ABSTRACT
The optimal technique for detecting thermal motion and organization of lipids at the molecular level is nuclear magnetic resonance (NMR). NMR is increasingly used to probe the physical state of membrane lipids. Since the formulation of the fluid mosaic model of membrane structure, it is customary and fashionable to talk about membrane “fluidity”: membranes are considered bi-dimensional fluids constituted by amphipathic lipids in a bilayer arrangement, where proteins and other components diffuse and rotate unless hindered by specific restrictions. Overwhelming evidence has accumulated stating that membrane fluidity is involved in the control of an increasing number of physiological processes and that derangements of normal fluidity are involved in the development of pathological states. The effects of physiological or external perturbants on fluidity may be direct on the hydrocarbon chain disposition, but also related to the interfacial water organization as already discussed for the electrostatic effects.
