Diffusion and binding analyzed with combined point FRAP and FCS.

Area of Science:

• Cellular dynamics and biophysics
• Molecular imaging and spectroscopy

Background:

• Accurate quantification of biomolecule diffusion and binding in living cells is crucial for understanding cellular processes.
• Existing methods may lack precision or comprehensive modeling of molecular interactions.

Purpose of the Study:

• To develop and validate a novel 3D closed description model for point Fluorescence Recovery After Photobleaching (FRAP) data.
• To precisely quantify diffusion and reaction properties of biomolecules, including transient or long-term binding.

Main Methods:

• A novel closed description in 3D for point FRAP data, covering coupled reaction-diffusion schemes.
• Numerical solutions of differential equations to assess model feasibility.
• Application to EYFP in HeLa cells using integrated point FRAP and Fluorescence Correlation Spectroscopy (FCS).
• Analysis of exon-exon junction complex (EJC) components (REF2-II, Magoh) in MCF7 cells.

Main Results:

• The model's feasibility was confirmed through numerical solutions.
• Validation by comparison with FCS results demonstrated applicability.
• Significant improvement in results by considering diffusion during bleaching and global analysis of bleach times.
• Obtained diffusion and binding properties of EJC factors at specific nuclear localizations.

Conclusions:

• The developed point FRAP model offers precise quantification of biomolecular diffusion and binding.
• Considering diffusion during bleaching and employing global analysis improves FRAP data interpretation.
• Combining point FRAP and FCS provides a powerful approach for dissecting molecular dynamics in cells.