What is FRET (Fluorescence/Forster Resonance Energy Transfer) primarily used for?

FRET, or Forster Resonance Energy Transfer, is primarily utilized to study interactions between molecular entities at very short ranges, typically within 1-10 nanometers of each other. The fundamental principle behind FRET is the non-radiative energy transfer that occurs when a donor fluorophore, when excited, can transfer its energy to a nearby acceptor fluorophore if they are in close proximity. This energy transfer is highly dependent on the distance between the two fluorophores and the overlap between the emission spectrum of the donor and the absorption spectrum of the acceptor.

When the donor is excited by a specific wavelength of light, if an acceptor fluorophore is within the right distance and orientation, some of the excited state energy from the donor can be transferred, leading to emission from the acceptor. This results in a measurable change in fluorescence intensity that can be quantitatively analyzed to infer the dynamics of biomolecular interactions, conformational changes, or even the localization of molecules within biological systems.

This unique ability to monitor interactions at the molecular level makes FRET an invaluable tool in biochemistry and cell biology research, particularly for understanding protein-protein interactions, studying conformational changes in proteins or nucleic acids, and investigating live-cell dynamics