The melting of pulmonary surfactant monolayers.
The melting of pulmonary surfactant monolayers.
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肺表面活性剂单层的熔化。
DOI：
10.1152/japplphysiol.00948.2006
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发表时间：
2007
期刊：
影响因子：
--
通讯作者：
Hall,StephenB
中科院分区：
文献类型：
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作者：
Yan,Wenfei;Biswas,SamaresC;Laderas,TedG;Hall,StephenB
超压缩至高表面压力（π）后，液体膨胀（LE）相中的磷脂单分子膜，远高于平衡表面压力（πe），在平衡表面压力下，流体膜从界面塌陷形成三维体相，以及倾斜冷凝（TC）相中的磷脂单分子膜都复制了肺中肺泡膜特有的抗塌陷性。为了提供确定哪种膜存在于肺泡中的基础，我们测量了含有TC二棕榈酰磷脂酰胆碱（DPPC）以及超压缩1-棕榈酰-2-油酰磷脂酰胆碱和小牛肺表面活性剂提取物（CLSE）的单层的熔化特性。通过对捕获气泡进行适当的操作产生的膜在高于πe的不同常数π下从≤27°C加热到≥60°C。DPPC表现出预期的TC-LE相变的突然膨胀，然后由崩溃产生的收缩。超压缩CLSE没有显示TC-LE膨胀的证据，认为超压缩并不简单地将混合脂质膜转化为TC DPPC。对于DPPC和CLSE，熔点（作为塌陷开始的温度）在较高的π下增加，与1-棕榈酰-2-油酰磷脂酰胆碱相反，较高的π在较低的温度下产生塌陷。对于50和65 mN/m之间的π，DPPC在48-55°C下熔化，远高于41°C下双层的主要转变。在每个π处，CLSE在低于>10°C的温度下熔化。TC DPPC和超压缩CLSE的不同熔点提供了依据，通过该依据可以从肺力学的温度依赖性确定肺泡膜的性质。
Monomolecular films of phospholipids in the liquid-expanded (LE) phase after supercompression to high surface pressures (π), well above the equilibrium surface pressure (πe) at which fluid films collapse from the interface to form a three-dimensional bulk phase, and in the tilted-condensed (TC) phase both replicate the resistance to collapse that is characteristic of alveolar films in the lungs. To provide the basis for determining which film is present in the alveolus, we measured the melting characteristics of monolayers containing TC dipalmitoyl phosphatidylcholine (DPPC), as well as supercompressed 1-palmitoyl-2-oleoyl phosphatidylcholine and calf lung surfactant extract (CLSE). Films generated by appropriate manipulations on a captive bubble were heated from ≤27°C to ≥60°C at different constant π above πe. DPPC showed the abrupt expansion expected for the TC-LE phase transition, followed by the contraction produced by collapse. Supercompressed CLSE showed no evidence of the TC-LE expansion, arguing that supercompression did not simply convert the mixed lipid film to TC DPPC. For both DPPC and CLSE, the melting point, taken as the temperature at which collapse began, increased at higher π, in contrast to 1-palmitoyl-2-oleoyl phosphatidylcholine, for which higher π produced collapse at lower temperatures. For π between 50 and 65 mN/m, DPPC melted at 48–55°C, well above the main transition for bilayers at 41°C. At each π, CLSE melted at temperatures >10°C lower. The distinct melting points for TC DPPC and supercompressed CLSE provide the basis by which the nature of the alveolar film might be determined from the temperature-dependence of pulmonary mechanics.