ABSTRACT
This chapter deals with the identification of the mesophases adopted by phospholipids and the determination of their structures and with the forms of the phase diagrams and the transitions between different phases, and the factors that control their relative stabilities. A major problem with the study of lipid phases is the difficulty of ensuring that the sample is at equilibrium. In part this may be due to the very slow rate at which a phase comes to equilibrium. However, a further problem is that the phase itself may be metastable, reverting to more stable forms over a time scale that can span seconds to months. Micelles can be formed by short chain phospholipids or by lysophospholipids in water. They may have a variety of shapes, such as spheres, rods, and discs. Heating lipids above the subtransition temperature enhances the torsional oscillations of the hydrocarbon chains until these turn into essentially unhindered long-axis rotation.
