Strickler-Berg analysis of excited singlet state dynamics in DNA and RNA nucleosides.
The excited singlet state lifetime of the ribonucleoside uridine was found to be 210+/-30 fs by femtosecond transient absorption spectroscopy. This value is considerably shorter than all previous time-domain measurements. This result and our previous lifetime measurements [see J.-M. L. Pecourt, J. Peon and B. Kohler, J. Am. Chem. Soc., 2001, 123, 10 370] for the other common nucleosides are compared with lifetimes calculated from available photophysical data using the Strickler-Berg (SB) equation. The calculated lifetimes for pyrimidine nucleosides are 10-25% lower than the lifetimes measured in femtosecond transient absorption experiments. For the purine nucleosides, guanosine and adenosine, consideration of just the lowest 1pi --> pi* transition led to predicted lifetimes that are three times greater than experimental ones. On the other hand, inclusion of both of the lowest energy 1pi --> pi* absorption bands in the SB equation resulted in much better agreement with the experimental values. This suggests that both 1pi pi* states of the purine nucleosides contribute to their emission. Decay by the bright 1pi pi* state (or states, in the case of the purines) is believed to be responsible for the experimentally observed lifetimes.
Department of Chemistry, The Ohio State University, Columbus, Ohio 43214, USA.
Boiko
B
Cohen
Carlos E
CE
Crespo-Hernández
Bern
B
Kohler
D004247:DNA / Q000737:chemistry*; D007700:Kinetics; D010777:Photochemistry; D011684:Purine Nucleosides / Q000737:chemistry; D011741:Pyrimidine Nucleosides / Q000737:chemistry; D012313:RNA / Q000737:chemistry*
D011684:Purine Nucleosides; D011741:Pyrimidine Nucleosides; D012313:RNA; D004247:DNA