Analytical form of the autocorrelation function for the fluorescence correlation spectroscopy

Area of Science:

• Physical Chemistry
• Chemical Physics
• Spectroscopy

Background:

• Fluorescence correlation spectroscopy (FCS) is vital for studying molecular dynamics.
• Accurate interpretation of FCS data relies on appropriate autocorrelation function models.
• Modeling complex systems involving diffusion and reactions remains a challenge.

Purpose of the Study:

• To develop a new analytical approximation for the autocorrelation function in FCS.
• To accurately model systems where fluorescent molecules diffuse and undergo binary reactions with massive particles (e.g., micelles).
• To provide a smooth interpolation between fast and slow reaction limits.

Main Methods:

• Theoretical derivation using the general formalism of FCS.
• Development of a novel analytical approximation for the autocorrelation function.
• Application of the derived model to experimental FCS data of micelle-dye interactions.

Main Results:

• A new analytical approximation for the autocorrelation function was derived.
• The approximation successfully bridges the gap between fast and slow reaction regimes.
• Experimental validation using FCS studies of noncovalent micelle-dye interactions confirmed the model's utility.

Conclusions:

• The new FCS model enhances the analysis of systems with simultaneous diffusion and binary reactions.
• This theoretical advancement improves the quantitative understanding of molecular interactions in complex media.
• The model offers a more robust tool for researchers studying diffusion-reaction dynamics.