Temperature dependent heterogeneous rotational correlation in lipids

Area of Science:

• Biophysics
• Materials Science
• Physical Chemistry

Background:

• Lipid structures are dynamic and crucial for membrane function.
• Molecular-scale density fluctuations are characteristic of liquids.
• Lateral heterogeneity in lipid dynamics is key to understanding membrane behavior.

Purpose of the Study:

• To explore lateral heterogeneity in free-standing lipid monolayers.
• To investigate the impact of temperature on lipid dynamics and relaxation.
• To characterize the dynamic behavior of a specific lipid monolayer (DMPC).

Main Methods:

• Utilized a fluorescent probe (PLPC) embedded in a 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) monolayer.
• Employed wide-field time-resolved fluorescence anisotropy to measure rotational diffusion.
• Analyzed dynamic distributions across a range of temperatures.

Main Results:

• At high temperatures, observed narrow, liquid-like relaxation (τ ~ 2.4 ns).
• Upon cooling, the relaxation distribution broadened significantly.
• A slower relaxation population (τ ~ 16.5 ns) emerged at lower temperatures, indicating dynamic heterogeneity.

Conclusions:

• Confirms dynamic heterogeneity in lipid monolayers, especially at higher packing densities.
• Demonstrates complex nanoscale diffusion and reorganization in simple lipid architectures.
• Highlights the significant impact of dynamical heterogeneity on lipid membrane organization, permeability, and energetics.