Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK.
Phys Chem Chem Phys. 2021 Feb 28;23(8):4597-4604. doi: 10.1039/d0cp05477a. Epub 2021 Feb 23.
Diphenylalanine (FF) has been shown to self-assemble from water into heterogeneous fibres that are among the stiffest biomaterials known. How and why the fibres form has, however, not been clear. In this work, the nucleation and growth of FF fibres was investigated in a combined experimental and theoretical study. Scanning electron microscopy and optical microscopy showed FF fibre morphology to be hollow tubes of varying widths with occasional endcaps. Molecular dynamics simulations of FF nanostructures based on the bulk crystalline geometry demonstrated that axial growth stablilises the fibres and that structures with different widths show similar stabilities, in accord with the wide range of fibre widths observed experimentally. Linear dichroism (LD) spectroscopy was used to determine the thermal stability of the fibres, showing that FF solutions are fully monomeric at 70 °C and that fibres begin to form at ∼40 °C upon cooling. The LD kinetic studies indicated a nucleation-driven assembly with subsequent fibre growth, but a secondary nucleation process is required to explain the data.
二苯丙氨酸（FF）已被证明可自组装成水相异质纤维，这些纤维是已知的最硬的生物材料之一。然而，纤维的形成方式和原因尚不清楚。在这项工作中，通过实验和理论相结合的研究，研究了 FF 纤维的成核和生长。扫描电子显微镜和光学显微镜显示，FF 纤维形态为具有不同宽度的空心管，偶尔带有端帽。基于块状晶体几何形状的 FF 纳米结构的分子动力学模拟表明，轴向生长稳定了纤维，并且具有不同宽度的结构表现出相似的稳定性，与实验中观察到的广泛纤维宽度一致。线性二色性（LD）光谱用于确定纤维的热稳定性，表明 FF 溶液在 70°C 时完全为单体，并且在冷却时，纤维在约 40°C 开始形成。LD 动力学研究表明，组装是由成核驱动的，随后是纤维生长，但需要二次成核过程来解释数据。
