Hybrid Proton and Electron Transport in Peptide Fibrils

Abstract

Protons and electrons are being exploited in different natural charge transfer processes. Both types of charge carriers could be, therefore, responsible for charge transport in biomimetic self‐assembled peptide nanostructures. The relative contribution of each type of charge carrier is studied in the present work for fibrils self‐assembled from amyloid‐β derived peptide molecules, in which two non‐natural thiophene‐based amino acids are included. It is shown that under low humidity conditions both electrons and protons contribute to the conduction, with current ratio of 1:2 respectively, while at higher relative humidity proton transport dominates the conductance. This hybrid conduction behavior leads to a bimodal exponential dependence of the conductance on the relative humidity. Furthermore, in both cases the conductance is shown to be affected by the peptide folding state under the entire relative humidity range. This unique hybrid conductivity behavior makes self‐assembled peptide nanostructures powerful building blocks for the construction of electric devices that could use either or both types of charge carriers for their function.

Natural melanin pigments and their interfaces with metal ions and oxides: emerging concepts and technologies

“…Electrical response of eumelanin: amorphous semiconductor model, mixed ionic-electronic conduction, electrochemical interfacial processes, and energy storage Biologic materials, such as proteins, peptides, and melanin, occur naturally in hydrated environments, such that their electrical response includes an important contribution from waterassisted proton transport. [31][32][33][34] The electrical properties of eumelanin have fascinated scientists since the late 1960s. After the observation of a reversible resistive switching in eumelanin pellets reported in 1974 by McGinness et al, [35] the amorphous semiconductor model was adopted to explain the strong hydration dependence of the conductivity.…”

Peptide‐Based Molecular Hydrogels as Supramolecular Protein Mimics

“…Interestingly, doping with iodine formed a mixed valence state and with TCNQ led to the formation of charge‐transfer state, both of which resulted in high charge carrier density and thus improved conductivity. Another example of hybrid electron and proton transport was observed in non‐natural thiophene‐based peptide nanofibers (Figure d) . Varying the humidity level was shown to dictate the transport mechanism with proton transport being the major factor at high humidity.…”

“…); d) I – V characteristics and AFM‐derived morphology of the investigated non‐natural peptide, showing proton and electron conductivity (adapted with permission from ref. ).…”

Peptide π-Electron Conjugates: Organic Electronics for Biology?

“…93 This hybrid conductivity behavior was explained to be a function of peptide folding behavior which is highly dependent on the humidity range. New electroactive supramolecular fibers have also been formed by Kato and co-workers from tetrathiafulvalene (TTF) bound to an oligopeptide scaffold in aromatic liquid crystals.…”