Discher B M, Maloney K M, Schief W R, Grainger D W, Vogel V, Hall S B
Department of Biochemistry, Oregon Health Sciences University, Portland 97201, USA.
Biophys J. 1996 Nov;71(5):2583-90. doi: 10.1016/S0006-3495(96)79450-X.
To determine if lateral phase separation occurs in films of pulmonary surfactant, we used epifluorescence microscopy and Brewster angle microscopy (BAM) to study spread films of calf lung surfactant extract (CLSE). Both microscopic methods demonstrated that compression produced domains of liquid-condensed lipids surrounded by a liquid-expanded film. The temperature dependence of the pressure at which domains first emerged for CLSE paralleled the behavior of its most prevalent component, dipalmitoyl phosphatidylcholine (DPPC), although the domains appeared at pressures 8-10 mN/m higher than for DPPC over the range of 20-37 degrees C. The total area occupied by the domains at room temperature increased to a maximum value at 35 mN/m during compression. The area of domains reached 25 +/- 5% of the interface, which corresponds to the predicted area of DPPC in the monolayer. At pressures above 35 mN/m, however, both epifluorescence and BAM showed that the area of the domains decreased dramatically. These studies therefore demonstrate a pressure-dependent gap in the miscibility of surfactant constituents. The monolayers separate into two phases during compression but remain largely miscible at higher and lower surface pressures.
为了确定肺表面活性剂薄膜中是否发生横向相分离，我们使用落射荧光显微镜和布儒斯特角显微镜（BAM）来研究小牛肺表面活性剂提取物（CLSE）的铺展薄膜。两种显微镜方法均表明，压缩产生了由液体扩张膜包围的液体凝聚脂质区域。CLSE中区域首次出现时的压力对温度的依赖性与其最主要成分二棕榈酰磷脂酰胆碱（DPPC）的行为相似，尽管在20至37摄氏度范围内，这些区域出现时的压力比DPPC高8 - 10 mN/m。在压缩过程中，室温下区域所占的总面积在35 mN/m时增加到最大值。区域面积达到界面的25±5%，这与单层中DPPC的预测面积相对应。然而，在高于35 mN/m的压力下，落射荧光显微镜和BAM均显示区域面积急剧减小。因此，这些研究证明了表面活性剂成分混合性中存在压力依赖性间隙。单层在压缩过程中分离为两个相，但在较高和较低表面压力下仍基本可混溶。
