Interaction between macrocyclic nickel complexes and the nucleotides GMP, AMP and ApG

Reactions between the nucleotides GMP, AMP and ApG and the complexes Ni(tren), Ni(cyclam) and NiCR in aqueous solution have been monitored by 1H, 15N NMR and UV spectroscopy. The three nickel complexes display different properties in reactions with nucleotides. Ni(tren) which has a pseudo-octahedral coordination geometry was shown to bind to all three nucleotides. Ni(cyclam) and NiCR, both with four nitrogen atoms in a square planar arrangement are not able to bind to nucleotides efficiently because of steric hindrance. Oxidation of Ni(cyclam) by KHSO 5 to produce trivalent Ni III(cyclam) improves the coordination capacity, while oxidation of NiCR does not produce a similar effect. The nucleotides interact with trivalent nickel complexes to different extent. Ni IIICR is seen to oxidize GMP gradually but does not affect AMP significantly. Ni III(cyclam), on the other hand, does not oxidize either GMP or AMP at the 1:1 concentration of oxidant used. This result is probably due to the lower redox potential of Ni(cyclam). ApG binds less efficiently to the Ni complexes but is easier oxidized than the mononucleotides.