The "Presodium" Hydrogen Evolution at the Dropping Mercury Electrode Catalysed by Simple Cysteine Peptides

"Presodium" catalytic currents at dropping mercury electrode of cysteine, cysteinylglycine, γ-glutamylcysteine and reduced glutathione were systematically studied in weakly alkaline solutions. They consist in shifts to positive potentials of current due to reduction of the blank solution, and, under some conditions, also in formation of "catalytic prewaves". The two cases have been qualitatively interpreted as based on a suggested common mechanism, differing by the occurrence of weak catalyst adsorption in the prewave case. The catalytic activity depends on the catalyst itself (concentration, structure, conformation at the electrode, partial protonation/ionisation, partial hydrophobic/hydrophilic character) as well as on the solution (pH, ionic strength, nature and concentration of components).