Valence isomerization of hexamethyl(dewar benzene) radical cation. Pulse radiolytic investigation

International Nuclear Information System (INIS)

Gebicki, J.; Marcinek, A.; Mayer, J.

1989-01-01

Organic radical ions are important intermediates in a wide variety of electron-transfer reactions. Both the steady-state and time-resolved techniques have been extensively applied to probe various aspects of their chemistry. We have recently established that low-temperature pulse radiolysis can be successfully applied to the kinetic study of radical ion transformations with very low activation barriers. The target of the present investigation is the hexamethyl(Dewar benzene) (HMDB)-hexamethylbenzene (HMDB) system. Studies by the CIDNP technique indicated the presence of two distinguishable radical cations in the system HMDB-HMB. This view has not been supported by a nanosecond spectroscopic observation which failed to reveal any evidence for a radical cation other than HMB sm-bullet+ . The aim of this work is to present spectroscopic evidence for two different radical cations HMDB sm-bullet+ -HMB sm-bullet+ and the activation barrier for their interconversion

Isomerization of Second-Generation Isoprene Peroxy Radicals

DEFF Research Database (Denmark)

D'Ambro, Emma L.; Møller, Kristian Holten; Lopez-Hilfiker, Felipe D.

2017-01-01

kinetics box model, we find that to explain the behavior of low-volatility products and SOA mass yields relative to input H2O2 concentrations, the second-generation dihydroxy hydroperoxy peroxy radical (C5H11O6·) must undergo an intramolecular H-shift with a net forward rate constant of order 0.1 s-1...... products under atmospheric conditions and, thus, on the importance of nonreactive gas-particle partitioning of isoprene oxidation products as an SOA source....

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

International Nuclear Information System (INIS)

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

1992-01-01

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

Insights in the Rhodium-Catalyzed Tandem Isomerization-Hydroformylation of 10-Undecenitrile: Evidence for a Fast Isomerization Regime

Directory of Open Access Journals (Sweden)

Lucas Le Goanvic

2018-04-01

Full Text Available The tandem isomerization-hydroformylation of 10-undecenitrile (1 into the corresponding linear aldehyde (2 with a Rh-biphephos system was studied and the formation of internal olefin isomers (1-int-x was monitored over time. The existence of an “isomerization phenomenon” was evidenced, where fast isomerization of 1 into up to 70% of 1-int-x followed by fast back-isomerization of 1-int-x into 1 and, in turn, into 2 occurs. This fast dynamic isomerization regime is favored at high syngas pressure (40 bar and low biphephos-to-Rh ratio (5–10, and it is best observed at relatively high catalyst loadings ([1]0/[Rh] ≤ 3000. The latter regime is indeed evanescent, and gives place to a second stage in which isomerization of internal olefins (and eventual conversion into 2 proceeds much more slowly. The results are tentatively rationalized by the formation of an unstable species that promotes dynamic isomerization and which slowly vanishes or collapses into a Rh-biphephos species which is the one responsible for hydroformylation.

Collision dynamics of methyl radicals and highly vibrationally excited molecules using crossed molecular beams

International Nuclear Information System (INIS)

Chu, P.M.Y.

1991-10-01

The vibrational to translational (V→T) energy transfer in collisions between large highly vibrationally excited polyatomics and rare gases was investigated by time-of-flight techniques. Two different methods, UV excitation followed by intemal conversion and infrared multiphoton excitation (IRMPE), were used to form vibrationally excited molecular beams of hexafluorobenzene and sulfur hexafluoride, respectively. The product translational energy was found to be independent of the vibrational excitation. These results indicate that the probability distribution function for V→T energy transfer is peaked at zero. The collisional relaxation of large polyatomic molecules with rare gases most likely occurs through a rotationally mediated process. Photodissociation of nitrobenzene in a molecular beam was studied at 266 nm. Two primary dissociation channels were identified including simple bond rupture to produce nitrogen dioxide and phenyl radical and isomerization to form nitric oxide and phenoxy radical. The time-of-flight spectra indicate that simple bond rupture and isomerization occurs via two different mechanisms. Secondary dissociation of the phenoxy radicals to carbon monoxide and cyclopentadienyl radicals was observed as well as secondary photodissociation of phenyl radical to give H atom and benzyne. A supersonic methyl radical beam source is developed. The beam source configuration and conditions were optimized for CH 3 production from the thermal decomposition of azomethane. Elastic scattering of methyl radical and neon was used to differentiate between the methyl radicals and the residual azomethane in the molecular beam

Is isomerism a risk factor for intestinal volvulus?

Science.gov (United States)

Landisch, Rachel M; Loomba, Rohit S; Salazar, Jose H; Buelow, Matthew W; Frommelt, Michele; Anderson, Robert H; Wagner, Amy J

2018-03-06

Isomerism, or heterotaxy syndrome, affects many organ systems anatomically and functionally. Intestinal malrotation is common in patients with isomerism. Despite a low reported risk of volvulus, some physicians perform routine screening and prophylactic Ladd procedures on asymptomatic patients with isomerism who are found to have intestinal malrotation. The primary aim of this study was to determine if isomerism is an independent risk factor for volvulus. Kid's Inpatient Database data from 1997 to 2012 was utilized for this study. Characteristics of admissions with and without isomerism were compared with a particular focus on intestinal malrotation, volvulus, and Ladd procedure. A logistic regression was conducted to determine independent risk factors for volvulus with respect to isomerism. 15,962,403 inpatient admissions were included in the analysis, of which 7970 (0.05%) patients had isomerism, and 6 patients (0.1%) developed volvulus. Isomerism was associated with a 52-fold increase in the odds of intestinal malrotation by univariate analysis. Of 251 with isomerism and intestinal malrotation, only 2.4% experienced volvulus. Logistic regression demonstrated that isomerism was not an independent risk factor for volvulus. Isomerism is associated with an increased risk of intestinal malrotation but is not an independent risk factor for volvulus. Prognosis study. Level III. Copyright © 2018 Elsevier Inc. All rights reserved.

Quantum optimal control of ozone isomerization

International Nuclear Information System (INIS)

Artamonov, Maxim; Ho, Tak-San; Rabitz, Herschel

2004-01-01

We present a feasibility study of ozone isomerization based on a recent ab initio potential energy surface and a model Hamiltonian constructed by holding the bond lengths constant and using the valence angle as the isomerization coordinate. Optimal control theory is used to find an electric field that drives isomerization with a yield of 95% to the symmetric metastable triangular form of ozone. A frequency filter is applied as an additional spectral constraint limiting the field bandwidth. A post-facto analysis is performed showing a degree of inherent robustness of the isomerization yield to field noise

One-electron reduction of anthraquinone sulphonates: a pulse radiolysis study

International Nuclear Information System (INIS)

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

1991-01-01

Semiquinone free radicals, derived from 2-sulphonate, 1,5-disulphonate and 2,6-disulphonate derivatives of 9,10-anthraquinone, have been studied using pulse radiolysis and kinetic absorption spectrophotometry techniques. Spectroscopic characteristics of both neutral and anionic species have been ascertained. Kinetics of formation and decay, reactivity with oxygen and one-electron reduction potential values have been estimated. The semiquinone radicals have been shown to be very stable under suitable pH conditions where the equilibrium (2 semiquinone ↔ quinone + hydroquinone) lies predominantly to the left. From a measurement of the equilibrium constants at different pH, values of E 2 and E m have been calculated. (author)

Reduction of antitumour mitosenes in non-aqueous and aqueous environment. An electron spin resonance and cyclic voltammetry study

NARCIS (Netherlands)

Maliepaard, M.; de Mol, N.J.; Janssen, H.L.; Goeptar, A R; te Koppele, J.M.; Vermeulen, N P; Verboom, W.; Reinhoudt, David N

Chemical reduction of mitosenes under aerobic conditions in DMSO showed characteristic ESR signals of the mitosene derived semiquinone free radicals. However, these signals diminished strongly upon addition of water to the reaction mixture, indicating a short lifetime of the mitosene semiquinone

Reduction of antitumour mitosenes in non-aqueous and aqueous environment. An electron spin resonance and cyclic voltammetry study.

NARCIS (Netherlands)

Maliepaard, M.; de Mol, N.J.; Janssen, L.H.M.; Goeptar, A.R.; te Koppele, J.M.; Vermeulen, N.P.E.; Verboom, W.; Reinhoudt, D.N.

1995-01-01

Chemical reduction of mitosenes under aerobic conditions in DMSO showed characteristic ESR signals of the mitosene derived semiquinone free radicals. However, these signals diminished strongly upon addition of water to the reaction mixture, indicating a short lifetime of the mitosene semiquinone

Isomeric Targets and Beams

International Nuclear Information System (INIS)

Oganesyan, Yu.Ts.; Karamyan, S.A.

1994-01-01

One of the main topics of modern nuclear physics is the investigation of exotic nuclei including hyper-nuclei, trans fermium elements, proton and neutron rich isotopes near drip lines as well as high-spin excited states and states with anomalous deformation. The isomerism of nuclei is closely related with such phenomena as the alignment of single-particle orbitals, the coexistence of various deformations and the manifestation of intruder-levels from neighbouring shells. The investigation of electromagnetic and nuclear interactions of isomers could give important information on their shell structure and its role in the mechanism of nuclear reactions. For such experiments one can either make isomeric targets (sufficiently long-lived) or use the methods of acceleration of isomeric nuclei. Recently, an exotic 16 + four-quasiparticle isomer of 178 Hf m 2 was produced in a micro weight quantity and the first nuclear reactions on it were successfully observed. The talk describes these experiments as well as new ideas for the continuation of the studies and some advantageous ways for the isomeric beams production by the method of direct acceleration or by the secondary beam method. 35 refs., 15 figs., 8 tabs

One electron transfer equilibria and redox potentials of radicals studies by pulse radiolysis. Progress report, September 1, 1975--July 1, 1976

International Nuclear Information System (INIS)

Meisel, D.; Czapski, G.

1976-01-01

The pulse radiolysis technique is utilized for measurements of the equilibrium constants for electron transfer between the durosemiquinone radical anion and oxygen, menadione and indigo disulfonate. These equilibrium constants are in turn used for calculations of one-electron redox potentials for these systems. Each of these equilibrium constants was determined experimentally and independently and found to be self consistent. Only for the reactions of the semiquinones with oxygen could the electron transfer reaction be followed directly. For the reactions between the various quinone/semiquinone systems substantial indirect evidence is presented that these equilibria are achieved rapidly. In those cases equilibrium constants were determined from studies of the effect of quinone concentrations on the relative yields of the semiquinones. A method for distinguishing between kinetic competition and equilibrium is outlined and its usefulness is emphasized. The DQ/DQ - (DQ = duroquinone) and IDS/IDS - (IDS = indigo disulfonate) systems were employed as reference couples as the redox potentials for those systems are either available in the literature (IDS/IDS - ) or may be calculated from available data (DQ/DQ - ). Taking E 7 1 , the redox potential for the first one-electron reduction step at pH 7, of DQ/DQ - as -0.235 volts or of IDS/IDS - as -0.125 volts, both yield E 7 1 = -0.325 V for the O 2 /O 2 - system (1 atm O 2 ) and E 7 1 = -0.20 for the menadione system

Laser spectroscopy of hydrocarbon radicals

Energy Technology Data Exchange (ETDEWEB)

Chen, P. [Harvard Univ., Cambridge, MA (United States)

1993-12-01

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

Experimental grounds for nuclear shape isomerism

International Nuclear Information System (INIS)

Makarenko, V.E.

1995-11-01

Experimental data on fission isomeric states of actinide nuclei - half lives, energies, quantum numbers, decay branches and spectroscopic properties - are discussed. Quite a few results find their explanation in the framework of nuclear shape isomerism hypothesis being the in-thing for about thirty years. Others seem to be the hints to the quasiparticle nature of fission isomers. The problem could be solved by direct measurement of nuclear spin for isomeric states. (author). 44 refs, 1 tab

Xylene isomerization

KAUST Repository

Bilaus, Rakan Sulaiman; Pinnau, Ingo

2016-01-01

at isomenzation conditions and producing an isomerized product comprising a higher proportion of p-xylene than in the feed mixture, wherein the catalyst comprises an acidic sulfonated catalytic membrane. Xylene isomenzation can also be coupled with a p

Experiments with neutron-rich isomeric beams

International Nuclear Information System (INIS)

Rykaczewski, K.; Lewitowicz, M.; Pfuetzner, M.

1998-01-01

A review of experimental results obtained on microsecond-isomeric states in neutron-rich nuclei produced in fragmentation reactions and studied with SISSI-Alpha-LISE3 spectrometer system at GANIL Caen is given. The perspectives of experiments based on secondary reactions with isomeric beams are presented

One-electron reduction of 1,2-dihydroxy-9,10-anthraquinone and some of its transition metal complexes in aqueous solution and in aqueous isopropanol-acetone-mixed solvent: a steady-state and pulse radiolysis study

International Nuclear Information System (INIS)

Das, S.; Bhattacharya, A.; Mandal, P.C.; Rath, M.C.; Mukherjee, T.

2002-01-01

One-electron reduction of 1,2-dihydroxy-9,10-anthraquinone (DHA) and its complexes with Cu(II), Ni(II) and Fe(III), by acetone ketyl radical, (CH 3 ) 2 C·OH, was carried out in aqueous solution and in aqueous isopropanol acetone mixed solvent using both steady-state gamma radiolysis and pulse radiolysis techniques. The rate constants for the reduction of DHA at different pH values by the ketyl radical are in the order of ∼10 9 dm 3 mol -1 s -1 , whereas those for the metal complexes are comparatively less. These rate constants are, however, in conformity with the one-electron reduction potentials of the ligand in free DHA and in its metal complexes. Decay kinetics of the one-electron reduced semiquinones of the free ligand and its metal complexes suggest disproportionation of the semiquinone in the case of the free ligand and intermolecular electron transfer from the co-ordinated semiquinone radical to the metal centre in the case of the metal complexes

Synthesis, characterization and ESR study of polyesters containing isomeric naphthylene units by gamma irradiation

International Nuclear Information System (INIS)

Choi, B.K.; Hill, D.J.T.; Choi, E.J.; Ahn, H.K.

1998-01-01

Full text: Aromatic polyesters containing naphthalene groups have interesting properties because the geometry of the naphthalene group can provide many of the structural features for the polymer chain. In this study we synthesized six polyesters from 4,4 ' - (hexafluoroisopropyl-idene)bis(benzoic acid) and isomeric naphthylene-diols. An ESR study of the radicals formed on gamma radiolysis of the polyesters has been undertaken to investigate their relative radiation sensitivities. The structures of the polyesters were characterized by means of IR spectroscopy. Inherent viscosities were measured in the range of 0.11 - 0.46 dL/g. Thermal properties of polyesters were determined by DSC and TGA thermograms, respectively. All polyesters were irradiated in an AECL Gamma cell with a dose rate of approximately 6.7kGy h -1 to doses in the range of 0 - 15kGy at 77K and 300K, respectively. In order to identify other radicals present at 77K, annealing studies were utilized by taking advantage of the different reactivities of these radicals

Observation of vibronic emission spectrum of jet-cooled 3,5-difluorobenzyl radical.

Science.gov (United States)

Lee, Seung Woon; Yoon, Young Wook; Lee, Sang Kuk

2010-09-02

We applied the technique of corona-excited supersonic expansion using a pinhole-type glass nozzle to observe the vibronic emission spectrum of jet-cooled benzyl-type radicals from the corona discharge of precursor 3,5-difluorotoluene seeded in a large amount of inert helium carrier gas. The vibronically well-resolved emission spectrum was recorded with a long-path monochromator in the visible region. After subtracting the vibronic bands originating from isomeric difluorobenzyl radicals from the observed spectrum, we identified for the first time the bands belonging to the 3,5-difluorobenzyl radical, from which the electronic energy and vibrational mode frequencies of the 3,5-difluorobenzyl radical were accurately determined in the ground electronic state by comparison with those of the precursor and with those from an ab initio calculation.

Ti-Catalyzed Selective Isomerization of Terminal Mono-substituted Olefins

International Nuclear Information System (INIS)

Lee, Hyung Soo; Lee, Gab Yong

2005-01-01

The isomerization of olefins occurs either by a metal hydride addition-elimination or by a π-allyl metal hydride intermediate. HCo(CO) 4 , [(C 2 H 4 ) 2 RhCl] 2 , Ni[P(OEt) 3 ] 4 , and PtCl 2 (PPh 3 ) 2 -SnCl 2 are effective catalysts for isomerization of olefins via a metal hydride addition-elimination mechanism, 3,4 and Fe 3 (CO) 12 catalyzed isomerization of 3-ethyl-1-pentene and isomerization of 1-heptene catalyzed by (PhCN) 2 PdCl 2 occur via a π-allyl metal hydride mechanism. The cis/trans ratio of 2-butene obtained from isomerization of 1-butene by RhH(CO)(PPh 3 ) 3 has also been investigated. The skeletal isomerization of olefins catalyzed by (R 3 P) 2 NiCl 2 is developed such as conversion of cis-1,4-hexadiene to trans-2-methyl-1,3-pentadiene. Titanium complexes serve as an effective catalysts for a variety of reactions such as hydroalumination, hydroboration, and hydrogenation of unsaturated hydrocarbons. We have been interested in the selective reactions of unsaturated hydrocarbons by using titanium and zirconium compounds. The reagent system composed of LiAlH 4 /Cp 2 TiCl 2 ≤ 2 in the molar ratio promotes the isomerization of 1-octene, but the detailed reaction for isomerization of olefins has not been reported. We report here a selective isomerization of olefins with low valent titanium complex generated from Cp 2 TiCl 2 (Cp=cyclopentadienyl) and LiAlH 4

Cat's claw oxindole alkaloid isomerization induced by common extraction methods

Directory of Open Access Journals (Sweden)

Samuel Kaiser

2013-01-01

Full Text Available Cat's claw oxindole alkaloids are prone to isomerization in aqueous solution. However, studies on their behavior in extraction processes are scarce. This paper addressed the issue by considering five commonly used extraction processes. Unlike dynamic maceration (DM and ultrasound-assisted extraction, substantial isomerization was induced by static maceration, turbo-extraction and reflux extraction. After heating under reflux in DM, the kinetic order of isomerization was established and equations were fitted successfully using a four-parameter Weibull model (R² > 0.999. Different isomerization rates and equilibrium constants were verified, revealing a possible matrix effect on alkaloid isomerization.

One-electron reduction of 9,10-anthraquinone, 1-amino-9,10-anthraquinone and 1-hydroxy-9,10-anthraquinone in aqueous-isopropanol-acetone mixed solvent: a pulse radiolysis study

International Nuclear Information System (INIS)

Pal, H.; Mukherjee, T.; Mittal, J.P.

1994-01-01

The semiquinone radicals produced by one-electron reduction of 9,10-anthraquinone, 1-amino- 9,10-anthraquinone and 1-hydroxy-9,10-anthraquinone have been characterized in aqueous-organic mixed solvent comprising of 30.2 mol dm -3 water, 5 mol dm -3 isopropanol and 1 mol dm -3 acetone, using the pulse radiolysis technique. Spectroscopic characteristics, the kinetic parameters of formation and decay and one acid dissociation constants of the semiquinones and one-electron reduction potentials of the quinones have been estimated. The characteristics of the present semiquinone systems have been compared with those of other similar systems. The observed differences in characteristics of the semiquinones due to different substitutions have been analysed. (Author)

Mechanism of free radical generation in platelets and primary hepatocytes: A novel electron spin resonance study.

Science.gov (United States)

Wang, Chiun-Lang; Yang, Po-Sheng; Tsao, Jeng-Ting; Jayakumar, Thanasekaran; Wang, Meng-Jiy; Sheu, Joen-Rong; Chou, Duen-Suey

2018-01-01

Oxygen free radicals have been implicated in the pathogenesis of toxic liver injury and are thought to be involved in cardiac dysfunction in the cirrhotic heart. Therefore, direct evidence for the electron spin resonance (ESR) detection of how D‑galactosamine (GalN), an established experimental hepatotoxic substance, induced free radicals formation in platelets and primary hepatocytes is presented in the present study. ESR results demonstrated that GalN induced hydroxyl radicals (OH•) in a resting human platelet suspension; however, radicals were not produced in a cell free Fenton reaction system. The GalN‑induced OH• formation was significantly inhibited by the cyclooxygenase (COX) inhibitor indomethasin, though it was not affected by the lipoxygenase (LOX) or cytochrome P450 inhibitors, AA861 and 1‑aminobenzotriazole (ABT), in platelets. In addition, the present study demonstrated that baicalein induced semiquinone free radicals in platelets, which were significantly reduced by the COX inhibitor without affecting the formed OH•. In the mouse primary hepatocytes, the formation of arachidonic acid (AA) induced carbon‑centered radicals that were concentration dependently enhanced by GalN. These radicals were inhibited by AA861, though not affected by indomethasin or ABT. In addition, GalN did not induce platelet aggregation prior to or following collagen pretreatment in human platelets. The results of the present study indicated that GalN and baicalein may induce OH• by COX and LOX in human platelets. GalN also potentiated AA induced carbon‑centered radicals in hepatocytes via cytochrome P450. The present study presented the role of free radicals in the pathophysiological association between platelets and hepatocytes.

Reaction kinetics of resveratrol with thiyl and alkoxyl radicals

International Nuclear Information System (INIS)

Dzeba, I.; Mihaljevic, B.

2011-01-01

Complete text of publication follows. Plant derived resveratrol (trans-3,5,4'-trihydroxystilbene) possesses a broad spectrum of biological activities, one of them are very well known its antioxidative properties. Our work aims to provide kinetic data with regard to the reactivity of resveratrol with uninvestigated short-lived bioradicals, identified as mediators in oxidative lipid degradation processes. Radicals of our interest are alkoxyl radicals, well known propagators of the chain free radical reactions in lipids, and thiyl radicals which protect lipids from their degradation pathway, but at the same time cause the isomerization of the double bonds. In order to investigate these reactions of resveratrol laser flash photolysis was used. On the basis of competitive kinetics the rate constants were determined under pseudo-first order conditions in acetonitrile solutions at room temperature. Thiyl radicals were generated indirectly in solution containing 1-octadecanthiol and photosensitive benzophenone in acetonitrile using the light pulses at 347 nm from ruby laser. Tert-butoxyl radicals were generated directly by peroxide bond cleavage from di-tert-butyl peroxide in acetonitrile by light pulses of Nd:YAG at 355 nm, and ruby at 347 nm. Obtained rate constants for the reactions of resveratrol and radicals generated by laser flash photolysis will be summarized and compared with rare literature data for the rate constants of investigated reactions of resveratrol and other radicals generated by pulse radiolysis.

Isomers chart; Table des isomeres

Energy Technology Data Exchange (ETDEWEB)

Dupont-Gautier, P; Chantelot, S; Moisson, N [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1967-07-01

The nuclear isomers are nuclides offering the same mass number and the same atomic number, but different energy levels. In the following chart the zero energy ground states are omitted and the metastable isomers, i.e. of non-zero energy, known and of measurable lifetime, are listed. The lower limit of this lifetime was set here to 0.1 x 10{sup -6} s. The various isomers were classified in increasing lifetimes. (authors) [French] Les isomeres nucleaires sont des nucleides presentant le meme nombre de masse et le meme numero atomique, mais des niveaux energetiques differents. Dans la table suivante, on a neglige les etats fondamentaux d'energie nulle et on a recense les isomeres metastables, c'est-a-dire d'energie non nulle, connus et de periode mesurable. La limite inferieure de cette periode a ete fixee ici a 0,1 x 10{sup -6} s. Les differents isomeres ont ete classes par periodes croissantes. (auteurs)

Isomers chart; Table des isomeres

Energy Technology Data Exchange (ETDEWEB)

Dupont-Gautier, P.; Chantelot, S.; Moisson, N. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1967-07-01

The nuclear isomers are nuclides offering the same mass number and the same atomic number, but different energy levels. In the following chart the zero energy ground states are omitted and the metastable isomers, i.e. of non-zero energy, known and of measurable lifetime, are listed. The lower limit of this lifetime was set here to 0.1 x 10{sup -6} s. The various isomers were classified in increasing lifetimes. (authors) [French] Les isomeres nucleaires sont des nucleides presentant le meme nombre de masse et le meme numero atomique, mais des niveaux energetiques differents. Dans la table suivante, on a neglige les etats fondamentaux d'energie nulle et on a recense les isomeres metastables, c'est-a-dire d'energie non nulle, connus et de periode mesurable. La limite inferieure de cette periode a ete fixee ici a 0,1 x 10{sup -6} s. Les differents isomeres ont ete classes par periodes croissantes. (auteurs)

EFFECT OF CADMIUM(II) ON FREE RADICALS IN DOPA-MELANIN TESTED BY EPR SPECTROSCOPY.

Science.gov (United States)

Zdybel, Magdalena; Pilawa, Barbara; Chodurek, Ewa

2015-01-01

Electron paramagnetic resonance (EPR) spectroscopy may be applied to examine interactions of melanin with metal ions and drugs. In this work EPR method was used to examination of changes in free radical system of DOPA-melanin--the model eumelanin after complexing with diamagnetic cadmium(II) ions. Cadmium(II) may affect free radicals in melanin and drugs binding by this polymer, so the knowledge of modification of properties and free radical concentration in melanin is important to pharmacy. The effect of cadmium(II) in different concentrations on free radicals in DOPA-melanin was determined. EPR spectra of DOPA-melanin, and DOPA-melanin complexes with cadmium(II) were measured by an X-band (9.3 GHz) EPR spectrometer produced by Radiopan (Poznań, Poland) and the Rapid Scan Unit from Jagmar (Krak6w, Poland). The DOPA (3,4-dihydroxyphenylalanine) to metal ions molar ratios in the reaction mixtures were 2:1, 1:1, and 1: 2. High concentrations of o-semiquinone (g ~2.0040) free radicals (~10(21)-10(22) spin/g) characterize DOPA-melanin and its complexes with cadmium(II). Formation of melanin complexes with cadmium(II) increase free radical concentration in DOPA-melanin. The highest free radical concentration was obtained for DOPA-melanin-cadmium(II) (1:1) complexes. Broad EPR lines with linewidths: 0.37-0.73 mT, were measured. Linewidths increase after binding of cadmium(II) to melanin. Changes of integral intensities and linewidths with increasing microwave power indicate the homogeneous broadening of EPR lines, independently on the metal ion concentration. Slow spin-lattice relaxation processes existed in all the tested samples, their EPR lines saturated at low microwave powers. Cadmium(II) causes fastening of spin-lattice relaxation processes in DOPA-melanin. The EPR results bring to light the effect of cadmium(II) on free radicals in melanin, and probably as the consequence on drug binding to eumelanin.

Easy Synthesis of Two Positional Isomeric Tetrazole Libraries

NARCIS (Netherlands)

Wang, Yuanze; Patil, Pravin; Dömling, Alexander

2016-01-01

A fast and efficient synthesis of libraries of positional isomeric 1H-tetrazoles and 5H-tetrazoles, for the purpose of testing binding hypothesis of isomeric tetrazoles in fragment-based drug discovery, is described.

Kinetics and mechanism of the reaction of recombination of vinyl and hydroxyl radicals

Science.gov (United States)

Knyazev, Vadim D.

2017-10-01

The recombination of the vinyl (C2H3) and the hydroxyl (OH) radicals was studied computationally using quantum chemistry and master equation/RRKM. The reaction mechanism includes the initial addition, several isomerization steps, and decomposition via seven different channels. The spectrum of products demonstrates temperature dependence in the 300-3000 K range. At low temperatures (below 1600 K), CH3 + HCO products are dominant but at elevated temperatures vinoxy radical (CH2CHO) and hydrogen atom become more important. The acetyl (CH3CO) + H products and formation of vinylidene (CH2C:) and water products are minor but non-negligible.

Tracer kinetic investigations on isomerization and synthesis of /sup 8/C-aromates. II. Isomerization of ethylbenzene by means of heterogeneous catalysts

Energy Technology Data Exchange (ETDEWEB)

Dermietzel, J; Roesseler, M; Jockisch, W; Wienhold, C [Akademie der Wissenschaften der DDR, Leipzig. Zentralinstitut fuer Isotopen- und Strahlenforschung; Franke, H; Klempin, J; Barz, H J [VEB Petrolchemisches Kombinat Schwedt (German Democratic Republic)

1978-01-01

The mechanism of ethylbenzene isomerization on Pt/Al/sub 2/O/sub 3/ catalysts by means of /sup 14/C labelled compounds has been investigated, measuring the isotope distribution between ring and alkyl carbon atoms. The results suggest that ethylbenzene isomerizes via structure rearrangement involving ring carbon atoms. A similar mechanism takes place in xylene isomerization under increased hydrogen partial pressure, while under normal pressure 1,2-methyl group shifting is dominating. All three xylenes are formed from ethylbenzene by parallel reactions.

One electron reduction of 1,2 dihydroxy 9,10 anthraquinone and its transition metal complexes in aqueous-isopropanol-acetone mixed solvent: a steady state-state and pulse radiolysis study

International Nuclear Information System (INIS)

Das, Saurabh; Mandal, Parikshit C.; Rath, Madhab C.; Mukherjee, Tulsi

1998-01-01

One electron reduction of 1,2 dihydroxy 9,10 anthraquinone and its Cu(II) and Ni(II) and Fe(III) complexes have been studied in aqueous-isopropanol-acetone solvent. Results indicate that the reducing ketyl radical generated reacts with the ligand forming semiquinones which undergoes a disproportionation reaction. Formation and decay rates of semiquinones was calculated using pulse radiolysis. (author)

Graphene oxide catalyzed cis-trans isomerization of azobenzene

Directory of Open Access Journals (Sweden)

Dongha Shin

2014-09-01

Full Text Available We report the fast cis-trans isomerization of an amine-substituted azobenzene catalyzed by graphene oxide (GO, where the amine functionality facilitates the charge transfer from azobenzene to graphene oxide in contrast to non-substituted azobenzene. This catalytic effect was not observed in stilbene analogues, which strongly supports the existence of different isomerization pathways between azobenzene and stilbene. The graphene oxide catalyzed isomerization is expected to be useful as a new photoisomerization based sensing platform complementary to GO-based fluorescence quenching methods.

Reaction of Pentanol isomers with OH radical – A theoretical perspective

Science.gov (United States)

Aazaad, Basheer; Lakshmipathi, Senthilkumar

2018-05-01

The stability of all the three isomeric forms of Pentanol has been examined with relative energy analysis. Even though 2-Pentanol is predicted to be most stable isomeric form, all the three isomeric forms undergo hydrogen atom abstraction reaction with OH radical. Among the proposed 18 different hydrogen atom abstraction reaction, the abstraction from CH2 and CH functional group is found to be a favourable reactive site with low energy barrier in M06-2X/6-311+G(d,p) level of theory. Wiberg bond order analysis shows all the abstraction reactions are concreted but not synchronic in nature. Using force analysis, the calculated work done of individual reaction regions illustrates that structural rearrangements drive the reaction with higher contribution to the energy barrier. The rate constant calculated at M06-2X method for the most favourable reaction is well matched with available experimental data. Using the reported atmospheric OH concentration (1 × 106 molecules/cm3), the life time of 1-Pentanol, 2-Pentanol and 3-Pentanol has calculated to be 18.66, 0.36 and 2.86 days, respectively.

Radical zinc-atom-transfer-based carbozincation of haloalkynes with dialkylzincs

Directory of Open Access Journals (Sweden)

Fabrice Chemla

2013-02-01

Full Text Available The formation of alkylidenezinc carbenoids by 1,4-addition/carbozincation of dialkylzincs or alkyl iodides based on zinc atom radical transfer, in the presence of dimethylzinc with β-(propargyloxyenoates having pendant iodo- and bromoalkynes, is disclosed. Formation of the carbenoid intermediate is fully stereoselective at −30 °C and arises from a formal anti-selective carbozincation reaction. Upon warming, the zinc carbenoid is stereochemically labile and isomerizes to its more stable form.

Free radicals produced by the oxidation of gallic acid: An electron paramagnetic resonance study

Directory of Open Access Journals (Sweden)

Wagner Brett A

2010-08-01

Full Text Available Abstract Background Gallic acid (3,4,5-trihydroxybenzoic acid is found in a wide variety of plants; it is extensively used in tanning, ink dyes, as well as in the manufacturing of paper. The gallate moiety is a key component of many functional phytochemicals. In this work electron paramagnetic spectroscopy (EPR was used to detect the free radicals generated by the air-oxidation of gallic acid. Results We found that gallic acid produces two different radicals as a function of pH. In the pH range between 7-10, the spectrum of the gallate free radical is a doublet of triplets (aH = 1.00 G, aH = 0.23 G, aH = 0.28 G. This is consistent with three hydrogens providing hyperfine splitting. However, in a more alkaline environment, pH >10, the hyperfine splitting pattern transforms into a 1:2:1 pattern (aH (2 = 1.07 G. Using D2O as a solvent, we demonstrate that the third hydrogen (i.e. aH = 0.28 G at lower pH is a slowly exchanging hydron, participating in hydrogen bonding with two oxygens in ortho position on the gallate ring. The pKa of this proton has been determined to be 10. Conclusions This simple and novel approach permitted the understanding of the prototropic equilibrium of the semiquinone radicals generated by gallic acid, a ubiquitous compound, allowing new insights into its oxidation and subsequent reactions.

[Correlation of Persistent Free Radicals, PCDD/Fs and Metals in Waste Incineration Fly Ash].

Science.gov (United States)

Wang, Tian-jiao; Chen, Tong; Zhan, Ming-xiu; Guo, Ying; Li, Xiao-dong

2016-03-15

Environmentally persistent free radicals (EPFRs) are relatively highly stable and found in the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Recent studies have concentrated on model dioxin formation reactions and there are few studies on actual waste incineration fly ash. In order to study EPFRs and the correlation with dioxins and heavy metals in waste incineration fly ash, the spins of EPFRs, concentration of PCDD/Fs and metals in samples from 6 different waste incinerators were detected. The medical waste incineration fly ash from Tianjin, municipal solid waste incineration fly ash from Jiangxi Province, black carbon and slag from municipal solid waste incinerator in Lanxi, Zhejiang Province, all contained EPFRs. Above all the signal in Tianjin sample was the strongest. Hydroxyl radicals, carbon-center radicals and semiquinone radicals were detected. Compared with other samples, Jiangxi fly ash had the highest toxic equivalent quantity (TEQ) of dioxins, up to 7.229 4 ng · g⁻¹. However, the dioxin concentration in the Tianjin sample containing the strongest EPFR signals was only 0.092 8 ng · g⁻¹. There was perhaps little direct numeric link between EPFRs and PCDD/Fs. But the spins of EPFRs in samples presented an increasing trend as the metal contents increased, especially with Al, Fe, Zn. The signal strength of radicals was purposed to be related to the metal contents. The concentration of Zn (0.813 7% ) in the Tianjin sample was the highest and this sample contained much more spins of oxygen-center radicals. We could presume the metal Zn had a greater effect on the formation of EPFRs, and was easier to induce the formation of radicals with a longer half-life period.

Thermal E/ Z Isomerization in First Generation Molecular Motors.

Science.gov (United States)

Kuwahara, Shunsuke; Suzuki, Yuri; Sugita, Naoya; Ikeda, Mari; Nagatsugi, Fumi; Harada, Nobuyuki; Habata, Yoichi

2018-04-20

Determination of a thermal E/ Z isomerization barrier of first generation molecular motors is reported. Stable ( E)-1a directly converts to stable ( Z)-1c without photochemical E/ Z isomerization. The activation Gibbs energy of the isomerization was determined to be 123 kJ mol -1 by circular dichroism spectral changes. Density functional theory calculations show that ( Z)-1c is ∼11.4 kJ mol -1 more stable than ( E)-1a.

Designing bifunctional alkene isomerization catalysts using predictive modelling

NARCIS (Netherlands)

Landman, I.R.; Paulson, E.R.; Rheingold, A.L.; Grotjahn, D.B.; Rothenberg, G.

2017-01-01

Controlling the isomerization of alkenes is important for the manufacturing of fuel additives, fine-chemicals and pharmaceuticals. But even if isomerization seems to be a simple unimolecular process, the factors that govern catalyst performance are far from clear. Here we present a set of models

Iodine-Catalyzed Isomerization of Dimethyl Muconate

Energy Technology Data Exchange (ETDEWEB)

Settle, Amy E [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Berstis, Laura R [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Zhang, Shuting [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Rorrer, Nicholas [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Hu, Haiming [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Richards, Ryan [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Beckham, Gregg T [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Crowley, Michael F [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Vardon, Derek R [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

2018-04-12

cis,cis-Muconic acid is a platform biobased chemical that can be upgraded to drop-in commodity and novel monomers. Among the possible drop-in products, dimethyl terephthalate can be synthesized via esterification, isomerization, Diels-Alder cycloaddition, and dehydrogenation. The isomerization of cis,cis-dimethyl muconate (ccDMM) to the trans,trans-form (ttDMM) can be catalyzed by iodine; however, studies have yet to address (i) the mechanism and reaction barriers unique to DMM, and (ii) the influence of solvent, potential for catalyst recycle, and recovery of high-purity ttDMM. To address this gap, we apply a joint computational and experimental approach to investigate iodine-catalyzed isomerization of DMM. Density functional theory calculations identified unique regiochemical considerations due to the large number of halogen-diene coordination schemes. Both transition state theory and experiments estimate significant barrier reductions with photodissociated iodine. Solvent selection was critical for rapid kinetics, likely due to solvent complexation with iodine. Under select conditions, ttDMM yields of 95% were achieved in <1 h with methanol, followed by high purity recovery (>98%) with crystallization. Lastly, post-reaction iodine can be recovered and recycled with minimal loss of activity. Overall, these findings provide new insight into the mechanism and conditions necessary for DMM isomerization with iodine to advance the state-of-the-art for biobased chemicals.

Photodissociaton of allyl-d2 iodide excited at 193 nm: Stability of highly rotationally excited H2CDCH2 radicals to C-D fission

International Nuclear Information System (INIS)

Szpunar, D.E.; Liu, Y.; McCullagh, M.J.; Butler, L.J.; Shu, J.

2003-01-01

The photodissociation of allyl-d2 iodide (H2C=CDCH2I) and the dynamics of the nascent allyl-d2 radical (H2CCDCH2) were studied using photofragment translational spectroscopy. A previous study found the allyl radical stable at internal energies up to 15 kcal/mol higher than the 60 kcal/mol barrier to allene + H formation as the result of a centrifugal barrier. The deuterated allyl radical should then also show a stability to secondary dissociation at internal energies well above the barrier due to centrifugal effects. A comparison in this paper shows the allyl-d2 radical is stable to allene + D formation at energies of 2-3 kcal/mol higher than that of the non-deuterated allyl radical following photolysis of allyl iodide at 193 nm. This is most likely a result of a combination of the slight raising of the barrier from the difference in zero-point levels and a reduction of the impact parameter of the dissociative fragments due to the decrease in frequency of the C-D bending modes, and the refore allene + D product orbital angular momentum. Integrated signal taken at m/e = 40 (allene) and m/e = 41 (allene-d1 and propyne-d3) shows a minor fraction of the allyl-d2 radicals isomerize to the 2-propenyl radical, in qualitative support of earlier conclusions of the domination of direct allene + H formation over isomerization

Characterizing gamma fields using isomeric activation ratios

Science.gov (United States)

Venkataraman, Ramkumar; Fleming, Ronald F.

1994-12-01

Isomeric activities were induced in indium by gamma irradiation in three different gamma fields, through the reactions 115In(γ, γ') 115mIn and 113In(γ, γ') 113mIn. The irradiation fields were (i) the 15 kCi 60Co source available in the University, (ii) the spent fuel gamma irradiator in the pool of the University's Ford Nuclear Reactor (FNR) and (iii) south face of the core of the FNR during routine shut downs. Isomeric activation ratios can serve to characterize gamma fields, provided the response functions of the two (γ, γ') reactions sample different energy regimes of the gamma spectrum present in the irradiation fields. The response of an isomeric activation detector, in turn, depends on the number of activation energy levels of the nuclide and the probabilities with which the activation levels de-populate to the isomeric level. The reaction rate ratio RIn115m/ RIn113m was measured in the three gamma fields. The measured ratios were (i) 1.210 ± 0.011 in the 60Co source, (ii) 1.314 ± 0.060 in the spent fuel gamma irradiator and (iii) 1.298 ± 0.039 in a location alongside the FNR core during routine shut downs. The measured reaction rate ratios are not only close to each other, but close to unity as well. This indicates that the excitation functions for the reactions 115In(γ, γ') 115mIn and 113In(γ, γ') 113mIn have similar shapes and that for the nuclides 115In and 113In, the number of activation energy levels and the probabilities with which they populate the isomeric levels are very similar to each other. Thus, the ratio RIn115m/ RIn113m will not yield any information regarding the shape of gamma spectrum in the field of measurement. However by choosing (γ, γ') reactions with different shapes for the excitation functions one can measure a set of isomeric activation ratios that characterize a given gamma field.

Radiochemical study of isomerization of free butyl cations

International Nuclear Information System (INIS)

Sinotova, E.N.; Nefedov, V.D.; Skorokhodov, S.S.; Arkhipov, Yu.M.

1987-01-01

Ion-molecular reactions of free butyl cations, generated by nuclear chemical method, with carbon monoxide containing small quantities of ethanol vapors are studied. Carbon monoxide was used to fix instable butyl cations in the form of corresponding acyl ions. Ester of α-methyl-butyric acid appears to be the only product of free butyl cation interaction with carbon monoxide in the presence of ethanol vapors. That means, that up to the moment of butyl cation reaction with carbon monoxide, the primary butyl cations are almost completely isomerized into secondary in agreement with results of previous investigations. This allows one to study free butyl cation isomerization process according to ion-molecular reaction product isomeric composition

Highly Functionalized and Potent Antiviral Cyclopentane Derivatives Formed by a Tandem Process Consisting of Organometallic, Transition-Metal-Catalyzed, and Radical Reaction Steps

Czech Academy of Sciences Publication Activity Database

Jagtap, Pratap; Ford, Leigh Robert; Deister, E.; Pohl, Radek; Císařová, I.; Hodek, Jan; Weber, Jan; Mackman, R.; Bahador, G.; Jahn, Ullrich

2014-01-01

Roč. 20, č. 33 (2014), s. 10298-10304 ISSN 0947-6539 R&D Projects: GA ČR GA203/09/1936 Institutional support: RVO:61388963 Keywords : antiviral activity * cyclopentanes * isomerization * organic synthesis * radicals Subject RIV: CC - Organic Chemistry Impact factor: 5.731, year: 2014

EPR examination of Zn2+ and Cu2+ binding by pigmented soil fungi Cladosporium cladosporioides

International Nuclear Information System (INIS)

Buszman, Ewa; Pilawa, Barbara; Zdybel, Magdalena; Wilczynski, Slawomir; Gondzik, Anna; Witoszynska, Teresa; Wilczok, Tadeusz

2006-01-01

The purpose of this study was to examine the usefulness of electron paramagnetic resonance spectroscopy (EPR) to estimate zinc and copper ions biosorption from the environment by pigmented soil fungi Cladosporium cladosporioides. The existence of a low amount of pheomelanin, besides eumelanin, in C. cladosporioides samples was proved by the analysis of shape of their EPR spectra. Concentration of o-semiquinone free radicals in crude mycelium was 2.4 x 10 17 spin/g. Changes in free radicals system of C. cladosporioides cultured in the presence of Zn 2+ and Cu 2+ were analysed. Both magnetic and chemical interactions of zinc and copper ions with free radicals in C. cladosporioides melanin were found. Magnetically interacting diamagnetic Zn 2+ ions increased the concentration of o-semiquinone free radicals in melanin existing in C. cladosporioides mycelium, whereas paramagnetic Cu 2+ ions decreased this concentration. Chemical interactions of Zn 2+ and Cu 2+ ions decreased the free radical concentrations in C. cladosporioides melanin. Homogeneously distributed free radicals in C. cladosporioides melanin rise its activity in biosorption processes

Isomeric states in 253No and 253Fm

International Nuclear Information System (INIS)

Antalic, S.; Kalaninova, Z.; Saro, S.; Venhart, M.; Hessberger, F.P.; Ackermann, D.; Heinz, S.; Kindler, B.; Khuyagbaatar, J.; Kojouharov, I.; Kuusiniemi, P.; Lommel, B.; Mann, R.; Sulignano, B.; Hofmann, S.; Leino, M.; Nishio, K.; Streicher, B.

2011-01-01

Nuclear structure and decay of isomeric states in 253 No were investigated. The isotope was produced by the reaction 48 Ca + 207 Pb. The excitation energy of the known single-particle isomeric state (5/2 + [622]) was measured by delayed coincidences between γ-rays and implanted evaporation residues and was placed into the level scheme. In addition, decay of a high-lying multi-quasiparticle isomer in 253 No was studied using e - -γ coincidence measurements. A rotational band populated by its de-excitation was identified in 253 No. A new isomeric state in 253 Fm was observed and a partial-level scheme for this isotope is suggested. In addition γ transitions from excited levels are reported for 253 Md. (orig.)

Xylene isomerization

KAUST Repository

Bilaus, Rakan Sulaiman

2016-06-23

A process for producing xylenes, in particular para-xylene that is less energy intensive than conventional processes is provided. In an embodiment the process comprises contacting a feed mixture in an isomenzation zone with a catalyst at isomenzation conditions and producing an isomerized product comprising a higher proportion of p-xylene than in the feed mixture, wherein the catalyst comprises an acidic sulfonated catalytic membrane. Xylene isomenzation can also be coupled with a p-xylene extraction process, where the raffinate (p-xylene deprived stream) from the extraction process is fed to an isomenzation reactor to produce p-xylene. In an embodiment, the process can comprise: a) providing a feed stream comprising a mixture of xylene isomers including p-xylene; b) extracting p-xylene from the feed stream using a separator to separate the feed stream into a p-xylene rich stream and a p-xylene deprived stream; and c) delivering the p-xylene deprived stream to an isomenzation unit, the isomenzation unit including an acidic sulfonated catalytic membrane, and using the isomenzation unit to produce an isomerized product comprising a higher proportion of p-xylene than in the p-xylene deprived stream delivered to the isomenzation unit. In any one or more aspects, the isomenzation unit can be operated at a temperature in the range of less than 350°, for example about 20°C to about 200°C.

EPR studies of the vitamin K 1 semiquinone radical anion. Comparison to the electron acceptor A 1 in green plant photosystem I

Science.gov (United States)

Thurnauer, Marion C.; Brown, James W.; Gast, P.; Feezel, Laura L.

Suggestions that the electron acceptor, A 1, in Photosystem I is a quinone have come from both optical and epr experiments. Vitamin K 1 (phylloquinone) is present in the PSI complex with a stoichiometry of two molecules per reaction center. In order to determine if A 1 can be identified with vitamin K 1, X-band and Q-band epr properties of the vitamin K 1 radical anion in frozen alcohol solutions are examined. The results are compared to the epr properties that have been observed for the reduced A 1 acceptor in vivo. The g-values obtained for the vitamin K 1 radical anion are consistent with identifying A 1 with vitamin K 1.

A new fundamental type of conformational isomerism

Science.gov (United States)

Canfield, Peter J.; Blake, Iain M.; Cai, Zheng-Li; Luck, Ian J.; Krausz, Elmars; Kobayashi, Rika; Reimers, Jeffrey R.; Crossley, Maxwell J.

2018-06-01

Isomerism is a fundamental chemical concept, reflecting the fact that the arrangement of atoms in a molecular entity has a profound influence on its chemical and physical properties. Here we describe a previously unclassified fundamental form of conformational isomerism through four resolved stereoisomers of a transoid (BF)O(BF)-quinoxalinoporphyrin. These comprise two pairs of enantiomers that manifest structural relationships not describable within existing IUPAC nomenclature and terminology. They undergo thermal diastereomeric interconversion over a barrier of 104 ± 2 kJ mol-1, which we term `akamptisomerization'. Feasible interconversion processes between conceivable synthesis products and reaction intermediates were mapped out by density functional theory calculations, identifying bond-angle inversion (BAI) at a singly bonded atom as the reaction mechanism. We also introduce the necessary BAI stereodescriptors parvo and amplo. Based on an extended polytope formalism of molecular structure and stereoisomerization, BAI-driven akamptisomerization is shown to be the final fundamental type of conformational isomerization.

Isomerization of C[sub 4] alkenes

Science.gov (United States)

Smith, L.A. Jr.

1984-11-13

A method is described for isomerizing isobutene or n-butene to produce a mixture of isobutene and normal butene, and polymerizing at least a portion thereof to produce isobutene/n-butene co-dimer, which comprises feeding at least 80 weight % of either the isobutene or n-butene to a catalytic distillation reactor containing a fixed bed acidic cation exchange resin catalyst packing which provides both the catalyst sites and distillation sites for the reaction products, isomerizing a portion of the isobutene or n-butene to produce a mixture of isobutene and n-butene and reacting at least a portion of the isobutene and n-butene to form co-dimer of isobutene and n-butene, whereby an overhead fraction containing any unreacted isobutene and n-butene and a bottoms fraction containing co-dimer is produced. The result of the reaction is substantially the same regardless whether the feed is isobutene or n-butene. Other aspects of the invention, include combinations of procedures to produce high purity isobutene and n-butene. Either isobutene or n-butene product (depending on the desired product) can be recycled as feed, thus substantially carrying out the isomerization to extinction and total conversion to the desired product. 1 fig.

Evaluation of excitation functions for isomeric levels in neutron reactions

International Nuclear Information System (INIS)

Grudzevich, O.T.; Zelenetskij, A.V.; Zolotarev, K.I.; Kornilov, N.V.; Pashchenko, A.B.

1993-07-01

The authors consider the use of theoretical models to describe experimental excitation functions for isomeric levels in neutron reactions and to predict the cross-sections when no experimental data are available. It is shown that, in many cases, experimental data can be described quite satisfactorily by calculations without adjustment of parameters. For threshold reactions at a neutron energy of ∼ 14 MeV the agreement between calculated and experimental isomeric ratios is ∼ 20%, and is determined mainly by errors in the experimental ratios. However, for some reactions there are considerable differences between experimental and calculated data, which are due, in the authors' opinion, to uncertainties in the schemes of the low-lying levels and of gamma transitions between levels and to the spin dependence of level density. The small isomeric ratio values R<0.1 are described with the lowest accuracy. A formula is suggested for the energy dependence of the isomeric ratio in the (n,γ) reaction. (author)

Glucose Isomerization by Enzymes and Chemo-catalysts: Status and Current Advances

DEFF Research Database (Denmark)

Li, Hu; Yang, Song; Saravanamurugan, Shunmugavel

2017-01-01

of isomerization of aldoses in terms of yields, catalysts, solvents, catalytic systems, etc., by both enzymatic and chemo-catalytic approaches. Among aldose ketose interconversion reactions, fructose production by glucose isomerization to make high-fructose corn syrup (HFCS) is an industrially important and large....../intermediate fructose. This review focuses on how both enzyme and chemo-catalysts are being useful for the isomerization of glucose to fructose. Specifically, development of Lewis acid containing zeolites for glucose isomerization is reviewed in detail, including mechanism, isotopic labeling, and computational studies....... biocatalytic process today, and a large number of studies have been reported on the process development. In parallel, also alternative chemo-catalytic systems have emerged, as enzymatic conversion has drawbacks, though they are typically more selective and produce fructose under mild reaction conditions...

Ab Initio Chemical Kinetics for the CH3 + O((3)P) Reaction and Related Isomerization-Decomposition of CH3O and CH2OH Radicals.

Science.gov (United States)

Xu, Z F; Raghunath, P; Lin, M C

2015-07-16

The kinetics and mechanism of the CH3 + O reaction and related isomerization-decomposition of CH3O and CH2OH radicals have been studied by ab initio molecular orbital theory based on the CCSD(T)/aug-cc-pVTZ//CCSD/aug-cc-pVTZ, CCSD/aug-cc-pVDZ, and G2M//B3LYP/6-311+G(3df,2p) levels of theory. The predicted potential energy surface of the CH3 + O reaction shows that the CHO + H2 products can be directly generated from CH3O by the TS3 → LM1 → TS7 → LM2 → TS4 path, in which both LM1 and LM2 are very loose and TS7 is roaming-like. The result for the CH2O + H reaction shows that there are three low-energy barrier processes including CH2O + H → CHO + H2 via H-abstraction and CH2O + H → CH2OH and CH2O + H → CH3O by addition reactions. The predicted enthalpies of formation of the CH2OH and CH3O radicals at 0 K are in good agreement with available experimental data. Furthermore, the rate constants for the forward and some key reverse reactions have been predicted at 200-3000 K under various pressures. Based on the new reaction pathway for CH3 + O, the rate constants for the CH2O + H and CHO + H2 reactions were predicted with the microcanonical variational transition-state/Rice-Ramsperger-Kassel-Marcus (VTST/RRKM) theory. The predicted total and individual product branching ratios (i.e., CO versus CH2O) are in good agreement with experimental data. The rate constant for the hydrogen abstraction reaction of CH2O + H has been calculated by the canonical variational transition-state theory with quantum tunneling and small-curvature corrections to be k(CH2O + H → CHO + H2) = 2.28 × 10(-19) T(2.65) exp(-766.5/T) cm(3) molecule(-1) s(-1) for the 200-3000 K temperature range. The rate constants for the addition giving CH3O and CH2OH and the decomposition of the two radicals have been calculated by the microcanonical RRKM theory with the time-dependent master equation solution of the multiple quantum well system in the 200-3000 K temperature range at 1 Torr to

Pulse radiolytic one-electron reduction of 2-hydroxy- and 2,6-dihydroxy-9,10-anthraquinones

International Nuclear Information System (INIS)

Pal, Haridas; Mukherjee, Tulsi; Mittal, J.P.

1994-01-01

The semiquinone free radicals produced by one-electron reduction of 2-hydroxy-9-10-anthraquinone (2HAQ) and 2,6-dihydroxy-9,10-anthraquinone (26DHAQ) in aqueous formate solution, water-isopropyl alcohol-acetone mixed solvent and isopropyl alcohol have been studied using the pulse radiolysis technique. The absorption characteristics, kinetic parameters of formation and decay, acid-base behaviour and redox characteristics of the semiquinones have been investigated and compared with the corresponding characteristics of a few intramolecularly hydro-bonded anthrasemiquinone derivatives. The non-hydrogen-bonded semiquinones show two pKsub(a) values (4.7 and 10.7 for 2HAQ and 5.4 and 8.7 for 26DHAQ, respectively) within the pH range 1-14, whereas other intramolecularly hydrogen-bonded semiquinones show only one pKsub(a). The one-electron reduction potential (E' 7 ) values for 2HAQ (-440 mV) and 26DHAQ (- 400 mV) are more negative than those of the intramolecularly hydrogen-bonded systems. (Author)

High-spin μs isomeric states in 96 Ag

International Nuclear Information System (INIS)

Becerril, A. D.; Lorusso, G.; Amthor, A. M.; Brown, B. A.; Estrade, A.; Guess, C. J.; Hitt, G. W.; Meharchand, R.; Schatz, H.; Smith, K.; Zegers, R. G. T.; Baumann, T.; Bazin, D.; Ginter, T.; Hausmann, M.; Minamisono, K.; Portillo, M.; Stolz, A.; Berryman, J. S.; Crawford, H. L.

2011-01-01

The isomeric and β decays of the N=Z+2 nucleus 96 Ag were investigated at the National Superconducting Cyclotron Laboratory. A cascade of γ-ray transitions originating from the deexcitation of a microsecond isomer was observed for the first time and was found in coincidence with two previously known transitions with energies of 470 and 667 keV. The isomeric half-life was determined as 1.45(7) μs, more precise than previously reported. The existence of a second, longer-lived microsecond isomer, associated with a 743-keV γ transition, is also proposed here. Shell model results within the (p 3/2 p 1/2 f 5/2 g 9/2 ) model space, using the jj44b interaction, reproduced level energies and isomeric decay half-lives reasonably well.

Xylose Isomerization with Zeolites in a Two-Step Alcohol–Water Process

DEFF Research Database (Denmark)

Paniagua, Marta; Shunmugavel, Saravanamurugan; Melián Rodriguez, Mayra

2015-01-01

Isomerization of xylose to xylulose was efficiently catalyzed by large-pore zeolites in a two-step methanol–water process that enhanced the product yield significantly. The reaction pathway involves xylose isomerization to xylulose, which, in part, subsequently reacts with methanol to form methyl...

Structural characteristics of marine sedimentary humic acids by CP/MAS sup(13)C NMR spectroscopy

Digital Repository Service at National Institute of Oceanography (India)

Sardessai, S.; Wahidullah, S.

quino- nes or semiquinones which exhibit 13C resonance at around 195 ppm. Free radicals of semiquinone type have been reported from the aquatic environment [2]. Spectra of all the four samples show absorption at 195 ppm. The total acidity of marine..., significant resonance at 55 ppm (8.9) from aromatic methoxy carbon suggests that phenol is present mostly as methyl ether and not as free phenol. The signal at 55 ppm is also attributed to aliphatic carbon adjacent to the amino functional group as in amino...

The development of isomerization catalysts for production of high-octane products

Energy Technology Data Exchange (ETDEWEB)

Pedrosa, A.M. Garrido; Melo, D.M.A.; Araujo, A.S. [Universidade Federal do Rio Grande do Norte, Natal, RN (Brazil). Dept. de Quimica; Souza, M.J.B.; Silva, A.O.S. [Universidade Federal do Rio Grande do Norte, Natal, RN (Brazil). Dept. de Engenharia Quimica

2004-07-01

In current petroleum industry, paraffins larger than C5 are used for catalytic reform. The catalytic reform is one of the most important processes for petroleum refine in reason of all reactions they drive to production of high-octane products. Reformate has high-octane products, but they contain 60% aromatics. Isomerization of C5- C7 can improve the octane number. The octane number of n-heptane is zero and increases after isomerization. For tri branched C7, the octane number reaches 113, which is higher than that of benzene. So, isomerization of C5-C7 is suggested to be a reasonable way to replace or partly replace the catalytic reforming process. It can decrease aromatics content with enhancement of octane number. Liquid acid catalysts were widely used in chemical industry in past decades. However, they face strong environmental challenges. The heavy corrosion of the reactor system is one of the main problems. Thus, solid acid catalysts are investigated for the isomerization reactions. The aim of this work is to develop a catalysts for the production of reformate products. Isomerization is catalyzed by metal-acid bifunctional catalysts. The metal components aid in hydrogenation, while the support, such as, zirconium, clays or zeolites, is the acidic component. (author)

Cryo-EM structure of isomeric molluscan hemocyanin triggered by viral infection.

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Hongtao Zhu

Full Text Available Hemocyanins (Hcs of arthropods and mollusks function not only as oxygen transporters, but also as phenoloxidases (POs. In invertebrates, PO is an important component in the innate immune cascade, where it functions as the initiator of melanin synthesis, a pigment involved in encapsulating and killing of pathogenic microbes. Although structures of Hc from several species of invertebrates have been reported, the structural basis for how PO activity is triggered by structural changes of Hc in vivo remains poorly understood. Here, we report a 6.8 Å cryo-electron microscopy (cryo-EM structure of the isomeric form of hemocyanin, which was isolated from Abalone Shriveling syndrome-associated Virus (AbSV infected abalone (Halitotis diversicolor, and build a pseudoatomic model of isomeric H. diversicolor hemocyanin 1 (HdH1. Our results show that, compared with native form of HdH1, the architecture of isomeric HdH1 turns into a more relaxed form. The interactions between certain functional units (FUs present in the native form of Hc either decreased or were totally abolished in the isomeric form of Hc. As a result of that, native state Hc switches to its isomeric form, enabling it to play its role in innate immune responses against invading pathogens.

Improving gasoline quality produced from MIDOR light naphtha isomerization unit

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M.F. Mohamed

2017-03-01

Full Text Available Isomerization process became one of the best gasoline production sources, as it gives a high octane product while saving environment from pollution impacts. This paper presents a practical study that aims to improve the gasoline quality and economic income of an existing light naphtha isomerization unit used for octane improvement. The study included selecting the optimum combination of isomerization unit equipment that gives better product specifications for a specified feed. Eight scenarios were studied and simulated to predict the product specs. The original studied unit is MIDOR light naphtha isomerization unit at Alexandria-Egypt that recycles the unconverted hexane (C6. The other studied scenarios were adding fractionators for separating feed iso-pentanes, and recycling unconverted pentanes, hexanes and/or combinations of these fractionators. The results show a change in octane number of gasoline product for a specific feed. Once through process with no extra fractionators has lower octane number of 81 while that with de-iso-pentanizer–de-pentanizer and de-hexanizer produces gasoline with 92.3 octane number. Detailed economic study was done to calculate the return on investment “ROI” for each process option based on equipment, utilities, feed and product prices. Once through simple isomerization unit had the lowest ROI of 14.3% per year while the combination of De-iso-pentanizer with the De-hexanizer had the best ROI of 26.6% per year.

Isomerization Intermediates In Solution Phase Photochemistry Of Stilbenes

Science.gov (United States)

Doany, F. E.; Hochstrasser, R. M.; Greene, B. I.

1985-04-01

Picosecond and subpicosecond spectroscopic studies have revealed evidence for an isomerization intermediate between cis and trans in the photoinduced isomerism of both stilbene and biindanyledene ("stiff" stilbene). In stiff stilbene, a transient absorption at 351 nm displays time evolution and viscosity dependence consistent with absorption by a twisted intermediate ("phantom" state) with a lOps lifetime. An analagous bottleneck state with a life-time of 4ps is also consistent with the ground state recovery dynamics of t-stilbene following excitation of c-stilbene when monitored with 0.1ps resolution.

cis–trans Isomerization of silybins A and B

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Michaela Novotná

2014-05-01

Full Text Available Methods were developed and optimized for the preparation of the 2,3-cis- and the 10,11-cis-isomers of silybin by the Lewis acid catalyzed (BF3∙OEt2 isomerization of silybins A (1a and B (1b (trans-isomers. The absolute configuration of all optically pure compounds was determined by using NMR and comparing their electronic circular dichroism data with model compounds of known absolute configurations. Mechanisms for cis–trans-isomerization of silybin are proposed and supported by quantum mechanical calculations.

Why Nature Uses Radical SAM Enzymes so Widely: Electron Nuclear Double Resonance Studies of Lysine 2,3-Aminomutase Show the 5'-dAdo• "Free Radical" Is Never Free.

Science.gov (United States)

Horitani, Masaki; Byer, Amanda S; Shisler, Krista A; Chandra, Tilak; Broderick, Joan B; Hoffman, Brian M

2015-06-10

Lysine 2,3-aminomutase (LAM) is a radical S-adenosyl-L-methionine (SAM) enzyme and, like other members of this superfamily, LAM utilizes radical-generating machinery comprising SAM anchored to the unique Fe of a [4Fe-4S] cluster via a classical five-membered N,O chelate ring. Catalysis is initiated by reductive cleavage of the SAM S-C5' bond, which creates the highly reactive 5'-deoxyadenosyl radical (5'-dAdo•), the same radical generated by homolytic Co-C bond cleavage in B12 radical enzymes. The SAM surrogate S-3',4'-anhydroadenosyl-L-methionine (anSAM) can replace SAM as a cofactor in the isomerization of L-α-lysine to L-β-lysine by LAM, via the stable allylic anhydroadenosyl radical (anAdo•). Here electron nuclear double resonance (ENDOR) spectroscopy of the anAdo• radical in the presence of (13)C, (2)H, and (15)N-labeled lysine completes the picture of how the active site of LAM from Clostridium subterminale SB4 "tames" the 5'-dAdo• radical, preventing it from carrying out harmful side reactions: this "free radical" in LAM is never free. The low steric demands of the radical-generating [4Fe-4S]/SAM construct allow the substrate target to bind adjacent to the S-C5' bond, thereby enabling the 5'-dAdo• radical created by cleavage of this bond to react with its partners by undergoing small motions, ∼0.6 Å toward the target and ∼1.5 Å overall, that are controlled by tight van der Waals contact with its partners. We suggest that the accessibility to substrate and ready control of the reactive C5' radical, with "van der Waals control" of small motions throughout the catalytic cycle, is common within the radical SAM enzyme superfamily and is a major reason why these enzymes are the preferred means of initiating radical reactions in nature.

Left cardiac isomerism in the Sonic hedgehog null mouse.

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Hildreth, Victoria; Webb, Sandra; Chaudhry, Bill; Peat, Jonathan D; Phillips, Helen M; Brown, Nigel; Anderson, Robert H; Henderson, Deborah J

2009-06-01

Sonic hedgehog (Shh) is a secreted morphogen necessary for the production of sidedness in the developing embryo. In this study, we describe the morphology of the atrial chambers and atrioventricular junctions of the Shh null mouse heart. We demonstrate that the essential phenotypic feature is isomerism of the left atrial appendages, in combination with an atrioventricular septal defect and a common atrioventricular junction. These malformations are known to be frequent in humans with left isomerism. To confirm the presence of left isomerism, we show that Pitx2c, a recognized determinant of morphological leftness, is expressed in the Shh null mutants on both the right and left sides of the inflow region, and on both sides of the solitary arterial trunk exiting from the heart. It has been established that derivatives of the second heart field expressing Isl1 are asymmetrically distributed in the developing normal heart. We now show that this population is reduced in the hearts from the Shh null mutants, likely contributing to the defects. To distinguish the consequences of reduced contributions from the second heart field from those of left-right patterning disturbance, we disrupted the movement of second heart field cells into the heart by expressing dominant-negative Rho kinase in the population of cells expressing Isl1. This resulted in absence of the vestibular spine, and presence of atrioventricular septal defects closely resembling those seen in the hearts from the Shh null mutants. The primary atrial septum, however, was well formed, and there was no evidence of isomerism of the atrial appendages, suggesting that these features do not relate to disruption of the contributions made by the second heart field. We demonstrate, therefore, that the Shh null mouse is a model of isomerism of the left atrial appendages, and show that the recognized associated malformations found at the venous pole of the heart in the setting of left isomerism are likely to arise from

An EPR study on tea: Identification of paramagnetic species, effect of heat and sweeteners

Science.gov (United States)

Bıyık, Recep; Tapramaz, Recep

2009-10-01

Tea ( Camellia Sinensis) is the most widely consumed beverage in the world, and is known to be having therapeutic, antioxidant and nutritional effects. Electron paramagnetic resonance (EPR) spectral studies made on the tea cultivated along the shore of Black Sea, Turkey, show Mn 2+ and Fe 3+ centers in green tea leaves and in black tea extract. Dry black tea flakes and dry extract show additional sharp line attributed to semiquinone radical. The origins of the paramagnetic species in black tea are defined and discussed. Effect of humidity and heat are investigated. It is observed that dry extract of black tea melts at 100 °C and the semiquinone radical lives up to 140 °C while Mn 2+ sextet disappears just above 100 °C in tea extract. Natural and synthetics sweeteners have different effects on the paramagnetic centers. White sugar (sucrose) quenches the Mn 2+ and semiquinone lines in black tea EPR spectrum, and glucose, fructose, lactose and maltose quench Fe 3+ line while synthetic sweeteners acesulfam potassium, aspartame and sodium saccharine do not have any effect on paramagnetic species in tea.

Tandem ring-closing metathesis/isomerization reactions for the total synthesis of violacein

DEFF Research Database (Denmark)

Petersen, Mette Terp; Nielsen, Thomas Eiland

2013-01-01

A series of 5-substituted 2-pyrrolidinones was synthesized through a one-pot ruthenium alkylidene-catalyzed tandem RCM/isomerization/nucleophilic addition sequence. The intermediates resulting from RCM/isomerization showed reactivity toward electrophiles in aldol condensation reactions which...

Synthesis, structure and isomerism of three-bridge exo-nido-osmacarborane clusters

International Nuclear Information System (INIS)

Kolomnikova, G.D.; Petrovskij, P.V.; Sorokin, P.V.; Dolgushin, F.M.; Yanovskij, A.I.; Chizhevskij, I.T.

2001-01-01

The structure and isomerism of exo-nido-osmacarboranes prepared by reaction between coordination-unsaturated complex OsCl 2 (PPh 3 ) 3 (Ph-phenyl) in benzene at 20 deg C and K + -salts of nido-dicarbaundecarborate anions were studied by the methods of 1 H and 11 B NMR (including usual and two-dimensional spectra) and X-ray diffraction analysis. It was ascertained that in the compounds prepared osmium-containing group is bound with nido-carborane ligand via three-center bonds, open pentagonal plane of carborane ligand being retained in the isomers. In it nature isomerism in the compounds mentioned is geometrical cis-trans-isomerism [ru

Photoisomerization and photodissociation dynamics of reactive free radicals

Energy Technology Data Exchange (ETDEWEB)

Bise, Ryan T. [Univ. of California, Berkeley, CA (United States)

2000-08-01

The photofragmentation pathways of chemically reactive free radicals have been examined using the technique of fast beam photofragment translational spectroscopy. Measurements of the photodissociation cross-sections, product branching ratios, product state energy distributions, and angular distributions provide insight into the excited state potential energy surfaces and nonadiabatic processes involved in the dissociation mechanisms. Photodissociation spectroscopy and dynamics of the predissociative $\\tilde{A}$²A₁ and $\\tilde{B}$²A₂ states of CH₃S have been investigated. At all photon energies, CH₃ + S(³P_j), was the main reaction channel. The translational energy distributions reveal resolved structure corresponding to vibrational excitation of the CH₃ umbrella mode and the S(³P_j) fine-structure distribution from which the nature of the coupled repulsive surfaces is inferred. Dissociation rates are deduced from the photofragment angular distributions, which depend intimately on the degree of vibrational excitation in the C-S stretch. Nitrogen combustion radicals, NCN, CNN and HNCN have also been studied. For all three radicals, the elimination of molecular nitrogen is the primary reaction channel. Excitation to linear excited triplet and singlet electronic states of the NCN radical generates resolved vibrational structure of the N₂ photofragment. The relatively low fragment rotational excitation suggests dissociation via a symmetric C_2V transition state. Resolved vibrational structure of the N₂ photofragment is also observed in the photodissociation of the HNCN radical. The fragment vibrational and rotational distributions broaden with increased excitation energy. Simple dissociation models suggest that the HNCN radical isomerizes to a cyclic intermediate (c-HCNN) which then dissociates via a tight cyclic

Photochromic ruthenium sulfoxide complexes: evidence for isomerization through a conical intersection.

Science.gov (United States)

McClure, Beth Anne; Mockus, Nicholas V; Butcher, Dennis P; Lutterman, Daniel A; Turro, Claudia; Petersen, Jeffrey L; Rack, Jeffrey J

2009-09-07

The complexes [Ru(bpy)(2)(OS)](PF(6)) and [Ru(bpy)(2)(OSO)](PF(6)), where bpy is 2,2'-bipyridine, OS is 2-methylthiobenzoate, and OSO is 2-methylsulfinylbenzoate, have been studied. The electrochemical and photochemical reactivity of [Ru(bpy)(2)(OSO)](+) is consistent with an isomerization of the bound sulfoxide from S-bonded (S-) to O-bonded (O-) following irradiation or electrochemical oxidation. Charge transfer excitation of [Ru(bpy)(2)(OSO)](+) in MeOH results in the appearance of two new metal-to-ligand charge transfer (MLCT) maxima at 355 and 496 nm, while the peak at 396 nm diminishes in intensity. The isomerization is reversible at room temperature in alcohol or propylene carbonate solution. In the absence of light, solutions of O-[Ru(bpy)(2)(OSO)](+) revert to S-[Ru(bpy)(2)(OSO)](+). Kinetic analysis reveals a biexponential decay with rate constants of 5.66(3) x 10(-4) s(-1) and 3.1(1) x 10(-5) s(-1). Cyclic voltammograms of S-[Ru(bpy)(2)(OSO)](+) are consistent with electron-transfer-triggered isomerization of the sulfoxide. Analysis of these voltammograms reveal E(S)(o)' = 0.86 V and E(O)(o)' = 0.49 V versus Ag/Ag(+) for the S- and O-bonded Ru(3+/2+) couples, respectively, in propylene carbonate. We found k(S-->O) = 0.090(15) s(-1) in propylene carbonate and k(S-->O) = 0.11(3) s(-1) in acetonitrile on Ru(III), which is considerably slower than has been reported for other sulfoxide isomerizations on ruthenium polypyridyl complexes following oxidation. The photoisomerization quantum yield (Phi(S-->O) = 0.45, methanol) is quite large, indicating a rapid excited state isomerization rate constant. The kinetic trace at 500 nm is monoexponential with tau = 150 ps, which is assigned to the excited S-->O isomerization rate. There is no spectroscopic or kinetic evidence for an O-bonded (3)MLCT excited state in the spectral evolution of S-[Ru(bpy)(2)(OSO)](+) to O-[Ru(bpy)(2)(OSO)](+). Thus, isomerization occurs nonadiabatically from an S-bonded (or eta(2

Isomerization of glucose into fructose by environmentally friendly Fe/β zeolite catalysts.

Science.gov (United States)

Xu, Siquan; Zhang, Lei; Xiao, Kehao; Xia, Haian

2017-06-29

Herein, the environmentally friendly Fe/β zeolite for glucose isomerization to fructose in aqueous media was reported for the first time. The effects of various reaction conditions including reaction temperature, reaction time, catalyst dosage, etc. on the isomerization reaction over Fe/β zeolite were studied in detail. Under the optimized conditions, yield of fructose higher than 20% were obtained. Moreover, the Fe/β zeolite catalysts were stable and remained constant catalytic activity after five consecutive runs. The possible active Fe species for isomerization of glucose in Fe/β zeolite is also discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

Deconstructing field-induced ketene isomerization through Lagrangian descriptors.

Science.gov (United States)

Craven, Galen T; Hernandez, Rigoberto

2016-02-07

The time-dependent geometrical separatrices governing state transitions in field-induced ketene isomerization are constructed using the method of Lagrangian descriptors. We obtain the stable and unstable manifolds of time-varying transition states as dynamic phase space objects governing configurational changes when the ketene molecule is subjected to an oscillating electric field. The dynamics of the isomerization reaction are modeled through classical trajectory studies on the Gezelter-Miller potential energy surface and an approximate dipole moment model which is coupled to a time-dependent electric field. We obtain a representation of the reaction geometry, over varying field strengths and oscillation frequencies, by partitioning an initial phase space into basins labeled according to which product state is reached at a given time. The borders between these basins are in agreement with those obtained using Lagrangian descriptors, even in regimes exhibiting chaotic dynamics. Major outcomes of this work are: validation and extension of a transition state theory framework built from Lagrangian descriptors, elaboration of the applicability for this theory to periodically- and aperiodically-driven molecular systems, and prediction of regimes in which isomerization of ketene and its derivatives may be controlled using an external field.

Tobacco Smoke: Involvement of Reactive Oxygen Species and Stable Free Radicals in Mechanisms of Oxidative Damage, Carcinogenesis and Synergistic Effects with Other Respirable Particles

Science.gov (United States)

Valavanidis, Athanasios; Vlachogianni, Thomais; Fiotakis, Konstantinos

2009-01-01

Tobacco smoke contains many toxic, carcinogenic and mutagenic chemicals, as well as stable and unstable free radicals and reactive oxygen species (ROS) in the particulate and the gas phase with the potential for biological oxidative damage. Epidemiological evidence established that smoking is one of the most important extrinsic factor of premature morbidity and mortality. The objective of this study was to investigate oxidative and carcinogenic mechanisms of tobacco and synergistic action with other respirable particles in the respiratory system of smokers. Electron Paramagnetic Resonance (EPR) and spin-trapping techniques were used to study stable free radicals in the cigarette tar, and unstable superoxide anion (O2•−) and hydroxyl (HO•) radicals in the smoke Results showed that the semiquinone radical system has the potential for redox recycling and oxidative action. Further, results proved that aqueous cigarette tar (ACT) solutions can generate adducts with DNA nucleobases, particularly the mutagenic 8-hydroxy-2’-deoxyguanosine (a biomarker for carcinogenesis). Also, we observed synergistic effects in the generation of HO•, through the Fenton reaction, with environmental respirable particles (asbestos fibres, coal dust, etc.) and ambient particulate matter (PM), such as PM10, PM2.5 and diesel exhaust particles (DEP). The highest synergistic effects was observed with the asbestos fibres (freshly grounded), PM2.5 and DEP. Finally, we discuss results from our previous study of conventional cellulose acetate filters and “bio-filters” with hemoglobin impregnated activated carbon, which showed that these filters do not substantially alter the free radical content of smoke in the particulate and in the gaseous phase. PMID:19440393

Tobacco Smoke: Involvement of Reactive Oxygen Species and Stable Free Radicals in Mechanisms of Oxidative Damage, Carcinogenesis and Synergistic Effects with Other Respirable Particles

Directory of Open Access Journals (Sweden)

Konstantinos Fiotakis

2009-02-01

Full Text Available Tobacco smoke contains many toxic, carcinogenic and mutagenic chemicals, as well as stable and unstable free radicals and reactive oxygen species (ROS in the particulate and the gas phase with the potential for biological oxidative damage. Epidemiological evidence established that smoking is one of the most important extrinsic factor of premature morbidity and mortality. The objective of this study was to investigate oxidative and carcinogenic mechanisms of tobacco and synergistic action with other respirable particles in the respiratory system of smokers. Electron Paramagnetic Resonance (EPR and spin- trapping techniques were used to study stable free radicals in the cigarette tar, and unstable superoxide anion (O2·- and hydroxyl (HO· radicals in the smoke Results showed that the semiquinone radical system has the potential for redox recycling and oxidative action. Further, results proved that aqueous cigarette tar (ACT solutions can generate adducts with DNA nucleobases, particularly the mutagenic 8-hydroxy-2’-deoxyguanosine (a biomarker for carcinogenesis.Also, we observed synergistic effects in the generation of HO·, through the Fenton reaction, with environmental respirable particles (asbestos fibres, coal dust, etc. and ambient particulate matter (PM, such as PM10, PM2.5 and diesel exhaust particles (DEP. The highest synergistic effects was observed with the asbestos fibres (freshly grounded, PM2.5 and DEP. Finally, we discuss results from our previous study of conventional cellulose acetate filters and “bio-filters” with hemoglobin impregnated activated carbon, which showed that these filters do not substantially alter the free radical content of smoke in the particulate and in the gaseous phase.

Thermal decomposition and isomerization of cis-permethrin and beta-cypermethrin in the solid phase.

Science.gov (United States)

González Audino, Paola; Licastro, Susana A; Zerba, Eduardo

2002-02-01

The stability to heart of cis-permethrin and beta-cypermethrin in the solid phase was studied and the decomposition products identified. Samples heated at 210 degrees C in an oven in the dark showed that, in the absence of potassium chlorate (the salt present in smoke-generating formulations of these pyrethroids), cis-permethrin was not isomerized, although in the presence of that salt, decomposition was greater and thermal isomerization occurred. Other salts of the type KXO3 or NaXO3, with X being halogen or nitrogen, also led to a considerable thermal isomerization. Heating the insecticides in solution in the presence of potassium chlorate did not produce isomerization in any of the solvents assayed. Salt-catalysed thermal cis-trans isomerization was also found for other pyrethroids derived from permethrinic or deltamethrinic acid but not for those derived from chrysanthemic acid. The main thermal degradation processes of cis-permethrin and beta-cypermethrin decomposition when potassium chlorate was present were cyclopropane isomerization, ester cleavage and subsequent oxidation of the resulting products. Permethrinic acid, 3-phenoxybenzyle chloride, alcohol, aldehyde and acid were identified in both cases, as well as 3-phenoxybenzyl cyanide from beta-cypermethrin. A similar decomposition pattern occurred after combustion of pyrethroid fumigant formulations.

Excitation functions and isomeric ratios for the isomeric pair sup(106m)Ag and sup(106g)Ag in the 107Ag (d,t) reaction

International Nuclear Information System (INIS)

Lalli, M.E.; Wasilevsky de Lammirato, C.; Herreros, O.R.; Nassiff, S.J.

1976-09-01

Excitation functions and isomeric cross section ratios have been measured for the 107 Ag (d,t), reaction in which the isomeric pair sup(106m/106g)Ag is produced. Thick-target yields have been determined for different irradiation times and as a function of deuteron energy. Stacked silver foils with aluminium foils as monitors were bombarded with deuterons up to 27 MeV and the activities of products measured with a calibrated Ge(Li) counter. (author) [es

The influence of ligand field effects on the magnetic exchange of high-spin Co(II)-semiquinonate complexes.

Science.gov (United States)

Bencini, Alessandro; Beni, Alessandra; Costantino, Ferdinando; Dei, Andrea; Gatteschi, Dante; Sorace, Lorenzo

2006-02-07

[Co(Me(4)cyclam)(tropolonate)](PF(6)) was synthesised and structurally characterised. Its electronic and W-band EPR spectra have been analysed by means of the angular overlap calculation of the Spin Hamiltonian parameters that provided also a satisfactory reproduction of the temperature dependence of the magnetic susceptibility. The present results can be interpreted assuming a pseudo-octahedral character for the Co(II) center. This prompted us to reconsider the model formerly used for the analysis of the magnetic coupling between hs-Co(II) and the paramagnetic o-semiquinonate ligand in the corresponding derivatives [Co(Me(4)cyclam)(PhenSQ)](PF(6)) and [Co(Me(4)cyclam)(DTBSQ)](PF(6)). These results indicate that the effect of the magnetic coupling is active only below 50 K and that a more refined model of exchange coupling between Co(II) and semiquinonato ligands is needed to quantitatively analyze the magnetic behaviour of this class of systems.

Green Synthesis of Carvenone by Montmorillonite-Catalyzed Isomerization of 1,2-Limonene Oxide

DEFF Research Database (Denmark)

Nguyen, Thao-Tran Thi; Chau, Duy-Khiem Nguyen; Duus, Fritz

2013-01-01

Montmorillonite was considered as a good heterogeneous catalyst for the isomerization of 1,2-limonene oxide into car-venone under solvent-free condition. Both conventional heating and green activations were tested in this research. The microwave-assisted isomerization afforded carvenone in high...

Tin-containing zeolites are highly active catalysts for the isomerization of glucose in water.

Science.gov (United States)

Moliner, Manuel; Román-Leshkov, Yuriy; Davis, Mark E

2010-04-06

The isomerization of glucose into fructose is a large-scale reaction for the production of high-fructose corn syrup (HFCS; reaction performed by enzyme catalysts) and recently is being considered as an intermediate step in the possible route of biomass to fuels and chemicals. Here, it is shown that a large-pore zeolite that contains tin (Sn-Beta) is able to isomerize glucose to fructose in aqueous media with high activity and selectivity. Specifically, a 10% (wt/wt) glucose solution containing a catalytic amount of Sn-Beta (150 Sn:glucose molar ratio) gives product yields of approximately 46% (wt/wt) glucose, 31% (wt/wt) fructose, and 9% (wt/wt) mannose after 30 min and 12 min of reaction at 383 K and 413 K, respectively. This reactivity is achieved also when a 45 wt% glucose solution is used. The properties of the large-pore zeolite greatly influence the reaction behavior because the reaction does not proceed with a medium-pore zeolite, and the isomerization activity is considerably lower when the metal centers are incorporated in ordered mesoporous silica (MCM-41). The Sn-Beta catalyst can be used for multiple cycles, and the reaction stops when the solid is removed, clearly indicating that the catalysis is occurring heterogeneously. Most importantly, the Sn-Beta catalyst is able to perform the isomerization reaction in highly acidic, aqueous environments with equivalent activity and product distribution as in media without added acid. This enables Sn-Beta to couple isomerizations with other acid-catalyzed reactions, including hydrolysis/isomerization or isomerization/dehydration reaction sequences [starch to fructose and glucose to 5-hydroxymethylfurfural (HMF) demonstrated here].

Trimethylphosphide isomerization in lanthanum ions presence

International Nuclear Information System (INIS)

Zacharias, M.A.; Massabni, A.M.G.

1984-01-01

The integration between the trimethilphosphide and the lanthanum ions carry to the formation of solid complexes in a relation of 6:1 where the ligand is the phosphonate what is resultant of the isomerization of trimetylphosphite. By the RMN -1 H and infra-red spectra the products were characterized. (L.M.J.) [pt

Consequences of acid strength for isomerization and elimination catalysis on solid acids.

Science.gov (United States)

Macht, Josef; Carr, Robert T; Iglesia, Enrique

2009-05-13

We address here the manner in which acid catalysis senses the strength of solid acids. Acid strengths for Keggin polyoxometalate (POM) clusters and zeolites, chosen because of their accurately known structures, are described rigorously by their deprotonation energies (DPE). Mechanistic interpretations of the measured dynamics of alkane isomerization and alkanol dehydration are used to obtain rate and equilibrium constants and energies for intermediates and transition states and to relate them to acid strength. n-Hexane isomerization rates were limited by isomerization of alkoxide intermediates on bifunctional metal-acid mixtures designed to maintain alkane-alkene equilibrium. Isomerization rate constants were normalized by the number of accessible protons, measured by titration with 2,6-di-tert-butylpyridine during catalysis. Equilibrium constants for alkoxides formed by protonation of n-hexene increased slightly with deprotonation energies (DPE), while isomerization rate constants decreased and activation barriers increased with increasing DPE, as also shown for alkanol dehydration reactions. These trends are consistent with thermochemical analyses of the transition states involved in isomerization and elimination steps. For all reactions, barriers increased by less than the concomitant increase in DPE upon changes in composition, because electrostatic stabilization of ion-pairs at the relevant transition states becomes more effective for weaker acids, as a result of their higher charge density at the anionic conjugate base. Alkoxide isomerization barriers were more sensitive to DPE than for elimination from H-bonded alkanols, the step that limits 2-butanol and 1-butanol dehydration rates; the latter two reactions showed similar DPE sensitivities, despite significant differences in their rates and activation barriers, indicating that slower reactions are not necessarily more sensitive to acid strength, but instead reflect the involvement of more unstable organic

Stability and isomerization reactions of phenyl cation C{sub 6}H{sub 5}{sup +} isomers

Energy Technology Data Exchange (ETDEWEB)

Shi, Dandan [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China); Jilin Provincial Key Laboratory of Applied Atomic and Molecular Spectroscopy (Jilin University), Changchun 130012 (China); Yang, Xue [College of Science, Jilin Institute of Chemical Technology, Jilin 132022 (China); Zhang, Xiaomei; Shan, Shimin [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China); Jilin Provincial Key Laboratory of Applied Atomic and Molecular Spectroscopy (Jilin University), Changchun 130012 (China); Xu, Haifeng, E-mail: xuhf@jlu.edu.cn [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China); Jilin Provincial Key Laboratory of Applied Atomic and Molecular Spectroscopy (Jilin University), Changchun 130012 (China); Yan, Bing, E-mail: yanbing@jlu.edu.cn [Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China); Jilin Provincial Key Laboratory of Applied Atomic and Molecular Spectroscopy (Jilin University), Changchun 130012 (China)

2016-03-01

Highlights: • A total of 60 isomers of C{sub 6}H{sub 5}{sup +} cations were obtained at density functional theory. • The stability and isomerization reactions of C{sub 6}H{sub 5}{sup +} isomers were performed. • The structures, frequencies, thermodynamic properties of isomers were summarized. • Ring to ring or chain isomerization pathways were investigated using IRC method. • Result shows reactions contain hydrogen transfer, bond broken and reconstruction. - Abstract: As a key polyatomic molecular cation that plays a pivotal role in growth of the polycyclic aromatic hydrocarbons, phenyl cation C{sub 6}H{sub 5}{sup +} exhibits various isomers and isomerization reactions. Investigation on the structure and stability of the isomers as well as the isomerization is important for better understanding the chemical reactions involving C{sub 6}H{sub 5}{sup +} cations. In this work, we have performed a theoretical study on the stability and isomerization reactions of C{sub 6}H{sub 5}{sup +} isomers at density functional theory B3LYP/6-311G (d, p) level. We have obtained a total of 60 isomers of C{sub 6}H{sub 5}{sup +} cations, most of which are reported for the first time. The geometries, vibrational frequencies, thermodynamic properties and stability of 28 out of 60 isomers have been summarized in detail. Different ring-to-ring and ring-to-chain isomerization pathways, which are connected via 28 transition states, have been investigated using the intrinsic reaction coordinate method. The results show that the isomerization reactions occur via hydrogen migration followed by bond-breaking and reconstruction.

Dehydrogenation and concurrent isomerization of n-butenes on mixed tin and antimony oxide catalysts

Energy Technology Data Exchange (ETDEWEB)

Irvine, E.A.; Taylor, D.

1978-01-01

The dehydrogenation and concurrent isomerization of n-butenes on mixed tin and antimony oxide catalysts which had been outgassed at 698/sup 0/K were carried out in the presence of oxygen at 474/sup 0/K, and the initial approximately zero-order rates of 1,3-butadiene formation and rates of isomerization were used as a measure of catalytic activity to construct activity patterns as a function of catalyst composition. A comparison of the patterns with those for the isomerization of 3,3-dimethyl-1-butene and for the selective oxidation of propane on the same catalysts indicated that the dehydrogenation of 1-butene involves a m-allyl intermediate, but isomerization occurs through carbonium ion formation. For the cis- and trans-isomers, both reactions apparently occurred via a common allyl (but not m-allyl) intermediate. Dehydrogenation to butadiene decreased in the order 1-butene > cis-2-butene trans-2-butene and was maximum at 10% antimony for 1-butene and 21% antimony for 2-butene. Isomerization was always slower than dehydrogenation and showed two maEima, at 21 (or 27%) and at 75% antimony.

Crystal structure of isomeric boron difluoride acetylnaphtholates

International Nuclear Information System (INIS)

Bukvetskij, B.V.; Fedorenko, E.V.; Mirochnik, A.G.; Karasev, V.E.

2006-01-01

Crystal structures of luminescent isomeric acetylnaphtholates of boron difluoride are investigated. Full X-ray structural analysis is done at 293 K. Coordinated of atoms, bond angles, bond lengths, interatomic distances are determined. Results of comparative evaluations of the isomers are represented [ru

REPEATED TREATMENTS WITH DOXORUBICIN CAUSES ELECTROCARDIOGRAM (ECG) CHANGES AND INCREASED VENTRICULAR PREMATURE BEATS IN WISTAR-KYOTO (WKY) RATS

Science.gov (United States)

Doxorubicin (DOX) is a widely used anthracycline anti-neoplastic drug used to treat tumors. However it has been implicated in irreversible cardiac toxicity via the generation of a proxidant semiquinone free radical, which often results in cardiomyopathy and changes in the ECG. Ac...

Evaluation of isomeric excitation functions in neutron induced reactions

International Nuclear Information System (INIS)

Grudzevich, O.; Ignatyuk, A.; Zolotarev, K.

1992-01-01

The possibilities of isomer levels experimental excitation functions description with theoretical models are discussed. It is shown that the experimental data in many cases can be described by theoretical models quite well without parameter fitting. However, large discrepancies are observed for some reactions. In our opinion, these discrepancies are due to uncertainties of discrete level schemes, schemes of gamma-transitions between levels and spin dependence of level density. Small values of isomeric ratios (< 0.1) have been described with the largest errors. The simple formulae for energy dependence of isomeric ratio for (n,g) reaction has been proposed. (author). 53 refs, 10 figs, 8 tabs

Spectroscopic detection, characterization and dynamics of free radicals relevant to combustion processes

Energy Technology Data Exchange (ETDEWEB)

Miller, Terry [The Ohio State Univ., Columbus, OH (United States)

2015-06-04

Combustion chemistry is enormously complex. The chemical mechanisms involve a multitude of elementary reaction steps and a comparable number of reactive intermediates, many of which are free radicals. Computer simulations based upon these mechanisms are limited by the validity of the mechanisms and the parameters characterizing the properties of the intermediates and their reactivity. Spectroscopy can provide data for sensitive and selective diagnostics to follow their reactions. Spectroscopic analysis also provides detailed parameters characterizing the properties of these intermediates. These parameters serve as experimental gold standards to benchmark predictions of these properties from large-scale, electronic structure calculations. This work has demonstrated the unique capabilities of near-infrared cavity ringdown spectroscopy (NIR CRDS) to identify, characterize and monitor intermediates of key importance in complex chemical reactions. Our studies have focussed on the large family of organic peroxy radicals which are arguably themost important intermediates in combustion chemistry and many other reactions involving the oxidation of organic compounds. Our spectroscopic studies have shown that the NIR Ã - ˜X electronic spectra of the peroxy radicals allows one to differentiate among chemical species in the organic peroxy family and also determine their isomeric and conformic structure in many cases. We have clearly demonstrated this capability on saturated and unsaturated peroxy radicals and β-hydroxy peroxy radicals. In addition we have developed a unique dual wavelength CRDS apparatus specifically for the purpose of measuring absolute absorption cross section and following the reaction of chemical intermediates. The utility of the apparatus has been demonstrated by measuring the cross-section and self-reaction rate constant for ethyl peroxy.

Control of structural isomerism in noncovalent hydrogen-bonded assemblies using peripheral chiral information

NARCIS (Netherlands)

Prins, L.J.; Jolliffe, K.A.; Hulst, A.J.R.L.; Timmerman, P.; Reinhoudt, David

2000-01-01

The results of a systematic study of the structural isomerism in more than 30 noncovalent hydrogen-bonded assemblies are described. These dynamic assemblies, composed of three calix[4]arene dimelamines and six barbiturates/cyanurates, can be present in three isomeric forms with either D3, C3h, or Cs

High spin states and isomeric decays in doubly-odd 208Fr

International Nuclear Information System (INIS)

Kanjilal, D.; Bhattacharya, S.; Goswami, A.; Kshetri, R.; Raut, R.; Saha, S.; Bhowmik, R.K.; Gehlot, J.; Muralithar, S.; Singh, R.P.; Jnaneswari, G.; Mukherjee, G.; Mukherjee, B.

2010-01-01

Neutron deficient isotopes of francium (Z=87, N∼121-123) as excited nuclei were produced in the fusion-evaporation reaction: 197 Au( 16 O, xn) 213-x Fr at 100 MeV. The γ rays from the residues were observed through the high sensitivity Germanium Clover detector array INGA. The decay of the high spin states and the isomeric states of the doubly-odd 208 Fr nuclei, identified from the known sequence of ground state transitions, were observed. The half-lives of the E γ =194(2) keV isomeric transition, known from earlier observations, was measured to be T 1/2 =233(18) ns. A second isomeric transition at E γ =383(2) keV and T 1/2 =33(7) ns was also found. The measured half-lives were compared with the corresponding single particle estimates, based on the level scheme obtained from the experiment.

Isomeric periodic mesoporous organosilicas with controllable properties

NARCIS (Netherlands)

Vercaemst, C.; Ide, I.; Friedrich, H.; de Jong, K.P.; Verpoort, F.; van der Voort, P.

2009-01-01

The synthesis procedure for isomeric periodic mesoporous organosilicas with E-configured ethenylene bridges was investigated using the homemade pure E-isomer of 1,2-bis(triethoxysilyl)ethene. The pH, aging temperature and the presence of cosolvents played a key role in obtaining well-ordered

Effects of alkali or acid treatment on the isomerization of amino acids.

Science.gov (United States)

Ohmori, Taketo; Mutaguchi, Yuta; Doi, Katsumi; Ohshima, Toshihisa

2012-10-01

The effect of alkali treatment on the isomerization of amino acids was investigated. The 100×D/(D+L) values of amino acids from peptide increased with increase in the number of constituent amino acid residues. Furthermore, the N-terminal amino acid of a dipeptide was isomerized to a greater extent than the C-terminal residue. Copyright © 2012. Published by Elsevier B.V.

Molecular isomerization induced by ultrashort infrared pulses. II. Pump-dump isomerization using pairs of time-delayed half-cycle pulses.

Science.gov (United States)

Uiberacker, Christoph; Jakubetz, Werner

2004-06-22

We investigate population transfer across the barrier in a double-well potential, induced by a pair of time-delayed single-lobe half-cycle pulses. We apply this setup both to a one-dimensional (1D) quartic model potential and to a three-dimensional potential representing HCN-->HNC isomerization. Overall the results for the two systems are similar, although in the 3D system some additional features appear not seen in the 1D case. The generic mechanism of population transfer is the preparation by the pump pulse of a wave packet involving delocalized states above the barrier, followed by the essentially 1D motion of the delocalized part of wave packet across the barrier, and the eventual de-excitation by the dump pulse to localized states in the other well. The correct timing is given by the well-to-well passage time of the wave packet and its recurrence properties, and by the signs of the field lobes which determine the direction and acceleration or deceleration of the wave packet motion. In the 3D system an additional pump-pump-dump mechanism linked to wave packet motion in the reagent well can mediate isomerization. Since the transfer time and the pulse durations are of the same order of magnitude, there is also a marked dependence of the dynamics and the transfer yield on the pulse duration. Our analysis also sheds light on the pronounced carrier envelope phase dependence previously observed for isomerization and molecular dissociation with one-cycle and sub-one-cycle pulses. (c) 2004 American Institute of Physics.

Isomeric rations study for the α + 70 Ge

International Nuclear Information System (INIS)

Hora Villano, M.H. da.

1984-12-01

Isomeric ratios for 73 Se F,I produced in the reaction α + 70 Ge with incidence laboratory energy ranging from 8 to 28 MeV, have been measured using off-line γ-ray spectroscopy. Relative formation cross-section for isomeric and ground states were obtained with NAT Ge targets. Compound nucleus statistical analyses were performed using computer codes Alice and Julian. Unlike to Alice code, the Julian code predictions agreed quite well with the experimental results. This agreement may be explained by the inclusion of the γ competition in the deexcitation channels of the compound nucleus and by the correct level density calculation of the emission probabilities in the Julian code. Finally angular momentum populations for isomers formations in the reaction 70 Ge(α, n) 73 have been determined. (author)

Elucidation of structural isomers from the homogeneous rhodium-catalyzed isomerization of vegetable oils.

Science.gov (United States)

Andjelkovic, Dejan D; Min, Byungrok; Ahn, Dong; Larock, Richard C

2006-12-13

The structural isomers formed by the homogeneous rhodium-catalyzed isomerization of several vegetable oils have been elucidated. A detailed study of the isomerization of the model compound methyl linoleate has been performed to correlate the distribution of conjugated isomers, the reaction kinetics, and the mechanism of the reaction. It has been shown that [RhCl(C8H8)2]2 is a highly efficient and selective isomerization catalyst for the production of highly conjugated vegetable oils with a high conjugated linoleic acid (CLA) content, which is highly desirable in the food industry. The combined fraction of the two major CLA isomers [(9Z,11E)-CLA and (10E,12Z)-CLA] in the overall CLA mixture is in the range from 76.2% to 93.4%. The high efficiency and selectivity of this isomerization method along with the straightforward purification process render this approach highly promising for the preparation of conjugated oils and CLA. Proposed improvements in catalyst recovery and reusability will only make this method more appealing to the food, paint, coating, and polymer industries in the future.

Possible evidence for shape isomeric γ-decay in μ- atoms of 238U

International Nuclear Information System (INIS)

Fromm, W.D.; Ortlepp, H.-G.; Polikanov, S.M.; Schmidt, U.; Zorin, G.N.; Arlt, R.; Musiol, G.

1977-01-01

A search for the γ-decay of the shape isomer in muonic 238 U excited by radiationless transitions has been performed. Seven delayed transitions in the energy region of 700 to 3200 keV have been observed with a large Ge(Li) detector. Two transitions with Esub(γ)=2215 and 3131 keV have been attributed to the decay of the shape isomeric state into levels in the first well. The isomeric shift of the second minimum Esub(II) approximately 600 keV in the presence of the muon and the decrease of the lifetime of the shape isomer to tau=12+-2 ns give arguments in favour of the connection of shape isomerism with large quadrupole deformations. (Auth.)

Low-lying isomeric levels in Cu75

Science.gov (United States)

Daugas, J. M.; Faul, T.; Grawe, H.; Pfützner, M.; Grzywacz, R.; Lewitowicz, M.; Achouri, N. L.; Angélique, J. C.; Baiborodin, D.; Bentida, R.; Béraud, R.; Borcea, C.; Bingham, C. R.; Catford, W. N.; Emsallem, A.; de France, G.; Grzywacz, K. L.; Lemmon, R. C.; Lopez Jimenez, M. J.; de Oliveira Santos, F.; Regan, P. H.; Rykaczewski, K.; Sauvestre, J. E.; Sawicka, M.; Stanoiu, M.; Sieja, K.; Nowacki, F.

2010-03-01

Isomeric low-lying states were identified and investigated in the Cu75 nucleus. Two states at 61.8(5)- and 128.3(7)-keV excitation energies with half-lives of 370(40)- and 170(15)-ns were assigned as Cu75m1 and Cu75m2, respectively. The measured half-lives combined with the recent spin assignment of the ground state allow one to deduce tentatively spin and parity of the two isomers and the dominant multipolarities of the isomeric transitions with respect to the systematics of the Cu isotopes. Shell-model calculations using an up-to-date effective interaction reproduce the evolution of the 1/2-, 3/2-, and 5/2- states for the neutron-rich odd-mass Cu isotopes when filling the νg9/2. The results indicate a significant change in the nuclear structure in this region, where a single-particle 5/2- state coexists with more and more collective 3/2- and 1/2- levels at low excitation energies.

Multi-quasiparticle high-K isomeric states in deformed nuclei

Directory of Open Access Journals (Sweden)

Xu F. R.

2016-01-01

Full Text Available In the past years, we have made many theoretical investigations on multi-quasiparticle high-K isomeric states. A deformation-pairing-configuration self-consistent calculation has been developed by calculating a configuration-constrained multi-quasiparticle potential energy surface (PES. The specific single-particle orbits that define the high-K configuration are identified and tracked (adiabatically blocked by calculating the average Nilsson numbers. The deformed Woods-Saxon potential was taken to give single-particle orbits. The configuration-constrained PES takes into account the shape polarization effect. Such calculations give good results on excitation energies, deformations and other structure information about multi-quasiparticle high-K isomeric states. Many different mass regions have been investigated.

Promotion or suppression of glucose isomerization in subcritical aqueous straight- and branched-chain alcohols.

Science.gov (United States)

Gao, Da-Ming; Kobayashi, Takashi; Adachi, Shuji

2015-01-01

The influence of water-miscible alcohols (methanol, 1-propanol, 2-propanol, and t-butyl alcohol) on the isomerization of glucose to fructose and mannose was investigated under subcritical aqueous conditions (180-200 °C). Primary and secondary alcohols promoted the conversion and isomerization of glucose to afford fructose and mannose with high and low selectivity, respectively. On the other hand, the decomposition (side-reaction) of glucose was suppressed in the presence of the primary and secondary alcohols compared with that in subcritical water. The yield of fructose increased with increasing concentration of the primary and secondary alcohols, and the species of the primary and secondary alcohols tested had little effect on the isomerization behavior of glucose. In contrast, the isomerization of glucose was suppressed in subcritical aqueous t-butyl alcohol. Both the conversion of glucose and the yield of fructose decreased with increasing concentration of t-butyl alcohol. In addition, mannose was not detected in reactions using subcritical aqueous t-butyl alcohol.

A Novel Technique that Enables Efficient Conduct of Simultaneous Isomerization and Fermentation (SIF) of Xylose

Science.gov (United States)

Rao, Kripa; Chelikani, Silpa; Relue, Patricia; Varanasi, Sasidhar

Of the sugars recovered from lignocellulose, D-glucose can be readily converted into ethanol by baker's or brewer's yeast (Saccharomyces cerevisiae). However, xylose that is obtained by the hydrolysis of the hemicellulosic portion is not fermentable by the same species of yeasts. Xylose fermentation by native yeasts can be achieved via isomerization of xylose to its ketose isomer, xylulose. Isomerization with exogenous xylose isomerase (XI) occurs optimally at a pH of 7-8, whereas subsequent fermentation of xylulose to ethanol occurs at a pH of 4-5. We present a novel scheme for efficient isomerization of xylose to xylulose at conditions suitable for the fermentation by using an immobilized enzyme system capable of sustaining two different pH microenvironments in a single vessel. The proof-of-concept of the two-enzyme pellet is presented, showing conversion of xylose to xylulose even when the immobilized enzyme pellets are suspended in a bulk solution whose pH is sub-optimal for XI activity. The co-immobilized enzyme pellets may prove extremely valuable in effectively conducting "simultaneous isomerization and fermentation" (SIF) of xylose. To help further shift the equilibrium in favor of xylulose formation, sodium tetraborate (borax) was added to the isomerization solution. Binding of tetrahydroxyborate ions to xylulose effectively reduces the concentration of xylulose and leads to increased xylose isomerization. The formation of tetrahydroxyborate ions and the enhancement in xylulose production resulting from the complexation was studied at two different bulk pH values. The addition of 0.05 M borax to the isomerization solution containing our co-immobilized enzyme pellets resulted in xylose to xylulose conversion as high as 86% under pH conditions that are suboptimal for XI activity. These initial findings, which can be optimized for industrial conditions, have significant potential for increasing the yield of ethanol from xylose in an SIF approach.

Electron transfer rates and equilibria between substituted phenoxide ions and phenoxyl radicals

International Nuclear Information System (INIS)

Steenken, S.; Neta, P.

1979-01-01

The rate constants for electron transfer from a series of substituted isomeric dihydroxy- and diaminobenzenes to different substituted phenoxyl radicals were measured by observing the decay or buildup of one of the radicals invoved. In many cases the electron transfer reactions were reversible and the equilibrium constants could be calculated from the individual rate constants for attainment of equilibrium and from the concentrations of the species involved at equilibrium. From the equilibrium constants the one-electron redox potentials for 15 individual Q - ./Q 2- pairs were determined, using the value for hydroquinone (23 mV at pH 13.5) as a reference. The potential for catechol (43 mV) is near that of hydroquinone; resorcinol is oxidized much less readily (300 mV), while phenol is even a weaker reductant (>500mV). Methyl, methoxy, and hydroxy substituents decrease the redox potentials while acetyl and carboxyl substituents increase these values. Ascorbate has a potential (15mV) similar to that of hydroquinone, while TMPD (82mV) and p-phenylenediamine (183mV) are less easily oxidized

Artificial Metalloproteins for Binding and Stabilization of a Semiquinone Radical

NARCIS (Netherlands)

Segaud, Nathalie; Drienovska, Ivana; Chen, Juan; Browne, Wesley R.; Roelfes, Gerard

2017-01-01

The interaction of a number of first-row transition-metal ions with a 2,2'-bipyridyl alanine (bpyA) unit incorporated into the lactococcal multidrug resistance regulator (LmrR) scaffold is reported. The composition of the active site is shown to influence binding affinities. In the case of Fe(II),

New isomeric states in 152,154,156Nd produced by spontaneous fission of 252Cf

International Nuclear Information System (INIS)

Gautherin, C.; Houry, M.; Korten, W.; Le Coz, Y.; Lucas, R.; Phan, X.H.; Theisen, C.; Belier, G.; Girod, M.; Meot, V.; Peru, S.; Astier, A.; Ducroux, L.; Meyer, M.; Redon, N.

1998-01-01

Isomeric states have been observed in fission-fragments produced by spontaneous fission of 252 Cf. These states are found in neutron rich nuclei of different structure and deformations. About 50 isomeric nuclei have been observed using coincidences between γ-rays identified in EUROGAM II and fission fragments detected in photovoltaic cells (SAPhIR). Lifetimes in the range from 20 ns to 2μs have been measured. Presented calculations based on HFB+D1S force on new measured isomeric states in the 152,154,156 Nd show evidence for K-isomers. (orig.)

Determination of the active site and mechanism for alkene isomerization in Cu(II) exchnaged Y-type zeolite

Energy Technology Data Exchange (ETDEWEB)

John, C S; Leach, H F

1977-01-01

An ESR study of 1-butene isomerization at 315/sup 0/-375/sup 0/C, 3,3-dimethyl-1-butene isomerization to 2,3-dimethyl-1- and -2-butene at 293/sup 0/K, and deuterium redistribution in 3,3-dideuteriopropene at 363/sup 0/-396/sup 0/K showed the presence of two copper(II) species in different environments, which reacted with the olefins at different rates. Although activation energies for the three reactions differed and only dideuteriopropene showed an induction period, a similar mechanism is proposed in all cases, involving preliminary reduction of copper(II), with the rates of reduction and isomerization differing from olefin to olefin. Apparently, the active site for the isomerization is a Broensted acid generated by the reduction, and the isomerization follows an associative (proton addition-elimination) mechanism with a carbonium ion intermediate. Spectra, graphs, diagram, and 12 references.

Pulse-radiolytic investigations of catechols and catecholamines

International Nuclear Information System (INIS)

Bors, W.; Saran, M.; Michel, C.; Lengfelder, E.; Fuchs, C.; Spoettl, R.

1975-01-01

Adrenaline (epinephrine), adrenochrome and C 4 -substituted catechol model compounds were pulse-irradiated in aqueous neutral and alkaline solutions. Transient spectra are reported after oxidizing adrenaline and reducing adrenochrome. All species appearing during the 20 msec interval after the pulse have been identified: the OH adduct with an absorption maximum at 300 to 310 nm, the semiquinone (at 245 nm), and adrenaline quinone (at 340 nm). The reaction of superoxide anions (O 2 - ) with adrenaline was less efficient, compared with OH radicals. A novel oxidation product, derived from the semiquinone and O 2 - , has been identified as the 4-hydroxy-3,6-dioxo derivate. The pulse-radiolytic reduction of adrenochrome by hydrated electrons (esub(aq) - ) yielded the semiquinone of adrenochrome (absorbing at 470 nm), which subsequently decayed by a second-order process. The dismutation products leucoadrenochrome (absorbing at 300 nm, pH 9.8) and the adrenochrome tautomer (absorbing at 375 nm) were unstable, forming a 5,6-dihydro-N-methyl indole and regenerating adrenochrome. (author)

Iridium-Catalyzed Dynamic Kinetic Isomerization: Expedient Synthesis of Carbohydrates from Achmatowicz Rearrangement Products.

Science.gov (United States)

Wang, Hao-Yuan; Yang, Ka; Bennett, Scott R; Guo, Sheng-rong; Tang, Weiping

2015-07-20

A highly stereoselective dynamic kinetic isomerization of Achmatowicz rearrangement products was discovered. This new internal redox isomerization provided ready access to key intermediates for the enantio- and diastereoselective synthesis of a series of naturally occurring sugars. The nature of the de novo synthesis also enables the preparation of both enantiomers. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparing isomerically pure beams of short-lived nuclei at JYFLTRAP

Energy Technology Data Exchange (ETDEWEB)

Eronen, T. [Department of Physics, University of Jyvaeskylae, P.O. Box 35 (YFL), FIN-40014 (Finland)], E-mail: tommi.eronen@jyu.fi; Elomaa, V.-V.; Hager, U.; Hakala, J.; Jokinen, A.; Kankainen, A.; Rahaman, S.; Rissanen, J.; Weber, C.; Aystoe, J. [Department of Physics, University of Jyvaeskylae, P.O. Box 35 (YFL), FIN-40014 (Finland)

2008-10-15

A new procedure to prepare isomerically clean samples of short-lived ions with a mass resolving power of more than 1 x 10{sup 5} has been developed at the JYFLTRAP tandem Penning trap system. The method utilises a dipolar rf-excitation of the ion motion with separated oscillatory fields in the precision trap. During a subsequent retransfer to the purification trap, the contaminants are rejected and as a consequence, the remaining bunch is isomerically cleaned. This newly-developed method is suitable for very high-resolution cleaning and is at least a factor of five faster than the methods used so far in Penning trap mass spectrometry.

Synthesis and Characterisation of Eight Isomeric Bis(2-pyridyloxynaphthalenes

Directory of Open Access Journals (Sweden)

Peter J. Steel

2006-09-01

Full Text Available Eight isomeric bis(2-pyridyloxynaphthalenes have been prepared from reactions of 2-bromopyridine with the appropriate dihydroxynaphthalene and the products fully characterised by 1- and 2-D NMR spectroscopy.

Combined Function of Brønsted and Lewis Acidity in the Zeolite-Catalyzed Isomerization of Glucose to Fructose in Alcohols

DEFF Research Database (Denmark)

Shunmugavel, Saravanamurugan; Riisager, Anders; Taarning, Esben

2016-01-01

Glucose conversion via fructose to useful chemicals and fuels has attracted considerable attention. Isomerization of glucose to fructose can proceed along several different reaction pathways involving different sugar intermediates and isomeric forms. Presently, the roles of the substrate isomeric...

Formation, isomerization, and derivatization of keggin tungstoaluminates.

Science.gov (United States)

Jennifer J. Cowan; Alan J. Bailey; Robert A. Heintz; Bao T. Do; Kenneth I. Hardcastle; Craig L. Hill; Ira A. Weinstock

2001-01-01

Trends in the stability of ¥á and ©¬-Keggin heteropolytungstates of the second-row main-group heteroatoms Al(III), Si(IV), and P(V) are elaborated by data that establish the roles of kinetic and thermodynamic control in the formation and isomerization of Keggin tungstoaluminates. Slow, room-temperature co-...

Semiquinone glucoside derivative isolated from Bacillus sp. INM-1 offers protection to male reproductive system of mice against γ-radiation induced toxicity

International Nuclear Information System (INIS)

Singh, Praveen K.; Malhotra, Poonam; Gupta, Ashutosh; Chhachhia, Neha; Singh, Shravan K.; Kumar, Raj; Dubey, Kashyap Kumar

2014-01-01

Ionizing radiation causes reversible/irreversible damages to the testis by inducing oxidative stress through reactive oxygen species lead to impotency in young cancer patients undergoing lower abdomen radiotherapy. Therefore, protection of testicular cells against gamma radiation is of utmost significance. Present study was focused to evaluate radioprotective efficacy of a semiquinone rich fraction isolated from radioresistant bacterium Bacillus sp. INM-1. In the present study, mice were pre-treated with semiquinone glucoside derivative (SQGD; 50 mg/ kg.b.wt. i.p.) 2h before irradiation (5Gy) and various radioprotective cellular parameters including histology, quantitative analysis of spermatids, spermatocytes, sperm counts, sperm abnormalities, structural and morphological analysis of seminiferous tubules were observed for complete two cycles (70 days) of spermatogenesis and compared with irradiated (5 Gy) control group. Results of the study demonstrated that untreated control and SQGD treated groups showed no significant difference in sperm counts even after 70 days post treatment time. However, whole body irradiation reduced the sperm count significantly (p<0.05%) from the day 1 st to day 70 th . SQGD treatment to irradiated mice significantly increased the sperm count, reduced morphological abnormality in the sperms as compared to irradiated group. Untreated control mice showed a higher seminiferous tubular area compared to irradiation control at 35 th and 70 th day post irradiation time. SQGD pretreatment to irradiated mice led to significant increase in seminiferous tubule area compared to irradiated control. Concomitantly, seminiferous lumen size increases in radiation control mice compared to SQGD pre-treated mice at 35 th and 70 th day due to germ cells depletion. Qualitative histological study of testis at all tested time points suggests that drug treatment protects the spermatogenesis by enhancing the spermatogonial proliferation, enhancing the stem cell

K isomerism and collectivity in neutron-rich rare-earth isotopes

Science.gov (United States)

Patel, Zena

Neutron-rich rare-earth isotopes were produced by in-flight fission of 238U ions at the Radioactive Isotope Beam Factory (RIBF), RIKEN, Japan. In-flight fission of a heavy, high-intensity beam of 238U ions on a light target provides the cleanest secondary beams of neutron-rich nuclei in the rare-earth region of isotopes. In-flight fission is advantageous over other methods of nuclear production, as it allows for a secondary beam to be extracted, from which the beam species can be separated and identified. The excited states of nuclei are studied by delayed isomeric or beta-delayed gamma-ray spectroscopy. New K isomers were found in Sm (Z=62), Eu (Z=63), and Gd (Z=64) isotopes. The key results are discussed here. Excited states in the N=102 isotones 166Gd and 164Sm have been observed following isomeric decay for the first time. The K-isomeric states in 166Gd and 164Sm are due to 2-quasiparticle configurations. Based on the decay patterns and potential energy surface calculations, including beta6 deformation, both isomers are assigned a (6-) spin-parity. The half-lives of the isomeric states have been measured to be 950(60)ns and 600(140)ns for 166Gd and 164Sm respectively. Collective observables are discussed in light of the systematics of the region, giving insight into nuclear shape evolution. The decrease in the ground state band energies of 166Gd and 164Sm (N=102) compared to 164Gd and 162Sm (N=100) respectively, presents evidence for the predicted deformed shell closure at N=100. A 4-quasiparticle isomeric state has been discovered in 160Sm: the lightest deformed nucleus with a 4-quasiparticle isomer to date. The isomeric state is assigned an (11+) spin-parity with a measured half-life of 1.8(4)us. The (11+) isomeric state decays into a rotational band structure, based on a (6-) v5/2-[523] ⊗ v7/2+[633] bandhead, determined from the extracted gK-gR values. Potential energy surface and blocked BCS calculations were performed in the deformed midshell region

The study of a new short-life isomeric state in 38K

International Nuclear Information System (INIS)

Iordachescu, A.

1976-01-01

The 38 K nucleus having a protone and neutron hole coupled with a 40 Ca inert core has a structure analysed easily by the shell model. A new short life, high spin and highly excited isomeric state of the 38 K nucleus has been studied in detail using this model. Theoretical aspects connected with static and dynamic electromagnetic moments of the nucleus state, with the magnetic moment of the nucleus and the selection rules according to the isotopic spin are presented in the case of gamma transitions. Experimentallz/ presented in the case of gamma transitions. Experimentally, it has been used a combination between a natural pulsation of the cyclotron beam and an external pulsation by electrostatic deflexion, thus obtaining a pulsation beam of 12-26 MeV alpha particles. As targets, a series of chemical chlorine combinations have been utilized, the isomeric state being obtained by the reaction 35 Cl(α,n) 38 K, having the isomeric level (1fsub(7/2))sub(7+)sup(2). (author)

High spin states and isomeric decays in doubly-odd {sup 208}Fr

Energy Technology Data Exchange (ETDEWEB)

Kanjilal, D.; Bhattacharya, S.; Goswami, A.; Kshetri, R.; Raut, R. [Nuclear and Atomic Physics Division, Saha Institute of Nuclear Physics, Kolkata 700064 (India); Saha, S., E-mail: satyajit.saha@saha.ac.i [Nuclear and Atomic Physics Division, Saha Institute of Nuclear Physics, Kolkata 700064 (India); Bhowmik, R.K.; Gehlot, J.; Muralithar, S.; Singh, R.P. [Inter University Accelerator Centre, New Delhi 110067 (India); Jnaneswari, G. [Department of Physics, Andhra University, Vishakhapatnam 530003 (India); Mukherjee, G. [Variable Energy Cyclotron Centre, Kolkata 700064 (India); Mukherjee, B. [Department of Physics, Visva Bharati, Santiniketan 731235 (India)

2010-10-15

Neutron deficient isotopes of francium (Z=87, N{approx}121-123) as excited nuclei were produced in the fusion-evaporation reaction: {sup 197}Au({sup 16}O, xn) {sup 213-x}Fr at 100 MeV. The {gamma} rays from the residues were observed through the high sensitivity Germanium Clover detector array INGA. The decay of the high spin states and the isomeric states of the doubly-odd {sup 208}Fr nuclei, identified from the known sequence of ground state transitions, were observed. The half-lives of the E{sub {gamma}=}194(2) keV isomeric transition, known from earlier observations, was measured to be T{sub 1/2}=233(18) ns. A second isomeric transition at E{sub {gamma}=}383(2) keV and T{sub 1/2}=33(7) ns was also found. The measured half-lives were compared with the corresponding single particle estimates, based on the level scheme obtained from the experiment.

Environmentally persistent free radicals amplify ultrafine particle mediated cellular oxidative stress and cytotoxicity

Directory of Open Access Journals (Sweden)

Balakrishna Shrilatha

2009-04-01

Full Text Available Abstract Background Combustion generated particulate matter is deposited in the respiratory tract and pose a hazard to the lungs through their potential to cause oxidative stress and inflammation. We have previously shown that combustion of fuels and chlorinated hydrocarbons produce semiquinone-type radicals that are stabilized on particle surfaces (i.e. environmentally persistent free radicals; EPFRs. Because the composition and properties of actual combustion-generated particles are complex, heterogeneous in origin, and vary from day-to-day, we have chosen to use surrogate particle systems. In particular, we have chosen to use the radical of 2-monochlorophenol (MCP230 as the EPFR because we have previously shown that it forms a EPFR on Cu(IIO surfaces and catalyzes formation of PCDD/F. To understand the physicochemical properties responsible for the adverse pulmonary effects of combustion by-products, we have exposed human bronchial epithelial cells (BEAS-2B to MCP230 or the CuO/silica substrate. Our general hypothesis was that the EPFR-containing particle would have greater toxicity than the substrate species. Results Exposure of BEAS-2B cells to our combustion generated particle systems significantly increased reactive oxygen species (ROS generation and decreased cellular antioxidants resulting in cell death. Resveratrol treatment reversed the decline in cellular glutathione (GSH, glutathione peroxidase (GPx, and superoxide dismutase (SOD levels for both types of combustion-generated particle systems. Conclusion The enhanced cytotoxicity upon exposure to MCP230 correlated with its ability to generate more cellular oxidative stress and concurrently reduce the antioxidant defenses of the epithelial cells (i.e. reduced GSH, SOD activity, and GPx. The EPFRs in MCP230 also seem to be of greater biological concern due to their ability to induce lipid peroxidation. These results are consistent with the oxidizing nature of the CuO/silica ultrafine

Impacts of daily intakes on the isomeric profiles of perfluoroalkyl substances (PFASs) in human serum.

Science.gov (United States)

Shan, Guoqiang; Wang, Zhi; Zhou, Lianqiu; Du, Pin; Luo, Xiaoxiao; Wu, Qiannian; Zhu, Lingyan

2016-01-01

Perfluoroalkyl substances (PFASs) have been well studied in human daily intake for assessment of potential health risks. However, little is known about the isomeric compositions of PFASs in daily intake and their impacts on isomeric profiles in humans. In this study, we investigated the occurrence of PFASs with isomeric analysis in various human exposure matrices including foodstuffs, tap water and indoor dust. Perfluorooctanesulfonate (PFOS) and/or perfluorooctanoate (PFOA) were predominant in these exposure matrices collected in Tianjin, China. In fish and meat, linear (n-) PFOA was enriched with a percentage of 92.2% and 99.6%, respectively. Although n-PFOS was higher in fish (84.8%) than in technical PFOS (ca. 70%), it was much lower in meat (63.1%) and vegetables (58.5%). Dietary intake contributed >99% of the estimated daily intake (EDI) for the general population. The isomeric profiles of PFOA and PFOS in human serum were predicted based on the EDI and a one-compartment, first-order pharmacokinetic model. The isomeric percentage of n-PFOA in the EDI (98.6%) was similar to that in human serum (predicted: 98.2%, previously measured: 99.7%) of Tianjin residents. The results suggest direct PFOA intake plays an important role in its isomeric compositions in humans. For PFOS, the predicted n-PFOS (69.3%) was much higher than the previously measured values (59.2%) in human serum. This implies that other factors, such as indirect exposure to PFOS precursors and multiple excretion pathways, may contribute to the lower percentage of n-PFOS in humans than of technical PFOS. Copyright © 2016 Elsevier Ltd. All rights reserved.

A system to measure isomeric state half-lives in the 10 ns to 10 μs range

Energy Technology Data Exchange (ETDEWEB)

Toufen, D. L., E-mail: dennis@if.usp.br [Institute of Physics, University of São Paulo, C.P. 66318, 05315-970 São Paulo, São Paulo (Brazil); Federal Institute of Education, Science and Technology of São Paulo - IFSP, 07115-000 Guarulhos, São Paulo (Brazil); Allegro, P. R. P.; Medina, N. H.; Oliveira, J. R. B.; Cybulska, E. W.; Seale, W. A.; Ribas, R. V. [Institute of Physics, University of São Paulo, C.P. 66318, 05315-970 São Paulo, São Paulo (Brazil); Linares, R. [Fluminense Federal University, 24220-900 Niterói, Rio de Janeiro (Brazil); Silveira, M. A. G. [Universitary Center of FEI, 09850-901 São Bernardo do Campo, São Paulo (Brazil)

2014-07-15

The Isomeric State Measurement System (SISMEI) was developed to search for isomeric nuclear states produced by fusion-evaporation reactions. The SISMEI consists of 10 plastic phoswich telescopes, two lead shields, one NaI(Tl) scintillation detector, two Compton suppressed HPGe γ-ray detectors, and a cone with a recoil product catcher. The new system was tested at the 8 UD Pelletron tandem accelerator of the University of São Paulo with the measurement of two known isomeric states: {sup 54}Fe, 10{sup +} state (E = 6527.1 (11) keV, T{sub 1/2} = 364(7) ns) and the 5/2{sup +} state of {sup 19}F (E = 197.143 (4) keV, T{sub 1/2} = 89.3 (10) ns). The results indicate that the system is capable of identifying delayed transitions, of measuring isomeric state lifetimes, and of identifying the feeding transitions of the isomeric state through the delayed γ-γ coincidence method. The measured half-life for the 10{sup +} state was T{sub 1/2} = 365(14) ns and for the 5/2{sup +} state, 100(36) ns.

A system to measure isomeric state half-lives in the 10 ns to 10 μs range

Science.gov (United States)

Toufen, D. L.; Allegro, P. R. P.; Medina, N. H.; Oliveira, J. R. B.; Cybulska, E. W.; Seale, W. A.; Linares, R.; Silveira, M. A. G.; Ribas, R. V.

2014-07-01

The Isomeric State Measurement System (SISMEI) was developed to search for isomeric nuclear states produced by fusion-evaporation reactions. The SISMEI consists of 10 plastic phoswich telescopes, two lead shields, one NaI(Tl) scintillation detector, two Compton suppressed HPGe γ-ray detectors, and a cone with a recoil product catcher. The new system was tested at the 8 UD Pelletron tandem accelerator of the University of São Paulo with the measurement of two known isomeric states: 54Fe, 10+ state (E = 6527.1 (11) keV, T1/2 = 364(7) ns) and the 5/2+ state of 19F (E = 197.143 (4) keV, T1/2 = 89.3 (10) ns). The results indicate that the system is capable of identifying delayed transitions, of measuring isomeric state lifetimes, and of identifying the feeding transitions of the isomeric state through the delayed γ-γ coincidence method. The measured half-life for the 10+ state was T1/2 = 365(14) ns and for the 5/2+ state, 100(36) ns.

Structural and spectral comparisons between isomeric benzisothiazole and benzothiazole based aromatic heterocyclic dyes

Science.gov (United States)

Wang, Yin-Ge; Wang, Yue-Hua; Tao, Tao; Qian, Hui-Fen; Huang, Wei

2015-09-01

A pair of isomeric heterocyclic compounds, namely 3-amino-5-nitro-[2,1]-benzisothiazole and 2-amino-6-nitrobenzothiazole, are used as the diazonium components to couple with two N-substituted 4-aminobenzene derivatives. As a result, two pairs of isomeric aromatic heterocyclic azo dyes have been produced and they are structurally and spectrally characterized and compared including single-crystal structures, electronic spectra, solvatochromism and reversible acid-base discoloration, thermal stability and theoretically calculations. It is concluded that both benzisothiazole and benzothiazole based dyes show planar molecular structures and offset π-π stacking interactions, solvatochromism and reversible acid-base discoloration. Furthermore, benzisothiazole based aromatic heterocyclic dyes exhibit higher thermal stability, larger solvatochromic effects and maximum absorption wavelengths than corresponding benzothiazole based ones, which can be explained successfully by the differences of their calculated isomerization energy, dipole moment and molecular band gaps.

Scope and mechanism in palladium-catalyzed isomerizations of highly substituted allylic, homoallylic, and alkenyl alcohols.

Science.gov (United States)

Larionov, Evgeny; Lin, Luqing; Guénée, Laure; Mazet, Clément

2014-12-03

Herein we report the palladium-catalyzed isomerization of highly substituted allylic alcohols and alkenyl alcohols by means of a single catalytic system. The operationally simple reaction protocol is applicable to a broad range of substrates and displays a wide functional group tolerance, and the products are usually isolated in high chemical yield. Experimental and computational mechanistic investigations provide complementary and converging evidence for a chain-walking process consisting of repeated migratory insertion/β-H elimination sequences. Interestingly, the catalyst does not dissociate from the substrate in the isomerization of allylic alcohols, whereas it disengages during the isomerization of alkenyl alcohols when additional substituents are present on the alkyl chain.

Study of the isomeric states of 66As

International Nuclear Information System (INIS)

Czajkowski, S.; Blank, B.; Andriamonje, S.; Attallah, F.; Boue, F.; Davi, F.; Del Moral, R.; Fleury, A.; Musquere, A.; Pravikoff, M.S.; Dufour, J-P; Grzywacz, R.; Janas, Z.; Karny, M.; Pfuetzner, M.; Donzaud, C.; Grewe, A.; Heinz, A.; Junghans, A.; Lewitowicz, M.; Sauvestre, J-E.

1997-01-01

The most neutron-deficient isotopes in the N = Z region are an important source of information on the neutron-proton interaction far off stability. The isotopes in this region are characterized by an extreme sensitivity of the deformation to the isospin variations. Here the structure of deformed shells are favoring the high spin states the lifetime of which being sufficient long to be observed after flight time of the order of the microsecond. The study of the decay of this isomeric states permits to approach the structure of the first excited levels of this isotopes. Recent experiments at GANIL with the SISSI - LISE 3 spectrometer were performed to study the neutron deficient nucleus 66 As. This nucleus was produced in the fragmentation of 70 MeV/u 78 Kr primary beam in a nickel target. Two new isomeric states have been observed. From the observed γ transitions a decay scheme is proposed

Environmental tobacco smoke is just as damaging to DNA as mainstream smoke.

OpenAIRE

Bermúdez, E; Stone, K; Carter, K M; Pryor, W A

1994-01-01

This study demonstrates the ability of tar isolated from environmental tobacco smoke (ETS) to nick DNA in mammalian cells. Solutions of ETS tar behave similarly to aqueous solutions of cigarette tar from mainstream smoke. Both solutions contain the tar semiquinone radical, and this radical associates with the DNA in viable rat alveolar macrophages. Solutions of tar from ETS cause single-strand DNA breaks in rat thymocytes in proportion to the amount of tar present, until a plateau is reached....

Isomerization of β-carotene by titanium tetrachloride catalyst

Indian Academy of Sciences (India)

TECS

2007-05-04

May 4, 2007 ... antioxidant because of the presence of a long chain of conjugated carbon-carbon double bonds. ... such as extraction, chromatography etc. It has been reported that the chlorinated solvents can promote isomerization of trans conjugated polyenes such as β-carotene during extraction.5. Also, the isomeriza-.

Excitation of isomeric states 1h11/2 in (γ, n) reactions

International Nuclear Information System (INIS)

Tonchev, A.P.; Gangrskij, Yu.P.; Belov, A.G.

1995-01-01

The cross sections of (γ, n) reactions were measured for ground and isomeric states 1h 11/2 in 16 isotopes of Pd, Cd, Sn, Te, Ba, Ce, Nd and Sm. The energy of γ-rays was placed in the region of Giant Dipole Resonance. An activation method of measurements has been used. IR dependence of neutron and proton number in nucleus was detected and of excitation energy of residual nucleus as well. Different factors influencing the values of the isomeric ratios are discussed. 20 refs., 5 figs., 2 tabs

Photofragment imaging study of the CH2CCH2OH radical intermediate of the OH+allene reaction

International Nuclear Information System (INIS)

Raman, Arjun S.; Justine Bell, M.; Lau, K.-C.; Butler, Laurie J.

2007-01-01

These velocity map imaging experiments characterize the photolytic generation of one of the two radical intermediates formed when OH reacts via an addition mechanism with allene. The CH 2 CCH 2 OH radical intermediate is generated photolytically from the photodissociation of 2-chloro-2-propen-1-ol at 193 nm. Detecting the Cl atoms using [2+1] resonance-enhanced multiphoton ionization evidences an isotropic angular distribution for the Cl+CH 2 CCH 2 OH photofragments, a spin-orbit branching ratio for Cl( 2 P 1/2 ):Cl( 2 P 3/2 ) of 0.28, and a bimodal recoil kinetic energy distribution. Conservation of momentum and energy allows us to determine from this data the internal energy distribution of the nascent CH 2 CCH 2 OH radical cofragment. To assess the possible subsequent decomposition pathways of this highly vibrationally excited radical intermediate, we include electronic structure calculations at the G3//B3LYP level of theory. They predict the isomerization and dissociation transition states en route from the initial CH 2 CCH 2 OH radical intermediate to the three most important product channels for the OH+allene reaction expected from this radical intermediate: formaldehyde+C 2 H 3 , H+acrolein, and ethene+CHO. We also calculate the intermediates and transition states en route from the other radical adduct, formed by addition of the OH to the center carbon of allene, to the ketene+CH 3 product channel. We compare our results to a previous theoretical study of the O+allyl reaction conducted at the CBS-QB3 level of theory, as the two reactions include several common intermediates

Photofragment imaging study of the CH2CCH2OH radical intermediate of the OH +allene reaction

Science.gov (United States)

Raman, Arjun S.; Justine Bell, M.; Lau, Kai-Chung; Butler, Laurie J.

2007-10-01

These velocity map imaging experiments characterize the photolytic generation of one of the two radical intermediates formed when OH reacts via an addition mechanism with allene. The CH2CCH2OH radical intermediate is generated photolytically from the photodissociation of 2-chloro-2-propen-1-ol at 193nm. Detecting the Cl atoms using [2+1] resonance-enhanced multiphoton ionization evidences an isotropic angular distribution for the Cl +CH2CCH2OH photofragments, a spin-orbit branching ratio for Cl(P1/22):Cl(P3/22) of 0.28, and a bimodal recoil kinetic energy distribution. Conservation of momentum and energy allows us to determine from this data the internal energy distribution of the nascent CH2CCH2OH radical cofragment. To assess the possible subsequent decomposition pathways of this highly vibrationally excited radical intermediate, we include electronic structure calculations at the G3//B3LYP level of theory. They predict the isomerization and dissociation transition states en route from the initial CH2CCH2OH radical intermediate to the three most important product channels for the OH +allene reaction expected from this radical intermediate: formaldehyde+C2H3, H +acrolein, and ethene+CHO. We also calculate the intermediates and transition states en route from the other radical adduct, formed by addition of the OH to the center carbon of allene, to the ketene+CH3 product channel. We compare our results to a previous theoretical study of the O +allyl reaction conducted at the CBS-QB3 level of theory, as the two reactions include several common intermediates.

Determination of the production rate of low intensity isomeric transitions

International Nuclear Information System (INIS)

Lakosi, L.; Veres, A.; Tam, N.C.; Pavlicsek, I.

1992-01-01

Flat 2π and cylindrical 4π multiwire proportional counters were built for counting for low energy internal conversion electrons from the nuclear isomers 83m Kr, 103m Rh and 189m Os, induced by irradiation with high intensity 60 Co and 4 MeV bremsstrahlung sources. The β-decay of 176m Lu was recorded by a plastic scintillator. In this way higher sensitivities were attained than by detecting γ-rays or characteristic X-rays associated with the isomeric transitions, and the excitation of 189m Os by low energy 137 Cs and 300 kV X-ray sources also became detectable. Comparatively large isomeric activities produced by linac irradiation were standardizing by a Ge spectrometer for calibrating proportional and scintillation counting. (orig.)

cis-trans Isomerization of silybins A and B

Czech Academy of Sciences Publication Activity Database

Novotná, Michaela; Gažák, Radek; Biedermann, David; Di Meo, F.; Marhol, Petr; Kuzma, Marek; Bednárová, Lucie; Fuksová, Kateřina; Trouillas, P.; Křen, Vladimír

-, č. 10 (2014), s. 1047-1063 ISSN 1860-5397 R&D Projects: GA ČR GAP207/10/0288; GA MŠk LH13097; GA MŠk(CZ) LD13041 Institutional support: RVO:61388971 ; RVO:61388963 Keywords : isomerization * silibinin * silybin Subject RIV: CC - Organic Chemistry Impact factor: 2.762, year: 2014

Analysis of Optimal Process Flow Diagrams of Light Naphtha Isomerization Process by Mathematic Modelling Method

OpenAIRE

Chuzlov, Vyacheslav Alekseevich; Molotov, Konstantin

2016-01-01

An approach to simulation of hydrocarbons refining processes catalytic reactors. The kinetic and thermodynamic research of light naphtha isomerization process was conducted. The kinetic parameters of hydrocarbon feedstock chemical conversion on different types of platinum-content catalysts was established. The estimation of efficiency of including different types of isomerization technologies in oil refinery flow diagram was performed.

Discussion of isomeric ratios in (p, n) and (d, 2n) reaction

Energy Technology Data Exchange (ETDEWEB)

Bakhshiyan, T. M., E-mail: tiruhi44@mail.ru [Yerevan State University (Armenia)

2016-01-15

Isomeric ratios (IR) in the (p, n) and (d, 2n) reactions are considered. The dependence of IR values on the projectile type and energy, the target- and product-nucleus spin, the spin difference between the isomeric and ground states of products, and the product mass number is discussed. The isomeric ratios for 46 product nuclei (from {sup 44m,g}Sc to {sup 127m,g}Xe) obtained in reactions where target and product nuclei have identical mass numbers were calculated at energies from the reaction threshold to 50 MeV (with a step of ΔE = 1 MeV). The calculations in question were performed with the aid of the TALYS 1.4 code package. The calculated IR values were compared with their experimental counterparts available from the literature (EXFOR database). In the majority of cases, the calculated IR values agree well with the experimental data in question. It is noteworthy that the IR values obtained in (d, 2n) reactions are substantially greater than those in (p, n) reactions.

Special features of isomeric ratios in nuclear reactions induced by various projectile particles

Energy Technology Data Exchange (ETDEWEB)

Danagulyan, A. S.; Hovhannisyan, G. H., E-mail: hov-gohar@ysu.am; Bakhshiyan, T. M.; Martirosyan, G. V. [Yerevan State University (Armenia)

2016-05-15

Calculations for (p, n) and (α, p3n) reactions were performed with the aid of the TALYS-1.4 code. Reactions in which the mass numbers of target and product nuclei were identical were examined in the range of A = 44–124. Excitation functions were obtained for product nuclei in ground and isomeric states, and isomeric ratios were calculated. The calculated data reflect well the dependence of the isomeric ratios on the projectile type. A comparison of the calculated and experimental data reveals, that, for some nuclei in a high-spin state, the calculated data fall greatly short of their experimental counterparts. These discrepancies may be due to the presence of high-spin yrast states and rotational bands in these nuclei. Calculations involving various level-density models included in the TALYS-1.4 code with allowance for the enhancement of collective effects do not remove the discrepancies in the majority of cases.

Analysis of Optimal Process Flow Diagrams of Light Naphtha Isomerization Process by Mathematic Modelling Method

Directory of Open Access Journals (Sweden)

Chuzlov Vjacheslav

2016-01-01

Full Text Available An approach to simulation of hydrocarbons refining processes catalytic reactors. The kinetic and thermodynamic research of light naphtha isomerization process was conducted. The kinetic parameters of hydrocarbon feedstock chemical conversion on different types of platinum-content catalysts was established. The estimation of efficiency of including different types of isomerization technologies in oil refinery flow diagram was performed.

Catalyst compositions useful for olefin isomerization and disproportionation

International Nuclear Information System (INIS)

Drake, C.A.

1987-01-01

A process is described for the double bond isomerization of an aliphatic olefinic hydrocarbon feed which comprises contacting the feed under isomerization conditions with a catalyst prepared by: (a) impregnating an alumina support having a surface area of at least 200 m/sup 2//g and a pore volume of at least 0.45 cm/sup 3//g with: 1 up to 20 wt. % of at least one magnesium compound convertible to the oxide, based on the weight of support and calculated as the metal; 0 up to 5 wt. % of at least one alkali metal compound convertible to the oxide, based on the weight of support and calculated as the metal; and 0 up to 5 wt. % of at least one zirconium compound convertible to the oxide, based on the weight of support and calculated as the metal; and (b) heating the alumina support impregnated in accordance with step (a) in an oxygen-containing atmosphere under conditions suitable to convert at least a portion of the magnesium, alkali metal, and zirconium compounds to the oxide form

New isomeric states in {sup 152,154,156}Nd produced by spontaneous fission of {sup 252}Cf

Energy Technology Data Exchange (ETDEWEB)

Gautherin, C.; Houry, M.; Korten, W.; Le Coz, Y.; Lucas, R.; Phan, X.H.; Theisen, C. [Commissariat l`Energie Atomique de Saclay, Gif sur Yvette (France). DSM/DAPINA/SPhN; Badimon, C.; Barreau, G.; Doan, T.P.; Pedemay, G. [Centre d`Etudes Nucleaires de Bordeaux-Gradignan, Domaine du Haut Vigneau, F-33175 Gradignan (France); Belier, G.; Girod, M.; Meot, V.; Peru, S. [Commissariat a l`Energie Atomique de Bruyeres-le-Chatel, DAM/SPN, BP12, F-91680 Bruyeres-le-Chatel (France); Astier, A.; Ducroux, L.; Meyer, M.; Redon, N. [Institut de Physique Nucleaire de Lyon, F-69622 Villeurbanne Cedex (France)

1998-04-01

Isomeric states have been observed in fission-fragments produced by spontaneous fission of {sup 252}Cf. These states are found in neutron rich nuclei of different structure and deformations. About 50 isomeric nuclei have been observed using coincidences between {gamma}-rays identified in EUROGAM II and fission fragments detected in photovoltaic cells (SAPhIR). Lifetimes in the range from 20 ns to 2{mu}s have been measured. Presented calculations based on HFB+D1S force on new measured isomeric states in the {sup 152,154,156}Nd show evidence for K-isomers. (orig.) With 8 figs., 27 refs.

Peptide models of protein metastable binding sites: competitive kinetics of isomerization and hydrolysis.

Science.gov (United States)

Khan, S A; Sekulski, J M; Erickson, B W

1986-09-09

alpha 2-Macroglobulin and the complement components C3 and C4 each contain a metastable binding site that is essential for covalent attachment. Two cyclic peptides are useful models of these unusual protein sites. Five-membered lactam 1 (CH3CO-Gly-Cys-Gly-Glu-Glp-Asn-NH2) contains an internal residue of pyroglutamic acid (Glp). Fifteen-membered thiolactone 2 (CH3CO-Gly-Cys-Gly-Glu-Glu-Asn-NH2 15-thiolactone) contains a thiol ester bond between Cys-2 and Glu-5. These isomeric hexapeptides are spontaneously interconverted in water. Competing with the two isomerization reactions are three reactions involving hydrolysis of 1 and 2. These five processes were found to occur simultaneously under physiologic conditions (phosphate-buffered saline, pH 7.3, 37 degrees C). Best estimates of the five rate constants for these apparent first-order reactions were obtained by comparing the observed molar percentages of peptides 1-4 with those calculated from a set of exponential equations. Both isomerization reactions (ring expansion of 1 to 2, k1 = 6.4 X 10(-5) s-1; ring contraction of 2 to 1, k-1 = 69 X 10(-5) s-1) proceeded faster than any of the hydrolysis reactions: alpha-cleavage of 1 with fragmentation to form dipeptide 3 (k2 = 3.3 X 10(-5) s-1), gamma-cleavage of 1 with ring opening to yield mercapto acid 4 (k3 = 0.35 X 10(-5) s-1), and hydrolysis of 2 with ring opening to give 4 (k4 = 1.9 X 10(-5) s-1). The isomerization rate ratio (k1/k-1 = 10.9) agreed with the isomer ratio at equilibrium (1:2 = 11 starting from 1 and 10 starting from 2). The alpha/gamma regioselectivity ratio (k2/k3 = 9.7) for hydrolysis of the internal Glp residue of 1 was consistent with results for model tripeptides. Part of the chemistry of the protein metastable binding sites can be explained by similar isomerization and hydrolysis reactions.

Pulse radiolytic reduction of amino and hydroxy disubstituted anthraquinones (Preprint no. RC-15)

International Nuclear Information System (INIS)

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

1991-01-01

One-electron reduction of 1-amino-4-hydroxy-9, 10-anthraquinone (AHAQ) and 1,4-diamino-9, 10-anthraquinone (DAAQ) in various matrices has been investigated by electron pulse radiolysis. Spectroscopic and kinetic parameters, acid dissociation constants (pK a ) of the reduced semiquinone radicals and one-electron reduction potential for AHAQ have been measured. (author). 2 tabs

Tin-containing zeolites are highly active catalysts for the isomerization of glucose in water

OpenAIRE

Moliner, Manuel; Román-Leshkov, Yuriy; Davis, Mark E.

2010-01-01

The isomerization of glucose into fructose is a large-scale reaction for the production of high-fructose corn syrup (HFCS; reaction performed by enzyme catalysts) and recently is being considered as an intermediate step in the possible route of biomass to fuels and chemicals. Here, it is shown that a large-pore zeolite that contains tin (Sn-Beta) is able to isomerize glucose to fructose in aqueous media with high activity and selectivity. Specifically, a 10% (wt/wt) glucose solution containin...

cis-Stilbene and (1 alpha,2 beta,3 alpha)-(2-ethenyl-3-methoxycyclopropyl)benzene as mechanistic probes in the Mn(III)(salen)-catalyzed epoxidation: influence of the oxygen source and the counterion on the diastereoselectivity of the competitive concerted and radical-type oxygen transfer.

Science.gov (United States)

Adam, Waldemar; Roschmann, Konrad J; Saha-Möller, Chantu R; Seebach, Dieter

2002-05-08

cis-Stilbene (1) has been epoxidized by a set of diverse oxygen donors [OxD], catalyzed by the Mn(III)(salen)X complexes 3 (X = Cl, PF(6)), to afford a mixture of cis- and trans-epoxides 2. The cis/trans ratios range from 29:71 (extensive isomerization) to 92:8, which depends both on the oxygen source [OxD] and on the counterion X of the catalyst. When (1 alpha,2 beta,3 alpha)-(2-ethenyl-3-methoxycyclopropyl)-benzene (4) is used as substrate, a mechanistic probe which differentiates between radical and cationic intermediates, no cationic ring-opening products are found in this epoxidation reaction; thus, isomerized epoxide product arises from intermediary radicals. The dependence of the diastereoselectivity on the oxygen source is rationalized in terms of a bifurcation step in the catalytic cycle, in which concerted Lewis-acid-activated oxygen transfer competes with stepwise epoxidation by the established Mn(V)(oxo) species. The experimental counterion effect is attributed to the computationally assessed ligand-dependent reaction profiles and stereoselectivities of the singlet, triplet, and quintet spin states available to the manganese species.

Concurrent Mass Measurement and Laser Spectroscopy for Unambiguous Isomeric State Assignment

Science.gov (United States)

Lascar, Daniel; Babcock, Carla; Henderson, Jack; Pearson, Matt

2017-09-01

Recent work by the TITAN group at TRIUMF on isomeric state mass measurements of odd-A, neutron-rich cadmium nuclei has shown a disconnect between experiment and theory in 127 g , mCd. The spin and parity assignments of the ground and isomeric states are assigned as 3/2+ and 11/2-, respectively, primarily via systematic arguments. Conversely, state of the art shell model and ab initio calculations show a reversal of the states, predicting a ground state of 11/2- and a 3/2+ isomer. Penning Trap Mass Spectrometry (PTMS) can measure the energy separation between the ground state and the isomer without ambiguity but cannot, on its own, comment on the spin and parity. Collinear Laser Spectroscopy (CLS) experiments have been performed on 127Cd and have elegantly demonstrated the existence of both 3/2+ and 11/2- states. What CLS cannot do, on its own, is assign an ordering to those states. If, however, a PTMS and CLS experiment could be performed concurrently using identical beams from the same facility then there exists sufficient information shared between both experiments that a definitive assignment can be made. We present a concept for a new slate of measurements using existing experimental facilities simultaneously, with shared resources, to definitively assign spin and parity for ground and isomeric states in short-lived nuclei.

High-pressure liquid chromatographic determination of chlorphenesin carbamate and the beta-isomeric carbamate.

Science.gov (United States)

Beyer, W F

1976-12-01

A high-pressure liquid chromatographic assay was developed for the determination of chlorphenesin carbamate and its beta-isomeric carbamate. A single 4-mm i.d. X 30-cm column, prepacked with 10 micrometer fully porous silica gel particles, is used with 3% methanol in 50% water-saturated butyl chloride as the mobile phase. The procedure separates chlorphenesin carbamate from several possible impurities in addition to the beta-isomeric carbamate. The assay was applied to bulk drug and compressed tablets. The relative standard deviations for the assays of chlorphenesin carbamate and the beta-isomer are approximately 1 and 2%, respectively.

Isomeric ratio measurements for the radiative neutron capture 176Lu(n,γ at DANCE

Directory of Open Access Journals (Sweden)

Denis-Petit D.

2017-01-01

Full Text Available The isomeric ratios for the neutron capture reaction 176Lu(n,γ to the Jπ = 5/2−, 761.7 keV, T1/2 = 32.8 ns and the Jπ = 15/2+, 1356.9 keV, T1/2 = 11.1 ns levels of 177Lu, have been measured for the first time with the Detector for Advanced Neutron Capture Experiments (DANCE at the Los Alamos National Laboratory. These measured isomeric ratios are compared with TALYS calculations.

POSSIBLE NATURE OF THE RADIATION-INDUCED SIGNAL IN NAILS: HIGH-FIELD EPR, CONFIRMING CHEMICAL SYNTHESIS, AND QUANTUM CHEMICAL CALCULATIONS

Science.gov (United States)

Tipikin, Dmitriy S.; Swarts, Steven G.; Sidabras, Jason W.; Trompier, François; Swartz, Harold M.

2016-01-01

Exposure of finger- and toe-nails to ionizing radiation generates an Electron Paramagnetic Resonance (EPR) signal whose intensity is dose dependent and stable at room temperature for several days. The dependency of the radiation-induced signal (RIS) on the received dose may be used as the basis for retrospective dosimetry of an individual's fortuitous exposure to ionizing radiation. Two radiation-induced signals, a quasi-stable (RIS2) and stable signal (RIS5), have been identified in nails irradiated up to a dose of 50 Gy. Using X-band EPR, both RIS signals exhibit a singlet line shape with a line width around 1.0 mT and an apparent g-value of 2.0044. In this work, we seek information on the exact chemical nature of the radiation-induced free radicals underlying the signal. This knowledge may provide insights into the reason for the discrepancy in the stabilities of the two RIS signals and help develop strategies for stabilizing the radicals in nails or devising methods for restoring the radicals after decay. In this work an analysis of high field (94 GHz and 240 GHz) EPR spectra of the RIS using quantum chemical calculations, the oxidation–reduction properties and the pH dependence of the signal intensities are used to show that spectroscopic and chemical properties of the RIS are consistent with a semiquinone-type radical underlying the RIS. It has been suggested that semiquinone radicals formed on trace amounts of melanin in nails are the basis for the RIS signals. However, based on the quantum chemical calculations and chemical properties of the RIS, it is likely that the radicals underlying this signal are generated from the radiolysis of L-3,4-dihydroxyphenylalanine (DOPA) amino acids in the keratin proteins. These DOPA amino acids are likely formed from the exogenous oxidation of tyrosine in keratin by the oxygen from the air prior to irradiation. We show that these DOPA amino acids can work as radical traps, capturing the highly reactive and unstable

Second-chance forward isomerization dynamics of the red/green cyanobacteriochrome NpR6012g4 from Nostoc punctiforme.

Science.gov (United States)

Kim, Peter W; Freer, Lucy H; Rockwell, Nathan C; Martin, Shelley S; Lagarias, J Clark; Larsen, Delmar S

2012-01-11

The primary ultrafast Z-to-E isomerization photodynamics of the phytochrome-related cyanobacteriochrome NpR6012g4 from Nostoc punctiforme was studied by transient absorption pump-dump-probe spectroscopy. A 2 ps dump pulse resonant with the stimulated emission band depleted 21% of the excited-state population, while the initial photoproduct Lumi-R was depleted by only 11%. We observed a red-shifted ground-state intermediate (GSI) that we assign to a metastable state that failed to isomerize fully. Multicomponent global analysis implicates the generation of additional Lumi-R from the GSI via crossing over the ground-state thermal barrier for full isomerization, explaining the discrepancy between excited-state and Lumi-R depletion by the dump pulse. This second-chance ground-state dynamics provides a plausible explanation for the unusually high quantum yield of 40% for the primary isomerization step in the forward reaction of NpR6012g4. © 2011 American Chemical Society

Measurement of millisecond half-lives of isomeric levels in some nuclei

Energy Technology Data Exchange (ETDEWEB)

Garg, K C; Khurana, C S [Punjabi Univ., Patiala (India). Nuclear Science Labs.

1976-09-01

Half-lives of 2.7, 14.5, 17, 20, 20.4, 44 and 2230 msec, of isomeric levels in /sup 208/Bi, /sup 88/Y, /sup 75/As, /sup 24/Na, /sup 71/Ge, /sup 114/In and /sup 167/Er respectively have been measured, employing on-line irradiation system. These millisecond isomeric levels are produced by 14.7 MeV neutrons through (n,p), (n,..cap alpha..), (n,n') and (n,2n) reactions on natural target samples. A ..gamma..-ray scintillation detector coupled with NTA-512B, 1024 channel analyzer has been used to follow the decay of the millisecond activities. Deflected deuteron beam bursts have been used to reduce the long-time background to initial count ratios in the decay curves to achieve a better accuracy of measurements.

NaSO2Ph Induced Exclusive Isomerization of 1,2-Allenyl Sulfoxides to 2-Alkynylic Phenyl Sulfoxides

Institute of Scientific and Technical Information of China (English)

傅春玲; 麻生明

2005-01-01

The clean isomerization of 1,2-allenyl sulfoxides in the presence of NaSO2Ph afforded 2-alkynylic phenyl sulfoxides in good yields and selectivities. Although strong base-catalyzed isomerization of allenes to alkynes is known, the mechanism for the current reaction is interesting for the obvious reason that NaSOEPh is a weak base.

An infrared study of the nitro—nitrito linkage isomerization in solid nitro- and nitritopentamminecobalt(III) chloride

Science.gov (United States)

Heyns, A. M.; de Waal, D.

1989-01-01

The photochemical isomerization reaction of [Co(NH 3) 5NO 2]Cl 2 to [Co(NH 3) 5ONO]Cl 2 has been studied in the solid state by means of i.r. spectroscopy. The reaction is first order with k = 2.53±0.05 × 10 -4s -1 and is much faster ( t1/2=49min) than the well-known spontaneous nitrito → nitro isomerization ( t1/2 = 6 days). The i.r. bands of both the NH 3 and ONO - -groups in the range 4000-50 cm -1 indicate minor differences between the structures of freshly and photochemically prepared [Co(NH 3) 5ONO]Cl 2. The far i.r. spectra indicate the disorder existing in the intermediate products during the isomerization processes.

Isomerization of 2-phospha-4-silabicyclo[1.10]butane

NARCIS (Netherlands)

Slootweg, J.C.; Ehlers, A.W.; Lammertsma, K.

2004-01-01

In analogy with the valence isomerism of the hydrocarbons bicyclobutane, 1,3-butadiene and cyclobutene, the rearrangements for 2-phospha-4-sila- bicyclo[1.1.0]butane were studied at the B3LYP/6-311+G** level of theory. The monocyclic 1,2-dihydro-1,2-phosphasilete is shown to be the thermodynamically

Radical fashion and radical fashion innovation

NARCIS (Netherlands)

Zhang, D.; Benedetto, Di A.C.

2010-01-01

This is a study of the related concepts of radical fashion and radical fashion innovation. Radical fashions are defined here as those that may never enter the market at all, and exist primarily on runway shows, in exhibitions and in publicity; by contrast, radical fashion innovations may be very

Efficient assembly of polysubstituted pyrroles via a (3 + 2) cycloaddition/skeletal rearrangement/redox isomerization cascade reaction.

Science.gov (United States)

Yu, Yuanyuan; Wang, Chunyu; He, Xinze; Yao, Xiaotong; Zu, Liansuo

2014-07-03

An unprecedented cascade strategy, used in conjunction with a redox isomerization, for the synthesis of 3-allyl pyrroles is reported. In a single step, readily accessible simple starting materials are transformed into highly substituted pyrroles with high efficiency. The products obtained contain allyl substituents, which can be readily elaborated to other useful functional groups. The reaction proceeds through an unusual (3 + 2) cycloaddition/skeletal rearrangement/redox isomerization pathway.

Isomerization and dissociation in competition: the two-component dissociation rates of methyl acetate ions

Science.gov (United States)

Mazyar, Oleg A.; Mayer, Paul M.; Baer, Tomas

1997-11-01

Threshold photoelectron-photoion coincidence (TPEPICO) spectroscopy has been used to investigate the unimolecular chemistry of metastable methyl acetate ions, CH3COOCH3.+. The rate of molecular ion fragmentation with the loss of CH3O. and CH2OH radicals as a function of ion internal energy was obtained from the coincidence data and used in conjunction with Rice-Ramsperger-Kassel-Markus and ab initio molecular orbital calculations to model the dissociation/isomerization mechanism of the methyl acetate ion (A). The data were found to be consistent with the mechanism involving a hydrogen-bridged complex CH3CO[middle dot][middle dot][middle dot]H[middle dot][middle dot][middle dot]OCH2.+(E) as the direct precursor of the observed fragments CH3CO+ and CH2OH.. The two-component decay rates were modeled with a three-well-two-product potential energy surface including the distonic ion CH3C(OH)OCH2.+(B) and enol isomer CH2C(OH)OCH3.+(C), which are formed from the methyl acetate ion by two consecutive [1,4]-hydrogen shifts. The 0 K heats of formation of isomers B and C as well as transition states TSAB, TSBC, and TSBE (relative to isomer A) were calculated from Rice-Ramsperger-Kassel-Markus (RRKM) theory.

EThcD Discrimination of Isomeric Leucine/Isoleucine Residues in Sequencing of the Intact Skin Frog Peptides with Intramolecular Disulfide Bond

Science.gov (United States)

Samgina, Tatiana Yu; Kovalev, Sergey V.; Tolpina, Miriam D.; Trebse, Polonca; Torkar, Gregor; Lebedev, Albert T.

2018-05-01

Our scientific interests involve de novo sequencing of non-tryptic natural amphibian skin peptides including those with intramolecular S-S bond by means of exclusively mass spectrometry. Reliable discrimination of the isomeric leucine/isoleucine residues during peptide sequencing by means of mass spectrometry represents a bottleneck in the workflow for complete automation of the primary structure elucidation of these compounds. MS3 is capable of solving the problem. Earlier we demonstrated the advanced efficiency of ETD-HCD method to discriminate Leu/Ile in individual peptides by consecutive application of ETD to the polyprotonated peptides followed by HCD applied to the manually selected primary z-ions with the targeted isomeric residues at their N-termini and registration of the characteristic w-ions. Later this approach was extended to deal with several (4-7) broad band mass ranges, without special isolation of the primary z-ions. The present paper demonstrates an advanced version of this method when EThcD is applied in the whole mass range to a complex mixture of natural non-tryptic peptides without their separation and intermediate isolation of the targeted z-ions. The proposed EThcD method showed over 81% efficiency for the large natural peptides with intact disulfide ring, while the interfering process of radical site migration is suppressed. Due to higher speed and sensitivity, the proposed EThcD approach facilitates the analytical procedure and allows for the automation of the entire experiment and data processing. Moreover, in some cases it gives a chance to establish the nature of the residues in the intact intramolecular disulfide loops. [Figure not available: see fulltext.

Determination of the isomeric fraction in a postaccelerated radioactive ion beam using the coupled decay-chain equations

CERN Document Server

Ekstrom, A; Dijulio, D D; Cederkall, J; Van de Walle, J

2010-01-01

A method based on the coupled decay-chain equations for extracting the isotopic and the isomeric composition of a postaccelerated radioactive ion beam is presented and demonstrated on a data set from a Coulomb excitation experiment. This is the first attempt of analyzing the content of a postaccelerated radioactive ion beam using this technique. The beam composition is required for an absolute normalization of the measurement. The strength of the method, as compared to present online-based methods, lies in the determination of the isomeric fraction of a partially isomeric beam using all data accumulated during the experiment. We discuss the limitations and sensitivity of the method with respect to the gamma-ray detection efficiency and the accumulated flux. (C) 2010 Elsevier B.V. All rights reserved.

Direct Measurement of the Isomerization Barrier of the Isolated Retinal Chromophore

DEFF Research Database (Denmark)

Dilger, Jonathan; Musbat, Lihi; Sheves, Mordechai

2015-01-01

Isomerizations of the retinal chromophore were investigated using the IMS-IMS technique. Four different structural features of the chromophore were observed, isolated, excited collisionally, and the resulting isomer and fragment distributions were measured. By establishing the threshold activatio...

Histidine, lysine, and arginine radical cations: isomer control via the choice of auxiliary ligand (L) in the dissociation of [CuII(L)amino acid]*2+ complexes.

Science.gov (United States)

Ke, Yuyong; Zhao, Junfang; Verkerk, Udo H; Hopkinson, Alan C; Siu, K W Michael

2007-12-27

Histidine, lysine, and arginine radical cations have been generated through collision-induced dissociation (CID) of complexes [CuII(auxiliary ligand)namino acid]*2+, using tri-, bi-, as well as monodentate auxiliary ligands. On the basis of the observed CID products, the existence of two isomeric amino-acid populations is postulated. The Type 1 radical cations of histidine and lysine, stable on the mass spectrometer time scale, were found to lose water, followed by the loss of carbon monoxide under more energetic CID conditions. The arginine Type 1 radical cation behaved differently, losing dehydroalanine. The Type 2 radical cations were metastable and easily fragmented by the loss of carbon dioxide, effectively preventing direct observation. Type 1 radical cations are proposed to result from neutral (canonical) amino-acid coordination, whereas Type 2 radical cations are from zwitterionic amino-acid coordination to copper in the complex. The ratio of Type 1/Type 2 ions was found to be dependent on the auxiliary ligand, providing a method of controlling which radical cation would be formed primarily. Density functional calculations at B3LYP/6-311++G(d,p) have been used to determine the relative energies of five His*+ isomers. Barriers against interconversion between the isomers and against fragmentation have been calculated, giving insight as to why the Type 1 ions are stable, while only fragmentation products of the Type 2 ions are observable under CID conditions.

Observation of excited states and isomeric decays in doubly-odd 208Fr

International Nuclear Information System (INIS)

Kanjilal, D.; Bhattacharya, S.; Goswami, A.; Kshetri, R.; Raut, R.; Saha, S.; Bhowmik, R.K.; Gehlot, J.; Jnaneswari, G.; Muralithar, S.; Singh, R.P.; Mukherjee, B.; Mukherjee, G.

2009-01-01

The nuclei near the doubly magic 208 Pb are predicted to exhibit various interesting structural phenomena, one of which is a wealth of isomerism. However, a detailed study of high spin states of 211, 212, 213 Fr has already been done. Structure of such trans-Lead nuclei can be interpreted in terms of the shell model states, and the high spin states of these nuclei are interpreted. One of the major interests in the spectroscopic investigation of these nuclei is the role played by the i 13/2 state in creating isomeric levels which decay through transitions of higher muiltipolarity, or are hindered by the close proximity of the levels below. A systematic study of these nuclei will possibly reveal many other interesting structural features

Isomeric cross-section ratios of some (n,2n) reactions at 14. 7 MeV

Energy Technology Data Exchange (ETDEWEB)

Garg, K C; Khurana, C S [Punjabi Univ., Patiala (India). Nuclear Science Labs.

1979-08-01

Isomeric cross-section ratios of (n,2n) reactions at 14.7 MeV leading to the millisecond isomeric levels have been calculated theoretically using the statistical theory of nuclear reactions and the spin distribution form due to Bethe and Bloch. The theoretical ratios have been compared with the experimentally measured values in order to evaluate the spin cut-off parameter sigma. This parameter has been used to calculate the effective moment of inertia of the nucleus to draw useful conclusions from the results of present calculations.

Compartmental and noncompartmental modeling of ¹³C-lycopene absorption, isomerization, and distribution kinetics in healthy adults.

Science.gov (United States)

Moran, Nancy E; Cichon, Morgan J; Riedl, Kenneth M; Grainger, Elizabeth M; Schwartz, Steven J; Novotny, Janet A; Erdman, John W; Clinton, Steven K

2015-12-01

Lycopene, which is a red carotenoid in tomatoes, has been hypothesized to mediate disease-preventive effects associated with tomato consumption. Lycopene is consumed primarily as the all-trans geometric isomer in foods, whereas human plasma and tissues show greater proportions of cis isomers. With the use of compartmental modeling and stable isotope technology, we determined whether endogenous all-trans-to-cis-lycopene isomerization or isomeric-bioavailability differences underlie the greater proportion of lycopene cis isomers in human tissues than in tomato foods. Healthy men (n = 4) and women (n = 4) consumed (13)C-lycopene (10.2 mg; 82% all-trans and 18% cis), and plasma was collected over 28 d. Unlabeled and (13)C-labeled total lycopene and lycopene-isomer plasma concentrations, which were measured with the use of high-performance liquid chromatography-mass spectrometry, were fit to a 7-compartment model. Subjects absorbed a mean ± SEM of 23% ± 6% of the lycopene. The proportion of plasma cis-(13)C-lycopene isomers increased over time, and all-trans had a shorter half-life than that of cis isomers (5.3 ± 0.3 and 8.8 ± 0.6 d, respectively; P lycopene bioavailability and endogenous trans-to-cis-lycopene isomerization was predictive of plasma (13)C and unlabeled cis- and all-trans-lycopene concentrations. Although the bioavailability of cis (24.5% ± 6%) and all-trans (23.2% ± 8%) isomers did not differ, endogenous isomerization (0.97 ± 0.25 μmol/d in the fast-turnover tissue lycopene pool) drove tissue and plasma isomeric profiles. (13)C-Lycopene combined with physiologic compartmental modeling provides a strategy for following complex in vivo metabolic processes in humans and reveals that postabsorptive trans-to-cis-lycopene isomerization, and not the differential bioavailability of isomers, drives tissue and plasma enrichment of cis-lycopene. This trial was registered at clinicaltrials.gov as NCT01692340. © 2015 American Society for Nutrition.

Compartmental and noncompartmental modeling of 13C-lycopene absorption, isomerization, and distribution kinetics in healthy adults123

Science.gov (United States)

Moran, Nancy E; Cichon, Morgan J; Riedl, Kenneth M; Grainger, Elizabeth M; Schwartz, Steven J; Novotny, Janet A; Erdman, John W; Clinton, Steven K

2015-01-01

Background: Lycopene, which is a red carotenoid in tomatoes, has been hypothesized to mediate disease-preventive effects associated with tomato consumption. Lycopene is consumed primarily as the all-trans geometric isomer in foods, whereas human plasma and tissues show greater proportions of cis isomers. Objective: With the use of compartmental modeling and stable isotope technology, we determined whether endogenous all-trans-to-cis-lycopene isomerization or isomeric-bioavailability differences underlie the greater proportion of lycopene cis isomers in human tissues than in tomato foods. Design: Healthy men (n = 4) and women (n = 4) consumed 13C-lycopene (10.2 mg; 82% all-trans and 18% cis), and plasma was collected over 28 d. Unlabeled and 13C-labeled total lycopene and lycopene-isomer plasma concentrations, which were measured with the use of high-performance liquid chromatography–mass spectrometry, were fit to a 7-compartment model. Results: Subjects absorbed a mean ± SEM of 23% ± 6% of the lycopene. The proportion of plasma cis-13C-lycopene isomers increased over time, and all-trans had a shorter half-life than that of cis isomers (5.3 ± 0.3 and 8.8 ± 0.6 d, respectively; P lycopene bioavailability and endogenous trans-to-cis-lycopene isomerization was predictive of plasma 13C and unlabeled cis- and all-trans-lycopene concentrations. Although the bioavailability of cis (24.5% ± 6%) and all-trans (23.2% ± 8%) isomers did not differ, endogenous isomerization (0.97 ± 0.25 μmol/d in the fast-turnover tissue lycopene pool) drove tissue and plasma isomeric profiles. Conclusion: 13C-Lycopene combined with physiologic compartmental modeling provides a strategy for following complex in vivo metabolic processes in humans and reveals that postabsorptive trans-to-cis-lycopene isomerization, and not the differential bioavailability of isomers, drives tissue and plasma enrichment of cis-lycopene. This trial was registered at clinicaltrials.gov as NCT01692340. PMID

A Comparative Study of the Radical-scavenging Activity of the Phenolcarboxylic Acids Caffeic Acid, p-Coumaric Acid, Chlorogenic Acid and Ferulic Acid, With or Without 2-Mercaptoethanol, a Thiol, Using the Induction Period Method

Directory of Open Access Journals (Sweden)

Seiichiro Fujisawa

2008-10-01

Full Text Available Phenolcarboxylic acid antioxidants do not act in vivo as radical-scavengers in isolation, but rather together with GSH (glutathione, a coantioxidant, they constitute an intricate antioxidant network. Caffeic acid, p-coumaric acid, ferulic acid and chlorogenic acid with or without 2-mercaptoethanol (ME, as a substitute for GSH, was investigated by the induction period (IP method for polymerization of methyl methacrylate (MMA initiated by thermal decomposition of 2,2'-azobisisobutyronitrile (AIBN, a source of alkyl radicals, R. and benzoyl peroxide (BPO, a source of peroxy radicals, PhCOO. using differential scanning calorimetry (DSC. Upon PhCOO. radical scavenging, the stoichiometric factors (n, number of free radical trapped by one mole of antioxidant for caffeic acid, ferulic acid, p-coumaric acid and chlorogenic acid were 2.4, 1.8, 1.7 and 0.9, whereas upon R. radical scavenging, the corresponding values were 1.3, 1.2, 1.0 and 0.8, respectively. Antioxidants with n values close to 2 suggest the stepwise formation of semiquinone radicals and quinones. By contrast, those with n values close to 1 suggest the formation of dimers after single-electron oxidation, possibly due to recombination of corresponding aryloxy radicals. The ratio of the rate constant of inhibition to that of propagation (kinh/kp declined in the order chlorogenic acid > p-coumaric acid > ferulic acid > caffeic acid. The ratio of the observed IP for the phenolcarboxylic acid/2-mercapto-ethanol (ME mixture (1:1 molar ratio (A to the calculated IP (the simple sum of phenol acid antioxidant and ME (B was investigated. Upon R. scavenging, the caffeic acid or p-coumaric acid/ME mixture was A/B > 1, particularly the former was 1.2, suggesting a synergic effect. By contrast, upon PhCOO. scavenging, the corresponding mixture was A/B < 1, particularly the latter was 0.7, suggesting an antagonistic effect. Upon both radicals scavenging, the A/B for the ferulic acid or chlorogenic acid

Changes in Atmospheric Butanes and Pentanes and Their Isomeric Ratios in the Continental United States

Science.gov (United States)

Rossabi, Sam; Helmig, Detlev

2018-04-01

Nonmethane hydrocarbons have been used as tracers in research on emissions and atmospheric oxidation chemistry. This research investigates source region mixing ratio trends of the nonmethane hydrocarbons i-butane, n-butane, i-pentane, and n-pentane, and the (i/n) isomeric ratios of these compounds between 2001 and 2015. Data collected at Photochemical Assessment Monitoring Stations, mandated by the U.S. Environmental Protection Agency in ozone nonattainment areas, and data collected at Global Greenhouse Gas Reference Network sites within the National Oceanic and Atmospheric Administration network, and analyzed at the Institute of Arctic and Alpine Research at the University of Colorado-Boulder, were examined. Among all considered species, linear regression analyses on concentration time series had negative slopes at 81% of sites, indicating predominantly declining butane and pentane atmospheric concentrations. Mostly negative slopes (78% of sites) were found for the (i/n) butane and pentane isomeric ratios, including all six and seven statistically significant (i/n) butane and pentane trends, respectively. Over the 15 year investigation period and averaged over all sites, total relative changes were 30 and 45% for the (i/n) ratios of butanes and pentanes, respectively, with a relative increase in the prominence of the n-isomers. Most likely causes include changing isomeric ratios in gasoline sector emissions, and increasing influence of oil and natural gas industry emissions. Changes in concentrations and isomeric ratios depend on proximity of contributing emission sources to measurement sites.

Destabilization in the isomeric nitrobenzonitriles: an experimental thermochemical study

International Nuclear Information System (INIS)

Roux, Maria Victoria; Jimenez, Pilar; Davalos, Juan Z.; Temprado, Manuel; Liebman, Joel F.

2003-01-01

The enthalpies of combustion and of sublimation, respectively, of the three isomeric nitrobenzonitriles have been measured: o-, {(-3456.3±2.9), (88.1±1.4)} kJ·mol -1 ; m-, {(-3442.8±3.3), (92.8±0.3)} kJ·mol -1 ; p-, {(-3448.2±3.6), (91.1±1.3)} kJ·mol -1 . In turn, from these values, the standard molar enthalpies of formation for the condensed and gaseous state, respectively, have been derived: o-, {(130.1±3.1), (218.2±3.4)} kJ·mol -1 ; m-, {(116.5±3.5), (209.3±3.5)} kJ·mol -1 ; p-, {(122.0±3.8), (213.1±4.0)} kJ·mol -1 . Destabilization energies associated with the presence of the two electron-withdrawing groups have been determined, for o-, m-, and p-nitrobenzonitrile, {(17.6±4.1), (8.7±4.2), and (12.5±4.6)} kJ·mol -1 , respectively, and are consistent with those obtained for the corresponding sets of isomeric methyl benzenedicarboxylates, dicyanobenzenes, dinitrobenzenes, and (neutral and ionized) nitrobenzoic acids

Light-induced linkage isomerization of photochromic [Ru(bpy){sub 2}(R-OSO)]{sup +} compounds

Energy Technology Data Exchange (ETDEWEB)

Springfeld, Kristin; Dieckmann, Volker; Eicke, Sebastian; Imlau, Mirco [Department of Physics, University of Osnabrueck (Germany); Rack, Jeffrey J. [Department of Chemistry and Biochemistry, Ohio University, Athens, Ohio (United States)

2010-07-01

Ruthenium sulfoxides exhibit light-induced linkage isomerization of the SO-bond with remarkable photosensitivity S=(0.25{+-}0.03) Ws cm{sup -1} and extended lifetimes of the related metastable states in the order of 10{sup 4} s. The isomerization is accompanied with tremendous changes of the optical extinction up to 9350 cm{sup -1} mol{sup -1} thus enabling the study of linkage isomerization by means of time-resolved optical spectroscopy. Here, the influence of ligand substitution is studied via inspection of the photosensitivity and the generation and relaxation dynamics of the photochromic response as a function of temperature (pump at {lambda}=405 nm, probe at {lambda}=532 nm). The spectra of the modified compounds, where ligands R=Bn, BnCl, and BnMe were attached to OSO, were compared with the reference system [Ru(bpy){sub 2}(OSO)]{sup +}. It turns out, that the new ligands affect the absorption features and the photosensitivity of the system only slightly. In contrast, a strong influence of the thermal relaxation of the metastable states is uncovered. Remarkably, the influence on the frequency factors is much more pronounced than on the activation energies achieved by Arrhenius' law.

Porphyrin Co(III-Nitrene Radical Mediated Pathway for Synthesis of o-Aminoazobenzenes

Directory of Open Access Journals (Sweden)

Monalisa Goswami

2018-05-01

Full Text Available Azobenzenes are versatile compounds with a range of applications, including dyes and pigments, food additives, indicators, radical reaction initiators, molecular switches, etc. In this context, we report a general method for synthesizing o-aminoazobenzenes using the commercially available cobalt(II tetraphenyl porphyrin [CoII(TPP]. The net reaction is a formal dimerization of two phenyl azides with concomitant loss of two molecules of dinitrogen. The most commonly used methodology to synthesize azobenzenes is based on the initial diazotization of an aromatic primary amine at low temperatures, which then reacts with an electron rich aromatic nucleophile. As such, this limits the synthesis of azobenzenes with an amine functionality. In contrast, the method we report here relies heavily on the o-amine moiety and retains it in the product. The reaction is metal catalyzed and proceeds through a porphyrin Co(III-nitrene radical intermediate, which is known to form on activation of organic azides at the cobalt center. The synthesized o-aminoazobenzenes are bathochromatically shifted, as compared to azobenzenes without amine substituents. Based on the crystal structure of one of the products, strong H-bonding between the N-atom of the azo functionality and the H of the NH2 substituent is shown to stabilize the trans isomeric form of the product. The NH2 substituents offers possibilities for further functionalization of the synthesized azo compounds.

Investigation of the interaction between isomeric derivatives and human serum albumin by fluorescence spectroscopy and molecular modeling

Energy Technology Data Exchange (ETDEWEB)

Wang, Ruiyong, E-mail: wangry@zzu.edu.cn; Dou, Huanjing; Yin, Yujing; Xie, Yuanzhe; Sun, Li; Liu, Chunmei; Dong, Jingjing; Huang, Gang; Zhu, Yanyan; Song, Chuanjun, E-mail: chjsong@zzu.edu.cn; Chang, Junbiao, E-mail: changjunbiao@zzu.edu.cn

2014-10-15

In this paper, we have synthesized 9H-pyrrolo[1,2-a]indol-9-ones and the isomeric indeno[2,1-b]pyrrol-8-ones. The interactions of human serum albumin with series of isomeric derivatives have been studied by spectrophotometric methods. Results show the intrinsic fluorescence is quenched by the derivatives with a static quenching procedure. The thermodynamics parameters indicate that van der Waals forces and hydrogen bonds play a major role in the interactions. The results of synchronous fluorescence spectra demonstrate that the microenvironments of Trp residue of human serum albumin are disturbed by most derivatives. Thermodynamic results showed that the 9H-pyrrolo[1,2-a]indol-9-ones are stronger quenchers and bind to human serum albumin with the higher affinity than isomeric indeno[2,1-b]pyrrol-8-ones. The influence of molecular structure on the binding aspects has been investigated. - Highlights: • The interactions between isomeric derivatives and HSA have been investigated. • Results reveal that 9H-pyrrolo[1,2-a]indol-9-ones are stronger quenchers for HSA. • Hydrogen bonds and van der Waals forces play major role in the binding process. • The influence of molecular structure on the binding aspects has been investigated. • The binding study was also modeled by molecular docking.

Investigation of the interaction between isomeric derivatives and human serum albumin by fluorescence spectroscopy and molecular modeling

International Nuclear Information System (INIS)

Wang, Ruiyong; Dou, Huanjing; Yin, Yujing; Xie, Yuanzhe; Sun, Li; Liu, Chunmei; Dong, Jingjing; Huang, Gang; Zhu, Yanyan; Song, Chuanjun; Chang, Junbiao

2014-01-01

In this paper, we have synthesized 9H-pyrrolo[1,2-a]indol-9-ones and the isomeric indeno[2,1-b]pyrrol-8-ones. The interactions of human serum albumin with series of isomeric derivatives have been studied by spectrophotometric methods. Results show the intrinsic fluorescence is quenched by the derivatives with a static quenching procedure. The thermodynamics parameters indicate that van der Waals forces and hydrogen bonds play a major role in the interactions. The results of synchronous fluorescence spectra demonstrate that the microenvironments of Trp residue of human serum albumin are disturbed by most derivatives. Thermodynamic results showed that the 9H-pyrrolo[1,2-a]indol-9-ones are stronger quenchers and bind to human serum albumin with the higher affinity than isomeric indeno[2,1-b]pyrrol-8-ones. The influence of molecular structure on the binding aspects has been investigated. - Highlights: • The interactions between isomeric derivatives and HSA have been investigated. • Results reveal that 9H-pyrrolo[1,2-a]indol-9-ones are stronger quenchers for HSA. • Hydrogen bonds and van der Waals forces play major role in the binding process. • The influence of molecular structure on the binding aspects has been investigated. • The binding study was also modeled by molecular docking

Primary photodissociation pathways of epichlorohydrin and analysis of the C-C bond fission channels from an O(3P)+allyl radical intermediate

International Nuclear Information System (INIS)

FitzPatrick, Benjamin L.; Alligood, Bridget W.; Butler, Laurie J.; Lee, Shih-Huang; Lin, Jim Jr-Min

2010-01-01

This study initially characterizes the primary photodissociation processes of epichlorohydrin, c-(H 2 COCH)CH 2 Cl. The three dominant photoproduct channels analyzed are c-(H 2 COCH)CH 2 +Cl, c-(H 2 COCH)+CH 2 Cl, and C 3 H 4 O+HCl. In the second channel, the c-(H 2 COCH) photofission product is a higher energy intermediate on C 2 H 3 O global potential energy surface and has a small isomerization barrier to vinoxy. The resulting highly vibrationally excited vinoxy radicals likely dissociate to give the observed signal at the mass corresponding to ketene, H 2 CCO. The final primary photodissociation pathway HCl+C 3 H 4 O evidences a recoil kinetic energy distribution similar to that of four-center HCl elimination in chlorinated alkenes, so is assigned to production of c-(H 2 COC)=CH 2 ; the epoxide product is formed with enough vibrational energy to isomerize to acrolein and dissociate. The paper then analyzes the dynamics of the C 3 H 5 O radical produced from C-Cl bond photofission. When the epoxide radical photoproduct undergoes facile ring opening, it is the radical intermediate formed in the O( 3 P)+allyl bimolecular reaction when the O atom adds to an end C atom. We focus on the HCO+C 2 H 4 and H 2 CO+C 2 H 3 product channels from this radical intermediate in this report. Analysis of the velocity distribution of the momentum-matched signals from the HCO+C 2 H 4 products at m/e=29 and 28 shows that the dissociation of the radical intermediate imparts a high relative kinetic energy, peaking near 20 kcal/mol, between the products. Similarly, the energy imparted to relative kinetic energy in the H 2 CO+C 2 H 3 product channel of the O( 3 P)+allyl radical intermediate also peaks at high-recoil kinetic energies, near 18 kcal/mol. The strongly forward-backward peaked angular distributions and the high kinetic energy release result from tangential recoil during the dissociation of highly rotationally excited nascent radicals formed photolytically in this experiment

Primary photodissociation pathways of epichlorohydrin and analysis of the C-C bond fission channels from an O(3P)+allyl radical intermediate

Science.gov (United States)

FitzPatrick, Benjamin L.; Alligood, Bridget W.; Butler, Laurie J.; Lee, Shih-Huang; Lin, Jim-Min, Jr.

2010-09-01

This study initially characterizes the primary photodissociation processes of epichlorohydrin, c-(H2COCH)CH2Cl. The three dominant photoproduct channels analyzed are c-(H2COCH)CH2+Cl, c-(H2COCH)+CH2Cl, and C3H4O+HCl. In the second channel, the c-(H2COCH) photofission product is a higher energy intermediate on C2H3O global potential energy surface and has a small isomerization barrier to vinoxy. The resulting highly vibrationally excited vinoxy radicals likely dissociate to give the observed signal at the mass corresponding to ketene, H2CCO. The final primary photodissociation pathway HCl+C3H4O evidences a recoil kinetic energy distribution similar to that of four-center HCl elimination in chlorinated alkenes, so is assigned to production of c-(H2COC)=CH2; the epoxide product is formed with enough vibrational energy to isomerize to acrolein and dissociate. The paper then analyzes the dynamics of the C3H5O radical produced from C-Cl bond photofission. When the epoxide radical photoproduct undergoes facile ring opening, it is the radical intermediate formed in the O(P3)+allyl bimolecular reaction when the O atom adds to an end C atom. We focus on the HCO+C2H4 and H2CO+C2H3 product channels from this radical intermediate in this report. Analysis of the velocity distribution of the momentum-matched signals from the HCO+C2H4 products at m/e=29 and 28 shows that the dissociation of the radical intermediate imparts a high relative kinetic energy, peaking near 20 kcal/mol, between the products. Similarly, the energy imparted to relative kinetic energy in the H2CO+C2H3 product channel of the O(P3)+allyl radical intermediate also peaks at high-recoil kinetic energies, near 18 kcal/mol. The strongly forward-backward peaked angular distributions and the high kinetic energy release result from tangential recoil during the dissociation of highly rotationally excited nascent radicals formed photolytically in this experiment. The data also reveal substantial branching to an HCCH+H3

Computational Studies of Bridging Structures and Isomerism in Substituted Disilynes.

Science.gov (United States)

Serafin, Lukasz M; Law, Mark M; van Mourik, Tanja

2013-06-11

The substituted disilyne molecules, Si2Li2 and Si2HX, where X = Li, F, and Cl, have been investigated using the high-level CCSD(T) and CCSD(T)-F12 ab initio methods. The calculations have found or confirmed the existence of several isomeric forms and transition states for each molecule. Optimized geometries, relative energies, and harmonic vibration frequencies are reported. Bridging structures exist in all cases. Comparisons are made with existing literature results for the related Si2H2, C2X2, and C2HX isomerizing systems. Additionally, CCSD(T) and CCSD(T)-F12 calculations were performed for Si2H2, for which experimental spectroscopic data are available. Results calculated with CCSD(T)-F12 and the cc-pVTZ-F12 basis set are of comparable quality as those computed with CCSD(T) and the much larger cc-pV(6+d)Z basis set, at much less computational cost. We recommend the CCSD(T)-F12/cc-pVTZ-F12 level of theory as a very attractive alternative to conventional CCSD(T).

Isomeric Diruthenium Complexes Bridged by Deprotonated Indigo in cis and trans Configuration

Czech Academy of Sciences Publication Activity Database

Chatterjee, M.; Ghosh, P.; Beyer, K.; Paretzki, A.; Fiedler, Jan; Kaim, W.; Lahiri, G. K.

2018-01-01

Roč. 13, č. 1 (2018), s. 118-125 ISSN 1861-4728 Institutional support: RVO:61388955 Keywords : isomerism * ruthenium * spectroelectrochemistry * structure Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 4.083, year: 2016

Pulse radiolysis studies on the formation and transformation of the one-electron reduced intermediate of Kalafungin and an analogue solution

International Nuclear Information System (INIS)

Anderson, R.F.; Packer, J.E.; Brimble, A.; Nairn, M.R.

1996-01-01

Kalafungin 1 is a member of the pyranonaphthoquinone family of antibiotics which are produced various species of Streptomyces and have in common the benzoisochromanquinone skeleton. Apart from their already documented activity against Gram-positive bacteria, fungi, and mycoplasmas, it has been suggested that in vivo reduction causes a transformation to an active hydroquinone form which functions as a bis-alkylating agent. 2 Moore 2 , 3 has suggested that these pyranonaphthoquinones may exhibit antitumour activity since the proposed mechanism of action resembles that of the anticancer agent mitomycin C 3. 2 . Rapid one-electron reduction of kalafungin 1 and a closely related analogue 2 has been carried out using The University of Auckland's pulse radiolysis facility. Pulsed electrons (4 Gy in 200 ns from a 4 MeV linear accelerator) were delivered to de-aerated aqueous solutions (10 mmol.L -1 phosphate, pH 7.0) containing 0.1 mol.L -1 sodium formate and 50 - 200 μmol.L -1 kalafungin 1 or lactol 2. Radical formation and transformations were followed by time-resolved uv/visible spectrophotometry. The transformations observed are independent of both the concentration of the parent compound and radiation doses (i.e. semiquinone concentration). The accompanying changes in absorption are consistent with the radical centre of the semiquinone species undergoing intramolecular rearrangement onto the fused non-aromatic ring structure of the compound. Possible ring opening mechanisms and the position of radical relocalisation will be discussed, as well as the involvement of radical transformation and redox chemistry in the biological activity of kalafungin1

Thermal isomerization of azobenzenes: on the performance of Eyring transition state theory

Science.gov (United States)

Rietze, Clemens; Titov, Evgenii; Lindner, Steven; Saalfrank, Peter

2017-08-01

The thermal Z\\to E (back-)isomerization of azobenzenes is a prototypical reaction occurring in molecular switches. It has been studied for decades, yet its kinetics is not fully understood. In this paper, quantum chemical calculations are performed to model the kinetics of an experimental benchmark system, where a modified azobenzene (AzoBiPyB) is embedded in a metal-organic framework (MOF). The molecule can be switched thermally from cis to trans, under solvent-free conditions. We critically test the validity of Eyring transition state theory for this reaction. As previously found for other azobenzenes (albeit in solution), good agreement between theory and experiment emerges for activation energies and activation free energies, already at a comparatively simple level of theory, B3LYP/6-31G* including dispersion corrections. However, theoretical Arrhenius prefactors and activation entropies are in qualitiative disagreement with experiment. Several factors are discussed that may have an influence on activation entropies, among them dynamical and geometric constraints (imposed by the MOF). For a simpler model—Z\\to E isomerization in azobenzene—a systematic test of quantum chemical methods from both density functional theory and wavefunction theory is carried out in the context of Eyring theory. Also, the effect of anharmonicities on activation entropies is discussed for this model system. Our work highlights capabilities and shortcomings of Eyring transition state theory and quantum chemical methods, when applied for the Z\\to E (back-)isomerization of azobenzenes under solvent-free conditions.

POSSIBLE NATURE OF THE RADIATION-INDUCED SIGNAL IN NAILS: HIGH-FIELD EPR, CONFIRMING CHEMICAL SYNTHESIS, AND QUANTUM CHEMICAL CALCULATIONS.

Science.gov (United States)

Tipikin, Dmitriy S; Swarts, Steven G; Sidabras, Jason W; Trompier, François; Swartz, Harold M

2016-12-01

Exposure of finger- and toe-nails to ionizing radiation generates an Electron Paramagnetic Resonance (EPR) signal whose intensity is dose dependent and stable at room temperature for several days. The dependency of the radiation-induced signal (RIS) on the received dose may be used as the basis for retrospective dosimetry of an individual's fortuitous exposure to ionizing radiation. Two radiation-induced signals, a quasi-stable (RIS2) and stable signal (RIS5), have been identified in nails irradiated up to a dose of 50 Gy. Using X-band EPR, both RIS signals exhibit a singlet line shape with a line width around 1.0 mT and an apparent g-value of 2.0044. In this work, we seek information on the exact chemical nature of the radiation-induced free radicals underlying the signal. This knowledge may provide insights into the reason for the discrepancy in the stabilities of the two RIS signals and help develop strategies for stabilizing the radicals in nails or devising methods for restoring the radicals after decay. In this work an analysis of high field (94 GHz and 240 GHz) EPR spectra of the RIS using quantum chemical calculations, the oxidation-reduction properties and the pH dependence of the signal intensities are used to show that spectroscopic and chemical properties of the RIS are consistent with a semiquinone-type radical underlying the RIS. It has been suggested that semiquinone radicals formed on trace amounts of melanin in nails are the basis for the RIS signals. However, based on the quantum chemical calculations and chemical properties of the RIS, it is likely that the radicals underlying this signal are generated from the radiolysis of L-3,4-dihydroxyphenylalanine (DOPA) amino acids in the keratin proteins. These DOPA amino acids are likely formed from the exogenous oxidation of tyrosine in keratin by the oxygen from the air prior to irradiation. We show that these DOPA amino acids can work as radical traps, capturing the highly reactive and unstable sulfur

Kinetic and mass transfer studies on the isomerization of cellulose hydrolyzate using immobilized Streptomyces cells

Energy Technology Data Exchange (ETDEWEB)

Ghose, T K; Chand, S

1978-01-01

Streptomyces cells possessing glucose isomerase activity, heat-treated and confined within polyester sacs have been used in batch/continuous isomerization of enzymatically hydrolyzed microcrystalline cellulose. Conversion data at different concentrations of substrate closely follow the reactor performance equation based on the reaction kinetics. The effect of external film and pore diffusional resistances were experimentally found to be negligible. The dispersion effects in the packed bed column have been evaluated by pulse input tracer analysis. Continuous operation of the column to isomerize cellulose hydrolyzate (2.0 M glucose) showed an exponential deactivation of enzyme activity with a half-life of 447 h.

A comprehensive mechanistic picture of the isomerizing alkoxycarbonylation of plant oils.

Science.gov (United States)

Roesle, Philipp; Caporaso, Lucia; Schnitte, Manuel; Goldbach, Verena; Cavallo, Luigi; Mecking, Stefan

2014-12-03

Theoretical studies on the overall catalytic cycle of isomerizing alkoxycarbonylation reveal the steric congestion around the diphosphine coordinated Pd-center as decisive for selectivity and productivity. The energy profile of isomerization is flat with diphosphines of variable steric bulk, but the preference for the formation of the linear Pd-alkyl species is more pronounced with sterically demanding diphosphines. CO insertion is feasible and reversible for all Pd-alkyl species studied and only little affected by the diphosphine. The overall rate-limiting step associated with the highest energetic barrier is methanolysis of the Pd-acyl species. Considering methanolysis of the linear Pd-acyl species, whose energetic barrier is lowest within all the Pd-acyl species studied, the barrier is calculated to be lower for more congesting diphosphines. Calculations indicate that energy differences of methanolysis of the linear versus branched Pd-acyls are more pronounced for more bulky diphosphines, due to involvement of different numbers of methanol molecules in the transition state. Experimental studies under pressure reactor conditions showed a faster conversion of shorter chain olefin substrates, but virtually no effect of the double bond position within the substrate. Compared to higher olefins, ethylene carbonylation under identical conditions is much faster, likely due not just to the occurrence of reactive linear acyls exclusively but also to an intrinsically favorable insertion reactivity of the olefin. The alcoholysis reaction is slowed down for higher alcohols, evidenced by pressure reactor and NMR studies. Multiple unsaturated fatty acids were observed to form a terminal Pd-allyl species upon reaction with the catalytically active Pd-hydride species. This process and further carbonylation are slow compared to isomerizing methoxycarbonylation of monounsaturated fatty acids, but selective.

A comprehensive mechanistic picture of the isomerizing alkoxycarbonylation of plant oils

KAUST Repository

Roesle, Philipp

2014-12-03

Theoretical studies on the overall catalytic cycle of isomerizing alkoxycarbonylation reveal the steric congestion around the diphosphine coordinated Pd-center as decisive for selectivity and productivity. The energy profile of isomerization is flat with diphosphines of variable steric bulk, but the preference for the formation of the linear Pd-alkyl species is more pronounced with sterically demanding diphosphines. CO insertion is feasible and reversible for all Pd-alkyl species studied and only little affected by the diphosphine. The overall rate-limiting step associated with the highest energetic barrier is methanolysis of the Pd-acyl species. Considering methanolysis of the linear Pd-acyl species, whose energetic barrier is lowest within all the Pd-acyl species studied, the barrier is calculated to be lower for more congesting diphosphines. Calculations indicate that energy differences of methanolysis of the linear versus branched Pd-acyls are more pronounced for more bulky diphosphines, due to involvement of different numbers of methanol molecules in the transition state. Experimental studies under pressure reactor conditions showed a faster conversion of shorter chain olefin substrates, but virtually no effect of the double bond position within the substrate. Compared to higher olefins, ethylene carbonylation under identical conditions is much faster, likely due not just to the occurrence of reactive linear acyls exclusively but also to an intrinsically favorable insertion reactivity of the olefin. The alcoholysis reaction is slowed down for higher alcohols, evidenced by pressure reactor and NMR studies. Multiple unsaturated fatty acids were observed to form a terminal Pd-allyl species upon reaction with the catalytically active Pd-hydride species. This process and further carbonylation are slow compared to isomerizing methoxycarbonylation of monounsaturated fatty acids, but selective.

Photo-isomerization and oxidation of bilirubin in mammals is dependent on albumin binding.

Science.gov (United States)

Goncharova, Iryna; Jašprová, Jana; Vítek, Libor; Urbanová, Marie

2015-12-01

The bilirubin (BR) photo-conversion in the human body is a protein-dependent process; an effective photo-isomerization of the potentially neurotoxic Z,Z-BR as well as its oxidation to biliverdin in the antioxidant redox cycle is possible only when BR is bound on serum albumin. We present a novel analytical concept in the study of linear tetrapyrroles metabolic processes based on an in-depth mapping of binding sites in the structure of human serum albumin (HSA). A combination of fluorescence spectroscopy, circular dichroism (CD) spectroscopy, and molecular modeling methods was used for recognition of the binding site for BR, its derivatives (mesobilirubin and bilirubin ditaurate), and the products of the photo-isomerization and oxidation (lumirubin, biliverdin, and xanthobilirubic acid) on HSA. The CD spectra and fluorescent quenching of the Trp-HSA were used to calculate the binding constants. The results of the CD displacement experiments performed with hemin were interpreted together with the findings of molecular docking performed on the pigment-HSA complexes. We estimated that Z,Z-BR and its metabolic products bind on two independent binding sites. Our findings support the existence of a reversible antioxidant redox cycle for BR and explain an additional pathway of the photo-isomerization process (increase of HSA binding capacity; the excess free [unbound] BR can be converted and also bound to HSA). Copyright © 2015 Elsevier Inc. All rights reserved.

Excitation function and isomeric ratio of Tc-isotopes from the 93Nb(α, xn) reaction

International Nuclear Information System (INIS)

Kim, K.; Kim, G.N.; Naik, H.; Zaman, M.; Yang, S.-C.; Song, T.-Y.; Guin, R.; Das, S.K.

2015-01-01

The excitation functions of 94–96 Tc isotopes and independent isomeric ratios of 93m, g Tc, 94m, g Tc, and 95m, g Tc from the 93 Nb(α, xn) reaction within the energy range below 40 MeV have been determined by using a stacked-foil activation and an off-line γ-ray spectrometric technique at the Variable Energy Cyclotron Center, Kolkota, India. The excitation function of 94–96 Tc in the 93 Nb(α, xn) reaction was also calculated by using the computer code TALYS 1.6. The present data are found to be in general agreement with the literature data but have similar trend with some deviation from calculated data of the TALYS 1.6 code. The isomeric ratios of 93m, g Tc, 94m, g Tc, and 95m, g Tc in the 93 Nb(α, xn) reactions from the present work and literature data were compared with similar data in the 93 Nb( 3 He, xn) and 96 Mo(p, xn) reactions. In all the three reactions, the isomeric ratios increase with the increasing excitation energy. However, at all excitation energies, the isomeric ratios of 93m, g Tc, 94m, g Tc, and 95m, g Tc in the 93 Nb(α, xn) and 93 Nb( 3 He, xn) reactions are higher than those in the 96 Mo(p, xn) reactions, which indicate the role of input angular momentum besides excitation energy. Above the excitation energy of 35–55 MeV, the isomeric ratios of 95m, g Tc, 94m, g Tc, and 93m, g Tc decrease in all the 93 Nb(α, xn), 93 Nb( 3 He, xn) and 96 Mo(p, xn) reactions. This decreasing trend at higher excitation energy indicates the starting of pre-equilibrium reaction, which depends on the target, projectile, and type of reaction products

Linkage isomerism in trimeric and polymeric 2,3-cis-procyanindins

Science.gov (United States)

Richard W. Hemingway; Lai Yeap Foo; Lawrence J. Porter

1982-01-01

Procyanindins polymers consist of chains of 5,7,3',4'-tetrahydroxyflavan-3-ol units linked by C(4)-C(6) or C(4)-C(8) bonds.1 Whereas the procyanidin-B group of dimers are known to exist as pairs of isomers with common flavan-3-ol units, but different interflavanoid linkages,2,3 the extent of such isomerism in...

Spectroscopic and Theoretical Identification of Two Thermal Isomerization Pathways for Bistable Chiral Overcrowded Alkenes.

Science.gov (United States)

Kistemaker, Jos C M; Pizzolato, Stefano F; van Leeuwen, Thomas; Pijper, Thomas C; Feringa, Ben L

2016-09-12

Chiroptical molecular switches play an important role in responsive materials and dynamic molecular systems. Here we present the synthesis of four chiral overcrowded alkenes and the experimental and computational study of their photochemical and thermal behavior. By irradiation with UV light, metastable diastereoisomers with opposite helicity were generated through high yielding E-Z isomerizations. Kinetic studies on metastable 1-4 using CD spectroscopy and HPLC analysis revealed two pathways at higher temperatures for the thermal isomerization, namely a thermal E-Z isomerization (TEZI) and a thermal helix inversion (THI). These processes were also studied computationally whereby a new strategy was developed for calculating the TEZI barrier for second-generation overcrowded alkenes. To demonstrate that these overcrowded alkenes can be employed as bistable switches, photochromic cycling was performed, which showed that the alkenes display good selectivity and fatigue resistance over multiple irradiation cycles. In particular, switch 3 displayed the best performance in forward and backward photoswitching, while 1 excelled in thermal stability of the photogenerated metastable form. Overall, the alkenes studied showed a remarkable and unprecedented combination of switching properties including dynamic helicity, reversibility, selectivity, fatigue resistance, and thermal stability. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An isomerization-induced cage-breaking process in a molecular glass former below Tg

International Nuclear Information System (INIS)

Teboul, V.; Saiddine, M.; Accary, J.-B.; Nunzi, J.-M.

2011-01-01

A recent experimental [P. Karageorgiev, D. Neher, B. Schulz, B. Stiller, U. Pietsch, M. Giersig, L. Brehmer, Nature Mater. 4, 699 (2005)] study has found liquidlike diffusion below the glass-transition temperature in azobenzene-containing materials under irradiation. This result suggests that the isomerization-induced massive mass transport that leads to surface relief gratings formation in these materials, is induced by this huge increase of the matrix diffusion coefficient around the probe. In order to investigate the microscopic origin of the increase of the diffusion, we use molecular dynamics simulations of the photoisomerization of probe dispersed red 1 molecules dispersed inside a glassy molecular matrix. Results show that the increased diffusion is due to an isomerization-induced cage-breaking process. A process that explains the induced cooperative motions recently observed in these photoactive materials.

Revisiting the polytopal rearrangements in penta-coordinate d7-metallocomplexes: modified Berry pseudorotation, octahedral switch, and butterfly isomerization.

Science.gov (United States)

Asatryan, Rubik; Ruckenstein, Eli; Hachmann, Johannes

2017-08-01

This paper provides a first-principles theoretical investigation of the polytopal rearrangements and fluxional behavior of five-coordinate d 7 -transition metal complexes. Our work is primarily based on a potential energy surface analysis of the iron tetracarbonyl hydride radical HFe˙(CO) 4 . We demonstrate the existence of distorted coordination geometries in this prototypical system and, for the first time, introduce three general rearrangement mechanisms, which account for the non-ideal coordination. The first of these mechanisms constitutes a modified version of the Berry pseudorotation via a square-based pyramidal C 4v transition state that connects two chemically identical edge-bridged tetrahedral stereoisomers of C 2v symmetry. It differs from the classical Berry mechanism, which involves two regular D 3h equilibrium structures and a C 4v transition state. The second mechanism is related to the famous "tetrahedral jump" hypothesis, postulated by Muetterties for a number of d 6 HML 4 and H 2 ML 4 complexes. Here, our study suggests two fluxional rearrangement pathways via distinct types of C 2v transition states. Both pathways of this mechanism can be described as a single-ligand migration to a vacant position of an "octahedron", thus interchanging (switching) the apical and basal ligands of the initial quasi-square pyramidal isomer, which is considered as an idealized octahedron with a vacancy. Accordingly, we call this mechanism "octahedral switch". The third mechanism follows a butterfly-type isomerization featuring a key-angle deformation, and we thus call it "butterfly isomerization". It connects the quasi-square pyramidal and edge-bridged tetrahedral isomers of HFe˙(CO) 4 through a distorted edge-bridged tetrahedral transition state of C s symmetry. Our paper discusses the overall features of the isomers and rearrangement mechanisms as well as their implications. We rationalize the existence of each stationary point through an electronic structure

The thermal Z-isomerization-induced change in solubility and physical properties of (all-E)-lycopene.

Science.gov (United States)

Murakami, Kazuya; Honda, Masaki; Takemura, Ryota; Fukaya, Tetsuya; Kubota, Mitsuhiro; Wahyudiono; Kanda, Hideki; Goto, Motonobu

2017-09-16

The effect of Z-isomerization of (all-E)-lycopene on its solubility in organic solvents and physical properties was investigated. Lycopene samples containing different Z-isomer contents (23.8%, 46.9%, and 75.6% of total lycopene) were prepared from high-purity (all-E)-lycopene by thermal Z-isomerization in dichloromethane (CH 2 Cl 2 ). As the Z-isomer content increased, the relative solubility of lycopene significantly improved. Although (all-E)-lycopene barely dissolved in ethanol (0.6 mg/L), the solubilities of lycopene containing 23.8%, 46.9%, and 75.6% Z-isomers were 484.5, 914.7, and 2401.7 mg/L, respectively. Furthermore, differential scanning calorimetry (DSC), powder X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses clearly indicated that (all-E)-lycopene was present in the crystal state, while Z-isomers of lycopene were present in amorphous states. A number of studies have suggested that Z-isomers of lycopene are better absorbed in the human body than the all-E-isomer. This may be due to the change in solubility and physical properties of lycopene by the Z-isomerization. Copyright © 2017 Elsevier Inc. All rights reserved.

Isomeric ratios in photonuclear reactions of molybdenum isotopes induced by bremsstrahlung in the giant dipole resonance region

International Nuclear Information System (INIS)

Tran Duc Thiep; Truong Thi An; Phan Viet Cuong; Nguyen The Vinh; Bui Minh Hue; Belov, A.G.; Maslov, O.D.; Mishinsky, G.V.; Zhemenik, V.I.

2017-01-01

We have determined the isomeric ratios of isomeric pairs "9"7"m","gNb, "9"5"m","gNb and "9"1"m","gMo produced in "9"8Mo(γ, p)"9"7"m","gNb, "9"6Mo(γ, p)"9"5"m","gNb and "9"2Mo(γ, n)"9"1"m","gMo photonuclear reactions in the giant dipole resonance (GDR) region by the activation method. The results were analyzed, discussed and compared with the similar data from literature to examine the role of excitation energy, neutron configuration, channel effect, and direct and pre-equilibrium processes in (γ, p) photonuclear reactions. In this work the isomeric ratios for "9"7"m","gNb from 14 to 19 MeV, for "1"9"5"m","gNb from 14 to 24 MeV except 20 and 23.5 MeV and for "9"1"m","gMo at 14 and 15 MeV were first measured.

Specific racemization and isomerization of the aspartyl residue of αA-crystallin due to UV-B irradiation

International Nuclear Information System (INIS)

Fujii, Noriko; Momose, Yuko; Ishibasi, Yoshihiro; Uemura, Toshimasa; Takita, Masatoshi; Takehana, Makoto

1997-01-01

We have reported that the aspartyl (Asp)-151 residue in αA-crystallin in human eye lens was inverted to the D-isomer and isomerized to β-Asp residue with age. We report here that ultraviolet (UV)-B irradiation induces the racemization and isomerization of the Asp-151 residue of αA-crystallin from lenses of 6-week-old rats to form D-isomer and β-Asp residue. Simultaneous racemization and isomerization of the specific Asp residue indicate that the reaction proceeds via formation of a succinimide intermediate. This modification was not observed in UV-A irradiated and normal lenses. UV-B irradiation induced the racemization of only the Asp-151 residue and did not affect the other Asp residues in αA-crystallin. On the other hand, the high molecular weight fraction of the lens protein increased upon UV-B irradiation. Modification of the Asp residue would affect the three-dimensional packing array of the lens protein. (author)

Modulating the Physical and Electronic Properties over Positional Isomerism: The Dispirofluorene-Dihydroindacenodithiophene (DSF-IDT) Family.

Science.gov (United States)

Peltier, Jean-David; Heinrich, Benoît; Donnio, Bertrand; Jeannin, Olivier; Rault-Berthelot, Joëlle; Poriel, Cyril

2017-12-06

We report the first studies on the intrinsic properties of a meta-substituted dihydroindacenodithienyl fragment and more generally the strong impact of positional isomerism on dihydroindacenodithiophene derivatives. The influence of the para and meta linkages has notably been highlighted not only for the electronic properties in solution (electrochemical properties, anodic polymerization, HOMO/LUMO energy levels, optical transitions, fluorescence spectra) but also on the physical properties in the solid state (molecular organization, crystallinity, and phase transitions). The positional isomerism hence appears to be a very efficient tool to drastically tune the properties of dihydroindacenodithiophene derivatives. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polymeric proanthocyanidins: Interflavanoid linkage isomerism in (epicatechin-4)-(epicatechin-4)-catechin procyanidins

Science.gov (United States)

Richard W. Hemingway; L. Yeap Foo; L. J. Porter

1981-01-01

Procyanidin trimers have been isolated from a variety of plants,1-3 but their structures remain unresolved. We have now isolated three configurational isomers of (epicatechin-4)-(epicatechin-4)-catechin from Pinus taeda L. (loblolly pine) phloem which exhibit isomerism of the interflavanoid linkages.

Investigation of molecular mechanisms in photodynamic action and radiobiology with nanosecond flash photolysis and pulse radiolysis. Progress report, July 1, 1974--June 30, 1975

International Nuclear Information System (INIS)

Grossweiner, L.I.

1975-01-01

Initial mechanisms in the UV photooxidation of aromatic amino acids are being investigated with laser flash photolysis at 265 nm in connection with enzyme inactivation. Aqueous tryptophan (Trp) is photoionized by an efficient monophotonic process, followed by a hitherto unreported pseudo-first order recombination competing with bimolecular e - /sub aq/ decay and electron scavengers. Measurements of the photoionization quantum efficiency, the aromatic radical extinction coefficients, and the electron decay kinetics are reported. The flash photolysis of N-formylkynurenine (FK) has been studied in connection with its role in ''internal'' photodynamic action in bovine carbonic anhydrase (BCA). The triplet state of FK oxidizes Trp to the radical formed also by UV photolysis, leading to the FK semiquinone which reacts with oxygen to produce O 2 - . The same FK semiquinone species is formed by radiolytic reduction by e - /sub aq/ and CO 2 - . A parallel radiolysis study on BCA using radical anions as probes of specific residues has shown that the zinc atom protects against the inactivating attack of e - /sub aq/ and CO 2 - . Evidence for sensitive aromatic residues in BCA has been found with this technique. Photodynamic damage to biological membranes is being studied with spin label ESR methods. New work is reported on damage to unsaturated lipids sensitized by Eosin based on changes in the temperature-dependence of the spin label rotational correlation time. Preliminary results with diploid yeast membranes (Saccharomyces cerevisiae) show a loosening of the structure accompanying photodynamic inactivation. (U.S.)

Pion condensation and density isomerism in nuclear matter

International Nuclear Information System (INIS)

Hecking, P.; Weise, W.

1979-01-01

The possible existence of density isomers in nuclear matter, induced by pion condensation, is discussed; the nuclear equation of state is treated within the framework of the sigma model. Repulsive short-range baryon-baryon correlations, the admixture of Δ (1232) isobars and finite-range pion-baryon vertex form factors are taken into account. The strong dependence of density isomerism on the high density extrapolation of the equation of state for normal nuclear matter is also investigated. We find that, once finite range pion-baryon vertices are introduced, the appearance of density isomers becomes unlikely

Geometrical Optimization Approach to Isomerization: Models and Limitations.

Science.gov (United States)

Chang, Bo Y; Shin, Seokmin; Engel, Volker; Sola, Ignacio R

2017-11-02

We study laser-driven isomerization reactions through an excited electronic state using the recently developed Geometrical Optimization procedure. Our goal is to analyze whether an initial wave packet in the ground state, with optimized amplitudes and phases, can be used to enhance the yield of the reaction at faster rates, driven by a single picosecond pulse or a pair of femtosecond pulses resonant with the electronic transition. We show that the symmetry of the system imposes limitations in the optimization procedure, such that the method rediscovers the pump-dump mechanism.

Isomeric island in the vicinity of 66Fe

International Nuclear Information System (INIS)

Daugas, J. M.; Belier, G.; Girod, M.; Goutte, H.; Meot, V.; Perru, O.; Roig, O.; Sauvestre, J. E.; Sawicka, M.; Pfuetzner, M.; Zylicz, J.; Matea, I.; Giovinazzo, J.; Grawe, H.; Becker, F.; Mayet, P.; Grzywacz, R.; Achouri, N. L.; Angelique, J. C.; Baiborodin, D.

2006-01-01

An island of isomers have recently been observed on both sides of the N=40 shell below the Ni isotopes. Isomeric states in the 65Fe and 67Fe allow the knowledge of the single particle structure around the νg9/2 shell. Moreover, the excitation energy of the first 2+ and 4+ states in the 68Fe have been established by β-γ correlation. The evolution of the structure of the Fe isotopes going far away from the valley of stability is, for the first time, given for N>40

Surface study of mixtures containing cyclic ethers and isomeric chlorobutanes

International Nuclear Information System (INIS)

Royo, F.M.; Villares, A.; Martin, S.; Giner, B.; Lafuente, C.

2007-01-01

Experimental surface tensions and the corresponding surface tensions deviations for the mixtures containing 1,3-dioxolane or 1,4-dioxane and 1-chlorobutane, 2-chlorobutane, 1-chloro-2-methylpropane or 2-chloro-2-methylpropane, measured with a drop volume tensiometer, are reported at the temperatures of 298.15 K and 313.15 K. The excess surface concentrations of isomeric chlorobutanes are also evaluated using a monolayer model

Efficient Isomerization of Glucose to Fructose over Zeolites in Consecutive Reactions in Alcohol and Aqueous Media

DEFF Research Database (Denmark)

Shunmugavel, Saravanamurugan; Paniagua, Marta; Melero, Juan A

2013-01-01

glucose isomerization to fructose and subsequent reaction with methanol to form methyl fructoside (step 1), followed by hydrolysis to re-form fructose after water addition (step 2). NMR analysis with (13)C-labeled sugars confirmed this reaction pathway. Conversion of glucose for 1 h at 120 °C with H......-USY (Si/Al = 6) gave a remarkable 55% yield of fructose after the second reaction step. A main advantage of applying alcohol media and a catalyst that combines Brønsted and Lewis acid sites is that glucose is isomerized to fructose at low temperatures, while direct conversion to industrially important...

Preclinical Evaluation of the Synthetic Adjuvant SQS-21 and its Constituent Isomeric Saponins

Science.gov (United States)

Ragupathi, Govind; Damani, Payal; Deng, Kai; Adams, Michelle M.; Hang, Jianfeng; George, Constantine; Livingston, Philip O.; Gin, David Y.

2010-01-01

The saponin fraction QS-21 from Quillaja saponaria has been demonstrated to be a potent immunological adjuvant when mixed with keyhole limpet hemocyanin conjugate vaccines, as well as with other classes of subunit antigen vaccines. QS-21 adjuvant is composed of two isomers that include the apiose and xylose forms in a ratio of 65:35, respectively. The chemical syntheses of these two isomers in pure form have recently been disclosed. Herein we describe detailed in vivo immunological evaluations of these synthetic QS-21 isomeric constituents, employing the GD3-KLH melanoma antigen. With this vaccine construct, high antibody titers against GD3 ganglioside and KLH were elicited when GD3-KLH was co-administered with adjuvant, either as the individual separate synthetic QS-21 isomers (SQS-21-Api or SQS-21-Xyl), or as its reconstituted 65:35 isomeric mixture (SQS-21). These antibody titer levels were comparable to that elicited by vaccinations employing naturally derived QS-21 (PQS-21). Moreover, toxicities of the synthetic saponin adjuvants were also found to be comparable to that of naturally derived PQS-21. These findings demonstrate unequivocally that the adjuvant activity of QS-21 resides in these two principal isomeric forms, and not in trace contaminants within the natural extracts. This lays the foundation for future exploration of structure-function correlations to enable the discovery of novel saponins with increased potency, enhanced stability, and attenuated toxicity. PMID:20450868

The Isomerization of (-)-Menthone to (+)-Isomenthone Catalyzed by an Ion-Exchange Resin

Science.gov (United States)

Ginzburg, Aurora L.; Baca, Nicholas A.; Hampton, Philip D.

2014-01-01

A traditional organic chemistry laboratory experiment involves the acid-catalyzed isomerization of (-)-menthone to (+)-isomenthone. This experiment generates large quantities of organic and aqueous waste, and only allows the final ratio of isomers to be determined. A "green" modification has been developed that replaces the mineral acid…

One-electron reduction of 2- and 6-methyl-1,4-naphthoquinone bioreductive alkylating agents

International Nuclear Information System (INIS)

Wilson, I.; Wardman, P.; Lin, T.S.; Sartorelli, A.C.

1986-01-01

The semiquinones, Q.-, of derivatives of 2- and 6-methyl-1,4-naphthoquinones, some incorporating leaving groups with substituents such as CH 2 Br or CH 2 OCONHCH 3 , have been produced by radiolytic reduction of Q by (CH 3 )2COH radicals. The absorption spectra and decay kinetics of Q.- were all closely similar to that produced from 2-methyl-1,4-naphthoquinone, with no evidence for unimolecular elimination of a leaving group in the semiquinone form, but immediate loss of leaving group upon two-electron reduction of Q to the hydroquinone. The redox equilibria between Q/Q.- and O2/O2.- were characterized, and reduction potentials of the couples Q/Q.- in water at pH 7.6 were calculated. The implications of these observations for the use of these compounds as bioreductive alkylating agents or as radiosensitizers with potential selective activity toward hypoxic cells are discussed

Collective coordinates and an accompanying metric force in structural isomerization dynamics of molecules

International Nuclear Information System (INIS)

Yanao, Tomohiro; Takatsuka, Kazuo

2003-01-01

Structural isomerization dynamics of three- and four-atom clusters of vanishing total angular momentum is studied in terms of internal coordinates of n-body systems on the basis of a gauge theory. The so-called principal-axis hyperspherical coordinates are employed effectively as collective variables for the study of isomerization reactions. It turns out that the non-Euclidean metric on the internal space gives rise to a force, which works in response to internal motions called the democratic (kinematic) rotations in the internal space. This metric force generally tends to induce an asymmetry in mass balance of a system, and is coupled with the usual potential force to give rise to trapped motions in the vicinity of the transition states of the cluster. This observation provides a different perspective for the so-called recrossing problem in chemical reaction dynamics

Magnetic interactions as a stabilizing factor of semiquinone species of lawsone by metal complexation

International Nuclear Information System (INIS)

Valle-Bourrouet, Grettel; Ugalde-Saldivar, Victor M.; Gomez, Martin; Ortiz-Frade, Luis A.; Gonzalez, Ignacio; Frontana, Carlos

2010-01-01

Changes in electrochemical reactivity for lawsone anions (lawsone, 2-hydroxy-1,4-naphthoquinone, HLw) being coordinated to a series of metallic ions in dimethylsulfoxide solution were evaluated. Upon performing cyclic voltammetry experiments for metal complexes of this quinone with pyridine (Py) - structural formula M(II)(Lw - ) 2 (Py) 2 ; M: Co(II), Ni(II), Zn(II) - it was found that the reduction of coordinated Lw - units occurs during the first and second electron uptake in the analyzed compounds. The stability of the electrogenerated intermediates for each complex depends on the d electron configuration in each metal center and is determined by magnetic interactions with the available spins considering an octahedral conformation for all the compounds. This was evidenced by in situ spectroelectrochemical-ESR measurements in the Zn(II) complex in which due to the lack of magnetic interaction owing to its electron configuration, the structure of the coordinated anion radical species was determined. Successive reduction of the associated Lw - units leads to partial dissociation of the complex, determined by the identification of free radical dianion structures in solution. These results show some insights on how metal-lawsone complexation can modify the solution reactivity and stability of the electrogenerated radical species.

Magnetic interactions as a stabilizing factor of semiquinone species of lawsone by metal complexation

Energy Technology Data Exchange (ETDEWEB)

Valle-Bourrouet, Grettel [Universidad de Costa Rica, Escuela de Quimica, San Jose (Costa Rica); Ugalde-Saldivar, Victor M. [Facultad de Quimica, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, C.P. 04510, Mexico, D.F. (Mexico); Gomez, Martin [Departamento de Sistemas Biologicos, Universidad Autonoma Metropolitana-Xochimilco, C.P. 04960, Mexico, D.F. (Mexico); Ortiz-Frade, Luis A. [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, Parque Tecnologico Queretaro, Sanfandila, 76703, Pedro Escobedo, Queretaro (Mexico); Gonzalez, Ignacio [Universidad Autonoma Metropolitana - Iztapalapa, Departamento de Quimica, Area de Electroquimica, Apartado postal 55-534, 09340, Mexico, D.F. (Mexico); Frontana, Carlos, E-mail: ultrabuho@yahoo.com.m [Departamento de Quimica, Centro de Investigacion y Estudios Avanzados, Av. Instituto Politecnico Nacional No. 2508 Col. San Pedro Zacatenco, C.P. 07360, Mexico, D.F. (Mexico)

2010-12-01

Changes in electrochemical reactivity for lawsone anions (lawsone, 2-hydroxy-1,4-naphthoquinone, HLw) being coordinated to a series of metallic ions in dimethylsulfoxide solution were evaluated. Upon performing cyclic voltammetry experiments for metal complexes of this quinone with pyridine (Py) - structural formula M(II)(Lw{sup -}){sub 2}(Py){sub 2}; M: Co(II), Ni(II), Zn(II) - it was found that the reduction of coordinated Lw{sup -} units occurs during the first and second electron uptake in the analyzed compounds. The stability of the electrogenerated intermediates for each complex depends on the d electron configuration in each metal center and is determined by magnetic interactions with the available spins considering an octahedral conformation for all the compounds. This was evidenced by in situ spectroelectrochemical-ESR measurements in the Zn(II) complex in which due to the lack of magnetic interaction owing to its electron configuration, the structure of the coordinated anion radical species was determined. Successive reduction of the associated Lw{sup -} units leads to partial dissociation of the complex, determined by the identification of free radical dianion structures in solution. These results show some insights on how metal-lawsone complexation can modify the solution reactivity and stability of the electrogenerated radical species.

Photo-isomerization induced rapid photo-degradation of optical nonlinearity in cyano substituted stilbene derivative doped poled polymer

International Nuclear Information System (INIS)

Yan Jieyun; Liu Liying; Ji Liyong; Ye Mingxin; Xu Lei; Wang Wencheng

2004-01-01

We found that, although alpha'-cyano-4'-nitro-4-N, N-dimethylaminostilbene has larger hyperpolarizability than that of conventional 4'-N, N-dimethylamino-nitrostilbene, the addition of the cyano group makes it much more easy to photo-isomerize, thus destroying the molecular ordering in poled chromophore doped polymers. Experimental evidence was obtained by monitoring the second-harmonic generation intensity, UV-Vis absorption spectrum, and FTIR spectrum. The photo-isomerization reaction process was monitored by optical pump induced absorption anisotropy measurement. Comparisons with the behaviour of a azobenzene dye are also made

{sup 13}C-NMR studies on disulfide bond isomerization in bovine pancreatic trypsin inhibitor (BPTI)

Energy Technology Data Exchange (ETDEWEB)

Takeda, Mitsuhiro [Kumamoto University, Department of Structural BioImaging, Faculty of Life Sciences (Japan); Miyanoiri, Yohei [Nagoya University, Structural Biology Research Center, Graduate School of Science (Japan); Terauchi, Tsutomu [Tokyo Metropolitan University, Graduate School of Science and Engineering (Japan); Kainosho, Masatsune, E-mail: kainosho@tmu.ac.jp [Nagoya University, Structural Biology Research Center, Graduate School of Science (Japan)

2016-09-15

Conformational isomerization of disulfide bonds is associated with the dynamics and thus the functional aspects of proteins. However, our understanding of the isomerization is limited by experimental difficulties in probing it. We explored the disulfide conformational isomerization of the Cys14–Cys38 disulfide bond in bovine pancreatic trypsin inhibitor (BPTI), by performing an NMR line-shape analysis of its Cys carbon peaks. In this approach, 1D {sup 13}C spectra were recorded at small temperature intervals for BPTI samples selectively labeled with site-specifically {sup 13}C-enriched Cys, and the recorded peaks were displayed in the order of the temperature after the spectral scales were normalized to a carbon peak. Over the profile of the line-shape, exchange broadening that altered with temperature was manifested for the carbon peaks of Cys14 and Cys38. The Cys14–Cys38 disulfide bond reportedly exists in equilibrium between a high-populated (M) and two low-populated states (m{sub c14} and m{sub c38}). Consistent with the three-site exchange model, biphasic exchange broadening arising from the two processes was observed for the peak of the Cys14 α-carbon. As the exchange broadening is maximized when the exchange rate equals the chemical shift difference in Hz between equilibrating sites, semi-quantitative information that was useful for establishing conditions for {sup 13}C relaxation dispersion experiments was obtained through the carbon line-shape profile. With respect to the m{sub c38} isomerization, the {sup 1}H-{sup 13}C signals at the β-position of the minor state were resolved from the major peaks and detected by exchange experiments at a low temperature.

A combined crossed molecular beam and theoretical investigation of the reaction of the meta-tolyl radical with vinylacetylene--toward the formation of methylnaphthalenes.

Science.gov (United States)

Yang, Tao; Muzangwa, Lloyd; Kaiser, Ralf I; Jamal, Adeel; Morokuma, Keiji

2015-09-07

Crossed molecular beam experiments and electronic structure calculations on the reaction of the meta-tolyl radical with vinylacetylene were conducted to probe the formation of methyl-substituted naphthalene isomers. We present the compelling evidence that under single collision conditions 1- and 2-methylnaphthalene can be formed without an entrance barrier via indirect scattering dynamics through a bimolecular collision of two non-PAH reactants: the meta-tolyl radical and vinylacetylene. The electronic structure calculations, conducted at the UCCSD(T)-F12b/cc-pVDZ//UM06-2x/cc-pVTZ + ZPE(UM06-2x/cc-pVTZ) level of theory, reveal that this reaction is initiated by the barrierless addition of the meta-tolyl radical to the terminal vinyl carbon (C1) of vinylacetylene, via a van-der-Waals complex implying that this mechanism can play a key role in forming methyl-substituted PAHs in low temperature extreme environments such as the low temperature interstellar medium and hydrocarbon-rich atmospheres of planets and their moons in the outer solar system. The reaction mechanism, proposed from the C11H11 potential energy surface, involves a sequence of isomerizations involving hydrogen transfer and ring closure, followed by hydrogen dissociation, which eventually leads to 1- and 2-methylnaphthalene in an overall exoergic process.

Five Stereoactive Orbitals on Silicon: Charge and Spin Localization in the n-Si4Me10(-•) Radical Anion by Trigonal Bipyramidalization.

Science.gov (United States)

MacLeod, Matthew K; Michl, Josef

2013-05-16

RIUMP2/def2-TZVPPD calculations show that in addition to its usual conformation with charge and spin delocalized over the Si backbone, the isolated Si4Me10(-•) radical anion also has isomeric conformations with localized charge and spin. A structure with localization on a terminal Si atom has been examined in detail. In vacuum, it is calculated to lie 11.5 kcal/mol higher in energy than the charge-and-spin delocalized conformation, and in water the difference is as little as 1.6 kcal/mol. According to natural orbital and localized orbital analyses, the charge-and-spin-carrying terminal Si atom uses five stereoactive hybrid orbitals in a trigonal bipyramidal geometry. Four are built mostly from 3s and 3p atomic orbitals (AOs) and are used to attach a Si3(CH3)7 and three CH3 groups, whereas the larger equatorial fifth orbital is constructed from 4s and 4p AOs and acts as a nonbonding (radical) hybrid orbital with an occupancy of about 0.65 e.

Conserving Coherence and Storing Energy during Internal Conversion: Photoinduced Dynamics of cis- and trans-Azobenzene Radical Cations

KAUST Repository

Munkerup, Kristin

2017-10-24

Light harvesting via energy storage in azobenzene has been a key topic for decades, and the process of energy distribution over the molecular degrees of freedom following photoexcitation remains to be understood. Dynamics of a photoexcited system can exhibit high degrees of non-ergodicity when it is driven by just a few degrees of freedom. Typically, an internal conversion leads to the loss of such localization of dynamics, as the intramolecular energy becomes statistically redistributed over all molecular degrees of freedom. Here, we present a unique case where the excitation energy remains localized even subsequent to internal conversion. Strong-field ionization is used to prepare cis- and trans-azobenzene radical cations on the D1 surface with little excess energy, at the equilibrium neutral geometry. These D1 ions are preferably formed because in this case D1 and D0 switch place in the presence of the strong laser field. The post-ionization dynamics is dictated by the potential energy landscape. The D1 surface is steep downhill along the cis/trans isomerization coordinate and towards a common minimum shared by the two isomers in the region of D1/D0 conical intersection. Coherent cis/trans torsional motion along this coordinate is manifested in the ion transients by a cosine modulation. In this scenario, D0 becomes populated with molecules that are energized mainly along the cis-trans isomerization coordinate, with the kinetic energy above the cis-trans inter-conversion barrier. These activated azobenzene molecules easily cycle back and forth along the D0 surface, and give rise to several periods of modulated signal before coherence is lost. This persistent localization of the internal energy during internal conversion is provided by the steep downhill potential energy surface, small initial internal energy content, and a strong hole-lone pair interaction that drives the molecule along the cis-trans isomerization coordinate to facilitate the transition between

Deposition of radiation energy in solids as visualized by the distribution, structure and properties of alkyl radicals in γ-irradiated n-alkane single crystals

International Nuclear Information System (INIS)

Gillbro, T.; Lund, A.

1976-01-01

This paper summarizes results obtained earlier from ESR studies of γ-irradiated n-alkane single crystals. It also contains some new experimental results that serve to give a more complete picture of the deposition of radiation energy in solid alkanes. The experiments performed with solid n-alkanes have thus far provided structural data that permit the nature and even the conformation of alkyl radicals to be clearly understood. Two types of radical exist namely, one where the unpaired electron is located next to the end methyl group and one with the unpaired electron in the interior of the chain. The first type has a conformation which differs from that of the undamaged molecule. Microwave saturation data show that there is a difference in relaxation properties of these radicals which can be understood in terms of a difference in mobility. Relative yield measurements give the distribution of isomeric alkyl, the result differing from that obtained using product analysis in liquids. For protiated n-alkanes n-alkyl is lacking and the 2-alkyl concentration is higher than expected. For deuterated n-alkanes the ESR spectrum is mainly that of radicals with the unpaired electron located in the interior of the carbon chain. This isotope effect is again contrary to observations in liquid n-alkanes. The broad lines observed in protiated alkanes irradiated at 77 K and deuterated alkanes irradiated at 4.2 K are not believed to arise from strong spin-spin interactions. They are thought instead to arise from distorted crystal and radical structures relating to the damaged regions of the crystals. (Auth.)

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

International Nuclear Information System (INIS)

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

1988-01-01

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

Synthesis of Isomeric Phosphoubiquitin Chains Reveals that Phosphorylation Controls Deubiquitinase Activity and Specificity

Directory of Open Access Journals (Sweden)

Nicolas Huguenin-Dezot

2016-07-01

Full Text Available Ubiquitin is post-translationally modified by phosphorylation at several sites, but the consequences of these modifications are largely unknown. Here, we synthesize multi-milligram quantities of ubiquitin phosphorylated at serine 20, serine 57, and serine 65 via genetic code expansion. We use these phosphoubiquitins for the enzymatic assembly of 20 isomeric phosphoubiquitin dimers, with different sites of isopeptide linkage and/or phosphorylation. We discover that phosphorylation of serine 20 on ubiquitin converts UBE3C from a dual-specificity E3 ligase into a ligase that primarily synthesizes K48 chains. We profile the activity of 31 deubiquitinases on the isomeric phosphoubiquitin dimers in 837 reactions, and we discover that phosphorylation at distinct sites in ubiquitin can activate or repress cleavage of a particular linkage by deubiquitinases and that phosphorylation at a single site in ubiquitin can control the specificity of deubiquitinases for distinct ubiquitin linkages.

High spin states in 63Cu. 17/2+ isomeric yrast state

International Nuclear Information System (INIS)

Tsan Ung Chan; Bruandet, J.F.; Dauchy, A.; Giorni, A.; Glasser, F.; Morand, C.; Chambon, B.; Drain, D.

1979-01-01

The 63 Cu nucleus has been studied via the reaction 61 Ni(α, pnγ), using different in beam γ spectroscopy techniques. An isomeric high-spin Yrast state 17/2 + (tau = 6.1 +- 0.6ns) is located at 4498 keV. The gsub(9/2) shell must be involved to explain positive high-spin states established in this work [fr

Isomerization of Internal Alkynes to Iridium(III Allene Complexes via C–H Bond Activation: Expanded Substrate Scope, and Progress towards a Catalytic Methodology

Directory of Open Access Journals (Sweden)

Neha Phadke

2015-11-01

Full Text Available The synthesis of a series of allene complexes (POCOPIr(η2-RC=.=CR’ 1b–4b (POCOP = 2,6-bis(di-tert-butylphosphonitobenzene via isomerization of internal alkynes is reported. We have demonstrated that the application of this methodology is viable for the isomerization of a wide variety of alkyne substrates. Deuterium labeling experiments support our proposed mechanism. The structures of the allene complexes 1b–4b were determined using spectroscopic data analysis. Additionally, the solid-state molecular structure of complex 2b was determined using single crystal X-ray diffraction studies and it confirmed the assignment of an iridium-bound allene isomerization product. The rates of isomerization were measured using NMR techniques over a range of temperatures to allow determination of thermodynamic parameters. Finally, we report a preliminary step towards developing a catalytic methodology; the allene may be liberated from the metal center by exposure of the complex to an atmosphere of carbon monoxide.

Why Nature Uses Radical SAM Enzymes so Widely: Electron Nuclear Double Resonance Studies of Lysine 2,3-Aminomutase Show the 5′-dAdo• “Free Radical” Is Never Free

Science.gov (United States)

Horitani, Masaki; Byer, Amanda S.; Shisler, Krista A.; Chandra, Tilak; Broderick, Joan B.; Hoffman, Brian M.

2015-01-01

Lysine 2,3-aminomutase (LAM) is a radical S-adenosyl-L-methionine (SAM) enzyme and, like other members of this superfamily, LAM utilizes radical-generating machinery comprising SAM anchored to the unique Fe of a [4Fe-4S] cluster via a classical five-membered N,O chelate ring. Catalysis is initiated by reductive cleavage of the SAM S–C5′ bond, which creates the highly reactive 5′-deoxyadenosyl radical (5′-dAdo•), the same radical generated by homolytic Co–C bond cleavage in B12 radical enzymes. The SAM surrogate S-3′,4′-anhydroadenosyl-L-methionine (anSAM) can replace SAM as a cofactor in the isomerization of L-α-lysine to L-β-lysine by LAM, via the stable allylic anhydroadenosyl radical (anAdo•). Here electron nuclear double resonance (ENDOR) spectroscopy of the anAdo• radical in the presence of 13C, 2H, and 15N-labeled lysine completes the picture of how the active site of LAM from Clostridium subterminale SB4 “tames” the 5′-dAdo• radical, preventing it from carrying out harmful side reactions: this “free radical” in LAM is never free. The low steric demands of the radical-generating [4Fe-4S]/SAM construct allow the substrate target to bind adjacent to the S–C5′ bond, thereby enabling the 5′-dAdo• radical created by cleavage of this bond to react with its partners by undergoing small motions, ~0.6 Å toward the target and ~1.5 Å overall, that are controlled by tight van der Waals contact with its partners. We suggest that the accessibility to substrate and ready control of the reactive C5′ radical, with “van der Waals control” of small motions throughout the catalytic cycle, is common within the radical SAM enzyme superfamily and is a major reason why these enzymes are the preferred means of initiating radical reactions in nature. PMID:25923449

Phase space conduits for reaction in multidimensional systems : HCN isomerization in three dimensions

NARCIS (Netherlands)

Waalkens, Holger; Burbanks, Andrew; Wiggins, Stephen

2004-01-01

The three-dimensional hydrogen cyanide/isocyanide isomerization problem is taken as an example to present a general theory for computing the phase space structures which govern classical reaction dynamics in systems with an arbitrary (finite) number of degrees of freedom. The theory, which is

Application of cinchona-sulfonate-based chiral zwitterionic ion exchangers for the separation of proline-containing dipeptide rotamers and determination of on-column isomerization parameters from dynamic elution profiles.

Science.gov (United States)

Wernisch, Stefanie; Trapp, Oliver; Lindner, Wolfgang

2013-09-17

The interconversion of cis and trans isomers of dipeptides containing C-terminal proline was studied by dynamic chromatography on zwitterionic chiral stationary phases at temperatures ranging from -15°C to +45°C The cis-trans isomers could be separated below 0°C and above 0-10°C plateau formation and peak coalescence phenomena occurred, which is characteristic for a dynamic process at the time-scale of partitioning. At and above room temperature, full coalescence was observed, which allowed separations of enantiomers without interference from interconversion effects. Analysis of the dynamic elution profiles of the interconverting peptides allowed the determination of isomerization rate constants and thermodynamic activation parameters (isomerization enthalpy, entropy and activation energy). In accordance with established results, isomerization rates and thermodynamic parameters were found to depend on the nature of the N-terminal amino acid. Isomerization barriers were only slightly lower than values determined with other methods but significant differences in the relative contributions of the activation enthalpy and entropy as well as isomerization rates pointed toward selector-moderated isomerization dynamics. Copyright © 2013 Elsevier B.V. All rights reserved.

Hydro-isomerization of n-hexane on bi-functional catalyst: Effect of total and hydrogen partial pressures

Science.gov (United States)

Thoa, Dao Thi Kim; Loc, Luu Cam

2017-09-01

The effect of both total pressure and hydrogen partial pressure during n-hexane hydro-isomerization over platinum impregnated on HZSM-5 was studied. n-Hexane hydro-isomerization was conducted at atmospheric pressure and 0.7 MPa to observe the influence of total pressure. In order to see the effect of hydrogen partial pressure, the reaction was taken place at different partial pressure of hydrogen varied from 307 hPa to 718 hPa by dilution with nitrogen to keep the total pressure at 0.1 MPa. Physico-chemical characteristics of catalyst were determined by the methods of nitrogen physi-sorption BET, SEM, XRD, TEM, NH3-TPD, TPR, and Hydrogen Pulse Chemi-sorption. Activity of catalyst in the hydro-isomerization of n-hexane was studied in a micro-flow reactor in the temperature range of 225-325 °C; the molar ratio H2/ hydrocarbon: 5.92, concentration of n-hexane: 9.2 mol.%, GHSV 2698 h-1. The obtained catalyst expressed high acid density, good reducing property, high metal dispersion, and good balance between metallic and acidic sites. It is excellent contact for n-hexane hydro-isomerization. At 250 °C, n-hexane conversion and selectivity were as high as 59-76 % and 85-99 %, respectively. It was found that catalytic activity was promoted either by total pressure or hydrogen partial pressure. At total pressure of 0.7 MPa while hydrogen partial pressure of 718 hPa, catalyst produced 63 RON liquid product containing friendly environmental iso-paraffins which is superior blending stock for green gasoline. Hydrogen did not only preserve catalyst actives by depressing hydrocracking and removing coke precursors but also facilitated hydride transfer step in the bi-functional bi-molecular mechanism.

Silver complexation and tandem mass spectrometry for differentiation of isomeric flavonoid diglycosides.

Science.gov (United States)

Zhang, Junmei; Brodbelt, Jennifer S

2005-03-15

For detection and differentiation of isomeric flavonoids, electrospray ionization mass spectrometry is used to generate silver complexes of the type (Ag + flavonoid)+. Collisionally activated dissociation (CAD) of the resulting 1:1 silver/flavonoid complexes allows isomer differentiation of flavonoids. Eighteen flavonoid diglycosides constituting seven isomeric series are distinguishable from each other based on the CAD patterns of their silver complexes. Characteristic dissociation pathways allow identification of the site of glycosylation, the type of disaccharide (rutinose versus neohesperidose), and the type of aglycon (flavonol versus flavone versus flavanone). This silver complexation method is more universal than previous metal complexation methods, as intense silver complexes are observed even for flavonoids that lack the typical metal chelation sites. To demonstrate the feasibility of using silver complexation and tandem mass spectrometry to characterize flavonoids in complex mixtures, flavonoids extracted from grapefruit juice are separated by high-performance liquid chromatography and analyzed via a postcolumn complexation ESI-MS/MS strategy. Diagnostic fragmentation pathways of the silver complexes of the individual eluting flavonoids allow successful identification of the six flavonoids in the extract.

Cardiopulmonary Exercise Testing in Fontan Patients With and Without Isomerism (Heterotaxy) as Compared to Patients With Primary Ciliary Dyskinesia and Subjects With Structurally Normal Hearts

DEFF Research Database (Denmark)

Loomba, Rohit S; Danduran, Michael; Nielsen, Kim G

2017-01-01

with and without isomerism. We have now compared these finding with those from patients with primary ciliary dyskinesia, as many patients with isomerism have ciliary dyskinesia. We identified patients having the Fontan circulation with and without isomerism who had undergone cardiopulmonary exercise testing......, comparing the findings from healthy individuals undergoing exercise, and a comparable number of individuals with primary ciliary dyskinesia but no congenital heart disease. We were able to include a total of 68 patients in our study, with 17 in each of the four groups. Cardiopulmonary exercise testing...

Thermal solid-state Z/E isomerization of 2-alkylidene-4-oxothiazolidines: effects of non-covalent interactions

Directory of Open Access Journals (Sweden)

ZDRAVKO DŽAMBASKI

2011-03-01

Full Text Available Configurational isomerization of stereo-defined 5-substituted and unsubstituted 2-alkylidene-4-oxothiazolidines (1 in the solid state, giving the Z/E mixtures in various ratios, was investigated by 1H-NMR spectroscopy, X-ray powder crystallography and differential scanning calorimetry (DSC. The Z/E composition can be rationalized in terms of non-covalent interactions, involving intermolecular and intramolecular hydrogen bonding and directional non-bonded 1,5-type S×××O interactions. X-Ray powder crystallography, using selected crystalline (Z-4-oxothiazolidine substrates, revealed transformation to the amorphous state during the irreversible Z®E process. A correlation between previous results on the Z/E isomerization in solution and now in the solid state was established.

Nitrite-reductase and peroxynitrite isomerization activities of Methanosarcina acetivorans protoglobin.

Directory of Open Access Journals (Sweden)

Paolo Ascenzi

Full Text Available Within the globin superfamily, protoglobins (Pgb belong phylogenetically to the same cluster of two-domain globin-coupled sensors and single-domain sensor globins. Multiple functional roles have been postulated for Methanosarcina acetivorans Pgb (Ma-Pgb, since the detoxification of reactive nitrogen and oxygen species might co-exist with enzymatic activity(ies to facilitate the conversion of CO to methane. Here, the nitrite-reductase and peroxynitrite isomerization activities of the CysE20Ser mutant of Ma-Pgb (Ma-Pgb* are reported and analyzed in parallel with those of related heme-proteins. Kinetics of nitrite-reductase activity of ferrous Ma-Pgb* (Ma-Pgb*-Fe(II is biphasic and values of the second-order rate constant for the reduction of NO2- to NO and the concomitant formation of nitrosylated Ma-Pgb*-Fe(II (Ma-Pgb*-Fe(II-NO are k(app1= 9.6 ± 0.2 M(-1 s(-1 and k(app2 = 1.2 ± 0.1 M(-1 s(-1 (at pH 7.4 and 20 °C. The k(app1 and k(app2 values increase by about one order of magnitude for each pH unit decrease, between pH 8.3 and 6.2, indicating that the reaction requires one proton. On the other hand, kinetics of peroxynitrite isomerization catalyzed by ferric Ma-Pgb* (Ma-Pgb*-Fe(III is monophasic and values of the second order rate constant for peroxynitrite isomerization by Ma-Pgb*-Fe(III and of the first order rate constant for the spontaneous conversion of peroxynitrite to nitrate are h(app = 3.8 × 10(4 M(-1 s(-1 and h0 = 2.8 × 10(-1 s(-1 (at pH 7.4 and 20 °C. The pH-dependence of hon and h0 values reflects the acid-base equilibrium of peroxynitrite (pKa = 6.7 and 6.9, respectively; at 20 °C, indicating that HOONO is the species that reacts preferentially with the heme-Fe(III atom. These results highlight the potential role of Pgbs in the biosynthesis and scavenging of reactive nitrogen and oxygen species.

Synthesis of heterocycles through transition-metal-catalyzed isomerization reactions

DEFF Research Database (Denmark)

Ishøy, Mette; Nielsen, Thomas Eiland

2014-01-01

of structurally complex and diverse heterocycles. In this Concept article, we attempt to cover this area of research through a selection of recent versatile examples. A sea of opportunities! Transition-metal-catalyzed isomerization of N- and O-allylic compounds provides a mild, selective and synthetically...... versatile method to form iminium and oxocarbenium ions. Given the number of reactions involving these highly electrophilic intermediates, this concept provides a sea of opportunities for heterocycle synthesis, (see scheme; Nu=nucleophile). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim....

Hydroxyl-radical-induced oxidation of cyclic dipeptides: Reactions of free peptide radicals and their peroxyl radicals

International Nuclear Information System (INIS)

Mieden, O.J.

1989-01-01

In the course of this study investigations were carried out into the reactions of hydroxyl radicals and hydrogen atoms with cyclic dipeptides as well as the subsequent reactions of peptide radicals and their peroxyl radicals in aqueous solution. The radiolysis products formed in the absence and presence of oxygen or transient metal complexes were characterized and determined on a quantitative basis. The linking of information from product analyses to the kinetic data for transient species obtained by time-resolving UV/VIS and conductivity measurements (pulse radiolysis) as well as computer-assisted simulations of individual events during the reaction permitted an evaluation of the mechanisms underlying the various processes and an identification of interim products with short life-times, which did or did not belong to the group of radicals. Through the characterization of key reactions of radicals and peroxyl radicals of this substance class a major advance has been made towards a better understanding of the role of radicals in the peptide compound and the mechanisms involved in indirect radiation effects on long-chain peptides and proteins. (orig.) [de

A radical approach to radical innovation

NARCIS (Netherlands)

D. Deichmann (Dirk); J.C.M. van den Ende (Jan)

2014-01-01

textabstractInnovation pays. Amazon, Apple, Facebook, Google – nearly every one of today’s most successful companies has a talent for developing radical new ideas. But how best to encourage radical initiative taking from employees, and does their previous success or failure at it play a role?

Yields and isomeric ratio of xenon and krypton isotopes from thermal neutron fission of 235U

International Nuclear Information System (INIS)

Hsu, S.S.; Lin, J.T.; Yang, C.M.; Yu, Y.W.

1981-01-01

The experimental cumulative yields of 85 Kr/sup m/, 87 Kr, 88 Kr, 133 Xe/sup g/, 135 Xe/sup m/, and 135 Xe/sup g/ and the independent isomeric yield of 133 Xe/sup m/ in the thermal neutron fission of 235 U have been measured by the gas chromatographic method. The independent yields of 133 Xe/sup g/, 135 Xe/sup m/, and 135 Xe/sup g/ were deduced with the aid of 133 I and 135 I data. The isomeric yield ratios of 133 Xe and 135 Xe have been computed and compared with theoretical values since they have the same high spin state J = 11/2 - and low spin ground state J = 3/2 + . The influence of the shell effect on the fission isomeric yield ratio is discussed. From the measured independent yield of Xe isotopes plus the reported data, the Xe-isotopic distribution curve has been constructed. The curve is compared with the isotopic distribution curves of Xe isotopes formed in 11.5 GeV proton interactions with 238 U and Cs isotopes formed in 24 GeV proton interactions with 238 U. Upon fitting the yield curves we find that only those products with N/Z> or =1.48 fit a curve typical of a binary fission process

Radicalization In Pakistan And The Spread Of Radical Islam In Pakistan

Directory of Open Access Journals (Sweden)

Bahir ahmad

2015-08-01

Full Text Available ABSTRACT It is pertinent to mention that radicalism is not intrinsic to Islam and radical interpretations of the religion or for that matter may occur within any way of life and religion Saikal 2003 and yet the question remains as to why Muslims in certain geographical regions have more radical approaches towards their religion and also that what are the causes of such radicalization. Becoming a radical Muslim is not even a matter of a day nor is it a sudden process. There are several reasons behind making a person radical peaceful angry smiling or tolerant. For knowing the reason behind radicalization or radicals persons one has to understand the causes. Tracing these causes is one of the ways to eliminate such behavior. The first step in the elimination of the radical sentiments in a person is to develop peace in his personality Fair Malhotra amp Shapiro 2010. The chapter which has been addressed here is going to shed light on the roots and symptoms of the radicalism. There will be a brief discussion on how the roots of radicalism can be traced and can be eliminated. The assessment and discussion will be conducted on the parameters of the economy media politics and theology from social cultural point of view. According to the analysis of Ahrari 2000 political factor is one of the major and direct factors which have resulted in causing of the radicalism. These factors however intertwine with one another. Radical actions cannot take place only because of the political factors.

Production cross sections and isomeric ratios for sup(110m)In/sup(110g)In formed in Cd (d,xn) reactions

International Nuclear Information System (INIS)

Herreros Usher, Oscar; Maceiras de Jefimowicz, Elena; De la Vega Vedoya, Mario; Jorge Nassiff, Sonia

1980-01-01

Excitation functions and isomeric cross sections ratios have been measured for the 110 Cd (d,2n) and 111 Cd (d,3n) reactions in which the isomeric pair sup(110m)In/sup(110g)In is produced. Activation method was employed and the irradiations were performed at the synchrocyclotron of the Comision Nacional de Energia Atomica, Argentina, with an incident energy of 27.MeV. (author) [es

Radiolysis of methylene blue studied by ESR

International Nuclear Information System (INIS)

Contineau, M.; Iliescu, C.; Ciureanu, M.

1983-01-01

Electron spin resonance spectra have been used to gain information on the mechanism of radiolysis of aqueous solutions of methylene blue. The identity and behaviour of the semiquinone radicals formed as intermediate reduction products were discussed for strongly acid and for alcaline solutions. In order to obtain information on the radiolytic mechanism in strongly acidic media, irradiation was performed in the presence of various types of scavengers: sodium formate, glucose, succinic acid, hydroquinone and D,L-α alanine. (author)

Catalytic Isomerization of Dihydroxyacetone to Lactic Acid and Alkyl Lactates over Hierarchical Zeolites Containing Tin

Directory of Open Access Journals (Sweden)

Agnieszka Feliczak-Guzik

2018-01-01

Full Text Available Hierarchical zeolites containing tin were obtained, characterized and used in a reaction of catalytic isomerization of dihydroxyacetone (DHA to lactic acid and alkyl lactates. These catalysts are characterized by preserved crystallinity and primary microporosity with the simultaneous existence of secondary porosity regarding mesopores, which facilitates access of large molecules of reagents to active centers. Creation of additional porosity was confirmed by X-ray diffraction and low-temperature nitrogen adsorption/desorption studies. The reaction of dihydroxyacetone isomerization was conducted in different reaction media such as methanol, ethanol or water with the use of two heating methods: microwave radiation and conventional heating. The application of microwave radiation enabled to reduce the reaction time to 1 h and achieve dihydroxyacetone conversion of >90% and high yields of the desired reaction products.

Process for paraffin isomerization of a distillate range hydrocarbon feedstock

Energy Technology Data Exchange (ETDEWEB)

Chen, N.Y.; Garwood, W.E.; McCullen, S.B.

1993-01-19

Various catalytic processes have been proposed to isomerize n-paraffins so as to lower the pour point of distillate range hydrocarbon feedstocks. However, many available feedstocks contain nitrogen impurities which tend to poison conventional paraffin isomerization catalysts. A process has been developed to obviate or alleviate this problem. According to the invention, the paraffin-containing feedstock is contacted with a crystalline aluminosilicate zeolite catalyst having pore openings defined by a ratio of sorption of n-hexane to o-xylene of over 3 vol % and the ability to crack 3-methylpentane in preference to 2,3 dimethylbutane under defined conditions. The zeolite catalyst includes a Group VIII metal and has a zeolite SiO[sub 2]/Al[sub 2]O[sub 3] ratio of at least 20:1. The contacting is carried out at 199-454 C and a pressure of 100-1,000 psig, preferably 250-600 psig. The group of medium pore zeolites which can be used in the process of the invention includes ZSM-22, ZSM-23, and ZSM-35. The Group VIII metals used in the catalyst are preferably selected from Pt, Pd, Ir, Os, Rh, and Ru and the metal is preferably incorporated into the zeolite by ion exchange up to a metal content of preferably 0.1-3 wt %. Experiments are described to illustrate the invention. 1 tab.

Abnormal radioactive decays out of long-lived super- and hyper-deformed isomeric states

International Nuclear Information System (INIS)

Marinov, A.; Gelberg, S.; Kolb, D.

2000-01-01

Complete text of publication follows. Recently (1-3) long-lived isomeric states have been found in the super- and hyper-deformed wells of the potential. These isomers manifested themselves by abnormal particle decays. An isomeric state in the superdeformed well of the potential in the parent nucleus can decay by very enhanced α-particle groups to superdeformed states in the daughter (1) or by very retarded α-particles (3) and also by protons (2) to normal states in the daughters. Similarly an isomeric state in the hyper-deformed well may decay by very retarded α-particle groups to superdeformed states (3), or by very enhanced α-groups to hyper-deformed states in the daughter nucleus (4). All these very unusual decay modes have been observed experimentally (1-4). For instance, a very high energy α-group of 8.6 MeV with 40d ≤ t 1/2 ≤ 2y (retardation factor of ∼10 13 ) has been observed in 195 Hg and interpreted as a III min → II min α-transition (3). Likewise, relatively low-energy and very enhanced α-particle groups (enhancement factors of 10 5 to 10 7 ) have been seen in several actinide sources and interpreted as due to II min → II min and III min → III min transitions (4). These unusual decay modes introduce new considerations in the study of heavy and superheavy elements. For instance, if low-energy α-particle groups around 4.4 - 4.6 MeV have been seen in nature (5), they may be interpreted as due to very enhanced III min → III min transitions in the superheavy element region around Z = 108 (eka-Os) with t 1/2 ∼10 8 y rather than ∼10 15 y as expected for normal α-transitions of such energies in this region, or due to very retarded III min → II min or II min → I min decays in nuclei around Os itself. In both cases, if such activities have been seen in nature, they indicate that the existence of the II min and III min isomeric states may be important in the nucleosynthesis process. It should be mentioned that long-lived high

Manipulating radicals: Using cobalt to steer radical reactions

OpenAIRE

Chirilă, A.

2017-01-01

This thesis describes research aimed at understanding and exploiting metallo-radical reactivity and explores reactions mediated by square planar, low-spin cobalt(II) complexes. A primary goal was to uncover novel reactivity of discrete cobalt(III)-bound carbene radicals generated upon reaction of the cobalt(II) catalysts with carbene precursors. Another important goal was to replace cobalt(II)-porphyrin catalysts with cheaper and easier to prepare metallo-radical analogues. Therefore the cata...

Theoretical study of isomerization and decomposition of propenal

International Nuclear Information System (INIS)

Chin, Chih-Hao; Lee, Shih-Huang

2011-01-01

We investigated the dynamics of isomerization and multi-channel dissociation of propenal (CH 2 CHCHO), methyl ketene (CH 3 CHCO), hydroxyl propadiene (CH 2 CH 2 CHOH), and hydroxyl cyclopropene (cyclic-C 3 H 3 -OH) in the ground potential-energy surface using quantum-chemical calculations. Optimized structures and vibrational frequencies of molecular species were computed with method B3LYP/6-311G(d,p). Total energies of molecules at optimized structures were computed at the CCSD(T)/6-311+G(3df,2p) level of theory. We established the potential-energy surface for decomposition to CH 2 CHCO + H, CH 2 CH + HCO, CH 2 CH 2 /CH 3 CH + CO, CHCH/CH 2 C + H 2 CO, CHCCHO/CH 2 CCO + H 2 , CHCH + CO + H 2 , CH 3 + HCCO, CH 2 CCH + OH, and CH 2 CC/cyclic-C 3 H 2 + H 2 O. Microcanonical rate coefficients of various reactions of trans-propenal with internal energies 148 and 182 kcal mol -1 were calculated using Rice-Ramsperger-Kassel-Marcus and Variational transition state theories. Product branching ratios were derivable using numerical integration of kinetic master equations and the steady-state approximation. The concerted three-body dissociation of trans-propenal to fragments C 2 H 2 + CO + H 2 is the prevailing channel in present calculations. In contrast, C 3 H 3 O + H, C 2 H 3 + HCO and C 2 H 4 + CO were identified as major channels in the photolysis of trans-propenal. The discrepancy between calculations and experiments in product branching ratios indicates that the three major photodissociation channels occur mainly on an excited potential-energy surface whereas the other channels occur mainly on the ground potential-energy surface. This work provides profound insight in the mechanisms of isomerization and multichannel dissociation of the system C 3 H 4 O.

Isomeric Detergent Comparison for Membrane Protein Stability

DEFF Research Database (Denmark)

Cho, Kyung Ho; Hariharan, Parameswaran; Mortensen, Jonas S.

2016-01-01

and utility, particularly for eukaryotic membrane proteins and membrane protein complexes. Thus, a number of new agents have been devised; some have made significant contributions to membrane protein structural studies. However, few detergent design principles are available. In this study, we prepared meta...... and ortho isomers of the previously reported para-substituted xylene-linked maltoside amphiphiles (XMAs), along with alkyl chain-length variation. The isomeric XMAs were assessed with three membrane proteins, and the meta isomer with a C12 alkyl chain was most effective at maintaining solubility....../stability of the membrane proteins. We propose that interplay between the hydrophile–lipophile balance (HLB) and alkyl chain length is of central importance for high detergent efficacy. In addition, differences in inter-alkyl-chain distance between the isomers influence the ability of the detergents to stabilise membrane...

Results of a Direct Search Using Synchrotron Radiation for the Low-Energy (229)Th Nuclear Isomeric Transition.

Science.gov (United States)

Jeet, Justin; Schneider, Christian; Sullivan, Scott T; Rellergert, Wade G; Mirzadeh, Saed; Cassanho, A; Jenssen, H P; Tkalya, Eugene V; Hudson, Eric R

2015-06-26

We report the results of a direct search for the (229)Th (I(π)=3/2(+)←5/2(+)) nuclear isomeric transition, performed by exposing (229)Th-doped LiSrAlF(6) crystals to tunable vacuum-ultraviolet synchrotron radiation and observing any resulting fluorescence. We also use existing nuclear physics data to establish a range of possible transition strengths for the isomeric transition. We find no evidence for the thorium nuclear transition between 7.3 eV and 8.8 eV with transition lifetime (1-2) s≲τ≲(2000-5600)  s. This measurement excludes roughly half of the favored transition search area and can be used to direct future searches.

Free radical inactivation of trypsin

International Nuclear Information System (INIS)

Cudina, Ivana; Jovanovic, S.V.

1988-01-01

Reactivities of free radical oxidants, radical OH, Br2-anion radical and Cl 3 COO radical and a reductant, CO2-anion radical, with trypsin and reactive protein components were determined by pulse radiolysis of aqueous solutions at pH 7, 20 0 C. Highly reactive free radicals, radical OH, Br2-anion radical and CO2-anion radical, react with trypsin at diffusion controlled rates. Moderately reactive trichloroperoxy radical, k(Cl 3 COO radical + trypsin) preferentially oxidizes histidine residues. The efficiency of inactivation of trypsin by free radicals is inversely proportional to their reactivity. The yields of inactivation of trypsin by radical OH, Br2-anion radical and CO2-anion radical are low, G(inactivation) = 0.6-0.8, which corresponds to ∼ 10% of the initially produced radicals. In contrast, Cl 3 COO radical inactivates trypsin with ∼ 50% efficiency, i.e. G(inactivation) = 3.2. (author)

First observation of high spin states and isomeric decay in 210Fr

International Nuclear Information System (INIS)

Kanjilal, D.; Saha, S.; Bhattacharya, S.; Goswami, A.; Kshetri, R.; Raut, R.; Muralithar, S.; Singh, R. P.; Mukherjee, G.; Mukherjee, B.

2011-01-01

The first observation of the prompt and the delayed γ transitions involving the high spin states in 210 Fr is reported. The decay of the high spin states and the isomeric levels of 210 Fr, identified for the first time from the known sequence of low-lying transitions found earlier in the α decay of 214 Ac, were studied. High spin states of the doubly-odd 210 Fr, which were produced by the fusion evaporation reaction 197 Au ( 16 O, xn) 213-x Fr, were populated and the subsequent emitted γ rays were detected through the high-sensitivity germanium clover detector array INGA. The level scheme up to yrast levels of 5.3 MeV excitation energy and ∼20(ℎ/2π) angular momentum could be established for the first time through γγ, γγΔT coincidence, and DCO ratio measurements. A new low-lying isomeric transition at E γ = 203(2) keV was observed. The half-life was measured to be T 1/2 = 41(2) ns. The measured half-life was compared with the corresponding single-particle estimate, based on the level scheme obtained from the experiment.

Left atrial isomerism associated with asplenia: prenatal echocardiographic detection of complex congenital cardiac malformations

NARCIS (Netherlands)

Stewart, P. A.; Becker, A. E.; Wladimiroff, J. W.; Essed, C. E.

1984-01-01

Complex congenital heart disease with suspected isomerism of the atria was diagnosed in two fetuses of 20 and 29 weeks' gestation using two-dimensional and M-mode scanning techniques. The first pregnancy was terminated at 21 weeks' gestation and stillbirth occurred at 31 weeks' gestation in the

Biosynthesis of monoterpenes: Stereochemistry of the coupled isomerization and cyclization of geranyl pyrophosphate to camphane and isocamphane monoterpenes

International Nuclear Information System (INIS)

Croteau, R.; Gershenzon, J.; Wheeler, C.J.; Satterwhite, D.M.

1990-01-01

The conversion of geranyl pyrophosphate to (+)-bornyl pyrophosphate and (+)-camphene is considered to proceed by the initial isomerization of the substrate to (-)-(3R)-linalyl pyrophosphate and the subsequent cyclization of this bound intermediate. In the case of (-)-bornyl pyrophosphate and (-)-camphene, isomerization of the substrate to the (+)-(3S)-linalyl intermediate precedes cyclization. The geranyl and linalyl precursors were shown to be mutually competitive substrates (inhibitors) of the relevant cyclization enzymes isolated from Salvia officinalis (sage) and Tanacetum vulgare (tansy) by the mixed substrate analysis method, demonstrating that isomerization and cyclization take place at the same active site. Incubation of partially purified enzyme preparations with (3R)-[1Z-3H]linalyl pyrophosphate plus [1-14C]geranyl pyrophosphate gave rise to double-labeled (+)-bornyl pyrophosphate and (+)-camphene, whereas incubation of enzyme preparations catalyzing the antipodal cyclizations with (3S)-[1Z-3H]-linalyl pyrophosphate plus [1-14C]geranyl pyrophosphate yielded double-labeled (-)-bornyl pyrophosphate and (-)-camphene. Each product was then transformed to the corresponding (+)- or (-)-camphor without change in the 3H:14C isotope ratio, and the location of the tritium label was deduced in each case by stereoselective, base-catalyzed exchange of the exo-alpha-hydrogen of the derived ketone. The finding that the 1Z-3H of the linalyl precursor was positioned at the endo-alpha-hydrogen of the corresponding camphor in all cases, coupled to the previously demonstrated retention of configuration at C1 of the geranyl substrate in these transformations, confirmed the syn-isomerization of geranyl pyrophosphate to linalyl pyrophosphate and the cyclization of the latter via the anti,endo- conformer

Ruthenium Hydride/Brønsted Acid-Catalyzed Tandem Isomerization/N-Acyliminium Cyclization Sequence for the Synthesis of Tetrahydro-β-carbolines

DEFF Research Database (Denmark)

Hansen, Casper Lykke; Clausen, Janie Regitse Waël; Ohm, Ragnhild Gaard

2013-01-01

This paper describes an efficient tandem sequence for the synthesis of 1,2,3,4-tetrahydro-β-carbolines (THBCs) relying on a ruthenium hydride/Brønsted acid- catalyzed isomerization of allylic amides to N-acyliminium ion intermediates which are trapped by a tethered indolenucleophile. The methodol...... the Suzuki cross-coupling reaction to the isomerization/N-acyliminium cyclization sequence. Finally, diastereo- and enantioselective versions of the title reaction have been examined using substrate control (with dr >15: 1) and asymmetric catalysis (ee up to 57%), respectively...

First spatial separation of a heavy ion isomeric beam with a multiple-reflection time-of-flight mass spectrometer

Science.gov (United States)

Dickel, T.; Plaß, W. R.; Ayet San Andres, S.; Ebert, J.; Geissel, H.; Haettner, E.; Hornung, C.; Miskun, I.; Pietri, S.; Purushothaman, S.; Reiter, M. P.; Rink, A.-K.; Scheidenberger, C.; Weick, H.; Dendooven, P.; Diwisch, M.; Greiner, F.; Heiße, F.; Knöbel, R.; Lippert, W.; Moore, I. D.; Pohjalainen, I.; Prochazka, A.; Ranjan, M.; Takechi, M.; Winfield, J. S.; Xu, X.

2015-05-01

211Po ions in the ground and isomeric states were produced via 238U projectile fragmentation at 1000 MeV/u. The 211Po ions were spatially separated in flight from the primary beam and other reaction products by the fragment separator FRS. The ions were energy-bunched, slowed-down and thermalized in a gas-filled cryogenic stopping cell (CSC). They were then extracted from the CSC and injected into a high-resolution multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). The excitation energy of the isomer and, for the first time, the isomeric-to-ground state ratio were determined from the measured mass spectrum. In the subsequent experimental step, the isomers were spatially separated from the ions in the ground state by an ion deflector and finally collected with a silicon detector for decay spectroscopy. This pioneering experimental result opens up unique perspectives for isomer-resolved studies. With this versatile experimental method new isomers with half-lives longer than a few milliseconds can be discovered and their decay properties can be measured with highest sensitivity and selectivity. These experiments can be extended to studies with isomeric beams in nuclear reactions.

Measurement of excitation functions and analysis of isomeric population in some reactions induced by proton on natural indium at low energy

Science.gov (United States)

Muhammed Shan, P. T.; Musthafa, M. M.; Najmunnisa, T.; Mohamed Aslam, P.; Rajesh, K. K.; Hajara, K.; Surendran, P.; Nair, J. P.; Shanbagh, Anil; Ghugre, S.

2018-06-01

The excitation functions for reaction residues populated via 115In(p , p) 115 mIn, 115In(p , pn) 114 mIn, 115In(p , p 2 n) 113 mIn, 113In(p , p) 113 mIn, 115In(p , nα) 111 mCd, 115In(p , 3 n) 113Sn and 113In(p , n) 113Sn channels were measured over the proton energy range of 8-22 MeV using stacked foil activation technique. Theoretical analysis of the data were performed within the framework of two statistical model codes EMPIRE-3.2 and TALYS-1.8. Isomeric cross section ratio for isomeric pairs m,g 115In, m,g 114In, m,g 113In, 113Sn m,g and m,g 111Cd were determined for the first time. The dependence of isomeric cross section ratio on various factors are analysed.

Synthesis of zeolite-zeolite (mfi-fau) composite catalysts for the isomerization of n-hexane

International Nuclear Information System (INIS)

Ghouri, A.S; Usman, M.R.

2017-01-01

In this research work, the aim is to produce a relatively novel zeolite-zeolite (MFI-FAU) composite catalyst having better potential of catalyzing isomerization of lighter hydrocarbons such as light naphtha, n-pentane, n-hexane, n-heptane and mixture thereof. A series of zeolite-zeolite (MFI-FAU) composite catalysts have been synthesized by incorporating previous practices and techniques. The catalytic performance of as-synthesized zeolite-zeolite (MFI-FAU) composite catalysts have been investigated by isomerizing 95% pure n-hexane in conventional fixed bed flow micro-reactor at temperature 200-240 ºC under atmospheric pressure. In order to explore chemical and physical features of zeolite-zeolite (MFI-FAU) composite catalysts, they are examined and characterized using powder X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectrometry (EDX), N2 adsorption-desorption measurements (BET, BJH, t-plot measurements) and Fourier transform infrared (FTIR) spectroscopy equipped with attenuated total reflectance (ATR) arrangements. (author)

Material Balance And Reaction Kinetics Modeling For Penex Isomerization Process In Daura Refinery

Directory of Open Access Journals (Sweden)

Hamadi Adel Sharif

2017-01-01

Full Text Available Penex Deisohexanizer isomerization of light straight run naphtha is a significant process for petroleum refining and proved to be effective technology to produce gasoline components with a high octane number. Modeling of the chemical kinetic reactions is an important tool because it is a better tool for optimization of the experimental data into parameters used for industrial reactors. The present study deals on the isomerization process in Daura refinery. Material balance calculations were done mathematically on the unit for the kinetics prediction purpose. A kinetic mathematical model was derived for the prediction rate constants K1 and K2 and activation energy Ea at operating temperatures range 120-180°C. According to the model, the results show that with increasing of temperature leads to increased K1 directly, where the K2 values proportional inversely. The activation energy results show that Ea1(nC6

Isotopic study on mechanism for skeletal isomerization of n-butane over solid acids

International Nuclear Information System (INIS)

Suzuki, Tetsuo; Okuhara, Toshio

2000-01-01

Reaction mechanism for skeletal isomerization of n-butane over typical strong solid acids were investigated by using 1,4- 13 C 2 -n-butane. We used FI MASS for the analysis of 13 C distribution to get the parent pattern. 13 C-distribution of isobutane formed at 423 K over SO 3 2- /ZrO 2 (SZ) and Cs 2.5 H 0.5 PW 12 O 40 (Cs2.5) were close to binomial distributions, indicating that the isomerization proceeded mainly via a bimolecular mechanism on these catalysts. On the other hand, at 523 K over Cs2.5, the isotopic distribution pattern in isobutane was quite different from the binomial one; the fraction of 13 C 2 -isobutane was much greater than the binomial distribution. This result demonstrates that an intramolecular (monomolecular) rearrangement became significant at 523 K over Cs2.5. The contribution of monomolecular pathway was higher on Cs2.5 than on SZ. We presumed that the contribution of mechanism is related to the acidic property and the dehydrogenation ability of the catalyst. (S.Y.)

Supercharging by m-NBA Improves ETD-Based Quantification of Hydroxyl Radical Protein Footprinting

Science.gov (United States)

Li, Xiaoyan; Li, Zixuan; Xie, Boer; Sharp, Joshua S.

2015-08-01

Hydroxyl radical protein footprinting (HRPF) is an MS-based technique for analyzing protein structure based on measuring the oxidation of amino acid side chains by hydroxyl radicals diffusing in solution. Spatial resolution of HRPF is limited by the smallest portion of the protein for which oxidation amounts can be accurately quantitated. Previous work has shown electron transfer dissociation (ETD) to be the most reliable method for quantifying the amount of oxidation of each amino acid side chain in a mixture of peptide oxidation isomers, but efficient ETD requires high peptide charge states, which limits its applicability for HRPF. Supercharging reagents have been used to enhance peptide charge state for ETD analysis, but previous work has shown supercharging reagents to enhance charge state differently for different peptides sequences; it is currently unknown if different oxidation isomers will experience different charge enhancement effects. Here, we report the effect of m-nitrobenzyl alcohol ( m-NBA) on the ETD-based quantification of peptide oxidation. The addition of m-NBA to both a defined mixture of synthetic isomeric oxidized peptides and Robo-1 protein subjected to HRPF increased the abundance of higher charge state ions, improving our ability to perform efficient ETD of the mixture. No differences in the reported quantitation by ETD were noted in the presence or absence of m-NBA, indicating that all oxidation isomers were charge-enhanced to a similar extent. These results indicate the utility of m-NBA for residue-level quantification of peptide oxidation in HRPF and other applications.

Retrieving molecular structural information and tracking HNC/HCN isomerization process with high harmonic generation by ultrashort laser pulses

International Nuclear Information System (INIS)

Nguyen Ngoc Ty; Le Van Hoang; Vu Ngoc Tuoc; Le Anh Thu

2010-01-01

We investigate the possibility of applying the iterative method, suggested in our previous work, for HCN molecule and its HNC isomer. We found that the high-order harmonic generation (HHG) spectra are quite insensitive to the change of H-C (or H-N) bond length so that only the inter-nuclear C-N distance can be retrieved from the high-order harmonic spectra using ultrashort intense lasers. Furthermore, by analyzing the HHG spectra emitted by HCN during the chemical reaction path of isomerization we identify the intensity peaks nearby the stable, metastable and transition states. this finding can be useful for tracking the HNC/HNC isomerization process. (author)

A novel base-induced isomerization gives access to unprecedented (E)-exo-glycals.

Science.gov (United States)

Eppe, Guillaume; Dumitrescu, Lidia; Pierrot, Olivier; Li, Tianlei; Pan, Weidong; Vincent, Stéphane P

2013-08-26

Bump the base: This study reports the discovery of the base-induced Z-to-E isomerization of exo-glycals bearing an electron-withdrawing group (EWG). The scope of this novel transformation regarding the carbohydrate unit is also discussed. After elucidating the mechanism, preparation of novel (E)-exo- glycals was performed (TBS = tert-butyldimethylsilyl). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Palladium Hydride Promoted Stereoselective Isomerization of Unactivated Di(exo)methylenes to Endocyclic Dienes

OpenAIRE

Jung, Michael E.; Lee, Gloria S.; Pham, Hung V.; Houk, K. N.

2014-01-01

The exomethylenes of 2,6-disubstituted bicyclo[3.3.1]nonan-9-ones 2 are readily isomerized over a palladium catalyst under an atmosphere of hydrogen to predominantly form the isomer 3 with C 2 symmetry with very little formation of the analogous product with C s symmetry. A hydrogen source is essential to effect the rearrangement.

Magnetic dipole moments of High-K isomeric states in Hf isotopes

CERN Multimedia

Walters, W; Nishimura, K; Bingham, C R

2007-01-01

It is proposed to make precision measurements of the magnetic moments of 5 multi-quasi-particle K-isomers in Hf nuclei by the Nuclear Magnetic Resonance of Oriented Nuclei (NMR/ON) technique using the NICOLE on-line nuclear orientation facility and exploiting the unique HfF$_{3}$ beams recently available at ISOLDE. Results will be used to extract single-particle and collective g-factors of the isomeric states and their excitations and to shed new light on their structure.

Conversion of alkyl radicals to allyl radicals in irradiated single crystal mats of polyethylene

International Nuclear Information System (INIS)

Fujimura, T.; Hayakawa, N.; Kuriyama, I.

1978-01-01

The decay of alkyl radicals, the conversion of alkyl radicals to allyl radicals and the trapping of allyl radicals in irradiated single crystal mats of polyethylene have been studied by electron spin resonance (e.s.r.). It has been suggested that in the crystal core alkyl radicals react with trans-vinylene double bonds and are converted into trans-vinylene allyl radicals; at the crystal surface, alkyl radicals react with vinyl end groups and are converted into allyl radicals with vinyl end groups. The decay of radical pairs and the formation of trans-vinylene double bonds are discussed. (author)

Isomeric N-Annulated Perylene Diimide Dimers for Organic Solar Cells.

Science.gov (United States)

Ma, Zetong; Fu, Huiting; Meng, Dong; Jiang, Wei; Sun, Yanming; Wang, Zhaohui

2018-04-16

Two isomeric N-annulated perylene diimide dimers, namely, p-BDNP and m-BDNP were designed and synthesized via geometric tuning. The distinct molecular geometry and packing arrangements of isomers with almost identical optical and electrochemical properties rendered us an in-depth understanding of the molecular structure-aggregation state-photovoltaic performance relationship. Blended with the commercially available donor PCE-10, p-BDNP and m-BDNP showed distinct differences in photovoltaic performance with power conversion efficiencies (PCEs) of 5.01 % and 4.15 %, respectively. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

g-factor of the 7- isomeric state in 128Ba

International Nuclear Information System (INIS)

Kaur, J.; Bansal, N.; Bhati, A.K.; Sharma, V.R.; Kumar, H.; Kumar, R.; Bhowmik, R.K.; Kumar, V.

2014-01-01

The time differential perturbed angular distribution technique (TDPAD) has been used to measure the g-factor of the 2396 keV, 7 - isomeric state in 128 Ba. The measured value of g(7 - ) is 1.21 ± 0.01. This value is about 80% higher than the value for the expected configuration of the state and also different in sign. This clearly shows that the configuration of the state does not correspond to the pure two quasineutron configuration that was assigned to it through previous results of in-beam γ-ray spectroscopy

Guest Editorial: Processes of Radicalization and De-Radicalization

Directory of Open Access Journals (Sweden)

Donatella Della Porta

2012-05-01

Full Text Available The study of radicalization and de-radicalization, understood as processes leading towards the increased or decreased use of political violence, is central to the question of how political violence emerges, how it can be prevented, and how it can be contained. The focus section of this issue of the International Journal of Conflict and Violence addresses radicalization and de-radicalization, seeking to develop a more comprehensive understanding of the processes, dynamics, and mechanisms involved and taking an interdisciplinary approach to overcome the fragmentation into separate disciplines and focus areas. Contributions by Pénélope Larzillière, Felix Heiduk, Bill Kissane, Hank Johnston, Christian Davenport and Cyanne Loyle, Veronique Dudouet, and Lasse Lindekilde address repressive settings, legitimacy, institutional aspects, organizational outcomes, and dynamics in Europe, Asia, Africa, and North and South America.

Metal-catalyzed living radical polymerization and radical polyaddition for precision polymer synthesis

Energy Technology Data Exchange (ETDEWEB)

Mizutani, M; Satoh, K [Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Kamigaito, M, E-mail: kamigait@apchem.nagoya-u.ac.j

2009-08-01

The metal-catalyzed radical addition reaction can be evolved into two different polymerization mechanisms, i.e.; chain- and step-growth polymerizations, while both the polymerizations are based on the same metal-catalyzed radical formation reaction. The former is a widely employed metal-catalyzed living radical polymerization or atom transfer radical polymerization of common vinyl monomers, and the latter is a novel metal-catalyzed radical polyaddition of designed monomer with an unconjugated C=C double bond and a reactive C-Cl bond in one molecule. The simultaneous ruthenium-catalyzed living radical polymerization of methyl acrylate and radical polyaddition of 3-butenyl 2-chloropropionate was achieved with Ru(Cp*)Cl(PPh{sub 3}){sub 2} to afford the controlled polymers, in which the homopolymer segments with the controlled chain length were connected by the ester linkage.

The introduction of hydrogen bond and hydrophobicity effects into the rotational isomeric states model for conformational analysis of unfolded peptides

Science.gov (United States)

Engin, Ozge; Sayar, Mehmet; Erman, Burak

2009-03-01

Relative contributions of local and non-local interactions to the unfolded conformations of peptides are examined by using the rotational isomeric states model which is a Markov model based on pairwise interactions of torsion angles. The isomeric states of a residue are well described by the Ramachandran map of backbone torsion angles. The statistical weight matrices for the states are determined by molecular dynamics simulations applied to monopeptides and dipeptides. Conformational properties of tripeptides formed from combinations of alanine, valine, tyrosine and tryptophan are investigated based on the Markov model. Comparison with molecular dynamics simulation results on these tripeptides identifies the sequence-distant long-range interactions that are missing in the Markov model. These are essentially the hydrogen bond and hydrophobic interactions that are obtained between the first and the third residue of a tripeptide. A systematic correction is proposed for incorporating these long-range interactions into the rotational isomeric states model. Preliminary results suggest that the Markov assumption can be improved significantly by renormalizing the statistical weight matrices to include the effects of the long-range correlations.

The introduction of hydrogen bond and hydrophobicity effects into the rotational isomeric states model for conformational analysis of unfolded peptides

International Nuclear Information System (INIS)

Engin, Ozge; Sayar, Mehmet; Erman, Burak

2009-01-01

Relative contributions of local and non-local interactions to the unfolded conformations of peptides are examined by using the rotational isomeric states model which is a Markov model based on pairwise interactions of torsion angles. The isomeric states of a residue are well described by the Ramachandran map of backbone torsion angles. The statistical weight matrices for the states are determined by molecular dynamics simulations applied to monopeptides and dipeptides. Conformational properties of tripeptides formed from combinations of alanine, valine, tyrosine and tryptophan are investigated based on the Markov model. Comparison with molecular dynamics simulation results on these tripeptides identifies the sequence-distant long-range interactions that are missing in the Markov model. These are essentially the hydrogen bond and hydrophobic interactions that are obtained between the first and the third residue of a tripeptide. A systematic correction is proposed for incorporating these long-range interactions into the rotational isomeric states model. Preliminary results suggest that the Markov assumption can be improved significantly by renormalizing the statistical weight matrices to include the effects of the long-range correlations

Differentiation of isomeric 2-aryldimethyltetrahydro-5-quinolinones by electron ionization and electrospray ionization mass spectrometry.

Science.gov (United States)

Kumar, Ch Dinesh; Chary, V Naresh; Dinesh, A; Reddy, P S; Srinivas, K; Gayatri, G; Sastry, G N; Prabhakar, S

2011-10-15

A series of isomeric 2-aryl-6,6-dimethyltetrahydro-5-quinolinones (set I) and 2-aryl-7,7-dimethyltetrahydro-5-quinolinones (set II) were studied under positive ion electron ionization (EI) and electrospray ionization (ESI) techniques. Under EI conditions, the molecular ions were found to be less stable in set I isomers, and they resulted in abundant fragment ions, i.e., [M-CH(3)](+), [M-CO](+.), [M-HCO](+), [M-(CH(3),CO)](+), and [M-(CH(3),CH(2)O)](+), when compared with set II isomers. In addition, the set I isomers showed specific fragment ions corresponding to [M-OH](+) and [M-OCH(3)](+). The retro-Diels-Alder (RDA) product ion was always higher in set II isomers. The ESI mass spectra produced [M + H](+) ions, and their decomposition showed favorable loss of CH(3) radical, CH(4) and C(2)H(6) molecules in set I isomers. The set II isomers, however, showed predominant RDA product ions, and specific loss of H(2)O. The selectivity in EI and ESI was attributed to the instability of set I isomers by the presence of a gem-dimethyl group at the α-position, and it was supported by the data from model compounds without a gem-dimethyl group. Density functional theory (DFT) calculations successfully corroborated the fragmentation pathways for diagnostic ions. This study revealed the effect of a gem-dimethyl group located at the α-position to the carbonyl having aromatic/unsaturated carbon on the other side of the carbonyl group. Copyright © 2011 John Wiley & Sons, Ltd.

Photoionization and trans-to-cis isomerization of β-cyclodextrin-encapsulated azobenzene induced by two-color two-laser-pulse excitation.

Science.gov (United States)

Takeshita, Tatsuya; Hara, Michihiro

2018-03-15

Azobenzene (1) and the complex resulting from the incorporation of 1 with cyclodextrin (1/CD) are attractive for light-driven applications such as micromachining and chemical biology tools. The highly sensitive photoresponse of 1 is crucial for light-driven applications containing both 1 and 1/CD to reach their full potential. In this study, we investigated the photoionization and trans-to-cis isomerization of 1/CD induced by one- and two-color two-laser pulse excitation. Photoionization of 1/CD, which was induced by stepwise two-photon absorption, was observed using laser pulse excitation at 266nm. Additionally, simultaneous irradiation with 266 and 532nm laser pulses increased the trans-to-cis isomerization yield (Υ t→c ) by 27%. It was concluded that the increase in Υ t→c was caused by the occurrence of trans-to-cis isomerization in the higher-energy singlet state (S n ), which was reached by S 1 →S n transition induced by laser pulse excitation at 532nm. The results of this study are potentially applicable in light-driven applications such as micromachining and chemical biology tools. Copyright © 2018 Elsevier B.V. All rights reserved.

Macrocyclic effects upon isomeric Cu M and M Cu cores. Formation ...

Indian Academy of Sciences (India)

Administrator

from the iminic site to the aminic site in the synthesis of 10 is explained by ... Our previous studies suggest that isomeric MIICuII ... Calcd. for C24H27Br2ClCuN4NiO8: C 35⋅28; H 3⋅33; N 6⋅86; Cu 7⋅78; Ni .... Electronic absorption spectra in .... 3. 1497(1). 1452. ⋅3(5). 2992(1). 1860(2). 3206(1). Z. 2. 2. 4. 2. 4. D calcd. /g.

Communication: An accurate calculation of the S1 C2H2 cis-trans isomerization barrier height

International Nuclear Information System (INIS)

Baraban, Joshua H.; Matthews, Devin A.; Stanton, John F.

2016-01-01

A high level ab initio calculation of the cis-trans isomerization barrier height in the first excited singlet electronic state of acetylene is found to agree very well with a recent experimental determination.

Isomerization of 2-butene-1,4-diol in aqueous solutions catalyzed by palladium(II) complexes

Energy Technology Data Exchange (ETDEWEB)

Kalabin, S.M.; Novikov, N.A.; Belov, A.P.

1989-02-01

The authors studied the isomerization of 2-butene-1,4-diol into 3-butene-1,2-diol at 18-25/degree/C. The concentrations of the diol and PdCl/sub 2/ were (1.0-5.0) /times/ 10/sup /minus/2/ mole/liter at 5-10-fold excess amounts of HCl and NaCl. These additives were used because of their inhibiting action on the oxidation of olefinic compounds. 3-Butene-1,2-diol was identified by /sup 1/H NMR method directly in the reaction solutions in which the reaction solutions in which the reactions in D/sub 2/O were carried out. It was found that palladium(II) complexes catalyze the isomerization of 2-butene-1,4-diol into 3-butene-1,2-diol. A mechanism is proposed for the reaction, which includes the intermediate formation of /eta//sup 3/-allyl complex of palladium with a coordinated hydroxyl group.

Dipole-resonance assisted isomerization in the electronic ground state using few-cycle infrared pulses.

Science.gov (United States)

Skocek, Oliver; Uiberacker, Christoph; Jakubetz, Werner

2011-06-30

A computational investigation of HCN → HNC isomerization in the electronic ground state by one- and few-cycle infrared pulses is presented. Starting from a vibrationally pre-excited reagent state, isomerization yields of more than 50% are obtained using single one- to five-cycle pulses. The principal mechanism includes two steps of population transfer by dipole-resonance (DR), and hence, the success of the method is closely linked to the polarity of the system and, in particular, the stepwise change of the dipole moment from reactant to transition state and on to products. The yield drops massively if the diagonal dipole matrix elements are artificially set to zero. In detail, the mechanism includes DR-induced preparation of a delocalized vibrational wavepacket, which traverses the barrier region and is finally trapped in the product well by DR-dominated de-excitation. The excitation and de-excitation steps are triggered by pulse lobes of opposite field direction. As the number of optical cycles is increased, the leading field lobes prepare a vibrational superposition state by off-resonant ladder climbing, which is then subjected to the three steps of the principal isomerization mechanism. DR excitation is more efficient from a preformed vibrational wavepacket than from a molecular eigenstate. The entire process can be loosely described as Tannor-Kosloff-Rice type transfer mechanism on a single potential surface effected by a single pulse, individual field lobes assuming the roles of pump- and dump-pulses. Pre-excitation to a transient wavepacket can be enhanced by applying a separate, comparatively weak few-cycle prepulse, in which the prepulse prepares a vibrational wavepacket. The two-pulse setup corresponds to a double Tannor-Kosloff-Rice control scheme on a single potential surface.

Schiff base switch II precedes the retinal thermal isomerization in the photocycle of bacteriorhodopsin.

Directory of Open Access Journals (Sweden)

Ting Wang

Full Text Available In bacteriorhodopsin, the order of molecular events that control the cytoplasmic or extracellular accessibility of the Schiff bases (SB are not well understood. We use molecular dynamics simulations to study a process involved in the second accessibility switch of SB that occurs after its reprotonation in the N intermediate of the photocycle. We find that once protonated, the SB C15 = NZ bond switches from a cytoplasmic facing (13-cis, 15-anti configuration to an extracellular facing (13-cis, 15-syn configuration on the pico to nanosecond timescale. Significantly, rotation about the retinal's C13 = C14 double bond is not observed. The dynamics of the isomeric state transitions of the protonated SB are strongly influenced by the surrounding charges and dielectric effects of other buried ions, particularly D96 and D212. Our simulations indicate that the thermal isomerization of retinal from 13-cis back to all-trans likely occurs independently from and after the SB C15 = NZ rotation in the N-to-O transition.

Thermodynamic calculation of simultaneous reactions of n-butane isomerization and isobutane alkylation with ethylene

Energy Technology Data Exchange (ETDEWEB)

Batyrshin, N.N.; Beresneva, L.D.; Sidorov, V.A.

1981-08-01

Industrial production of ethylene alkylate has gained further development in connection with worldwide ecological problems and the planned changeover of automobile transport to unleaded gasolines, but the scale of production is still substantially less than that of sulfuric acid or hydrogen fluoride alkylates. This is due both to the instability of market prices for ethylene and the shortage of isobutane - a raw material for these large-tonnage production processes and for the synthetic rubber industry. The latter difficulty can be overcome by combining processes of isomerization of n-butane and alkylation of the resultant isobutane with ethylene in a single reaction unit. The possibility of combining these reactions using AlCl/sub 3/-based catalysts has been pointed out previously but in the literature there are no theoretical developments of technology or thermodynamic substantiation of a combined process. We have made a thermodynamic calculation of the consecutive (series-parallel) reactions of isomerization and alkylation with the goal of determining suitable technological conditions for carrying them out simultaneously and establishing the expected equilibrium yields of target products and the compositions of the reaction mixture.

Model-Based Analysis and Efficient Operation of a Glucose Isomerization Reactor Plant

DEFF Research Database (Denmark)

Papadakis, Emmanouil; Madsen, Ulrich; Pedersen, Sven

2015-01-01

efficiency. The objective of this study is the application of the developed framework on an industrial case study of a glucose isomerization (GI) reactor plant that is part of a corn refinery, with the objective to improve the productivity of the process. Therefore, a multi-scale reactor model...... is developedfor use as a building block for the GI reactor plant simulation. An optimal operation strategy is proposed on the basis of the simulation results...

Thermally and vibrationally induced conformational isomerizations, infrared spectra, and photochemistry of gallic acid in low-temperature matrices

Energy Technology Data Exchange (ETDEWEB)

Justino, Licínia L. G., E-mail: liciniaj@ci.uc.pt; Reva, Igor; Fausto, Rui [CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra (Portugal)

2016-07-07

Near-infrared (near-IR) narrowband selective vibrational excitation and annealing of gallic acid (3,4,5-trihydroxybenzoic acid) isolated in cryogenic matrices were used to induce interconversions between its most stable conformers. The isomerizations were probed by infrared spectroscopy. An extensive set of quantum chemical calculations, carried out at the DFT(B3LYP)/6-311++G(d,p) level of approximation, was used to undertake a detailed analysis of the ground state potential energy surface of the molecule. This investigation of the molecule conformational space allowed extracting mechanistic insights into the observed annealing- or near-IR-induced isomerization processes. The infrared spectra of the two most stable conformers of gallic acid in N{sub 2}, Xe, and Ar matrices were fully assigned. Finally, the UV-induced photochemistry of the matrix isolated compound was investigated.

Thermally and vibrationally induced conformational isomerizations, infrared spectra, and photochemistry of gallic acid in low-temperature matrices

Science.gov (United States)

Justino, Licínia L. G.; Reva, Igor; Fausto, Rui

2016-07-01

Near-infrared (near-IR) narrowband selective vibrational excitation and annealing of gallic acid (3,4,5-trihydroxybenzoic acid) isolated in cryogenic matrices were used to induce interconversions between its most stable conformers. The isomerizations were probed by infrared spectroscopy. An extensive set of quantum chemical calculations, carried out at the DFT(B3LYP)/6-311++G(d,p) level of approximation, was used to undertake a detailed analysis of the ground state potential energy surface of the molecule. This investigation of the molecule conformational space allowed extracting mechanistic insights into the observed annealing- or near-IR-induced isomerization processes. The infrared spectra of the two most stable conformers of gallic acid in N2, Xe, and Ar matrices were fully assigned. Finally, the UV-induced photochemistry of the matrix isolated compound was investigated.

Thermally and vibrationally induced conformational isomerizations, infrared spectra, and photochemistry of gallic acid in low-temperature matrices

International Nuclear Information System (INIS)

Justino, Licínia L. G.; Reva, Igor; Fausto, Rui

2016-01-01

Near-infrared (near-IR) narrowband selective vibrational excitation and annealing of gallic acid (3,4,5-trihydroxybenzoic acid) isolated in cryogenic matrices were used to induce interconversions between its most stable conformers. The isomerizations were probed by infrared spectroscopy. An extensive set of quantum chemical calculations, carried out at the DFT(B3LYP)/6-311++G(d,p) level of approximation, was used to undertake a detailed analysis of the ground state potential energy surface of the molecule. This investigation of the molecule conformational space allowed extracting mechanistic insights into the observed annealing- or near-IR-induced isomerization processes. The infrared spectra of the two most stable conformers of gallic acid in N 2 , Xe, and Ar matrices were fully assigned. Finally, the UV-induced photochemistry of the matrix isolated compound was investigated.

An investigation of the olive phenols activity as a natural medicine

Directory of Open Access Journals (Sweden)

Faik Gökalp

2018-04-01

Full Text Available The natural antioxidants of olive oil have phenolic structure and their activities are related to the formation of stable derivatives. In this study, the single components of the phenolic fraction of olive oil (1,4-hydroquinone, Semiquinone and 1,4-benzoquinone have been studied as theoretical by using DFT (Density functional Theory. The behaviors of phenolic compounds of olive against to the alkyl peroxy radicals were investigated. Our data show that 1,4-benzoquinone is the best electron transfer agent in primary metabolic processes to human life. The frontier orbital gap, namely HOMO (highest occupied molecular orbital–LUMO (lowest unoccupied molecular orbital gap is the smallest for 1,4-benzoquinone. Hence, it is more stable than the others in blood. The natural phenolic compound's mechanism of many plants can be explained by using DFT method without consuming time and money. In this study, we have indicated the behaviors of natural antioxidants of olive oil's single components phenolic structure in blood phase. Keywords: 1,4-Hydroquinone, Semiquinone, 1,4-Benzoquinone, Blood, DFT

Electrochemical Behavior of Quinoxalin-2-one Derivatives at Mercury Electrodes and Its Analytical Use

Directory of Open Access Journals (Sweden)

Milan Zimpl

2012-01-01

Full Text Available Derivatives of quinoxalin-2-one are interesting compounds with potential pharmacological activity. From this point of view, understanding of their electrochemical behavior is of great importance. In the present paper, a mechanism of electrochemical reduction of quinoxalin-2-one derivatives at mercury dropping electrode was proposed. Pyrazine ring was found to be the main electroactive center undergoing a pH-dependent two-electron reduction process. The molecule protonization of nitrogen in the position 4 precedes the electron acceptance forming a semiquinone radical intermediate which is relatively stable in acidic solutions. Its further reduction is manifested by separated current signal. A positive mesomeric effect of the nonprotonized amino group in the position 7 of the derivative III accelerates the semiquinone reduction yielding a single current wave. The suggested reaction mechanism was verified by means of direct current polarography, differential pulse, cyclic and elimination voltammetry, and coulometry with subsequent GC/MS analysis. The understanding of the mechanism was applied in developing of analytical method for the determination of the studied compounds.

Electrochemical behavior of quinoxalin-2-one derivatives at mercury electrodes and its analytical use.

Science.gov (United States)

Zimpl, Milan; Skopalova, Jana; Jirovsky, David; Bartak, Petr; Navratil, Tomas; Sedonikova, Jana; Kotoucek, Milan

2012-01-01

Derivatives of quinoxalin-2-one are interesting compounds with potential pharmacological activity. From this point of view, understanding of their electrochemical behavior is of great importance. In the present paper, a mechanism of electrochemical reduction of quinoxalin-2-one derivatives at mercury dropping electrode was proposed. Pyrazine ring was found to be the main electroactive center undergoing a pH-dependent two-electron reduction process. The molecule protonization of nitrogen in the position 4 precedes the electron acceptance forming a semiquinone radical intermediate which is relatively stable in acidic solutions. Its further reduction is manifested by separated current signal. A positive mesomeric effect of the nonprotonized amino group in the position 7 of the derivative III accelerates the semiquinone reduction yielding a single current wave. The suggested reaction mechanism was verified by means of direct current polarography, differential pulse, cyclic and elimination voltammetry, and coulometry with subsequent GC/MS analysis. The understanding of the mechanism was applied in developing of analytical method for the determination of the studied compounds.

Modelling of tracer-kinetic results using xylene isomerization as an example

International Nuclear Information System (INIS)

Bauer, F.J.; Dermietzel, J.; Roesseler, M.; Koch, H.

1976-01-01

The analysis of results from differential or/and integral reactor experiments often admits the interpretation of a chemical reaction in several ways. In addition, the use of mathematical methods for the model selection and planning of experiments is rendered more difficult by great confidence intervals of the ascertained model parameters. The application of radioactively labelled molecules results in improving the knowledge of reaction mechanisms as well as the assessment of parameters obtained. This is shown on the basis of modelling the isomerization of xylene. (author)

Radical Change by Entrepreneurial Design

National Research Council Canada - National Science Library

Roberts, Nancy C

1998-01-01

.... How radical change in public policy has occurred in the past is then documented. We find examples of radical change by chance, radical change by consensus, radical change by learning, and radical change by entrepreneurial design...

The isomerization of allylrhodium intermediates in the rhodium-catalyzed nucleophilic allylation of cyclic imines.

Science.gov (United States)

Hepburn, Hamish B; Lam, Hon Wai

2014-10-20

Allylrhodium species generated from potassium allyltrifluoroborates can undergo isomerization by 1,4-rhodium(I) migration to give more complex isomers, which then react with cyclic imines to provide products with up to three new stereochemical elements. High enantioselectivities are obtained using chiral diene-rhodium complexes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Outcomes following the Kawashima procedure for single-ventricle palliation in left atrial isomerism.

Science.gov (United States)

Vollebregt, Anne; Pushparajah, Kuberan; Rizvi, Maleeha; Hoschtitzky, Andreas; Anderson, David; Austin, Conal; Tibby, Shane M; Simpson, John

2012-03-01

Patients with left atrial isomerism and interrupted inferior vena cava palliated with a superior cavopulmonary connection or Kawashima procedure (KP) have a high incidence of developing pulmonary arteriovenous malformations. The necessity for hepatic vein redirection (HVR) and its timing remains a controversy. We aimed to assess the clinical outcome of patients with left atrial isomerism following a KP. The main end points were death, requirement for HVR and the impact of HVR on oxygen saturation. Retrospective review of 21 patients with a diagnosis of left atrial isomerism, interruption of the inferior vena cava and single-ventricle physiology managed with a KP at a single centre between January 1990 and March 2010. Twenty-one patients had a KP, with 12 subsequently undergoing HVR. There was relatively a constant monthly decrement in the proportion of patients who were free from death or HVR up until 60 months following the KP, with a dramatic increase in the hazard after this time. The Cox proportional hazards regression model demonstrated a reduced early risk for HVR or death in patients who underwent pulmonary artery banding versus arterial shunt as the primary procedure (hazard ratio: 0.10; P = 0.01), and an increased risk with bilateral superior vena cavas (SVCs) (hazard ratio: 3.4; P = 0.04) and age at KP (hazard ratio: 1.02 per month increase in age at KP; P = 0.02). HVR mortality was relatively high with 3 of 12 patients dying in the early postoperative period with profound cyanosis. The timing of HVR after the KP did not influence the postoperative rate of increase in oxygen saturation. These findings confirm that the majority of patients who undergo a KP will require HVR. Patients who are older at the time of the KP or having an initial arterial shunt or bilateral SVCs are at higher risk of HVR or death. The relatively high mortality at HVR was characterized by severe postoperative cyanosis.

Mechanistic features of isomerizing alkoxycarbonylation of methyl oleate

KAUST Repository

Roesle, Philipp

2012-10-24

The weakly coordinated triflate complex [(P̂P)Pd(OTf)] +(OTf)- (1) (P̂P = 1,3-bis(di-tert- butylphosphino)propane) is a suitable reactive precursor for mechanistic studies of the isomerizing alkoxcarbonylation of methyl oleate. Addition of CH 3OH or CD3OD to 1 forms the hydride species [(P ̂P)PdH(CH3OH)]+(OTf)- (2-CH3OH) or the deuteride [(P̂P)PdD(CD 3OD)]+(OTf)- (2D-CD3OD), respectively. Further reaction with pyridine cleanly affords the stable and isolable hydride [(P̂P)PdH(pyridine)]+(OTf) - (2-pyr). This complex yields the hydride fragment free of methanol by abstraction of pyridine with BF3OEt2, and thus provides an entry to mechanistic observations including intermediates reactive toward methanol. Exposure of methyl oleate (100 equiv) to 2D-CD 3OD resulted in rapid isomerization to the thermodynamic isomer distribution, 94.3% of internal olefins, 5.5% of α,β-unsaturated ester and <0.2% of terminal olefin. Reaction of 2-pyr/BF3OEt 2 with a stoichiometric amount of 1-13C-labeled 1-octene at -80 °C yields a 50:50 mixture of the linear alkyls [(P ̂P)Pd13CH2(CH2) 6CH3]+ and [(P̂P)PdCH 2(CH2)6 13CH3] + (4a and 4b). Further reaction with 13CO yields the linear acyls [(P̂P)Pd13C(=O)12/13CH 2(CH2)6 12/13CH3(L)] + (5-L; L = solvent or 13CO). Reaction of 2-pyr/BF 3·OEt2 with a stoichiometric amount of methyl oleate at -80 °C also resulted in fast isomerization to form a linear alkyl species [(P̂P)PdCH2(CH2) 16C(=O)OCH3]+ (6) and a branched alkyl stabilized by coordination of the ester carbonyl group as a four membered chelate [(P̂P)PdCH{(CH2)15CH 3}C(=O)OCH3]+ (7). Addition of carbon monoxide (2.5 equiv) at -80 °C resulted in insertion to form the linear acyl carbonyl [(P̂P)PdC(=O)(CH2)17C(=O)OCH 3(CO)]+ (8-CO) and the five-membered chelate [(P ̂P)PdC(=O)CH{(CH2)15CH3}C(=O) OCH3]+ (9). Exposure of 8-CO and 9 to 13CO at -50 °C results in gradual incorporation of the 13C label. Reversibility of 7 + CO ⇄ 9 is also evidenced by ΔG = -2.9 kcal mol-1 and

The games radicals play : special issue on free radicals and radical ions

OpenAIRE

Walton, J.C.; Williams, F.

2015-01-01

Chemistry and Physics have aptly been described as “most excellent children of Intellect and Art” [1]. Both these “children” engage with many playthings, and molecules rank as one of their first favorites, especially radicals, which are amongst the most lively and exciting. Checking out radicals dancing to the music of entropy round their potential energy ballrooms is surely both entertaining and enlightening. Radicals’ old favorite convolutions are noteworthy, but the new styles, modes and a...

Isomeric States in the Second and Third Well of the Potential and Long-Lived Superheavy Element

International Nuclear Information System (INIS)

Marinov, A.; Gelberg, S.; Kolb, D.

1999-01-01

Recently, in a study of the 16 O + 197 Au and 28 Si + 181 Ta reactions near and below the Coulomb barrier, long-lived high spin isomeric states have been found by us in the second and third well of the potential-energy surfaces. Such isomeric states have very unusual physical properties. In addition to their very long lifetimes, much longer than of their corresponding ground states, they have very unusual decay properties. They may decay by 5 to 7 orders of magnitude enhanced alpha particles, in transitions from the second or third well of the potential in the parent nuclei to the respective well in the daughters, or by very retarded alpha particles, in transitions from the second well in the parent nucleus to normal states in the daughter, or from the third well in the parent to the second well in the daughter. They also may decay by long-lived proton activities, in transitions from the second well in the parent nucleus to the normal states in the daughter. Experimental evidences for all these new phenomena will be presented in the conference. The existence of long-lived isomeric states in the second and third well of the potential is very important when the production of superheavy elements is considered. Because of the very much reduced extra-push energy needed for their production, they may be produced much easier than the normal states, in reactions between very heavy nuclei. In particular, the discovery of the long-lived superheavy element with Z = 112 can consistently be understood

Time resolved resonance Raman spectra of anilino radical and aniline radical cation

International Nuclear Information System (INIS)

Tripathi, G.N.R.; Schuler, R.H.

1987-01-01

We report, in this paper, submicrosecond time resolved resonance Raman spectra of anilino radical and its radical cation as observed in pulse radiolytic studies of the oxidation of aniline in aqueous solution. By excitation in resonance with the broad and weak electronic transition of anilino radical at 400 nm (ε--1250 M -1 cm -1 ) we have observed, for the first time, the vibrational features of this radical. The Wilson ν 8 /sub a/ ring stretching mode at 1560 cm -1 is most strongly resonance enhanced. The ν 7 /sub a/ CN stretching band at 1505 cm -1 , which is shifted to higher frequency by 231 cm -1 with respect to aniline, is also prominent. The frequency of this latter mode indicates that the CN bond in the radical has considerable double bond character. The Raman spectrum of aniline radical cation, excited in resonance with the --425 nm electronic absorption (ε--4000 M -1 cm -1 ), shows features which are similar to phenoxyl radical. Most of the observed frequencies of this radical in solution are in good agreement with vibrational energies determined by recent laser photoelectron spectroscopic studies in the vapor phase. The bands most strongly enhanced in the resonance Raman spectrum are, however, weak in the photoelectron spectrum. While the vibrational frequencies observed for anilino radical and its isoelectronic cation are quite similar, the resonance enhancement patterns are very different. In particular the ν 14 b 2 mode of anilino radical observed at 1324 cm -1 is highly resonance enhanced because of strong vibronic coupling between the 400 nm 2 A 2 -- 2 B 1 and the higher 2 B 1 -- 2 B 1 electronic transitions

Nuclear isomerism in fission fragments produced by the spontaneous fission of {sup 252}Cf; Isomerisme nucleaire dans les fragments de fission produits dans la fission spontanee du {sup 252}Cf

Energy Technology Data Exchange (ETDEWEB)

Gautherin, C

1997-09-01

This thesis is devoted to the study of the nuclear structure of neutron-rich nuclei, via the search of isomeric nuclear states. Neutron-rich nuclei were produced in the spontaneous fission of {sup 252}Cf. The experimental study of isomeric states in these nuclei was performed with the {gamma}-array EUROGAM II, coupled to an additional and original fission fragment detector composed by photovoltaic cells, SAPhIR. The photovoltaic cells are well adapted to detect low energy heavy ions and have good energy and time resolutions to obtain a good fission fragment detection. This experiment led to the discovery of new isomeric states in {sup 135}Xe, {sup 104}Mo, {sup 146,147,148}Ce and {sup 152,154,156}Nd, with lifetimes between 60 ns and 2 {mu}s. Level schemes of these nuclei have been completed. An interpretation of the isomeric states in the nuclei {sup 154,156}Nd and {sup 156,158}Sm was performed by Hartree-Fock-Bogolyubov calculations using the DIS Gogny force with two quasi-particles excitations. The confrontation with the experimental results led to an interpretation of these isomeric states as K-isomers. (author)

Cascade olefin isomerization/intramolecular Diels-Alder reaction catalyzed by N-heterocyclic carbenes.

Science.gov (United States)

Kowalczyk, Marcin; Lupton, David W

2014-05-19

The addition of an N-heterocyclic carbene to the carbonyl group of an α,β,γ,δ-unsaturated enol ester affords a hemiacetal azolium intermediate that enables a cascade olefin isomerization/Diels-Alder reaction, for which mechanistic studies implicate Lewis base catalysis. Preliminary studies into the utility of the products have been undertaken with reductive and oxidative cleavage, giving materials for potential use in complex-target synthesis. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Photoionization ion mobility spectrometry (UV-IMS) for the isomeric volatile organic compounds].

Science.gov (United States)

Li, Hu; Niu, Wen-qi; Wang, Hong-mei; Huang, Chao-qun; Jiang, Hai-he; Chu, Yan-nan

2012-01-01

The construction and performance study is reported for a newly developed ultraviolet photoionization ion mobility spectrometry (UV-IMS). In the present paper, an UV-IMS technique was firstly developed to detect eleven isomeric volatile organic compounds including the differences in the structure of carbon chain, the style of function group and the position of function group. Their reduced mobility values were determined and increased in this order: linears alcohols homemade UV-IMS was around ppb-ppm.

Intramolecular transformation of thiyl radicals to α-aminoalkyl radicals: 'ab initio' calculations on homocystein

International Nuclear Information System (INIS)

Chhun, S.; Berges, J.; Bleton, V.; Abedinzadeh, Z.

2000-01-01

One-electron oxidation of thiols by oxidizing radicals leads to the formation of thiyl radical and carbon-centered radicals. It has been shown experimentally that in the absence of oxygen, the thiyl radicals derived from certain thiols of biological interest such as glutathion, cysteine and homocysteine decay rapidly by intramolecular rearrangement reactions into the carbon-centered radical. In the present work we have investigated theoretically the structure and the stability of thiyl and carbon-centered radicals of homocysteine in order to check the possibility of this rearrangement. (author)

Resolution of isomeric new designer stimulants using gas chromatography - Vacuum ultraviolet spectroscopy and theoretical computations

Czech Academy of Sciences Publication Activity Database

Škultéty, L'udovít; Fryčák, P.; Qiu, CL.; Smuts, J.; Shear-Laude, L.; Lemr, Karel; Mao, J.X.; Kroll, P.; Schug, K. A.; Szewczak, A.; Vaught, C.; Lurie, I.; Havlíček, Vladimír

2017-01-01

Roč. 971, JUNE 8 (2017), s. 55-67 ISSN 0003-2670 R&D Projects: GA MŠk(CZ) LO1509 Institutional support: RVO:61388971 Keywords : Gas phase absorption * Time-dependent density functional theory * Isomeric drugs Subject RIV: CB - Analytical Chemistry, Separation OBOR OECD: Analytical chemistry Impact factor: 4.950, year: 2016

Free radical transfer in polymers

International Nuclear Information System (INIS)

Sonntag, C. von; Bothe, E.; Ulanski, P.

1998-01-01

For the present study of free-radical transfer in polymers pulse radiolysis and product studies have been carried out in aqueous solutions using thus far only the water-soluble polymers polyacrylic acid, polymethacrylic acid and polyvinyl alcohol. When OH radicals, generated in the radiolysis of N 2 O-saturated aqueous solutions, react with polymers the lifetime of the polymer radical thus created very much depends on the number of radicals per polymer chain. When there are a large number of radicals per chain their bimolecular decay may be faster than the corresponding (diffusion controlled) decay of monomeric radicals, but when the macromolecule contains only few or even just one radical their lifetime is considerably prolonged. Highly charged polymers such as polyacrylic acid at high pH attain a rod-like conformation which again favors a long lifetime of the radicals. Under such conditions, radical transfer reactions can occur. For example, in polyacrylic acid OH radicals generate two kinds of radicals side by side. The radical in β-position to the carboxylate group converts into the thermodynamically more stable α-radicals by an H-transfer reaction as can be followed by spectrophotometry. Besides radical transfer reactions β-fragmentation reactions occur causing chain scission. Such reactions can be followed in a pulse radiolysis experiment by conductometry, because counter ions are released upon chain scission. Such a process is especially effective in the case of polymethacrylic acid, where it results in a chain depolymerization. An intramolecular H-abstraction is also observed in the γ-radiolysis of polyacrylic acid with the corresponding peroxyl radicals. This causes a chain reaction to occur. The resulting hydroperoxides are unstable and decarboxylate given rise to acetylacetone-like products. In polyvinyl alcohol the peroxyl radicals in α-position to the alcohol function undergo HO 2 -elimination. This prevents a scission of the polymer chain in the

Internal conversion of the (13/2+→5/2-) isomeric transition in 199Hg

International Nuclear Information System (INIS)

Radha Krishna, K.; Chandrasekhar Rao, M.V.S.; Sree Krishna Murty, G.; Venkateswara Rao, N.; Bhuloka Reddy, S.; Satyanarayana, G.; Sastry, D.L.; Iyer, M.R.; Sahasrabhude, S.G.

1990-01-01

The total conversion coefficient of the M4 transition (374 KeV) in the decay of the 13/2 + isomeric state to 5/2 - state in 199 Hg measured using the relative gamma intensity method α T is determined to be 6.34 ± 0.29 in agreement with the theory due to Rosel et al. (author). 1 tab., 3 figs., 11 refs

Distinguishing PCB Isomeric Congeners with their Gas Chromatographic and Mass Spectrometric Ortho Effect using Comprehensive Gas Chromatography

Science.gov (United States)

The 209 polychlorinated biphenyl (PCB) congeners and associated nine isomeric groups (nine groups of PCBs with the same degree of chlorination) have been long recorded as high endocrine disrupting chemicals in the environment. Difficult analytical problems exist, in those frequen...

Anion-assisted trans-cis isomerization of palladium(II) phosphine complexes containing acetanilide functionalities through hydrogen bonding interactions.

Science.gov (United States)

Lu, Xiao-Xia; Tang, Hau-San; Ko, Chi-Chiu; Wong, Jenny Ka-Yan; Zhu, Nianyong; Yam, Vivian Wing-Wah

2005-03-28

The anion-assisted shift of trans-cis isomerization equilibrium of a palladium(II) complex containing acetanilide functionalities brought about by allosteric hydrogen bonding interactions has been established by UV/Vis, 1H NMR, 31P NMR and ESI-MS studies.

Quantification of isomerically summed hydrocarbon contributions to crude oil by carbon number, double bond equivalent, and aromaticity using gas chromatography with tunable vacuum ultraviolet ionization.

Science.gov (United States)

Nowak, Jeremy A; Weber, Robert J; Goldstein, Allen H

2018-03-12

The ability to structurally characterize and isomerically quantify crude oil hydrocarbons relevant to refined fuels such as motor oil, diesel, and gasoline represents an extreme challenge for chromatographic and mass spectrometric techniques. This work incorporates two-dimensional gas chromatography coupled to a tunable vacuum ultraviolet soft photoionization source, the Chemical Dynamics Beamline 9.0.2 of the Advanced Light Source at the Lawrence Berkeley National Laboratory, with a time-of-flight mass spectrometer (GC × GC-VUV-TOF) to directly characterize and isomerically sum the contributions of aromatic and aliphatic species to hydrocarbon classes of four crude oils. When the VUV beam is tuned to 10.5 ± 0.2 eV, both aromatic and aliphatic crude oil hydrocarbons are ionized to reveal the complete chemical abundance of C 9 -C 30 hydrocarbons. When the VUV beam is tuned to 9.0 ± 0.2 eV only aromatic hydrocarbons are ionized, allowing separation of the aliphatic and aromatic fractions of the crude oil hydrocarbon chemical classes in an efficient manner while maintaining isomeric quantification. This technique provides an effective tool to determine the isomerically summed aromatic and aliphatic hydrocarbon compositions of crude oil, providing information that goes beyond typical GC × GC separations of the most dominant hydrocarbon isomers.

Toward spectroscopically accurate global ab initio potential energy surface for the acetylene-vinylidene isomerization

International Nuclear Information System (INIS)

Han, Huixian; Li, Anyang; Guo, Hua

2014-01-01

A new full-dimensional global potential energy surface (PES) for the acetylene-vinylidene isomerization on the ground (S 0 ) electronic state has been constructed by fitting ∼37 000 high-level ab initio points using the permutation invariant polynomial-neural network method with a root mean square error of 9.54 cm −1 . The geometries and harmonic vibrational frequencies of acetylene, vinylidene, and all other stationary points (two distinct transition states and one secondary minimum in between) have been determined on this PES. Furthermore, acetylene vibrational energy levels have been calculated using the Lanczos algorithm with an exact (J = 0) Hamiltonian. The vibrational energies up to 12 700 cm −1 above the zero-point energy are in excellent agreement with the experimentally derived effective Hamiltonians, suggesting that the PES is approaching spectroscopic accuracy. In addition, analyses of the wavefunctions confirm the experimentally observed emergence of the local bending and counter-rotational modes in the highly excited bending vibrational states. The reproduction of the experimentally derived effective Hamiltonians for highly excited bending states signals the coming of age for the ab initio based PES, which can now be trusted for studying the isomerization reaction

Isomeric signatures in the fragmentation of pyridazine and pyrimidine induced by fast ion impact

Energy Technology Data Exchange (ETDEWEB)

Wolff, Wania, E-mail: wania@if.ufrj.br; Luna, Hugo; Montenegro, Eduardo C. [Instituto de Física, Universidade Federal do Rio de Janeiro, 21941-972 Rio de Janeiro, RJ (Brazil)

2015-07-28

We present fast proton impact induced fragmentations of pyrimidine and pyridazine as an experimental resource to investigate isomeric signatures. Major isomeric imprints are identified for few fragment ions and differences of more than an order of magnitude for the cross sections of fragments of the same mass were measured. The observation of the molecular structure of these isomers gives no apparent indication for the reasons for such substantial differences. It is verified that the simple displacement of the position of one nitrogen atom strongly inhibits or favors the production of some ionic fragment species. The dependency of the fragmentation cross sections on the proton impact energy, investigated by means of time of flight mass spectroscopy and of a model calculation based in first order perturbation theory, allows us to disentangle the complex collision dynamics of the ionic fragments. The proton-induced fragmentation discriminates rather directly the association between a molecular orbital ionization and the fragment-ions creation and abundance, as well as how the redistribution of the energy imparted to the molecules takes place, triggering not only single but also double vacancy and leads to specific fragmentation pathways.

Toward spectroscopically accurate global ab initio potential energy surface for the acetylene-vinylidene isomerization

Science.gov (United States)

Han, Huixian; Li, Anyang; Guo, Hua

2014-12-01

A new full-dimensional global potential energy surface (PES) for the acetylene-vinylidene isomerization on the ground (S0) electronic state has been constructed by fitting ˜37 000 high-level ab initio points using the permutation invariant polynomial-neural network method with a root mean square error of 9.54 cm-1. The geometries and harmonic vibrational frequencies of acetylene, vinylidene, and all other stationary points (two distinct transition states and one secondary minimum in between) have been determined on this PES. Furthermore, acetylene vibrational energy levels have been calculated using the Lanczos algorithm with an exact (J = 0) Hamiltonian. The vibrational energies up to 12 700 cm-1 above the zero-point energy are in excellent agreement with the experimentally derived effective Hamiltonians, suggesting that the PES is approaching spectroscopic accuracy. In addition, analyses of the wavefunctions confirm the experimentally observed emergence of the local bending and counter-rotational modes in the highly excited bending vibrational states. The reproduction of the experimentally derived effective Hamiltonians for highly excited bending states signals the coming of age for the ab initio based PES, which can now be trusted for studying the isomerization reaction.

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

Directory of Open Access Journals (Sweden)

Béla Fiser

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

β-γ and isomeric decay spectroscopy of 168Dy

Directory of Open Access Journals (Sweden)

Zhang G.X.

2018-01-01

Full Text Available This contribution will report on the experimental work on the level structure of 168Dy. The experimental data have been taken as part of the EURICA decay spectroscopy campaign at RIBF, RIKEN in November 2014. In the experiment, a 238U primary beam is accelerated up to 345 MeV/u with an average intensity of 12 pnA. The nuclei of interest are produced by in-flight fission of 238U impinging on Be target with a thickness of 5 mm. The excited states of 168Dy have been populated through the decay from a newly identified isomeric state and via the β decay from 168Tb. In this contribution, scientific motivations, experimental procedure and some preliminary results for this study are presented.

β-γ and isomeric decay spectroscopy of 168Dy

Science.gov (United States)

Zhang, G. X.; Watanabe, H.; Kondev, F. G.; Lane, G. J.; Regan, P. H.; Söderström, P.-A.; Walker, P. M.; Kanaoka, H.; Korkulu, Z.; Lee, P. S.; Liu, J. J.; Nishimura, S.; Wu, J.; Yagi, A.; Ahn, D. S.; Alharbi, T.; Baba, H.; Browne, F.; Bruce, A. M.; Carroll, R. J.; Chae, K. Y.; Dombradi, Zs.; Doornenbal, P.; Estrade, A.; Fukuda, N.; Griffin, C.; Ideguchi, E.; Inabe, N.; Isobe, T.; Kanaya, S.; Kojouharov, I.; Kubo, T.; Kubono, S.; Kurz, N.; Kuti, I.; Lalkovski, S.; Lee, C. S.; Lee, E. J.; Lorusso, G.; Lotay, G.; Moon, C.-B.; Nishizuka, I.; Nita, C. R.; Odahara, A.; Patel, Z.; Phong, V. H.; Podolyák, Zs.; Roberts, O. J.; Sakurai, H.; Schaffner, H.; Shand, C. M.; Shimizu, Y.; Sumikama, T.; Suzuki, H.; Takeda, H.; Terashima, S.; Vajta, Zs.; Valiente-Dóbon, J. J.; Xu, Z. Y.

2018-05-01

This contribution will report on the experimental work on the level structure of 168Dy. The experimental data have been taken as part of the EURICA decay spectroscopy campaign at RIBF, RIKEN in November 2014. In the experiment, a 238U primary beam is accelerated up to 345 MeV/u with an average intensity of 12 pnA. The nuclei of interest are produced by in-flight fission of 238U impinging on Be target with a thickness of 5 mm. The excited states of 168Dy have been populated through the decay from a newly identified isomeric state and via the β decay from 168Tb. In this contribution, scientific motivations, experimental procedure and some preliminary results for this study are presented.

Isomer-specific detection in the UV photodissociation of the propargyl radical by chirped-pulse mm-wave spectroscopy in a pulsed quasi-uniform flow.

Science.gov (United States)

Broderick, Bernadette M; Suas-David, Nicolas; Dias, Nureshan; Suits, Arthur G

2018-02-21

Isomer-specific detection and product branching fractions in the UV photodissociation of the propargyl radical is achieved through the use of chirped-pulse Fourier-transform mm-wave spectroscopy in a pulsed quasi-uniform flow (CPUF). Propargyl radicals are produced in the 193 nm photodissociation of 1,2-butadiene. Absorption of a second photon leads to H atom elimination giving three possible C 3 H 2 isomers: singlets cyclopropenylidene (c-C 3 H 2 ) and propadienylidene (l-C 3 H 2 ), and triplet propargylene ( 3 HCCCH). The singlet products and their appearance kinetics in the flow are directly determined by rotational spectroscopy, but due to the negligible dipole moment of propargylene, it is not directly monitored. However, we exploit the time-dependent kinetics of H-atom catalyzed isomerization to infer the branching to propargylene as well. We obtain the overall branching among H loss channels to be 2.9% (+1.1/-0.5) l-C 3 H 2 + H, 16.8% (+3.2/-1.3) c-C 3 H 2 + H, and 80.2 (+1.8/-4.2) 3 HCCCH + H. Our findings are qualitatively consistent with earlier RRKM calculations in that the major channel in the photodissociation of the propargyl radical at 193 nm is to 3 HCCCH + H; however, a greater contribution to the energetically most favorable isomer, c-C 3 H 2 + H is observed in this work. We do not detect the predicted HCCC + H 2 channel, but place an upper bound on its yield of 1%.

Development of a new free radical absorption capacity assay method for antioxidants: aroxyl radical absorption capacity (ARAC).

Science.gov (United States)

Nagaoka, Shin-ichi; Nagai, Kanae; Fujii, Yuko; Ouchi, Aya; Mukai, Kazuo

2013-10-23

A new free radical absorption capacity assay method is proposed with use of an aroxyl radical (2,6-di-tert-butyl-4-(4'-methoxyphenyl)phenoxyl radical) and stopped-flow spectroscopy and is named the aroxyl radical absorption capacity (ARAC) assay method. The free radical absorption capacity (ARAC value) of each tocopherol was determined through measurement of the radical-scavenging rate constant in ethanol. The ARAC value could also be evaluated through measurement of the half-life of the aroxyl radical during the scavenging reaction. For the estimation of the free radical absorption capacity, the aroxyl radical was more suitable than the DPPH radical, galvinoxyl, and p-nitrophenyl nitronyl nitroxide. The ARAC value in tocopherols showed the same tendency as the free radical absorption capacities reported previously, and the tendency was independent of an oxygen radical participating in the scavenging reaction and of a medium surrounding the tocopherol and oxygen radical. The ARAC value can be directly connected to the free radical-scavenging rate constant, and the ARAC method has the advantage of treating a stable and isolable radical (aroxyl radical) in a user-friendly organic solvent (ethanol). The ARAC method was also successfully applied to a palm oil extract. Accordingly, the ARAC method would be useful in free radical absorption capacity assay of antioxidative reagents and foods.

Investigating the large deformation of the 5 /2+ isomeric state in 73Zn: An indicator for triaxiality

Science.gov (United States)

Yang, X. F.; Tsunoda, Y.; Babcock, C.; Billowes, J.; Bissell, M. L.; Blaum, K.; Cheal, B.; Flanagan, K. T.; Garcia Ruiz, R. F.; Gins, W.; Gorges, C.; Grob, L. K.; Heylen, H.; Kaufmann, S.; Kowalska, M.; Krämer, J.; Malbrunot-Ettenauer, S.; Neugart, R.; Neyens, G.; Nörtershäuser, W.; Otsuka, T.; Papuga, J.; Sánchez, R.; Wraith, C.; Xie, L.; Yordanov, D. T.

2018-04-01

Recently reported nuclear spins and moments of neutron-rich Zn isotopes measured at ISOLDE-CERN [C. Wraith et al., Phys. Lett. B 771, 385 (2017), 10.1016/j.physletb.2017.05.085] show an uncommon behavior of the isomeric state in 73Zn. Additional details relating to the measurement and analysis of the Znm73 hyperfine structure are addressed here to further support its spin-parity assignment 5 /2+ and to estimate its half-life. A systematic investigation of this 5 /2+ isomer indicates that significant collectivity appears due to proton/neutron E 2 excitations across the proton Z = 28 and neutron N = 50 shell gaps. This is confirmed by the good agreement of the observed quadrupole moments with large scale Monte Carlo shell model calculations. In addition, potential energy surface calculations in combination with T plots reveal a triaxial shape for this isomeric state.

Activation cross section and isomeric cross section ratios for the (n ,2 n ) reaction on 153Eu

Science.gov (United States)

Luo, Junhua; Jiang, Li; Li, Suyuan

2017-10-01

The 153Eu(n ,2 n ) m1,m2,g152Eu cross section was measured by means of the activation technique at three neutron energies in the range 13-15 MeV. The quasimonoenergetic neutron beam was formed via the 3H(d ,n ) 4He reaction, in the Pd-300 Neutron Generator at the Chinese Academy of Engineering Physics (CAEP). The activities induced in the reaction products were measured using high-resolution γ-ray spectroscopy. The cross section of the population of the second high-spin (8-) isomeric state was measured along with the reaction cross section populating both the ground (3-) and the first isomeric state (0-). Cross sections were also evaluated theoretically using the numerical code TALYS-1.8, with different level density options at neutron energies varying from the reaction threshold to 20 MeV. Results are discussed and compared with the corresponding literature.

Ligand induced structural isomerism in phosphine coordinated gold clusters revealed by ion mobility mass spectrometry

Energy Technology Data Exchange (ETDEWEB)

Ligare, Marshall R.; Baker, Erin M.; Laskin, Julia; Johnson, Grant E.

2017-01-01

Structural isomerism in ligated gold clusters is revealed using electrospray ionization ion mobility spectrometry mass spectrometry. Phosphine ligated Au8 clusters are shown to adopt more “extended” type structures with increasing exchange of methyldiphenylphosphine (MePPh2) for triphenylphosphine (PPh3). These ligand-dependant structure-property relationships are critical to applications of clusters in catalysis.

DFT study on the isomerization and tautomerism in vitamins B3 (niacin), B5 (pantothenic acid) and B7 (biotin)

Science.gov (United States)

Valadbeigi, Younes; Farrokhpour, Hossein; Tabrizchi, Mahmoud

2014-05-01

Isomerization and tautomerism of the three water soluble vitamins including B3, B5 and B7 were studied applying density functional theory using B3LYP method in gas and aqueous phases. Activation energies (Ea), Gibbs free energies of activation (ΔG#), and imaginary frequencies of the transition state structures were calculated for all the isomerization and tautomerism reactions. Activation energies of the neutral → zwitterion (amine-enamine) tautomerism in vitamin B3 were 310-360 kJ/mol where these values for the keto-enol tautomerism were 100-130 kJ/mol. It was found that water molecule catalyzes the tautomerism and decreases the activation energies about 90-160 kJ/mol.

Positionally isomeric organic gelators: structure-gelation study, racemic versus enantiomeric gelators, and solvation effects.

Science.gov (United States)

Caplar, Vesna; Frkanec, Leo; Sijaković Vujicić, Natasa; Zinić, Mladen

2010-03-08

Low molecular weight gelator molecules consisting of aliphatic acid, amino acid (phenylglycine), and omega-aminoaliphatic acid units have been designed. By varying the number of methylene units in the aliphatic and omega-aminoaliphatic acid chains, as defined by descriptors m and n, respectively, a series of positionally isomeric gelators having different positions of the peptidic hydrogen-bonding unit within the gelator molecule has been obtained. The gelation properties of the positional isomers have been determined in relation to a defined set of twenty solvents of different structure and polarity and analyzed in terms of gelator versatility (G(ver)) and effectiveness (G(eff)). The results of gelation tests have shown that simple synthetic optimizations of a "lead gelator molecule" by variation of m and n, end-group polarity (carboxylic acid versus sodium carboxylate), and stereochemistry (racemate versus optically pure form) allowed the identification of gelators with tremendously improved versatility (G(ver)) and effectiveness (G(eff)). Dramatic differences in G(eff) values of up to 70 times could be observed between pure racemate/enantiomer pairs of some gelators, which were manifested even in the gelation of very similar solvents such as isomeric xylenes. The combined results of spectroscopic ((1)H NMR, FTIR), electron microscopy (TEM), and X-ray diffraction studies suggest similar organization of the positionally isomeric gelators at the molecular level, comprising parallel beta-sheet hydrogen-bonded primary assemblies that form inversed bilayers at a higher organizational level. Differential scanning calorimetry (DSC) studies of selected enantiomer/racemate gelator pairs and their o- and p-xylene gels revealed the simultaneous presence of different polymorphs in the racemate gels. The increased gelation effectiveness of the racemate compared to that of the single enantiomer is most likely a consequence of its spontaneous resolution into enantiomeric

Structural and Functional Characterization of a Short-Chain Flavodoxin Associated with a Noncanonical 1,2-Propanediol Utilization Bacterial Microcompartment

Energy Technology Data Exchange (ETDEWEB)

Plegaria, Jefferson S. [MSU-DOE; Sutter, Markus [MSU-DOE; Molecular; Ferlez, Bryan [MSU-DOE; Aussignargues, Clément [MSU-DOE; Niklas, Jens [Solar; Poluektov, Oleg G. [Solar; Fromwiller, Ciara [MSU-DOE; TerAvest, Michaela [Department; amp, Molecular Biology, Michigan State University, East; Utschig, Lisa M. [Solar; Tiede, David M. [Solar; Kerfeld, Cheryl A. [MSU-DOE; Molecular; Department; amp, Molecular Biology, Michigan State University, East; Berkeley Synthetic Biology Institute, Berkeley, California 94720, United States

2017-09-21

Bacterial microcompartments (BMCs) are proteinaceous organelles that encapsulate enzymes involved in CO2 fixation (carboxysomes). or carbon catabolism (metabolosomes). Metabolosomes share a common core of enzymes and a distinct signature enzyme for substrate degradation that defines the function of the BMC (e,g., propanediol or ethanolamine utilization BMCs, or glycyl-radical enzyme microcompartments). Loci encoding metabolosomes also typically contain genes for proteins that support organelle function, such as regulation, transport of substrate, and cofactor (e.g., vitamin B-12) synthesis and recycling. Flavoproteins are frequently among these ancillary gene products, suggesting that these redox active proteins play an undetermined function in many metabolosomes. Here, we report the first characterization of a BMC-associated flavodoxin (Fld1C), a small flavoprotein, derived from the noncanonical 1,2-propanediol utilization BMC locus (PDU1C) of Lactobacillus reuteri. The 2.0 angstrom X-ray structure of Fld1C displays the alpha/beta flavodoxin fold, which noncovalently binds a single flavin mononucleotide molecule. Fld1C is a short-chain flavodoxin with redox potentials of -240 +/- 3 mV oxidized/semiquinone and -344 +/- 1 mV semiquinone/hydroquinone versus the standard hydrogen electrode at pH 7.5. It can participate in an electron transfer reaction with a photoreductant to form a stable semiquinone species. Collectively, our structural and functional results suggest that PDU1C BMCs encapsulate Fld1C to store and transfer electrons for the reactivation and/or recycling of the B-12 cofactor utilized by the signature enzyme.

Comparison of Separation of Seed Oil Triglycerides Containing Isomeric Conjugated Octadecatrienoic Acid Moieties by Reversed-Phase HPLC

Directory of Open Access Journals (Sweden)

Anh Van Nguyen

2017-12-01

Full Text Available Relative retention analysis and increment approach were applied for the comparison of triglycerides (TGs retention of a broad set of plant seed oils with isomeric conjugated octadecatrienoic acids (CLnA by reversed-phase HPLC for “propanol-2-acetonitrile” mobile phases and Kromasil 100-5C18 stationary phase with diode array detection (DAD and mass spectrometric (MS detection. The subjects of investigation were TGs of seed oils: Calendula officinalis, Catalpa ovata, Jacaranda mimosifolia, Centranthus ruber, Momordica charantia, Trichosanthes anguina, Punica granatum, Thladiantha dubia, Valeriana officinalis, and Vernicia montana. It was found that a sequence of elution of TGs of the same types is the same without any inversions for full range of mobile phase compositions: punicic (C18:39Z11E13Z < jacaric (C18:38Z10E12Z < catalpic (C18:39E11E13Z < α-eleostearic (C18:39Z11E13E < calendic (C18:38E10E12Z < β-eleostearic (C18:39E11E13E < all-E calendic (C18:38E10E12E acids. TGs and fatty acid compositions were calculated for all oil samples. Regularities of solute retentions as a function of isomeric conjugated octadecatrienoic acid moiety structure are discussed. Thus, it was proven that it is possible to differentiate TGs of complex composition with moieties of all natural CLnA by retention control accomplished by electronic spectra comparison, even though there are only three types of electronic-vibration spectra for seven isomeric CLnA.

Differential Selectivity of the Escherichia coli Cell Membrane Shifts the Equilibrium for the Enzyme-Catalyzed Isomerization of Galactose to Tagatose▿

Science.gov (United States)

Kim, Jin-Ha; Lim, Byung-Chul; Yeom, Soo-Jin; Kim, Yeong-Su; Kim, Hye-Jung; Lee, Jung-Kul; Lee, Sook-Hee; Kim, Seon-Won; Oh, Deok-Kun

2008-01-01

An Escherichia coli galactose kinase gene knockout (ΔgalK) strain, which contains the l-arabinose isomerase gene (araA) to isomerize d-galactose to d-tagatose, showed a high conversion yield of tagatose compared with the original galK strain because galactose was not metabolized by endogenous galactose kinase. In whole cells of the ΔgalK strain, the isomerase-catalyzed reaction exhibited an equilibrium shift toward tagatose, producing a tagatose fraction of 68% at 37°C, whereas the purified l-arabinose isomerase gave a tagatose equilibrium fraction of 36%. These equilibrium fractions are close to those predicted from the measured equilibrium constants of the isomerization reaction catalyzed in whole cells and by the purified enzyme. The equilibrium shift in these cells resulted from the higher uptake and lower release rates for galactose, which is a common sugar substrate, than for tagatose, which is a rare sugar product. A ΔmglB mutant had decreased uptake rates for galactose and tagatose, indicating that a methylgalactoside transport system, MglABC, is the primary contributing transporter for the sugars. In the present study, whole-cell conversion using differential selectivity of the cell membrane was proposed as a method for shifting the equilibrium in sugar isomerization reactions. PMID:18263746

Differential selectivity of the Escherichia coli cell membrane shifts the equilibrium for the enzyme-catalyzed isomerization of galactose to tagatose.

Science.gov (United States)

Kim, Jin-Ha; Lim, Byung-Chul; Yeom, Soo-Jin; Kim, Yeong-Su; Kim, Hye-Jung; Lee, Jung-Kul; Lee, Sook-Hee; Kim, Seon-Won; Oh, Deok-Kun

2008-04-01

An Escherichia coli galactose kinase gene knockout (DeltagalK) strain, which contains the l-arabinose isomerase gene (araA) to isomerize d-galactose to d-tagatose, showed a high conversion yield of tagatose compared with the original galK strain because galactose was not metabolized by endogenous galactose kinase. In whole cells of the DeltagalK strain, the isomerase-catalyzed reaction exhibited an equilibrium shift toward tagatose, producing a tagatose fraction of 68% at 37 degrees C, whereas the purified l-arabinose isomerase gave a tagatose equilibrium fraction of 36%. These equilibrium fractions are close to those predicted from the measured equilibrium constants of the isomerization reaction catalyzed in whole cells and by the purified enzyme. The equilibrium shift in these cells resulted from the higher uptake and lower release rates for galactose, which is a common sugar substrate, than for tagatose, which is a rare sugar product. A DeltamglB mutant had decreased uptake rates for galactose and tagatose, indicating that a methylgalactoside transport system, MglABC, is the primary contributing transporter for the sugars. In the present study, whole-cell conversion using differential selectivity of the cell membrane was proposed as a method for shifting the equilibrium in sugar isomerization reactions.

Physiology of free radicals

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Stevanović Jelka

2011-01-01

Full Text Available Free radicals imply that every atom, molecule, ion, group of atoms, or molecules with one or several non-paired electrons in outer orbital. Among these are: nitrogenoxide (NO•, superoxide-anion-radical (O2•-, hydroxyl radical (OH•, peroxyl radical (ROO•, alcoxyl radical (RO• and hydroperoxyl radical (HO2•. However, reactive oxygen species also include components without non-paired electrons in outer orbital (so-called reactive non-radical agents, such as: singlet oxygen (1O2, peroxynitrite (ONOO-, hydrogen-peroxide (H2O2, hypochloric acid (eg. HOCl and ozone (O3. High concentrations of free radicals lead to the development of oxidative stress which is a precondition for numerous pathological effects. However, low and moderate concentrations of these matter, which occur quite normally during cell metabolic activity, play multiple significant roles in many reactions. Some of these are: regulation of signal pathways within the cell and between cells, the role of chemoattractors and leukocyte activators, the role in phagocytosis, participation in maintaining, changes in the position and shape of the cell, assisting the cell during adaption and recovery from damage (e.g.caused by physical effort, the role in normal cell growth, programmed cell death (apoptosis and cell ageing, in the synthesis of essential biological compounds and energy production, as well as the contribution to the regulation of the vascular tone, actually, tissue vascularization.

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

Science.gov (United States)

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

2015-04-01

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

Ruthenium Stilbenyl and Diruthenium Distyrylethene Complexes: Aspects of Electron Delocalization and Electrocatalyzed Isomerization of the Z-Isomer

Czech Academy of Sciences Publication Activity Database

Linseis, M.; Záliš, Stanislav; Zabel, M.; Winter, R. F.

2012-01-01

Roč. 134, č. 40 (2012), s. 16671-16692 ISSN 0002-7863 R&D Projects: GA MŠk LD11086 Institutional support: RVO:61388955 Keywords : CIS-TRANS-ISOMERIZATION * MIXED-VALENCE COMPOUNDS * VIBRATIONAL TIME -SCALE Subject RIV: CG - Electrochemistry Impact factor: 10.677, year: 2012

Vinylcyclopropylacyl and polyeneacyl radicals. Intramolecular ketene alkyl radical additions in ring synthesis.

Science.gov (United States)

De Boeck, Benoit; Herbert, Nicola M A; Harrington-Frost, Nicole M; Pattenden, Gerald

2005-01-21

Treatment of a variety of substituted vinylcyclopropyl selenyl esters, e.g. 11, with Bu(3)SnH-AIBN in refluxing benzene leads to the corresponding acyl radical intermediates, which undergo rearrangement and intramolecular cyclisations via their ketene alkyl radical equivalents producing cyclohexenones in 50-60% yield. By contrast, treatment of conjugated triene selenyl esters, e.g. 32, with Bu(3)SnH-AIBN produces substituted 2-cyclopentenones via intramolecular cyclisations of their ketene alkyl radical intermediates. Under the same radical-initiating conditions the selenyl esters derived from o-vinylbenzoic acid and o-vinylcinnamic acid undergo intramolecular cyclisations producing 1-indanone and 5,6-dihydrobenzocyclohepten-7-one respectively in 60-70% yields. A tandem radical cyclisation from the alpha,beta,gamma,delta-diene selenyl ester 31 provides an expeditious synthesis of the diquinane 35 in 69% yield.

Gamma-irradiation effects to posttranslational modification and chaperon function of bovine α-crystalline

International Nuclear Information System (INIS)

Hiroki, K; Matsumoto, S.; Awakura, M.; Fujii, N.

2001-01-01

The formation of D-asparate (D-Asp) in αA-crystallin of the aged human eye and the cataract crystalline lens has been reported. Crystalline lens keeps the transparency by forming α-crystallin which consists of a high order association of αA-and αB-crystallin. Bovine α-crystallin for investigating a chaperone function which protects the crystalline lens from getting to opaque or disordered agglutination with heat or light, is irradiated by gamma-ray (Co-60) at 0, 1, 2, 3, and 4 kGy, respectively. The irradiated bovine α-crystallin are analyzed with electrophoresis, gel permeation chromatograph, and UV absorption spectrometer for checking on the agglutination and the isomerization of macromolecules. Oxidation of methionine residues (Met-1) and isomerization of asparagine residues (Asp-151) in the αA-crystallin are ascertained in molecular levels with reversed phase liquid chromatography. The Met-1 oxidation and the Asp-151 isomerization depend on gamma-irradiation doses. It is thought that OH radical and H radical in water generated by the irradiation lead to the oxidation and the isomerization. Stereoinversion in the α-crystallin following to such a chemical change are considered to lead to the agglutination of polymer and the reduction of chaperon function. (M. Suetake)

Serum Hydroxyl Radical Scavenging Capacity as Quantified with Iron-Free Hydroxyl Radical Source

Science.gov (United States)

Endo, Nobuyuki; Oowada, Shigeru; Sueishi, Yoshimi; Shimmei, Masashi; Makino, Keisuke; Fujii, Hirotada; Kotake, Yashige

2009-01-01

We have developed a simple ESR spin trapping based method for hydroxyl (OH) radical scavenging-capacity determination, using iron-free OH radical source. Instead of the widely used Fenton reaction, a short (typically 5 seconds) in situ UV-photolysis of a dilute hydrogen peroxide aqueous solution was employed to generate reproducible amounts of OH radicals. ESR spin trapping was applied to quantify OH radicals; the decrease in the OH radical level due to the specimen’s scavenging activity was converted into the OH radical scavenging capacity (rate). The validity of the method was confirmed in pure antioxidants, and the agreement with the previous data was satisfactory. In the second half of this work, the new method was applied to the sera of chronic renal failure (CRF) patients. We show for the first time that after hemodialysis, OH radical scavenging capacity of the CRF serum was restored to the level of healthy control. This method is simple and rapid, and the low concentration hydrogen peroxide is the only chemical added to the system, that could eliminate the complexity of iron-involved Fenton reactions or the use of the pulse-radiolysis system. PMID:19794928

Radical transfer between proteins: role of tyrosine, tryptophan and protein peroxyl radicals

International Nuclear Information System (INIS)

Irwin, J.A.; Ostdal, H.; Davies, M.J.

1998-01-01

Reaction of the Fe(III) forms of the heme proteins myoglobin (Mb) and horseradish peroxidase (HRP) with H 2 O 2 gives rise to high-oxidation-state heme-derived species which can be described as a Fe(IV)-oxo porphyrin radical-cation ('Compound 1'). In the case of Mb, the Fe(IV)-oxo porphyrin radical-cation undergoes rapid electron transfer with the surrounding protein to give protein (globin)-derived radicals and an Fe(lV)-oxo species ('Compound 2'). The globin-derived radicals have been shown to be located at two (or more) sites: Tyr-103 or Trp-14, with the latter radical known to react with oxygen to give a Trp-derived peroxyl radical (Mb-Trp-OO*). With HRP, the Fe(lV)-oxo porphyrin radical-cation carries out two successive one-electron oxidation reactions at the exposed heme edge to give firstly 'Compound 2' [the Fe(lV)oxo species] and then the resting Fe(III) state of the enzyme. n this study we have investigated whether the Trp-14 peroxyl radical from Mb and the Compound 1 and 2 species from HRP (in the absence and presence of free Tyr) can oxidise amino acids, peptides and proteins. Such reactions constitute intermolecular protein-to-protein radical transfer reactions and hence protein chain-oxidation. We have also examined whether these oxidants react with antioxidants. Reaction of these heme-protein derived oxidants with amino acids, proteins and antioxidants has been carried out at room temperature for defined periods of time before freeze-quenching to 77K to halt reaction. The radical species present in the reaction system at the time of freezing were subsequently examined by EPR spectroscopy at 77K. Three free amino acids, Tyr, Trp and Cys (with Cys the least efficient) have been shown to react rapidly with Mb-Trp-OO*, as evidenced by the loss of the characteristic EPR features of Mb-Trp-OO* on inclusion of increasing concentrations of the amino acids. All other amino acids are much less reactive. Evidence has also been obtained for (inefficient) hydrogen

Isomeric cross section ratios in 55Mn(α, n)58m,gCo reaction

International Nuclear Information System (INIS)

Long Xianguan; He Fuqing; Peng Xiufen; Liu Mantian

1989-01-01

The isomeric cross section ratios in 55 Mn(α, n) 58m,g Co reaction are measured for incident alpha-particle energies ranging from 10.4 to 26.5 MeV by using activation method and stacked-foil technique. The measured values are compared with theoretical calculations performed by using Huizenga and Vandenbosch method and the values of spin cutoff factor are obtained for product nucleus 58 Co

Homegrown religious radicalization

DEFF Research Database (Denmark)

Khawaja, Iram

It has been reported that a growing number of youngsters from Western Europe are engaging in conflicts motivated by religious and political conflicts in the Middle East. This paper explores the reasons behind this seemingly religious radicalization from the point of view of the youngsters...... youngsters and parents of youngsters who have chosen a radicalized path in life. The paper will shed light on how the sense of and yearning for belonging and recognition have to be taken into account in our understanding of homegrown religious radicalization...

Evidence for tunneling in base-catalyzed isomerization of glyceraldehyde to dihydroxyacetone by hydride shift under formose conditions.

Science.gov (United States)

Cheng, Liang; Doubleday, Charles; Breslow, Ronald

2015-04-07

Hydrogen atom transfer reactions between the aldose and ketose are key mechanistic features in formose chemistry by which formaldehyde is converted to higher sugars under credible prebiotic conditions. For one of these transformations, we have investigated whether hydrogen tunneling makes a significant contribution to the mechanism by examining the deuterium kinetic isotope effect associated with the hydrogen transfer during the isomerization of glyceraldehyde to the corresponding dihydroxyacetone. To do this, we developed a quantitative HPLC assay that allowed us to measure the apparent large intrinsic kinetic isotope effect. From the Arrhenius plot of the kinetic isotope effect, the ratio of the preexponential factors AH/AD was 0.28 and the difference in activation energies Ea(D) - Ea(H) was 9.1 kJ·mol(-1). All these results imply a significant quantum-mechanical tunneling component in the isomerization mechanism. This is supported by multidimensional tunneling calculations using POLYRATE with small curvature tunneling.

General and Facile Route to Isomerically Pure Tricyclic Peptides Based on Templated Tandem CLIPS/CuAAC Cyclizations.

Science.gov (United States)

Richelle, Gaston J J; Ori, Sumeet; Hiemstra, Henk; van Maarseveen, Jan H; Timmerman, Peter

2018-01-08

We report a one-pot ligation/cyclization technology for the rapid and clean conversion of linear peptides into tricyclic peptides that is based on using tetravalent scaffolds containing two benzyl bromide and two alkyne moieties. These react via CLIPS/CuAAC reactions with cysteines and azides in the peptide. Flexibility in the scaffolds is key to the formation of isomerically pure products as the flexible scaffolds T4 1 and T4 2 mostly promote the formation of single isomeric tricycles while the rigid scaffolds T4 3 and T4 4 do not yield clean products. There seems to be no limitation to the number and types of amino acids present as 18 canonical amino acids were successfully implemented. We also observed that azides at the peptide termini and cysteine residues in the center gave better results than compounds with the functional groups placed the other way round. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Theoretical Kinetic Study of the Formic Acid Catalyzed Criegee Intermediate Isomerization: Multistructural Anharmonicity and Atmospheric Implications

KAUST Repository

Monge Palacios, Manuel

2018-01-29

We performed a theoretical study on the double hydrogen shift isomerization reaction of a six carbon atom Criegee intermediate (C6-CI), catalyzed by formic acid (HCOOH), to produce vinylhydroperoxide (VHP), C6-CI+HCOOH→VHP+HCOOH. This Criegee intermediate can serve as a surrogate for larger CIs derived from important volatile organic compounds like monoterpenes, whose reactivity is not well understood and are difficult to handle computationally. The reactant HCOOH exerts a pronounced catalytic effect on the studied reaction by lowering the barrier height, but the kinetic enhancement is hindered by the multistructural anharmonicity. First, the rigid ring-structure adopted by the saddle point to facilitate simultaneous transfer of two atoms does not allow formation of as many conformers as those formed by the reactant C6-CI. And second, the flexible carbon chain of C6-CI facilitates the formation of stabilizing intramolecular C–H···O hydrogen bonds; this stabilizing effect is less pronounced in the saddle point structure due to its tightness and steric effects. Thus, the contribution of the reactant C6-CI conformers to the multistructural partition function is larger than that of the saddle point conformers. The resulting low multistructural anharmonicity factor partially cancels out the catalytic effect of the carboxylic acid, yielding in a moderately large rate coefficient, k(298 K) = 4.9·10-13 cm3 molecule-1 s-1. We show that carboxylic acids may promote the conversion of stabilized Criegee intermediates into vinylhydroperoxides in the atmosphere, which generates OH radicals and leads to secondary organic aerosol, thereby affecting the oxidative capacity of the atmosphere and ultimately the climate.

Laparoscopic radical trachelectomy.

Science.gov (United States)

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

2012-01-01

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

EFFECT OF TIME AND TEMPERATURE ON ISOMERIZATION REACTION OF ?-PINENEUSING CATALYST ZR 4+ Nanik Wijayati, Supartono, Nuni Widiarti, Tri Handayani /NATURAL ZEOLITE

Directory of Open Access Journals (Sweden)

Nanik Wijayati

2016-03-01

Full Text Available Effects of time and temperature on ?-pinene isomerization reaction using catalysts Zr/natural zeolitewas studied. Characterization of the catalysts include: crystallinity, observed using X-Ray Diffraction, count Zr 4+ carried observed using X-Ray Fluorescence, area and porosity catalyst was observed using the Surface Area Analyzer, and acidity catalyst observed through gravimetric method. Isomerization reaction carried out in a batch reactor with temperature variations 90, 120 and 150 C and reaction time variations of 60, 90, 120, 150 and 180 minutes. Best results of isomerisation in this study was obtained at 150 derajat C with a reaction time of 180 minutes. Kindsof isomer obtained was observed using GCMS. Catalyst characterization results indicate that modification of the catalyst by cation Zr increases the acidity from 2.76 to 6.64 mmol/g and does not damage the crystal structure significantly. The highest product conversion in this research is 9.24%, less than the maximum results caused by pre-treatment of the catalyst produces a low area. Thus, temperature and reaction time affect the concentration of ? pinene isomerization product in addition to the effect of the catalyst used.

Acidic ionic liquids for n-alkane isomerization in a liquid-liquid or slurry-phase reaction mode

Energy Technology Data Exchange (ETDEWEB)

Meyer, C.; Hager, V.; Geburtig, D.; Kohr, C.; Wasserscheid, P. [Erlangen-Nuernberg Univ. (Germany). Lehrstuhl fuer Chemische Reaktionstechnik; Haumann, M. [Chemical Reaction Engineering, FAU Busan Campus, Korea (Korea, Republic of)

2011-07-01

Highly acidic ionic liquid (IL) catalysts offer the opportunity to convert n-alkanes at very low reaction temperatures. The results of IL catalyzed isomerization and cracking reactions of pure n-octane are presented. Influence of IL composition, [C{sub 4}C{sub 1}Im]Cl / AlCl{sub 3} / H{sub 2}SO{sub 4} and [C{sub 4}C{sub 1}Im]Cl / AlCl{sub 3} / 1-chlorooctane, on catalyst activity and selectivities to branched alkanes was investigated. Acidic chloroaluminate IL catalysts form liquid-liquid biphasic systems with unpolar organic product mixtures. Thus, recycling of the acidic IL is enabled by simple phase separation in the liquid-liquid biphasic reaction mode or the IL can be immobilized on an inorganic support with a large specific surface area. These supported ionic liquid phase (SILP) catalysts offer the advantage to get a macroscopically heterogeneous system while still preserving all benefits of the homogeneous catalyst which can be used for the slurry-phase n-alkane isomerization. The interaction of the solid support and acidic IL influences strongly the catalytic activity. (orig.)

Radical Evil

Directory of Open Access Journals (Sweden)

Carlos Manrique

2007-12-01

Full Text Available There is an aporia in Kant’s analysis of evil: he defines radical evilas an invisible disposition of the will, but he also demands an inferential connection between visible evil actions and this invisible disposition. This inference,however, undermines the radical invisibility of radical evil according to Kant’s own definition of the latter. Noting how this invisibility of moral worth is a distinctive feature of Kant’s approach to the moral problem, the paper then asks why, in the Groundwork, he nonetheless forecloses a question about evil that seems to be consistent with this approach. It is argued that to account for this aporia and this foreclosure, one has to interrogate the way in which the category of religion orients Kant’s incipient philosophy of history in Die Religion.

The role of dissociation channels of excited electronic states in quantum optimal control of ozone isomerization: A three-state dynamical model

Energy Technology Data Exchange (ETDEWEB)

Kurosaki, Yuzuru, E-mail: kurosaki.yuzuru@jaea.go.jp [Quantum Beam Science Directorate, Tokai Research and Development Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Ho, Tak-San, E-mail: tsho@Princeton.EDU [Department of Chemistry, Princeton University, Princeton, NJ 08544 (United States); Rabitz, Herschel, E-mail: hrabitz@Princeton.EDU [Department of Chemistry, Princeton University, Princeton, NJ 08544 (United States)

2016-05-01

The prospect of performing the open → cyclic ozone isomerization has attracted much research attention. Here we explore this consideration theoretically by performing quantum optimal control calculations to demonstrate the important role that excited-state dissociation channels could play in the isomerization transformation. In the calculations we use a three-state, one-dimensional dynamical model constructed from the lowest five {sup 1}A′ potential energy curves obtained with high-level ab initio calculations. Besides the laser field-dipole couplings between all three states, this model also includes the diabatic coupling between the two excited states at an avoided crossing leading to competing dissociation channels that can further hinder the isomerization process. The present three-state optimal control simulations examine two possible control pathways previously considered in a two-state model, and reveal that only one of the pathways is viable, achieving a robust ∼95% yield to the cyclic target in the three-state model. This work represents a step towards an ultimate model for the open → cyclic ozone transformation capable of giving adequate guidance about the necessary experimental control field resources as well as an estimate of the ro-vibronic spectral character of cyclic ozone as a basis for an appropriate probe of its formation.

Synthesis of Heterocycles through a Ruthenium‐Catalyzed Tandem Ring‐Closing Metathesis/Isomerization/N‐Acyliminium Cyclization Sequence

DEFF Research Database (Denmark)

Ascic, Erhad; Jensen, Jakob Feldthusen; Nielsen, Thomas Eiland

2011-01-01

Tandem bicycle: In the title reaction double bonds created during ring-closing metathesis isomerize to generate reactive iminium intermediates that undergo intramolecular cyclization reactions with tethered heteroatom and carbon nucleophiles. In this way, a series of biologically interesting hete...... heterocyclic compounds can be made, including a known precursor for the total synthesis of the antiparasitic natural product harmicine....

Radical constructivism: Between realism and solipsism

Science.gov (United States)

Martínez-Delgado, Alberto

2002-11-01

This paper criticizes radical constructivism of the Glasersfeld type, pointing out some contradictions between the declared radical principles and their theoretical and practical development. These contradictions manifest themselves in a frequent oscillation between solipsism and realism, despite constructivist claims to be an anti-realist theory. The paper also points out the contradiction between the relativism of the radical constructivist principles and the constructivist exclusion of other epistemological or educational paradigms. It also disputes the originality and importance of the radical constructivist paradigm, suggesting the idea of an isomorphism between radical constructivist theory and contemplative realism. In addition, some pedagogical and scientific methodological aspects of the radical constructivist model are examined. Although radical constructivism claims to be a rational theory and advocates deductive thinking, it is argued that there is no logical deductive connection between the radical principles of constructivism and the radical constructivist ideas about scientific research and learning. The paper suggests the possibility of an ideological substratum in the construction and hegemonic success of subjective constructivism and, finally, briefly advances an alternative realist model to epistemological and educational radical constructivism.

Quantum control of isomerization by robust navigation in the energy spectrum

Energy Technology Data Exchange (ETDEWEB)

Murgida, G. E., E-mail: murgida@tandar.cnea.gov.ar [Centro Atómico Constituyentes, GIyA, CNEA, San Martín, and Consejo Nacional de Investigaciones Científicas y Técnicas, C1033AAJ Buenos Aires (Argentina); Arranz, F. J., E-mail: fj.arranz@upm.es [Grupo de Sistemas Complejos, Universidad Politécnica de Madrid, 28040 Madrid (Spain); Borondo, F., E-mail: f.borondo@uam.es [Departamento de Química, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Instituto de Ciencias Matemáticas (ICMAT), Cantoblanco, 28049 Madrid (Spain)

2015-12-07

In this paper, we present a detailed study on the application of the quantum control technique of navigation in the energy spectrum to chemical isomerization processes, namely, CN–Li⇆ Li–CN. This technique is based on the controlled time variation of a Hamiltonian parameter, an external uniform electric field in our case. The main result of our work establishes that the navigation involved in the method is robust, in the sense that quite sizable deviations from a pre-established control parameter time profile can be introduced and still get good final results. This is specially relevant thinking of a experimental implementation of the method.

Iron-Mediated Oxidation of Methoxyhydroquinone under Dark Conditions: Kinetic and Mechanistic Insights.

Science.gov (United States)

Yuan, Xiu; Davis, James A; Nico, Peter S

2016-02-16

Despite the biogeochemical significance of the interactions between natural organic matter (NOM) and iron species, considerable uncertainty still remains as to the exact processes contributing to the rates and extents of complexation and redox reactions between these important and complex environmental components. Investigations on the reactivity of low-molecular-weight quinones, which are believed to be key redox active compounds within NOM, toward iron species, could provide considerable insight into the kinetics and mechanisms of reactions involving NOM and iron. In this study, the oxidation of 2-methoxyhydroquinone (MH2Q) by ferric iron (Fe(III)) under dark conditions in the absence and presence of oxygen was investigated within a pH range of 4-6. Although Fe(III) was capable of stoichiometrically oxidizing MH2Q under anaerobic conditions, catalytic oxidation of MH2Q was observed in the presence of O2 due to further cycling between oxygen, semiquinone radicals, and iron species. A detailed kinetic model was developed to describe the predominant mechanisms, which indicated that both the undissociated and monodissociated anions of MH2Q were kinetically active species toward Fe(III) reduction, with the monodissociated anion being the key species accounting for the pH dependence of the oxidation. The generated radical intermediates, namely semiquinone and superoxide, are of great importance in reaction-chain propagation. The kinetic model may provide critical insight into the underlying mechanisms of the thermodynamic and kinetic characteristics of metal-organic interactions and assist in understanding and predicting the factors controlling iron and organic matter transformation and bioavailability in aquatic systems.

Thermal decay of rhodopsin: role of hydrogen bonds in thermal isomerization of 11-cis retinal in the binding site and hydrolysis of protonated Schiff base.

Science.gov (United States)

Liu, Jian; Liu, Monica Yun; Nguyen, Jennifer B; Bhagat, Aditi; Mooney, Victoria; Yan, Elsa C Y

2009-07-01

Although thermal stability of the G protein-coupled receptor rhodopsin is directly related to its extremely low dark noise level and has recently generated considerable interest, the chemistry behind the thermal decay process of rhodopsin has remained unclear. Using UV-vis spectroscopy and HPLC analysis, we have demonstrated that the thermal decay of rhodopsin involves both hydrolysis of the protonated Schiff base and thermal isomerization of 11-cis to all-trans retinal. Examining the unfolding of rhodopsin by circular dichroism spectroscopy and measuring the rate of thermal isomerization of 11-cis retinal in solution, we conclude that the observed thermal isomerization of 11-cis to all-trans retinal happens when 11-cis retinal is in the binding pocket of rhodopsin. Furthermore, we demonstrate that solvent deuterium isotope effects are involved in the thermal decay process by decreasing the rates of thermal isomerization and hydrolysis, suggesting that the rate-determining step of these processes involves breaking hydrogen bonds. These results provide insight into understanding the critical role of an extensive hydrogen-bonding network on stabilizing the inactive state of rhodopsin and contribute to our current understanding of the low dark noise level of rhodopsin, which enables this specialized protein to function as an extremely sensitive biological light detector. Because similar hydrogen-bonding networks have also been suggested by structural analysis of two other GPCRs, beta1 and beta2 adrenergic receptors, our results could reveal a general role of hydrogen bonds in facilitating GPCR function.

Salvage robotic radical prostatectomy

Directory of Open Access Journals (Sweden)

Samuel D Kaffenberger

2014-01-01

Full Text Available Failure of non-surgical primary treatment for localized prostate cancer is a common occurrence, with rates of disease recurrence ranging from 20% to 60%. In a large proportion of patients, disease recurrence is clinically localized and therefore potentially curable. Unfortunately, due to the complex and potentially morbid nature of salvage treatment, radical salvage surgery is uncommonly performed. In an attempt to decrease the morbidity of salvage therapy without sacrificing oncologic efficacy, a number of experienced centers have utilized robotic assistance to perform minimally invasive salvage radical prostatectomy. Herein, we critically evaluate the existing literature on salvage robotic radical prostatectomy with a focus on patient selection, perioperative complications and functional and early oncologic outcomes. These results are compared with contemporary and historical open salvage radical prostatectomy series and supplemented with insights we have gained from our experience with salvage robotic radical prostatectomy. The body of evidence by which conclusions regarding the efficacy and safety of robotic salvage radical prostatectomy can be drawn comprises fewer than 200 patients with limited follow-up. Preliminary results are promising and some outcomes have been favorable when compared with contemporary open salvage prostatectomy series. Advantages of the robotic platform in the performance of salvage radical prostatectomy include decreased blood loss, short length of stay and improved visualization. Greater experience is required to confirm the long-term oncologic efficacy and functional outcomes as well as the generalizability of results achieved at experienced centers.

Muoniated acyl and thioacyl radicals

International Nuclear Information System (INIS)

McKenzie, Iain; Brodovitch, Jean-Claude; Ghandi, Khashayar; Percival, Paul W.

2006-01-01

The product of the reaction of muonium with tert-butylisocyanate was previously assigned as the muoniated tert-butylaminyl radical (I. McKenzie, J.-C. Brodovitch, K. Ghandi, S. Kecman, P. W. Percival, Physica B 326 (2003) 76). This assignment is incorrect since the muon and 14 N hyperfine-coupling constants (hfcc) of this radical would have the opposite sign, which is in conflict with the experimental results. The radical is now reassigned as the muoniated N-tert-butylcarbamoyl radical, based on the similarities between the experimental muon and 14 N hfcc and hfcc calculated at the UB3LYP/6-311G(d,p)//UB3LYP/EPR-III level. The large zero-point energy in the N-Mu bond results in the dissociation barrier of the muoniated N-tert-butylcarbamoyl radical being above the combined energy of the reactants, in contrast to the N-tert-butylcarbamoyl radical where the dissociation barrier lies below the combined energy of the reactants. The reaction of muonium with tert-butylisothiocyanate produced both conformers of the muoniated N-tert-butylthiocarbamoyl radical and their assignment was based on the similarities between the experimental and calculated muon hfcc. These are the first acyl and thioacyl radicals to be directly detected by muon spin spectroscopy

Muoniated acyl and thioacyl radicals

Energy Technology Data Exchange (ETDEWEB)

McKenzie, Iain [TRIUMF and Department of Chemistry, 8888 University Drive, Simon Fraser University, Burnaby B.C., V5A 1S6 (Canada); Brodovitch, Jean-Claude [TRIUMF and Department of Chemistry, 8888 University Drive, Simon Fraser University, Burnaby B.C., V5A 1S6 (Canada); Ghandi, Khashayar [TRIUMF and Department of Chemistry, 8888 University Drive, Simon Fraser University, Burnaby B.C., V5A 1S6 (Canada); Percival, Paul W. [TRIUMF and Department of Chemistry, 8888 University Drive, Simon Fraser University, Burnaby B.C., V5A 1S6 (Canada)]. E-mail: percival@sfu.ca

2006-03-31

The product of the reaction of muonium with tert-butylisocyanate was previously assigned as the muoniated tert-butylaminyl radical (I. McKenzie, J.-C. Brodovitch, K. Ghandi, S. Kecman, P. W. Percival, Physica B 326 (2003) 76). This assignment is incorrect since the muon and {sup 14}N hyperfine-coupling constants (hfcc) of this radical would have the opposite sign, which is in conflict with the experimental results. The radical is now reassigned as the muoniated N-tert-butylcarbamoyl radical, based on the similarities between the experimental muon and {sup 14}N hfcc and hfcc calculated at the UB3LYP/6-311G(d,p)//UB3LYP/EPR-III level. The large zero-point energy in the N-Mu bond results in the dissociation barrier of the muoniated N-tert-butylcarbamoyl radical being above the combined energy of the reactants, in contrast to the N-tert-butylcarbamoyl radical where the dissociation barrier lies below the combined energy of the reactants. The reaction of muonium with tert-butylisothiocyanate produced both conformers of the muoniated N-tert-butylthiocarbamoyl radical and their assignment was based on the similarities between the experimental and calculated muon hfcc. These are the first acyl and thioacyl radicals to be directly detected by muon spin spectroscopy.

Isomeric and high-spin states of 94Tc and the search for yrast isomers near Napprox.50

International Nuclear Information System (INIS)

Lee, I.Y.; Johnson, N.R.; McGowan, F.K.; Young, G.R.; Guidry, M.W.; Yates, S.W.

1981-01-01

A search for isomers in the Napprox.50 region has produced no evidence of high-spin yrast isomerism. A new 4.5-ns low-multiplicity isomer has been identified and assigned to 94 Tc, while the yrast sequence of 94 Tc has been established to more than 5 MeV in excitation energy

Valence isomerization of 2-phospha-4-silabicyclo[1.1.0]butane: a high-level ab initio study

NARCIS (Netherlands)

Slootweg, J.C.; Ehlers, A.W.; Lammertsma, K.

2006-01-01

The rearrangements for 2-phospha-4-silabicyclo[1.1.0]butane, analogous to the valence isomerization of the hydrocarbons bicyclobutane, 1,3-butadiene, and cyclobutene, were studied at the (U)QCISD(T)/ 6-311+G**//(U)QCISD/6-31G* level of theory. The monocyclic 1,2-dihydro-1,2-phosphasiletes are shown

Muonium and muonic radicals

International Nuclear Information System (INIS)

Burkhard, P.; Fischer, H.; Roduner, E.; Strub, W.; Geeson, D.; Symons, M.C.R.

1985-01-01

An energetic positive muon which is injected in a liquid sample of substrate molecules (S) creates an ionization track consisting of substrate cations (S + ) and electrons. Near the end of this track the muon may combine with an electron to form muonium (Mu) which is observable in inert liquids, but which reacts by addition to form a radical. Alternatively, the electron can add to S to form S - , which then combines with the muon to form the radical. Furthermore, instead of ending up in Mu or in a radical the muon may stay in a diamagnetic environment as a solvated muon, or as a muon substituting a proton in a molecule. Of interest in these schemes are the mechanisms and rates of formation of muonated radicals and in particular the rate constants for their reactions to products. Investigations are based on the observation of Mu and the radical by means of the μSR technique in transverse magnetic fields. (Auth.)

Leghemoglobin-derived radicals. Evidence for multiple protein-derived radicals and the initiation of peribacteroid membrane damage

DEFF Research Database (Denmark)

Moreau, S; Davies, Michael Jonathan; Mathieu, C

1996-01-01

, with the consequent generation of lipid-derived radicals. The formation of such radicals may result in the depletion of membrane antioxidants and the initiation of lipid peroxidation. This transfer of damage from the heme center via the protein surface to neighboring membranes may be of considerable biological......-derived phenoxyl radical present at Tyr-133 in the soybean protein and Tyr-138 in the lupin protein. To obtain further information on these protein radicals and their potential interaction with the physiologically important peribacteroid membrane (which surrounds the microsymbiont in vivo), EPR spin trapping......); these radicals may be side chain- or alpha-carbon-derived, their exact sites have not been determined. Some of these radicals are on the protein surface and may be key intermediates in the formation of protein dimers. These radicals have been shown to be capable of reacting with peribacteroid membrane fractions...

Studies of radiation-produced radicals and radical ions. Progress report, June 1, 1981-August 31, 1982

International Nuclear Information System (INIS)

Williams, T.F.

1982-01-01

The discovery and characterization of novel radical ions produced by the γ irradiation of solids continues to be a fertile field for investigation. This Progress Report describes the generation and ESR identification of several new paramagnetic species, some of which have long been sought as important intermediates in radiation chemistry. We have also contributed to a general theoretical problem in ESR spectroscopy. Solid-state studies of electron attachment reactions, both non-dissociative and dissociative, reveal interesting structural and chemical information about the molecular nature of these processes for simple compounds. In particular, ESR measurements of the spin distribution in the products allow a fairly sharp distinction to be drawn between radical anions and radical-anion pairs or adducts. Dimer radical anion formation can also take place but the crystal structure plays a role in this process, as expected. Some radical anions undergo photolysis to give radical-anion pairs which may then revert back to the original radical anion by a thermal reaction. The chemistry of these reversible processes is made more intricate by a competing reaction in which the radical abstracts a hydrogen atom from a neighboring molecule. However, the unraveling of this complication has also served to extend our knowledge of the role of quantum tunneling in chemical reactions. The results of this investigation testify to the potential of solid-state techniques for the study of novel and frangible radical ions. Progress in this field shows no sign of abating, as witness the recent discovery of perfluorocycloalkane radical anions and alkane radical cations

β decay and isomeric properties of neutron-rich Ca and Sc isotopes

International Nuclear Information System (INIS)

Crawford, H. L.; Mantica, P. F.; Berryman, J. S.; Stoker, J. B.; Janssens, R. V. F.; Carpenter, M. P.; Kay, B. P.; Lauritsen, T.; Zhu, S.; Broda, R.; Cieplicka, N.; Fornal, B.; Grinyer, G. F.; Minamisono, K.; Hoteling, N.; Stefanescu, I.; Walters, W. B.

2010-01-01

The isomeric and β-decay properties of neutron-rich 53-57 Sc and 53,54 Ca nuclei near neutron number N=32 are reported, and the low-energy level schemes of 53,54,56 Sc and 53-57 Ti are presented. The low-energy level structures of the 21 Sc isotopes are discussed in terms of the coupling of the valence 1f 7/2 proton to states in the corresponding 20 Ca cores. Implications with respect to the robustness of the N=32 subshell closure are discussed, as well as the repercussions for a possible N=34 subshell closure.

Muonium-containing vinyl radicals

International Nuclear Information System (INIS)

Rhodes, C.J.; Symons, M.C.R.; Roduner, E.; Heming, M.

1987-01-01

Exposure of trimethylsilylacetylene and bis(trimethylsilyl)acetylene to positive muons gave radicals whose muon-electron hyperfine coupling constants establish that the corresponding vinyl radicals were formed. (author)

Radicals in arithmetic

NARCIS (Netherlands)

W.J. Palenstijn (Willem Jan)

2014-01-01

htmlabstractLet K be a field. A radical is an element of the algebraic closure of K of which a power is contained in K. In this thesis we develop a method for determining what we call entanglement. This describes unexpected additive relations between radicals, and is encoded in an entanglement

Isomerization of butene-1 on rare earth oxides. [Rare earths: La, Nd, Dy

Energy Technology Data Exchange (ETDEWEB)

Khodakov, Yu S; Nesterov, V K; Minachev, Kh M [AN SSSR, Moscow. Inst. Organicheskoj Khimii

1975-09-01

A study has been made into the isomerization of butene-1 on oxides of rare-earth elements. The dependence of the reaction rate at 20/sup 0/C on the baking temperature of La and Nd oxides have the maximum at 700/sup 0/C. A decrease in the activity of these oxides after bakinq at 800/sup 0/C is observed, as well as during experiments at -30 deq C. In the case of Dy/sub 2/O/sub 3/, the activity at 20/sup 0/C increases gradually with Tsub(bak)=500 to 800/sup 0/C Zeolite 0.57LaNaY exhibits maximum activity at Tsub(bak)=500/sup 0/C Similar data as to the effect of the baking temperature on the catalyst activity were obtained earlier for hydrogenation of ethylene. According to their maximum activity, oxides of rare-earth elements, in the isomerization as well as hydrogenation reactions, can be arranged as follows: La/sub 2/O/sub 3/>Nd/sub 2/O/sub 3/

In vitro metabolism of nitric oxide-donating aspirin: the effect of positional isomerism.

Science.gov (United States)

Gao, Jianjun; Kashfi, Khosrow; Rigas, Basil

2005-03-01

NO-donating aspirin (NO-ASA) is a potentially important chemopreventive agent against cancer. Since positional isomerism affects strongly its potency in inhibiting colon cancer cell growth, we studied the metabolic transformations of its ortho-, meta-, and para-isomers in rat liver and colon cytosolic, microsomal, and mitochondrial fractions as well as in intact HT-29 human colon cancer cells. NO-ASA and metabolites were determined by high-performance liquid chromatography and products identified by mass spectroscopy, as required. For all three isomers, the acetyl group on the ASA moiety was hydrolyzed rapidly. This was followed by hydrolysis of the ester bond linking the salicylate anion to the spacer. The ortho- and para-isomers produced salicylic acid and a putative intermediate consisting of the remainder of the molecule, which via a rapid step generated nitrate, (hydroxymethyl)phenol, and a conjugate of spacer with glutathione. The meta-isomer, in contrast, generated salicylic acid and (nitroxymethyl)phenol, the latter leading to (hydroxymethyl)phenol and the glutathione-spacer conjugate. This metabolic pathway takes place in its entirety only in the cytosolic fraction of the tissues tested and in intact human colon cancer cells, perhaps reflecting exposure to the cytosolic glutathione S-transferase, which catalyzes the formation of the spacer-glutathione conjugate. Thus, the three positional isomers of NO-ASA differ in their metabolism and these differences correlate with their differential effects on cancer cell growth, underscoring the importance of positional isomerism in modulating drug effects.

Multiple free-radical scavenging capacity in serum

Science.gov (United States)

Oowada, Shigeru; Endo, Nobuyuki; Kameya, Hiromi; Shimmei, Masashi; Kotake, Yashige

2012-01-01

We have developed a method to determine serum scavenging-capacity profile against multiple free radical species, namely hydroxyl radical, superoxide radical, alkoxyl radical, alkylperoxyl radical, alkyl radical, and singlet oxygen. This method was applied to a cohort of chronic kidney disease patients. Each free radical species was produced with a common experimental procedure; i.e., uv/visible-light photolysis of free-radical precursor/sensitizer. The decrease in free-radical concentration by the presence of serum was quantified with electron spin resonance spin trapping method, from which the scavenging capacity was calculated. There was a significant capacity change in the disease group (n = 45) as compared with the healthy control group (n = 30). The percent values of disease’s scavenging capacity with respect to control group indicated statistically significant differences in all free-radical species except alkylperoxyl radical, i.e., hydroxyl radical, 73 ± 12% (p = 0.001); superoxide radical, 158 ± 50% (p = 0.001); alkoxyl radical, 121 ± 30% (p = 0.005); alkylperoxyl radical, 123 ± 32% (p>0.1); alkyl radical, 26 ± 14% (p = 0.001); and singlet oxygen, 57 ± 18% (p = 0.001). The scavenging capacity profile was illustrated using a radar chart, clearly demonstrating the characteristic change in the disease group. Although the cause of the scavenging capacity change by the disease state is not completely understood, the profile of multiple radical scavenging capacities may become a useful diagnostic tool. PMID:22962529

Preoperative radiochemotherapy and radical surgery in comparison with radical surgery alone

International Nuclear Information System (INIS)

Mohr, C.; Schettler, D.; Bohndorf, W.

1994-01-01

A multicentric, randomized study of squamous cell carcinoma (SCC) of the oral cavity and the oropharynx has been undertaken by DOeSAK. The results after radical surgery alone have been compared with the results of combined preoperative radiochemotherapy followed by radical surgery. Patients with primary (biopsy proven) SCC of the oral cavity or the oropharynx with tumor nodes metastasis (TNM) stages T2-4, N0-3, M0 were included in the study. A total of 141 patients were treated by radical surgery alone, whereas 127 patients were treated by radical surgery preceded by preoperative radiochemotherapy. The pre-operative treatment consisted of conventionally fractioned irradiation on the primary and the regional lymph nodes with a total dose of 36 Gy (5 x 2 Gy per week) and low-dose cisplatin chemotherapy with 5 x 12.5 mg cisplatin per m 2 of body surface during the first week of treatment. Radical surgery according to be DOeSAK definitions (DOeSAK, 1982) was performed after a delay of 10-14 days. During the follow-up period, 28.2% of all patients suffered from locoregional recurrence, and 27.2% of the patients died. The percentages were higher after radical surgery alone for locoregional recurrence (31% and 15.6%) and for death (28% and 18.6%). The life-table analysis showed improved survival rates of 4.5% after 1 year and 8.3% after 2 years in the group of patients treated with combined therapy. The demonstrated improvement appeared to be significant with the Gehan-Wilcoxon test as well as with the log rank test below a P value of 5%. (au) (29 refs.)

Radicals in arithmetic

NARCIS (Netherlands)

Palenstijn, Willem Jan

2014-01-01

Let K be a field. A radical is an element of the algebraic closure of K of which a power is contained in K. In this thesis we develop a method for determining what we call entanglement. This describes unexpected additive relations between radicals, and is encoded in an entanglement group. We give

Radicalization as a Vector: Exploring Non-Violent and Benevolent Processes of Radicalization.

Directory of Open Access Journals (Sweden)

Ken Reidy

2018-03-01

Full Text Available Successful radicalization posits three outcomes: extremism, terrorism or both. As these are undesirable, radicalization is understood as wholly malevolent and governments work to prevent and/or stop it. Nonetheless, a handful of scholars have recognized that the same radicalization process which results in either outcome may, theoretically at least, also have beneficial outcomes such as environmental awareness or human rights. This article explores one such outcome. Based on interviews with British Muslim aid workers (n=6 operating in Jihadist conflict zones post Arab spring and using constructivist grounded theory, it illustrates how the research participants radicalized to humanitarianism which resulted in them assisting the most plighted of Muslims by deploying to the most wanton of areas: ones commonly referred to as Jihadist conflict zones. Evidently, these destinations are shared with Jihadists and given the array of other observable similarities (socio-demographics and [pre-]mobilization behaviours, these morally opposed groups become conflated by the security services. This is further compounded by the fact that Jihadists manipulate and/or impersonate aid workers so as to funnel people and funds. To distinguish both, this article documents the benevolent pathway of the research participants and juxtaposes it to scholarly knowledge on Jihadist pathways. Socialization was revealed to be the key distinguishing feature rather than descriptive risk factors (such as ideology or moral outrage because the process of radicalization was not found to be the start of the radicalized pathway. It concludes that benevolently radicalized Islamic groups constitute an effective means of pathway divergence for particular typologies by offering an attractive and prosocial alternative to Jihadism. This strengths-based preventative approach (“what’s right” takes the form of a community-centric market competitor to Jihadism rather than a problem

Isotope exchange study of nickel xanthate in presence of aniline and isomeric toluidines

International Nuclear Information System (INIS)

Naidu, G.R.K.; Naidu, P.R.

1982-01-01

Isotopic exchange behaviour of nickel xanthate is studied in the presence of aniline and three isomeric toluidines at 18degC. The effect of base concentration is also studied on the exchange rate. The results show that the complex is labile in the kinetic sense in the presence of aniline meta and para toluidines. The rate of exchange increases with and para toluidines. The rate of exchange increases with increase in concentration of the base. The complex displays inert behaviour in the presence of o-toluidine and it is ascribed to dominant steric effect. (author)

Radical cations of quadricyclane and norbornadiene in polar ZSM-5 matrices: Radical cation photochemical transformations without photons

International Nuclear Information System (INIS)

Barnabas, M.V.; Trifunac, A.D.

1994-01-01

Radical cations of quadricyclane (Q) and norbornadiene (NBD) are produced by γ-radiolysis in zeolites. In polar ZSM-5, only one radical cation is initially observed below 100K. Increasing the temperature above 200K gives rise to the cyclopentadiene radical cation. Higher temperatures (>360K) give rise to the cyclopenten-4-yl radical. The observation of cyclopentadiene radical cation implies the occurrence of the reverse Diels-Alder reaction. This is a thermally forbidden, photochemically allowed, process, which is made possible by the interaction of the polar zeolite matrix sites with parent NBD and Q radical cations

An Insight into Flotation Chemistry of Pyrite with Isomeric Xanthates: A Combined Experimental and Computational Study

Directory of Open Access Journals (Sweden)

Guihong Han

2018-04-01

Full Text Available The flotation chemistry between pyrite and isomeric xanthates (butyl xanthate and isobutyl xanthate was investigated by means of adsorption experiments, surface tension tests, and molecular dynamic simulations in this work. The flotation chemical results were confirmed and further interpreted by quantum chemical calculations. The experiment results demonstrated that the isobutyl xanthate exhibited superior adsorption capacity and surface activity than those of butyl xanthate in flotation chemistry. In addition, molecular dynamic simulations were simultaneously performed in constant number, constant volume and temperature (NVT, and constant number, constant volume, and pressure (NPT ensemble, indicating that the NPT ensemble was more suitable to the flotation system and the isobutyl xanthate was easier to be adsorbed on pyrite surface compared with butyl xanthate during an appropriate range of concentrations. Furthermore, the quantum chemical calculations elucidated that the isobutyl xanthate presented higher reactivity than that of the corresponding butyl xanthate based on the frontier molecular orbital theory of chemical reactivity, which was consistent with experimental and simulation results obtained. This work can provide theoretical guidance for an in-depth study of the flotation chemistry of pyrite with isomeric xanthates.

Study of the photochemical isomerization of ergosterol

International Nuclear Information System (INIS)

Mermet-Bouvier, Rene

1972-01-01

The photochemical reaction scheme of Ergosterol-Vitamin D 2 was studied. The schemes proposed in published literature are described together with earlier methods used for the analysis and determination. The method used is then discussed. In the first part, the factors concerning the changes occurring in molecular systems exposed to radiation, and the formalism used, are examined. Investigations of linear molecular systems and their applications to the reaction scheme of Ergosterol-Vitamin D 2 are discussed. The properties which enable the last three reaction schemes proposed in the literature to be distinguished are described. In the second part, the experimental analytical methods and the determinations made of the different isomers formed are presented. Chromatographic techniques (thin films, columns, gaseous phase) suitable for separating the various isomeric species are used. The existence of 8 isomers was established as well as a transformation occurring in one of them. The ultraviolet and infrared spectra were obtained. A reaction scheme is proposed (in which all the quantum yield values are given) from comparisons between the calculated and experimental values of the eigenvalue of the absolute minimum value λ m and the eigenvector corresponding to V m . (author) [fr

Measurements of 14-MeV neutron cross-sections for the production of isomeric states in hafnium isotopes

International Nuclear Information System (INIS)

Patrick, B.H.; Sowerby, M.G.; Wilkins, C.G.; Russen, L.C.

1990-01-01

The cross sections for the production of isomeric states in the reactions 179 Hf(n,2n) 178m2 Hf, 180 Hf(n,2n) 179m2 Hf, 179 Hf(n,n') 179m2 Hf with 14 MeV neutrons have been measured and compared with the theoretical ones. 4 refs, 3 figs, 4 tabs

Behavior of the excited deformed band and search for shape isomerism in 184Hg

International Nuclear Information System (INIS)

Cole, J.D.; Hamilton, J.H.; Ramayya, A.V.; Nettles, W.G.; Kawakami, H.; Spejewski, E.H.; Ijaz, M.A.; Toth, K.S.; Robinson, E.L.; Sastry, K.S.R.; Lin, J.; Avignone, F.T.; Brantley, W.H.; Rao, P.V.G.

1976-01-01

The new isotope 184 Tl has been identified with T 1 / 2 =11 +- 1 sec and the levels in 184 Hg investigated from its decay. The 0 + band head of a deformed band was found to drop to 375 keV in agreement with theoretical predictions. The mean life of the 375-keV 0 + level was measured to be 0.9 +- 0.3 nsec which is a factor of 10 faster than theoretically predicted for a shape-isomeric E2 transition

Youth De-Radicalization: A Canadian Framework

Directory of Open Access Journals (Sweden)

Hafal (Haval Ahmad

2017-09-01

Full Text Available Youth radicalization leading to violence has become a growing fear among Canadians, as terrorist attacks are carried out in Western states. Although Canada has suffered relatively fewer acts of violence, this fear has intensified and a de-radicalization strategy is needed in the Canadian context. In a qualitative case study methodology, interviews were conducted with school counsellors, religious leaders, and academics to explore solutions to youth radicalization. Youth de-radicalization approaches from the United Kingdom were analyzed and found that community-based initiatives were missing from programming. Social identity theory is used to explain that youth join radicalized groups to feel a sense of belonging and have to be provided an alternative and moderate group identity to de-radicalize. This study found youth de-radicalization in Canada is best served through a community collaboration approach.

The Wolff rearrangement in radical cations

International Nuclear Information System (INIS)

Ohashi, Mamoru; Tsujimoto, Kazuo; Shida, Yasuo; Yamada, Yasuji.

1975-01-01

The mass spectrometric behavior of 1-phenyl-4,5,6,7-tetrahydrobenzotriazole and its seven membered analog is described. The principal fragmentation process of the molecular ions is loss of nitrogen. It was concluded from the results of deuterium labeling and accurate mass measurements that the subsequent fragmentation of the M-N 2 ions proceeds via isomerization to the ring-contracted ketenimine ions by the Wolff rearrangement, in sharp contrast to the case of 1-phenylbenzotriazole. (auth.)

Peroxyl radical reactions with carotenoids in microemulsions: Influence of microemulsion composition and the nature of peroxyl radical precursor.

Science.gov (United States)

El-Agamey, Ali; McGarvey, David J

2016-01-01

The reactions of acetylperoxyl radicals with different carotenoids (7,7'-dihydro-β-carotene and ζ-carotene) in SDS and CTAC microemulsions of different compositions were investigated using laser flash photolysis (LFP) coupled with kinetic absorption spectroscopy. The primary objective of this study was to explore the influence of microemulsion composition and the type of surfactant used on the yields and kinetics of various transients formed from the reaction of acetylperoxyl radicals with carotenoids. Also, the influence of the site (hydrocarbon phases or aqueous phase) of generation of the peroxyl radical precursor was examined by using 4-acetyl-4-phenylpiperidine hydrochloride (APPHCl) and 1,1-diphenylacetone (11DPA) as water-soluble and lipid-soluble peroxyl radical precursors, respectively. LFP of peroxyl radical precursors with 7,7'-dihydro-β-carotene (77DH) in different microemulsions gives rise to the formation of three distinct transients namely addition radical (λmax=460 nm), near infrared transient1 (NIR, λmax=700 nm) and 7,7'-dihydro-β-carotene radical cation (77DH(•+), λmax=770 nm). In addition, for ζ-carotene (ZETA) two transients (near infrared transient1 (NIR1, λmax=660 nm) and ζ-carotene radical cation (ZETA(•+), λmax=730-740 nm)) are generated following LFP of peroxyl radical precursors in the presence of ζ-carotene (ZETA) in different microemulsions. The results show that the composition of the microemulsion strongly influences the observed yield and kinetics of the transients formed from the reactions of peroxyl radicals (acetylperoxyl radicals) with carotenoids (77DH and ZETA). Also, the type of surfactant used in the microemulsions influences the yield of the transients formed. The dependence of the transient yields and kinetics on microemulsion composition (or the type of surfactant used in the microemulsion) can be attributed to the change of the polarity of the microenvironment of the carotenoid. Furthermore, the nature of

Glutathione as a radical scavenger and the biological consequences of thiyl radical production

International Nuclear Information System (INIS)

Winterbourn, C.C.

1996-01-01

A large number of compounds that have toxic effects can be metabolised to free radicals and secondary reactive oxygen species. These may be directly damaging or affect cell function by altering regulatory mechanisms through changing redox status. Protection is provided by an integrated system of antioxidant defenses. This includes reduced glutathione (GSH), one of the functions of which is as a free radical scavenger. For GSH to be an effective radical scavenging antioxidant, therefore, it must act in concert with superoxide dismutase to remove the superoxide so generated. Superoxide is produced in a variety of metabolic processes. It is also a secondary product of radicals reacting with oxygen either directly or through GSH. The biological reactivity of superoxide has been the subject of much debate ever since the discovery of superoxide dismutase in 1968. It has more recently become apparent that its rapid reaction with nitric oxide to give peroxynitrite, and its ability to reversibly oxidise and inactivate iron sulphur enzymes, contribute to the toxicity of superoxide. Another mechanism that could be important involves addition reactions of superoxide with other radicals to give organic peroxides. This reaction, to form a tyrosine peroxide, has come to authors attention through the study of the scavenging of tyrosyl radicals by GSH. It is also shown that a tyrosine peroxide is a major product of the oxidation of tyrosine by neutrophils

Taking a radical position: Evidence for position specific radical representations in Chinese character recognition using masked priming ERP

Directory of Open Access Journals (Sweden)

I-Fan eSu

2012-09-01

Full Text Available In the investigation of orthographic representation of Chinese characters, one question that has stimulated much research is whether radicals (character components are specified for spatial position in a character (e.g. Ding, Peng, & Taft, 2004; Tsang & Chen, 2009. Differing from previous work, component or radical position information in this study is conceived in terms of relative frequency across different positions of characters containing it. A lexical decision task in a masked priming paradigm focusing on radicals with preferred position of occurrence was conducted. A radical position that encompasses more characters than other positions was identified to be the preferred position of a particular radical. The prime that was exposed for 96ms might share a radical with the target in the same or different positions. Moreover, the shared radical appeared either in its preferred or non-preferred position in the target. While response latencies only revealed the effect of graphical similarity, both effects of graphical similarity and radical position preference were found in the ERP results. The former effect was reflected in greater positivity in occipital P1 and greater negativity in N400 for radicals in different positions in prime and target characters. The latter effect manifested as greater negativity in occipital N170 and greater positivity in frontal P200 in the same time window elicited by radicals in their non-preferred position. Equally interesting was the reversal of the effect of radical position preference in N400 with greater negativity associated with radicals in preferred position. These findings identify the early ERP components associated with activation of position-specific radical representations in the orthographic lexicon, and reveal the change in the nature of competition from processing at the radical level to the lexical level.

Radical production in biological systems

International Nuclear Information System (INIS)

Johnson, J.R.; Akabani, G.

1994-10-01

This paper describes our effort to develop a metric for radiation exposure that is more fundamental than adsorbed dose and upon which a metric for exposure to chemicals could be based. This metric is based on the production of radicals by the two agents. Radicals produced by radiation in biological systems commonly assumed to be the same as those produced in water despite the presence of a variety of complex molecules. This may explain why the extensive efforts to describe the relationship between energy deposition (track structure) and molecular damage to DNA, based on the spectrum of radicals produced, have not been successful in explaining simple biological effects such as cell killing. Current models assume that DNA and its basic elements are immersed in water-like media and only model the production and diffusion of water-based radicals and their interaction with DNA structures; these models lack the cross sections associated with each macro-component of DNA and only treat water-based radicals. It has been found that such models are not realistic because DNA is not immersed in pure water. A computer code capable of simulating electron tracks, low-energy electrons, energy deposition in small molecules, and radical production and diffusion in water like media has been developed. This code is still in at a primitive stage and development is continuing. It is being used to study radical production by radiation, and radical diffusion and interactions in simple molecular systems following their production. We are extending the code to radical production by chemicals to complement our PBPK modeling efforts. It therefore has been developed primarily for use with radionuclides that are in biological materials, and not for radiation fields

Half-lives of ground and isomeric states in {sup 97}Cd and the astrophysical origin of {sup 96}Ru

Energy Technology Data Exchange (ETDEWEB)

Lorusso, G., E-mail: lorusso@ribf.riken.j [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824 (United States); Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Becerril, A.; Amthor, A. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824 (United States); Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Baumann, T.; Bazin, D. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Berryman, J.S. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Department of Chemistry, Michigan State University, East Lansing, MI 48824 (United States); Brown, B.A. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824 (United States); Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Cyburt, R.H. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824 (United States); Crawford, H.L. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Department of Chemistry, Michigan State University, East Lansing, MI 48824 (United States)

2011-05-09

First experimental evidence for a high-spin isomer (25/2{sup +}) in {sup 97}Cd, a waiting point in the astrophysical rapid proton capture process, is presented. The data were obtained in {beta}-decay studies at NSCL using the new RF Fragment Separator system and detecting {beta}-delayed protons and {beta}-delayed {gamma} rays. Decays from ground and isomeric states were disentangled, and proton emission branches were determined for the first time. We find half-lives of 1.10(8) s and 3.8(2) s, and {beta}-delayed proton emission branches of 12(2)% and 25(4)% were deduced for the ground and isomeric states, respectively. With these results, the nuclear data needed to determine an rp-process contribution to the unknown origin of solar {sup 96}Ru are in place. When the new data are included in astrophysical rp-process calculations, one finds that an rp-process origin of {sup 96}Ru is unlikely.

Along the N=126 closed shell: study of $^{205}$Au through its $\\pi h_{11/2}^{-1}$ isomeric decay

CERN Multimedia

2002-01-01

Excited states have been identified in only three of the N=126 closed shell nuclei 'below' $^{208}$Pb, $^{207}$Tl, $^{206}$Hg and very recently $^{204}$Pt. We aim to extend our knowledge of the neutron-rich N=126 nuclei by observing the internal decay of the $\\pi h^{-1}_{11/2}$ excited state in $^{205}$Au, which is expected to be isomeric. In addition, the decay of the analogous states in the N=122 and N=124 $^{201,203}$Au will be studied. The lifetimes of the expected isomeric states are crucial for the success of the experiment, and they are estimated to be in the range of 0.3-20 s. These are long enough to enable the extraction from the source, but shorter than the $\\beta$-decay half-lives. Proton single-particle energies and transition rates will be extracted, providing information about the robustness of the N=126 shell-closure. Three days of beam-time is requested.

Chemical repair of trypsin-histidinyl radical

International Nuclear Information System (INIS)

Jovanovic, S.V.; Ruvarac, I.; Jankovic, I.; Josimovic, L.

1991-01-01

Oxyl radicals, such as hydroxyl, alkoxyl and peroxyl, react with biomolecules to produce bioradicals. Unless chemically repaired by suitable antioxidants, these bioradicals form stable products. This leads to loss of biological function of parent biomolecules with deleterious biological results, such as mutagenesis and cancer. Consequently, the understanding of the mechanisms of oxyl radical damage to biomolecules and chemical repair of such damage is crucial for the development of strategies for anticarcinogenesis and radioprotection. In this study the chemical repair of the histidinyl radical generated upon the trichloromethylperoxyl radical reaction with trypsin vas investigated by gamma radiolysis. The trypsin histidinyl radical is a resonance-stabilized heterocyclic free radical which was found to be unreactive with oxygen. The efficacy of the chemical repair of the trypsin-histidinyl radical by endogenous antioxidants which are electron donors (e.g. 5-hydroxytryptophan, uric acid) is compared to that of antioxidants which are H-atom donors (e. g. glutathione). 9 refs., 2 figs., 1 tab

Gnosticism and Radical Feminism

DEFF Research Database (Denmark)

Cahana, Jonathan

2016-01-01

and radical feminism would easily fall under this definition. There is, however, one major difference: since radical feminism is a relatively recent phenomenon which also benefited from modern modes of text production and preservation, almost all of the sources are still with us. This, in turn, may allow us...... to use radical feminism to make certain aspects of ancient Gnosticism re-emerge from their long submersion, provided that enough similarities can be independently drawn between the two phenomena to merit such a comparison. This paper therefore presents a comparison between concepts and positions...

Radical's view of sciences

International Nuclear Information System (INIS)

Mittal, J.P.

2004-01-01

Full text: General concept in radiation biology is that free radicals are highly reactive and they can damage vital cellular molecules leading to injurious effects. However, in this talk, evidence will be presented through the techniques of electron paramagnetic resonance ( EPR ) and pulse radiolysis that free radicals can be highly selective in their reaction with the target molecules. In addition, attempts will be made to present a brief account of emerging scenario of free radical generation, identification and their involvement in radiation damage mechanisms in chemical and biological systems

Metallocene-catalyzed ethylene−α-olefin isomeric copolymerization: A perspective from hydrodynamic boundary layer mass transfer and design of MAO anion

KAUST Repository

Adamu, Sagir; Atiqullah, Muhammad; Malaibari, Zuhair O.; Al-Harthi, Mamdouh A.; Emwas, Abdul-Hamid M.; Ul-Hamid, Anwar

2015-01-01

-catalyzed ethylene polymerization. This approach was illustrated by conducting homo- and isomeric copolymerization of ethylene with 1-hexene and 4-methyl-1-pentene in the presence of bis(n-butylcyclopentadienyl) zirconium dichloride (nBuCp)2ZrCl2, using (i) MAO anion

Reduced dimension rovibrational variational calculations of the S{sub 1} state of C{sub 2}H{sub 2}. II. The S{sub 1} rovibrational manifold and the effects of isomerization

Energy Technology Data Exchange (ETDEWEB)

Changala, P. Bryan, E-mail: bryan.changala@colorado.edu; Baraban, Joshua H.; Field, Robert W. [Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Stanton, John F. [Department of Chemistry and Biochemistry, Institute for Theoretical Chemistry, The University of Texas at Austin, Austin, Texas 78712 (United States); Merer, Anthony J. [Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan and Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1 (Canada)

2014-01-14

Reduced dimension variational calculations have been performed for the rovibrational level structure of the S{sub 1} state of acetylene. The state exhibits an unusually complicated level structure, for various reasons. First, the potential energy surface has two accessible conformers, trans and cis. The cis conformer lies about 2700 cm{sup −1} above the trans, and the barrier to cis-trans isomerization lies about 5000 cm{sup −1} above the trans minimum. The trans vibrations ν{sub 4} (torsion) and ν{sub 6} (asym. bend) interact very strongly by Darling-Dennison and Coriolis resonances, such that their combination levels and overtones form polyads with unexpected structures. Both conformers exhibit very large x{sub 36} cross-anharmonicity since the pathway to isomerization is a combination of ν{sub 6} and ν{sub 3} (sym. bend). Near the isomerization barrier, the vibrational levels show an even-odd K-staggering of their rotational levels as a result of quantum mechanical tunneling through the barrier. The present calculations address all of these complications, and reproduce the observed K-structures of the bending and C–C stretching levels with good qualitative accuracy. It is expected that they will assist with the assignment of the irregular patterns near the isomerization barrier.

EPR spin trapping of protein radicals

DEFF Research Database (Denmark)

Davies, Michael Jonathan; Hawkins, Clare Louise

2004-01-01

Electron paramagnetic resonance (EPR) spin trapping was originally developed to aid the detection of low-molecular-mass radicals formed in chemical systems. It has subsequently found widespread use in biology and medicine for the direct detection of radical species formed during oxidative stress...... tumbling radicals are often broad and relatively poor in distinctive features, a number of techniques have been developed that allow a wealth of information to be obtained about the nature, site, and reactions of such radicals. This article summarizes recent developments in this area and reviews selected...... examples of radical formation on proteins....

Fragmentation characteristics of the unstable [CH3 CO][radical sign] radicals generated by neutralization of [CH3CO]+ cations

Science.gov (United States)

Hop, C. E. C. A.; Holmes, J. L.

1991-03-01

The stability and fragmentation characteristics of [CH3 CO][radical sign] radicals, generated by vertical charge exchange between acetyl cations and permanent gases or metal vapours (He, Xe, NO, Cd, Na and K), were examined mass spectrometrically. Two dissociation reactions were observed, the losses of CH[radical sign]3 and H[radical sign]. The H[radical sign] loss reaction, the higher energy dissociation, became of greater importance as the exothermicity of the charge exchange was increased. Based on the analysis of the kinetic energy releases it was concluded that these decompositions arose from the population of two excited states of the [CH3 CO][radical sign] radical.

Metal-Diazo Radicals of α-Carbonyl Diazomethanes

Science.gov (United States)

Li, Feifei; Xiao, Longqiang; Liu, Lijian

2016-03-01

Metal-diazo radicals of α-carbonyl diazomethanes are new members of the radical family and are precursors to metal-carbene radicals. Herein, using electron paramagnetic resonance spectroscopy with spin-trapping, we detect diazo radicals of α-carbonyl diazomethanes, induced by [RhICl(cod)]2, [CoII(por)] and PdCl2, at room temperature. The unique quintet signal of the Rh-diazo radical was observed in measurements of α-carbonyl diazomethane adducts of [RhICl(cod)]2 in the presence of 5,5-dimethyl-pyrroline-1-N-oxide (DMPO). DFT calculations indicated that 97.2% of spin density is localized on the diazo moiety. Co- and Pd-diazo radicals are EPR silent but were captured by DMPO to form spin adducts of DMPO-N• (triplet-of-sextets signal). The spin-trapping also provides a powerful tool for detection of metal-carbene radicals, as evidenced by the DMPO-trapped carbene radicals (DMPO-C•, sextet signal) and 2-methyl-2-nitrosopropane-carbene adducts (MNP-C•, doublet-of-triplets signal). The transformation of α-carbonyl diazomethanes to metal-carbene radicals was confirmed to be a two-step process via metal-diazo radicals.

Reaction between protein radicals and other biomolecules

DEFF Research Database (Denmark)

Østdal, H.; Davies, M.J.; Andersen, Henrik Jørgen

2002-01-01

The present study investigates the reactivity of bovine serum albumin (BSA) radicals towards different biomolecules (urate, linoleic acid, and a polypeptide, poly(Glu-Ala-Tyr)). The BSA radical was formed at room temperature through a direct protein-to-protein radical transfer from H(2)O(2....... Subsequent analysis showed a decrease in the concentration of urate upon reaction with the BSA radical, while the BSA radical in the presence of poly(Glu-Ala-Tyr) resulted in increased formation of the characteristic protein oxidation product, dityrosine. Reaction between the BSA radical and a linoleic acid...

Radical intermediates involved in the bleaching of the carotenoid crocin. Hydroxyl radicals, superoxide anions and hydrated electrons

International Nuclear Information System (INIS)

Bors, W.; Saran, M.; Michel, C.

1982-01-01

The participation of the primary radicals in the bleaching of aqueous solutions of the carotenoid crocin by ionizing radiation was investigated, employing both X-radiolysis and pulse radiolysis. The pulse-radiolytic data demonstrated a very rapid diffusion-controlled attack by both hydroxyl radicals (radicalsOH) and hydrated electrons (e - sub(aq)), while superoxide anions (O 2 - ) did not react at all. The site of the initial reaction of these radicals was not limited to the polyene chromophore. Slower secondary reactions involving crocin alkyl or peroxy radicals contribute mainly to the overall bleaching, in particular during steady-state irradiation. (author)

Formation of long-lived radicals on proteins by radical transfer from heme enzymes--a common process?

DEFF Research Database (Denmark)

Ostdal, H; Andersen, H J; Davies, Michael Jonathan

1999-01-01

concentrations were observed after limited digestion, although this effect was less marked with the HRP/H2O2/BSA system than with Fe(III)Mb/H2O2/BSA, consistent with different modes of radical transfer. More extensive digestion of BSA decreased the radical concentration to levels below those detected with native...... investigated using horseradish peroxidase (HRP)/H2O2, in the presence and absence of added tyrosine. Incubation of HRP with H2O2 and bovine or human serum albumins, in the presence and absence of tyrosine, gave long-lived albumin-derived radicals as detected by EPR spectroscopy. Evidence has been obtained...... for these albumin radicals being located on buried tyrosine residues on the basis of blocking experiments. The effect of protein conformation on radical transfer has been investigated using partial proteolytic digestion prior to protein oxidation. With HRP/H2O2/BSA and Fe(III)Mb/H2O2/BSA increased radical...

Use of Isomerization and Hydroisomerization Reactions to Improve the Cold Flow Properties of Vegetable Oil Based Biodiesel

Directory of Open Access Journals (Sweden)

Stephen J. Reaume

2013-01-01

Full Text Available Biodiesel is a promising alternative to petroleum diesel with the potential to reduce overall net CO2 emissions. However, the high cloud point of biodiesel must be reduced when used in cold climates. We report on the use of isomerization and hydroisomerization reactions to reduce the cloud point of eight different fats and oils. Isomerization was carried out at 260 °C and 1.5 MPa H2 pressure utilizing beta zeolite catalyst, while hydroisomerization was carried out at 300 °C and 4.0 MPa H2 pressure utilizing 0.5 wt % Pt-doped beta zeolite catalyst. Reaction products were tested for cloud point and flow properties, in addition to catalyst reusability and energy requirements. Results showed that high unsaturated fatty acid biodiesels increased in cloud point, due to the hydrogenation side reaction. In contrast, low unsaturated fatty acid biodiesels yielded cloud point reductions and overall improvement in the flow properties. A maximum cloud point reduction of 12.9 °C was observed with coconut oil as the starting material. Results of the study have shown that branching can reduce the cloud point of low unsaturated fatty acid content biodiesel.

Radical surgery compared with intracavitary cesium followed by radical surgery in cervical carcinoma stage IB

Energy Technology Data Exchange (ETDEWEB)

Tinga, D.J.; Bouma, J.; Aalders, J.G. (Dept. of Obstetrics and Gynaecology, State Univ. Hospital, Groningen (Netherlands)); Hollema, H. (Dept. of Pathology, State Univ. Hospital, Groningen (Netherlands))

1990-01-01

Forty-nine patients aged {le} 45 years, with cervical carcinoma stage IB ({le} 3 cm) were treated with either primary radical surgery (n = 26), or intracavitary irradiation followed by radical surgery (n = 23). With primary surgery, ovarian function had been preserved in 15 of the 25 patients, who were alive and well. Seven of the primary surgery patients were irradiated postoperatively and 2 others with a central recurrence were cured by irradiation. One other patient, who was not irradiated postoperatively, had an intestinal metastasis and died of the disease. If any of the adverse prognostic factors (as reported in the literature) had been considered as an indication for postoperative irradiation, 17 patients instead of 7 would have been irradiated after primary radical surgery. In the comparable group of 23 patients treated by intracavitary irradiation and radical surgery (and in 4 cases postoperative irradiation as well) there was no recurrence. There was no significant statistical difference between the treatment results in the cesium + surgery group and those who underwent primary radical surgery. Young patients with early cervical carcinoma without prognostic indicators for postoperative irradiation can benefit from primary radical surgery, because their ovarian function can be preserved. (authors).

Radical surgery compared with intracavitary cesium followed by radical surgery in cervical carcinoma stage IB

International Nuclear Information System (INIS)

Tinga, D.J.; Bouma, J.; Aalders, J.G.; Hollema, H.

1990-01-01

Forty-nine patients aged ≤ 45 years, with cervical carcinoma stage IB (≤ 3 cm) were treated with either primary radical surgery (n = 26), or intracavitary irradiation followed by radical surgery (n = 23). With primary surgery, ovarian function had been preserved in 15 of the 25 patients, who were alive and well. Seven of the primary surgery patients were irradiated postoperatively and 2 others with a central recurrence were cured by irradiation. One other patient, who was not irradiated postoperatively, had an intestinal metastasis and died of the disease. If any of the adverse prognostic factors (as reported in the literature) had been considered as an indication for postoperative irradiation, 17 patients instead of 7 would have been irradiated after primary radical surgery. In the comparable group of 23 patients treated by intracavitary irradiation and radical surgery (and in 4 cases postoperative irradiation as well) there was no recurrence. There was no significant statistical difference between the treatment results in the cesium + surgery group and those who underwent primary radical surgery. Young patients with early cervical carcinoma without prognostic indicators for postoperative irradiation can benefit from primary radical surgery, because their ovarian function can be preserved. (authors)

Free radicals in an Adamantane matrix. XI. Electron paramagnetic resonance study of conformations in the β-halo-tert-butyl radicals

International Nuclear Information System (INIS)

Lloyd, R.V.; Wood, D.E.

1975-01-01

The β-halo-tert-butyl radicals were prepared by x-irradiation of the corresponding isobutyl halides in an adamantane matrix at 77 0 K and their conformations were determined by analysis of their EPR spectra. The radicals are nonplanar at the radical site, the fluoro and chloro radicals trans eclipsed and the bromo and iodo radicals gauche staggered with respect to the relative orientation of the carbon halogen bond and the direction of the singly occupied orbital. Vibration-rotation motions about the favored conformation are much larger for the fluoro radical than for the others. The rate of interconversion of the inequivalent methylene protons is approximately 1.5 x 10 9 sec -1 for the bromo radical at 202 0 K while it is too slow to measure for the iodo radical at the same temperature. The barrier to interconversion has a lower limit of 3 kcal/mol for the bromo radical and higher than that for the iodo radical. The halogen and proton hfsc in gauss and the g values for the XCH 2 C(CH 3 ) 2 radicals are: 19 F = 103.7, CH 2 = 10.4, CH 3 = 23.3, g = 2.0030 at 214 K; 35 Cl = 19.5, CH 2 = 6.3, CH 3 = 21.1, g = 2.0042 at 215 K; 81 Br = 6.7, CH 2 = 21.4, 42.7, CH 3 = 21.4, g = 2.0010 at 202 K; 127 I = 7.0, CH 2 = 21.9, 43.8, CH 3 = 21.9, g = 2.0009 at 208 K. The fluoro radical decays to nonradical products above 318 0 K, the chloro radical converts to 2-methyl allyl radical above 306 0 K, the bromo radical converts to tert-butyl radical by exchange with a matrix proton (or deuteron) at 209 0 K as does the iodo radical above 225 0 K. Photolysis with a Xe lamp converts the bromo and iodo radicals to nonradical products in less than the experimental time constant of 0.3 sec. The hypothesis is put forward that the nonplanarity and high barrier to rotation observed explain the retention of stereochemical configuration in reactions involving β-chloro, β-bromo, and β-iodo alkyl radicals. (auth)

Anesthetic implications of total anomalous systemic venous connection to left atrium with left isomerism

Directory of Open Access Journals (Sweden)

Parimala Prasanna Simha

2012-01-01

Full Text Available Total anomalous systemic venous connection (TASVC to the left atrium (LA is a rare congenital anomaly. An 11-year-old girl presented with complaints of palpitations and cyanosis. TASVC with left isomerism and noncompaction of LV was diagnosed after contrast echocardiogram and computed tomography angiogram. The knowledge of anatomy and pathophysiology is essential for the successful management of these cases. Anesthetic concerns in this case were polycythemia, paradoxical embolism and rhythm abnormalities. The patient was successfully operated by rerouting the systemic venous connection to the right atrium.

Amino acid-catalyzed conversion of citral : cis-trans isomerization and its conversion into 6-methyl-5-hepten-2-one and acetaldehyde

NARCIS (Netherlands)

Wolken, W.A.M.; Have, R. ten; Werf, M.J. van der

2000-01-01

Under alkaline conditions, amino acids or proteins catalyze the deacetylation of citral, a major aroma component, resulting in methylheptenone and acetaldehyde formation. 3-Hydroxycitronellal is an intermediate in this reaction. Amino acids also catalyze the cis-trans isomerization of the pure

17.9.3 Radical cations of diazo compounds

Science.gov (United States)

Davies, A. G.

This document is part of Subvolume E2 `Phosphorus-Centered Radicals, Radicals Centered on Other Heteroatoms, Organic Radical Ions' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

Inhibition of radiation-induced DNA strand breaks by hoechst 33258: OH-radical scavenging and DNA radical quenching

International Nuclear Information System (INIS)

Adhikary, A.; Bothe, E.; Von Sonntag, C.; Adhikary, A.

1997-01-01

The minor-groove-binding dye Hoechst 33258 has been found to protect pBR322 DNA in aqueous solution against radiation-induced single-strand breaks (ssb). This protective effect has been assumed to be largely due to the scavenging of the strand-break-generating OH radicals by Hoechst. From D 37 values for ssb at different Hoechst concentrations the value of the OH radical scavenging constant of DNA-bound Hoechst has been estimated at k Ho/DNA = 2.7 * 10 11 dm 3 mol -1 . This unexpectedly high value has led us to study the reactions of OH radicals with Hoechst in the absence and in the presence of double-stranded calf thymus DNA (ds DNA) by pulse radiolysis, and the formation of radiation-induced ssb by low angle laser light scattering. The D 37 /D 37 0 values at different Hoechst concentrations agree with the values obtained by Martin and al. and demonstrate the protection. However, this protection cannot be explained on the basis of OH radical scavenging alone using the above rate constants. There must, in addition, be some quenching of DNA radicals. Hoechst radicals are formed in the later ms time range, i.e a long time after the disappearance of the OH radicals. This delayed Hoechst radical formation has been assigned to a a reaction of DNA radicals with Hoechst, thereby inhibiting strand breakage. In confirmation, pulse radiolysis of aqueous solution of nucleotides in the presence of Hoechst yields a similar delayed Hoechst radical formation. The data indicate that in DNA the cross-section of this quenching has a diameter of 3 to 4 base pairs per Hoechst molecule. (N.C.)

Radical-Local Teaching and Learning

DEFF Research Database (Denmark)

Hedegaard, Mariane; Chaiklin, Seth

Radical-Local Teaching and Learning presents a theoretical perspective for analyzing and planning educational programmes for schoolchildren. To realize both general societal interests and worthwhile personal development, the content of educational programmes for children must be grounded in the l......Radical-Local Teaching and Learning presents a theoretical perspective for analyzing and planning educational programmes for schoolchildren. To realize both general societal interests and worthwhile personal development, the content of educational programmes for children must be grounded...... radical-local teaching and learning approach. The first half of the book introduces the idea of radical-local teaching and learning and develops the theoretical background for this perspective, drawing on the cultural-historical research tradition, particularly from Vygotsky, El'konin, Davydov......, and Aidarova. The second half of the book addresses the central concern of radical-local teaching and learning - how to relate educational practices to children's specific historical and cultural conditions. The experiment was conducted for an academic year in an afterschool programme in the East Harlem...

Electronic structure of Co islands grown on the {radical}3 x {radical}3-Ag/Ge(111) surface

Energy Technology Data Exchange (ETDEWEB)

Huang, Xiao-Lan; Chou, Chi-Hao; Lin, Chun-Liang; Tomaszewska, Agnieszka; Fu, Tsu-Yi, E-mail: phtifu@phy.ntnu.edu.tw

2011-09-30

By means of room temperature scanning tunneling spectroscopy (RT STS), we have studied the electronic structure of two different Ag/Ge(111) phases as well as Co islands grown on the {radical}3 x {radical}3-Ag/Ge (111) forming either {radical}13 x {radical}13 or 2 x 2 patterns. The spectrum obtained from 4 x 4-Ag/Ge(111) structure shows the existence of a shoulder at 0.7 V which is also present in the electronic structure of the Ge(111)-c2 x 8 and indicates donation of Ge electrons to electronic states of the Ag-driven phase. However, this fact is not supported by the electronic spectrum taken from the {radical}3 x {radical}3-Ag/Ge (111). The complexity of the Co-{radical}13 x {radical}13 islands bonding with the substrate is mirrored by a large number of peaks in their electronic spectra. The spectra obtained from the Co-2 x 2 islands which had grown on the step differ from those taken from Co-2 x 2 islands located along the edge of the terrace by a number of peaks at negative sample bias. This discrepancy is elucidated in terms of dissimilarities of Co-substrate interaction accompanying Co islands growth on different areas of the stepped surface.

Understanding political radicalization: The two-pyramids model.

Science.gov (United States)

McCauley, Clark; Moskalenko, Sophia

2017-04-01

This article reviews some of the milestones of thinking about political radicalization, as scholars and security officials struggled after 9/11 to discern the precursors of terrorist violence. Recent criticism of the concept of radicalization has been recognized, leading to a 2-pyramids model that responds to the criticism by separating radicalization of opinion from radicalization of action. Security and research implications of the 2-pyramids model are briefly described, ending with a call for more attention to emotional experience in understanding both radicalization of opinion and radicalization of action. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Orgasm after radical prostatectomy

NARCIS (Netherlands)

Koeman, M; VanDriel, MF; Schultz, WCMW; Mensink, HJA

Objective To evaluate the ability to obtain and the quality of orgasm after radical prostatectomy, Patients and methods The orgasms experienced after undergoing radical prostatectomy were evaluated in 20 men (median age 65 years, range 56-76) using a semi-structured interview and a self-administered

O Behaviorismo Radical como filosofia da mente Radical Behaviorism as philosophy of mind

Directory of Open Access Journals (Sweden)

Carlos Eduardo Lopes

2003-01-01

Full Text Available O Behaviorismo Radical de B. F. Skinner é constantemente acusado de eliminar a mente de sua explicação do comportamento humano. Uma análise do livro The Concept of Mind, de Gilbert Ryle, sugere a possibilidade de defender a existência de uma mente relacional, diferente da categoria de existência da mente defendida em interpretações cartesianas (mente substancial. A análise de alguns textos de Skinner sugere que o conceito de uma mente relacional também pode ser defendido no Behaviorismo Radical. Esse fato, culminaria na possibilidade de que, além de filosofia da Ciência do Comportamento, o Behaviorismo Radical, também pode ser uma filosofia da mente, o que traria conseqüências ao estudo e à aplicação da Análise do Comportamento.B. F. Skinner's Radical Behaviorism has been repeatedly accused of eliminating the mind from its explanation of human behavior. An analysis of Gilbert Ryle's book, The Concept of Mind, suggests the possibility of defending the existence of a relational mind, different from the category of existence of mind defended in Cartesian interpretations (substantial mind. The analysis of some texts of Skinner suggests that the concept of a relational mind can also be defended in Radical Behaviorism. This fact would lead to the possibility that, beyond a philosophy of Behavior Science, Radical Behaviorism may also be a philosophy of mind, which would bring consequences to the study and application of Analysis of Behavior.

Stability constants of mixed ligand complexes of dioxouranium(II) and thorium(IV) with complexones and isomeric alanines

International Nuclear Information System (INIS)

Singh, R.K.; Saxena, M.C.

1992-01-01

The present work reports on the stability sequence between UO 2 II and Th IV ions for their mixed ligands complexes with the two isomeric alanines, α-alanine (α-ala) and β-alanine (β-ala) containing a complexone as primary ligand. The complexones used are iminodiacetate (IMDA), nitrilotricetate (NTA), 2-hydroxyethylenediaminetriacetate (HEDTA), ethylenediaminetetraacetate (EDTA), 1,2-diaminocyclohexanetraacetate (CDTA) and diethylenetriminepentaacetate (DTPA). (author). 9 refs., 1 tab

Muonium radicals in benzene-styrene mixtures

International Nuclear Information System (INIS)

Ng, B.W.; Stadlbauer, J.W.; Walker, D.C.

1984-01-01

Muonium radicals were observed through their μ + SR precession frequencies in high transverse magnetic fields in pure benzene, pure styrene and their mixtures, all as liquids at room temperature. In benzene-styrene mixtures, the radicals obtained in each pure liquid are both present, so no slow (10 -9 -10 -5 s) intermolecular exchange occurs; but strong selectivity was found with the formation of the radical from styrene being about eight-times more probable than the radical from benzene. (Auth.)

Single-Step Access to Long-Chain α,ω-Dicarboxylic Acids by Isomerizing Hydroxycarbonylation of Unsaturated Fatty Acids

KAUST Repository

Goldbach, Verena

2016-11-09

Dicarboxylic acids are compounds of high value, but to date long-chain alpha,omega-dicarboxylic acids have been difficult to access in a direct way. Unsaturated fatty acids are ideal starting materials with their molecular structure of long methylene sequences and a carboxylate functionality, in addition to a double bond that offers itself for functionalization. Within this paper, we established a direct access to alpha,omega-dicarboxylic acids by combining isomerization and selective terminal carbonylation of the internal double bond with water as a nucleophile on unsaturated fatty acids. We identified the key elements of this reaction: a homogeneous reaction mixture ensuring sufficient contact between all reactants and a catalyst system allowing for activation of the Pd precursor under aqueous conditions. Experiments under pressure reactor conditions with [(dtbpx)Pd(OTf)(2)] as catalyst precursor revealed the importance of nucleophile and reactant concentrations and the addition of the diprotonated diphosphine ligand (dtbpxH(2))(OTf)(2) to achieve turnover numbers >120. A variety of unsaturated fatty acids, including a triglyceride, were converted to valuable long-chain dicarboxylic acids with high turnover numbers and selectivities for the linear product of >90%. We unraveled the activation pathway of the Pd-II precursor, which proceeds via a reductive elimination step forming a Pd species and oxidative addition of the diprotonated diphosphine ligand, resulting in the formation of the catalytically active Pd hydride species. Theoretical calculations identified the hydrolysis as the rate-determining step. A low nucleophile concentration in the reaction mixture in combination with this high energetic barrier limits the potential of this reaction. In conclusion, water can be utilized as a nucleophile in isomerizing functionalization reactions and gives access to long-chain dicarboxylic acids from a variety of unsaturated substrates. The activity of the catalytic

Kinetics of isomerization and inversion of aspartate 58 of αA-crystallin peptide mimics under physiological conditions.

Directory of Open Access Journals (Sweden)

Kenzo Aki

Full Text Available Although proteins consist exclusively of L-amino acids, we have reported that aspartyl (Asp 58 and Asp 151 residues of αA-crystallin of eye lenses from elderly cataract donors are highly inverted and isomerized to D-β, D-α and L-β-Asp residues through succinimide intermediates. Of these Asp isomers, large amounts of D-β- and L-β-isomers are present but the amount of D-α-isomer is not significant. The difference in abundance of the Asp isomers in the protein may be due to the rate constants for the formation of the isomers. However, the kinetics have not been well defined. Therefore, in this study, we synthesized a peptide corresponding to human αA-crystallin residues 55 to 65 (T(55VLD(58SGISEVR(65 and its isomers in which L-α-Asp at position 58 was replaced with L-β-, D-β- and D-α-Asp and determined the rate of isomerization and inversion of Asp residues under physiological conditions (37°C, pH7.4. The rate constant for dehydration from L-α-Asp peptide to L-succinimidyl peptide was 3 times higher than the rate constant for dehydration from L-β-Asp peptide to L-succinimidyl peptide. The rate constant for hydrolysis from L-succinimidyl peptide to L-β-Asp peptide was about 5 times higher than the rate constant for hydrolysis from L-succinimidyl peptide to L-α-Asp peptide. The rate constant for dehydration from L-α-Asp peptide to L-succinimidyl peptide was 2 times higher than the rate constant for dehydration from D-α-Asp peptide to D-succinimidyl peptide. The rate constants for hydrolysis from L-succinimidyl peptide to L-β-Asp peptide and for hydrolysis from D-succinimidyl peptide to D-β-Asp peptide were almost equal. Using these rate constants, we calculated the change in the abundance ratios of the 4 Asp isomers during a human lifespan. This result is consistent with the fact that isomerized Asp residues accumulate in proteins during the ageing process.

Sugar Profile, Mineral Content, and Rheological and Thermal Properties of an Isomerized Sweet Potato Starch Syrup

OpenAIRE

Dominque, Brunson; Gichuhi, Peter N.; Rangari, Vijay; Bovell-Benjamin, Adelia C.

2013-01-01

Currently, corn is used to produce more than 85% of the world's high fructose syrup (HFS). There is a search for alternative HFS substrates because of increased food demand and shrinking economies, especially in the developing world. The sweet potato is a feasible, alternative raw material. This study isomerized a high glucose sweet potato starch syrup (SPSS) and determined its sugar profile, mineral content, and rheological and thermal properties. Rheological and thermal properties were meas...

Magnetic field effects on geminate reactions. Study of anthraquinone - hydrogen donors systems

International Nuclear Information System (INIS)

Vidal, Marie-Helene

1987-01-01

This study is devoted to magnetic field effects on chemical reactions which involve a radical pair with correlated spins (radical in a 'cage'). In the first part, the radical pair theory is described: mechanisms of singlet-triplet mixing, the different interactions inside the pair and a quantum mechanical treatment of the radical pair. The details of the experimental method (nanosecond laser flash photolysis) are reported in the second part. In the third part are shown experimental results obtained on Anthraquinone (AQ) - Hydrogen donors systems: - There is no magnetic field effect in homogeneous solution even at a high viscosity. The absorption spectra of the different reaction intermediates are obtained. - However a magnetic field effect is put forward when AQ is introduced in SDS micelles which are hydrogen donors. The absorption spectrum of the AQH · . semi-quinone radical in 'cage' is shown and a mechanism is proposed for its disappearance to generate the AQH-S and AQH 2 species. - The addition of 9, 10 Dihydroanthracene (DH2) inside the micelle near AQ induces an increase of the magnetic field effect by creation of (AQH · . - DH · . ) pairs which diffuse slowly. - Fixed radical pairs in a protein matrix were studied in reaction centers of photosynthetic bacteria: in that case, the half effect field is shifted to low fields when compared to the previously described systems. (author) [fr

Laparoscopic radical cystectomy: key points

Directory of Open Access Journals (Sweden)

D. V. Perlin

2018-01-01

Full Text Available Background. Radical cystectomy remains the golden standard for treatment of muscle invasive bladder cancer. Objective: to duplicate with highest accuracy the open radical cystectomy procedure, which we successfully utilized earlier in our clinic, in the of laparoscopic conditions in order to preserve the advantages of minimally invasive procedures and retain the reliability of the tried and tested open surgery.Materials and methods. In the report were included 35 patients (27 men and 8 women with bladder cancer, who underwent laparoscopic radical cystectomy in Volgograd Regional Center of Urology and Nephrology between April 2013 and March 2016. Only the patients who had been submitted to full intracorporal ileal conduits were included.Results. The mean operative time was 378 minutes, the mean blood loss was 285 millilitres, the mean length of hospital stay was 12.4 days, only 20 % of patients required the narcotic anesthetics. The postoperative complication rate was 11.4 %. However, the majority of the patients were successfully treated with minimally invasive procedures. Generally, our results were similar to other reported studies.Conclusion. Laparoscopic radical cystectomy is a safe and efficient modality of treatment of bladder cancer. However, it needs more procedures and longer observation period to establish laparoscopic radical cystectomy as an alternative to open radical cystectomy.

Effects of Molecular Iodine and 4-tert-Butylcatechol Radical Inhibitor on the Radical Polymerization of Styrene

Directory of Open Access Journals (Sweden)

Mojtaba Bozorg

2017-05-01

Full Text Available The presence of molecular iodine was studied in relation the molecular weight and molecular weight distribution of polystyrene, produced by radical poly merization. Radical polymerization of styrene initiated by 2,2׳-azobisisobutyronitrile (AIBN was performed at 70°C in the presence of molecular iodine. The synthesized polymers were characterized by gel permeation chromatography (GPC and proton- nuclear magnetic resonance (1H NMR techniques. The results of these reactions including conversion data, number-average molecular weight and molecular weight distribution were compared with those obtained for styrene radical polymerization initiated by AIBN at the same temperature in the absence of molecular iodine. It was found that the presence of iodine had a profound effect on the molecular weight and its distribution in the produced polystyrene. This was attributed to the ability of iodine to control the polymerization of styrene initiated by AIBN via reverse iodine transfer polymerization (RITP mechanism. The polymer produced by this method had a molecular weight of 10600 g/mol with a molecular weight polydispersity index of 1.3. Due to the importance of induction period in reverse iodine transfer radical polymerization, increasing the temperature to 120°C during the induction period resulted in shorter induction periods and the produced species led to better control of the molecular weight. Also, due to the role of iodine molecules as a radical inhibitor, the presence of a secondary radical inhibitor, i.e. 4-tert-butylcatechol, along with the iodine was investigated in radical polymerization of polystyrene initiated by AIBN. It was observed that the secondary radical inhibitor prevented the consumption of the iodine molecules by the radicals produced from decomposition of the AIBN initiator; therefore, alkyl halides were not produced during the induction period.

Radical chemistry of artemisinin

Energy Technology Data Exchange (ETDEWEB)

Denisov, Evgenii T; Solodova, S L; Denisova, Taisa G [Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow Region (Russian Federation)

2011-12-29

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

Radical chemistry of artemisinin

Science.gov (United States)

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

2010-12-01

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

Radical chemistry of artemisinin

International Nuclear Information System (INIS)

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

2010-01-01

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

Radical chemistry of artemisinin

Energy Technology Data Exchange (ETDEWEB)

Denisov, Evgenii T; Solodova, S L; Denisova, Taisa G [Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow Region (Russian Federation)

2010-12-29

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

Oxygen free radicals in rheumatoid arthritis

NARCIS (Netherlands)

P. Biemond (Pieter)

1986-01-01

textabstractCurrent knowledge strongly suggests that oxygen free radicals are involved in the pathogenesis of RA. Additional information about the mechanism of free radical attack is necessary in order to find out if interaction with the mechanism of free radical damage can be used in the treatment

Free radicals in health and disease

International Nuclear Information System (INIS)

Gonet, B.

1993-01-01

Free radicals appear in the cells as the result of exogenic factors (ionizing radiation, UV) or reactions naturally occurring in the cell. Free radical reactions may cause destruction of macromolecules (DNA, lipids, proteins). Free radical pathology is important in many diseases and aging processes in organisms

Free radicals in wood induced by γ-radiation

International Nuclear Information System (INIS)

Xu Honglin; Zhang Wenhui

1994-01-01

The free radicals in wood induced by γ-radiation were studied by electron spin resonance. The fine structure of the ESR signal from sawdust samples irradiated could be resolved into various radicals. These free radicals have a very long lifetime. The major spectrum for the free radicals will exponentially increased along with the radiation dose according to Y 1-Exp(-α a D). The intensity of radiation radicals is dependent on tree species. The stronger the intensity of mechanic free radicals is, the stronger the intensity of radiation free radicals

Cis-to- Trans Isomerization of Azobenzene Derivatives Studied with Transition Path Sampling and Quantum Mechanical/Molecular Mechanical Molecular Dynamics.

Science.gov (United States)

Muždalo, Anja; Saalfrank, Peter; Vreede, Jocelyne; Santer, Mark

2018-04-10

Azobenzene-based molecular photoswitches are becoming increasingly important for the development of photoresponsive, functional soft-matter material systems. Upon illumination with light, fast interconversion between a more stable trans and a metastable cis configuration can be established resulting in pronounced changes in conformation, dipole moment or hydrophobicity. A rational design of functional photosensitive molecules with embedded azo moieties requires a thorough understanding of isomerization mechanisms and rates, especially the thermally activated relaxation. For small azo derivatives considered in the gas phase or simple solvents, Eyring's classical transition state theory (TST) approach yields useful predictions for trends in activation energies or corresponding half-life times of the cis isomer. However, TST or improved theories cannot easily be applied when the azo moiety is part of a larger molecular complex or embedded into a heterogeneous environment, where a multitude of possible reaction pathways may exist. In these cases, only the sampling of an ensemble of dynamic reactive trajectories (transition path sampling, TPS) with explicit models of the environment may reveal the nature of the processes involved. In the present work we show how a TPS approach can conveniently be implemented for the phenomenon of relaxation-isomerization of azobenzenes starting with the simple examples of pure azobenzene and a push-pull derivative immersed in a polar (DMSO) and apolar (toluene) solvent. The latter are represented explicitly at a molecular mechanical (MM) and the azo moiety at a quantum mechanical (QM) level. We demonstrate for the push-pull azobenzene that path sampling in combination with the chosen QM/MM scheme produces the expected change in isomerization pathway from inversion to rotation in going from a low to a high permittivity (explicit) solvent model. We discuss the potential of the simulation procedure presented for comparative calculation of

Radical-Local Teaching and Learning

DEFF Research Database (Denmark)

Hedegaard, Mariane; Chaiklin, Seth

radical-local teaching and learning approach. The first half of the book introduces the idea of radical-local teaching and learning and develops the theoretical background for this perspective, drawing on the cultural-historical research tradition, particularly from Vygotsky, El'konin, Davydov......, and Aidarova. The second half of the book addresses the central concern of radical-local teaching and learning - how to relate educational practices to children's specific historical and cultural conditions. The experiment was conducted for an academic year in an afterschool programme in the East Harlem......Radical-Local Teaching and Learning presents a theoretical perspective for analyzing and planning educational programmes for schoolchildren. To realize both general societal interests and worthwhile personal development, the content of educational programmes for children must be grounded...

Bicyclic Guanidine Catalyzed Asymmetric Tandem Isomerization Intramolecular-Diels-Alder Reaction: The First Catalytic Enantioselective Total Synthesis of (+)-alpha-Yohimbine.

Science.gov (United States)

Feng, Wei; Jiang, Danfeng; Kee, Choon-Wee; Liu, Hongjun; Tan, Choon-Hong

2016-02-04

Hydroisoquinoline derivatives were prepared in moderate to good enantioselectivities via a bicyclic guanidine-catalyzed tandem isomerization intramolecular-Diels-Alder (IMDA) reaction of alkynes. With this synthetic method, the first enantioselective synthesis of (+)-alpha-yohimbine was completed in 9 steps from the IMDA products. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

What is Radical Behaviorism? A Review of Jay Moore's Conceptual Foundations of Radical Behaviorism

Science.gov (United States)

Baum, William M

2011-01-01

B. F. Skinner founded both radical behaviorism and behavior analysis. His founding innovations included: a versatile preparation for studying behavior; explicating the generic nature of stimulus and response; a pragmatic criterion for defining behavioral units; response rate as a datum; the concept of stimulus control; the concept of verbal behavior; and explicating the explanatory power of contingencies. Besides these achievements, however, Skinner also made some mistakes. Subsequent developments in radical behaviorist thought have attempted to remedy these mistakes. Moore's book presents a “party line” version of radical behaviorism. It focuses narrowly on a few of Skinner's concepts (mostly mentalism and verbal behavior) and contains no criticism of his mistakes. In fact, Moore adds a few mistakes of his own manufacture; for example, he insists that the mental realm does not exist—an unprovable and distracting assertion. The book's portrayal of behavior analysis would have been current around 1960; it mentions almost none of the developments since then. It also includes almost no developments in radical behaviorism since Skinner. Moore's book would give an unwary reader a highly distorted picture of contemporary behavior analysis and radical behaviorism.

Orthographic Skills Important to Chinese Literacy Development: The Role of Radical Representation and Orthographic Memory of Radicals

Science.gov (United States)

Yeung, Pui-sze; Ho, Connie Suk-han; Chan, David Wai-ock; Chung, Kevin Kien-hoa

2016-01-01

A 3-year longitudinal study among 239 Chinese students in Grades 2-4 was conducted to investigate the relationships between orthographic skills (including positional and functional knowledge of semantic radicals and phonetic radicals, and orthographic memory of radicals) and Chinese literacy skills (word reading, word spelling, reading…

The Games Radicals Play: Special Issue on Free Radicals and Radical Ions

Directory of Open Access Journals (Sweden)

John C. Walton

2015-02-01

Full Text Available Chemistry and Physics have aptly been described as “most excellent children of Intellect and Art” [1]. Both these “children” engage with many playthings, and molecules rank as one of their first favorites, especially radicals, which are amongst the most lively and exciting. Checking out radicals dancing to the music of entropy round their potential energy ballrooms is surely both entertaining and enlightening. Radicals’ old favorite convolutions are noteworthy, but the new styles, modes and arrangements appearing on the scene are even more interesting. Some of these are ephemeral and enjoy only a brief appearance, others are retro-types reappearing in new guises, still others are genuinely new and “go viral” in the scientific world. This Special Issue of Molecules contains the observations and reflections of a select group of chemists and physicists fascinated by this spectacle. It contains an eclectic mix reflecting on new modes and advances as well as on permutations and combinations that revive mature themes. [...

Radical-pair based avian magnetoreception

Science.gov (United States)

Procopio, Maria; Ritz, Thorsten

2014-03-01

Behavioural experiments suggest that migratory birds possess a magnetic compass sensor able to detect the direction of the geomagnetic. One hypothesis for the basis of this remarkable sensory ability is that the coherent quantum spin dynamics of photoinduced radical pair reactions transduces directional magnetic information from the geomagnetic field into changes of reaction yields, possibly involving the photoreceptor cryptochrome in the birds retina. The suggested radical-pair based avian magnetoreception has attracted attention in the field of quantum biology as an example of a biological sensor which might exploit quantum coherences for its biological function. Investigations on such a spin-based sensor have focussed on uncovering the design features for the design of a biomimetic magnetic field sensor. We study the effects of slow fluctuations in the nuclear spin environment on the directional signal. We quantitatively evaluate the robustness of signals under fluctuations on a timescale longer than the lifetime of a radical pair, utilizing two models of radical pairs. Our results suggest design principles for building a radical-pair based compass sensor that is both robust and highly directional sensitive.

Isomerization of α-pinene in the terpentin oil with TCA/Natural Zeolite using microwave irradiation

Science.gov (United States)

Wijayati, N.; Supartono; Kusumastuti, E.

2018-04-01

The catalytic potensial of trichloroacetic acid (TCA)//Natural Zeolite in the isomerization of α-pinene in the terpentin oil was investigated. The purpose of this study is to investigate the influence of the power of microvawe on activity and selectivity of catalyst. The main product were champhene, terpinene, limonene, p-cymene, and terpinolene. The highest selectivity was 28.26% with a conversion of 23.25%, whereas the higher conversion was 98.99% with selectivity of 16.90% at room temperature using power of microwave 640 W.

Radically enhanced molecular recognition

KAUST Repository

Trabolsi, Ali

2009-12-17

The tendency for viologen radical cations to dimerize has been harnessed to establish a recognition motif based on their ability to form extremely strong inclusion complexes with cyclobis(paraquat-p-phenylene) in its diradical dicationic redox state. This previously unreported complex involving three bipyridinium cation radicals increases the versatility of host-guest chemistry, extending its practice beyond the traditional reliance on neutral and charged guests and hosts. In particular, transporting the concept of radical dimerization into the field of mechanically interlocked molecules introduces a higher level of control within molecular switches and machines. Herein, we report that bistable and tristable [2]rotaxanes can be switched by altering electrochemical potentials. In a tristable [2]rotaxane composed of a cyclobis(paraquat-p-phenylene) ring and a dumbbell with tetrathiafulvalene, dioxynaphthalene and bipyridinium recognition sites, the position of the ring can be switched. On oxidation, it moves from the tetrathiafulvalene to the dioxynaphthalene, and on reduction, to the bipyridinium radical cation, provided the ring is also reduced simultaneously to the diradical dication. © 2010 Macmillan Publishers Limited. All rights reserved.

Radically enhanced molecular recognition

KAUST Repository

Trabolsi, Ali; Khashab, Niveen M.; Fahrenbach, Albert C.; Friedman, Douglas C.; Colvin, Michael T.; Coti, Karla K.; Bení tez, Diego S.; Tkatchouk, Ekaterina; Olsen, John Carl; Belowich, Matthew E.; Carmieli, Raanan; Khatib, Hussam A.; Goddard, William Andrew III; Wasielewski, Michael R.; Stoddart, Fraser Fraser Raser

2009-01-01

The tendency for viologen radical cations to dimerize has been harnessed to establish a recognition motif based on their ability to form extremely strong inclusion complexes with cyclobis(paraquat-p-phenylene) in its diradical dicationic redox state. This previously unreported complex involving three bipyridinium cation radicals increases the versatility of host-guest chemistry, extending its practice beyond the traditional reliance on neutral and charged guests and hosts. In particular, transporting the concept of radical dimerization into the field of mechanically interlocked molecules introduces a higher level of control within molecular switches and machines. Herein, we report that bistable and tristable [2]rotaxanes can be switched by altering electrochemical potentials. In a tristable [2]rotaxane composed of a cyclobis(paraquat-p-phenylene) ring and a dumbbell with tetrathiafulvalene, dioxynaphthalene and bipyridinium recognition sites, the position of the ring can be switched. On oxidation, it moves from the tetrathiafulvalene to the dioxynaphthalene, and on reduction, to the bipyridinium radical cation, provided the ring is also reduced simultaneously to the diradical dication. © 2010 Macmillan Publishers Limited. All rights reserved.

Formation and spectroscopy of {alpha}-muoniated radicals

Energy Technology Data Exchange (ETDEWEB)

McKenzie, I.; Brodovitch, J.C.; Ghandi, K.; Kecman, S.; Percival, P.W

2003-02-01

Several novel {alpha}-muoniated radicals have been produced by the reaction of muonium with compounds containing diazo, isocyanate or carbene functional groups. In {alpha}-muoniated radicals the muon is attached directly to the radical centre; they can be formed either directly or indirectly via a {beta}-muoniated radical intermediate. The hyperfine coupling constants of the resulting radicals have been measured by transverse field muon spin rotation and muon avoided level-crossing resonance. The effect of muonium substitution was investigated for cases where ESR data are available for comparison.

Formation and spectroscopy of α-muoniated radicals

International Nuclear Information System (INIS)

McKenzie, I.; Brodovitch, J.C.; Ghandi, K.; Kecman, S.; Percival, P.W.

2003-01-01

Several novel α-muoniated radicals have been produced by the reaction of muonium with compounds containing diazo, isocyanate or carbene functional groups. In α-muoniated radicals the muon is attached directly to the radical centre; they can be formed either directly or indirectly via a β-muoniated radical intermediate. The hyperfine coupling constants of the resulting radicals have been measured by transverse field muon spin rotation and muon avoided level-crossing resonance. The effect of muonium substitution was investigated for cases where ESR data are available for comparison

Synthesis, crystal structure and photo physical properties of isomeric fluorinated s-shaped polyaromatic dibenzo[c,l]chrysene derivatives

Science.gov (United States)

Moriguchi, Tetsuji; Tabuchi, Daichi; Yakeya, Daisuke; Tsuge, Akihiko; Jalli, Venkataprasad; Yoza, Kenji

2018-01-01

Two s-shaped fluorinated isomeric polyaromatic dibenzo[c,l]chrysene derivatives have been synthesized by a two step process using the Wittig, Heck and iodine promoted cyclization reactions. These cyclized compounds were characterized by 1H NMR and EI-MS. Further, absolute configurations of isomeric 4a and 4b were determined by X-ray diffraction analysis. Compound 4a crystallized under monoclinic system with space group P21/c and compound 4b crystallized under monoclinic system with space group Cc. They have good solubility in common organic solvents such as dichloromethane, chloroform and THF. Photophysical properties of 4a and 4b were evaluated by using UV-Visible and Fluorescence spectrophotometer. Compounds 4a and 4b showed strong absorption maximum wavelength at 317 nm. The emission spectra of 4a and 4b displayed sharp peaks in the visible region from 417 to 441 nm. The shape of the UV-Visible and Fluorescence spectra of 4a and 4b looks almost identical. But compound 4a exhibited better fluorescence intensity than compound 4b. This difference may be due to the difference in the configuration of compounds 4a and 4b.

Semantic Radicals Contribute More Than Phonetic Radicals to the Recognition of Chinese Phonograms: Behavioral and ERP Evidence in a Factorial Study

Directory of Open Access Journals (Sweden)

Xieshun Wang

2017-12-01

Full Text Available The Chinese phonograms consist of a semantic radical and a phonetic radical. The two types of radicals have different functional contributions to their host phonogram. The semantic radical typically signifies the meaning of the phonogram, while the phonetic radical usually contains a phonological clue to the phonogram’s pronunciation. However, it is still unclear how they interplay with each other when we attempt to recognize a phonogram because previous studies rarely manipulated the functionality of the two types of radicals in a single design. Using a full factorial design, the present study aimed to probe this issue by directly manipulating the functional validity of the two types of radicals in a lexical decision task with both behavioral and event-related potential (ERP measurements. The results showed that recognition of phonograms which were related to their semantic radicals in meaning took a shorter reaction time, showed a lower error rate, and elicited a smaller P200 and a larger N400 than did recognition of those which had no semantic relation with their semantic radicals. However, the validity of phonetic radicals did not show any main effect or interaction with that of semantic radicals on either behavioral or ERP measurements. These results indicated that semantic radicals played a dominant role in the recognition of phonograms. Transparent semantic radicals, which provide valid semantic cues to phonograms, can facilitate the recognition of phonograms.

Pyrimidine nucleobase radical reactivity in DNA and RNA

Science.gov (United States)

Greenberg, Marc M.

2016-11-01

Nucleobase radicals are major products of the reactions between nucleic acids and hydroxyl radical, which is produced via the indirect effect of ionizing radiation. The nucleobase radicals also result from hydration of cation radicals that are produced via the direct effect of ionizing radiation. The role that nucleobase radicals play in strand scission has been investigated indirectly using ionizing radiation to generate them. More recently, the reactivity of nucleobase radicals resulting from formal hydrogen atom or hydroxyl radical addition to pyrimidines has been studied by independently generating the reactive intermediates via UV-photolysis of synthetic precursors. This approach has provided control over where the reactive intermediates are produced within biopolymers and facilitated studying their reactivity. The contributions to our understanding of pyrimidine nucleobase radical reactivity by this approach are summarized.

Tuning light-emitting properties of N-phenylcarbazole-capped anthrylvinyl derivatives by symmetric and isomeric effects

Energy Technology Data Exchange (ETDEWEB)

Hu, Qingli; Wang, Jianfeng; Yin, Ling; Chen, Mingshuai [Key Laboratory of Rubber-Plastics of Ministry of Education/Shandong Province (QUST), School of Polymer Science & Engineering, Qingdao University of Science & Technology, 53-Zhengzhou Road, Qingdao 266042 (China); Xue, Shanfeng, E-mail: sfxue@qust.edu.cn [Key Laboratory of Rubber-Plastics of Ministry of Education/Shandong Province (QUST), School of Polymer Science & Engineering, Qingdao University of Science & Technology, 53-Zhengzhou Road, Qingdao 266042 (China); State Key Laboratory of Luminescent Materials and Devices, Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou 510640 (China); Yang, Wenjun, E-mail: ywjph2004@qust.edu.cn [Key Laboratory of Rubber-Plastics of Ministry of Education/Shandong Province (QUST), School of Polymer Science & Engineering, Qingdao University of Science & Technology, 53-Zhengzhou Road, Qingdao 266042 (China)

2017-03-15

This paper focuses on effects of molecular symmetry and isomerisation on light-emitting properties based on N-phenylcarbazole-capped anthrylvinyl derivatives. We have designed and synthesized three isomeric 10-(arylvinyl)anthracenes with N-phenylcarbazole as the mono aryl moiety whose 2-, 3-, or carbazole-9-yl-phenyl positions are linked, and their optical and electroluminescence properties are investigated and compared with analogous 9,10-bis(arylvinyl)anthracenes. The results showed that, contrary to the dual N-phenylcarbazole-capped analogues, the three mono N-phenylcarbazole-capped isomers have neither aggregation-induced emission nor mechanofluorochromism although they are characterized by twisted π-backbone and grinding-induced amorphization. It is observed that the mono substitution can significantly blue-shift the emission spectra and greatly improve the electroluminescence performances, accompanying by the remarkably isomeric effect. This finding demonstrates that changing the molecular substitution patterns could effectively alter and tune the light-emitting properties to greatly widen the scope of molecular candidates applicable in optical and optoelectronic fields. - Highlights: • Three monoN-phenylcarbazole-capped 10-vinylanthracenes are designed to investigate the geometric symmetry and isomer effects. • The three backbone-twisted luminogens do not exhibit AIE and MFC activity. • The grinding-induced amorphization does not necessarily cause the change in fluorescence color. • 10-Arylvinylanthracenes show the better EL performances than 9,10-di(aryl- vinyl)anthracenes. • Subtly manipulating molecular geometric symmetry could tune and alter the solid-state aggregation and stimuli-responsive behaviors.

Quantification of hydroxyl radical produced during phacoemulsification.

Science.gov (United States)

Gardner, Jonathan M; Aust, Steven D

2009-12-01

To quantitate hydroxyl radicals produced during phacoemulsification with various irrigating solutions and conditions used in cataract surgery. Chemistry and Biochemistry Department, Utah State University, Logan, Utah, USA. All experiments were performed using an Infiniti Vision System phacoemulsifier with irrigation and aspiration. Hydroxyl radicals were quantitated using electron spin resonance spectroscopy and a spectrophotometric assay for malondialdehyde, which is formed by the oxidation of deoxyribose by the hydroxyl radical. Hydroxyl radical production increased during longitudinal-stroking phacoemulsification as power levels were increased in a nonlinear, nonexponential fashion. The detection of hydroxyl radical was reduced in irrigating solutions containing organic molecules (eg, citrate, acetate, glutathione, dextrose) and further reduced in Navstel, an irrigating solution containing a viscosity-modifying agent, hydroxypropyl methylcellulose. Hydroxyl radicals produced in settings representative of those used in phacoemulsification cataract surgery were quantitated using the deoxyribose method. Hydroxyl radical production was dependent on the level of ultrasound power applied and the irrigating solution used. Oxidative stress on the eye during phacoemulsification may be minimized by using irrigating solutions that contain organic molecules, including the viscosity-modifying agent hydroxypropyl methylcellulose, that can compete for reaction with hydroxyl radicals.

Free radicals in biology. Volume II

International Nuclear Information System (INIS)

Pryor, W.A.

1976-01-01

This volume continues the treatment of topics in free radical biology and free radical pathology from Volume I. In the first chapter, pyridinyl radicals, radicals which are models for those derived from NAD, are discussed. Pyridinyl radicals can be synthesized and isolated and directly studied in a number of chemical systems. The next chapter treats the role of glutathione in the cell. It is becoming even more apparent that this vital thiol controls a large number of important cellular functions. The GSH/GSSG balance has recently been implicated as a control for cellular development; this balance also may be important in relaying the effects of oxidants from one site to another in the body. The next chapter outlines the reactions of singlet oxygen; some of these involve free radicals and some do not. This reactive intermediate appears to be important both in photochemical smog and in cellular chemistry where singlet oxygen is produced by nonphotochemical processes. The production of free radicals from dry tissues, a controversial area with conflicting claims is reviewed. The next chapter outlines the current status of the studies of photochemical smog. The next two chapters treat specific reactive materials which are present in smog. The first discusses the chemistry of nitrogen oxides and ozone. The second chapter treats the chemistry of the peroxyacyl nitrites. These compounds, although present in only small concentration, are among the most toxic components of smog. The last two chapters treat radiation damage to proteins and radiation protection and radical reactions produced by radiation in nucleic acids

Multi-arrangement quantum dynamics in 6D: cis-trans isomerization and 1,3-hydrogen transfer in HONO

International Nuclear Information System (INIS)

Luckhaus, David

2004-01-01

The overtone spectrum and wave packet dynamics of nitrous acid (HONO) are studied with a global six-dimensional potential energy function interpolated directly from density functional calculations together with the corresponding dipole hypersurfaces. The quantum dynamics for the cis-trans isomerization and the symmetric 1,3-hydrogen transfer are treated in full dimensionality in terms of the generalized Z-matrix discrete variable representation. For the quantum mechanical description of complicated rearrangements a new approach to multi-arrangement quantum dynamics is introduced and applied to the symmetric hydrogen exchange tunneling in cis-HONO. The cis-trans isomerization is found to be dominated by adiabatic barrier crossing with only minor tunneling contributions, but with pronounced mode selectivity. The OH-stretching overtones of trans-HONO are adiabatically almost completely separated from the OH torsional dynamics with extremely slow intramolecular energy redistribution. The 1,3-hydrogen transfer, by contrast, proceeds largely via coherent tunneling even significantly below the barrier. The process is clearly non-adiabatic (at least in terms of valence coordinates) but remains highly state specific. While the absorption spectrum of trans-HONO remains largely unaffected, OH-stretching overtones of cis-HONO (above the barrier between 2ν OH and 3ν OH ) decompose into highly fragmented absorption patterns with corresponding tunneling periods on the picosecond time scale

Detection of Anisotropic Hyperfine Components of Chemically Prepared Carotenoid Radical Cations:1D and 2D ESEEM and Pulsed ENDOR Study

International Nuclear Information System (INIS)

Konovalova, Tatyana A.; Dikanov, Sergei A.; Bowman, Michael K.; Kispert, Lowell D.

2001-01-01

Canthaxanthin and 8'-apo-B-caroten-8'-al radical cations chemically prepared on activated silica-alumina and in CH2CI2 solution containing A1C13 were studied by pulsed EPR and ENDOR spectroscopies. Both the 1D three-pulse ESEEM and the 2D HYSCORE spectra of the carotenoid-A1C13 mixtures exhibited the 27 A1 nuclei peak at 3.75 MHz. This indicates electron-transfer interactions between carotenoids and A1III ions resulting in the formation and stabilization of carotenoid radical cations. Davies ENDOR measurements of the canthaxanthin radical cation on silica-alumina determined the hyperfine couplings of B protons belonging to three different methyl groups with ahI=2.6 MHz, aH2=8.6MHz, and ah3 ca. 13 MHz. The principal components of the proton hyperfine tensors were obtained from HYSCORE spectra in A1C13 solutions and on the solid support. Identification of the protons was made on the basis of isotropic hyperfine couplings determined by RHF-INDO/SP molecular orbital calculations. In frozen A1C13 solution, the C(7, 7')Ha and C(14, 14')-Ha a protons were observed for Canthaxanthin and the C(8 or 14')-Ha, C(15')-Ha were observed for 8'-apo-B-caroten-8'-al. On the silica-alumina support, the C(10, 10')-Ha, C(11, 11')-Ha, and C(15,15')-Ha a protons were measured for Canthaxanthin and the C(12)-Ha and C(15')-Ha were measured for 8' apo-B-caroten-8'-al. Some protons with large isotropic couplings (> 10 MHz) determined from HYSCORE analysis could be assigned to B protons, but the principal components of their hyperfine tensors are much more anisotropic than those reported previously for B protons. We suggest that cis/trans isomerization of carotenoids on silica-alumina results in stabilization of di-cis isomers with large isotropic couplings for some a protons which are comparable to those of B protons

O conceito de mal radical The concept of radical evil

Directory of Open Access Journals (Sweden)

Adriano Correia

2005-01-01

Full Text Available A noção de mal radical aparece em Kant no contexto da discussão da religião nos limites da simples razão e busca dar conta da complexa relação entre o respeito pela lei moral e o amor-próprio na definição do móbil para a ação. Na busca por identificar o fundamento da propensão para o mal no homem, Kant se vê diante da dificuldade de ter de articular natureza e liberdade, e ainda que a noção de mal radical possa conservar algumas ambigüidades, permite conceber uma noção de responsabilidade compatível com uma inata propensão para o mal. Neste texto busco explicitar alguns passos fundamentais na construção do conceito por Kant.The concept of radical evil appears in Kant's theory when he discusses the religion in the limits of the mere reason and aims explain the complex relationship between respect for the moral law and the self-love, for establish the motive of the action. By aiming identify the basis of human inclination to evil, Kant is faced with the trouble of have to put nature and freedom in connection. Despite of the concept of radical evil retain some ambiguity, it allows conceive a notion of responsibility suitable to an inherent inclination to evil. In this paper is my purpose to explain some basic moments of Kantian formulation of that notion.

HPLC-ESR techniques for detection of complex trapped radicals

International Nuclear Information System (INIS)

Tu Tiecheng; Dong Jirong; Lin Nianyun; Xie Leidong; Liu Rengzhong

1992-01-01

High performance liquid chromatography (HPLC) and ESR combined examination of radical species is an advanced techniques for separation and identification of complex radical species. At SRCL, Waters 990 HPLC has been used to separate the complex trapped radicals and Varian E-112 ESR spectrometer to record the spectra of single trapped radicals after HPLC separation. The advantages of the combined techniques are described as bellow: HPLC is used to separate the long-lived complex trapped radicals derived from reaction of short-lived radicals with spin trap. ESR spectra from single trapped radicals, obtained following HPLC separation of complex trapped radicals, are recorded one by one and well resolved. The structures of short-lived radicals can be inferred from the ESR spectra of the long-lived trapped radicals

Scavenging of free-radical metabolites of aniline xenobiotics and drugs by amino acid derivatives: toxicological implications of radical-transfer reactions.

Science.gov (United States)

Michail, Karim; Baghdasarian, Argishti; Narwaley, Malyaj; Aljuhani, Naif; Siraki, Arno G

2013-12-16

We investigated a novel scavenging mechanism of arylamine free radicals by poly- and monoaminocarboxylates. Free radicals of arylamine xenobiotics and drugs did not react with oxygen in peroxidase-catalyzed reactions; however, they showed marked oxygen uptake in the presence of an aminocarboxylate. These free-radical intermediates were identified using the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and electron paramagnetic resonance (EPR) spectrometry. Diethylenetriaminepentaacetic acid (DTPA), a polyaminocarboxylate, caused a concentration-dependent attenuation of N-centered radicals produced by the peroxidative metabolism of arylamines with the subsequent formation of secondary aliphatic carbon-centered radicals stemming from the cosubstrate molecule. Analogously, N,N-dimethylglycine (DMG) and N-methyliminodiacetate (MIDA), but not iminodiacetic acid (IDA), demonstrated a similar scavenging effect of arylamine-derived free radicals in a horseradish peroxidase/H2O2 system. Using human promyelocytic leukemia (HL-60) cell lysate as a model of human neutrophils, DTPA, MIDA, and DMG readily reduced anilinium cation radicals derived from the arylamines and gave rise to the corresponding carbon radicals. The rate of peroxidase-triggered polymerization of aniline was studied as a measure of nitrogen-radical scavenging. Although, IDA had no effect on the rate of aniline polymerization, this was almost nullified in the presence of DTPA and MIDA at half of the molar concentration of the aniline substrate, whereas a 20 molar excess of DMPO caused only a partial inhibition. Furthermore, the yield of formaldehyde, a specific reaction endproduct of the oxidation of aminocarboxylates by aniline free-radical metabolites, was quantitatively determined. Azobenzene, a specific reaction product of peroxidase-catalyzed free-radical dimerization of aniline, was fully abrogated in the presence of DTPA, as confirmed by GC/MS. Under aerobic conditions, a radical-transfer reaction

Solution NMR structure and inhibitory effect against amyloid-β fibrillation of Humanin containing a D-isomerized serine residue

Energy Technology Data Exchange (ETDEWEB)

Alsanousi, Nesreen [Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871 (Japan); Sugiki, Toshihiko, E-mail: sugiki@protein.osaka-u.ac.jp [Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871 (Japan); Furuita, Kyoko; So, Masatomo; Lee, Young-Ho; Fujiwara, Toshimichi [Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871 (Japan); Kojima, Chojiro, E-mail: kojima-chojiro-xk@ynu.ac.jp [Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871 (Japan); Graduate School of Engineering, Yokohama National University, Tokiwadai 79-5, Hodogaya-ku, Yokohama 240-8501 (Japan)

2016-09-02

Humanin comprising 24 amino acid residues is a bioactive peptide that has been isolated from the brain tissue of patients with Alzheimer's disease. Humanin reportedly suppressed aging-related death of various cells due to amyloid fibrils and oxidative stress. There are reports that the cytoprotective activity of Humanin was remarkably enhanced by optical isomerization of the Ser14 residue from L to D form, but details of the molecular mechanism remained unclear. Here we demonstrated that Humanin D-Ser14 exhibited potent inhibitory activity against fibrillation of amyloid-β and remarkably higher binding affinity for amyloid-β than that of the Humanin wild-type and S14G mutant. In addition, we determined the solution structure of Humanin D-Ser14 by nuclear magnetic resonance (NMR) and showed that D-isomerization of the Ser14 residue enables drastic conformational rearrangement of Humanin. Furthermore, we identified an amyloid-β-binding site on Humanin D-Ser14 at atomic resolution by NMR. These biophysical and high-resolution structural analyses clearly revealed structure–function relationships of Humanin and explained the driving force of the drastic conformational change and molecular basis of the potent anti-amyloid-β fibrillation activity of Humanin caused by D-isomerization of the Ser14 residue. This is the first study to show correlations between the functional activity, tertiary structure, and partner recognition mode of Humanin and may lead to elucidation of the molecular mechanisms of the cytoprotective activity of Humanin. - Highlights: • Humanin D-Ser14 showed the strongest inhibitory activity against Aβ40 fibrillation. • NMR structure of Humanin D-Ser14 was determined in alcohol/water mixture solution. • Humanin D-Ser14 directly bound Aβ40 stronger than Humanin wild-type and Humanin S14G. • Aβ40 and zinc ion binding sites of Humanin D-Ser14 were identified. • Structure around Ser14 of Humanin is critical for Aβ40 binding and

Photochemical generation of highly destabilized vinyl cations: the effects of alpha- and beta-trifluoromethyl versus alpha- and beta-methyl substituents

NARCIS (Netherlands)

Alem, van K.; Belder, G.; Lodder, G.; Zuilhof, H.

2005-01-01

The photochemical reactions in methanol of the vinylic halides 1-4, halostyrenes with a methyl or a trifluoromethyl substituent at the - or -position, have been investigated quantitatively. Next to E/Z isomerization, the reactions are formation of vinyl radicals, leading to reductive dehalogenation

Reactions of carbonate radical with cobalt(II) aminopolycarboxylates

International Nuclear Information System (INIS)

Mandal, P.C.; Bardhan, D.K.; Bhattacharyya, S.N.

1992-01-01

Reactions of carbonate (CO 3 - radical) and bicarbonate (HCO 3 radical) radicals generated by photolysis of a carbonate or bicarbonate solution at pH 11.2 and 8.5, respectively, with Co(II) complexes of iminodiacetic acid (IDA) and ethylenediaminetetraacetic acid (EDTA) have been studied. The rate constants for the reactions were in the order of 10 6 -10 7 dm 3 mol -1 s -1 . From the time-resolved spectroscopy of the products formed after reaction of CO 3 - radical or HCO 3 radical, it is observed that CO 3 - radical or HCO 3 radical oxidize the metal center to its higher oxidation state. (author) 26 refs.; 2 figs.; 1 tab

Comparison of Separation of Seed Oil Triglycerides Containing Isomeric Conjugated Octadecatrienoic Acid Moieties by Reversed-Phase HPLC

OpenAIRE

Anh Van Nguyen; Victor Deineka; Lumila Deineka; Anh Vu Thi Ngoc

2017-01-01

Relative retention analysis and increment approach were applied for the comparison of triglycerides (TGs) retention of a broad set of plant seed oils with isomeric conjugated octadecatrienoic acids (CLnA) by reversed-phase HPLC for “propanol-2-acetonitrile” mobile phases and Kromasil 100-5C18 stationary phase with diode array detection (DAD) and mass spectrometric (MS) detection. The subjects of investigation were TGs of seed oils: Calendula officinalis, Catalpa ovata, Jacaranda mimosifolia, ...

Self-Terminating, Oxidative Radical Cyclizations

Directory of Open Access Journals (Sweden)

Uta Wille

2004-05-01

Full Text Available The recently discovered novel concept of self-terminating, oxidative radical cyclizations, through which alkynes can be converted into carbonyl compounds under very mild reaction conditions using O-centered inorganic and organic radicals as oxidants, is described

Oxidation of aromatic amines and diamines by OH radicals. Formation and ionization constants of amine cation radicals in water

International Nuclear Information System (INIS)

Hayon, E.; Rao, P.S.

1975-01-01

The one-electron oxidation by hydroxyl radicals of aromatic amines and diamines in water was studied using the fast-reaction technique of pulse radiolysis and kinetic absorption spectrophotometry. The following compounds were examined: N,N,N 1 ,N 1 - tetramethyl-p-phenylenediamine (TMPD), p-phenylenediamine (PD), N,N-dimethyl-p-phenylenediamene (DMPD), N,N,N 1 ,N 1 -tetramethylbenzidine (TMB), and diphenylamine (DPA). The main initial reaction of the OH radicals is suggested to be an addition to these compounds to give absorption spectra which absorb strongly in the visible and uv regions. These OH radical adducts decay by first-order kinetics and have lifetimes of approximately 5-50 μsec, dependent on the pH, buffer concentration, and the nature of the aromatic amines and diamines. They decay to give species with somewhat similar absorption spectra and extinction coefficients, which are very long lived in the absence of oxygen. The latter species are assigned to the cation radicals TMPD. + , PD. + , DMPD. + , TMB. + , and DPA. + . The OH radical adducts and the cation radicals have acid-base properties. The pK/sub a/ values of the cation radicals TMPDH. 2+ , PDH. 2+ , DMPDH. 2+ , TMBH. 2+ , and DPAH. 2+ were found to be 5.3, 5.9, 6.1, 5.1, and 4.2, respectively. The results indicate that these aromatic amines and diamines can be oxidized by free radicals to yield the corresponding cation radicals. (U.S.)

Near-Infrared Free-Radical and Free-Radical-Promoted Cationic Photopolymerizations by In-Source Lighting Using Upconverting Glass.

Science.gov (United States)

Kocaarslan, Azra; Tabanli, Sevcan; Eryurek, Gonul; Yagci, Yusuf

2017-11-13

A method is presented for the initiation of free-radical and free-radical-promoted cationic photopolymerizations by in-source lighting in the near-infrared (NIR) region using upconverting glass (UCG). This approach utilizes laser irradiation of UCG at 975 nm in the presence of fluorescein (FL) and pentamethyldiethylene triamine (PMDETA). FL excited by light emitted from the UCG undergoes electron-transfer reactions with PMDETA to form free radicals capable of initiating polymerization of methyl methacrylate. To execute the corresponding free-radical-promoted cationic polymerization of cyclohexene oxide, isobutyl vinyl ether, and N-vinyl carbazole, it was necessary to use FL, dimethyl aniline (DMA), and diphenyliodonium hexafluorophosphate as sensitizer, coinitiator, and oxidant, respectively. Iodonium ions promptly oxidize DMA radicals formed to the corresponding cations. Thus, cationic polymerization with efficiency comparable to the conventional irradiation source was achieved. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

OH radical induced depolymerization of poly(methacrylic acid)

Science.gov (United States)

Ulanski, Piotr; Bothe, Eberhard; von Sonntag, Clemens

1999-05-01

Hydroxyl radicals (generated pulse radiolytically in dilute N 2O-saturated aqueous solutions) react with poly(methacrylic acid) producing two kinds of radicals. The primary radical is converted into a secondary one by H-abstraction ( k=3.5 × 10 2 s -1) as monitored by changes in the UV spectrum. Subsequently, the secondary radicals undergo chain scission ( k=1.8 s -1 at pH 7-9). This process has been followed both by spectrophotometry as well as by conductometry. In competition with the bimolecular decay of the radicals the ensuing end-chain radicals undergo efficient depolymerization resulting in the release of monomer. Since the lifetime of the radicals is much longer at high pH, where the polymer attains a rod-like conformation, depolymerization is most efficient in basic solution.

Electron spin resonance study of radicals in irradiated polyethylene

International Nuclear Information System (INIS)

Fujimura, Takashi

1979-02-01

In order to elucidate radiation effect in polyethylene, the nature and behavior of radicals produced in polyethylene and the model compound of polyethylene irradiated at 77 0 K were studied by using electron spin resonance. The structure of radical pairs, which are composed of two radicals produced very closely each other, was investigated in drawn polyethylene and the single crystal of n-eicosane. The radical pairs of intrachain type and interchain type were found in polyethylene and n-eicosane respectively. It was suggested that these two types of radical pairs are the precursors of double bonds and crosslinks respectively. The thermal decay reactions of radicals themselves produced in irradiated polyethylene were investigated. It was made clear that the short range distances between two radicals play an important role in the decay reaction of alkyl radicals at low temperatures. The trapping regions of radicals were studied and it was clarified that allyl radicals, which are produced by the reaction of alkyl radicals with double bonds, are trapped both in the crystalline and non-crystalline regions. (author)

Redox properties of free radicals

International Nuclear Information System (INIS)

Neta, P.

1981-01-01

Results of electron transfer reactions observed and monitored by pulse radiolysis are reported. This technique allows determination of the first one-electron reduction or oxidation of a compound rather than the overall two-electron transfer usually reported. Pulse radiolysis allows the determination of absolute rate constants for reactions of free radicals and helps elucidate the mechanisms involved. Studies using this technique to study radicals derived from quinones, nitro compounds, pyridines, phenols, and anilines are reported. Radicals of biochemical interest arising from riboflavin, ascorbic acid, vitamin K 3 , vitamin E, MAD + , porphyrins, etc. have also been studied

Hot wire radicals and reactions

International Nuclear Information System (INIS)

Zheng Wengang; Gallagher, Alan

2006-01-01

Threshold ionization mass spectroscopy is used to measure radical (and stable gas) densities at the substrate of a tungsten hot wire (HW) reactor. We report measurements of the silane reaction probability on the HW and the probability of Si and H release from the HW. We describe a model for the atomic H release, based on the H 2 dissociation model. We note major variations in silicon-release, with dependence on prior silane exposure. Measured radical densities versus silane pressure yield silicon-silane and H-silane reaction rate coefficients, and the dominant radical fluxes to the substrate

Synthesis and Characterization of Ethylenedithio-MPTTF-PTM Radical Dyad as a Potential Neutral Radical Conductor

DEFF Research Database (Denmark)

Souto, Manuel; Bendixen, Dan; Jensen, Morten

2016-01-01

During the last years there has been a high interest in the development of new purely-organic single-component conductors. Very recently, we have reported a new neutral radical conductor based on the perchlorotriphenylmethyl (PTM) radical moiety linked to a monopyrrolo-tetrathiafulvalene (MPTTF...

Physico-chemical basis of radioprotection by melanin: a fungal pigment

International Nuclear Information System (INIS)

Barik, A.; Kunwar, A.; Singh, B.G.; Priyadarsini, K.I.; Raghukumar, S.

2014-01-01

Melanin is a biopolymer with wide spread biological activity like protection from UV-radiation damage, decrease of oxidative stress, binding to metals and drugs etc. Recently it has been observed that melanized fungal species grow in areas of high-radiation background in Chernobyl, and also in cooling pool water of nuclear reactors. Some of these organisms survived even after radiation exposure up to 6400 Gy. This prompted us to evaluate the radioprotecting ability of melanin. Although there are various types of melanin available, for the present radioprotection studies, melanin isolated from the culture filtrate of a fungus Gliocephalotrichum simplex was used. Chemically this particular type of melanin is the oligomeric form of dihydroxy indole and dihydroxy indole carboxylic acid and termed as eumelanin. Due to the presence of dihydroxy group in the benzene ring, they are in equilibrium with the partially oxidized (semiquinone radical form) and fully oxidized (quinone, non-radical) form. The radical nature of melanin was detected by electron paramagnetic resonance (EPR) spectrum and quantitative estimation of radical was made, in terms of spin density i. e. as 6.62 x 1017 spins/g. The protective activity of melanin was primarily due to inhibition of radiation-induced hematopoietic damages as evidenced by improvement in spleen parameters. To further understand the physico-chemical properties associated with radioprotection, reactions radiolytically generated free radicals with melanin was studied using pulse radiolysis

Multicomponent kinetic analysis and theoretical studies on the phenolic intermediates in the oxidation of eugenol and isoeugenol catalyzed by laccase.

Science.gov (United States)

Qi, Yan-Bing; Wang, Xiao-Lei; Shi, Ting; Liu, Shuchang; Xu, Zhen-Hao; Li, Xiqing; Shi, Xuling; Xu, Ping; Zhao, Yi-Lei

2015-11-28

Laccase catalyzes the oxidation of natural phenols and thereby is believed to initialize reactions in lignification and delignification. Numerous phenolic mediators have also been applied in laccase-mediator systems. However, reaction details after the primary O-H rupture of phenols remain obscure. In this work two types of isomeric phenols, EUG (eugenol) and ISO (trans-/cis-isoeugenol), were used as chemical probes to explore the enzymatic reaction pathways, with the combined methods of time-resolved UV-Vis absorption spectra, MCR-ALS, HPLC-MS, and quantum mechanical (QM) calculations. It has been found that the EUG-consuming rate is linear to its concentration, while the ISO not. Besides, an o-methoxy quinone methide intermediate, (E/Z)-4-allylidene-2-methoxycyclohexa-2,5-dienone, was evidenced in the case of EUG with the UV-Vis measurement, mass spectra and TD-DFT calculations; in contrast, an ISO-generating phenoxyl radical, a (E/Z)-2-methoxy-4-(prop-1-en-1-yl) phenoxyl radical, was identified in the case of ISO. Furthermore, QM calculations indicated that the EUG-generating phenoxyl radical (an O-centered radical) can easily transform into an allylic radical (a C-centered radical) by hydrogen atom transfer (HAT) with a calculated activation enthalpy of 5.3 kcal mol(-1) and then be fast oxidized to the observed eugenol quinone methide, rather than an O-radical alkene addition with barriers above 12.8 kcal mol(-1). In contrast, the ISO-generating phenoxyl radical directly undergoes a radical coupling (RC) process, with a barrier of 4.8 kcal mol(-1), while the HAT isomerization between O- and C-centered radicals has a higher reaction barrier of 8.0 kcal mol(-1). The electronic conjugation of the benzyl-type radical and the aromatic allylic radical leads to differentiation of the two pathways. These results imply that competitive reaction pathways exist for the nascent reactive intermediates generated in the laccase-catalyzed oxidation of natural phenols, which is

Theoretical and spectroscopic investigation of the oxidation and degradation of protocatechuic acid

International Nuclear Information System (INIS)

Hatzipanayioti, Despina; Karaliota, Alexandra; Kamariotaki, Mary; Aletras, Vasilios; Petropouleas, Panayiotis

2006-01-01

In this work, we report a combined experimental and theoretical study on molecular structure and spectroscopic properties of the most stable conformers of PCA. 1 H, 13 C NMR and 2D COSY NMR, ESR, IR and electronic spectroscopies were coupled with DFT theoretical calculations performed at the B3LYP/6-31G** level. The calculated geometrical parameters for the neutral protocatechuic acid PCA-H 3 , its anions, its oxidized forms and the peroxo-derivative [PCA-H-O 2 ] 2- are in line with the experimental data. The neutral catecholate is the most stable form of PCA-H 3 whilst the dianion [PCA-H] 2- presents higher energy. This anion is (experimentally) stable only under argon, reacting with dioxygen, in the presence of air. The semiquinone [PCA-H-sq(3)] - is very close in energy from [PCA-H-sq(4)] - form and an equilibrium between these two oxidized radical forms might be expected. The energetically advantageous pathway for preparation of the symmetrically delocalized [PCA-sq] 2- is to oxidize the [PCA] 3- . The occurrence of this radical dianion form was justified experimentally by ESR, IR, UV-vis and NMR spectra. The structural calculations for [PCA-H-O 2 ] 2- indicate that C 3 (and to a lesser extent C1) may undergo a nucleophilic attack from the 'co-ordinated' peroxo-group. The conditions for the non-enzymatic degradation of PCA have been established and some new products are observed: ionization of PCA-H 3 , the presence of O 2 and aprotic solvents provide the semiquinone-superoxo adduct which is then degraded to lactones, while in protic solvents, addition of H 2 O 2 and the presence of air, are essential, providing aliphatic degradation products

Transient-Absorption Spectroscopy of Cis-Trans Isomerization of N,N-dimethyl-4,4'-Azodianiline with 3D-Printed Temperature-Controlled Sample Holder

Science.gov (United States)

Kosenkov, Dmytro; Shaw, James; Zuczek, Jennifer; Kholod, Yana

2016-01-01

The laboratory unit demonstrates a project based approach to teaching physical chemistry laboratory where upper-division undergraduates carry out a transient-absorption experiment investigating the kinetics of cis-trans isomerization of N,N-dimethyl-4,4'-azodianiline. Students participate in modification of a standard flash-photolysis spectrometer…

Free radicals trapped in polyethylene matrix

International Nuclear Information System (INIS)

Shimada, S.; Maeda, M.; Hori, Y.; Kashiwabara, H.

1977-01-01

Two types of alkyl radicals were found to be trapped in irradiated crystals grown from polyethylene solution. One of them corresponds to the broad sextet pattern of the e.s.r. spectrum and the other corresponds to the sharp sextet pattern. The free radicals attributed to the broad sextet began to disappear at a lower temperature than the temperature at which the free radicals attributed to the sharp sextet disappeared. When butadiene molecules were brought into contact with the specimen, the decay of the free radicals corresponding to the broad sextet was accelerated. When the specimen was subjected to fuming nitric acid treatment, no broad sextet was observed. The mat of the crystals was aligned so that the c-axes of its crystallites were perpendicular to its surface. The broad sextet showed no anisotropy when the angle between the direction of applied magnetic field and that of the c-axis of the crystallite was varied. On the other hand, the sharp component of the spectrum showed apparent anisotropy. It can be concluded that the broad component comes from the free radicals trapped in the lamellar surface and the sharp component is attributed to the free radicals trapped in the inner part of the crystallite. (author)

Free radicals generated by radiolysis of aqueous solutions

International Nuclear Information System (INIS)

Schwarz, H.A.

1981-01-01

The free radicals produced in the radiolysis of aqueous solutions span the range of redox potentials from -2.9 to +2.65 volts. The identity and nature of these radicals were discussed. Most of the discussion was results obtained with low LET radiation sources ( 60 Co gamma radiation or electron accelerators). Water radiolysis provides the synthesis of many radicals and radical ions in aqueous solution. The primary radicals, e/sub aq/ - H, OH, are well characterized. The radical population can be made to be 90% pure OH (or O - ) if N 2 O solutions are irradiated, the remaining 10% being H atoms. 55% of the radicals can be converted to H atoms in acid solution or in neutral phosphate solutions(e/sub aq/ - reacts with H 2 PO 4- to produce H). The remaining 45% (OH radicals) are difficult to convert to H by reaction with H 2 , due to the slow rate of the reaction. About 100 atmospheres of H 2 are required to do the conversion in less than 10 - 6 sec. 3 figures, 3 tables. (DP)

From laboratory catalysts to a new prototype: a novel real candidate for the isomerization of C5–C6 paraffins

Czech Academy of Sciences Publication Activity Database

Hidalgo, J. M.; Kaucký, Dalibor; Bortnovsky, O.; Černý, R.; Sobalík, Zdeněk

2015-01-01

Roč. 5, JUN 2015 (2015), s. 56625-56628 ISSN 2046-2069 R&D Projects: GA MPO FR-TI3/316 Institutional support: RVO:61388955 Keywords : C5-C6 paraffins * isomeration * Pt/WO3–ZrO2 materials Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.289, year: 2015

Photoinduced intramolecular charge transfer and trans-cis isomerization of the DCM styrene dye. Picosecond and nanosecond laser spectroscopy, high-performance liquid chromatography, and nuclear magnetic resonance studies

Energy Technology Data Exchange (ETDEWEB)

Meyer, M.; Mialocq, J.C.; Perly, B. (CNRS, Gif-sur-Yvette (France))

1990-01-11

The photoexcitation of 4-(dicyanomethylene)-2-methyl-6-(p-(dimethylamino)styryl)-4H-pyran (DCM) induces a large intramolecular charge transfer (ICT) from the dimethylamino electron-donor group to the dicyanomethylene acceptor group. The dramatic effect of the solvent polarity on the absorption and fluorescence spectra on the one hand and the competition between the nonradiative S{sub 1} {yields} S{sub 0} deactivation and trans {yields} cis isomerization processes on the other hand has been examined. Our results clearly show that DCM isomerization efficiency is very low in the more polar solvents. The S{sub 1} {yields} S{sub 0} internal conversion may intervene at a torsional angle smaller than 90{degree} before reaching the perpendicular configuration.

Radical carbonylations using a continuous microflow system

Directory of Open Access Journals (Sweden)

Takahide Fukuyama

2009-07-01

Full Text Available Radical-based carbonylation reactions of alkyl halides were conducted in a microflow reactor under pressurized carbon monoxide gas. Good to excellent yields of carbonylated products were obtained via radical formylation, carbonylative cyclization and three-component coupling reactions, using tributyltin hydride or TTMSS as a radical mediator.

Radical-Mediated Enzymatic Polymerizations

Science.gov (United States)

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

2016-01-01

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

Interaction of slow neutrons with the second isomeric level Kπ=16+ of the 178Hf isotope

International Nuclear Information System (INIS)

Pangault, Laurence

1999-01-01

In this work, we study the interaction of low energy neutrons (E≤ 10 eV) with the second isomeric level of 178 Hf (l π =K π =16 + , T 1/2 =31 y) in (n,γ) reactions which proceed through the formation of a compound nucleus. The radiative decay of high K states in 179 Hf is investigated using an isomeric I π =16 + 178 Hf target, 40 ng in weight. The first experiment, performed at the high flux reactor in the Laue Langevin Institute in Grenoble, consisted in γ-ray spectroscopy measurements. For this purpose, an experimental set-up has been built. lt consists of four large Ge detectors shielded against background using a specific F 6 Li collimations ensemble. The second experiments performed at the Fakel (Kurchatov lnstitute, Moscow) and Gelina (IRMM Geel, Belgium) linear accelerators consisted in the investigation of neutron resonances in the 178 Hf m2 (n,γ) reaction using time of flight technique and their γ-decay paths. A high efficiency spectrometer has been built and used for the measurements at bath sites. Two resonances located at 1.82 eV and 0.75 eV have been observed and unambiguously assigned to the (n+ 178 Hf m2 ) compound system. The γ-decay properties of these resonances are very different. Furthermore, the γ-decay path followed by the 0.75 eV resonance is at odd with that expected form statistical model predictions. (author) [fr

Allylthioketone Mediated Free Radical Polymerization of Methacrylates

Directory of Open Access Journals (Sweden)

Feng Zhong

2017-11-01

Full Text Available By combination of high trapping free radical efficiency of the thioketone and resonance of the allylic radical, a new type of mediating agent, 1,3,3-triphenylprop-2-ene-1-thione (TPPT has been successfully synthesized, and then is used to study controlled free radical polymerization of methacrylates. Very stable TPPT radicals at the end of poly(methyl methacrylate (PMMA are detected in the polymerization of MMA using TPPT and AIBN as the control agent and initiator. The MALDI-TOF MS spectra are used to identify terminal groups of the resultant poly(glycidyl methacrylate (PGMA, and major component of the obtained polymer has the structure, (CH32(CNC-PGMA-C7H9O3. Chain extension reaction tests ascertain formation of the dead polymers during the polymer storage and purification process of the polymers. Owing to very slow fragmentation reaction of the TPPT-terminated polymethacrylate radical and addition reaction of this radical with a primary radical, the growing chain radicals are difficult to be regenerated, leading to an unobvious change of the molecular weight with monomer conversion. The molecular weights of polymers can be controlled by the ratios of monomer/initiator and TPPT/initiator. However, the first order kinetics of the polymerization and the polymers with narrow polydispersity are obtained, and these phenomena are discussed. This study provides useful information on how to design a better controlling agent.

Fluorescence lifetime measurement of radical ions

International Nuclear Information System (INIS)

Ichinose, Nobuyuki; Kinugasa, Jun-ichiro; Hagiri, Masahide; Nakayama, Toshihiro; Murakami, Hiroshi; Kishimoto, Maki; Daido, Hiroyuki

2004-01-01

One-photonic excitation of a charge transfer complex of hexamethoxybenzene (HMB) and nitrosonium tetrafluoroborate (NO + BF 4 - ) in acetonitrile afforded fluorescences emission from excited radical cation of HMB (HMB + *). Lifetime of the excited radical ion species was measured to be 7 ps by the pump-probe transient absorption technique. The lifetime was much shorter than that of free radical ion (63 ps), indicating the presence of an interaction between HMB + * and NO in the excited complex. (author)

Generation and propagation of radical reactions on proteins

DEFF Research Database (Denmark)

Hawkins, C L; Davies, Michael Jonathan

2001-01-01

The oxidation of proteins by free radicals is thought to play a major role in many oxidative processes within cells and is implicated in a number of human diseases as well as ageing. This review summarises information on the formation of radicals on peptides and proteins and how radical damage may...... be propagated and transferred within protein structures. The emphasis of this article is primarily on the deleterious actions of radicals generated on proteins, and their mechanisms of action, rather than on enzymatic systems where radicals are deliberately formed as transient intermediates. The final section...

Radical scavenging activity of crude polysaccharides from Camellia sinensis

Directory of Open Access Journals (Sweden)

Yang Fan

2011-01-01

Full Text Available A preparation of crude polysaccharides (TPS was isolated from Camellia sinensis by precipitation and ultrafiltration. TPS1, TPS2, and TPS3 had molecular weights of 240, 21.4, and 2.46 kDa, respectively. The radical scavenging activities of TPS were evaluated by DPPH free radical, hydroxyl radical and superoxide radical scavenging. These results revealed that TPS exhibited strong radical scavenging activity in a concentration-dependent manner. TPS3 with lowest molecular weight showed a higher radical scavenging activity.

Is HO3 minimum cis or trans? An analytic full-dimensional ab initio isomerization path.

Science.gov (United States)

Varandas, A J C

2011-05-28

The minimum energy path for isomerization of HO(3) has been explored in detail using accurate high-level ab initio methods and techniques for extrapolation to the complete basis set limit. In agreement with other reports, the best estimates from both valence-only and all-electron single-reference methods here utilized predict the minimum of the cis-HO(3) isomer to be deeper than the trans-HO(3) one. They also show that the energy varies by less than 1 kcal mol(-1) or so over the full isomerization path. A similar result is found from valence-only multireference configuration interaction calculations with the size-extensive Davidson correction and a correlation consistent triple-zeta basis, which predict the energy difference between the two isomers to be of only Δ = -0.1 kcal mol(-1). However, single-point multireference calculations carried out at the optimum triple-zeta geometry with basis sets of the correlation consistent family but cardinal numbers up to X = 6 lead upon a dual-level extrapolation to the complete basis set limit of Δ = (0.12 ± 0.05) kcal mol(-1). In turn, extrapolations with the all-electron single-reference coupled-cluster method including the perturbative triples correction yield values of Δ = -0.19 and -0.03 kcal mol(-1) when done from triple-quadruple and quadruple-quintuple zeta pairs with two basis sets of increasing quality, namely cc-cpVXZ and aug-cc-pVXZ. Yet, if added a value of 0.25 kcal mol(-1) that accounts for the effect of triple and perturbative quadruple excitations with the VTZ basis set, one obtains a coupled cluster estimate of Δ = (0.14 ± 0.08) kcal mol(-1). It is then shown for the first time from systematic ab initio calculations that the trans-HO(3) isomer is more stable than the cis one, in agreement with the available experimental evidence. Inclusion of the best reported zero-point energy difference (0.382 kcal mol(-1)) from multireference configuration interaction calculations enhances further the relative

Vibronic Spectroscopy of the Phenylcyanomethyl Radical

Science.gov (United States)

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

2011-06-01

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

Introducing Stable Radicals into Molecular Machines.

Science.gov (United States)

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

2017-09-27

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

Some reactions of oxidizing radicals with enzymes in aqueous solution

International Nuclear Information System (INIS)

Cundall, R.B.; Bisby, R.H.; Hoe, S.T.; Sims, H.E.; Anderson, R.F.

1979-01-01

A range of oxidizing radicals including some inorganic radical anions and the superoxide radical, can be generated by radiolysis of aqueous solutions. These radicals are more selective in their reactions with amino acids than the hydroxyl radical. Factors controlling the apparent reactivity of radical anions with proteins, such as free radical equilibria and ion-binding, are described. The superoxide radical inactivates papain by reaction with the cysteine residue. This reaction has been studied in solutions subjected to radiations of varying linear energy transfer. (Auth.)

Long-lived gas-phase radicals from combustion

Energy Technology Data Exchange (ETDEWEB)

Kaneko, Takashi; Furusawa, Koji; Amano, Toshiji; Okubo, Yoichi; Tsuchiya, Jun' ichi; Yoshizawa, Fujiroku; Akutsu, Yoshiaki; Tamura, Masamitsu; Yoshida, Tadao (Univ. of Tokyo (Japan))

1989-04-20

On indoor air pollution or fire, it is feared that the gas-phase radicals from the combustion of inflammables or fuel seriously exert an influence on the organisms as harmful matter. The gas-phase radicals were studied using the electron spin resonance (ESR) spin-trapping technique. For the spin trap solution, 0.1 mol solution of {alpha}-phenyl-N-t-butylnitron in benzene was used. As a result, apparently long-lived and highly reactive oxygen-centered radicals were detected in the smoke from polyethylene, polypropylene, polystyrene, polymethylmethacrylate, cellulose, kerosene, benzene, acetone, methanol and butylalcohol. It is suggested that the production mechanism for the radicals should be different from olefin-NOx-air system reaction, which is considered for the radicals from cigarette smoke. 11 refs., 6 figs., 2 tabs.

[Research progress on free radicals in human body].

Science.gov (United States)

Wang, Q B; Xu, F P; Wei, C X; Peng, J; Dong, X D

2016-08-10

Free radicals are the intermediates of metabolism, widely exist in the human bodies. Under normal circumstances, the free radicals play an important role in the metabolic process on human body, cell signal pathway, gene regulation, induction of cell proliferation and apoptosis, so as to maintain the normal growth and development of human body and to inhibit the growth of bacteria, virus and cancer. However, when organic lesion occurs affected by external factors or when equilibrium of the free radicals is tipped in the human body, the free radicals will respond integratedly with lipids, protein or nucleic acid which may jeopardize the health of human bodies. This paper summarizes the research progress of the free radicals conducted in recent years, in relations to the perspective of the types, origins, test methods of the free radicals and their relationship with human's health. In addition, the possible mechanisms of environmental pollutants (such as polycyclic aromatic hydrocarbons) mediating oxidative stress and free radicals scavenging in the body were also summarized.

Aging of SRC liquids

Science.gov (United States)

Hara, T.; Jones, L.; Tewari, K. C.; Li, N. C.

1981-02-01

The viscosity of SRC-LL liquid increases when subjected to accelerated aging by bubbling oxygen in the presence of copper strip at 62°C. Precipitates are formed and can be separated from the aged liquid by Soxhlet extraction with pentane. A 30-70 blend of SRC-I with SRC-LL was subjected to oxygen aging in the absence of copper, and the viscosity increased dramatically after 6 days at 62°. The content of preasphaltene and its molecular size increase with time of aging, accompanied by decrease of asphaltene and pentane-soluble contents. For the preasphaltene fraction on aging, gel permeation chromatography shows formation of larger particles. ESR experiments show that with oxygen aging, spin concentration in the preasphaltene fraction decreases. Perhaps some semiquinone, together with di- and tri-substituted phenoxy radicals, generated by oxygen aging of the coal liquid, interact with the free radicals already present in coal to yield larger particles and reduce free radical concentration. We are currently using the very high-field (600-MHz) NMR spectrometer at Mellon Institute to determine changes in structural parameters before and after aging of SRC-II and its chromatographically separated fractions.

Deciphering free-radical code of radiation effects

International Nuclear Information System (INIS)

Volovyk, S.; Bazyka, D.; Loganovsky, K.; Bebeshko, V.

2007-01-01

Complete text of publication follows. Objective: Ionizing radiation is fundamental environmental factor for life origin and evolution. Free radicals, primordial 'sea' for life conceiving and existence, induced by cosmic and terrestrial background radiation, are evolutionally archetypal, ubiquitous, and omnipotent in physiological- pathophysiological dichotomy. Classical free-radical paradigm in radiation biology and medicine, focused in essence on oxidative damage, needs new conceptualization and generalization. Methods: Suggested novel insights into free radicals dual immanent nature and functions in organism systems are based on original concepts of radicals dynamic charge transfer (CT) - redox ambivalence (interactional nucleo-, electro-, and ambiphilicity spectrum); pertinent chemical reactivity and selectivity delocalization model; physiological functional ambivalence and complementarity, and dynamic free-radical homeostasis. Results: Subtle perturbations in radicals CT spatiotemporal homeodynamics, in responsive signaling / controlling networks, concomitant alterations in genes expression, transcription, and apoptosis, redox control of mitochondrial ET chain, telomere/telomerase balance, DNA CT, circadian clock, hemispheric biochemical dominance/accentuation, including alteration of nitric oxide-superoxide complementarity, membranes permeability, neurotransmission pattern, synaptic circuitry, etc under radiation exposure have more fundamental impact on organism systems (especially CNS and CVS) deterioration than simple radicals inflicted oxidative (nitrosative) damage of cellular constituents. Conclusions: This novel conceptualization of free-radical paradigm constitutes new dimension in deciphering molecular mechanisms of radiation effects on subtle borderline norm-pathology and continuity-discontinuity dichotomy in organisms systems disorders - CT(redox)omics, which involves investigation of CT, redox, and spin states of free radicals, DNA bases

Zwitterion radicals and anion radicals from electron transfer and solvent condensation with the fingerprint developing agent ninhydrin.

Science.gov (United States)

Schertz, T D; Reiter, R C; Stevenson, C D

2001-11-16

Ninhydrin (the fingerprint developing agent) spontaneously dehydrates in liquid ammonia and in hexamethylphosphoramide (HMPA) to form indantrione, which has a sufficiently large solution electron affinity to extract an electron from the solvent (HMPA) to produce the indantrione anion radical. In liquid NH(3), the presence of trace amounts of amide ion causes the spontaneous formation of an anion radical condensation product, wherein the no. 2 carbon (originally a carbonyl carbon) becomes substituted with -NH(2) and -OH groups. In HMPA, the indantrione anion radical spontaneously forms condensation products with the HMPA to produce a variety of zwitterionic radicals, wherein the no. 2 carbon becomes directly attached to a nitrogen of the HMPA. The mechanisms for the formation of the zwitterionic paramagnetic condensation products are analogous to that observed in the reaction of ninhydrin with amino acids to yield Ruhemann's Purple, the contrast product in fingerprint development. The formation of anion and zwitterionic radical condensation products from ninhydrin and nitrogen-containing solvents may represent an example of a host of analogous polyketone-solvent reactions.

Contribution to the production of lactulose-rich whey by in situ electro-isomerization of lactose and effect on whey proteins after electro-activation as confirmed by matrix-assisted laser desorption/ionization time-of-flight-mass spectrometry and sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

Science.gov (United States)

Kareb, Ourdia; Champagne, Claude P; Aïder, Mohammed

2016-04-01

Cheese-whey, a major co-product of the dairy industry, has recently been the subject of many technological applications. We studied the bioconversion of whey into valuable bio-products such as a potential lactulose prebiotic and compounds with antioxidant properties. This paper examines efficiency, safety, and economics of electro-activation as an eco-friendly technology for a maximum valorization of whey. Thus, a bottom-up approach was therefore addressed. The effect of 4 experimental parameters--low working temperatures (0, 10, and 25 °C), current intensities (400, 600, and 800 mA), volume conditions (100, 200, and 300 mL), and feed concentrations [7, 14, and 28% (wt/vol)]--on lactose-whey isomerization to lactulose under electro-activation process were studied. Structural characteristics of whey proteins and antioxidant functionality were also investigated. The results showed a compromise to be reached between both parameters. Therefore, the maximum yield of 35% of lactulose was achieved after 40 min of reaction at the working temperature of 10 °C under 400 mA electric current field and 100-mL volume conditions with using feed solution at 7% (wt/vol). The isomerization of lactose to lactulose is accomplished by subsequent degradation to galactose, but only at a very small amount. Additionally, whey electro-activation showed significantly elevated antioxidant capacity compared with the untreated samples. The enhancement of antioxidant functionality of whey electro-activation resulted from the synergistic effect of its partial hydrolysis and the formation of antioxidant components that were able to scavenge free radicals. In conclusion, the findings of this study reveal that the whey treated by the safety electro-activation technology has both lactulose-prebiotic and antioxidant properties and could have a substantial application in the manufacture of pharmaceutical and functional foods. Copyright © 2016 American Dairy Science Association. Published by Elsevier

Free radical scavenging injectable hydrogels for regenerative therapy

Energy Technology Data Exchange (ETDEWEB)

Komeri, Remya [Sree Chitra Tirunal Institute for Medical Sciences and Technology, Polymer Science Division, BMT Wing, Thiruvananthapuram 695 012, Kerala State (India); Thankam, Finosh Gnanaprakasam [Dept. of Biomedical Sciences, Creighton University, 2500 California Plaza, Omaha NE68178 (United States); Muthu, Jayabalan, E-mail: mjayabalan52@gmail.com [Sree Chitra Tirunal Institute for Medical Sciences and Technology, Polymer Science Division, BMT Wing, Thiruvananthapuram 695 012, Kerala State (India)

2017-02-01

Pathological free radicals generated from inflamed and infarcted cardiac tissues interferes natural tissue repair mechanisms. Hypoxic microenvironment at the injured zone of non-regenerating cardiac tissues hinders the therapeutic attempts including cell therapy. Here we report an injectable, cytocompatible, free radical scavenging synthetic hydrogel formulation for regenerative therapy. New hydrogel (PEAX-P) is prepared with D-xylitol-co-fumarate-co-poly ethylene adipate-co-PEG comaromer (PEAX) and PEGDiacrylate. PEAX-P hydrogel swells 4.9 times the initial weight and retains 100.07 kPa Young modulus at equilibrium swelling, which is suitable for cardiac applications. PEAX-P hydrogel retains elastic nature even at 60% compressive strain, which is favorable to fit with the dynamic and elastic natural tissue counterparts. PEAX-P hydrogel scavenges 51% DPPH radical, 40% hydroxyl radicals 41% nitrate radicals with 31% reducing power. The presence of hydrogel protects 62% cardiomyoblast cells treated with stress inducing media at LD 50 concentration. The free hydroxyl groups in sugar alcohols of the comacromer influence the free radical scavenging. Comparatively, PEAX-P hydrogel based on xylitol evinces slightly lower scavenging characteristics than with previously reported PEAM-P hydrogel containing mannitol having more hydroxyl groups. The possible free radical scavenging mechanism of the present hydrogel relies on the free π electrons associated with uncrosslinked fumarate bonds, hydrogen atoms associated with sugar alcohols/PEG and radical dilution by free water in the matrix. Briefly, the present PEAX-P hydrogel is a potential injectable system for combined antioxidant and regenerative therapy. - Graphical abstract: Injectable hydrogel with inherent free radical scavenging property for regenerative tissue engineering application. - Highlights: • Novel injectable hydrogel (PEAX-P) is prepared using D-xylitol-co-fumarate-co-poly ethylene adipate-co-PEG comaromer

Free radical scavenging injectable hydrogels for regenerative therapy

International Nuclear Information System (INIS)

Komeri, Remya; Thankam, Finosh Gnanaprakasam; Muthu, Jayabalan

2017-01-01

Pathological free radicals generated from inflamed and infarcted cardiac tissues interferes natural tissue repair mechanisms. Hypoxic microenvironment at the injured zone of non-regenerating cardiac tissues hinders the therapeutic attempts including cell therapy. Here we report an injectable, cytocompatible, free radical scavenging synthetic hydrogel formulation for regenerative therapy. New hydrogel (PEAX-P) is prepared with D-xylitol-co-fumarate-co-poly ethylene adipate-co-PEG comaromer (PEAX) and PEGDiacrylate. PEAX-P hydrogel swells 4.9 times the initial weight and retains 100.07 kPa Young modulus at equilibrium swelling, which is suitable for cardiac applications. PEAX-P hydrogel retains elastic nature even at 60% compressive strain, which is favorable to fit with the dynamic and elastic natural tissue counterparts. PEAX-P hydrogel scavenges 51% DPPH radical, 40% hydroxyl radicals 41% nitrate radicals with 31% reducing power. The presence of hydrogel protects 62% cardiomyoblast cells treated with stress inducing media at LD 50 concentration. The free hydroxyl groups in sugar alcohols of the comacromer influence the free radical scavenging. Comparatively, PEAX-P hydrogel based on xylitol evinces slightly lower scavenging characteristics than with previously reported PEAM-P hydrogel containing mannitol having more hydroxyl groups. The possible free radical scavenging mechanism of the present hydrogel relies on the free π electrons associated with uncrosslinked fumarate bonds, hydrogen atoms associated with sugar alcohols/PEG and radical dilution by free water in the matrix. Briefly, the present PEAX-P hydrogel is a potential injectable system for combined antioxidant and regenerative therapy. - Graphical abstract: Injectable hydrogel with inherent free radical scavenging property for regenerative tissue engineering application. - Highlights: • Novel injectable hydrogel (PEAX-P) is prepared using D-xylitol-co-fumarate-co-poly ethylene adipate-co-PEG comaromer

Radical Transversal Lightlike Submanifolds of Indefinite Para-Sasakian Manifolds

OpenAIRE

Shukla S.S.; Yadav Akhilesh

2014-01-01

In this paper, we study radical transversal lightlike submanifolds and screen slant radical transversal lightlike submanifolds of indefinite para-Sasakian manifolds giving some non-trivial examples of these submanifolds. Integrability conditions of distributions D and RadTM on radical transversal lightlike submanifolds and screen slant radical transversal lightlike submanifolds of indefinite para-Sasakian manifolds, have been obtained. We also study totally contact umbilical radical transvers...

Structure and reactivity of the N-acetyl-cysteine radical cation and anion: does radical migration occur?

NARCIS (Netherlands)

Osburn, S.; Berden, G.; Oomens, J.; O'Hair, R.A.J.; Ryzhov, V.

2011-01-01

The structure and reactivity of the N-acetyl-cysteine radical cation and anion were studied using ion-molecule reactions, infrared multi-photon dissociation (IRMPD) spectroscopy, and density functional theory (DFT) calculations. The radical cation was generated by first nitrosylating the thiol of

Structure and Reactivity of the N-Acetyl-Cysteine Radical Cation and Anion: Does Radical Migration Occur?

NARCIS (Netherlands)

Osburn, S.; G. Berden,; Oomens, J.; O' Hair, R. A. J.; Ryzhov, V.

2011-01-01

The structure and reactivity of the N-acetyl-cysteine radical cation and anion were studied using ion-molecule reactions, infrared multi-photon dissociation (IRMPD) spectroscopy, and density functional theory (DFT) calculations. The radical cation was generated by first nitrosylating the thiol of

Cation radicals of xanthophylls.

Science.gov (United States)

Galinato, Mary Grace I; Niedzwiedzki, Dariusz; Deal, Cailin; Birge, Robert R; Frank, Harry A

2007-10-01

Carotenes and xanthophylls are well known to act as electron donors in redox processes. This ability is thought to be associated with the inhibition of oxidative reactions in reaction centers and light-harvesting pigment-protein complexes of photosystem II (PSII). In this work, cation radicals of neoxanthin, violaxanthin, lutein, zeaxanthin, beta-cryptoxanthin, beta-carotene, and lycopene were generated in solution using ferric chloride as an oxidant and then studied by absorption spectroscopy. The investigation provides a view toward understanding the molecular features that determine the spectral properties of cation radicals of carotenoids. The absorption spectral data reveal a shift to longer wavelength with increasing pi-chain length. However, zeaxanthin and beta-cryptoxanthin exhibit cation radical spectra blue-shifted compared to that of beta-carotene, despite all of these molecules having 11 conjugated carbon-carbon double bonds. CIS molecular orbital theory quantum computations interpret this effect as due to the hydroxyl groups in the terminal rings selectively stabilizing the highest occupied molecular orbitals of preferentially populated s-trans-isomers. The data are expected to be useful in the analysis of spectral results from PSII pigment-protein complexes seeking to understand the role of carotene and xanthophyll cation radicals in regulating excited state energy flow, in protecting PSII reaction centers against photoinhibition, and in dissipating excess light energy absorbed by photosynthetic organisms but not used for photosynthesis.

Conformational control of cofactors in nature: The effect of methoxy group orientation on the electronic structure of ubisemiquinone

Science.gov (United States)

De Almeida, Wagner B.; O'Malley, Patrick J.

2018-03-01

Ubiquinone is the key electron and proton transfer agent in biology. Its mechanism involves the formation of its intermediate one-electron reduced form, the ubisemiquinone radical. This is formed in a protein-bound form which permits the semiquinone to vary its electronic and redox properties. This can be achieved by hydrogen bonding acceptance by one or both oxygen atoms or as we now propose by restricted orientations for the methoxy groups of the headgroup. We show how the orientation of the two methoxy groups of the quinone headgroup affects the electronic structure of the semiquinone form and demonstrate a large dependence of the ubisemiquinone spin density distribution on the orientation each methoxy group takes with respect to the headgroup ring plane. This is shown to significantly modify associated hyperfine couplings which in turn needs to be accounted for in interpreting experimental values in vivo. The study uncovers the key potential role the methoxy group orientation can play in controlling the electronic structure and spin density of ubisemiquinone and provides an electronic-level insight into the variation in electron affinity and redox potential of ubiquinone as a function of the methoxy orientation. Taken together with the already known influence of cofactor conformation on heme and chlorophyll electronic structure, it reveals a more widespread role for cofactor conformational control of electronic structure and associated electron transfer in biology.

Violent Radicalization in Europe

DEFF Research Database (Denmark)

Dalgaard-Nielsen, Anja

2010-01-01

When, why, and how do people living in a democracy become radicalized to the point of being willing to use or directly support the use of terrorist violence against fellow citizens? This question has been at the center of academic and public debate over the past years as terrorist attacks...... within this field and to answer the question: From an empirical point of view, what is known and what is not known about radicalization connected to militant Islamism in Europe?...

Application of ABTS radical cation for selective on-line detection of radical scavengers in HPLC eluates

NARCIS (Netherlands)

Koleva, [No Value; Niederlander, HAG; van Beek, TA

2001-01-01

The radical cation 2,2 ' -azinobis-(3 -ethylbenzothiazoline-6-sulfonate), (ABTS(.+)) was utilized in an on-line HPLC method for the detection of radical scavengers in complex matrixes. The HPLC-separated analytes react postcolumn with the preformed ABTS(.+), and the induced bleaching is detected as

Critical appraisal of outcomes following open radical prostatectomy.

Science.gov (United States)

Galvin, David J; Eastham, James A

2009-05-01

Radical prostatectomy has evolved enormously over the last 25 years. Improvements include the use of smaller incisions, reduced blood loss, shorter hospital stays, and surgical refinement to improve the recovery of continence and potency. In addition, new technologies and minimally invasive techniques with the potential to further improve patient outcomes have been introduced. This article focuses on outcomes with open radical prostatectomy and is not meant to compare open radical prostatectomy and minimally invasive approaches. Despite a lack of randomized controlled trials, strong observational cohort studies demonstrate lower rates of positive surgical margins, high 10-year and 15-year biochemical recurrence-free rates, excellent prostate cancer-specific mortality rates, and improved recovery of urinary incontinence and erectile function after open radical prostatectomy. We review publications from the past 24 months regarding oncologic outcome, continence, and erectile function, as well as some earlier manuscripts that emphasize key aspects of open radical prostatectomy. Today open radical prostatectomy is a less-invasive procedure with low morbidity providing excellent control of clinically localized prostate cancer. Although open radical prostatectomy now accounts for a minority of radical prostatectomies in the United States, the concepts that have improved oncologic and quality-of-life outcomes are equally applicable to minimally invasive procedures.

NOx removal characteristics of corona radical shower with ammonia and methylamine radical injections

Energy Technology Data Exchange (ETDEWEB)

Urashima, K.; Ara, M.; Chang, J.S. [McMaster Univ., Hamilton, ON (Canada). Dept. of Engineering Physics; Uchida, Y. [Aichi Inst. of Technology, (Japan). Dept. of Engineering

2010-07-01

Air pollutants such as nitrogen oxides (NOx) and sulfur oxides (SOx) are the major cause of acid rain. There are different types of NOx and SOx conversion techniques such as wet scrubber, selective catalytic reactor, sorbent injection, and low NOx burner. Non-thermal plasma techniques have also been utilized in commercial plants, but the energy efficiency of the non-thermal plasma reactors have not yet been optimized. The direct plasma treatments of flue gases including, the electron beam, barrier discharge and pulsed corona reactors, may lose input energy to activate unwanted components of flue gases such as carbon dioxide (CO{sub 2}) and nitrogen (N{sub 2}). The corona discharge ammonia radical shower system has demonstrated significant NOx removal with higher energy efficiency for large bench scale and pilot plant tests for combustion exhausts. An experiment has also demonstrated that methane can replace ammonia as an injection gas with less NOx removal efficiency. This paper presented an experimental investigation that compared methylamine radical injection with traditional ammonia and methane radical injections. The paper discussed the bench scale test facilities and corona radical shower plasma reactor. It was concluded that the processes to form ammonium nitrate could be observed from trace white solid particles deposited on the reactor wall as observed by scanning electron microscopy pictures. 10 refs., 5 figs., 2 appendices.

Radical Sustainable Innovation of office buildings

DEFF Research Database (Denmark)

Koch, Christian; Berker, Thomas; Koch-Ørvad, Nina

2017-01-01

by high degrees of newness in the entire life cycle. RSI should offer significant enhancements of known benefits, entirely new benefits, or substantial cost reductions, leading to the transformation of existing markets, the creation of sustainable growth, and global sustainability. Thus, if buildings were....../could be radically new. How to evaluate radicality is a major challenge. It is tentatively proposed, to use standards for sustainable office buildings. Standards are developed to accelerate the sustainable development but has to some extent come to constrain possibilities of radical innovation. As the criteria...... of newness is incorporated in standards, going beyond them, could be viewed as radical. Empirically a selection of international cases of office buildings with very high scores of BREEAM, LEED and DGNB are examined. Six selected cases were analysed more in detail, one of them, Geelens...

User involvement competence for radical innovation

DEFF Research Database (Denmark)

Lettl, Christopher

2007-01-01

-assisted navigation systems. The case study analysis reveals that firms who closely interact with specific users benefit significantly for their radical innovation work. These users have a high motivation toward new solutions, are open to new technologies, possess diverse competencies, and are embedded into a very......One important market related capability for firms which seek to develop radical innovations is the competence to involve the 'right' users at the 'right' time in the 'right' form. While former studies have identified a rather passive role of users in the radical innovation process, this paper...

User involvement competence for radical innovation

DEFF Research Database (Denmark)

Lettl, Christopher

2007-01-01

One important market related capability for firms which seek to develop radical innovations is the competence to involve the 'right' users at the 'right' time in the 'right' form. While former studies have identified a rather passive role of users in the radical innovation process, this paper......-assisted navigation systems. The case study analysis reveals that firms who closely interact with specific users benefit significantly for their radical innovation work. These users have a high motivation toward new solutions, are open to new technologies, possess diverse competencies, and are embedded into a very...

Intramolecular hydrogen bonding in malonaldehyde and its radical analogues.

Science.gov (United States)

Lin, Chen; Kumar, Manoj; Finney, Brian A; Francisco, Joseph S

2017-09-28

High level Brueckner doubles with triples correction method-based ab initio calculations have been used to investigate the nature of intramolecular hydrogen bonding and intramolecular hydrogen atom transfer in cis-malonaldehyde (MA) and its radical analogues. The radicals considered here are the ones that correspond to the homolytic cleavage of C-H bonds in cis-MA. The results suggest that cis-MA and its radical analogues, cis-MA RS , and cis-MA RA , both exist in planar geometry. The calculated intramolecular O-H⋯O=C bond in cis-MA is shorter than that in the radical analogues. The intramolecular hydrogen bond in cis-MA is stronger than in its radicals by at least 3.0 kcal/mol. The stability of a cis-malonaldehyde radical correlates with the extent of electron spin delocalization; cis-MA RA , in which the radical spin is more delocalized, is the most stable MA radical, whereas cis-MA RS , in which the radical spin is strongly localized, is the least stable radical. The natural bond orbital analysis indicates that the intramolecular hydrogen bonding (O⋯H⋯O) in cis-malonaldehyde radicals is stabilized by the interaction between the lone pair orbitals of donor oxygen and the σ * orbital of acceptor O-H bond (n → σ * OH ). The calculated barriers indicate that the intramolecular proton transfer in cis-MA involves 2.2 kcal/mol lower barrier than that in cis-MA RS .

Hydroxyl radical reactivity with diethylhydroxylamine

International Nuclear Information System (INIS)

Gorse, R.A. Jr.; Lii, R.R.; Saunders, B.B.

1977-01-01

Diethylhydroxylamine (DEHA) reacts with gas-phase hydroxyl radicals on every third collision, whereas the corresponding reaction in aqueous solution is considerably slower. The high gas-phase reactivity explains the predicted inhibitory effect of DEHA in atmospheric smog processes. Results from the studies in the aqueous phase are helpful in predicting the mechanism of the reaction of DEHA with hydroxyl radicals

Radical dematerialization and degrowth

Science.gov (United States)

Kallis, Giorgos

2017-05-01

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

Thermal evolution of the morphology of Ni/Ag/Si(111)-{radical}3 Multiplication-Sign {radical}3 surface

Energy Technology Data Exchange (ETDEWEB)

Tomaszewska, Agnieszka; Huang, Xiao-Lan; Chang, Kuo-Wei; Fu, Tsu-Yi, E-mail: phtifu@phy.ntnu.edu.tw

2012-08-31

The temperature-driven changes in morphology of the interface formed by room temperature (RT) deposition of Ni atoms onto an Ag/Si(111)-{radical}3 Multiplication-Sign {radical}3 surface were investigated by scanning tunneling microscopy. Roughly 70% of Ni deposition diffused into bulk substrate within the temperature range between RT and 573 K. The images as obtained after annealing up to 670 K correspond to the formation of nano-sized islands of nickel silicides. Two types of islands, large triangular islands typical of the whole range of applied coverage, and smaller islands of different shapes, coexist at Ni coverage higher than 1 monolayer. Annealing above 870 K led to the formation of a 7 Multiplication-Sign 7 phase in coexistence with small 5 Multiplication-Sign 5 domains at the expense of a complete disappearance of the {radical}3 Multiplication-Sign {radical}3 phase. Also, formation of Ni,Si alloy was observed at the temperature, along with segregation of bulk-dissolved Ni species onto the surface. - Highlights: Black-Right-Pointing-Pointer We examine changes in morphology of Ni/Ag/Si(111)-{radical}3 Multiplication-Sign {radical}3 surface upon annealing. Black-Right-Pointing-Pointer 70% of deposited Ni atoms diffuse into the bulk after annealing at 570 K. Black-Right-Pointing-Pointer A variety of nano-sized Ni, Si islands develops after annealing at 670 K. Black-Right-Pointing-Pointer 5 Multiplication-Sign 5 reconstruction as an evidence for mass transport during the island growth.

Ring-Expansion/Contraction Radical Crossover Reactions of Cyclic Alkoxyamines: A Mechanism for Ring Expansion-Controlled Radical Polymerization

Directory of Open Access Journals (Sweden)

Atsushi Narumi

2018-06-01

Full Text Available Macrocyclic polymers present an important class of macromolecules, displaying the reduced radius of gyration or impossibility to entangle. A rare approach for their synthesis is the ring expansion-controlled radical “vinyl” polymerization, starting from a cyclic alkoxyamine. We here describe ring-expansion radical crossover reactions of cyclic alkoxyamines which run in parallel to chain-propagation reactions in the polymerization system. The radical crossover reactions extensively occurred at 105–125 °C, eventually producing high molecular weight polymers with multiple inherent dynamic covalent bonds (NOC bonds. A subsequent ring-contraction radical crossover reaction and the second ring-expansion radical crossover reaction are also described. The major products for the respective three stages were shown to possess cyclic morphologies by the molecular weight profiles and the residual ratios for the NOC bonds (φ in %. In particular, the high φ values ranging from ca. 80% to 98% were achieved for this cyclic alkoxyamine system. This result verifies the high availability of this system as a tool demonstrating the ring-expansion “vinyl” polymerization that allows them to produce macrocyclic polymers via a one-step vinyl polymerization.

Biochemistry and pathology of radical-mediated protein oxidation

DEFF Research Database (Denmark)

Dean, R T; Fu, S; Stocker, R

1997-01-01

Radical-mediated damage to proteins may be initiated by electron leakage, metal-ion-dependent reactions and autoxidation of lipids and sugars. The consequent protein oxidation is O2-dependent, and involves several propagating radicals, notably alkoxyl radicals. Its products include several catego...

How to counter radical narratives: Dutch deradicalization policy in the case of Moluccan and Islamic radicals

NARCIS (Netherlands)

Demant, F.; de Graaf, B.

2010-01-01

This article deals with the role of government in encouraging the decline of radical movements. The question posed is: "Which story can the government tell to encourage the decline of radical groups and the disengagement of their members?" The article makes use of the survey of factors promoting

In-tube collision-induced dissociation for selected ion flow-drift tube mass spectrometry, SIFDT-MS: a case study of NO+ reactions with isomeric monoterpenes

Czech Academy of Sciences Publication Activity Database

Spesyvyi, Anatolii; Sovová, Kristýna; Španěl, Patrik

2016-01-01

Roč. 30, č. 18 (2016), s. 2009-2016 ISSN 0951-4198 R&D Projects: GA ČR GA13-28882S Institutional support: RVO:61388955 Keywords : mass spectroscopy * SIFDT-MS * isomeric monoterpenes Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.998, year: 2016

Structure and Reactivity of the Glutathione Radical Cation: Radical Rearrangement from the Cysteine Sulfur to the Glutamic Acid alpha-Carbon Atom

NARCIS (Netherlands)

Osburn, S.; Berden, G.; Oomens, J.; Gulyuz, K.; Polfer, N.C.; O'Hair, R.A.J.; Ryzhov, V.

2013-01-01

A gas-phase radical rearrangement through intramolecular hydrogen-atom transfer (HAT) was studied in the glutathione radical cation, [-ECG](+.), which was generated by a homolytic cleavage of the protonated S-nitrosoglutathione. Ion-molecule reactions suggested that the radical migrates from the

Hydrotreating NiMo/sepiolite catalysts: influence of catalyst preparation on activity for HDS, hydrogenation and chain isomerization reactions

International Nuclear Information System (INIS)

Melo, F.V.; Sanz, E.; Corma, A.; Mifsud, A.

1987-01-01

A series of NiMo catalysts supported on a sepiolite: a) in its natural state, b) modified by acid leaching, and c) modified by cation exchange, have been prepared. The preparation variables studied were: Method of metal deposition, amount of active phase, sepiolite pretreatment, and temperature and time of sulfurization. The catalytic activity for HDS, hydrogenation, and cracking-isomerization has been studied by feeding a thiophene-cyclohexene-cyclohexane mixture and carrying out the reaction in the following conditions: 300 0 and 400 0 C reaction temperature, 20 Kg.cm -2 total pressure, and 3 to 1 molar ratio of H 2 to hydrocarbons. An optimium for HDS and hydrogenation activity was found for a 12% wt MoO 3 , and 5% wt NiO, prepared by simultaneous impregnation by the pore volume method at Ph = 5.0. The optimum conditions with these catalysts are 400 0 C and 3 hours of sulfurization. An increase in the acidity of the support produces a decrease of HDS and hydrogenation and an increase of the cracking-isomerization activities. A good correlation between HDS and the concentration of an XNiO.MoO 3 phase is found. The XNiO.MoO 3 phase is completely sulfurized to a modified MoS 2 , while NiMoO 4 and MoO 3 are only slightly sulfurized. 31 refs.; 7 figs.; 1 table

Photodynamically generated bovine serum albumin radicals

DEFF Research Database (Denmark)

Silvester, J A; Timmins, G S; Davies, Michael Jonathan

1998-01-01

Porphyrin-sensitized photoxidation of bovine serum albumin (BSA) results in oxidation of the protein at (at least) two different, specific sites: the Cys-34 residue giving rise to a thiyl radical (RS.); and one or both of the tryptophan residues (Trp-134 and Trp-214) resulting in the formation...... of tertiary carbon-centred radicals and disruption of the tryptophan ring system. In the case of porphyrins such as hematoporphyrin, which bind at specific sites on BSA, these species appear to arise via long-range transfer of damage within the protein structure, as the binding site is some distance from...... the ultimate site of radical formation. This transfer of damage is shown to depend on a number of factors including the conformation of the protein, the presence of blocking groups and pH. Alteration of the protein conformation results in radical formation at additional (or alternative) sites, as does blocking...

Measurements of isomeric yield ratios of fission products from proton-induced fission on natU and 232Th via direct ion counting

Directory of Open Access Journals (Sweden)

Rakopoulos Vasileios

2017-01-01

Full Text Available Independent isomeric yield ratios (IYR of 81Ge, 96Y, 97Y, 97Nb, 128Sn and 130Sn have been determined in the 25 MeV proton-induced fission of natU and 232Th. The measurements were performed at the Ion Guide Isotope Separator On-Line (IGISOL facility at the University of Jyväskylä. A direct ion counting measurement of the isomeric fission yield ratios was accomplished for the first time, registering the fission products in less than a second after their production. In addition, the IYRs of natU were measured by means of γ-spectroscopy in order to verify the consistency of the recently upgraded experimental setup. From the obtained results, indications of a dependence of the production rate on the fissioning system can be noticed. These data were compared with data available in the literature, whenever possible. Using the TALYS code and the experimentally obtained IYRs, we also deduced the average angular momentum of the fission fragments after scission.

The Rise of Radicals in Bioinorganic Chemistry