Fig. 2.
FRET as a molecular ruler. a FRET efficiency (E RET; and hence the signal) is proportional to the distance between the fluorophores. R 0 Förster distance, R distance between donor and acceptor molecules. b Schematic representation of a GPCR dimer in which monomers are labelled at the intracellular surfaces of transmembrane helix 3 (red star) or 5 (green star). Intracellular loops are shown between helices. Multiple pairs of fluorophores at different locations can be used to build a model of the dimer and observe conformational changes upon ligand binding