Aryl-bis-(scorpiand)-aza receptors differentiate between nucleotide monophosphates by a combination of aromatic, hydrogen bond and electrostatic interactions

Bis-polyaza pyridinophane scorpiands bind nucleotides in aqueous medium with 10-100 micromolar affinity, predominantly by electrostatic interactions between nucleotide phosphates and protonated aliphatic amines and assisted by aromatic stacking interactions. The pyridine-scorpiand receptor showed rare selectivity toward CMP with respect to other nucleotides, whereby two orders of magnitude affinity difference between CMP and UMP was the most appealing. The phenanthroline-scorpiand receptor revealed at pH 5 strong selectivity toward AMP with respect to other NMPs, based on the protonation of adenine heterocyclic N1. The results stress that the efficient recognition of small biomolecules within scorpiand-like receptors relies mostly on the electrostatic and H-bonding interactions despite the competitive interactions in the bulk solvent, thus supporting further optimisation of this versatile artificial moiety.