Department of Chemistry, Durham University, Durham, UK.
SPOCK Group, Department of Mathematical Sciences, Durham University, Durham, UK.
Nat Chem. 2019 Apr;11(4):375-381. doi: 10.1038/s41557-019-0222-0. Epub 2019 Mar 4.
Helical nanofibres play key roles in many biological processes. Entanglements between helices can aid gelation by producing thick, interconnected fibres, but the details of this process are poorly understood. Here, we describe the assembly of an achiral oligo(urea) peptidomimetic compound into supramolecular helices. Aggregation of adjacent helices leads to the formation of fibrils, which further intertwine to produce high-fidelity braids with periodic crossing patterns. A braid theory analysis suggests that braiding is governed by rigid topological constraints, and that branching occurs due to crossing defects in the developing braids. Mixed-chirality helices assemble into relatively complex, odd-stranded braids, but can also form helical bundles by undergoing inversions of chirality. The oligo(urea) assemblies are also highly sensitive to chiral amplification, proposed to occur through a majority-rules mechanism, whereby trace chiral materials can promote the formation of gels containing only homochiral helices.
螺旋纳米纤维在许多生物过程中起着关键作用。螺旋之间的缠结可以通过产生较厚的相互连接的纤维来帮助凝胶化，但是这个过程的细节还不太清楚。在这里，我们描述了一种非手性寡聚（脲）类肽模拟物化合物组装成超分子螺旋的过程。相邻螺旋的聚集导致纤维的形成，进一步缠绕以产生具有周期性交叉图案的高保真辫子。辫子理论分析表明，辫子的形成受刚性拓扑约束控制，分支是由于发展中的辫子中的交叉缺陷引起的。混合手性螺旋组装成相对复杂的奇数股辫子，但也可以通过手性反转形成螺旋束。寡聚（脲）组装体对手性放大也非常敏感，据推测，手性放大是通过多数规则机制发生的，其中痕量手性物质可以促进形成仅含有同手性螺旋的凝胶。
