Oda R, Huc I, Schmutz M, Candau S J, MacKintosh F C
Institut Européen de Chimie et Biologie, Talence, France.
Nature. 1999 Jun 10;399(6736):566-9. doi: 10.1038/21154.
From seashells to DNA, chirality is expressed at every level of biological structures. In self-assembled structures it may emerge cooperatively from chirality at the molecular scale. Amphiphilic molecules, for example, can form a variety of aggregates and mesophases that express the chirality of their constituent molecules at a supramolecular scale of micrometres. Quantitative prediction of the large-scale chirality based on that at the molecular scale remains a largely unsolved problem. Furthermore, experimental control over the expression of chirality at the supramolecular level is difficult to achieve: mixing of different enantiomers usually results in phase separation. Here we present an experimental and theoretical description of a system in which chirality can be varied continuously and controllably ('tuned') in micrometre-scale structures. We observe the formation of twisted ribbons consisting of bilayers of gemini surfactants (two surfactant molecules covalently linked at their charged head groups). We find that the degree of twist and the pitch of the ribbons can be tuned by the introduction of opposite-handed chiral counterions in various proportions. This degree of control might be of practical value; for example, in the use of the helical structures as templates for helical crystallization of macromolecules.
从贝壳到脱氧核糖核酸（DNA），手性在生物结构的各个层面都有体现。在自组装结构中，它可能从分子尺度的手性协同产生。例如，两亲分子可以形成各种聚集体和中间相，在微米级的超分子尺度上表现出其组成分子的手性。基于分子尺度的手性对大规模手性进行定量预测在很大程度上仍是一个未解决的问题。此外，在超分子水平上对手性表达进行实验控制很难实现：不同对映体的混合通常会导致相分离。在此，我们给出了一个系统的实验和理论描述，在该系统中，手性可以在微米级结构中连续且可控地（“调节”）变化。我们观察到由双子表面活性剂（两个表面活性剂分子在其带电头部基团处共价连接）双层组成的扭曲带的形成。我们发现，通过以不同比例引入相反手性的手性抗衡离子，可以调节带的扭曲程度和螺距。这种控制程度可能具有实际价值；例如，在将螺旋结构用作大分子螺旋结晶的模板方面。
