Informal Statistical Physics Seminar

Date
Tue, Feb 16, 2016 1:15 pm - 2:30 pm
Location
IPST Building Room 1116

Description

Speaker Name: John Williamson

Speaker Institution : Georgetown University

Title : Domains, asymmetry and flip-flop: the statistical thermodynamics of a phase-separating lipid bilayer

Abstract : Domain formation and heterogeneity within lipid bilayer membranes is associated with a vast array of physiological roles - cell membranes contain, among everything else, hundreds of lipid species. Simpler membranes composed of two or three species allow modelling such domain formation, and have their own engineering applications in drug delivery and synthetic biology. A phase-separating lipid bilayer is an immensely rich object due to its separate, yet coupled, leaflets. Experiments pose questions about the nature of inter-leaflet interactions, the symmetry or otherwise of domains, and the role of "flip-flop" or direct inter-leaflet exchange. I show how a semi-microscopic model of a phase-separating bilayer can provide valuable theoretical insight. Distantly related to the Ising model, it can be analytically solved to yield coarse-grained free energy. Phase behaviour and kinetics can then be predicted in a thermodynamic framework that properly treats the distinct ! leaflets and, unlike purely phenomenological approaches, "knows about" the bilayer microstructure. After surveying data and observations from the literature, I will outline how our theory unifies apparently disparate or contradictory findings, and predicts novel phenomena.

Notes: By tradition, each seminar is preceded by an informal cafeteria lunch to which all are welcome, departing from Room 1108 about five minutes after 12:00 noon.