Ultraviolet Absorption Induces Hydrogen-Atom Transfer in G⋅C Watson-Crick DNA Base Pairs in Solution

Katharina Röttger, Hugo J B Marroux, Michael P Grubb, Philip M Coulter, Hendrik Böhnke, Alexander S Henderson, M Carmen Galan, Friedrich Temps, Andrew J Orr-Ewing, Gareth M Roberts

Research output: Contribution to journalArticle (Academic Journal)peer-review

44 Citations (Scopus)
368 Downloads (Pure)

Abstract

Ultrafast deactivation pathways bestow photostability on nucleobases and hence preserve the structural integrity of DNA following absorption of ultraviolet (UV) radiation. One controversial recovery mechanism proposed to account for this photostability involves electron-driven proton transfer (EDPT) in Watson-Crick base pairs. The first direct observation is reported of the EDPT process after UV excitation of individual guanine-cytosine (G⋅C) Watson-Crick base pairs by ultrafast time-resolved UV/visible and mid-infrared spectroscopy. The formation of an intermediate biradical species (G[-H]⋅C[+H]) with a lifetime of 2.9 ps was tracked. The majority of these biradicals return to the original G⋅C Watson-Crick pairs, but up to 10 % of the initially excited molecules instead form a stable photoproduct G*⋅C* that has undergone double hydrogen-atom transfer. The observation of these sequential EDPT mechanisms across intermolecular hydrogen bonds confirms an important and long debated pathway for the deactivation of photoexcited base pairs, with possible implications for the UV photochemistry of DNA.

Original languageEnglish
Pages (from-to)14719-14722
Number of pages4
JournalAngewandte Chemie - International Edition
Volume54
Issue number49
Early online date13 Oct 2015
DOIs
Publication statusPublished - 1 Dec 2015

Structured keywords

  • BCS and TECS CDTs

Keywords

  • biophysics
  • DNA
  • photochemistry
  • proton transfer
  • ultrafast spectroscopy

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