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Philippe Dugourd - One of the best experts on this subject based on the ideXlab platform.

  • Electron Photodetachment dissociation for structural characterization of synthetic and bio-polymer anions
    Mass Spectrometry Reviews, 2014
    Co-Authors: Rodolphe Antoine, Jérôme Lemoine, Philippe Dugourd
    Abstract:

    Tandem mass spectrometry (MS-MS) is a generic term evoking techniques dedicated to structural analysis, detection or quantification of molecules based on dissociation of a precursor ion into fragments. Searching for the most informative fragmentation patterns has led to the development of a vast array of activation modes that offer complementary ion reactivity and dissociation pathways. Collisional activation of ions using atoms, molecules or surface resulting in unimolecular dissociation of activated ions still plays a key role in tandem mass spectrometry. The discovery of Electron capture dissociation (ECD) and then the development of other Electron-ion or ion/ion reaction methods, constituted a significant breakthrough, especially for structural analysis of large biomolecules. Similarly, photon activation opened promising new frontiers in ion fragmentation owing to the ability of tightly controlled internal energy deposition and easy implementation on commercial instruments. Ion activation by photons includes slow heating methods such as infrared multiple photon dissociation (IRMPD) and black-body infrared radiative dissociation (BIRD) and higher energy methods like ultra-violet photodissociation (UVPD) and Electron photo detachment dissociation (EPD). EPD occurs after UV irradiation of multiply negatively charged ions resulting in the formation of oxidized radical anions. The present paper reviews the hypothesis regarding the mechanisms of Electron photo-detachment, radical formation and direct or activated dissociation pathways that support the observation of odd and even Electron product ions. Finally, the value of EPD as a complementary structural analysis tool is illustrated through selected examples of synthetic polymers, oligonucleotides, polypeptides, lipids, and polysaccharides

  • Prompt and slow Electron-detachment-dissociation/Electron-Photodetachment-dissociation of a 21-mer Peptide.
    Chemistry - A European Journal, 2013
    Co-Authors: Marie Pérot-taillandier, Rodolphe Antoine, Philippe Dugourd, Séverine Zirah, Quentin Enjalbert, Jérôme Lemoine, Sylvie Rebuffat, Jean-claude Tabet, Carlos Afonso
    Abstract:

    Electron detachment dissociation (EDD) and Electron Photodetachment dissociation (EPD) are relatively new dissociation methods that involve Electron detachment followed by radical-driven dissociation from multiply deprotonated species. EDD yields prompt dissociation whereas only Electron detachment is obtained by EPD; subsequent vibrational activation of the charge-reduced radical anion is required to obtain the product ions. Herein, the fragmentation patterns that were obtained by EDD and by vibrational activation of the charge-reduced radical anions that were produced through EDD or EPD (activated-EDD and activated-EPD) were compared. The observed differences were related to the dissociation kinetics and/or the contribution of Electron-induced dissociation (EID). Time-resolved double-resonance experiments were performed to measure the dissociation rate constants of the EDD product ions. Differences in the formation kinetics were revealed between the classical EDD/EPD 'a(.) (i) /''x(j) complementary ions and some 'a(.) (i) /c(i) /'''z(.) (j) product ions, which were produced with slower dissociation rate constants, owing to the presence of specific neighbouring side chains. A new fragmentation pathway is proposed for the formation of the slow-kinetics 'a(.) (i) ions.

  • prompt and slow Electron detachment dissociation Electron Photodetachment dissociation of a 21 mer peptide
    Chemistry: A European Journal, 2013
    Co-Authors: Rodolphe Antoine, Philippe Dugourd, Séverine Zirah, Quentin Enjalbert, Jérôme Lemoine, Sylvie Rebuffat, Jean-claude Tabet, Marie Perottaillandier, Carlos Afonso
    Abstract:

    Electron detachment dissociation (EDD) and Electron Photodetachment dissociation (EPD) are relatively new dissociation methods that involve Electron detachment followed by radical-driven dissociation from multiply deprotonated species. EDD yields prompt dissociation whereas only Electron detachment is obtained by EPD; subsequent vibrational activation of the charge-reduced radical anion is required to obtain the product ions. Herein, the fragmentation patterns that were obtained by EDD and by vibrational activation of the charge-reduced radical anions that were produced through EDD or EPD (activated-EDD and activated-EPD) were compared. The observed differences were related to the dissociation kinetics and/or the contribution of Electron-induced dissociation (EID). Time-resolved double-resonance experiments were performed to measure the dissociation rate constants of the EDD product ions. Differences in the formation kinetics were revealed between the classical EDD/EPD 'a(.) (i) /''x(j) complementary ions and some 'a(.) (i) /c(i) /'''z(.) (j) product ions, which were produced with slower dissociation rate constants, owing to the presence of specific neighbouring side chains. A new fragmentation pathway is proposed for the formation of the slow-kinetics 'a(.) (i) ions.

  • Formation and Fragmentation of Radical Peptide Anions: Insights from Vacuum Ultra Violet Spectroscopy
    Journal of The American Society for Mass Spectrometry, 2012
    Co-Authors: Claire Brunet, Rodolphe Antoine, Philippe Dugourd, Francis Canon, Alexandre Giuliani, Laurent Nahon
    Abstract:

    We have studied the photodissociation of gas-phase deprotonated caerulein anions by vacuum ultraviolet (VUV) photons in the 4.5 to 20 eV range, as provided by the DESIRS beamline at the synchrotron radiation facility SOLEIL (France). Caerulein is a sulphated peptide with three aromatic residues and nine amide bonds. Electron loss is found to be the major relaxation channel at every photon energy. However, an increase in the fragmentation efficiency (neutral losses and peptide backbone cleavages) as a function of the energy is also observed. The oxidized ions, generated by Electron Photodetachment were further isolated and activated by collision (CID) in a MS^3 scheme. The branching ratios of the different fragments observed by CID as a function of the initial VUV photon energy are found to be independent of the initial photon energy. Thus, there is no memory effect of the initial excitation energy on the fragmentation channels of the oxidized species on the time scale of our tandem MS experiment. We also report photofragment yields as a function of photon energy for doubly deprotonated caerulein ions, for both closed-shell ([M–2H]^2–) non-radical ions and open-shell ([M–3H]^2–•) radical ions. These latter ions are generated by Electron Photodetachment from [M–3H]^3– precursor ions. The detachment yield increases monotonically with the energy with the appearance of several absorption bands. Spectra for radical and non-radical ions are quite similar in terms of observed bands; however, the VUV fragmentation yield is enhanced by the presence of a radical in caerulein peptides.

  • Formation and Fragmentation of Radical Peptide Anions: Insights from Vacuum Ultra Violet Spectroscopy
    Journal of The American Society for Mass Spectrometry, 2012
    Co-Authors: Claire Brunet, Rodolphe Antoine, Philippe Dugourd, Francis Canon, Alexandre Giuliani, Laurent Nahon
    Abstract:

    We have studied the photodissociation of gas-phase deprotonated caerulein anions by vacuum ultraviolet (VUV) photons in the 4.5 to 20 eV range, as provided by the DESIRS beamline at the synchrotron radiation facility SOLEIL (France). Caerulein is a sulphated peptide with three aromatic residues and nine amide bonds. Electron loss is found to be the major relaxation channel at every photon energy. However, an increase in the fragmentation efficiency (neutral losses and peptide backbone cleavages) as a function of the energy is also observed. The oxidized ions, generated by Electron Photodetachment were further isolated and activated by collision (CID) in a MS3 scheme. The branching ratios of the different fragments observed by CID as a function of the initial VUV photon energy are found to be independent of the initial photon energy. Thus, there is no memory effect of the initial excitation energy on the fragmentation channels of the oxidized species on the time scale of our tandem MS experiment. We also report photofragment yields as a function of photon energy for doubly deprotonated caerulein ions, for both closed-shell ([M - 2H](2-)) non-radical ions and open-shell ([M - 3H](2-center dot)) radical ions. These latter ions are generated by Electron Photodetachment from[M - 3H](3-) precursor ions. The detachment yield increases monotonically with the energy with the appearance of several absorption bands. Spectra for radical and non-radical ions are quite similar in terms of observed bands; however, the VUV fragmentation yield is enhanced by the presence of a radical in caerulein peptides.

Rodolphe Antoine - One of the best experts on this subject based on the ideXlab platform.

  • Electron Photodetachment dissociation for structural characterization of synthetic and bio-polymer anions
    Mass Spectrometry Reviews, 2014
    Co-Authors: Rodolphe Antoine, Jérôme Lemoine, Philippe Dugourd
    Abstract:

    Tandem mass spectrometry (MS-MS) is a generic term evoking techniques dedicated to structural analysis, detection or quantification of molecules based on dissociation of a precursor ion into fragments. Searching for the most informative fragmentation patterns has led to the development of a vast array of activation modes that offer complementary ion reactivity and dissociation pathways. Collisional activation of ions using atoms, molecules or surface resulting in unimolecular dissociation of activated ions still plays a key role in tandem mass spectrometry. The discovery of Electron capture dissociation (ECD) and then the development of other Electron-ion or ion/ion reaction methods, constituted a significant breakthrough, especially for structural analysis of large biomolecules. Similarly, photon activation opened promising new frontiers in ion fragmentation owing to the ability of tightly controlled internal energy deposition and easy implementation on commercial instruments. Ion activation by photons includes slow heating methods such as infrared multiple photon dissociation (IRMPD) and black-body infrared radiative dissociation (BIRD) and higher energy methods like ultra-violet photodissociation (UVPD) and Electron photo detachment dissociation (EPD). EPD occurs after UV irradiation of multiply negatively charged ions resulting in the formation of oxidized radical anions. The present paper reviews the hypothesis regarding the mechanisms of Electron photo-detachment, radical formation and direct or activated dissociation pathways that support the observation of odd and even Electron product ions. Finally, the value of EPD as a complementary structural analysis tool is illustrated through selected examples of synthetic polymers, oligonucleotides, polypeptides, lipids, and polysaccharides

  • Prompt and slow Electron-detachment-dissociation/Electron-Photodetachment-dissociation of a 21-mer Peptide.
    Chemistry - A European Journal, 2013
    Co-Authors: Marie Pérot-taillandier, Rodolphe Antoine, Philippe Dugourd, Séverine Zirah, Quentin Enjalbert, Jérôme Lemoine, Sylvie Rebuffat, Jean-claude Tabet, Carlos Afonso
    Abstract:

    Electron detachment dissociation (EDD) and Electron Photodetachment dissociation (EPD) are relatively new dissociation methods that involve Electron detachment followed by radical-driven dissociation from multiply deprotonated species. EDD yields prompt dissociation whereas only Electron detachment is obtained by EPD; subsequent vibrational activation of the charge-reduced radical anion is required to obtain the product ions. Herein, the fragmentation patterns that were obtained by EDD and by vibrational activation of the charge-reduced radical anions that were produced through EDD or EPD (activated-EDD and activated-EPD) were compared. The observed differences were related to the dissociation kinetics and/or the contribution of Electron-induced dissociation (EID). Time-resolved double-resonance experiments were performed to measure the dissociation rate constants of the EDD product ions. Differences in the formation kinetics were revealed between the classical EDD/EPD 'a(.) (i) /''x(j) complementary ions and some 'a(.) (i) /c(i) /'''z(.) (j) product ions, which were produced with slower dissociation rate constants, owing to the presence of specific neighbouring side chains. A new fragmentation pathway is proposed for the formation of the slow-kinetics 'a(.) (i) ions.

  • prompt and slow Electron detachment dissociation Electron Photodetachment dissociation of a 21 mer peptide
    Chemistry: A European Journal, 2013
    Co-Authors: Rodolphe Antoine, Philippe Dugourd, Séverine Zirah, Quentin Enjalbert, Jérôme Lemoine, Sylvie Rebuffat, Jean-claude Tabet, Marie Perottaillandier, Carlos Afonso
    Abstract:

    Electron detachment dissociation (EDD) and Electron Photodetachment dissociation (EPD) are relatively new dissociation methods that involve Electron detachment followed by radical-driven dissociation from multiply deprotonated species. EDD yields prompt dissociation whereas only Electron detachment is obtained by EPD; subsequent vibrational activation of the charge-reduced radical anion is required to obtain the product ions. Herein, the fragmentation patterns that were obtained by EDD and by vibrational activation of the charge-reduced radical anions that were produced through EDD or EPD (activated-EDD and activated-EPD) were compared. The observed differences were related to the dissociation kinetics and/or the contribution of Electron-induced dissociation (EID). Time-resolved double-resonance experiments were performed to measure the dissociation rate constants of the EDD product ions. Differences in the formation kinetics were revealed between the classical EDD/EPD 'a(.) (i) /''x(j) complementary ions and some 'a(.) (i) /c(i) /'''z(.) (j) product ions, which were produced with slower dissociation rate constants, owing to the presence of specific neighbouring side chains. A new fragmentation pathway is proposed for the formation of the slow-kinetics 'a(.) (i) ions.

  • Formation and Fragmentation of Radical Peptide Anions: Insights from Vacuum Ultra Violet Spectroscopy
    Journal of The American Society for Mass Spectrometry, 2012
    Co-Authors: Claire Brunet, Rodolphe Antoine, Philippe Dugourd, Francis Canon, Alexandre Giuliani, Laurent Nahon
    Abstract:

    We have studied the photodissociation of gas-phase deprotonated caerulein anions by vacuum ultraviolet (VUV) photons in the 4.5 to 20 eV range, as provided by the DESIRS beamline at the synchrotron radiation facility SOLEIL (France). Caerulein is a sulphated peptide with three aromatic residues and nine amide bonds. Electron loss is found to be the major relaxation channel at every photon energy. However, an increase in the fragmentation efficiency (neutral losses and peptide backbone cleavages) as a function of the energy is also observed. The oxidized ions, generated by Electron Photodetachment were further isolated and activated by collision (CID) in a MS^3 scheme. The branching ratios of the different fragments observed by CID as a function of the initial VUV photon energy are found to be independent of the initial photon energy. Thus, there is no memory effect of the initial excitation energy on the fragmentation channels of the oxidized species on the time scale of our tandem MS experiment. We also report photofragment yields as a function of photon energy for doubly deprotonated caerulein ions, for both closed-shell ([M–2H]^2–) non-radical ions and open-shell ([M–3H]^2–•) radical ions. These latter ions are generated by Electron Photodetachment from [M–3H]^3– precursor ions. The detachment yield increases monotonically with the energy with the appearance of several absorption bands. Spectra for radical and non-radical ions are quite similar in terms of observed bands; however, the VUV fragmentation yield is enhanced by the presence of a radical in caerulein peptides.

  • Efficient Structural Characterization of Poly(Methacrylic Acid) by Activated-Electron Photodetachment Dissociation
    Journal of The American Society for Mass Spectrometry, 2012
    Co-Authors: Marion Girod, Rodolphe Antoine, Philippe Dugourd, Jérôme Lemoine, Claire Brunet, Laurence Charles
    Abstract:

    Characterization of end-groups in poly(methacrylic acid) (PMAA) was achieved using tandem mass spectrometry after activated-Electron Photodetachment dissociation (activated-EPD). In this technique, multiply deprotonated PMAA oligomers produced in the negative-ion mode of electrospray ionization were oxidized into radical anions upon Electron Photodetachment using a 220 nm laser wavelength, and further activated by collision. In contrast to conventional collision induced dissociation of negatively charged PMAA, which mainly consists of multiple dehydration steps, fragmentation of odd-Electron species is shown to proceed via a radical-induced decarboxylation, followed by reactions involving backbone bond cleavages, giving rise to product ions containing one or the other oligomer termination. A single radical-induced mechanism accounts for the four main fragment series observed in MS/MS. The relative position of the radical and of the anionic center in distonic precursor ions determines the nature of the reaction products. Experiments performed using PMAA sodium salts allowed us to account for relative abundances of product ions in series obtained from PMAA, revealing that ion stability is ensured by hydrogen bonds within pairs of MAA units.

Stephen E. Bradforth - One of the best experts on this subject based on the ideXlab platform.

  • Photodetachment of the Tribromocuprate(I) Anion: Observation of Vibrational Wave Packets
    Frontiers in Optics 2007 Laser Science XXIII Organic Materials and Devices for Displays and Energy Conversion, 2007
    Co-Authors: Diana Suffern, V. A. Lenchenkov, Stephen E. Bradforth
    Abstract:

    Electron Photodetachment of the tribromocuprate(I) anion CuBr3 2-in water is achieved by ultrafast pump-dispersed probe spectroscopy resulting in a transient absorption signal containing oscillatory features that correspond to the vibrational frequencies in the detached product.

  • Electron Photodetachment from Aqueous Anions. III. Dynamics of Geminate Pairs Derived from Photoexcitation of Mono- vs. Poly- atomic Anions
    The journal of physical chemistry. A, 2006
    Co-Authors: Rui Lian, Robert A. Crowell, Ilya A. Shkrob, Dmitri A. Oulianov, Chen, Xiyi, Stephen E. Bradforth
    Abstract:

    Photostimulated Electron detachment from aqueous inorganic anions is the simplest example of solvent-mediated Electron transfer. Here we contrast the behavior of halide anions with that of small polyatomic anions, such as pseudohalide anions (e.g., HS-) and common polyvalent anions (e.g., SO32-). Geminate recombination dynamics of hydrated Electrons generated by 200 nm photoexcitation of aqueous anions (I-, Br-, OH-, HS-, CNS-, CO32-, SO32-, and Fe(CN)64-) have been studied. Prompt quantum yields for the formation of solvated, thermalized Electrons and quantum yields for free Electrons were determined. Pump-probe kinetics for 200 nm photoexcitation were compared with kinetics obtained at lower photoexcitation energy (225 nm or 242 nm) for the same anions, where possible. Free diffusion and mean force potential models of geminate recombination dynamics were used to analyze these kinetics. These analyses suggest that for polyatomic anions (including all polyvalent anions studied) the initial Electron distribution has a broad component, even at relatively low photoexcitation energy. There seem to be no well-defined threshold energy below which the broadening of the distribution does not occur, as is the case for halide anions. Direct ionization to the conduction band of water is the most likely photoprocess broadening the Electron distribution. Our study suggests that halide anions are in the class of their own; Electron Photodetachment from polyatomic, especially polyvalent, anions follows a different set of rules.

  • Electron Photodetachment from aqueous anions 3 dynamics of geminate pairs derived from photoexcitation of mono vs polyatomic anions
    Journal of Physical Chemistry A, 2006
    Co-Authors: Rui Lian, Robert A. Crowell, Ilya A. Shkrob, Dmitri A. Oulianov, Xiyi Chen, Stephen E. Bradforth
    Abstract:

    Photostimulated Electron detachment from aqueous inorganic anions is the simplest example of solvent-mediated Electron transfer reaction. As such, this photoreaction became the subject of many ultrafast studies. Most of these studied focused on the behavior of halide anions, in particular, iodide, that is readily accessible in the UV. In this study, we contrast the behavior of these halide anions with that of small polyatomic anions, such as pseudohalide anions (e.g., HS(-)) and common polyvalent anions (e.g., SO(3)(2-)). Geminate recombination dynamics of hydrated Electrons generated by 200 nm photoexcitation of aqueous anions (I(-), Br(-), OH(-), HS(-), CNS(-), CO(3)(2-), SO(3)(2-), and Fe(CN)(6)(4-)) have been studied. Prompt quantum yields for the formation of solvated, thermalized Electrons and quantum yields for free Electrons were determined. Pump-probe kinetics for 200 nm photoexcitation were compared with kinetics obtained at lower photoexcitation energy (225 or 242 nm) for the same anions, where possible. Free diffusion and mean force potential models of geminate recombination dynamics were used to analyze these kinetics. These analyses suggest that for polyatomic anions (including all polyvalent anions studied) the initial Electron distribution has a broad component, even at relatively low photoexcitation energy. There seems to be no well-defined threshold energy below which the broadening of this Electron distribution does not occur, as is the case for halide anions. The constancy of (near-unity) prompt quantum yields vs the excitation energy as the latter is scanned across the lowest charge-transfer-to-solvent band of the anion is observed for halide anions but not for other anions: the prompt quantum yields are considerably less than unity and depend strongly on the excitation energy. Our study suggests that halide anions are in the class of their own; Electron Photodetachment from polyatomic, especially polyvalent, anions exhibits qualitatively different behavior.

  • Ultrafast dynamics for Electron Photodetachment from aqueous hydroxide.
    The Journal of chemical physics, 2004
    Co-Authors: Robert A. Crowell, Ilya A. Shkrob, Rui Lian, Xiyi Chen, David M. Bartels, Stephen E. Bradforth
    Abstract:

    Charge-transfer-to-solvent reactions of hydroxide induced by 200 nm monophotonic or 337 and 389 nm biphotonic excitation of this anion in aqueous solution have been studied by means of pump–probe ultrafast laser spectroscopy. Transient absorption kinetics of the hydrated Electron, eaq−, have been observed, from a few hundred femtoseconds out to 600 ps, and studied as function of hydroxide concentration and temperature. The geminate decay kinetics are bimodal, with a fast exponential component (∼13 ps) and a slower power “tail” due to the diffusional escape of the Electrons. For the biphotonic excitation, the extrapolated fraction of escaped Electrons is 1.8 times higher than for the monophotonic 200 nm excitation (31% versus 17.5% at 25 °C, respectively), due to the broadening of the Electron distribution. The biphotonic Electron detachment is very inefficient; the corresponding absorption coefficient at 400 nm is

  • ultrafast dynamics for Electron Photodetachment from aqueous hydroxide
    Journal of Chemical Physics, 2004
    Co-Authors: Robert A. Crowell, Ilya A. Shkrob, Rui Lian, Xiyi Chen, David M. Bartels, Stephen E. Bradforth
    Abstract:

    Charge-transfer-to-solvent reactions of hydroxide induced by 200 nm monophotonic or 337 and 389 nm biphotonic excitation of this anion in aqueous solution have been studied by means of pump–probe ultrafast laser spectroscopy. Transient absorption kinetics of the hydrated Electron, eaq−, have been observed, from a few hundred femtoseconds out to 600 ps, and studied as function of hydroxide concentration and temperature. The geminate decay kinetics are bimodal, with a fast exponential component (∼13 ps) and a slower power “tail” due to the diffusional escape of the Electrons. For the biphotonic excitation, the extrapolated fraction of escaped Electrons is 1.8 times higher than for the monophotonic 200 nm excitation (31% versus 17.5% at 25 °C, respectively), due to the broadening of the Electron distribution. The biphotonic Electron detachment is very inefficient; the corresponding absorption coefficient at 400 nm is <4 cm TW−1 M−1 (assuming unity quantum efficiency for the Photodetachment). For [OH−] betwee...

Pavel Jungwirth - One of the best experts on this subject based on the ideXlab platform.

  • Nonadiabatic chemical reaction triggered by Electron Photodetachment: an ab initio quantum dynamical study.
    Physical review letters, 2004
    Co-Authors: Shai Ronen, Burkhard Schmidt, Dana Nachtigallová, Pavel Jungwirth
    Abstract:

    Dynamics following Electron Photodetachment in a complex of a chloride anion with ammonia is explored by a combination of Electronic structure and quantum dynamical methods. This system serves as a prototype for investigating a hithertho unexplored class of chemical reactions - non-adiabatic proton transfer triggered by a detachment of an Electron. All the reactive and non-reactive channels of this process are characterized and the respective quantum yields are presented.

  • Quantum Dynamics and Spectroscopy of Electron Photodetachment in Cl-···H2O and Cl-···D2O Complexes
    The Journal of Physical Chemistry A, 2002
    Co-Authors: Martina Roeselova, Burkhard Schmidt, Martin Mucha, Pavel Jungwirth
    Abstract:

    We have modeled Zero Electron Kinetic Energy (ZEKE) spectra of Cl-…H2O and Cl-…D2O complexes using 3D quantum dynamical simulations on the three low-lying Electronic states of the nascent neutral systems. Time-dependent quantum simulations combined with anionic and neutral stationary-state calculations by imaginary time propagation allowed for a detailed interpretation of the spectral features in terms of the underlying dynamics. Because of large differences between the anionic and neutral potential surfaces, the systems are found after Electron Photodetachment primarily high above the dissociation threshold. Nevertheless, pronounced long-lived resonances are observed, particularly for the lowest neutral state, reflecting the fact that a significant portion of the excess energy is initially deposited into nondissociative modes, that is, to (hindered) water rotation. These resonances form bands corresponding to water rotational states with a fine structure due to intermolecular stretch progressions. Comparison is made to experimental zero Electron kinetic energy (ZEKE) spectra of the I-…H2O complex, where analogous anharmonic vibrational progressions have been observed.

  • Ultrafast Dynamics of Chlorine-Water and Bromine-Water Radical Complexes Following Electron Photodetachment in Their Anionic Precursors
    The Journal of Physical Chemistry A, 2000
    Co-Authors: Martina Roeselova, Uzi Kaldor, Pavel Jungwirth
    Abstract:

    Picosecond dynamics initiated by Electron Photodetachment in Cl‚‚‚H2O and Br‚‚‚H2O complexes is explored using classical Wigner trajectories which correctly map the initial quantum vibrational state of the systems. The three lowest potential energy surfaces of the neutral clusters reached after Electron Photodetachment are constructed by the ab initio Fock-Space Coupled Cluster Method and then quantitatively fitted to a Diatomicsin-Molecule Model which also allows for a simple inclusion of spin-orbit interactions. Because of large differences between the shapes of the anionic and neutral potential energy surfaces, and due to the presence of light hydrogen atoms, an unusual dynamical behavior is observed. Although the vertical Photodetachment process places the systems above the dissociation threshold, the clusters do not dissociate directly. Instead, relatively long-lived vibrational resonances are observed. This is due to a strong excitation of the nondissociative (internal) water rotation and only a weak excitation of the dissociative intermolecular stretch upon Photodetachment. Implications of the observed dynamics for the interpretation of experimental vibrationally resolved ZEKE spectra are discussed.

  • Electron Photodetachment in C60−: Quantum molecular dynamics with a non-empirical, `on-the-fly' calculated potential
    Chemical Physics Letters, 2000
    Co-Authors: Olaf Knospe, Pavel Jungwirth
    Abstract:

    Abstract An approximate quantum dynamical simulation of a large polyatomic system employing a non-empirical potential, which is calculated `on-the-fly' using a Kohn–Sham approach within the local density approximation is presented. A mean-field calculation based on the classical separable potential (CSP) method for 41 coupled vibrational modes allows for a detailed analysis of the fast dynamics following Electron Photodetachment in the buckminsterfullerene anion and provides a vibrationally resolved photoElectron spectrum that is in good agreement with experiment.

  • relaxation of chlorine anions solvated in small water clusters upon Electron Photodetachment
    Chemical Physics Letters, 1998
    Co-Authors: Martina Roeselova, Gal Jacoby, Uzi Kaldor, Pavel Jungwirth
    Abstract:

    Abstract The three lowest potential energy surfaces of the Cl ⋅ ⋯H 2 O cluster, relevant for the study of the dynamics following Electron Photodetachment in the Cl − (H 2 O) n complexes are presented. An ab initio Fock-space multireference coupled cluster scan of the three lowest Cl ⋅ ⋯H 2 O potentials is performed and followed by a diatomics-in-molecule fit of a near-quantitative accuracy, suitable for dynamical calculations.

Jérôme Lemoine - One of the best experts on this subject based on the ideXlab platform.

  • Electron Photodetachment dissociation for structural characterization of synthetic and bio-polymer anions
    Mass Spectrometry Reviews, 2014
    Co-Authors: Rodolphe Antoine, Jérôme Lemoine, Philippe Dugourd
    Abstract:

    Tandem mass spectrometry (MS-MS) is a generic term evoking techniques dedicated to structural analysis, detection or quantification of molecules based on dissociation of a precursor ion into fragments. Searching for the most informative fragmentation patterns has led to the development of a vast array of activation modes that offer complementary ion reactivity and dissociation pathways. Collisional activation of ions using atoms, molecules or surface resulting in unimolecular dissociation of activated ions still plays a key role in tandem mass spectrometry. The discovery of Electron capture dissociation (ECD) and then the development of other Electron-ion or ion/ion reaction methods, constituted a significant breakthrough, especially for structural analysis of large biomolecules. Similarly, photon activation opened promising new frontiers in ion fragmentation owing to the ability of tightly controlled internal energy deposition and easy implementation on commercial instruments. Ion activation by photons includes slow heating methods such as infrared multiple photon dissociation (IRMPD) and black-body infrared radiative dissociation (BIRD) and higher energy methods like ultra-violet photodissociation (UVPD) and Electron photo detachment dissociation (EPD). EPD occurs after UV irradiation of multiply negatively charged ions resulting in the formation of oxidized radical anions. The present paper reviews the hypothesis regarding the mechanisms of Electron photo-detachment, radical formation and direct or activated dissociation pathways that support the observation of odd and even Electron product ions. Finally, the value of EPD as a complementary structural analysis tool is illustrated through selected examples of synthetic polymers, oligonucleotides, polypeptides, lipids, and polysaccharides

  • Prompt and slow Electron-detachment-dissociation/Electron-Photodetachment-dissociation of a 21-mer Peptide.
    Chemistry - A European Journal, 2013
    Co-Authors: Marie Pérot-taillandier, Rodolphe Antoine, Philippe Dugourd, Séverine Zirah, Quentin Enjalbert, Jérôme Lemoine, Sylvie Rebuffat, Jean-claude Tabet, Carlos Afonso
    Abstract:

    Electron detachment dissociation (EDD) and Electron Photodetachment dissociation (EPD) are relatively new dissociation methods that involve Electron detachment followed by radical-driven dissociation from multiply deprotonated species. EDD yields prompt dissociation whereas only Electron detachment is obtained by EPD; subsequent vibrational activation of the charge-reduced radical anion is required to obtain the product ions. Herein, the fragmentation patterns that were obtained by EDD and by vibrational activation of the charge-reduced radical anions that were produced through EDD or EPD (activated-EDD and activated-EPD) were compared. The observed differences were related to the dissociation kinetics and/or the contribution of Electron-induced dissociation (EID). Time-resolved double-resonance experiments were performed to measure the dissociation rate constants of the EDD product ions. Differences in the formation kinetics were revealed between the classical EDD/EPD 'a(.) (i) /''x(j) complementary ions and some 'a(.) (i) /c(i) /'''z(.) (j) product ions, which were produced with slower dissociation rate constants, owing to the presence of specific neighbouring side chains. A new fragmentation pathway is proposed for the formation of the slow-kinetics 'a(.) (i) ions.

  • prompt and slow Electron detachment dissociation Electron Photodetachment dissociation of a 21 mer peptide
    Chemistry: A European Journal, 2013
    Co-Authors: Rodolphe Antoine, Philippe Dugourd, Séverine Zirah, Quentin Enjalbert, Jérôme Lemoine, Sylvie Rebuffat, Jean-claude Tabet, Marie Perottaillandier, Carlos Afonso
    Abstract:

    Electron detachment dissociation (EDD) and Electron Photodetachment dissociation (EPD) are relatively new dissociation methods that involve Electron detachment followed by radical-driven dissociation from multiply deprotonated species. EDD yields prompt dissociation whereas only Electron detachment is obtained by EPD; subsequent vibrational activation of the charge-reduced radical anion is required to obtain the product ions. Herein, the fragmentation patterns that were obtained by EDD and by vibrational activation of the charge-reduced radical anions that were produced through EDD or EPD (activated-EDD and activated-EPD) were compared. The observed differences were related to the dissociation kinetics and/or the contribution of Electron-induced dissociation (EID). Time-resolved double-resonance experiments were performed to measure the dissociation rate constants of the EDD product ions. Differences in the formation kinetics were revealed between the classical EDD/EPD 'a(.) (i) /''x(j) complementary ions and some 'a(.) (i) /c(i) /'''z(.) (j) product ions, which were produced with slower dissociation rate constants, owing to the presence of specific neighbouring side chains. A new fragmentation pathway is proposed for the formation of the slow-kinetics 'a(.) (i) ions.

  • Efficient Structural Characterization of Poly(Methacrylic Acid) by Activated-Electron Photodetachment Dissociation
    Journal of The American Society for Mass Spectrometry, 2012
    Co-Authors: Marion Girod, Rodolphe Antoine, Philippe Dugourd, Jérôme Lemoine, Claire Brunet, Laurence Charles
    Abstract:

    Characterization of end-groups in poly(methacrylic acid) (PMAA) was achieved using tandem mass spectrometry after activated-Electron Photodetachment dissociation (activated-EPD). In this technique, multiply deprotonated PMAA oligomers produced in the negative-ion mode of electrospray ionization were oxidized into radical anions upon Electron Photodetachment using a 220 nm laser wavelength, and further activated by collision. In contrast to conventional collision induced dissociation of negatively charged PMAA, which mainly consists of multiple dehydration steps, fragmentation of odd-Electron species is shown to proceed via a radical-induced decarboxylation, followed by reactions involving backbone bond cleavages, giving rise to product ions containing one or the other oligomer termination. A single radical-induced mechanism accounts for the four main fragment series observed in MS/MS. The relative position of the radical and of the anionic center in distonic precursor ions determines the nature of the reaction products. Experiments performed using PMAA sodium salts allowed us to account for relative abundances of product ions in series obtained from PMAA, revealing that ion stability is ensured by hydrogen bonds within pairs of MAA units.

  • Photoinduced Dissociation of Heparin-Derived Oligosaccharides Controlled by Charge Location
    Journal of The American Society for Mass Spectrometry, 2010
    Co-Authors: Amandine Racaud, Rodolphe Antoine, Philippe Dugourd, Jérôme Lemoine
    Abstract:

    The development of strategies based on mass spectrometry to help for deep structural analysis of acidic oligosaccharides remains topical. We thus examined the dissociation behavior of deprotonated ions of heparin-derived di- to tetra-saccharides under UV irradiation at 220 nm. Depending on the ionization state of the carboxylic groups, an oxidized species issued from Electron Photodetachment was observed in complement to photoinduced fragmentation of precursor ions. The influence of the charge location in the oligosaccharide dianions on the balance between photodissociation and Electron Photodetachment is examined and a way to direct the relaxation pathways, (i.e., dissociation versus Electron detachment), is proposed using sodium adducts. The oxidized species was subjected to activated-Electron Photodetachment (activated-EPD) leading to complementary informative fragment ions to those issued from photodissociation. Directed photoinduced dissociation at 220 nm and activated-EPD should complement the more conventional CAD and IRMPD activation modes for deeper structural analysis of acidic oligosaccharides-derived anions.