Search

Interactions of protonated forms of kanamycin A with nucleotides and several simple phosphate anions have been studied by potentiometric and NMR titrations. The affinity of kanamycin A to anions is comparable to that observed with other aliphatic polyammonium receptors of similar charge, but it discriminates triphosphate nucleotides with different nucleobases with binding constants following the order GTP≫CTP ≈ ATP. Kanamycin A also binds the respective uncharged nucleosides with the same selectivity. Binding of ATP is exothermic with a negative entropic contribution in contrast to what is expected for simple ion pairing. Other tested aminoglycosides, amikacin and streptomycin, bind ATP less efficiently than kanamycin A. Models of structures of kanamycin A complexes with ATP and GTP obtained by molecular mechanics (OPLS-2005) calculations based on 1H and 31P NMR data confirm the possibility of nucleotide discrimination by simultaneous ion pairing of terminal nucleotide phosphate groups with ammonium sites...

A new water soluble 26-membered macrocyclic pyridinophane functionalized by amide and carboxymethyl groups has been synthesized in a single step reaction and characterized by elemental analysis, mass spectrometry (FAB+), UV-vis, fluorescence, and 1H NMR spectroscopy as well as single-crystal X-ray diffraction analysis. Its complexation properties with the nucleobases thymine and uracil have been explored in aqueous media by performing 1H NMR titration experiments and potentiometric studies. The binding constants of the 1:1 host-guest complexes were determined as 103 M− 1 by proton NMR and 102–103 M− 1 by potentiometry. Semiempirical molecular modelling studies have shown that the nucleobases are included within the cavity of the macrocyclic receptor and that the complexes are stabilized by hydrogen bonding.