Electrocatalysis of ferricyanide reduction mediated by electron transfer through the DNA duplex: Kinetic analysis by thin layer voltammetry

DNA-mediated electron transfer (ET) underlies a variety of bioelectronics applications, and, thus, simple approaches for its kinetic analysis are required. Here, electrocatalysis of a ferricyanide reduction catalyzed by methylene blue (MB) bound to either (dGdC)(20) or (dAdT)(25) duplexes tethered to gold via an alkanethiol linker was voltammetrically studied at stationary electrodes, and its kinetics was analyzed by two theoretical models. A thin layer voltammetry analysis, assuming that the reaction occurs within the l-nm thick layer formed by the DNA duplexes of the length l, yielded the electrocatalytic rate constant k(1) of (2.1 +/- 0.4)10(5) and (2.4 +/- 0.5)10(6) M-1 s(-1), for (dGdC)(20) and (dAdT)(25). The sequence-specific k(1) values were consistent with structural differences of (dGdC)(20) or (dAdT)(25) at the negatively polarized interface and approached the k(1) previously reported for the rotating disk electrode system (Angew. Chemie Int. Ed. 58 (2019) 3048). These results offer new tools for immediate kinetic analysis of electrocatalytic reactions involving long-range ET along the DNA duplexes, the tools that allow differentiating electrical properties of nucleic acids in the most convenient and simple way. (C) 2019 Elsevier Ltd. All rights reserved.