调控人工膜形态：pH诱导两亲性共轭聚合物的颜色转变及纳米结构转变——从蓝色螺旋带变为红色纳米纤维

Modulating artificial membrane morphology: pH-induced chromatic transition and nanostructural transformation of a bolaamphiphilic conjugated polymer from blue helical ribbons to red nanofibers.

作者信息

Song J, Cheng Q, Kopta S, Stevens R C

机构信息

Materials Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720, USA.

出版信息

J Am Chem Soc. 2001 Apr 11;123(14):3205-13. doi: 10.1021/ja0035046.

DOI:10.1021/ja0035046

PMID:11457054

Abstract

Design and characterization of helical ribbon assemblies of a bolaamphiphilic conjugated polymer and their color-coded transformation into nanofibers are described. An L-glutamic acid modified bolaamphiphilic diacetylene lipid was synthesized and self-assembled into right-handed helical ribbons with micron scale length and nano scale thickness under mild conditions. The ribbon structures were further stabilized by polymerizing well-aligned diacetylene units to form bisfunctional polydiacetylenes (PDAs). Transitions from flat sheets to helical ribbons and tubes were observed by transmission electron microscopy. The helical ribbons appear to originate from the rupture of flat sheets along domain edges and the peeling off between stacked lipid layers. These results point to the applicability of chiral packing theory in bolaamphiphilic supramolecular assemblies. Contact mode atomic force microscopy observations revealed that high order existed in the surface packing arrangement. Hexagonal and pseudorectangular packings were observed in flat and twisted regions of the ribbons, respectively, suggesting a correlation between microscopic morphologies and nanoscopic packing arrangements. The tricarboxylate functionalities of the bolaamphiphilic lipid provide a handle for the manipulation of the bisfunctional PDAs' morphology. Increasing solution pH caused the fraying of helical ribbons into nanofibers accompanied by a sharp blue-to-red chromatic transition. A dramatic change in circular dichroism spectra was observed during this process, suggesting the loss of chirality in packing. A model is proposed to account for the pH-induced morphological change and chromatic transition. The color-coded transition between two distinct microstructures would be useful in the design of sensors and other "smart" nanomaterials requiring defined molecular templates.

摘要

本文描述了一种双亲性共轭聚合物的螺旋带状组装体的设计与表征，以及它们通过颜色编码转变为纳米纤维的过程。合成了一种L-谷氨酸修饰的双亲性二乙炔脂质，并在温和条件下自组装成具有微米级长度和纳米级厚度的右手螺旋带。通过聚合排列良好的二乙炔单元形成双功能聚二乙炔（PDA），使带状结构进一步稳定。通过透射电子显微镜观察到从平板到螺旋带和管的转变。螺旋带似乎起源于平板沿畴边缘的破裂以及堆叠脂质层之间的剥离。这些结果表明手性堆积理论在双亲性超分子组装体中的适用性。接触模式原子力显微镜观察表明，表面堆积排列存在高阶结构。在带的平坦区域和扭曲区域分别观察到六边形和伪矩形堆积，这表明微观形态与纳米级堆积排列之间存在相关性。双亲性脂质的三羧酸官能团为双功能PDA的形态操纵提供了一个途径。提高溶液pH值会导致螺旋带磨损成纳米纤维，同时伴随着从蓝色到红色的急剧颜色转变。在此过程中观察到圆二色光谱发生了显著变化，这表明堆积中的手性丧失。提出了一个模型来解释pH值诱导的形态变化和颜色转变。两种不同微观结构之间的颜色编码转变将有助于设计需要确定分子模板的传感器和其他“智能”纳米材料。