ESR (electron spin resonance) and spin trapping of free radicals produced in poly U and /poly A using the boron-neutron capture reaction
Powdered samples of poly U and poly A containing sodium tetraborate and controls without tetraborate were irradiated at room temperature with thermal neutrons. Radical formation occurred only in the samples containing tetraborate. Thermal neutrons interact with /sup 10/B (10% naturally occurring in tetraborate) via the boron-neutron capture reaction. This reaction generates alpha particles and /sup 7/Li ions with mean kinetic energies of 1.48 and 0.85 MeV, respectively. The identification and location of the free radicals produced by the interaction of these particles with poly U and poly A, was determined by ESR and spin trapping using the spin trap 2-methyl-2-nitrosopropane (MNP). Following dissolution of irradiated poly U in an MNP solution, the spin-trapped poly U was hydrolyzed with base (NaOH, pH 12.6). On readjusting the pH to pH 7.5, the spin-adduct ESR spectrum showed that in poly U, radical formation occurs at the C(6) carbon of the uracil residues. For poly A the solid-state ESR spectrum suggests that radicals are formed at the N(3) and/or N(7) nitrogens and at the C(4) and/or C(5) carbons. However, only the C(5) carbon-centered radicals were spin trapped. In addition, the results for poly A indicate that sugar-phosphate backbone is disrupted by the alpha particles and 7Li ions. The nature of this interactions is still unclear.
- Research Organization:
- Armed Forces Radiobiology Research Inst., Bethesda, MD (USA)
- OSTI ID:
- 6450323
- Report Number(s):
- AD-A-200249/1/XAB; AFRRI-SR-88-11
- Country of Publication:
- United States
- Language:
- English
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