On the low surface tension of lung surfactant.
On the low surface tension of lung surfactant.
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DOI：
10.1021/la201482n
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发表时间：
2011-07-05
期刊：
影响因子：
--
通讯作者：
Zuo YY
中科院分区：
文献类型：
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作者：
Zhang H;Wang YE;Fan Q;Zuo YY
天然肺表面活性物质含有少于40%的二饱和磷脂，主要是二棕榈酰磷脂酰胆碱（DPPC）。肺表面活性物质达到非常低的近零表面张力（远低于其平衡值）的机制尚未完全了解。迄今为止，肺表面活性剂的低表面张力通常由挤出模型来解释，该模型预测在膜压缩时，非DPPC组分逐渐从空气-水界面排除到表面相关的表面活性剂储层中。然而，在生理相关的高表面压力范围内挤出的详细实验证据仍然缺乏。在本工作中，我们研究了四种动物源性临床表面活性剂制剂，包括Survanta，Curosurf，Infasurf和BLES。通过比较这些表面活性剂膜的压缩等温线和横向结构，通过原子力显微镜获得的生理相关的高表面压力范围内，我们推导出一个更新的挤出模型。我们的模型表明，挤出源于相分离单层的流体相。挤出过程遵循成核-生长模型，并且仅发生在肺表面活性物质平衡扩散压力附近的狭窄表面压力范围内。在挤出之后，三维核停止生长，从而导致DPPC富集的界面单层，以将空气-水表面张力降低到非常低的值。
Natural lung surfactant contains less than 40% disaturated phospholipids, mainly dipalmitoylphosphatidylcholine (DPPC). The mechanism by which lung surfactant achieves very low near-zero surface tensions, well below its equilibrium value, is not fully understood. To date, the low surface tension of lung surfactant is usually explained by a squeeze-out model which predicts that upon film compression non-DPPC components are gradually excluded from the air–water interface into a surface-associated surfactant reservoir. However, detailed experimental evidence of the squeeze-out within the physiologically relevant high surface pressure range is still lacking. In the present work, we studied four animal-derived clinical surfactant preparations, including Survanta, Curosurf, Infasurf, and BLES. By comparing compression isotherms and lateral structures of these surfactant films obtained by atomic force microscopy within the physiologically relevant high surface pressure range, we have derived an updated squeeze-out model. Our model suggests that the squeeze-out originates from fluid phases of a phase-separated monolayer. The squeeze-out process follows a nucleation–growth model and only occurs within a narrow surface pressure range around the equilibrium spreading pressure of lung surfactant. After the squeeze-out, three-dimensional nuclei stop growing, thereby resulting in a DPPC-enriched interfacial monolayer to reduce the air–water surface tension to very low values.