Exploiting the interplay of quantum interference and backbone rigidity on electronic transport in peptides: a step towards bio-inspired quantum interferometers

Abstract

Deposition and sharing rightsWhen the author accepts the licence to publish for a journal article, he/she retains certain rights concerning the deposition of the whole article. This table summarises how you may distribute the accepted manuscript and version of record of your article. Electron transfer in peptides provides an opportunity to mimic nature for applications in bio-inspired molecular electronics. However, quantum interference effects, which become significant at the molecular level, have yet to be addressed in this context. Electrochemical and theoretical studies are reported on a series of cyclic and linear peptides of both β-strand and helical conformation, to address this shortfall and further realize the potential of peptides in molecular electronics. The introduction of a side-bridge into the peptides provides both additional rigidity to the backbone, and an alternative pathway for electron transport. Electronic transport studies reveal an interplay between quantum interference and vibrational fluctuations. We utilize these findings to demonstrate two distinctive peptide-based quantum interferometers, one exploiting the tunable effects of quantum interference (β-strand) and the other regulating the interplay between the two phenomena (310-helix).

A controllable mechanistic transition of charge transfer in helical peptides: from hopping to superexchange

“…The calculated conductance for both peptides was found to be remarkably similar, contrasting the approximate ten-fold difference in the electron transfer rate constants observed in the electrochemical study. 28 Similar results were also recently reported in helical peptides based on the same theoretical approach. 13 This suggests that different charge transfer mechanisms may be operating in these helical peptides, which cannot be determined using ballistic scattering transport simulations.…”

“…We and others have previously demonstrated that the addition of a tether linking the side-chains of peptides via Huisgen cycloaddition, [21][22][23] ring closing metathesis, [24][25][26][27] or lactamization, [28][29][30] xes the structural conformation into a well-dened helical geometry. The resulting decrease in backbone exibility leads to a reduction of torsional motion necessary for facile electron transfer through the peptide via a hopping mechanism, which in turn impacts the associated electron transfer dynamics and hence their electronic properties.…”

“…1), one further constrained into this geometry by way of a lactam side-bridge. 28 An electrochemical study of the two peptides found the electron transfer rate constant in the constrained peptide 1 to be approximately one order of magnitude lower than that of the linear counterpart 2, with a corresponding and signicant increase in the formal potential. Complementary quantum transport (ballistic scattering) simulations, using density functional theory (DFT) coupled with the non-equilibrium Green's function (NEGF) 31 were performed.…”

Peptides as Bio-Inspired Electronic Materials: An Electrochemical and First-Principles Perspective

“…The component geminally disubstituted Aib (α-aminoisobutyric acid) residues of 3-8 promote formation of a common 3 10 -helical geometry, as demonstrated by molecular modelling and spectroscopic characterization. 16,28,29 Thus, as these peptides each share a similar well-defined backbone geometry, any disparity in the electron transfer kinetics can be directly correlated to the associated dynamic effects arising from the presence (or absence) of the side-bridge constraint. with the magnitude of this shift significantly higher than other conformation-dependent structures such as cis-trans cyclohexasilanes (110 mV), 31 placing it between the voltage drops across a germanium (300 mV-350 mV) and a silicon (600 mV-700 mV) p-n junction.…”

“…14 (3) An electrode-supported monolayer of peptides comprising a redox active probe for electrochemical measurements. This is a particularly versatile technique adopted by a broader research community (Kimura 1 , Kraatz 15 and our group 16 ). In the literature, the terminology referred to in the first instance is "electronic transport", while in the latter two it is commonly referred to as "electron transfer".…”