# Single-Molecule Electron Transport in Peptoids

## TL;DR

This study explores how the structure of peptoids affects their ability to transport electrons at the molecular level.

## Contribution

The research provides new insights into how peptoid sequence and conformation influence electron transport.

## Key findings

- Peptoids with aromatic side groups and no hydrogen bonds show distinct electron transport behavior.
- Electron transport in peptoids differs fundamentally from that in peptides due to the absence of hydrogen bonds.
- Computational models align qualitatively with experimental results on peptoid conductance behavior.

## Abstract

Peptoids are structural analogs of peptides in which
side chains
are appended to the backbone nitrogen rather than the α-carbon.
The sequence-defined modularity of peptoids enables precise control
over structure–function relationships, enabling applications
in energy storage and biomedical materials. Despite recent progress,
the role of sequence and conformation on electron transport in peptoid
molecules is not fully understood. Here, we synthesize a library of
peptoid oligomers and characterize their molecular electronic properties
using the scanning tunneling microscope-break junction (STM-BJ) technique.
Our results show well-defined electron transport behavior for peptoid
sequences containing aromatic side groups lacking hydrogen bonds (H-bonds)
and without chemical substitutions at the N–Cα position. This behavior fundamentally differs from electron transport
in peptides, where H-bond interactions give rise to higher conductance
states. All-atom molecular dynamics (MD) simulations are used to understand
the conformational heterogeneity of peptoids, and molecular conformations
obtained from MD simulations are used in quantum mechanical calculations
based on the nonequilibrium Green’s function–density
functional theory (NEGF-DFT) formalism. In all cases, computational
results are in reasonable qualitative agreement with experiments.
Our work demonstrates that the conductance behavior of peptoids depends
on monomer identity, including side-chain aromaticity and substitution
at the N–Cα position. Overall, this work provides
new insights into the structure–function relationships governing
electron transport in peptoid-based materials and establishes design
rules for peptoid-based molecular junctions.