Electrochemistry of hemoglobin at modified silver electrodes is not a redox-process of iron protoporphyrin IX

The direct heterogenous electron transfer between hemoglobin and modified silver and gold electrodes has been investigated using cyclic voltammetry. Cathodic and anodic peak currents have been obtained for hemoglobin, methemoglobin, carbonylhemoglobin, cyanohemoglobin and oxyhemoglobin, as well as for apohemoglobin and bovine serum albumin, exclusively at modified silver electrodes at potentials around 70 and 270 mV (vs. Ag/AgCl). The results demonstrate that the observed redox chemistry was not a result of direct electron transfer to the redox centre protoporphyrin IX. Spectrometrical measurements were made to substantiate this conclusion. A possible reaction mechanism which takes place at the modified silver electrode is suggested.