Seminar "Lateral anomalous diffusion in lipid bilayers: stochasticity, molecular crowding, and the breakdown of the Saffman-Delbrück theory" By Prof. Jae-Hyung Jeon

• Date: Wed, May 22nd
• Time: 15:00-16:00
• Venue: C016-Lab1
• Speaker: Jae-Hyung Jeon, Department of Physics, POSTECH, Korea

Title:

Lateral anomalous diffusion in lipid bilayers: stochasticity, molecular crowding, and the breakdown of the Saffman-Delbrück theory

Abstract:

Lipid bilayers are quasi two-dimensional, crowded systems composed of various phospholipid molecules and membrane proteins [1]. It is known that the lipids and proteins carry out thermally driven lateral diffusion and thus constantly reorganize the membrane. Using the molecular dynamics simulations, theoretical modeling of anomalous diffusion, and the single-molecule experiments, we quantify the stochastic properties of the lateral diffusion in membranes at varying circumstances. We show that the lateral diffusion attains more anomalous characters as the membrane complexity is increased by adding cholesterol molecules and/or proteins. In the absence of membrane proteins the anomalous motion is universally described by the gaussian anomalous diffusive process called fractional Brownian motion (FBM) regardless of molecular details of the lipid structure and lipid phases [2]. However, it is found that this FBM picture is no longer valid if the membrane is crowded with proteins [3]. We present how the crowding of membrane proteins changes statistical complexities of the anomalous diffusion in membranes. Finally, we investigate the case that the lateral diffusion of proteins is hindered by antibodies attached to extracellular domain of them outside the membrane [4]. We show by the experiment that the diffusivity of the proteins is significantly reduced beyond the Saffman-Delbrück theory by the effects of attachment of antibodies and their crowding. We explain the observed diffusion dynamics in terms of two-body collisions and their excess entropy, and also provide numerical evidence from the corresponding coarse-grained simulation.

[1] R. Metzler, J.-H. Jeon, and A. G. Cherstvy, BBA 1858, 2451 (2016).

[2] J.-H. Jeon, H. M.-S. Monne, M. Javanainen, & R. Metzler, Phys Rev Lett 109, 188103 (2012).

[3] J.-H. Jeon, M. Javanainen, H. Martinez-Seara, R. Metzler, and I. Vattulainen, Phys Rev X 6, 021006 (2016).

[4] D.-K. Kim, S. Joo, J.-H. Jeon, and N. K. Lee, manuscript in preparation.