| Sumari: | <p>Thiol-disulfide interchange occurs widely in cellular processes including redox sensing and homeostasis, protein folding, cell signalling, and the regulation of apoptosis. Nature exploits this chemistry in a highly selective manner, which is challenging to recapitulate in vitro. In this thesis, we report site selective and regioselective thioldisulfide interchange on macromolecular disulfide substrates elongated within a protein nanoreactor, where they react with cysteine thiolates presented at different locations along the length of a β strand. Numerous individual reaction events were detected by promoting the substrate turnover. For each substrate, we defined the most reactive cysteines on the β strand and which sulfur atom in the disulfide was attacked and found that the chemistry can be controlled with atomic precision.</p> <p>We further applied our control over the selectivity of thiol-disulfide interchange to the development of a molecular machine. Intrigued by technological potential, scientists have long attempted to control molecular motion. We monitor the individual 0.7-nm steps of a single molecular hopper as it moves in an electric field along a track in a nanopore controlled by a chemical ratchet based on thiol-disulfide interchange. The hopper demonstrates characteristics desired in a moving molecule: defined start- and end-points, processivity, fuel autonomy, directional motion and external control. The hopper is readily functionalized to carry cargos. For example, DNA can be ratcheted along the track in either direction, a prerequisite for nanopore sequencing.</p>
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