Case Studies
Fluorescence Resonance Energy Transfer (FRET)
FRET false-color image captured with the iXon DU-897 camera of single RNA molecules
labeled with FRET. A FRET donor and acceptor are attached to either end of an intron
that requires magnesium and a protein cofactor (CBP2) to splice together the exon
sequences on either side of it. On the left is a false-color image (donor emitting
greenish light, acceptor emitting red light)showing low FRET transfer to the acceptor
dye due to the dyes being relatively distant, and the intron being in an inactive,
unfolded form.
On the right is an image taken when the intron folds into its active form, bringing the two exons (and their attached FRET dyes) close together for the splicing reaction, causing high energy transfer to the red dye. Thus, the structural change from an inactive to the active form in the RNA causes the colors emitted by the single molecules to change from green to red due to FRET.
Image courtesy of Zhuang Lab, Department of Chemistry and Chemical Biology at Harvard University in Cambridge, Massachusetts.