Abstract
Two-dimensional polarization imaging (2D POLIM) is an experimental method where correlations between fluorescence excitation- and fluorescence emission-polarization properties are measured. One way to analyze 2D POLIM data is to apply a so-called single funnel approximation (SFA). The SFA allows for quantitative assessment of energy transfer between chromophores with identical spectra [homo-FRET (Förster resonance energy transfer)]. In this paper, we run a series of computer experiments to investigate the applicability of the analysis based on the SFA to various systems ranging from single multichromophoric systems to isotropic ensembles. By setting various scenarios of energy transfer between individual chromophores within a single object, we were able to define the borders of the practical application of SFA. It allowed us to reach a more comprehensive interpretation of the experimental data in terms of uncovering the internal arrangement of chromophores in the system and energy transfer between them. We also found that the SFA can always formally explain the data for isotropic ensembles and derived a formula connecting the energy funneling efficiency parameter and traditional fluorescence anisotropy.
Highlights
Excitation energy transfer [EET, i.e., energy transfer from a donor (D) in the excited state to an acceptor (A) in the ground state]1,2 is a common process between closely located chromophores in concentrated solutions of dyes, in molecular crystals, and within multichromophoric systems, such as pi-conjugated polymers,3,4 natural light-harvesting complexes,5 and molecular aggregates.6 EET is widely used in biological science as an indicator of the distance between fluorescent labels.7,8 Förster resonance energy transfer (FRET) is EET via a weak dipole–dipole coupling.2When the donor and the acceptor have distinguishable absorption and fluorescence spectra, EET is called hetero-FRET
We present a series of computer experiments where we apply the single funnel approximation (SFA) approach to diversely organized multichromophoric systems with different scenarios of internal EET
With an increase in the number of subsystems, we found that the SFA methodology always works well for isotropic ensembled samples and that the energy transfer efficiency parameter has strict mathematical relations to classical fluorescence anisotropy
Summary
Excitation energy transfer [EET, i.e., energy transfer from a donor (D) in the excited state to an acceptor (A) in the ground state]1,2 is a common process between closely located chromophores in concentrated solutions of dyes, in molecular crystals, and within multichromophoric systems (fluorescent macromolecules), such as pi-conjugated polymers, natural light-harvesting complexes, and molecular aggregates. EET is widely used in biological science as an indicator of the distance between fluorescent labels. Förster resonance energy transfer (FRET) is EET via a weak dipole–dipole coupling.2When the donor and the acceptor have distinguishable absorption and fluorescence spectra, EET is called hetero-FRET. Excitation energy transfer [EET, i.e., energy transfer from a donor (D) in the excited state to an acceptor (A) in the ground state]1,2 is a common process between closely located chromophores in concentrated solutions of dyes, in molecular crystals, and within multichromophoric systems (fluorescent macromolecules), such as pi-conjugated polymers, natural light-harvesting complexes, and molecular aggregates.. EET is widely used in biological science as an indicator of the distance between fluorescent labels.. When the donor and the acceptor have distinguishable absorption and fluorescence spectra, EET is called hetero-FRET. Hetero-FRET can be studied in great detail using steady-state and time-resolved fluorescence spectroscopy because of substantial energetic/spectroscopic differences between the donor and the acceptor.. The efficiency of hetero-FRET can be assessed by comparing the fluorescence intensities of the spectrally resolved donor and acceptor. Hetero-FRET can be studied in great detail using steady-state and time-resolved fluorescence spectroscopy because of substantial energetic/spectroscopic differences between the donor and the acceptor. For example, the efficiency of hetero-FRET can be assessed by comparing the fluorescence intensities of the spectrally resolved donor and acceptor.
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