Electron Attachment to Wobble Base Pairs

TL;DR

This study investigates how low-energy electrons attach to wobble base pairs in DNA, revealing a doorway mechanism involving dipole-bound states and proton transfer, with implications for understanding DNA damage processes.

Contribution

It introduces a detailed quantum mechanical analysis of electron attachment to wobble base pairs, highlighting a specific doorway mechanism and proton transfer pathway.

Findings

Formation of dipole-bound anions facilitates electron attachment.

Valence-bound state formation involves proton transfer in wobble pairs.

Transition rates differ from Watson-Crick base pairs.

Abstract

We have analyzed the low-energy electron attachment to wobble base pairs using the equation motion coupled cluster method and extended basis sets. A doorway mechanism exists for the attachment of the additional electron to the base pairs, where the initially formed dipole-bound anion captures the incoming electron. The doorway dipole-bound anionic state subsequently leads to the formation of a valence-bound state, and the transfer of extra electron occurs by mixing of electronic and nuclear degrees of freedom. The formation of the valence-bound anion is associated with proton transfer in hypoxanthine-cytosine and hypoxanthine-adenine base pairs, which happens through a concerted electron-proton transfer process. The calculated rate constant for the dipole-bound to valence-bound transition in wobble base pairs is slower than that observed in the Watson-Crick guanine-cytosine base pair.