Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 26 for “"Fragment ions"”.
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Studies of the dissociation and energetics of gaseous ions
… and ion coincidence mass spectra, enables fragment ions formed by dissociative single, double, and triple ionization, to be distinguished and quantified. Relative partial ionization cross sections (PICS) and precursor specific relative PICS are derived for the formation of positively …
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Low-Energy Electron Impact Fragmentations of the Polycyclic Aromatic Hydrocarbon Anthracene
… Masters of Science thesis was to investigate the fragmentation processes induced by low-energy electron impact with anthracene. This research is relevant in the study of low-energy electron interactions with molecules in gaseous environments, including potentially in the interstellar medium where …
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The mass spectra and correlations with structure for some 1-(5-ethyl-2-thienyl)-1-thiaalkanes
… have been obtained. Fragmentation paths, rearrangement mechanisms supported by low ionization voltage data have been discussed. The parent peaks are moderately strong. The rearrangement ion at m/e 144 is prominent for all spectra of the compounds. A large amount of …
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Applications of Mass Spectrometry to Analysis of Prodiginines, Bioactivated Methylenedianiline Intermediates, and Hypoxia Induced Changes in the Zebrafish Skeletal Muscle Proteome
… During the last two decades, its applications were dramatically extended and remarkable progress has been made in many fields, in particular, environmental and biological analyses. This dissertation focuses on identification and characterization of biologically active compounds and …
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Characterization of Oligosaccharides and Nanoparticles by MALDI-TOF Mass Spectrometry
The possibilities of differentiating linkage positions and anomeric configurations of small oligosaccharides by negative ion mode MALDI using anion attachment followed by PSD are investigated. By careful initial adjustment of the focusing mirror ratios allowing acquisition of the peaks of interest …
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Identification and imaging different lipid species within phase-separated model membranes by integration of TOF-SIMS and principal component analysis
… enables chemically imaging the distributions of various lipid species in model membranes. However, discriminating the TOF-SIMS spectra of structurally similar lipids is very difficult because the low mass fragment ions that are abundant in the spectra are common to multiple lipid species. …
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Determination of disulfide bond connecting patterns via tandem mass spectrometry (MSn) and biomolecular ion/radical reactions
… of the most common post translational modifications to occur in proteins and naturally occurring peptides. Disulfide bond formation plays a critical role in stabilizing their three-dimensional structure; therefore, it is very important to pinpoint the correct disulfide bond connecting pattern in …
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Development of liquid chromatography with tandem mass spectrometry method for measurement of sepsis biomarkers
… spectrometer, respectively, for measurement of fragment ions of the chosen surrogate peptides. The detection performance such as limit of detection (LOD), limit of quantification (LOQ), and specificity of these two methods were compared. Results: The result highlighted superiority of PRM method …
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Synthesis, structure and mechanism of polyoxometalate self-assembly: towards designed nanoscale architectures
… of the rearrangement of molybdenum Lindqvist anions, [Mo6O19] 2-, in the presence of silver(I) ions, into a silver-linked β-octamolybdate structure, has allowed elucidation of the role of small isopolyoxomolybdate fragments and AgI ions in the assembly process. The observation of higher mass …
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The Study of Positive-Ion Mass Spectrometry of 5-Fluorouracil Using Low-Energy Electron Impact
… beam of 5-fluorouracil and to investigate the fragmentation processes that were induced by low-energy electron impact. The apparatus is contained in a vacuum chamber with three main compartments: the expansion chamber, the collision chamber and the flight-tube. The expansion chamber is where …
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Study of Electron-Impact Induced Fragmentation of Thymine
… molecular beam of thymine and to investigate the fragmentation processes induced by low-energy electron impact. A molecular beam of thymine is generated by placing thymine in powder form inside a resistively heated oven. The beam of thymine is then crossed by a pulsed electron beam from an …
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Gas-phase Ion Chemistry of Hydroxy and Amino-substituted Interstellar Polycyclic Aromatic Hydrocarbons and Protonated Polycyclic Aromatic Hydrocarbons
… were studied using mass spectrometry. Ions were generated using an electron ionization (EI) source and the unimolecular chemistry of metastable ions was studied by performing mass-analysed ion kinetic energy spectrometry (MIKES) experiments with a magnetic sector tandem mass …
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Accurate ionic bond energy measurements with TCID mass spectrometry and imaging PEPICO spectroscopy
… (BDEs) were measured for seven metallocene ions (Cp<sub>2</sub>M<sup>+</sup>, Cp = η<sup>5</sup>-cyclopentadienyl = c-C<sub>5</sub>H<sub>5</sub>, M = Ti, V, Cr, Mn, Fe, Co, Ni) using threshold collision-induced dissociation (TCID) performed in a guided ion beam tandem mass spectrometer. For …
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Data analysis in proteomics novel computational strategies for modeling and interpreting complex mass spectrometry data
… to identify and map post-translational modifications on individual peptides, and to identify SILAC modification-containing spectra in a full-scale proteomic analysis. Secondly, matrix decomposition and projection approaches are explored; these use an eigen-decomposition to extract general trends …
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Bioreactor design for scaleup of Catharanthus roseus hairy root cultures for production of indole alkaloids
… GC/MS indicated the presence of vindoline fragment ions. A novel method based on non-linear regression analysis was developed for online measurement of oxygen uptake rates. Thus, mass transfer rates could be adjusted in bioreactor cultures to provide sufficient oxygen. Three different …
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Improved Dynamic Range, Quantitation, and Characterization of Histone H4 Post-Translational Modifications: A Top Down Mass Spectrometric Approach
… (PTM) of histones H2A, H2B, H3 and H4. Combinations of modifications such as acetylation, methylation, and phosphorylation have been hypothesized to create a ""histone code"" that influences gene transcription, gene silencing, and chromatin formation. Essential for complete understanding of this …
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Development of an LCMS Analytical Method with Applicability to Determination of Trace Level Explosives in Environmental Waters
… for each analyte, but rather having common fragment ions. The author has developed a mass spectrometric method, where MRMs are manually selected in such way to offer distinctive fragmentation features for each target compound. As such, this method would be useful in the positive …
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DEVELOPMENT OF A LC/MS/MS ENZYME METHOD FOR N8 - ACETYLSPERMIDINE MEASUREMENTS IN ENZYME ASSAYS
… value of 0.9996, where y is the peak area of the fragment-ion SRM (selected reaction monitoring: <em>m/z</em>: 188/114) chromatograms from N<sup>8</sup> -acetylspermindine and x is the concentration of N<sup>8</sup> - acetylspermindine. Acetylation of spermidine (SPD) and …
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Rapid identification, confirmation, and quantitation using an open-air ion source coupled to a time-of-flight mass spectrometer
… or sample preparation due to the interactions of helium metastable atoms with gas molecules commonly found in air. The coupling of the DART to a time-of-flight (TOF) mass spectrometer allows the rapid determination of an analyte's elemental composition based on accurate mass measurement …
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Evaluation and assignment of significance levels to peptide identifications from the database search programs using resampling approach
… (where k denotes the type and number of permutations) were evaluated for accurate computation of match significance levels. K-permuted decoy databases were generated by: (a) complete permutations of peptide sequences (Whole), (b) permutation of terminal positions of peptide sequences (End), and …
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