Base Sequence and Higher-Order Structure Induce the Complex Excited-State Dynamics in DNA
Nina K. Schwalb and
Friedrich Temps
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.
