| 1. |
- Bernigaud, Virgile, et al.
(författare)
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Electron capture-induced dissociation of AK dipeptide dications : Influence of ion velocity, crown-ether complexation and collision gas
- 2008
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Ingår i: International Journal of Mass Spectrometry. - : Elsevier BV. - 1387-3806 .- 1873-2798. ; 276:2-3, s. 77-81
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Tidskriftsartikel (refereegranskat)abstract
- The fragmentation of doubly protonated AK dipeptide ions has been investigated after collisional electron transfer. Electron capture leads to three dominant channels, H loss, NH3 loss, and N–Cα bond breakage to give either c+ or z+ fragment ions. The relative importance of these channels has been explored as a function of ion velocity, the degree of complexation with crown ether, and collision gas. Our results indicate that H loss and NH3 loss are competing channels whereas the probability of N–Cα bond breakage is more or less constant.
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| 2. |
- de Ruette, Nathalie, et al.
(författare)
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DESIREE electrospray ion source test bench and setup for collision induced dissociation experiments
- 2018
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 89:7
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we give a detailed description of an electrospray ion source test bench and a single-pass setup for ion fragmentation studies at the Double ElectroStatic Ion Ring ExpEriment infrastructure at Stockholm University. This arrangement allows for collision-induced dissociation experiments at the center-of-mass energies between 10 eV and 1 keV. Charged fragments are analyzed with respect to their kinetic energies (masses) by means of an electrostatic energy analyzer with a wide angular acceptance and adjustable energy resolution.
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| 3. |
- Fischer, D., et al.
(författare)
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Importance of Thomas single-electron transfer in fast p-He collisions
- 2010
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 81:1, s. 12714-
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Tidskriftsartikel (refereegranskat)abstract
- We report experimental angular differential cross sections for nonradiative single-electron capture in p-He collisions (p + He -> H + He+) with a separate peak at the 0.47 mrad Thomas scattering angle for energies in the 1.3-12.5 MeV range. We find that the intensity of this peak scales with the projectile velocity as v(P)(-11). This constitutes the first experimental test of the prediction from 1927 by L. H. Thomas [Proc. R. Soc. 114, 561 (1927)]. At our highest energy, the peak at the Thomas angle contributes with 13.5% to the total integrated nonradiative single-electron capture cross section.
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| 4. |
- Haag, Nicole, et al.
(författare)
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Collisions with biomolecules embedded in smallwater clusters
- 2009
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Konferensbidrag (refereegranskat)abstract
- We have studied fragmentation of water embedded adenosine 5’-monophosphate(AMP) anions after collisions with neutral sodium atoms. At a collision energy of 50 keV,loss of water molecules from the collisionally excited cluster ions is the dominant process andfragmentation of the AMP itself is almost completely prohibited if the number of attachedwater molecules is larger than 13. However, regardless of the initial number of water moleculesattached to the ion, capture of an electron, i.e. formation of a dianion, always leads to loss ofa single hydrogen atom accompanied by evaporation of water molecules. This damaging effectbecomes more important as the size of the water cluster increases, which is just the oppositeto the protective behavior observed for collision induced dissociation (CID) without electrontransfer. For both cases, the loss of water molecules within the experimental time frame isqualitatively well described by means of a common model of an evaporative ensemble. Thesesimulations, however, indicate that characteristically different distributions of internal energyare involved in CID and electron capture induced dissociation.
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| 5. |
- Haag, Nicole, et al.
(författare)
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Electron capture induced dissociation of doubly protonated pentapeptides : Dependence on molecular structure and charge separation
- 2011
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 134:3, s. 035102-
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Tidskriftsartikel (refereegranskat)abstract
- We have studied electron capture induced dissociation of a set of doubly protonated pentapeptides, all composed of one lysine (K) and either four glycine (G) or four alanine (A) residues, as a function of the sequence of these building blocks. Thereby the separation of the two charges, sequestered on the N-terminal amino group and the lysine side chain, is varied. The characteristic cleavage of N–Cα bonds is observed for all peptides over the whole backbone length, with the charge carrying fragments always containing K. The resulting fragmentation patterns are very similar if G is replaced by A. In the case of [XKXXX+2H]2+ (X=A or G), a distinct feature is observed in the distribution of backbone cleavage fragments and the probability for ammonia loss is drastically reduced. This may be due to an isomer with an amide oxygen as protonation site giving rise to the observed increase in breakage at a specific site in the molecule. For the other peptides, a correlation with the distance between amide oxygen and the charge at the lysine side chain has been found. This may be an indication that it is only the contribution from this site to the charge stabilization of the amide π* orbitals which determines relative fragment intensities. For comparison, complexes with two crown ether molecules have been studied as well. The crown ether provides a shielding of the charge and prevents the peptide from folding and internal hydrogen bonding, which leads to a more uniform fragmentation behavior.
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| 6. |
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| 7. |
- Haag, Nicole, 1981-
(författare)
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Probing biomolecular fragmentation
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with fragmentation of complex molecular ions, especially biomolecules, in gas phase collision experiments. The aim is to investigate the relations between energy deposition and fragmentation and to shed light on the mechanisms behind energy and charge transfer processes in collisions involving the building blocks of life. Further, the question how a solvent environment influences the dissociation behavior is elucidated. In the first part of the thesis, results from different collision experiments with biomolecular ions are presented, focusing on electron capture induced dissociation of hydrated nucleotides and small peptides. The investigated processes may be relevant for the understanding of radiation damage and the optimization of sequencing methods used in protein research. Our results clearly demonstrate that effects due to surrounding solvent molecules are substantial. While the dissipation of internal energy by evaporation of the loosely bound solvent molecules may protect the biomolecule, the influence which this environment has on the electronic structure may lead to an enhancement or suppression of certain dissociation channels. The second part of the thesis focuses on recent instrumental developments. Here, the aim was to optimize and complement the techniques used in the experiments above and to have versatile tools available for different kinds of gas phase collision studies involving complex molecular ions. Therefore, we have constructed an electrospray ion source platform for the preparation of intense beams, with options of accumulation and cooling of mass selected ions, allowing for a large variety of experiments. This device is also intended to serve as an ion source for the new storage ring facility DESIREE (DoubleElectroStatic Ion Ring ExpEriment), which is currently under construction at Stockholm University. In these unique storage rings, oppositely charged ions may interact at very low relative velocities in a cryogenically cooled and ultrahigh vacuum environment.
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| 8. |
- Johansson, Henrik A. B., et al.
(författare)
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Unimolecular dissociation of anthracene and acridine cations : The importance of isomerization barriers for the C2H2 loss and HCN loss channels
- 2011
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 135, s. 084304-
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Tidskriftsartikel (refereegranskat)abstract
- The loss of C2H2 is a low activation energy dissociation channel for anthracene (C14H10) and acridine (C13H9N) cations. For the latter ion another prominent fragmentation pathway is the loss of HCN. We have studied these two dissociation channels by collision induced dissociation experiments of 50 keV anthracene cations and protonated acridine, both produced by electrospray ionization, in collisions with a neutral xenon target. In addition, we have carried out density functional theory calculations on possible reaction pathways for the loss of C2H2 and HCN. The mass spectra display features of multi-step processes, and for protonated acridine the dominant first step process is the loss of a hydrogen from the N site, which then leads to C2H2/HCN loss from the acridine cation. With our calculations we have identified three pathways for the loss of C2H2 from the anthracene cation, with three different cationic products: 2-ethynylnaphthalene, biphenylene, and acenaphthylene. The third product is the one with the overall lowest dissociation energy barrier. For the acridine cation our calculated pathway for the loss of C2H2 leads to the 3-ethynylquinoline cation, and the loss of HCN leads to the biphenylene cation. Isomerization plays an important role in the formation of the non-ethynyl containing products. All calculated fragmentation pathways should be accessible in the present experiment due to substantial energy deposition in the collisions.
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| 9. |
- Liu, B., et al.
(författare)
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Electron capture induced dissociation of nucleotide anions in water nanodroplets
- 2008
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 128:7, s. 075102-
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the outcome of collisions between the hydrated nucleotide anion adenosine 5′-monophosphate (AMP) and sodium. Electron capture leads to hydrogen loss as well as water evaporation regardless of the initial number m of water molecules attached to the parent ion (m ⩽ 16). The yield of dianions with microsecond lifetimes increases strongly with m, which is explained from dielectric screening of the two charges by the water nanodroplet. For comparison, collision induced dissociation results in water losses with no or very little damage of the AMP molecule itself.
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| 10. |
- Misra, Deepankar, et al.
(författare)
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Two-Center Double-Capture Interference in Fast He2++H2 Collisions
- 2009
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:15, s. 153201-
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Tidskriftsartikel (refereegranskat)abstract
- We report the first observation of Young-type interference effects in a two-electron transfer process. These effects change strongly as the projectile velocity changes in fast (1.2 and 2.0 MeV) He^{2+}-H_2 collisions as manifested in strong variations of the double-electron capture rates with the H_2 orientation. This is consistent with fully quantum mechanical calculations, which ignore sequential electron transfer, and a simple projectile de Broglie wave picture assuming that two-electron transfer probabilities are higher in collisions where the projectile passes close to either one of the H_2 nuclei.
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