Direct Electron Transfer Observed for Peroxidase to Screen‐Printed Graphite Electrodes

Native and recombinant horseradish peroxidase were immobilized onto screen-printed graphite electrodes by depositing and drying an enzyme solution onto the transducer surface followed by coverage with an UV-polymerizable paste. Direct electron transfer from the transducer to the enzymes was obtained by applying a potential of −100 mV (vs. Ag/AgCl reference electrode) in the presence of hydrogen peroxide as substrate. Docking of the enzymes to graphite was modelled to estimate the distances from the active site to the electrode surface. The electrode current was increased threefold by adding Gafquat 755N to the enzyme solution. Modelling calculations indicated unspecific but strong binding of Gafquat subunits to the protein.