Document Type
Article
Publication Date
3-1-2024
Abstract
Prolonged ultraviolet exposure results in the formation of cyclobutane pyrimidine dimers (CPDs) in RNA. Consequently, prebiotic photolesion repair mechanisms should have played an important role in the maintenance of the structural integrity of primitive nucleic acids. 2,6-Diaminopurine is a prebiotic nucleobase that repairs CPDs with high efficiency when incorporated into polymers. We investigate the electronic deactivation pathways of 2,6-diaminopurine-2′-deoxyribose and 9-methyl-2,6-diaminopurine in acetonitrile and aqueous solution to shed light on the photophysical and excited state properties of the 2,6-diaminopurine chromophore. Evidence is presented that both are photostable compounds exhibiting similar deactivation mechanisms upon the population of the S1(ππ* La) state at 290 nm. The mechanism involves deactivation through the C2- and C6-reaction coordinates and >99% of the excited state population decays through nonradiative pathways involving two conical intersections with the ground state. The radiative and nonradiative lifetimes are longer in aqueous solution compared to acetonitrile. While τ1 is similar in both derivatives, τ2 is ca. 1.5-fold longer in 2,6-diaminopurine-2′-deoxyribose due to a more efficient trapping in the S1(ππ* La) minimum. Therefore, 2,6-diaminopurine could have accumulated in significant quantities during prebiotic times to be incorporated into non-canonical RNA and play a significant role in its photoprotection.
Keywords
chemical origins of life, photostability, prebiotic nucleobases, prebiotic photochemistry
Language
English
Publication Title
Photochemistry and Photobiology
Grant
CHE‐1800052
Rights
© 2023 The Authors. Photochemistry and Photobiology published by Wiley Periodicals LLC on behalf of American Society for Photobiology. This is an open access work distributed under the terms of the Creative Commons Attribution-Non-Commercial (https://creativecommons.org/licenses/by-nc/4.0/) which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License
Recommended Citation
Ortiz-Rodríguez LA, Caldero-Rodríguez NE, Seth SK, Díaz-González K, Crespo-Hernández CE. Electronic relaxation mechanism of 9-methyl-2,6-diaminopurine and 2,6-diaminopurine-2′-deoxyribose in solution. Photochem Photobiol. 2024; 100: 393-403. doi:10.1111/php.13887
Manuscript Version
Final Publisher Version