Upon dispersing in aqueous solution amphiphilic phospholipid molecules extracted from biomembranes (e.g. POPC = 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine), the formation of lipid vesicles (liposomes) is observed [1]. These vesicles are molecular aggregates which have an aqueous internal volume which is separated from the external medium by one or several concentric shells (lamellae) which are composed of thousand of phospholipid molecules. Each lamella in a vesicle is a self-closed bilayer of amphiphilic lipid molecules. Unilamellar vesicles have one single bilayer which defines the boundary of the vesicles, just like the plasma membrane defines the boundary of every biological cells. Obviously, the plasma membrane is a highly sophisticated, complex assembly of amphiphilic lipids, proteins and other molecules, while lipid vesicles are much simpler structures.
Despite this, unilamellar lipid vesicles are being studied since many years as simple model systems of biomembranes for several reasons. First of all, lipid vesicles can easily be prepared from a number of different lipids and lipid mixtures that are present in biological membranes, allowing studies for gaining insight into some of the physico-chemical properties of the lipid matrix of biomembranes. Secondly, membrane proteins can be reconstituted in vesicles, allowing the investigation of membrane embedded proteins in a biomimicking environment, outside the living cell. Thirdly, the size of the vesicles prepared can be controlled to some extent, varying between less than 100 nm and more than 10 μm [2,3], allowing studies by using various methodologies.
Recent advances in the preparation and application of lipid vesicles as biomimetic systems will be discussed. The topics covered will include peptide-phospholipid membrane interactions and peptide translocation across phospholipid membranes.
- Gregoriadis, G., Alec Douglas Bangham, Biogr. Mems Fell. R. Soc.57, 25-43 (2011);
- Walde, P., in Encycl. Nanosci. Nanotechnol., (Nalwa, H. S., ed.), Vol. 9, pp. 43.79 (2004);
- Walde, P.; Cosentino, K.; Engel, H.; Stano, P., ChemBioChem 11, 848-865 (2010).