Development of track-walking DNA nanomotors

Abstract

Artificial nanowalkers are inspired by bimolecular counterparts from living cells. More than a dozen of nanowalkers have been fabricated and demonstrated by various rectification mechanisms and driving methods, including ratchet and burn-the-bridge for the former and fuels, enzymes, light for the latter. These nanowalkers have been applied to nanoscale molecular transportation, chemical synthesis and more. However, the design principles of these artificial nanowalkers remain far from comparable to the biomotors. In this study, we developed two DNA bipedal walkers based on design principles derived from cellular walkers. The first one is light-powered. This walker gains a direction by pure physical mechanisms that autonomously amplify a local asymmetry into a ratchet effect for long-range directional motion. Besides, this fully light-driven walker has a distinct thermodynamic feature that it possesses the same equilibrium before and after operation, but generates a truly nonequilibrium distribution during operation. The second walker is fuel-driven and autonomously operated. This nanowalker couples both a ratchet effect and a power stroke to its fuel consumption cycle in a stepwise, controlled manner, thereby effectively channels the chemical energy of a single fuel molecule into productive directional motion before its decay into random heat. Implementing both ratchet and power stroke mechanically, this rationally designed system provides clues on how purely mechanical effects enable efficient chemical energy utilization at the single-molecule level. The design principles demonstrated by the two nanowalkers exploit mechanical effects and are adaptable for use in other nanomachines.