Theory of sample translation in fluorescence correlation spectroscopy

Area of Science:

• Biophysics
• Chemical Kinetics
• Spectroscopy

Background:

• Fluorescence Correlation Spectroscopy (FCS) is a powerful technique for studying molecular dynamics.
• New applications necessitate sample translation through a focused laser beam.
• Understanding the impact of translation on FCS data is crucial for experimental design.

Purpose of the Study:

• To investigate the effect of lateral sample translation on the FCS autocorrelation function.
• To identify conditions under which the FCS autocorrelation function simplifies.
• To facilitate data analysis in translation-based FCS experiments.

Main Methods:

• Theoretical examination of the FCS autocorrelation function under lateral sample translation.
• Analysis of the relationship between transport coefficients, reaction rate constants, and the autocorrelation function.

Main Results:

• The FCS autocorrelation function can simplify into a product of two independent functions under specific conditions.
• One function depends solely on transport coefficients (e.g., diffusion).
• The other function depends solely on chemical reaction rate constants.

Conclusions:

• Lateral sample translation in FCS can lead to a mathematically simplified autocorrelation function.
• This simplification is contingent upon the lateral diffusion coefficients of fluorescent species meeting certain criteria.
• The simplified form enables more manageable data analysis for novel FCS applications involving sample translation.