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Neil C Bruce - One of the best experts on this subject based on the ideXlab platform.
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the substrate spectra of Pentaerythritol Tetranitrate reductase morphinone reductase n ethylmaleimide reductase and estrogen binding protein in the asymmetric bioreduction of activated alkenes
Advanced Synthesis & Catalysis, 2010Co-Authors: Nicole J. Mueller, Neil C Bruce, Clemens Stueckler, Bernhard Hauer, Nina Baudendistel, Hazel R. Housden, Kurt FaberAbstract:Four flavoproteins from the old yellow enzyme (OYE) family, Pentaerythritol Tetranitrate (PETNR) reductase, N-ethylmaleimide reductase (NEMR), morphinone reductase (MorR) and estrogen-binding protein (EBP1), exhibited a broad substrate tolerance by accepting conjugated enals, enones, imides, dicarboxylic acids and esters, as well as a nitroalkene and therefore can be employed for the asymmetric bioreduction of carbon-carbon double (C=C) bonds. In particular, morphinone reductase and estrogen-binding protein often showed a complementary stereochemical preference in comparison to that of previously investigated OYEs.
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kinetic and structural basis of reactivity of Pentaerythritol Tetranitrate reductase with nadph 2 cyclohexenone nitroesters and nitroaromatic explosives
Journal of Biological Chemistry, 2002Co-Authors: Huma Khan, Richard J Harris, Terez Barna, Daniel H Craig, Neil C Bruce, Andrew W Munro, Peter C E Moody, Nigel S ScruttonAbstract:Abstract The reaction of Pentaerythritol Tetranitrate reductase with reducing and oxidizing substrates has been studied by stopped-flow spectrophotometry, redox potentiometry, and X-ray crystallography. We show in the reductive half-reaction of Pentaerythritol Tetranitrate (PETN) reductase that NADPH binds to form an enzyme-NADPH charge transfer intermediate prior to hydride transfer from the nicotinamide coenzyme to FMN. In the oxidative half-reaction, the two-electron-reduced enzyme reacts with several substrates including nitroester explosives (glycerol trinitrate and PETN), nitroaromatic explosives (trinitrotoluene (TNT) and picric acid), and α,β-unsaturated carbonyl compounds (2-cyclohexenone). Oxidation of the flavin by the nitroaromatic substrate TNT is kinetically indistinguishable from formation of its hydride-Meisenheimer complex, consistent with a mechanism involving direct nucleophilic attack by hydride from the flavin N5 atom at the electron-deficient aromatic nucleus of the substrate. The crystal structures of complexes of the oxidized enzyme bound to picric acid and TNT are consistent with direct hydride transfer from the reduced flavin to nitroaromatic substrates. The mode of binding the inhibitor 2,4-dinitrophenol (2,4-DNP) is similar to that observed with picric acid and TNT. In this position, however, the aromatic nucleus is not activated for hydride transfer from the flavin N5 atom, thus accounting for the lack of reactivity with 2,4-DNP. Our work with PETN reductase establishes further a close relationship to the Old Yellow Enzyme family of proteins but at the same time highlights important differences compared with the reactivity of Old Yellow Enzyme. Our studies provide a structural and mechanistic rationale for the ability of PETN reductase to react with the nitroaromatic explosive compounds TNT and picric acid and for the inhibition of enzyme activity with 2,4-DNP.
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biodegradation of explosives by transgenic plants expressing Pentaerythritol Tetranitrate reductase
Nature Biotechnology, 1999Co-Authors: Susan J Rosser, Christopher E French, Gareth J Davies, Stephen Nicklin, Neil C BruceAbstract:Plants offer many advantages over bacteria as agents for bioremediation; however, they typically lack the degradative capabilities of specially selected bacterial strains. Transgenic plants expressing microbial degradative enzymes could combine the advantages of both systems. To investigate this possibility in the context of bioremediation of explosive residues, we generated transgenic tobacco plants expressing Pentaerythritol Tetranitrate reductase, an enzyme derived from an explosive-degrading bacterium that enables degradation of nitrate ester and nitroaromatic explosives. Seeds from transgenic plants were able to germinate and grow in the presence of 1 mM glycerol trinitrate (GTN) or 0.05 mM trinitrotoluene, at concentrations that inhibited germination and growth of wild-type seeds. Transgenic seedlings grown in liquid medium with 1 mM GTN showed more rapid and complete denitration of GTN than wild-type seedlings. This example suggests that transgenic plants expressing microbial degradative genes may provide a generally applicable strategy for bioremediation of organic pollutants in soil.
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aerobic degradation of 2 4 6 trinitrotoluene by enterobacter cloacae pb2 and by Pentaerythritol Tetranitrate reductase
Applied and Environmental Microbiology, 1998Co-Authors: Christopher E French, Stephen Nicklin, Neil C BruceAbstract:Enterobacter cloacae PB2 was originally isolated on the basis of its ability to utilize nitrate esters, such as Pentaerythritol Tetranitrate (PETN) and glycerol trinitrate, as the sole nitrogen source for growth. The enzyme responsible is an NADPH-dependent reductase designated PETN reductase. E. cloacae PB2 was found to be capable of slow aerobic growth with 2,4,6-trinitrotoluene (TNT) as the sole nitrogen source. Dinitrotoluenes were not produced and could not be used as nitrogen sources. Purified PETN reductase was found to reduce TNT to its hydride-Meisenheimer complex, which was further reduced to the dihydride-Meisenheimer complex. Purified PETN reductase and recombinant Escherichia coli expressing PETN reductase were able to liberate nitrogen as nitrite from TNT. The ability to remove nitrogen from TNT suggests that PB2 or recombinant organisms expressing PETN reductase may be useful for bioremediation of TNT-contaminated soil and water.
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sequence and properties of Pentaerythritol Tetranitrate reductase from enterobacter cloacae pb2
Journal of Bacteriology, 1996Co-Authors: Christopher E French, S Nicklin, Neil C BruceAbstract:Pentaerythritol Tetranitrate reductase, which reductively liberates nitrite from nitrate esters, is related to old yellow enzyme. Pentaerythritol Tetranitrate reductase follows a ping-pong mechanism with competitive substrate inhibition by NADPH, is strongly inhibited by steroids, and is capable of reducing the unsaturated bond of 2-cyclohexen-1-one.
Y M Gupta - One of the best experts on this subject based on the ideXlab platform.
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anisotropic material model and wave propagation simulations for shocked Pentaerythritol Tetranitrate single crystals
Journal of Applied Physics, 2010Co-Authors: J M Winey, Y M GuptaAbstract:An anisotropic continuum material model was developed to describe the thermomechanical response of unreacted Pentaerythritol Tetranitrate (PETN) single crystals to shock wave loading. Using this model, which incorporates nonlinear elasticity and crystal plasticity in a thermodynamically consistent tensor formulation, wave propagation simulations were performed to compare to experimental wave profiles [J. J. Dick and J. P. Ritchie, J. Appl. Phys. 76, 2726 (1994)] for PETN crystals under plate impact loading to 1.2 GPa. Our simulations show that for shock propagation along the [100] orientation where deformation across shear planes is sterically unhindered, a dislocation-based model provides a good match to the wave profile data. For shock propagation along the [110] direction, where deformation across shear planes is sterically hindered, a dislocation-based model cannot account for the observed strain-softening behavior. Instead, a shear cracking model was developed, providing good agreement with the data ...
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second order elastic constants of Pentaerythritol Tetranitrate and cyclotrimethylene trinitramine using impulsive stimulated thermal scattering
Journal of Applied Physics, 2008Co-Authors: B Sun, J M Winey, Y M Gupta, Zbigniew A Dreger, N Hemmi, K A Zimmerman, Darius Torchinsky, Keith A NelsonAbstract:Impulsive stimulated thermal scattering (ISTS) was used to determine the complete set of second-order elastic constants for Pentaerythritol Tetranitrate (PETN) and cyclotrimethylene trinitramine (RDX) single crystals. Despite the weak scattering efficiency of these materials, excellent signal quality was obtained by using an optical heterodyne detection approach. The elastic constants for PETN agree well with previous values obtained from ultrasonic velocity measurements. The elastic constants for RDX are consistent with previous values obtained from ultrasonic velocity measurements and from resonant ultrasound spectroscopy, but show significant differences with values obtained from Brillouin scattering data. The present results demonstrate that the ISTS method, with optical heterodyne detection, provides a useful and accurate approach for determining the elastic constants of energetic crystals.
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raman spectra of shock compressed Pentaerythritol Tetranitrate single crystals anisotropic response
Journal of Physical Chemistry B, 2006Co-Authors: N Hemmi, J M Winey, Zbigniew A Dreger, Yuri A Gruzdkov, Y M GuptaAbstract:To gain insight into the anisotropic sensitivity of shocked Pentaerythritol Tetranitrate (PETN) single crystals, single-pulse Raman spectroscopy was used to examine the response of crystals shocked along the [100] (insensitive) and [110] (sensitive) orientations. High-resolution Raman spectra revealed several orientation-dependent features under shock compression: (i) substantially different stress dependence of the Raman shift for the CH2 and NO2 stretching modes for the two orientations, (ii) discontinuity in the stress dependence of the Raman shift for the CH2 stretching modes above 4 GPa for the [110] orientation, and (iii) large broadening for the CH2 and NO2 asymmetric stretching modes for stresses above 4 GPa for the [110] orientation. The present data in combination with previous static pressure results provide support for conformational changes in PETN molecules for shock compression along the [110] (sensitive) orientation. Implications of the present results for the anisotropic sensitivity of s...
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first principles study of Pentaerythritol Tetranitrate single crystals under high pressure vibrational properties
Chemical Physics Letters, 2006Co-Authors: Warren F Perger, J M Winey, Jijun Zhao, Y M GuptaAbstract:Abstract First-principles theoretical methods were used to investigate the vibrational properties of Pentaerythritol Tetranitrate (PETN) under hydrostatic compression up to 4 GPa. Bond lengths and bond angles for the PETN molecules and the pressure–volume relation for the crystal under high pressure were calculated and compared with previous calculations and with experimental results. Based on the calculated optimized geometries at ambient conditions and under hydrostatic pressure, the frequencies of the internal vibrational modes of the PETN molecules in the crystal and pressure-induced frequency shifts of these vibrational modes were obtained. The calculated vibrational frequencies are compared with previous single molecule calculations and with experimental data.
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experimental and theoretical study of Pentaerythritol Tetranitrate conformers
Journal of Physical Chemistry A, 2004Co-Authors: Yuri A Gruzdkov, Zbigniew A Dreger, Y M GuptaAbstract:Raman measurements and density functional theory (DFT) calculations were carried out to evaluate the propensity of Pentaerythritol Tetranitrate (PETN) to conformational changes. In the crystalline phase under ambient conditions, the PETN molecule has S4 symmetry. Two instances of symmetry change were found and presented in this work. One involved compressing the PETN crystal statically to ≥5 GPa in a diamond anvil cell. The other was observed upon dissolving PETN in a polar solvent (acetone-d6). DFT calculations indicate that changes in conformation/symmetry can be observed readily through changes in the vibrational spectrum. Several representative stable PETN conformations of various symmetries were found and examined. The calculated Raman spectra provide support for the conclusion that the S4 symmetry, at ambient conditions, changes to C2 under static high-pressure loading and to C2 or C1 in solution.
Christopher E French - One of the best experts on this subject based on the ideXlab platform.
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biodegradation of explosives by transgenic plants expressing Pentaerythritol Tetranitrate reductase
Nature Biotechnology, 1999Co-Authors: Susan J Rosser, Christopher E French, Gareth J Davies, Stephen Nicklin, Neil C BruceAbstract:Plants offer many advantages over bacteria as agents for bioremediation; however, they typically lack the degradative capabilities of specially selected bacterial strains. Transgenic plants expressing microbial degradative enzymes could combine the advantages of both systems. To investigate this possibility in the context of bioremediation of explosive residues, we generated transgenic tobacco plants expressing Pentaerythritol Tetranitrate reductase, an enzyme derived from an explosive-degrading bacterium that enables degradation of nitrate ester and nitroaromatic explosives. Seeds from transgenic plants were able to germinate and grow in the presence of 1 mM glycerol trinitrate (GTN) or 0.05 mM trinitrotoluene, at concentrations that inhibited germination and growth of wild-type seeds. Transgenic seedlings grown in liquid medium with 1 mM GTN showed more rapid and complete denitration of GTN than wild-type seedlings. This example suggests that transgenic plants expressing microbial degradative genes may provide a generally applicable strategy for bioremediation of organic pollutants in soil.
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aerobic degradation of 2 4 6 trinitrotoluene by enterobacter cloacae pb2 and by Pentaerythritol Tetranitrate reductase
Applied and Environmental Microbiology, 1998Co-Authors: Christopher E French, Stephen Nicklin, Neil C BruceAbstract:Enterobacter cloacae PB2 was originally isolated on the basis of its ability to utilize nitrate esters, such as Pentaerythritol Tetranitrate (PETN) and glycerol trinitrate, as the sole nitrogen source for growth. The enzyme responsible is an NADPH-dependent reductase designated PETN reductase. E. cloacae PB2 was found to be capable of slow aerobic growth with 2,4,6-trinitrotoluene (TNT) as the sole nitrogen source. Dinitrotoluenes were not produced and could not be used as nitrogen sources. Purified PETN reductase was found to reduce TNT to its hydride-Meisenheimer complex, which was further reduced to the dihydride-Meisenheimer complex. Purified PETN reductase and recombinant Escherichia coli expressing PETN reductase were able to liberate nitrogen as nitrite from TNT. The ability to remove nitrogen from TNT suggests that PB2 or recombinant organisms expressing PETN reductase may be useful for bioremediation of TNT-contaminated soil and water.
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sequence and properties of Pentaerythritol Tetranitrate reductase from enterobacter cloacae pb2
Journal of Bacteriology, 1996Co-Authors: Christopher E French, S Nicklin, Neil C BruceAbstract:Pentaerythritol Tetranitrate reductase, which reductively liberates nitrite from nitrate esters, is related to old yellow enzyme. Pentaerythritol Tetranitrate reductase follows a ping-pong mechanism with competitive substrate inhibition by NADPH, is strongly inhibited by steroids, and is capable of reducing the unsaturated bond of 2-cyclohexen-1-one.
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degradation of Pentaerythritol Tetranitrate by enterobacter cloacae pb2
Applied and Environmental Microbiology, 1996Co-Authors: P R Binks, S Nicklin, Christopher E French, Neil C BruceAbstract:A mixed microbial culture capable of metabolizing the explosive Pentaerythritol Tetranitrate (PETN) was obtained from soil enrichments under aerobic and nitrogen-limiting conditions. A strain of Enterobacter cloacae, designated PB2, was isolated from this culture and was found to use PETN as a sole source of nitrogen for growth. Growth yields suggested that 2 to 3 mol of nitrogen was utilized per mol of PETN. The metabolites Pentaerythritol dinitrate, 3-hydroxy-2,2-bis-[(nitrooxy)methyl]propanal, and 2,2-bis-[(nitrooxy)methyl]-propanedial were identified by mass spectrometry and 1H-nuclear magnetic resonance. An NADPH-dependent PETN reductase was isolated from cell extracts and shown to liberate nitrite from PETN, producing Pentaerythritol tri- and dinitrates which were identified by mass spectrometry. PETN reductase was purified to apparent homogeneity by ion-exchange and affinity chromatography. The purified enzyme was found to be a monomeric flavoprotein with a M(r) of approximately 40,000, binding flavin mononucleotide noncovalently.
Hanneke Brust - One of the best experts on this subject based on the ideXlab platform.
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accurate quantitation of Pentaerythritol Tetranitrate and its degradation products using liquid chromatography atmospheric pressure chemical ionization mass spectrometry
Journal of Chromatography A, 2014Co-Authors: Hanneke Brust, Arian C Van Asten, Mattijs Koeberg, Jan Dalmolen, Antoine E D M Van Der Heijden, Peter J SchoenmakersAbstract:After an explosion of Pentaerythritol Tetranitrate (PETN), its degradation products Pentaerythritol trinitrate (PETriN), dinitrate (PEDiN) and mononitrate (PEMN) were detected using liquid chromatography-atmospheric-pressure chemical-ionization-mass spectrometry (LC-APCI-MS). Discrimination between post-explosion and naturally degraded PETN could be achieved based on the relative amounts of the degradation products. This information can be used as evidence when investigating a possible relationship between a suspect and a post-explosion crime scene. The present work focuses on accurate quantitation of PETN and its degradation products, using PETriN, PEDiN and PEMN standards specifically synthesized for this purpose. With the use of these standards, the ionization behavior of these compounds was studied, and a quantitative method was developed. Quantitation of PETN and trace levels of its degradation products was shown to be possible with accuracy between 85.7% and 103.7% and a precision ranging from 1.3% to 11.5%. The custom-made standards resulted in a more robust and reliable method to discriminate between post-explosion and naturally-degraded PETN. © 2014 Elsevier B.V.
Thomas D Sewell - One of the best experts on this subject based on the ideXlab platform.
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Shock-Induced Inelastic Deformation in Oriented Crystalline Pentaerythritol Tetranitrate
2016Co-Authors: Reilly M Eason, Thomas D SewellAbstract:Molecular dynamics simulations were used to study the mechanisms of shock-induced inelastic deformation in oriented single crystals of the energetic material Pentaerythritol Tetranitrate (PETN). Supported planar shock waves with Rankine–Hugoniot shock pressures PR–H ∼ 9 GPa were propagated along two different crystal directions: one that is sensitive to initiation ([001]) and another that is relatively insensitive to initiation ([100]). Qualitatively, it was observed that for the sensitive orientation only elastic compression occurred, leading to the propagation of a single wave through the material, whereas for the insensitive direction elastic compression at and immediately behind the shock front was followed by inelastic deformation, leading to a two-wave structure in which the sharp elastic front moves through the crystal at a higher speed than the broader plastic wave. The detailed responses were characterized by calculating several structural and thermal properties including: relative center-of-mass molecular displacements (RMDs), classification of molecules behind the shock front as either elastically compressed or inelastically displaced, spatially resolved intermolecular and intramolecular temperatures (kinetic energies), and pre- and postshock intramolecular dihedral angle distributions. A quasi-2D system was studied for the [100] shock to further characterize the inelastic deformation mechanisms. Subregions exhibiting differing types of deformation were identified and examined in greater detail; specifically, time histories of the total kinetic energy (expressed in temperature units) and the rotational order parameter were calculated separately for elastically compressed and inelastically displaced molecules in a given subregion. The times required for re-establishment of the Maxwell–Boltzmann distribution of atomic kinetic energies and molecular center-of-mass kinetic energies in the shocked material were determined
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shock induced inelastic deformation in oriented crystalline Pentaerythritol Tetranitrate
Journal of Physical Chemistry C, 2012Co-Authors: Reilly M Eason, Thomas D SewellAbstract:Molecular dynamics simulations were used to study the mechanisms of shock-induced inelastic deformation in oriented single crystals of the energetic material Pentaerythritol Tetranitrate (PETN). Supported planar shock waves with Rankine–Hugoniot shock pressures PR–H ∼ 9 GPa were propagated along two different crystal directions: one that is sensitive to initiation ([001]) and another that is relatively insensitive to initiation ([100]). Qualitatively, it was observed that for the sensitive orientation only elastic compression occurred, leading to the propagation of a single wave through the material, whereas for the insensitive direction elastic compression at and immediately behind the shock front was followed by inelastic deformation, leading to a two-wave structure in which the sharp elastic front moves through the crystal at a higher speed than the broader plastic wave. The detailed responses were characterized by calculating several structural and thermal properties including: relative center-of-mass...
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terahertz spectrum and normal mode relaxation in Pentaerythritol Tetranitrate effect of changes in bond stretching force field terms
Journal of Chemical Physics, 2011Co-Authors: Andrey Pereverzev, Thomas D SewellAbstract:Terahertz (THz) active normal-mode relaxation in crystalline Pentaerythritol Tetranitrate (PETN) was studied using classical molecular dynamics simulations for energy and density conditions corresponding to room temperature and atmospheric pressure. Two modifications to the fully flexible non-reactive force field due to Borodin et al. [J. Phys. Chem. B 112, 734 (2008)]10.1021/jp076149f used in a previous study of THz-active normal-mode relaxation in PETN [J. Chem. Phys. 134, 014513 (2011)]10.1063/1.3518423 were considered to assess the sensitivity of the earlier predictions to details of the covalent bond-stretching terms in the force field. In the first modification the harmonic bond-stretching potential was replaced with the Morse potential to study the effect of bond anharmonicity on the THz-region mode relaxation. In the second modification the C-H and nitro-group N-O bond lengths were constrained to constant values to mimic lower quantum occupation numbers for those high-frequency modes. The results ...
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terahertz normal mode relaxation in Pentaerythritol Tetranitrate
Journal of Chemical Physics, 2011Co-Authors: Andrey Pereverzev, Thomas D SewellAbstract:Normal vibrational modes for a three-dimensional defect-free crystal of the high explosive Pentaerythritol Tetranitrate were obtained in the framework of classical mechanics using a previously published unreactive potential-energy surface [J. Phys. Chem. B 112, 734 (2008)]. Using these results the vibrational density of states was obtained for the entire vibrational frequency range. Relaxation of selectively excited terahertz-active modes was studied using isochoric-isoergic (NVE) molecular dynamics simulations for energy and density conditions corresponding to room temperature and atmospheric pressure. Dependence of the relaxation time on the initial modal excitation was considered for five excitation energies between 10 and 500 kT and shown to be relatively weak. The terahertz absorption spectrum was constructed directly using linewidths obtained from the relaxation times of the excited modes for the case of 10 kT excitation. The spectrum shows reasonably good agreement with experimental results. Dynami...
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terahertz normal mode relaxation in Pentaerythritol Tetranitrate
Journal of Chemical Physics, 2011Co-Authors: Andrey Pereverzev, Thomas D SewellAbstract:Normal vibrational modes for a three-dimensional defect-free crystal of the high explosive Pentaerythritol Tetranitrate were obtained in the framework of classical mechanics using a previously published unreactive potential-energy surface [J. Phys. Chem. B 112, 734 (2008)]. Using these results the vibrational density of states was obtained for the entire vibrational frequency range. Relaxation of selectively excited terahertz-active modes was studied using isochoric-isoergic (NVE) molecular dynamics simulations for energy and density conditions corresponding to room temperature and atmospheric pressure. Dependence of the relaxation time on the initial modal excitation was considered for five excitation energies between 10 and 500 kT and shown to be relatively weak. The terahertz absorption spectrum was constructed directly using linewidths obtained from the relaxation times of the excited modes for the case of 10 kT excitation. The spectrum shows reasonably good agreement with experimental results. Dynamics of redistribution of the excited mode energy among the other normal modes was also studied. The results indicate that, for the four terahertz-active initially excited modes considered, there is a small subset of zero wave vector (k = 0) modes that preferentially absorb the energy on a few-picosecond time scale. The majority of the excitation energy, however, is transferred nonspecifically to the bath modes of the system.