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Applied Math Colloquium

Friday, Nov 16, 2012, 11:30 AM
Cullimore Lecture Hall, Lecture Hall II
New Jersey Institute of Technology

Compositional Interface Dynamics within Symmetric and Asymmetric Planar Lipid Bilayer Membranes

Mikko Haataja

Department of Mechanical Engineering, Princeton University

Abstract

Compositional domains within multicomponent lipid bilayer membranes are believed to facilitate many important cellular processes. Experimentally, it has been shown that synthetic membranes whose overall compositions mimic those of the extracellular leaflet of the cell membrane can phase separate into distinct liquid phases, while the ones whose compositions mimic those of the cytoplasmic leaflet do not display any compositional heterogeneities or domains. Interestingly, in asymmetric membranes, where the two leaflets have compositions mimicking those of the extracellular and cytoplasmic leaflets of the cell membrane, phase separation can either be induced or suppressed altogether. Furthermore, when both leaflets contain compositional lipid domains, they are often found in perfect registry. These observations indicate that a significant thermodynamic coupling exists between the lipids across the two leaflets.

While the effects of the thermodynamic coupling between the leaflets has been theoretically investigated recently with regard to equilibrium behavior of asymmetric multicomponent lipid bilayer membranes, its effects on the compositional domain dynamics have received less attention. In this talk, I will first derive the general equations that describe the dynamics of compositional domains within planar membranes with asymmetry in leaflet properties and in the presence of a thermodynamic coupling between the leaflets. These equations are then employed to develop analytical solutions to the dynamics of the recurrence of registration for both laminar and circular domains in the case of weak coupling. It is shown that experimentally measuring these dynamics will enable one to determine the strength of the thermodynamic coupling between the leaflets. A closed-form expression for the decay rate of interface fluctuations in the case in which only one leaflet supports compositional domains, is also derived.