Surface chemistry of binary mixtures of phospholipids in monolayers. Infrared studies of surface composition at varying surface pressures in a pulmonary surfactant model system.
Surface chemistry of binary mixtures of phospholipids in monolayers. Infrared studies of surface composition at varying surface pressures in a pulmonary surfactant model system.
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单层磷脂二元混合物的表面化学。
DOI：
10.1021/bi00063a032
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发表时间：
1993
期刊：
影响因子：
2.9
通讯作者：
Dluhy,RA
中科院分区：
文献类型：
--
作者：
Rana,FR;Mautone,AJ;Dluhy,RA
摘要：用Langmuir-Blodgett(LB)表面化学、31P核磁共振和红外光谱研究了空气/水界面的磷脂单分子膜。这些单分子膜是由1，2-二棕榈酰基-甘油-3-磷酸胆碱(DPPC-IFO)和2-二棕榈酰基-2-甘油-3-磷酸甘油(IE，DPPG)组成的二元单分子膜。之所以选择这种特殊的PC-PG二元混合物进行研究，是因为这种脂质体系已被用作肺表面活性物质的模型，特别是与肺力学中所谓的“挤出”假说相结合。这一理论预测，在连续的压缩-膨胀循环中，表面活性剂表面膜将重新组织，以排除除DPPC以外的所有组分，从而产生稳定的低表面张力膜。从这些实验中得到了几个一般性的结果。首先，我们开发了一种结合高分辨率31P核磁共振光谱和从红外光谱中获得的CH和CD振动强度的组合光谱分析方法，其中一个组分是酰链过氚。利用转移的LB膜的衰减全反射红外光谱，这种结合的光谱方法使我们能够定量地描述二元单分子膜中各组分的分数组成。其次，当这些方法应用于DPPC-ífa和DPPG(初始PC：PG摩尔比为7：1)的转移单层膜时，我们没有发现证据表明在高表面压力下DPPG单层组分被“挤出”，导致DPPC组分在转移单层膜中的浓缩。相反，IR结果表明，在高表面压下，DPPC-肺表面活性物质都是由肺泡II型细胞分泌的异质脂蛋白复合体。这种表面活性剂的作用是将体内空气-肺泡界面的表面张力降低到接近零的水平[参见Scarpelli(1988)]。肺表面活性物质的脂类成分已被鉴定为七大类磷脂(King&Clements，1972；Goerke&Clements，1986；Bonnano et al.，1992)。含有磷胆碱的磷脂(PC)1占表面活性物质磷脂的80~85%，其中一半以上属于饱和物种L，即2-二棕榈酰甘油-3-磷胆碱(DPPC)。第二种最丰富的类脂通常是磷甘油(PG)，它约占表面活性物质磷脂总量的5%-10%。表面活性剂脂质的其余部分由磷乙醇胺、磷肌醇、磷酸盐-
Revised Manuscript Received January 11, 1993 abstract: Phospholipid monomolecular films at the air/water interface were studied using Langmuir-Blodgett (LB) surface chemistry, 31P NMR spectroscopy, and infrared (IR) spectroscopy. These monolayers were composed of binary mixtures of acyl chain perdeuterated 1, 2-dipalmitoyl-szi-glycero-3-phosphocholine (ie, DPPC-ifo) with l, 2-dipalmitoyl-jn-glycero-3-phosphoglycerol (ie, DPPG). Thisparticular PC-PG binary mixture was chosen for study since this lipid system has been used as a model for pulmonary surfactant, especially in conjunction with theso-called “squeezing-out” hypothesis of pulmonary mechanics. This theory predicts that upon successive compression-expansion cycles, a surfactant surface film will reorganize to exclude all components except DPPC, thus resulting in a stable, low surface tension film. Several general results were obtained from these experiments. First, we have developed a combined spectroscopic assay using high-resolution 31P NMR spectroscopy in combination with the CH and CD vibrational intensities obtained from the IR spectroscopy of binary mixtures in which one component is acyl chain perdeuterated. Using attenuated total reflectance IR spectroscopy of transferred LB films, this combined spectroscopic approach allows us to quantitatively describe the fractional composition of each component in the binary monomolecular film. Second, when these methods are applied to transferred monolayer filmsof DPPC-ífa and DPPG (at an initial PC: PG mole ratio of 7: 1), we find no evidence for a “squeezing-out” of the DPPG monolayer component at high surfacepressure resulting in an enrichment of the DPPC component in the transferred monolayer film. On the contrary, the IR results indicatethat at high surfacepressures, both DPPC-Pulmonary surfactant is a heterogeneous lipid-protein complex which is secreted by type II cells of the pulmonary alveolus. The function of this surfactant is to reduce the surface tension in vivo at the air-alveolar interface to near zero [see, eg, Scarpelli (1988)]. The lipid constitutents of pulmonary surfactant have been characterizedchromatographically as belonging to as many as seven major phospholipid classes (King & Clements, 1972; Goerke & Clements, 1986; Bonnano et al., 1992). Lipid containing phosphocholine (PC) 1 can comprise up to 80^ 85% of surfactant phospholipids, with over half of the PC fraction belonging to the saturated species l, 2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). The second most abundant lipid class is usually phosphoglycerol (PG), which accounts for approximately 5-10% of the total surfactant phospholipid. The remainder of the surfactant lipid consists of phosphoethanolamines, phosphoinositols, phos-