Small-Angle X-ray Scattering Studies on the Structure of Mixed DPPC/diC7PC Micelles in Aqueous Solutions

Po-Wei Yang ； Tsang-Lang Lin ； Yuan Hu ； U-Ser Jeng

《Chinese Journal of Physics》 50卷2期 (2012/04) Pp. 349-356

並列摘要

The phase behavior of mixed DPPC/diC7PC micelles in aqueous solutions was investigated using small-angle x-ray scattering (SAXS) and Transmission electron microscopy (TEM). Phase transitions from multilamellar vesicle (MLV) to disc bicelle, ribbon-like, and rodlike aggregates are observed as the percentage of the short-chain diC7PC is increased. At DPPC/diC7PC molar ratio 3/1, the multilamellar liposomes are all transformed into disc bicelles. The long-chain DPPC lipid and short-chain diC7PC lipid, respectively, form the planar and rim part of the bicelle with a radius and thickness of 98.4 and 55.3 Å, respectively, for the DPPC/diC7PC mixing ratio of 3/1. Temperature-induced structure transformation is also observed for such a mixed system. The structural transformation is induced by the solubilization of diC7PC into the planar long-chain lipid bilayer. An intermediate ribbon phase was found and coexisted with DPPC/diC7PC multilamellar liposome phase at 40℃; while only multilamellar liposome phase was found at 45℃ which is higher above the chain melting temperature of DPPC.