Fluorescence correlation spectroscopy, combined with bimolecular fluorescence complementation, reveals the effects of β-arrestin complexes and endocytic targeting on the membrane mobility of neuropeptide Y receptors

► First FCS / PCH analysis of the plasma membrane diffusion characteristics of NPY receptors. ► Demonstration that NPY changes in receptor diffusion and oligomeric state depend on early events in endocytosis. ► Design of a new GFP BiFC system for use in combination with FCS techniques. ► Isolation of the mobility and molecular brightness of defined receptor-arrestin complexes undergoing endocytosis.