Fig. 3.

Schematic representation of fluorescence recovery after photobleaching (FRAP). Anti-YFP antibodies added to cells containing YFP-GPCR and GPCR–CFP fusions cause immobilisation of the YFP-tagged receptors. A region of the cell is then photobleached (dashed circle) and, after a period of time, the bleached region is monitored for fluorescent molecules which have diffused from outside. In the case of monomeric receptors, FRAP of the GPCR–CFP molecules, but not of the YFP–GPCR molecules, will occur. For dimeric receptors, no FRAP will be observed as the GPCR–CFP molecules are immobilised via the YFP-tagged receptors