Simple, rapid method for detecting phase transititons of lipids.

A simple rapid method was worked out for studying the physical and structural state of lipids by measuring the refractive indices of a layered lipid film. Melting processes of n-paraffins and phase transitions of phospholipids and the lecithin-cholesterol system also can be followed as a function of temperature. In accordance with data from the relevant literature, the measured refractive indices show that cholesterol lowers the phase transition temperature of lecithin. By isorefraction curves, the most ordered structure of the layers is indicated to occur at the equimolar ratio of cholesterol and lecithin. The method may be applied to study the effect of lipid-soluble agents upon lipid structure and is applicable for routine investigations and industrial purposes as well.