Adenine nucleotide recognition by spiramycin and some of its aromatic derivatives

Association of adenine nucleotides with the macrocyclic antibiotic Spiramycin and two of its aromatic derivatives was studied by potentiometric titrations, 1H and 31P NMR spectrometry and molecular modelling. Spiramycin binds adenine nucleotides with K ≈ 103–104 M−1 and selectivity for ADP over ATP or AMP. The introduction of aromatic moieties reduces the strength of the binding but, selectivity order changes to ATP > ADP > AMP. Molecular models showed that complexes are mainly stabilized by electrostatic interactions between the protonated amino groups of the receptors and the phosphate groups of the nucleotides.