Fluorescence correlation spectroscopy of finite-sized particles.

Area of Science:

• Physical Chemistry
• Spectroscopy
• Nanotechnology

Background:

• Fluorescence Correlation Spectroscopy (FCS) is a powerful technique for studying molecular dynamics.
• Traditional FCS models often assume point-like particles, which can lead to inaccuracies when analyzing larger structures.

Purpose of the Study:

• To develop a theoretical framework for FCS analysis of particles with dimensions comparable to the observation volume's beam waist.
• To investigate the influence of particle size and internal/surface fluorophore distribution on FCS measurements.

Main Methods:

• Derivation of analytical correlation curves for various particle geometries.
• Experimental validation using fluorescent spheres with controlled size and labeling (surface vs. internal).

Main Results:

• Finite particle size generally reduces correlation amplitude and increases correlation time compared to point-particle models.
• Fluorophore distribution (surface vs. internal) demonstrably alters the correlation function shape.
• Experimental results align with theoretical predictions for spheres of varying radii.

Conclusions:

• The developed theory provides a more accurate description of FCS for finite-sized particles.
• Accurate interpretation of FCS data requires consideration of particle dimensions and fluorophore arrangement.
• This work enhances the application of FCS in fields like nanotechnology and biophysics.