Tancrède P
Can J Biochem Cell Biol. 1984 Aug;62(8):789-95.
We have examined the interactions in a mixed monomolecular film between the 11-cis and all-trans isomers of retinal and different saturated and unsaturated phosphatidylcholines and phosphatidylethanolamines. The phase diagrams of the different binary mixtures are drawn using the surface pressure isotherms measured on 10(-3) M phosphate buffer at 21 +/- 1 degree C. Analysis of the results shows that the unsaturated chain phospholipids (dioleoyl L-phosphatidylcholine and dioleoyl L-phosphatidylethanolamine extracted from bovine retinas) and the retinal isomers are miscible at the interface. In addition, the excess free energies of mixing are identical for these mixtures. On the other hand, the saturated phospholipids (distearoyl L-phosphatidylcholine and distearoyl L-phosphatidylethanolamine) are not miscible with the retinal isomers under the same conditions. The comparison between the results obtained with the saturated lipid and unsaturated lipid mixtures shows the importance of hydrophobic forces in the thermodynamics of the interactions of these systems. In addition, the isotherms of the mixtures containing phosphatidylethanolamine do not vary with the pH of the subphase in the region studied, pH 5.5 to 8.2. These results raise serious doubts about the existence of a Schiff base between phosphatidylethanolamine and the retinals at the interface. The possible implications of this phenomenon for the disc membrane are analyzed, particularly with respect to the stability of the retinals in vivo.
我们研究了视网膜的11-顺式和全反式异构体与不同饱和及不饱和磷脂酰胆碱和磷脂酰乙醇胺在混合单分子膜中的相互作用。使用在21±1℃下10⁻³M磷酸盐缓冲液上测量的表面压力等温线绘制了不同二元混合物的相图。结果分析表明，不饱和链磷脂（从牛视网膜中提取的二油酰基L-磷脂酰胆碱和二油酰基L-磷脂酰乙醇胺）与视网膜异构体在界面处可混溶。此外，这些混合物的混合超额自由能相同。另一方面，在相同条件下，饱和磷脂（二硬脂酰基L-磷脂酰胆碱和二硬脂酰基L-磷脂酰乙醇胺）与视网膜异构体不可混溶。饱和脂质和不饱和脂质混合物结果的比较显示了疏水作用力在这些系统相互作用热力学中的重要性。此外，在所研究的pH 5.5至8.2区域内，含磷脂酰乙醇胺混合物的等温线不随亚相pH值变化。这些结果对界面处磷脂酰乙醇胺与视网膜之间席夫碱的存在提出了严重质疑。分析了这一现象对盘膜的可能影响，特别是关于视网膜在体内的稳定性。
