Physical Sciences and Mathematics Commons^™

Instrument And Application Development In Saturation Recovery And Rapid Scan Electron Paramagnetic Resonance, Joseph E. Mcpeak

Electronic Theses and Dissertations

Enhanced signal sensitivity by the use of Rapid Scan (RS) electron paramagnetic resonance (EPR), a technique that allows for much faster magnetic field scans than traditional field-swept techniques, has facilitated improved data acquisition for many types of samples. For example, irradiated fingernails for radiation dosimetry have been studied using RS-EPR, which resulted in substantial decreases in detection limits. Samarium-mediated reduction mechanisms in organic synthesis have been investigated by RS-EPR providing evidence for a radical intermediate. Spectra of organic radicals exhibiting both narrow lines and closely spaced hyperfine interactions have been recorded via RS-EPR. Well-resolved spectra can be recorded at a …

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 …

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 …

X-Band Rapid-Scan Epr, Deborah Gale Mitchell

Electronic Theses and Dissertations

The advantages of rapid-scan EPR relative to CW and pulse techniques for samples with long longitudinal relaxation time T₁ (N_s⁰ defects in diamond, N@C₆₀, and amorphous hydrogenated silicon), heterogeneous samples (crystalline 1:1 α,γ-bisdiphenylene-β-phenylallyl (BDPA):benzene), lossy samples (aqueous nitroxyl radicals), and transient radicals (5-tert-butoxycarbonyl-5-methyl-1-pyrroline-N-oxide (BMPO)-superoxide adduct) were studied.

For samples with long relaxation times, CW (continuous wave) EPR is challenging due to power saturation and distortions from passage effects. In rapid-scan EPR, the field is swept through resonance in a time that is short relative to T₂. In rapid-scan EPR, the magnetic field is …