Submicrosecond phospholipid dynamics using a long-lived fluorescence emission anisotropy probe

Area of Science:

• Biophysics
• Materials Science
• Physical Chemistry

Background:

• Understanding lipid bilayer dynamics is crucial for membrane function.
• Submicrosecond lipid dynamics below the phase transition remain challenging to probe.
• Coronene is a long-lived fluorescence probe suitable for time-resolved studies.

Purpose of the Study:

• To investigate submicrosecond lipid dynamics in DPPC model bilayers below the phase transition temperature (T(C)).
• To interpret time-resolved fluorescence anisotropy decay data using dynamic lipid bilayer models.
• To characterize the exchange rate between gel and fluid lipid phases.

Main Methods:

• Utilized time-resolved fluorescence emission anisotropy decay of coronene-labeled DPPC small unilamellar vesicles (SUVs).
• Measured decay profiles at increasing temperatures below T(C).
• Applied compartmental and distribution models to analyze rotational decay components.

Main Results:

• Decay profiles were best described by three rotational decay components.
• An intermediate correlation time (50-100 ns) increased with temperature, indicating lipid fluidization.
• A distribution model with seven parameters accurately predicted anisotropy decay curves.

Conclusions:

• The study successfully characterized submicrosecond lipid dynamics and gel-fluid lipid exchange rates below the phase transition.
• The findings support a model of distributed lipid fluctuation-induced probe rotation.
• The developed model offers a general, probe-independent approach for studying bilayer dynamics.