Chapter three - A Multi Time-Scale Approach of the Lipid Bilayer Dynamics

Abstract

Abstract The lipid bilayer is a supramolecular aggregate with complex dynamics. Independent and collective motions of lipid molecules span a wide range of timescales. In order to understand the lipid bilayer functioning, the correlation between various motions needs to be understood. Molecules with low molecular weight, when placed in the lipid bilayer, may alter membrane properties depending on their location. The effect of two membrane active molecules, ethanol and lidocaine, on the lipid bilayer was investigated in three different timescales by means of dedicated fluorescence techniques. The interfacial water dynamics was measured using “solvent relaxation” technique at picosecond timescale. The lateral lipid molecule mobility along the lipid bilayer surface was determined with fluorescence correlation spectroscopy at millisecond timescale, and collective lipid processes, such as spontaneous lipid pore formation, were monitored with fluorescence stopped-flow technique at the timescale of seconds and longer. When the lipid bilayer was exposed to the ethanol molecules, changes at all probed timescales have been detected, whereas in the presence of lidocaine, only the alterations in interfacial water mobility and spontaneous lipid pore formation were observed. The introduction of lidocaine left the lateral lipid mobility unaffected. These results indicate that there might happen loose correlations between processes occurring in different timescales within the same lipid bilayer.