Förster resonance energy transfer (FRET) is a phenomenon in which energy is transferred between two fluorescent molecules that are in close proximity to each other. FRET is a powerful tool for studying molecular interactions and conformational changes in biological samples. Here are the basic principles of FRET:
- Excitation: FRET requires two fluorescent molecules, a donor and an acceptor. The donor molecule is excited by a light source, typically a laser or a lamp, at a specific wavelength. The donor molecule absorbs the excitation energy and becomes excited to a higher energy state.
- Energy transfer: If the acceptor molecule is in close proximity to the excited donor molecule, the excited donor can transfer its energy to the acceptor molecule without emitting light. This energy transfer occurs through dipole-dipole coupling, also known as resonance energy transfer.
- Emission: The acceptor molecule then emits light at a longer wavelength, producing a characteristic emission spectrum. The amount of energy transfer depends on the distance between the donor and acceptor molecules, as well as their orientation and spectral overlap.
- Efficiency: FRET efficiency is a measure of the amount of energy transfer that occurs between the donor and acceptor molecules. It is calculated as the ratio of the acceptor fluorescence intensity to the donor fluorescence intensity, with and without the acceptor molecule present.
FRET can be used to study a wide range of molecular interactions, such as protein-protein interactions, protein-DNA interactions, and protein-lipid interactions. It can also be used to study conformational changes in proteins, such as changes in structure or dynamics. FRET can be performed in solution or in live cells using fluorescent probes and dyes that are specifically designed for FRET measurements. FRET is a valuable tool in biochemistry, biophysics, and cell biology research, and has applications in drug discovery and development.