Lipid Rearrangement inDSPC/DMPC Bilayers: A NeutronReflectometry Study.

Lipid translocation in membranes is still far from beingunderstoodand well characterized for natural cell membranes as well as for simplerbilayer model systems. Several discrepancies with respect to its occurrenceand its characteristic time scale are present in the literature. Inthe current work, the structural changes induced by lipid rearrangementin a distearoyl-/dimyristoyl-phosphocholine binary lipid system havebeen addressed by means of neutron reflectivity. It has been shownthat a fast, spontaneous compositional reorganization with lipid transferbetween the two leaflets of the bilayer takes place only when thelipid species are both in the fluid phase. This process has been identifiedas the so-called lipid flip-flop. Moreover, the influence of the preparationprotocol on the structural properties of the system has been investigated. [ABSTRACT FROM AUTHOR]