Hetero-FRET

Tramier M, Gautier I, Piolot T, Ravalet S, Kemnitz K, Coppey J, Durieux C, Mignotte V, Coppey-Moisan M (2002) Picosecond-hetero-FRET microscopy to probe protein-protein interactions in live cells. Biophys J 83 3570-3577... 

The collective effects of directed energy flow can be strongly enhanced when the dyes playing the role of donors and acceptors are different and optimally selected. The hetero-FRET (described in Sect. 3.2) occurring within an ensemble of dissimilar molecules allows many possibilities for this. The transfer and the quenching... 

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. 

Selection of the most convenient excitation wavelength and shifting of wavelength in a broader range using cascade hetero-FRET. 

M. Tramier, I. Gautier, T. Piolot, S. Ravalet, K. Kemnitz, J. Coppey, C. Durieux, V. Mignotte, M. Coppey-Moisan, Pieoseeond-hetero-FRET microscopy to probe protein-protein interaetions in live eells, Biophys. J. 83, 3570-3577 (2002)... 

In the substrate, the fluorescence of the donor is quenched by the quenching label in close proximity. Upon cleavage of the substrate by the protease, this proximity is lost and a strong increase in fluorescence can be recorded. Table 2.3 summarizes a selection of fluorescence donor and acceptor pairs frequently used for protease activity assays based on a FRET quench readout. In principle, the FRET quench effect can be achieved by labeling the substrate with two different dyes with overlapping spectra (hetero-double labeling). 

These FRET half-Uves were found to increase more dramatically with the increase in the concentration for pyrogaUol[4]arene hexamers than for the resor-cin[4]arene hexamers. In addition, the FRET experiments also corroborated what was previously known from diffusirMi NMR Pyrogallol[4]arene hexamers are more stable than resorcin[4]arene hexamers and form both in dry and in water-samrated organic solvents, whereas resorcin[4]arene hexamers rally form in water-samrated organic solvents [19, 20, 41]. These results showed that similar conclusions are reached from diffusion NMR [19, 20] and FRET experiments [41]. It should be noted that in the gas phase hetero-hexamers of resorcin[4]arenes and pyrogallol[4] arenes were found [30], a fact that is not easy to reconcile with solution data. In the gas phase, a charged ruthenium complex was added to the solution to allow detection of the hexameric capsule by the MS detector. This ruthenium complex could not be encapsulated in any of these hexamers in solution. In other dimeric cpasules, however, hetero-capsules are observed in solution. For example, heterodimers are observed in which resorcin [4]arene is, in fact, one panel of the heterodimer [42]. 

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