Lipids are biological amphiphiles that are essential constituents of a number of living membrane structures. In the laboratory, natural and synthetic lipids can be used to make model membranes, with well-defined composition and properties. We study such model membranes using microscopy. Specifically, we use preferentially-partitioning dyes to visualize the domains that result from lateral phase separation in membranes made of two or three lipid species. We find that the shapes and other properties of these domains are directly related to the ordering of lipids in the different phases. This allows identification of both equilibrium and kinetic pathways in phase separation. It also allows identification of unexpected phase behaviour. The latter has been seen in a set of three related system that show clear evidence of adhesion-modulated phase separation. We propose a possible mechanism by which adhesion could cause demixing and show that this mechanism could hold in other lipid systems as well. This may have implications for the importance of membrane hetergeneities in biological processes such as vesicle fusion and cell adhesion. Some of you still owe me 70p for Christmas crackers.
This is a weekly series of informal talks given primarily by members of the soft condensed matter and statistical mechanics groups, but is also open to members of other groups and external visitors. The aim of the series is to promote discussion and learning of various topics at a level suitable to the broad background of the group. Everyone is welcome to attend..