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- Hansen, Klavs, 1958, et al.
(författare)
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Cluster cooling issue - Foreword
- 2006
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Ingår i: Int. J. Mass Spec.. - : Elsevier BV. - 1387-3806. ; 252:2
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 6. |
- Onthong, U., et al.
(författare)
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Ab initio study of the interaction of dimethylsulfoxide with the ions Li+ and I
- 2003
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Ingår i: International Journal of Mass Spectrometry. - 1387-3806 .- 1873-2798. ; 223:03-jan, s. 263-270:263, s. 223-
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Tidskriftsartikel (refereegranskat)abstract
- We report analytical expressions for the dimethylsulfoxide (DMSO)-Li+ and DMSO-I- potential energy hypersurfaces. Quantum chemically calculated energies were fitted to polynomial functions of different number of parameters. These calculations are augmented by calculations of the electrostatic potential in the vicinity of DMSO. Global geometry optimizations and calculations of ion-induced frequency shifts have been performed. We find that at its global energy minima, Li+ in the DMSO-Li+ complex is bound to the oxygen atom with an energy of about 2.6 eV while I- in the vicinity is bound between the two methyl groups in a shallow energy minimum with about 0.6 eV.
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| 7. |
- Wesendrup, R., et al.
(författare)
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Ab initio spectroscopic properties for HgTl
- 2000
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Ingår i: International Journal of Mass Spectrometry. - : Elsevier BV. - 1387-3806 .- 1873-2798. ; 201:03-jan, s. 17-21
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Tidskriftsartikel (refereegranskat)abstract
- Relativistic coupled cluster calculations are presented, which describe the potential energy curve of the yet unknown molecule HgTl+, and predict its spectroscopic properties. Correlation consistent pseudopotential valence basis sets were used in order to minimize the basis set superposition error for the weakly interacting atoms. The vibrational-rotational constants were obtained as R-e = 334.2 pm, D-0 = 2272 cm(-1), omega(e) = 46 cm(-1), omega(e)x(e) = 0.17 cm(-1), and B-e = 0.0147 cm(-1) at the CCSD(T) level. The bonding in HgTl+ can be described mainly as a charge induced dipole interaction, thus explaining why this species is stronger bound than isoelectronic Hg-2, which can mainly be described by dispersion forces (R-e = 363 +/- 4 pm, D-0 = 380 +/- 15 cm(-1), omega(e) = 19 cm(-1)).
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| 9. |
- Adams, Christopher, et al.
(författare)
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Probing Solution-Phase and Gas-Phase Structures of Trp-cage Cations by Chiral Substitution and Spectroscopic Techniques
- 2006
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Ingår i: International Journal of Mass Spectrometry. - : Elsevier BV. - 1387-3806 .- 1873-2798. ; 253:3, s. 263-273
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Tidskriftsartikel (refereegranskat)abstract
- The relevance of gas-phase protein structure to its solution structure is of the utmost importance in studying biomolecules by mass spectrometry. D-Amino acid substitutions within a minimal protein. Trp-cage. were used to correlate solution-phase properties as measured by circular dichroism with solution/gas-phase conformational features of protein cations probed via charge state distribution (CSD) in electrospray ionization. and gas-phase features revealed by tandem mass spectrometry (MS/MS). The gas-phase features were additionally supported by force-field molecular dynamics simulations. CD data showed that almost any single-residue D-substitution destroys the most prominent CD feature of the "native" all-L isomer, alpha-helicity. CSD was able to qualitatively assess the degree of compactness of solution-phase molecular structures. CSD results were consistent with the all-L form being the most compact in solution among all studied stereoisomers except for the D-Asn(1) isomer. D-substitutions of the aromatic Y(3), W(6) and Q(5) residues generated the largest deviations in CSD data among single amino acid substitutions. consistent with the critical role of these residues in Trp-cage stability. Electron capture dissociation of the stereoisomer dications gave an indication that some gas-phase structural features of Trp-cage are similar to those in solution. This result is supported by MDS data oil five of the studied stereoisomer dications in the gas-phase. The MDS-derived minimum-energy structures possessed more extensive hydrogen bonding than the solution-phase structure of the native form, deviating from the latter by 3-4 angstrom and were not 'inside-out' compared to native structures. MDS data could be correlated with CD data and even with ECD results. which aided in providing a long-range structural constraint for MDS. The overall conclusion is the general resemblance, despite the difference on the detailed level, of the preferred structures in both phases for the mini protein Trp-cage.
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| 10. |
- Andersson, Patrik U, 1970, et al.
(författare)
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Cluster ions DN + ejected from dense and ultra-dense deuterium by Coulomb explosions: Fragment rotation and D+ backscattering from ultra-dense clusters in the surface phase
- 2012
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Ingår i: International Journal of Mass Spectrometry. - : Elsevier BV. - 1387-3806. ; 310, s. 32-43
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Tidskriftsartikel (refereegranskat)abstract
- The two forms of condensed atomic deuterium, dense deuterium D(1) and ultra-dense deuterium D(−1), can be studied by laser-induced Coulomb explosion time-of-flight mass spectrometry and neutral timeof- flight. In the present study pulsed laser intensity below 1014W cm−2 is used. Cluster ions DN + from D(1) are observed with N = 3, 4, 12 and 17, thus not in close-packed forms. Clusters DN(1) are mainly in the form of chains of D2 and D3 groups, a shape derived from the D(−1) material which D(1) is spontaneously converted to. Only atomic ions D+ with initial kinetic energy of hundreds of eV are observed from D(−1). Half of these ions are ejected from the emitter surface, half of them penetrate into the ultra-dense D(−1) layer on the emitter surface. This second half of the ions is reflected completely from the surface layer formed by ultra-dense D(−1) strongly bonded clusters D3(−1) and D4(−1).
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