Edwards William, Smith David K
Department of Chemistry, University of York, Heslington, York YO10 5DD, UK.
Gels. 2018 Mar 29;4(2):31. doi: 10.3390/gels4020031.
The impact of chirality on the self-assembly of supramolecular gels is of considerable importance, as molecular-scale programming can be translated into nanostructuring and ultimately affect macroscopic performance. This paper explores the effect of chirality on the assembly of two-component gels comprised of a second-generation dendritic lysine peptide acid, containing three chiral centres, and an amine. This combination forms an acid⁻amine complex that assembles into nanofibres through peptide-peptide hydrogen bonds, leading to organogels. With achiral amines, a racemic mixture of l,l,l and d,d,d dendritic peptide acids surprisingly forms the best gels-more commonly, mixing enantiomers suppresses gelation. Thermodynamic studies demonstrate that depending on the amine, the greater stability of heterochiral gels can either be entropically or enthalpically driven. With amines possessing "" chirality, the l,l,l peptide acid consistently forms more effective gels than its d,d,d analogue. Furthermore, in mixed gels, l,l,l sometimes imposes its assembly preference onto d,d,d. In summary, this paper demonstrates a rare example in which heterochiral gels are preferred, and also explores directing effects when each component in a two-component gel is chiral.
手性对超分子凝胶自组装的影响至关重要，因为分子尺度的编程可转化为纳米结构并最终影响宏观性能。本文探讨了手性对由含三个手性中心的第二代树枝状赖氨酸肽酸和一种胺组成的双组分凝胶组装的影响。这种组合形成了一种酸⁻胺复合物，该复合物通过肽 - 肽氢键组装成纳米纤维，从而形成有机凝胶。使用非手性胺时，l,l,l和d,d,d树枝状肽酸的外消旋混合物出人意料地形成了最佳凝胶——更常见的是，混合对映体抑制凝胶化。热力学研究表明，取决于胺的种类，异手性凝胶的更高稳定性可以由熵或焓驱动。对于具有“”手性的胺，l,l,l肽酸始终比其d,d,d类似物形成更有效的凝胶。此外，在混合凝胶中，l,l,l有时会将其组装偏好强加于d,d,d。总之，本文展示了一个异手性凝胶更受青睐的罕见例子，并且还探讨了双组分凝胶中每个组分都是手性时的导向效应。
