing the hydrogels prepared from the solution of 1.0% (w/v) Ph-chitosan and 3.0% (w/v) Ph-PVA and that of 3.0% (w/v) Ph-chitosan and 1.0% (w/v) Ph-PVA, the gelation time of the former hydrogel was 47 s, while was 10s longer than that of the latter one. The breaking point for the former hydrogel under stretching (114% strain) was approximately twice larger than that for the latter one. The swelling ratio of the former hydrogel in saline was about half of the latter one. Fibroblastic cells did not adhere on the former hydrogel but adhered and spread on the latter one. The growth of Escherichia coli cells was fully suppressed on the latter hydrogel during 48 h cultivation.

  18. Plasma enhanced chemical vapour deposition of silica onto Ti: Analysis of surface chemistry, morphology and functional hydroxyl groups.

    PubMed

    Szili, Endre J; Kumar, Sunil; Smart, Roger St C; Lowe, Rachel; Saiz, Eduardo; Voelcker, Nicolas H

    2008-07-15

    Previously, we have developed and characterised a procedure for the deposition of thin silica films by a plasma enhanced chemical vapour deposition (PECVD) procedure using tetraethoxysilane (TEOS) as the main precursor. We have used the silica coatings for improving the corrosion resistance of metals and for enhancing the bioactivity of biomedical metallic implants. Recently, we have been fine-tuning the PECVD method for producing high quality and reproducible PECVD-silica (PECVD-Si) coatings on metals, primarily for biomaterial applications. In order to understand the interaction of the PECVD-Si coatings with biological species (such as proteins and cells), it is important to first analyse the properties of the silica films deposited using the optimised parameters. Therefore, this current investigation was carried out to analyse the characteristic features of PECVD-Si deposited on Ti substrates (PECVD-Si-Ti). We determined that the PECVD-Si coatings on Ti were conformal to the substrate surface, strongly adhered to the underlying substrate and were resistant to delamination. The PECVD-Si surface was composed of stoichiometric SiO(2), showed a low carbon content (below 10 at.%) and was very hydrophilic (contact angle <10°). Finally, we also showed that the PECVD-Si coatings contain functional hydroxyl groups.

  19. Possible mechanism of structural incorporation of Al into diatomite during the deposition process I. Via a condensation reaction of hydroxyl groups.

    PubMed

    Liu, Dong; Yu, Wenbin; Deng, Liangliang; Yuan, Weiwei; Ma, Lingya; Yuan, Peng; Du, Peixin; He, Hongping

    2016-01-01

    The structural incorporation of aluminium (Al) into diatomite is investigated by preparing several Al-diatomite composites by loading an Al precursor, hydroxyl aluminum polymer (Al13), onto the surface of diatomite and heating at various temperatures. The results indicate that Al was incorporated and implanted into the structure of diatomite by the condensation reaction of the hydroxyl groups of Al13 and diatomite, and the Si-O-Al(OH) groups were formed during the condensation reaction. Al incorporation by the condensation reaction of hydroxyl groups of Al13 with single silanols of diatomite occurred more readily than that with geminal silanols. The Al incorporation increased solid acidity of diatomite after Al incorporation. The acidity improvement was various for different types of acid sites, depending on the preparation temperature of the Al-incorporated diatomite. Both Brønsted and Lewis acid sites increased greatly after heating at 250 and 350 °C, but only L acid sites significantly improved after heating at 500 °C. These results demonstrate that the structural incorporation of Al(3+) ions into diatomite can occur by the condensation reaction of the hydroxyl groups of the Al precursors and diatomite. Moreover, the rich solid acid sites of Al-incorporated diatomite show its promising application as a solid acid catalyst.

  20. Energies and 2'-Hydroxyl Group Orientations of RNA Backbone Conformations. Benchmark CCSD(T)/CBS Database, Electronic Analysis, and Assessment of DFT Methods and MD Simulations.

    PubMed

    Mládek, Arnošt; Banáš, Pavel; Jurečka, Petr; Otyepka, Michal; Zgarbová, Marie; Šponer, Jiří

    2014-01-14

    Sugar-phosphate backbone is an electronically complex molecular segment imparting RNA molecules high flexibility and architectonic heterogeneity necessary for their biological functions. The structural variability of RNA molecules is amplified by the presence of the 2'-hydroxyl group, capable of forming multitude of intra- and intermolecular interactions. Bioinformatics studies based on X-ray structure database revealed that RNA backbone samples at least 46 substates known as rotameric families. The present study provides a comprehensive analysis of RNA backbone conformational preferences and 2'-hydroxyl group orientations. First, we create a benchmark database of estimated CCSD(T)/CBS relative energies of all rotameric families and test performance of dispersion-corrected DFT-D3 methods and molecular mechanics in vacuum and in continuum solvent. The performance of the DFT-D3 methods is in general quite satisfactory. The B-LYP-D3 method provides the best trade-off between accuracy and computational demands. B3-LYP-D3 slightly outperforms the new PW6B95-D3 and MPW1B95-D3 and is the second most accurate density functional of the study. The best agreement with CCSD(T)/CBS is provided by DSD-B-LYP-D3 double-hybrid functional, although its large-scale applications may be limited by high computational costs. Molecular mechanics does not reproduce the fine energy differences between the RNA backbone substates. We also demonstrate that the differences in the magnitude of the hyperconjugation effect do not correlate with the energy ranking of the backbone conformations. Further, we investigated the 2'-hydroxyl group orientation preferences. For all families, we conducted a QM and MM hydroxyl group rigid scan in gas phase and solvent. We then carried out set of explicit solvent MD simulations of folded RNAs and analyze 2'-hydroxyl group orientations of different backbone families in MD. The solvent energy profiles determined primarily by the sugar pucker match well with the

  1. A practical catalytic asymmetric addition of alkyl groups to ketones.

    PubMed

    García, Celina; LaRochelle, Lynne K; Walsh, Patrick J

    2002-09-18

    Many catalysts will promote the asymmetric addition of alkylzinc reagents to aldehydes. In contrast, there are no reports of additions to ketones that are both general and highly enantioselective. We describe herein a practical catalytic asymmetric addition of ethyl groups to ketones. The catalyst is derived from reaction of camphor sulfonyl chloride and trans-1,2-diaminocyclohexane. The resulting diketone is reduced with NaBH4 to give the C2-symmetric exo diastereomer. Use of this ligand with titanium tetraisopropoxide and dialkylzinc at room temperature results in enantioselective addition of the alkyl group to the ketone. The resulting tertiary alcohols are isolated with high enantiomeric excess (all cases give greater than 87% ee, except one). The reaction has been run with 37 mmol (5 g) 3-methylacetophenone and 2 mol % catalyst to afford 73% yield of the resulting tertiary alcohol with 99% ee.

  2. Effect of replacing a hydroxyl group with a methyl group on arsenic (V) species adsorption on goethite (alpha-FeOOH).

    PubMed

    Zhang, J S; Stanforth, R S; Pehkonen, S O

    2007-02-01

    Arsenate and methylated arsenicals, such as dimethylarsinate (DMA) and monomethylarsonate (MMA), are being found with increasing frequency in natural water systems. The mobility and bioavailability of these arsenic species in the environment are strongly influenced by their interactions with mineral surface, especially iron and aluminum oxides. Goethite (alpha-FeOOH), one of the most abundant ferric (hydr)oxides in natural systems, has a high retention capacity for arsenic species. Unfortunately, the sorption mechanism for the species is not completely understood, which limits our ability to model their behavior in natural systems. The purpose of this study is to investigate the effect of replacing a hydroxyl group with a methyl group on the adsorption behaviors of arsenic (V) species using adsorption edges, the influence of the background electrolyte on arsenic adsorption, and their effect on the zeta potential of goethite. The affinity of the three species to the goethite surface decreases in the order of AsO4=MMA>DMA. The uptake of DMA and MMA is independent of the concentration of background electrolyte, indicating that both species form inner-sphere complexes on the goethite surface and the most charge of adsorbed DMA and MMA locates at the surface plane. Arsenate uptake increases with increasing concentrations of background electrolyte at pH above 4, possibly due to that the charge of adsorbed arsenate is distributed between the surface plane and another electrostatic plane. DMA and lower concentrations of MMA have small effect on the zeta potential, whereas the zeta potential of goethite decreases in the presence of arsenate. The small effect on zeta potential of DMA or MMA adsorption suggests that the sorption sites for the anions is not important in controlling the surface charge. This observation is inconsistent with most adsorption models that postulate a singly coordinated hydroxyls contributing to both the adsorption and the surface charge, but

  3. [PhSiO1.5]8,10,12 as nanoreactors for non-enzymatic introduction of ortho, meta or para-hydroxyl groups to aromatic molecules.

    PubMed

    Bahrami, Mozhgan; Zhang, Xingwen; Ehsani, Morteza; Jahani, Yousef; Laine, Richard M

    2017-03-20

    Traditional electrophilic bromination follows long established "rules": electron-withdrawing substituents cause bromination selective for meta positions, whereas electron-donating substituents favor ortho and para bromination. In contrast, in the [PhSiO1.5]8,10,12 silsesquioxanes, the cages act as bulky, electron withdrawing groups equivalent to CF3; yet bromination under mild conditions, without a catalyst, greatly favors ortho substitution. Surprisingly, ICl iodination without a catalyst favors (>90%) para substitution [p-IC6H4SiO1.5]8,10,12. Finally, nitration and Friedel-Crafts acylation and sulfonylation are highly meta selective, >80%. In principle, the two halogenation formats coupled with the traditional electrophilic reactions provide selective functionalization at each position on the aromatic ring. Furthermore, halogenation serves as a starting point for the synthesis of two structural isomers of practical utility, i.e. in drug prospecting. The o-bromo and p-iodo compounds are easily modified by catalytic cross-coupling to append diverse functional groups. Thereafter, F(-)/H2O2 treatment cleaves the Si-C bonds replacing Si with OH. This represents a rare opportunity to introduce hydroxyl groups to aromatic rings, a process not easily accomplished using traditional organic synthesis methods. The as-produced phenol provides additional opportunities for modification. Each cage can be considered a nanoreactor generating 8-12 product molecules. Examples given include syntheses of 4,2'-R,OH-stilbenes and 4,4'-R,OH-stilbenes (R = Me, CN). Unoptimized cleavage of the Br/I derivatives yields 55-85% phenol. Unoptimized cleavage of the stilbene derivatives yields 35-40% (3-5 equivalents of phenol) in the preliminary studies presented here. In contrast, meta R-phenol yields are 80% (7-10 mol per cage).

  4. Stabilization of organometal halide perovskite films by SnO2 coating with inactive surface hydroxyl groups on ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Zhao, Jinjin; Liu, Jinxi; Wei, Liyu; Liu, Zhenghao; Guan, Lihao; Cao, Guozhong

    2017-01-01

    Perovskite solar cells have advanced rapid in the last few years, however the thermal instability of perovskite film on ZnO nanorods (NRs) remains a big challenge limiting its commercialization. The present work demonstrated effective suppression of the decomposition of CH3NH3PbI3 perovskite through inserting a thin tin oxide (SnO2) passivation layer between ZnO NRs and perovskite films. Although X-ray photoelectron spectroscopy (XPS) results showed no distinct difference in the amount of hydroxyl groups and oxygen vacancies on the surface of ZnO NRs and ZnO@SnO2 NRs, Raman spectra suggested the hydroxyl groups might be trapped in oxygen vacancies on SnO2 surface, preventing the decomposition of CH3NH3PbI3 perovskite through reacting with the hydroxyl groups. The power conversion efficiency of perovskite solar cells was significantly increased from 6.92% to 12.17% and became hysteresis-free by applying SnO2 passivating layer between perovskite and ZnO layers.

  5. Opioids and efflux transporters. Part 3: P-glycoprotein substrate activity of 3-hydroxyl addition to meperidine analogs.

    PubMed

    Mercer, Susan L; Cunningham, Christopher W; Eddington, Natalie D; Coop, Andrew

    2008-06-15

    Numerous studies have shown that many clinically employed opioid analgesics are substrates for P-glycoprotein (P-gp), suggesting that up-regulation of P-gp may contribute to the development of central tolerance to opioids. The studies herein focus on the development of SAR for P-gp substrate activity in the meperidine series of opioids. Addition of a 3-OH to meperidine and the ketone analog of meperidine yielding bemidone and ketobemidone, respectively, significantly increased P-gp substrate affinity. The results of this study have implications in the development of novel analgesics to be utilized as tools to study the contribution of P-gp on the development of central tolerance to opioids.

  6. Interaction of water, hydrogen and their mixtures with SnO2 based materials: the role of surface hydroxyl groups in detection mechanisms.

    PubMed

    Pavelko, Roman G; Daly, Helen; Hardacre, Christopher; Vasiliev, Alexey A; Llobet, Eduard

    2010-03-20

    DRIFTS, TGA and resistance measurements have been used to study the mechanism of water and hydrogen interaction accompanied by a resistance change (sensor signal) of blank and Pd doped SnO(2). It was found that a highly hydroxylated surface of blank SnO(2) reacts with gases through bridging hydroxyl groups, whereas the Pd doped materials interact with hydrogen and water through bridging oxygen. In the case of blank SnO(2) the sensor signal maximum towards H(2) in dry air (R(0)/R(g)) is observed at approximately 345 degrees C, and towards water, at approximately 180 degrees C, which results in high selectivity to hydrogen in the presence of water vapors (minor humidity effect). In contrast, on doping with Pd the response to hydrogen in dry air and to water occurred in the same temperature region (ca. 140 degrees C) leading to low selectivity with a high effect of humidity. An increase in water concentration in the gas phase changes the hydrogen interaction mechanism of Pd doped materials, while that of blank SnO(2) is unchanged. The interaction of hydrogen with the catalyst doped SnO(2) occurs predominantly through hydroxyl groups when the volumetric concentration of water in the gas phase is higher than that of H(2) by a factor of 1000.

  7. Influence of lipids with hydroxyl-containing head groups on Fe2+ (Cu2+)/H2O2-mediated transformation of phospholipids in model membranes.

    PubMed

    Olshyk, Viktoriya N; Melsitova, Inna V; Yurkova, Irina L

    2014-01-01

    Under condition of ROS formation in lipid membranes, free radical reactions can proceed in both hydrophobic (peroxidation of lipids, POL) and polar (free radical fragmentation) parts of the bilayer. Free-radical fragmentation is typical for the lipids containing a hydroxyl group in β-position with respect to an ester or amide bond. The present study has been undertaken to investigate free-radical transformations of phospholipids in model membranes containing lipids able to undergo fragmentation in their polar part. Liposomes from egg yolk lecithin containing saturated or monounsaturated glycero- and sphingolipids were subjected to the action of an HO* - generating system - Fe(2+)(Cu(2+))/H2O2/Asc, and the POL products were investigated. In parallel with this, the effects of monoacylglycerols and scavengers of reactive species on Fe(2+)(Cu(2+))/H2O2/Asc - mediated free-radical fragmentation of phosphatidylglycerols were studied. Hydroxyl-containing sphingolipids and glycerolipids, which undergo free-radical fragmentation under such conditions, manifested antioxidant properties in the model membranes. In the absence of HO groups in the lipid structure, the effect was either pro-oxidant or neutral. Monoacylglycerols slowed down the rate of both peroxidation in the hydrophobic part and free-radical fragmentation in the hydrophilic part of phospholipid membrane. Scavengers of reactive species inhibited the fragmentation of phosphatidylglycerol substantially. Thus, the ability of hydroxyl-containing lipids to undergo free-radical fragmentation in polar part apparently makes a substantial contribution to the mechanism of their protector action.

  8. Polyetherurethane oligomers with aldehyde groups as additives for lubricating oils

    SciTech Connect

    Nikolaev, V.N.; Abramov, E.G.; Tenyushev, A.I.

    1995-01-01

    Polyetherurethane oligomers with aldehyde groups, which we synthesized from polyoxypropylene diols (molecular weight 500, 1000, 1500, 2000, or 3000) with toluene diisocyanate and salicylaldehyde, are of interest as additives for lubricating oils. The effects of these oligomers on the service properties and physicochemical characteristics of lubricating oils were investigated by methods prreviously described. As the lube base stocks we used castor oil, a polyoxypropylene diol and a polyethoxysiloxane. The oligomers are readily soluble in organic solvents and in the lube base stocks, and their solutions are stable during storage and use. We found that the optimal concentration of oligomers is 5%, providing the best lubricating properties, in particular the best antiwear properties.

  9. The presence of a hydroxyl group at the C-1 atom of the transketolase substrate molecule is necessary for the enzyme to perform the transferase reaction.

    PubMed

    Meshalkina, L E; Neef, H; Tjaglo, M V; Schellenberger, A; Kochetov, G A

    1995-11-20

    Transketolase catalyzes the transfer of an aldehyde residue from keto sugars to aldo sugars. The intermediate product is dihydroxyethylthiamine pyrophosphate (DHETPP). In the absence of an acceptor substrate, the reaction is stopped at this stage and DHETPP does not undergo subsequent transformations. Pyruvate decarboxylase catalyses pyruvate decarboxylation to yield free aldehyde. The intermediate product is hydroxyethylthiamine pyrophosphate (HETPP). It differs from DHETPP only in that it has no hydroxyl at the C-2 atom of the aldehyde residue. We have shown that transketolase can bind HETPP and split the aldehyde residue from it. This fact suggests that the path of the reaction is determined by the absence (in HETPP) or presence (in DHETPP) of a hydroxyl group. In the former case the reaction will yield free aldehyde, in the latter the aldehyde residue will be transferred onto an acceptor substrate.

  10. Variation in optoelectronic properties of azo dye-sensitized TiO2 semiconductor interfaces with different adsorption anchors: carboxylate, sulfonate, hydroxyl and pyridyl groups.

    PubMed

    Zhang, Lei; Cole, Jacqueline M; Dai, Chencheng

    2014-05-28

    The optoelectronic properties of four azo dye-sensitized TiO2 interfaces are systematically studied as a function of a changing dye anchoring group: carboxylate, sulfonate, hydroxyl, and pyridyl. The variation in optoelectronic properties of the free dyes and those in dye/TiO2 nanocomposites are studied both experimentally and computationally, in the context of prospective dye-sensitized solar cell (DSSC) applications. Experimental UV/vis absorption spectroscopy, cyclic voltammetry, and DSSC device performance testing reveal a strong dependence on the nature of the anchor of the optoelectronic properties of these dyes, both in solution and as dye/TiO2 nanocomposites. First-principles calculations on both an isolated dye/TiO2 cluster model (using localized basis sets) and each dye modeled onto the surface of a 2D periodic TiO2 nanostructure (using plane wave basis sets) are presented. Detailed examination of these experimental and computational results, in terms of light harvesting, electron conversion and photovoltaic device performance characteristics, indicates that carboxylate is the best anchoring group, and hydroxyl is the worst, whereas sulfonate and pyridyl groups exhibit competing potential. Different sensitization solvents are found to affect critically the extent of dye adsorption achieved in the dye-sensitization of the TiO2 semiconductor, especially where the anchor is a pyridyl group.

  11. Number of Hydroxyl Groups on the B-Ring of Flavonoids Affects Their Antioxidant Activity and Interaction with Phorbol Ester Binding Site of PKCδ C1B Domain: In Vitro and in Silico Studies.

    PubMed

    Kongpichitchoke, Teeradate; Hsu, Jue-Liang; Huang, Tzou-Chi

    2015-05-13

    Although flavonoids have been reported for their benefits and nutraceutical potential use, the importance of their structure on their beneficial effects, especially on signal transduction mechanisms, has not been well clarified. In this study, three flavonoids, pinocembrin, naringenin, and eriodictyol, were chosen to determine the effect of hydroxyl groups on the B-ring of flavonoid structure on their antioxidant activity. In vitro assays, including DPPH scavenging activity, ROS quantification by flow cytometer, and proteins immunoblotting, and in silico analysis by molecular docking between the flavonoids and C1B domain of PKCδ phorbol ester binding site were both used to complete this study. Eriodictyol (10 μM), containing two hydroxyl groups on the B-ring, exhibited significantly higher (p < 0.05) antioxidant activity than pinocembrin and naringenin. The IC50 values of eriodictyol, naringenin, and pinocembrin were 17.4 ± 0.40, 30.2 ± 0.61, and 44.9 ± 0.57 μM, respectively. In addition, eriodictyol at 10 μM remarkably inhibited the phosphorylation of PKCδ at 63.4% compared with PMA-activated RAW264.7, whereas pinocembrin and naringenin performed inhibition activity at 76.8 and 72.6%, respectively. According to the molecular docking analysis, pinocembrin, naringenin, and eriodictyol showed -CDOCKER_energy values of 15.22, 16.95, and 21.49, respectively, reflecting that eriodictyol could bind with the binding site better than the other two flavonoids. Interestingly, eriodictyol had a remarkably different pose to bind with the kinase as a result of the two hydroxyl groups on its B-ring, which consequently contributed to greater antioxidant activity over pinocembrin and naringenin.

  12. The Hydroxyl at Position C1 of Genipin Is the Active Inhibitory Group that Affects Mitochondrial Uncoupling Protein 2 in Panc-1 Cells

    PubMed Central

    Hou, Jianwei; Ding, Yue; Zhang, Tong; Zhang, Yong; Wang, Jianying; Shi, Chenchen; Fu, Wenwei; Cai, Zhenzhen

    2016-01-01

    Genipin (GNP) effectively inhibits uncoupling protein 2 (UCP2), which regulates the leakage of protons across the inner mitochondrial membrane. UCP2 inhibition may induce pancreatic adenocarcinoma cell death by increasing reactive oxygen species (ROS) levels. In this study, the hydroxyls at positions C10 (10-OH) and C1 (1-OH) of GNP were hypothesized to be the active groups that cause these inhibitory effects. Four GNP derivatives in which the hydroxyl at position C10 or C1 was replaced with other chemical groups were synthesized and isolated. Differences in the inhibitory effects of GNP and its four derivatives on pancreatic carcinoma cell (Panc-1) proliferation were assessed. The effects of GNP and its derivatives on apoptosis, UCP2 inhibition and ROS production were also studied to explore the relationship between GNP’s activity and its structure. The derivatives with 1-OH substitutions, geniposide (1-GNP1) and 1-ethyl-genipin (1-GNP2) lacked cytotoxic effects, while the other derivatives that retained 1-OH, 10-piv-genipin (10-GNP1) and 10-acetic acid-genipin (10-GNP2) exerted biological effects similar to those of GNP, even in the absence of 10-OH. Thus, 1-OH is the key functional group in the structure of GNP that is responsible for GNP’s apoptotic effects. These cytotoxic effects involve the induction of Panc-1 cell apoptosis through UCP2 inhibition and subsequent ROS production. PMID:26771380

  13. The effect of ethanol on hydroxyl and carbonyl groups in biopolyol produced by hydrothermal liquefaction of loblolly pine: (31)P-NMR and (19)F-NMR analysis.

    PubMed

    Celikbag, Yusuf; Via, Brian K; Adhikari, Sushil; Buschle-Diller, Gisela; Auad, Maria L

    2016-08-01

    The goal of this study was to investigate the role of ethanol and temperature on the hydroxyl and carbonyl groups in biopolyol produced from hydrothermal liquefaction of loblolly pine (Pinus spp.) carried out at 250, 300, 350 and 390°C for 30min. Water and water/ethanol mixture (1/1, wt/wt) were used as liquefying solvent in the HTL experiments. HTL in water and water/ethanol is donated as W-HTL and W/E-HTL, respectively. It was found that 300°C and water/ethanol solvent was the optimum liquefaction temperature and solvent, yielding up to 68.1wt.% bio-oil and 2.4wt.% solid residue. (31)P-NMR analysis showed that biopolyol produced by W-HTL was rich in phenolic OH while W/E-HTL produced more aliphatic OH rich biopolyols. Moreover, biopolyols with higher hydroxyl concentration were produced by W/E-HTL. Carbonyl groups were analyzed by (19)F-NMR, which showed that ethanol reduced the concentration of carbonyl groups.

  14. Residues of the human nuclear vitamin D receptor that form hydrogen bonding interactions with the three hydroxyl groups of 1alpha,25-dihydroxyvitamin D3.

    PubMed

    Reddy, Madhuri D; Stoynova, Ludmilla; Acevedo, Alejandra; Collins, Elaine D

    2007-03-01

    Most of the biological effects of 1,25-dihydroxyvitamin D(3) (hormone D) are mediated through the nuclear vitamin D receptor (VDR). Hormone binding induces conformational changes in VDR that enable the receptor to activate gene transcription. It is known that residues S237 and R274 form hydrogen bonds with the 1-hydroxyl group of hormone D, while residues Y143 and S278, and residues H305 and H397 form hydrogen bonds with the 3-hydroxyl and the 25-hydroxyl groups of the hormone. A series of VDR mutations were constructed (S237A, R274A, R274Q, Y143F, Y143A, S278A, H305A, and H397F; double mutants: S237A/R274A, Y143F/S278A, Y143A/S278A, and H305A/H397F). The relative binding affinities of the wild-type and variant VDRs were assessed. All of the mutants except H397F resulted in lower binding affinity compared to wild-type VDR. Binding to hormone was barely detectable in Y143F, H305A, and H305A/H397F mutants, and undetectable in mutants R274A, R274Q, Y143A, S237A/R274A, and Y143A/S278A, indicating the importance of these residues. Ability to activate gene transcription was also assessed. All of the VDR mutants, except the single mutant S278A, required higher doses of hormone D for half-maximal response. Defining the role of hormone D-VDR binding will lead to a better understanding of the vitamin D signal transduction pathway.

  15. Synthesis and evaluation of antibacterial polyurethane coatings made from soybean oil functionalized with dimethylphenylammonium iodide and hydroxyl groups.

    PubMed

    Bakhshi, Hadi; Yeganeh, Hamid; Mehdipour-Ataei, Shahram

    2013-06-01

    Preparation of antibacterial polyurethane coatings from novel functional soybean oil was considered in this work. First, epoxidized soybean oil (ESBO) as a low price and widely available renewable resource raw material was subjected to the reaction with aniline using an ionic liquid as a green catalyst. The intermediate phenylamine containing polyol (SAP) was then methylated by reaction with methyl iodide to produce a polyol (QAP) with pendant dimethylphenylammonium iodide groups. To regulate the physical and mechanical properties as well as biological characteristics of final coatings, QAP was mixed with different portions of a similar soybean oil-based polyol (MSP) without quaternary ammonium groups. The mixtures were reacted with isophorone diisocyanate to produce crosslinked polyurethane coatings. Evaluation of viscoelastic properties by DMA method revealed single phase structure with Tg in the range of 50-82°C. Stress-strain analysis of the prepared polyurethanes showed initial modulus, tensile strength, and elongation at break in the ranges of 13-299 MPa, 4.5-13.8 MPa, and 16-109%, respectively. Additionally, the coatings showed good adherence to aluminum and PVC substrates. The solvent extracted samples showed excellent biocompatibility as determined by monitoring L929 fibroblast cells morphology and MTT assay. Meanwhile, very promising antibacterial properties against both Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria with bacterial reduction in the range of 83-100% was observed.

  16. Effect of substituted hydroxyl groups in the changes of solution turbidity in the oxidation of aromatic contaminants.

    PubMed

    Villota, N; Jm, Lomas; Lm, Camarero

    2017-01-01

    This paper deals with the changes of turbidity that are generated in aqueous solutions of phenol when they are oxidized by using different Fenton technologies. Results revealed that if the Fenton reaction was promoted with UV light, the turbidity that was generated in the water doubled. Alternatively, the use of ultrasonic waves produced an increase in turbidity which initially proceeded slowly, reaching intensities eight times higher than in the conventional Fenton treatment. As well, the turbidity showed a high dependence on pH. It is therefore essential to control acidity throughout the reaction. The maximum turbidity was generated when operating at pH = 2.0, and it slowly decreased with increasing to a value of pH = 3.0, at which the turbidity was the lowest. This result was a consequence of the presence of ferric ions in solution. At pH values greater than 3.5, the turbidity increased almost linearly until at pH = 5.0 reached its maximum intensity. In this range, ferrous ions may generate an additional contribution of radicals that promote the degradation of the phenol species that produce turbidity. Turbidity was enhanced at ratios R = 4.0 mol H2O2/mol C6H6O. This value corresponds to the stoichiometric ratio that leads to the production of turbidity-precursor species. Therefore, muconic acid would be a species that generate high turbidity in solution according to its isomerism. Also, the results revealed that the turbidity is not a parameter to which species contribute additively since interactions may occur among species that would enhance their individual contributions to it. Analyzing the oxidation of phenol degradation intermediates, the results showed that meta-substituted compounds (resorcinol) generate high turbidity in the wastewater. The presence of polar molecules, such as muconic acid, would provide the structural features that are necessary for resorcinol to act as a clip between two carboxylic groups, thus establishing directional

  17. Mechanistic Insights of Ethanol Steam Reforming over Ni–CeO x (111): The Importance of Hydroxyl Groups for Suppressing Coke Formation

    DOE PAGES

    Liu, Zongyuan; Duchoň, Tomáš; Wang, Huanru; ...

    2015-07-30

    We have studied the reaction of ethanol and water over Ni–CeO2-x(111) model surfaces to elucidate the mechanistic steps associated with the ethanol steam reforming (ESR) reaction. Our results provide insights about the importance of hydroxyl groups to the ESR reaction over Ni-based catalysts. Systematically, we have investigated the reaction of ethanol on Ni–CeO2-x(111) at varying Ce³⁺ concentrations (CeO1.8–2.0) with absence/presence of water using a combination of soft X-ray photoelectron spectroscopy (sXPS) and temperature-programmed desorption (TPD). Consistent with previous reports, upon annealing, metallic Ni formed on reduced ceria while NiO was the main component on fully oxidized ceria. Ni⁰ is themore » active phase leading to both the C–C and C–H cleavage of ethanol but is also responsible for carbon accumulation or coking. We have identified a Ni₃C phase that formed prior to the formation of coke. At temperatures above 600K, the lattice oxygen from ceria and the hydroxyl groups from water interact cooperatively in the removal of coke, likely through a strong metal–support interaction between nickel and ceria that facilitates oxygen transfer.« less

  18. Preferential adsorption behavior of methylene blue dye onto surface hydroxyl group enriched TiO2 nanotube and its photocatalytic regeneration.

    PubMed

    Natarajan, Thillai Sivakumar; Bajaj, Hari C; Tayade, Rajesh J

    2014-11-01

    The present manuscript focus on the synthesis of surface hydroxyl group enriched titanium dioxide nanotube (TNT) by hydrothermal method for preferential adsorption of methylene blue (MB) dye. The mixture of methylene blue (MB) and rhodamine B (RhB) dye was used to study the preferential adsorption nature of TNT. The synthesized TNT were characterized by various techniques such as powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption, and ammonia-temperature programmed desorption (NH3-TPD) analysis. Result demonstrated that enhancement in the surface area of TNT and higher number of hydroxyl group on the surface of TNT. In the binary mixture, the adsorption of MB dye was 12.9 times higher as compared to RhB dye, which clearly indicated the preferential adsorption of MB dye on TNT surface. The preferential interaction of MB on TNT is due to the electrostatic interaction between the cationic MB and negatively charged TNT surface. The preferential adsorption of MB dye was studied by applying Langmuir, Freundlich and Sips isotherm; pseudo-first and second-order kinetic model. Furthermore, the regeneration of dye adsorbed TNT was carried out by eco-friendly photocatalytic process under the irradiation of ultraviolet light.

  19. Photo and Chemical Reduction of Copper onto Anatase-Type TiO2 Nanoparticles with Enhanced Surface Hydroxyl Groups as Efficient Visible Light Photocatalysts.

    PubMed

    Eskandarloo, Hamed; Badiei, Alireza; Behnajady, Mohammad A; Mohammadi Ziarani, Ghodsi

    2015-01-01

    In this study, the photocatalytic efficiency of anatase-type TiO2 nanoparticles synthesized using the sol-gel low-temperature method, were enhanced by a combined process of copper reduction and surface hydroxyl groups enhancement. UV-light-assisted photo and NaBH4 -assisted chemical reduction methods were used for deposition of copper onto TiO2. The surface hydroxyl groups of TiO2 were enhanced with the assistance of NaOH modification. The prepared catalysts were immobilized on glass plates and used as the fixed-bed systems for the removal of phenazopyridine as a model drug contaminant under visible light irradiation. NaOH-modified Cu/TiO2 nanoparticles demonstrated higher photocatalytic efficiency than that of pure TiO2 due to the extending of the charge carriers lifetime and enhancement of the adsorption capacity of TiO2 toward phenazopyridine. The relationship of structure and performance of prepared nanoparticles has been established by using various techniques, such as XRD, XPS, TEM, EDX, XRF, TGA, DRS and PL. The effects of preparation variables, including copper content, reducing agents rate (NaBH4 concentration and UV light intensity) and NaOH concentration were investigated on the photocatalytic efficiency of NaOH-modified Cu/TiO2 nanoparticles.

  20. Solid-state MAS NMR, TEM, and TGA studies of structural hydroxyl groups and water in nanocrystalline apatites prepared by dry milling.

    PubMed

    Pajchel, Lukasz; Kolodziejski, Waclaw

    2013-01-01

    A series of nanocrystalline calcium hydroxyapatites was prepared by dry milling and characterized using proton and (31)P MAS NMR, TEM, and TGA methods. The samples contained stubby rod-shaped crystals, which length and width varied in the 130-30 and 95-20 nm ranges, respectively. It was confirmed that concentration of structural hydroxyl groups in nanocrystalline apatites decreases with the decreasing crystal size. In the series of the studied apatites, the decrease was from 86 to ca. 50 % in reference to stoichiometric apatite. Water was found in the surface hydrated layer and in the c-axis channels, in which compartments existed as adsorbed and structural, respectively. Molecules of the adsorbed water were capable of moving from the crystal surface into the lattice c-axis channels of apatite. This process introduced considerable structural disorder within and around those channels and reduced the content of the structural hydroxyl groups, particularly in the region underneath the apatite crystal surface.

  1. Mechanistic Insights of Ethanol Steam Reforming over Ni–CeO x (111): The Importance of Hydroxyl Groups for Suppressing Coke Formation

    SciTech Connect

    Liu, Zongyuan; Duchoň, Tomáš; Wang, Huanru; Peterson, Erik W.; Zhou, Yinghui; Luo, Si; Zhou, Jing; Matolín, Vladimir; Stacchiola, Dario J.; Rodriguez, José A.; Senanayake, Sanjaya D.

    2015-07-30

    We have studied the reaction of ethanol and water over Ni–CeO2-x(111) model surfaces to elucidate the mechanistic steps associated with the ethanol steam reforming (ESR) reaction. Our results provide insights about the importance of hydroxyl groups to the ESR reaction over Ni-based catalysts. Systematically, we have investigated the reaction of ethanol on Ni–CeO2-x(111) at varying Ce³⁺ concentrations (CeO1.8–2.0) with absence/presence of water using a combination of soft X-ray photoelectron spectroscopy (sXPS) and temperature-programmed desorption (TPD). Consistent with previous reports, upon annealing, metallic Ni formed on reduced ceria while NiO was the main component on fully oxidized ceria. Ni⁰ is the active phase leading to both the C–C and C–H cleavage of ethanol but is also responsible for carbon accumulation or coking. We have identified a Ni₃C phase that formed prior to the formation of coke. At temperatures above 600K, the lattice oxygen from ceria and the hydroxyl groups from water interact cooperatively in the removal of coke, likely through a strong metal–support interaction between nickel and ceria that facilitates oxygen transfer.

  2. A Comparison of Group-Oriented Contingencies for Addition Fluency

    ERIC Educational Resources Information Center

    Gross, Thomas J.; Duhon, Gary J.; Shutte, Greg; Rowland, Julie E.

    2016-01-01

    Math fact fluency is critical for understanding complex mathematics. Explicit timing interventions have shown promise for improving math fluency, and they may benefit from being paired with group-oriented contingencies. Further, investigations of independent and dependent group-oriented contingencies would help to identify their relative…

  3. Additives

    NASA Technical Reports Server (NTRS)

    Smalheer, C. V.

    1973-01-01

    The chemistry of lubricant additives is discussed to show what the additives are chemically and what functions they perform in the lubrication of various kinds of equipment. Current theories regarding the mode of action of lubricant additives are presented. The additive groups discussed include the following: (1) detergents and dispersants, (2) corrosion inhibitors, (3) antioxidants, (4) viscosity index improvers, (5) pour point depressants, and (6) antifouling agents.

  4. Proton-bridge motions in amine conjugate acid ions having intramolecular hydrogen bonds to hydroxyl and amine groups.

    PubMed

    Ung, Hou U; Moehlig, Aaron R; Khodagholian, Sevana; Berden, Giel; Oomens, Jos; Morton, Thomas Hellman

    2013-02-14

    Vibrational spectra of two gaseous cations having NH···O intramolecular ionic hydrogen bonds and of nine protonated di- and polyamines having NH···N internal proton bridges, recorded using IR Multiple Photon Dissociation (IRMPD) of mass-selected ions, are reported. The band positions of hydroxyl stretching frequencies do not shift when a protonated amine becomes hydrogen bonded to oxygen. In three protonated diamines, lower frequency bands (550-650 cm(-1)) disappear upon isotopic substitution, as well as several bands in the 1100-1350 cm(-1) region. By treating the internal proton bridge as a linear triatomic, theory assigns the lowest frequency bands to N-H···N asymmetric stretches. A 2-dimensional model, based on quantization on a surface fit to points calculated using a double hybrid functional B2-P3LYP/cc-pVTZ//B3LYP/6-31G**, predicts their positions accurately. In at least one case, the conjugate acid of 1,5-cis-bis(dimethylamino)cyclooctane, a N-H···N bend shows up in the domain predicted by DFT normal mode calculations, but in most other cases the observed bands have frequencies 20-25% lower than expected for bending vibrations. Protonated Me(2)NCH(2)CMe(2)CH(2)CH(2)CH(2)NMe(2) shows three well-resolved bands at 620, 1200, and 1320 cm(-1), of which the lowest can be assigned to the asymmetric stretch. Other ions observed include doubly protonated 1,2,4,5-(Me(2)NCH(2))(4)-benzene and 1,2,4-(Me(2)NCH(2))(3)-benzene-5-CH(2)OH. Apart from the aforementioned rigid ion derived from the alicyclic diamine, the other ions enjoy greater conformational mobility, and coupling to low-frequency C-C bond torsions may account for the shift of vibrations with N-H···N character to lower frequencies. Low-barrier hydrogen bonding (LBHB) accounts for the fact that N-H···N asymmetric stretching vibrations of near linear proton bridges occur at frequencies below 650 cm(-1).

  5. 34 CFR 300.308 - Additional group members.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Educational Placements Additional Procedures for Identifying Children with Specific Learning Disabilities... learning disability is a child with a disability as defined in § 300.8, must be made by the child's parents... examinations of children, such as a school psychologist, speech-language pathologist, or remedial...

  6. 34 CFR 300.308 - Additional group members.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Educational Placements Additional Procedures for Identifying Children with Specific Learning Disabilities... learning disability is a child with a disability as defined in § 300.8, must be made by the child's parents...) If the child does not have a regular teacher, a regular classroom teacher qualified to teach a...

  7. 34 CFR 300.308 - Additional group members.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Educational Placements Additional Procedures for Identifying Children with Specific Learning Disabilities... learning disability is a child with a disability as defined in § 300.8, must be made by the child's parents...) If the child does not have a regular teacher, a regular classroom teacher qualified to teach a...

  8. Effect of hydroxyl and amino groups on electrochemiluminescence activity of tertiary amines at low tris(2,2'-bipyridyl)ruthenium(II) concentrations.

    PubMed

    Han, Shuang; Niu, Wenxin; Li, Haijuan; Hu, Lianzhe; Yuan, Yali; Xu, Guobao

    2010-04-15

    ECL of several amines containing different numbers of hydroxyl and amino groups was investigated. N-butyldiethanolamine is found to be more effective than 2-(dibutylamino)ethanol at gold and platinum electrodes, and is the most effective coreactant reported until now. Surprisingly, ECL intensities of monoamines, such as 2-(dibutylamino)ethanol and N-butyldiethanolamine, are much stronger than that of diamines including N,N,N',N'-tetrakis-(2-hydroxyethyl)-ethylenediamine and N,N,N',N'-tetrakis-(2-hydroxypropyl)ethlenediamine. The striking contrast between ECL signals of the investigated monoamines and diamines may result from more significant side reactions of diamines, such as the intramolecular side reactions between oxidative amine cation radicals and reductive amine free radicals.

  9. The influence of surface oxygen and hydroxyl groups on the dehydrogenation of ethylene, acetic acid and hydrogenated vinyl acetate on pure Pd(1 0 0): A DFT study

    NASA Astrophysics Data System (ADS)

    Huang, Yanping; Dong, Xiuqin; Yu, Yingzhe; Zhang, Minhua

    2016-12-01

    On the basis of a Langmuir-Hinshelwood-type mechanism, the dehydrogenation of ethylene, acetic acid and hydrogenated vinyl acetate (VAH) on pure Pd(1 0 0) with surface oxygen atoms (Os) and hydroxyl groups (OHs) was studied with density functional theory (DFT) method. Our calculation results show that both Os and OHs can consistently reduce the activation energies of dehydrogenation of ethylene, acetic acid and VAH to some degree with only one exception that OHs somehow increase the activation energy of VAH. Based on Langmuir-Hinshelwood mechanism, the three dehydrogenation reactions in presence of surface Os and OHs are almost consistently favored, compared with the corresponding processes on clean Pd(1 0 0) surfaces, and thus a Langmuir-Hinshelwood-type mechanism may not be excluded beforehand when investigating the microscopic performance of the oxygen-assisted vinyl acetate synthesis on Pd(1 0 0) catalysts.

  10. 21 CFR 172.814 - Hydroxylated lecithin.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Multipurpose Additives § 172.814 Hydroxylated lecithin. The food additive hydroxylated lecithin may be safely used as an emulsifier in foods in accordance with the following conditions: (a) The additive...

  11. The effect of surfactant-free TiO2 surface hydroxyl groups on physicochemical, optical and self-cleaning properties of developed coatings on polycarbonate

    NASA Astrophysics Data System (ADS)

    Yaghoubi, H.; Dayerizadeh, A.; Han, S.; Mulaj, M.; Gao, W.; Li, X.; Muschol, M.; Ma, S.; Takshi, A.

    2013-12-01

    TiO2 is a prototypical transition metal oxide with physicochemical properties that can be modified more readily through sol-gel synthesis than through other techniques. Herein, we report on the change in the density of the hydroxyl groups on the surface of synthesized surfactant-free TiO2 nanoparticles in water due to varying the pH (7.3, 8.3, 9.3 and 10.3) of the peroxotitanium complex, i.e. the amorphous sol, prior to refluxing. This resulted in colloidal solutions with differing crystallinity, nanoparticle size, optical indirect bandgaps and photocatalytic activity. It was shown that increasing the density of hydroxyl groups on TiO2 particles coupled with low-temperature annealing (90 °C) induced an anatase to rutile transformation. Increasing the pH of the peroxotitanium complex interrupted the formation of anatase phase in crystalline sol, as evidenced by intensity increases of the Raman bands at ˜822 (Ti-O-H) and 906 cm-1 (vibrational Ti-O-H) and an intensity decrease of the band at 150 cm-1 (anatase photonic Eg). Films prepared from higher pH suspensions showed lower roughness. The reaction rate constants for photo-induced self-cleaning activity of TiO2 films prepared from colloidal solutions at pH 7.3, 8.3, 9.3 and 10.3 were estimated at 0.017 s-1, 0.014 s-1, 0.007 s-1 and 0.006 s-1, respectively.

  12. Infrared spectroscopy of OD vibrators in minerals at natural dilution: hydroxyl groups in talc and kaolinite, and structural water in beryl and emerald.

    PubMed

    de Donato, Philippe; Cheilletz, Alain; Barres, Odile; Yvon, Jacques

    2004-05-01

    An infrared (IR) study of natural deuteration is conducted on minerals containing hydroxyl groups (talc and kaolinite) and channel-water-bearing minerals (beryl and emerald). In talc, the OD valence vibration is located at 2710 cm(-1), corresponding to OD groups surrounded by 3 Mg atoms. In kaolinite, the OD valence vibrations are located at 2671 cm(-1) (inner OD group), 2712, 2706, and 2700 cm(-1) (three inner-surface OD groups). In beryl and emerald, natural deuteration of channel water is observed for the first time by infrared microspectroscopy. In beryl from Minas Gerais (Brazil), the OD profiles are characterized by four bands at 2735, 2686, 2672, and 2641 cm(-1). In emeralds from Colombia and Brazil, the OD profiles are characterized by five or four bands, respectively, at 2816, 2737, 2685, 2673, and 2641 cm(-1) (Colombia) and 2730, 2684, 2672, and 2640 cm(-1) (Brazil). The band at 2816 cm(-1) can be assigned to -OD or OD(-), and bands at 2686-2684, 2673-2672, and 2641-2640 cm(-1) can be assigned to type-I and type-II HOD molecules. The band at 2737-2730 cm(-1) is partially disturbed by combination bands of the mineral. Such OD profiles are different from those obtained by artificial deuteration at higher OD dilution.

  13. Oxidation of amino groups by hydroxyl radicals in relation to the oxidation degree of the alpha-carbon.

    PubMed

    Leitner, N Karpel Vel; Berger, P; Legube, B

    2002-07-15

    Nitrogen organic compounds constitute a large class of aqueous pollutants. These compounds include not only azoic structures, nitrogen heterocycles, and nitrous groups but also amides and amines. This work consisted in studying the OH* induced oxidation of simple primary amines in dilute aqueous solution with special attention to mineralization of the nitrogen group as a function of the nature of the alpha-carbon. H2O2/UV and gamma-irradiation processes were used for the production of OH* radicals, and the molecules studied were one alpha-amino acid i.e., glycine (HOOCCH2NH2), and two primary amides i.e., acetamide (CH3CONH2) and oxamic acid (HOOCCONH2). It was shown that the oxidation of glycine leads to the formation of ammonia, whereas the acetamide molecule is first oxidized into oxamic acid ending in complete mineralization with production of nitrates. Reaction mechanisms are proposed which account for the observed inorganic nitrogen end product depending on the oxidation degree of the carbon atoms of the molecules. It follows that the present study will allow for prediction of the fate of nitrogen resulting from the oxidation of primary amino groups by OH* radicals.

  14. Adsorption and desorption of DNA tuned by hydroxyl groups in graphite oxides-based solid extraction material.

    PubMed

    Akceoglu, Garbis Atam; Li, Oi Lun; Saito, Nagahiro

    2015-12-01

    The extraction of DNA is the most crucial method used in molecular biology. Up to date silica matrices has been widely applied as solid support for selective DNA adsorption and extraction. However, since adsorption force of SiOH functional groups is much greater than that of desorption force, the DNA extraction efficiency of silica surfaces is limited. In order to increase the DNA extraction yield, a new surface with different functional groups which possess of greater desorption property is required. In this study, we proposed cellulose/graphite oxide (GO) composite as an alternative material for DNA adsorption and extraction. GO/Cellulose composite provides the major adsorption and desorption of DNA by COH, which belongs to alkyl or phenol type of OH functional group. Compared to SiOH, COH is less polarized and reactive, therefore the composite might provide a higher desorption of DNA during the elution process. The GO/cellulose composite were prepared in spherical structure by mixing urea, cellulose, NaOH, Graphite oxide and water. The concentration of GO within the composites were controlled to be 0-4.15 wt.%. The extraction yield of DNA increased with increasing weight percentage of GO. The highest yield was achieved at 4.15 wt.% GO, where the extraction efficiency was reported as 660.4 ng/μl when applying 2M GuHCl as the binding buffer. The absorbance ratios between 260 nm and 280 nm (A260/A280) of the DNA elution was demonstrated as 1.86, indicating the extracted DNA consisted of high purity. The results proved that GO/cellulose composite provides a simple method for selective DNA extraction with high extraction efficiency of pure DNA.

  15. Site-specific labeling of RNA at internal ribose hydroxyl groups: terbium-assisted deoxyribozymes at work.

    PubMed

    Büttner, Lea; Javadi-Zarnaghi, Fatemeh; Höbartner, Claudia

    2014-06-04

    A general and efficient single-step method was established for site-specific post-transcriptional labeling of RNA. Using Tb(3+) as accelerating cofactor for deoxyribozymes, various labeled guanosines were site-specifically attached to 2'-OH groups of internal adenosines in in vitro transcribed RNA. The DNA-catalyzed 2',5'-phosphodiester bond formation proceeded efficiently with fluorescent, spin-labeled, biotinylated, or cross-linker-modified guanosine triphosphates. The sequence context of the labeling site was systematically analyzed by mutating the nucleotides flanking the targeted adenosine. Labeling of adenosines in a purine-rich environment showed the fastest reactions and highest yields. Overall, practically useful yields >70% were obtained for 13 out of 16 possible nucleotide (nt) combinations. Using this approach, we demonstrate preparative labeling under mild conditions for up to ~160-nt-long RNAs, including spliceosomal U6 small nuclear RNA and a cyclic-di-AMP binding riboswitch RNA.

  16. Hydroxyl end groups influence in vibrational and transport properties in polymer/monomer solutions: the PEO/EG case

    NASA Astrophysics Data System (ADS)

    Crupi, V.; Faraone, A.; Majolino, D.; Migliardo, P.; Venuti, V.; Villari, V.

    A study has been made of vibrational properties in ethylene glycol (EG; H(OCH2CH2)OH) and EG monomethyl ether (EGmE; CH3(OCH2CH2)OH) in solution together with poly(ethylene oxide) (PEO; H(OCH2CH2)nOH) at different concentrations, performed by Fourier transform infrared absorbance (FT-IR) spectroscopy. The results ae compared with previous viscometry and photon correlation spectroscopy (PCS) studies, using EG dimethyl ether (EGdE; CH3(OCH2CH2)OCH3) as solvent as well. These homologous systems differ from each other in the number of OH end groups, in particular two for EG, one for EgmE and zero for EGdE. Combining analysis of the vibrational and transport properties of EG, EGmE and EGdE in solution with PEO over a wide range of concentration made it possible to check the quality (good theta or poor) of these three different solvents and the role played by the hydrogen bond in the various solute-solvent interaction mechanisms, resulting in the well known de Gennes scaling law.

  17. A new method for immediate derivatization of hydroxyl groups by fluoroalkyl chloroformates and its application for the determination of sterols and tocopherols in human serum and amniotic fluid by gas chromatography-mass spectrometry.

    PubMed

    Řimnáčová, L; Hušek, P; Šimek, P

    2014-04-25

    A new method has been described for efficient derivatization of secondary alicyclic hydroxyl groups in steroids by alkyl chloroformates (RCFs). Cholesterol, an essential human sterol and a steroid precursor in eukaryotic cells, was used as a model for treatment with various RCFs in an aqueous and non-aqueous environment. While the cholesterol hydroxyl group did not react completely with any of the tested RCFs reagents in the former case, trifluoroethyl chloroformate (TFECF) or heptafluorobutyl chloroformate (HFBCF) fully converts cholesterol and related metabolites into the corresponding mixed carbonates under anhydrous conditions in seconds. The acylation reaction was combined with liquid-liquid microextraction (LLME) between isooctane and acetonitrile phase. The sample preparation requires just a stepwise addition of 50μl isooctane with 5μl of a pyridine catalyst, 100μl acetonitrile and 100μl isooctane with dissolved 5μl of the fluoroalkyl chloroformate reagent to a dried sample. The protocol developed in this study was successfully tested for GC-MS analysis of 12 important model steroids and four main tocopherols. Each analyte provided a single peak with excellent GC separation properties, well defined EI spectra containing diagnostic fragment ions suitable for their identification and quantitation. The new method was further validated for the determination of six diagnostic non-cholesterol sterols and four main tocopherols in human serum and in amniotic fluid. Satisfactory data were obtained in terms of calibration, quantitation limits (for sterols and tocopherols, 0.05 and 0.15μg/ml, respectively), within-run precision (0.9-19.5%) and between-run precision (0.2-19.0%), accuracy (82-115%) and recovery (90-110%). The validated method was successfully applied to GC-MS analysis of the analytes in woman sera and amniotic fluids and the results are well-comparable with those reported by other authors. The presented work demonstrates for the first time

  18. Novel relationship between hydroxyl radical initiation and surface group of ceramic honeycomb supported metals for the catalytic ozonation of nitrobenzene in aqueous solution.

    PubMed

    Zhao, Lei; Sun, Zhizhong; Ma, Jun

    2009-06-01

    Comparative experiments have been performed to investigate the degradation efficiency of nitrobenzene and the removal efficiency of TOC in aqueous solution bythe processes of ceramic honeycomb supported different metals (Fe, Ni, and Zn) catalytic ozonation, indicating that the modification with metals can enhance the activity of ceramic honeycomb for the catalytic ozonation of nitrobenzene, and the loading percentage of metal and the metallicity respectively presents a positive influence on the degradation of nitrobenzene. The degradation efficiency of nitrobenzene is determined by the initiation of hydroxyl radical (*OH) according to a good linear correlation in all the processes of modified ceramic honeycomb catalytic ozonation at the different loading percentages of metals. The modification of ceramic honeycomb with metals results in the conversion of the pH at the point of zero charge (pHpzc) and the evolution of surface groups. Divergence from the conventional phenomenon, the enhancement mechanism of ozone decomposition on the modified ceramic honeycomb with metals is proposed due to the basic attractive forces of electrostatic forces or/and hydrogen bonding. Consequently, a novel relationship between the initiation of *OH and the surface-OH2+ group on the modified catalyst is established based on the synergetic effect between homogeneous and heterogeneous reaction systems.

  19. Oxidation of primary hydroxyl groups in chitooligomer by a laccase-TEMPO system and physico-chemical characterisation of oxidation products.

    PubMed

    Pei, Jicheng; Yin, Yunbei; Shen, Zhenghui; Bu, Xin; Zhang, Fangdong

    2016-01-01

    The aim of this study was to investigate the oxidation of chitooligomer by a laccase-TEMPO system which had not previously been examined. Chitooligomer was treated with laccase and TEMPO in order to evaluate the potential of a laccase-TEMPO system to improve the moisture absorption, moisture retention, and antioxidant abilities of chitooligomer. Chitooligomer was prepared by degradation of high molecular weight chitosan with hydrogen peroxide followed by oxidation using a laccase-TEMPO system. (13)C NMR and carboxylate ion content detection results indicated that the laccase-TEMPO system could selectively oxidise the C6 hydroxyl group of the chitooligomer into carboxyl group; molecular weight distribution changes suggest that the structure of the oxidised product had changed and the molecular size and molecular weight decreased with the molecules in aqueous solution having a compact structure. Oxidation of chitooligomer by a laccase-TEMPO system resulted in a significant improvement in the moisture absorption, moisture retention and antioxidant abilities. The oxidised product has potential application values in the pharmaceutical and cosmetics industries.

  20. NMR spectroscopy of hydroxyl protons in aqueous solutions of peptides and proteins.

    PubMed

    Liepinsh, E; Otting, G; Wüthrich, K

    1992-09-01

    Hydroxyl groups of serine and threonine, and to some extent also tyrosine are usually located on or near the surface of proteins. NMR observations of the hydroxyl protons is therefore of interest to support investigations of the protein surface in solution, and knowledge of the hydroxyl NMR lines is indispensable as a reference for studies of protein hydration in solution. In this paper, solvent suppression schemes recently developed for observation of hydration water resonances were used to observe hydroxyl protons of serine, threonine and tyrosine in aqueous solutions of small model peptides and the protein basic pancreatic trypsin inhibitor (BPTI). The chemical shifts of the hydroxyl protons of serine and threonine were found to be between 5.4 and 6.2 ppm, with random-coil shifts at 4 degrees C of 5.92 ppm and 5.88 ppm, respectively, and those of tyrosine between 9.6 and 10.1 ppm, with a random-coil shift of 9.78 ppm. Since these spectral regions are virtually free of other polypeptide 1H NMR signals, cross peaks with the hydroxyl protons are usually well separated even in homonuclear two-dimensional 1H NMR spectra. To illustrate the practical use of hydroxyl proton NMR in polypeptides, the conformations of the side-chain hydroxyl groups in BPTI were characterized by measurements of nuclear Overhauser effects and scalar coupling constants involving the hydroxyl protons. In addition, hydroxyl proton exchange rates were measured as a function of pH, where simple first-order rate processes were observed for both acid- and base-catalysed exchange of all but one of the hydroxyl-bearing residues in BPTI. For the conformations of the individual Ser, Thr and Tyr side chains characterized in the solution structure with the use of hydroxyl proton NMR, both exact coincidence and significant differences relative to the corresponding BPTI crystal structure data were observed.

  1. Experimental and theoretical study of hydroxyquinolines: hydroxyl group position dependent dipole moment and charge-separation in the photoexcited state leading to fluorescence

    NASA Astrophysics Data System (ADS)

    Singh Mehata, Mohan; Singh, Ajay K.; Sinha, Ravindra Kumar

    2016-12-01

    Optical absorption and fluorescence (FL) spectra of 2-, 6-, 7-, 8-hydroxyquinolines (2-,6-,7- and 8-HQs) have been measured at room temperature in the wide range of solvents of different polarities, dielectric constant and refractive index. The ground state dipole moment (µ g) and excited state dipole moment (µ e) of 2-, 6-, 7- and 8-HQs were obtained using solvatochromic shift (SS) methods and microscopic solvent polarity parameters (MSPP). Change in the dipole moment (Δµ) between the ground and photo-excited states was estimated from SS and MSPP methods. DFT and TDDFT based theoretical calculations were performed for the ground and excited states dipole moments, and for vertical transitions. A significant enhancement in the excited state dipole moment was observed following photo-excitation. The large value of Δµ clearly indicates to the charge-separation in the photo-excited states, which in turn depends on the position of the hydroxyl group in the ring.

  2. Experimental and theoretical study of hydroxyquinolines: hydroxyl group position dependent dipole moment and charge-separation in the photoexcited state leading to fluorescence.

    PubMed

    Mehata, Mohan Singh; Singh, Ajay K; Sinha, Ravindra Kumar

    2016-11-17

    Optical absorption and fluorescence (FL) spectra of 2-, 6-, 7-, 8-hydroxyquinolines (2-,6-,7- and 8-HQs) have been measured at room temperature in the wide range of solvents of different polarities, dielectric constant and refractive index. The ground state dipole moment (µ g) and excited state dipole moment (µ e) of 2-, 6-, 7- and 8-HQs were obtained using solvatochromic shift (SS) methods and microscopic solvent polarity parameters (MSPP). Change in the dipole moment (Δµ) between the ground and photo-excited states was estimated from SS and MSPP methods. DFT and TDDFT based theoretical calculations were performed for the ground and excited states dipole moments, and for vertical transitions. A significant enhancement in the excited state dipole moment was observed following photo-excitation. The large value of Δµ clearly indicates to the charge-separation in the photo-excited states, which in turn depends on the position of the hydroxyl group in the ring.

  3. Structure–activity relationship of Au/ZrO2 catalyst on formation of hydroxyl groups and its influence on CO oxidation

    SciTech Connect

    Karwacki, Christopher J.; Ganesh, P.; Kent, Paul R. C.; Gordon, Wesley O.; Peterson, Gregory W.; Niu, Jun Jie; Gogotsi, Yury

    2013-01-01

    The effect of changes in morphology and surface hydroxyl species upon thermal treatment of zirconia on the oxidation activity of Au/ZrO2 catalyst was studied. We observed using transmission fourier transform infrared (FTIR) spectroscopy progressive changes in the presence of monodentate (type I), bidentate (type II) and hydrogen bridged species (type III) for each of the thermally treated (85 to 500 C) supports consisting of bare zirconia and Au/ZrO2 catalysts. Furthermore, structural changes in zirconia were accompanied by an increase in crystal size (7 to 58 nm) and contraction of the supports porosity (SSA 532 to 7 m2/g) with increasing thermal treatment. Deposition of gold nanoparticles under similar preparation conditions on different thermally treated zirconia resulted in changes in the mean gold cluster size, ranging from 3.7 to 5.6 nm. Changes in the surface hydroxyl species, support structure and size of the gold centers are important parameters responsible for the observed decrease (> 90 %) in CO conversion activity for the Au/ZrO2 catalysts. Density functional theory calculations provide evidence of increased CO binding to Au nanoclusters in the presence of surface hydroxyls on zirconia, which increases charge transfer at the perimeter of the gold nanocluster on zirconia support. This further helps in reducing a model CO-oxidation reaction barrier in the presence of surface hydroxyls. This work demonstrates the need to understand the structure-activity relationship of both the support and active particles for the design of catalytic materials.

  4. Structure-activity relationship of Au-ZrO2 catalyst on formation of hydroxyl groups and its influence on CO oxidation

    SciTech Connect

    Karwacki, Christopher J; Ganesh, Panchapakesan; Kent, P. R. C.; Gordon, Wesley O; Peterson, Gregory W; Niu, Jun Jie; Gogotsi, Yury G.

    2013-01-01

    The effect of changes in morphology and surface hydroxyl species upon thermal treatment of zirconia on the oxidation activity of Au/ZrO2 catalyst was studied. We observed using transmission Fourier transform infrared (FTIR) spectroscopy progressive changes in the presence of monodentate (type I), bidentate (type II) and hydrogen bridged species (type III) for each of the thermally treated (85 to 500 C) supports consisting of bare zirconia and Au/ZrO2 catalysts. Furthermore, structural changes in zirconia were accompanied by an increase in crystal size (7 to 58 nm) and contraction of the supports porosity (SSA 532 to 7 m2 g 1) with increasing thermal treatment. Deposition of gold nanoparticles under similar preparation conditions on different thermally treated zirconia resulted in changes in the mean gold cluster size, ranging from 3.7 to 5.6 nm. Changes in the surface hydroxyl species, support structure and size of the gold centers are important parameters responsible for the observed decrease (>90%) in CO conversion activity for the Au/ZrO2 catalysts. Density functional theory calculations provide evidence of increased CO binding to Au nanoclusters in the presence of surface hydroxyls on zirconia, which increases charge transfer at the perimeter of the gold nanocluster on zirconia support. This further helps in reducing a model CO-oxidation reaction barrier in the presence of surface hydroxyls. This work demonstrates the need to understand the structure activity relationship of both the support and active particles for the design of catalytic materials.

  5. Additivity of Feature-Based and Symmetry-Based Grouping Effects in Multiple Object Tracking.

    PubMed

    Wang, Chundi; Zhang, Xuemin; Li, Yongna; Lyu, Chuang

    2016-01-01

    Multiple object tracking (MOT) is an attentional process wherein people track several moving targets among several distractors. Symmetry, an important indicator of regularity, is a general spatial pattern observed in natural and artificial scenes. According to the "laws of perceptual organization" proposed by Gestalt psychologists, regularity is a principle of perceptual grouping, such as similarity and closure. A great deal of research reported that feature-based similarity grouping (e.g., grouping based on color, size, or shape) among targets in MOT tasks can improve tracking performance. However, no additive feature-based grouping effects have been reported where the tracking objects had two or more features. "Additive effect" refers to a greater grouping effect produced by grouping based on multiple cues instead of one cue. Can spatial symmetry produce a similar grouping effect similar to that of feature similarity in MOT tasks? Are the grouping effects based on symmetry and feature similarity additive? This study includes four experiments to address these questions. The results of Experiments 1 and 2 demonstrated the automatic symmetry-based grouping effects. More importantly, an additive grouping effect of symmetry and feature similarity was observed in Experiments 3 and 4. Our findings indicate that symmetry can produce an enhanced grouping effect in MOT and facilitate the grouping effect based on color or shape similarity. The "where" and "what" pathways might have played an important role in the additive grouping effect.

  6. Additivity of Feature-Based and Symmetry-Based Grouping Effects in Multiple Object Tracking

    PubMed Central

    Wang, Chundi; Zhang, Xuemin; Li, Yongna; Lyu, Chuang

    2016-01-01

    Multiple object tracking (MOT) is an attentional process wherein people track several moving targets among several distractors. Symmetry, an important indicator of regularity, is a general spatial pattern observed in natural and artificial scenes. According to the “laws of perceptual organization” proposed by Gestalt psychologists, regularity is a principle of perceptual grouping, such as similarity and closure. A great deal of research reported that feature-based similarity grouping (e.g., grouping based on color, size, or shape) among targets in MOT tasks can improve tracking performance. However, no additive feature-based grouping effects have been reported where the tracking objects had two or more features. “Additive effect” refers to a greater grouping effect produced by grouping based on multiple cues instead of one cue. Can spatial symmetry produce a similar grouping effect similar to that of feature similarity in MOT tasks? Are the grouping effects based on symmetry and feature similarity additive? This study includes four experiments to address these questions. The results of Experiments 1 and 2 demonstrated the automatic symmetry-based grouping effects. More importantly, an additive grouping effect of symmetry and feature similarity was observed in Experiments 3 and 4. Our findings indicate that symmetry can produce an enhanced grouping effect in MOT and facilitate the grouping effect based on color or shape similarity. The “where” and “what” pathways might have played an important role in the additive grouping effect. PMID:27199875

  7. Effects of hydroxyl group numbers on the B-ring of 5,7-dihydroxyflavones on the differential inhibition of human CYP 1A and CYP1B1 enzymes.

    PubMed

    Kim, Hyun-Jung; Lee, Sang Bum; Park, Song-Kyu; Kim, Hwan Mook; Park, Young In; Dong, Mi-Sook

    2005-10-01

    Flavonoids are polyphenols composed of two aromatic rings (A, B) and a heterocyclic ring (C). In order to determine the effects of the number of hydroxyl groups in the B-ring of the flavonoids on human cytochrome P450 (CYP) 1 family enzymes, we evaluated the inhibition of CYP1A-dependent 7-ethoxyresorufin omicron-deethylation activity by chrysin, apigenin and luteolin, using bacterial membranes that co-express human CYP1A1, CYP1A2, or CYP1B1 with human NADPH-cytochrome P450 reductase. Chrysin, which possesses no hydroxyl groups in its B-ring, exhibited the most pronounced inhibitory effects on CYP1A2-dependent EROD activity, followed by apigenin and luteolin. On the contrary, CYP1A1-mediated EROD activity was most potently inhibited by luteolin, which is characterized by two hydroxyl groups in its B-ring, followed by apigenin and chrysin. However, all of the 5,7-dihydroxyflavones were determined to similarly inhibit CYP1B1 activity. Chrysin, apigenin, and luteolin exhibited a mixed-type mode of inhibition with regard to CYP1A2, CYP1B1, and CYP1A1, with apparent Ki values of 2.4, 0.5, and 2.0 microM, respectively. These findings suggested that the number of hydroxyl groups in the B-ring of 5,7-dihydroxyflavone might have some influence on the degree to which CYP1A enzymes were inhibited, but not on the degree to which CYP1B1 enzymes were inhibited.

  8. Discovery of pyrazine carboxamide CB1 antagonists: the introduction of a hydroxyl group improves the pharmaceutical properties and in vivo efficacy of the series.

    PubMed

    Ellsworth, Bruce A; Wang, Ying; Zhu, Yeheng; Pendri, Annapurna; Gerritz, Samuel W; Sun, Chongqing; Carlson, Kenneth E; Kang, Liya; Baska, Rose A; Yang, Yifan; Huang, Qi; Burford, Neil T; Cullen, Mary Jane; Johnghar, Susan; Behnia, Kamelia; Pelleymounter, Mary Ann; Washburn, William N; Ewing, William R

    2007-07-15

    Structure-activity relationships for a series of pyrazine carboxamide CB1 antagonists are reported. Pharmaceutical properties of the series are improved via inclusion of hydroxyl-containing sidechains. This structural modification sufficiently improved ADME properties of an orally inactive series such that food intake reduction was achieved in rat feeding models. Compound 35 elicits a 46% reduction in food intake in ad libidum fed rats 4-h post-dose.

  9. Reaction of aromatic compounds with nucleophilic reagents in liquid ammonia. VIII. The origin of the oxygen atom of the hydroxy group in the products from the hydroxylation of 1-nitronaphthalene with alkali and molecular oxygen

    SciTech Connect

    Malykhin, E.V.; Shteingarts, V.D.

    1987-10-20

    In the reaction of 1-nitronaphthalene with K/sup 18/OH and /sup 16/O/sub 2/ in liquid ammonia 1-nitro-2- and 4-nitro-1-naphthols labeled with the /sup 18/O isotope in the hydroxyl group are formed. The ratio of the isomers and the content of the /sup 18/O isotope depend on the ratio of 1-nitronaphthalene and alkali, on the temperature, and on the presence of moisture in the ammonia. The amount of the /sup 18/O isotope in the hydroxylation products indicates that in contrast to the analogous reaction of nitrobenzene and its derivatives the hydroxy function of the products in this case is formed not only from the alkali but also to a significant degree form the oxygen of the O/sub 2/.

  10. Effects of addition of Aspergillus oryzae culture and 2-hydroxyl-4-(methylthio) butanoic acid on milk performance and rumen fermentation of dairy cows.

    PubMed

    Sun, Hua; Wu, Yueming; Wang, Yanming; Wang, Chong; Liu, Jianxin

    2017-04-01

    To investigate effects of Aspergillus oryzae culture (AOC) and 2-hydroxy-4-(methylthio) butanoic acid (HMB) on milk performance and rumen fermentation of dairy cows. Sixty-four multiparous Chinese Holstein cows were randomly allocated into four experimental diets: (i) Control diet; (ii) AOC diet: 5 g AOC/day per head; (iii) HMB diet: 25 g HMB/day; and (iv) AH diet: 5 g AOC plus 25 g HMB/day. Added HMB tended to increase the yield of milk protein (P = 0.06) and 3.5% fat-corrected milk (P = 0.08) and milk fat content (P = 0.09). Milk fat yield (P = 0.03) and the contents of milk protein (P = 0.05) were increased by adding HMB. The cows fed on AOC diet had a tendency for higher body weight (BW) gain (P = 0.08). Addition of AOC, HMB and AH increased content of microbial protein (MCP) and total volatile fatty acids (VFA) (P < 0.01) in rumen fluid. Populations of rumen fungi, Fibrobacter succinogenes and Ruminococcus flavefaciens relative to total bacterial 16S rDNA (P ≤ 0.03) and activity of carboxymethylcellulase (CMCase) (P < 0.01) were increased with added AOC or HMB. It is inferred that added AOC or HMB can increase the contents of MCP and total VFA potentially by stimulating rumen microbe populations and CMCase activity.

  11. The radiocarbon hydroxyl technique

    NASA Technical Reports Server (NTRS)

    Campbell, Malcolm J.; Sheppard, John C.

    1994-01-01

    The Radiocarbon Technique depends upon measuring the rate of oxidation of CO in an essentially unperturbed sample of air. The airborne technique is slightly different. Hydroxyl concentrations can be calculated directly; peroxyl concentrations can be obtained by NO doping.

  12. Testing for Additivity at Select Mixture Groups of Interest Based on Statistical Equivalence Testing Methods

    SciTech Connect

    Stork, LeAnna M.; Gennings, Chris; Carchman, Richard; Carter, Jr., Walter H.; Pounds, Joel G.; Mumtaz, Moiz

    2006-12-01

    Several assumptions, defined and undefined, are used in the toxicity assessment of chemical mixtures. In scientific practice mixture components in the low-dose region, particularly subthreshold doses, are often assumed to behave additively (i.e., zero interaction) based on heuristic arguments. This assumption has important implications in the practice of risk assessment, but has not been experimentally tested. We have developed methodology to test for additivity in the sense of Berenbaum (Advances in Cancer Research, 1981), based on the statistical equivalence testing literature where the null hypothesis of interaction is rejected for the alternative hypothesis of additivity when data support the claim. The implication of this approach is that conclusions of additivity are made with a false positive rate controlled by the experimenter. The claim of additivity is based on prespecified additivity margins, which are chosen using expert biological judgment such that small deviations from additivity, which are not considered to be biologically important, are not statistically significant. This approach is in contrast to the usual hypothesis-testing framework that assumes additivity in the null hypothesis and rejects when there is significant evidence of interaction. In this scenario, failure to reject may be due to lack of statistical power making the claim of additivity problematic. The proposed method is illustrated in a mixture of five organophosphorus pesticides that were experimentally evaluated alone and at relevant mixing ratios. Motor activity was assessed in adult male rats following acute exposure. Four low-dose mixture groups were evaluated. Evidence of additivity is found in three of the four low-dose mixture groups.The proposed method tests for additivity of the whole mixture and does not take into account subset interactions (e.g., synergistic, antagonistic) that may have occurred and cancelled each other out.

  13. Addition of lysophospholipids with large head groups to cells inhibits Shiga toxin binding

    PubMed Central

    Ailte, Ieva; Lingelem, Anne Berit Dyve; Kavaliauskiene, Simona; Bergan, Jonas; Kvalvaag, Audun Sverre; Myrann, Anne-Grethe; Skotland, Tore; Sandvig, Kirsten

    2016-01-01

    Shiga toxin (Stx), an AB5 toxin, binds specifically to the neutral glycosphingolipid Gb3 at the cell surface before being transported into cells. We here demonstrate that addition of conical lysophospholipids (LPLs) with large head groups inhibit Stx binding to cells whereas LPLs with small head groups do not. Lysophosphatidylinositol (LPI 18:0), the most efficient LPL with the largest head group, was selected for in-depth investigations to study how the binding of Stx is regulated. We show that the inhibition of Stx binding by LPI is reversible and possibly regulated by cholesterol since addition of methyl-β-cyclodextrin (mβCD) reversed the ability of LPI to inhibit binding. LPI-induced inhibition of Stx binding is independent of signalling and membrane turnover as it occurs in fixed cells as well as after depletion of cellular ATP. Furthermore, data obtained with fluorescent membrane dyes suggest that LPI treatment has a direct effect on plasma membrane lipid packing with shift towards a liquid disordered phase in the outer leaflet, while lysophosphoethanolamine (LPE), which has a small head group, does not. In conclusion, our data show that cellular treatment with conical LPLs with large head groups changes intrinsic properties of the plasma membrane and modulates Stx binding to Gb3. PMID:27458147

  14. Catalytic enantioselective 1,6-conjugate additions of propargyl and allyl groups.

    PubMed

    Meng, Fanke; Li, Xiben; Torker, Sebastian; Shi, Ying; Shen, Xiao; Hoveyda, Amir H

    2016-09-15

    Conjugate (or 1,4-) additions of carbanionic species to α,β-unsaturated carbonyl compounds are vital to research in organic and medicinal chemistry, and there are several chiral catalysts that facilitate the catalytic enantioselective additions of nucleophiles to enoates. Nonetheless, catalytic enantioselective 1,6-conjugate additions are uncommon, and ones that incorporate readily functionalizable moieties, such as propargyl or allyl groups, into acyclic α,β,γ,δ-doubly unsaturated acceptors are unknown. Chemical transformations that could generate a new bond at the C6 position of a dienoate are particularly desirable because the resulting products could then be subjected to further modifications. However, such reactions, especially when dienoates contain two equally substituted olefins, are scarce and are confined to reactions promoted by a phosphine-copper catalyst (with an alkyl Grignard reagent, dialkylzinc or trialkylaluminium compounds), a diene-iridium catalyst (with arylboroxines), or a bisphosphine-cobalt catalyst (with monosilyl-acetylenes). 1,6-Conjugate additions are otherwise limited to substrates where there is full substitution at the C4 position. It is unclear why certain catalysts favour bond formation at C6, and-although there are a small number of catalytic enantioselective conjugate allyl additions-related 1,6-additions and processes involving a propargyl unit are non-existent. Here we show that an easily accessible organocopper catalyst can promote 1,6-conjugate additions of propargyl and 2-boryl-substituted allyl groups to acyclic dienoates with high selectivity. A commercially available allenyl-boron compound or a monosubstituted allene may be used. Products can be obtained in up to 83 per cent yield, >98:2 diastereomeric ratio (for allyl additions) and 99:1 enantiomeric ratio. We elucidate the mechanistic details, including the origins of high site selectivity (1,6- versus 1,4-) and enantioselectivity as a function of the catalyst

  15. Catalytic enantioselective 1,6-conjugate additions of propargyl and allyl groups

    PubMed Central

    Meng, Fanke; Li, Xiben; Torker, Sebastian; Shi, Ying; Shen, Xiao; Hoveyda, Amir H.

    2016-01-01

    Conjugate (or 1,4-) additions of carbanionic species to α,β-unsaturated carbonyl compounds are vital to research in organic and medicinal chemistry, and there are several known chiral catalysts that facilitate the catalytic enantioselective additions of nucleophiles to enoates1. However, catalytic enantioselective 1,6-conjugate additions are uncommon, and ones that are able to incorporate readily functionalizable moieties, such as propargyl or allyl groups, into acyclic α,β,γ,δ-doubly unsaturated acceptors are unknown2. Chemical transformations that could generate a new bond at the C6 position of a dienoate are particularly desirable, as the resulting products would be subjected to further modifications; such reactions, especially when dienoates contain two equally substituted olefins, are scarce3 and are confined to reactions promoted by a phosphine–copper (with alkyl Grignard4,5, dialkylzinc or trialkylaluminum compounds6,7), a diene–iridium (with arylboroxines)8,9, and a bisphosphine–cobalt catalyst (with monosilyl-acetylenes)10. 1,6-conjugate additions are otherwise limited to substrates where there is full substitution at C411. It is not clear why certain catalysts favor bond formation at C6, and – while there are a small number of catalytic enantioselective conjugate allyl additions12,13,14,15 – related 1,6-additions and processes involving a propargyl unit are non-existent. In this manuscript, we show that an easily accessible organocopper catalyst can promote 1,6-conjugate additions of propargyl and 2-boryl-substituted allyl groups to acyclic dienoates with high selectivity. A commercially available allenylboron compound or a monosubstituted allene may be used. Products can be obtained in up to 83 percent yield, >98 percent diastereo- (for allyl additions) and 99:1 enantiomeric ratio. Mechanistic details, including the origins of high site- (1,6- versus 1,4-) and enantioselectivity as a function of the catalyst structure and reaction type

  16. 21 CFR 172.814 - Hydroxylated lecithin.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... label of the food additive container shall bear, in addition to the other information required by the... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Hydroxylated lecithin. 172.814 Section 172.814 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED)...

  17. Surface studies of hydroxylated multi-wall carbon nanotubes

    SciTech Connect

    Bradley, Robert; Cassity, Kelby; Andrews, Rodney; Meier, Mark; Osbeck, Susan; Andreu, Aurik; Johnston, Colin; Crossley, Alison

    2012-01-01

    CVD grown MWCNTs, of typical diameter 5 to 50 nm and with approximately 15-20 concentric graphene layers in the multi-walls, have been surface functionalised using the Fenton hydroxylation reaction. HRTEM reveals little physical difference between the treated and untreated materials; images from both exhibit similar multi-wall structure and contain evidence for some low-level disruption of the very outermost layers. Raman spectra from the two types of nanotubes are almost identical displaying the disorder (D) peaks at approximately 1350 cm{sup -1} and graphite (G) peaks at approximately 1580 cm{sup -1}, characteristic of graphene-based carbon materials, in approximately equal intensity ratios. Equilibrium adsorption data for nitrogen at 77 K leads to BET surface areas of 60.4 m{sup 2} g{sup -1} for the untreated and 71.8 m{sup 2} g{sup -1} for the hydroxylated samples; the increase in area being due to separation of the tube-bundles during functionalization. This is accompanied by a decrease in measured porosity, mostly at high relative pressures of nitrogen, i.e. where larger (meso 2-5 nm and macro >5 nm) pores are being filled, which is consistent with an attendant loss of inter-tube capillarity. X-ray photoelectron spectroscopy (XPS) shows that hydroxylation increases the nanotube surface oxygen level from 4.3 at.% to 22.3 at.%; chemical shift data indicate that approximately 75% of that oxygen is present as hydroxyl (-OH) groups. Water vapour adsorption by the hydroxylated surfaces leads to Type II isotherms which are characteristic of relatively high numbers of hydrogen bonding interactions compared to the untreated materials which exhibit Type III curves. This difference in polar surface energy is confirmed by calorimetric enthalpies of immersion in water which are -54 mJ m{sup -2} for the untreated and -192 mJ m{sup -2} for the hydroxylated materials. The treated materials therefore have significantly increased water wettability/dispersivity and a greater

  18. Catalytic enantioselective 1,6-conjugate additions of propargyl and allyl groups

    NASA Astrophysics Data System (ADS)

    Meng, Fanke; Li, Xiben; Torker, Sebastian; Shi, Ying; Shen, Xiao; Hoveyda, Amir H.

    2016-09-01

    Conjugate (or 1,4-) additions of carbanionic species to α,β-unsaturated carbonyl compounds are vital to research in organic and medicinal chemistry, and there are several chiral catalysts that facilitate the catalytic enantioselective additions of nucleophiles to enoates. Nonetheless, catalytic enantioselective 1,6-conjugate additions are uncommon, and ones that incorporate readily functionalizable moieties, such as propargyl or allyl groups, into acyclic α,β,γ,δ-doubly unsaturated acceptors are unknown. Chemical transformations that could generate a new bond at the C6 position of a dienoate are particularly desirable because the resulting products could then be subjected to further modifications. However, such reactions, especially when dienoates contain two equally substituted olefins, are scarce and are confined to reactions promoted by a phosphine-copper catalyst (with an alkyl Grignard reagent, dialkylzinc or trialkylaluminium compounds), a diene-iridium catalyst (with arylboroxines), or a bisphosphine-cobalt catalyst (with monosilyl-acetylenes). 1,6-Conjugate additions are otherwise limited to substrates where there is full substitution at the C4 position. It is unclear why certain catalysts favour bond formation at C6, and—although there are a small number of catalytic enantioselective conjugate allyl additions—related 1,6-additions and processes involving a propargyl unit are non-existent. Here we show that an easily accessible organocopper catalyst can promote 1,6-conjugate additions of propargyl and 2-boryl-substituted allyl groups to acyclic dienoates with high selectivity. A commercially available allenyl-boron compound or a monosubstituted allene may be used. Products can be obtained in up to 83 per cent yield, >98:2 diastereomeric ratio (for allyl additions) and 99:1 enantiomeric ratio. We elucidate the mechanistic details, including the origins of high site selectivity (1,6- versus 1,4-) and enantioselectivity as a function of the catalyst

  19. Molecular dynamics simulation study of the effect of glycerol dialkyl glycerol tetraether hydroxylation on membrane thermostability.

    PubMed

    Huguet, Carme; Fietz, Susanne; Rosell-Melé, Antoni; Daura, Xavier; Costenaro, Lionel

    2017-02-16

    Archaeal tetraether membrane lipids span the whole membrane width and present two C40 isoprenoid chains bound by two glycerol groups (or one glycerol and calditol). These lipids confer stability and maintain the membrane fluidity in mesophile to extremophile environments, making them very attractive for biotechnological applications. The isoprenoid lipid composition in archaeal membranes varies with temperature, which has placed these lipids in the focus of paleo-climatological studies for over a decade. Non-hydroxylated isoprenoid archaeal lipids are typically used as paleo-thermometry proxies, but recently identified hydroxylated (OH) derivatives have also been proposed as temperature proxies. The relative abundance of hydroxylated lipids increases at lower temperatures, but the physiological function of the OH moiety remains unknown. Here we present molecular dynamics simulations of membranes formed by the acyclic glycerol-dialkyl-glycerol-tetraether caldarchaeol (GDGT-0), the most widespread archaeal core lipid, and its mono-hydroxylated variant (OH-GDGT-0) to better understand the physico-chemical properties conferred to the membrane by this additional moiety. The molecular dynamics simulations indicate that the additional OH group forms hydrogen bonds mainly with the sugar moieties of neighbouring lipids and with water molecules, effectively increasing the size of the polar headgroups. The hydroxylation also introduces local disorder that propagates along the entire alkyl chains, resulting in a slightly more fluid membrane. These changes would help to maintain trans-membrane transport in cold environments, explaining why the relative abundance of hydroxylated Archaea lipids increases at lower temperatures. The in silico approach aids to understand the underlying physiological mechanisms behind the hydroxylated lipid based paleo-thermometer recently proposed.

  20. Side Group Addition to the PAH Coronene by UV Photolysis in Cosmic Ice Analogs

    NASA Technical Reports Server (NTRS)

    Bernstein, Max P.; Elsila, Jamie E.; Dworkin, Jason P.; Sandford, Scott A.; Allamandola, Louis J.; Zare, Richard N.; DeVincenzi, D. (Technical Monitor)

    2002-01-01

    Ultraviolet photolysis of various ice mixtures at low temperature and pressure caused the addition of amino (-NH2), methyl (-CH3), methoxy (-OCH3), and cyano (-CN) functional groups to the polycyclic aromatic hydrocarbon (PAH) coronene (C22H12). The implications of these results for interstellar and meteoritic chemistry are discussed. Previously only simple PAH photo-oxidation had been reported. This work represents the first experimental evidence that ice photochemistry may have contributed to aromatics bearing carbon and nitrogen containing side groups that are detected in primitive meteorites and interplanetary dust particles. Furthermore, these results suggest a wider range of modified PAHs should be expected in interstellar lees and materials predating solar system formation.

  1. The role of hydroxyl group acidity on the activity of silica-supported secondary amines for the self-condensation of n-butanal.

    PubMed

    Shylesh, Sankaranarayanapillai; Hanna, David; Gomes, Joseph; Canlas, Christian G; Head-Gordon, Martin; Bell, Alexis T

    2015-02-01

    The catalytic activity of secondary amines supported on mesoporous silica for the self-condensation of n-butanal to 2-ethylhexenal can be altered significantly by controlling the Brønsted acidity of M--OH species present on the surface of the support. In this study, M--OH (M=Sn, Zr, Ti, and Al) groups were doped onto the surface of SBA-15, a mesoporous silica, prior to grafting secondary propyl amine groups on to the support surface. The catalytic activity was found to depend critically on the synthesis procedure, the nature and amount of metal species introduced and the spatial separation between the acidic sites and amine groups. DFT analysis of the reaction pathway indicates that, for weak Brønsted acid groups, such as Si--OH, the rate-limiting step is C--C bond formation, whereas for stronger Brønsted acid groups, such as Ti and Al, hydrolysis of iminium species produced upon C--C bond formation is the rate-limiting step. Theoretical analysis shows further that the apparent activation energy decreases with increasing Brønsted acidity of the M--OH groups, consistent with experimental observation.

  2. LINE-1 gene hypomethylation and p16 gene hypermethylation in HepG2 cells induced by low-dose and long-term triclosan exposure: The role of hydroxyl group.

    PubMed

    Zeng, Liudan; Ma, Huimin; Pan, Shangxia; You, Jing; Zhang, Gan; Yu, Zhiqing; Sheng, Guoying; Fu, Jiamo

    2016-08-01

    Triclosan (TCS), a frequently used antimicrobial agent in pharmaceuticals and personal care products, exerts liver tumor promoter activities in mice. Previous work showed high-dose TCS (1.25-10μM) induced global DNA hypomethylation in HepG2 cells. However, whether or how tumor suppressor gene methylation changed in HepG2 cells after low-dose and long-term TCS exposure is still unknown. We investigate here the effects and mechanisms of DNA methylation of global DNA(GDM), repetitive genes, and liver tumor suppressor gene (p16) after exposing HepG2 cells to low-dose TCS (0.625-5nM)for two weeks using HPLC-MS/MS, Methylight, Q-MSP, Pyrosequencing, and Massarray methods. We found that low-dose TCS exposure decreased repetitive elements LINE-1 methylation levels, but not global DNA methylation, through down-regulating DNMT1 (DNA methyltransferase 1) and MeCP2 (methylated DNA binding domain) expression, and up-regulating 8-hydroxy-2-deoxyguanosine (8-OHdG) levels. Interestingly, low-dose TCS elevated p16 gene methylation and inhibited p16 expression, which were not observed in high-dose (10μM) group. Meanwhile, methyl-triclosan could not induce these two types of DNA methylation changes, suggesting the involvement of hydroxyl in TCS-mediated DNA methylation changes. Collectively, our results suggested low concentrations of TCS adversely affected HepG2 cells through DNA methylation dysregulation, and hydroxyl group in TCS played an important role in the effects. This study provided a better understanding on hepatotoxicity of TCS at environmentally relevant concentrations through epigenetic pathway.

  3. Hydroxyl ionic liquids: the differentiating effect of hydroxyl on polarity due to ionic hydrogen bonds between hydroxyl and anions.

    PubMed

    Zhang, Shiguo; Qi, Xiujuan; Ma, Xiangyuan; Lu, Liujin; Deng, Youquan

    2010-03-25

    The polarity of a series of ionic liquids (ILs) based on hydroxyethyl-imidazolium moiety with various anions ([PF(6)], [NTf(2)], [ClO(4)], [DCA], [NO(3)], [AC], and [Cl]) and their corresponding nonhydroxyl ILs was investigated by solvatochromic dyes and fluorescence probe molecules. Most of the nonhydroxyl ILs exhibit anion-independent polarity with similar E(T)(30) in the narrow range of 50.7-52.6 kcal/mol, except [EMIm][AC] (49.7 kcal/mol). However, the polarity of the hydroxyl ILs covers a rather wide range (E(T)(30) = 51.2-61.7 kcal/mol) and is strongly anion-dependent. According to their E(T)(30) or E(T)(33) values, the hydroxyl ILs can be further classified into the following three groups: (Iota) acetate-based hydroxyl ILs [HOEMIm][AC] exhibit polarity scale (E(T)(30) = 51.2 kcal/mol) similar to short chain alcohol and fall in the range of the nonhydroxyl ILs; (II) Hydroxyl ILs containing anions [NO(3)], [DCA], and [Cl] exhibit comparable polarity (E(T)(30) = 55.5-56.9 kcal/mol), moderately higher than those of their nonhydroxyl ILs; (III) Hydroxyl ILs containing anions [PF(6)], [NTf(2)], and [ClO(4)] possess unusual "hyperpolarity" (E(T)(30) = 60.3-61.7 kcal/mol) close to protic ILs and water. Kamlet-Taft parameters and density functional theory calculations indicated that the greatly expanded range of polarity of hydroxyl ILs is correlated to an intramolecular synergistic solvent effect of the ionic hydrogen-bonded HBD/HBA complexes generated by intrasolvent HBD/HBA association between the anions and the hydroxyl group on cations, wherein hydroxyl group exhibits a significant differentiating effect on the strength of H-bonding and thus the polarity. Spiropyran-merocyanine equilibrium acted as a model polarity-sensitive reaction indeed shows obviously polarity-dependent solvatochromism, photochromism, and thermal reversion in hydroxyl ILs.

  4. Development of a Concise Synthesis of Ouabagenin and Hydroxylated Corticosteroid Analogues

    PubMed Central

    2016-01-01

    The natural product ouabagenin is a complex cardiotonic steroid with a highly oxygenated skeleton. This full account describes the development of a concise synthesis of ouabagenin, including the evolution of synthetic strategy to access hydroxylation at the C19 position of a steroid skeleton. In addition, approaches to install the requisite butenolide moiety at the C17 position are discussed. Lastly, methodology developed in this synthesis has been applied in the generation of novel analogues of corticosteroid drugs bearing a hydroxyl group at the C19 position. PMID:25594682

  5. ProPhenol-Catalyzed Asymmetric Additions by Spontaneously Assembled Dinuclear Main Group Metal Complexes

    PubMed Central

    2016-01-01

    Conspectus The development of catalytic enantioselective transformations has been the focus of many research groups over the past half century and is of paramount importance to the pharmaceutical and agrochemical industries. Since the award of the Nobel Prize in 2001, the field of enantioselective transition metal catalysis has soared to new heights, with the development of more efficient catalysts and new catalytic transformations at increasing frequency. Furthermore, catalytic reactions that allow higher levels of redox- and step-economy are being developed. Thus, alternatives to asymmetric alkene dihydroxylation and the enantioselective reduction of α,β-unsaturated ketones can invoke more strategic C–C bond forming reactions, such as asymmetric aldol reactions of an aldehyde with α-hydroxyketone donors or enantioselective alkynylation of an aldehyde, respectively. To facilitate catalytic enantioselective addition reactions, including the aforementioned aldol and alkynylation reactions, our lab has developed the ProPhenol ligand. In this Account, we describe the development and application of the ProPhenol ligand for asymmetric additions of both carbon- and heteroatom-based nucleophiles to various electrophiles. The ProPhenol ligand spontaneously forms chiral dinuclear metal complexes when treated with an alkyl metal reagent, such as Et2Zn or Bu2Mg. The resulting complex contains both a Lewis acidic site to activate an electrophile and a Brønsted basic site to deprotonate a pronucleophile. Initially, our research focused on the use of Zn-ProPhenol complexes to facilitate the direct aldol reaction. Fine tuning of the reaction through ligand modification and the use of additives enabled the direct aldol reaction to proceed in high yields and stereoselectivities with a broad range of donor substrates, including acetophenones, methyl ynones, methyl vinyl ketone, acetone, α-hydroxy carbonyl compounds, and glycine Schiff bases. Additionally, an analogous

  6. Hydroxyl radical scavengers inhibit lymphocyte mitogenesis.

    PubMed Central

    Novogrodsky, A; Ravid, A; Rubin, A L; Stenzel, K H

    1982-01-01

    Agents that are known to be scavengers of hydroxyl radicals inhibit lymphocyte mitogenesis induced by phorbol myristate acetate (PMA) to a greater extent than they inhibit mitogenesis induced by concanavalin A or phytohemagglutinin. These agents include dimethyl sulfoxide, benzoate, thiourea, dimethylurea, tetramethylurea, L-tryptophan, mannitol, and several other alcohols. Their inhibitory effect is not associated with cytotoxicity. The hydroxyl radical scavengers do not inhibit PMA-dependent amino acid transport in T cells or PMA-induced superoxide production by monocytes. Thus, they do not inhibit the primary interaction of PMA with responding cells. Treatment of peripheral blood mononuclear cells with PMA increased cellular guanylate cyclase in most experiments, and dimethyl sulfoxide tended to inhibit this increase. In addition to inhibition of PMA-induced mitogenesis, hydroxyl radical scavengers markedly inhibited the activity of lymphocyte activating factor (interleukin 1). The differential inhibition of lymphocyte mitogenesis induced by different mitogens appears to be related to the differential macrophage requirements of the mitogens. The data suggest that hydroxyl radicals may be involved in mediating the triggering signal for lymphocyte activation. Some of the hydroxyl radical scavengers are inducers of cellular differentiation,. nd it is possible that their differentiating activity is related to their ability to scavenge free radicals. PMID:6122209

  7. Electron stimulated hydroxylation of a metal supported silicate film.

    PubMed

    Yu, Xin; Emmez, Emre; Pan, Qiushi; Yang, Bing; Pomp, Sascha; Kaden, William E; Sterrer, Martin; Shaikhutdinov, Shamil; Freund, Hans-Joachim; Goikoetxea, Itziar; Wlodarczyk, Radoslaw; Sauer, Joachim

    2016-02-07

    Water adsorption on a double-layer silicate film was studied by using infrared reflection-absorption spectroscopy, thermal desorption spectroscopy and scanning tunneling microscopy. Under vacuum conditions, small amounts of silanols (Si-OH) could only be formed upon deposition of an ice-like (amorphous solid water, ASW) film and subsequent heating to room temperature. Silanol coverage is considerably enhanced by low-energy electron irradiation of an ASW pre-covered silicate film. The degree of hydroxylation can be tuned by the irradiation parameters (beam energy, exposure) and the ASW film thickness. The results are consistent with a generally accepted picture that hydroxylation occurs through hydrolysis of siloxane (Si-O-Si) bonds in the silica network. Calculations using density functional theory show that this may happen on Si-O-Si bonds, which are either parallel (i.e., in the topmost silicate layer) or vertical to the film surface (i.e., connecting two silicate layers). In the latter case, the mechanism may additionally involve the reaction with a metal support underneath. The observed vibrational spectra are dominated by terminal silanol groups (ν(OD) band at 2763 cm(-1)) formed by hydrolysis of vertical Si-O-Si linkages. Film dehydroxylation fully occurs only upon heating to very high temperatures (∼ 1200 K) and is accompanied by substantial film restructuring, and even film dewetting upon cycling hydroxylation/dehydroxylation treatment.

  8. Poly(hydroxyl urethane) compositions and methods of making and using the same

    DOEpatents

    Luebke, David; Nulwala, Hunaid; Tang, Chau

    2014-12-16

    Methods and compositions relating to poly(hydroxyl urethane) compounds are described herein that are useful as, among other things, binders and adhesives. The cross-linked composition is achieved through the reaction of a cyclic carbonate, a compound having two or more thiol groups, and a compound having two or more amine functional groups. In addition, a method of adhesively binding two or more substrates using the cross-linked composition is provided.

  9. Poly(hydroxyl urethane) compositions and methods of making and using the same

    SciTech Connect

    Luebke, David; Nulwala, Hunaid; Tang, Chau

    2016-01-26

    Methods and compositions relating to poly(hydroxyl urethane) compounds are described herein that are useful as, among other things, binders and adhesives. The cross-linked composition is achieved through the reaction of a cyclic carbonate, a compound having two or more thiol groups, and a compound having two or more amine functional groups. In addition, a method of adhesively binding two or more substrates using the cross-linked composition is provided.

  10. Peptidyl-CCA deacylation on the ribosome promoted by induced fit and the O3'-hydroxyl group of A76 of the unacylated A-site tRNA.

    PubMed

    Simonović, Miljan; Steitz, Thomas A

    2008-11-01

    The last step in ribosome-catalyzed protein synthesis is the hydrolytic release of the newly formed polypeptide from the P-site bound tRNA. Hydrolysis of the ester link of the peptidyl-tRNA is stimulated normally by the binding of release factors (RFs). However, an unacylated tRNA or just CCA binding to the ribosomal A site can also stimulate deacylation under some nonphysiological conditions. Although the sequence of events is well described by biochemical studies, the structural basis of the mechanism underlying this process is not well understood. Two new structures of the large ribosomal subunit of Haloarcula marismortui complexed with a peptidyl-tRNA analog in the P site and two oligonucleotide mimics of unacylated tRNA, CCA and CA, in the A site show that the binding of either CA or CCA induces a very similar conformational change in the peptidyl-transferase center as induced by aminoacyl-CCA. However, only CCA positions a water molecule appropriately to attack the carbonyl carbon of the peptidyl-tRNA and stabilizes the proper orientation of the ester link for hydrolysis. We, thus, conclude that both the ability of the O3'-hydroxyl group of the A-site A76 to position the water and the A-site CCA induced conformational change of the PTC are critical for the catalysis of the deacylation of the peptidyl-tRNA by CCA, and perhaps, an analogous mechanism is used by RFs.

  11. Peptidyl-CCA deacylation on the ribosome promoted by induced fit and the O3′-hydroxyl group of A76 of the unacylated A-site tRNA

    SciTech Connect

    Simonović, Miljan; Steitz, Thomas A.

    2008-11-24

    The last step in ribosome-catalyzed protein synthesis is the hydrolytic release of the newly formed polypeptide from the P-site bound tRNA. Hydrolysis of the ester link of the peptidyl-tRNA is stimulated normally by the binding of release factors (RFs). However, an unacylated tRNA or just CCA binding to the ribosomal A site can also stimulate deacylation under some nonphysiological conditions. Although the sequence of events is well described by biochemical studies, the structural basis of the mechanism underlying this process is not well understood. Two new structures of the large ribosomal subunit of Haloarcula marismortui complexed with a peptidyl-tRNA analog in the P site and two oligonucleotide mimics of unacylated tRNA, CCA and CA, in the A site show that the binding of either CA or CCA induces a very similar conformational change in the peptidyl-transferase center as induced by aminoacyl-CCA. However, only CCA positions a water molecule appropriately to attack the carbonyl carbon of the peptidyl-tRNA and stabilizes the proper orientation of the ester link for hydrolysis. We, thus, conclude that both the ability of the O3'-hydroxyl group of the A-site A76 to position the water and the A-site CCA induced conformational change of the PTC are critical for the catalysis of the deacylation of the peptidyl-tRNA by CCA, and perhaps, an analogous mechanism is used by RFs.

  12. Hydroxyl speciation in felsic magmas

    NASA Astrophysics Data System (ADS)

    Malfait, Wim J.; Xue, Xianyu

    2014-09-01

    The hydroxyl speciation of hydrous, metaluminous potassium and calcium aluminosilicate glasses was investigated by 27Al-1H cross polarization and quantitative 1H MAS NMR spectroscopy. Al-OH is present in both the potassium and the calcium aluminosilicate glasses and its 1H NMR partial spectrum was derived from the 27Al-1H cross polarization data. For the calcium aluminosilicate glasses, the abundance of Al-OH could not be determined because of the low spectral resolution. For the potassium aluminosilicate glasses, the fraction of Al-OH was quantified by fitting its partial spectrum to the quantitative 1H NMR spectra. The degree of aluminum avoidance and the relative tendency for Si-O-Si, Si-O-Al and Al-O-Al bonds to hydrolyze were derived from the measured species abundances. Compared to the sodium, lithium and calcium systems, potassium aluminosilicate glasses display a much stronger degree of aluminum avoidance and a stronger tendency for the Al-O-Al linkages to hydrolyze. Combining our results with those for sodium aluminosilicate glasses (Malfait and Xue, 2010a), we predict that the hydroxyl groups in rhyolitic and phonolitic magmas are predominantly present as Si-OH (84-89% and 68-78%, respectively), but with a significant fraction of Al-OH (11-16% and 22-32%, respectively). For both rhyolitic and phonolitic melts, the AlOH/(AlOH + SiOH) ratio is likely smaller than the Al/(Al + Si) ratio for the lower end of the natural temperature range but may approach the Al/(Al + Si) ratio at higher temperatures.

  13. An NADPH and FAD dependent enzyme catalyzes hydroxylation of flavonoids in position 8.

    PubMed

    Halbwirth, Heidrun; Stich, Karl

    2006-06-01

    Yellow flavonols contribute to flower pigmentation in Asteraceae. In contrast to common flavonols, they show additional hydroxyl groups in position 6 and/or 8 of the aromatic A-ring in addition to the basic 5,7-hydroxylation pattern. An enzyme introducing a hydroxyl group in position 8 of flavonols and flavones was demonstrated for the first time with enzyme preparations from petals of Chrysanthemum segetum. Flavanones, dihydroflavonols and glucosylated flavonols and flavones were not accepted as substrates. The enzyme was localized in the microsomal fraction and uses NADPH and FAD as cofactors. Experiments with carbon monoxide/blue light and with antibodies specific for cytochrome P450 reductase did not indicate the involvement of a classical cytochrome P450 dependent monooxygenase in the reaction. Thus, the flavonoid 8-hydroxylase represents a novel type of hydroxylating enzyme in the flavonoid pathway. Apart from flavonoid 8-hydroxylase activity, the presence of all enzymes involved in the formation of flavonoid 7-O-glucosides in C. segetum was demonstrated. The pathway leading to 8-hydroxyflavonoids in C. segetum has been derived from enzyme activities and substrate specificities observed.

  14. 40 CFR 79.56 - Fuel and fuel additive grouping system.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...-sponsored testing and analysis conducted on a product which is representative of all products in that group... nitroso-compounds; mixed nitro-compounds; mixed alkyl nitrates; mixed alkyl nitrites; peroxides;...

  15. 40 CFR 79.56 - Fuel and fuel additive grouping system.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...-sponsored testing and analysis conducted on a product which is representative of all products in that group... nitroso-compounds; mixed nitro-compounds; mixed alkyl nitrates; mixed alkyl nitrites; peroxides;...

  16. 40 CFR 79.56 - Fuel and fuel additive grouping system.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...-sponsored testing and analysis conducted on a product which is representative of all products in that group... nitroso-compounds; mixed nitro-compounds; mixed alkyl nitrates; mixed alkyl nitrites; peroxides;...

  17. 40 CFR 79.56 - Fuel and fuel additive grouping system.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...-sponsored testing and analysis conducted on a product which is representative of all products in that group... nitroso-compounds; mixed nitro-compounds; mixed alkyl nitrates; mixed alkyl nitrites; peroxides;...

  18. 40 CFR 79.56 - Fuel and fuel additive grouping system.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...-sponsored testing and analysis conducted on a product which is representative of all products in that group... nitroso-compounds; mixed nitro-compounds; mixed alkyl nitrates; mixed alkyl nitrites; peroxides;...

  19. Experimental evidence for efficient hydroxyl radical regeneration in isoprene oxidation

    NASA Astrophysics Data System (ADS)

    Fuchs, H.; Hofzumahaus, A.; Rohrer, F.; Bohn, B.; Brauers, T.; Dorn, H.-P.; Häseler, R.; Holland, F.; Kaminski, M.; Li, X.; Lu, K.; Nehr, S.; Tillmann, R.; Wegener, R.; Wahner, A.

    2013-12-01

    Most pollutants in the Earth's atmosphere are removed by oxidation with highly reactive hydroxyl radicals. Field measurements have revealed much higher concentrations of hydroxyl radicals than expected in regions with high loads of the biogenic volatile organic compound isoprene. Different isoprene degradation mechanisms have been proposed to explain the high levels of hydroxyl radicals observed. Whether one or more of these mechanisms actually operates in the natural environment, and the potential impact on climate and air quality, has remained uncertain. Here, we present a complete set of measurements of hydroxyl and peroxy radicals collected during isoprene-oxidation experiments carried out in an atmospheric simulation chamber, under controlled atmospheric conditions. We detected significantly higher concentrations of hydroxyl radicals than expected based on model calculations, providing direct evidence for a strong hydroxyl radical enhancement due to the additional recycling of radicals in the presence of isoprene. Specifically, our findings are consistent with the unimolecular reactions of isoprene-derived peroxy radicals postulated by quantum chemical calculations. Our experiments suggest that more than half of the hydroxyl radicals consumed in isoprene-rich regions, such as forests, are recycled by these unimolecular reactions with isoprene. Although such recycling is not sufficient to explain the high concentrations of hydroxyl radicals observed in the field, we conclude that it contributes significantly to the oxidizing capacity of the atmosphere in isoprene-rich regions.

  20. Towards a full understanding of the nature of Ni(II) species and hydroxyl groups over highly siliceous HZSM-5 zeolite supported nickel catalysts prepared by a deposition-precipitation method.

    PubMed

    Chen, Bao-Hui; Chao, Zi-Sheng; He, Hao; Huang, Chen; Liu, Ya-Juan; Yi, Wen-Jun; Wei, Xue-Ling; An, Jun-Fang

    2016-02-14

    Highly siliceous HZSM-5 zeolite supported nickel catalysts prepared by a deposition-precipitation (D-P) method were characterized by Fourier transform infrared (FT-IR), hydrogen temperature programmed reduction (H2-TPR), X-ray diffraction (XRD), N2-absorption/desorption, field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and (27)Al magic-angle nuclear magnetic resonance (MAS NMR) techniques. The results showed that the D-P of nickel species occurred predominantly on the internal surface of highly siliceous HZSM-5 zeolite, in which the internal silanol groups located on the hydroxylated mesopores or nanocavities played a key role. During the D-P process, nickel hydroxide was first deposited-precipitated via olation/polymerization of neutral hydroxoaqua nickel species over the HZSM-5 zeolite. With the progress of the D-P process, 1 : 1 nickel phyllosilicate was formed over the HZSM-5 via the hetero-condensation/polymerization between charged hydroxoaqua nickel species and monomer silicic species generated due to the partial dissolution of the HZSM-5 framework. The 1 : 1 nickel phyllosilicate could also be generated via the hydrolytic adsorption of hydroxoaqua nickel species and their subsequent olation condensation. After calcination, the deposited-precipitated nickel hydroxide was decomposed into nickel oxide, while the 1 : 1 nickel phyllosilicate was transformed into 2 : 1 nickel phyllosilicate. According to the above mechanism, Ni(ii) species were present both in the form of nickel oxide and 2 : 1 nickel phyllosilicate, which were mutually separated from each other, being highly dispersed over HZSM-5 zeolite.

  1. Hydroxylated PBDEs induce developmental arrest in zebrafish

    SciTech Connect

    Usenko, Crystal Y. Hopkins, David C.; Trumble, Stephen J. Bruce, Erica D.

    2012-07-01

    The ubiquitous spread of polybrominated diphenyl ethers (PBDEs) has led to concerns regarding the metabolites of these congeners, in particular hydroxylated PBDEs. There are limited studies regarding the biological interactions of these chemicals, yet there is some concern they may be more toxic than their parent compounds. In this study three hydroxylated PBDEs were assessed for toxicity in embryonic zebrafish: 3-OH-BDE 47, 5-OH-BDE 47, and 6-OH-BDE 47. All three congeners induced developmental arrest in a concentration-dependent manner; however, 6-OH-BDE 47 induced adverse effects at lower concentrations than the other congeners. Furthermore, all three induced cell death; however apoptosis was not observed. In short-term exposures (24–28 hours post fertilization), all hydroxylated PBDEs generated oxidative stress in the region corresponding to the cell death at 5 and 10 ppm. To further investigate the short-term effects that may be responsible for the developmental arrest observed in this study, gene regulation was assessed for embryos exposed to 0.625 ppm 6-OH-BDE 47 from 24 to 28 hpf. Genes involved in stress response, thyroid hormone regulation, and neurodevelopment were significantly upregulated compared to controls; however, genes related to oxidative stress were either unaffected or downregulated. This study suggests that hydroxylated PBDEs disrupt development, and may induce oxidative stress and potentially disrupt the cholinergic system and thyroid hormone homeostasis. -- Highlights: ► OH-PBDEs induce developmental arrest in a concentration-dependent manner. ► Hydroxyl group location influences biological interaction. ► OH-PBDEs induce oxidative stress. ► Thyroid hormone gene regulation was disrupted following exposure. ► To our knowledge, this is the first whole organism study of OH-PBDE toxicity.

  2. Additional Validity Evidence and Across-Group Equivalency of the "HOPE Teacher Rating Scale"

    ERIC Educational Resources Information Center

    Peters, Scott J.; Gentry, Marcia

    2013-01-01

    The "HOPE Scale" was developed to identify academic and social components of giftedness and talent in elementary-aged students with particular attention to students from low-income and/or culturally diverse families. Based on previous findings, additional research was conducted on revisions made to the "HOPE Scale". Items were…

  3. Petroleum films exposed to sunlight produce hydroxyl radical.

    PubMed

    Ray, Phoebe Z; Tarr, Matthew A

    2014-05-01

    Sunlight exposed oil films on seawater or pure water produced substantial amounts of hydroxyl radical as a result of irradiation. Oil was collected from the surface of the Gulf of Mexico following the Deepwater Horizon spill and exposed to simulated sunlight in thin films over water. Photochemical production of hydroxyl radical was measured with benzoic acid as a selective chemical probe in the aqueous layer. Total hydroxyl radical formation was studied using high benzoic acid concentrations and varying exposure time. The total amount of hydroxyl radical produced in 24 h irradiations of thin oil films over Gulf of Mexico water and pure water were 3.7×10(-7) and 4.2×10(-7) moles respectively. Steady state concentrations of hydroxyl radical were measured using a competition kinetics approach. Hydroxyl radical concentrations of 1.2×10(-16) to 2.4×10(-16) M were observed for seawater and pure water under oil films. Titanium dioxide (TiO2) nanomaterials were added to the system in an effort to determine if the photocatalyst would enhance oil photodegradation. The addition of TiO2 nanoparticles dramatically changed the observed formation rate of hydroxyl radical in the systems with NP water at pH 3, showing increased formation rate in many cases. With photocatalyst, the steady state concentration of radical decreased, predominantly due to an increase in the hydroxyl radical scavenging rate with oxide present. This study illustrates that oil is a strong and important source of hydroxyl radical when exposed to sunlight. The fate of oil and other dissolved species following oil spills will be heavily dependent on the formation and fate of hydroxyl radical.

  4. Selective behavioral alterations on addition of a 4'-phenyl group to cocaine.

    PubMed

    Seale, T W; Niekrasz, I; Chang, F; Singh, S; Basmadjian, G P

    1996-01-31

    We synthesized a cocaine analog in which a phenyl group was added at the para-position of the benzene ring of cocaine. This substitution caused a modest reduction (four-fold compared with cocaine) in binding potency for the primate (Papio) dopamine transporter as judged by displacement of [3H]WIN 35,428 binding from caudate/putamen membranes. Behavioral effects of this structural modification in the mouse were complex and selective, comprising absence of stimulation of locomotor activity, enhanced inhibition of locomotion and reduced lethal potency. Convulsant potency was unaltered. Substituents at the 4'-position of cocaine are important in its actions. Simple changes in the chemical structure of this drug may produce complex and selective changes in its neurochemical and behavioral actions.

  5. Activity related to the carcinogenicity of plastic additives in the benzophenone group.

    PubMed

    Nakajima, Daisuke; Asada, Shin; Kageyama, Shiho; Yamamoto, Takashi; Kuramochi, Hidetoshi; Tanaka, Noriho; Takeda, Ken; Goto, Sumio

    2006-06-01

    This study examines the activities relating to the carcinogenicity of six types of benzophenone derivatives (benzophenone, 2-hydroxy-4-octyloxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone and 2,2'-dihydroxy-4,4'-dimethoxybenzophenone) currently used in plastic products as additives to serve as ultraviolet absorbing agents. The evaluation of the initiation activity used a light absorption umu-test, a luminescent umu-test and the Ames test. The promotion activity was examined by a Bhas assay, a method that uses Bhas 42 cells for the formation of transformation foci. The luminescent umu-test indicated positive initiation activity of 2-hydroxy-4-methoxybenzophenone, and pseudo-positive activity of 2,4-dihydroxybenzophenone and 2,2'-dihydroxy-4-methoxybenzophenone. In the Ames test, 2-hydroxy-4-octyloxybenzophenone showed pseudo-positive initiation activity. Conversely, 2,4-dihydroxybenzophenone indicated weak promotion activity at 10 microg/ml concentration.

  6. Hydroxyl radical-mediated conversion of morphine to morphinone.

    PubMed

    Kumagai, Y; Ikeda, Y; Toki, S

    1992-05-01

    1. The hydroxyl radical-mediated conversion of morphine to morphinone (MO) was examined as an alternative to the enzymic reaction. 2. Hydroxyl radicals were generated by autoxidation of ascorbate in the presence of iron and EDTA. This system oxidized morphine to MO which was identified by h.p.l.c. and t.l.c. The reaction was dependent on the concentration of added Fe2+ and required the addition of ascorbate when Fe3+ was used. 3. Catalase inhibited production of MO whereas superoxide dismutase (SOD) had no effect. Addition of a large amount of H2O2 to the system resulted in a significant decrease in production of MO. No MO production was initiated by H2O2 itself. The oxidation of morphine was inhibited by typical hydroxyl radical-scavenging agents. These results indicate that morphine undergoes oxidation to MO by hydroxyl radical.

  7. Additive opportunistic capture explains group hunting benefits in African wild dogs.

    PubMed

    Hubel, Tatjana Y; Myatt, Julia P; Jordan, Neil R; Dewhirst, Oliver P; McNutt, J Weldon; Wilson, Alan M

    2016-03-29

    African wild dogs (Lycaon pictus) are described as highly collaborative endurance pursuit hunters based on observations derived primarily from the grass plains of East Africa. However, the remaining population of this endangered species mainly occupies mixed woodland savannah where hunting strategies appear to differ from those previously described. We used high-resolution GPS and inertial technology to record fine-scale movement of all members of a single pack of six adult African wild dogs in northern Botswana. The dogs used multiple short-distance hunting attempts with a low individual kill rate (15.5%), but high group feeding rate due to the sharing of prey. Use of high-level cooperative chase strategies (coordination and collaboration) was not recorded. In the mixed woodland habitats typical of their current range, simultaneous, opportunistic, short-distance chasing by dogs pursuing multiple prey (rather than long collaborative pursuits of single prey by multiple individuals) could be the key to their relative success in these habitats.

  8. Additional duplicated Hox genes in the earthworm: Perionyx excavatus Hox genes consist of eleven paralog groups.

    PubMed

    Cho, Sung-Jin; Vallès, Yvonne; Kim, Kyong Min; Ji, Seong Chul; Han, Seock Jung; Park, Soon Cheol

    2012-02-10

    Annelida is a lophotrochozoan phylum whose members have a high degree of diversity in body plan morphology, reproductive strategies and ecological niches among others. Of the two traditional classes pertaining to the phylum Annelida (Polychaete and Clitellata), the structure and function of the Hox genes has not been clearly defined within the Oligochaeta class. Using a PCR-based survey, we were able to identify five new Hox genes from the earthworm Perionyx excavatus: a Hox3 gene (Pex-Hox3b), two Dfd genes (Pex-Lox6 and Pex-Lox18), and two posterior genes (Pex-post1 and -post2a). Our result suggests that the eleven earthworm Hox genes contain at least four paralog groups (PG) that have duplicated. We found the clitellates-diagnostic signature residues and annelid signature motif. Also, we show by semi-quantitative RT-PCR that duplicated Hox gene orthologs are differentially expressed in six different anterior-posterior body regions. These results provide essential data for comparative evolution of the Hox cluster within the Annelida.

  9. Additive opportunistic capture explains group hunting benefits in African wild dogs

    PubMed Central

    Hubel, Tatjana Y.; Myatt, Julia P.; Jordan, Neil R.; Dewhirst, Oliver P.; McNutt, J. Weldon; Wilson, Alan M.

    2016-01-01

    African wild dogs (Lycaon pictus) are described as highly collaborative endurance pursuit hunters based on observations derived primarily from the grass plains of East Africa. However, the remaining population of this endangered species mainly occupies mixed woodland savannah where hunting strategies appear to differ from those previously described. We used high-resolution GPS and inertial technology to record fine-scale movement of all members of a single pack of six adult African wild dogs in northern Botswana. The dogs used multiple short-distance hunting attempts with a low individual kill rate (15.5%), but high group feeding rate due to the sharing of prey. Use of high-level cooperative chase strategies (coordination and collaboration) was not recorded. In the mixed woodland habitats typical of their current range, simultaneous, opportunistic, short-distance chasing by dogs pursuing multiple prey (rather than long collaborative pursuits of single prey by multiple individuals) could be the key to their relative success in these habitats. PMID:27023355

  10. A group additivity algorithm for polychlorinated dibenzofurans derived from selected DFT analyses.

    PubMed

    Thompson, Dennis; Ewan, Bruce C R

    2007-06-14

    The difficulty in measuring the heats of combustion of polychlorinated dibenzofurans (PCDFs) has resulted in a shortage of data on their heats of formation, required for the purpose of developing an understanding of the role of thermodynamics and kinetics in their production via industrial processes. B3LYP density functional theory calculations have been carried out on a number of PCDFs using 6-31G(d) and 6-311+G(3df,p) basis sets to estimate their heats of formation based on the known experimental values for dibenzofuran, benzene and chlorobenzene. By examining the interactions among chlorine substituents, it is shown that energy contributions arising from successive chlorination can be interpreted in a predictable way, based on a small number of key energy parameters associated with ring position and chlorine atom repulsions. These parameters have been presented as the basis for a simplified prediction algorithm, which can be used to reproduce the predicted DFT heat of formation to within a few kJ/mol, avoiding the need to carry out extensive DFT calculations on the possible 135 isomers of the dibenzofuran group.

  11. Hydroxyl radical generation by red tide algae.

    PubMed

    Oda, T; Akaike, T; Sato, K; Ishimatsu, A; Takeshita, S; Muramatsu, T; Maeda, H

    1992-04-01

    The unicellular marine phytoplankton Chattonella marina is known to have toxic effects against various living marine organisms, especially fishes. However, details of the mechanism of the toxicity of this plankton remain obscure. Here we demonstrate the generation of superoxide and hydroxyl radicals from a red tide unicellular organism, C. marina, by using ESR spectroscopy with the spin traps 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and N-t-butyl-alpha-phenylnitrone (PBN), and by using the luminol-enhanced chemiluminescence response. The spin-trapping assay revealed productions of spin adduct of superoxide anion (O2-) (DMPO-OOH) and that of hydroxyl radical (.OH) (DMPO-OH) in the algal suspension, which was not observed in the ultrasonic-ruptured suspension. The addition of superoxide dismutase (500 U/ml) almost completely inhibited the formation of both DMPO-OOH and DMPO-OH, and carbon-centered radicals were generated with the disappearance of DMPO-OH after addition of 5% dimethyl sulfoxide (Me2SO) and 5% ethanol. Furthermore, the generation of methyl and methoxyl radicals, which are thought to be produced by the reaction of hydroxyl radical and Me2SO under aerobic condition, was identified using spin trapping with a combination of PBN and Me2SO. Luminol-enhanced chemiluminescence assay also supported the above observations. These results clearly indicate that C. marina generates and releases the superoxide radical followed by the production of hydroxyl radical to the surrounding environment. The velocity of superoxide generation by C. marina was about 100 times faster than that by mammalian phagocytes per cell basis. The generation of oxygen radical is suggested to be a pathogenic principle in the toxication of red tide to susceptible aquaculture fishes and may be directly correlated with the coastal pollution by red tide.

  12. Sum Frequency Vibrational Spectroscopy (SFVS) of Water and Hydroxyls on the Corundum (1-102) surface: Acid-base properties from direct observation of protonation states

    NASA Astrophysics Data System (ADS)

    Waychunas, G.; Sung, J.; Shen, R.

    2010-12-01

    SFVS is a powerful tool for quantitative measurement of protonated functional groups on mineral surfaces. We demonstrate this for the Corundum (1-102) interface where the orientation and nature of surface hydroxyls on the dry neutral surface can be obtained and compared with Crystal Truncation Rod (CTR) models for the surface termination and most likely functional groups, effectively allowing testing of such models. A scheme for describing the hydrogen bonding among these protonated groups is found to be consistent with surface symmetry and the particular vibrational frequencies observed. The addition of water to the interface alters the hydrogen bonding of the hydroxyls and introduces water-functional group hydrogen bonding. Direct measurement of the SFVS hydroxyl and water band amplitudes can be used to test expected pKa values, and hence link acid-base properties to precise molecular surface entities. The analysis methodology can be applied to analogous nanoparticle surfaces, though with some limitations.

  13. Glutathione--hydroxyl radical interaction: a theoretical study on radical recognition process.

    PubMed

    Fiser, Béla; Jójárt, Balázs; Csizmadia, Imre G; Viskolcz, Béla

    2013-01-01

    Non-reactive, comparative (2 × 1.2 μs) molecular dynamics simulations were carried out to characterize the interactions between glutathione (GSH, host molecule) and hydroxyl radical (OH(•), guest molecule). From this analysis, two distinct steps were identified in the recognition process of hydroxyl radical by glutathione: catching and steering, based on the interactions between the host-guest molecules. Over 78% of all interactions are related to the catching mechanism via complex formation between anionic carboxyl groups and the OH radical, hence both terminal residues of GSH serve as recognition sites. The glycine residue has an additional role in the recognition of OH radical, namely the steering. The flexibility of the Gly residue enables the formation of further interactions of other parts of glutathione (e.g. thiol, α- and β-carbons) with the lone electron pair of the hydroxyl radical. Moreover, quantum chemical calculations were carried out on selected GSH/OH(•) complexes and on appropriate GSH conformers to describe the energy profile of the recognition process. The relative enthalpy and the free energy changes of the radical recognition of the strongest complexes varied from -42.4 to -27.8 kJ/mol and from -21.3 to 9.8 kJ/mol, respectively. These complexes, containing two or more intermolecular interactions, would be the starting configurations for the hydrogen atom migration to quench the hydroxyl radical via different reaction channels.

  14. Glutathione – Hydroxyl Radical Interaction: A Theoretical Study on Radical Recognition Process

    PubMed Central

    Fiser, Béla; Jójárt, Balázs; Csizmadia, Imre G.; Viskolcz, Béla

    2013-01-01

    Non-reactive, comparative (2×1.2 μs) molecular dynamics simulations were carried out to characterize the interactions between glutathione (GSH, host molecule) and hydroxyl radical (OH•, guest molecule). From this analysis, two distinct steps were identified in the recognition process of hydroxyl radical by glutathione: catching and steering, based on the interactions between the host-guest molecules. Over 78% of all interactions are related to the catching mechanism via complex formation between anionic carboxyl groups and the OH radical, hence both terminal residues of GSH serve as recognition sites. The glycine residue has an additional role in the recognition of OH radical, namely the steering. The flexibility of the Gly residue enables the formation of further interactions of other parts of glutathione (e.g. thiol, α- and β-carbons) with the lone electron pair of the hydroxyl radical. Moreover, quantum chemical calculations were carried out on selected GSH/OH• complexes and on appropriate GSH conformers to describe the energy profile of the recognition process. The relative enthalpy and the free energy changes of the radical recognition of the strongest complexes varied from −42.4 to −27.8 kJ/mol and from −21.3 to 9.8 kJ/mol, respectively. These complexes, containing two or more intermolecular interactions, would be the starting configurations for the hydrogen atom migration to quench the hydroxyl radical via different reaction channels. PMID:24040010

  15. Glucose dehydrogenase polymorphism among ethnic groups of Singapore--with report of two additional alleles (GDH4 and GDH5).

    PubMed

    Saha, N; Bhattacharyya, S P; Yeoh, S C; Chua, S P; Ratnam, S S

    1987-02-01

    Placental glucose dehydrogenase (GDH; E.C.1.1.1.47) polymorphism was studied in 254 Chinese, 104 Malays, and 47 Indians from Singapore using isoelectric focusing. There is suggestive evidence of two additional anodal alleles (GDH4 and GDH5) in addition to the three alleles described in earlier studies. Altogether, 14 phenotypes have been observed in the present investigation, compared with six phenotypes described in earlier studies. It appears that placental GDH is controlled by five codominant autosomal alleles producing 15 possible phenotypes. The gene frequencies of GDH1, GDH2, and GDH3 in these ethnic groups are significantly different from those reported in Caucasians. There were slight differences in the gene frequencies between the three ethnic groups, with those of Indians being nearer to the frequency in Caucasians. In general, the distribution of GDH phenotypes was at Hardy-Weinberg equilibrium in all three ethnic groups studied.

  16. Hyperglycemia induces apoptosis in rat liver through the increase of hydroxyl radical: new insights into the insulin effect.

    PubMed

    Francés, Daniel E; Ronco, María T; Monti, Juan A; Ingaramo, Paola I; Pisani, Gerardo B; Parody, Juan P; Pellegrino, José M; Sanz, Paloma Martín; Carrillo, María C; Carnovale, Cristina E

    2010-05-01

    In this study, we analyzed the contribution of hydroxyl radical in the liver apoptosis mediated by hyperglycemia through the Bax-caspase pathway and the effects of insulin protection against the apoptosis induced by hyperglycemia. Male adult Wistar rats were randomized in three groups: control (C) (sodium citrate buffer, i.p.), streptozotocin (STZ)-induced diabetic (SID) (STZ 60 mg/kg body weight, i.p.), and insulin-treated SID (SID+I; 15 days post STZ injection, SID received insulin s.c., twice a day, 15 days). Rats were autopsied on day 30. In liver tissue, diabetes promoted a significant increase in hydroxyl radical production which correlated with lipid peroxidation (LPO) levels. Besides, hyperglycemia significantly increased mitochondrial BAX protein expression, cytosolic cytochrome c levels, and caspase-3 activity leading to an increase in apoptotic index. Interestingly, the treatment of diabetic rats with desferoxamine or tempol (antioxidants/hydroxyl radical scavengers) significantly attenuated the increase in both hydroxyl radical production and in LPO produced by hyperglycemia, preventing apoptosis by reduction of mitochondrial BAX and cytosolic cytochrome c levels. Insulin treatment showed similar results. The finding that co-administration of antioxidants/hydroxyl radical scavengers together with insulin did not provide any additional benefit compared with those obtained using either inhibitors or insulin alone shows that it is likely that insulin prevents oxidative stress by reducing the effects of hydroxyl radicals. Importantly, insulin significantly increased apoptosis inhibitor protein expression by induction of its mRNA. Taken together, our studies support that, at least in part, the hydroxyl radical acts as a reactive intermediate, which leads to liver apoptosis in a model of STZ-mediated hyperglycemia. A new anti-apoptosis signal for insulin is shown, given by an increase of apoptosis inhibitor protein.

  17. Adenine oxidation by pyrite-generated hydroxyl radicals.

    PubMed

    Cohn, Corey A; Fisher, Shawn C; Brownawell, Bruce J; Schoonen, Martin Aa

    2010-04-26

    Cellular exposure to particulate matter with concomitant formation of reactive oxygen species (ROS) and oxidization of biomolecules may lead to negative health outcomes. Evaluating the particle-induced formation of ROS and the oxidation products from reaction of ROS with biomolecules is useful for gaining a mechanistic understanding of particle-induced oxidative stress. Aqueous suspensions of pyrite particles have been shown to form hydroxyl radicals and degrade nucleic acids. Reactions between pyrite-induced hydroxyl radicals and nucleic acid bases, however, remain to be determined. Here, we compared the oxidation of adenine by Fenton-generated (i.e., ferrous iron and hydrogen peroxide) hydroxyl radicals to adenine oxidation by hydroxyl radicals generated in pyrite aqueous suspensions. Results show that adenine oxidizes in the presence of pyrite (without the addition of hydrogen peroxide) and that the rate of oxidation is dependent on the pyrite loading. Adenine oxidation was prevented by addition of either catalase or ethanol to the pyrite/adenine suspensions, which implies that hydrogen peroxide and hydroxyl radicals are causing the adenine oxidation. The adenine oxidation products, 8-oxoadenine and 2-hydroxyadenine, were the same whether hydroxyl radicals were generated by Fenton or pyrite-initiated reactions. Although nucleic acid bases are unlikely to be directly exposed to pyrite particles, the formation of ROS in the vicinity of cells may lead to oxidative stress.

  18. Summation solute hydrogen bonding acidity values for hydroxyl substituted flavones determined by NMR spectroscopy.

    PubMed

    Whaley, William L; Okoso-amaa, Ekua M; Womack, Cody L; Vladimirova, Anna; Rogers, Laura B; Risher, Margaret J; Abraham, Michael H

    2013-01-01

    The flavonoids are a structurally diverse class of natural products that exhibit a broad spectrum of biochemical activities. The flavones are one of the most studied flavonoid subclasses due to their presence in dietary plants and their potential to protect human cells from reactive oxygen species (ROS). Several flavone compounds also mediate beneficial actions by direct binding to protein receptors and regulatory enzymes. There is current interest in using Quantitative Structure Activity Relationships (QSARs) to guide drug development based on flavone lead structures. This approach is most informative when it involves the use of accurate physical descriptors. The Abraham summation solute hydrogen bonding acidity (A) is a descriptor in the general solvation equation. It defines the tendency of a molecule to act as a hydrogen bond donor, or acid, when surrounded by solvent molecules that are hydrogen bonding acceptors, or bases. As a linear free energy relationship, it is useful for predicting the absorption and uptake of drug molecules. A previously published method, involving nuclear magnetic resonance (NMR) spectroscopy, was used to evaluate A for the monohydroxyflavones (MHFs). Values of A ranged from 0.02, for 5-hydroxyflavone, to 0.69 for 4'-hydroxyflavone. The ability to examine separate NMR signals for individual hydroxyl groups allowed the investigation of intramolecular interactions between functional groups. The value of A for the position 7 hydroxyl group of 7-hydroxyflavone was 0.67. The addition of a position 5 hydroxyl group (in 5,7-dihydroxyflavone) increased the value of A for the position 7 hydroxyl group to 0.76. Values of A for MHFs were also calculated by the program ACD-Absolve and these agreed well with values measured by NMR. These results should facilitate more accurate estimation of the values of A for structurally complex flavones with pharmacological activities.

  19. Hydroxyl Radical-Mediated Novel Modification of Peptides: N-Terminal Cyclization through the Formation of α-Ketoamide.

    PubMed

    Lee, Seon Hwa; Kyung, Hyunsook; Yokota, Ryo; Goto, Takaaki; Oe, Tomoyuki

    2015-01-20

    The hydroxyl radical-mediated oxidation of peptides and proteins constitutes a large group of post-translational modifications that can result in structural and functional changes. These oxidations can lead to hydroxylation, sulfoxidation, or carbonylation of certain amino acid residues and cleavage of peptide bonds. In addition, hydroxyl radicals can convert the N-terminus of peptides to an α-ketoamide via abstraction of the N-terminal α-hydrogen and hydrolysis of the ketimine intermediate. In the present study, we identified N-terminal cyclization as a novel modification mediated by a hydroxyl radical. The reaction of angiotensin (Ang) II (DRVYIHPF) and the hydroxyl radical generated by the Cu(II)/ascorbic acid (AA) system or UV/hydrogen peroxide system produced N-terminal cyclized-Ang II (Ang C) and pyruvamide-Ang II (Ang P, CH3COCONH-RVYIHPF). The structure of Ang C was confirmed by mass spectrometry and comparison to an authentic standard. The subsequent incubation of isolated Ang P in the presence of Cu(II)/AA revealed that Ang P was the direct precursor of Ang C. The proposed mechanism involves the formation of a nitrogen-centered (aminyl) radical, which cyclizes to form a five-membered ring containing the alkoxy radical. The subsequent β-scission reaction of the alkoxyl radical results in the cleavage of the terminal CH3CO group. The initial aminyl radical can be stabilized by chelation to the Cu(II) ions. The affinity of Ang C toward the Ang II type 1 receptor was significantly lower than that of Ang II or Ang P. Ang C was not further metabolized by aminopeptidase A, which converts Ang II to Ang III. Hydroxyl radical-mediated N-terminal cyclization was also observed in other Ang peptides containing N-terminal alanine, arginine, valine, and amyloid β 1-11 (DAEFRHDSGYE).

  20. Group additive values for the gas-phase standard enthalpy of formation, entropy and heat capacity of oxygenates.

    PubMed

    Paraskevas, Paschalis D; Sabbe, Maarten K; Reyniers, Marie-Françoise; Papayannakos, Nikos; Marin, Guy B

    2013-11-25

    A complete and consistent set of 60 Benson group additive values (GAVs) for oxygenate molecules and 97 GAVs for oxygenate radicals is provided, which allow to describe their standard enthalpies of formation, entropies and heat capacities. Approximately half of the GAVs for oxygenate molecules and the majority of the GAVs for oxygenate radicals have not been reported before. The values are derived from an extensive and accurate database of thermochemical data obtained by ab initio calculations at the CBS-QB3 level of theory for 202 molecules and 248 radicals. These compounds include saturated and unsaturated, α- and β-branched, mono- and bifunctional oxygenates. Internal rotations were accounted for by using one-dimensional hindered rotor corrections. The accuracy of the database was further improved by adding bond additive corrections to the CBS-QB3 standard enthalpies of formation. Furthermore, 14 corrections for non-nearest-neighbor interactions (NNI) were introduced for molecules and 12 for radicals. The validity of the constructed group additive model was established by comparing the predicted values with both ab initio calculated values and experimental data for oxygenates and oxygenate radicals. The group additive method predicts standard enthalpies of formation, entropies, and heat capacities with chemical accuracy, respectively, within 4 kJ mol(-1) and 4 J mol(-1) K(-1) for both ab initio calculated and experimental values. As an alternative, the hydrogen bond increment (HBI) method developed by Lay et al. (T. H. Lay, J. W. Bozzelli, A. M. Dean, E. R. Ritter, J. Phys. Chem.- 1995, 99, 14514) was used to introduce 77 new HBI structures and to calculate their thermodynamic parameters (Δ(f)H°, S°, C(p)°). The GAVs reported in this work can be reliably used for the prediction of thermochemical data for large oxygenate compounds, combining rapid prediction with wide-ranging application.

  1. Degradation pathways of lamotrigine under advanced treatment by direct UV photolysis, hydroxyl radicals, and ozone.

    PubMed

    Keen, Olya S; Ferrer, Imma; Michael Thurman, E; Linden, Karl G

    2014-12-01

    Lamotrigine is recently recognized as a persistent pharmaceutical in the water environment and wastewater effluents. Its degradation was studied under UV and ozone advanced oxidation treatments with reaction kinetics of lamotrigine with ozone (≈4 M(-1)s(-1)), hydroxyl radical [(2.1 ± 0.3) × 10(9)M(-1)s(-1)] and by UV photolysis with low and medium pressure mercury vapor lamps [quantum yields ≈0 and (2.7 ± 0.4)× 10(-4) respectively] determined. All constants were measured at pH 6 and at temperature ≈20°C. The results indicate that lamotrigine is slow to respond to direct photolysis or oxidation by ozone and no attenuation of the contaminant is expected in UV or ozone disinfection applications. The compound reacts rapidly with hydroxyl radicals indicating that advanced oxidation processes would be effective for its treatment. Degradation products were identified under each treatment process using accurate mass time-of-flight spectrometry and pathways of decay were proposed. The main transformation pathways in each process were: dechlorination of the benzene ring during direct photolysis; hydroxyl group addition to the benzene ring during the reaction with hydroxyl radicals; and triazine ring opening after reaction with ozone. Different products that form in each process may be to a varying degree less environmentally stable than the parent lamotrigine. In addition, a novel method of ozone quenching without addition of salts is presented. The new quenching method would allow subsequent mass spectrometry analysis without a solid phase extraction clean-up step. The method involves raising the pH of the sample to approximately 10 for a few seconds and lowering it back and is therefore limited to applications for which temporary pH change is not expected to affect the outcome of the analysis.

  2. Selectivity in the Addition Reactions of Organometallic Reagents to Aziridine-2-carboxaldehydes: The Effects of Protecting Groups and Substitution Patterns

    PubMed Central

    Kulshrestha, Aman; Schomaker, Jennifer M.; Holmes, Daniel; Staples, Richard J.; Jackson, James E.; Borhan, Babak

    2014-01-01

    Good to excellent stereo-selectivity has been found in the addition reactions of Grignard and organo-zinc reagents to N-protected aziridine-2-carboxaldehydes. Specifically, high syn selectivity was obtained with benzyl-protected cis, tert-butyloxycar-bonyl-protected trans, and tosyl-pro-tected 2,3-disubstituted aziridine-2-car-boxaldehydes. Furthermore, rate and selectivity effects of ring substituents, temperature, solvent, and Lewis acid and base modifiers were studied. The diastereomeric preference of addition is dominated by the substrate aziri-dines’ substitution pattern and especially the electronic character and conformational preferences of the nitrogen protecting groups. To help rationalize the observed stereochemical outcomes, conformational and electronic structural analyses of a series of model systems representing the various substitution patterns have been explored by density functional calculations at the B3LYP/6–31G* level of theory with the SM8 solvation model to account for solvent effects. PMID:21928447

  3. Synthesis and antioxidant capacities of hydroxyl derivatives of cinnamoylphenethylamine in protecting DNA and scavenging radicals.

    PubMed

    Yang, Yang; Song, Zhi-Guang; Liu, Zai-Qun

    2011-04-01

    Cinnamoylphenethylamine (CNPA) derivatives including feruloylphenethylamine (FRPA), caffeoylphenethylamine (CFPA), cinnamoyltyramine (CNTA), feruloyltyramine (FRTA) and caffeoyltyramine (CFTA) were synthesized in order to investigate the influence of the number and position of hydroxyl group on Cu(2+)/glutathione (GSH) and 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH)-induced oxidation of DNA. The radical-scavenging properties of these CNPA derivatives were also evaluated by trapping 2,2'-azinobis(3-ethylbenzothiazoline-6-sulphonate) cationic radical (ABTS(+•)), 2,2'-diphenyl-1-picrylhydrazyl radical (DPPH) and galvinoxyl radical. In addition, these CNPA derivatives were tested by linoleic acid (LH)-β-carotene-bleaching experiment. The chemical kinetic was employed to treat the results from AAPH-induced oxidation of DNA and gave the order of antioxidant ability as CFTA > CFPA > FRTA > FRPA. CFTA and CFPA also possessed high abilities to inhibit Cu²(+)/GSH-mediated degradation of DNA, whereas FRPA and FRTA can protect LH against the auto-oxidation efficiently. Finally, CFPA and FRPA exhibited high activity in trapping ABTS(+•), DPPH and galvinoxyl radicals. Therefore, the cinnamoyl group bearing ortho-dihydroxyl or hydroxyl with ortho-methoxyl benefited for CNPA derivatives to protect DNA, while hydroxyl in tyramine cannot enhance the radical-scavenging abilities of CNPA derivatives.

  4. A quantum chemical study of the mechanisms of olefin addition to group 9 transition metal dioxo compounds.

    PubMed

    Ahmed, Issahaku; Tia, Richard; Adei, Evans

    2016-01-01

    triplet PES than on the singlet PES for the formation of similar analogues. There are fewer competitive reaction pathways on the triplet surface than on the singlet PES. Also, cycloadditions that seem impossible on the singlet PES seem possible on the doublet and or triplet PESs, this is the case typically for the Rh and Co complexes, illustrating the importance of multiple spin states in organometallic reactions.Graphical AbstractTable of Contents Synopsis: A study of the mechanism of ethylene addition to MO2(CH2)(CH3)(M=Co,Rh,Ir) shows the reactions of the Co complex have lower activation barriers for the preferred [3+2] and [2+2] addition pathways and fewer side reactions than those of Rh and Ir. Reactions are more feasible and selective on the triplet PES than on the singlet PES. These illustrate the importance of multiple spin states in organometallic reactions and shows catalyst activity and selectivity decreases down the group.

  5. An Iminium Salt Organocatalyst for Selective Aliphatic C-H Hydroxylation.

    PubMed

    Wang, Daoyong; Shuler, William G; Pierce, Conor J; Hilinski, Michael K

    2016-08-05

    The first examples of catalysis of aliphatic C-H hydroxylation by an iminium salt are presented. The method allows the selective organocatalytic hydroxylation of unactivated 3° C-H bonds at room temperature using hydrogen peroxide as the terminal oxidant. Hydroxylation of an unactivated 2° C-H bond is also demonstrated. Furthermore, improved functional group compatibility over other catalytic methods is reported in the form of selectivity for aliphatic C-H hydroxylation over alcohol oxidation. On the basis of initial mechanistic studies, an oxaziridinium species is proposed as the active oxidant.

  6. Copper-Catalyzed Hydroxylation of (Hetero)aryl Halides under Mild Conditions.

    PubMed

    Xia, Shanghua; Gan, Lu; Wang, Kailiang; Li, Zheng; Ma, Dawei

    2016-10-05

    The combination of Cu(acac)2 and N,N'-bis(4-hydroxyl-2,6-dimethylphenyl)oxalamide (BHMPO) provides a powerful catalytic system for hydroxylation of (hetero)aryl halides. A wide range of (hetero)aryl chlorides bearing either electron-donating or -withdrawing groups proceeded well at 130 °C, delivering the corresponding phenols and hydroxylated heteroarenes in good to excellent yields. When more reactive (hetero)aryl bromides and iodides were employed, the hydroxylation reactions completed at relatively low temperatures (80 and 60 °C, respectively) at low catalytic loadings (0.5 mol % Cu).

  7. Ab initio dynamics of the cytochrome P450 hydroxylation reaction

    PubMed Central

    Elenewski, Justin E.; Hackett, John C

    2015-01-01

    The iron(IV)-oxo porphyrin π-cation radical known as Compound I is the primary oxidant within the cytochromes P450, allowing these enzymes to affect the substrate hydroxylation. In the course of this reaction, a hydrogen atom is abstracted from the substrate to generate hydroxyiron(IV) porphyrin and a substrate-centered radical. The hydroxy radical then rebounds from the iron to the substrate, yielding the hydroxylated product. While Compound I has succumbed to theoretical and spectroscopic characterization, the associated hydroxyiron species is elusive as a consequence of its very short lifetime, for which there are no quantitative estimates. To ascertain the physical mechanism underlying substrate hydroxylation and probe this timescale, ab initio molecular dynamics simulations and free energy calculations are performed for a model of Compound I catalysis. Semiclassical estimates based on these calculations reveal the hydrogen atom abstraction step to be extremely fast, kinetically comparable to enzymes such as carbonic anhydrase. Using an ensemble of ab initio simulations, the resultant hydroxyiron species is found to have a similarly short lifetime, ranging between 300 fs and 3600 fs, putatively depending on the enzyme active site architecture. The addition of tunneling corrections to these rates suggests a strong contribution from nuclear quantum effects, which should accelerate every step of substrate hydroxylation by an order of magnitude. These observations have strong implications for the detection of individual hydroxylation intermediates during P450 catalysis. PMID:25681906

  8. Ab initio dynamics of the cytochrome P450 hydroxylation reaction

    SciTech Connect

    Elenewski, Justin E.; Hackett, John C

    2015-02-14

    The iron(IV)-oxo porphyrin π-cation radical known as Compound I is the primary oxidant within the cytochromes P450, allowing these enzymes to affect the substrate hydroxylation. In the course of this reaction, a hydrogen atom is abstracted from the substrate to generate hydroxyiron(IV) porphyrin and a substrate-centered radical. The hydroxy radical then rebounds from the iron to the substrate, yielding the hydroxylated product. While Compound I has succumbed to theoretical and spectroscopic characterization, the associated hydroxyiron species is elusive as a consequence of its very short lifetime, for which there are no quantitative estimates. To ascertain the physical mechanism underlying substrate hydroxylation and probe this timescale, ab initio molecular dynamics simulations and free energy calculations are performed for a model of Compound I catalysis. Semiclassical estimates based on these calculations reveal the hydrogen atom abstraction step to be extremely fast, kinetically comparable to enzymes such as carbonic anhydrase. Using an ensemble of ab initio simulations, the resultant hydroxyiron species is found to have a similarly short lifetime, ranging between 300 fs and 3600 fs, putatively depending on the enzyme active site architecture. The addition of tunneling corrections to these rates suggests a strong contribution from nuclear quantum effects, which should accelerate every step of substrate hydroxylation by an order of magnitude. These observations have strong implications for the detection of individual hydroxylation intermediates during P450 catalysis.

  9. The Use of Nominal Group Technique to Determine Additional Support Needs for a Group of Victorian TAFE Managers and Senior Educators

    ERIC Educational Resources Information Center

    Bailey, Anthony

    2013-01-01

    The nominal group technique (NGT) is a structured process to gather information from a group. The technique was first described in 1975 and has since become a widely-used standard to facilitate working groups. The NGT is effective for generating large numbers of creative new ideas and for group priority setting. This paper describes the process of…

  10. Climate Impacts on Tropospheric Ozone and Hydroxyl

    NASA Technical Reports Server (NTRS)

    Shindell, Drew T.; Bell, N.; Faluvegi, G.

    2003-01-01

    Climate change may influence tropospheric ozone and OH via several main pathways: (1) altering chemistry via temperature and humidity changes, (2) changing ozone and precursor sources via surface emissions, stratosphere-troposphere exchange, and light- ning, and (3) affecting trace gas sinks via the hydrological cycle and dry deposition. We report results from a set of coupled chemistry-climate model simulations designed to systematically study these effects. We compare the various effects with one another and with past and projected future changes in anthropogenic and natural emissions of ozone precursors. We find that white the overall impact of climate on ozone is probably small compared to emission changes, some significant seasonal and regional effects are apparent. The global effect on hydroxyl is quite large, however, similar in size to the effect of emission changes. Additionally, we show that many of the chemistry-climate links that are not yet adequately modeled are potentially important.

  11. A mechanistic study of manganese(iii) acetate-mediated phosphonyl group additions to [60]- and [70]-fullerenes: the oxidative-ion-transfer mechanism vs. free radical addition.

    PubMed

    Tumanskii, Boris L; Sabirov, Denis S; Lyakhovetsky, Yury I

    2016-11-14

    The phosphonylation of C60 with HP(O)(OAlk)2 and Mn(OAc)3·2H2O has been considered to occur via a free radical (FR) path involving intermediate radicals ˙P(O)(OAlk)2. The present study provides evidence in support of another mechanism for the reactions, oxidative-ion-transfer (OIT). The mechanism involves the change of an acetate group in Mn(OAc)3 for the phosphonate group and oxidation of C60 by the Mn(OAc)2P(O)(OAlk)2 formed to a pair: (C60˙(+), Mn(OAc)2P(O)(OAlk)2˙(-)) followed by the transfer of the phosphonate anion to give the monophposphonylfullerenyl radical. It undergoes reversible dimerization. The polyaddition occurs analogously. Moreover, the compounds Mn(OAc)2P(O)(OAlk)2 (Alk = Et and i-Pr) obtained make novel reagents for phosphonylation of fullerenes working by the OIT mechanism. The reactions of C60 in benzene with equimolar amounts of Mn(OAc)2P(O)(OPr-i)2 or Hg[P(O)(OPr-i)2]2 which is known as working by the FR mechanism since it produces radical ˙P(O)(OPr-i)2 under UV-irradiation, furnished the same radical ˙C60P(O)(OPr-i)2. However, at a 20-fold molar excess of the reagent toward C60, a single derivative C60[P(O)(OPr-i)2]4 and a mixture of derivatives bearing between two and eight phosphonyls were obtained in the former and latter cases, respectively. With C70, the change of the mechanism produced a change in the regioselectivity: 5 and 3 isomers of ˙C70P(O)(OPr-i)2 were obtained, respectively. DFT-calculations provided the hyperfine coupling (hfc) constants of the isomers and explained the regioselectivity change.

  12. Separating the effects of shelter from additional cage enhancements for group-housed BALB/cJ mice.

    PubMed

    Swetter, Brentt J; Karpiak, Christie P; Cannon, J Timothy

    2011-05-20

    Enrichment studies with rodents have demonstrated that cage enhancements can improve animal welfare and performance on common behavioral measures, but few studies have compared more than one type of enrichment or controlled for confounds, and some have revealed undesirable effects including increased aggression. We compared effects on male (n=51) and female (n=52) BALB/cJ mice of three common additions to a standard home cage: shelter, shelter+running wheel, and shelter+novel objects. Mice in all conditions lived in standard sized cages with 3-4 mice per cage. Males evidenced significant condition effects. Shelter increased longevity and maintained low levels of aggression. Adding a running wheel increased aggression over shelter alone, changed behavior in the elevated plus (EP) and open field (OF), and maintained the improved longevity seen in all shelter conditions. Novel objects impacted behavioral measures compared to the standard condition. An Igloo shelter without running wheel creates a very different home cage environment than the same shelter with the running wheel attached. Shelter, with positive impact on animal welfare, minimal effects on some common behavioral measures, and some positive effects on test variance, warrants consideration for routine inclusion with group-housed BALB/cJ males.

  13. The Additive Impact of Group and Individual Publicly Displayed Feedback: Examining Individual Response Patterns and Response Generalization in a Safe-Driving Occupational Intervention

    ERIC Educational Resources Information Center

    Ludwig, Timothy D.; Geller, E. Scott; Clarke, Steven W.

    2010-01-01

    Additive effects of publicly posting individual feedback following group goal-setting and feedback were evaluated. The turn-signal use of pizza deliverers was studied in a multiple baseline design across two pizza stores. After baseline observations, pizza deliverers voted on a group turn-signal goal and then received 4 weeks of group feedback on…

  14. Generation of hydroxyl radicals during ascites experimentally induced in broilers.

    PubMed

    Arab, H A; Jamshidi, R; Rassouli, A; Shams, G; Hassanzadeh, M H

    2006-04-01

    Increased metabolic rates, pulmonary hypertension and cardiac dysfunction are the most important features of the ascites syndrome in broiler chickens. However, the mechanism of cell injury causing the pathogenesis of the syndrome is not clearly understood. Our study aimed to examine the generation of hydroxyl radicals (OH*) in broiler chickens experiencing ascites. The hundred and fifty 1-d-old chickens were purchased from a local hatchery and reared in an open poultry house for 46 d. They were divided at random into three groups and ascites was induced in two groups by exposing them to low temperature or administration of triiodothyronine (T(3)). The third group served as control and was reared normally. Haematological, biochemical and pathological tests were used to determine the incidence of ascites: including total red blood cell (RBC), packed cell volume (PCV), release of alanine transaminase (ALT) and aspartate transaminase (AST) and ratio of right ventricular weight to total ventricular weight (RV/TV). A salicylate hydroxylation method was used to examine the generation of hydroxyl radicals (OH*) in treated groups. TWo hydroxylated salicylic acid metabolites, 2,3- and 2,5-dihydroxy benzoic acid (2,3- and 2,5-DHBA), were measured by HPLC to detect the generation of OH*. An ascites syndrome was observed in T(3) and low-temperature treated groups, as shown by necropsy changes and increases in f RBC, PCV, ALT, AST and the ratio of RV/TV. Concentrations of 2,3- and 2,5-DHBA were increased in groups experiencing ascites compared to control group. It is suggested that reactive oxygen species that is OH* ions, may be involved in the pathogenesis of the ascites syndrome in broiler chickens.

  15. Regioselective and stereospecific hydroxylation of GR24 by Sorghum bicolor and evaluation of germination inducing activities of hydroxylated GR24 stereoisomers toward seeds of Striga species.

    PubMed

    Ueno, Kotomi; Ishiwa, Shunsuke; Nakashima, Hitomi; Mizutani, Masaharu; Takikawa, Hirosato; Sugimoto, Yukihiro

    2015-09-15

    Bioconversion of GR24, the most widely used synthetic strigolactone (SL), by hydroponically grown sorghum (Sorghum bicolor) and biological activities of hydroxylated GR24 stereoisomers were studied. Analysis of extracts and exudates of sorghum roots previously fed with a racemic and diastereomeric mixture of GR24, using liquid chromatography-tandem mass spectrometry with multiple reaction monitoring (MRM), confirmed uptake of GR24 and suggested its conversion to mono-hydroxylated products. Two major GR24 metabolites, 7-hydroxy-GR24 and 8-hydroxy-GR24, were identified in the root extracts and exudates by direct comparison of chromatographic behavior with a series of synthetic mono-hydroxylated GR24 analogues. Separate feeding experiments with each of the GR24 stereoisomers revealed that the hydroxylated products were derived from 2'-epi-GR24, an evidence of sterical recognition of the GR24 molecule by sorghum. Trans-4-hydroxy-GR24 isomers derived from all GR24 stereoisomers were detected in the exudates as minor metabolites. The synthetic hydroxy-GR24 isomers induced germination of Striga hermonthica in decreasing order of C-8>C-7>C-6>C-5>C-4. In contrast the stereoisomers having the same configuration of orobanchol, irrespective of position of hydroxylation, induced germination of Striga gesnerioides. The results confirm previous reports on structural requirements of SLs and ascribe a critical role to hydroxylation, but not to the position of the hydroxyl group in the AB part of the molecule, in induction of S. gesnerioides seed germination.

  16. Creation of localized spins in graphene by ring-opening of epoxy derived hydroxyl

    PubMed Central

    Chen, Jie; Zhang, Weili; Sun, Yuanyuan; Zheng, Yongping; Tang, Nujiang; Du, Youwei

    2016-01-01

    Creation of high-density localized spins in the basal plane of graphene sheet by introduction of sp3-type defects is considered to be a potential route for the realization of high-magnetization graphene. Theoretical and experimental studies confirmed that hydroxyl can be an effective sp3-type candidate for inducing robust magnetic moment. However, the artificial generation of hydroxyl groups for creating high-density spins on the basal plane of graphene sheet is very scarce. Here we demonstrate that high-content hydroxyl groups can be generated on the basal plane of graphene oxide (GO) sheet by ring opening of epoxy groups. We show that by introduction of 10.74 at.% hydroxyl groups, the density of localized spins of GO can be significantly increased from 0.4 to 5.17 μB/1000 C. Thus, this study provided an effective method to obtain graphene with high-density localized spins. PMID:27225991

  17. Hydroxyl Radical and Its Scavengers in Health and Disease

    PubMed Central

    Lipinski, Boguslaw

    2011-01-01

    It is generally believed that diseases caused by oxidative stress should be treated with antioxidants. However, clinical trials with such antioxidants as ascorbic acid and vitamin E, failed to produce the expected beneficial results. On the other hand, important biomolecules can be modified by the introduction of oxygen atoms by means of non-oxidative hydroxyl radicals. In addition, hydroxyl radicals can reduce disulfide bonds in proteins, specifically fibrinogen, resulting in their unfolding and scrambled refolding into abnormal spatial configurations. Consequences of this reaction are observed in many diseases such as atherosclerosis, cancer and neurological disorders, and can be prevented by the action of non-reducing substances. Moreover, many therapeutic substances, traditionally classified as antioxidants, accept electrons and thus are effective oxidants. It is described in this paper that hydroxyl radicals can be generated by ferric ions without any oxidizing agent. In view of the well-known damaging effect of poorly chelated iron in the human body, numerous natural products containing iron binding agents can be essential in the maintenance of human health. However, beneficial effects of the great number of phytochemicals that are endowed with hydroxyl radical scavenging and/or iron chelating activities should not be considered as a proof for oxidative stress. PMID:21904647

  18. Polar Addition to C=C Group: Why Is Anti-Markovnikov Hydroboration-Oxidation of Alkenes Not "Anti-"?

    ERIC Educational Resources Information Center

    Ilich, Predrag-Peter; Rickertsen, Lucas S.; Becker, Erienne

    2006-01-01

    For 137 years Markovnikov's rule has been extensively used in organic chemical education and research to describe the regioselectivity in electrophilic addition reactions to alkenes and alkynes. When the structures of the final reaction products are used as reference, the rule requests that certain polar addition reactions be termed…

  19. Bacterial metabolism of hydroxylated biphenyls.

    PubMed Central

    Higson, F K; Focht, D D

    1989-01-01

    Isolates able to grow on 3- or 4-hydroxybiphenyl (HB) as the sole carbon source were obtained by enrichment culture. The 3-HB degrader Pseudomonas sp. strain FH12 used an NADPH-dependent monooxygenase restricted to 3- and 3,3'-HBs to introduce an ortho-hydroxyl. The 4-HB degrader Pseudomonas sp. strain FH23 used either a mono- or dioxygenase to generate a 2,3-diphenolic substitution pattern which allowed meta-fission of the aromatic ring. By using 3-chlorocatechol to inhibit catechol dioxygenase activity, it was found that 2- and 3-HBs were converted by FH23 to 2,3-HB, whereas biphenyl and 4-HB were attacked by dioxygenation. 4-HB was metabolized to 2,3,4'-trihydroxybiphenyl. Neither organism attacked chlorinated HBs. The degradation of 3- and 4-HBs by these strains is therefore analogous to the metabolism of biphenyl, 2-HB, and naphthalene in the requirement for 2,3-catechol formation. PMID:2729993

  20. Vertical Distribution of Vibrationally Excited Hydroxyl

    NASA Astrophysics Data System (ADS)

    Grygalashvyly, Mykhaylo; Becker, Erich; Sonnemann, Gerd

    2016-04-01

    Knowledge about the vertical distribution of the vibrationally excited states of hydroxyl (OH*) is important for the interpretation of airglow measurements with respect to dynamical processes in the mesopause region. We derive an approximate analytical expression for the distribution of OH* that highlights the dependence on atomic oxygen and temperature. In addition, we use an advanced numerical model for the formation and relaxation of OH* and investigate the distributions of the different vibrationally exited states of OH*. For the production of OH*, the model includes the reaction of atomic hydrogen with ozone, as well as the reaction of atomic oxygen with hydroperoxy radicals. As loss processes we include 1) deactivation by atomic oxygen, molecular oxygen, and molecular nitrogen, 2) spontaneous emission, and 3) loss due to chemical reaction with atomic oxygen. All these processes take the dependence on the vibrational number into account. The quenching by molecular and atomic oxygen is parameterized by a multi-quantum relaxation scheme. This diagnostic model for OH* has been implemented as part of a chemistry-transport model that is driven by the dynamics simulated with the KMCM (Kühlungsborn Mechanistic general Circulation Model). Numerical results confirm that emission from excited states with higher vibrational number is weaker and emanates from higher altitudes. In addition we find that the OH*-peak altitudes depend significantly on season and latitude. This behavior is mainly controlled by the corresponding variations of atomic oxygen and temperature, as is also confirmed by the aforementioned approximate theory.

  1. A characterization study of a hydroxylated polycrystalline tin oxide surface

    NASA Technical Reports Server (NTRS)

    Hoflund, Gar B.; Grogan, Austin L., Jr.; Asbury, Douglas A.; Schryer, David R.

    1989-01-01

    In this study Auger electron spectroscopy, electron spectroscopy for chemical analysis (ESCA) and electron-stimulated desorption (ESD) have been used to examine a polycrystalline tin oxide surface before and after annealing in vacuum at 500 C. Features due to surface hydroxyl groups are present in both the ESCA and ESD spectra, and ESD shows that several chemical states of hydrogen are present. Annealing at 500 C causes a large reduction in the surface hydrogen concentration but not complete removal.

  2. Evaluation and Optimization of TSNCO Method for Hydroxyl Analysis

    DTIC Science & Technology

    1985-01-01

    containing materials. The method involves the reaction of the hydroxyl group with toluenesulfonyl isocyanate and subsequent •acidimetric titrotion of the... reaction product in a nonuqueous solution. The method is rapid, selecti•., yields reproducible results, and in qIdely applicable INTRODUCTION The... reaction with p-tolupaesulfonyl isocyanate (TSNCO). Acetylation and phthalation have been used for a number of years and have been fairly well-characterized

  3. Solvation free energy of the peptide group: its model dependence and implications for the additive-transfer free-energy model of protein stability.

    PubMed

    Tomar, Dheeraj S; Asthagiri, D; Weber, Valéry

    2013-09-17

    The group-additive decomposition of the unfolding free energy of a protein in an osmolyte solution relative to that in water poses a fundamental paradox: whereas the decomposition describes the experimental results rather well, theory suggests that a group-additive decomposition of free energies is, in general, not valid. In a step toward resolving this paradox, here we study the peptide-group transfer free energy. We calculate the vacuum-to-solvent (solvation) free energies of (Gly)n and cyclic diglycine (cGG) and analyze the data according to experimental protocol. The solvation free energies of (Gly)n are linear in n, suggesting group additivity. However, the slope interpreted as the free energy of a peptide unit differs from that for cGG scaled by a factor of half, emphasizing the context dependence of solvation. However, the water-to-osmolyte transfer free energies of the peptide unit are relatively independent of the peptide model, as observed experimentally. To understand these observations, a way to assess the contribution to the solvation free energy of solvent-mediated correlation between distinct groups is developed. We show that linearity of solvation free energy with n is a consequence of uniformity of the correlation contributions, with apparent group-additive behavior in the water-to-osmolyte transfer arising due to their cancellation. Implications for inferring molecular mechanisms of solvent effects on protein stability on the basis of the group-additive transfer model are suggested.

  4. Production of hydroxylated fatty acids in genetically modified plants

    DOEpatents

    Somerville, Chris; Broun, Pierre; van de Loo, Frank; Boddupalli, Sekhar S.

    2011-08-23

    This invention relates to plant fatty acyl hydroxylases. Methods to use conserved amino acid or nucleotide sequences to obtain plant fatty acyl hydroxylases are described. Also described is the use of cDNA clones encoding a plant hydroxylase to produce a family of hydroxylated fatty acids in transgenic plants. In addition, the use of genes encoding fatty acid hydroxylases or desaturases to alter the level of lipid fatty acid unsaturation in transgenic plants is described.

  5. Production of hydroxylated fatty acids in genetically modified plants

    DOEpatents

    Somerville, Chris; Broun, Pierre; van de Loo, Frank; Boddupalli, Sekhar S.

    2005-08-30

    This invention relates to plant fatty acyl hydroxylases. Methods to use conserved amino acid or nucleotide sequences to obtain plant fatty acyl hydroxylases are described. Also described is the use of cDNA clones encoding a plant hydroxylase to produce a family of hydroxylated fatty acids in transgenic plants. In addition, the use of genes encoding fatty acid hydroxylases or desaturases to alter the level of lipid fatty acid unsaturation in transgenic plants is described.

  6. Stereoselective synthesis of tricyclic compounds by intramolecular palladium-catalyzed addition of aryl iodides to carbonyl groups

    PubMed Central

    Saadi, Jakub; Bentz, Christoph; Redies, Kai; Lentz, Dieter; Zimmer, Reinhold

    2016-01-01

    Summary Starting from γ-ketoesters with an o-iodobenzyl group we studied a palladium-catalyzed cyclization process that stereoselectively led to bi- and tricyclic compounds in moderate to excellent yields. Four X-ray crystal structure analyses unequivocally defined the structure of crucial cyclization products. The relative configuration of the precursor compounds is essentially transferred to that of the products and the formed hydroxy group in the newly generated cyclohexane ring is consistently in trans-arrangement with respect to the methoxycarbonyl group. A transition-state model is proposed to explain the observed stereochemical outcome. This palladium-catalyzed Barbier-type reaction requires a reduction of palladium(II) back to palladium(0) which is apparently achieved by the present triethylamine. PMID:27559374

  7. Remote sulfonamido group enhances reactivity and selectivity for asymmetric Michael addition of nitroalkanes to α,β-unsaturated aldehydes.

    PubMed

    Huang, Yu-Chao; Uang, Biing-Jiun

    2014-09-01

    The pyrrolidine-camphorsulfonamide-based catalyst 1 a catalyzes the enantioselective conjugate addition of nitroalkanes to α,β-unsaturated aldehydes in the presence of five equivalents of water in iPrOH to give the corresponding chiral Michael adducts in good yields and high enantioselectivities (up to 99% ee) with a catalyst loading as low as 1 mol%.

  8. Hydroxylated chalcones with dual properties: xanthine oxidase inhibitors and radical scavengers

    PubMed Central

    Hofmann, Emily; Webster, Jonathan; Do, Thuy; Kline, Reid; Snider, Lindsey; Hauser, Quintin; Higginbottom, Grace; Campbell, Austin; Ma, Lili; Paula, Stefan

    2016-01-01

    In this study, we evaluated the abilities of a series of chalcones to inhibit the activity of the enzyme xanthine oxidase (XO) and to scavenge radicals. 20 mono- and polyhydroxylated chalcone derivatives were synthesized by Claisen-Schmidt condensation reactions and then tested for inhibitory potency against XO, a known generator of reactive oxygen species (ROS). In parallel, the ability of the synthesized chalcones to scavenge a stable radical was determined. Structure-activity relationship analysis in conjunction with molecular docking indicated that the most active XO inhibitors carried a minimum of three hydroxyl groups. Moreover, the most effective radical scavengers had two neighboring hydroxyl groups on at least one of the two phenyl rings. Since it has been proposed previously that XO inhibition and radical scavenging could be useful properties for reduction of ROS-levels in tissue, we determined the chalcones’ effects to rescue neurons subjected to ROS-induced stress created by the addition of β-amyloid peptide. Best protection was provided by chalcones that combined good inhibitory potency with high radical scavenging ability in a single molecule, an observation that points to a potential therapeutic value of this compound class. PMID:26762836

  9. Hydroxylated chalcones with dual properties: Xanthine oxidase inhibitors and radical scavengers.

    PubMed

    Hofmann, Emily; Webster, Jonathan; Do, Thuy; Kline, Reid; Snider, Lindsey; Hauser, Quintin; Higginbottom, Grace; Campbell, Austin; Ma, Lili; Paula, Stefan

    2016-02-15

    In this study, we evaluated the abilities of a series of chalcones to inhibit the activity of the enzyme xanthine oxidase (XO) and to scavenge radicals. 20 mono- and polyhydroxylated chalcone derivatives were synthesized by Claisen-Schmidt condensation reactions and then tested for inhibitory potency against XO, a known generator of reactive oxygen species (ROS). In parallel, the ability of the synthesized chalcones to scavenge a stable radical was determined. Structure-activity relationship analysis in conjunction with molecular docking indicated that the most active XO inhibitors carried a minimum of three hydroxyl groups. Moreover, the most effective radical scavengers had two neighboring hydroxyl groups on at least one of the two phenyl rings. Since it has been proposed previously that XO inhibition and radical scavenging could be useful properties for reduction of ROS-levels in tissue, we determined the chalcones' effects to rescue neurons subjected to ROS-induced stress created by the addition of β-amyloid peptide. Best protection was provided by chalcones that combined good inhibitory potency with high radical scavenging ability in a single molecule, an observation that points to a potential therapeutic value of this compound class.

  10. Adamantyl-Substituted Retinoid-Derived Molecules That Interact with the Orphan Nuclear Receptor Small Heterodimer Partner: Effects of Replacing the 1-Adamantyl or Hydroxyl Group on Inhibition of Cancer Cell Growth, Induction of Cancer Cell Apoptosis, and Inhibition of Src Homology 2 Domain-Containing Protein Tyrosine Phosphatase-2 Activity

    PubMed Central

    Dawson, Marcia I.; Xia, Zebin; Jiang, Tao; Ye, Mao; Fontana, Joseph A.; Farhana, Lulu; Patel, Bhaumik; Xue, Li Ping; Bhuiyan, Mohammad; Pellicciari, Roberto; Macchiarulo, Antonio; Nuti, Roberto; Zhang, Xiao-Kun; Han, Young-Hoon; Tautz, Lutz; Hobbs, Peter D.; Jong, Ling; Waleh, Nahid; Chao, Wan-ru; Feng, Gen-Sheng; Pang, Yuhong; Su, Ying

    2014-01-01

    (E)-4-[3-(1-Adamantyl)-4′-hydroxyphenyl]-3-chlorocinnamic acid (3-Cl-AHPC) induces the cell-cycle arrest and apoptosis of leukemia and cancer cells. Studies demonstrated that 3-Cl-AHPC bound to the atypical orphan nuclear receptor small heterodimer partner (SHP). Although missing a DNA-binding domain, SHP heterodimerizes with the ligand-binding domains of other nuclear receptors to repress their abilities to induce or inhibit gene expression. 3-Cl-AHPC analogues having the 1-adamantyl and phenolic hydroxyl pharmacophoric elements replaced with isosteric groups were designed, synthesized, and evaluated for their inhibition of proliferation and induction of human cancer cell apoptosis. Structure–anticancer activity relationship studies indicated the importance of both groups to apoptotic activity. Docking of 3-Cl-AHPC and its analogues to an SHP computational model that was based on the crystal structure of ultraspiracle complexed with 1-stearoyl-2-palmitoylglycero-3-phosphoethanolamine suggested why these 3-Cl-AHPC groups could influence SHP activity. Inhibitory activity against Src homology 2 domain-containing protein tyrosine phosphatase 2 (Shp-2) was also assessed. The most active Shp-2 inhibitor was found to be the 3′-(3,3-dimethylbutynyl) analogue of 3-Cl-AHPC. PMID:18759424

  11. [Decomposition of hemoglobin UV absorption spectrum into absorption spectra of prosthetic group and apoprotein by means of an additive model].

    PubMed

    Lavrinenko, I A; Vashanov, G A; Artyukhov, V G

    2015-01-01

    The decomposition pathways of hemoglobin UV absorption spectrum into the absorption spectra of the protein and non-protein components are proposed and substantiated by means of an additive model. We have established that the heme component has an absorption band with a maximum at λ(max) = 269.2 nm (ε = 97163) and the apoprotein component has an absorption band with a maximum at λ(max) = 278.4 nm (ε = 48669) for the wavelength range from 240.0 to 320.0 nm. An integral relative proportion of absorption for the heme fraction (78.8%) and apoprotein (21.2%) in the investigating wavelength range is defined.

  12. Additional borehole geophysical logging at Waste Area Grouping 1 at Oak Ridge National Laboratory, Oak Ridge, Tennessee

    SciTech Connect

    Not Available

    1994-07-01

    This technical memorandum describes the borehole geophysical logging performed at selected coreholes at Waste Area Grouping 1 between March and November 1991 in support of the remedial investigation. The primary objectives of the borehole geophysical logging program were to (1) identify fractured bedrock zones and identify those fractured bedrock zones participating in active groundwater flow, (2) correlate the fractured intervals with the regional stratigraphy described, and (3) further characterize local bedrock geology and hydrogeology and gain insight about the bedrock aquifer flow system. A secondary objective was to provide stratigraphic correlations with existing logs for coreholes CH001 through CH005. Fractured bedrock zones and active or open fractures were identified in all coreholes logged. The fracture identification and analysis process was intended to distinguish between open or active fractures participating in active groundwater flow and closed or inactive fractures that are partially or completely filled (such as with calcite mineralization) and do not support groundwater circulation. Most of the fractures identified are bedding plane. Fracture occurrence varies with the different units of the Chickamauga Group; the greatest density of fractures and active fractures occurs in the upper 150 ft of stratum cored. Fractures actively contributing to groundwater flow were also identified, and direction of fluid movement within fractures was identified for those coreholes with flowmeter data.

  13. Hydroxyl radical induced transformation of phenylurea herbicides: A theoretical study

    NASA Astrophysics Data System (ADS)

    Mile, Viktória; Harsányi, Ildikó; Kovács, Krisztina; Földes, Tamás; Takács, Erzsébet; Wojnárovits, László

    2017-03-01

    Aromatic ring hydroxylation reactions occurring during radiolysis of aqueous solutions are studied on the example of phenylurea herbicides by Density Functional Theory calculations. The effect of the aqueous media is taken into account by using the Solvation Model Based on Density model. Hydroxyl radical adds to the ring because the activation free energies (0.4-47.2 kJ mol-1) are low and also the Gibbs free energies have high negative values ((-27.4) to (-5.9) kJ mol-1). According to the calculations in most of cases the ortho- and para-addition is preferred in agreement with the experimental results. In these reactions hydroxycyclohexadienyl type radicals form. In a second type reaction, when loss of chlorine atom takes place, OH/Cl substitution occurs without cyclohexadienyl type intermediate.

  14. Treating ballast water with hydroxyl radical on introduced organisms

    NASA Astrophysics Data System (ADS)

    Zhang, Zhitao; Bai, Mindi; Xiao, Yu; Bai, Mindong; Yang, Bo; Bai, Xiyao

    2006-06-01

    With physical method of micro-gap gas discharge, a large amount of hydroxyl radical can be produced in 20t/h pilot-scale system using the ionization of O2 and H2O. In this paper, the effect of biochemistry of hydroxyl radicals on introduced organisms in ballast water was experimentally investigated. The results indicate that the contents of chlorophyl- a, chlorophyl- b, chlorophyl- c and carotenoid are decreased by 35% 64% within 8.0s and further to the lowest limit of test 5 minutes. In addition, the main reasons of cell death are the lipid peroxidation, the strong destruction to the monose, amylose, protein, DNA and RNA of cell, and damage in CAT, POD and SOD of antioxidant enzyme system.

  15. Adsorption and dissociation of NH3 on clean and hydroxylated TiO2 rutile (110) surfaces: a computational study.

    PubMed

    Chang, Jee-Gong; Chen, Hsin-Tsung; Ju, Shin-Pon; Chang, Ching-Sheng; Weng, Meng-Hsiung

    2011-04-30

    The adsorption and dissociation of NH(3) on the clean and hydroxylated TiO(2) rutile (110) surfaces have been investigated by the first-principles calculations. The monodentate adsorbates such as H(3)N-Ti(a), H(2)N-Ti(a), N-Ti(a), H(2)N-O(a), HN-O(a), N-O(a) and H-O(a), as well as the bidentate adsorbate, Ti-N-Ti(a) can be formed on the clean surface. It is found that the hydroxyl group enhances the adsorption of certain adsorbates on the five-fold-coordinated Ti atoms (5c-Ti), namely H(2)N-Ti(a), HN-Ti(a), N-Ti(a) and Ti-N-Ti(a). In addition, the adsorption energy increases as the number of hydroxyl groups increases. On the contrary, the opposite effect is found for those on the two-fold-coordinated O atoms (2c-O). The enhanced adsorption of NH(x) (x = 1-2) on the 5c-Ti is due to the large electronegativity of the OH group, increasing the acidity of the Ti center. This also contributes to diminish the adsorption of NH(x) (x = 1-2) on the two-fold-coordinated O atoms (2c-O) decreasing its basicity. According to potential energy profile, the NH(3) dissociation on the TiO(2) surface is endothermic and the hydroxyl group is found to lower the energetics of H(2)N-Ti(a)+H-O(a) and HN-Ti(a)+2{H-O(a)}, but slightly raise the energetic of Ti-N-Ti(a)+3{H-O(a)} compare to those on the clean surface. However, the dissociation of NH(3) is found to occur on the hydroxylated surface with an overall endothermic by 31.8 kcal/mol and requires a barrier of 37.5 kcal/mol. A comparison of NH(3) on anatase surface has been discussed. The detailed electronic analysis is also carried out to gain insights into the interaction nature between adsorbate and surface.

  16. Thermochemical Properties Enthalpy, Entropy, and Heat Capacity of C1-C4 Fluorinated Hydrocarbons: Fluorocarbon Group Additivity.

    PubMed

    Wang, Heng; Castillo, Álvaro; Bozzelli, Joseph W

    2015-07-23

    Enthalpies of formation for 14 C2–C4 fluorinated hydrocarbons were calculated with nine popular ab initio and density functional theory methods: B3LYP, CBS-QB3, CBS-APNO, M06, M06-2X, ωB97X, G4, G4(MP2)-6X, and W1U via several series of isodesmic reactions. The recommended ideal gas phase ΔHf298° (kcal mol(–1)) values calculated in this study are the following: −65.4 for CH3CH2F; −70.2 for CH3CH2CH2F; −75.3 for CH3CHFCH3; −75.2 for CH3CH2CH2CH2F; −80.3 for CH3CHFCH2CH3; −108.1 for CH2F2; −120.9 for CH3CHF2; −125.8 for CH3CH2CHF2; −133.3 for CH3CF2CH3; −166.7 for CHF3; −180.5 for CH3CF3; −185.5 for CH3CH2CF3; −223.2 for CF4; and −85.8 for (CH3)3CF. Entropies (S298° in cal mol(–1) K(–1)) were estimated using B3LYP/6-31+G(d,p) computed frequencies and geometries. Rotational barriers were determined and hindered internal rotational contributions for S298°, and Cp(T) were calculated using the rigid rotor harmonic oscillator approximation, with direct integration over energy levels of the intramolecular rotation potential energy curve. Thermochemical properties for the fluorinated carbon groups C/C/F/H2, C/C2/F/H, C/C/F2/H, C/C2/F2, and C/C/F3 were derived from the above target fluorocarbons. Previously published enthalpies and groups for 1,2-difluoroethane, 1,1,2-trifluoroethane, 1,1,2,2-tetrafluoroethane, 1,1,1,2-tetrafluoroethane, 1,1,1,2,2-pentafluoroethane, 2-fluoro-2-methylpropane that were previously determined via work reaction schemes are revised using updated reference species values. Standard deviations are compared for the calculation methods.

  17. Synthesis, spectral features and biological activity of some novel hetarylazo dyes derived from 8-chloro-4-hydroxyl-2-quinolone

    NASA Astrophysics Data System (ADS)

    Yahyazadeh, Asieh; Yousefi, Hessamoddin

    2014-01-01

    In this study, 8-chloro-4-hydroxyl-2-quinolone was synthesized from cyclocondensation of corresponding dianilide and subsequently used as a potent coupling component with some diazotized heterocyclic amines. These compounds were characterized by UV-vis, FT-IR, 1H NMR spectroscopic techniques and elemental analysis. Absorption spectra of these dyes were measured in six polar solvents and discussed with respect to the nature of solvents and substituted groups. The effects of acid, base, temperature and concentration on the visible absorption spectra of the dyes were reported. In addition, the antimicrobial activity of the dyes was explored in detail.

  18. Ammonia formation from NO reaction with surface hydroxyls on rutile TiO2 (110) - 1×1

    SciTech Connect

    Kim, Boseong; Kay, Bruce D.; Dohnalek, Zdenek; Kim, Yu Kwon

    2015-01-15

    The reaction of NO with hydroxylated rutile TiO2(110)-1×1 surface (h-TiO2) was investigated as a function of NO coverage using temperature-programmed desorption. Our results show that NO reaction with h-TiO2 leads to formation of NH3 which is observed to desorb at ~ 400 K. Interestingly, the amount of NH3 produced depends nonlinearly on the coverage of NO. The yield increases up to a saturation value of ~1.3×1013 NH3/cm2 at a NO dose of 5×1013 NO/cm2, but subsequently decreases at higher NO doses. Preadsorbed H2O is found to have a negligible effect on the NH3 desorption yield. Additionally, no NH3 is formed in the absence of surface hydroxyls (HOb’s) upon coadsorption of NO and H2O on a stoichiometric TiO2(110) (s-TiO2(110)). Based on these observations, we conclude that nitrogen from NO has a strong preference to react with HOb’s on the bridge-bonded oxygen rows (but not with H2O) to form NH3. The absolute NH3 yield is limited by competing reactions of HOb species with titanium-bound oxygen adatoms to form H2O. Our results provide new mechanistic insight about the interactions of NO with hydroxyl groups on TiO2(110) .

  19. Three Additional Linkage Groups That Repress Transcription and Meiotic Recombination in the Mating-Type Region of Schizosaccharomyces Pombe

    PubMed Central

    Thon, G.; Cohen, A.; Klar, A. J.

    1994-01-01

    The mating-type genes of Schizosaccharomyces pombe are found at three locations in the same chromosomal region. These genes are in an active configuration at the mat1 locus and in an inactive configuration at the mat2 and mat3 loci. The mechanism that represses transcription of mat2 and mat3 also inactivates other promoters introduced nearby and is accompanied by a block to meiotic recombination in the mat2-mat3 interval, suggesting that this mechanism involves a particular chromatin structure. We present evidence that the transcription and recombination blocks require three newly defined trans-acting loci, clr2, clr3 and clr4, in addition to the previously identified clr1, rik1 and swi6 loci. We also investigated the role of mat2 cis-acting sequences in silencing. Four cis-acting elements that repress mat2 in a plasmid context were previously identified. Deletion of two of these elements proved to have little effect in a chromosomal context. However, when combined with mutations in trans-acting genes, deletion of the same two elements greatly enhanced mat2 expression. The observed cumulative effects suggest a redundancy in the silencing mechanism. PMID:8001791

  20. Hydroxyl radical oxidation of cylindrospermopsin (cyanobacterial toxin) and its role in the photochemical transformation.

    PubMed

    Song, Weihua; Yan, Shuwen; Cooper, William J; Dionysiou, Dionysios D; O'Shea, Kevin E

    2012-11-20

    Cylindrospermopsin (CYN), an alkaloid guanidinium sulfated toxin, is produced by a number of cyanobacteria regularly found in lakes, rivers, and reservoirs. Steady-state and time-resolved radiolysis methods were used to determine reaction pathways and kinetic parameters for the reactions of hydroxyl radical with CYN. The absolute bimolecular reaction rate constant for the reaction of hydroxyl radical with CYN is (5.08 ± 0.16) × 10(9) M(-1) s(-1). Comparison of the overall reaction rate of CYN with hydroxyl radical with the individual reaction rate for addition to the uracil ring in CYN indicate the majority of the hydroxyl radicals (84%) react at the uracil functionality of CYN. Product analyses using liquid chromatography-mass spectrometry indicate the major products from the reaction of hydroxyl radical with CYN involve attack of hydroxyl radical at the uracil ring and hydrogen abstraction from the hydroxy-methine bridge linking the uracil ring to the tricyclic guanidine functionality. The role of hydroxyl radical initiated pathways in the natural organic matter (NOM) photosensitized transformation of CYN were evaluated. Scavenger and trapping experiments indicate that hydroxyl radical mediated transformations account for approximately ~70% of CYN destruction in surface waters under solar irradiation in the presence of NOM. The absence of solvent isotope effect indicates singlet oxygen does not play a significant role in the NOM sensitized transformation of CYN. The primary degradation pathways for HO• mediated and NOM photosensitized destruction of CYN involve destruction of the uracil ring. The fundamental kinetic parameters determined from these studies are critical for the accurate evaluation of hydroxyl-radical based technologies for the remediation of this problematic cyanotoxin in drinking water and important in the assessment of the environmental oxidative transformation of uracil based compounds.

  1. Hydroxyl radical oxidation of feruloylated arabinoxylan.

    PubMed

    Bagdi, Attila; Tömösközi, Sándor; Nyström, Laura

    2016-11-05

    Feruloylated arabinoxylan (AX) has a unique capacity to form covalent gels in the presence of certain oxidizing agents. The present study demonstrates that hydroxyl radical oxidation does not provoke ferulic acid dimerization and thus oxidative gelation. We studied the hydroxyl radical mediated oxidation of an alkali-extracted AX preparation (purity: 92g/100g dry matter) that showed gel-forming capability upon peroxidase/hydrogen peroxide treatment. Hydroxyl radicals were produced with ascorbate-driven Fenton reaction and the radical formation was monitored with electron paramagnetic resonance, using a POBN/EtOH spin trapping system. Oxidation was carried out at different catalytic concentrations of iron (50 and 100μM) and at different temperatures (20°C, 50°C, and 80°C). It was demonstrated that hydroxyl radical oxidation does not provoke gel formation, but viscosity decrease in AX solution, which suggests polymer degradation. Furthermore, it was demonstrated that hydroxyl radical formation in AX solution can be initiated merely by increasing temperature.

  2. A first report of hydroxylated apatite as structural biomineral in Loasaceae – plants’ teeth against herbivores

    NASA Astrophysics Data System (ADS)

    Ensikat, Hans-Jürgen; Geisler, Thorsten; Weigend, Maximilian

    2016-05-01

    Biomineralization provides living organisms with various materials for the formation of resilient structures. Calcium phosphate is the main component of teeth and bones in vertebrates, whereas especially silica serves for the protection against herbivores on many plant surfaces. Functional calcium phosphate structures are well-known from the animal kingdom, but had not so far been reported from higher plants. Here, we document the occurrence of calcium phosphate biomineralization in the South-American plant group Loasaceae (rock nettle family), which have stinging trichomes similar to those of the well-known stinging nettles (Urtica). Stinging hairs and the smaller, glochidiate trichomes contained nanocrystalline hydroxylated apatite, especially in their distal portions, replacing the silica found in analogous structures of other flowering plants. This could be demonstrated by chemical, spectroscopic, and diffraction analyses. Some species of Loasaceae contained both calcium phosphate and silica in addition to calcium carbonate. The intriguing discovery of structural hydroxylated apatite in plants invites further studies, e.g., on its systematic distribution across the family, the genetic and cellular control of plant biomineralization, the properties and ultrastructure of calcium phosphate. It may prove the starting point for the development of biomimetic calcium phosphate composites based on a cellulose matrix.

  3. A first report of hydroxylated apatite as structural biomineral in Loasaceae – plants’ teeth against herbivores

    PubMed Central

    Ensikat, Hans-Jürgen; Geisler, Thorsten; Weigend, Maximilian

    2016-01-01

    Biomineralization provides living organisms with various materials for the formation of resilient structures. Calcium phosphate is the main component of teeth and bones in vertebrates, whereas especially silica serves for the protection against herbivores on many plant surfaces. Functional calcium phosphate structures are well-known from the animal kingdom, but had not so far been reported from higher plants. Here, we document the occurrence of calcium phosphate biomineralization in the South-American plant group Loasaceae (rock nettle family), which have stinging trichomes similar to those of the well-known stinging nettles (Urtica). Stinging hairs and the smaller, glochidiate trichomes contained nanocrystalline hydroxylated apatite, especially in their distal portions, replacing the silica found in analogous structures of other flowering plants. This could be demonstrated by chemical, spectroscopic, and diffraction analyses. Some species of Loasaceae contained both calcium phosphate and silica in addition to calcium carbonate. The intriguing discovery of structural hydroxylated apatite in plants invites further studies, e.g., on its systematic distribution across the family, the genetic and cellular control of plant biomineralization, the properties and ultrastructure of calcium phosphate. It may prove the starting point for the development of biomimetic calcium phosphate composites based on a cellulose matrix. PMID:27194462

  4. Degradation mechanism of cyanobacterial toxin cylindrospermopsin by hydroxyl radicals in homogeneous UV/H₂O₂ process.

    PubMed

    He, Xuexiang; Zhang, Geshan; de la Cruz, Armah A; O'Shea, Kevin E; Dionysiou, Dionysios D

    2014-04-15

    The degradation of cylindrospermopsin (CYN), a widely distributed and highly toxic cyanobacterial toxin (cyanotoxin), remains poorly elucidated. In this study, the mechanism of CYN destruction by UV-254 nm/H2O2 advanced oxidation process (AOP) was investigated by mass spectrometry. Various byproducts identified indicated three common reaction pathways: hydroxyl addition (+16 Da), alcoholic oxidation or dehydrogenation (-2 Da), and elimination of sulfate (-80 Da). The initiation of the degradation was observed at the hydroxymethyl uracil and tricyclic guanidine groups; uracil moiety cleavage/fragmentation and further ring-opening of the alkaloid were also noted at an extended reaction time or higher UV fluence. The degradation rates of CYN decreased and less byproducts (species) were detected using natural water matrices; however, CYN was effectively eliminated under extended UV irradiation. This study demonstrates the efficiency of CYN degradation and provides a better understanding of the mechanism of CYN degradation by hydroxyl radical, a reactive oxygen species that can be generated by most AOPs and is present in natural water environment.

  5. Clumped fluoride-hydroxyl defects in forsterite: Implications for the upper-mantle

    NASA Astrophysics Data System (ADS)

    Crépisson, Céline; Blanchard, Marc; Bureau, Hélène; Sanloup, Chrystèle; Withers, Anthony C.; Khodja, Hicham; Surblé, Suzy; Raepsaet, Caroline; Béneut, Keevin; Leroy, Clémence; Giura, Paola; Balan, Etienne

    2014-03-01

    The mechanism and magnitude of fluorine incorporation in H-bearing forsterite were investigated through a combined experimental and theoretical approach. Forsterite samples were synthesized in a piston cylinder press at 2 and 4 GPa, in hydrous conditions, with or without fluorine. High fluorine solubilities of 1715 and 1308 ppm F were measured by particle induced gamma-ray emission (PIGE) in forsterite samples synthesized at 2 and 4 GPa, respectively. In addition, first-principles calculations based on density functional theory were performed in order to investigate the coupled incorporation mechanisms of fluorine and water in forsterite. Our results demonstrate the close association of fluoride, hydroxyl groups and Si vacancies. Comparison of experimental and theoretical infrared absorption spectra enables assignment of the nine OH stretching bands (3500-3700 cm-1) observed in F-rich synthetic forsterite to clumped fluoride-hydroxyl defects in the forsterite crystal structure. Noteworthily, similar bands were previously recorded on some natural olivine with Mg/(Mg+Fe) molar ratio down to 0.86. Fluorine and water cycles are therefore strongly coupled through the nominally anhydrous minerals and the mantle fluorine budget can be entirely accommodated by these mineral phases.

  6. Hydroxyl-modified magnetite nanoparticles as novel carrier for delivery of methotrexate.

    PubMed

    Farjadian, Fatemeh; Ghasemi, Sahar; Mohammadi-Samani, Soliman

    2016-05-17

    In this work, novel hydroxyl-modified magnetite nanocarriers are introduced as efficient host for methotrexate conjugation. The modification was based on the Micheal type addition reaction between tris(hydroxymethyl) aminomethane and acrylamidopropyl functionalized, silica-coated magnetite nanoparticle. The chemical structure characterization was carried out by FT-IR and the organic content was determined by CHN analysis. The topography was studied by SEM, TEM, AFM. DLS was performed to show particles' mean diameter. Furthermore, the magnetite properties of modified particles were evaluated by VSM and the crystallinity was proved by XRD. To illustrate the efficiency of the modified particles, the anti-cancer drug methotrexate was conjugated to hydroxyl groups through estric bond formation. The controlled release activity of established nanoparticles was evaluated in simulated cellular fluid. Later, the anti-cancer behavior of drug conjugated nanoparticles was evaluated in vitro in MCF-7 cell line which showed enhanced toxicity after 48 h. Conclusively, the modified nanoparticles have remarked as powerful carrier to be applied as an anti-cancer agent.

  7. Development of a reaxff reactive force field for silicon/oxygen/hydrogen/fluoride interactions and applications to hydroxylation and friction

    NASA Astrophysics Data System (ADS)

    Yeon, Jejoon

    Molecular dynamics (MD) simulations with the ReaxFF reactive force field were carried out to find the atomistic mechanisms for tribo-chemical reactions occurring at the sliding interface of fully-hydroxylated amorphous silica and oxidized silicon as a function of interfacial water amount. The ReaxFF-MD simulations showed a significant amount of mass transfer across the interface occurs during the sliding. In the absence of water molecules, the interfacial mixing was initiated by dehydroxylation followed by the Si-O-Si bond formation bridging two solid surfaces. In the presence of sub-monolayer thick water, the dissociation of water molecules can provide additional reaction pathways to form the Si-O-Si bridge bonds and mass transfers across the interface. However, when the amount of interfacial water molecules was large enough to form full monolayer, the degree of mass transfer was substantially reduced since the silicon atoms at the sliding interface were terminated with hydroxyl groups rather than forming interfacial Si-O-Si bridge bonds. The ReaxFF-MD simulations clearly showed the role of water molecules in atomic scale mechano-chemical processes during the sliding and provided physical insights into tribochemical wear processes of silicon oxide surfaces observed experimentally. In addition to this, we performed reactive force field molecular dynamics simulation to observe the hydrolysis reactions between water molecules and locally strained SiO2 geometries. We improved the Si/O/H force field from Fogarty et al.1, to more accurately describe the hydroxylation reaction barrier for strained and non-strained Si-O structures, which are about 20 kcal/mol and 30 kcal/mol, respectively. After optimization, energy barrier for the hydroxylation shows a good agreement with DFT data. The observation of silanol formation at the high-strain region of a silica nano-rod also supports the concept that the adsorption of water molecule: hydroxyl formation favors the geometry with

  8. Structure, electronic properties, and aggregation behavior of hydroxylated carbon nanotubes

    SciTech Connect

    López-Oyama, A. B.; Silva-Molina, R. A.; Ruíz-García, J.; Guirado-López, R. A.; Gámez-Corrales, R.

    2014-11-07

    We present a combined experimental and theoretical study to analyze the structure, electronic properties, and aggregation behavior of hydroxylated multiwalled carbon nanotubes (OH–MWCNT). Our MWCNTs have average diameters of ∼2 nm, lengths of approximately 100–300 nm, and a hydroxyl surface coverage θ∼0.1. When deposited on the air/water interface the OH–MWCNTs are partially soluble and the floating units interact and link with each other forming extended foam-like carbon networks. Surface pressure-area isotherms of the nanotube films are performed using the Langmuir balance method at different equilibration times. The films are transferred into a mica substrate and atomic force microscopy images show that the foam like structure is preserved and reveals fine details of their microstructure. Density functional theory calculations performed on model hydroxylated carbon nanotubes show that low energy atomic configurations are found when the OH groups form molecular islands on the nanotube's surface. This patchy behavior for the OH species is expected to produce nanotubes having reduced wettabilities, in line with experimental observations. OH doping yields nanotubes having small HOMO–LUMO energy gaps and generates a nanotube → OH direction for the charge transfer leading to the existence of more hole carriers in the structures. Our synthesized OH–MWCNTs might have promising applications.

  9. Lysyl hydroxylation in collagens from hyperplastic callus and embryonic bones.

    PubMed Central

    Lehmann, H W; Bodo, M; Frohn, C; Nerlich, A; Rimek, D; Notbohm, H; Müller, P K

    1992-01-01

    Tissue from two patients with osteogenesis imperfecta suffering from a hyperplastic callus was studied. Although collagen type I from the compact bone and the skin and fibroblast cultures of these patients showed normal lysyl hydroxylation, collagen types I, II, III and V from the callus tissue were markedly overhydroxylated. Furthermore, the overhydroxylation of lysine residues covered almost equally the entire alpha 1 (I) collagen chain, as demonstrated by the analysis of individual CNBr-derived peptides. In addition, collagen type I was isolated from femoral compact bone of 33 individuals who died between the 16th week of gestational age and 22 years. Lysyl hydroxylation rapidly decreased in both collagen alpha 1 (I) and alpha 2 (I) chains during fetal development, and only little in the postnatal period. The transient increase in lysyl hydroxylation and the involvement of various collagen types in callus tissue argue for a regulatory mechanism that may operate in bone repair and during fetal development. Images Fig. 1. Fig. 3. PMID:1546948

  10. Generation of hydroxyl radicals from metal-loaded humic acids

    SciTech Connect

    Paciolla, M.D.; Jansen, S.A.; Davies, G.

    1999-06-01

    Humic acids (HAs) are naturally occurring biopolymers that are ubiquitous in the environment. They are most commonly found in the soil, drinking water, and a variety of plants. Pharmacological and therapeutic studies involving humic acids have been reported to some extent. However, when certain transition metals are bound to humic acids, e.g., iron and copper, they can be harmful to biological organisms. For this study, humic acids were extracted from German, Irish, and New Hampshire soils that were selectively chosen because of their reich abundance in humic material. Each sample was treated at room temperature with 0.1 M ferric and cupric solutions for 48 h. The amount of iron and copper adsorbed by humic acid was accurately quantitated using atomic absorption spectroscopy. The authors further demonstrate that these metal-loaded humic acids can produce deleterious oxidizing species such as the hydroxyl radical (HO*) through the metal-driven Fenton reaction. Electron paramagnetic resonance (EPR) employing spin trapping techniques with 5,5-dimethylpyrroline N-oxide (DMPO) is used to confirm the generation of hydroxyl radicals. The DMPO-OH adduct with hyperfine splitting constants A{sub N} = A{sub H} = 14.9 G is observed upon the addition of exogenous hydrogen peroxide. The concentration of hydroxyl radical was determined using 4-hydroxytempo (TEMPO-OH) as a spin standard. The presence of another oxidizing species, Fe{double_bond}O{sup 2+}, is also proposed in the absence of hydrogen peroxide.

  11. Water makes the difference: rearrangement of water solvation layer triggers non-additivity of functional group contributions in protein-ligand binding.

    PubMed

    Biela, Adam; Betz, Michael; Heine, Andreas; Klebe, Gerhard

    2012-08-01

    The binding of four congeneric peptide-like thermolysin inhibitors has been studied by high-resolution crystal structure analysis and isothermal titration calorimetry. The ligands differ only by a terminal carboxylate and/or methyl group. A surprising non-additivity of functional group contributions for the carboxylate and/or methyl groups is detected. Adding the methyl first and then the carboxylate group results in a small Gibbs free energy increase and minor enthalpy/entropy partitioning for the first modification, whereas the second involves a strong affinity increase combined with large enthalpy/entropy changes. However, first adding the carboxylate and then the methyl group yields reverse effects: the acidic group attachment now causes minor effects, whereas the added methyl group provokes large changes. As all crystal structures show virtually identical binding modes, affinity changes are related to rearrangements of the first solvation layer next to the S(2)' pocket. About 20-25 water molecules are visible next to the studied complexes. The added COO(-) groups perturb the local water network in both carboxylated complexes, and the attached methyl groups provide favorable interaction sites for water molecules. Apart from one example, a contiguously connected water network between protein and ligand functional groups is observed in all complexes. In the complex with the carboxylated ligand, which still lacks the terminal methyl group, the water network is unfavorably ruptured. This results in a surprising thermodynamic signature showing only a minor affinity increase upon COO(-) group attachment. Because the further added methyl group provides a favorable interaction site for water, the network can be reestablished, and a strong affinity increase with a large enthalpy/entropy signature is then detected.

  12. Phosphazene additives

    DOEpatents

    Harrup, Mason K; Rollins, Harry W

    2013-11-26

    An additive comprising a phosphazene compound that has at least two reactive functional groups and at least one capping functional group bonded to phosphorus atoms of the phosphazene compound. One of the at least two reactive functional groups is configured to react with cellulose and the other of the at least two reactive functional groups is configured to react with a resin, such as an amine resin of a polycarboxylic acid resin. The at least one capping functional group is selected from the group consisting of a short chain ether group, an alkoxy group, or an aryloxy group. Also disclosed are an additive-resin admixture, a method of treating a wood product, and a wood product.

  13. 46 CFR Appendix F to Subpart C of... - Optional Rider for Additional NVOCC Financial Responsibility for Group Bonds [Optional Rider to...

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 9 2011-10-01 2011-10-01 false Optional Rider for Additional NVOCC Financial Responsibility for Group Bonds F Appendix F to Subpart C of Part 515 Shipping FEDERAL MARITIME COMMISSION... Against Ocean Transportation Intermediaries Pt. 515, Subpt. C, App. F Appendix F to Subpart C of Part...

  14. 46 CFR Appendix F to Subpart C of... - Optional Rider for Additional NVOCC Financial Responsibility for Group Bonds [Optional Rider to...

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 9 2010-10-01 2010-10-01 false Optional Rider for Additional NVOCC Financial Responsibility for Group Bonds F Appendix F to Subpart C of Part 515 Shipping FEDERAL MARITIME COMMISSION... Against Ocean Transportation Intermediaries Pt. 515, Subpt. C, App. F Appendix F to Subpart C of Part...

  15. Role of oxygen functional groups in reduced graphene oxide for lubrication

    PubMed Central

    Gupta, Bhavana; Kumar, Niranjan; Panda, Kalpataru; Kanan, Vigneshwaran; Joshi, Shailesh; Visoly-Fisher, Iris

    2017-01-01

    Functionalized and fully characterized graphene-based lubricant additives are potential 2D materials for energy-efficient tribological applications in machine elements, especially at macroscopic contacts. Two different reduced graphene oxide (rGO) derivatives, terminated by hydroxyl and epoxy-hydroxyl groups, were prepared and blended with two different molecular weights of polyethylene glycol (PEG) for tribological investigation. Epoxy-hydroxyl-terminated rGO dispersed in PEG showed significantly smaller values of the friction coefficient. In this condition, PEG chains intercalate between the functionalized graphene sheets, and shear can take place between the PEG and rGO sheets. However, the friction coefficient was unaffected when hydroxyl-terminated rGO was coupled with PEG. This can be explained by the strong coupling between graphene sheets through hydroxyl units, causing the interaction of PEG with the rGO to be non- effective for lubrication. On the other hand, antiwear properties of hydroxyl-terminated rGO were significantly enhanced compared to epoxy-hydroxyl functionalized rGO due to the integrity of graphene sheet clusters. PMID:28344337

  16. Binding of hydroxylated single-walled carbon nanotubes to two hemoproteins, hemoglobin and myoglobin.

    PubMed

    Wang, Yan-Qing; Zhang, Hong-Mei; Cao, Jian

    2014-12-01

    Herein, we studied the binding interactions between hydroxylated single-walled carbon nanotubes and hemoglobin and myoglobin by the use of multi-spectral techniques and molecular modeling. The ultraviolet-vis absorbance and circular dichroism spectral results indicated that the binding interactions existed between hydroxylated single-walled carbon nanotubes and hemoglobin/myoglobin. These binding interactions partially affected the soret/heme bands of hemoglobin and myoglobin. The secondary structures of hemoproteins were partially destroyed by hydroxylated single-walled carbon nanotubes. Fluorescence studies suggested that the complexes formed between hydroxylated single-walled carbon nanotubes and hemoglobin/myoglobin by hydrogen bonding, hydrophobic, and π-π stacking interactions. In addition, molecular modeling analysis well supported the experimental results.

  17. Nucleophilic Addition of Organozinc Reagents to 2-Sulfonyl Cyclic Ethers

    PubMed Central

    Kim, Hyoungsu; Kasper, Amanda C.; Moon, Eui Jung; Park, Yongho; Wooten, Ceshea M.; Dewhirst, Mark W.; Hong, Jiyong

    2009-01-01

    A convergent route to the synthesis of manassantins A and B, potent inhibitors of HIF-1, is described. Central to the synthesis is a stereoselective addition of an organozinc reagent to a 2-benzenesulfonyl cyclic ether to achieve the 2,3-cis-3,4-trans-4,5-cis-tetrahydrofuran of the natural products. Preliminary structure—activity relationships suggested that the (R)-configuration at C-7 and C-7″′ is not critical for HIF-1 inhibition. In addition, the hydroxyl group at C-7 and C-7″′ can be replaced with carbonyl group without loss of activity. PMID:19111058

  18. Addition of surfactants in ozonated water cleaning for the suppression of functional group formation and particle adhesion on the SiO2 surface

    NASA Astrophysics Data System (ADS)

    Yang, Jahyun; Im, Kyungtaek; Lim, Sangwoo

    2011-04-01

    Various kinds of surfactants were added to a cleaning solution and deionized (DI) water, and their effect on the suppression of organic function group formation and particle adhesion to a SiO2 surface was analyzed using multi-internal reflection Fourier transform infrared spectroscopy. The results implied that attached organic functional groups are affected by the chemical structure of a surfactant in DI water. Furthermore, the addition of anionic glycolic acid ethoxylate 4-tert-butylphenyl ether (GAE4E) is the most effective in terms of preventing organic group attachment and particle adhesion to the SiO2 surface, whether it was added to the cleaning solution or post-cleaning rinse water, with or without polystyrene latex particles. Moreover, it was possible to completely prevent particle adhesion to the SiO2 surface with the proper addition of GAE4E in DIO3 solution.

  19. Kinetic isotope effects of peptidylglycine alpha-hydroxylating mono-oxygenase reaction.

    PubMed Central

    Takahashi, K; Onami, T; Noguchi, M

    1998-01-01

    Many bioactive polypeptides or neuropeptides possess a C-terminal alpha-amide group as a critical determinant for their optimal bioactivities. The amide functions are introduced by the sequential actions of peptidylglycine alpha-hydroxylating mono-oxygenase (PHM; EC 1.14.17.3) and peptidylamidoglycollate lyase (PAL; EC 4.3.2.5) from their glycine-extended precursors. In the present study we examined the kinetic isotope effects of the frog PHM reaction by competitive and non-competitive approaches. In the competitive approach we employed the double-label tracer method with D-Tyr-[U-14C]Val-Gly, D-Tyr-[3,4-3H]Val-[2,2-2H2]-Gly, and D-Tyr-Val-(R,S)[2-3H]Gly as substrates, and we determined the deuterium and tritium effects on Vmax/Km as 1.625+/-0.041 (mean+/-S. D.) and 2.71+/-0.16 (mean+/-S.D.), respectively. The intrinsic deuterium isotope effect (Dk) on the glycine hydroxylation reaction was estimated to be 6.5-10.0 (mean 8.1) by the method of Northrop [Northrop (1975) Biochemistry 14, 2644-2651]. In the non-competitive approach with N,N-dimethyl-1,4-phenylenediamine as a reductant, however, the deuterium effect on Vmax (DV) was approximately unity, although the deuterium effect on Vmax/Km (DV/K) was comparable to that obtained by the competitive approach. These results indicated that DV was completely masked by the presence of one or more steps much slower than the glycine hydroxylation step and that DV/K was diminished from Dk by a large forward commitment to catalysis. The addition of PAL, however, increased the apparent DV from 1.0 to 1.2, implying that the product release step was greatly accelerated by PAL. These results suggest that the product release is rate-limiting in the overall PHM reaction. The large Dk indicated that the glycine hydroxylation catalysed by PHM might proceed in a stepwise mechanism similar to that proposed for the dopamine beta-hydroxylase reaction [Miller and Klinman (1983) Biochemistry 22, 3091-3096]. PMID:9806894

  20. Unusual hydroxyl migration in the fragmentation of β-alanine dication in the gas phase.

    PubMed

    Piekarski, Dariusz Grzegorz; Delaunay, Rudy; Maclot, Sylvain; Adoui, Lamri; Martín, Fernando; Alcamí, Manuel; Huber, Bernd A; Rousseau, Patrick; Domaracka, Alicja; Díaz-Tendero, Sergio

    2015-07-14

    We present a combined experimental and theoretical study of the fragmentation of doubly positively charged β-alanine molecules in the gas phase. The dissociation of the produced dicationic molecules, induced by low-energy ion collisions, is analysed by coincidence mass spectrometric techniques; the coupling with ab initio molecular dynamics simulations allows rationalisation of the experimental observations. The present strategy gives deeper insights into the chemical mechanisms of multiply charged amino acids in the gas phase. In the case of the β-alanine dication, in addition to the expected Coulomb explosion and hydrogen migration processes, we have found evidence of hydroxyl-group migration, which leads to unusual fragmentation products, such as hydroxymethyl cation, and is necessary to explain some of the observed dominant channels.

  1. Establishment of a series of alien monosomic addition lines of Japanese bunching onion (Allium fistulosum L.) with extra chromosomes from shallot (A. cepa L. aggregatum group).

    PubMed

    Shigyo, M; Tashiro, Y; Isshiki, S; Miyazaki, S

    1996-12-01

    Forty one plants of alien monosomic addition lines of Allium fistulosum L. with extra chromosomes from A. cepa L. Aggregatum group (FF + nA) were produced through the second backcross of amphidiploids between these two species to A. fistulosum. Identification of the extra chromosomes in the 16 plants by elaborate karyotype analyses indicate that a complete series (eight different types) of the alien monosomic addition lines was established in Allium for the first time in this study. Chromosomal locations of malate dehydrogenase (MDH) gene, triosephosphate isomerase (TPI) gene and 5S rDNA of A. cepa Aggregatum group were determined using the series; The gene locus Mdh-1 was located on 4A, Tpi-1 on 3A and a 5S rDNA locus on 7A. Our previous and present studies using the alien monosomic addition lines revealed 11 genetic markers (isozyme and 5S rDNA) assigned to all eight chromosomes of A. cepa Aggregatum group, and these markers reconfirmed the completion of the series. Extra chromosomes of 25 other plants were examined by means of simple analyses of the chromosome markers and karyotypes. Of the total 41 plants, frequencies of the alien monosomic addition lines with extra chromosomes 1A to 8A were as follows: 1A, 5 plants; 2A, 3; 3A, 5; 4A, 9; 5A, 4; 6A, 2; 7A, 11; and 8A, 2.

  2. Hydroxylated PBDEs induce developmental arrest in zebrafish.

    PubMed

    Usenko, Crystal Y; Hopkins, David C; Trumble, Stephen J; Bruce, Erica D

    2012-07-01

    The ubiquitous spread of polybrominated diphenyl ethers (PBDEs) has led to concerns regarding the metabolites of these congeners, in particular hydroxylated PBDEs. There are limited studies regarding the biological interactions of these chemicals, yet there is some concern they may be more toxic than their parent compounds. In this study three hydroxylated PBDEs were assessed for toxicity in embryonic zebrafish: 3-OH-BDE 47, 5-OH-BDE 47, and 6-OH-BDE 47. All three congeners induced developmental arrest in a concentration-dependent manner; however, 6-OH-BDE 47 induced adverse effects at lower concentrations than the other congeners. Furthermore, all three induced cell death; however apoptosis was not observed. In short-term exposures (24-28 hours post fertilization), all hydroxylated PBDEs generated oxidative stress in the region corresponding to the cell death at 5 and 10 ppm. To further investigate the short-term effects that may be responsible for the developmental arrest observed in this study, gene regulation was assessed for embryos exposed to 0.625 ppm 6-OH-BDE 47 from 24 to 28 hpf. Genes involved in stress response, thyroid hormone regulation, and neurodevelopment were significantly upregulated compared to controls; however, genes related to oxidative stress were either unaffected or downregulated. This study suggests that hydroxylated PBDEs disrupt development, and may induce oxidative stress and potentially disrupt the cholinergic system and thyroid hormone homeostasis.

  3. Group additivity values for estimating the enthalpy of formation of organic compounds: an update and reappraisal. 2. C, H, N, O, S, and halogens.

    PubMed

    Holmes, John L; Aubry, Christiane

    2012-07-05

    This study extends a previous publication on group additivity values (GAVs) for the elements C, H, and O, to include the elements nitrogen, sulfur, and the halogens. The present state and utility of the Benson additivity schemes for estimating the enthalpy of formation (Δ(f)H(0)) of organic compounds are again described, extending them to include more elements. Old and new GAVs for a wide variety of compounds are provided and are revised where necessary. When new terms are proposed, or old ones are significantly altered, the rationale for so doing is presented. GAV derived ring strain values for benzene and pyridine indicate that the aromatic stabilization of each is essentially the same. As before, the thermochemical consequences of replacing one functional group by another are also shown, thus permitting quick shortcuts to the estimation of new Δ(f)H(0) values.

  4. Silver nanoparticles induce apoptotic cell death in Candida albicans through the increase of hydroxyl radicals.

    PubMed

    Hwang, In-sok; Lee, Juneyoung; Hwang, Ji Hong; Kim, Keuk-Jun; Lee, Dong Gun

    2012-04-01

    Silver nanoparticles have been shown to be detrimental to fungal cells although the mechanism(s) of action have not been clearly established. In this study, we used Candida albicans cells to show that silver nanoparticles exert their antifungal effect through apoptosis. Many studies have shown that the accumulation of reactive oxygen species induces and regulates the induction of apoptosis. Furthermore, hydroxyl radicals are considered an important component of cell death. Therefore, we assumed that hydroxyl radicals were related to apoptosis and the effect of thiourea as a hydroxyl radical scavenger was investigated. We measured the production of reactive oxygen species and investigated whether silver nanoparticles induced the accumulation of hydroxyl radicals. A reduction in the mitochondrial membrane potential shown by flow cytometry analysis and the release of cytochrome c from mitochondria were also verified. In addition, the apoptotic effects of silver nanoparticles were detected by fluorescence microscopy using other confirmed diagnostic markers of yeast apoptosis including phosphatidylserine externalization, DNA and nuclear fragmentation, and the activation of metacaspases. Cells exposed to silver nanoparticles showed increased reactive oxygen species and hydroxyl radical production. All other phenomena of mitochondrial dysfunction and apoptotic features also appeared. The results indicate that silver nanoparticles possess antifungal effects with apoptotic features and we suggest that the hydroxyl radicals generated by silver nanoparticles have a significant role in mitochondrial dysfunctional apoptosis.

  5. Iron chlorin e6 scavenges hydroxyl radical and protects human endothelial cells against hydrogen peroxide toxicity.

    PubMed

    Yu, J W; Yoon, S S; Yang, R

    2001-09-01

    Iron chlorin e6 (FeCe6) has recently been proposed to be potentially antimutagenic and antioxidative. However, the antioxidant property of FeCe6 has not been elucidated in detail. In this study, we investigated the ability of FeCe6 to scavenge hydroxyl radical and to protect biomolecules and mammalian cells from oxidative stress-mediated damage. In electron spin resonance (ESR) experiments, FeCe6 showed excellent hydroxyl radical scavenging activity, whereas its iron-deficient molecule, chlorin e6 (Ce6) showed little effect. FeCe6 also significantly reduced hydroxyl radical-induced thiobarbituric acid reactive substance (TBARS) formation and benzoate hydroxylation in a dose-dependent manner. The rate constant for reaction between FeCe6 and hydroxyl radical was measured as 8.5 x 10(10) M(-1) s(-1) by deoxyribose degradation method, and this value was much higher than that of most hydroxyl radical scavengers. Superoxide dismutase (SOD) activity of FeCe6 was also confirmed by ESR study and cytochrome c reduction assay, but its in vitro activity appeared to be less efficient in comparison with other well-known SOD mimics. In addition, FeCe6 appreciably diminished hydroxyl radical-induced DNA single-strand breakage and protein degradation in Fe-catalyzed and Cu-catalyzed Fenton systems, and it significantly protected human endothelial cells against hydrogen peroxide (H2O2) toxicity. These results suggest that FeCe6 is a novel hydroxyl radical scavenger and may be useful for preventing oxidative injury in biological systems.

  6. Taxonomy of the hyper-diverse ant genus Tetramorium Mayr in the Malagasy region (Hymenoptera, Formicidae, Myrmicinae) – first record of the T. setigerum species group and additions to the Malagasy species groups with an updated illustrated identification key

    PubMed Central

    Hita Garcia, Francisco; Fisher, Brian L.

    2015-01-01

    Abstract In this study we provide an update to the taxonomy of the ant genus Tetramorium Mayr in Madagascar. We report the first record of the Tetramorium setigerum species group in Madagascar and describe the only Malagasy representative as Tetramorium cavernicola sp. n., which is known only from a cave in Ankarana. In addition, we provide an overview of the 19 proposed Malagasy species groups, and discuss their zoogeography and relationships to other groups and larger lineages within the hyper-diverse genus Tetramorium. At present, we recognise a highly unique Malagasy Tetramorium fauna with 113 species endemic to the island of Madagascar out of a total of 125 translating into an endemism rate of 93%. We hypothesise that this fauna is based on one or a few colonisation events from the Afrotropical region, with subsequent adaptive radiation in Madagascar. Furthermore, we present an updated and illustrated identification key to the Tetramorium species groups in the Malagasy region. PMID:26257564

  7. Targeted acylation for all the hydroxyls of (+)-catechin and evaluation of their individual contribution to radical scavenging activity.

    PubMed

    Hong, Shan; Liu, Songbai

    2016-04-15

    The reactivity profile of all the hydroxyl groups in (+)-catechin towards acylation and their respective contribution to radical scavenging activity were systematically explored in this work. Selective acylation of the hydroxyls on different rings was carried out employing either a basic or acidic activation strategy. Monoacylation of B ring was achieved effectively with the aid of dimethyltin dichloride. Monoacylation of A ring was accomplished by sequential protection and deprotection of B and C rings. Based on specific acylation of all the individual hydroxyls of (+)-catechins, the structure radical scavenging activity relationship of each hydroxyl of (+)-catechin was established. It was demonstrated that the vicinal phenolic hydroxyls on B ring played the most important role in the ABTS radical scavenging activity and those on A and C rings made a much smaller contribution. This study has laid solid groundwork for further modification of the catechins and improvement of their properties.

  8. Determination of surface-accessible acidic hydroxyls and surface area of lignin by cationic dye adsorption.

    PubMed

    Sipponen, Mika Henrikki; Pihlajaniemi, Ville; Littunen, Kuisma; Pastinen, Ossi; Laakso, Simo

    2014-10-01

    A new colorimetric method for determining the surface-accessible acidic lignin hydroxyl groups in lignocellulose solid fractions was developed. The method is based on selective adsorption of Azure B, a basic dye, onto acidic hydroxyl groups of lignin. Selectivity of adsorption of Azure B on lignin was demonstrated using lignin and cellulose materials as adsorbents. Adsorption isotherms of Azure B on wheat straw (WS), sugarcane bagasse (SGB), oat husk, and isolated lignin materials were determined. The maximum adsorption capacities predicted by the Langmuir isotherms were used to calculate the amounts of surface-accessible acidic hydroxyl groups. WS contained 1.7-times more acidic hydroxyls (0.21 mmol/g) and higher surface area of lignin (84 m(2)/g) than SGB or oat husk materials. Equations for determining the amount of surface-accessible acidic hydroxyls in solid fractions of the three plant materials by a single point measurement were developed. A method for high-throughput characterization of lignocellulosic materials is now available.

  9. Inhibition of hydroxyl radical reaction with aromatics by dissolved natural organic matter

    USGS Publications Warehouse

    Lindsey, M.E.; Tarr, M.A.

    2000-01-01

    Reaction of aromatic compounds with hydroxyl radical is inhibited by dissolved natural organic matter (NOM). The degree of inhibition is significantly greater than that expected based on a simple model in which aromatic compound molecules bound to NOM are considered to be unreactive. In this study, hydroxyl radical was produced at steady-state concentrations using Fenton chemistry (H2O2 + Fe2+ ??? Fe3+ + HO- + HO??). Suwannee River fulvic acid and humic acid were used as NOM. The most likely mechanism for the observed inhibition is that hydroxyl radical formation occurs in microenvironmental sites remote from the aromatic compounds. In addition to changes in kinetics, pyrene hydroxyl radical reaction also exhibited a mechanistic change in the presence of fulvic acid. The mechanism changed from a reaction that was apparently firstorder in pyrene to one that was apparently secondorder in pyrene, indicating that pyrene self-reaction may have become the dominant mechanism in the presence of fulvic acid. Dissolved NOM causes significant changes in the rate and mechanism of hydroxyl radical degradation of aromatic compounds. Consequently, literature rate constants measured in pure water will not be useful for predicting the degradation of pollutants in environmental systems. The kinetic and mechanistic information in this study will be useful for developing improved degradation methods involving Fenton chemistry.Reaction of aromatic compounds with hydroxyl radical is inhibited by dissolved natural organic matter (NOM). The degree of inhibition is significantly greater than that expected based on a simple model in which aromatic compounds molecules bounds to NOM are considered to be unreactive. In this study, hydroxyl radical was produced at steady-state concentrations using Fenton chemistry (H2O2 + Fe2+ ??? Fe3+ + HO- + HO??). Suwannee River fulvic acid and humic acid were used as NOM. The most likely mechanisms for the observed inhibition is that hydroxyl radical

  10. Group additivity equations of state for calculating the standard molal thermodynamic properties of aqueous organic species at elevated temperatures and pressures

    NASA Astrophysics Data System (ADS)

    Amend, Jan P.; Helgeson, Harold C.

    1997-01-01

    Group additivity equations of state for aqueous organic molecules have been generated by combining the revised Helgeson-Kirkham-Flowers (HKF) equations of state ( Shock and Helgeson, 1988, 1990; Tanger and Helgeson, 1988; Shock et al., 1989, 1992) with experimental values of the standard molal properties of aqueous alkanes, alkanols, alkylbenzenes, car☐ylic acids, amides, and amines. Equations of state parameters for the groups represented by -CH 2-, -CH 3, -CHCH 3-, -C 6H 5, -CH 2OH, -COOH, -CONH 2, and -CH 2NH 2 were determined by regression of the experimental data. This procedure permits calculation of the standard molal thermodynamic properties of these groups at elevated temperatures and pressures. Although curves representing the apparent standard molal Gibbs free energies (Δ G°) and enthalpies (Δ H°) of formation, and the standard molal entropies ( S°) of the groups as a function of temperature and pressure are respectively similar for each of them, the temperature dependence of the standard molal heat capacities ( Cp°) and volumes ( V°) of a number of the groups are quite different from one another. For example, the standard molal heat capacities of the hydrocarbon groups minimize with increasing temperature, but those of -CH 2OH and -CH 2NH 2 maximize. Computed values of Δ G°, Δ H°, S°, Cp°, V°, and the equations of state parameters for the various groups were used together with group additivity relations to generate corresponding values of these properties for aqueous n-alkanes, 2-methylalkanes, n-alkylbenzenes, n-alkanols, n-car☐ylic acids, n-amides, and n-amines at temperatures ≤ 250°C and pressures ≤ 1 kbar. The validity and generality of the equations of state are supported by the fact that predicted equilibrium constants for liquid n-alkane solubility reactions in water compare favorably with experimental values reported in the literature for temperatures as high as 200°C. Furthermore, equilibrium constants for aqueous ethane

  11. Selective Aromatic Hydroxylation with Dioxygen and Simple Copper Imine Complexes.

    PubMed

    Becker, Jonathan; Gupta, Puneet; Angersbach, Friedrich; Tuczek, Felix; Näther, Christian; Holthausen, Max C; Schindler, Siegfried

    2015-08-10

    The formation of a bis(μ-oxido)dicopper complex with the ligand 2-(diethylaminoethyl)-6-phenylpyridine (PPN) and its subsequent hydroxylation of the pendant phenyl group (studied earlier by Holland et al., Angew. Chem. Int. Ed.- 1999, 38, 1139-1142) has been reinvestigated to gain a better understanding of such systems in view of the development of new synthetic applications. To this end, we prepared a simple copper imine complex system that also affords selective o-hydroxylation of aromatic aldehydes by using dioxygen as the oxidant: Applying the ligand N'-benzylidene-N,N-diethylethylenediamine (BDED), salicylaldehyde was prepared in good yields and we show that this reaction also occurs through an intermediate bis-μ-oxido copper complex. The underlying reaction mechanism for the PPN-supported complex was studied at the BLYP-D/TZVP level of density functional theory and the results for representative stationary points along reaction paths of the BDED-supported complex reveal a closely related mechanistic scenario. The results demonstrate a new facile synthetic way to introduce OH groups into aromatic aldehydes.

  12. STM and HREELS investigation of gas phase silanization on hydroxylated Si(100)

    NASA Astrophysics Data System (ADS)

    Fan, C.; Lopinski, G. P.

    2010-06-01

    The gas phase anhydrous reaction of glycidoxypropyldimethylethoxysilane (GPDMES) with a model hydroxylated surface has been investigated using high-resolution electron energy loss spectroscopy (HREELS) and scanning tunneling microscopy (STM). Water dissociation on the clean reconstructed (2 × 1)-Si(100) surface was used to create an atomically flat surface with ~ 0.5 ML of hydroxyl groups. Exposure of this surface to GPDMES at room temperature under vacuum was found to lead to formation of covalent Si-O-Si bonds although high exposures (6 × 10 8 L) were required for saturation. STM images at the early stages of reaction indicate that the reaction occurs randomly on the surface with no apparent clustering. The STM images together with semi-empirical (AM1) calculations provide evidence for hydrogen bonding interactions between the oxygen atoms in the molecule and surface hydroxyl groups at low coverage.

  13. Probing RNA folding by hydroxyl radical footprinting.

    PubMed

    Costa, Maria; Monachello, Dario

    2014-01-01

    In recent years RNA molecules have emerged as central players in the regulation of gene expression. Many of these noncoding RNAs possess well-defined, complex, three-dimensional structures which are essential for their biological function. In this context, much effort has been devoted to develop computational and experimental techniques for RNA structure determination. Among available experimental tools to investigate the higher-order folding of structured RNAs, hydroxyl radical probing stands as one of the most informative and reliable ones. Hydroxyl radicals are oxidative species that cleave the nucleic acid backbone solely according to the solvent accessibility of individual phosphodiester bonds, with no sequence or secondary structure specificity. Therefore, the cleavage pattern obtained directly reflects the degree of protection/exposure to the solvent of each section of the molecule under inspection, providing valuable information about how these different sections interact together to form the final three-dimensional architecture. In this chapter we describe a robust, accurate and very sensitive hydroxyl radical probing method that can be applied to any structured RNA molecule and is suitable to investigate RNA folding and RNA conformational changes induced by binding of a ligand.

  14. Different Effect of the Additional Electron-Withdrawing Cyano Group in Different Conjugation Bridge: The Adjusted Molecular Energy Levels and Largely Improved Photovoltaic Performance.

    PubMed

    Li, Huiyang; Fang, Manman; Hou, Yingqin; Tang, Runli; Yang, Yizhou; Zhong, Cheng; Li, Qianqian; Li, Zhen

    2016-05-18

    Four organic sensitizers (LI-68-LI-71) bearing various conjugated bridges were designed and synthesized, in which the only difference between LI-68 and LI-69 (or LI-70 and LI-71) was the absence/presence of the CN group as the auxiliary electron acceptor. Interestingly, compared to the reference dye of LI-68, LI-69 bearing the additional CN group exhibited the bad performance with the decreased Jsc and Voc values. However, once one thiophene moiety near the anchor group was replaced by pyrrole with the electron-rich property, the resultant LI-71 exhibited a photoelectric conversion efficiency increase by about 3 folds from 2.75% (LI-69) to 7.95% (LI-71), displaying the synergistic effect of the two moieties (CN and pyrrole). Computational analysis disclosed that pyrrole as the auxiliary electron donor (D') in the conjugated bridge can compensate for the lower negative charge in the electron acceptor, which was caused by the CN group as the electron trap, leading to the more efficient electron injection and better photovoltaic performance.

  15. Identification of hydroxylated metabolites of hexabromocyclododecane in wildlife and 28-days exposed Wistar rats.

    PubMed

    Brandsma, Sicco H; Van der Ven, Leo T M; De Boer, Jacob; Leonards, Pim E G

    2009-08-01

    We studied the presence of hydroxylated metabolites of hexabromocyclododecane (HBCD) in three wildlife species (tern egg, seal, and flounder) and in Wistar rats exposed to 30 and 100 mg HBCD/kg bw/day for 28 days. A nondestructive extraction, fractionation, and cleanup method was developed to separate the hydroxylated HBCD metabolites from the biotic sample matrix. Four different groups of hydroxylated HBCD metabolites were identified in rat adipose, liver, lung, and muscle tissues by liquid and gas chromatography (LC and GC) combined with mass spectrometry (MS): monohydroxy metabolites of HBCD, pentabromocyclododecene (PBCDe), tetrabromocyclododecene (TBCDe), and dihydroxy-HBCD. Dihydroxy-PBCDe was identified by GC-MS but could not be confirmed by LCMS. Debromination of HBCD to PBCDe was another metabolic pathway observed. In tern eggs from the Western Scheldt the monohydroxy-HBCD was found and in the blubber of harbor seal (Wadden Sea) the monohydroxy metabolites of HBCD and PBCDe were found. No hydroxylated metabolites were detected in the tissue of flounder (Wadden Sea). To our knowledge, this is the first study to identify different hydroxylated metabolite groups of HBCD in rat and wildlife samples.

  16. Measurement of the intramolecular isotope effect on aliphatic hydroxylation by Chromobacterium violaceum phenylalanine hydroxylase.

    PubMed

    Panay, Aram J; Fitzpatrick, Paul F

    2010-04-28

    The non-heme iron enzyme phenylalanine hydroxylase from Chromobacterium violaceum has previously been shown to catalyze the hydroxylation of benzylic and aliphatic carbons in addition to the normal aromatic hydroxylation reaction. The intrinsic isotope effect for hydroxylation of 3-cyclochexylalanine by the enzyme was determined in order to gain insight into the reactivity of the iron center. With 3-[(2)H(11)-cyclohexyl]alanine as the substrate, the isotope effect on the k(cat) value was 1, consistent with an additional step in the overall reaction being significantly slower than hydroxylation. Consequently, the isotope effect was determined as an intramolecular effect by measuring the amount of deuterium lost in the hydroxylation of 3-[1,2,3,4,5,6-(2)H(6)-cyclohexyl]alanine. The ratio of 4-HO-cyclohexylalanine that retained deuterium to that which lost one deuterium atom was 2.8. This gave a calculated value of 12.6 for the ratio of the primary deuterium kinetic isotope effect to the secondary isotope effect. This value is consistent with hydrogen atom abstraction by an electrophilic Fe(O) center and a contribution of quantum-mechanical tunneling to the reaction.

  17. Group additivity calculation of the standard molal thermodynamic properties of aqueous amino acids, polypeptides and unfolded proteins as a function of temperature, pressure and ionization state

    NASA Astrophysics Data System (ADS)

    Dick, J. M.; Larowe, D. E.; Helgeson, H. C.

    2005-10-01

    Thermodynamic calculation of the chemical speciation of proteins and the limits of protein metastability affords a quantitative understanding of the biogeochemical constraints on the distribution of proteins within and among different organisms and chemical environments. These calculations depend on accurate determination of the ionization states and standard molal Gibbs free energies of proteins as a function of temperature and pressure, which are not generally available. Hence, to aid predictions of the standard molal thermodynamic properties of ionized proteins as a function of temperature and pressure, calculated values are given below of the standard molal thermodynamic properties at 25°C and 1 bar and the revised Helgeson-Kirkham-Flowers equations of state parameters of the structural groups comprising amino acids, polypeptides and unfolded proteins. Group additivity and correlation algorithms were used to calculate contributions by ionized and neutral sidechain and backbone groups to the standard molal Gibbs free energy (Δ G°), enthalpy (Δ H°), entropy (S°), isobaric heat capacity (C°P), volume (V°) and isothermal compressibility (κ°T) of multiple reference model compounds. Experimental values of C°P, V° and κ°T at high temperature were taken from the recent literature, which ensures an internally consistent revision of the thermodynamic properties and equations of state parameters of the sidechain and backbone groups of proteins, as well as organic groups. As a result, Δ G°, Δ H°, S° C°P, V° and κ°T of unfolded proteins in any ionization state can be calculated up to T~-300°C and P~-5000 bars. In addition, the ionization states of unfolded proteins as a function of not only pH, but also temperature and pressure can be calculated by taking account of the degree of ionization of the sidechain and backbone groups present in the sequence. Calculations of this kind represent a first step in the prediction of chemical affinities of many

  18. Investigating Hydroxyl at Asteroid 951 Gaspra

    NASA Astrophysics Data System (ADS)

    Granahan, James C.

    2015-11-01

    Recent investigations [Granahan, 2011; 2014] of Galileo Near Infrared Mapping Spectrometer (NIMS) observations of asteroid 951 Gaspra have detected an infrared absorption feature near 2.8 micrometers. These were detected in NIMS data acquired by the Galileo spacecraft on October 29, 1991 at wavelengths ranging from 0.7 - 5.2 micrometers [Carlson et al., 1992]. This abstract presents a summary of the investigation to identify the material creating the 2.8 micrometer spectral absorption feature. The current best match for the observed 951 Gaspra feature is the phyllosilicate bound hydroxyl signature present in a thermally desiccated QUE 99038 carbonaceous chondrite as measured by Takir et al. [2013].The 951 Gaspra absorption feature has been compared to a variety of hydroxyl bearing signatures. Many phyllosilicates, hydroxyl bearing minerals, have absorption minima at different positions (2.7 or 2.85 micrometers). It also differs from similar absorptions in a potential R chondrite analog, LAP 04840. The spectra LAP 04840 has a 2.7 micrometer feature due to biotite and a 2.9 micrometer feature due to adsorbed water [Klima et al., 2007]. 2.8 micrometer absorption minima have been found for adsorbed hydroxyl on the Moon [McCord et al., 2011] and various carbonaceous chondrites [Calvin and King, 1997; Takir et al., 2013]. The best match, with a minimum Euclidean distance difference to the 951 Gaspra feature, is found in the spectrum of QUE 99038 [Takir et al., 2013]. This spectrum is the product of an infrared measurement of a sample that had its adsorbed water baked off and removed in a vacuum chamber. The remaining hydroxyl in the sample belongs to a mixture of phyllosilicates dominated by the presence of cronstedtite.References: Calvin, W. M., and T. V. King (1997), Met. Planet. Sci., 32, 693-702. Carlson, R. W., et al. (1992), Bull. American Astro. Soc., 24, 932. Granahan, J. C. (2011), Icarus, 213, 265-272. Granahan, J. C. (2014), 45th LPSC, #1092. Klima, R., C. et

  19. Cell-specific CO2 fixation rates of two distinct groups of plastidic protists in the Atlantic Ocean remain unchanged after nutrient addition.

    PubMed

    Grob, Carolina; Jardillier, Ludwig; Hartmann, Manuela; Ostrowski, Martin; Zubkov, Mikhail V; Scanlan, David J

    2015-04-01

    To assess the role of open-ocean ecosystems in global CO2 fixation, we investigated how picophytoplankton, which dominate primary production, responded to episodic increases in nutrient availability. Previous experiments have shown nitrogen alone, or in combination with phosphorus or iron, to be the proximate limiting nutrient(s) for total phytoplankton grown over several days. Much less is known about how nutrient upshift affects picophytoplankton CO2 fixation over the duration of the light period. To address this issue, we performed a series of small volume (8-60 ml) - short term (10-11 h) nutrient addition experiments in different regions of the Atlantic Ocean using NH4 Cl, FeCl3 , K medium, dust and nutrient-rich water from 300 m depth. We found no significant nutrient stimulation of group-specific CO2 fixation rates of two taxonomically and size-distinct groups of plastidic protists. The above was true regardless of the region sampled or nutrient added, suggesting that this is a generic phenomenon. Our findings show that at least in the short term (i.e. daylight period), nutrient availability does not limit CO2 fixation by the smallest plastidic protists, while their taxonomic composition does not determine their response to nutrient addition.

  20. Thermochemical properties, rotation barriers, and group additivity for unsaturated oxygenated hydrocarbons and radicals resulting from reaction of vinyl and phenyl radical systems with O2.

    PubMed

    Sebbarand, Nadia; Bockhorn, Henning; Bozzelli, Joseph W

    2005-03-17

    Oxidation of unsaturated and aromatic hydrocarbons in atmospheric and combustion processes results in formation of linear and cyclic unsaturated, oxygenated-hydrocarbon intermediates. The thermochemical parameters delatafH degrees 298, S degrees 298, and C(p)(f298)(T) for these intermediates are needed to understand their stability and reaction paths in further oxidation. These properties are not available for a majority of these unsaturated oxy-hydrocarbons and their corresponding radicals, even via group additivity methods. Enthalpy, entropy, and heat capacity of a series of 40 oxygenated and non-oxygenated molecules, or radicals corresponding to hydrogen atom loss from the parent stable molecules are determined in this study. Enthalpy (delatafH degrees 298 in kcal mol(-1)) is derived from the density function calculations at the B3LYP/6-311g(d,p) calculated enthalpy of reaction (delatafH degrees rxn,298) and by use of isodesmic (work) reactions. Estimation of error in enthalpy delatafH degrees 298, from use of computational chemistry coupled with work reactions analysis, is presented using comparisons between the calculated and literature enthalpies of reaction. Entropies (S degrees 298) and heat capacities (C(p)(f298)(T)) were calculated using the B3LYP/6-311G(d,p) determined frequencies and geometries. Potential barriers for internal rotors in each molecule were determined and used (in place of torsion frequencies) to calculate contributions to S and C(p)(T) from the hindered rotors. Twenty-six groups for use in group additivity (GA) are also developed.

  1. Production and characterization of alien chromosome additions in shallot (Allium cepa L. Aggregatum group) carrying extra chromosome(s) of Japanese bunching onion (A. fistulosum L.).

    PubMed

    Hang, Tran Thi Minh; Shigyo, Masayoshi; Yamauchi, Naoki; Tashiro, Yosuke

    2004-10-01

    First and second backcrosses of amphidiploid hybrids (2n = 4x = 32, genomes AAFF) between shallot (Allium cepa Aggregatum group) and A. fistulosum were conducted to produce A. cepa - A. fistulosum alien addition lines. When shallot (A. cepa Aggregatum group) was used as a pollinator, the amphidiploids and allotriploids set germinable BC(1) and BC(2) seeds, respectively. The 237 BC(1) plants mainly consisted of 170 allotriploids (2n = 3x = 24, AAF) and 42 hypo-allotriploids possessing 23 chromosomes, i.e., single-alien deletions (2n = 3x-1 = 23, AAF-nF). The single-alien deletions in the BC(1) progeny showed dwarfing characteristics and were discriminated from the allotriploids (2n = 24) and hyper-allotriploids (2n = 25) by means of flow cytometric analysis. The chromosome numbers of 46 BC(2) seedlings varied from 16 to 24. Eight monosomic additions (2n = 2x+1 = 17, AA+nF) and 20 single-alien deletions were found in these BC(2) seedlings. Consequently, six kinds of A. cepa - A. fistulosum alien chromosome additions possessing different chromosome numbers (2n = 17, 18, 20, 21, 22, 23) were recognized in the BC(1) and BC(2) populations. A total of 79 aneuploids, including 62 single-alien deletions, were analyzed by a chromosome 6F-specific isozyme marker (Got-2) in order to recognize its existence in their chromosome complements. This analysis revealed that two out of 62 single-alien deletions did not possess 6F. One (AAF-6F) out of the possible eight single-alien deletions could be identified at first. The present study is a first step toward the development of a useful tool, such as a complete set of eight different single-alien deletions, for the rapid chromosomal assignment of genes and genetic markers in A. fistulosum.

  2. Hydroxyl radical mediated DNA base modification by manmade mineral fibres.

    PubMed Central

    Leanderson, P; Söderkvist, P; Tagesson, C

    1989-01-01

    Manmade mineral fibres (MMMFs) were examined for their ability to hydroxylate 2-deoxyguanosine (dG) to 8-hydroxydeoxyguanosine (8-OH-dG), a reaction that is mediated by hydroxyl radicals. It appeared that (1) catalase and the hydroxyl radical scavengers, dimethylsulphoxide and sodium benzoate, inhibited the hydroxylation, whereas Fe2+ and H2O2 potentiated it; (2) pretreatment of MMMFs with the iron chelator, deferoxamine, or with extensive heat (200-400 degrees C), attenuated the hydroxylation; (3) the hydroxylation obtained by various MMMFs varied considerably; (4) there was no apparent correlation between the hydroxylation and the surface area of different MMMFs, although increasing the surface area of a fibre by crushing it increased its hydroxylating capacity; and (5) there was good correlation between the hydroxylation of dG residues in DNA and the hydroxylation of pure dG in solution for the 16 different MMMFs investigated. These findings indicate that MMMFs cause a hydroxyl radical mediated DNA base modification in vitro and that there is considerable variation in the reactivity of different fibre species. The DNA modifying ability seems to depend on physical or chemical characteristics, or both, of the fibre. PMID:2765416

  3. Hydroxylation of organic polymer surface: method and application.

    PubMed

    Yang, Peng; Yang, Wantai

    2014-03-26

    It may be hardly believable that inert C-H bonds on a polymeric material surface could be quickly and efficiently transformed into C-OH by a simple and mild way. Thanks to the approaches developed recently, it is now possible to transform surface H atoms of a polymeric substrate into monolayer OH groups by a simple/mild photochemical reaction. Herein the method and application of this small-molecular interfacial chemistry is highlighted. The existence of hydroxyl groups on material surfaces not only determines the physical and chemical properties of materials but also provides effective reaction sites for postsynthetic sequential modification to fulfill the requirements of various applications. However, organic synthetic materials based on petroleum, especially polyolefins comprise mainly C and H atoms and thus present serious surface problems due to low surface energy and inertness in reactivity. These limitations make it challenging to perform postsynthetic surface sequential chemical derivatization toward enhanced functionalities and properties and also cause serious interfacial problems when bonding or integrating polymer substrates with natural or inorganic materials. Polymer surface hydroxylation based on direct conversion of C-H bonds on polymer surfaces is thus of significant importance for academic and practical industrial applications. Although highly active research results have reported on small-molecular C-H bond activation in solution (thus homogeneous), most of them, featuring the use of a variety of transition metals as catalysts, present a slow reaction rate, a low atom economy and an obvious environmental pollution. In sharp contrast to these conventional C-H activation strategies, the present Spotlight describes a universal confined photocatalytic oxidation (CPO) system that is able to directly convert polymer surface C-H bonds to C-OSO3(-) and, subsequently, to C-OH through a simple hydrolysis. Generally speaking, these newly implanted hydroxyl

  4. Perinatal manganese exposure and hydroxyl radical formation in rat brain.

    PubMed

    Bałasz, Michał; Szkilnik, Ryszard; Brus, Ryszard; Malinowska-Borowska, Jolanta; Kasperczyk, Sławomir; Nowak, Damian; Kostrzewa, Richard M; Nowak, Przemysław

    2015-01-01

    The present study was designed to investigate the role of pre- and postnatal manganese (Mn) exposure on hydroxyl radical (HO(•)) formation in the brains of dopamine (DA) partially denervated rats (Parkinsonian rats). Wistar rats were given tap water containing 10,000 ppm manganese chloride during the duration of pregnancy and until the time of weaning. Control rat dams consumed tap water without added Mn. Three days after birth, rats of both groups were treated with 6-hydroxydopamine at one of three doses (15, 30, or 67 µg, intraventricular on each side), or saline vehicle. We found that Mn content in the brain, kidney, liver, and bone was significantly elevated in dams exposed to Mn during pregnancy. In neonates, the major organs that accumulated Mn were the femoral bone and liver. However, Mn was not elevated in tissues in adulthood. To determine the possible effect on generation of the reactive species, HO(•) in Mn-induced neurotoxicity, we analyzed the contents of 2.3- and 2.5-dihydroxybenzoic acid (spin trap products of salicylate; HO(•) being an index of in vivo HO(•) generation), as well as antioxidant enzyme activities of superoxide dismutase (SOD) isoenzymes and glutathione S-transferase (GST). 6-OHDA-depletion of DA produced enhanced HO(•) formation in the brain tissue of newborn and adulthood rats that had been exposed to Mn, and the latter effect did not depend on the extent of DA denervation. Additionally, the extraneuronal, microdialysate, content of HO(•) in neostriatum was likewise elevated in 6-OHDA-lesioned rats. Interestingly, there was no difference in extraneuronal HO(•) formation in the neostriatum of Mn-exposed versus control rats. In summary, findings in this study indicate that Mn crosses the placenta but in contrast to other heavy metals, Mn is not deposited long term in tissues. Also, damage to the dopaminergic system acts as a "trigger mechanism," initiating a cascade of adverse events leading to a protracted increase in

  5. Hydroxyl radical generation by a light-dependent Fenton reaction.

    PubMed

    Van der Zee, J; Krootjes, B B; Chignell, C F; Dubbelman, T M; Van Steveninck, J

    1993-02-01

    Illumination of Fe3+, with light of a wavelength varying from 250 to 450 nm, in the presence of the iron chelators ethylenediamine N,N,N',N'-tetraacetic acid (EDTA), ethyleneglycol-bis-(beta-aminoethylether)N,N,N',N'-tetraacet ic acid (EGTA), diethylenetriamine-N,N,N',N',N'-pentaacetic acid (DTPA), or citrate resulted in the reduction of Fe3+ to Fe2+. Fe2+ formation was measured by the formation of its complex with bathophenanthroline disulfonic acid. In all cases Fe2+ formation was completely dependent on the presence of the iron chelator and on the wavelength used for illumination. A correlation was found between the absorption spectrum of the iron-chelator complex and the amount of Fe3+ reduced, suggesting that the absorption of light induced an electron transfer from the chelator to the iron ion. Exposure to oxygen, either during or after illumination, resulted in degradation of the chelator molecule. Illumination of the Fe(3+)-chelator complexes in the presence of H2O2 resulted in the formation of hydroxyl radicals, which could be determined by the formation of the 5,5-dimethyl-1-pyrroline N-oxide (DMPO)-hydroxyl radical adduct, using electron spin resonance spectroscopy. Formation of the spin adduct was inhibited by addition of catalase, mannitol, ethanol, or formate, whereas superoxide dismutase had no effect.

  6. Hydroxyl orientations in cellobiose and other polyhydroxy compounds – modeling versus experiment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Theoretical and experimental gas-phase studies of carbohydrates show that their hydroxyl groups are located in homodromic partial rings that resemble cooperative hydrogen bonds, albeit with long H…O distances and small O-H…O angles. On the other hand, anecdotal experience with disaccharide crystal ...

  7. Highly efficient synthesis of phenols by copper-catalyzed hydroxylation of aryl iodides, bromides, and chlorides.

    PubMed

    Yang, Kai; Li, Zheng; Wang, Zhaoyang; Yao, Zhiyi; Jiang, Sheng

    2011-08-19

    8-Hydroxyquinolin-N-oxide was found to be a very efficient ligand for the copper-catalyzed hydroxylation of aryl iodides, aryl bromides, or aryl chlorides under mild reaction conditions. This methodology provides a direct transformation of aryl halides to phenols and to alkyl aryl ethers. The inexpensive catalytic system showed great functional group tolerance and excellent selectivity.

  8. DFT STUDY OF ALPHA-MALTOSE: INFLUENCE OF HYDROXYL ORIENTATIONS ON THE GLYCOSIDIC BOND

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The result of DFT geometry optimization of 68 unique alpha-maltose conformers at the B3LYP/6-311++G** level of theory is described. Particular attention is paid to the hydroxyl group rotational positions and their influence on the glycosidic bond dihedral angles. The orientation of lone pair elect...

  9. Transformations and reactions of Re2(CO)8(mu-SbPh2)(mu-H) induced by the addition of a platinum(tri-t-butylphosphine) group.

    PubMed

    Adams, Richard D; Hall, Michael B; Pearl, William C; Yang, Xinzheng

    2009-01-19

    Three products Re(2)[Pt(PBu(t)(3))](mu-SbPh(2))(CO)(8)(mu-H), 2, Re(2)[Pt(CO)(PBu(t)(3))]Ph(CO)(8)(mu(3)-SbPh)(mu-H), 3, and Re(2)[Pt(PBu(t)(3))](2)(CO)(8)(mu(4)-Sb(2)Ph(2))(mu-H)(2), 4, were obtained from the reaction of Re(2)(CO)(8)(mu-SbPh(2))(mu-H), 1, with Pt(PBu(t)(3))(2). Compound 3 was also obtained from 2 by further reaction with Pt(PBu(t)(3))(2). Compound 2 is a Pt(PBu(t)(3)) adduct of 1 formed by the insertion of the platinum atom into one of the Re-Sb bonds of 1 with formation of two Pt-Re bonds. Compound 3 contains an open Re(2)Pt cluster and was also obtained in a low yield by the addition of CO to 2. The addition of SbPh(3) to 2 yielded the compound Re(2)Pt(PBu(t)(3))(Ph)(CO)(8)(SbPh(3))(mu(3)-SbPh)(mu-H), 5, a SbPh(3) derivative of 3. Compound 4 can be viewed as a dimer of the fragment Re[Pt(PBu(t)(3))](CO)(4)(SbPh)(mu-H). The two halves of the molecule are held together by Pt-Sb bonds and a significant interaction directly between the Sb atoms, Sb-Sb distance, 2.9834(7) A. The Sb-Sb bonding in 4 was explained by density functional calculations. Compound 4 adds 2 equiv of CO at 1 atm/25 degrees C, one to each platinum atom, to yield the compound [Re(CO)(4)Pt(H)(CO)(PBu(t)(3))(mu(3)-SbPh)](2) which exists as a mixture of two noninterconverting isomers, cis-6 and trans-6. Both isomers of 6 were isolated and structurally characterized. Each isomer of 6 consists of a central planar Re(2)Sb(2) core composed of two Re(CO)(4) groups with two bridging SbPh ligands. There is a Pt(H)(CO)(PBu(t)(3)) group coordinated to each antimony atom of 6. In the cis-isomer both Pt(H)(CO)(PBu(t)(3)) groups lie on the same side of the Re(2)Sb(2) plane. In the trans-isomer the Pt(H)(CO)(PBu(t)(3)) groups lie on opposite sides of the Re(2)Sb(2) plane.

  10. Assessing the contribution of free hydroxyl radical in organic matter-sensitized photohydroxylation reactions.

    PubMed

    Page, Sarah E; Arnold, William A; McNeill, Kristopher

    2011-04-01

    Photochemical formation of reactive oxygen species from dissolved organic matter (DOM) is incompletely understood, especially in the case of hydroxyl radical (•OH) production. Many studies have used various probes to detect photochemically produced •OH from DOM, but the fundamental reactions of these probes are not necessarily specific for free •OH and may also detect lower-energy hydroxylation agents. In this study, two tests were applied that have previously been used as a diagnostic for the presence of free •OH: methane quenching of •OH and hydroxybenzoic acid (hBZA) product yields. Upon application of these two tests to a set of five DOM isolates, it was found that methane quenching and the hBZA ratio results were not necessarily consistent. Overall, the results provide compelling evidence that all isolates studied photochemically produce free •OH. The hydroxylating acitivity of Elliot Soil Humic Acid and Pony Lake Fulvic Acid, however, also had a significant contribution from a photochemically generated hydroxylating agent that is lower in energy than free •OH. Catalase quenching experiments were conducted to assess whether hydrogen peroxide was the immediate precursor to hydroxyl in these systems. In all cases, catalase addition slowed photohydroxylation of terephthalate, but the contribution of hydrogen peroxide photolysis was determined to be less than 50%.

  11. EPR studies on hydroxyl radical-scavenging activities of pravastatin and fluvastatin.

    PubMed

    Vandjelovic, Nathan; Zhu, Hong; Misra, Hara P; Zimmerman, Ryan P; Jia, Zhenquan; Li, Yunbo

    2012-05-01

    Statins are known clinically by their cholesterol reduction properties through the inhibition of HMG-CoA reductase. There is mounting evidence suggesting a protective role of statins in certain types of cancer, cardiac, and vascular disease through a mechanism that extends beyond their lipid lowering ability. The root mechanism of damage likely involves the inflammatory cascade, specifically compounds known as reactive oxygen species such as the hydroxyl radical. However, direct evidence for the hydroxyl-scavenging capacity of pravastatin and fluvastatin, two forms of statins being widely used to lower LDL cholesterol, is still lacking in literature. In this study, electron paramagnetic resonance spectroscopy in combination with 5,5-dimethyl-1-pyrroline N-oxide (DMPO)-spin-trapping technique was utilized to determine the abilities of pravastatin and fluvastatin in scavenging hydroxyl radical generated from Fe(II) with H(2)O(2) system. In addition, we examined the effects of pravastatin and fluvastatin on oxidative-induced φX-174 RF I plasmid DNA damage. We have demonstrated here for the first time that pravastatin and fluvastatin at physiologically relevant concentrations significantly decreased formation of DMPO-OH adduct indicating that both compounds could directly scavenge hydroxyl radicals. However, pravastatin and fluvastatin were not able to directly protect against oxidative DNA plasmid damage. The hydroxyl radical sequestering ability of pravastatin and fluvastatin reported in this study may contribute to their beneficial use in certain types of cancer and in cardiovascular disease.

  12. Aliphatic peptidyl hydroperoxides as a source of secondary oxidation in hydroxyl radical protein footprinting.

    PubMed

    Saladino, Jessica; Liu, Mian; Live, David; Sharp, Joshua S

    2009-06-01

    Hydroxyl radical footprinting is a technique for studying protein structure and binding that entails oxidizing a protein system of interest with diffusing hydroxyl radicals, and then measuring the amount of oxidation of each amino acid. One important issue in hydroxyl radical footprinting is limiting amino acid oxidation by secondary oxidants to prevent uncontrolled oxidation, which can cause amino acids to appear more solvent accessible than they really are. Previous work suggested that hydrogen peroxide was the major secondary oxidant of concern in hydroxyl radical footprinting experiments; however, even after elimination of all hydrogen peroxide, some secondary oxidation was still detected. Evidence is presented for the formation of peptidyl hydroperoxides as the most abundant product upon oxidation of aliphatic amino acids. Both reverse phase liquid chromatography and catalase treatment were shown to be ineffective at eliminating peptidyl hydroperoxides. The ability of these peptidyl hydroperoxides to directly oxidize methionine is demonstrated, suggesting the value of methionine amide as an in situ protectant. Hydroxyl radical footprinting protocols require the use of an organic sulfide or similar peroxide scavenger in addition to removal of hydrogen peroxide to successfully eradicate all secondary oxidizing species and prevent uncontrolled oxidation of sulfur-containing residues.

  13. Hydroxyl-platelet-activating factor exists in blood of healthy volunteers and periodontal patients.

    PubMed Central

    Antonopoulou, Smaragdi; Tsoupras, Alexandros; Baltas, George; Kotsifaki, Helen; Mantzavinos, Zacharias; Demopoulos, Constantinos A

    2003-01-01

    Periodontal diseases are localized chronic inflammatory conditions of the gingival and underlying bone and connective tissue. Platelet-activating factor (PAF), a potent inflammatory phospholipid mediator that has been previously detected in elevated levels in inflamed gingival tissues, in gingival crevicular fluid and in saliva, is implicated in periodontal disease. Our results from previous studies showed that the biologically active phospholipid detected in gingival crevicular fluid is a hydroxyl-PAF analogue. In this study, hydroxyl-PAF analogue was detected for the first time in human blood derived from patients with chronic periodontitis as well as from periodontally healthy volunteers. The hydroxyl-PAF analogue was purified by high-performance liquid chromatography, detected by biological assays and identified by electrospray analysis. In addition, the quantitative determination of PAF and hydroxyl-PAF analogue (expressed as PAF-like activity) showed a statistically significant increase in the ratio of hydroxyl-PAF analogue levels to PAF levels in periodontal patients, suggesting that this bioactive lipid may play a role in oral inflammation. PMID:14514473

  14. Clustering of Oxygen Vacancies at CeO2(111 ) : Critical Role of Hydroxyls

    NASA Astrophysics Data System (ADS)

    Wu, Xin-Ping; Gong, Xue-Qing

    2016-02-01

    By performing density functional theory calculations corrected by an on site Coulomb interaction, we find that the defects at the CeO2(111 ) surface observed by the scanning tunneling microscopy (STM) measurements of Esch et al. [Science 309, 752 (2005)] are not mere oxygen vacancies or fluorine impurities as suggested by Kullgren et al. [Phys. Rev. Lett. 112, 156102 (2014)], but actually the hydroxyl-vacancy combined species. Specifically, we show that hydroxyls play a critical role in the formation and propagation of oxygen vacancy clusters (VCs). In the presence of neighboring hydroxyls, the thermodynamically unstable VCs can be significantly stabilized, and the behaviors of oxygen vacancies become largely consistent with the STM observations. In addition to the clarification of the long term controversy on the surface defect structures of CeO2(111 ) , the "hydroxyl-vacancy model" proposed in this work emphasizes the coexistence of hydroxyls and oxygen vacancies, especially VCs, which is important for understanding the catalytic and other physicochemical properties of reducible metal oxides.

  15. HYDROXYL RADICAL/OZONE RATIOS DURING OZONATION PROCESSES. I. THE RCT CONCEPT

    EPA Science Inventory

    The ozonation of model systems and several natural waters was examined in bench-scale batch experiments. In addition to measuring the concentration of ozone (03), the rate of depletion of an in situ hydroxyl radical probe compound was monitored, thus providing information on the ...

  16. Effect of Surface-active Additives on Physical Properties of Slurries of Vapor-process Magnesium

    NASA Technical Reports Server (NTRS)

    Pinns, Murray L

    1955-01-01

    The presence of 3 to 5 percent surface-active additive gave the lowest Brookfield apparent viscosity, plastic viscosity, and yield value that were obtained for slurry fuels containing approximately 50 percent vapor-process magnesium in JP-1 fuel. The slurries settled little and were easily remixed. A polyoxyethylene dodecyl alcohol was the most effective of 13 additives tested in reducing the Brookfield apparent viscosity and the yield value of the slurry. The seven most effective additives all had a hydroxyl group plus an ester or polyoxethylene group in the molecule. The densities of some of the slurries were measured.

  17. Aromatic-Hydroxyl Interaction of a Lignin Model Compound on SBA-15, Present at Pyrolysis Temperatures

    DOE PAGES

    Kandziolka, III, Michael V.; Kidder, Michelle; Gill, Lance W.; ...

    2014-07-14

    An aromatic alpha-aryl ether compound (a benzyl phenyl ether analogue) was covalently grafted to mesoporous silica SBA-15, to create BPEa-SBA-15. The BPEa-SBA-15 was subjected to successive heating cycles up to 600 °C, with in situ monitoring by DRIFTS. It was found that the toluene moiety coordinates to SBA-15 surface silanol hydroxyl groups via an aromatic–hydroxyl interaction. This interaction is evidenced by a red-shift of the aromatic C–H stretches, as well as a red-shift and broadening of the surface hydroxyl O–H stretches, which are features characteristic of a hydrogen bond. These features remain present during heating until ~400 °C whereupon themore » ether linkage of BPEa-SBA-15 is cleaved, accompanied by loss of the toluene moiety.« less

  18. Aromatic-Hydroxyl Interaction of a Lignin Model Compound on SBA-15, Present at Pyrolysis Temperatures

    SciTech Connect

    Kandziolka, III, Michael V.; Kidder, Michelle; Gill, Lance W.; Wu, Zili; Savara, Aditya Ashi

    2014-07-14

    An aromatic alpha-aryl ether compound (a benzyl phenyl ether analogue) was covalently grafted to mesoporous silica SBA-15, to create BPEa-SBA-15. The BPEa-SBA-15 was subjected to successive heating cycles up to 600 °C, with in situ monitoring by DRIFTS. It was found that the toluene moiety coordinates to SBA-15 surface silanol hydroxyl groups via an aromatic–hydroxyl interaction. This interaction is evidenced by a red-shift of the aromatic C–H stretches, as well as a red-shift and broadening of the surface hydroxyl O–H stretches, which are features characteristic of a hydrogen bond. These features remain present during heating until ~400 °C whereupon the ether linkage of BPEa-SBA-15 is cleaved, accompanied by loss of the toluene moiety.

  19. Plutonium Uptake By Brucite And Hydroxylated Periclase

    SciTech Connect

    Farr, J.D.; Neu, M.P.; Schulze, R.K.; Honeyman, B.D.

    2009-06-02

    Batch adsorption experiments and spectroscopic investigations consistently show that aqueous Pu(IV) is quickly removed from solution and becomes incorporated in a brucite or hydroxylated MgO surface to a depth of at least 50 nm, primarily as Pu(IV) within a pH range of 8.5--12.5, and is unaffected by the presence of the organic ligand, citrate. X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS) and Rutherford backscattering spectroscopy (RBS) were used to estimate Pu penetration depth and provide information about its chemical state.

  20. Recombinant expression of hydroxylated human collagen in Escherichia coli.

    PubMed

    Rutschmann, Christoph; Baumann, Stephan; Cabalzar, Jürg; Luther, Kelvin B; Hennet, Thierry

    2014-05-01

    Collagen is the most abundant protein in the human body and thereby a structural protein of considerable biotechnological interest. The complex maturation process of collagen, including essential post-translational modifications such as prolyl and lysyl hydroxylation, has precluded large-scale production of recombinant collagen featuring the biophysical properties of endogenous collagen. The characterization of new prolyl and lysyl hydroxylase genes encoded by the giant virus mimivirus reveals a method for production of hydroxylated collagen. The coexpression of a human collagen type III construct together with mimivirus prolyl and lysyl hydroxylases in Escherichia coli yielded up to 90 mg of hydroxylated collagen per liter culture. The respective levels of prolyl and lysyl hydroxylation reaching 25 % and 26 % were similar to the hydroxylation levels of native human collagen type III. The distribution of hydroxyproline and hydroxylysine along recombinant collagen was also similar to that of native collagen as determined by mass spectrometric analysis of tryptic peptides. The triple helix signature of recombinant hydroxylated collagen was confirmed by circular dichroism, which also showed that hydroxylation increased the thermal stability of the recombinant collagen construct. Recombinant hydroxylated collagen produced in E. coli supported the growth of human umbilical endothelial cells, underlining the biocompatibility of the recombinant protein as extracellular matrix. The high yield of recombinant protein expression and the extensive level of prolyl and lysyl hydroxylation achieved indicate that recombinant hydroxylated collagen can be produced at large scale for biomaterials engineering in the context of biomedical applications.

  1. Anticancer effect of linalool via cancer-specific hydroxyl radical generation in human colon cancer

    PubMed Central

    Iwasaki, Kenichi; Zheng, Yun-Wen; Murata, Soichiro; Ito, Hiromu; Nakayama, Ken; Kurokawa, Tomohiro; Sano, Naoki; Nowatari, Takeshi; Villareal, Myra O; Nagano, Yumiko N; Isoda, Hiroko; Matsui, Hirofumi; Ohkohchi, Nobuhiro

    2016-01-01

    AIM To investigate the anticancer mechanisms of the monoterpenoid alcohol linalool in human colon cancer cells. METHODS The cytotoxic effect of linalool on the human colon cancer cell lines and a human fibroblast cell line was examined using the WST-8 assay. The apoptosis-inducing effect of linalool was measured using the terminal deoxynucleotidyl transferase dUTP nick-end labeling assay and flow cytometry with Annexin V. Oxidative stress was investigated by staining for diphenyl-1-pyrenylphosphine, which is a cellular lipid peroxidation marker, and electron spin resonance spectroscopy. Sixteen SCID mice xenografted with human cancer cells were randomized into 3 groups for in vivo analysis: control and low-dose and high-dose linalool groups. The control group was administered tap water orally every 3 d. The linalool treatment groups were administered 100 or 200 μg/kg linalool solution orally for the same period. All mice were sacrificed under anesthesia 21 d after tumor inoculation, and tumors and organs were collected for immunohistochemistry using an anti-4-hydroxynonenal antibody. Tumor weights were measured and compared between groups. RESULTS Linalool induced apoptosis of cancer cells in vitro, following the cancer-specific induction of oxidative stress, which was measured based on spontaneous hydroxyl radical production and delayed lipid peroxidation. Mice in the high-dose linalool group exhibited a 55% reduction in mean xenograft tumor weight compared with mice in the control group (P < 0.05). In addition, tumor-specific lipid peroxidation was observed in the in vivo model. CONCLUSION Linalool exhibited an anticancer effect via cancer-specific oxidative stress, and this agent has potential for application in colon cancer therapy. PMID:27956800

  2. Temperature, pressure, and electrochemical constraints on protein speciation: Group additivity calculation of the standard molal thermodynamic properties of ionized unfolded proteins

    NASA Astrophysics Data System (ADS)

    Dick, J. M.; Larowe, D. E.; Helgeson, H. C.

    2006-07-01

    Thermodynamic calculations can be used to quantify environmental constraints on the speciation of proteins, such as the pH and temperature dependence of ionization state, and the relative chemical stabilities of proteins in different biogeochemical settings. These calculations depend in part on values of the standard molal Gibbs energies of proteins and their ionization reactions as a function of temperature and pressure. Because these values are not generally available, we calculated values of the standard molal thermodynamic properties at 25°C and 1 bar as well as the revised Helgeson-Kirkham-Flowers equations of state parameters of neutral and charged zwitterionic reference model compounds including aqueous amino acids, polypeptides, and unfolded proteins. The experimental calorimetric and volumetric data for these species taken from the literature were combined with group additivity algorithms to calculate the properties and parameters of neutral and ionized sidechain and backbone groups in unfolded proteins. The resulting set of group contributions enables the calculation of the standard molal Gibbs energy, enthalpy, entropy, isobaric heat capacity, volume, and isothermal compressibility of unfolded proteins in a range of proton ionization states to temperatures and pressures exceeding 100°C and 1000 bar. This approach provides a useful frame of reference for thermodynamic studies of protein folding and complexation reactions. It can also be used to assign provisional values of the net charge and Gibbs energy of ionized proteins as a function of temperature and pH. Using these values, an Eh-pH diagram for a reaction representing the speciation of extracellular proteins from Pyrococcus furiosus and Bacillus subtilis was generated. The predicted predominance limits of these proteins correspond with the different electrochemical conditions of hydrothermal vents and soils. More comprehensive calculations of this kind may reveal pervasive chemical potential

  3. Global tropospheric hydroxyl distribution, budget and reactivity

    NASA Astrophysics Data System (ADS)

    Lelieveld, Jos; Gromov, Sergey; Pozzer, Andrea; Taraborrelli, Domenico

    2016-10-01

    The self-cleaning or oxidation capacity of the atmosphere is principally controlled by hydroxyl (OH) radicals in the troposphere. Hydroxyl has primary (P) and secondary (S) sources, the former mainly through the photodissociation of ozone, the latter through OH recycling in radical reaction chains. We used the recent Mainz Organics Mechanism (MOM) to advance volatile organic carbon (VOC) chemistry in the general circulation model EMAC (ECHAM/MESSy Atmospheric Chemistry) and show that S is larger than previously assumed. By including emissions of a large number of primary VOC, and accounting for their complete breakdown and intermediate products, MOM is mass-conserving and calculates substantially higher OH reactivity from VOC oxidation compared to predecessor models. Whereas previously P and S were found to be of similar magnitude, the present work indicates that S may be twice as large, mostly due to OH recycling in the free troposphere. Further, we find that nighttime OH formation may be significant in the polluted subtropical boundary layer in summer. With a mean OH recycling probability of about 67 %, global OH is buffered and not sensitive to perturbations by natural or anthropogenic emission changes. Complementary primary and secondary OH formation mechanisms in pristine and polluted environments in the continental and marine troposphere, connected through long-range transport of O3, can maintain stable global OH levels.

  4. Effects of a Phytogenic Feed Additive Versus an Antibiotic Feed Additive on Oxidative Stress in Broiler Chicks and a Possible Mechanism Determined by Electron Spin Resonance.

    PubMed

    Settle, T; Leonard, S S; Falkenstein, E; Fix, N; Van Dyke, K; Klandorf, H

    Phytogenic feed additives are plant-derived products used in poultry feeding to improve overall performance of broilers. In this study, 588 one day-old Cobb 500 chicks were fed one of four diets and housed on either dirty or clean litter for 3wks. Treatments included: Group I: commercial diet with no additive and housed on clean litter; Group II: commercial diet with no additive and housed on dirty litter; Group III: commercial diet with a 0.05% inclusion of the anitobiotic, BMD (bacitracin methylene disalicylate); Group IV: commercial diet with a 0.05% inclusion of a phytogenic feed additive (PFA). The study was designed around a random block assignment of treatments allocated to groups of twenty-one birds per pen. Blood samples were obtained from chicks at 18 days of age for measurement of leukocyte oxidative activity by a bioluminescence technique. Results of the study showed that chicks in the treatment groups fed the PFA had significantly lower oxidative stress (p<0.02) when compared to the BMD treatment group. Once this was determined, electron spin resonance (ESR) spin trapping was used to detect and measure hydroxyl or superoxide radicals in. Fenton chemistry was utilized for production of hydroxyl radicals and a xanthine/xanthine oxidase reaction for the production of superoxide radicals in the diet and in RAW 264.7 mouse peritoneal monocytes exposed to the diet. Results from the reactions showed that the antibiotic scavenges hydroxyl and superoxide radicals more efficiently than the phytogenic. The results were comparable to those measured in the RAW 264.7 cells.

  5. Effects of a Phytogenic Feed Additive Versus an Antibiotic Feed Additive on Oxidative Stress in Broiler Chicks and a Possible Mechanism Determined by Electron Spin Resonance

    PubMed Central

    Settle, T.; Leonard, S.S.; Falkenstein, E.; Fix, N.; Van Dyke, K.; Klandorf, H.

    2015-01-01

    Phytogenic feed additives are plant-derived products used in poultry feeding to improve overall performance of broilers. In this study, 588 one day-old Cobb 500 chicks were fed one of four diets and housed on either dirty or clean litter for 3wks. Treatments included: Group I: commercial diet with no additive and housed on clean litter; Group II: commercial diet with no additive and housed on dirty litter; Group III: commercial diet with a 0.05% inclusion of the anitobiotic, BMD (bacitracin methylene disalicylate); Group IV: commercial diet with a 0.05% inclusion of a phytogenic feed additive (PFA). The study was designed around a random block assignment of treatments allocated to groups of twenty-one birds per pen. Blood samples were obtained from chicks at 18 days of age for measurement of leukocyte oxidative activity by a bioluminescence technique. Results of the study showed that chicks in the treatment groups fed the PFA had significantly lower oxidative stress (p<0.02) when compared to the BMD treatment group. Once this was determined, electron spin resonance (ESR) spin trapping was used to detect and measure hydroxyl or superoxide radicals in. Fenton chemistry was utilized for production of hydroxyl radicals and a xanthine/xanthine oxidase reaction for the production of superoxide radicals in the diet and in RAW 264.7 mouse peritoneal monocytes exposed to the diet. Results from the reactions showed that the antibiotic scavenges hydroxyl and superoxide radicals more efficiently than the phytogenic. The results were comparable to those measured in the RAW 264.7 cells. PMID:26180524

  6. Evidence for hydroxyl radical generation during lipid (linoleate) peroxidation.

    PubMed

    Frenette, Mathieu; Scaiano, Juan C

    2008-07-30

    The autoxidation of methyl linoleate in benzene at 37 degrees C by peroxyl radicals was found to generate hydroxyl radicals (.OH) from a secondary oxidation mechanism. The yield of hydroxyl radicals (approximately 2%) was determined by trapping these reactive radicals with benzene to give phenol. We propose that alphaC-H hydrogen abstraction from lipid hydroperoxides, the main autoxidation products, is the source of hydroxyl radicals.

  7. Water, Hydroxyl, and the Search for Alteration and Oxidation on the Moon (Invited)

    NASA Astrophysics Data System (ADS)

    Clark, R. N.; Pieters, C. M.; Green, R. O.; Boardman, J. W.; Buratti, B. J.; Head, J. W.; Isaacson, P.; Livo, K. E.; McCord, T. B.; Mustard, J. F.; Nettles, J. W.; Petro, N. E.; Sunshine, J. M.; Taylor, L. A.

    2009-12-01

    Recent reports using imaging spectroscopy data from three spacecraft show absorption due to water and hydroxyl on the moon (Pieters et al, 2009; Clark, 2009; Sunshine, 2009). The Moon Mineralogy Mapper (M3) on Chandrayaan-1 provides high spatial resolution data showing extensive water and hydroxyl-bearing minerals in both polar regions and in some fresh lunar craters and mountains. A broad 3-micron bsorption is observed in many locations on the moon, with extensive deposits toward the lunar poles and small localized outcrops at all latitudes, often associated with fresh craters. Narrower absorptions attributed to hydroxyl are also observed regionally and in local outcrops, often associated with fresh craters. Hydroxyl absorption at ~2.85 microns is commonly found in association with anorthositic highlands rocks and soils, whereas an absorption near 2.73 microns is found in association with basaltic mare materials. Current M3 data do not yet allow us to assign specific mineralogy, but additional higher resolution targeted mode data might supply the needed spectral resolution to make identifications. Many OH-bearing minerals can be rejected, as their band positions do not match those observed in the lunar data. Hydroxyl absorptions in minerals cover a wide range of wavelength positions ranging from about 2.7 to beyond 3 microns. Several minerals, including altered anorthite and pyroxenes, have hydroxyl fundamentals in the 2.8-micron region and show spectral structure consistent with the lunar spectra. We find varying water, 2.73- and 2.85-micron absorption strengths with spatial location, and the three seem to vary independently, implying that multiple processes are responsible for the observed signatures. The existence of hydroxyl-bearing minerals in the lunar surface indicates probable alteration on the moon. This leads to the question: Could there be additional indications of alteration and oxidation on the moon? We are currently searching the M3 data for

  8. Ultraviolet irradiation-induced substitution of fluorine with hydroxyl radical for mass spectrometric analysis of perfluorooctane sulfonyl fluoride.

    PubMed

    Wang, Peng; Tang, Xuemei; Huang, Lulu; Kang, Jie; Zhong, Hongying

    2016-01-28

    A rapid and solvent free substitution reaction of a fluorine atom in perfluorooctane sulfonyl fluoride (PFOSF) with a hydroxyl radical is reported. Under irradiation of ultraviolet laser on semiconductor nanoparticles or metal surfaces, hydroxyl radicals can be generated through hole oxidization. Among all fluorine atoms of PFOSF, highly active hydroxyl radicals specifically substitute the fluorine of sulfonyl fluoride functional group. Resultant perfluorooctane sulfonic acid is further ionized through capture of photo-generated electrons that switch the neutral molecules to negatively charged odd electron hypervalent ions. The unpaired electron subsequently initiates α O-H bond cleavage and produces perfluorooctane sulfonate negative ions. Hydroxyl radical substitution and molecular dissociation of PFOSF have been confirmed by masses with high accuracy and resolution. It has been applied to direct mass spectrometric imaging of PFOSF adsorbed on surfaces of plant leaves.

  9. Molecular and biochemical identification of alien chromosome additions in shallot (Allium cepa L. Aggregatum group) carrying extra chromosome(s) of bunching onion (A. fistulosum L.).

    PubMed

    Yaguchi, Shigenori; Hang, Tran Thi Minh; Tsukazaki, Hikaru; Hoa, Vu Quynh; Masuzaki, Shin-ichi; Wako, Tadayuki; Masamura, Noriya; Onodera, Shuichi; Shiomi, Norio; Yamauchi, Naoki; Shigyo, Masayoshi

    2009-02-01

    To develop the bunching onion (Allium fistulosum L.; genomes, FF) chromosome-specific genetic markers for identifying extra chromosomes, eight shallot (A. cepa L. Aggregatum group; genomes, AA)--A. fistulosum monosomic addition plants (AA+nF) and 62 shallot--A. fistulosum single-alien deletion plants (AAF-nF) were analyzed by 23 different chromosome-specific genetic markers of shallot. The eight monosomic addition plants consisted of one AA+2F, two AA+6F, and five AA+8F. Of the 62 single-alien deletion plants, 60 could be identified as six different single-alien deletion lines (AAF-1F, -3F, -4F, -6F, -7F, and -8F) out of the eight possible types. Several single-alien deletion lines were classified on the basis of leaf and bulb characteristics. AAF-8F had the largest number of expanded leaves of five deletion plants. AAF-7F grew most vigorously, as expressed by its long leaf blade and biggest bulb size. AAF-4F had very small bulbs. AAF-7F and AAF-8F had different bulbs from those of shallot as well as other types of single-alien deletion lines in skin and outer scale color. Regarding the sugar content of the bulb tissues, the single-alien deletion lines showed higher fructan content than shallot. Moreover, shallot could not produce fructan with degree of polymerization (DP) 12 or higher, although the single-alien deletion lines showed DP 20 or higher. The content of S-alk(en)yl-L-cysteine sulfoxide (ACSO) in the single-alien deletion lines was significantly lower than that in shallot. These results indicated that chromosomes from A. fistulosum might carry anonymous factors to increase the highly polymerized fructan production and inhibit the synthesis of ACSO in shallot bulbs. Accordingly, alien chromosomes from A. fistulosum in shallot would contribute to modify the quality of shallot bulbs.

  10. Evidence that phenylalanine hydroxylation rates are overestimated in neonatal subjects receiving total parenteral nutrition with a high phenylalanine content.

    PubMed

    House, J D; Thorpe, J M; Wykes, L J; Pencharz, P B; Ball, R O

    1998-04-01

    Recent publications have indicated that the parenterally fed neonate has a substantial ability to hydroxylate phenylalanine. Examination of these data suggests that, at high phenylalanine intakes, estimated rates of hydroxylation exceed rates of intake. This implies significant net tissue breakdown. However, the quantitative validity of the estimates of phenylalanine hydroxylation cannot be assessed without nitrogen balance data. We have recently developed a parenterally fed neonatal piglet model and have used this to study aromatic amino acid metabolism in piglets fed different amino acid solutions. Reappraisal of the data from these studies has allowed us to estimate both phenylalanine hydroxylation and tissue protein accretion. Piglets were parenterally fed Vamin [292 micromol of Phe x kg(-1) x h(-1), 26 micromol of Tyr x kg(-1) x h(-1)], Vaminolact + Phe [VLP, 277 micromol of Phe x kg(-1) x h(-1), 26 micromol Tyr x kg(-1) x h(-1)], or Vaminolact + glycyl-L-tyrosine [VLGT, 152 micromol of Phe x kg(-1) x h(-1), 159 micromol of Tyr x kg(-1) x h(-1)] for 8 d. Nitrogen balance was measured over the last 5 study d, and aromatic amino acid kinetics were determined using a primed continuous infusion of L-[1-4C]phenylalanine on d 8. Average body protein gain, derived from nitrogen balance, was 11 g x kg(-1) x d(-1). For the Vamin and VLP groups, the rates of phenylalanine hydroxylation were estimated to be 139 and 90% of intake, respectively. However, phenylalanine hydroxylation was only 16% of intake for the VLGT group. In view of the tissue protein accretion data, it appears that the rate of phenylalanine hydroxylation may be overestimated in neonates fed high phenylalanine parenteral nutrition. The extent to which the parenterally fed neonate can adapt to a high phenylalanine intake, by increasing the rate of phenylalanine hydroxylation, remains to be determined.

  11. Effects of silver and group II fluoride solid lubricant additions to plasma-sprayed chromium carbide coatings for foil gas bearings to 650 C

    NASA Technical Reports Server (NTRS)

    Wagner, R. C.; Sliney, Harold E.

    1986-01-01

    A new self-lubricating coating composition of nickel aluminide-bonded chromium carbide formulated with silver and Group II fluorides was developed in a research program on high temperature solid lubricants. One of the proposed applications for this new coating composition is as a wide temperature spectrum solid lubricant for complaint foil gas bearings. Friction and wear properties were obtained using a foil gas bearing start-stop apparatus at temperatures from 25 to 650 C. The journals were Inconel 748. Some were coated with the plasma sprayed experimental coating, others with unmodified nickel aluminide/chromium carbide as a baseline for comparison. The additional components were provided to assist in achieving low friction over the temperature range of interest. Uncoated, preoxidized Inconel X-750 foil bearings were operated against these surfaces. The foils were subjected to repeated start/stop cycles under a 14-kPa (2-Psi) bearing unit loading. Sliding contact occurred during lift-off and coastdown at surface velocities less than 6 m/s (3000 rPm). Testing continued until 9000 start/stop cycles were accumulated or until a rise in starting torque indicated the journal/bearing had failed. Comparison in coating performance as well as discussions of their properties and methods of application are given.

  12. Hydroxylation of progesterone by some Trichoderma species.

    PubMed

    El-Kadi, I A; Mostafa, M Eman

    2004-01-01

    Thirty-three isolates belonging to six species of the genus Trichoderma were tested for the ability to hydroxylate progesterone to 11alpha-, 11beta-, 11alpha,17alpha- and 6beta, 17alpha-derivatives, and epicortisol. T. aureoviride, T. harzianum, T. polysporum and T. pseudokoningii produced 11alpha-hydroxyprogesterone. T. harzianum and T. hamatum can form only the 11beta-isomer. T. koningii and T. hamatum produced 11alpha-, 11beta-, 11alpha,17alpha- and 6beta,11alpha-hydroxy derivatives. 11alpha, 11beta, 6beta,11alpha- and 11alpha,17alpha-hydroxyprogesterones and epicortisol are produced by T. aureoviride and T. pseudokoningii. Cortisol was produced only when the medium was fortified by 10 g/L peptone. This is the first record of conversion of progesterone to mono-, di- and trihydroxyprogesterones by these Trichoderma species.

  13. Effects of hydroxylation and silanization on the surface properties of ZnO nanowires.

    PubMed

    García Núñez, C; Sachsenhauser, M; Blashcke, B; García Marín, A; Garrido, Jose A; Pau, Jose L

    2015-03-11

    Silanization is commonly used to form bonds between inorganic materials and biomolecules as a step in the surface preparation of solid-state biosensors. This work investigates the effects of silanization with amino-propyldiethoxymethylsilane on hydroxylated sidewalls of zinc oxide (ZnO) nanowires (NWs). The surface properties and electrical characteristics of NWs are analyzed by different techniques after their hydroxylation and later silanization. Contact angle measurements reveal a stronger hydrophobic behavior after silanization, and X-ray photoelectron spectroscopy (XPS) results show a reduction of the surface dipole induced by the replacement of the hydroxyl group with the amine terminal group. The lower work function obtained after silanization in contact potential measurements corroborates the attenuation of the surface dipole observed in XPS. Furthermore, the surface band bending of NWs is determined from surface photovoltage measurements upon irradiation with UV light, yielding a 0.5 eV energy in hydroxylated NWs, and 0.18 eV, after silanization. From those results, a reduction in the surface state density of 3.1 × 10(11) cm(-2) is estimated after silanization. The current-voltage (I-V) characteristics measured in a silanized single NW device show a reduction of the resistance, due to the enhancement of the conductive volume inside the NW, which also improves the linearity of the I-V characteristic.

  14. Thermochemical Properties and Bond Dissociation Energies for Fluorinated Methanol, CH3-xFxOH, and Fluorinated Methyl Hydroperoxides, CH3-xFxOOH: Group Additivity.

    PubMed

    Wang, Heng; Bozzelli, Joseph W

    2016-09-08

    Oxygenated fluorocarbons are routinely found in sampling of environmental soils and waters as a result of the widespread use of fluoro and chlorofluoro carbons as heat transfer fluids, inert materials, polymers, fire retardants and solvents; the influence of these chemicals on the environment is a growing concern. The thermochemical properties of these species are needed for understanding their stability and reactions in the environment and in thermal process. Structures and thermochemical properties on the mono- to trifluoromethanol, CH3-xFxOH, and fluoromethyl hydroperoxide, CH3-xFxOOH (1 ≤ x ≤ 3), are determined by CBS-QB3, CBS-APNO, and G4 calculations. Entropy, S°298, and heat capacities, Cp(T)'s (300 ≤ T/K ≤ 1500) from vibration, translation, and external rotation contributions are calculated on the basis of the vibration frequencies and structures obtained from the B3LYP/6-31+G(d,p) density functional method. Potential barriers for the internal rotations are also calculated from this method and used to calculate hindered rotor contributions to S°298 and Cp(T)'s using direct integration over energy levels of the internal rotational potentials. Standard enthalpies of formation, ΔfH°298 (units in kcal mol(-1)) are CH2FOOH (-83.7), CHF2OOH (-138.1), CF3OOH (-193.6), CH2FOO(•) (-44.9), CHF2OO(•) (-99.6), CF3OO(•) (-153.8), CH2FOH (-101.9), CHF2OH (-161.6), CF3OH (-218.1), CH2FO(•) (-49.1), CHF2O(•) (-97.8), CF3O(•) (-150.5), CH2F(•) (-7.6), CHF2(•) (-58.8), and CF3(•) (-112.6). Bond dissociation energies for the R-OOH, RO-OH, ROO-H, R-OO(•), RO-O(•), R-OH, RO-H, R-O(•), and R-H bonds are determined and compared with methyl hydroperoxide to observe the trends from added fluoro substitutions. Enthalpy of formation for the fluoro-hydrocarbon oxygen groups C/F/H2/O, C/F2/H/O, C/F3/O, are derived from the above fluorinated methanol and fluorinated hydroperoxide species for use in Benson's Group Additivity. It was determined that

  15. Probing the human estrogen receptor-α binding requirements for phenolic mono- and di-hydroxyl compounds: A combined synthesis, binding and docking study

    PubMed Central

    McCullough, Christopher; Neumann, Terrence S.; Gone, Jayapal Reddy; He, Zhengjie; Herrild, Christian; Wondergem, Julie; Pandey, Rajesh K.; Donaldson, William A.; Sem, Daniel S.

    2014-01-01

    Various estrogen analogs were synthesized and tested for binding to human ERα using a fluorescence polarization displacement assay. Binding affinity and orientation were also predicted using docking calculations. Docking was able to accurately predict relative binding affinity and orientation for estradiol, but only if a tightly bound water molecule bridging Arg394/Glu353 is present. Di-hydroxyl compounds sometimes bind in two orientations, which are flipped in terms of relative positioning of their hydroxyl groups. Di-hydroxyl compounds were predicted to bind with their aliphatic hydroxyl group interacting with His524 in ERα. One nonsteroid-based dihdroxyl compound was 1000-fold specific for ERβ over ERα, and was also 25-fold specific for agonist ERβ versus antagonist activity. Docking predictions suggest this specificity may be due to interaction of the aliphatic hydroxyl with His475 in the agonist form of ERβ, versus with Thr299 in the antagonist form. But, the presence of this aliphatic hydroxyl is not required in all compounds, since mono-hydroxyl (phenolic) compounds bind ERα with high affinity, via hydroxyl hydrogen bonding interactions with the ERα Arg394/Glu353/water triad, and van der Waals interactions with the rest of the molecule. PMID:24315190

  16. Effective L-Tyrosine Hydroxylation by Native and Immobilized Tyrosinase

    PubMed Central

    Lewańczuk, Marcin; Koźlecki, Tomasz; Liesiene, Jolanta; Bryjak, Jolanta

    2016-01-01

    Hydroxylation of L-tyrosine to 3,4-dihydroxyphenylalanine (L-DOPA) by immobilized tyrosinase in the presence of ascorbic acid (AH2), which reduces DOPA-quinone to L-DOPA, is characterized by low reaction yields that are mainly caused by the suicide inactivation of tyrosinase by L-DOPA and AH2. The main aim of this work was to compare processes with native and immobilized tyrosinase to identify the conditions that limit suicide inactivation and produce substrate conversions to L-DOPA of above 50% using HPLC analysis. It was shown that immobilized tyrosinase does not suffer from partitioning and diffusion effects, allowing a direct comparison of the reactions performed with both forms of the enzyme. In typical processes, additional aeration was applied and boron ions to produce the L-DOPA and AH2 complex and hydroxylamine to close the cycle of enzyme active center transformations. It was shown that the commonly used pH 9 buffer increased enzyme stability, with concomitant reduced reactivity of 76%, and that under these conditions, the maximal substrate conversion was approximately 25 (native) to 30% (immobilized enzyme). To increase reaction yield, the pH of the reaction mixture was reduced to 8 and 7, producing L-DOPA yields of approximately 95% (native enzyme) and 70% (immobilized). A three-fold increase in the bound enzyme load achieved 95% conversion in two successive runs, but in the third one, tyrosinase lost its activity due to strong suicide inactivation caused by L-DOPA processing. In this case, the cost of the immobilized enzyme preparation is not overcome by its reuse over time, and native tyrosinase may be more economically feasible for a single use in L-DOPA production. The practical importance of the obtained results is that highly efficient hydroxylation of monophenols by tyrosinase can be obtained by selecting the proper reaction pH and is a compromise between complexation and enzyme reactivity. PMID:27711193

  17. Cellulose based hybrid hydroxylated adducts for polyurethane foams

    NASA Astrophysics Data System (ADS)

    De Pisapia, Laura; Verdolotti, Letizia; Di Mauro, Eduardo; Di Maio, Ernesto; Lavorgna, Marino; Iannace, Salvatore

    2012-07-01

    Hybrid flexible polyurethane foams (HPU) were synthesized by using a hybrid hydroxilated adduct (HHA) based on renewable resources. In particular the HHA was obtained by dispersing cellulose wastes in colloidal silica at room temperature, pressure and humidity. The colloidal silica was selected for its ability of modifying the cellulose structure, by inducing a certain "destructurization" of the crystalline phase, in order to allow cellulose to react with di-isocyanate for the final synthesis of the polyurethane foam. In fact, cellulose-polysilicate complexes are engaged in the reaction with the isocyanate groups. This study provides evidence of the effects of the colloidal silica on the cellulose structure, namely, a reduction of the microfiber cellulose diameter and the formation of hydrogen bonds between the polysilicate functional groups and the hydroxyl groups of the cellulose, as assessed by IR spectroscopy and solid state NMR. The HHA was added to a conventional polyol in different percentages (between 5 and 20%) to synthesize HPU in presence of catalysts, silicone surfactant and diphenylmethane diisocyanate (MDI). The mixture was expanded in a mold and cured for two hours at room temperature. Thermal analysis, optical microscopy and mechanical tests were performed on the foams. The results highlighted an improvement of thermal stability and a decrease of the cell size with respect neat polyurethane foam. Mechanical tests showed an improvement of the elastic modulus and of the damping properties with increasing HHA amount.

  18. Study on the multiple mechanisms underlying the reaction between hydroxyl radical and phenolic compounds by qualitative structure and activity relationship.

    PubMed

    Cheng, Zhiyong; Ren, Jie; Li, Yuanzong; Chang, Wenbao; Chen, Zhida

    2002-12-01

    The activity-structure relationships (ASR) of phenolic compounds as hydroxyl-radical scavengers have mostly been studied and discussed with regard to their iron-chelating and hydrogen-donation properties in Fenton-type system, but extensive elucidation of multiple mechanisms underlying the hydroxyl radical scavenging reaction is out of obtaining up to now. In the present paper, a series of phenolic compounds was studied for their reactivity with hydroxyl radical by computed chemistry and deoxyribose degradation assay. The rate constant (K(S)), an index dependent markedly on the reaction mechanism and intrinsic reactivity of antioxidants, was found to have good correlation with hydroxyl O-H bond strength (DeltaH(f)), electron-donating ability (ionization potential approximated by HOMO energy level), enthalpy of single electron transfer (E(a)), and spin distribution of phenoxyl radicals (Ds(r)) after H-abstraction. Moreover, the theoretical parameters were highly intercorrelated, suggesting that multiple mechanisms co-exist in the hydroxyl-radical-scavenging reaction and interact with each other. Multi-linear regression analysis indicated that, in addition to H-atom transfer, electron transfer process and stability of the resulted phenoxyl radicals also significantly influence the reactivity of quenching hydroxyl radicals. The QSAR model so established here was based on the elucidation of the complex molecular mechanisms, and may reasonably predict the antioxidant activity using simple experimental and calculated parameters.

  19. Interactions of Kraft lignin and wheat gluten during biomaterial processing: evidence for the role of phenolic groups.

    PubMed

    Kaewtatip, Kaewta; Menut, Paul; Auvergne, Remi; Tanrattanakul, Varaporn; Morel, Marie-Helene; Guilbert, Stephane

    2010-04-14

    The chemical interactions between Kraft lignin and wheat gluten under processing conditions were investigated by determining the extent of the protein network formation. To clarify the role of different chemical functions found in lignin, the effect of Kraft lignin was compared with that of an esterified lignin, in which hydroxyl groups had been suppressed by esterification, and with a series of simple aromatics and phenolic structures with different functionalities (conjugated double bonds, hydroxyl, carboxylic acid, and aldehyde). The protein solubility was determined by using the Kjeldahl method. The role of the hydroxyl function was assessed by the significantly lower effect of esterified lignin. The importance of the phenolic radical scavenging structure is evidenced by the effect of guaiacol, which results in a behavior similar to that of the Kraft lignin. In addition, the significant effect of conjugated double bonds on gluten reactivity, through nucleophilic addition, was demonstrated.

  20. Glutathione conjugation of busulfan produces a hydroxyl radical-trapping dehydroalanine metabolite.

    PubMed

    Peer, Cody J; Younis, Islam R; Leonard, Stephen S; Gannett, Peter M; Minarchick, Valerie C; Kenyon, Allison J; Rojanasakul, Yon; Callery, Patrick S

    2012-12-01

    The Phase 2 drug metabolism of busulfan yields a glutathione conjugate that undergoes a β-elimination reaction. The elimination product is an electrophilic metabolite that is a dehydroalanine-containing tripeptide, γ-glutamyldehydroalanylglycine (EdAG). In the process, glutathione lacks thiol-related redox properties and gains a radical scavenging dehydroalanine group. EdAG scavenged hydroxyl radical generated in the Fenton reaction in a concentration-dependent manner was monitored by electron paramagnetic resonance (EPR) spectroscopy. The apparent rate of hydroxyl radical scavenging was in the same range as published values for known antioxidants, including N-acyl dehydroalanines. A captodatively stabilized carbon-centered radical intermediate was spin trapped in the reaction of EdAG with hydroxyl radical. The proposed structure of a stable product in the Fenton reaction with EdAG was consistent with that of a γ-glutamylserylglycyl dimer. Observation of the hydroxyl trapping properties of EdAG suggests that the busulfan metabolite EdAG may contribute to or mitigate redox-related cytotoxicity associated with the therapeutic use of busulfan, and reaffirms indicators that support a role in free radical biology for dehydroalanine-containing peptides and proteins.

  1. The effect of hydroxylation on CNT to form Chitosan-CNT composites: A DFT study

    NASA Astrophysics Data System (ADS)

    Yu, Rui; Ran, Maofei; Wen, Jie; Sun, Wenjing; Chu, Wei; Jiang, Chengfa; He, Zhiwei

    2015-12-01

    The effect of types of CNTs (pristine and hydroxylated) on the synthesis of Chitosan-CNT (CS-CNT) composites was investigated theoretically. The adsorption energy (Eads) of CS on the pristine CNT and hydroxylated CNTs (CNT-OHn, n = 1-6) as well as the structural and electronic properties of said composites have been investigated. Results show that the adsorption of CS on CNT and CNT-OHn is thermodynamically favored. The Eads of CS on CNTs was calculated to be -20.387 kcal/mol from electrostatic interactions. For CS adsorbed into CNT-OHn, Eads ranges from -20.612 to -37.567 kcal/mol. Hydroxyl groups on CNT are the main adsorption sites for CS loading onto CNT-OHn via hydrogen-bond interactions. The CS-CNT-OH3 is the most sable composite among tested complexes. The energy gap (ΔEgap) of CS-CNT-OH3 was calculated less than pristine CNT and CNT-OH3, indicative of the composites being more reactive than that of pristine CNTs and CNT-OH3. It was proved that CS can transfer electron to the hydroxylated CNTs, thus overcoming the drawbacks of CNTs being chemically inert.

  2. [Effects of hydroxyl radicals on purified angiotensin I converting enzyme].

    PubMed

    Michel, B; Nirina, L B; Grima, M; Ingert, C; Coquard, C; Barthelmebs, M; Imbs, J L

    1998-08-01

    Somatic angiotensin-converting enzyme (ACE) is a protein which contains two similar domains (N and C), each possessing a functional active site. The relationship between ACE, its natural substrates and oxygen free radicals is starting to be explored. On one hand, superoxide anions production is induced by angiotensin II and on the other hand, activated polynuclear neutrophils, through free radicals generation, alter endothelial ACE activity. In this study, we examined the impact of hydroxyl radicals (.OH) on purified ACE. .OH were produced using a generator: 2,2'-azo-bis 2-amidinopropane (GRH) provided by Lara-Spiral (Fr). GRH (3 mM), in a time-dependent fashion, inhibited ACE activity. When ACE was co-incubated for 4 h with GRH, its activity decreased by 70%. Addition of dimethylthiourea (DMTU: 0.03 to 1 mM) or mannitol + methionine (20/10 mM), two sets of .OH scavengers, produced a dose-dependent protection on ACE activity. To examine whether oxidation of thiol groups in the ACE molecule could be involved in the action of GRH, the effects of thiol reducing agents: mercaptoethanol and dithiotreitol (DTT) were investigated. These compounds produced a dose-dependent and significant protection; with 100% protection at 0.2 and 0.3 mM for mercaptoethanol and at 0.1 mM for DTT. The hydrolysis of two natural and domain-specific substrates were also explored. The hydrolysis of angiotensin I preferentially cleaved by the C domain was significantly (p < 0.01) inhibited by 57, 58 and 69% in contact with 0.3, 1 and 3 mM GRH [in nmol angio II formed/min/nmol of ACE, n = 4; 35.9 +/- 0.6 (control), 15.5 +/- 2.8 (GRH : 0.3 mM), 15.1 +/- 0.5 (1), 10.9 +/- 0.6 (3)]. The hydrolysis of the hemoregulatory peptide (hp), preferential substrate for the N domain was not affected by GRH at 0.3 mM and inhibited by 28% (not significant) by 1 mM GRH [in nmol ph hydrolized/min/nmol ACE, n = 4; 12.6 +/- 1.9 (control), 14.9 (GRH : 0.3 mM), 8.3 +/- 4.0 (1). These results demonstrated that .OH

  3. Hydroxyl Emission in the Westbrook Nebula

    NASA Astrophysics Data System (ADS)

    Strack, Angelica; Araya, Esteban; Ghosh, Tapasi; Arce, Hector G.; Lebron, Mayra E.; Salter, Christopher J.; Minchin, Robert F.; Pihlstrom, Ylva; Kurtz, Stan; Hofner, Peter; Olmi, Luca

    2016-06-01

    CRL 618, also known as the Westbrook Nebula, is a carbon-rich pre-planetary nebula. Hydroxyl (OH) transitions are typically not detected in carbon-rich late-type stellar objects, however observations conducted with the 305m Arecibo Telescope in 2008 resulted in the detection of 4765 MHz OH emission in CRL 618. We present results of observations carried out a few months after the original detection that confirm the line. This is the first detection of 4765 MHz OH emission (most likely a maser) in a pre-planetary nebula. Follow up observations conducted in 2015 resulted in non-detection of the 4765 MHz OH transition. This behavior is consistent with the high level of variability of excited OH lines that have been detected toward a handful of other pre-planetary nebulae. Our work supports that excited OH masers are short-lived during the pre-planetary nebula phase. We also conducted a search for other OH transitions from 1612 MHz to 8611 MHz with the Arecibo Telescope; we report no other detections at rms levels of ~5 mJy.This work has made use of the computational facilities donated by Frank Rodeffer to the WIU Astrophysics Research Laboratory. We also acknowledge support from M. & C. Wong RISE scholarships and a grant from the WIU College of Arts and Sciences.

  4. A pro-chelator triggered by hydrogen peroxide inhibits iron-promoted hydroxyl radical formation.

    PubMed

    Charkoudian, Louise K; Pham, David M; Franz, Katherine J

    2006-09-27

    The synthesis and structural characterization of a new pro-chelating agent, isonicotinic acid [2-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-benzylidene]-hydrazide (BSIH), are presented. BSIH only weakly interacts with iron unless hydrogen peroxide (H2O2) is present to remove the boronic ester protecting group to reveal a phenol that is a key metal-binding group of tridentate salicylaldehyde isonicotinoyl hydrazone (SIH). BSIH prevents deoxyribose degradation caused by hydroxyl radicals that are generated from H2O2 and redox-active iron by sequestering Fe3+ and preventing iron-promoted hydroxyl radical formation. The rate-determining step for iron sequestration is conversion of BSIH to SIH, followed by rapid Fe3+ complexation. The pro-chelate approach of BSIH represents a promising strategy for chelating a specific pool of detrimental metal ions without disturbing healthy metal ion distribution.

  5. Spectral Response and Diagnostics of Biological Activity of Hydroxyl-Containing Aromatic Compounds

    NASA Astrophysics Data System (ADS)

    Tolstorozhev, G. B.; Mayer, G. V.; Bel'kov, M. V.; Shadyro, O. I.

    2016-08-01

    Using IR Fourier spectra and employing quantum-chemical calculations of electronic structure, spectra, and proton-acceptor properties, synthetic derivatives of aminophenol exhibiting biological activity in the suppression of herpes, influenza, and HIV viruses have been investigated from a new perspective, with the aim of establishing the spectral response of biological activity of the molecules. It has been experimentally established that the participation of the aminophenol hydroxyl group in intramolecular hydrogen bonds is characteristic of structures with antiviral properties. A quantum-chemical calculation of the proton-acceptor ability of the investigated aminophenol derivatives has shown that biologically active structures are characterized by a high proton-acceptor ability of oxygen of the hydroxyl group. A correlation that has been obtained among the formation of an intramolecular hydrogen bond, high proton-acceptor ability, and antiviral activity of substituted aminophenols enables us to predict the pharmacological properties of new medical preparations of the given class of compounds.

  6. Production of hydroxyl radical by redox active flavonoids

    SciTech Connect

    Kalyanaraman, B.; Hodnick, W.F.; Pardini, R.S.

    1986-05-01

    The authors have previously shown that flavonoids autoxidize and generate superoxide (O/sub 2//sup -/) and hydrogen peroxide (H/sub 2/O/sub 2/), suggesting that hydroxyl radical (OH) could be formed via the metal-ion catalyzed Haber-Weiss reaction. In the presence of ethylenediamine tetraacetic acid (EDTA) and 5,5-dimethyl-1-pyrroline-1-oxide (DMPO), myricetin, quercetagetin and quercetin gave an ESR signal for the DMPO-OH spin adduct, and the DMPO-Eto adduct in the presence of excess ethanol, indicating the production of free OH. The addition of FeCl/sub 3/ to the reaction mixture resulted in a dramatic increase in the DMPO-OH signal. Without chelator (EDTA) there was no signal and the presence of diethylenetriamine-pentaacetic acid (DETAPAC) greatly diminished the signal. The presence of superoxide dismutase (SOD) had no effect on the signal while catalase completely abrogated the signal. The addition of Fe (III)-EDTA to flavonoid solutions under anaerobic conditions produced time dependent auxochromic shifts in their absorption spectra and resulted in the reduction of Fe (III) to Fe (II). These data suggest that the flavonoids autoxidize to produce O/sub 2//sup -/ and H/sub 2/O/sub 2/ by dismutation and in the presence of Fe (III)-EDTA the flavonoid can directly reduce the Fe (III) to Fe (II) resulting in the production of OH through Fenton chemistry.

  7. Hydroxylation of p-substituted phenols by tyrosinase: Further insight into the mechanism of tyrosinase activity

    SciTech Connect

    Munoz-Munoz, Jose Luis; Berna, Jose; Garcia-Molina, Maria del Mar; Garcia-Molina, Francisco; Garcia-Ruiz, Pedro Antonio; Varon, Ramon [Departamento de Quimica-Fisica, Escuela de Ingenieros Industriales de Albacete, Universidad de Castilla la Mancha, Avda. Espana s and others

    2012-07-27

    Highlights: Black-Right-Pointing-Pointer The action the copper complexes and tyrosinase on phenols is equivalent. Black-Right-Pointing-Pointer Isotope effect showed that nucleophilic attack to copper atom may be the slower step. Black-Right-Pointing-Pointer The value of {rho} (Hammett constant) supports an electrophilic aromatic substitution. Black-Right-Pointing-Pointer Data obtained in steady state pH 7 conditions support the mechanism of Scheme 1SM. -- Abstract: A study of the monophenolase activity of tyrosinase by measuring the steady state rate with a group of p-substituted monophenols provides the following kinetic information: k{sub cat}{sup m} and the Michaelis constant, K{sub M}{sup m}. Analysis of these data taking into account chemical shifts of the carbon atom supporting the hydroxyl group ({delta}) and {sigma}{sub p}{sup +}, enables a mechanism to be proposed for the transformation of monophenols into o-diphenols, in which the first step is a nucleophilic attack on the copper atom on the form E{sub ox} (attack of the oxygen of the hydroxyl group of C-1 on the copper atom) followed by an electrophilic attack (attack of the hydroperoxide group on the ortho position with respect to the hydroxyl group of the benzene ring, electrophilic aromatic substitution with a reaction constant {rho} of -1.75). These steps show the same dependency on the electronic effect of the substituent groups in C-4. Furthermore, a study of a solvent deuterium isotope effect on the oxidation of monophenols by tyrosinase points to an appreciable isotopic effect. In a proton inventory study with a series of p-substituted phenols, the representation of k{sub cat}{sup f{sub n}}/k{sub cat}{sup f{sub 0}} against n (atom fractions of deuterium), where k{sub cat}{sup f{sub n}} is the catalytic constant for a molar fraction of deuterium (n) and k{sub cat}{sup f{sub 0}} is the corresponding kinetic parameter in a water solution, was linear for all substrates. These results indicate that

  8. Measurements of snow grain hydroxyl radical at Summit, Greenland

    NASA Astrophysics Data System (ADS)

    Anastasio, C.; Galbavy, E.; Hutterli, M.; Friel, D.; Bales, R.

    2004-12-01

    Sunlit snowpacks release a number of volatile organic compounds (VOCs) such as formaldehyde and other carbonyls, carboxylic acids, alkenes, and alkyl halides. It has been hypothesized that this flux of VOCs to the overlying atmosphere is in part due to reactions of hydroxyl radical (OH) with snowgrain organic matter. Recent laboratory measurements by Grannas et al. support this idea by showing that the photolysis of polar snow releases formaldehyde, and that this release is enhanced by the addition of nitrate, a photochemical source of OH. In addition to its effects on organic chemistry, OH is probably also important in other snowpack reactions such as the oxidation of halides to form volatile, reactive gaseous halogens. However, the possible role of OH in these reactions has not been quantified. To begin to address the importance of OH in snowpack chemistry, we have measured the photochemical formation of hydroxyl radicals on snow grains at Summit, Greenland during the spring and summer. Measurements were made using a chemical probe technique where benzoate is added to the snow sample in order to scavenge OH and convert it into p-hydroxybenzoate, which is measured by HPLC. We found that OH is formed on snow grains during both seasons and that the rate of formation in the summer was more than an order of magnitude greater than the typical springtime value. Expressed on a bulk (melted) snow volume basis, the average summer value was approximately 200 nM/hr. Assuming that this reactivity occurs within a snowgrain "quasi-liquid layer" (QLL) that represents approximately 0.001% of the bulk liquid volume, rates of OH photoformation in the QLL are on the order of 10 mM/hr. The possible implications of this enormous rate of OH formation for snowpack chemistry (e.g., for VOC release) will be discussed. We have also examined the relative importance of nitrate and hydrogen peroxide as sources of photoformed OH on snow grains at Summit. Based on quantum yields determined in

  9. Monitoring equilibrium changes in RNA structure by 'peroxidative' and 'oxidative' hydroxyl radical footprinting.

    PubMed

    Bachu, Ravichandra; Padlan, Frances-Camille S; Rouhanifard, Sara; Brenowitz, Michael; Schlatterer, Jörg C

    2011-10-17

    RNA molecules play an essential role in biology. In addition to transmitting genetic information, RNA can fold into unique tertiary structures fulfilling a specific biologic role as regulator, binder or catalyst. Information about tertiary contact formation is essential to understand the function of RNA molecules. Hydroxyl radicals (•OH) are unique probes of the structure of nucleic acids due to their high reactivity and small size. When used as a footprinting probe, hydroxyl radicals map the solvent accessible surface of the phosphodiester backbone of DNA and RNA with as fine as single nucleotide resolution. Hydroxyl radical footprinting can be used to identify the nucleotides within an intermolecular contact surface, e.g. in DNA-protein and RNA-protein complexes. Equilibrium and kinetic transitions can be determined by conducting hydroxyl radical footprinting as a function of a solution variable or time, respectively. A key feature of footprinting is that limited exposure to the probe (e.g., 'single-hit kinetics') results in the uniform sampling of each nucleotide of the polymer. In this video article, we use the P4-P6 domain of the Tetrahymena ribozyme to illustrate RNA sample preparation and the determination of a Mg(II)-mediated folding isotherms. We describe the use of the well known hydroxyl radical footprinting protocol that requires H(2)O(2) (we call this the 'peroxidative' protocol) and a valuable, but not widely known, alternative that uses naturally dissolved O(2)(we call this the 'oxidative' protocol). An overview of the data reduction, transformation and analysis procedures is presented.

  10. Inhibition of hydroxyl radical reaction with aromatics by dissolved natural organic matter

    SciTech Connect

    Lindsey, M.E.; Tarr, M.A.

    2000-02-01

    Remediation of hydrophobic pollutants is complicated by sorption of these compounds to hydrophobic sites of dissolved natural organic matter (NOM), suspended particulates, soil, and sediment. This sorption causes the pollutants to be less easily degraded by remediation techniques. Reaction of aromatic compounds with hydroxyl radical is inhibited by dissolved natural organic matter (NOM). The degree of inhibition is significantly greater than that expected based on a simple model in which aromatic compound molecules bound to NOM are considered to be unreactive. In this study, hydroxyl radical was produced at steady-state concentrations using Fenton chemistry (H{sub 2}O{sub 2} + Fe{sup 2+} {yields} Fe{sup 3+} + HO{sup {minus}} + HO{sm_bullet}). Suwannee River fulvic acid and humic acid were used as NOM. The most likely mechanism for the observed inhibition is that hydroxyl radical formation occurs in microenvironmental sites remote from the aromatic compounds. In addition to changes in kinetics, pyrene hydroxyl radical reaction also exhibited a mechanistic change in the presence of fulvic acid. The mechanism changed from a reaction that was apparently first-order in pyrene to one that was apparently second-order in pyrene, indicating that pyrene self-reaction may have become the dominant mechanism in the presence of fulvic acid. Dissolved NOM causes significant changes in the rate and mechanism of hydroxyl radical degradation of aromatic compounds. Consequently, literature rate constants measured in pure water will not be useful for predicting the degradation of pollutants in environmental systems. The kinetic and mechanistic information in this study will be useful for developing improved degradation methods involving Fenton chemistry.

  11. Human hydroxylated metabolites of BDE-47 and BDE-99 are glucuronidated and sulfated in vitro.

    PubMed

    Erratico, Claudio; Zheng, Xiaobo; Ryden, Andreas; Marsh, Goran; Maho, Walid; Covaci, Adrian

    2015-07-16

    Polybrominated diphenyl ethers (PBDEs) were used worldwide as additive flame retardants and are classified as persistent, bioaccumulable and toxic environmental pollutants. In humans, the hydroxylated metabolites of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) and 2,2',4,4',5-pentabromodiphenyl ether (BDE-99) formed in vitro have also been detected in vivo. To further characterize the metabolism of BDE-47 and BDE-99 and to identify candidate markers for monitoring the human exposure to PBDEs using non-invasive approaches, glucuronidation and sulfation of hydroxylated metabolites of BDE-47 and BDE-99 were investigated using human liver microsomes and cytoplasm, respectively. The formed Phase II metabolites were analyzed by liquid chromatography-tandem mass spectrometry using a novel approach to develop analytical methods in absence of authentic standards. All available standards for hydroxylated metabolites of BDE-47 and BDE-99 were glucuronidated and sulfated, showing that glucuronidation and sulfation are part of the metabolism pathway of BDE-47 and BDE-99 in vitro. The major glucuronidated and sulfated analogs of hydroxylated metabolites of BDE-47 were (a) 2,4-DBP-Gluc and 5-Gluc-BDE-47, and (b) 2'-Sulf-BDE-28, 4-Sulf-BDE-42 and 3-Sulf-BDE-47, respectively. The major glucuronidated and sulfated analogs of hydroxylated metabolites of BDE-99 were (a) 2,4,5-TBP-Gluc and 6'-Gluc-BDE-99, and (b) 3'-Sulf-BDE-99 and 5'-Sulf-BDE-99, respectively. Apparent Km values associated with the formation of sulfated metabolites of BDE-47 and BDE-99 were ten times lower than those of the corresponding glucuronidated metabolites, suggesting that sulfated rather than glucuronidated metabolites of OH-PBDEs might be used as markers of human exposure to PBDEs using a non-invasive approach based on urine sample collection.

  12. Oxygenase-catalyzed ribosome hydroxylation occurs in prokaryotes and humans.

    PubMed

    Ge, Wei; Wolf, Alexander; Feng, Tianshu; Ho, Chia-hua; Sekirnik, Rok; Zayer, Adam; Granatino, Nicolas; Cockman, Matthew E; Loenarz, Christoph; Loik, Nikita D; Hardy, Adam P; Claridge, Timothy D W; Hamed, Refaat B; Chowdhury, Rasheduzzaman; Gong, Lingzhi; Robinson, Carol V; Trudgian, David C; Jiang, Miao; Mackeen, Mukram M; McCullagh, James S; Gordiyenko, Yuliya; Thalhammer, Armin; Yamamoto, Atsushi; Yang, Ming; Liu-Yi, Phebee; Zhang, Zhihong; Schmidt-Zachmann, Marion; Kessler, Benedikt M; Ratcliffe, Peter J; Preston, Gail M; Coleman, Mathew L; Schofield, Christopher J

    2012-12-01

    The finding that oxygenase-catalyzed protein hydroxylation regulates animal transcription raises questions as to whether the translation machinery and prokaryotic proteins are analogously modified. Escherichia coli ycfD is a growth-regulating 2-oxoglutarate oxygenase catalyzing arginyl hydroxylation of the ribosomal protein Rpl16. Human ycfD homologs, Myc-induced nuclear antigen (MINA53) and NO66, are also linked to growth and catalyze histidyl hydroxylation of Rpl27a and Rpl8, respectively. This work reveals new therapeutic possibilities via oxygenase inhibition and by targeting modified over unmodified ribosomes.

  13. Regioselective alkane hydroxylation with a mutant AlkB enzyme

    DOEpatents

    Koch, Daniel J.; Arnold, Frances H.

    2012-11-13

    AlkB from Pseudomonas putida was engineered using in-vivo directed evolution to hydroxylate small chain alkanes. Mutant AlkB-BMO1 hydroxylates propane and butane at the terminal carbon at a rate greater than the wild-type to form 1-propanol and 1-butanol, respectively. Mutant AlkB-BMO2 similarly hydroxylates propane and butane at the terminal carbon at a rate greater than the wild-type to form 1-propanol and 1-butanol, respectively. These biocatalysts are highly active for small chain alkane substrates and their regioselectivity is retained in whole-cell biotransformations.

  14. Quantum Chemical Study on the Antioxidation Mechanism of Piceatannol and Isorhapontigenin toward Hydroxyl and Hydroperoxyl Radicals

    PubMed Central

    Lu, Yang; Wang, AiHua; Shi, Peng; Zhang, Hui; Li, ZeSheng

    2015-01-01

    A systematic study of the antioxidation mechanisms behind hydroxyl (•OH) and hydroperoxyl (•OOH) radical scavenging activity of piceatannol (PIC) and isorhapontigenin (ISO) was carried out using density functional theory (DFT) method. Two reaction mechanisms, abstraction (ABS) and radical adduct formation (RAF), were discussed. A total of 24 reaction pathways of scavenging •OH and •OOH with PIC and ISO were investigated in the gas phase and solution. The thermodynamic and kinetic properties of all pathways were calculated. Based on these results, we evaluated the antioxidant activity of every active site of PIC and ISO and compared the abilities of PIC and ISO to scavenge radicals. According to our results, PIC and ISO may act as effective •OH and •OOH scavengers in organism. A4-hydroxyl group is a very important active site for PIC and ISO to scavenge radicals. The introducing of -OH or -OCH3 group to the ortho-position of A4-hydroxyl group would increase its antioxidant activity. Meanwhile, the conformational effect was researched, the results suggest that the presence and pattern of intramolecular hydrogen bond (IHB) are considerable in determining the antioxidant activity of PIC and ISO. PMID:26176778

  15. Production of hydroxyl radicals by copper-containing metallothionein: roles as prooxidant.

    PubMed

    Suzuki, K T; Rui, M; Ueda, J; Ozawa, T

    1996-11-01

    Production of hydroxyl radicals by copper (Cu)-containing metallothionein (MT) and its relation to zinc (Zn) bound to MT were studied in vitro with reference to the mechanism of the Cu toxicity in the liver of LEC rats. Zn-MT prepared from the liver of Zn-injected rats was reacted with cupric ions at various Cu/Zn ratios, and the concentrations of the two metals bound to MT and in the solution, valence states of Cu in the solution, production of hydroxyl radicals were determined. Cupric ions replaced Zn in MT after being reduced by thiol groups, and MT, worked as an antioxidant. Cupric ions added to MT that did not contain Zn were reduced to cuprous ions by thiol groups in Cu-MT, and the Cu bound to MT was liberated in a form of cuprous ions. Hydroxyl radicals were produced in the presence of hydrogen peroxide in proportion to the amount of cuprous ions liberated from MT. Cu-containing MT was proposed to work as a prooxidant until all thiol groups in MT were oxidized when Zn was not present in MT. The results indicate that MT works as an antioxidant as long as Zn is present in Cu-containing MT, while it works as a prooxidant when Zn is not present by liberating 1.5 M equivalents of cuprous ions relative to cupric ions added, and hydroxyl radicals are produced in the presence of hydrogen peroxide. On the other hand, MT not bound by Cu does not work as a prooxidant throughout.

  16. Effect of Curcumin Against Oxidation of Biomolecules by Hydroxyl Radicals

    PubMed Central

    Mahendra, Jaideep; Gurumurthy, Prema; Jayamathi; Iqbal, Shabeer S; Mahendra, Little

    2014-01-01

    Background: Among various reactive oxygen species, hydroxyl radicals have the strongest chemical activity, which can damage a wide range of essential biomolecules such as lipids, proteins, and DNA. Objective: The objective of this study was to investigate the beneficial effects of curcumin on prevention of oxidative damage of biomolecules by hydroxyl radicals generated in in vitro by a Fenton like reaction. Materials and Methods: We have incubated the serum, plasma and whole blood with H2O2/Cu2+/ Ascorbic acid system for 4 hours at 37 0C and observed the oxidation of biomolecules like albumin, lipids, proteins and DNA. Results: Curcumin at the concentrations of 50,100 and 200 μmoles, prevented the formation of ischemia modified albumin, MDA, protein carbonyls, oxidized DNA and increased the total antioxidant levels and GSH significantly. Conclusion: These observations suggest the hydroxyl radical scavenging potentials of curcumin and protective actions to prevent the oxidation of biomolecules by hydroxyl radicals. PMID:25478334

  17. Hydroxyl radical production in plasma electrolysis with KOH electrolyte solution

    SciTech Connect

    Saksono, Nelson; Febiyanti, Irine Ayu Utami, Nissa; Ibrahim

    2015-12-29

    Plasma electrolysis is an effective technology for producing hydroxyl radical (•OH). This method can be used for waste degradation process. This study was conducted to obtain the influence of applied voltage, electrolyte concentration, and anode depth in the plasma electrolysis system for producing hydroxyl radical. The materials of anode and cathode, respectively, were made from tungsten and stainless steel. KOH solution was used as the solution. Determination of hydroxyl radical production was done by measuring H{sub 2}O{sub 2} amount formed in plasma system using an iodometric titration method, while the electrical energy consumed was obtained by measuring the electrical current throughout the process. The highest hydroxyl radical production was 3.51 mmol reached with 237 kJ energy consumption in the power supply voltage 600 V, 0.02 M KOH, and 0.5 cm depth of anode.

  18. Hydroxyl radical production in plasma electrolysis with KOH electrolyte solution

    NASA Astrophysics Data System (ADS)

    Saksono, Nelson; Febiyanti, Irine Ayu; Utami, Nissa; Ibrahim

    2015-12-01

    Plasma electrolysis is an effective technology for producing hydroxyl radical (•OH). This method can be used for waste degradation process. This study was conducted to obtain the influence of applied voltage, electrolyte concentration, and anode depth in the plasma electrolysis system for producing hydroxyl radical. The materials of anode and cathode, respectively, were made from tungsten and stainless steel. KOH solution was used as the solution. Determination of hydroxyl radical production was done by measuring H2O2 amount formed in plasma system using an iodometric titration method, while the electrical energy consumed was obtained by measuring the electrical current throughout the process. The highest hydroxyl radical production was 3.51 mmol reached with 237 kJ energy consumption in the power supply voltage 600 V, 0.02 M KOH, and 0.5 cm depth of anode.

  19. Male mice housed in groups engage in frequent fighting and show a lower response to additional bone loading than females or individually housed males that do not fight.

    PubMed

    Meakin, Lee B; Sugiyama, Toshihiro; Galea, Gabriel L; Browne, William J; Lanyon, Lance E; Price, Joanna S

    2013-05-01

    Experiments to investigate bone's physiological adaptation to mechanical loading frequently employ models that apply dynamic loads to bones in vivo and assess the changes in mass and architecture that result. It is axiomatic that bones will only show an adaptive response if the applied artificial loading environment differs in a significant way from that to which the bones have been habituated by normal functional loading. It is generally assumed that this normal loading is similar between experimental groups. In the study reported here we found that this was not always the case. Male and female 17-week-old C57BL/6 mice were housed in groups of six, and a single episode (40 cycles) of non-invasive axial loading, engendering 2,200 με on the medial surface of the proximal tibiae in sample mice, was applied to right tibiae on alternate days for two weeks. This engendered an adaptive increase in bone mass in females, but not males. Observation revealed the main difference in behaviour between males and females was that males were involved in fights 1.3 times per hour, whereas the females never fought. We therefore housed all mice individually. In females, there was a similar significant osteogenic response to loading in cortical and trabecular bone of both grouped and individual mice. In contrast, in males, adaptive increases in the loaded compared with non-loaded control bones was only apparent in animals housed individually. Our interpretation of these findings is that the frequent vigorous fighting that occurs between young adult males housed in groups could be sufficient to engender peak strains and strain rates that equal or exceed the stimulus derived from artificial loading. This indicates the importance of ensuring that physical activity is consistent between groups. Reducing the background level of the naturally engendered strain environment allows adaptive responses to artificial loading to be demonstrated at lower loads.

  20. The impact of the hydroxyl radical photochemical sources on the rivastigmine drug transformation in mimic and natural waters.

    PubMed

    Passananti, Monica; Temussi, Fabio; Iesce, Maria Rosaria; Mailhot, Gilles; Brigante, Marcello

    2013-09-15

    In this paper we investigated the degradation of the rivastigmine drug induced by hydroxyl radical in synthetic and natural waters focusing on both reactivity and photoproducts identification. The hydroxyl radical formation rate was quantified by using terephthalic acid as trapping molecule and it was related with the rivastigmine degradation rate. The second order rate constant between hydroxyl radical and rivastigmine was estimated to be ≈ 5.8 × 10(9) M(-1) s(-1). Irradiation of rivastigmine in three natural waters (rain, lake and river) and comparison with degradation rates observed in synthetic solutions using nitrite, nitrate and hydrogen peroxide suggest that, in addition to hydroxyl radical, also nitroderived radicals (NO/NO2) are responsible for the pollutant degradation in natural media. In fact, the evaluated degradation rates in three natural waters are greatly higher than those estimated considering only the reactivity with photogenerated hydroxyl radical. Using nitrites and nitrates as photochemical OH source, the rivastigmine degradation cannot be described considering only the hydroxyl radical reactivity suggesting that NO and NO2 radicals could play a key role during indirect degradation. Moreover main degradation products have been identified by means of HPLC-MS. Hydroxylation of the aromatic ring as well as carbamate and amino chain oxidation were suggested as main reaction mechanisms, but also nitroderived compounds were characterized. Finally polychromatic irradiations of three rivastigmine doped natural waters (rain, river and lake) underlined the role of the indirect degradation that needs to be considered when direct degradation of selected pollutants is negligible under environmental-like conditions.

  1. Oxidation of acetovanillone by photochemical processes and hydroxyl radicals.

    PubMed

    Benitez, F Javier; Real, Francisco J; Acero, Juan L; Leal, Ana I; Cotilla, Sonia

    2005-01-01

    Acetovanillone [Ethanone, 1-(4-hydroxy-3-metoxyphenyl)] is one of the major pollutants that is present in the wastewater produced during the boiling of raw material in the cork industry. The oxidation of its aqueous solutions by monochromatic UV radiation alone and combined with hydrogen peroxide, Fenton's reagent and the photo-Fenton system has been investigated. In the single UV radiation process, the apparent rate constants and the quantum yields are determined, and in the UV/H2O2 combination, the additional efficiency in the oxidation process due to the presence of hydrogen peroxide is established. The influence of some operating variables, such as initial concentrations of H2O2 and Fe(II), as well as the pH, is discussed in the Fenton and photo-Fenton systems, and the partial contribution of the radical pathways to the global oxidation rates are evaluated. The rate constant for the reaction of acetovanillone with hydroxyl radicals is also determined by means of a competition kinetics model, its value being 5.62 x 10(9) M(-1)s(-1). Finally, chemical oxidation experiments of wastewaters generated in this industry were carried out by using the same advanced oxidation processes. Specifically, the elimination of acetovanillone in these effluents was determined, and the removal of the global organic pollutant content was also evaluated.

  2. The hydroxyl radical in plants: from seed to seed.

    PubMed

    Richards, Siân L; Wilkins, Katie A; Swarbreck, Stéphanie M; Anderson, Alexander A; Habib, Noman; Smith, Alison G; McAinsh, Martin; Davies, Julia M

    2015-01-01

    The hydroxyl radical (OH(•)) is the most potent yet short-lived of the reactive oxygen species (ROS) radicals. Just as hydrogen peroxide was once considered to be simply a deleterious by-product of oxidative metabolism but is now acknowledged to have signalling roles in plant cells, so evidence is mounting for the hydroxyl radical as being more than merely an agent of destruction. Its oxidative power is harnessed to facilitate germination, growth, stomatal closure, reproduction, the immune response, and adaptation to stress. It features in plant cell death and is a key tool in microbial degradation of plant matter for recycling. Production of the hydroxyl radical in the wall, at the plasma membrane, and intracellularly is facilitated by a range of peroxidases, superoxide dismutases, NADPH oxidases, and transition metal catalysts. The spatio-temporal activity of these must be tightly regulated to target substrates precisely to the site of radical production, both to prevent damage and to accommodate the short half life and diffusive capacity of the hydroxyl radical. Whilst research has focussed mainly on the hydroxyl radical's mode of action in wall loosening, studies now extend to elucidating which proteins are targets in signalling systems. Despite the difficulties in detecting and manipulating this ROS, there is sufficient evidence now to acknowledge the hydroxyl radical as a potent regulator in plant cell biology.

  3. Hemibonding of hydroxyl radical and halide anion in aqueous solution.

    PubMed

    Yamaguchi, Makoto

    2011-12-29

    Molecular geometries and properties of the possible reaction products between the hydroxyl radical and the halide anions in aqueous solution were investigated. The formation of two-center three-electron bonding (hemibonding) between the hydroxyl radical and halide anions (Cl, Br, I) was examined by density functional theory (DFT) calculation with a range-separated hybrid (RSH) exchange-correlation functional. The long-range corrected hybrid functional (LC-ωPBE), which have given quantitatively satisfactory results for odd electron systems and excited states, was examined by test calculations for dihalogen radical anions (X(2)(-); X = Cl, Br, I) and hydroxyl radical-water clusters. Equilibrium geometries with hemibonding between the hydroxyl radical and halide anions were located by including four hydrogen-bonded water molecules. Excitation energies and oscillator strengths of σ-σ* transitions calculated by the time-dependent DFT method showed good agreement with observed values. Calculated values of the free energy of reaction on the formation of hydroxyl halide radical anion from the hydroxyl radical and halide anion were endothermic for chloride but exothermic for bromide and iodide, which is consistent with experimental values of equilibrium constants.

  4. Relationship between phenytoin and tolbutamide hydroxylations in human liver microsomes.

    PubMed Central

    Doecke, C J; Veronese, M E; Pond, S M; Miners, J O; Birkett, D J; Sansom, L N; McManus, M E

    1991-01-01

    1. The metabolic interaction of phenytoin and tolbutamide in human liver microsomes was investigated. 2. Phenytoin 4-hydroxylation (mean Km 29.6 microM, n = 3) was competitively inhibited by tolbutamide (mean Ki 106.2 microM, n = 3) and tolbutamide methylhydroxylation (mean Km 85.6 microM, n = 3) was competitively inhibited by phenytoin (mean Ki 22.6 microM, n = 3). 3. A significant correlation was obtained between phenytoin and tolbutamide hydroxylations in microsomes from 18 human livers (rs = 0.82, P less than 0.001). 4. Sulphaphenazole was a potent inhibitor of both phenytoin and tolbutamide hydroxylations with IC50 values of 0.4 microM and 0.6 microM, respectively. 5. Mephenytoin was a poor inhibitor of both phenytoin and tolbutamide hydroxylations with IC50 values greater than 400 microM for both reactions. 6. Anti-rabbit P450IIC3 IgG inhibited both phenytoin and tolbutamide hydroxylations in human liver microsomes by 62 and 68%, respectively. 7. These in vitro studies are consistent with phenytoin 4-hydroxylation and tolbutamide methylhydroxylation being catalysed by the same cytochrome P450 isozyme(s) in human liver microsomes. PMID:2049228

  5. Replacing C6F5 groups with Cl and H atoms in frustrated Lewis pairs: H2 additions and catalytic hydrogenations.

    PubMed

    Chernichenko, K; Kótai, B; Nieger, M; Heikkinen, S; Pápai, I; Repo, T

    2017-02-14

    2-(Dialkylamino)phenylboranes containing the BXZ group, where X, Z = C6F5, Cl, and H, were prepared in a few synthetic steps and demonstrated the cleavage of H2 under mild conditions. Depending on the nature of the dialkylamino group, X, and Z, the stability of the produced zwitterionic H2 adducts varies from isolated solids indefinitely stable in an inert atmosphere to those quickly equilibrating with the initial aminoborane and H2. Using a combined experimental/computational approach on a series of isostructural aminoboranes (dialkylamino = 2,2,6,6-tetramethylpiperid-1-yl), it was demonstrated that the electronegativity and the steric effect of the substituents generally follow the trend C6F5 ∼ Cl ≫ H. This observation is useful for designing new FLPs for practical applications. As an example, we demonstrated the hydrogenation of alkynes to cis-alkenes under mild conditions that was catalyzed by a chloro-analogue of the C6F5-substituted aminoborane developed previously. The presence of a BHCl group in the aminochloroboranes or in their H2 adducts features facile redistribution of the H and Cl atoms and the formation of polychloro and polyhydrido species.

  6. Inhibition of membrane lipid peroxidation by a radical scavenging mechanism: a novel function for hydroxyl-containing ionophores.

    PubMed

    Grijalba, M T; Andrade, P B; Meinicke, A R; Castilho, R F; Vercesi, A E; Schreier, S

    1998-03-01

    In the present study we show that K+/H+ hydroxyl-containing ionophores lasalocid-A (LAS) and nigericin (NIG) in the nanomolar concentration range, inhibit Fe2+-citrate and 2,2'-azobis(2-amidinopropane) dihydrochloride (ABAP)-induced lipid peroxidation in intact rat liver mitochondria and in egg phosphatidylcholine (PC) liposomes containing negatively charged lipids--dicetyl phosphate (DCP) or cardiolipin (CL)--and KCl as the osmotic support. In addition, monensin (MON), a hydroxyl-containing ionophore with higher affinity for Na+ than for K+, promotes a similar effect when NaCl is the osmotic support. The protective effect of the ionophores is not observed when the osmolyte is sucrose. Lipid peroxidation was evidenced by mitochondrial swelling, antimycin A-insensitive O2 consumption, formation of thiobarbituric acid-reactive substances (TBARS), conjugated dienes, and electron paramagnetic resonance (EPR) spectra of an incorporated lipid spin probe. A time-dependent decay of spin label EPR signal is observed as a consequence of lipid peroxidation induced by both inductor systems in liposomes. Nitroxide destruction is inhibited by butylated hydroxytoluene, a known antioxidant, and by the hydroxyl-containing ionophores. In contrast, valinomycin (VAL), which does not possess alcoholic groups, does not display this protective effect. Effective order parameters (Seff), determined from the spectra of an incorporated spin label are larger in the presence of salt and display a small increase upon addition of the ionophores, as a result of the increase of counter ion concentration at the negatively charged bilayer surface. This condition leads to increased formation of the ion-ionophore complex, the membrane binding (uncharged) species. The membrane-incorporated complex is the active species in the lipid peroxidation inhibiting process. Studies in aqueous solution (in the absence of membranes) showed that NIG and LAS, but not VAL, decrease the Fe2+-citrate-induced production

  7. ipso-Hydroxylation and Subsequent Fragmentation: a Novel Microbial Strategy To Eliminate Sulfonamide Antibiotics

    PubMed Central

    Ricken, Benjamin; Cichocka, Danuta; Parisi, Martina; Lenz, Markus; Wyss, Dominik; Martínez-Lavanchy, Paula M.; Müller, Jochen A.; Shahgaldian, Patrick; Tulli, Ludovico G.; Kohler, Hans-Peter E.; Kolvenbach, Boris A.

    2013-01-01

    Sulfonamide antibiotics have a wide application range in human and veterinary medicine. Because they tend to persist in the environment, they pose potential problems with regard to the propagation of antibiotic resistance. Here, we identified metabolites formed during the degradation of sulfamethoxazole and other sulfonamides in Microbacterium sp. strain BR1. Our experiments showed that the degradation proceeded along an unusual pathway initiated by ipso-hydroxylation with subsequent fragmentation of the parent compound. The NADH-dependent hydroxylation of the carbon atom attached to the sulfonyl group resulted in the release of sulfite, 3-amino-5-methylisoxazole, and benzoquinone-imine. The latter was concomitantly transformed to 4-aminophenol. Sulfadiazine, sulfamethizole, sulfamethazine, sulfadimethoxine, 4-amino-N-phenylbenzenesulfonamide, and N-(4-aminophenyl)sulfonylcarbamic acid methyl ester (asulam) were transformed accordingly. Therefore, ipso-hydroxylation with subsequent fragmentation must be considered the underlying mechanism; this could also occur in the same or in a similar way in other studies, where biotransformation of sulfonamides bearing an amino group in the para-position to the sulfonyl substituent was observed to yield products corresponding to the stable metabolites observed by us. PMID:23835177

  8. Diffusion of hydroxyl ions from calcium hydroxide and Aloe vera pastes.

    PubMed

    Batista, Victor Eduardo de Souza; Olian, Douglas Dáquila; Mori, Graziela Garrido

    2014-01-01

    This study evaluated the diffusion through the dentinal tubules of hydroxyl ions from different calcium hydroxide (CH) pastes containing Aloe vera. Sixty single-rooted bovine teeth were used. The tooth crowns were removed, the root canals were instrumented and the specimens were assigned to 4 groups (n=15) according to the intracanal medication: Group CH/S - CH powder and saline paste; Group CH/P - CH powder and propylene glycol paste; Group CH/A - calcium hydroxide powder and Aloe vera gel paste; Group CH/A/P - CH powder, Aloe vera powder and propylene glycol paste. After placement of the root canal dressings, the teeth were sealed coronally and apically with a two-step epoxy adhesive. The teeth were placed in identified flasks containing deionized water and stored in an oven with 100% humidity at 37 °C. After 3 h, 24 h, 72 h, 7 days, 15 days and 30 days, the deionized water in the flasks was collected and its pH was measured by a pH meter. The obtained data were subjected to statistical analysis at a significance level of 5%. The results demonstrated that all pastes provided diffusion of hydroxyl ions through the dentinal tubules. The combination of Aloe vera and CH (group CH/A) provided a constant release of calcium ions. Group CH/A/P showed the highest pH at 24 and 72 h. In conclusion, the experimental pastes containing Aloe vera were able to enable the diffusion of hydroxyl ions through the dentinal tubules.

  9. Hydroxylation, conjugation and sulfation of bile acids in primary monolayer cultures of rat hepatocytes

    SciTech Connect

    Princen, H.M.; Meijer, P.

    1988-08-15

    Hydroxylation of lithocholic, chenodeoxycholic, deoxycholic and cholic acids was studied in monolayers of rat hepatocytes cultured for 76 h. The majority of added lithocholic and chenodeoxycholic acids was metabolized to beta-muricholic acid (56-76%). A small part of these bile acids (9%), however, and a considerable amount of deoxycholic and cholic acids (21%) were converted into metabolites more polar than cholic acid in the first culture period. Formation of these compounds decreased during the last day of culture. Bile acids synthesized after addition of (4-/sup 14/C)-cholesterol were almost entirely (97%) sulfated and/or conjugated, predominantly with taurine (54-66%), during culture. Sulfated bile acids were mainly composed of free bile acids. The ability of hepatocytes to sulfurylate bile acids declined with culture age. Thus, rat hepatocytes in primary monolayer culture are capable to sulfurylate bile acids and to hydroxylate trihydroxylated bile acids, suggesting formation of polyhydroxylated metabolites.

  10. Sulfonic-hydroxyl-type heterogemini surfactants synthesized from unsaturated fatty acids.

    PubMed

    Sakai, Kenichi; Sangawa, Yuta; Takamatsu, Yuichiro; Kawai, Takeshi; Matsumoto, Mutsuyoshi; Sakai, Hideki; Abe, Masahiko

    2010-01-01

    Novel anionic heterogemini surfactants have been synthesized from two kinds of unsaturated fatty acids (oleic acid and petroselinic acid). The hydrocarbon chain is covalently bound to the terminal carbonyl group of the unsaturated fatty acids and hydrophilic headgroups (i.e., sulfonic and hydroxyl groups) are introduced to the cis double bond. The aqueous solution properties of the surfactants synthesized here have been studied on the basis of static/dynamic surface tension, conductivity, fluorescence, and dynamic light scattering (DLS) data. We have mainly focused on the following two factors that may significantly impact the aqueous solution properties of the surfactants: one is hydrocarbon chain length and the other is molecular symmetry. The first key result from our current study is that increased hydrocarbon chain length results in a closely packed monolayer film at the air/aqueous solution interface, even at low concentrations as a result of the increased hydrophobicity of the longer chain analogue. We have previously observed a similar trend when aqueous solution properties of oleic acid-based phosphate-type heterogemini surfactants were studied. The second key finding of our current research is that increased molecular symmetry results in greater surface activities (which include lower aqueous surface tension and greater molecular packing at the air/aqueous solution interface). In addition, it seems likely that the size of molecular assemblies spontaneously formed in bulk solution decreases when the molecular symmetry increases. These results suggest that the symmetric analogue provides greater hydrophobic environments, although the exact reason for this is not yet known.

  11. Nucleophilic addition of organozinc reagents to 2-sulfonyl cyclic ethers: stereoselective synthesis of manassantins A and B.

    PubMed

    Kim, Hyoungsu; Kasper, Amanda C; Moon, Eui Jung; Park, Yongho; Wooten, Ceshea M; Dewhirst, Mark W; Hong, Jiyong

    2009-01-01

    A convergent route to the synthesis of manassantins A and B, potent inhibitors of HIF-1, is described. Central to the synthesis is a stereoselective addition of an organozinc reagent to a 2-benzenesulfonyl cyclic ether to achieve the 2,3-cis-3,4-trans-4,5-cis-tetrahydrofuran of the natural products. Preliminary structure-activity relationships suggested that the (R)-configuration at C-7 and C-7''' is not critical for HIF-1 inhibition. In addition, the hydroxyl group at C-7 and C-7''' can be replaced with a carbonyl group without loss of activity.

  12. Catalytic hydrofunctionalization of alkynes through P-H bond addition: the unique role of orientation and properties of the phosphorus group in the insertion step.

    PubMed

    Ananikov, Valentine P; Makarov, Anton V; Beletskaya, Irina P

    2011-11-04

    The puzzling question of alkyne insertion into Pd-P and Pd-H bonds leading to the formation of new Pd-C, C-P, and C-H bonds was explored by theoretical calculations at the CCSD(T) and B3LYP levels of theory. The key factors responsible for selectivity of catalytic hydrofunctionalization of alkynes were resolved and studied in details for the models of hydrophosphorylation, hydrophosphinylation, and hydrophospination reactions. In contrast with the generally accepted mechanistic picture, the calculations have shown that several pathways are possible depending on the nature and geometrical arrangement of the phosphorus group. It was found that the product of alkyne insertion into the metal-hydrogen bond should be easily formed under kinetic-control conditions, while the product of alkyne insertion into the metal-phosphorus bond may be formed in certain cases under thermodynamic control. For the first time, the calculations have revealed the role of the oxygen atom in the reactivity of P=P(O)R(2) groups and the role of the interactions involving the lone pair of the P=PR(2) group in the reagent. The fundamental properties of the Pd-P, C-P, and P-H bonds were reported, and the larger bond strength upon increasing the number of oxygen atoms bound to phosphorus (P=PR(2), P(O)R(2), and P(O)(OR)(2)) have been shown. The relationship between bond energy, acidity, and reactivity of the studied phosphorus compounds has been determined.

  13. Outcomes of Total Parathyroidectomy with Autotransplantation versus Subtotal Parathyroidectomy with Routine Addition of Thymectomy to both Groups: Single Center Experience of Secondary Hyperparathyroidism

    PubMed Central

    Sakman, Gürhan; Parsak, Cem Kaan; Balal, Mustafa; Seydaoglu, Gülşah; Eray, İsmail Cem; Sarıtaş, Gökhan; Demircan, Orhan

    2014-01-01

    Background: Secondary hyperparathyroidism is a common acquired disorder seen in chronic renal failure. It may result in potentially serious complications including metabolic bone diseases, severe atherosclerosis and undesirable cardiovascular events. Parathyroidectomy is required in about 20% of patients after 3–10 years of dialysis and in up to 40% after 20 years. Aims: The aim of the current study was to evaluate the short-term and long-term outcomes of patients with secondary hyperparathyroidism who had undergone total parathyroidectomy with autotransplantation and thymectomy or subtotal parathyroidectomy with thymectomy by the same surgical team during the study period. Study Design: Retrospective comparative study. Methods: Clinical data of 50 patients who underwent parathyroid surgery for secondary hyperparathyroidism between 2003 and 2011 were reviewed retrospectively. Patients were divided into two subgroups of total parathyroidectomy with autotransplantation or subtotal parathyroidectomy. Thymectomy was routinely performed for both groups. Short term outcome parameters included intact parathyroid hormone, ionized calcium and alkaline phosphatase levels. Bone pain, bone fractures, persistent or recurrent disease were included in long term outcome parameters. Results: The mean duration of dialysis was eight years. The mean ionized calcium levels dropped significantly in the total parathyroidectomy with autotransplantation group (p=0.016). No serious postoperative complications were observed. Postoperative intravenous calcium supplementation was required in four patients in the total parathyroidectomy with autotransplantation group (total PTX+AT) and in three patients in the subtotal parathyroidectomy group (subtotal PTX). Postoperatively, all patients received oral calcium carbonate and calcitriol. The length of average hospital stay was 5 (3–10) days. Including nine patients who underwent successful renal transplantation pre-operative bone symptoms

  14. Possible involvement of hydroxyl radical on the stimulation of tetrahydrobiopterin synthesis by hydrogen peroxide and peroxynitrite in vascular endothelial cells.

    PubMed

    Shimizu, Shunichi; Ishii, Masakazu; Miyasaka, Yoshiyuki; Wajima, Teruaki; Negoro, Takaharu; Hagiwara, Tamio; Kiuchi, Yuji

    2005-04-01

    We recently described that hydrogen peroxide (H2O2) stimulates the synthesis of tetrahydrobiopterin (BH4) through the induction of the rate-limiting enzyme GTP-cyclohydrolase I (GTPCH), and increases tetrahydrobiopterin content in vascular endothelial cells. Tetrahydrobiopterin is easily oxidized by peroxynitrite (ONOO-), but not by hydrogen peroxide. The aim of this study was to determine the effect of hydroxyl radical and peroxynitrite, which are both toxic biological oxidants, on tetrahydrobiopterin synthesis and the regulation of its content in vascular endothelial cells. In the cell-free assay system, tetrahydrobiopterin was rapidly oxidized by the hydroxyl radical and peroxynitrite, but not by hydrogen peroxide. However, the addition of not only hydrogen peroxide but also the hydroxyl radical and peroxynitrite to vascular endothelial cells transiently decreased tetrahydrobiopterin content, and then markedly increased its content. Interestingly, total biopterin content was also decreased by early treatment with oxidants. Moreover, oxidants induced the expression of GTP-cyclohydrolase I, and the increase of the tetrahydrobiopterin content was blocked by the treatment with GTP-cyclohydrolase I inhibitor. Both the hydrogen peroxide- and peroxynitrite-induced increases in tetrahydrobiopterin content and findings suggest that not only hydrogen peroxide but also the hydroxyl radical and peroxynitrite stimulates tetrahydrobiopterin synthesis through GTP-cyclohydrolase I expression, and that the hydroxyl radical plays a central role in the stimulation of tetrahydrobiopterin synthesis. Moreover, the transient decrease in BH4 to tetrahydrobiopterin.

  15. Vitamin C (ascorbic acid) induced hydroxyl radical formation in copper contaminated household drinking water: role of bicarbonate concentration.

    PubMed

    Jansson, Patric J; Asplund, Klara U M; Mäkelä, Johanna C; Lindqvist, Christer; Nordström, Tommy

    2003-08-01

    We have previously shown that Vitamin C (ascorbic acid) can trigger hydroxyl radical formation in copper contaminated household drinking water. We report here that the capacity of ascorbic acid to catalyze hydroxyl radical generation in the drinking water samples is strongly dependent on the bicarbonate concentration (buffer capacity and pH) of the samples. We found that at least 50 mg/l bicarbonate was required in the water samples to maintain the pH over 5.0 after ascorbic acid addition. At this pH, that is higher than the pKa1 4.25 of ascorbic acid, a hydroxyl radical generating redox cycling reaction involving the mono-anion of vitamin C and copper could take place. The ascorbic acid induced hydroxyl radical generating reaction could easily be mimicked in Milli-Q water by supplementing the water with copper and bicarbonate. Our results demonstrate that ascorbic acid can induce a pH dependent hydroxyl radical generating reaction in copper contaminated household tap water that is buffered with bicarbonate. The impact of consuming ascorbic acid together with copper and bicarbonate containing drinking water on human health is discussed.

  16. The addition of sirolimus to tacrolimus/methotrexate GVHD prophylaxis in children with ALL: a phase 3 Children's Oncology Group/Pediatric Blood and Marrow Transplant Consortium trial.

    PubMed

    Pulsipher, Michael A; Langholz, Bryan; Wall, Donna A; Schultz, Kirk R; Bunin, Nancy; Carroll, William L; Raetz, Elizabeth; Gardner, Sharon; Gastier-Foster, Julie M; Howrie, Denise; Goyal, Rakesh K; Douglas, James G; Borowitz, Michael; Barnes, Yvonne; Teachey, David T; Taylor, Candace; Grupp, Stephan A

    2014-03-27

    Sirolimus has activity against acute lymphoblastic leukemia (ALL) in xenograft models and efficacy in preventing acute graft-versus-host disease (aGVHD). We tested whether addition of sirolimus to GVHD prophylaxis of children with ALL would decrease aGVHD and relapse. Patients were randomized to tacrolimus/methotrexate (standard) or tacrolimus/methotrexate/sirolimus (experimental). The study met futility rules for survival after enrolling 146 of 259 patients. Rate of Grade 2-4 aGVHD was 31% vs 18% (standard vs experimental, P = .04), however, grade 3-4 aGVHD was not different (13% vs 10%, P = .28). Rates of veno-occlusive disease (VOD) and thrombotic microangiopathy (TMA) were lower in the nonsirolimus arm (9% vs 21% VOD, P = .05; 1% vs 10% TMA, P = .06). At 2 years, event free survival (EFS) and overall survival (OS) were 56% vs 46%, and 65% vs 55% (standard vs experimental), respectively (P = .28 and .23). Multivariate analysis showed increased relapse risk in children with ≥0.1% minimal residual disease (MRD) pretransplant, and decreased risk in patients with grades 1-3 aGVHD (P = .04). Grades 1-3 aGVHD were associated with improved EFS (P = .02), whereas grade 4 aGVHD and extramedullary disease at diagnosis led to inferior OS. Although addition of sirolimus decreased aGVHD, survival was not improved. This study is registered with ClinicalTrials.gov as #NCT00382109.

  17. Demonstration of hydroxyl radical generation in stunned' myocardium of intact dogs using aromatic hydroxylation of phenylalanine

    SciTech Connect

    Bolli, R.; Kaur, H.; Li, X.Y.; Triana, J.F.; Halliwell, B. Univ. of California, Davis King's College, London )

    1991-03-11

    Numerous studies have shown that postischemic myocardial dysfunction is attenuated by scavengers of hydroxyl ({sup {sm bullet}}OH) radicals and by iron chelators, suggesting an important pathogenetic role of {sup {sm bullet}}OH. However, the evidence provided by these studies is indirect. Since phenyl-alanine (PH) has been shown to react with {sup {sm bullet}}OH to form o-, m-, and p-tyrosines (TYR), the authors used aromatic hydroxylation of PH to detect {sup {sm bullet}}OH in stunned myocardium. Open-chest dogs underwent a 15-min coronary occlusion (O) followed by reperfusion (R). PH was infused i.v. starting 5 min pre-O and ending 10 min after R (n = 3) or starting at R and ending 10 min later (n = 8). TYR concentration in local coronary venous effluent plasma was measured using HPLC with electrochemical detection. No appreciable production of TYR was observed before or during O. After R, however, in all dogs there was a dramatic increase in myocardial production of o-, m-, and p-TYR which peaked at 1-3 min and ceased after 10 min. In 5 control dogs, infusion of PH without O/R did not result in any TYR production. These results provide evidence that the highly reactive {sup {sm bullet}}OH radical is produced after brief regional ischemia in the intact animal and indicate that PH may be a useful probe for measuring this species. The findings support the hypothesis that {sup {sm bullet}}OH contributes to myocardial stunning.'

  18. Chemical characterization of SOA formed from aqueous-phase reactions of phenols with the triplet excited state of carbonyl and hydroxyl radical

    SciTech Connect

    Yu, Lu; Smith, Jeremy; Laskin, Alexander; Anastasio, Cort N.; Laskin, Julia; Zhang, Qi

    2014-01-01

    Phenolic compounds, which are emitted in significant amounts from biomass burning, can undergo fast reactions in atmospheric aqueous phases to form secondary organic aerosol (aqSOA). In this study, we investigate the reactions of phenol and two methoxy-phenols (syringol and guaiacol) with two major aqueous phase oxidants – the triplet excited states of an aromatic carbonyl (3C*) and hydroxyl radical (•OH). We thoroughly characterize the low-volatility species produced from these reactions and interpret their formation mechanisms using aerosol mass spectrometry (AMS), desorption electrospray ionization mass spectrometry (DESIMS), and ion chromatography (IC). A large number of oxygenated molecules are identified, including oligomers containing up to six monomer units, functionalized monomer and oligomers with carbonyl, carboxyl, and hydroxyl groups, and small organic acid anions (e.g., formate, acetate, oxalate, and malate). The average atomic oxygen-to-carbon (O/C) ratios of phenolic aqSOA are in the range of 0.85-1.23, similar to those of low-volatility oxygenated organic aerosol (LV-OOA) observed in ambient air. The aqSOA compositions are overall similar for the same precursor, but the reactions mediated by 3C* are faster than •OH-mediated reactions and produce more oligomers and hydroxylated species at the point when 50% of the phenol had reacted. Profiles determined using a thermodenuder indicate that the volatility of phenolic aqSOA is influenced by both oligomer content and O/C ratio. In addition, the aqSOA shows enhanced light absorption in the UV-vis region, suggesting that aqueous-phase reactions of phenols are likely an important source of brown carbon in the atmosphere, especially in regions influenced by biomass burning.

  19. Chemical characterization of SOA formed from aqueous-phase reactions of phenols with the triplet excited state of carbonyl and hydroxyl radical

    DOE PAGES

    Yu, L.; Smith, J.; Laskin, A.; ...

    2014-08-19

    Phenolic compounds, which are emitted in significant amounts from biomass burning, can undergo fast reactions in atmospheric aqueous phases to form secondary organic aerosol (aqSOA). In this study, we investigate the reactions of phenol and two methoxy-phenols (syringol and guaiacol) with two major aqueous phase oxidants – the triplet excited states of an aromatic carbonyl (3C*) and hydroxyl radical (·OH). We thoroughly characterize the low-volatility species produced from these reactions and interpret their formation mechanisms using aerosol mass spectrometry (AMS), nanospray desorption electrospray ionization mass spectrometry (nano-DESI MS), and ion chromatography (IC). A large number of oxygenated molecules are identified,more » including oligomers containing up to six monomer units, functionalized monomer and oligomers with carbonyl, carboxyl, and hydroxyl groups, and small organic acid anions (e.g., formate, acetate, oxalate, and malate). The average atomic oxygen-to-carbon (O / C) ratios of phenolic aqSOA are in the range of 0.85–1.23, similar to those of low-volatility oxygenated organic aerosol (LV-OOA) observed in ambient air. The aqSOA compositions are overall similar for the same precursor, but the reactions mediated by 3C* are faster than ·OH-mediated reactions and produce more oligomers and hydroxylated species at the point when 50% of the phenol had reacted. Profiles determined using a thermodenuder indicate that the volatility of phenolic aqSOA is influenced by both oligomer content and O / C ratio. In addition, the aqSOA shows enhanced light absorption in the UV-vis region, suggesting that aqueous-phase reactions of phenols are likely an important source of brown carbon in the atmosphere, especially in regions influenced by biomass burning.« less

  20. Chemical characterization of SOA formed from aqueous-phase reactions of phenols with the triplet excited state of carbonyl and hydroxyl radical

    DOE PAGES

    Yu, L.; Smith, J.; Laskin, A.; ...

    2014-12-23

    Phenolic compounds, which are emitted in significant amounts from biomass burning, can undergo fast reactions in atmospheric aqueous phases to form secondary organic aerosol (aqSOA). In this study, we investigate the reactions of phenol (compound with formula C6H5OH)), guaiacol (2-methoxyphenol), and syringol (2,6-dimethoxyphenol) with two major aqueous-phase oxidants – the triplet excited states of an aromatic carbonyl (3C*) and hydroxyl radical (· OH). We thoroughly characterize the low-volatility species produced from these reactions and interpret their formation mechanisms using aerosol mass spectrometry (AMS), nanospray desorption electrospray ionization mass spectrometry (nano-DESI MS), and ion chromatography (IC). A large number of oxygenatedmore » molecules are identified, including oligomers containing up to six monomer units, functionalized monomer and oligomers with carbonyl, carboxyl, and hydroxyl groups, and small organic acid anions (e.g., formate, acetate, oxalate, and malate). The average atomic oxygen-to-carbon (O / C) ratios of phenolic aqSOA are in the range of 0.85–1.23, similar to those of low-volatility oxygenated organic aerosol (LV-OOA) observed in ambient air. The aqSOA compositions are overall similar for the same precursor, but the reactions mediated by 3C* are faster than · OH-mediated reactions and produce more oligomers and hydroxylated species at the point when 50% of the phenolic compound has reacted. Profiles determined using a thermodenuder indicate that the volatility of phenolic aqSOA is influenced by both oligomer content and O / C ratio. In addition, the aqSOA shows enhanced light absorption in the UV–visible region, suggesting that aqueous-phase reactions of phenols may contribute to formation of secondary brown carbon in the atmosphere, especially in regions influenced by biomass burning.« less

  1. Evolving P450pyr Monooxygenase for Regio- and Stereoselective Hydroxylations.

    PubMed

    Yang, Yi; Li, Zhi

    2015-01-01

    P450pyr monooxygenase from Sphingomonas sp. HXN-200 catalysed the regio- and stereoselective hydroxylation at a non-activated carbon atom, a useful but challenging reaction in classic chemistry, with unique substrate specificity for a number of alicyclic compounds. New P450pyr mutants were developed by directed evolution with improved catalytic performance, thus significantly extending the application of the P450pyr monooxygenase family in biohydroxylation to prepare useful and valuable chiral alcohols. Directed evolution of P450pyr created new enzymes with improved S-enantioselectivity or R-enantioselectivity for the hydroxylation of N-benzyl pyrrolidine, enhanced regioselectivity for the hydroxylation of N-benzyl pyrrolidinone, and increased enantioselectivity for the hydroxylation of N-benzyl piperidinone, respectively. Directed evolution of P450pyr generated also mutants with fully altered regioselectivity (from terminal to subterminal) and newly created excellent S-enantioselectivity for the biohydroxylation of n-octane and propylbenzene, respectively, providing new opportunities for the regio- and enantioselective alkane functionalization. New P450pyr mutants were engineered as the first catalyst for highly selective terminal hydroxylation of n-butanol to 1,4-butanediol. Several novel, accurate, sensitive, simple, and HTS assays based on colorimetric or MS detection for measuring the enantio- and/or regioselectivity of hydroxylation were developed and proven to be practical in directed evolution. The P450pyr X-ray structure was obtained and used to guide the evolution. In silico modelling and substrate docking provided some insight into the influence of several important amino acid mutations of the engineered P450pyr mutants on the altered or enhanced regio- and enantioselectivity as well as new substrate acceptance. The obtained information and knowledge is useful for further engineering of P450pyr for other hydroxylations and oxidations.

  2. Effects of silver and group 2 fluorides addition to plasma sprayed chromium carbide high temperature solid lubricant for foil gas bearing to 650 deg C

    NASA Technical Reports Server (NTRS)

    Wagner, R. C.; Sliney, H. E.

    1984-01-01

    A new self-lubricating coating composition of nickel aluminide-bonded chromium carbide formulated with silver and Group II fluorides was developed in a research program on high temperature solid lubricants. One of the proposed applications for this new coating composition is as a wide temperature spectrum solid lubricant for complaint foil gas bearings. Friction and wear properties were obtained using a foil gas bearing start/stop apparatus at temperatures from 25 to 650 C. The journals were Inconel 718. Some were coated with the plasma sprayed experimental coating, others with unmodified nickel aluminide/chromium carbide as a baseline for comparison. The addtitional components were provided to assist in achieving low friction over the temperature range of interest. Uncoated, preoxidized Inconel X-750 foil bearings were operated against these surfaces. The foils were subjected to repeated start/stop cycles under a 14-kPa (2-psi) bearing unit loading. Sliding contact occurred during lift-off and coastdown at surface velocities less than 6 m/s (3000 rpm). Testing continued until 9000 start/stop cycles were accumulated or until a rise in starting torque indicated the journal/bearing had failed. Comparison in coating performance as well as discussions of their properties and methods of application are given.

  3. [Introduction of additional thiol groups into glucoamylase in Aspergillus awamori and their effect on the thermal stability and catalytic activity of the enzyme].

    PubMed

    Surzhik, M A; Shmidt, A E; Glazunov, E A; Firsov, D L; Petukhov, M G

    2014-01-01

    Five mutant forms of glucoamylase (GA) from the filamentous fungus Aspergillus awamori with artificial disulfide bonds (4D-G137A\\A14C, 6D-A14C\\Y419C\\G137A, 10D-V13C\\G396C, 11D-V13C\\G396C\\A14C\\Y419C\\G137A, and 20D-G137A\\A246C\\A14C) were constructed using computer simulation and experimentally tested for thermostability. The introduction of two additional disulfide bonds between its first and thirteenth alpha-helices and that of the loop located close to a catalytic residue--E400--made it possible to assess the effects of disulfide bridges on protein thermostability. The mutant proteins with combined amino acid substitutions G137A\\A14C, V13C\\G396C\\A14C\\Y419C\\G137A, and G137A\\A246C\\A14C showed higher thermal stability as compared to the wild-type protein. At the same time, new disulfide bridges in the mutant A14C\\Y419C\\G137A and V13C\\G396C proteins led to the destabilization of their structure and the loss of thermal stability.

  4. Morphology-dependent interplay of reduction behaviors, oxygen vacancies and hydroxyl reactivity of CeO2 nanocrystals.

    PubMed

    Gao, Yuxian; Li, Rongtan; Chen, Shilong; Luo, Liangfeng; Cao, Tian; Huang, Weixin

    2015-12-21

    Reduction behaviors, oxygen vacancies and hydroxyl groups play decisive roles in the surface chemistry and catalysis of oxides. Employing isothermal H2 reduction we simultaneously reduced CeO2 nanocrystals with different morphologies, created oxygen vacancies and produced hydroxyl groups. The morphology of CeO2 nanocrystals was observed to strongly affect the reduction process and the resultant oxygen vacancy structure. The resultant oxygen vacancies are mainly located on the surfaces of CeO2 cubes and rods but in the subsurface/bulk of CeO2 octahedra. The reactivity of isolated bridging hydroxyl groups on CeO2 nanocrystals was found to depend on the local oxygen vacancy concentration, in which they reacted to produce water at low local oxygen vacancy concentrations but to produce both water and hydrogen with increasing local oxygen vacancy concentration. These results reveal a morphology-dependent interplay among the reduction behaviors, oxygen vacancies and hydroxyl reactivity of CeO2 nanocrystals, which deepens the fundamental understanding of the surface chemistry and catalysis of CeO2.

  5. Additional cytogenetic abnormalities in adults with Philadelphia chromosome-positive acute lymphoblastic leukaemia: a study of the Cancer and Leukaemia Group B.

    PubMed

    Wetzler, Meir; Dodge, Richard K; Mrózek, Krzysztof; Stewart, Carleton C; Carroll, Andrew J; Tantravahi, Ramana; Vardiman, James W; Larson, Richard A; Bloomfield, Clara D

    2004-02-01

    We analysed the nature and prognostic significance of secondary cytogenetic changes in 111 newly diagnosed adults with acute lymphoblastic leukaemia (ALL) and t(9;22)(q34;q11.2) or its variants. Secondary aberrations were seen in 75 (68%) patients. They included, in order of descending frequency: +der(22)t(9;22), +21, abnormalities of 9p, high hyperdiploidy (>50 chromosomes), +8, -7, +X and abnormalities resulting in loss of material from 8p, gain of 8q, gain of 1q and loss of 7p. Eighty patients (72%) had > or =1 normal metaphase in their karyotype. There were four balanced and 12 unbalanced translocations previously unreported in ALL with t(9;22). The t(2;7)(p11;p13) and der(18)t(8;18)(q11.2;p11.2) were seen in two cases each, and have never before been reported in haematological malignancy. All but four patients were treated on front-line Cancer and Leukaemia Group B clinical protocols. The presence of -7 as a sole secondary abnormality was associated with a lower complete remission (CR) rate (P = 0.004), while the presence of > or =3 aberrations was associated with a higher CR rate (P = 0.009) and +der(22)t(9;22) with a higher cumulative incidence of relapse (P = 0.02). It will be of interest to see if newly diagnosed t(9;22)-positive adult ALL patients with these and other secondary aberrations respond differently to treatment regimens that include imatinib mesylate.

  6. Escalation of daunorubicin and addition of etoposide in the ADE regimen in acute myeloid leukemia patients aged 60 years and older: Cancer and Leukemia Group B Study 9720.

    PubMed

    Baer, M R; George, S L; Sanford, B L; Mrózek, K; Kolitz, J E; Moore, J O; Stone, R M; Powell, B L; Caligiuri, M A; Bloomfield, C D; Larson, R A

    2011-05-01

    Untreated de novo (n=421) and secondary (n=189) acute myeloid leukemia (AML) patients ≥60 years received intensified chemotherapy, including daunorubicin 60 mg/m(2) and etoposide 100 mg/m(2) during days 1, 2, 3 with cytarabine 100 mg/m(2) during days 1-7, with a second induction if needed and one consolidation course with these drugs and doses for 2, 2 and 5 days, respectively. In all, 287 (47%) achieved complete remission (CR), 136 (22%) died and 187 (31%) were non-responders. CR rates were 27, 44 and 52% for complex karyotypes, rare aberrations and neither (P<0.001), 52 and 37% for de novo and secondary AML (P=0.003), and 53 and 42% for age 60-69 and ≥70 years (P=0.015). In multivariable analysis, CR predictors included non-complex/non-rare karyotypes (P<0.001), de novo AML (P<0.001), better performance status (PS) (P<0.001) and younger age (P=0.001). Disease-free (DFS) and overall (OS) survival medians were 6.8 (95% CI: 6.2, 7.8) and 7.2 (95% CI: 6.4, 8.6) months. In multivariable analysis, DFS was shorter for complex karyotypes (P<0.001) and increasing white blood count (WBC) (P<0.001) and age (P=0.038), and OS for complex karyotypes (P<0.001), increasing WBC (P=0.001) and age (P<0.001), poorer PS (P<0.001) and secondary AML (P=0.010). Outcomes and prognostic factors were similar to those in previous Cancer and Leukemia Group B studies.

  7. Lethal hydroxyl radical accumulation by a lactococcal bacteriocin, lacticin Q.

    PubMed

    Li, Mengqi; Yoneyama, Fuminori; Toshimitsu, Nayu; Zendo, Takeshi; Nakayama, Jiro; Sonomoto, Kenji

    2013-08-01

    The antimicrobial mechanism of a lactococcal bacteriocin, lacticin Q, can be described by the toroidal pore model without any receptor. However, lacticin Q showed different degrees of activity (selective antimicrobial activity) against Gram-positive bacteria even among related species. The ability of lacticin Q to induce pore formation in liposomes composed of lipids from different indicator strains indicated that its selective antimicrobial activity could not be attributed only to membrane lipid composition. We investigated the accumulation of deleterious hydroxyl radicals after exposure to lacticin Q as a contributing factor to cell death in the indicator strains. When lacticin Q of the same concentration as the MIC or minimum bactericidal concentration was added to the indicator cultures, high levels of hydroxyl radical accumulation were detected. Treatment with hydroxyl radical scavengers, thiourea and 2,2'-bipyridyl, decreased the levels of hydroxyl radical accumulation and recovered cell viability. These results suggest that, with or without pore formation, the final antimicrobial mechanism of lacticin Q is the accumulation of hydroxyl radicals, which varies by strain, resulting in the selective antimicrobial activity of lacticin Q.

  8. Lethal Hydroxyl Radical Accumulation by a Lactococcal Bacteriocin, Lacticin Q

    PubMed Central

    Li, Mengqi; Yoneyama, Fuminori; Toshimitsu, Nayu; Zendo, Takeshi; Nakayama, Jiro

    2013-01-01

    The antimicrobial mechanism of a lactococcal bacteriocin, lacticin Q, can be described by the toroidal pore model without any receptor. However, lacticin Q showed different degrees of activity (selective antimicrobial activity) against Gram-positive bacteria even among related species. The ability of lacticin Q to induce pore formation in liposomes composed of lipids from different indicator strains indicated that its selective antimicrobial activity could not be attributed only to membrane lipid composition. We investigated the accumulation of deleterious hydroxyl radicals after exposure to lacticin Q as a contributing factor to cell death in the indicator strains. When lacticin Q of the same concentration as the MIC or minimum bactericidal concentration was added to the indicator cultures, high levels of hydroxyl radical accumulation were detected. Treatment with hydroxyl radical scavengers, thiourea and 2,2′-bipyridyl, decreased the levels of hydroxyl radical accumulation and recovered cell viability. These results suggest that, with or without pore formation, the final antimicrobial mechanism of lacticin Q is the accumulation of hydroxyl radicals, which varies by strain, resulting in the selective antimicrobial activity of lacticin Q. PMID:23733459

  9. Ortho-hydroxyl effect and proton transfer via ion-neutral complex: the fragmentation study of protonated imine resveratrol analogues in mass spectrometry.

    PubMed

    Yue, Lei; Li, Jing; Xie, Xiaodong; Guo, Cheng; Yin, Xinchi; Yin, Qi; Chen, Yinjuan; Pan, Yuanjiang; Ding, Chuanfan

    2016-07-01

    The fragmentation pathways of protonated imine resveratrol analogues in the gas-phase were investigated by electrospray ionization-tandem mass spectrometry. Benzyl cations were formed in the imine resveratrol analogues that had an ortho-hydroxyl group on the benzene ring A. The specific elimination of the quinomethane neutral, CH2  = C6 H4  = O, from the two isomeric ions [M1 + H](+) and [M3 + H](+) via the corresponding ion-neutral complexes was observed. The fragmentation pathway for the related meta-isomer, ion [M2 + H](+) and the other congeners was not observed. Accurate mass measurements and additional experiments carried out with a chlorinated analogue and the trideuterated isotopolog of M1 supported the overall interpretation of the fragmentation phenomena observed. It is very helpful for understanding the intriguing roles of ortho-hydroxyl effect and ion-neutral complexes in fragmentation reactions and enriching the knowledge of the gas-phase chemistry of the benzyl cation. Copyright © 2016 John Wiley & Sons, Ltd.

  10. Complex Cure Kinetics of the Hydroxyl-Epoxide Reaction in DGEBA Epoxy Hardened with Diethanolamine

    NASA Astrophysics Data System (ADS)

    Ancipink, Windy; McCoy, John; Kropka, Jamie; Celina, Mathias

    The curing of a diglycidyl ether of bisphenol-A Epoxy (Epon 828) with diethanolamine (DEA) involves a fast amine-epoxide reaction followed by a slower hydroxyl-epoxide reaction. At curing temperatures below 100°C, the time scales of these two reactions are well separated, and the hydroxyl addition can be studied as an ''isolated'' reaction. The hydroxyl-epoxide reaction is of great interest due to the complex kinetics involved, which are brought about by competing reactions. The reaction kinetics are believed to be tertiary amine catalyzed and are well fit to a modified form of the Kamal-type equation. Here we study the complex long term reaction kinetics at various temperatures, by using isothermal modulated differential scanning calorimetry, micro calorimetry, and infrared spectroscopy. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  11. Role of hydrogen peroxide and hydroxyl radical in pyrite oxidation by molecular oxygen

    NASA Astrophysics Data System (ADS)

    Schoonen, Martin A. A.; Harrington, Andrea D.; Laffers, Richard; Strongin, Daniel R.

    2010-09-01

    Hydrogen peroxide and hydroxyl radical are readily formed during the oxidation of pyrite with molecular oxygen over a wide range of pH conditions. However, pretreatment of the pyrite surface influences how much of the intermediates are formed and their fate. Acid-washed pyrite produces significant amounts of hydrogen peroxide and hydroxyl radical when suspended in air-saturated water. However, the hydrogen peroxide concentration shows an exponential decrease with time. Suspensions made with partially oxidized pyrite yield significantly lower amounts of hydrogen peroxide product. The presence of Fe(III)-oxide or Fe(III)-hydroxide patches facilitates the conversion of hydrogen peroxide to oxygen and water. Hence, the degree to which a pyrite surface is covered with patches of Fe(III)-oxide or Fe(III)-hydroxide patches is an important control on the concentration of hydrogen peroxide in solution. Hydrogen peroxide appears to be an important intermediate in the four-electron transfer from pyrite to molecular oxygen. Addition of catalase, an enzyme that decomposes hydrogen peroxide to water and molecular oxygen, to a pyrite suspension reduces the oxidation rate by 40%. By contrast, hydroxyl radical does not appear to play a significant role in the oxidation mechanism. It is estimated on the basis of a molecular oxygen and sulfate mass balance that 5-6% of the molecular oxygen is consumed without forming sulfate.

  12. The hydroxyl-water megamaser connection. I. Water emission toward OH megamaser hosts

    SciTech Connect

    Wiggins, Brandon K.; Migenes, Victor; Smidt, Joseph M.

    2016-02-05

    Questions surround the connection of luminous extragalactic masers to galactic processes. The observation that water and hydroxyl megamasers rarely coexist in the same galaxy has given rise to a hypothesis that the two species appear in different phases of nuclear activity. The detection of simultaneous hydroxyl and water megamaser emission toward IC694 has called this hypothesis into question, but, because many megamasers have not been surveyed for emission in the other molecule, it remains unclear whether IC694 occupies a narrow phase of galaxy evolution or whether the relationship between megamaser species and galactic processes is more complicated than previously believed. In this paper, we present results of a systematic search for 22 GHz water maser emission among OH megamaser hosts to identify additional objects hosting both megamasers. Our work roughly doubles the number of galaxies searched for emission in both molecules, which host at least one confirmed maser. We confirm with a high degree of confidence ($\\gt 8\\sigma $) the detection of water emission toward IIZw96, firmly establishing it as the second object to cohost both water and hydroxyl megamasers after IC694. We find high luminosity, narrow features in the water feature in IIZw96. All dual megamaser candidates appear in merging galaxy systems suggestive that megamasers that coexistance may signal a brief phase along the merger sequence. In conclusion, a statistical analysis of the results of our observations provide possible evidence for an exclusion of H2O kilomasers among OH megamaser hosts.

  13. The Hydroxyl-Water Megamaser Connection. I. Water Emission toward OH Megamaser Hosts

    NASA Astrophysics Data System (ADS)

    Wiggins, Brandon K.; Migenes, Victor; Smidt, Joseph M.

    2016-01-01

    Questions surround the connection of luminous extragalactic masers to galactic processes. The observation that water and hydroxyl megamasers rarely coexist in the same galaxy has given rise to a hypothesis that the two species appear in different phases of nuclear activity. The detection of simultaneous hydroxyl and water megamaser emission toward IC694 has called this hypothesis into question, but, because many megamasers have not been surveyed for emission in the other molecule, it remains unclear whether IC694 occupies a narrow phase of galaxy evolution or whether the relationship between megamaser species and galactic processes is more complicated than previously believed. In this paper, we present results of a systematic search for 22 GHz water maser emission among OH megamaser hosts to identify additional objects hosting both megamasers. Our work roughly doubles the number of galaxies searched for emission in both molecules, which host at least one confirmed maser. We confirm with a high degree of confidence (\\gt 8σ ) the detection of water emission toward IIZw96, firmly establishing it as the second object to cohost both water and hydroxyl megamasers after IC694. We find high luminosity, narrow features in the water feature in IIZw96. All dual megamaser candidates appear in merging galaxy systems suggestive that megamasers that coexistance may signal a brief phase along the merger sequence. A statistical analysis of the results of our observations provide possible evidence for an exclusion of H2O kilomasers among OH megamaser hosts.

  14. Role for the propofol hydroxyl in anesthetic protein target molecular recognition.

    PubMed

    Woll, Kellie A; Weiser, Brian P; Liang, Qiansheng; Meng, Tao; McKinstry-Wu, Andrew; Pinch, Benika; Dailey, William P; Gao, Wei Dong; Covarrubias, Manuel; Eckenhoff, Roderic G

    2015-06-17

    Propofol is a widely used intravenous general anesthetic. We synthesized 2-fluoro-1,3-diisopropylbenzene, a compound that we call "fropofol", to directly assess the significance of the propofol 1-hydroxyl for pharmacologically relevant molecular recognition in vitro and for anesthetic efficacy in vivo. Compared to propofol, fropofol had a similar molecular volume and only a small increase in hydrophobicity. Isothermal titration calorimetry and competition assays revealed that fropofol had higher affinity for a protein site governed largely by van der Waals interactions. Within another protein model containing hydrogen bond interactions, propofol demonstrated higher affinity. In vivo, fropofol demonstrated no anesthetic efficacy, but at high concentrations produced excitatory activity in tadpoles and mice; fropofol also antagonized propofol-induced hypnosis. In a propofol protein target that contributes to hypnosis, α1β2γ2L GABAA receptors, fropofol demonstrated no significant effect alone or on propofol positive allosteric modulation of the ion channel, suggesting an additional requirement for the 1-hydroxyl within synaptic GABAA receptor site(s). However, fropofol caused similar adverse cardiovascular effects as propofol by a dose-dependent depression of myocardial contractility. Our results directly implicate the propofol 1-hydroxyl as contributing to molecular recognition within protein targets leading to hypnosis, but not necessarily within protein targets leading to side effects of the drug.

  15. Environmentally Persistent Free Radicals (EPFRs). 3. Free versus Bound Hydroxyl Radicals in EPFR Aqueous Solutions

    PubMed Central

    2015-01-01

    Additional experimental evidence is presented for in vitro generation of hydroxyl radicals because of redox cycling of environmentally persistent free radicals (EPFRs) produced after adsorption of 2-monochlorophenol at 230 °C (2-MCP-230) on copper oxide supported by silica, 5% Cu(II)O/silica (3.9% Cu). A chemical spin trapping agent, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), in conjunction with electron paramagnetic resonance (EPR) spectroscopy was employed. Experiments in spiked O17 water have shown that ∼15% of hydroxyl radicals formed as a result of redox cycling. This amount of hydroxyl radicals arises from an exogenous Fenton reaction and may stay either partially trapped on the surface of particulate matter (physisorbed or chemisorbed) or transferred into solution as free OH. Computational work confirms the highly stable nature of the DMPO–OH adduct, as an intermediate produced by interaction of DMPO with physisorbed/chemisorbed OH (at the interface of solid catalyst/solution). All reaction pathways have been supported by ab initio calculations. PMID:25036238

  16. The hydroxyl-water megamaser connection. I. Water emission toward OH megamaser hosts

    DOE PAGES

    Wiggins, Brandon K.; Migenes, Victor; Smidt, Joseph M.

    2016-02-05

    Questions surround the connection of luminous extragalactic masers to galactic processes. The observation that water and hydroxyl megamasers rarely coexist in the same galaxy has given rise to a hypothesis that the two species appear in different phases of nuclear activity. The detection of simultaneous hydroxyl and water megamaser emission toward IC694 has called this hypothesis into question, but, because many megamasers have not been surveyed for emission in the other molecule, it remains unclear whether IC694 occupies a narrow phase of galaxy evolution or whether the relationship between megamaser species and galactic processes is more complicated than previously believed. In this paper, we present results of a systematic search for 22 GHz water maser emission among OH megamaser hosts to identify additional objects hosting both megamasers. Our work roughly doubles the number of galaxies searched for emission in both molecules, which host at least one confirmed maser. We confirm with a high degree of confidence (more » $$\\gt 8\\sigma $$) the detection of water emission toward IIZw96, firmly establishing it as the second object to cohost both water and hydroxyl megamasers after IC694. We find high luminosity, narrow features in the water feature in IIZw96. All dual megamaser candidates appear in merging galaxy systems suggestive that megamasers that coexistance may signal a brief phase along the merger sequence. In conclusion, a statistical analysis of the results of our observations provide possible evidence for an exclusion of H2O kilomasers among OH megamaser hosts.« less

  17. Reactivity of aqueous phase hydroxyl radical with halogenated carboxylate anions: experimental and theoretical studies.

    PubMed

    Minakata, Daisuke; Song, Weihua; Crittenden, John

    2011-07-15

    With concerns about emerging contaminants increasing, advanced oxidation processes have become attractive technologies because of potential mineralization of these contaminants via radical involved reactions that are induced by highly reactive hydroxyl radical. Considering the expensive and time-consuming experimental studies of degradation intermediates and byproduct, there is a need to develop a first-principles computer-based kinetic model that predict reaction pathways and associated reaction rate constants. In this study, we measured temperature-dependent hydroxyl radical reaction rate constants for a series of haloacetate ions and obtained their Arrhenius kinetic parameters. We found a linear correlation between these reaction rate constants and theoretically calculated aqueous-phase free energies of activation. To understand the quantitative effects on entropy of solvation due to solvent water molecules, we calculate each portion of the entropic energies that contribute to the overall aqueous phase entropy of activation; cavity formation is a dominant portion. For the series of reactions of hydroxyl radical with carboxylate ions, the increase in the entropy of activation during the solvation process is approximately 10-15 cal mol(-1)K(-1) because of interactions with solvent water molecules and the transition state. Finally, charge distribution analysis for the aqueous-phase reactions of hydroxyl radical with acetate/haloacetate ions reveals that in the aqueous phase, the degree of polarizability at the transition state is less substantial than those that are in the gaseous phase resulting in a high charge density. In the presence of electronegative halogenated functional groups, the transition state is less polarized and hydrogen bonding interactions are expected to be weaker.

  18. Hydroxyl and water molecule orientations in trypsin: Comparison to molecular dynamics structures

    SciTech Connect

    McDowell, R.S.; Kossiakoff, A.A.

    1994-12-31

    A comparison is presented of experimentally observed hydroxyl and water hydrogens in trypsin determined from neutron density maps with the results of a 140ps molecular dynamics (MD) simulation. Experimental determination of hydrogen and deuterium atom positions in molecules as large as proteins is a unique capability of neutron diffraction. The comparison addresses the degree to which a standard force-field approach can adequately describe the local electrostatic and van der Waals forces that determine the orientations of these hydrogens. Neutron densities, derived from 2.1{Angstrom} D{sub 2}O-H{sub 2}O difference Fourier maps, provide a database of 27 well-ordered hydroxyl hydrogens. Most of the simulated hydroxyl orientations are within a standard deviation of the experimentally-observed positions, including several examples in which both the simulation and the neutron density indicate that a hydroxyl group is shifted from a {open_quote}standard{close_quote} rotamer. For the most highly ordered water molecules, the hydrogen distributions calculated from the trajectory were in good agreement with neutron density; simulated water molecules that displayed multiple hydrogen bonding networks had correspondingly broadened neutron density profiles. This comparison was facilitated by development of a method to construct a pseudo 2{Angstrom} density map based on the hydrogen atom distributions from the simulation. The degree of disorder of internal water molecules is shown to result primarily from the electrostatic environment surrounding that water molecule as opposed to the cavity size available to the molecule. A method is presented for comparing the discrete observations sampled in a dynamics trajectory with the time- averaged data obtained from X-ray or neutron diffraction studies. This method is particularly useful for statically-disordered water molecules, in which the average location assigned from a trajectory may represent a site of relatively low occupancy.

  19. Enantioselective aliphatic hydroxylations of racemic 1-hydroxy-3-methylcholanthrene by rat liver microsomes.

    PubMed

    Shou, M G; Yang, S K

    1990-01-01

    Enantiomeric pairs of 1-hydroxy-3-hydroxymethylcholanthrene (1-OH-3-OHMC), 3-methylcholanthrene (3MC) trans- and cis-1,2-diols, and 1-hydroxy-3-methylcholanthrene (1-OH-3MC) were resolved by HPLC using a covalently bonded (R)-N-(3,5-dinitrobenzoyl)phenylglycine chiral stationary phase (Pirkle type 1A) column. The absolute configuration of an enantiomeric 3MC trans-1,2-diol was established by the exciton chirality CD method following conversion to a bis-p-N,N-dimethylaminobenzoate. Incubation of an enantiomeric 1-OH-3MC with rat liver microsomes resulted in the formation of enantiomeric 3MC trans- and cis-1,2-diols; the absolute configurations of the enantiomeric 1-OH-3MC and 3MC cis-1,2-diol were established on the basis of the absolute configuration of an enantiomeric 3MC trans-1,2-diol. Absolute configurations of enantiomeric 1-OH-3-OHMC were determined by comparing their CD spectra with those of enantiomeric 1-OH-3MC. The relative amount of three aliphatic hydroxylation products formed by rat liver microsomal metabolism of racemic 1-OH-3MC was 1-OH-3-OHMC greater than 3MC cis-1,2-diol greater than 3MC trans-1,2-diol. Enzymatic hydroxylation at C2 of racemic 1-OH-3MC was enantioselective toward the 1S-enantiomer over the 1R-enantiomer (approximately 3/1); hydroxylation at the C3-methyl group was enantioselective toward the 1R-enantiomer over the 1S-enantiomer (approximately 58/42). Rat liver microsomal C2-hydroxylation of racemic 1-OH-3MC resulted in a 3MC trans-1,2-diol with a (1S,2S)/(1R,2R) ratio of 63/37 and a 3MC cis-1,2-diol with a (1S,2R)/(1R,2S) ratio of 12/88, respectively.

  20. A QSAR for the hydroxyl radical reaction rate constant: validation, domain of application, and prediction

    NASA Astrophysics Data System (ADS)

    Öberg, Tomas

    A large number of anthropogenic organic chemicals are emitted into the troposphere. Reactions with the hydroxyl radical are a dominant removal pathway for most organic compounds, but experimentally determined gas-phase reaction rate constants are only available for about 750 compounds. The lack of experimental data increases the importance of applying quantitative structure-activity relationships (QSAR) to evaluate and predict reactivities. It is generally acknowledged that these empirical relationships are valid only within the same domain for which they were developed. However, model validation is sometimes neglected and the application domain is not always well defined. The purpose of this paper is to outline how validation and domain definition can facilitate the modeling and prediction of the hydroxyl radical reaction rates for a large database. A substantial number of theoretical descriptors (867) were generated from 2D molecular structures for compounds present in the Syracuse Research Corporation's PhysProp Database. A QSAR model was developed for the hydroxyl radical reaction rate constant using a projection-based regression technique, partial least squares regression (PLSR). The PLSR model was subsequently validated with an external test set. The main factors of variation could be attributed to two reaction pathways, hydrogen atom abstraction and addition to double bonds or aromatic systems. A set of 17 293 compounds, drawn from the PhysProp Database, was projected onto the PLSR model and 74% were inside the applicability domain. The predicted hydroxyl reaction rates for 25% of these compounds were slow or negligible, with atmospheric half-lives in the range from days to years. Finally, the list of persistent organic compounds was matched against the OECD list of high production volume chemicals (HPVC). Together with the experimental data, nearly three hundred compounds were identified as both persistent and in high volume production.

  1. Hydroxylated Metabolites of 4-Monochlorobiphenyl and Its Metabolic Pathway in Whole Poplar Plants

    PubMed Central

    Zhai, Guangshu; Lehmler, Hans-Joachim; Schnoor, Jerald L.

    2010-01-01

    4-Monochlorobiphenyl (CB3), mainly an airborne pollutant, undergoes rapid biotransformation to produce hydroxylated metabolites (OH-CB3s). However, up to now, hydroxylation of CB3 has not been studied in living organisms. In order to explore the formation of hydroxylated metabolites of CB3 in whole plants, poplars (Populus deltoides × nigra, DN34) were exposed to CB3 for 10 days. Poplars are a model plant with complete genomic sequence, and they are widely used in phytoremediation. Results showed poplar plants can metabolize CB3 into OH-CB3s. Three monohydroxy metabolites, including 2′-hydroxy-4-chlorobiphenyl (2′OH-CB3), 3′-hydroxy-4-chlorobiphenyl (3′OH-CB3) and 4′-hydroxy-4-chlorobiphenyl (4′OH-CB3), were identified in hydroponic solution and in different parts of poplar plant. The metabolite 4′OH-CB3 was the major product. In addition, there were two other unknown monohydroxy metabolites of CB3 found in whole poplar plants. Based on their physical and chemical properties, they are likely to be 2-hydroxy-4-chlorobiphenyl (2OH-CB3) and 3-hydroxy-4-chlorobiphenyl (3OH-CB3). Compared to the roots and leaves, the middle portion of the plant (the middle wood and bark) had higher concentrations of 2′OH-CB3, 3′OH-CB3 and 4′OH-CB3, which suggests that these hydroxylated metabolites of CB3 are easily translocated in poplars from roots to shoots. The total masses of 2′OH-CB3, 3′OH-CB3 and 4′OH-CB3 in whole poplar plants were much higher than those in solution, strongly suggesting that it is mainly the poplar plant itself which metabolizes CB3 to OH-CB3s. Finally, the data suggest that the metabolic pathway be via epoxide intermediates. PMID:20402517

  2. Promotional effect of surface hydroxyls on electrochemical reduction of CO2 over SnOx/Sn electrode

    DOE PAGES

    Cui, Chaonan; Han, Jinyu; Zhu, Xinli; ...

    2016-01-16

    In this study, tin oxide (SnOx) formation on tin-based electrode surfaces during CO2 electrochemical reduction can have a significant impact on the activity and selectivity of the reaction. In the present study, density functional theory (DFT) calculations have been performed to understand the role of SnOx in CO2 reduction using a SnO monolayer on the Sn(112) surface as a model for SnOx. Water molecules have been treated explicitly and considered actively participating in the reaction. The results showed that H2O dissociates on the perfect SnO monolayer into two hydroxyl groups symmetrically on the surface. CO2 energetically prefers to react withmore » the hydroxyl, forming a bicarbonate (HCO3(t)*) intermediate, which can then be reduced to either formate (HCOO*) by hydrogenating the carbon atom or carboxyl (COOH*) by protonating the oxygen atom. Both steps involve a simultaneous Csingle bondO bond breaking. Further reduction of HCOO* species leads to the formation of formic acid in the acidic solution at pH < 4, while the COOH* will decompose to CO and H2O via protonation. Whereas the oxygen vacancy (VO) in the oxide monolayer maybe formed by the reduction, it can be recovered by H2O dissociation, resulting in two embedded hydroxyl groups. The results show that the hydroxylated surface with two symmetric hydroxyls is energetically more favorable for CO2 reduction than the hydroxylated VO surface with two embedded hydroxyls. The reduction potential for the former has a limiting-potential of –0.20 V (RHE), lower than that for the latter (–0.74 V (RHE)). Compared to the pure Sn electrode, the formation of SnOx monolayer on the electrode under the operating conditions promotes CO2 reduction more effectively by forming surface hydroxyls, thereby providing a new channel via COOH* to the CO formation, although formic acid is still the major reduction product.« less

  3. Promotional effect of surface hydroxyls on electrochemical reduction of CO2 over SnOx/Sn electrode

    SciTech Connect

    Cui, Chaonan; Han, Jinyu; Zhu, Xinli; Liu, Xiao; Wang, Hua; Mei, Donghai; Ge, Qingfeng

    2016-11-01

    Tin oxide (SnOx) formation on tin-based electrode surfaces during CO2 electrochemical reduction can have a significant impact on the activity and selectivity of the reaction. In the present study, density functional theory (DFT) calculations have been performed to understand the role of SnOx in CO2 reduction using a SnO monolayer on the Sn(112) surface as a model for SnOx. Water molecules have been treated explicitly and considered actively participating in the reaction. The results showed that H2O dissociates on the perfect SnO monolayer into two hydroxyl groups symmetrically on the surface. CO2 energetically prefers to react with the hydroxyl, forming a bicarbonate (HCO3(t)*) intermediate, which can then be reduced to either formate (HCOO*) by hydrogenating the carbon atom or carboxyl (COOH*) by protonating the oxygen atom. Both steps involve a simultaneous C-O bond breaking. Further reduction of HCOO* species leads to the formation of formic acid in the acidic solution at pH < 4, while the COOH* will decompose to CO and H2O via protonation. Whereas the oxygen vacancy (VO) in the monolayer maybe formed by the reduction of the monolayer, it can be recovered by H2O dissociation, resulting in two embedded hydroxyl groups. However, the hydroxylated surface with two symmetric hydroxyls is energetically more favorable for CO2 reduction than the hydroxylated VO surface with two embedded hydroxyls. The reduction potential for the former has a limiting-potential of -0.20 V (RHE), lower than that for the latter (-0.74 V (RHE)). Compared to the pure Sn electrode, the formation of SnOx monolayer on the electrode under the operating conditions promotes CO2 reduction more effectively by forming surface hydroxyls, thereby, providing a new channel via COOH* to the CO formation, although formic acid is still the major reduction product. The work was supported in part by National Natural Sciences Foundation of China (Grant #21373148 and #21206117). The High Performance Computing

  4. Amino group combined P/Ge and P/Sn Lewis pairs: synthesis and dipolar addition reactions to alkyne and aldehyde molecules.

    PubMed

    Yu, Ying; Li, Jiancheng; Liu, Weiping; Ye, Qingsong; Zhu, Hongping

    2016-04-14

    Amino group combined P/Ge-based frustrated Lewis pairs (FLPs) Ph2PN(R)GeCl3 (R = 2,6-iPr2C6H3 (1), 2,4,6-Me3C6H2 (2), and C6H11 (3)) and Ph2PN(2,6-iPr2C6H3)GeMe3 (4) as well as P/Sn-based FLP Ph2PN(2,6-iPr2C6H3)SnMe3 (5) were prepared and utilized for reactions with alkyne and aldehyde molecules. Compounds 1-3 each reacted with MeO2CC[triple bond, length as m-dash]CCO2Me to give zwitterionic cyclic vinyls [Ph2PN(R)GeCl3](MeO2CC[double bond, length as m-dash]CCO2Me) (6-8) and compound 1 reacted with HC[triple bond, length as m-dash]CCO2Me to give the similar compound [Ph2PN(2,4,6-Me3C6H2)GeCl3](HC[double bond, length as m-dash]CCO2Me) (9). Compound 4 reacted with RC[triple bond, length as m-dash]CCO2Me to afford acyclic vinyls 2,6-iPr2C6H3N[double bond, length as m-dash]P(Ph2)C(R)[double bond, length as m-dash]C(CO2Me)GeMe3 (R = CO2Me (10), H (11)) and 5 reacted with MeO2CC[triple bond, length as m-dash]CCO2Me to give 2,6-iPr2C6H3N[double bond, length as m-dash]P(Ph2)C(CO2Me)[double bond, length as m-dash]C(CO2Me)SnMe3 (12). The reactions of 1 with CH3CH2CHO and 1,4-(CHO)2C6H4 were also investigated and yielded novel zwitterionic OCPNGe five-heteroatom cycles [Ph2PN(2,6-iPr2C6H3)GeCl3][CH(CH2CH3)O] (13) and [Ph2PN(2,6-iPr2C6H3)GeCl3][p-(OCH)C6H4CHO][Cl3GeN(2,6-iPr2C6H3)PPh2] (14). Compounds 1-14 were characterized by NMR ((1)H, (13)C, and (31)P) and CHN elemental analysis, of which 1, 7, and 10-14 were further studied by X-ray crystallography. The reactions of 4 (or 5) with RC[triple bond, length as m-dash]CCO2Me to produce 10-12 present a novel way of obtaining the germyl (or stannyl) and iminophosphoranyl co-substituted vinyls.

  5. Physiological activities of hydroxyl fatty acids

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In the search of value-added products from surplus soybean oil, we produced many new hydroxy fatty acids through microbial bioconversion. Hydroxy fatty acids are used in a wide range of industrial products, such as resins, waxes, nylons plastics, lubricants, cosmetics, and additives in coatings and...

  6. Hydroxyl radical-induced formation of highly oxidized organic compounds

    NASA Astrophysics Data System (ADS)

    Berndt, Torsten; Richters, Stefanie; Jokinen, Tuija; Hyttinen, Noora; Kurtén, Theo; Otkjær, Rasmus V.; Kjaergaard, Henrik G.; Stratmann, Frank; Herrmann, Hartmut; Sipilä, Mikko; Kulmala, Markku; Ehn, Mikael

    2016-12-01

    Explaining the formation of secondary organic aerosol is an intriguing question in atmospheric sciences because of its importance for Earth's radiation budget and the associated effects on health and ecosystems. A breakthrough was recently achieved in the understanding of secondary organic aerosol formation from ozone reactions of biogenic emissions by the rapid formation of highly oxidized multifunctional organic compounds via autoxidation. However, the important daytime hydroxyl radical reactions have been considered to be less important in this process. Here we report measurements on the reaction of hydroxyl radicals with α- and β-pinene applying improved mass spectrometric methods. Our laboratory results prove that the formation of highly oxidized products from hydroxyl radical reactions proceeds with considerably higher yields than previously reported. Field measurements support these findings. Our results allow for a better description of the diurnal behaviour of the highly oxidized product formation and subsequent secondary organic aerosol formation in the atmosphere.

  7. Hydroxyl radical-induced formation of highly oxidized organic compounds

    PubMed Central

    Berndt, Torsten; Richters, Stefanie; Jokinen, Tuija; Hyttinen, Noora; Kurtén, Theo; Otkjær, Rasmus V.; Kjaergaard, Henrik G.; Stratmann, Frank; Herrmann, Hartmut; Sipilä, Mikko; Kulmala, Markku; Ehn, Mikael

    2016-01-01

    Explaining the formation of secondary organic aerosol is an intriguing question in atmospheric sciences because of its importance for Earth's radiation budget and the associated effects on health and ecosystems. A breakthrough was recently achieved in the understanding of secondary organic aerosol formation from ozone reactions of biogenic emissions by the rapid formation of highly oxidized multifunctional organic compounds via autoxidation. However, the important daytime hydroxyl radical reactions have been considered to be less important in this process. Here we report measurements on the reaction of hydroxyl radicals with α- and β-pinene applying improved mass spectrometric methods. Our laboratory results prove that the formation of highly oxidized products from hydroxyl radical reactions proceeds with considerably higher yields than previously reported. Field measurements support these findings. Our results allow for a better description of the diurnal behaviour of the highly oxidized product formation and subsequent secondary organic aerosol formation in the atmosphere. PMID:27910849

  8. Unexpectedly high indoor hydroxyl radical concentrations associated with nitrous acid.

    PubMed

    Gómez Alvarez, Elena; Amedro, Damien; Afif, Charbel; Gligorovski, Sasho; Schoemaecker, Coralie; Schoemacker, Coralie; Fittschen, Christa; Doussin, Jean-Francois; Wortham, Henri

    2013-08-13

    The hydroxyl (OH) radical is the most important oxidant in the atmosphere since it controls its self-oxidizing capacity. The main sources of OH radicals are the photolysis of ozone and the photolysis of nitrous acid (HONO). Due to the attenuation of solar radiation in the indoor environment, the possibility of OH formation through photolytic pathways indoors has been ignored up to now. In the indoor air, the ozonolysis of alkenes has been suggested as an alternative route of OH formation. Models and indirect measurements performed up to now according to this hypothesis suggest concentrations of OH radicals on the order of 10(4)-10(5) molecules per cubic centimeter. Here, we present direct measurements of significant amounts of OH radicals of up to 1.8⋅10(6) molecules per cubic centimeter during an experimental campaign carried out in a school classroom in Marseille. This concentration is on the same order of magnitude of outdoor OH levels in the urban scenario. We also show that photolysis of HONO is an important source of OH radicals indoors under certain conditions (i.e., direct solar irradiation inside the room). Additionally, the OH concentrations were found to follow a linear dependence with the product J(HONO)⋅[HONO]. This was also supported by using a simple quasiphotostationary state model on the OH radical budget. These findings force a change in our understanding of indoor air quality because the reactivity linked to OH would involve formation of secondary species through chemical reactions that are potentially more hazardous than the primary pollutants in the indoor air.

  9. Unexpectedly high indoor hydroxyl radical concentrations associated with nitrous acid

    PubMed Central

    Gómez Alvarez, Elena; Amedro, Damien; Afif, Charbel; Gligorovski, Sasho; Schoemaecker, Coralie; Fittschen, Christa; Doussin, Jean-Francois; Wortham, Henri

    2013-01-01

    The hydroxyl (OH) radical is the most important oxidant in the atmosphere since it controls its self-oxidizing capacity. The main sources of OH radicals are the photolysis of ozone and the photolysis of nitrous acid (HONO). Due to the attenuation of solar radiation in the indoor environment, the possibility of OH formation through photolytic pathways indoors has been ignored up to now. In the indoor air, the ozonolysis of alkenes has been suggested as an alternative route of OH formation. Models and indirect measurements performed up to now according to this hypothesis suggest concentrations of OH radicals on the order of 104–105 molecules per cubic centimeter. Here, we present direct measurements of significant amounts of OH radicals of up to 1.8⋅106 molecules per cubic centimeter during an experimental campaign carried out in a school classroom in Marseille. This concentration is on the same order of magnitude of outdoor OH levels in the urban scenario. We also show that photolysis of HONO is an important source of OH radicals indoors under certain conditions (i.e., direct solar irradiation inside the room). Additionally, the OH concentrations were found to follow a linear dependence with the product J(HONO)⋅[HONO]. This was also supported by using a simple quasiphotostationary state model on the OH radical budget. These findings force a change in our understanding of indoor air quality because the reactivity linked to OH would involve formation of secondary species through chemical reactions that are potentially more hazardous than the primary pollutants in the indoor air. PMID:23898188

  10. Identification, Synthesis, and Biological Evaluation of Metabolites of the Experimental Cancer Treatment Drugs Indotecan (LMP400) and Indimitecan (LMP776) and Investigation of Isomerically Hydroxylated Indenoisoquinoline Analogues as Topoisomerase I Poisons

    PubMed Central

    Cinelli, Maris A.; Reddy, P.V. Narasimha; Lv, Peng-Cheng; Liang, Jian-Hua; Chen, Lian; Agama, Keli; Pommier, Yves; van Breemen, Richard B.; Cushman, Mark

    2012-01-01

    Hydroxylated analogues of the anticancer topoisomerase I (Top1) inhibitors indotecan (LMP400) and indimitecan (LMP76) have been prepared because: 1) a variety of potent Top1 poisons are known that contain strategically placed hydroxyl groups, which provides a clear rationale for incorporating them in the present case, and 2) the hydroxylated compounds could conceivably serve as synthetic standards for the identification of metabolites. Indeed, incubating LMP400 and LMP776 with human liver microsomes resulted in two major metabolites of each drug, which had HPLC retention times and mass fragmentation patterns identical to the synthetic standards. The hydroxylated indotecan and indimitecan metabolites and analogues were tested as Top1 poisons and for antiproliferative activity in a variety of human cancer cell cultures, and in general were found to be very potent. Differences in activity resulting from the placement of the hydroxyl group are explained by molecular modeling analyses. PMID:23215354

  11. Hydroxyl Radical Dosimetry for High Flux Hydroxyl Radical Protein Footprinting Applications Using a Simple Optical Detection Method.

    PubMed

    Xie, Boer; Sharp, Joshua S

    2015-11-03

    Hydroxyl radical protein footprinting (HRPF) by fast photochemical oxidation of proteins (FPOP) is a powerful benchtop tool used to probe protein structure, interactions, and conformational changes in solution. However, the reproducibility of all HRPF techniques is limited by the ability to deliver a defined concentration of hydroxyl radicals to the protein. This ability is impacted by both the amount of radical generated and the presence of radical scavengers in solution. In order to compare HRPF data from sample to sample, a hydroxyl radical dosimeter is needed that can measure the effective concentration of radical that is delivered to the protein, after accounting for both differences in hydroxyl radical generation and nonanalyte radical consumption. Here, we test three radical dosimeters (Alexa Fluor 488, terepthalic acid, and adenine) for their ability to quantitatively measure the effective radical dose under the high radical concentration conditions of FPOP. Adenine has a quantitative relationship between UV spectrophotometric response, effective hydroxyl radical dose delivered, and peptide and protein oxidation levels over the range of radical concentrations typically encountered in FPOP. The simplicity of an adenine-based dosimeter allows for convenient and flexible incorporation into FPOP applications, and the ability to accurately measure the delivered radical dose will enable reproducible and reliable FPOP across a variety of platforms and applications.

  12. Mechanisms of hydroxyl radical-induced contraction of rat aorta.

    PubMed

    Li, Jianfeng; Li, Wenyan; Liu, Weimin; Altura, Bella T; Altura, Burton M

    2004-09-19

    The present study was designed to investigate the effects of hydroxyl radicals (*OH), generated via the Fe2+-mediated Fenton reaction, on isolated rat aortic rings with and without endothelium. In the absence of any vasoactive agent, generation of *OH alone elicited an endothelium-independent contraction in rat aortic rings in a concentration-dependent manner. Hydroxyl radical-induced contractions of denuded rat aortic rings appeared, however, to be slightly stronger than those on intact rat aortic rings. The contractile responses to *OH were neither reversible nor reproducible in the same ring; even small concentrations of *OH radicals resulted in tachyphylaxis. Removal of extracellular calcium ions (Ca2+) or buffering intracellular Ca2+ with 10 microM acetyl methyl ester of bis(o-aminophenoxy) ethane-N,N,N',N',-tetraacetic acid (BAPTA-AM) significantly attenuated the contractile actions of *OH radicals. The presence of 1 microM staurosporine, 1 microM bisindolylmaleimide I, 1 microM Gö6976 [inhibitor of protein kinase C (PKC)], 2 microM PD-980592 (inhibitor of ERK), 10 microM genistein, and 1 microM wortmannin significantly inhibited the contractions induced by *OH. Proadifen (10 microM), on the other hand, significantly potentiated the hydroxyl radical-induced contractions. Exposure of primary cultured aortic smooth muscle cells to *OH produced significant, rapid rises of intracellular free Ca2+ ([Ca2+]i). Several, specific antagonists of possible endogenously formed vasoconstrictors did not inhibit or attenuate either hydroxyl radical-induced contractions or the elevation of [Ca2+]i. Our new results suggest that hydroxyl radical-triggered contractions on rat aortic rings are Ca2+-dependent. Several intracellular signal transduction systems seem to play some role in hydroxyl radical-induced vasoconstriction of rat aortic rings.

  13. Scavenging property of three cresol isomers against H2O2, hypochlorite, superoxide and hydroxyl radicals.

    PubMed

    Yeung, S Y; Lan, W H; Huang, C S; Lin, C P; Chan, C P; Chang, M C; Jeng, J H

    2002-10-01

    Formocresol has long been used for pulpotomy of primary teeth and as an intracanal medicament. Little is known, however, about the pharmacological effect of tricresols. This study showed that three cresol isomers, o-cresol, m-cresol and p-cresol, are H2O2 scavengers with a 50% inhibitory concentration (IC50) of 502, 6.7 and 10.16 microM, respectively. o-, m- and p-cresol were also shown to be effective scavengers of superoxide radicals generated by xanthine/xanthine oxidase with an IC50 of 282, 153 and > 4000 microM, respectively, as analyzed by luminometer. o-, m- and p-cresol showed protective effects on the DNA breaks generated by H2O2/FeCl2 and FeCl3/ascorbate/H2O2 systems at concentrations ranging from 70 microM to 1.43 mM, o-, m- and p-cresol also showed differential protective effects against DNA breaks induced by 0.17% NaOCl with 100% inhibitory concentration (IC100) of about 10, 1 and 10 mM, respectively. In addition, reaction with 3% H2O2 and 0.17% NaOCl completely prevented NaOCl-induced DNA breaks. The results indicate that the three cresol isomers are effective ROS scavengers and may prevent ROS induced damage when used as pulpotomy agents or as intracanal medicaments. Owing to the difference in the position of the functional hydroxyl group in the three cresol isomers, m-cresol is the most effective ROS scavenger. Concomitant use of H2O2 for root canal irrigation may diminish both the tissue dissolving capacity of NaOCl and NaOCl-induced DNA damage.

  14. Beta Hydroxylation of Glycolipids from Ustilago maydis and Pseudozyma flocculosa by an NADPH-Dependent β-Hydroxylase▿

    PubMed Central

    Teichmann, Beate; Lefebvre, François; Labbé, Caroline; Bölker, Michael; Linne, Uwe; Bélanger, Richard R.

    2011-01-01

    Flocculosin and ustilagic acid (UA), two highly similar antifungal cellobiose lipids, are respectively produced by Pseudozyma flocculosa, a biocontrol agent, and Ustilago maydis, a plant pathogen. Both glycolipids contain a short-chain fatty acid hydroxylated at the β position but differ in the long fatty acid, which is hydroxylated at the α position in UA and at the β position in flocculosin. In both organisms, the biosynthesis genes are arranged in large clusters. The functions of most genes have already been characterized, but those of the P. flocculosa fhd1 gene and its homolog from U. maydis, uhd1, have remained undefined. The deduced amino acid sequences of these genes show homology to those of short-chain dehydrogenases and reductases (SDR). We disrupted the uhd1 gene in U. maydis and analyzed the secreted UA. uhd1 deletion strains produced UA lacking the β-hydroxyl group of the short-chain fatty acid. To analyze the function of P. flocculosa Fhd1, the corresponding gene was used to complement U. maydis Δuhd1 mutants. Fhd1 was able to restore wild-type UA production, indicating that Fhd1 is responsible for β hydroxylation of the flocculosin short-chain fatty acid. We also investigated a P. flocculosa homolog of the U. maydis long-chain fatty-acid alpha hydroxylase Ahd1. The P. flocculosa ahd1 gene, which does not reside in the flocculosin gene cluster, was introduced into U. maydis Δahd1 mutant strains. P. flocculosa Ahd1 neither complemented the U. maydis Δahd1 phenotype nor resulted in the production of β-hydroxylated UA. This suggests that P. flocculosa Ahd1 is not involved in flocculosin hydroxylation. PMID:21926207

  15. Hydroxyl radical induced degradation of salicylates in aerated aqueous solution

    NASA Astrophysics Data System (ADS)

    Szabó, László; Tóth, Tünde; Homlok, Renáta; Rácz, Gergely; Takács, Erzsébet; Wojnárovits, László

    2014-04-01

    Ionizing radiation induced degradation of acetylsalicylic acid, its hydrolysis product salicylic acid and a salicylic acid derivative 5-sulpho-salicylic acid, was investigated in dilute aqueous solutions by UV-vis spectrophotometry, HPLC separation and diode-array or MS/MS detection, chemical oxygen demand, total organic carbon content and by Vibrio fischeri toxicity measurements. Hydroxyl radicals were shown to degrade these molecules readily, and first degradation products were hydroxylated derivatives in all cases. Due to the by-products, among them hydrogen peroxide, the toxicity first increased and then decreased with the absorbed dose. With prolonged irradiation complete mineralization was achieved.

  16. Detection of adsorbed water and hydroxyl on the Moon.

    PubMed

    Clark, Roger N

    2009-10-23

    Data from the Visual and Infrared Mapping Spectrometer (VIMS) on Cassini during its flyby of the Moon in 1999 show a broad absorption at 3 micrometers due to adsorbed water and near 2.8 micrometers attributed to hydroxyl in the sunlit surface on the Moon. The amounts of water indicated in the spectra depend on the type of mixing and the grain sizes in the rocks and soils but could be 10 to 1000 parts per million and locally higher. Water in the polar regions may be water that has migrated to the colder environments there. Trace hydroxyl is observed in the anorthositic highlands at lower latitudes.

  17. Detection of adsorbed water and hydroxyl on the moon

    USGS Publications Warehouse

    Clark, R.N.

    2009-01-01

    Data from the Visual and Infrared Mapping Spectrometer (VIAAS) on Cassini during its flyby of the AAoon in 1999 show a broad absorption at 3 micrometers due to adsorbed water and near 2.8 micrometers attributed to hydroxyl in the sunlit surface on the AAoon. The amounts of water indicated in the spectra depend on the type of mixing and the grain sizes in the rocks and soils but could be 10 to 1000 parts per million and locally higher. Water in the polar regions may be water that has migrated to the colder environments there. Trace hydroxyl is observed in the anorthositic highlands at lower latitudes.

  18. Radiocarbon tracer measurements of atmospheric hydroxyl radical concentrations

    NASA Technical Reports Server (NTRS)

    Campbell, M. J.; Farmer, J. C.; Fitzner, C. A.; Henry, M. N.; Sheppard, J. C.

    1986-01-01

    The usefulness of the C-14 tracer in measurements of atmospheric hydroxyl radical concentration is discussed. The apparatus and the experimental conditions of three variations of a radiochemical method of atmosphere analysis are described and analyzed: the Teflon bag static reactor, the flow reactor (used in the Wallops Island tests), and the aircraft OH titration reactor. The procedure for reduction of the aircraft reactor instrument data is outlined. The problems connected with the measurement of hydroxyl radicals are discussed. It is suggested that the gas-phase radioisotope methods have considerable potential in measuring tropospheric impurities present in very low concentrations.

  19. Food additives

    PubMed Central

    Spencer, Michael

    1974-01-01

    Food additives are discussed from the food technology point of view. The reasons for their use are summarized: (1) to protect food from chemical and microbiological attack; (2) to even out seasonal supplies; (3) to improve their eating quality; (4) to improve their nutritional value. The various types of food additives are considered, e.g. colours, flavours, emulsifiers, bread and flour additives, preservatives, and nutritional additives. The paper concludes with consideration of those circumstances in which the use of additives is (a) justified and (b) unjustified. PMID:4467857

  20. Quenching Dynamics of Electronically Excited Hydroxyl Radicals

    DTIC Science & Technology

    2008-05-19

    the research of graduate students Margaret Greenslade , Erika Derro, Ilana Pollack, Logan Dempsey, and Eunice Li. In addition, postdoctoral...acknowledging AFOSR support 1) M. E. Greenslade , M. 1. Lester, D. C. Radenovi6, A. J. A. van Roij, and D. H. Parker, "(2+1) Resonance Enhanced Ionization...Spectroscopy of a State Selected Beam of OH Radicals", J. Chem. Phys. 123, 074309 (2005). 4 2) E. L. Derro, I. B. Pollack, L. Dempsey, M. E. Greenslade , Y

  1. Quenching Dynamics of Electronically Excited Hydroxyl Radicals

    DTIC Science & Technology

    2007-01-19

    Margaret Greenslade , Erika Derro, Ilana Pollack, Logan Dempsey, and Eunice Li. In addition, postdoctoral researchers Patricia Cleary, Craig Murray...6. E. L. Derro, I. B. Pollack, L. Dempsey, M. E. Greenslade , Y. Lei, D. 4ý. Radenovie, and M. I. Lester, J. Chem. Phys. 122, 244313 (2005). 7. G...Parlant and D. R. Yarkony, J. Chem. Phys. 110, 363 (1999). 8. M. E. Greenslade , M. 1. Lester, D. (1 Radenovi6, A. J. A. van Roij, and D. H. Parker, J

  2. Identification of hydroxyl protons, determination of their exchange dynamics, and characterization of hydrogen bonding in a microcrystallin protein.

    PubMed

    Agarwal, Vipin; Linser, Rasmus; Fink, Uwe; Faelber, Katja; Reif, Bernd

    2010-03-10

    Heteronuclear correlation experiments employing perdeuterated proteins enable the observation of all hydroxyl protons in a microcrystalline protein by MAS solid-state NMR. Dipolar-based sequences allow magnetization transfers that are >50 times faster compared to scalar-coupling-based sequences, which significantly facilitates their assignment. Hydroxyl exchange rates were measured using EXSY-type experiments. We find a biexponential decay behavior for those hydroxyl groups that are involved in side chain-side chain C-O-H...O horizontal lineC hydrogen bonds. The quantification of the distances between the hydroxyl proton and the carbon atoms in the hydrogen-bonding donor as well as acceptor group is achieved via a REDOR experiment. In combination with X-ray data and isotropic proton chemical shifts, availability of (1)H,(13)C distance information can aid in the quantitative description of the geometry of these hydrogen bonds. Similarly, correlations between backbone amide proton and carbonyl atoms are observed, which will be useful in the analysis of the registry of beta-strand arrangement in amyloid fibrils.

  3. Bacterial adhesion to hydroxyl- and methyl-terminated alkanethiol self-assembled monolayers.

    PubMed Central

    Wiencek, K M; Fletcher, M

    1995-01-01

    The attachment of bacteria to solid surfaces is influenced by substratum chemistry, but to determine the mechanistic basis of this relationship, homogeneous, well-defined substrata are required. Self-assembled monolayers (SAMs) were constructed from alkanethiols to produce a range of substrata with different exposed functional groups, i.e., methyl and hydroxyl groups and a series of mixtures of the two. Percentages of hydroxyl groups in the SAMs and substratum wettability were measured by X-ray photoelectron spectroscopy and contact angles of water and hexadecane, respectively. SAMs exhibited various substratum compositions and wettabilities, ranging from hydrophilic, hydroxyl-terminated monolayers to hydrophobic, methyl-terminated monolayers. The kinetics of attachment of an estuarine bacterium to these surfaces in a laminar flow chamber were measured over periods of 120 min. The initial rate of net adhesion, the number of cells attached after 120 min, the percentage of attached cells that adsorbed or desorbed between successive measurements, and the residence times of attached cells were quantified by phase-contrast microscopy and digital image processing. The greatest numbers of attached cells occurred on hydrophobic surfaces, because (i) the initial rates of adhesion and the mean numbers of cells that attached after 120 min increased with the methyl content of the SAM and the contact angle of water and (ii) the percentage of cells that desorbed between successive measurements (ca. 2 min) decreased with increasing substratum hydrophobicity. With all surfaces, 60 to 80% of the cells that desorbed during the 120-min exposure period had residence times of less than 10 min, suggesting that establishment of firm adhesion occurred quickly on all of the test surfaces. PMID:7721687

  4. Hydroxyl radical Thymine adduct induced DNA damages

    NASA Astrophysics Data System (ADS)

    Schyman, Patric; Eriksson, Leif A.; Zhang, Ru bo; Laaksonen, Aatto

    2008-06-01

    DNA damages caused by a 5-hydroxy-5,6-dihydrothymine-6-yl radical (5-OHT-6yl) abstracting a C2‧ hydrogen from a neighboring sugar (inter-H abstraction) have been theoretically investigated using hybrid DFT in gas phase and in water solution. The inter-H abstraction was here shown to be comparable in energy (24 kcal mol-1) with the intra-H abstraction in which the 5-OHT-6yl abstracts a C2‧ hydrogen from its own sugar. The effect of a neutrally or a negatively charged phosphate group was also studied and the results show no significant impact on the activation energy of the hydrogen abstraction whereas base release and strand break reactions are affected.

  5. Vanadium promotes hydroxyl radical formation by activated human neutrophils.

    PubMed

    Fickl, Heidi; Theron, Annette J; Grimmer, Heidi; Oommen, Joyce; Ramafi, Grace J; Steel, Helen C; Visser, Susanna S; Anderson, Ronald

    2006-01-01

    This study was undertaken to investigate the effects of vanadium in the +2, +3, +4, and +5 valence states on superoxide generation, myeloperoxidase (MPO) activity, and hydroxyl radical formation by activated human neutrophils in vitro, using lucigenin-enhanced chemiluminescence (LECL), autoiodination, and electron spin resonance with 5,5-dimethyl-l-pyrroline N-oxide as the spin trap, respectively. At concentrations of up to 25 microM, vanadium, in the four different valence states used, did not affect the LECL responses of neutrophils activated with either the chemoattractant, N-formyl-l-methionyl-l-leucyl-l-phenylalanine (1 microM), or the phorbol ester, phorbol 12-myristate 12-acetate (25 ng/ml). However, exposure to vanadium in the +2, +3, and +4, but not the +5, valence states was accompanied by significant augmentation of hydroxyl radical formation by activated neutrophils and attenuation of MPO-mediated iodination. With respect to hydroxyl radical formation, similar effects were observed using cell-free systems containing either hydrogen peroxide (100 microM) or xanthine/xanthine oxidase together with vanadium (+2, +3, +4), while the activity of purified MPO was inhibited by the metal in these valence states. These results demonstrate that vanadium in the +2, +3, and +4 valence states interacts prooxidatively with human neutrophils, competing effectively with MPO for hydrogen peroxide to promote formation of the highly toxic hydroxyl radical.

  6. Hydroxyl radical reactivity at the air-ice interface

    NASA Astrophysics Data System (ADS)

    Kahan, T. F.; Zhao, R.; Donaldson, D. J.

    2010-01-01

    Hydroxyl radicals are important oxidants in the atmosphere and in natural waters. They are also expected to be important in snow and ice, but their reactivity has not been widely studied in frozen aqueous solution. We have developed a spectroscopic probe to monitor the formation and reactions of hydroxyl radicals in situ. Hydroxyl radicals are produced in aqueous solution via the photolysis of nitrite, nitrate, and hydrogen peroxide, and react rapidly with benzene to form phenol. Similar phenol formation rates were observed in aqueous solution and bulk ice. However, no reaction was observed at air-ice interfaces, or when bulk ice samples were crushed prior to photolysis to increase their surface area. We also monitored the heterogeneous reaction between benzene present at air-water and air-ice interfaces with gas-phase OH produced from HONO photolysis. Rapid phenol formation was observed on water surfaces, but no reaction was observed at the surface of ice. Under the same conditions, we observed rapid loss of the polycyclic aromatic hydrocarbon (PAH) anthracene at air-water interfaces, but no loss was observed at air-ice interfaces. Our results suggest that the reactivity of hydroxyl radicals toward aromatic organics is similar in bulk ice samples and in aqueous solution, but is significantly suppressed in the quasi-liquid layer (QLL) that exists at air-ice interfaces.

  7. Hydroxyl radical reactivity at the air-ice interface

    NASA Astrophysics Data System (ADS)

    Kahan, T. F.; Zhao, R.; Donaldson, D. J.

    2009-10-01

    Hydroxyl radicals are important oxidants in the atmosphere and in natural waters. They are also expected to be important in snow and ice, but their reactivity has not been widely studied in frozen aqueous solution. We have developed a spectroscopic probe to monitor the formation and reactions of hydroxyl radicals in situ. Hydroxyl radicals are produced in aqueous solution via the photolysis of nitrite, nitrate, and hydrogen peroxide, and react rapidly with benzene to form phenol. Similar phenol formation rates were observed in aqueous solution and bulk ice. However, no reaction was observed at the air-ice interface, or when bulk ice samples were crushed prior to photolysis to increase their surface area. We also monitored the heterogeneous reaction between benzene present at air-water and air-ice interfaces with gas-phase OH produced from HONO photolysis. Rapid phenol formation was observed on water surfaces, but no reaction was observed at the surface of ice. Under the same conditions, we observed rapid loss of the polycyclic aromatic hydrocarbon (PAH) anthracene at the air-water interface, but no loss was observed at the air-ice interface. Our results suggest that the reactivity of hydroxyl radicals toward aromatic organics is similar in bulk ice samples and in aqueous solution, but is significantly suppressed in the quasi-liquid layer (QLL) that exists at the air-ice interface.

  8. Lysine hydroxylation of collagen in a fibroblast cell culture system

    NASA Technical Reports Server (NTRS)

    Uzawa, Katsuhiro; Yeowell, Heather N.; Yamamoto, Kazushi; Mochida, Yoshiyuki; Tanzawa, Hideki; Yamauchi, Mitsuo

    2003-01-01

    The lysine (Lys) hydroxylation pattern of type I collagen produced by human fibroblasts in culture was analyzed and compared. Fibroblasts were cultured from normal human skin (NSF), keloid (KDF), fetal skin (FDF), and skin tissues of Ehlers-Danlos syndrome type VIA and VIB patients (EDS-VIA and -VIB). The type I collagen alpha chains with or without non-helical telopeptides were purified from the insoluble matrix and analyzed. In comparison with NSFs, KDF and FDF showed significantly higher Lys hydroxylation, particularly in the telopeptide domains of both alpha chains. Both EDS-VIA and -VIB showed markedly lower Lys hydroxylation in the helical domains of both alpha chains whereas that in the telopeptides was comparable with those of NSFs. A similar profile was observed in the tissue sample of the EDS-VIB patient. These results demonstrate that the Lys hydroxylation pattern is domain-specific within the collagen molecule and that this method is useful to characterize the cell phenotypes in normal/pathological connective tissues.

  9. Production of hydroxylated fatty acids in genetically modified plants

    DOEpatents

    Somerville, Chris; Broun, Pierre; van de Loo, Frank

    2001-01-01

    This invention relates to plant fatty acyl hydroxylases. Methods to use conserved amino acid or nucleotide sequences to obtain plant fatty acyl hydroxylases are described. Also described is the use of cDNA clones encoding a plant hydroxylase to produce a family of hydroxylated fatty acids in transgenic plants.

  10. Effect of thyme/cumin essential oils and butylated hydroxyl anisole/butylated hydroxyl toluene on physicochemical properties and oxidative/microbial stability of chicken patties.

    PubMed

    Sariçoban, Cemalettin; Yilmaz, Mustafa Tahsin

    2014-02-01

    In this study, effects of thyme/cumin essential oils (EO) and butylated hydroxyl anisole (BHA)/butylated hydroxyl toluene (BHT) on physicochemical properties and storage stability of chicken patties were compared in different storage periods (0, 3, 7, 14, 21, and 28 d). It was found that there were significant (P < 0.05) differences between physicochemical properties of patty samples treated with EO and the synthetic antioxidants. The EO showed similar performance to those of BHA and BHT in limiting TBARS values of chicken patty samples. Similarity in performance was also the case for microbial stability (total aerobic mesophilic, psychrotrophic, lactic acid, and coliform bacteria as well as molds and yeasts); namely, their effects were significant (P < 0.05). Effect of thyme EO was significant (P < 0.05) and remarkable, not allowing any coliform bacteria to grow in the samples. Given that EO were obtained from natural sources, the data suggested that the EO might be more useful than their synthetic counterparts, BHA and BHT, as additives for chicken patties to maintain oxidative/microbial stability and increase shelf life.

  11. Chemoenzymatic collective synthesis of optically active hydroxyl(methyl)tetrahydronaphthalene-based bioactive terpenoids.

    PubMed

    Batwal, Ramesh U; Argade, Narshinha P

    2015-12-14

    Starting from succinic anhydride and 2-methylanisole, a chemoenzymatic collective formal/total synthesis of several optically active tetrahydronaphthalene based bioactive natural products has been presented via advanced level common precursors; the natural product and antipode (-)/(+)-aristelegone B. Regioselective benzylic oxidations, stereoselective introduction of hydroxyl groups at the α-position of ketone moiety in syn-orientation, efficient enzymatic resolutions with high enantiomeric purity, stereoselective reductions, samarium iodide induced deoxygenations and tandem acylation-Wittig reactions without racemization and/or eliminative aromatization were the key features. An attempted diastereoselective synthesis of (±)-vallapin has also been described.

  12. Aflatoxins, hydroxylated metabolites, and aflatoxicol from breast muscle of laying hens.

    PubMed

    Díaz-Zaragoza, M; Carvajal-Moreno, M; Méndez-Ramírez, I; Chilpa-Galván, N C; Avila-González, E; Flores-Ortiz, C M

    2014-12-01

    Aflatoxins (AF) are toxic fungal secondary metabolites that are pathological to animals and humans. This study identified and quantified AF (AFB(1), AFB(2), AFG(1), AFG(2)) and their hydroxylated metabolites (AFM(1), AFM(2), AFP(1)) and aflatoxicol (AFL) from laying hen breast muscles. Aflatoxins pass from cereal feed to the laying hen tissues, causing economic losses, and from there to humans. To detect the passage of AF from feed to hen breast muscle tissues, an experiment that included 25 Hy-Line W36 121-wk-old hens was performed for 8 d. Hens in individual cages were distributed into 3 groups: a control group, with feed free of AFB(1), and 2 experimental groups, with feed spiked with 2 AFB(1) dosages: 30 µg·kg(-1) (low) or 500 µg·kg(-1) (high). The daily feed consumption per hen was recorded and afterward hens were euthanized and breast muscles were collected, weighed, and dried individually. Aflatoxins were extracted by 2 chemical methods and quantified by HPLC. Both methods were validated by lineality (calibration curves), recovery percentage (>80%), limit of detection, and limit of quantification. The AF (µg·kg(-1)) averages recovered in control breast muscles were as follows: AFB(1) (18); AFG(1), AFM(2), and AFL (0); AFG(2) (1.3); AFM(1) (52), and AFP1 (79). Hens fed with feed spiked with 30 µg·kg(-1) of AFB(1) had AFG(1) (16); AFG(2) (72); AFM(1) (0); AFM(2) (18); AFP(1) (145); and AFL (5 µg·kg(-1)). Hens with feed spiked with 500 µg·kg(-1) of AFB(1) had AFG(1) (512); AFG(2) (7); AFM(1) (4,775); AFM(2) (0); AFP(1) (661); and AFL (21 µg·kg(-1)). The best AF extraction method was Qian and Yang's method, modified by adding additional AF from both Supelclean LC18 SPE columns; its limit of detection (0.5 ng·mL(-1)) was lower compared with that of Koeltzow and Tanner, which was 1 ng·mL(-1).

  13. Hydroxyl Radical (OH•) Reaction with Guanine in an Aqueous Environment: A DFT Study

    PubMed Central

    Kumar, Anil; Pottiboyina, Venkata; Sevilla, Michael D.

    2011-01-01

    The reaction of hydroxyl radical (OH•) with DNA accounts for about half of radiation-induced DNA damage in living systems. Previous literature reports point out that the reaction of OH• with DNA proceeds mainly through the addition of OH• to the C=C bond of the DNA bases. However, recently it has been reported that the principal reaction of OH• with dGuo (deoxyguanosine) is the direct hydrogen atom abstraction from its exocyclic amine group rather than addition of OH• to the C=C bond. In the present work, these two reaction pathways of OH• attack on guanine (G) in the presence of water molecules (aqueous environment) are investigated using the density functional theory (DFT) B3LYP method with 6-31G* and 6-31++G** basis sets. The calculations show that the initial addition of the OH• at C4=C5 double bond of guanine is barrier free and the adduct radical (G-OH•) has only a small activation barrier of ca. 1 – 6 kcal/mol leading to the formation of a metastable ion-pair intermediate (G•+---OH−). The formation of ion-pair is a result of the highly oxidizing nature of the OH• in aqueous media. The resulting ion-pair (G•+---OH−) deprotonates to form H2O and neutral G radicals favoring G(N1-H)• with an activation barrier of ca. 5 kcal/mol. The overall process from the G(C4)-OH• (adduct) to G(N1-H)• and water is found to be exothermic in nature by more than 13 kcal/mol. (G-OH•), (G•+---OH−), and G(N1-H)• were further characterized by the CAM-B3LYP calculations of their UV-visible spectra and good agreement between theory and experiment is achieved. Our calculations for the direct hydrogen abstraction pathway from N1 and N2 sites of guanine by the OH• show that this is also a competitive route to produce G(N2-H)•, G(N1-H)• and H2O. PMID:22050033

  14. Aqueous-phase oxidation of green leaf volatiles by hydroxyl radical as a source of SOA: Product identification from methyl jasmonate and methyl salicylate oxidation

    NASA Astrophysics Data System (ADS)

    Hansel, Amie K.; Ehrenhauser, Franz S.; Richards-Henderson, Nicole K.; Anastasio, Cort; Valsaraj, Kalliat T.

    2015-02-01

    Green leaf volatiles (GLVs) are a group of biogenic volatile organic compounds (BVOCs) released into the atmosphere by vegetation. BVOCs produce secondary organic aerosol (SOA) via gas-phase reactions, but little is known of their aqueous-phase oxidation as a source of SOA. GLVs can partition into atmospheric water phases, e.g., fog, mist, dew or rain, and be oxidized by hydroxyl radicals (˙OH). These reactions in the liquid phase also lead to products that have higher molecular weights, increased polarity, and lower vapor pressures, ultimately forming SOA after evaporation of the droplet. To examine this process, we investigated the aqueous, ˙OH-mediated oxidation of methyl jasmonate (MeJa) and methyl salicylate (MeSa), two GLVs that produce aqueous-phase SOA. High performance liquid chromatography/electrospray ionization mass spectrometry (HPLC-ESI-MS) was used to monitor product formation. The oxidation products identified exhibit higher molecular mass than their parent GLV due to either dimerization or the addition of oxygen and hydroxyl functional groups. The proposed structures of potential products are based on mechanistic considerations combined with the HPLC/ESI-MS data. Based on the structures, the vapor pressure and the Henry's law constant were estimated with multiple methods (SPARC, SIMPOL, MPBPVP, Bond and Group Estimations). The estimated vapor pressures of the products identified are significantly (up to 7 orders of magnitude) lower than those of the associated parent compounds, and therefore, the GLV oxidation products may remain as SOA after evaporation of the water droplet. The contribution of the identified oxidation products to SOA formation is estimated based on measured HPLC-ESI/MS responses relative to previous aqueous SOA mass yield measurements.

  15. Biological role of prolyl 3-hydroxylation in type IV collagen.

    PubMed

    Pokidysheva, Elena; Boudko, Sergei; Vranka, Janice; Zientek, Keith; Maddox, Kerry; Moser, Markus; Fässler, Reinhard; Ware, Jerry; Bächinger, Hans Peter

    2014-01-07

    Collagens constitute nearly 30% of all proteins in our body. Type IV collagen is a major and crucial component of basement membranes. Collagen chains undergo several posttranslational modifications that are indispensable for proper collagen function. One of these modifications, prolyl 3-hydroxylation, is accomplished by a family of prolyl 3-hydroxylases (P3H1, P3H2, and P3H3). The present study shows that P3H2-null mice are embryonic-lethal by embryonic day 8.5. The mechanism of the unexpectedly early lethality involves the interaction of non-3-hydroxylated embryonic type IV collagen with the maternal platelet-specific glycoprotein VI (GPVI). This interaction results in maternal platelet aggregation, thrombosis of the maternal blood, and death of the embryo. The phenotype is completely rescued by producing double KOs of P3H2 and GPVI. Double nulls are viable and fertile. Under normal conditions, subendothelial collagens bear the GPVI-binding sites that initiate platelet aggregation upon blood exposure during injuries. In type IV collagen, these sites are normally 3-hydroxylated. Thus, prolyl 3-hydroxylation of type IV collagen has an important function preventing maternal platelet aggregation in response to the early developing embryo. A unique link between blood coagulation and the ECM is established. The newly described mechanism may elucidate some unexplained fetal losses in humans, where thrombosis is often observed at the maternal/fetal interface. Moreover, epigenetic silencing of P3H2 in breast cancers implies that the interaction between GPVI and non-3-hydroxylated type IV collagen might also play a role in the progression of malignant tumors and metastasis.

  16. Redox regulation of protein tyrosine phosphatase activity by hydroxyl radical.

    PubMed

    Meng, Fan-Guo; Zhang, Zhong-Yin

    2013-01-01

    Substantial evidence suggests that transient production of reactive oxygen species (ROS) such as hydrogen peroxide (H(2)O(2)) is an important signaling event triggered by the activation of various cell surface receptors. Major targets of H(2)O(2) include protein tyrosine phosphatases (PTPs). Oxidation of the active site Cys by H(2)O(2) abrogates PTP catalytic activity, thereby potentially furnishing a mechanism to ensure optimal tyrosine phosphorylation in response to a variety of physiological stimuli. Unfortunately, H(2)O(2) is poorly reactive in chemical terms and the second order rate constants for the H(2)O(2)-mediated PTP inactivation are ~10M(-1)s(-1), which is too slow to be compatible with the transient signaling events occurring at the physiological concentrations of H(2)O(2). We find that hydroxyl radical is produced from H(2)O(2) solutions in the absence of metal chelating agent by the Fenton reaction. We show that the hydroxyl radical is capable of inactivating the PTPs and the inactivation is active site directed, through oxidation of the catalytic Cys to sulfenic acid, which can be reduced by low molecular weight thiols. We also show that hydroxyl radical is a kinetically more efficient oxidant than H(2)O(2) for inactivating the PTPs. The second-order rate constants for the hydroxyl radical-mediated PTP inactivation are at least 2-3 orders of magnitude higher than those mediated by H(2)O(2) under the same conditions. Thus, hydroxyl radical generated in vivo may serve as a more physiologically relevant oxidizing agent for PTP inactivation. This article is part of a Special Issue entitled: Chemistry and mechanism of phosphatases, diesterases and triesterases.

  17. Formation of long-lived hydroxyl free radical adducts of proline and hydroxyproline in a Fenton reaction.

    PubMed

    Floyd, R A; Nagy, I

    1984-10-09

    Proline and hydroxyproline when exposed to the hydroxyl free radical generating system of ADP-Fe(II)-H2O2 yielded long-lived free radicals. An analysis of the electron paramagnetic resonance spectra of the long-lived hydroxyl free radical adducts of proline and hydroxyproline is consistent with a free electron on a nitroxyl group interacting with the nitrogen atom as well as with three separate protons. In the case of proline, nitroxide formation was observed under the influence of tert-butyl-hydroperoxide, giving a similar EPR spectrum (Lin, J.S., Tom, T.C. and Olcott, H.S. (1974) J. Agr. Food Chem. 22, 526-528); however, the hydroxyl free radical adduct of hydroxyproline has not been described yet. In the case of the proline nitroxide radical, two of the three protons involved interact with the free electron equivalently. The coupling constants for the hydroxyl free radical adduct of proline are AN = 1.58 mT, AH1 beta = AH2 beta = 2.13 mT, AH3 beta = 1.77 mT and for hydroxyproline are AN = 1.54 mT, AH1 beta = 2.56 mT, AH2 beta = 2.03 and AH3 beta = 1.51. The data are consistent with the amine nitrogen of proline and hydroxyproline being oxidized to a nitroxyl group and the free electron of the nitroxyl interacting with the beta-protons of these amino acid hydroxyl free radical adducts.

  18. CYP3A7*1C allele is associated with reduced levels of 2-hydroxylation pathway oestrogen metabolites

    PubMed Central

    Sood, Deepti; Johnson, Nichola; Jain, Pooja; Siskos, Alexandros P; Bennett, Mark; Gilham, Clare; Busana, Marta Cecilia; Peto, Julian; dos-Santos-Silva, Isabel; Keun, Hector C; Fletcher, Olivia

    2017-01-01

    Background: Endogenous sex hormones are well-established risk factors for breast cancer; the contribution of specific oestrogen metabolites (EMs) and/or ratios of specific EMs is less clear. We have previously identified a CYP3A7*1C allele that is associated with lower urinary oestrone (E1) levels in premenopausal women. The purpose of this analysis was to determine whether this allele was associated with specific pathway EMs. Methods: We measured successfully 12 EMs in mid-follicular phase urine samples from 30 CYP3A7*1C carriers and 30 non-carriers using HPLC-MS/MS. Results: In addition to having lower urinary E1 levels, CYP3A7*1C carriers had significantly lower levels of four of the 2-hydroxylation pathway EMs that we measured (2-hydroxyestrone, P=1.1 × 10−12; 2-hydroxyestradiol, P=2.7 × 10−7; 2-methoxyestrone, P=1.9 × 10−12; and 2-methoxyestradiol, P=0.0009). By contrast, 16α-hydroxylation pathway EMs were slightly higher in carriers and significantly so for 17-epiestriol (P=0.002). Conclusions: The CYP3A7*1C allele is associated with a lower urinary E1 levels, a more pronounced reduction in 2-hydroxylation pathway EMs and a lower ratio of 2-hydroxylation:16α-hydroxylation EMs in premenopausal women. To further characterise the association between parent oestrogens, EMs and subsequent risk of breast cancer, characterisation of additional genetic variants that influence oestrogen metabolism and large prospective studies of a broad spectrum of EMs will be required. PMID:28072767

  19. Food additives

    MedlinePlus

    ... or natural. Natural food additives include: Herbs or spices to add flavor to foods Vinegar for pickling ... Certain colors improve the appearance of foods. Many spices, as well as natural and man-made flavors, ...

  20. Ability of TiO2(110) Surface to Be Fully Hydroxylated and Fully Reduced

    SciTech Connect

    Wang, Zhitao; Garcia, Juan C.; Deskins, N. A.; Lyubinetsky, Igor

    2015-08-06

    Many TiO2 applications (e.g., in heterogeneous catalysis) involve contact with ambient atmosphere and/or water. The resulting hydroxylation can significantly alter its surface properties. While behavior of single, isolated OH species on the model metal oxide surface of rutile TiO2(110) is relatively well understood, much less is known regarding highly-hydroxylated surfaces and/or whether TiO2(110) could be fully-hydroxylated under ultra-high vacuum conditions. Here we report in situ formation of a well-ordered, fully-hydroxylated TiO2(110)-(1 x 1) surface using an enhanced photochemical approach, key parts of which are pre-dosing of water and multi-step dissociative adsorption and subsequent photolysis of the carboxylic (trimethyl acetic) acid. Combining scanning tunneling microscopy, ultra-violet photoelectron spectroscopy and density functional theory results, we show that the attained “super OH” surface is also fully-reduced, as a result of the photochemical trapping of electrons at the OH groups.

  1. CYP153A6, a Soluble P450 Oxygenase Catalyzing Terminal-Alkane Hydroxylation

    PubMed Central

    Funhoff, Enrico G.; Bauer, Ulrich; García-Rubio, Inés; Witholt, Bernard; van Beilen, Jan B.

    2006-01-01

    The first and key step in alkane metabolism is the terminal hydroxylation of alkanes to 1-alkanols, a reaction catalyzed by a family of integral-membrane diiron enzymes related to Pseudomonas putida GPo1 AlkB, by a diverse group of methane, propane, and butane monooxygenases and by some membrane-bound cytochrome P450s. Recently, a family of cytoplasmic P450 enzymes was identified in prokaryotes that allow their host to grow on aliphatic alkanes. One member of this family, CYP153A6 from Mycobacterium sp. HXN-1500, hydroxylates medium-chain-length alkanes (C6 to C11) to 1-alkanols with a maximal turnover number of 70 min−1 and has a regiospecificity of ≥95% for the terminal carbon atom position. Spectroscopic binding studies showed that C6-to-C11 aliphatic alkanes bind in the active site with Kd values varying from ∼20 nM to 3.7 μM. Longer alkanes bind more strongly than shorter alkanes, while the introduction of sterically hindering groups reduces the affinity. This suggests that the substrate-binding pocket is shaped such that linear alkanes are preferred. Electron paramagnetic resonance spectroscopy in the presence of the substrate showed the formation of an enzyme-substrate complex, which confirmed the binding of substrates observed in optical titrations. To rationalize the experimental observations on a molecular scale, homology modeling of CYP153A6 and docking of substrates were used to provide the first insight into structural features required for terminal alkane hydroxylation. PMID:16816194

  2. CYP153A6, a soluble P450 oxygenase catalyzing terminal-alkane hydroxylation.

    PubMed

    Funhoff, Enrico G; Bauer, Ulrich; García-Rubio, Inés; Witholt, Bernard; van Beilen, Jan B

    2006-07-01

    The first and key step in alkane metabolism is the terminal hydroxylation of alkanes to 1-alkanols, a reaction catalyzed by a family of integral-membrane diiron enzymes related to Pseudomonas putida GPo1 AlkB, by a diverse group of methane, propane, and butane monooxygenases and by some membrane-bound cytochrome P450s. Recently, a family of cytoplasmic P450 enzymes was identified in prokaryotes that allow their host to grow on aliphatic alkanes. One member of this family, CYP153A6 from Mycobacterium sp. HXN-1500, hydroxylates medium-chain-length alkanes (C6 to C11) to 1-alkanols with a maximal turnover number of 70 min(-1) and has a regiospecificity of > or =95% for the terminal carbon atom position. Spectroscopic binding studies showed that C6-to-C11 aliphatic alkanes bind in the active site with Kd values varying from approximately 20 nM to 3.7 microM. Longer alkanes bind more strongly than shorter alkanes, while the introduction of sterically hindering groups reduces the affinity. This suggests that the substrate-binding pocket is shaped such that linear alkanes are preferred. Electron paramagnetic resonance spectroscopy in the presence of the substrate showed the formation of an enzyme-substrate complex, which confirmed the binding of substrates observed in optical titrations. To rationalize the experimental observations on a molecular scale, homology modeling of CYP153A6 and docking of substrates were used to provide the first insight into structural features required for terminal alkane hydroxylation.

  3. Influence of surface hydroxylation on 3-aminopropyltriethoxysilane growth mode during chemical functionalization of GaN Surfaces: an angle-resolved X-ray photoelectron spectroscopy Study.

    PubMed

    Arranz, A; Palacio, C; García-Fresnadillo, D; Orellana, G; Navarro, A; Muñoz, E

    2008-08-19

    A comparative study of the chemical functionalization of undoped, n- and p-type GaN layers grown on sapphire substrates by metal-organic chemical vapor deposition was carried out. Both types of samples were chemically functionalized with 3-aminopropyltriethoxysilane (APTES) using a well-established silane-based approach for functionalizing hydroxylated surfaces. The untreated surfaces as well as those modified by hydroxylation and APTES deposition were analyzed using angle-resolved X-ray photoelectron spectroscopy. Strong differences were found between the APTES growth modes on n- and p-GaN surfaces that can be associated with the number of available hydroxyl groups on the GaN surface of each sample. Depending on the density of surface hydroxyl groups, different mechanisms of APTES attachment to the GaN surface take place in such a way that the APTES growth mode changes from a monolayer to a multilayer growth mode when the number of surface hydroxyl groups is decreased. Specifically, a monolayer growth mode with a surface coverage of approximately 78% was found on p-GaN, whereas the formation of a dense film, approximately 3 monolayers thick, was observed on n-GaN.

  4. Tribological properties of novel imidazolium ionic liquids bearing benzotriazole group as the antiwear/anticorrosion additive in poly(ethylene glycol) and polyurea grease for steel/steel contacts.

    PubMed

    Cai, Meirong; Liang, Yongmin; Zhou, Feng; Liu, Weimin

    2011-12-01

    The imidazolium ionic liquids (ILs) bearing benzotriazole group were synthesized and evaluated as antiwear (AW) and anticorrosion additive in poly(ethylene glycol) (PEG) and polyurea grease for steel/steel contacts at room temperature and 150 °C. The physical properties of the synthetic ILs and PEG with the additive were measured. The anticorrosion property of the synthetic ILs was assessed via the accelerated corrosion test and copper strip corrosion test, which reveals the excellent anticorrosion properties in comparison with pure PEG and the selected conventional ILs having no benzotriazole group. Tribological results indicated that these ILs as the additives could effectively reduce friction and wear of sliding pairs in PEG and also in polyurea grease. The tribological properties were generally better than the normally used zincdialkyldithiophosphate-based additive package (T204) in polyurea grease. The wear mechanisms are tentatively discussed according to the morphology observation of worn surfaces of steel discs by scanning electron microscope (SEM) and the surface composition analysis by X-ray photoelectron spectroscopy (XPS).

  5. The effect of addition of low dose fentanyl to epidural bupivacaine (0.5%) in patients undergoing elective caesarean section: A randomized, parallel group, double blind, placebo controlled study

    PubMed Central

    Parate, LH; Manjrekar, SP; Anandaswamy, TC; Manjunath, B

    2015-01-01

    Background: Opioids have synergistic action with local anesthetics which may alter characteristics of epidural block. Giving opioids to mother before delivery of baby is still fully not accepted with some fearing risk of neonatal depression. Aims: Our primary aim was to evaluate the analgesic effect of addition of 50 μg fentanyl to epidural 0.5% bupivacaine in patients undergoing elective caesarean section using visual analog scale. The secondary aim was to assess onset of analgesia, volume of drug required to achieve T6 level, grade and duration of motor block and Apgar score. Materials and Methods: In this prospective, randomized, double blind, placebo controlled study 64 patients scheduled for elective caesarean section under epidural anesthesia were randomly divided into two groups of 32 each. The fentanyl group received 1ml of 50 μg fentanyl and the saline group received 1ml of normal saline mixed with 10ml of 0.5% bupivacaine for epidural anesthesia. VAS score, time to achieve T6 level, dose of bupivacaine, intraoperative analgesic consumption and duration of analgesia, grade and duration of motor block and any adverse maternal and neonatal effects were noted. Statistical Analysis: Data was analyzed using Students t test, chi-square test and Mann-Whitney U-test. The values of P < 0.05 were considered statistically significant. Results: Fentanyl improved the VAS score significantly (1.6 ± 1.32) compared to the saline group (3.77 ± 1.0, P < 0.0001). It also reduced the intraoperaitve analgesic supplementation compared to the saline group. (P = 0.031). The postoperative duration of analgesia was prolonged in the fentanyl group (275.80 ± 13.61 min) compared to the saline group (191.47 ± 12.16 min, P < 0.0001). The other characteristics of epidural block were unaltered. Conclusion: Addition of 50 μg fentanyl to epidural 0.5% bupivacaine significantly reduces the VAS score. It also reduces intra-operative analgesia supplementation and prolongs the duration

  6. Do carboximide-carboxylic acid combinations form co-crystals? The role of hydroxyl substitution on the formation of co-crystals and eutectics.

    PubMed

    Kaur, Ramanpreet; Gautam, Raj; Cherukuvada, Suryanarayan; Guru Row, Tayur N

    2015-05-01

    Carboxylic acids, amides and imides are key organic systems which provide understanding of molecular recognition and binding phenomena important in biological and pharmaceutical settings. In this context, studies of their mutual interactions and compatibility through co-crystallization may pave the way for greater understanding and new applications of their combinations. Extensive co-crystallization studies are available for carboxylic acid/amide combinations, but only a few examples of carboxylic acid/imide co-crystals are currently observed in the literature. The non-formation of co-crystals for carboxylic acid/imide combinations has previously been rationalized, based on steric and computed stability factors. In the light of the growing awareness of eutectic mixtures as an alternative outcome in co-crystallization experiments, the nature of various benzoic acid/cyclic imide combinations is established in this paper. Since an additional functional group can provide sites for new intermolecular inter-actions and, potentially, promote supramolecular growth into a co-crystal, benzoic acids decorated with one or more hydroxyl groups have been systematically screened for co-crystallization with one unsaturated and two saturated cyclic imides. The facile formation of an abundant number of hydroxybenzoic acid/cyclic carboximide co-crystals is reported, including polymorphic and variable stoichiometry co-crystals. In the cases where co-crystals did not form, the combinations are shown invariably to result in eutectics. The presence or absence and geometric disposition of hydroxyl functionality on benzoic acid is thus found to drive the formation of co-crystals or eutectics for the studied carboxylic acid/imide combinations.

  7. Two-point time-series measurementsof hydroxyl concentration in a turbulent nonpremixed flame.

    PubMed

    Zhang, Jiayao; King, Galen B; Laurendeau, Normand M; Renfro, Michael W

    2007-08-10

    Quantitative two-point hydroxyl time-series measurements have been performed in a turbulent nonpremixed flame by using two-point picosecond time-resolved laser-induced fluorescence. The current diagnostic system has been improved from its preliminary version to address optical aberrations and fluorescence lifetime fluctuations. In particular, with a newly designed collection system, the aberration-limited blur spot is reduced from 6 mm to 180 microm. Additional photon-counting channels enable the recovery of absolute OH concentrations through a triple-bin integration method. The present research represents what we believe to be the first application of this two-point technique to turbulent flames. Two independent schemes have been applied to remove uncorrelated noise in the derived two-point statistics. We show that optical aberrations can have a significant effect on space-time correlations. However, the sampling rate and fluctuations in the fluorescence lifetime barely affect the spatial autocorrelation function and thus the integral length scale. Such length scales for hydroxyl are found to rise linearly with increasing axial distance at peak [OH] locations. Along the jet centerline, the integral length scale varies slightly below the flame tip but increases rapidly above the flame tip. In addition, the OH length scale demonstrates the same trend as the OH time scale along the jet centerline, but the opposite trend at peak [OH] locations.

  8. Nanoscale hydroxyl radical generation from multiphoton ionization of tryptophan.

    PubMed

    Bisby, Roger H; Crisostomo, Ana G; Botchway, Stanley W; Parker, Anthony W

    2009-01-01

    Exposure of solutions containing both tryptophan and hydrogen peroxide to a pulsed ( approximately 180 fs) laser beam at 750 nm induces luminescence characteristic of 5-hydroxytryptophan. The results indicate that 3-photon excitation of tryptophan results in photoionization within the focal volume of the laser beam. The resulting hydrated electron is scavenged by hydrogen peroxide to produce the hydroxyl radical. The latter subsequently reacts with tryptophan to form 5-hydroxytryptophan. The involvement of hydroxyl radicals is confirmed by the use of ethanol and nitrous oxide as scavengers and their effects on the fluorescence yield in this system. It is postulated that such multiphoton ionization of tryptophanyl residues in cellular proteins may contribute to the photodamage observed during imaging of cells and tissues using multiphoton microscopy.

  9. Twilight Intensity Variation of the Infrared Hydroxyl Airglow

    NASA Technical Reports Server (NTRS)

    Lowe, R. P.; Gilbert, K. L.; Niciejewski, R. J.

    1984-01-01

    The vibration rotation bands of the hydroxyl radical are the strongest features in the night airglow and are exceeded in intensity in the dayglow only by the infrared atmospheric bands of oxygen. The variation of intensity during evening twilight is discussed. Using a ground-based Fourier Transform Spectrometer (FTS), hydroxyl intensity measurements as early as 3 deg solar depression were made. Models of the twilight behavior show that this should be sufficient to provide measurement of the main portion of the twilight intensity change. The instrument was equipped with a liquid nitrogen-cooled germanium detector whose high sensitivity combined with the efficiency of the FTS technique permits spectra of the region 1.1 to 1.6 microns at high signal-to-noise to be obtained in two minutes. The use of a polarizer at the entrance aperture of the instrument reduces the intensity of scattered sunlight by a factor of at least ten for zenith observations.

  10. Hydroxylated polychlorinated biphenyls in the environment: sources, fate, and toxicities.

    PubMed

    Tehrani, Rouzbeh; Van Aken, Benoit

    2014-05-01

    Hydroxylated polychlorinated biphenyls (OH-PCBs) are produced in the environment by the oxidation of PCBs through a variety of mechanisms, including metabolic transformation in living organisms and abiotic reactions with hydroxyl radicals. As a consequence, OH-PCBs have been detected in a wide range of environmental samples, including animal tissues, water, and sediments. OH-PCBs have recently raised serious environmental concerns because they exert a variety of toxic effects at lower doses than the parent PCBs and they are disruptors of the endocrine system. Although evidence about the widespread dispersion of OH-PCBs in various compartments of the ecosystem has accumulated, little is currently known about their biodegradation and behavior in the environment. OH-PCBs are, today, increasingly considered as a new class of environmental contaminants that possess specific chemical, physical, and biological properties not shared with the parent PCBs. This article reviews recent findings regarding the sources, fate, and toxicities of OH-PCBs in the environment.

  11. Hydroxylated biphenyls as tyrosinase inhibitor: A spectrophotometric and electrochemical study.

    PubMed

    Ruzza, Paolo; Serra, Pier Andrea; Fabbri, Davide; Dettori, Maria Antonietta; Rocchitta, Gaia; Delogu, Giovanna

    2017-01-27

    A small collection of C2-symmetry hydroxylated biphenyls was prepared by straightforward methods and the capability to act as inhibitors of tyrosinase has been evaluated by both spectrophotometric and electrochemical assays. Our attention was focused on the diphenolase activity of this enzyme characterized by the absence of the characteristic lag time of enzymatic reaction of its monophenolase activity. To this purpose, we evaluated the capability of tyrosinase to oxidize a natural o-diphenol substrate to o-quinone analyzing the changes in the UV-Vis spectrum of a solution of caffeic acid and the reduction of the cathodic current in a tyrosinase-biosensor, respectively. Results of both the methods were comparable. Most of the compounds possessed higher inhibitory activity compared to compound 1, a known hydroxylated biphenyl inhibitor of tyrosinase.

  12. Novel denture-cleaning system based on hydroxyl radical disinfection.

    PubMed

    Kanno, Taro; Nakamura, Keisuke; Ikai, Hiroyo; Hayashi, Eisei; Shirato, Midori; Mokudai, Takayuki; Iwasawa, Atsuo; Niwano, Yoshimi; Kohno, Masahiro; Sasaki, Keiichi

    2012-01-01

    The purpose of this study was to evaluate a new denture-cleaning device using hydroxyl radicals generated from photolysis of hydrogen peroxide (H2O2). Electron spin resonance analysis demonstrated that the yield of hydroxyl radicals increased with the concentration of H2O2 and light irradiation time. Staphylococcus aureus, Pseudomonas aeruginosa, and methicillin-resistant S aureus were killed within 10 minutes with a > 5-log reduction when treated with photolysis of 500 mM H2O2; Candida albicans was killed within 30 minutes with a > 4-log reduction with photolysis of 1,000 mM H2O2. The clinical test demonstrated that the device could effectively reduce microorganisms in denture plaque by approximately 7-log order within 20 minutes.

  13. An evaluation of atomic and molecular mixture rules and group additivity concepts for the estimation of radiation absorption by long-chained, saturated hydrocarbons at vacuum UV and soft X-ray energies

    NASA Astrophysics Data System (ADS)

    Au, Jennifer W.; Cooper, Glyn; Burton, Gordon R.; Brion, C. E.

    1994-10-01

    The feasibility of using atomic and molecular mixture rules as well as group additivity concepts for predicting valence shell photoabsorption oscillator strengths (cross sections) for long-chained alkane molecules has been investigated over a wide energy range from 18 to 220 eV. The predictions are discussed with reference to recently reported experimental measurements (Chem. Phys. 173 (1993) 209) for normal alkanes, C nH 2 n+2 ( n=1-8). Atomic mixture rules based on either theoretical or experimental atomic oscillator strength sums are found to be unsatisfactory, giving very large errors at most photon energies. A wide range of molecular mixture rules based on linear combinations of measured oscillator strength values for small 'component' alkane molecules and molecular hydrogen have also been evaluated. Although good agreement with experiment is obtained with some linear combinations, many others result in substantial errors. Molecular mixture rules constructed using oscillator strength for larger component alkanes generally give better estimates of the experimentally measured data; however, since no other a priori physical or chemical reasons can be advanced for any particular choice of molecular mixture rule, this procedure is unsatisfactory for general application. In contrast, a group additivity procedure based on oscillator strength estimates for the methylene (CH 2) and methyl (CH 3) alkane group fragments, derived entirely from the photoabsorption measurements for lower alkanes, provides excellent agreement with the measured oscillator strengths for C 8H 18 over the entire energy range studied (18-220 eV). The absolute photoabsorption group oscillator strengths derived for the CH 2 and CH 3 fragments should be applicable to assessing the contributions from saturated hydrocarbon groupings to vacuum UV and soft X-ray absorption in larger chemical and biochemical systems.

  14. Effects of bis homoallylic and homoallylic hydroxyl substitution on the olefinic 13C resonance shifts in fatty acid methyl esters.

    PubMed

    Pfeffer, P E; Sonnet, P E; Schwartz, D P; Osman, S F; Weisleder, D

    1992-04-01

    Substitution of a hydroxyl group at the bis homoallylic position (OH group located three carbons away from the olefinic carbon) in C18 unsaturated fatty acid esters (FAE) induces a 0.73 +/- 0.05 ppm upfield and a 0.73 +/- 0.06 ppm downfield shift on the delta and epsilon olefinic 13C resonances relative to the unsubstituted FAE, respectively. If the hydroxyl group is located on the carboxyl side of the double bond of the bis homoallylic hydroxy fatty acid esters (BHAHFA), the olefinic resonances are uniformly shifted apart by [formula: see text] where delta delta dbu represents the absolute value of the double bond resonance separation in the unsubstituted FAE and 1.46 ppm is the sum of the absolute values of the delta and epsilon shift parameters. With hydroxyl substitution on the terminal methyl side of the double bond, the olefinic shift separation is equal to [formula: see text] In homoallylic (OH group located two carbons away from the olefinic carbon) substituted FAE the gamma and delta induced hydroxyl shifts for the cis double bond resonances are +3.08 and -4.63 ppm, respectively while the trans double bond parameters are +4.06 and -4.18 ppm, respectively. The double bond resonance separation in homoallylic hydroxy fatty acid esters (HAHFA) can be calculated from the formula [formula: see text] for cis and [formula: see text] for the trans case when the OH substitution is on the carboxyl side of the double bond. Conversely, when the OH resides on the terminal methyl side, the double bond shift separations for cis and trans isomers are [formula: see text] and [formula: see text] respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

  15. Purification and characterization of a two-component monooxygenase that hydroxylates nitrilotriacetate from "Chelatobacter" strain ATCC 29600.

    PubMed Central

    Uetz, T; Schneider, R; Snozzi, M; Egli, T

    1992-01-01

    An assay based on the consumption of nitrilotriacetate (NTA) was developed to measure the activity of NTA monooxygenase (NTA-Mo) in cell extracts of "Chelatobacter" strain ATCC 29600 and to purify a functional, NTA-hydroxylating enzyme complex. The complex consisted of two components that easily dissociated during purification and upon dilution. Both components were purified to more than 95% homogeneity, and it was possible to reconstitute the functional, NTA-hydroxylating enzyme complex from pure component A (cA) and component B (cB). cB exhibited NTA-stimulated NADH oxidation but was unable to hydroxylate NTA. It had a native molecular mass of 88 kDa and contained flavin mononucleotide (FMN). cA had a native molecular mass of 99 kDa. No catalytic activity has yet been shown for cA alone. Under unfavorable conditions, NADH oxidation was partly or completely uncoupled from hydroxylation, resulting in the formation of H2O2. Optimum hydroxylating activity was found to be dependent on the molar ratio of the two components, the absolute concentration of the enzyme complex, and the presence of FMN. Uncoupling of the reaction was favored in the presence of high salt concentrations and in the presence of flavin adenine dinucleotide. The NTA-Mo complex was sensitive to sulfhydryl reagents, but inhibition was reversible by addition of excess dithiothreitol. The Km values for Mg(2+)-NTA, FMN, and NADH were determined as 0.5 mM, 1.3 microM, and 0.35 mM, respectively. Of 26 tested compounds, NTA was the only substrate for NTA-Mo. Images PMID:1735711

  16. How Do Perfluorinated Alkanoic Acids Elicit Cytochrome P450 to Catalyze Methane Hydroxylation? An MD and QM/MM Study.

    PubMed

    Li, Chunsen; Shaik, Sason

    2013-03-07

    Recent experimental studies show that usage of perfluoro decanoic acid (PFDA), as a dummy substrate, can elicit P450BM3 to perform hydroxylation of small alkanes, such as methane (ref. 17) and propane (ref. 17 and ref. 18). To comprehend the mechanism whereby PFDA operates to potentiate P450BM3 to catalyze the hydroxylation of small alkanes, we used molecular dynamics (MD) and hybrid quantum mechanical / molecular mechanical (QM/MM) calculations. The MD results show that without the PFDA, methane escapes the active site, while the presence of PFDA can potentially induce a productive Cpd I-Methane juxtaposition for rapid oxidation. Nevertheless, when only a single methane molecule is present near the PFDA, it still escapes the pocket within less than a nanosecond. However, when three methane molecules are present in the pocket, they alternate quasi-periodically such that at all times (within 10 ns), a molecule of methane is always present in the proximity of Cpd I in a reactive conformation. Our results further demonstrate that the PFDA does not exert any electrostatic catalysis, whether the PFDA is in the protonated or deprotonated forms. Taken together, we conclude that methane hydroxylation requires, in addition to PFDA, a high partial pressure of methane that will cause a high methane concentration in the active site. Further study of ethane and propane hydroxylations demonstrates that higher alkane concentration is helpful for all the three small alkanes. Thus for the smallest alkane, methane, at least three molecules are necessary whereas for the larger ethane, two molecules are needed to force one ethane to be closer to Cpd I. Finally, for propane a second molecule is helpful but not absolutely necessary; for this molecule the PFDA may well be sufficient to keep propane close to Cpd I for efficient oxidation. We therefore propose that high alkane pressure should assist small alkane hydroxylation by P450 in a manner inversely proportional to the size of the

  17. Solubility constants of hydroxyl sodalite at elevated temperatures evaluated from hydrothermal experiments: Applications to nuclear waste isolation

    DOE PAGES

    Xiong, Yongliang

    2016-09-17

    In this study, solubility constants of hydroxyl sodalite (ideal formula, Na8[Al6Si6O24][OH]2·3H2O) from 25°C to 100°C are obtained by applying a high temperature Al—Si Pitzer model to evaluate solubility data on hydroxyl sodalite in high ionic strength solutions at elevated temperatures. A validation test comparing model-independent experimental data to model predictions demonstrates that the solubility values produced by the model are in excellent agreement with the experimental data. In addition, the equilibrium constants obtained in this study have a wide range of applications, including synthesis of hydroxyl sodalite, de-silication in the Bayer process for extraction of alumina, and the performance ofmore » proposed sodalite waste forms in geological repositories in various lithologies including salt formations. The thermodynamic calculations based on the equilibrium constants obtained in this work indicate that the solubility products in terms of mΣAl×mΣSi for hydroxyl sodalite are very low (e.g., ~10-13 [mol·kg-1]2 at 100°C) in brines characteristic of salt formations, implying that sodalite waste forms would perform very well in repositories located in salt formations. Finally, the information regarding the solubility behavior of hydroxyl sodalite obtained in this study provides guidance to investigate the performance of other pure end-members of sodalite such as chloride- and iodide-sodalite, which may be of interest for geological repositories in various media.« less

  18. Solubility constants of hydroxyl sodalite at elevated temperatures evaluated from hydrothermal experiments: Applications to nuclear waste isolation

    SciTech Connect

    Xiong, Yongliang

    2016-09-17

    In this study, solubility constants of hydroxyl sodalite (ideal formula, Na8[Al6Si6O24][OH]2·3H2O) from 25°C to 100°C are obtained by applying a high temperature Al—Si Pitzer model to evaluate solubility data on hydroxyl sodalite in high ionic strength solutions at elevated temperatures. A validation test comparing model-independent experimental data to model predictions demonstrates that the solubility values produced by the model are in excellent agreement with the experimental data. In addition, the equilibrium constants obtained in this study have a wide range of applications, including synthesis of hydroxyl sodalite, de-silication in the Bayer process for extraction of alumina, and the performance of proposed sodalite waste forms in geological repositories in various lithologies including salt formations. The thermodynamic calculations based on the equilibrium constants obtained in this work indicate that the solubility products in terms of mΣAl×mΣSi for hydroxyl sodalite are very low (e.g., ~10-13 [mol·kg-1]2 at 100°C) in brines characteristic of salt formations, implying that sodalite waste forms would perform very well in repositories located in salt formations. Finally, the information regarding the solubility behavior of hydroxyl sodalite obtained in this study provides guidance to investigate the performance of other pure end-members of sodalite such as chloride- and iodide-sodalite, which may be of interest for geological repositories in various media.

  19. How Do Perfluorinated Alkanoic Acids Elicit Cytochrome P450 to Catalyze Methane Hydroxylation? An MD and QM/MM Study

    PubMed Central

    Li, Chunsen; Shaik, Sason

    2013-01-01

    Recent experimental studies show that usage of perfluoro decanoic acid (PFDA), as a dummy substrate, can elicit P450BM3 to perform hydroxylation of small alkanes, such as methane (ref. 17) and propane (ref. 17 and ref. 18). To comprehend the mechanism whereby PFDA operates to potentiate P450BM3 to catalyze the hydroxylation of small alkanes, we used molecular dynamics (MD) and hybrid quantum mechanical / molecular mechanical (QM/MM) calculations. The MD results show that without the PFDA, methane escapes the active site, while the presence of PFDA can potentially induce a productive Cpd I-Methane juxtaposition for rapid oxidation. Nevertheless, when only a single methane molecule is present near the PFDA, it still escapes the pocket within less than a nanosecond. However, when three methane molecules are present in the pocket, they alternate quasi-periodically such that at all times (within 10 ns), a molecule of methane is always present in the proximity of Cpd I in a reactive conformation. Our results further demonstrate that the PFDA does not exert any electrostatic catalysis, whether the PFDA is in the protonated or deprotonated forms. Taken together, we conclude that methane hydroxylation requires, in addition to PFDA, a high partial pressure of methane that will cause a high methane concentration in the active site. Further study of ethane and propane hydroxylations demonstrates that higher alkane concentration is helpful for all the three small alkanes. Thus for the smallest alkane, methane, at least three molecules are necessary whereas for the larger ethane, two molecules are needed to force one ethane to be closer to Cpd I. Finally, for propane a second molecule is helpful but not absolutely necessary; for this molecule the PFDA may well be sufficient to keep propane close to Cpd I for efficient oxidation. We therefore propose that high alkane pressure should assist small alkane hydroxylation by P450 in a manner inversely proportional to the size of the

  20. Hydroxyl radical scavengers inhibit human lectin-dependent cellular cytotoxicity.

    PubMed

    Melinn, M; McLaughlin, H

    1986-06-01

    The role of oxygen-derived free radicals (ODFR) in lectin-dependent cellular cytotoxicity (LDCC) in humans was investigated. The hydroxyl radical traps thiourea, methanol, ethanol and phenol were effective in inhibiting LDCC, as was DABCO, a singlet oxygen quencher. The proposed pathway of hydroxyl radical production in living cells is either an iron catalysed Haber-Weiss reaction or a Fenton reaction. The effect of inhibitors of these pathways was investigated. The superoxide anion scavengers superoxide dismutase, ferricytochrome c and Tiron were without effect. It was shown that Tiron inhibits the lucigenin-amplified chemiluminescence produced by the action of xanthine oxidase, and also the lucigenin-amplified chemiluminescence produced by activated PMN, suggesting that this agent (Tiron) scavenges intracellular superoxide anion. Catalase gave slight inhibition of LDCC only. The ferric iron chelator desferrioxamine gave no protection of the target cells, while the ferrous chelator, 1,10-phenanthroline, inhibited LDCC and partially prevented the detection of hydroxyl radicals generated by the Fe2+-H2O2 system. Cibacron blue, an agent that inhibits NAD(P)H linked enzymes, also inhibited LDCC. The cyclo-oxygenase inhibitors indomethacin and salicylate were without effect, while the lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA) inhibited cytolysis. None of the LDCC inhibitors was cytotoxic to the effector cells or to the target cells, neither did they inhibit lymphocyte-target binding. The findings would suggest that hydroxyl radicals have a role to play in human T-cell mediated cytolysis, either as the active lytic agent or as an epiphenomenon.

  1. Fuel additives

    SciTech Connect

    Gheysens, J.L.G.

    1990-11-27

    This patent describes a composition for the improvement of hydrocarbon fuels exhibiting a boiling range of gasoline being suitable for use in spark ignition-type engines. It comprises an aromatic amine; a polyaminated detergent; a catalyst comprising a colloidal suspension or amine salt of transition/alkali/alkaline earth metal organic coordinations having at least one metal oxidehydroxide linked to an alkyl chain via a carboxyl group; and a solvent comprising an alkanol-aliphatic ether oxygenated hydrocarbon.

  2. Potlining Additives

    SciTech Connect

    Rudolf Keller

    2004-08-10

    In this project, a concept to improve the performance of aluminum production cells by introducing potlining additives was examined and tested. Boron oxide was added to cathode blocks, and titanium was dissolved in the metal pool; this resulted in the formation of titanium diboride and caused the molten aluminum to wet the carbonaceous cathode surface. Such wetting reportedly leads to operational improvements and extended cell life. In addition, boron oxide suppresses cyanide formation. This final report presents and discusses the results of this project. Substantial economic benefits for the practical implementation of the technology are projected, especially for modern cells with graphitized blocks. For example, with an energy savings of about 5% and an increase in pot life from 1500 to 2500 days, a cost savings of $ 0.023 per pound of aluminum produced is projected for a 200 kA pot.

  3. Addition of cladribine to the standard induction treatment improves outcomes in a subset of elderly acute myeloid leukemia patients. Results of a randomized Polish Adult Leukemia Group (PALG) phase II trial.

    PubMed

    Pluta, Agnieszka; Robak, Tadeusz; Wrzesien-Kus, Agata; Katarzyna Budziszewska, Bozena; Sulek, Kazimierz; Wawrzyniak, Ewa; Czemerska, Magdalena; Zwolinska, Malgorzata; Golos, Aleksandra; Holowiecka-Goral, Aleksandra; Kyrcz-Krzemien, Slawomira; Piszcz, Jaroslaw; Kloczko, Janusz; Mordak-Domagala, Monika; Lange, Andrzej; Razny, Małgorzata; Madry, Krzysztof; Wiktor-Jedrzejczak, Wieslaw; Grosicki, Sebastian; Butrym, Aleksandra; Kuliczkowski, Kazimierz; Warzocha, Krzysztof; Holowiecki, Jerzy; Giebel, Sebastian; Szydlo, Richard; Wierzbowska, Agnieszka

    2017-04-01

    Intensive induction chemotherapy using anthracycline and cytarabine backbone is considered the most effective upfront therapy in physically fit older patients with acute myeloid leukemia (AML). However, outcomes of the standard induction in elderly AML are inferior to those observed in younger patients, and they are still unsatisfactory. As addition of cladribine to the standard induction therapy is known to improve outcome in younger AML patients. The present randomized phase II study compares efficacy and toxicity of the DAC (daunorubicin plus cytarabine plus cladribine) regimen with the standard DA (daunorubicin plus cytarabine) regimen in the newly diagnosed AML patients over 60 years of age. A total of 171 patients were enrolled in the study (DA, 86; DAC, 85). A trend toward higher complete remission (CR) was observed in the DAC arm compared to the DA arm (44% vs. 34%; P = .19), which did not lead to improved median overall survival, which in the case of the DAC group was 8.6 months compared to in 9.1 months in the DA group (P = .64). However, DAC appeared to be superior in the group of patients aged 60-65 (CR rate: DAC 51% vs. DA 29%; P = .02). What is more, a subgroup of patients, with good and intermediate karyotypes, benefited from addition of cladribine also in terms of overall survival (P = .02). No differences in hematological and nonhematological toxicity between the DA and DAC regimens were observed.

  4. Neighboring group participation in the additions of iodonium and bromonium ions to N-alkoxycarbonyl-2-azabicyclo[2.2.n]alk-5-enes (n = 1,2).

    PubMed

    Krow, Grant R; Gandla, Deepa; Guo, Weiwei; Centafont, Ryan A; Lin, Guoliang; DeBrosse, Charles; Sonnet, Philip E; Ross, Charles W; Ramjit, Harri G; Carroll, Patrick J; Cannon, Kevin C

    2008-03-21

    Additions of iodonium-X reagents to N-alkoxycarbonyl-2-azabicyclo[2.2.1]hept-5-enes and the homologous 2-azabicyclo[2.2.2]oct-5-enes have been found to mirror the outcomes of additions of bromonium-X reagents. Only rearranged products were observed for reactions of either of these halonium ion reagents with the azabicylo[2.2.1]hept-5-enes. For the azabicyclo[2.2.2]oct-5-enes, nitrogen participation in addition of IOH or BrOH was dependent on the N-alkoxycarbonyl group. With larger N-Boc, N-Cbz, or N-Troc protecting groups, unrearranged 5-anti-hydroxy-6-syn-I(or Br)-2-azabicyclo[2.2.2]octanes were formed by nucleophilic attack at C(5) on syn-halonium ions. The structure of N-methyl-8-anti-bromo-4-anti-hydroxy-2-azabicyclo[3.2.1]octane has been reassigned by X-ray analysis.

  5. Immunogenicity of mitochondrial DNA modified by hydroxyl radical.

    PubMed

    Alam, Khurshid; Moinuddin; Jabeen, Suraya

    2007-05-01

    Mitochondria consume about 90 percent of oxygen used by the body, and are a particularly rich source of reactive oxygen species (ROS). In this research communication mitochondrial DNA (mtDNA) was isolated from fresh goat liver and modified in vitro by hydroxyl radical generated from UV irradiation (254 nm) of hydrogen peroxide. As a consequence of hydroxyl radical modification, mtDNA showed hyperchromicity and sensitivity to nuclease S1 digestion as compared to control mtDNA. Animals immunized with mtDNA and ROS-modified mtDNA induced antibodies as detected by direct binding and competition ELISA. The data suggest that immunogenicity of mtDNA got augmented after treatment with hydroxyl radical. IgG isolated from immune sera showed specificity for respective immunogen and cross-reaction with other nucleic acids. Binding of induced antibodies with array of antigens clearly indicates their polyspecific nature. Moreover, the polyspecificity exhibited by induced antibodies is unique in view of similar multiple antigen binding properties of naturally occurring anti-DNA antibodies derived from SLE patients.

  6. Two Structures of an N-Hydroxylating Flavoprotein Monooxygenase

    PubMed Central

    Olucha, Jose; Meneely, Kathleen M.; Chilton, Annemarie S.; Lamb, Audrey L.

    2011-01-01

    The ornithine hydroxylase from Pseudomonas aeruginosa (PvdA) catalyzes the FAD-dependent hydroxylation of the side chain amine of ornithine, which is subsequently formylated to generate the iron-chelating hydroxamates of the siderophore pyoverdin. PvdA belongs to the class B flavoprotein monooxygenases, which catalyze the oxidation of substrates using NADPH as the electron donor and molecular oxygen. Class B enzymes include the well studied flavin-containing monooxygenases and Baeyer-Villiger monooxygenases. The first two structures of a class B N-hydroxylating monooxygenase were determined with FAD in oxidized (1.9 Å resolution) and reduced (3.03 Å resolution) states. PvdA has the two expected Rossmann-like dinucleotide-binding domains for FAD and NADPH and also a substrate-binding domain, with the active site at the interface between the three domains. The structures have NADP(H) and (hydroxy)ornithine bound in a solvent-exposed active site, providing structural evidence for substrate and co-substrate specificity and the inability of PvdA to bind FAD tightly. Structural and biochemical evidence indicates that NADP+ remains bound throughout the oxidative half-reaction, which is proposed to shelter the flavin intermediates from solvent and thereby prevent uncoupling of NADPH oxidation from hydroxylated product formation. PMID:21757711

  7. The environmental formation of n-hydroxylated amines

    SciTech Connect

    Spurgeon, C.; Crosby, D. )

    1989-01-01

    Aromatic amines and nitro compounds are used extensively in many industries and because many of these compounds are known or suspected carcinogens they are becoming of increasing concern as environmental pollutants. Although the exact mechanism of the carcinogenic effects of these compounds is not yet fully understood, N-hydroxylation is regarded as an essential step. N-hydroxylated amines are known to be formed metabolically but it is not yet known if N-hydroxylation occurs in the environment or if the arylhydroxylamines are environmentally stable. The authors research focused on the environmental formation of N-hydroxylamines, specifically the formation of N-hydroxy-o-toluidine via the photooxidation in water of o-toluidine or the reduction in soil of 2-nitrotoluene. The photooxidation and reduction products were identified and the rates of formation and stabilities of the major products determined. N-hydroxy-o-toluidine was shown to be unstable in aqueous environments, oxidizing to 2-nitrosotoluene within 24 hours.

  8. 19-Hydroxylation of androgens in the rat brain.

    PubMed Central

    Hahn, E F; Miyairi, S; Fishman, J

    1985-01-01

    Aromatization of androgens in the central nervous system is linked with sexual differentiation of the brain and, thus, determines the nature of sexual behavior and the control of gonadotropin secretion. The process of aromatization, as determined in the human placenta, proceeds through two successive hydroxylations at C-19, the products of which are then virtually completely converted via a third hydroxylation at C-2 to estrogens. We now report that in the rat brain, 19-hydroxylation of androgens greatly exceeds aromatization and the 19-hydroxy- and 19-oxoandrogen products accumulate in quantities 5 times greater than the estrogens. This relationship implies that the aromatization sequence in the brain is deficient in the terminal hydroxylase, and the process is distinct from that in other tissues. The function of 19-hydroxy- and 19-oxotestosterone in the central nervous system is unknown but, unlike the reduced or aromatized metabolites of the male hormone, these substances cannot be delivered from the circulation and their presence in the brain is totally dependent on in situ formation, making them logical candidates for modulators of neuronal functions. PMID:3857612

  9. A spectrofluorimetric study of the 7-hydroxylation of coumarin by liver microsomes.

    PubMed

    Creaven, P J; Parke, D V; Williams, R T

    1965-08-01

    1. The fluorescence characteristics of 3- and 7-hydroxycoumarin, and 7-hydroxy-and 7-methoxy-4-methylcoumarin, have been determined. 7-Hydroxycoumarin shows excited-state ionization from pH1 to 9. 2. A sensitive and specific fluorimetric method for the determination of 7-hydroxycoumarin (umbelliferone), and its application to liver homogenates and other tissue preparations, are described. 3. The enzymic hydroxylation of coumarin to 7-hydroxycoumarin has been studied by this method and the optimum conditions have been determined for rabbit-liver preparations. The enzymic activity was found in the microsomal fraction and required NADPH(2) and oxygen. Activity with NADH(2) was one-third of that with NADPH(2). 4. Addition of NADP was necessary for full activity of 10000g supernatant preparations of liver. Nicotinamide added during preparation preserved coenzymic activity in tissue stored at -12 degrees . Glucose 6-phosphate had no effect on the activity of stored or fresh tissue. 5. Inhibition occurred with p-chloromercuribenzoate, and with the usual inhibitors of the microsomal drug-metabolizing enzymes, SKF acid, SKF 525A, and Lilly 7132, but not with 2,2'-bipyridyl. 6. Liver homogenates from rabbit, guinea pig, coypu, cat and pigeon showed activity, but preparations of rat or mouse liver, and of locust fat bodies, did not hydroxylate coumarin to umbelliferone. The enzyme system was absent from rat-liver homogenates and microsomal preparations. Moreover, rat liver also contained inhibitors of the rabbit-liver coumarin-7-hydroxylase system and of the further metabolism of umbelliferone by guinea-pig liver. Guinea-pig-liver preparations hydroxylated coumarin to umbelliferone and then converted this product into its glucuronide. 7. The coumarin-7-hydroxylase activity of female rabbit liver was two to three times that of male rabbit liver.

  10. Exploring Pd adsorption, diffusion, permeation, and nucleation on bilayer SiO2/Ru as a function of hydroxylation and precursor environment: From UHV to catalyst preparation

    NASA Astrophysics Data System (ADS)

    Pomp, Sascha; Kaden, William E.; Sterrer, Martin; Freund, Hans-Joachim

    2016-10-01

    The hydroxylation-dependent permeability of bilayer SiO2 supported on Ru(0001) was investigated by XPS and TDS studies in a temperature range of 100 K to 600 K. For this, the thermal behavior of Pd evaporated at 100 K, which results in surface and sub-surface (Ru-supported) binding arrangements, was examined relative to the extent of pre-hydroxylation. Samples containing only defect-mediated hydroxyls showed no effect on Pd diffusion through the film at low temperature. If, instead, the concentration of strongly bound hydroxyl groups and associated weakly bound water molecules was enriched by an electron-assisted hydroxylation procedure, the probability for Pd diffusion through the film is decreased via a pore-blocking mechanism. Above room temperature, all samples showed similar behavior, reflective of particle nucleation above the film and eventual agglomeration with any metal atoms initially binding beneath the film. When depositing Pd onto the same SiO2/Ru model support via adsorption of [Pd(NH3)4]Cl2 from alkaline (pH 12) precursor solution, we observe notably different adsorption and nucleation mechanisms. The resultant Pd adsorption complexes follow established decomposition pathways to produce model catalyst systems compatible with those created exclusively within UHV despite lacking the ability to penetrate the film due to the increased size of the initial Pd precursor groups.

  11. Radical addition-initiated domino reactions of conjugated oxime ethers.

    PubMed

    Ueda, Masafumi

    2014-01-01

    The application of conjugated oxime ethers to the synthesis of complex chemical scaffolds using domino radical reactions has been described in detail. The triethylborane-mediated hydroxysulfenylation reaction allows for the regioselective construction of a carbon-sulfur bond and a carbon-oxygen bond in a single operation for the formation of β-hydroxy sulfides. This reaction proceeds via a radical pathway involving regioselective thiyl addition and the subsequent trapping of the resulting α-imino radical with O₂, where the imino group enhances the stability of the intermediate radical. Hydroxyalkylation reactions that occur via a carbon radical addition reaction followed by the hydroxylation of the resulting N-borylenamine with O₂ have also been developed. We investigated sequential radical addition aldol-type reactions in detail to explore the novel domino reactions that occur via the generation of N-borylenamine. The radical reaction of a conjugated oxime ether with triethylborane in the presence of an aldehyde affords γ-butyrolactone via sequential processes including ethyl radical addition, the generation of N-borylenamine, an aldol-type reaction with an aldehyde, and a lactonization reaction. A novel domino reaction has also been developed involving the [3,3]-sigmatropic rearrangement of N-boryl-N-phenoxyenamine. The triethylborane-mediated domino reactions of O-phenyl-conjugated oxime ethers afforded the corresponding benzofuro[2,3-b]pyrrol-2-ones via a radical addition/[3,3]-sigmatropic rearrangement/cyclization/lactamization cascade.

  12. Inhibition of Cytochromes P450 and the Hydroxylation of 4-Monochlorobiphenyl in Whole Poplar

    PubMed Central

    Zhai, Guangshu; Lehmler, Hans-Joachim; Schnoor, Jerald L.

    2013-01-01

    Cytochromes P450 (CYPs) are potential enzymes responsible for hydroxylation of many xenobiotics and endogenous chemicals in living organisms. It has been found that 4-monochlorobiphenyl (PCB3), mainly an airborne pollutant, can be metabolized to hydroxylated transformation products (OH-PCB3s) in whole poplars. However, the enzymes involved in the hydroxylation of PCB3 in whole poplars have not been identified. Therefore, two CYP suicide inhibitors, 1-aminobenzotriazole (ABT) and 17-octadecynoic acid (ODYA), were selected to probe the hydroxylation reaction of PCB3 in whole poplars in this work. Poplars (Populus deltoides × nigra, DN34) were exposed to PCB3 with or without inhibitor for 11 days. Results showed both ABT and ODYA can decrease the concentrations and yields of five OH-PCB3s in different poplar parts via the inhibition of CYPs. Furthermore, both ABT and ODYA demonstrated a dose-dependent relationship to the formation of OH-PCB3s in whole poplars. The higher the inhibitor concentrations, the lower the total yields of OH-PCB3s. For ABT spiked-additions, the total mass yield of five OH-PCB3s was inhibited by a factor of 1.6 times at an ABT concentration of 2.5 mg L−1, 4.0 times at 12.5 mg L−1, and 7.0 times at 25 mg L−1. For the inhibitor ODYA, the total mass of five OH-PCB3s was reduced by 2.1 times compared to the control at an ODYA concentration of 2.5 mg L−1. All results pointed to the conclusion that CYP enzymes were the agents which metabolized PCB3 to OH-PCB3s in whole poplars because suicide CYP inhibitors ABT and ODYA both led to sharp decreases of OH-PCB3s formation in whole poplars. A dose-response curve for each of the suicide inhibitors was developed. PMID:23320482

  13. Insights into the catalytic mechanisms of phenylalanine and tryptophan hydroxylase from kinetic isotope effects on aromatic hydroxylation.

    PubMed

    Pavon, Jorge Alex; Fitzpatrick, Paul F

    2006-09-12

    Phenylalanine hydroxylase (PheH) and tryptophan hydroxylase (TrpH) catalyze the aromatic hydroxylation of phenylalanine and tryptophan, forming tyrosine and 5-hydroxytryptophan, respectively. The reactions of PheH and TrpH have been investigated with [4-(2)H]-, [3,5-(2)H(2)]-, and (2)H(5)-phenylalanine as substrates. All (D)k(cat) values are normal with Delta117PheH, the catalytic core of rat phenylalanine hydroxylase, ranging from 1.12-1.41. In contrast, for Delta117PheH V379D, a mutant protein in which the stoichiometry between tetrahydropterin oxidation and amino acid hydroxylation is altered, the (D)k(cat) value with [4-(2)H]-phenylalanine is 0.92 but is normal with [3,5-(2)H(2)]-phenylalanine. The ratio of tetrahydropterin oxidation to amino acid hydroxylation for Delta117PheH V379D shows a similar inverse isotope effect with [4-(2)H]-phenylalanine. Intramolecular isotope effects, determined from the deuterium contents of the tyrosine formed from [4-(2)H]-and [3,5(2)H(2)]-phenylalanine, are identical for Delta117PheH and Delta117PheH V379D, suggesting that steps subsequent to oxygen addition are unaffected in the mutant protein. The inverse effects are consistent with the reaction of an activated ferryl-oxo species at the para position of the side chain of the amino acid to form a cationic intermediate. The normal effects on the (D)k(cat) value for the wild-type enzyme are attributed to an isotope effect of 5.1 on the tautomerization of a dienone intermediate to tyrosine with a rate constant 6- to7-fold that for hydroxylation. In addition, there is a slight ( approximately 34%) preference for the loss of the hydrogen originally at C4 of phenylalanine. With (2)H(5)-indole-tryptophan as a substrate for Delta117PheH, the (D)k(cat) value is 0.89, consistent with hydroxylation being rate-limiting in this case. When deuterated phenylalanines are used as substrates for TrpH, the (D)k(cat) values are within error of those for Delta117PheH V379D. Overall, these results

  14. A Preliminary Link between Hydroxylated Metabolites of Polychlorinated Biphenyls and Free Thyroxin in Humans

    PubMed Central

    Dirinck, Eveline; Dirtu, Alin C.; Malarvannan, Govindan; Covaci, Adrian; Jorens, Philippe G.; Van Gaal, Luc F.

    2016-01-01

    Background: Polychlorinated biphenyls (PCBs) and their hydroxylated metabolites (HO-PCBs) interfere with thyroid hormone action both in vitro and in vivo. However, epidemiologic studies on the link between PCB exposure and thyroid function have yielded discordant results, while very few data are available for HO-PCBs. Objectives: Our study aimed at investigating the relationship between clinically available markers of thyroid metabolism and serum levels of both PCBs and HO-PCBs. Subjects and Methods: In a group of 180 subjects, thyroid-stimulating hormone (TSH) and free thyroxin (fT4), 29 PCBs (expressed both in lipid weight and in wet weight) and 18 HO-PCBs were measured in serum. Results: In regression models, adjusted for gender, age, current smoking behavior, BMI and total lipid levels, serum levels of 3HO-PCB118 and 3HO-PCB180, and PCB95lw, PCB99lw and PCB149lw were independent, significant predictors of fT4. A stepwise, multiple regression with gender, age, current smoking behavior, BMI and total lipid levels and all five previously identified significant compounds retained age, BMI, PCB95lw, PCB99lw and 3HO-PCB180 as significant predictors of fT4. TSH levels were not predicted by serum levels of any of the PCBs or HO-PCBs. Conclusions: Our study indicates that in vivo, circulating fT4 levels can be linked to serum levels of several PCBs and hydroxylated PCB metabolites. PMID:27089353

  15. Reaction Mechanism of the Bicopper Enzyme Peptidylglycine α-Hydroxylating Monooxygenase*

    PubMed Central

    Abad, Enrique; Rommel, Judith B.; Kästner, Johannes

    2014-01-01

    Peptidylglycine α-hydroxylating monooxygenase is a noninteracting bicopper enzyme that stereospecifically hydroxylates the terminal glycine of small peptides for its later amidation. Neuroendocrine messengers, such as oxytocin, rely on the biological activity of this enzyme. Each catalytic turnover requires one oxygen molecule, two protons from the solvent, and two electrons. Despite this enzyme having been widely studied, a consensus on the reaction mechanism has not yet been found. Experiments and theoretical studies favor a pro-S abstraction of a hydrogen atom followed by the rebinding of an OH group. However, several hydrogen-abstracting species have been postulated; because two protons are consumed during the reaction, several protonation states are available. An electron transfer between the copper atoms could play a crucial role for the catalysis as well. This leads to six possible abstracting species. In this study, we compare them on equal footing. We perform quantum mechanics/molecular mechanics calculations, considering the glycine hydrogen abstraction. Our results suggest that the most likely mechanism is a protonation of the abstracting species before the hydrogen abstraction and another protonation as well as a reduction before OH rebinding. PMID:24668808

  16. Metal-induced hydroxyl radical generation by Cu(+)-metallothioneins from LEC rat liver.

    PubMed

    Nakamura, M; Nakayama, K; Shishido, N; Yumino, K; Ohyama, T

    1997-02-24

    Reactions of LEC (Long-Evans rats with a cinnamonlike coat color) rat liver Cu(I)-metallothioneins (MTs) with HgCl2 or K3Fe(CN)6 were investigated by ESR spectroscopy and generation of hydroxyl radicals was demonstrated using the ESR spin trap, 5,5-dimethyl-1-pyrroline N-oxide (DMPO). When Cu(I)-MTs were incubated with more than one equivalent mole HgCl2 or K3Fe(CN)6 to Cu+ bound to MTs, strong signals due to Cu2+ appeared. ESR spectra, which were a combination of the DMPO-OH adduct signal and a six-line signal, were observed in the reaction of Cu(I)-MTs with HgCl2, whereas no oxygen radical signal was seen with K3Fe(CN)6. The DMPO-OH signal intensity was greater in the presence of SOD while the signal disappeared in the presence of catalase. The results suggest that addition of HgCl2 causes the liberation of cuprous ions from MTs followed by a reaction with oxygen, leading to hydroxyl radical formation through a Fenton-type Haber-Weiss reaction.

  17. Tyrosine Hydroxylation in Betalain Pigment Biosynthesis Is Performed by Cytochrome P450 Enzymes in Beets (Beta vulgaris).

    PubMed

    Sunnadeniya, Rasika; Bean, Alexander; Brown, Matthew; Akhavan, Neda; Hatlestad, Gregory; Gonzalez, Antonio; Symonds, V Vaughan; Lloyd, Alan

    2016-01-01

    Yellow and red-violet betalain plant pigments are restricted to several families in the order Caryophyllales, where betacyanins play analogous biological roles to anthocyanins. The initial step in betalain biosynthesis is the hydroxylation of tyrosine to form L-DOPA. Using gene expression experiments in beets, yeast, and Arabidopsis, along with HPLC/MS analysis, the present study shows that two novel cytochrome P450 (CYP450) enzymes, CYP76AD6 and CYP76AD5, and the previously described CYP76AD1 can perform this initial step. Co-expressing these CYP450s with DOPA 4,5-dioxygenase in yeast, and overexpression of these CYP450s in yellow beets show that CYP76AD1 efficiently uses L-DOPA leading to red betacyanins while CYP76AD6 and CYP76AD5 lack this activity. Furthermore, CYP76AD1 can complement yellow beetroots to red while CYP76AD6 and CYP76AD5 cannot. Therefore CYP76AD1 uniquely performs the beet R locus function and beets appear to be genetically redundant for tyrosine hydroxylation. These new functional data and ancestral character state reconstructions indicate that tyrosine hydroxylation alone was the most likely ancestral function of the CYP76AD alpha and beta groups and the ability to convert L-DOPA to cyclo-DOPA evolved later in the alpha group.

  18. Tyrosine Hydroxylation in Betalain Pigment Biosynthesis Is Performed by Cytochrome P450 Enzymes in Beets (Beta vulgaris)

    PubMed Central

    Sunnadeniya, Rasika; Bean, Alexander; Brown, Matthew; Akhavan, Neda; Hatlestad, Gregory; Gonzalez, Antonio; Symonds, V. Vaughan; Lloyd, Alan

    2016-01-01

    Yellow and red-violet betalain plant pigments are restricted to several families in the order Caryophyllales, where betacyanins play analogous biological roles to anthocyanins. The initial step in betalain biosynthesis is the hydroxylation of tyrosine to form L-DOPA. Using gene expression experiments in beets, yeast, and Arabidopsis, along with HPLC/MS analysis, the present study shows that two novel cytochrome P450 (CYP450) enzymes, CYP76AD6 and CYP76AD5, and the previously described CYP76AD1 can perform this initial step. Co-expressing these CYP450s with DOPA 4,5-dioxygenase in yeast, and overexpression of these CYP450s in yellow beets show that CYP76AD1 efficiently uses L-DOPA leading to red betacyanins while CYP76AD6 and CYP76AD5 lack this activity. Furthermore, CYP76AD1 can complement yellow beetroots to red while CYP76AD6 and CYP76AD5 cannot. Therefore CYP76AD1 uniquely performs the beet R locus function and beets appear to be genetically redundant for tyrosine hydroxylation. These new functional data and ancestral character state reconstructions indicate that tyrosine hydroxylation alone was the most likely ancestral function of the CYP76AD alpha and beta groups and the ability to convert L-DOPA to cyclo-DOPA evolved later in the alpha group. PMID:26890886

  19. Finding synergies in fuels properties for the design of renewable fuels--hydroxylated biodiesel effects on butanol-diesel blends.

    PubMed

    Sukjit, E; Herreros, J M; Piaszyk, J; Dearn, K D; Tsolakis, A

    2013-04-02

    This article describes the effects of hydroxylated biodiesel (castor oil methyl ester - COME) on the properties, combustion, and emissions of butanol-diesel blends used within compression ignition engines. The study was conducted to investigate the influence of COME as a means of increasing the butanol concentration in a stable butanol-diesel blend. Tests were compared with baseline experiments using rapeseed methyl esters (RME). A clear benefit in terms of the trade-off between NOX and soot emissions with respect to ULSD and biodiesel-diesel blends with the same oxygen content was obtained from the combination of biodiesel and butanol, while there was no penalty in regulated gaseous carbonaceous emissions. From the comparison between the biodiesel fuels used in this work, COME improved some of the properties (for example lubricity, density and viscosity) of butanol-diesel blends with respect to RME. The existence of hydroxyl group in COME also reduced further soot emissions and decreased soot activation energy.

  20. Quantitative aspects of ESR and spin trapping of hydroxyl radicals and hydrogen atoms in gamma-irradiated aqueous solutions.

    PubMed

    Carmichael, A J; Makino, K; Riesz, P

    1984-11-01

    The efficiency of 5,5-dimethylpyrroline-1-N-oxide (DMPO) and alpha-(4-pyridyl-1-oxide)-N-tert.-butylnitrone (POBN) to spin trap hydroxyl radicals and hydrogen atoms, respectively, was studied in gamma-irradiated solutions where the radical yields are accurately known. The effects of dose, spin trap concentration, and pH and of the stability of the spin adducts on the spin-trapping efficiency were investigated. In degassed or N2-saturated solutions the spin-trapping efficiencies were 35% for DMPO and hydroxyl radicals and 14% for POBN and hydrogen atoms. The low spin-trapping efficiencies were shown not to be due to the instability of the DMPO-OH and POBN-H spin adducts or to the effects of H2O2 or O2. The low spin-trapping efficiency of DMPO may be explained by the reaction of hydroxyl radicals to abstract hydrogen from the DMPO molecule to produce carbon radicals as well as addition to the N = C double bond to form nitroxide radicals. For POBN the low spin-trapping efficiency for hydrogen atoms is explained in terms of addition reactions of hydrogen atoms to the aromatic ring and the pyridinium and nitrone oxygens.

  1. Grape skins (Vitis vinifera L.) catalyze the in vitro enzymatic hydroxylation of p-coumaric acid to caffeic acid.

    PubMed

    Arnous, Anis; Meyer, Anne S

    2009-12-01

    The ability of grape skins to catalyze in vitro conversion of p-coumaric acid to the more potent antioxidant caffeic acid was studied. Addition of different concentrations of p-coumaric to red grape skins (Cabernet Sauvignon) resulted in formation of caffeic acid. This caffeic acid formation (Y) correlated positively and linearly to p-coumaric acid consumption (X): Y = 0.5 X + 9.5; R (2) = 0.96, P < 0.0001. The kinetics of caffeic acid formation with time in response to initial p-coumaric acid levels and at different grape skin concentrations, indicated that the grape skins harboured an o-hydroxylation activity, proposedly a monophenol- or a flavonoid 3'-monooxygenase activity (EC 1.14.18.1 or EC 1.14.13.21). The K (m) of this crude o-hydroxylation activity in the red grape skin was 0.5 mM with p-coumaric acid.

  2. Towards reducing DBP formation potential of drinking water by favouring direct ozone over hydroxyl radical reactions during ozonation.

    PubMed

    De Vera, Glen Andrew; Stalter, Daniel; Gernjak, Wolfgang; Weinberg, Howard S; Keller, Jurg; Farré, Maria José

    2015-12-15

    When ozonation is employed in advanced water treatment plants to produce drinking water, dissolved organic matter reacts with ozone (O3) and/or hydroxyl radicals (OH) affecting disinfection byproduct (DBP) formation with subsequently used chlorine-based disinfectants. This study presents the effects of varying exposures of O3 and •OH on DBP concentrations and their associated toxicity generated after subsequent chlorination. DBP formation potential tests and in vitro bioassays were conducted after batch ozonation experiments of coagulated surface water with and without addition of tertiary butanol (t-BuOH, 10 mM) and hydrogen peroxide (H2O2, 1 mg/mg O3), and at different pH (6-8) and transferred ozone doses (0-1 mg/mg TOC). Although ozonation led to a 24-37% decrease in formation of total trihalomethanes, haloacetic acids, haloacetonitriles, and trihaloacetamides, an increase in formation of total trihalonitromethanes, chloral hydrate, and haloketones was observed. This effect however was less pronounced for samples ozonated at conditions favoring molecular ozone (e.g., pH 6 and in the presence of t-BuOH) over •OH reactions (e.g., pH 8 and in the presence of H2O2). Compared to ozonation only, addition of H2O2 consistently enhanced formation of all DBP groups (20-61%) except trihalonitromethanes. This proves that •OH-transformed organic matter is more susceptible to halogen incorporation. Analogously, adsorbable organic halogen (AOX) concentrations increased under conditions that favor •OH reactions. The ratio of unknown to known AOX, however, was greater at conditions that promote direct O3 reactions. Although significant correlation was found between AOX and genotoxicity with the p53 bioassay, toxicity tests using 4 in vitro bioassays showed relatively low absolute differences between various ozonation conditions.

  3. Identification of the active components in Shenmai injection that differentially affect Cyp3a4-mediated 1'-hydroxylation and 4-hydroxylation of midazolam.

    PubMed

    Zeng, Caiwen; He, Fang; Xia, Chunhua; Zhang, Hong; Xiong, Yuqing

    2013-04-01

    Shenmai injection (SMI) is a popular herbal preparation that is widely used for the treatment of atherosclerotic coronary heart disease and viral myocarditis. In our previous study, SMI was shown to differentially affect CYP3A4-mediated 1'-hydroxylation and 4-hydroxylation of midazolam (MDZ). The present study was conducted to identify the active components in SMI responsible for the differential effects on MDZ metabolism, using in vitro incubation systems (rat and human liver microsomes and a recombinant CYP3A4 system) to measure 1'-hydroxylation and 4-hydroxylation of MDZ. First, different fractions of SMI were obtained by gradient elution on an solid phase extraction system and individually tested for their effects on MDZ metabolism. The results demonstrated that lipid-soluble constituents were likely to be the predominant active components of SMI. Second, the possible active components were gradually separated on an high-performance liquid chromatography system under different conditions and individually tested in vitro for their effects on MDZ metabolism. Third, the active component obtained in the above experiment was collected and subjected to structural analysis, and identified as panaxytriol (PXT). Finally, it was validated that PXT had significant differential effects on 1'-hydroxylation and 4-hydroxylation of MDZ in various in vitro systems that were similar to those of SMI. We conclude that PXT is the constituent of SMI responsible for the differential effects on CYP3A4-mediated 1'-hydroxylation and 4-hydroxylation of MDZ.

  4. Mucor hiemalis mediated 14α-hydroxylation on steroids: in vivo and in vitro investigations of 14α-hydroxylase activity.

    PubMed

    Kolet, Swati P; Haldar, Saikat; Niloferjahan, Siddiqui; Thulasiram, Hirekodathakallu V

    2014-07-01

    Transformation of testosterone and progesterone into synthetically challenging 14α-hydroxy derivatives was achieved by using fungal strain Mucor hiemalis. Prolonged incubation led to the formation of corresponding 6β/7α,14α-dihydroxy metabolites. The position and stereochemistry of newly introduced hydroxyl group was determined by detailed spectroscopic analyses. The time course experiment indicated that fungal strain initiated transformation by hydroxylation at 14α-position followed by at 6β- or 7α-positions. Studies using cell-free extracts suggest that the 14α-hydroxylase activity is NADPH dependent and belongs to the cytochrome P450 family.

  5. Modeling and predicting pKa values of mono-hydroxylated polychlorinated biphenyls (HO-PCBs) and polybrominated diphenyl ethers (HO-PBDEs) by local molecular descriptors.

    PubMed

    Yu, Haiying; Wondrousch, Dominik; Yuan, Quan; Lin, Hongjun; Chen, Jianrong; Hong, Huachang; Schüürmann, Gerrit

    2015-11-01

    Hydroxylated polychlorinated biphenyls (HO-PCBs) and polybrominated diphenyl ethers (HO-PBDEs) are attracting considerable concerns because of their multiple endocrine-disrupting effects and wide existence in environment and organisms. The hydroxyl groups enable these chemicals to be ionizable, and dissociation constant, pKa, becomes an important parameter for investigating their environmental behavior and biological activities. In this study, a new pKa prediction model was developed using local molecular descriptors. The dataset contains 21 experimental pKa values of HO-PCBs and HO-PBDEs. The optimized geometries by ab initio HF/6-31G(∗∗) algorithm were used to calculate the site-specific molecular readiness to accept or donate electron charges. The developed model obtained good statistical performance, which significantly outperformed commercial software ACD and SPARC. Mechanism analysis indicates that pKa values increase with the charge-limited donor energy EQocc on hydroxyl oxygen atom and decrease with the energy-limited acceptor charge QEvac on hydroxyl hydrogen atom. The regression model was also applied to calculate pKa values for all 837 mono-hydroxylated PCBs and PBDEs in each class, aiming to provide basic data for the ecological risk assessment of these chemicals.

  6. HipH Catalyzes the Hydroxylation of 4-Hydroxyisophthalate to Protocatechuate in 2,4-Xylenol Catabolism by Pseudomonas putida NCIMB 9866

    PubMed Central

    Chao, Hong-Jun; Chen, Yan-Fei; Fang, Ti; Xu, Ying; Huang, Wei E.

    2015-01-01

    In addition to growing on p-cresol, Pseudomonas putida NCIMB 9866 is the only reported strain capable of aerobically growing on 2,4-xylenol, which is listed as a priority pollutant by the U.S. Environmental Protection Agency. Several enzymes involved in the oxidation of the para-methyl group, as well as the corresponding genes, have previously been reported. The enzyme catalyzing oxidation of the catabolic intermediate 4-hydroxyisophthalate to the ring cleavage substrate protocatechuate was also purified from strain NCIMB 9866, but its genetic determinant is still unavailable. In this study, the gene hipH, encoding 4-hydroxyisophthalate hydroxylase, from strain NCIMB 9866 was cloned by transposon mutagenesis. Purified recombinant HipH-His6 was found to be a dimer protein with a molecular mass of approximately 110 kDa. HipH-His6 catalyzed the hydroxylation of 4-hydroxyisophthalate to protocatechuate with a specific activity of 1.54 U mg−1 and showed apparent Km values of 11.40 ± 3.05 μM for 4-hydroxyisophthalate with NADPH and 11.23 ± 2.43 μM with NADH and similar Km values for NADPH and NADH (64.31 ± 13.16 and 72.76 ± 12.06 μM, respectively). The identity of protocatechuate generated from 4-hydroxyisophthalate hydroxylation by HipH-His6 has also been confirmed by high-performance liquid chromatography and mass spectrometry. Gene transcriptional analysis, gene knockout, and complementation indicated that hipH is essential for 2,4-xylenol catabolism but not for p-cresol catabolism in this strain. This fills a gap in our understanding of the gene that encodes a critical step in 2,4-xylenol catabolism and also provides another example of biochemical and genetic diversity of microbial catabolism of structurally similar compounds. PMID:26567311

  7. A Polymeric Prodrug of 5-Fluorouracil-1-Acetic Acid Using a Multi-Hydroxyl Polyethylene Glycol Derivative as the Drug Carrier

    PubMed Central

    Sun, Xun; Gong, Tao; Zhang, Zhirong

    2014-01-01

    Purpose Macromolecular prodrugs obtained by covalently conjugating small molecular drugs with polymeric carriers were proven to accomplish controlled and sustained release of the therapeutic agents in vitro and in vivo. Polyethylene glycol (PEG) has been extensively used due to its low toxicity, low immunogenicity and high biocompatibility. However, for linear PEG macromolecules, the number of available hydroxyl groups for drug coupling does not change with the length of polymeric chain, which limits the application of PEG for drug conjugation purposes. To increase the drug loading and prolong the retention time of 5-fluorouracil (5-Fu), a macromolecular prodrug of 5-Fu, 5-fluorouracil-1 acid-PAE derivative (5-FA-PAE) was synthesized and tested for the antitumor activity in vivo. Methods PEG with a molecular weight of 38 kDa was selected to synthesize the multi-hydroxyl polyethylene glycol derivative (PAE) through an addition reaction. 5-fluorouracil-1 acetic acid (5-FA), a 5-Fu derivative was coupled with PEG derivatives via ester bond to form a macromolecular prodrug, 5-FA-PAE. The in vitro drug release, pharmacokinetics, in vivo distribution and antitumor effect of the prodrug were investigated, respectively. Results The PEG-based prodrug obtained in this study possessed an exceedingly high 5-FA loading efficiency of 10.58%, much higher than the maximum drug loading efficiency of unmodified PEG with the same molecular weight, which was 0.98% theoretically. Furthermore, 5-FA-PAE exhibited suitable sustained release in tumors. Conclusion This study provides a new approach for the development of the delivery to tumors of anticancer agents with PEG derivatives. PMID:25389968

  8. The evaluation of hydroxyl ions as a nucleating agent for apatite on electrospun non-woven poly( ϵ -caprolactone) fabric.

    PubMed

    Kim, Hyung-Sup; Um, Seung-Hoon; Rhee, Sang-Hoon

    2012-01-01

    The capacity of hydroxyl ions when used as a nucleating agent to form apatite in simulated body fluid (SBF) was investigated. A 25 wt% poly(ϵ-caprolactone) solution was prepared using 1,1,3,3-hexafluoro-2-propanol as a solvent and was electrospun under an electric field of 1 kV/cm. Subsequently, non-woven poly(ϵ-caprolactone) fabrics were dipped into 4 M NaOH solution and the experimental group was then directly air-dried (NaOH coated), while the control group was washed with deionized water and air-dried (NaOH treated) under ambient conditions. The non-woven poly(ϵ-caprolactone) fabrics that were coated and treated with NaOH were exposed to SBF for 1 week, which resulted in the deposition of a layer of apatite crystals on the non-woven poly(ϵ-caprolactone) fabric coated with NaOH only. On the other hand, when the non-woven poly(ϵ-caprolactone) fabrics were dipped into 0.05, 0.1, 1 and 4 M NaOH solutions, respectively, air-dried, and then soaked in SBF, the apatite forming capacity was gradually increased according to the concentration of NaOH solution. These results were explained in terms of the degree of apatite supersaturation in SBF induced by the release of hydroxyl ions from the coated NaOH because hydroxyl ions are one of the constituent elements of apatite. These results suggest that hydroxyl ions have a good potential for use as a nucleating agent for apatite on a previously non-bioactive polymer surface.

  9. Future Directions of Structural Mass Spectrometry using Hydroxyl Radical Footprinting

    SciTech Connect

    J Kiselar; M Chance

    2011-12-31

    Hydroxyl radical protein footprinting coupled to mass spectrometry has been developed over the last decade and has matured to a powerful method for analyzing protein structure and dynamics. It has been successfully applied in the analysis of protein structure, protein folding, protein dynamics, and protein-protein and protein-DNA interactions. Using synchrotron radiolysis, exposure of proteins to a 'white' X-ray beam for milliseconds provides sufficient oxidative modification to surface amino acid side chains, which can be easily detected and quantified by mass spectrometry. Thus, conformational changes in proteins or protein complexes can be examined using a time-resolved approach, which would be a valuable method for the study of macromolecular dynamics. In this review, we describe a new application of hydroxyl radical protein footprinting to probe the time evolution of the calcium-dependent conformational changes of gelsolin on the millisecond timescale. The data suggest a cooperative transition as multiple sites in different molecular subdomains have similar rates of conformational change. These findings demonstrate that time-resolved protein footprinting is suitable for studies of protein dynamics that occur over periods ranging from milliseconds to seconds. In this review, we also show how the structural resolution and sensitivity of the technology can be improved as well. The hydroxyl radical varies in its reactivity to different side chains by over two orders of magnitude, thus oxidation of amino acid side chains of lower reactivity are more rarely observed in such experiments. Here we demonstrate that the selected reaction monitoring (SRM)-based method can be utilized for quantification of oxidized species, improving the signal-to-noise ratio. This expansion of the set of oxidized residues of lower reactivity will improve the overall structural resolution of the technique. This approach is also suggested as a basis for developing hypothesis

  10. Method of making a membrane having hydrophilic and hydrophobic surfaces for adhering cells or antibodies by using atomic oxygen or hydroxyl radicals

    NASA Technical Reports Server (NTRS)

    Koontz, Steven L. (Inventor); Spaulding, Glenn F. (Inventor)

    1994-01-01

    A portion of an organic polymer article such as a membrane is made hydrophilic by exposing a hydrophobic surface of the article to a depth of about 50 to about 5000 angstroms to atomic oxygen or hydroxyl radicals at a temperature below 100C., preferably below 40 C, to form a hydrophilic uniform surface layer of hydrophilic hydroxyl groups. The atomic oxygen and hydroxyl radicals are generated by a flowing afterglow microwave discharge, and the surface is outside of a plasma produced by the discharge. A membrane having both hydrophilic and hydrophobic surfaces can be used in an immunoassay by adhering antibodies to the hydrophobic surface. In another embodiment, the membrane is used in cell culturing where cells adhere to the hydrophilic surface. Prior to adhering cells, the hydrophilic surface may be grafted with a compatibilizing compound. A plurality of hydrophilic regions bounded by adjacent hydrophobic regions can be produced such that a maximum of one cell per each hydrophilic region adheres.

  11. Aromatic-hydroxyl interaction of an alpha-aryl ether lignin model-compound on SBA-15, present at pyrolysis temperatures.

    PubMed

    Kandziolka, M V; Kidder, M K; Gill, L; Wu, Z; Savara, A

    2014-11-28

    An aromatic alpha-aryl ether compound (a benzyl phenyl ether analogue) was covalently grafted to mesoporous silica SBA-15, to create BPEa-SBA-15. The BPEa-SBA-15 was subjected to successive heating cycles up to 600 °C, with in situ monitoring by DRIFTS. It was found that the toluene moiety coordinates to SBA-15 surface silanol hydroxyl groups via an aromatic-hydroxyl interaction. This interaction is evidenced by a red-shift of the aromatic C-H stretches, as well as a red-shift and broadening of the surface hydroxyl O-H stretches, which are features characteristic of a hydrogen bond. These features remain present during heating until ∼400 °C whereupon the ether linkage of BPEa-SBA-15 is cleaved, accompanied by loss of the toluene moiety.

  12. Cytotoxic hydroxylated triterpene alcohol ferulates from rice bran.

    PubMed

    Luo, Hong-Feng; Li, Qinglin; Yu, Shanggong; Badger, Thomas M; Fang, Nianbai

    2005-01-01

    Three hydroxylated triterpene alcohol ferulates, (24S)-cycloart-25-ene-3 beta,24-diol-3 beta-trans-ferulate (1), (24R)-cycloart-25-ene-3 beta,24-diol-3 beta-trans-ferulate (2), and cycloart-23Z-ene-3 beta,25-diol-3 beta-trans-ferulate (3), along with known compounds cycloartenol trans-ferulate (4) and 24-methylenecycloartanol trans-ferulate (5) were isolated from rice bran. Their structures were elucidated by means of chemical and spectroscopic analysis. Compounds 2-5 showed moderate cytotoxicity against MCF-7 cells.

  13. Tropospheric concentrations of the hydroxyl radical—a review

    NASA Astrophysics Data System (ADS)

    Hewitt, C. N.; Harrison, Roy M.

    The dominant role played by the hydroxyl radical in tropospheric photochemistry makes essential a better definition of its atmospheric abundance. The measurement techniques employed to date are critically evaluated and the reported concentrations of HO in ambient air are reviewed. Photochemical models used to predict HO concentrations are discussed, and a comparison between measured and modelled concentrations made. Tropospheric concentrations in the ranges (0.5-5) × 10 6HO cm-3 daytime mean (measurements) and (0.3-3) × 10 6HO cm-3 24 h mean (models) are suggested. A seasonal variation of about 3-fold is indicated by model studies.

  14. Electrolytic coloration of hydroxyl-doped potassium iodide polycrystals

    NASA Astrophysics Data System (ADS)

    Wang, Na; Gu, Hongen; Han, Li; Guo, Meili; Qin, Fang

    2007-03-01

    Hydroxyl-doped potassium iodide polycrystals were successfully colored electrolytically by using a pointed cathode and a flat anode at various temperatures and electric field strengths, which mainly benefits appropriate coloration temperatures and electric field strengths. Characteristic OH-, O2--Va+ , U, V2, V3, Cu+, Cu-related, I2- , I2, K, F, R1 and R2 spectral bands were observed in Kubelka-Munk functions of the colored polycrystals, and the OH- and O2--Va+ spectral bands at room temperature were determined from Mollwo-Ivey plots. Color center formation in the electrolytic coloration was explained.

  15. Anticancer system created by acrolein and hydroxyl radical generated in enzymatic oxidation of spermine and other biochemical reactions.

    PubMed

    Alarcon, R A

    2012-10-01

    A hypothesis suggesting the existence of a ubiquitous physiological anticancer system created by two highly reactive oxidative stress inducers with anticancer properties, acrolein and hydroxyl radical, is reported in this communication. Both components can originate separately or together in several biochemical interactions, among them, the enzymatic oxidation of the polyamine spermine, which appear to be their main source. The foundations of this hypothesis encompass our initial search for growth-inhibitors or anticancer compounds in biological material leading to the isolation of spermine, a polyamine that became highly cytotoxic through the generation of acrolein, when enzymatically oxidized. Findings complemented with pertinent literature data by other workers and observed anticancer activities by sources capable of producing acrolein and hydroxyl radical. This hypothesis obvious implication: spermine enzymatic oxidations or other biochemical interactions that would co-generate acrolein and hydroxyl radical, the anticancer system components, should be tried as treatments for any given cancer. The biochemical generation of acrolein observed was totally unexpected, since this aldehyde was known; as a very toxic and highly reactive xenobiotic chemical produced in the pyrolysis of fats and other organic material, found as an atmospheric pollutant, in tobacco smoke and car emissions, and mainly used as a pesticide or aquatic herbicide. Numerous studies on acrolein, considered after our work a biological product, as well, followed. In them, acrolein widespread presence, its effects on diverse cellular proteins, such as, growth factors, and its anticancer activities, were additionally reported. Regarding hydroxyl radical, the second component of the proposed anticancer system, and another cytotoxic product in normal cell metabolism, it co-generates with acrolein in several biochemical interactions, occurrences suggesting that these products might jointly fulfill some

  16. Intracellular-produced hydroxyl radical mediates H2O2-induced Ca2+ influx and cell death in rat beta-cell line RIN-5F.

    PubMed

    Ishii, Masakazu; Shimizu, Shunichi; Hara, Yuji; Hagiwara, Tamio; Miyazaki, Akira; Mori, Yasuo; Kiuchi, Yuji

    2006-06-01

    The melastatin-related transient receptor potential channel TRPM2 is a Ca(2+)-permeable channel that is activated by H(2)O(2), and the Ca(2+) influx through TRPM2 mediates cell death. However, the responsible oxidants for TRPM2 activation remain to be identified. In the present study, we investigated the involvement of hydroxyl radical on TRPM2 activation in TRPM2-expressing HEK293 cells and the rat beta-cell line RIN-5F. In both cell types, H(2)O(2) induced Ca(2+) influx in a concentration-dependent manner. However, the addition of hydroxyl radical, which was produced by mixing FeSO(4) and H(2)O(2), to the cells, did not increase intracellular Ca(2+) concentration. Interestingly, when H(2)O(2) was added to the cells under intracellular Fe(2+)-accumulated conditions, Ca(2+) influx was markedly enhanced compared to H(2)O(2) alone. In addition, the H(2)O(2)-induced Ca(2+) influx was reduced by hydroxyl radical scavengers and an iron chelator. Under intracellular Fe(2+)-accumulated conditions, H(2)O(2)-induced RIN-5F cell death through TRPM2 activation was also markedly enhanced. Hydroxyl radical scavengers and an iron chelator suppressed the RIN-5F cell death by H(2)O(2). These results strongly suggest that the intracellular hydroxyl radical plays a key role in the activation of TRPM2 during H(2)O(2) treatment, and TRPM2 activation mediated by hydroxyl radical is implicated in H(2)O(2)-induced cell death in the beta-cell line RIN-5F.

  17. Structural Characterization of Hydroxyl Radical Adducts in Aqueous Media

    NASA Astrophysics Data System (ADS)

    Janik, Ireneusz; Tripathi, G. N. R.

    2015-06-01

    The oxidation by the hydroxyl (OH) radical is one of the most widely studied reactions because of its central role in chemistry, biology, organic synthesis, and photocatalysis in aqueous environments, wastewater treatment, and numerous other chemical processes. Although the redox potential of OH is very high, direct electron transfer (ET) is rarely observed. If it happens, it mostly proceeds through the formation of elusive OH adduct intermediate which facilitates ET and formation of hydroxide anion. Using time resolved resonance Raman technique we structurally characterized variety of OH adducts to sulfur containing organic compounds, halide ions as well as some metal cations. The bond between oxygen of OH radical and the atom of oxidized molecule differs depending on the nature of solute that OH radical reacts with. For most of sulfur containing organics, as well as halide and pseudo-halide ions, our observation suggested that this bond has two-center three-electron character. For several metal aqua ions studied, the nature of the bond depends on type of the cation being oxidized. Discussion on spectral parameters of all studied hydroxyl radical adducts as well as the role solvent plays in their stabilization will be presented.

  18. Iron reduction potentiates hydroxyl radical formation only in flavonols.

    PubMed

    Macáková, Kateřina; Mladěnka, Přemysl; Filipský, Tomáš; Říha, Michal; Jahodář, Luděk; Trejtnar, František; Bovicelli, Paolo; Proietti Silvestri, Ilaria; Hrdina, Radomír; Saso, Luciano

    2012-12-15

    Flavonoids, substantial components of the human diet, are generally considered to be beneficial. However, they may possess possible pro-oxidative effects, which could be based on their reducing potential. The aims of this study were to evaluate the ability of 26 flavonoids to reduce ferric ions at relevant pH conditions and to find a possible relationship with potentiation of hydroxyl radical production. A substantial ferric ions reduction was achieved under acidic conditions, particularly by flavonols and flavanols with the catecholic ring B. Apparently corresponding bell-shaped curves displaying the pro-oxidant effect of flavonols quercetin and kaempferol on iron-based Fenton reaction were documented. Several flavonoids were efficient antioxidants at very low concentrations but rather inefficient or pro-oxidative at higher concentrations. Flavonols, morin and rutin were progressively pro-oxidant, while 7-hydroxyflavone and hesperetin were the only flavonoids with dose-dependent inhibition of hydroxyl radical production. Conclusively, administration of flavonoids may lead to unpredictable consequences with few exceptions.

  19. Self-assembly of fatty acids and hydroxyl derivative salts.

    PubMed

    Novales, Bruno; Navailles, Laurence; Axelos, Monique; Nallet, Frédéric; Douliez, Jean-Paul

    2008-01-01

    We report the dispersions of a fatty acid and hydroxyl derivative salts in aqueous solutions that were further used to produce foams and emulsions. The tetrabutyl-ammonium salts of palmitic acid, 12-hydroxy stearic acid, and omega-hydroxy palmitic acid formed isotropic solutions of micelles, whereas the ethanolamine salts of the same acids formed turbid birefringent lamellar solutions. The structure and dimension of those phases were confirmed by small-angle neutron scattering and NMR. Micelles exhibited a surprisingly small radius of about 20 A, even for hydroxyl fatty acids, suggesting the formation of hydrogen bonds between lipids in the core of the micelles. In the case of ethanolamine salts of palmitic and 12-hydroxy stearic acids, the lipids were arranged in bilayers, with a phase transition from gel to fluid upon heating, whereas for omega-hydroxy palmitic acid, monolayers formed in accordance with the bola shape of this lipid. Foams and emulsions produced from ethanolamine salt solutions were more stable than those obtained from tetrabutyl-ammonium salt solutions. We discuss these results in terms of counterion size, lipid molecular shape, and membrane curvature.

  20. Study of umbelliferone hydroxylation to esculetin catalyzed by polyphenol oxidase.

    PubMed

    Garcia-Molina, Mary Of The Sea; Munoz-Munoz, Joseph Louis; Garcia-Molina, Francis; Rodriguez-Lopez, Joseph Neptune; Garcia-Canovas, Francis

    2013-01-01

    We characterize umbelliferone, a derivative of 2,4-dihydroxycoumaric acid, as a substrate of polyphenol oxidase. This enzyme hydroxylates umbelliferone to esculetin, its o-diphenol, and then oxidizes it to o-quinone. The findings show that umbelliferone, an intermediate in one of the coumarin biosynthesis pathways, may be transformed into its o-diphenol, esculetin, which is also an intermediate in the same pathway. The activity of the enzyme on umbelliferone was followed by measuring the consumption of oxygen, spectrophotometrically and by HPLC. Kinetic constants characterizing the hydroxylation process were: kcat=0.09±0.02 s(-1) and Km=0.17±0.06 mM. The o-diphenol, esculetin, was a better substrate and when its oxidation was followed spectrophotometrically, the kinetic constants were: kcat=1.31±0.25 s(-1) and Km=0.035±0.002 mM. Both compounds therefore can be considered as alternative substrates to L-tyrosine and L-3,4-dihydroxyphenylalanine (L-DOPA), since both indirectly inhibit melanogenesis.

  1. Role of the hydroxyl radical in soot formation

    NASA Technical Reports Server (NTRS)

    King, Galen B.; Laurendeau, Normand M.

    1983-01-01

    The goal of this project is to determine the role of the hydroxyl radical during formation of soot. Correlations will be sought between OH concentration and (1) the critical equivalence ratio for incipient soot formation and (2) soot yield as a function of higher equivalence ratios. The ultimate aim is the development of a quasi-global kinetic model for the pre-particulate chemistry leading to soot nucleation. Hydroxyl radical concentration profiles are measured directly in both laminar premixed and diffusion flames using the newly developed technique, laser saturated fluorescence (LSF). This method is capable of measuring OH in the presence of soot particles. Aliphatic and aromatic fuels will be used to assess the influence of fuel type on soot formation. The influence of flame temperature on the critical equivalence ratio and soot yield will be related to changes in the OH concentration profiles. LSF measurements will be augmented with auxiliary measurements of soot and PAH concentrations to allow the development of a quasi-global model for soot formation.

  2. Hydroxylated Polychlorinated Biphenyls in the Environment: Sources, Fate, and Toxicities

    PubMed Central

    Tehrani, Rouzbeh; Van Aken, Benoit

    2013-01-01

    Hydroxylated polychlorinated biphenyls (OH-PCBs) are produced in the environment by the oxidation of PCBs through a variety of mechanisms, including metabolic transformation in living organisms and abiotic reactions with hydroxyl radicals. As a consequence, OH-PCBs have been detected in a wide range of environmental samples, including animal tissues, water, and sediments. OH-PCBs have recently raised serious environmental concerns because they exert a variety of toxic effects at lower doses than the parent PCBs and they are disruptors of the endocrine system. Although evidence has accumulated about the widespread dispersion of OH-PCBs in various compartments of the ecosystem, little is currently known about their biodegradation and behavior in the environment. OH-PCBs are today increasingly considered as a new class of environmental contaminants that possess specific chemical, physical, and biological properties not shared with the parent PCBs. This article reviews recent findings regarding the sources, fate, and toxicities of OH-PCBs in the environment. PMID:23636595

  3. Synthesis of a stationary phase based on silica modified with branched octadecyl groups by Michael addition and photoinduced thiol-yne click chemistry for the separation of basic compounds.

    PubMed

    Huang, Guang; Ou, Junjie; Wang, Hongwei; Ji, Yongsheng; Wan, Hao; Zhang, Zhang; Peng, Xiaojun; Zou, Hanfa

    2016-04-01

    A novel silica-based stationary phase with branched octadecyl groups was prepared by the sequential employment of the Michael addition reaction and photoinduced thiol-yne click chemistry with 3-aminopropyl-functionalized silica microspheres as the initial material. The resulting stationary phase denoted as SiO2 -N(C18)4 was characterized by elemental analysis, FTIR spectroscopy and Raman spectroscopy, demonstrating the existence of branched octadecyl groups in silica microspheres. The separations of benzene homologous compounds, acid compounds and amine analogues were conducted, demonstrating mixed-mode separation mechanism on SiO2 -N(C18)4 . Baseline separation of basic drugs mixture was acquired with the mobile phase of acetonitrile/H2 O (5%, v/v). SiO2 -N(C18)4 was further applied to separate Corydalis yanhusuo Wang water extracts, and more baseline separation peaks were obtained for SiO2 -N(C18)4 than those on Atlantis dC18 column. It can be expected that this new silica-based stationary phase will exhibit great potential in the analysis of basic compounds.

  4. A site-holding effect of TiO2 surface hydroxyl in the photocatalytic direct synthesis of 1,1-diethoxyethane from ethanol.

    PubMed

    Zhang, Hongxia; Zhang, Wenqin; Zhao, Min; Yang, Pengju; Zhu, Zhenping

    2017-01-26

    To understand the mechanism of the photocatalytic direct synthesis of 1,1-diethoxyethane (DEE) from ethanol is vital for enhancing the reaction efficiency. Based on photocatalytic data of different phase TiO2 and F-TiO2 catalysts, radical trapping data, and GC-MS data, we proposed a photocatalytic mechanism for the preparation of both DEE in neat ethanol and 2,3-butanediol (2,3-BD) in ethanol-H2O using photocatalytic methods. In neat ethanol, hydroxyl isn't involved in the catalytic cyclic process but hydroxyl has an indirect site-holding effect, thus leading to more hydroxyl groups with higher activity. In ethanol-H2O, although the strong oxidant ˙OH radical is involved, fewer OH groups lead to higher selectivity of 2,3-BD. The interaction of the reactant/solvent with the surface group of the catalyst is important in the activity and selectivity of photocatalytic reactions. This finding gives fundamental insight into the role of TiO2 surface hydroxyl in the photocatalytic dehydrogenation process of alcohols and opens a promising path to obtaining both high selectivity and high conversion in TiO2-based photocatalytic activity.

  5. Hydroxylamine as an oxygen nucleophile: substitution of sulfonamide by a hydroxyl group in benzothiazole-2-sulfonamides.

    PubMed

    Kamps, Jos J A G; Belle, Roman; Mecinović, Jasmin

    2013-02-21

    Benzothiazole-2-sulfonamides react with an excess of hydroxylamine in aqueous solutions to form 2-hydroxybenzothiazole, sulfur dioxide, and the corresponding amine. Mechanistic studies that employ a combination of structure-reactivity relationships, oxygen labeling experiments, and (in)direct detection of intermediates and products reveal that the reaction proceeds via oxygen attack, and that oxygen incorporated in the 2-hydroxybenzothiazole product derives from hydroxylamine. The reaction, which is performed under mild conditions, can be used as a deprotection method for cleavage of benzothiazole-2-sulfonyl-protected amino acids.

  6. ONE STEP BIOCATALYTIC SYNTHESIS OF LINEAR POLYESTERS WITH PENDANT HYDROXYL GROUPS. (R825338)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  7. Insights into the mechanism of the reaction between tetrachloro-p-benzoquinone and hydrogen peroxide and their implications in the catalytic role of water molecules in producing the hydroxyl radial.

    PubMed

    Li, Ping; Wang, Weihua; Sun, Qiao; Li, Zhen; Du, Aijun; Bi, Siwei; Zhao, Yan

    2013-08-26

    Detailed mechanisms for the formation of hydroxyl or alkoxyl radicals in the reactions between tetrachloro-p-benzoquinone (TCBQ) and organic hydroperoxides are crucial for better understanding the potential carcinogenicity of polyhalogenated quinones. Herein, the mechanism of the reaction between TCBQ and H2O2 has been systematically investigated at the B3LYP/6-311++G** level of theory in the presence of different numbers of water molecules. We report that the whole reaction can easily take place with the assistance of explicit water molecules. Namely, an initial intermediate is formed first. After that, a nucleophilic attack of H2O2 onto TCBQ occurs, which results in the formation of a second intermediate that contains an OOH group. Subsequently, this second intermediate decomposes homolytically through cleavage of the O-O bond to produce a hydroxyl radical. Energy analyses suggest that the nucleophilic attack is the rate-determining step in the whole reaction. The participation of explicit water molecules promotes the reaction significantly, which can be used to explain the experimental phenomena. In addition, the effects of F, Br, and CH3 substituents on this reaction have also been studied.

  8. Hydroxylated fluorescent dyes for live cell labeling: synthesis, spectra and superresolution STED** microscopy.

    PubMed

    Belov, Vladimir N; Butkevich, Alexey N; Kolmakov, Kirill; Sokolov, Viktor V; Shojaei, Heydar; Sidenstein, Sven C; Kamin, Dirk; Matthias, Jessica; Vlijm, Rifka; Engelhardt, Johann; Hell, Stefan W

    2017-03-29

    Hydroxylated rhodamines, carbopyronines, silico- and germanorhodamines with absorption maxima in the range of 530-640 nm were prepared and applied in specific labeling of living cells. The direct and high-yielding entry to germa- and silaxanthones tolerates the presence of protected heteroatoms and may be considered for the syntheses of various sila- and germafluoresceins, as well as -rhodols. Application in stimulated emission depletion (STED) fluorescence microscopy revealed a resolution of 50-75 nm in one- and two-color imaging of vimentin-HaloTag fused protein and native tubulin. The established structure-property relationships allow prediction of the spectral properties and the positions of spirolactone/zwitterion equilibria for the new analogs of rhodamines, carbo-, silico- and germanorhodamines using simple additive schemes.

  9. Theoretical study on the gas phase reaction of allyl chloride with hydroxyl radical

    NASA Astrophysics Data System (ADS)

    Zhang, Yunju; Chao, Kai; Sun, Jingyu; Zhang, Wanqiao; Shi, Haijie; Yao, Cen; Su, Zhongmin; Pan, Xiumei; Zhang, Jingping; Wang, Rongshun

    2014-02-01

    The reaction of allyl chloride with the hydroxyl radical has been investigated on a sound theoretical basis. This is the first time to gain a conclusive insight into the reaction mechanism and kinetics for important pathways in detail. The reaction mechanism confirms that OH addition to the C=C double bond forms the chemically activated adducts, IM1 (CH2CHOHCH2Cl) and IM2 (CH2OHCHCH2Cl) via low barriers, and direct H-abstraction paths may also occur. Variational transition state model and multichannel RRKM theory are employed to calculate the temperature-, pressure-dependent rate constants. The calculated rate constants are in good agreement with the experimental data. At 100 Torr with He as bath gas, IM6 formed by collisional stabilization is the major products in the temperature range 200-600 K; the production of CH2CHCHCl via hydrogen abstractions becomes dominant at high temperatures (600-3000 K).

  10. Regioselective hydroxylation and glucosylation of flavanones with cultured plant cells of Eucalyptus perriniana.

    PubMed

    Hosoda, Ryusuke; Horio, Yoshiyuki; Shimoda, Kei; Hamada, Manabu; Hamada, Hatsuyuki; Hamada, Hiroki

    2013-07-01

    Cultured plant cells of Eucalyptus perriniana catalyzed reduction, regioselective hydroxylation, and regioselective glycosylation of flavanones. (2S)-Flavanone was converted into (2S)-flavan-4-ol, (2S)-flavan-4,7-diol, (2S)-flavan-7-ol, (2S)-flavan-7-yl glucoside, and (2S)-flavan-7-yl gentiobioside. The cells glucosylated (2S)-flavan-6-ol to (2S)-flavan-6-yl glucoside. (2S)-Flavan-2'-ol was transformed to (2S)-flavan-2',4-diol, (2S)-flavan-2',7-diol, (2S)-flavan-2'-yl glucoside. In addition, (2S)-flavan-4'-ol was transformed to (2S)-flavan-4,4'-diol, (2S)-flavan-4',7-diol, (2S)-flavan-4'-yl glucoside.

  11. A comparison of two strategies to modify the hydroxylation of condensed tannin polymers in Lotus corniculatus L.

    PubMed

    Robbins, Mark P; Bavage, Adrian D; Allison, Gordon; Davies, Teri; Hauck, Barbara; Morris, Phillip

    2005-05-01

    A full-length sense Antirrhinum majus dihydroflavonol reductase (DFR) sequence was introduced into birdsfoot trefoil (Lotus corniculatus L.) in experiments aimed at modifying condensed tannin content and polymer hydroxylation in a predictable manner. Analysis of transgenic plants indicated lines that showed enhanced tannin content in leaf and stem tissues. In contrast to previous data from root cultures, levels of propelargonidin units were not markedly elevated in lines with enhanced tannin content. RT-PCR analysis of four selected lines indicated a correlation between enhanced tannin content and expression of the introduced DFR transgene. Using a contrasting approach we introduced a flavonoid 3'5' hydroxylase (F3'5'H) sequence derived from Eustoma grandiflorum into Lotus root cultures. Expression of the transgene was associated with increased levels of condensed tannins and in this case there was also no alteration in polymer hydroxylation. These results suggest that additional mechanisms may exist that control the hydroxylation state of condensed tannins in this model species.

  12. Insights into the O-Acetylation Reaction of Hydroxylated Heterocyclic Amines by Human Arylamine N-Acetyltransferases: A Computational Study

    SciTech Connect

    Lau, E Y; Felton, J S; Lightstone, F C

    2006-06-06

    A computational study was performed to better understand the differences between human arylamine N-acetyltransferase (NAT) 1 and 2. Homology models were constructed from available crystal structures and comparisons of the active site residues 125, 127, and 129 for these two enzymes provide insight into observed substrate differences. The NAT2 model provided a basis for understanding how some of the common mutations may affect the structure of the protein. Molecular dynamics simulations of the human NAT models and the template structure (NAT from Mycobacterium smegmatis) were performed and showed the models to be stable and reasonable. Docking studies of hydroxylated heterocyclic amines in the models of NAT1 and NAT2 probed the differences exhibited by these two proteins with mutagenic agents. The hydroxylated heterocyclic amines were only able to fit into the NAT2 active site, and an alternative binding site by the P-loop was found using our models and will be discussed. Additionally, quantum mechanical calculations were performed to study the O-acetylation reaction of the hydroxylated heterocyclic amines N-OH MeIQx and N-OH PhIP. This study has given us insight into why there are substrate differences among isoenzymes and explains some of the polymorphic activity differences.

  13. Hydroxyl radicals form in natural sediments - effects on sedimentary organic matter

    NASA Astrophysics Data System (ADS)

    Skoog, Annelie; Alejandro Arias-Esquivel, Victor

    2010-05-01

    We show that hydroxyl radicals form at the oxic anoxic interface in marine sediments from ferrous iron reacting with hydrogen peroxide in the Fenton reaction. The aggressive nature of hydroxyl radicals makes it likely that they participate in degradation of sedimentary organic matter (SOM). We used terephthalic acid (TPA) to trap the hydroxyl radicals in sediment cores - TPA reacts with hydroxyl radicals to form the highly fluorescent product TPAOH. Results indicated formation of TPAOH at high concentrations at the oxic-anoxic interface. We also subjected SOM to hydroxyl radicals formed by the Fenton reaction, which resulted in changes in fluorescence properties and chemical composition. This is the first study showing formation of hydroxyl radicals and their effect on SOM, which is a previously unknown mechanism in the global carbon cycle.

  14. Evaluation of 2'-hydroxyl protection in RNA-synthesis using the H-phosphonate approach.

    PubMed Central

    Rozners, E; Westman, E; Strömberg, R

    1994-01-01

    A number of different protecting groups were compared with respect to their usefulness for protection of 2'-hydroxyl functions during synthesis of oligoribonucleotides using the H-phosphonate approach. The comparison was between the t-butyldimethylsilyl (t-BDMSi), the o-chlorobenzoyl (o-CIBz), the tetrahydropyranyl (THP), the 1-(2-fluorophenyl)-4-methoxypiperidin-4-yl (Fpmp), the 1-(2-chloro-4-methylphenyl)-4-methoxypiperidin-4-yl (Ctmp), and the 1-(2-chloroethoxy)ethyl (Cee) protecting groups. All these groups were tested in synthesis of dodecamers, (Up)11U and (Up)11A, using 5'-O-(4-monomethoxytrityl) or (4,4'-dimethoxytrityl) uridine H-phosphonate building blocks carrying the respective 2'-protection. The performance of the t-BDMSi and o-CIBz derivatives were also compared in synthesis of (Up)19U. The most successful syntheses were clearly those where the t-butyldimethylsilyl group was used. The o-chlorobenzoyl group also gave satisfactory results but seems somewhat limited with respect to synthesis of longer oligomers. The results with all tested acetal derivatives (Fpmp, Ctmp, Cee, THP) were much less successful due to some accompanying cleavage of internucleotidic H-phosphonate functions during removal of 5'-O-protection (DMT). PMID:8127660

  15. Phase Segregation and Dynamics in Strongly Interacting Small Molecule Additive - Block Copolymer Surfactant Complexes

    NASA Astrophysics Data System (ADS)

    Kothari, Rohit; Khalil, Ahmed; Henning Winter, H.; Watkins, James J.

    2012-02-01

    Rheology and Small Angle X-Ray Scattering (SAXS) were used to investigate order to disorder transitions (ODTs) and disorder to order transitions (DOTs) of poly(ethyleneoxide-b-propyleneoxide-b-ethyleneoxide) block copolymer surfactants mixed with hydrogen-bond-donating small molecule additives. A series of additives having a core benzene ring and systematic variation in the number of carboxylic or hydroxyl groups attached to the ring were of particular interest. Ordered cylindrical morphologies, confirmed using SAXS, were obtained only in a certain additive concentration region. ODTs were characterized by sudden changes in the linear viscoelastic properties in low frequency region upon increasing temperature. The locations of ODTs varied widely with hydrogen-bond-donating ability of the functional group and were found to be strongly dependent on the number of functional groups attached to the ring. For a given additive, the temperature at which ODT occur was strong function of the additive loading, whereas the linear viscoelastic properties of the ordered state were little changed upon varying additive concentration in ordered region. The location and dynamics of DOTs upon cooling were comparable to the ODTs upon heating. Studies using these model systems provide insight into the design of well-ordered hybrid materials.

  16. Promotional effect of surface hydroxyls on electrochemical reduction of CO2 over SnOx/Sn electrode

    SciTech Connect

    Cui, Chaonan; Han, Jinyu; Zhu, Xinli; Liu, Xiao; Wang, Hua; Mei, Donghai; Ge, Qingfeng

    2016-01-16

    In this study, tin oxide (SnOx) formation on tin-based electrode surfaces during CO2 electrochemical reduction can have a significant impact on the activity and selectivity of the reaction. In the present study, density functional theory (DFT) calculations have been performed to understand the role of SnOx in CO2 reduction using a SnO monolayer on the Sn(112) surface as a model for SnOx. Water molecules have been treated explicitly and considered actively participating in the reaction. The results showed that H2O dissociates on the perfect SnO monolayer into two hydroxyl groups symmetrically on the surface. CO2 energetically prefers to react with the hydroxyl, forming a bicarbonate (HCO3(t)*) intermediate, which can then be reduced to either formate (HCOO*) by hydrogenating the carbon atom or carboxyl (COOH*) by protonating the oxygen atom. Both steps involve a simultaneous Csingle bondO bond breaking. Further reduction of HCOO* species leads to the formation of formic acid in the acidic solution at pH < 4, while the COOH* will decompose to CO and H2O via protonation. Whereas the oxygen vacancy (VO) in the oxide monolayer maybe formed by the reduction, it can be recovered by H2O dissociation, resulting in two embedded hydroxyl groups. The results show that the hydroxylated surface with two symmetric hydroxyls is energetically more favorable for CO2 reduction than the hydroxylated VO surface with two embedded hydroxyls. The reduction potential for the former has a limiting-potential of –0.20 V (RHE), lower than that for the latter (–0.74 V (RHE)). Compared to the pure Sn electrode, the formation of SnOx monolayer on the electrode under the operating conditions promotes CO2 reduction more effectively by forming surface hydroxyls, thereby providing a new channel via COOH* to the CO formation, although formic acid is still

  17. Enhancement of L-tryptophan 5-hydroxylation activity by structure-based modification of L-phenylalanine 4-hydroxylase from Chromobacterium violaceum.

    PubMed

    Kino, Kuniki; Hara, Ryotaro; Nozawa, Ai

    2009-09-01

    The objective of this study was to enhance l-tryptophan hydroxylation activity of l-phenylalanine 4-hydroxylase. It had been known that l-phenylalanine 4-hydroxylase from Chromobacterium violaceum could convert l-tryptophan to 5-hydroxy-l-tryptophan and l-phenylalanine to l-tyrosine; however, the activity for l-tryptophan was extremely low compared to l-phenylalanine activity levels. We used the information on the crystal structures of aromatic amino acid hydroxylases to generate C. violaceuml-phenylalanine 4-hydroxylase with high l-tryptophan hydroxylating activity. In silico structural modeling analysis suggested that hydrophobic and/or stacking interactions with the substrate and cofactor at L101 and W180 in C. violaceuml-phenylalanine 4-hydroxylase would increase hydroxylation activity. Based on this hypothesis, we introduced a saturation mutagenesis towards these sites followed by the evaluation of 5-hydroxy-l-tryptophan productivity using a modified Gibbs assay. Three and nine positive mutants were obtained from the L101 and W180 mutant libraries, respectively. Among the mutants, L101Y and W180F showed the highest l-tryptophan hydroxylation activity at the respective residues. Steady-state kinetic analysis revealed that k(cat) values for l-tryptophan hydroxylation were increased from 0.40 (wild-type) to 1.02 (L101Y) and 0.51 s(-1) (W180F). In addition, the double mutant (L101Y-W180F) displayed higher l-tryptophan hydroxylation activity than the wild-type and the W180F and L101Y mutants. The k(cat) value of L101Y-W180F increased to 2.08 s(-1), showing a 5.2-fold increase compared to wild-type enzyme levels.

  18. The Crystal Structure of Cytochrome P450 4B1 (CYP4B1) Monoxygenase Complexed with Octane Discloses Several Structural Adaptations for ω-Hydroxylation.

    PubMed

    Hsu, Mei-Hui; Baer, Brian R; Rettie, Allan E; Johnson, Eric F

    2017-02-06

    P450 family 4 fatty acid ω-hydroxylases preferentially oxygenate primary C-H bonds over adjacent, energetically favored secondary C-H bonds, but the mechanism explaining this intriguing preference is unclear. To this end, the structure of rabbit P450 4B1 complexed with its substrate octane was determined by X-ray crystallography to define features of the active site that contribute to a preference for ω-hydroxylation. The structure indicated that octane is bound in a narrow active site cavity that limits access of the secondary C-H bond to the reactive intermediate. A highly conserved sequence motif on helix I contributes to positioning the terminal carbon of octane for ω-hydroxylation. Glu-310 of this motif auto-catalytically forms an ester bond with the heme 5-methyl, and the immobilized E310 contributes to substrate positioning. The preference for ω-hydroxylation was decreased in a E310A mutant having a shorter side-chain, but overall rates of metabolism were retained. E310D and E310Q substitutions having longer side-chains exhibit lower overall rates, likely due to higher conformational entropy for these residues, but they retained high preferences for octane ω-hydroxylation. Sequence comparisons indicated that active-site residues constraining octane for ω-hydroxylation are conserved in family 4 P450s. Moreover, the heme 7-propionate is positioned in the active site and provides additional restraints on substrate binding. In conclusion, P450 4B1 exhibits structural adaptations for ω-hydroxylation that include changes in the conformation of the heme and changes in a highly conserved helix I motif that is associated with selective oxygenation of un-activated primary C-H bonds.

  19. Spectroscopy and reaction dynamics of collision complexes containing hydroxyl radicals

    SciTech Connect

    Lester, M.I.

    1993-12-01

    The DOE supported work in this laboratory has focused on the spectroscopic characterization of the interaction potential between an argon atom and a hydroxyl radical in the ground X{sup 2}II and excited A {sup 2}{summation}{sup +} electronic states. The OH-Ar system has proven to be a test case for examining the interaction potential in an open-shell system since it is amenable to experimental investigation and theoretically tractable from first principles. Experimental identification of the bound states supported by the Ar + OH (X {sup 2}II) and Ar + OH(A {sup 2}{summation}{sup +}) potentials makes it feasible to derive realistic potential energy surfaces for these systems. The experimentally derived intermolecular potentials provide a rigorous test of ab initio theory and a basis for understanding the dramatically different collision dynamics taking place on the ground and excited electronic state surfaces.

  20. Crystal structure of tris-(hydroxyl-ammonium) orthophosphate.

    PubMed

    Leinemann, Malte; Jess, Inke; Boeckmann, Jan; Näther, Christian

    2015-11-01

    The crystal structure of the title salt, ([H3NOH](+))3·[PO4](3-), consists of discrete hydroxyl-ammonium cations and ortho-phos-phate anions. The atoms of the cation occupy general positions, whereas the anion is located on a threefold rotation axis that runs through the phospho-rus atom and one of the phosphate O atoms. In the crystal structure, cations and anions are linked by inter-molecular O-H⋯O and N-H⋯O hydrogen bonds into a three-dimensional network. Altogether, one very strong O-H⋯O, two N-H⋯O hydrogen bonds of medium strength and two weaker bifurcated N-H⋯O inter-actions are observed.

  1. SPLASH: A Southern Parkes Large Area Survey in Hydroxyl

    NASA Astrophysics Data System (ADS)

    Dawson, Joanne; Caswell, James; Gomez, Jose F.; Mcclure-Griffiths, Naomi; Lo, Nadia; Jones, Paul; Dickey, John; Cunningham, Maria; Green, James; Carretti, Ettore; Ellingsen, Simon; Walsh, Andrew; Purcell, Cormac; Breen, Shari; Hennebelle, Patrick; Imai, Hiroshi; Lowe, Vicki; Gibson, Steven; Brown, Courtney; Krishnan, Vasaant

    2014-04-01

    The OH 18 cm lines are powerful and versatile probes of diffuse molecular gas, that trace a largely unstudied component of the Galactic ISM. SPLASH (the Southern Parkes Large Area Survey in Hydroxyl) is a large, unbiased and fully-sampled survey of OH emission, absorption and masers in the Galactic Plane that will achieve sensitivities an order of magnitude better than previous work. The survey is answering critical questions on the global distribution of diffuse OH, the degree to which it traces ‘hidden’ material caught between the regimes probed by traditional tracers of the neutral ISM, and its role as a probe of molecular cloud formation. As a blind survey for all four ground-state transitions, SPLASH is also detecting many new OH masers, facilitating a broad range of astrophysical studies. This proposal requests 250 hours to complete Phase 1 of the SPLASH project, which is mapping 152 square degrees in the inner Galactic Plane, including the Galactic Centre.

  2. [Formation of hydrogen peroxide and hydroxyl radicals in aqueous solutions of L-amino acids by the action of X-rays and heat].

    PubMed

    Shtarkman, I N; Gudkov, S V; Chernikov, A V; Bruskov, V I

    2008-01-01

    The action of 1 mM solutions of L-amino acids in 5 mM phosphate buffer, pH 7.4, on the production of hydrogen peroxide and hydroxyl radicals under the action of X-rays and heating has been studied. Hydrogen peroxide was estimated by the method of enhanced luminescence in a system luminol-paraiodophenol-peroxidase and hydroxyl radicals were determined by using the fluorescence probe coumarin-3-carboxylic acid. It was shown that amino acids can be divided by their influence on H202 formation into three groups: those that reduce the yield of H202, that do not influence it, and that increase it. A similar action of amino acids was observed upon heating, but the composition of the groups was different. All amino acids lowered the formation of hydroxyl radicals under the action of X-rays, and the most effective among them were Cys > His > Phe = Met = Trp > Tyr. Met, His and Phe lowered the amount of hydroxyl radicals by heating, Ser raised it, whereas Tyr and Pro did not change it. Thus, amino acids differently influence the formation of reactive oxygen species by the action of X-rays and heat, and some of amino acids reveal themselves as effective natural antioxidants.

  3. Finding and characterizing the complexes of drug like molecules with quadruplex DNA: combined use of an enhanced hydroxyl radical cleavage protocol and NMR.

    PubMed

    Ranpura, Harikrushan; Bialonska, Dobroslawa; Bolton, Philip H

    2014-01-01

    Structural information on the complexes of drug like molecules with quadruplex DNAs can aid the development of therapeutics and research tools that selectively target specific quadruplex DNAs. Screening can identify candidate molecules that require additional evaluation. An enhanced hydroxyl radical cleavage protocol is demonstrated that can efficiently provide structural information on the complexes of the candidate molecules with quadruplex DNA. NMR methods have been used to offer additional structural information about the complexes as well as validate the results of the hydroxyl radical approach. This multi-step protocol has been demonstrated on complexes of the chair type quadruplex formed by the thrombin binding aptamer, d(GGTTGGTGTGGTTGG). The hydroxyl radical results indicate that NSC 176319, Cain's quinolinium that was found by screening, exhibits selective binding to the two TT loops. The NMR results are consistent with selective disruption of the hydrogen bonding between T4 and T13 as well as unstacking of these residues from the bottom quartet. Thus, the combination of screening, hydroxyl radical footprinting and NMR can find new molecules that selectively bind to quadruplex DNAs as well as provide structural information about their complexes.

  4. Photochemical formation of hydroxyl radical from effluent organic matter.

    PubMed

    Dong, Mei Mei; Rosario-Ortiz, Fernando L

    2012-04-03

    The photochemical formation of hydroxyl radical (HO•) from effluent organic matter (EfOM) was evaluated using three bulk wastewater samples collected at different treatment facilities under simulated sunlight. For the samples studied, the formation rates of HO•(R(HO•)) were obtained from the formation rate of phenol following the hydroxylation of benzene. The values of R(HO•) ranged from 2.3 to 3.8 × 10(-10) M s(-1) for the samples studied. The formation rate of HO• from nitrate photolysis (R(NO3)(HO•)) was determined to be 3.0 × 10(-7) M(HO)• M(NO3)(-1) s(-1). The HO• production rate from EfOM (R(EfOM)(HO•)) ranged from 0.76 to 1.3 × 10(-10) M s(-1). For the wastewater samples studied, R(EfOM)(HO•) varied from 1.5 to 2.4 × 10(-7) M(HO)• M(C)(-1) (s-1) on molarcarbon basis, which was close to HO• production from nitrate photolysis. The apparent quantum yield for the formation of HO• from nitrate (Φ(NO3-HO•)(a)) was determined as 0.010 ± 0.001 for the wavelength range 290-400 nm in ultrapure water. The apparent quantum yield for HO• formation in EfOM (Φ(EfOM-HO•)(a)) ranged from 6.1 to 9.8 × 10(-5), compared to 2.99 to 4.56 × 10(-5) for organic matter (OM) isolates. The results indicate that wastewater effluents could produce significant concentrations of HO•, as shown by potential higher nitrate levels and relatively higher quantum yields of HO• formation from EfOM.

  5. Electrophilic addition and cyclization reactions of allenes.

    PubMed

    Ma, Shengming

    2009-10-20

    Modern organic synthesis depends on the development of highly selective methods for the efficient construction of potentially useful target molecules. A primary goal in our laboratory is the discovery of new reactions that convert readily available starting materials to complex products with complete control of regio- and stereoselectivity. Allenes are one underused moiety in organic synthesis, because these groups are often thought to be highly reactive. However, many compounds containing the allene group, including natural products and pharmaceuticals, are fairly stable. The chemistry of allenes has been shown to have significant potential in organic synthesis. Electrophilic additions to allenes have often been considered to be synthetically less attractive due to the lack of efficient control of the regio- and stereoselectivity. However, this Account describes electrophilic reactions of allenes with defined regio- and stereoselectivity developed in our laboratory. Many substituted allenes are readily available from propargylic alcohols. Our work has involved an exploration of the reactions of these allenes with many different electrophiles: the E- or Z-halo- or seleno-hydroxylations of allenyl sulfoxides, sulfones, phosphine oxides, carboxylates, sulfides or selenides, butenolides, and arenes, and the halo- or selenolactonization reactions of allenoic acids and allenoates. These reactions have produced a host of new compounds such as stereodefined allylic alcohols, ethers, amides, thiiranes, and lactones. In all these reactions, water acts as a reactant and plays an important role in determining the reaction pathway and the stereoselectivity. The differing electronic properties of the two C=C bonds in these allenes determine the regioselectivity of these reactions. Through mechanistic studies of chirality transfer, isolation and reactivity of cyclic intermediates, (18)O-labeling, and substituent effects, we discovered that the E-stereoselectivity of some

  6. Moringa oleifera Lam. seed extract prevents fat diet induced oxidative stress in mice and protects liver cell-nuclei from hydroxyl radical mediated damage.

    PubMed

    Das, Nilanjan; Ganguli, Debdutta; Dey, Sanjit

    2015-12-01

    High fat diet (HFD) prompts metabolic pattern inducing reactive oxygen species (ROS) production in mitochondria thereby triggering multitude of chronic disorders in human. Antioxidants from plant sources may be an imperative remedy against this disorder. However, it requires scientific validation. In this study, we explored if (i) Moringa oleifera seed extract (MoSE) can neutralize ROS generated in HFD fed mice; (ii) protect cell-nuclei damage developed by Fenton reaction in vitro. Swiss mice were fed with HFD to develop oxidative stress model (HFD group). Other groups were control, seed extract alone treated, and MoSE simultaneously (HS) treated. Treatment period was of 15 days. Antioxidant enzymes with tissue nitrite content (TNC) and lipid peroxidation (LPO) were estimated from liver homogenate. HS group showed significantly higher (P < 0.05) superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), reduced glutathione (GSH) activity, and ferric reducing antioxidant power (FRAP) compared to only HFD fed group. Further, TNC and LPO decreased significantly (P < 0.05) in HS group compared to HFD fed group. MoSE also protected hepatocytes nuclei from the hydroxyl radicals generated by Fenton reaction. MoSE was found to be polyphenol rich with potent reducing power, free radicals and hydroxyl radicals scavenging activity. Thus, MoSE exhibited robust antioxidant prospective to neutralize ROS developed in HFD fed mice and also protected the nuclei damage from hydroxyl radicals. Hence, it can be used as herbal medication against HFD induced ROS mediated disorders.

  7. Phenylethynyl Containing Reactive Additives

    NASA Technical Reports Server (NTRS)

    Connell, John W. (Inventor); Smith, Joseph G., Jr. (Inventor); Hergenrother, Paul M. (Inventor)

    2002-01-01

    Phenylethynyl containing reactive additives were prepared from aromatic diamine, containing phenylethvnvl groups and various ratios of phthalic anhydride and 4-phenylethynviphthalic anhydride in glacial acetic acid to form the imide in one step or in N-methyl-2-pvrrolidinone to form the amide acid intermediate. The reactive additives were mixed in various amounts (10% to 90%) with oligomers containing either terminal or pendent phenylethynyl groups (or both) to reduce the melt viscosity and thereby enhance processability. Upon thermal cure, the additives react and become chemically incorporated into the matrix and effect an increase in crosslink density relative to that of the host resin. This resultant increase in crosslink density has advantageous consequences on the cured resin properties such as higher glass transition temperature and higher modulus as compared to that of the host resin.

  8. Phenylethynyl Containing Reactive Additives

    NASA Technical Reports Server (NTRS)

    Connell, John W. (Inventor); Smith, Joseph G., Jr. (Inventor); Hergenrother, Paul M. (Inventor)

    2002-01-01

    Phenylethynyl containing reactive additives were prepared from aromatic diamines containing phenylethynyl groups and various ratios of phthalic anhydride and 4-phenylethynylphthalic anhydride in glacial acetic acid to form the imide in one step or in N-methyl-2-pyrrolidi none to form the amide acid intermediate. The reactive additives were mixed in various amounts (10% to 90%) with oligomers containing either terminal or pendent phenylethynyl groups (or both) to reduce the melt viscosity and thereby enhance processability. Upon thermal cure, the additives react and become chemically incorporated into the matrix and effect an increase in crosslink density relative to that of the host resin. This resultant increase in crosslink density has advantageous consequences on the cured resin properties such as higher glass transition temperature and higher modulus as compared to that of the host resin.

  9. Supercharging by m-NBA Improves ETD-Based Quantification of Hydroxyl Radical Protein Footprinting.

    PubMed

    Li, Xiaoyan; Li, Zixuan; Xie, Boer; Sharp, Joshua S

    2015-08-01

    Hydroxyl radical protein footprinting (HRPF) is an MS-based technique for analyzing protein structure based on measuring the oxidation of amino acid side chains by hydroxyl radicals diffusing in solution. Spatial resolution of HRPF is limited by the smallest portion of the protein for which oxidation amounts can be accurately quantitated. Previous work has shown electron transfer dissociation (ETD) to be the most reliable method for quantifying the amount of oxidation of each amino acid side chain in a mixture of peptide oxidation isomers, but efficient ETD requires high peptide charge states, which limits its applicability for HRPF. Supercharging reagents have been used to enhance peptide charge state for ETD analysis, but previous work has shown supercharging reagents to enhance charge state differently for different peptides sequences; it is currently unknown if different oxidation isomers will experience different charge enhancement effects. Here, we report the effect of m-nitrobenzyl alcohol (m-NBA) on the ETD-based quantification of peptide oxidation. The addition of m-NBA to both a defined mixture of synthetic isomeric oxidized peptides and Robo-1 protein subjected to HRPF increased the abundance of higher charge state ions, improving our ability to perform efficient ETD of the mixture. No differences in the reported quantitation by ETD were noted in the presence or absence of m-NBA, indicating that all oxidation isomers were charge-enhanced to a similar extent. These results indicate the utility of m-NBA for residue-level quantification of peptide oxidation in HRPF and other applications.

  10. Supercharging by m-NBA Improves ETD-Based Quantification of Hydroxyl Radical Protein Footprinting

    NASA Astrophysics Data System (ADS)

    Li, Xiaoyan; Li, Zixuan; Xie, Boer; Sharp, Joshua S.

    2015-08-01

    Hydroxyl radical protein footprinting (HRPF) is an MS-based technique for analyzing protein structure based on measuring the oxidation of amino acid side chains by hydroxyl radicals diffusing in solution. Spatial resolution of HRPF is limited by the smallest portion of the protein for which oxidation amounts can be accurately quantitated. Previous work has shown electron transfer dissociation (ETD) to be the most reliable method for quantifying the amount of oxidation of each amino acid side chain in a mixture of peptide oxidation isomers, but efficient ETD requires high peptide charge states, which limits its applicability for HRPF. Supercharging reagents have been used to enhance peptide charge state for ETD analysis, but previous work has shown supercharging reagents to enhance charge state differently for different peptides sequences; it is currently unknown if different oxidation isomers will experience different charge enhancement effects. Here, we report the effect of m-nitrobenzyl alcohol ( m-NBA) on the ETD-based quantification of peptide oxidation. The addition of m-NBA to both a defined mixture of synthetic isomeric oxidized peptides and Robo-1 protein subjected to HRPF increased the abundance of higher charge state ions, improving our ability to perform efficient ETD of the mixture. No differences in the reported quantitation by ETD were noted in the presence or absence of m-NBA, indicating that all oxidation isomers were charge-enhanced to a similar extent. These results indicate the utility of m-NBA for residue-level quantification of peptide oxidation in HRPF and other applications.

  11. Synthesis, photocatalytic activity, and photogenerated hydroxyl radicals of monodisperse colloidal ZnO nanospheres

    NASA Astrophysics Data System (ADS)

    Yang, Chong; Li, Qingsong; Tang, Limei; Xin, Kun; Bai, Ailing; Yu, Yingmin

    2015-12-01

    In the present study, monodisperse colloidal zinc oxide (ZnO) nanospheres were successfully synthesized via a newly developed two-stage solution method followed by facile calcination at various temperatures. The effects of calcination temperature on the structure, morphology, and optical properties as well as the photocatalytic activity of the as-made ZnO samples were investigated systematically by Fourier transform infrared spectrometry, X-ray diffraction, field emission scanning electron microscopy, nitrogen adsorption/desorption isotherms, diffuse reflectance UV-visible spectroscopy (DRS), photoluminescence, and related photocatalytic activity tests. The thermal decomposition was analyzed by thermogravimetric analysis. The crystallinity was found to gradually increase with increasing calcination temperature, whereas the decrease in the Brunauer-Emmett-Teller specific surface area of the samples with calcination may be ascribed to the increased particle size. The DRS results provided clear evidence for the decrease in band gap energy of ZnO samples with an increase in calcination temperature. The photoluminescence spectra demonstrated the calcination-dependent emission features, especially the UV emission intensity. In particular, the ZnO product calcined at 400 °C exhibited the highest photocatalytic activity, degrading methylene blue by almost 99.1% in 70 min, which is ascribed to the large specific surface area and pore volume, high electron-hole pair separation efficient, and great redox potential of the obtained ZnO nanoparticles. In addition, the production of photogenerated hydroxyl radicals (•OH) was consistent with the methylene blue degradation efficiency over the as-made ZnO nanoparticles. Using isopropanol as a hydroxyl radical scavenger, •OH was determined to be the main active oxygen species in the photocatalytic process. A possible mechanism of photodegradation under UV light irradiation also is proposed.

  12. Hydroxyl functionalized polytriazole-co-polyoxadiazole as substrates for forward osmosis membranes.

    PubMed

    Duong, Phuoc H H; Chisca, Stefan; Hong, Pei-Ying; Cheng, Hong; Nunes, Suzana P; Chung, Tai-Shung

    2015-02-25

    Hydroxyl functionalized polytriazole-co-polyoxadiazole (PTA-POD) copolymers have been synthesized and cast as promising highly thermally stable, chemically resistant, and antiorganic/biological fouling porous substrates for the fabrication of thin-film composite (TFC) forward osmosis (FO) membranes. The roles of PTA/POD ratios in the membrane substrates, TFC layers, and FO membrane performance have been investigated. This study demonstrates that the substrate fabricated from the copolymer containing 40 mol % PTA is optimal for the TFC membranes. Compared to the POD-TFC membrane, the 40 mol % PTA-TFC membrane exhibits a remarkable decrease in structural parameter (S) of more than 3.3 times. In addition, the 40 mol % PTA-TFC membrane is characterized by high water fluxes of 24.9 LMH and 47.2 LMH using 1 M NaCl as the draw solution and DI water as the feed under FO and pressure retarded osmosis (PRO) modes, respectively. Compared to a polysulfone (PSU) supported TFC-FO membrane under similar fabrication conditions, the 40% mol PTA-TFC membrane shows better FO performance and enhanced antifouling properties on the support (lower protein binding propensity and improved bacterial inhibition). Moreover, the performance of the 40 mol % PTA supported TFC-FO membrane can be improved to 37.5 LMH (FO mode)/78.4 LMH (PRO mode) and potentially higher by optimizing the support morphology, the TFC formation, and the post-treatment process. Hence, the use of newly developed hydroxyl functionalized polytriazole-co-polyoxadiazole copolymers may open up a new class of material for FO processes.

  13. Protective Effect against Hydroxyl-induced DNA Damage and Antioxidant Activity of Radix Glycyrrhizae (Liquorice Root)

    PubMed Central

    Li, Xican; Chen, Weikang; Chen, Dongfeng

    2013-01-01

    Purpose: As a typical Chinese herbal medicine, Radix Glycyrrhizae (RG) possesses various pharmacological effects involved in antioxidant ability. However, its antioxidant has not been explored so far. The aim of the study was to investigate its antioxidant ability, then further discuss the antioxidant mechanism. Methods: RG was extracted by ethanol to obtain ethanolic extract of Radix Glycyrrhizae (ERG). ERG was then determined by various antioxidant methods, including DNA damage assay, DPPH assay, ABTS assay, Fe3+-reducing assay and Cu2+-reducing assay. Finally, the contents of total phenolics and total flavonoids were analyzed by spectrophotometric methods. Results: Our results revealed that ERG could effectively protect against hydroxyl-induced DNA damage (IC50 517.28±26.61μg/mL). In addition, ERG could scavenge DPPH· radical (IC50165.18±6.48μg/mL) and ABTS+• radical (IC507.46±0.07μg/mL), reduce Fe3+ (IC50 97.23±2.88 μg/mL) and Cu2+ (IC50 59.21±0.18 μg/mL). Chemical analysis demonstrated that the contents of total phenolics and flavonoids in ERG were 111.48±0.88 and 218.26±8.57 mg quercetin/g, respectively. Conclusion: Radix Glycyrrhizae can effectively protect against hydroxyl-induced DNA damage. One mechanism of protective effect may be radical-scavenging which is via donating hydrogen atom (H·), donating electron (e). Its antioxidant ability can be mainly attributed to the flavonoids or total phenolics. PMID:24312831

  14. Protective Effect against Hydroxyl-induced DNA Damage and Antioxidant Activity of Citri reticulatae Pericarpium

    PubMed Central

    Li, Xican; Huang, Yanping; Chen, Dongfeng

    2013-01-01

    Purpose: As a typical Chinese herbal medicine, Citri reticulatae pericarpium (CRP) possesses various pharmacological effects involved in antioxidant ability. However, its antioxidant effects have not been reported yet. The objective of this work was to investigate its antioxidant ability, then further discuss the antioxidant mechanism. Methods: CRP was extracted by ethanol to obtain ethanol extract of Citri reticulatae pericarpium (ECRP). ECRP was then measured by various antioxidant methods, including DNA damage assay, DPPH assay, ABTS assay, Fe3+-reducing assay and Cu2+-reducing assay. Finally, the content of total flavonoids was analyzed by spectrophotometric method. Results: Our results revealed that ECRP could effectively protect against hydroxyl-induced DNA damage (IC50 944.47±147.74 μg/mL). In addition, it could also scavenge DPPH· radical (IC50349.67±1.91 μg/mL) and ABTS+• radical (IC5011.33±0.10 μg/mL), reduce Fe3+ (IC50 140.95±2.15 μg/mL) and Cu2+ (IC50 70.46±1.77 μg/mL). Chemical analysis demonstrated that the content of total flavonoids in ECRP was 198.29±12.24 mg quercetin/g. Conclusion: Citri reticulatae pericarpium can effectively protect against hydroxyl-induced DNA damage. One mechanism of protective effect may be radical-scavenging which is via donating hydrogen atom (H·), donating electron (e). Its antioxidant ability can be mainly attributed to the flavonoids, especially hesperidin and narirutin. PMID:24312832

  15. Oxidation of carboxylic acids regenerates hydroxyl radicals in the unpolluted and nighttime troposphere.

    PubMed

    da Silva, Gabriel

    2010-07-01

    The hydroxyl radical (OH) controls the removal of organic compounds from the troposphere. Atmospheric chemistry models significantly under-predict OH levels in unpolluted environments, implying that they are regenerated via some unknown mechanism(s). This work uses computational chemistry to demonstrate that the photochemical oxidation of alkyl carboxylic acids can efficiently regenerate the hydroxyl radical via unimolecular decomposition of alpha-carboxyalkylperoxy radicals. For acetic acid and propanoic acid the proposed mechanism is predicted to dominate in the unpolluted lower troposphere, and it may also operate to some extent in the mid to upper troposphere. Alkyl carboxylic acids are also predicted to act as a new source of nighttime OH throughout the planetary boundary layer, where OH levels are also under-predicted. The thermodynamic requirements for reactions of this class are discussed, and some candidate OH-reforming molecules particularly relevant to aromatic photooxidation are identified. Adopting a broader perspective, the alpha-carboxyalkyl radical precursors that react with O(2) to form the unstable alpha-carboxyalkylperoxy type radicals are also expected to form during combustion, in the interstellar medium, and from the gamma-irradiation of glycine and related amino acids, and the potential importance of this new chemistry in these environments is discussed. Master equation simulations suggest that alpha-carboxyalkyl + O(2) reactions provide a prompt OH source during the autoignition and combustion of biodiesel and other oxygenated biofuels, where carboxylic acids are formed as early stage oxidation products. Ketene combustion is also thought to proceed via these OH-reforming alpha-carboxyalkyl radicals. The in vivo formation of alpha-carboxyalkylperoxy radicals followed by oxidation to the highly reactive OH radical may induce oxidative stress in the human body, in a process initiated by gamma-rays. Finally, the reaction of ketenes with OH to

  16. Radiation-induced cell lethality of samonella typhimurium ATCC 14028: Cooperative effect of hydroxyl radical and oxygen

    SciTech Connect

    Kim, Y.A.; Thayer, D.W.

    1995-10-01

    The lethality of {gamma}-radiation doses of 0.2 to 1.0 kGy for Salmonella typhimurium ATCC 14028 was measured in the presence of air, N{sub 2} and N{sub 2}O and with the hydroxyl radical scavengers formate and polyethylene glycol (PEG), M{sub r} 8,000. Saturation of cell suspensions with either N{sub 2}O or N{sub 2}/N{sub 2}/N{sub 2}O (1:1, v/v) gas was expected to double the number of hydroxyl radicals (OH{center_dot}) and to produce an equivalent increase in lethality, but this did not occur. Adding 10% (v/v) O{sub 2} to either N{sub 2}/N{sub 2}O gas produced approximately the same {gamma}-irradiation lethality for S. typhimurium as did air. Addition of hydroxyl radical scavengers, 40 mM formate and 1.5% (w/v) PEG, significantly reduced the lethality of {gamma} radiation for S. typhimurium in the presence of air but not in the presence of N{sub 2} or N{sub 2}O gases. Membrane-permeable formate provided slightly better protection than nonpermeable PEG. Cells of S. typhimurium grown under anaerobic conditions were more sensitive to radiation, and were less protected by hydroxyl radical scavengers, especially formate, than when cells grown under aerobic conditions were irradiated in the presence of oxygen. Hydroxyl radical scavengers provided no further protection during irradiation in the absence of oxygen. These results indicated that the increased radiation sensitivity of cells grown under anaerobic conditions may be related to superoxide radicals which could increase intercellular damage during irradiation in the presence of oxygen. However, endogenous superoxide dismutase and catalase activities did not protect cells from the radiation-induced lethality of S. typhimurium. Cytoplasmic extracts protected bacterial DNA in vitro in either the presence of absence of oxygen, and no radiation-induced lipid peroxidation of the cellular components was identified by measuring the levels of 2-thiobarbituric acid. 38 refs., 4 figs., 2 tabs.

  17. Kinetic studies on the hydroxylation of p-coumaric acid to caffeic acid by spinach-beet phenolase.

    PubMed Central

    McIntyre, R J; Vaughan, P F

    1975-01-01

    1. A spectrophotometric assay is described that enables the hydroxylation of p-coumaric acid to caffeic acid, catalysed by spinach-beet phenolase, to be followed continuously. 2. Initial-velocity and inhibitor studies indicate that the order of substrate addition is oxygen, p-coumaric acid and electron donor, with an irreversible step separating the binding of each substrate. 3. Caffeic acid is most likely to act as electron donor at the active site; other electron donors, such as ascorbic acid, NADH and dimethyltetrahydropteridine, function mainly to recycle cofactor amounts of caffeic acid. 4. A reaction scheme, consistent with these data, is proposed. PMID:170916

  18. Theoretical study on the initial reaction mechanisms of ansa-metallocene zirconium precursor on hydroxylated Si(1 0 0) surface.

    PubMed

    Zhou, Guangfen; Ren, Jie; Zhang, Shaowen

    2016-05-01

    The initial reaction mechanisms for depositing ZrO2 thin films using ansa-metallocene zirconium (Cp2CMe2)ZrMe2 precursor were studied by density functional theory (DFT) calculations. The (Cp2CMe2)ZrMe2 precursor could be absorbed on the hydroxylated Si(1 0 0) surface via physisorption. Possible reaction pathways of (Cp2CMe2)ZrMe2 were proposed. For each reaction, the activation energies and reaction energies were compared, and stationary points along the reaction pathways were shown. In addition, the influence of dispersion effects on the reactions was evaluated by non-local dispersion corrected DFT calculations.

  19. Comparison of fluorescence-based techniques for the quantification of particle-induced hydroxyl radicals

    PubMed Central

    Cohn, Corey A; Simon, Sanford R; Schoonen, Martin AA

    2008-01-01

    Background Reactive oxygen species including hydroxyl radicals can cause oxidative stress and mutations. Inhaled particulate matter can trigger formation of hydroxyl radicals, which have been implicated as one of the causes of particulate-induced lung disease. The extreme reactivity of hydroxyl radicals presents challenges to their detection and quantification. Here, three fluorescein derivatives [aminophenyl fluorescamine (APF), amplex ultrared, and dichlorofluorescein (DCFH)] and two radical species, proxyl fluorescamine and tempo-9-ac have been compared for their usefulness to measure hydroxyl radicals generated in two different systems: a solution containing ferrous iron and a suspension of pyrite particles. Results APF, amplex ultrared, and DCFH react similarly to the presence of hydroxyl radicals. Proxyl fluorescamine and tempo-9-ac do not react with hydroxyl radicals directly, which reduces their sensitivity. Since both DCFH and amplex ultrared will react with reactive oxygen species other than hydroxyl radicals and another highly reactive species, peroxynitite, they lack specificity. Conclusion The most useful probe evaluated here for hydroxyl radicals formed from cell-free particle suspensions is APF due to its sensitivity and selectivity. PMID:18307787

  20. Proteomic analysis reveals diverse proline hydroxylation-mediated oxygen-sensing cellular pathways in cancer cells

    PubMed Central

    Liu, Bing; Gao, Yankun; Ruan, Hai-Bin