Derksen A, Ekman S, Small D M
Department of Medicine, Boston University School of Medicine, Massachusetts 02118-2394.
J Biol Chem. 1989 Apr 25;264(12):6935-40.
Apoprotein (apo) A-1 binding to large triolein-rich emulsion particles saturated with cholesterol has been examined as a function of the oleic acid content. Six emulsion systems were formed containing 0.3-1.0% (by weight) oleic acid, 82.9-86.3% triolein, 10.6-7.2% egg yolk phosphatidylcholine, and 6.7-5.5% cholesterol. The average emulsion particle diameters calculated from these lipid compositions ranged between 84 and 116 nm. Negative stain electron microscopy of an emulsion containing 1% oleic acid showed a polydisperse population of only large spherical particles with a mean diameter of 116 +/- 54 nm. The calculated cholesterol concentrations of the particles surface and core for the six emulsions were 43.3 +/- 1.1 and 5.6 +/- 0.2 mol%, respectively, and were rather constant. Therefore, when the surface oleic acid concentrations increased from 2.6 to 10.1 mol%, the phospholipid concentration decreased from 55.1 to 45.9 mol%. In the core, oleic acid increased at the expense of triolein. In the range studied a nearly 4-fold increase in the surface oleic acid content produces a similar increase in the binding capacity (N) and reduces the dissociation constant (Kd). The changes in the Kd and N values were linearly dependent on the surface oleic acid concentration. These data show that oleic acid allows more apoA-1 to bind with higher affinity to large emulsion particles saturated with cholesterol.
已研究了载脂蛋白（apo）A-1与富含三油酸甘油酯且胆固醇饱和的大乳液颗粒的结合情况，该结合情况是油酸含量的函数。形成了六种乳液体系，其包含0.3 - 1.0%（重量）的油酸、82.9 - 86.3%的三油酸甘油酯、10.6 - 7.2%的蛋黄磷脂酰胆碱以及6.7 - 5.5%的胆固醇。根据这些脂质组成计算出的平均乳液颗粒直径在84至116纳米之间。对含1%油酸的乳液进行负染电子显微镜观察显示，只有平均直径为116 ± 54纳米的大球形颗粒的多分散群体。六种乳液颗粒表面和核心的计算胆固醇浓度分别为43.3 ± 1.1和5.6 ± 0.2摩尔%，且相当恒定。因此，当表面油酸浓度从2.6摩尔%增加到10.1摩尔%时，磷脂浓度从55.1摩尔%降至45.9摩尔%。在核心中，油酸增加而三油酸甘油酯减少。在所研究的范围内，表面油酸含量增加近4倍会使结合能力（N）产生类似的增加，并降低解离常数（Kd）。Kd和N值的变化与表面油酸浓度呈线性相关。这些数据表明，油酸能使更多的apoA-1以更高的亲和力与富含胆固醇的大乳液颗粒结合。
