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  • Chemistry  (7)
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  • 1
    Electronic Resource
    Electronic Resource
    Thermal decomposition kinetics of protonated peptides and peptide dimers, and comparison with surface-induced dissociation (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 829-836 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Rate constants for the unimolecular decomposition of peptide monomer and dimer ions by thermal and surface-induced dissociation (SID) are measured and compared. Rate constants for thermal dissociation are measured in a heated wide-bore capillary flow reactor attached in front of the capillary leading into the mass spectrometer. Thermal decomposition of the leucine enkephalin ion (YGGFL)H+ is observed between 600 and 680 K with rate constants of 20-200 s-1, and yields many of the same fragments as SID at 35 eV, although with different relative intensities. The thermal decomposition yields the Arrhenius parameters Ea = 38.3 kcal/mol, log A = 15.7. The decomposition of the monomer and dimer ions are also observed by using SID on C18 and fluorinated hydrocarbon surfaces, with rate constants of 2 × 104 to 40 × 104 s-1. The SID activated monomer ions are assigned equivalent temperatures of 710-840 K by extrapolation of the thermal activation parameters. The protonated dimer ion (YGGFL)2 H+ decomposes thermally at 500-540 K to yield the monomer ion. The dimer also decomposes by SID at low collision energies 10-20 eV on both surfaces to yield the monomer ion, and at much higher energies of 60-80 eV to yield fragments identical to the decomposition of the monomer. The large energy requirement for fragmentation from the dimer is due to energy deposition into more degrees of freedom plus the additional energy required for dissociation of the dimer to the monomer. It is assumed that the energy deposition is linear with collision energy up to 80 eV, and that the energy becomes randomized throughout the dimer, including energy flow through the hydrogen bond(s). These mechanistic assumptions are supported quantitatively by the SID energy relations between monomer and dimer fragmentation. Thermal decomposition of the larger, multiply protonated melittin ion [M + 3H]3+ occurs at substantially higher temperatures, between 810-840 K, than those required for thermal decomposition of (YGGFL)H+, to yield many of the same sequence ions as produced by SID at 135 eV on a fluorinated surface.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290090922
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  • 2
    Electronic Resource
    Electronic Resource
    Energy deposition in [Fe(CO)5]+· upon collision with a metal surface (1986)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 21 (1986), S. 193-195 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Collision of the title ion upon a stainless steel surface at near-normal incidence leads to deposition of internal energy in a well-defined narrow distribution. The energy deposited increases with laboratory collision energy and exceeds 7 eV (average) for 100 eV collisions. The translational-to-vibrational energy transfer efficiency is 15% (assuming an infinitely massive target) at 25 eV collision energy. Comparison is made with the internal energy distributions associated with gas-phase collisional activation using both low and high ion kinetic energies. The narrowness of the distribution of internal energies, the easy access to ions excited to different extents, and the high internal energies accessible, make the ion/surface collision process superior to gas-phase collisional activation for this system.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210210405
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  • 3
    Electronic Resource
    Electronic Resource
    Reactions between doubly charged [C6H6]2+ ions and self-assembled monolayer surface (1993)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 28 (1993), S. 283-284 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210280323
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  • 4
    Electronic Resource
    Electronic Resource
    Reactive ion-surface collisions: Application of ionized acetone-d6, DMSO-d6 and pyridine-d5 as probes for the characterization of self-assembled monolayer films on gold (1993)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 28 (1993), S. 1665-1673 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Low-energy collisions of ionized acetone-d6, DMSO-d6 and pyridine-d5 with alkanethiolate self-assembled monolayer (SAM) surfaces prepared on gold were investigated. These experiments can be used to monitor routinely the condition of the surfaces and to determine whether a surface is acceptable for a given application. In addition to the surface-induced dissociation of the molecular ions, intense peaks corresponding to the addition of H (or D) to the ionized molecules are observed in the ion-surface collision spectra. The relative abundance of the [M + H(D)]+ reaction products was found to be dependent on several variables, including (i) the chemical composition of the monolayers (alkanethiolate, perdeuteroalkanethiolate, fluorinated alkanethiolate), (ii) the chain length of the alkanethiolate monolayers, (iii) the time for which the vapor-deposited Au surfaces are exposed to the thiol solution during surface preparation and (iv) the degree of deliberate damage of the SAM film (70 eV Ar+· beam bombardment). The variation in [M + H(D)]+ abundance with induced surface changes illustrates the utility of these adduct ions for the characterization of the quality of the monolayers. The general trend observed is an increase in the [M + H]+ peak with the increased presence of hydrocarbon adsorbates, which in turn is believed to be directly related to increased disorder (inherent or induced) of the monolayer film. The increase in [M + H]+ is seen with a decrease in chain length, with shorter monolayer preparation times, and with an increase in surface damage. In general, a fluorinated surface that has been intentionally damaged by an Ar+· beam retains its highenergy deposition characteristics and is appropriate for use as a collision target for many types of projectiles.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210281244
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  • 5
    Electronic Resource
    Electronic Resource
    Linkage position determination of lithium-cationized disaccharides by surface-induced dissociation tandem mass spectrometry (1994)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 29 (1994), S. 700-702 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210291123
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  • 6
    Electronic Resource
    Electronic Resource
    Internal energy requirements for remote site fragmentation (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 23 (1988), S. 627-633 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Attempts to induce remote site fragmentation by using low-energy collisional activation with a neutral target gas or with a surface (surface-induced dissociation) are reported. These data, in conjunction with knowledge of the internal energy deposition associated with these activation methods, provide information on the amount of internal energy needed to promote remote site fragmentation in selected compounds. The internal energy required for remote site fragmentation of lithiated oleyl alcohol was recently estimated to be 1.3-1.9 eV. Our experiments suggest that internal energies much greater than 2 eV are required to produce detectable remote site fragmentation in several different ions, including lithiated oleyl alcohol, n-dodecylbenzenesulfonate anion, stearylsulfate anion, stearate anion and protonated octadecylamine. The results also suggest that the internal energy required to record spectra which show remote site fragmentation is compound-dependent, i.e. strongly dependent on the nature of the ionic group.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210230902
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  • 7
    Electronic Resource
    Electronic Resource
    Internal energy distribution of benzene molecular ions in surface-induced dissociation (1995)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 30 (1995), S. 212-217 
    Details
    ISSN: 1076-5174
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The so-called ‘deconvolution’ method has been used to determine the internal energy distribution of molecular ions of an organic compound, benzene, excited by collisions with self-assembled monolayer surfaces formed on gold. The average internal energy was found to increase linearly with the laboratory collision energy. The kinetic energy-internal energy (T-V) conversion was 17% for the octadecanethiolate monolayer and 28% for the 2-(perfluorooctyl)-ethanethiolate monolayer surface. The results are similar to those obtained for metal carbonyl projectiles, though they indicate somewhat higher energy conversion. In addition, excitation of the projectile ion well beyond 20 eV internal energy is observed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jms.1190300132
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