Electrochemical Switching Driven by Structural Change in Secondary Structure and by Complexation to Ligand at the Modified Au(Ⅲ) Electrode with Polylysine having Phenanthroline and Terpyridine as Ligands

摘要

Electrochemical reactions at the modified electrode surfaces are effected by the surface properties such as charge and secondary structure of the modifiers. In order to clear the effect of secondary structure of the modifiers and the change in the micro environment by complexation, we synthesized an α-helix forming peptide (LL-phen) and a random-coiled peptide (DL-phen). Both peptides have a cystein as the anchor to the electrode surface and the identical amino acid sequences. The LL-phen and DL-phen formed self assembled monolayer (SAM) on Au(111) electrode. By comparing the behavior of these peptide modified electrode, we have found, for the first time, that the secondary structure of the peptide and complexation play roles in controling the electrochemical reaction of Fe(CN)_6~(4-). The electrochemical responses of Fe(CN)_6~(4-) were suppressed at the random coiled LL-phen and DL-phen SAMs modified electrodes. However, at the α-helical structured LL-phen SAM modified electrode, the reaction was almost reversible. The heterogeneous electron transfer rate increased at the random coiled LL-phen SAM and DL-phen SAM due to the complexation of La~(3+). On the other hand, this rate decreased slightly at the a-helical coiled LL-phen SAM.