Synthesis and G-quadruplex binding studies of new 4-N-methylpyridinium porphyrins

A series of cationic porphyrins carrying 1-3 meso-N-pyridinium groups has been synthesised, and their binding to G-quadruplex DNA has been explored by surface plasmon resonance (SPR) and circular dichroism spectroscopy. Two trans substituents appear to be sufficient for tight binding; preferential binding to the anti-parallel intramolecular human telomeric DNA was observed for the A2trans and A3 porphyrins. The A2trans is able to induce the formation of an anti-parallel G-quadruplex in a K+ free solution, mimicking the effect of a molecular chaperone.