2009 MU dissertations - Access restricted to UM
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Item Purification and characterization of A[beta] and probing the interactions between myricetin and A[beta] using various spectroscopic methods(University of Missouri--Columbia, 2009) Wang, Mingjuan; JiJi, Renée Denise[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Worldwide, millions of people suffer from symptoms of memory loss and confusion associated with Alzheimer's disease (AD). Mounting evidence suggests a close relationship between AD and aggregation of a naturally occurring protein fragment, the amyloid [beta]-peptide (A[beta]). Soluble oligomers of A[beta] are now considered to be the primary neurotoxic agent. Naturally occurring flavonoid compounds have been reported to inhibit/reverse A[beta] aggregation and reduce the A[beta]-induced neurotoxicity both in vitro and in vivo. Previous spectroscopic studies suggest multiple forms of interaction between A[beta] and myricetin, a flavonoid compound. In this study, two A[beta] fragments, A[beta](1-16) and A[beta](25-40), together with A[beta](1-42) were investigated. HPLC purification was conducted on crude A[beta](1-16) and A[beta](25-40) using a Beckman System Gold HPLC system, a Vydac C18 column and a combination of acetonitrile and water as mobile phase. The purified A[beta](1-16) and A[beta](25-40) has a purity of 91% and 90%, respectively. CD, UVRR spectroscopy and DLS have been employed to study the different aggregation states of A[beta](1-42) obtained by using 10 kDa and 30 kDa molecular weight cut-off filters or unfiltered (referred to LMW, IMW and HMW A[beta](1-42)). The studies have shown that LMW A[beta](1-42) is fully unstructured, containing oligomers up to tetramers; IMW A[beta](1-42) is likely a combination of disordered and some [beta]-sheet structure, containing large aggregates ranging from 30 kDa to 60 kDa; whereas HMW has high content of large aggregates. The solution conformation of A[beta] and A[beta] fragments were characterized using CD and UVRR spectroscopic methods. Both A[beta](1-42) and A[beta](25-40) are fully unordered, whereas A[beta](25-40) is likely has higher content of [beta]-strand structure. A[beta](1-16) is predominantly PPII structure. Various spectroscopic methods were employed to investigate the binding interactions between disordered A[beta] and myricetin, one of the flavonoid compounds. A[beta]-myricetin complex formation was visualized by myricetin's intrinsic fluorescence. ThT fluorescence assay and CD study showed that myricetin can inhibit A[beta](25-40) and A[beta](1-42) from forming [beta]-sheet structured fibril. CD and UVRR studies further evidenced conformational changes from both A[beta](25-40) and A[beta](1-42) induced by myricetin. In parallel, UV resonance Raman spectra indicate that the environment around one or more of the aromatic residues is altered when myricetin is present. These findings suggest that both hydrophobic interaction and hydrophilic interaction play a role in the binding of myricetin with A[beta].Item Development and applications of label-free optofluidic ring resonator biosensor(University of Missouri--Columbia, 2009) Zhu, Hongying, 1982-; Fan, Xudong[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] This dissertation presents the development and applications of label-free optofluidic ring resonator (OFRR) sensor platform. The OFRR sensor naturally integrates the optical ring resonator with the capillary microfluidics by employing a micro-sized glass capillary with a thin wall. Each capillary cross section forms an optical ring resonator to support the circulating optical resonance called whispering gallery modes (WGMs) via total internal reflection (TIR). The OFRR sensor utilizes the resonance wavelength shift in response to the surrounding refractive index change as the transduction signal to monitor the biomolecular interaction on the sensor surface. The OFRR sensing principle, fabrication methods, and experimental setup design are introduced in detail. Based on the OFRR sensor platform, four different investigations are performed to demonstrate the OFRR label-free biosensing capability. A theory is developed to analyze the OFRR surface sensing sensitivity and to estimate the biomolecule surface density. Experiments are performed to demonstrate the non-specific protein binding detection, specific protein binding detection, and specific virus detection in the PBS buffer with the OFRR sensor, which characterize the OFRR sensor biosensing performance. Further study utilizes the OFRR sensor to quantify the breast cancer biomarker in clinical human serum, which marks the first application of the optical ring resonator sensor for real clinical applications.Item Development and evaluation of a novel germanium-68/gallium-68 generator(University of Missouri--Columbia, 2009) Chang, Yu-Wen, 1980-; Cutler, Cathy S.[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Nuclear medicine is a branch of medical imaging that uses small amounts of radioactive material to diagnose or treat a variety of diseases, including many types of cancers, heart disease and certain other abnormalities within the body. Positron emission tomography, also called PET imaging or a PET scan, is a type of nuclear medicine imaging. Radioactive materials used in medical imaging (called radiopharmaceuticals) are produced by cyclotron or radionuclide generator. Current radiopharmaceuticals used in PET scans are mainly cyclotron produced which increases the expense and manufacturing complexities of such radiopharmaceuticals. A radionuclide generator is a mobile device which produces radioactive material and provides a more efficient method and an less expensive choice in the manufacturing of PET imaging agents. There is a need to develop an effective radionuclide generator for PET imaging. This research is to develop and evaluate a novel mother/daughter Germanium-68/Gallium-68 generator for PET imaging. This type of generator has been investigated for over fifty years but many problems still exist which need to be resolved before application in a clinical setting can be achieved. Such problems include metal impurities, mother radionulide contamination, and diluted daughter radionuclide. It was found in this research that the Fajans adsorption technique is a way to produce higher purified and concentrated Ga-68 radionuclide while lowering Ge-68 contamination. The progressive lowering of metals detected in the final solutions collected from the borosilicate bead Fajans adsorption generator points towards a very workable separation system. The potential benefits of a Fajans adsorption Ge-68/Ga-68 generator system are substantial and will greatly improve the efficiency and delivery of Ga-68 as a PET imaging agent.Item Genetic engineering of soybean using candidate genes to improve drought tolerance(University of Missouri--Columbia, 2009) Guttikonda, Satish Kumar; Nguyen, Henry T.[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Drought is one of the major abiotic stresses which affect productivity in soybean. Plants respond and adapt to drought stress through various biochemical and physiological processes, and they induce several stress-responsive genes including osmolyte biosynthesis genes and transcription factors. To date, most of the abiotic stress-related genes have been constitutively expressed. Constitutive overexpression of a transgene requires additional building blocks and energy, which may affect the normal growth of transgenic plants. The use of stress-inducible promoters can help express the gene under stress conditions and can also protect transgenic plants from growth suppression under non-stress conditions. Arabidopsis thaliana dehydration response element binding transcription factor (DREB1D) and three osmolyte genes driven by a constitutive, ABAinducible and stress-inducible promoters were introduced in soybean through Agrobacterium tumefaciens-mediated gene transfer. Several transgenic lines were generated and molecular analysis was performed to confirm transgene integration. Transgenic plants overexpressing the AtDREB1D transcription factor showed reduced total leaf area and shoot biomass compared to non-transgenic plants under well-watered conditions. No significant difference in root length or root biomass was observed between transgenic and nontransgenic plants under well-watered conditions. When subjected to gradual water-deficit, transgenic plants maintained higher relative water content because the transgenic lines used water more slowly due to reduced total leaf area, which caused them to wilt slowler than nontransgenic plants. The transgenic plants showed improved drought tolerance by maintaining 17- 24% higher leaf cell membrane stability compared to non-transgenic plants. The results demonstrate the feasibility of engineering soybean for increased drought tolerance by expressing stress-responsive genes.Item Reluctant sublime(University of Missouri--Columbia, 2009) Langemak, Elizabeth; Cairns, Scott; Dickey, Frances, 1970-[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] This dissertation consists of two parts: a critical essay on the Canadian poet Anne Carson's place in the lineage of confessional poetry, as well as a book-length poetry manuscript, entitled "Anne's Carson's 'The Glass Essay': Confessional Evolution Through Scholarly Intervention." The critical essay argues that Carson's poem, "The Glass Essay" not only manifests traits common to the American confessional tradition, but also represents a new stage of confessional verse in its combination of confessional and scholarly techniques.