Antenna-Enhanced Fluorescence Correlation Spectroscopy Resolves Calcium-Mediated Lipid-Lipid Interactions

Area of Science:

• Membrane biophysics
• Nanotechnology
• Spectroscopy

Background:

• Fluorescence correlation spectroscopy (FCS) provides insights into cell membrane dynamics.
• Current limitations in spatial resolution hinder the study of nanoscale biophysical interactions.

Purpose of the Study:

• To develop a method for achieving nanoscale spatial and temporal resolution in FCS measurements.
• To investigate the role of calcium ions in lipid diffusion dynamics within artificial cell membranes.

Main Methods:

• Fabrication of artificial cell membranes on dimeric, nanoplasmonic antennas.
• Utilizing antenna-enhanced FCS to shrink the probe volume to ~20 nm.
• Analyzing fluorescence bursts from tagged lipids using autocorrelation functions.

Main Results:

• Achieved a temporal resolution increase of up to 3 orders of magnitude by confining the optical readout volume.
• Demonstrated that lipid molecules diffuse as single entities or pairs, influenced by calcium ions.
• Observed that calcium chelation with EDTA significantly reduces complex diffusion contributions.

Conclusions:

• Antenna-enhanced FCS offers unprecedented spatial and temporal resolution for membrane studies.
• Calcium ions play a crucial role in mediating transient interactions between zwitterionic lipids.
• This technique can address complex membrane biophysics questions, including lipid clustering and protein dynamics.