Molecular recognition of nucleotides by the protonated macrocyclic ligand 3,6,9,17,20,23-hexaazatricyclo[23.3.1.1 11,15]triaconta-1(29),11(30),12,14,25,27-hexaene and by its Cu(II) complexes; catalysis of the conversion of ATP to ADP

Abstract

The hexaaza macrocyclic ligand 3,6,9,17,20,23-hexaazatricycli[23.3.1.1 11,15]triaconta-1(29),11(30),12,14,25,27-hexaene (BMXD) forms binary complexes with the nucleotides AMP, ADP and ATP as a result of coulombic attraction and hydrogen bonding interactions. Formation constants for the binary species found have been measured using potentiometric titration methods. The protonated forms of BMXD are able to recognize the nucleotides in solution and the strength of binding is of the order ATP > ADP > AMP. The mono- and dinuclear copper(II) complexes of BMXD also form stable ternary complexes with ADP and ATP in solution although the formation constants are somewhat less than those with the macrocycle alone. The catalysis of the conversion of ATP to ADP and orthophosphate at 70°C has been followed by HPLC techniques. The rates of hydrolysis increase with decreasing pH and are compared to the rates catalyzed by other hexaaza macrocyclic ligands. The presence of copper(II) ions has an inhibitory effect on the hydrolysis of ATP by BMXD.