Fluorescence correlation spectroscopy of finite-sized particles
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Updated: Jul 9, 2026

Dual-Color Fluorescence Cross-Correlation Spectroscopy to Study Protein-Protein Interaction and Protein Dynamics in Live Cells
Published on: December 11, 2021
Bin Wu1, Yan Chen, Joachim D Müller
1School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA. binwu@physics.umn.edu
Abstract:
A theory is presented to study fluorescence correlation spectroscopy for particles with size comparable to the beam waist of the observation volume. Analytical correlation curves are derived for some experimentally interesting particle geometries. It is found that the finiteness of the particle generally decreases the value of the correlation amplitude and increases the correlation time compared to a point particle model. Furthermore, not only the size but also the distribution of fluorophores affects the shape of the correlation function. This is experimentally demonstrated with surface and internally labeled fluorescent spheres. In addition, experiments are performed on fluorescent spheres of different radii to validate the model by comparing the results to theoretical predictions.
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