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Electronic Spectroscopy of Isolated Nucleic Acid Polyanions


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 mass spectrometry and ion mobility 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, and in light of electron binding energies measured by photoelectron spectroscopy, and 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) efficiency reveal interesting phenomena: EPD depends on the charge state in a manner depending on electron binding energies, and is particularly efficient for purines but not pyrimidines. EPD thus reflects not only absorption, but also particular relaxation pathways of the electronic excited states. As these pathways lead to photo-oxidation, their investigation on model gas-phase systems may prove useful to elucidate mechanisms of photo-oxidative damages, which are linked to mutations and cancers.

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Publication details

The article was received on 26 Nov 2018, accepted on 20 Dec 2018 and first published on 20 Dec 2018

Article type: Paper
DOI: 10.1039/C8FD00207J
Citation: Faraday Discuss., 2018, Accepted Manuscript

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    Electronic Spectroscopy of Isolated Nucleic Acid Polyanions

    S. Daly, M. Porrini, F. Rosu and V. Gabelica, Faraday Discuss., 2018, Accepted Manuscript , DOI: 10.1039/C8FD00207J

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