Author

Yuk Ki Lee

Date

September 2007

Document Type

Thesis

Degree Name

M.S.

Department

Dept. of Environmental and Biomolecular Systems

Institution

Oregon Health & Science University

Abstract

The EPR spectrum of the Tyr-Cys· free radical in oxidized apoGAOX has been investigated, using a combination of approaches. Power saturation analysis has been used to resolve two unique spectra through Evolving Factor Analysis (EFA) global fitting, indicating the presence of two distinct free radical species in the sample. The component that dominates at low microwave power arises from the Tyr-Cys· side chain, while the high power component has not yet been assigned. The experimental results show that the EPR spectrum collected at low power includes approximately 7% of the high power component. EPR spectra have been collected for ten different isotope derivatives of GAOX, including ²H-labeled, ¹³C-labeled, 17[superscript]O-labeled, and ³³S-labeled forms. XSophe simulation of the EPR spectra has been performed for the isotopically labeled samples in order to determine the spectroscopic parameters - g-values, hyperfine coupling constants, and linewidths. The g-values and the methylene proton hyperfine coupling constants obtained for the isotopically labeled samples are consistent with the literature values. The magnitude of the hyperfine coupling constants associated with each of the nuclei confirms that significant electron spin density is found on the methylene protons, the alternating carbon atoms within the aromatic π system and the 2p[subscript]z orbital of both sulfur and oxygen. Moreover, the rotation angle of the methylene protons to the phenoxyl ring around the C1-C7 bond has been evaluated based on the experimentally defined hyperfine coupling constants of the two methylene protons.

Identifier

doi:10.6083/M4445JDB

School

OGI School of Science and Engineering

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