Self-limited self-assembly of chiral filaments

TL;DR

This paper investigates how chiral interactions influence the self-assembly of filamentous bundles, leading to finite diameters or defect formation, with implications for biological and nanomaterial design.

Contribution

It introduces a simulation and free energy framework to understand self-limited filament assembly driven by chirality and frustration effects.

Findings

Chirality causes twist, preventing long-range order.

Finite diameter bundles are stable under certain conditions.

Defects form to relieve frustration in some assemblies.

Abstract

The assembly of filamentous bundles with controlled diameters is common in biological systems and desirable for the development of nanomaterials. We discuss dynamical simulations and free energy calculations on patchy spheres with chiral pair interactions that spontaneously assemble into filamentous bundles. The chirality frustrates long-range crystal order by introducing twist between interacting subunits. For some ranges of system parameters this constraint leads to bundles with a finite diameter as the equilibrium state, and in other cases frustration is relieved by the formation of defects. While some self-limited structures can be modeled as twisted filaments arranged with local hexagonal symmetry, other structures are surprising in their complexity.