Spatially Multiplexed Imaging: Fluorescence Correlation Spectroscopy for Efficient Measurement of Molecular Diffusion...

Area of Science:

• Biophysics
• Surface Science
• Spectroscopy

Background:

• Fluorescence Correlation Spectroscopy (FCS) analyzes intensity fluctuations to study molecular dynamics at interfaces.
• Traditional FCS requires time-averaging for low signal-to-noise ratios, limiting measurement speed.
• Electron-multiplying charge-coupled device (EM-CCD) cameras enable imaging-based FCS (Imaging-FCS).

Purpose of the Study:

• To exploit the spatial multiplexing advantage of Imaging-FCS for enhanced molecular diffusion measurements.
• To improve signal-to-noise ratios and reduce measurement times at interfaces.
• To validate the multiplexed Imaging-FCS approach for determining molecular diffusion rates.

Main Methods:

• Utilized Imaging-FCS with EM-CCD detectors to acquire fluorescence data from multiple addressable areas simultaneously.
• Employed spatial multiplexing by averaging autocorrelation traces from multiple surface areas.
• Measured the diffusion of 1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine perchlorate (DiI) on a C18-modified interface.

Main Results:

• Spatial multiplexing in Imaging-FCS achieved an eightyfold time saving to reach equivalent signal-to-noise ratios.
• Demonstrated accurate measurement of molecular diffusion rates using the multiplexed method.
• Overcame limitations of slow thermal recovery in EM-CCD detectors through parallel data acquisition.

Conclusions:

• Spatial multiplexing is a powerful strategy to accelerate Imaging-FCS measurements.
• Imaging-FCS offers significant advantages over traditional focused-spot FCS for interface studies.
• This method enhances efficiency and applicability of FCS for characterizing molecular dynamics.