Physics of shell assembly: Line tension, hole implosion, and closure catastrophe

Abstract

The self-assembly of perfectly ordered closed shells is a challenging process involved in many biological and nanoscale systems. However, most of the aspects that determine their formation are still unknown. Here we investigate the growth of shells by simulating the assembly of spherical structures made of N identical subunits. Remarkably, we show that the formation and energetics of partially assembled shells are dominated by an effective line-tension that can be described in simple thermodynamic terms. In addition, we unveil two mechanisms that can prevent the correct formation of defect-free structures: "hole implosion," which leads to a premature closure of the shell; and "closure catastrophe," which causes a dramatic production of structural disorder during the later stages of the growth of big shells.

Self-Assembly of an Alphavirus Core-like Particle Is Distinguished by Strong Intersubunit Association Energy and Structural Defects

“…However, when viruses use strong interactions we find the irregularity predicted from models. 3–6, 8, 46, 47, 58, 59 Irregularity is not necessarily a bad thing. Models based on cones, irregular structures, and spheres show that novel interactions will be accommodated.…”

Detection of Late Intermediates in Virus Capsid Assembly by Charge Detection Mass Spectrometry

“…1,2 Despite a large effort, the underlying principles of capsid assembly are far from fully understood. 3−5 The geometric control shown in forming a virus capsid far exceeds our ability to control assembly in man-made chemical systems. Thus, understanding virus assembly at a molecular level will not only increase our knowledge of a process of great biological and medical importance, but it will also help to develop new self-assembly strategies for materials science.…”

The Robust Assembly of Small Symmetric Nanoshells

“…There have been many studies investigating the equilibrium shapes of shells formed from one or two identical subunits under external constraints (7)(8)(9)11,16,(19)(20)(21)(22). The simple case of spherical colloids or circular disks constrained to reside on the surface of a sphere shows that the stability of formed shells depends strongly on the number of assembly subunits and interactions between them.…”

“…One would then expect that the assembly of highly symmetric shells proceeds reversibly. In fact, most previous studies and simulations were done assuming that the process of assembly is to some extent reversible, and that the subunits can dissociate from the shell, at least at the early stages of growth (10,15,20,23,(25)(26)(27)(28)(29). This process of dissociation also allows the shell to correct mistakes in the growth process to some extent.…”

“…Biophysical Journal 109(5) 956-965 surface of a sphere show that it is impossible to assemble icosahedral or other symmetric shells when following reversible growth pathways that allow for the rearrangement of particles at any position in the growing shell (20). This effect could be explained by the work of Fejer et al (23), in which the authors find that during the assembly process the incomplete shells relax to nonspherical configurations, and thus a spherical template with isotropic Lennard-Jones interaction between particles might not be able to completely explain the kinetic assembly of viral shells.…”