Structure and orientation of lung surfactant SP-C and L-alpha-dipalmitoylphosphatidylcholine in aqueous monolayers
Structure and orientation of lung surfactant SP-C and L-alpha-dipalmitoylphosphatidylcholine in aqueous monolayers
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DOI：
10.1016/s0006-3495(97)78087-1
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发表时间：
1997-07-01
影响因子：
3.4
通讯作者：
Mendelsohn, R
中科院分区：
文献类型：
--
作者：
Gericke, A;Flach, CR;Mendelsohn, R
SP-C是一种肺表面活性剂特异性蛋白，有助于主要表面活性剂磷脂L-α-二棕榈酰磷脂酰胆碱（DPPC）在空气/水界面上的扩散，这一过程可能影响体内功能。为了了解这一过程的分子机理，我们利用红外光谱（IRRAS）在空气/水界面上原位测定了DPPC/SP-C混合单分子膜中DPPC酰基链的构象和取向以及SP-C二级结构和螺旋倾角，SP-C螺旋倾斜角从脂质双层中与界面法线成近似24度变为混合单层膜中的近似70度，而DPPC的酰基链倾斜角从纯脂质单层（与双层相当）中的近似26度降低到混合单层膜中的近似10度。该蛋白质通过最大化其与脂质酰基链的相互作用而充当“疏水性蛋白质”，同时允许脂质保持构象有序。除了为有序脂质的蛋白质辅助扩散提供合理的分子机制外，这些测量构成了第一个：定量测定朗缪尔膜中SP-C取向，朗缪尔膜是广泛用于模拟空气/肺泡界面过程的范例。
SP-C, a pulmonary surfactant-specific protein, aids the spreading of the main surfactant phospholipid L-alpha-dipalmitoylphosphatidylcholine (DPPC) across air/water Interfaces, a process that has possible implications for in vivo function. To understand the molecular mechanism of this process, we have used external infrared reflection-absorption spectroscopy (IRRAS)to determine DPPC acyl chain conformation and orientation as well as SP-C secondary structure and helix tilt angle in mixed DPPC/SP-C monolayers in situ at the air/water interface, The SP-C helix tilt angle changed from similar to 24 degrees to the interface normal in lipid bilayers to similar to 70 degrees in the mixed monolayer films, whereas the acyl chain tilt angle of DPPC decreased from similar to 26 degrees in pure lipid monolayers (comparable to bilayers) to similar to 10 degrees in the mixed monolayer films. The protein acts as a ''hydrophobic lever'' by maximizing Its interactions with the lipid acyl chains while simultaneously permitting the lipids to remain conformationally ordered. in addition to providing a reasonable molecular mechanism for protein-aided spreading of ordered lipids, these measurements constitute the first: quantitative determination ol SP-C orientation in Langmuir films, a paradigm widely used to simulate processes at the air/alveolar interface.