Electronic and vibrational spectroscopy of metal-mediated (Cytosine2Ag+) DNA base pair

M. BERDAKIN; G. FERAUD; V. STEINMETZ; P. MAITRE; C. DEDONDER-LARDEUX; C. JOUVET; G. A. PINO

Congreso; IBBI 14 - Conference on Isolated Biomolecules and Biomolecular Interactions; 2014

In the past years, natural and artificial DNA molecules have been of great interest because of their potential applications in biological and material science. Metal mediated base paring constitutes a major advance in the attempt of expanding the genetic code, and has proven to be a suitable and powerful tool for the potential development of artificial DNA based devices. Besides, silver clusters synthesized within DNA templates constitute a new generation of small and biocompatible fluorophores as biological labels. We report here a complete spectroscopy study (IR-MPD and UV) of the gas phase [Cytosine2-Ag]+ ([C2Ag]+) complex and its comparison with the [C2H]+ complex. The IR-MPD spectrum recorded with the Free-Electron-Laser at Orsay (CLIO) combined with theoretical calculations, show that the structure of [C2Ag]+ mimics the structure of the [C2H]+ pair occurring in i-motif DNA, with the formal replacement of one N?H+?N intermolecular bond by a stronger N?Ag+?N bond. On the other hand, from the bandwidth of the vibronic transitions of the UV photofragmentation spectrum of the cold (40 K) [C2Ag]+ complex recorded at the University of Marseille, we estimate that its excited state lifetime (> 5000fs) is much longer than that of the [C2H]+ complex (> 80 fs). The enlarged excited state lifetime of the [C2Ag]+ complex could be related to the high fluorescence quantum yield presented by DNA-Ag clusters.