Molecular aggregation characterized by high order autocorrelation in fluorescence correlation spectroscopy

Area of Science:

• Physical Chemistry
• Biophysics
• Spectroscopy

Background:

• Fluorescence correlation spectroscopy (FCS) is a powerful technique for studying molecular dynamics.
• Investigating molecular aggregation is crucial for understanding biological processes and material properties.
• Existing methods may have limitations in characterizing complex aggregate structures.

Purpose of the Study:

• To introduce and validate a high-order autocorrelation method for fluorescence correlation spectroscopy.
• To enable the quantitative analysis of molecular aggregation in fluorescent samples.
• To provide a tool for characterizing fluorescently labeled biological molecules.

Main Methods:

• Derivation of theoretical expressions for high-order fluorescence fluctuation autocorrelation functions (gm,n(tau)).
• Utilizing Gm,n(0) values to determine number densities and relative fluorescence yields of aggregates.
• Application of the method to 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate in water and ethanol.

Main Results:

• Successful derivation of theoretical expressions for gm,n(tau).
• Demonstration of methods to quantify aggregate number densities and fluorescence yields.
• Experimental validation using a model fluorescent molecule in different solvents.

Conclusions:

• High-order autocorrelation in FCS is effective for investigating molecular aggregation.
• The developed method allows for the characterization of aggregate size and concentration.
• This technique holds promise for studying aggregates of fluorescently labeled biological molecules, such as cell surface receptors.