Department of Chemistry and Biochemistry, University of Kitakyushu , 1-1 Hibikino, Kitakyushu, Fukuoka 808-0135, Japan.
Langmuir. 2017 Apr 25;33(16):4019-4027. doi: 10.1021/acs.langmuir.7b00603. Epub 2017 Apr 11.
We have prepared a new calix[4]arene-based lipid containing glutamic acid as the hydrophilic group. The α-amine and the γ-carboxylic acid groups of the glutamic acid moiety allowed a continuous change in the state of the headgroup from cationic to zwitterionic and then to anionic with increasing pH. Accompanying this headgroup change, micelles of the lipid underwent a morphological transformation from spherical to cylindrical and again to spherical. The morphological transition was ascribed to the change in the lipid conformation corresponding to the pH conditions. Interestingly, at acidic and basic pH, the spherical micelles demonstrated monodispersity in terms of the aggregation number, which agreed with the vertex numbers of Platonic solids, indicating the formation of Platonic micelles. At acidic and basic pH, the lipid conformations were almost identical, but there was a slight difference in the hydrophilic volume, which might affect the packing behavior of the lipid in micelles and account for the difference in the aggregation number. This study clearly demonstrates the precise pH-controllable aggregation number of micelles, which belong to the Platonic micelle systems.
我们制备了一种新型杯[4]芳烃基脂质，其中包含作为亲水基团的谷氨酸。谷氨酸部分的α-氨基和γ-羧酸基允许头基的状态连续变化，从阳离子到两性离子，再到随着 pH 值的增加变为阴离子。伴随这个头基变化，脂质的胶束经历了从球形到圆柱形再到球形的形态转变。这种形态转变归因于与 pH 条件相对应的脂质构象变化。有趣的是，在酸性和碱性 pH 下，球形胶束在聚集数方面表现出单分散性，这与柏拉图立体的顶点数一致，表明形成了柏拉图胶束。在酸性和碱性 pH 下，脂质构象几乎相同，但亲水体积略有差异，这可能影响脂质在胶束中的组装行为，并解释聚集数的差异。本研究清楚地表明，属于柏拉图胶束体系的胶束具有精确的 pH 可控聚集数。
