Zerrouki D, Baudry J, Pine D, Chaikin P, Bibette J
Laboratoire Colloïdes et Matériaux Divisés, ESPCI, UPMC, CNRS, ParisTech, 10 rue Vauquelin, 75005 Paris, France.
Nature. 2008 Sep 18;455(7211):380-2. doi: 10.1038/nature07237.
Chirality is an important element of biology, chemistry and physics. Once symmetry is broken and a handedness is established, biochemical pathways are set. In DNA, the double helix arises from the existence of two competing length scales, one set by the distance between monomers in the sugar backbone, and the other set by the stacking of the base pairs. Here we use a colloidal system to explore a simple forcing route to chiral structures. To do so we have designed magnetic colloids that, depending on both their shape and induced magnetization, self-assemble with controlled helicity. We model the two length scales with asymmetric colloidal dumbbells linked by a magnetic belt at their waist. In the presence of a magnetic field the belts assemble into a chain and the steric constraints imposed by the asymmetric spheres force the chain to coil. We show that if the size ratio between the spheres is large enough, a single helicity is adopted, right or left. The realization of chiral colloidal clusters opens up a new link between colloidal science and chemistry. These colloidal clusters may also find use as mesopolymers, as optical and light-activated structures, and as models for enantiomeric separation.
手性是生物学、化学和物理学中的一个重要元素。一旦对称性被打破且一种手性得以确立，生物化学途径就会被设定。在DNA中，双螺旋的形成源于两种相互竞争的长度尺度的存在，一种由糖骨架中单体之间的距离设定，另一种由碱基对的堆积设定。在此，我们使用一种胶体系统来探索通往手性结构的简单强迫途径。为此，我们设计了磁性胶体，其根据自身形状和感应磁化强度，以可控的螺旋度进行自组装。我们用腰部由磁带来连接的不对称胶体哑铃对这两种长度尺度进行建模。在磁场存在的情况下，这些带组装成一条链，不对称球体施加的空间位阻迫使链发生卷曲。我们表明，如果球体之间的尺寸比足够大，就会采用单一的螺旋度，左旋或右旋。手性胶体簇的实现为胶体科学与化学之间开辟了新的联系。这些胶体簇还可能用作介观聚合物、光学和光激活结构以及对映体分离的模型。
