Electrical characteristics of amyloid beta peptides in vertical junctions

Abstract

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

Single-molecular protein-based bioelectronicsviaelectronic transport: fundamentals, devices and applications

“…Seo et al investigated the electrical characteristics of amyloid beta peptides using a vertical junction, where they reported sequence-and conformation-dependence of the conductance. 173 Smith et al demonstrated a molecular device to quantify the concentration of ammonia, utilizing protein nanowires harvested from Geobacter sulfurreducens. 174 This device featured a protein nanowire film deposited on the interdigitated electrodes as the sensing layer.…”

Low-Temperature Layer-by-Layer Growth of Semiconducting Few-Layer γ-Graphyne to Exploit Robust Biocompatibility

“…The Aβ 40 peptide was dissolved in 10 mM phosphate buffer (PB, pH 7.4, purchased from Sigma-Aldrich) containing a 1% ammonium hydroxide (NH 4 OH) solution. 36 Aβ 40 monomers were adsorbed to a γ-GY/SiO 2 substrate by placing a 50 μL droplet of PB solution containing 50 μM Aβ 40 monomers on the substrate in a sealed vial and incubating at 4 °C for 1 h. Aβ 40 fibrils were grown on the target surfaces, such as highly oriented pyrolytic graphite (HOPG) and γ-GY/SiO 2 , by placing a 50 μL droplet of PB solution containing 50 μM Aβ 40 and 0.15 M sodium chloride (NaCl, Sigma-Aldrich) in a sealed vial and incubating at 37 °C for 1−6 h. The Aβ samples were washed with PB and DI water and dried with inert gas.…”

“…Aβ 40 peptide molecules, as critical components of Alzheimer's disease, can change their morphologies as a result of fibrillation via oligomerization of Aβ monomers during aggregation. 36 These toxic Aβ 40 peptides can form biocompatible nanostructures as mature Aβ 40 fibrils grown on few-layer γ-GY surfaces. The nanostructure formation and biocompatibility of γ-GY were investigated (Figures 4 and 5).…”

Probing Interfacial Charge Transfer between Amyloid-β and Graphene during Amyloid Fibrillization Using Raman Spectroscopy

“…In addition, Aβ aggregation accompanies extensive reconfiguration of molecular orientation and surface dipole moment that can cause additional shifts in energy levels . The shift in the redox potential of Aβ 1–40 peptides during oligomerization was observed by the electrical transport measurement previously . And the optical conductance of Aβ 42 monomers, oligomers, and fibrils gauged by terahertz (THz) spectroscopy suggests that there is an intraband splitting near the highest occupied (HOMO) and lowest unoccupied (LUMO) molecular orbital levels .…”

“…6 The shift in the redox potential of Aβ 1−40 peptides during oligomerization was observed by the electrical transport measurement previously. 7 And the optical conductance of Aβ 42 monomers, oligomers, and fibrils gauged by terahertz (THz) spectroscopy suggests that there is an intraband splitting near the highest occupied (HOMO) and lowest unoccupied (LUMO) molecular orbital levels. 8 Together, these studies suggest that the electronic energy structure of Aβ evolves significantly during aggregation.…”