Bridging the gap between single molecule and ensemble methods for measuring lateral dynamics in the plasma membrane

Area of Science:

• Biophysics
• Cell Biology
• Microscopy

Background:

• Lateral dynamics of cell membrane proteins and lipids are complex and heterogeneous.
• Current methods for studying these dynamics have limitations in flexibility and comparability.
• A unified method for analyzing dynamics across different labeling densities is needed.

Purpose of the Study:

• To demonstrate the utility of k-space image correlation spectroscopy (kICS) for analyzing single-molecule data.
• To show kICS can bridge measurements from single-molecule to ensemble levels.
• To investigate the impact of label size on diffusion measurements using kICS.

Main Methods:

• Application of kICS analysis to single-molecule data of lipids and proteins labeled with quantum dots (QDs).
• Comparison of kICS results using different labeling densities (high vs. sparse) and fluorescent labels (Atto647N-streptavidin vs. streptavidin-QDs).
• Utilized conventional wide-field microscopy.

Main Results:

• kICS accurately analyzes single-molecule density data for lipids and proteins.
• kICS successfully bridges measurements from single-molecule to ensemble labeling densities.
• Label size impacts measured diffusion rates, with smaller labels yielding higher rates.

Conclusions:

• kICS is a versatile and accurate method for analyzing lateral dynamics in biological membranes.
• kICS can be applied to data with labeling densities ranging from single molecules to ensembles.
• The choice of fluorescent label and its size significantly influences the interpretation of lipid and protein dynamics.