Resonance energy transfer distance dependence

Deniz A A, Dahan M, Grunwell J R, Ha T, Faulhaber A E, Chemla D S, Weiss S and Schultz P G 1999 Single-pair fluorescence resonance energy transfer on freely diffusing molecules observation of Forster distance dependence and subpopulations Proc. Natl Acad. Sc/. USA 96 3670-5... 

The sixth power dependence explains why resonance energy transfer is most sensitive to the donor-acceptor distance when this distance is comparable to the Forster critical radius. 

INTRINSIC AND EXTRINSIC FLUORESCENCE. Intrinsic fluorescence refers to the fluorescence of the macromolecule itself, and in the case of proteins this typically involves emission from tyrosinyl and tryptopha-nyl residues, with the latter dominating if excitation is carried out at 280 nm. The distance for tyrosine-to-tryp-tophan resonance energy transfer is approximately 14 A, suggesting that this mode of tyrosine fluorescence quenching should occur efficiently in most proteins. Moreover, tyrosine fluorescence is quenched whenever nearby bases (such as carboxylate anions) accept the phenolic proton of tyrosine during the excited state lifetime. To examine tryptophan fluorescence only, one typically excites at 295 nm, where tyrosine weakly absorbs. [Note While the phenolate ion of tyrosine absorbs around 293 nm, its high pXa of 10-11 in proteins typically renders its concentration too low to be of practical concern.] The tryptophan emission is maximal at 340-350 nm, depending on the local environment around this intrinsic fluorophore. 

Fluorescence resonance energy transfer (FRET) is a spectroscopic means of obtaining distance information over a range up to 80 A in solution. It is based on the dipolar coupling between the electronic transition moments of a donor and acceptor fluorophore attached at known positions on the RNA species of interest. It can be applied in ensembles of molecules, either by steady-state fluorescence or by lifetime measurements, but it is also very appropriate for single-molecule studies. In addition to the provision of distance information, recent studies have emphasized the orientation dependence of energy transfer. 

Deniz, A. A., Dahan, M., Gmnwell, J. R., Ha, T., Faulhaber, A. E., Chemla, D. S., Weiss, S., and Schultz, P. G. (1999). Single-pair fluorescence resonance energy transfer on freely diffusing molecules Observation of Forster distance dependence and subpopulations. Proc. Natl. Acad. Sci. USA 96, 3670—3675. 

The first term is due to spontaneous radiative relaxation and nonradiative phonon relaxation as described in eq. (13), where / , is the probability of ion i in the excited state. The second term is due to energy transfer induced by ion-ion interaction, where W es and W A are rates of resonant and phonon-assistant energy transfer, which depend on distance between donor and acceptor RtJ. For resonant energy transfer... 

Optical excitation transfer can occur between molecules as much as 10 nm apart when the dipole-dipole coupling between molecules (one excited "photon donor" chromophore, the other an unexcited "photon acceptor" chromophore) by a mechanism known as Forster79 resonance transfer or fluorescence resonance energy transfer (FRET) its characteristic dependence on the distance r between the two chromophores is r 6. 

Saini S, Singh H, Bagghi B. Fluorescence resonance energy transfer (FRET) in chemistry and biology Non-Forster distance dependence of the FRET rate. J. Chem. Sci. 2006 118 23-35. Schrodinger E. Energieaustausch nach der Wellenmechanik. Ann. Physik. 1927 83 956-968. 

It is useful in discussion of weak coupling between nanostructures to remember the nonradiative mechanism of Forster resonant energy transfer from an excited molecule (a donor) to some other molecule (an acceptor) which can be in the ground or in an excited state. The probability of such a transfer is determined by the Coulomb nonretarded (instantaneous) dipole-dipole interaction between molecules and is proportional to Rp/R6 where Rp is the Forster radius and R is the distance between molecules. For organic materials the Forster radius is usually about several nanometers and strongly depends on the overlapping... 

In the present paper, we report on observation of the pronounced enhancement of photoluminescence of semiconductor nanocrystals near nanostructured metal surfaces which is shown to depend essentially on nanocrystal-metal spacing. Unlike conventional SERS, the surface enhanced PL should exhibit non-monotonous character with distance between emitting dipole (QD) and metal surface (Au colloid). The reason is that at smallest distances when QDs and colloidal particles are in close contact, the QD emission should be damped due to resonant energy transfer (RET) from photoexcited QDs to metal colloidal nanoparticles. Enhancement of photoluminescence (PL) is possibly promoted by surface plasmons excited in the metal. So, at a certain distance the enhanced QD emission would exhibit a maximum. We use a polyelectrolyte multilayers as the most appropriate... 

Fluorescence resonance energy transfer (FRET) is a powerful method for the determination of macromolecular conformation and folding in solution [188, 190-194]. The method relies on the incorporation into the macromolecule of a donor dye molecule and an acceptor dye molecule that undergo singlet-singlet Forster energy transfer, which is distance dependent over the 10-100 A range [190-194]. Early work in the field focused on probes noncovalently associated with the macromolecule, but covalent attachment of probes, while harder to do,... 

The distance between two different fiuorophore molecules can be probed by fluorescence resonance energy transfer (FRET) [308]. The energy transfer rate from the donor to the aeeeptor depends on the sixth power of the distance. FRET becomes noticeable at distanees on the order of a few mn and therefore occurs only if the donor and aeeeptor are physically linked. With FLIM techniques, FRET results are obtained from a single lifetime image of the donor [15, 32, 38, 61, 62, 63, 73, 80, 93, 147, 209, 405, 508]. 

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