High pressure effects on the structure and mesophase behaviour of supramolecular lipid aggregates and model membrane systems

Lipids, which provide valuable model systems for membranes, display a variety of polymorphic phases, depending on their molecular structure and environmental conditions. By use of X-ray and neutron diffraction, infrared and fluorescence depolarization spectroscopy, calorimetry and volumetric measurements, the temperature and pressure dependent structure and phase behaviour of several lipid systems, differing in chain configuration and headgroup structure have been studied. Hydrostatic pressure has been used as a physical parameter, because high pressure is an important feature of certain natural membrane environments (e.g., marine biotopes), and because the high pressure phase behaviour of biomolecules is also of considerable biotechnological interest [1]. An understanding of the energetics of these lipid assemblies and of the various lipid phase transitions should help in assessing the role of such molecules in natural membranes.