Small D H, Phillips M
Department of Biophysics, Housman Medical Research Center, Boston MA 02118-2394.
Adv Colloid Interface Sci. 1992 Sep 28;41:1-8. doi: 10.1016/0001-8686(92)80003-g.
The apparent pressures in the surface monolayer of emulsion particles can be estimated by comparing the absorption of an apolipoprotein to planar lipid monolayers and to emulsions. Lipids are spread at an air-water interface in a Pockels/Langmuir surface balance and the adsorption of [14C]-labeled apolipoproteins placed in the subphase is studied as a function of surface pressure using the surface radioactivity method. An apoprotein surface concentration/initial lipid surface pressure curve (gamma/pi i) is constructed. The maximum apolipoprotein surface concentration gamma e of emulsions is derived from standard emulsion/apolipoprotein binding isotherms. The apparent emulsion surface pressure is then estimated by comparing gamma e to the gamma/pi i curve. Apolipoprotein A-I has been used as an example of a probe to estimate the effective surface pressure in approximately 1000 A diameter egg yolk phosphatidylcholine/cholesterol/triolein emulsion particles. When the cholesterol content of emulsions is low, the surface pressure of the emulsion is about 17 dyne cm-1. At high cholesterol concentrations (0.49 cholesterol/phospholipid mole ratio) the surface pressure is increased to 25 dyne cm-1. The addition of the maximum amounts of apoA-I to these particles raises the effective surface pressure of the emulsion to about 30 dyne cm-1 and stabilizes the particles.
通过比较载脂蛋白在平面脂质单分子层和乳液中的吸收情况，可以估算乳液颗粒表面单分子层的表观压力。脂质在Pockels/Langmuir表面平衡仪的气-水界面上铺展，使用表面放射性方法研究置于亚相中[14C]标记的载脂蛋白的吸附情况，作为表面压力的函数。构建载脂蛋白表面浓度/初始脂质表面压力曲线（γ/πi）。乳液的最大载脂蛋白表面浓度γe来自标准乳液/载脂蛋白结合等温线。然后通过将γe与γ/πi曲线进行比较来估算表观乳液表面压力。载脂蛋白A-I已被用作探针的示例，以估算直径约为1000 Å的蛋黄磷脂酰胆碱/胆固醇/三油酸甘油酯乳液颗粒中的有效表面压力。当乳液中的胆固醇含量较低时，乳液的表面压力约为17达因/厘米。在高胆固醇浓度（胆固醇/磷脂摩尔比为0.49）下，表面压力增加到25达因/厘米。向这些颗粒中添加最大量的载脂蛋白A-I可将乳液的有效表面压力提高到约30达因/厘米，并使颗粒稳定。
