JACS article hot of the press (published on the web 10 July 2007)
10 July 2007:
Ultrafast Electronic Relaxation in Guanosine is Promoted by Hydrogen Bonding with Cytidine
Nina K. Schwalb and Friedrich Temps
J. Am. Chem. Soc. 129, 9272 - 9273 (2007), DOI: 10.1021/ja073448+
The excited electronic state lifetime of the guanosine−cytidine (G···C) Watson−Crick (WC) base pair has been directly measured in comparison to free G and C. Measurements have been carried out in solution in chloroform, where the formation of H-bonded base pairs is strongly favored, using the technique of femtosecond fluorescence up-conversion spectroscopy. The results show that the formation of the H-bonded WC pair leads to steep acceleration of the ultrafast nonradiative electronic deactivation compared to the free nucleosides, especially G, which can be explained by an intermolecular G-to-C electron-induced proton-transfer mechanism in the excited state. The results are of vital interest for bridging the huge gap between the well-known electronic properties of the isolated nucleobases and the strikingly different dynamics of DNA molecules.