Investigations on the order-disorder behaviour of various phospholipids of natural and synthetic origin by optical and calorimetric techniques

Abstract

The regulation of metabolic processes in cells (e.g. active and passive transport, enzymatic activity) is highly governed by the composition of the cell membrane usually composed as a bilayer of phospholipids. Under physiological conditions the membrane is - at least partially - in the liquid crystalline state. This is achieved by biosynthesis of appropriate phospholipids varying in the kind of polar head-groups and in length and degree of saturation of the hydrocarbon chains in dependence on the ambient temperature and milieu. Starting with pure phospholipids (PL) of synthetic and natural origin the thermodynamic states of physiological relevant PL's and PL-mixtures and the thermotropic gel to liquid crystalline phase transition were investigated. From a combination of DTA and different optical techniques statements are deduced about structure andorientation of lipid molecules, microviscosity of the lipid bilayer,cooperativity of the phase transition, and permeability of the membrane.