Förster resonance energy transfer (FRET) is a phenomenon in which nonradiative transfer of energy occurs between donor and acceptor molecules in close proximity (2-7 nm). Since FRET efficiency decays as a function of the inverse sixth power of the distance between the donor and acceptor, this phenomenon can be leveraged to provide solid evidence of the proximity between a donor and acceptor in a FRET pair.
In FRET, the donor molecule is returned to a ground state without fluorescence emission while the acceptor molecule is raised to an excited state. Upon decay of the acceptor's excited state, fluorescence emission may be witnessed. Thus, an increase in FRET between label molecules will result in a decrease in donor emission and a simultaneous increase in acceptor emission. Using methods of FRET detection, interactions between molecules can be monitored in subcellular compartments and tracked as a function of time.
Photometrics CCD cameras deliver the superb low-noise performance needed to provide a perfect platform for FRET imaging under low-light, slow-scan conditions. Furthermore, the wide dynamic range of Photometrics cameras extends application flexibility by permitting a greater span of intensity values to be quantified in the same image. For higher-speed acquisition under the low-light conditions typical of FRET imaging, Photometrics EMCCD cameras offer a number of exceptional solutions.