Electrochemical studies of rubredoxin from Desulfovibrio vulgaris at modified electrodes

The electrochemical behaviour of rubredoxin from Desulfovibrio vulgaris is analysed in 0.1 M KCl at pH 7.6±0.1 (10 mM Tris buffer) using gold disk electrodes (r=12.5 μm and r=0.08 cm) in the presence of Mg2+ and/or neomycin, and revisited using a carbon electrode (r=0.15 cm) in the presence of Mg2+ and further analysed in solutions with neomycin with and without Mg2+. The results show that, depending on the modifier and its concentration, the electrode surface may have different densities of electroactive sites and so different mass transport processes may take place, thus accounting for the shape of the voltammograms. Values for ks, D and E°′ determined under all conditions agreed with each other within experimental error, no matter what the size or material of the electrode or the modifier used.