Impact of Amino Acid Environment on Electron Attachment to DNA: The Role of Zwitterionic Form

TL;DR

This study investigates how the zwitterionic form of amino acids influences electron attachment to DNA, revealing that zwitterionic glycine enhances electron trapping and shielding without causing proton transfer, thus affecting DNA damage mechanisms.

Contribution

It demonstrates the role of zwitterionic amino acids in modulating electron transfer and protection in DNA, a novel insight into DNA-electron interactions.

Findings

Zwitterionic glycine acts as a better electron trap than native glycine.

Presence of zwitterionic glycine does not induce proton transfer to thymine.

Zwitterionic glycine enhances electron shielding without damaging DNA.

Abstract

We have studied the effect of zwitterionic form of the amino acid on the electron attachment to DNA using thymine glycine as a model system. The electron attachment to thymine in the presence of glycine takes place through a "doorway mechanism", where the electron density in the initial anionic state remains away from the nuclear framework of thymine. The electron gets transferred to nucleobase through mixing of electronic and nuclear degrees of freedom and glycine plays an important role in modulating the rate of electron transfer. The charge separation in the zwitterionic glycine make them a better trap for the electron than the native glycine and it can act as a better shield to the incoming electron. However, in the bulk solvated thymine anion the presence of zwitterionic glycine does not lead to any proton transfer to nucleobase, which makes it more resilient to base damage.