Masserini M, Freire E
Biochemistry. 1986 Mar 11;25(5):1043-9. doi: 10.1021/bi00353a014.
The thermotropic behavior of dipalmitoylphosphatidylcholine and distearoylphosphatidylcholine large unilamellar vesicles containing ganglioside GM1 of homogeneous long chain base composition has been studied by high-sensitivity differential scanning calorimetry and fluorescence spectroscopy. At neutral pH and in the absence of Ca2+, the thermotropic behavior of these systems is independent of the ganglioside chain length composition. The presence of Ca2+ at concentrations higher than 5 mM induces ganglioside phase separation in a manner dependent upon the length difference between the ganglioside long chain base and the phosphatidylcholine acyl chains. The analysis of the chain length dependence of the thermotropic behavior suggests that the driving force for ganglioside phase separation is not a Ca2+-induced cross-bridging of the ganglioside head group but a passive ganglioside exclusion from Ca2+-perturbed phosphatidylcholine-rich regions within the bilayer. Experiments with native ganglioside GM1, primarily a mixture of C18:1 and C20:1 long chain bases, indicate that the individual components of the mixture maintain their characteristic behavior within the lipid bilayer matrix. These results, together with the presence of a phase transition in native GM1 micellar dispersions, absent in purified C18:1 or C20:1 ganglioside micelles, strengthen the idea of a possible role of chain length composition in the modulation of ganglioside function.
通过高灵敏度差示扫描量热法和荧光光谱法研究了含有均一长链碱基组成的神经节苷脂GM1的二棕榈酰磷脂酰胆碱和二硬脂酰磷脂酰胆碱大单层囊泡的热致行为。在中性pH且不存在Ca2+的情况下，这些体系的热致行为与神经节苷脂的链长组成无关。浓度高于5 mM的Ca2+的存在会以一种依赖于神经节苷脂长链碱基与磷脂酰胆碱酰基链之间长度差异的方式诱导神经节苷脂相分离。对热致行为的链长依赖性分析表明，神经节苷脂相分离的驱动力不是Ca2+诱导的神经节苷脂头部基团的交联，而是双层中富含磷脂酰胆碱的Ca2+扰动区域对神经节苷脂的被动排斥。对天然神经节苷脂GM1（主要是C18:1和C20:1长链碱基的混合物）的实验表明，混合物中的各个组分在脂质双层基质中保持其特征行为。这些结果，连同天然GM1胶束分散体中存在相变（纯化的C18:1或C20:1神经节苷脂胶束中不存在），强化了链长组成在调节神经节苷脂功能中可能起作用的观点。
