Department of Material Chemistry, Graduate School of Engineering , Kyoto University , Kyoto-Daigaku-Katsura, Nishikyo-ku, Kyoto 615-8510 , Japan.
J Phys Chem B. 2018 Jul 19;122(28):7178-7184. doi: 10.1021/acs.jpcb.8b03419. Epub 2018 Jul 5.
Two kinds of amphiphilic polypeptoids having different types of hydrophilic polypeptoids, poly(sarcosine)- b-(l-Leu-Aib) (ML12) and poly( N-ethyl glycine)- b-(l-Leu-Aib) (EL12), were self-assembled via two paths to phase-separated nanotubes. One path was via sticking ML12 nanotubes with EL12 nanotubes and the other was a preparation from a mixture of ML12 and EL12 in solution. In either case, nanotubes showed temperature-induced phase separation along the long axis, which was observed by two methods of labeling one phase with gold nanoparticles and fluorescence resonance energy transfer between the components. The phase separation was ascribed to aggregation of poly( N-ethyl glycine) blocks over the cloud point temperature. The addition of 5% trifluoroethanol was needed for the phase separation because the tight association of the helices in the hydrophobic region should be loosened to allow lateral diffusion of the components to be separated. The phase separation in molecular assemblies in water based on the hydrophilic-region-driven-type mechanism therefore requires sophisticated balances of association forces exerting among the hydrophilic and hydrophobic regions of the amphiphilic polypeptoids.
两种两亲性聚肽两亲体具有不同类型的亲水聚肽两亲体，聚（肌氨酸）-b-（l-亮氨酸-Aib）（ML12）和聚（N-乙基甘氨酸）-b-（l-亮氨酸-Aib）（EL12），通过两条路径自组装成相分离的纳米管。一条路径是通过将 ML12 纳米管与 EL12 纳米管粘合并，另一条是从 ML12 和 EL12 在溶液中的混合物制备而来。在这两种情况下，纳米管都表现出沿长轴的温度诱导相分离，这可以通过两种标记方法之一观察到，即用金纳米颗粒标记一个相和组件之间的荧光共振能量转移。相分离归因于聚（N-乙基甘氨酸）块在浊点温度以上的聚集。需要添加 5%的三氟乙醇来进行相分离，因为疏水区中螺旋的紧密缔合应该被削弱，以便分离的组件能够侧向扩散。因此，基于亲水区域驱动型机制的水相中的分子组装中的相分离需要在两亲性聚肽两亲体的亲水和疏水区域之间施加的缔合力之间进行精细的平衡。
