Wrap and Slide

摘要

In rotaxanes, a central building block in the burgeoning field of nanometer-scale synthetic machines, a molecular ring can shuttle back and forth along a molecular rod but is kept from falling off by bulky stopper groups at each end. Gan et al. (p. 1172) have designed a variant of this motif in which the ring is replaced by a tightly wound helix. Because the unwinding rate is relatively slow, the helix can slide between binding sites on the rod, despite topologically remaining an open structure. This strategy confers flexibility on the assembly process, which no longer requires kinetically delicate ring-closing and/or stopper-addition reactions.