Proton Conduction in a Tyrosine‐Rich Peptide/Manganese Oxide Hybrid Nanofilm

Abstract

Proton conduction is an essential process that regulates an integral part of several enzymatic catalyses and bioenergetics. Proton flows in biological entities are sensitively controlled by several mechanisms. To understand and manipulate proton conduction in biosystems, several studies have investigated bulk proton conduction in biomaterials such as polyaspartic acid, collagen, reflectin, serum albumin mats, and eumelanin. However, little is known about the bulk proton conductivity of short peptides and their sequence‐dependent behavior. Here, this paper focuses on a short tyrosine‐rich peptide that has redox‐active and cross‐linkable phenol groups. The spin‐coated peptide nanofilm is immersed in potassium permanganate solution to induce cross‐linking and oxidation, simultaneously leading to hybridization with manganese oxide (MnOx). The peptide/MnOx hybrid nanofilm can efficiently transport protons, and its proton conductivity is ≈18.6 mS cm−1 at room temperature. This value is much higher than that of biomaterials and comparable to those of other synthetic proton‐conducting materials. These results suggest that peptide‐based hybrid materials can be a promising new class of proton conductor.

Intrinsic electronic conductivity of individual atomically resolved amyloid crystals reveals micrometer-long hole hopping via tyrosines

“…The mean four-probe conductance of a single X1 microcrystal was 74.8 ± 19.9 pS, which is the highest conductance reported for a single amyloid protein macrostructure (33). Although conductance values have been reported in networks of amyloid and peptide fibrils (34)(35)(36)(37), the lack of a consistent, uniform macromolecular conformation of amyloids as well as the dependence of conductance values on electrode and sample geometries prevented direct comparisons between these measurements (38). The electrical resistance of the sample measured using twoprobe is dependent on the crystal size and the nature of contacts, whereas the four-probe conductivity is an intrinsic property of the material.…”

Proton-enabled activation of peptide materials for biological bimodal memory

“…Previously, we identified the Tyr-Tyr-Ala-Cys-la-Tyr-Tyr (YYACAYY, Y7C) peptide, which can form a helix dimer and assemble spontaneously into a 2-D film 17 . We have investigated the proton conductivity in manganese oxide hybridized Y7C films 18 . Through the measurement of the Onsager coefficient to understand the coupling of electrons and protons, it became evident that tyrosine can be involved in PCET and metal ion redox even in the thick films 19 .…”

Natural biopolymers as proton conductors in bioelectronics

“…[145] Nam and co-workers reported a short tyrosine-rich peptide and manganese oxide hybrid film that showed enhanced proton conductivity ($18.6 mS cm À1 ) by synergistic effect, which suggests that hybrid composites can also be a promising method for designing proteinbased ionic conductors with high conductivity. [146] F I G U R E 9 A, Schematic of a two-terminal device in which a reflectin protein film bridged two gold electrodes. B, A typical Nyquist plot for a reflectin-bridged two-terminal device in the presence of water vapor (black) and in the presence of deuterium oxide vapor (red), both at an RH of 90%.…”