Fast Confined Dynamics in Lipid Bilayers*

The physics of lipid bilayer in cell membranes is one of the most exciting topic in modern science. We have investigated the molecular dynamics of complex phospholipid membranes in their fluid phases by neutron spin echo spectroscopy. Our study reveals the origin of anomalous motions in different Phospholipids that leaves a generalized fingerprint in their mean square displacement (MSD). It shows a t^0.26 dependence in the pico- to nanosecond region that indicates a new localized motion that is related to the tail group of the lipid. At longer times, t > 3 ns, the MSD shows a t^0.66 dependence describing membrane undulation, followed by a translational diffusion (t¹), that is visible at the edge of instrumental resolution. The analysis reveals the range in which we can analyze the membrane fluctuations to determine the membrane rigidity. Our study reveals the existence of the complex dynamic organization of the lipid bilayer in terms of localized anomalous motions. In biological cell membranes, these anomalous motions would imply a substantial difference in cellular signaling and regulatory process.

S. Gupta et al., J Phys Chem Lett, 9, 2956-2960. (2018); Current Opinion in Colloid & Interface Science, 42, 121-136. (2019).