Cell-Surface ProteinProtein Interaction Analysis with Time-Resolved FRET and Snap-Tag Technologies

F�rster resonance energy transfer (FRET) is a proximity-dependent quantum effect that allows the measurement of protein interactions and conformational changes which are invisible to traditional forms of fluorescence or electron microscopy. However, FRET experiments often have difficulty detecting interactions that are transient and localized or occur in low abundance against a large background. This protocol describes a method of improving on the sensitivity and quantifiability of FRET experiments by using time-specific detection to isolate FRET-mediated acceptor emission from cross-talk excitation and all other sources of nonspecific fluorescence background.