Lorentzian spatial intensity distribution in one-photon fluorescence correlation spectroscopy.

Area of Science:

• Physical Chemistry
• Spectroscopy
• Biophysics

Background:

• Fluorescence correlation spectroscopy (FCS) relies on autocorrelation function analysis.
• Standard FCS analysis often assumes Gaussian spatial intensity distributions.
• Limitations exist when experimental conditions deviate from Gaussian assumptions.

Purpose of the Study:

• To extend autocorrelation function analysis in FCS to Lorentzian intensity distributions.
• To develop and validate an analytical solution for diffusion in Lorentzian profiles.
• To broaden the applicability of analytical FCS methods.

Main Methods:

• Theoretical application of autocorrelation function theory to Lorentzian distributions.
• Derivation of an analytical solution for diffusion.
• Experimental validation using a confocal setup with an enlarged detector aperture.
• Fitting experimental data to the derived autocorrelation function.

Main Results:

• An analytical solution for the autocorrelation function of diffusion in Lorentzian distributions was successfully deduced.
• Experimental data fitted well to the derived function, providing estimates of the spatial distribution.
• Comparison with molecular detection efficiency simulations confirmed the estimates.

Conclusions:

• Lorentzian intensity distributions can be effectively analyzed using FCS.
• This approach complements Gaussian models, expanding the utility of analytical correlation functions.
• The study enhances the versatility of FCS for various experimental setups.