Silvius J R, Lyons M, Yeagle P L, O'Leary T J
Biochemistry. 1985 Sep 24;24(20):5388-95. doi: 10.1021/bi00341a017.
Diisopalmitoylphosphatidylcholine (DIPPC), -phosphatidylethanolamine (DIPPE), and -phosphatidylglycerol (DIPPG) have been synthesized, and the structures of aqueous dispersions of these lipids have been examined by high-sensitivity differential scanning calorimetry, 31P nuclear magnetic resonance, and Raman spectroscopy. DIPPC at temperatures below 23.1 degrees C readily forms a gel phase with the acyl chains packed in an orthorhombic subcell. Above this temperature, this "orthorhombic" phase converts directly to the liquid-crystalline phase. The phase diagram for the system DIPPC--dipalmitoyl-PC (DIPPC-DPPC) shows that the gel phases formed by either lipid can accommodate only limited amounts of the other species and suggests that the low-temperature orthorhombic phase of DIPPC is distinct in its structure from the "subgel" phase of DPPC. DIPPE forms a well-ordered gel phase only in samples that are equilibrated at low temperatures for long times (approximately days to weeks) or at very high lipid concentrations. However, this lipid readily forms an "intermediate" phase with a very disordered acyl chain packing upon cooling from the liquid-crystalline state. Mixtures of DIPPE with DIPPG exhibit similar thermotropic properties. Hydrated DIPPE appears to be stable in the lamellar phase up to at least 98 degrees C, while di-cis- and di-trans-9-hexadecenoyl-PE convert to the hexagonal II phase at 43.5 and 92.5 degrees C, respectively. We discuss the relevance of these results to the structure and stability of bacterial membranes containing branched-chain acyl lipids.
已合成了二异棕榈酰磷脂酰胆碱（DIPPC）、二异棕榈酰磷脂酰乙醇胺（DIPPE）和二异棕榈酰磷脂酰甘油（DIPPG），并通过高灵敏度差示扫描量热法、³¹P核磁共振和拉曼光谱对这些脂质的水分散体结构进行了研究。温度低于23.1℃时，DIPPC容易形成凝胶相，其酰基链堆积在正交亚晶胞中。高于此温度，这种“正交”相直接转变为液晶相。DIPPC - 二棕榈酰磷脂酰胆碱（DIPPC - DPPC）体系的相图表明，由任何一种脂质形成的凝胶相只能容纳有限量的另一种物质，这表明DIPPC的低温正交相在结构上与DPPC的“亚凝胶”相不同。DIPPE仅在长时间（约数天至数周）低温平衡或脂质浓度非常高的样品中形成有序的凝胶相。然而，这种脂质从液晶态冷却时很容易形成酰基链堆积非常无序的“中间”相。DIPPE与DIPPG的混合物表现出类似的热致性质。水合DIPPE在层状相中至少在98℃时似乎是稳定的，而二顺式和二反式 - 9 - 十六碳烯酰磷脂酰乙醇胺分别在43.5℃和92.5℃转变为六方II相。我们讨论了这些结果与含有支链酰基脂质的细菌膜的结构和稳定性的相关性。
