Chang Wei-Han, Chuang Yun-Ting, Yu Cheng-Yeh, Chang Chien-Hsiang, Yang Yu-Min
Department of Chemical Engineering, National Cheng Kung University.
J Oleo Sci. 2017 Nov 1;66(11):1229-1238. doi: 10.5650/jos.ess17086. Epub 2017 Oct 11.
The incorporation of additive in lipid bilayers is one of the ordinary approaches for modulating their properties. Additive effect on phase transition of ion-pair amphiphile (IPA) bilayers, however, is not known. In this work, four double-chained IPAs with different hydrocarbon chain lengths and symmetry were designed and synthesized from single-chained cationic and anionic surfactants by the precipitation method. By using differential scanning calorimetry (DSC), the thermotropic transition behavior from gel phase (L) through rippled phase (P) if any to liquid-crystalline phase (L) was studied for bilayers of these lipid-like IPAs in excess water. The effects of three sterol-like additives (cholesterol, α-tocopherol, and α-tocopheryl acetate) in IPA bilayers on thermal phase behavior were then systematically investigated. The experimental results revealed that with increasing concentration of additive, the phase transition temperatures were unaffected on the one hand and the enthalpies of phase transition were decreased on the other hand. When the addition of additive exceeded a specific amount, the phase transition disappeared. More hasty disappearance of phase transition was found for IPAs with lower total number of carbon atoms in the hydrocarbon chains. For IPAs with the same total number of carbon atoms in the hydrocarbon chains, the disappearance of phase transition is more hasty for the asymmetric one than for the symmetric one. Similar effects on thermal phase behavior of four IPA bilayers were exhibited by the three additives with similar chemical structures. Possible mechanism of additive effects on phase transition of IPA bilayers was then proposed in line with that of lipid bilayers.
在脂质双层中加入添加剂是调节其性质的常用方法之一。然而，添加剂对离子对两亲物（IPA）双层相变的影响尚不清楚。在这项工作中，通过沉淀法由单链阳离子和阴离子表面活性剂设计并合成了四种具有不同烃链长度和对称性的双链IPA。使用差示扫描量热法（DSC），研究了这些类脂质IPA双层在过量水中从凝胶相（L）通过波纹相（P）（如果有的话）到液晶相（L）的热致转变行为。然后系统地研究了IPA双层中三种类甾醇添加剂（胆固醇、α-生育酚和α-生育酚乙酸酯）对热相行为的影响。实验结果表明，随着添加剂浓度的增加，一方面相变温度不受影响，另一方面相变焓降低。当添加剂的添加量超过特定量时，相变消失。对于烃链中碳原子总数较少的IPA，相变消失得更快。对于烃链中碳原子总数相同的IPA，不对称的IPA比对称的IPA相变消失得更快。三种化学结构相似的添加剂对四种IPA双层的热相行为表现出相似的影响。然后根据脂质双层的情况提出了添加剂对IPA双层相变影响的可能机制。
