What is FRET?
FRET stands for Förster (or Fluorescence) Resonance Energy Transfer. Under certain conditions, if two fluorescent chemicals are very close together (generally around 1-10 nanometers), energy from one molecule (the donor) can be transferred to the other (the acceptor). The idea is illustrated in the figure to the right (from the Queens University Cancer Biology and Genetics web site). Cayenne fluorescent protein (CFP) is illuminated with an excitation light at a particular wavelength, in this case 458 nanometers (nm). The excitation will cause the CFP to glow (fluoresce) at another wavelength, in this case 480 nm. The excitation will not cause the yellow fluorescent protein (YFP) to fluoresce because YFP needs a different excitation wavelength. But if the CFP and YFP are very close together, the CFP will cause the YFP to glow. In this example, CFP acts as the donor, and YFP as the acceptor, because energy is transferred from CFP to YFP. Check out The University of Virginia Departments o
