LIPID AND PROTEIN EFFECTS ON MONOLAYER STABILITY

开发新的表面活性剂替代品需要：(1)了解天然肺表面活性剂中脂质和蛋白质的作用；(2)开发易于合成的天然表面活性剂蛋白类似物；(3)优化脂质组成，实现低表面张力和快速扩散吸附；(4)了解血清蛋白对表面活性剂的抑制作用，并优化表面活性剂的组成以减少这种抑制作用。我们将使用现代生物物理技术，包括朗缪尔等温线、荧光和布鲁斯特角光学显微镜、原子力显微镜、粘度法和x射线衍射来确定肺表面活性剂的相行为和形态。具体而言：(1)SP-B消除了不饱和脂质的挤压，使单层坍塌更具可逆性。SP-C在消除挤压方面效率更高，而在改变坍塌方面效率较低。SP-B和SP-C的最佳比例是否存在，或者这两种蛋白质是否可以互换？(2)我们能做出更好的SP-B和/或SP-C吗？基于已知的SP-B和SP-C的氨基酸序列，我们将合成一个类似SP-B和SP-C特征的同二聚体肽家族。(3)单表面活性剂中是否存在最佳固相分数？棕榈酸（PA）的加入影响了DPPC的流固相转变，有助于降低表面张力。我们计划确定模型表面活性剂和Survanta中固相的组成。(4)是什么导致表面活性剂被血清蛋白抑制？血液、血浆和血清蛋白、溶脂和胎便可能争夺界面面积，或溶解或降解表面活性剂成分，从而损害单层功能。我们建议研究肺表面活性物质混合物与人血清白蛋白的相互作用，以确定表面活性物质抑制的分子机制。(5)我们能将单层粘度与单层的形态和组成联系起来吗？我们建立了一个磁针粘度计，系统地研究了LS单层剪切粘弹性与蛋白质含量的关系：1)蛋白质含量；Ii)单层的相态。同时，现有的双屏障Langmuir槽将在相同条件下适用于膨胀粘弹性。

Developing new surfactant substitutes requires (1) understanding the roles of the lipids and proteins in native lung surfactant; (2) developing easy to synthesize analogs of the native surfactant proteins; (3) optimizing lipid composition for low surface tension and rapid respreading and adsorption; (4) understanding surfactant inhibition by serum proteins and optimizing surfactant composition to minimize this inhibition. We will use modern biophysical techniques including Langmuir isotherms, fluorescence and Brewster angle optical microscopy, atomic force microscopy, viscometry, and x-ray diffraction to determine the phase behavior and morphology of lung surfactants. Specifically: (1) SP-B eliminates squeeze-out of unsaturated lipids and makes monolayer collapse more reversible. SP-C is more efficient at eliminating squeeze-out, and is less efficient at altering collapse. Is there an optimal ratio of SP-B to SP-C, or are the proteins interchangable? (2) Can we make a better SP-B and/or SP-C? Based on the known amino acid sequences of SP-B and SP-C, we will synthesize a family of homodimer peptides that mimic the characteristics of SP-B and SP-C. (3) Is there an optimal solid phase fraction in surfactant monolayers? Adding palmitic acid (PA) to DPPC influences the fluid to solid phase transitions and helps lower the surface tension. We plan to determine the composition of the solid phase in model surfactants and Survanta. (4) What leads to surfactant inhibition by serum proteins? Blood, plasma and serum proteins, lysolipids, and meconium may compete for interfacial area or might solubilize or degrade constituents of surfactant, thereby impairing monolayer function. We propose to investigate the interaction of model lung surfactant mixtures with human serum albumin to determine the molecular mechanisms of surfactant inhibition. (S) Can we relate monolayer viscosity to monolayer morphology and composition? We have built a magnetic needle viscometer to carry out systematic studies of LS monolayer shear viscoelasticity as a function of: i) protein content; ii) phase state of the monolayer. Concurrently, an existing double-barrier Langmuir trough will be adapted to do dilational viscoelasticity under the same conditions.