The interaction of Cu(II), Ni(II), Co(II), Zn(II), Mn(II), Mg(II) and Ca(II) with inosine and secondary ligands histidine and glycine in a 1:1:1 ratio was determined by potentiometric equilibrium measurements at 35°C and 0.10 M (KNO3) ionic strength. The stability constants of the ternary complexes of xanthosine with histidine and glycine are also included for effective comparison. The ternary complexes were found to be stabler than the corresponding binary complexes. This higher stability of the ternary complexes is measured in terms of Δ logK which is the difference between the overall 1:1:1 stability constant and the corresponding 1:1 constant. Histidine forms stabler ternary complexes with inosine than does glycine. This is attributed to the π-accepting capacity of the imidazole ring of histidine and also to the stacking interaction between the purine part of inosine and the imidazole moiety of histidine.
Volume 134, 2022
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