Date of Award
Cole, Richard B.
Tarr, Matthew A.
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 within the same PSD segment, it is possible to obtain highly reproducible relative ion abundances. Discrimination of different linkage types is achieved by analysis of structurally-informative diagnostic peaks offered by PSD spectra of chloride adducts of oligosaccharides, whereas the relative peak intensities of selected diagnostic fragment pairs make differentiation of anomeric configuration possible. F- and Ac- cannot form anionic adducts with the oligosaccharides in significant yields. However, Br-, I- and NO3- anionic adducts consistently appear in higher abundances relative to [M - H]-, just like Cl-. Mildly acidic saccharides form both deprotonated molecules and anionic adducts, making it possible to simultaneously detect neutral and acidic oligosaccharides via anion attachment. PSD of [oligosaccharide + Cl]- yields structurally-informative fragment ions that retain the charge on the sugar molecule rather than solely forming Cl-, whereas PSD of Br-, I- and NO3- adducts of oligosaccharides yield the respective anions as the main product ions without offering structural information concerning the sugar. PSD of the chloride adduct of saccharides containing 1-2 linkages also yields chlorine-containing fragment ions. MALDI-TOF-MS and LDI-TOF-MS are shown to be useful for characterization of ultra-small titania nanoparticles. Peak maxima in MALDI-TOF mass spectra are found to correlate with nanoparticle size. The size distributions of TiO2 nanoparticles, obtained from MALDI- and LDI-TOF-MS are in good agreement with parallel TEM observations. PSD analysis of inorganic x nanomaterials is performed and valuable information about the structure of analytes has been obtained. A group of inorganic nitrate and perchlorate salts of forensic and health interest are investigated by LDI- and MALDI-TOF MS. In each case, a series of characteristic cluster ions are predominant in the negative-ion mode. The number and identity of metal atoms and anions in the recorded cluster ions can be positively identified by their m/z values, distinctive isotopic patterns and characteristic PSD fragmentation patterns.
Guan, Bing, "Characterization of Oligosaccharides and Nanoparticles by MALDI-TOF Mass Spectrometry" (2007). University of New Orleans Theses and Dissertations. 585.