Precise Fabrication of De Novo Nanoparticle Lattices on Dynamic 2D Protein Crystalline Lattices

The science of protein self-assembly has experienced significant development, from discrete building blocks of self-assembled nanoarchitectures to advanced nanostructures with adaptive functionalities. Despite the prominent achievements in the field, the desire of designing de novo protein-nanoparticle (NP) complexes and constructing dynamic NP systems remains highly challenging. In previous works, l-rhamnulose-1-phosphate aldolase (^C98RhuA) tetramers were self-assembled into two-dimensional (2D) lattices via disulfide bond interactions. These interactions provided 2D lattices with high structural quality and a sophisticated assembly mode. In this study, we devised a rational design for RhuA building blocks to fabricate 2D functionalized protein lattices. More importantly, the lattices were used to direct the precise assembly of NPs into highly ordered and diverse nanoarchitectures. These structures can be employed as an excellent tool to adequately verify the self-assembly mode and structural quality of the designed RhuA crystals. The subsequent redesign of RhuA building blocks enabled us to predictably produce a novel protein lattice whose conformational dynamics can be controllably regulated. Thus, a dynamic system of AuNP lattices was achieved. Transmission electron microscopy and small-angle X-ray scattering indicated the presence of these diverse NP lattices. This contribution enables the fabrication of future NP structures in a more programmable manner with more expected properties for potential applications in nanoelectronics and other fields.

Self-assembly of coherently dynamic, auxetic, two-dimensional protein crystals

Two-dimensional (2D) crystalline materials possess unique structural, mechanical and electronic properties that make them highly attractive in many applications. Although there have been advances in preparing 2D materials that consist of one or a few atomic or molecular layers, bottom-up assembly of 2D crystalline materials remains a challenge and an active area of development. More challenging is the design of dynamic 2D lattices that can undergo large-scale motions without loss of crystallinity. Dynamic behaviour in porous three-dimensional (3D) crystalline solids has been exploited for stimuli-responsive functions and adaptive behaviour. As in such 3D materials, integrating flexibility and adaptiveness into crystalline 2D lattices would greatly broaden the functional scope of 2D materials. Here we report the self-assembly of unsupported, 2D protein lattices with precise spatial arrangements and patterns using a readily accessible design strategy. Three single- or double-point mutants of the C4-symmetric protein RhuA were designed to assemble via different modes of intermolecular interactions (single-disulfide, double-disulfide and metal-coordination) into crystalline 2D arrays. Owing to the flexibility of the single-disulfide interactions, the lattices of one of the variants ((C98)RhuA) are essentially defect-free and undergo substantial, but fully correlated, changes in molecular arrangement, yielding coherently dynamic 2D molecular lattices. (C98)RhuA lattices display a Poisson's ratio of -1-the lowest thermodynamically possible value for an isotropic material-making them auxetic.