Identifying three-way DNA junction-specific small-molecules.

Three-way junction DNA (TWJ-DNA, also known as 3WJ-DNA) is an alternative secondary DNA structure comprised of three duplex-DNAs that converge towards a single point, termed the branch point. This point is characterized by unique geometrical properties that make its specific targeting by synthetic small-molecules possible. Such a targeting has already been demonstrated in the solid state but not thoroughly biophysically investigated in solution. Herein, a set of simple biophysical assays has been developed to identify TWJ-specific small-molecule ligands; these assays, inspired by the considerable body of work that has been reported to characterize the interactions between small-molecules and other higher-order DNA (notably quadruplex-DNA), have been calibrated with a known non-specific DNA binder (the porphyrin TMPyP4) and validated via the study of a small series of triazacyclononane (TACN) derivatives (metal-free or not) and the identification of a fairly-affinic and exquisitely TWJ-selective candidate (a TACN-quinoline construct named TACN-Q).