G-quadruplex on oligo affinity support (G4-OAS): an easy affinity chromatography-based assay for the screening of G-quadruplex ligands.

A simple, cheap, and highly reproducible affinity chromatography-based method has been developed for the screening of G-quadruplex binders. The tested compounds were flowed through a polystyrene resin functionalized with an oligonucleotide able to form, in proper conditions, a G-quadruplex structure. Upon cation-induced control of the folding/unfolding processes of the immobilized G-quadruplex-forming sequence, small molecules specifically interacting with the oligonucleotide structure were first captured and then released depending on the used working solution. This protocol, first optimized for different kinds of known G-quadruplex ligands and then applied to a set of putative ligands, has allowed one to fully reuse the same functionalized resin batch, recycled for several tens of experiments without loss in efficiency and reproducibility.