Effects of cysteine derivatization on its behavior in the electrode process giving the polarographic hydrogen prewave

The derivatization of cysteine influences its ability to induce the catalytic hydrogen prewave according to the group masked. Thus, the masking of sulfur (by carboxymethylation) or nitrogen (by benzoylation) results in the loss of the catalytic activity, whereas the esterification produces only minor changes. Compounds which give catalytic prewave of nickel or cobalt (methionine, 6-methylthiouracil, bismuthiol, N-benzoylcysteine) or even catalytic hydrogen waves of the Brdicka type (thioglycolic acid, ovalbumins) are still not able to induce the catalytic hydrogen prewave. The occurrence of this wave is strongly dependent on the possibility of the ligand to chelate the nickel ion by the thiol and amino groups. Consequently, the catalytic hydrogen prewave appears to be much more sensitive to the structure of the ligand catalyst as compared to both the Brdicka wave or the catalytic prewave of the metal-ion.