A Fourier transform EPR study of uracil and thymine radical anions in aqueous solution

Abstract

Hydrated electrons are generated by two photon ionization of anthraquinone-1,5-disulfonate in H₂O and D₂O solutions. The electron attachment to the pyrimidine-type bases thymine and uracil results in the thymine and uracil radical anions. By simulation of the EPR splitting patterns of the protonated and deuterated forms of the radical anions their hyperfine coupling constants are assigned unambiguously. This new assignment of all hfs coupling constants is supported by quantum chemical calculations. The kinetics of electron attachment to the pyrimidine-type bases was studied by the method of kinetic linebroadening effects of the hydrated electron. The rate constants of the electron attachment were determined as k_att(thymine) = k_att(uracil) = (2.7 ± 0.1) × 10⁹ M⁻¹ s⁻¹.