X-ray Diffraction Studies on the Effect of Additives on the Phase Behaviour of Lipids

Abstract

In this chapter we will expand the discussion of lipids in bilayers to lipids in non-lamellar phases. Non-lamellar phases are important for a number of reasons: i) from the biologist’s point of view the lipids in a biological cell membrane are in the lamellar phase. However, it is important to note that non-lamellar phases must occur —: at least locally and transiently —: during many cellular processes like cell division or exo- and endocytosis. ii) for the physicist, the rich polymorphism imposes a real challenge in describing the delicate balance of forces involved in these systems and even more difficult, to describe their phase transitions. Due to the manifold lyotropic, thermotropic and barotropic phase behaviour, lipid systems provide valuable models for kinetic and thermodynamic studies. Phase behaviour and its relation to the molecular structure of the membrane’s various components is complex and far from being understood.