Sterol evolution and the physics of membranes

Sterols are important molecular components of the plasma membranes of eucar yotic cells. Using deuterium NMR spectroscopy in conjunction with statistic al mechanical modelling, we present a unifying picture of how the evolution -engineered differences in molecular chemistry between cholesterol and its precursor lanosterol are manifested in the physical properties of model mem branes in terms of molecular order and phase equilibria. Cholesterol optimi zes the stability of a particular membrane phase, the liquid-ordered phase, that is a liquid and at the same time exhibits high molecular conformation al order.