Browsing by Author "Dr. Edmond Bowden, Committee Member"

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Kinetic Studies of Dehaloperoxidase-Hemoglobin From Amphitrite Ornata
(2006-09-19) Gilvey, Lauren Brenna Galvagni; Dr. Clay Clark, Committee Member; Dr. Edmond Bowden, Committee Member; Dr. Stefan Franzen, Committee Chair
The focus of this research was to determine how three different factors affect the kinetics of the reaction between Dehaloperoxidase — Hemoglobin (DHP-Hb), a halogenated phenol substrate, and a peroxide co-substrate. The factors examined were the order of addition of the substrate and co-substrate, the pH of the solutions, and the difference between using hydrogen peroxide (H2O2) and m-Chloroperbenzoic acid (MCPBA) as the co-substrates. The order of addition studies were carried out on a stop-flow apparatus. The results presented here demonstrate that the substrate must bind to DHP-Hb prior to the addition of the peroxide co-substrate. The effect of pH was examined using stop-flow and photodiode array spectrometry. These studies show how the pKa of the substrate affects the mechanism of the reaction. The kinetic results actually depend on the pKa of the substrate used. Stop-flow studies and UV-Vis assays were used to compare H2O2 and MCPBA as co-substrates. These studies demonstrate that the use of MCPBA as the co-substrate yields a faster rate of product formation. The use of H2O2 as the co-substrate results in a larger amount of product formation at all pHs studied, with the exception of pH 6.0.
Synthesis and Characterization of Nanoparticle Assemblies for Electronic Applications
(2009-07-27) Ayres, Jennifer Ann; Dr. Stefan Franzen, Committee Member; Dr. Edmond Bowden, Committee Member; Dr. Gregory Parsons, Committee Member; Dr. Christopher B. Gorman, Committee Chair
While significant effort has been made to synthesize molecular wires for electronic applications, the ability to insert these molecules between two metallic contacts with directional control has yet to be demonstrated. Control over molecular orientation is critical to the development of molecular devices such as diodes, capacitors and transistors. In this study, directional control is achieved using orthogonal self-assembly to synthesize electronic junctions between nanoparticles of different compositions. Phenyl ethynylene oligomers were synthesized with different end groups. One molecule was functionalized with a thiol which exhibits preferential binding to gold and an isocyanide which exhibits preferential binding to platinum. The other was functionalized with a thiol for binding to gold and a carboxylic acid which exhibits preferential binding to metal oxides. One of the major challenges of this work was the synthesis of nanoparticle building blocks that were suitable for the formation of these heterodimeric structures. Metal and metal oxide particles were synthesized with capping ligands that provided stability yet did not sterically hinder heterodimer formation. Once appropriate nanoparticles had been identified, preliminary studies indicated heterodimer formation. However, characterizing these structures presented additional challenges. Several characterization techniques, including transmission electron microscopy (TEM), size-exclusion chromatography (SEC), several types of electrophoresis and small-angle x-ray scattering (SAXS), were evaluated for their ability to characterize these structures with statistical accuracy. While all of these techniques did indicate the presence of dimers or larger aggregates in solution, accurate statistical information was not obtained using any single method.
Synthesis of Amphiphilic Iron-Sulfur Core Dendrimers and Investigations into Their Encapsulation Abilities in Different Solutions
(2005-10-30) Cameron, Christopher Stan; Dr. Christopher B. Gorman, Committee Chair; Dr. David Shultz, Committee Member; Dr. Edmond Bowden, Committee Member; Dr. James D. Martin, Committee Member
Several novel amphiphilic iron-sulfur core dendrimers were synthesized by modifying the tips of the dendrons to install hydrophilic peripheries. These dendrimers were synthesized via standard convergent and a 'modular' synthetic strategy. The electrochemistry of the dendrimers was investigated in dimethylformamide and dimethylformamide/water solutions. Positive shifts in the redox potential of the iron-sulfur cores corresponding to dendrimer size and periphery type were recorded. Secondary peaks in the anodic wave of cyclic voltammograms of dendrimers in dimethylformamide/water solutions were possible indications of limited access of water molecules to the iron-sulfur cores of some of the dendrimers.
Tailored Surfaces: Modifying Chemical and Physical Properties at the Liquid/Solid Interface to Address Optimizing Surface Chemistry Applications
(2007-03-22) Bailey, Tiffani Nicole; Dr. Chris Gorman, Committee Co-Chair; Dr. Jan Genzer, Committee Co-Chair; Dr. Edmond Bowden, Committee Member; Dr. Christine Grant, Committee Member
The research presented in this PhD thesis focuses on surface modification techniques to enhance potentially useful behavior of materials on surfaces. The principal objectives of this work include (1) investigating the physico-chemical phenomena at the liquid⁄substrate interface to enhance current methods of moving meso- scale liquid droplets (2) developing a polymer brush gradient on silicon to enhance the efficiency in binding and detection of probe molecules and (3) tailoring a poled substrate by electrostatically binding polar molecules to form a molecular assembly. Research was conducted by varying the physical properties of a liquid in motion (including, surface tension, viscosity) and the characteristics of the substrate upon which the liquid moves. The latter will include both physical and "chemical" roughness (i.e., variation of chemical functionalities present at the surface unit) of the substrate. We also identified an efficient method of increasing DNA immobilization and hybridization. A polymer brush molecular weight gradient was used as a platform for DNA attachment. Fluorescence microscopy was used to obtain relative fluorescence intensity values indicating DNA hybridization and attachment to the polymer backbone. The microscopy technique provided evidence indicating an increase in DNA attachment to the polymer backbone as the polymer chain length increased. A method of using self-assembly to develop interactions between a polarized ferroelectric domain and polar molecules was also studied. We demonstrated selective binding of bromoacetic acid to a single faced poled lithium niobate surface using XPS. Thus, a poled substrate was tailored by electrostatically binding polar molecules to form a molecular assembly.