Physical Sciences and Mathematics Commons^™

Electron Paramagnetic Resonance Imaging And Probes, Hanan B. Elajaili

Electronic Theses and Dissertations

EPR imaging at low frequency is an important method to measure in vivo physiology. Because native paramagnetic species exist at low concentrations in living systems, exogenous paramagnetic species are needed for in vivo EPR. Selection of the appropriate EPR probe allows the experimenter to obtain information about the environment of the imaged probe and its spatial distribution. Relaxation times for several nitroxide radicals were studied with the aim of understanding the relaxation mechanisms, which provides criteria for design of suitable in vivo imaging probes.

Amino-substituted trityl radicals have the potential to monitor pH in vivo, and the suitability for this …

Molecular Encapsulation In Kinetically Trapped, Hydrogen-Bonded Pyrogallolarene Hexamers, Jennifer Christine Chapin Lake

Electronic Theses and Dissertations

Pyrogallolarene and resorcinarene hexamers are hydrogen-bonded capsules that self-assemble in the solid state and can be studied in gaseous and solution phases. Guest loading within pyrogallolarene hexamers in solution has primarily been comprised of solvent molecules with some tertiary amines. A novel solvent-free method for loading guests into the interior of the hexamer has been shown to be effective for encapsulation of a variety of molecules. Aromatic and aliphatic compounds have particularly high guest loading within the hexamers and often result in kinetically stable guest-filled capsules in solution.

Kinetic studies of the encapsulation complexes of anthracene, biphenyl, fluoranthene, fluorene, naphthalene, …

Nitroxide Radicals For Low Frequency Electron Paramagnetic Resonance Imaging (Epri), Joshua R. Biller

Electronic Theses and Dissertations

Optimization of nitroxides as probes for EPR imaging requires detailed understanding of spectral properties such as spin lattice relaxation times, spin packet linewidths, and nuclear hyperfine splitting. Initial measurements of relaxation times for six low molecular weight nitroxides at X-band stimulated further measurement at frequencies between 250 MHz and 34 GHz. The impact of tumbling was studied with perdeuterated 2,2,6,6-tetramethyl-4-piperidinyl-1-oxyl (PDT) in five solvents with viscosities resulting in tumbling correlation times, τ_R, between 4 and 50 ps. A set of three ¹⁴N/¹⁵N pairs of nitroxides in water was selected such that τ_R varied between …

Photoassisted Access To New Polyheterocycles, Teresa M. Cowger

Electronic Theses and Dissertations

Photoassisted diversity-oriented synthesis holds great promise in its ability to provide rapid access to complex and diverse molecular scaffolds. As it stands, while photochemical techniques have this potential, their implementation in the field of synthetic organic chemistry is very limited. The main goal of this project was to utilize photochemically assisted techniques in the synthesis of a variety of novel polyheterocycles.

Initially, we explored the how the strain installed in these polycycles could be harnessed to trigger cationic rearrangements in the framework of the system. This was achieved via the high yield and rapid assembly of a highly strained system …

Probing Structure For Photophysical Properties Through Synthesis Of Novel Nucleosides, Brittney Jean Rodgers

Electronic Theses and Dissertations

A brief history of nucleosides and their photophysics provides the background information for the discussion of synthesis, photophysics and incorporation of fluorescent nucleotide analogs during enzymatic DNA synthesis. Through the use of nucleoside starting material, it is possible to synthesize a number of modified nucleotides for use as fluorescent probes in biochemical research. Synthetic endeavors into the synthesis of these and related molecules from nucleobase starting materials are also presented. The synthesis of these molecules involved re-development of the synthetic routes to broaden substrate scope by overcoming the changed reactivity resulting from the presence of additional functionality.

While many highly …

Degradation Of High Voltage Glass Fiber-Reinforced Polymer Matrix Composites By Aggressive Environmental Conditions, Tianyi Lu

Electronic Theses and Dissertations

Polymer matrix composites reinforced with either E glass or ECR glass fibers-reinforced are used in a variety of high voltage electrical applications because of their advantages like lower weight and cost. However, they can be damaged by aggressive in-service conditions such as high temperature, ultraviolet radiation, moisture, ozone and corrosive environments. Different degradation mechanisms can develop in high voltage PMCs under those extreme environments, which, in turn, can affect the long term structural durability of the composites. A set of PMCs reinforced with ECR-glass and E-glass fibers embedded in four different resins has been investigated in this study. In addition, …

Applications Of Epr With An Emphasis On Tau Fibril Structure, Virginia Meyer

Electronic Theses and Dissertations

Substances containing unpaired electrons have been studied by electron paramagnetic resonance (EPR) for nearly 70 years. With continual development and enhancement of EPR techniques, questions have arisen regarding optimum method selection for a given sample based on its properties. In this work, radiation defects, natural lattice defects, solid organic radicals, radicals in solution, and spin-labeled proteins were analyzed using CW, pulse, and rapid scan EPR to compare methods. Studies of solid BDPA, E' in quartz, N_s⁰ in diamond, and a-Si:H, showed that rapid scan could overcome many obstacles presented by other techniques, cementing rapid scan as an effective …