Liquid ordered phase

Regarding biological membranes, the liquid ordered phase is a liquid crystalline phase of a lipid bilayer, and is of significant biological importance. It occurs in many lipid mixtures combining cholesterol with a phospholipid and/or sphingolipids e.g. sphingomyelin. This phase has been related to lipid rafts that may exist in plasma membranes.

Definition

The liquid ordered phase can be defined as:

fluid and lamellar phase, including the Wide angle X-ray scattering pattern centered by broad diffraction peak at 4.2Å
acyl hydrocarbon chains are in the all-trans state
rapid lateral diffusion²H-NMR quadrupolar splitting is ca. 50 kHz

History

This was first called the liquid ordered phase by Ipsen et al.. However, it has also been called the LG_I subgel phase by Huang et al. and the β phase by Vist and Davis.