A unique DNA scaffold was prepared for the one-step self-assembly of hierarchical nanostructures onto which multiple proteins or nanoparticles are positioned on a single template with precise relative spatial orientation. The architecture is a topologically complex ladder-shaped polycatenane in which the ''rungs'' of the ladder are used to bring together the individual rings of the mechanically interlocked structure, and the ''rails'' are available for hierarchical assembly, whose effectiveness has been demonstrated with proteins, complementary DNA, and gold nanoparticles. The ability of this template to form from linear monomers and simultaneously bind two proteins was demonstrated by chemical force microscopy, transmission electron microscopy, and confocal fluorescence microscopy. Finally, fluorescence resonance energy transfer between adjacent fluorophores confirmed the programmed spatial arrangement between two different nanomaterials. DNA templates that bring together multiple nanostructures with precise spatial control have applications in catalysis, biosensing, and nanomaterials design.chemical force microscopy ͉ proteins ͉ wires ͉ nanoparticle ͉ catenane V ersatile scaffolds for the immobilization of proteins and other nanosized objects are targets of intensive research in the broader field of nanotechnology because of their potential applications (1) in the areas of catalysis, biosensing, and nanomaterials. In nature, complex catalytic cascades, such as the Krebs cycle (2), photosynthesis (3), or glycolysis (4), involve multiple proteins assembled with exact relative spatial orientations to facilitate cooperative binding, to facilitate electron or energy transfer, and to optimize substrate conversion. Enzymatic cascades that are used industrially (5-7) could also benefit from such closely arranged proteins if a template with the ability to fix precisely various proteins were available. Although functional synthetic polymers (8) are potential matrices for forming useful scaffolds, this approach is limited by polymer compatibility with biomolecules and the flexibility of the polymerization protocol to synthesize macromolecules that controllably bind multiple proteins. DNA, however, is a robust biopolymer that, through Watson-Crick base pairing and the multitude of sequences that can be formulated, might yield self-assembled protein scaffolds. Indeed, DNA has been used for the organization of proteins (9, 10) and elegant, topologically complex 3D architectures, such as Borromean rings (11), nanotubes (12), [2]catenanes (13), 2D tilings (14-18), and chains (19), onto which nanoparticles (20-28) and proteins (19,20,(29)(30)(31)(32) have been tethered by using complementary single-stranded DNA (ssDNA), biotin-streptavidin interactions, or gold-thiol bonds. These studies, however, have been limited to the immobilization of a single biomolecule or nanoparticle onto the scaffold or require multistep protocols to organize more than one nanomaterial onto the template.
Results and DiscussionsIn this report, we desc...