A CALORIMETRY AND DEUTERIUM NMR-STUDY OF MIXED MODEL MEMBRANES OF 1-PALMITOYL-2-OLEYLPHOSPHATIDYLCHOLINE AND SATURATED PHOSPHATIDYLCHOLINES
A CALORIMETRY AND DEUTERIUM NMR-STUDY OF MIXED MODEL MEMBRANES OF 1-PALMITOYL-2-OLEYLPHOSPHATIDYLCHOLINE AND SATURATED PHOSPHATIDYLCHOLINES
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DOI：
10.1016/0005-2736(85)90027-6
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发表时间：
1985-01-01
期刊：
影响因子：
--
通讯作者：
NEURINGER, LJ
中科院分区：
文献类型：
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作者：
CURATOLO, W;SEARS, B;NEURINGER, LJ
利用差示扫描量热法（DSC）数据构建了1-棕榈酰-2-油基磷脂酰胆碱(POPC)/二myristoyl磷脂酰胆碱（DMPC）、POPC/二棕榈酰磷脂酰胆碱（DPPC）和POPC/二硬脂酰磷脂酰胆碱（DSC）体系的二元相图。POPC和DMPC的混合物在凝胶和液晶状态下表现出完全的混溶性。POPC与DPPC或与dsc的混合物在0-75% DPPC（或dsc）的组成范围内表现出凝胶相不混溶性。这些结果，当与先前对磷脂酰胆碱混合物的研究结合在一起时，与PC的有序-无序转变温度（Tm值）相差小于33度的假设一致。C表现为凝胶态混相。Tm值相差超过33度者。C表现为凝胶态不混相。用2H-NMR进一步研究了由POPC和DPPC组成的混合模型膜，其中脂质在棕榈酰链的2-、10-或16位或胆碱头基团的n -甲基上用氘标记。在相同温度下，脂质结晶态的POPC/DPPC混合物介于纯POPC和DPPC之间。在液晶POPC/DPPC混合物中，POPC棕榈酰链总是比DPPC棕榈酰链更无序。这是由于POPC棕榈酰链受到直接键的约束，在其最近的邻居中至少有1个油基链，而DPPC棕榈酰链必须至少有1个相邻的棕榈酰链。当液晶POPC、DPPC和POPC/DPPC混合物在降低温度下进行比较时（相对于酰基链的有序-无序转变），POPC/DPPC混合物比纯组分的行为预测的更无序，这与DSC研究得出的焓数据一致。在1:1 POPC/DPPC的宽相变温度范围内，1:1 POPC/[2H]DPPC的凝胶和液晶光谱叠加，而1:1 [2H]POPC/DPPC仅呈现液晶光谱。在相变区域内，液晶相富含popc，凝胶相富含dppc。热相变范围内液晶四极分裂的比较表明，残余液晶POPC和DPPC的混合是非常不理想的。
Binary phase diagrams were constructed from differential scanning calorimetry (DSC) data for the systems 1-palmitoyl-2-oleylphosphatidylcholine (POPC)/dimyristoylphosphatidylcholine (DMPC), POPC/dipalmitoylphosphatidylcholine (DPPC) and POPC/distearoylphosphatidylcholine (DSPC). Mixtures of POPC with DMPC exhibit complete miscibility in the gel and liquid crystalline states. Mixtures of POPC with DPPC or with DSPC exhibit gel phase immiscibility over the composition range 0-75% DPPC (or DSPC). These results, when taken together with previous studies of mixtures of phosphatidylcholines, are consistent with the hypothesis that PC whose order-disorder transition temperatures (Tm values) differ by less than 33.degree. C exhibit gel state miscibility. Those whose Tm values differ by more than 33.degree. C exhibit gel state immiscibility. 2H-NMR spectroscopy was used to further study mixed model membranes composed of POPC and DPPC, in which either lipid was labeled with deuterium in the 2-, 10- or 16-position of the palmitoyl chain(s) or in the N-methyls of the choline head group. POPC/DPPC mixtures in the lipid crystalline state are intermediate in order between pure POPC and DPPC at the same temperature. The POPC palmitoyl chains is always more disorderd than the palmitoyl chains of DPPC in liquid crystalline POPC/DPPC mixtures. This is attributed to the fact that a POPC palmitoyl chain is constrained by direct bonding to have at least 1 oleyl chain among its nearest neighbors, while a DPPC palmitoyl chain must have at least 1 neighboring palmitoyl chain. When liquid crystalline POPC, DPPC and POPC/DPPC mixtures are compared at a reduced temperature (relative to the acyl chain order-disorder transition), POPC/DPPC mixtures are more disordered than predicted from the behavior of the pure components, in agreement with enthalpy data derived from DSC studies. Within the temperature range of the broad phase transition of 1:1 POPC/DPPC, a superposition of gel and liquid crystalline spectra is observed for 1:1 POPC/[2H]DPPC, while 1:1 [2H]POPC/DPPC exhibits only a liquid crystalline spectrum. At temperatures within the phase transition region, the liquid crystalline phase is POPC-rich and the gel phase is DPPC-rich. Comparison of the liquid crystalline quadrupole splittings within the thermal phase transition range suggests that mixing of the residual liquid crystalline POPC and DPPC is highly non-ideal.