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首页> 外文期刊>Biophysical Chemistry: An International Journal Devoted to the Physical Chemistry of Biological Phenomena >Effect of hydrophobic surfactant protein SP-C on binary phospholipid monolayers. Molecular machinery at the air/water interface.
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Effect of hydrophobic surfactant protein SP-C on binary phospholipid monolayers. Molecular machinery at the air/water interface.

机译：疏水表面活性剂蛋白SP-C对二元磷脂单层的影响。空气/水界面处的分子机械。

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Fluorescent and modified dark-field microscopies were used to investigate the phase behavior of physiologically relevant lipid/protein monomolecular films containing surfactant protein C(SP-C). Synthetic human SP-C(1-34) was labeled at its N-terminus using the fluorescent probe 6-(((4(4,4-difluoro-5-(2-thienyl)-4-bora-3a,4a-diaza-s-indacene-3-yl)pheno xy)acetyl)amino)hexanoic acid (BODIPY/TR-X). Using dual fluorescent labeling (lipid and protein) in the monolayers, we have correlated (at physiologically small concentrations of the protein) the lipid phase separation and protein distribution in situ. A comparison of the lipid and protein dye fluorescent micrographs indicates that SP-C(1-34) is preferentially associated with the disordered lipid phase. Three concepts arise from our results. (1) The presence of SP-C alone does not result in the complete dissolution of condensed phase domains in a fashion that we have previously reported for the entire hydrophobic surfactant protein (SP-B/C) fraction (Biophys. J. 77 (1999) 903). Rather, the use of relatively high amounts ( approximately 10 wt.%) of the labeled SP-C protein is needed to reproduce the fluorescence monolayer morphology previously observed for small concentrations ( approximately 1 wt.%) of the natural SP-B/C mixture. (2) Scattered light, dark-field microscopy performed using grazing angle laser illumination reveals the presence of surface-associated, three-dimensional (3D) structures of micrometer-sized dimensions when the labeled BODIPY/TR-X:SP-C(1-34) protein is included in the monolayer, as previously observed with the naturally isolated SP-B/C mixture. The 3D structures are associated exclusively with the presence of the SP-C protein in disordered monolayer phases. (3) To explain these results, we have derived a molecular model accounting for the structure and physico-chemical properties of the SP-C protein in terms of its energetics. The molecular events involved in the SP-C-mediated production of the 3D surface particles are explained using the analogy of a simple molecular machine, namely a loaded spring. This interpretation is supported by an energetic analysis that suggests the major factor contributing to the formation of the 3D particles is the energy liberated by re-expansion of the surrounding phospholipid film into the area vacated by the SP-C protein as it re-orients away from the surface.
机译：荧光和改进的暗场显微镜检查被用来调查生理相关的脂质/蛋白质表面活性剂蛋白C（SP-C）的单分子膜的相行为。使用荧光探针6-（（（（（4（4,4-difluoro-5-（2-thienyl）-4-bora-3a，4a-）将合成的人SP-C（1-34）标记在其N末端diaza-s-indacene-3-yl）phen xy）乙酰基）氨基）己酸（BODIPY / TR-X）。在单层中使用双重荧光标记（脂质和蛋白质），我们已将脂质相分离和蛋白质原位相关联（在蛋白质的生理浓度较低时）。脂质和蛋白质染料荧光显微照片的比较表明SP-C（1-34）优先与无序的脂质相相关。我们的结果提出了三个概念。 （1）单独存在SP-C并不能完全按照我们先前报道的整个疏水性表面活性剂蛋白（SP-B / C）组分的方式完全溶解缩合相域（Biophys.J.77（ 1999）903）。相反，需要使用相对大量（约10 wt。％）的标记SP-C蛋白来再现先前在小浓度（约1 wt。％）的天然SP-B / C中观察到的荧光单层形态混合物。 （2）当使用标记的BODIPY / TR-X：SP-C（1）时，使用掠角激光照射进行的散射光暗场显微镜检查发现存在与表面相关的，微米级尺寸的三维（3D）结构。 -34）蛋白包含在单层中，如先前在自然分离的SP-B / C混合物中观察到的那样。 3D结构仅与无序单层相中SP-C蛋白的存在相关。 （3）为了解释这些结果，我们推导了一个分子模型，该模型解释了SP-C蛋白的结构和理化性质。使用简单分子机器（即加载的弹簧）的类比解释了SP-C介导的3D表面粒子生产中涉及的分子事件。这种解释得到了高能分析的支持，该分析表明，促成3D颗粒形成的主要因素是通过将周围的磷脂膜重新膨胀到SP-C蛋白腾空的区域中而重新释放所释放的能量。从表面。

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