Forster distance

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... 

Patterson, G. H., Piston, D. W. and Barisas, B. G. (2000). Forster distances between green fluorescent protein pairs. Anal. Biochem. 284, 438-40. 

The PAH polymeric layer played an important role in our fluorescence sensor design. First, its positive charges enabled the deposition of anionic dextran that was labeled with the pH indicator fluorescein on the surface of the nanoparticles. More importantly, the PAH polymeric layer separated between the fluorescein molecules and the metal particle. In fact, the thickness of the polymeric layer was over 10 nm, which is larger than the Forster distance required for efficient energy transfer between the fluorophore and the metallic gold particles. 

A simplified theory of FRET is sufficient to describe affinity sensors used in fluorescence transduction of glucose concentrations. A key quantity that describes the potential FRET interaction between a donor-acceptor pair is the Forster distance, Ro, the distance at which half the donor molecules are quenched by the acceptor molecules. Ro is proportional to several parameters of the fluorophores, in accordance with Ro = K6 Jx2n 4 cf>DJ l], where K is a constant. The variable k2 refers to the relative spatial orientation of the dipoles of D and A, taking on values from 0 to 4 for completely orthogonal dipoles and collinear and parallel transitional dipoles k2 = 4,... 

The energy transfer efficiency is directly proportional to the spectral overlap, and this also directly affects the Forster distance of a particular D-A pair. Figure 10.5 shows the D and A excitation and emission spectra in an ideal energy transfer system, wherein D and A have very distinct excitation spectra (so that A can only be excited by energy transfer and not by direct photon absorption at the wavelengths used to excite D)—the D emission and A excitation spectra overlap strongly—and the D and A emission maxima are well separated, so that the quenching of D fluorescence and the enhancement of A fluorescence can be individually measured.98 99... 

Figure 10.6 Distance-dependent efficiency of energy transfer between donor and acceptor molecules, where r is the intermolecular distance and R0 is the Forster distance for the pair of molecules.

Another way to express the rate introduces Rq, the Forster distance or critical transfer distance, at which the EET efficiency is 0.5 ... 

Figure 8.1 The dependence of FRET efficiency (Efret) as a function of the separation of donor and acceptor fluorophores (rDA) normahzed to the Forster distance Ro (Eq. (8.2)), assuming a constant value of R0.

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 Forster distance R0 (A) at which the energy-transfer efficiency is 50% is calculated using Equation (14.5) ... 

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. 

By attaching a donor-acceptor TMR/Texas Red pair of dye molecules site-specifically to noninterfering sites on the enzyme (Fig. 24.1a) [12], we were able to measure the hinge-bending motions of the enzyme by monitoring the donor-acceptor emission intensities (Fig. 24.1b) as a function of time. We estimated the Forster distance Rq [19] of a TMR/Texas Red pair to be about... 

Analysis of the data showed the presence of a fast intramolecular photoinduced energy transfer process from pyrene -perylene to pyrene-perylene (ken 6.2 x 109 s 1) with a high yield (>90%), followed by efficient intramolecular electron transfer from pyrene-perylene to pyrene +-perylene (70%, ket 6.6 x 109s 1). Both processes occur from the pyrene unit to the perylene moiety. The Forster distance was calculated to be 3.4 nm and the corresponding donor-acceptor distance was calculated from the energy transfer rate as 0.9 nm. No indications for energy hopping between different pyrene moieties were observed. 

Referring to the spectra of anthracene (Figure 2.11) and biacetyl (Figure 6.5), give a quick-and-dirty estimate of the critical Forster distance R0 (Equation 2.37) for FRET... 

Roller, R. S., Winnik, M. A., The Determination of the Forster Distance (Rf) for Phenanthrene and Anthracene Derivatives in Poly(methyl methacrylate) Films, J. Phys. Chem. B 2005,109, 12261 12269. 

The Forster distance Rq (in A) at which the efficiency of energy transfer is 50% was calculated with equation 6.12 ... 

Typical Forster distances separate the donor and acceptor range between 2 and 8 nm. FRET signals are detectable up to about twice the Forster distance separating the donor-acceptor pair. If, however, the acceptor unit is tethered to n donor sites, the FRET efficiency increases and is given by Eq. (6.4) ... 

The use of RET to measure protein association and distance is shown in Figure 1.23 for two monom s which associate to form a dimer. Suppose one monomer contains a tryptophan (trp) residue, and the other a dansyl group. The Forster distance is determined by the spectral overlap of the trp donor emission with the dansyl acceptor absorption. Upon association, RET will occur, which decreases the intensity of the donor emission (Figure 1.23). The extent of donor quenching can be used to calculate the donor-to-acceptor distance in the dimer (Eq. [1.12]). It is also important to notice that RET provides a method to measure protein association because it occurs whenever the donor and acceptor are within the Forster distance. 

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