Molecular weight dependence of the depletion attraction and its effects on the competitive adsorption of lung surfactant.
Molecular weight dependence of the depletion attraction and its effects on the competitive adsorption of lung surfactant.
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DOI：
10.1016/j.bbamem.2008.03.019
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发表时间：
2008-10
期刊：
影响因子：
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通讯作者：
P. Stenger;Stephen G Isbell;J. Zasadzinski
中科院分区：
文献类型：
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作者：
P. Stenger;Stephen G Isbell;J. Zasadzinski
白蛋白与肺表面活性剂竞争空气-水界面，导致表面活性剂吸附减少，表面张力增加。聚乙二醇（PEG）和其他亲水聚合物恢复了表面活性剂对界面的正常吸附速率，从而在压缩时重新建立了低表面张力。聚乙二醇这样做是通过在表面活性剂聚集体和界面之间产生熵耗吸引，减少白蛋白施加的吸附能量屏障。对于10 g/L （1% wt.）的固定组成，表面活性剂的吸附增加了PEG分子量的0.1倍，从6 kDa到35 kDa，通过简单的排除损耗吸引力的体积模型预测。分子量在6 kDa以下的聚乙二醇的耗损吸引范围小于白蛋白的尺寸，对表面活性剂的吸附没有影响。大于35 kDa的PEG在1% wt时达到重叠浓度，导致耗竭引力降低和表面活性剂吸附降低。荧光图像显示，耗竭吸引使表面活性剂突破空气-水界面的白蛋白膜，形成单层扩散。在这一转变过程中，存在不混溶的白蛋白和表面活性剂结构域共存。表面压力远高于白蛋白的正常平衡表面压力是在膜压缩过程中迫使白蛋白离开界面所必需的。
Albumin competes with lung surfactant for the air–water interface, resulting in decreased surfactant adsorption and increased surface tension. Polyethylene glycol (PEG) and other hydrophilic polymers restore the normal rate of surfactant adsorption to the interface, which re-establishes low surface tensions on compression. PEG does so by generating an entropic depletion attraction between the surfactant aggregates and interface, reducing the energy barrier to adsorption imposed by the albumin. For a fixed composition of 10 g/L (1% wt.), surfactant adsorption increases with the 0.1 power of PEG molecular weight from 6 kDa–35 kDa as predicted by simple excluded volume models of the depletion attraction. The range of the depletion attraction for PEG with a molecular weight below 6 kDa is less than the dimensions of albumin and there is no effect on surfactant adsorption. PEG greater than 35 kDa reaches the overlap concentration at 1% wt. resulting in both decreased depletion attraction and decreased surfactant adsorption. Fluorescence images reveal that the depletion attraction causes the surfactant to break through the albumin film at the air–water interface to spread as a monolayer. During this transition, there is a coexistence of immiscible albumin and surfactant domains. Surface pressures well above the normal equilibrium surface pressure of albumin are necessary to force the albumin from the interface during film compression.