Radiation damage of DNA constituents: ESR study of the adenosine:5-iodouracil cocrystal
Single cocrystals of adenosine:5-iodouracil and partially deuterated adenosine:5-iodouracil were irradiated at 4.2K, 77K, and 300K with x-rays from a 3Mev Van de Graaff electron accelerator. Several types of free radicals were produced by the radiation and were studied by X-Band and Q-Band ESR from 77K to 300K. Six radicals were identified. Two electron addition products (radicals I1 and As1) and one electron abstraction product (radical 12) are stabilized at 77K. At room temperature two hydrogen addition radicals (I3 and As2) and a singlet radical (As3) are stabilized. Upon annealing to 165K after low temperature irradiation, radicals I1 and I2 decay to nonparamagnetic species. Radical As1 remains stable from 77K to 240K. From 240K to 300K the As1 radical decays and radicals As2 and I3 gradually grow in. Irradiation and observation at room temperature produces predominantly a singlet radical (As3). The electron addition radical, I1, is a sigma*-type radical that presents the unpaired electron spin density localized mainly on the iodine atom. This radical does not de-halogenate, to produce the reactive uracilyl radical, but instead it decays into a non paramagnetic species when annealed from 77K to 300K. The low temperature radical population obtained in this cocrystal and the subsequent radical reactions upon annealing, contradict the hypothesis that, in the presence of purine:pyrimidine stacking interactions, electrons are transferred to the pyrimidines while holes are transferred to the purines.
- Research Organization:
- Florida State Univ., Tallahassee (USA)
- OSTI ID:
- 6402714
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
DNA
BIOLOGICAL RADIATION EFFECTS
IODOURACILS
ELECTRON SPIN RESONANCE
RADICALS
RADIOINDUCTION
ADENOSINE
DEUTERIUM COMPOUNDS
TEMPERATURE EFFECTS
X RADIATION
ANTIMETABOLITES
AZINES
BIOLOGICAL EFFECTS
DRUGS
ELECTROMAGNETIC RADIATION
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
IONIZING RADIATIONS
MAGNETIC RESONANCE
NUCLEIC ACIDS
NUCLEOSIDES
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC IODINE COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PYRIMIDINES
RADIATION EFFECTS
RADIATIONS
RESONANCE
RIBOSIDES
URACILS
560120* - Radiation Effects on Biochemicals
Cells
& Tissue Culture