Orientation of lipids in solid supported lipid bilayers studied by polarized ATR-FTIR spectroscopy1

Solid supported lipid bilayers (SSLB) play an important role as biomimetic membranes to study protein-membrane interactions. We investigated the orientation of lipids in SSLBs at different temperatures and over time. Especially the stability of the lipid bilayer and structural changes upon lipid phase transition were analyzed by polarized ATR-FTIR spectroscopy and with SSLBs of different lipid compositions. The integrity of a lipid bilayer consisting of POPC or a 1:1 mixture of POPC and POPG is conserved over a wide temperature range and over several hours. Furthermore, we were able to monitor changes in the orientation of the lipid alkyl chains upon lipid phase transition for DMPC and DSPC. This study shows that the combination of solid supported lipid bilayers and polarized ATR-FTIR spectroscopy is very powerful to characterize lipid membranes under different environmental conditions. The sensitivity of this technique will be exploited in future studies to analyze the effect of protein-membrane interaction on lipid orientation.