The binding of scandium ions to transferrin in vivo and in vitro.
1 
Studies on the binding of scandium to human apotransferrin showed that two Sc3+ were bound specifically at the two iron-binding sites. 
 
2 
The binding of each Sc3+ involves the ionisation of two phenolic tyrosyl residues. 
 
3 
The scandium · protein complex has similar resistance to denaturants and chemical reagents as the iron complex. 
 
4 
The only protein complex observed, when quantities of Sc3+ below the free iron binding capacity of serum were added to whole serum in vitro, was the Sc3+· transferrin complex. 
 
5 
The injection of Sc3+, as a 1:2 citrate complex, into rabbits led after 48 h to all the plasma Sc3+ being present as the transferrin complex.