The interactions of gallium with various buffers and chelating agents in aqueous solution: Gallium-71 and hydrogen-1 NMR studies

The interactions of gallium (Ga) with the ligands, EDTA, NTA, phosphate, lactate, MOPS, TRIS and HEPES are investigated using both ⁷¹Ga and ¹H nmr measurements. Both EDTA and NTA form strong complexes with gallium, which have a 1:1 stoichiometry. In alkaline solution the tetrahedral Ga(OD)₄ ^- competes strongly with EDTA in complex formation. In the lactate complex, there are probably three lactates per gallium present. The phosphate complexes of gallium are difficult to characterize on the basis of this investigation. The buffers, MOPS, TRIS, and HEPES, do not interact with gallium significantly. The ability of the ligands to bind gallium correlates well with their ability to inhibit gallium incorporation by L1210 leukemic cells.