Fluorescence correlation spectroscopy is a noninvasive technique for studying ligand-receptor interactions in live cells as shown for β2-adrenergic receptors

Fluorescence correlation spectroscopy (FCS) is a noninvasive technique for high-resolution spatial and temporal analysis of extremely low concentrated biomolecules. FCS is based on measuring fluctuations in fluorescence intensity caused by single fluorescently labelled molecules diffusing through a tiny confocal volume element, which is generated by a focused laser beam with a defined detection volume size of about 1 fL. The photons emitted by the illuminated molecules within this focus are recorded in a time-resolved manner via single-photon detection avalanche photo-diodes. The recorded fluorescence fluctuatio…