Electron and radical cation of sulfur-substituted thymine derivatives produced near photoionization threshold can alter and distort double-helix DNA structure

Results from DFT calculations show that the aqueous adiabatic ionization energies for thymine, 2-thiothymine, 2,4-dithiothymine, and 4-thiothymine are 4.95, 4.99 eV, 4.94 eV and 4.81 eV, respectively. The calculated absorption spectra for the radical cations of thymine and 4-thiothymine exhibit significant red-shift and show characteristics of noncanonical structures. The calculated large aqueous adiabatic electron affinity for 2,4-dithiothymine (AEA 2.67 eV) suggests that it can be a potent radio chemotherapeutic agent in cancer treatment.