by Jun Ma, Sergey A. Denisov, Jean-Louis Marignier, Pascal Pernot, Amitava Adhikary, Shu Seki and Mehran Mostafavi
The primary localization process of radiation-induced charges (holes (cation radical sites) and excess electrons) remains poorly understood, even at the level of monomeric DNA/RNA models, in particular, in an aqueous environment. We report the first spectroscopic study of charge transfer occurring in radiolysis of aqueous uridine 5′-monophosphate (UMP) solutions and its components: uridine, uracil, ribose, and phosphate. Our results show that prehydrated electrons effectively attach to the base site of UMP; the holes in UMP formed by either direct ionization or reaction of UMP with the radiation-mediated water cation radical (H2O•+) facilely localize on the ribose site, despite the fact that a part of them were initially created on either the phosphate or uracil. The nature of phosphate-to-sugar hole transfer is characterized as a barrierless intramolecular electron transfer with a time constant of 2.5 ns, while the base-to-sugar hole transfer occurs much faster, within a 5 ps electron pulse.