Reversible Electronic Energy Transfer (Homo-FRET) in Cyclic Molecular and Supramolecular Systems: Fluorescence Anisotropy Decays for the Isotropic Interaction

Abstract

Reversible electronic energy transfer (homo-FRET) in cyclic multichromophoric systems is studied for sets of n identical fluorophores arranged in regular polygons (triangle, square, pentagon, etc.). A general analytic expression for the anisotropy decay is obtained for a regular polygon of any order, under the assumptions of isotropic interaction and nearest-neighbor FRET. A graphical way of connecting the decay form and polygon geometry based on the Frost circle is also presented. The consequences of the relaxation of these assumptions on the anisotropy decay are also discussed and analyzed in detail for the heptagon.

Pursuing excitonic energy transfer with programmable DNA-based optical breadboards

“…This was another crucial result as it confirmed the viability of modeling for extended homoFRET relays. 147,323 Another important point realized was that initial dye selection was critical; efficient homoFRET relays (i.e., with long excited state lifetimes and large homo-R 0 ) improve transfer efficiency even over the directionality provided by heteroFRET. The efficiency of the homoFRET relay module could be even further improved by modification of the environment around the DNA nanostructure when depositing it in polyvinyl alcohol (PVA) films as well as cooling to cryogenic temperatures; this resulted in up to a 2.5-fold increase in E FRET by removing many of the competing, parasitic, and non-radiative decay pathways.…”

“…This was another crucial result as it confirmed the viability of modeling for extended homoFRET relays. 147,323 Another important point realized was that initial dye selection was critical; efficient homoFRET relays ( i.e. , with long excited state lifetimes and large homo- R 0 ) improve transfer efficiency even over the directionality provided by heteroFRET.…”

“… 322 This reflects that it is a stochastic process in which an object moves in a series of random steps. Assuming symmetric positioning of the fluorophores, the probability of moving to any contiguous position is therefore equivalent, 323 and this results in the lack of ET directionality within homoFRET systems. The critical point to be appreciated when designing homoFRET sections within a DNA structure is that the positive attributes, including large absorption cross-sections and high transfer efficiency increase with the number of fluorophores present, which will in turn, minimize the probability of any particular fluorophore being excited while increasing the potential number of ET steps along with possibilities of random directionality.…”