What are the principles of FRET?

FRET is a physical interaction between molecules or atoms, where energy from an excited donor molecule is transferred to an acceptor molecule through long-range coupling of their dipoles. This transfer occurs when the donor and acceptor are within 8 to 10 nanometers of each other or less. In protein interaction studies, donor and acceptor fluorophores are attached to the proteins of interest, either through direct fusion or antibody labeling. FRET is detected by a decrease in donor fluorescence and an increase in acceptor fluorescence emission. However, FRET provides qualitative rather than quantitative information due to the precise distance required for a FRET signal and limitations in signal-to-noise ratio in cell biology applications.