The Effect of Base-Pairing on the Shape Resonances of Nucleobases

TL;DR

This study investigates how base-pairing influences the shape resonances of guanine and cytosine, revealing shifts in resonance energies and highlighting the roles of electronic interactions and geometric factors.

Contribution

It provides new insights into the effect of base-pairing on nucleobase resonances, emphasizing the importance of electronic and geometric factors in resonance stabilization.

Findings

Cytosine resonances are red shifted upon pairing.

Guanine-centered states are blue shifted upon pairing.

Electronic interactions significantly stabilize the resonances.

Abstract

In this work, we have studied the effect of base-pairing on the shape resonances of guanine and cytosine nucleobases. Among the seven {\pi}* resonances we identified in the guanine-cytosine (GC) anion radical, three were centered on cytosine, and the remaining were guanine-centered. Relative to the isolated bases, upon base pair formation, the cytosine resonances were red shifted, while the guanine-centered states showed an opposite trend - where their energy was blue shifted. In addition to the electronic interactions, geometric distortion and basis set superposition error plays a crucial role in the resonance positions and widths of the GC radical anion. The electronic interaction from the complementary base seems to have a larger effect on the stabilization of the anionic resonances than the surrounding environment.