Structure and permeability properties of biomimetic membranes of bolaform archaeal tetraether lipids

This review is a general survey of the properties of membranes formed by tetraether lipids extracted from microorganisms living in extreme conditions, named Archaea. After describing the unusual structure and physico-chemical properties of the membrane-spanning lipids, which allow Archaea to maintain membrane integrity in harsh environments, we consider their molecular organization in model systems such as monolayers, artificial black membranes and liposomes. The latter, due to their remarkable thermal stability, can lead to attractive biotechnological applications. Membrane permeability, local membrane fluidity and packing characteristics are reviewed with the aim of correlating structural features to permeability properties. In particular, studies on the very low passive proton permeation and leakage of entrapped molecules are reported and discussed in terms of membrane structure. Work on synthetic tetraether compounds is also reported.