Kinetics of Surface-Driven Self-Assembly and Fatigue-Induced Disassembly of a Virus-Based Nanocoating

Abstract

Self-assembling protein layers provide a ''bottom-up'' approach for precisely organizing functional elements at the nanoscale over a large solid surface area. The design of protein sheets with architecture and physical properties suitable for nanotechnological applications may be greatly facilitated by a thorough understanding of the principles that underlie their self-assembly and disassembly. In a previous study, the hexagonal lattice formed by the capsid protein (CA) of human immunodeficiency virus (HIV) was self-assembled as a monomolecular layer directly onto a solid substrate, and its mechanical properties and dynamics at equilibrium were analyzed by atomic force microscopy. Here, we use atomic force microscopy to analyze the kinetics of self-assembly of the planar CA lattice on a substrate and of its disassembly, either spontaneous or induced by materials fatigue. Both selfassembly and disassembly of the CA layer are cooperative reactions that proceed until a phase equilibrium is reached. Self-assembly requires a critical protein concentration and is initiated by formation of nucleation points on the substrate, followed by lattice growth and eventual merging of CA patches into a continuous monolayer. Disassembly of the CA layer showed hysteresis and appears to proceed only after large enough defects (nucleation points) are formed in the lattice, whose number is largely increased by inducing materials fatigue that depends on mechanical load and its frequency. Implications of the kinetic results obtained for a better understanding of self-assembly and disassembly of the HIV capsid and protein-based two-dimensional nanomaterials and the design of anti-HIV drugs targeting (dis)assembly and biocompatible nanocoatings are discussed.

The interaction of dengue virus capsid protein with negatively charged interfaces drives the in vitro assembly of nucleocapsid-like particles

“…In fact, in solution (absence of a surface), DENVC is dimeric and does not oligomerize to large particles, as it was observed in many conditions [ 21 , 23 , 50 ]. In agreement with the surface effect, a previous AFM study demonstrated fast and efficient self-assembly of capsid protein from human immunodeficiency virus (HIV) at very low protein concentration when applied directly onto a negatively charged substrate, showing the need for a surface to drive the process [ 46 , 47 ]. Ionic strength, pH, temperature, the concentration of molecules, and molecular sequence can affect surface interactions [ 48 , 49 ].…”

“…Thus, we hypothesize that DENVC self-assembly is surface-driven, as described for other proteins, including viral proteins [ 46 – 49 ]. In fact, in solution (absence of a surface), DENVC is dimeric and does not oligomerize to large particles, as it was observed in many conditions [ 21 , 23 , 50 ].…”

Physics of viral dynamics

“…The human immunodeficiency virus (HIV) capsid consists of ~1,000–1,500 copies of the viral capsid protein 41 , and the self-assembly kinetics of a 2D lattice of this capsid protein has been examined by AFM 42 . Assembly starts at specific sites on the surface, followed by the growth of the lattice and fusion of the different patches, eventually producing full coverage of the surface.…”

“…For norovirus, the intermediate assembly structure is a double pentamer of dimers, connected by one dimer 39 , whereas for CCMV, half-formed capsids with a lifetime of several seconds have been found 40 . The human immunodeficiency virus (HIV) capsid consists of ~1,000-1,500 copies of the viral capsid protein 41 , and the self-assembly kinetics of a 2D lattice of this capsid protein has been examined by AFM 42 .…”

A Genetically Engineered, Chain Mail‐Like Nanostructured Protein Material with Increased Fatigue Resistance and Enhanced Self‐Healing

“…[16] For many materials (including metals, ceramics and composites), fatigue is by far the most common cause of failure, [17,18] and protein assemblies in general are prone to mechanical failure and highly susceptible to fatigue. [19][20][21][22][23] The susceptibility of protein nanostructures to fatigue may be mitigated, but not compensated, by their self-healing potential, [8,24] observed also in other soft supramolecular materials. [25,26] Thus, there is a strong need for modified protein-based materials with improved mechanical properties.…”