The fluorescence resonance energy transfer (FRET) gate: a time-resolved study.
The two-step energy-transfer process in a self-assembled complex comprising a cationic conjugated polymer (CCP) and a dsDNA is investigated by using pump-dump-emission spectroscopy and time-correlated single-photon counting; energy is transferred from the CCP to an ethidium bromide (EB) molecule intercalated into the dsDNA through a fluorescein molecule linked to one terminus of the DNA. Time-dependent anisotropy measurements indicate that the inefficient direct energy transfer from the CCP to the intercalated EB results from the near orthogonality of their transition moments. These measurements also show that the transition moment of the fluorescein spans a range of angular distributions and lies between that of the CCP and EB. Consequently, the fluorescein acts as a fluorescence resonance energy-transfer gate to relay the excitation energy from the CCP to the EB.
Xu
Qing-Hua
QH
Institute for Polymers and Organic Solids, University of California, Santa Barbara, CA 93106, USA.
Wang
Shu
S
Korystov
Dmitry
D
Mikhailovsky
Alexander
A
Bazan
Guillermo C
GC
Moses
Daniel
D
Heeger
Alan J
AJ
D004247:DNA / Q000737:chemistry; D004996:Ethidium / Q000737:chemistry; D019793:Fluorescein / Q000737:chemistry; D005454:Fluorescence Polarization; D031541:Fluorescence Resonance Energy Transfer / Q000379:methods*; D007700:Kinetics; D011073:Polyamines / Q000737:chemistry; D000071228:Polyelectrolytes
D004247:DNA; D004996:Ethidium; D019793:Fluorescein; D011073:Polyamines; D000071228:Polyelectrolytes