Directional control of a processive molecular hopper

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Science  31 Aug 2018:
Vol. 361, Issue 6405, pp. 908-912
DOI: 10.1126/science.aat3872

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Tiny cargos ferried along a track

Control of molecules at the nanometer scale requires motors that convert potential energy into movement. Qing et al. designed a small molecule that could hop along a track of cysteine residues within a membrane-embedded protein pore. The direction of processive movement along the track was reversible, driven by an applied potential across the membrane. Cargos were attached to a carrier motor, and their position and chemical identity read out from changes in the current through the pore. These features enabled repeat observations of a single molecule as it moved back and forth on the track.

Science, this issue p. 908


Intrigued by the potential of nanoscale machines, scientists have long attempted to control molecular motion. We monitored the individual 0.7-nanometer steps of a single molecular hopper as it moved in an electric field along a track in a nanopore controlled by a chemical ratchet. The hopper demonstrated characteristics desired in a moving molecule: defined start and end points, processivity, no chemical fuel requirement, directional motion, and external control. The hopper was readily functionalized to carry cargos. For example, a DNA molecule could be ratcheted along the track in either direction, a prerequisite for nanopore sequencing.

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