Anomalous surplus energy transfer observed with multiple FRET acceptors

Area of Science:

• Biophysics
• Molecular Biology
• Fluorescence Spectroscopy

Background:

• Förster resonance energy transfer (FRET) describes energy transfer between donor and acceptor fluorophores via dipole-dipole interactions.
• Current FRET models primarily focus on single donor-acceptor pairs.
• Understanding FRET with multiple acceptors is crucial for applications like studying protein-protein interactions in cells.

Purpose of the Study:

• To investigate how Förster resonance energy transfer (FRET) efficiency is affected by the presence of multiple acceptors.
• To test the validity of existing FRET kinetic models when multiple acceptors are involved.

Main Methods:

• Ensemble FRET efficiency was measured in constructs with one donor and multiple acceptors (two or three).
• Individual donor-acceptor FRET transfer rates were determined by systematically mutating acceptors.
• Experimental FRET efficiencies were compared to predictions from a kinetic model.

Main Results:

• Observed FRET efficiency in constructs with multiple acceptors was significantly higher than predicted by summing individual transfer rates.
• This indicates a deviation from the standard FRET kinetic model under multi-acceptor conditions.

Conclusions:

• The discrepancy suggests the existence of an additional energy transfer pathway when multiple acceptors are present.
• Alternatively, a fundamental assumption within the current FRET kinetic model may be incorrect.