Fluorescence of natural DNA: from the femtosecond to the nanosecond time scales.
The fluorescence of calf thymus DNA is studied by steady-state and time-resolved spectroscopy combining fluorescence upconversion and time-correlated single photon counting. The fluorescence spectrum is very similar to that of a stoichiometric mixture of monomeric chromophores, arising from bright pi pi* states, and contrasts with the existing picture of exciplex emission in natural DNA. Yet, the DNA fluorescence decays span over five decades of time, with 98% of the photons being emitted at times longer than 10 ps. These findings, in association with recent studies on model duplexes, are explained by the involvement of dark states, possibly related to charge separation, serving as a reservoir for the repopulation of the bright pi pi* states.
Vayá
Ignacio
I
Laboratoire Francis Perrin, CEA/DSM/IRAMIS/SPAM-CNRS URA 2453, CEA/Saclay, 91191 Gif-sur-Yvette, France.
Gustavsson
Thomas
T
Miannay
François-Alexandre
FA
Douki
Thierry
T
Markovitsi
Dimitra
D
D000818:Animals; D002417:Cattle; D004247:DNA / Q000737:chemistry*; D005453:Fluorescence; D013050:Spectrometry, Fluorescence; D013997:Time Factors
D004247:DNA; C427203:calf thymus DNA