McKersie B D, Lepock J R, Kruuv J, Thompson J E
Biochim Biophys Acta. 1978 Apr 4;508(2):197-212. doi: 10.1016/0005-2736(78)90325-5.
The phospholipid content of rough and smooth microsomal fractions from cotyledons of germinating bean declines as the tissue becomes senescent. Both types of membrane contain comparable proportions of three major phospholipids, phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol, which collectively comprise about 90% of the total. This proportionality does not change appreciably during senescence. Only small quantities of lysophosphatides were noted at all stages of senescence. The unsaturated:saturated fatty acid ratio for total extracted lipid declined only slightly in both membrane systems, but pronounced differences in this ratio were observed among the major phospholipids of the membranes. The most striking alteration in lipid composition with advancing senescence was an increase in the sterol:phospholipid ratio; this rose by about 50% for rough microsomes and 400% for smooth microsomes. For both types of membrane the patterns of change in this ratio correlated with previously reported changes in bulk lipid transition temperature, suggesting that the increase in sterol level may contribute to changes in phase behaviour of the membranes during senescence. Arrhenius plots of rotational correlation times for the electron spin label 2,2-dimethyl-5-dodecyl-5-methyloxazolidine-N-oxide (2N14) partitioned into the membrane lipid showed an increase in viscosity with advancing senescence and a corresponding increase in activation energy for both types of membrane. These changes in activation energy and viscosity correlated closely with the increase in sterol:phospholipid ratio. However, no phase transitions were detectable between temperatures of 2 and 55 degrees C despite the fact that transitions from a lipid-crystalline to gel state are detectable within this temperature range by wide angle X-ray diffraction.
发芽豆的子叶中，粗糙型和光滑型微粒体组分的磷脂含量会随着组织衰老而下降。两种类型的膜中都含有比例相当的三种主要磷脂，即磷脂酰胆碱、磷脂酰乙醇胺和磷脂酰肌醇，它们总共约占总量的90%。这种比例在衰老过程中没有明显变化。在衰老的各个阶段都只发现了少量的溶血磷脂。两种膜系统中，总提取脂质的不饱和脂肪酸与饱和脂肪酸的比例仅略有下降，但在膜的主要磷脂之间观察到了该比例的显著差异。随着衰老进程，脂质组成最显著的变化是固醇与磷脂的比例增加；粗糙微粒体中该比例上升了约50%，光滑微粒体中则上升了400%。对于两种类型的膜，该比例的变化模式与先前报道的大量脂质转变温度的变化相关，这表明固醇水平的增加可能有助于膜在衰老过程中的相行为变化。电子自旋标记物2,2 - 二甲基 - 5 - 十二烷基 - 5 - 甲基恶唑烷 - N - 氧化物（2N14）分配到膜脂质中的旋转相关时间的阿累尼乌斯图显示，随着衰老进程，两种类型的膜的粘度增加，活化能相应增加。活化能和粘度的这些变化与固醇与磷脂比例的增加密切相关。然而，尽管通过广角X射线衍射在此温度范围内可检测到从脂质晶体态到凝胶态的转变，但在2至55摄氏度之间未检测到相变。
