Akerman K E, Saris N E
Biochim Biophys Acta. 1976 Apr 5;426(4):624-9. doi: 10.1016/0005-2736(76)90126-7.
Liposomes were prepared from phosphatidylcholine and cardiolipin in a KCl medium and suspended in a choline chloride medium with safranine. When efflux of K+ was induced by valinomycin, spectral shifts characteristic of stacking were observed. Ca2+ inhibited the rate of stacking in a competitive manner with a Ki of about 200 muM, while La3+ was about 10 times more potent. When liposomes were prepared from phospholipids with a higher ratio of cardiolipin to phosphatidylcholine the inhibition was more potent. No effect on the stacking phenomena was seen when CA2+ was added after the stacking was completed. When CA2+ or an organic cation with four charges, spermine was trapped in the intraliposomal compartment, no significant change in the rate of stacking was seen. However, the extent of stacking was decreased. It is suggested that safranine is driven by a diffusion potential to a site that is inaccessible to CA2+ in the medium, presumably to the inner boundaries of the liposomal membranes.
脂质体由磷脂酰胆碱和心磷脂在氯化钾培养基中制备而成，并悬浮于含有番红的氯化胆碱培养基中。当缬氨霉素诱导钾离子外流时，观察到了堆积特征性的光谱位移。钙离子以竞争性方式抑制堆积速率，其抑制常数约为200 μM，而镧离子的效力约为钙离子的10倍。当用的心磷脂与磷脂酰胆碱比例更高的磷脂制备脂质体时，抑制作用更强。堆积完成后添加钙离子，对堆积现象没有影响。当钙离子或带四个电荷的有机阳离子精胺被困在脂质体内腔时，堆积速率没有明显变化。然而，堆积程度降低。有人提出，番红是由扩散电位驱动到培养基中钙离子无法到达的位点，大概是脂质体膜的内边界。
