Fluorescence resonance energy transfer to characterize cholesterol-induced domains

Cholesterol is a major component of mammalian cell membranes. It has remarkable effects on the properties of phospholipids bilayers, and is implicated in the lipid raft model. Depending on the membrane composition, cholesterol-containing bilayers can exist either as single phase or as mixture of coexisting phases. These are organized in domains of variant size determined by composition, but can be smaller than the optical microscopy resolution limit. This chapter describes a methodology based on fluorescence resonance energy transfer, which is sensitive to phase separation and can provide estimates of domain size in these usually hard to characterize systems.