Optimising Electrical Interfacing between the Trimeric Copper Nitrite Reductase and Carbon Nanotubes

The immobilization of copper-containing nitrite reductase (NiR) from Alcaligenes faecalis on functionalised multi-walled carbon nanotube (MWCNT) electrodes is reported. It is demonstrated that this immobilization is mainly driven by hydrophobic interactions, promoted by the modification of MWCNTs with adamantyl groups. Direct electrochemistry shows high bioelectrochemical reduction of nitrite at the redox potential of NiR with high current density of 1.41 mA cm^-2 . Furthermore, the desymmetrization of the trimer upon immobilization induces an independent electrocatalytic behavior for each of the three enzyme subunits, corroborated by an electron-tunneling distance dependence.