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Exploring ultraviolet photoinduced charge-transfer dynamics in a model dinucleotide of guanine and thymine

Duchi, Marta; O'Hagan, Michael; Kumar, Rhea; Bennie, Simon; Galan, M. Carmen; Curchod, Basile F.E.; Oliver, Tom

Exploring ultraviolet photoinduced charge-transfer dynamics in a model dinucleotide of guanine and thymine Thumbnail


Authors

Marta Duchi

Michael O'Hagan

Rhea Kumar

Simon Bennie

M. Carmen Galan

Tom Oliver



Abstract

An understanding of the initial photoexcited states of DNA is essential to unravelling deleterious photoinduced chemical reactions and the intrinsic ultrafast photoprotection of the genetic code for all life. In our combined experimental and theoretical study, we have elucidated the primary non-radiative relaxation dynamics of a model nucleotide of guanine and thymine (2'-deoxyguanosine 3'-monophospate 5'-thymidine, d(GpT)) in buffered aqueous solution. Experimentally, we unequivocally demonstrate that the Franck-Condon excited states of d(GpT) are significantly delocalised across both nucleobases, and mediate d(G+pT–) exciplex product formation on an ultrafast (< 350 fs) timescale. Theoretical studies show that the nature of the vertical excited states are very dependent on the specific geometry of the dinucleotide, and dictate the degree of delocalised, charge-transfer or localised character. Our mechanism for prompt exciplex formation involves a rapid change in electronic structure and includes a diabatic surface crossing very close to the Franck-Condon region mediating fast d(G+pT–) formation. Exciplexes are quickly converted back to neutral ground state molecules on a ~10 ps timescale with a high quantum yield, ensuring the photostability of the nucleotide sequence.

Citation

Duchi, M., O'Hagan, M., Kumar, R., Bennie, S., Galan, M. C., Curchod, B. F., & Oliver, T. (2019). Exploring ultraviolet photoinduced charge-transfer dynamics in a model dinucleotide of guanine and thymine. Physical Chemistry Chemical Physics, 21(26), 14407-14417. https://doi.org/10.1039/c8cp07864e

Journal Article Type Article
Acceptance Date Mar 5, 2019
Online Publication Date Mar 6, 2019
Publication Date Jul 14, 2019
Deposit Date Mar 6, 2019
Publicly Available Date Mar 28, 2024
Journal Physical Chemistry Chemical Physics
Print ISSN 1463-9076
Electronic ISSN 1463-9084
Publisher Royal Society of Chemistry
Peer Reviewed Peer Reviewed
Volume 21
Issue 26
Pages 14407-14417
DOI https://doi.org/10.1039/c8cp07864e

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Copyright Statement
This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence.





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