Base sequence and higher-order structure induce the complex excited-state dynamics in DNA.
The high photostability of DNA is commonly attributed to efficient radiationless electronic relaxation processes. We used femtosecond time-resolved fluorescence spectroscopy to reveal that the ensuing dynamics are strongly dependent on base sequence and are also affected by higher-order structure. Excited electronic state lifetimes in dG-doped d(A)20 single-stranded DNA and dG.dC-doped d(A)20.d(T)20 double-stranded DNA decrease sharply with the substitution of only a few bases. In duplexes containing d(AGA).d(TCT) or d(AG).d(TC) repeats, deactivation of the fluorescing states occurs on the subpicosecond time scale, but the excited-state lifetimes increase again in extended d(G) runs. The results point at more complex and molecule-specific photodynamics in native DNA than may be evident in simpler model systems.
Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstrasse 40, D-24098 Kiel, Germany. schwalb@phc.uni-kiel.de
Nina K
NK
Schwalb
Friedrich
F
Temps
D020029:Base Pairing; D001483:Base Sequence; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D004277:DNA, Single-Stranded / Q000737:chemistry; D006860:Hydrogen Bonding; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry*; D010777:Photochemistry; D011687:Purines / Q000737:chemistry; D011743:Pyrimidines / Q000737:chemistry; D013050:Spectrometry, Fluorescence
D004277:DNA, Single-Stranded; D009838:Oligodeoxyribonucleotides; D011687:Purines; D011743:Pyrimidines; D004247:DNA