Protein-protein interactions determined by fluorescence correlation spectroscopy.

Fluorescence correlation spectroscopy (FCS) is an emerging technique where the interaction between biomolecules is detected through their correlated motion. It offers the advantage of high (single-molecule) sensitivity; independence of molecular orientation or distance; and simultaneous measurement of molecular interactions, concentrations, and mobilities. Here we introduce the principle of the technique and review some recent examples from the literature where FCS has been used with autofluorescent proteins for measuring protein-protein interactions and mobilities in living cells.