A study of the structure and chiral selectivity of micelles of two isomeric D-glucopyranoside-based surfactants
作者:David Tickle、Ashley George、Kevin Jennings、Patrick Camilleri、Anthony J. Kirby
DOI:10.1039/a708418h
日期:——
We have synthesised the sodium salts of two isomeric surfactants that differ in the anomeric orientation of the C14 hydrocarbon chain to the D-glucopyranoside fused ring structure, containing a phosphate polar head group. The inclusion of α- and β-anomers in the separation buffer, using micellar electrokinetic capillary chromatography (MECC) shows that the latter is the superior chiral selector. The critical micelle concentration (cmc) for both surfactants was around 0.6 mM, and the mean aggregation number is 65 for both anomers. In an attempt to understand the possible mechanism of chiral discrimination, we have calculated minimum energy conformations of micelles produced by these surfactants, and have established the importance of their chiral head groups and the sodium counter-ions in the discriminating process. We have also investigated the micro-structures of the two surfactants by transmission electron microscopy. This technique shows that the two enantiomers aggregate very differently; whereas the α-anomer shows randomly orientated string-like forms the β-anomer forms ordered ‘whorl’ arrays.
我们合成了两种异构表面活性剂的钠盐,它们的 C14 碳氢链与含有磷酸极性头基的 D-吡喃葡萄糖苷融合环结构的异构取向不同。使用胶束电动毛细管色谱法(MECC)在分离缓冲液中加入α和β异构体,结果表明后者是更好的手性选择剂。两种表面活性剂的临界胶束浓度(cmc)都在 0.6 mM 左右,两种异构体的平均聚集数都是 65。为了了解手性识别的可能机制,我们计算了这些表面活性剂产生的胶束的最小能量构象,并确定了它们的手性头基和钠反离子在识别过程中的重要性。我们还利用透射电子显微镜研究了这两种表面活性剂的微观结构。该技术表明,这两种对映体的聚集方式截然不同;α-对映体呈现出随机定向的串状形式,而 β-对映体则形成了有序的 "轮状 "阵列。