Date of Award

1-1-2019

Document Type

Dissertation

Degree Name

Ph.D.

Department

Chemistry and Biochemistry

First Advisor

Gareth R. Eaton, Ph.D.

Second Advisor

Sandra S. Eaton, Ph.D.

Keywords

Electron paramagnetic resonance, EPR, Imaging, Nitroxide, Python, Rapid-scan, Trityl

Abstract

EPR imaging at low frequency is a powerful tool to obtain important biological information in vivo in a non-invasive way. Properties of nitroxide and trityl radical imaging reagents have been studied. Developments in rapid scan imaging techniques are reported that improve efficiency of experiments and user-friendliness of software.

Relaxation and signal-to-noise ratio (S/N) in pulse experiments on trityl radicals were measured at frequencies between 400 MHz and 1.5 GHz. Relaxation time increases as the frequency increases and the radical concentration decreases. Since relaxation time is a sensitive and accurate measure of oxygen pressure, this study provides criteria for the selection of the frequencies for in vivo applications.

Rapid-scan EPR of irradiated solids at L-band was studied. The results show that for the same data acquisition time, S/N for rapid-scans was significantly higher than for conventional continuous wave spectra.

Rapid scan EPR imaging of nitroxide was performed at 250 MHz. Experimental parameters for the sinusoidal single-sweep method were varied to get better image quality. The results show that larger gradient strength provides higher spatial resolution while smaller gradient step size provides finer texture. Another method based on field-stepped linear-scans was developed; field step size, rapid-scan segment width, rapid-scan frequencies and some other parameters were varied. The field-stepped linear-scan method was compared with the sinusoidal single-sweep method using criteria including linewidth and S/N, and the former turned out to be a less effective alternative to the latter.

New developments have been made to expand what can be achieved with EPR imaging, such as reduced data acquisition time, quantification of image features, efficient use of instrument time, and simplified experimental procedures from data acquisition to spectral analysis. The Python programming language was used successfully as a new and comprehensive approach to run EPR imaging experiments compared to the prior method that used multiple software packages. These developments will make EPR imaging more accessible for a much wider user group.

Publication Statement

Copyright is held by the author. User is responsible for all copyright compliance.

Provenance

Received from ProQuest

Rights holder

Yilin Shi

File size

293 p.

File format

application/pdf

Language

en

Discipline

Chemistry

Included in

Chemistry Commons

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