Binary and ternary complexes of metal ions, nucleoside 5′-monophosphates, and amino acids☆

摘要: The aromatic-ring stacking interactions between the indole moiety of L-tryptophan and purine or pyrimidine moieties AMP2− CMP2+, respectively, were studied by 1H NMR spectroscopy. Under influence increasing concentrations L-trytophan resonance H-2, H-8 H-1′ a H-5 H-6 CMP2− are shifted upfield. Computer curve fitting shift data gave stability constants K(AMP)(H·Trp)(AMP) = 6.83 ± 0.81 M−1 K(CMP)(H·Trp)CMP 0.77 0.35 (in D2O; 27°C; I 0.1 M) which show that forms more stable stacks. Repetition experiments under conditions where amino acid exists as anion, i.e. tryptophanate, K(AMP)(Trp)(AMP) 2.24 0.29 K(CMP)(Trp)(CMP) 0.14 0.05 0.1–0.15 M). Hence, it is evident formation an ionic bridge negatively charged phosphate nucleotides positively ammonium group favors stack nucleic bases residue. In case with constant this ion pair could be estimated, KIP ≅ 0.6 M), value compares well 1.35 0.76 for (CH3)4N+/Trp− interaction. Intramolecular equilibrium interaction within stacked complex also estimated discussed. Stability metal complexes only determined Ni2+ precipitate formed Cu2+ Zn2+. binary systems, Ni2+/AMP2−, Ni2+/CMP2−, Ni2+/Trp−, Ni2+/Ala−, potentiometric pH-titrations. somewhat enhanced Ni(Trp)2 compared Ni(Ala)2, Ni(AMP)22− Ni(CMP)22− (for no evidence was observed) explained self-stacking these 1:2 complexes. Based on following ternary systems corresponding determined: Ni2+/AMP2−/Trp−, Ni2+/AMP2−/Ala−, Ni2+/CMP2−/Trp−, Ni2+/CMP2−/Ala−. A most likely intramolecular purine/indole in Ni(AMP)(Trp)− not significantly reflected measured constants. This observation implications regard to complexes, general importance “bridged” adducts biological briefly