Date of Award
5-2026
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Chemistry
Committee Chair/Advisor
Dr. Julia L. Brumaghim
Committee Member
Dr. Shanna L. Estes
Committee Member
Dr. Daniel C. Whitehead
Committee Member
Dr. Joseph W. Kolis
Abstract
Radicals cause damage in biological systems, polymerization reactions, nanoparticle syntheses, and during food and medical sterilization. Radical-mediated oxidative stress in the body is prevented by biological thiols (biothiols), including glutathione and cysteine. Biothiol levels are a measure of oxidative stress, and biothiol concentrations correlate with prognosis in diseases such as Parkinson’s disease and HIV. Cellular biothiol concentrations are commonly measured using Ellman’s assay to quantify reduced biothiol concentrations. In this dissertation, Chapter 1 focuses on reviewing how Ellman’s assay has been used to determine biothiol concentrations. It also describes other analytical methods used to accomplish the same goal and highlights the need to use multiple methods to determine biothiol concentrations. Chapter 2 focuses on studying the effects that copper, iron, and zinc, have on oxidation of the biothiols glutathione, cysteine, and cysteamine using Ellman’s assay combined with liquid chromatography-mass spectrometry (LC-MS) methods. Redox-active copper and iron catalytically promote biothiol oxidation, even at very low concentrations. In contrast, redox-inactive zinc has no effect or slows biothiol oxidation rates. Additionally, results show that LC-MS can corroborate results from Ellman’s assay for glutathione and cysteine, but not cysteamine. Irradiation also forms radicals, and radiation is problematic in applications such as during nuclear waste separation processes, where extractants must be radiolytically stable. Radiation effects on extractant stability are often studied using gamma irradiation, a low-throughput, high-cost, and less-accessible method. Chapter 3 presents the first non-radioactive radical assay that can be used as a screening tool for complexant stability before gamma irradiation studies. We have examined monoamide degradation as a test case for assay development, due to the increasing interest in monoamides for nuclear waste separation processes. Chapter 4 focuses on expanding the scope of this non-radioactive radical assay by studying smaller monoamide complexants and extending the assay to more process relevant, nitric-acid-contacted conditions. Broadening the scope of this non-radioactive radical assay will help predict the degradation products for a variety of monoamide complexants, accelerating development of nuclear waste separations. Overall, radical-mediated damage impacts many fundamentally different areas. Each area involves its own unique challenges and requires development of different analysis methods to study each distinct system. The research presented in this dissertation highlights methods developed to understand and predict radical-mediated damage in a range of areas from disease prognosis to nuclear waste separations.
Recommended Citation
Vicente, Madison R., "Assay Development to Examine Radical-Mediated Oxidation of Biothiols and Degradation of Monoamide Complexants" (2026). All Dissertations. 4254.
https://open.clemson.edu/all_dissertations/4254
Author ORCID Identifier
0009-0002-0873-0473