Reactive oxygen species (eg. superoxide anion radical) causes deleterious effect such as DNA damage. Superoxide dismutases (SODs) are the ubiquitous metalloenzymes found in all aerobic organisms which disproportionate the superoxide to H₂O₂ and O₂. Nickel containing superoxide dismutase (NiSOD) is a new class of SOD. NiSOD utilizes a unique coordination environment in its active site. Ni^II is coordinated to the free N-terminus amino group of His(1), amide nitrogen of Cys(2), thiolate of Cys(2) and Cys(6). When oxidized to Ni^III, the imidazole side chain of His(1) is coordinated to Nickel center affording a square pyramidal active site. To probe the role of this unique coordination environment toward promoting catalytic disproportionation of superoxide, we have made SOD^M1-Ac [H₃CC(O)NH-HCDLPCGVYDPA-COOH] using standard Fmoc solid phase peptide synthesis procedure. The amino acid sequence is based on the 12 residues from N-terminus of S. coelicolor with an N-terminus acetyl cap. The titration of pure SOD^M1-Ac with Ni^II shows that 1.2 equivalent of Ni^II is bound per SOD^M1-Ac peptide while Gel Permeation Chromatography (GPC) shows the monomeric NiSOD^M1-Ac. We are exploring electrochemical and superoxide reactivity studies to probe the catalytic behavior of NiSOD^M1-Ac. We will also compare the NiSOD^M1-Ac catalytic activity with NiSOD^M1, NiSOD^M2 (H₂N-HCDLPCG-COOH) and NiSOD^M2-Ac [H₃CC(O)NH-HCDLPCG-COOH).