Peptide-based biopolymers represent highly promising biocompatible materials with multiple applications, such as tailored drug delivery, tissue engineering and regeneration, and as stimuli-responsive materials. Herein, we report the pH- and concentration-dependent self-assembly and conformational transformation of the newly synthesized octapeptide PEP-1. At pH 7.4, PEP-1 forms β-sheet-rich secondary structures into fractal-like morphologies, as verified by circular dichroism (CD), Fourier-transform infrared (FTIR) spectroscopy, thioflavin T (ThT) fluorescence spectroscopy assay, and atomic force microscopy (AFM). Upon changing the pH value (using pH 5.5 and 13.0), PEP-1 forms different types of secondary structures and resulting morphologies due to electrostatic repulsion between charged amino acids. PEP-1 can also form helical or random-coil secondary structures at a relatively low concentration. The obtained pH-sensitive self-assembly behavior of the target octapeptide is expected to contribute to the development of novel drug nanocarrier assemblies.

中文翻译：

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天然八肽的pH和浓度依赖性超分子自组装。

基于肽的生物聚合物代表了具有多种应用的高度有前途的生物相容性材料，例如量身定制的药物输送，组织工程和再生，以及作为刺激反应性材料。在这里，我们报告了新合成的八肽PEP-1的pH和浓度依赖性自组装和构象转化。在pH 7.4时，PEP-1将富含β-折叠的二级结构形成为类似分形的形态，这已通过圆二色性（CD），傅立叶变换红外（FTIR）光谱，硫代黄素T（ThT）荧光光谱法和原子分析证实力显微镜（AFM）。在改变pH值（使用pH 5.5和13.0）时，PEP-1由于带电氨基酸之间的静电排斥作用而形成不同类型的二级结构和所形成的形态。PEP-1还可以以相对较低的浓度形成螺旋或无规螺旋二级结构。目标八肽的pH敏感的自组装行为有望有助于新型药物纳米载体组装的发展。