Dendrimeric DNA Nanostructures as Scaffolds for Efficient Bidirectional BRET-FRET Cascades

DNA scaffolds offer advantages for biomolecular devices capable of generating and controlling energy flow. Through attachment of the bioluminescent protein luciferase and precise positioning of organic fluorophores, these structures form efficient self-illuminating energy transfer cascades. Luciferase initiates a bioluminescent resonance energy transfer step, which is then propagated by Forster resonance energy transfer (FRET) through the rest of the structure. Two related DNA dendrimeric nanostructures are investigated; the first funnels energy inward toward the center, while the second radiates it outward. When attached to the DNA dendrimer, luciferase bioluminescence is harnessed by an initial AlexaFluor 488 dye and transferred via a series of FRET steps through Cy3, Cy3.5, and Cy5 dyes - to a terminal Cy5.5 acceptor. In the inward funneling construct, the luciferase is displayed on the dendrimer periphery and uses two donor fluorophores for each subsequent acceptor. The outward funneling construct anchors luciferase at the core and energies of successive donor fluorophores are captured by two acceptor dyes. The inward configuration yields end-to-end and anywhere-to-end efficiencies of 16% and 25%, respectively, while the outward configuration approaches 25% and 50%, respectively. The performance of each construct is detailed and potential applications of these self-illuminating biophotonic assemblies are discussed.