A combined EMR and DFT study of radiation-induced defects in sucrose and glucose 1-phosphate

Ionizing radiation induces radicals in organic matter, i.e. molecules with one or more unpaired electrons. This dissertation deals with a detailed study of radicals induced by X-ray radiation in solid sucrose (also known as common household sugar) and in the dipotassium salt of glucose 1-phosphate (K2G1P). The radiation chemistry of these materials is relevant in the context of radiation damage to DNA and (emergency) dosimetry. Next to the actual research results, which will be discussed below, the dissertation contains several, quite extensive chapters of a more general nature. The research strategy employed mainly comprises electron-magnetic-resonance (EMR) measurements (EPR, ENDOR, HYSCORE, …) and theoretical ab-initio calculations based on density functional theory (DFT). Essentially, radical structures are identified and scrutinized by comparing DFT-calculated and experimentally determined EMR parameters. These are the main results with respect to radiation-induced radicals in sucrose: (i) all major stable radiation-induced radicals are characterized and identified. Each of them requires formation of a carbonyl group and scission of the glycosidic bond. (ii) The transformation of the EPR spectrum during the first four hours after RT irradiation is shown to be due to the decay of several semistable species to diamagnetic products. (iii) Six (more) primary radicals (studied by in-situ irradiation at 10 K and subsequent EMR measurements at 10 K) were characterized and three of the four dominant radicals were identified as H-abstracted species. In K2G1P, the radicals present at 77 K after in-situ X-ray irradiation at 77 K were studied. Four radical species were characterized and identified. The dominant radical is chemically identical to one of the major radicals in sucrose and has a broken sugar-phosphate junction. Finally, it was shown, via first-order perturbation theory, that an ambiguity can arise in the determination of hyperfine tensors for low-symmetry paramagnetic centers with S=1/2 and I=1/2 – which can lead to erroneous radical identification. A firm theoretical basis is thus provided for a problem that was since long known to exist, but not always recognized or adequately dealt with in the literature.

Grantor dc:publisher

Ghent University. Faculty of Sciences

Year dc:date

2009

Author dc:creator

• De Cooman, Hendrik

Contributors dc:contributor

• Callens, Freddy
• Waroquier, Michel

• Physics and Astronomy
• Hyperfine coupling
• DFT
• Sucrose
• Radiation
• Fitting results
• Temperature dependenceKeywords
• EPR
• ENDOR
• Ambiguity
• Calculations

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://biblio.ugent.be/publication/677287
https://biblio.ugent.be/publication/677287/file/4334982

OAI identifier oai:identifier

oai:archive.ugent.be:677287