THE COORDINATION OF 5'-DERIVATIVES OF ADENOSINE TO VANADATE

The aqueous systems vanadate-Aden have been investigated by V-51 NMR. Aden is an adenosine derivative with O5' replaced by a secondary amine nitrogen tailed by nCH(2) groups and a terminal OH; n = 2, 3, 5. The preparation of these new ligands and their spectroscopic characteristics are reported. The complex formation constants K, at ambient temperatures, for the dinuclear biligate complexes formed between vanadate (in the concentration range 1-4 mM) and Aden are 3.9 X 10(7) M(-3) (n = 2), 3.3 X 10(6) M -3 (n = 3) and 9.2 X 10(6) M(-3) (n = 5). The K values are of about the same order of magnitude as for adenosine itself (2.5 X 10(7) M(-3)) and for Ade2a, an adenosine derivative with a tertiary amine nitrogen (K = 2.9 X 10(7) M(-3)), but larger than for ribose (K = 5.0 x 10(5) M(-3)).