NA structural technology affords the unparalleled ability to position multiple attendant molecules and especially fluorophores within any designer 1-, 2-, and 3-dimensional nanoscale architecture with precise controlled spacing relative to each other. Although many applications can be undertaken with such capabilities, we have focused on light harvesting and exciton directing and delivery based on creating Förster resonance energy transfer networks and cascades; these are sometimes referred to as DNA-based photonic wires. One of our long-term goals in this area is in understanding the design principles that can allow almost any fluorescent material, ranging from organic dyes to fluorescent nanoparticles such as quantum dots, to be incorporated into these type of structures while still allowing for optimal functionality. Another critical goal for these types of devices is to increase their ability to harvest excitonic energy and then transfer it over multiple steps both across extended portions of the spectra and physical space. Several examples that we have studied in detail will be presented including linear photonic wires, star-shaped structures, multigenerational dendrimers and photonic wires incorporating semiconductor quantum dots, long-lifetime Terbium cryptates and bioluminescent enzymes such as luciferase. Given its importance, some details will be provided on purification and characterization of DNA assembly efficiency and dye incorporation. The data will be presented in the context of detailed energy transfer analysis and modeling of the underlying processes. Overall, these studies have generally revealed that each photonic wire configuration brings with it both a set of functional benefits and liabilities that must be accommodated in order to facilitate continuing studies and this will also be discussed.
Center for Bio/Molecular Science and Engineering, U.S. Naval Research Laboratory, Washington D.C.