Imaging protein-protein interactions by fluorescence resonance energy transfer (FRET) microscopy.

FRET microscopy enables the detection of different biochemical states of proteins in cells. The use of fluorescence in the detection of proteins, by chemical modification, by immunofluorescence, or by genetic encoding of a green fluorescent protein fusion protein, provides more information than just the location of the protein in the cell. The properties of the fluorophore can be exploited to extract information on protein-protein interactions. A straightforward, quantitative imaging approach is presented to measure FRET that is based on internal calibration by acceptor photobleaching.