Homo-FRET, detection

Exploration of collective effects in multiple transfers that appear when the donor and acceptor are the same molecules and display the so-called homotransfer. In this case, the presence of only one molecular quencher can quench fluorescence of the whole ensemble of emitters coupled by homotransfer [32]. The other possibility of using homo-FRET is the detection of intermolecular interactions by the decrease of anisotropy [33]. 

Finally, it should be noted that homo-FRET, which is just the exchange of energies between the same dyes, is undetected by common spectroscopic or lifetime measurements and needs the hetero-FRET probing for its detection. The Red-Edge effect allows the easy distinguishing of the decrease of anisotropy due to FRET (static effect) from that occurring due to rotational freedom of fluorophores (dynamic effect), which does not depend on excitation wavelength. 

Homo-FRET is a useful tool to study the interactions in living cells that can be detected by the decrease in anisotropy [106, 107]. Since commonly the donor and acceptor dipoles are not perfectly aligned in space, the energy transfer results in depolarization of acceptor emission. Imaging in polarized light can be provided both in confocal and time-resolved microscopies. However, a decrease of steady-state anisotropy can be observed not only due to homo-FRET, but also due to rotation of the fluorescence emitter. The only possibility of discriminating them in an unknown system is to use the variation of excitation wavelength and apply the... 

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