Coordination mode of adenosine 5'-diphosphate in ternary systems containing Cu(II), Cd(II) or Hg(II) ions and polyamines

The interactions of adenosine 5'-diphosphate (ADP) with some polyamines (PA) (1,3-diaminopropane (tn), 1,4-diaminobutane (Put), 1,7-diamino-4-azaheptane (3,3-tri) and 1,8-diamino-4-azaoctane (Spd)) both in presence and in the absence of metal ions (Cu(II), Cd(II) and Hg(II)) have been studied. In the metal-free systems the formation of adducts (ADP)Hx(PA) has been observed, in which the main reaction centres are the endocyclic nitrogen atoms of the purine ring, the phosphate group of the nucleotide and the protonated nitrogen atoms of the polyamine. The effectiveness of the phosphate group in formation of adducts has been found to decrease in the series Put > Spd > Spm and to be lower than in the reactions with shorter homologues of biogenic amines. In the ternary systems with metal ions the formation of molecular complexes (ML L' type) has been evidenced in which the protonated polyamine interacts with the nitrogen atoms N(1) or N(7) of the purine ring of the nucleotide. In the ternary systems Cu(II)/ADP/polyamine the coordination dichotomy observed in the binary system Cu(II)/ADP disappears. In the systems with Hg(II) ions the pH range of the dichotomy is extended, while for the systems Cd(II)/ADP/polyamine no changes of the range relative to the binary system Cd(II)/ADP have been noted.