Study of Amyloid beta-Peptide (A beta 12-28-Cys) Interactions with Congo Red and beta-Sheet Breaker Peptides Using Electrochemical Impedance Spectroscopy

A surface-based approach is presented to study the interactions of A beta 12-28-Cys assembled on gold surfaces with Congo red (CR) and a beta-sheet breaker (BSB) peptide. The various aspects of the peptide film have been examined using different electrochemical and surface analytical techniques. Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) results using redox probes Fe(CN)(6) show that A beta 12-28-Cys on gold forms a stable and reproducible blocking film. EIS analysis shows that CR and BSB have different effects on the electrochemical properties of A beta 12-28-Cys films, presumably due to changes in the interactions between the film and CR and BSB. EIS results indicate that in the case of CR film resistance decreases significantly presumably due to better penetration of the solution-based redox probe into the film, whereas in the case of BSB, the film resistance increases. We interpret this difference to BSB being able to interact with the A beta 12-28-Cys on the surface and presumably forming a film that presents a higher resistance for electron transfer from the redox probe to the solution.