ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
Excitation energy transfer in a system where the spatial relationship between the donor and acceptor is not fixed generally leads to a nonexponential decay of donor fluorescence. A single-exponential decay, however, is expected as a limiting form when the diffusion of the donors and/or acceptors is sufficiently rapid. The exponential character at the rapid diffusion limit will greatly facilitate the analysis of experimental data. In this paper a theoretical framework is presented that allows the calculation of the criterion for the rapid diffusion limit. Explicit criteria are given for various donor–acceptor geometries, all for the case of energy transfer via the resonance interaction of the Förster type. The criteria, except for the cases of densely distributed acceptors under a wide surface, have a common form DτDa4/R0(very-much-greater-than)λ, where τD is the lifetime of donor fluorescence in the absence of acceptors, D is the sum of diffusion coefficients of the donor and acceptor, a is the distance of closest approach between the donor and acceptor, R0 is the critical distance for energy transfer, and λ is a geometrical constant with a value less than one. Exponential decays are not easily obtained when acceptors are densely distributed under a wide surface. The results are compared with the criterion given earlier by Thomas et al. [D. D. Thomas, W. F. Carlsen, and L. Stryer, Proc. Natl. Acad. Sci. U.S.A. 75, 5746 (1978)]. Experimental aspects, such as the effect of heterogeneity in a sample, are also discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.451986
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