Calorimetric and fatty acid spin label study of subgel and interdigitated gel phases formed by asymmetric phosphatidylcholines.
Calorimetric and fatty acid spin label study of subgel and interdigitated gel phases formed by asymmetric phosphatidylcholines.
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由不对称磷脂酰胆碱形成的亚凝胶和叉指凝胶相的量热和脂肪酸自旋标记研究。
DOI：
10.1016/0005-2736(86)90263-4
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
Mason,JT
中科院分区：
文献类型：
--
作者：
Boggs,JM;Mason,JT
通过 ESR 光谱和差示扫描量热法研究了几种饱和不对称和对称磷脂酰胆碱，以确定在混合交指凝胶相和 Lcsubgel 相中在其末端甲基 16-doxylstearate 附近标记的脂肪酸自旋的行为以及这些脂质的其他特性。该自旋标签在 18:10PC 和 18:12PC 的混合指状凝胶相中受到运动限制。运动限制与之前报道的完全叉指相类似。这种自旋标签在 10:18PC 中几乎受到相同程度的运动限制，表明这种不对称脂质也可能形成混合的叉指双层。相比之下，自旋标记在 18:14PC 的凝胶相中比在对称形式的 PC 中具有更多的运动，这与 X 射线衍射研究的结论一致，即这种不对称程度较低的脂质不会形成混合的叉指相。自旋标签部分地从对称形式的PC和18:14PC的Lcsubgel相中冷冻出来，该Lcsubgel相是通过低温储存形成的。其他不对称脂质的相行为也取决于样品历史。低温储存导致10:18PC和18:12PC进入有序阶段。这些有序相向液晶相的转变焓比从液晶相冷却回时形成的凝胶相的转变焓高 2-2.4 倍。对于 18:12PC，这种高焓转变的温度比液晶相变的低焓转变温度低 0.8 K，但对于 10:18PC 则高 4.6 K。自旋标签被冻结在这些有序相之外，因为它在 Lcsubgel 相之外，这表明 18:12PC 和 10:18PC 也可能形成 Lc 相。没有观察到 18:10PC 形成有序相，尽管样品在低温下储存确实影响了其在相变循环中从液晶相转变回凝胶相的温度。
Several saturated asymmetric and symmetric phosphatidylcholines were studied by ESR spectroscopy and differential scanning calorimetry in order to determine the behavior of a fatty acid spin labeled near its terminal methyl, 16-doxylstearate, in the mixed interdigitated gel phase and the Lcsubgel phase and other properties of these lipids. This spin label was motionally restricted in the mixed interdigitated gel phases of 18:10PC and 18:12PC. The motional restriction was similar to that reported earlier for fully interdigitated phases. This spin label was motionally restricted almost to the same degree in 10:18PC suggesting that this asymmetric lipid may also form a mixed interdigitated bilayer. In contrast the spin label had more motion in the gel phase of 18:14PC than in symmetric forms of PC, consistent with conclusions from X-ray diffraction studies that this less asymmetric lipid does not form a mixed interdigitated phase. The spin label was partially frozen out of the Lcsubgel phases of symmetric forms of PC and 18:14PC formed by storage at low temperature. The phase behavior of the other asymmetric lipids also depended on the sample history. Storage at low temperature caused 10:18PC and 18:12PC to go into ordered phases. The enthalpy of the transition of these ordered phases to the liquid-crystalline phase was 2–2.4-times greater than that of the transition of the gel phase formed on cooling back from the liquid-crystalline phase. The temperature of this high enthalpy transition was 0.8 K below that of the lower enthalpy get to liquid-crystalline phase transition for 18:12PC, but 4.6 K higher for 10:18PC. The spin label was frozen out of these ordered phases, as it was out of the Lcsubgel phases, suggesting that 18:12PC and 10:18PC may also form an Lcphase. 18:10PC was not observed to form an ordered phase although storage of the sample at low temperatures did affect the temperature of its transition from the liquid-crystalline phase back to the gel phase upon cycling through its phase transition.