Lipid monolayers: why use half a membrane to characterize protein-membrane interactions?

Variants of membrane-active proteins and peptides are increasingly available through synthesis and molecular engineering. When determining the effects of structural changes upon the interaction of these proteins with lipid membranes, monomolecular films of lipids at the air-water interface have significant advantages over bilayers and other lipid dispersions. In the past year, a variety of protein-lipid interactions has been characterized successfully using relatively simple surface measurements.