Programmable Aggregation of Self-Assembled DNA Constructs.

Biomolecular aggregates ensure the optimum concentration and proximity required for biochemical processes to take place. Synthetic aggregating systems are becoming increasingly essential to study/mimic dynamic condensates in nature. Herein the ratiometric DNA aggregation of self-assembled DNA constructs using lanthanide salts is reported. In addition, the aggregation is shown to be reversed by the addition of specific lanthanide-binding ligands. The aggregate formation is confirmed by dynamic light scattering experiment, electrophoretic mobility shift assay, and field emission scanning electron microscope. This programmed DNA aggregation and its reversion are applied to evaluating the lanthanide-DNA and lanthanide-ligand binding constants, respectively. To achieve this, Forster resonance energy transfer (FRET) pair dyes at the 3' or 5' end of the DNA strands are strategically placed that generate unique fluorescence patterns upon interaction with the DNA constructs and different triggers such as lanthanides/ligands/monovalent cations, thus enabling the tracking of various states of binding. It also demonstrates a "fast method" to form and stabilize G-quadruplex (GQ) using lanthanides which complements the existing slow formation of GQs with Na/K ions. The formation of GQ by lanthanides is corroborated by FRET, circular dichroism (CD), and enzyme linked immunosorbent assay (ELISA) experiments. These DNA constructs, formed by lanthanides, have shown resistance to cleavage by DNase I, and distinctive binding to Protoporphyrin dyes and Thioflavin T.