The Electron Attachment Induced Radiation Damage to Genetic Materials : The Role of Water
Radiation damage to genetic material is one of the active fields of chemical research with implications in both the cause and cure of cancer. The origin of the damage for a long time is attributed to ionization and excitation process created by the high energy radiation. But recent experiments have highlighted the critical role played by the low-energy secondary electron in the radiation damage process. Water has been shown to accelerate the process of radiation damage. We have proposed a mechanism for the water-mediated attachment of electron to nucleobases. The initial electron attached state is localized on the water, and the water bound states act as a doorway for the electron attachment to nucleobases. Subsequently, the electron is transferred to the nucleobase due to the mixing of the electronic and the nuclear degrees of freedom in the solvated nucleobase. Our theoretical simulations show that the presence of bulk water increases the rate of the electron transfer, which takes place in the ultrafast time scale. The local structure of water around the nucleobase anion plays a crucial role in the electron attachment process. The computed adiabatic electron affinity of nucleobases and rate of electron transfer from water to the nucleobases shows good agreement with the experimental results validating our proposed mechanism.
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