Geometrically-programmable assembly of self-limiting material structures
Greg Grason (U Mass, Amherst)
Living systems make a variety of functional and remarkably adaptive material structures via assembly of highly complex, nanoscale protein “building blocks”. Many of these architectures, from viral capsid shells to multi-filament extracellular protein fibers, have well-defined and finite sizes, and moreover, their functional properties (e.g. transport mediation, mechanics) rely on specific control of that finite size. Notably this class “self-limiting” assembly is distinct from almost all types of synthetic self-assembled materials, which often target well-defined and complex local structures, such as crystals, but exhibit unregulated, if not unlimited, dimensions at the large scale. In this talk, I discuss recent progress in understanding and engineering /self-limiting assemblies/, in which the equilibrium dimensions of complex material structure are encoded in complex building blocks from which they assemble. This is motivated both by aspirational examples of finite-size, functional assemblies in biology, but also new classes of programmable particles that incorporate many key features of protein-like assembly (e.g. lock-and-key type “specific” interactions and geometrically-defined subunit shapes). I will discuss combined experimental and theoretical studies of a basic mechanism of /self-closing, curvature-controlled assembly/ of a range of bioinspired capsules, tubules and bicontinuous structures, recently realized via DNA-origami based colloids. These reveal basic trade-offs between design economy and size-selectivity of target structures, and further, suggest strong symmetry-based rules for minimal-complexity, high-fidelity assembly in the limit of large self-closing size.