The effect of amphiphilic molecules, temperature and pressure on conformational and dynamic properties of phospholipid bilayers - A FT-IR, 2D-NMR and time-resolved fluorescence anisotropy study

We have investigated the effect of incorporation of amphiphilic molecules on the structure, dynamics and phase behaviour of aqueous dispersions of the model biomembranes 1,2-dipalmitoylphosphatidylcholine (DPPC) and 1,2-dimyristoylphosphatidylcholine (DMPC) using fluorescence dynamics depolarisation, 2D-NMR and Fourier-transform infrared spectroscopy (FT-IR). Infrared spectral parameters such as frequencies, intensities, bandshapes and band splittings, and fluorescence spectral parameters such as lifetime, rotational correlation time and order parameter of fluorescence probes have been used to detect conformational and dynamical changes upon incorporation of the additives into the lipid bilayers. We present data on aqueous DPPC/cholesterol and DMPC/tetracaine dispersions in the pressure range from 0.001 to 20 kbar at selected temperatures. The two different kinds of amphiphilic molecules exhibit significant differences in their conformational and dynamic properties when incorporated into lipid bilayers. In particular, cholesterol is shown to be able to efficiently regulate the conformation, hydrophobicity and motional freedom of membranes, so that they can withstand even drastic changes in environmental conditions, such as high external hydrostatic pressure.