Förster resonance energy transfer (FRET) is a mechanism describing the transfer of energy between two closely spaced fluorescent molecules. This phenomenon is named after the German scientist Theodor Förster, who first described it in the context of dipole-dipole interactions between molecules.
In FRET, two fluorophores (molecules that fluoresce, or emit light, upon excitation) are involved: a donor and an acceptor. The donor fluorophore absorbs a photon and, instead of emitting a fluorescence photon, transfers its energy to the acceptor fluorophore through non-radiative dipole-dipole coupling. The acceptor then emits light at its characteristic wavelength.
Several conditions must be met for FRET to occur effectively:
Overlap of emission and absorption spectra: The emission spectrum of the donor should overlap with the absorption spectrum of the acceptor. This ensures efficient energy transfer.
Proximity: The donor and acceptor molecules must be in close spatial proximity, typically within a range of 1 to 10 nanometers.
Orientation of dipoles: The orientation of the donor and acceptor dipoles should be favorable for efficient energy transfer.
FRET is widely used as a tool in molecular and cell biology for studying interactions between biomolecules, such as proteins or nucleic acids. It can provide information about distances and interactions at the nanoscale level. FRET is employed in various applications, including fluorescence microscopy, flow cytometry, and techniques like fluorescence resonance energy transfer (FRET) microscopy. By monitoring changes in FRET signals, researchers can gain insights into molecular conformation changes, protein-protein interactions, and dynamic processes within biological systems.