Forster-type resonant energy transfer

Fig. 4.1.17 Graphic illustration of Forster-type resonance energy transfer from aequorin to Aequorea GFP. In the vessel at left, a solution contains the molecules of aequorin and GFP randomly distributed in a low ionic strength buffer. The vessel at right contains a solution identical with the left, except that it contains some particles of DEAE cellulose. In the solution at right, the molecules of aequorin and GFP are coadsorbed on the surface of DEAE particles. Upon an addition of Ca2+, the solution at left emits blue light from aequorin (Xmax 465 nm), and the solution at right emits green light from GFP (Xmax 509 nm).

The Forster-type resonance energy transfer (FRET) has become a common practice in the study of macromolecular structures, conformational changes, in vitro and cellular complex formation, and so on [15]. Ullman introduced its use for clinical diagnostics as a way to make homogeneous immunoassays [16]. 

Time resolved fluorescence measurements have become an important tool in applied fluorescence spectroscopy. Recently, it has been pointed out that the controlled manipulation of fluorescence decay rates opens a new dimension in applied fluorescence spectroscopy. The fluorescence decay rate depends on two independent contributions, the pure rachative rate and the nonradiative rate. The latter one can be influenced by the well known Forster-type resonant energy transfer processes, while the radiative rate can be changed if the molecules are embedded or close to media comprising a dielectric constant markedly different from vacuum. Especially metal nanostructures have been used to alter both decay paths of fluorescent molecules. Apart from a change of those two rates, the absorption cross-section might also be altered. 

Fluorescence resonance energy transfer (FRET) experiments commonly use the fluorescent spectrum and relaxation times of the Forster donor and acceptor chromophores to find the distances between fluorescent dyes at labeled sites in protein, DNA, RNA, etc. FRET is a type of spectroscopic ruler . The computation uses either experimental quantum yields or relaxation lifetimes to calculate the efficiency of resonance energy transfer Ej. 

Type 1 Forster (or fluorescent) resonance energy transfer (FRET)-based biosensors Type 2 Bimolecular fluorescence complementation (BiFC)-based biosensors Type 3 Single FP-based biosensors... 

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