American Chemical Society
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Unified Description of Ultrafast Excited State Decay Processes in Epigenetic Deoxycytidine Derivatives

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journal contribution
posted on 2021-11-08, 18:07 authored by Piotr Kabaciński, Marco Romanelli, Eveliina Ponkkonen, Vishal Kumar Jaiswal, Thomas Carell, Marco Garavelli, Giulio Cerullo, Irene Conti
Epigenetic DNA modifications play a fundamental role in modulating gene expression and regulating cellular and developmental biological processes, thereby forming a second layer of information in DNA. The epigenetic 2′-deoxycytidine modification 5-methyl-2′-deoxycytidine, together with its enzymatic oxidation products (5-hydroxymethyl-2′-deoxycytidine, 5-formyl-2′-deoxycytidine, and 5-carboxyl-2′-deoxycytidine), are closely related to deactivation and reactivation of DNA transcription. Here, we combine sub-30-fs transient absorption spectroscopy with high-level correlated multiconfigurational CASPT2/MM computational methods, explicitly including the solvent, to obtain a unified picture of the photophysics of deoxycytidine-derived epigenetic DNA nucleosides. We assign all the observed time constants and identify the excited state relaxation pathways, including the competition of intersystem crossing and internal conversion for 5-formyl-2′-deoxycytidine and ballistic decay to the ground state for 5-carboxy-2′-deoxycytidine. Our work contributes to shed light on the role of epigenetic derivatives in DNA photodamage as well as on their possible therapeutic use.