Jiménez-Monreal A M, Villalaín J, Aranda F J, Gómez-Fernández J C
Departamento de Bioquímica y Biología Molecular 'A', Facultad de Veterinaria, Universidad de Murcia, Apartado Postal 4021, E-30080 Murcia, Spain.
Biochim Biophys Acta. 1998 Aug 14;1373(1):209-19. doi: 10.1016/s0005-2736(98)00106-0.
The phase behavior of mixtures of 1-palmitoyl-2-oleoyl-sn-glycerol (1,2-POG) with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoserine (POPS) was studied by using DSC, small-angle X-ray diffraction and 31P-NMR. The results have been used to construct phase diagrams for both type of mixtures, in the 0-45 degreesC range. It is concluded that 1, 2-POG form complexes in the gel phases with both POPC and POPS. In the case of POPC, two complexes are postulated, the first one at a 1, 2-POG/POPC molar ratio of 40:60, and the second one at 70:30, defining three different regions in the phase diagram. Two eutectic points are proposed to occur: one at a very low 1,2-POG concentration and the other at a 1,2-POG concentration slightly lower than 70%. In the case of the 1,2-POG/POPS mixtures, the pattern was similar, but the first complex was seen to happen at a higher concentration, about 50 mol% of 1,2-POG, whereas the second was found at 80 mol% of 1,2-POG. This indicated a bigger presence of 1,2-POG in the complexes with POPS than with POPC. In the first region of the phase diagram, i.e. at concentrations of 1,2-POG lower than that required for the formation of the first complex, and at temperatures above the phase transition, lamellar phases were seen in all the cases. In region 2 of the phase diagram, i.e. at concentrations where the first and the second complexes coexist, a mixture of lamellar and non-lamellar phases was observed. Finally, at high concentrations of 1,2-POG, non-lamellar phases were detected as predominant, these phases being of an isotropic nature, according to 31P-NMR. An important conclusion of this study is that, using unsaturated lipids, similar to those found in biological membranes, it has been shown that diacylglycerols are found separated in domains, and that this process starts at very low concentrations of diacylglycerols. The formation of separated domains enriched in diacylglycerol is biologically relevant as it will allow them to have important effects on the membrane structure besides the fact that their concentration in the biomembrane is relatively low.
采用差示扫描量热法（DSC）、小角X射线衍射法和31P核磁共振法研究了1-棕榈酰-2-油酰-sn-甘油（1,2-POG）与1-棕榈酰-2-油酰-sn-甘油-3-磷酸胆碱（POPC）以及1-棕榈酰-2-油酰-sn-甘油-3-磷酸丝氨酸（POPS）混合物的相行为。研究结果用于构建0-45℃范围内这两种混合物类型的相图。得出的结论是，1,2-POG在凝胶相中与POPC和POPS均形成复合物。对于POPC，推测存在两种复合物，第一种复合物的1,2-POG/POPC摩尔比为40:60，第二种为70:30，这在相图中定义了三个不同区域。提出存在两个共晶点：一个在1,2-POG浓度非常低时，另一个在1,2-POG浓度略低于70%时。对于1,2-POG/POPS混合物，情况类似，但第一种复合物在较高浓度时出现，约为1,2-POG的50 mol%，而第二种在1,2-POG的80 mol%时出现。这表明与POPC形成的复合物相比，1,2-POG在与POPS形成的复合物中占比更大。在相图的第一个区域，即1,2-POG浓度低于形成第一种复合物所需浓度且温度高于相变温度时，在所有情况下均观察到层状相。在相图的区域2，即第一种和第二种复合物共存的浓度下，观察到层状相和非层状相的混合物。最后，在1,2-POG高浓度时，检测到以非层状相为主，根据31P核磁共振，这些相具有各向同性。这项研究的一个重要结论是，使用与生物膜中发现的类似的不饱和脂质，已表明二酰基甘油在结构域中是分离存在的，并且这个过程在二酰基甘油浓度非常低时就开始了。富含二酰基甘油的分离结构域的形成在生物学上具有重要意义，因为这将使它们除了在生物膜中的浓度相对较低这一事实外，还能对膜结构产生重要影响。
