In this paper presents data showing the electrochemistry of immobilised cytochrome c at an N-acetyl cysteine modified gold electrode. The electron transfer rate between the immobilised protein and the gold electrode was estimated as 3.4 +/- 1.2 s-1 and the formal potential of the immobilised protein electrode was calculated as 2 mV vs. SCE. Studies were also carried out to investigate the nature of the protein-electrode interface. FT-IR and scanning tunneling microscopy were used in a semi-quantitative manner in order to optimise the immobilisation procedure, and thereby maximise the surface coverage of the electrode. FT-IR studies showed that the protein-electrode exhibited characteristic peak absorptions at 1703 cm-1, 1494 cm-1, 1367 cm-1 and 1166 cm-1. The peaks at 1703 cm-1 and 1494 cm-1 were attributed to amide I and II bands (respectively). The 1367 cm-1 and 1166 cm-1 peaks were associated with the amide III band of the immobilised protein. The application of this electrode was investigated as a biosensor for the determination of superoxide ion production.