Physical Sciences and Mathematics Commons^™

Dually Modified Transmembrane Proteoglycan Tβriii/Betaglycan In Cell Signaling And Cancer, Laura M. Jenkins

Theses and Dissertations

During tumor progression, cancer cells undergo a number of alterations to evade tumor inhibitory mechanisms, proliferate, invade surrounding tissues and metastasize to distant sites. These properties reflect changes in their cell signaling pathways that, in normal cells, control aberrant cell proliferation, motility, and survival. Over the past few decades, hyperactive Wnt/β-catenin signaling has been linked to the formation of multiple cancers, including malignant ovarian cancer, making identification of molecules regulating Wnt/β-catenin signaling crucial to the development of early detection methods and cancer treatment strategies. Proteoglycans, which regulate transmission of cellular signals, are implicated in the pathophysiology of diseases, including cancer, …

Design, Synthesis, Characterization, And Applications Of Matrix Free Polymer Nanocomposites, Yucheng Huang

Theses and Dissertations

This dissertation focuses on the design, synthesis, characterization and application of matrix free polymer nanocomposites. Reversible addition-fragmentation chain transfer (RAFT) polymerization was used to synthesize block copolymers and polymer grafted silica nanoparticles with precise control over architectures.

In the first chapter, thermoplastic elastomer (TPE) grafted nanoparticles were prepared by grafting block copolymer poly(styrene-block-(n-butyl acrylate)) onto silica nanoparticles (NPs) (~15nm) via surface initiated RAFT polymerization. The effects of polymer chain length and graft density on the mechanical properties were investigated using films made solely from the grafted NPs. The ultimate tensile stress and elastic modulus increased with the increase of PS …

Instrumentation For, And Application Of, Novel Electrochemical Tools For In Vivo Analysis Of Neurotransmitters In The Context Of Psychiatric Disease, Rhiannon Robke

Theses and Dissertations

ABSTRACTSerotonin’s involvement in many physiological processes including anxiety, stress, compulsivity, and mood has been speculated for decades. Insufficient progress in our understanding of serotonin chemistry is due to the lack of effective tools to selectively measure this neurotransmitter on a neurotransmission-relevant time scale in vivo. An analytical technique for serotonin measurements, fast-scan cyclic voltammetry (FSCV), was pioneered in the last decade in anesthetized rodents and is beginning to shed light on the complexity of serotonergic activity on a sub-second timescale. Complementary, more recent technological innovations have enabled ambient neurotransmitter levels to be determined every few seconds using a method called …

Understanding The Adsorption And Nucleation Of Transition Metals On A Model Carbon Support, Grant S. Seuser

Theses and Dissertations

Heterogeneous catalysis plays a vital role in the commercial production of chemicals. However, much is still unknown about the fundamental surface chemistry involved in catalyst preparation and the surface chemistry of the catalysts themselves. In the first part of this work, a surface science approach was employed to develop a fundamental understanding of the surface chemistry of strong electrostatic adsorption (SEA) of metal precursors on a model carbon support, highly oriented pyrolytic graphite (HOPG). SEA is a wet impregnation method in which anionic/cationic metal precursors are adsorbed onto positively/negatively charged functional groups by adjusting the pH of the solution above …

Synthesis And Reactivity Of Carborane Backbone Pincer Complexes, Bennett J. Eleazer

Theses and Dissertations

In organometallic chemistry, boron-centered ligand systems represent a powerful synthetic strategy for the promotion of a variety of catalytic transformations. These ligands offer a versatile array of bonding motifs, which can function as borane, boratrane, boryl, borate, or borylenes type ligands, and are likely the strongest σ-donors in the anionic series of ligands based on boron, carbon, nitrogen, and oxygen. Carboranes, which are icosahedral boron clusters of the type C2B10H12, offer unique potential as metal ligands, such as their bonding to exohedral metal centers being dominated by two-center-two-electron σ-bond interactions, their three-dimensional cluster structure providing considerable steric shielding to a …

Structural Transformations Of Multimetallic Nanoparticles, Guangfang Li

Theses and Dissertations

Atomic-level understanding of the structural transformations of multimetallic nanoparticles (NPs) triggered by external stimuli is of vital importance to the enhancement of our capabilities to precisely fine-tailor the key structural parameters and thereby to fine-tune the catalytic properties of the NPs. In this work, I firstly show that Au-Cu bimetallic NPs demonstrate stoichiometry-dependent architectural evolutions during chemical dealloying processes and nanoporosity-evolving percolation dealloying only occurs for Au-Cu alloy NPs with Cu atomic fractions above the parting limit. The electrochemically active surface area and the specific activity of the dealloyed nanoframes can be systematically tuned to achieve the optimal electrocatalytic activity. …

Mechanisms Of Decarboxylation In The Cyp152 Family Of Cytochrome P450s, José Armando Amaya

Theses and Dissertations

Intense interest has focused on the development of enzymes as next-generation catalysts for the production of molecules with biotechnological potential. OleTJE, a member of the cytochrome P450 CYP152 family is an excellent candidate for the generation of advanced biofuels. OleTJE catalyzes the hydrogen peroxide-dependent decarboxylation of Cn fatty acids to produce Cn-1 terminal alkenes. Despite the ability of this enzyme to yield long chain alkenes with nearly exclusive chemoselectivity, its reactivity towards shorter chain length substrates results in undesired levels of hydroxylated side-products, limiting its industrial potential. Previous transient kinetic studies have demonstrated that, despite its unusual chemistry, the reaction …

Hydrothermal Synthesis: A Gateway To Metastable Crystals With Unusual Properties, Justin B. Felder

Theses and Dissertations

Research into crystalline matter has long been of interest to humanity, both in order to advance our society by creating new technologically useful materials and in order to better understand to nature of the properties we depend on for so much of our existing technology. In recent decades, solution-based crystal growth syntheses including hydrothermal and molten flux techniques have risen to the forefront of solid-state chemistry as superior methods of synthesizing new materials as single crystals ripe for structure determination and property measurements.

This work seeks to educate readers on recent advances in the hydrothermal realm of crystal growth: namely …

Sustainable Soybean Oil And Lignin Derived Monomers And Polymers For Potential Use In Polymeric Materials, Ryan Miskin

Theses and Dissertations

In this thesis project, high oleic soybean oil and lignin derived monomers and polymers are investigated. The properties of these monomers and polymers are characterized and discussed.

Chapter 1 details the potential impact of bio-based resources, monomers, and polymers on the environment. An introduction on polymerization techniques is given, and the overall objectives of my research are discussed.

In Chapter 2, attempts are made at modifying a soybean oil derived thermoplastic polymer into a vitrimer. The synthesis of thermoplastics is reviewed and the vitrimer trials outlined. Different scenarios that arose are examined and discussed.

Chapter 3 outlines the preparation of …

Cationic Metallocene-Containing Biomaterials For Antimicrobial Applications, Parasmani Pageni

Theses and Dissertations

Metal-containing polymers or metallopolymers, are one of the major classes of polymers which stand out independently because of a unique combination of organic and inorganic components in one macromolecular system. Among the variety of metallopolymers, metallocene-containing polymers have been widely utilized for applications ranging from electrochemical sensors to templates for advanced inorganic catalysts to battery materials, due to their unique physicochemical properties. This dissertation is focused on the synthesis, characterization, and application of cationic metallocene-containing polymeric materials. Cationic-cobaltocenium was grafted in various inorganic nanoparticles using polymerization techniques such as reversible addition-fragmentation chain transfer polymerization.

In Chapter 1, the overall background …

Block Copolymer Control Of Nanoscale Porous Materials, Amrita Sarkar

Theses and Dissertations

The controlled fabrications of porous materials are crucial for a wide variety of uses spanning the gamut from energy applications to filtration. Despite decades of developments based upon block copolymer self-assembly there remain numerous limitations to achieve simple ends such as fully-tunable nanomaterials or well-defined macroscopic forms. For example, fundamental studies of nanostructure-performance relationships need systematic series of nanomaterials to identify the separate effects of wall and pore dimensions. Such precision control is impossible under the constraints of equilibrating systems. Persistent Micelle Templating (PMT) is rather based on kinetic control and enables robust and independent tuning of each feature. However, …

Construction Of Supramolecular And Coordination Compounds From Pyridyl Bis-Urea Macrocycles, Bozumeh Som

Theses and Dissertations

The self-assembly of macrocyclic molecules in solution and in the solid state modulates and in many cases enhances their properties for applications in sensing, catalysis and optoelectronics. The self-assembled structures are typically organized by non-covalent interactions such as hydrogen bonding, π-π stacking and dipole-dipole interactions. Our group has focused on the design and synthesis of bis-urea macrocycles that can self-assemble into solid cylinders or tubular structures affording crystalline materials. These macrocycles consist of two urea groups and two rigid C-shaped spacers. Easy functionalization of this system enables access to bis-urea macrocycle structures that could serve as molecular reactors, coordinating ligands …

Investigation Of The Spatial Dependence Of Carrier Dynamics In Semiconductor Optoelectronic Devices, Bobby G. Barker Jr.

Theses and Dissertations

Optoelectronic devices, such as solar cells and photodetectors, rely on separating and transporting charge through semiconductors that have excess electron-hole pairs created by photon absorption. This talk will focus of several different semiconductor materials of various dimensionality, such as lead halide perovskites, wide bandgap SiC, graphene, semiconductor nanowires (NWs), and quantum dots (QDs).

The results of Chapter 2 demonstrate the dependence of the perovskite/hole transport layer on carrier transport of perovskite films for solar cells. Efficient charge separation at the interfaces of the perovskite with the carrier transport layers is crucial for perovskite solar cells to achieve high power conversion …

Studies Of The Activation Of Carbon-Gold And Carbon-Hydrogen Bonds By The Pentaruthenium Carbonyl Cluster Ru5(Μ5-C)(Co)15, Jonathan Darrell Tedder

Theses and Dissertations

The current practical uses of hydrocarbons by industry are discussed in Chapter 1. Carbon-hydrogen (C-H) bond activation and selective functionalization by transition metal complexes is presented as a possible alternative for the upgrading of hydrocarbons. The comparison of carbon-gold (C-Au) bond activation to C-H bond activation based on isolobal principles by transition metal complexes is presented. The high nuclearity ruthenium cluster complexes Ru6C and Ru5C are presented and their early chemistry is discussed.

The reactions of high nuclearity carbido cluster complexes, Ru6C(CO)17 and Ru5C(CO)15, with PhAuNHC are presented in Chapter 2. The reaction of Ru6C(CO)17 with PhAuNHC yields the π-arene …

Electrochemical Methods To Study Real-Time In Vivo Neurochemistry, Aya Abdalla

Theses and Dissertations

Serotonin neurotransmission has multiple facets that are challenging to characterize, due to the lack of analytical tools that can measure serotonin in the brain. In addition, the mechanisms of serotonin modulation by other neurotransmitters, such as histamine, are not well understood. These limitations make the study and treatment of disorders in which serotonin is implicated problematic. This dissertation presents novel electrochemical methods, in addition to the well-established serotonin fast-scan cyclic voltammetry (FSCV), to better understand the dynamics of serotonin and histamine neurotransmission in vivo. In Chapter 1, a method, known as fast-scan controlled adsorption voltammetry, was optimized to selectively and …

Probing Solvent Effects In Aromatic Interactions Using Molecular Balances, Josef M. Maier

Theses and Dissertations

Aromatic interactions play a key role in many important processes, such as the formation and stability of biological and synthetic assemblies, facilitation of molecular recognition processes, and catalysis of chemical reactions. One of the key factors determining the strength of aromatic interaction is the solvent environment. Therefore, developing model systems that can accurately measure the influence or effects of solvents on non-polar interaction strengths is a task of great importance. Over the years, we have been approaching this challenge via designing and analyzing molecular devices that can quantitatively report aromatic interaction energies under various solvent and chemical environments. With this …

Synthesis Of Small-Molecule Fluorescent Probe And Polymers For Bioapplication: Bioimaging And Enzyme Stabilization, Yanmei Xu

Theses and Dissertations

In chapter one, we designed, synthesized and characterized two cysteine sensors CCPAP and CCPAN, with improved water solubility, cell penetration ability, and potential targeting selectivity. Two types of positive charged groups, i.e. triphenylphosphonium and pyridinium were introduced respectively to the frame structure CCP by coupling carboxylic acid with amine to improve the cell permeability and cysteine selectivity. ESI-MS, NMR and IR were employed to characterize the molecular structures of the two novel probes. These probes have better water solubility than the parent molecule DCP, and better cell penetration capability than CEP, which could further distinguish the cysteine concentration differences in …

Crystallomagnetic Studies Of First And Third Row Transition Metal Containing Oxides Grown Via The Molten Flux Method, Timothy Ferreira

Theses and Dissertations

The primary objective of this dissertation is to inform about the single crystal growth of complex first and third row transition metal oxides via molten flux methods. Particular focus is given to complex oxides that contain transition metals with unpaired electrons. This fundamental research is motivated by a singular question: What can a critical analysis of chemical structure elucidate about magnetic order in oxide materials? Throughout the eight chapters of this dissertation, including an introductory chapter, this structure-property relationship will be investigated. These seven chapters will be organized into three parts, each corresponding to the general structure type of the …

Iron Transport Machinery: A Potential Therapeutic Target In Escherichia Coli, Clorissa L. Washington – Hughes

Theses and Dissertations

Iron metabolism is an integral part of life for most organisms. Despite its essentiality, iron can also become toxic. There are many aspects to maintaining iron balance within the cell. The aim of this work is to provide insight into the function of several components involved in bacterial iron homeostasis. This work is significant for the development of novel antibiotics for treating resistant or pathogenic bacteria. Herein, it is shown that nickel can disrupt normal bacterial iron metabolism and that bacterial resistance can be affected by expression of iron acquisition genes. Once iron is obtained by the cell, it can …

Characterization Of Sufs And Sufe Of Suf Pathway For Fe-S Cluster Assembly In Escherichia Coli, Guangchao Dong

Theses and Dissertations

Fe-S clusters are one major type of the sulfur-containing cofactors, which conduct essential functions in organisms. The Suf pathway is one of the three main pathways for the biosynthesis of Fe-S clusters. In E. coli, the Suf pathway is utilized under iron limitation and oxidative stress. This ability is important for pathogens to survive. Also, the Suf pathway is found to be exclusive in bacteria, so it is a good target for novel antibiotic design. SufS is a cysteine desulfurase in the Suf pathway to extract sulfur from L-cysteine. It needs the enhancement of SufE. To better understand the catalytic …

Assessing Aberrant Glycosylation With Synthetic Lectins To Detect And Stage Prostate Cancer, Anna Veldkamp

Theses and Dissertations

Aberrant glycosylation takes place during the onset of cancer and throughout the progression of the disease allowing certain glycans to serve as biomarkers1. Boronic acid functionalized synthetic lectins (SLs) have been shown to bind selectively and crossreactively to certain glycoproteins through covalent yet reversible interactions between the boronic acids and 1,2- or 1,3-diols found on saccharides2. This project focuses on 1) data acquisition optimization of an existing SL array; 2) the identification, isolation, and characterization of new SLs that interact with proteins and glycoproteins targeting the prostate and prostate cancer; and 3) the utilization of new SLs in cross-reactive sensor …

Mechanistic Studies Of Nucleic Acid Chaperone Activities Of Retroviral Nucleocapsid Protein, Lichao Sun

Theses and Dissertations

In this dissertation, I have used single molecule Fluorescence Resonance Energy Transfer (sm-FRET), as a nanoscale spectroscopic ruler to gain quantitative, molecular-level understanding about the kinetics and mechanism of NC-chaperoned TAR sequence rearrangements. Firstly, I have resolved the complex kinetics and underlying reaction pathways of TAR sequence annealing in the presence of HIV-1 NC over a broad NC concentration by performing the time-resolved sm-FRET measurements in a unique aggregation-free environment. I have further gained the insights that the NC-induced secondary structural changed of TAR hairpins modulate the annealing pathways and consequently affect the overall kinetics of the TAR sequence annealing. …

Fast Scan Cyclic Voltammetry For Real-Time Metal Speciation Analysis, Hettige. M. Thushani Siriwardhane

Theses and Dissertations

Electrochemistry is a powerful analytical tool that has been widely used to detect trace metals in natural systems. However, studying the speciation of metals during dynamic events, such as storms and floods, is analytically challenging due to the limited temporal resolution of traditional electrochemical techniques. Additionally, most techniques report the total metal concentration (both complexed and free) that does not reflect the toxicity of these metals, which arise mostly from the free state. To overcome these issues, we previously pioneered the use of fast scan cyclic voltammetry (FSCV) to measure free copper (Cu(II)) and lead (Pb(II)) in real-time in laboratory …

Disinfection By-Products: Formation In Pool Water And The Role Of Iodinated Medical Imaging Compounds As A Potential Precursor In The Formation Of Iodo-Dbps, Christina Marie Joseph

Theses and Dissertations

Disinfection by-products (DBPs) are the unintended consequence of using chemical disinfectants to kill pathogens in water. 1-11 They are formed from the reaction between disinfectants and natural organic matter (NOM), anthropogenic contaminants, and bromide/iodide present in the raw source water. DBPs are cause for concern because studies have found them to be toxic.11-16 This research focuses on identifying and studying the formation of DBPs. Specifically, the presence of DBPs in chlorinated pool water and tap water from Barcelona, Spain was studied to better understand which DBPs are formed in the pool as compared to those that enter the pool from …

Elucidation Of Protein Interactions And The Re-Tuning Of Porphyrin Electronics For Hydroxylases, Steven Charles Ratigan

Theses and Dissertations

Non-Ribosomal Peptide Synthetases (NRPSs) and their exogenous tailoring partners have been heavily studied but not in the context of non-cognate systems. Orf78, a dinuclear iron β-hydroxylase from the lysobacter pathway and homologous to CmlA from the chloramphenicol pathway, is used to test affinities for one native and two non-native T-domains. Results indicate that there is enough difference between Type I and Type II NRPS systems to disfavor common recognition motifs. Additionally, the β-hydroxylase P450sky, from the skyllamycin biosynthetic pathway, is used in conjunction with the NRPS ATdomain NikP1AT from the nikkomycin biosynthetic pathway, in lieu of the homolog P450nikQ. The …

Structural And Functional Studies Of Proteins From The Agricultural Pests Tetranychus Urticae And Aspergillus Fumigatus, Caleb Schlachter

Theses and Dissertations

Agricultural pests are a worldwide problem and cause billions of dollars in crop loss. In the United States alone, an estimated $40 billion USD is lost per year due to insecticide resistance [1]. Studied here are proteins (potentially new pesticide targets) from the agricultural pests Tetranychus urticae and Aspergillus fumigatus. T. urticae, or twospotted spidermite, is a polyphagous pest, and three proteins from this pest, a cyanase, a glutathione S-transferase and an intradiol ring-cleavage dioxygenase are described [2]. Cyanase is involved in the conversion of bicarbonate and cyanate, a toxic self-defense metabolite produced by plants, into ammonia and carbon dioxide. …

Investigation Of Iron(Ii) Autoxidation Rate And Iron Mediated Geochemical Production Of Reactive Oxygen Species At Oxic-Anoxic Interfaces, Dewamunnage Muditha Chathurangani Dias

Theses and Dissertations

Biogeochemical cycles in ecosystems regulate the flow of energy between reduced species (typically carbon compounds) and a variety of oxidants via both biotic and abiotic reactions. A key class of chemical compounds that can link these cycles through abiotic pathways are Reactive Oxygen Species (ROS). The production of ROS via photochemical pathways is well known. More recently, the non-photochemical production of ROS via the one electron oxidation of ferrous iron (Fe(II)) by dioxygen (O2) has been detected in a range of environments. The oxidation of Fe(II) initiates a pathway that generates an array of ROS as Fe is cycled between …

Kinetic-Control Of Block Copolymer Micelles For Tunable Nanomaterials Towards Energy Devices, Hasala Nadeesini Lokupitiya

Theses and Dissertations

Nano-scale inorganic porous materials are crucial for numerous applications ranging from electronics to energy conversion. The ability to control the morphology and the key architectural parameters of nanomaterials largely determines the transport characteristics and performance of such devices. But, there is very little understanding and development to tune these key architectural parameters such as inorganic wall-thickness and pore diameter. Even though there are numerous examples available on the fabrication of porous nanomaterials via block copolymer co-assembly, there is limited understanding on independent control over key architectural parameters. Because of that the major focus of this thesis is to explore and …

Polymer Grafted Nanoparticles For Designed Interfaces In Polymer Nanocomposites, Mohammad Mohammadkhani

Theses and Dissertations

This dissertation presents the design, synthesis, and characterization of polymer nanocomposite interfaces and the property enhancement from this interface design. Through the use of reversible addition fragmentation chain transfer (RAFT) polymerization for the grafting of polymer chains to silica nanoparticles, the surface of silica nanoparticles can be manipulated to tune the properties of nanocomposites by controlling the interface between the particles and the polymer matrix.

In the first part of this work, compatibility of 15 nm silica nanoparticles grafted with different alkyl methacrylates with linear low density polyethylene was investigated. SI-RAFT polymerization of hexyl, lauryl, and stearyl methacrylate on silica …

Redirecting P450 Ferryl-Oxo Intermediates From Oxygenation To Decarboxylation, Job Logan Grant

Theses and Dissertations

A recently discovered cytochrome P450 has garnered much interest for its ability to oxidatively decarboxylate n length fatty acids to n-1 terminal olefins using hydrogen peroxide as an oxidant. This enzyme (P450 OleT) is mechanistically peculiar, as it seemingly abrogates the oxygen insertion chemistry that typifies the P450 superfamily. In this work we explore the origin of this deviant catalysis.

Using stopped-flow and transient kinetic methodologies the ferryl-oxo pi-cation radical and ferryl-hydroxo intermediates, known as compound-I (Cpd-I) and compound-II (Cpd-II) respectively, were isolated in high yield. This is the first time either species has been observed in a substrate bound …