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dc.date.accessioned2012-02-10T16:09:14Zen
dc.date.available2012-02-10T16:09:14Zen
dc.date.created2010en
dc.date.issueden
dc.identifier.otherAPT-BAG: georgetown.edu.10822_552872.tar;APT-ETAG: 8cb23b2297a6fb30b73200b38fa23b13en
dc.identifier.urien
dc.descriptionThesis (Ph.D.)--Georgetown University, 2010.; Includes bibliographical references.; Text (Electronic thesis) in PDF format. Uric acid, a component in human kidney stones, crystallizes in an anhydrous (UA), a metastable dihydrate (UAD), a rare monohydrate, and an ionized monosodium urate form in vivo. In the body, these crystals exhibit a variety of morphologies and colors which differ from laboratory grown uric acids. These observations provided the motivation to study the effect of several molecular dyes and physiologically relevant metal cations on the crystallization of UA and UAD. All cationic and neutral dopants investigated were included in UA and UAD crystals, while anionic dyes were excluded. At low concentrations, the dyes were preferentially incorporated into the {001} and {201} growth sectors of UA. In UAD, variable inclusion behaviors were encountered. Inclusions occurred on the {011} growth sector/hillock, on the {102} growth sector, and non-specific inclusions were also observed. Most of the dyes induced morphological changes in UA and UAD crystals at higher concentrations. The amount of dye/metal cation included and absorption spectra of the dyes in the single crystals of both UA and UAD were determined.; Unlike physiologically derived crystals, laboratory grown UAD crystals are less stable and spontaneously transform to UA under ambient conditions. Using a combination of techniques, the mechanism and kinetics of the phase transformation of pure and doped UAD crystals were investigated. Intrinsic sample parameters (e.g. crystal size and shape) and environmental conditions (e.g. temperature and humidity) were considered. The dehydration reaction was found to be irreversible and highly anisotropic. This was rationalized on the basis of crystal structure and morphology. Most of the included dyes exhibited a stabilizing effect on UAD crystals, which was explained in terms of host-guest interactions as a function of variability in the structure of the dyes.; To better understand the microscopic effects of the dye impurities, the (100) face of UA crystals was studied in the presence of Bismarck brown dyes by atomic force microscopy. From topographical imaging, growth inhibition along the c-direction was observed in the presence of the dyes. Incremental dye concentrations also pinned advancing steps and reduced the velocity of b-steps due to high impurity incorporation. These results complement what was observed in bulk UA crystal growth.en
dc.formatapplication/pdfen
dc.languageengen
dc.publisherGeorgetown Universityen
dc.sourceDept. of Chemistry, Doctoral dissertations, 2010.en
dc.subjectChemistry, Organic; Chemistry, Analytical; Chemistry, Pharmaceuticalen
dc.titleCrystallization and phase transformation of uric acidsen
dc.typethesisen


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