Arnett E M, Gold J M, Harvey N, Johnson E A, Whitesell L G
Department of Chemistry, Duke University, Durham, North Carolina 27706.
Adv Exp Med Biol. 1988;238:21-36. doi: 10.1007/978-1-4684-7908-9_3.
During the past ten years we have investigated the stereochemistry of intermolecular interactions in monolayers at the air-water interface, a field which has never been developed explicitly before to our knowledge. Although we demonstrated clear enantiomeric and diastereomeric interactions for a number of chiral surfactants, we found no evidence whatsoever for stereoselective interaction in dipalmitoylphosphatidylcholine (DPPC) monolayers or vesicles by standard monolayer techniques, differential scanning calorimetry or ultra-highfield NMR. The present article extends these observations to dimyristoyl- and dilauroylphosphatidylcholine. Results from dynamic surface tension studies are also reported. In no case could chiral recognition be demonstrated using the 95% confidence limit as the criterion. In our previous study of DPPC mixtures with another chiral surfactant the question arose as to whether chiral interactions could be transmitted through intervening phospholipid molecules. This question is addressed by examining the force-area curves for a variety of mixed monolayers composed of chiral surfactants and phospholipids. We conclude that the chiral discrimination observed in some of these mixed monolayers is due to the direct interaction of chiral centers, and not due to the transmission of chirality from one stereocenter to the next through intermediate achiral molecules. Finally, we will consider the question of why phospholipids, the most ubiquitous of natural chiral surfactants, should show so little chiral discrimination in view of the wide occurrence of high stereoselectivity in many natural processes.
在过去十年中，我们研究了空气-水界面单分子层中分子间相互作用的立体化学，据我们所知，这一领域此前从未得到明确发展。尽管我们已证明多种手性表面活性剂存在明显的对映体和非对映体相互作用，但通过标准单分子层技术、差示扫描量热法或超高场核磁共振，我们在二棕榈酰磷脂酰胆碱（DPPC）单分子层或囊泡中未发现任何立体选择性相互作用的证据。本文将这些观察结果扩展至二肉豆蔻酰磷脂酰胆碱和二月桂酰磷脂酰胆碱。还报告了动态表面张力研究的结果。在任何情况下，均无法以95%置信限作为标准来证明手性识别。在我们之前对DPPC与另一种手性表面活性剂混合物的研究中，出现了手性相互作用是否可通过中间的磷脂分子传递的问题。通过检查由手性表面活性剂和磷脂组成的各种混合单分子层的力-面积曲线来解决这个问题。我们得出结论，在其中一些混合单分子层中观察到的手性识别是由于手性中心的直接相互作用，而非由于手性从一个立体中心通过中间的非手性分子传递到下一个立体中心。最后，鉴于在许多自然过程中广泛存在高立体选择性，我们将思考为什么磷脂这种最普遍存在的天然手性表面活性剂却表现出如此少的手性识别。
