Simulation of Self-Assembled Monolayers of Polyalanine $\alpha$-Helices: Development and Application of an Effective Potential for Film Structure Predictions

TL;DR

This study models and experimentally investigates the self-assembly of polyalanine α-helices, revealing how chiral composition influences supramolecular structures and providing insights for designing peptide-based spintronic devices.

Contribution

It introduces an effective potential model for predicting film structures of self-assembled peptide monolayers based on chiral interactions and validates it with experimental STM data.

Findings

Enantiopure systems form hexagonal lattices.

Racemic mixtures organize into rectangular stripe phases.

Opposite-handed helix pairs exhibit stronger binding and closer packing.

Abstract

Self-assembled monolayers of polyalanine $\alpha$-helices exhibit distinct structural phases with implications for chiral-induced spin selectivity. We combine scanning tunneling microscopy and theoretical modeling to reveal how chiral composition governs supramolecular organization. Enantiopure systems form hexagonal lattices, while racemic mixtures organize into rectangular phases with stripe-like features. Our interaction potentials derived from density-functional based tight binding calculations show that opposite-handed helix pairs exhibit stronger binding and closer packing, explaining the denser racemic structures. Crucially, we demonstrate that the observed STM contrast arises from anti-parallel alignment of opposite-handed helices rather than physical height variations. These findings establish fundamental structure-property relationships for designing peptide-based spintronic materials.