The electron spin resonance spectrum of γ-irradiated deoxyribonucleic acid: a novel interpretation based on molecular orbital calculations and computer simulations

Abstract

A novel interpretation of the e.s.r. spectrum of irradiated deoxyribonucleic acid is put forward on the basis of the linear combination of three hyperfine components: the previously known thymine octet [7–15% radical (T₁)], a doublet of ca. 20 G (10–20%). a singlet (70–80%). Tentative proposals for the assignment of the doublet have been made involving radicals arising from the pyrimidine and purine bases and from the ribose and protein moiety. No definite interpretation of the singlet could be attained because of the lack of resolution; however, it is worth pointing out that this signal has the characteristics expected, under the experimental conditions employed, from the hydrogen atom adducts at O(2) and O(4) of thymine and cytosine and at O(6) of adenine, whose formation is likely to be favoured by the hydrogen-bond system.