Bright G-Quadruplex Nanostructures Functionalized with Porphyrin Lanterns.

ABSTRACT

The intricate arrangement of numerous and closely placed chromophores on nanoscale scaffolds can lead to key photonic applications ranging from optical waveguides and antennas to signal-enhanced fluorescent sensors. In this regard, the self-assembly of dye-appended DNA sequences into programmed photonic architectures is promising. However, the dense packing of dyes can result in not only compromised DNA assembly (leading to ill-defined structures and precipitates) but also to essentially nonfluorescent systems (due to π-π aggregation). Here, we introduce a two-step "tether and mask" strategy wherein large porphyrin dyes are first attached to short G-quadruplex-forming sequences and then reacted with per-O-methylated ß-cyclodextrin (PMßCD) caps, to form supramolecular synthons featuring the porphyrin fluor fixed into a masked porphyrin lantern (PL) state, due to intramolecular host-guest interactions in water. The PL-DNA sequences can then be self-assembled into cyclic architectures or unprecedented G-wires tethered with hundreds of porphyrin dyes. Importantly, despite the closely arrayed PL units (∼2 nm), the dyes behave as bright chromophores (up to 180-fold brighter than the analogues lacking the PMßCD masks). Since other self-assembling scaffolds, dyes, and host molecules can be used in this modular approach, this work lays out a general strategy for the bottom-up aqueous self-assembly of bright nanomaterials containing densely packed dyes.