Abstract
We could isolate metal complexes of inosinic acid (IMP) with Pb, Cd, Co (II), Zn, Cu (II), Ni and Mn as crystalline precipitates and Hg (II) was amorphous one from the solution of pH 3.0-7.0
The elementary analysis revealed that the isolated metal complexes had the composition of 1:1 of IMP to metal, except Hg-IMP whose composition is 2:3. And we discussed the infrared (IR) absorption spectra of these metal complexes and compared with thos eof IMP Na, IMP 2Na, IMP 2K, IMP Ca and IMP Ba salt. Metal complexes with Co (II), Ni, Mn, Cd, and Pb as well as the above salt compounds showed the C=O stretching absorption in the region of about 1690cm-1.
Complexation with Cu (II), Zn and Hg (II) shifted this frequency to 1710, 1708, and 1640cm-1 respectively.
In the region of 1200-900cm-1 absorptions due to the phosphate group are expected, the metal complexes except Cu-IMP and Zn-IMP showed the similar spectra to those of IMP salt compounds, such as IMP 2Na and IMP 2K. Cu-IMP and Zn-IMP showed a little complicated spectra also in this region.
From the above results we concluded that Cu (II), Zn and Hg (II) coordinated not only to the phosphate group but also to the hypoxanthine moiety of IMP The coordination sites of Cu (II) and Zn on the hypoxanthine moiety were considered N-7 and that of Hg (II) was C-O from the spectral changes and elementary analysis.
Additional experiments of NMR spectra in D20 revealed the protonation to N-7 of hypoxanthine moiety from the phsophate group of IMP free acid.
