Department of Pharmacy, Uppsala University, Uppsala, Sweden.
PLoS One. 2012;7(9):e44702. doi: 10.1371/journal.pone.0044702. Epub 2012 Sep 6.
Dioctadecyldimethylammonium bromide (DODAB) is a double chain cationic lipid, which assembles as bilayer structures in aqueous solution. The precise structures formed depend on, e.g., lipid concentration and temperature. We here combine differential scanning calorimetry (DSC) and X-ray scattering (SAXS and WAXS) to investigate the thermal and structural behavior of up to 120 mM DODAB in water within the temperature range 1-70 °C. Below 1 mM, this system is dominated by unilamellar vesicles (ULVs). Between 1 and 65 mM, ULVs and multilamellar structures (MLSs) co-exist, while above 65 mM, the MLSs are the preferred structure. Depending on temperature, DSC and X-ray data show that the vesicles can be either in the subgel (SG), gel, or liquid crystalline (LC) state, while the MLSs (with lattice distance d = 36.7 Å) consist of interdigitated lamellae in the SG state, and ULVs in the LC state (no Bragg peak). Critical temperatures related to the thermal transitions of these bilayer structures obtained in the heating and cooling modes are reported, together with the corresponding transition enthalpies.
双十八烷基二甲基溴化铵（DODAB）是一种双链阳离子脂质，在水溶液中组装成双层结构。精确的形成结构取决于例如脂质浓度和温度。在这里，我们结合差示扫描量热法（DSC）和 X 射线散射（SAXS 和 WAXS）来研究高达 120mM DODAB 在 1-70°C 温度范围内的水热和结构行为。在 1mM 以下，该系统主要由单层囊泡（ULV）组成。在 1 至 65mM 之间，ULV 和多层结构（MLS）共存，而在 65mM 以上，MLS 是首选结构。根据温度的不同，DSC 和 X 射线数据表明，囊泡可以处于亚凝胶（SG）、凝胶或液晶（LC）状态，而 MLS（晶格距离 d = 36.7Å）在 SG 状态下由交错的薄片组成，ULV 在 LC 状态下（没有布拉格峰）。报告了在加热和冷却模式下获得的这些双层结构热转变相关的临界温度，以及相应的转变焓。
