Using FRET to Explore Protein-Protein Interactions in Vivo Figure 12-8 shows the interaction between B-arrestin and the -adrenergic receptor. How would you use FRET (see Box 12-3) to demonstrate this interaction in living cells? Which proteins would you fuse? Which wavelengths would you use to illuminate the cells, and which would you monitor? What would you expect to observe if the interaction occurred? If it did not occur? How might you explain the failure of this approach to demonstrate this interaction?