Department of Physics, Center for Molecular Study of Condensed Soft Matter (μCoSM), Pritzker Institute of Biomedical Science and Engineering, Illinois Institute of Technology, Chicago, Illinois 60616, United States.
X-ray Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States.
Langmuir. 2020 Nov 17;36(45):13439-13447. doi: 10.1021/acs.langmuir.0c01813. Epub 2020 Oct 20.
When compressed by the shrinking alveolar surface area during exhalation, films of pulmonary surfactant reduce surface tension to levels at which surfactant monolayers collapse from the surface . Vesicles of pulmonary surfactant added below these monolayers slow collapse. X-ray scattering here determined the structural changes induced by the added vesicles. Grazing incidence X-ray diffraction on monolayers of extracted calf surfactant detected an ordered phase. Mixtures of dipalmitoyl phosphatidylcholine and cholesterol, but not the phospholipid alone, mimic that structure. At concentrations that stabilize the monolayers, vesicles in the subphase had no effect on the unit cell, and X-ray reflection showed that the film remained monomolecular. The added vesicles, however, produced a concentration-dependent increase in the diffracted intensity. These results suggest that the enhanced resistance to collapse results from enlargement by the additional material of the ordered phase.
在呼气时，肺泡表面积缩小会对肺表面活性物质产生压缩，使其降低表面张力，达到使表面活性物质单层从表面坍塌的水平。添加到这些单层下面的肺表面活性物质小泡会减缓坍塌。此处的 X 射线散射确定了添加的小泡所引起的结构变化。对提取的小牛肺表面活性剂单层进行掠入射 X 射线衍射检测到有序相。二棕榈酰磷脂酰胆碱和胆固醇的混合物，但不是单独的磷脂，可以模拟该结构。在稳定单层的浓度下，亚相中的小泡对单位晶胞没有影响，X 射线反射表明该膜仍然是单分子的。然而，添加的小泡会导致衍射强度的浓度依赖性增加。这些结果表明，增强的抗坍塌能力是由于额外物质使有序相扩大所致。
