Effect of 108-o concentration on iron exchange between 108-o-Fe and fluorescein-DFO (Fl-DFO).

Complexes of 108-o:Fe were preformed by mixing Fe:NTA (5 mM ferrous ammonium sulfate/35 mm nitrilotriacetate) with 108-o in HBS to yield solutions containing 10 μM Fe and increasing concentrations of 108-o (0, 15.6, 31.3, 62.5, 125, 250, and 500 μM), followed by incubation for 1 hour at room temperature. At 0 minutes, 25 μL each chelator-Fe complex was mixed with 100 μL of 2.5 μM Fl-DFO in HBS, and the fluorescence was monitored over time in a fluorescence plate reader. Final concentrations of Fe and Fl-DFO were 2 μM in each system, whereas the final concentration of 108-o varied from 0 through 100 μM. The fluorescence of Fl-DFO without added chelator or Fe is indicated by “Fl-DFO alone.”