The Experts below are selected from a list of 210 Experts worldwide ranked by ideXlab platform
Kelly R. Thornburg - One of the best experts on this subject based on the ideXlab platform.
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Design and performance of an in-line surface-induced dissociation device in a four-Sector Mass Spectrometer
Journal of the American Society for Mass Spectrometry, 1995Co-Authors: Kevin L. Scheycor, David A. Durkin, Kelly R. ThornburgAbstract:A new in-line surface-induced dissociation device has been designed and characterized in a high performance four-Sector tandem Mass Spectrometer. The design incorporates a target electrode parallel to the ion beam axis and an angled deflector plate (45° relative to the ion beam) to provide large collision angles. In addition, an extraction electrode (parallel to the target electrode) is employed to efficiently extract product ions from the target surface. Results obtained with this device indicate high internal energy deposition (up to 16. 3 eV) as measured with the thermometer ions W(CO) _6 ^+· and Si(C_2H_5)_4/+·, as evidenced by extensive dissociation of the refractory pyrene molecular ion, and as indicated by the b _3/ y _2 ratio in the product ion spectrum of leucine enkephalin. High resolution provided by the four-Sector instrument for both precursor ions and product ions allows the observation of previously unobserved dissociation products in the surface-induced dissociation spectra of Si(C_2H_5)_4/+· and novel ion-surface reaction products in spectra of W(CO)_6/+· ions after collisions with hydrocarbon-covered surfaces. Both hydrogen atom and hydrocarbon abstraction products are observed. The dissociation efficiencies measured with the in-line device are approximately 1% when hydrocarbon-coated surfaces are used and increase fivefold with a fluorinated surface.
Catherine Fenselau - One of the best experts on this subject based on the ideXlab platform.
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Collision energy effects on the collision‐induced dissociation of multiply charged melittin
Rapid communications in mass spectrometry : RCM, 1994Co-Authors: Daniele Fabris, Michele Kelly, Catherine Fenselau, Keith R. JenningsAbstract:The fragmentation of the inelittin 4+ ion has been studied over a range of collision energies from 28 eV to 12 keV in a four-Sector Mass Spectrometer. Patterns of fragmentation and energy conversion were found to be analogous to those observed for singly charged peptides. High numbers of collisions were not required for activation at low energies.
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hydrogen deuterium exchange of Mass selected peptide ions with nd3 in a tandem Sector Mass Spectrometer
International Journal of Mass Spectrometry and Ion Processes, 1992Co-Authors: Xueheng Cheng, Catherine FenselauAbstract:Abstract Hydrogen/deuterium exchange of Mass-selected protonated peptide ions with ND3 is investigated in a four Sector tandem Mass Spectrometer equipped with a high-pressure collision cell. The dependence of H/D exchange on the pressure of ND3, on collision energy and on proton affinities (PAs) of the peptides is examined. For leucine enkephalin, a peptide without strongly basic residues, the maximum number of H/D exchanges observed can correspond to the maximum number of active hydrogen atoms in the ions. In peptides with basic residues such as arginine, the H/D exchange proceeds more slowly and more selectively. H/D exchange is observed for renin substrate whose PA is estimated to be higher than ND3 by more than 50 kcal mol−. The pattern of H/D exchange of leucine enkephalin shows discrepancy with the number of hydrogen atoms in the peptide ion expected to undergo fast H/D exchange, thus indicating possible conformational effects. When protonated leucine enkephalin is reacted with ND3 under predominantly single-collision conditions, the incorporation of deuterium into fragment ions is found to vary, depending on the type of fragment ion. This differential incorporation of deuterium may be informative about the nature of the processes leading to the formation of fragment ions.
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Hydrogen/deuterium exchange of Mass-selected peptide ions with ND3 in a tandem Sector Mass Spectrometer
International Journal of Mass Spectrometry and Ion Processes, 1992Co-Authors: Xueheng Cheng, Catherine FenselauAbstract:Abstract Hydrogen/deuterium exchange of Mass-selected protonated peptide ions with ND3 is investigated in a four Sector tandem Mass Spectrometer equipped with a high-pressure collision cell. The dependence of H/D exchange on the pressure of ND3, on collision energy and on proton affinities (PAs) of the peptides is examined. For leucine enkephalin, a peptide without strongly basic residues, the maximum number of H/D exchanges observed can correspond to the maximum number of active hydrogen atoms in the ions. In peptides with basic residues such as arginine, the H/D exchange proceeds more slowly and more selectively. H/D exchange is observed for renin substrate whose PA is estimated to be higher than ND3 by more than 50 kcal mol−. The pattern of H/D exchange of leucine enkephalin shows discrepancy with the number of hydrogen atoms in the peptide ion expected to undergo fast H/D exchange, thus indicating possible conformational effects. When protonated leucine enkephalin is reacted with ND3 under predominantly single-collision conditions, the incorporation of deuterium into fragment ions is found to vary, depending on the type of fragment ion. This differential incorporation of deuterium may be informative about the nature of the processes leading to the formation of fragment ions.
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triple Mass spectrometry ms ms ms with a floated collision cell in a four Sector tandem Mass Spectrometer
Journal of Mass Spectrometry, 1991Co-Authors: Joseph Bordasnagy, Catherine FenselauAbstract:A method is described for carrying out triple Mass spectrometry (MS/MS/MS) experiments with an electrically floated collision cell in the third field-free region on a tandem double-focusing Mass Spectrometer. The method described may use magnet calibration obtained at any accelerating voltage and is generally applicable at any value of the collision cell voltage. The utility of the method to acquire MS/MS/MS spectra of enhanced quality is demonstrated on a JEOL JMS-HX110/HX110 four-Sector Mass Spectrometer.
Yong-chien Ling - One of the best experts on this subject based on the ideXlab platform.
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surface study of polymers by static secondary ion Mass spectrometry using a magnetic Sector Mass Spectrometer
Journal of The Chinese Chemical Society, 1993Co-Authors: Yi-feng Lin, Yong-chien LingAbstract:Results from static SIMS analysis of six thermoplastic polymers — polytetrafluoroethylene (PTFE), polyethylene (PE), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polystyrene (PS) and polycarbonate (PC) — using a magnetic-Sector SIMS instrument and O2+ primary beam are presented. For PTFE as a representative sample, the charging effect is reduced only with a metal grid when analyzing positive secondary ions. When negative secondary ions are analyzed, excessive charges are self-compensated with a normal-incidence electron gun. Positive-ion spectra collected agree with spectra obtained using either a quadrupole or time-of-flight SIMS instrument and noble-gas ion beams. The agreement is objectively demonstrated by means of the capability to compare spectra in the NIST/EPA/MSDC Mass spectral database. The merits of the use of high-Mass resolution, of which magnetic-Sector SIMS is inherently capable, to provide analytical information about the molecular species native to the sample are demonstrated in distinguishing three ambiguous peaks with nominal Mass ratios m/z = 27, 39 and 59 from PMMA.
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Surface Study of Polymers by Static Secondary Ion Mass Spectrometry Using a Magnetic‐Sector Mass Spectrometer
Journal of the Chinese Chemical Society, 1993Co-Authors: Yi-feng Lin, Yong-chien LingAbstract:Results from static SIMS analysis of six thermoplastic polymers — polytetrafluoroethylene (PTFE), polyethylene (PE), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polystyrene (PS) and polycarbonate (PC) — using a magnetic-Sector SIMS instrument and O2+ primary beam are presented. For PTFE as a representative sample, the charging effect is reduced only with a metal grid when analyzing positive secondary ions. When negative secondary ions are analyzed, excessive charges are self-compensated with a normal-incidence electron gun. Positive-ion spectra collected agree with spectra obtained using either a quadrupole or time-of-flight SIMS instrument and noble-gas ion beams. The agreement is objectively demonstrated by means of the capability to compare spectra in the NIST/EPA/MSDC Mass spectral database. The merits of the use of high-Mass resolution, of which magnetic-Sector SIMS is inherently capable, to provide analytical information about the molecular species native to the sample are demonstrated in distinguishing three ambiguous peaks with nominal Mass ratios m/z = 27, 39 and 59 from PMMA.
Stephen A. Martin - One of the best experts on this subject based on the ideXlab platform.
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A comparison of the peptide fragmentation obtained from a reflector matrix-assisted laser desorption-ionization time-of-flight and a tandem four Sector Mass Spectrometer
Journal of the American Society for Mass Spectrometry, 1995Co-Authors: Jason C. Rousecor, Stephen A. MartinAbstract:The types, extent, and overall distribution of peptide fragmentation produced by matrix-assisted laser desorption-ionization-postsource decay (MALDI-PSD) on a reflector time-of-flight Mass Spectrometer were compared with those obtained from high and low energy collision-induced dissociation (CID) on a four-Sector Mass Spectrometer and from liquid secondary ion Mass spectrometry (LSIMS) ion source fragmentation and LSIMS metastable ion (MI) decomposition on a two-Sector Mass Spectrometer. The model peptides studied had sequences and compositions that yielded predominantly either N - or C -terminal fragmentation from CID. For des-Arg^1 and des-Arg^9 bradykinin (i.e., H -PPGFSPFR- OH and H -RP-PGFSPF- OH , respectively), the types of fragment ions and the extent to which each type is formed in both MALDI-PSD and low energy CID spectra are remarkably similar. This observation suggests that both methods deposit comparable internal energies (IE) into [M + H]^+ precursor ions. The distribution of N -terminal, C -terminal, immonium, and internal fragmentation from MALDI-PSD spectra of des-Arg^1 and des-Arg^9 bradykinin did not change dramatically with respect to the terminal arginine position, contrary to those from LSIMS MI decomposition, high and low energy CID spectra. This observation in combination with the prominent immonium, internal, and minus 17 fragment ion types in PSD indicates that the imparted IE from MALDI and the 14 µs of flight time may promote steady-state decomposition kinetics. Fragmentation distributions of MALDI-PSD spectra are also similar to those in LSIMS spectra. This implies that the distribution of protonation sites in [M + H]^+ is comparable for both techniques.
Keith R. Jennings - One of the best experts on this subject based on the ideXlab platform.
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Utilising precursor ion and second-generation product ion scanning techniques in a four-Sector Mass Spectrometer for the analysis of polymer additives
European Journal of Mass Spectrometry, 1997Co-Authors: Anthony T. Jackson, Richard C. Jennings, Hilary T. Yates, James H. Scrivens, Keith R. JenningsAbstract:The analysis of organic polymer additives by means of Mass spectrometry (MS) has been shown to be aided by the utilisation of precursor ion and second-generation product ion (MS3) scanning experiments. These techniques have been used to determine the fragmentation pathways of these materials under high-energy conditions. A four-Sector Mass Spectrometer was employed to generate precursor ion and MS3 spectra which indicated that the routes of dissociation for the generation of many fragment ions, observed as intense peaks in the product ion spectra, were relatively complex. Fragmentation schemes are proposed to account for the data observed in the spectra.
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Collision energy effects on the collision‐induced dissociation of multiply charged melittin
Rapid communications in mass spectrometry : RCM, 1994Co-Authors: Daniele Fabris, Michele Kelly, Catherine Fenselau, Keith R. JenningsAbstract:The fragmentation of the inelittin 4+ ion has been studied over a range of collision energies from 28 eV to 12 keV in a four-Sector Mass Spectrometer. Patterns of fragmentation and energy conversion were found to be analogous to those observed for singly charged peptides. High numbers of collisions were not required for activation at low energies.
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The effect of collision energy and nature of the surface on the surface-induced dissociation Mass spectra of fluorobenzene using a four-Sector Mass Spectrometer
International Journal of Mass Spectrometry and Ion Processes, 1992Co-Authors: Dominique Despeyroux, Keith R. Jennings, Andrew D. Wright, Sid Evans, Alex RiddochAbstract:Abstract The effects on the surface-induced Mass spectrum of fluorobenzene, recorded using a four-Sector Mass Spectrometer, of changing the collision energy and the nature of the surface are reported. At higher collision energies, although the overall ion current is reduced, the relative abundance of product ions is increased, particularly those of low m/z . The use of a rough surface, such as a film of PTFE, increases the abundance of low Mass fragment ions for a given translational energy, especially at higher collision energies.