Excited States of Protonated DNA Bases

M. BERDAKIN; G. FÉRAUD; C. DEDONDER-LARDEUX; G. GRÉGOIRE; M. BROQUIER; S. SOORKIA; C. JOUVET; G. A. PINO *

Porquerolles

Congreso; Isolated Biomolecules and Biomolecular Interactions; 2014

The very fast relaxation of the excited states to the ground state in DNA/RNA bases is a necessary process to ensure the photostability of DNA. This relaxation process is very sensitive to any substitution or environmental change, and protonation is one of the simplest. We report here the photofragmentation spectra of the five protonated DNA/RNA bases (uracil is shown in Fig. 1). Some of them present two systems of bands that were assigned to different tautomers. Most of the spectra of the protonated bases exhibit well resolved vibrational structures, with different widths of vibronic bands. For the bases showing the sharpest bands, the lifetimes were measured with picosecond pump-probe spectroscopy (Fig. 1) and were found to decrease with the excitation energy.