Thermodynamic size control in curvature-frustrated tubules: Self-limitation with open boundaries

TL;DR

This study uses computational modeling to explore how geometrically frustrated particles assemble into finite-sized tubules, revealing conditions for self-limiting assembly and mechanisms to prevent unlimited growth.

Contribution

It introduces a particle-based model for frustrated assembly, analyzing the thermodynamics and identifying parameters that lead to stable, finite-sized structures.

Findings

Finite-temperature self-limiting assembly occurs within specific parameter ranges.

Two mechanisms allow the system to escape frustration and grow indefinitely.

Particle properties can suppress unbounded growth, stabilizing finite structures.

Abstract

We use computational modeling to investigate the assembly thermodynamics of a particle-based model for geometrically frustrated assembly, in which the local packing geometry of subunits is incompatible with uniform, strain-free large-scale assembly. The model considers discrete triangular subunits that drive assembly towards a closed, hexagonal-ordered tubule, but have geometries that locally favor negative Gaussian curvature. We use dynamical Monte Carlo simulations and enhanced sampling methods to compute the free energy landscape and corresponding self-assembly behavior as a function of experimentally accessible parameters that control assembly driving forces and the magnitude of frustration. The results determine the parameter range where finite-temperature self-limiting assembly occurs, in which the equilibrium assembly size distribution is sharply peaked around a well-defined finite size. The simulations also identify two mechanisms by which the system can escape frustration and assemble to unlimited size, and determine the particle-scale properties of subunits that suppress unbounded growth.