Continuous observation of the stochastic motion of an individual small-molecule walker.

ABSTRACT: Motion--whether it the ability to change shape, rotate or translate--is an important potential asset for functional nanostructures. For translational motion, a variety of DNA-based and small-molecule walkers have been created, but observing the translational motion of individual molecules in real time remains a significant challenge. Here, we show that the movement of a small-molecule walker along a five-foothold track can be monitored continuously within a protein nanoreactor. The walker is an organoarsenic(III) molecule with exchangeable thiol ligands, and the track a line of cysteine residues 6?Å apart within an ?-haemolysin protein pore that acts as the nanoreactor. Changes in the flow of ionic current through the pore reflect the individual steps of a single walker, which require the making and breaking of As-S bonds, and occur in aqueous solution at neutral pH and room temperature. The walker moves considerably faster (?0.7?s per step) than previous walkers based on covalent chemistry and is weakly processive (6?±?1 steps per outing). It shows weak net directional movement, which can be described by a thermodynamic sink arising from the different environments of the cysteines that constitute the track.

SUBMITTER: Pulcu GS 

PROVIDER: S-EPMC5011421 | biostudies-literature | 2015 Jan

REPOSITORIES: biostudies-literature