Designing matrix models for fluorescence energy transfer between moving donors and acceptors

Area of Science:

• Photophysics and Molecular Dynamics
• Theoretical Chemistry
• Biophysical Modeling

Background:

• Donor-acceptor systems often exhibit coupled fluorescence energy transfer (FRET) and molecular motion.
• Accurate modeling requires accounting for both FRET and dynamics without simplifying assumptions.
• Distinguishing between discrete (jumping) and continuous (diffusion) motion is crucial for understanding system dynamics.

Purpose of the Study:

• To develop a theoretical modeling framework for systems with simultaneous FRET and motion.
• To apply the framework to model donor-acceptor systems with rotational and translational dynamics.
• To analyze time-resolved FRET data without restrictive assumptions on motional averaging and orientation.

Main Methods:

• A state-transition model was developed, defining system states by coordinates and conditions.
• Rates of transition between states were used to describe system evolution over time.
• Fluorescence intensities and anisotropies were calculated by solving eigensystems for example systems.

Main Results:

• The model successfully simulates FRET and motion in various donor-acceptor systems.
• Calculated fluorescence quantities depend on the size of motional steps only when FRET occurs.
• The dependence of fluorescence on motional step size differentiates between jumping and diffusion dynamics.

Conclusions:

• The proposed method provides a versatile approach for analyzing time-resolved FRET data.
• FRET studies can elucidate the nature of molecular dynamics, distinguishing discrete jumps from diffusion.
• This framework aids in understanding the dynamics of complex systems like proteins.