Single Molecule FRET Combined with Defocus Imaging

Fluorescence resonance energy transfer (FRET) is a physical process where the excitation energy of a donor molecule is transferred to a neighboring acceptor molecule via dipole-dipole interaction when the donor and acceptor molecules approach within a few nano meters. FRET efficiency depends on an intermolecular distance between the donor and acceptor molecules. Therefore FRET is widely used to measure distances between specific positions of biomolecules or proteins at a nano scale and clarify their dynamics.