Probing the interaction between single molecules: fluorescence resonance energy transfer between a single donor and a single acceptor

Fluorescence resonance energy transfer is a standard spectroscopic technique for measuring distances in the 10-75 angstrom range. This study extends the technique's sensitivity by measuring energy transfer between a single donor fluorophore and a single acceptor fluorophore. Near-field scanning optical microscopy was used to obtain simultaneous dual color imaging and emission spectra from a single pair of donor and acceptor fluorophores linked by a short (10 or 20 bases long) DNA molecule. The DNA was dried on amino-propyl-silanized glass. Near-field fluorescence images and emission spectra were taken on single DNA molecules labeled with donor only, with acceptor only, or with both donor and acceptor.