A comparison of the translational diffusion of a normal and a membrane-spanning lipid in L alpha phase 1-palmitoyl-2-oleoylphosphatidylcholine bilayers.

We have used the fluorescence recovery after photobleaching technique to study the translational diffusion, in L alpha phase multibilayers of 1-palmitoyl-2-oleoylphosphatidylcholine (POPC), of fluorescent derivatives of 1-palmitoyl-2-oleoylphosphatidylethanolamine (NBD-POPE) and a membrane-spanning phosphatidylethanolamine (NBD-MSPE). The latter derivative was prepared from a membrane-spanning glycerol-dialkyl-glycerol tetraether lipid isolated from the thermophilic and acidophilic archaebacterium Sulfolobus solfataricus. The translational diffusion was examined between about 15 degrees and 45 degrees C. It is shown that over this temperature range the translational diffusion coefficient for NBD-MSPE is approximately 2/3 that for NBD-POPE which spans only one monolayer of the bilayer. The result is interpreted in terms of existing models for translational diffusion in lipid membranes.