In medical and health physics, we are interested in the effects of ionizing radiation on biological systems, in particular, human biology. The main process by which ionizing radiations causes damage to biological systems, is through the creation of radicals close to DNA strands. The radicals are very reactive and those created within close proximity to DNA will react with the DNA causing damage, in particular single strand or double strand breaks. This damage to the DNA can cause mutations that can kill the cell, either mitotically or apoptotically, or possibly lead to a cancerous formation. Therefore it is important to study how these radicals interact with DNA strands for a correlation between the resultant products of radical reactions and DNA strand breaks. For this study, we look at the most important radical, the OH radical and it's addition to DNA bases. We will study, through quantum chemistry, the thermodynamics of OH radical addition to the four bases, Adenine, Guanine, Cytosine and Thymine. The Jaguar program developed by Schrodinger was used for DFT calculations of the Gibbs free energy of the addition. In addition, calculations for the partial charge, HOMO's and Fukui indices were calculated and compared to experiment.

Thesis (M. Phil.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 81-86).

Thesis (Ph. D.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains x, 210 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 154-185).

published_or_final_version / abstract / toc / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Master / Master of Philosophy

Using computational methods, the formation pathways and structures of four experimentally-observed DNA intrastrand cross-links are determined. These lesions originate from the uracil radical and are of particular importance due to their potential role in the activity of the 5-halouracils as radiosensitizing agents in anti-tumour treatments. The formation pathways are studied with density functional theory under conditions relevant to both UV and ionizing radiation. Results reveal these intrastrand cross-links are likely to form under therapeutic conditions and provide an explanation for their observed formation preferences. The structures of the cross-links in DNA are determined with molecular dynamics simulations to reveal the distortions these lesions induce to the helix. This has provided information about the potential biological implications of these lesions, where results indicate intrastrand cross-links are likely both mutagenic and cytotoxic. Therefore, these lesions may contribute to tumour cell death in the therapeutic use of halouracils. / xvi, 147 leaves : ill. (chiefly col.) ; 29 cm + 1 CD-ROM

Using computational methods, we have investigated the chemistry of 3-phenylpropyl radical systems. These systems are of importance to polymer chemistry as free radical additions involving these species are integral in the production of styrene-containing plastics. Although the addition reactions have been well studied, the other reaction pathways, namely f3-fragmentation and cyclization, have not been as comprehensively studied. As a result, our computational study involved 3-phenylpropyl radical systems that had been systematically mono-substituted at five positions, two on the propyl chain and three on the aromatic ring. This computational analysis consisted of calculation of optimized geometries and energies for reactants, products, and transition states, followed by examination of derived thermochemical quantities (enthalpies of activation and reaction), and critical structural parameters (transition bond lengths and bond angles) of the systems. Finally correlation of structure and reactivity of the various systems was attempted. Density functional theory (DFT) using the B3-LYP functional and the 6-31 G(d) basis set was selected as the level of theory. / Department of Chemistry

Thesis (Ph.D.)--McMaster University (Canada), 1991. / Source: Dissertation Abstracts International, Volume: 53-01, Section: B, page: 0308. Supervisor: John Warkentin.

Thesis (PhD) -- Macquarie University, Division of Environmental and Life Sciences, Dept. of Chemistry and Biomolecular Sciences, 2007. / Bibliography: leaves 295-322.

Thesis (M.S.)--Rutgers University, 2007. / "Graduate Program in Biomedical Engineering." Includes bibliographical references (p. 80-85).