*4.18. Chelator Solutions*

2,2'-Dipyridine (2'2-DPD) was obtained commercially (Sigma Aldrich, D216305) and the intracellular prochelator (TC3-S)2 was prepared as previously reported [54]. Extracellular chelator EC1 was synthesized as described above. For experiments in cell cultures, stock solutions were prepared at a standard concentration of 100 μM in dimethyl sulfoxide (DMSO) and were always prepared freshly in degassed DMSO.
