ABSTRACT
Analysis of a number of derivatized enkephalins and other peptides (ArgGly-Gly, TyrGly, Gly-Gly-Phe, Tyr-Gly-Gly to name a few) revealed an average half-wave potential of +0.65 V versus Ag/AgCl. Only a slight increase in half-wave potential (+35 mV) is seen with increasing chain length from glycine to tetra-glycine and the half-wave potential is largely independent of scan rate. When the derivatized peptide contains an electroactive amino acid such as tyrosine or tryptophan, a signal may be seen from both the derivative and the amino acid. In addition, the presence of arginine in the derivatized peptide can significantly affect the oxidation potential, depending on the position of the amino acid in the sequence. The limited data suggest that the presence of arginine at the carboxy terminus may lower the half-wave potential. In addition, doubly derivatized peptides (i.e. those containing lysine) are oxidized at lower applied potentials than those that are single derivatives.
