(607e) DNA-Programmable Assembly of Enzyme Superlattices

Enzymes are one of Natureâ??s most diverse and powerful nanoparticles. Assembling them into multicomponent crystals has been of great interest and can be accomplished through a variety of means, typically based on protein surface chemistry. The programmability of DNA makes it an attractive structure-directing ligand for assembling nanoparticles into well-defined materials. Recently, DNA has emerged as an effective ligand by which catalytically active proteins can be assembled into extended crystalline superlattices of CsCl symmetry. In these systems, protein surfaces are covalently functionalized with nucleic acid ligands, which direct interparticle interactions through Watson-Crick base pairing. In this study, we predicted that under certain conditions the anisotropic shape and surface chemistry of the enzyme could induce directional bonding interactions resulting in the assembly of a different lattice symmetry. To probe this, the enzyme catalase was functionalized with DNA ligands of varying flexibility and co-assembled with gold nanoparticles possessing different numbers of DNA bonding ligands. A phase transformation was observed with decreasing DNA flexibility and increasing gold nanoparticle ligand number from CsCl to Th₃P₄ symmetry, with mixtures of the two lattice symmetries present at intermediate states. Through fitting of the SAXS diffraction patterns, the composition of the mixtures was quantified. Coarse grained molecular dynamics simulations were used to further understand the energetics of the two phases. This is the first instance in these systems that phase transformation has been observed by tuning ligand flexibility, expanding on the means by which well-defined functional materials can be assembled from proteins using DNA.