Abstract
Damage to DNA via dissociative electron attachment has been well-studied in both the gas and condensed phases; however, understanding this process in bulk solution at a fundamental level is still a challenge. Here, we use a picosecond pulse of a high energy electron beam to generate electrons in liquid diethylene glycol and observe the electron attachment dynamics to ribothymidine at different stages of electron relaxation. Our transient spectroscopic results reveal that the quasi-free electron with energy near the conduction band effectively attaches to ribothymidine leading to a new absorbing species that is characterized in the UV-visible region. This species exhibits a nearly concentration-independent decay with a time constant of ~350 ps. From time-resolved studies under different conditions, combined with data analysis and theoretical calculations, we assign this intermediate to an excited anion radical that undergoes N1-C1′ glycosidic bond dissociation rather than relaxation to its ground state.
Highlights
Damage to DNA via dissociative electron attachment has been well-studied in both the gas and condensed phases; understanding this process in bulk solution at a fundamental level is still a challenge
The low-energy resonance features in the yield of double strand breaks (DSBs), single strand breaks (SSBs), and anions produced by the impact of low-energy electrons (LEEs) on model pyrimidine bases suggested that the initial step involves electron capture into the unoccupied molecular orbitals that are above the lowest unoccupied molecular orbitals (LUMOs) of the parent nucleobase, creating excited transient negative ions (TNIs*)
Our spectroscopic observations in DEG establish that the quasifree electrons form two localized electron-solvent configuration states (in the infrared region and in the visible region within the timescale of the electron pulse (
Summary
Damage to DNA via dissociative electron attachment has been well-studied in both the gas and condensed phases; understanding this process in bulk solution at a fundamental level is still a challenge. It is known that fully solvated electrons (esol-) are ineffective at triggering DNA bond cleavage because they generally reside on biomolecules as stable anions[6] For this reason, the conventional notion of electroninduced damage to the genome is mainly due to those electrons with sufficient energy to ionize or excite DNA, thereby leading to the formation of electron-loss radicals (holes) and excited states that cause subsequent molecular fragmentation[7]. In 2000 and onwards, the experimental observations from Sanche and coworkers showed that LEEs were able to cause single strand breaks (SSBs), as well as DSBs via dissociative electron attachment (DEA)[8,9] This observation motivated a great number of mechanistic studies on the interaction of LEEs with DNA and its components in both the gas and condensed phases[10,11,12,13,14,15]. DNA) were often carried out under vacuum conditions; these experiments were limited to gas phase and condensed phase or micro-hydrated molecular targets[10,11,12,13,14,15]
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