Division of Physical Chemistry, Lund University, SE-22100 Lund, Sweden.
Soft Matter. 2020 Mar 21;16(11):2642-2651. doi: 10.1039/c9sm02244a. Epub 2020 Mar 2.
We report here on a peptide hydrogel system, which in contrast to most other such systems, is made up of relatively short fibrillar aggregates, discussing resemblance with colloidal rods. The synthetic model peptides AK and AK, where A denotes alanine and K lysine, self-assemble in aqueous solutions into ribbon-like aggregates having an average length 〈L〉 on the order of 100 nm and with a diameter d≈ 6 nm. The aggregates can be seen as weakly charged rigid rods and they undergo an isotropic to nematic phase transition at higher concentrations. Translational motion perpendicular to the rod axis gets strongly hindered when the concentration is increased above the overlap concentration. Similarly, the rotational motion is hindered, leading to very long stress relaxation times. The peptide self-assembly is driven by hydrophobic interactions and due to a net peptide charge the system is colloidally stable. However, at the same time short range, presumably hydrophobic, attractive interactions appear to affect the rheology of the system. Upon screening the long range electrostatic repulsion, with the addition of salt, the hydrophobic attraction becomes more dominant and we observe a transition from a repulsive glassy state to an attractive gel-state of the rod-like peptide aggregates.
我们在这里报告一个肽水凝胶系统，与大多数其他此类系统相比，它由相对较短的纤维状聚集体组成，讨论与胶体棒的相似之处。合成模型肽 AK 和 AK，其中 A 表示丙氨酸，K 表示赖氨酸，在水溶液中自组装成具有平均长度〈L〉约 100nm 且直径 d≈6nm 的带状聚集体。这些聚集体可以看作是带弱电荷的刚性棒，并且在较高浓度下经历各向同性到向列相转变。当浓度高于重叠浓度时，垂直于棒轴的平移运动受到强烈阻碍。同样，旋转运动受到阻碍，导致非常长的应力松弛时间。肽自组装由疏水相互作用驱动，由于肽的净电荷，该系统具有胶体稳定性。然而，同时，短程的、可能是疏水的吸引力似乎会影响系统的流变学性质。通过筛选长程静电排斥，加入盐后，疏水吸引力变得更加占主导地位，我们观察到从排斥的玻璃态到棒状肽聚集体的吸引的凝胶态的转变。
