Thermotropic properties of bilayers containing branched-chain phospholipids. Calorimetric, Raman, and 31P NMR studies.
Thermotropic properties of bilayers containing branched-chain phospholipids. Calorimetric, Raman, and 31P NMR studies.
复制标题
含有支链磷脂的双层的热致性质。
DOI：
10.1021/bi00341a017
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发表时间：
1985
期刊：
影响因子：
2.9
通讯作者：
O'Leary,TJ
中科院分区：
文献类型：
--
作者：
Silvius,JR;Lyons,M;Yeagle,PL;O'Leary,TJ
合成了二异棕榈酰磷脂酰胆碱（DIPPC）、-磷脂酰乙醇胺（DIPPE）和-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检查了这些脂质的水分散体的结构。 DIPPC 在低于 23.1 C 的温度下很容易与酰基链形成凝胶相，酰基链堆积在斜方晶系亚晶格中。高于该温度，这种“斜方”相直接转变为液晶相。 DIPPC-二棕榈酰-PC (DIP-PC-DPPC) 系统的相图显示，由任一脂质形成的凝胶相只能容纳有限量的其他物质，这表明 DIPPC 的低温斜方晶相在结构上与 DPPC 的“亚凝胶”相不同。 DIPPE 仅在低温下长时间（大约数天至数周）或在非常高的脂质浓度下平衡的样品中形成有序的凝胶相。然而，这种脂质在从液晶状态冷却后很容易形成具有非常无序的酰基链堆积的“中间”相。 DIPPE 与 DIPPG 的混合物表现出相似的热致性能。水合 DIPPE 在至少 98°C 的层状相中似乎是稳定的，而 di-ti-r- 和 di-í/wM-9-十六烯酰基-PE 分别在 43.5°C 和 92.5°C 时转化为六方 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。
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 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 thesystem DIPPC-dipalmitoyl-PC (DIP-PC-DPPC) shows that the gel phases formed by either lipid can accommodate onlylimited amounts of the other species and suggests that the low-temperatureorthorhombic phase of DIPPC is distinct inits 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 C, while di-ti-r-and di-í/wM-9-hexadecenoyl-PE convert to the hexagonal II phase at 43.5 and 92.5 C, respectively. We discuss the relevance of these results tothe structure and stability of bacterialmembranes containing branched-chain acyl lipids.