Phase properties of the aqueous dispersions of n-octadecylphosphocholine.

ABSTRACT

Properties of the aqueous dispersions of n-octadecylphosphocholine are examined by differential scanning calorimetry, fluorescence depolarization, light scattering, 31P-NMR, pig pancreatic phospholipase A2 binding, and X-ray diffraction. On heating, these dispersions exhibit a sharp lamellar to micelle transition at 20.5 degrees C. The lamellar phase consists of frozen (gel-state) alkyl chains which do not bind phospholipase A2. The kinetics of the transition are asymmetric the micelle to lamellar transition is very slow and the lamellar to micelle transition is fast. It is suggested that the lamellar phase is a frozen chain bilayer in which the chains interdigitate.