All About the Lipid Membrane: Phase Transition and Deformation

Speaker: 
Dr. Jun Fan
Event Date and Time: 
Wed, 2016-03-30 14:00 - 15:00
Location: 
Room 311 – 2355 East Mall Brimacombe Building
Intended Audience: 
Public
A lipid membrane envelops the cell, isolates itself from the surroundings, and strictly controls materials and information going in and out. The plasma cell membrane consists of various lipids and proteins. Different species form dynamic nano-sized clusters, the so-called “lipid rafts” or the liquid ordered phase, surrounded by the liquid disordered phase. Rafts play significant roles in many important cellular activities such as signal transduction, protein sorting, and viral assembly. However the raft formation mechanism is not fully understood yet. In this talk, I will address this issue by simulating the raft formation process using the continuum model [1]. Simulation results suggest a practical method to test the formation mechanism through experiments [2]. At the meantime, the lipid membrane may generate lipid vesicles during the endocytosis process in order to transport materials from the exterior to the interior of the cell. Many proteins are found at the vesicle formation spots, such as BAR family proteins. How the membrane deforms under membrane-BAR protein interactions is the second topic of the talk. Molecular dynamics simulation results reveal amazing molecular details of the novel phenomena that a symmetrical dimer protein, containing BAR and PH domains, may asymmetrically bind to the lipid membrane [3]. It is the first time to observe such a behavior among BAR family proteins [4]. We further propose a model to explain this puzzle from the energy point of view. Moreover, our computation results predict that BAR-PH domains form a helical lattice on the membrane through strong electrostatic interactions, which have been verified by our experimental collaborators both in vitro and in vivo. This combined computational and experimental investigation contributes a new mechanism to the membrane remodeling process [5].
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