H-bonded base pairs & aggregates
Proton transfer along the intermolecular hydrogen bonds between the conjugate nucleobases in the Watson-Crick (WC) base pairs has long been assumed as a possible precursor state for mutagenesis and carcinogenesis. However, recent theoretical studies postulated that ultrafast inter-strand electron-driven proton transfer (EDPT) instead contributes to the prevention of mutagenic photolesions in UV-photoexcited DNA.
Proposed deactivation mechanism of UV-photoexcited G-C Watson-Crick base pairs.
Particular interest arises in the guanosine-cytidine (G--C) WC base pair, where an ultrafast transition from the photoexcited πGπG* state to a G-to-C charge transfer (CT) state followed by the transfer of a proton along the central G--C hydrogen bond has been proposed. In collaboration with the Orr-Ewing group at Bristol, we recently succeded to observe the resulting G-H]--[C+H] biradical by transient electronic absorption spectroscopy and by transient vibrational absorption spectroscopy. In our ongoing work, we investigate the possible role of EDPT processes in selected DNA sequences.
- K. Röttger, H. J. B. Marroux, M. P. Grubb, P. M. Coulter, H. Böhnke, A. S. Henderson, M. C. Galan, F. Temps, A. J. Orr-Ewing, G. M. Roberts, "Ultraviolet Absorption Induces Hydrogen-Atom Transfer in G∙C Watson-Crick DNA Base Pairs in Solution", Angew. Chem. Int. Ed. 54, 14719 - 14722 (2015). DOI: 10.1002/anie.201506940
- K. Röttger, F. D. Sönnichsen, F. Temps, "Ultrafast Electronic Deactivation Dynamics of the Inosine Dimer - A Model Case for H-Bonded Purine Base Pairs", Photochem. Photobiol. Sci. 12, 1466 - 1473 (2013). DOI: 10.1039/C3PP50093D
- K. Röttger, N. K. Schwalb, F. Temps, "Electronic Deactivation of Guanosine in Extended Hydrogen-Bonded Self-Assemblies", J. Phys. Chem. A 117, 2469 - 2478 (2013), DOI: 10.1021/jp3095193
- N. K. Schwalb, F. Temps, "Ultrafast Electronic Relaxation in Guanosine is Promoted by Hydrogen Bonding with Cytidine", J. Am. Chem. Soc. 129, 9272 - 9273 (2007). DOI: 10.1021/ja073448+