Interactions of 1,12-diamino-4,9-dioxadodecane (OSpm) and Cu(II) ions with pyrimidine and purine nucleotides: Adenosine-5′-monophosphate (AMP) and cytidine-5′-monophosphate (CMP)

The interactions of Cu(II) ions with adenosine-5′-monophosphate (AMP), cytidine-5′-monophosphate (CMP) and 1,12-diamino-4,9-dioxadodecane (OSpm) were studied. A potentiometric method was applied to determine the composition and stability constants of complexes formed, while the mode of interactions was analysed by spectral methods (ultraviolet and visible spectroscopy (UV-Vis), electron paramagnetic resonance (EPR), 13C NMR, 31P NMR). In metal-free systems, molecular complexes nucleotide-polyamine (NMP)Hx(OSpm) were formed. The endocyclic nitrogen atoms of the purine ring N(1), N(7), the nitrogen atom of the pyrimidine ring N(3), the oxygen atoms of the phosphate group of the nucleotide and the protonated nitrogen atoms of the polyamine were the reaction centres. The mode of interaction of the metal ion with OSpm and the nucleotides (AMP or CMP) in the coordination compounds was established. In the system Cu(II)/OSpm the dinuclear complex Cu2(OSpm) forms, while in the ternary systems Cu(II)/nucleotide/OSpm the species type MHxLL′ and MLL′ appear. In the MHxLL′ type species, the main centres of copper (II) ion binding in the nucleotide are the phosphate groups. The protonated amino groups of OSpm are involved in non-covalent interaction with the nitrogen atoms N(1), N(7) or N(3) of the purine or pyrimidine ring, whereas at higher pH, deprotonated nitrogen atoms of polyamine are engaged in metallation in MLL′ species.