Electrical characteristics of amyloid beta peptides in vertical junctions

Abstract

© 2021 Springer Nature Limited. Assembled amyloid beta (A beta) peptides have been considered pathological assemblies involved in human brain diseases, and the electron transfer or electron transport characteristics of A beta are important for the formation of structured assemblies. Here, we report the electrical characteristics of surface-assembled A beta peptides similar to those observed in Alzheimer's patients. These characteristics correlate to their electron transfer characteristics. Electrical current-voltage plots of A beta vertical junction devices show the A beta sequence dependence of the current densities at both A beta monomers (mono-A beta s) and A beta oligomers (oli-A beta s), while A beta sequence dependence is not clearly observed in the electrical characteristics of A beta planar field effect transistors (FETs). In particular, surface oligomerization of A beta peptides drastically decreases the activity of electron transfer, which presents a change in the electron transport pathway in the A beta vertical junctions. Electron transport at oli-A beta junctions is symmetric (tunneling/tunneling) due to the weak and voltage-independent coupling of the less redox-reactive oli-A beta to the contacts, while that at mono-A beta junctions is asymmetric (hopping/tunneling) due to redox levels of mono-A beta voltage-dependently coupled with contact electrodes. Consequently, through vertical junctions, the sequence- and conformation-dependent electrical characteristics of A beta s can reveal their electron transfer activities.