Protein or peptide chips are expected to be valuable tools for detecting and analyzing interactions involving proteins and peptides in post-genome projects. As a preliminary study aimed at such a chip technology, a differential pulse voltammetry was successfully used to detect the electrostatic interaction between the charged chemical species on an electrode and those in the solution. Specifically, a gold electrode surface was modified through thiol chemistry by anionically-/cationically- and multi-charged peptides (peptide electrodes). The electrodes were used to detect anionically or catinonically charged ferrocene-containing species (ligands; including a peptidic derivative) in solution. Unique DPV signals due to a ferrocene redox reaction were obtained when the nature of charge on the peptide electrode matched that of the ligand in solution. The magnitude of the signal correlated with the charge of the peptide molecule on the electrode, indicating that the binding affinity of the ligands was based on an electrostatic interaction with the peptides on the electrode surface. The results as a whole indicate that ferrocene labeling can be a useful means to electrochemically detect some specific interactions taking place between peptides on an electrode surface and those in solution.
