Single-molecule approaches to chemical reaction analysis can provide information that is not accessible by studying ensemble systems. Changes in the molecular structures of compounds tethered to the inner wall of a protein pore are known to affect the current carried through the pore by aqueous ions under a fixed applied potential. Here, we use this approach to study the substitution reactions of arsenic(III) compounds with thiols, stretching the limits of the protein pore technology to track the interconversion of seven reaction components in a network that comprises interconnected Walden cycles. Single-molecule pathway analysis of 'allowed' and 'forbidden' reactions reveals that sulfur-sulfur substitution occurs with stereochemical inversion at the arsenic centre. Hence, we demonstrate that the nanoreactor approach can be a valuable technique for the analysis of dynamic reaction systems of relevance to biology.
Bibliographical noteFunding Information:
This work was supported by the Medical Research Council and a European Research Council advanced grant. H.B. was the holder of a Royal Society–Wolfson Research Merit Award. M.B.S. was the holder of a Ruth L. Kirschstein NIH Postdoctoral Fellowship (F32L078236).