Electrochemical Investigations of Protein Denaturating Agents Dithiobutylamine and Dithiothreitol and of the Antineoplastic Alemtuzumab at Glassy Carbon Electrode

A study to establish redox and thermodynamic properties of the protein denaturing agents dithiobutylamine (DTBA) and dithiothreitol (DTT) and of the monoclonal antibody alemtuzumab (ATZ), in aqueous electrolytes, with different pH values, under different experimental conditions, was carried out on a glassy carbon electrode (GCE), using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV). The voltammetric study demonstrated that DTBA, as well as DTT, were both susceptible to direct electro-oxidation on the electrode surface. The study established that the oxidation of DTBA and DTT took place in three subsequent steps, the first two occurring in the thiol groups forming a cyclic intermediate. The oxidation mechanisms of DTBA and DTT were postulated and proposed. The results using DPV and SWV clearly demonstrated the spontaneous adsorption of ATZ on the hydrophobic GCE surface and that it undergoes electro-oxidation in amino acid residues of tyrosine and tryptophan, exposed superficially on the three-dimensional structure of the protein and on the electrode. An oxidation mechanism of ATZ was also proposed.

Keywords:
protein denaturing agents; dithiobutylamine; dithiothreitol; cysteine; alemtuzumab