Increased water solubility and long-range intermolecular ordering have been introduced into the fluorescent organic molecule thiophene-diketopyrrolopyrrole (TDPP) via its conjugation to the octapeptide HEFISTAH, which is derived from the protein–protein β-interface of the homo-tetramer protein diaminopimelate decarboxylase. The octapeptide, and its TDPP mono- and cross-linked conjugates were synthesised using 9-fluorenylmethoxycarbonyl (Fmoc) based solid-phase peptide synthesis (SPPS). Unlike the unmodified peptide, the resulting mono-linked and cross-linked peptides showed a fibrous morphology and formed hydrogels at 4 wt% in water at neutral pH, but failed to assemble at pH 2 and pH 9. Further peptide characterization showed that the TDPP organic core enhances peptide self-assembly and that both peptides assembled into fibers with a parallel β-sheet structure. Furthermore, UV-vis spectroscopic analysis suggests that the TDPP molecules form H-type aggregates where the chromophores are likely to be co-facially packed, but rotationally and/or laterally offset from one another. This intermolecular coupling indicates that π–π stacking interactions are highly likely – a favourable sign for charge transport. The enhanced aqueous solubility and self-assembling properties of the TDPP–peptide conjugates allowed the successful preparation of thin films. Atomic force microscopy, X-ray diffraction and UV-vis spectroscopic analysis of these thin films revealed that the hybrid materials retained a fibrous morphology, β-sheet structures and strong intermolecular coupling between neighbouring TDPP molecules. These results open an exciting avenue for bio-organic materials development, through structural and electronic tuning of the TDPP core.

中文翻译：

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肽-二酮吡咯并吡咯共轭物的定向自组装-生物有机薄膜制备的平台。

增加的水溶解性和长程有序的分子间导入了荧光有机分子噻吩二酮吡咯并吡咯（TDPP）经由它与八肽HEFISTAH结合，后者源自同四聚体蛋白质二氨基庚二酸酯脱羧酶的蛋白质-蛋白质β-界面。使用基于9-芴基甲氧基羰基（Fmoc）的固相肽合成（SPPS）合成八肽及其TDPP单和交联缀合物。与未修饰的肽不同，所得的单链和交联肽在中性pH值下于水中以4 wt％表现出纤维形态并形成水凝胶，但在pH 2和pH 9下无法组装。进一步的肽表征表明TDPP有机核心增强了肽的自组装，并且两个肽都组装成具有平行β折叠结构的纤维。此外，紫外可见光谱分析表明，TDPP分子形成H型聚集体，发色团很可能被共面堆积，但在旋转和/或侧向相互错位。这种分子间的耦合表明π-π堆积相互作用极有可能，这是电荷传输的有利信号。TDPP-肽共轭物的增强的水溶性和自组装性能使薄膜得以成功制备。这些薄膜的原子力显微镜，X射线衍射和紫外可见光谱分析表明，杂化材料保留了纤维形态，β片层结构以及相邻TDPP分子之间的强分子间偶联。这些结果为生物有机材料的开发开辟了令人兴奋的途径，