Theses and Dissertations from UMD
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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
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Item FEASIBILITY OF BINDING ANTIOXIDATIVE FOOD PIGMENTS USING RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE OXYGENASE(2010) Yachetti, Sarah M.; Lo, Y. Martin; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Antioxidative food pigments during manufacturing are subjected to harsh conditions that can attenuate the antioxidant benefits and alter its color significantly. Thus, stabilization of these pigments is desired to increase the product's nutritional and commercial value. Ribulose-1, 5-bisphosphate carboxylase oxygenase (RuBisCO), an abundant protein with a balanced amino acid profile, may serve as a good binding agent to increase stability of pigments due to the fact that it is naturally bound to chlorophyll in plants besides its highly stable structure. This research investigated the binding capacity of purified RuBisCO to riboflavin, annatto extract, and beta-carotene. Protein-pigment complexes were promoted with mixing, sonicating, heating and freeze thawing techniques. Raman spectroscopy, surface plasmon resonance, and UV-Vis were used to measure binding potential. A method to extract RuBisCO from tobacco with paramagnetic antibody-coated beads was also investigated. Not only does this exploratory research provide the baseline understanding of the challenges and hurdles in forming a protein-pigment complex, but the detection techniques established could also be of value for developing quantitative measurements of such complexes. While further research is still needed to elucidate the interaction between the pigments and RuBisCO, it was confirmed that the binding ability of RuBisCo to the pigments investigated could be greatly hindered by the structural conformation of RuBisCo.Item Top-Down Analysis of Bacterial Proteins by High-Resolution Mass Spectrometry(2010) Wynne, Colin Michael; Fenselau, Catherine; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In the biodefense and medical diagnostic fields, MALDI mass spectrometry-based systems are used for rapid characterization of microorganisms generally by detecting and discriminating the highly abundant protein mass-to-charge peaks. It is important that these peaks eventually are identified, but few bacteria have publicly available, annotated genome or proteome from which this identification can be made. This dissertation proposes a method of top-down proteomics using a high-resolution, high mass accuracy analyzer coupled with bioinformatics tools to identify proteins from bacteria with unavailable genome sequences by comparison to protein sequences from closely-related microorganisms. Once these proteins are identified and a link between the unknown target bacteria and the annotated related bacteria is established, phylogenetic trees can be constructed to characterize where the target bacteria relates to other members of the same phylogenetic family. First, the top-down proteomic approach using an Orbitrap mass analyzer is tested using a well known, well studied single protein. After this is demonstrated to be successful, the approach is demonstrated on a bacterium without a sequenced genome, only matching proteins from other organisms which are thought to have 100% homology with the proteins studied by the top-down approach. Finally, the proposed method is changed slightly to be more inclusive and the proteins from two other bacteria without publicly available genomes or proteomes are matched to known proteins that differ in mass and may not be 100% homologous to the proteins of the studied bacteria. This more inclusive method is shown to also be successful in phylogenetically characterizing the bacteria lacking sequence information. Furthermore, some of the mass differences are localized to a small window of amino acids and proposed changes are made that increase confidence in identification while lowering the mass difference between the studied protein and the matched, homologous, known protein.Item Steriod Hormones in Biosolids and Poultry Litter: A Comparison of Potential Environmental Inputs(2010) Bevacqua, Christine Elizabeth; Torrents, Alba; Rice, Clifford; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Steroid hormones can act as potent endocrine disruptors when released into the environment. The main sources of these chemicals are thought to be wastewater treatment plant discharges and waste from animal feeding operations. While these compounds have frequently been found in wastewater effluents, few studies have investigated biosolids or manure, which are routinely land applied, as potential sources. This study assessed the relative environmental contribution of steroid hormones from biosolids and chicken litter. Samples of limed biosolids collected over a four year period and chicken litter from 12 mid-Atlantic farms were analyzed for 17β-estradiol (E2), estrone (E1), estriol (E3), 17α-ethinylestradiol (EE2), progesterone, and testosterone, and the conjugated hormones E1-sulfate (E1-S), E2-3-sulfate (E2-3-S), and E2-17-sulfate (E2-17-3). Results showed that E1 and progesterone were the most prevalent compounds in both of these materials, with E1-S also present in chicken litter.Item A Novel Pre-fluorescent Nitroxide Probe for the Highly Sensitive Determination of Peroxyl and Other Radical Oxidants(2009) Jia, Min; Blough, Neil V; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)ABSTRACT Peroxyl and other radical oxidants react with stable cyclic nitroxides, such as the piperidinyl and pyrrolidinyl nitroxides to form initially the one electron oxidation product, the oxoammonium cation. For most of the nitroxides studied thus far, the oxoammonium cation can in part be regenerated to the nitroxide through reduction by solution constituents. The reaction mechanisms, however, remain a matter of debate. Further, the highly-sensitive, quantitative determination of peroxyl and other radical oxidants has yet to be achieved, posing a major hurdle to a further understanding of the impact of peroxyl radicals in many biological and environmental processes. A unique, amino-pyrrolidinyl nitroxide, 3-amino-2,2,5,5,-tetramethyl-1-pyrrolidinyloxy (3-ap) is shown to undergo an irreversible reaction with peroxyl radicals and other radical oxidants to generate a diamagnetic product. When a fluorophore, fluorescamine is covalently linked through the amino group on the nitroxide, the resulting compound (3-apf, or I) has very low fluorescence quantum yield. Upon reaction with peroxyl and other radical oxidants, the quantum yield of the product increases dramatically (~100 fold), and thus 3-ap or 3-apf can be used as a highly sensitive and versatile probe to determine oxidant production optically, either by monitoring the changes in fluorescence intensity using a spectrofluorometer, by HPLC analysis with fluorescence detection, or by a combination of both approaches. By changing the [O2]/[nitroxide] ratio, it is shown that peroxyl radicals can be detected and quantified preferentially in the presence of other radical oxidants, such as *NO2 and CO3*-. When decreasing the [O2]/[nitroxide] ratio, the oxidation product decreases, with a concomitant increase of the alkoxylamine product resulting from reaction of 3-ap (3-apf) with carbon centered radicals. Preliminary studies suggest that the reactions of 3-ap and 3-apf with peroxyl radical produce different final products. High resolution mass spectrometry and NMR studies indicate that 3-ap is oxidized to form a cyclic peroxide structure, while 3-apf is oxidized to form a cyclic -NH-O- structure, with this difference resulting possibly from the presence of the fluorescamine moiety in 3-apf. Detection of photochemically produced peroxyl radicals is achieved by employing 3-amino-2,2,5,5,-tetramethyl-1-pyrrolidinyloxy (3-ap) alone, followed by derivatization with fluorescamine, while detection of thermally-generated peroxyl radicals employs 3-apf. Preliminary applications include the detection of peroxyl radicals generated thermally in soybean phosphatidylcholine liposomes by 3-apf and produced photochemically in tap water by 3-ap.Item AN IMPROVED PSEUDO-DETERMINISTIC RECEPTOR MODEL (iPDRM) TO APPORTION AMBIENT PM CONSTITUENTS TO SOURCES IN TAMPA, FL(2009) Beachley, Gregory Marcus; Ondov, John M; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In 2005, Park et al., developed a new Pseudo-Deterministic Receptor Model (PDRM) to apportion SO2 and ambient particulate matter (PM) constituents to local sources near Tampa Bay. Ambient pollutant measurements were fit to products of emission rates and dispersion factors constrained with a Gaussian plume model for individual sources. In our study, the original samples were reanalyzed by ICPMS for 10 additional elements to improve the resolving power. Chemical mass balance (CMB) terms were added to PDRM to allow fitting of background aerosol sources. More accurate, curvilinear plume trajectories were computed to predict arrival times in both surface and aloft layers. This allowed application of the PDRM complicated meteorological conditions, e.g. wind shifts. Predicted emission rates for particle-bound elements were constrained using chemical compositional information obtained from published source profiles for generic source types. Constraints applied to source emissions of known tracer species allowed the "conditioning" of predicted dispersion factors for those sources to tracer species concentration profiles to better determine the dispersion factor temporal profiles. This enabled the model to apportion pollutants to individual sources with intermittent emissions the omission of which in Park et al. lead to significant residuals. Excellent fits were obtained for all modeled pollutants: 14 of 22 species have Normalized Mean Square Error (NMSE) values of < 2.5% and 21 of 22 have values < 8%. These were improved for SO2 and 8 of 10 elements (by 7-35% for Al, Cu, Ni, Pb, and Zn) modeled by Park et al. Our predicted emission rates are in much better agreement with chemical compositions for generic source types. Key results include: (1) predicted SO2 contributions to ambient levels from a small, lead battery recycling plant that were reduced from 50-59% at its peak influence to a more reasonable 2-4%, (2) Pb/Zn ratios from that plant increased from 1.0 to 734 and better agree with published ratios of 67-440, (3) predicted Ni emission rates for one of the oil-fired power plants (OFPP) was increased by 100-fold (larger than Park's), and now better agrees with its published National Emissions Inventory (NEI) emission rate and with X/Ni ratios for generic OFPP emissions derived from EPA's SPECIATE database, and (4) our predicted emission rates for hazardous air pollutants and toxics from power plants agree with ~75% of those reported annual emission rates from NEI and Toxic Release Inventories (TRI) to within a factor of 5. This suggests that these reported data provide a good qualitative estimate of emissions, but should not be treated as accurate in a predictive model to quantify source emissions. It was also observed that the TRI values for As emission rates from coal-fired power plants are more accurate that their NEI values.Item TEMPLATE SYNTHESIZED NANOTUBES, NANOWIRES AND HETEROGENEOUS COAXIAL NANOWIRES FOR ELECTROCHEMICAL ENERGY STORAGE(2009) Liu, Ran; Lee, Sang Bok; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Template synthesized nanomaterials have been successfully applied in electrochemical energy storage systems such as supercapacitors and lithium ion batteries. The first part of present study will list examples of applying various nanomaterials such as nanowires, nanotubes and heterostructured nanowires in different electrochemical energy storage systems for enhancing their charge/discharge rates, energy densities and power densities, etc. The following of the thesis will describe the template synthesis of nanomaterials in details. The experimental part of this thesis will concentrate on the fabrication of alumina template and the detailed experimental setups for aluminum anodization and template synthesis of nanomaterials. The rest of the thesis analyzes four cases of using template synthesized nanomaterials in electrochemical energy storage, which include my major work during my PhD studies. The first one is utilizing poly(3,4- ethylenedioxythiophene) (PEDOT) nanotubes as electrode materials for highpowered supercapacitor. The thin-walled nanotubes allow fast charge/discharge of the PEDOT to achieve high power. The second one is related to synthesis and characterization of RuO2/PEDOT composite nanotubes for supercapacitors. Loading appropriate amount of RuO2 can effectively enhance the specific capacitance of PEDOT nanotube. The third case illustrates the synthesis of MnO2/PEDOT coaxial nanowires by one step coelectrodeposition for electrochemical energy storage. The combined properties of MnO2 and PEDOT enable the coaxial nanowires to have very high specific capacitances at high current densities. Their formation mechanism will be explored and their nanostructures are tuned for optimized electrochemical properties. The final case reports the MnO2-Nanoparticles enriched PEDOT nanowires for enhanced electrochemical energy storage capacity. Large amount of the MnO2 nanoparticles can be loaded into PEDOT nanowires after they are soaked in KMnO4 solution. Thus loaded MnO2 nanoparticles effective enhance the energy densities of PEDOT nanowires without causing too much volume expansion to them.Item Synthesis, Characterization and Catalytic Properties of Bimetallic Nanoparticles(2009) Dylla, Anthony Greg; Walker, Robert A; Eichhorn, Bryan W; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Due to the ever-increasing desire for catalysts that possess high activities and selectivities for industrially relevant reactions, much effort is being spent on the synthesis of mono and bimetallic nanoparticles with tunable characteristics such as size, shape and bimetallic composition. Understanding how these characteristics influence catalytic performance is the key to rationally designing catalysts for a specific reaction. While significant breakthroughs have been made, particularly in the area of monometallic nanoparticles with regard to shape and size, relating the bimetallic structure, i.e., core@shell or alloy to a specific reactivity remains a difficult task. Work presented in this thesis describes the synthesis, characterization and catalytic properties of mono and bimetallic nanoparticles. Our efforts were motivated by the desire to understand the relationships that exist between metallic nanoparticle structure and their function as catalysts. This work also seeks to better understand the dynamic changes a nanoparticle's structure undergoes during typical catalytic operating conditions. Our approach is to use a wide array of analytical tools including optical methods, electron microscopy, XRD and mass spectrometry to provide an interlocking description of nanoparticle structure, function and durability. We show how the polymer coatings and degraded carbonaceous deposits affect propene hydrogenation catalytic activity of Pt nanoparticles. We also present a unique view of the interplay between thermodynamic and kinetic variables that control bimetallic nanoparticle alloy structures by looking at ordered and disordered PdCu alloy nanoparticles as a function of particle size. In another study we show that Ru@Pt and PtRu alloy nanoparticle catalysts have similar surface structures under oxidizing conditions but completely different surface structures under reducing conditions as probed by vibrational spectroscopy. These differences and similarities in surface composition correlate very well to their catalytic activity for CO oxidation under oxidizing and reducing environments, respectively. Finally, we present the synthesis and characterization of Cu@Pt nanoparticles with a particular focus on the core@shell formation mechanism. We also show how dramatic changes in the surface electronic structure of Cu versus Cu@Pt nanoparticles can affect their ability to transform light into heat by using Raman spectroscopy to observe graphite formation on the surface of these nanoparticles.Item A Molecular and Isotopic Approach to Examine the Role of Terrestrial Organic Matter in the Carbon Cycle of the Arctic Ocean(2008) Belicka, Laura Lee; Harvey, H. Rodger; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The organic carbon cycle in the Arctic Ocean is complicated by the delivery and redistribution of terrigenous material through rivers, sea-ice, and erosion. This dissertation combines an isotopic and molecular biomarker approach to assess the role that terrestrial organic carbon plays in the Arctic organic carbon cycle, with a focus on a comparison of geochemical proxies for the quantification of organic matter, an analysis of the sources and transformation of organic carbon to particulate organic matter (POM) and sediments, and an experimental investigation on the kinetics of recycling. Estimates for preserved terrestrial organic components varied considerably for identical sediment samples, suggesting that proxies account for different sources of terrestrial material (i.e., soil versus vascular plants). In spite of the variability, an estimated 12-43% of the organic carbon preserved in surface sediments was terrestrial in origin. This contrasted sharply with surface and halocline POM, in which marine inputs dominated despite spatial variability. With depth, POC composition reflected the increasing significance of inputs from secondary production and microbial degradation, as well as continental material. Acid-volatile sulfide (AVS) and redox-sensitive elements coupled with δ13C and lipid biomarkers demonstrated a transition from intense metabolism of labile marine organic matter in shelf sediments to slower sedimentary metabolism from occasional delivery of labile organic matter in the basin. Experimental determinations of the kinetics of microbial recycling revealed striking contrasts in marine and terrestrial organic carbon lability. Marine organic matter was recycled on very short timescales compared to terrestrial organic matter, corresponding to results of sedimentary and particle analyses. A simplified box model of organic carbon cycling in the Chukchi/Alaskan Beaufort Sea region reveals that 0.9 Mt and 0.7 Mt of marine and terrestrial organic matter, respectively, are buried in shelf sediments, while an additional 0.2 Mt marine and 0.1 Mt of terrestrial organic carbon are buried in basin sediments annually, confirming that land-derived organic matter plays a large role in carbon dynamics in Arctic systems, even on non-river dominated margins.Item ENVIRONMENTAL FATE OF POLYBROMINATED DIPHENYL ETHERS IN AGRICULTURAL SOILS WHICH HAVE RECEIVED BIOSOLIDS APPLICATION(2008) Andrade, Natasha Almeida; Torrents, Alba; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Polybrominated diphenyl ethers (PBDEs) are used as additives in consumer products for their fire-retardant properties. While scientists observe PBDEs in various environmental media, little is known of their fate in soils. This study examines the potential fate of PBDEs in soils treated with biosolids. Surface soil samples were collected from commercial farms in the Mid-Atlantic region. Biosolids samples from the source wastewater treatment plant were collected to evaluate PBDE levels and trends. Results show that mean concentration of PBDEs in biosolids from this plant is 1496±158µg/kgd.w., mean concentration in soil from fields that had not received biosolids was 6.8µg/kgd.w., fields with a single application had a mean of 18µg/kgd.w., and fields with multiple applications had a mean of 52µg/kgd.w. Statistical analysis revealed that concentrations in the multiple application group were significantly higher than those in the single application group. This work suggests that PBDEs are relatively persistent in agricultural soils.Item Total Synthesis of (3R,3'R,6'R)-Lutein, (3R,3'R)-Zeaxanthin and Their Stereoisomers(2008) Chang, An-Ni; Khachik, Frederick; DeShong, Philip; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)(3R,3'R,6'R)-Lutein (1) and (3R,3'R)-zeaxanthin (5) are dietary carotenoids that are found in most fruits and vegetables. Numerous studies have shown that 1 and 5 play an important role in the prevention of age-related macular degeneration (AMD) that is the leading cause of blindness. To date, the metabolic pathways of 1 and 5 in ocular tissues of an animal model in relation to AMD have not been explored. This is primarily because of the lack of a viable method for the synthesis of 1 and 5 that can be labeled with a stable isotope. Among the eight possible stereoisomers of lutein, only 1 has been previously prepared by total synthesis in 14 steps in an overall yield of 0.5%. The total synthesis of lutein, zeaxanthin, and their stereoisomers from (rac)-alpha-ionone has been accomplished by a C15+C10+C15 coupling strategy. Therefore, (3R,3'R,6'R)-lutein (1, 8%), (3R,3'S,6'S)-lutein (2, 7%), (3R,3'S,6'R)-lutein (3, 6%), and (3R,3'R,6'S)-lutein (4, 7%) were each prepared in a high optical purity in 7 steps. 3-Hydroxy-alpha-ionylideneacetaldehyde served as a common precursor to afford luteins 1 - 4 by a much shorter synthetic sequence and a higher overall yield than that of a published method for 1. The other four stereoisomers of lutein can be similarly prepared. (3R,3'R)-Zeaxanthin (5, 12%) and (3S,3'S)-zeaxanthin (6, 11%) were prepared in 8 steps from (rac)-alpha-ionone via 3-hydroxy-alpha-ionone which was transformed into 3-hydroxy-beta-ionone (3R-42, 22%) and its enantiomer (3S-42, 21%), respectively. The key intermediates, 3R-42 and 3S-42 were converted into the corresponding C15-Wittig salts 3R-16 and 3S-16 that were used in a double Wittig reaction with the C10-dialdehyde 17 to afford 5 (98% ee) and 6 (98% ee). Utilizing Wittig salts 3R-16 and 3S-16, (3R)-beta-cryptoxanthin (135, 8%) and (3S)-beta-cryptoxanthin (136, 9%) were each prepared in optical purity of 98%. The most important feature of the strategies presented here is its application to the total synthesis of isotopically labeled and optically pure lutein, zeaxanthin, and their stereoisomers for metabolic studies. This synthesis also provides access to the C15-precursors of optically active carotenoids with 3-hydroxy-alpha- and 3-hydroxy-beta-end groups that are otherwise difficult to synthesize.