Electronic Spectroscopy of Isolated DNA Polyanions

TL;DR

This study investigates the electronic spectroscopy of isolated DNA polyanions in the gas phase, comparing action spectroscopy results with structural and electronic data to understand their photophysical behavior.

Contribution

It demonstrates that action spectroscopy can effectively probe gas-phase DNA ions, providing insights into their electronic structure and fragmentation pathways.

Findings

Action spectra from fragmentation align with absorption spectra.

Electron photodetachment spectra reveal electron binding energies.

Gas-phase DNA structures validated by ion mobility and IR spectroscopy.

Abstract

In solution, UV-vis spectroscopy is often used to investigate structural changes in biomolecules (i.e., nucleic acids), owing to changes in the environment of their chromophores (i.e., the nucleobases). Here we address whether action spectroscopy could achieve the same for gas-phase ions, while taking the advantage of additional spectrometric separation of complex mixtures. We therefore systematically studied the action spectroscopy of homo-base 6-mer DNA strands (dG6, dA6, dC6, dT6) and discuss the results in light of gas-phase structures validated by ion mobility spectrometry and infrared ion spectroscopy, of electron binding energies measured by photoelectron spectroscopy, and of calculated electronic photo-absorption spectra. When UV photons interact with oligonucleotide polyanions, two main actions may take place: (1) fragmentation and (2) electron detachment. The action spectra reconstructed from fragmentation follow the absorption spectra well, and result from multiple cycles of absorption and internal conversion. The action spectra reconstructed from the electron photodetachment (ePD)