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Sample records for multiple one-electron oxidations

  1. One-electron oxidation of DNA: mechanism and consequences.

    PubMed

    Schuster, Gary B

    2009-01-01

    All living organisms store the information necessary to maintain life in their DNA. Any process that damages DNA and causes loss or corruption of that information threatens the viability of the organism. One-electron oxidation is such a process. Loss of an electron from DNA generates a radical cation that is located primarily on its nucleobases. The radical cation migrates reversibly through duplex DNA by hopping until it is eventually trapped in an irreversible chemical reaction. The particular sequence of nucleobases in a DNA oligomer determines both the efficiency of hopping and the specific location and nature of the damaging chemical reaction. In its normal aqueous solutions, DNA is a polyanion because of the negative charge carried by its phosphate groups. Counter ions (typically Na(+)) to the phosphate groups play an important role in facilitating both the migration of the radical cation and in its eventual reaction with H(2)O. Irreversible reaction of a radical cation with H(2)O in duplex DNA occurs preferentially at the most reactive site. In normal DNA that is comprised of the four common DNA nucleobases, reaction occurs most commonly at a guanine and results in its conversion primarily to 8-oxo-7,8-dihydroguanine (8-OxoG). Both electronic and steric effects control the outcome of this process. If the DNA oligomer does not contain a suitable guanine, then reaction of the radical cation occurs at the thymine of a TT step primarily by a tandem process. The general outcomes revealed in the one-electron oxidation of DNA oligomers in solution appear to be generally valid also for more complex DNA structures and for the cellular DNA of living organisms. PMID:19749272

  2. Anomalous one-electron processes in the chemistry of uranium nitrogen multiple bonds.

    PubMed

    Mullane, Kimberly C; Lewis, Andrew J; Yin, Haolin; Carroll, Patrick J; Schelter, Eric J

    2014-09-01

    Novel reaction pathways are illustrated in the synthesis of uranium(IV), uranium(V), and uranium(VI) monoimido complexes. In contrast to the straightforward preparation of U(V)(═NSiMe3)[N(SiMe3)2]3 (1), the synthesis of a uranium(V) tritylimido complex, U(V)(═NCPh3)[N(SiMe3)2]3 (4), from U(III)[N(SiMe3)2]3 and Ph3CN3 was found to proceed through multiple one-electron steps. Whereas the oxidation of 1 with copper(II) salts produced the uranium(VI) monoimido complexes U(VI)(═NSiMe3)X[N(SiMe3)2]3 (X = Cl, Br), the reaction of 4 with CuBr2 undergoes sterically induced reduction to form the uranium(VI) monoimido complex U(VI)(═NCPh3)Br2[N(SiMe3)2]2, demonstrating a striking difference in reactivity based on imido substituent. The facile reduction of compounds 1 and 4 with KC8 allowed for the synthesis of the uranium(IV) monoimido derivatives, K[U(IV)(═NSiMe3)[N(SiMe3)2]3] (1-K) and K[U(IV)(═NCPh3)[N(SiMe3)2]3] (4-K), respectively. In contrast, an analogous uranium(IV) monoimido complex, K[U(IV)(═NPh(F))[N(SiMe3)Ph(F)

  3. One-Electron Oxidation of Hydrogen Sulfide by a Stable Oxidant: Hexachloroiridate(IV).

    PubMed

    Hu, Ying; Stanbury, David M

    2016-08-01

    Detailed reports on the oxidation of aqueous H2S by mild one-electron oxidants are lacking, presumably because of the susceptibility of these reactions to trace metal-ion catalysis and the formation of turbid sulfur sols. Here we report on the reaction of [IrCl6](2-) with H2S in acetate buffers. Dipicolinic acid (dipic) is shown to be effective in suppressing metal-ion catalysis. In the presence of dipic the reaction produces [IrCl6](3-) and polysulfides; turbidity develops primarily after the Ir(IV) oxidant is consumed. Water-soluble phosphines are shown to prevent the development of turbidity; in the case of tris-hydroxymethylphosphine (THMP) the product is the corresponding sulfide, THMP═S. THMP diminishes the rates of reduction of Ir(IV), and the rate law with sufficient THMP is first order in [Ir(IV)] and first order in [HS(-)]. The rate-limiting step is inferred to be electron transfer from HS(-) to Ir(IV) with ket = 2.9 × 10(4) M(-1) s(-1) at 25.0 °C and μ = 0.1 M. The kinetic inhibition by THMP is attributed to its interception of a polysulfide chain elongation process. PMID:27410173

  4. COMPUTATIONAL ELECTROCHEMISTRY: AQUEOUS ONE-ELECTRON OXIDATION POTENTIALS FOR SUBSTITUTED ANILINES

    EPA Science Inventory

    Semiempirical molecular orbital theory and density functional theory are used to compute one-electron oxidation potentials for aniline and a set of 21 mono- and di-substituted anilines in aqueous solution. Linear relationships between theoretical predictions and experiment are co...

  5. Highly Oxidizing Excited States of One-Electron Oxidized Guanine in DNA: Wavelength and pH Dependence

    PubMed Central

    Khanduri, Deepti; Adhikary, Amitava; Sevilla, Michael D.

    2011-01-01

    Excited states of one-electron oxidized guanine in DNA are known to induce hole transfer to the sugar moiety and on deprotonation result in neutral sugar radicals that are precursors of DNA-strand breaks. This work carried out in homogeneous aqueous glass (7.5 M LiCl) at low temperatures (77 to 175 K) shows the extent of photoconversion of one-electron oxidized guanine and the associated yields of individual sugar radicals and are crucially controlled by photon energy, protonation state, and strandedness of the oligomer. In addition to forming sugar radicals, highly oxidizing excited states of one-electron oxidized guanine are produced with 405 nm light at pH 5 and below that are able to oxidize chloride ion in the surrounding solution to form Cl2•− via an excited state hole transfer process. Among the various DNA model systems studied in this work, the maximum amount of Cl2•− is produced with ds (double stranded) DNA where the one-electron oxidized guanine exists in its cation radical (G•+:C) form. Thus, via excited state hole transfer, the dsDNA is apparently able to protect itself from cation radical excited states by transfer of damage to the surrounding environment. PMID:21381665

  6. Molecular mechanism of base pairing infidelity during DNA duplication upon one-electron oxidation

    PubMed Central

    Reynisson, Jóhannes

    2010-01-01

    The guanine radical cation (G•+) is formed by one-electron oxidation from its parent guanine (G). G•+ is rapidly deprotonated in the aqueous phase resulting in the formation of the neutral guanine radical [G(-H)•]. The loss of proton occurs at the N1 nitrogen, which is involved in the classical Watson-Crick base pairing with cytosine (C). Employing the density functional theory (DFT), it has been observed that a new shifted base pairing configuration is formed between G(-H)• and C constituting only two hydrogen bonds after deprotonation occurs. Using the DFT method, G(-H)• was paired with thymine (T), adenine (A) and G revealing substantial binding energies comparable to those of classical G-C and A-T base pairs. Hence, G(-H)• does not display any particular specificity for C compared to the other bases. Taking into account the long lifetime of the G(-H)• radical in the DNA helix (5 s) and the rapid duplication rate of DNA during mitosis/meiosis (5-500 bases per s), G(-H)• can pair promiscuously leading to errors in the duplication process. This scenario constitutes a new mechanism which explains how one-electron oxidation of the DNA double helix can lead to mutations. PMID:21603305

  7. XeF(2) /fluoride acceptors as versatile one-electron oxidants.

    PubMed

    Poleschner, Helmut; Seppelt, Konrad

    2013-12-01

    No phlogiston but xenon is released when XeF2 /F(-) acceptors act as new one-electron oxidants. F(-) acceptors are Lewis acids BF3 , B(C6 F5 )3 , and Al{OC(CF3 )3 }3 , and silyl derivatives TfOSiMe3 , Tf2 NSiMe3 , Me3 Si(+)  B(C6 F5 )4 (-) , and Me3 Si(+)  CHB11 Cl11 (-) . The anions BF4 (-) , TfO(-) , Tf2 N(-) , FB(C6 F5 )3 (-) , FAl{OC(CF3 )3 }3 (-) , B(C6 F5 )4 (-) , or CHB11 Cl11 (-) can be introduced into oxidation products of R2 E2 (E=S, Se, Te), [FeCp2 ], [(FeCpS)4 ], tetrathiafulvalene, thianthrene, and (2,4-Br2 C6 H3 )3 N. PMID:24127390

  8. One-electron oxidation chemistry and subsequent reactivity of diiron imido complexes.

    PubMed

    Kuppuswamy, Subramaniam; Powers, Tamara M; Johnson, Bruce M; Brozek, Carl K; Krogman, Jeremy P; Bezpalko, Mark W; Berben, Louise A; Keith, Jason M; Foxman, Bruce M; Thomas, Christine M

    2014-06-01

    The chemical oxidation and subsequent group transfer activity of the unusual diiron imido complexes Fe((i)PrNPPh2)3Fe≡NR (R = tert-butyl ((t)Bu), 1; adamantyl, 2) was examined. Bulk chemical oxidation of 1 and 2 with Fc[PF6] (Fc = ferrocene) is accompanied by fluoride ion abstraction from PF6(-) by the iron center trans to the Fe≡NR functionality, forming F-Fe((i)PrNPPh2)3Fe≡NR ((i)Pr = isopropyl) (R = (t)Bu, 3; adamantyl, 4). Axial halide ligation in 3 and 4 significantly disrupts the Fe-Fe interaction in these complexes, as is evident by the >0.3 Å increase in the intermetallic distance in 3 and 4 compared to 1 and 2. Mössbauer spectroscopy suggests that each of the two pseudotetrahedral iron centers in 3 and 4 is best described as Fe(III) and that one-electron oxidation has occurred at the tris(amido)-ligated iron center. The absence of electron delocalization across the Fe-Fe≡NR chain in 3 and 4 allows these complexes to readily react with CO and (t)BuNC to generate the Fe(III)Fe(I) complexes F-Fe((i)PrNPPh2)3Fe(CO)2 (5) and F-Fe((i)PrNPPh2)3Fe((t)BuNC)2 (6), respectively. Computational methods are utilized to better understand the electronic structure and reactivity of oxidized complexes 3 and 4. PMID:24833117

  9. Monitoring one-electron photo-oxidation of guanine in DNA crystals using ultrafast infrared spectroscopy.

    PubMed

    Hall, James P; Poynton, Fergus E; Keane, Páraic M; Gurung, Sarah P; Brazier, John A; Cardin, David J; Winter, Graeme; Gunnlaugsson, Thorfinnur; Sazanovich, Igor V; Towrie, Michael; Cardin, Christine J; Kelly, John M; Quinn, Susan J

    2015-12-01

    To understand the molecular origins of diseases caused by ultraviolet and visible light, and also to develop photodynamic therapy, it is important to resolve the mechanism of photoinduced DNA damage. Damage to DNA bound to a photosensitizer molecule frequently proceeds by one-electron photo-oxidation of guanine, but the precise dynamics of this process are sensitive to the location and the orientation of the photosensitizer, which are very difficult to define in solution. To overcome this, ultrafast time-resolved infrared (TRIR) spectroscopy was performed on photoexcited ruthenium polypyridyl-DNA crystals, the atomic structure of which was determined by X-ray crystallography. By combining the X-ray and TRIR data we are able to define both the geometry of the reaction site and the rates of individual steps in a reversible photoinduced electron-transfer process. This allows us to propose an individual guanine as the reaction site and, intriguingly, reveals that the dynamics in the crystal state are quite similar to those observed in the solvent medium. PMID:26587711

  10. Monitoring one-electron photo-oxidation of guanine in DNA crystals using ultrafast infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Hall, James P.; Poynton, Fergus E.; Keane, Páraic M.; Gurung, Sarah P.; Brazier, John A.; Cardin, David J.; Winter, Graeme; Gunnlaugsson, Thorfinnur; Sazanovich, Igor V.; Towrie, Michael; Cardin, Christine J.; Kelly, John M.; Quinn, Susan J.

    2015-12-01

    To understand the molecular origins of diseases caused by ultraviolet and visible light, and also to develop photodynamic therapy, it is important to resolve the mechanism of photoinduced DNA damage. Damage to DNA bound to a photosensitizer molecule frequently proceeds by one-electron photo-oxidation of guanine, but the precise dynamics of this process are sensitive to the location and the orientation of the photosensitizer, which are very difficult to define in solution. To overcome this, ultrafast time-resolved infrared (TRIR) spectroscopy was performed on photoexcited ruthenium polypyridyl-DNA crystals, the atomic structure of which was determined by X-ray crystallography. By combining the X-ray and TRIR data we are able to define both the geometry of the reaction site and the rates of individual steps in a reversible photoinduced electron-transfer process. This allows us to propose an individual guanine as the reaction site and, intriguingly, reveals that the dynamics in the crystal state are quite similar to those observed in the solvent medium.

  11. One-electron oxidation of ruthenocene: reactions of the ruthenocenium ion in gentle electrolyte media.

    PubMed

    Swarts, Jannie C; Nafady, Ayman; Roudebush, John H; Trupia, Sabrina; Geiger, William E

    2009-03-01

    The electrochemical oxidation of ruthenocene, RuCp(2) (Cp = eta(5)-C(5)H(5)), 1, has been studied in dichloromethane using a supporting electrolyte containing either the [B(C(6)F(5))(4)](-) (TFAB) or the [B(C(6)H(3)(CF(3))(2))(4)](-) (BArF(24)) counteranion. A quasi-Nernstian process was observed in both cases, with E(1/2) values of 0.41 and 0.57 V vs FeCp(2) in the respective electrolyte media. The ruthenocenium ion 1(+) equilibrates with a metal-metal bonded dimer [Ru(2)Cp(4)](2+), 2(2+), that is increasingly preferred at low temperatures. Dimerization equilibrium constants determined by digital simulation of cyclic voltammetry (CV) curves were in the range of 10(2)-10(4) M(-1) at temperatures of 256 to 298 K. Near room temperature, and particularly when BArF(24) is the counteranion, the dinuclear species [Ru(2)Cp(2)(sigma:eta(5)-C(5)H(4))(2)] (2+), 3(2+), in which each metal is sigma-bonded to a cyclopentadienyl ring, was the preferred electrolytic oxidation product. Cathodic reduction of 3(2+) regenerated ruthenocene. The two dinuclear products, 2(2+) and 3(2+), were characterized by (1)H NMR spectroscopy on anodically electrolyzed solutions of 1 at low temperatures in CD(2)Cl(2)/[NBu(4)][BArF(24)]. The variable temperature NMR behavior of these solutions showed that 3(2+) and 2(2+) take part in a thermal equilibrium, the latter being dominant at the lowest temperatures. Ruthenocene hydride, [1-H](+), was also identified as being present in the electrolysis solutions. The oxidation of ruthenocene is shown to be an inherent one-electron process, giving a ruthenocenium ion which is highly susceptible to reactions that allow it to regain an 18-electron configuration. In a dry non-donor solvent, and in the absence of nucleophiles, this electronic configuration is attained by self-reactions involving formation of Ru-Ru or Ru-C bonds. The present data offer a mechanistic explanation for the previously described results on the chemical oxidation of osmocene (Droege, M

  12. Novel reactions of one-electron oxidized radicals of selenomethionine in comparison with methionine.

    PubMed

    Mishra, B; Sharma, A; Naumov, S; Priyadarsini, K I

    2009-05-28

    Pulse radiolysis studies on hydroxyl (*OH) radical reactions of selenomethionine (SeM), a selenium analogue of methionine, were carried out, and the resultant transient radical cations and their subsequent reactions have been reported. At pH<3, the >Se*-OH radical adducts produced on reaction of SeM with *OH radical were converted to selenium centered radical cations (Se*+M), which react with another molecule of SeM to form dimer radical cation M(Se therefore Se)M+. At pH 7, the >Se*-OH radical adducts were converted to a monomer radical of the type (Se therefore N)M+ that acquires intramolecular stability through interaction with the lone pair of the N atom and this radical is denoted as SeM*+. SeM*+ decayed by first order kinetics, and the reduction potential of the couple SeM*+/SeM was determined to be 1.21+/-0.05 V vs NHE at pH 7. SeM*+ oxidized ABTS2- and TMPD with rate constants of (2.5+/-0.1)x10(8) and (6.1+/-0.2)x10(8) M(-1) s(-1), respectively, and reacted with hydroxide ion with a rate constant of (3.8+/-0.9)x10(5) M(-1) s(-1). SeM*+ reacts with molecular oxygen, and the rate constant for this reaction was determined to be (4.3+/-0.2)x10(8) M(-1) s(-1); similar reaction with methionine could not be observed experimentally. Like methionine radical cations, SeM*+ undergoes decarboxylation, although with lesser yield, to produce reducing 3-methyl-selenopropyl amino radicals (referred as alpha-amino radicals). The formation of these radicals was confirmed both by the estimation of the liberated CO2 and by one-electron reduction of MV2+, thionine, and PNAP. These results have been supported by quantum chemical calculations. Implications of these results in the biological role of SeM have also been briefly discussed. PMID:19408939

  13. One-Electron Reduction of Penicillins in Relation to the Oxidative Stress Phenomenon

    PubMed Central

    Szabó, László; Tóth, Tünde; Takács, Erzsébet; Wojnárovits, László

    2015-01-01

    Certain bactericidal antibiotics target mitochondrial components and, due to the leakage of electrons from the electron transport chain, one-electron reduction might occur that can lead to intermediates passing the electron to suitable acceptors. This study aimed at investigating the one-electron reduction mechanism of selected penicillin derivatives using pulse radiolysis techniques. Penicillins can accommodate the electron on each of their carbonyl carbon. Ketyl radicals are thus produced, which are reducing agents with possibility to interact with suitable biomolecules. A detailed mechanism of the reduction is reported. PMID:26690427

  14. One electron-controlled multiple-valued dynamic random-access-memory

    NASA Astrophysics Data System (ADS)

    Kye, H. W.; Song, B. N.; Lee, S. E.; Kim, J. S.; Shin, S. J.; Choi, J. B.; Yu, Y.-S.; Takahashi, Y.

    2016-02-01

    We propose a new architecture for a dynamic random-access-memory (DRAM) capable of storing multiple values by using a single-electron transistor (SET). The gate of a SET is designed to be connected to a plurality of DRAM unit cells that are arrayed at intersections of word lines and bitlines. In this SET-DRAM hybrid scheme, the multiple switching characteristics of SET enables multiple value data stored in a DRAM unit cell, and this increases the storage functionality of the device. Moreover, since refreshing data requires only a small amount of SET driving current, this enables device operating with low standby power consumption.

  15. Prototropic Equilibria in DNA Containing One-electron Oxidized GC: Intra-duplex vs. Duplex to Solvent Deprotonation

    PubMed Central

    Adhikary, Amitava; Kumar, Anil; Munafo, Shawn A.; Khanduri, Deepti; Sevilla, Michael D.

    2015-01-01

    By use of ESR and UV-vis spectral studies, this work identifies the protonation states of one-electron oxidized G:C (viz. G•+:C, G(N1-H)•:C(+H+), G(N1-H)•:C, and G(N2-H)•:C) in a DNA oligomer d[TGCGCGCA]2. Benchmark ESR and UV-vis spectra from one electron oxidized 1-Me-dGuo are employed to analyze the spectral data obtained in one-electron oxidized d[TGCGCGCA]2 at various pHs. At pH ≥7, the initial site of deprotonation of one-electron oxidized d[TGCGCGCA]2 to the surrounding solvent is found to be at N1 forming G(N1-H)•:C at 155 K. However, upon annealing to 175 K, the site of deprotonation to the solvent shifts to an equilibrium mixture of G(N1-H)•:C and G(N2-H)•:C. For the first time, the presence of G(N2-H)•:C in a ds DNA-oligomer is shown to be easily distinguished from the other prototropic forms, owing to its readily observable nitrogen hyperfine coupling (Azz(N2)= 16 G). In addition, for the oligomer in H2O, an additional 8 G N2-H proton HFCC is found. This ESR identification is supported by a UV-vis absorption at 630 nm which is characteristic for G(N2-H)• in model compounds and oligomers. We find that the extent of photo-conversion to the C1′ sugar radical (C1′•) in the one-electron oxidized d[TGCGCGCA]2 allows for a clear distinction among the various G:C protonation states which can not be easily distinguished by ESR or UV-vis spectroscopies with this order for the extent of photo-conversion: G•+:C > G(N1-H)•:C(+H+) >> G(N1-H)•:C. We propose that it is the G•+:C form that undergoes deprotonation at the sugar and this requires reprotonation of G within the lifetime of exited state. PMID:21491657

  16. One-electron oxidation of gemcitabine and analogs: mechanism of formation of C3' and C2' sugar radicals.

    PubMed

    Adhikary, Amitava; Kumar, Anil; Rayala, Ramanjaneyulu; Hindi, Ragda M; Adhikary, Ananya; Wnuk, Stanislaw F; Sevilla, Michael D

    2014-11-01

    Gemcitabine is a modified cytidine analog having two fluorine atoms at the 2'-position of the ribose ring. It has been proposed that gemcitabine inhibits RNR activity by producing a C3'• intermediate via direct H3'-atom abstraction followed by loss of HF to yield a C2'• with 3'-keto moiety. Direct detection of C3'• and C2'• during RNR inactivation by gemcitabine still remains elusive. To test the influence of 2'- substitution on radical site formation, electron spin resonance (ESR) studies are carried out on one-electron oxidized gemcitabine and other 2'-modified analogs, i.e., 2'-deoxy-2'-fluoro-2'-C-methylcytidine (MeFdC) and 2'-fluoro-2'-deoxycytidine (2'-FdC). ESR line components from two anisotropic β-2'-F-atom hyperfine couplings identify the C3'• formation in one-electron oxidized gemcitabine, but no further reaction to C2'• is found. One-electron oxidized 2'-FdC is unreactive toward C3'• or C2'• formation. In one-electron oxidized MeFdC, ESR studies show C2'• production presumably from a very unstable C3'• precursor. The experimentally observed hyperfine couplings for C2'• and C3'• match well with the theoretically predicted ones. C3'• to C2'• conversion in one-electron oxidized gemcitabine and MeFdC has theoretically been modeled by first considering the C3'• and H3O(+) formation via H3'-proton deprotonation and the subsequent C2'• formation via HF loss induced by this proximate H3O(+). Theoretical calculations show that in gemcitabine, C3'• to C2'• conversion in the presence of a proximate H3O(+) has a barrier in agreement with the experimentally observed lack of C3'• to C2'• conversion. In contrast, in MeFdC, the loss of HF from C3'• in the presence of a proximate H3O(+) is barrierless resulting in C2'• formation which agrees with the experimentally observed rapid C2'• formation. PMID:25296262

  17. Defining the Electronic and Geometric Structure of One-Electron Oxidized Copper–Bis-phenoxide Complexes

    PubMed Central

    Storr, Tim; Verma, Pratik; Pratt, Russell C.; Wasinger, Erik C.; Shimazaki, Yuichi; Stack, T. Daniel P.

    2009-01-01

    The geometric and electronic structure of an oxidized Cu complex ([CuSal]+; Sal = N, N′-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexane-(1R,2R)-diamine) with a non-innocent salen ligand has been investigated both in the solid state and in solution. Integration of information from UV–vis–NIR spectroscopy, magnetic susceptibility, electrochemistry, resonance Raman spectroscopy, X-ray crystallography, X-ray absorption spectroscopy, and density functional theory calculations provides critical insights into the nature of the localization/delocalization of the oxidation locus. In contrast to the analogous Ni derivative [NiSal]+ (Storr, T.; et al. Angew. Chem., Int. Ed. 2007, 46, 5198), which exists solely in the Ni(II) ligand-radical form, the locus of oxidation is metal-based for [CuSal]+, affording exclusively a Cu(III) species in the solid state (4–300 K). Variable-temperature solution studies suggest that [CuSal]+ exists in a reversible spin-equilibrium between a ligand-radical species [Cu(II)Sal•]+ (S = 1) and the high-valent metal form [Cu(III)Sal]+ (S = 0), indicative of nearly isoenergetic species. It is surprising that a bis-imine–bis-phenolate ligation stabilizes the Cu(III) oxidation state, and even more surprising that in solution a spin equilibrium occurs without a change in coordination number. The oxidized tetrahydrosalen analogue [CuSalred]+ (Salred = N, N′-bis(3,5-di-tert-butylhydroxybenzyl)-1,2-cyclohexane-(1R,2R)-diamine) exists as a temperature-invariant Cu(II)–ligand-radical complex in solution, demonstrating that ostensibly simple variations of the ligand structure affect the locus of oxidation in Cu–bis-phenoxide complexes. PMID:18939830

  18. π vs σ-Radical States of One-Electron Oxidized DNA/RNA Bases: A Density Functional Theory Study

    PubMed Central

    Kumar, Anil; Sevilla, Michael D.

    2013-01-01

    As a result of their inherent planarity, DNA base radicals generated by one electron oxidation/reduction or bond cleavage form π- or σ-radicals. While most DNA base systems form π-radicals there are a number of nucleobase analogs such as one-electron oxidized 6-azauraci1, 6-azacytosine, and 2-thiothymine or one-electron reduced 5-bromouracil that form more reactive σ-radicals. Elucidating the availability of these states within DNA, base radical electronic structure is important to the understanding of the reactivity of DNA base radicals in different environments. In this work, we address this question by the calculation of the relative energies of π- and σ-radical states in DNA/RNA bases and their analogs. We used density functional theory B3LYP/6-31++G** method to optimize the geometries of π- and σ-radicals in Cs symmetry (i.e., planar) in the gas phase and in solution using the polarized continuum model (PCM). The calculations predict that σ- and π-radical states in one electron oxidized bases of thymine, T(N3-H)•, and uracil, U(N3-H)• are very close in energy, i.e., the π-radical is only ca. 4 kcal/mol more stable than the σ-radical. For the one electron oxidized radicals of cytosine, C•+, C(N4-H)•, adenine, A•+, A(N6-H)•, and guanine, G•+, G(N2-H)•, G(N1-H)• the π-radicals are ca. 16 to 41 kcal/mol more stable than their corresponding σ-radicals. Inclusion of solvent (PCM) is found to stabilize the π- over σ-radical of each of the systems. U(N3-H)• with three discrete water molecules in the gas phase, is found to form a three-electron σ bond between N3 atom of uracil and O atom of a water molecule but on inclusion of full solvation and discrete hydration the π-radical remains most stable.. PMID:24000793

  19. The one-electron oxidation of a dithiolate molecule: The importance of chemical intuition

    SciTech Connect

    Bushnell, Eric A. C.; Burns, Thomas D.; Boyd, Russell J.

    2014-05-14

    A series of nine commonly used density functional methods were assessed to accurately predict the oxidation potential of the (C{sub 2}H{sub 2}S{sub 2}{sup −2}/C{sub 2}H{sub 2}S{sub 2}{sup •−}) redox couple. It was found that due to their greater tendency for charge delocalization the GGA functionals predict a structure where the radical electron is delocalized within the alkene backbone of C{sub 2}H{sub 2}S{sub 2}{sup •−}, whereas the hybrid functionals and the reference QCISD/cc-pVTZ predict that the radical electron remains localized on the sulfurs. However, chemical intuition suggests that the results obtained with the GGA functionals should be correct. Indeed, with the use of the geometries obtained at the HCTH/6-311++G(3df,3pd) level of theory both the QCISD and hybrid DFT methods yield a molecule with a delocalized electron. Notably, this new molecule lies at least 53 kJ mol{sup −1} lower in energy than the previously optimized one that had a localized radical. Using these new structures the calculated oxidation potential was found to be 2.71–2.97 V for the nine DFT functionals tested. The M06-L functional provided the best agreement with the QCISD/cc-pVTZ reference oxidation potential of 3.28 V.

  20. Thymidine radical formation via one-electron transfer oxidation photoinduced by pterin: Mechanism and products characterization.

    PubMed

    Serrano, Mariana P; Vignoni, Mariana; Lorente, Carolina; Vicendo, Patricia; Oliveros, Esther; Thomas, Andrés H

    2016-07-01

    UV-A radiation (320-400nm), recognized as a class I carcinogen, induces damage to the DNA molecule and its components through different mechanisms. Pterin derivatives are involved in various biological functions, including enzymatic processes, and it has been demonstrated that oxidized pterins may act as photosensitizers. In particular, they accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder. We have investigated the ability of pterin (Ptr), the parent compound of oxidized pterins, to photosensitize the degradation of the pyrimidine nucleotide thymidine 5'-monophosphate (dTMP) in aqueous solutions under UV-A irradiation. Although thymine is less reactive than purine nucleobases, our results showed that Ptr is able to photoinduce the degradation of dTMP and that the process is initiated by an electron transfer from the nucleotide to the triplet excited state of Ptr. In the presence of molecular oxygen, the photochemical process leads to the oxidation of dTMP, whereas Ptr is not consumed. In the absence of oxygen, both compounds are consumed to yield a product in which the pterin moiety is covalently linked to the thymine. This compound retains some of the spectroscopic properties of Ptr, such as absorbance in the UV-A region and fluorescence properties. PMID:27154982

  1. Magnetic Resonance Characterization of One-Electron Oxidized Cyclic Dipeptides with Thioether Groups.

    PubMed

    Köchling, Talea; Morozova, Olga B; Yurkovskaya, Alexandra V; Vieth, Hans-Martin

    2016-09-01

    Photo-oxidation of seven cyclic dipeptides containing methionine, Met, and/or S-methylcysteine, Cys(Me) by electron transfer from the sulfur atom was studied in aqueous solution by time-resolved and field dependent CIDNP (chemically induced dynamic nuclear polarization). Hyperpolarized high resolution NMR spectral patterns of the starting peptides detected immediately after pulsed laser excitation show signals of all protons that are bound to carbons neighboring the sulfur atom, thus proving the involvement of sulfur-centered cation radicals. The magnetic field dependence of CIDNP shows a pronounced maximum that is determined by the g-factors and hyperfine coupling constants of the transient radical species. From simulation of the experimental data obtained for the magnetic field dependences of CIDNP, three types of radical structures were characterized: (1) a linear sulfur-centered cation radical of the methionine (Met) residue (g = 2.0107 ± 0.0010) for cyclo-(d-Met-l-Met) (trans-configuration), cyclo-(d-Met-l-Cys(Me)) (trans-configuration), and cyclo-(Gly-Met); (2) a cyclic radical (S∴O)(+) (g = 2.0088 ± 0.0010) with a two-center three-electron bond (2c-3e) structure between the sulfur atom of the Cys(Me) residue and the oxygen atom of cyclo-(d-Met-l-Cys(Me)) and cyclo-(Gly-Cys(Me)); (3) a cyclic radical (S∴S)(+) (g = 2.013 ± 0.0020) with a two-center three-electron bond structure between the two sulfur atoms of the peptides cyclo-(l-Met-l-Met), cyclo-(l-Met-l-Cys(Me)), and cyclo-(l-Cys(Me)-l-Cys(Me)). In contrast, no indication of any type of cyclic radicals with a two-center three-electron bond between sulfur and nitrogen atoms was found. In addition, the hyperfine coupling constants (HFCCs) were determined. PMID:27518876

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

    PubMed Central

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

    2013-01-01

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

  3. π-Radical to σ-Radical Tautomerization in One-Electron-Oxidized 1-Methylcytosine and Its Analogs.

    PubMed

    Adhikary, Amitava; Kumar, Anil; Bishop, Casandra T; Wiegand, Tyler J; Hindi, Ragda M; Adhikary, Ananya; Sevilla, Michael D

    2015-09-01

    In this work, iminyl σ-radical formation in several one-electron-oxidized cytosine analogs, including 1-MeC, cidofovir, 2'-deoxycytidine (dCyd), and 2'-deoxycytidine 5'-monophosphate (5'-dCMP), were investigated in homogeneous, aqueous (D2O or H2O) glassy solutions at low temperatures by employing electron spin resonance (ESR) spectroscopy. Upon employing density functional theory (DFT) (DFT/B3LYP/6-31G* method), the calculated hyperfine coupling constant (HFCC) values of iminyl σ-radical agree quite well with the experimentally observed ones, thus confirming its assignment. ESR and DFT studies show that the cytosine iminyl σ-radical is a tautomer of the deprotonated cytosine π-cation radical [cytosine π-aminyl radical, C(N4-H)(•)]. Employing 1-MeC samples at various pHs ranging from ca. 8 to 11, ESR studies show that the tautomeric equilibrium between C(N4-H)(•) and the iminyl σ-radical at low temperature is too slow to be established without added base. ESR and DFT studies agree that, in the iminyl σ-radical, the unpaired spin is localized on the exocyclic nitrogen (N4) in an in-plane pure p-orbital. This gives rise to an anisotropic nitrogen hyperfine coupling (Azz = 40 G) from N4 and a near isotropic β-nitrogen coupling of 9.7 G from the cytosine ring nitrogen at N3. Iminyl σ-radical should exist in its N3-protonated form, as the N3-protonated iminyl σ-radical is stabilized in solution by over 30 kcal/mol (ΔG = -32 kcal/mol) over its conjugate base, the N3-deprotonated form. This is the first observation of an isotropic β-hyperfine ring nitrogen coupling in an N-centered DNA radical. Our theoretical calculations predict that the cytosine iminyl σ-radical can be formed in double-stranded DNA by a radiation-induced ionization-deprotonation process that is only 10 kcal/mol above the lowest energy path. PMID:26237072

  4. Formation of isodialuric acid lesion within DNA oligomers via one-electron oxidation of 5-hydroxyuracil: characterization, stability and excision repair.

    PubMed

    Simon, Philippe; Gasparutto, Didier; Gambarelli, Serge; Saint-Pierre, Christine; Favier, Alain; Cadet, Jean

    2006-01-01

    5-Hydroxyuracil is a major oxidized nucleobase that can be generated by the action of (*)OH radical and one-electron oxidants. The latter modified base that exhibits a low ionization potential is highly susceptible to further degradation upon exposure to various oxidants. Emphasis was placed in this work on the formation and characterization of one-electron oxidation products of 5-hydroxyuracil within DNA fragments of defined sequence. For this purpose, 5-hydroxyuracil containing single- and double-stranded oligonucleotides of various lengths were synthesized and then exposed to the oxidizing action of iridium salts. Isodialuric acid was found to be formed almost quantitatively by a one-electron oxidation mechanism for which relevant information was inferred from a freeze-quenched ESR study. Information on the stability of isodialuric acid thus formed and its conversion products in aqueous solutions was also gained from experiments performed at acidic, neutral and alkali pH's. Moreover, biochemical features dealing with the substrate specificity of several bacterial and yeast base excision repair enzymes to remove isodialuric acid from site-specifically modified DNA fragments were determined. PMID:16885239

  5. Formation of isodialuric acid lesion within DNA oligomers via one-electron oxidation of 5-hydroxyuracil: characterization, stability and excision repair

    PubMed Central

    Simon, Philippe; Gasparutto, Didier; Gambarelli, Serge; Saint-Pierre, Christine; Favier, Alain; Cadet, Jean

    2006-01-01

    5-Hydroxyuracil is a major oxidized nucleobase that can be generated by the action of •OH radical and one-electron oxidants. The latter modified base that exhibits a low ionization potential is highly susceptible to further degradation upon exposure to various oxidants. Emphasis was placed in thiswork on the formation and characterization of one-electron oxidation products of 5-hydroxyuracil within DNA fragments of defined sequence. For this purpose, 5-hydroxyuracil containing single- and double-stranded oligonucleotides of various lengths were synthesized and then exposed to the oxidizing action of iridium salts. Isodialuric acid was found to be formed almost quantitatively by a one-electron oxidation mechanism for which relevant information was inferred from a freeze-quenched ESR study. Information on the stability of isodialuric acid thus formed and its conversion products in aqueous solutions was also gained from experiments performed at acidic, neutral and alkali pH’s. Moreover, biochemical features dealing with the substrate specificity of several bacterial and yeast base excision repair enzymes to remove isodialuric acid from site-specifically modified DNA fragments were determined. PMID:16885239

  6. The intriguing enhancement of chloroperoxidase mediated one-electron oxidations by azide, a known active-site ligand

    SciTech Connect

    Andrew, Daniel; Hager, Lowell; Manoj, Kelath Murali

    2011-12-02

    Highlights: Black-Right-Pointing-Pointer Azide is a well known heme-enzyme active site ligand and inhibitor. Black-Right-Pointing-Pointer Herein, azide is reported to enhance a set of heme-enzyme mediated reactions. Black-Right-Pointing-Pointer This effect is disconnected from native enzyme-azide binding. Black-Right-Pointing-Pointer Azide could enhance heme-enzyme reactions via a newly proposed mechanism. Black-Right-Pointing-Pointer Azide contained in reagents could impact reaction outcomes in redox biochemistry. -- Abstract: Azide is a well-known inhibitor of heme-enzymes. Herein, we report the counter-intuitive observation that at some concentration regimes, incorporation of azide in the reaction medium enhances chloroperoxidase (CPO, a heme-enzyme) mediated one-electron abstractions from several substrates. A diffusible azidyl radical based mechanism is proposed for explaining the phenomenon. Further, it is projected that the finding could have significant impact on routine in situ or in vitro biochemistry studies involving heme-enzyme systems and azide.

  7. One-Electron Oxidation of Gemcitabine and Analogs: Mechanism of Formation of C3′ and C2′ Sugar Radicals

    PubMed Central

    2015-01-01

    Gemcitabine is a modified cytidine analog having two fluorine atoms at the 2′-position of the ribose ring. It has been proposed that gemcitabine inhibits RNR activity by producing a C3′• intermediate via direct H3′-atom abstraction followed by loss of HF to yield a C2′• with 3′-keto moiety. Direct detection of C3′• and C2′• during RNR inactivation by gemcitabine still remains elusive. To test the influence of 2′- substitution on radical site formation, electron spin resonance (ESR) studies are carried out on one-electron oxidized gemcitabine and other 2′-modified analogs, i.e., 2′-deoxy-2′-fluoro-2′-C-methylcytidine (MeFdC) and 2′-fluoro-2′-deoxycytidine (2′-FdC). ESR line components from two anisotropic β-2′-F-atom hyperfine couplings identify the C3′• formation in one-electron oxidized gemcitabine, but no further reaction to C2′• is found. One-electron oxidized 2′-FdC is unreactive toward C3′• or C2′• formation. In one-electron oxidized MeFdC, ESR studies show C2′• production presumably from a very unstable C3′• precursor. The experimentally observed hyperfine couplings for C2′• and C3′• match well with the theoretically predicted ones. C3′• to C2′• conversion in one-electron oxidized gemcitabine and MeFdC has theoretically been modeled by first considering the C3′• and H3O+ formation via H3′-proton deprotonation and the subsequent C2′• formation via HF loss induced by this proximate H3O+. Theoretical calculations show that in gemcitabine, C3′• to C2′• conversion in the presence of a proximate H3O+ has a barrier in agreement with the experimentally observed lack of C3′• to C2′• conversion. In contrast, in MeFdC, the loss of HF from C3′• in the presence of a proximate H3O+ is barrierless resulting in C2′• formation which agrees with the experimentally observed rapid C2′• formation. PMID:25296262

  8. DNA damage by the sulfate radical anion: hydrogen abstraction from the sugar moiety versus one-electron oxidation of guanine.

    PubMed

    Roginskaya, Marina; Mohseni, Reza; Ampadu-Boateng, Derrick; Razskazovskiy, Yuriy

    2016-07-01

    The products of oxidative damage to double-stranded (ds) DNA initiated by photolytically generated sulfate radical anions SO4(•-) were analyzed using reverse-phase (RP) high-performance liquid chromatography (HPLC). Relative efficiencies of two major pathways were compared: production of 8-oxoguanine (8oxoG) and hydrogen abstraction from the DNA 2-deoxyribose moiety (dR) at C1,' C4,' and C5' positions. The formation of 8oxoG was found to account for 87% of all quantified lesions at low illumination doses. The concentration of 8oxoG quickly reaches a steady state at about one 8oxoG per 100 base pairs due to further oxidation of its products. It was found that another guanine oxidation product identified as 2-amino-5-(2'-alkylamino)-4H-imidazol-4-one (X) was released in significant quantities from its tentative precursor 2-amino-5-[(2'-deoxy-β-d-erythro-pentofuranosyl)amino]-4H-imidazol-4-one (dIz) upon treatment with primary amines in neutral solutions. The linear dose dependence of X release points to the formation of dIz directly from guanine and not through oxidation of 8oxoG. The damage to dR was found to account for about 13% of the total damage, with majority of lesions (33%) originating from the C4' oxidation. The contribution of C1' oxidation also turned out to be significant (17% of all dR damages) despite of the steric problems associated with the abstraction of the C1'-hydrogen. However, no evidence of base-to-sugar free valence transfer as a possible alternative to direct hydrogen abstraction at C1' was found. PMID:27043476

  9. Two-Electron Reduction versus One-Electron Oxidation of the Type 3 Pair in the Multicopper Oxidases.

    PubMed

    Kjaergaard, Christian H; Jones, Stephen M; Gounel, Sébastien; Mano, Nicolas; Solomon, Edward I

    2015-07-15

    Multicopper oxidases (MCOs) utilize an electron shuttling Type 1 Cu (T1) site in conjunction with a mononuclear Type 2 (T2) and a binuclear Type 3 (T3) site, arranged in a trinuclear copper cluster (TNC), to reduce O2 to H2O. Reduction of O2 occurs with limited overpotential indicating that all the coppers in the active site can be reduced via high-potential electron donors. Two forms of the resting enzyme have been observed in MCOs: the alternative resting form (AR), where only one of the three TNC Cu's is oxidized, and the resting oxidized form (RO), where all three TNC Cu's are oxidized. In contrast to the AR form, we show that in the RO form of a high-potential MCO, the binuclear T3 Cu(II) site can be reduced via the 700 mV T1 Cu. Systematic spectroscopic evaluation reveals that this proceeds by a two-electron process, where delivery of the first electron, forming a high energy, metastable half reduced T3 state, is followed by the rapid delivery of a second energetically favorable electron to fully reduce the T3 site. Alternatively, when this fully reduced binuclear T3 site is oxidized via the T1 Cu, a different thermodynamically favored half oxidized T3 form, i.e., the AR site, is generated. This behavior is evaluated by DFT calculations, which reveal that the protein backbone plays a significant role in controlling the environment of the active site coppers. This allows for the formation of the metastable, half reduced state and thus the complete reductive activation of the enzyme for catalysis. PMID:26075678

  10. Two-electron Reduction versus One-electron Oxidation of the Type 3 Pair in the Multicopper Oxidases

    PubMed Central

    Kjaergaard, Christian H.; Jones, Stephen M.; Gounel, Sébastien; Mano, Nicolas; Solomon, Edward I.

    2015-01-01

    Multicopper Oxidases (MCOs) utilize an electron shuttling Type 1 Cu (T1) site in conjunction with a mononuclear Type 2 (T2) and a binuclear Type 3 (T3) site, arranged in a trinuclear copper cluster (TNC), to reduce O2 to H2O. Reduction of O2 occurs with limited overpotential indicating that all the coppers in the active site can be reduced via high-potential electron donors. Two forms of the resting enzyme have been observed in MCOs: the Alternative Resting form (AR), where only one of the three TNC Cu’s is oxidized, and the Resting Oxidized form (RO), where all three TNC Cu’s are oxidized. In contrast to the AR form, we show that in the RO form of a high-potential MCO, the binuclear T3 Cu(II) site can be reduced via the 700 mV T1 Cu. Systematic spectroscopic evaluation reveals that this proceeds by a two-electron process, where delivery of the first electron, forming a high energy, meta-stable half reduced T3 state, is followed by the rapid delivery of a second energetically favorable electron to fully reduce the T3 site. Alternatively, when this fully reduced binuclear T3 site is oxidized via the T1 Cu, a different thermodynamically favored half oxidized T3 form, i.e. the AR site, is generated. This behavior is evaluated by DFT calculations, which reveal that the protein backbone plays a significant role in controlling the environment of the active site coppers. This allows for the formation of the meta-stable, half reduced state and thus the complete reductive activation of the enzyme for catalysis. PMID:26075678

  11. Detailed Evaluation of the Geometric and Electronic Structures of One-electron Oxidized Group 10 (Ni, Pd, and Pt) Metal(II)-(Disalicylidene)diamine Complexes

    PubMed Central

    Stack, T. Daniel P.

    2009-01-01

    The geometric and electronic structures of a series of one-electron oxidized group 10 metal salens (Ni, Pd, Pt) have been investigated in solution and in the solid state. Ni (1) and Pd (2) complexes of the tetradentate salen ligand N,N’-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine (H2Salcn) have been examined along with the Pt (3) complex of the salen ligand N,N’-bis(3,5-di-tert-butylsalicylidene)-1,2-ethylenediamine (H2Salen). All three oxidized compounds exist as ligand radical species in solution and in the solid state. The solid state structures of [1]+ and [3]+ exhibit a symmetric coordination sphere contraction relative to the neutral forms. By contrast, the coordination sphere of the Pd derivative [2]+ exhibits a pronounced asymmetry in the solid state. In solution, the oxidized derivatives display intense low-energy NIR transitions consistent with their classification as ligand radical compounds. Interestingly, the degree of communication between the phenolate moieties depends strongly on the central metal ion, within the Ni, Pd, and Pt series. Electrochemical measurements and UV-Vis-NIR spectroscopy, in conjunction with DFT calculations provide insights into the degree of delocalization of the one-electron hole in these systems. The Pd complex [2]+ is the least delocalized and is best described as a borderline Class II/III intervalence complex based on the Robin-Day classification system. The Ni [1]+ and Pt [3]+ analogues are Class III (fully delocalized) intervalence compounds. Delocalization is dependent on the electronic coupling between the redox-active phenolate ligands, mediated by overlap between the formally filled metal dxz orbital and the appropriate ligand molecular orbital. The degree of coupling increases in the order Pd < Ni < Pt for the one-electron oxidized group 10 metal salens. PMID:19639970

  12. Double proton transfer behavior and one-electron oxidation effect in double H-bonded glycinamide-formic acid complex.

    PubMed

    Li, Ping; Bu, Yuxiang

    2004-11-22

    The behavior of double proton transfer occurring in a representative glycinamide-formic acid complex has been investigated at the B3LYP/6-311 + + G( * *) level of theory. Thermodynamic and, especially, kinetic parameters, such as tautomeric energy, equilibrium constant, and barrier heights have been discussed, respectively. The relevant quantities involved in the double proton transfer process, such as geometrical changes, interaction energies, and intrinsic reaction coordinate calculations have also been studied. Computational results show that the participation of a formic acid molecule favors the proceeding of the proton transfer for glycinamide compared with that without mediate-assisted case. The double proton transfer process proceeds with a concerted mechanism rather than a stepwise one since no ion-pair complexes have been located during the proton transfer process. The calculated barrier heights are 11.48 and 0.85 kcal/mol for the forward and reverse directions, respectively. However, both of them have been reduced by 2.95 and 2.61 kcal/mol to 8.53 and -1.76 kcal/mol if further inclusion of zero-point vibrational energy corrections, where the negative barrier height implies that the reverse reaction should proceed with barrierless spontaneously, analogous to that occurring between glycinamide and formamide. Furthermore, solvent effects on the thermodynamic and kinetic processes have also been predicted qualitatively employing the isodensity surface polarized continuum model within the framework of the self-consistent reaction field theory. Additionally, the oxidation process for the double H-bonded glycinamide-formic acid complex has also been investigated. Contrary to that neutral form possessing a pair of two parallel intermolecular H bonds, only a single H bond with a comparable strength has been found in its ionized form. The vertical and adiabatic ionization potentials for the neutral complex have been determined to be about 9.40 and 8.69 e

  13. Nitrite Reduction to Nitrous Oxide and Ammonia by TiO2 Electrons in a Colloid Solution via Consecutive One-Electron Transfer Reactions.

    PubMed

    Goldstein, Sara; Behar, David; Rajh, Tijana; Rabani, Joseph

    2016-04-21

    The mechanism of nitrite reduction by excess electrons on TiO2 nanoparticles (eTiO2(-)) was studied under anaerobic conditions. TiO2 was loaded with up to 75 electrons per particle, induced by γ-irradiation of acidic TiO2 colloid solutions containing 2-propanol. Time-resolved kinetics and material analysis were performed, mostly at 1.66 g L(-1) TiO2. At relatively low nitrite concentrations (R = [eTiO2(-)]o/[nitrite]o > 1.5), eTiO2(-) decays via two consecutive processes; at higher concentrations, only one decay step is observed. The stoichiometric ratio Δ[eTiO2(-)]/[nitrite]o of the faster process is about 2. This process involves the one-electron reduction of nitrite, forming the nitrite radical (k1 = (2.0 ± 0.2) × 10(6) M(-1) s(-1)), which further reacts with eTiO2(-) (k2) in competition with its dehydration to nitric oxide (NO) (k3). The ratios k2/k3 = (3.0 ± 0.5) × 10(3) M(-1) and k2 > 1 × 10(6) M(-1) s(-1) were derived from kinetic simulations and product analysis. The major product of this process is NO. The slower stage of the kinetics involves the reduction of NO by eTiO2(-), and the detailed mechanism of this process has been discussed in our earlier publication. The results reported in this study suggest that several intermediates, including NO and NH2OH, are adsorbed on the titanium nanoparticles and give rise to inverse dependency of the respective reaction rates on the TiO2 concentration. It is demonstrated that the reduction of nitrite by eTiO2(-) yields mainly N2O and NH3 via consecutive one-electron transfer reactions. PMID:27050805

  14. One-electron oxidation of alcohols by the 1,3,5-trimethoxybenzene radical cation in the excited state during two-color two-laser flash photolysis.

    PubMed

    Cai, Xichen; Sakamoto, Masanori; Fujitsuka, Mamoru; Majima, Tetsuro

    2007-03-15

    One-electron oxidation of alcohols such as methanol, ethanol, and 2-propanol by 1,3,5-trimethoxybenzene radical cation (TMB*+) in the excited state (TMB*+*) was observed during the two-color two-laser flash photolysis. TMB*+ was formed by the photoinduced bimolecular electron-transfer reaction from TMB to 2,3,5,6-tetrachlorobenzoquinone (TCQ) in the triplet excited-state during the first 355-nm laser flash photolysis. Then, TMB*+* was generated from the selective excitation of TMB*+ during the second 532 nm laser flash photolysis. Hole transfer rate constants from TMB*+* to methanol, ethanol, and 2-propanol were calculated to be (5.2 +/- 0.5) x 10(10), (1.4 +/- 0.3) x 10(11), and (3.2 +/- 0.6) x 10(11) M-1 s-1, respectively. The order of the hole transfer rate constants is consistent with oxidation potentials of alcohol. Formation of TCQH radical (TCQH*) with a characteristic absorption peak at 435 nm was observed in the microsecond time scale, suggesting that deprotonation of the alcohol radical cation occurs after the hole transfer and that TCQ radical anion (TCQ*-), generated together with TMB*+ by the photoinduced electron-transfer reaction, reacts with H+ to give TCQH*. PMID:17295459

  15. Calmodulin Methionine Residues are Targets For One-Electron Oxidation by Hydroxyl Radicals: Formation of S therefore N three-electron bonded Radical Complexes

    SciTech Connect

    Nauser, Thomas; Jacoby, Michael E.; Koppenol, Willem H.; Squier, Thomas C.; Schoneich, Christian

    2005-02-01

    The one-electron (1e) oxidation of organic sulfides and methionine (Met) constitutes an important reaction mechanism in vivo.1,2 Evidence for a Cu(II)-catalyzed oxidation of Met35 in the Alzheimer's disease -amyloid peptide was obtained,3 and, based on theoretical studies, Met radical cations were proposed as intermediates.4 In the structure of -amyloid peptide, the formation of Met radical cations appears to be facilitated by a preexisting close sulfur-oxygen (S-O) interaction between the Met35 sulfur and the carbonyl oxygen of the peptide bond C-terminal to Ile31.5 Substitution of Ile31 with Pro31 abolishes this S-O interaction,5 significantly reducing the ability of -amyloid to reduce Cu(II), and converts the neurotoxic wild-type -amyloid into a non-toxic peptide.6 The preexisting S-O bond characterized for wild-type -amyloid suggests that electron transfer from Met35 to Cu(II) is supported through stabilization of the Met radical cation by the electron-rich carbonyl oxygen, generating an SO-bonded7 sulfide radical cation (Scheme 1, reaction 1).5

  16. One-Electron Oxidation of a Disilicon(0) Compound: An Experimental and Theoretical Study of [Si2](+) Trapped by N-Heterocyclic Carbenes.

    PubMed

    Arz, Marius I; Straßmann, Martin; Meyer, Andreas; Schnakenburg, Gregor; Schiemann, Olav; Filippou, Alexander C

    2015-08-24

    One-electron oxidation of the disilicon(0) compound Si2(Idipp)2 (1, Idipp = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) with [Fe(C5Me5)2][B(Ar(F))4] (Ar(F) = C6H3-3,5-(CF3)2) affords selectively the green radical salt [Si2(Idipp)2][B(Ar(F))4] (1-[B(Ar(F))4). Oxidation of the centrosymmetric 1 occurs reversibly at a low redox potential (E1/2 = -1.250 V vs. Fc(+)/Fc), and is accompanied by considerable structural changes as shown by single-crystal X-ray structural analysis of 1-B(Ar(F))4. These include a shortening of the Si-Si bond, a widening of the Si-Si-CNHC angles, and a lowering of the symmetry, leading to a quite different conformation of the NHC substituents at the two inequivalent Si sites in 1(+). Comparative quantum chemical calculations of 1 and 1(+) indicate that electron ejection occurs from the symmetric (n+) combination of the Si lone pairs (HOMO). EPR studies of 1-B(Ar(F))4 in frozen solution verified the inequivalency of the two Si sites observed in the solid-state, and point in agreement with the theoretical results to an almost equal distribution of the spin density over the two Si atoms, leading to quite similar (29)Si hyperfine coupling tensors in 1(+). EPR studies of 1-B(Ar(F))4 in liquid solution unraveled a topomerization with a low activation barrier that interconverts the two Si sites in 1(+). PMID:26246231

  17. Double proton transfer and one-electron oxidation behavior in double H-bonded glycinamide-glycine complex in the gas phase.

    PubMed

    Li, Ping; Bu, Yuxiang

    2005-04-30

    The behaviors of double proton transfer (DPT) occurring in a representative glycinamide-glycine complex have been investigated employing the B3LYP/6-311++G** level of theory. Thermodynamic and especially kinetic parameters, such as tautomerization energy, equilibrium constant, and barrier heights have been discussed, respectively. The relevant quantities involved in the DPT process including geometrical changes, interaction energies, and deformation energies have also been studied. Analogous to that of tautomeric process assisted with a formic acid molecule, the participation of a glycine molecule favors the proceeding of the proton transfer (PT) for glycinamide compared with that without mediator-assisted case. The DPT process proceeds with a concerted mechanism rather than a stepwise one because no zwitterionic complexes have been located during the DPT process. The barrier heights are 12.14 and 0.83 kcal/mol for the forward and reverse directions, respectively. However, both of them have been reduced by 3.10 and 2.66 kcal/mol to 9.04 and -1.83 kcal/mol with further inclusion of zero-point vibrational energy (ZPVE) corrections, where the disappearance of the reverse barrier height implies that the reverse reaction should proceed with barrierless spontaneously, analogous to those of DPTs occurring between glycinamide and formic acid (or formamide). Additionally, the oxidation process for the double H-bonded glycinamide-glycine complex has also been investigated. The oxidated product is characterized by a distonic radical cation due to the fact that one-electron oxidation takes place on glycine fragment and a proton has been transferred from glycine to glycinamide fragment spontaneously. As a result, the vertical and adiabatic ionization potentials for the neutral complex have been determined to be about 8.71 and 7.85 eV, respectively, where both of them have been reduced by about 0.54 (1.11) and 0.75 (1.13) eV relative to those of isolated glycinamide (glycine

  18. Formation of aminyl radicals on electron attachment to AZT: Abstraction from the sugar phosphate backbone vs. one-electron oxidation of Guanine

    PubMed Central

    Adhikary, Amitava; Khanduri, Deepti; Pottiboyina, Venkata; Rice, Cory T.; Sevilla, Michael D.

    2010-01-01

    Employing electron spin resonance (ESR) spectroscopy, we have characterized the radicals formed in 3′-Azido-3′-deoxythymidine (3′-AZT) and in its 5′-analog 5′-azido-5′-deoxythymidine (5′-AZT) after electron attachment in γ-irradiated aqueous (H2O or D2O) glassy (7.5 M LiCl) systems. ESR spectral studies and theoretical calculations show that the predominant site of electron capture in 3′-AZT and in 5′-AZT is at the azide group and not at the thymine moiety. The azide group in AZT is therefore more electron affinic than the most electron affinic DNA base, thymine. Electron attachment to 3′-AZT and 5′-AZT results in an unstable azide anion radical intermediate (RN3•−) that is too short lived to be observed in our work even at 77 K. At 77 K we observe the neutral aminyl radical (RNH•) after loss of N2 from RN3•− followed by protonation of nitrene anion radical (RN•−) to give RNH•. The expected RN•− intermediate is not observed as protonation from water is complete at 77 K even in under highly basic conditions. Formation of RND• in D2O solutions confirms water as the source of the NH proton in the RNH•. Our assignments to these radicals are aided by DFT calculations for hyperfine coupling constants which closely match the experimental values. On annealing to higher temperatures (ca. 160–170 K), RNH• undergoes bimolecular hydrogen abstraction reactions from the thymine methyl group and the sugar moiety resulting in the formation of the thymine allyl radical (UCH2•) and two sugar radicals - C3′•, C5′•. RNH• also results in one-electron oxidation of the guanine base in 3′-AZG. This work provides a potential mechanism for the reported radiosensitization effects of AZT. PMID:20575557

  19. 8-Oxo-7,8-dihydro-2'-deoxyguanosine produces a long-lived charge-separated state during the photosensitized one-electron oxidation of DNA resulting in efficient and exclusive degradation.

    PubMed

    Kawai, Kiyohiko; Matsutani, Eri; Majima, Tetsuro

    2010-05-21

    The kinetics and efficiency of oxidative degradation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) in DNA during the photosensitized one-electron oxidation of DNA was investigated. The presence of 8-oxodGuo was shown to increase the lifetime of the charge-separated state in DNA by serving as a "hole sink" resulting in efficient and exclusive degradation. PMID:20442885

  20. Seebeck coefficient of one electron

    SciTech Connect

    Durrani, Zahid A. K.

    2014-03-07

    The Seebeck coefficient of one electron, driven thermally into a semiconductor single-electron box, is investigated theoretically. With a finite temperature difference ΔT between the source and charging island, a single electron can charge the island in equilibrium, directly generating a Seebeck effect. Seebeck coefficients for small and finite ΔT are calculated and a thermally driven Coulomb staircase is predicted. Single-electron Seebeck oscillations occur with increasing ΔT, as one electron at a time charges the box. A method is proposed for experimental verification of these effects.

  1. Computational studies of the geometry and electronic structure of an all-inorganic and homogeneous tetra-Ru-polyoxotungstate catalyst for water oxidation and its four subsequent one-electron oxidized forms.

    PubMed

    Quiñonero, David; Kaledin, Alexey L; Kuznetsov, Aleksey E; Geletii, Yurii V; Besson, Claire; Hill, Craig L; Musaev, Djamaladdin G

    2010-01-14

    Geometry and electronic structure of five species [{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(gamma-SiW(10)O(36))(2)](10-) (1), [{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(gamma-SiW(10)O(36))(2)](9-) (2), [{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(gamma-SiW(10)O(36))(2)](8-) (3), [{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(gamma-SiW(10)O(36))(2)](7-) (4), and [{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(gamma-SiW(10)O(36))(2)](6-) (5) with different oxidation states of Ru centers were studied at the density functional and COSMO levels of theory. These species are expected to be among the possible intermediates of the recently reported 1-catalyzed water oxidation (Geletii, Y. V.; Botar, B.; Kogerler, P.; Hillesheim, D. A.; Musaev, D. G.; Hill, C. L. Angew. Chem. Int. Ed. 2008, 47, 3896-3899 and Sartorel, A.; Carraro, M.; Scorrano, G.; Zorzi, R. D.; Geremia, S.; McDaniel, N. D.; Bernhard, S.; Bonchio, M. J. Am. Chem. Soc. 2008, 130, 5006-5007). It was shown that RI-BP86 correctly describes the geometry and energy of the low-lying electronic states of compound 1, whereas the widely used B3LYP approach overestimates the energy of its high-spin states. Including the solvent and/or countercation effects into calculations improves the agreement between the calculated and experimental data. It was found that the several HOMOs and LUMOs of the studied complexes are bonding and antibonding orbitals of the [Ru(4)O(4)(OH)(2)(H(2)O)(4)](6+) core, and four subsequent one-electron oxidations of 1, leading to formation of 2, 3, 4, and 5, respectively, involve only {Ru(4)} core orbitals. In other words, catalyst instability due to ligand oxidation in the widely studied Ru-blue dimer, [(bpy)(2)(O)Ru(V)-(mu-O)-Ru(V)(O)(bpy)(2)](4+), is not operable for 1: the latter all-inorganic catalyst is predicted to be stable under water oxidation turnover conditions. The calculated HOMOs and LUMOs of all the studied species are very close in energy and exhibit a "quasi-continuum" or "nanoparticle-type" electronic structure similar to that of nanosized transition

  2. Multiple hearth furnace for reducing iron oxide

    DOEpatents

    Brandon, Mark M.; True, Bradford G.

    2012-03-13

    A multiple moving hearth furnace (10) having a furnace housing (11) with at least two moving hearths (20) positioned laterally within the furnace housing, the hearths moving in opposite directions and each moving hearth (20) capable of being charged with at least one layer of iron oxide and carbon bearing material at one end, and being capable of discharging reduced material at the other end. A heat insulating partition (92) is positioned between adjacent moving hearths of at least portions of the conversion zones (13), and is capable of communicating gases between the atmospheres of the conversion zones of adjacent moving hearths. A drying/preheat zone (12), a conversion zone (13), and optionally a cooling zone (15) are sequentially positioned along each moving hearth (30) in the furnace housing (11).

  3. Antioxidant capacity of foods for scavenging reactive oxidants and inhibition of plasma lipid oxidation induced by multiple oxidants.

    PubMed

    Niki, Etsuo

    2016-05-18

    Unregulated oxidation of biological molecules induced by multiple oxidants has been implicated in the pathogenesis of various diseases. Consequently, the effects of antioxidants contained in foods, beverages and supplements on the maintenance of health and prevention of diseases have attracted much attention of the public as well as scientists. However, recent human studies have shown inconsistent results and failed to demonstrate the beneficial effects of antioxidants. The mechanisms and dynamics of antioxidant action and assessment of antioxidant capacity have been the subject of extensive studies and arguments. In the present article, the antioxidant capacity has been reviewed focusing on two main issues: the capacity of antioxidants to scavenge multiple reactive oxidants and to inhibit plasma lipid oxidation induced by different biological oxidants. It is emphasized that the capacity of antioxidants to scavenge reactive oxidants does not always correlate linearly with the capacity to inhibit lipid oxidation and that it is necessary to specify the oxidant to assess the efficacy of antioxidants, since multiple oxidants contribute to oxidative damage in vivo and the effects of antioxidants depend on the nature of oxidants. A convenient and rapid method using a microplate reader is discussed for assessing the antioxidant capacity against plasma lipid oxidation induced by multiple oxidants including peroxyl radicals, peroxynitrite, hypochlorite, 15-lipoxygenase, and singlet oxygen. PMID:27090496

  4. Interactions between manganese oxides and multiple-ringed aromatic compounds

    SciTech Connect

    Whelan, G. ); Sims, R.C. . Dept. of Civil and Environmental Engineering)

    1992-08-01

    Objective is to determine whether Mn reductive dissolution can oxidize multiple-ringed aromatics, such as PAHs, in an oxic environment Research indicated that certain PAHs (eg, dihydrodiols and diones that form free-radical intermediates) are susceptible to oxidation and polymerization. Over 14 days, 83, 76, 54, 70, and 20% of the Mn was reduced by 2,3-, 1,3-, and 1,4-naphthalenediol, quinizarin, and 1,4-naphthoquinone, respectively. 100, 100, and 65% of the first three PAHs were oxidized, respectively. Aromatics with diol functional groups were more easily oxidized than those with only dione groups. Relatively insoluble compounds like quinizarin can be oxidized; insoluble ''humic-like'' material precipitated, indicating a polymerization-humification process. Results suggest that electron transfer/organic release from the oxide surface is the rate-limiting step.

  5. Interactions between manganese oxides and multiple-ringed aromatic compounds

    SciTech Connect

    Whelan, G.; Sims, R.C.

    1992-08-01

    Objective is to determine whether Mn reductive dissolution can oxidize multiple-ringed aromatics, such as PAHs, in an oxic environment? Research indicated that certain PAHs (eg, dihydrodiols and diones that form free-radical intermediates) are susceptible to oxidation and polymerization. Over 14 days, 83, 76, 54, 70, and 20% of the Mn was reduced by 2,3-, 1,3-, and 1,4-naphthalenediol, quinizarin, and 1,4-naphthoquinone, respectively. 100, 100, and 65% of the first three PAHs were oxidized, respectively. Aromatics with diol functional groups were more easily oxidized than those with only dione groups. Relatively insoluble compounds like quinizarin can be oxidized; insoluble ``humic-like`` material precipitated, indicating a polymerization-humification process. Results suggest that electron transfer/organic release from the oxide surface is the rate-limiting step.

  6. Comparison of the One-electron Oxidations of CO-Bridged vs Unbridged Bimetallic Complexes: Electron-transfer Chemistry of Os2Cp2(CO)4 and Os2Cp*2(μ-CO)2(CO)2 (Cp = η5-C5H5, Cp* = η5-C5Me5)

    SciTech Connect

    Laws, Derek R.; Bullock, R. Morris; Lee, Richmond; Huang, Kuo-Wei; Geiger, William J.

    2014-09-22

    The one-electron oxidations of two dimers of half-sandwich osmium carbonyl complexes have been examined by electrochemistry, spectro-electrochemistry, and computational methods. The all-terminal carbonyl complex Os2Cp2(CO)4 (1, Cp = η5-C5H5) undergoes a reversible one-electron anodic reaction at E1/2 = 0.41 V vs ferrocene in CH2Cl2/0.05 M [NBu4][B(C6F5)4], giving a rare example of a metal-metal bonded radical cation unsupported by bridging ligands. The IR spectrum of 1+ is consistent with an approximately 1:1 mixture of anti and gauche structures for the 33 e- radical cation in which it has retained all-terminal bonding of the CO ligands. DFT calculations, including orbital-occupancy-perturbed Mayer bond-order analyses, show that the HOMOs of anti-1 and gauche-1 are metal-ligand delocalized. Removal of an electron from 1 has very little effect on the Os-Os bond order, accounting for the resistance of 1+ to heterolytic cleavage. The Os-Os bond distance is calculated to decrease by 0.10 Å and 0.06 Å as a consequence of one-electron oxidation of anti-1 and gauche-1, respectively. The CO-bridged complex Os2Cp*2(μ-CO)2(CO)2 (Cp* = η5-C5Me5), trans-2, undergoes a more facile oxidation, E1/2 = - 0.11 V, giving a persistent radical cation shown by solution IR analysis to preserve its bridged-carbonyl structure. However, ESR analysis of frozen solutions of 2+ is interpreted in terms of the presence of two isomers, most likely anti-2+ and trans-2+, at low temperature. Calculations show that the HOMO of trans-2 is highly delocalized over the metal-ligand framework, with the bridging carbonyls accounting for about half of the orbital makeup. The Os-Os bond order again changes very little with removal of an electron, and the Os-Os bond length actually undergoes minor shortening. Calculations suggest that the second isomer of 2+ has both the trans CO-bridged and the anti all-terminal CO structures. DRL and WEG acknowledge the support of the National Science Foundation under

  7. Oxidative stress and proteasome inhibitors in multiple myeloma.

    PubMed

    Lipchick, Brittany C; Fink, Emily E; Nikiforov, Mikhail A

    2016-03-01

    Multiple myeloma is a form of plasma cell neoplasm that accounts for approximately 10% of all hematological malignancies. Recently, several novel drugs have been discovered that almost doubled the overall survival of multiple myeloma patients. One of these drugs, the first-in-class proteasome inhibitor bortezomib (Velcade) has demonstrated remarkable response rates in multiple myeloma patients, and yet, currently this disease remains incurable. The major factor undermining the success of multiple myeloma treatment is a rapidly emerging resistance to the available therapy. Thus, the development of stand-alone or adjuvant anti-myeloma agents becomes of paramount importance. Overproduction of intracellular reactive oxygen species (ROS) often accompanies malignant transformation due to oncogene activation and/or enhanced metabolism in tumor cells. As a result, these cells possess higher levels of ROS and lower levels of antioxidant molecules compared to their normal counterparts. Unbalanced production of ROS leads to oxidative stress which, if left unchecked, could be toxic for the cell. In multiple myeloma cells where high rates of immunoglobulin synthesis is an additional factor contributing to overproduction of ROS, further induction of oxidative stress can be an effective strategy to cope with this disease. Here we will review the available data on the role of oxidative stress in the cytotoxicity of proteasome inhibitors and the use of ROS-inducing compounds as anti-myeloma agents. PMID:26827824

  8. Oxygen dependency of one-electron reactions generating ascorbate radicals and hydrogen peroxide from ascorbic acid.

    PubMed

    Boatright, William L

    2016-04-01

    The effect of oxygen on the two separate one-electron reactions involved in the oxidation of ascorbic acid was investigated. The rate of ascorbate radical (Asc(-)) formation (and stability) was strongly dependent on the presence of oxygen. A product of ascorbic acid oxidation was measurable levels of hydrogen peroxide, as high as 32.5 μM from 100 μM ascorbic acid. Evidence for a feedback mechanism where hydrogen peroxide generated during the oxidation of ascorbic acid accelerates further oxidation of ascorbic acid is also presented. The second one-electron oxidation reaction of ascorbic acid leading to the disappearance of Asc(-) was also strongly inhibited in samples flushed with argon. In the range of 0.05-1.2 mM ascorbic acid, maximum levels of measurable hydrogen peroxide were achieved with an initial concentration of 0.2 mM ascorbic acid. Hydrogen peroxide generation was greatly diminished at ascorbic acid levels of 0.8 mM or above. PMID:26593628

  9. One-electron singular branch lines of the Hubbard chain

    NASA Astrophysics Data System (ADS)

    Carmelo, J. M. P.; Penc, K.; Martelo, L. M.; Sacramento, P. D.; Lopes dos Santos, J. M. B.; Claessen, R.; Sing, M.; Schwingenschlögl, U.

    2004-07-01

    The momentum and energy dependence of the weight distribution in the vicinity of the one-electron spectral-function singular branch lines of the 1D Hubbard model is studied for all values of the electronic density and on-site repulsion U. To achieve this goal, we use the recently introduced pseudofermion dynamical theory. Our predictions agree quantitatively for the whole momentum and energy bandwidth with the peak dispersions observed by angle-resolved photoelectron spectroscopy in the quasi-1D organic conductor TTF-TCNQ.

  10. One-electron reduction of adriamycin: properties of the semiquinone

    SciTech Connect

    Land, E.J.; Mukherjee, T.; Swallow, A.J.; Bruce, J.M.

    1983-08-01

    Pulse radiolysis of aqueous solutions containing adriamycin and redox indicators of known one-electron reduction potential (E1) shows that its E1 at pH 7 is -328 mV (vs NHE). The variation E1 with pH in the range 6-12 shows that the net charge on the semiquinone at pH 7 is zero. As well as the pKa values of 2.9 and greater than or equal to 14 established independently, the semiquinone has a pKa close to 9.2. The new data enable the structure and likely reactivity of the semiquinone to be specified.

  11. Oxidative injury in multiple sclerosis cerebellar grey matter.

    PubMed

    Kemp, Kevin; Redondo, Juliana; Hares, Kelly; Rice, Claire; Scolding, Neil; Wilkins, Alastair

    2016-07-01

    Cerebellar dysfunction is a significant contributor to disability in multiple sclerosis (MS). Both white matter (WM) and grey matter (GM) injury occurs within MS cerebellum and, within GM, demyelination, inflammatory cell infiltration and neuronal injury contribute to on-going pathology. The precise nature of cerebellar GM injury is, however, unknown. Oxidative stress pathways with ultimate lipid peroxidation and cell membrane injury occur extensively in MS and the purpose of this study was to investigate these processes in MS cerebellar GM. Post-mortem human cerebellar GM from MS and control subjects was analysed immunohistochemically, followed by semi-quantitative analysis of markers of cellular injury, lipid peroxidation and anti-oxidant enzyme expression. We have shown evidence for reduction in myelin and neuronal markers in MS GM, coupled to an increase in expression of a microglial marker. We also show that the lipid peroxidation product 4-hydroxynonenal co-localises with myelin and its levels negatively correlate to myelin basic protein levels. Furthermore, superoxide dismutase (SOD1 and 2) enzymes, localised within cerebellar neurons, are up-regulated, yet the activation of subsequent enzymes responsible for the detoxification of hydrogen peroxide, catalase and glutathione peroxidase are relatively deficient. These studies provide evidence for oxidative injury in MS cerebellar GM and further help define disease mechanisms within the MS brain. PMID:27086975

  12. Simultaneous evaluation of one-electron reducing systems and radical reactions in cells by nitroxyl biradical as probe.

    PubMed

    Araki, Yoko; Koshiishi, Ichiro

    2016-07-01

    In the present study, a novel probe for the simultaneous evaluation of one-electron reducing systems (electron transport chain) and one-electron oxidizing systems (free radical reactions) in cells by electron chemical detection was developed. Six-membered cyclic nitroxyl radicals (2,2,6,6-tetramethylpiperidine-1-oxyl; TEMPO series) are sensitive to one-electron redox systems, generating the hydroxylamine form [TEMPO(H)] via one-electron reduction, and the secondary amine form [TEMPO(N)] via one-electron oxidation in the presence of thiols. In contrast, the sensitivities of five-membered cyclic nitroxyl radicals (2,2,5,5-tetramethylpyrrolidine-1-oxyl; PROXYL series) to the one-electron redox systems are comparatively low. The electron chemical detector can detect 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), TEMPO(H) and PROXYL but not TEMPO(N). Therefore, nitroxyl biradical, TEMPO-PROXYL, as a probe for the evaluation of one-electron redox systems was employed. TEMPO-PROXYL was synthesized by the conjunction of 4-amino-TEMPO with 3-carboxyl-PROXYL via the conventional dicyclohexyl carbodiimide reaction. TEMPO-PROXYL, TEMPO(H)-PROXYL and TEMPO(N)-PROXYL were simultaneously quantified by HPLC with Coularray detection. Calibration curves for the quantification of TEMPO-PROXYL, TEMPO(H)-PROXYL and TEMPO(N)-PROXYL were linear in the range from 80 nm to 80 μm, and the lowest quantification limit of each molecule was estimated to be <80 nm. The relative standard deviations at 0.8 and 80 μm were within 10% (n = 5). Copyright © 2015 John Wiley & Sons, Ltd. PMID:26613564

  13. Modeling of nitrous oxide production by autotrophic ammonia-oxidizing bacteria with multiple production pathways.

    PubMed

    Ni, Bing-Jie; Peng, Lai; Law, Yingyu; Guo, Jianhua; Yuan, Zhiguo

    2014-04-01

    Autotrophic ammonia oxidizing bacteria (AOB) have been recognized as a major contributor to N2O production in wastewater treatment systems. However, so far N2O models have been proposed based on a single N2O production pathway by AOB, and there is still a lack of effective approach for the integration of these models. In this work, an integrated mathematical model that considers multiple production pathways is developed to describe N2O production by AOB. The pathways considered include the nitrifier denitrification pathway (N2O as the final product of AOB denitrification with NO2(-) as the terminal electron acceptor) and the hydroxylamine (NH2OH) pathway (N2O as a byproduct of incomplete oxidation of NH2OH to NO2(-)). In this model, the oxidation and reduction processes are modeled separately, with intracellular electron carriers introduced to link the two types of processes. The model is calibrated and validated using experimental data obtained with two independent nitrifying cultures. The model satisfactorily describes the N2O data from both systems. The model also predicts shifts of the dominating pathway at various dissolved oxygen (DO) and nitrite levels, consistent with previous hypotheses. This unified model is expected to enhance our ability to predict N2O production by AOB in wastewater treatment systems under varying operational conditions. PMID:24571180

  14. Cytotoxicity of graphene oxide and graphene oxide loaded with doxorubicin on human multiple myeloma cells

    PubMed Central

    Wu, Shaoling; Zhao, Xindong; Cui, Zhongguang; Zhao, Chunting; Wang, Yuzhen; Du, Li; Li, Yanhui

    2014-01-01

    The purpose of this study was to evaluate the cytotoxicity of human multiple myeloma cells (RPMI-8226) treated with graphene oxide (GO), doxorubicin (DOX), and GO loaded with DOX (GO/DOX). Cell viability was determined using the Cell Counting Kit-8 assay and analyzing the cell cycle and cell apoptosis. Cells treated with GO, GO/DOX, and pure DOX for 24 hours showed a decrease in proliferation. GO/DOX significantly inhibited cell proliferation as compared with pure DOX (P<0.01). When the effects of GO were removed, there was no observed difference between GO/DOX and pure DOX (P>0.05). Flow cytometry analysis of untreated and GO-, DOX-, and GO/DOX-treated cells found no significant differences in the G0/G1 phase (P>0.05), while significant differences were observed in the total apoptotic rates (P<0.05). No significant differences existed in the total apoptotic rates of GO-treated and untreated cells (P>0.05). These findings suggest that GO caused low cytotoxicity and did not induce cell apoptosis or change the cell cycle in multiple myeloma cells. Moreover, GO did not affect the antitumor activity of DOX. In conclusion, GO would be suitable as an anticancer drug nanocarrier and used to treat hematological malignancies. PMID:24672235

  15. Analysis of active neutron multiplicity data for Y-12 skull oxide samples

    SciTech Connect

    Krick, M.S.; Ensslin, N.; Ceo, R.N.; May, P.K.

    1996-09-01

    Previous work on active neutron multiplicity measurements and analyses is summarized. New active multiplicity measurements are described for samples of Y-12 skull oxide using an Active Well Coincidence Counter and MSR4 multiplicity electronics. Neutron multiplication values for the samples were determined from triples/doubles ratios. Neutron multiplication values were also obtained from Monte Carlo calculations using the MCNP code and the results compared with the experimental values. A calibration curve of AmLi source-sample coupling vs neutron multiplication was determined and used for active multiplicity assay of the skull oxides. The results are compared with those obtained from assay with the conventional calibration-curve technique, where the doubles rate is calibrated vs the {sup 235}U mass. The coupling-multiplication relationship determined for the skull oxides is compared with that determined earlier for pure high-enrichment uranium metal and pure uranium oxide. Conclusions are drawn about the application of active multiplicity techniques to uranium assay. Additional active multiplicity measurements and calculations are recommended.

  16. One-electron redox processes in a cyclic selenide and a selenoxide: a pulse radiolysis study.

    PubMed

    Singh, Beena G; Thomas, Elizabeth; Kumakura, Fumio; Dedachi, Kenichi; Iwaoka, Michio; Priyadarsini, K Indira

    2010-08-19

    One-electron redox reactions of cyclic selenium compounds, DL-trans-3,4-dihydroxy-1-selenolane (DHS(red)), and DL-trans-3,4-dihydroxy-1-selenolane oxide (DHS(ox)) were carried out in aqueous solutions using nanosecond pulse radiolysis, and the resultant transients were detected by absorption spectroscopy. Both *OH radical and specific one-electron oxidant, Br(2)(*-) radical reacted with DHS(red) to form similar transients absorbing at 480 nm, which has been identified as a dimer radical cation (DHS(red))(2)(*+). Secondary electron transfer reactions of the (DHS(red))(2)(*+) were studied with 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS(2-)) and superoxide (O(2)(*-)) radicals. The bimolecular rate constants for the electron transfer reaction between (DHS(red))(2)(*+) with ABTS(2-) was determined as 2.4 +/- 0.4 x 10(9) M(-1) s(-1). From this reaction, the yield of (DHS(red))(2)(*+) formed on reaction with *OH radical was estimated in the presence of varying phosphate concentrations. (DHS(red))(2)(*+) reacted with O(2)(*-) radical with a bimolecular rate constant of 2.7 +/- 0.1 x 10(9) M(-1) s(-1) at pH 7. From the same reaction, the positive charge on (DHS(red))(2)(*+) was confirmed by the kinetic salt effect. HPLC analysis of the products formed in the reaction of (DHS(red))(2)(*+) with O(2)(*-) radicals showed formation of the selenoxide, DHS(ox). In order to know if a similar mechanism operated during the reduction of DHS(ox), its reactions with e(aq)(-) were studied at pH 7. The rate constant for this reaction was determined as 5.6 +/- 0.9 x 10(9) M(-1) s(-1), and no transient absorption could be observed in the wavelength region from 280 to 700 nm. It is proposed that the radical anion (DHS(ox))(*-) formed by a one-electron reduction would get protonated to form a hydroxyl radical adduct, which in presence of proton donors, would undergo dehydration to form DHS(*+). Evidence for this mechanism was obtained by converting DHS(*+) to (DHS(red))(2

  17. Oxidative Stress is Increased in Serum from Mexican Patients with Relapsing-Remitting Multiple Sclerosis

    PubMed Central

    Ortiz, Genaro Gabriel; Macías-Islas, Miguel Ángel; Pacheco-Moisés, Fermín P.; Cruz-Ramos, José A.; Sustersik, Silvia; Barba, Elías Alejandro; Aguayo, Adriana

    2009-01-01

    Objective: To determine the oxidative stress markers in serum from patients with relapsing-remitting multiple sclerosis. Methods: Blood samples from healthy controls and 22 patients 15 women (7 aged from 20 to 30 and 8 were > 40 years old) and 7 men (5 aged from 20 to 30 and 2 were > 40 years old) fulfilling the McDonald Criteria and classified as having Relapsing-Remitting Multiple Sclerosis accordingly with Lublin were collected for oxidative stress markers quantification. Results: Nitric oxide metabolites (nitrates/nitrites), lipid peroxidation products (malondialdehyde plus 4-hidroxialkenals), and glutathione peroxidase activity were significantly increased in serum of subjects with relapsing-remitting multiple sclerosis in comparison with that of healthy controls. These data support the hypothesis that multiple sclerosis is a component closely linked to oxidative stress. PMID:19242067

  18. Estimation of interfacial shear strength between superconducting oxides and silver sheath from multiple-fracture phenomenon of the oxide

    SciTech Connect

    Ochiai, Shojiro; Hayasi, Kenji; Osamura, Kozo )

    1994-02-01

    The influence of interfacial shear strength superconducting Y-Ba-Cu-O and silver and that between Bi-Pb-Sr-Ca-Cu-O and silver on the multiple fracture of the oxides embedded in silver-sheathed composite wires, prepared by a powder-in-tube method, on the multiple fracture of the oxides was analyzed. The stress distribution in the oxide was calculated based on the proposed method, and the multiple-fracture phenomenon was simulated by means of a Monte Carlo simulation method. From the comparison of the experimental results with those obtained by the simulation, the interfacial shear strength between Y-Ba-Cu-O and silver and that between Bi-Pb-Sr-Ca-Cu-O and silver were estimated to be nearly 30 and 40 MPa, respectively.

  19. Microbial Mn(IV) reduction requires an initial one-electron reductive solubilization step

    NASA Astrophysics Data System (ADS)

    Lin, Hui; Szeinbaum, Nadia H.; DiChristina, Thomas J.; Taillefert, Martial

    2012-12-01

    Mn(IV) and Mn(II) are the most stable and prevalent forms of manganese in natural environments. The occurrence of Mn(III) in minerals and the detection of soluble Mn(III) in natural waters, however, suggest that Mn(III) is an intermediate in both the oxidation of Mn(II) and the reduction of Mn(IV). Mn(III) has recently been proposed as an intermediate during the oxidation of Mn(II) by Mn-oxidizing bacteria but has never been considered as an intermediate during the bio-reduction of Mn(IV). Here we show for the first time that microbial Mn(IV) reduction proceeds step-wise via two successive one-electron transfer reactions with production of soluble Mn(III) as transient intermediate. Incubations with mutant strains demonstrate that the reduction of both solid Mn(IV) and soluble Mn(III) occurs at the outer membrane of the cell. In addition, pseudo-first order rate constants obtained from these incubations indicate that Mn(IV) respiration involves only one of the two potential terminal reductases (c-type cytochrome MtrC and OmcA) involved in Fe(III) respiration. More importantly, only the second electron transfer step is coupled to production of dissolved inorganic carbon, suggesting that the first electron transfer reaction is a reductive solubilization step that increases Mn bioavailability. These findings oppose the long-standing paradigm that microbial Mn(IV) reduction proceeds via a single two-electron transfer reaction coupled to organic carbon oxidation, and suggest that diagenetic models should be revised to correctly account for the impact of manganese reduction in the global carbon cycle.

  20. Optimal Biofilm Featues: metabolic and geometric response to multiple oxidants

    NASA Astrophysics Data System (ADS)

    Kempes, C.; Okegbe, C.; Mears-Clarke, Z.; Follows, M. J.; Dietrich, L.

    2014-12-01

    An important challenge in understanding complex microbial mat communities is determining how groups of a single species balance metabolic requirements with the dynamics of resource supply. We have investigated this problem in the context of redox resources within a single-species bacterial biofilm. We developed a mathematical model of oxidant availability and metabolic response within biofilm features and we show that observed biofilm geometries maximize cellular reproduction and growth efficiency. Our model accurately predicts the measured distribution of two types of electron acceptors: oxygen, which is available from the environment, and phenazines, redox-active small molecules produced by the bacterium. Because our model is based on resource dynamics, we are also able to predict observed shifts in feature geometry based on changes in the availability of redox resources such as variations in the external availability of oxygen or the removal of phenazines. This analysis suggests various avenues for understanding microstructure and the evolution of spatial metabolism in microbial mats.

  1. Achieving accurate nuetron-multiplicity analysis of metals and oxides with weighted point model equations.

    SciTech Connect

    Burward-Hoy, J. M.; Geist, W. H.; Krick, M. S.; Mayo, D. R.

    2004-01-01

    Neutron multiplicity counting is a technique for the rapid, nondestructive measurement of plutonium mass in pure and impure materials. This technique is very powerful because it uses the measured coincidence count rates to determine the sample mass without requiring a set of representative standards for calibration. Interpreting measured singles, doubles, and triples count rates using the three-parameter standard point model accurately determines plutonium mass, neutron multiplication, and the ratio of ({alpha},n) to spontaneous-fission neutrons (alpha) for oxides of moderate mass. However, underlying standard point model assumptions - including constant neutron energy and constant multiplication throughout the sample - cause significant biases for the mass, multiplication, and alpha in measurements of metal and large, dense oxides.

  2. Diluted II-VI oxide semiconductors with multiple band gaps.

    PubMed

    Yu, K M; Walukiewicz, W; Wu, J; Shan, W; Beeman, J W; Scarpulla, M A; Dubon, O D; Becla, P

    2003-12-12

    We report the realization of a new mult-band-gap semiconductor. Zn(1-y)Mn(y)OxTe1-x alloys have been synthesized using the combination of oxygen ion implantation and pulsed laser melting. Incorporation of small quantities of isovalent oxygen leads to the formation of a narrow, oxygen-derived band of extended states located within the band gap of the Zn(1-y)Mn(y)Te host. When only 1.3% of Te atoms are replaced with oxygen in a Zn0.88Mn0.12Te crystal the resulting band structure consists of two direct band gaps with interband transitions at approximately 1.77 and 2.7 eV. This remarkable modification of the band structure is well described by the band anticrossing model. With multiple band gaps that fall within the solar energy spectrum, Zn(1-y)Mn(y)OxTe1-x is a material perfectly satisfying the conditions for single-junction photovoltaics with the potential for power conversion efficiencies surpassing 50%. PMID:14683137

  3. Phenol coupling initiated by one-electron oxidation of tyrosine units in peptides and histone.

    PubMed

    Prütz, W A; Butler, J; Land, E J

    1983-08-01

    Phenoxyl radicals generated pulse radiolytically by the reaction of N.3 with Gly-Tyr decay biomolecularly (2k = 4.7 X 10(8)M-1 s-1) with efficient formation of 2,2'-dimers, which enolize rapidly (k = 2.7 X 10(4) s-1) to produce the 2,2'-biphenolic product. The build-up of the characteristic 2,2'-biphenol fluorescence (400 nm) and absorption also indicated a delayed (k = 80 s-1) process, probably involving the phenoxyl <-> phenoxy-quinol equilibrium. About 60 per cent of the Gly-Tyr phenoxyls were found to dimerize to the 2,2'-biphenol, and a similarly efficient 2,2'-coupling seems to occur with other tyrosyls, such as Lys-Tyr-Lys and histone. gamma-Radiolysis was applied to estimate relative yields of formation of 2,2'-biphenols under various conditions. Dimerization is almost completely inhibited by cysteine or oxygen, consistent with phenoxyl 'repair' by cysteine or O-.2; disproportionation of O-.2 with SOD prevents repair. The phenol 2,2'-coupling is less efficient for .OH- and inefficient for e-aq-initiation. PMID:6603438

  4. Multiple transport systems mediate virus-induced acquired resistance to oxidative stress

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this paper, we report the phenomenon of acquired cross-tolerance to oxidative (UV-C and H2O2) stress in Nicotiana benthamiana plants infected with Potato virus X (PVX) and investigate the functional expression of transport systems in mediating this phenomenon. By combining multiple approaches, we...

  5. Serum nitric oxide concentrations in patients with multiple sclerosis and patients with epilepsy.

    PubMed

    Ibragic, Saida; Sofic, Emin; Suljic, Enra; Avdagic, Nesina; Bajraktarevic, Azra; Tahirovic, Ismet

    2012-01-01

    Nitric oxide (NO), a neurotransmitter and a free radical, has been purported to be involved in numerous neurological diseases. We investigated the serum nitric oxide concentration in 30 patients with multiple sclerosis (MS), in 30 patients with epilepsy and in 30 control subjects. The aim was also to determine whether a statistically significant difference in serum NO concentrations exists between the groups of interest. The total serum nitric oxide concentration was measured using the Griess reaction after reducing nitrates to nitrites with elemental zinc. In the group multiple sclerosis, the mean NO concentrations were X ± SEM = 31.02 ± 1.79 μmol/l, in the control group X ± SEM = 25.31 ± 1.44 μmol/l and in the group epilepsy X ± SEM = 22.51 ± 1.28 μmol/l. Student's t test showed a statistically significant difference between subjects with multiple sclerosis and the control group (p = 0.013), as well as between the groups multiple sclerosis and epilepsy (p = 0.0002). This data confirms that NO may play an important role in the pathogenesis of multiple sclerosis, whereas its role in epilepsy still remains unclear. PMID:21779769

  6. Predicting efficient C(60) epoxidation and viable multiple oxide formation by theoretical study

    PubMed

    Manoharan

    2000-02-25

    The epoxidation of C(60) by various oxidizing agents such as dimethyldioxirane (DMD), methyl(trifluoromethyl)dioxirane (MTMD), and bis(trifluoromethyl)dioxirane (BTMD) has been probed computationally by the AM1 method. The computations have revealed that for the reaction forming C(60)O through a concerted "spiro" transition state, the currently used DMD involves its HOMO lone-pair and the LUMO (pi) of fullerene in an inverse electron demand fashion. This is distinct from the DMD reaction with ethylene. On the other hand, the addition of CF(3) groups lowers the LUMO (peroxide sigma) of MTMD and BTMD by virtue of negative hyperconjugation; the oxidants can then attack the fullerene nucleophilically at an increased rate to the maximum extent. These estimations have thus established that the strong electrophilic oxidizing agents remarkably enhance the fullerene epoxidation. DMD further produces C(60)O(2) and C(60)O(3) via multiple epoxidations, as C(60)O might best be produced quantitatively by MTMD and BTMD. The regiochemistry of the multiple oxidation products in which the subsequent oxidations take place at the adjacent sites is consistent with the increased nucleophilicity of the nearest double bonds attached to the prevailing epoxide function. PMID:10814058

  7. Superparamagnetic Iron Oxide Nanoparticles: Promises for Diagnosis and Treatment of Multiple Sclerosis

    PubMed Central

    2011-01-01

    Smart superparamagnetic iron oxide nanoparticles (SPIONs) are the most promising candidate for theragnosis (i.e., diagnosis and treatment) of multiple sclerosis. A deep understanding of the dynamics of the in vivo neuropathology of multiple sclerosis can be achieved by improving the efficiency of various medical techniques (e.g., positron emission tomography and magnetic resonance imaging) using multimodal SPIONs. In this Review, recent advances and challenges in the development of smart SPIONs for theragnostic applications are comprehensively described. In addition, critical outlines of emerging developments are provided from the points of view of both clinicians and nanotechnologists. PMID:22778862

  8. Multiple Oxidative Modifications in the Ophiobolin Biosynthesis: P450 Oxidations Found in Genome Mining.

    PubMed

    Narita, Koji; Chiba, Ryota; Minami, Atsushi; Kodama, Motoichiro; Fujii, Isao; Gomi, Katsuya; Oikawa, Hideaki

    2016-05-01

    Heterologous expression of four candidate genes found in ophiobolin gene clusters from three fungal strains was employed to elucidate the late-stage biosynthetic pathway of phytotoxin ophiobolin. Expression of oblBAc (cytochrome P450) from the cryptic gene cluster gave unexpected products, and that of oblBBm/oblBEv from the gene cluster of ophiobolin producers, with oblDBm as the transporter, yielded intermediate ophiobolin C through an unusual four-step oxidation process. The observation made in this study may provide a useful guideline for the elucidation of genuine biosynthetic pathways of natural products. PMID:27116000

  9. Evidence of extensive RNA oxidation in normal appearing cortex of multiple sclerosis brain.

    PubMed

    Kharel, Prakash; McDonough, Jennifer; Basu, Soumitra

    2016-01-01

    The role of reactive oxygen species (ROS) in the progression of neurodegenerative and neuroinflammatory disorders such as multiple sclerosis (MS) has been highlighted in recent years. Due to the debilitated cellular antioxidant defense mechanism in the neurons in MS, and their vulnerability to ROS effects, the cellular components in neuronal cells are susceptible to oxidative damage. The damage due to ROS in various biomolecules including proteins and DNA has already been shown in MS lesions. Using an in situ approach we have detected hitherto unidentified RNA oxidative damage in the neuronal cells of normal appearing cortex of postmortem MS brains. We analyzed the presence of oxidative damage marker nucleoside 8-hydroxyguanosine (8-OHG) to determine the presence of oxidized RNA in MS brain. Immunohistochemical analyses with anti 8-OHG antibody showed significant oxidation in the cytoplasm and to a conspicuously lesser extent in the nucleus of neuronal cells within the normal appearing cortex of MS brain, whereas similar areas were weakly immunopositive in control brain tissues. Pretreatment with RNase 1 greatly reduced the immune reaction with anti 8-OHG antibody while it was only slightly diminished by DNase I pre-treatment, indicating extensive oxidative damage in the RNA pool of MS brain. The abundance of 8-OHG, hence the high extent of RNA oxidative damage was further confirmed by immunoprecipitation and HPLC analyses of total RNA isolated from MS brain. To our knowledge, this is the first evidence of increased RNA oxidation in normal appearing cortex of MS brain. The current study begins to define the link of RNA oxidation to MS pathophysiology. PMID:26706235

  10. Electrochemical and Spectroscopic Evidence on the One-Electron Reduction of U(VI) to U(V) on Magnetite.

    PubMed

    Yuan, Ke; Ilton, Eugene S; Antonio, Mark R; Li, Zhongrui; Cook, Peter J; Becker, Udo

    2015-05-19

    Reduction of U(VI) to U(IV) on mineral surfaces is often considered a one-step two-electron process. However, stabilized U(V), with no evidence of U(IV), found in recent studies indicates U(VI) can undergo a one-electron reduction to U(V) without further progression to U(IV). We investigated reduction pathways of uranium by reducing U(VI) electrochemically on a magnetite electrode at pH 3.4. Cyclic voltammetry confirms the one-electron reduction of U(VI) to U(V). Formation of nanosize uranium precipitates on the magnetite surface at reducing potentials and dissolution of the solids at oxidizing potentials are observed by in situ electrochemical atomic force microscopy. XPS analysis of the magnetite electrodes polarized in uranium solutions at voltages from -0.1 to -0.9 V (E(0)(U(VI)/U(V))= -0.135 V vs Ag/AgCl) show the presence of only U(V) and U(VI). The sample with the highest U(V)/U(VI) ratio was prepared at -0.7 V, where the longest average U-O(axial) distance of 2.05 ± 0.01 Å was evident in the same sample revealed by extended X-ray absorption fine structure analysis. The results demonstrate that the electrochemical reduction of U(VI) on magnetite only yields U(V), even at a potential of -0.9 V, which favors the one-electron reduction mechanism. U(V) does not disproportionate but stabilizes on magnetite through precipitation of mixed-valence state U(V)/U(VI) solids. PMID:25893535

  11. Electrochemical and spectroscopic evidence on the one-electron reduction of U(VI) to U(V) on magnetite

    SciTech Connect

    Yuan, Ke; Ilton, Eugene S.; Antonio, Mark R.; Li, Zhongrui; Cook, Peter J.; Becker, Udo

    2015-05-19

    Reduction of U(VI) to U(IV) on mineral surfaces has been considered as a one-step two electron process. However, stabilized U(V), with no evidence of U(IV), found in recent studies indicates U(VI) can undergo a one electron reduction to U(V) without further progression to U(IV). We investigated the mechanisms of uranium reduction by reducing U(VI) electrochemically on a magnetite electrode at pH 3.4 . The one electron reduction of U(VI) was first confirmed using the cyclic voltammetry method. Formation of nano-size uranium precipitates on the surface of magnetite at reducing potentials and dissolution of the solids at oxidizing potentials were observed by in situ electrochemical AFM. XPS analysis of the magnetite electrodes polarized in uranium solutions at voltages from 0.1 ~ 0.9 V (vs. Ag/AgCl) showed the presence of only U(V) and U(VI). The highest amount of U(V) relative to U(VI) was prepared at 0.7 V, where the longest average U–Oaxial distance of 2.05 ± 0.01 Å was evident in the same sample revealed by EXAFS analysis. The results demonstrate that the electrochemical reduction of U(VI) on magnetite only yields U(V), even at a potential of 0.9 V, which favors the one-electron reduction mechanism. U(V) did not disproportionate but stabilized on magnetite through precipitation of mixed-valence state U(VI)/U(V) solids.

  12. Inflammation, Iron, Energy Failure, and Oxidative Stress in the Pathogenesis of Multiple Sclerosis

    PubMed Central

    Haider, Lukas

    2015-01-01

    Multiple sclerosis is a chronic inflammatory demyelinating disease of the central nervous system. Different trigger pathologies have been suggested by the primary cytodegenerative “inside-out” and primary inflammation-driven “outside-in” hypotheses. Recent data indicate that mitochondrial injury and subsequent energy failure are key factors in the induction of demyelination and neurodegeneration. The brain weighs only a few percent of the body mass but accounts for approximately 20% of the total basal oxygen consumption of mitochondria. Oxidative stress induces mitochondrial injury in patients with multiple sclerosis and energy failure in the central nervous system of susceptible individuals. The interconnected mechanisms responsible for free radical production in patients with multiple sclerosis are as follows: (i) inflammation-induced production of free radicals by activated immune cells, (ii) liberation of iron from the myelin sheets during demyelination, and (iii) mitochondrial injury and thus energy failure-related free radical production. In the present review, the different sources of oxidative stress and their relationships to patients with multiple sclerosis considering tissue injury mechanisms and clinical aspects have been discussed. PMID:26106458

  13. Role of dimethyl fumarate in oxidative stress of multiple sclerosis: A review.

    PubMed

    Suneetha, A; Raja Rajeswari, K

    2016-04-15

    Multiple sclerosis (MS) is a chronic inflammatory disease of the CNS affecting both white and grey matter. Inflammation and oxidative stress are also thought to promote tissue damage in multiple sclerosis. Recent data point at an important role of anti-oxidative pathways for tissue protection in chronic MS, particularly involving the transcription factor nuclear factor (erythroid-derived 2)-related factor 2 (Nrf2). Thus, novel therapeutics enhancing cellular resistance to free radicals could prove useful for MS treatment. Oxidative stress and anti-oxidative pathways are important players in MS pathophysiology and constitute a promising target for future MS therapy with dimethyl fumarate. The clinical utility of DMF in multiple sclerosis is being explored through phase III trials with BG-12, which is an oral therapeutic agent. Currently a wide research is going on to find out the exact mechanism of DMF, till date it is not clear. Based on strong signals of nephrotoxicity in non-humans and the theoretical risk of renal cell cancer from intracellular accumulation of fumarate, post-marketing study of a large population of patients will be necessary to fully assess the long-term safety of dimethyl fumarate. The current treatment goals are to shorten the duration and severity of relapses, prolong the time between relapses, and delay progression of disability. In this regard, dimethyl fumarate offers a promising alternative to orally administered fingolimod (GILENYA) or teriflunomide (AUBAGIO), which are currently marketed in the United States under FDA-mandated Risk Evaluation and Mitigation Strategy (REMS) programs because of serious safety concerns. More clinical experience with all three agents will be necessary to differentiate the tolerability of long-term therapy for patients diagnosed with multiple sclerosis. This write-up provides the detailed information of dimethyl fumarate in treating the neuro disease, multiple sclerosis and its mechanism involved via

  14. Melatonin Improves Outcomes of Heatstroke in Mice by Reducing Brain Inflammation and Oxidative Damage and Multiple Organ Dysfunction

    PubMed Central

    Hsu, Shu-Fen; Lin, Mao-Tsun

    2013-01-01

    We report here that when untreated mice underwent heat stress, they displayed thermoregulatory deficit (e.g., animals display hypothermia during room temperature exposure), brain (or hypothalamic) inflammation, ischemia, oxidative damage, hypothalamic-pituitary-adrenal axis impairment (e.g., decreased plasma levels of both adrenocorticotrophic hormone and corticosterone during heat stress), multiple organ dysfunction or failure, and lethality. Melatonin therapy significantly reduced the thermoregulatory deficit, brain inflammation, ischemia, oxidative damage, hypothalamic-pituitary-adrenal axis impairment, multiple organ dysfunction, and lethality caused by heat stroke. Our data indicate that melatonin may improve outcomes of heat stroke by reducing brain inflammation, oxidative damage, and multiple organ dysfunction. PMID:24369441

  15. One-electron standard reduction potentials of nitroaromatic and cyclic nitramine explosives

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Extensive studies have been conducted in the past decades to predict the environmental abiotic and biotic redox fate of nitroaromatic and nitramine explosives. However, surprisingly little information is available on one-electron standard reduction potentials (Eo(R-NO2/R-NO2_)). The Eo(R-NO2/R-NO2...

  16. Immunology and Oxidative Stress in Multiple Sclerosis: Clinical and Basic Approach

    PubMed Central

    Ortiz, Genaro G.; Pacheco-Moisés, Fermín P.; Bitzer-Quintero, Oscar K.; Ramírez-Anguiano, Ana C.; Flores-Alvarado, Luis J.; Ramírez-Ramírez, Viridiana; Macias-Islas, Miguel A.; Torres-Sánchez, Erandis D.

    2013-01-01

    Multiple sclerosis (MS) exhibits many of the hallmarks of an inflammatory autoimmune disorder including breakdown of the blood-brain barrier (BBB), the recruitment of lymphocytes, microglia, and macrophages to lesion sites, the presence of multiple lesions, generally being more pronounced in the brain stem and spinal cord, the predominantly perivascular location of lesions, the temporal maturation of lesions from inflammation through demyelination, to gliosis and partial remyelination, and the presence of immunoglobulin in the central nervous system and cerebrospinal fluid. Lymphocytes activated in the periphery infiltrate the central nervous system to trigger a local immune response that ultimately damages myelin and axons. Pro-inflammatory cytokines amplify the inflammatory cascade by compromising the BBB, recruiting immune cells from the periphery, and activating resident microglia. inflammation-associated oxidative burst in activated microglia and macrophages plays an important role in the demyelination and free radical-mediated tissue injury in the pathogenesis of MS. The inflammatory environment in demyelinating lesions leads to the generation of oxygen- and nitrogen-free radicals as well as proinflammatory cytokines which contribute to the development and progression of the disease. Inflammation can lead to oxidative stress and vice versa. Thus, oxidative stress and inflammation are involved in a self-perpetuating cycle. PMID:24174971

  17. Immunology and oxidative stress in multiple sclerosis: clinical and basic approach.

    PubMed

    Ortiz, Genaro G; Pacheco-Moisés, Fermín P; Bitzer-Quintero, Oscar K; Ramírez-Anguiano, Ana C; Flores-Alvarado, Luis J; Ramírez-Ramírez, Viridiana; Macias-Islas, Miguel A; Torres-Sánchez, Erandis D

    2013-01-01

    Multiple sclerosis (MS) exhibits many of the hallmarks of an inflammatory autoimmune disorder including breakdown of the blood-brain barrier (BBB), the recruitment of lymphocytes, microglia, and macrophages to lesion sites, the presence of multiple lesions, generally being more pronounced in the brain stem and spinal cord, the predominantly perivascular location of lesions, the temporal maturation of lesions from inflammation through demyelination, to gliosis and partial remyelination, and the presence of immunoglobulin in the central nervous system and cerebrospinal fluid. Lymphocytes activated in the periphery infiltrate the central nervous system to trigger a local immune response that ultimately damages myelin and axons. Pro-inflammatory cytokines amplify the inflammatory cascade by compromising the BBB, recruiting immune cells from the periphery, and activating resident microglia. inflammation-associated oxidative burst in activated microglia and macrophages plays an important role in the demyelination and free radical-mediated tissue injury in the pathogenesis of MS. The inflammatory environment in demyelinating lesions leads to the generation of oxygen- and nitrogen-free radicals as well as proinflammatory cytokines which contribute to the development and progression of the disease. Inflammation can lead to oxidative stress and vice versa. Thus, oxidative stress and inflammation are involved in a self-perpetuating cycle. PMID:24174971

  18. Chemical modification of oxidized and silicon oxide covered aluminium surfaces studied by FTIR/multiple specular reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Sondag, A. H.; Raas, M. C.; Touwslager, F. J.; Ponjee, J. J.

    1989-12-01

    Multiple Specular Reflectance (MSR) infrared reflection-absorption spectroscopy has been applied to study surface modification by organosilane (sub)monomolecular layers. The spectrum of octadecyldimethylmethoxysilane immobilized on an oxidized aluminium substrate is compared to the absorption spectra of the monomer and the disiloxane condensation product. Formation of hydroxyl groups on a Si02 covered aluminium substrate by a UV-ozon treatment is shown. Simultaneously, organic contaminants are removed from the surface by the UV-ozon treatment. The chemisorption of 3-methacryloxypropyldimethylethoxysilane on UV-ozon treated Si02 has been examined at different surface coverages. An increase of the number of organosilane species at the surface is accompanied by a decrease of surface hydroxyl groups.

  19. Global methane and nitrous oxide emissions from terrestrial ecosystems due to multiple environmental changes

    DOE PAGESBeta

    Tian, Hanqin; Chen, Guangsheng; Lu, Chaoqun; Xu, Xiaofeng; Ren, Wei; Zhang, Bowen; Banger, Kamaljit; Tao, Bo; Pan, Shufen; Chu, Mingliang; et al

    2015-03-16

    Greenhouse gas (GHG)-induced climate change is among the most pressing sustainability challenges facing humanity today, posing serious risks for ecosystem health. Methane (CH4) and nitrous oxide (N2O) are the two most important GHGs after carbon dioxide (CO2), but their regional and global budgets are not well known. In this paper, we applied a process-based coupled biogeochemical model to concurrently estimate the magnitude and spatial and temporal patterns of CH4 and N2O fluxes as driven by multiple environmental changes, including climate variability, rising atmospheric CO2, increasing nitrogen deposition, tropospheric ozone pollution, land use change, and nitrogen fertilizer use.

  20. Experimental efforts at NIST towards one-electron ions in circular Rydberg states

    NASA Astrophysics Data System (ADS)

    Tan, Joseph N.; Brewer, Samuel M.; Guise, Nicholas D.

    2011-06-01

    Experimental effort is underway at NIST to enable tests of theory with one-electron ions synthesized in circular Rydberg states from captured bare nuclei. Problematic effects that limit the accuracy of predicted energy levels for low-lying states are vanishingly small for high-angular-momentum (high-L) states; in particular, the nuclear size correction for high-L states is completely negligible for any foreseeable improvement of measurement precision. As an initial step towards realizing such states, highly charged ions are extracted from the NIST electron beam ion trap (EBIT) and steered through the electrodes of a Penning trap. The goal is to capture bare nuclei in the Penning trap for experiments to make one-electron atoms in circular Rydberg states with dipole (E1) transitions in the optical domain accessible to a frequency comb.

  1. Oxidative tissue injury in multiple sclerosis is only partly reflected in experimental disease models.

    PubMed

    Schuh, Cornelia; Wimmer, Isabella; Hametner, Simon; Haider, Lukas; Van Dam, Anne-Marie; Liblau, Roland S; Smith, Ken J; Probert, Lesley; Binder, Christoph J; Bauer, Jan; Bradl, Monika; Mahad, Don; Lassmann, Hans

    2014-08-01

    Recent data suggest that oxidative injury may play an important role in demyelination and neurodegeneration in multiple sclerosis (MS). We compared the extent of oxidative injury in MS lesions with that in experimental models driven by different inflammatory mechanisms. It was only in a model of coronavirus-induced demyelinating encephalomyelitis that we detected an accumulation of oxidised phospholipids, which was comparable in extent to that in MS. In both, MS and coronavirus-induced encephalomyelitis, this was associated with massive microglial and macrophage activation, accompanied by the expression of the NADPH oxidase subunit p22phox but only sparse expression of inducible nitric oxide synthase (iNOS). Acute and chronic CD4(+) T cell-mediated experimental autoimmune encephalomyelitis lesions showed transient expression of p22phox and iNOS associated with inflammation. Macrophages in chronic lesions of antibody-mediated demyelinating encephalomyelitis showed lysosomal activity but very little p22phox or iNOS expressions. Active inflammatory demyelinating lesions induced by CD8(+) T cells or by innate immunity showed macrophage and microglial activation together with the expression of p22phox, but low or absent iNOS reactivity. We corroborated the differences between acute CD4(+) T cell-mediated experimental autoimmune encephalomyelitis and acute MS lesions via gene expression studies. Furthermore, age-dependent iron accumulation and lesion-associated iron liberation, as occurring in the human brain, were only minor in rodent brains. Our study shows that oxidative injury and its triggering mechanisms diverge in different models of rodent central nervous system inflammation. The amplification of oxidative injury, which has been suggested in MS, is only reflected to a limited degree in the studied rodent models. PMID:24622774

  2. Multiple factors affect diversity and abundance of ammonia-oxidizing microorganisms in iron mine soil.

    PubMed

    Xing, Yi; Si, Yan-Xiao; Hong, Chen; Li, Yang

    2015-07-01

    Ammonia oxidation by microorganisms is a critical process in the nitrogen cycle. In this study, four soil samples collected from a desert zone in an iron-exploration area and others from farmland and planted forest soil in an iron mine surrounding area. We analyzed the abundance and diversity of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in iron-mining area near the Miyun reservoir using ammonia monooxygenase. A subunit gene (amoA) as molecular biomarker. Quantitative polymerase chain reaction was applied to explore the relationships between the abundance of AOA and AOB and soil physicochemical parameters. The results showed that AOA were more abundant than AOB and may play a more dominant role in the ammonia-oxidizing process in the whole region. PCR-denaturing gradient gel electrophoresis was used to analyze the structural changes of AOA and AOB. The results showed that AOB were much more diverse than AOA. Nitrosospira cluster three constitute the majority of AOB, and AOA were dominated by group 1.1b in the soil. Redundancy analysis was performed to explore the physicochemical parameters potentially important to AOA and AOB. Soil characteristics (i.e. water, ammonia, organic carbon, total nitrogen, available phosphorus, and soil type) were proposed to potentially contribute to the distributions of AOB, whereas Cd was also closely correlated to the distributions of AOB. The community of AOA correlated with ammonium and water contents. These results highlight the importance of multiple drivers in microbial niche formation as well as their affect on ammonia oxidizer composition, both which have significant consequences for ecosystem nitrogen functioning. PMID:25860433

  3. A Tandem Catalyst with Multiple Metal Oxide Interfaces Produced by Atomic Layer Deposition.

    PubMed

    Ge, Huibin; Zhang, Bin; Gu, Xiaomin; Liang, Haojie; Yang, Huimin; Gao, Zhe; Wang, Jianguo; Qin, Yong

    2016-06-13

    Ideal heterogeneous tandem catalysts necessitate the rational design and integration of collaborative active sites. Herein, we report on the synthesis of a new tandem catalyst with multiple metal-oxide interfaces based on a tube-in-tube nanostructure using template-assisted atomic layer deposition, in which Ni nanoparticles are supported on the outer surface of the inner Al2 O3 nanotube (Ni/Al2 O3 interface) and Pt nanoparticles are attached to the inner surface of the outer TiO2 nanotube (Pt/TiO2 interface). The tandem catalyst shows remarkably high catalytic efficiency in nitrobenzene hydrogenation over Pt/TiO2 interface with hydrogen formed in situ by the decomposition of hydrazine hydrate over Ni/Al2 O3 interface. This can be ascribed to the synergy effect of the two interfaces and the confined nanospace favoring the instant transfer of intermediates. The tube-in-tube tandem catalyst with multiple metal-oxide interfaces represents a new concept for the design of highly efficient and multifunctional nanocatalysts. PMID:27122357

  4. Oxidative metabolism is associated with physiological disorders in fruits stored under multiple environmental stresses.

    PubMed

    Lum, Geoffrey B; Shelp, Barry J; DeEll, Jennifer R; Bozzo, Gale G

    2016-04-01

    In combination with low temperature, controlled atmosphere storage and 1-methylcyclopropene (ethylene antagonist) application are used to delay senescence of many fruits and vegetables. Controlled atmosphere consists of low O2 and elevated CO2. When sub-optimal partial pressures are used, these practices represent multiple abiotic stresses that can promote the development of physiological disorders in pome fruit, including flesh browning and cavities, although there is some evidence for genetic differences in susceptibility. In the absence of surface disorders, fruit with flesh injuries are not easily distinguished from asymptomatic fruit until these are consumed. Oxidative stress metabolites tend to accumulate (e.g., γ-aminobutyrate) or rapidly decline (e.g., ascorbate and glutathione) in vegetative tissues exposed to hypoxic and/or elevated CO2 environments. Moreover, these phenomena can be associated with altered energy and redox status. Biochemical investigations of Arabidopsis and tomato plants with genetically-altered levels of enzymes associated with the γ-aminobutyrate shunt and the ascorbate-glutathione pathway indicate that these metabolic processes are functionally related and critical for dampening the oxidative burst in vegetative and fruit tissues, respectively. Here, we hypothesize that γ-aminobutyrate accumulation, as well energy and antioxidant depletion are associated with the development of physiological injury in pome fruit under multiple environmental stresses. An improved understanding of this relationship could assist in maintaining the quality of stored fruit. PMID:26940499

  5. Multiple isoforms of mitochondrial glutathione S-transferases and their differential induction under oxidative stress.

    PubMed Central

    Raza, Haider; Robin, Marie-Anne; Fang, Ji-Kang; Avadhani, Narayan G

    2002-01-01

    The mitochondrial respiratory chain, which consumes approx. 85-90% of the oxygen utilized by cells, is a major source of reactive oxygen species (ROS). Mitochondrial genetic and biosynthetic systems are highly susceptible to ROS toxicity. Intramitochondrial glutathione (GSH) is a major defence against ROS. In the present study, we have investigated the nature of the glutathione S-transferase (GST) pool in mouse liver mitochondria, and have purified three distinct forms of GST: GSTA1-1 and GSTA4-4 of the Alpha family, and GSTM1-1 belonging to the Mu family. The mitochondrial localization of these multiple GSTs was confirmed using a combination of immunoblot analysis, protease protection assay, enzyme activity, N-terminal amino acid sequencing, peptide mapping and confocal immunofluorescence analysis. Additionally, exogenously added 4-hydroxynonenal (HNE), a reactive byproduct of lipid peroxidation, to COS cells differentially affected the cytosolic and mitochondrial GSH pools in a dose- and time-dependent manner. Our results show that HNE-mediated mitochondrial oxidative stress caused a decrease in the GSH pool, increased membrane lipid peroxidation, and increased levels of GSTs, glutathione peroxidase and Hsp70 (heat-shock protein 70). The HNE-induced oxidative stress persisted for longer in the mitochondrial compartment, where the recovery of GSH pool was slower than in the cytosolic compartment. Our study, for the first time, demonstrates the presence in mitochondria of multiple forms of GSTs that show molecular properties similar to those of their cytosolic counterparts. Our results suggest that mitochondrial GSTs may play an important role in defence against chemical and oxidative stress. PMID:12020353

  6. Multiple sample characterization of coals and other substances by controlled-atmosphere programmed temperature oxidation

    DOEpatents

    LaCount, Robert B.

    1993-01-01

    A furnace with two hot zones holds multiple analysis tubes. Each tube has a separable sample-packing section positioned in the first hot zone and a catalyst-packing section positioned in the second hot zone. A mass flow controller is connected to an inlet of each sample tube, and gas is supplied to the mass flow controller. Oxygen is supplied through a mass flow controller to each tube to either or both of an inlet of the first tube and an intermediate portion between the tube sections to intermingle with and oxidize the entrained gases evolved from the sample. Oxidation of those gases is completed in the catalyst in each second tube section. A thermocouple within a sample reduces furnace temperature when an exothermic condition is sensed within the sample. Oxidized gases flow from outlets of the tubes to individual gas cells. The cells are sequentially aligned with an infrared detector, which senses the composition and quantities of the gas components. Each elongated cell is tapered inward toward the center from cell windows at the ends. Volume is reduced from a conventional cell, while permitting maximum interaction of gas with the light beam. Reduced volume and angulation of the cell inlets provide rapid purgings of the cell, providing shorter cycles between detections. For coal and other high molecular weight samples, from 50% to 100% oxygen is introduced to the tubes.

  7. Numerology, hydrogenic levels, and the ordering of excited states in one-electron atoms

    NASA Astrophysics Data System (ADS)

    Armstrong, Lloyd, Jr.

    1982-03-01

    We show that the observed ordering of Rydberg states of one-electron atoms can be understood by assuming that these states are basically hydrogenic in nature. Much of the confusion concerning this point is shown to arise from the failure to differentiate between hydrogenic ordering as the nuclear charge approaches infinity, and hydrogenic ordering for an effective charge of one. The origin of κ ordering of Rydberg levels suggested by Sternheimer is considered within this picture, and the predictions of κ ordering are compared with those obtained by assuming hydrogenic ordering.

  8. Redox behaviour of nifuroxazide: generation of the one-electron reduction product.

    PubMed

    Squella, J A; Letelier, M E; Lindermeyer, L; Nuñez-Vergara, L J

    1996-01-01

    The electrochemical properties of nifuroxazide have been investigated in aqueous and aqueous-DMF mixed solvents. In aqueous media, a single, irreversible four-electron reduction occurs to give the hydroxylamine derivative. In mixed media, a reversible one-electron reduction to form a nitro radical anion takes place. Cyclic voltammetric studies show that the anion radical product is stable, although the nitro radical anion intermediate shows a tendency to undergo further chemical reactions. A comparison with the voltammetric behaviour of other nitrofurans such as nifurtimox, nitrofurazone and furazolidone is made. The electrochemically-obtained parameters are correlated with the in vivo studies of oxygen consumption on Trypanosoma cruzi cell suspensions. PMID:8620571

  9. On the existence of intramolecular one-electron Be-Be bonds.

    PubMed

    Brea, Oriana; Mó, Otilia; Yáñez, Manuel; Alkorta, Ibon; Elguero, José

    2016-08-11

    Although the Be-Be bond is extremely weak in Be2 dimers, we have shown that rather stable Be-Be one-electron sigma bonds are formed upon electron attachment to 1,8-diBeX-naphthalene derivatives. Wavefunction analyses corroborate the formation of Be-Be covalent linkages in which the extra electron is accommodated between the Be atoms as reflected in the dramatic shortening of the Be-Be distance with respect to the corresponding neutral molecule. PMID:27398934

  10. One-electron excitations, correlation effects, and the plasmon in cesium metal

    SciTech Connect

    Fleszar, A. ||; Stumpf, R.; Eguiluz, A.G. ||

    1997-01-01

    We study the dynamical electronic response of Cs at a first-principles level. The spatially localized 5p semicore shell induces a physical interplay between crystal local fields and electron correlations, leading to a novel, and relatively large, many-body shift of the plasmon energy. This effect, combined with that of one-electron transitions into empty states near the plasmon energy, yields a plasmon dispersion curve which is in excellent agreement with experiment for small wave vectors. In addition, our results feature a flat dispersion for large wave vectors, in qualitative agreement with experiment. {copyright} {ital 1997} {ital The American Physical Society}

  11. One-electron diatomics in momentum space. II. Second and third iterated LCAO solutions

    SciTech Connect

    Koga, T.; Kawa-ai, R.

    1986-05-15

    Recurrence formulas are derived for the iterative LCAO solution of the one-electron two-center Schroedinger equation in the Fock representation. The results are applied to the second and third iterated LCAO solutions of the H/sup +//sub 2/ system at various internuclear distances R. For 0< or =R< or =20 (a.u.), the maximum errors in the electronic energy are reduced to 2.7% (second iterated) and 1.6% (third iterated), which should be compared with the previous errors of 28.2% (zeroth iterated) and 4.7% (first iterated).

  12. Global methane and nitrous oxide emissions from terrestrial ecosystems due to multiple environmental changes

    SciTech Connect

    Tian, Hanqin; Chen, Guangsheng; Lu, Chaoqun; Xu, Xiaofeng; Ren, Wei; Zhang, Bowen; Banger, Kamaljit; Tao, Bo; Pan, Shufen; Chu, Mingliang; Zhang, Chi; Bruhwiler, Lori; Wofsy, Steven

    2015-03-16

    Greenhouse gas (GHG)-induced climate change is among the most pressing sustainability challenges facing humanity today, posing serious risks for ecosystem health. Methane (CH4) and nitrous oxide (N2O) are the two most important GHGs after carbon dioxide (CO2), but their regional and global budgets are not well known. In this paper, we applied a process-based coupled biogeochemical model to concurrently estimate the magnitude and spatial and temporal patterns of CH4 and N2O fluxes as driven by multiple environmental changes, including climate variability, rising atmospheric CO2, increasing nitrogen deposition, tropospheric ozone pollution, land use change, and nitrogen fertilizer use.

  13. Investigations of the oxidation capacities of polar atmospheres with multiple oxygen isotopes

    NASA Astrophysics Data System (ADS)

    McCabe, Justin R.

    This study provides new perspectives on the atmospheric chemistry in Polar Regions using multiple oxygen isotopes of nitrate and sulfate. Despite their remote locations, these unique environments play an important role in the present state of global climate and contain invaluable clues to observing past relationships between earth's atmosphere and surface temperature. With current temperatures and greenhouse gas concentrations rising rapidly as a result of human activities, continued investigation of the effects on polar environments will elucidate their relationship to the global climate system. Three studies are presented here to constrain the oxidation pathways of nitrogen and sulfur compounds in polar atmospheres. These findings provide a new means to observe current and past oxidation conditions of tropospheric and stratospheric polar atmospheres. Currently, two uncertain aspects of climate are the projected changes in tropospheric and stratospheric oxidation chemistry and the role of aerosols in cloud formation and the global radiation budget. Because the levels of oxidants in the atmosphere directly influence greenhouse gas concentrations and aerosol distribution, the following work presents results implicit to improving knowledge of the climate system. The results presented in this dissertation include measurements of oxygen isotopes (delta17O, delta18O, and Delta 17O) in nitrate and sulfate from South Pole, Antarctica and Alert, Canada, respectively. In addition, a photochemistry experiment was conducted to measure the effects of ultraviolet (UV) irradiation on oxygen isotopes of nitrate in water and ice. Chapter 2 compares oxygen isotopes in sulfate aerosol collected at Alert, Canada over the course of one year (July 1999--June 2000) to a chemical transport model describing sulfate formation. Chapter 3 presents the results from the nitrate photochemistry experiments conducted at California Institute of Technology in Pasadena, California. Chapter 4

  14. Tests of Theory in Rydberg States of One-Electron Ions

    NASA Astrophysics Data System (ADS)

    Tan, Joseph N.; Mohr, Peter J.

    Comparison of optical frequency measurements to predictions of quantum electrodynamics (QED) for Rydberg states of one-electron ions can test theory and allow new determinations of constants of nature to be made. Simplifications in the QED theory of high-angular-momentum states reduces the uncertainty in the prediction of transition frequencies to a level where a new value of the Rydberg constant which is independent of the proton radius can be determined. Since the energy-level spacing between neighbouring Rydberg states grows as the square of the nuclear charge number, it is possible to study transitions with optical frequencies that are accessible to femtosecond laser frequency combs. Recently at the US National Institute of Standards and Technology (NIST), highly charged ions (including bare nuclei) created in an Electron Beam Ion Trap (EBIT) were extracted and captured in a novel compact Penning trap. An ongoing experiment aims to produce one-electron ions isolated in an ion trap designed for laser spectroscopy. Tests of theory in a regime free of nuclear effects would be valuable in shedding light on the puzzle surrounding the large discrepancy in the value of the proton radius inferred from the observed Lamb shift in muonic hydrogen as compared to the value deduced from hydrogen and deuterium spectroscopy and electron scattering measurements.

  15. Generalization of the Kohn-Sham system that can represent arbitrary one-electron density matrices

    NASA Astrophysics Data System (ADS)

    van Dam, Hubertus J. J.

    2016-05-01

    Density functional theory is currently the most widely applied method in electronic structure theory. The Kohn-Sham method, based on a fictitious system of noninteracting particles, is the workhorse of the theory. The particular form of the Kohn-Sham wave function admits only idempotent one-electron density matrices whereas wave functions of correlated electrons in post-Hartree-Fock methods invariably have fractional occupation numbers. Here we show that by generalizing the orbital concept and introducing a suitable dot product as well as a probability density, a noninteracting system can be chosen that can represent the one-electron density matrix of any system, even one with fractional occupation numbers. This fictitious system ensures that the exact electron density is accessible within density functional theory. It can also serve as the basis for reduced density matrix functional theory. Moreover, to aid the analysis of the results the orbitals may be assigned energies from a mean-field Hamiltonian. This produces energy levels that are akin to Hartree-Fock orbital energies such that conventional analyses based on Koopmans' theorem are available. Finally, this system is convenient in formalisms that depend on creation and annihilation operators as they are trivially applied to single-determinant wave functions.

  16. QED calculations in heavy many-electron atoms and one-electron quasi-molecules

    NASA Astrophysics Data System (ADS)

    Tupitsyn, I. I.; Safronova, M. S.; Kozlov, M. G.; Porsev, S. G.; Shabaev, V. M.

    2016-05-01

    Construction of simple one-electron approach to one-loop QED operator is an important task for the relativistic quantum theory of atoms and molecules. In this work we used two modifications of the model QED potential approach to calculations of the Lamb shift in many-electron atoms and one-electron quasi-molecules. The model potential is constructed as a sum of local and nonlocal (separable) potentials. The nonlocal part of the model potential was introduced to reproduce exactly the diagonal elements and also off-diagonal elements of the one-loop ab initio QED operator. The one-particle model QED operator was introduced in the Dirac-Fock and CI+MBPT relativistic calculations of the heavy and super-heavy atoms and in the calculations of the diatomic quasi-molecules. The comparison of the data obtained in different approaches to the one-loop QED operator is presented. Model QED potential is applied to calculate Lamb shift in the U91+- U92+ dimer. The results are compared with Ref..

  17. Generalization of the Kohn-Sham system that can represent arbitrary one-electron density matrices

    DOE PAGESBeta

    Hubertus J. J. van Dam

    2016-05-23

    Density functional theory is currently the most widely applied method in electronic structure theory. The Kohn-Sham method, based on a fictitious system of noninteracting particles, is the workhorse of the theory. The particular form of the Kohn-Sham wave function admits only idempotent one-electron density matrices whereas wave functions of correlated electrons in post-Hartree-Fock methods invariably have fractional occupation numbers. Here we show that by generalizing the orbital concept and introducing a suitable dot product as well as a probability density, a noninteracting system can be chosen that can represent the one-electron density matrix of any system, even one with fractionalmore » occupation numbers. This fictitious system ensures that the exact electron density is accessible within density functional theory. It can also serve as the basis for reduced density matrix functional theory. Moreover, to aid the analysis of the results the orbitals may be assigned energies from a mean-field Hamiltonian. This produces energy levels that are akin to Hartree-Fock orbital energies such that conventional analyses based on Koopmans' theorem are available. Lastly, this system is convenient in formalisms that depend on creation and annihilation operators as they are trivially applied to single-determinant wave functions.« less

  18. Modulation of physical properties of oxide thin films by multiple fields

    NASA Astrophysics Data System (ADS)

    Hua-Li, Yang; Bao-Min, Wang; Xiao-Jian, Zhu; Jie, Shang; Bin, Chen; Run-Wei, Li

    2016-06-01

    Recent studies of the modulation of physical properties in oxide thin films by multiple fields are reviewed. Some of the key issues and prospects of this area of study are also addressed. Oxide thin films exhibit versatile physical properties such as magnetism, ferroelectricity, piezoelectricity, metal–insulator transition (MIT), multiferroicity, colossal magnetoresistivity, switchable resistivity. More importantly, the exhibited multifunctionality can be tuned by various external fields, which has enabled demonstration of novel electronic devices. Project supported by the State Key Project of Fundamental Research of China (Grant No. 2012CB933004), the National Natural Science Foundation of China (Grant Nos. 11474295, 51571208, 51525103, and 11274322), Overseas, Hong Kong & Macao Scholars Collaborated Researching Fund (Grant No. 51428201), the Instrument Developing Project of the Chinese Academy of Sciences (Grant No. YZ201327), Ningbo Major Project for Science and Technology (Grant No. 2014B11011), Ningbo International Cooperation Projects (Grant Nos. 2012D10018 and 2014D10005), the Fund for Ningbo Science and Technology Innovation Team (Grant No. 2015B11001), the Youth Innovation Promotion Association of the Chinese Academy of Sciences, and the Key Research Program of the Chinese Academy of Sciences (Grant No. KJZD-EW-M05).

  19. Targeting multiple types of tumors using NKG2D-coated iron oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Wu, Ming-Ru; Cook, W. James; Zhang, Tong; Sentman, Charles L.

    2014-11-01

    Iron oxide nanoparticles (IONPs) hold great potential for cancer therapy. Actively targeting IONPs to tumor cells can further increase therapeutic efficacy and decrease off-target side effects. To target tumor cells, a natural killer (NK) cell activating receptor, NKG2D, was utilized to develop pan-tumor targeting IONPs. NKG2D ligands are expressed on many tumor types and its ligands are not found on most normal tissues under steady state conditions. The data showed that mouse and human fragment crystallizable (Fc)-fusion NKG2D (Fc-NKG2D) coated IONPs (NKG2D/NPs) can target multiple NKG2D ligand positive tumor types in vitro in a dose dependent manner by magnetic cell sorting. Tumor targeting effect was robust even under a very low tumor cell to normal cell ratio and targeting efficiency correlated with NKG2D ligand expression level on tumor cells. Furthermore, the magnetic separation platform utilized to test NKG2D/NP specificity has the potential to be developed into high throughput screening strategies to identify ideal fusion proteins or antibodies for targeting IONPs. In conclusion, NKG2D/NPs can be used to target multiple tumor types and magnetic separation platform can facilitate the proof-of-concept phase of tumor targeting IONP development.

  20. Targeting multiple types of tumors using NKG2D-coated iron oxide nanoparticles

    PubMed Central

    Wu, Ming-Ru; Cook, W. James; Zhang, Tong; Sentman, Charles L.

    2015-01-01

    Iron oxide nanoparticles (IONPs) hold great potential for cancer therapy. Actively targeting IONPs to tumor cells can further increase therapeutic efficacy and decrease off-target side effects. To target tumor cells, a natural killer (NK) cell activating receptor, NKG2D, was utilized to develop pan-tumor targeting IONPs. NKG2D ligands are expressed on many tumor types and its ligands are not found on most normal tissues under steady state conditions. The data showed that mouse and human fragment crystallizable (Fc) -fusion NKG2D (Fc-NKG2D) coated IONPs (NKG2D/NPs) can target multiple NKG2D ligand positive tumor types in vitro in a dose dependent manner by magnetic cell sorting. Tumor targeting effect was robust even under a very low tumor cell to normal cell ratio and targeting efficiency correlated with NKG2D ligand expression level on tumor cells. Furthermore, the magnetic separation platform utilized to test NKG2D/NP specificity has the potential to be developed into high throughput screening strategies to identify ideal fusion proteins or antibodies for targeting IONPs. In conclusion, NKG2D/NPs can be used to target multiple tumor types and magnetic separation platform can facilitate the proof-of-concept phase of tumor targeting IONP development. PMID:25371538

  1. Biodegradation of individual and multiple chlorinated aliphatic hydrocarbons by methane-oxidizing cultures.

    PubMed Central

    Chang, H L; Alvarez-Cohen, L

    1996-01-01

    The microbial degradation of chlorinated and nonchlorinated methanes, ethanes, and ethanes by a mixed methane-oxidizing culture grown under chemostat and batch conditions is evaluated and compared with that by two pure methanotrophic strains: CAC1 (isolated from the mixed culture) and Methylosinus trichosporium OB3b. With the exception of 1,1-dichloroethylene, the transformation capacity (Tc) for each chlorinated aliphatic hydrocarbon was generally found to be in inverse proportion to its chlorine content within each aliphatic group (i.e., methanes, ethanes, and ethenes), whereas similar trends were not observed for degradation rate constants. Tc trends were similar for all methane-oxidizing cultures tested. None of the cultures were able to degrade the fully chlorinated aliphatics such as perchloroethylene and carbon tetrachloride. Of the four cultures tested, the chemostat-grown mixed culture exhibited the highest Tc for trichloroethylene, cis-1,2-dichloroethylene, tetrachloroethane, 1,1,1-trichloroethane, and 1,2-dichloroethane, whereas the pure batch-grown OB3b culture exhibited the highest Tc for all other compounds tested. The product toxicity of chlorinated aliphatic hydrocarbons in a mixture containing multiple compounds was cumulative and predictable when using parameters measured from the degradation of individual compounds. The Tc for each chlorinated aliphatic hydrocarbon in a mixture (Tcmix) and the total Tc for the mixture (sigma Tcmix) are functions of the individual Tc, the initial substrate concentration (S0), and the first-order rate constant (k/Ks) of each compound in the mixture, indicating the importance of identifying the properties and compositions of all potentially degradable compounds in a contaminant mixture. PMID:8795228

  2. Anti-oxidative stress response genes: bioinformatic analysis of their expression and relevance in multiple cancers

    PubMed Central

    Melino, Gerry; Knight, Richard A.

    2013-01-01

    Cells mount a transcriptional anti-oxidative stress (AOS) response program to scavenge reactive oxygen species (ROS) that arise from chemical, physical, and metabolic challenges. This protective program has been shown to reduce carcinogenesis triggered by chemical and physical insults. However, it is also hijacked by established cancers to thrive and proliferate within the hostile tumor microenvironment and to gain resistance against chemo- and radiotherapies. Therefore, targeting the AOS response proteins that are exploited by cancer cells is an attractive therapeutic strategy. In order to identify the AOS genes that are suspected to support cancer progression and resistance, we analyzed the expression patterns of 285 genes annotated for being involved in oxidative stress in 994 tumors and 353 normal tissues. Thereby we identified a signature of 116 genes that are highly overexpressed in multiple cancers while being only minimally expressed in normal tissues. To establish which of these genes are more likely to functionally drive cancer resistance and progression, we further identified those whose overexpression correlates with negative patient outcome in breast and lung carcinoma. Gene-set enrichment, gene ontology, network, and pathway analyses revealed that members of the thioredoxin and glutathione pathways are prominent components of this oncogenic signature and that activation of these pathways is common feature of many cancer entities. Interestingly, a large fraction of these AOS genes are downstream targets of the transcription factors NRF2, NF-kappaB, and FOXM1, and rely on NADPH for their enzymatic activities highlighting promising drug targets. We discuss these findings and propose therapeutic strategies that may be applied to overcome cancer resistance. PMID:24342878

  3. Oxidative stress in severe pulmonary trauma in critical ill patients. Antioxidant therapy in patients with multiple trauma--a review.

    PubMed

    Bedreag, Ovidiu Horea; Rogobete, Alexandru Florin; Sarandan, Mirela; Cradigati, Alina Carmen; Papurica, Marius; Dumbuleu, Maria Corina; Chira, Alexandru Mihai; Rosu, Oana Maria; Sandesc, Dorel

    2015-01-01

    Multiple trauma patients require extremely good management and thus, the trauma team needs to be prepared and to be up to date with the new standards of intensive therapy. Oxidative stress and free radicals represent an extremely aggressive factor to cells, having a direct consequence upon the severity of lung inflammation. Pulmonary tissue is damaged by oxidative stress, leading to biosynthesis of mediators that exacerbate inflammation modulators. The subsequent inflammation spreads throughout the body, leading most of the time to multiple organ dysfunction and death. In this paper, we briefly present an update of biochemical effects of oxidative stress and free radical damage to the pulmonary tissue in patients in critical condition in the intensive care unit. Also, we would like to present a series of active substances that substantially reduce the aggressiveness of free radicals, increasing the chances of survival. PMID:26037258

  4. Pluriformity of inflammation in multiple sclerosis shown by ultra-small iron oxide particle enhancement.

    PubMed

    Vellinga, Machteld M; Oude Engberink, Raoul D; Seewann, Alexandra; Pouwels, Petra J W; Wattjes, Mike P; van der Pol, Susanne M A; Pering, Christiane; Polman, Chris H; de Vries, Helga E; Geurts, Jeroen J G; Barkhof, Frederik

    2008-03-01

    Gadolinium-DTPA (Gd-DTPA) is routinely used as a marker for inflammation in MRI to visualize breakdown of the blood-brain barrier (BBB) in multiple sclerosis. Recent data suggest that ultra-small superparamagnetic particles of iron oxide (USPIO) can be used to visualize cellular infiltration, another aspect of inflammation. This project aimed to compare the novel USPIO particle SHU555C to the longitudinal pattern of Gd-DTPA enhancement in multiple sclerosis. Nineteen relapsing-remitting patients were screened monthly using Gd-enhanced MRI. In case of new enhancing lesions, USPIO were injected and 24 h later, MRI was performed and blood was collected to confirm USPIO loading of circulating monocytes. Lesion development was monitored by 3 monthly Gd-DTPA-enhanced scans and a final scan 7-11 months after injection. USPIO-enhancement was observed as hyperintensity on T1-weighted images, whereas no signal changes were observed on T2-weighted-gradient-echo images. In 14 patients with disease activity, 188 USPIO-positive lesions were seen, 144 of which were Gd-negative. By contrast, there were a total of 59 Gd-positive lesions, 15 of which were USPIO negative. Three patterns of USPIO-enhancement were seen: (i) focal enhancement; (ii) ring-like enhancement and (iii) return to isointensity of a previously hypointense lesion. The latter pattern was most frequently observed for lesions that turned out to be transiently hypointense on follow-up scans, and ring-enhancing lesions were less likely to evolve into black holes at follow-up than lesions without ring-like USPIO-enhancement; we speculate this to be associated with repair. In 4% of the USPIO-positive/Gd negative lesions, USPIO-enhancement preceded Gd-enhancement by 1 month. USPIO-enhancement remained visible for up to 3 months in 1.5% of all USPIO-positive lesions. In 29% of the lesions enhancing with both contrast agents, USPIO-enhancement persisted whereas Gd-enhancement had already resolved. In conclusion, the new

  5. Predicting reduction rates of energetic nitroaromatic compounds using calculated one-electron reduction potentials.

    PubMed

    Salter-Blanc, Alexandra J; Bylaska, Eric J; Johnston, Hayley J; Tratnyek, Paul G

    2015-03-17

    The evaluation of new energetic nitroaromatic compounds (NACs) for use in green munitions formulations requires models that can predict their environmental fate. Previously invoked linear free energy relationships (LFER) relating the log of the rate constant for this reaction (log(k)) and one-electron reduction potentials for the NAC (E1NAC) normalized to 0.059 V have been re-evaluated and compared to a new analysis using a (nonlinear) free-energy relationship (FER) based on the Marcus theory of outer-sphere electron transfer. For most reductants, the results are inconsistent with simple rate limitation by an initial, outer-sphere electron transfer, suggesting that the linear correlation between log(k) and E1NAC is best regarded as an empirical model. This correlation was used to calibrate a new quantitative structure-activity relationship (QSAR) using previously reported values of log(k) for nonenergetic NAC reduction by Fe(II) porphyrin and newly reported values of E1NAC determined using density functional theory at the M06-2X/6-311++G(2d,2p) level with the COSMO solvation model. The QSAR was then validated for energetic NACs using newly measured kinetic data for 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4-DNT), and 2,4-dinitroanisole (DNAN). The data show close agreement with the QSAR, supporting its applicability to other energetic NACs. PMID:25671710

  6. Flash-quench studies on the one-electron reduction of triiodide.

    PubMed

    Farnum, Byron H; Ward, William M; Meyer, Gerald J

    2013-01-18

    The one-electron reduction of triiodide (I(3)(-)) by a series of reduced ruthenium polypyridyl compounds was studied in an acetonitrile solution at room temperature using the flash-quench technique. Reductive quenching of the metal-to-ligand charge-transfer excited state of [Ru(bpy)(2)(deeb)](2+), [Ru(deeb)(2)(bpy)](2+), or [Ru(deeb)(3)](2+), where bpy is 2,2'-bipyridine and deeb is 4,4'-(CO(2)CH(2)CH(3))(2)-2,2'-bipyridine, by iodide generated the reduced ruthenium compounds and diiodide (I(2)(•-)). Charge recombination of the reduced ruthenium compounds and I(2)(•-) occurred with rate constants near the calculated diffusion limit of 2.6 × 10(10) M(-1) s(-1). The reaction of the reduced ruthenium compounds with I(3)(-) was characterized spectroscopically through the addition of I(3)(-) into the experimental solution prior to the laser flash. Transient absorption data indicated that I(2)(•-) was a reaction product of I(3)(-) reduction and appeared with an average second-order rate constant of (5.0 ± 0.6) × 10(9) M(-1) s(-1) for all three compounds. The insensitivity of the rate constants for I(3)(-) reduction over an 80 meV change in the driving force was unexpected. The relevance of these findings to solar energy conversion within dye-sensitized solar cells is discussed. PMID:23276296

  7. Dipole transition-matrix elements of the one-electron heterodiatomic quasimolecules

    SciTech Connect

    Devdariani, A.; Kereselidze, T.M.; Noselidze, I. L.; Dalimier, E.; Angelo, P.; Schott, R.; Sauvan, P.

    2005-02-01

    The problem of dipole transition-matrix element calculation for optical transitions in multiply charged one-electron diatomic quasimolecules with unequal nuclear charges Z{sub 1} and Z{sub 2} has been stated and solved. The quasimolecule Z{sub 1}eZ{sub 2} is a unique example of a two-center system for which the energy terms and dipole transition moments have been calculated precisely in the frame of a nonrelativistic approach. Particular examples for the optical transitions with Z{sub 1}=1.5,2,2.5,3 and Z{sub 2}=1 and with the principal quantum number of the united ion n{sub u}=1,2,3,4 have been tabulated. The scaling rules make it possible to determine the matrix elements for quasimolecules having nuclear charge ratios such as 2:1, 3:1, 3:2, and 5:2. Zeros at intermediate R and zero limiting values at large R are the highlighted features of the matrix elements. The heteronucleus case generates a large number of asymptotically forbidden transitions corresponding to transitions of an electron from one ion to another.

  8. One-electron standard reduction potentials of nitroaromatic and cyclic nitramine explosives.

    PubMed

    Uchimiya, Minori; Gorb, Leonid; Isayev, Olexandr; Qasim, Mohammad M; Leszczynski, Jerzy

    2010-10-01

    Extensive studies have been conducted in the past decades to predict the environmental abiotic and biotic redox fate of nitroaromatic and nitramine explosives. However, surprisingly little information is available on one-electron standard reduction potentials (Eo(R-NO2/R-NO2-)). The Eo(R-NO2/R-NO2-) is an essential thermodynamic parameter for predicting the rate and extent of reductive transformation for energetic residues. In this study, experimental (linear free energy relationships) and theoretical (ab initio calculation) approaches were employed to determine Eo(R-NO2/R-NO2-) for nitroaromatic, (caged) cyclic nitramine, and nitroimino explosives that are found in military installations or are emerging contaminants. The results indicate a close agreement between experimental and theoretical Eo(R-NO2/R-NO2-) and suggest a key trend: Eo(R-NO2/R-NO2-) value decreases from di- and tri-nitroaromatic (e.g., 2,4-dinitroanisole) to nitramine (e.g., RDX) to nitroimino compound (e.g., nitroguanidine). The observed trend in Eo(R-NO2/R-NO2-) agrees with reported rate trends for reductive degradation, suggesting a thermodynamic control on the reduction rate under anoxic/suboxic conditions. PMID:20656388

  9. Predicting Reduction Rates of Energetic Nitroaromatic Compounds Using Calculated One-Electron Reduction Potentials

    DOE PAGESBeta

    Salter-Blanc, Alexandra; Bylaska, Eric J.; Johnston, Hayley; Tratnyek, Paul G.

    2015-02-11

    The evaluation of new energetic nitroaromatic compounds (NACs) for use in green munitions formulations requires models that can predict their environmental fate. The susceptibility of energetic NACs to nitro reduction might be predicted from correlations between rate constants (k) for this reaction and one-electron reduction potentials (E1NAC) / 0.059 V, but the mechanistic implications of such correlations are inconsistent with evidence from other methods. To address this inconsistency, we have reevaluated existing kinetic data using a (non-linear) free-energy relationship (FER) based on the Marcus theory of outer-sphere electron transfer. For most reductants, the results are inconsistent with rate limitation bymore » an initial, outer-sphere electron transfer, suggesting that the strong correlation between k and E1NAC is justified only as an empirical model. This empirical correlation was used to calibrate a new quantitative structure-activity relationship (QSAR) using previously reported values of k for non-energetic NAC reduction by Fe(II) porphyrin and newly reported values of E1NAC determined using density functional theory at the B3LYP/6-311++G(2d,2p) level with the COSMO solvation model. The QSAR was then validated for energetic NACs using newly measured kinetic data for 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4-DNT), and 2,4-dinitroanisole (DNAN). The data show close agreement with the QSAR, supporting its applicability to energetic NACs.« less

  10. Predicting Reduction Rates of Energetic Nitroaromatic Compounds Using Calculated One-Electron Reduction Potentials

    SciTech Connect

    Salter-Blanc, Alexandra; Bylaska, Eric J.; Johnston, Hayley; Tratnyek, Paul G.

    2015-02-11

    The evaluation of new energetic nitroaromatic compounds (NACs) for use in green munitions formulations requires models that can predict their environmental fate. The susceptibility of energetic NACs to nitro reduction might be predicted from correlations between rate constants (k) for this reaction and one-electron reduction potentials (E1NAC) / 0.059 V, but the mechanistic implications of such correlations are inconsistent with evidence from other methods. To address this inconsistency, we have reevaluated existing kinetic data using a (non-linear) free-energy relationship (FER) based on the Marcus theory of outer-sphere electron transfer. For most reductants, the results are inconsistent with rate limitation by an initial, outer-sphere electron transfer, suggesting that the strong correlation between k and E1NAC is justified only as an empirical model. This empirical correlation was used to calibrate a new quantitative structure-activity relationship (QSAR) using previously reported values of k for non-energetic NAC reduction by Fe(II) porphyrin and newly reported values of E1NAC determined using density functional theory at the B3LYP/6-311++G(2d,2p) level with the COSMO solvation model. The QSAR was then validated for energetic NACs using newly measured kinetic data for 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4-DNT), and 2,4-dinitroanisole (DNAN). The data show close agreement with the QSAR, supporting its applicability to energetic NACs.

  11. One-electron reduced density matrices of strongly correlated harmonium atoms

    SciTech Connect

    Cioslowski, Jerzy

    2015-03-21

    Explicit asymptotic expressions are derived for the reduced one-electron density matrices (the 1-matrices) of strongly correlated two- and three-electron harmonium atoms in the ground and first excited states. These expressions, which are valid at the limit of small confinement strength ω, yield electron densities and kinetic energies in agreement with the published values. In addition, they reveal the ω{sup 5/6} asymptotic scaling of the exchange components of the electron-electron repulsion energies that differs from the ω{sup 2/3} scaling of their Coulomb and correlation counterparts. The natural orbitals of the totally symmetric ground state of the two-electron harmonium atom are found to possess collective occupancies that follow a mixed power/Gaussian dependence on the angular momentum in variance with the simple power-law prediction of Hill’s asymptotics. Providing rigorous constraints on energies as functionals of 1-matrices, these results are expected to facilitate development of approximate implementations of the density matrix functional theory and ensure their proper description of strongly correlated systems.

  12. Metal mobilization by iron- and sulfur-oxidizing bacteria in a multiple extreme mine tailings in the Atacama Desert, Chile.

    PubMed

    Korehi, H; Blöthe, M; Sitnikova, M A; Dold, B; Schippers, A

    2013-03-01

    The marine shore sulfidic mine tailings dump at the Chañaral Bay in the Atacama Desert, northern Chile, is characterized by extreme acidity, high salinity, and high heavy metals concentrations. Due to pyrite oxidation, metals (especially copper) are mobilized under acidic conditions and transported toward the tailings surface and precipitate as secondary minerals (Dold, Environ. Sci. Technol. 2006, 40, 752-758.). Depth profiles of total cell counts in this almost organic-carbon free multiple extreme environment showed variable numbers with up to 10(8) cells g(-1) dry weight for 50 samples at four sites. Real-time PCR quantification and bacterial 16S rRNA gene diversity analysis via clone libraries revealed a dominance of Bacteria over Archaea and the frequent occurrence of the acidophilic iron(II)- and sulfur-oxidizing and iron(III)-reducing genera Acidithiobacillus, Alicyclobacillus, and Sulfobacillus. Acidophilic chemolithoautotrophic iron(II)-oxidizing bacteria were also frequently found via most-probable-number (MPN) cultivation. Halotolerant iron(II)-oxidizers in enrichment cultures were active at NaCl concentrations up to 1 M. Maximal microcalorimetrically determined pyrite oxidation rates coincided with maxima of the pyrite content, total cell counts, and MPN of iron(II)-oxidizers. These findings indicate that microbial pyrite oxidation and metal mobilization preferentially occur in distinct tailings layers at high salinity. Microorganisms for biomining with seawater salt concentrations obviously exist in nature. PMID:23373853

  13. Conditions for zeros in the generalized oscillator strength: One-electron atom and diatomic molecule examples

    SciTech Connect

    Peek, J.M. ); Madsen, M.M. )

    1991-01-01

    Requirements for the existence of isolated zeros in the generalized oscillator strength (GOS) for one-electron atoms and molecules are considered. It is shown that in certain limits the atomic GOS cannot be zero for any value of the momentum-transfer magnitude {h bar}{ital K}{ne}0 unless it is zero for all values. A relationship between the existence of a zero and the angular momentum of the target's states is pointed out for the atomic case and a numerical example is provided. The conditions for the existence of an isolated zero for a molecular GOS are derived and, using the atom case as a model, they indicate that one is unlikely for 0{lt}{ital K}{lt}{infinity} and the internuclear separation {ital R} restricted to 0{lt}{ital R}{lt}{infinity}. Minima, or possibly zeros, in the molecular GOS occur in both experiment and theory. It is postulated here that these structures are minima and not zeros. They appear to be due to zeros in a matrix element related to the leading term of the small-{ital K} GOS expansion while higher terms remain finite. Several numerical examples are provided and the speculation is supported by the correlation of the GOS minimum as a function of {ital K} and {ital R} to a zero in the dipole oscillator strength. Attention is brought to the existence of zeros in the molecular dipole oscillator strength when a nodeless function appears in this matrix element, contrary to the atomic case, and an explanation for this difference is given.

  14. Iron Oxide Nanoparticles Induce Autophagosome Accumulation through Multiple Mechanisms: Lysosome Impairment, Mitochondrial Damage, and ER Stress.

    PubMed

    Zhang, Xudong; Zhang, Hongqiu; Liang, Xin; Zhang, Jinxie; Tao, Wei; Zhu, Xianbing; Chang, Danfeng; Zeng, Xiaowei; Liu, Gan; Mei, Lin

    2016-07-01

    Magnetite (iron oxide, Fe3O4) nanoparticles have been widely used for drug delivery and magnetic resonance imaging (MRI). Previous studies have shown that many metal-based nanoparticles including Fe3O4 nanoparticles can induce autophagosome accumulation in treated cells. However, the underlying mechanism is still not clear. To investigate the biosafety of Fe3O4 and PLGA-coated Fe3O4 nanoparticles, some experiments related to the mechanism of autophagy induction by these nanoparticles have been investigated. In this study, the results showed that Fe3O4, PLGA-coated Fe3O4, and PLGA nanoparticles could be taken up by the cells through cellular endocytosis. Fe3O4 nanoparticles extensively impair lysosomes and lead to the accumulation of LC3-positive autophagosomes, while PLGA-coated Fe3O4 nanoparticles reduce this destructive effect on lysosomes. Moreover, Fe3O4 nanoparticles could also cause mitochondrial damage and ER and Golgi body stresses, which induce autophagy, while PLGA-coated Fe3O4 nanoparticles reduce the destructive effect on these organelles. Thus, the Fe3O4 nanoparticle-induced autophagosome accumulation may be caused by multiple mechanisms. The autophagosome accumulation induced by Fe3O4 was also investigated. The Fe3O4, PLGA-coated Fe3O4, and PLGA nanoparticle-treated mice were sacrificed to evaluate the toxicity of these nanoparticles on the mice. The data showed that Fe3O4 nanoparticle treated mice would lead to the extensive accumulation of autophagosomes in the kidney and spleen in comparison to the PLGA-coated Fe3O4 and PLGA nanoparticles. Our data clarifies the mechanism by which Fe3O4 induces autophagosome accumulation and the mechanism of its toxicity on cell organelles and mice organs. These findings may have an important impact on the clinical application of Fe3O4 based nanoparticles. PMID:27287467

  15. Characteristics of multiple-year nitrous oxide emissions from conventional vegetable fields in southeastern China

    NASA Astrophysics Data System (ADS)

    Mei, Baoling; Zheng, Xunhua; Xie, Baohua; Dong, Haibo; Yao, Zhisheng; Liu, Chunyan; Zhou, Zaixing; Wang, Rui; Deng, Jia; Zhu, Jianguo

    2011-06-01

    The annual and interannual characteristics of nitrous oxide (N2O) emissions from conventional vegetable fields are poorly understood. We carried out 4 year measurements of N2O fluxes from a conventional vegetable cultivation area in the Yangtze River delta. Under fertilized conditions subject to farming practices, approximately 86% of the annual total N2O release occurred following fertilization events. The direct emission factors (EFd) of the 12 individual vegetable seasons investigated ranged from 0.06 to 14.20%, with a mean of 3.09% and a coefficient of variation (CV) of 142%. The annual EFd varied from 0.59 to 4.98%, with a mean of 2.88% and an interannual CV of 74%. The mean value is much larger than the latest default value (1.00%) of the Intergovernmental Panel on Climate Change. Occasional application of lagoon-stored manure slurry coupled with other nitrogen fertilizers, or basal nitrogen addition immediately followed by heavy rainfall, accounted for a substantial portion of the large EFds observed in warm seasons. The large CVs suggest that the emission factors obtained from short-term observations that poorly represent seasonality and/or interannual variability will inevitably yield large uncertainties in inventory estimation. The results of this study indicate that conventional vegetable fields associated with intensive nitrogen addition, as well as occasional applications of manure slurry, may substantially account for regional N2O emissions. However, this conclusion needs to be further confirmed through studies at multiple field sites. Moreover, further experimental studies are needed to test the mitigation options suggested by this study for N2O emissions from open vegetable fields.

  16. Aptamer-Conjugated Graphene Oxide Membranes for Highly Efficient Capture and Accurate Identification of Multiple Types of Circulating Tumor Cells

    PubMed Central

    2016-01-01

    Tumor metastasis is responsible for 1 in 4 deaths in the United States. Though it has been well-documented over past two decades that circulating tumor cells (CTCs) in blood can be used as a biomarker for metastatic cancer, there are enormous challenges in capturing and identifying CTCs with sufficient sensitivity and specificity. Because of the heterogeneous expression of CTC markers, it is now well understood that a single CTC marker is insufficient to capture all CTCs from the blood. Driven by the clear need, this study reports for the first time highly efficient capture and accurate identification of multiple types of CTCs from infected blood using aptamer-modified porous graphene oxide membranes. The results demonstrate that dye-modified S6, A9, and YJ-1 aptamers attached to 20–40 μm porous garphene oxide membranes are capable of capturing multiple types of tumor cells (SKBR3 breast cancer cells, LNCaP prostate cancer cells, and SW-948 colon cancer cells) selectively and simultaneously from infected blood. Our result shows that the capture efficiency of graphene oxide membranes is ∼95% for multiple types of tumor cells; for each tumor concentration, 10 cells are present per milliliter of blood sample. The selectivity of our assay for capturing targeted tumor cells has been demonstrated using membranes without an antibody. Blood infected with different cells also has been used to demonstrate the targeted tumor cell capturing ability of aptamer-conjugated membranes. Our data also demonstrate that accurate analysis of multiple types of captured CTCs can be performed using multicolor fluorescence imaging. Aptamer-conjugated membranes reported here have good potential for the early diagnosis of diseases that are currently being detected by means of cell capture technologies. PMID:25565372

  17. How the multiple antioxidant properties of ascorbic acid affect lipid oxidation in oil-in-water emulsions.

    PubMed

    Uluata, Sibel; McClements, D Julian; Decker, Eric A

    2015-02-18

    Lipid oxidation is a serious problem for oil-containing food products because it negatively affects shelf life and nutritional composition. An antioxidant strategy commonly employed to prevent or delay oxidation in foods is to remove oxygen from the closed food-packaging system. An alternative technique is use of an edible oxygen scavenger to remove oxygen within the food. Ascorbic acid (AA) is a particularly promising antioxidant because of its natural label and multiple antioxidative functions. In this study, AA was tested as an oxygen scavenger in buffer and an oil-in-water (O/W) emulsion. The effects of transition metals on the ability of AA to scavenge oxygen were determined. Headspace oxygen decrease less than 1% in the medium-chain triacylglycerol (MCT) O/W emulsion system (pH 3 and 7). AA was able to almost completely remove dissolved oxygen (DO) in a buffered solution. Transition metals (Fe(2+) and Cu(+)) significantly accelerated the degradation of AA; however, iron and copper only increased DO depletion rates, by 10.6-16.4% from day 1 to 7, compared to the control. AA (2.5-20 mM) decreased DO in a 1% O/W emulsion system 32.0-64.0% and delayed the formation of headspace hexanal in the emulsion from 7 to over 20 days. This research shows that, when AA is used in an O/W emulsion system, oxidation of the emulsion system can be delay by multiple mechanisms. PMID:25650525

  18. Biocompatible nanocarriers that respond to oxidative environments via interactions between chitosan and multiple metal ions

    PubMed Central

    Zhang, Shichang; Xia, Liye; Ding, Chenchen; Wen, Lu; Wan, Weihua; Chen, Gang

    2016-01-01

    Hydrogen peroxide (H2O2) functions as an early damage signal contributing to the oxidative stress response and can act as a trigger in smart oxidation-responsive drug delivery systems that are currently in development. Current H2O2-triggered oxidation-responsive polymeric systems are usually derived from chemical synthesis and rarely include natural polymers. Herein, we report two series of nanoparticle (NP) complexes prepared with the biopolymer chitosan (CS) and four different metal ions (Cu2+, Ca2+, Zn2+, and Fe3+), defined as CSNPs-metal complexes (Series 1) and CS-metal complexes NPs (Series 2), which responded to oxidation by dissolving upon H2O2 exposure. Experiments examining Nile red release and H2O2-triggered degradation confirmed that both series of complexes showed better sensitivity to oxidation than the CSNPs alone. Furthermore, preliminary cytotoxicity and histological observations indicated that the two series exhibited little or no cytotoxicity and generated a mild inflammatory response. Our work provides a novel and promising strategy for developing NPs for use as intelligent oxidation-responsive systems. PMID:27358564

  19. Modulation of Cell Metabolic Pathways and Oxidative Stress Signaling Contribute to Acquired Melphalan Resistance in Multiple Myeloma Cells

    PubMed Central

    Zub, Kamila Anna; de Sousa, Mirta Mittelstedt Leal; Sarno, Antonio; Sharma, Animesh; Demirovic, Aida; Rao, Shalini; Young, Clifford; Aas, Per Arne; Ericsson, Ida; Sundan, Anders; Jensen, Ole Nørregaard; Slupphaug, Geir

    2015-01-01

    Alkylating agents are widely used chemotherapeutics in the treatment of many cancers, including leukemia, lymphoma, multiple myeloma, sarcoma, lung, breast and ovarian cancer. Melphalan is the most commonly used chemotherapeutic agent against multiple myeloma. However, despite a 70–80% initial response rate, virtually all patients eventually relapse due to the emergence of drug-resistant tumour cells. By using global proteomic and transcriptomic profiling on melphalan sensitive and resistant RPMI8226 cell lines followed by functional assays, we discovered changes in cellular processes and pathways not previously associated with melphalan resistance in multiple myeloma cells, including a metabolic switch conforming to the Warburg effect (aerobic glycolysis), and an elevated oxidative stress response mediated by VEGF/IL8-signaling. In addition, up-regulated aldo-keto reductase levels of the AKR1C family involved in prostaglandin synthesis contribute to the resistant phenotype. Finally, selected metabolic and oxidative stress response enzymes were targeted by inhibitors, several of which displayed a selective cytotoxicity against the melphalan-resistant cells and should be further explored to elucidate their potential to overcome melphalan resistance. PMID:25769101

  20. Hybrid functional for correlated electrons in the projector augmented-wave formalism: Study of multiple minima for actinide oxides

    NASA Astrophysics Data System (ADS)

    Jollet, F.; Jomard, G.; Amadon, B.; Crocombette, J. P.; Torumba, D.

    2009-12-01

    Exact (Hartree-Fock) exchange for correlated electrons is implemented to describe correlated orbitals in the projector augmented-waves (PAW) framework, as suggested recently in another context [P. Novák , Phys. Status Solidi B 243, 563 (2006)]. Hartree-Fock exchange energy is applied to strongly correlated electrons only inside the PAW atomic spheres. This allows the use of PBE0 hybrid exchange-correlation functional for correlated electrons. This method is tested on NiO and results agree well with already published results and generalized gradient approximation, GGA+U calculations. It is then applied to plutonium oxides and UO2 for which the results are comparable with the ones of GGA+U calculations but without adjustable parameter. As evidenced in the uranium oxide case, the occurrence of multiple energy minima may lead to very different results depending on the initial electronic configurations and on the symmetries taken into account in the calculation.

  1. Nitric oxide and muscle repair: multiple actions converging on therapeutic efficacy.

    PubMed

    Rovere-Querini, Patrizia; Clementi, Emilio; Brunelli, Silvia

    2014-05-01

    Muscular dystrophies comprise an heterogeneous group of diseases characterised by primary wasting of skeletal muscle, in the most severe forms leading to progressive paralysis and death. Current therapies for these conditions are extremely limited and based on corticosteroids that bear significant side effects. Several studies have proposed possible alternative strategies, ranging from cell and gene therapy to more classical pharmacological approaches. Nitric oxide is a gaseous messenger involved in many mechanisms responsible for preserving muscle function and stimulating muscle repair. We herein review the most recent pre-clinical and clinical findings that open new prospective for the development of nitric oxide as a therapeutic tool for muscular dystrophies. PMID:24269596

  2. Effect of temperature in multiple biomarkers of oxidative stress in coastal shrimp.

    PubMed

    Vinagre, Catarina; Madeira, Diana; Mendonça, Vanessa; Dias, Marta; Roma, Joma; Diniz, Mário S

    2014-04-01

    Various studies in captivity and in the wild have pointed to the effect of season, and temperature in particular, in the levels of the oxidative stress biomarkers currently used for environmental quality assessment. However, knowledge on how temperature affects the oxidative stress response is unavailable for most species. This study investigated the effect of increasing temperature on lipid peroxidation, catalase activity, superoxide dismutase and glutathione-S-transferase in the shrimps, Palaemon elegans and Palaemon serratus. It was concluded that increasing temperatures significantly affect all the biomarkers tested in both species, with the exception of superoxide dismutase in P. serratus which was not affected by temperature. The oxidative stress response was more intense in P. elegans, than in P. serratus, producing higher peaks of all biomarkers at temperatures between 22°C and 26°C, followed by low levels at higher temperatures. It was concluded that monitoring of ecosystems using oxidative stress biomarkers should take into account the species and thermal history of the organisms. Sampling should be avoided during heat waves and immediately after heat waves. PMID:24679970

  3. Native LDL-induced oxidative stress in human proximal tubular cells: multiple players involved

    PubMed Central

    Piccoli, Claudia; Quarato, Giovanni; D’Aprile, Annamaria; Montemurno, Eustacchio; Scrima, Rosella; Ripoli, Maria; Gomaraschi, Monica; Cirillo, Pietro; Boffoli, Domenico; Calabresi, Laura; Gesualdo, Loreto; Capitanio, Nazzareno

    2011-01-01

    Abstract Dyslipidemia is a well-established condition proved to accelerate the progression of chronic kidney disease leading to tubulo-interstitial injury. However, the molecular aspects of the dyslipidemia-induced renal damage have not been fully clarified and in particular the role played by low-density lipoproteins (LDLs). This study aimed to examine the effects of native non-oxidized LDL on cellular oxidative metabolism in cultured human proximal tubular cells. By means of confocal microscopy imaging combined to respirometric and enzymatic assays it is shown that purified native LDL caused a marked increase of cellular reactive oxygen species (ROS) production, which was mediated by activation of NADPH oxidase(s) and by mitochondrial dysfunction by means of a ROS-induced ROS release mechanism. The LDL-dependent mitochondrial alterations comprised inhibition of the respiratory chain activity, enhanced ROS production, uncoupling of the oxidative phosphorylation efficiency, collapse of the mtΔΨ, increased Ca2+ uptake and loss of cytochrome c. All the above LDL-induced effects were completely abrogated by chelating extracellular Ca2+ as well as by inhibition of the Ca2+-activated cytoplas-mic phospholipase A2, NADPH oxidase and mitochondrial permeability transition. We propose a mechanicistic model whereby the LDL-induced intracellular redox unbalance is triggered by a Ca2+ inward flux-dependent commencement of cPLA2 followed by activation of a lipid- and ROS-based cross-talking signalling pathway. This involves first oxidants production via the plasmamembrane NADPH oxidase and then propagates downstream to mitochondria eliciting redox- and Ca2+-dependent dysfunctions leading to cell-harming conditions. These findings may help to clarify the mechanism of dyslipidemia-induced renal damage and suggest new potential targets for specific therapeutic strategies to prevent oxidative stress implicated in kidney diseases. PMID:19863698

  4. Cellular Protection using Flt3 and PI3Kα inhibitors demonstrates multiple mechanisms of oxidative glutamate toxicity

    PubMed Central

    Kang, Yunyi; Tiziani, Stefano; Park, Goonho; Kaul, Marcus; Paternostro, Giovanni

    2014-01-01

    Glutamate-induced oxidative stress is a major contributor to neurodegenerative diseases. Here we identify small molecule inhibitors of this process. We screen a kinase inhibitor library on neuronal cells and identify Flt3 and PI3Kα inhibitors as potent protectors against glutamate toxicity. Both inhibitors prevented reactive oxygen species (ROS) generation, mitochondrial hyperpolarization, and lipid peroxidation in neuronal cells, but they do so by distinct molecular mechanisms. The PI3Kα inhibitor protects cells by inducing partial restoration of depleted glutathione levels and accumulation of intracellular amino acids, whereas the Flt3 inhibitor prevents lipid peroxidation, a key mechanism of glutamate-mediated toxicity. We also demonstrate that glutamate toxicity involves a combination of ferroptosis, necrosis, and AIF-dependent apoptosis. We confirm the protective effect by using multiple inhibitors of these kinases and multiple cell types. Our results not only identify compounds that protect against glutamate-stimulated oxidative stress, but also provide new insights into the mechanisms of glutamate toxicity in neurons. PMID:24739485

  5. Purple carrot extract protects against cadmium intoxication in multiple organs of rats: Genotoxicity, oxidative stress and tissue morphology analyses.

    PubMed

    Claudio, Samuel Rangel; Gollucke, Andrea Pittelli Boiago; Yamamura, Hirochi; Morais, Damila Rodrigues; Bataglion, Giovana Anceski; Eberlin, Marcos Nogueira; Peres, Rogerio Correa; Oshima, Celina Tizuko Fujiyama; Ribeiro, Daniel Araki

    2016-01-01

    The aim of this study was to investigate if purple carrot extract is able to protect against the noxious activities induced by cadmium exposure in multiple organs of rats. For this purpose, histopathological analysis, genotoxicity and oxidative status were investigated in this setting. A total of twenty Wistar rats weighing 250g on the average, and 8 weeks age were distributed into four groups (n=5), as follows: Control group (non-treated group, CTRL); Cadmium group (Cd) and Purple carrot extract groups at 400mg/L or 800mg/L. Histopathological analysis revealed that liver from animals treated with purple carrot extract improved tissue degeneration induced by cadmium intoxication. Genetic damage was reduced in blood and hepatocytes as depicted by comet and micronucleus assays in animals treated with purple carrot extract. SOD-CuZn and cytocrome C gene expression increased in groups treated with purple carrot extract. Purple carrot extract also reduced the 8OHdG levels in liver cells when compared to cadmium group. Taken together, our results demonstrate that purple carrot extract is able to protect against cadmium intoxication by means of reducing tissue regeneration, genotoxicity and oxidative stress in multiple organs of Wistar rats. PMID:26653742

  6. Prognostic value of HMGB1 and oxidative stress markers in multiple trauma patients: A single-centre prospective study.

    PubMed

    Polito, Francesca; Cicciu', Marco; Aguennouz, Mohammed; Cucinotta, Maria; Cristani, Mariateresa; Lauritano, Floriana; Sindoni, Alessandro; Gioffre'-Florio, Maria; Fama, Fausto

    2016-09-01

    Serious multiple traumatic injuries may rapidly become fatal or be complicated by a life-threatening sequelae leading to a significant increase of the mortality rate. Trauma scoring systems are used to evaluate the critical status of the patient and recently many different biomarkers have been taken into account to better estimate the potential clinical outcome. The aim of the present study is to analyse the expression pattern of high-mobility group box-1 (HMGB1), oxidative stress markers and nuclear factor erythroid 2-related (Nrf2) in critically ill traumatic patients (at hospital admittance and after 6 and 24 h), in order to find out their potential role as early post-traumatic predictors markers. Forty-seven patients admitted for multiple trauma and 15 healthy participants were prospectively recruited. Eight patients (17%) died within 92 h of admission; this subgroup of patients presented the highest severity scores and their HMGB1 expression levels were significantly correlated with ISS, whereas patients with higher ISS exhibited higher levels of HMGB1 (P <0.001). Our study suggests the role of HMGB1 as a predictive biomarker of outcome in injured patients and hypothesizes the protective role of Nrf2 in bringing down the oxidative stress and HMGB1 release; measuring HMGB1 in combination with Nrf2 might represent a potentially useful tool in the early detection of post-trauma complications. PMID:27343243

  7. Multiple ink-jet printed zinc tin oxide layers with improved TFT performance

    NASA Astrophysics Data System (ADS)

    Sykora, Benedikt; Wang, Di; von Seggern, Heinz

    2016-07-01

    In the last two decades, metal-oxides, like zinc tin oxide (ZTO), are widely studied semiconductors for transistor applications. This study presents a simple, non-toxic, stable, and cost efficient precursor route for ZTO deposition by ink-jet printing. Such fabricated thin films are composed of an amorphous phase with embedded ZnO nanocrystals. The saturation mobility of ink-jet printed transistors increases from 0.05 cm2 V-1 s-1 for a single semiconducting layer to 7.8 cm2 V-1 s-1 for a transistor composed of 8 layers. This constitutes the highest saturation mobility of an ink-jet printed ZTO transistor reported so far. The devices exhibit large output currents (up to 38.7 mA) and high on/off ratios (exceeding 108). The large improvement in transistor performance with the number of layers is ascribed to an improved degree of substrate coverage confirmed by AFM investigations.

  8. HCV core protein uses multiple mechanisms to induce oxidative stress in human hepatoma Huh7 cells.

    PubMed

    Ivanov, Alexander V; Smirnova, Olga A; Petrushanko, Irina Y; Ivanova, Olga N; Karpenko, Inna L; Alekseeva, Ekaterina; Sominskaya, Irina; Makarov, Alexander A; Bartosch, Birke; Kochetkov, Sergey N; Isaguliants, Maria G

    2015-06-01

    Hepatitis C virus (HCV) infection is accompanied by the induction of oxidative stress, mediated by several virus proteins, the most prominent being the nucleocapsid protein (HCV core). Here, using the truncated forms of HCV core, we have delineated several mechanisms by which it induces the oxidative stress. The N-terminal 36 amino acids of HCV core induced TGF\\(\\upbeta\\)1-dependent expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases 1 and 4, both of which independently contributed to the production of reactive oxygen species (ROS). The same fragment also induced the expression of cyclo-oxygenase 2, which, however, made no input into ROS production. Amino acids 37-191 of HCV core up-regulated the transcription of a ROS generating enzyme cytochrome P450 2E1. Furthermore, the same fragment induced the expression of endoplasmic reticulum oxidoreductin 1\\(\\upalpha\\). The latter triggered efflux of Ca2+ from ER to mitochondria via mitochondrial Ca2+ uniporter, leading to generation of superoxide anions, and possibly also H2O2. Suppression of any of these pathways in cells expressing the full-length core protein led to a partial inhibition of ROS production. Thus, HCV core causes oxidative stress via several independent pathways, each mediated by a distinct region of the protein. PMID:26035647

  9. Barley has two peroxisomal ABC transporters with multiple functions in β-oxidation

    PubMed Central

    Mendiondo, Guillermina M.; Medhurst, Anne; van Roermund, Carlo W.; Zhang, Xuebin; Devonshire, Jean; Scholefield, Duncan; Fernández, José; Axcell, Barry; Ramsay, Luke; Waterham, Hans R.; Waugh, Robbie; Theodoulou, Frederica L.; Holdsworth, Michael J.

    2014-01-01

    In oilseed plants, peroxisomal β-oxidation functions not only in lipid catabolism but also in jasmonate biosynthesis and metabolism of pro-auxins. Subfamily D ATP-binding cassette (ABC) transporters mediate import of β-oxidation substrates into the peroxisome, and the Arabidopsis ABCD protein, COMATOSE (CTS), is essential for this function. Here, the roles of peroxisomal ABCD transporters were investigated in barley, where the main storage compound is starch. Barley has two CTS homologues, designated HvABCD1 and HvABCD2, which are widely expressed and present in embryo and aleurone tissues during germination. Suppression of both genes in barley RNA interference (RNAi) lines indicated roles in metabolism of 2,4-dichlorophenoxybutyrate (2,4-DB) and indole butyric acid (IBA), jasmonate biosynthesis, and determination of grain size. Transformation of the Arabidopsis cts-1 null mutant with HvABCD1 and HvABCD2 confirmed these findings. HvABCD2 partially or completely complemented all tested phenotypes of cts-1. In contrast, HvABCD1 failed to complement the germination and establishment phenotypes of cts-1 but increased the sensitivity of hypocotyls to 100 μM IBA and partially complemented the seed size phenotype. HvABCD1 also partially complemented the yeast pxa1/pxa2Δ mutant for fatty acid β-oxidation. It is concluded that the core biochemical functions of peroxisomal ABC transporters are largely conserved between oilseeds and cereals but that their physiological roles and importance may differ. PMID:24913629

  10. Arsenite oxidizing multiple metal resistant bacteria isolated from industrial effluent: their potential use in wastewater treatment.

    PubMed

    Naureen, Ayesha; Rehman, Abdul

    2016-08-01

    Arsenite oxidizing bacteria, isolated from industrial wastewater, showed high resistance against arsenite (40 mM) and other heavy metals (10 mM Pb; 8 mM Cd; 6 mM Cr; 10 mM Cu and 26.6 mM As(5+)). Bacterial isolates were characterized, on the basis of morphological, biochemical and 16S rRNA ribotyping, as Bacillus cereus (1.1S) and Acinetobacter junii (1.3S). The optimum temperature and pH for the growth of both strains were found to be 37 °C and 7. Both the strains showed maximum growth after 24 h of incubation. The predominant form of arsenite oxidase was extracellular in B. cereus while in A. junii both types of activities, intracellular and extracellular, were found. The extracellular aresenite oxidase activity was found to be 730 and 750 µM/m for B. cereus and A. junii, respectively. The arsenite oxidase from both bacterial strains showed maximum activity at 37 °C, pH 7 and enhanced in the presence of Zn(2+). The presence of two protein bands with molecular weight of approximately 70 and 14 kDa in the presence of arsenic points out a possible role in arsenite oxidation. Arsenite oxidation potential of B. cereus and A. junii was determined up to 92 and 88 % in industrial wastewater after 6 days of incubation. The bacterial treated wastewater improved the growth of Vigna radiata as compared to the untreated wastewater. It indicates that these bacterial strains may find some potential applications in wastewater treatment systems to transform toxic arsenite into less toxic form, arsenate. PMID:27339314

  11. INTERCONNECTION BETWEEN NITRIC OXIDE FORMATION AND HYPERSENSITIVITY PARAMETERS UNDER GUINEA PIG MODEL OF ACUTE ASTHMA WITH MULTIPLE CHALLENGES.

    PubMed

    Parilova, O O; Shandrenko, S G

    2015-01-01

    An immunoregulatory role of nitric oxide (NO) in the development of adaptive immune responses associated with allergic diseases is very important. The present study extended these observations by the examination of the reciprocal changes in characteristic immunologic parameters of the disease and NO level of bronchoalveolar lavage (BAL) cells under guinea pig model of acute asthma with multiple challenges. Development of guinea pig Th2 mediated asthma was accompanied by increasing the level of allergic markers: ovalbumin (OVA) specific IgG and IL-4. We demonstrated that the infiltrate of airway cells contributes to NO synthesis in the respiratory tract during allergic inflammation. The level of intracellular NO formation significantly correlated with plasma allergen specific IgG value in OVA-induced asthma. The presented data evidence that the elevated intracellular NO level in BAL fluid may reflect a nitrosative stress in respiratory tract in general, when allergic asthma exacerbation is present. PMID:26717602

  12. Electronic structure of tin oxides by electron energy loss spectroscopy and real-space multiple scattering calculations

    SciTech Connect

    Moreno, M. S.; Egerton, R.F.; Rehr, J.J.; Midgley, P.A.

    2005-01-15

    The electronic structure of the tin oxides SnO and SnO{sub 2} is studied using the fine structure of the Sn-M{sub 4,5} and oxygen K-edges measured by electron energy loss spectroscopy (EELS). The experimental results are compared with real-space multiple scattering calculations. It is observed that both edges are overlapped. The calculations reveal that the observed fine structure is due largely to the oxygen states, and that it can be used to fingerprint each phase. The calculated densities of states are similar for both compounds and suggest a covalent nature. The structures appearing within the first 10 eV above the threshold arise from a covalent mixing of mainly O 2p and Sn 5s-p. For SnO the oxygen edge is satisfactorily reproduced. Discrepancies in the predicted energy position of the features in the EELS of SnO{sub 2} are briefly discussed.

  13. Self-interaction correction in multiple scattering theory: application to transition metal oxides

    SciTech Connect

    Daene, Markus W; Lueders, Martin; Ernst, Arthur; Diemo, Koedderitzsch; Temmerman, Walter M; Szotek, Zdzislawa; Wolfam, Hergert

    2009-01-01

    We apply to transition metal monoxides the self-interaction corrected (SIC) local spin density (LSD) approximation, implemented locally in the multiple scattering theory within the Korringa-Kohn-Rostoker (KKR) band structure method. The calculated electronic structure and in particular magnetic moments and energy gaps are discussed in reference to the earlier SIC results obtained within the LMTO-ASA band structure method, involving transformations between Bloch and Wannier representations to solve the eigenvalue problem and calculate the SIC charge and potential. Since the KKR can be easily extended to treat disordered alloys, by invoking the coherent potential approximation (CPA), in this paper we compare the CPA approach and supercell calculations to study the electronic structure of NiO with cation vacancies.

  14. One electron reduced square planar bis(benzene-1,2-dithiolato) copper dianionic complex and redox switch by O2/HO(-).

    PubMed

    Maiti, Biplab K; Maia, Luisa B; Pal, Kuntal; Pakhira, Bholanath; Avilés, Teresa; Moura, Isabel; Pauleta, Sofia R; Nuñez, José L; Rizzi, Alberto C; Brondino, Carlos D; Sarkar, Sabyasachi; Moura, José J G

    2014-12-15

    The complex [Ph4P]2[Cu(bdt)2] (1(red)) was synthesized by the reaction of [Ph4P]2[S2MoS2CuCl] with H2bdt (bdt = benzene-1,2-dithiolate) in basic medium. 1(red) is highly susceptible toward dioxygen, affording the one electron oxidized diamagnetic compound [Ph4P][Cu(bdt)2] (1(ox)). The interconversion between these two oxidation states can be switched by addition of O2 or base (Et4NOH = tetraethylammonium hydroxide), as demonstrated by cyclic voltammetry and UV-visible and EPR spectroscopies. Thiomolybdates, in free or complex forms with copper ions, play an important role in the stability of 1(red) during its synthesis, since in its absence, 1(ox) is isolated. Both 1(red) and 1(ox) were structurally characterized by X-ray crystallography. EPR experiments showed that 1(red) is a Cu(II)-sulfur complex and revealed strong covalency on the copper-sulfur bonds. DFT calculations confirmed the spin density delocalization over the four sulfur atoms (76%) and copper (24%) atom, suggesting that 1(red) has a "thiyl radical character". Time dependent DFT calculations identified such ligand to ligand charge transfer transitions. Accordingly, 1(red) is better described by the two isoelectronic structures [Cu(I)(bdt2, 4S(3-,)*)](2-) ↔ [Cu(II)(bdt2, 4S(4-))](2-). On thermodynamic grounds, oxidation of 1(red) (doublet state) leads to 1(ox) singlet state, [Cu(III)(bdt2, 4S(4-))](1-). PMID:25470763

  15. Investigation of hair dye deposition, hair color loss, and hair damage during multiple oxidative dyeing and shampooing cycles.

    PubMed

    Zhang, Guojin; McMullen, Roger L; Kulcsar, Lidia

    2016-01-01

    Color fastness is a major concern for consumers and manufacturers of oxidative hair dye products. Hair dye loss results from multiple wash cycles in which the hair dye is dissolved by water and leaches from the hair shaft. In this study, we carried out a series of measurements to help us better understand the kinetics of the leaching process and pathways associated with its escape from the fiber. Hair dye leaching kinetics was measured by suspending hair in a dissolution apparatus and monitoring the dye concentration in solution (leached dye) with an ultraviolet-visible spectrophotometer. The physical state of dye deposited in hair fibers was evaluated by a reflectance light microscopy technique, based on image stacking, allowing enhanced depth of field imaging. The dye distribution within the fiber was monitored by infrared spectroscopic imaging of hair fiber cross sections. Damage to the ultrafine structure of the hair cuticle (surface, endocuticle, and cell membrane complex) and cortex (cell membrane complex) was determined in hair cross sections and on the hair fiber surface with atomic force microscopy. Using differential scanning calorimetry, we investigated how consecutive coloring and leaching processes affect the internal proteins of hair. Further, to probe the surface properties of hair we utilized contact angle measurements. This study was conducted on both pigmented and nonpigmented hair to gain insight into the influence of melanin on the hair dye deposition and leaching processes. Both types of hair were colored utilizing a commercial oxidative hair dye product based on pyrazole chemistry. PMID:27319056

  16. Multiple myeloma–associated chromosomal translocation activates orphan snoRNA ACA11 to suppress oxidative stress

    PubMed Central

    Chu, Liang; Su, Mack Y.; Maggi, Leonard B.; Lu, Lan; Mullins, Chelsea; Crosby, Seth; Huang, Gaofeng; Chng, Wee Joo; Vij, Ravi; Tomasson, Michael H.

    2012-01-01

    The histone methyltransferase WHSC1 (also known as MMSET) is overexpressed in multiple myeloma (MM) as a result of the t(4;14) chromosomal translocation and in a broad variety of other cancers by unclear mechanisms. Overexpression of WHSC1 did not transform wild-type or tumor-prone primary hematopoietic cells. We found that ACA11, an orphan box H/ACA class small nucleolar RNA (snoRNA) encoded within an intron of WHSC1, was highly expressed in t(4;14)-positive MM and other cancers. ACA11 localized to nucleoli and bound what we believe to be a novel small nuclear ribonucleoprotein (snRNP) complex composed of several proteins involved in postsplicing intron complexes. RNA targets of this uncharacterized snRNP included snoRNA intermediates hosted within ribosomal protein (RP) genes, and an RP gene signature was strongly associated with t(4;14) in patients with MM. Expression of ACA11 was sufficient to downregulate RP genes and other snoRNAs implicated in the control of oxidative stress. ACA11 suppressed oxidative stress, afforded resistance to chemotherapy, and increased the proliferation of MM cells, demonstrating that ACA11 is a critical target of the t(4;14) translocation in MM and suggesting an oncogenic role in other cancers as well. PMID:22751105

  17. Is warmer better? Decreased oxidative damage in notothenioid fish after long-term acclimation to multiple stressors.

    PubMed

    Enzor, Laura A; Place, Sean P

    2014-09-15

    Antarctic fish of the suborder Notothenioidei have evolved several unique adaptations to deal with subzero temperatures. However, these adaptations may come with physiological trade-offs, such as an increased susceptibility to oxidative damage. As such, the expected environmental perturbations brought on by global climate change have the potential to significantly increase the level of oxidative stress and cellular damage in these endemic fish. Previous single stressor studies of the notothenioids have shown they possess the capacity to acclimate to increased temperatures, but the cellular-level effects remain largely unknown. Additionally, there is little information on the ability of Antarctic fish to respond to ecologically relevant environmental changes where multiple variables change concomitantly. We have examined the potential synergistic effects that increased temperature and Ṗ(CO2) have on the level of protein damage in Trematomus bernacchii, Pagothenia borchgrevinki and Trematomus newnesi, and combined these measurements with changes in total enzymatic activity of catalase (CAT) and superoxide dismutase (SOD) in order to gauge tissue-specific changes in antioxidant capacity. Our findings indicate that total SOD and CAT activity levels displayed only small changes across treatments and tissues. Short-term acclimation to decreased seawater pH and increased temperature resulted in significant increases in oxidative damage. Surprisingly, despite no significant change in antioxidant capacity, cellular damage returned to near-basal levels, and significantly decreased in T. bernacchii, after long-term acclimation. Overall, these data suggest that notothenioid fish currently maintain the antioxidant capacity necessary to offset predicted future ocean conditions, but it remains unclear whether this capacity comes with physiological trade-offs. PMID:25013114

  18. Evaluation of Delta-Aminolevulinic Dehydratase Activity, Oxidative Stress Biomarkers, and Vitamin D Levels in Patients with Multiple Sclerosis.

    PubMed

    Polachini, Carla Roberta Nunes; Spanevello, Roselia Maria; Zanini, Daniela; Baldissarelli, Jucimara; Pereira, Luciane Belmonte; Schetinger, Maria Rosa Chitolina; da Cruz, Ivana Beatrice Mânica; Assmann, Charles Elias; Bagatini, Margarete Dulce; Morsch, Vera Maria

    2016-02-01

    Multiple sclerosis (MS) is an autoimmune neurological disorder of unknown etiology. Oxidative stress and alterations in vitamin D levels have been implicated in the pathophysiology of MS. The aim of this study was to investigate δ-aminolevulinate dehydratase (δ-ALA-D) activity as well as the levels of vitamin D, lipid peroxidation levels, carbonyl protein content, DNA damage, superoxide dismutase (SOD) and catalase (CAT) activities, and the vitamin C, vitamin E, and non-protein thiol (NPSH) content in samples from patients with the relapsing-remitting form of MS (RRMS). The study population consisted of 29 RRMS patients and 29 healthy subjects. Twelve milliliters of blood was obtained from each individual and used for biochemical determinations. The results showed that δ-ALA-D and CAT activities were significantly increased, while SOD activity was decreased in the whole blood of RRMS patients compared to the control group (P < 0.05). In addition, we observed a significant increase in lipid peroxidation, carbonyl protein levels in serum and damaged DNA in leucocytes in RRMS patients compared with the control group (P < 0.05). Nonetheless, the levels of vitamin C, vitamin E, NPSH, and vitamin D were significantly decreased in RRMS patients in relation to the healthy individuals (P < 0.05). In conclusion, our results suggested that the increase in δ-ALA-D activity may be related to the inflammatory and immune process in MS in an attempt to maintain the cellular metabolism and reduce oxidative stress. Moreover, the alterations in the oxidant/antioxidant balance and lower vitamin D levels may contribute to the pathophysiology of MS. PMID:26690779

  19. Achieving Low Overpotential Li-O₂ Battery Operations by Li₂O₂ Decomposition through One-Electron Processes.

    PubMed

    Xie, Jin; Dong, Qi; Madden, Ian; Yao, Xiahui; Cheng, Qingmei; Dornath, Paul; Fan, Wei; Wang, Dunwei

    2015-12-01

    As a promising high-capacity energy storage technology, Li-O2 batteries face two critical challenges, poor cycle lifetime and low round-trip efficiencies, both of which are connected to the high overpotentials. The problem is particularly acute during recharge, where the reactions typically follow two-electron mechanisms that are inherently slow. Here we present a strategy that can significantly reduce recharge overpotentials. Our approach seeks to promote Li2O2 decomposition by one-electron processes, and the key is to stabilize the important intermediate of superoxide species. With the introduction of a highly polarizing electrolyte, we observe that recharge processes are successfully switched from a two-electron pathway to a single-electron one. While a similar one-electron route has been reported for the discharge processes, it has rarely been described for recharge except for the initial stage due to the poor mobilities of surface bound superoxide ions (O2(-)), a necessary intermediate for the mechanism. Key to our observation is the solvation of O2(-) by an ionic liquid electrolyte (PYR14TFSI). Recharge overpotentials as low as 0.19 V at 100 mA/g(carbon) are measured. PMID:26583874

  20. One-electron pseudopotential investigation of the RbAr and FrAr van der Waals systems

    NASA Astrophysics Data System (ADS)

    Dhiflaoui, J.; Berriche, H.

    2012-12-01

    The potential energy curves of the ground state and many excited states of RbAr and FrAr van der Waals systems have been determined using a one-electron pseudopotential approach. The pseudopotential technique is used to replace the effect of the Rb+ and Fr+ cores and the electron-Ar interaction. In addition a core-core interaction is included. This has permitted to reduce the number of active electrons of the RbAr and FrAr systems to only one electron, the valence electron. This has led to use very large basis sets for Rb, Fr and Ar atoms. In this context, the potential energy curves of the ground and many excited states are performed at the SCF level. The core-core interactions for Rb+Ar and Fr+Ar are included using the CCSD(T) accurate potentials of Hickling et al. [H. Hickling, L. Viehland, D. Shepherd, P. Soldan, E. Lee and T. Wright, Phys. Chem. Chem. Phys. 6 (2004) 4233]. In addition, the spectroscopic constants of these states are derived and compared with the available theoretical works. Such comparison for RbAr has shown a very good agreement for the ground and the first excited states. However, the FrAr system was not studied previously and its spectroscopic constants are presented here for the first time.

  1. [Multiplication of Brucella abortus and production of nitric oxide in two macrophage cell lines of different origin].

    PubMed

    Serafino, J; Conde, S; Zabal, O; Samartino, L

    2007-01-01

    Brucella abortus is a bacterium which causes abortions and infertility in cattle and undulant fever in humans. It multiplies intracellularly, evading the mechanisms of cellular death. Nitric oxide (NO) is important in the regulation of the immune response. In the present work, we studied the ability of three B. abortus strains to survive intracellularly in two macrophage cell lines. The bacterial multiplication in both cell lines was determined at two different times in UFC/ ml units. Moreover the inoculated cells were also observed under light-field and fluorescence microscopy stained with Giemsa and acridine orange, respectively. The stain of both cellular lines showed similar results with respect to the UFC/ml determination. The presence of B. abortus was confirmed by electronic microscopy. In both macrophage cell lines inoculated with the rough strain RB51, the multiplication diminished and the level of NO was higher, compared with cells inoculated with smooth strains (S19 and 2308). These results suggest that the absence of O-chain of LPS probably affects the intracellular growth of B. abortus. PMID:18390151

  2. Striking multiple synergies created by combining reduced graphene oxides and carbon nanotubes for polymer nanocomposites.

    PubMed

    Song, Ping'an; Liu, Lina; Fu, Shenyuan; Yu, Youming; Jin, Chunde; Wu, Qiang; Zhang, Yan; Li, Qian

    2013-03-29

    The extraordinary properties of carbon nanotubes (CNTs) and graphene stimulate the development of advanced composites. Recently, several studies have reported significant synergies in the mechanical, electrical and thermal conductivity properties of polymer nanocomposites by incorporating their nanohybrids. In this work, we created polypropylene nanocomposites with homogeneous dispersion of CNTs and reduced graphene oxides via a facile polymer-latex-coating plus melt-mixing strategy, and investigated their synergistic effects in their viscoelastic, gas barrier, and flammability properties. Interestingly, the results show remarkable synergies, enhancing their melt modulus and viscosity, O2 barrier, and flame retardancy properties and respectively exhibiting a synergy percentage of 15.9%, 45.3%, and 20.3%. As previously reported, we also observed remarkable synergistic effects in their tensile strength (14.3%) and Young's modulus (27.1%), electrical conductivity (32.3%) and thermal conductivity (34.6%). These impressive results clearly point towards a new strategy to create advanced materials by adding binary combinations of different types of nanofillers. PMID:23459335

  3. NPGPx (GPx7): a novel oxidative stress sensor/transmitter with multiple roles in redox homeostasis

    PubMed Central

    Chen, Yi-Ing; Wei, Pei-Chi; Hsu, Jye-Lin; Su, Fang-Yi; Lee, Wen-Hwa

    2016-01-01

    NPGPx (GPx7) is a member of the glutathione peroxidase (GPx) family without any GPx activity. GPx7 displays a unique function which serves as a stress sensor/transmitter to transfer the signal to its interacting proteins by shuttling disulfide bonds in response to various stresses. In this review, we focus on the exceptional structural and biochemical features of GPx7 compared to other 7 family members and described how GPx7 regulates the diverse signaling targets including GRP78, PDI, CPEB2, and XRN2, and their different roles in unfolded protein response, oxidative stress, and non-targeting siRNA stress response, respectively. The phenotypes associated with GPx7 deficiency in mouse or human including ROS accumulations, highly elevated cancer incidences, auto-immune disorders, and obesity are also revealed in this paper. Finally, we compare GPx8 with GPx7, which shares the highest structural similarity but different biological roles in stress response. These insights have thus provided a more comprehensive understanding of the role of GPx7 in the maintenance of redox homeostasis. PMID:27186289

  4. Striking multiple synergies created by combining reduced graphene oxides and carbon nanotubes for polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Song, Ping'an; Liu, Lina; Fu, Shenyuan; Yu, Youming; Jin, Chunde; Wu, Qiang; Zhang, Yan; Li, Qian

    2013-03-01

    The extraordinary properties of carbon nanotubes (CNTs) and graphene stimulate the development of advanced composites. Recently, several studies have reported significant synergies in the mechanical, electrical and thermal conductivity properties of polymer nanocomposites by incorporating their nanohybrids. In this work, we created polypropylene nanocomposites with homogeneous dispersion of CNTs and reduced graphene oxides via a facile polymer-latex-coating plus melt-mixing strategy, and investigated their synergistic effects in their viscoelastic, gas barrier, and flammability properties. Interestingly, the results show remarkable synergies, enhancing their melt modulus and viscosity, O2 barrier, and flame retardancy properties and respectively exhibiting a synergy percentage of 15.9%, 45.3%, and 20.3%. As previously reported, we also observed remarkable synergistic effects in their tensile strength (14.3%) and Young’s modulus (27.1%), electrical conductivity (32.3%) and thermal conductivity (34.6%). These impressive results clearly point towards a new strategy to create advanced materials by adding binary combinations of different types of nanofillers.

  5. Effects of nitric oxide on magnocellular neurons of the supraoptic nucleus involve multiple mechanisms

    PubMed Central

    da Silva, M.P.; Cedraz-Mercez, P.L.; Varanda, W.A.

    2014-01-01

    Physiological evidence indicates that the supraoptic nucleus (SON) is an important region for integrating information related to homeostasis of body fluids. Located bilaterally to the optic chiasm, this nucleus is composed of magnocellular neurosecretory cells (MNCs) responsible for the synthesis and release of vasopressin and oxytocin to the neurohypophysis. At the cellular level, the control of vasopressin and oxytocin release is directly linked to the firing frequency of MNCs. In general, we can say that the excitability of these cells can be controlled via two distinct mechanisms: 1) the intrinsic membrane properties of the MNCs themselves and 2) synaptic input from circumventricular organs that contain osmosensitive neurons. It has also been demonstrated that MNCs are sensitive to osmotic stimuli in the physiological range. Therefore, the study of their intrinsic membrane properties became imperative to explain the osmosensitivity of MNCs. In addition to this, the discovery that several neurotransmitters and neuropeptides can modulate their electrical activity greatly increased our knowledge about the role played by the MNCs in fluid homeostasis. In particular, nitric oxide (NO) may be an important player in fluid balance homeostasis, because it has been demonstrated that the enzyme responsible for its production has an increased activity following a hypertonic stimulation of the system. At the cellular level, NO has been shown to change the electrical excitability of MNCs. Therefore, in this review, we focus on some important points concerning nitrergic modulation of the neuroendocrine system, particularly the effects of NO on the SON. PMID:24519124

  6. Are there multiple mechanisms of anaerobic sulfur oxidation with ferric iron in Acidithiobacillus ferrooxidans?

    PubMed

    Kucera, Jiri; Pakostova, Eva; Lochman, Jan; Janiczek, Oldrich; Mandl, Martin

    2016-06-01

    To clarify the pathway of anaerobic sulfur oxidation coupled with dissimilatory ferric iron reduction in Acidithiobacillus ferrooxidans strain CCM 4253 cells, we monitored their energy metabolism gene transcript profiles. Several genes encoding electron transporters involved in aerobic iron and sulfur respiration were induced during anaerobic growth of ferrous iron-grown cells. Most sulfur metabolism genes were either expressed at the basal level or their expression declined. However, transcript levels of genes assumed to be responsible for processing of elemental sulfur and other sulfur intermediates were elevated at the beginning of the growth period. In contrast, genes with predicted functions in formation of hydrogen sulfide and sulfate were significantly repressed. The main proposed mechanism involves: outer membrane protein Cyc2 (assumed to function as a terminal ferric iron reductase); periplasmic electron shuttle rusticyanin; c4-type cytochrome CycA1; the inner membrane cytochrome bc1 complex I; and the quinone pool providing connection to the sulfur metabolism machinery, consisting of heterodisulfide reductase, thiosulfate:quinone oxidoreductase and tetrathionate hydrolase. However, an alternative mechanism seems to involve a high potential iron-sulfur protein Hip, c4-type cytochrome CycA2 and inner membrane cytochrome bc1 complex II. Our results conflict with findings regarding the type strain, indicating strain- or phenotype-dependent pathway variation. PMID:26924114

  7. Using multiple hydrogen bonding cross-linkers to access reversibly responsive three dimensional graphene oxide architecture

    NASA Astrophysics Data System (ADS)

    Han, Junkai; Shen, Yongtao; Feng, Wei

    2016-07-01

    Three-dimensional (3D) graphene materials have attracted a lot of attention for efficiently utilizing inherent properties of graphene sheets. However, 3D graphene materials reported in the previous literature are constructed through covalent or weak non-covalent interactions, causing permanent structure/property changes. In this paper, a novel 3D graphene material of dynamic interactions between lamellas with 2-ureido-4[1H]-pyrimidinone as a supra-molecular motif has been synthesized. This 3D graphene material shows enhanced sheet interactions while the cross-linking takes place. With proper solvent stimulation, the integrated 3D graphene material can disassemble as isolated sheets. The driving force for the 3D structure assembly or disassembly is considered to be the forming or breaking of the multiple hydrogen bonding pairs. Furthermore, the 3D material is used as an intelligent dye adsorber to adsorb methylene blue and release it. The controllable and reversible characteristic of this 3D graphene material may open an avenue to the synthesis and application of novel intelligent materials.Three-dimensional (3D) graphene materials have attracted a lot of attention for efficiently utilizing inherent properties of graphene sheets. However, 3D graphene materials reported in the previous literature are constructed through covalent or weak non-covalent interactions, causing permanent structure/property changes. In this paper, a novel 3D graphene material of dynamic interactions between lamellas with 2-ureido-4[1H]-pyrimidinone as a supra-molecular motif has been synthesized. This 3D graphene material shows enhanced sheet interactions while the cross-linking takes place. With proper solvent stimulation, the integrated 3D graphene material can disassemble as isolated sheets. The driving force for the 3D structure assembly or disassembly is considered to be the forming or breaking of the multiple hydrogen bonding pairs. Furthermore, the 3D material is used as an

  8. Using multiple hydrogen bonding cross-linkers to access reversibly responsive three dimensional graphene oxide architecture.

    PubMed

    Han, Junkai; Shen, Yongtao; Feng, Wei

    2016-08-01

    Three-dimensional (3D) graphene materials have attracted a lot of attention for efficiently utilizing inherent properties of graphene sheets. However, 3D graphene materials reported in the previous literature are constructed through covalent or weak non-covalent interactions, causing permanent structure/property changes. In this paper, a novel 3D graphene material of dynamic interactions between lamellas with 2-ureido-4[1H]-pyrimidinone as a supra-molecular motif has been synthesized. This 3D graphene material shows enhanced sheet interactions while the cross-linking takes place. With proper solvent stimulation, the integrated 3D graphene material can disassemble as isolated sheets. The driving force for the 3D structure assembly or disassembly is considered to be the forming or breaking of the multiple hydrogen bonding pairs. Furthermore, the 3D material is used as an intelligent dye adsorber to adsorb methylene blue and release it. The controllable and reversible characteristic of this 3D graphene material may open an avenue to the synthesis and application of novel intelligent materials. PMID:27378190

  9. Nitric Oxide Mediated Transcriptome Profiling Reveals Activation of Multiple Regulatory Pathways in Arabidopsis thaliana.

    PubMed

    Hussain, Adil; Mun, Bong-Gyu; Imran, Qari M; Lee, Sang-Uk; Adamu, Teferi A; Shahid, Muhammad; Kim, Kyung-Min; Yun, Byung-Wook

    2016-01-01

    Imbalance between the accumulation and removal of nitric oxide and its derivatives is a challenge faced by all plants at the cellular level, and is especially important under stress conditions. Exposure of plants to various biotic and abiotic stresses causes rapid changes in cellular redox tone potentiated by the rise in reactive nitrogen species that serve as signaling molecules in mediating defensive responses. To understand mechanisms mediated by these signaling molecules, we performed a large-scale analysis of the Arabidopsis transcriptome induced by nitrosative stress. We generated an average of 84 and 91 million reads from three replicates each of control and 1 mM S-nitrosocysteine (CysNO)-infiltrated Arabidopsis leaf samples, respectively. After alignment, more than 95% of all reads successfully mapped to the reference and 32,535 genes and 55,682 transcripts were obtained. CysNO infiltration caused differential expression of 6436 genes (3448 up-regulated and 2988 down-regulated) and 6214 transcripts (3335 up-regulated and 2879 down-regulated) 6 h post-infiltration. These differentially expressed genes were found to be involved in key physiological processes, including plant defense against various biotic and abiotic stresses, hormone signaling, and other developmental processes. After quantile normalization of the FPKM values followed by student's T-test (P < 0.05) we identified 1165 DEGs (463 up-regulated and 702 down-regulated) with at least 2-folds change in expression after CysNO treatment. Expression patterns of selected genes involved in various biological pathways were verified using quantitative real-time PCR. This study provides comprehensive information about plant responses to nitrosative stress at transcript level and would prove helpful in understanding and incorporating mechanisms associated with nitrosative stress responses in plants. PMID:27446194

  10. Nitric Oxide Mediated Transcriptome Profiling Reveals Activation of Multiple Regulatory Pathways in Arabidopsis thaliana

    PubMed Central

    Hussain, Adil; Mun, Bong-Gyu; Imran, Qari M.; Lee, Sang-Uk; Adamu, Teferi A.; Shahid, Muhammad; Kim, Kyung-Min; Yun, Byung-Wook

    2016-01-01

    Imbalance between the accumulation and removal of nitric oxide and its derivatives is a challenge faced by all plants at the cellular level, and is especially important under stress conditions. Exposure of plants to various biotic and abiotic stresses causes rapid changes in cellular redox tone potentiated by the rise in reactive nitrogen species that serve as signaling molecules in mediating defensive responses. To understand mechanisms mediated by these signaling molecules, we performed a large-scale analysis of the Arabidopsis transcriptome induced by nitrosative stress. We generated an average of 84 and 91 million reads from three replicates each of control and 1 mM S-nitrosocysteine (CysNO)-infiltrated Arabidopsis leaf samples, respectively. After alignment, more than 95% of all reads successfully mapped to the reference and 32,535 genes and 55,682 transcripts were obtained. CysNO infiltration caused differential expression of 6436 genes (3448 up-regulated and 2988 down-regulated) and 6214 transcripts (3335 up-regulated and 2879 down-regulated) 6 h post-infiltration. These differentially expressed genes were found to be involved in key physiological processes, including plant defense against various biotic and abiotic stresses, hormone signaling, and other developmental processes. After quantile normalization of the FPKM values followed by student's T-test (P < 0.05) we identified 1165 DEGs (463 up-regulated and 702 down-regulated) with at least 2-folds change in expression after CysNO treatment. Expression patterns of selected genes involved in various biological pathways were verified using quantitative real-time PCR. This study provides comprehensive information about plant responses to nitrosative stress at transcript level and would prove helpful in understanding and incorporating mechanisms associated with nitrosative stress responses in plants. PMID:27446194

  11. Oxidative Stress Triggers Body-Wide Skipping of Multiple Exons of the Spinal Muscular Atrophy Gene

    PubMed Central

    Seo, Joonbae; Singh, Natalia N.; Ottesen, Eric W.; Sivanesan, Senthilkumar; Shishimorova, Maria; Singh, Ravindra N.

    2016-01-01

    Humans carry two nearly identical copies of Survival Motor Neuron gene: SMN1 and SMN2. Loss of SMN1 leads to spinal muscular atrophy (SMA), the most frequent genetic cause of infant mortality. While SMN2 cannot compensate for the loss of SMN1 due to predominant skipping of exon 7, correction of SMN2 exon 7 splicing holds the promise of a cure for SMA. Previously, we used cell-based models coupled with a multi-exon-skipping detection assay (MESDA) to demonstrate the vulnerability of SMN2 exons to aberrant splicing under the conditions of oxidative stress (OS). Here we employ a transgenic mouse model and MESDA to examine the OS-induced splicing regulation of SMN2 exons. We induced OS using paraquat that is known to trigger production of reactive oxygen species and cause mitochondrial dysfunction. We show an overwhelming co-skipping of SMN2 exon 5 and exon 7 under OS in all tissues except testis. We also show that OS increases skipping of SMN2 exon 3 in all tissues except testis. We uncover several new SMN2 splice isoforms expressed at elevated levels under the conditions of OS. We analyze cis-elements and transacting factors to demonstrate the diversity of mechanisms for splicing misregulation under OS. Our results of proteome analysis reveal downregulation of hnRNP H as one of the potential consequences of OS in brain. Our findings suggest SMN2 as a sensor of OS with implications to SMA and other diseases impacted by low levels of SMN protein. PMID:27111068

  12. Optimal control of the electronic current density: Application to one- and two-dimensional one-electron systems

    SciTech Connect

    Kammerlander, David; Marques, Miguel A. L.; Castro, Alberto

    2011-04-15

    Quantum optimal control theory is a powerful tool for engineering quantum systems subject to external fields such as the ones created by intense lasers. The formulation relies on a suitable definition for a target functional, that translates the intended physical objective to a mathematical form. We propose the use of target functionals defined in terms of the one-particle density and its current. A strong motivation for this is the possibility of using time-dependent density-functional theory for the description of the system dynamics. We exemplify this idea by defining an objective functional that on one hand attempts a large overlap with a target density and on the other hand minimizes the current. The latter requirement leads to optimized states with increased stability, which we prove with a few examples of one- and two-dimensional one-electron systems.

  13. Theoretical study of the protonation of the one-electron-reduced guanine-cytosine base pair by water.

    PubMed

    Hsu, Sodio C N; Wang, Tzu-Pin; Kao, Chai-Lin; Chen, Hui-Fen; Yang, Po-Yu; Chen, Hsing-Yin

    2013-02-21

    Prototropic equilibria in ionized DNA play an important role in charge transport and radiation damage of DNA and, therefore, continue to attract considerable attention. Although it is well-established that electron attachment will induce an interbase proton transfer from N1 of guanine (G) to N3 of cytosine (C), the question of whether the surrounding water in the major and minor grooves can protonate the one-electron-reduced G:C base pair still remains open. In this work, density functional theory (DFT) calculations were employed to investigate the energetics and mechanism for the protonation of the one-electron-reduced G:C base pair by water. Through the calculations of thermochemical cycles, the protonation free energies were estimated to be in the range of 11.6-14.2 kcal/mol. The calculations for the models of C(•-)(H(2)O)(8) and G(-H1)(-)(H(2)O)(16), which were used to simulate the detailed processes of protonation by water before and after the interbase proton transfer, respectively, revealed that the protonation proceeds through a concerted double proton transfer involving the water molecules in the first and second hydration shells. Comparing the present results with the rates of interbase proton transfer and charge transfer along DNA suggests that protonation on the C(•-) moiety is not competitive with interbase proton transfer, but the possibility of protonation on the G(-H1)(-) moiety after interbase proton transfer cannot be excluded. Electronic-excited-state calculations were also carried out by the time-dependent DFT approach. This information is valuable for experimental identification in the future. PMID:23363248

  14. Oxidative stress, inflammation, and DNA damage in multiple organs of mice acutely exposed to amorphous silica nanoparticles

    PubMed Central

    Nemmar, Abderrahim; Yuvaraju, Priya; Beegam, Sumaya; Yasin, Javed; Kazzam, Elsadig E; Ali, Badreldin H

    2016-01-01

    The use of amorphous silica (SiO2) in biopharmaceutical and industrial fields can lead to human exposure by injection, skin penetration, ingestion, or inhalation. However, the in vivo acute toxicity of amorphous SiO2 nanoparticles (SiNPs) on multiple organs and the mechanisms underlying these effects are not well understood. Presently, we investigated the acute (24 hours) effects of intraperitoneally administered 50 nm SiNPs (0.25 mg/kg) on systemic toxicity, oxidative stress, inflammation, and DNA damage in the lung, heart, liver, kidney, and brain of mice. Lipid peroxidation was significantly increased by SiNPs in the lung, liver, kidney, and brain, but was not changed in the heart. Similarly, superoxide dismutase and catalase activities were significantly affected by SiNPs in all organs studied. While the concentration of tumor necrosis factor α was insignificantly increased in the liver and brain, its increase was statistically significant in the lung, heart, and kidney. SiNPs induced a significant elevation in pulmonary and renal interleukin 6 and interleukin-1 beta in the lung, liver, and brain. Moreover, SiNPs caused a significant increase in DNA damage, assessed by comet assay, in all the organs studied. SiNPs caused leukocytosis and increased the plasma activities of lactate dehydrogenase, creatine kinase, alanine aminotranferase, and aspartate aminotransferase. These results indicate that acute systemic exposure to SiNPs causes oxidative stress, inflammation, and DNA damage in several major organs, and highlight the need for thorough evaluation of SiNPs before they can be safely used in human beings. PMID:27022259

  15. Protection by and anti-oxidant mechanism of berberine against rat liver fibrosis induced by multiple hepatotoxic factors.

    PubMed

    Zhang, Ben-Jian; Xu, Dan; Guo, Yu; Ping, Jie; Chen, Liao-Bin; Wang, Hui

    2008-03-01

    1. The aim of the present study was to investigate the effect and mechanism of berberine, an alkaloid extracted from the traditional Chinese medicine coptis, on rat liver fibrosis induced by multiple hepatotoxic factors. 2. Male Wistar rats were separated into five groups, a normal control group, a fibrotic control group and fibrotic groups treated with three different doses of berberine. The fibrotic models were established by introduction of multiple hepatotoxic factors, including CCl(4), ethanol and high cholesterol. Rats in the treatment groups were administered 50, 100 or 200 mg/kg berberine, intragastrically, daily for 4 weeks. Serum levels of alanine aminotransferase (ALT) and serum aspartate aminotransferase (AST), hepatic activity of superoxide dismutase (SOD) and hepatic malondialdehyde (MDA) and hepatic hydroxyproline (Hyp) content were determined. Liver biopsies were obtained for histological and immunohistochemical studies to detect the expressions of alpha-smooth muscle actin (SMA) and transforming growth factor (TGF)-beta1. 3. The results showed that, compared with the fibrotic control group, serum levels of ALT and AST and hepatic content of MDA and Hyp were markedly decreased, but the activity of hepatic SOD was significantly increased in berberine-treated groups in a dose-dependent manner. In addition, histopathological changes, such as steatosis, necrosis and myofibroblast proliferation, were reduced and the expression of a-SMA and TGF-b1 was significantly downregulated in the berberine-treated groups (P < 0.01). 4. These results suggest that berberine could be used to prevent experimental liver fibrosis through regulation of the anti-oxidant system and lipid peroxidation. PMID:17973934

  16. Evaluation of multiple low doses of copper oxide wire particles compared with levamisole for control of Haemonchus contortus in lambs.

    PubMed

    Burke, J M; Miller, J E

    2006-06-30

    High levels of anthelmintic resistance in gastrointestinal nematodes (GIN) of small ruminants have created the need for alternative approaches to parasite control. Copper oxide wire particles (COWP; 2g) have proven effective in decreasing GIN infection in lambs. However, the risk of copper toxicity has limited the usefulness of this approach. Recently, smaller doses (0.5 and 1g) have proven effective in GIN control, reducing the risk of toxicity. The objective of this study was to examine the effectiveness and risk of toxicity using multiple small doses of COWP for GIN control in lambs between weaning and market weight. Dorper crossbred ram lambs were orally administered levamisole (Levasol, 8.0mg/kg; n=8), 0.5g (n=9), or 1g COWP (n=9) at weaning (Day 0; 118+/-2 days of age; late May 2005) and again at 6-week intervals for a total of four treatments. A pooled fecal culture determined that Haemonchus contortus was the predominant gastrointestinal parasite at weaning. Lambs grazed bermudagrass pastures and were supplemented with up to 500g corn/soybean meal and free choice trace mineralized salt. Fecal egg counts (FEC), packed cell volume (PCV), and plasma aspartate aminotransferase (AST) activity were determined every 14 days and lambs weighed every 28 days. GIN infection reached a peak at Day 42 (high FEC, low PCV). COWP effectively reduced FEC on Days 0 and 42 compared with the previous week, but did not reduce FEC on Days 84 and 126 (treatment by time interaction, P<0.005). Plasma AST activity and weight gains were similar among treatment groups throughout the study period. Concentrations of copper in the liver on Day 155 were greater in COWP-treated lambs (P<0.001), but all concentrations were normal. Multiple doses of COWP were as effective as levamisole for control of H. contortus without risk of copper toxicity. PMID:16574324

  17. Impact of graphene oxide on the structure and function of important multiple blood components by a dose-dependent pattern.

    PubMed

    Feng, Ru; Yu, Yueping; Shen, Chaoxuan; Jiao, Yanpeng; Zhou, Changren

    2015-06-01

    Graphene and its derivatives have become great concern in biomedical fields. Though many investigations about their toxicity have been reported, systematic investigation on the interaction with multiple blood components is lacking. In this work, we studied the effects of the graphene oxide (GO) on the structure and function of the blood components, especially, on morphology and hemolysis of red blood cells (RBCs), bovine serum albumin (BSA) and fibrinogen conformation, complement activation, and blood coagulation function. Scanning electron microscopy observation and hemolysis test results showed that the GO can affect RBC morphology and membrane integrity in a concentration-dependent way. Fluorescence and circular dichroism spectra showed that GO could alter the secondary structures and conformation of BSA and fibrinogen. In addition, the presence of GO could also trigger complement activation by detecting their key biomarker molecules in plasma. In the blood clotting process, the GO showed significant adverse effect on the activated partial thromboplastin time but not on prothrombin time of the platelet-poor plasma. Meanwhile, the GO also caused abnormal thromboelastography parameters of the whole blood coagulation. The results obtained in this study provides good insight into understanding the biomedical application of GO in vivo. PMID:25257186

  18. Hyperfine-changing transitions in {sup 3}He II and other one-electron ions by electron scattering

    SciTech Connect

    Bartschat, Klaus; Sadeghpour, H. R. E-mail: hrs@cfa.harvard.edu

    2014-06-10

    We consider the spin-exchange (SE) cross-section in electron scattering from {sup 3}He II, which drives the hyperfine-changing 3.46 cm (8.665 GHz) line transition. Both the analytical quantum defect method—applicable at very low energies—and accurate R-matrix techniques for electron-He{sup +} scattering are employed to obtain SE cross-sections. The quantum defect theory is also applied to electron collisions with other one-electron ions in order to demonstrate the utility of the method and derive scaling relations. At very low energies, the hyperfine-changing cross-sections due to e-He{sup +} scattering are much larger in magnitude than for electron collisions with neutral hydrogen, hinting at large rate constants for equilibration. Specifically, we obtain rate coefficients of K(10 K) = 1.10 × 10{sup –6} cm{sup 3} s{sup –1} and K(100 K) = 3.49 × 10{sup –7} cm{sup 3} s{sup –1}.

  19. A simple quasi-diabatization scheme suitable for spectroscopic problems based on one-electron properties of interacting states

    NASA Astrophysics Data System (ADS)

    Cave, Robert J.; Stanton, John F.

    2016-02-01

    We present a simple quasi-diabatization scheme applicable to spectroscopic studies that can be applied using any wavefunction for which one-electron properties and transition properties can be calculated. The method is based on rotation of a pair (or set) of adiabatic states to minimize the difference between the given transition property at a reference geometry of high symmetry (where the quasi-diabatic states and adiabatic states coincide) and points of lower symmetry where quasi-diabatic quantities are desired. Compared to other quasi-diabatization techniques, the method requires no special coding, facilitates direct comparison between quasi-diabatic quantities calculated using different types of wavefunctions, and is free of any selection of configurations in the definition of the quasi-diabatic states. On the other hand, the method appears to be sensitive to multi-state issues, unlike recent methods we have developed that use a configurational definition of quasi-diabatic states. Results are presented and compared with two other recently developed quasi-diabatization techniques.

  20. Generalized Pauli conditions on the spectra of one-electron reduced density matrices of atoms and molecules

    NASA Astrophysics Data System (ADS)

    Chakraborty, Romit; Mazziotti, David A.

    2014-04-01

    The Pauli exclusion principle requires the spectrum of the occupation numbers of the one-electron reduced density matrix (1-RDM) to be bounded by one and zero. However, for a 1-RDM from a wave function, there exist additional conditions on the spectrum of occupation numbers, known as pure N-representability conditions or generalized Pauli conditions. For atoms and molecules, we measure through a Euclidean-distance metric the proximity of the 1-RDM spectrum to the facets of the convex set (polytope) generated by the generalized Pauli conditions. For the ground state of any spin symmetry, as long as time-reversal symmetry is considered in the definition of the polytope, we find that the 1-RDM's spectrum is pinned to the boundary of the polytope. In contrast, for excited states, we find that the 1-RDM spectrum is not pinned. Proximity of the 1-RDM to the boundary of the polytope provides a measurement and classification of electron correlation and entanglement within the quantum system. For comparison, this distance to the boundary of the generalized Pauli conditions is also compared to the distance to the polytope of the traditional Pauli conditions, and the distance to the nearest 1-RDM spectrum from a Slater determinant. We explain the difference in pinning in the ground- and excited-state 1-RDMs through a connection to the N-representability conditions of the two-electron reduced density matrix.

  1. Protein oxidation and peroxidation.

    PubMed

    Davies, Michael J

    2016-04-01

    Proteins are major targets for radicals and two-electron oxidants in biological systems due to their abundance and high rate constants for reaction. With highly reactive radicals damage occurs at multiple side-chain and backbone sites. Less reactive species show greater selectivity with regard to the residues targeted and their spatial location. Modification can result in increased side-chain hydrophilicity, side-chain and backbone fragmentation, aggregation via covalent cross-linking or hydrophobic interactions, protein unfolding and altered conformation, altered interactions with biological partners and modified turnover. In the presence of O2, high yields of peroxyl radicals and peroxides (protein peroxidation) are formed; the latter account for up to 70% of the initial oxidant flux. Protein peroxides can oxidize both proteins and other targets. One-electron reduction results in additional radicals and chain reactions with alcohols and carbonyls as major products; the latter are commonly used markers of protein damage. Direct oxidation of cysteine (and less commonly) methionine residues is a major reaction; this is typically faster than with H2O2, and results in altered protein activity and function. Unlike H2O2, which is rapidly removed by protective enzymes, protein peroxides are only slowly removed, and catabolism is a major fate. Although turnover of modified proteins by proteasomal and lysosomal enzymes, and other proteases (e.g. mitochondrial Lon), can be efficient, protein hydroperoxides inhibit these pathways and this may contribute to the accumulation of modified proteins in cells. Available evidence supports an association between protein oxidation and multiple human pathologies, but whether this link is causal remains to be established. PMID:27026395

  2. Protein oxidation and peroxidation

    PubMed Central

    Davies, Michael J.

    2016-01-01

    Proteins are major targets for radicals and two-electron oxidants in biological systems due to their abundance and high rate constants for reaction. With highly reactive radicals damage occurs at multiple side-chain and backbone sites. Less reactive species show greater selectivity with regard to the residues targeted and their spatial location. Modification can result in increased side-chain hydrophilicity, side-chain and backbone fragmentation, aggregation via covalent cross-linking or hydrophobic interactions, protein unfolding and altered conformation, altered interactions with biological partners and modified turnover. In the presence of O2, high yields of peroxyl radicals and peroxides (protein peroxidation) are formed; the latter account for up to 70% of the initial oxidant flux. Protein peroxides can oxidize both proteins and other targets. One-electron reduction results in additional radicals and chain reactions with alcohols and carbonyls as major products; the latter are commonly used markers of protein damage. Direct oxidation of cysteine (and less commonly) methionine residues is a major reaction; this is typically faster than with H2O2, and results in altered protein activity and function. Unlike H2O2, which is rapidly removed by protective enzymes, protein peroxides are only slowly removed, and catabolism is a major fate. Although turnover of modified proteins by proteasomal and lysosomal enzymes, and other proteases (e.g. mitochondrial Lon), can be efficient, protein hydroperoxides inhibit these pathways and this may contribute to the accumulation of modified proteins in cells. Available evidence supports an association between protein oxidation and multiple human pathologies, but whether this link is causal remains to be established. PMID:27026395

  3. Ruthenium-tris(bipyridine) complexes with multiple redox-active amine substituents: tuning of spin density distribution and deep-red to NIR electrochromism and electrofluorochromism.

    PubMed

    Nie, Hai-Jing; Yang, Wen-Wen; Shao, Jiang-Yang; Zhong, Yu-Wu

    2016-06-21

    In response to the application of low electrochemical potentials, ruthenium-tris(bipyridine) complexes decorated with multiple electron-rich and redox-active amine substituents show reversible absorption and emission spectral changes in the deep-red to NIR region. The number of amine substituents strongly affects the electrochemical and spectroscopic properties and the spin density distributions of the complex in the one-electron-oxidized state. PMID:27240642

  4. Performance enhancement of multiple-gate ZnO metal-oxide-semiconductor field-effect transistors fabricated using self-aligned and laser interference photolithography techniques

    PubMed Central

    2014-01-01

    The simple self-aligned photolithography technique and laser interference photolithography technique were proposed and utilized to fabricate multiple-gate ZnO metal-oxide-semiconductor field-effect transistors (MOSFETs). Since the multiple-gate structure could improve the electrical field distribution along the ZnO channel, the performance of the ZnO MOSFETs could be enhanced. The performance of the multiple-gate ZnO MOSFETs was better than that of the conventional single-gate ZnO MOSFETs. The higher the drain-source saturation current (12.41 mA/mm), the higher the transconductance (5.35 mS/mm) and the lower the anomalous off-current (5.7 μA/mm) for the multiple-gate ZnO MOSFETs were obtained. PMID:24948884

  5. Multiple sulfur isotope composition of oxidized Samoan melts and the implications of a sulfur isotope 'mantle array' in chemical geodynamics

    NASA Astrophysics Data System (ADS)

    Labidi, J.; Cartigny, P.; Jackson, M. G.

    2015-05-01

    To better address how subducted protoliths drive the Earth's mantle sulfur isotope heterogeneity, we report new data for sulfur (S) and copper (Cu) abundances, S speciation and multiple S isotopic compositions (32S, 33S, 34S, 36S) in 15 fresh submarine basaltic glasses from the Samoan archipelago, which defines the enriched-mantle-2 (EM2) endmember. Bulk S abundances vary between 835 and 2279 ppm. About 17 ± 11% of sulfur is oxidized (S6+) but displays no consistent trend with bulk S abundance or any other geochemical tracer. The S isotope composition of both dissolved sulfide and sulfate yield homogeneous Δ33S and Δ36S values, within error of Canyon Diablo Troilite (CDT). In contrast, δ34S values are variable, ranging between +0.11 and +2.79‰ (±0.12‰ 1σ) for reduced sulfur, whereas oxidized sulfur values vary between +4.19 and +9.71‰ (±0.80‰, 1σ). Importantly, δ34S of the reduced S pool correlates with the 87Sr/86Sr ratios of the glasses, in a manner similar to that previously reported for South-Atlantic MORB, extending the trend to δ34S values up to + 2.79 ± 0.04 ‰, the highest value reported for undegassed oceanic basalts. As for EM-1 basalts from the South Atlantic ridge, the linear δ34S-87Sr/86Sr trend requires the EM-2 endmember to be relatively S-rich, and only sediments can account for these isotopic characteristics. While many authors argue that both the EM-1 and EM-2 mantle components record subduction of various protoliths (e.g. upper or lower continental crust, lithospheric mantle versus intra-metasomatized mantle, or others), it is proposed here that they primarily reflect sediment recycling. Their distinct Pb isotope variation can be accounted for by varying the proportion of S-poor recycled oceanic crust in the source of mantle plumes.

  6. Efficacy of Fish Oil on Serum of TNFα, IL-1β, and IL-6 Oxidative Stress Markers in Multiple Sclerosis Treated with Interferon Beta-1b

    PubMed Central

    Ramirez-Ramirez, V.; Macias-Islas, M. A.; Ortiz, G. G.; Pacheco-Moises, F.; Torres-Sanchez, E. D.; Sorto-Gomez, T. E.; Cruz-Ramos, J. A.; Orozco-Aviña, G.; Celis de la Rosa, A. J.

    2013-01-01

    Multiple sclerosis (MS) is a chronic inflammatory disease, which leads to focal plaques of demyelination and tissue injury in the central nervous system. Oxidative stress is also thought to promote tissue damage in multiple sclerosis. Current research findings suggest that omega-3 polyunsaturated fatty acids (PUFAs) such as eicosapenta-enoic acid (EPA) and docosahexaenoic acid (DHA) contained in fish oil may have anti-inflammatory, antioxidant, and neuroprotective effects. The aim of the present work was to evaluate the efficacy of fish oil supplementation on serum proinflammatory cytokine levels, oxidative stress markers, and disease progression in MS. 50 patients with relapsing-remitting MS were enrolled. The experimental group received orally 4 g/day of fish oil for 12 months. The primary outcome was serum TNFα levels; secondary outcomes were IL-1β 1b, IL-6, nitric oxide catabolites, lipoperoxides, progression on the expanded disability status scale (EDSS), and annualized relapses rate (ARR). Fish oil treatment decreased the serum levels of TNFα, IL-1β, IL-6, and nitric oxide metabolites compared with placebo group (P ≤ 0.001). There was no significant difference in serum lipoperoxide levels during the study. No differences in EDSS and ARR were found. Conclusion. Fish oil supplementation is highly effective in reducing the levels of cytokines and nitric oxide catabolites in patients with relapsing-remitting MS. PMID:23861993

  7. Neuronal Nitric Oxide Synthase is Involved in Vascular Hyporeactivity and Multiple Organ Dysfunction Associated with Hemorrhagic Shock.

    PubMed

    Sordi, Regina; Chiazza, Fausto; Collino, Massimo; Assreuy, Jamil; Thiemermann, Christoph

    2016-05-01

    Severe hemorrhage can lead to global ischemia and hemorrhagic shock (HS), resulting in multiple organ failure (MOF) and death. Restoration of blood flow and re-oxygenation is associated with an exacerbation of tissue injury and inflammatory response. The neuronal nitric oxide synthase (nNOS) has been implicated in vascular collapse and systemic inflammation of septic shock; however, the role of nNOS in HS is poorly understood. The aim of this study was to evaluate the role of nNOS in the MOF associated with HS.Rats were subjected to HS under anesthesia. Mean arterial pressure was reduced to 30 mmHg for 90 min, followed by resuscitation with shed blood. Rats were randomly treated with two chemically distinct nNOS inhibitors [ARL 17477 (1 mg/kg) and 7-nitroindazol (5 mg/kg)] or vehicle upon resuscitation. Four hours later, parameters of organ injury and dysfunction were assessed.HS was associated with MOF development. Inhibition of nNOS activity at resuscitation protected rats against the MOF and vascular dysfunction. In addition, treatment of HS rats with nNOS inhibitors attenuated neutrophil infiltration into target organs and decreased the activation of NF-κB, iNOS expression, NO production, and nitrosylation of proteins. Furthermore, nNOS inhibition also reduced the levels of pro-inflammatory cytokines TNF-α and IL-6 in HS rats.In conclusion, two distinct inhibitors of nNOS activity reduced the MOF, vascular dysfunction, and the systemic inflammation associated with HS. Thus, nNOS inhibitors may be useful as an adjunct therapy before fluids and blood administration in HS patients to avoid the MOF associated with reperfusion injury during resuscitation. PMID:26863124

  8. Chronic Kidney Disease Influences Multiple Systems: Describing the Relationship between Oxidative Stress, Inflammation, Kidney Damage, and Concomitant Disease

    PubMed Central

    Tucker, Patrick S.; Scanlan, Aaron T.; Dalbo, Vincent J.

    2015-01-01

    Chronic kidney disease (CKD) is characterized by increased levels of oxidative stress and inflammation. Oxidative stress and inflammation promote renal injury via damage to molecular components of the kidney. Unfortunately, relationships between inflammation and oxidative stress are cyclical in that the inflammatory processes that exist to repair radical-mediated damage may be a source of additional free radicals, resulting in further damage to renal tissue. Oxidative stress and inflammation also have the ability to become systemic, serving to injure tissues distal to the site of original insult. This review describes select mediators in the exacerbatory relationship between oxidative stress, inflammation, and CKD. This review also discusses oxidative stress, inflammation, and CKD as they pertain to the development and progression of common CKD-associated comorbidities. Lastly, the utility of several widely accessible and cost-effective lifestyle interventions and their ability to reduce oxidative stress and inflammation are discussed and recommendations for future research are provided. PMID:25861414

  9. Identification of one-electron reductases that activate both the hypoxia prodrug SN30000 and diagnostic probe EF5.

    PubMed

    Wang, Jingli; Guise, Chris P; Dachs, Gabi U; Phung, Yen; Hsu, Annie Huai-Ling; Lambie, Neil K; Patterson, Adam V; Wilson, William R

    2014-10-15

    SN30000 is a second-generation benzotriazine-N-oxide hypoxia-activated prodrug scheduled for clinical trial. Previously we showed that covalent binding of the hypoxia probe EF5 predicts metabolic activation of SN30000 in a panel of cancer cell lines under anoxia, suggesting that they are activated by the same reductases. However the identity of these reductases is unknown. Here, we test whether forced expression of nine oxidoreductases with known or suspected roles in bioreductive prodrug metabolism (AKR1C3, CYB5R3, FDXR, MTRR, NDOR1, NOS2A, NQO1, NQO2 and POR) enhances oxic or anoxic reduction of SN30000 and EF5 by HCT116 cells. Covalent binding of (14)C-EF5 and reduction of SN30000 to its 1-oxide and nor-oxide metabolites was highly selective for anoxia in all lines, with significantly elevated anoxic metabolism of both compounds in lines over-expressing POR, MTRR, NOS2A or NDOR1. There was a strong correlation between EF5 binding and SN30000 metabolism under anoxia across the cell lines (R(2)=0.84, p=0.0001). Antiproliferative potency of SN30000 under anoxia was increased most strongly by overexpression of MTRR and POR. Transcript abundance in human tumours, evaluated using public domain mRNA expression data, was highest for MTRR, followed by POR, NOS2A and NDOR1, with little variation between tumour types. Immunostaining of tissue microarrays demonstrated variable MTRR protein expression across 517 human cancers with most displaying low expression. In conclusion, we have identified four diflavin reductases (POR, MTRR, NOS2A and NDOR1) capable of reducing both SN30000 and EF5, further supporting use of 2-nitroimidazole probes to predict the ability of hypoxic cells to activate SN30000. PMID:25130546

  10. Graphene oxide selectively targets cancer stem cells, across multiple tumor types: Implications for non-toxic cancer treatment, via “differentiation-based nano-therapy”

    PubMed Central

    Fiorillo, Marco; Verre, Andrea F.; Iliut, Maria; Peiris-Pagés, Maria; Ozsvari, Bela; Gandara, Ricardo; Cappello, Anna Rita; Sotgia, Federica; Vijayaraghavan, Aravind; Lisanti, Michael P.

    2015-01-01

    Tumor-initiating cells (TICs), a.k.a. cancer stem cells (CSCs), are difficult to eradicate with conventional approaches to cancer treatment, such as chemo-therapy and radiation. As a consequence, the survival of residual CSCs is thought to drive the onset of tumor recurrence, distant metastasis, and drug-resistance, which is a significant clinical problem for the effective treatment of cancer. Thus, novel approaches to cancer therapy are needed urgently, to address this clinical need. Towards this end, here we have investigated the therapeutic potential of graphene oxide to target cancer stem cells. Graphene and its derivatives are well-known, relatively inert and potentially non-toxic nano-materials that form stable dispersions in a variety of solvents. Here, we show that graphene oxide (of both big and small flake sizes) can be used to selectively inhibit the proliferative expansion of cancer stem cells, across multiple tumor types. For this purpose, we employed the tumor-sphere assay, which functionally measures the clonal expansion of single cancer stem cells under anchorage-independent conditions. More specifically, we show that graphene oxide effectively inhibits tumor-sphere formation in multiple cell lines, across 6 different cancer types, including breast, ovarian, prostate, lung and pancreatic cancers, as well as glioblastoma (brain). In striking contrast, graphene oxide is non-toxic for “bulk” cancer cells (non-stem) and normal fibroblasts. Mechanistically, we present evidence that GO exerts its striking effects on CSCs by inhibiting several key signal transduction pathways (WNT, Notch and STAT-signaling) and thereby inducing CSC differentiation. Thus, graphene oxide may be an effective non-toxic therapeutic strategy for the eradication of cancer stem cells, via differentiation-based nano-therapy. PMID:25708684

  11. The Statistical Evolution of Multiple Generations of Oxidation Products in the Photochemical Aging of Chemically Reduced Organic Aerosol

    SciTech Connect

    Wilson, Kevin R.; Smith, Jared D.; Kessler, Sean; Kroll, Jesse H.

    2011-10-03

    The heterogeneous reaction of hydroxyl radicals (OH) with squalane and bis(2-ethylhexyl) sebacate (BES) particles are used as model systems to examine how distributions of reactionproducts evolve during the oxidation of chemically reduced organic aerosol. A kinetic model of multigenerational chemistry, which is compared to previously measured (squalane) and new(BES) experimental data, reveals that it is the statistical mixtures of different generations of oxidation products that control the average particle mass and elemental composition during thereaction. The model suggests that more highly oxidized reaction products, although initially formed with low probability, play a large role in the production of gas phase reaction products.In general, these results highlight the importance of considering atmospheric oxidation as a statistical process, further suggesting that the underlying distribution of molecules could playimportant roles in aerosol formation as well as in the evolution of key physicochemical properties such as volatility and hygroscopicity.

  12. Neuromuscular electrical stimulation and dietary interventions to reduce oxidative stress in a secondary progressive multiple sclerosis patient leads to marked gains in function: a case report.

    PubMed

    Reese, David; Shivapour, Ezzatolah T; Wahls, Terry L; Dudley-Javoroski, Shauna D; Shields, Richard

    2009-01-01

    Neuromuscular electrical stimulation has been used to aid musculoskeletal recovery. Excessive oxidative stress and excitoxicity are implicated in secondary progressive multiple sclerosis. A 52-year-old white female with SPMS had been scooter- and cane-dependent for 4 years. She requested and received a trial of neuromuscular electrical stimulation. Two months after initiating NMES the patient adopted several nutritional interventions to lower oxidative stress and excito-toxicity. During the first 2 months of neuromuscular electrical stimulation, the therapist observed modest gait improvements. Following the addition of nutritional interventions, more rapids gains in strength and endurance, including muscle groups not receiving neuromuscular electrical stimulation were observed by both the therapist and the patient. After 8 months of neuromuscular electrical stimulation (6 months of nutritional intervention) the patient's function had improved sufficiently that she no longer used a scooter or cane and rode her bicycle routinely 8 miles, including hills. PMID:19918474

  13. Multiple CO Oxidation Promoted by Au2 Dimers in Au2 TiO4 (-) Cluster Anions.

    PubMed

    Li, Xiao-Na; Li, Zi-Yu; Li, Hai-Fang; He, Sheng-Gui

    2016-06-20

    Time-of-flight mass spectrometry experiments demonstrated that laser ablation generated and mass selected Au2 TiO4 (-) cluster anions can unexpectedly oxidize three CO molecules in an ion trap reactor. This is an improvement on the more commonly observed oxidation of at most two CO molecules by a doped cluster. Quantum chemistry calculations were performed to rationalize the reactions. The lowest energy isomer of Au2 TiO4 (-) contains a superoxide unit, the participation of which in CO oxidation can be promoted by the Au2 dimer. The Au2 dimer functions as a rather flexible electron reservoir in each CO oxidation step in terms of the release and storage of electrons to drive the dissociation of superoxide to peroxide and then to lattice oxygen atoms, which can be removed by reaction with CO molecules. This gas-phase study enriches our understanding toward the nature of reactive oxygen species involved in gold-catalyzed oxidation reactions. PMID:27172816

  14. Applications of time-dependent Raman scattering theory to the one-electron reduction of 4-cyano-n-methylpyridinium

    SciTech Connect

    Johnson, C.S. )

    1992-02-01

    Activation barrier heights, and therefore rates, for molecule-based electron-transfer (ET) reactions are governed by redox thermodynamics and Frank-Condon effects. Quantitative assessment of the latter requires a detailed, quantitative knowledge of all internal and external normal-coordinate displacements, together with appropriate vibrational frequencies (v) or force constants (f). In favorable cases, the desire internal or vibrational displacement information can be satisfactorily estimated from redox-induced bond-length changes as provided, for example, by x-ray crystallography or extended x-ray absorption fine structure (EXAFS) measurements. Other potentially useful methods include Franck-Condon analysis of structured emission or absorption spectra, hole burning techniques, and application of empirical structure/frequency relationships (E.g., Badger's rules). There are, however, a number of limitations. The most obvious limitations for crystallography are that measurements can be made only in a crystalline environment and that experiments cannot be done on short-lived electron-transfer excited states or on systems which suffer from chemical decomposition following oxidation or reduction. For EXAFS there are additional constrains in that only selected elements display useful scattering and only atoms in close proximity to the scattering center may be detected. This report contains the first successful applications of the Raman methodology to a much larger class of ET reactions, namely, outer-sphere reactions. The report also necessarily represents the first application to a monomeric redox system.

  15. Multiple Sulfate Isotopic Evidence on the Formation of Oxide Copper Ore at Spence, Atacama Desert, Northern Chile

    NASA Astrophysics Data System (ADS)

    Sun, T.; Bao, H.; Reich, M.; Palacios, C.

    2007-12-01

    In the Atacama Desert of northern Chile, one of the world's richest metallogenic provinces, porphyry copper deposits are characterized by the unique occurrence of atacamite in their oxidized zones. The origin and formation of the oxide zone of these copper deposits is, however, controversial. It was proposed that Cl-rich deep formation water pumping-up events along faults by earthquakes, after onset of the hyperaridity, were required (Cameron et al., 2007). Their model would imply that supplies of saline deep formation water from fractures to the surface should have left behind a homogeneous or fracture-controlled salt profile from surface down to the oxide zone. While no excluding the deep formation water model in other deposit, here we propose that, in our sampling region, the alternative saline source, which is critical for atacamite formation, could be locally evaporated groundwater, Cl-rich salts leached from arid surface by meteoric water, or brines from eastern salar basins at a time when the climate in northern Chile was changing from arid to hyperarid. At this climate transition, arid- requiring minerals such as atacamite in the oxide zone were formed and, more importantly, preserved upon evaporation beneath the surface alluvial deposits. Since salt accumulation at the surface remain active during hyperarid condition, our model would predict that water-soluble salt profile from surface to the oxide zone should have a characteristic pattern: salts with an atmospheric component on the surface gradually transitioning to salts of the oxide ore zone on the bottom and a mixing zone in between. To test these two alternative models, we focus on sulfate salts, one of the common water-soluble salts in arid environments. An added advantage is that sulfate accumulated on desert surface has a secondary atmospheric component that bears a unique triple oxygen isotope signature, easily distinguishable from sulfate formed by the oxidation of sulfide minerals at the oxide

  16. X-ray absorption spectra of graphene and graphene oxide by full-potential multiple scattering calculations with self-consistent charge density

    NASA Astrophysics Data System (ADS)

    Xu, Junqing; Krüger, Peter; Natoli, Calogero R.; Hayakawa, Kuniko; Wu, Ziyu; Hatada, Keisuke

    2015-09-01

    The x-ray absorption near-edge structure of graphene, graphene oxide, and diamond is studied by the recently developed real-space full potential multiple scattering (FPMS) theory with space-filling cells. It is shown how accurate potentials for FPMS can be generated from self-consistent charge densities obtained with other schemes, especially the projector augmented wave method. Compared to standard multiple scattering calculations in the muffin-tin approximation, FPMS gives much better agreement with experiment. The effects of various structural modifications on the graphene spectra are well reproduced. (1) Stacking of graphene layers increases the peak intensity in the higher energy region. (2) The spectrum of the C atom located at the edge of a graphene sheet shows a prominent pre-edge structure. (3) Adsorption of oxygen gives rise to the so-called interlayer-state peak. Moreover, O K-edge spectra of graphene oxide are calculated for three types of bonding, C-OH, C-O-C, and C-O, and the proportions of these bondings at 800 ∘C are deduced by fitting them to the experimental spectrum.

  17. Vegetables’ juice influences polyol pathway by multiple mechanisms in favour of reducing development of oxidative stress and resultant diabetic complications

    PubMed Central

    Tiwari, Ashok K.; Kumar, D. Anand; Sweeya, Pisupati S.; Chauhan, H. Anusha; Lavanya, V.; Sireesha, K.; Pavithra, K.; Zehra, Amtul

    2014-01-01

    Objective: Hyperglycemia induced generation of free radicals and consequent development of oxidative stress by polyol pathway is one of the crucial mechanisms stirring up development of diabetic complications. We evaluated influence of ten vegetables’ juice on polyol pathway along with their antioxidant and antioxidative stress potentials. Materials and Methods: Aldose reductase activity was determined utilising goat lens and human erythrocytes. In goat lens, utilization of nicotinamine adenine dinucleotide phosphate (NADPH) and aldose reductase inhibition was assayed. In human erythrocytes, sorbitol formation was measured as an index of aldose reductase activity under normoglycemic and hyperglycemic conditions. Ability of juices in inhibiting oxidative damage to deoxyribose sugar and calf thymus DNA and inhibitory activity against hydrogen peroxide induced hemolysis of erythrocytes was also analysed. Phytochemical contents like total polyphenol, total flavonoid and total protein were measured to find their influence on biological activities. Results: Vegetables’ juice displayed varying degrees of inhibitory potentials in mitigating NADPH dependent catalytic activity of aldose reductase in goat lens, accumulation of sorbitol in human erythrocytes under different glucose concentrations; Fenton-reaction induced oxidative damage to deoxyribose sugar, and calf thymus DNA. Substantial variations in vegetables phytochemicals content were also noticed in this study. Conclusions: Vegetables’ juice possesses potent activities in influencing polyol pathway by various mechanisms in favour of reducing development of oxidative stress independent of their inherent antioxidative properties. Juice of ivy gourd followed by green cucumber and ridge gourd were among the most potent for they displayed strong activities on various parameters analysed in this study. These vegetables’ juice may become part of mechanism-based complementary antioxidant therapy to prevent

  18. An Overview of Methods in Plant Nitric Oxide (NO) Research: Why Do We Always Need to Use Multiple Methods?

    PubMed

    Yamasaki, Hideo; Watanabe, Naoko S; Sakihama, Yasuko; Cohen, Michael F

    2016-01-01

    The free radical nitric oxide (NO) is a universal signaling molecule among living organisms. To investigate versatile functions of NO in plants it is essential to analyze biologically produced NO with an appropriate method. Owing to the uniqueness of NO, plant researchers may encounter difficulties in applying methods that have been developed for mammalian study. Based on our experience, we present here a practical guide to NO measurement fitted to plant biology. PMID:27094406

  19. Au-ionic liquid functionalized reduced graphene oxide immunosensing platform for simultaneous electrochemical detection of multiple analytes.

    PubMed

    Liu, Na; Ma, Zhanfang

    2014-01-15

    In this work, an Au-ionic liquid functionalized reduced graphene oxide nanocomposite (IL-rGO-Au) was fabricated via the self-assembly of ionic liquid functionalized reduced graphene oxide (IL-rGO) and gold nanoparticles (AuNPs) by electrostatic interaction. The IL-rGO can be synthesized and stabilized by introducing the cations of the amine-terminated ionic liquids (IL-NH2) into the graphene oxide (GO). With the assistance of IL-NH2, AuNPs were uniformly and densely absorbed on the surfaces of the IL-rGO. The proposed IL-rGO-Au nanocomposite can be used as an immunosensing platform because it can not only facilitate the electrons transfer of the electrode surface but also provide a large accessible surface area for the immobilization of abundant antibody. To assess the performance of the IL-rGO-Au nanocomposite, a sandwich-type electrochemical immunosensor was designed for simultaneous multianalyte detection (carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP) as model analytes). The chitosan (CS) coated prussian blue nanoparticles (PBNPs) or cadmium hexacyanoferrate nanoparticles (CdNPs) and loaded with AuNPs were used as distinguishable signal tags. The resulting immunosensor exhibited high selectivity and sensitivity in simultaneous determination of CEA and AFP in a single run. The linear ranges were from 0.01 to 100 ng mL(-1) for both CEA and AFP. The detection limits reached 0.01 ng mL(-1) for CEA and 0.006 ng mL(-1) for AFP, respectively. No obvious nonspecific adsorption and cross-talk was observed during a series of analyses to detect target analytes. In addition, for the detection of clinical serum samples, it is well consistent with the data determined by the ELISA, indicating that the immunosensor provides a possible application for the simultaneous multianalyte determination of CEA and AFP in clinical diagnostics. PMID:23962704

  20. Biodistribution of a High Dose of Diamond, Graphite, and Graphene Oxide Nanoparticles After Multiple Intraperitoneal Injections in Rats.

    PubMed

    Kurantowicz, Natalia; Strojny, Barbara; Sawosz, Ewa; Jaworski, Sławomir; Kutwin, Marta; Grodzik, Marta; Wierzbicki, Mateusz; Lipińska, Ludwika; Mitura, Katarzyna; Chwalibog, André

    2015-12-01

    Carbon nanoparticles have recently drawn intense attention in biomedical applications. Hence, there is a need for further in vivo investigations of their biocompatibility and biodistribution via various exposure routes. We hypothesized that intraperitoneally injected diamond, graphite, and graphene oxide nanoparticles may have different biodistribution and exert different effects on the intact organism. Forty Wistar rats were divided into four groups: the control and treated with nanoparticles by intraperitoneal injection (4 mg of nanoparticles/kg body weight) eight times during the 4-week period. Blood was collected for evaluation of blood morphology and biochemistry parameters. Photographs of the general appearance of each rat's interior were taken immediately after sacrifice. The organs were excised and their macroscopic structure was visualized using a stereomicroscope. The nanoparticles were retained in the body, mostly as agglomerates. The largest agglomerates (up to 10 mm in diameter) were seen in the proximity of the injection place in the stomach serous membrane, between the connective tissues of the abdominal skin, muscles, and peritoneum. Numerous smaller, spherical-shaped aggregates (diameter around 2 mm) were lodged among the mesentery. Moreover, in the connective and lipid tissue in the proximity of the liver and spleen serosa, small aggregates of graphite and graphene oxide nanoparticles were observed. However, all tested nanoparticles did not affect health and growth of rats. The nanoparticles had no toxic effects on blood parameters and growth of rats, suggesting their potential applicability as remedies or in drug delivery systems. PMID:26459428

  1. Biodistribution of a High Dose of Diamond, Graphite, and Graphene Oxide Nanoparticles After Multiple Intraperitoneal Injections in Rats

    NASA Astrophysics Data System (ADS)

    Kurantowicz, Natalia; Strojny, Barbara; Sawosz, Ewa; Jaworski, Sławomir; Kutwin, Marta; Grodzik, Marta; Wierzbicki, Mateusz; Lipińska, Ludwika; Mitura, Katarzyna; Chwalibog, André

    2015-10-01

    Carbon nanoparticles have recently drawn intense attention in biomedical applications. Hence, there is a need for further in vivo investigations of their biocompatibility and biodistribution via various exposure routes. We hypothesized that intraperitoneally injected diamond, graphite, and graphene oxide nanoparticles may have different biodistribution and exert different effects on the intact organism. Forty Wistar rats were divided into four groups: the control and treated with nanoparticles by intraperitoneal injection (4 mg of nanoparticles/kg body weight) eight times during the 4-week period. Blood was collected for evaluation of blood morphology and biochemistry parameters. Photographs of the general appearance of each rat's interior were taken immediately after sacrifice. The organs were excised and their macroscopic structure was visualized using a stereomicroscope. The nanoparticles were retained in the body, mostly as agglomerates. The largest agglomerates (up to 10 mm in diameter) were seen in the proximity of the injection place in the stomach serous membrane, between the connective tissues of the abdominal skin, muscles, and peritoneum. Numerous smaller, spherical-shaped aggregates (diameter around 2 mm) were lodged among the mesentery. Moreover, in the connective and lipid tissue in the proximity of the liver and spleen serosa, small aggregates of graphite and graphene oxide nanoparticles were observed. However, all tested nanoparticles did not affect health and growth of rats. The nanoparticles had no toxic effects on blood parameters and growth of rats, suggesting their potential applicability as remedies or in drug delivery systems.

  2. Lung injury in guinea pigs caused by multiple exposures to ultrafine zinc oxide: changes in pulmonary lavage fluid

    SciTech Connect

    Conner, M.W.; Flood, W.H.; Rogers, A.E.; Amdur, M.O.

    1988-01-01

    Metal oxide particles with diameters of less than 0.1 micron (ultrafine particles) are important products of fossil fuel combustion. Pulmonary lavage fluid was obtained from guinea pigs given 1, 2, or 3 consecutive, daily, 3-h, nose-only exposures to 0, 2.3, 5.9, or 12.1 mg/m3 of freshly generated zinc oxide (ZnO) particles with a projected area diameter of 0.05 micron. Exposure to ZnO at 5.9 or 12.1 mg/m3 was associated with increased protein, neutrophils, and activities of angiotensin-converting enzyme, alkaline phosphatase, acid phosphatase and lactate dehydrogenase in lavage fluid, and with histologic evidence of pulmonary damage characterized by centriacinar inflammation. The severity of inflammation, graded by the number of inflammatory foci per square centimeter of lung, correlated with the amount of protein and the activity of angiotensin-converting enzyme and other enzymes in lavage fluid. These results indicate that analysis of pulmonary lavage fluid is a useful and sensitive method for quantitative evaluation of pulmonary damage caused by inhalation of low levels of ultrafine ZnO.

  3. Assembly and benign step-by-step post-treatment of oppositely charged reduced graphene oxides for transparent conductive thin films with multiple applications

    NASA Astrophysics Data System (ADS)

    Zhu, Jiayi; He, Junhui

    2012-05-01

    We report a new approach for the fabrication of flexible and transparent conducting thin films via the layer-by-layer (LbL) assembly of oppositely charged reduced graphene oxide (RGO) and the benign step-by-step post-treatment on substrates with a low glass-transition temperature, such as glass and poly(ethylene terephthalate) (PET). The RGO dispersions and films were characterized by means of atomic force microscopy, UV-visible absorption spectrophotometery, Raman spectroscopy, transmission electron microscopy, contact angle/interface systems and a four-point probe. It was found that the graphene thin films exhibited a significant increase in electrical conductivity after the step-by-step post-treatments. The graphene thin film on the PET substrate had a good conductivity retainability after multiple cycles (30 cycles) of excessively bending (bending angle: 180°), while tin-doped indium oxide (ITO) thin films on PET showed a significant decrease in electrical conductivity. In addition, the graphene thin film had a smooth surface with tunable wettability.We report a new approach for the fabrication of flexible and transparent conducting thin films via the layer-by-layer (LbL) assembly of oppositely charged reduced graphene oxide (RGO) and the benign step-by-step post-treatment on substrates with a low glass-transition temperature, such as glass and poly(ethylene terephthalate) (PET). The RGO dispersions and films were characterized by means of atomic force microscopy, UV-visible absorption spectrophotometery, Raman spectroscopy, transmission electron microscopy, contact angle/interface systems and a four-point probe. It was found that the graphene thin films exhibited a significant increase in electrical conductivity after the step-by-step post-treatments. The graphene thin film on the PET substrate had a good conductivity retainability after multiple cycles (30 cycles) of excessively bending (bending angle: 180°), while tin-doped indium oxide (ITO) thin films on

  4. Coulomb Blockade of the Conductivity of SiO{sub x} Films Due to One-Electron Charging of a Silicon Quantum Dot in a Chain of Electronic States

    SciTech Connect

    Efremov, M.D.; Kamaev, G.N.; Volodin, V.A.; Arzhannikova, S.A.; Kachurin, G.A.; Cherkova, S.G.; Kretinin, A.V.; Malyutina-Bronskaya, V.V.; Marin, D.V.

    2005-08-15

    The electrical characteristics of metal-oxide-semiconductor (MOS) structures with silicon nanoparticles embedded in silicon oxide have been studied. The nanocrystals are formed by decomposition of an oversaturated solid solution of implanted silicon during thermal annealing at a temperature of {approx}1000 deg. C. At liquid-nitrogen temperature, a stepped current-voltage characteristic is observed in a MOS structure consisting of Si nanocrystals in a SiO{sub 2} film. The stepped current-voltage characteristic is, for the first time, quantitatively described using a model in which charge transport occurs via a chain of local states containing a silicon nanocrystal. The presence of steps is found to be associated with one-electron charging of the silicon nanocrystal and Coulomb blockade of the probability of a hop from the nearest local state to the conducting chain. The local states in silicon dioxide are assumed to be related to an excess of silicon atoms. The presence of such states is confirmed by measurements of the differential conductance and capacitance. For MOS structures implanted with silicon, the differential capacitance and conductance are found to be higher, compared to the reference structures, in the range of biases exceeding 0.2 V. In the same bias range, the conductance is observed to decrease under ultraviolet irradiation due to a change in the population of the states in the conductivity chains.

  5. Data of multiple regressions analysis between selected biomarkers related to glutamate excitotoxicity and oxidative stress in Saudi autistic patients.

    PubMed

    El-Ansary, Afaf

    2016-06-01

    This work demonstrates data of multiple regression analysis between nine biomarkers related to glutamate excitotoxicity and impaired detoxification as two mechanisms recently recorded as autism phenotypes. The presented data was obtained by measuring a panel of markers in 20 autistic patients aged 3-15 years and 20 age and gender matching healthy controls. Levels of GSH, glutathione status (GSH/GSSG), glutathione reductase (GR), glutathione-s-transferase (GST), thioredoxin (Trx), thioredoxin reductase (TrxR) and peroxidoxins (Prxs I and III), glutamate, glutamine, glutamate/glutamine ratio glutamate dehydrogenase (GDH) in plasma and mercury (Hg) in red blood cells were determined in both groups. In Multiple regression analysis, R (2) values which describe the proportion or percentage of variance in the dependent variable attributed to the variance in the independent variables together were calculated. Moreover, β coefficients values which show the direction either positive or negative and the contribution of the independent variable relative to the other independent variables in explaining the variation of the dependent variable were determined. A panel of inter-related markers was recorded. This paper contains data related to and supporting research articles currently published entitled "Mechanism of nitrogen metabolism-related parameters and enzyme activities in the pathophysiology of autism" [1], "Novel metabolic biomarkers related to sulfur-dependent detoxification pathways in autistic patients of Saudi Arabia [2], and "A key role for an impaired detoxification mechanism in the etiology and severity of autism spectrum disorders" [3]. PMID:26933667

  6. Rheological kinetics of thermo-sensitive supramolecular assemblies from poly( N-isopropyl acrylamide) and adenine-functionalized poly(ethylene oxide) stabilized by complementary multiple hydrogen bonds

    NASA Astrophysics Data System (ADS)

    Cui, Hui-Wang; Kuo, Shiao-Wei

    2014-05-01

    In this study, we synthesized a poly( N-isopropylacrylamide) (PNIPAm) through the polymerization of N-isopropylacrylamide in distilled water with azodiisobutyronitrile as the initiator and a bisadenine-functionalized poly(ethylene oxide) (A-PEO-A) from the reaction of adenine with a difunctionalized toluenesulfonyl-PEO. When blended together in distilled water, PNIPAm and A-PEO-A formed supramolecular aggregates stabilized through complementary multiple hydrogen bonds between the amide groups of PNIPAm and the adenine units of A-PEO-A. Agrawal integral equation and rheometry revealed the rheological kinetics of supramolecular assemblies, which were influenced significantly by the spherical micelles, large associated aggregates of spherical micelles, network structures, and toroid structures formed in aqueous solutions.

  7. Multiple-stimuli responsive bioelectrocatalysis based on reduced graphene oxide/poly(N-isopropylacrylamide) composite films and its application in the fabrication of logic gates.

    PubMed

    Wang, Lei; Lian, Wenjing; Yao, Huiqin; Liu, Hongyun

    2015-03-11

    In the present work, reduced graphene oxide (rGO)/poly(N-isopropylacrylamide) (PNIPAA) composite films were electrodeposited onto the surface of Au electrodes in a fast and one-step manner from an aqueous mixture of a graphene oxide (GO) dispersion and N-isopropylacrylamide (NIPAA) monomer solutions. Reflection-absorption infrared (IR) and Raman spectroscopies were employed to characterize the successful construction of the rGO/PNIPAA composite films. The rGO/PNIPAA composite films exhibited reversible potential-, pH-, temperature-, and sulfate-sensitive cyclic voltammetric (CV) on-off behavior to the electroactive probe ferrocenedicarboxylic acid (Fc(COOH)2). For instance, after the composite films were treated at -0.7 V for 7 min, the CV responses of Fc(COOH)2 at the rGO/PNIPAA electrodes were quite large at pH 8.0, exhibiting the on state. However, after the films were treated at 0 V for 30 min, the CV peak currents became much smaller, demonstrating the off state. The mechanism of the multiple-stimuli switchable behaviors for the system was investigated not only by electrochemical methods but also by scanning electron microscopy and X-ray photoelectron spectroscopy. The potential-responsive behavior for this system was mainly attributed to the transformation between rGO and GO in the films at different potentials. The film system was further used to realize multiple-stimuli responsive bioelectrocatalysis of glucose catalyzed by the enzyme of glucose oxidase and mediated by the electroactive probe of Fc(COOH)2 in solution. On the basis of this, a four-input enabled OR (EnOR) logic gate network was established. PMID:25686462

  8. Relationship between the Increased Haemostatic Properties of Blood Platelets and Oxidative Stress Level in Multiple Sclerosis Patients with the Secondary Progressive Stage

    PubMed Central

    Bijak, Michał; Miller, Elżbieta; Miller, Sergiusz

    2015-01-01

    Multiple sclerosis (MS) is the autoimmune disease of the central nervous system with complex pathogenesis, different clinical courses and recurrent neurological relapses and/or progression. Despite various scientific papers that focused on early stage of MS, our study targets selective group of late stage secondary progressive MS patients. The presented work is concerned with the reactivity of blood platelets in primary hemostasis in SP MS patients. 50 SP MS patients and 50 healthy volunteers (never diagnosed with MS or other chronic diseases) were examined to evaluate the biological activity of blood platelets (adhesion, aggregation), especially their response to the most important physiological agonists (thrombin, ADP, and collagen) and the effect of oxidative stress on platelet activity. We found that the blood platelets from SP MS patients were significantly more sensitive to all used agonists in comparison with control group. Moreover, the platelet hemostatic function was advanced in patients suffering from SP MS and positively correlated with increased production of O2−∙ in these cells, as well as with Expanded Disability Status Scale. We postulate that the increased oxidative stress in blood platelets in SP MS may be primarily responsible for the altered haemostatic properties of blood platelets. PMID:26064417

  9. Polymerized nano-curcumin attenuates neurological symptoms in EAE model of multiple sclerosis through down regulation of inflammatory and oxidative processes and enhancing neuroprotection and myelin repair.

    PubMed

    Mohajeri, Maryam; Sadeghizadeh, Majid; Najafi, Farhood; Javan, Mohammad

    2015-12-01

    Multiple Sclerosis (MS) is an inflammatory demyelinating disorder of central nervous system (CNS). Polyphenol curcumin has been used in traditional medicine as an effective drug for a variety of diseases. Different formulations of curcumin are introduced to increase its stability and effectiveness. Here we have examined the effect of polymerized form of nano-curcumin (PNC) on experimental autoimmune encephalomyelitis (EAE) as an animal model of MS. EAE was induced in female Lewis rats and PNC or curcumin was daily administrated intraperitonealy from day 12-29 post immunization. When the prophylactic effect of PNC was under investigation, rats received PNC from the first day of immunization. Treatment with PNC resulted in decreased scores of disease in therapeutic and prophylactic administration when compared with control group. Staining by luxol fast blue and H&E and immuno-staining of lumbar spinal cord cross sections, confirmed a significant decrease in the amounts of demyelination, inflammation and BBB breaking down. Gene expression studies in lumbar spinal cord showed a corrected balance of pro-inflammatory and anti-inflammatory genes expression, decreased oxidative stress, improved remyelination and increased progenitor cell markers after treatment with PNC. Our results demonstrated an efficient therapeutic effect of PNC as an anti-inflammatory and anti-oxidative stress agent, with significant effects on the EAE scores and myelin repair mechanisms. PMID:26211978

  10. Z-Scan Analysis: a New Method to Determine the Oxidative State of Low-Density Lipoprotein and Its Association with Multiple Cardiometabolic Biomarkers

    NASA Astrophysics Data System (ADS)

    de Freitas, Maria Camila Pruper; Figueiredo Neto, Antonio Martins; Giampaoli, Viviane; da Conceição Quintaneiro Aubin, Elisete; de Araújo Lima Barbosa, Milena Maria; Damasceno, Nágila Raquel Teixeira

    2016-04-01

    The great atherogenic potential of oxidized low-density lipoprotein has been widely described in the literature. The objective of this study was to investigate whether the state of oxidized low-density lipoprotein in human plasma measured by the Z-scan technique has an association with different cardiometabolic biomarkers. Total cholesterol, high-density lipoprotein cholesterol, triacylglycerols, apolipoprotein A-I and apolipoprotein B, paraoxonase-1, and glucose were analyzed using standard commercial kits, and low-density lipoprotein cholesterol was estimated using the Friedewald equation. A sandwich enzyme-linked immunosorbent assay was used to detect electronegative low-density lipoprotein. Low-density lipoprotein and high-density lipoprotein sizes were determined by Lipoprint® system. The Z-scan technique was used to measure the non-linear optical response of low-density lipoprotein solution. Principal component analysis and correlations were used respectively to resize the data from the sample and test association between the θ parameter, measured with the Z-scan technique, and the principal component. A total of 63 individuals, from both sexes, with mean age 52 years (±11), being overweight and having high levels of total cholesterol and low levels of high-density lipoprotein cholesterol, were enrolled in this study. A positive correlation between the θ parameter and more anti-atherogenic pattern for cardiometabolic biomarkers together with a negative correlation for an atherogenic pattern was found. Regarding the parameters related with an atherogenic low-density lipoprotein profile, the θ parameter was negatively correlated with a more atherogenic pattern. By using Z-scan measurements, we were able to find an association between oxidized low-density lipoprotein state and multiple cardiometabolic biomarkers in samples from individuals with different cardiovascular risk factors.

  11. The detectability of nitrous oxide mitigation efficacy in intensively grazed pastures using a multiple plot micrometeorological technique

    NASA Astrophysics Data System (ADS)

    McMillan, A. M. S.; Harvey, M. J.; Martin, R. J.; Bromley, A. M.; Evans, M. J.; Mukherjee, S.; Laubach, J.

    2013-10-01

    Methodologies are required to verify agricultural greenhouse gas mitigation at scales relevant to farm management. Micrometeorological techniques provide a viable approach for comparing fluxes between fields receiving mitigation treatments and control fields. However, they have rarely been applied to spatially verifying treatments aimed at mitigating nitrous oxide emission from intensively grazed pastoral systems. We deployed a micrometeorological system to compare N2O flux among several ~ 1.5 ha plots in intensively grazed dairy pasture. The sample collection and measurement system is referred to as the Field-Scale Nitrous Oxide Mitigation Assessment System (FS-NOMAS) and used a tuneable diode laser absorption spectrometer to measure N2O gradients to high precision at four locations along a 300 m transect. The utility of the FS-NOMAS to assess mitigation efficacy depends largely on its ability to resolve very small vertical N2O gradients. The performance of the FS-NOMAS was assessed in this respect in laboratory and field-based studies. The FS-NOMAS could reliably resolve gradients of 0.039 ppb between a height of 0.5 m and 1.0 m. The gradient resolution achieved corresponded to the ability to detect an inter-plot N2O flux difference of 26.4 μg N2O-N m-2 h-1 under the most commonly encountered conditions of atmospheric mixing (quantified here by a turbulent transfer coefficient), but this ranged from 11 to 59 μg N2O-N m-2 h-1 as the transfer coefficient ranged between its 5th and 95th percentile. Assuming a likely value of 100 μg N2O-N m-2 h-1 for post-grazing N2O fluxes from intensively grazed New Zealand dairy pasture, the system described here would be capable of detecting a mitigation efficacy of 26% for a single (40 min) comparison. We demonstrate that the system has considerably greater sensitivity to treatment effects by measuring cumulative fluxes over extended periods.

  12. Thiocyanate complexes of uranium in multiple oxidation states: a combined structural, magnetic, spectroscopic, spectroelectrochemical, and theoretical study.

    PubMed

    Hashem, Emtithal; Platts, James A; Hartl, František; Lorusso, Giulia; Evangelisti, Marco; Schulzke, Carola; Baker, Robert J

    2014-08-18

    A comprehensive study of the complexes A4[U(NCS)8] (A = Cs, Et4N, (n)Bu4N) and A3[UO2(NCS)5] (A = Cs, Et4N) is described, with the crystal structures of [(n)Bu4N]4[U(NCS)8]·2MeCN and Cs3[UO2(NCS)5]·O0.5 reported. The magnetic properties of square antiprismatic Cs4[U(NCS)8] and cubic [Et4N]4[U(NCS)8] have been probed by SQUID magnetometry. The geometry has an important impact on the low-temperature magnetic moments: at 2 K, μeff = 1.21 μB and 0.53 μB, respectively. Electronic absorption and photoluminescence spectra of the uranium(IV) compounds have been measured. The redox chemistry of [Et4N]4[U(NCS)8] has been explored using IR and UV-vis spectroelectrochemical methods. Reversible 1-electron oxidation of one of the coordinated thiocyanate ligands occurs at +0.22 V vs Fc/Fc(+), followed by an irreversible oxidation to form dithiocyanogen (NCS)2 which upon back reduction regenerates thiocyanate anions coordinating to UO2(2+). NBO calculations agree with the experimental spectra, suggesting that the initial electron loss of [U(NCS)8](4-) is delocalized over all NCS(-) ligands. Reduction of the uranyl(VI) complex [Et4N]3[UO2(NCS)5] to uranyl(V) is accompanied by immediate disproportionation and has only been studied by DFT methods. The bonding in [An(NCS)8](4-) (An = Th, U) and [UO2(NCS)5](3-) has been explored by a combination of DFT and QTAIM analysis, and the U-N bonds are predominantly ionic, with the uranyl(V) species more ionic that the uranyl(VI) ion. Additionally, the U(IV)-NCS ion is more ionic than what was found for U(IV)-Cl complexes. PMID:25072532

  13. The Cooling Effect on Proinflammatory Cytokines Interferon-Gamma, Tumor Necrosis Factor-Alpha, and Nitric Oxide in Patients with Multiple Sclerosis

    PubMed Central

    Poyraz, Turan; Idiman, Egemen; Uysal, Sezer; Iyilikci, Leyla; Özakbaş, Serkan; Coskuner Poyraz, Esra; Idiman, Fethi

    2013-01-01

    Multiple sclerosis (MS) is the most common inflammatory demyelinating disease of the central nervous system (CNS) in young adults. The proinflammatory cytokines such as interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), and nitric oxide (NO) which are known to be produced by inflammatory cells play a key role in the pathogenesis of MS. Some metabolic changes may have an effect on axonal transmission, and white blood cells NO and other inflammatory mediators such as cytokines may be affected from cooling process. In this study, we evaluated the effects of body cooling procedure on proinflammatory cytokines such as TNF-α, IFN-γ, and NO levels. Twenty patients with MS were evaluated. Thirteen of the patients were women, 7 were men (mean age: 33.6 ± 7.5 yrs.). Body temperature was reduced by an average of 1°C approximately in 1 hour with using the “Medivance Arctic Sun Temperature Management System” device. In our study, the decrease in TNF-α, IFN-γ levels after the cooling procedure has no statistical significance, whereas the decrease in the mean level of NO level after the cooling procedure is 4.63 ± 7.4 μmol/L which has statistical significance (P = 0.002). These results suggested that the decrease in NO level improves conduction block in demyelinated axonal segments after cooling procedure in multiple sclerosis. PMID:23762603

  14. Quantification of multiple DNA adducts formed through oxidative stress using liquid chromatography and electrospray tandem mass spectrometry.

    PubMed

    Churchwell, Mona I; Beland, Frederick A; Doerge, Daniel R

    2002-10-01

    Damage to DNA can arise through covalent modification of bases by reaction with oxidants and products of lipid peroxidation derived through normal aerobic metabolism. Such premutagenic lesions, including 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG), pyrimido[1,2alpha]purine-10(3H)one-2'-deoxyribose (M1-dG), etheno-2'-deoxyadenosine (epsilon-dA), and etheno-2'-deoxycytidine (epsilon-dC), are believed to be important in the development of human cancers related to diet, disease states, and lifestyle. We report the development of a method for concurrent quantification of these four adducts in DNA hydrolysates of 100 microg or less using on-line sample preparation coupled with liquid chromatography and tandem mass spectrometry. The sensitive detection permitted adduct quantification at levels below one adduct in 10(8) normal nucleotides and measurement of these adducts in DNA from untreated rodent liver and normal human liver samples. This methodology should prove useful in hypothesis-driven studies of cancer etiology in laboratory animals and humans. PMID:12387628

  15. Multiple strategies to prevent oxidative stress in Arabidopsis plants lacking the malate valve enzyme NADP-malate dehydrogenase

    PubMed Central

    Hebbelmann, Inga; Selinski, Jennifer; Wehmeyer, Corinna; Goss, Tatjana; Voss, Ingo; Mulo, Paula; Kangasjärvi, Saijaliisa; Aro, Eva-Mari; Oelze, Marie-Luise; Dietz, Karl-Josef; Nunes-Nesi, Adriano; Do, Phuc T.; Fernie, Alisdair R.; Talla, Sai K.; Raghavendra, Agepati S.; Linke, Vera; Scheibe, Renate

    2012-01-01

    The nuclear-encoded chloroplast NADP-dependent malate dehydrogenase (NADP-MDH) is a key enzyme controlling the malate valve, to allow the indirect export of reducing equivalents. Arabidopsis thaliana (L.) Heynh. T-DNA insertion mutants of NADP-MDH were used to assess the role of the light-activated NADP-MDH in a typical C3 plant. Surprisingly, even when exposed to high-light conditions in short days, nadp-mdh knockout mutants were phenotypically indistinguishable from the wild type. The photosynthetic performance and typical antioxidative systems, such as the Beck–Halliwell–Asada pathway, were barely affected in the mutants in response to high-light treatment. The reactive oxygen species levels remained low, indicating the apparent absence of oxidative stress, in the mutants. Further analysis revealed a novel combination of compensatory mechanisms in order to maintain redox homeostasis in the nadp-mdh plants under high-light conditions, particularly an increase in the NTRC/2-Cys peroxiredoxin (Prx) system in chloroplasts. There were indications of adjustments in extra-chloroplastic components of photorespiration and proline levels, which all could dissipate excess reducing equivalents, sustain photosynthesis, and prevent photoinhibition in nadp-mdh knockout plants. Such metabolic flexibility suggests that the malate valve acts in concert with other NADPH-consuming reactions to maintain a balanced redox state during photosynthesis under high-light stress in wild-type plants. PMID:22140244

  16. Simple and cost-effective fabrication of size-tunable zinc oxide architectures by multiple size reduction technique

    NASA Astrophysics Data System (ADS)

    Park, Hyeong-Ho; Zhang, Xin; Hwang, Seon-Yong; Jung, Sang Hyun; Kang, Semin; Shin, Hyun-Beom; Kang, Ho Kwan; Park, Hyung-Ho; Hill, Ross H.; Ko, Chul Ki

    2012-04-01

    We present a simple size reduction technique for fabricating 400 nm zinc oxide (ZnO) architectures using a silicon master containing only microscale architectures. In this approach, the overall fabrication, from the master to the molds and the final ZnO architectures, features cost-effective UV photolithography, instead of electron beam lithography or deep-UV photolithography. A photosensitive Zn-containing sol-gel precursor was used to imprint architectures by direct UV-assisted nanoimprint lithography (UV-NIL). The resulting Zn-containing architectures were then converted to ZnO architectures with reduced feature sizes by thermal annealing at 400 °C for 1 h. The imprinted and annealed ZnO architectures were also used as new masters for the size reduction technique. ZnO pillars of 400 nm diameter were obtained from a silicon master with pillars of 1000 nm diameter by simply repeating the size reduction technique. The photosensitivity and contrast of the Zn-containing precursor were measured as 6.5 J cm-2 and 16.5, respectively. Interesting complex ZnO patterns, with both microscale pillars and nanoscale holes, were demonstrated by the combination of dose-controlled UV exposure and a two-step UV-NIL.

  17. Nitric Oxide-cGMP Signaling Stimulates Erythropoiesis through Multiple Lineage-Specific Transcription Factors: Clinical Implications and a Novel Target for Erythropoiesis

    PubMed Central

    Ikuta, Tohru; Sellak, Hassan; Odo, Nadine; Adekile, Adekunle D.; Gaensler, Karin M. L.

    2016-01-01

    Much attention has been directed to the physiological effects of nitric oxide (NO)-cGMP signaling, but virtually nothing is known about its hematologic effects. We reported for the first time that cGMP signaling induces human γ-globin gene expression. Aiming at developing novel therapeutics for anemia, we examined here the hematologic effects of NO-cGMP signaling in vivo and in vitro. We treated wild-type mice with NO to activate soluble guanylate cyclase (sGC), a key enzyme of cGMP signaling. Compared to untreated mice, NO-treated mice had higher red blood cell counts and total hemoglobin but reduced leukocyte counts, demonstrating that when activated, NO-cGMP signaling exerts hematopoietic effects on multiple types of blood cells in vivo. We next generated mice which overexpressed rat sGC in erythroid and myeloid cells. The forced expression of sGCs activated cGMP signaling in both lineage cells. Compared with non-transgenic littermates, sGC mice exhibited hematologic changes similar to those of NO-treated mice. Consistently, a membrane-permeable cGMP enhanced the differentiation of hematopoietic progenitors toward erythroid-lineage cells but inhibited them toward myeloid-lineage cells by controlling multiple lineage-specific transcription factors. Human γ-globin gene expression was induced at low but appreciable levels in sGC mice carrying the human β-globin locus. Together, these results demonstrate that NO-cGMP signaling is capable of stimulating erythropoiesis in both in vitro and vivo settings by controlling the expression of multiple lineage-specific transcription factors, suggesting that cGMP signaling upregulates erythropoiesis at the level of gene transcription. The NO-cGMP signaling axis may constitute a novel target to stimulate erythropoiesis in vivo. PMID:26727002

  18. Role of multiple gene copies in particulate methane monooxygenase activity in the methane-oxidizing bacterium Methylococcus capsulatus Bath.

    PubMed

    Stolyar, S; Costello, A M; Peeples, T L; Lidstrom, M E

    1999-05-01

    Genes for the subunits of particulate methane monooxygenase, PmoABC, have been sequenced from the gamma-proteobacterial methanotroph Methylococcus capsulatus Bath. M. capsulatus Bath contains two complete copies of pmoCAB, as well as a third copy of pmoC. The two pmoCAB regions were almost identical at the nucleotide sequence level, differing in only 13 positions in 3183 bp. At the amino acid level, each translated gene product contained only one differing residue in each copy. However, the pmoC3 sequence was more divergent from the two other pmoC copies at both the far N-terminus and far C-terminus. Chromosomal insertion mutations were generated in all seven genes. Null mutants could not be obtained for pmoC3, suggesting that it may play an essential role in growth on methane. Null mutants were obtained for pmoC1, pmoC2, pmoA1, pmoA2, pmoB1 and pmoB2. All of these mutants grew on methane, demonstrating that both gene copies were functional. Copy 1 mutants showed about two-thirds of the wild-type whole-cell methane oxidation rate, while copy 2 mutants showed only about one-third of the wild-type rate, indicating that both gene copies were necessary for wild-type particulate methane monooxygenase activity. It was not possible to obtain double null mutants that were defective in both pmo copies, which may indicate that some expression of pMMO is important for growth. PMID:10376840

  19. Communication: Satisfying fermionic statistics in the modeling of open time-dependent quantum systems with one-electron reduced density matrices

    NASA Astrophysics Data System (ADS)

    Head-Marsden, Kade; Mazziotti, David A.

    2015-02-01

    For an open, time-dependent quantum system, Lindblad derived the most general modification of the quantum Liouville equation in the Markovian approximation that models environmental effects while preserving the non-negativity of the system's density matrix. While Lindblad's modification is correct for N-electron density matrices, solution of the Liouville equation with a Lindblad operator causes the one-electron reduced density matrix (1-RDM) to violate the Pauli exclusion principle. Consequently, after a short time, the 1-RDM is not representable by an ensemble N-electron density matrix (not ensemble N-representable). In this communication, we derive the necessary and sufficient constraints on the Lindbladian matrix within the Lindblad operator to ensure that the 1-RDM remains N-representable for all time. The theory is illustrated by considering the relaxation of an excitation in several molecules F2, N2, CO, and BeH2 subject to environmental noise.

  20. Communication: satisfying fermionic statistics in the modeling of open time-dependent quantum systems with one-electron reduced density matrices.

    PubMed

    Head-Marsden, Kade; Mazziotti, David A

    2015-02-01

    For an open, time-dependent quantum system, Lindblad derived the most general modification of the quantum Liouville equation in the Markovian approximation that models environmental effects while preserving the non-negativity of the system's density matrix. While Lindblad's modification is correct for N-electron density matrices, solution of the Liouville equation with a Lindblad operator causes the one-electron reduced density matrix (1-RDM) to violate the Pauli exclusion principle. Consequently, after a short time, the 1-RDM is not representable by an ensemble N-electron density matrix (not ensemble N-representable). In this communication, we derive the necessary and sufficient constraints on the Lindbladian matrix within the Lindblad operator to ensure that the 1-RDM remains N-representable for all time. The theory is illustrated by considering the relaxation of an excitation in several molecules F2, N2, CO, and BeH2 subject to environmental noise. PMID:25662627

  1. MiR-17-5p Impairs Trafficking of H-ERG K+ Channel Protein by Targeting Multiple ER Stress-Related Chaperones during Chronic Oxidative Stress

    PubMed Central

    Wang, Qi; Hu, Weina; Lei, Mingming; Wang, Yong; Yan, Bing; Liu, Jun; Zhang, Ren; Jin, Yuanzhe

    2013-01-01

    Background To investigate if microRNAs (miRNAs) play a role in regulating h-ERG trafficking in the setting of chronic oxidative stress as a common deleterious factor for many cardiac disorders. Methods We treated neonatal rat ventricular myocytes and HEK293 cells with stable expression of h-ERG with H2O2 for 12 h and 48 h. Expression of miR-17-5p seed miRNAs was quantified by real-time RT-PCR. Protein levels of chaperones and h-ERG trafficking were measured by Western blot analysis. Luciferase reporter gene assay was used to study miRNA and target interactions. Whole-cell patch-clamp techniques were employed to record h-ERG K+ current. Results H-ERG trafficking was impaired by H2O2 after 48 h treatment, accompanied by reciprocal changes of expression between miR-17-5p seed miRNAs and several chaperones (Hsp70, Hsc70, CANX, and Golga2), with the former upregulated and the latter downregulated. We established these chaperones as targets for miR-17-5p. Application miR-17-5p inhibitor rescued H2O2-induced impairment of h-ERG trafficking. Upregulation of endogenous by H2O2 or forced miR-17-5p expression either reduced h-ERG current. Sequestration of AP1 by its decoy molecule eliminated the upregulation of miR-17-5p, and ameliorated impairment of h-ERG trafficking. Conclusions Collectively, deregulation of the miR-17-5p seed family miRNAs can cause severe impairment of h-ERG trafficking through targeting multiple ER stress-related chaperones, and activation of AP1 likely accounts for the deleterious upregulation of these miRNAs, in the setting of prolonged duration of oxidative stress. These findings revealed the role of miRNAs in h-ERG trafficking, which may contribute to the cardiac electrical disturbances associated with oxidative stress. PMID:24386440

  2. Effects of green tea extract and α-tocopherol on the lipid oxidation rate of omega-3 oils, incorporated into table spreads, prepared using multiple emulsion technology.

    PubMed

    Dwyer, Sandra P O'; O'Beirne, David; Ní Eidhin, Deirdre; O'Kennedy, Brendan T

    2012-12-01

    This study examined the effectiveness of fat and water soluble antioxidants on the oxidative stability of omega (ω)-3 rich table spreads, produced using novel multiple emulsion technology. Table spreads were produced by dispersing an oil-in-water (O/W) emulsion (500 g/kg 85 camelina/15 fish oil blend) in a hardstock/rapeseed oil blend, using sodium caseinate and polyglycerol polyricinoleate as emulsifiers. The O/W and oil-in-water-in-oil (O/W/O) emulsions contained either a water soluble antioxidant (green tea extract [GTE]), an oil soluble antioxidant (α-Tocopherol), or both. Spreads containing α-Tocopherol had the highest lipid hydroperoxide values, whereas spreads containing GTE had the lowest (P < 0.05), during storage at 5°C, while p-Anisidine values did not differ significantly. Particle size was generally unaffected by antioxidant type (P < 0.05). Double emulsion (O/W/O) structures were clearly seen in confocal images of the spreads. By the end of storage, none of the spreads had significantly different G' values. Firmness (Newtons) of all spreads generally increased during storage (P < 0.05). PMID:23171419

  3. Accelerated aging of 28 Gb s-1 850 nm vertical-cavity surface-emitting laser with multiple thick oxide apertures

    NASA Astrophysics Data System (ADS)

    Kropp, J. R.; Steinle, G.; Schäfer, G.; Shchukin, V. A.; Ledentsov, N. N.; Turkiewicz, J. P.; Zoldak, M.

    2015-04-01

    850 nm vertical-cavity surface-emitting lasers with multiple thick oxide apertures suitable for temperature-insensitive error free transmission at 28 Gb s-1 are subjected to accelerated aging at high current densities and chip temperatures. The devices withstand a 20% power change test at a high current density (18 kA c{{m}-2}) at an ambient temperature of 120 {}^\\circ C for 2500 h. At 90-95 {}^\\circ C at this current density no degradation was observed up to 5000 h. We performed the studies at further elevated current densities and temperatures and define the acceleration factor as AF={{({{J}stress}/{{J}use})}8}exp [(1.3 eV/{{k}B})(1/{{T}use}-1/{{T}stress})]. The extrapolated lifetime for 20% power drop is estimated as 20 thousand years at 300 K at current density of 18 kA c{{m}-2} which is sufficient for 28 Gb s-1 error-free temperature-insensitive data transmission.

  4. Solution of the Dirac equation using the Rayleigh-Ritz method: Flexible basis coupling large and small components. Results for one-electron systems

    NASA Astrophysics Data System (ADS)

    Baǧcı, A.; Hoggan, P. E.

    2016-07-01

    An algebraic solution of the Dirac equation is reinvestigated. Slater-type spinor orbitals and their corresponding system of differential equations are defined in two- and four-component formalism. They describe the radial function in components of the wave function of the Dirac equation solution to high accuracy. They constitute the matrix elements arising in a generalized eigenvalue equation. These terms are evaluated through prolate spheroidal coordinates. The corresponding integrals are calculated by the numerical global-adaptive method taking into account the Gauss-Kronrod numerical integration extension. Sample calculations are performed using flexible basis sets generated with both signs of the relativistic angular momentum quantum number κ . Applications to one-electron atoms and diatomics are detailed. Variationally optimum values for orbital parameters are obtained at given nuclear separation. Methods discussed in this work are capable of yielding highly accurate relativistic two-center integrals for all ranges of orbital parameters. This work provides an efficient way to overcome the problems that arise in relativistic calculations.

  5. Solution of the Dirac equation using the Rayleigh-Ritz method: Flexible basis coupling large and small components. Results for one-electron systems.

    PubMed

    Bağcı, A; Hoggan, P E

    2016-07-01

    An algebraic solution of the Dirac equation is reinvestigated. Slater-type spinor orbitals and their corresponding system of differential equations are defined in two- and four-component formalism. They describe the radial function in components of the wave function of the Dirac equation solution to high accuracy. They constitute the matrix elements arising in a generalized eigenvalue equation. These terms are evaluated through prolate spheroidal coordinates. The corresponding integrals are calculated by the numerical global-adaptive method taking into account the Gauss-Kronrod numerical integration extension. Sample calculations are performed using flexible basis sets generated with both signs of the relativistic angular momentum quantum number κ. Applications to one-electron atoms and diatomics are detailed. Variationally optimum values for orbital parameters are obtained at given nuclear separation. Methods discussed in this work are capable of yielding highly accurate relativistic two-center integrals for all ranges of orbital parameters. This work provides an efficient way to overcome the problems that arise in relativistic calculations. PMID:27575231

  6. New Measurement of the Electron Magnetic Moment and the Fine Structure Constant: A First Application of a One-Electron Quantum Cyclotron

    ScienceCinema

    Gabrielse, Gerald [Harvard University, Cambridge, Massachusetts, United States

    2009-09-01

    Remarkably, the famous UW measurement of the electron magnetic moment has stood since 1987. With QED theory, this measurement has determined the accepted value of the fine structure constant. This colloquium is about a new Harvard measurement of these fundamental constants. The new measurement has an uncertainty that is about six times smaller, and it shifts the values by 1.7 standard deviations. One electron suspended in a Penning trap is used for the new measurement, like in the old measurement. What is different is that the lowest quantum levels of the spin and cyclotron motion are resolved, and the cyclotron as well as spin frequencies are determined using quantum jump spectroscopy. In addition, a 0.1 mK Penning trap that is also a cylindrical microwave cavity is used to control the radiation field, to suppress spontaneous emission by more than a factor of 100, to control cavity shifts, and to eliminate the blackbody photons that otherwise stimulate excitations from the cyclotron ground state. Finally, great signal-to-noise for one-quantum transitions is obtained using electronic feedback to realize the first one-particle self-excited oscillator. The new methods may also allow a million times improved measurement of the 500 times small antiproton magnetic moment.

  7. A study on the immobilization of selenium oxyanions by H 2/Pd(s) in aqueous solution . Confirmation of the one-electron reduction barrier of selenate

    NASA Astrophysics Data System (ADS)

    Puranen, Anders; Jansson, Mats; Jonsson, Mats

    2010-07-01

    Selenium is a trace element of concern in several geochemical contexts, due to the potentially high mobility of the selenium oxyanions and the narrow range between deficiency and toxicity of the element. For high level nuclear waste repositories the long-lived fission product 79Se has been identified as a potential key dose contributor for the long-term safety. This paper deals with the catalytic effect of Pd(s) on the H 2 reduction of selenium oxyanions which was studied experimentally in aqueous solutions containing bicarbonate and chloride. Pd-catalysts and hydrogen have been proposed for the remediation of various groundwater contaminants and can also serve as a model substance for catalytic noble metal inclusions present in spent nuclear fuel. In this study selenite (SeO 32-) was found to adsorb on Pd. In the presence of hydrogen the rate of selenite removal increased yielding elemental Se. However, no adsorption or reduction of selenate (SeO 42-) was observed. A simple radiation chemical experiment revealed a notable barrier towards stepwise one-electron reduction of selenate to selenite. This provides an explanation for the lower reactivity of selenate in systems where reductive immobilization of selenite as well as selenate is thermodynamically favorable.

  8. Communication: Satisfying fermionic statistics in the modeling of open time-dependent quantum systems with one-electron reduced density matrices

    SciTech Connect

    Head-Marsden, Kade; Mazziotti, David A.

    2015-02-07

    For an open, time-dependent quantum system, Lindblad derived the most general modification of the quantum Liouville equation in the Markovian approximation that models environmental effects while preserving the non-negativity of the system’s density matrix. While Lindblad’s modification is correct for N-electron density matrices, solution of the Liouville equation with a Lindblad operator causes the one-electron reduced density matrix (1-RDM) to violate the Pauli exclusion principle. Consequently, after a short time, the 1-RDM is not representable by an ensemble N-electron density matrix (not ensemble N-representable). In this communication, we derive the necessary and sufficient constraints on the Lindbladian matrix within the Lindblad operator to ensure that the 1-RDM remains N-representable for all time. The theory is illustrated by considering the relaxation of an excitation in several molecules F{sub 2}, N{sub 2}, CO, and BeH{sub 2} subject to environmental noise.

  9. Deviations from one-electron behavior in the Ag and Pd M4,5-VV Auger spectra of AgcPd1-c alloys

    NASA Astrophysics Data System (ADS)

    Mariot, J.-M.; Hague, C. F.; Dufour, G.

    1981-04-01

    A systematic investigation of the Ag and Pd M4,5-VV Auger spectra in the pure metals and in the AgcPd1-c(0.1<=c<=0.9) alloys is presented. The shape of the Auger spectra is discussed in relation to the values of the effective Coulomb interaction Ueff between the two holes present in the final state of the Auger transition and of the width W of the one-electron local densities of states as obtained from Lβ2,15 soft-x-ray emission bands. The Auger spectra of Ag in the metal and the alloys have a pronounced quasiatomic character, as can be expected from the Ueff2W ratio which is found to be close to unity. The Auger spectrum of pure Pd (Ueff2W~0.4) can be explained in terms of an atomic model in which strong band effects are present. For alloys with low-Pd content where Pd forms an impurity state, it is shown that final states other than the localized [4d2] two-hole state have to be invoked to explain the line shape.

  10. Timing of multiple hydrothermal events in the iron oxide-copper-gold deposits of the Southern Copper Belt, Carajás Province, Brazil

    NASA Astrophysics Data System (ADS)

    Moreto, Carolina P. N.; Monteiro, Lena V. S.; Xavier, Roberto P.; Creaser, Robert A.; DuFrane, S. Andrew; Melo, Gustavo H. C.; Delinardo da Silva, Marco A.; Tassinari, Colombo C. G.; Sato, Kei

    2015-06-01

    The Southern Copper Belt, Carajás Province, Brazil, hosts several iron oxide-copper-gold (IOCG) deposits, including Sossego, Cristalino, Alvo 118, Bacuri, Bacaba, Castanha, and Visconde. Mapping and U-Pb sensitive high-resolution ion microprobe (SHRIMP) IIe zircon geochronology allowed the characterization of the host rocks, situated within regional WNW-ESE shear zones. They encompass Mesoarchean (3.08-2.85 Ga) TTG orthogneiss, granites, and remains of greenstone belts, Neoarchean (ca. 2.74 Ga) granite, shallow-emplaced porphyries, and granophyric granite coeval with gabbro, and Paleoproterozoic (1.88 Ga) porphyry dykes. Extensive hydrothermal zones include albite-scapolite, biotite-scapolite-tourmaline-magnetite alteration, and proximal potassium feldspar, chlorite-epidote and chalcopyrite formation. U-Pb laser ablation multicollector inductively coupled mass spectrometry (LA-MC-ICP-MS) analysis of ore-related monazite and Re-Os NTIMS analysis of molybdenite suggest multiple Neoarchean (2.76 and 2.72-2.68 Ga) and Paleoproterozoic (2.06 Ga) hydrothermal events at the Bacaba and Bacuri deposits. These results, combined with available geochronological data from the literature, indicate recurrence of hydrothermal systems in the Southern Copper Belt, including 1.90-1.88-Ga ore formation in the Sossego-Curral ore bodies and the Alvo 118 deposit. Although early hydrothermal evolution at 2.76 Ga points to fluid migration coeval with the Carajás Basin formation, the main episode of IOCG genesis (2.72-2.68 Ga) is related to basin inversion coupled with Neoarchean (ca. 2.7 Ga) felsic magmatism. The data suggest that the IOCG deposits in the Southern Copper Belt and those in the Northern Copper Belt (2.57-Ga Salobo and Igarapé Bahia-Alemão deposits) do not share a common metallogenic evolution. Therefore, the association of all IOCG deposits of the Carajás Province with a single extensive hydrothermal system is precluded.

  11. Acute paraquat exposure determines dose-dependent oxidative injury of multiple organs and metabolic dysfunction in rats: impact on exercise tolerance.

    PubMed

    Novaes, Rômulo D; Gonçalves, Reggiani V; Cupertino, Marli C; Santos, Eliziária C; Bigonha, Solange M; Fernandes, Geraldo J M; Maldonado, Izabel R S C; Natali, Antônio J

    2016-04-01

    This study investigated the pathological morphofunctional adaptations related to the imbalance of exercise tolerance triggered by paraquat (PQ) exposure in rats. The rats were randomized into four groups with eight animals each: (a) SAL (control): 0.5 ml of 0.9% NaCl solution; (b) PQ10: PQ 10 mg/kg; (c) PQ20: PQ 20 mg/kg; and (d) PQ30: PQ 30 mg/kg. Each group received a single injection of PQ. After 72 hours, the animals were subjected to an incremental aerobic running test until fatigue in order to determine exercise tolerance, blood glucose and lactate levels. After the next 24 h, lung, liver and skeletal muscle were collected for biometric, biochemical and morphological analyses. The animals exposed to PQ exhibited a significant anticipation of anaerobic metabolism during the incremental aerobic running test, a reduction in exercise tolerance and blood glucose levels as well as increased blood lactate levels during exercise compared to control animals. PQ exposure increased serum transaminase levels and reduced the glycogen contents in liver tissue and skeletal muscles. In the lung, the liver and the skeletal muscle, PQ exposure also increased the contents of malondialdehyde, protein carbonyl, 8-hydroxy-2'-deoxyguanosine, superoxide dismutase and catalase, as well as a structural remodelling compared to the control group. All these changes were dose-dependent. Reduced exercise tolerance after PQ exposure was potentially influenced by pathological remodelling of multiple organs, in which glycogen depletion in the liver and skeletal muscle and the imbalance of glucose metabolism coexist with the induction of lipid, protein and DNA oxidation, a destructive process not counteracted by the upregulation of endogenous antioxidant enzymes. PMID:27277193

  12. Multiple Pathways for Benzyl Alcohol Oxidation by RuV=O3+ and RuIV=O2+

    SciTech Connect

    Paul, Amit; Hull, Jonathan F.; Norris, Michael R.; Chen, Zuofeng; Ess, Daniel H.; Concepcion, Javier J.; Meyer, Thomas J.

    2011-01-20

    Significant rate enhancements are found for benzyl alcohol oxidation by the RuV=O3+ form of the water oxidation catalyst [Ru(Mebimpy)(bpy)(OH2)]2+ [Mebimpy = 2,6-bis(1-methylbenzimidazol-2-yl)pyridine; bpy = 2,2'-bipyridine] compared to RuIV=O2+ and for the RuIV=O2+ form with added bases due to a new pathway involving concerted hydride proton transfer (HPT).

  13. Multiple Pathways for Benzyl Alcohol Oxidation by RuV=O3+ and RuIV=O2+

    SciTech Connect

    Paul, Amit; Hull, Jonathan F.; Norris, Michael R.; Chen, Zuofeng; Ess, Daniel H.; Concepcion, Javier J.; Meyer, Thomas J.

    2011-01-20

    Significant rate enhancements are found for benzyl alcohol oxidation by the RuV=O3+ form of the water oxidation catalyst [Ru(Mebimpy)(bpy)(OH2)]2+ [Mebimpy = 2,6-bis(1-methylbenzimidazol-2-yl)pyridine; bpy = 2,2'-bipyridine] compared to RuIV=O2+ and for the RuIV=O2+ form with added bases due to a new pathway, concerted hydride proton transfer (HPT).

  14. H(2)O(2) detection from intact mitochondria as a measure for one-electron reduction of dioxygen requires a non-invasive assay system.

    PubMed

    Staniek, K; Nohl, H

    1999-10-01

    Evaluation of the existence of superoxide radicals (O*-(2)), the site of generation and conditions required for one-e(-) transfer to oxygen from biological redox systems is a prerequisite for the understanding of the deregulation of O(2) homeostasis leading to oxidative stress. Mitochondria are increasingly considered the major O*-(2) source in a great variety of diseases and the aging process. Contradictory reports on mitochondrial O*-(2) release prompted us to critically investigate frequently used O*-(2) detection methods for their suitability. Due to the impermeability of the external mitochondrial membrane for most constituents of O*-(2) detection systems we decided to follow the stable dismutation product H(2)O(2). This metabolite was earlier shown to readily permeate into the cytosol. With the exception of tetramethylbenzidine none of the chemical reactants indicating the presence of H(2)O(2) by horseradish peroxidase-catalyzed absorbance change were suited due to solubility problems or low extinction coefficients. Tetramethylbenzidine-dependent H(2)O(2) detection was counteracted by rereduction of the dye through e(-) carriers of the respiratory chain. Although the fluorescent dyes scopoletin and homovanillic acid were found to be suited for the detection of mitochondrial H(2)O(2) release, fluorescence change was strongly affected by mitochondrial protein constituents. The present study has resolved this problem by separating the detection system from H(2)O(2)-producing mitochondria. PMID:10514548

  15. One-electron reduction of iron(II) porphyrin and characterization of iron(I) porphyrin in aqueous medium. Steady-state and pulse radiolysis studies. [Gamma radiation

    SciTech Connect

    Brault, D.; Santus, R.; Land, E.J.; Swallow, A.J.

    1984-11-22

    Iron(II) deuteroporphyrin reacts with the reducing (CH/sub 3/)/sub 2/CO/sup -/ radicals produced by radiolysis of deoxygenated alkaline aqueous 2-propanol solutions with rate constant of (6.3 +/- 0.3) x 10/sup 8/ M/sup -1/ s/sup -1/. The product has the same optical spectrum whether obtained from steady-state or pulse irradiation. It reoxidizes slowly even in the absence of oxygen to the ferrous state with a rate constant of (1.35 +/- 0.15) x 10/sup -3/ s/sup -1/. Water is suggested as the oxidizing agent. When sodium dithionite is used, reoxidation is fast due to side reactions. The reoxidation of the radiolytic product to the ferric state in the presence of oxygen shows very good reversibility. The deuteroporphyrin anion radical produced by pulse radiolysis of deuteroporphyrin in the same solvent mixture is much less stable than the iron(II) deuteroporphyrin product, consistent with the view that the latter should be formulated as an iron(I) form.

  16. Lung injury in guinea pigs caused by multiple exposures to submicron zinc oxide mixed with sulfur dioxide in a humidified furnace

    SciTech Connect

    Conner, M.W.; Lam, H.F.; Rogers, A.E.; Fitzgerald, S.; Amdur, M.O.

    1985-01-01

    Sulfur dioxide, water vapor, and ultrafine particles rich in oxides of zinc and other surface-deposited trace elements are important products of coal combustion. In order to study the toxicity of zinc oxide generated under conditions simulating combustion, guinea pigs were exposed in a nose-only apparatus for 3 h on 6 consecutive days to 6 mg/mT of submicron zinc oxide particles (count median diameter of 0.05 m, sigma/sub g/ 2.0), which were generated in a humid furnace and mixed with 1 ppm sulfur dioxide. The exposures caused increases in lung weight and (TH)thymidine labeling index of terminal bronchiolar cell nuclei and inflammation of the proximal portion of the alveolar duct. The lung weights and labeling index had returned to normal and inflammatory changes had nearly resolved by 72 h after the last exposure. Total lung capacity, functional residual volume, alveolar volume, and diffusing capacity for carbon monoxide were decreased following exposure and had not returned to normal by 72 h after the last exposure. Large airways were not affected by the repeated exposures, as indicated by normal morphology of trachea and bronchi, unchanged secretory cell concentration, and unaltered epithelial permeability to horseradish peroxidase. These results are essentially identical to changes the authors reported in guinea pigs exposed to zinc oxide alone, suggesting that surface-deposited sulfur compounds, which are important determinants of the response to a single exposure to these ultrafine particles, become less important as exposure progresses.

  17. Phagocytes and oxidative stress.

    PubMed

    Babior, B M

    2000-07-01

    Neutrophils and other phagocytes manufacture O(2)(-) (superoxide) by the one-electron reduction of oxygen at the expense of NADPH. Most of the O(2)(-) reacts with itself to form H(2)O(2) (hydrogen peroxide). From these agents a large number of highly reactive microbicidal oxidants are formed, including HOCl (hypochlorous acid), which is produced by the myeloperoxidase-catalyzed oxidation of Cl(-) by H(2)O(2); OH(*) (hydroxyl radical), produced by the reduction of H(2)O(2) by Fe(++) or Cu(+); ONOO(-) (peroxynitrite), formed by the reaction between O(2)(-) and NO(*); and many others. These reactive oxidants are manufactured for the purpose of killing invading microorganisms, but they also inflict damage on nearby tissues, and are thought to be of pathogenic significance in a large number of diseases. Included among these are emphysema, acute respiratory distress syndrome, atherosclerosis, reperfusion injury, malignancy and rheumatoid arthritis. PMID:10936476

  18. The chemistry of rhenium and tungsten porphyrin complexes in low oxidation states. Synthesis and characterization of rhenium and tungsten porphyrin dimers containing metal-metal multiple bonds

    SciTech Connect

    Collmann, J.P.; Garner, J.M.; Woo, L.K. )

    1989-10-11

    The coordination chemistry of rhenium and tungsten porphyrin complexes in low oxidation states is presented. W{sup IV}(Por)(Cl){sub 2}, W{sup II}(Por)(H{sub 5}C{sub 6}C{identical to}CC{sub 6}H{sub 5}) and W{sup II}(OEP)(PEt{sub 3}){sub 2} complexes (Por = 5,10,15,20-tetra(4-tolyl)porphyrin (TTP) or 2,3,7,8,12,13,17,18-octaethylporphyrin (OEP) dianions) were found to be similar to the analogous molybdenum porphyrin complexes by spectroscopic and magnetic measurements. UV-visible and vibrational spectroscopies indicate that these oxidations occur at the metal-metal bond rather than the porphyrin ligand.

  19. Multiple-mask chemical etching

    NASA Technical Reports Server (NTRS)

    Cannon, D. L.

    1969-01-01

    Multiple masking techniques use lateral etching to reduce the total area of the high etch-rate oxide exposed to the chemical etchant. One method uses a short-term etch to remove the top layer from the silicon oxide surface, another acts before the top layer is grown.

  20. Multiple myeloma

    MedlinePlus

    Plasma cell dyscrasia; Plasma cell myeloma; Malignant plasmacytoma; Plasmacytoma of bone; Myeloma - multiple ... Multiple myeloma most commonly causes: Low red blood cell count ( anemia ), which can lead to fatigue and ...

  1. Multiple Sclerosis

    MedlinePlus

    Multiple sclerosis (MS) is a nervous system disease that affects your brain and spinal cord. It damages the ... attacks healthy cells in your body by mistake. Multiple sclerosis affects women more than men. It often begins ...

  2. Multiple Pregnancy

    MedlinePlus

    ... is called multiple pregnancy . If more than one egg is released during the menstrual cycle and each ... fraternal twins (or more). When a single fertilized egg splits, it results in multiple identical embryos. This ...

  3. Aqueous extract of some indigenous medicinal plants inhibits glycation at multiple stages and protects erythrocytes from oxidative damage-an in vitro study.

    PubMed

    Tupe, Rashmi S; Sankhe, Neena M; Shaikh, Shamim A; Phatak, Devyani V; Parikh, Juhi U; Khaire, Amrita A; Kemse, Nisha G

    2015-04-01

    Azadirachta indica, Emblica officinalis, Syzygium cumini and Terminalia bellirica are common in Indian system of traditional medicine for the prevention of diabetes and its complications. The aim of the present study was to comprehensively and comparatively investigate the antiglycation potential of these plant extracts at multiple stages and their possible protective effect against glycated albumin mediated toxicity to erythrocytes. Antiglycation activities of these plant extracts was measured by co-incubation of plant extract with bovine serum albumin-fructose glycation model. The multistage glycation markers- fructosamines (early stage), protein carbonyls (intermediate stage) and AGEs (late stage) are investigated along with measurement of thiols and β aggregation of albumin using amyloid-specific dyes-Congo red and Th T. Protection of erythrocytes from glycated albumin induced toxicity by these plant extracts was assessed by measuring erythrocytes hemolysis, lipid peroxidation, reduced glutathione and intracellular antioxidant capacity. Total phenolics, reducing power and antioxidant activities of the plant extracts were also measured. In vitro glycation assays showed that plant extracts exerted site specific inhibitory effects at multiple stages, with T. bellirica showing maximum attenuation. In erythrocytes, along with the retardation of glycated albumin induced hemolysis and lipid-peroxidation, T. bellirica considerably maintained cellular antioxidant potential. Significant positive correlations were observed between erythrocyte protection parameters with total phenolics. These plant extracts especially T. bellirica prevents glycation induced albumin modifications and subsequent toxicity to erythrocytes which might offer additional protection against diabetic vascular complications. PMID:25829572

  4. Finger Multiplication

    ERIC Educational Resources Information Center

    Simanihuruk, Mudin

    2011-01-01

    Multiplication facts are difficult to teach. Therefore many researchers have put a great deal of effort into finding multiplication strategies. Sherin and Fuson (2005) provided a good survey paper on the multiplication strategies research area. Kolpas (2002), Rendtorff (1908), Dabell (2001), Musser (1966) and Markarian (2009) proposed the finger…

  5. Multiple Sclerosis

    MedlinePlus

    ... Awards Enhancing Diversity Find People About NINDS NINDS Multiple Sclerosis Information Page Condensed from Multiple Sclerosis: Hope Through ... en Español Additional resources from MedlinePlus What is Multiple Sclerosis? An unpredictable disease of the central nervous system, ...

  6. The effects of oral Cardax (disodium disuccinate astaxanthin) on multiple independent oxidative stress markers in a mouse peritoneal inflammation model: influence on 5-lipoxygenase in vitro and in vivo.

    PubMed

    Lockwood, Samuel F; Penn, Marc S; Hazen, Stanley L; Bikádi, Zsolt; Zsila, Ferenc

    2006-06-01

    Disodium disuccinate astaxanthin ('rac'-dAST; Cardax) is a water-dispersible C40 carotenoid derivative under development for oral and parenteral administration for cardioprotection of the at-risk ischemic cardiovascular patient. In experimental infarction models in animals (rats, rabbits, and dogs), significant myocardial salvage has been obtained, up to 100% at the appropriate dose in dogs. The documented mechanism of action in vitro includes direct scavenging of biologically produced superoxide anion; in vivo in rabbits, modulation of the complement activity of serum has also been shown. A direct correlation between administration of the test compound in animals and reductions of multiple, independent markers of oxidative stress in serum was recently obtained in a rat experimental infarction model. For the current study, it was hypothesized that oral Cardax administration would inhibit oxidative damage of multiple relevant biological targets in a representative, well-characterized murine peritoneal inflammation model. A previously developed mass spectrometry-based (LC/ESI/MS/MS) approach was used to interrogate multiple distinct pathways of oxidation in a black mouse (C57/BL6) model system. In vivo markers of oxidant stress from peritoneal lavage samples (supernatants) were evaluated in mice on day eight (8) after treatment with either Cardax or vehicle (lipophilic emulsion without drug) orally by gavage at 500 mg/kg once per day for seven (7) days at five (5) time points: (1) baseline prior to treatment (t=0); (2) 16 h following intraperitoneal (i.p.) injection with thioglycollate to elicit a neutrophilic infiltrate; (3) 4 h following i.p. injection of yeast cell wall (zymosan; t=16 h/4 h thioglycollate+zymosan); (4) 72 h following i.p. injection with thioglycollate to elicit monocyte/macrophage infiltration; and (5) 72 h/4 h thioglycollate+zymosan. A statistically significant sparing effect on the arachidonic acid (AA) and linoleic acid (LA) substrates was

  7. Multiplicity Counting

    SciTech Connect

    Geist, William H.

    2015-12-01

    This set of slides begins by giving background and a review of neutron counting; three attributes of a verification item are discussed: 240Pueff mass; α, the ratio of (α,n) neutrons to spontaneous fission neutrons; and leakage multiplication. It then takes up neutron detector systems – theory & concepts (coincidence counting, moderation, die-away time); detector systems – some important details (deadtime, corrections); introduction to multiplicity counting; multiplicity electronics and example distributions; singles, doubles, and triples from measured multiplicity distributions; and the point model: multiplicity mathematics.

  8. Near-field-assisted localization: effect of size and filling factor of randomly distributed zinc oxide nanoneedles on multiple scattering and localization of light

    NASA Astrophysics Data System (ADS)

    Silies, Martin; Mascheck, Manfred; Leipold, David; Kollmann, Heiko; Schmidt, Slawa; Sartor, Janos; Yatsui, Takashi; Kitamura, Kokoro; Ohtsu, Motoicho; Kalt, Heinz; Runge, Erich; Lienau, Christoph

    2016-07-01

    We investigate the influence of the diameter and the filling factor of randomly arranged ZnO nanoneedles on the multiple scattering and localization of light in disordered dielectrics. Coherent, ultra-broadband second-harmonic (SH) microscopy is used to probe the spatial localization of light in representative nm-sized ZnO arrays of needles. We observe strong fluctuations of the SH intensity inside different ZnO needle geometries. Comparison of the SH intensity distributions with predictions based on a one-parameter scaling model indicate that SH fluctuations can be taken as a quantitative measure for the degree of localization. Interestingly, the strongest localization signatures are found for densely packed arrays of thin needles with diameters in the range of only 30 nm range, despite the small scattering cross section of these needles. FDTD simulations indicate that in this case coupling of electric near-fields between neighbouring needles governs the localization.

  9. Modeling coal chemistry: One electron catalytic reactions

    SciTech Connect

    Farcasiu, M.; Smith, C.; Hunter, E.A. )

    1991-01-01

    The complexity of the coal structure, in general, and of its organic part, in particular, prevents a rigorous study of coal chemistry. The use of model compounds with less complicated chemical structures to model specific reactions relevant to coal transformation into useful products is necessary and helpful. This is true, however, only if the modeling is properly applied and especially if the results are not excessively extrapolated to all aspects of coal reactivity. The emphasis on all catalytic routes in coal liquefaction has enhanced the interest in the study of the chemistry involved in heterogeneous catalytic reactions relevant to the first stage, solubilization, of coal. One of the important reactions associated with this first stage is the cleavage of carbon-carbon bonds linking aromatic rings with aliphatic moieties. In previous publications (1,2,3) we have used a model compound 4-(l-naphthylmethyl)bibenzyl (1) in which the bond linking the naphthalene ring to a methylene carbon can be selectively cleaved by specific catalysts (i.e. carbon materials, some iron catalysts) at temperatures at which thermal, free radical-initiated reactions, do not take place. Our data suggest that the above-mentioned catalytic cleavage is initiated by the ion radical of 1, with the unpaired electron localized in the naphthalene ring.

  10. Modeling coal chemistry: One electron catalytic reactions

    SciTech Connect

    Farcasiu, M.; Smith, C.; Hunter, E.A.

    1991-12-31

    The complexity of the coal structure, in general, and of its organic part, in particular, prevents a rigorous study of coal chemistry. The use of model compounds with less complicated chemical structures to model specific reactions relevant to coal transformation into useful products is necessary and helpful. This is true, however, only if the modeling is properly applied and especially if the results are not excessively extrapolated to all aspects of coal reactivity. The emphasis on all catalytic routes in coal liquefaction has enhanced the interest in the study of the chemistry involved in heterogeneous catalytic reactions relevant to the first stage, solubilization, of coal. One of the important reactions associated with this first stage is the cleavage of carbon-carbon bonds linking aromatic rings with aliphatic moieties. In previous publications (1,2,3) we have used a model compound 4-(l-naphthylmethyl)bibenzyl (1) in which the bond linking the naphthalene ring to a methylene carbon can be selectively cleaved by specific catalysts (i.e. carbon materials, some iron catalysts) at temperatures at which thermal, free radical-initiated reactions, do not take place. Our data suggest that the above-mentioned catalytic cleavage is initiated by the ion radical of 1, with the unpaired electron localized in the naphthalene ring.

  11. Enhancing optical power of GaN-based light-emitting diodes by nanopatterning on indium tin oxide with tunable fill factor using multiple-exposure nanosphere-lens lithography

    SciTech Connect

    Zhang, Yonghui; Wei, Tongbo Xiong, Zhuo; Chen, Yu; Zhen, Aigong; Shan, Liang; Zhao, Yun; Hu, Qiang; Li, Jinmin; Wang, Junxi

    2014-11-21

    In this study, the multiple-exposure nanosphere-lens lithography method utilizing the polystyrene nanospheres with focusing behavior is investigated and introduced to fabricate diverse photonic crystals (PCs) on indium tin oxide to enhance the optical output power of GaN-based light-emitting diode (LED). Simulated results indicate that the focused light intensity decreases with increasing tilted angle due to the shadow effect introduced by adjacent nanospheres. The fill factor of nanopattern is tunable by controlling tilted angles and exposure times. To attain quadruple PC without overlapping patterns, mathematical calculation model is used to define the optimum range of tilted angles. Angular emission patterns and three-dimensional finite-difference time domain simulated results indicate that the enhanced light extraction of PC LEDs results mainly from diffused scattering effects, and the diffraction effects of PC on light extracted efficiency increase with the increase of fill factor. Furthermore, it is confirmed that the multiple PC can extract more light from GaN into air than common PC with same period and fill factor.

  12. Reduced Graphene Oxide/Amaranth Extract/AuNPs Composite Hydrogel on Tumor Cells as Integrated Platform for Localized and Multiple Synergistic Therapy.

    PubMed

    Chang, Guanru; Wang, Yunlong; Gong, Baoyou; Xiao, Yazhong; Chen, Yan; Wang, Shaohua; Li, Shikuo; Huang, Fangzhi; Shen, Yuhua; Xie, Anjian

    2015-06-01

    Integration of multimodal treatment strategies combined with localized therapy to enhance antitumor efficacy and reduce side effects is still a challenge. Herein, a novel composite hydrogel containing rGO, amaranth extract (AE) and gold nanoparticles (AuNPs) was prepared by using AE as both reductant and cross-linking agent. The chlorophyll derivatives in AE were also employed as a photodynamic therapy drug. Meanwhile, AuNPs and rGO both have obvious photothermal effects and can accelerate the generation of cytotoxic singlet oxygen (1O2). The temperature increase of rGO/AE/AuNPs precursor is up to 6.3 °C under 808 nm laser irradiation at a power density of 200 mW·cm(-2). The hydrogel shell on in situ tumor cells was easily formed and regulated by near-infrared irradiation within 10 min, which could both retain a high concentration of drugs on the lesion site and prevent them from migrating to normal tissue, thus reducing the side effects. Compared with rGO/AE and AE, rGO/AE/AuNPs showed a remarkably improved and synergistic antitumor effect. The hydrogel possesses good biocompatibility and high hydrophilicity and could be used for loading chemotherapeutics, which provides a new approach for located and multiple antitumor therapies. PMID:25978657

  13. Evolution of Diterpene Metabolism: Sitka Spruce CYP720B4 Catalyzes Multiple Oxidations in Resin Acid Biosynthesis of Conifer Defense against Insects1[C][W][OA

    PubMed Central

    Hamberger, Björn; Ohnishi, Toshiyuki; Hamberger, Britta; Séguin, Armand; Bohlmann, Jörg

    2011-01-01

    Diterpene resin acids (DRAs) are specialized (secondary) metabolites of the oleoresin defense of conifers produced by diterpene synthases and cytochrome P450s of the CYP720B family. The evolution of DRA metabolism shares common origins with the biosynthesis of ent-kaurenoic acid, which is highly conserved in general (primary) metabolism of gibberellin biosynthesis. Transcriptome mining in species of spruce (Picea) and pine (Pinus) revealed CYP720Bs of four distinct clades. We cloned a comprehensive set of 12 different Sitka spruce (Picea sitchensis) CYP720Bs as full-length cDNAs. Spatial expression profiles, methyl jasmonate induction, and transcript enrichment in terpenoid-producing resin ducts suggested a role of CYP720B4 in DRA biosynthesis. CYP720B4 was characterized as a multisubstrate, multifunctional enzyme by the formation of oxygenated diterpenoids in metabolically engineered yeast, yeast in vivo transformation of diterpene substrates, in vitro assays with CYP720B4 protein produced in Escherichia coli, and alteration of DRA profiles in RNA interference-suppressed spruce seedlings. CYP720B4 was active with 24 different diterpenoid substrates, catalyzing consecutive C-18 oxidations in the biosynthesis of an array of diterpene alcohols, aldehydes, and acids. CYP720B4 was most active in the formation of dehydroabietic acid, a compound associated with insect resistance of Sitka spruce. We identified patterns of convergent evolution of CYP720B4 in DRA metabolism and ent-kaurene oxidase CYP701 in gibberellin metabolism and revealed differences in the evolution of specialized and general diterpene metabolism in a gymnosperm. The genomic and functional characterization of the gymnosperm CYP720B family highlights that the evolution of specialized metabolism involves substantial diversification relative to conserved, general metabolism. PMID:21994349

  14. Multiple myeloma

    PubMed Central

    2010-01-01

    Abstract Advances in the imaging and treatment of multiple myeloma have occurred over the past decade. This article summarises the current status and highlights how an understanding of both is necessary for optimum management. PMID:20159661

  15. Multiple myeloma.

    PubMed

    Raab, Marc S; Podar, Klaus; Breitkreutz, Iris; Richardson, Paul G; Anderson, Kenneth C

    2009-07-25

    Multiple myeloma is characterised by clonal proliferation of malignant plasma cells, and mounting evidence indicates that the bone marrow microenvironment of tumour cells has a pivotal role in myeloma pathogenesis. This knowledge has already expanded treatment options for patients with multiple myeloma. Prototypic drugs thalidomide, bortezomib, and lenalidomide have each been approved for the treatment of this disease by targeting both multiple myeloma cells and the bone marrow microenvironment. Although benefit was first shown in relapsed and refractory disease, improved overall response, duration of response, and progression-free and overall survival can be achieved when these drugs are part of first-line regimens. This treatment framework promises to improve outcome not only for patients with multiple myeloma, but also with other haematological malignancies and solid tumours. PMID:19541364

  16. Multiple Sclerosis

    MedlinePlus

    Multiple sclerosis (MS) is a nervous system disease that affects your brain and spinal cord. It damages the myelin sheath, the ... and your body, leading to the symptoms of MS. They can include Visual disturbances Muscle weakness Trouble ...

  17. Multiple myeloma

    MedlinePlus

    Plasma cell dyscrasia; Plasma cell myeloma; Malignant plasmacytoma; Plasmacytoma of bone; Myeloma - multiple ... myeloma most commonly causes a low red blood cell count ( anemia ), which can lead to fatigue and ...

  18. Multiple Sclerosis

    PubMed Central

    Hashimoto, S.A.; Jiwa, Theresa I.

    1991-01-01

    Successful management of patients with multiple sclerosis depends upon the involvement of the family physician. All contacts with either a multiple sclerosis clinic or a neurologist should be made at the instigation of the family practitioner. Constant contact with the family physician ensures that the individual receives proper care. While specialty care is needed for many of the symptoms, psychosocial problems are dealt with best by the individual's own family physician. PMID:21229090

  19. Application of least squares support vector regression and linear multiple regression for modeling removal of methyl orange onto tin oxide nanoparticles loaded on activated carbon and activated carbon prepared from Pistacia atlantica wood.

    PubMed

    Ghaedi, M; Rahimi, Mahmoud Reza; Ghaedi, A M; Tyagi, Inderjeet; Agarwal, Shilpi; Gupta, Vinod Kumar

    2016-01-01

    Two novel and eco friendly adsorbents namely tin oxide nanoparticles loaded on activated carbon (SnO2-NP-AC) and activated carbon prepared from wood tree Pistacia atlantica (AC-PAW) were used for the rapid removal and fast adsorption of methyl orange (MO) from the aqueous phase. The dependency of MO removal with various adsorption influential parameters was well modeled and optimized using multiple linear regressions (MLR) and least squares support vector regression (LSSVR). The optimal parameters for the LSSVR model were found based on γ value of 0.76 and σ(2) of 0.15. For testing the data set, the mean square error (MSE) values of 0.0010 and the coefficient of determination (R(2)) values of 0.976 were obtained for LSSVR model, and the MSE value of 0.0037 and the R(2) value of 0.897 were obtained for the MLR model. The adsorption equilibrium and kinetic data was found to be well fitted and in good agreement with Langmuir isotherm model and second-order equation and intra-particle diffusion models respectively. The small amount of the proposed SnO2-NP-AC and AC-PAW (0.015 g and 0.08 g) is applicable for successful rapid removal of methyl orange (>95%). The maximum adsorption capacity for SnO2-NP-AC and AC-PAW was 250 mg g(-1) and 125 mg g(-1) respectively. PMID:26414425

  20. [Multiple meningiomas].

    PubMed

    Terrier, L-M; François, P

    2016-06-01

    Multiple meningiomas (MMs) or meningiomatosis are defined by the presence of at least 2 lesions that appear simultaneously or not, at different intracranial locations, without the association of neurofibromatosis. They present 1-9 % of meningiomas with a female predominance. The occurrence of multiple meningiomas is not clear. There are 2 main hypotheses for their development, one that supports the independent evolution of these tumors and the other, completely opposite, that suggests the propagation of tumor cells of a unique clone transformation, through cerebrospinal fluid. NF2 gene mutation is an important intrinsic risk factor in the etiology of multiple meningiomas and some exogenous risk factors have been suspected but only ionizing radiation exposure has been proven. These tumors can grow anywhere in the skull but they are more frequently observed in supratentorial locations. Their histologic types are similar to unique meningiomas of psammomatous, fibroblastic, meningothelial or transitional type and in most cases are benign tumors. The prognosis of these tumors is eventually good and does not differ from the unique tumors except for the cases of radiation-induced multiple meningiomas, in the context of NF2 or when diagnosed in children where the outcome is less favorable. Each meningioma lesion should be dealt with individually and their multiple character should not justify their resection at all costs. PMID:27234913

  1. Multiple Sclerosis.

    ERIC Educational Resources Information Center

    Plummer, Nancy; Michael, Nancy, Ed.

    This module on multiple sclerosis is intended for use in inservice or continuing education programs for persons who administer medications in long-term care facilities. Instructor information, including teaching suggestions, and a listing of recommended audiovisual materials and their sources appear first. The module goal and objectives are then…

  2. Finger Multiplication

    ERIC Educational Resources Information Center

    Holmes, Bill

    2010-01-01

    The author has been prompted to write this article about finger multiplication for a number of reasons. Firstly there are a number of related articles in past issues of "Mathematics Teaching" ("MT") which have connections to this algorithm. Secondly, very few of his primary teaching students and professional colleagues appear to be aware of the…

  3. JS-K, a GST-activated nitric oxide generator, induces DNA double-strand breaks, activates DNA damage response pathways, and induces apoptosis in vitro and in vivo in human multiple myeloma cells.

    PubMed

    Kiziltepe, Tanyel; Hideshima, Teru; Ishitsuka, Kenji; Ocio, Enrique M; Raje, Noopur; Catley, Laurence; Li, Chun-Qi; Trudel, Laura J; Yasui, Hiroshi; Vallet, Sonia; Kutok, Jeffery L; Chauhan, Dharminder; Mitsiades, Constantine S; Saavedra, Joseph E; Wogan, Gerald N; Keefer, Larry K; Shami, Paul J; Anderson, Kenneth C

    2007-07-15

    Here we investigated the cytotoxicity of JS-K, a prodrug designed to release nitric oxide (NO(*)) following reaction with glutathione S-transferases, in multiple myeloma (MM). JS-K showed significant cytotoxicity in both conventional therapy-sensitive and -resistant MM cell lines, as well as patient-derived MM cells. JS-K induced apoptosis in MM cells, which was associated with PARP, caspase-8, and caspase-9 cleavage; increased Fas/CD95 expression; Mcl-1 cleavage; and Bcl-2 phosphorylation, as well as cytochrome c, apoptosis-inducing factor (AIF), and endonuclease G (EndoG) release. Moreover, JS-K overcame the survival advantages conferred by interleukin-6 (IL-6) and insulin-like growth factor 1 (IGF-1), or by adherence of MM cells to bone marrow stromal cells. Mechanistic studies revealed that JS-K-induced cytotoxicity was mediated via NO(*) in MM cells. Furthermore, JS-K induced DNA double-strand breaks (DSBs) and activated DNA damage responses, as evidenced by neutral comet assay, as well as H2AX, Chk2 and p53 phosphorylation. JS-K also activated c-Jun NH(2)-terminal kinase (JNK) in MM cells; conversely, inhibition of JNK markedly decreased JS-K-induced cytotoxicity. Importantly, bortezomib significantly enhanced JS-K-induced cytotoxicity. Finally, JS-K is well tolerated, inhibits tumor growth, and prolongs survival in a human MM xenograft mouse model. Taken together, these data provide the preclinical rationale for the clinical evaluation of JS-K to improve patient outcome in MM. PMID:17384201

  4. Nitric oxide synthases: structure, function and inhibition.

    PubMed Central

    Alderton, W K; Cooper, C E; Knowles, R G

    2001-01-01

    This review concentrates on advances in nitric oxide synthase (NOS) structure, function and inhibition made in the last seven years, during which time substantial advances have been made in our understanding of this enzyme family. There is now information on the enzyme structure at all levels from primary (amino acid sequence) to quaternary (dimerization, association with other proteins) structure. The crystal structures of the oxygenase domains of inducible NOS (iNOS) and vascular endothelial NOS (eNOS) allow us to interpret other information in the context of this important part of the enzyme, with its binding sites for iron protoporphyrin IX (haem), biopterin, L-arginine, and the many inhibitors which interact with them. The exact nature of the NOS reaction, its mechanism and its products continue to be sources of controversy. The role of the biopterin cofactor is now becoming clearer, with emerging data implicating one-electron redox cycling as well as the multiple allosteric effects on enzyme activity. Regulation of the NOSs has been described at all levels from gene transcription to covalent modification and allosteric regulation of the enzyme itself. A wide range of NOS inhibitors have been discussed, interacting with the enzyme in diverse ways in terms of site and mechanism of inhibition, time-dependence and selectivity for individual isoforms, although there are many pitfalls and misunderstandings of these aspects. Highly selective inhibitors of iNOS versus eNOS and neuronal NOS have been identified and some of these have potential in the treatment of a range of inflammatory and other conditions in which iNOS has been implicated. PMID:11463332

  5. Multiple sclerosis.

    PubMed

    Files, Daniel Kane; Jausurawong, Tani; Katrajian, Ruba; Danoff, Robert

    2015-06-01

    Multiple sclerosis (MS) is a chronic, debilitating disease that can have devastating effects. Presentation varies widely in symptoms, pace, and progression. In addition to a thorough history and physical examination, diagnostic tools required to diagnose MS and exclude other diagnoses include MRI, evoked potential testing, and cerebrospinal fluid analysis. Although the disease is not curable presently, quality of life can be improved by minimizing the frequency and severity of disease burden. Disease modification, symptom management, preservation of function, and treatment of psychosocial issues are paramount to enhance the quality of life for the patient affected with MS. PMID:25979578

  6. Multiple myeloma

    PubMed Central

    Rajkumar, S. Vincent

    2008-01-01

    Multiple myeloma is a clonal plasma cell malignancy that accounts for slightly more than 10% of all hematologic cancers. In this paper, we present a historically focused review of the disease, from the description of the first case in 1844 to the present. The evolution of drug therapy and stem-cell transplantation for the treatment of myeloma, as well as the development of new agents, is discussed. We also provide an update on current concepts of diagnosis and therapy, with an emphasis on how treatments have emerged from a historical perspective after certain important discoveries and the results of experimental studies. PMID:18332230

  7. Horseradish peroxidase catalyzed nitric oxide formation from hydroxyurea.

    PubMed

    Huang, Jinming; Sommers, Erin M; Kim-Shapiro, Daniel B; King, S Bruce

    2002-04-01

    Hydroxyurea represents an approved treatment for sickle cell anemia and a number of cancers. Chemiluminescence and electron paramagnetic resonance spectroscopic studies show horseradish peroxidase catalyzes the formation of nitric oxide from hydroxyurea in the presence of hydrogen peroxide. Gas chromatographic headspace analysis and infrared spectroscopy also reveal the production of nitrous oxide in this reaction, which provides evidence for nitroxyl, the one-electron reduced form of nitric oxide. These reactions also generate carbon dioxide, ammonia, nitrite, and nitrate. None of these products form within 1 h in the absence of hydrogen peroxide or horseradish peroxidase. Electron paramagnetic resonance spectroscopy and trapping studies show the intermediacy of a nitroxide radical and a C-nitroso species during this reaction. Absorption spectroscopy indicates that both compounds I and II of horseradish peroxidase act as one-electron oxidants of hydroxyurea. Nitroxyl, generated from Angeli's salt, reacts with ferric horseradish peroxidase to produce a ferrous horseradish peroxidase-nitric oxide complex. Electron paramagnetic resonance experiments with a nitric oxide specific trap reveal that horseradish peroxidase is capable of oxidizing nitroxyl to nitric oxide. A mechanistic model that includes the observed nitroxide radical and C-nitroso compound intermediates has been forwarded to explain the observed product distribution. These studies suggest that direct nitric oxide producing reactions of hydroxyurea and peroxidases may contribute to the overall pharmacological properties of this drug. PMID:11916434

  8. Photovoltaic multiplicities

    NASA Astrophysics Data System (ADS)

    Queisser, Hans J.

    1997-04-01

    A multicell solar energy converter, produced in 1959/60 at the Shockley Transistor Corporation, is reviewed. The feasibility of this device, one of the first involving principles of Si integrated circuits, was demonstrated in anticipation of large-area Si sheets, to be pulled from Si/Pb binary melts. Secondly, the generation of multiple carrier pairs by absorption of merely one photon is discussed. Experiments on high-quality Si solar cells demonstrated this effect, which relies on inverse Auger generation. In principle, much higher maximal conversion efficiencies would be possible; novel criteria for materials optimization result. The new challenge of the inverse band structure problem arises. Finally, multistage optical transitions via deep centers in solar cells are briefly appraised.

  9. [Multiple apheresis].

    PubMed

    Coffe, C

    2007-05-01

    Multiple apheresis makes it possible to obtain at least two labile blood components from a single donor using a cell separator. It can be either multicomponent apheresis leading to the preparation of at least two different blood component types or red blood cell apheresis providing two identical red blood cell concentrates. These techniques available in addition to whole blood donation, are modifying collection strategies in many Etablissements Français du Sang and will contribute to improve stock logistics in the future. In areas with insufficient stock, these procedures will help achieve blood component self-sufficiency. The author first describes the principle underlying different--current or future--techniques as well as their advantages and drawbacks. He finally addresses the potential impact of these processes on the evolution of blood collection and the advantages to be gained. PMID:17521944

  10. Multiple myeloma.

    PubMed

    Röllig, Christoph; Knop, Stefan; Bornhäuser, Martin

    2015-05-30

    Multiple myeloma is a malignant disease characterised by proliferation of clonal plasma cells in the bone marrow and typically accompanied by the secretion of monoclonal immunoglobulins that are detectable in the serum or urine. Increased understanding of the microenvironmental interactions between malignant plasma cells and the bone marrow niche, and their role in disease progression and acquisition of therapy resistance, has helped the development of novel therapeutic drugs for use in combination with cytostatic therapy. Together with autologous stem cell transplantation and advances in supportive care, the use of novel drugs such as proteasome inhibitors and immunomodulatory drugs has increased response rates and survival substantially in the past several years. Present clinical research focuses on the balance between treatment efficacy and quality of life, the optimum sequencing of treatment options, the question of long-term remission and potential cure by multimodal treatment, the pre-emptive treatment of high-risk smouldering myeloma, and the role of maintenance. Upcoming results of ongoing clinical trials, together with a pipeline of promising new treatments, raise the hope for continuous improvements in the prognosis of patients with myeloma in the future. PMID:25540889