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Sample records for alkoxy radicals

  1. Rotationally-resolved excitation spectroscopy of the alkoxy and alkylthio radicals in a supersonic jet

    NASA Technical Reports Server (NTRS)

    Misra, Prabhakar; Zhu, Xinming; Bryant, Hosie L.; Kamal, Mohammed M.

    1993-01-01

    Rotationally-resolved laser excitation spectra have been obtained for the alkoxy radicals (CH3O, C2H5O, i-C3H7O) and the alkylthio radicals (CH3S, C2H5S, i-C3H7S) in a supersonic jet expansion. Low resolution (0.2/cm) excitation spectra have helped identify several vibronic bands belonging to the A-X electronic system for these jet-cooled free radicals. High resolution (0.07/cm) laser-induced fluorescence excitation spectra have aided the unraveling of the associated rotational structure and in certain cases (CH3O and CH3S, for example) enabled explicit rotational (J,K) assignments of the transitions.

  2. Cyclopentadienone Oxidation Reaction Kinetics and Thermochemistry for the Alcohols, Hydroperoxides, and Vinylic, Alkoxy, and Alkylperoxy Radicals.

    PubMed

    Yommee, Suriyakit; Bozzelli, Joseph W

    2016-01-28

    Cyclopentadienone has one carbonyl and two olefin groups resulting in 4n + 2 π-electrons in a cyclic five-membered ring structure. Thermochemical and kinetic parameters for the initial reactions of cyclopentadienone radicals with O2 and the thermochemical properties for cyclopentadienone-hydroperoxides, alcohols, and alkenyl, alkoxy, and peroxy radicals were determined by use of computational chemistry. The CBS-QB3 composite and B3LYP density functional theory methods were used to determine the enthalpies of formation (ΔfH°298) using the isodesmic reaction schemes with several work reactions for each species. Entropy and heat capacity, S°(T) and Cp°(T) (50 K ≤ T ≤ 5000 K) are determined using geometric parameters, internal rotor potentials, and frequencies from B3LYP/6-31G(d,p) calculations. Standard enthalpies of formation are reported for parent molecules as cyclopentadienone, cyclopentadienone with alcohol, hydroperoxide substituents, and the cyclopentadienone-yl vinylic, alkoxy, and peroxy radicals corresponding to loss of a hydrogen atom from the carbon and oxygen sites. Entropy and heat capacity vs temperature also are reported for the parent molecules and for radicals. The thermochemical analysis shows The R(•) + O2 well depths are deep, on the order of 50 kcal mol(-1), and the R(•) + O2 reactions to RO + O (chain branching products) for cyclopentadienone-2-yl and cyclopentadienone-3-yl have unusually low reaction (ΔHrxn) enthalpies, some 20 or so kcal/mol below the entrance channels. Chemical activation kinetics using quantum RRK analysis for k(E) and master equation for falloff are used to show that significant chain branching as a function of temperature and pressure can occur when these vinylic radicals are formed.

  3. Strategies to control alkoxy radical-initiated relay cyclizations for the synthesis of oxygenated tetrahydrofuran motifs.

    PubMed

    Zhu, Hai; Leung, Joe C T; Sammis, Glenn M

    2015-01-16

    Radical relay cyclizations initiated by alkoxy radicals are a powerful tool for the rapid construction of substituted tetrahydrofurans. The scope of these relay cyclizations has been dramatically increased with the development of two strategies that utilize an oxygen atom in the substrate to accelerate the desired hydrogen atom transfer (HAT) over competing pathways. This has enabled a chemoselective 1,6-HAT over a competing 1,5-HAT. Furthermore, this allows for a chemoselective 1,5-HAT over competing direct cyclizations and β-fragmentations. Oxygen atom incorporation leads to a general increase in cyclization diastereoselectivity over carbon analogues. This chemoselective relay cyclization strategy was utilized in the improved synthesis of the tetrahydrofuran fragment in (−)-amphidinolide K.

  4. Alkoxy Radical Bond Scissions Explain the Anomalously Low Secondary Organic Aerosol and Organonitrate Yields From α-Pinene + NO3.

    PubMed

    Kurtén, Theo; Møller, Kristian H; Nguyen, Tran B; Schwantes, Rebecca H; Misztal, Pawel K; Su, Luping; Wennberg, Paul O; Fry, Juliane L; Kjaergaard, Henrik G

    2017-07-06

    Oxidation of monoterpenes (C10H16) by nitrate radicals (NO3) constitutes an important source of atmospheric secondary organic aerosol (SOA) and organonitrates. However, knowledge of the mechanisms of their formation is incomplete and differences in yields between similar monoterpenes are poorly understood. In particular, yields of SOA and organonitrates from α-pinene + NO3 are low, while those from Δ(3)-carene + NO3 are high. Using computational methods, we suggest that bond scission of the nitrooxy alkoxy radicals from Δ(3)-carene lead to the formation of reactive keto-nitrooxy-alkyl radicals, which retain the nitrooxy moiety and can undergo further reactions to form SOA. By contrast, bond scissions of the nitrooxy alkoxy radicals from α-pinene lead almost exclusively to the formation of the relatively unreactive and volatile product pinonaldehyde (C10H16O2), thereby limiting organonitrate and SOA formation. This hypothesis is supported by laboratory experiments that quantify products of the reaction of α-pinene + NO3 under atmospherically relevant conditions.

  5. Factors affecting the stability and equilibria of free radicals. XIII. N-alkoxy- and N-aralkoxypicrylamines and ESR spectra of the corresponding capto-dative persistent aminyls

    NASA Astrophysics Data System (ADS)

    Stanciuc, Gabriela; Caproiu, M. Teodor; Caragheorgheopol, Agneta; Caldararu, Horia; Balaban, Alexandru T.; Walter, Robert I.

    Five O-alkylhydroxylamines and three aralkylhydroxylamines have been picrylated to give O-alkyl- N-picrylhydroxylamines. These were converted to the corresponding N-(ar)alkoxy-picryl-aminyl radicals in toluene solution, and the ESR spectra were recorded. Simulations of the spectra with reasonable parameters and g values confirm the expected radical structures. Hyperfine coupling constants for nuclei in the picryl (acceptor) ring are smaller than those for the (ar)alkoxy group. This indication of competitive electron pair delocalization to the picryl ring, together with the long lifetimes of these radicals (compared with the symmetrically substituted diphenylaminyls), both support the concept of captodative stabilization.

  6. Effect of temperature on the EPR properties of a rhamnose alkoxy radical: a DFT molecular dynamics study.

    PubMed

    Pauwels, Ewald; Verstraelen, Toon; Waroquier, Michel

    2008-05-01

    It has been shown previously that two distinctive variants (called RHop and RO4) exist of the radiation-induced rhamnose alkoxy radical. Density functional theory (DFT) calculations of the electron paramagnetic resonance (EPR) properties were found to be consistent with two separate measurements at different temperatures [E. Pauwels, R. Declerck, V. Van Speybroeck, M. Waroquier, Radiat. Res., in press]. However, the agreement between theory and experiment was only of a qualitative nature, especially for the latter radical. In the present work, it is examined whether this residual difference between theoretical and experimental spectroscopic properties can be explained by explicitly accounting for temperature in DFT calculations. With the aid of ab-initio molecular dynamics, a temperature simulation was conducted of the RO4 variant of the rhamnose alkoxy radical. At several points along the MD trajectory, g and hyperfine tensors were calculated, yielding time (and temperature) dependent mean spectroscopic properties. The effect of including temperature is evaluated but found to be within computational error.

  7. Reactions of the alkoxy radicals formed following OH-addition to alpha-pinene and beta-pinene. C-C bond scission reactions.

    PubMed

    Dibble, T S

    2001-05-09

    The atmospheric degradation pathways of the atmospherically important terpenes alpha-pinene and beta-pinene are studied using density functional theory. We employ the correlation functional of Lee, Yang, and Parr and the three-parameter HF exchange functional of Becke (B3LYP) together with the 6-31G(d) basis set. The C-C bond scission reactions of the beta-hydroxyalkoxy radicals that are formed after OH addition to alpha-pinene and beta-pinene are investigated. Both of the alkoxy radicals formed from the alpha-pinene-OH adduct possess a single favored C-C scission pathway with an extremely low barrier (approximately 3 kcal/mol) leading to the formation of pinonaldehyde. Neither of these pathways produces formaldehyde, and preliminary computational results offer some support for suggestions that 1,5 or 1,6 H-shift (isomerization) reactions of alkoxy radicals contribute to formaldehyde production. In the case of the alkoxy radical formed following OH addition to the methylene group of beta-pinene, there exists two C-C scission reactions with nearly identical barrier heights (approximately 7.5 kcal/mol); one leads to known products (nopinone and formaldehyde) but the ultimate products of the competing reaction are unknown. The single C-C scission pathway of the other alkoxy radical from beta-pinene possesses a very low (approximately 4 kcal/mol) barrier. The kinetically favored C-C scission reactions of all four alkoxy radicals appear to be far faster than expected rates of reaction with O2. The rearrangement of the alpha-pinene-OH adduct, a key step in the proposed mechanism of formation of acetone from alpha-pinene, is determined to possess a barrier of 11.6 kcal/mol. This value is consistent with another computational result and is broadly consistent with the modest acetone yields observed in product yield studies.

  8. Wavelength-resolved emission spectroscopy of the alkoxy and alkylthio radicals in a supersonic jet

    NASA Technical Reports Server (NTRS)

    Misra, Prabhakar; Zhu, Xinming; Hsueh, Ching-Yu; Kamal, Mohammed M.

    1993-01-01

    Wavelength-resolved emission spectra of methoxy (CH3O) and methylthio (CH3S) radicals have been obtained in a supersonic jet environment with a resolution of 0.3 nm by dispersing the total laser-induced fluorescence with a 0.6 m monochromator. A detailed analysis of the single vibronic level dispersed fluorescence spectra yields the following vibrational frequencies for CH3O in the X(2)E state; nu(sub 1 double prime) = 2953/cm, nu(sub 2 double prime) = 1375/cm, nu(sub 3 double prime) = 1062/cm, nu(sub 4 double prime) = 2869/cm, nu(sub 5 double prime) = 1528/cm and nu(sub 6 double prime) = 688/cm. A similar analysis of the wavelength-resolved emission spectra of CH3S provides the following ground state vibrational frequencies: nu(sub 2 double prime) = 1329/cm, nu(sub 3 double prime) = 739/cm and nu(sub 6 double prime) = 601/cm. An experimental uncertainty of 20/cm is estimated for the assigned frequencies.

  9. Wavelength-resolved emission spectroscopy of the alkoxy and alkylthio radicals in a supersonic jet

    NASA Technical Reports Server (NTRS)

    Misra, Prabhakar; Zhu, Xinming; Hsueh, Ching-Yu; Kamal, Mohammed M.

    1993-01-01

    Wavelength-resolved emission spectra of methoxy (CH3O) and methylthio (CH3S) radicals have been obtained in a supersonic jet environment with a resolution of 0.3 nm by dispersing the total laser-induced fluorescence with a 0.6 m monochromator. A detailed analysis of the single vibronic level dispersed fluorescence spectra yields the following vibrational frequencies for CH3O in the X(2)E state; nu(sub 1 double prime) = 2953/cm, nu(sub 2 double prime) = 1375/cm, nu(sub 3 double prime) = 1062/cm, nu(sub 4 double prime) = 2869/cm, nu(sub 5 double prime) = 1528/cm and nu(sub 6 double prime) = 688/cm. A similar analysis of the wavelength-resolved emission spectra of CH3S provides the following ground state vibrational frequencies: nu(sub 2 double prime) = 1329/cm, nu(sub 3 double prime) = 739/cm and nu(sub 6 double prime) = 601/cm. An experimental uncertainty of 20/cm is estimated for the assigned frequencies.

  10. Reaction of Cu(I) with dialkyl peroxides: Cu(II)-alkoxides, alkoxy radicals, and catalytic C-H etherification.

    PubMed

    Gephart, Raymond T; McMullin, Claire L; Sapiezynski, Nicholas G; Jang, Eun Sil; Aguila, Mae Joanne B; Cundari, Thomas R; Warren, Timothy H

    2012-10-24

    Kinetic analysis of the reaction of the copper(I) β-diketiminate [Cl(2)NN]Cu ([Cu(I)]) with (t)BuOO(t)Bu to give [Cu(II)]-O(t)Bu (1) reveals first-order behavior in each component implicating the formation of free (t)BuO(•) radicals. Added pyridine mildly inhibits this reaction indicating competition between (t)BuOO(t)Bu and py for coordination at [Cu(I)] prior to peroxide activation. Reaction of [Cu(I)] with dicumyl peroxide leads to [Cu(II)]-OCMe(2)Ph (3) and acetophenone suggesting the intermediacy of the PhMe(2)CO(•) radical. Computational methods provide insight into the activation of (t)BuOO(t)Bu at [Cu(I)]. The novel peroxide adduct [Cu(I)]((t)BuOO(t)Bu) (4) and the square planar [Cu(III)](O(t)Bu)(2) (5) were identified, each unstable toward loss of the (t)BuO(•) radical. Facile generation of the (t)BuO(•) radical is harnessed in the catalytic C-H etherification of cyclohexane with (t)BuOO(t)Bu at rt employing [Cu(I)] (5 mol %) to give the ether Cy-O(t)Bu in 60% yield.

  11. Theoretical studies on atmospheric chemistry of HFE-245mc and perfluoro-ethyl formate: Reaction with OH radicals, atmospheric fate of alkoxy radical and global warming potential

    NASA Astrophysics Data System (ADS)

    Lily, Makroni; Baidya, Bidisha; Chandra, Asit K.

    2017-02-01

    Theoretical studies have been performed on the kinetics, mechanism and thermochemistry of the hydrogen abstraction reactions of CF3CF2OCH3 (HFE-245mc) and CF3CF2OCHO with OH radical using DFT based M06-2X method. IRC calculation shows that both hydrogen abstraction reactions proceed via weakly bound hydrogen-bonded complex preceding to the formation of transition state. The rate coefficients calculated by canonical transition state theory along with Eckart's tunnelling correction at 298 K: k1(CF3CF2OCH3 + OH) = 1.09 × 10-14 and k2(CF3CF2OCHO + OH) = 1.03 × 10-14 cm3 molecule-1 s-1 are in very good agreement with the experimental values. The atmospheric implications of CF3CF2OCH3 and CF3CF2OCHO are also discussed.

  12. A theoretical investigation on kinetics, mechanism, and thermochemistry of the gas-phase reactions of methyl fluoroacetate with OH radicals and fate of alkoxy radical.

    PubMed

    Mishra, Bhupesh Kumar; Deka, Ramesh Chandra

    2014-09-25

    We theoretically investigated OH-initiated hydrogen abstraction reactions of methyl fluoroacetate (MFA) CH2FC(O)OCH3 at the MPWB1K level of theory in conjunction with the 6-31+G(d,p) basis set. Thermodynamic and kinetic data are computed using the comparatively accurate G2(MP2) method. Two most stable conformers of MFA are identified, and the energy difference between them is found to be only 0.32 kcal mol(-1). Both of them are considered for rate coefficient calculations, and the contribution from each of the conformers is found to be quite significant. We propose an indirect mechanism due to validation of pre- and post-reactive complexes. The rate parameters are determined using canonical transition state theory and energetics at the G2(MP2) level. The temperature dependence of the rate constant can be described by the Arrhenius expressions: k = 8.79 × 10(-13) exp[(-377.27 ± 64)/T] cm(3) molecule(-1) s(-1) over a temperature range of 250-450 K. The ΔfH°298 for CH2FC(O)OCH3, CH2FC(O)OC(•)H2, and C(•)HFC(O)OCH3 are also computed using an isodesmic procedure. The OH-driven atmospheric lifetime of MFA was estimated to be 24 days. A mechanistic study to shed light on the atmospheric degradation and the sole fate for the consumption of CH2FC(O)OCH2O(•) radical has also been reported.

  13. Stereopentads derived from a sequence of Mukaiyama aldolization and free radical reduction on alpha-methyl-beta-alkoxy aldehydes: a general strategy for efficient polypropionate synthesis.

    PubMed

    Brazeau, Jean-François; Mochirian, Philippe; Prévost, Michel; Guindon, Yvan

    2009-01-02

    In a stereodivergent manner, all 16 diastereomeric stereopentads 7-22 were synthesized starting with alpha-methyl-beta-alkoxy aldehydes 25 and 27. We designed an approach based on a sequence of a Mukaiyama aldolization with enoxysilane 24 followed by a hydrogen transfer reaction. Recent advancements concerning these reactions are described, and novel key intermediates are characterized in the aldol step. The synthesis of C(1)-C(11) fragment 60 of zincophorin, which contains a synthetically challenging stereopentad unit, is described attesting the usefulness of our strategy.

  14. Symmetry-Driven Strategy for the Assembly of the Core Tetracycle of (+)-Ryanodine: Synthetic Utility of a Cobalt-Catalyzed Olefin Oxidation and α-Alkoxy Bridgehead Radical Reaction.

    PubMed

    Nagatomo, Masanori; Hagiwara, Koji; Masuda, Kengo; Koshimizu, Masaki; Kawamata, Takahiro; Matsui, Yuki; Urabe, Daisuke; Inoue, Masayuki

    2016-01-04

    Ryanodine (1) is a potent modulator of intracellular calcium release channels, designated as ryanodine receptors. The exceptionally complex molecular architecture of 1 comprises a highly oxygenated pentacyclic system with eleven contiguous stereogenic centers, which makes it a formidable target for organic synthesis. We identified the embedded C2 -symmetric tricyclic substructure within 1. This specific recognition permitted us to design a concise synthetic route to enantiopure tricycle 9 by utilizing a series of pairwise functionalizations. The four tetrasubstituted carbon centers of 9 were effectively constructed by three key reactions, a dearomatizing Diels-Alder reaction, the kinetic resolution of the obtained racemic 14 through asymmetric methanolysis, and the transannular aldol reaction of the eight-membered diketone 10. A new combination of cobalt-catalyzed hydroperoxidation and NfF-promoted elimination enabled conversion of the hindered olefin of 9 into the corresponding ketone, thus realizing the desymmetrization. Finally, the tetrasubstituted carbon was stereospecifically installed by utilizing the α-alkoxy bridgehead radical to deliver the core tetracycle 7 with the six contiguous tetrasubstituted carbon centers. Consequently, the present work not only accomplishes efficient assembly of four out of the five fused rings of 1, but also develops two new powerful methodologies: two-step ketone formation and bridgehead radical reaction. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Homolytic halogenation of 2-alkoxy-1, s-dioxacycloalkanes

    SciTech Connect

    Rol'nik, L.Z.; Pastushenko, E.V.; Rakmankulov, D.L.; Zlot-skii, S.S.

    1984-04-10

    This article examines the free-radical reactions of 2-alkoxy-1, 3-dioxacycloalkanes in the presence of polyhalomethanes. The influence of halogenation agents on the course of the process is studied for the case of 2-(hexyloxy)-1, 3-dioxolane with the use of CBrCl/sub 3/ and CCl/sub 4/. The infrared spectra of the compounds obtained were determined with a UR-20 spectrometer in the range 700-4000 cm/sup -1/ on capillary layers between NaCl plates. The results indicate that the main products of the free-radical transformations of 2-alkoxy-1, 3-dioxacycloalkanes in a medium of CHBr/sub 3/ are alkyl bromoalkyl carbonates, bromoalkyl formates, and aldehydes. It is concluded that the free-radical transformations of cyclic ortho esters in polyhalomethane media initiated by benzoyl peroxide go by an unbranched-chain mechanism.

  16. Synthesis of 4-alkoxy-8-hydroxyquinolines.

    PubMed

    Heiskanen, Juha P; Omar, Walaa A E; Ylikunnari, Mari K; Haavisto, Kirsi M; Juan, Maria J; Hormi, Osmo E O

    2007-02-02

    Quinolines with a hydroxyl group at the 8-position and an alkoxy group at the 4-position are rare compounds. In this paper the synthesis of five 4-alkoxy-8-hydroxyquinolines is reported. The key reaction in the synthetic route is a selective protection of the hydroxyl group at C-atom 8 in 4,8-dihydroxyquinoline with a tosyl group and the hydrolytic removal of the protective group after the alkylation. The tosyl group is stable during the alkylations with various alkylating agents in the presence of sodium hydride.

  17. Effects of alkoxy groups on arene rings of lignin β-O-4 model compounds on the efficiencies of single electron transfer-promoted photochemical and enzymatic C-C Bond Cleavage Reactions.

    PubMed

    Lim, Suk Hyun; Nahm, Keepyung; Ra, Choon Sup; Cho, Dae Won; Yoon, Ung Chan; Latham, John A; Dunaway-Mariano, Debra; Mariano, Patrick S

    2013-09-20

    To gain information about how alkoxy substitution in arene rings of β-O-4 structural units within lignin governs the efficiencies/rates of radical cation C1-C2 bond cleavage reactions, single electron transfer (SET) photochemical and lignin peroxidase-catalyzed oxidation reactions of dimeric/tetrameric model compounds have been explored. The results show that the radical cations derived from less alkoxy-substituted dimeric β-O-4 models undergo more rapid C1-C2 bond cleavage than those of more alkoxy-substituted analogues. These findings gained support from the results of DFT calculations, which demonstrate that C1-C2 bond dissociation energies of β-O-4 radical cations decrease as the degree of alkoxy substitution decreases. In SET reactions of tetrameric compounds consisting of two β-O-4 units, containing different degrees of alkoxy substitution, regioselective radical cation C-C bond cleavage was observed to occur in one case at the C1-C2 bond in the less alkoxy-substituted β-O-4 moiety. However, regioselective C1-C2 cleavage in the more alkoxy-substituted β-O-4 moiety was observed in another case, suggesting that other factors might participate in controlling this process. These observations show that lignins containing greater proportions of less rather than more alkoxylated rings as part of β-O-4 units would be more efficiently cleaved by SET mechanisms.

  18. 40 CFR 721.10493 - Tris-alkyl-alkoxy melamine polymer (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Tris-alkyl-alkoxy melamine polymer... Specific Chemical Substances § 721.10493 Tris-alkyl-alkoxy melamine polymer (generic). (a) Chemical... as tris-alkyl-alkoxy melamine polymer (PMN P-05-417) is subject to reporting under this section for...

  19. 40 CFR 721.10493 - Tris-alkyl-alkoxy melamine polymer (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Tris-alkyl-alkoxy melamine polymer... Specific Chemical Substances § 721.10493 Tris-alkyl-alkoxy melamine polymer (generic). (a) Chemical... as tris-alkyl-alkoxy melamine polymer (PMN P-05-417) is subject to reporting under this section for...

  20. 40 CFR 721.10496 - Amino alkoxy polydimethylsiloxane, hydroxy-terminated (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Amino alkoxy polydimethylsiloxane... Significant New Uses for Specific Chemical Substances § 721.10496 Amino alkoxy polydimethylsiloxane, hydroxy... substance identified generically as amino alkoxy polydimethylsiloxane, hydroxy-terminated (PMN P-06-9)...

  1. 40 CFR 721.10496 - Amino alkoxy polydimethylsiloxane, hydroxy-terminated (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Amino alkoxy polydimethylsiloxane... Significant New Uses for Specific Chemical Substances § 721.10496 Amino alkoxy polydimethylsiloxane, hydroxy... substance identified generically as amino alkoxy polydimethylsiloxane, hydroxy-terminated (PMN P-06-9)...

  2. The copper-catalysed Suzuki-Miyaura coupling of alkylboron reagents: disproportionation of anionic (alkyl)(alkoxy)borates to anionic dialkylborates prior to transmetalation.

    PubMed

    Basnet, Prakash; Thapa, Surendra; Dickie, Diane A; Giri, Ramesh

    2016-09-25

    We report the first example of Cu(I)-catalysed coupling of alkylboron reagents with aryl and heteroaryl iodides that affords products in good to excellent yields. Preliminary mechanistic studies with alkylborates indicate that the anionic (alkoxy)(alkyl)borates, generated from alkyllithium and alkoxyboron reagents, undergo disproportionation to anionic dialkylborates and that both anionic alkylborates are active for transmetalation to a Cu(I)-catalyst. Results from a radical clock experiment and the Hammett plot imply that the reaction likely proceeds via a non-radical pathway.

  3. Direct generation of oxygen-stabilized radicals by H• transfer from transition metal hydrides.

    PubMed

    Kuo, Jonathan L; Hartung, John; Han, Arthur; Norton, Jack R

    2015-01-28

    Transition-metal hydrides generate α-alkoxy radicals by H• transfer to enol ethers. We have measured the rate constant for transfer from CpCr(CO)3H to n-butyl vinyl ether and have examined the chemistry of radicals generated by such transfers. Radicals from appropriate substrates undergo 5-exo cyclization, with higher diastereoselectivity than the analogous all-carbon radicals. From such radicals it is straightforward to make substituted tetrahydrofurans.

  4. Isolable zwitterionic pyridinio-semiquinone pi-radicals. Mild and efficient single-step access to stable radicals.

    PubMed

    Yi, Chenyi; Blum, Carmen; Liu, Shi-Xia; Keene, Tony D; Frei, Gabriela; Neels, Antonia; Decurtins, Silvio

    2009-06-04

    A rational design based on the proton-coupled electron transfer (PCET) concept allows us to structurally characterize for the first time isolable, air- and moisture-stable semiquinone radicals in a zwitterionic neutral form. The presence of an alkoxy and the bulky pyridinio substituents causes only a minor perturbation of either the redox potentials or the spectral UV-vis characteristics of the semiquinone core but significantly stabilizes the new radicals.

  5. Development of the Ireland-Claisen rearrangement of alkoxy- and aryloxy-substituted allyl glycinates.

    PubMed

    Tellam, James P; Carbery, David R

    2010-11-19

    The Ireland-Claisen rearrangement of 3-alkoxy- and 3-aryloxy-substituted allyl glycinates is presented. This [3,3]-sigmatropic rearrangement route offers direct access to syn β-alkoxy and β-aryloxy α-amino acid systems. In particular, N,N-diboc glycine esters rearrange with excellent diastereoselectivities (dr > 25:1). The synthesis of substrates, rearrangement optimization, and a discussion of stereoselection are presented.

  6. Novel Alkoxy-Substituted Dipyrrins and Near-IR BODIPY Dyes-Preparation and Photophysical Properties.

    PubMed

    Schoder, Stefan; Kord Daoroun Kalai, Scheghajeh; Reissig, Hans-Ulrich

    2017-09-12

    Starting from 3-alkoxy-2-aryl-substituted pyrroles and aromatic aldehydes, a collection of new dipyrrins was prepared. Under the standard conditions of Treibs, these were converted into the corresponding boron dipyrrins (BODIPYs). Compounds of this type with alkoxy groups at C-3 position of both pyrrole subunits are new and hence the photophysical properties of this collection of novel dipyrrins and BODIPY dyes were investigated. The dipyrrins show absorption maxima up to 596 nm and emissions of up to 677 nm. For the BODIPY series a remarkable effect of the alkoxy groups was identified, resulting in red shifts for absorptions and emissions. The compound substituted with two 2-thien-2-yl groups and a meso-C6 F5 substituent shows an absorption maximum at 725 nm and emits at 754 nm and thus is a new representative of a near-IR BODIPY dye related to certain aza-BODIPYs. Our results demonstrate the influence of the alkoxy groups on the spectroscopic data and reveal the potential of 3-alkoxy-2-aryl-substituted pyrroles for the design of new fluorophores. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Hydrogen-atom transfer reactions from ortho-alkoxy-substituted phenols: an experimental approach.

    PubMed

    Amorati, Riccardo; Menichetti, Stefano; Mileo, Elisabetta; Pedulli, Gian Franco; Viglianisi, Caterina

    2009-01-01

    The role of intramolecular hydrogen bonding (HB) on the bond-dissociation enthalpy (BDE) of the phenolic O-H and on the kinetics of H-atom transfer to peroxyl radicals (k(inh)) of several 2-alkoxyphenols was experimentally quantified by the EPR equilibration technique and by inhibited autoxidation studies. These compounds can be regarded as useful models for studying the H-atom abstraction from 2-OR phenols, such as many lignans, reduced coenzyme Q and curcumin. The effects of the various substituents on the BDE(O-H) of 2-methoxy, 2-methoxy-4-methyl, 2,4-dimethoxyphenols versus phenol were measured in benzene solution as -1.8; -3.7; -5.4 kcal mol(-1), respectively. In the case of polymethoxyphenols, significant deviations from the BDE(O-H) values predicted by the additive effects of the substituents were found. The logarithms of the k(inh) constants in cumene were inversely related to the BDE(O-H) values, obeying a linear Evans-Polanyi plot with the same slope of other substituted phenols and a y-axis intercept slightly smaller than that of 2,6-dimethyl phenols. In the cases of phenols having the 2-OR substituent included in a five-membered condensed ring (i.e, compounds 9-11), both conformational isomers in which the OH group points toward or away from the oxygen in position 2 were detected by FTIR spectroscopy and the intramolecular HB strength was thus estimated. The contribution to the BDE(O-H) of the ortho-OR substituent in 9, corrected for intramolecular HB formation, was calculated as -5.6 kcal mol(-1). The similar behaviour of cyclic and non-cyclic ortho-alkoxy derivatives clearly showed that the preferred conformation of the OMe group in ortho-methoxyphenoxyl radicals is that in which the methyl group points away from the phenoxyl oxygen, in contrast to the geometries predicted by DFT calculations.

  8. Samarium(II) promoted stereoselective synthesis of antiproliferative cis-beta-alkoxy-gamma-alkyl-gamma-lactones.

    PubMed

    Donadel, Osvaldo J; Martín, Tomás; Martín, Víctor S; Padrón, José M

    2007-01-01

    Samarium(II) iodide promotes the stereoselective synthesis of cis-beta-alkoxy-gamma-alkyl-gamma-lactones under mild conditions starting from linear precursors. The in vitro antiproliferative activities were examined in the human solid tumor cell lines from diverse origin A2780, SW1573, and WiDr. From the growth inhibition data a structure-activity relationship was obtained. Overall the results point to the relevant role of cis-beta-alkoxy-gamma-alkyl-gamma-lactones as novel scaffolds for the development of new anticancer drugs.

  9. Iridium-Catalyzed Diastereoselective and Enantioselective Allylic Substitutions with Acyclic α-Alkoxy Ketones

    DOE PAGES

    Jiang, Xingyu; Chen, Wenyong; Hartwig, John F.

    2016-04-01

    The asymmetric alkylation of acyclic ketones is a longstanding challenge in organic synthesis. Here, are the diastereoselective and enantioselective allylic substitutions with acyclic α-alkoxy ketones catalyzed by a metallacyclic iridium complex to form products with contiguous stereogenic centers derived from the nucleophile and electrophile. These reactions occur between allyl methyl carbonates and unstabilized copper(I) enolates generated in situ from acyclic α-alkoxy ketones. The resulting products can be readily converted into enantioenriched tertiary alcohols and tetrahydrofuran derivatives without erosion of enantiomeric purity.

  10. Synthesis and antiepileptic activity of schiff's bases of dialkylamino alkoxy isatin derivatives.

    PubMed

    Swathi, Konda; Sarangapani, Manda

    2015-01-01

    In the present work, some new 5-[2(3)-dialkylamino alkoxy] Indole 3-thiosemicarbazone 2-ones and 5-[2(3)-dialkylamino alkoxy] Indole 3-hydrazone 2-one were prepared from 5-hydroxy isatin. The structures of the products were characterized by IR, NMR, and MASS Spectral studies. All the compounds were examined for antiepileptic activity by maximal electroshock seizure (MES) and pentylenetetrazole (PTZ) induced convulsion method. These compounds were also evaluated for their neurotoxicity study by rotarod method. Some of these compounds showed good antiepileptic activity when compared with standard drug Phenytoin and all the compounds showed less neurotoxicity when compared with standard drug Diazepam.

  11. An Ireland-Claisen approach to beta-alkoxy alpha-amino acids.

    PubMed

    Tellam, James P; Kociok-Köhn, Gabriele; Carbery, David R

    2008-11-20

    A diastereoselective Ireland-Claisen approach to beta-alkoxy alpha-amino acid esters is reported. Amino acid esters of enol ethereal allylic alcohols undergo facile syn-selective [3,3]-sigmatropic rearrangement via silyl ketene acetals. Substrate synthesis, rearrangement development, stereoselectivity, and product elaboration are discussed.

  12. Long-acting contraceptive agents: esters of norethisterone with alkoxy- and halogeno-substituted carboxylic acids.

    PubMed

    Shafiee, A; Vossoghi, M; Francisco, C G; Freire, R; Hernandez, R; Salazar, J A; Suarez, E; Sotheeswaran, S

    1983-03-01

    The chemical synthesis and physical data of several new esters of norethisterone (17 alpha-ethynyl-17 beta-hydroxyestr-4-en-3-one) are reported, which contain either a chloro- or an alkoxy-group as a substituent in the acid side-chain.

  13. Versatile approach to α-alkoxy carbamate synthesis and stimulus-responsive alcohol release†

    PubMed Central

    Mosey, R. Adam; Floreancig, Paul E.

    2012-01-01

    A series of α-alkoxy carbamates that cleave under mild conditions to release alcohols has been synthesized through a multicomponent process. The relationship between structural features in these compounds and the rate of alcohol release in the presence of basic hydrogen peroxide has been studied. The preparation of carbamates that cleave under other conditions has been demonstrated. PMID:22936329

  14. N,N-bond-forming heterocyclization: synthesis of 3-alkoxy-2H-indazoles.

    PubMed

    Mills, Aaron D; Nazer, Musa Z; Haddadin, Makhluf J; Kurth, Mark J

    2006-03-31

    A one-step heterocyclization of o-nitrobenzylamines to 3-alkoxy-2H-indazoles is reported. The electronic nature of the nitrophenyl group, the steric and electronic nature of the R1-functionalized benzylic amine, and the nature of the alcoholic solvent affect the efficiency of this heterocyclization reaction (approximately 40-90%).

  15. Synthesis and properties of alkoxy- and alkenyl-substituted peralkylated imidazolium ionic liquids.

    PubMed

    Maton, Cedric; Brooks, Neil R; Van Meervelt, Luc; Binnemans, Koen; Schaltin, Stijn; Fransaer, Jan; Stevens, Christian V

    2013-10-21

    Novel peralkylated imidazolium ionic liquids bearing alkoxy and/or alkenyl side chains have been synthesized and studied. Different synthetic routes towards the imidazoles and the ionic liquids comprising bromide, iodide, methanesulfonate, bis(trifluoromethylsulfonyl)imide ([NTf2](-)), and dicyanamide {[N(CN)2](-)} as the anion were evaluated, and this led to a library of analogues, for which the melting points, viscosities, and electrochemical windows were determined. Incorporation of alkenyl moieties hindered solidification, except for cations with high symmetry. The alkoxy-derivatized ionic liquids are often crystalline; however, room-temperature ionic liquids (RTILs) were obtained with the weakly coordinating anions [NTf2](-) and [N(CN)2](-). For the viscosities of the peralkylated RTILs, an opposite trend was found, that is, the alkoxy derivatives are less viscous than their alkenyl-substituted analogues. Of the crystalline compounds, X-ray diffraction data were recorded and related to their molecular properties. Upon alkoxy substitution, the electrochemical cathodic limit potential was found to be more positive, whereas the complete electrochemical window of the alkenyl-substituted imidazolium salts was shifted to somewhat more positive potentials.

  16. Aerosol Fragmentation Driven by Coupling of Acid–Base and Free-Radical Chemistry in the Heterogeneous Oxidation of Aqueous Citric Acid by OH Radicals

    DOE PAGES

    Liu, Matthew J.; Wiegel, Aaron A.; Wilson, Kevin R.; ...

    2017-07-14

    A key uncertainty in the heterogeneous oxidation of carboxylic acids by hydroxyl radicals (OH) in aqueous-phase aerosol is how the free-radical reaction pathways might be altered by acid-base chemistry. In particular, if acid-base reactions occur concurrently with acyloxy radical formation and unimolecular decomposition of alkoxy radicals, there is a possibility that differences in reaction pathways impact the partitioning of organic carbon between the gas and aqueous phases. To examine these questions, a kinetic model is developed for the OH-initiated oxidation of citric acid aerosol at high relative humidity. The reaction scheme, containing both free-radical and acid-base elementary reaction steps withmore » physically validated rate coefficients, accurately predicts the experimentally observed molecular composition, particle size, and average elemental composition of the aerosol upon oxidation. The difference between the two reaction channels centers on the reactivity of carboxylic acid groups. Free-radical reactions mainly add functional groups to the carbon skeleton of neutral citric acid, because carboxylic acid moieties deactivate the unimolecular fragmentation of alkoxy radicals. In contrast, the conjugate carboxylate groups originating from acid-base equilibria activate both acyloxy radical formation and carbon-carbon bond scission of alkoxy radicals, leading to the formation of low molecular weight, highly oxidized products such as oxalic and mesoxalic acid. Subsequent hydration of carbonyl groups in the oxidized products increases the aerosol hygroscopicity and accelerates the substantial water uptake and volume growth that accompany oxidation. These results frame the oxidative lifecycle of atmospheric aerosol: it is governed by feedbacks between reactions that first increase the particle oxidation state, then eventually promote water uptake and acid-base chemistry. When coupled to free-radical reactions, acid-base channels lead to formation of low

  17. Aerosol Fragmentation Driven by Coupling of Acid-Base and Free-Radical Chemistry in the Heterogeneous Oxidation of Aqueous Citric Acid by OH Radicals.

    PubMed

    Liu, Matthew J; Wiegel, Aaron A; Wilson, Kevin R; Houle, Frances A

    2017-08-10

    A key uncertainty in the heterogeneous oxidation of carboxylic acids by hydroxyl radicals (OH) in aqueous-phase aerosol is how the free-radical reaction pathways might be altered by acid-base chemistry. In particular, if acid-base reactions occur concurrently with acyloxy radical formation and unimolecular decomposition of alkoxy radicals, there is a possibility that differences in reaction pathways impact the partitioning of organic carbon between the gas and aqueous phases. To examine these questions, a kinetic model is developed for the OH-initiated oxidation of citric acid aerosol at high relative humidity. The reaction scheme, containing both free-radical and acid-base elementary reaction steps with physically validated rate coefficients, accurately predicts the experimentally observed molecular composition, particle size, and average elemental composition of the aerosol upon oxidation. The difference between the two reaction channels centers on the reactivity of carboxylic acid groups. Free-radical reactions mainly add functional groups to the carbon skeleton of neutral citric acid, because carboxylic acid moieties deactivate the unimolecular fragmentation of alkoxy radicals. In contrast, the conjugate carboxylate groups originating from acid-base equilibria activate both acyloxy radical formation and carbon-carbon bond scission of alkoxy radicals, leading to the formation of low molecular weight, highly oxidized products such as oxalic and mesoxalic acid. Subsequent hydration of carbonyl groups in the oxidized products increases the aerosol hygroscopicity and accelerates the substantial water uptake and volume growth that accompany oxidation. These results frame the oxidative lifecycle of atmospheric aerosol: it is governed by feedbacks between reactions that first increase the particle oxidation state, then eventually promote water uptake and acid-base chemistry. When coupled to free-radical reactions, acid-base channels lead to formation of low molecular

  18. Potential long-acting contraceptive agents: esters of testosterone with alkoxy- and halogeno-substituted carboxylic acids.

    PubMed

    Shafiee, A; Vosooghi, M; Francisco, C G; Freire, R; Hernandez, R; Salazar, J A; Suarez, E; Sotheeswaran, S; Gunatilaka, A A

    1987-01-01

    The chemical synthesis and physical data of several new esters of testosterone (17 beta-hydroxyandrost-4-en-3-one), which contain either a halogeno or an alkoxy substituent in the acid chain, are reported.

  19. Alkoxy-auxins Are Selective Inhibitors of Auxin Transport Mediated by PIN, ABCB, and AUX1 Transporters*

    PubMed Central

    Tsuda, Etsuko; Yang, Haibing; Nishimura, Takeshi; Uehara, Yukiko; Sakai, Tatsuya; Furutani, Masahiko; Koshiba, Tomokazu; Hirose, Masakazu; Nozaki, Hiroshi; Murphy, Angus S.; Hayashi, Ken-ichiro

    2011-01-01

    Polar auxin movement is a primary regulator of programmed and plastic plant development. Auxin transport is highly regulated at the cellular level and is mediated by coordinated transport activity of plasma membrane-localized PIN, ABCB, and AUX1/LAX transporters. The activity of these transporters has been extensively analyzed using a combination of pharmacological inhibitors, synthetic auxins, and knock-out mutants in Arabidopsis. However, efforts to analyze auxin-dependent growth in other species that are less tractable to genetic manipulation require more selective inhibitors than are currently available. In this report, we characterize the inhibitory activity of 5-alkoxy derivatives of indole 3-acetic acid and 7-alkoxy derivatives of naphthalene 1-acetic acid, finding that the hexyloxy and benzyloxy derivatives act as potent inhibitors of auxin action in plants. These alkoxy-auxin analogs inhibit polar auxin transport and tropic responses associated with asymmetric auxin distribution in Arabidopsis and maize. The alkoxy-auxin analogs inhibit auxin transport mediated by AUX1, PIN, and ABCB proteins expressed in yeast. However, these analogs did not inhibit or activate SCFTIR1 auxin signaling and had no effect on the subcellular trafficking of PIN proteins. Together these results indicate that alkoxy-auxins are inactive auxin analogs for auxin signaling, but are recognized by PIN, ABCB, and AUX1 auxin transport proteins. Alkoxy-auxins are powerful new tools for analyses of auxin-dependent development. PMID:21084292

  20. Alkoxy-auxins are selective inhibitors of auxin transport mediated by PIN, ABCB, and AUX1 transporters.

    PubMed

    Tsuda, Etsuko; Yang, Haibing; Nishimura, Takeshi; Uehara, Yukiko; Sakai, Tatsuya; Furutani, Masahiko; Koshiba, Tomokazu; Hirose, Masakazu; Nozaki, Hiroshi; Murphy, Angus S; Hayashi, Ken-ichiro

    2011-01-21

    Polar auxin movement is a primary regulator of programmed and plastic plant development. Auxin transport is highly regulated at the cellular level and is mediated by coordinated transport activity of plasma membrane-localized PIN, ABCB, and AUX1/LAX transporters. The activity of these transporters has been extensively analyzed using a combination of pharmacological inhibitors, synthetic auxins, and knock-out mutants in Arabidopsis. However, efforts to analyze auxin-dependent growth in other species that are less tractable to genetic manipulation require more selective inhibitors than are currently available. In this report, we characterize the inhibitory activity of 5-alkoxy derivatives of indole 3-acetic acid and 7-alkoxy derivatives of naphthalene 1-acetic acid, finding that the hexyloxy and benzyloxy derivatives act as potent inhibitors of auxin action in plants. These alkoxy-auxin analogs inhibit polar auxin transport and tropic responses associated with asymmetric auxin distribution in Arabidopsis and maize. The alkoxy-auxin analogs inhibit auxin transport mediated by AUX1, PIN, and ABCB proteins expressed in yeast. However, these analogs did not inhibit or activate SCF(TIR1) auxin signaling and had no effect on the subcellular trafficking of PIN proteins. Together these results indicate that alkoxy-auxins are inactive auxin analogs for auxin signaling, but are recognized by PIN, ABCB, and AUX1 auxin transport proteins. Alkoxy-auxins are powerful new tools for analyses of auxin-dependent development.

  1. Cholinesterase inhibitors: SAR and enzyme inhibitory activity of 3-[omega-(benzylmethylamino)alkoxy]xanthen-9-ones.

    PubMed

    Piazzi, Lorna; Belluti, Federica; Bisi, Alessandra; Gobbi, Silvia; Rizzo, Stefano; Bartolini, Manuela; Andrisano, Vincenza; Recanatini, Maurizio; Rampa, Angela

    2007-01-01

    In this work, we further investigated a previously introduced class of cholinesterase inhibitors. The removal of the carbamic function from the lead compound xanthostigmine led to a reversible cholinesterase inhibitors 3. Some new 3-[omega-(benzylmethylamino)alkoxy]xanthen-9-one analogs were designed, synthesized, and evaluated for their inhibitory activity against both acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). The length of the alkoxy chain of compound 3 was increased and different substituents were introduced. From the IC(50) values, it clearly appears that the carbamic residue is crucial to obtain highly potent AChE inhibitors. On the other hand, peculiarity of these compounds is the high selectivity toward BuChE with respect to AChE, being compound 12 the most selective one (6000-fold). The development of selective BuChE inhibitors may be of great interest to clarify the physiological role of this enzyme and to provide novel therapeutics for various diseases.

  2. Bringing forward the new generation of alkoxy-thiourea as potential treatment for Acanthamoeba keratitis

    NASA Astrophysics Data System (ADS)

    Khairul, Wan M.; Goh, Yit-Peng; Daud, Adibah Izzati; Nakisah, M. A.

    2017-02-01

    Alkoxy substituted thiourea derivatives with general formula of A-ArC(O)NHC(S)NHAr-D which A represents the methoxy group and D denotes -OCnH2n+1 have been successfully synthesised and characterized. In turn, all the synthesised molecules were assayed for anti-amoebic activities towards Acanthamoeba sp to examine the cytotoxicity effect at their IC50 and membrane permeability. As predicted, the findings showed that the synthesised molecules owing promising anti-amoebic activity towards Acanthamoeba sp. To support, the Acridine-orange/Propidium iodide (AOPI) staining result under fluorescence microscopy revealed the treated amoeba cells by these alkoxy thiourea derivatives exhibited loss in their membrane permeability.

  3. Synthesis and properties of mononuclear group 10 alkoxy-biscarbene complexes.

    PubMed

    López-Alberca, María P; Mancheño, María J; Fernández, Israel; Gómez-Gallego, Mar; Sierra, Miguel A; Torres, Rosario

    2009-01-01

    The synthesis, isolation, and complete characterization (NMR and X-Ray diffraction techniques) of stable mononuclear (palladium and platinum) alkoxy-biscarbene complexes is reported. These compounds are easily accessible through stoichiometric transmetalation reactions from Fischer alkoxy-chromium(0) carbene complexes. By a combination of experimental (UV/Vis spectroscopy, cyclic voltammetry) and computational methods (DFT), the structure, bonding situation, and the electronic and redox properties of these complexes are studied. Although they have structures quite similar, their electronic properties strongly depend on the metal and also on the substitution in the aromatic rings in the aniline moieties. Electron-withdrawing groups stabilize the HOMO causing the shifting of the oxidation waves to lower anodic potentials in the corresponding cyclic voltammograms.

  4. Lewis Acid Promoted Oxonium Ion Driven Carboamination of Alkynes for the Synthesis of 4-Alkoxy Quinolines.

    PubMed

    Gharpure, Santosh J; Nanda, Santosh K; Adate, Priyanka A; Shelke, Yogesh G

    2017-02-17

    Lewis acid mediated multisegment coupling cascade is designed for the synthesis of densely substituted 4-alkoxy quinolines via an oxonium ion triggered alkyne carboamination sequence involving C-C and C-N bond formations. Cyclic ether fused-quinolines could also be accessed using this fast, operationally simple, high yielding, chemoselective and functional group tolerant method. Versatility and utility of this methodology is demonstrated by postfunctionalization of products obtained and its use in synthesis of potent drug molecules.

  5. Cycloaddition reactions of alkoxy alkynyl Fischer carbene complexes with o-quinodimethanes (oQDMs).

    PubMed

    Barluenga, José; Fernández-Rodríguez, Manuel A; Aguilar, Enrique

    2002-10-17

    [reaction: see text] The reaction of o-quinodimethanes (oQDMs) with alkoxy alkynyl Fischer carbene complexes is highly dependent on the carbene complex. Thus, for arylalkynyl carbene complexes, the initial [4 + 2]-cycloadduct evolves opening a new entry to the benzo[b]fluorene skeleton, which is present in many natural products. However, for alkenylalkynyl carbene complexes, the reaction takes place through the double bond, instead of the triple bond, in an unprecedented fashion, leading to new functionalized alkynyl carbene complexes.

  6. Direct assembly of multiply oxygenated carbon chains by decarbonylative radical-radical coupling reactions.

    PubMed

    Masuda, Kengo; Nagatomo, Masanori; Inoue, Masayuki

    2017-03-01

    Pentoses and hexoses contain more than three oxygen-bearing stereocentres and are ideal starting materials for the synthesis of multiply oxygenated natural products such as sagittamide D, maitotoxin and hikizimycin. Here we demonstrate new radical-radical homocoupling reactions of sugar derivatives with minimal perturbation of their chiral centres. The radical exchange procedure using Et3B/O2 converted sugar-derived α-alkoxyacyl tellurides into α-alkoxy radicals via decarbonylation and rapidly dimerized the monomeric radicals. The robustness of this process was demonstrated by a single-step preparation of 12 stereochemically diverse dimers with 6-10 secondary hydroxy groups, including the C5-C10 stereohexad of sagittamide D and the enantiomer of the C51-C60 stereodecad of maitotoxin. Furthermore, the optimally convergent radical-radical cross-coupling reaction achieved a one-step assembly of the protected C1-C11 oxygenated carbon chain of the anthelmintic hikizimycin. These exceptionally efficient homo- and heterocoupling methods together provide a powerful strategy for the expedited total synthesis of contiguously hydroxylated natural products.

  7. Direct assembly of multiply oxygenated carbon chains by decarbonylative radical-radical coupling reactions

    NASA Astrophysics Data System (ADS)

    Masuda, Kengo; Nagatomo, Masanori; Inoue, Masayuki

    2016-10-01

    Pentoses and hexoses contain more than three oxygen-bearing stereocentres and are ideal starting materials for the synthesis of multiply oxygenated natural products such as sagittamide D, maitotoxin and hikizimycin. Here we demonstrate new radical-radical homocoupling reactions of sugar derivatives with minimal perturbation of their chiral centres. The radical exchange procedure using Et3B/O2 converted sugar-derived α-alkoxyacyl tellurides into α-alkoxy radicals via decarbonylation and rapidly dimerized the monomeric radicals. The robustness of this process was demonstrated by a single-step preparation of 12 stereochemically diverse dimers with 6-10 secondary hydroxy groups, including the C5-C10 stereohexad of sagittamide D and the enantiomer of the C51-C60 stereodecad of maitotoxin. Furthermore, the optimally convergent radical-radical cross-coupling reaction achieved a one-step assembly of the protected C1-C11 oxygenated carbon chain of the anthelmintic hikizimycin. These exceptionally efficient homo- and heterocoupling methods together provide a powerful strategy for the expedited total synthesis of contiguously hydroxylated natural products.

  8. Effect of chain length on thermal conversion of alkoxy-substituted copper phthalocyanine precursors.

    PubMed

    Fukuda, Takamitsu; Kikukawa, Yuu; Tsuruya, Ryota; Fuyuhiro, Akira; Ishikawa, Naoto; Kobayashi, Nagao

    2011-11-21

    A series of dialkoxy-substituted copper phthalocyanine (CuPc) precursors (4a-4d) have been prepared by treating phthalonitrile with the corresponding lithium alkoxide under mild conditions. The precursors exhibited high solubilities in common organic solvents, including acetone, toluene, tetrahydrofuran (THF), CH(2)Cl(2), and CHCl(3). Elongation of the alkoxy chains improved the solubilities of the precursors effectively, and accordingly, the butoxy-substituted derivative (4d) showed the highest solubility among 4a-4d. X-ray crystallography clarified that the conjugated skeletons of 4a-4d are all isostructural, and have two alkoxy groups in a syn-conformation fashion, leading to highly bent structures. Thermal conversions of the precursors examined by thermogravimetry (TG) and differential thermal analysis (DTA) demonstrate that 4a was converted into CuPc via two distinct exothermic processes in the 200-250 °C temperature range, while 4d exhibits only one exothermic signal in the DTA. In the field emission scanning electron microscopy (FESEM) images of 4a, the presence of two types of distinct crystal morphology (prismatic and plate-like crystals) can be recognized, implying that the two observed exothermic processes in the DTA can be attributed to the different crystal morphologies of the samples rather than the step-by-step elimination of the alkoxy groups. The thermal formation of CuPc from the precursors has been unambiguously confirmed by X-ray powder diffraction, UV-vis spectroscopy, and elemental analysis. The precursors were converted into CuPc at lower temperature with increasing chain length, presumably because of the increased void volume in the crystals. Thermal conversion performed in the solution phase results in a bright blue-colored solution with prominent absorption bands in the 650-700 nm region, strongly supporting the formation of CuPc.

  9. Simple vector considerations to assess the polarity of partially fluorinated alkyl and alkoxy groups.

    PubMed

    Müller, Klaus

    2014-01-01

    While H/F exchange at aryl groups or introduction of CF3 units have dominated medicinal chemistry for decades, the use of partially fluorinated alkyl and alkoxy groups has come into focus more recently. A simple bond vector analysis scheme, based on the assumption of context-independent bond polarities as well as idealized configurational and conformational geometries, is applied to small alkyl and alkoxy groups with prototypic fluorination patterns for qualitative assessments of relative polarities as well as polarity modulation by conformational change. Combined with a constant volume increase for each hydrogen/fluorine exchange these polarity estimates can be translated into expected lipophilicity shifts (ΔlogP), using a simple parameterization scheme derived from experimental logP values. While terminal monofluoro- and gem-difluoromethyl groups in small aliphatic units are correctly predicted to show lower lipophilicity compared to their tri- or non-fluorinated congeners, vicinal difluoro and bis-vicinal trifluoro patterns are identified to exhibit significantly lower lipophilicities than their respective geminal di- and trifluoro substituted counterparts. The trifluoromethoxy group is diagnosed as an intrinsically lipophilic unit compared to the parent methoxy group. The difluoromethoxy group is of particular interest as it can easily interconvert between a highly lipophilic and a polar conformation, thus enabling this unit to adjust to polarity changes of the molecular environment. For di- and trifluoroalkoxy groups, again the vic-difluoro and bis-vic-trifluoro substitution patterns stand out as most promising to keep lipophilicity low. The 1,3-difluoro pattern next to an ether moiety shows an interesting conformational dependence of polarity, similar to the difluoromethoxy group. While very qualitative in nature, the simple bond vector analysis promises to be a useful tool for the identification of lipophilicity-lowering fluorinated alkyl or alkoxy groups

  10. Co(III)(salen)-catalyzed HKR of two stereocentered alkoxy- and azido epoxides: a concise enantioselective synthesis of (S,S)-reboxetine and (+)-epi-cytoxazone.

    PubMed

    Reddy, R Santhosh; Chouthaiwale, Pandurang V; Suryavanshi, Gurunath; Chavan, Vilas B; Sudalai, Arumugam

    2010-07-21

    The HKR of racemic syn- or anti- alkoxy- and azido epoxides catalyzed by Co(salen) complex affords a practical access to a series of enantioenriched syn- or anti- alkoxy- and azido epoxides and the corresponding 1,2-diols. This strategy has been successfully employed in the concise, enantioselective synthesis of bioactive molecules such as (S,S)-reboxetine and (+)-epi-cytoxazone.

  11. The Influence of Alkoxy Substitutions on the Properties of Diketopyrrolopyrrole-Phenyl Copolymers for Solar Cells

    PubMed Central

    George, Zandra; Kroon, Renee; Gehlhaar, Robert; Gbabode, Gabin; Lundin, Angelica; Hellström, Stefan; Müller, Christian; Geerts, Yves; Heremans, Paul; Andersson, Mats R.

    2013-01-01

    A previously reported diketopyrrolopyrrole (DPP)-phenyl copolymer is modified by adding methoxy or octyloxy side chains on the phenyl spacer. The influence of these alkoxy substitutions on the physical, opto-electronic properties, and photovoltaic performance were investigated. It was found that the altered physical properties correlated with an increase in chain flexibility. Well-defined oligomers were synthesized to verify the observed structure-property relationship. Surprisingly, methoxy substitution on the benzene spacer resulted in higher melting and crystallization temperatures in the synthesized oligomers. This trend is not observed in the polymers, where the improved interactions are most likely counteracted by the larger conformational possibilities in the polymer chain upon alkoxy substitution. The best photovoltaic performance was obtained for the parent polymer: fullerene blends whereas the modifications on the other two polymers result in reduced open-circuit voltage and varying current densities under similar processing conditions. The current densities could be related to different polymer: fullerene blend morphologies. These results show that supposed small structural alterations such as methoxy substitution already significantly altered the physical properties of the parent polymer and also that oligomers and polymers respond divergent to structural alterations made on a parent structure. PMID:28811420

  12. Rate Constants and Deuterium Kinetic Isotope Effects for Methoxy Radical Reacting with NO_2 and O_2

    NASA Astrophysics Data System (ADS)

    Chai, J.; Hu, H.; Dibble, T. S.; Tyndall, G. S.; Orlando, J. J.

    2013-06-01

    Alkoxy radicals (RO) are important intermediates in the photooxidation of volatile organic compounds due to their great impacts on ozone formation and gas-particle partitioning of stable oxidation products. Methoxy radical (CH_3O) is the prototype for all alkoxy radicals. The absolute rate constants k_N_O_2(T) for reaction of CH_3O and CD_3O with NO_2 have been measured using laser flash photolysis to generate radicals and laser-induced fluorescence for time-resolved detection. The pressure and temperature dependence for k_N_O_2 have been observed over the range 30-700 Torr and 250-335 K. This will be the first direct measurement of k_N_O_2 for CH_3O near ambient pressure and the first ever for CD_3O.The relative rate constants k_N_O_2/k_O_2(T) have been measured in an environmental chamber with FTIR detection. This combination enables the first determination of k_O_2 (T) for CH_3O and CD_3O for T < 298 K. The results will also help validate theoretical methods for studying alkoxy + O_2 reactions, which are challenging for quantum chemistry.

  13. New Evidence for Hydroxyalkyl Radicals and Light- and Thermally Induced Trapped Electron Reactions in Rhamnose.

    PubMed

    Aalbergsjø, Siv G; Sagstuen, Einar

    2015-08-01

    Radical formation and trapping of radicals in X-irradiated crystals of rhamnose at 6 K were investigated using electron paramagnetic resonance (EPR), electron-nuclear double resonance (ENDOR) and ENDOR-induced EPR (EIE) techniques, complemented with periodic density functional theory (DFT) calculations. The two major radical species at 6 K were the O4-centered alkoxy radical and the intermolecularly trapped electron (IMTE), previously also detected by other authors. The current experimental results provided hyperfine coupling constants for these two species in good agreement with the previous data, thus providing a consistency check that improves their credibility. In addition to the O4-centered alkoxy radical and the IMTE, the C3-centered and C5-centered hydroxyalkyl radicals are the most prominent primary species at 6 K. The C3-centered radical appears in two slightly different conformations at 6 K, designated C and D. The C5-centered radical exhibits a coupling to a methyl group with tunneling rotation at 6 K, and analysis of one of the rotational substates (A) of the spin system yielded an understanding of the structure of this radical. Visible light bleaching of the IMTE at 6 K led to the C3-centered radical C, and thermal annealing above 6 K resulted in a conversion of the C to the D conformation. In addition, thermal annealing releases the IMTE, apparently resulting in the formation of the C2-centered radical. It is possible that the thermal decay of the IMTE also contributes to a small part of the C3-centered radical (D) population at 85 K. There are several other products trapped in rhamnose crystals directly after irradiation at 6 K, among which are resonance lines due to the C2 H-abstraction product. However, these other products are minority species and were not fully characterized in the current work.

  14. Design and characterization of alkoxy-wrapped push-pull porphyrins for dye-sensitized solar cells.

    PubMed

    Ripolles-Sanchis, Teresa; Guo, Bo-Cheng; Wu, Hui-Ping; Pan, Tsung-Yu; Lee, Hsuan-Wei; Raga, Sonia R; Fabregat-Santiago, Francisco; Bisquert, Juan; Yeh, Chen-Yu; Diau, Eric Wei-Guang

    2012-05-07

    Three alkoxy-wrapped push-pull porphyrins were designed and synthesized for dye-sensitized solar cell (DSSC) applications. Spectral, electrochemical, photovoltaic and electrochemical impedance spectroscopy properties of these porphyrin sensitizers were well investigated to provide evidence for the molecular design.

  15. Large enhancement in the heterogeneous oxidation rate of organic aerosols by hydroxyl radicals in the presence of nitric oxide

    DOE PAGES

    Richards-Henderson, Nicole K.; Goldstein, Allen H.; Wilson, Kevin R.

    2015-10-27

    In this paper we report an unexpectedly large acceleration in the effective heterogeneous OH reaction rate in the presence of NO. This 10–50 fold acceleration originates from free radical chain reactions, propagated by alkoxy radicals that form inside the aerosol by the reaction of NO with peroxy radicals, which do not appear to produce chain terminating products (e.g., alkyl nitrates), unlike gas phase mechanisms. Lastly, a kinetic model, constrained by experiments, suggests that in polluted regions heterogeneous oxidation plays a much more prominent role in the daily chemical evolution of organic aerosol than previously believed.

  16. Large enhancement in the heterogeneous oxidation rate of organic aerosols by hydroxyl radicals in the presence of nitric oxide

    SciTech Connect

    Richards-Henderson, Nicole K.; Goldstein, Allen H.; Wilson, Kevin R.

    2015-10-27

    In this paper we report an unexpectedly large acceleration in the effective heterogeneous OH reaction rate in the presence of NO. This 10–50 fold acceleration originates from free radical chain reactions, propagated by alkoxy radicals that form inside the aerosol by the reaction of NO with peroxy radicals, which do not appear to produce chain terminating products (e.g., alkyl nitrates), unlike gas phase mechanisms. Lastly, a kinetic model, constrained by experiments, suggests that in polluted regions heterogeneous oxidation plays a much more prominent role in the daily chemical evolution of organic aerosol than previously believed.

  17. The interplay between acid-base and free radical chemistry in the heterogeneous oxidation and fragmentation of citric acid in aqueous aerosol by OH radicals

    NASA Astrophysics Data System (ADS)

    Liu, M.; Wiegel, A. A.; Wilson, K. R.; Houle, F. A.

    2016-12-01

    A key uncertainty in the oxidation of organic compounds such as carboxylic acids in aqueous phase aerosol is how β-scission of alkoxy radicals is altered by acid-base chemistry. In particular, the differences between the unimolecular fragmentation rates of radical anions and their neutral forms may impact the partitioning of organic carbon between the gas and aqueous phase. To investigate the fragmentation reactions that occur during the oxidation of highly oxygenated organic aqueous aerosol, a kinetics model is developed for the OH initiated oxidation of citric acid aerosol at high relative humidities. The reaction scheme includes both free radical and acid-base reactions, uses physically validated rate coefficients, and thus accurately predicts the experimentally observed molecular composition, particle size, and average elemental composition of the aerosol upon oxidation. Free radical reactions functionalize the carbon skeleton while carboxylate groups from acid-base chemistry activate the carbon-carbon bond fragmentation of alkoxy radicals, leading to the formation of low molecular weight, highly oxidized products such as oxaloacetic and mesoxalic acid. Subsequent hydration of carbonyl groups in the oxidized products increases the aerosol hygroscopicity and causes the substantial water uptake and volume growth observed to accompany oxidation. These results highlight the significant role of water in controlling not only changes in physical properties but also the mechanisms of oxidation and fragmentation of aerosol in the atmosphere.

  18. Oxygen radical functionalization of boron nitride nanosheets.

    PubMed

    Sainsbury, Toby; Satti, Amro; May, Peter; Wang, Zhiming; McGovern, Ignatius; Gun'ko, Yurii K; Coleman, Jonathan

    2012-11-14

    The covalent chemical functionalization of exfoliated hexagonal boron-nitride nanosheets (BNNSs) is achieved by the solution-phase oxygen radical functionalization of boron atoms in the h-BN lattice. This involves a two-step procedure to initially covalently graft alkoxy groups to boron atoms and the subsequent hydrolytic defunctionalization of the groups to yield hydroxyl-functionalized BNNSs (OH-BNNSs). Characterization of the functionalized-BNNSs using HR-TEM, Raman, UV-vis, FTIR, NMR, and TGA was performed to investigate both the structure of the BNNSs and the covalent functionalization methodology. OH-BNNSs were used to prepare polymer nanocomposites and their mechanical properties analyzed. The influence of the functional groups grafted to the surface of the BNNSs is investigated by demonstrating the impact on mechanical properties of both noncovalent and covalent bonding at the interface between the nanofiller and polymer matrixes.

  19. Kinetics and Near-Infrared Spectroscopy of Organic Peroxy Radicals

    NASA Astrophysics Data System (ADS)

    Smarte, M. D.; Okumura, M.

    2016-12-01

    Organic peroxy radicals are important intermediates in atmospheric chemistry with fates that control the rate of radical propagation in an oxidation mechanism. Laboratory methods for detecting peroxy radicals are essential to measuring precise rate constants that constrain these fates. In this work, we discuss the use of near-infrared cavity ringdown spectroscopy to detect organic peroxy radicals for the purpose of laboratory kinetics measurements. We focus on chlorine-substituted peroxy radicals generated in the oxidation of alkenes by chlorine, a minor tropospheric oxidant found in marine and coastal regions. Previous kinetics experiments on peroxy radicals have largely used UV absorption spectroscopy via the dissociative B-X transition. However, the spectra produced are featureless and exhibit substantial overlap; determining the concentration profile of an individual peroxy radical can be an arduous task. In our work, we probe the forbidden peroxy radical A-X transition in the near-infrared. While this approach requires overcoming small cross sections ( 10-21 cm2), the A state is bound and leads to structured absorption spectra that may be useful in constraining the kinetics of mixtures of organic peroxy radicals formed in the oxidation of complex hydrocarbons. Only a few kinetics studies utilizing the A-X transition exist in the literature and they are focused on small, unsubstituted species. This presentation explores the ability of the A-X transition to unravel the kinetics of more complex peroxy radicals in laboratory experiments using several example systems: (1) Determining rate constants for the self and cross reactions of β-chloroethylperoxy and HO2. (2) Detecting the second generation of peroxy radicals formed from alkoxy radical decomposition in the chlorine-initiated oxidation of 2-butene. (3) Observing different rates of reactivity with NO across the pool of peroxy radical isomers formed in the chlorine-initiated oxidation of isoprene.

  20. Alkoxy bridged binuclear rhenium (I) complexes as a potential sensor for β-amyloid aggregation.

    PubMed

    Sathish, Veerasamy; Babu, Eththilu; Ramdass, Arumugam; Lu, Zong-Zhan; Velayudham, Murugesan; Thanasekaran, Pounraj; Lu, Kuang-Lieh; Rajagopal, Seenivasan

    2014-12-01

    Alkoxy bridged binuclear rhenium(I) complexes are used as a probe for the selective and sensitive detection of aggregation of β-amyloid fibrils that are consorted with Alzheimer's disease (AD). The strong binding of the complexes is affirmed by the fluorescence enhancement and calculated binding constant value in the order of 10(5)M(-1) is obtained from the Scatchard plots. The binding of β-amyloid can be attributed to π-π stacking interaction of naphthalene moiety present in rhenium(I) complexes, and it is supported by docking studies. The selectivity is quite high towards other proteins and the formation of fibrils can be observed in the range of 30-40 nm through the AFM and TEM techniques. Copyright © 2014 Elsevier B.V. All rights reserved.

  1. Effects of Alkylthio and Alkoxy Side Chains in Polymer Donor Materials for Organic Solar Cells.

    PubMed

    Cui, Chaohua; Wong, Wai-Yeung

    2016-02-01

    Side chains play a considerable role not only in improving the solubility of polymers for solution-processed device fabrication, but also in affecting the molecular packing, electron affinity and thus the device performance. In particular, electron-donating side chains show unique properties when employed to tune the electronic character of conjugated polymers in many cases. Therefore, rational electron-donating side chain engineering can improve the photovoltaic properties of the resulting polymer donors to some extent. Here, a survey of some representative examples which use electron-donating alkylthio and alkoxy side chains in conjugated organic polymers for polymer solar cell applications will be presented. It is envisioned that an analysis of the effect of such electron-donating side chains in polymer donors would contribute to a better understanding of this kind of side chain behavior in solution-processed conjugated organic polymers for polymer solar cells.

  2. Investigation of Third Order Optical Nonlinearity and Reverse Saturable Absorption of Octa-alkoxy Metallophthalocyanines

    NASA Technical Reports Server (NTRS)

    Sanghadasa, Mohan; Shin, In-Seek; Barr, Thomas A.; Clark, Ronald D.; Guo, Huai-Song; Martinez, Angela; Penn, Benjamin G.

    1998-01-01

    In recent years, there has been a growing interest in the development of passive optical power limiters for the protection of the human eye and solid-state sensors from damage caused by energetic light pulses and also for other switching applications. One of the key issues involved is the search for appropriate materials that show effective reverse saturable absorption. Phthalocyanines seem to be good candidates for such applications because of their higher third order nonlinearity and the unique electronic absorption characteristics. A series of 1,4,8,11,15, 18,22,25-octa-alkoxy metallophthalocyanines containing various central metal atoms such as zinc, copper, palladium, cobalt and nickel were characterized for their third order nonlinearity and for their nonlinear absorptive properties to evaluate their suitability to function as reverse saturable absorbers.

  3. Solvent effect on nucleation-growth of titanium-oxo-alkoxy nanoparticles

    NASA Astrophysics Data System (ADS)

    Cheng, Khley; Chhor, Khay; Kanaev, Andrei

    2017-03-01

    The nucleation-growth of titanium oxo-alkoxy (TOA) nanoparticles was studied in n-propanol and isopropanol solvents. A common feature is quasi-instantaneous appearance of stable clusters with the hydrodynamic radius 1.6 nm, which form nanoparticles aggregated during the induction period. In contrast to clusters, the nanoparticle size and growth kinetics were affected by solvent: their size was 3.8 nm in n-propanol and 5.2 nm in isopropanol and the growth kinetics in isopropanol was significantly faster. The results suggest that the stability of the growing TOA units decreases with an increase of size, supporting the hierarchical model of the sol-gel growth.

  4. Investigation of Third Order Optical Nonlinearity and Reverse Saturable Absorption of Octa-alkoxy Metallophthalocyanines

    NASA Technical Reports Server (NTRS)

    Sanghadasa, Mohan; Shin, In-Seek; Barr, Thomas A.; Clark, Ronald D.; Guo, Huai-Song; Martinez, Angela; Penn, Benjamin G.

    1998-01-01

    In recent years, there has been a growing interest in the development of passive optical power limiters for the protection of the human eye and solid-state sensors from damage caused by energetic light pulses and also for other switching applications. One of the key issues involved is the search for appropriate materials that show effective reverse saturable absorption. Phthalocyanines seem to be good candidates for such applications because of their higher third order nonlinearity and the unique electronic absorption characteristics. A series of 1,4,8,11,15, 18,22,25-octa-alkoxy metallophthalocyanines containing various central metal atoms such as zinc, copper, palladium, cobalt and nickel were characterized for their third order nonlinearity and for their nonlinear absorptive properties to evaluate their suitability to function as reverse saturable absorbers.

  5. Synthesis of cyclic polyesters: effects of alkoxy side chains in salicylaldiminato tin(II) complexes.

    PubMed

    Wongmahasirikun, Phonpimon; Prom-on, Paweenuch; Sangtrirutnugul, Preeyanuch; Kongsaeree, Palangpon; Phomphrai, Khamphee

    2015-07-21

    A new class of salicylaldiminato tin(II) catalysts having different alkoxy side chains has been developed. The ligands were modified to have different lengths and flexibilities such as –(CH2)2– (2a), –(CH2)3– (2b), –(ortho-C6H4)CH2– (2c) and –(CH2)2–O–(CH2)2– (2d). Complexes 2a, b were characterized crystallographically revealing a more constrained environment around the metal in complex 2a. These catalysts are active for the solvent-free polymerization of L-lactide and ε-caprolactone. Complex 2a having a shorter side chain was shown to better promote intramolecular transesterification affording cyclic polylactides and cyclic poly(ε-caprolactone). Complexes 2b and 2d having longer side chains produced cyclic poly(ε-caprolactone) as a major product but failed to give cyclic polylactides.

  6. Hydroxy- and alkoxy-bridged dinuclear uranyl-Schiff base complexes: hydrolysis, transamination and extraction studies.

    PubMed

    Bharara, Mohan S; Heflin, Kathryn; Tonks, Stephen; Strawbridge, Kara L; Gorden, Anne E V

    2008-06-14

    The reaction of uranyl nitrate with 1,3-bis(salicylideneamino)-2-propanol (H(3)L1) and 1,3-bis(3,5-di-tert-butylsalicylideneamino)-2-propanol (H(3)L2) in the presence of triethylamine (Et(3)N) yielded hydroxy- and alkoxy-bridged dinuclear complexes; [(UO(2))(2)(L1)(OH)(MeOH)(2)].(MeOH)(2) (.(MeOH)(2)) and [(UO(2))(2)(L2)(OH)(MeOH)(2)].(MeOH)(2) (.(MeOH)(2)). The crystal structures of .(DMF)(2) and .(DMF)(2) exhibit an unsymmetrical central U(2)O(2) core involving bridging alkoxy- and hydroxy-oxygen atoms. The geometry around the uranium center in .(DMF)(2) and .(DMF)(2) is that of a distorted pentagonal bipyramid with the solvent molecule occupying the fifth coordination site. The flexible nature of the ligand backbone is more pronounced in .(DMF)(2) compared to .(DMF)(2), yielding two molecules per unit cell in different conformations. Under similar reaction conditions, using ethylenediamine as a base, the respective Salen-based uranyl compounds, [UO(2)(Salen)(MeOH)] () and [UO(2)(Bu(t)(2)-Salen)(MeOH)] () are obtained due to transamination of the ligand backbone. Complexes .(MeOH)(2) and .(MeOH)(2) when reacted with an excess of ethylenediamine failed to yield the respective Salen-based complexes, and , respectively. The new compounds have been characterized using solution (NMR and UV-Vis) and solid-state (IR, X-ray crystallography) techniques. Hydrolysis of .(MeOH)(2) and .(MeOH)(2) in the pH range 1-14 was studied using UV-Vis spectroscopy and compared with the hydrolysis of and [UO(2)(Salophen)(MeOH)] (). A two-phase extraction study suggests quantitative removal of uranyl ions from the aqueous phase at higher pH conditions.

  7. Binding of alkyl- and alkoxy-substituted simple phenolic compounds to human serum proteins.

    PubMed

    Ogata, N; Shibata, T

    2000-01-01

    Wood creosote, primarily a mixture of simple alkyl- and/or alkoxy-substituted phenolic compounds with closely related structures, has long been used as an oral antidiarrheal agent. The use of wood creosote as a parenteral antidiarrheal agent was investigated, and for basic pharmacokinetic data we measured the extent of equilibrium binding of its six major constituent phenolic compounds to human serum proteins using an ultrafiltration method. The percent binding of these major constituent phenolic compounds, namely phenol, guaiacol, p-cresol, o-cresol, creosol and 4-ethylguaiacol, bound to 40-mg/ml human serum albumin was 15.5+/-0.9, 28.0+/-1.5, 37.2+/-0.7, 52.3+/-5.3, 36.8+/-2.0 and 56.7+/-2.4%, respectively, while percent binding to human serum (68 mg protein/ml) was 41.3+/-0.7, 42.6+/-0.5, 64.8+/-0.4, 70.1+/-1.6, 65.7+/-0.2 and 83.1+/-0.1% (mean +/- standard deviation, n = 4), respectively, when tested individually at a concentration of 500 micromol/l. Saturation of binding was not observed for the phenolic compounds up to a concentration of 50 mmol/l. Phenolic compounds with a lipophilic substituent showed higher percent binding to proteins than those without it. We conclude that simple phenolic compounds having alkyl- and/or alkoxy-substituents bind to serum proteins to a considerable extent and that the binding is hydrophobic and nonspecific.

  8. The enhanced stability of the cross-linked hylan structure to hydroxyl (OH) radicals compared with the uncross-linked hyaluronan

    NASA Astrophysics Data System (ADS)

    Al-Assaf, Saphwan; Phillips, Glyn O.; Deeble, D. J.; Parsons, Barry; Starnes, Hazel; Von Sonntag, C.

    1995-08-01

    A comparison has been made of the relative stabilities of hyaluronan and hylan to degradation by OH radicals produced by γ-irradiation of aqueous solutions in N 2O, when G (yield per 100 eV) for OH radicals is 5.6 and H atoms 0.6. Using low angle light scattering and viscometric methods, the change in molecular weight of the polysaccharides was measured with increasing dose. From the yield/dose curves (expressed as breaks per molecule), the initial G value for hyaluronan degradation is ˜ 4. A further slow post-irradiation decrease in molecular weight is observed, which can be brought to completion by incubating the solutions for 1 h at 60°C. Thereafter, the G value for degradation is ˜ 6. A similar post-irradiation degradation was found for hylan. A technique using tetranitromethane (TNM) has been used to distinguish between two types of radicals formed on the hyaluronan backbone. Radicals of the 1-hydroxy-2-alkoxy type (C-2, C-4, C-2 and C3 of the glucuronic acid) would induce strand breakage by alkoxy elimination. For the equivalent alkoxy radical at C6 of the acetamido monosaccharide, ring opening would occur with formation of a hemi-acetal, leading also to strand breakage. The C-2 and C-3 radicals would eliminate water rather than produce breaks by β-alkoxy elimination. Thus three out of the initially formed radicals would produce breaks by β-alkoxy formation. These can be stabilised with TNM and distinguished. It is concluded that these are the radicals involved in the post-irradiation thermal degradation process. Comparison of hylan and hyaluronan is, therefore, most valid when this post-irradiation process has been completed. Therefore, all G values for degradation were measured after incubation for 1 h at 60°. This investigation establishes the greater stability of hylan ( Gdegradation = 2) compared to hylan ( Gdegradation = 6). Therefore, in an environment such as supplementation of an inflammed joint where OH radicals are released, hylan is able to

  9. Effective 1,5-, 1,6- and 1,7-remote stereocontrol in reactions of alkoxy- and hydroxy-substituted allylstannanes with aldehydes.

    PubMed

    Carey, John S; MacCormick, Somhairle; Stanway, Steven J; Teerawutgulrag, Aphiwat; Thomas, Eric J

    2011-05-21

    Alk-2-enylstannanes with 4-, 5- and 6-alkoxy- or -hydroxy-substituents are transmetallated stereoselectively with tin(iv) halides to generate allyltin trihalides which react with aldehydes to give (Z)-alk-3-enols with useful levels of 1,5-, 1,6- and 1,7-stereocontrol. Alk-2-enylstannanes with a stereogenic centre bearing a hydroxy or alkoxy group at the 4-, 5- or 6-position, react with overall (Z)-1,5-, 1,6- and 1,7-syn-stereoselectivity with respect to the hydroxy and alkoxy substituents. The analogous reactions of alkoxy- and -hydroxyalk-2-enylstannanes with a methyl bearing stereogenic centre at the 4- or 5-position react with overall (Z)-1,5- and 1,6-anti-stereoselectivity with respect to the hydroxy and methyl substituents.

  10. Mechanism of alkoxy groups substitution by Grignard reagents on aromatic rings and experimental verification of theoretical predictions of anomalous reactions.

    PubMed

    Jiménez-Osés, Gonzalo; Brockway, Anthony J; Shaw, Jared T; Houk, K N

    2013-05-01

    The mechanism of direct displacement of alkoxy groups in vinylogous and aromatic esters by Grignard reagents, a reaction that is not observed with expectedly better tosyloxy leaving groups, is elucidated computationally. The mechanism of this reaction has been determined to proceed through the inner-sphere attack of nucleophilic alkyl groups from magnesium to the reacting carbons via a metalaoxetane transition state. The formation of a strong magnesium chelate with the reacting alkoxy and carbonyl groups dictates the observed reactivity and selectivity. The influence of ester, ketone, and aldehyde substituents was investigated. In some cases, the calculations predicted the formation of products different than those previously reported; these predictions were then verified experimentally. The importance of studying the actual system, and not simplified models as computational systems, is demonstrated.

  11. A physicochemical examination of the free radical scavenging activity of Trolox: mechanism, kinetics and influence of the environment.

    PubMed

    Alberto, Marta E; Russo, Nino; Grand, Andre; Galano, Annia

    2013-04-07

    The free radical scavenging activity of Trolox was studied for aqueous and lipid environments using the Density Functional Theory. Several reaction mechanisms and free radicals of different chemical nature have been included in this study, as well as the influence of the pH. Trolox was found to be a powerful ˙OH and alkoxy scavenger, regardless of the conditions under which the reaction takes place. It was also found to be very efficient as a peroxy radical scavenger in aqueous solution, while its protective effects against this particular kind of free radicals are significantly reduced in lipid solution. Four reaction mechanisms were found to significantly contribute to the ˙OH scavenging activity of Trolox in aqueous solution: hydrogen transfer (HT), radical adduct formation (RAF), single electron transfer (SET), and sequential proton loss electron transfer (SPLET), while in lipid media two of them are relevant: HT and RAF. The ˙OCH3, ˙OOH, and ˙OOCHCH2 scavenging processes are predicted to take place almost exclusively by HT from the phenolic OH group in lipid media, and in aqueous solution at pH < 11, while at higher pH values the SPLET mechanism is proposed as the main one. This is also the case for other non-halogenated alkyl or alkenyl peroxy (and alkoxy) radicals. The agreement with the available experimental data supports the reliability of the presented calculations.

  12. Secondary organic aerosol formation from reaction of tertiary amines with nitrate radical

    NASA Astrophysics Data System (ADS)

    Erupe, M. E.; Price, D. J.; Silva, P. J.; Malloy, Q. G. J.; Qi, L.; Warren, B.; Cocker, D. R., III

    2008-09-01

    Secondary organic aerosol formation from the reaction of tertiary amines with nitrate radical was investigated in an indoor environmental chamber. Particle chemistry was monitored using a high resolution aerosol mass spectrometer while gas-phase species were detected using a proton transfer reaction mass spectrometer. Trimethylamine, triethylamine and tributylamine were studied. Results indicate that tributylamine forms the most aerosol mass followed by trimethylamine and triethylamine respectively. Spectra from the aerosol mass spectrometer indicate the formation of complex non-salt aerosol products. We propose a reaction mechanism that proceeds via abstraction of a proton by nitrate radical followed by RO2 chemistry. Rearrangement of the aminyl alkoxy radical through hydrogen shift leads to the formation of hydroxylated amides, which explain most of the higher mass ions in the mass spectra. These experiments show that oxidation of tertiary amines by nitrate radical may be an important night-time source of secondary organic aerosol.

  13. Transformation of halogen-, alkyl-, and alkoxy-substituted anilines by a lactase of Trametes versicolor

    SciTech Connect

    Hoff, T.; Liu, S.Y.; Bollag, J.M.

    1985-05-01

    The lactase of the fungus Trametes versicolor was able to polymerize various halogen-, alkyl-, and alkoxy-substituted anilines, showing substrate specificity similar to that of horseradish peroxidase, whereas the lactase of Rhizoctonia praticola was active only with p-methoxyaniline. The substrate specificities of the enzymes were determined by using gas chromatography to measure the decrease in substrate concentration during incubation. With p-chloroaniline as the substrate, the peroxidase and the Trametes lactase showed maximum activity near pH 4.2. The transformation of this substrate gave rise to a number of oligomers, ranging from dimers to pentamers, as determined by mass spectrometry. The product profiles obtained by high-pressure liquid chromatography were similar for the two enzymes. A chemical reaction was observed between p-chloroaniline and an enzymatically formed dimer, resulting in the formation of a trimer. All three enzymes oxidized p-methoxyaniline to 2-amino-5-p-anisidinobenzoquinone di-p-methoxyphenylimine, but only the T. versicolor lactase and the peroxidase caused the formation of a pentamer (2,5-di-p-anisidinobenzoquinone di-p-methoxyphenylimine). These results demonstrate that in addition to horseradish peroxidase, a T. versicolor lactase can also polymerize aniline derivatives.

  14. Vacancy Assisted Diffusion of Alkoxy Species on Rutile TiO2(110)

    SciTech Connect

    Zhang, Zhenrong; Rousseau, Roger J.; Gong, Jinlong; Li, Shao-Chun; Kay, Bruce D.; Ge, Qingfeng; Dohnalek, Zdenek

    2008-10-10

    The catalytic and photocatalytic properties of TiO2 have attracted widespread interest in a variety of applications, such as air purification, self-cleaning glass, water splitting, solar cells and wastewater treatment. In many cases the catalytic chemistry of reducible oxides is dominated by oxygen vacancy sites. For reduced rutile TiO2(110)-1×1, the bridge-bonded oxygen (BBO) vacancies (BBOV’s) are the most prevalent surface defects and, as has been shown, they can readily dissociate small molecules such as H2O, O2, and alcohols.Here we demonstrate for the first time that BBOV’s can also catalyze the transport of adsorbed species which is a key ingredient in heterogeneous catalytic processes. Specifically, we show that at elevated temperatures (≥ 400 K), mobile BBOV’s can assist the diffusion of alkoxy groups formed by the dissociation of alcohols at BBOV’s. This type of mechanism is likely applicable to other adsorbates bound to BBO atoms of TiO2(110).

  15. Adsorption kinetics of 3-alkoxy-2-hydroxypropyl trimethyl ammonium chloride at oil-water interface

    NASA Astrophysics Data System (ADS)

    Wei, Xi-lian; Wang, Xiu-hong; Liu, Jie; Sun, De-zhi; Yin, Bao-lin; Wang, Xiu-jie

    2012-11-01

    Dynamic interfacial tension (DIT) between aqueous solution of 3-alkoxy-2-hydroxypropyl trimethyl ammonium chloride (RnHTAC) and n-octane was measured using spinning drop method. The effects of RnHTAC concentration (the concentration below the CMC) and temperature on DIT have been investigated. The cause of the change of DIT with time has been discussed. The effective diffusion coefficient, Da, and the adsorption barrier, ɛa, have been obtained with extended Word-Tordai equation. The results show that the higher the concentration of the surfactant is, the smaller the DIT will be and the lower the curve of the DIT, and the aqueous RnHTAC solutions follow a mixed diffusion-activation adsorption mechanism. With increase of RnHTAC concentration in the bulk solution, Da decreases and ɛa increases. Da of aqueous R14HTAC solution decreases from 0.090 × 10-13 m2 s-1 to 0.081 × 10-13 m2 s-1 and ɛa increases from 10.12 kJ mol-1 to 11.89 kJ mol-1, with the temperature increasing from 30 °C to 50 °C. This phenomenon indicates that the diffusion tendency becomes weak with the strengthening of the interaction between the surfactant molecules and that the thermo-motion of molecules benefits interface adsorption.

  16. Transformation of photophysical properties from solution to solid state in alkoxy-cyano-diphenylacetylene molecules.

    PubMed

    Karunakaran, Venugopal; Prabhu, Deepak D; Das, Suresh; Varughese, Sunil

    2015-07-28

    Detailed photophysical properties of cyano and mono (MA)/bis alkoxy (DA) substituted diphenylacetylene moieties with different alkyl chain lengths (methyl (1), octyl (8) and dodecyl (12)) were investigated in solution and the solid state in an effort to determine the effect of self-aggregation on these properties. The solvated molecules showed a minimal bathochromic shift with an increase of solvent polarity in their absorption spectra, whereas a significant shift was observed in the emission spectra. This could be attributed to the relatively low change in dipole moment between ground and Franck-Condon excited states and luminescence arising from the intramolecular charge transfer state with a dipole moment significantly higher than that of the ground state. In solid state the emission quantum yields of these materials were significantly higher than in solution. For DA1, polymorphic materials with distinct photophysical properties were obtained. The DA1 materials obtained by fast precipitation (DA1) showed broad fluorescence with peaks at 398, 467 and 535 nm upon excitation at different wavelengths. Detailed analysis of absorption, emission and excitation spectra and lifetime experiments indicated that these peaks could be attributed to the monomer, J- and H-type aggregates respectively. Whereas the crystals obtained by slow crystallization (DA1C) showed only one emission peak at around 396 nm attributed to the monomer. This is supported by the single crystal X-ray structure which consists of a monomer molecule having minimal interaction with nearest neighbour molecules.

  17. Osteoclast radicals.

    PubMed

    Silverton, S

    1994-11-01

    In biological research, new ideas arise and quickly spread to encompass the entire field. Thus, the evolution of molecular biology has significantly changed our methods of approaching our research. A similar far-reaching finding has been the advent of radical reactions into biology. Although radical chemistry has been utilized for many technological advances that affect our daily lives, the appreciation of this same process within our cells has opened an unexplored arena for research enquiry. As cellular messengers, radical molecules seem whimsically designed: they are evanescent, rapidly and apparently indiscriminately reactive, and barely detectable by most biological methods. Yet, our initial probing of these reactive agents in cells and organisms has led us to postulate a virtually undescribed system of communication within and among cells which may have significant effects in multiple organs. In bone, radical reactants have been attributed with an important role in the control of bone resorption.

  18. Alkoxy-Siloxide Metal Complexes: Precursors to Metal Silica, Metal Oxide Silica, and Metal Silicate Materials.

    NASA Astrophysics Data System (ADS)

    Terry, Karl William

    The alkoxy-siloxide complexes M (OSi(O ^{rm t}Bu)_3 ]_4 (M = Ti(1), Zr(2), Hf(3)), were prepared by reaction with their respective metal diethylamides. These compounds readily undergo low-temperature decomposition to their respective metal oxide silica materials rm(MO_2{cdot}4SiO_2). The volatile products of the thermolysis of 2 (ca. 200 ^circC) were isobutylene (11.7 equiv) and water (5.4 equiv). The rm ZrO _2{cdot}4SiO_2 material from the decomposition of 2 at 400^circ C was amorphous until ca. 1100^ circC where crystallization of t-ZrO _2 occurred. After thermolysis to 1500 ^circC, t-ZrO_2 and cristobalite were the major products with minor amounts of m-ZrO_2. The rm HfO_2{cdot}4SiO_2 material from the decomposition of 3 at 400^ circC was amorphous until ca. 1000 ^circC where crystallization of c/t -HfO_2 was observed. Thermolysis to 1460^circC yielded c/t -HfO_2, m-HfO_2, and minor amounts of cristobalite. The crystallization of anatase in the rm TiO_2{cdot }4SiO_2 material from decomposed 1 at 400^circC was apparent after thermolysis to 1000^circC. Thermolysis to 1400^circC gave a mixture of anatase, rutile, and cristobalite. Compound 2 was decomposed in xylenes and yielded a transparent gel which was isolated as a white powder upon drying in vacuuo. The compounds [ Me _2AlOSi(O^{t}Bu)_3] _2 (4) and [( ^{t}BuO)MeAlOSi(O^{t}Bu) _3]_2 (5) were structurally characterized and contain bent and planar rm Al_2O_2 four membered rings, respectively. Both 4 and 5 yield isobutylene upon thermolysis (ca. 200 ^circC) and the crystallization of mullite occurs at 1034^circC and 1017^circC, respectively (by DTA). The solution thermolysis of 4 in refluxing toluene yields an opaque white gel. The crystallization of mullite occurs at 1029^circC (by DTA). The compounds [ CuOSi(O ^{t}Bu)_3]_{n } (6) and [ CuOSi(O ^{t}Bu)_2Ph]_4 (7) were prepared by reaction with [ CuO^{t}Bu]_4. The thermolysis of 6 at 1000^circ C under argon gave Cu^circ and amorphous silica and thermolysis under

  19. Unusual cis-diprotonated forms and fluorescent aggregates of non-peripherally alkoxy-substituted metallophthalocyanines.

    PubMed

    Kasprzycki, P; Sobotta, L; Lijewski, S; Wierzchowski, M; Goslinski, T; Mielcarek, J; Radzewicz, C; Fita, P

    2017-08-16

    Protonation and aggregation of two metallophthalocyanines (zinc and magnesium) non-peripherally substituted with 1,4,7-trioxanonyl moieties were studied by steady-state and time-resolved optical spectroscopy. Both compounds are easily protonated in organic solvents, but the central metal ion strongly affects the character of this process. In particular, the magnesium derivative forms the cis-diprotonated isomer observed for the first time in phthalocyanines, in contrast to its zinc counterpart which forms the typical trans-diprotonated isomer. In addition, studies performed on phthalocyanines substituted with n-butoxy groups at their non-peripheral positions indicated that the formation of the cis-diprotonated forms is a more common feature of alkoxy-substituted magnesium metallophthalocyanines, in contrast to derivatives with other metal ions. The cis-diprotonated forms of the magnesium derivatives are formed at much lower proton concentrations than the trans-diprotonated forms of their zinc counterparts. The cis-isomers were also found to have more advantageous photophysical properties for photoactive applications than the trans-isomers. Aggregation studies of the trioxanonyl phthalocyanines revealed that the magnesium derivative aggregates much more easily in non-coordinating solvents than its zinc counterpart. Both the derivatives form fluorescent aggregates, which is typically attributed to the presence of oxygen-to-metal intermolecular coordination preventing the formation of non-fluorescent face-to-face stacks. The results indicate that the oxygen-to-metal coordination plays a significant role in the studied systems and the stronger oxygen-coordination ability of magnesium ions compared to zinc ions may underlie the observed differences between the phthalocyanines metallated with these two ions.

  20. Empirical Calculations of {sup 29}Si NMR Chemical Shielding Tensors: A Partial Charge Model Investigation of Hydrolysis in Organically Modified Alkoxy Silanes

    SciTech Connect

    Alam, Todd M.; Henry, Marc

    1999-08-05

    Organically modified alkoxy silanes play an important role in tailoring different properties of silica produced by the sol-gel method. Changes in the size and functionality of the organic group allows control of both physical and chemical properties of the resulting gel, with the kinetics of the polymerization process playing an important role in the design of new siloxane materials. High resolution {sup 29}Si NMR has proven to be valuable tool for monitoring the polymerization reaction, and has been used to investigate a variety of organically modified alkoxy silane systems.

  1. Theoretical investigations on the structure and properties of p-n-alkoxy benzoic acid based liquid crystals

    NASA Astrophysics Data System (ADS)

    Subhapriya, P.; Dhanapal, V.; Sadasivam, K.; Vijayanand, P. S.

    2016-05-01

    The present study focused on the structural conformations, alkoxy chain lengths and mesogenic properties of two mole of alkoxy benzoic acid(nOBA) and one mole of suberic acid (SA) hydrogen bonded (nOBASA) complexes (n=8 to 10) by density functional theory (DFT) calculations and the Fourier Transform Infrared (FT-IR) spectrum. The intermolecular hydrogen bond formation was confirmed by the optimized geometric bond lengths and bond angles obtained by computation. Using the natural bond orbital (NBO) analysis, the stability of the molecule arising from hyper conjugative interactions and charge delocalization has been analyzed. Results obtained shows that the charge in electron density (ED) in σ*and π* antibonding orbital and second order delocalization energies E(2) authorizes the occurrence of intermolecular charge transfer. The molecular electrostatic potential (MEP) surface map is plotted over the optimized geometry of the molecule to obtain the chemical reactivity of the molecule. From the local charge distributions, the mesomorphic behavior and the nematic phase stabilities for each of the molecule have been predicted. Finally the calculated result is applied to simulated infrared spectra of 8OBASA mesogens which shows good agreement with the observed spectra. The comparison of the theoretical results obtained with the experimental ones shows the reliability of this DFT method.

  2. Theoretical investigations on the structure and properties of p-n-alkoxy benzoic acid based liquid crystals

    SciTech Connect

    Subhapriya, P. Dhanapal, V.; Sadasivam, K.; Vijayanand, P. S.

    2016-05-06

    The present study focused on the structural conformations, alkoxy chain lengths and mesogenic properties of two mole of alkoxy benzoic acid(nOBA) and one mole of suberic acid (SA) hydrogen bonded (nOBASA) complexes (n=8 to 10) by density functional theory (DFT) calculations and the Fourier Transform Infrared (FT-IR) spectrum. The intermolecular hydrogen bond formation was confirmed by the optimized geometric bond lengths and bond angles obtained by computation. Using the natural bond orbital (NBO) analysis, the stability of the molecule arising from hyper conjugative interactions and charge delocalization has been analyzed. Results obtained shows that the charge in electron density (ED) in σ*and π* antibonding orbital and second order delocalization energies E(2) authorizes the occurrence of intermolecular charge transfer. The molecular electrostatic potential (MEP) surface map is plotted over the optimized geometry of the molecule to obtain the chemical reactivity of the molecule. From the local charge distributions, the mesomorphic behavior and the nematic phase stabilities for each of the molecule have been predicted. Finally the calculated result is applied to simulated infrared spectra of 8OBASA mesogens which shows good agreement with the observed spectra. The comparison of the theoretical results obtained with the experimental ones shows the reliability of this DFT method.

  3. Rod shaped oxovanadium(IV) Schiff base complexes: Synthesis, mesomorphism and influence of flexible alkoxy chain lengths

    NASA Astrophysics Data System (ADS)

    Gupta, Bishop Dev; Datta, Chitraniva; Das, Gobinda; Bhattacharjee, Chira R.

    2014-06-01

    A series of oxovanadium(IV) complexes of bidentate [N,O] donor Schiff-base ligands of the type [VO(L)2], [L = N-(4-n-alkoxysalicylaldimine)-4‧-octadecyloxyaniline, n = 8, 10, 12, 14, 16 and 18] have been synthesized. The compounds were characterized by elemental analyses, Fourier transform infrared spectroscopy (FTIR), 1H, 13C nuclear magnetic resonance (NMR), ultraviolet-visible spectroscopy (UV-Vis), and fast atom bombardment (FAB) mass spectrometry. The mesomorphic behavior of the compounds was studied by polarized optical microscopy (POM) and differential scanning calorimetry (DSC). The ligands and complexes are all thermally stable exhibiting smectic mesomorphism. The ligands 8-OR to16-OR show SmC phase at ∼113-118 °C and an unidentified SmX phase reminiscent of soft crystal at ∼77-91 °C whereas the complexes all showed SmA phases. Interestingly the complexes with C10 and C12 alkoxy chain length exhibited additionally SmC phases also. The melting points of the ligands linearly increases whereas mesophase to isotropic transition temperature decreases as a function of increasing carbon chain length of alkoxy arm while no trend was apparently noticeable for the complexes.

  4. The development of alkoxy-based sol-gel processing for magnetoresistive manganite thin films

    NASA Astrophysics Data System (ADS)

    Clothier, Brent Allen

    This dissertation presents, for the first time, the successful development of an all-alkoxy based, sol-gel process for integrating thin films of magnetoresistive doped-lanthanide manganites onto silicon-based substrates. Crystallization of the requisite perovskite phase at temperatures below 650°C resulted from the incorporation of all-alkoxide precursors, and in particular, Mn[OC(CH 3)3)]2. This latter precursor, when combined with the polyfunctional solvent, 2-methoxyethanol, exhibited high solubility and hydrolytic reactivity. This accomplishment represents a significant new contribution because low carbon-content manganese(II) alkoxides are stable, insoluble coordinate polymers. Orange and pinkish-orange solutions, also synthesized for the first time, were free from products of aerobic oxidation, and hence, contained no brown discoloration. A partial hydrolysis of h = 0.25 produced a polymeric sol system, conferring both spinnable viscosities and excellent sol longevity. Post-coating hydrolysis via humidified air proved essential to yield transparent, dense, and defect-free amorphous coatings. Conversion into a fine-grain, polycrystalline microstructure occurred above 600°C on platinized-Si(100) and above 650°C on Si(100). The cubic lattice parameters of the films (i.e., a = ˜ 3.90 A) were in excellent agreement with values published in the literature for bulk, polycrystalline powders. Typical grain sizes started at 10--15 nm, increasing to 20--25 nm by 750°C. For films deposited on Si(100), magnetoresistance was observed in specimens heat treated at 700°C and 750°C, and for platinized-Si(100), 650°C, 700°C, and 750°C. Magnetoresistive response improved with heat-treatment temperature for the more refractory La0.67Ba0.33MnO3 composition. The lead-doped counterpart offered the best property evolution, with TC = 320 K and TIM = 254 K by 750°C on platinized-Si(100). All corresponding transport curves were symmetric, demonstrating clear metal

  5. Structure, dynamics, and reactivity of an alkoxy intermediate formed from acetylene on zeolite catalysts: An in situ solid-state NMR study

    SciTech Connect

    Lazo, N.D.; White, J.L.; Munson, E.J.; Lambregts, M.; Haw, J.F. )

    1990-05-09

    Recently, there has been much interest in reactive intermediates formed by the adsorption of organic compounds on zeolites and alumina. In this communication, they present evidence for a vinyl alkoxy species, analogous to IV, which is formed at high temperatures from acetylene on zeolites HY and HZSM-5. Upon exposure of the catalyst to water, the intermediate was converted quantitatively to acetaldehyde.

  6. In vitro and in vivo antiproliferative effect of a combination of ultraviolet-A and alkoxy furocoumarins isolated from Umbelliferae medicinal plants, in melanoma cells.

    PubMed

    Kimura, Yoshiyuki; Sumiyoshi, Maho; Sakanaka, Masahiro; Taniguchi, Masahiko; Baba, Kimiye

    2013-01-01

    We examined the effects of six furocoumarins with alkoxy groups at the C-5 or C-8 position isolated from Umbelliferae medicinal plants on cell proliferation, and their mechanisms of action against B16F10 melanoma cells or in melanin-possessing hairless mice implanted with B16F10 cells, under UVA irradiation. Three furocoumarins with an alkoxy group at C-5, isoimperatorin (1), oxypeucedanin (2) and oxypeucedanin hydrate (3), showed antiproliferative activity and caused G2/M arrest at concentrations of 0.1-10.0 μm. Furthermore, three furocoumarins with an alkoxy group at C-8, imperatorin (4), heraclenin (5) and heraclenol (6), inhibited the proliferation of melanoma cells and cell cycle at G2/M at concentrations of 0.1-1.0 μm. UVA plus 1, 2, 3, 4 and 6 reduced tumor growth and final tumor weight in B16F10-bearing mice at a dose of 0.3, 0.5 or 1.0 mg kg(-1) (intraperitoneal injection). UVA plus 1, 3 and 6 increased Chk1 phosphorylation and reduced cdc2 (Thr 161) phosphorylation in melanoma cells. We suggest that the antitumor actions of UVA plus furocoumarins with an alkoxy group at C-5 or C-8 were due to G2/M arrest of the cell cycle by an increase in phosphor-Chk1 and decrease in phospho-cdc2. © 2013 The American Society of Photobiology.

  7. Vibronic Analysis for widetilde{B} - widetilde{X} Transition of Isopropoxy Radical

    NASA Astrophysics Data System (ADS)

    Chhantyal-Pun, Rabi; Miller, Terry A.

    2013-06-01

    Alkoxy radicals are important intermediates in combustion and atmospheric chemistry. Alkoxy radicals are also of significant spectroscopic interest for the study of Jahn Teller and pseudo Jahn Teller effects, involving the widetilde{X} and widetilde{A} states. The Jahn Teller effect has been studied in methoxy. Substitution of one or two hydrogens by methyl groups transforms the interaction to a pseudo Jahn Teller effect in ethoxy and isopropoxy. Previously, moderate resolution scans have been obtained for widetilde{B} - widetilde{X} and widetilde{B} - widetilde{A} transition systems, the latter observable at higher temperature. These measurements have shown that the widetilde{X} and widetilde{A} states of isopropoxy are separated by only 60.7(7) cm^{-1} which indicates a strong pseudo Jahn Teller effect in the widetilde{X} state. Such pseduo Jahn Teller coupling should also introduce additional bands into the widetilde{B} - widetilde{X} spectrum and a number of weaker transitions have been observed which may be caused by such effects. In this talk we present a vibronic analysis for the widetilde{B} - widetilde{X} transition based on the experimental results and also the results from recent quantum chemistry calculations.

  8. Dispersed Fluorescence Spectroscopy of Jet-Cooled Isobutoxy, 2-METHYL-1-BUTOXY, and Isopentoxy Radicals

    NASA Astrophysics Data System (ADS)

    Reza, Md Asmaul; Reilly, Neil J.; Alam, Jahangir; Mason, Amy; Liu, Jinjun

    2015-06-01

    It is well known that rate constants of certain reactions of alkoxy radicals, e.g., unimolecular dissociation (decomposition by C-C bond fission) and isomerization via 1,5 H-shift, are highly sensitive to the molecular structure. In the present and the next talks, we report dispersed fluorescence (DF) spectra of various alkoxy radicals obtained under supersonic jet-cooled conditions by pumping different vibronic bands of their tilde B ← tilde X laser induced fluorescence (LIF) excitation spectra. This talk focuses on the DF spectra of 2-methyl-1-propoxy (isobutoxy), 2-methyl-1-butoxy, and 3-methyl-1-butoxy (isopentoxy). In all cases, strong CO-stretch progressions were observed, as well as transitions to other vibrational levels, including low-frequency ones. Quantum chemical calculations were carried out to aid the assignment of the DF spectra. Franck-Condon factors were calculated using the ezSpectrum program. Wu, Q.; Liang, G.; Zu, L.; Fang, W. J. Phys. Chem A 2012, 116, 3156-3162. Lin, J.; Wu, Q.; Liang, G.; Zu, L.; Fang, W. RSC Adv. 2012, 2, 583-589. Liang, G.; Liu , C.; Hao, H.; Zu, L.; Fang, W. J. Phys. Chem. A 2013, 117, 13229- 13235. V. Mozhayskiy and A. I. Krylov, http://iopenshell.usc.edu/

  9. Low dielectric and low surface free energy flexible linear aliphatic alkoxy core bridged bisphenol cyanate ester based POSS nanocomposites

    NASA Astrophysics Data System (ADS)

    Alagar, Muthukaruppan; Devaraju, S.; Prabunathan, P.; Selvi, M.

    2013-10-01

    The aim of the present work is to develop a new type of flexible linear aliphatic alkoxy core bridged bisphenol cyanate ester (AECE) based POSS nanocomposites for low k applications. The POSS-AECE nanocomposites were developed by incorporating varying weight percentages (0, 5 and 10 wt %) of octakis (dimethylsiloxypropylglycidylether) silsesquioxane (OG-POSS) into cyanate esters. Data from thermal and dielectric studies imply that the POSS reinforced nanocomposite exhibits higher thermal stability and low dielectric value of k=2.4 (10 wt% POSS-AECE4) compared than those of neat AECE. From the contact angle measurement, it is inferred that, the increase in the percentage incorporation of POSS in to AECE, the values of water contact angle was enhanced. Further, the value of surface free energy was lower when compared to that of neat AECE. The molecular level dispersion of POSS into AECE was ascertained from SEM and TEM analyses.

  10. Synthesis and anticonvulsant activity of 6-alkoxy-[1,2,4]triazolo[3,4-a]phthalazines.

    PubMed

    Zhang, Lei; Guan, Li-Ping; Sun, Xian-Yu; Wei, Cheng-Xi; Chai, Kyu-Yun; Quan, Zhe-Shan

    2009-03-01

    A new series of 6-alkoxy-[1,2,4]triazolo[3,4-a]phthalazines (3a-3v) were synthesized and their anticonvulsant activity and neurotoxicity were evaluated by the maximal electroshock test and the rotarod test respectively. Significant anticonvulsant activity was displayed by a number of compounds. The most promising compounds 6-(4-chlorobenzyloxy)-[1,2,4]triazolo[3,4-a]phthalazine (3f) and 6-heptyloxy-[1,2,4]triazolo[3,4-a]phthalazine (3s) showed a median effective dose of 7.1 and 11.0 mg/kg, and had protective index value of 5.2 and 8.0 respectively. The two compounds were further found to have potent activity against seizures induced by pentylenetetrazole, isoniazid, thiosemicarbazide, 3-mercaptopropionic acid but not seizures induced by strychnine, indicating that the two compounds might function by enhancing gamma-aminobutyric acid neurotransmission.

  11. Adlayer structure of octa-alkoxy-substituted copper(II) phthalocyanine on Au(111) by electrochemical scanning tunneling microscopy.

    PubMed

    Wang, Li; Ou-Yang, Liangyue; Yau, Shueh-Lin

    2008-01-01

    Electrochemical scanning tunneling microscopy (ECSTM) has been used to examine the adlayer of octa-alkoxy-substituted copper(II) phthalocyanines (CuPc(OC(8)H(17))(8)) on Au(111) in 0.1 M HClO(4), where the molecular adlayer was prepared by spontaneous adsorption from a benzene solution containing this molecule. Topography STM scans revealed long-range ordered, interweaved arrays of CuPc(OC(8)H(17))(8) with coexistent rectangular and hexagonal symmetries. High-quality STM molecular resolution yielded the internal molecular structure and the orientation of CuPc(OC(8)H(17))(8) admolecules. These STM results could shed insight into the method of generating ordered molecular assemblies of phthalocyanine molecules with long-chained substitutes on metal surface.

  12. Low dielectric and low surface free energy flexible linear aliphatic alkoxy core bridged bisphenol cyanate ester based POSS nanocomposites

    PubMed Central

    Devaraju, S.; Prabunathan, P.; Selvi, M.; Alagar, M.

    2013-01-01

    The aim of the present work is to develop a new type of flexible linear aliphatic alkoxy core bridged bisphenol cyanate ester (AECE) based POSS nanocomposites for low k applications. The POSS-AECE nanocomposites were developed by incorporating varying weight percentages (0, 5, and 10 wt %) of octakis (dimethylsiloxypropylglycidylether) silsesquioxane (OG-POSS) into cyanate esters. Data from thermal and dielectric studies imply that the POSS reinforced nanocomposite exhibits higher thermal stability and low dielectric value of k = 2.4 (10 wt% POSS-AECE4) compared than those of neat AECE. From the contact angle measurement, it is inferred that, the increase in the percentage incorporation of POSS in to AECE, the values of water contact angle was enhanced. Further, the value of surface free energy was lower when compared to that of neat AECE. The molecular level dispersion of POSS into AECE was ascertained from SEM and TEM analyses. PMID:24790947

  13. Preparation and structures of aryloxy- and alkoxy-Ti(IV) complexes and their evaluation in ethylene oligomerisation and polymerisation.

    PubMed

    Suttil, James A; McGuinness, David S; Pichler, Markus; Gardiner, Michael G; Morgan, David H; Evans, Stephen J

    2012-06-14

    A range of aryloxy and alkoxy ligands, both monodenate and chelating, have been coordinated to Ti(IV) to yield complexes of the form [Ti(OAr)(2)Cl(2)], [Ti(RO^O)Cl(3)] and [Ti(RO^O)(2)Cl(2)] (R = aryl, alkyl). The complexes vary in their Lewis base solvation and/or aggregation state, as revealed by X-ray crystallography of selected examples. The complexes have been evaluated as catalysts for ethylene oligomerisation and polymerisation following activation with alkylaluminium reagents (AlEt(3), methylaluminoxane). While polyethylene is the major product, ethylene oligomers also result, ranging from dimers to higher oligomers. The results indicate a number of different active species are formed upon activation, with oligomers likely arising through a metallacyclic mechanism. The findings are discussed in the context of the commercial Alphabutol dimerisation system [Ti(OR)(4)], and the development of group 4 based ethylene trimerisation catalysts.

  14. Evaluation of free radical scavenging and anti-oxidative capacity of polydatin-nanostructured lipid carriers

    NASA Astrophysics Data System (ADS)

    Meng, Xiang-Ping; Shi, Fan; Li, Hai-Jie; Yin, Li-De; Wang, Yi-Fei; Wang, Zhi-ping; Chen, Tong-sheng

    2016-10-01

    Cellular damage induced by free-radicals like reactive oxygen species has been implicated in several diseases. 2, 2-azobis(2-amidino-propane) dihydrochloride(AAPH) generates two potent ROS capable of inducing lipid peroxidation: alkoxy radical(RO-) and peroxy radical (ROO-). These radicals are similar to those that are physiologically active and thus might initiate a cascade of intracellular toxic events leading to oxidation, lipid peroxidation, DNA damage and subsequent cell death. Hence naturally anti-oxidant play a vital role in combating these conditions. In this study, polydatin loaded nanostructured lipid carriers (Pol-NLC) was prepared by hot melting and then high pressure homogenization technique. The effects of Pol-NLC on free radical scavenging and anti-oxidative capacity is investigated. The particle size and zeta potential of Pol-NLC were 113.9 +/- 1.1 nm and -16.3 1 +/- 0.27 mV, respectively. By free radical scavenging assays, the IC50 value of Pol-NLC were 28.71, 9.83 μg/mL with DPPH, ABTS assay respectively, and 0.143 mg ferrous sulfate/1 mg Pol-NLC with FRAP assay. These results indicated that the antioxidant properties of Pol-NLC hold great potential used as an alternative to more toxic synthetic anti-oxidants as an additive in food, cosmetic and pharmaceutical preparations for the oxidative diseases treatment.

  15. Orientational order parameter, S, in N-(p-n-ethoxy benzylidene)-p-n-alkoxy anilines, 2O.Om LC compounds

    NASA Astrophysics Data System (ADS)

    Sastry, P. S.; Srinivasu, Ch.; Pardhasaradhi, P.; Pisipati, V. G. K. M.

    2016-01-01

    The orientational order parameter, S, is estimated in N-(p-n-ethoxy benzylidene)-p-n-alkoxy anilines, 2O.Om liquid crystalline (LC) compounds with alkoxy chain number, m = 3, 4, and 6-10 using four different methods. The methods employed are (1) from birefringence, ? where ne and no are extraordinary and ordinary refractive indices, (2) from effective geometry parameter, αg, where α = no/ne, (3) from the Haller approximation (1 - T/TNIβ where β is obtained from method (1), and (4) the Maier and Saupe method from density. In the four methods proposed no field is chosen to explain the nematic liquid crystal and provides the S values obtained are identical to one another except in the case of 2O.O9 compound where the S values are higher when compared to the others. All the methods are explained in detail.

  16. Key Role of End-Capping Groups in Optoelectronic Properties of Poly-p-phenylene Cation Radicals

    PubMed Central

    2015-01-01

    Poly-p-phenylenes (PPs) are prototype systems for understanding the charge transport in π-conjugated polymers. In a combined computational and experimental study, we demonstrate that the smooth evolution of redox and optoelectronic properties of PP cation radicals toward the polymeric limit can be significantly altered by electron-donating iso-alkyl and iso-alkoxy end-capping groups. A multiparabolic model (MPM) developed and validated here rationalizes this unexpected effect by interplay of the two modes of hole stabilization: due to the framework of equivalent p-phenylene units and due to the electron-donating end-capping groups. A symmetric, bell-shaped hole in unsubstituted PPs becomes either slightly skewed and shifted toward an end of the molecule in iso-alkyl-capped PPs or highly deformed and concentrated on a terminal unit in PPs with strongly electron-donating iso-alkoxy capping groups. The MPM shows that the observed linear 1/n evolution of the PP cation radical properties toward the polymer limit originates from the hole stabilization due to the growing chain of p-phenylene units, while shifting of the hole toward electron-donating end-capping groups leads to early breakdown of these 1/n dependencies. These insights, along with the readily applicable and flexible multistate parabolic model, can guide studies of complex donor–spacer–acceptor systems and doped molecular wires to aid the design of the next generation materials for long-range charge transport and photovoltaic applications. PMID:25264475

  17. Structural Basis of Species-Dependent Differential Affinity of 6-Alkoxy-5-Aryl-3-Pyridinecarboxamide Cannabinoid-1 Receptor Antagonists.

    PubMed

    Iyer, Malliga R; Cinar, Resat; Liu, Jie; Godlewski, Grzegorz; Szanda, Gergö; Puhl, Henry; Ikeda, Stephen R; Deschamps, Jeffrey; Lee, Yong-Sok; Steinbach, Peter J; Kunos, George

    2015-08-01

    6-Alkoxy-5-aryl-3-pyridincarboxamides, including the brain-penetrant compound 14G: [5-(4-chlorophenyl)-6-(cyclopropylmethoxy)-N-[(1R,2R)-2-hydroxy-cyclohexyl]-3-pyridinecarboxamide] and its peripherally restricted analog 14H: [5-(4-chlorophenyl)-N-[(1R,2R)-2-hydroxycyclohexyl]-6-(2-methoxyethoxy)-3-pyridinecarboxamide], have been recently introduced as selective, high-affinity antagonists of the human cannabinoid-1 receptor (hCB1R). Binding analyses revealed two orders of magnitude lower affinity of these compounds for mouse and rat versus human CB1R, whereas the affinity of rimonabant is comparable for all three CB1Rs. Modeling of ligand binding to CB1R and binding assays with native and mutant (Ile105Met) hCB1Rs indicate that the Ile105 to Met mutation in rodent CB1Rs accounts for the species-dependent affinity of 14G: and 14H: . Our work identifies Ile105 as a new pharmacophore component for developing better hCB1R antagonists and invalidates rodent models for assessing the antiobesity efficacy of 14G: and 14H: .

  18. Original 2-(3-Alkoxy-1H-pyrazol-1-yl)azines Inhibitors of Human Dihydroorotate Dehydrogenase (DHODH)

    PubMed Central

    2016-01-01

    Following our discovery of human dihydroorotate dehydrogenase (DHODH) inhibition by 2-(3-alkoxy-1H-pyrazol-1-yl)pyrimidine derivatives as well as 2-(4-benzyl-3-ethoxy-5-methyl-1H-pyrazol-1-yl)-5-methylpyridine, we describe here the syntheses and evaluation of an array of azine-bearing analogues. As in our previous report, the structure–activity study of this series of human DHODH inhibitors was based on a phenotypic assay measuring measles virus replication. Among other inhibitors, this round of syntheses and biological evaluation iteration led to the highly active 5-cyclopropyl-2-(4-(2,6-difluorophenoxy)-3-isopropoxy-5-methyl-1H-pyrazol-1-yl)-3-fluoropyridine. Inhibition of DHODH by this compound was confirmed in an array of in vitro assays, including enzymatic tests and cell-based assays for viral replication and cellular growth. This molecule was found to be more active than the known inhibitors of DHODH, brequinar and teriflunomide, thus opening perspectives for its use as a tool or for the design of an original series of immunosuppressive agent. Moreover, because other series of inhibitors of human DHODH have been found to also affect Plasmodium falciparum DHODH, all the compounds were assayed for their effect on P. falciparum growth. However, the modest in vitro inhibition solely observed for two compounds did not correlate with their inhibition of P. falciparum DHODH. PMID:26079043

  19. 14-Alkoxy- and 14-acyloxypyridomorphinans: μ agonist/δ antagonist opioid analgesics with diminished tolerance and dependence side effects.

    PubMed

    Ananthan, Subramaniam; Saini, Surendra K; Dersch, Christina M; Xu, Heng; McGlinchey, Nicholas; Giuvelis, Denise; Bilsky, Edward J; Rothman, Richard B

    2012-10-11

    In the search for opioid ligands with mixed functional activity, a series of 5'-(4-chlorophenyl)-4,5α-epoxypyridomorphinans possessing alkoxy or acyloxy groups at C-14 was synthesized and evaluated. In this series, the affinity and functional activity of the ligands were found to be influenced by the nature of the substituent at C-14 as well as by the substituent at N-17. Whereas the incorporation of a 3-phenylpropoxy group at C-14 on N-methylpyridomorhinan gave a dual MOR agonist/DOR agonist 17h, its incorporation on N-cyclopropylmethylpyridomorphinan gave a MOR agonist/DOR antagonist 17d. Interestingly, 17d, in contrast to 17h, did not produce tolerance or dependence effects upon prolonged treatment in cells expressing MOR and DOR. Moreover, 17d displayed greatly diminished analgesic tolerance as compared to morphine upon repeated administration, thus supporting the hypothesis that ligands with MOR agonist/DOR antagonist functional activity could emerge as novel analgesics devoid of tolerance, dependence, and related side effects.

  20. 14-Alkoxy- and 14-Acyloxypyridomorphinans: Mu Agonist/Delta Antagonist Opioid Analgesics with Diminished Tolerance and Dependence Side Effects

    PubMed Central

    Ananthan, Subramaniam; Saini, Surendra K.; Dersch, Christina M.; Xu, Heng; McGlinchey, Nicholas; Giuvelis, Denise; Bilsky, Edward J.; Rothman, Richard B.

    2012-01-01

    In the search for opioid ligands with mixed functional activity, a series of 5′-(4-chlorophenyl)-4,5α-epoxypyridomorphinans possessing alkoxy or acyloxy groups at C-14 was synthesized and evaluated. In this series, the affinity and functional activity of the ligands were found to be influenced by the nature of the substituent at C-14 as well as by the substituent at N-17. Whereas the incorporation of a 3-phenylpropoxy group at C-14 on N-methylpyridomorhinan gave a dual MOR agonist/DOR agonist 17h its incorporation on N-cyclopropylmethylpyridomorphinan gave a MOR agonist/DOR antagonist 17d. Interestingly, 17d, in contrast to 17h, did not produce tolerance or dependence effects on prolonged treatment in cells expressing MOR and DOR. Moreover, 17d displayed greatly diminished analgesic tolerance as compared to morphine on repeated administration, thus supporting the hypothesis that ligands with MOR agonist/DOR antagonist functional activity could emerge as novel analgesics devoid of tolerance, dependence and related side effects. PMID:23016952

  1. 4-alkoxy and 4-thioalkoxyquinoline derivatives as chemosensitizers for the chloramphenicol-resistant clinical Enterobacter aerogenes 27 strain.

    PubMed

    Gallo, Sandrine; Chevalier, Jacqueline; Mahamoud, Abdallah; Eyraud, Annie; Pagès, Jean-Marie; Barbe, Jacques

    2003-09-01

    Enterobacter aerogenes is a Gram-negative bacteria frequently responsible for nosocomial respiratory tract infections. Strains resistant to chloramphenicol are frequently isolated. Alkoxy and thio-alkoxyquinolines have a potential to act as chemosensitizers that would render multi-drug-resistant (MDR) bacterial infections susceptible to antibiotics to which they were originally resistant. Several new quinoline derivatives have been prepared, characterized and studied for their ability to increase chloramphenicol sensitivity of E. aerogenes 27, a clinical strain that exhibits the MDR phenotype. Drugs investigated were either quinoline ethers or quinoline thio-ethers. Thio-ethers are much more efficient in increasing chloramphenicol sensitivity than other corresponding ethers. In particular, 4-piperidinoethylthio-quinoline increases the strain sensitivity to chloramphenicol by about 20 times at 2 mM concentration. Similarly, sensitivity to quinolone antibiotics dramatically increases. Because these quinoline derivatives act as inhibitors of the drug efflux pump responsible for bacterial resistance to chloramphenicol, they may serve as adjunct to conventional therapy of E. aerogenes infections.

  2. Immobilization of calcium phosphate nano-clusters into alkoxy-derived porous TiO2 coatings.

    PubMed

    Shirkhanzadeh, M; Sims, S

    1997-10-01

    Alkoxy-derived porous coatings of titanium oxide were fabricated on commercially pure titanium substrates by an electrochemical method in methanolic electrolytes. Nano-clusters of brushite (CaHPO4. 2H2O) were immobilized into the pores of the oxide network by reacting these coatings in acidic calcium phosphate solutions at 50 degrees C. The acid-base reaction between calcium phosphate solutions and the hydroxyl groups of the oxide network resulted in the formation of nano-clusters of brushite crystals immobilized inside the oxide pores. This treatment resulted in the conversion of the porous oxide network into a coherent mass with improved physical integrity. Nano-clusters of brushite crystals immobilized in the oxide matrix were converted into amorphous calcium phosphate (ACP) and poorly crystallized hydroxyapatite (HA) by further treatment of the oxide in alkaline solutions. The porous oxide coating also reacted strongly with concentrated phosphoric acid. The phosphate-modified oxide resulting from this reaction was further treated in calcium hydroxide solution to form nano-clusters of poorly crystallized HA within the oxide network.

  3. Contemporary Radical Economics.

    ERIC Educational Resources Information Center

    Sherman, Howard J.

    1984-01-01

    The origins of contemporary radical economics are examined. Applications of radical economics to price and value theory, labor segmentation theory, business cycles, industrial organization, government and business, imperialism and development, and comparative systems are reviewed. (Author/RM)

  4. Contemporary Radical Economics.

    ERIC Educational Resources Information Center

    Sherman, Howard J.

    1984-01-01

    The origins of contemporary radical economics are examined. Applications of radical economics to price and value theory, labor segmentation theory, business cycles, industrial organization, government and business, imperialism and development, and comparative systems are reviewed. (Author/RM)

  5. Radical prostatectomy - discharge

    MedlinePlus

    ... prostatectomy - discharge; Laparoscopic radical prostatectomy - discharge; LRP - discharge; Robotic-assisted laparoscopic prostatectomy - discharge ; RALP - discharge; Pelvic lymphadenectomy - ...

  6. The radical amplifier

    NASA Technical Reports Server (NTRS)

    Hastie, D. R.

    1994-01-01

    The radical amplifier as a method for measuring radical concentrations in the atmosphere has received renewed attention lately. In principle, it can measure the total concentration of HO(x) and RO(x) radicals by reacting ambient air with high concentrations of CO (3-10 percent) and NO (2-6 ppmv), and measuring the NO2 produced.

  7. Photo-reorganization of 3-alkoxy-6-chloro-2-(benzo[b]thiophen-2-yl)-4H-chromen-4-ones: a green and convenient synthesis of angular pentacyclics.

    PubMed

    Dalal, Aarti; Khanna, Radhika; Kumar, Parvin; Kamboj, Ramesh C

    2017-05-17

    Photo-reorganization of 3-alkoxy-6-chloro-2-(benzo[b]thiophen-2-yl)-4H-chromen-4-ones in methanol with Pyrex filtered UV-light from a medium pressure 125 W Hg-vapor lamp led to the formation of angular pentacyclic compounds (dihydro and aromatic products) along with some rearranged chromenones where the product(s) distribution depended upon the structure of 3-alkoxy groups (methoxy, ethoxy, allyloxy and benzyloxy). The phenyl moiety in the 3-benzyloxy group had a profound effect on the dihydro product(s) formation as the latter was in high yield when the alkoxy group was benzyloxy followed by allyloxy, ethoxy and methoxy groups. The present photochemical study represents a general method for the synthesis of some angular pentacyclic - benzothiophene fused xanthenone derivatives in a single step without using any specific and toxic reagent. The structures of the new organic scaffolds obtained were established by their spectral data (UV, IR and NMR).

  8. [Lavoisier and radicals].

    PubMed

    Lafont, Olivier

    2007-01-01

    Lavoisier and his co-workers (Guyton de Morveau, Bertholet, Fourcroy) considered that acids were constituted of oxygen and of something else that they called radicals. These radicals were known in some cases, i.e. nitrogen for nitrous acid, carbon for carbonic acid, phosphorus for phosphoric acid. In the case of sulfur, the sulfuric radical could be associated with different quantities of oxigen leading to sulfuric or sulfurous acids. In other cases radicals remained unknown at the time i.e. muriatic radical for muriatic acid, or benzoyl radical for benzoic acid. It is interesting to notice that Lavoisier evoked the case of compound radicals constituted of different substances such as carbon and hydrogen.

  9. 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).

  10. Low-temperature sol-gel synthesis of nanostructured polymer/titania hybrid films based on custom-made poly(3-alkoxy thiophene).

    PubMed

    Niedermeier, Martin A; Rawolle, Monika; Lellig, Philipp; Körstgens, Volker; Herzig, Eva M; Buffet, Adeline; Roth, Stephan V; Gutmann, Jochen S; Fröschl, Thomas; Hüsing, Nicola; Müller-Buschbaum, Peter

    2013-02-25

    A low-temperature route to directly obtain polymer/titania hybrid films is presented. For this, a custom-made poly(3-alkoxy thiophene) was synthesized and used in a sol-gel process together with an ethylene-glycol-modified titanate (EGMT) as a suitable titania precursor. The poly(3-alkoxy thiophene) was designed to act as the structure-directing agent for titanium dioxide through selective incorporation of the titania precursor. The nanostructured titania network, embedded in the polymer matrix, is examined with atomic force microscopy (AFM) and scanning electron microscopy (SEM) measurements. By means of the scattering technique grazing incidence wide-angle X-ray scattering (GIWAXS), a high degree of crystallinity of the polymer as well as successful transformation of the precursor into the rutile phase of titania is verified. UV/Vis measurements reveal an absorption behavior around 500 nm which is similar to poly(3-hexyl thiophene), a commonly used polymer for photoelectronic applications, and in addition, the typical UV absorption behavior of rutile titania is observed.

  11. Selectivity Guidelines and a Reductive Elimination-Based Model for Predicting the Stereochemical Course of Conjugate Addition Reactions of Organocuprates to γ-Alkoxy-α,β-Enoates

    PubMed Central

    Kireev, Artem S.; Manpadi, Madhuri; Kornienko, Alexander

    2008-01-01

    Current models used to predict the stereochemical outcome of organocopper conjugate addition processes focus on the nucleophilic addition step as stereochemistry-determining. Recent kinetic, NMR, kinetic isotope effect and theoretical density functional studies strongly support the proposal that stereochemical preferences in these processes are dictated by the reductive elimination step, transforming CuIII to CuI intermediates. A new model that considers various steric and stereoelectronic factors involved in the transition state of the reductive elimination step is proposed and then used to interpret the results of systematic studies of arylcuprate conjugate addition reactions with cis and trans γ-alkoxy-α,β-enoates. The results give rise to the following selectivity guidelines for this process. To achieve high anti-addition diastereoselectivities the use of trans esters with a bulky non-alkoxy substituent at the γ-position is recommended. While stereoelectronics disfavor syn-addition, a judicious choice of properly sized γ-substituents may lead to the predominant formation of syn-products, especially with cis enoates. However, high syn-selelectivities may be achieved by using γ-amino-α,β-enoates. PMID:16555814

  12. Silicon, silica and its surface patterning/activation with alkoxy- and amino-silanes for nanomedical applications.

    PubMed

    Rother, Dag; Sen, Tapas; East, Daniel; Bruce, Ian James

    2011-02-01

    Silica and silicates are widely used in nanomedicine with applications as diverse as medical device coatings to replacement materials in tissue engineering. Although much is known about silica and its synthesis, relatively few biomedical scientists fully appreciate the link that exists between its formulation and its resultant structure and function. This article attempts to provide insight into relevant issues in that context, as well as highlighting their importance in the material's eventual surface patterning/activation with alkoxy- and organo-silanes. The use of aminosilanes in that context is discussed at some length to permit an understanding of the specific variables that are important in the reproducible and robust aminoactivation of surfaces using such molecules. Recent investigative work is cited to underline the fact that although aminosilanization is a historically accepted mechanism for surface activation, there is still much to be explained about how and why the process works in the way it does. In the last section of this article, there is a detailed discussion of two classical approaches for the use of aminosilanized materials in the covalent immobilization of bioligands, amino-aldehyde and amino-carboxyl coupling. In the former case, the use of the homobifunctional coupler glutaraldehyde is explored, and in the latter, carbodiimides. Although these chemistries have long been employed in bioconjugations, it is apparent that there are still variables to be explored in the processes (as witnessed by continuing investigations into the chemistries concerned). Aspects regarding optimization, standardization and reproducibility of the fabrication of amino functionalized surfaces are discussed in detail and illustrated with practical examples to aid the reader in their own studies, in terms of considerations to be taken into account when producing such materials. Finally, the article attempts to remind readers that although the chemistry and materials

  13. Forgotten Radicals in Biology

    PubMed Central

    Luc, Rochette; Vergely, Catherine

    2008-01-01

    Redox reactions play key roles in intra- and inter-cellular signaling, and in adaptative processes of tissues towards stress. Among the major free radicals with essential functions in cells are reactive oxygen species (ROS) including superoxide anion (O2•-), hydroxyl radical (•OH) and reactive nitrogen species (RNS) such as nitric oxide (•NO). In this article, we review the forgotten and new radicals with potential relevance to cardiovascular pathophysiology. Approximately 0.3% of O2•- present in cytosol exists in its protonated form: hydroperoxyl radical (HO2•). Water (H2O) can be split into two free radicals: •OH and hydrogen radical (H•). Several free radicals, including thiyl radicals (RS•) and nitrogen dioxide (NO2•) are known to isomerize double bonds. In the omega-6 series of poly-unsaturated fatty acids (PUFAs), cis-trans isomerization of γ-linolenate and arachidonate catalyzed by RS• has been investigated. Evidence is emerging that hydrogen disulphide (H2S) is a signaling molecule in vivo which can be a source of free radicals. The Cu-Zn superoxide dismutase (SOD) enzyme can oxidize the ionized form of H2S to hydro-sulphide radical: HS•. Recent studies suggest that H2S plays an important function in cardiovascular functions. Carbonate radical, which can be formed when •OH reacts with carbonate or bicarbonate ions, is also involved in the activity of Cu-Zn-SOD. Recently, it has been reported that carbonate anion were potentially relevant oxidants of nucleic acids in physiological environments. In conclusion, there is solid evidence supporting the formation of many free radicals by cells leading which may play an important role in their homeostasis. PMID:23675099

  14. Evaluation of free radical scavenging capacity and antioxidative damage effect of resveratrol-nanostructured lipid carriers

    NASA Astrophysics Data System (ADS)

    Jin, Ju; Shi, Fan; Li, Qiu-wen; Li, Pei-shan; Chen, Tong-sheng; Wang, Yi-fei; Wang, Zhi-ping

    2016-03-01

    Cellular damage induced by free-radicals like reactive oxygen species has been implicated in several diseases. 2, 2-azobis(2-amidino-propane) dihydrochloride(AAPH) generates two potent ROS capable of inducing lipid peroxidation: alkoxy radical(RO-) and peroxy radical(ROO-). These radicals are similar to those that are physiologically active and thus might initiate a cascade of intracellular toxic events leading to oxidation, lipid peroxidation, DNA damage and subsequent cell death. Hence naturally anti-oxidant play a vital role in combating these conditions. In this study, resveratrol loaded nanostructured lipid carriers (Res-NLC) was prepared by hot melting and then high pressure homogenization technique. The effects of Res-NLC on free radical scavenging capacity and antioxidative damage is investigated. The particle size and zeta potential of Res-NLC were 139.3 ± 1.7 nm and -11.21 ± 0.41 mV, respectively. By free radical scavenging assays, the IC50 value of Res-NLC were 19.25, 5.29 μg/mL with DPPH, ABTS assay respectively, and 0.161 mg ferrous sulfate/1 mg Res-NLC with FRAP assay; and by AAPH-induced oxidative injury cell model assay, Res-NLC showed the strong protective effect against the human liver tumor HepG2 cell oxidative stress damage. These results indicated that the antioxidant properties of Res-NLC hold great potential used as an alternative to more toxic synthetic antioxidants as an additive in food, cosmetic and pharmaceutical preparations for the oxidative diseases treatment.

  15. Structural features, kinetics and SAR study of radical scavenging and antioxidant activities of phenolic and anilinic compounds

    PubMed Central

    2013-01-01

    Background Phenolic compounds are widely distributed in plant kingdom and constitute one of the most important classes of natural and synthetic antioxidants. In the present study fifty one natural and synthetic structurally variant phenolic, enolic and anilinic compounds were examined as antioxidants and radical scavengers against DPPH, hydroxyl and peroxyl radicals. The structural diversity of the used phenolic compounds includes monophenols with substituents frequently present in natural phenols e.g. alkyl, alkoxy, ester and carboxyl groups, besides many other electron donating and withdrawing groups, in addition to polyphenols with 1–3 hydroxyl groups and aminophenols. Some common groups e.g. alkyl, carboxyl, amino and second OH groups were incorporated in ortho, meta and para positions. Results SAR study indicates that the most important structural feature of phenolic compounds required to possess good antiradical and antioxidant activities is the presence of a second hydroxyl or an amino group in o- or p-position because of their strong electron donating effect in these positions and the formation of a stable quinone-like products upon two hydrogen-atom transfer process; otherwise, the presence of a number of alkoxy (in o or p-position) and /or alkyl groups (in o, m or p-position) should be present to stabilize the resulted phenoxyl radical and reach good activity. Anilines showed also similar structural feature requirements as phenols to achieve good activities, except o-diamines which gave low activity because of the high energy of the resulted 1,2-dimine product upon the 2H-transfer process. Enols with ene-1,2-diol structure undergo the same process and give good activity. Good correlations were obtained between DPPH inhibition and inhibition of both OH and peroxyl radicals. In addition, good correlations were obtained between DPPH inhibition and antioxidant activities in sunflower oil and liver homogenate systems. Conclusions In conclusion, the

  16. Reaction between radicals and N-alkoxyamines As coordinated cleavage with fragmentation

    NASA Astrophysics Data System (ADS)

    Denisov, E. T.; Shestakov, A. F.

    2015-08-01

    Quantum chemical calculations of the enthalpy and activation energy of two reactions with MeO{2/⊙} attacking the CH- and CH2-groups of 2,2,6,6-tetramethylpiperidineoxy-2'-butane are performed. It is shown that the cleavage of hydrogen atoms is accompanied by coordinated breaking of N-O-bonds in the former case and C-O-bonds in the latter. Based on the obtained results, a new scheme is proposed for the cyclic mechanism behind the cleavage of chains on nitroxyl radicals in oxidizing hydrocarbons and polymers that agrees with experimental data. At the center of this cyclic mechanism lies the fast exothermic reaction between peroxyl radicals and N-alkoxyamine with the cleavage of H atoms and the coordinated fragmentation of molecules. Using the model of intersecting parabolas, an algorithm for calculating the enthalpies, activation energies, and rate constants of these reactions with the participation of alkyl, alkoxy, aminyl, peroxyl, phenoxyl, thiyl, and hydroxyl radicals is proposed.

  17. Thermochemistry and kinetics for 2-butanone-1-yl radical (CH2·C(═O)CH2CH3) reactions with O2.

    PubMed

    Sebbar, N; Bozzelli, J W; Bockhorn, H

    2014-01-09

    Thermochemistry of reactants, intermediates, transition state structures, and products along with kinetics on the association of CH2·C(═O)CH2CH3 (2-butanone-1-yl) with O2 and dissociation of the peroxy adduct isomers are studied. Thermochemical properties are determined using ab initio (G3MP2B3 and G3) composite methods along with density functional theory (B3LYP/6-311g(d,p)). Entropy and heat capacity contributions versus temperature are determined from structures, vibration frequencies, and internal rotor potentials. The CH2·C(═O)CH2CH3 radical + O2 association results in a chemically activated peroxy radical with 27 kcal mol(-1) excess of energy. The chemically activated adduct can react to stabilized peroxy or hydroperoxide alkyl radical adducts, further react to lactones plus hydroxyl radical, or form olefinic ketones and a hydroperoxy radical. Kinetic parameters are determined from the G3 composite methods derived thermochemical parameters, and quantum Rice-Ramsperger-Kassel (QRRK) analysis to calculate k(E) with master equation analysis to evaluate falloff in the chemically activated and dissociation reactions. One new, not previously reported, peroxy chemistry reaction is presented. It has a low barrier path and involves a concerted reaction resulting in olefin formation, H2O elimination, and an alkoxy radical.

  18. Synthesis and anti-inflammatory activity evaluation of some novel 6-alkoxy(phenoxy)-[1,2,4]triazolo[3,4-a]phthalazine-3-amine derivatives.

    PubMed

    Sun, Xian-Yu; Hu, Chuan; Deng, Xian-Qing; Wei, Cheng-Xi; Sun, Zhi-Gang; Quan, Zhe-Shan

    2010-11-01

    Starting from phthalic anhydride, several new 6-alkoxy(phenoxy)-[1,2,4]triazolo[3,4-a]phthalazine-3-amine derivatives were synthesized as potent anti-inflammatory agent. The study showed that the compounds 6h (6-(2-chlorophenoxy)-[1,2,4]triazolo[3,4-a]phthalazine-3-amine) and 6s (6-(4-aminophenoxy)-[1,2,4] triazolo[3,4-a]phthalazine-3-amine) exhibited the highest anti-inflammatory activity (81% and 83% inhibition, respectively, at 0.5 h after i.p. administration) which were slightly more potent than the reference drug Ibuprofen (61%). Furthermore, the peak activity of 6h and 6s was observed at the 3 h after p.o. administration, and they exhibited stronger anti-inflammatory activity than Ibuprofen at the dose of 50 mg/kg at the peak time.

  19. Acidolytic cleavage of tris(alkoxy)benzylamide (PAL) "internal reference" amino acyl (IRAA) anchoring linkages: validation of accepted procedures in solid-phase peptide synthesis (SPPS).

    PubMed

    Albericio, F; Barany, G

    1993-03-01

    Under the normal conditions of acidolytic cleavage/deprotection of tris(alkoxy)benzylamide (PAL) anchoring linkages in Fmoc solid-phase peptide synthesis (SPPS), product release occurs by a straightforward single-step pathway. A recently reported cleavage of the NH--alpha CH bond of an amino acyl residue adjacent to PAL [see Int. J. Peptide Protein Res. 38, 146-153 (1991)] could not be confirmed in novel experiments incorporating a double "internal reference" amino acid (IRAA) design. The results of the present work revalidate the widely accepted application of IRAAs to monitor yields in SPPS, and confirm the reliability of PAL methodology for the preparation of C-terminal peptide amides.

  20. Radical chemistry of artemisinin

    NASA Astrophysics Data System (ADS)

    Denisov, Evgenii T.; Solodova, S. L.; Denisova, Taisa G.

    2010-12-01

    The review summarizes physicochemical characteristics of the natural sesquiterpene peroxide artemisinin. The kinetic schemes of transformations of artemisinin radicals under anaerobic conditions are presented and analyzed. The sequence of radical reactions of artemisinin in the presence of oxygen is considered in detail. Special emphasis is given to the intramolecular chain oxidation resulting in the transformation of artemisinin into polyatomic hydroperoxide. The kinetic characteristics of elementary reaction steps involving alkyl, alkoxyl, and peroxyl radicals generated from artemisinin are discussed. The results of testing of artemisinin and its derivatives for the antimalarial activity and the scheme of the biochemical synthesis of artemisinin in nature are considered.

  1. Radical aminomethylation of imines.

    PubMed

    Fujii, Shintaro; Konishi, Takehito; Matsumoto, Yusuke; Yamaoka, Yousuke; Takasu, Kiyosei; Yamada, Ken-Ichi

    2014-09-05

    Taking advantage of the high level of performance of N-alkoxycarbonyl-imines, we achieved the first example of addition of the aminomethyl radical to imine. The reaction efficiency depended on the structure of the radical precursor, whether it is an iodide or a xanthate, and an electron-withdrawing group on the nitrogen atom of the radical. This reaction allows direct introduction of an N-substituted aminomethyl group onto imine to provide 1,2-diamine as well as the short-step synthesis of ICI-199,441.

  2. Online Radicalization: Bangladesh Perspective

    DTIC Science & Technology

    2017-06-09

    will work on developing a sustainable social awareness against radicalization. It will be responsible for coordinating and integrating all government...PAGE Form Approved OMB No. 0704-0188 Public reporting burden for this collection of information is estimated to average 1 hour per response , including...coordination among the counter-terrorism agencies, and lack of positive initiatives to grow enduring social resilience against radicalization. Bangladesh

  3. Influence of Parent Compound Branching on the Products Formed in the Radical-initiated Heterogeneous Oxidation of Octacosane and Squalane

    NASA Astrophysics Data System (ADS)

    Ruehl, C.; Nah, T.; Isaacman, G. A.; Worton, D. R.; Chan, A. W.; Kolesar, K.; Cappa, C. D.; Goldstein, A. H.; Wilson, K. R.

    2012-12-01

    Radical-initiated heterogeneous oxidation can affect the lifetime and climatic influence of airborne particles as well as their chemical composition in general, but the chemical mechanisms by which it occurs are not as well known as gas-phase parallels. We gain insight into these mechanisms by identifying products of the reaction of both n-octacosane (C28H58, a linear alkane) and squalane (C30H62, a highly branched alkane) submicron particles with OH radicals, at exposures ranging from 0 to 6e12 molec cm-3 s. We did so with two-dimensional gas chromatography - high resolution mass spectrometry, under conditions which allowed products with more than ~12 carbon atoms, but less than ~3 oxygen atoms, including ketones, diones, aldehydes, and lactones, to be quantified. Use of vacuum ultraviolet light allowed for "soft" ionization, which aided in both identification of molecular formula due to high parent ion signal and distinguishing ketone isomers due to relatively simple fragmentation patterns. For n-octacosane, the most prevalent oxidation products that we observed were octacosanones (C28 ketones), and those towards the end of the molecule were dominant. Specifically, while all octacosanones in positions greater than 5 were formed with similar yields, 5-, 4-, 3-, and 2-octacosanone were enriched relative to the more interior ketones by factors of 1.5, 2.2, 4.8, and 10, respectively. This suggests that relatively large linear alkanes, which are solids in macroscopic quantities at room temperature, are also structured in submicron particles such that their ends are oriented towards the surface. For squalane, a highly branched alkane with six tertiary carbons, ketones were favored on alpha-carbons (i.e., carbons immediately adjacent to tertiary carbons) overbeta-carbons (carbons separated from tertiary carbons byalpha-carbons). This suggests that alkoxy radicals are important intermediates for radical-initiated heterogeneous oxidation of branched hydrocarbons, and that

  4. Free Radical Reactions in Food.

    ERIC Educational Resources Information Center

    Taub, Irwin A.

    1984-01-01

    Discusses reactions of free radicals that determine the chemistry of many fresh, processed, and stored foods. Focuses on reactions involving ascorbic acid, myoglobin, and palmitate radicals as representative radicals derived from a vitamin, metallo-protein, and saturated lipid. Basic concepts related to free radical structure, formation, and…

  5. Free Radical Reactions in Food.

    ERIC Educational Resources Information Center

    Taub, Irwin A.

    1984-01-01

    Discusses reactions of free radicals that determine the chemistry of many fresh, processed, and stored foods. Focuses on reactions involving ascorbic acid, myoglobin, and palmitate radicals as representative radicals derived from a vitamin, metallo-protein, and saturated lipid. Basic concepts related to free radical structure, formation, and…

  6. Alkyl Nitrites as a Model System to Probe the Autoxidation of Peroxy Radicals

    NASA Astrophysics Data System (ADS)

    Praske, E.; Crounse, J.; Kjaergaard, H.; Wennberg, P. O.; Otkjaer, R.

    2015-12-01

    The formation and fate of peroxy radicals (RO2) plays a key role in constraining the atmospheric oxidative capacity. RO2 H-shift chemistry, or autoxidation, has been implicated in sustaining the radical pool as the removal of species requires fewer oxidative steps. Recent studies have suggested that autoxidation plays a role in the chemistry of isoprene and terpenes, in many cases forming highly oxidized multifunctional compounds with low vapor pressures. A fundamental understanding of the mechanism and products is needed for models to accurately characterize the effect of autoxidation. A laboratory kinetics study of autoxidation in a model system of alkyl nitrites is presented. The nitrites (1-hexylnitrite, 2-hexylnitrite, and 2-methyl-2-hexylnitrite) possess varying structural properties which influence the H-shift kinetics. The compounds were photolyzed in an environmental chamber to produce RO2 following an alkoxy H-shift and CF3O- chemical ionization mass spectrometry (CIMS) was employed in the detection of products. The RO2 isomerization coefficients were derived at 296 and 313 K, and relied on the relative production yields of the alkyl nitrate and isomerization product. Our results support a quantitative ranking of these substituent effects. This knowledge will aid both laboratory and simulation work in evaluating the importance of autoxidation in relevant atmospheric systems.

  7. Stochastic methods for aerosol chemistry: a compact molecular description of functionalization and fragmentation in the heterogeneous oxidation of squalane aerosol by OH radicals.

    PubMed

    Wiegel, A A; Wilson, K R; Hinsberg, W D; Houle, F A

    2015-02-14

    The heterogeneous oxidation of organic aerosol by hydroxyl radicals (OH) can proceed through two general pathways: functionalization, in which oxygen functional groups are added to the carbon skeleton, and fragmentation, in which carbon-carbon bonds are broken, producing higher volatility, lower molecular weight products. An ongoing challenge is to develop a quantitative molecular description of these pathways that connects the oxidative evolution of the average aerosol properties (e.g. size and hygroscopicity) to the transformation of free radical intermediates. In order to investigate the underlying molecular mechanism of aerosol oxidation, a relatively compact kinetics model is developed for the heterogeneous oxidation of squalane particles by OH using free radical intermediates that convert reactive hydrogen sites into oxygen functional groups. Stochastic simulation techniques are used to compare calculated system properties over ten oxidation lifetimes with the same properties measured in experiment. The time-dependent average squalane aerosol mass, volume, density, carbon number distribution of scission products, and the average elemental composition are predicted using known rate coefficients. For functionalization, the calculations reveal that the distribution of alcohol and carbonyl groups is controlled primarily by the initial OH abstraction rate and to lesser extent by the branching ratio between secondary peroxy radical product channels. For fragmentation, the calculations reveal that the formation of activated alkoxy radicals with neighboring functional groups controls the molecular decomposition, particularly at high O/C ratios. This kinetic scheme provides a framework for understanding the oxidation chemistry of a model organic aerosol and informs parameterizations of more complex systems.

  8. Chemistry of ascorbic acid radicals

    SciTech Connect

    Bielski, B.H.J.

    1982-01-01

    The chemistry of ascorbic acid free radicals is reviewed. Particular emphasis is placed on identification and characterization of ascorbate radicals by spectrophotometric and electron paramagnetic resonance techniques, the kinetics of formation and disappearance of ascorbate free radicals in enzymatic and nonenzymatic reactions, the effect of pH upon the spectral and kinetic properties of ascorbate anion radical, and chemical reactivity of ascorbate free radicals.

  9. Laparoscopic radical trachelectomy.

    PubMed

    Rendón, Gabriel J; Ramirez, Pedro T; Frumovitz, Michael; Schmeler, Kathleen M; Pareja, Rene

    2012-01-01

    The standard treatment for patients with early-stage cervical cancer has been radical hysterectomy. However, for women interested in future fertility, radical trachelectomy is now considered a safe and feasible option. The use of minimally invasive surgical techniques to perform this procedure has recently been reported. We report the first case of a laparoscopic radical trachelectomy performed in a developing country. The patient is a nulligravid, 30-y-old female with stage IB1 adenocarcinoma of the cervix who desired future fertility. She underwent a laparoscopic radical trachelectomy and bilateral pelvic lymph node dissection. The operative time was 340 min, and the estimated blood loss was 100mL. There were no intraoperative or postoperative complications. The final pathology showed no evidence of residual disease, and all pelvic lymph nodes were negative. At 20 mo of follow-up, the patient is having regular menses but has not yet attempted to become pregnant. There is no evidence of recurrence. Laparoscopic radical trachelectomy with pelvic lymphadenectomy in a young woman who desires future fertility may also be an alternative technique in the treatment of early cervical cancer in developing countries.

  10. Laparoscopic Radical Trachelectomy

    PubMed Central

    Rendón, Gabriel J.; Ramirez, Pedro T.; Frumovitz, Michael; Schmeler, Kathleen M.

    2012-01-01

    Introduction: The standard treatment for patients with early-stage cervical cancer has been radical hysterectomy. However, for women interested in future fertility, radical trachelectomy is now considered a safe and feasible option. The use of minimally invasive surgical techniques to perform this procedure has recently been reported. Case Description: We report the first case of a laparoscopic radical trachelectomy performed in a developing country. The patient is a nulligravid, 30-y-old female with stage IB1 adenocarcinoma of the cervix who desired future fertility. She underwent a laparoscopic radical trachelectomy and bilateral pelvic lymph node dissection. The operative time was 340 min, and the estimated blood loss was 100mL. There were no intraoperative or postoperative complications. The final pathology showed no evidence of residual disease, and all pelvic lymph nodes were negative. At 20 mo of follow-up, the patient is having regular menses but has not yet attempted to become pregnant. There is no evidence of recurrence. Conclusion: Laparoscopic radical trachelectomy with pelvic lymphadenectomy in a young woman who desires future fertility may also be an alternative technique in the treatment of early cervical cancer in developing countries. PMID:23318085

  11. Thermal, photonic and magnetic studies of thiazyl radicals

    NASA Astrophysics Data System (ADS)

    Beldjoudi, Yassine

    Chapter 1 provides an overview of the area of 1,2,3,5-dithiadiazolyl (DTDA) radical chemistry which is central to this thesis, including a review of the crystal engineering principles and the physical properties of DTDA radicals, focusing on structure-property relationships. The magnetic properties of the beta-polymorph of p-NCC 6F4CNSSN have been almost exhaustively studied since 1993 when it was found to exhibit the highest magnetic ordering temperature (T N = 36 K) for an organic magnet. Conversely the structure and physical properties of the alpha-polymorph have barely been explored. The conditions for the selective preparation of alpha and beta-polymorphs of this radical are investigated in Chapter 2. The relative polymorph stability is probed through detailed DSC and PXRD studies and the magnetic properties of the alpha-polymorph fully examined through dc and ac susceptibility measurements coupled with heat capacity studies. In Chapters 3 and 4, systematic structural studies on the variation of substituent groups are undertaken, comprising a series of alkoxy-functionalised perfluorophenyl DTDA radicals, p-ROC6F4CNSSN (R = Me, Et, Pr, Bu) and a comparison of the substitution pattern of the tolyl group on PhDTDA derivatives, MeC6H4C6H 4CNSSN and their polymorphs. These studies use a combination of single crystal and VT-PXRD, SQUID magnetometry and VT EPR spectroscopy combined with DSC measurements and computational studies to probe relative polymorph stabilities and magnetic properties. A new generation of DTDA radicals where the R substituent is "non-innocent" are described in Chapters 5 and 6. In Chapter 5 the synthesis and characterisation of a series of DTDA-functionalised polyaromatic hydrocarbons (PAH) are described and their polymorphism examined as well as their solution and solid state optical properties. These reveal fluorescence quantum efficiencies up to 50%. Radical stability can be enhanced through incorporation into polymer matrices (PMMA and PS

  12. A fluorine 1,2-migration via aryl cation/radical/radical anion/radical sequence.

    PubMed

    Pretali, Luca; Dondi, Daniele; D'Angelantonio, Mila; Manet, Ilse; Fasani, Elisa; Monti, Sandra; Bovio, Bruna; Albini, Angelo

    2013-08-02

    Irradiation of a 7-piperazino-8-fluoroquinolone causes formal 1,2-fluorine migration, piperazine loss and reduction, or nucleophile addition in 8. Product study, laser flash photolysis, and computational modeling support F(-) detachment to yield a triplet 8-quinolyl cation that either inserts intramolecularly or is trapped by Cl(-), Br(-). However, iodide and pyrrole reduce it to the radical that continues the 'redox tour' (aryl cation→ radical→ radical anion→ radical and then again radical or radical anion) leading to the rearranged products.

  13. Density Functional Theory and Mass Spectrometry of Phthalate Fragmentations Mechanisms: Modeling Hyperconjugated Carbocation and Radical Cation Complexes with Neutral Molecules

    NASA Astrophysics Data System (ADS)

    Jeilani, Yassin A.; Cardelino, Beatriz H.; Ibeanusi, Victor M.

    2011-11-01

    This is the first ab initio study of the energetics of the fragmentation mechanisms of phthalate, by mass spectrometry, leading to protonated phthalic anhydride ( m/z 149). Phthalates fragment by two major pathways; namely, the McLafferty + 1 rearrangement and the loss of alkoxy. Both pathways involve a carbonyl oxygen attack to the ortho-carbonyl carbon leading to structures with tetrahedral carbon intermediates that eventually give m/z 149. These pathways were studied by collision induced dissociation (CID) using triple quadrupole mass spectrometry. The proposed McLafferty + 1 pathway proceeds through a distonic M•+, leading to the loss of an allylic-stabilized alkene radical. The McLafferty rearrangement step proceeds through a six-membered ring transition state with a small activation energy ranging 0.4-6.2 kcal/mol; the transfer of a second H from the distonic ion of the rearrangement step proceeds through a radical cation molecule complex. Based on quantum chemical modeling of the cation molecule complexes, two kinds of cation molecule complexes were identified as radical cation molecule complex and hyperconjugated cation molecule complex. This distinction is based on the cation and simplifies future modeling of similar complexes. Optimization of important fragments in these pathways showed cyclized and hydrogen-bonded structures to be favored. An exception was the optimized structure of the protonated phthalic anhydride ( m/z 149) that showed a structure with an open anhydride ring.

  14. Radical dematerialization and degrowth.

    PubMed

    Kallis, Giorgos

    2017-06-13

    The emission targets agreed in Paris require a radical reduction of material extraction, use and disposal. The core claim of this article is that a radical dematerialization can only be part and parcel of degrowth. Given that capitalist economies are designed to grow, this raises the question of whether, and under what circumstances, the inevitable 'degrowth' can become socially sustainable. Three economic policies are discussed in this direction: work-sharing, green taxes and public money.This article is part of the themed issue 'Material demand reduction'. © 2017 The Author(s).

  15. Radical dematerialization and degrowth

    NASA Astrophysics Data System (ADS)

    Kallis, Giorgos

    2017-05-01

    The emission targets agreed in Paris require a radical reduction of material extraction, use and disposal. The core claim of this article is that a radical dematerialization can only be part and parcel of degrowth. Given that capitalist economies are designed to grow, this raises the question of whether, and under what circumstances, the inevitable `degrowth' can become socially sustainable. Three economic policies are discussed in this direction: work-sharing, green taxes and public money. This article is part of the themed issue 'Material demand reduction'.

  16. Competition Between π-π and C-H/π Interactions: A Comparison of the Structural and Electronic Properties of Alkoxy-Substituted 1,8-Bis((propyloxyphenyl)ethynyl)naphthalenes.

    PubMed

    Carson, Bradley E; Parker, Trent M; Hohenstein, Edward G; Brizius, Glen L; Komorner, Whitney; King, Rollin A; Collard, David M; Sherrill, C David

    2015-12-21

    The structural and electronic consequences of π-π and C-H/π interactions in two alkoxy-substituted 1,8-bis- ((propyloxyphenyl)ethynyl)naphthalenes are explored by using X-ray crystallography and electronic structure computations. The crystal structure of analogue 4, bearing an alkoxy side chain in the 4-position of each of the phenyl rings, adopts a π-stacked geometry, whereas analogue 8, bearing alkoxy groups at both the 2- and the 5-positions of each ring, has a geometry in which the rings are splayed away from a π-stacked arrangement. Symmetry-adapted perturbation theory analysis was performed on the two analogues to evaluate the interactions between the phenylethynyl arms in each molecule in terms of electrostatic, steric, polarization, and London dispersion components. The computations support the expectation that the π-stacked geometry of the alkoxyphenyl units in 4 is simply a consequence of maximizing π-π interactions. However, the splayed geometry of 8 results from a more subtle competition between different noncovalent interactions: this geometry provides a favorable anti-alignment of C-O bond dipoles, and two C-H/π interactions in which hydrogen atoms of the alkyl side chains interact favorably with the π electrons of the other phenyl ring. These favorable interactions overcome competing π-π interactions to give rise to a geometry in which the phenylethynyl substituents are in an offset, unstacked arrangement.

  17. Beyond Radical Educational Cynicism.

    ERIC Educational Resources Information Center

    Wood, George H.

    1982-01-01

    An alternative is presented to counter current radical arguments that the schools cannot bring about social change because they are instruments of capitalism. The works of Samuel Bowles, Herbert Gintis, and Louis Althusser are discussed. Henry Giroux's "Ideology, Culture and the Process of Schooling" provides an alternative to cynicism.…

  18. Radical School Reform.

    ERIC Educational Resources Information Center

    Gross, Beatrice, Ed.; Gross, Ronald, Ed.

    This book provides a comprehensive examination of the nature of the school crisis and the ways in which radical thinkers and educators are dealing with it. Excerpts from the writings of Jonathan Kozol, John Holt, Kenneth Clark, and others are concerned with the realities of education in ghettos and suburbs. Paul Goodman, Marshall McLuhan, Sylvia…

  19. Against Radical Multiculturalism.

    ERIC Educational Resources Information Center

    Zorn, Jeff

    This essay presents two strands of arguments against radical or critical emancipatory multiculturalism. In strand 1, "'Culture' is...whatever..." the looseness of the core concept of "culture," which can refer to anything at all concerning a social group that itself may exist only theoretically, is shown. In strand 2, "From ideology to leveling,…

  20. Beyond Radical Educational Cynicism.

    ERIC Educational Resources Information Center

    Wood, George H.

    1982-01-01

    An alternative is presented to counter current radical arguments that the schools cannot bring about social change because they are instruments of capitalism. The works of Samuel Bowles, Herbert Gintis, and Louis Althusser are discussed. Henry Giroux's "Ideology, Culture and the Process of Schooling" provides an alternative to cynicism.…

  1. Radically enhanced molecular recognition

    NASA Astrophysics Data System (ADS)

    Trabolsi, Ali; Khashab, Niveen; Fahrenbach, Albert C.; Friedman, Douglas C.; Colvin, Michael T.; Cotí, Karla K.; Benítez, Diego; Tkatchouk, Ekaterina; Olsen, John-Carl; Belowich, Matthew E.; Carmielli, Raanan; Khatib, Hussam A.; Goddard, William A.; Wasielewski, Michael R.; Stoddart, J. Fraser

    2010-01-01

    The tendency for viologen radical cations to dimerize has been harnessed to establish a recognition motif based on their ability to form extremely strong inclusion complexes with cyclobis(paraquat-p-phenylene) in its diradical dicationic redox state. This previously unreported complex involving three bipyridinium cation radicals increases the versatility of host-guest chemistry, extending its practice beyond the traditional reliance on neutral and charged guests and hosts. In particular, transporting the concept of radical dimerization into the field of mechanically interlocked molecules introduces a higher level of control within molecular switches and machines. Herein, we report that bistable and tristable [2]rotaxanes can be switched by altering electrochemical potentials. In a tristable [2]rotaxane composed of a cyclobis(paraquat-p-phenylene) ring and a dumbbell with tetrathiafulvalene, dioxynaphthalene and bipyridinium recognition sites, the position of the ring can be switched. On oxidation, it moves from the tetrathiafulvalene to the dioxynaphthalene, and on reduction, to the bipyridinium radical cation, provided the ring is also reduced simultaneously to the diradical dication.

  2. Radical Socioeducational Analysis.

    ERIC Educational Resources Information Center

    Sigmon, Scott B.

    This book describes an interactive-interdisciplinary way of looking at the social conditions which impinge upon schooling, and which impact upon the social facts of life. It examines current schooling problems from the perspective of radical social democratic thought. The book is organized into four major sections. Part 1 provides an overview and…

  3. The Oxonium Rydberg Radical

    NASA Astrophysics Data System (ADS)

    Lavín, C.; Martin, I.

    The Quantum Defect Orbital (QDO) method has been applied to the study of transition probabiUties in the oxonium Rydberg radical H3O. Absorption oscillator strengths and Einstein emission coefficients are reported and compared with the results of an earlier, simplified, molecular version of QDO method.

  4. Interrogating Hydrocarbon Radicals

    NASA Astrophysics Data System (ADS)

    Schmidt, Timothy W.

    2010-06-01

    Motivated by astrophysical problems (and a sense of fun) for some years my research group has been obtaining new spectra of hitherto unobserved hydrocarbon radicals. We employ the complementary techniques of resonant ionization and laser induced fluorescence to rigorously identify radicals by matching their ground state vibrational frequencies to those obtained using density functional theory (DFT). While some radicals were made to order in our pulsed electrical discharge source, others of particular chemical importance have been found lurking in the congested forest of dicarbon and tricarbon fluorescence. Using a 2-dimensional fluorescence (2df) map, we have extracted pure spectra, unpolluted by C_2 and C_3, from a benzene discharge. One spectrum was first presented at this symposium in 2006, but at that stage was not identified. Subsequent measurement of a matching resonant ionization spectrum revealed a mass of 115, much higher than the benzene precursor. With the aid of DFT calculations, the species was positively identified, giving clues to hydrocarbon-building chemistry of relevance to combustion; planetary atmospheres; and the interstellar and circumstellar space. Further experiments revealed other surprising additions to the radical zoo, also identified with the help of 2df. Along the way we have also identified two new band systems of C_2, the first involving the hidden c^3Σ_u^+ state, and have ventured into the world of larger molecules, such as hexabenzocoronene, C42H18.

  5. Tyrosyl Radicals in Dehaloperoxidase

    PubMed Central

    Dumarieh, Rania; D'Antonio, Jennifer; Deliz-Liang, Alexandria; Smirnova, Tatyana; Svistunenko, Dimitri A.; Ghiladi, Reza A.

    2013-01-01

    Dehaloperoxidase (DHP) from Amphitrite ornata, having been shown to catalyze the hydrogen peroxide-dependent oxidation of trihalophenols to dihaloquinones, is the first oxygen binding globin that possesses a biologically relevant peroxidase activity. The catalytically competent species in DHP appears to be Compound ES, a reactive intermediate that contains both a ferryl heme and a tyrosyl radical. By simulating the EPR spectra of DHP activated by H2O2, Thompson et al. (Thompson, M. K., Franzen, S., Ghiladi, R. A., Reeder, B. J., and Svistunenko, D. A. (2010) J. Am. Chem. Soc. 132, 17501–17510) proposed that two different radicals, depending on the pH, are formed, one located on either Tyr-34 or Tyr-28 and the other on Tyr-38. To provide additional support for these simulation-based assignments and to deduce the role(s) that tyrosyl radicals play in DHP, stopped-flow UV-visible and rapid-freeze-quench EPR spectroscopic methods were employed to study radical formation in DHP when three tyrosine residues, Tyr-28, Tyr-34, and Tyr-38, were replaced either individually or in combination with phenylalanines. The results indicate that radicals form on all three tyrosines in DHP. Evidence for the formation of DHP Compound I in several tyrosine mutants was obtained. Variants that formed Compound I showed an increase in the catalytic rate for substrate oxidation but also an increase in heme bleaching, suggesting that the tyrosines are necessary for protecting the enzyme from oxidizing itself. This protective role of tyrosines is likely an evolutionary adaptation allowing DHP to avoid self-inflicted damage in the oxidative environment. PMID:24100039

  6. Radicals in ionic liquids.

    PubMed

    Strehmel, Veronika

    2012-05-14

    Stable radicals and recombination of photogenerated lophyl radicals are investigated in ionic liquids. The 2,2,6,6-tetramethylpiperidine-1-yloxyl derivatives contain various substituents at the 4-position to the nitroxyl group, including hydrogen-bond-forming or ionic substituents that undergo additional interactions with the individual ions of the ionic liquids. Some of these spin probes contain similar ions to ionic liquids to avoid counter-ion exchange with the ionic liquid. Depending on the ionic liquid anion, the Stokes-Einstein theory or the Spernol-Gierer-Wirtz theory can be applied to describe the temperature dependence of the average rotational correlation time of the spin probe in the ionic liquids. Furthermore, the spin probes give information about the micropolarity of the ionic liquids. In this context the substituent at the 4-position to the nitroxyl group plays a significant role. Covalent bonding of a spin probe to the imidazolium ion results in bulky spin probes that are strongly immobilized in the ionic liquid. Furthermore, lophyl radical recombination in the dark, which is chosen to understand the dynamics of bimolecular reactions in ionic liquids, shows a slow process at longer timescale and a rise time at a shorter timescale. Although various reactions may contribute to the slower process during lophyl radical recombination, it follows a second-order kinetics that does not clearly show solvent viscosity dependence. However, the rise time, which may be attributed to radical pair formation, increases with increasing solvent viscosity. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. 6-Alkoxy-5-aryl-3-pyridinecarboxamides, a new series of bioavailable cannabinoid receptor type 1 (CB1) antagonists including peripherally selective compounds.

    PubMed

    Röver, Stephan; Andjelkovic, Mirjana; Bénardeau, Agnès; Chaput, Evelyne; Guba, Wolfgang; Hebeisen, Paul; Mohr, Susanne; Nettekoven, Matthias; Obst, Ulrike; Richter, Wolfgang F; Ullmer, Christoph; Waldmeier, Pius; Wright, Matthew B

    2013-12-27

    We identified 6-alkoxy-5-aryl-3-pyridinecarboxamides as potent CB1 receptor antagonists with high selectivity over CB2 receptors. The series was optimized to reduce lipophilicity compared to rimonabant to achieve peripherally active molecules with minimal central effects. Several compounds that showed high plasma exposures in rats were evaluated in vivo to probe the contribution of central vs peripheral CB1 agonism to metabolic improvement. Both rimonabant and 14g, a potent brain penetrant CB1 receptor antagonist, significantly reduced the rate of body weight gain. However, 14h, a molecule with markedly reduced brain exposure, had no significant effect on body weight. PK studies confirmed similarly high exposure of both 14h and 14g in the periphery but 10-fold lower exposure in the brain for 14h. On the basis of these data, which are consistent with reported effects in tissue-specific CB1 receptor KO mice, we conclude that the metabolic benefits of CB1 receptor antagonists are primarily centrally mediated as originally believed.

  8. 3-alkoxy-pyrrolo[1,2-b]pyrazolines as selective androgen receptor modulators with ideal physicochemical properties for transdermal administration.

    PubMed

    Ullrich, Thomas; Sasmal, Sanjita; Boorgu, Venkatesham; Pasagadi, Srinivasu; Cheera, Srisailam; Rajagopalan, Sujatha; Bhumireddy, Archana; Shashikumar, Dhanya; Chelur, Shekar; Belliappa, Charamanna; Pandit, Chetan; Krishnamurthy, Narasimharao; Mukherjee, Subhendu; Ramanathan, Anuradha; Ghadiyaram, Chakshusmathi; Ramachandra, Murali; Santos, Paulo G; Lagu, Bharat; Bock, Mark G; Perrone, Mark H; Weiler, Sven; Keller, Hansjoerg

    2014-09-11

    We describe the synthesis and characterization of 3-alkoxy-pyrrolo[1,2-b]pyrazolines as novel selective androgen receptor (AR) modulators that possess excellent physicochemical properties for transdermal administration. Compound 26 bound to human AR with an IC50 of 0.7 nM with great selectivity over other nuclear hormone receptors and potently activated AR in a C2C12 muscle cell reporter gene assay with an EC50 of 0.5 nM. It showed high aqueous solubility of 1.3 g/L at pH 7.4, and an in silico model as well as a customized parallel artificial membrane permeability assay indicated good skin permeation. Indeed, when measuring skin permeation through excised human skin, an excellent flux of 2 μg/(cm(2)·h) was determined without any permeation enhancers. In a 2 week Hershberger model using castrated rats, the compound showed dose-dependent effects fully restoring skeletal muscle weight at 0.3 mg/kg/day after subcutaneous administration with high selectivity over prostate stimulation.

  9. Synthesis and Anticonvulsant Activity Evaluation of 3-alkoxy-4-(4-(hexyloxy/heptyloxy)phenyl)-4H-1,2,4 -triazole

    PubMed Central

    Fang, Ying-Quan; Sun, Chun-Ling; Liu, Da-Chuan; Wang, Shi-Ben; Quan, Zhe-San

    2015-01-01

    A series of 3-alkoxy-4-(4-(hexyloxy/heptyloxy) phenyl)-4H-1,2,4-triazole was synthesized. The anticonvulsant effect and neurotoxicity of the compounds were calculated with maximal electroshock (MES) test and rotarod tests with intraperitoneally injected mice. Among the synthesized compounds, compound 3-heptyloxy-4-(4-(hexyloxy) phenyl)-4H-1,2,4-triazole (5f) was the most active one and also had the lowest toxicity. In the anti-MES potency test, it showed median effective dose (ED50) of 37.3 mg/Kg, median toxicity dose (TD50) of 422.5 mg/Kg, and the protective index (PI) of 11.3 which is much greater than the reference drug carbamazepine with PI value of 6.4. As well as demonstrating the anti-MES efficacy of compound 5f, its potency against seizures induced by pentylenetetrazole, 3-mercaptopropionic acid, and bicuculline were also established, with the results suggesting that GABA-mediated mechanisms might be involved in its anticonvulsant activity, such as enhancing of GABAergic neurotransmission or activity, activate GAD or inhibit GABA-T, and GABAA-mediated mechanisms. PMID:25561914

  10. Selectivity guidelines and a reductive elimination-based model for predicting the stereochemical course of conjugate addition reactions of organocuprates to gamma-alkoxy-alpha,beta-enoates.

    PubMed

    Kireev, Artem S; Manpadi, Madhuri; Kornienko, Alexander

    2006-03-31

    Current models used to predict the stereochemical outcome of organocopper conjugate addition processes focus on the nucleophilic addition step as stereochemistry-determining. Recent kinetic, NMR, kinetic isotope effect, and theoretical density functional studies strongly support the proposal that stereochemical preferences in these processes are dictated by the reductive elimination step, transforming Cu(III) to Cu(I) intermediates. A new model that considers various steric and stereoelectronic factors involved in the transition state of the reductive elimination step is proposed and then used to interpret the results of systematic studies of arylcuprate conjugate addition reactions with cis and trans gamma-alkoxy-alpha,beta-enoates. The results give rise to the following selectivity guidelines for this process. To achieve high anti-addition diastereoselectivities the use of trans esters with a bulky nonalkoxy substituent at the gamma-position is recommended. While stereoelectronics disfavor syn-addition, a judicious choice of properly sized gamma-substituents may lead to the predominant formation of syn-products, especially with cis enoates. However, high syn-selectivities may be achieved by using gamma-amino-alpha,beta-enoates.

  11. N-(Pivaloyloxy)alkoxy-carbonyl Prodrugs of the Glutamine Antagonist 6-Diazo-5-oxo-l-norleucine (DON) as a Potential Treatment for HIV Associated Neurocognitive Disorders.

    PubMed

    Nedelcovych, Michael T; Tenora, Lukáš; Kim, Boe-Hyun; Kelschenbach, Jennifer; Chao, Wei; Hadas, Eran; Jančařík, Andrej; Prchalová, Eva; Zimmermann, Sarah C; Dash, Ranjeet P; Gadiano, Alexandra J; Garrett, Caroline; Furtmüller, Georg; Oh, Byoungchol; Brandacher, Gerald; Alt, Jesse; Majer, Pavel; Volsky, David J; Rais, Rana; Slusher, Barbara S

    2017-08-24

    Aberrant excitatory neurotransmission associated with overproduction of glutamate has been implicated in the development of HIV-associated neurocognitive disorders (HAND). The glutamine antagonist 6-diazo-5-oxo-l-norleucine (DON, 14) attenuates glutamate synthesis in HIV-infected microglia/macrophages, offering therapeutic potential for HAND. We show that 14 prevents manifestation of spatial memory deficits in chimeric EcoHIV-infected mice, a model of HAND. 14 is not clinically available, however, because its development was hampered by peripheral toxicities. We describe the synthesis of several substituted N-(pivaloyloxy)alkoxy-carbonyl prodrugs of 14 designed to circulate inert in plasma and be taken up and biotransformed to 14 in the brain. The lead prodrug, isopropyl 6-diazo-5-oxo-2-(((phenyl(pivaloyloxy)methoxy)carbonyl)amino)hexanoate (13d), was stable in swine and human plasma but liberated 14 in swine brain homogenate. When dosed systemically in swine, 13d provided a 15-fold enhanced CSF-to-plasma ratio and a 9-fold enhanced brain-to-plasma ratio relative to 14, opening a possible clinical path for the treatment of HAND.

  12. A new stable perfluoroalkyl radical

    SciTech Connect

    Allayarov, S.R.; Barkalov, I.M.; Mikhailov, A.I.

    1986-01-01

    This paper uses ESR spectroscopy to study the radical formed upon the gamma-irradiation of liquid perfluoro-methyl-2-pentene (PMP). The ESR spectrum of this radical shows a well resolved doublet of triplets with splitting 6.2 and 1.5 mT with additional splitting of each component by 0.25 mT. This ESR corresponds to a radical formed upon the addition of a radical r, in particlular, CF/sub 3/ to PMP.

  13. Toward Radicalizing Community Service Learning

    ERIC Educational Resources Information Center

    Sheffield, Eric C.

    2015-01-01

    This article advocates a radicalized theoretical construction of community service learning. To accomplish this radicalization, I initially take up a discussion of traditional understandings of CSL rooted in pragmatic/progressive thought. I then suggest that this traditional structural foundation can be radicalized by incorporating Deborah…

  14. Toward Radicalizing Community Service Learning

    ERIC Educational Resources Information Center

    Sheffield, Eric C.

    2015-01-01

    This article advocates a radicalized theoretical construction of community service learning. To accomplish this radicalization, I initially take up a discussion of traditional understandings of CSL rooted in pragmatic/progressive thought. I then suggest that this traditional structural foundation can be radicalized by incorporating Deborah…

  15. Free radical explosive composition

    DOEpatents

    Walker, Franklin E.; Wasley, Richard J.

    1979-01-01

    An improved explosive composition is disclosed and comprises a major portion of an explosive having a detonation velocity between about 1500 and 10,000 meters per second and a minor amount of a getter additive comprising a compound or mixture of compounds capable of capturing or deactivating free radicals or ions under mechanical or electrical shock conditions and which is not an explosive. Exemplary getter additives are isocyanates, olefins and iodine.

  16. Probability and radical behaviorism

    PubMed Central

    Espinosa, James M.

    1992-01-01

    The concept of probability appears to be very important in the radical behaviorism of Skinner. Yet, it seems that this probability has not been accurately defined and is still ambiguous. I give a strict, relative frequency interpretation of probability and its applicability to the data from the science of behavior as supplied by cumulative records. Two examples of stochastic processes are given that may model the data from cumulative records that result under conditions of continuous reinforcement and extinction, respectively. PMID:22478114

  17. Radicals in melanin biochemistry.

    PubMed

    Riley, P A

    1988-01-01

    Melanins are light-absorbant polymeric pigments found widely dispersed in nature. They possess many interesting physicochemical properties. One of these is the expression in the polymer of stable free radicals which appear to have a protective action in cells, probably by acting as a sink for diffusible free-radical species. Polymer formation is thought to occur by a free-radical process in which semiquinones are added to the chain. Semiquinones are formed by redox equilibration interactions between metabolic intermediates formed during the tyrosinase-catalyzed oxidation process. In the continued presence of substrate, steady-state concentrations of reactive species are predicted in the reaction system, and the melanogenic pathway may be considered as potentially hazardous for pigment-generating cells. This feature has been exploited by the use of analogue substrates to generate cytotoxic species as a possible rational approach to the treatment of malignant melanoma. One such substance is 4-hydroxyanisole, the oxidation of which gives rise to semiquinone radical species. The possibility that the anisyl semiquinone initiates a mechanism leading to cell damage has not been excluded. However, the current view is that the major cytotoxicity due to the oxidation products of this compound is the result of the action of the corresponding orthoquinone. A number of mechanisms exist for detoxifying quinones if they reach the cytosol such as O-methylation and the formation of thiol adducts with cysteine or glutathione, and these can be used as markers of melanogenesis. In general, however, only small amounts of reactive intermediates of melanogenesis escape from the confines of the melanosome, probably because of their limited lipid solubility. The selective toxic action of anisyl quinone in the treatment of melanoma may, in part, be due to membrane defects in the melanosomes of malignant melanocytes.

  18. THERMOCHEMISTRY OF HYDROCARBON RADICALS

    SciTech Connect

    Kent M. Ervin, Principal Investigator

    2004-08-17

    Gas phase negative ion chemistry methods are employed to determine enthalpies of formation of hydrocarbon radicals that are important in combustion processes and to investigate the dynamics of ion-molecule reactions. Using guided ion beam tandem mass spectrometry, we measure collisional threshold energies of endoergic proton transfer and hydrogen atom transfer reactions of hydrocarbon molecules with negative reagent ions. The measured reaction threshold energies for proton transfer yield the relative gas phase acidities. In an alternative methodology, competitive collision-induced dissociation of proton-bound ion-molecule complexes provides accurate gas phase acidities relative to a reference acid. Combined with the electron affinity of the R {center_dot} radical, the gas phase acidity yields the RH bond dissociation energy of the corresponding neutral molecule, or equivalently the enthalpy of formation of the R{center_dot} organic radical, using equation: D(R-H) = {Delta}{sub acid}H(RH) + EA(R) - IE(H). The threshold energy for hydrogen abstraction from a hydrocarbon molecule yields its hydrogen atom affinity relative to the reagent anion, providing the RH bond dissociation energy directly. Electronic structure calculations are used to evaluate the possibility of potential energy barriers or dynamical constrictions along the reaction path, and as input for RRKM and phase space theory calculations. In newer experiments, we have measured the product velocity distributions to obtain additional information on the energetics and dynamics of the reactions.

  19. Diaryldichalcogenide radical cations.

    PubMed

    Mallow, Ole; Khanfar, Monther A; Malischewski, Moritz; Finke, Pamela; Hesse, Malte; Lork, Enno; Augenstein, Timo; Breher, Frank; Harmer, Jeffrey R; Vasilieva, Nadezhda V; Zibarev, Andrey; Bogomyakov, Artem S; Seppelt, Konrad; Beckmann, Jens

    2015-01-01

    One-electron oxidation of two series of diaryldichalcogenides (C6F5E)2 (13a-c) and (2,6-Mes2C6H3E)2 (16a-c) was studied (E = S, Se, Te). The reaction of 13a and 13b with AsF5 and SbF5 gave rise to the formation of thermally unstable radical cations [(C6F5S)2]˙(+) (14a) and [(C6F5Se)2]˙(+) (14b) that were isolated as [Sb2F11](-) and [As2F11](-) salts, respectively. The reaction of 13c with AsF5 afforded only the product of a Te-C bond cleavage, namely the previously known dication [Te4](2+) that was isolated as [AsF6](-) salt. The reaction of (2,6-Mes2C6H3E)2 (16a-c) with [NO][SbF6] provided the corresponding radical cations [(2,6-Mes2C6H3E)2]˙(+) (17a-c; E = S, Se, Te) in the form of thermally stable [SbF6](-) salts in nearly quantitative yields. The electronic and structural properties of these radical cations were probed by X-ray diffraction analysis, EPR spectroscopy, and density functional theory calculations and other methods.

  20. Types of radical hysterectomies

    PubMed Central

    Marin, F; Plesca, M; Bordea, CI; Moga, MA; Blidaru, A

    2014-01-01

    Abstract The treatment for cervical cancer is a complex, multidisciplinary issue, which applies according to the stage of the disease. The surgical elective treatment of cervical cancer is represented by the radical abdominal hysterectomy. In time, many surgeons perfected this surgical technique; the ones who stood up for this idea were Thoma Ionescu and Ernst Wertheim. There are many varieties of radical hysterectomies performed by using the abdominal method and some of them through vaginal and mixed way. Each method employed has advantages and disadvantages. At present, there are three classifications of radical hysterectomies which are used for the simplification of the surgical protocols: Piver-Rutledge-Smith classification which is the oldest, GCG-EORTC classification and Querlow and Morrow classification. The last is the most evolved and recent classification; its techniques can be adapted for conservative operations and for different types of surgical approaches: abdominal, vaginal, laparoscopic or robotic. Abbreviations: GCG-EORTC = Gynecologic Cancer Group of the European Organization of Research and Treatment of Cancer; LEEP = loop electrosurgical excision procedure; I.O.B. = Institute of Oncology Bucharest; PRS = Piver-Rutledge-Smith PMID:25408722

  1. [Radical prostatectomy - pro robotic].

    PubMed

    Gillitzer, R

    2012-05-01

    Anatomical radical prostatectomy was introduced in the early 1980s by Walsh and Donker. Elucidation of key anatomical structures led to a significant reduction in the morbidity of this procedure. The strive to achieve similar oncological and functional results to this gold standard open procedure but with further reduction of morbidity through a minimally invasive access led to the establishment of laparoscopic prostatectomy. However, this procedure is complex and difficult and is associated with a long learning curve. The technical advantages of robotically assisted surgery coupled with the intuitive handling of the device led to increased precision and shortening of the learning curve. These main advantages, together with a massive internet presence and aggressive marketing, have resulted in a rapid dissemination of robotic radical prostatectomy and an increasing patient demand. However, superiority of robotic radical prostatectomy in comparison to the other surgical therapeutic options has not yet been proven on a scientific basis. Currently robotic-assisted surgery is an established technique and future technical improvements will certainly further define its role in urological surgery. In the end this technical innovation will have to be balanced against the very high purchase and running costs, which remain the main limitation of this technology.

  2. Free radical propulsion concept

    NASA Technical Reports Server (NTRS)

    Hawkins, C. E.; Nakanishi, S.

    1981-01-01

    The concept of a free radical propulsion system, utilizing the recombination energy of dissociated low molecular weight gases to produce thrust, is analyzed. The system, operating at a theoretical impulse with hydrogen, as high as 2200 seconds at high thrust to power ratio, is hypothesized to bridge the gap between chemical and electrostatic propulsion capabilities. A comparative methodology is outlined by which characteristics of chemical and electric propulsion for orbit raising mission can be investigated. It is noted that free radicals proposed in rockets previously met with difficulty and complexity in terms of storage requirements; the present study proposes to eliminate the storage requirements by using electric energy to achieve a continuous-flow product of free radicals which are recombined to produce a high velocity propellant. Microwave energy used to dissociate a continuously flowing gas is transferred to the propellant via three-body-recombination for conversion to propellant kinetic energy. Microwave plasma discharge was found in excess of 90 percent over a broad range of pressure in preliminary experiments, and microwave heating compared to electrothermal heating showed much higher temperatures in gasdynamic equations.

  3. 2.10 Titanium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  4. 1.35 Ruthenium-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  5. 2.33 Mercury-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  6. 2.32 Gold-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  7. 2.8 Potassium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  8. 2.28 Tantalum-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  9. 1.42 Iodine-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  10. 4.6.3 Vinyl radicals

    NASA Astrophysics Data System (ADS)

    Beckwith, A. L. J.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  11. 1.48 Gold-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  12. 2.7 Phosphorus-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  13. 1.46 Iridium-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  14. 2.16 Zinc-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  15. 1.38 Cadmium-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  16. 2.15 Copper-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  17. 2.4 Sodium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  18. 2.17 Gallium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  19. 2.31 Iridium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  20. 2.21 Niobium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  1. 1.36 Palladium-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  2. 2.3 Boron-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  3. 1.37 Silver-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  4. 2.24 Silver-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  5. 2.18 Rubidium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  6. 2.20 Zirconium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  7. 1.40 Tin-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  8. 1.41 Tellurium-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  9. 2.2 Lithium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  10. 2.5 Aluminum-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  11. 2.22 Molybdenum-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  12. 2.12 Chromium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  13. 2.14 Cobalt-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  14. 2.9 Scandium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  15. 2.6 Silicon-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  16. 2.19 Yttrium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  17. 2.27 Lanthanum-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  18. 2.23 Rhodium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  19. 2.13 Manganese-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  20. 4.6.2 Aryl radicals

    NASA Astrophysics Data System (ADS)

    Beckwith, A. L. J.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  1. 1.34 Molybdenum-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  2. 1.43 Lanthanum-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  3. 2.30 Osmium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  4. 2.29 Tungsten-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  5. 1.47 Platinum-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  6. 2.26 Cesium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  7. 1.45 Osmium-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  8. 1.44 Tantalum-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  9. 2.11 Vanadium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  10. 2.25 Cadmium-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  11. 1.49 Mercury-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  12. 1.39 Indium-centered radicals

    NASA Astrophysics Data System (ADS)

    Claridge, R. F. C.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  13. Catalysis of Radical Reactions: A Radical Chemistry Perspective.

    PubMed

    Studer, Armido; Curran, Dennis P

    2016-01-04

    The area of catalysis of radical reactions has recently flourished. Various reaction conditions have been discovered and explained in terms of catalytic cycles. These cycles rarely stand alone as unique paths from substrates to products. Instead, most radical reactions have innate chains which form products without any catalyst. How do we know if a species added in "catalytic amounts" is a catalyst, an initiator, or something else? Herein we critically address both catalyst-free and catalytic radical reactions through the lens of radical chemistry. Basic principles of kinetics and thermodynamics are used to address problems of initiation, propagation, and inhibition of radical chains. The catalysis of radical reactions differs from other areas of catalysis. Whereas efficient innate chain reactions are difficult to catalyze because individual steps are fast, both inefficient chain processes and non-chain processes afford diverse opportunities for catalysis, as illustrated with selected examples. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Mutagenesis by peroxy radical is dominated by transversions at deoxyguanosine: evidence for the lack of involvement of 8-oxo-dG1 and/or abasic site formation.

    PubMed

    Valentine, M R; Rodriguez, H; Termini, J

    1998-05-12

    Oxidative damage of DNA by endogenously generated oxygen radicals contributes to the mutagenic process. Hydroxy, alkoxy, and peroxy radicals all have the potential to react with DNA, giving rise to strand breaks and potentially mutagenic oxidative base damage. Although reactions of the hydroxy radical with DNA have been well studied, far less is known about the reactivities of these other radicals with DNA and their mutation-inducing potential. Frequencies of DNA base modifications and strand break densities caused by peroxy radical (ROO*) oxidation were measured by glyoxal gel electrophoretic analysis. We report the spectrum of mutations induced in Escherichia coli upon transfection with peroxy radical treated DNA carrying the lacZ alpha gene as a reporter. Transfection of DNA exposed to micromolar amounts of peroxy radical resulted in a 30-fold increase in mutation frequency in non-SOS-inducible cells. Sequencing analysis of DNA isolated from mutants showed that among base substitution mutants 88% consisted of transversions at G, with a nearly equal number of G --> C and G --> T mutants. Transition mutations were rarely detected, in contrast to control experiments. Electrophoretic analysis of peroxy radical treated DNA exposed to NaOH, Nth, and Fpg proteins demonstrated that abasic sites are not formed to any detectable degree. The oxidative G lesions are sensitive to digestion by the Fpg protein. We were unable to detect the formation of 8-oxo-dG by HPLC/electrochemical analysis of peroxy radical oxidation of dG, suggesting that the G --> T transversions were not caused by this base lesion.

  15. Scandium versus yttrium{amino-alkoxy-bis(phenolate)} complexes for the stereoselective ring-opening polymerization of racemic lactide and β-butyrolactone.

    PubMed

    Chapurina, Yulia; Klitzke, Joice; Casagrande, Osvaldo de L; Awada, Mouhamad; Dorcet, Vincent; Kirillov, Evgueni; Carpentier, Jean-François

    2014-10-14

    Scandium and yttrium amide complexes Ln{ONXO(R1,R2)}(N(SiHMe2)2)(THF)n (Ln = Sc, n = 0 or Y, n = 1; X = NMe2 or OMe; R(1) = Cumyl or p-Cl-Cumyl; R(2) = Me or Cumyl) were prepared by aminolysis of Ln[N(SiHMe2)2]3(THF) with the corresponding tetradentate diamino- or alkoxy-amino-bis(phenol) pro-ligands {ONXO(R1,R2)}H2. In the solid state and in toluene solution, the scandium complexes are monomeric and 5-coordinated, while the analogous yttrium complexes all bear an extra THF-coordinated molecule and are 6-coordinated. Sc{ONXO(R1,R2)}(N(SiHMe2)2) complexes are single-site initiators for the ring-opening polymerization (ROP) of racemic lactide but are less active than their yttrium analogues Y{ONXO(R1,R2)}(N(SiHMe2)2)(THF); also, in contrast to the latter ones, they are inactive in the ROP of the more demanding racemic β-butyrolactone. On the other hand, the scandium amide complexes feature a significantly improved control over the ROP of lactide, yielding PLAs with much narrower molecular weight distributions (Đ(M) < 1.1 for Sc vs. 1.5-2.0 for Y). The yttrium complex with the very bulky o,p-dicumyl-substituted ligand is more heteroselective than its scandium analogue (P(r) = 0.88 vs. 0.83), while the opposite is observed with complexes based on p-methyl-substituted ligands (P(r) = 0.50 in toluene or 0.72-0.75 in THF for Y vs. P(r) = 0.75-0.83 for Sc in toluene). These reactivity and selectivity trends are rationalized by a much more sterically crowded coordination sphere in scandium than in yttrium complexes.

  16. Radically innovative steelmaking technologies

    NASA Astrophysics Data System (ADS)

    Szekely, Julian

    1980-09-01

    The steel industry is faced with serious problems caused by the increasing cost of energy, labor and capital and by tough overseas competition, employing new highly efficient process plants. The very high cost of capital and of capital equipment renders the construction of new green field site plants, exemplifying the best available technology economically unattractive. For this reason, over the long term the development radically innovative steelmaking technologies appears to be the only satisfactory resolution of this dilemma. The purpose of this article is to present a critical review of some of the radically innovative steelmaking technologies that have been proposed during the past few years and to develop the argument that these indeed do deserve serious consideration at the present time. It should be stressed, however, that these innovative technologies can be implemented only as part of a carefully conceived long range plan, which contains as a subset short term solutions, such as trigger prices improved investment credits, and so forth and intermediate term solutions, such as more extensive use of continuous casting, external desulfurization and selective modernization in general.

  17. Oligorotaxane Radicals under Orders.

    PubMed

    Wang, Yuping; Frasconi, Marco; Liu, Wei-Guang; Sun, Junling; Wu, Yilei; Nassar, Majed S; Botros, Youssry Y; Goddard, William A; Wasielewski, Michael R; Stoddart, J Fraser

    2016-02-24

    A strategy for creating foldameric oligorotaxanes composed of only positively charged components is reported. Threadlike components-namely oligoviologens-in which different numbers of 4,4'-bipyridinium (BIPY(2+)) subunits are linked by p-xylylene bridges, are shown to be capable of being threaded by cyclobis(paraquat-p-phenylene) (CBPQT(4+)) rings following the introduction of radical-pairing interactions under reducing conditions. UV/vis/NIR spectroscopic and electrochemical investigations suggest that the reduced oligopseudorotaxanes fold into highly ordered secondary structures as a result of the formation of BIPY(•+) radical cation pairs. Furthermore, by installing bulky stoppers at each end of the oligopseudorotaxanes by means of Cu-free alkyne-azide cycloadditions, their analogous oligorotaxanes, which retain the same stoichiometries as their progenitors, can be prepared. Solution-state studies of the oligorotaxanes indicate that their mechanically interlocked structures lead to the enforced interactions between the dumbbell and ring components, allowing them to fold (contract) in their reduced states and unfold (expand) in their fully oxidized states as a result of Coulombic repulsions. This electrochemically controlled reversible folding and unfolding process, during which the oligorotaxanes experience length contractions and expansions, is reminiscent of the mechanisms of actuation associated with muscle fibers.

  18. Oligorotaxane Radicals under Orders

    PubMed Central

    2016-01-01

    A strategy for creating foldameric oligorotaxanes composed of only positively charged components is reported. Threadlike components—namely oligoviologens—in which different numbers of 4,4′-bipyridinium (BIPY2+) subunits are linked by p-xylylene bridges, are shown to be capable of being threaded by cyclobis(paraquat-p-phenylene) (CBPQT4+) rings following the introduction of radical-pairing interactions under reducing conditions. UV/vis/NIR spectroscopic and electrochemical investigations suggest that the reduced oligopseudorotaxanes fold into highly ordered secondary structures as a result of the formation of BIPY•+ radical cation pairs. Furthermore, by installing bulky stoppers at each end of the oligopseudorotaxanes by means of Cu-free alkyne–azide cycloadditions, their analogous oligorotaxanes, which retain the same stoichiometries as their progenitors, can be prepared. Solution-state studies of the oligorotaxanes indicate that their mechanically interlocked structures lead to the enforced interactions between the dumbbell and ring components, allowing them to fold (contract) in their reduced states and unfold (expand) in their fully oxidized states as a result of Coulombic repulsions. This electrochemically controlled reversible folding and unfolding process, during which the oligorotaxanes experience length contractions and expansions, is reminiscent of the mechanisms of actuation associated with muscle fibers. PMID:27163033

  19. Theoretical investigation on the atmospheric fate of CF3C(O)OCH 2O radical: alpha-ester rearrangement vs oxidation at 298 K.

    PubMed

    Mishra, Bhupesh Kumar

    2014-09-01

    A theoretical study on the mechanism of the thermal decomposition of CF(3)C(O)OCH(2)O radical is presented for the first time. Geometry optimization and frequency calculations were performed at the MPWB1K/6-31 + G(d, p) level of theory and energetic information further refined by calculating the energy of the species using G2(MP2) theory. Three plausible decomposition pathways including α-ester rearrangement, reaction with O(2) and thermal decomposition (C-O bond scission) were considered in detail. Our results reveal that reaction with O(2) is the dominant path for the decomposition of CF(3)C(O)OCH(2)O radical in the atmosphere, involving the lowest energy barrier, which is in accord with experimental findings. Our theoretical results also suggest that α-ester rearrangement leading to the formation of trifluoroacetic acid TFA makes a negligible contribution to decomposition of the title alkoxy radical. The thermal rate constants for the above decomposition pathways were evaluated using canonical transition state theory (CTST) at 298 K.

  20. Free radical propulsion concept

    NASA Technical Reports Server (NTRS)

    Hawkins, C. E.; Nakanishi, S.

    1981-01-01

    A free radical propulsion concept utilizing the recombination energy of dissociated low molecular weight gases to produce thrust was examined. The concept offered promise of a propulsion system operating at a theoretical impulse, with hydrogen, as high as 2200 seconds at high thrust to power ratio, thus filling the gas existing between chemical and electrostatic propulsion capabilities. Microwave energy used to dissociate a continuously flowing gas was transferred to the propellant via three body recombination for conversion to propellant kinetic energy. Power absorption by the microwave plasma discharge was in excess of 90 percent over a broad range of pressures. Gas temperatures inferred from gas dynamic equations showed much higher temperatures from microwave heating than from electrothermal heating. Spectroscopic analysis appeared to corroborate the inferred temperatures of one of the gases tested.

  1. Radicals in Berkeley?

    PubMed Central

    Linn, Stuart

    2015-01-01

    In a previous autobiographical sketch for DNA Repair (Linn, S. (2012) Life in the serendipitous lane: excitement and gratification in studying DNA repair. DNA Repair 11, 595–605), I wrote about my involvement in research on mechanisms of DNA repair. In this Reflections, I look back at how I became interested in free radical chemistry and biology and outline some of our bizarre (at the time) observations. Of course, these studies could never have succeeded without the exceptional aid of my mentors: my teachers; the undergraduate and graduate students, postdoctoral fellows, and senior lab visitors in my laboratory; and my faculty and staff colleagues here at Berkeley. I am so indebted to each and every one of these individuals for their efforts to overcome my ignorance and set me on the straight and narrow path to success in research. I regret that I cannot mention and thank each of these mentors individually. PMID:25713083

  2. Radicals in Berkeley?

    PubMed

    Linn, Stuart

    2015-04-03

    In a previous autobiographical sketch for DNA Repair (Linn, S. (2012) Life in the serendipitous lane: excitement and gratification in studying DNA repair. DNA Repair 11, 595-605), I wrote about my involvement in research on mechanisms of DNA repair. In this Reflections, I look back at how I became interested in free radical chemistry and biology and outline some of our bizarre (at the time) observations. Of course, these studies could never have succeeded without the exceptional aid of my mentors: my teachers; the undergraduate and graduate students, postdoctoral fellows, and senior lab visitors in my laboratory; and my faculty and staff colleagues here at Berkeley. I am so indebted to each and every one of these individuals for their efforts to overcome my ignorance and set me on the straight and narrow path to success in research. I regret that I cannot mention and thank each of these mentors individually.

  3. Radical Change by Entrepreneurial Design

    DTIC Science & Technology

    1998-01-01

    This article offers a conceptual framework to understand radical change. It opens with a typology that defines change in terms of its pace and scope...known entrepreneurs who have been successful in molding and shaping the radical change process. The implications of this conceptual framework to

  4. THE SYNTHESIS AND EVALUATION OF NEW BASE STOCK FLUIDS FOR GAS TURBINE APPLICATION

    DTIC Science & Technology

    GAS TURBINES, *LUBRICANTS, *OXYGEN HETEROCYCLIC COMPOUNDS, ALKOXY RADICALS, ALKYL RADICALS, AMIDES, ANILINES , CHEMICAL REACTIONS , DISPLACEMENT... REACTIONS , INFRARED SPECTROSCOPY, LUBRICATION, OXIDATION, PHENYL RADICALS, STABILITY, SUBSTITUTION REACTIONS , SYNTHESIS, TEMPERATURE, VISCOSITY.

  5. RAIN REPELLENT

    DTIC Science & Technology

    COATINGS, *RAINDROPS, *SILANES, *ULTRASONIC RADIATION, ACIDS, AEROSOLS, ALKOXY RADICALS, ALKYL RADICALS, CHLORIDES, FILMS, FLUORIDES, GLASS, LIQUIDS...MATERIALS, METHYL RADICALS, MIXTURES, ORGANIC COMPOUNDS, SALTS, STABILITY, STORAGE, SURFACES

  6. Antichagasic and trichomonacidal activity of 1-substituted 2-benzyl-5-nitroindazolin-3-ones and 3-alkoxy-2-benzyl-5-nitro-2H-indazoles.

    PubMed

    Fonseca-Berzal, Cristina; Ibáñez-Escribano, Alexandra; Reviriego, Felipe; Cumella, José; Morales, Paula; Jagerovic, Nadine; Nogal-Ruiz, Juan José; Escario, José Antonio; da Silva, Patricia Bernardino; Soeiro, Maria de Nazaré C; Gómez-Barrio, Alicia; Arán, Vicente J

    2016-06-10

    Two series of new 5-nitroindazole derivatives, 1-substituted 2-benzylindazolin-3-ones (6-29, series A) and 3-alkoxy-2-benzyl-2H-indazoles (30-37, series B), containing differently functionalized chains at position 1 and 3, respectively, have been synthesized starting from 2-benzyl-5-nitroindazolin-3-one 5, and evaluated against the protozoan parasites Trypanosoma cruzi and Trichomonas vaginalis, etiological agents of Chagas disease and trichomonosis, respectively. Many indazolinones of series A were efficient against different morphological forms of T. cruzi CL Brener strain (compounds 6, 7, 9, 10 and 19-21: IC50 = 1.58-4.19 μM for epimastigotes; compounds 6, 19-21 and 24: IC50 = 0.22-0.54 μM for amastigotes) being as potent as the reference drug benznidazole. SAR analysis suggests that electron-donating groups at position 1 of indazolinone ring are associated with an improved antichagasic activity. Moreover, compounds of series A displayed low unspecific toxicities against an in vitro model of mammalian cells (fibroblasts), which were reflected in high values of the selectivity indexes (SI). Compound 20 was also very efficient against amastigotes from Tulahuen and Y strains of T. cruzi (IC50 = 0.81 and 0.60 μM, respectively), showing low toxicity towards cardiac cells (LC50 > 100 μM). In what concerns compounds of series B, some of them displayed moderate activity against trophozoites of a metronidazole-sensitive isolate of T. vaginalis (35 and 36: IC50 = 9.82 and 7.25 μM, respectively), with low unspecific toxicity towards Vero cells. Compound 36 was also active against a metronidazole-resistant isolate (IC50 = 9.11 μM) and can thus be considered a good prototype for the development of drugs directed to T. vaginalis resistant to 5-nitroimidazoles.

  7. Studies of radiation-produced radicals and radical ions

    SciTech Connect

    Williams, T.F.

    1991-01-01

    The radiolytic oxidation of anti-5-methylbicyclo(2.1.0)pentane gives the 1-methylcyclopentene radical cation as the sole rearrangement product H migration whereas oxidation of its syn isomer results in the highly selective formation of the 3-methylcyclopentene radical cation by methyl group migration. Since exactly the same stereoselectivity of olefin formation was observed in corresponding PET (photosensitized electron transfer) studies in the liquid phase, it is concluded that the rearrangement in this case also occurs through the intermediacy of radical cations. Clearly, the radical cation rearrangement must occur very rapidly (10{sup {minus}8}--10{sup {minus}9}s) under liquid-phase conditions at room temperature to compete with back electron transfer, and therefore the hydrogen (or methyl) migration is a fast process under these conditions. An intramolecular cycloaddition reaction was demonstrated in the radical cation rearrangement of 4-vinylcyclohexene to bicyclo(3.2.1)oct-2-ene. ESR studies show that the radiolytic oxidation of quadricyclane in Freon matrices under conditions of high substrate dilution leads to the bicyclo(3.2.0)hepta-2,6-diene radical cation as well as the previously reported norbornadiene radical cation, the former species predominating at sufficiently low concentrations.

  8. Free radicals and male reproduction.

    PubMed

    Agarwal, Ashok; Allamaneni, Shyam S R

    2011-03-01

    Male factor accounts for almost 50% cases of infertility. The exact mechanism of sperm dysfunction is not known in many cases. Extensive research in the last decade has led to the identification of free radicals (reactive oxygen species) as mediators of sperm dysfunction in both specific diagnoses and idiopathic cases of male infertility. Elevated levels of reactive oxygen species are seen in up to 30-80% of men with male infertility. The role of free radicals has been studied extensively in the process of human reproduction. We know now that a certain level of free radicals is necessary for normal sperm function, whereas an excessive level of free radicals can cause detrimental effect on sperm function and subsequent fertilisation and offspring health. Oxidative stress develops when there is an imbalance between generation of free radicals and scavenging capacity of anti-oxidants in reproductive tract. Oxidative stress has been shown to affect both standard semen parameters and fertilising capacity. In addition, high levels of free radicals have been associated with lack of or poor fertility outcome after natural conception or assisted reproduction. Diagnostic techniques to quantify free radicals in infertile patients can assist physicians treating patients with infertility to plan for proper treatment strategies. In vivo anti-oxidants can be used against oxidative stress in male reproductive tract. Supplementation of in vitro anti-oxidants can help prevent the oxidative stress during sperm preparation techniques in assisted reproduction.

  9. Synthesis of chloro alkoxy and alkoxy derivatives of methyl oleate

    USDA-ARS?s Scientific Manuscript database

    Vegetable oil based lubricants typically have improved lubricity and biodegradability over their mineral oil based counterparts. However, vegetable oil lubricants often fail to meet the performance standards of mineral based oils with respect to cold temperature and resistance to oxidation. Olefins ...

  10. Atmospheric chemistry of isoflurane, desflurane, and sevoflurane: kinetics and mechanisms of reactions with chlorine atoms and OH radicals and global warming potentials.

    PubMed

    Sulbaek Andersen, Mads P; Nielsen, Ole J; Karpichev, Boris; Wallington, Timothy J; Sander, Stanley P

    2012-06-21

    The smog chamber/Fourier-transform infrared spectroscopy (FTIR) technique was used to measure the rate coefficients k(Cl + CF(3)CHClOCHF(2), isoflurane) = (4.5 ± 0.8) × 10(-15), k(Cl + CF(3)CHFOCHF(2), desflurane) = (1.0 ± 0.3) × 10(-15), k(Cl + (CF(3))(2)CHOCH(2)F, sevoflurane) = (1.1 ± 0.1) × 10(-13), and k(OH + (CF(3))(2)CHOCH(2)F) = (3.5 ± 0.7) × 10(-14) cm(3) molecule(-1) in 700 Torr of N(2)/air diluent at 295 ± 2 K. An upper limit of 6 × 10(-17) cm(3) molecule(-1) was established for k(Cl + (CF(3))(2)CHOC(O)F). The laser photolysis/laser-induced fluorescence (LP/LIF) technique was employed to determine hydroxyl radical rate coefficients as a function of temperature (241-298 K): k(OH + CF(3)CHFOCHF(2)) = (7.05 ± 1.80) × 10(-13) exp[-(1551 ± 72)/T] cm(3) molecule(-1); k(296 ± 1 K) = (3.73 ± 0.08) × 10(-15) cm(3) molecule(-1), and k(OH + (CF(3))(2)CHOCH(2)F) = (9.98 ± 3.24) × 10(-13) exp[-(969 ± 82)/T] cm(3) molecule(-1); k(298 ± 1 K) = (3.94 ± 0.30) × 10(-14) cm(3) molecule(-1). The rate coefficient of k(OH + CF(3)CHClOCHF(2), 296 ± 1 K) = (1.45 ± 0.16) × 10(-14) cm(3) molecule(-1) was also determined. Chlorine atoms react with CF(3)CHFOCHF(2) via H-abstraction to give CF(3)CFOCHF(2) and CF(3)CHFOCF(2) radicals in yields of approximately 83% and 17%. The major atmospheric fate of the CF(3)C(O)FOCHF(2) alkoxy radical is decomposition via elimination of CF(3) to give FC(O)OCHF(2) and is unaffected by the method used to generate the CF(3)C(O)FOCHF(2) radicals. CF(3)CHFOCF(2) radicals add O(2) and are converted by subsequent reactions into CF(3)CHFOCF(2)O alkoxy radicals, which decompose to give COF(2) and CF(3)CHFO radicals. In 700 Torr of air 82% of CF(3)CHFO radicals undergo C-C scission to yield HC(O)F and CF(3) radicals with the remaining 18% reacting with O(2) to give CF(3)C(O)F. Atmospheric oxidation of (CF(3))(2)CHOCH(2)F gives (CF(3))(2)CHOC(O)F in a molar yield of 93 ± 6% with CF(3)C(O)CF(3) and HCOF as minor products. The IR

  11. [Simultaneous radical retropubic prostatectomy, diverticulectomy].

    PubMed

    Loran, O B; Sokolov, A E; Guspanov, R I; Polegen'kiĭ, V V

    2014-01-01

    Presented clinical case demonstrates a combination of rare congenital abnormality - giant true diverticula of the bladder - and high-risk prostate cancer, as well as a successful result of simultaneous operation - a radical prostatectomy with diverticulectomy.

  12. Free radical inactivation of pepsin

    NASA Astrophysics Data System (ADS)

    Josimović, Lj; Ruvarac, I.; Janković, I.; Jovanović, S. V.

    1994-06-01

    Alkylperoxy radicals containing one, two or three chlorine atoms, CO -2, O 2 - were reacted with pepsin in aqueous solutions. It was found that only Cl 3COO and CO -2 inactive pepsin, attacking preferentially the disulfide bridge. Transient spectra obtained upon completion of the Cl 3COO + pepsin reaction at pH 5 indicate that 20% of initially produced Cl 3COO radicals oxidizes tryptophan residues, and 40% disulfide bridges. The inactivation induced by the Cl 3COO radical increases at lower pH, and the maximal inactivation, Gin = 5.8, was observed at pH 1.5. The inactivation of pepsin by CO -2 radicals depends on the absorbed dose. The maximal inactivation, Gin = 4.5, was determined in the dose range from 38 to 53 Gy.

  13. Redox Properties of Free Radicals.

    ERIC Educational Resources Information Center

    Neta, P.

    1981-01-01

    Describes pulse radiolysis as a useful means in studing one-electron redox potentials. This method allows the production of radicals and the determination of their concentration and rates of reaction. (CS)

  14. Redox Properties of Free Radicals.

    ERIC Educational Resources Information Center

    Neta, P.

    1981-01-01

    Describes pulse radiolysis as a useful means in studing one-electron redox potentials. This method allows the production of radicals and the determination of their concentration and rates of reaction. (CS)

  15. Peroxy radical oxidation of thymidine.

    PubMed

    Martini, M; Termini, J

    1997-02-01

    The peroxy radical (ROO) is unique among reactive oxygen species implicated in the production of DNA damage in that it possesses an extremely long half-life (order of seconds) and is predicted to have a relatively greater chemical selectivity in its reactions relative to other radical intermediates. Yet no product studies of the reactions of ROO with bases, nucleosides, or DNA have appeared, and thus no meaningful predictions can be made regarding its potential involvement in the production of DNA base damage and the mutagenic process. We report here on the reaction products formed by peroxy radical with thymidine, major target of oxidative base damage. ROO reacts with thymine to yield predominantly 5-Me oxidation products. The highly mutagenic 5-(hydroperoxymethyl)-2'-deoxyuridine, 5-formyl-2'-deoxyuridine, and 5-(hydroxymethyl)-2'-deoxyuridine are produced by peroxy radical oxidation. In contrast, 5Me oxidation products are minor products of thymidine oxidation by OH, which yields predominantly saturated derivatives via addition to the 5,6 double bound. A plausible mechanistic scheme for the formation of the base oxidation products of thymidine by peroxy radicals is presented. Attach at the deoxyribose moiety resulting in oxidative depyrimidination is also found to occur, as indicated by free base release. Phosphodiester backbone cleavage resulting in single and double strand breaks is also catalyzed by peroxy radical, as demonstrated using a plasmid nicking assay.

  16. Crystalline bipyridinium radical complexes and uses thereof

    DOEpatents

    Fahrenbach, Albert C.; Barnes, Jonathan C.; Li, Hao; Stoddart, J. Fraser; Basuray, Ashish Neil; Sampath, Srinivasan

    2015-09-01

    Described herein are methods of generating 4,4'-bipyridinium radical cations (BIPY.sup..cndot.+), and methods for utilizing the radical-radical interactions between two or more BIPY.sup..cndot.+ radical cations that ensue for the creation of novel materials for applications in nanotechnology. Synthetic methodologies, crystallographic engineering techniques, methods of physical characterization, and end uses are described.

  17. Effects of alkoxy substitution on molecular structure, physicochemical and photovoltaic properties of 2D-conjugated polymers based on benzo[1,2-b:4,5-b‧]dithiophene and fluorinated benzothiadiazole

    NASA Astrophysics Data System (ADS)

    Wang, Wengong; Wang, Guo; Yang, Jie; Zhang, Jing; Chen, Lixia; Weng, Chao; Zhang, Zhi-Guo; Li, Yongfang; Shen, Ping

    2017-03-01

    Two donor-acceptor (D-A) copolymers (PMT-FBT and PET-FBT) with alkoxythiophene-substituted benzo[1,2-b:4,5-b‧]dithiophene as donor unit and difluorobenzothiazole as acceptor unit, were synthesized and employed as donor material for polymer solar cells (PSCs). The comparative study showed that the type (methoxyl versus ethylenedioxyl) and the position (3- and 4-positons) of alkoxy substituents on thiophene side chains have great effects on the molecular geometries and optoelectronic properties of these copolymers. PSCs based on two polymers exhibit maximum power conversion efficiencies of 3.29% and 2.40%, with open-circuit voltage (Voc) values as high as 0.85 and 1.02 V for PMT-FBT and PET-FBT, respectively.

  18. Standard Electrode Potentials Involving Radicals in Aqueous Solution: Inorganic Radicals

    SciTech Connect

    Armstrong, David A.; Huie, Robert E.; Koppenol, Willem H.; Lymar, Sergei V.; Merenyi, Gabor; Neta, Pedatsur; Ruscic, Branko; Stanbury, David M.; Steenken, Steen; Wardman, Peter

    2015-12-01

    Recommendations are made for standard potentials involving select inorganic radicals in aqueous solution at 25 °C. These recommendations are based on a critical and thorough literature review and also by performing derivations from various literature reports. The recommended data are summarized in tables of standard potentials, Gibbs energies of formation, radical pKa’s, and hemicolligation equilibrium constants. In all cases, current best estimates of the uncertainties are provided. An extensive set of Data Sheets is appended that provide original literature references, summarize the experimental results, and describe the decisions and procedures leading to each of the recommendations

  19. Composition and yields of secondary organic aerosol formed from OH radical-initiated reactions of linear alkenes in the presence of NO x: Modeling and measurements

    NASA Astrophysics Data System (ADS)

    Matsunaga, Aiko; Docherty, Kenneth S.; Lim, Yong B.; Ziemann, Paul J.

    The products and mechanism of secondary organic aerosol (SOA) formation from the OH radical-initiated reactions of linear alkenes in the presence of NO x were investigated in an environmental chamber. The SOA consisted primarily of products formed through reactions initiated by OH radical addition to the C dbnd C double bond, including β-hydroxynitrates and dihydroxynitrates, as well as cyclic hemiacetals, dihydrofurans, and dimers formed from particle-phase reactions of dihydroxycarbonyls. 1,4-Hydroxynitrates formed through reactions initiated by H-atom abstraction also appeared to contribute. Product yields and OH radical and alkoxy radical rate constants taken from the literature or calculated using structure-reactivity methods were used to develop a quantitative chemical mechanism for these reactions. SOA yields were then calculated using this mechanism with gas-particle partitioning theory and estimated product vapor pressures for comparison with measured values. Calculated and measured SOA yields agreed very well at high carbon numbers when semi-volatile products were primarily in the particle phase, but diverged with decreasing carbon number to a degree that depended on the model treatment of dihydroxycarbonyls, which appeared to undergo reversible reactions in the particle phase. The results indicate that the chemical mechanism developed here provides an accurate representation of the gas-phase chemistry, but the utility of the SOA model depends on the partitioning regime. The results also demonstrate some of the advantages of studying simple aerosol-forming reactions in which the majority of products can be identified and quantified, in this case leading to insights into both gas- and particle-phase chemistry.

  20. [Laparoscopic radical cystectomy: initial experience].

    PubMed

    Núñez Mora, C; García Mediero, J Ma; Cáceres Jiménez, F; Cabrera Castillo, P M

    2007-09-01

    To review our initial experience with laparoscopic radical cystectomy. Between September 2004 and June 2006 we performed 16 laparoscopic radical cystectomies (14 males and 2 females) with a median age of 63.8 y.o. (51-85). 12 ileal neobladder (with laparoscopic ileal-urethra anastomosis), 3 cutaneous ureteroileostomies and 1 cutaneous ureterostomy were performed as derivation techniques. Median follow up was 12.4 months Mean operation time was 340 minutes. Estimated blood loss was 350 ml. and 3 cases required intra-op blood transfusion. Mean hospitalization discharged was at 7.6 days. Median linph node dissection was 22.9 finding node metastasis in 6 cases. Most frequent complication was ileo in two cases. No local recurrentes in trocar placement was achieved. Laparoscopic Radical cystectomy is a challenged long-lasting procedure but with the advantage of a less transfusion rate and short hospital stay. Oncologycal outcomes are similar as tose from open surgery.

  1. Radical-Mediated Enzymatic Polymerizations

    PubMed Central

    Zavada, Scott R.; Battsengel, Tsatsral; Scott, Timothy F.

    2016-01-01

    Polymerization reactions are commonly effected by exposing monomer formulations to some initiation stimulus such as elevated temperature, light, or a chemical reactant. Increasingly, these polymerization reactions are mediated by enzymes―catalytic proteins―owing to their reaction efficiency under mild conditions as well as their environmental friendliness. The utilization of enzymes, particularly oxidases and peroxidases, for generating radicals via reduction-oxidation mechanisms is especially common for initiating radical-mediated polymerization reactions, including vinyl chain-growth polymerization, atom transfer radical polymerization, thiol–ene step-growth polymerization, and polymerization via oxidative coupling. While enzyme-mediated polymerization is useful for the production of materials intended for subsequent use, it is especially well-suited for in situ polymerizations, where the polymer is formed in the place where it will be utilized. Such polymerizations are especially useful for biomedical adhesives and for sensing applications. PMID:26848652

  2. Epistemological barriers to radical behaviorism.

    PubMed

    O'Donohue, W T; Callaghan, G M; Ruckstuhl, L E

    1998-01-01

    The historian and philosopher of science Gaston Bachelard proposed the concept of epistemological barriers to describe the intellectual challenges encountered by scientists in their work. In order to embrace novel ways of approaching a problem in science, scientists must overcome barriers or obstacles posed by their prior views. For example, Einsteinian physics presents scientists with claims that space is curved and that time and space are on the same continuum. We utilize Bachelard's concept of epistemological barriers to describe the differences between the intellectual journeys students pursuing advanced studies face when attempting to accept cognitive psychology or radical behaviorism. We contend that the folk psychological beliefs that students typically hold when entering these studies pose less challenge to cognitive psychology than to radical behaviorism. We also suggest that these barriers may also partly be involved in the problematic exegesis that has plagued radical behaviorism. In close, we offer some suggestions for dealing with these epistemological barriers.

  3. Epistemological barriers to radical behaviorism

    PubMed Central

    O'Donohue, William T.; Callaghan, Glenn M.; Ruckstuhl, L. E.

    1998-01-01

    The historian and philosopher of science Gaston Bachelard proposed the concept of epistemological barriers to describe the intellectual challenges encountered by scientists in their work. In order to embrace novel ways of approaching a problem in science, scientists must overcome barriers or obstacles posed by their prior views. For example, Einsteinian physics presents scientists with claims that space is curved and that time and space are on the same continuum. We utilize Bachelard's concept of epistemological barriers to describe the differences between the intellectual journeys students pursuing advanced studies face when attempting to accept cognitive psychology or radical behaviorism. We contend that the folk psychological beliefs that students typically hold when entering these studies pose less challenge to cognitive psychology than to radical behaviorism. We also suggest that these barriers may also partly be involved in the problematic exegesis that has plagued radical behaviorism. In close, we offer some suggestions for dealing with these epistemological barriers. PMID:22478314

  4. Donor free radical explosive composition

    DOEpatents

    Walker, Franklin E. [15 Way Points Rd., Danville, CA 94526; Wasley, Richard J. [4290 Colgate Way, Livermore, CA 94550

    1980-04-01

    An improved explosive composition is disclosed and comprises a major portion of an explosive having a detonation velocity between about 1500 and 10,000 meters per second and a minor amount of a donor additive comprising an organic compound or mixture of organic compounds capable of releasing low molecular weight free radicals or ions under mechanical or electrical shock conditions and which is not an explosive, or an inorganic compound or mixture of inorganic compounds capable of releasing low molecular weight free radicals or ions under mechanical or electrical shock conditions and selected from ammonium or alkali metal persulfates.

  5. Laparoscopic radical and partial cystectomy

    PubMed Central

    Challacombe, Ben J.; Rose, Kristen; Dasgupta, Prokar

    2005-01-01

    Radical cystectomy remains the standard treatment for muscle invasive organ confined bladder carcinoma. Laparoscopic radical cystoprostatectomy (LRC) is an advanced laparoscopic procedure that places significant demands on the patient and the surgeon alike. It is a prolonged procedure which includes several technical steps and requires highly developed laparoscopic skills including intra-corporeal suturing. Here we review the development of the technique, the indications, complications and outcomes. We also examine the potential benefits of robotic-assisted LRC and explore the indications and technique of laparoscopic partial cystectomy. PMID:21206662

  6. VUV Photoionisation of hydrocarbon radicals

    NASA Astrophysics Data System (ADS)

    Alcaraz, C.; Noller, Bastian; Hemberger, Patrick; Fischer, Ingo; Gans, Bérenger; Boyé-Peronne, Séverine; Douin, Stéphane; Gauyacq, Dolorès; Soldi-Lose, Héloïse; Garcia, Gustavo

    2008-09-01

    Hydrocarbon radicals CxHy are constituents of various planetary atmospheres, in particular Titan, as a result of the methane photochemistry induced by the solar radiation. They contribute to the neutral chemistry, but are also important for the ionosphere through their photoionisation leading to their cations CxHy +. These cations are also produced by ion-molecule reactions starting from the reaction of the primary ions CH4 + and CH3 + which are created in the non-dissociative and dissociative photoionisation of CH4. This work aims at caracterizing the VUV photoionisation of small hydrocarbon radicals as a function of photon energy. The objective is to provide laboratory data for modelers on the spectroscopy, the thermochemistry, and the reactivity of the radicals and their cations. The hydrocarbon radicals are much less caracterized than stable molecules since they have to be produced in situ in the laboratory experiment. We have adapted at Orsay [1-3] a pyrolysis source (Figure 1) well suited to produce cold beams of hydrocarbon radicals to our experimental setups. Available now at Orsay, we have two new sources of VUV radiation, complementary in terms of tunability and resolution, that can be used for these studies. The first one is the DESIRS beamline [4] at the new french synchrotron, SOLEIL. The second one is the VUV laser developped at the Centre Laser de l'Université Paris-Sud (CLUPS) [5]. At SOLEIL, a photoelectron-photoion coincidence spectrometer is used to monitor the photoionisation on a large photon energy range. At the CLUPS, a pulsedfield ionisation (PFI-ZEKE) spectrometer allows studies at higher resolution on selected photon energies. The first results obtained with these new setups will be presented. References [1] Fischer, I., Schussler, T., Deyerl, H.J., Elhanine, M. & Alcaraz, C., Photoionization and dissociative photoionization of the allyl radical, C3H5. Int. J. Mass Spectrom., 261 (2-3), 227-233 (2007) [2] Schüßler, T., Roth, W., Gerber

  7. Students' Ideas and Radical Constructivism

    ERIC Educational Resources Information Center

    Sánchez Gómez, Pedro J.

    2016-01-01

    In this article, I study, from the point of view of the analytic philosophy of mind, the compatibility of students' ideas studies (SIS) with radical constructivism (RC). I demonstrate that RC is based on a psychology of "narrow mental states"; that is, the idea that the mental content of an individual can be fully characterised without…

  8. The Other Women: Radicalizing Feminism.

    ERIC Educational Resources Information Center

    Puigvert, Lidia; Darder, Antonia; Merrill, Barbara; de los Reyes, Eileen; Stromquist, Nelly

    A recent international symposium on radicalizing feminism explored ways of developing a dialogic feminism that emphasizes working in different settings under the common goal of including women who have been invisible in the dominant feminist literature by furthering theories and practices based on the principles of dialogic feminism. The seminar…

  9. [Reprodcutive results of radical trachelectomy].

    PubMed

    Martínez-Chapa, Arnulfo; Alonso-Reyes, Nelly; Luna-Macías, Miguel

    2015-12-01

    Historically, cervical cancer in early stages has been treated with radical hysterectomy and radiotherapy with no option in keeping the uterine-ovarian function. Since two decades ago, evidence shows these cases are candidates for radical trachelectomy, a procedure capable of preserving the fertility without affecting the oncological outcome. To analyze reproductive results among patients treated with radical trachelectomy, in a reference center from the northeast of Mexico. Between March 1999 and December 2013, 27 cases with cervical cancer in early stages were treated with vaginal or abdominal radical trachelectomy in the ISSSTE Regional Hospital in Monterrey, NL (Mexico). We obtained the gynecological, medical and surgical clinical history. Plan of analysis consisted of descriptive statistics. Age range was 27-39 years. Main complications were cervical stenosis (n=1) and erosion of cerclaje (n=2). Eighteen patients tried to get pregnant, 8 of them got a spontaneous pregnancy; 1 more patient required assisted reproduction technics and did not succeed. All pregnancies were delivered by cesarean section and were preterm births; 3 underwent premature rupture of membranes. Two pregnancies ended in abortion, one at 10 weeks with severe hemorrhage that needed hysterectomy; the second one, at 1 7 weeks, received a fine uterine curettage. Only 6 cases (33%) got a live birth. Only one third of the attempted pregnancies got a live birth. Assisted reproduction technics play an important role and should be offer to all cases. Cerclaje is an important factor to carry a pregnancy up to the third trimester.

  10. Mitigating Radicalism in Northern Nigeria

    DTIC Science & Technology

    2013-08-01

    radicalization in northern Nigeria. u Active engagement of youth and communities in peacebuilding programs that facilitate interactions among individuals...leaders, sustained development investments in marginalized communities , promotion of values of inclusivity to mitigate the spread of extremist ideology...claiming to have repelled Boko Haram, the militants return, regroup, and seek revenge. As a result, social and economic activities in the northern

  11. Students' Ideas and Radical Constructivism

    ERIC Educational Resources Information Center

    Sánchez Gómez, Pedro J.

    2016-01-01

    In this article, I study, from the point of view of the analytic philosophy of mind, the compatibility of students' ideas studies (SIS) with radical constructivism (RC). I demonstrate that RC is based on a psychology of "narrow mental states"; that is, the idea that the mental content of an individual can be fully characterised without…

  12. REVERSIBILITY OF RADICAL-OLEFIN REACTIONS.

    DTIC Science & Technology

    ALKENES, *STYRENES, *POLYVINYL CHLORIDE, CHEMICAL EQUILIBRIUM, POLYMERIZATION, POLYMERIZATION, FREE RADICALS , MOLECULAR ISOMERISM, TRACER STUDIES, CHEMICAL REACTIONS, DECOMPOSITION, SYNTHESIS(CHEMISTRY).

  13. Free-radical chemistry of sulfite.

    PubMed Central

    Neta, P; Huie, R E

    1985-01-01

    The free-radical chemistry of sulfite oxidation is reviewed. Chemical transformations of organic and biological molecules induced by sulfite oxidation are summarized. The kinetics of the free-radical oxidations of sulfite are discussed, as are the kinetics of the reactions of the sulfite-derived radicals SO3 and the peroxy derivative SO5 with organic compounds. PMID:3830699

  14. REACTIONS OF FREE RADICALS CONTAINING NITROGEN.

    DTIC Science & Technology

    deduced. The reactions of methyl and ethyl radicals with a variety of amino compounds were studied. The reactions of difluoroamino radicals in the...Hydrazines, Anilines and Cyanides were pyrolysed and the heats of formation of the resultant radicals and the strengths of the bonds formed by them

  15. The Radical Axis: A Motion Study

    ERIC Educational Resources Information Center

    McGivney, Ray; McKim, Jim

    2006-01-01

    Interesting problems sometimes have surprising sources. In this paper we take an innocent looking problem from a calculus book and rediscover the radical axis of classical geometry. For intersecting circles the radical axis is the line through the two points of intersection. For nonintersecting, nonconcentric circles, the radical axis still…

  16. Highly durable photochromic radical complexes having no steric protections of radicals.

    PubMed

    Kobayashi, Yoichi; Mishima, Yasuhiro; Mutoh, Katsuya; Abe, Jiro

    2017-04-21

    Steric protection groups are usually necessary for stable radicals. However, here, we developed novel photochromic radical complexes which generate sterically unprotected imidazolyl and phenoxyl radicals upon UV light irradiation based on the phenoxyl-imidazolyl radical complex (PIC) framework. These photochromic compounds show excellent durability against repeated irradiation of intense nanosecond laser pulses even in polar protic solvents, such as ethanol.

  17. Atmospheric chemistry of CF{sub 3}C(O)OCH{sub 2}CF{sub 3}: UV spectra and kinetic data for CF{sub 3}C(O)OCH({sm_bullet})CF{sub 3} and CF{sub 3}C(O)OCH(OO{sm_bullet})CF{sub 3} radicals, and atmospheric fate of CF{sub 3}C(O)OCH(O{sm_bullet})CF{sub 3} radicals

    SciTech Connect

    Stein, T.N.N.; Christensen, L.K.; Platz, J.; Sehested, J.; Nielsen, O.J.; Wallington, T.J.

    1999-07-22

    Recognition of the adverse effect of chlorofluorocarbon (CFC) release into the atmosphere has led to an international effort to replace CFCs with environmentally acceptable alternatives. Hydrofluoroethers (HFEs) are fluids designed to replace CFCs in applications such as the cleaning of electronic equipment, heat transfer agents in refrigeration systems, and carrier fluids for lubricant deposition. HFEs are volatile compounds and will be released into the atmosphere during its use. In the atmosphere, photochemical oxidation of HFEs will lead to the formation of fluorinated esters and fluorinated formates. The atmospheric fate of these products is unknown at the present. To improve their understanding of the atmospheric chemistry of esters the authors have studied the atmospheric chemistry of 2,2,2-trifluoroethyltrifluoroacetate CF{sub 3}C(O)OCH{sub 2}CF{sub 3} (bp = 55.0 C). This compound provides insight into the behavior of alkyl, alkyl peroxy, and alkoxy radicals formed {alpha} to the ester functionality. The atmospheric fate of CF{sub 3}C(O)OCH(O{sup {sm_bullet}})CF{sub 3} radicals was investigated in a FTIR smog chamber. Three loss processes for the CF{sub 3}C(O)OCH(O{sup {sm_bullet}})CF{sub 3} radicals were identified at 296 K and 700 Torr total pressure, reaction with O{sub 2} to form CF{sub 3}C(O)OC(O)CF{sub 3}, {alpha}-rearrangement to form CF{sub 3}C(O){sm_bullet} radicals and CF{sub 3}C(O)OH, and decomposition via a mechanism which is unclear. In 760 Torr of air at 296 K, 65% of the CF{sub 3}C(O)OCH(O{sm_bullet})CF{sub 3} radicals react with oxygen, 18% undergo {alpha}-rearrangement, while the fate of the remaining 17% is unclear.

  18. Mutagenicity of Oxygen Free Radicals

    NASA Astrophysics Data System (ADS)

    Moody, Carmella S.; Hassan, Hosni M.

    1982-05-01

    Paraquat 1,1'-dimethyl-4,4'-bipyridinium dichloride) was used as an intracellular generator of oxygen free radicals and was found to be highly mutagenic for Salmonella typhimurium. It caused both base-pair substitution and frameshift mutations. Paraquat was much more toxic and mutagenic in a simple nutritionally restricted medium than in a rich complex medium. The mutagenicity of paraquat was dependent upon the presence of a supply of both electrons and oxygen. Cells containing high levels of superoxide dismutase (superoxide:superoxide oxidoreductase, EC 1.15.1.1) were more resistant to the toxicity and the mutagenicity of paraquat than were cells containing normal levels of this enzyme. The mutagenicity of paraquat thus appears to be due to its ability to exacerbate the intracellular production of superoxide radicals.

  19. Geoscientists and the Radical Middle

    NASA Astrophysics Data System (ADS)

    Tinker, S. W.

    2015-12-01

    Addressing the great challenges facing society requires industry, government, and academia to work together. I call this overlap space, where compromises are made and real solutions determined, the Radical Middle. Radical because it can appear at times as if the loudest and most publicly influential voices lie outside of the actual solution space, content to provoke but not problem-solve. One key area where geoscientists can play a lead role in the Radical Middle is in the overlap between energy, the environment, and the economy. Globally, fossil fuels still represent 85% of the aggregate energy mix. As existing conventional oil and natural-gas reservoir production continues to slowly decline, unconventional reservoirs, led today by shale and other more expensive resources, will represent a growing part of the oil and gas production mix. Many of these unconventional reservoirs require hydraulic fracturing. The positive economic impact of hydraulic fracturing and associated natural gas and oil production on the United States economy is well documented and undeniable. Yet there are environmental concerns about fracking, and some states and nations have imposed moratoria. This energy-environment-economy space is ideal for leadership from the geosciences. Another such overlap space is the potential for geoscience leadership in relations with China, whose economy and global presence continue to expand. Although China is building major hydropower and natural-gas power plants, as well as nuclear reactors, coal is still king—with the associated environmental impacts. Carbon sequestration—onshore in brine and to enhance oil recovery, as well as offshore—could prove viable. It is vital that educated and objective geoscientists from industry, government, and academia leave their corners and work together in the Radical Middle to educate the public and develop and deliver balanced, economically sensible energy and environmental strategies.

  20. Radical Islam in East Africa

    DTIC Science & Technology

    2009-01-01

    carrying out operations. The documents paint a portrait of al-Qaeda cells operating freely in Kenya without concern about being monitored or detained...against Ethiopian Christians.80 For the United States, the Ethiopian occupation has removed the immediate problem of a radical ICU faction sheltering...the U.S. decision to support the Ethiopian invasion and occupation of 8 William Reno, review of monograph. 9 International Crisis Group, Counter

  1. Hydroxyl radical detection in vivo

    SciTech Connect

    Chevion, M.; Floyd, R.A.

    1986-05-01

    Hydroxyl radicals have been implicated as the actual species responsible for the deleterious effects of active oxygen in biology. However, in most cases, its presence has only been inferred by circumstantial evidence. Using electrochemical detection coupled to HPLC separation technique the authors can identify and quantitate (at sub-picomole level) the hydroxylated products of 3 aromatic compounds (phenol, salicylate, and 2-deoxy-guanosine) as a direct measure of hydroxyl radical formation. Firstly, the authors showed that mixing ascorbate with copper ions (in the absence of presence of a protein) yields catechols, dihydroxybenzoic acids and 8-OH-deoxy-guanosine (8-OHdG). This approach has been used to study the formation of OH in vivo. Human granulocytes stimulated with TPA showed that 8-OHdG was formed in the cellular DNA at high levels (one 8-OHdG/800 DNA bases). Unstimulated granulocytes contained 8-OHdG below detection level. Formation of 8-OHdG in the TPA-stimulated granulocytes DNA was decreased by the addition of SOD and catalase. Using salicylate as an in vivo scavenger of hydroxyl radicals the authors showed that the level of trapped-dihydroxybenzoic acids is increased approx.8 and approx.3 fold in the lungs and liver of paraquat-poisoned mice, respectively, as compared to normal animals. Similarly, the detected level of dihydroxybenzoic acids in the hearts of adriamycin-treated rats was increased over 100-fold as compared to the hearts of control animals.

  2. A radical way to burn

    SciTech Connect

    Ashley, S.

    1996-08-01

    By manipulating chamber geometries as well as engine cycle pressures and timing, engineers are exploiting a long-obscure technology known as activated radical combustion. Piston-driven internal combustion engines generally come in two varieties: compression-ignited diesels and spark-ignited gasoline power plants. There, is however, a third way to initiate burning of the fuel-air mixture. The technique--variously called radical ignition (RI), activated radical (AR) combustion, Toyota-Soken combustion, and active thermo-atmosphere combustion--is not exactly new, but only recently have engineers begun to exploit the process in practical power plants. These new units include a lightweight two-stroke racing-motorcycle engine, truck diesels with reduced soot output, and lean-burn spark-ignited car engines. This long-obscure combustion process is based on a range of specialized chemical kinetic and physical acoustic techniques developed over decades. Engineers manipulate fundamental combustion parameter such as chamber geometries, valving and porting configurations, and engine cycle pressures and timing to foster the formation of certain highly reactive chemical species that lower the fuel-air mixture`s flash point so that even modest compression make sit self-ignite. These chemical initiators are then retained into the next cycle to start combustion, allowing the engineer to run stably with no spark.

  3. Radical scavengers from heavy hydrocarbons

    SciTech Connect

    Kubo, Junichi

    1996-10-01

    The hydrogen-donating properties of some hydrocarbons form the basis for processes such as coal liquefaction and heavy oil upgrading. However, these hydrocarbons have seldom been used for other purposes, because their potential applications have not been well recognized. Research has indicated that these hydrogen-donating hydrocarbons can be used in important reactions as radical scavengers and have properties particular to those of pure hydrocarbons without functional groups containing heteroatoms. Over years of study researchers have found that pure hydrocarbons with radical-scavenging effects nearly as high as those in conventional hindered phenolic antioxidants can be produced from petroleum, and these hydrogen-donating hydrocarbons exhibit such effects even in oxidative atmospheres (i.e., they function as antioxidants). He has also shown that these mixtures have some properties particular to pure hydrocarbons without functional groups containing heteroatoms, and they`ve seen that a mechanism based on the steric effects appears when these hydrocarbons are used in heavy oil hydroprocessing. Hydrogen-donating hydrocarbons should be a viable resource in many applications. In this article, he presents radical-scavenging abilities, characteristics as pure hydrocarbons, and applications on the basis of the studies.

  4. Chemistry of The Oio Radical

    NASA Astrophysics Data System (ADS)

    Joseph, M.; Ashworth, S. H.; Plane, J. M. C.

    This paper will describe a laboratory study of the chemistry that the OIO radical under- goes in the marine boundary layer. The radical was produced by the pulsed photolysis at 193 nm of a N2O/CF3I mixture. The resulting OIO radicals, formed by the self- reaction of IO, were then observed by time-resolved cavity ringdown spectroscopy, using the vibrational bands between 540 and 620 nm. A high resoluting spectral scan found no rotational structure in these bands, indicating that the upper state of this electronic transition is predissociative (lifetime = 150 fs). Ab initio quantum calcula- tions indicate that I + O2 is formed, and this was confirmed by adding a third laser to photolyse OIO as a function of wavelength, with detection of atomic I by resonance fluorescence at 178 nm. This system was also used to measure the absolute absorption cross-section of OIO (1.6 x 10(-17) cm2 at 568 nm). The photodissociation lifetime of OIO is about 0.5 s at midday. Although of minor atmospheric importance, the reac- tions of OIO with NO and OH will also be discussed.

  5. 4.6.1 Acyl and related radicals

    NASA Astrophysics Data System (ADS)

    Beckwith, A. L. J.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  6. 4.5.2.2 Radicals from bridged rings

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  7. Free-radical-mediated DNA binding.

    PubMed Central

    O'Brien, P J

    1985-01-01

    Free-radical metabolites can be generated metabolically by a one-electron reductase-catalyzed reaction or a "peroxidase" catalyzed oxidation or by photoactivation of a wide variety of aromatic xenobiotics. Radicals may also be generated during lipid peroxidation. Some radicals can react with DNA or bind covalently or noncovalently as a dismutation product or as a dimer, trimer or polymeric product. Modification to the DNA can result in single-strand breaks, loss of template activity, and crosslinking. The binding can prevent enzymic digestion. In some cases, the radicals react with oxygen, resulting before conversion to DNA reactive oxygen species. Most radicals probably do not interact with DNA. PMID:3007090

  8. Oxidative stress, free radicals and protein peroxides.

    PubMed

    Gebicki, Janusz M

    2016-04-01

    Primary free radicals generated under oxidative stress in cells and tissues produce a cascade of reactive secondary radicals, which attack biomolecules with efficiency determined by the reaction rate constants and target concentration. Proteins are prominent targets because they constitute the bulk of the organic content of cells and tissues and react readily with many of the secondary radicals. The reactions commonly lead to the formation of carbon-centered radicals, which generally convert in vivo to peroxyl radicals and finally to semistable hydroperoxides. All of these intermediates can initiate biological damage. This article outlines the advantages of the application of ionizing radiations to studies of radicals, with particular reference to the generation of desired radicals, studies of the kinetics of their reactions and correlating the results with events in biological systems. In one such application, formation of protein hydroperoxides in irradiated cells was inhibited by the intracellular ascorbate and glutathione. Copyright © 2015 Elsevier Inc. All rights reserved.

  9. Synthesis and Photophysical and Electroluminescent Properties of Poly(1,4-phenylene–ethynylene)-alt-poly(1,4-phenylene–vinylene)s with Various Dissymmetric Substitution of Alkoxy Side Chains

    PubMed Central

    2016-01-01

    The synthesis and characterization of a set of conjugated polymers, poly(1,4-phenylene–ethynylene)-alt-poly(1,4-phenylene–vinylene)s (PPE–PPVs), with a dissymmetrical configuration (partial or total) of alkoxy side chains is reported. Five new polymers bearing octyloxy and/or octadecyloxy side chains at the phenylene–ethynylene and phenylene–vinylene segments, respectively, were obtained. Two symmetrical substituted polymers were used for comparison. Polymers with weight-average molecular weight, Mw, up to 430 000 g/mol and degree of polymerization between 17 and 322 were obtained by a Horner–Wadsworth–Emmons olefination polycondensation reaction of the respective luminophoric dialdehydes and bisphosphonates. As expected, identical conjugated backbones in all polymers results in very similar photophysical response in dilute solution, with high fluorescence quantum yields between 50% and 80%. In contrast, the thin film properties are dependent on the combinatorial effects of side chain configuration, molecular weight, and film thickness parameters, which are the basis of the resulting comparison and discussion. PMID:26877550

  10. Synthesis and biological evaluation of 14-alkoxymorphinans. 22.(1) Influence of the 14-alkoxy group and the substitution in position 5 in 14-alkoxymorphinan-6-ones on in vitro and in vivo activities.

    PubMed

    Lattanzi, Roberta; Spetea, Mariana; Schüllner, Falko; Rief, Silvia B; Krassnig, Roland; Negri, Lucia; Schmidhammer, Helmut

    2005-05-05

    Novel 14-alkoxy-substituted (e.g. allyloxy, benzyloxy, naphthylmethoxy) morphinan-6-one derivatives were synthesized and biologically evaluated. Compounds 6-9 and 11 displayed affinities in the subnanomolar range to mu opioid receptors which were comparable to 14-O-methyloxymorphone (1) and 14-methoxymetopon (3), and higher than oxymorphone (2). Opioid binding affinity was sensitive to the character and length of the substituent in position 14. In smooth muscle preparations they behaved as potent agonists. Antinociceptive potencies of compounds 6-11 in the hot-plate test after sc administration in mice were considerably greater than the potency of morphine. In the colonic propulsion test, the most potent analgesic compound 7 showed negligible constipating activity at the analgesic dose. These findings provide further evidence that the nature of the substituent at position 14 has a major impact on the abilities of morphinans to interact with opioid receptors. Introduction of a 5-methyl group has no significant effect on in vitro biological activities, but resulted in decreased antinociceptive potency.

  11. Urinary incontinence following radical vulvectomy.

    PubMed

    Reid, G C; DeLancey, J O; Hopkins, M P; Roberts, J A; Morley, G W

    1990-05-01

    Although incontinence has been reported after radical vulvectomy, its relationship to operative technique, anatomy, and treatment has not been defined. Twenty-one patients having vulvectomies for vulvar cancer were prospectively evaluated preoperatively and postoperatively with urodynamic function studies. A portion of the urethra was removed in four patients undergoing radical vulvectomy, and 14 had a vulvectomy excision that came within 1 cm of the distal urethra. Six patients (28%) developed a change of continence, with three developing total incontinence, two stress incontinence, and one urge incontinence. All four patients who had a portion of the urethra excised developed stress or total incontinence. The other two patients with incontinence (one total, one urge) had the vulvectomy excision that came close to the urethra. No patient had a change in continence when surgery did not involve or come close to the urethra. When the four patients with a distal urethral resection were compared with patients in whom the urethra was not excised, there was a significant decrease postoperatively in functional urethral length (P less than .0001), anatomical urethral length (P less than .0001), and distal urethral pressure transmission ratios in Q3 (P = .004), Q4 (P = .02), and Q5 (P = .005); but no difference in urethral support (Q-tip test), flow rates, residual urine, bladder capacity, maximal urethral pressure, resting closure pressure, or squeeze pressure. Histologic examination of urethral specimens demonstrated that a portion of the compressor urethrae muscle was often excised. Radical vulvectomy by itself does not cause incontinence, but it would appear that removal of a portion of the urethra increases the chance of incontinence.(ABSTRACT TRUNCATED AT 250 WORDS)

  12. Iron and iron derived radicals

    SciTech Connect

    Borg, D.C.; Schaich, K.M.

    1987-04-01

    We have discussed some reactions of iron and iron-derived oxygen radicals that may be important in the production or treatment of tissue injury. Our conclusions challenge, to some extent, the usual lines of thought in this field of research. Insofar as they are born out by subsequent developments, the lessons they teach are two: Think fastexclamation Think smallexclamation In other words, think of the many fast reactions that can rapidly alter the production and fate of highly reactive intermediates, and when considering the impact of competitive reactions on such species, think how they affect the microenvironment (on the molecular scale) ''seen'' by each reactive molecule. 21 refs., 3 figs., 1 tab.

  13. Aromatic-radical oxidation chemistry

    SciTech Connect

    Glassman, I.; Brezinsky, K.

    1993-12-01

    The research effort has focussed on discovering an explanation for the anomalously high CO{sub 2} concentrations observed early in the reaction sequence of the oxidation of cyclopentadiene. To explain this observation, a number of plausible mechanisms have been developed which now await experimental verification. One experimental technique for verifying mechanisms is to probe the reacting system by perturbing the radical concentrations. Two forms of chemical perturbation of the oxidation of cyclopentadiene were begun during this past year--the addition of NO{sub 2} and CO to the reacting mixture.

  14. Laser spectroscopy of hydrocarbon radicals

    SciTech Connect

    Chen, P.

    1993-12-01

    The author reports the application of supersonic jet flash pyrolysis to the specific preparation of a range of organic radicals, biradicals, and carbenes in a skimmed molecular beam. Each species was produced cleanly and specifically, with little or no secondary reactions by the thermal dissociation of appropriately designed and synthesized organic precursors. Photoelectron spectra of the three isomeric C{sub 3}H{sub 2} carbenes, ortho-benzyne, and the {alpha},3-dehydrotoluene biradical, were used to establish adiabatic ionization potentials for use in thermochemical determinations.

  15. Neuroprotective strategies in radical prostatectomy.

    PubMed

    Schiff, Jonathan D; Mulhall, John P

    2005-01-01

    In this section, authors from New York give their views on the various neuroprotective strategies for patients having a radical prostatectomy, such as the use of nerve grafts and other approaches. A joint study from Korea, the USA, Canada and the UK is presented in a paper on the importance of patient perception in the clinical assessment and management of BPH. There is also a review of robotic urological surgery. Finally, authors from New York give a review on the life of Isaac Newton. This is a new historical review in the journal, but one that will be of general interest.

  16. Atmospheric Sink of (E)-3-Hexen-1-ol, (Z)-3-Hepten-1-ol, and (Z)-3-Octen-1-ol: Rate Coefficients and Mechanisms of the OH-Radical Initiated Degradation.

    PubMed

    Gibilisco, Rodrigo G; Blanco, María B; Bejan, Iustinian; Barnes, Ian; Wiesen, Peter; Teruel, Mariano A

    2015-07-07

    A kinetic study of the gas-phase reactions of OH radicals with three unsaturated biogenic alcohols, (E)-3-hexen-1-ol, (Z)-3-hepten-1-ol, and (Z)-3-octen-1-ol, has been performed. The rate coefficients obtained are (in units of 10(-10) cm(3) molecule(-1) s(-1)) k1 (OH + (E)-CH2(OH)CH2CH═CHCH2CH3) = (1.14 ± 0.14), k2 (OH + (Z)-CH2(OH)CH2CH═CHCH2CH2CH3) = (1.28 ± 0.23), and k3 (OH + (Z)-CH2(OH)CH2CH═CHCH2CH2CH2CH3) = (1.49 ± 0.35). In addition, a product study on the reactions of OH with (E)-3-hexen-1-ol and (Z)-3-hepten-1-ol is reported. All the experiments were performed at (298 ± 2) K and 1 atm of NOx-free air in a 1080 L photoreactor with in situ FTIR detection of organics. This work constitutes the first kinetic study of the reactions of OH radicals with (Z)-3-hepten-1-ol and (Z)-3-octen-1-ol as well as the first determination of the fate of the hydroxy alkoxy radicals formed in the title reactions. An analysis of the available rates of addition of OH and Cl to the double bond of different unsaturated alcohols at 298 K has shown that they can be related by the expression log kOH = (0.29 ± 0.04) log kCl - 10.8. The atmospheric lifetimes of the alcohols studies were estimated to be around 1 h for reaction with OH radicals. The products formed in the title reactions are mainly carbonylic compounds that can contribute to the formation of ozone and PANs-type compounds in the troposphere.

  17. Bioinspired terpene synthesis: a radical approach.

    PubMed

    Justicia, José; Álvarez de Cienfuegos, Luis; Campaña, Araceli G; Miguel, Delia; Jakoby, Verena; Gansäuer, Andreas; Cuerva, Juan M

    2011-07-01

    This tutorial review highlights the development of radical-based bioinspired synthesis of terpenes from the initial proposal to the development of modern catalytic methods for performing such processes. The power of the radical approach is demonstrated by the straightforward syntheses of many natural products from readily available starting materials. The efficiency of these processes nicely complements the described cationic polyolefin cyclisations and even suggests that modern radical methods provide means to improve upon nature's synthetic pathways.

  18. Emergence of oxyl radicals as selective oxidants.

    PubMed

    Ramasarma, T

    2012-10-01

    Hydroxyl radicals (HO*) are derived in Fenton reaction with ferrous salt and H2O2 in acid medium, and at neutral pH, metal-oxyl radicals (M-O*) predominate. Evidence is accumulating that M-O* radicals are also active in oxidation reactions, in addition to metal-oxo (M=O) now shown in many publications. Reactivity of these radicals gives selective oxidized products useful in cellular activities, in contrast to purported indiscriminate cell damage by hydroxyl radicals. Reactions with vanadium compounds, such as diperoxovanadate, peroxo-bridged mixed valency divanadate, vanadium-oxyl radical, tetravalent vanadyl and decavanadate illustrates selective gain in oxidative capacity of oxo- and oxyl- species. Occurrence of ESR signals typical of hydroxyl radicals is demonstrated in cell homogenates and tissue perfusates treated with spin trap agents. It is known for a long time lipid peroxides are formed in tissue microsomal systems exclusively in presence of salts of iron, among many metals tested. Oxygen and a reducing agent, ascorbate (non-enzymic) or NADPH (enzymic) are required to produce 'ferryl', the chelated Fe=O active form (possibly Fe-O* and Fe-O-O-Fe ?) for the crucial step of H-atom abstraction. Yet literature is replete with unsupported affirmations that hydroxyl radicals initiate lipid peroxidation, an unexplained fixation of mindset. The best-known *OH generator, a mixture of ferrous salt and H2O2, does not promote lipid peroxidation, nor do the many hydroxyl radical quenching agents stop it. The availability of oxo and oxyl-radical forms with transition metals, and also with non metals, P, S, N and V, calls for expansion of vision beyond superoxide and hydroxyl radicals and explore functions of multiple oxygen radicals for their biological relevance.

  19. Quantitative determination of atmospheric hydroperoxyl radical

    DOEpatents

    Springston, Stephen R.; Lloyd, Judith; Zheng, Jun

    2007-10-23

    A method for the quantitative determination of atmospheric hydroperoxyl radical comprising: (a) contacting a liquid phase atmospheric sample with a chemiluminescent compound which luminesces on contact with hydroperoxyl radical; (b) determining luminescence intensity from the liquid phase atmospheric sample; and (c) comparing said luminescence intensity from the liquid phase atmospheric sample to a standard luminescence intensity for hydroperoxyl radical. An apparatus for automating the method is also included.

  20. Laser induced photoluminescence spectroscopy of cometary radicals

    NASA Technical Reports Server (NTRS)

    Jackson, W. M.; Cody, R. J.; Sabety-Dzvonik, M.

    1976-01-01

    Flash photolysis together with laser excitation of the product fragments was used in laboratory studies of cometary radicals. The LIPS method has been applied to the CN radical to determine: (1) Radiative lifetimes of individual rotational levels in the zeroth vibrational level of the B state; (2) energy partitioning during photodissociation of C2N2; and (3) vibrational and rotational excitation during formation of CN radicals in the photodissociation of dicyanoacetylene.

  1. The tyrosyl free radical in ribonucleotide reductase.

    PubMed Central

    Gräslund, A; Sahlin, M; Sjöberg, B M

    1985-01-01

    The enzyme, ribonucleotide reductase, catalyses the formation of deoxyribonucleotides from ribonucleotides, a reaction essential for DNA synthesis in all living cells. The Escherichia coli ribonucleotide reductase, which is the prototype of all known eukaryotic and virus-coded enzymes, consists of two nonidentical subunits, proteins B1 and B2. The B2 subunit contains an antiferromagnetically coupled pair of ferric ions and a stable tyrosyl free radical. EPR studies show that the tyrosyl radical, formed by loss of ferric ions and a stable tyrosyl free radical. EPR studies show that the tyrosyl radical, formed by loss of an electron, has its unpaired spin density delocalized in the aromatic ring of tyrosine. Effects of iron-radical interaction indicate a relatively close proximity between the iron center and the radical. The EPR signal of the radical can be studied directly in frozen packed cells of E. coli or mammalian origin, if the cells are made to overproduce ribonucleotide reductase. The hypothetic role of the tyrosyl free radical in the enzymatic reaction is not yet elucidated, except in the reaction with the inhibiting substrate analogue 2'-azido-CDP. In this case, the normal tyrosyl radical is destroyed with concomitant appearance of a 2'-azido-CDP-localized radical intermediate. Attempts at spin trapping of radical reaction intermediates have turned out negative. In E. coli the activity of ribonucleotide reductase may be regulated by enzymatic activities that interconvert a nonradical containing form and the fully active protein B2. In synchronized mammalian cells, however, the cell cycle variation of ribonucleotide reductase, studied by EPR, was shown to be due to de novo protein synthesis. Inhibitors of ribonucleotide reductase are of medical interest because of their ability to control DNA synthesis. One example is hydroxyurea, used in cancer therapy, which selectively destroys the tyrosyl free radical. PMID:3007085

  2. Long-lived radical cation salts obtained by interaction of monocyclic arenes with niobium and tantalum pentahalides at room temperature: EPR and DFT studies.

    PubMed

    Marchetti, Fabio; Pampaloni, Guido; Pinzino, Calogero

    2013-10-04

    The 1:3 reactions of the alkoxy arenes 1,4-(MeO)2 C6 H4 and 1,4-F2 -2,5-(MeO)2 C6 H2 with TaF5 in chloroform at 40-50 °C resulted in formation in about 35 % yield of the long-lived radical cation salts [1,4-(MeO)2 C6 H4 ][Ta2 F11 ] (2 a) and [1,4-F2 -2,5-(MeO)2 C6 H2 ][Ta2 F11 ] (2 b), respectively. The non-alkoxy-substituted [arene][M2 X11 ] [M=Ta, X=F: arene=C6 H5 Me (2 c), 1,4-C6 H4 Me2 (2 d), C6 H5 F (2 e), C6 H5 NO2 (2 f); M=Nb, X=F: arene=C6 H5 Me (4 a), 1,4-C6 H4 Me2 (4 b), C6 H5 F (4 c), C6 H5 NO2 (4 d); M=Ta, X=Cl: arene=1,4-C6 H4 Me2 (5)] were obtained from the 3:1 reactions of MX5 with the appropriate arene in chloroform at temperatures in the range 40-90 °C. Compounds 2-5 were detected by EPR spectroscopy (in CHCl3 ) at room temperature, and their gas-phase structures were optimized by DFT calculations. Formation of the M(IV) species [MX4 (NCMe)2 ] [M=Ta, X=F (3 a); M=Nb, X=F (3 b); M=Ta, X=Cl (3 c)] was ascertained by EPR spectroscopy on solutions obtained by treatment of the reaction mixtures with acetonitrile. Non-selective reactions occurred upon combination of 1,4-F2 -2,5-(MeO)2 C6 H2 with AgNbF6 (in CH2 Cl2 ) and 1,4-(MeO)2 C6 H4 with SbF5 . Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Formation of free radicals during phacoemulsification.

    PubMed

    Holst, A; Rolfsen, W; Svensson, B; Ollinger, K; Lundgren, B

    1993-04-01

    During phacoemulsification cavitation bubbles are formed. These bubbles are believed to be one source of damage to corneal endothelium seen after phacoemulsification. Free radicals are induced whenever cavitation bubbles implode. The aim of this study was to confirm the initiation of free radicals by phacoemulsification and to correlate the power of ultrasound in the phacoemulsification process to the amount of free radicals formed, using both in vitro and in vivo techniques. The formation of free radicals was determined by adding luminol to a buffer and measuring the chemoluminescence in vitro and in rabbit eyes (Lumacounter 2080 or a single-photon-counting apparatus) during phacoemulsification. The data obtained show that free radicals are formed during phacoemulsification and that the amount of free radicals correlates with the power of ultrasound. Furthermore, the radical formation could be inhibited by the radical scavengers SOD, Healon and Healon GV. These results were achieved both in vitro in the test tube and in vivo in rabbit eyes. By showing that the addition of SOD to the irrigation buffer during phacoemulsification decreases the corneal endothelial cell damage, we show that free radicals could have a role in postoperative complications seen clinically.

  4. Physiological aspects of free-radical reactions.

    PubMed Central

    Yamazaki, I; Tamura, M; Nakajima, R; Nakamura, M

    1985-01-01

    Enzymes which catalyze the formation of free radicals in vitro will catalyze similar reactions in vivo. We believe that the formation of some kinds of free radicals has definite physiological meanings in metabolism. In this sense, the enzymes forming such free radicals are concluded to be in evolutionally advanced states. Elaborated structure and function of enzymes such as horseradish peroxidase and microsomal flavoproteins support the idea. Deleterious and side reactions caused by free radicals are assumed to be minimized in vivo by localizing the reactions, but this assumption should be verified by future studies. PMID:3007098

  5. Dynamics of Radical-Mediated Enzyme Catalyses

    NASA Astrophysics Data System (ADS)

    Warncke, Kurt

    1997-11-01

    An emergent class of enzymes harnesses the extreme reactivity of electron-deficient free radical species to perform some of the most difficult reactions in biology. The regio- and stereo-selectivity achieved by these enzymes defies long-held ideas that radical reactions are non-specific. The common primary step in these catalyses is metal- or metallocenter-assisted generation of an electron-deficient organic "initiator radical". The initiator radical abstracts a hydrogen atom from the substrate, opening a new reaction channel for rearrangement to the product. Our aim is to elucidate the detailed molecular mechanisms of the radical pair separation and radical rearrangement steps. Radical pair separation and substrate radical rearrangement are tracked by using time-resolved (10-7 to 10-3 s) techniques of pulsed-electron paramagnetic resonance spectroscopy (FT-EPR, ESEEM). Synchronous time-evolution of the reactions is attained by triggering with a visible laser pulse. Transient non-Boltzmann population of the states of the spin-coupled systems, and resultant electron spin polarization, facilitates study at or near room temperature under conditions where the enzymes are operative. The systems examined include ethanolamine deaminase, a vitamin B12 coenzyme-dependent enzyme, ribonucleotide reductase and photosynthetic reaction centers. The electronic and nuclear structural and kinetic information obtained from the pulsed-EPR studies is used to address how the initiator radicals are stabilized against deleterious recombination with the metal, and to distinguish the participation of concerted versus sequential rearrangement pathways.

  6. Kinetics Studies of Radical-Radical Reactions: The NO2 + N2H3 System

    DTIC Science & Technology

    2013-10-01

    investigating the kinetics of this elementary reaction . 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES...Viewgraph 3. DATES COVERED (From - To) September 2013- October 2013 4. TITLE AND SUBTITLE Kinetics Studies of Radical-Radical Reactions (I): The NO2...characteristics in relevant operating environments. Here we report theoretical results obtained on the prototypical radical- radical reaction : NO2 + N2H3

  7. Peroxy radical measurements with NCAR's chemical amplifier

    NASA Technical Reports Server (NTRS)

    Cantrell, Christopher; Shetter, Richard; Calvert, Jack G.

    1994-01-01

    The present NCAR instrument for HO2/RO2 measurements has been described previously. It is based on the reactions involving HO2, RO2, and HO radicals with CO and NO. Since (HO2) + (RO2) + (HO) is much greater than (HO) for most atmospheres, it is useful as a peroxy radical detector. Operation of the instrument depends on the creation of a chemical chain reaction which is initiated as HO2 and RO2 radicals in ambient air encounter added NO gas; this forms an NO2 molecule and an HO or RO radical: HO2(RO2) + NO yields HO(RO) + NO2. RO radicals react relatively efficiently with O2 to form an HO2 radical, and subsequently an HO-radical, by reaction with NO. CO gas added to the reaction chamber during part of the operating cycle, recycles the HO to HO2; HO + CO (+O2) yields HO2 + CO2. The reaction sequence may form several hundred NO2 molecules per HO2 (RO2) originally present, before chain termination occurs. The added CO is replaced by N2 addition periodically so that the chain reaction is suppressed, and a 'blank' signal resulting from NO2, O3 and possibly other NO2-forming species (non-chain processes) in ambient air is recorded. The difference between the signal with and without CO is proportional to the peroxy radical concentration. The NO2 produced is monitored using a sensitive luminol chemiluminescence detector system. In the NCAR instrument the length of the amplification chain is determined using a stable source of HO2 radicals (H2O2 thermal decomposition); the ratio of the signal seen with CO present to that with N2 present gives the sensitivity of the instrument to HO2 (molecules of NO2 formed/peroxy radical). The instrument is automated to carry out in hourly repeated cycles: (1) chain length determination; (2) NO2 calibration; and (3) linearity check on the response of signals. One minute averages of signals are normally recorded. The sensitivity of the instrument to detect peroxy radicals is in the pptv range. The present instrument has operated

  8. Peroxy radical measurements with NCAR's chemical amplifier

    NASA Technical Reports Server (NTRS)

    Cantrell, Christopher; Shetter, Richard; Calvert, Jack G.

    1994-01-01

    The present NCAR instrument for HO2/RO2 measurements has been described previously. It is based on the reactions involving HO2, RO2, and HO radicals with CO and NO. Since (HO2) + (RO2) + (HO) is much greater than (HO) for most atmospheres, it is useful as a peroxy radical detector. Operation of the instrument depends on the creation of a chemical chain reaction which is initiated as HO2 and RO2 radicals in ambient air encounter added NO gas; this forms an NO2 molecule and an HO or RO radical: HO2(RO2) + NO yields HO(RO) + NO2. RO radicals react relatively efficiently with O2 to form an HO2 radical, and subsequently an HO-radical, by reaction with NO. CO gas added to the reaction chamber during part of the operating cycle, recycles the HO to HO2; HO + CO (+O2) yields HO2 + CO2. The reaction sequence may form several hundred NO2 molecules per HO2 (RO2) originally present, before chain termination occurs. The added CO is replaced by N2 addition periodically so that the chain reaction is suppressed, and a 'blank' signal resulting from NO2, O3 and possibly other NO2-forming species (non-chain processes) in ambient air is recorded. The difference between the signal with and without CO is proportional to the peroxy radical concentration. The NO2 produced is monitored using a sensitive luminol chemiluminescence detector system. In the NCAR instrument the length of the amplification chain is determined using a stable source of HO2 radicals (H2O2 thermal decomposition); the ratio of the signal seen with CO present to that with N2 present gives the sensitivity of the instrument to HO2 (molecules of NO2 formed/peroxy radical). The instrument is automated to carry out in hourly repeated cycles: (1) chain length determination; (2) NO2 calibration; and (3) linearity check on the response of signals. One minute averages of signals are normally recorded. The sensitivity of the instrument to detect peroxy radicals is in the pptv range. The present instrument has operated

  9. Fourier Transform Infrared Spectroscopy of Radicals

    NASA Astrophysics Data System (ADS)

    Rohrs, Henry William

    Radicals occur in many areas of chemistry as they are intermediates in reactions. They arise in combustion processes and several atmospheric phenomena and they have been located in interstellar space. In order to elucidate these areas of chemistry it is important to understand radicals. This is no easy task as these species are short -lived. This work focuses on determining the structure and bonding of these species using experimental measurements. Since it is specifically aimed at gas phase radicals, spectroscopy is the tool of choice for probing the radicals. This work developed a general technique for taking the rotation-vibration spectra of jet-cooled radicals. The work was based in the infrared since the desired structural information can be obtained in this region of the spectrum. The jet-cooling simplifies the enormous task of spectral assignment. A BOMEM FTIR was optically coupled to a supersonic expansion of radicals streaming from a homemade silicon carbide pyrolysis nozzle. This nozzle was heated to wall temperatures of 1500 K. A suitable organic precursor was entrained in an inert carrier gas, usually helium. Conditions were adjusted such that this precursor was nearly completely decomposed to produce high number densities of the radical of choice. The gas flows were adjusted such that the time for recombination and other radical destroying reactions were minimized. The first radical species observed was nitric oxide, NO, made from the pyrolysis of alkyl nitrites. Spectra with rotational temperatures from 20 K to 80 K were observed. This proved the viability of the method. It also demonstrated that fluid dynamics modeling and a separate photoionization mass spectrometry experiment would be invaluable aids in maximizing radical concentrations since the best chance of recording the spectra is when the most radicals are present.

  10. Photoionisation of the tropyl radical

    PubMed Central

    Fischer, Kathrin H; Bodi, Andras

    2013-01-01

    Summary We present a study on the photoionisation of the cycloheptatrienyl (tropyl) radical, C7H7, using tunable vacuum ultraviolet synchrotron radiation. Tropyl is generated by flash pyrolysis from bitropyl. Ions and electrons are detected in coincidence, permitting us to record mass-selected photoelectron spectra. The threshold photoelectron spectrum of tropyl, corresponding to the X + 1A1’ ← X 2E2” transition, reveals an ionisation energy of 6.23 ± 0.02 eV, in good agreement with Rydberg extrapolations, but slightly lower than the value derived from earlier photoelectron spectra. Several vibrations can be resolved and are reassigned to the C–C stretch mode ν16 + and to a combination of ν16 + with the ring breathing mode ν2 +. Above 10.55 eV dissociative photoionisation of tropyl is observed, leading to the formation of C5H5 + and C2H2. PMID:23616813

  11. Students' Ideas and Radical Constructivism

    NASA Astrophysics Data System (ADS)

    Sánchez Gómez, Pedro J.

    2016-08-01

    In this article, I study, from the point of view of the analytic philosophy of mind, the compatibility of students' ideas studies (SIS) with radical constructivism (RC). I demonstrate that RC is based on a psychology of narrow mental states; that is, the idea that the mental content of an individual can be fully characterised without any reference external to her or him. I show that this fact imposes some severe restrictions to SIS to be incorporated into RC. In particular, I argue that only qualitative studies can comply with the requirement of narrowness. Nevertheless, I propose that quantitative works can be employed as sources of types in order to study token actual students. I use this type-token dichotomy to put forward an outline of a theory of the relation between school contents and mental contents. In this view, token mental contents regarding a given topic can be defined, and probed, only by resorting to typical school contents.

  12. DNA Binding Hydroxyl Radical Probes.

    PubMed

    Tang, Vicky J; Konigsfeld, Katie M; Aguilera, Joe A; Milligan, Jamie R

    2012-01-01

    The hydroxyl radical is the primary mediator of DNA damage by the indirect effect of ionizing radiation. It is a powerful oxidizing agent produced by the radiolysis of water and is responsible for a significant fraction of the DNA damage associated with ionizing radiation. There is therefore an interest in the development of sensitive assays for its detection. The hydroxylation of aromatic groups to produce fluorescent products has been used for this purpose. We have examined four different chromophores which produce fluorescent products when hydroxylated. Of these, the coumarin system suffers from the fewest disadvantages. We have therefore examined its behavior when linked to a cationic peptide ligand designed to bind strongly to DNA.

  13. Hydroxyl radical reaction with trans-resveratrol: initial carbon radical adduct formation followed by rearrangement to phenoxyl radical.

    PubMed

    Li, Dan-Dan; Han, Rui-Min; Liang, Ran; Chen, Chang-Hui; Lai, Wenzhen; Zhang, Jian-Ping; Skibsted, Leif H

    2012-06-21

    In the reaction between trans-resveratrol (resveratrol) and the hydroxyl radical, kinetic product control leads to a short-lived hydroxyl radical adduct with an absorption maximum at 420 nm and a lifetime of 0.21 ± 0.01 μs (anaerobic acetonitrile at 25 °C) as shown by laser flash photolysis using N-hydroxypyridine-2(1H)-thione (N-HPT) as a "photo-Fenton" reagent. The transient spectra of the radical adduct are in agreement with density functional theory (DFT) calculations showing an absorption maximum at 442 or 422 nm for C2 and C6 hydroxyl adducts, respectively, and showing the lowest energy for the transition state leading to the C2 adduct compared to other radical products. From this initial product, the relative long-lived 4'-phenoxyl radical of resveratrol (τ = 9.9 ± 0.9 μs) with an absorption maximum at 390 nm is formed in a process with a time constant (τ = 0.21 ± 0.01 μs) similar to the decay constant for the C2 hydroxyl adduct (or a C2/C6 hydroxyl adduct mixture) and in agreement with thermodynamics identifying this product as the most stable resveratrol radical. The hydroxyl radical adduct to phenoxyl radical conversion with concomitant water dissociation has a rate constant of 5 × 10(6) s(-1) and may occur by intramolecular hydrogen atom transfer or by stepwise proton-assisted electron transfer. Photolysis of N-HPT also leads to a thiyl radical which adds to resveratrol in a parallel reaction forming a sulfur radical adduct with a lifetime of 0.28 ± 0.04 μs and an absorption maximum at 483 nm.

  14. Free Radical Mechanisms in Autoxidation Processes.

    ERIC Educational Resources Information Center

    Simic, Michael G.

    1981-01-01

    Discusses the use of steady-state radiation chemistry and pulse radiolysis for the generation of initial free radicals and formation of peroxy radicals in the autoxidation process. Provides information regarding the autoxidation process. Defines autoxidation reactions and antioxidant action. (CS)

  15. Radical Constructivism: Between Realism and Solipsism.

    ERIC Educational Resources Information Center

    Martinez-Delgado, Alberto

    2002-01-01

    Criticizes radical constructivism of the Glasersfeld type, pointing out some contradictions between the declared radical principles and their theoretical and practical development. Suggests the possibility of an ideological substratum in the construction and hegemonic success of subjective constructivism, and briefly advances an alternative…

  16. THE RADICAL OF A JORDAN ALGEBRA

    PubMed Central

    McCrimmon, Kevin

    1969-01-01

    In this paper we define a Jacobson radical for Jordan algebras analogous to that for associative algebras and show that it enjoys many of the properties of the associative radical. We then relate the corresponding notion of “semisimplicity” to the previously defined notion of “nondegeneracy” (Jacobson, N., these Proceedings, 55, 243-251 (1966)). PMID:16591736

  17. Rearrangement of sulfonamidyl radicals with hydrogen migration

    SciTech Connect

    Troyanskii, E.I.; Lazareva, M.I.; Nikishin, G.I.

    1987-01-20

    One-step outlying oxidative chlorination of alkanesulfonamides by the action of the Na/sub 2/S/sub 2/O/sub 8/-CuCl/sub 2/ system via intermediate sulfonamidyl radicals gives 3- and 4-chloroalkanesulfonamides. Rearrangements of sulfonamidyl radicals with H atom migration from the sulfonyl segment predominates over rearrangement with H atom migration from the amide segment.

  18. Radical Puppets and the Language of Art

    ERIC Educational Resources Information Center

    Asher, Rikki

    2009-01-01

    Radical puppets are puppets with a social message. Radical puppets encourage creative ideas that lead toward understanding global and environmental aspects of society through the "art of the puppet," a phrase coined by American puppeteer Bill Baird (1965). There is a blending of performance and visual art in puppetry. Through radical…

  19. Ideals Adrift: An Educational Approach to Radicalization

    ERIC Educational Resources Information Center

    van San, Marion; Sieckelinck, Stijn; de Winter, Micha

    2013-01-01

    These days, the radicalization of young people is above all viewed as a security risk. Almost all research into this phenomenon has been carried out from a legal, criminological or socio-psychological perspective with a focus on detecting and containing the risks posed by radicalization. In the light of the political developments since September…

  20. Free Radical Mechanisms in Autoxidation Processes.

    ERIC Educational Resources Information Center

    Simic, Michael G.

    1981-01-01

    Discusses the use of steady-state radiation chemistry and pulse radiolysis for the generation of initial free radicals and formation of peroxy radicals in the autoxidation process. Provides information regarding the autoxidation process. Defines autoxidation reactions and antioxidant action. (CS)

  1. Victimology: A Consideration of the Radical Critique.

    ERIC Educational Resources Information Center

    Friedrichs, David O.

    1983-01-01

    Discusses the emergence of a new radical model in criminology and a new subdisciplinary area of concern, victimology, with roots in Marx and Engels' original formulations. Argues that the radical understanding of victimization provides an important corrective to mainstream approaches and broadens the focus of the concept of victimization. (JAC)

  2. Alex Bloom, Pioneer of Radical State Education

    ERIC Educational Resources Information Center

    Fielding, Michael

    2005-01-01

    Alex Bloom is one of the greatest figures of radical state education in England. His approach to "personalised learning" and the development of a negotiated curriculum was immeasurably more profound and more inspiring than anything to emerge thus far from the current DfES. His approach to student voice was much more radical than anything…

  3. Victimology: A Consideration of the Radical Critique.

    ERIC Educational Resources Information Center

    Friedrichs, David O.

    1983-01-01

    Discusses the emergence of a new radical model in criminology and a new subdisciplinary area of concern, victimology, with roots in Marx and Engels' original formulations. Argues that the radical understanding of victimization provides an important corrective to mainstream approaches and broadens the focus of the concept of victimization. (JAC)

  4. Ideals Adrift: An Educational Approach to Radicalization

    ERIC Educational Resources Information Center

    van San, Marion; Sieckelinck, Stijn; de Winter, Micha

    2013-01-01

    These days, the radicalization of young people is above all viewed as a security risk. Almost all research into this phenomenon has been carried out from a legal, criminological or socio-psychological perspective with a focus on detecting and containing the risks posed by radicalization. In the light of the political developments since September…

  5. Radical Behaviorism and Buddhism: Complementarities and Conflicts

    ERIC Educational Resources Information Center

    Diller, James W.; Lattal, Kennon A.

    2008-01-01

    Comparisons have been made between Buddhism and the philosophy of science in general, but there have been only a few attempts to draw comparisons directly with the philosophy of radical behaviorism. The present review therefore considers heretofore unconsidered points of comparison between Buddhism and radical behaviorism in terms of their…

  6. Radical Behaviorism and Buddhism: Complementarities and Conflicts

    ERIC Educational Resources Information Center

    Diller, James W.; Lattal, Kennon A.

    2008-01-01

    Comparisons have been made between Buddhism and the philosophy of science in general, but there have been only a few attempts to draw comparisons directly with the philosophy of radical behaviorism. The present review therefore considers heretofore unconsidered points of comparison between Buddhism and radical behaviorism in terms of their…

  7. Organic chemistry: A radical step forward

    NASA Astrophysics Data System (ADS)

    Zhang, Wenhao; Li, Ang

    2017-02-01

    Free radicals are notorious for unselective coupling reactions; however, the coupling of free radicals generated from acyl tellurides has now been shown to form C-C bonds with remarkable fidelity, which enables easy one-step assembly of densely oxygenated natural product motifs.

  8. Radical Voices; A Film Course Study Guide.

    ERIC Educational Resources Information Center

    Kernan, Margot

    The leftist radical ideas current in the 1960s and 1970s are expressed in the films discussed in this cinema study guide. The radical film takes extreme and avant-garde approaches to the somewhat publicly taboo topics of sex, social issues, and religion. Among the films discussed, I AM CURIOUS (YELLOW) and SOMETHING DIFFERENT show women in their…

  9. Catalytic Radical Domino Reactions in Organic Synthesis.

    PubMed

    Sebren, Leanne J; Devery, James J; Stephenson, Corey R J

    2014-02-07

    Catalytic radical-based domino reactions represent important advances in synthetic organic chemistry. Their development benefits synthesis by providing atom- and step-economical methods to complex molecules. Intricate combinations of radical, cationic, anionic, oxidative/reductive, and transition metal mechanistic steps result in cyclizations, additions, fragmentations, ring-expansions, and rearrangements. This Perspective summarizes recent developments in the field of catalytic domino processes.

  10. Roaming radical pathways for the decomposition of alkanes.

    SciTech Connect

    Harding, L. B.; Klippenstein, S. J.

    2010-01-01

    CASPT2 calculations predict the existence of roaming radical pathways for the decomposition of propane, n-butane, isobutane and neopentane. The roaming radical paths lead to the formation of an alkane and an alkene instead of the expected radical products. The predicted barriers for the roaming radical paths lie {approx}1 kcal/mol below the corresponding radical asymptotes.

  11. Measurement of atmospheric radicals by chemical amplification

    NASA Astrophysics Data System (ADS)

    Arias, Maria Corina

    1998-11-01

    In this work, atmospheric radicals were measured using the chemical amplification technique. To calibrate the chemical amplifier, an UV water photolysis radical source was built and tested. This source proved to be reliable and portable, and capable of delivering radical concentrations within the range of values found in the troposphere. We tested the performance of our instrument at the Peroxy Radical InterComparison Exercise II (PRICE II). In this intercomparison seven chemical amplifiers participated measuring several HO2 and CH3O2 concentrations. Results from this campaign indicate that all of the chemical amplifiers are equally capable of measuring HO2 and CH3O2 radicals from two different radical sources (ICG-HO2 source and UEA- CH3O2 source). The average response towards the ICG and UEA sources were 70% and 45%, respectively. Losses in the delivery system are thought to be responsible for these low responses. Radical measurements were taken at 4 contrasting sites: Atlantic '96 (clean continental), SONTOS '92 and '93 (rural), Calabozo '93 (tropical clean continental), and Pacific '93 (predominantly urban), where maximum ROx concentrations ranged from 17 to 52 pptv. These values are consistent with those found in the literature for similar regions. The measured radical concentrations reflect the interaction between the main production and loss processes at the different sites, as for example ozone photolysis and HNO3 formation. At Calabozo, the combination of moderate O3, low NOx and small Zenith angles resulted in the highest ROx measured. At the Pacific '93 site, O3 is higher, but NOx concentrations are also very high, enhancing the radical loss processes, and explaining the moderate radical concentrations observed. At Atlantic '96 the very low NOx concentration might account for the radical concentrations observed, even in the presence of low O3 concentrations. At SONTOS, the highest ozone concentrations were observed, so we would expect the radical

  12. Intracellular signaling modifications involved in the anti-inflammatory effect of 4-alkoxy-6,9-dichloro[1,2,4]triazolo[4,3-a]quinoxalines on macrophages.

    PubMed

    Ruiz-Alcaraz, Antonio J; Tristán-Manzano, María; Guirado, Antonio; Gálvez, Jesús; Martínez-Esparza, María; García-Peñarrubia, Pilar

    2017-03-01

    Inflammation is part of a complex biological response directed by the immune system to fight pathogens and maintain homeostasis. Dysregulation of the inflammatory process leads to development of chronic inflammatory or autoimmune diseases. Several cell types, such as macrophages, and cytokines such as interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α) are involved in the regulation of inflammation. The important role played by these cytokines as mediators of the inflammatory process and the side effects of current therapies have promoted the search of new therapeutic alternatives. Quinoxalines are important compounds allowing a wide range of chemical modifications in order to provide an extensive repertoire of biological activities. We have previously shown that a series of 4-alkoxy-6,9-dichloro[1,2,4]triazolo[4,3-a]quinoxalines exhibit potent anti-inflammatory activity, inhibiting the production of TNF-α and IL-6. Our aim here was to study the mechanism thereby this series of compounds act upon different intracellular signaling pathways to uncover their potential molecular targets. By using immunoblotting assays, we found that these compounds inhibit ERK 1/2 and JNK/c-Jun cascades, and reduce c-Fos expression, while activate the anti-inflammatory PI3K/Akt route. These results provide further information on their effect upon the intracellular signal transduction mechanisms leading to inhibition of TNF-α and IL-6 secretion. Our results may be of great interest for the pharmaceutical industry, and could be used as a starting point for the development of new and more potent anti-inflammatory drugs derived from the quinoxaline core.

  13. Polymers based on stable phenoxyl radicals for the use in organic radical batteries.

    PubMed

    Jähnert, Thomas; Häupler, Bernhard; Janoschka, Tobias; Hager, Martin D; Schubert, Ulrich S

    2014-05-01

    Polymers with pendant phenoxyl radicals are synthesized and the electrochemical properties are investigated in detail. The monomers are polymerized using ring-opening metathesis polymerization (ROMP) or free-radical polymerization methods. The monomers and polymers, respectively, are oxidized to the radical either before or after the polymerization. These phenoxyl radicals containing polymers reveal a reversible redox behavior at a potential of -0.6 V (vs Ag/AgCl). Such materials can be used as anode-active material in organic radical batteries (ORBs).

  14. Synchrotron threshold photoelectron photoion coincidence spectroscopy of radicals produced in a pyrolysis source: The methyl radical

    NASA Astrophysics Data System (ADS)

    Zhu, Yupeng; Wu, Xiangkun; Tang, Xiaofeng; Wen, Zuoying; Liu, Fuyi; Zhou, Xiaoguo; Zhang, Weijun

    2016-11-01

    We present here a flash pyrolysis source coupled with a threshold photoelectron photoion coincidence (TPEPICO) spectrometer and vacuum ultraviolet synchrotron radiation to investigate the spectroscopy and photochemistry of free radicals. The radicals are produced from pyrolysis in a heated silicon carbide tube, and the TPEPICO scheme provides a strategy to obtain pure spectra of the radicals without contamination from other byproducts. As a representative example, the methyl radical was studied, and its threshold photoelectron spectrum shows a series of umbrella vibrational transitions. The adiabatic ionization energy of the methyl radical was determined to be 9.84 ± 0.01 eV.

  15. Characteristics of Radical Reactions, Spin Rules, and a Suggestion for the Consistent Use of a Dot on Radical Species

    ERIC Educational Resources Information Center

    Wojnarovits, Laszlo

    2011-01-01

    In many chemical reactions, reactive radicals have been shown to be transient intermediates. The free radical character of a chemical species is often, but not always, indicated by adding a superscript dot to the chemical formula. A consistent use of this radical symbol on all species that have radical character is suggested. Free radicals have a…

  16. Radical cation cyclization of 1,5-hexadiene to cyclohexene via the cyclohexane-2,5-diyl radical cation intermediate

    SciTech Connect

    Guo, Q.X.; Qin, X.Z.; Wang, J.T.; Williams, F.

    1988-03-16

    The classical example of a neutral carbon-centered radical cyclization reaction is the regioselective 1,5-ring closure (exocyclization) of the 5-hexenyl radical to the cyclopentylcarbinyl radical. Here the authors report the title reaction, a comparable addition process whereby an ..cap alpha.., omega-diene radical cation reacts by endocyclization and hydrogen shift(s) to produce a cycloolefin radical cation.

  17. Characteristics of Radical Reactions, Spin Rules, and a Suggestion for the Consistent Use of a Dot on Radical Species

    ERIC Educational Resources Information Center

    Wojnarovits, Laszlo

    2011-01-01

    In many chemical reactions, reactive radicals have been shown to be transient intermediates. The free radical character of a chemical species is often, but not always, indicated by adding a superscript dot to the chemical formula. A consistent use of this radical symbol on all species that have radical character is suggested. Free radicals have a…

  18. Structural effects on the reactivity 1,4-dihydropyridines with alkylperoxyl radicals and ABTS radical cation.

    PubMed

    Yáñez, C; López-Alarcón, C; Camargo, C; Valenzuela, V; Squella, J A; Núñez-Vergara, L J

    2004-05-01

    A series of eight commercial C-4 substituted 1,4-dihydropyridines and other synthesized related compounds were tested for direct potential scavenger effect towards alkylperoxyl radicals and ABTS radical cation in aqueous Britton-Robinson buffer pH7.4. A direct quenching radical species was established. The tested 1,4-dihydropyridines were 8.3-fold more reactive towards alkylperoxyl radicals than ABTS cation radical, expressed by their corresponding kinetic rate constants. Furthermore, NPD a photolyte of nifedipine and the C-4 unsubstituted 1,4-DHP were the most reactive derivatives towards alkylperoxyl radicals. The pyridine derivative was confirmed by GC/MS technique as the final product of reaction. In consequence, the reduction of alkylperoxyl and ABTS radicals by 1,4-dihydropyridines involved an electron transfer process. Also, the participation of the hydrogen of the 1-position appears as relevant on the reactivity. Results of reactivity were compared with Trolox.

  19. Halogenated silanes, radicals, and cations

    NASA Astrophysics Data System (ADS)

    Wang, Liming; He, Yi-Liang

    2008-09-01

    Quantum chemistry study has been carried out on the structure and energetics of halogenated silanes, radicals, and cations (SiHxXy0,+1, X = F, Cl, Br; x + y = 1-4). The geometries are optimized at B3LYP/6-31+G(2df,p) level. The adiabatic ionization energiess (IEas), relative energetics of cations, proton affinities (PAs) of silanes, and the enthalpies of formation are predicted using G3(CC) model chemistry. Non-classical ion complex structures are found for hydrogenated cations and transition states connecting classical and non-classical structures are also located. The most stable cations for silylene and silyl radicals have their classical divalent and trivalent structures, and those for silanes have non-classical structures except for SiH3Br+ and SiH2Br2+. The non-classical structures for halosilane cations imply difficulty in experimentally measurement of the adiabatic ionization energies using photoionization or photoelectron studies. For SiH3X, SiH2X2, and SiHX3, the G3(CC) adiabatic IEas to classical ionic structures closest to their neutrals agree better with the photoelectron spectroscopic measurements. The transition states between classical and non-classical structures also hamper the photoionization determination of the appearance energies for silylene cations from silanes. The G3(CC) results for SiHx0,+1 agree excellently with the photoionization mass spectrometric study, and the results for fluorinated and chlorinated species also agree with the previous theoretical predictions at correlation levels from BAC-MP4 to CCSD(T)/CBS. The predicted enthalpy differences between SiH2Cl+, SiHCl2+, and SiCl3+ are also in accordance with previous kinetics study. The G3(CC) results show large discrepancies to the collision-induced charge transfer and/or dissociation reactions involving SiFx+ and SiClx+ ions, for which the G3(CC) enthalpies of formation are also significantly differed from the previous theoretical predictions, especially on SiFx+ (x = 2-4). The G3

  20. Involvement of free radicals in breast cancer.

    PubMed

    Ríos-Arrabal, Sandra; Artacho-Cordón, Francisco; León, Josefa; Román-Marinetto, Elisa; Del Mar Salinas-Asensio, María; Calvente, Irene; Núñez, Maria Isabel

    2013-08-27

    Researchers have recently shown an increased interest in free radicals and their role in the tumor microenvironment. Free radicals are molecules with high instability and reactivity due to the presence of an odd number of electrons in the outermost orbit of their atoms. Free radicals include reactive oxygen and nitrogen species, which are key players in the initiation and progression of tumor cells and enhance their metastatic potential. In fact, they are now considered a hallmark of cancer. However, both reactive species may contribute to improve the outcomes of radiotherapy in cancer patients. Besides, high levels of reactive oxygen species may be indicators of genotoxic damage in non-irradiated normal tissues. The purpose of this article is to review recent research on free radicals and carcinogenesis in order to understand the pathways that contribute to tumor malignancy. This review outlines the involvement of free radicals in relevant cellular events, including their effects on genetic instability through (growth factors and tumor suppressor genes, their enhancement of mitogenic signals, and their participation in cell remodeling, proliferation, senescence, apoptosis, and autophagy processes; the possible relationship between free radicals and inflammation is also explored. This knowledge is crucial for evaluating the relevance of free radicals as therapeutic targets in cancer.

  1. Magnetic fields, radicals and cellular activity.

    PubMed

    Montoya, Ryan D

    2017-01-01

    Some effects of low-intensity magnetic fields on the concentration of radicals and their influence on cellular functions are reviewed. These fields have been implicated as a potential modulator of radical recombination rates. Experimental evidence has revealed a tight coupling between cellular function and radical pair chemistry from signaling pathways to damaging oxidative processes. The effects of externally applied magnetic fields on biological systems have been extensively studied, and the observed effects lack sufficient mechanistic understanding. Radical pair chemistry offers a reasonable explanation for some of the molecular effects of low-intensity magnetic fields, and changes in radical concentrations have been observed to modulate specific cellular functions. Applied external magnetic fields have been shown to induce observable cellular changes such as both inhibiting and accelerating cell growth. These and other mechanisms, such as cell membrane potential modulation, are of great interest in cancer research due to the variations between healthy and deleterious cells. Radical concentrations demonstrate similar variations and are indicative of a possible causal relationship. Radicals, therefore, present a possible mechanism for the modulation of cellular functions such as growth or regression by means of applied external magnetic fields.

  2. Kinetics of Propargyl Radical Dissociation.

    PubMed

    Klippenstein, Stephen J; Miller, James A; Jasper, Ahren W

    2015-07-16

    Due to the prominent role of the propargyl radical for hydrocarbon growth within combustion environments, it is important to understand the kinetics of its formation and loss. The ab initio transition state theory-based master equation method is used to obtain theoretical kinetic predictions for the temperature and pressure dependence of the thermal decomposition of propargyl, which may be its primary loss channel under some conditions. The potential energy surface for the decomposition of propargyl is first mapped at a high level of theory with a combination of coupled cluster and multireference perturbation calculations. Variational transition state theory is then used to predict the microcanonical rate coefficients, which are subsequently implemented within the multiple-well multiple-channel master equation. A variety of energy transfer parameters are considered, and the sensitivity of the thermal rate predictions to these parameters is explored. The predictions for the thermal decomposition rate coefficient are found to be in good agreement with the limited experimental data. Modified Arrhenius representations of the rate constants are reported for utility in combustion modeling.

  3. Orgasmic Dysfunction after Radical Prostatectomy

    PubMed Central

    Ventimiglia, Eugenio; Cazzaniga, Walter; Montorsi, Francesco; Salonia, Andrea

    2017-01-01

    In addition to urinary incontinence and erectile dysfunction, several other impairments of sexual function potentially occurring after radical prostatectomy (RP) have been described; as a whole, these less frequently assessed disorders are referred to as neglected side effects. In particular, orgasmic dysfunctions (ODs) have been reported in a non-negligible number of cases, with detrimental impacts on patients' overall sexual life. This review aimed to comprehensively discuss the prevalence and physiopathology of post-RP ODs, as well as potential treatment options. Orgasm-associated incontinence (climacturia) has been reported to occur in between 20% and 93% of patients after RP. Similarly, up to 19% of patients complain of postoperative orgasm-associated pain, mainly referred pain at the level of the penis. Moreover, impairment in the sensation of orgasm or even complete anorgasmia has been reported in 33% to 77% of patients after surgery. Clinical and surgical factors including age, the use of a nerve-sparing technique, and robotic surgery have been variably associated with the risk of ODs after RP, although robust and reliable data allowing for a proper estimation of the risk of postoperative orgasmic function impairment are still lacking. Likewise, little evidence regarding the management of postoperative ODs is currently available. In general, physicians should be aware of the prevalence of ODs after RP, in order to properly counsel all patients both preoperatively and immediately post-RP about the potential occurrence of bothersome and distressful changes in their overall sexual function. PMID:28459142

  4. Consciousness: the radical plasticity thesis.

    PubMed

    Cleeremans, Axel

    2008-01-01

    In this chapter, I sketch a conceptual framework which takes it as a starting point that conscious and unconscious cognition are rooted in the same set of interacting learning mechanisms and representational systems. On this view, the extent to which a representation is conscious depends in a graded manner on properties such as its stability in time or its strength. Crucially, these properties are accrued as a result of learning, which is in turn viewed as a mandatory process that always accompanies information processing. From this perspective, consciousness is best characterized as involving (1) a graded continuum defined over "quality of representation", such that availability to consciousness and to cognitive control correlates with quality, and (2) the implication of systems of metarepresentations. A first implication of these ideas is that the main function of consciousness is to make flexible, adaptive control over behavior possible. A second, much more speculative implication, is that we learn to be conscious. This I call the "radical plasticity thesis"--the hypothesis that consciousness emerges in systems capable not only of learning about their environment, but also about their own internal representations of it.

  5. Erectile preservation following radical prostatectomy

    PubMed Central

    Segal, Robert; Burnett, Arthur L.

    2011-01-01

    Prostate cancer is the most common cancer among men, representing approximately 25% of all new cancer diagnoses in the USA. For clinically localized prostate cancer, the gold standard for therapy remains radical prostatectomy. One of the main adverse effects of this procedure is erectile dysfunction, which can have a significant impact on the patient’s quality of life. There are several mechanisms of erectile dysfunction postprostatectomy, including arteriogenic, venogenic and neurogenic types, as well as the potentially heightened risk of postprostatectomy patients to develop Peyronie’s disease. The purpose of this review is to explain the various treatment options available, including phosphodiesterase type 5 inhibitors, intracavernosal injections, intraurethral alprostadil suppositories, vacuum erection devices, and penile prostheses. The role of these therapies in an erectile-dysfunction-treatment function, as well as in penile rehabilitation, will be discussed. Finally, a review of research on novel therapies will also be presented. A comprehensive literature review was performed using the PubMed database. Articles were chosen based on topical relevance and assessed for methodology and major findings. There are data to support the use of each of the therapeutic options in both treatment and rehabilitative roles. More study is needed, however, specifically in regard to penile rehabilitation, to confirm its benefits, as well as to determine optimal rehabilitation protocols. PMID:21789097

  6. Erectile preservation following radical prostatectomy.

    PubMed

    Segal, Robert; Burnett, Arthur L

    2011-02-01

    Prostate cancer is the most common cancer among men, representing approximately 25% of all new cancer diagnoses in the USA. For clinically localized prostate cancer, the gold standard for therapy remains radical prostatectomy. One of the main adverse effects of this procedure is erectile dysfunction, which can have a significant impact on the patient's quality of life. There are several mechanisms of erectile dysfunction postprostatectomy, including arteriogenic, venogenic and neurogenic types, as well as the potentially heightened risk of postprostatectomy patients to develop Peyronie's disease. The purpose of this review is to explain the various treatment options available, including phosphodiesterase type 5 inhibitors, intracavernosal injections, intraurethral alprostadil suppositories, vacuum erection devices, and penile prostheses. The role of these therapies in an erectile-dysfunction-treatment function, as well as in penile rehabilitation, will be discussed. Finally, a review of research on novel therapies will also be presented. A comprehensive literature review was performed using the PubMed database. Articles were chosen based on topical relevance and assessed for methodology and major findings. There are data to support the use of each of the therapeutic options in both treatment and rehabilitative roles. More study is needed, however, specifically in regard to penile rehabilitation, to confirm its benefits, as well as to determine optimal rehabilitation protocols.

  7. Pathways of arachidonic acid peroxyl radical reactions and product formation with guanine radicals.

    PubMed

    Crean, Conor; Geacintov, Nicholas E; Shafirovich, Vladimir

    2008-02-01

    Peroxyl radicals were derived from the one-electron oxidation of polyunsaturated fatty acids by sulfate radicals that were generated by the photodissociation of peroxodisulfate anions in air-equilibrated aqueous solutions. Reactions of these peroxyl and neutral guanine radicals, also generated by oxidation with sulfate radicals, were investigated by laser kinetic spectroscopy, and the guanine oxidation products were identified by HPLC and mass spectrometry methods. Sulfate radicals rapidly oxidize arachidonic (ArAc), linoleic (LnAc), and palmitoleic (PmAc) acids with similar rate constants, (2-4) x 10 (9) M (-1) s (-1). The C-centered radicals derived from the oxidation of ArAc and LnAc include nonconjugated Rn(.) ( approximately 80%) and conjugated bis-allylic Rba(.) ( approximately 20%) radicals. The latter were detectable in the absence of oxygen by their prominent, narrow absorption band at 280 nm. The Rn(.) radicals of ArAc (containing three bis-allylic sites) transform to the Rba(.) radicals via an intramolecular H-atom abstraction [rate constant (7.5 +/- 0.7) x 10 (4) s (-1)]. In contrast, the Rn(.) radicals of LnAc that contain only one bis-allylic site do not transform intramolecularly to the Rba(.) radicals. In the case of PmAc, which contains only one double bond, the Rba(.) radicals are not observed. The Rn(.) radicals of PmAc rapidly combine with oxygen with a rate constant of (3.8 +/- 0.4) x 10(9) M(-1) s(-1). The Rba(.) radicals of ArAc are less reactive and react with oxygen with a rate constant of (2.2 +/- 0.2) x 10 (8) M (-1) s (-1). The ArAc peroxyl radicals formed spontaneously eliminate superoxide radical anions [rate constant = (3.4 +/- 0.3) x 10 (4) M (-1) s (-1)]. The stable oxidative lesions derived from the 2',3',5'-tri- O-acetylguanosine or 2',3',5'-tri- O-acetyl-8-oxo-7,8-dihydroguanosine radicals and their subsequent reactions with ArAc peroxyl radicals were also investigated. The major products found were the 2,5-diamino-4 H

  8. Expanding Radical SAM Chemistry by Using Radical Addition Reactions and SAM Analogues.

    PubMed

    Ji, Xinjian; Li, Yongzhen; Xie, Liqi; Lu, Haojie; Ding, Wei; Zhang, Qi

    2016-09-19

    Radical S-adenosyl-l-methionine (SAM) enzymes utilize a [4Fe-4S] cluster to bind SAM and reductively cleave its carbon-sulfur bond to produce a highly reactive 5'-deoxyadenosyl (dAdo) radical. In almost all cases, the dAdo radical abstracts a hydrogen atom from the substrates or from enzymes, thereby initiating a highly diverse array of reactions. Herein, we report a change of the dAdo radical-based chemistry from hydrogen abstraction to radical addition in the reaction of the radical SAM enzyme NosL. This change was achieved by using a substrate analogue containing an olefin moiety. We also showed that two SAM analogues containing different nucleoside functionalities initiate the radical-based reactions with high efficiencies. The radical adduct with the olefin produced in the reaction was found to undergo two divergent reactions, and the mechanistic insights into this process were investigated in detail. Our study demonstrates a promising strategy in expanding radical SAM chemistry, providing an effective way to access nucleoside-containing compounds by using radical SAM-dependent reactions.

  9. Competition of charge- versus radical-directed fragmentation of gas-phase protonated cysteine sulfinyl radicals.

    PubMed

    Love, Chasity B; Tan, Lei; Francisco, Joseph S; Xia, Yu

    2013-04-24

    The fragmentation behavior of various cysteine sulfinyl ions (intact, N-acetylated, and O-methylated), new members of the gas-phase amino acid radical ion family, was investigated by low-energy collision-induced dissociation (CID). The dominant fragmentation channel for the protonated cysteine sulfinyl radicals ((SO•)Cys) was the radical-directed Cα-Cβ homolytic cleavage, resulting in the formation of glycyl radical ions and loss of CH2SO. This channel, however, was not observed for protonated N-acetylated cysteine sulfinyl radicals (Ac-(SO•)Cys); instead, charge-directed H2O loss followed immediately by SH loss prevailed. Counterintuitively, the H2O loss did not derive from the carboxyl group but involved the sulfinyl oxygen, a proton, and a Cβ hydrogen atom. Theoretical calculations suggested that N-acetylation significantly increases the barrier (~14 kcal mol(-1)) for the radical-directed fragmentation channel because of its reduced capability to stabilize the thus-formed glycyl radical ions via the captodative effect. N-Acetylation also assists in moving the proton to the sulfinyl site, which reduces the barrier for H2O loss. Our studies demonstrate that for cysteine sulfinyl radical ions, the stability of the product ions (glycyl radical ions) and the location of the charge (proton) can significantly modulate the competition between radical- and charge-directed fragmentation.

  10. Engineering a horseradish peroxidase C stable to radical attacks by mutating multiple radical coupling sites.

    PubMed

    Kim, Su Jin; Joo, Jeong Chan; Song, Bong Keun; Yoo, Young Je; Kim, Yong Hwan

    2015-04-01

    Peroxidases have great potential as industrial biocatalysts. In particular, the oxidative polymerization of phenolic compounds catalyzed by peroxidases has been extensively examined because of the advantage of this method over other conventional chemical methods. However, the industrial application of peroxidases is often limited because of their rapid inactivation by phenoxyl radicals during oxidative polymerization. In this work, we report a novel protein engineering approach to improve the radical stability of horseradish peroxidase isozyme C (HRPC). Phenylalanine residues that are vulnerable to modification by the phenoxyl radicals were identified using mass spectrometry analysis. UV-Vis and CD spectra showed that radical coupling did not change the secondary structure or the active site of HRPC. Four phenylalanine (Phe) residues (F68, F142, F143, and F179) were each mutated to alanine residues to generate single mutants to examine the role of these sites in radical coupling. Despite marginal improvement of radical stability, each single mutant still exhibited rapid radical inactivation. To further reduce inactivation by radical coupling, the four substitution mutations were combined in F68A/F142A/F143A/F179A. This mutant demonstrated dramatic enhancement of radical stability by retaining 41% of its initial activity compared to the wild-type, which was completely inactivated. Structure and sequence alignment revealed that radical-vulnerable Phe residues of HPRC are conserved in homologous peroxidases, which showed the same rapid inactivation tendency as HRPC. Based on our site-directed mutagenesis and biochemical characterization, we have shown that engineering radical-vulnerable residues to eliminate multiple radical coupling can be a good strategy to improve the stability of peroxidases against radical attack. © 2014 Wiley Periodicals, Inc.

  11. Iodine(III) Reagents in Radical Chemistry

    PubMed Central

    2017-01-01

    Conspectus The chemistry of hypervalent iodine(III) compounds has gained great interest over the past 30 years. Hypervalent iodine(III) compounds show valuable ionic reactivity due to their high electrophilicity but also express radical reactivity as single electron oxidants for carbon and heteroatom radical generation. Looking at ionic chemistry, these iodine(III) reagents can act as electrophiles to efficiently construct C–CF3, X–CF3 (X = heteroatom), C–Rf (Rf = perfluoroalkyl), X–Rf, C–N3, C–CN, S–CN, and C–X bonds. In some cases, a Lewis or a Bronsted acid is necessary to increase their electrophilicity. In these transformations, the iodine(III) compounds react as formal “CF3+”, “Rf+”, “N3+”, “Ar+”, “CN+”, and “X+” equivalents. On the other hand, one electron reduction of the I(III) reagents opens the door to the radical world, which is the topic of this Account that focuses on radical reactivity of hypervalent iodine(III) compounds such as the Togni reagent, Zhdankin reagent, diaryliodonium salts, aryliodonium ylides, aryl(cyano)iodonium triflates, and aryl(perfluoroalkyl)iodonium triflates. Radical generation starting with I(III) reagents can also occur via thermal or light mediated homolysis of the weak hypervalent bond in such reagents. This reactivity can be used for alkane C–H functionalization. We will address important pioneering work in the area but will mainly focus on studies that have been conducted by our group over the last 5 years. We entered the field by investigating transition metal free single electron reduction of Togni type reagents using the readily available sodium 2,2,6,6-tetramethylpiperidine-1-oxyl salt (TEMPONa) as an organic one electron reductant for clean generation of the trifluoromethyl radical and perfluoroalkyl radicals. That valuable approach was later successfully also applied to the generation of azidyl and aryl radicals starting with the corresponding benziodoxole (Zhdankin reagent

  12. Day case laparoscopic radical prostatectomy.

    PubMed

    Abboudi, Hamid; Doyle, Patrick; Winkler, Mathias

    2017-10-03

    To evaluate the feasibility of performing laparoscopic radical prostatectomy (LRP) as a day case procedure while maintaining patient satisfaction and safety. Herein we report our experience, selection criteria, and discharge criteria for day case LRP. We performed a prospective study with 32 patients undergoing extraperitoneal LRP. These patients were counselled before the procedure that they would go home the same evening of the procedure. Pain scores and quality of life data were recorded day 1 postoperatively via a telephone consultation. The patients underwent routine blood tests on day 2 and an outpatient review on day 7 and regularly thereafter via an assigned key worker. Socio-demographic data, comorbidities, and outcomes were collected for analysis. All patients were successfully discharged the same day of surgery. Mean patient age was 62 years with a mean body mass index of 25. Mean operative time was 147 minutes, and estimated blood loss was 101 ml. Three patients were treated for post operative urinary tract infections; two patients developed infected lymphoceles which required percutaneous drainage and one patient required re-catheterisation due to a burst catheter balloon. Of these six complications four patients required re-admission. Post-operative pain, nausea and vomiting were low whilst patient satisfaction scores were unanimously high in all patients surveyed. The early experience with extraperitoneal LRP as a same day surgery is promising although patients who are at high risk of lymphocele should be excluded. Preoperative patient counselling and selection is paramount. Patient satisfaction is not adversely affected by the shortened stay. Surgeon experience, a well-motivated patient, meticulous attention to detail through an integrated pathway, a multidisciplinary team and adequate postoperative assessment are essential.

  13. Magnetic Trapping of Cold Methyl Radicals

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Vashishta, Manish; Djuricanin, Pavle; Zhou, Sida; Zhong, Wei; Mittertreiner, Tony; Carty, David; Momose, Takamasa

    2017-03-01

    We have demonstrated that a supersonic beam of methyl radicals (CH3 ) in the ground rotational state of both para and ortho species has been slowed down to standstill with a magnetic molecular decelerator, and successfully captured spatially in an anti-Helmholtz magnetic trap for >1 s . The trapped CH3 radicals have a mean translational temperature of about 200 mK with an estimated density of >5.0 ×1 07 cm-3 . The methyl radical is an ideal system for the study of cold molecules not only because of its high reactivities at low temperatures, but also because further cooling below 1 mK is plausible via sympathetic cooling with ultracold atoms. The demonstrated trapping capability of methyl radicals opens up various possibilities for realizing ultracold ensembles of molecules towards Bose-Einstein condensation of polyatomic molecules and investigations of reactions governed by quantum statistics.

  14. A Mechanochemical Switch to Control Radical Intermediates

    PubMed Central

    2015-01-01

    B12-dependent enzymes employ radical species with exceptional prowess to catalyze some of the most chemically challenging, thermodynamically unfavorable reactions. However, dealing with highly reactive intermediates is an extremely demanding task, requiring sophisticated control strategies to prevent unwanted side reactions. Using hybrid quantum mechanical/molecular mechanical simulations, we follow the full catalytic cycle of an AdoB12-dependent enzyme and present the details of a mechanism that utilizes a highly effective mechanochemical switch. When the switch is “off”, the 5′-deoxyadenosyl radical moiety is stabilized by releasing the internal strain of an enzyme-imposed conformation. Turning the switch “on,” the enzyme environment becomes the driving force to impose a distinct conformation of the 5′-deoxyadenosyl radical to avoid deleterious radical transfer. This mechanochemical switch illustrates the elaborate way in which enzymes attain selectivity of extremely chemically challenging reactions. PMID:24846280

  15. A mechanochemical switch to control radical intermediates.

    PubMed

    Brunk, Elizabeth; Kellett, Whitney F; Richards, Nigel G J; Rothlisberger, Ursula

    2014-06-17

    B₁₂-dependent enzymes employ radical species with exceptional prowess to catalyze some of the most chemically challenging, thermodynamically unfavorable reactions. However, dealing with highly reactive intermediates is an extremely demanding task, requiring sophisticated control strategies to prevent unwanted side reactions. Using hybrid quantum mechanical/molecular mechanical simulations, we follow the full catalytic cycle of an AdoB₁₂-dependent enzyme and present the details of a mechanism that utilizes a highly effective mechanochemical switch. When the switch is "off", the 5'-deoxyadenosyl radical moiety is stabilized by releasing the internal strain of an enzyme-imposed conformation. Turning the switch "on," the enzyme environment becomes the driving force to impose a distinct conformation of the 5'-deoxyadenosyl radical to avoid deleterious radical transfer. This mechanochemical switch illustrates the elaborate way in which enzymes attain selectivity of extremely chemically challenging reactions.

  16. Fast beam studies of free radical photodissociation

    SciTech Connect

    Neumark, D.M.

    1993-12-01

    The authors have developed a novel technique for studying the photodissociation spectroscopy and dynamics of free radicals. In these experiments, radicals are generated by laser photodetachment of a fast (6-8 keV) mass-selected negative ion beam. The resulting radicals are photodissociated with a second laser, and the photofragments are collected and detected with high efficiency using a microchannel plate detector. The overall process is: ABC{sup -} {yields} ABC + e{sup -} {yields} A + BC, AB + C. Two types of fragment detection schemes are used. To map out the photodissociation cross-section of the radical, the photodissociation laser is scanned and the total photofragment yield is measured as a function of wavelength. In other experiments, the photodissociation frequency is fixed and the photofragment masses, kinetic energy release, and scattering angle is determined for each photodissociation event.

  17. RADICALLY CONTESTED ASSERTIONS IN ECOSYSTEM MANAGEMENT

    EPA Science Inventory

    Ecosystem management is a magnet for controversy, in part because some of its formulations rest on questionable assertions that are radically contested. These assertions are important to understanding much of the conflict surrounding ecosystem management and, therrefore, deserve...

  18. RADICALLY CONTESTED ASSERTIONS IN ECOSYSTEM MANAGEMENT

    EPA Science Inventory

    Ecosystem management is a magnet for controversy, in part because some of its formulations rest on questionable assertions that are radically contested. These assertions are important to understanding much of the conflict surrounding ecosystem management and, therrefore, deserve...

  19. Neutral radical deposition from silane discharges

    NASA Astrophysics Data System (ADS)

    Gallagher, Alan

    1988-04-01

    The fractional contributions of the various SiHn radicals (n=0-3) to deposition are calculated for low-power, pure-silane rf and dc discharges. This is done using a radical diffusion plus reaction equation, combined with current knowledge of SiH4 dissociation fractionation, of SiHn+SiH4 reactions, and of the distributed source of radicals. The conclusion reached is that more than 98% of neutral radical deposition is by SiH3 for typical deposition pressures (>100 mT at 240 °C). The effect of SiH3+SiH3 reactions at higher power is also evaluated using an estimated reaction rate coefficient (k3). The resulting loss in deposition rate is given as a function of film growth rate and of k3.

  20. Vertical Electron Transitions in Rydberg Radicals

    NASA Astrophysics Data System (ADS)

    Martin, I.; Lavín, C.; Pérez-Delgado, Y.; Karwowski, J.; Diercksen, G. H. F.

    Oscillator strengths and Einstein emission coefficients for several Rydberg radicals are reported. The Quantum Defect Orbital (QDO) method has been employed, and comparison is made with the results of more complex theorical procedures.

  1. Psychopathology according to behaviorism: a radical restatement.

    PubMed

    Pérez-Alvarez, Marino

    2004-11-01

    This article is a radical restatement of the predominant psychopathology, which is characterized by nosological systems and by its approach towards a neurobiological conception of the so-called mental disorders. The "radical" sense of this restatement is that of radical behaviorism itself. As readers will recall, "radical" applied to behaviorism means total (not ignoring anything that interests psychology), pragmatic (referring to the practical sense of knowledge), and it also derives from the Latin word for "root" (and thus implies change beginning at a system's roots or getting to the root of things, in this case, of psychological disorders). Based on this, I introduce the Aristotelian distinction of material and form, which, besides being behaviorist avant la lettre, is used here as a critical instrument to unmask the hoax of psychopathology as it is presented. The implications of this restatement are discussed, some of them already prepared for clinical practice.

  2. Radical formation in cytochrome c oxidase☆

    PubMed Central

    Yu, Michelle A.; Egawa, Tsuyoshi; Shinzawa-Itoh, Kyoko; Yoshikawa, Shinya; Yeh, Syun-Ru; Rousseau, Denis L.; Gerfen, Gary J.

    2015-01-01

    The formation of radicals in bovine cytochrome c oxidase (bCcO), during the O2 redox chemistry and proton translocation, is an unresolved controversial issue. To determine if radicals are formed in the catalytic reaction of bCcO under single turnover conditions, the reaction of O2 with the enzyme, reduced by either ascorbate or dithionite, was initiated in a custom-built rapid freeze quenching (RFQ) device and the products were trapped at 77 K at reaction times ranging from 50 µs to 6 ms. Additional samples were hand mixed to attain multiple turnover conditions and quenched with a reaction time of minutes. X-band (9 GHz) continuous wave electron paramagnetic resonance (CW-EPR) spectra of the reaction products revealed the formation of a narrow radical with both reductants. D-band (130 GHz) pulsed EPR spectra allowed for the determination of the g-tensor principal values and revealed that when ascorbate was used as the reductant the dominant radical species was localized on the ascorbyl moiety, and when dithionite was used as the reductant the radical was the SO2•− ion. When the contributions from the reductants are subtracted from the spectra, no evidence for a protein-based radical could be found in the reaction of O2 with reduced bCcO. As a surrogate for radicals formed on reaction intermediates, the reaction of hydrogen peroxide (H2O2) with oxidized bCcO was studied at pH 6 and pH 8 by trapping the products at 50 µs with the RFQ device to determine the initial reaction events. For comparison, radicals formed after several minutes of incubation were also examined, and X-band and D-band analysis led to the identification of radicals on Tyr-244 and Tyr-129. In the RFQ measurements, a peroxyl (R – O – O•) species was formed, presumably by the reaction between O2 and an amino acid-based radical. It is postulated that Tyr-129 may play a central role as a proton loading site during proton translocation by ejecting a proton upon formation of the radical

  3. 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.

  4. Mechanism of disproportionation of ascorbate radicals

    SciTech Connect

    Bielski, B.H.J.; Allen, A.O.; Schwarz, H.A.

    1981-06-17

    Existing data on the kinetics of ascorbate radical decay, together with some new data on the effects of temperature, ionic strength, and presence of phosphate buffers, suggest a mechanism in which the ascorbate radical ion is in equilibrium with a dimer. This dimer reacts with hydrogen ion, or with other proton donors present including water and buffers (at rates depending upon their acid strengths), to form the disproportionation products ascorbate ion and dehydroascorbate acid.

  5. The stabilization energies of polyenyl radicals

    NASA Astrophysics Data System (ADS)

    Luo, Yu-Ran; Holmes, John L.

    1994-10-01

    The resonance stabilization energies, Es, of polyenyl radicals can be estimated by the equation Es( N)=-13.2+[3.95-15.8(2) -2/ n] kcal mol -1, where N is the number of C, C-π bonds in the polyenyl radicals. This correlation has been extended for predicting the weakest HC, CC and COH bond dissociation energies in vitamin A and similar compounds.

  6. Radicals: Reactive Intermediates with Translational Potential

    PubMed Central

    2016-01-01

    This Perspective illustrates the defining characteristics of free radical chemistry, beginning with its rich and storied history. Studies from our laboratory are discussed along with recent developments emanating from others in this burgeoning area. The practicality and chemoselectivity of radical reactions enable rapid access to molecules of relevance to drug discovery, agrochemistry, material science, and other disciplines. Thus, these reactive intermediates possess inherent translational potential, as they can be widely used to expedite scientific endeavors for the betterment of humankind. PMID:27631602

  7. Radical behaviorism and buddhism: complementarities and conflicts.

    PubMed

    Diller, James W; Lattal, Kennon A

    2008-01-01

    Comparisons have been made between Buddhism and the philosophy of science in general, but there have been only a few attempts to draw comparisons directly with the philosophy of radical behaviorism. The present review therefore considers heretofore unconsidered points of comparison between Buddhism and radical behaviorism in terms of their respective goals, conceptualization of human beings, and the outcomes of following either philosophy. From these comparisons it is concluded that the commonalities discerned between these two philosophies may enhance both philosophical systems.

  8. Laser Studies of Gas Phase Radical Reactions.

    DTIC Science & Technology

    1989-01-01

    Acremonium chrysogenum , was prepared according to the published procedure [6]. This fungal enzyme had a specific activity of 0.023 IUmg1, and was estimated to...Dist-lbitionj Avdielbiity Codes jAvail atidjor Dist 6a A-I . p -1- Laser Studies of Gas Phase Radical Reactions G. Hancock Physical Chemistry...some additional experiments concerning the formation of carbene radicals in liquid phase enzyme cleavage studies are described. Keywords Laser

  9. Radical-water complexes in Earth's atmosphere.

    PubMed

    Aloisio, S; Francisco, J S

    2000-12-01

    In the atmosphere, many chemical processes are controlled by open-shell radical species. While these species are present in relatively small number densities, they initiate many of the cycles that control the chemistry of the atmosphere. The purpose of this Account is to examine recent studies of radical-water complexes that are composed of atmospherically important species. We hope this Account will provide a report on the status of this topical field, while encouraging new research directions.

  10. 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

  11. Inactivation of Bacillus atrophaeus by OH radicals

    NASA Astrophysics Data System (ADS)

    Ono, Ryo; Yonetamari, Kenta; Tokumitsu, Yusuke; Yonemori, Seiya; Yasuda, Hachiro; Mizuno, Akira

    2016-08-01

    The inactivation of Bacillus atrophaeus by OH radicals is measured. This study aims to evaluate the bactericidal effects of OH radicals produced by atmospheric-pressure nonthermal plasma widely used for plasma medicine; however, in this study, OH radicals are produced by vacuum ultraviolet (VUV) photolysis of water vapor instead of plasma to allow the production of OH radicals with almost no other reactive species. A 172 nm VUV light from a Xe2 excimer lamp irradiates a He-H2O mixture flowing in a quartz tube to photodissociate H2O to produce OH, H, O, HO2, H2O2, and O3. The produced reactive oxygen species (ROS) flow out of the quartz tube nozzle to the bacteria on an agar plate and cause inactivation. The inactivation by OH radicals among the six ROS is observed by properly setting the experimental conditions with the help of simulations calculating the ROS densities. A 30 s treatment with approximately 0.1 ppm OH radicals causes visible inactivation.

  12. 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. Copyright © 2016. Published by Elsevier Ltd.

  13. Radicalization and Radical Catalysis of Biomass Sugars: Insights from First-principles Studies

    NASA Astrophysics Data System (ADS)

    Yang, Gang; Zhu, Chang; Zou, Xianli; Zhou, Lijun

    2016-07-01

    Ab initio and density functional calculations are conducted to investigate the radicalization processes and radical catalysis of biomass sugars. Structural alterations due to radicalization generally focus on the radicalized sites, and radicalization affects H-bonds in D-fructofuranose more than in D-glucopyranose, potentially with outcome of new H-bonds. Performances of different functionals and basis sets are evaluated for all radicalization processes, and enthalpy changes and Gibbs free energies for these processes are presented with high accuracy, which can be referenced for subsequent experimental and theoretical studies. It shows that radicalization can be utilized for direct transformation of biomass sugars, and for each sugar, C rather than O sites are always preferred for radicalization, thus suggesting the possibility to activate C-H bonds of biomass sugars. Radical catalysis is further combined with Brønsted acids, and it clearly states that functionalization fundamentally regulates the catalytic effects of biomass sugars. In presence of explicit water molecules, functionalization significantly affects the activation barriers and reaction energies of protonation rather than dehydration steps. Tertiary butyl and phenyl groups with large steric hindrances or hydroxyl and amino groups resulting in high stabilities for protonation products drive the protonation steps to occur facilely at ambient conditions.

  14. Radicalization and Radical Catalysis of Biomass Sugars: Insights from First-principles Studies

    PubMed Central

    Yang, Gang; Zhu, Chang; Zou, Xianli; Zhou, Lijun

    2016-01-01

    Ab initio and density functional calculations are conducted to investigate the radicalization processes and radical catalysis of biomass sugars. Structural alterations due to radicalization generally focus on the radicalized sites, and radicalization affects H-bonds in D-fructofuranose more than in D-glucopyranose, potentially with outcome of new H-bonds. Performances of different functionals and basis sets are evaluated for all radicalization processes, and enthalpy changes and Gibbs free energies for these processes are presented with high accuracy, which can be referenced for subsequent experimental and theoretical studies. It shows that radicalization can be utilized for direct transformation of biomass sugars, and for each sugar, C rather than O sites are always preferred for radicalization, thus suggesting the possibility to activate C-H bonds of biomass sugars. Radical catalysis is further combined with Brønsted acids, and it clearly states that functionalization fundamentally regulates the catalytic effects of biomass sugars. In presence of explicit water molecules, functionalization significantly affects the activation barriers and reaction energies of protonation rather than dehydration steps. Tertiary butyl and phenyl groups with large steric hindrances or hydroxyl and amino groups resulting in high stabilities for protonation products drive the protonation steps to occur facilely at ambient conditions. PMID:27405843

  15. Ferromagnetic behavior of formyl-group-carrying stable thioaminyl radicals.

    PubMed

    Miura, Yozo; Nakamura, Shogo; Teki, Yoshio

    2003-10-17

    Four formyl-group-carrying thioaminyl radicals were generated, and one radical could be isolated as radical crystals. Magnetic susceptibility measurements of the isolated radical showed a ferromagnetic regular linear-chain interaction of 2J/k(B) = 3.2 K, which was explained in terms of the X-ray crystallographic results.

  16. Practicing Radical Pedagogy: Balancing Ideals with Institutional Constraints.

    ERIC Educational Resources Information Center

    Sweet, Stephen

    1998-01-01

    Describes radical pedagogy and observes that an overview of "Teaching Sociology" suggests that few teachers fully practice it. Argues that while professors are free to teach radical theory, radical pedagogy is hindered by institutional constraints. Concludes that radical teachers may benefit from remaining more within the confines imposed by their…

  17. Tuning the Reactivity of Radical through a Triplet Diradical Cu(II) Intermediate in Radical Oxidative Cross-Coupling

    PubMed Central

    Zhou, Liangliang; Yi, Hong; Zhu, Lei; Qi, Xiaotian; Jiang, Hanpeng; Liu, Chao; Feng, Yuqi; Lan, Yu; Lei, Aiwen

    2015-01-01

    Highly selective radical/radical cross-coupling is paid more attention in bond formations. However, due to their intrinsic active properties, radical species are apt to achieve homo-coupling instead of cross-coupling, which makes the selective cross-coupling as a great challenge and almost untouched. Herein a notable strategy to accomplish direct radical/radical oxidative cross-coupling has been demonstrated, that is metal tuning a transient radical to a persistent radical intermediate followed by coupling with another transient radical. Here, a transient nitrogen-centered radical is tuned to a persistent radical complex by copper catalyst, followed by coupling with a transient allylic carbon-centered radical. Firstly, nitrogen-centered radical generated from N-methoxybenzamide stabilized by copper catalyst was successfully observed by EPR. Then DFT calculations revealed that a triplet diradical Cu(II) complex formed from the chelation N-methoxybenzamide nitrogen-centered radical to Cu(II) is a persistent radical species. Moreover, conceivable nitrogen-centered radical Cu(II) complex was observed by high-resolution electrospray ionization mass spectrometry (ESI-MS). Ultimately, various allylic amides derivatives were obtained in good yields by adopting this strategy, which might inspire a novel and promising landscape in radical chemistry. PMID:26525888

  18. Formation and reactivity of phenylperoxyl radicals in aqueous solutions

    SciTech Connect

    Alfassi, Z.B.; Marguet, S.; Neta, P. )

    1994-08-18

    The reaction of phenyl radicals with oxygen, to produce phenylperoxyl radicals, and the reactions of several phenylperoxyl radicals with a number of organic compounds in aqueous solutions have been studied by pulse radiolysis. Phenyl radicals were produced by reduction of aryl halides with hydrated electrons. The rate constant for the reaction of 4-carboxyphenyl with O[sub 2] was determined from the rate of buildup of the peroxyl radical absorption at 520 nm as a function of [O[sub 2

  19. 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.

  20. Environmentally persistent free radicals (EPFRs)-2. Are free hydroxyl radicals generated in aqueous solutions?

    PubMed

    Khachatryan, Lavrent; Dellinger, Barry

    2011-11-01

    A chemical spin trap, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), in conjunction with electron paramagnetic resonance (EPR) spectroscopy was employed to measure the production of hydroxyl radical (·OH) in aqueous suspensions of 5% Cu(II)O/silica (3.9% Cu) particles containing environmentally persistent free radicals (EPFRs) of 2-monochlorophenol (2-MCP). The results indicate: (1) a significant differences in accumulated DMPO-OH adducts between EPFR containing particles and non-EPFR control samples, (2) a strong correlation between the concentration of DMPO-OH adducts and EPFRs per gram of particles, and (3) a slow, constant growth of DMPO-OH concentration over a period of days in solution containing 50 μg/mL EPFRs particles + DMPO (150 mM) + reagent balanced by 200 μL phosphate buffered (pH = 7.4) saline. However, failure to form secondary radicals using standard scavengers, such as ethanol, dimethylsulfoxide, sodium formate, and sodium azide, suggests free hydroxyl radicals may not have been generated in solution. This suggests surface-bound, rather than free, hydroxyl radicals were generated by a surface catalyzed-redox cycle involving both the EPFRs and Cu(II)O. Toxicological studies clearly indicate these bound free radicals promote various types of cardiovascular and pulmonary disease normally attributed to unbound free radicals; however, the exact chemical mechanism deserves further study in light of the implication of formation of bound, rather than free, hydroxyl radicals.

  1. The inclusive jet cross section at {radical}s = 630 GeV at D0

    SciTech Connect

    Krane, J.; D0 Collaboration

    1996-09-01

    The authors present a preliminary measurement of the cross section for central inclusive jet production at {radical}s = 630 GeV using {approximately} 400 nb{sup {minus}1} of data collected during the December 1995 Fermilab collider run at D0. These results are compared to NLO QCD predictions.

  2. [Lower urinary tract dysfunction following radical hysterectomy].

    PubMed

    Aoun, F; Roumeguère, T

    2015-12-01

    Radical hysterectomy is associated with a significant amount of urinary functional complications and a negative impact on quality of life. The aim of this review is to provide a comprehensive overview of the neurological etiology of lower urinary tract dysfunction following radical hysterectomy and to establish an optimal postoperative management strategy. We performed a comprehensive overview using the following terms: "radical hysterectomy" and "urologic diseases etiology" or "urologic disease prevention and control". The reported incidence of lower urinary tract dysfunction after radical hysterectomy varies from 12 to 85%. Several animal and clinical urodynamic studies corroborate the neurologic etiology of the dysfunction. Lower urinary tract dysfunction is a common postoperative finding (70-85%) but spontaneous recovery is to be expected within 6-12 months after surgery. The most frequent long term sequela is stress urinary incontinence (40% of cases) and its management is complex and challenging. Postoperative refractory overactive bladder and bladder underactivity can be treated by neuromodulation of sacral roots and superior hypogastric plexus, respectively. In the absence of good clinical predictors, preoperative urodynamic examinations could have a role in understanding the pathophysiology of the dysfunction before such interventions. The pathophysiology of lower urinary tract dysfunction following radical hysterectomy is multifactorial. Its management is complex and should be multidisciplinary. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

  3. Introducing Stable Radicals into Molecular Machines.

    PubMed

    Wang, Yuping; Frasconi, Marco; Stoddart, J Fraser

    2017-09-27

    Ever since their discovery, stable organic radicals have received considerable attention from chemists because of their unique optical, electronic, and magnetic properties. Currently, one of the most appealing challenges for the chemical community is to develop sophisticated artificial molecular machines that can do work by consuming external energy, after the manner of motor proteins. In this context, radical-pairing interactions are important in addressing the challenge: they not only provide supramolecular assistance in the synthesis of molecular machines but also open the door to developing multifunctional systems relying on the various properties of the radical species. In this Outlook, by taking the radical cationic state of 1,1'-dialkyl-4,4'-bipyridinium (BIPY(•+)) as an example, we highlight our research on the art and science of introducing radical-pairing interactions into functional systems, from prototypical molecular switches to complex molecular machines, followed by a discussion of the (i) limitations of the current systems and (ii) future research directions for designing BIPY(•+)-based molecular machines with useful functions.

  4. Introducing Stable Radicals into Molecular Machines

    PubMed Central

    2017-01-01

    Ever since their discovery, stable organic radicals have received considerable attention from chemists because of their unique optical, electronic, and magnetic properties. Currently, one of the most appealing challenges for the chemical community is to develop sophisticated artificial molecular machines that can do work by consuming external energy, after the manner of motor proteins. In this context, radical-pairing interactions are important in addressing the challenge: they not only provide supramolecular assistance in the synthesis of molecular machines but also open the door to developing multifunctional systems relying on the various properties of the radical species. In this Outlook, by taking the radical cationic state of 1,1′-dialkyl-4,4′-bipyridinium (BIPY•+) as an example, we highlight our research on the art and science of introducing radical-pairing interactions into functional systems, from prototypical molecular switches to complex molecular machines, followed by a discussion of the (i) limitations of the current systems and (ii) future research directions for designing BIPY•+-based molecular machines with useful functions. PMID:28979933

  5. Electrochemistry and spectroelectrochemistry of nitroxyl free radicals

    SciTech Connect

    Fish, J.R.; Swarts, S.G.; Sevilla, M.D.; Malinski, T.

    1988-06-30

    This work reports electrochemical and spectroelectrochemical studies of the two nitroxyl radicals 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) and 3-carbamoyl-2,2,5,5-tetramethyl-3-pyrrolin-1-yloxy (3-carbamoyl-PROXYL). Oxidation and reduction reactions have been observed in aqueous media over the pH range 2-12 in the potential range -0.8 to +0.8 V by differential pulse voltammetry, cyclic voltammetry, and thin-layer UV-visible spectroelectrochemistry, and the reaction products have been characterized by IR, NMR, and ESR spectrometry. At pH values less than 10, characteristic electrochemical behavior is observed to be analogous for both radicals, and the products from electron transfer compare quite favorably with those found by pulse radiolysis of aqueous solutions of nitroxyl radicals. At pH 2-9, a stable cation from a reversible oxidation and hydroxylamine following an irreversible reduction, as well as hydroxylated cation at pH higher than 9, are the same as those obtained in pulse radiolysis experiments. Spectroscopic evidence indicates that behavior following reduction at high pH differs for the two radicals. At pH 12, reduced TEMPO may undergo structural changes leading to the formation of a new radical consisting of a seven-membered ring.

  6. Vibronic Spectroscopy of the Phenylcyanomethyl Radical

    NASA Astrophysics Data System (ADS)

    Mehta, Deepali N.; Kidwell, Nathanael M.; Zwier, Timothy S.

    2011-06-01

    Resonance stabilized radicals (RSRs) are thought to be key intermediates in the formation of larger molecules in planetary atmospheres. Given the nitrogen-rich atmosphere of Titan, and the prevalence of nitriles there, it is likely that nitrile and isonitrile RSRs could be especially important in pathways leading to the formation of more complex nitrogen-containing compounds and the aerosols ("tholins") that are ultimately produced. In this talk, the results of a gas phase, jet-cooled vibronic spectroscopy study of the phenylcyanomethyl radical (C_6H_5.{C}HCN), the nitrogen-containing analog of the 1-phenylpropargyl radical, will be presented. A resonant two color photon ionization spectrum over the range 21,350-22,200 Cm-1 (450.0-468.0 nm) has been recorded, and the D_0-D_1 origin band has been tentatively identified at 21,400 Cm-1. Studies identifying the ionization threshold, and characterizing the vibronic structure will also be presented. An analogous study of the phenylisocyanomethyl radical, C_6H_5.{C}HNC, is currently being pursued for comparison with that of phenylcyanomethyl radical.

  7. Modeling Radicalization Phenomena in Heterogeneous Populations

    PubMed Central

    2016-01-01

    The phenomenon of radicalization is investigated within a mixed population composed of core and sensitive subpopulations. The latest includes first to third generation immigrants. Respective ways of life may be partially incompatible. In case of a conflict core agents behave as inflexible about the issue. In contrast, sensitive agents can decide either to live peacefully adjusting their way of life to the core one, or to oppose it with eventually joining violent activities. The interplay dynamics between peaceful and opponent sensitive agents is driven by pairwise interactions. These interactions occur both within the sensitive population and by mixing with core agents. The update process is monitored using a Lotka-Volterra-like Ordinary Differential Equation. Given an initial tiny minority of opponents that coexist with both inflexible and peaceful agents, we investigate implications on the emergence of radicalization. Opponents try to turn peaceful agents to opponents driving radicalization. However, inflexible core agents may step in to bring back opponents to a peaceful choice thus weakening the phenomenon. The required minimum individual core involvement to actually curb radicalization is calculated. It is found to be a function of both the majority or minority status of the sensitive subpopulation with respect to the core subpopulation and the degree of activeness of opponents. The results highlight the instrumental role core agents can have to hinder radicalization within the sensitive subpopulation. Some hints are outlined to favor novel public policies towards social integration. PMID:27166677

  8. Improving postoperative radiotherapy following radical prostatectomy.

    PubMed

    Lipman, D; Pieters, B R; De Reijke, Theo M

    2017-10-01

    Prostate cancer has one of the highest incidences in the world, with good curative treatment options like radiotherapy and radical prostatectomy. Unfortunately, about 30% of the patients initially treated with curative intent will develop a recurrence and need adjuvant treatment. Five randomized trials covered the role of postoperative radiotherapy after radical prostatectomy, but there is still a lot of debate about which patients should receive postoperative radiotherapy. Areas covered: This review will give an overview on the available literature concerning post-operative radiotherapy following radical prostatectomy with an emphasis on the five randomized trials. Also, new imaging techniques like prostate-specific membrane antigen positron emission tomography (PSMA-PET) and multiparametric magnetic resonance imaging (mp-MRI) and the development of biomarkers like genomic classifiers will be discussed in the search for an improved selection of patients who will benefit from postoperative radiotherapy following radical prostatectomy. With new treatment techniques like Intensity Modulated Radiotherapy, toxicity profiles will be kept low. Expert commentary: Patients with biochemical recurrence following radical prostatectomy with an early rise in prostate-specific antigen (PSA) will benefit most from postoperative radiotherapy. In this way, patients with only high risk pathological features can avoid unnecessary treatment and toxicity, and early intervention in progressing patients would not compromise the outcome.

  9. Substrate radical intermediates in soluble methane monooxygenase.

    PubMed

    Liu, Aimin; Jin, Yi; Zhang, Jingyan; Brazeau, Brian J; Lipscomb, John D

    2005-12-09

    EPR spin-trapping experiments were carried out using the three-component soluble methane monooxygenase (MMO). Spin-traps 5,5-dimethyl-1-pyrroline N-oxide (DMPO), alpha-4-pyridyl-1-oxide N-tert-butylnitrone (POBN), and nitrosobenzene (NOB) were used to investigate the possible formation of substrate radical intermediates during catalysis. In contrast to a previous report, the NADH-coupled oxidations of various substrates did not produce any trapped radical species when DMPO or POBN was present. However, radicals were detected by these traps when only the MMO reductase component and NADH were present. DMPO and POBN were found to be weak inhibitors of the MMO reaction. In contrast, NOB is a strong inhibitor for the MMO-catalyzed nitrobenzene oxidation reaction. When NOB was used as a spin-trap in the complete MMO system with or without substrate, EPR signals from an NOB radical were detected. We propose that a molecule of NOB acts simultaneously as a substrate and a spin-trap for MMO, yielding the long-lived radical and supporting a stepwise mechanism for MMO.

  10. Modeling Radicalization Phenomena in Heterogeneous Populations.

    PubMed

    Galam, Serge; Javarone, Marco Alberto

    2016-01-01

    The phenomenon of radicalization is investigated within a mixed population composed of core and sensitive subpopulations. The latest includes first to third generation immigrants. Respective ways of life may be partially incompatible. In case of a conflict core agents behave as inflexible about the issue. In contrast, sensitive agents can decide either to live peacefully adjusting their way of life to the core one, or to oppose it with eventually joining violent activities. The interplay dynamics between peaceful and opponent sensitive agents is driven by pairwise interactions. These interactions occur both within the sensitive population and by mixing with core agents. The update process is monitored using a Lotka-Volterra-like Ordinary Differential Equation. Given an initial tiny minority of opponents that coexist with both inflexible and peaceful agents, we investigate implications on the emergence of radicalization. Opponents try to turn peaceful agents to opponents driving radicalization. However, inflexible core agents may step in to bring back opponents to a peaceful choice thus weakening the phenomenon. The required minimum individual core involvement to actually curb radicalization is calculated. It is found to be a function of both the majority or minority status of the sensitive subpopulation with respect to the core subpopulation and the degree of activeness of opponents. The results highlight the instrumental role core agents can have to hinder radicalization within the sensitive subpopulation. Some hints are outlined to favor novel public policies towards social integration.

  11. Reactivity of 1,4-dihydropyridines toward alkyl, alkylperoxyl radicals, and ABTS radical cation.

    PubMed

    López-Alarcón, C; Navarrete, P; Camargo, C; Squella, J A; Núñez-Vergara, L J

    2003-02-01

    A series of C4-substituted 1,4-dihydropyridines (DHP) with either secondary or tertiary nitrogen in the dihydropyridine ring were synthesized. All of these compounds together with some commercial DHP derivatives were tested for potential scavenger effects toward alkyl, alkylperoxyl radicals, and ABTS radical cation in aqueous media at pH 7.4. Kinetic rate constants were assessed either by UV/vis spectroscopy or GC/MS techniques. Tested compounds reacted faster toward alkylperoxyl radicals and ABTS radical cation than alkyl ones. N-Ethyl-substituted DHPs showed the lowest reactivity. Kinetic results were compared with either trolox or nisoldipine. Using deuterium kinetic isotope effect studies, we have proved that the hydrogen of the 1-position of the DHP ring is involved in the proposed mechanism. This fact is mostly noticeable in the case of alkyl radicals. In all cases, the respective pyridine derivative was detected as the main product of the reaction.

  12. Bimolecular self-reactions of ketyl radicals of acetophenone and diphenylaminyl radicals

    NASA Astrophysics Data System (ADS)

    Khudyakov, I. V.; Koroli, L. L.

    1984-01-01

    The rate constants of self-reactions of ketyl radicals of acetophenone in n-heptane [2 k = (3.2 ± 0.5) × 10 9 M -1 s -1] and diphenylaminyl radicals in toluene [2 k = (3.3 ± 0.5) × 10 7 M -1 s -1] have been determined at 298 K using the flash photolysis technique. The rate constant of ketyl radicals is equal to the calculated diffusion constant and, therefore, this reaction is diffusion-controlled. The aminyl radical recombination rate is independent of the viscosity of the toluene/vaseline oil binary mixture (0.55 ⩽ η ⩽ 12 cP) and this reaction is activation-controlled. Reactivity anisotropy averaging due to the cage effect has been considered for ketyl and some other radicals. On the basis of the analysis it has been proposed that ketyl recombination involves formation of not only pinacol, but also iso-pinacols.

  13. A Radically Configurable Six-State Compound

    SciTech Connect

    Barnes, J.C.; Fahrenbach, Albert C.; Cao, Dennis; Dyar, Scott M.; Frasconi, M.; Giesener, M. A.; Benítez, D.; Tkatchouk, E.; Li, H.; Stern, Charlotte L.; Sarjeant, Amy A.; Hartlieb, K.J.; Liu, Z.; Carmieli, Raanan; Botros, Y.Y.; Wasielewski, M. R.; Goddard III, W.A.; Stoddart, J. Fraser

    2013-01-24

    Most organic radicals possess short lifetimes and quickly undergo dimerization or oxidation. Here, we report on the synthesis by radical templation of a class of air- and water-stable organic radicals, trapped within a homo[2]catenane composed of two rigid and fixed cyclobis(paraquat-p-phenylene) rings. The highly energetic octacationic homo[2]catenane, which is capable of accepting up to eight electrons, can be configured reversibly, both chemically and electrochemically, between each one of six experimentally accessible redox states (0, 2+, 4+, 6+, 7+, and 8+) from within the total of nine states evaluated by quantum mechanical methods. All six of the observable redox states have been identified by electrochemical techniques, three (4+, 6+, and 7+) have been characterized by x-ray crystallography, four (4+, 6+, 7+, and 8+) by electron paramagnetic resonance spectroscopy, one (7+) by superconducting quantum interference device magnetometry, and one (8+) by nuclear magnetic resonance spectroscopy.

  14. Resveratrol products resulting by free radical attack

    NASA Astrophysics Data System (ADS)

    Bader, Yvonne; Quint, R. M.; Getoff, Nikola

    2008-06-01

    Trans-resveratrol ( trans-3,4',5-trihydroxystilbene; RES), which is contained in red wine and many plants, is one of the most relevant and extensively investigated stilbenes with a broad spectrum of biological activities. Among other duties, RES has been reported to have anti-carcinogenetic activities, which could be attributed to its antioxidant properties. The degradation of RES was studied under various conditions. The products (aldehydes, carboxylic acids, etc.) generated from RES by the attack of free radicals were registered as a function of the radical concentration (absorbed radiation dose). Based on the obtained data it appears that the OH radicals are initiating the rather complicated process, which involves of the numerous consecutive reactions. A possible starting reaction mechanism is presented.

  15. Mechanically controlled radical polymerization initiated by ultrasound

    NASA Astrophysics Data System (ADS)

    Mohapatra, Hemakesh; Kleiman, Maya; Esser-Kahn, Aaron Palmer

    2017-02-01

    In polymer chemistry, mechanical energy degrades polymeric chains. In contrast, in nature, mechanical energy is often used to create new polymers. This mechanically stimulated growth is a key component of the robustness of biological materials. A synthetic system in which mechanical force initiates polymerization will provide similar robustness in polymeric materials. Here we show a polymerization of acrylate monomers initiated and controlled by mechanical energy provided by ultrasonic agitation. The activator for an atom-transfer radical polymerization is generated using piezochemical reduction of a Cu(II) precursor complex, which thus converts a mechanical activation of piezoelectric particles to the synthesis of a new material. This polymerization reaction has some characteristics of controlled radical polymerization, such as narrow molecular-weight distribution and linear dependence of the polymeric chain length on the time of mechanical activation. This new method of controlled radical polymerization complements the existing methods to synthesize commercially useful well-defined polymers.

  16. Radicality of surgical treatment for cervical cancer.

    PubMed

    Mirković, L; Petković, S; Mirković, D; Jeremić, K; Milenković, V; Maksimović, M

    2009-01-01

    Analyses were carried out on 545 Wertheim-Meigs radical hysterectomies performed at the Institute of Gynecology and Obstetrics of the Clinical Center of Serbia during a four-year period from 2002 to 2006. More than ten lymphatic glands in 84.4% of patients were removed. The apical part of the vagina was removed in 77.8% of cases, and 77.6% of patients had the right part of the vagina removed. Distribution of surgical radicality according to FIGO stage of disease has been demonstrated. Comparison of research results in the period from 1996 to 2000 shows a significantly more radical approach concerning the number of lymphatic glands removed during this period.

  17. High-Power-Density Organic Radical Batteries.

    PubMed

    Friebe, Christian; Schubert, Ulrich S

    2017-02-01

    Batteries that are based on organic radical compounds possess superior charging times and discharging power capability in comparison to established electrochemical energy-storage technologies. They do not rely on metals and, hence, feature a favorable environmental impact. They furthermore offer the possibility of roll-to-roll processing through the use of different printing techniques, which enables the cost-efficient fabrication of mechanically flexible devices. In this review, organic radical batteries are presented with the focus on the hitherto developed materials and the key properties thereof, e.g., voltage, capacity, and cycle life. Furthermore, basic information, such as significant characteristics, housing approaches, and applied additives, are presented and discussed in the context of organic radical batteries.

  18. Free radicals, antioxidant defense systems, and schizophrenia.

    PubMed

    Wu, Jing Qin; Kosten, Thomas R; Zhang, Xiang Yang

    2013-10-01

    The etiopathogenic mechanisms of schizophrenia are to date unknown, although several hypotheses have been suggested. Accumulating evidence suggests that excessive free radical production or oxidative stress may be involved in the pathophysiology of schizophrenia as evidenced by increased production of reactive oxygen or decreased antioxidant protection in schizophrenic patients. This review aims to summarize the basic molecular mechanisms of free radical metabolism, the impaired antioxidant defense system and membrane pathology in schizophrenia, their interrelationships with the characteristic clinical symptoms and the implications for antipsychotic treatments. In schizophrenia, there is accumulating evidence of altered antioxidant enzyme activities and increased levels of lipid peroxidation, as well as altered levels of plasma antioxidants. Moreover, free radical-mediated abnormalities may contribute to specific aspects of schizophrenic symptomatology and complications of its treatment with antipsychotic drugs, as well as the development of tardive dyskinesia (TD). Finally, the potential therapeutic strategies implicated by the accumulating data on oxidative stress mechanisms for the treatment of schizophrenia are discussed.

  19. Mechanically controlled radical polymerization initiated by ultrasound

    NASA Astrophysics Data System (ADS)

    Mohapatra, Hemakesh; Kleiman, Maya; Esser-Kahn, Aaron Palmer

    2016-10-01

    In polymer chemistry, mechanical energy degrades polymeric chains. In contrast, in nature, mechanical energy is often used to create new polymers. This mechanically stimulated growth is a key component of the robustness of biological materials. A synthetic system in which mechanical force initiates polymerization will provide similar robustness in polymeric materials. Here we show a polymerization of acrylate monomers initiated and controlled by mechanical energy provided by ultrasonic agitation. The activator for an atom-transfer radical polymerization is generated using piezochemical reduction of a Cu(II) precursor complex, which thus converts a mechanical activation of piezoelectric particles to the synthesis of a new material. This polymerization reaction has some characteristics of controlled radical polymerization, such as narrow molecular-weight distribution and linear dependence of the polymeric chain length on the time of mechanical activation. This new method of controlled radical polymerization complements the existing methods to synthesize commercially useful well-defined polymers.

  20. Antioxidant and radical scavenging properties of curcumin.

    PubMed

    Ak, Tuba; Gülçin, Ilhami

    2008-07-10

    Curcumin (diferuoyl methane) is a phenolic compound and a major component of Curcuma longa L. In the present paper, we determined the antioxidant activity of curcumin by employing various in vitro antioxidant assays such as 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH*) scavenging, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activity, N,N-dimethyl-p-phenylenediamine dihydrochloride (DMPD) radical scavenging activity, total antioxidant activity determination by ferric thiocyanate, total reducing ability determination by the Fe(3+)-Fe(2+) transformation method, superoxide anion radical scavenging by the riboflavin/methionine/illuminate system, hydrogen peroxide scavenging and ferrous ions (Fe(2+)) chelating activities. Curcumin inhibited 97.3% lipid peroxidation of linoleic acid emulsion at 15 microg/mL concentration (20 mM). On the other hand, butylated hydroxyanisole (BHA, 123 mM), butylated hydroxytoluene (BHT, 102 mM), alpha-tocopherol (51 mM) and trolox (90 mM) as standard antioxidants indicated inhibition of 95.4, 99.7, 84.6 and 95.6% on peroxidation of linoleic acid emulsion at 45 microg/mL concentration, respectively. In addition, curcumin had an effective DPPH* scavenging, ABTS*(+) scavenging, DMPD*(+) scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, ferric ions (Fe(3+)) reducing power and ferrous ions (Fe(2+)) chelating activities. Also, BHA, BHT, alpha-tocopherol and trolox, were used as the reference antioxidant and radical scavenger compounds. According to the present study, curcumin can be used in the pharmacological and food industry because of these properties.

  1. Nitrene Radical Intermediates in Catalytic Synthesis.

    PubMed

    Kuijpers, Petrus; van der Vlugt, Jarl Ivar; Schneider, Sven; de Bruin, Bas

    2017-07-04

    Nitrene radical complexes are reactive intermediates with discrete spin density at the nitrogen-atom of the nitrene moiety. These species have become important intermediates for organic synthesis, being invoked in a broad range of C-H functionalization and aziridination reactions. Nitrene radical complexes have intriguing electronic structures, and are best described as one-electron reduced Fischer-type nitrenes. They can be generated by intramolecular single electron transfer to the 'redox non-innocent' nitrene moiety at the metal. Nitrene radicals generated at open-shell cobalt(II) have thus far received most attention in terms of spectroscopic characterization, reactivity screening, catalytic application and (computational and experimental) mechanistic studies, but some interesting iron and precious metal catalysts have also been employed in related reactions involving nitrene radicals. In some cases, redox-active ligands are used to facilitate intramolecular single electron transfer from the complex to the nitrene moiety. Organic azides are among the most attractive nitrene precursors in this field, typically requiring pre-activated organic azides (e.g. RSO2N3, (RO)2P(=O)N3, ROC(=O)N3 and alike) to achieve efficient and selective catalysis. Challenging, non-activated aliphatic organic azides were recently added to the palette of synthetically useful reactions proceeding via nitrene radical intermediates. This concept article describes the electronic structure of nitrene radical complexes, emphasizes on their usefulness in the catalytic synthesis of various organic products, and highlights the important developments in the field. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Resonance ionization detection of combustion radicals

    SciTech Connect

    Cool, T.A.

    1993-12-01

    Fundamental research on the combustion of halogenated organic compounds with emphasis on reaction pathways leading to the formation of chlorinated aromatic compounds and the development of continuous emission monitoring methods will assist in DOE efforts in the management and disposal of hazardous chemical wastes. Selective laser ionization techniques are used in this laboratory for the measurement of concentration profiles of radical intermediates in the combustion of chlorinated hydrocarbon flames. A new ultrasensitive detection technique, made possible with the advent of tunable VUV laser sources, enables the selective near-threshold photoionization of all radical intermediates in premixed hydrocarbon and chlorinated hydrocarbon flames.

  3. Radical Behaviorism and Buddhism: Complementarities and Conflicts

    PubMed Central

    Diller, James W; Lattal, Kennon A

    2008-01-01

    Comparisons have been made between Buddhism and the philosophy of science in general, but there have been only a few attempts to draw comparisons directly with the philosophy of radical behaviorism. The present review therefore considers heretofore unconsidered points of comparison between Buddhism and radical behaviorism in terms of their respective goals, conceptualization of human beings, and the outcomes of following either philosophy. From these comparisons it is concluded that the commonalities discerned between these two philosophies may enhance both philosophical systems. PMID:22478509

  4. Evolution of radical mastectomy for breast cancer

    PubMed Central

    Plesca, M; Bordea, C; El Houcheimi, B; Ichim, E; Blidaru, A

    2016-01-01

    Surgical treatment of breast cancer has been marked by a constant evolution since the Halsted radical mastectomy described in the late 19th century has become the current standard Madden radical mastectomy, a breast surgery that involves the ablation of tissue with the axillary lymphatic preserving both pectoral muscles. The purpose of this paper was to present the stages that have marked the evolution of this intervention and to provide an overview of the way breast cancer has been understood and treated in the last century. PMID:27453752

  5. Carbon nanotubes: promising agents against free radicals.

    PubMed

    Galano, Annia

    2010-03-01

    The potential role of carbon nanotubes (CNTs) as free-radical scavengers is still an emerging area of research. So far some promising results have been reported strongly suggesting that CNTs can be very efficient for that task. The implications of such a valuable property for applications aimed at biomedical and environmental uses are encouraging. There are still abundant open questions related to the possible use of CNTs for scavenging free radicals. Thus much more work needs to be devoted to this fascinating topic. In this mini review the progress made so far is reviewed and some future perspectives are provided.

  6. Trisphenalenyl-based neutral radical molecular conductor.

    PubMed

    Pal, Sushanta K; Itkis, Mikhail E; Tham, Fook S; Reed, Robert W; Oakley, Richard T; Haddon, Robert C

    2008-03-26

    We report the preparation, crystallization, and solid-state characterization of the first member of a new family of tris(1,9-disubstituted phenalenyl)silicon neutral radicals. In the solid state, the radical packs as weak partial pi-dimers with intermolecular carbon...carbon contacts that fall at the van der Waals atomic separation. Magnetic susceptibility measurements indicate approximately 0.7 Curie spins per molecule from room temperature down to 50 K, below which antiferromagnetic coupling becomes apparent; the compound has a room-temperature single-crystal conductivity of sigmaRT = 2.4 x 10(-6) S cm(-1).

  7. Resonant cavity spectroscopy of radical species

    NASA Astrophysics Data System (ADS)

    Ritchie, Grant

    2015-04-01

    Photo-oxidation in the troposphere is highly complex, being initiated by short lived radical species, in the daytime dominated by the hydroxyl radical, OH, with contributions from Cl atoms, and at night by either NO3 radicals or ozone. Chemical oxidation cycles, which couple OH, HO2 and peroxy (RO2) radical species, remove primary emitted trace species which are harmful to humans or to the wider environment. However, many of the secondary products produced by atmospheric photo-oxidation are also directly harmful, for example O3, NO2, acidic and multifunctional species, many of which are of low volatility and are able to partition effectively to the condensed phase, creating secondary organic aerosol (SOA), which contributes a significant fraction of tropospheric aerosol, with associated impacts on climate and human health. The accuracy of atmospheric models to predict these impacts necessarily requires accurate knowledge of the chemical oxidative cycling. Two of the simplest intermediates are the hydroperoxy radical, HO2, and the smallest and dominant organic peroxy radical, CH3O2, formed directly by the reactions of OH with CO/O2 and CH4/O2, respectively, and indirectly following the oxidation of larger VOCs. OH, HO2 and RO2 (collectively known as ROx) are rapidly cycled, being at the centre of tropospheric oxidation, and hence are some of the best targets for models to compare with field data. The reaction of HO2 and RO2 with NO constitutes the only tropospheric in-situ source of O3. Despite their importance, neither HO2 nor CH3O2 is measured directly in the atmosphere. HO2 is only measured indirectly following its conversion to OH and CH3O2 is not measured at all. Typically only the sum of RO2 radicals is measured, making no distinction between different organic peroxy radicals. This contribution will detail recent studies using (i) optical feedback cavity enhanced absorption spectroscopy with both quantum and inter-band cascade lasers in the mid-IR, and (ii

  8. Free-radical kinetics of coal liquefaction

    SciTech Connect

    Wang, M.; Smith, J.M.; McCoy, B.J.

    1994-07-16

    A rate expression with first- and second-order terms in the concentration of extractable compounds in solid coal particles is derived from a fundamental free-radical mechanism. The expression was suggested empirically by prior experiments for coal liquefaction in the presence of a hydrogen-donor solvent. Radical reactions are considered to occur in both coal and in solvent. The long-chain approximation justifies the neglect of initiation, hydrogen abstraction, and termination rates as quantitatively insignificant relative to propagation reaction rates.

  9. Elementary radical formation and conversion processes in. gamma. -irradiated polyvinylchloride

    SciTech Connect

    Torikai, A.; Adachi, T.; Fueki, K.

    1981-11-01

    Elementary processes of ..gamma..-irradiated polyvinylchloride (PVC) have been investigated by both electron spin resonance (ESR) and optical absorption measurements. On irradiating PVC film with ..gamma.. rays at -196/sup 0/C, alkyl-type radicals are produced. When the PVC film is warmed to room temperature, the radicals convert to polyenyl type. ..gamma.. irradiation of PVC film containing biphenyl (Ph/sub 2/) or pyrene (Py) at -196/sup 0/C yields the corresponding radical cation. The relative ESR peak heights of the radicals decrease and the G values for the formation of cation radicals increase with increasing additive concentrations. These facts indicate that energy is transferred from the precursor of the radicals to the additive. In the case of PVC film containing Py, the Py cation radical decreases the cyclohexadienyl-type radical from Py is produced by thermal annealing. A possible mechanism for radical formation and conversion is proposed.

  10. Peroxy Radical Chemistry and Partitioning under a Ponderosa Pine Canopy

    NASA Astrophysics Data System (ADS)

    Wolfe, G. M.; Cantrell, C. A.; Mauldin, L.; Kim, S.; Henry, S. B.; Boyle, E. S.; Karl, T.; Harley, P. C.; Turnipseed, A.; Zheng, W.; Flocke, F. M.; Apel, E. C.; Hornbrook, R. S.; Hall, S. R.; Ullmann, K.; Guenther, A. B.; DiGangi, J. P.; Kaser, L.; Schnitzhofer, R.; Hansel, A.; Graus, M.; Nakashima, Y.; Kajii, Y. J.; Keutsch, F. N.

    2012-12-01

    As the first intermediates in the OH-initiated oxidation of hydrocarbons, peroxy radicals are central to the photochemistry of the lower atmosphere. Peroxy radical abundance and partitioning controls relative rates of radical propagation and termination in low-NOx regimes, and the coupled cycling of these molecules lies at the heart of recently-highlighted deficiencies in traditional chemical mechanisms. Using observations of hydroperoxy (HO2) and total peroxy (HO2 + RO2) radicals acquired during the summer 2010 BEACHON-ROCs campaign, we explore the processes affecting radical-mediated chemistry within a rural Ponderosa pine forest in central Colorado. Steady-state and fully-coupled 0-D modeling studies are used to provide complementary perspectives on our understanding of the radical budget in this environment. Analysis will focus on the nature and impact of unidentified radical sources and sinks and on how the composition of the peroxy radical pool modulates radical regeneration.

  11. The sensitivity of a radical pair compass magnetoreceptor can be significantly amplified by radical scavengers.

    PubMed

    Kattnig, Daniel R; Hore, P J

    2017-09-14

    Birds have a remarkable ability to obtain navigational information from the Earth's magnetic field. The primary detection mechanism of this compass sense is uncertain but appears to involve the quantum spin dynamics of radical pairs formed transiently in cryptochrome proteins. We propose here a new version of the current model in which spin-selective recombination of the radical pair is not essential. One of the two radicals is imagined to react with a paramagnetic scavenger via spin-selective electron transfer. By means of simulations of the spin dynamics of cryptochrome-inspired radical pairs, we show that the new scheme offers two clear and important benefits. The sensitivity to a 50 μT magnetic field is greatly enhanced and, unlike the current model, the radicals can be more than 2 nm apart in the magnetoreceptor protein. The latter means that animal cryptochromes that have a tetrad (rather than a triad) of tryptophan electron donors can still be expected to be viable as magnetic compass sensors. Lifting the restriction on the rate of the spin-selective recombination reaction also means that the detrimental effects of inter-radical exchange and dipolar interactions can be minimised by placing the radicals much further apart than in the current model.

  12. 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

  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. COST Action CM1201 "Biomimetic Radical Chemistry": free radical chemistry successfully meets many disciplines.

    PubMed

    Ferreri, Carla; Golding, Bernard T; Jahn, Ullrich; Ravanat, Jean-Luc

    2016-11-01

    The COST Action CM1201 "Biomimetic Radical Chemistry" has been active since December 2012 for 4 years, developing research topics organized into four working groups: WG1 - Radical Enzymes, WG2 - Models of DNA damage and consequences, WG3 - Membrane stress, signalling and defenses, and WG4 - Bio-inspired synthetic strategies. International collaborations have been established among the participating 80 research groups with brilliant interdisciplinary achievements. Free radical research with a biomimetic approach has been realized in the COST Action and are summarized in this overview by the four WG leaders.

  15. Tropospheric aqueous-phase free-radical chemistry: radical sources, spectra, reaction kinetics and prediction tools.

    PubMed

    Herrmann, Hartmut; Hoffmann, Dirk; Schaefer, Thomas; Bräuer, Peter; Tilgner, Andreas

    2010-12-17

    The most important radicals which need to be considered for the description of chemical conversion processes in tropospheric aqueous systems are the hydroxyl radical (OH), the nitrate radical (NO(3)) and sulphur-containing radicals such as the sulphate radical (SO(4)(-)). For each of the three radicals their generation and their properties are discussed first in the corresponding sections. The main focus herein is to summarize newly published aqueous-phase kinetic data on OH, NO(3) and SO(4)(-) radical reactions relevant for the description of multiphase tropospheric chemistry. The data compilation builds up on earlier datasets published in the literature. Since the last review in 2003 (H. Herrmann, Chem. Rev. 2003, 103, 4691-4716) more than hundred new rate constants are available from literature. In case of larger discrepancies between novel and already published rate constants the available kinetic data for these reactions are discussed and recommendations are provided when possible. As many OH kinetic data are obtained by means of the thiocyanate (SCN(-)) system in competition kinetic measurements of OH radical reactions this system is reviewed in a subchapter of this review. Available rate constants for the reaction sequence following the reaction of OH+SCN(-) are summarized. Newly published data since 2003 have been considered and averaged rate constants are calculated. Applying competition kinetics measurements usually the formation of the radical anion (SCN)(2)(-) is monitored directly by absorption measurements. Within this subchapter available absorption spectra of the (SCN)(2)(-) radical anion from the last five decades are presented. Based on these spectra an averaged (SCN)(2)(-) spectrum was calculated. In the last years different estimation methods for aqueous phase kinetic data of radical reactions have been developed and published. Such methods are often essential to estimate kinetic data which are not accessible from the literature. Approaches for

  16. Rate constants of the reaction of C2-C4 peroxy radicals with OH radicals

    NASA Astrophysics Data System (ADS)

    Assaf, Emmanuel; Tanaka, Shisei; Kajii, Yoshizumi; Schoemaecker, Coralie; Fittschen, Christa

    2017-09-01

    The rate constants for the reaction of three peroxy radicals with OH have been measured using different precursors. Peroxy radicals have been prepared by either the reaction of Cl-atoms with C2H6, C3H8 and n-C4H10 or through photolysis of the corresponding alkyliodide. Using Cl-atoms, the following rate constants have been measured: Experiments using 248 nm photolysis of the corresponding alkyliodides as precursor enhances the rate constants by a factor of two, bringing up the suspicion of a fast reaction between I-atoms and OH radicals.

  17. Understanding political radicalization: The two-pyramids model.

    PubMed

    McCauley, Clark; Moskalenko, Sophia

    2017-04-01

    This article reviews some of the milestones of thinking about political radicalization, as scholars and security officials struggled after 9/11 to discern the precursors of terrorist violence. Recent criticism of the concept of radicalization has been recognized, leading to a 2-pyramids model that responds to the criticism by separating radicalization of opinion from radicalization of action. Security and research implications of the 2-pyramids model are briefly described, ending with a call for more attention to emotional experience in understanding both radicalization of opinion and radicalization of action. (PsycINFO Database Record

  18. Hydroxyl Radical Dosimetry for High Flux Hydroxyl Radical Protein Footprinting Applications Using a Simple Optical Detection Method

    PubMed Central

    Xie, Boer; Sharp, Joshua S.

    2015-01-01

    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 non-analyte 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. PMID:26455423

  19. 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.

  20. Praxis: Implication for "Really" Radical Education.

    ERIC Educational Resources Information Center

    Allman, Paula; Wallis, John

    1990-01-01

    Explicates the concept of praxis in Marx's dialectical analysis of capitalism and relates it to radical education: issues of access to educational opportunities, the challenge to the status quo through curriculum change, the role of the intellectual, and the relationship between knowledge and action. (SK)

  1. Radical Negativity: Music Education for Social Justice

    ERIC Educational Resources Information Center

    McLaren, Peter

    2011-01-01

    According to Hedges (2010), the real enemies of the liberal class are radical thinkers such as Noam Chomsky and Ralph Nader, iconoclastic intellectuals who possess the moral autonomy to defy the power elite. While this author agrees with Hedges, he would take this argument even further. In this article, the author argues that the real enemy of…

  2. Cold and intense OH radical beam sources

    SciTech Connect

    Ploenes, Ludger; Meerakker, Sebastiaan Y. T. van de; Haas, Dominik; Zhang, Dongdong E-mail: stefan.willitsch@unibas.ch; Willitsch, Stefan E-mail: stefan.willitsch@unibas.ch

    2016-05-15

    We present the design and performance of two supersonic radical beam sources: a conventional pinhole-discharge source and a dielectric barrier discharge (DBD) source, both based on the Nijmegen pulsed valve. Both designs have been characterized by discharging water molecules seeded in the rare gases Ar, Kr, or Xe. The resulting OH radicals have been detected by laser-induced fluorescence. The measured OH densities are (3.0 ± 0.6) × 10{sup 11} cm{sup -3} and (1.0 ± 0.5) × 10{sup 11} cm{sup -3} for the pinhole-discharge and DBD sources, respectively. The beam profiles for both radical sources show a relative longitudinal velocity spread of about 10%. The absolute rotational ground state population of the OH beam generated from the pinhole-discharge source has been determined to be more than 98%. The DBD source even produces a rotationally colder OH beam with a population of the ground state exceeding 99%. For the DBD source, addition of O{sub 2} molecules to the gas mixture increases the OH beam density by a factor of about 2.5, improves the DBD valve stability, and allows to tune the mean velocity of the radical beam.

  3. Radical Negativity: Music Education for Social Justice

    ERIC Educational Resources Information Center

    McLaren, Peter

    2011-01-01

    According to Hedges (2010), the real enemies of the liberal class are radical thinkers such as Noam Chomsky and Ralph Nader, iconoclastic intellectuals who possess the moral autonomy to defy the power elite. While this author agrees with Hedges, he would take this argument even further. In this article, the author argues that the real enemy of…

  4. Globins Scavenge Sulfur Trioxide Anion Radical.

    PubMed

    Gardner, Paul R; Gardner, Daniel P; Gardner, Alexander P

    2015-11-06

    Ferrous myoglobin was oxidized by sulfur trioxide anion radical (STAR) during the free radical chain oxidation of sulfite. Oxidation was inhibited by the STAR scavenger GSH and by the heme ligand CO. Bimolecular rate constants for the reaction of STAR with several ferrous globins and biomolecules were determined by kinetic competition. Reaction rate constants for myoglobin, hemoglobin, neuroglobin, and flavohemoglobin are large at 38, 120, 2,600, and ≥ 7,500 × 10(6) m(-1) s(-1), respectively, and correlate with redox potentials. Measured rate constants for O2, GSH, ascorbate, and NAD(P)H are also large at ∼100, 10, 130, and 30 × 10(6) m(-1) s(-1), respectively, but nevertheless allow for favorable competition by globins and a capacity for STAR scavenging in vivo. Saccharomyces cerevisiae lacking sulfite oxidase and deleted of flavohemoglobin showed an O2-dependent growth impairment with nonfermentable substrates that was exacerbated by sulfide, a precursor to mitochondrial sulfite formation. Higher O2 exposures inactivated the superoxide-sensitive mitochondrial aconitase in cells, and hypoxia elicited both aconitase and NADP(+)-isocitrate dehydrogenase activity losses. Roles for STAR-derived peroxysulfate radical, superoxide radical, and sulfo-NAD(P) in the mechanism of STAR toxicity and flavohemoglobin protection in yeast are suggested.

  5. DNP with Trityl Radicals in Deuterated Polyethylene

    NASA Astrophysics Data System (ADS)

    Wang, Li; Meyer, W.; Berlin, A.; Herick, J.; Hess, C.; Reicherz, G.

    2016-02-01

    Chemically doping with trityl radicals was performed in fully deuterated polyethylene. The behavior of paramagnetic centers has been investigated by ESR X-band spectrometer. The highest deuteron polarization was 8% at 2.5 T and 1 K with a spin concentration of 3 × 1019 spins/g.

  6. Radical Constructivism, and the Sin of Relativism

    ERIC Educational Resources Information Center

    Quale, Andreas

    2007-01-01

    The epistemology of "relativism" that is featured by the theory of radical constructivism is addressed. In particular, I examine several objections, all based on this epistemic position of relativism, that are often raised by critics of the theory: the charge of "reality denial" (which, it is often claimed, must lead ultimately to the…

  7. Albert Einstein: Radical Pacifist and Democrat

    NASA Astrophysics Data System (ADS)

    Jayaraman, T.

    We draw attention here to the radical political grounding of Einstein's pacifism. We also drescribe some less commonly known aspects of his commitment to civil liberties, particularly in the context of the anti-l hysteria and anti-racism current in the United States of the late 1940s and 1950s. We also examine briefly his views on socialism.

  8. Prophetic Movements: A Study in Conservative Radicalism.

    ERIC Educational Resources Information Center

    Anderson, Ruth D.

    Dorothy Day and the American Catholic Worker Movement are paradoxical in that they are at the same time conservative and radical, liturgical and rebellious, holy and subversive. These apparently paradoxical qualities become clear when translated through the components of the prophetic movement model. Within this model, prophetic movements are…

  9. Combined radical retropubic prostatectomy and rectal resection.

    PubMed

    Klee, L W; Grmoljez, P

    1999-10-01

    To present our experience with a small series of men who underwent simultaneous radical retropubic prostatectomy and rectal resection. Three men with newly diagnosed prostate cancer were found to have concurrent rectal tumors requiring resection. All three men underwent non-nerve-sparing radical retropubic prostatectomy and abdominoperineal resection (APR) or low anterior resection (LAR) of the rectum at the same operation. In the 2 patients undergoing APR, the levators were approximated posterior to the urethra, and the bladder was secured to the pubis. The patient undergoing LAR had urinary diversion stents placed and a diverting transverse loop colostomy. All 3 patients had excellent return of urinary continence. One patient required reoperation in the early postoperative period for small bowel adhesiolysis and stoma revision. Another patient had a mild rectal anastomotic stricture and a bladder neck stricture; both were successfully treated with a single dilation. No other significant complications occurred in these patients. Radical retropubic prostatectomy can safely be performed with partial or complete rectal resection in a single operation. A few minor modifications of the standard radical retropubic prostatectomy in this setting are suggested.

  10. The Radical Faculty -- What Are Its Goals?

    ERIC Educational Resources Information Center

    Kampf, Louis

    According to radical faculty members and students, universities have been contradicting their humanistic educational ideals by concentrating on competitive professionalism and non-academic research in a struggle for institutional power in a preponderantly capitalistic society. It is their belief that meaningful education provides intellectual…

  11. Globins Scavenge Sulfur Trioxide Anion Radical*

    PubMed Central

    Gardner, Paul R.; Gardner, Daniel P.; Gardner, Alexander P.

    2015-01-01

    Ferrous myoglobin was oxidized by sulfur trioxide anion radical (STAR) during the free radical chain oxidation of sulfite. Oxidation was inhibited by the STAR scavenger GSH and by the heme ligand CO. Bimolecular rate constants for the reaction of STAR with several ferrous globins and biomolecules were determined by kinetic competition. Reaction rate constants for myoglobin, hemoglobin, neuroglobin, and flavohemoglobin are large at 38, 120, 2,600, and ≥ 7,500 × 106 m−1 s−1, respectively, and correlate with redox potentials. Measured rate constants for O2, GSH, ascorbate, and NAD(P)H are also large at ∼100, 10, 130, and 30 × 106 m−1 s−1, respectively, but nevertheless allow for favorable competition by globins and a capacity for STAR scavenging in vivo. Saccharomyces cerevisiae lacking sulfite oxidase and deleted of flavohemoglobin showed an O2-dependent growth impairment with nonfermentable substrates that was exacerbated by sulfide, a precursor to mitochondrial sulfite formation. Higher O2 exposures inactivated the superoxide-sensitive mitochondrial aconitase in cells, and hypoxia elicited both aconitase and NADP+-isocitrate dehydrogenase activity losses. Roles for STAR-derived peroxysulfate radical, superoxide radical, and sulfo-NAD(P) in the mechanism of STAR toxicity and flavohemoglobin protection in yeast are suggested. PMID:26381408

  12. Religious Radicalism and Security in South Asia

    DTIC Science & Technology

    2004-01-01

    reputation con- tinued to take a beating. The radical Islamist cum terrorist brand clung to it like a tar baby —even more tightly, it seemed, when linked...of Bangladesh, reflecting her rabid anti- Islamic, pro-Indian and anti-male bias in her writings—both in literary works (often classified as soft porn

  13. Rydberg electron transitions in the methyl radical

    NASA Astrophysics Data System (ADS)

    Velasco, A. M.; Martin, I.; Lavín, C.

    1997-01-01

    Transition probabilities corresponding to one-photon transitions to Rydberg states of the methyl radical have been calculated with a molecular-adapted version of the quantum defect orbital (QDO) method. The results appear to be in accord with those of an analysis of the experimental spectrum by Herzberg.

  14. Serendipitous Findings While Researching Oxygen Free Radicals

    PubMed Central

    Floyd, Robert A.

    2009-01-01

    This review is based on the honor of receiving the Discovery Award from the Society of Free Radical Biology and Medicine. The review is reflective and presents our thinking which led to experiments that yielded novel observations. Critical questioning of our understanding of oxygen free radicals in biomedical problems led us to use and develop more direct and extremely sensitive methods. This included nitrone free radical spin-trapping and HPLC-electrochemical detection. This technology led to the pioneering use of salicylate to trap hydroxyl free radicals and show increased flux in ischemia/reperfused brain regions and to also first sensitively detect 8-hydroxy-droxyguanosine (8-OHdG) in oxidative-damaged DNA and help assess its role in cancer development. We demonstrated that Methylene Blue (MB) photo-induced formation of 8-hydroxy-guanine in DNA and RNA and discovered that MB sensitively photo-inactivated RNA viruses including HIV and the West Nile Virus. Studies in experimental stroke led us to serendipitously discover that α-phenyl-tert-butylnitrone (PBN) was neuroprotective if given after the stroke. This led to extensive commercial development of NXY-059, a PBN derivative, for the treatment of stroke. More recently we discovered that PBN-nitrones have potent anti-cancer activity and are active in preventing hearing loss caused by acute acoustical trauma. PMID:19439210

  15. Serendipitous findings while researching oxygen free radicals.

    PubMed

    Floyd, Robert A

    2009-04-15

    This review is based on the honor of receiving the Discovery Award from the Society of Free Radical Biology and Medicine. The review is reflective and presents our thinking that led to experiments that yielded novel observations. Critical questioning of our understanding of oxygen free radicals in biomedical problems led us to use and develop more direct and extremely sensitive methods. This included nitrone free radical spin trapping and HPLC-electrochemical detection. This technology led to the pioneering use of salicylate to trap hydroxyl free radicals and show increased flux in ischemia/reperfused brain regions and also to first sensitively detect 8-hydroxyl-2-deoxyguanosine in oxidatively damaged DNA and help assess its role in cancer development. We demonstrated that methylene blue (MB) photoinduces formation of 8-hydroxyguanine in DNA and RNA and discovered that MB sensitively photoinactivates RNA viruses, including HIV and the West Nile virus. Studies in experimental stroke led us serendipitously to discover that alpha-phenyl-tert-butylnitrone (PBN) was neuroprotective if given after the stroke. This led to extensive commercial development of NXY-059, a PBN derivative, for the treatment of stroke. More recently we discovered that PBN nitrones have potent anti-cancer activity and are active in preventing hearing loss caused by acute acoustical trauma.

  16. Radical Constructivism, and the Sin of Relativism

    ERIC Educational Resources Information Center

    Quale, Andreas

    2007-01-01

    The epistemology of "relativism" that is featured by the theory of radical constructivism is addressed. In particular, I examine several objections, all based on this epistemic position of relativism, that are often raised by critics of the theory: the charge of "reality denial" (which, it is often claimed, must lead ultimately to the…

  17. Radical Change: Digital Age Literature and Learning.

    ERIC Educational Resources Information Center

    Dresang, Eliza T.; McClelland, Kathryn

    1999-01-01

    Describes the concept of radical change, a theoretical construct that identifies and explains books with characteristics reflecting the types of interactivity, connectivity, and access that permeate the emerging digital society. Highlights innovative ways that authors, illustrators, and designers incorporate these features into books for…

  18. Free radicals in adolescent varicocele testis.

    PubMed

    Romeo, Carmelo; Santoro, Giuseppe

    2014-01-01

    We examine the relationship between the structure and function of the testis and the oxidative and nitrosative stress, determined by an excessive production of free radicals and/or decreased availability of antioxidant defenses, which occur in the testis of adolescents affected by varicocele. Moreover, the effects of surgical treatment on oxidative stress were provided. We conducted a PubMed and Medline search between 1980 and 2014 using "adolescent," "varicocele," "free radicals," "oxidative and nitrosative stress," "testis," and "seminiferous tubules" as keywords. Cross-references were checked in each of the studies, and relevant articles were retrieved. We conclude that increased concentration of free radicals, generated by conditions of hypoxia, hyperthermia, and hormonal dysfunction observed in adolescent affected by varicocele, can harm germ cells directly or indirectly by influencing nonspermatogenic cells and basal lamina. With regard to few available data in current literature, further clinical trials on the pre- and postoperative ROS and RNS levels together with morphological studies of the cellular component of the testis are fundamental for complete comprehension of the role played by free radicals in the pathogenesis of adolescent varicocele and could justify its pharmacological treatment with antioxidants.

  19. Free Radicals in Adolescent Varicocele Testis

    PubMed Central

    Romeo, Carmelo; Santoro, Giuseppe

    2014-01-01

    We examine the relationship between the structure and function of the testis and the oxidative and nitrosative stress, determined by an excessive production of free radicals and/or decreased availability of antioxidant defenses, which occur in the testis of adolescents affected by varicocele. Moreover, the effects of surgical treatment on oxidative stress were provided. We conducted a PubMed and Medline search between 1980 and 2014 using “adolescent,” “varicocele,” “free radicals,” “oxidative and nitrosative stress,” “testis,” and “seminiferous tubules” as keywords. Cross-references were checked in each of the studies, and relevant articles were retrieved. We conclude that increased concentration of free radicals, generated by conditions of hypoxia, hyperthermia, and hormonal dysfunction observed in adolescent affected by varicocele, can harm germ cells directly or indirectly by influencing nonspermatogenic cells and basal lamina. With regard to few available data in current literature, further clinical trials on the pre- and postoperative ROS and RNS levels together with morphological studies of the cellular component of the testis are fundamental for complete comprehension of the role played by free radicals in the pathogenesis of adolescent varicocele and could justify its pharmacological treatment with antioxidants. PMID:25580183

  20. Radical Change: Digital Age Literature and Learning.

    ERIC Educational Resources Information Center

    Dresang, Eliza T.; McClelland, Kathryn

    1999-01-01

    Describes the concept of radical change, a theoretical construct that identifies and explains books with characteristics reflecting the types of interactivity, connectivity, and access that permeate the emerging digital society. Highlights innovative ways that authors, illustrators, and designers incorporate these features into books for…

  1. Neurotoxins: Free Radical Mechanisms and Melatonin Protection

    PubMed Central

    Reiter, Russel J.; Manchester, Lucien C.; Tan, Dun-Xian

    2010-01-01

    Toxins that pass through the blood-brain barrier put neurons and glia in peril. The damage inflicted is usually a consequence of the ability of these toxic agents to induce free radical generation within cells but especially at the level of the mitochondria. The elevated production of oxygen and nitrogen-based radicals and related non-radical products leads to the oxidation of essential macromolecules including lipids, proteins and DNA. The resultant damage is referred to as oxidative and nitrosative stress and, when the molecular destruction is sufficiently severe, it causes apoptosis or necrosis of neurons and glia. Loss of brain cells compromises the functions of the central nervous system expressed as motor, sensory and cognitive deficits and psychological alterations. In this survey we summarize the publications related to the following neurotoxins and the protective actions of melatonin: aminolevulinic acid, cyanide, domoic acid, kainic acid, metals, methamphetamine, polychlorinated biphenyls, rotenone, toluene and 6-hydroxydopamine. Given the potent direct free radical scavenging activities of melatonin and its metabolites, their ability to indirectly stimulate antioxidative enzymes and their efficacy in reducing electron leakage from mitochondria, it would be expected that these molecules would protect the brain from oxidative and nitrosative molecular mutilation. The studies summarized in this review indicate that this is indeed the case, an action that is obviously assisted by the fact that melatonin readily crosses the blood brain barrier. PMID:21358970

  2. Designed metalloprotein stabilizes a semiquinone radical

    NASA Astrophysics Data System (ADS)

    Ulas, Gözde; Lemmin, Thomas; Wu, Yibing; Gassner, George T.; Degrado, William F.

    2016-04-01

    Enzymes use binding energy to stabilize their substrates in high-energy states that are otherwise inaccessible at ambient temperature. Here we show that a de novo designed Zn(II) metalloprotein stabilizes a chemically reactive organic radical that is otherwise unstable in aqueous media. The protein binds tightly to and stabilizes the radical semiquinone form of 3,5-di-tert-butylcatechol. Solution NMR spectroscopy in conjunction with molecular dynamics simulations show that the substrate binds in the active site pocket where it is stabilized by metal-ligand interactions as well as by burial of its hydrophobic groups. Spectrochemical redox titrations show that the protein stabilized the semiquinone by reducing the electrochemical midpoint potential for its formation via the one-electron oxidation of the catechol by approximately 400 mV (9 kcal mol-1). Therefore, the inherent chemical properties of the radical were changed drastically by harnessing its binding energy to the metalloprotein. This model sets the basis for designed enzymes with radical cofactors to tackle challenging chemistry.

  3. The Radical Challenge of Family Learning

    ERIC Educational Resources Information Center

    West, Linden

    2005-01-01

    This article focuses on the nature of "family learning" programmes in marginalised communities. Such programmes present a series of radical challenges (in the sense of getting to the root of things) to policy makers and professionals alike: about, for instance, the kinds of "learning" on offer and the neglect, perhaps…

  4. Radicals derived from acetaldehyde and vinyl alcohol.

    PubMed

    Estep, Marissa L; Morgan, W James; Winkles, Alexander T; Abbott, Adam S; Villegas-Escobar, Nery; Mullinax, J Wayne; Turner, Walter E; Wang, Xiao; Turney, Justin M; Schaefer, Henry F

    2017-09-04

    Vinyl alcohol and acetaldehyde are isoelectronic products of incomplete butanol combustion. Along with the radicals resulting from the removal of atomic hydrogen or the hydroxyl radical, these species are studied here using ab initio methods as complete as coupled cluster theory with single, double, triple, and perturbative quadruple excitations [CCSDT(Q)], with basis sets as large as cc-pV5Z. The relative energies provided herein are further refined by including corrections for relativistic effects, the frozen core approximation, and the Born-Oppenheimer approximation. The effects of anharmonic zero-point vibrational energies are also treated. The syn conformer of vinyl alcohol is predicted to be lower in energy than the anti conformer by 1.1 kcal mol(-1). The alcoholic hydrogen of syn-vinyl alcohol is found to be the easiest to remove, requiring 84.4 kcal mol(-1). Five other radicals are also carefully considered, with four conformers investigated for the 1-hydroxyvinyl radical. Beyond energetics, we have conducted an overhaul of the spectroscopic literature for these species. Our results also provide predictions for fundamental modes yet to be reported experimentally. To our knowledge, the ν3 (3076 cm(-1)) and ν4 (2999 cm(-1)) C-H stretches for syn-vinyl alcohol and all but one of the vibrational modes for anti-vinyl alcohol (ν1-ν14) are yet to be observed experimentally. For the acetyl radical, ν6 (1035 cm(-1)), ν11 (944 cm(-1)), ν12 (97 cm(-1)), and accounting for our changes to the assignment of the 1419.9 cm(-1) experimental mode, ν10 (1441 cm(-1)), are yet to be observed. We have predicted these unobserved fundamentals and reassigned the experimental 1419.9 cm(-1) frequency in the acetyl radical to ν4 rather than to ν10. Our work also strongly supports reassignment of the ν10 and ν11 fundamentals of the vinoxy radical. We suggest that the bands assigned to the overtones of these fundamentals were in fact combination bands. Our findings may be

  5. [Radical prostatectomy--100 years of evolution].

    PubMed

    Gofrit, Ofer N; Shalhav, Arieh L

    2008-07-01

    Prostate cancer is the most common malignant disease in men. The incidence of prostate cancer has been rising since the early 1990s. Not all men inflicted by prostate cancer will develop clinical disease. Therefore, sorting these cases is a great clinical challenge. Radical prostatectomy has undergone evolution in the last 100 years. Better understanding of the pelvic anatomy has led to a decrease in the blood loss during surgery and in the rate of urinary incontinence and erectile dysfunction following surgery. The introduction of laparoscopy in the late 1990s to this surgery provided the surgeon with a magnified multi-angle field of view and facilitated accurate dissection and suturing. Decreased damage to neighboring tissue made recovery hastier. Nevertheless, laparoscopic radical prostatectomy is a technically challenging surgery and did not become popular. The last step in the evolution of radical prostatectomy is the introduction of robotic systems for assistance in laparoscopic radical prostatectomy. A master-slave robotic system is composed of console and mechanical arms. The surgeon is provided with a magnified three dimensional view of the operative field and with two mechanical arms that accurately replicate its fingers movements. The initial results of robotic-assisted laparoscopic prostatectomy seem promising, however, long-term follow-up and comparison to open surgeries are lacking. Robotic systems were rapidly implemented in the American market and in the year 2006, 40% of all radical prostatectomies were robotic assisted. Future systems may reveal deep structures to the visualized surface by superimposing MRI images on the surgical field.

  6. Cu, Zn-Superoxide Dismutase-driven Free Radical Modifications: Copper- and Carbonate Radical Anion-initiated Protein Radical Chemistry

    PubMed Central

    Ramirez, Dario C.; Gomez-Mejiba, Sandra E.; Corbett, Jean T.; Deterding, Leesa J.; Tomer, Kenneth B.; Mason, Ronald P.

    2009-01-01

    SYNOPSIS The understanding of the mechanism, oxidant(s) involved, and how/what protein radicals are produced during the reaction of wild type Cu, Zn-superoxide dismutase (SOD1) with H2O2 and their fate is incomplete, but a better understanding of the role of this reaction is needed. We used immuno-spin trapping and mass spectrometry analysis to study the protein oxidations driven by human (h) and bovine (b) SOD1 when reacting with H2O2 using human serum albumin (HSA) and mouse brain homogenate (mBH) as target models. In order to gain mechanistic information about this reaction, we considered both copper- and carbonate radical anion-initiated protein oxidation. We chose experimental conditions that clearly separated SOD1-driven oxidation via CO3 •− from that initiated by copper released from the SOD1 active site. In the absence of (bi)carbonate, site-specific radical-mediated fragmentation is produced by SOD1 active-site copper. In the presence of (bi)carbonate and DTPA (to suppress copper chemistry), CO3 •− radical produced distinct radical sites in both SOD1 and HSA, which caused protein aggregation without causing protein fragmentation. The CO3 •− produced by reaction of hSOD1 with H2O2 also produced distinctive DMPO nitrone adduct positive protein bands in the mBH. Finally, we propose a biochemical mechanism to explain CO3 •− production from carbon dioxide, enhanced protein radical formation, and protection by (bi)carbonate against H2O2-induced fragmentation of the SOD1 active site. Our study is important for establishing experimental conditions for studying the molecular mechanism and targets of oxidation during the reverse reaction of SOD1 with H2O2; these results are the first step in analyzing the critical targets of SOD1-driven oxidation during such pathological processes as neuroinflammation. PMID:18764780

  7. Cytochrome c catalyses the formation of pentyl radical and octanoic acid radical from linoleic acid hydroperoxide.

    PubMed Central

    Iwahashi, Hideo; Nishizaki, Koji; Takagi, Ichiro

    2002-01-01

    A reaction of 13-hydroperoxide octadecadienoic acid (13-HPODE) with cytochrome c was analysed using ESR, HPLC-ESR and HPLC-ESR-MS by the combined use of the spin-trapping technique. The ESR, HPLC-ESR and HPLC-ESR-MS analyses showed that cytochrome c catalyses formation of pentyl and octanoic acid radicals from 13-HPODE. On the other hand, only the alpha-(4-pyridyl-1-oxide)-N-t-butylnitrone/octanoic acid radical adduct was detected in the elution profile of HPLC-ESR for a mixture of 13-HPODE with haematin, indicating that haematin catalyses the formation of octanoic acid radical. In addition, the reaction of 13-HPODE with cytochrome c was inhibited by chlorogenic acid, caffeic acid and ferulic acid via two possible mechanisms, i.e. reducing cytochrome c (chlorogenic acid and caffeic acid) and scavenging the radical intermediates (chlorogenic acid, caffeic acid and ferulic acid). PMID:11742529

  8. Monolignol radical-radical coupling networks in western red cedar and Arabidopsis and their evolutionary implications

    NASA Technical Reports Server (NTRS)

    Kim, Myoung K.; Jeon, Jae-Heung; Davin, Laurence B.; Lewis, Norman G.

    2002-01-01

    The discovery of a nine-member multigene dirigent family involved in control of monolignol radical-radical coupling in the ancient gymnosperm, western red cedar, suggested that a complex multidimensional network had evolved to regulate such processes in vascular plants. Accordingly, in this study, the corresponding promoter regions for each dirigent multigene member were obtained by genome-walking, with Arabidopsis being subsequently transformed to express each promoter fused to the beta-glucuronidase (GUS) reporter gene. It was found that each component gene of the proposed network is apparently differentially expressed in individual tissues, organs and cells at all stages of plant growth and development. The data so obtained thus further support the hypothesis that a sophisticated monolignol radical-radical coupling network exists in plants which has been highly conserved throughout vascular plant evolution.

  9. Understanding the microsolvation of radicals: Infrared spectroscopy of benzyl radical water clusters

    NASA Astrophysics Data System (ADS)

    Leicht, Daniel; Kaufmann, Matin; Schwan, Raffael; Schäfer, Jan; Schwaab, Gerhard; Havenith, Martina

    2016-11-01

    The IR spectrum of benzyl radical:water clusters was recorded. Benzyl radicals were produced by vacuum flash pyrolysis and trapped in superfluid helium nanodroplets. The infrared spectrum of benzyl radical water aggregates in the range 2585-2820 cm-1 was recorded by subsequent addition of deuterated water. A total of seven peaks are observed at 2766, 2750, 2656, 2638, 2633, 2598, and 2593 cm-1. Based on pressure dependent measurements and comparison to accompanying ab initio calculations, five of these bands are assigned to distinct O-D stretch vibrations of benzyl:water clusters with one and two water molecules. In line with previous experiments on benzene:water clusters, we observe the formation of a water dimer-like motif that is attached to one face of the benzyl radical.

  10. Radical scavenging activity of antioxidants evaluated by means of electrogenerated HO radical.

    PubMed

    Oliveira, Raquel; Geraldo, Dulce; Bento, Fátima

    2014-11-01

    A method is proposed and tested concerning the characterization of antioxidants by means of their reaction with electrogenerated HO radicals in galvanostatic assays with simultaneous O2 evolution, using a Pt anode fairly oxidized. The consumption of a set of species with antioxidant activity, ascorbic acid (AA), caffeic acid (CA), gallic acid (GA) and trolox (T), is described by a first order kinetics. The rate of the processes is limited by the kinetics of reaction with HO radicals and by the kinetics of charge transfer. Information regarding the scavenger activity of antioxidants is obtained by the relative value of the rate constant of the reaction between antioxidants and HO radicals, k(AO,HO)/k(O2). The number of HO radicals scavenged per molecule of antioxidant is also estimated and ranged from 260 (ascorbic acid) to 500 (gallic acid). The method is applied successfully in the characterization of the scavenger activity of ascorbic acid in a green-tea based beverage.

  11. Pressure effects on the radical-radical recombination reaction of photochromic bridged imidazole dimers.

    PubMed

    Mutoh, Katsuya; Abe, Jiro

    2014-09-07

    The bridged imidazole dimers are some of the attractive fast photochromic compounds which have potential applications to the ophthalmic lenses, real-time hologram and molecular machines. The strategy for expanding their photochromic properties such as the colour variation and tuning the decolouration rates has been vigorously investigated, but the insight into the structural changes along the photochromic reactions has not been demonstrated in detail. Here, we demonstrated the pressure dependence of the radical-radical recombination reaction of the bridged imidazole dimers. The radical-radical interaction can be controlled by applying high pressure. Our results give fundamental information about the molecular dynamics of the bridged imidazole dimers, leading to the development of new functional photochromic machines and pressure-sensitive photochromic materials.

  12. Monolignol radical-radical coupling networks in western red cedar and Arabidopsis and their evolutionary implications

    NASA Technical Reports Server (NTRS)

    Kim, Myoung K.; Jeon, Jae-Heung; Davin, Laurence B.; Lewis, Norman G.

    2002-01-01

    The discovery of a nine-member multigene dirigent family involved in control of monolignol radical-radical coupling in the ancient gymnosperm, western red cedar, suggested that a complex multidimensional network had evolved to regulate such processes in vascular plants. Accordingly, in this study, the corresponding promoter regions for each dirigent multigene member were obtained by genome-walking, with Arabidopsis being subsequently transformed to express each promoter fused to the beta-glucuronidase (GUS) reporter gene. It was found that each component gene of the proposed network is apparently differentially expressed in individual tissues, organs and cells at all stages of plant growth and development. The data so obtained thus further support the hypothesis that a sophisticated monolignol radical-radical coupling network exists in plants which has been highly conserved throughout vascular plant evolution.

  13. TRANSITION METAL CATALYSIS IN CONTROLLED RADICAL POLYMERIZATION: ATOM TRANSFER RADICAL POLYMERIZATION. (R826735)

    EPA Science Inventory

    Novel and diversified macromolecular structures, which include polymers with designed topologies (top), compostions (middle), and functionalities (bottom), can be prepared by atom transfer radical polymerization processes. These polymers can be synthesized from a large variety of...

  14. Carbon radicals. Direct observation and kinetics of a hydroperoxyalkyl radical (QOOH).

    PubMed

    Savee, John D; Papajak, Ewa; Rotavera, Brandon; Huang, Haifeng; Eskola, Arkke J; Welz, Oliver; Sheps, Leonid; Taatjes, Craig A; Zádor, Judit; Osborn, David L

    2015-02-06

    Oxidation of organic compounds in combustion and in Earth's troposphere is mediated by reactive species formed by the addition of molecular oxygen (O2) to organic radicals. Among the most crucial and elusive of these intermediates are hydroperoxyalkyl radicals, often denoted "QOOH." These species and their reactions with O2 are responsible for the radical chain branching that sustains autoignition and are implicated in tropospheric autoxidation that can form low-volatility, highly oxygenated organic aerosol precursors. We report direct observation and kinetics measurements of a QOOH intermediate in the oxidation of 1,3-cycloheptadiene, a molecule that offers insight into both resonance-stabilized and nonstabilized radical intermediates. The results establish that resonance stabilization dramatically changes QOOH reactivity and, hence, that oxidation of unsaturated organics can produce exceptionally long-lived QOOH intermediates.

  15. Charge transfer from 2-aminopurine radical cation and radical anion to nucleobases: A pulse radiolysis study

    NASA Astrophysics Data System (ADS)

    Manoj, P.; Mohan, H.; Mittal, J. P.; Manoj, V. M.; Aravindakumar, C. T.

    2007-01-01

    Pulse radiolysis study has been carried out to investigate the properties of the radical cation of 2-aminopurine (2AP) and the probable charge transfer from the radical cation and radical anion of 2AP to natural nucleobases in aqueous medium. The radical cation of 2AP was produced by the reaction of sulfate radical anion ( SO4rad -). The time resolved absorption spectra obtained by the reaction of SO4rad - with 2AP at neutral pH have two distinct maxima at 380 and 470 nm and is assigned to the formation of a neutral radical of the form 2AP-N 2(-H) rad ( k2 = 4.7 × 10 9 dm 3 mol -1 s -1 at pH 7). This neutral radical is formed from the deprotonation reaction of a very short-lived radical cation of 2AP. The transient absorption spectra recorded at pH 10.2 have two distinct maxima at 400 and 480 nm and is assigned to the formation of a nitrogen centered radical (2AP-N(9) rad ). As the hole transport from 2AP to guanine is a highly probable process, the reaction of SO4rad - is carried out in the presence of guanosine, adenosine and inosine. The spectrum obtained in the presence of guanosine was significantly different from that in the absence and it showed prominent absorption maxima at 380 and 470 nm, and a weak broad maximum centered around 625 nm which match well with the reported spectrum of a neutral guanine radical (G(-H) rad ). The electron transfer reaction from the radical anion of 2AP to thymine (T), cytidine (Cyd) and uridine (Urd) was also investigated at neutral pH. Among the three pyrimidines, only the transient spectrum in the presence of T gave a significant difference from the spectral features of the electron adduct of 2AP, which showed a prominent absorption maximum at 340 nm and this spectrum is similar to the electron adduct spectrum of T. The preferential reduction of thymine by 2AP rad - and the oxidation of guanosine by 2AP rad + clearly follow the oxidation/reduction potentials of the purines and pyrimidines.

  16. FT-IR Study on Liquid Crystal Phase Transitions of Thermotropic Hydrogen-Bonded Cubic Mesogenes, 1,2-Bis(4'-n-alkoxybenzoyl)hydrazines (BABH-n) and 4'-n-Alkoxy-3'-nitrobiphenyl-4-carboxlic acid (ANBC-n): Spectroscopic Evidence for Quasibinary Picture Model.

    PubMed

    Ogawa, Ryoji; Miwa, Yohei; Kutsumizu, Shoichi

    2015-08-06

    Changes in intermolecular interactions and molecular geometry for two kinds of thermotropic cubic mesogenes, 4'-n-alkoxy-3'-nitrobiphenyl-4-carboxlic acid (denoted as ANBC-n, where n represents the number of carbon atoms in the alkoxy group) and 1,2-bis(4'-n-alkoxybenzoyl)hydrazines (BABH-n), at liquid crystal (LC) phase transitions were revealed utilizing the frequency shifts in Fourier transform infrared (FT-IR) bands as a guide. The ANBC-n and BABH-n form two kinds of bicontinuous cubic (Cub(bi)), Ia3d and Im3m types, and smectic LC phases depending on the length of the alkyl chain and temperature. In the present work, two kinds of phase transitions, i.e., smectic C ↔ Ia3d-Cub(bi) phase transition for the ANBC-16 and BABH-9 and Ia3d-Cub(bi) ↔ Im3m-Cub(bi) phase transition for the BABH-13 and BABH-16, were examined, and the experimental result was compared to the entropy changes predicted by the quasibinary picture model. In this model, it is postulated that the basic units in the BABH-n and ANBC-n, i.e., the "chain" and "core", would contribute to the phase transition entropy in different ways. A conclusion of the FT-IR result shows the adequacy of this model for the behavior of the alkyl chain. On the other hand, the FT-IR result suggested that entropy changes for the "core" predicted by this model are not directly related to changes in the intermolecular interactions between the aromatic cores of the LC molecules at the phase transitions.

  17. Free radical metabolism of ethanol by deermouse microsomes

    SciTech Connect

    Knecht, K.T.; Thurman, R.G.; Mason, R.P. NIEHS, Research Triangle Park, NC )

    1991-03-15

    One-electron oxidation of ethanol to the {alpha}-hydroxyethyl radical by rat liver microsomes was previously found to be cytochrome P-450-dependent in the presence of Desferal. With deermouse microsomes, the formation of {alpha}-hydroxyethyl radical from ethanol was demonstrated with the electron paramagnetic resonance (EPR) technique of spin trapping. Free radical formation was enhanced by pretreatment of the animals with ethanol. Boiling of the microsomes, omission of NADPH, or addition of superoxide dismutase abolished free radical formation, but addition of catalase or azide had no affect. Free radicals from the hydroxyl radical scavenger formate were detected when ethanol in the incubation medium was replaced by formate. When equal concentrations of ethanol and formate were added to microsomes, the intensity of each radical adduct signal was decreased by half. Thus, it is concluded that free radical formation in deermouse microsomes is mediated by a P-450-derived, superoxide-dependent oxidizing species.

  18. Pyrimidine nucleobase radical reactivity in DNA and RNA

    NASA Astrophysics Data System (ADS)

    Greenberg, Marc M.

    2016-11-01

    Nucleobase radicals are major products of the reactions between nucleic acids and hydroxyl radical, which is produced via the indirect effect of ionizing radiation. The nucleobase radicals also result from hydration of cation radicals that are produced via the direct effect of ionizing radiation. The role that nucleobase radicals play in strand scission has been investigated indirectly using ionizing radiation to generate them. More recently, the reactivity of nucleobase radicals resulting from formal hydrogen atom or hydroxyl radical addition to pyrimidines has been studied by independently generating the reactive intermediates via UV-photolysis of synthetic precursors. This approach has provided control over where the reactive intermediates are produced within biopolymers and facilitated studying their reactivity. The contributions to our understanding of pyrimidine nucleobase radical reactivity by this approach are summarized.

  19. Some Pluses and Minuses of Radical Constructivism in Mathematics Education.

    ERIC Educational Resources Information Center

    Ellerton, Nerida; Clements, M. A.

    1992-01-01

    Reviews the radical constructivism movement in mathematics education. Benefits identified include learner ownership of mathematical learning; importance of social interaction; and identification of principles for improving mathematics teaching and learning. Weaknesses identified include overzealousness of some radical constructivists; downplaying…

  20. Pyrimidine Nucleobase Radical Reactivity in DNA and RNA.

    PubMed

    Greenberg, Marc M

    2016-11-01

    Nucleobase radicals are major products of the reactions between nucleic acids and hydroxyl radical, which is produced via the indirect effect of ionizing radiation. The nucleobase radicals also result from hydration of cation radicals that are produced via the direct effect of ionizing radiation. The role that nucleobase radicals play in strand scission has been investigated indirectly using ionizing radiation to generate them. More recently, the reactivity of nucleobase radicals resulting from formal hydrogen atom or hydroxyl radical addition to pyrimidines has been studied by independently generating the reactive intermediates via UV-photolysis of synthetic precursors. This approach has provided control over where the reactive intermediates are produced within biopolymers and facilitated studying their reactivity. The contributions to our understanding of pyrimidine nucleobase radical reactivity by this approach are summarized.

  1. Nature of the lowest excited states of neutral polyenyl radicals and polyene radical cations

    NASA Astrophysics Data System (ADS)

    Starcke, Jan Hendrik; Wormit, Michael; Dreuw, Andreas

    2009-10-01

    Due to the close relation of the polyenyl radicals C2n+1H2n+3• and polyene radical cations C2nH2n+2•+ to the neutral linear polyenes, one may suspect their excited states to possess substantial double excitation character, similar to the famous S1 state of neutral polyenes and thus to be equally problematic for simple excited state theories. Using the recently developed unrestricted algebraic-diagrammatic construction scheme of second order perturbation theory and the equation-of-motion coupled-cluster method, the vertical excitation energies, their corresponding oscillator strengths, and the nature of the wave functions of the lowest excited electronic states of the radicals are calculated and analyzed in detail. For the polyenyl radicals two one-photon allowed states are found as D1 and D4 states, with two symmetry-forbidden D2 and D3 states in between, while in the polyene radical cations D1 and D2 are allowed and D3 is forbidden. The order of the states is conserved with increasing chain length. It is found that all low-lying excited states exhibit a significant but similar amount of doubly excited configuration in their wave functions of 15%-20%. Using extrapolation, predictions for the excitation energies of the five lowest excited states of the polyene radical cations are made for longer chain lengths.

  2. Spectroscopic Identification of New Benzyl-Type Radicals in Corona Excitation: CHLORO-α-METHYLBENZYL Radicals

    NASA Astrophysics Data System (ADS)

    Yoon, Young Wook; Lee, Seung Woon; Lee, Sang Kuk; Lee, Gi Woo

    2010-06-01

    Using a pinhole-type glass nozzle coupled with corona excited supersonic expansion (CESE), precursors o- and p-chloro-ethylbenzenes seeded in a large amount of inert carrier gas helium were corona discharged to produce jet-cooled benzyl-type radicals. The vibronic emission spectra were recorded with a long path monochromator to observe vibronic bands of benzyl-type radicals in the visible region. The analysis of the spectra shows the evidence of the o- and p-chlorobenzyl radicals as typical products in corona excitation as well as the o- and p-chloro-α-methylbenzyl radicals as unexpected species. After subtracting the bands belonging to chlorobenzyl radicals, we could construct the vibronic emission spectra of the o- and p-chloro-α-methylbenzyl radical in the D_1 → D_0 electronic transition at the gas phase. By comparing with those of ab initio calculation and of the known vibrational mode frequencies with similar structures, we could obtain the electronic transition and assign the vibrational modes to the bands observed. H. G. Ahn, G. W. Lee, and S. K. Lee J. Phys. Chem. A, 112 (51), 13427 (2008).

  3. Radical formation in the FMN-photosensitized reactions of unsaturated fatty acids bearing double bonds at different positions.

    PubMed

    Nishihama, Nao; Iwahashi, Hideo

    2016-08-15

    -carboxybutyl, 7-carboxyheptyl and 9-carboxynonyl radicals formed in the control reaction mixtures of (z)-6-octadecenoic acid, (z)-9-octadecenoic acid {or (z, z)-9,12-octadecadienoic acid} and (z)-11-octadecenoic acid, respectively. The 4-carboxybutyl, 7-carboxyheptyl and 9-carboxynonyl radicals are all generated through β-scission of alkoxy radicals formed on carboxyl ends of the double bonds of the unsaturated fatty acids. Thus, we could reveal reactive sites of unsaturated fatty acids in the photosensitized reaction of flavin mononucleotide with unsaturated fatty acids bearing a double bond at different positions. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Radical production from photosensitization of imidazoles

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  5. Education Research Will Not Profit from Radical Constructionism.

    ERIC Educational Resources Information Center

    Cobern, William W.

    This paper examines the historical roots of critical realism in western thought, highlights the dramatic nature of the shift in thought that the radical constructivists are seeking, and critically considers the relevance of radical constructivism in science teacher education. Radical constructivism is an epistemological philosophy that divorces…

  6. Hybrid radical energy storage device and method of making

    DOEpatents

    Gennett, Thomas; Ginley, David S.; Braunecker, Wade; Ban, Chunmei; Owczarczyk, Zbyslaw

    2016-04-26

    Hybrid radical energy storage devices, such as batteries or electrochemical devices, and methods of use and making are disclosed. Also described herein are electrodes and electrolytes useful in energy storage devices, for example, radical polymer cathode materials and electrolytes for use in organic radical batteries.

  7. Hybrid radical energy storage device and method of making

    DOEpatents

    Gennett, Thomas; Ginley, David S; Braunecker, Wade; Ban, Chunmei; Owczarczyk, Zbyslaw

    2015-01-27

    Hybrid radical energy storage devices, such as batteries or electrochemical devices, and methods of use and making are disclosed. Also described herein are electrodes and electrolytes useful in energy storage devices, for example, radical polymer cathode materials and electrolytes for use in organic radical batteries.

  8. Copper-catalyzed radical carbooxygenation: alkylation and alkoxylation of styrenes.

    PubMed

    Liao, Zhixiong; Yi, Hong; Li, Zheng; Fan, Chao; Zhang, Xu; Liu, Jie; Deng, Zixin; Lei, Aiwen

    2015-01-01

    A simple copper-catalyzed direct radical carbooxygenation of styrenes is developed utilizing alkyl bromides as radical resources. This catalytic radical difunctionalization accomplishes both alkylation and alkoxylation of styrenes in one pot. A broad range of styrenes and alcohols are well tolerated in this transformation. The EPR experiment shows that alkyl halides could oxidize Cu(I) to Cu(II) in this transformation.

  9. Primary radical yields in pulse irradiated alkaline aqueous solution

    NASA Technical Reports Server (NTRS)

    Fielden, E. M.; Hart, E. J.

    1969-01-01

    Primary radical yields of hydrated electrons, H atoms, and OH radicals are determined by measuring hydrated electron formation following a 4 microsecond pulse of X rays. The pH dependence of free radical yields beyond pH 12 is determined by observation of the hydrated electrons.

  10. Radical-Radical Cyclization Cascades of Barbiturates Triggered by Electron-Transfer Reduction of Amide-Type Carbonyls.

    PubMed

    Huang, Huan-Ming; Procter, David J

    2016-06-22

    Radical-radical cyclization cascades, triggered by single-electron transfer to amide-type carbonyls by SmI2-H2O, convert simple achiral barbiturates in one step to hemiaminal- or enamine-containing tricyclic scaffolds containing up to five contiguous stereocenters (including quaternary stereocenters). Furthermore, we describe the surprising beneficial effect of LiBr on the most challenging of the radical-radical cyclization cascades. An alternative fragmentation-radical cyclization sequence of related substrates allows access to bicyclic uracil derivatives. The radical-radical cyclization process constitutes the first example of a radical cascade involving ET reduction of the amide carbonyl. Products of the cascade can be readily manipulated to give highly unusual and medicinally relevant bi- and tricyclic barbiturates.

  11. Polarized absorption spectra of aromatic radicals in stretched polymer film. 3. Radical ions of acridine and phenazine

    SciTech Connect

    Sekigucki, K.; Hiratsuka, H.; Tanizaki, Y.; Hatano, Y.

    1980-02-21

    Radical anions and cations of acridine and phenazine have been prepared in polymer film by ..gamma..-ray irradiation at 77 K. For the preparation of radical anions the sample was incorporated into polyethylene film by sec-butylamine, while for radical cations poly(vinyl chloride) film and sec-butyl chloride were used. Polarized absorption spectra of these radical ions have been measured in stretched polymer film and analyzed qualitatively in terms of molecular orbital calculations.

  12. Coming to Grips with Radical Social Constructivisms

    NASA Astrophysics Data System (ADS)

    Phillips, D. C.

    This essay distinguishes two broad groups - psychological constructivists and social constructivists - but focusses upon the second of these, although it is stressed that there is great within group variation. More than half of the paper is devoted to general clearing of the ground, during which the reasons for the growing acrimony in the debates between social constructivists and their opponents are assessed, an important consequence of these debates for education is discussed, and an examination is carried out of the radical social constructivist tendency to make strong and exciting but untenable claims which are then backed away from (a tendency which is documented by a close reading of the early pages in Bloors classic book). The last portion of the essay focuses upon social constructivist accounts of the causes of belief in science - the more radical of which denegrate the role of warranting reasons, and which give an exalted place to quasi-anthropological or sociological studies of scientific communities.

  13. Chemiluminescent detection of neutral gaseous radicals.

    PubMed

    Grankin, V P; Styrov, V V; Karpov, E G

    2007-10-07

    This paper presents a systematic approach to the development of novel solid-state chemical sensors on the basis of heterogeneous chemiluminescence. The method is applicable for the identification and measurements of concentration of H, O, and other gaseous chemical radicals, where utilization of standard techniques is difficult. The luminescence is invoked during Eley-Rideal recombination of the radicals in question on the surface of the sensor core. A technique is discussed to separate the contributions of Eley-Rideal and Langmuir-Hinshelwood mechanisms, and to select appropriate materials for the sensor emitter fabrication. Typical sensor characteristics include sensitivity of 10(5) cm(-3), working gas pressures of 10(-8) - 10(1) Torr, and measurement time approximately 1 s.

  14. Spreading out spin density in polyphenalenyl radicals.

    PubMed

    Trinquier, Georges; Malrieu, Jean-Paul

    2017-10-05

    As suggested by simple topological arguments, monoradical arrangements of properly-oriented polycondensed phenalenyl units can produce highly-delocalized spin distributions. This work examines under which geometrical conditions and to which extent these flat distributions take place. UDFT calculations performed on various instances gathering up to 19 such fused phenalene units confirm the spin-density spreading over entire conjugated skeletons. This occurs, however, with more or less uniformity depending on the compacity of the arrangement, and simple linear stretches do not actually support the delocalized picture. Thermodynamic stability of the radicals is assessed, which follows their delocalization degree. Monocations and monoanions derived from these delocalized radicals are expected to support likewise delocalized charges, as checked by various calculations on corresponding closed-shell ions. Altogether, these attributes might lead to possible applications in organic design, electronic devices, and spintronics.

  15. Lipid modification processes induced by thiyl radicals

    NASA Astrophysics Data System (ADS)

    Mihaljević, Branka; Bujak, Ivana Tartaro

    2016-07-01

    Polyunsaturated fatty acid (PUFA) oxidation by thiyl radicals (RS•) is believed to be responsible for some of the biological radiation damage. At the same time, RS• can cause isomerization of PUFA double bonds with the formation of trans isomers. The aim of this study was to better understand the competition between lipid peroxidation and geometrical isomerization processes in biomimetic model system of linoleic acid in the presence of 2-mercaptoethanol using irradiation as a method for free radicals generation. In air-equilibrated conditions the propagation of lipid peroxidation was dominant up to the dose of 400 Gy, after which at higher doses up to 10 kGy the termination occurred with the predominance of geometrical isomerization. This study revealed that undesirable and permanent lipid modifications are possible at higher irradiation doses which should be considered in the planning of irradiation treatment of foods and feeds with high content of lipids and sulfur compounds.

  16. EPR study of free radicals in bread

    NASA Astrophysics Data System (ADS)

    Yordanov, Nicola D.; Mladenova, Ralitsa

    2004-05-01

    The features of the recorded EPR spectra of paramagnetic species formed in bread and rusk are reported. The appearance of free radicals in them is only connected with their thermal treatment since the starting materials (flour and grains) exhibit very weak EPR signal. The obtained EPR spectra are complex and indicate that: (i) the relative number of paramagnetic species depends on the temperature and treating time of the raw product; (ii) the g-values are strongly temperature dependent with a tendency to coincide at t≥220 °C. Because of the relatively low (150-220 °C) temperature of thermal treatment, the studied free radicals can be assumed to appear in the course of the browning (Maillard) reaction and not to the carbonization of the material.

  17. Electronic spectrum of 9-methylanthracenium radical cation

    NASA Astrophysics Data System (ADS)

    O'Connor, Gerard D.; Sanelli, Julian A.; Dryza, Vik; Bieske, Evan J.; Schmidt, Timothy W.

    2016-04-01

    The predissociation spectrum of the cold, argon-tagged, 9-methylanthracenium radical cation is reported from 8000 cm-1 to 44 500 cm-1. The reported spectrum contains bands corresponding to at least eight electronic transitions ranging from the near infrared to the ultraviolet. These electronic transitions are assigned through comparison with ab initio energies and intensities. The infrared D1←D0 transitions exhibit significant vibronic activity, which is assigned through comparison with TD-B3LYP excited state frequencies and intensities, as well as modelled vibronic interactions. Dissociation of 9-methylanthracenium is also observed at high visible-photon energies, resulting in the loss of either CH2 or CH3. The relevance of these spectra, and the spectra of other polycyclic aromatic hydrocarbon radical cations, to the largely unassigned diffuse interstellar bands, is discussed.

  18. Activist emotions: gay radicalism and melancholic attachments.

    PubMed

    Reynolds, Robert

    2010-01-01

    It has been argued recently that Australian historians have overlooked histories of emotion. In this article, through the life-history analysis of two long-standing Sydney gay activists, I trace the emotional currents of radical gay activism and suggest these histories point to a wider story of Left melancholy in the closing decades of the twentieth century. I argue that their melancholia is not a trauma-like despair but surprisingly is tinged with a sustaining hope.

  19. Chemical Studies of Free Radical Relocalization

    DTIC Science & Technology

    2015-01-13

    and wavefunctions on a 3D tonal, coupled cluster isomerization potential energy surface of cyclooctatetraenyl radical Gerardo Soriano, Peter Zajac...the alkyne-vinylidene isomerization on a heterocyclic ruthenium catalyst Babgen Manookian, Vy Le, Gerardo Soriano, Douglas B. Grotjahn, Andrew L...the presence of CH3I, rather than any of its isomers . This compound, while the first to be prepared, was also the least promising with regards to these

  20. Radical-free biology of oxidative stress

    PubMed Central

    Jones, Dean P.

    2008-01-01

    Free radical-induced macromolecular damage has been studied extensively as a mechanism of oxidative stress, but large-scale intervention trials with free radical scavenging antioxidant supplements show little benefit in humans. The present review summarizes data supporting a complementary hypothesis for oxidative stress in disease that can occur without free radicals. This hypothesis, which is termed the “redox hypothesis,” is that oxidative stress occurs as a consequence of disruption of thiol redox circuits, which normally function in cell signaling and physiological regulation. The redox states of thiol systems are sensitive to two-electron oxidants and controlled by the thioredoxins (Trx), glutathione (GSH), and cysteine (Cys). Trx and GSH systems are maintained under stable, but nonequilibrium conditions, due to a continuous oxidation of cell thiols at a rate of about 0.5% of the total thiol pool per minute. Redox-sensitive thiols are critical for signal transduction (e.g., H-Ras, PTP-1B), transcription factor binding to DNA (e.g., Nrf-2, nuclear factor-κB), receptor activation (e.g., αIIbβ3 integrin in platelet activation), and other processes. Nonradical oxidants, including peroxides, aldehydes, quinones, and epoxides, are generated enzymatically from both endogenous and exogenous precursors and do not require free radicals as intermediates to oxidize or modify these thiols. Because of the nonequilibrium conditions in the thiol pathways, aberrant generation of nonradical oxidants at rates comparable to normal oxidation may be sufficient to disrupt function. Considerable opportunity exists to elucidate specific thiol control pathways and develop interventional strategies to restore normal redox control and protect against oxidative stress in aging and age-related disease. PMID:18684987

  1. 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

  2. Prison Radicalization: The New Extremist Training Grounds?

    DTIC Science & Technology

    2007-09-01

    Virginia (Washington, D.C.: The George Washington University, September 2006), 8, at http://www.heathsystem.virginia.edu/ internet /ciag/publications...www.heathsystem.virginia.edu/ internet /ciag/publications/out_of_the_shadows.pdf (Accessed September 19, 2006), 1. 32 Rex A. Hudson, The Sociology and Psychology of...information, as was Media (publications/ print)(37%), Internet (31%), Books/academic journals (47%) and Informants (29%). Radical group publications were

  3. Addressing Free Radical Oxidation in Acne Vulgaris

    PubMed Central

    Criscito, Maressa C.; Schlesinger, Todd E.; Verdicchio, Robert; Szoke, Ernest

    2016-01-01

    Objective: Comparatively little attention has been paid to the role of free radical oxidation in acne vulgaris. Here, using the traditional abnormalities cited for acne, the authors address the role of free radical oxidation throughout the pathogenesis by detailing the chemistry that may contribute to clinical changes. To probe the effects of free radical oxidation and test an antioxidant, they conducted a preliminary study of topically applied vitamin E. Methods: Seventeen patients with mild-to-moderate acne vulgaris were evaluated over an eight-week period in two private dermatology practices in this open-label study. All patients enrolled were on the same baseline regimen of salicylic acid and benzoyl peroxide. This regimen was then supplemented with topical vitamin E in sunflower seed oil. Results: At the end of the eight-week period, all patients demonstrated clinical improvement, as indicated by a reduction in the number of lesions and global mean difference. A statistically significant reduction was noted as early as Week 2. Enrolled patients also expressed a positive experience due to good tolerability and easy application. Conclusion: Although the exact pathogenesis of acne vulgaris remains unknown, the presence of excessive reactive oxygen species can be implicated in each of the major abnormalities involved. This presence, along with the positive results of the authors’ preliminary study, demonstrates the need for more exploration on the use of topical antioxidants in limiting free radical oxidation in the acne model. This paper is designed to stimulate academic discussion regarding a new way of thinking about the disease state of acne. PMID:26962389

  4. Chromatin changes predict recurrence after radical prostatectomy

    PubMed Central

    Hveem, Tarjei S; Kleppe, Andreas; Vlatkovic, Ljiljana; Ersvær, Elin; Wæhre, Håkon; Nielsen, Birgitte; Kjær, Marte Avranden; Pradhan, Manohar; Syvertsen, Rolf Anders; Nesheim, John Arne; Liestøl, Knut; Albregtsen, Fritz; Danielsen, Håvard E

    2016-01-01

    Background: Pathological evaluations give the best prognostic markers for prostate cancer patients after radical prostatectomy, but the observer variance is substantial. These risk assessments should be supported and supplemented by objective methods for identifying patients at increased risk of recurrence. Markers of epigenetic aberrations have shown promising results in several cancer types and can be assessed by automatic analysis of chromatin organisation in tumour cell nuclei. Methods: A consecutive series of 317 prostate cancer patients treated with radical prostatectomy at a national hospital between 1987 and 2005 were followed for a median of 10 years (interquartile range, 7–14). On average three tumour block samples from each patient were included to account for tumour heterogeneity. We developed a novel marker, termed Nucleotyping, based on automatic assessment of disordered chromatin organisation, and validated its ability to predict recurrence after radical prostatectomy. Results: Nucleotyping predicted recurrence with a hazard ratio (HR) of 3.3 (95% confidence interval (CI), 2.1–5.1). With adjustment for clinical and pathological characteristics, the HR was 2.5 (95% CI, 1.5–4.1). An updated stratification into three risk groups significantly improved the concordance with patient outcome compared with a state-of-the-art risk-stratification tool (P<0.001). The prognostic impact was most evident for the patients who were high-risk by clinical and pathological characteristics and for patients with Gleason score 7. Conclusion: A novel assessment of epigenetic aberrations was capable of improving risk stratification after radical prostatectomy. PMID:27124335

  5. Free Radical Mechanisms of Xenobiotic Mammalian Cytotoxicities

    DTIC Science & Technology

    1991-06-30

    of iron increase the toxicity of halogenated hydrocarbons, while probu- col (an lipid-lowering drug with anti-oxidant properties, a- tocopherol , and...toluene or other solvents which do not assist in conversion of hydroperoxides to alkoxyl radicals. Page #5 F. HPLC Separation of Phospholipids from IRP...different tested agents could be detected in the usual phospholipid composition, the phospholipid HPLC profiles showed the occurrence of a new lipid peak

  6. Ultraviolet photodissociation dynamics of the phenyl radical

    SciTech Connect

    Song Yu; Lucas, Michael; Alcaraz, Maria; Zhang Jingsong; Brazier, Christopher

    2012-01-28

    Ultraviolet (UV) photodissociation dynamics of jet-cooled phenyl radicals (C{sub 6}H{sub 5} and C{sub 6}D{sub 5}) are studied in the photolysis wavelength region of 215-268 nm using high-n Rydberg atom time-of-flight and resonance enhanced multiphoton ionization techniques. The phenyl radicals are produced from 193-nm photolysis of chlorobenzene and bromobenzene precursors. The H-atom photofragment yield spectra have a broad peak centered around 235 nm and are in good agreement with the UV absorption spectra of phenyl. The H + C{sub 6}H{sub 4} product translational energy distributions, P(E{sub T})'s, peak near {approx}7 kcal/mol, and the fraction of average translational energy in the total excess energy, , is in the range of 0.20-0.35 from 215 to 268 nm. The H-atom product angular distribution is isotropic. The dissociation rates are in the range of 10{sup 7}-10{sup 8} s{sup -1} with internal energy from 30 to 46 kcal/mol above the threshold of the lowest energy channel H +o-C{sub 6}H{sub 4} (ortho-benzyne), comparable with the rates from the Rice-Ramsperger-Kassel-Marcus theory. The results from the fully deuterated phenyl radical are identical. The dissociation mechanism is consistent with production of H +o-C{sub 6}H{sub 4}, as the main channel from unimolecular decomposition of the ground electronic state phenyl radical following internal conversion of the electronically excited state.

  7. How Hume's Philosophy Informed Radical Behaviorism.

    PubMed

    Nuzzolilli, Andrew E; Diller, James W

    2015-05-01

    The present paper analyzes consistencies between the philosophical systems of David Hume and B. F. Skinner, focusing on their conceptualization of causality and attitudes about scientific behavior. The ideas that Hume initially advanced were further developed in Skinner's writings and shaped the behavior-analytic approach to scientific behavior. Tracing Skinner's logical antecedents allows for additional historical and philosophical clarity when examining the development of radical behaviorism.

  8. Orthographic Skills Important to Chinese Literacy Development: The Role of Radical Representation and Orthographic Memory of Radicals

    ERIC Educational Resources Information Center

    Yeung, Pui-sze; Ho, Connie Suk-han; Chan, David Wai-ock; Chung, Kevin Kien-hoa

    2016-01-01

    A 3-year longitudinal study among 239 Chinese students in Grades 2-4 was conducted to investigate the relationships between orthographic skills (including positional and functional knowledge of semantic radicals and phonetic radicals, and orthographic memory of radicals) and Chinese literacy skills (word reading, word spelling, reading…

  9. Orthographic Skills Important to Chinese Literacy Development: The Role of Radical Representation and Orthographic Memory of Radicals

    ERIC Educational Resources Information Center

    Yeung, Pui-sze; Ho, Connie Suk-han; Chan, David Wai-ock; Chung, Kevin Kien-hoa

    2016-01-01

    A 3-year longitudinal study among 239 Chinese students in Grades 2-4 was conducted to investigate the relationships between orthographic skills (including positional and functional knowledge of semantic radicals and phonetic radicals, and orthographic memory of radicals) and Chinese literacy skills (word reading, word spelling, reading…

  10. The photodissociation dynamics of alkyl radicals

    SciTech Connect

    Giegerich, Jens; Fischer, Ingo

    2015-01-28

    The photodisscociation dynamics of the alkyl radicals i-propyl (CH(CH{sub 3}){sub 2}) and t-butyl (C(CH{sub 3}){sub 3}) are investigated by H-atom photofragment imaging. While i-propyl is excited at 250 nm, the photodynamics of t-butyl are explored over a large energy range using excitation wavelengths between 347 nm and 233 nm. The results are compared to those obtained previously for ethyl, CH{sub 3}CH{sub 2}, and to those reported for t-butyl using 248 nm excitation. The translational energy (E{sub T}) distribution of the H-atom photofragments is bimodal and appears rather similar for all three radicals. The low E{sub T} part of the distribution shows an isotropic photofragment angular distribution, while the high E{sub T} part is associated with a considerable anisotropy. Thus, for t-butyl, two H-atom loss channels of roughly equal importance have been identified in addition to the CH{sub 3}-loss channel reported previously. A mechanism for the photodissociation of alkyl radicals is suggested that is based on interactions between Rydberg- and valence states.

  11. The Spectroscopy of the Formyl Radical.

    NASA Astrophysics Data System (ADS)

    Adamson, George William

    Fluorescence-excitation and stimulated emission pumping (SEP) spectroscopies were used to study the properties of photolytically generated, gas phase, formyl radical (HCO). This work focused on the ground doublet electronic state, between 4000-11 200cm^{-1} of energy, and the second excited doublet electronic state, between 38 590-38 750cm^{-1 } of energy. From the fluorescence-excitation spectrum the rotational, centrifugal distortion, and spin -rotational constants were determined for the vibrationless level of the second excited doublet electronic state. From the stimulated emission pumping spectrum vibrational term values, rotational constants, spin-rotational constants, and rotational linewidths were determined for ground electronic state vibrational levels--both above and below the dissociation limit for formyl radical dissociating to hydrogen atom and carbon monoxide. The systematics of the dissociation lifetimes, inferred from the observed rotational linewidths, for rovibrational levels of the ground electronic state were studied. The dissociating lifetimes were found to be strongly correlated with bending vibrational excitation and the amount of angular momentum about the minimum inertial axis of formyl radical. The observed dissociation lifetimes indicates the need for an upward adjustment of the currently accepted dissociation limit and barrier height. (Copies available exclusively from MIT Libraries, Rm. 14-0951, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253 -1690.).

  12. Gastric carcinoma: is radical gastrectomy worth while?

    PubMed Central

    Longmire, William P

    1980-01-01

    Total gastrectomy as the treatment of choice for gastric carcinoma was evaluated by a number of centres during the decade 1945-55. The operative mortality was found to be higher, the 5-year survival rate was lower, and the undesirable digestive side effects were greater than those following subtotal resection. The very radical subtotal resections with miniature gastric remnants were also found to result in postgastrectomy symptoms quite similar to those of total gastrectomy. Technical refinements of oesophagojejunal anastomoses and the use of nutritional supplements and antianaemic therapy have reduced but have not eliminated the sequelae of radical gastrectomy. A review of 15 reports of gastric cancer treatment from 8 countries suggests that in recent years total gastrectomy has been utilised in 25.4% of resections, with an average operative mortality of 21.7% and a 5-year survival of 12.3%. Radical resection or total gastrectomy is recommended for certain specific conditions, but for the usual antral gastric cancer subtotal resection distal to the vasa brevia with preservation of the gastric fundus and spleen is recommended PMID:7362184

  13. Free radical biology of the cardiovascular system.

    PubMed

    Chen, Alex F; Chen, Dan-Dan; Daiber, Andreas; Faraci, Frank M; Li, Huige; Rembold, Christopher M; Laher, Ismail

    2012-07-01

    Most cardiovascular diseases (CVDs), as well as age-related cardiovascular alterations, are accompanied by increases in oxidative stress, usually due to increased generation and/or decreased metabolism of ROS (reactive oxygen species; for example superoxide radicals) and RNS (reactive nitrogen species; for example peroxynitrite). The superoxide anion is generated by several enzymatic reactions, including a variety of NADPH oxidases and uncoupled eNOS (endothelial NO synthase). To relieve the burden caused by this generation of free radicals, which also occurs as part of normal physiological processes, such as mitochondrial respiratory chain activity, mammalian systems have developed endogenous antioxidant enzymes. There is an increased usage of exogenous antioxidants such as vitamins C and E by many patients and the general public, ostensibly in an attempt to supplement intrinsic antioxidant activity. Unfortunately, the results of large-scale trails do not generate much enthusiasm for the continued use of antioxidants to mitigate free-radical-induced changes in the cardiovascular system. In the present paper, we review the clinical use of antioxidants by providing the rationale for their use and describe the outcomes of several large-scale trails that largely display negative outcomes. We also describe the emerging understanding of the detailed regulation of superoxide generation by an uncoupled eNOS and efforts to reverse eNOS uncoupling. SIRT1 (sirtuin 1), which regulates the expression and activity of multiple pro- and anti-oxidant enzymes, could be considered a candidate molecule for a 'molecular switch'.

  14. Accurate Theoretical Thermochemistry for Fluoroethyl Radicals.

    PubMed

    Ganyecz, Ádám; Kállay, Mihály; Csontos, József

    2017-02-09

    An accurate coupled-cluster (CC) based model chemistry was applied to calculate reliable thermochemical quantities for hydrofluorocarbon derivatives including radicals 1-fluoroethyl (CH3-CHF), 1,1-difluoroethyl (CH3-CF2), 2-fluoroethyl (CH2F-CH2), 1,2-difluoroethyl (CH2F-CHF), 2,2-difluoroethyl (CHF2-CH2), 2,2,2-trifluoroethyl (CF3-CH2), 1,2,2,2-tetrafluoroethyl (CF3-CHF), and pentafluoroethyl (CF3-CF2). The model chemistry used contains iterative triple and perturbative quadruple excitations in CC theory, as well as scalar relativistic and diagonal Born-Oppenheimer corrections. To obtain heat of formation values with better than chemical accuracy perturbative quadruple excitations and scalar relativistic corrections were inevitable. Their contributions to the heats of formation steadily increase with the number of fluorine atoms in the radical reaching 10 kJ/mol for CF3-CF2. When discrepancies were found between the experimental and our values it was always possible to resolve the issue by recalculating the experimental result with currently recommended auxiliary data. For each radical studied here this study delivers the best heat of formation as well as entropy data.

  15. Retroperitoneal hematoma following radical orchiectomy: Two cases

    PubMed Central

    Glicksman, Rachel; Hamilton, Robert J.; Chung, Peter

    2017-01-01

    Treatment of testicular cancer is dependent on the stage of disease at presentation. Stage 1 testicular cancer is treated with radical orchiectomy, followed by active surveillance, radiotherapy, or chemotherapy. Occasionally, unusual and unexpected postoperative changes can be seen on computed tomography (CT), and may raise concern for metastatic disease. Here, we present two cases of testicular cancer patients who developed retroperitoneal hematomas post-radical orchiectomy, one as a classical clinical presentation, and the other as an atypical radiological entity only. The first is a case of a 38-year-old male with a non-seminoma testicular cancer, who developed severe flank pain, hemodynamic instability, and progressive anemia from a retroperitoneal hematoma in the immediate (<24 hours) postoperative period, requiring urgent surgical evacuation. The second is a case of a 33-year-old male with a testicular seminoma who had a large, suspicious retroperitoneal mass on a staging CT scan concerning for metastatic disease, which was later diagnosed as a retroperitoneal hematoma. These cases reveal the clinical variability with which a retroperitoneal hematoma post-radical orchiectomy may present. In addition, the second case demonstrates the importance of recognizing radiological postoperative changes and ensuring that these findings are not mistaken for and treated as metastatic disease. PMID:28163811

  16. [Free radicals and hepatic ischemia-reperfusion].

    PubMed

    Szijártó, Attila

    2015-11-22

    The critical importance of the ischemic-reperfusive injury is well documented with regards to numerous organs and clinical conditions. Oxygen free radicals play a central role in the mediation of the injury, which dominantly influences the prevalence of postoperative complications, (long term) organ damage, and the potential manifestation of systemic reactions. The both anatomically and pathophysiologically unique ischemic-reperfusive injury of the liver, which is expressively vulnerable to free radicals, is of utmost importance in liver surgery. Several techniques (adaptive maneuvers, chemical agents) are known to ameliorate the reperfusive injury. Based on the prior research of the workgroup of the author, the aim of the current article is to overview the set of measures capable of attenuating ischemic-reperfusive injury (ischemic preconditioning, -perconditioning, administration of adenosine, -inosine, -levosimendan, and -poly-ADP-ribose-polymerase inhibitor), with special attention to the ischemic-reperfusive injury of the liver, as well as the special pathophysiological role of free radicals in mediating hepatic damage.

  17. 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.

  18. Chemical Nonlinearities and Radical Pair Lifetime Estimation

    NASA Astrophysics Data System (ADS)

    Robinson, Gregory

    2013-03-01

    Much attention has recently developed around chemical reactions that depend on applied static magnetic fields as weak as earth's. This interest is largely motivated by experiments that implicate the role of spin-selective radical pair recombination in biological magnetic sensing. Existing literature uses a straightforward calculation to approximate the expected lifetime of coherent radical pairs as a function of the minimum RF amplitude that is observed to disrupt magnetic navigation, apparently by decohering the radical pair via electronic Zeeman excitations. But we show that chemical nonlinearities can preclude direct computation of coherent pair lifetime without considering the cellular signalling mechanisms involved, and discuss whether it can explain the surprising fragility of some animals' compass sense. In particular, we demonstrate that an autocatalytic cycle can introduce threshold effects on the disruption sensitivity to applied oscillatory magnetic fields. We will show examples in the mean-field limit and consider the consequences of noise and fluctuations in the Freidlin-Wentzell picture of perturbed dynamical systems.

  19. Free radical generation by selenium compounds

    SciTech Connect

    Yan, L.; Spallholz, J.E. )

    1991-03-11

    Sodium selenite, sodium selenate, selenocystine (SeCys) and selenomethionine (SeMet) were tested for their ability to generate free radicals in the absence and presence of glutathione (GSH) and in the presence of cells of the human mammary tumor cell line HTB123/DU4475. Free radical generation was measured by lucigenin or luminol enhanced chemiluminescence (CL). Lucigenin CL was observed form the reaction of selenite with GSH, 2-mercaptoethanol and L-cysteine. Catalase (CT), glutathione peroxidase (GSHPx) and superoxide dismutase (SOD) suppressed CL. Heat inactivated enzymes had no suppressive inhibition of CL. Luminol CL from the reaction of selenite with GSH was much less than that observed from lucigenin CL. In the presence of the human mammary tumor cells, lucigenin CL increased 5 times the CL produced by selenite or SeCys alone and GSH in the absence of tumor cells. The enhanced CL from these reactions in the presence of tumor cells was also suppressed by CT, GSHPx and SOD. These data suggest that free radicals, mainly superoxide (O{sub 2}{sup {minus}}) anion are produced by the reaction of selenite or SeCys with GSH. In the presence of tumor cells CL was enhanced which may account for selenite and Se Cys toxicity in vitro in comparison to the lesser toxicity of selenate or SeMet.

  20. 4.2.2 Primary alkyl radicals, type R2CH-CH2•

    NASA Astrophysics Data System (ADS)

    Beckwith, A. L. J.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  1. 4.3.6 Secondary alkyl radicals, type R1-ĊH-CHR2 2

    NASA Astrophysics Data System (ADS)

    Beckwith, A. L. J.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  2. 4.5.1.5 Alkyl radicals from 7- and higher membered rings

    NASA Astrophysics Data System (ADS)

    Beckwith, A. L. J.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  3. 4.5.2.1 Radicals from fused rings and spiro compounds

    NASA Astrophysics Data System (ADS)

    Beckwith, A. L. J.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  4. 4.2.4 Primary alkyl radicals, type R-CH2•

    NASA Astrophysics Data System (ADS)

    Beckwith, A. L. J.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  5. 4.2.1 Primary alkyl radicals, type R-CH2-CH2•

    NASA Astrophysics Data System (ADS)

    Beckwith, A. L. J.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  6. 4.5.1.3 Alkyl radicals from 5-membered rings

    NASA Astrophysics Data System (ADS)

    Beckwith, A. L. J.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  7. 4.3.7 Secondary alkyl radicals, type R1-ĊH-CR2 3

    NASA Astrophysics Data System (ADS)

    Beckwith, A. L. J.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  8. 4.5.1.2 Alkyl radicals from 4-membered rings

    NASA Astrophysics Data System (ADS)

    Beckwith, A. L. J.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  9. 4.3.8 Secondary alkyl radicals, type R1-ĊH-R2

    NASA Astrophysics Data System (ADS)

    Beckwith, A. L. J.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  10. 4.5.1.4 Alkyl radicals from 6-membered rings

    NASA Astrophysics Data System (ADS)

    Beckwith, A. L. J.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  11. 4.5.1.1 Alkyl radicals from 3-membered rings

    NASA Astrophysics Data System (ADS)

    Beckwith, A. L. J.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  12. 4.2.3 Primary alkyl radicals, type R3C-CH2•

    NASA Astrophysics Data System (ADS)

    Beckwith, A. L. J.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  13. The reaction of formyl radical with chlorine atom

    NASA Astrophysics Data System (ADS)

    Qu, Zhang-Wang; Dong, Feng; Zhang, Qiyuan; Kong, Fanao

    2004-03-01

    The radical-radical reaction of formyl radical with chlorine atom has been investigated by the time-resolved infrared emission spectroscopy and by the theoretical calculations at the UB3LYP/6-31++G(d,p) and single-point UCCSD(T)/6-311++G(d,p) levels. The products have been verified as the vibrationally excited CO ( v⩽4) and HCl. The reaction is initiated by radical-radical recombination forming an intermediate of formaldehyde chloride, which further dissociates into the products of HCl and CO.

  14. Formation of stable radicals in the radiolysis of hexafluoropropylene

    SciTech Connect

    Allayarov, S.R.; Barkalov, I.M.; Lebedeva, M.Yu.; Loginova, N.N.; Mikhailov, A.I.

    1986-08-20

    The radiolysis of the dimer (perfluoro-4-methyl-2-pentene) and trimer (perfluoro-2,4-dimethyl-3-ethyl-2-pentene) of hexafluoropropylene (HFP) gives thermally stable perfluoroalkyl radicals. The stability of these radicals is apparently related to the steric isolation of the unpaired electron. The formation of a growing oligomer chain perfluoroalkyl radical which is stable in the liquid phase is observed upon the radiolysis of hexafluoropropylene. The radio-chemical yield of such a radical G approx. 0.05 x 10/sup -2/ eV. The low capacity of hexafluoropropylene to undergo homopolymerization is related to the formation of similar inactive radicals.

  15. Radicals contributing to preirradiation graft polymerization onto porous polyethylene

    NASA Astrophysics Data System (ADS)

    Uezu, Kazuya; Saito, Kyoichi; Furusaki, Shintaro; Sugo, Takanobu; Ishigaki, Isao

    Porous polyethylene hollow fiber was irradiated by an electron beam at 160 kGy and 8 kGy/min. The concentrations of the radicals such as alkyl, allyl and peroxy were determined by analyzing an integral form of ESR spectra. The comparison of the decay of the radicals with and without contact with air demonstrated that the key radical contributing to the preirradiation graft polymerization is the alkyl radical. The decay of the alkyl radical was simulated by the diffusion-controlled model in the spherical crystallites of polyethylene.

  16. Formation of ions and radicals from icy grains in comets

    NASA Technical Reports Server (NTRS)

    Jackson, William M.

    1992-01-01

    Two theoretical models for the formation of radicals from ice grains are examined to determine if this can explain the jets in comets. It is shown that the production rates for these radicals by the photolysis of molecules in the icy grains are not high enough to explain the jets. A new mechanism is proposed involving the release of cations and anions in the gas phase as the icy mantle surrounding the grains is evaporated. Solar visible radiation can then form radicals by photodetachment of the electrons from these anions. The production rate of radicals formed in this manner is in accord with the production rates of the observed radicals.

  17. Substituent effect on electronic transition energy of dichlorobenzyl radicals

    NASA Astrophysics Data System (ADS)

    Yoon, Young Wook; Chae, Sang Youl; Lee, Sang Kuk

    2016-01-01

    Ring-substituted benzyl radicals exhibit electronic energies of the D1 ⿿ D0 transition being shifted to red region with respect to the benzyl radical. The red-shifts of disubstituted benzyl radicals are highly dependent on the substitution positions irrespective of substituents. By analyzing the red-shifts of dichlorobenzyl radicals observed, we found that the substituent effect on electronic transition energy is attributed to the molecular plane shape of delocalized Ͽ electrons. We will discuss the influences of locations of Cl substituents on the D1 ⿿ D0 transition energies of dichlorobenzyl radicals using Hückel's molecular orbital theory.

  18. Radicals Are Required for Thiol Etching of Gold Particles.

    PubMed

    Dreier, Timothy A; Ackerson, Christopher J

    2015-08-03

    Etching of gold with an excess of thiol ligand is used in both synthesis and analysis of gold particles. Mechanistically, the process of etching gold with excess thiol is unclear. Previous studies have obliquely considered the role of oxygen in thiolate etching of gold. Herein, we show that oxygen or a radical initiator is a necessary component for efficient etching of gold by thiolates. Attenuation of the etching process by radical scavengers in the presence of oxygen, and the restoration of activity by radical initiators under inert atmosphere, strongly implicate the oxygen radical. These data led us to propose an atomistic mechanism in which the oxygen radical initiates the etching process.

  19. What is Radical Behaviorism? A Review of Jay Moore's Conceptual Foundations of Radical Behaviorism

    PubMed Central

    Baum, William M

    2011-01-01

    B. F. Skinner founded both radical behaviorism and behavior analysis. His founding innovations included: a versatile preparation for studying behavior; explicating the generic nature of stimulus and response; a pragmatic criterion for defining behavioral units; response rate as a datum; the concept of stimulus control; the concept of verbal behavior; and explicating the explanatory power of contingencies. Besides these achievements, however, Skinner also made some mistakes. Subsequent developments in radical behaviorist thought have attempted to remedy these mistakes. Moore's book presents a “party line” version of radical behaviorism. It focuses narrowly on a few of Skinner's concepts (mostly mentalism and verbal behavior) and contains no criticism of his mistakes. In fact, Moore adds a few mistakes of his own manufacture; for example, he insists that the mental realm does not exist—an unprovable and distracting assertion. The book's portrayal of behavior analysis would have been current around 1960; it mentions almost none of the developments since then. It also includes almost no developments in radical behaviorism since Skinner. Moore's book would give an unwary reader a highly distorted picture of contemporary behavior analysis and radical behaviorism.

  20. Growing up Radical: Investigation of Benzyl-Like Radicals with Increasing Chain Lengths

    NASA Astrophysics Data System (ADS)

    Korn, Joseph A.; Jawad, Khadija M.; Hewett, Daniel M.; Zwier, Timothy S.

    2015-06-01

    Combustion processes involve complex chemistry including pathways leading to polyaromatic hydrocarbons (PAHs) from small molecule precursors. Resonance stabilized radicals (RSRs) likely play an important role in the pathways to PAHs due to their unusual stability. Benzyl radical is a prototypical RSR that is stabilized by conjugation with the phenyl ring. Earlier work on α-methyl benzyl radical showed perturbations to the spectroscopy due to a hindered methyl rotor. If the alkyl chain is lengthened then multiple conformations become possible. This talk will discuss the jet-cooled spectroscopy of α-ethyl benzyl radical and α-propyl benzyl radical produced from the discharge of 1-phenyl propanol and 1-phenyl butanol respectively. Electronic spectra were obtained via resonant two-photon ionization, and IR spectra were obtained by resonant ion-dip infrared spectroscopy. Kidwell, N. M.; Reilly, N. J.; Nebgen, B.; Mehta-Hurt, D. N.; Hoehn, R. D.; Kokkin, D. L.; McCarthy, M. C.; Slipchenko, L. V.; Zwier, T. S. The Journal of Physical Chemistry A 2013, 117, 13465.