Early-stage culprit in protein misfolding diseases investigated using electrochemical parameters: New insights over peptide-membrane interactions.

The dysfunctioning of β-cells caused by the unspecific misfolding of the human islet amyloid polypeptide (hIAPP) at the membrane results in type 2 diabetes mellitus. Here, we report for the first time, the early-stage interaction of hIAPP oligomers on the DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) lipid membrane using electrochemical parameters. Electrochemical techniques are better than other techniques to detect hIAPP at significantly lower concentrations. The surface level interactions between the peptide (hIAPP) and lipid membrane (DMPC) were investigated using atomic force microscopy (AFM), confocal microscopy (CM) and electrochemical techniques such as Tafel polarization, cyclic voltammetry (CV), differential pulse voltammetry (DPV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Inserting IAPP into the fluid domains results in breaking the lipid-to-lipid interaction, leading to restriction of membrane mobility. The SLateral values of the liposome and IAPP co-solubilized liposome indicates the cooperative insertion of IAPP. Further, a new method of immobilizing a membrane to the gold surface has been employed, resulting in an electrical contact with the buffer, preventing the direct utilization of a steady-state voltage across the bilayer. The electrochemical studies revealed that the charge transfer resistance decreased for 3-mercaptopropanoic acid modified gold (MPA-Au) electrode coated with the liposome and after the addition of IAPP, followed by an increase in the capacitance. The present study has opened up new dimensions to the understanding of peptide-membrane interactions and shows different experimental approaches for the future researchers in this domain.