Transferrin prerequisites

A further prerequisite for an indium complex to be useful for nuclear medicine applications is that it be resistant to exchange with the plasma protein transferrin. Indium binds to transferrin at the Fe binding site with a stability constant (/f ) of lO in the presence of bicarbonate [7]. The formation constants of indium with ethylenediaminetetraacetic acid (EDTA) (log = 25.0) and DTPA (log Ki = 29.0) are such that at infinite dilution equilibrium would favor the formation of indium transferrin [8J. The slow dissociation of indium from these complexes hinders the formation of indium transferrin. 

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