Molecular Materials, Department of Applied Physics and Center for New Materials, Helsinki University of Technology, Espoo, Finland.
Biomacromolecules. 2009 Oct 12;10(10):2787-94. doi: 10.1021/bm900630u.
This work describes the solid-state conformational and structural properties of self-assembled polypeptide-surfactant complexes with double-tailed surfactants. Poly(L-lysine) was complexed with three dialkyl esters of phosphoric acid (i.e., phosphodiester surfactants), where the surfactant tail branching and length was varied to tune the supramolecular architecture in a facile way. After complexation with the branched surfactant bis(2-ethylhexyl) phosphate in an aqueous solution, the polypeptide chains adopted an alpha-helical conformation. These rod-like helices self-assembled into cylindrical phases with the amorphous alkyl tails pointing outward. In complexes with dioctyl phosphate and didodecyl phosphate, which have two linear n-octyl or n-dodecyl tails, respectively, the polypeptide formed antiparallel beta-sheets separated by alkyl layers, resulting in well-ordered lamellar self-assemblies. By heating, it was possible to trigger a partial opening of the beta-sheets and disruption of the lamellar phase. After repeated heating/cooling, all of these complexes also showed a glass transition between 37 and 50 degrees C. Organic solvent treatment and plasticization by overstoichiometric amount of surfactant led to structure modification in poly(L-lysine)-dioctyl phosphate complexes, PLL(diC8)(x) (x = 1.0-3.0). Here, the alpha-helical PLL is surrounded by the surfactants and these bottle-brush-like chains self-assemble in a hexagonal cylindrical morphology. As x is increased, the materials are clearly plasticized and the degree of ordering is improved: The stiff alpha-helical backbones in a softened surfactant matrix give rise to thermotropic liquid-crystalline phases. The complexes were examined by Fourier transform infrared spectroscopy, small- and wide-angle X-ray scattering, transmission electron microscopy, differential scanning calorimetry, polarized optical microscopy, and circular dichroism.
本工作描述了具有双尾表面活性剂的自组装多肽-表面活性剂复合物的固态构象和结构性质。聚（L-赖氨酸）与三种磷酸二酯（即磷酸酯表面活性剂）的二烷基酯复合，其中通过改变表面活性剂支化和长度来轻松调节超分子结构。在水溶液中与支化表面活性剂双（2-乙基己基）磷酸酯复合后，多肽链采用α-螺旋构象。这些棒状螺旋体自组装成具有无定形烷基尾向外指向的圆柱相。在与具有两条线性正辛基或正十二烷基尾的辛基磷酸二酯和十二基磷酸二酯的复合物中，多肽形成由烷基层隔开的反平行β-折叠，导致有序的层状自组装。通过加热，可以触发β-折叠的部分打开和层状相的破坏。经过反复加热/冷却，所有这些复合物也在 37 至 50 摄氏度之间显示出玻璃化转变。有机溶剂处理和过量表面活性剂的塑化导致聚（L-赖氨酸）-辛基磷酸二酯复合物，PLL(diC8)(x)（x = 1.0-3.0）的结构修饰。在这里，α-螺旋 PLL 被表面活性剂包围，这些刷状链在六方圆柱形态中自组装。随着 x 的增加，材料明显被塑化，有序度提高：在软化的表面活性剂基质中僵硬的α-螺旋骨干赋予热致液晶相。通过傅里叶变换红外光谱、小角和广角 X 射线散射、透射电子显微镜、差示扫描量热法、偏光显微镜和圆二色性对复合物进行了研究。
