Chemistry electronic theses and dissertations (MU)
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The items in this collection are the theses and dissertations written by students of the Department of Chemistry. Some items may be viewed only by members of the University of Missouri System and/or University of Missouri-Columbia. Click on one of the browse buttons above for a complete listing of the works.
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Item The formation of a novel oxime adduct with abasic (AP) sites in duplex DNA with the alkoxyamine O-benzylhydroxylamine(University of Missouri--Columbia, 2025) Liyanarachchi, Don Pivithuru; Gates, Kent S.[EMBARGOED UNTIL 12/01/2026] Apurinic/apyrimidinic (AP) sites are among the most abundant DNA lesions, arising from spontaneous base loss or enzymatic activity during base excision repair (BER). These sites exist in equilibrium between a ring-closed hemiacetal and a reactive ring-open aldehyde, the latter serving as a potential target for covalent modification. Methoxyamine (MX), an aminooxy compound, has been investigated as a pharmacological agent capable of forming oxime adducts with AP sites to inhibit AP endonuclease 1 (APE1), a critical enzyme in BER. However, MX-AP adducts are incompletely resistant to APE1 processing, limiting their therapeutic potential. In this work, we report the formation of a novel oxime adduct between O-benzylhydroxylamine (OBHA) and AP sites in duplex DNA. Using gel electrophoresis and MALDI-TOF mass spectrometry, we confirmed covalent adduct formation under physiological conditions. Enzymatic assays demonstrated that, unlike MX, OBHA-AP adducts are completely resistant to APE1 cleavage, even at elevated enzyme concentrations and extended incubation times. Structural characterization revealed altered electrophoretic mobility consistent with a bulky, stable modification at the lesion site. These findings establish OBHA as a potent inhibitor of APE1-mediated repair of AP sites, highlighting its potential utility in synthetic lethality strategies for cancer therapy. By irreversibly blocking BER at abasic lesions, OBHA may enhance the cytotoxicity of DNAdamaging agents and overcome resistance mechanisms associated with elevated APE1 activity. This study provides mechanistic insight into oxime adduct formation at AP sites and identifies OBHA as a promising candidate for further evaluation in DNA repairtargeted therapeutics.Item Development of a ¹⁶¹Tb-based radiopharmaceutical for melanoma(University of Missouri--Columbia, 2025) Iweha, Ejike Valentine; Anderson, Carolyn J.[EMBARGOED UNTIL 12/01/2026] Melanoma continues to represent a disease with a high number of mortalities despite the clinical interventions, improvements in its diagnosis, and the different avenues of treatment; the incidence of total remission continues to be low. There is a pressing need for other treatment modalities and a combination of modalities for treatment. Targeted radiopharmaceuticals represent one of these modalities that hold the potential for diagnosing and treating diseases such as cancer. This work presents the preparation and characterization of two ¹⁶¹Tb radiolabeled radiopharmaceuticals which are developed with an aim to be used in the treatment of VLA-4 positive melanoma due to the emission properties of ¹⁶¹Tb (β-, Auger, and conversion electrons). Data on the radiosynthesis, Log D₇.₄, and serum stability of both radiotracers are presented and discussed in this study.Item Study of sensors using machine learning(University of Missouri--Columbia, 2025) Gopaul, Colin; Young, Matthias; Brorsen, Kurt[EMBARGOED UNTIL 12/01/2026] Effective long-term monitoring of nutrient pollutants such as nitrate and phosphate remains a central challenge in environmental and agricultural management. Excess concentrations of these anions in waterways contribute to eutrophication, soil degradation, and significant economic losses associated with impaired ecosystem services. While ion-selective electrodes (ISEs) offer a promising route for decentralized and continuous sensing, the dependence on highly selective membrane materials and the susceptibility of these membranes to drift, fouling, and degradation limit the scalability and long-term stability of traditional ISE-based sensors. To address this gap, this study investigates the feasibility of multi-ion quantification using pulsed-current sensing approach coupled with machine learning, thereby reducing the reliance on membrane specificity. In this work, three nonspecific ion-responsive electrodes were fabricated using membrane support materials that are widely available and mechanically robust – poly(vinyl acetate) (PVA), poly(vinyl chloride) (PVC), and poly(acrylonitrile) (PAN). Each electrode was subjected to potential-time measurements under pulsed-current excitation in solutions containing nitrate, phosphate, and chloride ions. These individual ion response profiles formed the basis profiles for constructing synthetic dataset representing mixtures of the target ions, enabling controlled exploration of multi-ion interactions without the experimental complexity of preparing large numbers of mixed standards. To evaluate the capacity of nonspecific sensors to resolve multi-ion signals, a suite of machine learning algorithms–including tree-based regressors and fully connected neural networks–was applied to the combined electrode responses. Model performance was assessed in terms of predictive accuracy, robustness to noise, and sensitivity to electrode-specific variations. Initial results demonstrate that machine learning can extract meaningful compositional information from pulsed-current responses, providing a proof of concept for low-selectivity, multi-ion sensing without the need for specialized membrane chemistries. However, several limitations remain, particularly the variability in electrode response arising from differences in membrane morphology, the constrained diversity of the training dataset, and idealized nature of synthetic mixture generation. Overall, this study highlights both the promise and present challenges of integrating pulsedcurrent electrochemical sensing with machine learning for environmental monitoring applications. The findings point toward future directions involving improved electrode fabrication reproducibility, the collection of larger and more representative training datasets, and the transition from synthetic data to experimentally validated mixture responses. Collectively, these advancements will be crucial for the realization of practical, durable, and cost-effective multi-ion monitoring systems suitable for field deployment.Item Electrochemical and interfacial characteristics of a choline chloride-ethylene glycol deep eutectic solvent at platinum electrode and palladium redox chemistry and electrodeposition in DES(University of Missouri--Columbia, 2025) Awakessien, Mildred; Zeng, Xiangqun; Baker, Gary[EMBARGOED UNTIL 12/01/2026] This study investigates the electrochemical and interfacial characteristics of the choline chloride–ethylene glycol deep eutectic solvent (ethaline) as a medium for palladium redox chemistry and electrodeposition. Through a combination of cyclic voltammetry (CV), chronoamperometry (CA), electrochemical impedance spectroscopy (EIS), and Karl Fischer titration, the work reveals how hydration level, electrochemical activation, and interfacial restructuring govern the electrochemical behavior of ethaline. Hydration studies demonstrate that even small amounts of water substantially alter solvent conductivity, viscosity, accessible proton populations, and the width of the electrochemical stability window. CV and CA experiments show that Pd electrodeposition proceeds through a diffusion-controlled nucleation mechanism, with deposition charge and electrochemically active surface area (ECSA) increasing proportionally with deposition time. When transferred into pristine ethaline, Pd-modified electrodes reproduce the characteristic voltametric signatures of the glassy-carbon–palladium–ethaline system, and early cycling reveals continuous growth of the Pd film, confirming successful metal deposition. In aqueous 0.5 M H₂SO₄, the Pd coatings exhibit the expected hydrogen adsorption/desorption, and Pd oxide formation features absent on bare glassy carbon, enabling quantitative assessment of the electrochemical surface area (ECSA) and demonstrating a direct relationship between Pd loading and catalytic surface development. EIS measurements further show that hydration increases charge-transfer resistance and modifies interfacial capacitance, indicating structural reorganization of the DES at the electrode surface during redox cycling. Collectively, these results establish that ethaline is a structurally dynamic, electrochemically responsive medium whose interfacial properties can be intentionally tuned by controlling water content and electrochemical history. The insights gained provide a framework for rational design of DES-based systems for electrodeposition, sensing, catalysis, and gas-interaction technologies.Item Advanced polymer thin films for functional materials via oxidative molecular layer deposition(oMLD)(University of Missouri--Columbia, 2025) Mehregan, Mahya; Young, Matthias J.[EMBARGOED UNTIL 12/01/2026] The development of advanced functional thin films is essential for next-generation energy storage, water purification, and electronic devices. In this dissertation, oxidative molecular layer deposition (oMLD) is employed as a versatile, gas-phase technique for the conformal growth of semiconducting polymers with precise thickness control at the molecular scale. Building on the principles of self-limiting surface reactions, this work explores the synthesis of poly(3,4-ethylenedioxythiophene) (PEDOT), polypyrrole (pPy), and related copolymers directly onto diverse substrates, including planar wafers, and porous scaffolds. Comprehensive in situ and ex situ characterization-- using quartz crystal microbalance (QCM), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Raman spectroscopy--was conducted to elucidate the relationships between deposition parameters, reaction kinetics, and resulting film properties. The effects of precursor chemistry, substrate type, and process temperature on polymer growth rate, composition, morphology, and electrical conductivity are systematically examined. Thermal stability was assessed via thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), revealing enhanced stability of oMLD-grown films compared to other common polymerization techniques. This research demonstrates that oMLD enables conformal polymer coatings with tunable composition and functionality, even within challenging 3D geometries, and highlights strategies to optimize electrical and structural performance. The findings advance the understanding of gas-phase polymer synthesis and open pathways for integrating conductive polymers into energy storage devices, desalination membranes, and thin-film electronic systems