Ultrafast transient-absorption and steady-state fluorescence measurements on 2-aminopurine substituted dinucleotides and 2-aminopurine substituted DNA duplexes

O.F.A. Larsen, I.H.M. van Stokkum, F.L. de Weerd, M. Vengris, C.T. Aravindakumar, R. van Grondelle, N.E. Geacintov, H. van Amerongen

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Abstract

Ultrafast transient-absorption and steady-state fluorescence measurements have been performed on dinucleotides comprising the fluorescent adenine analogue 2-aminopurine and guanine, adenine, cytosine, thymine or hypoxanthine, respectively. Two oligodeoxyribonucleotide duplexes that were site-selectively substituted with a single 2-aminopurine moiety were also studied. A strong quenching of the steady-state fluorescence was observed in all samples. The transient-absorption spectra were remarkably similar to those of the isolated 2-aminopurine (Larsen et al.; O. F. A. Larsen, I. H. M. van Stokkum, M.-L. Groot, J. T. M. Kennis, R. van Grondelle and H. van Amerongen, Chem. Phys. Lett., 2003, 371, 157-163), exhibiting both a fluorescent and a non-fluorescent excited state. There was no evidence for significant amounts of charge-separated states in the transient-absorption spectra. The probability that an excitation of 2AP leads to stable charge transfer products was estimated to be very low (0.1%). In the systems we studied, the observed fluorescence quenching can largely be explained by a shift of the equilibrium between the two excited states in 2AP, in which the non-fluorescent state is favored
Original languageEnglish
Pages (from-to)154-160
Number of pages6
JournalPhysical Chemistry Chemical Physics
Volume6
Issue number1
DOIs
Publication statusPublished - 2004

Keywords

  • electron-transfer
  • energy-transfer
  • charge-transfer
  • dynamics
  • base
  • oligonucleotides
  • photoionization
  • spectroscopy
  • nucleotides
  • conversion

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