Controlling the Assembly of Protein Cages towards Functional Supramolecular Materials

Abstract

In natural as well as synthetic systems, supramolecular interactions plays a vital role in essential life processes, such as catalysis, 1 protein synthesis, 2 cell replication and differentiation, 3 as well as molecule transport and delivery. 4 These supramolecular interactions are reversible, stimuli responsive and dynamic. Understanding and modulating these interactions would thus offer an effective manner to control the organization of a range of complexes which would benefit their potential properties and applications. Protein cages such as viruses and bacterial nano-compartment are perfect examples of natural assemblies formed by such supramolecular interactions. 5-8 Recent years have witnessed an increasing attempt to understand the assembly process of virus-like particles, in that way using these capsid proteins to construct functional materials for various applications. 9, 10 More specifically, plant viruses, as an example, consist of capsid proteins which envelop their genome inside highly symmetric cages via both electrostatic interactions and hydrophobic interaction. Furthermore, these viruses are uniform in size and hollow, which allows the encapsulation of functional cargos. These hollow nanometer-sized protein structures provide a template for the study of host-guest interactions in confined space, which in theory should be different from bulk solution, in addition, the specific interactions parameters could also provide vital information of the physical microenvironment inside protein cages. The work described in this thesis combined supramolecular chemistry and physical virology, by studying host-guest interactions inside the cowpea chlorotic mottle virus (CCMV) capsid, and ultimately utilize these interactions to induce the self-assembly of virus-based protein into structures with control in multi dimension. Chapter 2 provides an overview of recently reported assembly of virus-like particles induced by supramolecular interactions, that have been used as nanocontainers, nanoreactors and nano-templates for inorganic or organic material synthesis. Furthermore, the assembly of protein cages via supramolecular interactions into highly ordered 2D and 3D superstructures is described.