Backbone-Constrained Peptides: Temperature and Secondary Structure Affect Solid-State Electron Transport

Abstract

The primary sequence and secondary structure of a peptide are crucial to charge migration, not only in solution (electron transfer, ET), but also in the solid-state (electron transport, ETp). Hence, understanding the charge migration mechanisms is fundamental to the development of biomolecular devices and sensors. We report studies on four Aib-containing helical peptide analogues: two acyclic linear peptides with one and two electron-rich alkene-based side chains, respectively, and two peptides that are further rigidified into a macrocycle by a side bridge constraint, containing one or no alkene. ETp was investigated across Au/peptide/Au junctions, between 80 and 340 K in combination with the molecular dynamic (MD) simulations. The results reveal that the helical structure of the peptide and electron-rich side chain both facilitate the ETp. As temperature increases, the loss of helical structure, change of monolayer tilt angle, and increase of thermally activated fluctuations affect the conductance of peptides. Specifically, room temperature conductance across the peptide monolayers correlates well with previously observed ET rate constants, where an interplay between backbone rigidity and electron-rich side chains was revealed. Our findings provide new means to manipulate electronic transport across solid-state peptide junctions.

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

“…The doping effect was also location-sensitive, with conductance enhancement being stronger when located closer to the electrode. Moreover, the conductance of peptides with different secondary structures and side chain modifications was studied, 141 where the helical structure of the peptides and electron-rich alkene-based side chains facilitated the electron transport, a temperature-dependent phenomenon, as the secondary structure of peptides is sensitive to the temperature. These studies provide a strategy for modulating the electrical conductance in molecular electronics based on the versatile and readily available synthetic peptides.…”

Tuning Charge Transport of Oligopeptide Junctions via Interfacial Amino Acids†

“…[ 8‐15 ] The modulation through peptide matrices in proteins enables us not only to develop peptide‐ and protein‐based molecular devices but also to understand complex charge transport via proteins. This has been achieved through various strategies, such as amino acid sequence, [ 8,16‐17 ] peptide length, [ 18‐20 ] secondary structure, [ 16,21‐22 ] and skeleton rigidity, [ 22‐23 ] which are largely in a covalent manner. For example, the charge transport through hepta‐alanine peptide junctions can be enhanced by doping with tryptophan.…”

Constructing Dual-Molecule Junctions to Probe Intermolecular Crosstalk

“…Understanding and controlling charge transport across multiple parallel molecules are fundamental to the creation of efficient and functional electronic components, where future molecular devices will likely be multimolecular and utilize solid-state technology. , Self-assembled monolayers (SAMs), containing an ensemble of molecules, provide a densely packed, well-organized structure suitable for investigation of charge transport properties of a diverse range of molecular species at the mesoscopic level. − Both intramolecular (i.e., through-bond coupling within individual molecules) and intermolecular (i.e., molecule-to-molecule coupling) pathways contribute to charge transport within such a monolayer, − with the measured conductance (or electron transfer rate constants) reflecting the influence of both phenomena. At the molecular level, single-molecule electronic detection techniques, such as scanning tunneling microscopy-break junction (STM-BJ), have proven to be reliable platforms to unravel intramolecular charge transport pathways across a single molecule by transducing molecular information into quantized changes in conductance, offering precise spatial control and high temporal resolution. − Despite this, it is not clear how quantitative comparisons can be made between electronic measurements of molecular junctions that contain an ensemble of molecules and single-molecule junctions because this inevitably relies on normalization to a single molecule …”